Many industrial processes would require enormous amounts of water, which could ultimately result in wastewater. Water scarcity in many parts of the world makes this situation unsustainable. In order to reuse wastewater in industrial processes or for other purposes, wastewater must be treated properly.
In industrial wastewater treatment, electrocoagulation-flotation (ECF) can be used to dissolve sacrificial electrodes and produce metal coagulant in-situ by applying a current to the electrodes. The reactor design and electrode configuration can profoundly affect the performance of electrocoagulation-flotation (ECF). While most conventional ECF reactors use an open-vertical electrode configuration in rectangular cells, mixing is limited by vertical electrodes that make a barrier and disrupt the flow hydrodynamics. The effects of these factors may influence removal efficiency, flow hydrodynamic, floc formation, and flotation/settling characteristics.
The present work aimed to optimize the ECF process by developing an innovative electrode configuration. A variety of parameters were examined to determine the effectiveness of the removal of contaminants from industrial wastewater that had turbidity, emulsified oil, and heavy metals (Si, Zn, Pb, Ni, Cu, Cr, and Cd), as well as stirring speed and foaming. Additionally, the experimental results of the innovative electrode configuration were compared with those of the conventional rectangular cell with plate electrode configuration. Based on the results, the innovative electrode configuration consumed approximately 20% less energy than a conventional ECF for operating times of 10, 20, 30, 32, 48, and 70 minutes. As a result of the enhanced flow hydrodynamic, the formed gas bubbles tilted toward the center, significantly reducing foam formation.
There was also an investigation of the dominant operating parameters for electrocoagulation-flotation (ECF) that could affect the removal efficiency, including current density (CD), initial pH, electrolytic conductivity, dosage of coagulant, operating time, initial turbidity concentration, and stirring speed.
In addition, a novel approach has been proposed for evaluating EC performance and selecting an appropriate process for removing sludge based on the intake's initial concentration.
Keywords:
Electrode configuration, electrocoagulation process, electro-flotation, energy consumption, removal efficiency, Electrochemical treatment, Aluminium electrode, Turbidity removal, TOC removal, operating parameters, computational fluid dynamics, Reynolds number, mass transfer, pH evolution.:Table of Contents
Abstract 7
1. Introduction 16
1.1. The electrocoagulation process 17
1.2. Problem statement 19
1.3. Objectives 20
1.4. Scope of the work 21
2. Literature survey 23
2.1. Industrial wastewater and treatment methods 24
2.1.1. Impact of industrial growth 24
2.1.2. An analysis of global industrial growth based on statistics 25
2.1.3. Extensive sources of industrial effluent 26
2.1.4. Wastewater and reserve rehabilitation in industry 34
2.1.5. Applied techniques in industrial wastewater treatment 40
2.2. Electrocoagulation (ECF) 50
2.3. Comparison of EC with other treatment methods 50
2.4. Basic concepts and theory of coagulation and electrocoagulation 53
2.5. Electrocoagulation applications 58
2.5.4. Textile industry 60
2.5.5. Leather Tanning Industry 61
2.5.6. Metal-bearing industrial effluents 61
2.5.7. Pulp and paper industry 62
2.5.8. Petroleum refinery 63
2.6. Type and Configuration of the Electrodes 64
2.6.1. Case of Al electrodes 66
2.6.2. Case of Fe electrodes 68
2.7. Reactor design 71
2.6. Modeling 72
2.6.1. Kinetics 73
2.7. Impact of electrocoagulation operating condition on contaminant removal efficiency 75
2.7.1. Effect of current density 75
2.7.2. Effect of initial pH 75
2.7.3. Effect of operating time 76
2.7.4. Effect of electro conductivity 76
2.7.5. Effect of stirring speed 77
2.7.6. Effect of concentration 77
2.7.7. Effect of gap between the electrodes 77
2.7.8. Effect of temperature 78
2.8. Economical aspects and cost analysis 78
3. Material and methods of the tests 80
3.1. Test procedure 1: Impact of operating parameters on removal of turbidity 81
3.1.1. Operating conditions 81
3.1.2. EC cell construction and electrode arrangement 82
3.1.3. Synthetic wastewater 85
3.1.4. Analytical methods and EC procedure 86
3.1.5. Anodic and cathodic reactions 87
3.1.6. Electrical double layer and particle stability 89
3.2. Test procedure 2: Spiral electrode configuration 91
3.2.1. Experimental Setup 91
3.2.2. Sampling and analytical measurements 95
3.2.3. Experimental procedure 95
4. Results and discussion 97
4.1. Test procedure 1: Impact of operating parameters on removal of turbidity 98
4.1.1. Effect of current density (CD) 98
4.1.2. Effect of initial pH 100
4.1.3. Effect of electrolytic conductivity 104
4.1.4. Effect of coagulant dosage, electrode and energy consumption 106
4.1.5. Effect of current density and operating time on initial turbidity concentration 107
4.1.6. Effect of stirring speed 111
4.1.7. Effect of electrode passivation 112
4.2. Test procedure 2: Spiral electrode configuration 115
4.2.1. Removal efficiency of contaminants 115
4.2.2. Effect of stirring speed and ECF configuration on removal efficiency 119
4.2.3. Energy consumption and voltage rise 123
4.2.4. Foaming effect 126
4.3. Computational Fluid Dynamics (CFD) Simulation 128
5. Conclusions and future work 138
5.1. Conclusions 139
5.2. Future works 142
References 143
6. Appendix 159
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:90736 |
| Date | 11 April 2024 |
| Creators | Jafari, Ehsan |
| Contributors | Malayeri, Reza Mohammad, Eckert, Kerstin, Krebs, Peter, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/updatedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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