Organic Micropollutants from the Pulp Industry; Analyses of Lake Päijänne Water

Summary

Lake Päijänne has since 1982 been the raw water supply for the Helsinki metropolitan area. There are pulp mills along the upper reachers of the lake’s drainage area. In order to investigate the appearance and course of organic micropollutants derived from the pulp industry, TOC, lignosulphonates, TOC¹, trihalomethanes and some chlorinated phenols were analysed at several sampling stations in the Lake Päijänne area. Also the removal of these compouds in water treatment was studied in pilot plant tests. The highest value: of all analysed parameters has been observed immediately downstream of the pulp mills. All compound concentrations decreased with increase in distance from the pulp mills. At the Asikkalanselkä intake station only traces of organic chlorocompounds and lignosulphonates were detected. Water treatment and especially ozonization proved to be effective in reducing the content of organic compounds derived from the pulp industry and present in the raw waters used in the pilot plant runs. The Helsinki Waterworks will continue regular studies on the organic micropollutants in Päijänne water. The purpose is to secure the present good quality of the raw water and to investigate how organics behave in water treatment.