Modelling phosphorus (P), sulfur (S) and iron (Fe) interactions for dynamic simulations of anaerobic digestion processes. (15th May 2016)

• Record Type: Journal Article
• Authors: Flores-Alsina, Xavier; Solon, Kimberly; Kazadi Mbamba, Christian; Tait, Stephan; Gernaey, Krist V.; Jeppsson, Ulf; Batstone, Damien J.
• Is Part Of: Water research. Volume 95(2016)
• Page Start: 370
• Page End: 382
• Publication Date: 2016-05-15
• Subjects: ADM1 extensions -- Aqueous phase chemistry model -- Multiple mineral precipitation -- Phosphorus recovery -- Physico-chemical modelling -- Simulation -- Water resource recovery facilities; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.03.012
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: This paper proposes a series of extensions to functionally upgrade the IWA Anaerobic Digestion Model No. 1 (ADM1) to allow for plant-wide phosphorus (P) simulation. The close interplay between the P, sulfur (S) and iron (Fe) cycles requires a substantial (and unavoidable) increase in model complexity due to the involved three-phase physico-chemical and biological transformations. The ADM1 version, implemented in the plant-wide context provided by the Benchmark Simulation Model No. 2 (BSM2), is used as the basic platform ( A 0 ). Three different model extensions ( A 1, A 2, A 3 ) are implemented, simulated and evaluated. The first extension ( A 1 ) considers P transformations by accounting for the kinetic decay of polyphosphates ( X PP ) and potential uptake of volatile fatty acids (VFA) to produce polyhydroxyalkanoates ( X PHA ) by phosphorus accumulating organisms ( X PAO ). Two variant extensions ( A 2, 1 / A 2, 2 ) describe biological production of sulfides ( S IS ) by means of sulfate reducing bacteria ( X SRB ) utilising hydrogen only (autolithotrophically) or hydrogen plus organic acids (heterorganotrophically) as electron sources, respectively. These two approaches also consider a potential hydrogen sulfide ( Z H 2 S ) inhibition effect and stripping to the gas phase ( G H 2 S ). The third extension ( A 3 ) accounts for chemical iron (III) ( S Fe 3 + ) reduction to iron (II) ( S Fe 2 + ) using hydrogen ( S H 2 ) and sulfides ( S IS ) as electron donors. A set of pre/post interfaces between the Activated Sludge Model No. 2d (ASM2d) and ADM1 are furthermore proposed in order to allow for plant-wide (model-based) analysis and study of the interactions between the water and sludge lines. Simulation ( A 1 – A 3 ) results show that the ratio between soluble/particulate P compounds strongly depends on the pH and cationic load, which determines the capacity to form (or not) precipitation products. Implementations A 1 and A 2, 1 / A 2, 2 lead to a reduction in the predicted methane/biogas production (and potential energy recovery) compared to reference ADM1 predictions ( A 0 ). This reduction is attributed to two factors: (1) loss of electron equivalents due to sulfate ( S SO 4 ) reduction by X SRB and storage of X PHA by X PAO ; and, (2) decrease of acetoclastic and hydrogenotrophic methanogenesis due to Z H 2 S inhibition. Model A 3 shows the potential for iron to remove free S IS (and consequently inhibition) and instead promote iron sulfide ( X FeS ) precipitation. It also reduces the quantities of struvite ( X MgNH 4 PO 4 ) and calcium phosphate ( X Ca 3 ( PO 4 ) 2 ) that are formed due to its higher affinity for phosphate anions. This study provides a detailed analysis of the different model assumptions, the effect that operational/design conditions have on the model predictions and the practical implications of the proposed model extensions in view of plant-wide modelling/development of resource recovery strategies. Graphical abstract: Highlights: The ADM1 is extended with P, S and Fe biological and physico-chemical reactions. Key AD outputs depends on cationic load, formation of PHA, S:COD ratio and Fe availability. Functional plant-wide P modelling is enabled by ASM-ADM-ASM interfaces.