BioSand Filters: Appropriate Household Water Treatment for Floating Villages in Cambodia

Curry, K.D.1, M. Morgan2, S. H. Peang2, S. Seang2

1: Bridgewater State University, Bridgewater, MA, USA 023252. Water for Cambodia, Siem Reap, Cambodia.

Recent work done in Cambodia by Brown et al. (2007) and Liang et al. (2010) have documented ceramic water filters and biosand filters as cost effective point of use (POU) treatment systems capable of removing over 95% E. coli bacteria when properly used and maintained.

Water for Cambodia (WfC) constructs, installs and tests BSF’s in Siem Reap Province as part of their WASH outreach program and explored using BioSand filters (BSF) to provide microbiologically safe drinking water for people in the Moat Khla floating village community on the Tonle Sap Great Lake.

Moat Khla is a floating village in Siem Reap Province , where all 189 families use the natural lake/ river for their water source which by WHO standards is deemed unsafe.*10 BSF’s installed January 2010; village members requested more.•WfC evaluated BSF’s in December 2010 and February 2011 comparing 40 families using BSF’s and 40 families not using BSF’s.• Turbidity in lake source water decreased in December, and mean bacterial levels increased from 550 CFU’s to over 1100 in February. • >90 % of both households types were using high risk lake source water (>100 CFU’s of E. coli bacteria per 100 ml) using WHO standard.• 5 % of BSF and 40% of Non-BSF household storage water had bacteria levels in the high risk range (> 100 E.coli per 100ml) indicating some source of recontamination .•Non-BSF households untreated storage water showed significant reduction in mean Log10 E.coli levels compared to the lake source water.•Surveys revealed Non-BSF families use a wide range of treated and untreated sources for their drinking water showing wide variation in bacteria levels and the occurrence of diarrhea.•Recontamination occurred no matter the source or treatment.•Demand for BSF’s increased to over 80 by February 2011 even though a floating U.V. filtration system was available.

•Removal effectiveness of BSF’s ranged 2.2 to 2.4 Log Reduction however recontamination of treated water illustrates that WASH education is essential no matter what water treatment and storage method is used for remote floating villages in Cambodia.

Evaluate BSF’s as an effective treatment system to provide microbiologically safe drinking water for floating village communities on the Tonle Sap Great Lake.

Compare bacteria levels in lake source and household storage water for families with and without BSF’s as a treatment for their drinking water.

Confirm the removal efficiency of BSF’s where source water quality varies between the wet and dry season

Compare E. coli levels in lake source water used by participating households between geographic zones in a 1 to 1.5 km area of Moat Khla

Background and Overview

Objectives

Moat Khla   E. coliLog10 E. coli   E. coli

BSF Households CFU/100ml CFU/100ml E. coli CFU

  nMean and

(SD)Mean and

(SD) LRV%

Red.

Dec. 2010          

Lake Water 28550.0

(604.8) 2.56 (0.42)    

BSF filtered 28 3.2 (8.0) 0.30 (0.44) 2.26 > 99%

BSF filtered and stored 30 4.9 (13.4) 0.36 (0.52) 2.2 >99%

           

Feb. 2011          

Lake Water 391147.8

(1173.0) 2.84 (0.53)    

BSF filtered 39 4.8 (9.9) 0.41 (0.51) 2.43 >99%

BSF filtered and stored 38 8.2 (20.8) 0.48 (0.57) 2.36 >99%

BSFLake BSF

FWBSFHS

NonBSFLake

& other

nonBSFHS

December

February

Lake

Lake

BSFBSF

SW SW

Lake Lake

BSF BSFSW SW

December FebruaryLake

WaterBSF

Filter Water

Stored Water

Lake Water

Stored Water

NonBSF BSF

Moat Khla Non BSF Families: Number of Ecoli / 100ml in

Stored Water Feb 2011         

Which water do you use for your drinking water( dry season)

Mean E. coli per 100 ml

N Std. Dev.

Min Max

RDB UV water system 369.2 13 827.2 0 3000

BSF water from neighbor 550.0 2 678.8 70 1030

Buy water 720.0 1 . 720 720

Ceramic filter 13.0 2 18.4 0 26

Korea filter 70.0 1 . 70 70

River sometime RDB UV water 13.0 1 . 13 13

River water 781.5 13 951.1 5 2920

River water with boiling 339.7 6 823.2 0 2020

River water with alum 2.0 1 . 2 2

Total 473.2 40 808.5 0 3000

E. coli levels were significantly greater in lake water for homes in Zone 1 than Zone 4

Both BSF and Non-BSF homes had large variation in E.coli levels in their stored drinking water = Recontamination

Non BSF Households used many types of source water for drinking all of which showed wide variability in E.coli levels even UV treated and filtered water , Boiled water, and filtered water = Recontamination

AcknowledgementsThis study was made possible by the

generous support of Bridgewater State University

and the Middletown Rhode Island Rotary

Club but most of all the tireless commitment of all the staff at

Water for Cambodia.

Non BSF Households suffered diarrhea even when water was boiled or filtered = Recontamination

Zones of Floating Houses in Moat Khla

Methods

Samples of source water, filtered water, and household storage water for BSF and Non-BSF households obtained during user surveys in December 2010 and February 2011

Processed E. coli samples by membrane filtration and incubation at 44.5 °C on modified m-Tech media for 22-24 hours using a HACH portable incubator on site.

Turbidity levels evaluated using a HACH 2100P Turbidimeter.

Means compared using independent t-tests or Mann-Whitney U depending on Kolmogorov-Smirnof test of normality within SPSS.

Lake Source E. coli and Turbidity Increase as Lake Level Drops from December to February

WHO Microbial Risk Low Intermediate High

Range of E.coli (CFU/ 100 ml) <1 1 - 10 11 - 100

101 -1000 >1000

BSF households

Lake Water 0 0 3 (7.5) 23 (57.5) 14 (35)

Directly from BSF 19 (47.5) 15 (37.5) 5 (12.5) 1 (2.5) 0

BSF Treated and stored 17 (42.5) 15 (37.5) 6 (15) 0 2 (5)

Moat Kla Study February 2011: Number (percent) of 40 households drinking water from BSF assessed by WHO Microbial Risk

Categories for E. coli

Number (percent) of 40 BSF and 40 Non-BSF homes in Moat Khla in February 2011 assessed by WHO

microbial risk categories for E. coli

WHO Microbial Risk Low Intermediate High

Range of E.coli (CFU/ 100 ml) <1 1 - 10 11 - 100

101 -1000 >1000

NON-BSF households

Lake Water 0 (0) 1 (2.5) 3 (7.5)21

(52.5) 15 (37.5)NO BSF

NON-BSF stored 8 (20) 6 (15) 10 (25) 8 (20) 8 (20)

Moat Kla Study February 2011: Number (percent) of 40 NON BSFhouseholds drinking water from BSF assessed by WHO Microbial

Risk Categories

E. coli levels in lake source water increased downstream in sample zones closer to the

mouth of Moat Khla

≥ 2.2 Log Reduction of E. coli by BSF in both periods BSF’s provide Low Risk

Drinking Water

More BSF homesMoved from High Risk to

Low Risk than Non-BSF homes

Location of Moat Khla Village