Remediation of Domestic Wastewater by Electro- Oxidation of Dissolved Organic Substances
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Date
2025-11
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Kenyatta University
Abstract
Water pollution poses a significant threat globally, rendering vital water resources unsuitable for sustaining life. Detecting harmful substances dissolved in water can be done by observing changes in its colour, indicating the presence of pollutants like chemicals, trash, bacteria, and parasites. These contaminants alter water's appearance, affecting its clarity and overall quality. Basic methods to improve water clarity involve coagulation and settling techniques, but these can leave residues that lead to health issues. Efforts to treat wastewater have used strong oxidizing agents to eliminate pollutants, but this approach introduces secondary pollutants in treated water. Hence, there's a need for cost-effective techniques for domestic wastewater treatment. This study explores an electrochemical method to remove dissolved organic substances from water. It involves generating reactive oxidizing species at an electrode to interact with these substances. Two types of anode electrodes were used. A platinum electrode and a dimensionally stable anode (DSA) coated with iron (III) doped titanium dioxide on graphite. The incorporation of iron (III) ions within the structure and the crystal form of the material were both confirmed using SEM-EDX and XRD respectively. The experimental setup featured a two-chamber cell divided by a proton exchange membrane (PEM) made from a conducting polyaniline polymer. The polymeric material was characterized using Fourier Transformation Infrared spectroscopy (FTIR). The analysis confirmed the presence of conjugated bonds that can enable conduction of electricity by the organic material. The PEM was casted onto a fritz grid separating the two compartments of the cell. The setup for the oxidation process was done for the treatment of the domestic wastewater to enable a green chemistry treatment method without generating secondary pollutants. Treatment occurred in the anodic chamber where oxidizing species were generated. The platinum anode reduced oxygen from the air, while the DSA facilitated electron and holes generation through photo-oxidation, effectively degrading organic matter. Excess protons were discharged to the cathode through the casted PEM, separating the two halves of the reactor. The cell successfully purified a green leafy solution at 4.5 g/L concentration within 72 hours. Potential measurements reached a high voltage of about 105 mV within the initial 150 minutes of the oxidation process. Monitoring degradation through potential measurements and kinetics confirmed a gradual reduction in dispersed matter concentration over time. These findings illustrate the potential of this degradation process for remediating domestic wastewater, enabling its reuse at the source.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy (Chemistry) in the School of Pure and Applied Sciences of Kenyatta University. November, 2025
Supervisors
Isaac W. Mwangi
Ruth N. Wanjau
Sauda Swaleh