The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is...The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is generated on farms as an intermediate product in nitrification and denitrification, and methane （CH4） is also generated from organic degradation under anaerobic conditions by microorganisms in manure or wastewater. This study was carried out at five activated sludge treatment facilities across Japan between August 2014 and January 2015. Measurements were conducted over several weeks at wastewater purification facilities for swine farms： two in Chiba prefecture （East Japan）, two in Okayama prefecture （West Japan）, and one in Saga （Southern Japan）. Taking several environmental fluctuations into account, we collected measurement data continuously day and night, during both high-temperature and low-temperature periods. The results indicated that CH4 and N20 emission factors were 0.91% （kgCHa·kg volatile solids^-1） and 2.87% （g N2O-N·kg total N^-1）, respectively. Ammonia emissions were negligible in all of the measurements from the wastewater facilities. The N20 emission factor calculated under this experiment was low compared to our previous finding （5.0%; g N2O-N·kg N^-1） in a laboratory experiment. In contrast, the CH4 emission factor calculated herein was rather high compared to the laboratory measurements. There was great variation in daily GHG emission factors measured in the actual wastewater treatment facilities. In particular, the N2O emission rate was affected by several environmental conditions at each facility location, as well as by the management of the wastewater treatment.展开更多
文摘The activated sludge process to remove nitrogen and biochemical oxygen demand （BOD） is reportedly cost-effective for swine wastewater treatment, and it use has thus increased in pig farming. Nitrous oxide （N20） is generated on farms as an intermediate product in nitrification and denitrification, and methane （CH4） is also generated from organic degradation under anaerobic conditions by microorganisms in manure or wastewater. This study was carried out at five activated sludge treatment facilities across Japan between August 2014 and January 2015. Measurements were conducted over several weeks at wastewater purification facilities for swine farms： two in Chiba prefecture （East Japan）, two in Okayama prefecture （West Japan）, and one in Saga （Southern Japan）. Taking several environmental fluctuations into account, we collected measurement data continuously day and night, during both high-temperature and low-temperature periods. The results indicated that CH4 and N20 emission factors were 0.91% （kgCHa·kg volatile solids^-1） and 2.87% （g N2O-N·kg total N^-1）, respectively. Ammonia emissions were negligible in all of the measurements from the wastewater facilities. The N20 emission factor calculated under this experiment was low compared to our previous finding （5.0%; g N2O-N·kg N^-1） in a laboratory experiment. In contrast, the CH4 emission factor calculated herein was rather high compared to the laboratory measurements. There was great variation in daily GHG emission factors measured in the actual wastewater treatment facilities. In particular, the N2O emission rate was affected by several environmental conditions at each facility location, as well as by the management of the wastewater treatment.
