|Year : 2013 | Volume
| Issue : 1 | Page : 97-98
Evaluation of a commercially available polyvinylidene fluoride membrane filtration system for water decontamination
MR Francis1, S Roy2, R Sarkar2, V Balraj1, G Kang2
1 Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of astrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Submission||17-Jun-2012|
|Date of Acceptance||12-Aug-2012|
|Date of Web Publication||15-Mar-2013|
Department of astrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Francis M R, Roy S, Sarkar R, Balraj V, Kang G. Evaluation of a commercially available polyvinylidene fluoride membrane filtration system for water decontamination. Indian J Med Microbiol 2013;31:97-8
|How to cite this URL:|
Francis M R, Roy S, Sarkar R, Balraj V, Kang G. Evaluation of a commercially available polyvinylidene fluoride membrane filtration system for water decontamination. Indian J Med Microbiol [serial online] 2013 [cited 2020 Oct 25];31:97-8. Available from: https://www.ijmm.org/text.asp?2013/31/1/97/108758
Unsafe drinking water continues to be a leading cause of morbidity from water-borne diseases, especially in developing countries. Provision of safe drinking water, coupled with improvements in sanitation and hygiene, has been predicted to significantly reduce the global burden of disease.  In previous studies, the poor quality of public water sources in southern India has been demonstrated,  and the need for effective disinfection methods cannot be overemphasized.
Membrane filters are capable of effectively eliminating bacteria and microorganisms from water, require lower energy and can produce superior quality water.  We evaluated a commercially available membrane-based water filtration device for its efficacy in delivering microbiologically safe drinking water over a long period of time, while maintaining a constant throughput.
A commercially available polyvinylidene fluoride membrane water filtration system (PFM water filter), costing 150,000 INR (3300 USD), was installed at a residential campus and tested for a period of 6 months (February-July 2010). This gravity-fed implement has a pore size of 0.1 μm and can produce between 500 and 700 litres of drinking water per hour (L/h).
Untreated water from a sump filled with water from multiple deep protected bore wells was pumped into a 500 L Sintex™ (Sintex Industries Ltd., Gujarat, India) tank at a height of about 5 m. The water then flowed into the inlet of the PFM water filter by gravity and post-filtration into a storage sump. Water was continually pumped into the Sintex™ tank to maintain a steady input. On alternate days, the filter was manually flushed out to remove any accumulated waste. Every month, the system was chemically cleaned with chlorine as recommended by the manufacturer.
Water was collected pre- and post-filtration at weekly intervals and tested for the presence of coliforms by the most probable number (MPN) technique.  Thermotolerant coliforms were not estimated, as the aim of this study was to measure removal of bacteria. A commercial kit was used to test for residual chlorine (HiMedia Lab. Pvt. Ltd., Mumbai, India). The output was monitored by using a stopwatch to record the time taken in seconds for the water from the unit to fill a 5 L water can and calculating the unit flow rate (L/h) over time.
A total of 50 (25 pairs of pre- and post-) water samples were collected and analysed every week over 6 months. The majority (16/25, 64%) of input water samples from the sump were found to have coliforms pre-filtration samples, and of these, 7 (44%) had coliform counts greater than 100. There appeared to be no seasonal variation in the contamination of the samples, which were collected during the winter and summer seasons (February-July). No coliforms were detected in 24/25 (96%) post-filtration samples, and the only positive post-filtration sample had a coliform count of 54 per 100 ml of tested water (Fisher's exact test, P < 0.001) [Table 1].
The PFM water filter provided an average (SD) throughput of 442.6 (65.9) L/h, 393.5 (30.1) L/h, 410 (28.5) L/h and 432.7 (13.3) L/h of water, in the 1 st -4 th months of observation, which are less than the advertised range of 500-700 L/h. None of the samples had any residual chlorine, which was expected because the unit received untreated water.
Previous studies using seeding experiments in the laboratory have demonstrated high levels of efficacy with several methods for water decontamination, which have subsequently proved to be less or not effective in field conditions, where the physicochemical properties including the content of total dissolved solids and contaminants can be variable.  This PFM water filter has been evaluated previously with seeding experiments and is a commercialized technology, but its efficacy in a real-world setting has not been previously reported. In this study, the system was found to be effective over a 6-month period, with only 1/25 failures with a very heavily contaminated input. The PFM water filter was effective in eliminating coliforms from untreated water under field conditions, and the treated water satisfied the WHO criteria for safe water.
Water disinfection in rural south India relies heavily on centralized chlorination, usually by addition of bleaching powder to overhead tanks. However, the smell and taste of chlorine has been shown to be unacceptable to many people. , In this study, a device that does not require the addition of chlorine was tested, because previous studies have shown that leaving the taste of water unaltered results in a higher acceptability.
Over all, the long-term sustainability and acceptability of point-of-use water treatment methods is low among the poor, possibly due to the requirement for user activities, limited production of potable water or additional cost, , but the reliance on gravity and lack of need for electricity or chemicals reduce operational and maintenance costs and make this PFM water filter a potentially cost-effective method for providing safe drinking water, especially in low-income settings. With a constant output of 400 L/h, one unit will be able to meet the drinking water requirements of 50 families, providing 12 L per family, even with 1.5 h of water supply per day. If the device works for a year, although the stated life of the membrane is 10 years, this will amount to an additional expenditure of approximately 0.02 USD/L of drinking water produced.
The ability of this filtration system to purify large volumes of water at a consistent flow rate makes it a potentially ideal candidate for use in smaller communities, during disasters and in settings such as schools, where it has reportedly been used. However, the longer term ability to provide a constant outflow of water and effectiveness in reducing the burden of diarrheal illness in the communities where it is in use need to be tested.
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