Dr. Kubo Jun, a technical advisor from the Japan Environmental Trade Organisation, jumped into the tank set up in To Lich River in Hanoi on August 8.
He swam and washed his face with the water for around 20 minutes.
Speaking with reporters, he said that he found the water very clean without any bad smell. He did not feel uncomfortable or any skin problems after getting out of the tank.
After being treated with the Japanese bio-nanotechnology technology, he said the water in the tank could be safely used.
The Japanese nano-biotech treatment has been piloted for cleaning a section of To Lich since May this year. The technology produces oxygen in the water by activating both aerobic and anaerobic microorganisms in the water. Equipment used includes an aerator to quickly treat water using natural materials, which is installed on the bed of the river.
Dr. Kubo Jun swam in the tank
Some local experts, however, pointed out that water from Red River has stopped flowing into To Lich River and the direct discharge of untreated wastewater from households and factories are the two main causes of severe pollution.
To revive the river, the city needed a more comprehensive solution. However, the city should build a system to collect and treat the wastewater before discharging it into the river. It would also be necessary to resume the water supply from the Red River into the To Lich River, they suggested.
To Lich River is 14km long, running through the Hanoi districts of Ba Dinh, Cau Giay, Dong Da, Thanh Xuan, Hoang Mai and Thanh Tri. However, the river has been severely polluted as both industrial and household wastewater are discharged directly into the river.