1999 Volume 25 Issue 2 Pages 182-188
The batch aerobic digestion process is suitable for treating excess activated sludge collected from a small wastewater treatment plant. The effect of sludge concentration on treatment characteristics of the digestion process is investigated in this paper. Sample sludges are the excess activated sludges of a municipal wastewater treatment plant and the activated sludges acclimated to glucose and glucosepeptone, and these sludges are conditioned to four concentrations. In every concentration of each sludge, the final reduction ratio and the rate constant of decomposition of sludge solids are constant, and the decomposition rate could be related to the oxygen uptake rate based on the reaction model of aerobic digestion where the sludge composition formula is assumed as C5H7NO2. For the excess activated sludge and glucose-peptone acclimated sludge, organic nitrogen produced by aerobic digestion is transformed through NH4-N to NO3-N, pH decreases rapidly at the beginning of digestion, and the denitrification percentage is small. On the other hand, for glucose acclimated sludge, NO3-N is not detected and pH was between 7 and 8 during the first 1020 days, and the denitrification percentage increases. The sludge reduction ratio performed by anaerobic digestion in the municipal wastewater treatment plant could be attained in half the time by aerobic digestion, and the organic carbon concentration of supernatant in aerobic digestion is much smaller than that of anaerobic digestion.
