Decontamination Performance Of Phosphorus In Polluted Water By Micro-Aeration Enhanced Ecological Floating Bed

China is one of the world’s13countries severe water shortages. More than400of the600cities in China lack water, most of which belong to the water shortages due to contamination. According to "The Environmental State of China2012" issued by Ministry of Environmental Protection, in2012,25%of60state-controlled key lakes (reservoirs) which were monitored the nutritional status had the problem of eutrophication. Data showed that the situation of control water eutrophication problem.remained in serious condition in China.Ecological floating bed is a new in situ water renovation technology. Based on modern agriculture and ecological engineering measures, it is a soilless cultivation technology which plants aquatic plants on water to renovate polluted water. Less land cover, less investment, low operating cost, easy management were some advantages of ecological floating bed. Traditional ecological floating bed mainly relies on the absorption of root and degradation of microbes on plant root to purify the water. However, with the limitation of surface area available for microbe’s attachment, the number and types of microorganisms in the system are not enough to achieve perfect purification effect. Enhanced ecological floating bed was one of a modified ecological floating bed in recent years. Through some technical means, traditional floating bed can be strengthened to improve its treatment effect greatly.To contrast phosphorus removal effect between enhanced ecological floating bed and traditional one, in this paper, a "floating bed+Iris pseudacorus " types of traditional ecological floating bed was established as well as a "plant unit (traditional ecological floating bed)+microbial processing unit (combined packing)+aeration unit (microporous aeration)"enhanced ecological floating bed. After25days of monitoring on the removal of phosphorus in the test water of two types of floating bed, it is concluded that showed that the removal efficiency of Soluble Reactive Phosphate (SRP) in enhanced ecological floating bed and traditional ecological floating bed were69.74%and46.80%, which of Total Phosphorus (TP) were61.13%and40.97%. it is clearly that purifying effect for SRP, TP of strengthen ecological floating bed were superior to that of traditional ecological floating bed.Plants play a very important role in the water purification process by ecological floating bed. To explore the influence of plants species to purifying effect for phosphorus by enhanced ecological floating bed,3enhanced ecological floating beds made from Iris pseudacorus, Cyperus alternifolius and Iris sibirica were constructed. The results show that during the experiment, the average removal rate of SRP by Iris pseudacorus, Cyperus alternifolius and Iris sibirica floating bed were0.023mg/(L·d),0.019mg/(L·d) and0.017mg/(L·d) respectively, and the removal efficiency were85.17%,71.37%and60.79%respectively. The average removal rate of TP were0.030mg/(L·d),0.024mg/(L·d) and0.020mg/(L·d) respectively, and the removal efficiency were83.30%,65.82%and54.65%respectively. Iris pseudacorus had the best purification effect on SRP and TP, followed by Cyperus alternifolius, and Iris sibirica was the worst. In summary, Iris pseudacorus was recommended to use as the plants of enhanced ecological floating bed.In order to clarify the contribution of plants in the process of purifying phosphorus by enhanced floating bed, the change of phosphorus in the plants were analyzed before and after the experiment. The following results were obtained:(1) Respectively, the accumulation of phosphorus in Iris pseudacorus, Cyperus alternifolius and Iris sibirica were6.81mg/plant,6.81mg/plant and1.39mg/plant. In other words, Iris pseudacorus had the strongest ability to absorb phosphorus, followed by Cyperus alternifolius, and Iris sibirica was the weakest. From the perspective of uptake ability of phosphorus, Iris pseudacorus was elected to be the aquatic plants of enhanced floating bed.(2) The phosphors accumulation in the parts of Iris pseudacorus, Cyperus alternifolius and Iris sibirica above water accounted for73.4%,59.6%and97.9%of it in the whole plant. That is to say, The phosphors accumulation in the plants parts above water were higher than that underwater. Consequently, taking phosphorus away from water through harvesting plants parts above water was highly effective.(3) Absorbing phosphorus by Iris pseudacorus, Cyperus alternifolius and Iris sibirica Contributed45.2%,51.0%and14.1%respectively to the process of purifying phosphorus by enhanced floating bed, which indicated that plants uptake is an important method to removal of phosphorus. Additionally, the contribution of plants uptake in the process of purifying phosphorus by enhanced floating bed varies widely. Iris pseudacorus and Cyperus alternifolius’ uptake contributed a lot but Iris sibirica contributed little relatively.