Comparison of parameters characterizing organic matter in a combined sewerduring rainfall events and dry weather

To understand the effect of combined sewer overflows on the river Seine (Fr ance), a characterization of effluent in terms of organic matter and bacter ial biomass was carried out during several sampling campaigns performed in a combined sewer located in Parisian suburbs under wet and dry weather cond itions. Measurements classically used to study wastewater (suspended matter , chemical oxygen demand [COD] and biochemical oxygen demand [BOD]) were co mpared with the estimate of biodegradable and refractory fractions of parti culate and dissolved organic carbon. Relationships among different paramete rs used to describe organic material in effluent were established. Even for large fluctuations in organic matter concentrations, highly homogeneous ra tios between the different descriptors during wet and dry weather were obse rved, and no significant differences could be observed in two catchments st rongly differing by their sizes. The only two small differences in relative composition that could be observed between dry and wet weather were slight ly lower content of organic carbon in suspended solids biodegradability of this material during rain events. Accordingly, with the help of obtained re lationships and values of classical variables like turbidity, BOD, and COD for a given effluent, it is possible to make reasonably accurate estimates of its composition in terms of biodegradable and refractory fractions of di ssolved and particulate organic matter and bacterial biomass.