Evaluation of anionic surfactant concentrations in US effluents and probabilistic determination of their combined ecological risk in mixing zones

• Published in: The Science of the total environment 2016-12, Vol.572, p.434-441
• Main Authors: McDonough, Kathleen, Casteel, Kenneth, Itrich, Nina, Menzies, Jennifer, Belanger, Scott, Wehmeyer, Kenneth, Federle, Thomas
• Format: Article
• Language: English
• Subjects: Alkanesulfonates - analysis; Aquatic; Dilution factors; Environmental Monitoring; Humans; Risk Assessment; Sulfates - analysis; Surface-Active Agents - analysis; Toxic units; United States; Waste Disposal, Fluid; Waste Water - analysis; Water Pollutants, Chemical - analysis; WWTP monitoring
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.08.084

Alcohol sulfates (AS), alcohol ethoxysulfates (AES), linear alkyl benzenesulfonates (LAS) and methyl ester sulfonates (MES) are anionic surfactants that are widely used in household detergents and consumer products resulting in over 1 million tons being disposed of down the drain annually in the US. A monitoring campaign was conducted which collected grab effluent samples from 44 wastewater treatment plants (WWTPs) across the US to generate statistical distributions of effluent concentrations for anionic surfactants. The mean concentrations for AS, AES, LAS and MES were 5.03±4.5, 1.95±0.7, 15.3±19, and 0.35±0.13μg/L respectively. Since each of these surfactants consist of multiple homologues that differ in their toxicity, the concentration of each homologue measured in an effluent sample was converted into a toxic unit (TU) by normalizing to the predicted no effect concentration (PNEC) derived from high tier effects data (mesocosm studies). The statistical distributions of the combined TUs in the effluents were used in combination with distributions of dilution factors for WWTP mixing zones to conduct a US-wide probabilistic risk assessment for the aquatic environment for each of the surfactants. The 90th percentile level of TUs for AS, AES, LAS and MES in mixing zones were 1.89×10−2, 2.73×10−3, 2.72×10−2, and 3.65×10−5 under 7Q10 (lowest river flow occurring over a 7day period every 10years) low flow conditions. Because these surfactants have the same toxicological mode of action, the TUs were summed and the aquatic safety for anionic surfactants as a whole was assessed. At the 90th percentile level under the conservative 7Q10 low flow conditions the forecasted TUs were 4.21×10−2 which indicates that there is a significant margin of safety for the class of anionic surfactants in US aquatic environments. [Display omitted] •Anionic surfactant US-wide wastewater treatment plant effluent monitoring•Anionic surfactant toxic unit distributions in US effluents•US-wide anionic surfactant probabilistic risk assessment in WWTP mixing zones