Study On Treatment Of Domestic Sewage By Hydrolysisacidationand Stepped Wavy Subsurface Flow Constructed Wetland

According to the characteristics and treatment requirement of domesticsewage of small towns, the combination technology of hydrolysis acidificationand stepped wavy subsurface flow constructed wetland was put forward to treatdomestic sewage of small towns. Through establishing simulation facility, theremoval effect and influence factors of hydrolysis acidification processing unit,stepped wavy subsurface flow constructed wetland unit and the combinationtechnology system on CODCr, NH+4-N and TP in domestic sewage were studiedin this paper respectively, aiming at determining optimal processing parametersof union process. Furthermore, the influence of artificial aeration on the sewagepurification effect of wetland system was examined in this paper. Moreover,static water culture slection experiment of the common aquatic wetland plants inlocal place was also conducted. The results showed that:(1) For hydrolysis acidification processing unit, the best hydraulic retentiontime was6h. Under the optimum conditions, process presented perfect CODCr,SS removal efficiency. When the influent CODCrwas100~450mg·L-1, and theinfluent SS was150~380mg·L-1, the average removal rate of CODCrand SScould reach68.1%and88.3%, reducing the influent loading and influent SS ofwetland and preventing clogging.(2) For constructed wetland unit, the removal rate of stepped wavysubsurface flow constructed wetland on CODCrand TP in domestic sewagedecreased as the increasing hydraulic loading (5.5cm3·cm-2·d-1,11cm3·cm-2·d-1,22cm3·cm-2·d-1,44cm3·cm-2·d-1). Even if the hydraulic loading was44cm3·cm-2·d-1, the removal rate of CODCrwas still good, and the average removalrate could be up to44.8%. When the hydraulic loading was5.5cm3·cm-2·d-1, theremoval rate of TP was the best, and the average removal rate could be up to81.1%. Due to the low concentration of DO in wetland, the removal of NH+4-N mainly depended on the matrical adsorption. When the hydraulic loading was11cm3·cm-2·d-1, the removal rate of NH+4-N was the best, and the average removalrate could be up to50.7%. So the best hydraulic loading of constructed wetlandunit was11cm3·cm-2·d-1.(3) The artificial aeration experience was conducted under the hydraulicloading of44cm3·cm-2·d-1. After the wetland was aerated, DO in wetland and theactivity and the number of aerobic bacteria such as nitrifying bacteria wereincreasing. Therefore, the removal effect of CODCrand NH+4-N increasedsignificantly, and the average removal rate of COD+Crand NH4-N could reach65.8%and81.9%. However, artificial aeration had almost no effect on theremoval effect of TP.(4) The union process run for two months continuously under the optimumconditions (the hydraulic retention time of hydrolysis acidification reactor is6hand the hydraulic loading of stepped wavy subsurface flow constructed wetlandis11cm3·cm-2·d-1). During the test, the influent CODCrwas100~450mg·L-1, theinfluent NH+14-N was15~32mg·L-1, and the influent TP was2~6mg·L-, theaverage removal rate of CODCrand NH+4-N and TP was75.1%,50.3%and78.1%respectively.(5) The experimental results of the indoor static water culture showed that: thepurification effect of CODCrwas not good, but the removal rate of NH+4-N andTP increased continuously with the increasing culture time. When the test ended,the removal effect of Cyperus altemifolius, Lythrum salicaria, Cann indica onCODCrwas the better, the removal rate were56.34%,54.34%,52.64%respectively; the removal effect of Hydrocotyle vulgaris, Scirpus validus onNH+4-N was the better, the removal rate were95.5%,88.34%respectively; theremove effect of Cann indica, Hydrocotyle vulgaris on TP was the better, theremoval rate were68.38%,66.32%respectively.