Cooling towers scrub large volumes of air and effectively remove solids consisting of dust, microbiological organisms and airborne debris. Makeup water 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, 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 sidestream filter, according to U.S. Water Services in St. Michael, Minn.

The company explores the advantages and benefits from sidestream filters in an article on its website, noting that the process is a proven method to help manage water issues surrounding cooling. U.S. Water says sidestream filtration can benefit a water system through:
  • Reduced corrosion rates.
  • Increased equipment life.
  • Better system efficiency.
  • Reduced maintenance costs.
  • Better chemical control.
The installation of a sidestream filter is a capital expense that may be hard to justify, but U.S. Water suggests that the following questions about the existing system be answered as part of the decision-making process:
  1. Is the primary makeup from an unclarified water source (river, sewage treatment, etc.) that is high in suspended solids and/or iron?
  2. Is the system having a difficult biological problem even though a good biocide program is in effect?
  3. Are heat exchangers opening dirty even though a good anti-fouling program is in use?
  4. Can excessive corrosion rates be traced to fouling?
  5. Is loss of heat transfer attributed to deposition rather than corrosion?
  6. Are high levels of solids building up in the sump?
  7. Do heat exchangers require frequent mechanical cleanings?
For more on sidestream filtration and information on the filter media, go to