ABSTRACT Operational characteristics of dry anaerobic digestion on mixture of livestock waste and food waste Mo Kwon Lee Dept. of Environment Engineering Graduate School of Industry Hanbat National University Advisor : Prof. Sae-Eun Oh With increasing concerns regarding the conservation of resources...
ABSTRACT Operational characteristics of dry anaerobic digestion on mixture of livestock waste and food waste Mo Kwon Lee Dept. of Environment Engineering Graduate School of Industry Hanbat National University Advisor : Prof. Sae-Eun Oh With increasing concerns regarding the conservation of resources, and reduction of CO2 emissions, dry anaerobic digestion of organic solid waste has recently been gaining considerable attention. In this study, a continuous dry anaerobic digestion system treating a mixture of livestock waste and food waste was operated under mesophilic condition. The entire operation was divided into five phases according to the change of hydraulic retention time (HRT) and livestock waste content. And in order to reduce the ammonia concentration, ultrasonic treatment was carried out at 28kHz, pH 11. A batch test was performed to investigate the inhibitory effect of ammonia using sludge taken at 40th day. As the sludge was not acclimated at high concentration of ammonia, it showed decreased methane production as ammonia concentration increased. In continuous operation, however, by the stepwise increase of ammonia, the sludge could adapt to high concentration of ammonia. At Phase IV (HRT = 60 d and livestock content =40%), although the total ammonia concentration reached 7,000 mg NH4-N/L, it showed high biogas production yield of 0.59 ± 0.03 m3/kg VS (Volatile Solids) and VS reduction of 71.5 ± 1.9%. And, based on COD input, CH4 production yield was 0.26 m3/kg CODadded, indicating that 76% of energy content in the substrate was converted to CH4. At Phase V, when the livestock content increased to 60%, there was a sharp decrease of biogas production, which was attributed to the increase of free ammonia concentration to over 1,000 mg NH3-N/L. At further operation, the ultrasonic treatment was carried out using return sludge. According to experimental results, at 60 min of irradiation time ammonia concentration was decreasing 45% and methane production yield was increasing 20%.
ABSTRACT Operational characteristics of dry anaerobic digestion on mixture of livestock waste and food waste Mo Kwon Lee Dept. of Environment Engineering Graduate School of Industry Hanbat National University Advisor : Prof. Sae-Eun Oh With increasing concerns regarding the conservation of resources, and reduction of CO2 emissions, dry anaerobic digestion of organic solid waste has recently been gaining considerable attention. In this study, a continuous dry anaerobic digestion system treating a mixture of livestock waste and food waste was operated under mesophilic condition. The entire operation was divided into five phases according to the change of hydraulic retention time (HRT) and livestock waste content. And in order to reduce the ammonia concentration, ultrasonic treatment was carried out at 28kHz, pH 11. A batch test was performed to investigate the inhibitory effect of ammonia using sludge taken at 40th day. As the sludge was not acclimated at high concentration of ammonia, it showed decreased methane production as ammonia concentration increased. In continuous operation, however, by the stepwise increase of ammonia, the sludge could adapt to high concentration of ammonia. At Phase IV (HRT = 60 d and livestock content =40%), although the total ammonia concentration reached 7,000 mg NH4-N/L, it showed high biogas production yield of 0.59 ± 0.03 m3/kg VS (Volatile Solids) and VS reduction of 71.5 ± 1.9%. And, based on COD input, CH4 production yield was 0.26 m3/kg CODadded, indicating that 76% of energy content in the substrate was converted to CH4. At Phase V, when the livestock content increased to 60%, there was a sharp decrease of biogas production, which was attributed to the increase of free ammonia concentration to over 1,000 mg NH3-N/L. At further operation, the ultrasonic treatment was carried out using return sludge. According to experimental results, at 60 min of irradiation time ammonia concentration was decreasing 45% and methane production yield was increasing 20%.
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