Recent Advances in Polymeric Hydrogel Materials for Fat, Oil, and Grease Mitigation in Sewer Systems

Abstract Fat, oil, and grease (FOG) accumulation in sewer systems is a major environmental and operational challenge, leading to sewer blockages, reduced hydraulic capacity, increased maintenance costs, and the formation of persistent deposits known as fatbergs. These deposits arise from complex physicochemical processes involving the hydrolysis of triglycerides into free fatty acids, followed by their reaction with divalent metal ions, particularly calcium (Ca2+) and magnesium (Mg2+), resulting in insoluble metallic soaps. Hydrogels comprise a diverse class of three-dimensional hydrated materials, including polymeric and supramolecular systems. In this Review, we specifically focus on polymeric hydrogel-based materials because their tunable network structures, porosity, and surface functionalities may facilitate interactions with lipid-rich contaminants and provide potential platforms for FOG mitigation. The incorporation of ZnO nanomaterials, including poly(vinyl alcohol) (PVA)- and polyvinylpyrrolidone (PVP)-capped ZnO nanomaterials, into polymeric hydrogel matrices may modify adsorption behaviorand improve mechanical strength, structural stability, and multifunctionality. The discussion covers FOG formation mechanisms, hydrogel-mediated interactions, and advantages and limitations of current FOG management technologies. Particular emphasis is placed on natural-polymer-based hydrogels, highlighting their structural characteristics, adsorption mechanisms, and mitigation performance. However, direct evidence for hydrogel-based materials in established sewer FOG deposits remains limited, with much of the available evidence being derived from related oil-removal studies. Furthermore, the Review highlights key challenges associated with the scalability, long-term stability, regeneration, and potential applications of hydrogel-based materials while outlining future research directions for their rational design, performance evaluation, and eventual translation to practical sewer applications.