碳氮比及HRT_S对交替缺氧/好氧CAST去除营养物的影响

以实际生活污水为处理对象,分别研究了碳氮比(COD/TN)为2.6、3.5及4.4时,HRTS(选择器水力停留时间)对交替缺氧/好氧(A/O)CAST工艺去除营养物性能的影响.结果表明,采用交替A/O运行方式,进水COD/TN比及HRTS的变化对COD去除性能影响不明显;而对脱氮性能影响较大.当进水COD/TN比分别为2.6和3.5时,系统氨氮去除率均维持在98%以上,TN去除率则随HRTS的增大而升高;HRTS由1.8h增至5h时,2种碳氮比下的TN去除率分别由62.9%、72.1%升至76.2%、84.6%.当进水COD/TN比为4.4时,HRTS由1.8h增至5h导致系统硝化不完全,TN去除率由86.3%降至58.2%.研究还发现,提高COD/TN比和增大HRTS均能改善系统的除磷性能.本研究中交替A/O运行方式下,进水COD/TN比为4.4(远低于一般城市生活污水的8～10),HRTS为1.8h时,CAST工艺获得较好的脱氮除磷效果,TN及磷的去除率分别为86.3%和93.8%,出水达到我国城镇污水处理厂污染物排放标准(GB18918-2002)一级A要求.

Effects of COD/TN and HRTS on Nutrients Removal by an Alternating Anoxic/Oxic CAST

The effects of different COD/TN and HRT_S (hydraulic retention time of select) on nutrients removal were investigated by using an alternating anoxic/oxic CAST (cyclic activated sludge technology) fed with municipal wastewater. The results showed that various COD/TN and HRT_S had a bigger influence on the nitrogen removal efficiency rather than the COD removal efficiency. As the influent C/N ratios were about 2.6 and 3.5, ammonia was removed by 98% and TN removal efficiency was increased from 62.9% to 76.2% and 72.1% to 84.6%, respectively, by increasing the HRT_S from 1.8 h to 5 h. When the COD/TN ratio was increased to about 4.4, TN removal efficiency was decreased from 86.3% to 58.2% by enlarging the HRT_S, which was due to the incomplete nitrification of ammonia. It was also observed that both of increasing the COD/TN and HRT_S could improve the phosphorus removal performance of the system. Furthermore, effluent of CAST reached the demanded A of integrated wastewater discharge standards (GB 18918-2002) when the COD/TN and HRT_S were 4.4 and 1.8 h, respectively.