Dynamics Study on Two-Stage Constructed Wetland Treatment with Natural Reaeration to Treat Rural Sewage
Constructed wetland without natural reoxygenation is the reason of effluent quality deterioration. For the purpose of improving pollutants removing efficiency without oxygen increasing power,this study used a two-stage constructed wetland with an automatic increasing oxygen system to treat rural sewage,and used handy in-situ observation points to take water samples and observe the internal environment. Oxygen supply in the dropping flow process improved the removal efficiency of COD,TP,TN and NH3-N by 8.4%,4.1%,11.7% and 13.9% respectively. The pseudo-first order reaction analysis showed that COD,TP,TN and NH3-N all had a significant decline along the wetland. The aeration by dropping flow increased the decomposition rate of pollutants,but the shortcomings of the carbon source limited the nitrogen removal in the second wetland bed. Volume removal rate constant kv declined along with the decrease of temperature. Using Arrhenius equation to modify kv,the result showed that kv in the first land was bigger than that in the second land,with θ from 1.03 to 1.05 which can meet the correlational study.