Oil scum continues to be detected at Đầm Bài Lake, near the entrance of the Sông Đà Water Investment JSC’s water treatment system on October 8. —  VNA/VNS Photo

HÀ NỘI — The strange odour in domestic water detected by residents in some districts west of Hà Nội was due to an increase of chloride used to disinfect source water from the Đà River.

Director Nguyễn Văn Tốn of the Sông Đà Water Investment JSC made the statement on Monday regarding reports of the odour made by residents in the capital city’s outer districts of Hà Đông, Hoàng Mai, Nam Từ Liêm, Thanh Xuân on October 8.

Water used at households in these districts was reported to smell like “burnt plastic”.

By Sunday, the smell had subsided, but local residents remained sceptical and did not feel confident using the water at home.

Officials from the Hà Nội People's Committee and the Ministry of Environmental Resources and Environment on Monday requested clarification of the situation from the Sông Đà Water Investment JSC, which was in charge of supplying water for these households.

Director Tốn said the smell was caused by a water disinfection technique using chloride conducted in its water factory.

“We were trying to meet the Ministry of Health’s new standards for domestic water quality and increased the amount of chloride used in disinfecting source water,” he said.

After receiving complaints from local residents, on October 10, the company had reduced the amount of chloride used in water disinfection from 0.8mg per litre (in compliance with the health ministry’s new requirements) to the previous level of 0.3-0.5mg per litre, he added.

“The water disinfected with the new level of chloride is still safe for domestic use,” he said.

Regarding detection of oil scum near the entrance of the company’s water treatment system also on October 8, Tốn said on October 9 the company has closed its intermediate storage tank to stop receiving water from the Đà River, and assigned staff to examine the scum.

“The scum was discovered to be coming from the Bằng stream to the Đầm Bài Lake, from which water flowed to the company’s treatment plant,” he said.

Vũ Đức Toàn, deputy director of the company, said the company had applied measures to prevent the spread of the oil scum.

It had also reported the situation to local authorities for further investigation, he said. — VNS