The impact of Food Waste Disposers on the indoor sewer system

The impact of the use of food waste disposers (FWD) on the municipal sewer system and in wastewater treatment plants has been studied worldwide. However, the effects on indoor sewer have remained overlooked with very few studies available. There is still very limited knowledge of practical experiences with food remnants in the Netherlands. This has resulted into that the application of FWDs is prohibited, based on the assumption that they will cause problems affecting the sewer system infrastructure. There are no practical strong research results that confirm or contradict the use of FWDs in the Netherlands, and especially, there is not any study focusing on the indoor sewer effects. This TKI study aimed to find out whether the use of a food waste disposer in high-rise buildings households has any negative effects on the indoor sewer. The experiments and analyses carried out involved looking at conventional indoor sewer configurations that have been installed following the applicable guidelines (NEN 3215+C1+A1), both at the horizontal and vertical sections. Key wastewater and indoor sewer parameters were evaluated when combined with a food waste disposer. Furthermore, time-series analysis to describe the transport of the wastewater was assessed. In this case, the behavior of the water and ground food inside the sewer pipe was assessed taking into account 17 different food-types.
Results showed that mainly the COD added by the ground food to the sewer is particulate and could be separated in the primary sedimentation process. An increase of 1.3% in water consumption in the total average water use in the Netherlands per person was estimated by using a FWD. It was found that the slope of the horizontal pipe has the greatest influence on the quantity of food remnants in the indoor sewer pipe. No accumulation of ground food waste was observed in the vertical pipe or the bottom horizontal pipe. In fact, the inclusion of the vertical pipe demonstrated to have a positive effect on the sedimentation of food waste in the sewer pipe, as it increases the velocity of arrival.