| With the development of economy and accelerated urbanization process of China, population of villages and towns increases remarkably, which makes the increasing discharge of wastewater. It is a growing problem which impacts the whole fresh water environment of China. Because of excessive input of nitrogen and phosphorus, Yunnan Erhai Lake, Jiangsu Taihu Lake have a severe outbreak of algal bloom events, which restricts the sustainable development of economy and environment. Phytoplankton growth is the key process of eutrophication, the synthesis of1g algae need to consume0.009g phosphate and0.0063g nitrogen, according to Liebig’s law of the minimum, the influence of P on water eutrophication is more important. Therefore, strategies that control external P loading will control eutrophication over time.There are three methods of phosphorus removal from wastewater:biological phosphorus removal, chemical phosphorus removal and wetland treatment. The former two kinds is not applicable in rural areas for economic and technology reasons. Constructed wetland (CW) is of high efficiency and low energy consumption; furthermore, it is a sewage treatment system which has remarkable environmental value. The current widely applied to non-point source pollution control, river restoration and reconstruction, nature water purification and municipal waste water treatment.Wetland substrates is the core part of the wetland system, especially for the P removal.The thesis focus on the influence of screening of substrates and their spatial layout towards the phosphorus removal of CW, in order to obtain methods of CW substrates construction for long-term phosphorus removal, the main conclusions are as follows:(1) Four substrates was compared, vermiculite phosphorus adsorption capacity reached3473mg/kg, followed by brick584mg/kg, ceramiste132mg/kg, turfy soil126mg/kg. For the desorption rate, the largest is brick,4.16%, followed by ceramsite2.60%, turfy soil2.54%, vermiculite2.27%. Under appropriate operation, these four substrates are not easy to cause secondary pollution.(2) Four CWs with single substrate performed well on the treatment of polluted water.When the influent of TP was3.0±0.5mg/L, the removal rate of all CWs with single substrate are beyond88%. CWs with ceramiste, vermiculite, brick as single substrates performed well when the influent of TP were0.5±0.1mg/L and1.0±0.2mg/L. CW with turfy soil as substrate can’t achieve satisfactory removal rate when the influent of TP was0.5±0.1mg/L(3)The reducible soluble phosphorus(RSP) in substrate was tested., RSP in vermiculite was largest0.8mg/g, followed by brick0.62mg/g and ceramic0.49mg/g, respectively. The growth of plants will not be inhibited, when water soluble phosphorus in soil is0.2mg/kg,can meet the demand of. Plants can grow well in the CWs with substrates of brick, vermiculite, turfy soil, ceramsite.(4) Column1.2:vermiculite-brick-ceramsite-turfy soil column performed well when the influent of TP is0.5mg/L with average removal rate95%and average effluent TP of0.022mg/L; while, column3.2:turfy soil-vermiculite-ceramsite-bricks and column4.2:vermiculite-turfy soil-bricks-ceramsite can’t achieve satisfactory effluent. Accordingly, the layered substrate has a significant influence on the phosphorus removal of CW. |
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