Once Legionella is on a ship, it is impossible to eliminate as long as persistent and ever-present biofilm exists in the piping systems. If control measures, such as chlorination or temperature, fail to be maintained at proper levels for any period of time, dissemination of Legionella can occur. Therefore, the elimination of biofilm is the critical link to prevent or mitigate the presence of Legionella in the ship’s water systems and reduce the risk of potential cases of Legionnaire’s disease.
The MIOX system onboard the Celebrity Century cruise ship has shown positive results in removing biofilm and preventing Legionella. Water supplied to the recreational water facilities has demonstrated a significant difference in biofilm growth among the pipes carrying MIOX-treated water in comparison to the previous bottled chlorine method of disinfection.
For over a decade, De Nora MIOX has partnered with Howell Laboratories Inc. specialists in designing and installing shipboard equipment to bring its mixed oxidant solution technology to marine applications. Together, over 25 U.S. Navy ships have been equipped, including all aircraft carriers and three large cruise liners with MIOX onsite chemical generators.
Feedwater piping at a spa experienced substantial biofilm removal after six days of using mixed oxidant solution. After 22 days of treatment, biofilm was completely eliminated.
Better Legionella Control
The Legionella bacterial group is very easy to inactivate when it comes in direct contact with commodity sodium hypochlorite. However, when there is biofilm in the system, the Legionella behind the biofilm may not get in direct contact with the hypochlorite. These biofilm layers are often established by a bacteria group called Pseudomonas aeruginosa, which are extremely tough to inactivate with hypochlorite alone. In this case, water treatment programs require something more effective, like mixed oxidant solution, that can penetrate the biofilm layer and inactivate the Legionella. As confirmed by third-party studies, such as the study “Disinfection of Simulated Cooling Tower Water,” conducted by Larry Barton, Ph.D., “mixed oxidant solution is shown to be more effective at inactivating Pseudomonas aeruginosa compared to hypochlorite, and therefore is better at controlling Legionella pneumophilia.”