METHODS FOR STUDYING DISSOLVED-OXYGEN LEVELS IN COASTAL AND ESTUARINEWATERS RECEIVING COMBINED SEWER OVERFLOWS

One factor in determining the transport capacity of coastal intercepto rs in Combined Sewer Systems (CSS) is the reduction of Dissolved Oxyge n (DO) in coastal waters originating from the overflows. The study of the evolution of DO in coastal zones is complex. The high computationa l cost of using mathematical models discriminates against the required probabilistic analysis being undertaken. Alternative methods, based o n such mathematical modelling, employed in a limited number of Eases, are therefore needed. In this paper two alternative methods are presen ted for the study of oxygen deficit resulting from overflows of CSS, I n the first, statistical analyses focus on the causes of the deficit ( the volume discharged). The second concentrates on the effects (the co ncentrations of oxygen in the sea). Both methods have been applied in a study of the coastal interceptor at Pasajes Estuary (Guipuzcoa, Spai n) with similar results.