It’s in all pools and spas–that slimy, sticky, gooey stuff that appears along the tile line, in skimmer baskets, around air jets, on ladders, in the filters and in the pipes.

Beware biofilm!

While facility operators assumed it was just suntan and body oils, scientists concerned with problematic environments have another name for it, “biofilm.”

Over the past 20 years, an abundance of studies have attempted to understand biofilm’s effect on swimming pool and spa water. What have we learned? Trapped within the biofilm are microorganisms like algae, bacteria, fungi, protozoa or a mixture of these populations.

The U.S Centers for Disease Control and Prevention (CDC) estimates that 65 percent of human bacterial infections in aquatic environments involve biofilm (NSPF Pool & Spa Handbook, 2011 edition).

Many of these microorganisms are resistant to standard disinfection processes because the biofilm actually protects the microorganisms from being destroyed.

Even in well-maintained spas, microbes — especially Pseudomonas aeruginosa — can rapidly recolonize within spa environments. The spa’s hot water dilates the skin pores, which invites the bacteria and toxins into the skin, causing a rash, or an allergic reaction.

Rash outbreaks are an indicator of poor overall sanitation in an aquatic facility (Meyer and Klueger, Arch Chemical). This “hot tub rash,” indicated by itchy, red bumps, grows in warm water environments and survives in biofilm.

In addition to a rash, pathogens may be released from the biofilm into the air, causing respiratory diseases like Legionella (Miller, WAHC 2009). Legionnaires’ disease — named after the 1976 outbreak at a convention of the American Legion in Philadelphia — is a severe form of pneumonia. The Legionella bacteria are found naturally in warm water environments; therefore, they can be established (trapped) in the biofilm. If this pathogen is inhaled in or near the surface of a pool or spa — or through misters — the effects can be quite serious.

Most bacteria grow in biofilm attached to a surface. We all actually experience this — the slimy feeling in the mouth, plaque buildup on teeth, contact-lens solution kits, on toilets and in bathroom basins — all are examples of contamination lurking in biofilm.

Combating biofilm requires an understanding of what the substance actually is and then finding how to treat it.

What Is Biofilm?

Biofilm is a collection of microbes living together on a wet surface. Extracellular polysaccharide substance (EPS) is the slimy goo which encases the organisms and anchors them to a surface.

Pools and spas are excellent media for microbes; the wet, warm and nutrient-enriched waters encourage growth. Biofilm harbors algae and water mold as well as recreational water illnesses, such as Cryptosporidium, Giardia and E. coli.

If there is a wet surface, there is biofilm. Black, yellow and green algae are microscopic forms of plant life and can be free-floating or attached to the surface (biofilm). Algae on pool surfaces are much harder to kill. Operators who have examined black algae confirm there is a crusty film or gelatinous sheath over the black algae spore. This is actually a biofilm covering.

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