Changes in Sludge Components and Microflora During the Composting of Sewage Treatment Sludge

The sewage treatment sludge after being composted has been suggested as a soil conditioner. In this study, the changes in components and microflora of the sludge during the composting process were examined. The organic matter and water content decreased during composting. Achromobacter sp. were abundant in the raw material, but decreased gradually, while Bacillus sp. increased. The composting did not decrease viable bacteria or coliform groups. The effects of composting on pathogenic bacteria were not clear. These findings suggested that the decrease of organic matter, water content, and the changes in microflora could be useful indexes of the composting condition.