Owing to a fall in human activity, the water quality of the rivers of northern districts has seen a significant improvement in the last few months. The usual collection of debris, plastic waste and other rubbish is now gone and in its place is now pristine water.
Experts, however, fear the rivers will experience another surge of pollution once the shutdown is fully lifted.
The Department of Environment (Rajshahi Divisional office) regularly collects water samples to analyse from upstream and downstream of six rivers -- Korotoa, Padma, Jamuna, Teesta, Ichamati and Boral -- at 26 locations of the division.
The Daily Star obtained a copy of the water analysis reports -- three from 2019 and three from 2020 (March, April and May). It showed that the water quality of the six rivers improved during the shutdown.
According to the DoE, the most polluted rivers in Rajshahi division are Korotoa and Ichamati. Karotoa's water is heavily polluted in Bogura all year due to lack of sufficient waterflow and existing municipal waste.
In Pabna's Sadar upazila, Ichamati river is very polluted due to lack of sufficient water flow, and heavy presence of municipal, agricultural and industrial waste.
The pH levels in Korotoa and Ichamati's water was under 7 all through March, April, and May 2019. But starting April this year, the pH levels have increased to a steady 7 or a little above 7.
If the water's pH levels remain under 7 the water is considered acidic and harmful for aquatic lives, said Masud Rana, chemist of DoE (Bogura).
"A pH level of 7 is considered neutral and not acidic. It is healthy for aquatic organisms," said Chowdhury Sarwar Jahan, professor of the Department of Geology and Mining, Rajshahi University.
The reports showed Dissolved Oxygen (DO) increased in every river from March to May this year. The DO levels were much lower from March to May last year. Optimum DO levels are essential for the survival of aquatic organisms, said Masud Rana.
On May 8 last year, the DO of Korotoa River was only 2.8 mg/l near the Bogura Foteh Ali Bridge and it increased to 3.33 mg/l on May 5 this year.
In Ichamati River, near the Sweeper Colony under Pabna Sadar upazila, the DO level was 2.8 mg/l on May 14 last year which has increased to 3.76 mg/l on May 13, this year, said the reports.
The Biological Oxygen Demand (BOD) in both rivers slightly fell this year. "The higher pollutants represent higher rates of BOD. The higher rate of the BOD represents the lower dissolved oxygen in water," Masud Rana said.
Since the shutdown began, total dissolved solids (TDS) in the waters of Karotoa, Ichamati, Boral, Jamuna, Padma and Teesta reduced and fell to 250 mg/l, sometimes even dropping to 150 mg/l. But this was much, much higher in the previous years.
"Since last April, inorganic salts and organic matter are decreasing in river water. Therefore, TDS in every river is decreasing (except the Ichamati River in Pabna)," Masud added.
The other parameters of measuring water quality (as per the ECR Act '97) like suspended solids (SS) and electrical conductivity (EC) decreased significantly due to the low levels of pollutants in the river water during shutdown.
"During the coronavirus pandemic, our director general ordered us to measure and monitor water pollution of every river each month," said Md Ashrafuzzaman, director of the Department of Environment, Rajshahi Divisional Office.
"We found water pollution in each river has decreased significantly to the closure of industries. Now the general public will understand who pollutes our waters. Now industry owners who always denied responsibility for polluting water should admit their guilt," Md Ashrafuzzaman added.
"To reach our SDG goals, industry owners must stop polluting and they must establish ETP and use it seamlessly," he said.
According to the DoE, Bogura, "There are 50 to 60 large scale industries in the Rajshahi division and around seven to ten industries have no functional Effluent Treatment Plant."
"From my own experience in the last two years, many industries have undersized ETP which can't recycle the effluents perfectly and many industries don't run the ETP at all times to reduce their costs. Although they were fined over Tk 50 lakh in the last two years, we could not stop them from polluting the rivers," Ashrafuzzaman added.
According to the DoE, there are more than 200 small scale dyeing industries in Pabna and Sirajganj districts and they have no ETP. Therefore, they are polluting rivers waters, especially the Ichamati river.
There are more than 1,000 foundry and light engineering workshops in Bogura; many have no ETP.
When asked, Masud Rana of DoE, Bogura said: "In Sirajganj and Pabna those who have a dyeing industry have invested Tk 2-4 lakhs and if they construct a small-scale ETP the cost will go up to Tk 7 to 10 lakhs."
Masud Rana also lamented the lack of facilities in their lab to test heavy metal pollution like mercury, lead, cadmium.