Purification efficiency of the constructed wetland combined process for oil wastewater

In order to elaborate the advantages of constructed wetland and membrane technology and overcomes both shortcomings,the study investigated the feasibility of treatment of oil wastewater by the constructed wetland combined process.Experiment of the process of horizontal subsurface flow constructed wetland with ultra filtration membrane for oil wastewater was carried out.The results showed that the average removal rates of TN,COD,petroleum,BOD and NH4+-N in the constructed wetland system were 66.07%,82.98%,73.18%,58.99% and 55.36% respectively.When influent flow was 1.2 m3.d-1and the operating pressures of ultrafiltration membrane(PVDF) was 0.2 MPa,the constructed wetland combined process can achieve better effect of treatment.As influent TN,COD,petroleum,BOD and NH4+-N were 9.59,270.80,1.99,14.59 and 4.40 mg.L-1,respectively,the effluent were 3.23,46.02,0.53,5.97 and 1.96 mg.L-1,respectively.According to China Standard for Surface Water Resources(GB3838-2002),mean effluent TN and COD and petroleum can nearly reach Grade V,Grade V and Grade IV,and BOD and NH4+-N can reach Grade IV,respectively.In addition,seasonal variation analysis showed that purification efficiency of the constructed wetland combined process was the best in summer.The purification efficiency is better in spring than in autumn.Moreover,wetland plant plays an important role in treatment process.