Quorum sensing signals regulate various functions within activated sludge processes such as formation of microbial aggregates. Disturbance of this signaling system, known as quorum quenching (QQ), provides opportunities for eliminating some problems related to biological wastewater treatment (e.g., biofouling and excess sludge production). However, it is poorly understood how and to what extent QQ systems can affect the microbial aggregation processes and the following floc formation. In particular, an in-depth structural characterization at the scale of microbial aggregate while considering nutrient conditions in the reactor is still largely disregarded. Here, we evaluated the QQ effects at the short-term time scale (i.e., after 4 h for the exogenous period and 19 h for exogenous/endogenous period), by combining advanced techniques for microbial characterization (flow cytometry, CARD-FISH, and confocal laser scanning microscopy) and conventional physical-chemical assessments. The results indicated that by implementing QQ agents (immobilized Acylase I enzyme in porous alginate beads) the abundance of single cells and suspended microbial aggregates in the supernatant did not show significant changes during the exogenous period. Conversely, at the end of the exogenous/endogenous period a significant increase of single prokaryotic cells, small and large microbial aggregates favored the growth of grazers, including free-living nanoflagellates and ciliates. Flocs became looser and thinner than those in the control reactor, thus affecting the sludge settling behavior. Inability of microbial community in degradation of soluble protein during the endogenous period confirmed that the QQ agents are likely to inhibit the secretion of protease enzyme within microbial communities of activated sludge.

中文翻译：

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在短时间内调查定额猝灭和营养条件对活性污泥絮凝物的影响。

群体感应信号调节活性污泥过程中的各种功能，例如形成微生物聚集体。这种信号系统的干扰（称为群体猝灭（QQ））为消除与生物废水处理相关的一些问题（例如，生物污垢和过量污泥产生）提供了机会。但是，人们对QQ系统如何以及在多大程度上影响微生物的聚集过程和随后的絮凝物形成了解甚少。特别是，在很大程度上考虑微生物在反应器中的营养条件时，在微生物聚集体规模上的深入结构表征仍然被忽略。在这里，我们在短期时间范围内（即外生期4小时后，外源/内生期19小时后）评估了QQ效果，通过将先进的微生物表征技术（流式细胞仪，CARD-FISH和共聚焦激光扫描显微镜）与常规物理化学评估相结合。结果表明，通过实施QQ剂（固定在多孔藻酸盐微珠中的乙酰化酶I），上清液中的单细胞和悬浮的微生物聚集体的丰度在外源期间没有显示出显着变化。相反，在外源/内源期结束时，单个原核细胞，大小微生物聚集体的显着增加有利于放牧者的生长，包括自由生活的纳米鞭毛和纤毛。絮凝物变得比对照反应器中的絮凝物更薄，更细，从而影响了污泥的沉降行为。