Fecal contamination of Finnish fresh waters in 1962-1984

The faecal contamination of Finnish lakes and rivers was estimated from data on total coliform bacteria (TC), thermotolerant coliform bacteria (ThC) and faecal streptococci (FS) collected during a nationwide monitoring programme in the period 1962-1984. The waters were divided into 3 groups; discharges from municipal wastewaters, industrial wastewaters or diffuse loading. All loadings decreased from 1962 to 1976, apart from TC concentrations in industrialized and diffuse load areas. Concentrations of TC, ThC and FS decreased more slowly after 1976 and some, particularly TC, showed an occasional increase. The annual median bacterial concentrations showed similarities with the dynamics of bacterial loads. The effects of increase in population served by wastewater treatment plants, improved sewage treatment schemes, decrease in cattle population and reduction in wastewater from the forest industry were probably responsible for observed reductions in bacterial concentrations. There are 33 references.