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Peer-reviewed

Research Article

Water Filtration Using Plant Xylem

Contributed equally to this work with: Michael S. H. Boutilier, Jongho Lee

Affiliation Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America

* E-mail: [email protected]

• Michael S. H. Boutilier, 
• Jongho Lee, 
• Valerie Chambers, 
• Varsha Venkatesh, 
• Rohit Karnik

• Published: February 26, 2014
• https://doi.org/10.1371/journal.pone.0089934
• Reader Comments

Effective point-of-use devices for providing safe drinking water are urgently needed to reduce the global burden of waterborne disease. Here we show that plant xylem from the sapwood of coniferous trees – a readily available, inexpensive, biodegradable, and disposable material – can remove bacteria from water by simple pressure-driven filtration. Approximately 3 cm 3 of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person. The results demonstrate the potential of plant xylem to address the need for pathogen-free drinking water in developing countries and resource-limited settings.

Citation: Boutilier MSH, Lee J, Chambers V, Venkatesh V, Karnik R (2014) Water Filtration Using Plant Xylem. PLoS ONE 9(2): e89934. https://doi.org/10.1371/journal.pone.0089934

Editor: Zhi Zhou, National University of Singapore, Singapore

Received: October 17, 2013; Accepted: January 23, 2014; Published: February 26, 2014

Copyright: © 2014 Boutilier et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was supported by the James H. Ferry, Jr. Fund for Innovation in Research Education award to R.K. administered by the Massachusetts Institute of Technology. SEM imaging was performed at the Harvard Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

The scarcity of clean and safe drinking water is one of the major causes of human mortality in the developing world. Potable or drinking water is defined as having acceptable quality in terms of its physical, chemical, and bacteriological parameters so that it can be safely used for drinking and cooking [1] . Among the water pollutants, the most deadly ones are of biological origin: infectious diseases caused by pathogenic bacteria, viruses, protozoa, or parasites are the most common and widespread health risk associated with drinking water [1] , [2] . The most common water-borne pathogens are bacteria (e.g. Escherichia coli , Salmonella typhi , Vibrio cholerae ), viruses (e.g. adenoviruses, enteroviruses, hepatitis, rotavirus), and protozoa (e.g. giardia) [1] . These pathogens cause child mortality and also contribute to malnutrition and stunted growth of children. The World Health Organization reports [3] that 1.6 million people die every year from diarrheal diseases attributable to lack of access to safe drinking water and basic sanitation. 90% of these are children under the age of 5, mostly in developing countries. Multiple barriers including prevention of contamination, sanitation, and disinfection are necessary to effectively prevent the spread of waterborne diseases [1] . However, if only one barrier is possible, it has to be disinfection unless evidence exists that chemical contaminants are more harmful than the risk from ingestion of microbial pathogens [1] . Furthermore, controlling water quality at the point-of-use is often most effective due to the issues of microbial regrowth, byproducts of disinfectants, pipeline corrosion, and contamination in the distribution system [2] , [4] .

Common technologies for water disinfection include chlorination, filtration, UV-disinfection, pasteurization or boiling, and ozone treatment [1] , [2] , [5] . Chlorine treatment is effective on a large scale, but becomes expensive for smaller towns and villages. Boiling is an effective method to disinfect water; however, the amount of fuel required to disinfect water by boiling is several times more than what a typical family will use for cooking [1] . UV-disinfection is a promising point-of-use technology available [1] , yet it does require access to electricity and some maintenance of the UV lamp, or sufficient sunlight. While small and inexpensive filtration devices can potentially address the issue of point-of-use disinfection, an ideal technology does not currently exist. Inexpensive household carbon-based filters are not effective at removing pathogens and can be used only when the water is already biologically safe [1] . Sand filters that can remove pathogens require large area and knowledge of how to maintain them [1] , while membrane filters capable of removing pathogens [2] , [4] suffer from high costs, fouling, and often require pumping power due to low flow rates [6] that prevents their wide implementation in developing countries. In this context, new approaches that can improve upon current technologies are urgently needed. Specifically, membrane materials that are inexpensive, readily available, disposable, and effective at pathogen removal could greatly impact our ability to provide safe drinking water to the global population.

If we look to nature for inspiration, we find that a potential solution exists in the form of plant xylem – a porous material that conducts fluid in plants [7] . Plants have evolved specialized xylem tissues to conduct sap from their roots to their shoots. Xylem has evolved under the competing pressures of offering minimal resistance to the ascent of sap while maintaining small nanoscale pores to prevent cavitation. The size distribution of these pores – typically a few nanometers to a maximum of around 500 nm, depending on the plant species [8] – also happens to be ideal for filtering out pathogens, which raises the interesting question of whether plant xylem can be used to make inexpensive water filtration devices. Although scientists have extensively studied plant xylem and the ascent of sap, use of plant xylem in the context of water filtration remains to be explored. Measurements of sap flow in plants suggest that flow rates in the range of several liters per hour may be feasible with less than 10 cm-sized filters, using only gravitational pressure to drive the flow [7] .

We therefore investigated whether plant xylem could be used to create water filtration devices. First, we reason which type of plant xylem tissue is most suitable for filtration. We then construct a simple water filter from plant xylem and study the resulting flow rates and filtration characteristics. Finally, we show that the xylem filter can effectively remove bacteria from water and discuss directions for further development of these filters.

Materials and Methods

Branches were excised from white pine growing on private property in Massachusetts, USA, with permission of the owner and placed in water. The pine was identified as pinus strobus based on the 5-fold grouping of its needles, the average needle length of 4.5 inches, and the cone shape. Deionized water (Millipore) was used throughout the experiments unless specified otherwise. Red pigment (pigment-based carmine drawing ink, Higgins Inks) was dissolved in deionized water. Nile-red coated 20 nm fluorescent polystyrene nanospheres were obtained from Life Technologies. Inactivated, Alexa 488 fluorescent dye labeled Escherichia coli were obtained from Life Technologies. Wood sections were inserted into the end of 3/8 inch internal diameter PVC tubing, sealed with 5 Minute Epoxy, secured with hose clamps, and allowed to cure for ten minutes before conducting flow rate experiments.

Construction of the Xylem Filter

1 inch-long sections were cut from a branch with approximately 1 cm diameter. The bark and cambium were peeled off, and the piece was mounted at the end of a tube and sealed with epoxy. The filters were flushed with 10 mL of deionized water before experiments. Care was taken to avoid drying of the filter.

Filtration and Flow Rate Experiments

Approximately 5 mL of deionized water or solution was placed in the tube. Pressure was supplied using a nitrogen tank with a pressure regulator. For filtration experiments, 5 psi (34.5 kPa) pressure was used. The filtrate was collected in glass vials. For dye filtration, size distribution of the pigments was measured for the input solution and the filtrate. Higgins pigment-based carmine drawing ink, diluted ∼1000× in deionized water, was used as the input dye solution. For bacteria filtration, the feed solution was prepared by mixing 0.08 mg of inactivated Escherichia coli in 20 mL of deionized water (∼1.6×10 7 mL −1 ) after which the solution was sonicated for 1 min. The concentration of bacteria was measured in the feed solution and filtrate by enumeration with a hemacytometer (inCyto C-chip) mounted on a Nikon TE2000-U inverted epifluorescence microscope. Before measurement of concentration and filtration experiments, the feed solution was sonicated for 1 min and vigorously mixed.

Xylem structure was visualized in a scanning electron microscope (SEM, Zeiss Supra55VP). Samples were coated with gold of 5 nm thickness before imaging. To visualize bacteria filtration, 5 mL of solution at a bacteria concentration of ∼1.6×10 7 mL −1 was flowed into the filter. The filter was then cut longitudinally with a sharp blade. One side of the sample was imaged using a Nikon TE2000-U inverted epifluorescence microscope and the other was coated with gold and imaged with the SEM. Optical images were acquired of the cross section of a filter following filtration of 5 mL of the dye at a dilution of ∼100×.

Particle Sizing

Dynamic light scattering measurements of particle size distributions were performed using a Malvern Zetasizer Nano-ZS.

Xylem Structure and Rationale for use of Conifer Xylem

The flow of sap in plants is driven primarily by transpiration from the leaves to the atmosphere, which creates negative pressure in the xylem. Therefore, xylem evolution has occurred under competing pressures of providing minimal resistance to the flow of sap, while protecting against cavitation (i.e. nucleation) and growth of bubbles that could stop the flow of sap and kill the plant, and to do this while maintaining mechanical strength [7] . The xylem structure comprises many small conduits that work in parallel and operate in a manner that is robust to cavitation [7] , [8] ( Figure 1 ). In woody plants, the xylem tissue is called the sapwood, which often surrounds the heartwood (i.e. inactive, non-conducting lignified tissue found in older branches and trunks) and is in turn surrounded by the bark ( Figure 1b,c ). The xylem conduits in gymnosperms (conifers) are formed from single dead cells and are called tracheids ( Figure 1c ), with the largest tracheids reaching diameters up to 80 µm and lengths up to 10 mm [7] . Angiosperms (flowering plants) have xylem conduits called vessels that are derived from several cells arranged in a single file, having diameters up to 0.5 mm and lengths ranging from a few millimeters to several meters [7] . These parallel conduits have closed ends and are connected to adjacent conduits via “pits” [8] ( Figure 1d,e ). The pits have membranes with nanoscale pores that perform the critical function of preventing bubbles from crossing over from one conduit to another. Pits occur in a variety of configurations; Figure 1d,e shows torus-margo pit membranes that consist of a highly porous part shaped like a donut (margo) and an impermeable part in the center called torus, occurring in conifers [8] . The porosity of the pit membranes ranges in size from a few nanometers to a few hundred nanometers, with pore sizes in the case of angiosperms tending to be smaller than those in gymnosperms [8] , [9] . Pit membrane pore sizes have been estimated by examining whether gold colloids or particles of different sizes can flow through [8] , [10] . Remarkably, it was observed that 20 nm gold colloids could not pass through inter-vessel pit membranes of some deciduous tree species [10] , indicating an adequate size rejection to remove viruses from water. Furthermore, inter-tracheid pit membranes were found to exclude particles in the 200 nm range [8] , as required for removal of bacteria and protozoa.

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a) Structure of xylem vessels in flowering plants and tracheids in conifers. Longer length of the vessels can provide pathways that can bypass filtration through pit membranes that decorate their circumference. b) Photograph of ∼1 cm diameter pine ( pinus strobus ) branch used in the present study. c) Scanning electron microscope (SEM) image of cut section showing tracheid cross section and lengthwise profile. Scale bar is 40 µm. d) SEM image showing pits and pit membranes. Scale bar is 20 µm. e) Pit membrane with inset showing a cartoon of the pit cross-section. The pit cover has been sliced away to reveal the permeable margo surrounding the impermeable torus. Arrow indicates observed hole-like structures that may be defects. The margo comprises radial spoke-like structures that suspend the torus, which are only barely visible overlaying the cell wall in the background. Scale bar is 1 µm. f) Dependence of area amplification, defined as the pit membrane area divided by the nominal filter area, on the tracheid aspect ratio L / D and fractional area α occupied by pit membranes.

https://doi.org/10.1371/journal.pone.0089934.g001

Since angiosperms (flowering plants, including hardwood trees) have larger xylem vessels that are more effective at conducting sap, xylem tissue constitutes a smaller fraction of the cross-section area of their trunks or branches, which is not ideal in the context of filtration. The long length of their xylem vessels also implies that a large thickness (centimeters to meters) of xylem tissue will be required to achieve any filtration effect at all – filters that are thinner than the average vessel length will just allow water to flow through the vessels without filtering it through pit membranes ( Figure 1a ). In contrast, gymnosperms (conifers, including softwood trees) have short tracheids that would force water to flow through pit membranes even for small thicknesses (<1 cm) of xylem tissue ( Figure 1a ). Since tracheids have smaller diameters and are shorter, they offer higher resistance to flow, but typically a greater fraction of the stem cross-section area is devoted to conducting xylem tissue. For example, in the pine branch shown in Figure 1b used in this study, fluid-conducting xylem constitutes the majority of the cross-section. This reasoning leads us to the conclusion that in general the xylem tissue of coniferous trees – i.e. the sapwood – is likely to be the most suitable xylem tissue for construction of a water filtration device, at least for filtration of bacteria, protozoa, and other pathogens on the micron or larger scale.

The resistance to fluid flow is an important consideration for filtration. Pits can contribute a significant fraction (as much as 30–80%) [7] , [8] of the resistance to sap flow, but this is remarkably small considering that pit membrane pore sizes are several orders of magnitude smaller than the tracheid or vessel diameter. The pits and pit membranes form a hierarchical structure where the thin, highly-permeable pit membranes are supported across the microscale pits that are arranged around the circumference of the tracheids ( Figure 1a ). This arrangement permits the pit membranes to be thin, offering low resistance to fluid flow. Furthermore, the parallel arrangement of tracheids with pits around their circumference provides a high packing density for the pit membranes. For a given tracheid with diameter D and length L , where pit membranes occupy a fraction α of the tracheid wall area, each tracheid effectively contributes a pit membrane area of πDLα /2, where the factor of 2 arises as each membrane is shared by two tracheids. However, the nominal area of the tracheid is only πD 2 /4, and therefore, the structure effectively amplifies the nominal filter area by a factor of 2 α ( L / D ) ( Figure 1f ). The images in Figure 1c indicate that typical D ∼ 10–15 µm and α ∼ 0.2 yield an effective area amplification of ∼20 for tracheid lengths of 1–2 mm. Therefore, for a filter made by cutting a slice of thickness ∼ L of the xylem, the actual membrane area is greater by a large factor due to vertical packing of the pit membranes. Larger filter thicknesses further increase the total membrane area, but the additional area of the membrane is positioned in series rather than in parallel and therefore reduces the flow rate, but potentially improves the rejection performance of the filter due to multiple filtration steps as shown in Figure 1a .

Construction of the Xylem Filter and Measurement of Flow Rate

a) Construction of xylem filter. b) Effect of applied pressure on the water flux through the xylem filter. c) Hydrodynamic conductivity of the filter extracted at each measured pressure using the total filter cross-section area and thickness as defined by Equation 1 . Error bars indicate ±S.D. for measurements on three different xylem filters.

https://doi.org/10.1371/journal.pone.0089934.g002

Biologists have performed similar flow rate measurements by cutting a section of a plant stem under water, flushing to remove any bubbles, and applying a pressure difference to measure the flow rate [11] , [12] . Xylem conductivities of conifers [7] typically range from 1–4 kg s −1 m −1 MPa −1 , which compares very well with the conductivities measured in our experiments. Lower conductivities can easily result from introduction of bubbles [11] or the presence of some non-conducting heartwood. We can therefore conclude that the flow rate measurements in our devices are consistent with those expected from prior literature on conductivity of conifer xylem.

Filtration of Pigment Dye

After construction of the filter, we tested its ability to filter a pigment dye with a broad particle size distribution. The red color of the feed solution disappeared upon filtration ( Figure 3a ) indicating that the xylem filter could effectively filter out the dye.

a) Feed solution of a pigment dye before filtration (left), compared to the filtrate (right). b) Size distribution of the pigment particles in the feed and filtrate solutions measured by dynamic light scattering. c) Dependence of the rejection on the particle size estimated from the data in (b). d) Cross-section of the xylem filter after filtration. Scale is in centimeters and inches.

https://doi.org/10.1371/journal.pone.0089934.g003

Since the dye had a broad pigment size distribution, we investigated the size-dependence of filtration by quantifying the pigment size distribution before and after filtration using dynamic light scattering. We found that the feed solution comprised particles ranging in size from ∼70 nm to ∼500 nm, with some larger aggregates ( Figure 3b ). In contrast, the filtrate particle size distribution peaked at ∼80 nm, indicating that larger particles were filtered out. In a separate experiment, we observed that 20 nm fluorescent polystyrene nanoparticles could not be filtered by the xylem filter, confirming this size dependence of filtration. Assuming that pigment particles 70 nm or less in size were not rejected, the size distributions before and after filtration enable calculation of the rejection performance of the xylem filter as a function of particle size ( Figure 3c ). We find that the xylem filter exhibits excellent rejection for particles with diameters exceeding 100 nm, with the estimated rejection exceeding 99% for particles over 150 nm. Smaller particles are expected to pass through the larger porosity of the pit membrane: SEM images in Figure 1e indicate sub-micron spacing between the radial spoke-like margo membrane through which the pigment particles can pass, although the porosity is difficult to resolve in the SEM image.

After filtration, we cut the xylem filter parallel to the direction of flow to investigate the distribution of dye in the filter. We observed that the dye was confined to the top 2–3 millimeters of the xylem filter ( Figure 3d ), which compares well with the tracheid lengths on the millimeter scale expected for coniferous trees [7] . These results show that the majority of the filtration occurred within this length scale, and suggests that the thickness of the xylem filter may be reduced to below 1 cm while still rejecting the majority of the dye.

Filtration of Bacteria from Water

Finally, we investigated the ability of the xylem filter to remove bacteria from water. As a model bacterium, we used fluorescently labeled and inactivated Escherichia coli bacteria that are cylindrical in shape with a diameter of ∼1 µm. Use of fluorescently labeled bacteria enabled easy enumeration of their concentrations, and also allowed us to track the location in the xylem filter where they were trapped. Since filtration is dominated by size-exclusion at this length scale, we do not expect modification with the dye to significantly affect filtration characteristics. Filtration using three different xylem filters showed nearly complete rejection of the bacteria ( Figure 4a ). Using a hemacytometer to count the bacteria, we estimate that the rejection was at least 99.9%.

a) Concentrations of bacteria in the feed and filtrate solutions. Inset shows fluorescence images of the two solutions. Scale bar is 200 µm. Error bars indicate ±S.D. for experiments performed on three different xylem filters. b) Fluorescence image of xylem filter cross-section showing accumulation of bacteria over the margo pit membranes. Scale bar is 20 µm. c) Low-magnification fluorescence image shows that bacteria are trapped at the bottoms of tracheids within the first few millimeters of the top surface. Scale bar is 400 µm. Arrow indicates top surface of the xylem filter and also the direction of flow during filtration. Autofluorescence of the xylem tissue also contributes to the fluorescence signal in (b) and (c). d), e) SEM images showing bacteria accumulated on the margo pit membranes after filtration. Scale bars are 10 µm and 2 µm, respectively.

https://doi.org/10.1371/journal.pone.0089934.g004

To investigate the mechanism of filtration, the xylem filter was cut parallel to the direction of flow after filtration. When examined under a fluorescence microscope, we observed that the bacteria accumulated over the donut-shaped margo pit membranes ( Figure 4b ). This distribution is consistent with the expectation that the bacteria are filtered by the porous margo of the pit membranes. The distribution of trapped bacteria was not uniform across the cross section of the filter. Similar to the case of the dye, bacteria were observed only within the first few millimeters from the end through which the solution was infused (indicated by the white arrow in Figure 4c ). In addition, the low-magnification fluorescence image shows that the bacteria had accumulated primarily over pit membranes at the bottom of the tracheids, which is again not unexpected. Further investigation by SEM clearly showed individual bacterial cells accumulated on the pit membranes over the porous margo ( Figure 4d,e ). These results confirm the pit membranes as the functional units that provide the filtration effect in the xylem filter.

Wood has been investigated recently as a potential filtration material [13] , showing moderate improvement of turbidity. While we showed filtration using freshly cut xylem, we found that the flow rate dropped irreversibly by over a factor of 100 if the xylem was dried, even when the xylem was flushed with water before drying. We also examined flow through commercially available kiln-dried wood samples cut to similar dimensions. Wood samples that exhibited filtration showed two orders of magnitude smaller flow rates than in the fresh xylem filter, while those that had high flow rates did not exhibit much filtration effect and seemed to have ruptured tracheids and membranes when observed under SEM. Wetting with ethanol or vacuuming to remove air did not significantly increase the flow rate in the wood samples that exhibited the filtration effect, suggesting that the pit membranes may have a tendency to become clogged during drying. These results are consistent with literature showing that the pit membranes can become irreversibly aspirated against the cell wall, blocking the flow [14] . In fact, the pit membranes in the SEM images ( Figure 1d,e and Figure 4d,e ), which were acquired after drying the samples, appear to be stuck to the walls. Regardless, our results demonstrate that excellent rejection (>99.9%) of bacteria is possible using the pit membranes of fresh plant xylem, and also provide insight into the mechanism of filtration as well as guidelines for selection of the xylem material.

Peter-Varbanets et al. [2] have outlined the key requirements for point-of-use devices for water disinfection: a) performance (ability to effectively remove pathogens), b) ease of use (no time-consuming maintenance or operation steps), c) sustainability (produced locally with limited use of chemicals and non-renewable energy), and d) social acceptability. Meeting all of these requirements has proved to be challenging, but point-of-use methods that have been successfully used for low-cost water treatment in developing countries include free-chlorine/solar disinfections, combined coagulant-chlorine disinfection, and biosand/ceramic filtrations [5] . While chlorine is a very effective biocide, its reaction with organic matter can produce carcinogenic by-products [15] and some waterborne pathogens such as Cryptosporidium parvum and Mycobacterium avium are resistant to the chlorine [16] . Solar disinfection based on ultraviolet irradiation can effectively inactivate C. parvum , but this requires low turbidity of source water [17] and is not effective for control of viruses [16] . Filtration based on biosand and ceramic filters is also effective at removing pathogens, but the effectiveness against viruses is low or unknown [18] . Coagulation combined with chlorine disinfection removes or inactivates viruses and pathogens effectively. However, necessity of an additional filtration step and relatively high cost are potential barriers for practical use [18] . Among these methods, a review on field studies by Sobsey et al. [5] suggested that biosand and ceramic filtration are the most effective methods in practice, because once the apparatus is installed, the effort for use and dosage is significantly reduced and therefore promotes persistent use compared to disinfection approaches. Although membrane-based filtration is the most widely used for water treatment in industrialized nations and the cost of membranes has significantly decreased, membranes are still unaffordable to poor communities in the developing world [2] . Ultrafiltration systems run by hydrostatic pressure [19] and some recently invented point-of-use devices using ultrafiltration membranes may provide water to developing regions at reasonable cost [2] . However, membranes still require specialized chemicals and processes for manufacture, and need cleaning or replacement.

Xylem filter technology could be an attractive option for low-cost and highly efficient point-of-use water treatment by filtration, overcoming some of the challenges associated with conventional membranes. Xylem filters could provide the advantage of reduced human effort compared to existing point-of-use water treatment options, requiring only simple periodic filter replacement. In addition, the pressures of 1–5 psi used here are easily achievable using a gravitational pressure head of 0.7–3.5 m, implying that no pumps are necessary for filtration. The measured flow rates of about 0.05 mL/s using only ∼1 cm 2 filter area correspond to a flow rate of over 4 L/d, sufficient to meet the drinking water requirements of one person [20] . This is comparable to chlorination and biosand filtration, which have the highest production rates of prevalent point-of-use water treatment methods, and far exceeds typical production rates for solar disinfection. Xylem filters could potentially be produced locally and inexpensively, and disposed of easily owing to their biodegradability. The high flow rates and low cost would certainly help address the issues of maintenance and replacement. For example, 200 filters of 10 cm 2 area and 0.5 cm thickness could be packaged into a volume of about 1 L, which will be inexpensive and last a few years even with weekly replacement. Furthermore, as suggested by the dye filtration experiment, xylem filters should be able to significantly reduce water turbidity, enhancing the aesthetic qualities of the drinking water, which is hardly achieved by chlorination and solar disinfection.

Wood is an easily available material. While use of fresh xylem does not preclude its use as a filter material, dried membranes have definite practical advantages. Therefore, the process of wood drying and its influence on xylem conductivity needs further study. In particular, processes that yield intact yet permeable xylem tissues that can be stored long-term will be helpful for improving the supply chain if these filters are to be widely adopted. In addition, flow through xylem of different plants needs to be studied to identify locally available sources of xylem, which will truly enable construction of filters from locally available materials. In the present study, we report results using xylem derived from only one species. These xylem filters could not filter out 20 nm nanoparticles, which is a size comparable to that of the smallest viruses. It will be interesting to explore whether there exist any coniferous species that have pit membranes with smaller pore sizes that can filter out viruses, or whether conifer xylem can be impregnated with particles such as carbon black to improve rejection of viruses. In their absence, angiosperms with short vessels that yield practical filter lengths may be the best alternative due to their smaller pit membrane pore sizes [8] . Further exploration of xylem tissues from different plants with an engineering perspective is needed to construct xylem filters that can effectively reject viruses, exhibit improved flow rates, or that are amenable to easy storage. It is also conceivable that plants could be selected or developed for enhanced filtration characteristics, as has been the norm in agriculture for enhancement of many desirable characteristics including resistance to pests, flavor, or productivity.

Conclusions

Plant xylem is a porous material with membranes comprising nanoscale pores. We have reasoned that xylem from the sapwood of coniferous trees is suitable for disinfection by filtration of water. The hierarchical arrangement of the membranes in the xylem tissue effectively amplifies the available membrane area for filtration, providing high flow rates. Xylem filters were prepared by simply removing the bark of pine tree branches and inserting the xylem tissue into a tube. Pigment filtration experiments revealed a size cutoff of about 100 nm, with most of the filtration occurring within the first 2–3 mm of the xylem filter. The xylem filter could effectively filter out bacteria from water with rejection exceeding 99.9%. Pit membranes were identified as the functional unit where actual filtration of the bacteria occurred. Flow rates of about 4 L/d were obtained through ∼1 cm 2 filter areas at applied pressures of about 5 psi, which is sufficient to meet the drinking water needs of one person. The simple construction of xylem filters, combined with their fabrication from an inexpensive, biodegradable, and disposable material suggests that further research and development of xylem filters could potentially lead to their widespread use and greatly reduce the incidence of waterborne infectious disease in the world.

Acknowledgments

The authors thank Yukiko Oka for assistance with preparation of illustrations and Sunandini Chopra for help with dynamic light scattering measurements.

Author Contributions

Conceived and designed the experiments: MSHB JL VV VC RK. Performed the experiments: MSHB JL VV VC. Analyzed the data: MSHB JL RK. Contributed reagents/materials/analysis tools: VC. Wrote the paper: MSHB JL RK.

• View Article
• Google Scholar
• 3. World Health Organization. Available: http://www.who.int/water_sanitation_health/mdg1/en/ . Accessed 2014 Jan 14.
• 13. Sens ML, Emmendoerfer ML, Muller LC (2013) Water filtration through wood with helical cross-flow. Desalination and Water Treatment.
• 14. Petty JA (1972) Aspiration of bordered pits in conifer wood. Proceedings of the Royal Society Series B-Biological Sciences 181: 395-+.
• 18. Lantagne DS, Quick R, Mintz ED (2006) Household water treatment and safe storage options in developing countries: A review of current implementation practices. Woodrow Wilson International Center for Scholars. Environmental Change and Security Program.
• 20. Reed B, Reed B (2011) How much water is needed in emergencies. World Health Organization. Available: http://www.who.int/water_sanitation_health/publications/2011/tn9_how_much_water_en.pdf . Accessed 2014 Jan 14.

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• Published: 06 July 2020

Public health benefits of water purification using recycled hemodialyzers in developing countries

• Jochen G. Raimann   ORCID: orcid.org/0000-0002-8954-2783 1 , 2 , 3 , 4 ,
• Joseph Marfo Boaheng 4 , 5 ,
• Philipp Narh 4 , 6 ,
• Harrison Matti 4 ,
• Seth Johnson 1 , 4 ,
• Linda Donald 1 , 4 ,
• Hongbin Zhang 7 , 8 ,
• Friedrich Port 1 , 9 &
• Nathan W. Levin 1 , 4  

Scientific Reports volume  10 , Article number:  11101 ( 2020 ) Cite this article

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In rural regions with limited resources, the provision of clean water remains challenging. The resulting high incidence of diarrhea can lead to acute kidney injury and death, particularly in the young and the old. Membrane filtration using recycled hemodialyzers allows water purification. This study quantifies the public health effects. Between 02/2018 and 12/2018, 4 villages in rural Ghana were provided with a high-volume membrane filtration device (NuFiltration). Household surveys were collected monthly with approval from Ghana Health Services. Incidence rates of diarrhea for 5-month periods before and after implementation of the device were collected and compared to corresponding rates in 4 neighboring villages not yet equipped. Data of 1,130 villagers over 10 months from the studied communities were studied. Incidence rates showed a decline following the implementation of the device from 0.18 to 0.05 cases per person-month (ppm) compared to the control villages (0.11 to 0.08 ppm). The rate ratio of 0.27 for the study villages is revised to 0.38 when considering the non-significant rate reduction in the control villages. Provision of a repurposed hemodialyzer membrane filtration device markedly improves health outcomes as measured by diarrhea incidence within rural communities.

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Introduction.

Estimates from the World Health Organization and the World Bank place around 1.1 billion people in the world in a position of having to drink unsafe water. Water and sanitation, specifically access to clean water for the world population, were adopted as the Sustainable Development Goal-6 (SDG-6) by all member states of the United Nations. The deserved, widespread attention emphasizes the importance of the issue and the need for more improvement. Industrialized countries have to a large extent solved the problem and a majority of their populations has access to safe drinking water. This is mainly due to the effort of governments, strict laws, regular monitoring, efficient handling and cleaning of sewage, centralized and monitored provision of clean drinking water and lastly to a generally higher level of hygiene (including the use and provision of sanitary facilities). Due to high population growth rates, lack of economic development, and inadequate political efforts this remains a major problem in many countries with limited resources.

Rural areas in developing countries present problems of greatest magnitude. Water is still mainly carried from continually contaminated surface water such as ponds and rivers. Water is often polluted by coliform bacteria and viral pathogens. Factors such as a lack of sanitary facilities, inadequate hygiene practices and substantial flooding during rainy seasons aggravate the problem. Not only surface but also centralized, processed water are at high probability of being contaminated 1 . Wells may also be susceptible to pollution particularly when they are shallow or intermittently overcome by raising water tables. Further, in some low-income countries a flourishing business of sachet water exists, which is assumed to be safe for consumption. However, as shown in work from Nigeria these sachets are also in many cases contaminated due to improper packaging and storage, or inadequate hygiene in the processing. The incidence of diarrhea and its life threatening complications such as dehydration and acute kidney injury correlate with these factors 2 . Non-infectious contaminants in drinking water such as lead and other heavy metals, arsenic, and also organophosphates from pesticides and insecticides contribute to health hazards, problems that are not addressed with our work at present.

Since the first epidemiological studies by the physician John Snow in the nineteenth century, the deleterious effect of microbial pathogens in water has been well established. Estimates of the World Health Organization suggest that 88% of all diarrheal diseases are caused by the consumption of unsafe drinking water and the lack of adequate sanitation facilities 3 . A recent publication of the initiative has identified that a majority of cases of acute kidney injury in the developing world are (in contrast to the most frequently reported pathogenesis in first world countries) are associated with community-acquired disease and to a major part with diarrhea 4 . This is particularly evident in children 2 to 5 years of age in whom mortality is very high 5 . Overall, these data strongly corroborate why it must be a prime goal for the world community to jointly aim to achieve the SDG-6. These data provide a powerful stimulus for widespread joint action by the world community to achieve this goal.

Common approaches to counteract microbial pollution include various filtration devices: Microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Membrane filtration has long been recognized as an effective and likely efficient approach to partly solve the problem in rural regions, however membranes and filtration devices are expensive, and filters are prone to clogging without proper functioning flushing methodologies. The great need that is also building the basis of the SDG-6 of the United Nations, will require an affordable solution to be made available that is not overly prone to malfunction, can sustain functionality over a long period of time and does not require too extensive maintenance in terms of parts and labor. Surface water is often polluted with parasites, bacteria and viruses that can cause serious health issues 6 . Of note, all these pathogens are larger than the pore size of the hemodialyzer that is approximately 0.003 µm. This pore size notably is smaller than most commercially available purification devices, the operation of which has been claimed to be a feasible technique for water purification 2 .

Hemodialysis is a renal replacement therapy modality that uses hemodialyzers in those suffering from renal failure to counteract the consequences of not having kidney function and to ultimately save them from dying. These hemodialyzers are mainly comprised hollow fibers in a plastic casing. This allows, after cannulation of the patient, to pass the patient’s blood inside the fibers, and along the semipermeable membrane of the fiber, until it leaves the hemodialyzer and is returned to the patient. At the same time, dialysis water, containing anions and cations in specifically defined concentrations, passes, in a countercurrent fashion, on the other side of the membrane resulting in gradient-driven diffusion allowing for toxin removal from the blood and by producing a hydrostatic pressure also removes excess water from the patient through volumetric ultrafiltration. These hemodialyzers were commonly being reused after sterilization, a practice that has changed since earlier days of dialysis and current clinical practice commonly uses hemodialyzers only once and discards them after use. Of note, this alone results in approximately 30 kg of annual waste for every (out of approximately 2 million worldwide) dialysis patient 7 . It was shown recently that used and re-sterilized hemodialyzers (a process possible at less than $2 per hemodialyzer) are effective in producing clean water from microbiologically contaminated water when pushed through these hemodialyzers under high hydrostatic pressure.

We, Easy Water for Everyone (EWfE), report here the experience and some preliminary data from the use of this relatively simple technique for preparation of drinking water from polluted river water in rural villages in Ghana that have no electricity. We provided villages with devices containing re-sterilized hemodialyzers uniquely repurposed from their hemodialysis past, which are capable of producing large volumes of water (up to 500 L/h) free of bacteria and viruses for domestic use. Here we report public health outcomes based on prospectively collected self-reported public health information on diarrhea incidence collected before and after implementation of this device in several villages.

Material and methods

Easy Water for Everyone (EWfE) is a 501(c)(3) non-profit, non-governmental organization (NGO) in the United States, Ghana (and with other countries in progress). With the help of local politicians and stakeholders a need for water purification in the estuary of the Volta River in Ghana was identified. For those living in this region the river is the main source for drinking water even though it is known to carry pathogens. Under the supervision of local committees and administrators, EWfE started to install and maintain a device in each of the villages. The chronological order was arbitrary and data collection was commenced on the islands around Ada Foah since 02/2018.

Water purification method

The membrane filtration device (NUF500; NUFiltration, Israel), consists of a set of 8 hollow-fiber hemodialyzers, appropriate tubings and a faucet. These hollow fiber hemodialyzers in this project have been used as hemodialyzers once, then reprocessed and sterilized according to FDA/AAMI standards before installation into the water-purification device. Each hemodialyzer contains around 12,000 capillaries providing a membrane surface area of nearly 2 square meters per hemodialyzer. The membrane pore size is 0.003 µm, notably preventing passage of bacteria, parasites and notably also of pathogenic viruses. The output of pure water can be as high as 500 L/h when actively pumped into the device or up to 250 L/h passed into the device by gravity after being pumped into an overhead tank as used in this study. The pressure by gravity is caused by a height of about 12 feet from which the polluted water enters the eight dialyzers placed in parallel (see Fig.  1 a, b).

Hemodialyzer membrane filtration device used for our project. Setting with ( a ) a manual pump (up to 500 L/h) and ( b ) gravitational force (up to 250 L/h) for driving the contaminated into the re-sterilized and repurposed hemodialyzer filters.

Contaminated river water enters the inside of the capillaries (“blood” compartment) while clean water collects outside of the capillaries (“dialysate” compartment in clinical hemodialysis). Only water (and dissolved salts) passes through the pores. Organic matter that accumulates on the inside of the capillary fibers needs to be rinsed away by intermittently reversing the pressures and filtering clean water back across the membranes (backwashing) through manual pumping. It takes less than 5 min for the backflow to change from dirty to clean appearance and then regain full efficiency for providing clean water.

Data collection

Following the approval of our research project, embedded in the non-profit endeavor, by Ghana Health Services, we initiated data collection with trained local community members to support our endeavor. Next to demographic data and water results before and after passing through the filter, we collected data monthly from the heads of households on self-reported diarrhea events in 8 villages during the months February through November 2018. This was a subset of villages served by EWfE.

In late June 2018, the hemodialyzer filtration devices became operational in 4 of these villages so that this ongoing monthly data collection started 5 months before the installation. It was concluded 5 months after the installation of the hemodialyzer filtration device. Simultaneously the same data was collected in the 4 villages without the device. For each village and each month, the count of diarrhea events and the number of persons exposed to the data collection were analyzed to estimate the monthly diarrhea incidence rates. Monthly data were summarized for each of the two groups of villages, the control group of 4 villages never exposed to the hemodialyzer water treatment and the group of 4 villages exposed to the water treatment during their second 5 months of the 10-months study period. This approach allowed comparison of the incidence rates during the first and second 5-months periods and incidence rate ratios (second/first 5 months) for the study group and the control group. Having this concomitant data allows us, in a univariate fashion, to use village populations as their own controls and consider the potential confounding effect of seasonality.

The results of water testing showed coliform bacteria at 558 CFU/100 mL in the source water (Volta River) and zero CFU in the filtrate water at the beginning of our installations in the villages of Big Ada. We studied 8 villages (4 were designated control villages and 4 were study villages) in rural Ghana. Table 1 shows the population characteristics of the study arms. Of the village populations studied in this cohort study, 11% and 8% were younger than 5 years of age and notably showed a remarkably high proportion of villagers (96% and 99%) had to resort to open defecation.

Monthly diarrhea incidence rates averaged 0.18 counts per exposure month during the baseline period of the study villages and 0.11 for the same 5 months of the control group. During the first 5 months after the installation of the hemodialyzer filtration device, the rate reduced to 0.05, yielding a rate ratio for the study group of 0.28. For the control group the second 5 months gave an average rate of 0.08, showing modest non-significant reduction from the prior 5 months period with a rate ratio of 0.73 (Table 2 ). Figure  2 a and b show the monthly data for the two periods in both village groups. The control villages of the same region and during the same calendar months allow consideration of a seasonal effect on the diarrhea incidence in the study group. Thus, using the incidence rate ratio for the second 5 months over the first 5 months gives a seasonally adjusted rate ratio of 0.38 (0.28/0.73), which translates to a diarrhea incidence rate that is reduced by 62% following initiation of the hemodialyzer filtration device in the study villages.

Monthly diarrhea incidence rates between February (Month − 5) and November (Month + 5) 2018 in ( a ) study villages, where the device was installed in late June 2018 and ( b ) control villages with no device installation during the same months.

In many countries microbiologically contaminated water is the underlying cause of gastrointestinal disease, mainly diarrhea, associated with deleterious consequences such as acute kidney injury resulting in a high mortality rate, particularly in weaned children younger than five and the elderly. Our data, collected in 4 rural communities in the Ada-East distric of Greater Accra Region in Ghana, before and after the implementation of a hemodialyzer membrane filtration device to produce clean drinking water, shows a substantially reduced risk (rate) of self-reported diarrhea by 72%. This is a major public health outcome particularly since diarrhea is well known to be associated with deleterious consequences such as acute kidney injury and death, particularly in younger children and the elderly. This finding is striking and the rigorous analytic design where each community serves as their own control allows for drawing solid conclusions. Studying and comparing our data to that of a control group which presented only with modest reduction in the incidence of diarrhea over the same time period, corroborates an effect that can be attributed to implementation of our approach. The only modest reduction of diarrhea incidence in the control villages also reduces concerns of seasonality in the incidence rates confounding our interpretation.

Discussion of our approach in comparison with other approaches

The methods used in the present study have been effective in removing pathogens from consistently polluted river or lake water sources. During the past 3 years the on-site implementation of the hemodialyzer filtration device have allowed us to demonstrate the success of providing clean and pathogen-free drinking water to villages where the source of drinking water had been consistently contaminated. This system works well even in remote areas without requiring electricity or other external power sources. No restrictions on water use need to be imposed and use of clean water can be encouraged also for handwashing with soap. When more water is needed, the filling of the main water tank can be increased from weekly to two to three times a week (or even daily). There are several key elements that contrast our approach to other methods to produce drinking water: (1) Rejection of pathogens is highly effective and includes particles as small as pathogenic viruses, given the pore size of 0.003 µm, (2) no need to add bactericidal agents such as chlorine to kill remaining pathogens in drinking water, (3) the simplicity of this design allows its use in isolated rural villages even in areas that have no electricity, (4) this system becomes almost self-sufficient after a few villagers have been trained to do the thrice daily backwashing, (5) excellent filtration rates have been observed with this setup for over one year, (6) visits by a trained technician once or twice weekly or more frequently when necessary for refilling the large water tanks using a gas-driven pump provide some monitoring of the continued function and service and (7) relatively low cost since the reprocessed hemodialyzers are inexpensive and have shown in our 3-year experience to maintain high output rates of nearly 250 L/h (by gravity feed) for over one year. Furthermore, in circumstances where larger volumes of purified water are needed, an expanded device, employing far more dialyzers could be utilized. It would also be feasible to equip the device with solar panels which would increase water production substantially but would add to the cost.

Comparison of efficacy with other approaches

Attempts to purify water from microbiological contamination have been undertaken in a multitude of studies discussing purification of water from springs, boreholes, and wells, all sources with many opportunities for contamination to occur between sources and point of use. The source water is detoxified and infectious agents are reduced or removed by methods such as chlorination, membrane filtration, flocculation and others. Direct systems include conventional filtration, for example using sand through granular media which removes parasites, bacteria and possibly some viruses. Conventional filtration also includes chemical coagulants such as potassium alum added to source water which produce clots (flocs) which are in turn filtered. These processes are not easy and require expert handling by trained individuals.

Quite commonly reported is household chlorination which is a simple technique with widespread use. It improves water quality and effectively prevent diarrheal diseases. Quantity and acceptance (because of the resultant taste of the water) are downsides of this approach 5 .

With direct filtration, water passes through a medium such as sand or diatomaceous earth, a process which removes giardia lamblia, cryptosporidia, and bacteria from the water. These methods also remove color and turbidity. Filtration bags are warm bags or cartridges containing a filament to strain the water. These bags are however not useful for anything smaller than the giardia. Ceramics may be impregnated with tiny colloidal particles and allows for eradication of most bacteria and protozoan parasites. However, also this method is not adequate for virus removal. Most of these methods however are laborious, require specialized knowledge and infrastructure, and also time.

Membranes are widely used to produce safe drinking water and are the only means available to produce water free of parasites, bacteria and all pathogenic viruses.

Membranes can be divided into groups largely defined by their characteristics in regard to pore sizes. Depending on the degree of pore size, they can also produce water free of many chemical components. In the case of biologically contaminated water some membranes can produce water free of bacteria, parasites and viruses.

Hemodialyzers that are contained in the device we have chosen to implement in village structures have a semi-permeable membrane made of polysulphone and polyethersulphone. The pore size is around 0.003 µm and will not let parasites, bacteria and viruses pass, while still providing an output as large as 500 L/h.

Decreased microbial quantity in drinking water is effective in decreasing diarrhea. Effectiveness does not solely depend on the presence of improved water supplies but will also be affected by the use of sanitization facilities and handwashing with diligent soap procedures. In concert with appropriate education, these interventions will play a powerful role in improving public health outcomes. Also important in the context of effectiveness is the amount of water that is being produced over a defined period of time. In this context it is of note that our approach, even with the use of the gravitational device where water is pumped into an overhead tank and gravitation is being used to transfer contaminated water into the filter, allows for up to 250 L/h.

Household efforts

Household efforts include: improved water storage, chlorination, solar exposure, filtration by filter media in relationship to pore size, combined flocculation and disinfection methods. A combination of efforts including improved water supply and storage, and improved sanitation results in better water supplies thus reducing the risk of developing diarrhea. Various authors provide a range of figures for reduction of diarrhea but overall it is expected that household interventions will provide a risk reduction for diarrhea incidence 8 . The WHO promotes water treatment and safe storage of household water. Affordability, acceptability, sustainability and scale ability are all important factors and these small-scale solutions do provide improvement.

A current technology comparable to our approach are the “Aqua Towers”, an approach that also uses gravitational forces to pass water through the filter. More than 1,000 of these are active in Asia Pacific and Latin America. It utilizes ultrafiltration but the manufacturer does not reveal the membrane type. Activated carbon is used to enhance the quality of the drinking water. In addition, part of the water supply is used for hand washing. The authors claim that viruses larger than 0.01 microns are removed. However, a membrane with pore sizes as large will not exclude the rotavirus (a causative pathogen of diarrhea in up to 40% in some reported populations), and hepatitis B and C viruses, unlike the hollow fiber hemodialyzer membrane as discussed above. Of note, no outcome data have been published for the communities using the “Aqua Towers”, to the best of our knowledge.

Strengths and limitations of our study

Surveys of diarrhea in households may be considered soft data, however the magnitude of a relative 72% reduction in the incidence of diarrhea per monitored population is strikingly large. It is also corroborated by many mothers reporting a sudden virtual absence of diarrhea in their children after availability of the hemodialyzer-filtered water. The marked reduction in the diarrhea incidence may be due to using sterile water instead of river water polluted with known pathogens, such as E. coli , as the main source of drinking water. Additionally, handwashing with clean water may be an important contributor to our observations. While our study cannot prove causation with certainty, the nearly stable rates in the control group suggests a causative role of the change in the water source from river water to filter-sterilized water.

Of note, we decided to not adjust for population characteristics for two reasons: the same population served as their own controls for each household and the groups of villages and secondly the incidence rates during the initial 5 months were similar for the two groups of villages.

Further considerations beyond water purification

The effectiveness of pure drinking water, sanitation and hygiene by the Campbell/Cochrane collaboration showed 66 rigorous evaluations and 71 interventions (accounting for 30,000 children in 35 countries). Point of use water quality was associated with positive outcomes and so did hand-washing with soap. The Cochrane data base of systemic reviews discussed the effect of hand washing promotion for preventing diarrhea induced nutritional deficiency 9 , retarded child development 10 and deaths in low- and middle-income countries. The list of interventions to improve water quality by eliminating or reducing pathogens with the objective of preventing diarrhea is substantial.

Our results on markedly reduced incidence of diarrhea after implementation of the hemodialyzer filtration device agree with prior studies. In Clasen’s data synthesis paper 11 on 42 studies in 21 countries showed that all interventions to improve the microbial quality of drinking water were effective in reducing diarrheal incidents even though variations in design and application of water cleansing systems limit comparability of their cited studies. Results are less consistent for the role of other common environmental interventions (such as sanitation, or instruction in hygiene) 12 .

Our study using monthly surveys of diarrhea in households may be considered soft data, however the magnitude of a relative 72% reduction in the incidence of diarrhea per monitored population is strikingly large. It is also corroborated by many mothers reporting spontaneously a sudden virtual absence of diarrhea in their children after availability of the dialyzer-filtered water. The marked reduction in the diarrhea incidence is likely due to using sterile water instead of using river water polluted with known pathogens, such as E. coli , as the main source of drinking water. It may be expected that combination of installing a membrane filtration device and combining it with WASH initiatives will have a strong amplified effect as compared to clean water provision alone. This however remains to be shown in further prospective research.

The hemodialyzer membrane filtration device used in this study was clearly associated with a substantial reduction in the incidence of self-reported diarrhea compared to the prior period and compared to a control group without the device. Use of repurposed hemodialyzers, that had already saved lives once in their initial purpose in renal replacement therapy, can again serve as an affordable means of water purification to again save lives within entire communities. Our hemodialyzer membrane filtration approach using hollow fibers with pore size as tight as 0.003 µm in the a surface-maximizing configuration used in the technology of the device described in this paper is highly effective and unique. This renders it not only eligible but potentially highly effective to allow the world population to successfully accomplish the United Nations’ Sustainable Development Goal 6.

Kuberan, A. et al. Water and sanitation hygiene knowledge, attitude, and practices among household members living in rural setting of India. J. Nat. Sci. Biol. Med. 6 , S69-74. https://doi.org/10.4103/0976-9668.166090 (2015).

Article   PubMed   PubMed Central   Google Scholar  

Peter-Varbanets, M., Zurbrugg, C., Swartz, C. & Pronk, W. Decentralized systems for potable water and the potential of membrane technology. Water Res. 43 , 245–265. https://doi.org/10.1016/j.watres.2008.10.030 (2009).

Article   CAS   PubMed   Google Scholar  

Cerda, J. et al. Epidemiology of acute kidney injury. Clin. J. Am. Soc. Nephrol. 3 , 881–886. https://doi.org/10.2215/CJN.04961107 (2008).

Article   PubMed   Google Scholar  

Mehta, R. L. et al. Recognition and management of acute kidney injury in the International Society of Nephrology 0by25 Global Snapshot: a multinational cross-sectional study. Lancet 387 , 2017–2025. https://doi.org/10.1016/S0140-6736(16)30240-9 (2016).

Collaborators, G. B. D. L. R. I. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet. Infect. Dis. 18 , 1191–1210. https://doi.org/10.1016/S1473-3099(18)30310-4 (2018).

Article   Google Scholar  

Piper, J. D. et al. Water, sanitation and hygiene (WASH) interventions: effects on child development in low- and middle-income countries. Cochrane Database Syst. Rev. https://doi.org/10.1002/14651858.CD012613 (2017).

McAllister, D. A. et al. Global, regional, and national estimates of pneumonia morbidity and mortality in children younger than 5 years between 2000 and 2015: a systematic analysis. Lancet Glob. Health 7 , e47–e57. https://doi.org/10.1016/S2214-109X(18)30408-X (2019).

Patrier, L. et al. FGF-23 removal is improved by on-line high-efficiency hemodiafiltration compared to conventional high flux hemodialysis. J. Nephrol. 26 , 342–349. https://doi.org/10.5301/jn.5000150 (2013).

Abdoli, A. & Maspi, N. Commentary: estimates of global, regional, and national morbidity, mortality, and aetiologies of diarrhoeal diseases: a systematic analysis for the global burden of disease study 2015. Front. Med. 5 , 11. https://doi.org/10.3389/fmed.2018.00011 (2018).

Collaborators, G. L. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory tract infections in 195 countries: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. Infect. Dis. 17 , 1133–1161. https://doi.org/10.1016/S1473-3099(17)30396-1 (2017).

Canaud, B., Koehler, K., Bowry, S. & Stuard, S. What is the optimal target convective volume in on-line hemodiafiltration therapy?. Contrib. Nephrol. 189 , 9–16. https://doi.org/10.1159/000450634 (2017).

Bowry, S. K. & Canaud, B. Achieving high convective volumes in on-line hemodiafiltration. Blood Purif. 35 (Suppl 1), 23–28. https://doi.org/10.1159/000346379 (2013).

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Acknowledgments

First and foremost, we would like to thank those who have made this study possible by their generous donations. We further would like to thank all those that supported our work and helped us to get to the point we currently are. Last but certainly not least we would like to thank the village committees and everybody in the studied villages (Adzakeh, Agamakope, Alewusedekope, Amekutsekope, Anazome, Azizakope, Baitlenya and Tornyikope).

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Jochen G. Raimann, Seth Johnson, Linda Donald, Friedrich Port & Nathan W. Levin

Research Division, Renal Research Institute, New York, USA

Jochen G. Raimann

Katz School at Yeshiva University, New York, USA

Easy Water for Everyone, Accra, Ghana

Jochen G. Raimann, Joseph Marfo Boaheng, Philipp Narh, Harrison Matti, Seth Johnson, Linda Donald & Nathan W. Levin

Department of Field Epidemiology and Applied Biostatistics, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

Joseph Marfo Boaheng

Ghana Health Services, Big Ada, Ghana

Philipp Narh

Department of Epidemiology and Biostatistics, CUNY Graduate School of Public Health and Health Policy, City University of New York, New York, USA

Hongbin Zhang

CUNY Institute for Implementation Science in Population Health, New York, USA

Departments of Medicine (Nephrology) and Epidemiology, University of Michigan, Ann Arbor, MI, USA

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Contributions

Conceptualization: J. R., S. J., L. D. and N. L.; Data curation: J. R., J. M. B., P. N. and F. P.; Formal analysis: J. R., J. M. B., H. Z. and F. P.; Funding acquisition: L. D. and N. L.; Investigation: J. R., J. M. B., H. Z., F. P. and N. L.; Methodology: J. R., J. M. B., H. Z., F. P. and N. L.; Project administration: P. N., L. D. and N. L.; Resources: J. R., P. N., S. J., H. Z. and N. L.; Software: J. R. and J. M. B.; Supervision: N. L.; Validation: J. R., H. Z., F. P. and N. L.; Visualization: J. R., J. M. B. and F. P.; Writing—original draft: J. R., F. P. and N. L.; Writing—review & editing, J. R., J. M. B., P. N., S. J., L. D., H. Z., F. P. and N. L.

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Jochen Raimann and Seth Johnson are employees of Renal Research Institute/Fresenius Medical Care. All other authors have no financial disclosure.

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Raimann, J.G., Boaheng, J.M., Narh, P. et al. Public health benefits of water purification using recycled hemodialyzers in developing countries. Sci Rep 10 , 11101 (2020). https://doi.org/10.1038/s41598-020-68408-1

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Water filtration research has been undertaken for a variety of reasons. Studies have been performed to develop information for filtration theories and for design of filtration plants to remove suspended matter such as clays, algae, suspended matter in general, and asbestos fibers from water. Filtration studies related to removal of microorganisms have generally been motivated by the need to learn about the removal of pathogens or indicator organisms, or both. Reducing the risk of waterborne disease has been a goal of microbiologically related filtration research for nearly 100 years. This chapter briefly reviews that research and then discusses the results of recent investigations.

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Al-Ani, M.Y., Hendricks, D.W., Logsdon, G.S., and Hibler, C.P. 1986. Removing Giardia cysts from low turbidity water by rapid rate filtration. Journal American Water Works Association 78 (5): 66–73.

CAS   Google Scholar  

Al-Ani, M.Y., McElroy, J.M., Hibler, C.P., and Hendricks. D.W. 1985. Filtration of Giardia Cysts and Other Substances: Volume 3. Rapid Rate Filtration . EPA/600/2-85/027. U.S. Environmental Protection Agency, Cincinnati, Ohio.

Google Scholar  

U.S. Army and U.S. Public Health Service. 1944. Report 834. Efficiency of Standard Army Water Purification Equipment and of Diatomite Filters in Removing Cysts of Endamoeba histolytica from Water.

Arozarena, MM . 1979. Removal of Ciardia muris Cysts by Granular Media Filtration. Unpublished Master2019s Thesis, University of Cincinnati, Cincinnati, Ohio.

Baylis, J.R., Gullans, O., and Spector, B.K. 1936. The efficiency of rapid sand filters in removing the cysts of the amoebic dysentery organisms from water. Public Health Reports 51: 1567–1575.

Article   CAS   Google Scholar  

Bellamy, W.D., Silverman, G.P., Hendricks, D.W., and Logsdon, G.S. 1985a. Removing Giardia cysts with slow sand filtration. Journal American Water Works Association 77 (2): 52–60.

Bellamy, W.D., Hendricks, D.W., and Logsdon, G.S. 1985b. Slow sand filtration: influences of selected process variables. Journal American Water Works Association 77 (12): 62–66.

Brazos, B.J., O’Connor, J.T., and Lenau, C.W. 1987. Seasonal effects on total bacterial removals in a rapid sand filtration plant, pp 795–833 in Proceedings of the 1986 Water Quality Technology Conference . American Water Works Association, Denver, Colorado.

Brown, T.S., Malina, J.F., Jr. and Moore, B.D. 1974a. Virus removal by diatomaceous earth filtration-Part 1. Journal American Water Works Association 66 (2): 98–102.

Brown, T.S., Malina, J.F., Jr., and Moore, B.D. 1974b. Virus removal by diatomaecous earth filtration-Part 2. Journal American Water Works Association 66 (12): 735–738.

Bryck, J., Walker, B., and Mills, G. 1987. Giardia removal by slow sand filtration-pilot to full scale, pp. 49–58 in Proceedings AWWA Seminar on Coagulation and Filtration: Pilot to Full Scale , American Water Works Association, Denver, Colorado.

Bucklin, K., and Amirtharajah, A. 1988. The Characteristics of Initial Effluent Quality and Its Implications for the Filter to Waste Procedure . American Water Works Association Research Report. American Water Works Association, Denver, Colorado.

Chang, S.L. and Kabler, P.W. 1958. Removal of coxsackie and bacterial viruses in water by flocculation. Part 1. American Journal of Public Health 48: 51–61.

Cleasby, J.L., Hilmoe, D.J., and Dimitracopoulos, C.J. 1984. Slow sand and direct inline filtration of a surface water. Journal American Water Works Association 76 (12): 44–55.

Cullen, T.R. and Letterman, R.D. 1985. The effect of slow sand filter maintenance on water quality. Journal American Water Works Association 77 (12): 48–55.

DeWalle, F.B., Engeset, J., and Lawrence, W. 1984. Removal of Giardia lamblia Cysts by Drinking Water Treatment Plants. EPA-600/2-84-069. U.S. Environmental Protection Agency, Cincinnati, Ohio.

Edberg, S.C., Allen, M.J., and Smith, D.B. 1988. National field evaluation of a defined substrate method for simultaneous enumeration of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube fermentation method. Applied and Environmental Microbiology 54: 1595–1601.

Fayer, R. and Ungar, B.L.P. 1986. Cryptosporidium spp. and Cryptosporidiosis. Microbiological Reviews 50: 458–483.

Fox, K.R., Miltner, R.J., Logsdon, G.S., Dicks, D.L., and Drolet, L.F 1984. Pilot plant studies of slow rate filtration. Journal American Water Works Association 76 (12): 62–68.

Guy, M.D., Mclver, J.D., and Lewis, M.J. 1977. The removal of virus by a pilot treatment plant. Water Research 11: 421–428.

Article   Google Scholar  

Hazen, A. 1913. The Filtration of Public Water Supplies, 3rd Ed . John Wiley & Sons, New York.

Heer, J.M. 1987. Turbidity Standards, Calibration, and Practice. Water World News March/ April 18–22.

Hendricks, D.W., Seelaus, T. Janonis, B., Mosher, R.R., Gertig, K.R., Williamson-Jones, G.L., Jones, F.E., Alexander, B.D., Saterdal, R., and Blair, J. 1988. Filtration of Giardia Cysts and Other Particles Under Treatment Plant Conditions . American Water Works Association Research Foundation Research Report, American Water Works Association, Denver, Colorado.

Hilmoe, D.J. and Cleasby, J.L. 1986. Comparing constant-rate and declining-rate filtration. Journal American Water Works Association 78 (12): 26–34.

Howell, D.G. 1987. The Evaluation of Montana Surface Water Treatment Plants for Their Ability to Remove Giardia . pp. 437–448. In Proceedings of the 1986 Water Quality Technology Conference , American Water Works Association, Denver, Colorado.

Huisman, L. and Wood, WE. 1974. Slow Sand Filtration . World Health Organization, Geneva, Switzerland.

Johnson, G. 1916. The typhoid toll. Journal American Water Works Association 3:249–326 and 791–868.

Jordan, H.E. 1937. Epidemic amebic dysentery-The Chicago outbreak of 1933. Journal American Water Works Association 29: 133–137.

Lance, J.C., Gerba, C.P., and Melnick, J.L. 1976. Virus movement in soil columns flooded with secondary sewage effluent. Applied and Environmental Microbiology 32: 520–526.

Lange, K.P., Bellamy, W.D., Hendricks, D.W., and Logsdon, G.S. 1986. Diatomaceous earth filtration of Giardia cysts and other substances. Journal American Water Works Association 78 (1): 76–84.

Logsdon, G.S. 1987. Evaluating treatment plants for particulate contaminant removal. Journal American Water Works Association , 79 (9): 82–92.

Logsdon, G.S. and Rice, E.W. 1985. Evaluation of sedimentation and filtration for microorganism removal, pp. 1177–1197 In: Proceedings of the 1985 American Water Works Association Annual Conference , American Water Works Association, Denver, Colorado.

Logsdon, G.S., Symons, J.M., Hoye, R.L. Jr., and Arozarena, M.M. 1981. Alternative filtration methods for removal of cysts and cyst models. Journal American Water Works Association 73: 111–118.

McConnell, L.K. 1984. Evaluation of the Slow Rate Sand Filtration Process for Treatment of Drinking Water Containing Viruses and Bacteria . Unpublished Master of Science Thesis. Utah State University, Logan, Utah.

McCormick, R.F. and King, P.H. 1982. Factors that affect the use of direct filtration in treating surface waters. Journal American Water Works Association 74: 234–242.

Mosher, R.R. and Hendricks. D.W. 1986. Rapid rate filtration of low turbidity water using field-scale pilot filters. Journal American Water Works Association . 78 (12): 42–51.

O’Connor, J.T., Brazos, B.J., Ford, W.C., Plaskett, J.L., and Dusenberg, L.L. 1985. Chemical and Microbiological Evaluations of Drinking Water Systems in Missouri: Summer Conditions, pp. 1199–1225 in: Proceedings of the 1985 American Water Works Association Annual Conference , American Water Works Association, Denver, Colorado.

Ongerth, J. 1988. A study of water treatment practices for the removal of Giardia lamblia cysts, pp. 171–175 in: Proceedings of Conference on Current Research in Drinking Water Treatment, EPA/600/9-88/004, U.S. Environmental Protection Agency, Cincinnati, Ohio.

Poynter, S.F.B. and Slade, J.S. 1977. The removal of viruses by slow sand filtration. Progress in Water Technology 9: 75–88.

Pyper, G.R. 1985. Slow Sand Filter and Package Treatment Plant Evaluation: Operating Costs and Removal of Bacteria, Giardia and Trihalomethanes . EPA-600/2-85-052, U.S. Environmental Protection Agency, Cincinnati, Ohio.

Rao, V.C., Symons, J.M., Ling, A., Wang, P., Metcalf, T.G., Hoff, J.C., and Melnick, J.L. 1988. Removal of hepatitis A virus and rotavirus by drinking water treatment. Journal American Water Worfes Association 80 (2): 59–67.

Robeck, G.G., Clarke, N.A., and Dostal, K.A. 1962. Effectiveness of water treatment processes for virus removal. Journal American Water Works Association 54: 1275–1290.

Sayre, I.M. 1984. Filtration. Journal American Water Works Association 76 (12): 33.

Seelaus, T.J., Hendricks, D.W., and Janonis, B.A. 1986. Design and operation of a slow sand filter. Journal American Water Works Association 78 (12): 35–41.

Slade, J.S. 1978. Enteroviruses in slow sand filtered water. Journal of the Institution of Water Engineers and Scientists 32: 530–536.

Slezak, LA. and Sims, R.C. 1984. The application and effectiveness of slow sand filtration in the United States. Journal American Water Works Association 76 (12): 38–43.

Spector, B.K., Baylis, J.R., and Gullams, O. 1934. Effectiveness of filtration in removing from water, and of chlorine in killing, the causative organism of amoebic dysentery. Public Health Reports 49: 786–800.

Stetler, R.E., Ward, R.L., and Waltrip, S.C. 1984. Enteric virus and indicator bacteria levels in a water treatment system modified to reduce trihalomethane production. Applied and Environmental Microbiology 47: 319–324.

Streeter, H.W. 1927. Studies of the Efficiency of Water Purification Processes. Public Health Bulletin No . 172 , U.S. Public Health Service, Government Printing Office.

Streeter, H.W. 1929. Studies of the Efficiency of Water Purification Processes. Public Health Bulletin 193 . U.S. Public Health Service, Washington, D.C.

Tanner, S.A. 1987. Evaluation of Sand Filters in Northern Idaho . Unpublished Master’s Thesis, University of Washington, Seattle, Washington.

Taylor, E.W 1969–1970. Forty-Fourth Report on the Results of the Bacteriological. Chemical and Biological Examination of the London Waters for the Years 1969–1970 . Metropolitan Water Board, London, England.

Walton, H.W. 1988. Diatomite filtration: how it removes Giardia from water, pp. 113–116 In: Wallis, P.M. and Hammond, B.R. (editors), Advances in Giardia Research , University of Calgary Press, Calgary, Alberta.

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Logsdon, G.S. (1990). Microbiology and Drinking Water Filtration. In: McFeters, G.A. (eds) Drinking Water Microbiology. Brock/Springer Series in Contemporary Bioscience. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-4464-6_6

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Recent advances in biofiltration for ppcp removal from water.

1. Introduction

2. source and occurrence of ppcps, 2.1. source of ppcps, 2.2. occurrence of ppcps, 3. mechanism of biofiltration technology, 4. efficiency of biofiltration on ppcp removal, 4.1. biological granular activated carbon filtration, 4.2. biological sand filtration, 4.2.1. slow sand filtration, 4.2.2. rapid sand filtration, 4.3. benefit and cost analysis for biofiltration, 5. influencing factors of biofiltration on ppcps, 5.1. filter media, 5.2. backwash conditions, 5.3. empty bed contact time, 5.4. other parameters, 6. summary and prospect, author contributions, data availability statement, conflicts of interest.

• Wang, J.; Chu, L. Irradiation treatment of pharmaceutical and personal care products (PPCPs) in water and wastewater: An overview. Radiat. Phys. Chem. 2016 , 125 , 56–64. [ Google Scholar ] [ CrossRef ]
• Kumar, M.; Sridharan, S.; Sawarkar, A.D.; Shakeel, A.; Anerao, P.; Mannina, G.; Sharma, P.; Pandey, A. Current research trends on emerging contaminants pharmaceutical and personal care products (PPCPs): A comprehensive review. Sci. Total Environ. 2023 , 859 , 160031. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Daughton, C.G.; Ternes, T.A. Pharmaceuticals and personal care products in the environment: Agents of subtle change? Environ. Health Perspect. 1999 , 107 (Suppl. 6), 907–938. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Heberer, T. Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: A review of recent research data. Toxicol. Lett. 2002 , 131 , 5–17. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Zhang, X.-X.; Zhang, T.; Fang, H.H. Antibiotic resistance genes in water environment. Appl. Microbiol. Biot. 2009 , 82 , 397–414. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Lai, K.; Scrimshaw, M.; Lester, J. The effects of natural and synthetic steroid estrogens in relation to their environmental occurrence. CRC Crit. Rev. Toxicol. 2002 , 32 , 113–132. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Fan, B.; Li, J.; Wang, X.; Gao, X.; Chen, J.; Ai, S.; Li, W.; Huang, Y.; Liu, Z. Study of aquatic life criteria and ecological risk assessment for triclocarban (TCC). Environ. Pollut. 2019 , 254 , 112956. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Tumová, J.; Šauer, P.; Golovko, O.; Koba Ucun, O.; Grabic, R.; Máchová, J.; Kocour Kroupová, H. Effect of polycyclic musk compounds on aquatic organisms: A critical literature review supplemented by own data. Sci. Total Environ. 2019 , 651 , 2235–2246. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Brausch, J.M.; Rand, G.M. A review of personal care products in the aquatic environment: Environmental concentrations and toxicity. Chemosphere 2011 , 82 , 1518–1532. [ Google Scholar ] [ CrossRef ]
• Li, A.J.; Law, J.C.-F.; Chow, C.-H.; Huang, Y.; Li, K.; Leung, K.S.-Y. Joint Effects of Multiple UV Filters on Zebrafish Embryo Development. Environ. Sci. Technol. 2018 , 52 , 9460–9467. [ Google Scholar ] [ CrossRef ]
• Chen, X.; Lei, L.; Liu, S.; Han, J.; Li, R.; Men, J.; Li, L.; Wei, L.; Sheng, Y.; Yang, L.; et al. Occurrence and risk assessment of pharmaceuticals and personal care products (PPCPs) against COVID-19 in lakes and WWTP-river-estuary system in Wuhan, China. Sci. Total Environ. 2021 , 792 , 148352. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Huang, C.; Jin, B.; Han, M.; Yu, Y.; Zhang, G.; Arp, H.P.H. The distribution of persistent, mobile and toxic (PMT) pharmaceuticals and personal care products monitored across Chinese water resources. J. Hazard. Mater. Lett. 2021 , 2 , 100026. [ Google Scholar ] [ CrossRef ]
• Osuoha, J.O.; Anyanwu, B.O.; Ejileugha, C. Pharmaceuticals and personal care products as emerging contaminants: Need for combined treatment strategy. J. Hazard. Mater. Adv. 2023 , 9 , 100206. [ Google Scholar ] [ CrossRef ]
• Mehinto, A.C.; Hill, E.M.; Tyler, C.R. Uptake and Biological Effects of Environmentally Relevant Concentrations of the Nonsteroidal Anti-inflammatory Pharmaceutical Diclofenac in Rainbow Trout ( Oncorhynchus mykiss ). Environ. Sci. Technol. 2010 , 44 , 2176–2182. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Hartmann, A.; Alder, A.C.; Koller, T.; Widmer, R.M. Identification of fluoroquinolone antibiotics as the main source of umuC genotoxicity in native hospital wastewater. Environ. Toxicol. Chem. 1998 , 17 , 377–382. [ Google Scholar ] [ CrossRef ]
• Simpson, D.R. Biofilm processes in biologically active carbon water purification. Water Res. 2008 , 42 , 2839–2848. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Fu, J.; Lee, W.-N.; Coleman, C.; Nowack, K.; Carter, J.; Huang, C.-H. Removal of pharmaceuticals and personal care products by two-stage biofiltration for drinking water treatment. Sci. Total Environ. 2019 , 664 , 240–248. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Basu, O.D.; Dhawan, S.; Black, K. Applications of biofiltration in drinking water treatment—A review. J. Chem. Technol. Biotechnol. 2016 , 91 , 585–595. [ Google Scholar ] [ CrossRef ]
• Fu, J.; Lee, W.-N.; Coleman, C.; Meyer, M.; Carter, J.; Nowack, K.; Huang, C.-H. Pilot investigation of two-stage biofiltration for removal of natural organic matter in drinking water treatment. Chemosphere 2017 , 166 , 311–322. [ Google Scholar ] [ CrossRef ]
• Gibert, O.; Lefèvre, B.; Fernández, M.; Bernat, X.; Paraira, M.; Calderer, M.; Martínez-Lladó, X. Characterising biofilm development on granular activated carbon used for drinking water production. Water Res. 2013 , 47 , 1101–1110. [ Google Scholar ] [ CrossRef ]
• Krishnan, R.Y.; Manikandan, S.; Subbaiya, R.; Biruntha, M.; Govarthanan, M.; Karmegam, N. Removal of emerging micropollutants originating from pharmaceuticals and personal care products (PPCPs) in water and wastewater by advanced oxidation processes: A review. Environ. Technol. Innov. 2021 , 23 , 101757. [ Google Scholar ] [ CrossRef ]
• Kümmerer, K. The presence of pharmaceuticals in the environment due to human use—Present knowledge and future challenges. J. Environ. Manag. 2009 , 90 , 2354–2366. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• WHO. Antimicrobial Resistance: Global Report on Surveillance. Australas. Med. J. 2014 , 7 , 237. [ Google Scholar ]
• Ajay; Walters, W.P.; Murcko, M.A. Can We Learn To Distinguish between “Drug-like” and “Nondrug-like” Molecules? J. Med. Chem. 1998 , 41 , 3314–3324. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Zhang, G.; Fei, B.; Xiu, G. Characteristics of Volatile Organic Compound Leaks from Equipment Components: A Study of the Pharmaceutical Industry in China. Sustainability 2021 , 13 , 6274. [ Google Scholar ] [ CrossRef ]
• Wang, L.; Xu, Y.; Qin, T.; Wu, M.; Chen, Z.; Zhang, Y.; Liu, W.; Xie, X. Global trends in the research and development of medical/pharmaceutical wastewater treatment over the half-century. Chemosphere 2023 , 331 , 138775. [ Google Scholar ] [ CrossRef ]
• Oliveira, T.S.; Murphy, M.; Mendola, N.; Wong, V.; Carlson, D.; Waring, L. Characterization of pharmaceuticals and personal care products in hospital effluent and waste water influent/effluent by direct-injection LC-MS-MS. Sci. Total Environ. 2015 , 518 , 459–478. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Kovalova, L.; Siegrist, H.; Singer, H.; Wittmer, A.; McArdell, C.S. Hospital Wastewater Treatment by Membrane Bioreactor: Performance and Efficiency for Organic Micropollutant Elimination. Environ. Sci. Technol. 2012 , 46 , 1536–1545. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Khan, N.A.; Ahmed, S.; Farooqi, I.H.; Ali, I. Innovative method used in modern time for the treatment of hospital wastewater. Int. J. Environ. Anal. Chem. 2023 , 103 , 6445–6457. [ Google Scholar ] [ CrossRef ]
• Huang, A.; Yan, M.; Lin, J.; Xu, L.; Gong, H.; Gong, H. A Review of Processes for Removing Antibiotics from Breeding Wastewater. Int. J. Environ. Res. Public Health 2021 , 18 , 4909. [ Google Scholar ] [ CrossRef ]
• Wu, Y.; Song, S.; Chen, X.; Shi, Y.; Cui, H.; Liu, Y.; Yang, S. Source-specific ecological risks and critical source identification of PPCPs in surface water: Comparing urban and rural areas. Sci. Total Environ. 2023 , 854 , 158792. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Qi, C.; Huang, J.; Wang, B.; Deng, S.; Wang, Y.; Yu, G. Contaminants of emerging concern in landfill leachate in China: A review. Emerg. Contam. 2018 , 4 , 1–10. [ Google Scholar ] [ CrossRef ]
• Daughton, C.G. Cradle-to-cradle stewardship of drugs for minimizing their environmental disposition while promoting human health. I. Rationale for and avenues toward a green pharmacy. Environ. Health Perspect. 2003 , 111 , 757–774. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Wang, J.; Zhu, Y. Occurrence and risk assessment of estrogenic compounds in the East Lake, China. Environ. Toxicol. Pharmacol. 2017 , 52 , 69–76. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Li, W.; Gao, L.; Shi, Y.; Liu, J.; Cai, Y. Occurrence, distribution and risks of antibiotics in urban surface water in Beijing, China. Environ. Sci. Process. Impacts 2015 , 17 , 1611–1619. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Xu, J.; Zhao, Y.; Xu, H.; Zhang, H.; Yu, B.; Hao, L.; Liu, Z. Selective oxidation of glycerol to formic acid catalyzed by Ru(OH) 4 /r-GO in the presence of FeCl 3 . Appl. Catal. B Environ. 2014 , 154–155 , 267–273. [ Google Scholar ] [ CrossRef ]
• Wu, C.; Huang, X.; Witter, J.D.; Spongberg, A.L.; Wang, K.; Wang, D.; Liu, J. Occurrence of pharmaceuticals and personal care products and associated environmental risks in the central and lower Yangtze river, China. Ecotoxicol. Environ. Saf. 2014 , 106 , 19–26. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Bai, Y.; Meng, W.; Xu, J.; Zhang, Y.; Guo, C. Occurrence, distribution and bioaccumulation of antibiotics in the Liao River Basin in China. Environ. Science. Process. Impacts 2014 , 16 , 586–593. [ Google Scholar ] [ CrossRef ]
• Kasprzyk-Hordern, B.; Dinsdale, R.M.; Guwy, A.J. Multi-residue method for the determination of basic/neutral pharmaceuticals and illicit drugs in surface water by solid-phase extraction and ultra performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry. J. Chromatogr. A 2007 , 1161 , 132–145. [ Google Scholar ] [ CrossRef ]
• Kasprzyk-Hordern, B.; Dinsdale, R.M.; Guwy, A.J. The occurrence of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs in surface water in South Wales, UK. Water Res. 2008 , 42 , 3498–3518. [ Google Scholar ] [ CrossRef ]
• Osorio, V.; Larrañaga, A.; Aceña, J.; Pérez, S.; Barceló, D. Concentration and risk of pharmaceuticals in freshwater systems are related to the population density and the livestock units in Iberian Rivers. Sci. Total Environ. 2016 , 540 , 267–277. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ginebreda, A.; Muñoz, I.; de Alda, M.L.; Brix, R.; López-Doval, J.; Barceló, D. Environmental risk assessment of pharmaceuticals in rivers: Relationships between hazard indexes and aquatic macroinvertebrate diversity indexes in the Llobregat River (NE Spain). Environ. Int. 2010 , 36 , 153–162. [ Google Scholar ] [ CrossRef ]
• Alexy, R.; Schöll, A.; Kümpel, T.; Kümmerer, K. What Do We Know about Antibiotics in the Environment? In Pharmaceuticals in the Environment: Sources, Fate, Effects and Risks ; Kümmerer, K., Ed.; Springer: Berlin/Heidelberg, Germany, 2004; pp. 209–221. [ Google Scholar ]
• Buser, H.-R.; Müller, M.D.; Theobald, N. Occurrence of the Pharmaceutical Drug Clofibric Acid and the Herbicide Mecoprop in Various Swiss Lakes and in the North Sea. Environ. Sci. Technol. 1998 , 32 , 188–192. [ Google Scholar ] [ CrossRef ]
• Dai, G.; Wang, B.; Huang, J.; Dong, R.; Deng, S.; Yu, G. Occurrence and source apportionment of pharmaceuticals and personal care products in the Beiyun River of Beijing, China. Chemosphere 2015 , 119 , 1033–1039. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ma, R.; Wang, B.; Lu, S.; Zhang, Y.; Yin, L.; Huang, J.; Deng, S.; Wang, Y.; Yu, G. Characterization of pharmaceutically active compounds in Dongting Lake, China: Occurrence, chiral profiling and environmental risk. Sci. Total Environ. 2016 , 557–558 , 268–275. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Yang, L.; He, J.T.; Su, S.H.; Cui, Y.F.; Huang, D.L.; Wang, G.C. Occurrence, distribution, and attenuation of pharmaceuticals and personal care products in the riverside groundwater of the Beiyun River of Beijing, China. Environ. Sci. Pollut. Res. Int. 2017 , 24 , 15838–15851. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Sun, Q.; Li, Y.; Li, M.; Ashfaq, M.; Lv, M.; Wang, H.; Hu, A.; Yu, C.P. PPCPs in Jiulong River estuary (China): Spatiotemporal distributions, fate, and their use as chemical markers of wastewater. Chemosphere 2016 , 150 , 596–604. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Huerta-Fontela, M.; Galceran, M.T.; Ventura, F. Stimulatory drugs of abuse in surface waters and their removal in a conventional drinking water treatment plant. Environ. Sci. Technol. 2008 , 42 , 6809–6816. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ma, L.; Liu, Y.; Yang, Q.; Jiang, L.; Li, G. Occurrence and distribution of Pharmaceuticals and Personal Care Products (PPCPs) in wastewater related riverbank groundwater. Sci. Total Environ. 2022 , 821 , 153372. [ Google Scholar ] [ CrossRef ]
• Peng, X.; Ou, W.; Wang, C.; Wang, Z.; Huang, Q.; Jin, J.; Tan, J. Occurrence and ecological potential of pharmaceuticals and personal care products in groundwater and reservoirs in the vicinity of municipal landfills in China. Sci. Total Environ. 2014 , 490 , 889–898. [ Google Scholar ] [ CrossRef ]
• Wang, N.; Kang, G.; Hu, G.; Chen, J.; Qi, D.; Bi, F.; Chang, N.; Gao, Z.; Zhang, S.; Shen, W. Spatiotemporal distribution and ecological risk assessment of pharmaceuticals and personal care products (PPCPs) from Luoma Lake, an important node of the South-to-North Water Diversion Project. Environ. Monit. Assess. 2023 , 195 , 1330. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Cui, Y.; Wang, Y.; Pan, C.; Li, R.; Xue, R.; Guo, J.; Zhang, R. Spatiotemporal distributions, source apportionment and potential risks of 15 pharmaceuticals and personal care products (PPCPs) in Qinzhou Bay, South China. Mar. Pollut. Bull. 2019 , 141 , 104–111. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Chen, S.; Ling, J.; Blancheton, J.-P. Nitrification kinetics of biofilm as affected by water quality factors. Aquac. Eng. 2006 , 34 , 179–197. [ Google Scholar ] [ CrossRef ]
• Fried, J.; Mayr, G.; Berger, H.; Traunspurger, W.; Psenner, R.; Lemmer, H. Monitoring protozoa and metazoa biofilm communities for assessing wastewater quality impact and reactor up-scaling effects. Water Sci. Technol. 2000 , 41 , 309–316. [ Google Scholar ] [ CrossRef ]
• Srivastava, N.K.; Majumder, C.B. Novel biofiltration methods for the treatment of heavy metals from industrial wastewater. J. Hazard. Mater. 2008 , 151 , 1–8. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Rittmann, B.E.; Stilwell, D.; Ohashi, A. The transient-state, multiple-species biofilm model for biofiltration processes. Water Res. 2002 , 36 , 2342–2356. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Wang, L.K.; Wang, M.-H.S.; Shammas, N.K. Biological Processes for Water Resource Protection and Water Recovery. In Environmental and Natural Resources Engineering ; Wang, L.K., Wang, M.-H.S., Hung, Y.-T., Shammas, N.K., Eds.; Springer International Publishing: Cham, Switzerland, 2021; pp. 73–168. [ Google Scholar ]
• Liu, C.; Olivares, C.I.; Pinto, A.J.; Lauderdale, C.V.; Brown, J.; Selbes, M.; Karanfil, T. The control of disinfection byproducts and their precursors in biologically active filtration processes. Water Res. 2017 , 124 , 630–653. [ Google Scholar ] [ CrossRef ]
• Bai, X.; Dinkla, I.J.T.; Muyzer, G. Microbial ecology of biofiltration used for producing safe drinking water. Appl. Microbiol. Biot. 2022 , 106 , 4813–4829. [ Google Scholar ] [ CrossRef ]
• Fu, J.; Lee, W.-N.; Coleman, C.; Nowack, K.; Carter, J.; Huang, C.-H. Removal of disinfection byproduct (DBP) precursors in water by two-stage biofiltration treatment. Water Res. 2017 , 123 , 224–235. [ Google Scholar ] [ CrossRef ]
• Edition, F. Guidelines for drinking-water quality. WHO Chron. 2011 , 38 , 104–108. [ Google Scholar ]
• Li, J.; Campos, L.C.; Zhang, L.; Xie, W. Sand and sand-GAC filtration technologies in removing PPCPs: A review. Sci. Total Environ. 2022 , 848 , 157680. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Radovic, L.R. Chemistry & Physics of Carbon ; CRC Press: Boca Raton, FL, USA, 2004; Volume 29. [ Google Scholar ]
• Órfão, J.; Silva, A.; Pereira, J.; Barata, S.; Fonseca, I.; Faria, P.; Pereira, M. Adsorption of a reactive dye on chemically modified activated carbons—Influence of pH. J. Colloid Interface Sci. 2006 , 296 , 480–489. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Villacañas, F.; Pereira, M.F.R.; Órfão, J.J.; Figueiredo, J.L. Adsorption of simple aromatic compounds on activated carbons. J. Colloid Interface Sci. 2006 , 293 , 128–136. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Westerhoff, P.; Yoon, Y.; Snyder, S.; Wert, E. Fate of Endocrine-Disruptor, Pharmaceutical, and Personal Care Product Chemicals during Simulated Drinking Water Treatment Processes. Environ. Sci. Technol. 2005 , 39 , 6649–6663. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Wang, J.; Wang, S. Removal of pharmaceuticals and personal care products (PPCPs) from wastewater: A review. J. Environ. Manag. 2016 , 182 , 620–640. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Kim, S.D.; Cho, J.; Kim, I.S.; Vanderford, B.J.; Snyder, S.A. Occurrence and removal of pharmaceuticals and endocrine disruptors in South Korean surface, drinking, and waste waters. Water Res. 2007 , 41 , 1013–1021. [ Google Scholar ] [ CrossRef ]
• Grover, D.P.; Zhou, J.L.; Frickers, P.E.; Readman, J.W. Improved removal of estrogenic and pharmaceutical compounds in sewage effluent by full scale granular activated carbon: Impact on receiving river water. J. Hazard. Mater. 2011 , 185 , 1005–1011. [ Google Scholar ] [ CrossRef ]
• Newcombe, G.; Drikas, M. Adsorption of NOM onto activated carbon: Electrostatic and non-electrostatic effects. Carbon 1997 , 35 , 1239–1250. [ Google Scholar ] [ CrossRef ]
• Kilduff, J.E.; Karanfil, T.; Weber, W.J. Competitive effects of nondisplaceable organic compounds on trichloroethylene uptake by activated carbon. II. Model verification and applicability to natural organic matter. J. Colloid Interface Sci. 1998 , 205 , 280–289. [ Google Scholar ] [ CrossRef ]
• Pelekani, C.; Snoeyink, V. Competitive adsorption in natural water: Role of activated carbon pore size. Water Res. 1999 , 33 , 1209–1219. [ Google Scholar ] [ CrossRef ]
• De Ridder, D.; Verliefde, A.; Heijman, S.; Verberk, J.; Rietveld, L.; Van Der Aa, L.; Amy, G.; Van Dijk, J. Influence of natural organic matter on equilibrium adsorption of neutral and charged pharmaceuticals onto activated carbon. Water Sci. Technol. 2011 , 63 , 416–423. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Oh, H.; Urase, T.; Simazaki, D.; Kim, H. Effect of natural organic matter on adsorption of ionic and non-ionic pharmaceuticals to granular activated carbon. Environ. Prot. Eng. 2013 , 39 , 15–28. [ Google Scholar ]
• Yu, Z.; Peldszus, S.; Huck, P.M. Adsorption of selected pharmaceuticals and an endocrine disrupting compound by granular activated carbon. 1. Adsorption capacity and kinetics. Environ. Sci. Technol. 2009 , 43 , 1467–1473. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Newcombe, G. Activated carbon and soluble humic substances: Adsorption, desorption, and surface charge effects. J. Colloid Interface Sci. 1994 , 164 , 452–462. [ Google Scholar ] [ CrossRef ]
• Cyr, P.J.; Suri, R.P.; Helmig, E.D. A pilot scale evaluation of removal of mercury from pharmaceutical wastewater using granular activated carbon. Water Res. 2002 , 36 , 4725–4734. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ek, M.; Baresel, C.; Magnér, J.; Bergström, R.; Harding, M. Activated carbon for the removal of pharmaceutical residues from treated wastewater. Water Sci. Technol. 2014 , 69 , 2372–2380. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Snyder, S.A.; Adham, S.; Redding, A.M.; Cannon, F.S.; DeCarolis, J.; Oppenheimer, J.; Wert, E.C.; Yoon, Y. Role of membranes and activated carbon in the removal of endocrine disruptors and pharmaceuticals. Desalination 2007 , 202 , 156–181. [ Google Scholar ] [ CrossRef ]
• Matsui, Y.; Knappe, D.R.; Takagi, R. Pesticide adsorption by granular activated carbon adsorbers. 1. Effect of natural organic matter preloading on removal rates and model simplification. Environ. Sci. Technol. 2002 , 36 , 3426–3431. [ Google Scholar ] [ CrossRef ]
• Wang, Q.; Tang, X.; Zeng, W.; Wang, F.; Gong, W.; Chen, J.; Wang, J.; Li, G.; Liang, H. Pilot-Scale Biological Activated Carbon Filtration–Ultrafiltration System for Removing Pharmaceutical and Personal Care Products from River Water. Water 2022 , 14 , 367. [ Google Scholar ] [ CrossRef ]
• Lu, Z.; Sun, W.; Li, C.; Ao, X.; Yang, C.; Li, S. Bioremoval of non-steroidal anti-inflammatory drugs by Pseudoxanthomonas sp. DIN-3 isolated from biological activated carbon process. Water Res. 2019 , 161 , 459–472. [ Google Scholar ] [ CrossRef ]
• Liu, H.-L.; Li, X.; Li, N. Application of bio-slow sand filters for drinking water production: Linking purification performance to bacterial community and metabolic functions. J. Water Process Eng. 2023 , 53 , 103622. [ Google Scholar ] [ CrossRef ]
• Almeida-Naranjo, C.E.; Guerrero, V.H.; Villamar-Ayala, C.A. Emerging Contaminants and Their Removal from Aqueous Media Using Conventional/Non-Conventional Adsorbents: A Glance at the Relationship between Materials, Processes, and Technologies. Water 2023 , 15 , 1626. [ Google Scholar ] [ CrossRef ]
• Paredes, L.; Fernandez-Fontaina, E.; Lema, J.M.; Omil, F.; Carballa, M. Understanding the fate of organic micropollutants in sand and granular activated carbon biofiltration systems. Sci. Total Environ. 2016 , 551–552 , 640–648. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Welz, P.J.; Ramond, J.B.; Cowan, D.A.; Burton, S.G. Phenolic removal processes in biological sand filters, sand columns and microcosms. Bioresour. Technol. 2012 , 119 , 262–269. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Ho, L.; Hoefel, D.; Saint, C.P.; Newcombe, G. Isolation and identification of a novel microcystin-degrading bacterium from a biological sand filter. Water Res. 2007 , 41 , 4685–4695. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Yan, Y.E. Research on the Assessment Method of Zouping County Rural Drinking Water Safety. Master’s Thesis, University of Twente, Enschede, The Netherlands, 2018. [ Google Scholar ]
• Pompei, C.M.E.; Ciric, L.; Canales, M.; Karu, K.; Vieira, E.M.; Campos, L.C. Influence of PPCPs on the performance of intermittently operated slow sand filters for household water purification. Sci. Total Environ. 2017 , 581–582 , 174–185. [ Google Scholar ] [ CrossRef ]
• Zearley, T.L.; Summers, R.S. Removal of Trace Organic Micropollutants by Drinking Water Biological Filters. Environ. Sci. Technol. 2012 , 46 , 9412–9419. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Escolà Casas, M.; Bester, K. Can those organic micro-pollutants that are recalcitrant in activated sludge treatment be removed from wastewater by biofilm reactors (slow sand filters)? Sci. Total Environ. 2015 , 506–507 , 315–322. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• van Gijn, K.; Chen, Y.L.; van Oudheusden, B.; Gong, S.; de Wilt, H.A.; Rijnaarts, H.H.M.; Langenhoff, A.A.M. Optimizing biological effluent organic matter removal for subsequent micropollutant removal. J. Environ. Chem. Eng. 2021 , 9 , 106247. [ Google Scholar ] [ CrossRef ]
• D’Alessio, M.; Yoneyama, B.; Kirs, M.; Kisand, V.; Ray, C. Pharmaceutically active compounds: Their removal during slow sand filtration and their impact on slow sand filtration bacterial removal. Sci. Total Environ. 2015 , 524–525 , 124–135. [ Google Scholar ] [ CrossRef ]
• Nakada, N.; Shinohara, H.; Murata, A.; Kiri, K.; Managaki, S.; Sato, N.; Takada, H. Removal of selected pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting chemicals (EDCs) during sand filtration and ozonation at a municipal sewage treatment plant. Water Res. 2007 , 41 , 4373–4382. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Xu, L.; Campos, L.C.; Li, J.; Karu, K.; Ciric, L. Removal of antibiotics in sand, GAC, GAC sandwich and anthracite/sand biofiltration systems. Chemosphere 2021 , 275 , 130004. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Yapsakli, K.; Mertoglu, B.; Çeçen, F. Identification of nitrifiers and nitrification performance in drinking water biological activated carbon (BAC) filtration. Process Biochem. 2010 , 45 , 1543–1549. [ Google Scholar ] [ CrossRef ]
• Yapsakli, K.; Çeçen, F. Effect of type of granular activated carbon on DOC biodegradation in biological activated carbon filters. Process Biochem. 2010 , 45 , 355–362. [ Google Scholar ] [ CrossRef ]
• Liu, X.; Huck, P.M.; Slawson, R.M. Factors Affecting Drinking Water Biofiltration. J. AWWA 2001 , 93 , 90–101. [ Google Scholar ] [ CrossRef ]
• Seredyńska-Sobecka, B.; Tomaszewska, M.; Morawski, A.W. Removal of humic acids by the ozonation–biofiltration process. Desalination 2006 , 198 , 265–273. [ Google Scholar ] [ CrossRef ]
• Lin, T.; Yu, S.; Chen, W. Occurrence, removal and risk assessment of pharmaceutical and personal care products (PPCPs) in an advanced drinking water treatment plant (ADWTP) around Taihu Lake in China. Chemosphere 2016 , 152 , 1–9. [ Google Scholar ] [ CrossRef ] [ PubMed ]
• Velten, S.; Boller, M.; Köster, O.; Helbing, J.; Weilenmann, H.-U.; Hammes, F. Development of biomass in a drinking water granular active carbon (GAC) filter. Water Res. 2011 , 45 , 6347–6354. [ Google Scholar ] [ CrossRef ]
• Bai, L.; Liu, X.; Wu, Y.; Wang, C.; Wang, C.; Chen, W.; Jiang, H. Varying removal of emerging organic contaminants in drinking water treatment residue-based biofilter systems: Influence of hydraulic loading rates on microbiology. Chem. Eng. J. 2024 , 491 , 152169. [ Google Scholar ] [ CrossRef ]
• Kajitvichyanukul, P.; Shammas, N.K.; Hung, Y.-T.; Wang, L.K.; Ananpattarachai, J. Potable Water Biotechnology, Membrane Filtration and Biofiltration. In Membrane and Desalination Technologies ; Wang, L.K., Chen, J.P., Hung, Y.-T., Shammas, N.K., Eds.; Humana Press: Totowa, NJ, USA, 2011; pp. 477–523. [ Google Scholar ]

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Lin, P.; Liao, Z.; Wu, G.; Yang, L.; Fu, J.; Luo, Y. Recent Advances in Biofiltration for PPCP Removal from Water. Water 2024 , 16 , 1888. https://doi.org/10.3390/w16131888

Lin P, Liao Z, Wu G, Yang L, Fu J, Luo Y. Recent Advances in Biofiltration for PPCP Removal from Water. Water . 2024; 16(13):1888. https://doi.org/10.3390/w16131888

Lin, Pinyi, Zhuwei Liao, Gequan Wu, Liwei Yang, Jie Fu, and Yin Luo. 2024. "Recent Advances in Biofiltration for PPCP Removal from Water" Water 16, no. 13: 1888. https://doi.org/10.3390/w16131888

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MIT engineers make filters from tree branches to purify drinking water

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The interiors of nonflowering trees such as pine and ginkgo contain sapwood lined with straw-like conduits known as xylem, which draw water up through a tree’s trunk and branches. Xylem conduits are interconnected via thin membranes that act as natural sieves, filtering out bubbles from water and sap.

MIT engineers have been investigating sapwood’s natural filtering ability, and have previously fabricated simple filters from peeled cross-sections of sapwood branches, demonstrating that the low-tech design effectively filters bacteria.

Now, the same team has advanced the technology and shown that it works in real-world situations. They have fabricated new xylem filters that can filter out pathogens such as E. coli and rotavirus in lab tests, and have shown that the filter can remove bacteria from contaminated spring, tap, and groundwater. They also developed simple techniques to extend the filters’ shelf-life, enabling the woody disks to purify water after being stored in a dry form for at least two years.

The researchers took their techniques to India, where they made xylem filters from native trees and tested the filters with local users. Based on their feedback, the team developed a prototype of a simple filtration system, fitted with replaceable xylem filters that purified water at a rate of one liter per hour.

Their results, published today in Nature Communications , show that xylem filters have potential for use in community settings to remove bacteria and viruses from contaminated drinking water.

The researchers are exploring options to make xylem filters available at large scale, particularly in areas where contaminated drinking water is a major cause of disease and death. The team has launched an open-source website , with guidelines for designing and fabricating xylem filters from various tree types. The website is intended to support entrepreneurs, organizations, and leaders to introduce the technology to broader communities, and inspire students to perform their own science experiments with xylem filters.

“Because the raw materials are widely available and the fabrication processes are simple, one could imagine involving communities in procuring, fabricating, and distributing xylem filters,” says Rohit Karnik, professor of mechanical engineering and associate department head for education at MIT. “For places where the only option has been to drink unfiltered water, we expect xylem filters would improve health, and make water drinkable.”

Karnik’s study co-authors are lead author Krithika Ramchander and Luda Wang of MIT’s Department of Mechanical Engineering, and Megha Hegde, Anish Antony, Kendra Leith, and Amy Smith of MIT D-Lab.

Clearing the way

In their prior studies of xylem, Karnik and his colleagues found that the woody material’s natural filtering ability also came with some natural limitations. As the wood dried, the branches’ sieve-like membranes began to stick to the walls, reducing the filter’s permeance, or ability to allow water to flow through. The filters also appeared to “self-block” over time, building up woody matter that clogged the conduits.

Surprisingly, two simple treatments overcame both limitations. By soaking small cross-sections of sapwood in hot water for an hour, then dipping them in ethanol and letting them dry, Ramchander found that the material retained its permeance, efficiently filtering water without clogging up. Its filtering could also be improved by tailoring a filter’s thickness according to its tree type.

The researchers sliced and treated small cross-sections of white pine from branches around the MIT campus and showed that the resulting filters maintained a permeance comparable to commercial filters, even after being stored for up to two years, significantly extending the filters’ shelf life.

The researchers also tested the filters’ ability to remove contaminants such as E. coli and rotavirus — the most common cause of diarrheal disease. The treated filters removed more than 99 percent of both contaminants, a water treatment level that meets the “ two-star comprehensive protection ” category set by the World Health Organization.

“We think these filters can reasonably address bacterial contaminants,” Ramchander says. “But there are chemical contaminants like arsenic and fluoride where we don’t know the effect yet,” she notes.

Encouraged by their results in the lab, the researchers moved to field-test their designs in India, a country that has experienced the highest mortality rate due to water-borne disease in the world, and where safe and reliable drinking water is inaccessible to more than 160 million people.

Over two years, the engineers, including researchers in the MIT D-Lab, worked in mountain and urban regions, facilitated by local NGOs Himmotthan Society, Shramyog, Peoples Science Institute, and Essmart. They fabricated filters from native pine trees and tested them, along with filters made from ginkgo trees in the U.S., with local drinking water sources. These tests confirmed that the filters effectively removed bacteria found in the local water. The researchers also held interviews, focus groups, and design workshops to understand local communities’ current water practices, and challenges and preferences for water treatment solutions. They also gathered feedback on the design.

“One of the things that scored very high with people was the fact that this filter is a natural material that everyone recognizes,” Hegde says. “We also found that people in low-income households prefer to pay a smaller amount on a daily basis, versus a larger amount less frequently. That was a barrier to using existing filters, because replacement costs were too much.”

With information from more than 1,000 potential users across India, they designed a prototype of a simple filtration system, fitted with a receptacle at the top that users can fill with water. The water flows down a 1-meter-long tube, through a xylem filter, and out through a valve-controlled spout. The xylem filter can be swapped out either daily or weekly, depending on a household’s needs.

The team is exploring ways to produce xylem filters at larger scales, with locally available resources and in a way that would encourage people to practice water purification as part of their daily lives — for instance, by providing replacement filters in affordable, pay-as-you-go packets.

“Xylem filters are made from inexpensive and abundantly available materials, which could be made available at local shops, where people can buy what they need, without requiring an upfront investment as is typical for other water filter cartridges,” Karnik says. “For now, we’ve shown that xylem filters provide performance that’s realistic.”

This research was supported, in part, by the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT and the MIT Tata Center for Technology and Design.

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Press mentions, popular science.

MIT researchers have created a new filter from tree branches that could provide an inexpensive, biodegradable, low-tech option for water purification, writes Shaena Montanari for Popular Science . “We hope that our work empowers such people to further develop and commercialize xylem water filters tailored to local needs to benefit communities around the world,” says Prof. Rohit Karnik.

United Press International (UPI)

UPI reporter Brooks Hays writes that MIT researchers have created a new water filter from tree branches that can remove bacteria. “The filter takes advantage of the natural sieving abilities of xylem -- thin, interconnected membranes found in the sapwood branches of pine, ginkgo and other nonflowering trees,” writes Hays.

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• v.95(5); 2016 Nov 2

Effectiveness of Membrane Filtration to Improve Drinking Water: A Quasi-Experimental Study from Rural Southern India

Mark rohit francis.

1 Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India

Rajiv Sarkar

Shabbar jaffar.

2 London School of Hygiene and Tropical Medicine, London, United Kingdom

Venkata Raghava Mohan

3 Department of Community Health, Christian Medical College, Vellore, India

Gagandeep Kang

Vinohar balraj.

4 Society for Applied Studies, Vellore, India

Associated Data

Supplemental Tables.

Since point-of-use methods of water filtration have shown limited acceptance in Vellore, southern India, this study evaluated the effectiveness of decentralized membrane filtration 1) with safe storage, 2) without safe storage, versus 3) no intervention, consisting of central chlorination as per government guidelines, in improving the microbiological quality of drinking water and preventing childhood diarrhea. Periodic testing of water sources, pre-/postfiltration samples, and household water, and a biweekly follow up of children less than 2 years of age was done for 1 year. The membrane filters achieved a log reduction of 0.86 (0.69–1.06), 1.14 (0.99–1.30), and 0.79 (0.67–0.94) for total coliforms, fecal coliforms, and Escherichia coli , respectively, in field conditions. A 24% (incidence rate ratio, IRR [95% confidence interval, CI] = 0.76 [0.51–1.13]; P = 0.178) reduction in diarrheal incidence in the intervention village with safe storage and a 14% (IRR [95% CI] = 1.14 [0.75–1.77]; P = 0.530) increase in incidence for the intervention village without safe storage versus no intervention village was observed, although not statistically significant. Microbiologically, the membrane filters decreased fecal contamination; however, provision of decentralized membrane-filtered water with or without safe storage was not protective against childhood diarrhea.

Introduction

Worldwide, an estimated 1.1 billion people do not have access to a safe source of drinking water. 1 Water-borne pathogens of fecal origin are known to be associated with nearly 751,000 diarrheal deaths in children less than 5 years of age, more than half of which occur within the first year of life. 2 In India alone, an estimated 212,000 children under 5 years of age died due to diarrheal diseases in 2010, making India a leading contributor to the global burden. 2 , 3 Better access to and use of safe drinking water is crucial in preventing child deaths from diarrhea in low- and middle-income countries. 4

In rural southern India, ground water is pumped from deep borewells into overhead tanks and distributed through subterranean or surface-level water pipelines to communities at least once a day. 5 – 8 Despite a piped drinking water supply in most southern Indian villages, the quality of drinking water is poor. 9 , 10 In rural and urban Vellore, multiple studies have demonstrated fecal contamination of drinking water, likely due to poor design and maintenance of water supply systems, inadequate water treatment, and prolonged household storage. 7 , 10 – 12 Additional chlorination and solar disinfection have shown efficacy in reducing fecal contamination of drinking water at the point of use; however, poor uptake has led to only limited health gains from these interventions. 11 , 13

Decentralized water treatment solutions provide an important alternative to traditional source-based and point-of-use water treatment. 14 , 15 Small-scale systems are decentralized solutions that cater to several families or a small community and, by definition, are smaller than centralized systems. 15 Small-scale systems such as the water treatment and refill kiosks in Indonesia, India, Bangladesh, Ghana, Nigeria, and other developing countries have been used to provide microbiologically safe drinking water to urban residents. 14 , 15 A recent study from Indonesia reported reduced diarrhea among children from families using water kiosks. 14

Membrane filtration systems have long been used for water and waste-water treatment, with applications primarily in reverse osmosis plants in water-scarce regions. 15 , 16 Of the membrane filters, ultrafiltration membranes with a typical pore size between 0.002 and 0.1 μm have shown higher removal of pathogens such as Cryptosporidium , Giardia , and bacteria, viruses, and parasites. 15

For this report, we evaluated a source-based, low-pressure membrane filtration system which operates without electricity or conditioning materials such as glycerol or ethanol, and has been used in emergency and disaster relief situations such as after the tsunami of 2004 in Sri Lanka, India, and Indonesia, and other humanitarian installations in 16 other low-income countries. 17 , 18 In a preliminary study, the membrane filtration system effectively decontaminated drinking water in a residential campus in Vellore, over a 6-month period. 19 Herein, we report the results of a community-based interventional study which evaluated the effectiveness of a commercially available membrane filter, the Skyhydrant ™ water filtration system with a safe storage container versus without a safe storage container and central chlorination as per government guidelines in improving the microbiological quality of drinking water and preventing childhood diarrhea in rural southern India.

Materials and Methods

Study design and sample size..

The study was a three-arm (one village per arm), nonrandomized interventional trial.

• 1) Village 1: Households in the village received drinking water filtered by the membrane filtration system, that is, intervention-filtered water.
• 2) Village 2: Households in the village received both intervention-filtered water and a safe storage container with a narrow neck and a tap.
• 3) Village 3: The village was asked to continue water treatment, as per the existing guidelines, of adding 0.5 ppm bleaching powder to overhead tanks once fortnightly, and to collect water as per their normal practice.

The sample size calculation was based on an anticipated 25% reduction in under-two diarrheal incidence in the intervention village without safe storage versus no intervention and assuming three episodes of diarrhea per child per year 20 in the no intervention village. Adding a 10% dropout rate to the estimates resulted in a sample size of 80 children per village, that is, a total of 240 children to be followed up for a period of 1 year.

Study setting and participant eligibility.

The study was conducted between October 2013 and October 2014 in three large villages in the Kaniyambadi block (a rural administrative unit) of Vellore, Tamil Nadu, in southern India ( Figure 1 ). The Kaniyambadi block, comprising 85 villages (population = 104,792) is a demographic surveillance site of the Community Health Department (CHAD) of the Christian Medical College (CMC), Vellore. A list of villages with at least 80 children under 2 years of age or with expected births resulting in 80 children under 2 years of age were obtained from the CHAD census data, and three villages, Sholavaram, Kilarasampet, and Nanjukondapuram were selected as they were easily accessible by road, at a suitable distance from each other (between 1 and 5 km), and were representative of the larger villages in the block with respect to socioeconomic constitution, primary occupation, water sourcing, quality, and child-rearing practices.

Map of the study villages.

The primary livelihood of the heads of household in the villages was farming or farm work, skilled work (masons, electricians, painters, and drivers) and unskilled work (street vendors or manual laborers). Women in the village were mostly housewives with a few intermittently employed during harvest season and school-aged children studied in government-run primary schools. The villages are mainly dependent on piped drinking water from their own deep borewells and pumped through a subterranean distribution network to taps on each street. Water supply is intermittent and lasts for 1–3 hours each day. Families collect drinking water in plastic or metal pots and store the pots at home for further use.

This study was carried out after obtaining clearance from the Institutional Review Board of CMC, Vellore. Verbal consent was obtained from the participating community through village meetings held to explain the nature, scope, and duration of the study. Intervention allocation was purposive, and the two villages with the most cooperative leaders, Sholavaram and Kilarasampet, were considered as intervention villages. A list of all households with recent births and children under 2 years of age was obtained from existing CHAD census databases and all households were sequentially approached for participation based on the obtained list. Households were enrolled after obtaining written informed consent. Children under 2 years of age in the enrolled households were followed up for a period of 1 year, or until their second birthday, or until the end of the study. The field staff kept track of antenatal women expected to deliver during the study period and continued to recruit children until August 2014.

Intervention.

Membrane filtration system..

Households in Villages 1 and 2 were provided filtered water from a membrane filtration system. The membrane filtration system used was the Skyhydrant ™ water filtration system (Skyjuice ™ Foundation Inc., New South Wales, Australia), a commercially available gravity-fed, source-based water filtration system with a high throughput costing around INR 150,000 or USD 2,300. It uses a series of hollow fiber membrane tubes (about 1 m in length) composed of polyvinylidine fluoride with a pore size of 0.04 μm to filter water. Raw water passes in through a vent and out through another vent for collection or storage. Cleaning handles can be rotated to clean the internal filter module manually. The recommended head pressure for raw water flow of 3–6 psi, is achieved by positioning the reservoir tanks on the roof at a height of 3 m, which produces between 500 and 700 L of potable drinking water per hour. 20 Additional detail on membrane filter installation and maintenance are available in another manuscript. 22

Safe storage container.

Households in Village 2 were provided a polyvinylchloride container (25-L capacity, cost: INR 260 or USD 5) with a lid, tap, and a handle, for storage of filtered water. Study households were encouraged to rinse their containers with the filtered water before every collection. Single intervention and control households were asked to collect and store water as per their normal practice.

Outcome assessment.

Water quality..

Village leaders helped contract existing pump drivers, responsible for daily distribution of water, for the maintenance and use of the Skyhydrant in each study village. Water samples were collected every month on a rotating schedule from the overhead tanks in each village (primary water sources) and pre- and postfiltration samples from each membrane filtration unit. Samples were also collected from 10% of the study households from the in-use drinking container once every 2 months. All water samples were collected in sterile, 250-mL polypropylene bottles with a stopper. Prefiltration samples were collected from a water tap connected to the pipe feeding water from the raw water storage tank to the membrane filtration system and postfiltration samples were drawn from the postfiltration storage tanks. The field workers were trained to collect and transport the samples per protocol. 11 , 23 Taps were flamed for 2 minutes and water was allowed to flow for an additional minute before collection. Household container and source (overhead tank) samples were drawn using a designated scoop with a handle which was washed with distilled water and dried before and after every sample collection. The samples were tested for pH, nitrates, hardness, residual chlorine, and total dissolved solids (TDS) using standard testing kits (HiMedia Laboratories Pvt. Ltd., Mumbai, India). In addition, total coliforms (TC) colony-forming unit (CFU)/100 mL, fecal coliforms (FC) CFU/100 mL, and Escherichia coli CFU/100 mL were enumerated using MacConkey and M-FC media (HiMedia Laboratories Pvt. Ltd.). The range of detection for bacteria was 0–300 CFU/100 mL.

Diarrheal surveillance.

Trained field workers (one per village) visited households once during the first 4 days of the week and telephoned in the subsequent 3 days to achieve twice-weekly surveillance of each study household. They obtained information from the mother or the primary caregiver and recorded episodes of diarrhea in children less than 2 years of age in the preceding days. Diarrhea was defined as “passage of three or more loose or watery stools in 24 hours or, in case of infants, more frequent passage than normal.” 24 Episodes of diarrhea were distinguished if they occurred at least 48 hours after cessation of the previous episode. 24

Data collection, entry, and analysis.

A baseline questionnaire administered in October 2013 (and subsequently for new entrants) captured demographic details, socioeconomic characteristics, water usage, water handling, and hygiene practices. Surveillance data were double entered using EpiInfo 2002 (Centers for Disease Control and Prevention, Atlanta, GA) software. Laboratory water sampling reports, maintenance logs, and migration details were compiled in Microsoft Excel 2010 spreadsheets (One Microsoft Way, Redmond, WA). Data analysis was performed using STATA for Windows version 12.0 (StataCorp, College Station, TX).

Baseline comparisons for selected demographic, socioeconomic, water usage, and hygiene variables were performed using χ 2 test or Fisher's exact test for categorical variables and the analysis of variance F-test (with Scheffé's test for pairwise comparisons between villages) for continuous variables.

Arithmetic means of the microbiological parameters were presented using a Poisson distribution for the microbiological parameters and compared for the source and household water samples by study village and paired membrane filter pre- and postfiltration samples. The effectiveness of the membrane filters in reducing microbiological counts was presented as log-reduction values (LRVs) calculated as:

The LRVs are only presented for samples where the prefiltration microbiological concentration was > 0 CFU/100 mL sampled water.

The primary outcome, diarrheal incidence in children under 2 years of age was analyzed using an intention-to-treat analysis. Univariate survival analysis was performed for each of the baseline variables regressed against the incidence of diarrhea in children of the study. Type of house, socioeconomic status, and agent used for hand washing were found to be associated with childhood diarrhea at P < 0.10. These variables were adjusted using Poisson survival regression models and were presented as diarrheal incidence rate ratios (IRR [95% confidence interval, CI]) with a shared frailty to account for clustering of children within study households. We also investigated the effect of the microbiological quality of household drinking water on diarrheal incidence in the subset of intervention households ( N = 122) whose samples had been collected.

Participants.

At baseline in October 2013, there were 279 households with at least one child under 2 years of age. Of the 232 eligible households, 205 consented to participate in the study, whereas 27 households felt the study activities would take up too much of their time and be an inconvenience to them ( Figure 2 ). The total number of children under the age of 2 years recruited until August 2014 was 281 with 111, 66, and 104 children in the no intervention, intervention without safe storage, and intervention with safe storage container, respectively. They contributed to a total of 203.2 child years of follow-up: 84.7% of the total anticipated follow-up time and average follow-up contributions of 0.73, 0.67, and 0.74 years per child for the no intervention, intervention without safe storage, and intervention villages with safe storage container, respectively.

Consort diagram showing participant flow during the trial.

Baseline characteristics.

A majority (71.6%) of the study families belonged to the lower socioeconomic strata. The primary drinking water sources were public taps (54.2%), followed by private wells (21.3%), and house tap connections (16.9%) ( Table 1 ). A minority (12.8%) of the families reported treating water regularly at home, mainly by boiling. Nearly 94% of families reported washing hands with only water after defecation. Only one-third (91/268, 33.3%) of the families reported having a toilet and of them, 81.3% (74/91) reported using the toilets on a regular basis. Significant differences were observed between the study villages for mean number of individuals and children per household, type of family, primary source of drinking water, water treatment, toileting, and waste-disposal practices ( Table 1 ).

Baseline characteristics of study households ( N = 273)

IQR = interquartile range; SD = standard deviation.

There were 167 source-water, 60 paired (pre/postfiltration) membrane-filter, and 177 household-container water samples (total 464 samples) collected during the study. There was no residual chlorine in any of the source drinking water samples. Of source drinking water samples, 74% (149/202), 71.5% (128/179), and 67.3% (136/202) had detectable TC, FC, and E. coli , respectively. The intervention village without safe storage had the highest E. coli levels with an arithmetic mean (95% CI) of 92.4 (88.6–96.3) CFUs/100 mL followed by the intervention with safe storage and no intervention village at 35.6 (33.6–37.6) and 20.7 (20.0–21.5), respectively ( P value for trend < 0.001) ( Supplemental Table 1 ).

Overall, 65% (39/60) of prefiltration samples tested had microbiological contamination (TC, FC, or E. coli ), whereas only 3% (2/60) of postfiltration samples in the intervention villages were contaminated. Postfiltration contaminated samples had median (interquartile range, IQR) values of 11 (6–16) and 2 (0–4) for TC and E. coli , respectively, whereas prefiltration samples had median (IQR) values of 22 (7–37) and 11.5 (0–23). Arithmetic means of pre- and postfiltration samples tested are presented in Table 2 . The membrane filters achieved a LRV of 0.86 (0.69–1.06), 1.14 (0.99–1.30), and 0.79 (0.67–0.94) for TC, FC, and E. coli , respectively, when only paired samples with microbiological contamination prefiltration were analyzed. There were no differences in pH, nitrates, residual chlorine, hardness, and TDS between pre- and postfiltration samples for the Skyhydrant filter ( Supplemental Table 2 ). Households provided with safe storage containers had the lowest E. coli levels with an arithmetic mean of 13.5 (12.5–14.5) CFUs/100 mL compared with 48.6 (46.7–50.5) CFUs/100 mL and 63.4 (61.6–65.3) CFUs/100 mL) for household without the safe storage container and the no intervention villages ( P value for trend < 0.001) ( Table 3 ).

Comparison of microbiological parameters in pre- and postfiltration samples for the membrane filters

CFU = colony-forming unit; CI = confidence interval.

Comparison of average TC, FC, and Escherichia coli at the point of use in the no intervention and intervention with and without safe storage samples for the period of study

CFU = colony-forming unit; CI = confidence interval; FC = fecal coliforms; TC = total coliforms.

Diarrheal burden in the study villages.

A total of 200 episodes of diarrhea were reported in 119 children from 117 households; seven episodes were reported from more than one child belonging to the same household. The overall diarrheal incidence in children under 2 years of age reported as episodes per child-year (95% CI) were 1.05 (0.85–1.30), 1.22 (0.94–1.59), and 0.79 (0.62–1.02) for the no intervention, intervention without safe storage, and intervention with safe storage villages, respectively. The number of children who ever had an episode of diarrhea did not significantly differ between the study villages. Diarrheal incidence appeared to peak between May and July, but was consistently lower for the intervention village with safe storage compared with the other two villages for all months of the study. The median (IQR) length of a diarrheal episode was 2 (2–3) days, similar for all the study villages. Diarrheal incidence was similar for male and female children in the study: 0.99 (0.81–1.21) and 0.98 (0.80–1.20) episodes per child-year, respectively.

In the univariate analysis, a 23% (IRR [95% CI] = 0.77 [0.52–1.13], P = 0.190) reduction in under-two diarrheal incidence rate was observed for the intervention with safe storage village versus the no intervention village and a 15% (IRR [95% CI] = 1.15 [0.75–1.77], P = 0.517) increase in under-two diarrheal incidence rate was observed for the intervention without safe storage village as compared with the no intervention village.

In the multivariate analysis, the reduction in diarrheal incidence for the intervention with safe storage compared with the no intervention village was 24% (IRR [95% CI] = 0.76 [0.51–1.13], P = 0.178) and the intervention village without safe storage had a 14% increase under-two diarrheal rates compared with no intervention (IRR [95% CI] = 1.14 [0.75–1.77], P = 0.530). However, none of the reported differences in diarrheal rates between study villages were statistically significant. Also, diarrheal rates did not appear to vary by gender and appeared highest for children 6–12 months of age (IRR [95% CI] = 1.30 [0.85–1.98], P = 0.222) compared with the referent category of children 0–6 months of age. The results of the multivariate analysis are presented in Table 4 .

Diarrheal episodes, time at risk, and diarrheal incidence rates in children under 2 years of age

CI = confidence interval; IRR = incidence rate ratio.

Diarrhea and water quality.

We also explored the relationship between diarrheal incidence and average TC, FC, and E. coli contamination in household container samples in a subset of study households ( N = 122). Increased diarrheal rates were observed with increasing levels of median microbiological contamination (TC, FC, and E. coli ) in household container samples used independently in the survival regression models, although not statistically significant ( Table 5 ).

Effect of average water quality in the household on under-two diarrheal incidence ( N = 122)

CFU = colony-forming unit; CI = confidence interval; IRR = incidence rate ratio.

The adjusted IRRs were (1.59 [0.78–3.26], P = 0.199) and (2.18 [090–5.28], P = 0.084) for household container samples with FC levels of 1–180 CFU/100 mL and > 180 CFU/100 mL, respectively, relative to the lowest contamination group of < 1 CFU/100 mL ( Table 5 ).

The membrane filters produced microbiologically safe drinking water over the 1 year of testing with failures observed in only two of 60 postfiltration samples, possibly due to manual contamination of the storage tanks at the time of cleaning or water collection. The filters did not alter the physicochemical quality of water, 18 and can be used to provide safe water to smaller communities, especially in places without a continuous power supply. This is also a potentially scalable intervention to meet the requirements of larger communities. 19 The membrane filter achieved a log reduction of ∼1 for FC in field conditions, lower than what was reported from the laboratory assessment of a similar portable gravity-fed ultrafiltration device intended for household use, 25 but it must be noted that LRVs are contingent upon the concentration of microorganisms in prefiltered water, and in this field study, only a small proportion of prefiltration water samples had high levels of contamination. The membrane filter might achieve higher LRVs, that is, higher elimination of indicator organisms in highly contaminated drinking water.

Tested as an alternative to available point-of-use methods of water filtration, decentralized membrane filtration with or without safe storage was not protective against childhood diarrhea. Most field trials evaluating the effect of water quality on diarrhea in India have tended to focus on point-of-use disinfection; and while methods such as household chlorination, gravity filters (such as ceramic filters) and boiling have shown potential for microbiological disinfection, low compliance and acceptability reduce the benefits consumers might gain from their use. 11 , 26 – 29 Improving access to clean drinking water is millennium development goal 7c, and is the responsibility of the Ministry of Drinking Water and Sanitation in India.

The lack of association between safer water and childhood diarrhea in this study highlights the possible role of other modes of transmission that might drive endemic diarrhea among children in rural Vellore as reported by an earlier study. 30 Another critical factor contributing to the observed lack of association could be reduced adherence to the study interventions in the intervention villages. Previous studies testing water quality interventions in the region have reported varying levels of adherence, especially for point-of-use methods of water disinfection. 11 , 13 Adherence to the interventions was not assessed in our study, as it was intended to provide a more realistic estimate of the impact of decentralized membrane filtration if implemented as part of either governmental or nongovernmental programs in the region. High adherence to water quality interventions is crucial to realizing the health gains from them, 29 and we have reason to believe that adherence in our study was high as the filtered drinking water provided at no cost was highly valuable to the families. 22 Nevertheless, timely research on improving adherence and factors influencing acceptance to such water quality interventions is crucial to their long-term success in resource-limited settings.

This study had a few limitations: the intervention was provided at the community level, limiting its application to clusters (villages), and therefore, individual randomization could not be done. Since intervention allocation was purposive, the effect estimates in our study may be biased due to the presence of unmeasured confounding between the study villages. The villages selected for study were expected to have similar social and demographic characteristics, water sourcing and handling, and personal and household hygiene indicators. Baseline data collection therefore sought to exhaustively measure all known and potential confounders thought to differ between the study villages. The study villages were generally similar, except for observed differences in the numbers of individuals per household, family type, primary sources of drinking water, toileting, and waste-disposal practices ( Table 1 ). Therefore, the effect of unmeasured confounding due to variables related to the measured baseline variables is expected to be negligible, if present. All study arms were provided with some form of intervention: the no intervention village was encouraged to continue the government-recommended central chlorination, and therefore, may not be an ideal “control” for the comparisons made with the intervention villages. Blinding of participants or study personnel was not possible; Cairncross and others report the difficulty in blinding such studies and urge caution. 31 The primary outcome of study was diarrhea in children under 2 years of age, and a degree of underreporting of episodes may be likely, but we sought to reduce this by employing a twice-weekly surveillance using both home visit and telephonic interviews. Underreporting of diarrheal episodes may have still occurred in the no intervention village due to a lack of motivation among the families over time. We also failed to characterize the diarrheal episodes as having been reported during home visits or on telephonic surveillance. It is important to note that the consistently lower number of children in the intervention village without safe storage resulted in a lack of power to detect an effect on diarrhea. With the existing power, we would have been able to detect a difference of 27–31% between the intervention (without safe storage) and the no intervention. Also, the water quality of pretreatment samples may not accurately represent the water collected by study households as pretreatment samples were collected after flaming. Public taps have been implicated as a potential source of microbiological contamination in the past, 32 and it is therefore likely that study households were exposed to more contaminated water than represented by the pretreatment samples. Moreover, the frequency and quantum of unfiltered water provided to children in the study could not be estimated. These data may have provided better estimates of household risk factors for diarrhea.

Microbiologically, the membrane filters were effective in improving the quality of water with detectable fecal contamination; however, the provision of membrane filtered water with or without safe storage containers was not protective against childhood diarrhea. Decentralized infrastructure for water filtration may be useful in regions where the microbiological quality of water is insufficiently addressed, provided initial costs for set up and maintenance are available.

Supplementary Material

Acknowledgments.

We are grateful to the village leaders and the participants for their time and cooperation. We also acknowledge the efforts of study personnel Raja, Suguna, Muthulakshmi, and Satish for their help with the field trial; Senthil for his help with study setup and Skyhydrant ™ installations; Rachel, Vani, Sumathi, and Kaviarasu for assistance with data entry; and Karthikeyan for help with data management. We extend our gratefulness to Jann Hughes, Wendy Alt, and Larry James at the Skyjuice ™ Foundation Inc, Australia, for arranging donor subsidies for the Skyhydrant ™ filtration systems.

Financial support: The trial was supported by a Wellcome Trust Masters Training Fellowship in Public Health and Tropical Medicine (grant reference no. 098579/Z/12/Z) to Mark Rohit Francis. Rajiv Sarkar was supported by the Wellcome Trust/DBT India Alliance through an Early Career Fellowship (grant no. IA/E/12/1/500750).

Authors' addresses: Mark Rohit Francis, Rajiv Sarkar, Sheela Roy, and Gagandeep Kang, Division of Gastrointestinal Sciences, Christian Medical College, Vellore, India, E-mails: moc.liamg@82muisyle , ni.ca.erollevcmc@rakrasr , moc.liamg@1yoraleehs , and ni.ca.erollevcmc@gnakg . Shabbar Jaffar, Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, United Kingdom, E-mail: [email protected] . Venkata Raghava Mohan, Department of Community Health, Christian Medical College, Vellore, India, E-mail: ni.ca.erollevcmc@taknev . Vinohar Balraj, Society for Applied Studies, Vellore, India, E-mail: moc.liamg@jarlabrahoniv .