| In oder to dispose the wasterwater from students'dormitories, a project of constructed wetland (CW) was constructed in Yangzhen No.1 Middle School in Shunyi District, Beijing. In this paper, the operation of the wasterwater treatment system was monitored to analysis the treatment efficiency. The possible influence factors for the water pollutants romval in CW were researched, to optimize the actual operating conditions for the project and accumulate the experience for the future design and application of CWs. The application of this wasterwater treatment was discussed to verify the feasibility of the CW technology utilization in the boarding schools in suburbs of Beijing. The following results were:After the treatment in CW, the effluent quality was moderately stable. In the period of trial operation, the concentrations of main pollutants CODCr, TN, ammonia nitrogen and TP were 100~150 mg/L, 30~50 mg/L, 20~30mg/L and 2~3mg/L; in the period of normal operation, the concentrations of CODCr, TN, ammonia nitrogen and TP were 30~70mg/L, 20~35mg/L, 5~15mg/L and 1mg/L. In the period of trial operation, the average removal rates of CODCr, TN, ammonia nitrogen and TP in CW were 60.64%, 52.70%, 37.49% and 48.24%; in the period of normal operation, the average removal rates of CODCr, TN, ammonia nitrogen and TP in CW were 61.48%, 55.49%, 62.62% and 60.70%. After the strengthen in pretreatment, the removal rate of the ammonia nitrogen and TP in CW rose obviously. In the period of trial operation, the average removal rates of CODCr, TN, ammonia nitrogen and TP in the sewage treatment system were 67.48%, 54.03%, 43.11% and 57.88%; in the period of normal operation, the average removal rates of CODCr, TN, ammonia nitrogen and TP in the system were 85.41%, 66.97%, 79.23% and 75.83%. After the strengthen in pretreatment, the system's total removal rate of each pollutant enhanced largely.The potential effects on the wastewater treatment efficiency of CW were researched. Under the high load, the water quality was worse, but CW removed more pollutants in quantity; after the pretreatment strengthen, the pollution load reduced, the CW's pollutant removal rate increased, and the water quality was better. The different fluent way was dissimilar in the different pollutant's revomal effect. The surface flow wetland (FWS) was good at ammonia nitrogen's removal; the horizontal subsurface flow (HSF) wetland was better than FWS at the removal effect on COD, TN and TP; the combinational Vertical subsurface flow (VSF) wetland was best at each pollutant's removal effect. The combinational VSF (downflow + upflow) wetland performed good treatment efficiency, so it was suit to promote. The hydroli retention time (HRT) significantly affected CW's treatment efficiency. When the HRT was 3d, the concentrations of CODCr, TN and ammonia nitrogen in the effluent reached the first-level B standard basically, much better than in 2d. Different efficiency between the two combination sestems was small, though the combination system of HSF wetland+ HSF wetland + VSF wetland + oxidation pond was better than the combination system of HSF wetland+ FWS wetland + VSF wetland + oxidation pond.Campus wetlands purified the the effluent of CW effectively. In the period of trial operation, the water quality reached Environmental Quality Standard for Surface Water (GB 3838-2002) Class V. In the period of normal operation, water quality in campus wetlands reached the Class IV standard, achieved the design requirement.The study on inhibitory effect of wetland plants showed that Lemna minor and Acorus calamus could excrete metabolisms to inhibit the Escherichia coli. Decreasing BOD5 was another way to inhibit the Escherichia coli by wetland plants.Because of the environment benefits, economic effectiveness and social effects, the application of CW wasterwater treatment project was feasible. |
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