Biocides are needed for chemical water treatment of a cooling tower. There are two main types of biocides, oxidizing and non-oxidizing, each is more effective at eliminating a specific type of bacteria.
Cooling towers provide the ideal conditions for biological growth; this can include harmful bacteria with a health risk, such as Legionella. It can also cause dirty cooling towers with fouling and biofilm, reducing efficiency in the cooling tower. This article will discuss the role of biocides in cooling tower water treatment and cleaning.
Using biocide in your cooling towers controls bacteria and other microbial growth. There are two main classes of biocide:
The difference is found in how the chemical attacks and kills bacteria.
Oxidizing biocide kills bacteria through the electrochemical process of oxidation, where the biocide gains an electron from the bacteria, and this electron loss essentially kills the bacteria. Oxidizing biocides are typically made up of chlorine or bromine, and these halogens are the oxidizing agents disrupting the biological cell. Oxidizers are generally most effective in systems that have high water usage. This biocide class includes chlorine, chlorine dioxide, hydrogen peroxide, bromine, and ozone. Chlorine and Bromine are the most widely used cooling tower biocide chemicals.
Chlorine is relatively inexpensive compared to other biocide treatments available. As such, it is also the most common biocide used in cooling towers. It consists of 12.5% sodium hypochlorite. Additionally, it is corrosive and can degrade when it comes into contact with sunlight.
Bromine is considerably more expensive than chlorine. However, it does not have the same intense corrosive properties. Additionally, you can purchase bromine in solid forms, often as bromine tablets. It typically comes in a formulation of 16% hypobromous acid. Lastly, at high pH levels, the effectiveness of bromine is greater than chlorine.
There is a wide variety of chemistry related to non-oxidizing biocides. Non-oxidizers are typically used on a prescriptive basis and introduced when there are special challenges with the water relative to the particular biological growth, the quality of the water, the pH, discharge limits/toxicity, metallurgy, and chemical safety. This biocide class includes DBNPA, Isothiazolinone, Glutaraldehyde, and Quaternary Ammonium. Two of the most effective and widely utilized biocides are DBNPA and Glutaraldehyde.
DBNPA is a non-oxidizing biocide that acts quickly. It is formulated from 2,2-dibromo-3-nitrilopropionamide. It has an ideal pH range of 4-8 for effectiveness. It comes in liquid or solid/tablet form.
Glutaraldehyde is a widely used non-oxidizing biocide. It is effective at varying pH levels. It is non-foaming and is more widely used than DBNPA.
Bacteria and microorganisms cause a host of problems that require cooling tower biocide water treatment to resolve. Biocides can treat:
With the right cooling tower biocide water treatment, you can continue to run a cost-effective and energy-efficient operation.
Cooling tower biocide plans vary based on whether you use a non-oxidizing biocide or an oxidizing biocide. Oxidizing biocides destroy an organism’s cell walls almost immediately, and the protein in the cell undergoes a chemical reaction with oxygen. This process effectively kills the bacterial organism with constant feeding. Oxidizing biocides are cost-effective and fast-killing compared to non-oxidizing biocides.
In contrast, non-oxidizing biocides need a high concentration for long periods to kill bacteria. Though they are more costly than oxidizing biocides, they do not require constant feeding and remain in systems longer.
Of course, biocides are only effective if they come in contact with the bacteria within the system. Ensuring proper contact time and adequate dosage in the system is vital to keep bacteria under control in your tower.
Oxidizing biocides typically take a couple of hours of contact time at a specific dosage, while non-oxidizing biocides should remain in the system much longer. Other factors that inhibit biocide effectiveness include dead legs (areas of stagnation) in the piping, off-line pumps and filters, and areas of low flow. These are the main reasons why biocides would not be working in your cooling tower.
Deciding what biocide to use in your system is only part of what it takes to maintain a clean system. There is also a multitude of control measures that should be clearly outlined, communicated, and validated in a well-constructed Water Management Plan (WMP).
If you need help with algae, bacteria such as Legionella, fouling, etc., then contact Chardon Labs for fast, reliable cooling tower biocide treatment! We can be reached by filling out a quick contact form or by emailing sales@chardonlabs.com.
