Polycyclic Aromatic Hydrocarbons: Impact of municipal and industrial wastewater on river catchment water quality

Due to the environmental threat posed by polycyclic aromatic hydrocarbons (PAHs), these compounds are included on the priority substance lists of both the U.S. EPA and the European Union. Monitoring their sources is therefore crucial for protecting aquatic ecosystems. This study presents a comprehensive analysis of the PAH content of municipal and industrial wastewater and its transport and distribution along the Pilica River continuum, the largest left-bank tributary of the Vistula River. The highest PAH loads to the Pilica River were discharged by class IV municipal wastewater treatment plants (WWTPs); this was related to the volume of WWTP outflow, and the composition of treated wastewater, which was dominated by phenanthrene (PHE), pyrene (PYR) and naphthalene (NAP). Among industrial sources, the fruit and vegetable processing sector contributed the most PAHs, while the furniture sector showed the greatest variation in PAH composition. Despite the large PAH loads carried along the Pilica river continuum, none of the identified concentrations in the tested samples exceeded the standards contained in Directive 2013/39/EU of the European Parliament and Council. Furthermore, among all sample types, the emission of PAH loads peaked in the autumn-winter period; the samples also demonstrated common correlation patterns, indicating common sources and similar environmental properties. A key innovation of the study is its holistic approach, i.e. it treats the entire river basin as a unified research system. This perspective enables better understanding of PAH transport, retention, and degradation processes, which are essential for assessing ecological risk and developing effective pollution management strategies.