To study the optimum conditions of composting with industrial wastewater sludge, the variations of temperature and CO_2 generation amount during the composting periods were investigated. The conditions were that industrial wastewater added to bulking agents such as sawdust and rice hull was used, and differently treated with microorganism seeding or not, initial C/N ratios, air flow rate and initial moisture contents, respectively. The results were summarized as follows ; Seeding 5% of microorganism was higher the temperature than not seeding. And using sawdust as bulking agents, and adjusting 30∼40 of initial C/N ratio, 200㎎/ℓ·min. of air flow rate and 67∼68% of initial moisture contents were higher the temperature than any other conditions. Seeding 5% of microorganisms was higher CO_2 generation amount than not seeding. And that was much in the order of 7∼40, 30∼34 and 22∼23 of initial C/N ratio. Judging from the results, it should be considered that the optimum conditions in the composting of industrial wastewater sludge were seeding of 5% microorganisms, and adjusting 30∼34 of initial C/N ratio, 200㎎/ℓ·min. of air flow rate and 67∼68% of initial moisture contents. The contents of inorganic matters and C/N ratio during the composting periods at optimum condition were a little increased, and heavy metals contents after composting were lower than standard for fertilizer.

Chemical characteristics of the industrial wastewater sludge, degradation of the sludge in soil and CO2 generation and changes of nitrogen in soil treated with the sludge were investigated. The results obtained were summarized as follows: 1. Degradation rate of the sludge in soil was 26% at natural temperature, and 33% at incubation temperature at 12 weeks after treatment. 2. T-C, T-N and the C/N ratio of sludge in soil was 16.0%, 0.63% and 26, respectively, at natural temperature, and 15.0%, 0.65% and 23, respectively, at incubation temperature at 12 weeks after treatment. 3. Camulative CO2 generation in soil treated with 1%, 3% and 5% of sludge was 284, 440 and 512 ㎎/100g, respectively, at natural temperature, and 440, 558 g and 654 ㎎/100 g, respectively, at incubation temperature at 12 weeks after treatment. 4. Changes of inorganic nitrogen in soil treated with 1%, 3% and 5% of sludge were 7.8, 12.8 and 16.3 ㎎/100g, respectively, at incubation temperature at 12 weeks after treatment. Mineralization ratio of organic nitrogen in soil treated with 1%, 3% and 5% of sludge was 10.7%, 13.6% and 15.2%, respectively, at incubation temperature at 12 weeks after treatment. 5. Changes of pH in soil treated with 1%, 3% and 5% of Industrial wastewater sludge were in the range of 6.7∼7.5 at natural temperature, and 6.1∼7.9 at incubation temperature at 12 weeks after treatment.