Based on WHO drinking water quality standards and field studies conducted in Burkina Faso, Ethiopia, and Nepal, the Rain Water Harvesting Implementation Network (RAIN) has established the following standards:
To achieve these standards, RAIN has recommended the following techniques:
1. Sampling and collection:
Undertake sampling between rainfalls; agricultural pesticides and pathogens such as E-Coli are more concentrated immediately after runoffs from rainfall.
Clear debris and silt from storage tanks and runoff pipes.
Handle collected water in a hygienic manner.
2. Analytical process
Try to perform testing directly on-site. Harvesting systems are distant from large cities and require long transportation times which can alter results.
The testing process should be conducted by a trained professional, capable of collecting accurate storage samples in the field.
To improve drinking water quality, the following techniques may be used:
Chlorination: treating collected water with chlorine effectively removes and disinfects bacteria and virus, but may adversely affect taste.
Bio-sand filter: achieves moderate reduction in bacterial and virus removal and should be accompanied by other filtration techniques.
Aluminum Sulphate: treatment is especially effective for bacterial removal and moderately effective for virus removal. Post-cure may alter color, but not taste.
Moringa olelfera and stenopetala: these potent antioxidants enhances flocculation and are highly effective in removing bacteria and virus. May result in turbid water, but no affect on taste.
Boiling: this timeless method kills bacteria’s through heat with no affect on taste or color.
SODIS (Solar Water Disinfection): Place a PET or glass bottle, with tightened cap, under direct sun for 6 hours. Prolonged UV-radiation effectively removes bacterial pathogens and has no effect on taste or color.
RAIN has recently published a guidebook solely dedicated to instructing users on rainwater harvesting. Information was taken from researchers and institutions using concrete experiences in the field and best-practice examples. The ultimate objective is to help users “improve and maintain an acceptable water quality of harvested rainwater for drinking purposes.”