Title Page
Abstract
Contents
1. Introduction 15
1.1. Combined Reverse osmosis concentrated wastewater 15
1.2. Microplastics 19
1.3. Research trends for treatment processes of microplastics from wastewater 22
1.4. Coagulation for removal of microplastics from combined RO concentrate 24
1.5. Research purpose 27
2. Materials and methods 28
2.1. Experimental design 28
2.2. Collection of wastewater samples 30
2.3. Analytical methods for microplastics analysis 32
2.4. Lab Experiments of Chemical Coagulation 39
2.5. Lab-scale experiment of Electro-Coagulation 41
3. Results and discussion 45
3.1. Characteristics of Microplastics in RO Wastewater 45
3.2. Lab-scale experiment of Coagulation process 49
3.2.1. Effect of Coagulant Dosage 49
3.2.2. Effect of Initial pH 53
3.2.3. Coagulation Mechanisms with MPs 54
3.2.4. Removal efficiency of MPs in coagulation 56
3.3. Lab-scale experiment of Electro-Coagulation process 60
3.3.1. Electrode configuration selection 61
3.3.2. Choice of inter-electrode distance 66
3.3.3. Effect of conductivity 69
3.3.4. Effect of current density 70
3.3.5. Initial pH 72
3.3.6. Performance evaluation of the Electro-Coagulation process for MP removal 73
3.3.7. Removal mechanism of EC for MPs 75
3.4. Critical comparison between EC and CC 78
3.4.1. Removal performance of MPs 78
3.4.2. Operating cost analysis 81
3.4.3. Overall comparison between EC and CC 84
4. Conclusion 86
References 90
국문 초록 99
Table 2.1. Analytical methods for main parameters of wastewater 31
Table 2.2. Detection methods of microplastic. 35
Table 3.1. A summary of the sizes of microplastics at various phases of treatment 48
Table 3.2. Variations of pH, temperature, potential, turbidity, electrode, and energy consumption over time across various electric configuration modes, with specific conditions: an initial pH of 6.9, a current density of 3 mA/cm², and a din of 10 mm. 64
Table 3.3. Changes in pH, potential difference, temperature, turbidity removal, and energy consumption over time different inter-electrode distances. 67
Table 3.4. Effect of conductivity on voltage, U, energy consumption, E 69
Table 3.5. Overall comparison of EC and CC for the treatment of RO wastewater. 85
Figure 1.1. Structure of the reverse osmosis unit 15
Figure 1.2. At the country level, wastewater production (m³/y per individual) (a), collecting (%) (b), treatments (%) (c), and re-use (%) (d). 18
Figure 1.3. Different forms of plastic waste in environment. 19
Figure 1.4. Possibility of MPs release routes into the environment 20
Figure 2.1. Overall study architecture 29
Figure 2.2. Schematic diagram of A industrial water center 30
Figure 2.3. Schematic graph of MPs pretreatment process 36
Figure 2.4. Lab-scale set up for CC. 40
Figure 2.5. Schematic graph of lab-scale EC process 42
Figure 3.1. MP distribution particles in the inlet and outlet of SBR system for different polymer types. 46
Figure 3.2. ζ potential variations under various PAC dosages with an initial pH of 6.9. Each recorded ζ potential represents the average of three consecutive readings. 50
Figure 3.3. Variation of Turbidity and MPs removal: a) under different coagulant doses; b) under different pH range 52
Figure 3.4. Coagulation mechanisms for removing MPs. 55
Figure 3.5. MP distribution particles in the inlet of SBR, outlet of SBR, and outlet PAC (150 mg/L, pH=9) system for different polymer types. 57
Figure 3.6. MP Removal efficiencies in the influent of SBR, effluent of SBR, and effluent of PAC (150 mg/L, pH=9) system for different polymer types 59
Figure 3.7. Monopolar and bipolar electrode arrangement. 62
Figure 3.8. Variations of turbidity removal (A) and energy consumption (B) over time across various electric configuration modes, with specific conditions: an initial pH of 6.9, a current density of 3 mA/cm² 65
Figure 3.9. Changes in turbidity removal (A), and energy consumption (B) over time for different inter-electrode distances. (with specific conditions: an initial pH of 6.9, a current density of 3 mA/cm², and monopolar connection) 68
Figure 3.10. Variation of Turbidity removal under different A) current density (initial pH=6.9), b) different pH range. 71
Figure 3.11. ζ potential variations under various current densities with an initial pH of 6.9. (Each recorded ζ potential represents the average of three consecutive readings) 71
Figure 3.12. MPs removal performance of EC under different conditions. 73
Figure 3.13. EC mechanism for removal of MPs from wastewater. 76
Figure 3.14. Comparison between removal efficiency of SBR, EC and CC; A) by different polymer type of MPs, B) by different size of MPs and C) portion of remained MPs polymers. 80
Figure 3.15. Comparison between theoretical and experimental mass release of coagulant in EC process (Initial pH=6.9, din=10 mm, current density=3 mA/cm²)[이미지참조] 82