Turn lakes into pots

Ho Thien Quang, Thanh Cong, Giang Vo have just completed the renovation. Immediately, the people of Hanoi had to close their nose, scientists confirmed that there were signs of toxic algae.

In fact, the improvement of water quality of lakes in Hanoi in recent years has mainly used construction methods, but not scientific solutions. The work done during the renovation is usually to upgrade and rebuild the drainage system to separate rain water from the waste water so that the waste water does not flow into the lake, dredge the lake's mud . The above jobs were done. The landscape around the lake is more spacious but the quality of the lake water is not improved but it is somewhat ' going down '.

Renovating Thien Quang Lake (Photo: CVK)

According to Mr. Bui Tam Trung, the Association of Natural Environment and Capital Protection: 'Improving and dredging in the style of' internal realities, foreign realities ', for compacting the bottom of the lake is turning the lake into a basin of water!' . This has been warned by the scientists about the occurrence of toxic algae in three newly renovated lakes in Hanoi and specific figures for demonstration. This is not the first time the phenomenon of increasing the number of toxic algae appears after dredging lakes such as Hoan Kiem Lake, Ba Mau Lake . Every time dredging the lake, this phenomenon appears again. Accompanying the appearance of toxic algae is odor pollution. The smell that rises from the surface of the newly renovated lakes becomes worse during hot, hot days.

The cause of this phenomenon, according to Prof. Dr. Dang Dinh Kim, deputy director of the Institute of Environmental Technology (Vietnam Academy of Science and Technology), because toxic algae contain 50-60%, even over 70% of protein . After dying, the algae accumulate at the bottom of the lake getting more and more thick, while reducing the volume of lakes and dragging the dissolved oxygen in the water to disappear aquatic species and release harmful gases and smelling the stench. In addition, the sewage in the sewers continuously pouring into the lake makes the odor resonance more difficult to describe.

Another reason is that after the renovation, the lake has lost its mud layer - a stable habitat - that should cause disturbance of the ecosystem, especially floating plants and algae . Therefore, according to scientists, the dredging of the last three lakes is in fact just clearing garbage and mud from the bottom of the lake but not cleaning the water.

In the hot season, the smell of newly renovated lakes in Hanoi is even more dense. Other lakes such as Dac Di and Ba Mau died a lot, people screamed. According to GS Kim, this is suitable for the blooming season of algae. More dangerous, these algae can negatively affect human health if there is direct contact with water.

As noted by scientists at the Institute of Environmental Technology, new algae arises after the dredged lake has scientific name is Oscillatoria, M. aeruginusa - a very toxic algae. These poisonous algae can spread from lake to lake with unconscious human assistance.

HOANG LE - THU VAN VAN KY