Bengaluru: The National Green Tribunal (NGT) has raised the alarm over the risk of groundwater contamination in parts of eastern Bengaluru, particularly in 110 villages that continue to function without an underground drainage network.NGT’s southern bench, which took up a suo motu case on pollution of the South Pennar (Thenpennai) river near Hosur in Tamil Nadu, noted that untreated sewage from Bengaluru is entering the waterbody.Reviewing a compliance report submitted by the Bangalore Water Supply and Sewerage Board (BWSSB), the bench, led by Justice Pushpa Sathyanarayana, observed that nearly 30,000 households in these villages still depend on individual soak pits to dispose of sewage. “The continued use of such soak pits without septic tanks requires scrutiny as they may pose a long-term threat to groundwater quality,” the bench wrote in its order last week.The South Pennar river, which originates at Nandi Hills in Chikkaballapur and flows 497km through Karnataka and Tamil Nadu, has become heavily polluted with untreated industrial effluents and domestic sewage from Bengaluru’s urban areas. The frothing and foul odour reported at Kelavarapalli reservoir near Hosur prompted NGT to probe the issue.According to BWSSB, the catchment area in Karnataka generates about 1,329 million litres per day (MLD) of sewage. Sixteen sewage treatment plants (STPs) with a combined capacity of 621.5 MLD are currently in operation, treating around 550 MLD. To address the shortfall, the state govt has proposed 12 new STPs with a total capacity of 225 MLD in the Hebbal and KC Valley limits. Four of these are expected to be ready by Dec 2025, six more by Dec 2026, and the remainder by the end of 2027.Until then, BWSSB admitted, residents of the 30,000 households in question will continue relying on soak pits for sewage disposal, heightening the risk of contamination.
