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Community Controled Water Quality Monitoring
San Juan del Sur, Nicaragua
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The purpose of this project was to demonstrate the feasibility of community based monitoring and upgrading of the quality of drinking water, and to respond directly to the need expressed by community members in the San Juan del Sur district of Nicaragua for assistance in this effort. Project personnel worked with designated rural communities to develop procedures for periodic testing of the open dug wells that are the major source of water in the rural areas of the region, and to construct and maintain barrel treatment units.
For Nicaragua as a whole, the Pan American Health Organization presents the following picture in relation to water supply and waste disposal:
The estimated number of housing units in the country, as of 1992, was 621,926, of which 46.6% received drinking water from water supply systems administered by INAA [the formal government water and sanitation agency], 21.5% from excavated wells, 12.7% from rivers and ponds, 15.5% from public hydrants, and 3.9% from cistern trucks. As for disposal of excreta and wastewater, 21.9% of the housing units were connected to sewerage systems, 8.1% had cesspools or septic tanks, 55.7% had latrines, and 14.2% had no system (PAHO, 1998).
Within the project area, only the towns of Rivas and San Juan del Sur have piped water supply systems that are centrally administered. In the rural areas, water is obtained from dug wells and rivers. Enteric intestinal disease is among the three highest causes of mortality for the population as a whole, and for infants and young children, it is the leading cause of death (PAHO, 1998).
In the aftermath of hurricane Mitch, and after the extraordinary rains of 1999, there was an attempt by individual community members to conduct emergency dosing of community wells with chlorine bleach in manifestly contaminated wells. CTripleS provided these individuals with some basic guidelines on chlorine dose, contact time, well water mixing , and simplified residual chlorine measurement using swimming pool indicator strips. The outcome and efficacy of these limited response measures for the communities could not be evaluated as there was no capability for microbiological testing and monitoring.
It was apparent that improvement in drinking water quality sufficient to reduce water borne disease incidence in these isolated communities would require a routine testing and monitoring program conducted by the community in order to provide information to guide corrective action.
Goals: The focus of this project was consistent with one of the major goals of the Pan American Health Organization (PAHO) in regard to water and sanitation in the region:
To increase community participation in water and sanitation, specially (sic.) in rural and marginal urban areas.
To this end, the project had the following specific goals:
1. Develop procedures for the systematic monitoring of wells for enteric bacteria, in concert with community members and personnel from a local health center.
2. Assist community members in gaining the skills to implement the procedures effectively.
3. Validate the reliability, acceptability and ease of use of the H2S test in this environment.
4. Validate the reliability, acceptability and ease of use of the Phase Change Incubator in this environment.
5. Lead community assessment of environmental threats to water quality and propose strategies for their amelioration.
6. Document the process developed, identifying both difficulties and facilitating factors, so that the project could be replicated in other areas experiencing similar challenges to maintaining safe drinking water supplies.
Recognition that water quality monitoring is absolutely critical to the success of any water resource protection initiative in the communities led us to research existing technologies that would be appropriate and effective for this purpose. Given the extremely limited resources available in the communities and the lack of official commitment to this function, the standard methods routinely used in the U.S. for the microbial examination of drinking water had to be excluded from consideration. Running complex, expensive equipment, maintaining aseptic testing areas, assuring a dependable supply of expensive consumables, and training personnel to a high level of technical competence are all beyond the capability of a community run program. Commercial test methods designed specifically for use in the field also require prohibitive capital outlay for simplified field instruments, a reliable source of electricity, high levels of technical expertise, and expensive consumables (i.e. single-use, disposable, pre-sterilized test units). Millipore bacterial samplers were found to be the only commercial test unit which could “stand alone” and be successfully performed with minimal training. Unfortunately, obtainable sensitivity is very inadequate for point of use drinking water testing of coliform bacteria, and their cost of $5-6 U.S. per sample is not sustainable by the community.
The International Development Research Council (IDRC) in Canada has historically promoted the development of appropriate technology for conditions in less developed countries, with considerable emphasis on innovative public health measures. The organization has developed several simplified field methods for the determination of bacteria in drinking water for these settings. These are not rigid protocols, but are offered as general procedures to be tailored to site-specific conditions. One of these approaches, the H2S test, appeared capable of truly meeting the monitoring objectives within the resource constraints of the San Juan del Sur region of Nicaragua and similar settings.
The H2S Test: This is a very straightforward qualitative approach (potentially semi-quantitative) for determining the presence of enteric bacteria in water. Growth media for these bacteria, along with an indicator chemical for hydrogen sulfide, are impregnated into a strip of filter paper. The filter paper is placed in a reusable, capped glass test tube and sterilized before use. Sterilization is accomplished without an autoclave, successfully demonstrated in a can, an oven, and with some reports of successful use by placing the tubes by the side of a cookfire. For testing, a water sample is transferred into the sterilized tube, re-capped and incubated for 24 hours (preferably at 35-38 deg. C). Black color development in the tube indicates the presence of enteric bacteria in the water sample. The test tubes are reusable, with the only consumable being a new filter paper strip. The inexpensive impregnated filter paper strips are estimated to remain viable for up to six months at ambient temperatures. Semi-quantitative enumeration of bacteria can be achieved, rather than mere “presence or absence.”
Incubator: While use of an incubator is not strictly necessary for the most basic application of the H2S test, its incorporation greatly increases the sensitivity and reproducibility of the procedure. Existing commercial incubators which require electrical power and associated maintenance are too costly and complex for use by these communities. Recently, however, Amtek International has developed an inexpensive field incubator which is “no moving parts” simple, demonstrates good temperature control, and has no electrical power requirement. We sought to maximize the inherent potential of the H2S test by incorporating a prototype Phase Change Incubator fabricated specifically for this project.
Water Characterization Testing: Initial well water chemical characteristics and bacterial screening by Millipore samplers was carried out to provide a baseline for optimal chlorine disinfection regimens. After chlorination, residual chlorine was measured to verify the acurracy of chlorine test strips used by and left with the community.
Inter-Method Equivalency Trials: The H2S test has been successfully validated against standard methods in a number of environments in extensive field trials in Chile, Malaysia, Arctic Canada, and other areas (Sanchez and Dutka, 1998). The intermethod comparisons which are best documented, however, have for the most part involved trials in communities with at least some rudimentary water distribution system and formalized water management structure. Given the adverse conditions encountered in this field trial, it was important that H2S test results be site validated by an EPA approved method.
The referee method we chose to use was the Colilert* test. The choice was based on the following criteria: it is approved as a standard method by the USEPA; it is highly specific for E. Coli; it is easy to conduct in the field without an aseptic testing area; and the Phase Change Incubator can also be employed for the test in lieu of the commercial unit specified by the Colilert manufacturer. Its relatively high cost per test and requirement for consumables precludes its use for routine testing by the community. (Cost of the H2S test is estimated to be approximately $0.15 per sample once the procedures were established for this locale.) Ten percent of the project samples were verified by Cholilert, in accordance with EPA performance based protocol.* Cholilert is a registered trademark of IDEXX Laboratories, Inc.
Water Filterability Characterization: It is well recognized that a dependable supply of safe potable water cannot be developed in the communities and maintained over time solely by emergency response chlorine disinfection. Both cyst removal and maintenance of stable, low level disinfectant residual require pre-treatment by filtration. Filterability characteristics and their relation to chlorine requirements and bacterial removal were determined by syringe filter cartridges. We subsequently assisted community members to fabricate slow sand filters out of plastic barrels.
Disinfection of Stored Water: While the primary objective of this project was to assist local communities in acquiring the knowledge and skills necessary to monitor their primary drinking water sources, the high levels of contamination found led us to focus on targets for secondary disinfection, providing instruction for disinfection of household stored water supplies and test strips for routine monitoring of adequate disinfection residual.
To read a description of the challenges of implementing this project in the remote towns of Monte Cristo and San Antonio, click here
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