Mass production of methane from food wastes with concomitant wastewater treatment |
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Authors: | Kim Jung K Cho Jae H Lee Jung S Hahm Kyung S Park Don H Kim Si W |
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Institution: | (1) Department of Environmental Engineering, Chosun University, 501-759 Gwangju, Republic of Korea;(2) Department of Biological Science, Chosun University, 501-759 Gwangju, Republic of Korea;(3) Research Center for Proteineous Materials, Chosun University, 501-759 Gwangju, Republic of Korea;(4) Department of Biochemical Engineering, Chonnam National University, 500-757 Gwangju, Republic of Korea |
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Abstract: | We developed a process for production of methane at a pilot scale. This process consists of three stages. The first stage
is a semianaerobic hydrolysis/acidogenic step in which organic wastes are converted to various sugars, amino acids, and volatile
fatty acids (VFAs). Operation temperature and pH were 45°C, and 5.0–5.5, respectively. Hydraulic retention time (HRT) was
2 d. To remove the putrid odor and to enhance the hydrolysis of organic wastes, a mixture of bacteria isolated from landfill
soil was inoculated into the reactor. Total chemical oxygen demand (tCOD) and biological oxygen demand (BOD) were 36,000 mg/L
and 40,000 mg/L, respectively. The second stage was an anaerobic acidogenic process, which can produce large amount of VFAs
including acetate, propionate, butyrate, valerate, and caproate. Operation temperature and pH were 35°C, and 5.0–5.5, respectively.
HRT was 2 d. The third stage was a strictly anaerobic methane fermentation step producing methane and carbon dioxide from
VFAs. The working volume of upflow anaerobic sludge blanket (UASB) type reactor was 1200 L, and operation temperature and
pH were 41°C, and 7.7–7.9, respectively. HRT was 12 d. Seventy two percent of methane at maximum was generated and the yield
was 0.45–0.50 m3/kg VS of food wastes. Through the process, 88% of tCOD and 95% of BOD were removed. The wastewater was treated with the biological
aerobic and anaerobic filters immobilized with heterotrophic and autotrophic nitrifying and denitrifying bacteria. Ninety
percent of total nitrogen (T-N) was removed by this treatment. The residual T-N and total phosphorous (T-P) were removed by
the algal periphyton treatment system. The final concentrations of nitrogen and phosphorous in the drain water were 53 and
7 mg/L, respectively. |
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Keywords: | Anaerobic digestion volatile fatty acids methane biological filter algal periphyton treatment system |
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