Risk Management Approach
Our risk management approach is based on a system design which removes the risks associated with traditional rainwater harvesting and can be seen in the diagram below.
Risk management features :
- Leaf gaurd - keeps out larger objects which may contribute to bacterial loading or may provide nutrients for microorganisms.
- First flush diverter - diverts the first flow of water from a roof area away from the tank. This flush of water contains the highest levels of roof contaminants and these are effectively excluded from entering the tank.
- Enclosed tank - prevents human access and excludes light preventing algal growth which provides nutrients for microorganisms.
- Insect and animal screening - prevents animals entering the tank and dying which can be the most significant contributor of contamination to the storage tank.
- Graded base sloped towards a cleaning outlet - enables easy cleaning of the sediment layer which forms in the bottom of the tank. This layer contains microorganisms which if left to build up may contaminate the water. Yearly cleaning of the tank is recommended to prevente this build-up contaminating the water.
As a means to try to ensure consistent high quality water for drinking purposes, the WHO have introduced a risk management approach to drinking water supplies based on Hazard Analysis of Critical Control Points (HACCP).
This is documented as a water safety plan which “provides for an organised and structured system to minimise the chance of failure through oversight or lapse of management and for contingency plans to respond to system failures of unforeseen events”.
RainWater Cambodia has developed a water safety plan for rainwater harvesting, based on WHO recommendations. We are happy to share this with interested parties as we understand it is the only Water Safety Plan document specific to rain water harvesting systems.