Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion

Solon, Kimberly; Flores-Alsina, Xavier; Mbamba, Christian Kazadi; Volcke, Eveline; Tait, Stephan; Batstone, Damien J.; Gernaey, Krist V.; Jeppsson, Ulf

doi:10.1016/j.watres.2014.11.035

Cited by 68 publications

(53 citation statements)

References 29 publications

(31 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ionic strength of the solubility and dissolution media was calculated using Eq. (1) (25). The summation symbol, Σ, indicates that the products of cz 2 terms of all the ionic species in the solution, from the first one to the Jth species, are to be added together.…”

Section: Physicochemical Properties Of the Mediamentioning

confidence: 99%

pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

et al. 2015

View full text Add to dashboard Cite

Abstract. The objective of this study was to investigate the pH-dependent solubility and dissolution of weakly basic Biopharmaceutical Classification Systems (BCS) class II drugs, characterized by low solubility and high permeability, using carvedilol, a weak base with a pK a value of 7.8, as a model drug. A series of solubility and in vitro dissolution studies was carried out using media that simulate the gastric and intestinal fluids and cover the physiological pH range of the GI from 1.2 to 7.8. The effect of ionic strength, buffer capacity, and buffer species of the dissolution media on the solubility and dissolution behavior of carvedilol was also investigated. The study revealed that carvedilol exhibited a typical weak base pH-dependent solubility profile with a high solubility at low pH (545.1-2591.4 μg/mL within the pH range 1.2-5.0) and low solubility at high pH (5.8-51.9 μg/mL within the pH range 6.5-7.8). The dissolution behavior of carvedilol was consistent with the solubility results, where carvedilol release was complete (95.8-98.2% released within 60 min) in media simulating the gastric fluid (pH 1.2-5.0) and relatively low (15.9-86.2% released within 240 min) in media simulating the intestinal fluid (pH 6.5-7.8). It was found that the buffer species of the dissolution media may influence the solubility and consequently the percentage of carvedilol released by forming carvedilol salts of varying solubilities. Carvedilol solubility and dissolution decreased with increasing ionic strength, while lowering the buffer capacity resulted in a decrease in carvedilol solubility and dissolution rate.

show abstract

Section: Physicochemical Properties Of the Mediamentioning

confidence: 99%

pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

et al. 2015

View full text Add to dashboard Cite

show abstract

“…An alternative method of modelling pH is using a proton balance (Morel and Hering 1993). While the proton balance method generates the same equation set (Solon et al 2015), a charge balance method is used throughout this thesis as it is easier to conceptually integrate with the charge transport phenomena that dominates the study of ED. It also allows speciation of weak acids and bases in their total (component) form.…”

Section: Electro-physico-chemistrymentioning

confidence: 99%

“…The model accounts for ionic activity, ion-pairing and acid-base dissociation using a Generalized Physicochemical Modelling Framework (GPMF) developed by the International Water Association Physico-chemical Modelling Taskgroup Flores-Alsina et al 2016;Solon et al 2015).…”

Section: Chapter 2: a Non-ideal Mechanistic Model Of Electrodialysismentioning

confidence: 99%

“…Ionic activity (a i ) depends on the ionic strength of solution (μ) which is found by Equation 2.2 (Solon et al, 2015). The activity coefficient of the ion ( ) is then found using the Davies equation (Equation 2.3) (Solon et al, 2015).…”

Section: Ionic Activitymentioning

confidence: 99%

“…A limitation in existing electrochemical modelling is the lack of integration between existing electrochemistry theory and a robust physico-chemical process simulation framework such as that developed by Solon et al (2015) and . The aim of this study is to develop a physico-chemical modelling approach for electrochemical membrane systems which includes, and accounts for the relationships between the following mechanisms:…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nutrient recovery from wastewater using electrodialysis

Brewster¹

View full text Add to dashboard Cite

The production of synthetic fertilisers from traditional sources has several issues regarding sustainability, particularly the energy intensity required for production, limited mineral resources and loss of terrestrial environment. Nutrient recovery from wastewaters is an opportunity for alternative fertiliser manufacture, largely due to the high quantities of nutrients present. Electrodialysis (ED) is an optimal technology to recover, particularly, NH 4 + -N and K + -K. In this thesis, a mechanistic modelling approach is used to study ED for nutrient recovery. Existing ED models lack the capacity to mechanistically evaluate complex, multi-ion solutions (like real wastewater), the integration of electrochemistry and physicochemical phenomena across the whole reactor domain, and model validation using system dynamics. These limitations are addressed by development of a mechanistic modelling approach, with key mechanisms determined through targeted laboratory scale experiments using synthetic and real wastewaters. The first major study in this thesis includes development of a mechanistic model validated using dynamic experiments fed with synthetic wastewater. It was found that membrane resistance was the major contributor to potential drop and that apparent boundary layers were relatively thick (3 ± 1 mm) due to reactor design and operational conditions. This study also established that non-ideal solution effects such as ion pairing and ionic activity had a major impact, enhancing the capability of ED to recover monovalent nutrient ions such as K + and NH 4 + . The second major study used real centrifuged anaerobic digester rejection water (centrate) to study membrane scaling. Dynamic laboratory experiments demonstrated electro-concentration of nutrients in centrate to several times the feed concentration. An 87±7% by weight reduction in scale occurred when the centrate was pre-treated by upstream struvite recovery and the product pH was controlled at pH 5, compared to untreated centrate and no pH control. A mechanistic model for the inorganic processes was developed by extending the previously developed model to include the composition of a real wastewater feed solution and precipitation. This extended model revealed a reduction in struvite scale to the removal of phosphate during the struvite pretreatment, and reduction in calcium carbonate scale to pH control resulting in the stripping of carbonate as carbon dioxide gas; indicating that multiple strategies may be required to control precipitation. A third major study evaluated the mechanisms limiting high product concentrations during electro-concentration of synthetic urine. Modelling this system using similar methods to the first study identified that high concentrations in the product are prevented by back diffusion of ions across the membrane, current leakage (when buffering ii capacity is exhausted), and water fluxes across the membranes. Mechanistic discoveries in this thesis provide practical guidelines for pilot and full-scale operation of nutri...

show abstract

Model‐based analysis and optimization of a full‐scale industrial high‐rate anaerobic bioreactor

Feldman

Flores-Alsina

Kjellberg

et al. 2018

Biotech & Bioengineering

Self Cite

View full text Add to dashboard Cite

The objective of this paper is to present the model-based optimization results of an anaerobic granular sludge internal circulation reactor. The International Water Association Anaerobic Digestion Model No. 1 extended with phosphorus (P), sulfur (S), and ethanol is used to describe the main biological and physico-chemical processes. The high-rate conditions within the reactor are simulated using a flow + reactor model comprised of a series of continuous stirred tank reactors followed by an ideal total suspended solids separation unit. Following parameter estimation by least squares on the measured data, the model had a relative mean error of 13 and 15% for data set #1 and data set #2, respectively. Response surfaces show that the reactor performance index (a metric combining energy recovery in the form of heat and electricity, as well as chemicals needed for pH control) could be improved by 45% when reactor pH is reduced down to 6.8. Model-based results reveal that influent S does not impose sufficient negative impacts on energy recovery (+5.7%, in MWh/day,+0.20 M€/year when influent S is removed) to warrant the cost of its removal (3.58 M€/year). In fact, the process could handle even higher S loads (ensuring the same degree of conversion) as long as the pH is maintained above 6.8. Nevertheless, a higher S load substantially increases the amount of added NaOH to maintain the desired operational pH (>25%) due to the acidic behavior of HS . CO stripping decreases the buffer capacity of the system and hence use of chemicals for pH control. Finally, the paper discusses the possibilities and limitations of the proposed approach, and how the results of this study will be put into practice.

show abstract

Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion

Cited by 68 publications

References 29 publications

pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

Nutrient recovery from wastewater using electrodialysis

Model‐based analysis and optimization of a full‐scale industrial high‐rate anaerobic bioreactor

Contact Info

Product

Resources

About