LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
I. Identification Information
Format B: Monitoring Evaluation #2
(1) Activity associated with Monitoring Information
Sampling of wastewater treatment plant influents, effluents, and surface river waters from 50 locations in
11 U.S. States.
(2) Citation
McAvoy, D.C., Eckhoff, W.S., and Rapaport, R.A. 1993. Fate of linear alkylbenzene sulfonate in the
environment. Environ. Toxicol. Chem. 12:977-987.
II. Monitoring Study Design
(1) Monitoring Study Objective
Determination of real-world concentrations of LAS in wastewater treatment plants and surface waters.
(2) Description of Scenario Monitored
Samples were collected from a national distribution of drainage basins across the U.S. and from a variety of
treatment plant types. Sites were selected based on low effluent dilution and samples were collected during
the periods of lowest flow. Influent and effluent samples were collected from each wastewater treatment
plant. Receiving water samples were collected above and below the outfalls from each treatment plant.
The monitoring results were also used to verify mathematical modeling predictions.
III. Sampling and Analytical Methods
(1) Sampling
Twenty-four hour composite samples of influent and effluent were collected from each treatment plant over
a 3-5 day period, then further composited to represent the average concentration of LAS over the period.
Receiving water samples were collected midchannel above the wastewater treatment plant outfalls and
below the effluent mixing zones as a three-sample transect.
(2) Method/ Procedure
This monitoring study included sampling of wastewater treatment plant influents and effluents, as well as
surface waters above and below the mixing zone in 50 river locations across the U.S. Dissolved LAS was
isolated from solution by solid-phase separation using a SAX column and concentrations determined by
HPLC/fluorescence analysis. The analytical method was chemical specific for LAS, with a detection limit
of 2 µg/L for total LAS.
IV. Description and Results
(1) Media Sampled
Wastewater treatment influent and effluent, and river surface water samples above and below the mixing
zone.
(2) Results
Average LAS influent concentrations ranged from 4.2-5.7 mg/L. Based on effluent concentrations,
removal rates averaged 99.3% for activated sludge plants.
LAS concentrations in samples collected under low flow conditions below the mixing zone were generally
below 50 µg/L. The average alkyl chain length ranged from C11.8-11.9
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