Purifying Effects And Rules Research On River Water In Suzhou Ancient District By Plant Floating-bed Technology

Based on the national tenth five magnitude project — Suzhou City Water Environment Improvement and Synthesize Demonstration item, we carried out the static simulation test and the dynamic simulation test under the condition of heavy pollution loading rate and low transparency and dissolved oxygen in polluted river of suzhou ancient city district. These investigations were on the base of the formers' work. We analyzed the purification effects and rules of plant floating-bed technology on polluted river water, and also applied the technology to purify the polluted river water in Miaojia River. Conclusions were summed up in the following:The dominance plant option test was carried out among Oenanthe javanica, Lolium mutliflorum and Allium sativum under low temperature condition. The results showed that the Oenanthe javanica was the dominance floating-bed plant under low temperature condition. Its net removal rate of TN, NH₃-N, TP, COD_Mn were 51.3%, 65.2% , 55.6%, 57.6%, respectively, and inhibition rate of algae reached 92.3%.The test of survival adaptability and purification effects under different polluted grade water between Ipomoea aqutica and Canna generalis showed that, Ipomoea aqutica was inhibitted growing under heavy concentration polluted water (TN>30mg/L, TP>10mg/L), while Canna generalis grew well. To some extent, both the two plants had purification function on different grade of polluted water.The dynamic simulation test showed that, the removal rate of TN, NH₃-N,TP of Oenanthe javanica floating-bed was positive correlated with water temperature. The average removal loading rate of TN and TP were 0.80g/m.²Â·d and 0.11g/m²Â·d, respectively. The inhibition on algae was steady and the average inhibition rate was 57.3%. We also got the best value of hydraulic loading rate, floating-bed coverage rate, water depth under dynamic polluted river. They were 1.0m³/(m²Â·d), 30% , 30cm.The plant floating-bed technology application in Miaojia river showed that the water quality of the plant foating-bed technology applied had preceded evidently than the comparing water, though the water quantity was exchanged largely. There existed a micro-ecosystem at the root aera of floating-bed plant which mainly consists of organic grain, algae, zooplankton, zoobenthos. The mode of "Oenanthe javanica -Ipomoea aqutica" floating-bed mode application realized the whole year run of plant foating-bed technology on polluted water. Hence, the mode is suggested in the following application.In conclusion, the plant floating-bed technology could be applied widely as one of high efficient and economic biology restore technology in improving water environment quality of city polluted river.