Chemical-Free Cooling Water Treatment with the PeroxEgen™ H₂O₂ Generation System

Highlights:

• Controls growth of vegetative or slime-forming organisms that lead to fouling
  
• Reduces the costs of cleaning fouled heat exchangers and circulation lines
  
• Requires only water, air and electricity
  
• Improves efficiency to reduce water and power consumption, and reduce microbial emissions

Treating cooling tower water for microbial growth control can help reduce the costs of cleaning fouled heat exchangers and circulation lines. Controlling biofilm growth is very important in minimizing direct biological corrosion of surfaces as well as indirect corrosion caused by metabolizing corrosion inhibitors. Effective treatment also reduces inherent occupational hazards of exposure to infectious and pathogenic bacteria (such as Pseudomonas aeruginosa and Legionella pneumophila) and extremely high bacterial counts (>106 CFU/mL) in cooling tower blowdown.

More Efficient Cooling Tower Operation
Eltron Water has developed a flow-through cooling tower water treatment system that includes PeroxEgen. PeroxEgen, a turn-key, mobile electrolytic technology available from Eltron Water Systems, generates H₂O₂ on-site for a variety of water treatment, advanced oxidation, and cleansing applications. PeroxEgen requires only water, air, and electricity as
consumables for water treatment and allows pH to be controlled for a variety of applications. PeroxEgen can be operated in flow-through mode for direct treatment at low H₂O₂ concentrations (<100 mg/L) or in batch mode, recirculating H2O2 to build up higher concentrations. Unlike bulk catalytic production methods, Eltron’s electrolytic process is virtually insensitive to temperature.

H₂O₂ delivered by PeroxEgen has been shown to be effective for controlling growth of vegetative or slime-forming organisms that lead to fouling such as algae (Chlorella vulgaris, Nannochloropus) and bacteria (species of Pseudomonas, Staphylococcus, Enterobacter). The flow-through treatment process is compatible with the pH range (pH 6–8.8) and compatible with many common corrosion inhibitors including molybdate and phosphates. Side-stream injection concentrations of H₂O₂ (<10 mg/L) are well below the corrosive levels of dissolved oxygen and biological organisms.

Several species of Pseudomonas, such as P. cepacia, are especially problematic. They readily become resistant to
chlorine and other halogen-based disinfectants. These species were found to be killed with low levels of H2O2. Fungi
(Candida, Aspergillus), spores and especially spore-forming bacteria (Bacillus, Clostridium) have much higher resistance to antimicrobials. The use of low H2O2 concentrations against C. albicans, A. niger, and B. subtilus (a thermophile) was also found to be effective, depending on treatment conditions.

While H₂O₂ serves as a biocide, it also releases bubbles of oxygen as it is consumed. Gas bubbles generated at fouled
surfaces enhances turbulence and the cleaning action to break up biofilms, and even scale, on heat exchange surfaces.
The result is more efficient cooling tower operation, which translates into less water consumption, lower power
consumption, and reduced microbial emissions.

Simplifying the Logistics of Handling H2O2
Current methods for generating H₂O₂ require large, centralized industrial facilities. H₂O₂ has to be distributed by
truck or rail. Transportation, handling, and storing concentrated H₂O₂ (50%–75%) creates a number of hazards, and meeting the associated regulations imposes more capital investment. Distributing H₂O₂ to remote locations potentially creates significant liability for distributors and increases costs for isolated water treatment and environmental remediation operations. All of these issues are hurdles that have made H2O2 use less common or impractical.

Eltron’s PexoxEgen technology provides a different method for H₂O₂ delivery – at the point of use, simplifying the logistics, eliminating distribution costs, and minimizing hazards associated with handling and storage. There also are no
known regulatory issues for this source of H₂O₂ since the feedstocks are only water and air, and the H₂O₂
concentrations produced are relatively low.