ABSTRACT
A definitive removal of wastewater sludges is achieved by recycling into the natural circulation. This solution has to be aimed at, especially for small and middle-sized purification plants in rural areas. However, expensive sludge treatment technologies raise great problems in such communities. The cheapest sludge removal can be seen in the application on nearby agricultural areas. The utilization of liquid sludge proves to be favourable. It is a precondition to produce a fertilizer which may be used without risks in all respects. The sludges must be toxically and hygienically unobjectionable. A nearly odourless disposal should be guaranteed as well as economically reasonable transport quantities in relation to the fertilizer value.
