Purification Efficiency And Mechanism Of The Eutrophic Water By Combined Ecological Floating Bed

A combined ecological floating bed (CEFD) was built in this research to study its purifying effect on the eutrophic water body after methane fermentation in pig farm and the mechanism, which provided experimental and scientific basis for further improvement and promotion of this technology. In this research, various indexes of the sediment and the overlying water and the corrections of different indexes were studied to explore the purifying effect of CEFD on eutrophic water body. Besides, the population changes of bacteria, fungi and actinomycetes in the water and the roots of plant and the changes of alkaline phosphatase activity in sediment were studied during the CEFD operation. The effect of the CEFD on the growth and the phosphorus and nitrogen accumulation and absorption of plant were also analyzed in this research. The main research contents and research conclusions were as follows:(1) In the experiment, COD, TN, NH4+-N, NO3--N and TP were removed significantly, SD increased and the cotent of Chla decreased significantly in overlying water after the purification of the CEFD. The Eh was in the high level and the pH kept in7.63～8.23. The eutrophic state changed from high eutrophication to light one and the water quality was improved obviously. Thus, the CEFD had the significant purifying effect on the eutrophic water.(2) Organic nitrogen was the main form in the surfaced sediment and the NH4+-N was the main composition in the inorganic nitrogen in the sediment. NO3--N was uneven while the NH4+-N and TN was relatively even in sediment. Ca-P and OP as the main composition was higher than other phosphorus forms. Detr-P. Fe-P and Ads-P was12.41%.10.51%and9.37%of TP respectively. IP as the main composition of TP was the70.27%of TP when OP took up less proportion. The contents of various phosphorus forms in IP were different and the order was Ca-P>Detr-P>Fe-P>Ads-P.(3) The contents of TN, NH4+-N and NO3--N in sediment decreased obviously and showed the trend of slow and then fast change during the CEFD operation. Ca-P in the sediment took up the highest and stable content in TP and IP. The content of Fe-P showed the trend of minor decrease in both of IP and OP; The content of exchangeable phosphorus showed decreasing trend in both of IP and TP; The content of organic phosphorus showed increasing trend in TP; Ads-P decreased when Detr-P was stable.(4) The highest APA in the sediment in the start stage of the test was decreased during the test and was the lowest in the end of the test. And the order was spring>summer>fall. In various nitrogen forms, the TN and NO3--N had the strongest correlation with APA (p<0.01) and then NH4+-N(p<0.05); In various phosphorus forms, the Ads-P had the strongest correlation with APA (p<0.01) and then TP and Fe-P (p<0.01) when Ca-P and Detr-P had no correlation with APA.(5) Bacteria in the overlaying water and the roots of five kinds of plant showed the highest proportion in microorganism and then actinomycetes and fungi. Microorganism in the roots of plant showed the highest in July and relatively low in May and September. The numbers of bacterial, fungi and actinomycets in the plant showed the order:O. Saliva L.> Lythrum salicaria Lin> Acorus calamus Linn> Canna indica indica> Thalia dealbata.(6) The CEFD changed the physicochemical property of the overlying water and improved the exchange and transform of different nitrogen forms in the interface of overlying water and sediment. TN, NH4+-N and NO3--N in the water had the significant correction with TN in the sediment at α=0.01; TN and NH4+-N in the water had the significant correction with NH4+-N in the sediment at α=0.01; TN had the correction with NH4+-N in the sediment at α=0.05; NH4+-N in the water had the correction with NO3--N in the sediment at α=0.05. TP in the water had the significant correction with TP, OP and Fe-P in the sediment at α=0.01; TP had the significant correction with Ads-P in the sediment α=0.01; OP had the significant correction with Fe-P in the sediment α=0.01; IP had the significant correction with Ca-P in the sediment α=0.01; Ads-P had the significant correction with Fe-P in the sediment α=0.01.(7) In the five kinds of plants, the reproduce ability of Canna indica and Thalia dealbata was higher than that of O. Sativa L., Lythrum salicaria Lin and Acorus calamus Linn. The nitrogen content in the stem and leaves of Canna indica and Thalia dealbata was higher than that in their roots. The ratio of nitrogen in the stem and leaves and the roots in Canna indica and Thalia dealbata was1.20and1.92respectively. While the nitrogen content in the roots of O. Saliva L., Lythrum salicaria Lin and Acorus calamus Linn was higher than that in their stem and leaves. The ratio of nitrogen in the stem and leaves and the roots in O. Sativa L., Lythrum salicaria Lin and Acorus calamus Linn was0.86,0.94and0.84respectively. The phosphorus content in the stem and leaves of Canna indica, Thalia dealbata and O. Sativa L. was higher than that in their roots. The ratio of phosphorus in the stem and leaves and the roots in Canna indica, Thalia dealbata and O. Sativa L. was1.21.1.13and1.18respectively. While the phosphorus content in the roots of Lythrum salicaria Lin and Acorus calamus Linn was higher than that in their stem and leaves. The ratio of phosphorus in the stem and leaves and the roots in Lythrum salicaria Lin and Acorus calamus Linn was0.48and0.95respectively.(8) Nitrogen and phosphorus accumulations in five plants were significantly different. The absorption rate of Canna indica and Thalia dealbata was higher than that of Lythrum salicaria Lin, Acorus calamus Linn and O. Sativa L.. The absorption quantity of nitrogen and phosphorus in the stem and leaves of Canna indica and Thalia dealbata was higher that that in their roots. Thus, they were adapted to be used in the CEFD and remove the nitrogen and phosphorus in water with harvest of plants.