title: Trace metal speciation and bioavailability in anaerobic digestion: A review.
abstract: Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se; compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups; determine what factors influence metal sulfide dissolution; investigate whether chelating agents can increase trace metal bioavailability; develop and adapt specialized analytical techniques, and; determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).
authors.affiliation: Interdisciplinary Graduate School, Nanyang Technological University, Singapore 639798; Nanyang Environment & Water Research Institute, Advanced Environmental Biotechnology Centre, Nanyang Technological University, 637141, Singapore.
authors.forename: Pham Minh
authors.initials: PM
authors.lastname: Thanh
authors.affiliation: Nanyang Environment & Water Research Institute, Advanced Environmental Biotechnology Centre, Nanyang Technological University, 637141, Singapore.
authors.forename: Balachandran
authors.initials: B
authors.lastname: Ketheesan
authors.affiliation: Nanyang Environment & Water Research Institute, Advanced Environmental Biotechnology Centre, Nanyang Technological University, 637141, Singapore; School of Civil & Environmental Engineering, College of Engineering, Nanyang Technological University, 637141, Singapore.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Yan
authors.affiliation: Nanyang Environment & Water Research Institute, Advanced Environmental Biotechnology Centre, Nanyang Technological University, 637141, Singapore; Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom. Electronic address: d.stuckey@imperial.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Stuckey
mesh_terms: D000693:Anaerobiosis / Q000502:physiology*; D001421:Bacteria, Anaerobic / Q000378:metabolism / Q000502:physiology; D019149:Bioreactors / Q000382:microbiology*; D008670:Metals / Q000378:metabolism*
chemical_list: D008670:Metals
keywords: Anaerobic digestion; Bioavailability; Metal complexation; Metal deficiency; Metal sulfide; Metal supplementation; Speciation; Trace metals