ANNOUNCEMENTS
This thesis presents a detailed evaluation of Advanced Oxidation Processes (AOPs), focusing on the use of UV/TiO₂ photocatalysis for the treatment of textile wastewater—a critical environmental challenge due to the presence of hazardous dyes and organic pollutants. The overarching aim of this research was to assess the feasibility, efficiency, and sustainability of integrating UV/TiO₂ photocatalysis for achieving Zero Liquid Discharge (ZLD) compliance, while comparing it with other photochemical AOPs and conventional wastewater treatment methods. Additionally, the research evaluated the scalability of this technology for use in Common Effluent Treatment Plants (CETPs), where textile clusters discharge complex wastewater effluents.
The study was conducted in several phases. First, TiO₂ nanomaterials characterized to ensure they possessed ideal photocatalytic properties. Techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area analysis were employed to confirm particle size, surface area, porosity, and the anatase phase, which was identified as optimal for photocatalysis. These characterizations provided the foundation for the subsequent optimization of the UV/TiO₂ photocatalytic process. In the optimization phase, key parameters such as pH, catalyst concentration, and UV irradiation time were systematically varied to maximize pollutant removal. For synthetic dye bath wastewater, optimal conditions were found at pH 10.56, a catalyst loading of 0.5 g/L, and 120 minutes of UV exposure. Under these conditions, significant reductions in pollutants were achieved, including 91% removal of COD, 95% BOD reduction, and a 94% reduction in color. These optimized conditions were further applied to real textile wastewater samples.
Real effluent samples obtained from Sonipat (Haryana) and Guntur (Andhra Pradesh) were characterized by high COD concentrations (up to 1200 mg/L) and high levels of dye pollution. The application of UV/TiO₂ under the optimized conditions resulted in COD reductions of over 80% and BOD reductions of up to 90%. These results confirmed the versatility of UV/TiO₂ photocatalysis in treating complex effluents across different textile processing sites, validating its potential for wide-scale industrial use.
A major highlight of this thesis is the comprehensive techno-economic assessment (TEA) of the UV/TiO₂ photocatalysis process, which demonstrated its cost-effectiveness and operational viability compared to alternative Advanced Oxidation Processes (AOPs). The treatment cost for synthetic effluent was estimated at 1.12 USD/m³, while for real effluents like those from S1 (polyester dyeing effluent, Sonipat) and S2 (cotton dyeing effluent, Guntur), the cost was slightly higher at 1.65 USD/m³. This competitive cost advantage is primarily attributed to the lower energy consumption and minimal chemical usage of UV/TiO₂, particularly when compared to other AOPs such as UV/H₂O₂ and UV/FeSO₄/H₂O₂ (Photo-Fenton), which often require up to 30–40% more energy and continuous addition of reagents.
The process's energy efficiency was further validated through the calculation of Figures of Merit. For synthetic effluent, the Electrical Energy per Order (EEO) was determined to be 9.68 kWh/order for COD removal, 7.29 kWh/order for BOD removal, and 3.94 kWh/order for color removal. For real effluents, such as S1 and S2, the EEO for COD and color removal was 6.87 kWh/order and 3.94 kWh/order, respectively, with a slightly lower EEO of 5.24 kWh/order for BOD removal. Additionally, the energy consumed per kilogram of COD removed was calculated as 5.09 kWh/kg COD for real effluents and 7.3 kWh/kg COD for synthetic effluent. These values highlight the UV/TiO₂ system's superior energy efficiency, reinforcing its suitability for large-scale industrial applications.
At the CETP scale in Rooma, Kanpur, the integration of UV/TiO₂ photocatalysis as a pre-treatment step yielded remarkable results. The process achieved 80% COD removal and 90% TSS removal, substantially reducing the pollutant load on subsequent biological treatment systems. This pre-treatment not only lowered the retention times required for biological processes but also improved the overall treatment efficiency of the CETP. The results indicate that UV/TiO₂ photocatalysis can seamlessly integrate with existing wastewater treatment infrastructure, enhancing performance while maintaining cost-effectiveness. These findings collectively position UV/TiO₂ as a scalable and sustainable technology for industrial wastewater treatment. By addressing key challenges such as energy consumption, chemical usage, and operational costs, this process offers a viable pathway for industries to achieve regulatory compliance and adopt more sustainable effluent management practices.
In parallel, a comprehensive Life Cycle Assessment (LCA) was conducted to evaluate the environmental sustainability of UV/TiO₂ compared to other AOPs and conventional treatment systems. Three scenarios were modeled: (1) standalone AOPs for COD removal, (2) AOP integration into conventional treatment for CPCB discharge norms, and (3) AOP integration into ZLD systems. Under Scenario 1, UV/TiO₂ showed the lowest carbon footprint of 12.8 kg CO₂e per cubic meter of treated water compared to 15.2 kg CO₂e/m³ for UV/FeSO₄/H₂O₂ and 11.5 kg CO₂e/m³ for UV/H₂O₂. The overall reduction in carbon emissions was 18.42% when compared to conventional treatment methods.
In Scenario 2, which involved integration into CETP systems, UV/TiO₂ achieved a 25% reduction in CO₂ emissions compared to the baseline scenario of conventional treatment systems (which had a carbon footprint of 34.7 kg CO₂e/m³). The study found that integrating UV/TiO₂ with conventional biological treatment reduced overall energy consumption and chemical usage, making it an environmentally and economically superior solution. In Scenario 3, where UV/TiO₂ was integrated into a ZLD system, the carbon footprint was further reduced by 32.11%, with total CO₂ emissions of 23.6 kg CO₂e/m³ compared to 34.7 kg CO₂e/m³ for the conventional ZLD process. This reduction was primarily due to the efficient removal of pollutants in the pre-treatment phase, reducing the energy and chemical requirements for downstream processes. The UV/TiO₂ process proved to be more sustainable and scalable for industrial applications compared to other AOPs, with a lower environmental burden and reduced operational costs.
Overall, this thesis demonstrates that UV/TiO₂ photocatalysis is a highly effective, energy-efficient, and sustainable solution for the treatment of textile wastewater. Its scalability and adaptability to different types of effluents make it suitable for large-scale applications in CETPs, offering significant cost savings and environmental benefits. The integration of UV/TiO₂ into conventional wastewater treatment systems not only reduces the pollutant load but also lowers energy consumption and carbon emissions, aligning with global goals for sustainable industrial practices. Future work should focus on transitioning from batch-scale to continuous-flow systems, which will enable real-time monitoring and optimization. Additionally, further research on UV-LED systems, long-term catalyst stability, and hybrid AOP systems could improve process efficiency and reduce operational costs. The long-term implementation of UV/TiO₂ at industrial scales could potentially transform wastewater management in the textile industry, providing a viable pathway toward sustainable water treatment and ZLD compliance.
In conclusion, the findings of this thesis establish UV/TiO₂ photocatalysis as a cost-effective, scalable, and environmentally sustainable AOP for textile wastewater treatment. It offers a retrofittable solution for industries seeking to reduce their environmental footprint while achieving stringent regulatory standards for effluent discharge and ZLD compliance.
