Ecological technology using aquatic plants in eutrophycation treatment

05/08/2013

Organic substances, N and P from daily sewage and human production activities are the main causes for eutrophycation in freshwater. The interior surface waters of Vietnam, especially lakes and water reservoirs, are increasingly eutrophic, with the outbreak of microalgae, including toxic Cyanobacteria discovered in Microcystis aeruginosa, causing ecological imbalance and water quality decline.

Therefore, scientists are seeking solutions on eutrophycation treatment. Scientists are looking at ecological technology using aquatic plants to fight eutrophycation because of its advantages and friendliness with the environment.

Dr. Tran Van Tua and his coordinators from the Institute of Environmental Technology have carried out a study on ecological technology using aquatic plants in europhycation treatment at a small scale, in an effort to find a solution to water environment eutrophycation in Vietnam.

The study was conducted in a eutrophic lake in Co Nhue experimental area, the Vietnam Academy of Science and Technology. Aquatic plants were put into the system, including young and strong plants such as Eichhornia crassipes, Enydra fluctuans, Ipomoea aquatica and Rorippa nasturtium aquaticum.

Experimental treatment of eutrophic lake on small scale

The pilot treatment system includes four parallel canals, 5.6 meters long, 0.8 meter wide and 0.2 meter deep. Each canal has average water level of 10 centimeter. Eutrophic water was pumped in and equally distributed through the canals. This system operated continuously, taking annual samples to assess the europhycation index and analyse water quality norms such as TN, TP, TSS, COD and Chlorophin (Chla) before and after treatment methods.

Based on collected data, scientists analysed and adjusted the role of aquatic plants while rejecting eutrophycation elements, eutrophycation element treatment productivity in different water tonnages and microalgae treatment effectiveness and Cyanobacteria in the system of aquatic plants.

The role of the aquatic plants in rejecting eutrophic elements

The result showed ecological technology using aquatic plants such as NT, BT, CS and RM, not only reject water environment europhycation elements such as TN, TP, CS and RM, but also microalgae and toxic cyanobacteria. Among four aquatic plants, BT gave the highest treatment result. The output rejecting norms of TN, TSS, TP, COD and Chla increases in comparison with control, that is 2.10-3.19 ; 2.85-3.32; 1.87-2.14; 2.03-4.88 and 2.54 -2.89 correlative times.

The very high density of microalgae in BT input water eliminates 19.33% microalgae in the total and 82.80% cyanobacteria. The canals also showed significant digits which fluctuate from 49.83-65.25% of the total microalgae and 52.37-62.80% of cyanobacteria. Moreover, output water meets A1 level in the surface water quality according to QCVN08-2008/BTNMT of the Ministry of Environment and Natural Resources in coliform and well meeting the provision of daily life water. These plants can be used for breeding such as BT and green vegetables in the cases of NT, RM and CS.

Ecological technology using aquatic plants by scientists from the Institute of Environmental Technology has many advantages. It is not only friendly with environment, but also stable with low cost, bringing high effectiveness. The positive results in the pilot test are a foundation to apply this technology in eutrophycation treatment on a large scale.

Translated by Tuyet Nhung

Link to Vietnamese Version

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