Deep dewatering of oily sludge: Mechanism, characterization, and pretreatment technology

Oily sludge, characterized by its high organic pollution, poses significant challenges for treatment and disposal due to its high proportion of bound water and elevated viscosity from petroleum hydrocarbons. This study focuses on the deep dewatering of oily sludge, examining the role of internal bound water and the pretreatment mechanisms involved. The deep dewatering process is categorized into two main areas: liberation of bound water and modification of physicochemical properties. (1) Bound water is primarily found in two major categories: water bound within proteins, EPS, and cells through hydrophilic interactions, and water within an oil-water emulsion structure facilitated by inorganic particles. (2) Physicochemical properties: The formation of flocs in oily sludge is crucial for effective dewatering, while creating dewatering channels in later stages enhances efficiency. Advanced oxidation and emerging demulsification technologies are also discussed, summarizing the latest research. The significant potential of electric fields in the deep dewatering of oily sludge is emphasized, offering valuable insights for future advancements.