Determination of COD, BOD, and suspended solids loads during combined sewer overflow (CSO) events in some combined catchments in Spain

The main topic of the research project presented here in part is the determination of pollutant loads during combined sewer overflow events in several experimental catchments in Spain that were determined to obtain a pollution pattern which may be applied to other catchments in Spain or an order of magnitude of pollution loads in Spanish catchments. The existence or non-existence of a first-flush is also examined. Five catchments were monitored in five Spanish cities, and both hydraulic parameters and pollutant amounts were measured in dry conditions and during rainfall events. From the data obtained, some parameters were extracted for each catchment and an order of magnitude of the pollution amounts was proposed for Spanish catchments, in terms of event mean concentration (EMC) and maximum concentrations, since the moderate differences between catchments permit an estimation of a mean value.