Field trial of an automated batch chlorinator system at shared water points in an urban community of Dhaka, Bangladesh

Point-of-use water treatment with chlorine is underutilized in low-income households. The Zimba, an automated batch chlorinator, requires no electricity or moving parts, and can be installed at shared water points with intermittent flow. We conducted a small-scale trial to assess the acceptability and quality of Zimba-treated municipal water. Fieldworkers collected stored drinking water over a 10-week period from control (n1⁄4 24 households) and treatment (n1⁄4 30 households) compounds to assess levels of free chlorine and E. coli contamination. Overall, 80% of stored drinking water samples had a safe chlorine residual among treatment households, compared to 29% among control households (P< 0.001). Concentrations of E. coli were lower (mean difference1⁄4 0.4 log colony-forming units/ 100 mL, P1⁄4 0.004) in treatment compared to control households. Fifty-three percent of mothers (n1⁄4 17), thought the Zimba was easy to use and 76% were satisfied with the taste. The majority of mothers mentioned that collecting water from the Zimba took more time and created a long queue at the handpump. The Zimba successfully chlorinated household stored drinking water; however, further technology development is required to address user preferences. The Zimba may be a good option for point-of-collection water treatment in areas where queuing for water is uncommon. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). doi: 10.2166/washdev.2016.027 om https://iwaponline.com/washdev/article-pdf/6/1/32/595145/washdev0060032.pdf 2020 Nuhu Amin Leanne Unicomb Kishor K. Das Partha Sarathi Gope Zahid Hayat Mahmud M. Sirajul Islam Stephen P. Luby International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh Yoshika S. Crider Jennifer Davis Stephen P. Luby Amy J. Pickering (corresponding author) Stanford University, Stanford, CA, USA E-mail: amyjanel@stanford.edu

dosage volumes (i.e., for 5, 10 or 20 L) (Clasen & Edmondson ; Kremer et al. a, b), and users may not know how to measure out different sized chlorine doses. There are limited options for low-cost, accessible water treatment for larger (>10 L per day) quantities of water. Similarly, smaller amounts (i.e., one glass or jug) are not easily dosed with the same products used for more common larger collection volumes.
Because of the barriers to POU water treatment, manual chlorine dispensers have been promoted to encourage households to treat their water at the time they collect it (Kremer et al. a, b). Manual chlorine dispensers are designed to add 3 mL of diluted chlorine to 10-20 L of water (depending on the concentration) with the turn of a knob. These dispensers are installed next to communal water points (Kremer et al. a, b). Manual dispensers have certain advantages over POU treatments with liquid chlorine at the household level (Lantagne ), since the dispenser provides the correct dosing if the collection container is a standard size (no need to measure chlorine) and also takes advantage of peer-effects when installed at public sources (Kremer et al. a, b). Nevertheless, the manual chlorine dispenser still requires users to add chlorine during each water collection event, and to calculate the number of turns necessary for their vessel size (International Centre for Diarrhoeal Disease Research, Bangladesh icddr,b ).
The Zimba automated batch chlorinator was invented to reduce barriers to water treatment by focusing on automated treatment at the community level. The Zimba attaches to handpumps and dispenses a dose of 3 mL of NaOCl solution into a mixing chamber for every 10 L-batch of water that flows through the device. After chlorination, water is flushed by an automatic siphon into a storage reservoir In our study area, water was extracted through a motorized pump attached to network pipes that connect to a deep borewell maintained by the Dhaka Water Supply and Sewerage Authority (DWASA). The borewell was also equipped with a broken chlorine injector; the operator of DWASA did not know when it would be repaired. Regular interruptions in the pump's electricity supply cause the distribution system to become unpressurized. DWASA also intentionally distributes water intermittently in some areas because demand exceeds supply. When the system becomes unpressurized, sewage can be sucked into damaged pipes that pass through the open drainage system (Kumpel & Nelson ).
Each of the water collection points (handpumps) in our study area was located within a compound and was used for drinking and other household uses. All study compounds met the following eligibility criteria: (1) the water point was located in a compound and shared by 5-30 households, (2) the water point delivered water from the DWASA distribution system, (3) the water was extracted by a manual handpump, and (4) the water point was the compound's primary drinking water source.

Sample frame
We selected Dhamalcot slum at Bhashantek, Mirpur, where the household compounds were divided by four separate streets. From these streets we purposively selected the two longest streets and randomly assigned one street to control and another street to treatment with the Zimba. We assigned treatment by street to avoid contamination between treatment and control groups. Fieldworkers used convenience sampling to enroll six eligible compounds from the street of treatment compounds and five eligible compounds from the street of control compounds. Fieldworkers also used convenience sampling to select five households from each treatment and control compound to participate in household surveys at baseline and end-line; mothers with at least one child under 5 years were given preference for enrollment ( Figure S1).
Trained fieldworkers visited eligible households to describe the study prior to collecting baseline information.
Fieldworkers introduced the Zimba to mothers in the compounds, explained its advantages and disadvantages, and showed how it worked using pictorial cue cards. The fieldworker provided a consent form written in Bengali and requested mothers to discuss the study and the device with other household members, then collected the signed consent on the following visit. Fieldworkers also obtained written consent from the landlord/compound managers.
The study protocol was reviewed and approved by the Institutional Scientific and Ethical Review Committees at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) (protocol number # PR-09048).

Baseline survey and household water testing
Fieldworkers conducted quantitative surveys with mothers (five surveys from each compound) to gather information on demographic characteristics of households, perceptions of drinking water quality, water collection and storage practice, water treatment practice and satisfaction with the current water supply. In each compound, a fieldworker then tested the existing water supply (handpump and stored water) from all households for water turbidity and free and total chlorine using a digital colorimeter (LaMotte Model 1200, LaMotte Company, Chestertown, Maryland) and turbidity meter (LaMotte Model 2020i, LaMotte Company, Chestertown, Maryland). The fieldworker then collected handpump and stored water samples from all households using 300 mL sterile sample collection bags containing a sodium thiosulphate tablet (Nasco Whirl-Pak ® , 19 × 38 cm, Fort Atkinson, Wisconsin) to neutralize any chlorine that could be present. Samples were immediately placed into a cold box, maintained at <10 W C with ice packs, and sent to the Environmental Microbiology Laboratory at icddr,b to assess levels of E. coli and total coliform contamination.

Description of the Zimba
The Zimba is made of three parts: a dispenser containing diluted household bleach (NaOCl), a dosing chamber containing an automated siphon, and an outer box that holds the siphon tank and the dispenser ( fill the trap. The trap was designed to hold 3 mL of NaOCl.

Chlorine purchase and dilution
Two fieldworkers purchased household bleach (∼5.25% NaOCl) from the local market and diluted it with distilled water to a concentration of 0.6% NaOCl to achieve 2 mg/L of free residual chlorine when added by the Zimba to source water. The concentration of chlorine was closely monitored before delivery. We eventually reduced the NaOCl concentration to 0.4% to achieve ∼1.5 mg/L of free chlorine in source water because study participants complained about the strong smell of chlorine. The same two fieldworkers refilled all Zimba dispensers with chlorine twice a week.

Intervention delivery
At least one day prior to installation of the Zimba, an intervention promoter held compound-wide meetings with study participants to introduce chlorinated water and its potential health benefits and to give instructions for using the Zimba.
During promotional activities, fieldworkers advised study participants to drink the treated water 30 minutes after collection to allow time for disinfection. The fieldworkers also requested that study participants share this information with other household members. With the help of a local handpump mechanic, fieldworkers increased the height of the handpump by 12 inches and installed Zimba chlorine dispensers in the six treatment compounds. The mechanic also maintained the handpumps throughout the study period.

Follow-up and end-line surveys
During twice-weekly follow-up visits and one end-line visit, fieldworkers collected two types of water samples from treatment households: treated Zimba water directly from its secondary tank, and household stored drinking water.
From control households they collected handpump water and stored drinking water. At the end of the three-month intervention, fieldworkers conducted an end-line quantitative survey to assess satisfaction with the current water system and perceptions of water taste, smell, and water quality among control and treatment compounds enrolled at baseline. Fieldworkers also administered the survey to new households with children under 5 years old that moved into the compounds during the study period. One duplicate sample was analyzed for every 10th sample collected; one lab blank (100 mL distilled water) was filtered each day as a control. Plates with >500 CFU were not feasible to count because the colonies cannot be distinguished from each other; growth is also inhibited due to crowding.

Quantitative data analysis
To compare the mean difference between groups, microbial water quality samples under the detection limit were assigned the value of 0.5 CFU/100 mL and samples above the detection limit were assigned the value of 500 CFU/100 mL. To compare the mean difference within groups and between control and treatment stored water samples we converted bacterial counts into log 10 scale and performed regression modeling, adjusted for clustering at the compound level. We adjusted compound level clustering using robust standard error of the mean difference. See supplemental information for further details.

Qualitative data analysis
The fieldworker who recorded all in-depth interviews down-  (Table S1).

Water collection and storage practice
Fourteen (58%) mothers in control households and 13 (43%) mothers in treatment households collected their drinking water using a plastic pitcher/jug (2-3 L). All control and treatment households (100%) stored their drinking water; 19 (79%) control households and 20 (67%) treatment households reported usually covering their stored water with a lid.
On average, water was available at handpumps for more than 20 hours per day in all households (Table S1). About 8 L of water per person was collected for cooking, storing and drinking in a typical day in both control and treatment households.
Among all treatment and control households, only one treatment household reported treating their drinking water by boiling (Table S1).  (Table S1).

Follow-up and end-line visits
Accuracy and consistency of chlorine dosing at treatment households All water samples collected immediately after chlorination from the Zimba (100%) were within the 0.2-2 mg/L range for free chlorine (mean ¼ 1.3 mg/L, SD ¼ 0.54) and total chlorine (mean ¼ 1.4 mg/L, SD ¼ 0.58). Mean free and total chlorine levels in household stored water samples were significantly higher in treatment households compared to control households (mean difference of free chlorine ¼ 0.33, P < 0.001). In treatment households, 16 (20%) stored water samples contained <0.2 mg/L of free chlorine (Table 1). Average free chlorine in water samples collected directly from the Zimba was 1.3 mg/L and in stored water was 0.5 mg/L (Table 1, Figure 2).

Microbial water quality in control and treatment households
All processed laboratory blanks were free from contami-  (Figure 3). In treatment households, stored water samples with free chlorine within the 0.2-2 mg/L range had less bacterial contamination (log-mean E. coli ¼ À0.3CFU/ 100 mL) compared to samples with chlorine level <0.2 mg/L (log-mean E. coli ¼ 0.5 CFU/100 mL; log-mean difference ¼ 0.52, P ¼ 0.001).
Only 6% of E. coli samples were TNTC so this did not meaningfully affect E. coli analysis, but it may have affected the total coliform analysis.

End-line surveys
Acceptability and perception of water supply in control and treatment households At end-line, 3 (12%) mothers from control households stated that they were not satisfied with their water due to its poor quality, and 5 (29%) mothers from treatment households mentioned that they were not satisfied with their water due to the bad smell (chlorine). In control and treatment households 100% of mothers mentioned that the drinking water from their current water source is safe to drink (Supplemental information Table S2).

Acceptability of Zimba
At end-line, only one (4%) respondent from a control household and five (29%) respondents from treatment households reported a bad (chlorine) smell in their drinking water.
Among the Zimba users who kept using the Zimba for 12 weeks, only half (53%) the mothers thought the device was easy to use, but most (88%) were satisfied with it. Thirteen (76%) mothers were satisfied with the water taste, and 12 (71%) were satisfied with the smell. Fourteen (85%) mothers believed that drinking Zimba chlorinated water was healthier for their families.

Qualitative assessment
During the qualitative in-depth interviews (n ¼ 12) in treatment households, most of the mothers (9 out of 12) mentioned that the machine purified the water by killing germs. Some respondents also described the Zimba as a water filter. All mentioned that the water had a medicinal smell, but they became accustomed to it during the course   of the study. All mothers also mentioned that they obtained all drinking water from the Zimba because it was safe for their children. Most mothers (10 out of 12) mentioned that the first few weeks after installation of the Zimba they noticed a strong smell of chlorine but only two respondents complained of bad taste. All mothers also mentioned that they considered drinking chlorinated water to be safer than drinking untreated water and that treating water with chlorine could prevent diseases. Most users (9 out of 12) reported that they liked the Zimba but collecting small amounts of water (i.e., one glass or one jug [2-3 L]) took more time and created a long queue. One mother said, 'Before installing the machine (Zimba) we did not need to wait for water, but now we have to wait for water which makes a long queue.' Some (3 out of 12) mentioned that the increased height of the handpump made it difficult to pump water, particularly for children. Mothers also mentioned that they would not be able to refill the Zimba chlorine dispenser because of its complexity. They also requested technical assistance for repair and refilling of the Zimba dispenser.

DISCUSSION
The concentration of free residual chlorine in water samples collected directly from Zimba automated chlorine dispensers was consistently observed to be within the World

).
One important contribution to the low adoption rates of POU water treatment using NaOCl is the unpleasant taste and/or smell in treated water (Clasen &