Instituto de la Grasa, Spanish National Research Council (CSIC), Seville, Spain; University of Pablo de Olavide, Seville, Spain; Department of Civil, Architectural and Environmental Engineering, University of Naples Federico II, Naples, Italy.
Department of Mathematics and Applications "Renato Caccioppoli", University of Naples Federico II, Naples, Italy.
J Environ Manage. 2023 Oct 1;343:118144. doi: 10.1016/j.jenvman.2023.118144. Epub 2023 Jun 6.
Dosing trace metals into anaerobic digestors is proven to improve biogas production rate and yield by stimulating microorganisms involved in the metabolic pathways. Trace metal effects are governed by metal speciation and bioavailability. Though chemical equilibrium speciation models are well-established and widely used to understand metal speciation, the development of kinetic models considering biological and physicochemical processes has recently gained attention. This work proposes a dynamic model for metal speciation during anaerobic digestion which is based on a system of ordinary differential equations aimed to describe the kinetics of biological, precipitation/dissolution, gas transfer processes and, a system of algebraic equations to define fast ion complexation processes. The model also considers ion activity corrections to define effects of ionic strength. Results from this study shows the inaccuracy in predicting trace metal effects on anaerobic digestion by typical metal speciation models and the significance of considering non-ideal aqueous phase chemistry (ionic strength and ion pairing/complexation) to define speciation and metal labile fractions. Model results show a decrease in metal precipitation and increase in metal dissolved fraction and methane production yield with increase in ionic strength. Capability of the model to dynamically predict trace metal effects on anaerobic digestion under different conditions, like changing dosing conditions and initial iron to sulphide ratio, was also tested and verified. Dosing iron increases methane production and decreases hydrogen sulphide production. However, when iron to sulphide ratio is greater than 1, methane production decreases due to increase in dissolved iron which reaches inhibitory concentration levels.
向厌氧消化器中添加痕量金属已被证明可以通过刺激参与代谢途径的微生物来提高沼气的产生速率和产量。痕量金属的作用受金属形态和生物利用度的控制。虽然化学平衡形态模型已经成熟并广泛用于理解金属形态，但考虑生物和物理化学过程的动力学模型的开发最近引起了关注。这项工作提出了一种用于厌氧消化过程中金属形态的动态模型，该模型基于一组旨在描述生物、沉淀/溶解、气体转移过程动力学的常微分方程系统，以及一组用于定义快速离子络合过程的代数方程。该模型还考虑了离子活度校正来定义离子强度的影响。研究结果表明，典型的金属形态模型在预测痕量金属对厌氧消化的影响时存在不准确性，并且考虑非理想水相化学（离子强度和离子对/络合）来定义形态和金属不稳定分数的重要性。模型结果表明，随着离子强度的增加，金属沉淀减少，金属溶解分数和甲烷产量增加。还测试和验证了该模型在不同条件下（如改变投加条件和初始铁与硫化物的比例）动态预测痕量金属对厌氧消化影响的能力。投加铁会增加甲烷产量并减少硫化氢产量。然而，当铁与硫化物的比例大于 1 时，由于达到抑制浓度水平的溶解铁增加，甲烷产量会下降。
