污水生物生态处理工艺中的脱氮机理研究

Nitrogen removal mechanism of bio-ecological combination processes for decentralized wastewater treatment

通过水解池-美人蕉湿地、水解/接触氧化池-菖蒲湿地现场实验装置考察了生物-生态工艺深度净化分散生活污水的效果。结果表明,水解池-美人蕉湿地尽管湿地停留时间达到7 d,出水NH4+-N仍难以达到一级A(GB18918-2002)标准;而增加接触氧化池后,湿地停留时间仅2 d,组合工艺出水水质远优于一级A出水要求。美人蕉湿地脱氮的主要途径是湿地微生物的硝化/反硝化,植物吸收约占28%。对经接触氧化处理,NH4+-N、NO3--N浓度均较高的进水,菖蒲湿地可在C/N小于2时高效脱氮。菖蒲湿地对TN的去除占组合工艺TN去除量的79%,其中植物吸收仅占湿地除氮总量的8%。湿地介质的厌氧氨氧化活性试验表明,菖蒲湿地介质表面的微生物在无有机碳源存在的条件下,可使培养液中的NH4+-N与NO3--N、NO2--N短期内发生同步脱氮,厌氧氨氧化可能是菖蒲湿地在进水低碳源条件下脱氮的主要原因。

Two kinds of biological ecological combination processes were evaluated for decentralized wastewater nitrogen removal. The combination process 1 was hydrolytic-horizontal subsurface flow constructed wetland planted with Canna indica; and the combination process 2 was hydrolytic/bio-contact oxidation-horizontal subsurface flow constructed wetland planted with Acorus calamus. The concentration of ammonia in the effluent of combination process 1 could not meet the A-level standard of GB18918-2002, though the retention time of wetland was 7 days. After addition of biological contact oxidation, the effluent concentrations of ammonia and TN of the combination process 2 were much better than A-level standard of GB18918-2002 even with a 2 day retention time. The main mechanism of nitrogen removal in the wetland planted with canna indica was nitrification and denitrification, and the plant uptake was contributed for about 28%. With partially nitrification influent, removal rate of nitrogen in wetland achieved 79% when C/N in influent was less than ：2, in which the plant uptake took only 8%. Results of media activity experiment showed that ammonium can react with nitrite and nitrate without the addition of organic carbon and anaerobic ammonium oxidation（ANAMMOX） phenomenon existed in wetland and which may be responsible for the high level of nitrogen removal for the low C/N influent.