Development of Integrated Process of Electrocoagulation and Filtration in Textile Wastewater Treatment

Abstract

The rapid expansion of the textile industry has introduced significant environmental challenges, particularly in wastewater management, where effluents with high levels of chemical oxygen demand (COD), total suspended solids (TSS), turbidity, color, and total organic carbon (TOC) pose serious threats to water resources and regulatory compliance. Conventional treatment methods often struggle to achieve sufficient removal efficiencies while remaining economically feasible, especially for small and medium-sized textile operations. To address these limitations, this study conducts a comprehensive investigation into the development, optimization, and integration of electrocoagulation-based treatment systems for textile wastewater. The research systematically advances from process enhancements, including seawater integration and electrode selection, to the design of advanced multi-stage systems, supported by rigorous multi-criteria decision-making frameworks. The experimental methodology employed a three-phase approach to systematically evaluate and optimize electrocoagulation (EC) processes for textile wastewater treatment. Initially, the potential of seawater integration in EC processes was investigated using a custom-designed electrolytic reactor, with systematic variation of seawater percentages (0, 5, 10, and 15%) and retention times (45, and 90 min) analyzed through central composite design (CCD) and analysis of variance (ANOVA) using Design-Expert 11 software. Subsequently, comprehensive electrode pair optimization was conducted using thirty-six combinations of six materials including Aluminium (Al), Zinc (Zn), Carbon (C), Copper (Cu), Mild Steel (MS), and Stainless Steel (SS), with performance evaluation through three Multi-Criteria Decision-Making (MCDM) methods: TOPSIS, VIKOR, and PROMETHEE II to identify the optimal electrode configuration. Finally, an integrated system (IS) process was developed and evaluated, incorporating sequential EC, sedimentation (ST), aeration (AT), multimedia filtration (MM), and activated carbon (AC) filtration processes. Twenty-seven distinct IS process configurations were systematically tested by varying EC (20, 40, and 60 min), ST (60, 120, and 180 min), and AT (20, 40, and 60 min) retention times, with optimization achieved through four MCDM methods: TOPSIS, VIKOR, PROMETHEE II, and Analytical Hierarchy Process (AHP) for comprehensive performance assessment. The seawater integration study demonstrated significant improvements in EC efficiency, achieving maximum removal efficiencies of 99.52% for TSS, 99.30% for turbidity, 98.19% for color, and 47.26% for COD. The integration not only enhanced removal efficiency through xiii improved coagulation but also provided beneficial dilution effects, reducing overall pollutant concentrations. Power consumption was reduced to 15.769 Am⁻² with treatment costs approximately 0.20 USD/m³, making the process economically attractive. The quadratic models developed through CCD showed excellent correlation with experimental data, achieving R² values of 0.9121 (COD), 0.9535 (color), 0.9525 (turbidity), and 0.9433 (TSS). The electrode optimization study revealed that while individual electrode pairs achieved varying removal efficiencies with maximum values of 92.09% COD (Al-C pair), 99.66% TSS (Al-Cu pair), 99.17% turbidity (Al-MS pair), and 70.99% TOC (SS-SS pair), no single combination excelled across all pollutant categories. Through comprehensive MCDM analysis, the Al-Zn electrode combination emerged as the optimal balanced solution, delivering consistent high performance with 99.32% TSS, 98.88% turbidity, 68.62% COD, and 57.96% TOC removal efficiencies. The IS process demonstrated exceptional treatment performance, with the optimized configuration (IS process 27) achieving maximum removal efficiencies of 99.69% for TSS, 99.57% for turbidity, 95.23% for COD, and 99.1% for color. The EC stage served as the primary destabilization mechanism, while subsequent ST and AT processes facilitated solid-liquid separation and oxidative degradation. Multimedia and activated carbon filtration provided final polishing, ensuring effluent quality met stringent discharge standards. All four MCDM methods consistently identified IS process 27 as the optimal configuration, validating the robustness of the treatment approach. This study makes a meaningful contribution to industrial wastewater treatment by developing a systematic framework for enhancing and optimizing the EC process. The novel integration of seawater offers a cost-effective strategy that enhances pollutant removal and presents practical benefits for coastal textile facilities. The comprehensive electrode selection approach provides design flexibility, while the rigorous use of multiple multi-criteria decision-making (MCDM) methods ensures reliable and transparent optimization across complex treatment scenarios. The proposed multi-stage integrated system demonstrates scalable, sustainable performance, consistently achieving high removal efficiencies that meet strict discharge and water reuse standards while remaining economically viable. These findings offer immediate industrial applicability and contribute valuable knowledge to electrochemical water treatment. The study emphasizes the importance of sequential process synergy and optimized retention durations in maximizing treatment performance, offering a practical, adaptable, and high efficiency solution for textile wastewater management and related industrial applications.