Examining Bengaluru’s Potable Water Quality and the Usage and Consequences of Reverse Osmosis Technology in Treating the City’s Drinking Water

The presence of microbial and chemical impurities in surface and groundwater compels consumers to treat drinking water at the point of consumption. Chemically contaminated groundwater is usually purified by reverse osmosis (RO) technology. However, this technology wastes water as only a portion of raw water is treated and the remaining is discarded as RO reject with almost twice the salinity of the raw water. The study examines the potable water quality, the extent and consequences of usage of RO technology in the BBMP (Bruhat Bengaluru Mahanagara Palike) area of 575 km². Water quality maps indicated that the Cauvery river water is microbially contaminated during travel to the treatment plant. Comparatively, groundwater in some BBMP zones have TDS (total dissolved solids), F (fluoride) and Pb (lead) contamination, while all BBMP zones are contaminated by Fe (iron) and nitrate. Calculations projected that 49% of 29.1 lakh households consume 14.29 MLD (million liters per day) of RO water. Of the 49% households, 43% of households are treating the drinking water appropriately as they solely depend on groundwater. Six percent of households with Cauvery water supply are inappropriately using RO technology as they can consume UV treated Cauvery water. Usage of 14.29 MLD of RO water will generate 14.29–33.3 MLD of RO reject water with elevated salinity levels that eventually reach the inland water bodies. The consequences of elevated salinity levels from sewage discharge on a Bengaluru lake are illustrated.