A^(2)O与人工湿地组合工艺处理长三角平原地区农村生活污水的效果

Performance of A^(2)O combined with constructed wetland on treating rural domestic sewage in plain areas of Yangtze River delta region,China

对嘉兴海宁的28座A^(2)O+水平流人工湿地(horizontal flow constructed wetland,HFCWs)和46座A^(2)O+垂直流人工湿地(vertical flow constructed wetland,VFCWs)进行采样,测试了进出水COD、NH_(3)-N、TN、TP和SS,评价了出水稳定性及稳定达标率,比较研究了2种组合工艺对农村生活污水的处理效果及设计和运行问题。结果表明:A^(2)O+VFCWs的出水稳定达标率高于A^(2)O+HFCWs;A^(2)O+VFCWs的出水水质稳定性在冬季较好,但在夏季较差。A^(2)O+VFCWs组合工艺对COD、NH_(3)-N、TN和TP的平均去除率,在冬季为(82.0±18.5)%、(94.8±8.8)%、(49.3±16.8)%和(50.9±16.8)%,在夏季为(72.5±13.2)%、(80.0±16.9)%、(30.0±17.8)%和(30.7±18.9)%,对污染物去除起主要作用的单元是VFCWs。而A^(2)O+HFCWs组合工艺,对COD、NH_(3)-N、TN和TP的平均去除率在冬季为(59.3±21.4)%、(79.1±19.9)%、(42.3±17.3)%和(25.0±10.2)%,在夏季为(62.2±18.0)%、(58.1±30.8)%、(40.6±20.0)%和(28.9±15.7)%,对污染物去除起主要作用的单元是A^(2)O。A^(2)O+VFCWs的A^(2)O单元对TN和TP的平均去除率,在冬季为(20.7±16.3)%和(15.6±10.2)%,在夏季为(20.4±11.9)%和(12.6±13.9)%,而A^(2)O+HFCWs的A^(2)O单元对TN和TP的平均去除率,在冬季为(33.2±16.3)%和(25.0±10.2)%,在夏季为(31.3±24.1)%和(21.9±17.4)%,2种组合工艺中的A^(2)O单元去除效果均不理想,可能与进水碳氮比太低,且排泥少有关。A^(2)O+VFCWs的A^(2)O单元对各污染物去除率明显低于A^(2)O+HFCWs,主要原因是有效容积偏小且溶解氧控制不够。A^(2)O+VFCWs的VFCWs单元对COD、NH_(3)-N、TN和TP的平均去除率,在冬季为(58.8±25.4)%、(61.4±24.4)%、(22.7±8.5)%和(27.4±21.2)%,比HFCWs分别高出16.0%、36.9%、1.3%和9.5%,在夏季为(59.9±25.0)%、(71.6±26.5)%、(38.3±32.8)%和(39.2±32.9)%,比HFCWs高出28.8%、52.6%、10.5%和5.0%,这主要得益于VFCWs较低的设计水力负荷和较低的出水口位置。综合上述结果,建议该县级市从结构和运行2方面着手进行提升改造。

Samples from 28 A^(2)O combined with horizontal flow constructed wetlands(A^(2)O-HFCWs)and 46 A^(2)O combined with vertical flow constructed wetlands(A^(2)O-VFCWs)in Haining County,Jiaxing City were collected,chemical oxygen demand(COD),ammonia nitrogen(NH_(3)-N),total nitrogen(TN),total phosphorus(TP)and suspended solids(SS)in the influent and effluent were determined.Then the stability of effluent quality and compliance rate were evaluated,the comparisons between these two processes on the performance of rural domestic sewage treatment,and the problems of design and operation,were conducted.The results showed that:The compliance rates of A^(2)O-VFCWs were higher than those of A^(2)O-HFCWs.The effluent stability of A^(2)O-VFCWs was good in winter,but poor in summer.The average removal rates of COD,NH_(3)-N,TN and TP by A^(2)O+VFCWs were(82.0±18.5)%,(94.8±8.8)%,(49.3±16.8)%,and(50.9±16.8)%in winter,respectively,while they were(72.5±13.2)%,(80.0±16.9)%,(30.0±17.8)%,and(30.7±18.9)%in summer,respectively.The main unit being responsible for pollutants removal was VFCWs.For A^(2)O+HFCWs,the average removal rates of COD,NH_(3)-N,TN and TP by A^(2)O+VFCWs were(59.3±21.4)%,(79.1±19.9)%,(42.3±17.3)%and(25.0±10.2)%in winter,respectively,,while they were(62.2±18.0)%,(58.1±30.8)%,(40.6±20.0)%and(28.9±15.7)%in summer,respectively.The main unit being responsible for pollutants removal was A^(2)O.The average TN and TP removal rates of A^(2)O unit in A^(2)O+VFCWs were(20.7±16.3)%and(15.6±10.2)%in winter,(20.4±11.9)%and(12.6±13.9)%in summer,respectively,which were significantly lower than those of A^(2)O unit in A^(2)O+HFCWs:(33.2±16.3)%and(25.0±10.2)%in winter,(31.3±24.1)%and(21.9±17.4)%in summer,respectively,The reason was the small effective volume and insufficient dissolved oxygen control.The removal efficiencies of A^(2)O unit in these two combined processes were not ideal,which may be related to the low ratio of carbon to nitrogen and insufficient sludge discharge.The average removal rates of COD,NH_(3)-N,TN and TP of VFCWs unit in A^(2)O+VFCWs were(58.8±25.4)%,(61.4±24.4)%,(22.7±8.5)%,and(27.4±21.2)%in winter,which were 16.0%,36.9%,1.3%,and 9.5%higher than those of HFCWs,respectively;they were(59.9±25.0)%,(71.6±26.5)%,(38.3±32.8)%,and(39.2±32.9)%in summer,which were 28.8%,52.6%,10.5%,and 5.0%higher than those of HFCWs,respectively.The main reasons were the lower design hydraulic load and lower outlet level of VFCWs.To sum up,the county-level city was suggested to improve the performance of A^(2)O or constructed wetland by upgrading structure of the units and optimizing operation strategies.