Sanitizer residual
First and foremost, maintain a sanitizer residual in the pool or spa at all times. The ideal range for chlorine disinfection is three to five parts per million (ppm). Pool and spa operators should pay close attention to sustaining this residual, either through manual testing and/or automatic chemical feed control systems, with constant monitoring.
While the sanitizer residual must be constant in all parts of the pool, close attention should be paid to coves and dead zones. In addition, daily brushing must be performed on the tiles, walls and floor, as biofilm tends to attach to these sites (particularly to walls). By brushing these surfaces, the biofilm, containing algae spores, will detach and be released into the water, where it can be more easily killed by disinfectants and algaecides.
Filtration system cleaning
Improving water quality also requires a thorough cleaning of all the filtration systems with an efficient backwashing of sand filters. Degreasing of cartridges and diatomaceous earth (DE) grids must first be performed using tri-sodium phosphate; mere acid washing will not eradicate the biofilm.
As such, chemical cleansing of the filter systems is highly recommended. Dupont’s Roy D. Vore, PhD, a member of the Disinfection and Water Quality task force for the CDC Model Aquatic Health Code (MAHC) suggests, “The use of alkaline cleaners containing either bleach or quats will reduce biofilm; however they do not result in total kill.”
Other treatments
Ozone works effectively to destroy biofilm by rapidly cutting through the gelatinous biofilm bond. Once the biofilm breaks loose, the free-floating bacteria can be trapped in the filtration system or eradicated with chlorine sanitizers.
Additional recommended biofilm control tactics include the addition of surfactants and chelants, weekly shocking with 10 ppm of free available chlorine and use of enzymes (Klueger & Meyer).
Staying ahead of biofilms
Industry professionals are encouraged to learn from the many recent studies being performed by chemical manufacturers. For example, at the 2009 World Aquatic Health Conference (WAHC) in Atlanta, James J. Miller of Micronanosun Technology Group LLC, discussed his study on biofilm and the Legionella phenomenon. His findings included details on how biofilms are established and why they are difficult to control. He also discussed public health implications and concerns and offered some recommendations to the industry.
It is the duty of all pool and spa professionals to maintain safe and healthy swimming venues. Staying up to date on research—and ahead of biofilms—by adding effective, regular maintenance recommendations is the right thing to do, as it will help protect bathers, improve water quality and reduce RWIs.
Readers are invited to express their views, their experiences and additional comments on the issue of biofilm through email ccentrella@keiseruniversity.edu.
Thanks to the following for their expertise and input into this article’s research:
- Roy Vore, PhD, and Ed Lightcap, DuPont;
- Todd Klueger and Ellen Meyer, PhD, Arch Chemicals;
- James J. Miller, Micronanosun Technology Group LLC;
- Beth Hamil, DelOzone;
- World Aquatic Health Conference;
- National Swimming Pool Foundation; and
- Montana State University, Center for Biofilm Engineering
Connie Gibson Centrella, MBA, is professor and program director for the online Aquatic Engineering Degree Program at Keiser University eCampus, as well as director of education for Team Horner and a member of the National Swimming Pool Foundation (NSPF) Education Committee. She is also a sustainability officer, having been certified in the principles of green and sustainable business practices. Centrella, five-time recipient of the Evelyn C. Keiser Teaching Excellence Award, is celebrating more than 40 years in the pool and spa industry.
