A large volume of water treatment chemicals has been discharged into a canal in Ho Chi Minh City, where at least 70 metric tons of fish died earlier this week, the municipal environment department said Thursday.
Twenty-five metric tons of zeolite, a detox agent commonly used in aquatic cultivation, was used to purify the water in Nhieu Loc-Thi Nghe, one of the city’s major canals, according to the department director Nguyen Toan Thang.
The canal water was tainted by pollutants washed over by rainwater following a heavy downpour on Monday, which led to the mass fish kill.
The environment department has also poured 100kg of dissolved oxygen into the water to sustain marine life there, Thang added.
While the canal was filled with floating bodies of the deceased aquatic animals on Tuesday and Wednesday, competent agencies have so far finished picking up all the dead fish. Initial reports said 70 metric tons of fish died in the incident, but there has yet to be the final statistics.
The chemical discharges have indeed reduced the foul smell caused by the decomposed fish along the 8.7-km canal, snaking through District 1, District 3, Phu Nhuan District, Binh Thanh District and Tan Binh District.
However, test results found that the water in several parts of the canal still had ammonium and ammonia contents exceed allowable levels.
The latest fish death is not unprecedented, as similar incidents were recorded in May 2014 and 2015, when the rainy season began in Ho Chi Minh City, according to the municipal agency in charge of inspecting water quality.
With all of the steps taken so far only meant to resolve the consequences of the fish death instead of preventing similar incidents in the future, the water quality agency suggested that the city administration convene a meeting with competent agencies to figure out the solution.