By Ronald L. Barnes and D. Kevin Caskey

Results from a scientific study performed by a manufacturer at the University of Alabama in Huntsville indicate advanced oxidation processes (AOP) are very disruptive of bacterial biofilms that can be problematic in the plumbing of jetted tubs. Exposing artificial Pseudomonas biofilms to AOP in two physical states yielded very positive results.

This article describes the study in addition to discussing the issue of biofouling within the plumbing of jetted tubs. Also, AOP will be further defined.

Biofouling in jetted tubs
In general terms, biofouling is the accumulation of unwanted microbial growth on an artificial surface. In the case of jetted tubs, this refers to the biofilms or bioslimes known to grow within their plumbing. The combination of bather loading (body oil, perspiration and dead skin cells), pre-existing bacteria or bacterial flora and stagnant water within the plumbing of jetted tubs all contribute to biofilm formation. It is not uncommon for the whirlpool mechanisms of a jetted tub to go unused for days or even weeks, which exacerbates the problem. There is an established correlation between biofilms in jetted tubs and diseases of bathers and individuals in close proximity to the tub. These illnesses include infections of the eyes, skin and lungs. Small children, elderly individuals and anyone with a compromised immune system are even more susceptible to becoming ill.

Biofilms defined
Biofilms are the ultimate issue that must be addressed in relation to the biofouling of jetted tubs; these slimy plaques can form anywhere within the plumbing. A dense and highly adhesive substance produced by individual bacterial cells, biofilms are a natural occurrence in many types of water where adequate nutrition is present, including the circulating water systems of jetted tubs. Biofilms may be thought of as ‘bacterial cities’ where microorganisms shield and protect themselves from the outside environment. They are not just limited to bacteria: fungus, mold and viruses are also associated with biofilms. Their adhesive nature is due to outer sugar chains of the bacteria, which mesh together forming what could be considered the infrastructure for the bacterial city. Biofilms are constructed in a manner that is conducive for optimal nutrient delivery. Water channels are formed that allow nutrient rich water to infiltrate and pass through the biofilm. Water in a jetted tub will typically contain items such as body lotions, perspiration and dead skin cells; it is possible that soap and shampoo might be present as well. These are examples of organic matter, which provide an optimal environment for biofilm formation.

Advanced oxidation processes
Advanced oxidation processes may be defined as powerful sanitizers and oxidizers produced from ozone after a series of chemical reactions. The products of AOP are extremely reactive in nature. This characteristic is what makes AOP extremely effective in attacking and disrupting biofilms as well as killing all the hazardous microorganisms associated with it. AOP can come in an aqueous (water) form and in a gas form. In order to catalyze the reactions needed for conversion of ozone into AOP for this test, a special type of ozone generator called an advanced oxidation processor was required.

Test procedures
To test the effectiveness of AOP against biofilms, a model jetted tub system was set up. Within this system, a biofilm reactor was placed inline. Glass slides coated with artificial Pseudomonas aeruginosa biofilms were placed in the biofilm reactor. These biofilms were made from agarose, which has previously been used in another research project to mimic an actual biofilm due to similar physical properties. The thickness of the biofilms was standardized using microscopic techniques. The agarose solution was mixed with the Pseudomonas bacteria at a concentration of 5,000 cells/mL. One milliliter of this mixture was placed onto a glass slide. Six of these slides were placed into the biofilm reactor and exposed to AOP in three different manners. These three included: ozonated gas (gaseous AOP), ozonated water (aqueous AOP) and a combination of the two. The slides were introduced to the gas form at intervals of 15, 30 and 60 minutes. The water treatment lasted 15 minutes. The combination test consisted of 15 minutes of water treatment followed by 15 minutes of gas treatment. This cycle was repeated following a 30-minute pause. The results of these experiments are listed in Figures 2, 3 and 4.

(Part 2 will appear in WC&P, April 2007.)

About the product
The product tested was Prozone’s Advance Oxidation Hybrid Generator, which forces ozone to react via a free radical pathway with activation by UV radiation. The model PZ6-CT, tested and discussed here, is manufactured by Prozone Water Products, located at 2610 6th Street, Huntsville, AL 35805. For more information visit the company’s website, or contact the sales department at 1-800-632-6462.

About the authors
Ronald L. Barnes is founder and CEO of Prozone Water Products Inc. (established in 1977), Ecozone (founded in 1984) and Vistek Corp. (started in 1984). He has a Bachelor’s Degree in physics and a Master’s Degree in physics and electronic engineering. A successful consultant, (International Ozone Association, NASA, ASHRAE, The National Pool and Spa Institute, GE, Boeing and Lockheed), Barnes is a member of the International Ozone Association and several related organizations. He holds 10 patents for ozone water treatment, ozone generators, plasma generators, optical storage scanners, electrophoresis, laser Doppler radars and an ozone contact lens cleaner. He can be contacted at (256) 539-4570 or

D. Kevin Caskey is a Project Manager and microbiologist for Prozone Water Products. He holds a Bachelor’s and Master’s Degrees in microbiology. Prior to rejoining Prozone, where he was originally a Project Manger, he worked at Vanderbilt University in Nashville as a Lab Manager while conducting his own research projects. He can be reached at (256) 539-4570 or


Comments are closed.