DEGRADATION AND INHIBITION OF LCFA IN TWO-PHASE ANAEROBIC TREATMENT SYSTEM FOR FAT CONTAINING WASTEWATER

This study was conducted to investigate the feasibility of a two-phase anaerobic treatment system for fat containing wastewater. The two-phase system was composed of a continuously stirred tank reactor for acidogenesis and an upflow anaerobic sludge blanket (UASB) reactor for methanogenesis. Its performance was compared with a conventional single-phase system of a UASB reactor treating synthetic wastewater containing major long-chain fatty acids (LCFAs). LCFAs did not cause any significant problem up to the LCFA mixture loading rate of 1.21 kg LCFA-COD m−3 day−1 (3,500 mg LCFA-COD dm−3) in both systems. However, the efficiency of the single-phase system deteriorated at loading rates above 1.38 kg LCFA-COD m−3 day−1 (4,000 mg LCFA-COD dm−3), while that of the two-phase system was still satisfactory. More than 19.2% of LCFAs were degraded and 11.5% of unsaturated LCFAs were saturated in the acidogenesis of the two-phase system, which led to the enhanced specific methane production rate and the reduced scum layer of the subsequent UASB reactor.