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Side Stream Filtration of Cooling Tower

Side Stream Filtration of Cooling Tower

Cooling towers scrub large volumes of air and effectively remove solids consisting of dust, microbiological organisms, and various airborne debris. Makeup to the tower adds suspended solids in the form of corrosion products, microbiological growths and wood fibers from the tower, and process leaks. If allowed to settle out, these solids can and do generate many problems within the system. With heavy solids loading, even the best treatment program can be severely strained. Under these circumstances, significant improvement might be realized with the use of a side stream filter.

A proven method to help manage these and other issues surrounding cooling towers is to install a properly designed side stream filter. This can benefit your system through:
  • Reduced Corrosion Rates
  • Increased Equipment Life
  • Better System Efficiency
  • Reduced Maintenance Costs


When to Consider Sidestream Filters
The installation of a sidestream filter is a capital expense, which may be hard to justify in most plants. Consider the following as indications that a plant should look into the possibility of installing a filter.
  • The primary makeup is from an unclarified water source (river, sewage treatment, etc.) that is high in suspended solids and/or iron.
  • The system is having a difficult biological problem even though a good biocide program is in effect.
  • Heat exchangers are opening dirty even though a good antifoulant program is being used.
  • Excessive corrosion rates can be traced to fouling.
  • Loss of heat transfer is attributed to deposition rather than corrosion.
  • High levels of solids are building up in the sump.
  • Heat exchangers require frequent mechanical cleanings.


As stated, these are indicative only. By identifying potential threats to your systems and solutions to those threats, you can determine the paybacks of installing a sidestream filtration system. Often the payback is less time than you would think. This will vary widely from system to system; the final decision will always rest with a plant, and will always be decided on economic grounds.

Sidestream Filter Benefits
Once a problem has been recognized, several benefits can result from the use of a sidestream filter. Obviously, not all of those listed below apply to all systems, and good judgment must be applied before making any claims. However, bearing that in mind, the following benefits can be realized:
  • Since solids are removed from the system, the corrosion inhibitor will lay down its protective film on clean rather than dirty surfaces, thereby reducing corrosion rates and increasing equipment life.
  • When used with good chemical treatment, the filter will keep the system much cleaner, and, as a result, the need for mechanical cleaning of exchangers and sumps is reduced.
  • A cleaner system means better heat-transfer rates for longer periods of time.
  • In some cases, the removal of suspended solids from the circulating water allows higher cycle.
  • Large biological growths and dead organisms are removed with a sidestream filter. This reduces chlorine demand and makes nonoxidizing biocides more effective.