Wastewater as a Driver of Heavy Metal Pollution in River Catchments – a study of possible scenarios

Abstract

Heavy metal pollution is one of the main problems of the Baltic Sea, caused by the inflow of large loads with river waters. Heavy metals can enter rivers i.a. from point sources such as wastewater treatment plants and industrial plants with inadequately-treated wastewater. The present article examines (i) the impact of WWTPs and industrial facilities on the pollution of the Pilica River, (ii) heavy metal loads along its continuum, and (iii) the identification of common pollution patterns in wastewater and river water, and the effect of their physicochemical properties. Among WWTPs, the highest heavy metal concentrations are generated by the smallest plants, and the highest loads by the largest ones, which is related to the size of their flow. In addition, industrial plants are significant sources of point pollution of rivers, with arsenic, tin, zinc, cobalt, copper, molybdenum, nickel, lead, chromium, mercury and barium being detected in wastewater. The most common heavy metal in the Pilica was found to be Barium, with the highest loads observed in winter (66.29-216.98 kg/day). In addition to Ba, depending on the season, arsenic, copper and nickel were also detected. The article takes an innovative approach employing two data calculation variants, which allowed for a comprehensive analysis that captured both typical and less predictable scenarios of river pollution. It also presents an example of modification of the sedimentation-filtration system as a sustainable solution for removing heavy metals from treated wastewater.