Biofilm: The Hidden Accomplice
So many times when I hear the word biofilm all I can conjure is the movie BioDome and how much the two are alike. They are two protective enclosures with living organisms that can contain within themselves one or many different types of living organisms. But they are also different in that BioDome was many organisms working for a common good and being self sufficient where as biofilm is a nuisance due to its ability to harbor bacteria, fungi, algae and protozoa. Of course the movie did portray Pauley Shore to be a nuisance and example of what can go wrong. The same is true of the hidden accomplice of biofilm.
Biofilm is formed by the combination of water, a surface to grow on, and microorganisms. The water needed can be as little as high humidity and can be fresh or salt water. Surfaces can be solid where most types grow but also biofilm can grow on biological surfaces like organs. Microorganisms such as algae, bacteria, protozoan, fungi or a combination of such can be present in biofilm. Some are harmful that can cause illness such as Legionnaires disease, Pseudomonas rash, and intestinal illness as with giardia, e-coli, and cryptosporidium.
In our swimming pool environment we encounter water everywhere. The outside environment including the deck, chair and bench surfaces to of course inside surfaces of the pool including the piping. The moist outside areas out of the pool can harbor microorganisms that can be transferred into the pool.
Biofilm that is attached to a surface is more resistant to disinfection. In the pool there are areas of poor circulation or dead zones that will allow the microbes to attach themselves to the surface easily. In pools where the circulation is stopped such as in use of a timer, biofilm can began to grow easily. This is not an area that can be brushed. In circulation piping if the velocity of the water is fast the biofilm experiences erosion and it becomes smooth creating a strong biofilm harder for chemicals to penetrate. If the velocity is slow the biofilm will be rough and have an uneven surface creating an unstable biofilm. [Klueger and Meyer] Biofilm that has broken off and is free floating is more susceptible to disinfection.
Microbes are smart. They can talk to each other through chemical signals and know when to colonize. Once the microbes attach and start to colonize they secrete an Extracellular Polymeric Substance otherwise known as EPS or that slimy, sticky covering that protects the colony from normal levels of sanitizer and algaecides.
Then they invite their friends. So many different living organisms can be in the biofilm. They release part of the colony to find new areas to grow and find more friends. Also any harmful microbes can be released and cause a recreational water illness. The CDC has found that 65% of RWI involve a biofilm. [NSPF Pool & Spa Handbook, 2011 Edition]. The microbes can wait around in a well maintained pool or spa for an opportunity to get established again like when the sanitizer or algaecide level is low. Once treated for biofilm it is important to keep a higher than normal sanitizer level so they don’t come back again and again.
The conventional methods of microbe control for swimming pools have proven inadequate when associated with biofilm. Biofilm prevention is recommended as it is much harder to eliminate once allowed to establish. However there is evidence of less to no occurence and ease of removal in salt water systems. See Mixed Oxident Solution for further information and pictures.
Dental plaque is a type of biofilm. We brush our teeth to remove the biofilm and prevent dental decay, bad breath and such. The same is true in our pools and spas. If we perform regular brushing of all surfaces in the pool we can dislodge the biofilm that may be present so that it becomes free floating and more able to be disinfected by the sanitizer and algaecides we keep in our pools. Brushing the walls, skimmer throats, under ladder treads and around lights and fiberglass steps is a must to prevent biofilm from forming. As these can form on decks and be introduced into the pool it is wise to also periodically use bleach and scrub the deck area as well.
Keep an optimum level of sanitizer in the pool at all times not just when it is being used. This includes the off season of pool and spa use. If a spa is drained there are usually wet surfaces in the pipes that can form a biofilm. The majorities of spas are “wet tested” after manufacture and then may sit for long periods of time before having water introduced for use. This is why many spa manufacturers recommend that the spa is filled, super chlorinated, jets run and spa circulated for a few hours, drained and then refilled. I have found that when this is not done within a couple of weeks the water turns cloudy due to biofilm and cannot be cleared up with conventional methods.
If a pool is winterized the same can happen in the plumbing. Water mold although a different structure uses biofilm to adhere and during these dormant times is easily established. I have found that raising the chlorine to a minimum of 10ppm or more upon pool opening after a winterization has decreased the number of spring water mold and algae complaints. I use this method for chlorine and biguanide pools.
Cleaning of the filter is very important to discourage biofilm as well. If a filter is acid washed only but no degreaser type cleaning done the biofilm will not be removed. [Biofilm: That Gooey Stuff, Connie Sue Centrella]
Brushing of surfaces, keeping sanitizers in the recommended range at all times, weekly chlorine treatment of 10ppm, regular testing, chemical filter cleanings and the use of algaecides and enzymes are the best tools for combating biofilm.
Many pool and spa owners do not want to add more chemicals than necessary for fear of bad chemical implications. It is important to educate these owners that improper chemical levels and poor housekeeping is more of a hazard to their health.
Just like in the movie BioDome when it looked like all life had been destroyed one green leaf of vegetation started growing again. And in pools/spas you may think the biofilm is gone but one microbe that has survived can start the biofilm again.
Research materials used:
Understanding Biofilm in Recreational Water Environments, James J. Miller MS
Biofilm: That Gooey Stuff, Connie Sue Centrella
Understanding and Combating Biofilm, Todd Klueger & Ellen Meyer; Arch Chemicals
Miox Corporation: Biofilm Removal