Biofilm begins forming the moment a spa or pool is filled with water. Take a bucket of water, for example. Leave it outside and within three hours, you’ll notice a slimy buildup along the walls.
The same principle applies to pools and hot tubs. Before this gunky layer accumulates, it’s actually free-floating bacteria. These bacteria can include salmonella, aeromonas, E. coli, campylobacter, streptococcus and pseudomonas aeruginosa, among many other nasty things. Also, protist species such as cryptosporidium and giardia can be found. The latter will be rare in pools, but it is possible.
It’s the electrostatic load of the surface areas within the vessel (walls, stairs, pumps, tubes) that attracts planktonic bacteria, which quickly settle and begin colonizing. Gravity, along with flow and turbulence, provides a process by which the bacteria can thrive throughout the system.
Once bacteria adhere to the surface, they produce a protective mucous layer. This slime layer, so-called xPS (extracellular polysaccharide substance), is most commonly referred to as biofilm. In fact, biofilm could be considered as a “quasi-tissue” with measurable rates of respiration, and nutrient uptake serving as protection.
Inside this biofilm, growing within a few hours, the bacteria can live undisturbed and reproduce. Lotion, hair, dander, organic and inorganic pollution float along the sticky, slimy substance and become food for the bacteria living in the biofilm.
Confocal laser scanning microscopy shows that microcolonies within a biofilm are three-dimensional structures of mushroom-like bacterial growth with water channels running between them. The channels allow a constant supply of nutrients and oxygen. After a study of the biofilm and the behavior of bacteria, our researchers have indicated that the regrowth of bacteria out of the biofilm is even worse in comparison with bacteria entering the water by bathers and organic pollution. And, once they form, they rapidly begin to multiply and spread — and become much more difficult to treat.
All methods of microbial control with biocides and oxidizers have proven inadequate on biofilm. At best, sanitizers may be able to kill the bacteria closest to the surface, but can’t penetrate the depths of the xPS matrix where billions of bacteria remain. The oxidative power of chlorine and ozone rapidly disappears in the outer side of the microbial slime layer, and the few bacteria these ingredients manage to destroy are quickly replaced. In the meantime, the biofilm begins destroying the metal equipment of the pool or spa through microbial-induced corrosion. Even stainless steel is not safe from biocorrosion.
Stopping this process of regrowth and multiplication prevents huge numbers of bacteria, thus reducing the need for greater amounts of harsh chemicals. To do this, we must attack bacteria while they’re suspended in the water. That’s when they’re most vulnerable. All oxidizers such as ozone, chlorine, UV-C and bromine are effective defenses against free-floating bacteria.
To get the bacteria off the surface and into the water, we can brush walls, but this only removes what we see — typically, the gunky buildup along the waterline. What about bacteria harbored in the plumbing? Our research has shown that a negatively charged cleaner can creep under the biofilm, open it and lift it off the surface so that it can be mitigated with disinfectants.
Once the biofilm is removed, the cleaner leaves a negatively charged layer of anionic salts to prevent new attachment.
The CEO/founder of AquaFinesse, Jan de Rijk (left), has been studying bacteria behavior since 1998. Bob Snodgrass, vice president of sales and marketing (right) has over 35 years’ experience in sales, construction and education in the industry.