Experimental Study Of Constructed Wetland Treatment With Volcano Rock Filling Materials For Three Types Of Sewage

Currently, water shortage and water pollution has become a worldwide water environmental problem; this problem is particularly prominent in developing countries. Water pollution is a serious problem threatening the sustainability aspects of economic, social and humanities. Although the state has invested a lot of manpower and resources for water pollution control, however, the water environment has not completely been effectively improved. As recent rise of a new waste water treatment technology, Constructed wetland is playing an increasingly important role in water pollution control. Constructed wetlands sewage treatment technology has the characteristics such as large buffer capacity, good effect,simple process, low investment, low operating costs and so on, and it is very suitable for small town’s sewage treatment.Through the COD、NH4+-N、NO2--N、NO3--N、PO43--P and other indicators in waste water,this experiment investigates the actual effect of sewage, low concentration waste water and high concentration of nitrate nitrogen in sewage treatment of Constructed Wetlands with volcano rock fillings. During the test, according to the different influence factors and the deployment of their change control, this experiment studies on DO, HRT and C/N on the removal effect of pollutants. During the research, the following results were obtained:1) In the treatment of domestic sewage, by means of artificial aeration, Gradually increasing the aeration rate can improve the pollutant removal efficiency of Constructed Wetland, especially for COD 、NH4+-N. But for TP, it makes very little difference; results showed that phosphorus removal is mainly depended on the adsorption of matrix. When the dissolved oxygen in water is about 3mg/L, the removal of pollutants is best and the removal rate of COD、NH4+-N can reach above 90%, the quality of the effluent water is good. As the water content is low and the removal rate is not high, the phosphate removal rate is only about50%. 5mg/L of DO is chosen for the best parameter.2) In the treatment of low concentration waste water, the increase of the hydraulic retention time can improve the removal rate of COD and ammonia nitrogen. When HRT is 1.5,2.5 and 4 days, the average removal rate of CODcr were 57.1%, 72.6%, 78.1% and the average removal rate of ammonia nitrogen is 53.8%, 98%, 99%, significantly improved. While thehydraulic retention time is low, the removal of COD and ammonia nitrogen fluctuates and the biochemical reaction is not sufficient. However the longer residence time makes the denitrification effect reduce, all of the ammonia nitrogen is into NO3--N and discharge. The hydraulic retention time can affect the removal rate of phosphate, but little, and the removal of phosphorus in waste water mainly depends on the adsorption and ion exchanges. 2.5d of HRT is chosen for the best parameter.3) In the treatment of high nitrate waste water, the type of additional carbon source influences the process of nitrification and denitrification. This experiment is mainly for the high concentration of nitrate nitrogen waste water, so it makes the sodium acetate as additional carbon source and finds that with the increase of the ratio of carbon to nitrogen, the removal rate of nitrate nitrogen and phosphate increases significantly. From not removing when C/N is1:1 to 5:1, NO3--N and PO43--P removal rate respectively increase to 85% and65%. The increasing of the ratio of carbon to nitrogen has little effect on organic matter removal. 5:1 of C/N is chosen for the best parameter.4) While the volcano rock filling materials is as substrates in Constructed Wetland,conditions of the biofilm culturing is good, and organic matter, nitrogen removal rates are at a high level but the effect of the removal of phosphorus is not obvious.5) Constructed wetland is an ecological waste water treatment technology, has a good environmental function and ecological value and is worthy for promotion and application.