| Wetland treatment technology is based on a complete ecosystem model of sewage treatment technol ogy, it’s a new technology in wastewater treatment which is a constantly research both at home and abroad. Wetland system is formed a whole integral with surrounded animals, plants and microbes. As a typical representative of the land treatment method, its a one-time investment is relatively low in terms of other wastewater treatment technology. It also has a large area for plants cultivation, in through this, the wetland both have a function of high sewage capacity and landscaping. Less human intervention during wetland operation, the operation is relatively simple with a low maintenance and operating costs.The traditional technique of artificial wetlands in common in southern China, especially along the Yangtze River. Traditional wetland technology application is limited by many factors in the Northwest, so we take the vertical subsurface flow constructed wetlands technology for wastewater treatment. Different from traditional artificial wetland technologies, vertical subsurface flow constructed wetland technology has an good effect in treating higher concentration wastewater, and the system is relatively large depth which is good for insulation based for cold weather in the Northwest. Therefore, considering the cold weather in the Norwest, we choose vertical subsurface flow constructed wetland technology as research subjects. We set researches on the effect of different times of daily water importing under intermittent operating conditions of vertical flow constructed wetland treatment, the influence of running a series of wetlands under intermittent operating conditions of vertical flow wetland pollutant removal efficiency, and the experimental study of anaerobic biofilter monomer. The results shows:(1) Artificial wetland system under the intermittent operation condition, to determine the water flow as 6m3/d, set the two pools of artificial wetland as contrast experiment object, No.1 pool plants reeds,No.2 pool has Yi grass planted. Through automation system control wetland water per day is 1, 2, 3, 4 times respectively, the water flow is 6m3/time, 3m3/time, 2m3/time and 1.5m3/time. We study on the removal efficiency of various pollutants of the two pools of COD、SS、NH4+-N、TN and TP. The experimental results show that, No.1 pool(planting reeds), importing water twice a day, feed water flow is 3m3/time, the COD, NH4+-N and TN removal effect is best; importing water three times a day, feed water flow is 2m3/time, the SS and TP removal effect is best.No.2 pool(planting Yi grass), importing water once a day, feed water flow is 6m3/time, the TP removal effect is best; importing water twice a day, feed water flow is 3m3/time, the COD and SS removal effect is best; importing water three times a day, feed water flow is 2m3/time, the NH4+-N removal effect is best; importing water four times a day, feed water flow is 1.5m3/time, the TN removal effect is best. Importing water twice a day, the average concentration of SS and TP of the water out of No.1 pool is 12.67mg/L and1.71mg/L, closed to the condition of importing water three times a day. In the same as No.2 pool, importing water twice a day, the average removal rate of NH4+-N、TN and TP respectively are 69.04%、67.76% and 71.26%, and close to its optimum operation conditions of the three pollutants removal rate of 72.57%, 70.76% and 71.51%. Eventually we choose the condition of importing water twice a day, water flow 3m3/time as the best operation condition of the two pools under the intermittent operation condition of artificial wetland.(2) We change the artificial wetland system series operation instead of parallel operation. Under the intermittent operation condition, we import water once every six hours into the wetland, the two pools’ pollutants concentration as well as their respective for pollutants removal efficiency and total removal efficiency of wetland system are determined. The results shows, under the condition of series operation and the water flow is 4m3/d, the COD, SS, NH4+-N and TP removal can reach the B level of the first standard of the GB18918-2002, the removal of TN can only reach the second standard of GB18918-2002. Under the condition of series operation and the water flow is 8m3/d, the COD, SS and TP removal can reach the B level of the first standard of the GB18918-2002, the removal of NH4+-N and TN can only reach the second standard of GB18918-2002.(3) In order to further improve effluent water quality of artificial wetland system, we increase the pretreatment system of experimental research of artificial wetland system. The experiment adopted the anaerobic biological filter as the pretreatment of the constructed wetland system. We examines the change of removal efficiency of DO、COD、SS、NH4+-N、TN、TP under the condition of anaerobic biological filter in different water flow rate(1.6m3/d, 1.2m3/d,0.8m3/d).The results shows, the anaerobic biological filter for SS and COD removal effect is ideal, the nitrogen and phosphorus pollutants also has a certain degree of removal, but relative to the removal rate of SS and COD, not that high. As feed water flow is reduced, all kinds of pollutants removal rate basically there is a constant of high process, but the removal rate increase is not obvious. Only from a certain extent, as the flow rate decreases, the residence time of wastewater in anaerobic biological filter is longer, the microbial pollutant degradation in wastewater becomes more fully. |
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