Analysing the mechanisms of sludge digestion enhanced by iron

Journal article (2017)

Authors

Xiaodi Hao Beijing University of Civil Engineering & Architecture
Jing Wei Beijing University of Civil Engineering & Architecture
Mark C.M. van Loosdrecht Beijing University of Civil Engineering & Architecture, BT/Environmental Biotechnology - AS
Daqi Cao Beijing University of Civil Engineering & Architecture
Research Group
BT/Environmental Biotechnology (AS) (TU Delft)
Methane Anaerobic digestion Oxidation-reduction potential (ORP) Activity of enzymes Hydrogen-evolution corrosion Waste iron scraps (WISs)
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Published Date

2017

Language

English

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Faculty

Applied Sciences

Department

BT/Biotechnologie

Research Group

BT/Environmental Biotechnology

Abstract

Carbon-neutral operation of wastewater treatment plants (WWTPs) requires enhancing anaerobic digestion (AD) of excess sludge for a higher energy conversion efficiency. Among others, iron has been identified to function on enhancing methane production in AD. As an industrial residual, waste iron scraps (WISs) have been reported as potentially enhancing CH4 production in AD. With this study, the mechanisms of AD enhanced by WISs are analysed in a two-phase process: acidogenic phase (AP) and methanogenic phase (MP). Semi-continuous tests substantially excluded ORP reduction and hydrogen-evolution corrosion induced by WISs in enhancing CH4 production, although WISs (10 g Fe/L) could indeed increase CH4 production by 10.1% and 21.4% when added in AP and MP respectively. Detection on both FISH and enzymatic activities of involved microorganisms revealed that the stimulating effects of WISs on anaerobes (both catabolism and anabolism) could play an important (96.3%) role in enhancing CH4 production, which would facilitate hydrolysis of refractory organics and improvement of electron transport rate (ETR).