Characteristics of nitrogen transformation and microbial community in an aerobic composting reactor under two typical temperatures

Batch experiments were conducted for feces composting using an aerobic composting reactor with sawdust as bulky matrix. In the 14-day composting processes at 35 ± 2 and 55 ± 2 °C, compost samples were collected daily and chemical analyses and PCR-DGGE were carried out for investigating the influence of composting temperature on organic decomposition, nitrogen transformation, and microbial communities. At 55 ± 2 °C, in addition to a slightly higher COD removal, nitrogen loss was greatly restrained. As organic nitrogen took about 85% of the total nitrogen originated from human feces, the suppression of ammonification process under thermophilic environment might be the main reason for less nitrogen loss at 55 ± 2 °C. By PCR-DGGE analysis, the microbial community was found to undergo successions differently at 35 ± 2 and 55 ± 2 °C. Certain sequences identified from the compost at 55 ± 2 °C represented the microbial species which could perform nitrogen-fixation or sustain a lower pH in the compost so that gaseous ammonia emission was suppressed.