The Chattogram Water Supply and Sewerage Authority (Wasa) has almost doubled the use of chlorine in water since the last week of May to contain the spread of Covid-19.
Currently, it is adding 0.5-1.0 milligrams of chlorine per litre of water, while it previously used 0.2 to 0.8 milligrams.
Experts said the use of excessive amounts of chlorine could pose a health risk to people. They said drinking water with excessive amounts of chlorine, for a long time, could cause: breathing problems, congenital disabilities, colon cancer, bladder cancer, etc.
According to the experts, adding an excessive amount of chlorine to water, without proper research is not appropriate.
Maqsud Alam, chief engineer of Chattogram Wasa, admitted that extra chlorine is being added to the water. He said, "The step has been taken to maintain the chlorine level at 0.2 milligrams for per litre of water at the customers' end."
"It does not matter how much chlorine we are adding at the plant, because chlorine is a volatile substance. It also melts in the air from the water while it runs through the pipes," said Maqsud Alam.
"The Covid-19 guidelines of the World Health Organization (WHO) permit the use of 0.5-milligrams of chlorine per litre of water. We have started to add more chlorine to the water treatment plants and reservoirs according to that guideline," he added.
Recently, a research article published by the British weekly scientific journal Nature revealed that the novel coronavirus can spread through water.
Quoting the study, carried out by Netherlands' KWR Watercycle Research Institute on samples collected from areas in Sweden, Netherlands and the USA, the article also stated that the SARS-CoV-2 virus can survive in unclean or used water.
Water – after being used in toilets or for washing one's hands and face – could allow the deadly virus to infect other people, the research said.
Officials of Chattogram Wasa became alert after several reports surfaced of the novel coronavirus spreading via water in some European countries.
The organisation delivers more than 35 crore litres of water through a 6,000-kilometre pipeline in the city. The officials fear that the pipeline could be a medium of spreading Covid-19. That is why they started adding extra chlorine to disinfect the water.
According to Chattogram Wasa sources, it used to add 0.2-0.8 milligram chlorine per litre of water. However, this amount of chlorine did not reach the remote areas of the city like: Patenga, Halishahar, Pahartali, and Baklia.
As a result, water in these areas contained different bacteria.
After the Covid-19 pandemic hit the country, Chattogram Wasa aimed to ensure there was 0.15-0.2 milligrams of chlorine per litre of water in these areas. For this, they are ensuring 0.8-1.0 milligrams of chlorine per litre of water at the water treatment plants and reservoirs.
According to the Environment Conservation Rules 1997, 0.2 milligrams of chlorine is acceptable per litre of water. Any amount above this is harmful to human health.
Speaking to The Business Standard, Dr Chowdhury Md Monirul Hasan, professor of the Department of Biochemistry under Chattogram University, said, "I did not stumble across any information saying that the novel coronavirus can spread through water. All germs need carriers to spread."
"Germs that spread through coughs and sneezes will not spread through water. Besides, the pH level of the water prevents harmful germs from spreading. Meanwhile, Wasa should not have increased the use of chlorine in the water without prior studies," he added.
He added that the extra chlorine will have negative long-term effects on the human body.
Reiterating the opinion, Dr Asiful Hoque, chairman of the Water Resources Department of Chattogram Engineering and Technology University, said, "Higher levels of chlorine in water causes long term effects on the body. It can cause different skin diseases and cancer."
Chattogram Wasa collects 82 percent of its water from the Karnaphuli and Halda Rivers and 18 percent from deep tube wells. There are 73,000 residential and commercial users in the city.
Milon Kumar Chakraborti, former chemist of Chattogram Wasa, said, "Wasa generally adds chlorine in three steps. In the first step, it adds chlorine to the water while collecting it from the rivers.
"Later, it adds chlorine in the tank – after the water purification process and before running the water through the pipeline. In the third step, chlorine is added when the water reaches the Kalurghat booster, plus Batali Hill, Nasirabad, and Patenga reservoirs."