STRATEGIES FOR SLUDGE HANDLING IN THE STOCKHOLM REGION

The annual production of dewatered sludge from the municipal wastewate r treatment plants handled by Stockholm Water Company is about 75,000 tonnes. The policy of Stockholm Water Company is to find methods to us e the sludge as a resource by recovering its contents of nutrients and earth-forming substances. The most suitable sludge use is considered to be for agriculture. Intensive work has been done on reducing the sl udge concentration of toxic metals and other pollutants by use of cont rol of discharges of industrial waters into the sewer network, informa tion campaigns to households, and improved management of storm water. The sludge quality is measured by automatic samplers for dewatered slu dge and analyses of heavy metals and certain organic pollutants. Sludg es with better quality than limiting values from authorities may safel y be used in agriculture, while sludges not fulfilling stringent requi rements must be handled by other methods. Due to resistance from the f ood industry and a number of interest organisations, it is important t o find other handling methods also for high quality sludges. Such meth ods include the use of incineration together with municipal solid wast es or biomass or separation of the sludge into different products for internal or external use. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.