There are two types of chlorination for cooling towers: shock chlorination and chlorine water treatment. Shock chlorination involves feeding a high concentration of chlorine into the tower, usually in response to Legionella or high levels of bacteria. Chlorine water treatment involves the regular feeding of chlorine to maintain low levels of bacteria and biofilms, which can control Legionella before it reaches dangerous levels.
Shock Chlorination Steps
Online or Offline- The tower can remain online during a chlorination; it would only need to be offline if you are doing a physical cleaning of your cooling tower as well. If you decide to clean your cooling tower, chlorinating beforehand will make the cleaning process quicker.
Testing-For expert sampling, testing, and remediation services for Legionella and bacteria in cooling towers, get support now from Chardon Labs. Our service managers are certified to ASSE 12080 standards for Legionella water safety and management. It is important to test both bacteria and Legionella in your cooling tower. You should test before chlorination to see how severe the problem is, and after to make sure it has been remediated. There are two main tests you can take: culture spread plate and nucleic acid amplification (qPCR). A reasonable range for Legionella in a cooling tower is less than 10 CFU (certain colony-forming units) per mL. For genomic units (GU), 5 × 10³ GU/L is considered a reasonable range. Anything above these ranges generally requires action.
Culture spread plate testing involves a (CFU)/mL and takes 1-2 weeks. It can detect trends and is able to tell that the bacteria are alive. It may require more skill to effectively test.
Nucleic acid amplification testing (qPCR) can be performed quickly, generating results in less than 48 hours. It is measured in GU. A downside of this sort of test is that it cannot tell if the bacteria are dead or alive, as it does not measure growth.
Chlorine Concentration- The amount of chlorine chemical you will use for shock chlorination will be significantly more than the standard amount of chlorine used for regular water treatment. You will want to reach a certain concentration of “free chlorine”. This is the amount of chlorine present in the water that has not been bound yet; it is able to actively kill bacteria and biofilm. You will want at least 10 ppm of free chlorine present in the system for an hour as a minimum for small amounts of bacteria, and 6 hours for larger amounts of bacteria and positive Legionella tests.
Routine Chlorine Water Treatment Steps
Your cooling tower needs routine water treatment. There are several types of chemicals to fight common issues, for Legionella and bacteria, biocides are used. Biocides kill microorganisms, both aerobic and anaerobic. Chlorine is an oxidizing biocide, best used to kill aerobic bacteria like Legionella. Chlorine is one of the most common chemicals used due to its high effectiveness and relatively reasonable cost. Here are the two most important steps to effectively use chlorine to treat your cooling tower water:
Equipment- There are many parts that can make up an effective “chlorination system.”
Pumps are the most common way to feed chlorine into a cooling tower. Ideally, the pump will have a meter as well, so you can be sure you are feeding the correct amount of chlorine. Two common types of pumps are diaphragm pumps and peristaltic pumps. A diaphragm pump works by the diaphragm (membrane material) moving and filling up a chamber. A valve will then control the flow of the chemical. A peristaltic pump compresses a flexible tube that moves liquid from its source into the cooling tower. These are low-maintenance; the tubing is the only thing that requires regular replacement. These types of pumps cannot handle the types of pressure that a diaphragm pump can.
Controller equipment is useful to automate chemical feeding, connecting to your chemical feed pump. It is useful for controlling, measuring, and timing your chemicals. In addition to this, it can be useful to generate maintenance reports. Ideally, it would be set up for remote monitoring, allowing you to control it wirelessly from any location.
Storage of chlorine involves a barrel or pail, typically depending on the application. A pail could have a small amount of chlorine chemical and is typically 5 gallons. It could also contain chlorine tablets. Meanwhile, a drum would contain 55 gallons of chlorine chemicals. Labeling is important when it comes to cooling tower applications, so make sure you only use chlorine designated for use with a cooling tower, not just consumer-grade mislabeled chlorine. This is due to legal implications with the EPA.
Chlorine Chemical Program- Your chlorine chemical program should be substantially easier to operate and monitor with the right equipment installed. When it comes to normal operation, the concentration of chlorine needed in the water will be much less than a shock chlorination. Just .2 to .5ppm of free chlorine is needed in the cooling tower water for it to be considered treated during normal operation. The amount of chlorine needed to be regularly fed will depend on several factors, such as the makeup water quality, pH, other chemicals, bleed amount, tested bacteria levels, etc.
Cooling Tower & Legionella Services
Chardon Labs offers cooling tower treatment and Legionella testing/remediation in 14 states: Delaware, Illinois, Indiana, Kentucky, Maryland, Washington, DC, Michigan, New Jersey, New York (NYC Only), Ohio, Pennsylvania, Tennessee, West Virginia, & Wisconsin. We perform both routine cooling tower chlorination treatment and Legionella shock chlorination. If you need help, send us a quick message.
Matt Welsh
Matt Welsh is the Vice President and Water Consultant at Chardon Labs. He helps consult a wide range of customers utilizing various methods of water treatment, from chemical to chemical-free approaches, large and small applications, and across a wide range of geographical influences. With 20 years of water treatment experience, including a wide range of troubleshooting and service in potable water and non-potable HVAC and industrial applications, he is an expert in water treatment chemistry for cooling towers, boilers, and closed-loop systems.
