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Angela: Hello and welcome to Make It Clear, a conversational podcast about all things related to water and wastewater. I'm your host, Angela Bounds, and I'm joined by my co-host, Shawn Rapp. In each episode, we'll tackle a relevant topic with facts and expert opinions and make things clear.
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Angela: Hello and welcome back. Today, we're gonna be talking about intermittent flows. So as we all know in the industry, not all flows are created equal. So sometimes you have consistent flows, sometimes you have intermittent flow, and depending on what you have, you have to deal with it in different ways. So today,
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we're going to talk about what exactly intermittent flow is and how you design for it. And joining us is Bill Hensley. Hi Bill.
Bill: Hi, nice to be here with you guys.
Angela: Yeah, so Bill's been on with us before just as a little refresher. He has been here since he was a child, pretty much.
Shawn: Seems like it some days doesn't it?
Angela: Old enough to work, but...
Shawn: Right.
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Angela: He is what we affectionately call a lifer around here. He has been, I don't know, how many years have you been with us, Bill?
Bill: I started here 31 years ago.
Angela: Yeah.
Shawn: Yeah.
Angela: Bill worked out in the shops and I can vividly remember at times getting phone calls on products that, you know, sometimes we couldn't answer and it was like, well, just call Bill.
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So, we’d transfer phone calls out to the shop
Shawn: Exactly.
Angela: and have Bill troubleshoot the product. Because I was like, I don't know. That's beyond our depth. So we're going to get you in touch with Bill. And now, Bill actually works in our international region. Right? What's your title now, Bill?
Bill: Senior systems engineer.
Shawn: Nice.
Angela: Yeah. So, he is going to talk about intermittent flows with us today. So...
02:23
let's start it off and why don't you tell the listeners exactly what is or how do we define intermittent flow wastewater systems.
Bill: Yeah, I think you prefaced it really well. You know, you have some projects where you have kind of fairly consistent flows. You might have little peaks and valleys throughout the day. But when we talk about intermittent flows, we're talking generally about projects that have highly variable flows.
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And so in these type of projects, you may have the zero flow or very, very limited flow of wastewater for the bulk of the time with the bulk of it coming over a very short period of time or short number of days. You know, some examples of that could be like a church, you know, where maybe during most of the week you have very little to no flow, but over maybe a couple of days during the week. That's where you see
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almost all of your flows coming in.
Angela: So what other types of systems would be examples of intermittent flow systems?
Bill: Well, you know, another example would be like campgrounds. As we all know, generally campgrounds sit pretty much empty most of the year. And then during the summer, the warmer months of the years, especially in the weekends, that's when they just kind of get slammed. So that's another example. Schools,
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and especially schools that host sporting events.
Angela: Oh, yeah.
Bill: They're going to be slammed during short periods of the day. And sports facilities as well. There are some other venues, concerts, weddings, community centers, where really it would fall under that intermittent flow type of project.
Angela: Right. Rent machines. Well, what we call rent machines, right?
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Bill: Exactly.
Angela: Rentals that are hammered during periods of time and don't necessarily sit occupied all year round.
Shawn: Yeah.
Bill: That’s exactly right.
Angela: So, how do you design wastewater treatment systems for projects with intermittent flows? How do you approach that?
Bill: Well, you know, there's a couple of approaches you can take.
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Sometimes, and it depends on how variable those flows are that you're dealing with. One approach could be to design the treatment plant based on the worst case days, based on those peak daily flow rates. And when designing for that, of course, you have to have sufficient surge volume to accommodate those peak flow conditions. But
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That also means that that system could be over designed for most of the time. So the other method is designing this treatment plant based on an average daily flow during that peak season. And that's generally the most economical way of handling that. But that requires a pretty thorough evaluation of the
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amount of flows that are coming into the system daily during that peak season. And once you've kind of addressed that, you can actually size your surge control or buffering tanks appropriately. And then those use timer-operated pumps so that we then only dose a metered volume of that water into the treatment plant.
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So that allows us to minimize the size and the cost of the treatment plant while controlling those surge volumes upstream.
Angela: Interesting. So I don't know that there's much more to cover on intermittent flows. It's kind of a simple topic, but it is something that, if you don't know what it is.
Bill: I think you're right. I think where it gets more complicated is like we were talking about those projects that have very highly
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variable flows and really having to sit there and try to determine what those daily flows are over a period of time, generally an extended period of time. And so that can take a little time to do a thorough evaluation, but once you've done that, you've done your work up front, designing the plant and everything actually is fairly simple.
Angela: You have to be really careful though.
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there are products on the market that require a 30 day startup period that you can't just start up and take offline, start up and take offline in short order. They require a longer period of time to start working appropriately to treat to the levels that they're approved to treat for. So you have to be careful when you're choosing a product.
Bill: That's exactly right.
Angela: Yeah.
Bill: So, you know,
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like you said, certain types of wastewater treatment plants do not tolerate surge flows very well.
Angela: Right.
Bill: And so they rely on a fairly consistent type of flow coming into the system. Whereas others can accommodate a certain amount of surge. So you're exactly right. All of that, I guess, pre-design work doing your evaluation needs to be done upfront to determine,
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you know, how those flows are coming in and over what, what period of time.
Shawn: Yeah.
Angela: Yeah.
Shawn: You know, I think too, that if you always have designed residential systems and now you're moving to a commercial design where there is intermittent flows, that can be really confusing. So I think a little upfront work and trying to determine, cause if you, if you were to design an intermittent flow system, like you would approach a residential system, you're going to get in a lot of trouble.
Angela: Right.
Shawn: There's not going to be…
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You're not going to have the right volume, you're not going to have the right panels picked, those kinds of things, which are all considerations. So I think by just doing a little bit of work upfront and a little research, that's going to go a long way when you're trying to design something you're not familiar with.
Angela: It's true. It's very true.
Bill: Yeah, absolutely.
Angela: All right. Well, any parting words for us, Bill?
Bill: None that I can think of. Like I said, it's nice to...
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be with you guys again and thanks for the opportunity to come on and talk about intermittent flows.
Angela: Yeah.
Shawn: Hey, it was fun to have you here.
Angela: Yeah, thanks for joining us and thanks for listening.
Angela: We want to thank you again for joining us today. Before you go, don't forget to subscribe where you listen to podcasts so you're notified when new episodes are posted. Also, you can leave your comments or suggestions through the contact link on our website, www.orenco.com. Until next time, have a great day!