Evolution of the sewage treatment plant model SimpleTreat: Use of realistic biodegradability tests in probabilistic model simulations

• Published in: Integrated environmental assessment and management Vol. 9; no. 4; pp. 569 - 579
• Main Authors: Franco, Antonio, Struijs, Jaap, Gouin, Todd, Price, Oliver R
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Publishing Ltd 01-10-2013; Wiley
• Subjects: Activated sludge; Alkylbenzene sulfonate; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Assessments; Biodegradability; Biodegradation; Biological and medical sciences; Biotechnology; Chemicals; Computer simulation; Conservation, protection and management of environment and wildlife; Environmental assessment; Environmental Pollutants - metabolism; Environmental risk; Environmental risk assessment; Estimates; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Models, Statistical; Monte Carlo Method; Organic chemicals; Plants (organisms); Pollution; Probabilistic methods; Probabilistic modeling; Probability theory; Risk assessment; Sewage; Sewage treatment; Sewage treatment plants; SimpleTreat; Sludge; Uncertainty; Waste Disposal Facilities; Wastewater treatment; Wastewater treatment plants; Wastewaters; Water treatment and pollution; Environmental assessment; Probabilistic modeling; Probabilistic approach; Biodegradability; Risk analysis; Environmental management; Modeling; Wastewater treatment; Sewage treatment plant; Environmental risk assessment; Reality; SimpleTreat; Simulation; Risk assessment; Environment; Probabilistic model; Waste water purification
• ISSN: 1551-3777; 1551-3793
• DOI: 10.1002/ieam.1413

ABSTRACT
Given the large number of chemicals under regulatory scrutiny, models play a crucial role in the screening phase of the environmental risk assessment. The sewage treatment plant (STP) model SimpleTreat 3.1 is routinely applied as part of the European Union System for the Evaluation of Substances to estimate the fate and elimination of organic chemicals discharged via sewage. SimpleTreat estimates tend to be conservative and therefore only useful for lower‐tier assessments. A probabilistic version of SimpleTreat was built on the updated version of the model (SimpleTreat 3.2, presented in a parallel article in this issue), embracing likeliest as well as worst‐case conditions in a statistically robust way. Probabilistic parameters representing the variability of sewage characteristics, STP design, and operational parameters were based on actual STP conditions for activated sludge plants in Europe. An evaluation study was carried out for 4 chemicals with distinct sorption and biodegradability profiles: tonalide, triclosan, trimethoprim, and linear alkylbenzene sulfonate. Simulations incorporated information on biodegradability simulation studies with activated sludge (OECD 314B and OECD 303A tests). Good agreement for both median values and variability ranges was observed between model estimates and monitoring data. The uncertainty analysis highlighted the importance of refined data on partitioning and biodegradability in activated sludge to achieve realistic estimates. The study indicates that the best strategy to refine the exposure assessment of down‐the‐drain chemicals is by integrating higher‐tier laboratory data with probabilistic STP simulations and, if possible, by comparing them with monitoring data for validation. Integr Environ Assess Manag 2013;9:569–579. © 2013 SETAC