SLUDGE TREATMENT AND DISPOSAL SYSTEMS FOR RURAL-AREAS IN GERMANY

First an overview of the systems currently in use and being discussed for sludge treatment is presented with particular emphasis on distingu ishing between the object of the system (conditioning objective of the various phases in the system) and a system concept (concept of variou s phases of the system in sequence to attain the disposal objective). More detailed information is given as to the salient systems as used w ith smaller sewage treatment plants in rural areas, such as digestion, dewatering, hygienization, composting and thermal drying. A further i tem of discussion is how sludge treatment influences the sewage treatm ent process. For the critical emissions (nitrogen, phosphorus) demande d in Germany, and thus for the degree of sewage treatment required, th e load of the sewage treatment system resulting from sludge treatment needs to be taken into account. Accordingly, operation of sludge treat ment and sewage purification must always be harmonized. The extent of these return loads also limits the spatial centralization of the syste m phases; this applies in particular to smaller sewage treatment plant s in rural areas. In conclusion, an attempt is made to present a persp ective for the agricultural utilization of such sludge in Germany. Sin ce the critical values for emissions have been further tightened by ne w regulations, thus considerably elevating the associated sophisticati on of monitoring techniques, it is to be expected that the use of sewa ge sludge in agriculture will also be further reduced in rural areas, especially since public awareness of emission control has considerably reduced the acceptance of sewage sludge as fertilizer.