PREDICTION OF THE FATE OF ALCOHOL ETHOXYLATES IN SEWAGE-TREATMENT PLANTS

Alcohol ethoxylates (AE) are used in large amounts in detergents and c leaning agents and are disposed into the aquatic environment. It is kn own that sewage treatment plants (STP's) eliminate surfactants from wa stewater to a high extent. In this study SimpleTreat, a Mackay level I II box model, was applied to simulate the fate of AE in STP's. SimpleT reat uses data on physico-chemical properties, the emission rate of a chemical into the sewer system and the biodegradability of the chemica l. When Monod biodegradation kinetics were applied, predictions of the eliminination of the AE approximate those found in a monitoring study . The Henry's Law constant (H) of AE were calculated from data on vapo ur pressure and critical micelle concentrations. The H values of the A E did not exceed 10(-4) Pa m(3)/mol. Elimination of AE via volatilizat ion in the aeration tank is therefore negligible. Depending on the str ucture of the AE, elimination of the AE in STP's proceeds mainly via s orption on the primary sludge and biodegradation. (C) 1997 Elsevier Sc ience Ltd.