The thermophilic anaerobic process brings an acceleration of biochemical reactions and higher efficiency in the degradation of organic matter in comparison with the mesophilic process. The methanogenic activity of the thermophilic and mesophilic digested sludge was examined during the adaptation of full-scale digesters to an increasing temperature from 38 to 55°C. The results proved a higher activity of the thermophilic sludge after the addition of glucose, acetate and propionate in comparison with the mesophilic sludge; the maximum methane production rates and the methane yield of the raw sludge were always higher under thermophilic conditions; the stability of the degradation process at an increased substrate load was also better. After the adaptation of anaerobic biomass to the temperature of 55°C, the responses of this culture to addition of simple substrates substantially changed, especially in favor of acetate and propionate degradation rates.

The study is focused on the anaerobic degradation of different disintegrated materials containing a cell lysate. The aerobic cell lysate was produced by a disintegration of the excess activated sludge by means of a lysate-thickening centrifuge, and the anaerobic cell lysate, by a rapid thermal treatment of anaerobic digested sludge. The improvement of both the methane yield and the biodegradability of thickened activated sludge is influenced by the quality of input excess activated sludge and the parameters and efficiency of the thickening centrifuge. The improvement of the methane yield was on average 11.5-31.3% depending on the sludge quality. The relation of the stimulation effect, the disintegration rate and the anaerobic sludge activity suggest that the efficiency of the disintegration will be probably higher in the more intensive digestion process. The rapid thermal treatment of digested sludge produced a material with an active anaerobic lysate. The stimulation effect of the anaerobic lysate caused an improvement of the methane yield of raw sludge in the range of 35-49% depending on the lysate amount. The rapid thermal reactor produced a relatively very active cell lysate from anaerobic bacteria; the heat energy of the lysate can be utilised in the digester heating system.