Diversion of Electron in Mixed Microbial Culture to Treat the High Sulfate and LCFA Contaminated Wastewater Treatment

Abstract

Sulfate-rich wastewater effluents from the mining and mineral industries and long chain fatty acids (LCFAs) from the dairy industries are a major concern for contamination due to their toxic effects on microbial populations. Diversion of electron fluxes from glucose degradation and inhabitation of LCFAs in mixed anaerobic microbial communities is the remedy for these toxicity effects. Two cases were studied to get a better understanding of the pattern of electron flux in mixed microbial cultures. In the first case, electron flux was investigated in the presence of an inorganic terminal electron acceptor, sulfate, and in the second case, proton was a terminal electron acceptor in the absence of sulfate. In both cases, methanogenesis, a terminal metabolic stage in the anaerobic degradation of organic matter, was inhibited by LCFAs containing 18 carbons and the electron fluxes were subsequently redirected to the desired terminal product formation. In these studies, the LCFAs under consideration were LA, OA and SA. Diverting electron fluxes from glucose to SRBs (for sulfate reduction) were observed in LA and OA-fed cultures, although SA had no significant effect on sulfate elimination. This was due to the inhibitory effect of LA and OA on the methanogenic populations. In comparison to glucose plus sulfate controls, OA and LA selectively inhibited methanogens at all concentrations and caused a metabolic shift in the syntrophic electron consumption pathway. The highest degree of sulfate reduction in glucose receiving cultures with LA, OA and SA was found to be 92%, 72%, and 31% respectively.