Co-digestion of solid poultry manure with municipal sewage sludge

The anaerobic digestion was investigated using mixed sewage sludge and poultry manure. The experiments showed that a 30% addition of poultry manure to the sewage sludge did not increase specific gas yield (376 dm3/kg VS versus 384 dm3/kg VS), however gas production rate as calculated per unit volume was 1.5 higher for sludge and manure mixture. The anaerobic digestion turned out to be inefficient in terms of pathogen treatment, since the reduction of Enterobacteriaceae reached only two logarithmic units. In the course of the digestion processes, nutrients were released to the supernatant, and longer SRT favored that phenomenon. The liquor after the digestion of sludge alone was rich in phosphates (348–358 gP/m3) and contained a lot of organic carbon (COD of 2705–6034 gO2/m3). Conversely, more ammonium nitrogen was found in the supernatant after co-digestion of sludge with manure (2094–2221 gN/m3). However, there was no evidence of ammonia inhibition.