A SIMPLIFIED MODELING APPROACH USING MICROBIAL-GROWTH KINETICS FOR PREDICTING EXPOSURE CONCENTRATIONS OF ORGANIC-CHEMICALS IN TREATED WASTE-WATER EFFLUENTS

Various mathematical relationships have been used to assess exposure c oncentrations of organic chemicals when emissions occur via wastewater treatment. These relationships range from a simple removal factor cal culation to more sophisticated approaches using kinetic based mathemat ical models. While these existing approaches have been used by decisio n makers to screen new chemicals for exposure assessments, they all ha ve limitations in the predictive capabilities. Thus, a simplified mode ling approach grounded in sound scientific fundamentals that utilizes relatively easy to obtain input parameters is needed. In this paper a simplified modeling approach that utilizes microbial growth kinetics w as developed for predicting effluent concentrations in secondary biolo gical wastewater treatment systems. Receiving water predicted exposure concentrations (PEG) are assessed by using a dilution factor. One adv antage of this approach is that it allows for wastewater treatment pla nt effluent concentrations, and therefore receiving water exposure lev els, to be predicted with a minimum amount of experimental data. It al so provides quantitative data that can be used to assess the relative biodegradability of different chemicals for use in regulatory and risk assessment activities. (C) 1998 Elsevier Science Ltd. All rights rese rved.