DO对SBR短程硝化系统的短期和长期影响

采用实际的生活污水,在SBR反应器内分别考察了溶解氧(DO)对短程硝化效果及污泥种群结构的短期和长期影响.结果表明,通过采用实时控制曝气时间,高ρDO(ρ(DO)=(3±0.5)mg/L)与低ρDO(ρ(DO)=(0.5±0.1)mg/L)条件下SBR系统的亚硝酸盐积累率均能达到90%以上,而低ρDO相对于高ρDO更利于提高系统的同步硝化反硝化(SND)效果,两者的平均同步硝化反硝化率(SND率)分别为45.5%和9.5%,低ρDO下最高SND率达86%.FISH的检测结果表明,实时控制模式下反应器内亚硝酸氧化菌(NOB)逐渐被淘洗,而氨氧化细菌(AOB)变为优势硝化菌群.在高ρDO运行末期,稳定的短程污泥中AOB和NOB的相对数量分别为8%～10%和不足0.5%;在低ρDO运行末期,AOB数量出现了微弱上升,增至10%～12%,而NOB进一步被淘汰,基本检测不出.可见,采用好氧曝气时间实时控制,能对短程硝化系统内污泥种群起到优化作用,且在高、低ρDO下均能实现稳定的短程硝化效果,而低ρDO更有利于系统内亚硝酸氧化菌(NOB)的淘洗、短程硝化率的提高以及系统SND效果的加强.

Short-term and Long-term Effects of DO on the Partial Nitrification Process in an SBR Reactor

The performance of partial nitrification via nitrite and microbial community structure were investigated and compared in an SBR by operating under different DO conditions. The reactor achieved stable partial nitrification with nitrite accumulation ratio of above 90% both at high and low DO concentrations by using the real-time aeration duration control. Compared with high DO(ρ(DO) = 3 ± 0. 5 mg /L) ,distinct simultaneous nitrification and denitrification(SND) via nitrite was carried out at low DO(ρ(DO) = 0. 5 ± 0. 1 mg /L) despite with lower ammonia oxidation rate. The average efficiency of SND at high DO and low DO concentrations was 9. 5% and 45. 4%,respectively. The maximum SND efficiency reached 86% under low DO concentration. Fluorescence in situ hybridization(FISH) analysis showed that AOB(ammonia oxidizing bacteria) became the dominant nitrifying bacteria and NOB(nitrite oxidizing bacteria) was gradually washed out from the reactor when stable nitrite accumulation was established. The sizes of AOB and NOB were 8 ～ 10% and lower than 0. 5% at the end of high DO operation period,respectively. After the operation under low DO,AOB gradually increased to 10 ～ 12% but NOB decreased into negligible level. It can be concluded that the real-time aeration duration control has positive effect on the sludge population optimization under both high and low DO conditions. Keeping DO at a low level is not only beneficial to the wash-out of NOB and the increasing of nitrite accumulation ratio,but also favorable to the enhancement of SND efficiency.