| Aerobic composting is one of the effective ways to realize the utilization of municipal sludge resources.Nitrogen loss is one of the main reasons to reduce the value of compost products and limit the land use of sludge in the composting process.Hyperthermophilic aerobic composting(> 80℃)is a new type of aerobic composting technology,which has the advantages of high fermentation temperature,short composting cycle and complete harmless,hasing been gradually applied at home and abroad.At present,the researchs have proved that Hyperthermophilic aerobic composting can effectively reduce nitrogen loss,but the mechanism of controlling nitrogen loss is not clear,which needs further study.Therefore,this study carried out a comparative experimental study of nitrogen loss between Hyperthermophilic aerobic composting(HTC)and Thermophilic aerobic composting(TC)by the semi-closed aerobic composting device,analyzed the physical and chemical properties of HTC and TC processes and the evolution rule of nitrogen forms,discussed the nitrogen loss caused by the evolution characteristics of nitrogen functional factors(nir K,nir S,nor B and nos Z,etc.)and microbial(bacterial)communities,that revealed mechanism of controlling nitrogen loss in Hyperthermophilic aerobic composting.The main results are as follows:(1)In the aerobic composting process,the fermentation temperature of HTC is higher than that of TC(the highest temperature is 89.1℃),the duration of high temperature is longer,the content of humus is more,and the harmless degree is better.At the same time,HTC can effectively reduce nitrogen loss,the total nitrogen loss is only 7.0%,far lower than the total nitrogen loss of TC by 53.2%.In addition,through correlation analysis,we found that the total nitrogen of HTC has significant correlation with temperature and carbon nitrogen ratio.(2)The relative abundance of functional genes and enzyme activity analysis showed that HTC had lower relative abundance(nar G,nir S,nir K,nor B and nos Z)and denitrification intensity than TC,while TC had higher abundance and nitrification intensity of nitrification genes(AOB,AOA and nxr A).At the same time,the temperature of HTC was negatively correlated with denitrification gene,the total nitrogen of HTC was positively correlated with denitrification gene,while the total nitrogen of TC was not strongly correlated with functional gene.(3)The analysis of bacterial community structure based on high-throughput sequencing showed that HTC contained more Firmicutes,bacillus,Geobacillus and parageobacillius and bacterium＿ns1-3,which made the temperature of HTC much higher than that of TC.At the same time,Firmicutes had a significant positive correlation with ammonia nitrogen,and a significant negative correlation with denitrification gene.Under its branches,Amibacilli,Tissierella,Sinibacilli,Geobacilli,Bacillus and Ureibacillus all had a significant negative correlation with total nitrogen and denitrification gene.The above study shows that the Hyperthermophilic aerobic composting can effectively reduce the abundance of denitrification genes,thus reducing the denitrification intensity and nitrogen loss. |
