M3 PM Wastewater Treatment: Analysis, Fate and Removal of Emerging Contaminants
Monday, 14 November 2005: 1:50 PM - 5:30 PM in Ballroom 3

(HEI-1117-809434) Tracking the Fate of Triclosan during Activated Sludge Wastewater Treatment.

Heidler, J.¹, Halden, R.¹, ¹ Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA

ABSTRACT- Triclosan (TCS) is a polychlorinated aromatic antimicrobial used in many household products including soap, toothpaste and cosmetics. The first national reconnaissance of pharmaceuticals, hormones and other organic wastewater contaminants conducted by the United States Geological Survey (USGS) in 1999−2000 revealed triclosan as one of the top five microcontaminants in rivers nationwide. Besides its known persistence in the environment and its ability to bioaccumulate in fish and human milk, triclosan is also suspected to act as an endocrine disruptor and to cause cross-resistance to clinically important antibiotics. The fate of triclosan during wastewater treatment has been the subject of a number of investigations but few have considered municipal sludge as a potential sink. We conducted a complete mass balance for triclosan during passage through a typical activated sludge wastewater treatment plant located in the Mid-Atlantic region. Hourly samples of influent and effluent were collected using an automated sampler, whereas digested sludge was collected by grab sampling. To allow for accurate quantification, we employed an isotope dilution liquid chromatography mass spectrometry method using a 13C-labeled analog and a deuterated analog as surrogate and internal standards, respectively. The mass of triclosan found in influent and effluent was 3243 ± 1856 g/day and 48 ± 2 g/day (mean ± STDEV), respectively, indicating a removal efficiency in the aqueous stream of 98%. However, a significant amount of the antimicrobial withstood aerobic and anaerobic degradation and accumulated in wastewater residuals (biosolids). At 34 ± 11 mg/kg (mean ± STDEV), the concentration of triclosan found in digested sludge was four orders of magnitude higher than in the influent. Mass balance results suggest that a significant fraction of triclosan (∼57%) partitions into and persist in biosolids. Therefore, we conclude that the widespread land application of municipal biosolids as agricultural fertilizer represents an important, but currently underappreciated pathway for reentry of triclosan into the environment.

Key words: Triclosan, PPCP, wastewater treatment plant, mass balance