Slimy Cooling Tower

My cooling tower looks slimy.

Here’s why: Algae and fungi have built up in your system.

So what: Slimy masses not only look revolting, they bind foulants and clog systems, too. Algae and fungi cause extensive plugging and fouling of heat exchanger tubes, water lines, tower spray nozzles, distribution pans, screens, and fill. Microbiological fouling also contributes to under-deposit corrosion as well as the growth of corrosion-causing bacteria.

While changes in pH within the range of 6 .5–9 .5 do not significantly affect microbial growth rates in cooling water treatments, water velocity does. In areas of low velocity, such as in shell-side heat exchangers, debris can settle out and provide favorable conditions for microbial activity. Underfeeding a biocide can rapidly lead to rebounds in the population of microorganisms and not provide sufficient kill to ensure adequate control. In addition, removal of the biofilm on system surfaces is critical to prevent health hazards and the potential for corrosion.

How we fight: Controlling microbiological fouling depends upon effective control of water quality which can be compromised by organic contaminants (such as oil and grease), fertilizers, food products and by- products, dust and silt from the air, leaves and suspended solids.

Buckman, based on an integrated approach, will act on one or all the following strategies to inhibit biological growth. The advanced chemistries and control tools we use to decimate microbial populations can be grouped into four general classes based on their mode of action:

  • Oxidizing biocides—these break down organic substances and kill microorganisms, including bacteria, in cooling waters
  • Non-oxidizing biocides—these control microbiological activity by interfering with cell structure and function
  • Biodispersants—these break up and disperse deposits, such as slimes and biofilm Chlorine and bromine are oxidizers often used to control microbiological activity. In many cases, bromine can be more effective than chlorine gas. A process called Target Bromination uses sodium bromide and a safe, easy-to-handle source of chlorine, such as industrial sodium hypochlorite, to rapidly produce hypobromous acid instead of the hypochloromous acid produced using chlorine gas. Benefits include:
    • Stability under alkaline conditions
    • Efficacy against a wide variety of biofoulants
    • Rapid reaction rate
    • Reduced corrosivity to system metallurgy
    • Reduced fouling potential
    • Lower environmental impact
  • Low oxidizing chemistry—In systems with high organic demand, both chlorine and bromide become less effective and, because more has to be used, less cost efficient. In this situation, an alternative low oxidizing chemistry, such as Oxamine®, can be used. Unlike bromine and chlorine, its oxidative strength is low enough that only minimal amounts react with extraneous organic matter in cooling water, making it more effective at disrupting microbiological activity.