How UV disinfection works
Before we go into why UV disinfection works poorly, let us take a look at how it works. UV emits energy which is absorbed by bacteria and viruses. The energy absorption leads to a chemical transformation that inactivates the bacteria and viruses. However, bacteria and viruses are able to repair the damage and hence reactivate. Additionally, only the bacteria and viruses that are in direct contact with the UV light are deactivated. Since no substance is dissolved into the water, there is no residual effect on the other bacteria and viruses.
The point of use problem
Since UV light allows bacteria and viruses to grow in pipes and tanks with no UV light exposure, it is not enough on its own to purify water down to drinking purposes. It is normally combined with chlorine, which has a residual effect and can kill bacteria and viruses in the whole water system. A ship that uses water dispensers can install a UV filter at each dispenser while also dosing chlorine into the water tanks. This ensures safe drinking water, but there are still a few problems to consider.
The biofilm problem
UV and chlorine are not effective at removing biofilms in tanks and pipes. Biofilms are consortiums of microorganisms that could be responsible for brown and sludgy water. Additionally, they make it suitable for Legionella bacteria to grow. For this reason, a ship that employs a system consisting solely of UV and chlorine is vulnerable to Legionnairres' disease. In the worst-case scenario, this puts the crew members’ lives at risk.
Another problem is that an additional filter is required before the UV filter at the water dispensers. This filter fills up with brown sludge, and then the crew members have to clean the filter. They will then discover that the water they are drinking is filled with brown sludge, which will create distrust. Most of the crew members on ships are used to bottled drinking water and have a cultural distrust for tap water. As a result, they might refuse to drink water from the dispensers.
The Waterworks biocide system solves both of these problems. The biocides both remove biofilms and have a residual effect causing the whole water system to be free of biofilms, bacteria and viruses. Read more about our service or contact us for more information.