A Pilot Study Regarding the Use of Food Waste Grinders in a Multi-Unit Residential Building

Abstract

This study evaluated the impact of food waste grinders (FWGs) in multi-unit residential buildings (MURBs) that also had access to green bins (GBs) on solid waste and wastewater generation. A 15-month technical sampling program and two user experience surveys were conducted at a 32-unit MURB to gather information on potable water demand, wastewater and solid waste properties and user perceptions of factors that influence GB and FWG use. Data gathered during a four-month control period without access to FWGs was compared to that from an 11-month study period where access to FWGs was provided to assess the impact of the devices on the aforementioned areas of focus. There was no statistically significant change in the per unit potable water demand when access to FWGs were provided. FWG use did not result in any sewer-use bylaw exceedances although the fats oils and grease (FOG) content of the wastewater increased significantly suggesting that challenges associated with FOG during wastewater conveyance may be worsened by widespread FWG implementation. The mass loading of fixed dissolved solids (+9 g/unit/day, +16.2%, p = 0.01), and FOG (+4 g/unit/day, 45.1%, p = 0.01) to the sewer increased significantly with FWG use while all other wastewater analytes did not change significantly. The variability in most wastewater responses (nutrients, solids, FOG) as indicated by their standard deviation increased significantly. The impacts measured in this study were less than the reported impacts of literature, which was attributed to the FWGs being implemented alongside green bins. The results suggest that widespread FWG use may increase the discharge of fixed dissolved solids in wastewater treatment plant effluents. Further, the impact of increased FOG loadings on sewer systems and wastewater treatment plant operations may need to be considered. The amount of unavoidable food waste disposed of in the green bin decreased (-79 g/unit/day, -19%, p = 0.02) following FWG implementation, however, the amount of organics in the mixed waste stream (fugitive organics) was not affected by FWG access. The results suggest that FWGs were employed for materials that were disposed of in green bins prior to FWG access in this building. The results indicate that FWG access may not reduce the presence of fugitive organics in the mixed waste stream when implemented in this setting. Survey respondents indicated using both FWGs and GBs, with respondents preferring one or both technologies. Most respondents reported using the FWG devices primarily for fruits, vegetables, and plate scrapings while some respondents reported use of FWGs for FOG and dairy products despite these categories not being FWG targets as explained in educational materials provided to residents. When the survey responses on food waste generation and FWG use were combined with wastewater generation data; multiple lines of evidence suggest that wastewater treatment plants may experience more variable aeration requirements and sludge production with widescale FWG implementation. This study was the first evaluation to focus specifically on aspects of FWG implementation in a MURB population that also had access to GBs.