Health risks from drinking water sources can be grouped into microbiological, chemical and physical categories. In emergency situations, often the biological quality of the water is the most important to establish, as microbial pathogens (such as cholera) can have rapid adverse effects on the health of the population exposed to them. The most common source of these microbial pathogens is contamination with either human or animal faeces.
Coliforms are the most commonly used indicator
bacteria for faecal contamination of drinking water. The principle of testingfor indicator bacteria is well
established. It is not practical (especially in challenging
conditions) to test for each potential biological contaminant, as there are too
many possible species to test, and they can also be present and cause illness
in very low concentrations. Coliforms, especially thermotolerant coliforms,
have been selected as markers of biological contamination. They are
relatively simple to test for with a high degree of accuracy and
confirm the presence of generic faecal contamination within a water source.
The Potatest+, and all Wagtech kits, are based around the membrane filtration method for measuring coliforms. This is a laboratory method which has been adapted for field use in which the coliforms are isolated from a water sample by filtration then cultured in to visible-to-the-eye colonies by incubating them with specific culture media at 37◦C (total coliforms) or 44◦C (thermotolerant coliforms). After incubation the user can visually count the colonies and obtain a quantitative result detailing the level of contamination of the water source. This is important as it aids decision making in selecting between alternative potential drinking water sources and deciding treatment strategies for contaminated water.
Water Safety Plans
The other components of the Potatest+ allow
for simple on-site testing of free and total chlorine, pH and
turbidity. These are used for testing treated water, checking that addition of disinfectant chlorine
and pH modification has given the required results, and that the water is safe
to store and consume.
Furthermore, monitoring of chlorine, pH and turbidity assists the implementation of Water Safety Plans (WSPs). WSPs are risk-based assessments of water provision systems which focus on identifying and eliminating hazards.
Once a robust WSP has been implemented which minimises the risk of faecal contamination of drinking water by close management of infrastructure and processes, it is permissible to reduce the frequency of testing for microbial indicators, on the basis that frequent checks of the physical and chemical parameters demonstrate that the system is within control.
The Potatest+ is a lightweight and
portable kit, which contains all the equipment required for testing. The
digital incubator is battery-powered and can test 5 full cycles (up to 100
samples) between charges, making it suitable for remote and challenging
situations where uninterrupted mains power is not available. The kit is
accompanied with graphical instructions in multiple languages which
allow users to undertake the testing without the requirement for specialist
training. The Potatest has been deployed
emergency situations across the world by UN agencies, International NGOs and
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