Fat, oil and grease - induced sewer blockages: Mechanisms, modelling and monitoring strategies

Fat, oil and grease (FOG) discharged into sewer networks can accumulate and solidify into hardened deposits that commonly known as fatbergs, through saponification, crystallization, and calcium aggregation. These fatbergs contribute significantly to sanitary sewer overflows, posing serious environmental and public health risks. Despite growing interest in this issue, there remains an urgent need for robust, real-time monitoring and predictive technologies to mitigate FOG-induced blockages and their associated economic costs. This review presents a comprehensive synthesis of current knowledge on the mechanisms of FOG deposition in sewers and critically evaluates existing models for blockage prediction, including mechanistic, data-driven, and Internet of Things-based approaches. While most studies have focused on saponification-driven FOG formation, limited attention has been given to crystallization and calcium-based aggregation which are key pathways that remain underrepresented in modelling frameworks. A novel aspect of this review is the integration of environmental, social, and sewage system parameters that influence FOG accumulation, providing a more holistic basis for future model development. The review identifies key knowledge gaps and proposes the development of a hybrid modelling platform that combines mechanistic and data-driven tools for accurate and scalable FOG monitoring.