Legionnaires disease is back in the news. It is caused by the legionella bacteria. The disease is most commonly spread by dirty cooling towers. The legionella bacteria grows in dirty tower water, and is transported to the surrounding area in the mist droplets leaving the tower. When someone breathes in water mist contaminated with legionella, they may contract a pneumonia that can kill people in a few days.
The good news is that this is relatively easy to prevent by simply keeping the cooling towers clean. Normal tower water maintenance will prevent the legionella from growing in the tower in the first place. If you have ever had a back yard wading pool for the kids, you know how quickly water left outside can develop slime – literally in a couple of days. Now think how quickly stuff can grow in water that is being heated, as in a cooling tower. Cooling towers need constant maintenance to stay clean.
This can be done by testing the water weekly and adding chemicals as needed, or by using an automated chemical feed system. Even with an automated system, the water should be checked monthly to insure everything is working properly. Every building that uses a cooling tower should have someone on staff or contracted to keep an eye on the water condition. Some chemical salesmen will perform this service in exchange for buying all the chemicals from them. Obviously, the cost of their service is built into the price of the chemicals. In general, you want to maintain a slightly acidic ph to discourage calcium deposits and critter growth.
Another reason to keep your cooling tower clean is that the same water circulating through the tower is also circulating through your condenser. A coating of green slime inside your condenser will insulate the condenser from the water passing through, reducing system efficiency. This translates into higher operating cost. You are not saving money by skipping cooling tower maintenance, you are spending it on increased system operating cost. Here are a few links with more details on cooling tower maintenance.