Decentralised methods for the treatment of waste water, and in particular small-scale sewage treatment plants, were long held to be inadequate within the meaning of modern waste water purification due to their poor performance capability. However, realistic comparisons of the costs and performance of modern decentralised waste water purification, national research projects and the pressure created by a number of interest groups have led to a change in attitude in many federal states. We have taken on the task of devising new methods of treatment in research and study projects, and to implement these in agricultural practice. Due to its specific composition of organic constituents, agricultural production wastewater is often deemed to be hazardous material, and can lead to the overburdening of municipal wastewater treatment plants.