BENGALURU: Lack of foresight and coordination between two government departments was responsible for froth reaching the lakes of Kolar. The Minor Irrigation Department will flush out the water inside its 55km-long pipeline before resuming the filling of lakes in Kolar.
Both the departments - irrigation department and BWSSB - however, vary in their accounts on what caused the frothing.
While the irrigation department blames an additional supply of 108 MLD treated water by Bengaluru Water Supply and Sewerage Board (BWSSB) on the day of the froth, BWSSB sources point fingers at the demolition of an earthen bund built between Bellandur Lake and Chlorine Contact Tank - the last stage of secondary treatment before water is released.
However, activists fear that a repeat of such incidents could well prove detrimental for villagers in Kolar, where the water is being pumped for groundwater recharge and agriculture.
During a reality check by The New Indian Express, it was learnt that destruction of an earthen bund built to prevent Bellandur Lake water from entering the jackwell near the Chlorine Contact Tank - the last stage of secondary treatment before water is pumped to the lakes - could be one of the reasons for the froth to reach Kolar.
The outlets of all treatment units in the Koramangala-Challaghatta Valley project is directed towards Bellandur Lake. As there is a marginal increase in water levels during rainfall in the Lake, an earthen bund was constructed to prevent backflow.
However, according to sources, the bund - a temporary structure - was removed for some construction work taken up near the Pump House operated by the Minor Irrigation Department. Soon after, there was a back-flow from the Lake due to rainfall in Bengaluru, filling the Tank with untreated water from the lake.
Pumping of this water, according to sources, caused the froth, usually seen in Bellandur.
M Ravindrappa, Chief Engineer (South), Minor Irrigation Department, has disputed the same. “We had no complaint of frothing after we had launched the scheme on June 2.
It happened only after BWSSB started releasing an additional 108 MLD treated water. Within a day after that, we started witnessing froth,” he said.
After the frothing incident, the treated water supply was discontinued. “We have decided to open the slover sluices installed along the 55-km line to flush the water out and restart treated water supply,” he said.
Nityanand Kumar, Chief Engineer (Waste Management) BWSSB refuted the argument and said that only secondary treated water was being provided. “Works for pumping plant from these STPs by Minor Irrigation Department is yet to be completed and only one pump is up and running. Due to rainfall between July 14 and 16 and damage to the earthen bund near the jackwell, water from the lake has likely entered the jackwell,” he said.
Water levels of the Lake near the outlet for secondary treated water raises by about 100-200 mm depending on the amount of rainfall, he added.
Tertiary treatment
Despite assurances by government agencies on the quality of water, activists have demanded that only tertiary treated water is released. Experts feel that since tertiary treatment is expensive, other methods to ensure further treatment should be adopted.
R Anjaneya Reddy, President of Shashvatha Neeravari Horata Samithi said that the villagers were not sure about water quality. “Since problems can arise any time with the secondary treated water, the government should ensure tertiary treatment before releasing water,” he said.
Prof T V Ramachandra, a scientist at the Centre for Ecological Sciences said that it was very likely that secondary treated water contains heavy elements.
To a question on birds thriving at the Chlorine Contact Tank, he said that fish found there had to be tested to check the extent of heavy metal contamination. Noting that tertiary treatment of water will be an expensive affair, he said that BWSSB should adapt purification techniques used in Jakkur Lake to further improve the quality of water.
Second phase of project by March
After the first phase of the project was inaugurated in June this year, the second phase of the lake-filling project using treated sewage water from Bengaluru is expected to be completed by April next year.
Under the second phase of the project, treated water from Hebbal-Nagawara Valley will be used to fill 65 lakes in Bengaluru Urban, Bengaluru Rural and Chikkaballapur districts. According to M Ravindrappa, Chief Engineer (South), Minor Irrigation Department, around 210 MLD of water will be pumped to the lakes, using a pipeline running a total length of 14.93 kms.
Of the treated water, 150 MLD will be pumped from a treatment plant in Hebbal, 40 MLD from Hennur and 20 MLD from Horamavu.