SEWAGE-SLUDGE COMPOSTING PROCESS BY STATIC PILE METHOD

This paper reports the results of experiments on the static pile composting process undertaken in different conditions. The experiments have revealed the following: - In order to compost dewatered sludge with polymer without any bulking agents, we used recycled compost to adjust the moisture content of dewatered sludge. When the moisture content of feed mixture, which was dewatered sludges and recycled composts, was lowered to approximately 50%, the raw sludge could be composted by either natural ventilation or intermittent aeration. - When the BOD of feed mixture was lower than 50 g/kg-DS, the fermentation temperature did not reach 60-degrees-C and the moisture content of the mixture was not lowered during composting period. - The required composting time was approximately 50 days for natural ventilation (at an average temperature of 10-degrees-C or 24-degrees-C) and approximately 35 days for intermittent aeration (at an average temperature of 10-degrees-C to 24-degrees-C), when the moisture content and the BOD of finished compost was 40% or less and 30 g/kg-DS or less, respectively. - There was a highly positive correlation between the amount of water evaporated and the amount of BOD removed. This result suggested that the amount of water evaporation could be deduced from the amount of BOD removed.