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!
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.
A syndicated and widely circulated story last week on NPR reported how New York’s Newtown Creek Wastewater Treatment Plant is now processing food scraps to create renewable energy. The full story provides a glimpse into the growing trend of co-digesting food scraps with sewage sludge to boost biogas production with anaerobic digestion.
- Michael Utech/Vetta/Getty Images
Wastewater treatment plants protect human health and the environment by efficiently processing raw sewage. Anaerobic digestion is simply one part of the treatment system used to reduce harmful pathogens and the overall volume of solids left at the end of the process that must be managed. In New York, some biosolids are beneficially used (land applied as fertilizer), and some are landfilled as far away as Pennsylvania and Virginia.
In reading some of the comments, I am reminded how sewage treatment is out of sight and out of mind, and largely taken for granted by the public.
Newtown Creek is simply utilizing existing infrastructure to maximize its potential. What is unique is that the system is relying on separate collection of the food scraps from commercial establishments, which then must be processed to remove contaminants and be converted into pumpable slurry for injection into the digesters.
InSinkErator’s new Grind2Energy™ system prepares pumpable, contaminant-free slurry ready for anaerobic digesters, completely eliminating the need for pre-processing at a wastewater treatment plant. David Krems, Business Development Director for Grind2Energy™ said, “Food waste to energy via anaerobic digestion is in the nascent stage in the U.S. – however new technologies and businesses such as Grind2Energy™ offer food waste generators an alternative to divert their food scraps from landfills and create renewable energy within local communities!”
Missing in the story is that food waste disposers already divert residential food scraps from homes in New York directly to Newtown Creek. A prohibition on residential disposers was lifted in 1997.
Just what makes a sewer nice?
Does it offer to buy you coffee? Say please and thank you?
At the recent New York Water Environment Association’s 86th Annual Conference named, “Utilities of the 21st Century: Going from Net Zero to Net Positive” ‒ the hot topic was maximizing energy production utilizing additional feedstocks for anaerobic digestion, especially from commercial and industrial sources. A panel discussion by five wastewater people spent a lot of time on the addition of food waste to digesters from source-separated organics processed at the treatment plants. That’s a lot of work. Nobody on the panel mentioned food waste disposers. One of disposers’ chief benefits is that the waste generator does all of that work for you.
When prompted by a question from the audience about using “in-sink grinders” a panelist stated “…They only make sense for other cities with nice sewers.”
I guess that would make his city’s sewers mean. Of course not– the panelist was referring to his home city’s combined sewers. With that type of system, there is the potential of a wet weather combined sewer overflow, when food waste may end up in local waterways. The greater environmental health hazard from combined sewer overflows are the pathogens in raw sewage, not microscopic ground food waste. (I have noted numerous times in this blog that despite some misconceptions, “chunks” of food are not disbursed to sewers by disposers.)
Furthermore, according to Metcalf & Eddy’s 5th Edition of Wastewater Engineering, ground food waste makes up only about 20% of the suspended solids and biochemical oxygen demand in sewage.
Communities with combined sewers should be eliminating them, and are required by the EPA to do so as part of their Long Term Control Plans. Hopefully some day we will see the demise of the mean sewer. In the meantime, food waste is, and will continue to be, a small fraction of the total composition of wastewater.