Groundwater pollution at a pulp and paper mill at Sjasstroj near Lake Ladoga, Russia

Lake Ladoga, situated in north-west Russia, is the main source of drinking water for more than 6 million people in the region of St Petersburg. During recent years eutrophication of Lake Ladoga has increased, with pollution of the lake water and sediments by heavy metals, phenols and chloro-organic substances. This paper reports the influence of effluents from a pulp and paper mill at Sjasstroj situated on the southern shore of Lake Ladoga. At Sjasstroj, contamination of a wide area of land, and the production of large volumes of wastewater requiring treatment and disposal, threaten the sustainability of surface and domestic well supplies and lake ecosystems. A tiered approach to risk assessment was adopted in this investigation beginning with a survey of historical data and an initial field reconnaissance followed by more detailed, targeted hydrogeological and hydrochemical investigations. Concentrations of dissolved organic carbon (DOC) as high as 44 mg l(-1) and adsorbable organic halogens as high as 130 mug l(-1) were found in groundwater samples. The detailed field reconnaissance survey contradicted toxicity index values for the wastewater, sludge and groundwater samples calculated using a Russian method of risk characterization, which would otherwise predict a high potential environmental pollution risk. In reality, there is good evidence for natural attenuation of organic compounds in groundwater, with as much as 40-50% removal of DOC. However, the residual DOC can be problematic when chlorination of raw surface and groundwaters creates organo-chlorine byproducts in treated water.