India’s biggest natural sewage treatment plant coming up in Tirupati

TIRUPATI: The Municipal Corporation of Tirupati (MCT) has recently taken up an eco-friendly project – Natural Sewage Treatment Plant (STP) of five million litres per day (MLD) capacity. It is the biggest in the country after the 3 MLD natural STP in Delhi.

The civic body has proposed to recycle sewage – using natural materials and aquatic plants, and re-use it for a number of non-potable purposes.

Recycling and reuse of the treated wastewater are the suggested alternatives to bridge the gap between water demand and supply, and to reduce pressure on water resources.

According to reports, almost 80 per cent of the water supplied to a household is being discharged as wastewater and it has become a potential pollutant of groundwater because it is untreated. In Tirupati, only 30-40 per cent of sewage is being recycled, as of now.

Though the MCT is working on the new 25 MLD large conventional STP, the apathy with regard to this plant lies in the fact that it needs a large infrastructure network and high cost. Instead of relying only on such STPs, the civic body has now planned for the non-conventional STP, which can treat the wastewater in a natural way with less maintenance and minimum cost.

“Natural STPs have sustainable results, as the maintenance of the plant is very easy and cost effective. The treated water would have BOD (Biological Oxygen Demand) and TSS (Total Suspended Solids) values of 10 each. We are now building a 5 MLD natural STP”, MCT Commissioner P.S. Girisha told DC.

The project cost is estimated to be around Rs 14.97 crore and it is expected to be completed in 12 months. The plant will recycle sewage flowing through drains, starting from the upstream areas and passing through areas on the north side of the city, and join the escape drain close to Vinayak Sager lake.

The working process of natural STP is that the sedimentation tank allows the sewage to stand for a long time and the total suspended solids will settle down. Thereafter, the water is passed through chambers and compartments which have beds of pebbles of various sizes, which filters the sewage. At least four species of fast-growing aquatic plants feed on the organic matter in the water.

“What goes into the natural STP is black and grey-coloured highly polluted sewage water. And what comes out is clean water with a reduced level of BOD. The water isn’t potable, but it will be routed into the Vinayak Sagar Lake and in future, it could be routed to other water bodies, for horticulture or recharging ground water”, the Commissioner said.