The impact of ozone treatment on the removal effectiveness of various refractory compounds in wastewater from petroleum refineries

Abstract

Large volumes of wastewater are generated during petroleum refining processes. Petroleum refinery wastewater (PRW) can contain highly toxic compounds that can harm the environment. These toxic compounds can be a challenge in biological treatment technologies due to the effects of these compounds on microorganisms. These challenges can be overcome by using ozone (O₃) as a standalone or as a pretreatment to the biological treatment. Ozone was used in this study to degrade the organic pollutants in the heavily contaminated PRW from a refinery in Mpumalanga province of South Africa. The objective was achieved by treating the raw PRW using ozone at different ozone treatment times (15, 30, 45, and 60 min) at a fixed ozone concentration of 3.53 mg/dm³. The ozone treatment was carried out in a 2-liter custom-designed plexiglass cylindrical reactor. Ozone was generated from an Eco-Lab-24 corona discharge ozone generator using clean, dry air from the Afrox air cylinder as feed. The chemical oxygen demand, gas chromatograph characterization, and pH analysis were performed on the pretreated and post-treated PRW samples to ascertain the impact of the ozone treatment. The ozone treatment was effective in reducing the benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds in the PRW. The 60-min ozone treatment of different BTEX pollutants in the PRW resulted in the following percentage reduction: benzene 95%, toluene 77%, m + p-xylene 70%, ethylbenzene 69%, and o-xylene 65%. This study has shown the success of using ozone in reducing the toxic BTEX compounds in a heavily contaminated PRW.

Keywords:

• Ozone
• petroleum refining wastewater
• benzene
• toluene
• ethylbenzene
• and xylene

Acknowledgments

Vaal University of Technology is acknowledged for providing facilities.

Authors contributions

Nkosinathi Khoza: conceptualization, methodology, formal analysis, investigation, investigation, data curation, writing-original draft. Tumisang Seodigeng: formal analysis, investigation, data curation, writing-reviewing, and editing. Musamba Banza: formal analysis, investigation, data curation, writing-reviewing, and editing. Aoyi Ochieng: formal analysis, investigation, data curation, writing-reviewing, and editing.

Disclosure statement

The authors declare that they have no known competition for financial interests or personal relationships that could have influenced the work reported in this paper.

Data availability statement

The data presented in this study are available on request from the corresponding author.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.