Integrated expanded granular sludge bed and sequential batch reactor treating beet sugar industrial wastewater and recovering bioenergy

The exponential rise in energy demand vis-à-vis depletion of mineral oil resources has accelerated recovery of bioenergy from organic waste. In this study, a laboratory-scale anaerobic (An)/aerobic (Ar) system comprising of expanded granular sludge bed (EGSB) reactor coupled to an aerobic sequential batch reactor (SBR) was constructed to treat beet sugar industrial wastewater (BSIW) of chemical oxygen demand (COD) 1665 mg L⁻¹ while harnessing methane gas. The EGSB reactor generated methane at the rate of 235 mL/g COD added, with considerably higher than previously reported methane content of 86 %. Meanwhile, contaminants were successfully reduced in the combined An/Ar system, realizing a removal rate of more than 71.4, 97.3, 97.7, and 99.3 % of organic matter as total phosphorus, total nitrogen, biological oxygen demand (BOD), and soluble COD, respectively. Microbial community analysis showed that the bacterial genus Clostridium sp. and archaeal genus Methanosaeta sp. dominated the EGSB reactor, while Rhodobacter sp. dominance was observed in the SBR. The obtained experimental results indicate that the integration of expanded granular sludge bed and sequential batch reactor in treating BSIW obtained competitively outstanding performance.