Research On Subsurface Flow Constructed Wetlands Treating Wastewater Treatment Plant Tail Water

Constructed wetlands (CWs) are engineered wastewater treatment systemsincluding biological, chemical and physical processes. CWs have shown significantremoval efficiency of organic matter, nitrogen and phosphorus and other pollutants forwastewater treatment. Constructed wetlands for wastewater treatment plant (WTP) tailwater deep purification can solve both the problem of water pollution and waterresources shortage. In this study, a pilot and a bench scale experiment were utilized toexplore the feasibility of WTP tail water deep purification by CWs in term of microbialcontrol measures under aeration conditions and add organic carbon source. Conclusionsare as follows:1. The horizontal subsurface flow(HSSF) CW showed a good removal efficiencyof COD and TSS. Particularly, the TSS removal can reach more than80%. The effluentlooks transparent after treatment. Single HSSF CW showed poor removal efficiency ofTN and ammonia of the WTP tail water for its anaerobic environment. NotwithstandingHSSF CW exists suitable anaerobic conditions for denitrifying bacteria, it showed apoor removal of nitrate probably the lack of nitrate reactants. TN processing efficiencyby bench scale experiment via aeration measurement is greatly improved as comparedto the pilot experiment.2. The appropriate combination of bacteria and sufficient carbon source couldshorten the time of biofilm formation, which shorten the time of CWs stable runningand reduce the costs on runs and maintenance.3. The higher rate of organic carbon source added to the CWS can improve theefficiency of the nitrogen pollutants remove. Organic carbon source is the main factoraffecting the denitrification and also the necessary material and energy sources neededby denitrification bacteria. The addition of an organic carbon source can effectivelyimprove the nitrate removal by CWs, which result in the highly removal of TN.