Energy spilling by thermophilic aerobes in potassium-limited continuous culture

Multiple continuous-flow reactors were operated at 55°C under potassium-limited conditions to investigate energy spilling metabolism during thermophilic aerobic biological wastewater treatment. Energy spilling metabolism has been previously shown to reduce the observed cell growth yield at short mean cell residence times, which could potentially be used to promote autothermal operation during the biological treatment of high-strength wastewater. Under the potassium-limited conditions imposed during these experiments, cell yields decreased at lower residence times, commensurate with the characteristic pattern of energy spilling conditions. The minimum growth yield measured was 0.19 mg TSS per mg COD removed, which was believed to be too high to promote autothermal reactor operation for thermophilic treatment. These results suggest that operation of conventional biological treatment processes under energy spilling conditions could be used to reduce the net production of residual biomass.