Triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol) is a widely used antimicrobial agent. To understand its fate during sewage treatment, the biodegradation and removal of TCS were determined in activated sludge. In addition, the effects of TCS on treatment processes were assessed. Fate was determined by examining the biodegradation and removal of TCS radiolabeled with 14C in the 2,4-dichlorphenoxy ring in laboratory batch mineralization experiments and bench-top continuous activated-sludge (CAS) systems. In batch experiments with unacclimated sludge, TCS was mineralized to 14CO2, but the total yield varied as a function of test concentration. Systems that were redosed with TCS exhibited more extensive and faster mineralization, indicating that adaptation was a critical factor determining the rate and extent of biodegradation. In a CAS study in which the influent level of TCS was incrementally increased from 40 microg/L to 2,000 microg/L, removal of the parent compound exceeded 98.5% and removal of total radioactivity (parent and metabolites) exceeded 85%. Between 1.5 and 4.5% of TCS in the influent was sorbed to the wasted solids, whereas >94% underwent primary biodegradation and 81 to 92% was mineralized to CO2 or incorporated in biomass. Increasing levels of TCS in the influent had no major adverse effects on any wastewater treatment process, including chemical oxygen demand, biological oxygen demand, and ammonia removal. In a subsequent experiment, a CAS system, acclimated to TCS at 35 microg/L, received two separate 4-h shock loads of 750 microg/L TCS. Neither removal of TCS nor treatment processes exhibited major adverse effects. An additional CAS study was conducted to examine the removal of a low level (10 microg/L) of TCS. Removal of parent equaled 94.7%, and biodegradation remained the dominant removal mechanism. A subsequent series of CAS experiments examined removal at four influent concentrations (7.5, 11, 20, and 50 microg/L) of TCS and demonstrated that removal of parent ranged from 98.2 to 99.3% and was independent of concentration. Although TCS removal across all experiments appeared unrelated to influent concentration, removal was significantly correlated (r2 = 0.87) with chemical oxygen demand removal, indicating that TCS removal was related to overall treatment efficiency of specific CAS units. In conclusion, the experiments show that TCS is extensively biodegraded and removed in activated-sludge systems and is unlikely to upset sewage treatment processes at levels expected in household and manufacturing wastewaters.

译文

三氯生 (TCS; 5-氯-2-[2,4-二氯-苯氧基]-苯酚) 是一种广泛使用的抗菌剂。为了了解其在污水处理过程中的命运,确定了活性污泥中TCS的生物降解和去除。此外,还评估了TCS对治疗过程的影响。通过在实验室分批矿化实验和台式连续活性污泥 (CAS) 系统中检查2,4-二氯苯氧基环中用14C放射性标记的TCS的生物降解和去除来确定命运。在使用不适应污泥的分批实验中,TCS矿化为14CO2,但总产量随测试浓度的变化而变化。用TCS进行处理的系统表现出更广泛,更快的矿化作用,这表明适应性是决定生物降解速率和程度的关键因素。在CAS研究中,TCS的进水水平从40微克/升增加到2,000微克/升,母体化合物的去除超过98.5%,总放射性 (母体和代谢物) 的去除超过85%。在进水中的TCS 1.5至4.5% 之间被吸附到废弃的固体中,而> 94% 经历了初级生物降解,81至92% 被矿化成CO2或掺入生物质中。进水中TCS水平的增加对任何废水处理过程都没有重大不利影响,包括化学需氧量,生物需氧量和氨去除。在随后的实验中,以35微g/L适应TCS的CAS系统接收两个单独的750微g/L TCS的4小时休克载荷。TCS的去除和治疗过程均未显示出重大的不良反应。进行了另一项CAS研究,以检查低水平 (10微g/L) TCS的去除情况。母体的去除等于94.7%,生物降解仍然是主要的去除机制。随后的一系列CAS实验检查了在四种进水浓度 (7.5、11、20和50微克/升) 下TCS的去除,并证明亲本的去除范围为98.2至99.3%,并且与浓度无关。尽管所有实验中的TCS去除似乎与进水浓度无关,但去除与化学需氧量去除显著相关 (r2 = 0.87),表明TCS去除与特定CAS单元的总体处理效率相关。总之,实验表明,TCS在活性污泥系统中被广泛生物降解和去除,并且不太可能以家庭和制造废水中预期的水平破坏污水处理过程。

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