THE IMPORTANCE OF THE TREATMENT-PLANT PERFORMANCE DURING RAIN TO ACUTE WATER-POLLUTION

Rain causes not only pollution loads from combined sewer overflows but also from treatment plants. High hydraulic load conditions can affect the secondary clarifier performance, resulting in a massive loss of s ludge from the plant. The consequence to the oxygen concentration in t he recipient can be described by the same simplified mechanism, becaus e the principle remains the same. The difference that has to be accoun ted for, is the different organic characteristics of the discharged wa ter. The analysis of a hypothetical urban drainage system by means of a deterministic model reveals the importance of the treatment plant in this respect. Oxygen depletion in urban rivers is caused by intermitt ent discharges from both sewer system and wastewater treatment plant. Neglecting one of them in the evaluation of the environmental impact g ives a wrong impression of total system behavior. Linear sensitivity a nalysis provides useful information for Water quality management. The significant parameters in terms of acute water pollution are identifie d. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.