Effect of substrate composition on the stability and microbial community of an anaerobic expanded granular sludge bed reactor treating printing solvent mixtures of ethanol and glycol ethers

Abstract

The performance and microbial community analysis of an expanded granular sludge bed reactor (EGSB) treating wastewater polluted with mixtures of ethanol and glycol ethers –such as 1-ethoxy-2-propanol (E2P) and 1-methoxy-2-propanol (M2P)– were evaluated. The results showed good EGSB performance during start-up (100% of ethanol) in terms of global removal efficiency (RE > 95%). When glycol ethers were added, an initial adaptation period was observed of ~20 days. While the RE of M2P became complete, the RE of E2P reached only 65%. The proportion of glycol ethers was gradually increased and at the end of this study only a binary mixture of E2P and M2P was fed. In the last stage, the global RE dropped to 80% and a partial degranulation of the sludge bed occurred, revealing the importance of acetate-yielding compounds as co-substrate for maintaining the granular structure of the sludge. Microbial community analysis showed a relation between the substrate utilized in the reactor and the developed microbial populations, such as Methanosaeta, an acetate consumer, and Methanomethylovorans, a methanol consumer, which were the predominant microorganisms in the archaeal population; the predominant bacterium found was Geobacter, an ethanol consumer; this and Methanosaeta are synthropic partners.