Effect of aerations pattern on the sewage-purification capacity of series-operated subsurface flow constructed wetlands

The three-stage series subsurface flow constructed wetland(SFCW)was established with gravel,slag and zeolite as the graded substrates.The effect of aeration location and aeration quantity on pollutant removal efficiency was investigated,and the optimal aeration conditions were obtained through dualistic variance analysis.Aeration position was located in bottom,middle,surface of matrix,and the air-water ratio of SFCW was designed as 3∶1,6∶1,9∶1for adjusting the aeration quantity.Results showed that the COD and NH3-N removal efficiency of SFCW was greatly improved after aeration.The COD removal rate was increased from 5.42% to 23.04% and NH3-N removal rate increased from 7.80%to 23.79%,but for PO34-P,the removal rate was obviously decreased,from 24.32% to 9.76%.When the aeration located at bottom of wetland and air-water ratio was 6∶1,the three-stage series SFCW presented the best water purification efficiency,with the NH3-N,COD and PO34-P removal rate were 21.21%,23.04%,13.54%respectively.NH3-N and COD were significantly affected by interactions of aeration locations and aeration quantity,while the interaction effect on PO34-P was insignificant.