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The Pagla Sewage Treatment Plant was found to be effective in removing SARS-CoV-2 RNA from the raw sewage – study finds

Dhaka, 30 May 2022: Today, icddr,b and the Dhaka Water Supply and Sewerage Authority (DWASA) have jointly organised a dissemination seminar at Buriganga Hall, WASA Bhaban in Karwan Bazar, Dhaka, to share the findings of a recently concluded study that looked into the presence of Covid-19 virus (SARS-CoV-2) in sewage and other contaminated surface water sources in and around Dhaka city.
The shedding of the SARS-CoV-2 virus through human faeces begins within three days of infection, which ultimately goes into the sewerage system. This may lead to the contamination of the environment if the sewage is not properly treated and discharged. Thus, it is very important to understand this type of environmental contamination through sewage and other contaminated surface water sources in Dhaka city.
Accordingly, between September 2020 to January 2021, there were 22 sewage and 23 sludge samples collected from the DWASA’s Narinda, Basabo sewage pumping stations and Pagla sewage treatment plant (PSTP). Additionally, two composite water and two sediment samples were collected from the Mitford point of the Buriganga river and under the Abdullahpur bridge of the Turag river. A total of six samples (three water and three sediment samples) were also collected from three ponds, namely the Institute of Public Health (IPH) pond, Mirpur Mazar Pond and Shahidullah Hall pond at the campus of the University of Dhaka. The Shahidullah hall pond was selected as a control pond. All the samples were tested for the presence of SARS-CoV-2 by RT-qPCR assay and different physicochemical parameters.
From left – Dr Sirajul Islam, Professor John D Clemens, Mr Md Tazul Islam MP, Engineer Taqsem A Khan, Dr Shams El Arifeen, Dr Alamgir
Dr Sirajul Islam, Emeritus Scientist at icddr,b and the Principal Investigator of the study, presented the findings. The study showed that of the raw sewage and sludge samples, 57.1% and 53.3% samples were found to have SARS-CoV-2 RNA, respectively. There was no presence of SARS-CoV-2 in the samples collected after treatment by the PSTP. The SARS-CoV-2 RNA wasn’t found in the water and sediment samples collected from the river and pond ecosystems. The difference in physicochemical parameters such as pH, temperature, total dissolved solids, dissolved oxygen, conductivity, and dissolved solid in river and pond water samples were not prominent, but variation was observed in treated and untreated sewage samples collected from different sampling sites of the PSTP.
Mr Md Tazul Islam MP, Honourable Minister, Ministry of Local Government, Rural Development and Co-operatives, Government of Bangladesh, graced the seminar as the Chief Guest, while Professor John D Clemens, Former Executive Director at icddr,b and Dr Shams El Arifeen, Acting Executive Director at icddr,b attended as Special Guests. Engineer Taqsem A Khan, Managing Director and Chief Executive Officer at Dhaka WASA, presided over the seminar. The Honourable Minister Md Tazul Islam, in his remark, appreciated the initiative and thanked icddr,b and the DWASA. He said, “It was a great initiative of the DWASA to undertake this research and generate evidence which is important.”
Prof. Clemens appreciated the leadership of the DWASA for taking up this research at a time when there was not much knowledge about the environmental contamination of the Covid-19 virus. Dr Arifeen remarked that the findings of the study are indeed very reassuring for the residents of Dhaka. Eng. Khan said, “The DWASA partnered with many local and international institutions including icddr,b to strengthen its activities based on science and evidence.”
National public health experts, representatives from the WASA, icddr,b, and media were also present at the seminar. The study was supported by the DWASA.
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