Residents of some southern suburbs are digging deeper not just to find more water but also for better quality.
Groundwater in areas such as Pallavaram, Chromepet, Nagalkeni and Pammal suffers from effluents let out from leather tanneries over the past decades. Though the number of tanneries has dwindled and a common effluent treatment plant has been set up in Pallavaram, the concentration of chromium remains above the permissible limit of 0.05 mg/l.
While residents like S. Vasudevan of Nehru Nagar in Chromepet are purchasing drinking water on alternate days to tackle the water crisis, other residents are sinking deeper borewells. Ashok Thamburajan, a resident of Srinivasa Colony, Pallavaram, said groundwater had been contaminated for over three decades. Water from the wells cannot be used for bathing and is yellowish. “We used to have skin allergies earlier. I have sunk a borewell for 200 feet to source groundwater of better quality,” he said.
Residents noted the effluent was being treated now and released into open drains linked to the Adyar. But a recent study by the Department of Geology, Anna University, has revealed that the groundwater samples from these areas have chromium levels of up to 0.51 mg/litre. The chromium content found in groundwater in 2010 was up to 0.99 mg/l in these localities.
Presence of ions
G. Kanagaraj and Brinda, who were part of the research team, said the water samples were lifted from 36 locations and tested for parameters such as the presence of chromium and major ions, including calcium and sodium chloride. Chromium was found in the Adyar even during the 2015 deluge.
Even the processed effluent released from the plant has a small amount of chromium and high salinity, said Prof. L. Elango, Department of Geology, Anna University. The presence of sodium chloride in groundwater is double the permissible limit of 250 mg/l. “It is necessary to improve the efficiency of the treatment plant and also groundwater recharge structures,” he said.