— The oily sludge is a semi-solid waste, typically consisting of 15–50% petroleum hydrocarbons, 30–85% water, and 5–46% solid particles. It contains various organic pollutants and heavy metal pollutants that possess significant biological toxicity (Hu et al., 2013; Jerez et al., 2021; Aguelmous et al., 2019, Luo and He, 2022).

 — This paper provides an introduction to the origin, properties, and hazards of oil sludge while summarizing various treatment methods focused on reduction, recycling, and harmlessness.

 — This study reports the slurry phase treatment of oily sludge obtained from a petroleum refinery in India using specific oil-degrading microorganisms. The efficacy of bioaugmentation with strains Sphingomonas sp. (MSY) and Rhodococcus ruber (WSO) acclimatized to oil on treating oily sludge was explored. The initial oil content in the …

 — The oily sludge generated during these operations is a recalcitrant residue characterized by being a stable water-oil emulsion of water, solids, petroleum hydrocarbons and metals (Mazlova and Meshcheryakov, 1999).

 — A correct analysis of oily sludge characteristics is crucial for assessing its environmental impact and selecting appropriate treatment methods. Common indicators used to characterize oily sludge include oil content, water content, chemical oxygen demand (COD), viscosity, density, electrical conductivity, and petroleum hydrocarbon components.

 — Microbial fuel cell (MFC) technology is a simple way to accelerate the treatment of the oily sludge which is a major problem affecting the quality of oil fields and surrounding...

 — The formation of oily sludge can be categorized into three types, i.e., landing sludge, refinery sludge, and tank bottom sludge (Chen et al. 2019; Wu et al. 2019). Landing sludge is generated by mixture of crude oil with impurities such as water, sand, mud, and plastics in the process of oil exploitation and drilling processes.

 — Oily sludge has been classified as hazardous solid waste in China and is considered hazardous organic waste by the US Environmental Protection Agency (Ubani et al. 2013). The encroachment of oily sludge will disturb the physicochemical properties of local soils and cause morphological variation in the soil (Robertson et al. 2010).

 — Unlike oily sludge generated in oil storage tanks or from crude oil processing, oily sludge in oilfield waste pits is formed via a strong interaction of the dumped oily wastes with natural environmental factors such as solar radiation, atmospheric deposition, and underlying soils.

 — Effective treatment of oily sludge for biogas and methane gas production at mesophilic using anaerobic batch reactor (AnBR).