Conference Paper

Modelling of Food Waste Disposer particle transport through a sewer network

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Abstract

Managing domestic food waste is challenging due to potential environmental and financial impacts. One solution is to divert this waste from landfill by using domestic food waste disposers to grind this energy rich material so it can be removed via traditional sewer networks and subsequently making this resource available for anaerobic digesters. Water utilities however wish to understand the risks associated with this additional loading of food waste particles within their sewer systems. This work outlines the development of a novel modelling approach that has been empirically calibrated to predict transport and settling of food waste in sewers and to contribute to understanding if there are any risks associated with increased sewer settlement. The work has focused on dry weather flows as this poses the highest risk in terms of settlement and with specific attention on evening mealtimes (6 – 8 pm) when food is most likely to be added to the sewer. The improved understanding and modelling capability is important for policy makers to help make informed decisions on whether food waste disposers are a viable, and potentially beneficial solution, for food-waste management.

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Conference Paper
Food waste disposers (FWD) offer a potential alternative to curb-side collection of food waste, allowing for energy recovery through anaerobic digestion at wastewater treatment plants. A thorough characterisation of the particles produced by FWD is needed to ascertain the impact on sewer networks. This study presents initial characterisation of particle sizes and settling velocities for particles emitted by a FWD. The results give a particle size distribution for the tested food groups and shows increasing settling velocities with increasing particle sizes.
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Food wastes with typical US food composition were analyzed to characterize different constituents in both particulate and soluble phases i.e., solids, chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD), nitrogen (N), phosphorus (P). Relationships between various pollutants were also investigated using 50 samples. One gram of dry food waste generated 1.21g COD, 0.58g BOD5, 0.36g Total SS, 0.025g Total N, and 0.013g Total P. Distribution of constituents between particulate and aqueous phases indicated that 40% of COD and 30% of nitrogen were present in soluble form. Relative mass ratios of COD and nitrogen to solids were three to five times higher in particulates than in aqueous phase. However, COD/N ratios were higher in aqueous form than particulates at 63:1 versus 42:1. Detailed relationships between parameters showed that COD, nitrogen, and phosphorus in particulates are 200%, 3.6%, and 3.5% of the volatile suspended solids. Copyright © 2015 Elsevier Ltd. All rights reserved.
Article
To increase biogas generation and decrease vehicle transportation of solid waste, the integration of food waste disposers (FWDs) into the wastewater system has been proposed. However, concerns have been raised about the long-term impact of the additional load of the FWDs on sewer systems. To examine the said impact, this study has used closed-circuit television inspection techniques to evaluate the status of 181 concrete pipes serving single family housing areas with a diameter of 225 mm, ranging from a 100% connection rate of households with an FWD to none. A minor study was also performed on a multi-family housing area, where mainly plastic pipes (200 mm) were used. The extent and distribution of deposits related to the ratio of FWDs, inclination and pipe sagging (backfalls) were ascertained by using linear regression and analysis of variance. The results showed that FWDs have had an impact on the level of deposits in the sewer, but this has, in turn, been of minor significance. With a high connection rate of FWDs upstream of a pipe, the extent of the total level of deposits, as well as finer sediments, was statistically determined to be greater. However, the majority of the deposits were observed to be small, which would suggest the impact of FWDs on sewer performance to be minor. As food waste not compatible with the FWD was seen in the sewers, educational campaigns could be beneficial to further lower the risks of sewer blocking.
Scouring: hydraulic structures design manual
  • H Breusers
  • A Raudkivi
Breusers, H. & Raudkivi, A., 1991. Scouring: hydraulic structures design manual, A.A.Balkema. Rotterdam