Standards for harvested rainwater

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.

To for more information and to see full report, visit www.rainwaterfoundation.org

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.”