Takehiko Ogawa*, Shigeru Ohno** and Hideki Tatsumoto***

Abstract

The treatment and disposal of the waste excess sludge generated by night-soil treatment has become a serious social problem. The material balance and heat balance during the composting process were examined using a laboratory-scale composting reactor. The solid matter balance and organic matter balance were difficult to determine using a small-scaled apparatus because of the large loss. When more than 15% of the carbon and nitrogen was collected in the exhaust gas, the composting state was good judging from composting temperature, appearance, touch, and odor of product. The composting state was good after evaporation of 50-70% of sludge moisture. The generation of carbon dioxide during composting of sludge was about 170-230g C/kg organic matter, and that of ammonia was about 16g N/kg organic matter. The composting state was good when the composting heat was 15% or more of the calorific heat value in the raw material fed or exceeded 880kcal/kg organic matter fed.

Key words: sludge composting, night-soil treatment, material balance, heat balance