Grantee Research Project Results
Final Report: Optimizing the Biosand Filter for Drinking Water Treatment in Developing Countries
EPA Grant Number: SU834718Title: Optimizing the Biosand Filter for Drinking Water Treatment in Developing Countries
Investigators: Jellison, Kristen L. , Napotnik, Julie , Schweitzer, Ryan
Institution: Lehigh University , University of South Florida
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
More than one in six people worldwide, the equivalent of 894 million people, do not have access to safe drinking water, and the United Nations has included among the Millenium Development Goals (MDGs) the target of reducing by half the proportion of people without sustainable access to safe drinking water by 2015. The current pace of household water treatment implementation is not on target to meet the MDG for safe drinking water by 2015; therefore, making household water treatment options more accessible and affordable to a larger global market is an important goal ensure that the MDG for safe drinking water is met.
The Phase I project tested the hypothesis that biosand filtration can be effective on a smaller, cheaper scale than currently practiced with the concrete biosand filter (BSF). Although the efficacy of the concrete BSF has been confirmed in both the laboratory and the field, the concrete BSF can be too costly for some of the poorest households in the developing world. In addition, the size and weight of the concrete filter make it cumbersome and difficult to transport beyond the initial installation location. A smaller, lighter, less expensive BSF could more sustainably meet the needs of a larger global market.
The experimental set-up included four replicates of three different BSF sizes: the traditional concrete BSF, a 5-gallon (20-L) bucket BSF, and a 2-gallon (8-L) bucket BSF. The BSFs were all built and initially tested in the PI’s lab in Chandler-Ullmann Hall and were moved to the PI’s new lab in the STEPS Building in August 2010. Moving the filters led to sand compaction and, ultimately, flow rates below the acceptable range for the BSF. Therefore, filters were rebuilt in the fall of 2010, and testing resumed in January 2011. The lab tests are broken into three categories: (1) pre-move testing conducted in the Chandler-Ullmann lab, (2) post-move testing performed immediately after the BSFs were moved to the new laboratory in the STEPS building, and (3) tests performed after the deconstruction and re-commissioning of all twelve BSFs in the STEPS laboratory. Lab tests evaluated the efficacy of the three filter sizes in the removal of turbidity, total coliforms, E. coli, MS2 coliphage, and Cryptosporidium parvum oocysts.
Summary/Accomplishments (Outputs/Outcomes):
- Pre-Move Testing: In all three filter types, flow rates decreased over time as the pore spaces clogged; cleaning the filters typically restored flow rates close to their initial (clean bed) values of 0.3, 0.3, and 0.2 mL/min for the concrete, 5-gal bucket, and 2-gal bucket, respectively. The flow rate of the concrete BSFs dipped below the recommended minimum (defined as half of the clean-bed flow rate based on end user acceptability) much more frequently than for the bucket BSFs; the concrete BSFs required cleaning after each high turbidity loading period, whereas the flow rates of the 2-gal bucket BSFs never dipped below the minimum value. The difference in cleaning requirements is attributed to the greater volume of water charged to the concrete BSFs compared to the bucket BSFs (filters were filled three times per day, with a 3-hour pause period between fills; one fill volume is 12L per concrete filter, 3.6L per 5-gal bucket filter, and 1.5L per 2-gal bucket filter). All filter types effectively removed particulates and debris from influent water regardless of turbidity values; all effluents were consistently ≤1NTU. Average bacteria removals in the concrete, 5-gal bucket, and 2-gal bucket BSFs were all very similar, ranging from 97.4-99.5%. Filter flow rates and cleaning frequency did not adversely affect bacterial removal; bacterial removal remained high regardless of varying flow rates and cleaning times.
- Post-Move Testing: All filters were filled three times per day with a 3-hour pause period between fills. Influent turbidity was maintained at ~50 NTU, and rusty nails were added to the diffuser basins of two filters of each type (in an effort to enhance virus removal in the smaller filters via electrostatic forces). Bacteria removal was tested four times, and for all filters, both E. coli and total coliform removal was greater than 99%. However, after the move, filter flow rates were not increasing after cleaning as they had prior to the move. Even though filters were cleaned weekly, flow rates never increased to the clean bed values. The slower flow rates were attributed to compaction of the filter media (sand and rock) when the filters were moved to the new lab. Because the sand compaction altered the flow dynamics within the filter bed, and because the resulting flow rates were below the level deemed acceptable for real world use, the filters were decommissioned and reconstructed before additional tests were performed.
- Post-Rebuild Testing: In January 2011, testing of the rebuilt filters was initiated. Filters were ripened for four weeks, filled twice per day with a 6-hr pause period between each fill. Influent turbidity was maintained at ~50NTU. Bacteria removal for all filters was ≥99% during the ripening period, confirming observations from the pre-move testing that a four-week ripening period was not required to achieve sufficient bacteria removal. During the fifth week, rusty nails were added to the diffuser basins of two of each filter type. Bacteria testing continues to be performed on a weekly basis, and Cryptosporidium and MS2 bacteriophage testing has begun. The first set of data for Cryptosporidium removal in the filters show that for each filter type, the addition of rusty nails enhanced Cryptosporidium removal. Greater than 3-log removals (most removals greater than 4-log) were achieved in every filter type modified with rusty nails; however, even in the filters that were not modified with rusty nails, Cryptosporidium removals were almost always greater than 3-log. Initial results from the MS2 coliphage testing were not complete at time of this report deadline. The larger testing plan proposed in the Phase I proposal is expected to be completed by August 2011.
Conclusions:
The data we have collected to date has successfully confirmed our hypothesis that biosand filtration can be effective on a smaller scale. Results show that turbidity, total coliforms, E. coli, and Cryptosporidium removals are comparable for the concrete, 5-gal bucket, and 2-gal bucket filters. Results also show that the addition of rusty nails to the diffuser basin enhanced the removal of Cryptosporidium in all three filter types. The biggest barrier we faced was the impact of moving the filters on compaction of the sand bed and reduction of filter flow rates below acceptable levels. Although this setback delayed our progress for several months, it resulted in a very important recommendation for these scaled-down BSFs: despite their smaller size and the ease with which they can be moved, under no circumstances should the scaled-down BSFs be moved after they have been commissioned. Their smaller size will make the distribution of the filter components easier in remote, rural regions of the developing world, but the filters should never be transported once they have been built and used.
Results from Phase I validate the potential of the smaller bucket BSFs to provide an effective household water treatment option which could reach poor populations unable to afford a traditional concrete BSF or living in remote regions to which distribution of the cumbersome concrete BSF is a challenge. Affordable safe drinking water technology will benefit people who do not have access to improved drinking water sources, reducing the incidence of waterborne diarrheal disease and increasing the productivity and prosperity of the end users. Improvements in public health and productivity will lead to populations that can afford to take better care of themselves, their families, and their environment.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 2 publications | 2 publications in selected types | All 2 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Napotnik J, Baker D, Jellison K. Effect of Sand Bed Depth and Medium Age on Escherichia coli and Turbidity Removal in Biosand Filters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017;51(6):3402-3409 |
SU834718 (Final) |
Exit |
|
Napotnik J, Baker D, Jellison K. Influence of Sand depth and pause period on microbial removal in traditional and modified biosand filters. WATER RESEARCH 202;189(116577) |
SU834718 (Final) |
Exit |
Supplemental Keywords:
household water treatment; biosand filtration; safe drinking water; waterborne disease; public healthThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.