Testing Study Of Polluted Water In-Situ Remediation By Submerged Macrophytes And Bio-stimulant

The gardens mostly locate in the center of city of Suzhou. Similarly to the city rivers, the water in the gardens are easily polluted by the wastewaters from the surroundings. There are a few characteristics: (1)the detained time is long; (2) water area is small, the water environment capacity is small, the ability of self-purification is low; (3)because they locate in the city center, the water is easily polluted and difficult to restore; (4)the most water in the gardens are polluted, eutrophication turns seriously. Traditional wastewater treatment approaches can not be used for such water body. Since 1980s, bioremediation has been more and more popular with the environment workers. By summarizing the predecessor's research results and experimenting in lab, the suitable bioremediation projects are derived. The following is the main research activities and results:(a) By the experiments to three kinds of Submersed Macrophytes in the open air, including Ceratophyllum Demersum L, Vallisneria Spiralis and Elodea Nuttalli, it was shown that three kinds of Submersed Macrophyte have good ability in improving the water quality, removing nutriment (nitrogen and phosphor) from the water effectively. The concentrations of NH₄⁺-N and TN were reduced from 1.1¹.3 mg.L^-1 and 3.7⁴.6 mg.L^-1 to 0.1⁰.15 mg.L^-1 and 0.71¹.02 mg.L^-1, respectively, and the concentrations of PO₄³--P and TP were reduced from 0.06⁰.08 mg.L^-1 and 0.45⁰.47 mg.L^-1 to 014⁰.018 mg.L^-1 and 0.03⁰.071 mg.L^-1, respectively. At the sametime, each species can enhance the water transparence, and increase the dissolve oxygen (DO) as well, and thus promote the biodegradation by in-site microbes. The effect of purifying and removing the vegetable nutriment (nitrogen and phosphor) for three kinds of Submersed Macrophytes has the same trend from speediness to slowness, and to stabilization. Among three kinds of Submersed Macrophytes, at the point of decontamination efficiency and capacity of bioremediation, Elodea Nuttalli could obtain the best results, Ceratophyllum Demersum L is followed. The Submersed Macrophytes can increase the extent of alkalescence in the water, enhance the concentration of DO and thus promote the biodegradation. It is most excellent that dissolve oxygen can increase from 4.2 mg-L"1 initially to 8.2 mg-L'1 eventually at 14 o'clock in the gutter water of Elodea Nuttalli.(b) On the research of the similar river experiments to three kinds of Submersed Macrophytes, it is reported that the change of the quality of the water outside of the test area influences the quality of the water in the test area greatly. During the test, the quality of reference water greatly changed. Consequently in this short measure cycle, the effect of Submersed Macrophytes is not so marked. The three kind of Submersed Macrophytes have some ability to remove nitrogen and phosphor, the remove effect of TN and phosphor is quite well. Compared with the Submersed Macrophytes, Ceratophyllum Demersum L is the best, and Vallisneria Spiralis is the worst. Compared with the reference water, three kinds of Submersed Macrophytes all have the ability to improve the quality of the water.(c) When the concentration of the bio-stimulant (Bio-energizer) is lower than l.Oml-rrf3, the effect of bioremediation was not so obvious. Increasing with the concentrations of the bio-stimulant the effect of bioremediation became greatly. Yet, when the concentration of bio-stimulant reached at a certain level, the effect of bioremediation became stable. When the ratio is 1 between bio-stimulant and herbicide, the treatment effect was the best; when less than 1, herbicide could restrain the biodegradation, thus influence the effect of water bioremediation. At the point of effect of bioremediation, the 5ml-m"3 bio-stimulant mixing with 5ml-m"3 herbicide could obtain the best results. But considering on the economics and the effect oftreatment, 3ml-m ! bio-stimulant mixing with 3ml'mJ herbicide should be more practical.