Managing water in the home: accelerated health gains from improved water supply
Monitoring and evaluating the effectiveness of alternative household water treatment and storage systems and Hazard Analysis at Critical Control Points (HACCP)
The WHO Guidelines for Drinking-water Quality (GDWQ) are adopting the concept of Water Safety Plans and HACCP (Hazard Analysis - Critical Control Points). The WHO GDWQ have long emphasized the identification of key health-related quality constituents for which health-based guideline values are established. In addition, the GDWQ also identify and specify methods to monitor drinking water quality for constituents of health concern. However, an important development in the forthcoming revisions of the guidelines is an increased emphasis on water quality protection and control from source to consumer. Emphasis will be placed on management system to manage and monitor water quality from source to consumer according to a Water Safety Plan (WSP), to encourage stakeholder participation and mobilization, and to stress the need for communication and education about water quality and how safe water quality can be achieved. A Water Safety Plan includes: (1) risk assessment to define potential health outcomes of water supply, (2) system assessment to determine the ability of the water supply system to remove pathogens and achieve defined water quality targets, (3) process control using HACCP, and (4) process/system documentation for both steady state and incident-based (e.g., failure or fault event) management. It is recommended that HACCP for household water collection, treatment and storage be applied in the context of a Water Safety Plan that addresses source water quality, water collection, water treatment, water storage and water use.
2 HACCP for recommended household water storage and treatment systems
2.1 Household water storage
As shown in Table 18, the application of HACCP to water storage in household vessels is likely to address three hazards and their critical control points (CCPs): (1) vessel type (appropriate versus inappropriate), (1) vessel integrity (intact, damaged, parts missing, etc.), and (3) vessel sanitation (cleaned, not cleaned and a system to monitor and document cleaning frequency). For each type of storage vessel a set of specific hazards, critical control points and other criteria for a HACCP plan can be established. For example, for household storage of water according to the CDC "Safewater" system, a preferred vessel design and alternative vessel designs that are considered suitable are provided, as are vessel designs and types considered unsafe for sanitation reasons (no cover, wide opening allowing introduction of hands and dippers, etc.) (CDC Safewater, 2000). For the solar disinfection system using sunlight for heating and UV-irradiating water (SODIS and SOLAIR), recommended or preferred vessels are identified (including vessel size and type of plastic), criteria for the integrity of the vessel are specified (e.g., absence of scratches and surface damage that would reduce light penetration), and the maximum time period of water storage is specified (to avoid degradation of the microbial quality of water and biofilm accumulation due to bacterial regrowth). These and other hazards and their critical control points can be specified for each type of water storage vessel and system.
Table 18. HACCP for Household Water Storage Vessels: Hazards and Criteria for Critical Control Points
|Hazard||Vessel Type||Vessel Integrity||Vessel Sanitation|
|Critical Control Point(s)||Appropriate or not appropriate, based on design||Intact or not intact, based on visible damage (e.g., cracks, scratches), broken or missing parts (e.g., cap) and leaks||Sanitary or nor sanitary, based on frequency of cleaning and cleaning method|
2.2 Household water treatment
As previously stated above, it is recommended that HACCP for household water treatment be applied in the context of a Water Safety Plan that addresses source water quality, water collection, water treatment, water storage and use. For each type of household water treatment and its application in practice, generic water safety plans can be developed and these can then be adapted to site-specific conditions and situations of their use for drinking water management. As shown in Table 19, the hazards and critical control points for household water treatment include: choice of source water and type of treatment. Also important are methods of source water collection and conditions of treated water storage and use. The HACCP program within a Water Safety Plan should identify the hazards and critical control points for all steps and activities in the overall plan from source water quality to the product at the point of consumer use. Some of the key hazards and critical control points for source water and for alternative household water treatments are summarized in Table 19. The hazards and critical control points described here are not intended to be comprehensive or complete. Instead they are intended to be representative of the important hazards (failures and deficiencies) and their critical control points for some of the key household water treatments identified and recommended in this report. Further efforts will be needed to better specify and develop HACCP plans for these water treatment technologies on both a generic (general) as well as site-specific basis. It is important to note that HACCP plans are always best articulated on a site-specific basis, even though the key elements of the plan are often common to a particular type of commodity, technology and process train.
Table 19. HACCP for Household Water Treatment: Hazards and Critical Control Points
|Type of Treatment||Source Water Hazards||Source Water Critical Control Point(s)||Treatment Hazards||Treatment Critical Control Points|
|Heating to boiling with fuel||Contaminated or uncontaminated?||Choose best available source||Inadequate temperature achieved||Heat to a visible rolling boil|
|Solar Radiation in clear plastic bottles (heat + UV radiation or heat only)||Contaminated or uncontaminated?Turbid? UV-absorbing solutes||Choose best available source, with low turbidity and low UV-absorbing solutes||Inadequate sunlight to achieve target temperature and UV dose||Target temperature sensor (thermometer or melting wax); elapsed exposure time (timer, clock, sun position, etc.); monitor/observe weather (sunny, part sun or cloudy)|
|Solar radiation (cooker or reflector) in opaque vessel (heat only)||Contaminated or uncontaminated? Turbid?||Choose best available source, with low turbidity||Inadequate sunlight to achieve target temperature||Target temperature sensor (thermometer or melting wax); elapsed exposure time (timer, clock, sun position, etc.); monitor/observe weather (sunny, part sun or cloudy)|
|UV irradiation with lamps||Contaminated or uncontaminated? Turbid? UV-absorbing solutes?||Choose best available source, with low turbidity and low UV-absorbing solutes||No electrical power to UV lamp; poor water quality||Assure a reliable source of electrical power to UV lamp; assure adequate water quality (based on turbidity and UV-absorbing materials)|
|Settling; plain sedimentation||Contaminated or uncontaminated? Turbid?||Choose best available source, with low turbidity||Poor settling of turbidity (suspended matter)||Observe (monitor) for adequate turbidity (cloudiness) reduction|
|Filtration methods||Contaminated or uncontaminated? Turbid?||Choose best available source, with low turbidity||Poor filtration and turbidity reduction||Observe (monitor) for adequate turbidity (cloudiness) reduction|
|Chlorination or mixed oxidants from electrolysis of brine (NaCl)||Contaminated or uncontaminated? Turbid? Chlorine-demanding solutes?||Choose best available source, with low turbidity and low chlorine demand||Poor chlorination due to inadequate dose and contact time||Observe (monitor) for chlorine residual (C) and for adequate contact time (T), i.e., adequate CT|
|Combined chemical coagulation + chlorination systems||Contaminated or uncontaminated? Turbid? Chlorine-demanding solutes?||Choose best available source, with low turbidity and low chlorine demand||Poor treatment due to inadequate turbidity removal and chlorine dose||Observe (monitor) for turbidity (cloudiness) reduction and adequate CT (chlorine residual and contact time)|
2.3 Summary of HACCP for household water systems
Consistent with the forthcoming WHO GDWQ, collection, treatment and storage of household water should be developed and managed according to a Water Safety Plan that includes HACCP as a management tool. For household water, hazards and critical control points can be identified for the management steps in a water safety plan that includes source water selection and protection, water collection, water treatment and water storage, including storage vessel type and its use. The approaches and examples provided here are intended to be only exemplary and not comprehensive