| Summary: | 碩士 === 逢甲大學 === 綠色能源科技碩士學位學程 === 106 === The pig farms wastewater treatment were low in the efficiency of methane production due to unstable influent concentration, unstable wastewater volume or seasonal changes of wastewater quality.
In this study, gravity sedimentation was utilized to pretreat and separate pig wastewater into three parts including raw wastewater (RW), settled sludge (SS) and supernatant liquid (SL). The methane production rate (MPR) values were 0.51, 0.59 and 0.13 L-CH4/L-d, for RW, SS and SL, respectively. Methane Yield (MY) was defined as methane produced from each gram of COD removed and the values were 0.23, 0.78 and 0.04 L-CH4/g-CODre for RW, SS and SL, respectively. The SS volume was reduced by 63% compared to the RW. These results indicate that the SS is more appropriate for methanogenesis.
RSM experimental design method was used to investigate the operating conditions of acidification time and initial pH. The results indicate that MPR was 0.3 L-CH4/L-d at pH 6.5 and acidification time 1.5 days with volatile fatty acid 7 g-COD/L。
A continuously-feeding experiment was conducted to compare the capacity of single-stage and two-stage methane production. In the two-stage system, acid-producing phase had a volatile acid production of 5.5 g-COD/L with propionic and acetic acids accounting for approximately 50% in total. For methane concentration, the single-stage was 30% and the two-stage was 60%. The key to anaerobically ferment a wastewater containing high solid concentration is to control the rate of organic acid production. An excessive formation of organic acid would have an impact on gas production stability. The MPR of the single-stage and two-stage methane production were 0.04 and 0.09 mL-CH4/L-d, respectively. The microbial community structure analysis showed that the diversity of bacterial community for the two-stage was greater than that of the single-stage. The archaea (genus) was mainly Methanosarcina and Methanoculleus.
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