THE UK APPROACH TO IMPROVING THE SAFE OPERATION OF SEWAGE SLUDGE DRYING PLANTS

This paper is has been written to complement the papers by Lowe [1] presented to the WEF Biosolids and Organic Residuals Conference, Baltimore February 2003. That paper outlined the development of sludge drying in Europe and current and proposed legislation relevant to the drying operation. The paper also outlined some of the current issues relating to the problems of safety. This paper expands the issues relating to safety and how these have been resolved.Sewage sludge when dried has the potential to spontaneously combust given the appropriate conditions. Like other dried materials the risk is compounded by the behaviour of the dust particles generated during the processing and mechanical handling of the materials. Dried sewage sludge has a calorific value between 18 to 26kJ/tonne, which is similar to that of brown coal and as such must be handled and stored accordingly.Following fire and explosion incidents at thermal drying plants in the UK, the Government Agency of the Health and Safety Executive investigated with the UK Water Industry procedures to ensure a safe working environment. The resulting guidance has been used to upgrade existing plants and form the design basis for new plants. In addition changes in European legislation results in more stringent compliance requirements for thermal drying facilities.