Application Subsurface Flow Constructed Wetland Technology To Deal With The Study Of Rural Sewage

As a ecological treatment technology, constructed wetland system has many advantages, like high treatment efficiency, low investment, cheap operational fee, low energy, wild field of application and so on. However, there is lack of uniform design parameters and methods to build constructed wetland at present. Therefore, the construction of constructed wetland will usually expand the scale of construction after the successful of experiment.Drawing lessons from existing theory and design, the article adopts subsurface constructed wetland which owns high processing efficiency, and designing a pilot project to treat the domestic sewage of the region residential area in order to accumulate the design parameters and experience for Su Qian district. The main content of this study includes:1) confirming best hydraulic loading and residence time;2) confirming best combination of stuffing and plant;3) the study on removal of nitrogen and phosphorus.The test result indicateds that:1) the best hydraulic load is 0.2m3/m2.d by comparing the experiment results.2) under the best hydraulic load 0.2m3/m2.d, in the constructed wetland system, the influent COD concentration is 180 mg/L, the effluent COD concentration is 29.52-35.1mg/L, so the average removal rate is 80.5%-83.6%; the influent nitrogen concentration is 25 mg/L-, the effluent nitrogen concentration is 6.62-7.4mg/L, so the average nitrogen removal rate is 70.43%-73.53%; the influent TPconcentration is 2.8 mg/L, the effluent TP concentration is 0.41-0.66mg/L, so the average TP removal rate is 76.58%-85.45%;3)by determination, the absorbed nitrogen amount of bulrush and cat's-tail is 10.35 kg,this study proves that the absorbed nitrogen amount of plant is not much.4) by determination, the absorbed phosphorus amount of bulrush and cat's-tail is 0.172 kg,this study proves that the absorbed phosphorus amount of plant is also not much.5) by experiment result, the COD removal efficiency of the combining unit of cat's-tail+grail+limestone is better than the combining unit of bulrush+grail+limestone; and without reference to cat's-tail or bulrush constructed wetland, the TP removal efficiency of the combining unit of grail+limestone is better than the combining unit of sand+limestone, which explain there is advantage of calcium carbonate filling combining unit to remove phosphorus.