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.

This study was performed to develop the biological treatment technology of wastewater polluted with heavy metals. Zinc-tolerant microorganism, such as Pseudomonas chlororaphis which possessed the ability to accumulate zinc, was isolated from industrial wastewaters polluted with various heavy metals. The characteristics of zinc accumulation in the cells, recovery of the zinc from the cells accumulating zinc, were investigated. Removal rate of zinc from the solution containing 100 ㎎/ℓ of zinc by zinc-tolerant microorganism was more than 90% at 48 hours after inoculation of the microorganisms. A large number of the electron-dense granules were found mainly on the cell wall and membrane fractions, when determined by transmission electron microscope. Energy dispersive X-ray spectroscopy revealed that the electron-dense granules were zinc complex with the substances binding heavy metals. The zinc accumulated into cells was not desorbed by distilled water, but more than 80% of the zinc accumulated was desorbed by 0.1M-EDTA. The residues of the cells after combustion at 550℃ amounted to about 21% of the dry weight of the cells. EDS analysis showed that the residues were comparatively pure zinc compounds containing more than 79% of zinc.