侧流磷回收对低溶解氧EBPR系统性能的影响

实验采用交替厌氧/好氧(An/O)模式运行SBR反应器,考察控制DO=1 mg·L~(-1)条件下提取侧流比为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其对应的磷回收性能.整个实验阶段中NH_~+4-N去除率较为稳定,但系统后期COD出水的残余量达到81.3 mg·L~(-1).在未提取侧流比阶段中,平均除磷率为89.4%,提取1/4、1/3侧流比后除磷率不断上升,分别为98.5%、99.0%,但在1/2侧流比之后,除磷性能开始波动,除磷率最低为65.4%.提取侧流比各阶段中,1/3侧流比条件下仅实验初期第一天出水磷浓度未达到一级A标准,该阶段出水达标率93.3%远远大于1/2侧流比的45.5%,但侧流磷回收率随着侧流比的增大而不断升高.实验还发现,提取1/2侧流比后,TN去除率迅速下降至50.9%.因此,提取放磷上清液强化低好氧EBPR系统除磷性能的最优值为1/3侧流比,此时低好氧EBPR系统与侧流磷回收结合可以大大提高经济与环境效益.

Effects of Side-stream Phosphorus Recovery on the Performance of EBPR System Under Low Dissolved Oxygen Condition

A sequencing batch reactor (SBR) was operated with alternating anaerobic/oxic (An/O) condition to investigate the nitrogen and phosphorus removal performance of EBPR with DO=1 mg·L^-1 and the phosphorus recovery effect at extracting side stream ratio of 0, 1/4, 1/3, 1/2 anaerobic phosphorus supernatant. The removal efficiency of NH₄⁺-N was found to be relatively stable during all experimental stages but effluent COD of the system during later period remained as high as 81.3 mg·L^-1. In the absence of side stream, the average phosphorus removal efficiency was 89.4% and increased to 98.5% and 99.0% when the side stream ratio was 1/4 and 1/3, respectively. However, the phosphorus removal performance began to fluctuate with side stream ratio of 1/2 and the lowest phosphorus removal rate was 65.4%. During each experimental stage, only one day effluent TP failed to meet the national wastewater discharge standard A with side stream ratio of 1/3 in the initial period. Besides, 93.3% of effluent TP which could meet the national standard with side stream ratio of 1/3 was far better than 45.5% of that with side stream ratio of 1/2. Nevertheless, the phosphorus recovery rate improved with the increase of side stream ratio. It was also observed that the TN removal rate dramatically decreased to 50.9% when the side stream ratio increased to 1/2. Consequently, a side stream ratio of 1/3 was found to be the optimal condition in the whole experimental stage, and EBPR system under low dissolved oxygen condition combined with phosphorus recovery through extracting side stream could greatly improve the economic and environmental benefits.