Efficient Treatment and Simultaneous Energy Recovery from Cattle Wastewater by the Micro-Aerated UASB and SBR Coupled System

Abstract

The present study introduces a coupled system comprising an upflow anaerobic sludge blanket (UASB) and a sequencing batch reactor (SBR) to treat intensive cattle farming wastewater. The results confirmed that the optimal conditions for UASB were an organic load rate of 9.98 kg-COD m–3·day–1, a C/N ratio of 22, and a hydraulic retention time (HRT) of 1.5 h. For the SBR reactor, the optimal conditions are a dissolved oxygen (DO) concentration of 6.08 mg L–1 and the S2 aeration mode. Under these optimal conditions, the study achieved anaerobic and aerobic sludge granules (0.25–0.5 and 0.5–0.75 mm) with excellent properties due to the cooperation of a functional microbial community, including Synergistetes, Thermotogae, Acidobacteria, Proteobacteria, Chloroflexi, and Hyd24–12 in UASB and Paracoccus, Proteobacteria, Chloroflexi, and Acinetobacter in SBR. This hybrid system contributed 94% of chemical oxygen demand (COD), 90% of NH4 +-N, 90% of TN, and 61% of TP. Additionally, it achieved 18% net energy recovery from the real cattle wastewater, indicating that the UASB–SBR-coupled system holds potential as an approach for treating and recovering energy from cattle wastewater.