OPTIMAL STRATEGY FOR CHANGING TEMPERATURE FROM MESOPHILIC TO THERMOPHILIC CONDITIONS IN CSTR REACTORS TREATING SEWAGE SLUDGE
I. Angelidaki1, A. Boušková2, N. Christensen1, M. Dohányos2 and J. Ejbye Schmidt1
1 Environment & Resources DTU, Technical University of Denmark, Denmark;
2 Department of Water Technology and Environmental Engineering, Institute of Chemical
Technology, Czech Republic
(free)
Adaptation of stable mesophilic reactors to thermophilic temperature by applying a one step increase, and a stepwise increase of the temperature was investigated. The two different strategies for changing mesophilic (37ºC) to thermophilic operation (55ºC) were tested in continuous flow stirred tank reactors operating with a hydraulic retention time of 20 days and an organic loading rate of 1.38 gVS/l reactor/day. The overall adaptation of the process for the step-wise temperature increment took 70 days in total. Even though the one-step temperature increase caused a severe disturbance in all the process parameters, the system reached a new steady state operation after only 30 days indicating that the this strategy is the best when changing from mesophilic to thermophilic operation in anaerobic digestion plants. By using Clostridium perfringens as indicator organism we found that thermophilic anaerobic digestion resulted in reduction of pathogens.
KEYWORDS Anaerobic, sludge, thermophilic, biogas, VFA
