Kinetic analysis of thermophilic anaerobic digestion of wastewater sludge

Conventional mesophilic anaerobic digesters are sometimes subject to process upset and have earned the reputation of being difficult to cope with sludge overloading. This study was conducted to examine the thermophilic process as a viable alternative. An analysis of field data from an operating mesophilic sludge digester was conducted in parallel with experimental runs on a laboratory thermophilic reactor using similar sludge. The results showed that thermophilic anaerobic digestion was a viable alternative to the mesophilic process especially for overloaded digesters in warm climates. The optimum hydraulic retention time for the thermophilic process was 10 days which can lead to substantial savings in digester capacity. A simplified kinetic model was developed and applied in the analysis of steady-state operation of thermophilic anaerobic sludge digesters.