Study On Technologies For In Situ Ecological Remediation Engineering Of Eutrophic River

With over loading of inorganic nutrients to freshwater, rivers, lakes, steams and reservoirs, water eutrophication occurred more and more frequently, and therefore, it has become a worldwide environmental issue arising increasing public concern. Nitrogen (N) and phosphorous (P) are believed to be main factors influencing this process. Thus, many efforts were put trying to remove N and P to overcome this problem. Compared with other methods proposed, in situ remediation, based on ecology and phytoremediation, possessed a higher removal efficiency with relatively low cost and therefore shows great potential in application. In this paper, some technologies of ecological remediation engineering for eutrophic river were studied. The main results were summarized as follows:1. In order to screen out plant speices with highest inorganic nutrients removal efficiency, eight plant species (e.i. Vetiveria zizanioides L, Panicum virgatum, Jussiaea stipulacea Ohwi, Ceratophyllum demersum, Vallisneria spiralis, Myriophyllum aquaticum, Lolium perenne Topone) were selected. The results showed that there eight plants can purificate eutrophic water effectively. The highest removal rate of total nitrogen (TN) was91.3%with Myriophyllum aquaticum. While, highest removal efficiency of nitrogen oxides and ammonia was93.1%and94.8%respectively with Ceratophyllum demersum and Jussiaea stipulacea Ohwi, respectively. Lolium perenne Topone also possessed a high removal efficiency for ammonia nitrogen (NH4+-N) and total phosphorus (TP) of89.3%and69.1%, respectively compared to the mean of30%for NH4+-N and65%for TP. Besides, Myriophyllum aquaticum had the highest ability to remove chlorophyll, which reached90.8%.2.In either high or low eutrophic water, addition of anti-nitration bacteria with plants, i.e. Lolium perenne Topone (LPT), Geophila herbacea (L) O Kumtze (GHK), could increase the removal efficiency. The integration of anti-nitration bacteria and LPT, or, anti-nitration bacteria and GHK decreased the contents of TN, NH4+-N, nitrogen oxides, TP, CODMn in the water. There was no significant difference in chlorophyll a and pH compared with that of the0day treatment, while the DO decreased significantly. Compared with phytoremediation, the combination remediation system of plant and microorganism was better to remediate the eutrophic water.3. An integrated phytoremediation systems including emerged and submerged aquatic plant system near riversides and mosaic floating island system on water surface with adsorptive biofilms were constructed in Guanjinggang River of Jiaxing City, Zhejiang Province, to purify eutrophic river water, The engineering demonstration study showed that average removal rates for total nitrogen (TN), NH4+-N, NO3--N NO2--N, total phosphorus (TP) and chlorophyll a in summer-autumn season were36.9%,44.8%,25.6%,53.2%,43.3%and64.5%, respectively, which were16.2%,18.4%,12.8%,25.8%,26.3%and58.7%higher than those in winter-spring season. In addition, the concentrations of total suspended substance (TSS), Escherichia coli and heavy metals were also significantly decreased. Due to its greater biomass, Thalia dealbata showed the greatest element uptake, with N60.9g/m2, P8.2g/m2, C856.6g/m2and S6.2g/m2respectively.