A waste disposal problem in Khulna is tainting the rivers in and around the metropolitan city, posing a threat to the environment, public health and aquatic animals.
Khulna, the third-largest city in the country, is located at the confluence of the Bhairab and Rupsha rivers, and a tributary of the Rupsha River, called the Mayur, flows through the city.
Khulna City Corporation (KCC) does not have the capacity to dispose of all the waste generated by the people of the city. A large portion of solid waste is being discharged into these three rivers every day, polluting the water and the environment.
Among the three rivers, the water of the Mayur River has been tainted by waste the most, thanks to a sluice gate installed by the Bangladesh Water Development Board, according to two separate research papers, one from Khulna University and the other, "River Water Analysis Sheet", of the Department of Environment's Khulna office.
According to the Environment Conservation Rules, 1997, the standard of purity of inland surface water is usually determined by the measurement of dissolved oxygen (DO), biochemical oxygen demand (BOD), and total dissolved solids (TDS) in the water.
A survey of samples collected by the Department of Environment from the Mayur River in April 2022 shows that the quality of the water varies greatly from the standard of purity.
Amount of dissolved oxygen
According to the Department of Environment, the level of dissolved oxygen in the water of Mayur River is currently 0.2-0.6 mg per litre, whereas the ideal dose of DO should be more than 5 mg per litre of water.
Due to the low levels of DO, the river water is harmful to aquatic animals and to public health, according to the environment protection agency.
The amount of solid waste being dumped in the river every day needs a lot of dissolved oxygen to be neutralised by oxidation, said the government agency.
Biochemical oxygen demand
The amount of oxygen that microorganisms need to decompose wastewater is called BOD.
According to the World Health Organisation (WHO), the standard BOD of water is 6 mg per litre. If this value is above 10 then that water is considered contaminated.
According to the Department of Environment, the current level of BOD in Mayur River water is 78 to 86 mg per litre, which is many times higher than the norm.
Total dissolved solids
According to the World Health Organization, the standard amount of TDS in water is 300 mg per litre. And if this level goes above 1,000, the water is considered unsuitable for human consumption.
According to the Department of Environment, a maximum of 6,060 mg of TDS has been found in the water of Mayur River.
Emdadul Haque, deputy director of the Khulna office of the Department of Environment, said, "The biggest pollution in Khulna is now in the water. It is especially the water quality of the rivers around the city which is getting worse; and the level of pollution in Mayur River is very high."
Research of Khulna University
Khulna University has conducted two separate studies on the water of the Mayur River, in 2013 and 2020, led by Dilip Kumar Dutta, professor of the Department of Environmental Discipline.
"In a 2013 study, we found that the Mayur River had a high TDS content. The water was polluted and stinky. However, the soil quality of the river was found to be quite good, which is suitable for agricultural work," he said.
"If Khulna City Corporation had refrained from dumping waste in the river, the environment would have been much better," the professor said.
"Our research in 2020 was mainly on the water security of Khulna city. We found that to meet the water demand of Khulna city, the Mayur River can be developed as a reservoir of fresh water," Dilip Kumar said.
He said the length of the Mayur River from Beel Pabla to Alutala is about 11 kilometers, with an area of about 40 square meters.
"The river lost tide after being closed by a sluice gate at Alutala of Rupsha upazila. Six branches of this river entered various areas of Khulna city. About 80% of the city's polluted water, mixed with household waste, falls into the river through 22 drains," he said.
Professor Dilip Kumar said, "This river can be rehabilitated to hold fresh water during the monsoon season. With that water, the daily needs of the city people can be met."
Household wastes pouring into the river
Md Abdul Aziz, chief conservancy officer of KCC, said the city generates about 1,200-1,250 metric tonnes of solid waste every day, including 4-4.5 tonnes of medical waste.
"The workers of the city corporation collect 600 tonnes of waste and dump it in a landfill 6 km away from the city. People dump the remaining 400 to 450 tonnes of waste in drains or on vacant land," he said.
"We do not have adequate logistical support and staff to collect all the waste in the city. City dwellers should dump the garbage at the secondary transport station of KCC instead of dumping it into drains or on vacant land," Abdul Aziz stated.
"Every day, some 198 permanent and 710 temporary workers remove wastes from secondary transport stations in our 31 wards," he added.
Gauranga Nandi has been conducting research on the rivers and environment of Khulna region for about 25 years.
He said, "All the wastes collected by KCC eventually end up in the Mayur, Bhairab and Rupsha rivers through various drains. This problem is destroying the rivers' ecosystem."
"The Bhairab and Rupsha rivers still witness diurnal tides (one episode of high water and one episode of low water each day)," he said, adding that the KCC waste is spreading in different places.
"On the other hand, the closure of the Mayur River has worsened the problem. In order to protect the environment of the city, the river should be rehabilitated immediately," Gauranga Nandi added.