BWSSB's ambitious plan to treat sewage in Arkavathi

The BWSSB has embarked on an ambitious initiative to purify the sewage flowing from the Arkavathi River to Hesaraghatta in Thippagondanahalli dam using the Natural Biological System (NBS).

The Bangalore Water Supply and Sewage Board would grow several varieties of plants capable of treating the water along the 1.2-km waterbody. "This has worked in Hyderabad's Hussain Sagar dam. This would help purify 85% of the water," said Dr P N Ravindra, chief engineer (Cauvery), BWSSB.

He said Hyderabad-based Akhil Infrastructure Private Limited has been selected following a tender process to implement the Rs 11.49-crore project.

"We are also planning to store the water coming from Yettinahole in the Thippagondanahalli reservoir. The water-testing centre in Malleshwaram has reported that the water here is fit for drinking. The NBS method will stop sewage from entering the dam," he said.

Apart from Hesaraghatta, about 80 lakh litre sewage also enters Thippagondanahalli from Yeshwantpur and the Peenya industrial area through the Madiwala Lake.

Plants as filter

As in the underground system, the NBS would filter away contaminants, only that here plants would be used instead of mud and sand. The plants dissolve nitrate and magnesium, releasing pure water. "The plants would become floodgates that would purify the water as it flows," Ravindra said.

While the NBS unit will be built at Rs 1 lakh, 72 sensors will be fixed to indicate the level of pollution in the surrounding area. The unit would absorb dust, carbon dioxide, sulfur dioxide and nitrogen dioxide present in the immediate surrounding of about 50 metres.