Fate and Effects of Triclosan in Activated Sludge

Abstract

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.

Mass balance analysis of triclosan, diethyltoluamide, crotamiton and carbamazepine in sewage treatment plants

“…The almost complete removal of triclosan, limited removal of DEET, and the insignificant or negative removal of crotamiton and carbamazepine correspond well with the reported values. The excellent removal of triclosan may be due to sorption to solids as discussed below, and is comparable to that reported from the USA (Federle et al 2002;McAvoy et al 2002). The removal of DEET was higher in STP-2 than in STP-1.…”

Environmental Exposure of Aquatic and Terrestrial Biota to Triclosan and Triclocarban1

“…Concentrations toxic to algae also are in the parts-per-billion range, with values of 0.2 – 2.8 µg/l for TCS and 10 – 30 µg/l for TCC (Consortium 2002, Orvos et al 2002, Reiss et al 2002, Samosoe-Petersen et al 2003, Yang et al 2008). Inhibitory effects on microorganisms were shown to begin at levels ranging from 25 – 80,000 µg/l for TCS and 100,000 – 40,000,000 µg/l for TCC (Consortium 2002, Federle et al 2002, Samosoe-Petersen et al 2003, Sivaraman et al 2004, Neumegen et al 2005, Stasinakis et al 2007, Farre et al 2008, Stickler and Jones 2008). Readers will note that the upper range minimum inhibitory concentrations (MICs) reported are well in excess of published solubility limits for both biocides discussed here.…”

“… 1 NOEC = no-observed effects concentration; LOEC = lowest observed effects concentration; LC 50 = median lethal dose; EC 50 = half-maximal effective concentration; EC 100 = maximal effective concentration; IC 25 = growth inhibition of 25% concentration; IC 50 = growth inhibition of 50% concentration; MIC = minimum inhibitory concentration 2 Orvos et al 2002 3 Consortium 2002 4 Ishibashi et al 2004 5 Tatarazako et al 2004 6 Samosoe-Petersen et al 2003 7 Reiss et al 2002 8 Yange et al 2008 9 Neumegen et al 2005 10 Stasinakis et al 2007 11 Federle et al 2002 12 Sivaraman et al 2004 13 Stickler and Jones 2008 14 Farre et al 2008. …”

A Novel Magnetic Affinity Support for Protein Adsorption and Purification

“…Adam (2006) reported that the WWTP process entails high initial triclosan sorption to solids followed by degradation over time within the solid phase. Federle et al (2002) reported that more than 94% of triclosan was ultimately biodegraded in a laboratory experiment designed to simulate secondary treatment in an activated sludge WWTP. Similarly, Stasinakis et al (2007) found that 97% of triclosan was ultimately biodegraded in a 96‐d activated sludge WWTP.…”