Abstract

In this work, electro-oxidation which is one of the innovative and efficient processes was used to treat gray and fatty wastewater (oil residues) from ships. These wastewaters contain heavy metals and persistent organic pollutants that damage the marine environment, contaminate the food chain, and harm marine life. This project aimed to apply the electro-oxidation process for the treatment of gray wastewater from ships heavily loaded with COD (1310.4 mgO2/L), TOC (375 mg/L of TOC), lead (3.13), Zn (7.91), and turb (709.5 NTU) in order to comply with sea discharge standards. After the characterization of the effluent, the optimal conditions and the effects of the parameters (current intensity, electrolysis time, and concentration of the electrolyte) made it possible to monitor the degradation (λmax = 490 nm) of the effluent on the one hand as a function of the intensity of the current and on the other hand as a function of the concentration of the electrolyte. This optimization of the current intensity (1.25 A) and the concentration of the electrolyte (2 g/L) made it possible to obtain a respective reduction rate of 99.33, 70, and 67% for the turbidity, COD, and TOC after 6 h of electrolysis. Under the same conditions, a high reduction rate for metals such as Zn (84.11%), Hg (63.31%), and Ag (58.23%) was observed. A relatively low reduction rate was observed with Pb (30.1%). As for Cd and Se, they remained quantitatively in solution. This process made it possible to simultaneously eliminate the organic and mineral load at a satisfactory rate.

Key words: Advanced oxidation processes, organic load, effluent treatment, residual hydrocarbons.