Organic pollution killed fishes at Hajo
Pollution Control Board, Assam (PCBA) has detected high Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) in the Bishnu Puskar Pukhuri (pond), HayGrib Madhab Mandir, Hajo which resulted in death of large number of fishes in the pond recently.
In tests conducted by the experts of the PCBA in the central laboratory of the board on the water sample collected from the five different parts of the pond it was found that high COD and BOD values indicate organic pollution in the pond.
Chief environmental scientist of the central laboratory of the PCBA, KS Chakraborty told the media presence of organic waste contamination from external and internal sources resulting in depletion of dissolved oxygen in the pond water (low value of dissolved oxygen was observed in analysis report).
Chakraborty said low dissolved oxygen (DO) level could be one of the main reasons for such fish kill.
PCBA found pH, conductivity and alkalinity values were in normal range in the pond which eliminates the possibility of acidic and alkaline adversities.
Chloride, phosphate and nitrate concentrations appear to be in higher trend which indicate optimum nutritional value of pond water to facilitate over growth of phyto-plankton (algae and others) may have lead to damage of water quality through eutrophication,” Chakraborty said.
PCBA has also suggested measures for improvement of water quality and for survival of fishes of the Pukhuri.
PCBA’s expert said bottom benthic sludge in the pond need to be cleaned up immediately and partial change of stagnant water of the pond may be arranged immediately.
PCBA also suggested stopping discharge of waste matters or waste-water if any to the pond immediately.
Flowers, leaves, fruits and other food materials should either not be disposed in the pukhuri or removed before sun-set everyday.
Minimum 1.5 to 2.5 meter of water depth should be maintained in the pond all through the year.
Optimum level of fish population should be maintained in consultation with fishery department.
A fixed or floating fountain may be provided at the centre of the pond to maintain optimum dissolve oxygen level through aeration of the water. This will add to the beauty of the pond and help in the reduction of organic pollution load.