Operating characteristics of baffled reactor under microaerobic conditions

A comparative experimental study was conducted on chemical oxygen demand (COD) elimination, effluent volatile fatty acids (VFAs), biogas production, granular sludge average particle-size distribution, and other indicators of baffled reactors operated under microaerobic or anaerobic conditions. The results show that the addition of an appropriate amount of oxygen improves COD elimination rate, increases biogas production, and reduces the effluent VFA concentration of the anaerobic baffled reactor (ABR), with no toxicity toward the methane bacteria. Regarding influent COD levels in the microaerobic baffled reactor of 1,320 +/- 20 mg/L, 1,860 +/- 20 mg/L, 2,550 +/- 20 mg/L, 3,150 +/- 20 mg/L, 3,620 +/- 20 mg/L, and 4,150 +/- 20 mg/L, compared with those in the ABR, the COD elimination rates increased by 3.45%, 2.27%, 1.98%, 1.82%, 1.84%, and 1.50%, respectively, and biogas production levels increased by 155.76%, 114.93%, 94.90%, 92.16%, 87.38%, and 48.94%, respectively. The effluent VFA concentrations of the two reactors were both less than 150 mg/L, with the effluent VFAs of the microaerobic baffled reactor less volatile and lower in concentration, with steadier change. The granular sludge average particle-size distribution of the microaerobic baffled reactor was mainly concentrated at 1-2 mm, indicating the enhanced activity of the granular sludge.