TREATMENT AND BIOGAS PRODUCTION FROM FOOD WASTEUSING A PLUG FLOW REACTOR

นักวิจัย : ปยชน สังขกลิ่นหอม, อรรณพ นพรัตน, ภาวิณี ชัยประเสริฐเผยแพร : The 14th Annual Meeting of the Thai Society for Biotechnology, "Biotechnology for Better

Living in the New Economy", 12-15 พฤศจิกายน 2545, โรงแรมโซฟเทล ราชาออคิด, จ.ขอนแกน,หนา 87

Food waste is a major constituent in municipal solid waste. The degradation of organic substances in food waste without control causes pollution of land and water nearby. One of the methods to treat and utilize food waste is biogas technology. This study aimed to determine the anaerobic digestion of food waste using a plug-flow reactor (PFR). Food waste slurry was fed in 17 liters reactor at various solid contents from 2 to 10%. The PFR used in this study contain 10 compartments with zigzag-parallel baffles. The PFR was sloped down from the inlet towards the outlet. Steady-state runs were conducted at hydraulic retention time of 10 days and step increased organic loading rates (OLRs) of 2,461 to 12,308 kg COD/m3-d in 90 days operation.

For an OLR at 2,461 kg COD/m3-d, the acidogenic phase predominated within the first three compartments with total volatile acids (TVA) accumulation of 3,200 mg/1 and solution pH was acidic about 4.7. The pH of solution in down gradient towards the outlet was gradually increased until to 7. The methanogenic phase prevailed in the remainder of the PFR. The COD reduction and methane production yield were 92% and 0.15 m3/kg-COD added, respectively. During increasing step of OLR until to 12,308 kg COD/m3-d, the acidogenic phase was expanded while the methanogenic was narrow. The acidogenic phase was extended to 2/3 part of reactor from the PFR inlet (first seven compartments). The pH was dropped to 3.8 and TVA accumulated to 20,564 mg/1. The solution pH near the outlet was about 6. The COD reduction and methane yield were 73% and 0.05 m3/kg COD added, respectively.

The rate limiting step of degradation of food waste was found to be liquefaction-acidification step. To achieve a high efficiency, the method to accelerate the liquefaction-acidification step needs to be elucidated. On the steady-state runs, the potential of using recirculation of effluent to accelerate the liquefaction-acidification step could be further determined.