长期侧流提取对EBPR系统除磷及其磷回收性能的影响

实验采用交替厌氧/好氧(An/O)运行模式的SBR反应器,考察310 d内分3个批次提取侧流比为0、1/4、1/3、1/2的厌氧放磷上清液后EBPR系统的脱氮除磷效果及相应的磷回收性能.结果表明,整个实验阶段系统对COD和氨氮的去除较为稳定,出水均能满足《城镇污水处理厂污染物综合排放标准》一级A标准,总氮去除因厌氧阶段反硝化不断增强有所提升,达标率由88.2%显著上升至98.6%.然而,随着厌氧上清液提取次数的增多,系统释磷能力整体下降,但前两个批次中系统除磷均稳定高效,去除率在90%以上,相应地出水磷达标率大于75%,仅第3批次实验中侧流比为1/2时系统除磷率出现大幅波动,最低降为54.2%,并贡献该批次出水磷不达标率的60%,说明长期提取1/2侧流比不利于主流工艺出水稳定维持.研究还发现,长期进行侧流磷回收实验有利于污泥减量,且对污泥沉降性能影响不大.因此,在EBPR系统内长期提取适当侧流比的厌氧上清液以进行磷回收与主流工艺同步高效脱氮除磷具有可行性.

Effects of Long-term Side Stream Extracton on Phosphorus Removal and Recovery Performance of EBPR System

A sequencing batch reactor (SBR) with alternating anaerobic/oxic (An/O) operation was employed to investigate nitrogen and phosphorus removal performance and corresponding phosphate recovery effect of an enhanced biological phosphorus removal (EBPR) system when extracting side stream ratios of 0, 1/4, 1/3, 1/2 anaerobic phosphorus supernatant. The operation involved three runs within 310 days. Removal efficiencies of COD and NH₄⁺-N were found to be relatively stable over the entire experimental period and effluent could meet standard A of the national discharge standard of pollutants for municipal wastewater treatment plants. Total nitrogen removal improved due to enhancement of denitrification capability during the anaerobic phase, and the standard-reaching rate increased from 88.2% to 98.6%. Although phosphate releasing capability gradually decreased, phosphorus removal performances of the former two runs were stable and efficient. The removal rate was>90% and the corresponding standard-reaching rate was>75%. Nevertheless, phosphorus removal performance began to fluctuate with a side stream ratio of 1/2 during the third run. The lowest phosphorus removal rate was 54.2%, contributing to a 60% non-standard-reaching rate in this run. This suggests that long-term extraction of 1/2 side stream supernatant is not favorable for maintaining stable effluent of the main process. It was also found that long-term phosphate recovery through side stream extraction allowed reduction of sludge mass and had little impact on sludge settling performance. As a result, it is feasible to extract an appropriate side stream ratio of anaerobic supernatant to recover phosphate, combined with efficient removal of both nitrogen and phosphorus in the main process.