Removal of PAH compounds from refinery industrial sludge as hazardous environmental contaminants through anaerobic digestion

• Published in: International journal of environmental science and technology (Tehran) 2021-06, Vol.18 (6), p.1617-1626
• Main Authors: Kazemi Moayed, H., Panahi, M., Jalili Ghazizade, M., Abedi, Z., Ghaffarzadeh, H.
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Science and Engineering; Original Paper; Soil Science & Conservation; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 1735-1472; 1735-2630
• DOI: 10.1007/s13762-020-02904-9

Contaminated and carcinogenic sludge including polycyclic aromatic hydrocarbon compounds with hydrophobic properties is formed during wastewater treatment process in lubricant refineries. This sludge will cause environmental pollution in case of landfill or if incinerated. In the present study, an anaerobic digestion system based on the degradability of PAH compounds has been investigated, with the perspective toward reducing environmental risks. Also, it was found during anaerobic digestion the energy recovered and biogas produced can contribute to combustion sources in furnaces. To analyze the degradation and thermodynamic kinetics of PAH compounds, factors including optimum conditions of degradation temperature, time duration, methanogenic substrate and energy required for the removal of these compounds have been investigated. The degradation kinetics of the two naphthalene and acenaphthene compounds in industrial sludge of lubricant refinery, through anaerobic digestion, have been evaluated at different temperatures and time durations. The results are well consistent with Arrhenius’ hypothetical relationship, which is a first-order linear equation, and show that the concentration of PAH compounds does not affect the decomposition kinetics. 71% of these two compounds decompose at optimal temperatures of 60 °C after 40 days, and the results indicate that at temperatures above 60 °C, very little degradability occurs despite high energy consumption. It is possible to remove PAH compounds from industrial sewage sludge by imposing economic costs. Any attempt to reduce economic costs requires optimizing process conditions; thereby, environmental valuable resources will be better protected.