Bihar plans its largest sewage treatment plant (STP), a 400 million litres per day (MLD) facility in Patna, to prevent untreated wastewater reaching the Ganga. The urban development and housing department has directed the Bihar Urban Infrastructure Development Corporation (BUIDCO) to initiate the project after a Namami Gange review. The objective is to intercept city drains and divert flows to the STP for treatment prior to release.

Surveys from Digha to Didarganj have identified proposed sites between Danapur and Patna City, with the final location awaiting approval. The design will determine whether the facility is a single 400 MLD unit or two 200 MLD units and will seek to connect major outfalls. The plan will link drains in areas including Digha, Kurji, Rajapur, Mandiri, Anta Ghat and Mittan Ghat while seeking to minimise public inconvenience by using existing channels.

Bihar currently manages 39 STPs with a total outlay of Rs 77,520 mn and plans to increase the number to 45 to treat nearly 1,100 MLD of sewage along the Ganga. Of the 39 projects, 21 are operational in districts including Munger, Bhagalpur, Chhapra and Patna, and the capital runs four plants at Beur, Saidpur, Karmalichak and Pahadi. Facilities in Digha and Kankarbagh are partially functional and 13 further STPs are under construction in districts such as Motihari, Supaul, Jamui and Rohtas.

Officials said construction and commissioning typically take about three years and that the state is processing additional projects to strengthen wastewater management. In addition to the proposed Patna facility, five more STPs are being processed in Khagaria, Jamalpur, Barauni, Samastipur and Gaya to expand capacity. The department has prioritised tapping major drains to curb untreated discharge into the Ganga and to bolster sanitation infrastructure while limiting disruption to residents.