Disinfection of wastewater by electrocoagulation
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Date
2026-10-05
Authors
Σίδερη, Παναγιώτα-Ιωάννα
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Abstract
Wastewater reuse is becoming increasingly important as water resources become scarcer, but treated wastewater still needs to be properly disinfected before it can be safely reused. This thesis studies electrocoagulation (EC) with aluminum electrodes as a method for disinfecting wastewater, focusing on two common indicator bacteria, Escherichia coli, a Gram-negative bacterium, and Enter ococcus faecalis, a Gram-positive bacterium.Experiments were carried out using synthetic wastewater (SWW) with three different starting bacte rial concentrations (10², 10³, and 10⁴ CFU mL⁻¹), testing each bacterium separately as well as together in the same suspension. Two current densities were applied, 1.39 and 3.33 mA cm⁻², to see how the strength of the electrical current affects disinfection.The results showed that EC was very effective overall, removing more than 99% of the bacteria in most cases. At the lowest starting concentration, bacteria became completely undetectable after 20 minutes of treatment and 30 minutes of settling. However, removal became less efficient as the start ing bacterial concentration increased. The two bacteria did not behave the same way, E. faecalis was more affected by changes in current density than E. coli was. It was also observed that when the two bacteria were present together, removal was generally a bit lower than when each was treated alone, suggesting that the bacteria may interact with each other during treatment.To check whether these results also apply to real conditions, EC was also tested on real secondary wastewater collected from wastewater treatment plant of the University of Patras. The results were very similar to those from synthetic wastewater, with more than 99% removal of E. coli, enterococci, and total coliforms. A mathematical model was also used to describe how bacterial concentration decreased over time, and it fit the experimental data well.Finally, the thesis looks at the practical side of the process, estimating its energy use, electrode con sumption, and operating cost, and checking that the aluminum left in the treated water stays within safe limits. Overall, the results suggest that aluminum electrocoagulation is a promising, low-cost method for disinfecting wastewater and making it suitable for reuse.
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Keywords
Electrocoagulation, Disinfection, Enteroccocus faecalis, Escherichia coli, Wastewater, Microbes, Pathogenic, Microorganisms