Another study concludes no long-term impacts on sewers

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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!

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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?

Industry Indigestion

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Why is it taking so long for the hundreds of wastewater treatment plants with anaerobic digesters to become net energy producers?


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Reducing energy demand and costs through codigestion, as well as generating revenue from tip fees, enables a facility to improve the balance sheet. So why don’t more treatment plants consider alternative feedstocks for codigestion? One reason is that operators are concerned contaminants could be introduced into their digesters. This means more maintenance to clear the buildup of inert material and clogs in pumps and piping.

But the leaders in codigestion – East Bay Municipal Utility District, Sheboygan, Gloversville Johnstown, and Des Moines, among others – didn’t let maintenance stand in the way. Why not?

Earth Day 2014

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Without plumbers who connect homes and businesses to wastewater treatment plants, there would be no collection or transport of sewage, let alone food waste sent down the drain by disposers. So this Earth Day, I salute the local plumbers, trade associations and code officials that help make our world a safer place.

This past week I authored an article for Plumbing & Hydronic Contractor that mentions how food waste disposers can help the environment. My hope was that plumbers become the missing link between homeowners and resource recovery (aka treatment) plants. After all, it is the plumbers who normally install our toilets, sinks and disposers, and they have the first opportunity to help people understand plumbing products, as well as providing advice on their proper use. Moreover, they are usually considered by homeowners to be the voice of authority and knowledge, inspiring confidence.

Voices of Authority Can Be Very Persuasive!

Voices of Authority Can Be Very Persuasive!

Image from Terriermandotcom

Code officials are another important group in this industry because without their input, our plumbing would not properly convey sewage in a safe and efficient manner. Later this week, IAPMO (International Association of Plumbing and Mechanical Officials) will convene in Arlington, VA. A panel discussion on the first day entitled “Solutions for Wastewater Problems” will feature InSinkErator’s Casey Furlong, who will discuss why municipalities are now encouraging disposer use as a way to divert organics from landfills to wastewater facilities. Casey will also address misconceptions about disposers including water use and clogging of sewers. Clogs in sewers caused by deposits of calcium soaps are sometimes blamed on disposers (see Clear the FOG). But these blockages occur in sewers everywhere, including places where disposers are non-existent, putting the falsehood to rest.  If you are at the symposium, drop by and see Casey.