A comparison of alcohol ethoxylate environmental monitoring data using different analytical procedures.

Several analytical methods have been developed for analyzing alcohol ethoxylates (AE) in aqueous environmental samples. These methods differ widely in their selectivity and sensitivity for measuring the AE components; that is, they vary in their resolution of alkyl chain length homologs and ethoxymer distributions (degree of ethoxylation for each homolog). Given these differences, AE monitoring results from different studies often are inconsistent and, sometimes, are deemed to be incomparable. To address these differences, three currently available methods for determining AE concentrations in environmental matrices were compared among a common set of wastewater treatment plant samples. These methods included the detection of hydrogen bromide-derivatized homologs by gas chromatography/mass spectrometry, the detection of aqueous homologs by high-pressure liquid chromatography/electrospray mass spectrometry, and the detection of pyridinium-derivatized homologs by high-pressure liquid chromatography/electrospray mass spectrometry. Results from the present study showed that all three methods responded differently in determining the complex suite of chemical species that comprise AE in the environment. The collective information, however, allowed a consistent comparison among the methods. This comparison was then used to reevaluate results from previous AE monitoring studies. Results from this reevaluation provided a more realistic profile of both historical AE removal during wastewater treatment as well as the occurrence of AE in U.S. surface waters.

A field study of triclosan loss rates in river water (Cibolo Creek, TX).

Triclosan (TCS) is an anti-microbial agent used in down-the-drain consumer products. Following sewage treatment some of the triclosan will enter receiving waters. This study was designed to determine the die-away rate of triclosan released into a river as part of the sewage treatment plant effluent matrix. The study was conducted in Cibolo Creek, a moderate sized stream (discharge approximately 0.1 m(3)s(-1)) located in South Central Texas. Triclosan was analyzed from samples collected upstream of the sewage treatment plant, the sewage treatment plant effluent, and the river downstream from the effluent discharge. The first-order loss rate of parent triclosan from the water column was calculated from measured data (0.06 h(-1)) and this rate corresponded to a 76% reduction in triclosan over an 8 km river reach below the discharge. Mathematical modeling indicated that sorption and settling accounted for approximately 19% of total triclosan loss over 8 km. When removing sorption and settling, the remaining amount of triclosan had an estimated first-order loss rate of 0.25 h(-1). This loss rate was presumably due to other processes such as biodegradation and photolysis. These data show that loss of parent triclosan from the water column is rapid. Additional data are needed to fully document loss mechanisms.

Environmental fate of Triclosan in the River Aire Basin, UK.

The concentrations and removal rate of Triclosan, an antibacterial ingredient in consumer products, were measured at advanced trickling filter (TF) and activated sludge (AS) wastewater treatment plants (WWTPs) in the River Aire basin in the UK in September 2000. Additionally, the in-stream removal of Triclosan was measured directly in Mag Brook, the stream receiving the treated effluent from the TF plant, using a fluorescent dye tracer to determine the water plug travel times. The in-stream removal of the dissolved and un-ionized (i.e. bioavailable) fraction of the compound was measured using semipermeable membrane devices (SPMDs) deployed at various distances downstream from the WWTP discharge point. The estimated removal rates were used in the GREAT-ER (Geography-Referenced Regional Exposure Assessment Tool for European Rivers) model to predict the site-specific distribution of Triclosan concentrations in the Aire basin as well as to calculate regional concentrations. High WWTP (approximately 95%) and in-stream (0.21-0.33 h-1) removal rates of Triclosan in Mag Brook confirm that this chemical is rapidly eliminated from the aquatic environment.

Removal of fragrance materials during U.S. and European wastewater treatment.

The concentrations and removals of 16 fragrance materials (EMs) were measured in 17 U.S. and European wastewater treatment plants between 1997 and 2000 and were compared to predicted values. The average FM profile and concentrations in U.S. and European influent were similar. The average FM profile in primary effluent was similar to the average influent profile; however, the concentration of FMs was reduced by 14.6-50.6% in primary effluent. The average FM profile in final effluent was significantly different from the primary effluent profile and was a function of the design of the wastewater treatment plant. In general, the removal of sorptive, nonbiodegradable FMs was correlated with the removal of total suspended solids in the plant, while the removal of nonsorptive, biodegradable FMs was correlated with 5-day Biological Oxidation Demand removal in the plant. The overall plant removal (primary + secondary treatment) of FMs ranged from 87.8 to 99.9% for activated sludge plants, 58.6-99.8% for carousel plants, 88.9-99.9% for oxidation ditch plants, 71.3-98.6% for trickling filter plants, 80.8-99.9% for a rotating biological contactor plant, and 96.7-99.9% for lagoons. The average concentration of FMs in final effluent ranged from the limit of quantitation (1-3 ng/L) to 8 microg/L. Measured FM removal and concentrations were compared to predicted values, which were based on industry volume, per capita water use, octanol-water partition coefficient, and biodegradability.

Measurement of triclosan in wastewater treatment systems.

The objective of this study was to investigate the fate and removal of triclosan (TCS; 5-chloro-2-[2,4-dichloro-phenoxy]-phenol), an antimicrobial agent used in a variety of household and personal-care products, in wastewater treatment systems. This objective was accomplished by monitoring the environmental concentrations of TCS, higher chlorinated derivatives of TCS (4,5-dichloro-2-[2,4-dichloro-phenoxy]-phenol [tetra II]; 5,6-dichloro-2-[2,4-dichloro-phenoxy]-phenol [tetra III]; and 4,5,6-trichloro-2-(2,4-dichloro-phenoxy)-phenol [penta]), and a potential biotransformation by-product of TCS (5-chloro-2-[2,4-dicholoro-phenoxy]-anisole [TCS-OMe]) during wastewater treatment. These analytes were isolated from wastewater by using a C18 solid-phase extraction column and from sludge with supercritical fluid CO2. Once the analytes were isolated, they were derivatized to form trimethylsilylethers before quantitation by gas chromatography-mass spectrometry. Recovery of TCS from laboratory-spiked wastewater samples ranged from 79 to 88% for influent, 36 to 87% for final effluent, and 70 to 109% for primary sludge. Field concentrations of TCS in influent wastewater ranged from 3.8 to 16.6 microg/L and concentrations for final effluent ranged from 0.2 to 2.7 microg/L. Removal of TCS by activated-sludge treatment was approximately 96%, whereas removal by trickling-filter treatment ranged from 58 to 86%. The higher chlorinated tetra-II, tetra-III, and penta closans were below quantitation in all of the final effluent samples, except for one sampling event. Digested sludge concentrations of TCS ranged from 0.5 to 15.6 microg/g (dry wt), where the lowest value was from an aerobic digestion process and the highest value was from an anaerobic digestion process. Analysis of these results suggests that TCS is readily biodegradable under aerobic conditions, but not under anaerobic conditions. The higher chlorinated closans were near or below the limit of quantitation in all of the digested sludge samples. Based on results from this study, the chlorinated analogues and biotransformation by-product of TCS are expected to be very low in receiving waters and sludge-amended soils.