The Hanoi Drainage Company discharged the water and after a few hours the water in To Lich river changed significantly in color, turning from black to moss green, while the bad odor diminished.

According to Vu Trong Hong, former deputy minister of agriculture, the volume of 1 million cubic meters of water within two days won’t be able to cover the entire river, which is over 14 kilometers long.

“The first river section can become green, but nothing changes in the next section,” he said.

Meanwhile, the arrival of West Lake’s water will push part of the polluted To Lich River downstream to Nhue River.

Hong said that discharging water from the West Lake to To Lich River must not be done regularly.

He stressed that to clean the river domestic and industrial waste water sources must be controlled.

“Sanitary workers pick up waste from To Lich every day and dredge the river sometimes. But all the solutions only prevent it from becoming worse. They cannot help the river fully recover, "Hong said.

He suggested two options to recover To Lich river. First, there should be enough natural water to provide to To Lich. Many years ago,scientists suggested using water from Red River. However, that could not be done since the route that leads water from Red River to To Lich has filled up. It is also very costly and will have social and environmental consequences.

Second, it is necessary to disconnect waste water sources going to To Lich river. Rainwater will help clean the river.

Hong believes that the solution used for the Nhieu Loc – Thi Nghe canal in Binh Thanh district, HCM City, could be useful for To Lich in Hanoi.

To Lich has been treated with Japanese cleaning nano-technology to help reduce the bad smell from the polluted To Lich River.

The cleaning equipment creates and diffuses nano-gas streams into the surrounding water to stimulate microorganisms, which helps to release oxygen and decompose the mud in the riverbed, making the water cleaner, according to the Vietnam News Agency.

Nano-bioreactor technology has also been used in the West Lake, the largest lake in Hanoi.

Hai Van 

West Lake water pumped to refresh To Lich River

Hanoi Sewage and Drainage Ltd. Company on July 9 discharged more than one million cubic metres of water from West Lake into To Lich River.  

West Lake's hidden treasures

Hanoi’s Tay Ho district has the capital city’s largest lake called Ho Tay or West Lake.