Locals said ammonia-mixed water from around the dislodged gas tank at Di-Ammonium Phosphate Fertilizer Company Ltd was pouring into a nearby canal which goes into River Karnaphuli.
There is a creek running beside the fertiliser factory which is linked to Gobadia Khal. Locals said the ammonia-mixed water turned the canal water yellow and eventually loads of shrimp and other fish died.
The stench of rotting fish has spread all over the adjoining areas.
MA Kayum Shah, chairman of Baroshata Union under Anwara upazila said they had came across dead snakes and frogs beside the fertiliser factory.
“The toxic gas caused a massive damage to the environment. Trees within a one km radius from the tank have shriveled up and died. Rotten fish are spreading odour in the area,” said the UP chairman.
Kayum alleged that the massive amount of water that had been sprayed by authorities to keep the ammonia from the air was pouring out into all water bodies in the area.
District Fisheries Officer Prabhati Deb said the fertiliser factory must treat the ammonia water before releasing it into nearby water bodies.
The fertiliser company’s MD Amal Kanti Barua claimed that they were continuously monitoring the air and water quality in the area.
“I want to assure you that no untreated sprayed water will find its way into the nearby water bodies, river or the sea. We will use lime to neutralise the water in the fish enclosures,” Amal Kanti said.
35 tonnes of fish and shrimp dead
The claim of the official is, however, belied by the primary damage report prepared by the district Fisheries Office.
As per the report, the leak caused damage to 192 hectares of fish enclosures. The ammonia has killed 35.8 metric tonnes of shrimp and other fish belonging to 40 fish farmers, worth Tk1.27 crore, the report said.
Muhammad Edris Ali, an associate professor of chemistry at Chittagong Hazi Md Mohsin College, said maximum caution should be exercised while applying water to dilute the level of ammonia in the air.
“Ammonia is a highly corrosive chemical compound. The pH level increases and dissolved oxygen decreases simultaneously if ammonia gets mixed with a little amount of water, like a pond. We have to ensure that the aquatic environment will not be in peril due to the emission of the toxic gas in the air,” said the teacher.
“We have already seen fishes dying due to the toxic gas. The plants in the surrounding area have also turned black and shriveled. So we have to make it sure that no untreated sprayed water will find its way into the nearby water bodies. It is also preferable to reuse the sprayed water,” suggested the teacher, who is also a researcher on the Karnaphuli.
Ponds turn caustic
A team from the Chittagong Department of Environment (DoE) found that the levels of pH, dissolved oxygen (DO) and chemical oxygen demand (COD) in the water samples collected from nearby water bodies were well above tolerable levels.
The DoE team collected the water samples from 11am till 7:30pm on Tuesday.
The collected samples were tested in the Chittagong DoE laboratory on Wednesday.
The tests revealed that the pH level of the two ponds adjoining the fertiliser factory stood at 9.94 and 8.54 respectively.
The DO level of water collected from the two ponds stood at 1.39 and 4.00, where the normal level is above 4.5. The COD level was at 324 and 264, where the normal range is below 200.
The DoE team also collected air sample and the average level of ammonia in the air during eight hours of examination was recorded at 92ppm. The air sample was collected using ‘High Volume Sampler’ from 170 metres north-west of the source of emission.