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The aim of this study was to investigate the aerobic and anaerobic degradation of phenol and its derivatives in aerobic and anaerobic landfills. Phenolic compounds were extracted from leachate samples using the solid phase micro-extraction method. In this study, analysis of the 24 phenolic compounds included in the standard mixture and the change in the concentrations over time of 23 of the 24 compounds found in the calibration mix standard were determined in both aerobic and anaerobic landfill reactors. It can be concluded that faster and complete removal of phenol, chlorophenol, dichlorophenols, and trichlorophenol were achieved in the aerobic landfill while aerobic treatment was less effective on tetrachlorophenol and pentachlorophenol. In the anaerobic landfill, anaerobic reductive dechlorination probably occurred from all the highly chlorinated phenols and resulted in the accumulation of phenol and chlorophenol. The phenol could not be further degraded because the anaerobic methanogenic phase did not start during the 150 days of operation in an anaerobic landfill reactor. Nitrophenols can be degraded rapidly under aerobic conditions. These compounds are degraded to amino groups in the first step and then these amino groups are degraded to methane and CO2 under anaerobic conditions. Although the degradation could not reach the methanogenic phase in anaerobic landfill reactor during the operational period, it is indicated that nitrophenol concentrations decreased in the anaerobic reactor. This is revealed as a result of the formation of the amino groups. [ABSTRACT FROM AUTHOR]

The main aim of this study was to investigate the effect of leachate recirculation and aeration on volatile fatty acid (VFA) concentrations in aerobic and anaerobic landfill leachate samples. In this study, two aerobic (A1, A2) and two anaerobic (AN1, AN2) reactors with (A1, AN1) and without (A2, AN2) leachate recirculation were used in order to determine the change of volatile fatty acids components in landfill leachate. VFA degradation rate was almost 100% in each reactor but the degradation rate show notable differences. In aerobic landfill reactors, total VFA concentrations decreased below 1000 mg L−1 after 120 days of operation and only caproic and acetic acids were determined at this time. The stabilization of the VFA concentrations takes about 350 and 450 days for AN1 and AN2 reactors, respectively. VFA concentrations were higher than that of aerobic reactors because of the acidogenic phase occurred in anaerobic environment. According to the results of VFA components, the stabilization of the waste was achieved after 120 days of operation in aerobic landfills. At this time, anaerobic reactors were in the acidogenic phase which results with the high concentrations of VFA. The results also indicated that leachate recirculation does not affect the degradation rate in aerobic landfills as much as it does in anaerobic landfills [ABSTRACT FROM PUBLISHER]