Application of Wavy Subsurface Constructed Wetland in Treating Domestic Sewage

HE Cheng-da 1 ,TAN Ling 1 ,GE li-ying 1 ,JI Jun-jie 1 ,YE Ya-ling 1 ,HE Lian 1 ,WANG Hui-min 2(1.College of Environmental Science and Technology Engineering,Yangzh ou University,Yangzhou 225009,Chi na;2.College of Environmental Science and technolo gy engineering,Hohai University,Nanjing 210098,China)

wavy subsurface constructed wetla nd;subsurface constructed wetland;waste m atters degradation;sewage treatment

With interception of biological films on surface of the fillings,abund an t root system,topsoil and fillings,possessing good heat preservation and sanit ation,h orizontal subsurface flow constructed wetland has become a wetland syst emnow mostly studied and applied .A new type of constructed we tland system for sewage treatment wa s studied in the present study,which called Wavy Sub-surf ace Constructed Wetland(W-SFCW).By setting leading-flow plies regu larly i n the wetland in order to impro ve the flow condition in the traditional horizo ntal subsurface wetland(SFCW),the W-SFCWadopted wavy flow instead of horizon tal flow,made the sewage pass through the diff erent constructions in the verti cal direction several times,consequen tly the removal effect was improved.The W-SFCWsystem and the S FCWwere supplied with the same hydra ulic loading rate o f domestic sewage.The ex-periment lasted a year.The test wate r was from the cesspool,which had bee n disposed by two anaerobic reactors in short hydraulic residence time before pouring into t he wetlands.The experiment results showed that,comparing with SFCW,fo r CODNH 4+ and TP,the effluent fromW-SFCWwere 47.1mg ·L-1 ,10.4mg ·L-1 and 0.42mg ·L-1 ,and the effluent fromSFCWwere 59.4mg ·L-1 ,14.8mg ·L-1 and 0.70mg ·L-1 ,as it could be seen that,the removal efficiency of W-SFCWon COD,NH 4+ and TP are higher 8.2%,13.1%and 6.6%than SFCW in the same test condition;the mechanism analyses according to the test r esults considered tha t,the leading-flow i nstruments promoted the wavy flow,c onsequently the con tamination coul d pass through the upper part and bottom part of the wetland sy stem,so that it developed the potent ial of degrading contamination in we tland .What is more,W-SFCWmade the soil adsorbNH 4+ adequately,which was benefit for ni tration.The flow conditions in trad it ional wetland deter-mined partialNH 4+ unable to experience good aerobiotic state so that the nitration was not t h rough.While W-SFCWwas a multileve l A/O technology,it assumed aerobic-fac ultative-anaerobic conditions from the surface to bottom of the system,so W-SFCW possessed better capability of remo vingNH 4+ .However the flow resistance of W-SF CWsystem was bigger.In this test con ditions,the hydraulic lose in W-SFCWwetland bed was 220mm,while in SFCWwa s 70mm;the removal efficiency of W-SFCWand SFCWwere affected distinctly by t he temperature.During the winter,sin ce nitrification and denitrificati on act ivities fell,plants stopped growing,,but there were not deteriorations.The r emoval efficiency on phosphorus was hardly affected by the temperature.