title: Analysing the mechanisms of sludge digestion enhanced by iron.
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 CH4production 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 CH4production, although WISs (10 g Fe/L) could indeed increase CH4production 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 CH4production, which would facilitate hydrolysis of refractory organics and improvement of electron transport rate (ETR).
authors.affiliation: Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Key Laboratory of Urban Stormwater System and Water Environment, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China. Electronic address: xdhao@hotmail.com.
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Hao
authors.affiliation: Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Key Laboratory of Urban Stormwater System and Water Environment, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wei
authors.affiliation: Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Key Laboratory of Urban Stormwater System and Water Environment, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China; Dept. of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands.
authors.forename: Mark C M
authors.initials: MCM
authors.lastname: van Loosdrecht
authors.affiliation: Sino-Dutch R&D Centre for Future Wastewater Treatment Technologies/Key Laboratory of Urban Stormwater System and Water Environment, Beijing University of Civil Engineering & Architecture, Beijing 100044, PR China.
authors.forename: Daqi
authors.initials: D
authors.lastname: Cao
mesh_terms: D000693:Anaerobiosis; D019149:Bioreactors; D007501:Iron; D008697:Methane / Q000378:metabolism; D012722:Sewage; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage; D007501:Iron; D008697:Methane
keywords: Activity of enzymes; Anaerobic digestion; Hydrogen-evolution corrosion; Methane; Oxidation-reduction potential (ORP); Waste iron scraps (WISs)