Effect of temperature on composting of sewage sludge.

The effect of temperature on the composting reaction of sewage sludge was investigated at 50, 60, and 70 degrees C. The total amount of CO(2) evolved and the final conversion of volatile matter were maximum at 60 degrees C., suggesting that the optimal temperature for composting was around 60 degrees C. The specific CO(2) evolution rate (moles of CO(2) evolved per hour per viable cell) was maximum at 70 degrees C. The isolated thermophilic bacterium which was dominant at 60 degrees C but did not grow at 70 degrees C showed that the rate of O(2) consumption measured on the agar plate at 70 degrees C was four times higher than that at 60 degrees C. This showed that the energy yielded from catabolism is rather uncoupled with the anabolism at 70 degrees C in the metabolism of microorganisms indigenous in the compost. A higher respiratory quotient was observed at 70 degrees C than at any other temperature.