The characteristics and in-sewer transport potential of solids derived from domestic food waste disposers

The interactive force between fat, oil, and grease (FOG) deposits and the effect of food waste disposers on kitchen drainage systems

Food waste disposers (FWDs) streamline kitchen waste management and facilitate waste classification, whether they would increase the potential of blockage in kitchen drainage system is still unknown. This study conducted a theoretical analysis of the interactive forces between fat, oil, and grease (FOG) deposits and their aggregation on pipe walls. The study involved grading food waste particles processed by FWDs using sieving and weighing techniques to determine the mean weight diameter (MWD) of various aggregations. A full-scale experimental system, implemented in a 60-m high test tower, simulated blockages in horizontal pipes of high-rise buildings. The effect of pipeline materials and particle sizes on blockage were examined by measuring the adhesion of deposits on horizontal pipes. Energy dispersive spectrometer (EDS) analysis suggested that liquid bridge force is a primary factor in aggregate formation. Hand-cut particles formed aggregates with the highest MWD value. Particle size analysis revealed that sizes ranging from 2.36 to 4.75 mm, 1.18-2.36 mm, and 0.60-1.18 mm constituted over 80 % of particles ground by FWDs, with an average size of 2.16 mm. Results of full-scale experiment indicate particle diameters, friction coefficients and lipophilic coefficient significantly affected the propensity of these aggregates to adhere to pipes. Notably, particles processed by FWDs tended to cause blockages more frequently than hand-cut particles. These findings elucidate the deposition mechanism of FOG deposits and offer strategies to reduce blockages in kitchen drainage systems, such as reducing current grinding particle size by 18 % to 1.77 mm or selecting pipes like cast iron and high-density polyethylene.

Reducing particle accumulation in sewers for mitigation of combined sewer overflow impacts on urban rivers: a critical review of particles in sewer sediments

Sewer sediments contain various hazardous compounds, leading to significant pollution risks when combined sewer overflows (CSOs) occur without appropriate controls. This paper presents a comprehensive review of the issues associated with particles in sewers, specifically focusing on the non-negligible contribution of particulate matter to CSOs, which leads to pollution in urban rivers. Therefore, the sources of particulate matter in sewers, their contributions to the overflow particles, and the specific areas of concern when it comes to managing particulate matter during particle transportation are outlined. Overall, carefully considering the goal of avoiding sedimentation during the drainage system design is the most effective prevention and control method for pipeline sediment, where minimum velocity and minimum shear stress are the core parameters. The establishment of a flexible and adaptive particle simulation method in drainage pipelines requires reliable simulation of particle sedimentation and erosion, the development of sediment prevention facilities with strong adaptability, and a comprehensive evaluation of economic and environmental benefits. With the ongoing enhancement of urbanization in developing countries, such studies will have more practical significance.