Study On Screening Of Dominant Wetland Plant Species And Purification By Constructed Wetland In Beijing

The shortage and pollution of water resources have been directly affecting industrial production, human lives, and even human health. It is difficult to popularize traditional manufacturing disposal in small cities and underdeveloped areas because of its high cost. Constructed wetland is the biological technology of wastewater treatment with low cost and less energy consumption for nitrogen and phosphorus removal, so it has been applied widely in European countries. Wetland plants play an important role in constructed wetland. By assimilating, utilizing and adsorbing pollutants, transmitting oxygen, influencing the distribution of microorganisms and enzymes, accumulating organic substances, wetland plants remove nitrogen, phosphorus and heavy metals in wastewater and so on, which achieve the goal of purification of wastewater.By theoretical analysis and practical investigation, constructed wetland system in a small scale was established. This paper mainly studied plant selection, purification results and influence factors in the wetland system, in order to strengthen and popularize the technology in Beijing. Details were:(1) According to the species of plants in natural wetlands in Beijing, this paper selected eight plants, such as Phragmites communis, Typha orientalis, Scripus Validus, Acorus calamus, Zizania, Iris pseudacorus, Alisma orientate, Sagittaria sagittifolia, and researched on their growing status and their abilities of purifying wastewater in different water quality of influent, HRT, hydraulic loading. The results showed that Phragmites communis,Typha orientalis, Sagittaria sagittifolia, Alisma orientali had better effect.(2) The technical design of small-scale plots of constructed wetland and plants were described along with details of some associated wastewater purification effects, the results showed that the vertical constructed wetland performed better in removing contaminants and microorganisms from domestic sewage. For plants were different in physiology, they had different functions and assembled effects. In order to select the optimal plants and the optimum combinations, five plants were studied on purification efficiency in this paper. The main resultsshowed that the average removal efficiency on Total Nitrogen with planted Phragmites communis and Canna indica were higher than 90% for 1 day and 3 days, but the removal efficiency with planted Scirpus validus and Acorus calamus changed from 51.90% for 1 day to 90.90% for 3 days; The removal efficiency was not significantly different from each other on Total Phosphorus except for Phragmites communis; The combination of Phragmites communis and Canna indica, Typha orientalis and Acorus calamus were good at removing COD; the removal efficiency on NH₄⁺-N was the highest with planted Acorus calamus.(3) This paper studied the ability of four floating plants in purifying different sewage, and the factors which influenced that process, such as HRT,PH,temperature. In order to find which factor was principal and which was subordinate, this paper selected Salvinia natans (L.) All and studied their influences on Total nitrogen,Total phosphorus, organic matter by the arrangement of the orthogonal. The results indicated that the power of those factors was HRT,temperature >pH. The best condition was HRT 36h, pH 7.5,temperature 20℃; The results were looked forward to offering foundation for plants' filtration and combination.