We are joined by Dr. Darla Goeres, the world's leading biofilm researcher and expert. Dr. Goeres defines biofilms, explains why they matter and what we can do to prevent and remove them in recreational water.
00:00 - Introduction
04:07 - What is a biofilm?
07:36 - Biofilms encompass more than previously known
11:48 - Microbially-induced corrosion
17:14 - Are all biofilms bad?
20:26 - Biofilms are like Jell-o
24:32 - Biofilm ingredients and chlorine resistance
28:17 - Kill vs. Removal
32:23 - Prevention vs. Remediation
36:42 - How clean is clean?
40:01 - Log-reductions in disinfection
42:53 - How to remove and how to prevent biofilms in pools
48:15 - Where to learn more about biofilms
------------------------------------
Connect with Orenda Technologies
Website: https://www.orendatech.com
Help Center: https://ask.orendatech.com
Blog: https://blog.orendatech.com
YouTube: https://www.youtube.com/user/OrendaTechnologies
Facebook: https://www.facebook.com/orendatech/
Instagram: https://www.instagram.com/orendatechnologies/
Swim Across America | Team Orenda: https://www.swimacrossamerica.org/goto/orenda
120. Understanding Biofilm (w/ Darla Goeres, Ph.D.)
===
[00:00:00] Eric Knight: Welcome back to the rule your pool podcast. Today we have a very special guest and surprisingly, it's not Jarred. Jarred is a special guest, or at least we're told he's special. This is episode 120.
[00:00:10] Jarred Morgan: I am so glad that I don't have to do this with you and you only because we have an awesome guest today. It turns out I've actually met her and you haven't, so i'll just go ahead and keep that one in my back pocket.
[00:00:21] Eric Knight: All right. Well, why don't you introduce her?
[00:00:23] Jarred Morgan: Well, it's been a hot minute since I've talked to this special lady. Over 10 years, I would say. This is Dr. Darla Goeres of Montana State University in Bozeman, Montana. And we are extremely happy to have her on this podcast because I could not think of a better expert to talk about what we're going to talk about today.
[00:00:43] Eric Knight: Dr. Goeres, welcome to the Rule Your Pool podcast, the lowest point in the last 30 years of your career. Thank you for being here.
[00:00:51] Dr. Darla Goeres: Thank you for inviting me.
[00:00:52] Eric Knight: So just a little bit of a rundown on you, and then we'll get into the questions. We're here to talk about biofilms. So Dr. Goeres, how long have you been working on biofilms?
[00:01:01] Dr. Darla Goeres: I have been studying biofilms for about 30 years now. They intrigued me when I was a wee lassie working in undergraduate research in the late 1980s, early 1990s. So yeah, long time.
[00:01:16] Eric Knight: And you've evolved in your academic career. You're a professor of, what is it, regulatory science? Can you tell us a little bit about what that means?
[00:01:24] Dr. Darla Goeres: You bet. I am a research professor of regulatory science at the Center for Biofilm Engineering. And regulatory science is the development of tools for informed decision making by the U.S. regulators. So in this case, the U.S. EPA and FDA. Specifically, I'm focused in on the development of tools so that these individuals can make informed decisions on different products or processes that were designed and developed to kill, control, remove, prevent biofilm formation.
[00:02:02] Eric Knight: Right. So this would be like testing methods, test kits, killing agents. What do you mean by tools?
[00:02:09] Dr. Darla Goeres: Yep. That's a great, great question. So there are multiple different tools. Where I am focused on is the development of standard test methods. So I have a longstanding relationship with ASTM international. That's the American Society for Testing and Materials International.
[00:02:28] And I've been participating on their committee on antimicrobial agents for about 23 years now. In fact, chaired that committee for a number of years, but eventually timed out of that. And that committee is really focused on the development of standard test methods that describe a step by step process that laboratories follow to be able to determine how well an antimicrobial process works against biofilm or bacteria, in general, fungi, algae, microorganisms in general.
[00:03:05] Eric Knight: It's an honor to have you here to speak about something you truly are probably the world's leading biofilm expert.
[00:03:10] Jarred Morgan: I would hope you're passionate about it when you're committing almost 30 years to something.
[00:03:15] Dr. Darla Goeres: I am actually, yeah, biofilms amazing.
[00:03:19] Eric Knight: Well, I should say, because you have over 40 peer-reviewed studies and articles. I think you said 47? So you know a thing or two. You've done actually more peer-reviewed studies than Jarred has done podcast episodes, so that's great.
[00:03:31] Jarred Morgan: True. And more show notes than I've ever read. That's a fact.
[00:03:34] Eric Knight: Yeah, it's almost as many listeners as we have. 47 is a big number. Yeah. Well, that being said, this is the 120th episode of Rule Your Pool with Dr. Darla Goeres.
What is a biofilm?
---
[00:04:07] Eric Knight: Okay, Dr. Goeres, let's start with this. What is a biofilm?
[00:04:13] Dr. Darla Goeres: Great place to start. So I'm going to first begin with the definition that you would find if you were reading something like EPA regulations. Biofilm is considered a self-organized, cooperative community of microorganisms encased in extracellular matrix.
[00:04:37] Okay. So let's break that definition down a little bit because that's exceptionally complex.
[00:04:43] Eric Knight: Wow.
[00:04:43] Jarred Morgan: I was going to say, all I can say is, Oof.
[00:04:46] Dr. Darla Goeres: Yeah, yeah. That's very, very complex. And here's the thing about coming up with a definition of biofilm. There's two things. Number one, if you are sitting in a room of academics, as soon as biofilm is defined, there will be an academic in the room who will point out an exception to the definition. Right, because it's a natural system. So I'm going to add that disclaimer out there.
[00:05:10] And the second thing about definitions from a regulatory standpoint is it's important to have a definition that's defensible, right? Because when these companies want to treat or even just understand what a biofilm is in these swimming pools and hot tubs, it's important to define it for them so they know the starting point, they know what they're trying to kill or remove.
[00:05:37] On a more practical level though, in the morning, when you get up, before you've brushed your teeth, and you run your tongue across your teeth, and they're a little bit slimy? While dentists would call that plaque or plaque buildup, we would call it biofilm.
[00:05:51] Eric Knight: Hmm.
[00:05:52] Dr. Darla Goeres: If you're out in Montana, Montana's beautiful, there's a lot of wilderness. It's a gorgeous state, and we spend a lot of time outside hiking. So if you're outside hiking and crossing a small river and you're hopping rocks and they're kind of slimy? That slime is a biofilm.
[00:06:12] If you're in Yellowstone National Park, which if you haven't visited, is amazingly beautiful. And you're looking at those hot pools, you've probably seen pictures of Yellowstone Park and seen pictures of those hot pools, and they would call them bacterial mats. That's a biofilm.
[00:06:30] Eric Knight: So there are a lot of them.
[00:06:31] Dr. Darla Goeres: There's a lot of them.
[00:06:33] Jarred Morgan: I'm glad we're making disclaimers here because we make a few of those ourselves. Like, Eric thinks he knows what he's talking about to all these podcast listeners. 175 of them, I think. By now. It's gotta be.
[00:06:47] Eric Knight: But, well hold on, if Dr. Goeres subscribes, we're going to be at 176.
[00:06:50] Jarred Morgan: That's true. Um, but we'll try and keep this episode as serious as possible because we clearly are not. You actually have some really good value to bring here. And to me it sounds like everything is a biofilm. I mean is algae a biofilm? You keep saying slimy, you know slick...
[00:07:09] Eric Knight: Bacterial community. I mean algae is a plant though, isn't it?
[00:07:13] Jarred Morgan: Yeah. How are all these things, how do they play together?
[00:07:17] Dr. Darla Goeres: Because they start to join together. They do play together. That's why they're a biofilm. Right? They like to play together in the sandbox. And they cooperate together and what's important to understand is that, historically, most researchers and scientists have focused on bacterial biofilms.
Biofilms encompass more than previously known
---
[00:07:36] Dr. Darla Goeres: It's incredibly important to realize that they can include fungi, they can include algae, and they're these communities. And what specific microorganisms are there, and how they are either cooperating or not, depends on the system that's being studied. So the combination, the makeup, the ecology, so to speak, is really dependent on the system.
[00:08:01] So in something like treated recreational water, there'll be a lot of microorganisms that would be typically found in water. That's mostly what you're going to find existing in these systems are microorganisms that do well in water.
[00:08:18] One of the things, um, this is very nuanced. Most often, biofilm is associated with surfaces. So in the examples I gave you, those are always very surface specific. But a lot of the new thinking around biofilms is that they don't actually have to be only associated with surfaces. So typical biofilm would be a pipe, right? So if you have a hot tub and you have a recirculating pipe, and there's a lot of goo that's developed in that pipe.
[00:08:46] If you own a hot tub, the probability of you seeing that goo is pretty high. And it's gunk. It's gunk and gooey. That is a classic example of a biofilm. But our thinking has evolved to include like little chunks of the microorganisms, maybe floating at the air liquid interface of the pool.
[00:09:08] So maybe floating on top of the surface, and that, water surface could be the surface, as opposed to, like, a hard surface, like a cement wall or something like that. So it's like little bundles of floating microorganisms.
[00:09:24] Eric Knight: Oh, so like a film that kind of floats on the surface of the water. I've seen that before, when a pool is neglected for a long time.
[00:09:31] Dr. Darla Goeres: Yep. I'm sure you have. And that is also an example of biofilm. So it's not only just attached to a hard surface, it's also when they're attached to each other or they're existing at an interface.
[00:09:44] Um, we have a very encompassing definition. Because you can define biofilm, but what's important from a treated recreational water venue standpoint is that once these microorganisms become a part of a biofilm, they become exceptionally challenging to kill.
[00:10:04] There's historical research that dates back many, many years, and this is shown time and time again that once microorganisms are in a biofilm and you treat them with chlorine or any standard oxidizing agent, the biofilm, the bacteria, the microorganisms within that matrix are much more tolerant. To disinfection.
[00:10:30] Eric Knight: That's a great point We have heard that biofilms are sort of a chlorine resistant layer.
[00:10:35] Dr. Darla Goeres: Mm hmm
[00:10:36] Eric Knight: Is a biofilm organic? And if so, is it always organic? Or are there synthetic uh, combinations or anything like that?
[00:10:44] Dr. Darla Goeres: Right, so a biofilm is organic, but here's what's really fascinating. I'm guessing at some point in your life, you've cleaned out like a bathroom sink drain. And you have this very complex organic matrix in there.
[00:10:58] Eric Knight: That's a polite way of putting it. It looks like brownish black snot, but yeah.
[00:11:02] Dr. Darla Goeres: Yeah, gross. But there will also be other items that perhaps are inorganic that maybe are a part of that biofilm.
[00:11:11] Jarred Morgan: My daughter's hair ties. Every time.
[00:11:14] Dr. Darla Goeres: Hair ties, exactly. And things like that's a great example Jarred!
[00:11:18] Eric Knight: Come on. The hair tie is not part of the biofilm, is it?
[00:11:22] Dr. Darla Goeres: It's a surface. It's interesting because the bacteria, this is like a hair tie or hard water, right? So if you have water that's imbalanced and you have these hard water deposits, the biofilm and the hard water start to form these really complex architectural communities. And so, yes, the biofilm itself is organic.
[00:11:45] Jarred Morgan: So it's building its own shield.
Microbially-induced corrosion
---
[00:11:48] Dr. Darla Goeres: Kind of, yeah. So it can have hard water. It can have mineral deposits, or metal deposits like iron. It can have things like, uh, corrosion deposits.
[00:11:59] So, uh, so for a lot of years I actually studied biofilm in oil fields. Which is still just moving fluid in a pipe. Now, these are different microorganisms than treated recreational water, but what they do is they promote corrosion of the piping wall. It's called microbially-induced corrosion.
[00:12:17] And then those corrosion deposits get built and embedded into the matrix. And so it's very complex. So now if you have something like chlorine, which is an oxidizing agent. How is the chlorine going to perform against corrosion deposits or the hard water deposits?
[00:12:37] Eric Knight: Okay, hold on. So you're saying that there are biofilms that are causing corrosion in these pipes, or are they protecting it? You said it's kind of like a matrix where it's interacting with the pipes? Because it's me think about drinking water. What do you mean by this corrosion inside the pipes?
[00:12:53] Dr. Darla Goeres: Right. That's a great question. So in oil fields, these microorganisms are coming from underground. They're anaerobic. That means they grow without any oxygen. And when they're in these pipes, the microorganisms actually get in and attack and eat away at the pipe wall. Which causes huge damage and infrastructure issues.
[00:13:16] And so the goal is actually to prevent corrosion. You do not want pipe wall corrosion. And corrosion can happen chemically, of course, but it can also happen unbelievably, because of microorganisms.
[00:13:28] Eric Knight: Okay, and they're eating metal.
[00:13:30] Dr. Darla Goeres: Yeah, they're utilizing the components in the metal, like the iron. It's crazy.
[00:13:35] Eric Knight: It makes me think of the Flint, Michigan crisis, which has led to an EPA regulation of anti-corrosion measures. You probably know all about that. And what it has led to is phosphates in drinking water almost everywhere in the country. And our understanding of that is... they're using sequestering agents or orthophosphates to protect the pipes from corrosion. Does that have anything to do with biofilms?
[00:13:57] Dr. Darla Goeres: Um, so that's more of a chemical question that they're looking at, right? An infrastructure question. Because damage to the infrastructure would result in huge costs. Obviously, microorganisms need phosphate to grow, right? So it's a very nuanced and complex issue because their goal is to protect infrastructure and protect the piping and protect corrosion. But by adding that there may be some unforeseen or unplanned consequences with regards to microorganisms.
[00:14:29] That's why after treated recreational water, one of the areas I moved into was beer draft lines, which is just a hoot and a half of a fun area to study.
[00:14:40] Eric Knight: Did you get to taste the experiments?
[00:14:42] Dr. Darla Goeres: You know, I had to do some field research, most definitely, for that project, most definitely.
[00:14:47] Eric Knight: Yeah, good, good. That's a good call.
[00:14:49] Dr. Darla Goeres: Yep, and so it's not just the biofilm and the beer draft lines, it's also, you can get something called a beer stone. Isn't that fascinating? Kind of like a kidney stone, you can get a beer stone.
[00:14:59] Eric Knight: Fascinating and horrible to think about.
[00:15:01] Jarred Morgan: Very.
[00:15:02] Dr. Darla Goeres: Well, and so they have to like get in there and maybe not just use a biocide that's been designed for the organics, but then include like an acid that helps to disrupt the beer stone and have that get out of the system.
[00:15:20] Jarred Morgan: So we can conclude that combating biofilm is a multilayered approach.
[00:15:25] Dr. Darla Goeres: It's a multilayered approach. That's right.
[00:15:27] Eric Knight: So Dr. Goeres, you're saying the word hard water. To us in the recreational water industry, hard water usually means high calcium and high magnesium.
[00:15:36] Dr. Darla Goeres: Yes, to me too.
[00:15:38] Eric Knight: So it could be a high LSI, Langelier Saturation Index for calcium carbonate, to precipitate calcium carbonate scale or other calcium deposits. They can be interwoven into this biofilm? Is that what we're hearing?
[00:15:51] Dr. Darla Goeres: They can. A typical microorganism that forms biofilm is called Pseudomonas. It's a ubiquitous microorganism. And we have these beautiful pictures of the Pseudomonas growing in and on and around these hard water deposits. And we actually start in the laboratory. We start growing the biofilm first, and then we introduce these hard water deposits and it's like watching a lava lamp.
[00:16:17] They're fascinating, you watch the lava lamp and these hard water deposits tumble along the tubing and then they get entrenched into this biofilm. And then we take the hard water, like the generation out, and then we allow the biofilm to grow up and around these hard water deposits.
[00:16:34] Eric Knight: Well, you have my attention. This is actually a lot more engaging than I was expecting. And I was expecting it to be pretty engaging. Well, how I have so many questions. Go ahead.
[00:16:43] Jarred Morgan: This was like, man, this was so much better than I thought it was going to be. Dr. Goeres is wow.
[00:16:47] Eric Knight: No, I knew it was going to be good, but like, I didn't think we were going to be talking about beer and calcium deposits. Everything I read had nothing to do with calcium. And here we are, a company that talks about the LSI all the time, suddenly, we've been scientifically proven to be relevant. You hear that, Jarred? We are relevant.
[00:17:05] Jarred Morgan: I'm glad somebody gave us some validation because we don't have a lot of that.
[00:17:08] Eric Knight: Yeah, we needed it. Dr. Goeres, you need to come back. This has been great. Um, Jarred, did you have a question? You breathed.
Are all biofilms bad?
---
[00:17:14] Jarred Morgan: I was going to say, so it sounds to me like, I guess we need to make a distinct, you know, clarification here that not all biofilms are the same. Depending on what surface, body of water, industry, you name it, there's going to be large differences, you would say. Are all biofilms dangerous? Are there good? Or are there bad? Is there a happy medium? What's, what's your take on that statement?
[00:17:37] Dr. Darla Goeres: Well, I tend to study the bad players, right? So it's kind of like when you look at your garden and you see what you're going to classify as a weed growing in your garden, it's called a weed because you don't want it there, right?
[00:17:54] But if I'm hiking up in the back country and I happen to see the same plant, I wouldn't necessarily classify it as a weed. Because in that particular setting, growing in its native environment, it's beautiful and you call it a flower. But when it's growing in your garden, you call it a weed.
[00:18:13] So it's similar in treated recreational water venues, right? It's not like we want to get rid of all these organisms from the planet, because there's a lot of good that they do when they're found in their natural habitat, like in Yellowstone National Park. With carbon cycling and sulfur and nitrogen cycling.
[00:18:36] What happens, though, in treated recreational water is these microorganisms are growing in an engineered system where you don't want them to be. And, and low numbers probably aren't that big of a deal. But they start to grow up into these communities, these biofilm communities, and the real issue is they can harbor pathogens.
[00:19:04] So while you can start off with like in your mouth, your mouth is full of biofilm, it's full of plaque, even if you brush your teeth. Or your skin, you're covered in microorganisms. Your gut, your gut is full of microorganisms. These are all very positive microorganisms that promote human health.
[00:19:24] But if you get a bad player in your tooth, or if somehow something's compromised, and they start to cause a cavity, or you get a microorganism in your gut that's not supposed to be there from food poisoning,
[00:19:41] Jarred Morgan: Your body will let you know.
[00:19:43] Dr. Darla Goeres: Your body will let you know. And your body's like, get this out of here.
[00:19:47] So it's the same thing in treated recreational water. The probability that they could harbor a microorganism that's a frank pathogen. So a bug that's definitely going to make people sick is a real possibility. And of course the classic example is legionella.
[00:20:04] Eric Knight: I was going to say... go ahead, Jarred.
[00:20:08] Jarred Morgan: It just kind of drives home the point of being proactive on making sure that your chlorine levels, your sanitizer levels, whatever you want to call it, are in proper proportions to keep those pathogens and bad bacteria and viruses out of the water. But they do get introduced, they get oxidized.
Biofilms are like Jell-o
---
[00:20:26] Eric Knight: Well, you said, Dr. Goeres, to expand on that, you said that biofilms are exceptionally hard to kill.
[00:20:33] Dr. Darla Goeres: Yes.
[00:20:34] Eric Knight: So is the film itself living?
[00:20:36] Dr. Darla Goeres: Okay, how can you picture this? You could picture this... Do you eat Jell-o?
[00:20:41] Eric Knight: Uh, not really, but I know what Jell-o is.
[00:20:43] Dr. Darla Goeres: Okay, I don't even know if people eat Jell-o anymore. I am old enough... they drink it. okay. Jell-o shots, okay. I am old enough that my mother used to make Jell-o salad, and Jell-o and salad in the same sentence to me as craziness, you know, but whatever. My mom made Jell-o salad when I was growing up. And within that Jell-o salad, she would put bits of fruit, right? Like fruit cocktail. We're going old school here. Fruit cocktail, red Jell-o. You guys can picture what I'm saying.
[00:21:12] Jarred Morgan: I've seen this.
[00:21:13] Eric Knight: Oh, I had that growing up. Yeah.
[00:21:14] Dr. Darla Goeres: Okay. So if you think of the fruit cocktail as the microorganisms and you think of the Jell-o as the extracellular polymeric matrix, that's what I'm talking about.
[00:21:26] It's just that the Jell-o in this case, using this example, the, um, fruit cocktail would have actually generated the jell-o around it. And that matrix, when you're talking about an oxidizer, one of the reasons why... there's multiple different theories here, but for oxidizers, one of the reasons why when these microorganisms are encased in this, this matrix, right?
[00:21:53] So you can envision fruit in jell-o. Chlorine actually has to penetrate through that jell-o to actually get to the pear.
[00:22:05] And so when you have something like an oxidizing agent, it's not specific for microorganisms. It's oxidizing all the organics. So it's, it's slowly working its way through that jell-o. And as it's going through that matrix, it's reacting away. The jell-o is using up that chlorine, that oxidizer.
[00:22:27] Eric Knight: That's what makes it so difficult for chlorine to remove biofilms is what you're saying?
[00:22:31] Dr. Darla Goeres: Yeah. So if I were talking to a group of students, it's reaction diffusion. The problem is, can the oxidizer diffuse into that matrix and actually get to the cell at the concentration necessary to kill it before it gets all reacted away or used up?
[00:22:53] Eric Knight: That's a very good explanation of it. Let me see if I can read it back to you in a simplified way. You've got this jell-o slime kind of thing. In the case of a pool, the most common one that I can think of is touching green algae, right?
[00:23:05] Dr. Darla Goeres: Okay. Yeah.
[00:23:06] Eric Knight: We just did an episode on it and.
[00:23:09] Based on what I read, and I'd love for you to correct me if I have any of this wrong. It is an organic slime that contains polysaccharides.
[00:23:17] Dr. Darla Goeres: Yep, that's right. Yep. Extracellular polymeric saccharides. I could have used that. Instead I chose to say extracellular materials or something like that to make it more generic.
[00:23:29] Eric Knight: Well, I can also say supercalifragilisticexpialidocious without even trying, but in a previous episode on black algae there was a word that I did struggle with. Peptidoglycan?
[00:23:41] Dr. Darla Goeres: Oh, okay, yep. That was the layer. And so it's all of this organic matrix, this matrix that is being generated by the microorganism itself. It's like a protective shell.
[00:23:52] Eric Knight: So you've got this protective shell, you've got this slime. And it's more resistant it seems on black algae, which is that cyanobacteria. We talked about that with a peptidoglycan layer with polysaccharide is the word that keeps coming up.
[00:24:03] Green algae, same thing, polysaccharides once again. And that layer is chlorine resistant. It takes a lot of chlorine to oxidize through it. And hopefully you have enough chlorine at a high enough concentration for enough contact time to kill whatever is inside that biofilm. Is that correct?
[00:24:20] Dr. Darla Goeres: Yep, that's it.
[00:24:22] Eric Knight: Oh, alright. How'd I do, Jarred?
[00:24:24] Jarred Morgan: I think your head's going to explode here pretty soon. You said way too many words, way too fast.
[00:24:28] Eric Knight: I blacked out. I don't know how it went.
[00:24:30] Jarred Morgan: Yes, but I think you did a great job.
Biofilm ingredients and chlorine resistance
---
[00:24:32] Eric Knight: Okay, great. So let's move on. What ingredients make up the types of biofilms that we would most commonly find in swimming pools and hot tubs?
[00:24:43] Dr. Darla Goeres: Um, it really is a function of the microorganisms that are present. And so it's going to be a combination of these more complex compounds that these microorganisms are generating, right?
[00:24:58] Eric Knight: May I offer you some examples and then you can just kind of fire off. I don't need every, we're not going to be too specific on this, but...
[00:25:03] Dr. Darla Goeres: Sure.
[00:25:04] Eric Knight: Um, maybe what we can do is rate these on a scale of 1 to 10. 10 being like, you know of some biofilms that chlorine can't touch maybe. And 1 is it's super easy to kill.
[00:25:14] Dr. Darla Goeres: Okay. I see what you're saying. Okay.
[00:25:16] Eric Knight: How about the slime on green and yellow algae?
[00:25:19] Dr. Darla Goeres: It's going to be hard to kill.
[00:25:21] Eric Knight: Okay. Pretty hard. One to 10?
[00:25:24] Dr. Darla Goeres: Um, depending, it's a function of how thick it is as well. Right.
[00:25:29] Eric Knight: Enough to touch. You can feel it. It's nasty when you touch it.
[00:25:32] Dr. Darla Goeres: 10.
[00:25:32] Eric Knight: 10, wow. So chlorine is not going to get through that unless you have a really high level of chlorine.
[00:25:37] Dr. Darla Goeres: Or long contact time.
[00:25:39] Eric Knight: Okay. Excellent.
[00:25:39] Dr. Darla Goeres: Right? Combination of concentration and contact time.
[00:25:43] Eric Knight: How about the peptidoglycan shell or shield on black algae cyanobacteria?
[00:25:50] Dr. Darla Goeres: There again. It's how thick it is and how much it needs to penetrate through. All of these compounds are going to be reacting away that oxidizing agent. And so, yeah, it will also be incredibly challenging for it to penetrate and kill. If you have a mature biofilm,
[00:26:10] Eric Knight: Call it a 16th of an inch thick.
[00:26:12] Dr. Darla Goeres: That is an exceptionally thick biofilm. Um, we do not get that thick in my lab and they are...
[00:26:19] Eric Knight: Get some black algae. We'll hand you a brush from a pool that's covered in it and you can reproduce it all you want. In fact, I would love to do that. Jarred, we ought to see if we can get that study done. Because there is not a lot of research on black algae, and it's a big problem in our industry. I would love to see you grow black algae and learn from that. That would be so cool.
[00:26:38] Dr. Darla Goeres: So here's the thing. In the lab we're growing pretty dense biofilms, right? So the cell numbers are pretty high. And the thickness, so I'm going to talk in terms of logs, so a log eight, so a one with eight zeros after it, okay?
[00:26:55] So if we grow that, and that's barely visible to the naked eye. And that's per square centimeter, and that's barely, you can see it, you can definitely see there's something going on in the surface. You would feel it if, if you happen to touch it, it would have a slime feel. Okay, so that's, you get in the pool, it kind of has a slime feel.
[00:27:13] You can't really see it, maybe barely see it. Let's say it's, you know, that, uh, 10 to the 7th, 10 to the 8th CFUs per centimeter squared. And once that biofilm establishes to that level, we have to add somewhere towards 5,000 mg/L chlorine to achieve a six log kill. To take away six of those zeros.
[00:27:41] So we're talking orders of magnitude greater than what you would find in a pool. Now the difference is what you have in a pool is constantly there. So this would be a system that had been completely neglected. And these matrix, this biofilm had formed, and then, um, we're trying to go in and kill an established biofilm that's that thick.
[00:28:03] And like I said, in the lab, we're testing concentrations up to sometimes even slightly greater 5,000 mg/L.
[00:28:12] Eric Knight: And milligrams per liter for the listeners is parts per million. It's the same thing.
[00:28:15] Jarred Morgan: That's a lot.
Kill vs. Removal
---
[00:28:17] Dr. Darla Goeres: So kill is not the same as removal. And that's really, really important for your listeners to understand. There are chemistries and biocides. that are specifically formulated to kill these viable microorganisms. And many of them work great, right? There's a reason why chlorine's been around for as long as it has. It kills. It's an effective killing agent.
[00:28:40] Another approach that's often used, and a perfect example of this is in laundry soap. So when they formulate laundry soap, not only do they include some type of an oxidizing agent, they will also include something like an enzyme. And the goal with including something like an enzyme is to go in and to actually attack the matrix. And to find a way to loosen up or to deal with that matrix, and to remove the biofilm from the surface.
[00:29:15] Because there's a lot of instances like your toilet. Uh, what you want to do is remove, you don't necessarily need to kill because you're going to flush it down the toilet and it's going to go to a wastewater treatment plant. So there's multiple strategies that you can follow to combat biofilms. And killing is one strategy and can be effective, it's certainly not the only strategy.
[00:29:39] Jarred Morgan: I think we could just summarize that as. Back to the original, I guess in the original statement, I made it where it's a multi layered approach to, you know, tackling these things. There's not just one thing is going to be your answer. Throwing 5,000 ppm of chlorine into a body of water is not practical or very realistic.
[00:29:58] Eric Knight: Well, hold on.
[00:30:00] Jarred Morgan: It's going to require multiple layers of things.
[00:30:03] Eric Knight: If you spot treat down a pipe with liquid chlorine or cal hypo or trichlor. It's going to be a very high concentration of chlorine right there.
[00:30:12] Jarred Morgan: Yes.
[00:30:13] Eric Knight: It will be. I mean, I don't know if it's 5,000, but it's going to be very high. You add that to friction. But, Dr. Goeres, one of the analogies that I give, I would love to see if you think this is accurate because this is how I see it in my mind, with black algae in particular. If you have a scab on your skin and it hardens, you could pick at it... because no adults would ever do this. Only kids pick at scabs, right?
[00:30:34] Uh, but if you pick at it enough, it pops off. And then you've got that raw flesh underneath. But if you were to sit in a hot tub for two hours, what would that scab feel like?
[00:30:43] Dr. Darla Goeres: Exactly. It gets softened up.
[00:30:44] Eric Knight: Right. And it's a lot easier to remove. You can almost roll it off with your fingertips. And that's what we have noticed. It's been a lot easier to clean black algae up if you can soften that shield, so to speak. Maybe not fully remove it. We still need to brush, but that has been extraordinarily effective in our experience. What is your take on that?
[00:31:04] Dr. Darla Goeres: Yeah. Um, I think going back to what Jarred said is that biofilm is very nuanced and attacking the problem using various approaches is what's going to be most effective and there's cleaning and there's disinfecting. Right? And so this is for clean in place processes, First you want to clean and then you want to disinfect.
[00:31:26] The interesting thing, though, is that the recreational water industry really focuses in on prevention. So that's why they have 1 to 3 mg/L chlorine in their water if they're using a chlorine based system. Their goal is to prevent. And so someone jumps into the water, they slough off microorganisms, oils, what have you, and the idea is that you have enough chlorine in the water that any microorganism that perhaps sloughs off the individual, uh, Or maybe comes from the environment that that chlorine deals with, and it prevents the biofilm from ever forming.
[00:32:08] That's really, I think, the strategy that the industry has taken. That's a solid strategy, by the way, right? That's a solid approach. And I'm not ditching on that approach at all. It's incredibly solid.
[00:32:19] Eric Knight: That's us. We like proactive pool care ourselves. That's our whole M.O.
Prevention vs. Remediation
---
[00:32:23] Dr. Darla Goeres: Yeah. An ounce of prevention is worth a pound of cure. Keep on top of it. Never let the biofilm form. And what you're describing to me is a system that hasn't been maintained a system that has been allowed to foul.
[00:32:39] Now, those prevention strategies that the industry has used for a long time, and like I said, it's a solid approach, it's solid scientific thinking, they need to switch their thinking in that particular application. Now you're not talking about prevention, you're talking about remediation.
[00:32:58] The strategy that you use in a system that has become solidly fouled, for whatever reason, you know, and there's a lot of very good reasons why this happens. Someone has a hot tub they leave for three months on vacation, they come back. And they left the water in it. There's been no chlorine added or no disinfectants added to it. Of course, there were bacteria in there. Whatever organics were in the water these bacteria are utilizing as a food source. They're starting to grow up. So now they have a system that is fouled that they need to remediate.
[00:33:33] That is the thinking behind remediation. And the process that goes into remediation and the examples that you're giving me are remediation. That's entirely different. Like get that gunk, get that buildup off the surface and then whatever happens to be remaining, get in there and disinfect it.
[00:33:57] Eric Knight: So to get back to the earlier question, I gave you examples of how hard to remove green algae, black algae. When you brush black algae, you can see the little heads of it, the little shields on your brush. So I would estimate it's about, what do you think Jarred? A sixteenth of an inch is a fair estimate of the thickness of these things?
[00:34:14] Jarred Morgan: Yeah, that's thick, but that's, that's total. Like your total size. You're visibly seeing it so you know it's going to be larger because it has to be, because you can see it. But I don't know exactly.
[00:34:25] Eric Knight: I don't know how much of that is the actual bacteria versus the film protecting it. Uh, but you just brought up hot tubs. That pink slime stuff that comes out of the jets in those dirty hot tubs. I'm presuming that's a biofilm?
[00:34:39] Dr. Darla Goeres: Yeah, I would put money on that it's a biofilm.
[00:34:42] Eric Knight: Okay, well it's, it's a big common problem. How hard is that to kill with chlorine alone? Like the 1 to 10 thing again.
[00:34:49] Dr. Darla Goeres: Okay, so 1 to 10, there again it's, it depends. There's some factors. You know, because I'm from science, I can never give a concrete answer. I always have to say, give multiple disclaimers.
[00:35:02] Eric Knight: Listeners. I just want you to know, she rolled her eyes back and looked down her nose at the camera when she said that she's like, well, because I'm from science.
[00:35:10] Dr. Darla Goeres: So I just want you to know, yes.
[00:35:14] Eric Knight: Oh, fair enough. Okay.
[00:35:15] Dr. Darla Goeres: Fair enough. Fair enough. It's going to be incredibly challenging to kill once you have something built up to the point that you can see it.
[00:35:23] Eric Knight: Oh, wow, so these are supposed to be invisible usually?
[00:35:26] Dr. Darla Goeres: Well, when you have those initial cells on the surface and they're low numbers, the only way to see them is with a microscope.
[00:35:32] Jarred Morgan: Well, this is where it's funny because you're saying that it's very hard to kill. I think there's a different perception of very hard to kill in academia versus being a pool guy who walks up to a green pool and they dump a gallon of liquid chlorine right there in the deep end and it'll start turning blue almost immediately. That doesn't...
[00:35:54] Eric Knight: Well unless it's copper, of course. But yeah, it usually takes like I use six gallons in my pool of liquid chlorine and it,
[00:36:01] Jarred Morgan: It'll do the job. I mean, I think that's where maybe it's...
[00:36:03] Dr. Darla Goeres: For how long?
[00:36:04] Jarred Morgan: But it may not be the definition of what we're talking about here, where you're talking about something that has a protective shield around it on a surface, like a, just a perfect environment for, um, accumulating these bacteria and whatnot.
[00:36:19] Well, if it's a single cell algae, I guess multiple single cells, you can visibly see it. But if I go in and dump a gallon of liquid chlorine onto it, it's going to do a pretty good job.
[00:36:31] Dr. Darla Goeres: Chlorine is effective. Like I said, there's a reason why it's been around for a long time. But it's not only how much you're dumping in. It's how long do you allow that chlorine to come in contact?
[00:36:42] Jarred Morgan: Yes.
How clean is clean?
---
[00:36:42] Dr. Darla Goeres: And it will do a job, right? It is going to knock these bacteria down. The question is how clean is clean? So how clean do you need to get this system Like you said, I'm a regulatory science person. So when the EPA is going to regulate these products, and they're coming up with the regulations around what is an acceptable level of kill for these microorganisms, the question that you're asking in your mind is how clean is clean? How clean does it need to be?
[00:37:16] And the fact is, it's not a one answer fits all situation. Because if I'm a person that's going in for a surgery, and they were cleaning the operating room before I went in there, and they're cleaning all the hard surfaces. Man, I don't want there to really be any microorganisms on those surfaces or I want them to be incredibly low.
[00:37:40] Eric Knight: Sterilized.
[00:37:41] Dr. Darla Goeres: I want it to be as absolutely disinfected as possible with as minimum viable organisms as possible. Because at that moment in my life, I'm incredibly susceptible to infection and incredibly susceptible to getting sick.
[00:37:58] Conversely, if I am a healthy adult with a normal immune system, and I am drinking water that is not sterile, right? Because I drink it out of the tap. And I jump into a swimming pool, it doesn't need to be sterile. It doesn't need to be sterile. I have an immune system. My body is going to be able to handle a few microorganisms. Now, it depends upon what the microorganisms are.
[00:38:25] So how clean do you need to get a hot tub surface or a swimming pool surface? What is an acceptable level of disinfection for that application?
[00:38:38] And one of the areas I study actually is biofilm on the International Space Station. which is pretty damn cool. And we're looking at it in the urine distillate and condensate system.
[00:38:49] Jarred Morgan: Tell them you need to make a field visit. You think they'll do that?
[00:38:53] Dr. Darla Goeres: Yeah! There's a lot of different perspectives or approaches that we can use to kill the microorganisms, reduce how many microorganisms grow, you know, filter them out, all these different strategies. The question is, how low do we have to go so that it's safe on the International Space Station?
[00:39:15] Given that it's a very obviously incredibly different environment. And the same question is true for recreational water. I believe they use drinking water standards. There are no standards with biofilms. That's the problem in the recreational water field, is what I like to tell people is zero is not an answer. That is not an answer. Never say zero. Because A) it's very hard to demonstrate scientifically, and B) it's just unachievable in a system that's open to the environment. But you want it at a level that it's controlled. And so adding in the bleach, controlling the system, getting it to a level where your normal individual with a normal immune system is going to be fine, that's kind of the goal.
Log-reductions in disinfection
---
[00:40:01] Eric Knight: The one figure we hear a lot when we're looking at chlorination, sanitization is a three-log reduction and disinfection is a five-log reduction of harmful pathogens. Is that your understanding of it too? Or do you have different standards in different industries?
[00:40:17] Dr. Darla Goeres: So, um, like hospital level disinfectants, those sorts of things, the three log for sanitization holds. Six logs is actually for the disinfection.
[00:40:30] So when you're looking at bacteria and they're just floating around in the water and you get that log reduction, if you started off with a billion microorganisms and you get a three log reduction down to a million microorganisms, that's still a pretty high number that could make you sick.
[00:40:49] And so with drinking water, what they say is instead of getting a log reduction, they give you a maximum allowable amount. So you have to have under, for instance, 500 colony forming units per mil. And then it's even lower, that's heterotrophic bacteria. And then obviously for something like coliforms, it's maybe one. I can't remember what the coliform regulation is, but it's a very low number for that particular microorganism.
[00:41:19] So rather than looking at a kill, maybe what people with biofilms could do is look at what's left behind, and I'm going to use the example of an endoscope.
[00:41:31] So, endoscope is used in colonoscopy. They're, they're cleaned and they're chemically disinfected. If you are the next patient, don't you want what's left behind to be pretty damn low?
[00:41:44] Eric Knight: I should say. Yeah.
[00:41:45] Dr. Darla Goeres: Yeah. Right. I mean, that's what you want.
[00:41:47] Eric Knight: I can't speak for Jarred, but for me personally, I prefer my endoscopes to be very clean, Dr. Goeres.
[00:41:53] Dr. Darla Goeres: Very clean. Very clean. So maybe instead of really focusing in on these log reductions. Maybe we need to...
[00:42:01] Eric Knight: you just said log reductions in the same sentence as a colonoscopy. So this is weird.
[00:42:05] Jarred Morgan: God, we had a good track record of being serious here and then Eric
[00:42:09] Eric Knight: This, we tried. We tried. It's a professional podcast. We're doing our best and failing miserably. I told you this is the low part of your career. If we need to delete anything from this episode
[00:42:18] Jarred Morgan: I mean, I was going to make a joke about flowers and weeds and companies. We had a whole thing we could have worked with there, but I let it go. Eric, you...
[00:42:24] Eric Knight: oh, you let it go. I couldn't help myself.
[00:42:27] Dr. Darla Goeres: Yeah. Anyway, asking me is it good? How many have been reduced? My question would be, well, what can we leave behind, right? What's acceptable to leave behind in your industry?
[00:42:39] Eric Knight: Well, I, I actually don't know the answer to that. I do know that there are contact times that are established, and we may need to have you on another episode in the future to talk more about contact times because that is where the health departments get involved for pools.
How to remove and how to prevent biofilms in pools
---
[00:42:53] Eric Knight: But in the interest of time to focus on biofilms here, let's wrap this up. Uh, two final questions. What can be done to remove existing pool biofilms? So again, we're talking about things like the slime on algae and the common things that you might find in a pool or hot tub.
[00:43:09] Dr. Darla Goeres: Right.
[00:43:10] Eric Knight: And the other side of that question is, what can be done to prevent the biofilm formation sufficiently in the first place?
[00:43:17] Dr. Darla Goeres: Right. Those are great questions. So when it comes to removal, I'm going to say what my mama always told me, which is elbow grease. Did you know there's actually something called the Sinner circle of cleaning? Which I absolutely love. It was invented by Herbert Sinner back in 1959, and it's still used. That philosophy is still actually used in cleaning systems, right? Clean and place systems. And so it's time, temperature, mechanical removal, and chemistry.
[00:43:50] And so, what can you do? Well, you know, you can add chemistry for a long contact time. A higher, a little bit higher temperature will probably make it more effective. A lower temperature will keep it around for a little bit longer if it's chlorine. You can do mechanical removal. So, get in there and physically clean it with a scrub brush. Brush it. Clean it. Scrub it out. And then, throw away that scrub brush.
[00:44:16] And throw away... Scrub rag and get a new one, right? Don't, don't recontaminate a surface.
[00:44:21] Jarred Morgan: God we just touched on
[00:44:23] Eric Knight: this...
[00:44:23] That's what we were saying about black algae! That is the number one cause.
[00:44:26] Jarred Morgan: Okay, Eric, you didn't make it up. Good job.
[00:44:29] Eric Knight: I didn't. I totally didn't. I told you. I actually read to prepare for that episode. It is the number one cause of black algae in pools is a brush that just brushed black algae in another pool. And then you take it to another one and you've just contaminated it. Because you brought it in from the other one.
[00:44:43] Dr. Darla Goeres: Exactly.
[00:44:44] Eric Knight: Let's just use that example real quick, not to derail you from the second part of the question, but if I did just scrub black algae with a wire brush, what do I need to do? Like, how much of a log reduction, how much chlorination do I have to disinfect that brush with, theoretically, if I was to try to put it into a clean pool to kill whatever I just took off that cyanobacteria?
[00:45:05] Dr. Darla Goeres: Right, I'd probably try to put it in like a high wash cycle or a high pressure wash cycle with, uh, heat and then follow it up to get gunk, like to get the chunks off and then do some type of a biocide.
[00:45:18] Eric Knight: A high wash cycle, like a dishwasher?
[00:45:21] Dr. Darla Goeres: Um, not, I would never put that in my dishwasher, but you know, like a high pressure wash system that you could just use to spray it off.
[00:45:27] Jarred Morgan: Just to get the solids off.
[00:45:29] Dr. Darla Goeres: Just to get the solids off. And then, um, soak it in biocide. Before using it in the next system. I mean, cleaning your cleaning tools is actually really important. Touch transfer is very important.
[00:45:42] Eric Knight: So back to the second part of the question. You said it's the Sinner's circle of cleaning?
[00:45:46] Dr. Darla Goeres: The Sinner's circle of cleaning. Yep. So mechanical removal works, chemistry works, time and temperature works. So add one gallon, let it soak for a longer contact time. Add 10 gallons and you can probably let it go for a shorter contact time.
[00:46:02] Eric Knight: Nice. Okay. Now, how about prevention?
[00:46:04] Dr. Darla Goeres: Maintain your system.
[00:46:05] Jarred Morgan: Proactive maintenance. That's how you would prevent it.
[00:46:08] Dr. Darla Goeres: Proactive maintenance.
[00:46:09] Eric Knight: So, brushing weekly or every other week, just doing that cleaning just constantly, just being proactive.
[00:46:16] Dr. Darla Goeres: Maintaining your water chemistry. Getting in there and making sure that your water chemistry is correct, right? That you have balanced water chemistry. That you have the residual disinfectant that you think you do. Um, maybe like for hot tubs, those, um, the covers that go on hot tubs, actually cleaning those. Because if you get things that are dripping into the hot tub as a source of contamination. So getting in and just spending some time starting with a clean system and then proper maintenance. I always think of hot tubs as more of a hobby. Give them the time they need, right? Spend time taking care of them.
[00:46:59] Eric Knight: Go ahead, Jarred.
[00:47:00] Jarred Morgan: This is why they call it spring cleaning, because you need to get in there and just kind of get everything up to speed and ready to go for the year. And I think just keeping on good practice, good maintenance, good proactive care, no matter what you're trying to do, whether it's a pool, spa, a beer line, right? Just go ahead and be proactive.
[00:47:19] Eric Knight: Well, yeah, I mean spas, especially commercial spas, tend to be drained every month or every other month. Um, purge out the pipes and clean it out, rinse it, refill it. That sort of thing sounds pretty preventative to me. Uh, pools don't have that luxury, so if, if we're trying to be proactive, I guess that would be cleaning the filters? Cleaning the cartridges if you have those? Uh, backwashing regularly. You know, we do this filter purge, and it is amazing how sticky and nasty and slimy that sand is. And after purging it, it feels like new sand again, so I happen to believe this stuff is everywhere, I mean,
[00:48:00] Dr. Darla Goeres: It is.
[00:48:00] Eric Knight: It sounds like it's everywhere, you could just, Just imagine it. It's on tile, and it sounds like it's floating at the surface, too.
[00:48:06] Dr. Darla Goeres: It is. Yeah. Yeah.
[00:48:08] Eric Knight: So there's really no avoiding it.
[00:48:10] Dr. Darla Goeres: There's no avoiding it, but you definitely can control it by proper maintenance.
Where to learn more about biofilms
---
[00:48:15] Eric Knight: Outstanding. Well, where can our audience go to see your research?
[00:48:19] Dr. Darla Goeres: They can go to the Center for Biofilm Engineering, and learn all about biofilm and a whole bunch of different application areas. I recently have stepped into the position of industrial coordinator, so working with different companies to help them solve their biofilm related problems. Covering everything from, you know, engineered systems, built environment, to pharmaceutical companies. So a wide, wide range.
[00:48:48] Eric Knight: Right on. Well, it has been a pleasure having you on this podcast. Thank you so much and being generous with your time and tolerating us as hosts. Um,
[00:48:55] Dr. Darla Goeres: Yeah, my pleasure.
[00:48:57] Eric Knight: Well, thank you. Jarred, is there anything you'd like to add?
[00:48:59] Jarred Morgan: I'm glad we potentially scared the crap out of our 175 listeners. But, uh, I hope it makes them feel not better, but just understand that there are things that are all around us in our daily lives. They're obviously in swimming pools, on surfaces. It's just a matter of the maximum allowable limits. Understanding that we can only do so much to control, um, certain situations. But if you're in a residential backyard and the water is sparkling, crystal clear, pristine, looks inviting as it should.
[00:49:33] Are you really going to raise an eyebrow? I mean, I wouldn't. But I guess that's a question for you, Dr. Goeres. You study these things. How do you not walk around and just absolutely quinge every time you have to go to an airport and get on an airplane or, or go to a hotel swimming pool? Like, because those are things as a pool guy, I walk into a hotel or motel pool and I'm like, Nope.
[00:49:55] Eric Knight: Nope.
[00:49:55] Jarred Morgan: Everybody's giving it the side eye like, don't know about this.
[00:50:00] Dr. Darla Goeres: Yeah. I still drink beer and I know there's biofilm beer lines. But you give it the smell test and you taste that beer and you're like, this beer is skunky, you know. Right? You know, and then you send it back and get a different beer.
[00:50:15] Eric Knight: Well that that's great. And Dr. Goeres, in all seriousness, thank you so much for all the work you do.
[00:50:22] Dr. Darla Goeres: You're very welcome.
[00:50:22] Eric Knight: It's wonderful that you are helping with regulatory agencies to make sure that we are kept safe in all aspects of our lives. And recreational water to us and our livelihood is a big deal, but in the grand scheme of things, things like drinking water, beer lines,
[00:50:36] Jarred Morgan: Yeah,
[00:50:36] Eric Knight: all other aspects of food production, which you work with the FDA. Thank you for all your work.
[00:50:41] Jarred Morgan: Yes,
[00:50:41] Dr. Darla Goeres: You bet, you bet.
[00:50:43] Jarred Morgan: Thank you. It was good talking and seeing you again, even though no one else can see you. We're actually talking on video, and it's great. Um, but it's been a pleasure, and uh, Thank you for the time. I think we'll probably have you on again. I think you can add some value to our listeners.
[00:50:58] Dr. Darla Goeres: You think so, huh?
[00:50:59] Jarred Morgan: I do.
[00:51:00] Eric Knight: Well, let, I mean, you can. I'm not so sure about Jarred, but I'm sure you can. You're welcome anytime, Dr. Goeres.
[00:51:06] Well,
[00:51:06] Dr. Darla Goeres: thank you. Thank you. Thank you.
[00:51:08] Eric Knight: Well, this has been episode 120 of the Rule Your Pool podcast. In the next several episodes, we are going to be doing a multi part series on chemical conflicts.
[00:51:16] And then we're going to do an ask the chemist series where we get more experts on here because we are trying to up our game and make sure you're not just listening to Jarred and I make fun of each other the whole time. We want to make sure this podcast remains valuable. Dr. Goeres, you have done that exceptionally well. Thank you so much for being here.
[00:51:33] Dr. Darla Goeres: You're welcome.
[00:51:34] Eric Knight: Take care, everyone.
[00:51:35] Jarred Morgan: Thanks.