超低溶解氧条件下的EBPR系统除磷性能

实验采用两个交替厌氧/好氧(An/O)模式运行的SBR反应器,对不同溶解氧(DO)浓度梯度下EBPR系统除磷效果及工艺性能进行了为期127 d的研究.在未控制DO的对照组反应器R1中,好氧段DO≥6 mg·L~(-1),运行的前65 d内工艺除磷性能稳定,除磷率95.9%,出水总磷0.5 mg·L~(-1),但由于系统长期处于过曝气状态,65 d后除磷性能逐渐恶化,直至97 d后系统彻底失效,整个运行阶段(1~127 d)出水总磷一级A达标率为39.4%.对于实验组反应器R2,控制好氧段DO浓度分别为2、1、0.5、0.2、0.1 mg·L~(-1),各工况初期除磷性能均有小幅波动,但除磷率迅速回升,继而反应器达到稳定运行.统计发现,实验组反应器R2在整个运行阶段出水总磷一级A的达标率为94.6%,127 d内仅有6 d不达标,工艺性能远优于R1.DO=2 mg·L~(-1)系统的比吸磷速率接近最大值,而低DO条件对比吸磷速率影响较大.实验还发现,尽管由超低DO(0.1 mg·L~(-1))引起的有机物降解速率低导致系统发生污泥微膨胀,但出水总磷仍能100%达标排放,微好氧EBPR的节能除磷具有可行性.

Phosphorus Removal Performance in EBPR System under Extra-low Dissolved Oxygen Condition

Two sequencing batch reactors (SBRs) were operated with alternating anaerobic/oxic (An/O) for 127 days to study the phosphorus removal efficiency and process performance of the EBPR under different dissolved oxygen gradient. For the reactor (R₁) in which DO was not controlled and measured as high as 6 mg·L^-1 during the aerobic stage, a stable phosphorus removal performance was achieved in the former 65 days during the operational period. The phosphorus removal efficiency was greater than 95.9% and the total phosphorus in effluent was less than 0.5 mg·L^-1. However, the phosphorus removal performance subsequently deteriorated after 65 days and completely broke up until 97 day due to long-term excessive aeration. Throughout the operational period,only 39.4% of effluent TP met the national wastewater discharge standard A. For the test reactor (R₂) in which DO was controlled at the levels of 2, 1, 0.5, 0.2, 0.1 mg·L^-1 during the aerobic stage, respectively, the phosphorus removal performance showed a slight fluctuation at the beginning of each stage but rapidly increased to a stable state. According to the statistics, 94.6% of effluent TP in reactor R₂ could meet the national wastewater discharge standard A throughout the operational period. In only 6 days out of the 127 days, effluent TP failed to meet the national standard and the process performance was far better than that of R₁. The specific phosphate uptake rate under DO=2 mg·L^-1 was found to be nearly the maximum, but it was greatly influenced by the low DO. In addition, limited filamentous bulking resulted from low organic matter degradation rate under extra-low DO level (0.1 mg·L^-1) was observed. Nevertheless, 100% of effluent TP during this stage could meet the national standard. As a result, the phosphorus removal in micro-aerobic EBPR system for saving energy was feasible.