Activity and composition of ammonia oxidizing bacterial communities and emission dynamics of NH and NO in a compost reactor treating organic household waste

摘要

AIMS: To monitor emissions of NH(3) and N(2)O during composting and link these to ammonia oxidation rates and the community structure of ammonia oxidizing bacteria (AOB). METHODS AND RESULTS: A laboratory-scale compost reactor treating organic household waste was run for 2 months. NH(3) emissions peaked when pH started to increase. Small amounts of N(2)O and CH(4) were also produced. In total, 16% and less than 1% of the initial N was lost as NH(3)-N and N(2)O-N respectively. The potential ammonia oxidation rate, determined by a chlorate inhibition assay, increased fourfold during the first 9 days and then remained high. Initially, both Nitrosospira and Nitrosomonas populations were detected using DGGE analysis of AOB specific 16S rRNA fragments. Only Nitrosomonas europaea was detected under thermophilic conditions, but Nitrosospira populations re-established during the cooling phase. Conclusions: Thermophilic conditions favoured high potential ammonia oxidation rates, suggesting that ammonia oxidation contributed to reduced NH(3) emissions. Small but significant amounts of N(2)O were emitted during the thermophilic phase. The significance of different AOBs detected in the compost for ammonia oxidation is not clear. SIGNIFICANCE AND IMPACT OF STUDY: This study shows that ammonia oxidation occurs at high temperature composting and therefore most likely reduces NH(3) emissions.