When I speak about food waste disposers to wastewater professionals that oversee or manage sewage collection systems, one concern I hear is that food waste will settle out and even clog pipes. Previously, I’ve written about ground food waste becoming a slurry that it is efficiently transported in plumbing and sewers. See “The Voice Over.”
The misconception persists that disposer discharge contains food chunks, and that the use of disposers will lead to sedimentation problems. This further suggests that municipalities will have to pay for additional cleaning and maintenance of sewers because of disposers.
To which I say, it’s time that inspectors pull their head out of the sewer and read the research!
A recent study from Lulea University in Sweden looked at the long-term impacts of residential disposers on sewers to understand if pipe blockages are real or just perceived. The researchers focused on understanding the implications of disposer use, based on the ratio of their presence with the extent and distribution of deposits. Closed circuit television inspection of the sewers serving single family homes was conducted on 181 sewer pipes with a diameter of 225 mm (~9”). Using the videos taken during low flow conditions, the researchers classified deposits observed in the sewers on a score from one to four. They also included an evaluation of pipe slope and sags.
Based on statistical analysis of the scores tallied for the deposits found in the sewer, the researchers concluded that the use of food waste disposers has minimal impact on sewers. The study was funded by the Swedish Water and Wastewater Association and the Swedish Agency for Economic and Regional Growth. In recent years municipal leaders in Sweden have proposed the use of disposers to increase biogas production and decrease vehicle transportation of solid waste, and so the research was sponsored to address concerns raised with regard to potential sewer impacts.
To my wastewater and conveyance friends — I’m interested in knowing what else it will take to convince you… do you still need more?