Uncontrolled water pollution by industrial effluents has been posing a serious threat to fish and other aquatic lives in the Halda river, the country’s lone natural fish spawning centre.
The rampant pollution caused the death of many fish species and other aquatic lives in the river a few days back.
Researchers feared that if the extreme pollution cannot be stopped immediately the river having a huge contribution to country’s economy will lose its natural feature and turn unlivable for aquatic lives gradually.
Sources said liquid chemical wastes from the industries located in the city’s Bayezid Bostami, Oxygen and Kulgaon areas and Hathazari upazila find their ways to the Halda through canals connected to it.
Industries like tannery, paper mills, knitting, dyeing, washing plants, condensed milk and beverages factories are located in the areas.
The quantity of pollution to the Halda increased when Chattogram Development Authority (CDA) developed a master-drain connecting Bamunshahi Khal and Kuaish Khal for their Ananya Residential Area Project, said the sources.
Earlier, wastes from Bayezid Bostami industrial area used to fall into the Karnaphuli river through the Bamunshahi Khal. But now the effluents go to the Halda through Khandokia Khal following development of the master-drain.
Besides, Kuaish Khal is also connected to different canals, including Khandokia Khal, Bathua Khal, Krishnokhali Khal, Madari Khal, Madarsa Khal and Hamidia Khal under Hathazari upazila. All the canals flow into the Halda.
While visiting the areas, this correspondent found that black and stinky liquid industrial and household wastes were falling into the river through the canals.
Researcher and Coordinator of Halda River Research Laboratory of Chittagong University (CU) Prof Md Manzoorul Kibira said he has never seen such dire straits of the river as a huge quantity of fish and other aquatic animals have died recently.
Besides the regular pollution by industrial effluents and toxic wastes of poultry firms got mixed with the river water during the last flood following heavy rainfall and created the situation, observed the researcher.
He said they collected samples from different spots of the river on June 22.
Manzoorul informed that the level of dissolved oxygen has fallen below the tolerance level of aquatic species and even ammonia has gone 100 times of the optimum level.
Exceeding of acceptable levels of the parameters caused death of fish and aquatic lives, he said.
Meanwhile, Department of Environment (DoE) also conducted tests of the water collected from the Halda river and found the dissolved oxygen below the acceptable level.
Contacted, DoE Chattogram Metro Director Md Azadur Rahman Mollick told the daily sun that liquid wastes from Ananya Residential Area and some industries are now discharged into the river through the Khandokia Khal after the CDA developed the master-drain diverting the flow of wastes.
He said they regularly monitor the factories to check whether the effluent treatment plants (ETPs) are kept functional.
“We found the ETP running while visited the industries. But different scenario was found when test was conducted after collecting samples,” he said, adding that they are accelerating efforts to ensure keeping the ETPs functional.
Replying to a query, he said they sealed off a paper mill and a tannery for lacking in ETPs and clearance certificate from DoE in Oxygen Mor area on Sunday.
Locals said they noticed the river water started getting blackish since June 19 and turned worse spreading bad odour later.
After this, a large number of fish of different species and other aquatic animals were found dead floating on the river water.
The locals collected different species of dead fish, including shrimp, carp fish like rui and katla weighing up to 15 kilograms from the river.
However, Researcher Manzoorul said the situation improved following heavy rainfall after the incident.
Sources said some 22,680 kilograms of eggs of carp fish were collected from the river breaking all the previous records this year. Around 378 kilograms of fish fry were produced from the collected eggs.