Wastewater treatment and photo-reduction of CO2 using an integrated magnetized TiO2 anaerobic- photocatalytic system

Abstract

Conventionally, the treatment of municipal wastewater involves a sequence of treatment units aimed at reducing pollutants to acceptable discharge levels. Herein wastewater treatment plants in South Africa’s municipalities are being challenged recently due to emerging contaminants (nanomaterials, pesticides, antibiotics, COVID-19 RNA, etc.) that impede their efficiency. This calls for robust technological water solution systems targeted at promoting sustainable water supply and mitigating anthropogenic gas (CO2) emission via biogas production. Against this background, the novel of this study is aimed to develop an integrated AD-AOP (anaerobic digestion – advanced oxidation process) magnetized system to improve wastewater for reuse with biogas production and nanoparticles recoverability benefits. To obtain an optimal balance between robustness and cost-effectiveness of the integrated system, a series of feasibility and engineering works were explored. The first phase involved the synthesis via a co-precipitation technique, characterization, and applicability of the magnetized-photocatalysts (MPCs) for wastewater treatment. Analytically, the scanning electron microscopy and energy dispersive X-ray (SEM/EDX), Fourier transforms infrared spectra, X-ray diffraction (XRD), and Brunauer- Emmett-Teller (BET) techniques showed the tailored MPCs were successfully magnetized. Among the MPCs studied, Fe-TiO2 (with a BET surface area of 62.73 m2 /g) was found as the best with greater potential for above 75% decontamination of the wastewater and methane yield. In the technological design and evaluation, Fe-TiO2 was examined using biochemical methane potential (BMP), biophotocatalytic (BP), biomagnetic (BM), and biophotomagnetic (BPM) systems. Due to the external magnetic field influence on the BPMs, it was found very promising for future adventures. Above all, the novel integrated AD-AOP magnetized system proof of concept showed great potential for recoverability of the MPCs for reuse, reducing the toxicological effects of trace metals (27 elements considered), and improving water and biogas quality. The bioenergy economy of the integrated AD-AOP magnetized system demonstrated net energy being able to subsidize the energy required by the UV-lamp of the AOP system. Conclusively, this finding provides an insight into synthesizing novel MPCs and their applicability for wastewater remediation and biogas production. Also kinetics modeling and response surface methodology (RSM) optimization coupled with artificial neural network (ANN) predictability showed the potential to develop an optimized integrated AD-AOP magnetised system towards the treatment of industrial wastewater, biogas production , and CO2 emission reduction. The prospects necessitate a techno-scientific revolution to upscale the current integrated system into a pilot scale with smart-online monitoring towards improving the wastewater circular economy.