Composting of sewage sludge in a rotating vessel

Composting of sewage sludge can enhance its quality and suitability for agricultural use. In this work the optimal conditions for composting sewage sludge of small domestic wastewater treatment plants in a rotating vessel with the aim of sanitary safety were investigated. An intensive control programme with regard to viruses, bacteria and parasites was carried out that showed that the hygienic quality was satisfactory. A second aspect was the investigation of a possible reduction of hazardous organic and inorganic pollutants. The amount of inorganic micropollutants was low and did not change based on inorganic content Based on inorganic residues, losses of 15.7% of the AOX and 25% of the EOX could be found. Relatively high decreasing rates of detergent concentrations could be measured. Only 31.1% of the original load of anionic detergents (measured as MBAS), 38.7% of the calionic and 57.4% of the non-ionic detergents could be detected in the end material. For PAH concentration reduction between 31.5% of fluoranthene and 90.6% benzo(a)pyrene can be reported. All values are based on the inorganic residues. The quality of the resulting compost showed in the plant test a growth rate which qualified the compost to be used to increase soil quality.