Out of sight, out of mind. That is perhaps what the Bangalore Water Supply and Sewerage Board (BWSSB) is hoping for as it attempts to tackle the froth of Bellandur and Varthur lakes — the sight of which had catapulted them to national attention — through a siphon system.
After tasting success with their ‘trial’ at Varthur Kodi in April, officials plan to replicate the system at four other outlets that are prone to froth and foam. This, emphasise officials, is only a stop-gap method till Sewage Treatment Plants (STPs) are set up to weed out chemicals from raw sewage.
In April, a series of pipes was installed at Varthur Kodi where froth routinely overflowed into the busy intersection of Old Airport Road and Whitefield Main Road. Working on the principle of suction, the pipes allow water to flow out of the waste weir without cascading, thereby reducing the churning motion of the phosphorus-heavy sewage that causes froth.
The trial runs of the siphons at Varthur waste weir had reduced froth formation by nearly 75%, said Ramakrishna S.M., Chief Engineer (Waste Water Management), BWSSB. The system had cost the Board ₹5 lakh and less than a week to set up.
“Other methods, including sloping the waste weir, did not lead to reduction of froth. As siphons have helped, we have invited companies that can provide better designs to tackle froth in weirs,” he said.
The Board is now seeking to extend this system to four outlets where froth has been a problem: Kempapura and Bellandur outlets (cumulatively 460 million litres of sewage a day) of Bellandur lake; and Varthur and Panathur outlets of Varthur lake (558MLD of sewage).
“While froth has reduced in Varthur Kodi, the system has led to increased outflow in the other outlets,” said Jagadish Reddy of Varthur Rising. “The outflow of water through this weir has reduced by 30% due to the narrow pipes. This means that other outlets are seeing more water flow. We have apprehensions whether the system can function during or whether it can even withstand heavy rains,” he said.
