Thermophilic aerobic wastewater treatment in continuous-flow bioreactors

Thermophilic aerobic biological wastewater treatment was investigated at 55 degrees C in continuous-flow bioreactors using a synthetic wastewater cont aining gelatin and alpha-lactose as principal organic constituents. By oper ating multiple continuous-flow bioreactors at different hydraulic residence times (HRTs), the maintenance constant (k(d)) was calculated to be 0.046 d ay(-1), a value approximately 10-fold lower than that previously reported f or thermophilic processes but similar to that for mesophilic treatment. Inv estigation into the bacterial community structure by denaturing gradient ge l electrophoresis of polymerase chain reaction-amplified 16S ribosomal RNA genes revealed that the dominant phylotypes in the bioreactors changed as a function of HRT. Cell reactivity, measured as the specific content of prot ein and RNA, declined as HRT increased. Catabolic enzyme activities specifi c to the principal organics in the synthetic wastewater, however, increased at higher HRTs. In conclusion, the performance of thermophilic aerobic bio logical wastewater treatment processes was similar to that of conventional mesophilic processes with respect to maintenance requirements (i.e., cell y ields) as well as bacterial community shifts, cell reactivity, and cell act ivity.