Study On The Effects Of Heat Preservation In Winter And Complex Substrate On The Removal Of Nitrogen And Phosphorus From Tail Water

Nitrogen and phosphours are the main causes of eutrophication, therefore, the tail water needs further purify to meet enhanced requirements for effluent discharge. Constructed wetland is a kind of wasterwater treatment technology, which is low-cost, effective and easy to maintain. Current research on constructed wetland were limited to small experiment, the research on large scale were seldom conducted. Low removal rate in winter limited the application of constructed wetland. In the present study, we built an enhanced eco-wetland in Lin’an waste water treatment plant with treating capacity of 60,000 tons per day. We use this engineered platform to study the effects of low temperature and complex sustrate on N and P removal from the tail water through succesive two yeras’monitoruing and observation. The main results obtained were summarized as follows:1. The constructed enhanced eco-wetland systems were efficient in tail water purification. The average removal rate of NH4+-N, NO3--N, TN, TP, COD were 78.1%,32.7%,37.8%,77.2% and 45.6%. The removal rate of nitrogen and COD kept stable after one year’s running, and the removal rate of phosphours stay stable in the first year. In summer, the system reached the highest effective in removaing contaminants.2. Pollutants removal rate by the constructed enhanced eco-wetland with greenhouse pretection was kept at a high level in cold seasons. In December, January and February, the average removal rate of NH4+-N, NO3--N, TP, COD were 68%,34%,39%,87% and 34%. The constructed eco-wetland systems with greenhouse protection significantly improved the pollutant removal efficiency in cold season, and maintained the system running high effectively all through the year.3. The result of isothermal adsorption experiments showed that Langmuir isotherm fitted the adsorption characteristics of zeolite, shale and slags best. The result of adsorption kinetics experiments showed that the first-order kinetisc and the pseudo second-order kinetics was the best to describe the ammonia and phosphorus adsorption kinetics from zeolite, shale and slags. Compound substrates with zeolite were effective in ammonia adsorption and the removal rate was more than 90%. Compound substrates with slags were effective in phosphorus adsorption and the removal rate was more than 99%. Compound substrate consist of zeolite, slags and shale were effective in ammonia and phosphorus adsorption.