Abstract: Four sludge composting strains were isolated from high temperature samples, and were classified into the genus of Bacillus. These strains were mixed in the same proportion as microbial inoculum, and were added to the composting system to study the suitable microbial inoculum concentration and application potentials in sludge composting. The results showed that the temperature rising rate, water content decreasing rate and the maximum temperature of those treatments with inoculation were higher than the control (treatment without inoculation). The inoculated treatments completely maturated, while the control did not reach maturity standard. When the inoculating amount was 3%, the effect was the most obvious, as the maximum temperature was 63 ℃, the high temperature above 55 ℃ lasted for 4 days, and the seed germination index was 134.1% after composting. These results suggested that the proposed microbial inoculum had potential in sludge composting.

Key words: strain screening, microbial inoculum, sludge composting