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

Abstract

This study aims to assess the transportability of food waste disposer particles within a sewer system. A series of laboratory studies has examined the physical characteristics of solid particles derived from domestic food waste disposers. Particle size distributions and maximum settling velocity characteristics were measured for 18 common food types, and stored in a publicly accessible database. Particle size distributions are shown to fit well with a 2-parameter Gamma distribution. Settling velocity is generally higher for larger particles, except when particle density and sphericity change. For most food types, particle specific gravity was close to unity. Egg shell particles had a significantly higher specific gravity. This information, combined with the particle size data have been used to show that there is a very low likelihood of food waste particle deposition in sewers during normal operational flows, other than temporary transient deposits of egg shell particles. HIGHLIGHTS Particles characterised for 18 common food types.; Sizes fit a Gamma distribution, mode of 0.59 to 4.76 mm.; Most particles had apparent densities close to water.; Most particles entrained at low boundary shear stress, unlikely to form deposits in sewer pipes.; Egg shell showed higher entrainment threshold, but still expected to transport during dry weather flows.;

Keywords

• domestic food waste disposers
• food waste
• in-sewer deposition
• particle fall velocity
• sewer solid entrainment thresholds