Earlier this year, Pumps & Systems spoke with Tom Marshall, Northeast region municipal sales manager for Crane Pumps & Systems, on the changing wastewater stream in the United States. Marshall is a 25-year pump industry veteran who deals with water and wastewater on a daily basis in the Northeast.
This interview can be heard in its entirety on Episode 38 of the Pumps & Systems podcast.
It has been edited for clarity and to update readers on where things stand due to coronavirus.
What is the biggest problem facing America’s wastewater system?
That’s a common question that’s asked. Typically, there are two major issues that I’ve been seeing: the aging infrastructure of municipal wastewater networks and the problems associated with those aging infrastructures paired with a changing waste stream and how that is causing pump clogging. Regarding aging infrastructure, typically we only talk about water and wastewater when it fails. The Flint, Michigan, example years ago brought a lot of visibility to our aging infrastructure. It’s aging and in need of upgrades. In general, we haven’t seen a really big push for infrastructure change since the Clean Water Act that ran from basically the 1970s to 1992. The other major issue is clogging pumps. We see and hear about it on a daily basis, and there are numerous issues causing that. A lot of the issues are tied directly to the age of the pump, the type of pump that is being used, and the density and composition of the waste stream.
What creates the clogging and why is it worse now?
There’s two main causes that we identified. One is the amount of water that’s currently being used by the commercial entities and the typical homeowner. In the 1980s, households were using 119 gallons per day per capita. Since then, with the low flow fixtures, the water conservation efforts basically have reduced that down 29 or 30 percent. It’s a good thing that our sources of water are being more conservative and using less water, but now there’s a greater concentration of solids and the wastewater composition is more aggressive than in the past. The composition of this wastewater is not only more dense but it has become even more challenging as nonbiological, nonbiodegradable solids are becoming more and more popular in households and, inevitably, end up entering the waste stream. Everybody has heard the issues with rags, flushable wipes, whatever you want to call them. It’s really the scourge of our industry. Operators are being challenged with keeping the pumps operational, but these nonbiodegradable products weren’t an issue years ago and now they are.
The volume has increased dramatically. At first, disposable wipes were designed to be disposed of in a trash can, but now a lot of people are using a toilet as a trash can and operators are seeing high volumes of these flushable wipes and quickly
learning that are not, in fact, flushable or biodegradable.
What can users do to prevent the major clogs?
In light of the coronavirus and what’s going on now, we’re seeing a ramp-up of wipes, rags and T-shirts in lift stations. When I was at a major grocery store when the pandemic first hit the U.S., there was no toilet paper, no wipes and no rags. People are having to resort to other measures to take care of their bodily functions. The No. 1 plan of attack by most municipalities is informing the public that these rags, wipes and [mopping pads] are impacting the wastewater treatment plants and the collection systems throughout the U.S. and the world and how they can handle these items. There’s a concentrated effort to educate the community and change the habits. I hear over and over, if you don’t eat it, don’t flush it. That’s a little extreme, but everyone would agree that theory kind of gets the point across. That’s really the first line of attack. The second line of attack by operators is doing what they can to upgrade or modify their collection systems so they can handle these nonconcentrated, nonbiodegradable products.
What products exist for solids handling?
I’m going to classify it in three major categories. First, you can collect the material that is not supposed to be there in a lift station or passing through a pump in the first place. That can be done by using screens or trash baskets that have to be cleaned periodically. That will protect the manholes, pipes and pumps associated with collection systems.
The next option would be to grind up the material before it gets to the pumps and wastewater plants—you could do this by using a dual-channel grinder. They’re very aggressive and shred the material to manageable sizes so it can go through the piping and pumps without clogging.
Lastly, you have the option of chopper/slicer/grinder pumps that do both. These pumps chop material in the waste stream to a manageable size that can pass through the pump, then the check valve, and then the piping without causing major issues for the operator.
How do these products combat this?
With regards to grinder pumps, they typically handle 1.25- to 2-inch discharge pipe sizes. Grinders typically handle from 1 to 125 gallons per minute and they’re good for normal sewage coming out of a home that has a light concentration or a sporadic flushable wipe. The next and more aggressive pump that’s used at typical pump stations or headworks at a wastewater treatment plants are chopper pumps. They range from 2- to 10- to 12-inch discharge, going from 80 to 6,000 gallons a minute. They can definitely handle the nonbiodegradable rags and wipes. Chopper pumps can even handle baseball bats or wood chunks that make their way into the wastewater stream. We’re seeing a lot of communities gravitate toward that technology because it reduces the size of almost any solid before it passes the item through the pump so clogging is less likely both within the lift station and downstream through the headworks—saving municipalities from maintenance and service cost as well as the inconvenience of system downtime.
What other changes do you see affecting the treatment plants and/or the municipalities and industrial applications?
Pumps are near and dear to my heart, but another significant issue I’ve seen over the past 15 years is basically the aging population of our utility operators and municipal staff. I don’t see a lot of new blood getting into our industry. When you attend the events, there’s a push to get new blood into the industry. I encourage anyone, if they have mechanical aptitude, to take a trip to your local municipality. If you’re looking for another career, they’re definitely looking for new talent.
