William S. Eckhoff

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.

Measurement of alkyl ethoxylate surfactants in natural waters

Alkyl ethoxylate alcohols (AE) are used in a wide variety of household cleaning products. In order to monitor environmental levels of AE and to determine AE removal during wastewater treatment, an analytical procedure that provides total AE concentration resolved by alkyl chain length for various environmental matrices (influent, effluent, and river water) was developed. The method utilizes a reverse-phase column to extract and concentrate AE from surface waters and wastewaters and utilizes strong anionic and cationic exchange columns to remove potential interferences. AE were reacted with hydrogen bromide to form corresponding alkyl bromide derivatives that were analyzed by capillary gas chromatography with mass selective detection. Recovery of AE from influent, treatment plant effluent, and river water was quantitative (65-102%) over a range of concentrations for all matrices. AE removal was 99% at two activated sludge treatment plants and 92% at two trickling filter plants. Total AE in low dilution (effluent to river water) surface waters downstream from wastewater treatment plants were less than 0.037 mg/L.

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.