The Secret Life of Biofilm

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Although most people in the industry have heard of it, few know the risks and mysteries of biofilm.

Biofilm is almost everywhere. According to scientists who study it, wherever there's water, nutrients and a surface, biofilm is likely to form.

It exists in rivers, streams, lakes, ponds and oceans. It forms in all types of manmade water systems, from public utilities to factories, hospitals, dentist offices, dishwashers, cooling towers, washing machines, air conditioners and yes, pools and hot tubs. It also forms on living tissue. In fact, dental plaque, the stuff that decays our teeth, is a common form of biofilm.

Yet, for all its ubiquity, biofilm remains shrouded in mystery. Because it often exists in pipes and other hidden locations, most people don't realize it's there. Even in the pool and spa industry where water quality management is a big priority, biofilm is little understood.

According to Vance Fiegel, co-founder and chief scientific officer for Creative Water Solutions: "I think people know the word, but even in the pool and spa industry most people probably don't understand what it is biologically. Biofilm can be made up of anything that's in the water, so each biofilm is unique depending on the water system and collection of organisms."


According to the Center for Biofilm Engineering at Montana State University, "Biofilm forms when bacteria adhere to surfaces in moist environments by excreting a slimy, glue-like substance. Sites for biofilm formation include all kinds of surfaces: natural materials above and below ground, metals, plastics, medical implant materials – even plant and body tissue."

According to information published by the CBE, biofilm "communities" can form by a single bacterial species, but in nature, biofilm almost always consists of rich mixtures of many species of bacteria as well as fungi, algae, yeasts, protozoa, other microorganisms, debris and corrosion products. Biofilm is held together by sugary molecular strands, collectively termed "extracellular polymeric substances," or EPS. The cells produce EPS and are held together by these strands, allowing them to develop complex, three-dimensional, resilient, attached communities. Biofilms can be as thin as a few cell layers or many inches thick, depending on environmental conditions.

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The study of biofilm has increased dramatically in recent years. According researchers in Montana, biofilm costs the U.S. billions of dollars every year in energy losses, equipment damage, product contamination and medical infections.

"They create their own little environments for themselves by releasing complex polysaccharides; they create their own community," Fiegel explains. "It protects them from biocides, it allows them to communicate with each other. They can exist in a relatively dormant state until conditions change and its conducive for them to divide and reproduce. It's virtually impossible to keep a water system free of biofilm. It's really hard to get rid of once it's established."

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In nature, biofilm is an essential part of aquatic ecosystems and is in many respects beneficial. They can even beautiful, such as the colorful mats of biofilm found in the geothermal features of Yellowstone National Park.

In manmade systems, however, it is almost always problematic. Not only does it pose the risk of exposure to pathogens such as pseudomonas, E. coli, legionella and other waterborne diseases, it also makes water management more difficult. Biofilm drives up sanitizer and oxidizer demand, fuels the formation of disinfection byproducts, corrodes metal plumbing and components and, when neglected, can grow so thick it restricts plumbing flow. Therefore, even if pathogens are not present in biofilm, it's still a potential problem.

Of course, the greatest concern is that biofilm can make people sick. When bacteria is inside biofilm, it's not typically going to result in pathogenic exposure. It's not until it sloughs off into the water or is otherwise released from the biofilm matrix that it can harm people, which is one of the big reasons why maintaining an adequate sanitizer residual is so important. Not only is it difficult to know if biofilm is hiding in plumbing or other parts of the systems, it's also nearly impossible to know when it's released and becomes planktonic.

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According to Dr. Darla Goeres, associate research professor at the Center for Biofilm Engineering, understanding how outbreaks occur is far more complicated than people probably think.

"There has to be a combination of different factors that come together for an outbreak to occur," she says. "It's really a system, which includes the design of the treated venue, the water chemistry, the operators and the users. If you have a pathogen like legionella present in the water, depending on the immune response of the person being exposed, they might end up with Legionnaires' disease or Pontiac fever. In other opportunistic pathogens like pseudomonas, the person might end up with folliculitis, which is so common that people don't even report it."

"Bacteria in biofilm may not be an immediate hazard, but it's a reservoir of bacteria that can become planktonic if something changes in the system and that can lead to increased risk of exposure," Fiegel adds. "If the chlorine residual drops, all of sudden there's nothing present to inhibit their growth."


All of this information leads to the obvious question about how to contend with biofilm. Can it be prevented, managed or even eliminated? Again, the answers are surprisingly complex.

"It's a constant battle because every time someone jumps in a pool or relaxes in a spa, they're sloughing off bacteria," Goeres explains. "That's especially true in the U.S., where showering before you go in the water isn't as common as it is in other places. So the system is constantly being challenged, which is why it is important to have a residual in the water."

Yet bacteria in biofilm is far more resistant to chemical treatment and tends to form in inaccessible places, making it especially difficult to eradicate.

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Goeres finds it is difficult to provide treatment advice because of the vast differences in facility types, users and the biofilm itself.

"It could be mechanical cleaning, scrubbing everywhere you can. It could be replacing filter elements, it could be using an acid or a caustic to help remove the biofilm — especially if there's scale buildup that's part of the biofilm environment," she says. "It can't be simply targeting the biofilm, but instead considering the entire system: filtration, water balance, sanitizer levels, overall cleanliness, bather hygiene, all of it works together. There's not a blanket treatment that would apply to every system."

The way biofilm is treated and managed can also depend on how a facility is used.

"If it's a hydrotherapy pool where you have people with compromised immune systems, it's more risk averse," Goeres says. "If you have a pool that's frequented by very young children, there's a different set of issues."


There are products that claim to kill or at least control biofilm. As is true of other biocidal chemicals, registration of the product category is under the auspices of the EPA, which is required by federal law to register any products making biocidal claims.

Although a handful of products do make biocidal claims regarding biofilm, many do not carry EPA registration, which makes such claims technically illegal. It's useful to remember EPA standards are based on risks in medical environments and whether a product "kills" biofilm, rather than removing it.

Jerry Parker, president of Unique Solutions, says he has to be very specific in claiming that his product, Ahh-Some, a quaternary ammonia-based spa cleaner, will "aid in the removal of nonpublic health biofilms," which in effect precludes the product from being used in commercial pool and hot tub settings.

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For hot tub dealers like Grant Gislason, owner of Vintage Hot Tubs, Pool, Patio and Billiards in Victoria, B.C., contending with biofilm in hot tubs has been largely a process of trial and error. "We've been using the Ahh-Some product for a long time and have been thrilled with how well it works," he says. "I know we have to be very careful about what we claim it does, but let me put it this way: We have customers that come in a want to use it on their washers and dishwashers because they're so satisfied with the result in their hot tubs."

Similarly, products based on sphagnum moss have been associated with treating biofilm. According to Fiegel, whose company markets a sphagnum-moss based product, those claims are completely inappropriate. "We don't make that claim and we discourage our dealers from making those claims."

Researchers such as Goeres point out the need for much more specific research into biofilm and various remediation techniques and products. Given that a majority of studies about biocidal efficacy focus on planktonic forms of bacteria, it's fair to say that there is much work to do in understanding the amazing and troubling world of biofilm.

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