VARANASI, Nov. 1 -- The recent death of a large number of small fish along the banks of the Varuna river, between the Old Bridge and Nakkhi Ghat, was caused by low dissolved oxygen (DO) levels in the water, according to regional pollution control officer Rohit Singh. Singh said that water samples collected from various points in the river were tested at the Regional Pollution Control Office laboratory. The results showed dissolved oxygen levels of 0.5 mg/L at Nakkhi Ghat, 0.5 mg/L downstream, and 0.4 mg/L near the Old Bridge which is significantly below the healthy range of 6.5 to 8 mg/L. "At first glance, the incident appears to have occurred due to low dissolved oxygen levels in the Varuna river," Singh stated. He further noted that interceptors installed on both banks of the Varuna river, designed to collect and transport sewage from nearby drains, were found to be non-functional. As a result, untreated wastewater overflowed directly into the river, severely affecting water quality. The chief executive officer of the fishermen development agency also confirmed that a large number of small fish, including beadfish, were found dead near the site. A significant amount of garbage and untreated sewage was seen floating in the water, turning it black. He added that the absence of a functional sewage treatment plant (STP) along the Varuna river has worsened pollution levels. "Cloudy weather and the discharge of contaminated sewer water into the river may have increased carbon dioxide and reduced oxygen levels, leading to the deaths of fish species such as chelva, puthiya, girhi and bata," the officer said. Tests confirmed dissolved oxygen levels of 0.4-0.5 mg/L, which are fatal for aquatic life, as fish begin to die when oxygen levels drop below 2 ppm. During the inspection, officials observed people throwing religious offerings and garbage into the river from the overbridge, further polluting the water. The presence of flocculent deposits was also noted. To improve water quality, officials suggested spraying 20-25 tonnes of slaked lime over a one-kilometre stretch of the river from Nakkhi Ghat Bridge to restore oxygen levels and prevent further deaths of fish and birds. In response, additional municipal commissioner Savita Yadav said that surface waste such as plastic, flowers, garlands, and water hyacinth is being regularly removed by roster-wise trash skimmers. "Anti-larval insecticides are also sprayed periodically," she added....