Side Stream Filtration for Cooling Towers and Their Advantages

In various cooling towers, usually plenty of air is used to get rid of various solid particles like dust, microbiological organisms and many other airborne debris. If these gets settled in the cooling tower then it can create problem in the cooling tower.

Therefore, there is a necessity of suitable filtration of water during cooling water treatment so that the cooling plant can work efficiently.

As a proven method, side stream filters are often used however the cost of such arrangement can be quite high.

When you must consider side stream filters?

While installing any side stream filter one must consider return of investment, as it is a big capital expense and therefore for any company, it is necessary to obtain the approval from their senior authorities.

It is therefore necessary to look for following important indications so that the plant can really feel the necessity of installing a filter before making the real investment.

  • The entire primary make-up should be from any unclarified water source like river or sewage treatment, etc. which is very high with suspended solids or iron.
  • Even though there is good biocide program available but still the system has quite difficult biological problem
  • Even though there is good anti-foulant program available but still heat exchangers are constantly showing fouling
  • Often excessive corrosion rates are traced to fouling.
  • Heat transfer loss is attributed due to various deposition instead of corrosion.
  • In the sump, high solid levels are building up.
  • Heat exchangers need frequent mechanical cleaning.

Few benefits of using any side stream filters

By using any side stream filter, you can obtain several benefits.  Obviously, all the benefits that are listed below may not apply to all kind of systems, and therefore one has to use their own judgment before making the claims.

However, keep in mind, that following are few of the benefits that can be realized from side stream filters:

  1. As solids will be removed from your system, hence the corrosion inhibitor can protect clean and no dirty surfaces will be there thus reducing rate of corrosion and also increase equipment life.
  2. If the filter is used with any good chemical treatment, then filter will maintain the system cleaner, and therefore, the need for any mechanical cleaning of the exchangers and sumps will be reduced and maintenance costs will reduce.
  3. Having a cleaner system would mean better rate of heat-transfer and longer duration which will end up with lower operational cost.
  4. The removal of any suspended solids in few cases, from circulating water will allow higher cycles that leads to reduced membrane exchange and also maintenance cost.
  5. Dead organisms and large biological growth will be removed with such side stream filter.  It can also reduce biocide demand and make non-oxidizing biocides much more effective.


For control of fouling and deposition in cooling water system, side stream filtration will be an effective tool.  Therefore, before making capital investment, its use must be carefully considered.

For good engineering practice, it should however not just be used as substitute or a good operational program.

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