Study On Treatment Of Low-contaminated Water Withaerating Constructed Wetland

Eutrophication is concerned to be one of the most common and seriousissue, especially in China. Controlling the source of pollution could be aneffective way to improve the ecological water environment of Erhai Lake.Artificial wetland ecological is another engineering technology toimprove the environment, which has more advantages compared with theconventional wastewater treatment methods, and it is suitable for waterquality governance of Erhai Lake. Ordinary subsurface flow artificial wetlandis weak in nitrogen and phosphorus removal. The main reason is that thedissolved oxygen in the wetland is insufficient, and nitration reaction isrestrained. In this research, Aerating measures are used to improve dissolvedoxygen in subsurface flow wetland, therefore promoting the nitration reactionand improving the pollutants (total nitrogen, total phosphorus and organicmatter) removal rate.Main conclusions of this essay are as follows:1. DengBeiqiao wetland is a hybrid constructed wetland with surface flow and subsurface flow wetlands in ErHai Lake basin, it has an obviouseffect on nitrogen removal, especially in those non-point source pollutionareas, TN removal rate reaches48%on average and ammonia nitrogenremoval rate53%on average. Surface flow wetland and oxidation pond is themain unit of nitrification, while denitrification goes on very well insubsurface flow wetland. Its poor dissolved oxygen condition is an inhibitedfactor to nitrification.2. Small artificial wetland system was built in the Erhai Lake basin, twoaerating measures were used in the subsurface flow wetland in treatment oflow-polluted water in the river. The results showed that installingaggrandizement oxygenated equipments can effectively improve dissolvedoxygen condition in the artificial wetland. In the front of the wetlanddissolved oxygen concentration was increased to3.8-5.7mg/L from2mg/L(ordinary subsurface flow wetland). Ammonia nitrogen, total nitrogen andpotassium permanganate index removal rate both increased. The total nitrogenremoval rate of pump system, the electrolytic system, the blank group is47%,46%and43%respectively; ammonia nitrogen removal rate is72%,71%and62%respectively; The potassium permanganate index removal rate is29%,22%and14%,total phosphorus removal rate is57%,68%and59%respectively. Aerating measures can improve the bad internal dissolved oxygencondition in artificial wetland system. Both nitrifying bacteria and nitrosomasincrease, meanwhile removal rate of ammonia nitrogen also increasedaccordingly. Nitrate bacteria increased70%and71%, nitrous acid bacteriaincreased26%and64%in pump and electrolytic system, respectively.Intensity of nitrifying raised from0.06mg/Kg·h to0.1mg/Kg·h and0.077mg/Kg·h, conformably ammonia nitrogen processing rate increased to70%.Denitrifying bacteria number of these two oxygenated strengthening groupwere both much higher ordinary wetland, but carbon source shortage is a limitfactor of denitrification in treating micro-polluted water.