Pogue Amy J, Gilbride Kimberley A
Department of Chemistry and Biology, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada.
Can J Microbiol. 2007 May;53(5):559-71. doi: 10.1139/W07-027.
In activated sludge, protozoa feed on free-swimming bacteria and suspended particles, inducing flocculation and increasing the turnover rate of nutrients. In this study, the effect of protozoan grazing on nitrification rates under various conditions in municipal activated sludge batch reactors was examined, as was the spatial distribution of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) within the activated sludge. The reactors were monitored for ammonia, nitrite, nitrate, and total nitrogen concentrations, and bacterial numbers in the presence and absence of cycloheximide (a protozoan inhibitor), allylthiourea (an inhibitor of ammonia oxidation), and EDTA (a deflocculating agent). The accumulations of nitrate, nitrite, and ammonia were lower in batches without than with protozoa grazing. Inhibition of ammonia oxidation also decreased the amount of nitrite and nitrate accumulation. Inhibiting protozoan grazing along with ammonia oxidation further decreased the amounts of nitrite and nitrate accumulated. Induction of deflocculation led to high nitrate accumulation, indicating high levels of nitrification; this effect was lessened in the absence of protozoan grazing. Using fluorescent in situ hybridization and confocal laser scanning microscopy, AOB and NOB were found clustered within the floc, and inhibiting the protozoa, inhibiting ammonia oxidation, or inducing flocculation did not appear to lower the number of AOB and NOB present or affect their position within the floc. These results suggest that the AOB and NOB are present but less active in the absence of protozoa.
在活性污泥中，原生动物以自由游动的细菌和悬浮颗粒为食，促进絮凝并提高营养物质的周转率。在本研究中，考察了市政活性污泥间歇式反应器中不同条件下原生动物捕食对硝化速率的影响，以及活性污泥中氨氧化细菌（AOB）和亚硝酸盐氧化细菌（NOB）的空间分布。监测反应器中有无放线菌酮（一种原生动物抑制剂）、烯丙基硫脲（一种氨氧化抑制剂）和乙二胺四乙酸（一种反絮凝剂）时的氨、亚硝酸盐、硝酸盐和总氮浓度以及细菌数量。没有原生动物捕食的批次中硝酸盐、亚硝酸盐和氨的积累量低于有原生动物捕食的批次。氨氧化的抑制也减少了亚硝酸盐和硝酸盐的积累量。同时抑制原生动物捕食和氨氧化进一步减少了亚硝酸盐和硝酸盐的积累量。反絮凝的诱导导致高硝酸盐积累，表明硝化水平较高；在没有原生动物捕食的情况下，这种影响会减弱。使用荧光原位杂交和共聚焦激光扫描显微镜，发现AOB和NOB聚集在絮体中，抑制原生动物、抑制氨氧化或诱导絮凝似乎不会降低AOB和NOB的数量或影响它们在絮体中的位置。这些结果表明，在没有原生动物的情况下，AOB和NOB存在但活性较低。
