短好氧泥龄下A2/O和BAF联合工艺的脱氮除磷特性

采用小试装置,研究了短好氧污泥龄下A2/O和BAF联合工艺处理低C/N和C/P污水时的脱氮除磷特性.结果表明,通过提高A2/O工艺段的厌氧区有机负荷和缺氧区硝酸盐负荷对反硝化聚磷菌（DPAOs）进行选择和强化后,其在聚磷菌（PAOs）中的比例维持在28%左右,工艺具有部分反硝化除磷能力,能够减少脱氮除磷过程中对碳源的总需求量.但在联合工艺中,好氧除磷仍是主要的除磷方式.在A2/O工艺段内,好氧污泥龄在满足好氧PAOs存活的同时,还必须满足抑制硝化细菌生长的要求,且为了保证工艺对磷的整体去除效果,混合液在好氧区的接触时间须大于30 min.此外,以保证缺氧区出水中含有1～4 mg/L的硝态氮为原则来控制BAF出水的回流量,可达到较好的脱氮除磷效果.该联合工艺结合了活性污泥工艺和生物膜工艺的优点,运行稳定,出水水质优良,不仅适合于新建污水处理厂,也特别适合于不能脱氮除磷污水处理厂的技术改造.

Nitrogen and Phosphorus Removal Characteristics in Combined Short Aerobic SRT A2/O and BAF Process

A bench-scale study on the performance of combined short aerobic SRT A^2/O and BAF process for treating the wastewater with lower C/N and C/P ratio was conducted with the emphasis on nitrogen and phosphorus removal characteristics. The results indicate that the ratio of DPAOs to PAOs can be maintained at 28% through optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone to promote the development of DPAOs. The combined process has some anoxic phosphorus uptake capacity, which can decrease the total carbon source demand for nitrogen and phosphorus removal. However, the aerobic phosphorus over-uptake is the main mechanism of phosphorus removal in the combined process. Demands for the development of aerobic PAOs and the restraint on the nitrifier growth simultaneously must be met by the aerobic SRT in the A^2/O system. The contact time in the aerobic zone is more than 30 minutes, which ensures efficient phosphorus removal in the combined process. The adequate BAF effluent return rate is controlled with 1 -4 mg/L of nitrate in the anoxic zone effluent of A^2/O system to achieve optimal nitrogen and phosphorus removal efficiencies. The combined process unites the inherent characteristics of both activated sludge process and biofilm process and has the advantages of stable operation, and high quality of final effluent, which is fit not only for newly-built WWTPs, but also upgrading of the existing WWTPs without biological nitrogen and phosphorus removal capacity.