The Application Study On The Wastewater Treatment Technology For Constructed Wetlands Of Plateau Lakes In Yunnan Province

This paper summarises the application and development status of the constructed wetlands all over the world, and shows its advantages such as low investment and running cost, high efficiency and beautiful sightseeing, and the disadvantages such as big occupation area, being limited by climate condition, and being easy to be obstructed by pollutant, ect., Based on almost 100 scientific and technological periodical articles published, and the actual engineering.The constructed wetlands can be classified such four types as the constructed wetland which wastewater flows on its surface, the constructed wetland which wastewater flows vertically, the constructed wetland which wastewater flows flatly, and the complex constructed wetland formed by different tanks and beds. The last one is the most popular constructed wetland in Yunnan province, which also can mainly be classified four types. The constructed wetland has much fuction including decreasing pollution load, clearifiying wastewater, ecological diversity, adjustment of regional weather, beutifying environment, etc.According to the result of plants observation and wastewater monitoring about one year for 5 constructed wetland in Yunnan, the 9 kind of plants including water hyacinth, water celery, water nymph, etc., are more suitful to clearifiying wastewater and beutifying environment. The removal rate of TN, TP, COD_Cr and SS of constructed wetland is about 40-60%, 40-50%, 30-50% and 90% respectively, while the decreasing amount of TN, TP, COD_Cr and SS is about 15-35kgd, 1.0-4.0kg/d, 160-320kg/d, 120-17500 kg/d respectively.The effective facts of constructed wetland for keeping normally running and high clearificaiton rate depend on temperature, hydrological load, pollution load, detention time and growth status of plants. Generally speaking, the constructed wetland only suit for treatment of wastewater with low pollutant, for instance, rural non-piont wastewater, rainfall wastewater and effluent of domestic wastewater treatment plant, etc. The water quality of influent for the constructed wetland should be as follows: PH 6～9, TN≤5.0mg/l, TP≤ 1.0mg/l, COD_Cr≤50mg/1mg/l, BOD₅≤ 10mg/l.