하수처리시설에 대한 메탄배출계수 개발 및 적용성에 관한 연구

Abstract

The emission factor for calculating GHG emissions is an important parameter for the establishment of mitigation policies and establishing the inventory to implement an assessment. The emission factor that applies when calculating greenhouse gas emissions at the wastewater treatment plant in Korea was developed about 10 years ago, and it does not reflect the changed sewage policy. When the national emission factor was developed, uncertainty assessment, the most important factor for reliability was not done. Uncertainty about the national GHG emission in the WWTP was evaluated using the IPCC G/L default value. Through the categories analysis, This study evaluated a reasonable development range for the CH4 emission factor in the wastewater treatment plants and established a methodology for CH4 emission measurement. Seven sites were measured to develop the emission factor based on category analysis and established measurement methodology. To evaluate the uncertainty, the uncertainty factor that influences the CH4 emission factor was investigated. The uncertainty was calculated using a sample error propagation equation and the appropriateness was reviewed. The results of the CH4 emission calculation about the each WWTP reactor, showed a high correlation(R2=0.9284) between the total CH4 emission and the 1st clarifier CH4 emission. CH4 emission characteristics are determined by the operating characteristics such as a influent characteristics and sludge recycle rather than process-specific characteristics. CH4 emission factors of the WWTPs were calculated as 0.007 kg CH4/kg BOD(max value : 0.030 kg CH4/kg BOD, min value : 0.00076 kg CH4/kg BOD, standard deviation : 0.010 kg CH4/kg BOD). As of 2011 the national calculated GHG emission for the WWTP sector, using the emission factor developed in this study, is 7.1 Gg CH4. Survey results for uncertainty factors included CH4 concentration, carrier gas flow rate, chamber area, BOD concentration, sewage treatment plant influent flow rate and the site area. There are 21 variables at the detailed uncertainty component, including the representativeness of the measurement period and error of the analyzer. The evaluation results of the CH4 emission factor uncertainty, through the sample error propagation equation, is a 0.007±0.002 kg CH4/kg BOD(about 95% confidence interval, k=2). To identify the factors affecting the uncertainties, contribution portion analysis was undertaken. “Methane concentration(61.3%”) was the highest contributing factor. “The representativeness of the Measurement period(49.1%)” was the highest detailed contributing component. Further, The evaluation results of the CH4 emission factor uncertainty using the Monte Carlo simulation is presented to suggest the improvement directions of the uncertainty evaluation.