Infiltration of combined sewer overflow and tertiary municipal wastewater: an integrated laboratory and field study on nutrients and dissolved organics

A comparative field and laboratory study was conducted on the infiltration of combined sewer overflow (CSO), with the infiltration of tertiary municipal wastewater (TMW) studied in parallel. Compared to TMW quality, CSO exhibits elevated concentrations of dissolved organic carbon (DOC, 34±11 mg l−1), and nutrients (N, 24±10 mg l−1; P, 1.8± 0.5 mg l−1), while the adsorable organohalogen load (AOX) is significantly lower (23±10 μg l−1). During infiltration the DOC and AOX of CSO are biologically eliminated by 70 and 17%, respectively. Considering these parameters, groundwater quality under CSO infiltration is comparable to or better than under TMW infiltration, while nitrogen and phosphorous concentrations remain elevated. Site specific effects were observed in the field, such as desorption of nutrients and AOX, which were accumulated in the soil during wastewater infiltration over one century.