Biological polishing of liquid and biogas effluents from wastewater treatment systems

Abstract

Abstract In an ideal world the liquid and gaseous effluents of wastewater treatment plants (WWTPs) would be harmless to organisms and machinery. However, some compounds are recalcitrant to degradation while degradation products of other compounds can escape further treatment through volatilization. The addition of a terminal biological polishing step can expand the repertoire of compounds subject to removal. Phenolic compounds, for example, are often not well catabolized by the microbiota within WWTPs, leaving them in effluents at levels that can exert phytotoxic and endocrine-disrupting effects. Passage of WWTP effluents through vermifilters or constructed wetlands has been successfully applied to lower a wide range of phenolics. Likewise, corrosive hydrogen sulfide (H2S) in the biogas product of anaerobic digestion of wastewater solids can be utilized as an electron source by a variety of anaerobic respiratory bacteria and yet WWTPs are largely reliant on chemical-based H2S removal technologies. Biogas scrubbers colonized with sulfide-oxidizing bacteria are a more cost-effective and sustainable means to efficiently remove H2S and, potentially, nonmethane volatile organic compounds. In this chapter we focus on studies that have examined the potential of these biologically based polishing technologies for improving WWTP effluents. To further improve the feasibility and environmental sustainability of biological polishing systems, means can be established to convert the spent polishing material for other beneficial purposes, including energy generation and carbon dioxide capture.