IFAT-Entsorga 2010: Technologies for the mechanical thickening and dehydration of sewage sludge

摘要

Efficiency and sustainability were two frequently used words at last year's IFAT-ENTSORGA, also in connection with the treatment of sewage sludge. As already reported in issue F&S 4/2010 /1/, the share of sewage sludge that is used to produce energy is increasing, albeit with large regional differences. New sewage plant constructions and retrofitting, especially in Eastern Europe, have lead to an overall rise of the sewage sludge quantities to be treated. The demand for efficiency and sustainability is met even better the less energy and supplies have to be provided for sewage sludge treatment and transport between the place of origin and the incineration plant and the higher the calorific value of the produced fuel is. Besides the composition of the solid substance fraction (the organic share of solid substances is of special importance here), the calorific value depends on the degree of dryness achieved. Mechanical dewatering and often also transport always precede drying, so that each percentage point of DS content obtained in the dewatering phase reduces costs and energy for transport and drying. Muller /2/ provides one example of optimising energy consumption in sewage sludge treatment and combustion /2/. The degree of dewaterability through application of mechanical force is however limited to the share of free water /3/. So the task is not only to achieve this limit to the best extent possible through advanced development of the machines, but also to perform the process with as little expenditure as possible.