Greenhouse gas emission from the facility of cattle wastewater treatment with activated-sludge process

This study determined the accurate greenhouse gas emission factor of Greenhous gas (GHG) emission from wastewater treatment system for cattle manure based on several weeks of measurement result of the facility, and their fluctuation factor were discussed. These measurements had investigated at the wastewater treatment facility of dairy cattle in Okayama Prefectural Technology Center (35.02 deg N 133.50 deg E, 24cubic m of aeration tank and 2.6cubic m of sedimentation tank, for 40 heads of dairy cattle). Under 1.5cubic m/cubic m/hr aeration condition, GHG emission was measured with a dynamic chamber which covered the wastewater treatment facility. Fresh air (Inlet air, outside of this facility) and Outlet air (exhaust air, facility exit of exhaust air) were collected drawn through Teflon tube, and N2O, CH4 and NH3 were continuously measured with a Photo-acoustic Multi gas Monitor. Gas measurements were operated for several weeks in fifteen periods from 2008 to 2013, and the emission factor (EF) were calculated besed on the experimental results. According to the results of total measurement periods, the N2O and CH4 emission factors were 2.88% (g N2O-N/g total N) and 0.30% (g CH4/g volatile solids), respectively. N2O emission factor calculated under this experiment was low compared to present value (5.0% (g N2O-N/gTN)) of National Greenhouse Gas Inventory Report of JAPAN (2015). On the contrary, CH4 Emission factor calculated under this experiment was rather high compared to present value (0.00% (g CH4/g volatile solids)). N2O emission were dependent on organic compounds and nitrogen ratio of the influent wastewater, and the high N2O emission were occurred in the operating condition of under 6.0 of BODsub(5)/TN ratio or under 2.5 of COD/N ratios. N2O emission factor were fluctuate huge and there were high emission periods and low emission periods. The emission of CH4 is affected by the wastewater of the sump pit.