Microaerophilic treatment enhanced organic matter removal and methane production rates during swine wastewater treatment: A long-term engineering evaluation

Abstract

Anaerobic biotechnology has been widely used for swine wastewater (SWW) treatment. However, its organic loading rate (OLR) is far lower than expected, mainly because of the low rate of hydrolysis. In this study, the comparative process performance and efficiency of an up-flow anaerobic sludge blanket (UASB) reactor (R1) and an up-flow microaerobic sludge blanket (UMSB) reactor (R2) were evaluated for SWW treatment, operating for 264 days under higher OLRs and lower hydraulic retention times than those found in the literature. The R2 was subjected to the three different air doses: 0.09 (stage I), 0.17 (stage II), and 0.25 (stage III) LO2 Lfeed−1 d−1 aiming at enhancing the hydrolysis step of the anaerobic digestion (AD). The overall results showed that 0.17 LO2 Lfeed−1 d−1 was the best experimental condition evaluated, which provided volatile suspended solids, total chemical oxygen demand, and particulate chemical oxygen demand removal efficiencies of 85.0 ± 1.9%, 83.8 ± 2.5%, and 82.1 ± 4.8%, respectively. This performance was due to the higher organic matter hydrolysis, resulting in higher methane production. Therefore, the UMSB reactor treatment was demonstrated to be a feasible alternative for SWW, although some strategies to control biomass washout must be investigated.