| Constructed wetland which has advantage of convenience maintenance management, low-cost high-efficiency contamination removal can purify wastewater through the synergism of substrates, microorganisms and plants. Hydraulics is one of the most important factors effecting towards the whole system. Nowadays, however, there are few researches about theoretical Hydraulics Study so that the construction and design of the wetland always depends on traditional experience formula that has a bad influence on the efficiency of the refine function of the constructed wetland in a certain extent. The author monitored and analysed the removal efficiency of contamination throng two kinds of internal structure constructed wetland under different hydraulic loads in order to improve the treatment effect and provide the preferences of hydraulics design parameters.This study monitored the concentration of pollutants from different samples of constructed wetland with installing baffles or not, under hydraulic loads of0.1,0.2,0.3,0.4,0.5m3/(m2·d),then Fit Curve between hydraulic load and the removal of pollutants, the concentration of pollutants from the outlets and HRT. In addition, under hydraulic loads of0.2,0.3,0.4m3/(m2·d), the influence of catchment/distributor area in a vertical/horizontal direction on the removal of pollutants was surveyed to determine more appropriate design in the water distributor/catchment area.(1) This system had good pollutant removal efficiency under different hydraulic loads, with or without baffle. COD removal rate is62.1%～94.4%, TN removal rate is66.8%～88.6%, ammonia nitrogen removal rate is30.4%～80.0%, TP removal rate is78.4%～97.2%, soluble phosphate removal rate is80.5%～97.6%, which have achieved the first A standard of Discharge standard of pollutants for municipal wastewater treatment plant (GB18918-2002).(2) Under the same hydraulic load conditions, contamination removal rate can increase by adding the baffles in constructed wetland system. But the dead zones existed in the system with baffles under hydraulic load of0.1,0.2m3/(m2d-), With the increase of the hydraulic loading, the water flow became gradually plug-folw state and he dead zones will disappeared. For system without the baffles, pollutants content gradually reduced and have not seen obvious the dead zones.(3) There was straight linear correlation between hydraulic load and the removal rates of COD, TN, ammonia nitrogen and the correlation coefficients are quite good (0.9458≤R2≤0.9766). The results showed that COD, TN, ammonia nitrogen concentration from the outlet showed an Exponential Relationship with practical hydraulic retention time (0.8087≤R2≤0.9795), following the first order reaction kinetics model.(4) Under hydraulic load of0.2,0.3m3/(m2·d), the removal rates of COD, TN,TP, soluble phosphate shows that the design catchment/distributor area in a horizontal direction was better than a vertical direction,while under hydraulic load of0.4m3/(m2·d), in a vertical direction is better.The removal rates of NH4-N indicated the opposite phenomenon. By comprehensive comparison, the design of distribution/catchment area in a horizontal/vertical direction is desirable when the hydraulic load is low while in a vertical direction is better options when the hydraulic load is hign or unstable. Therefore, the author advise that the design of distribution/catchment area in a vertical direction is suitable for the practice.Through studies above, the author expects to provide reference for the optimization parameters of designing constructed wetland to benefit pollutants degradation, which will be promoted and developed in the practice to get better application. |
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