Lignosulphonates in Lake Päijänne Water

Abstract

The water requirements of the city of Helsinki and its adjacent urban areas can be satisfied from the present sources up to about 1978. In order to meet the demand from the 1980's on, water will be conveyed to Helsinki in a 120-km long rock tunnel from the southern end of Lake Paijanne, the central lake of the Kymi River Basin. The total volume of the lake is approximately 17.3 billion cu m as measured from mean water level. Industrial and domestic wastewaters are released into the lake and water courses empty into it. These wastes are mostly made up of the effluents of pulp mills and the spent liquor from the cooking processes. The lignosulphonic acids in these wastes have spread more or less over the whole lake and form an important factor in judging its water quality and suitability as a supply for drinking water purification. The Water Examination Bureau at the Helsinki City Waterworks has carried out water quality studies on the lake since 1965. These studies include measuring lignosulphonate content at sampling stations in central and southern parts of the lake and parallel pilot plant treatment runs with Lake Paijanne water and water from the present raw water supply.