Conjunctive monitoring of a sewer system and receiving waters in a medium sized community

Results of an urban runoff monitoring program are presented. Combined sewer overflow (CSO) samples were analysed for suspended solids (SS), five-day biochemical oxygen demand (BOD₅), total chemical oxygen demand (COD), total organic carbon (TOC), heavy metals (Cu, Zn, Cd, Pb, Ni), nitrogen compounds, biological and microbiological constituents. Study results indicate that CSOs largely contribute to the organic pollution of the local receiving streams. Cumulative pollution impacts were caused by sedimentation of suspended solids in the waste water treatment plant effluent discharged throughout the year. However, comparison of the various pollution sources indicated that pollution problems in the receiving waters were caused not only by the municipal effluents from the Town of Malacky, but also by diffuse, agricultural pollution characterised by elevated loads of nutrients (N and P), as well as by release of heavy metals (mainly Zn) from the surrounding area.