The Experimental Study Of Algal Growth Inhibition By Utilizing Allelopathic Plants-filter Floating Bed

The cascade reservoirs are important water resources of a large city in southernChinan. The cascade reservoirs have the problem of periodic outbreaks of algae. Theresearch of allelopathic plants-filler floating bed was conducted in order to protectregional water supply security and reduce the risk of algal outbreaks.The research of allelopathic plants compared the inhibitory effects of differentconcentrations of extracts on the Microcystis aeruginosa. The extracts are extractedfrom the roots of the floating bed plants anthurium, Spathiphyllum kochii Engl. etKrause and Hydrocotyle vulgaris. The study found that high dosage(3and4g/L) ofextracts can effectively inhibit the growth of Microcystis aeruginosa. The inhibitionrates are all over90percent. The photosynthetic activity of Microcystis aeruginosahave also been greatly damaged. TheΦmax, Φ, ETR, and Ikreduced. The enzymesystem of Microcystis aeruginosa cells are also inhibited. The cell membranes andorganelles membranes are attacked by free radicals seriously. MDA accumulatedrapidly and POD reduced drastically. The inhibition rates declined along with thereduction of extracts’ dosages. The low concentration dosage groups of Spathiphyllumkochii Engl. et Krause and Hydrocotyle vulgaris can even promote algal growth. Thelowest concentration to inhibit the growth of Microcystis aeruginosa is1g/L forSpathiphyllum kochii Engl. et Krause and2g/L for Hydrocotyle vulgaris. Theinhibitory effect on Microcystis aeruginosa of three plants’ root extract under thedosage of2g/L is Spathiphyllum kochii Engl. et Krause> Hydrocotyle vulgaris>anthurium in descending order. The planting water of three plants can all inhibit thegrowth of Microcystis aeruginosa. The inhibitory effect is Spathiphyllum kochii Engl.et Krause planting water better than Hydrocotyle vulgaris planting water better thananthurium planting water. The inhibitory effect of planting water is worse than that ofhigh concentrations of plants roots extract.The floating bed research is launched in two phases. In the first phase, the L9(34) orthogonal experiments of algal growth in microcosm environment were conducted.Nutrient concentrations in water, water flow velocity and the initial concentration ofalgae were selected as environmental factors, and the specific growth rate ofchlorophyll a was taken as evaluation index. In the second phase, five filters weretested to examine their abilities of removing significant environmental factor. Resultsshowed that the initial concentration of algae had significant influence on the growthof algae. The degree of impact of environmental factors on the algal growth was theinitial concentration of algae, the concentration of TN, velocity, the concentration ofTP in turn. The dominant species of algae in microcosm environment changed underdifferent conditions of orthogonal experiments. Five filters were selected in thesecong phase. They were gravel, maifanite, shell, activated alumina and polyurethane.In addition to shell, the other four filters can all effectively improve water quality andreduce the concentration of chlorophyll a. According to the conclusion drawn byorthogonal experiments, adding fillers can effectively reduce the risk of algaloutbreaks. Water quality improvement effect of four filters in descending order ismaifanite better than gravel better than activated alumina better than polyurethane.