Summary of the City
A large population in urban and peri-urban areas of Bengaluru depends on water from the Vrishabhavathi valley and Byramangala reservoir for meeting their drinking water needs. However, this water continues to be of questionable quality and has been found to be exposed to severe pollution and deterioration of ground water quality.
Water from eight villages namely Anchipura village, Anchipura colony, Bannigiri, Chikkakuntanahalli, Kodiyala Keranahalli, Kodiyala, Mahadevpura and Kodihalli were analysed.

Water quality information

Bengaluru City

Tap water can mean
(1) Cauvery water (or water supplied by BWSSB through pipelines) that is reasonably good quality
(2) Borewells normally dug in most of the houses
(3) Water supplied by tankers that draw water from very deep borewells with no concern for very dangerous dissolved impurities (including toxic elements like arsenic, mercury, etc.)

Contamination of Drinking water sources
A study finds drinking water in peri-urban areas around Bengaluru has high levels of bacteriological and chemical contaminants making it unfit for consumption.
- As high as 80 percent of water samples at the source was contaminated and presented a moderate to high risk for diarrhoea. Only 20.6 percent of the water samples tested complied with the WHO's permissible limits with respect to E. coli counts.
- The water quality got worse as it reached the household level. Only seven percent of household drinking water samples were found to comply with the WHO's permissible limits while all the remaining drinking water samples (93 percent) were found to be contaminated with coliforms.
- High levels of chemical pollution of water at the source was detected. The water was found to have high levels of total dissolved solids, calcium, magnesium, total alkalinity and nitrates.
- Drinking water from borewells at Byramangala Panchayat was found to be highly polluted with coliforms indicating the possibility of faecal contamination around the areas of the reservoir due to the inflow of sewage and industrial effluents into the reservoir.
- Nitrate levels were greater than the permissible levels in all drinking water sources from the villages surrounding Vrishabhavathi-Byramangala reservoir indicating progressive deterioration of groundwater quality and a high risk to health. High levels of nitrates can increase the risk of methaemoglobinaemia in infants and gastric and prostate cancers in adults.
- Changing seasons was found to influence microbial contamination. Contamination levels due to coliforms and E. coli were found to be lower from January to March during the winter season while they were maximum during September following the summer season.
- The levels of drinking water contamination at the household level were found to be higher than that at the source, which could be due to poor sanitation and hygiene practices, faulty handling and other socio-cultural practices.

Recommended Technology: (NMC)
If you have Cauvery water supply, it is reasonably good quality. May require basic filtration to remove visible impurities. This water is not hard (TDS is optimum) so one can use basic UF or UF + UV filteration.
If you are getting borewell water, make sure you get it tested and use NF 60 + UV or RO + UV filter. While using RO filter, ensure TDS is not very low.