CAN SLUDGE TREATMENT ADD VALUES?

The present paper gives a review of a brand new technology of sludge treatment developed by Sulzer Technology Corporation. The technology includes sludge stabilizing (digesting), mechanical dewatering, drying, incineration and granulating. According to the local requirements of environment regulation, a special system may be designed by combining the above mentioned operations. In order to add values during the sludge treatment, there are three major principles (three R's): Reduce, Recovery and Reuse. Different kinds of sludge may produce different products and byproducts for various usages. Thus different gains will be obtained from individual systems. Two typical engineering examples are described in detail. A utility power plant of STEAG, Germany has carried out tests of burning the dried sewage sludge in a 750 MW utility boiler. Tests have been ran with up to 25% contribution by the sewage sludge to the heat value. It proves that the sludge can be turned into fuel for Reuse rather than elimination only. The other example is the sewage treatment plant in Dornbirn, Austria. Its fluidized bed drying technology reduced the volume of sludge significantly. Meanwhile, the energy consumption and operation expenses are also reduced.