Silt rise in Aruvikkara dam sparks water supply fears

THIRUVANATHAPURAM: A sharp rise in silt levels in raw water drawn from the Aruvikkara dam has led to a steep increase in the use of treatment chemicals, raising concerns about the quality and supply of drinking water during the summer, Kerala Water Authority (KWA) officials said. Water treatment plants sourcing water from the reservoir have been forced to significantly step up the use of purification chemicals. These include anionic polymers, used to bind fine silt particles, as well as lime and chlorine. The higher chemical load has reduced treatment efficiency at plants already operating under lean-season conditions. Earlier, treatment facilities used around 250–300kg of chemicals per treatment cycle. That figure has now surged to nearly 3,000kg, placing additional operational stress on the system and making it more challenging to maintain consistent water quality and supply, officials said. A KWA engineer at Aruvikkara said the issue is largely seasonal. During summer, reduced river flow limits the natural flushing of silt. In contrast, monsoon inflows typically carry suspended particles downstream. "During the monsoon, excess flow washes away silt. As summer advances, silt remains suspended in the water for longer periods. This causes turbulence during treatment and affects plant efficiency," he said. He clarified that the increase in chemical usage is solely to manage the elevated silt content in raw water. "The use of anionic polymer has gone up only to remove fine silt. This has affected treatment efficiency, but corrective steps are underway," he added. As part of mitigation efforts, KWA installed a silt curtain in the reservoir to prevent suspended particles from reaching intake points supplying the treatment plants. However, the initial trial did not produce the expected results. "Despite installing the silt curtain, turbulence was still observed at the plants during the first trial. Additional measures are now being implemented, and we expect the situation to stabilize soon," the official said.