FLUIDIZED-BED INCINERATION OF SEWAGE-SLUDGE - A STRATEGY FOR THE DESIGN OF THE INCINERATOR AND THE FUTURE FOR INCINERATOR ASH UTILIZATION

In 1991, the sewage sludge production from municipal sewage treatment plants in Flanders was about 45000 ton/year in terms of dry solids. With additional sewage treatment plants being built, the sludge quantity will dramatically increase. Per capita and per day, about 50 grams of dry solids will be produced, to reach a total production in excess of 100000 ton/year by the end of the century. Most of the sludge is currently disposed by landfill, but it has become more and more difficult to find suitable sites for landfill, particularly in and around large cities. Reduction of the sludge volume to be disposed, therefore, is often a matter of primary concern. Of the new processes developed to ensure the safe disposal of sludges from municipal and industrial effluent treatment, plants, the fluidized bed incinerator is attracting increasing interest. This paper presents a practical strategy for their design and concentrates on the eventual utilization and beneficiation of incinerator ash, which can reduce the total cost of sludge treatment and disposal.