• Andrew Baker

Cooling Towers Need Fine Filtration

A cooling tower evaporates water in order to cool the water, with important results:

  1. Air drawn into the water breaks it up into small droplets. This evaporates the water faster but also draws very small airborne particles into the water.

  2. The dissolved minerals in the water concentrate as the water evaporates. The TDS (Total Dissolved Solids) increase, concentrating until they become suspended solids. These suspended solids are also very small.

  3. The process of pumping the recirculating water and any corrosive bi-products also add to the small particles in the cooling water.

Almost all the suspended particulate in a cooling tower is below 5 micron in size. The NuStream Filtration CT 70 filter removes 99% of the particulate by using a surface-scrubbing design that allows ultra-fine sand to be used for filtration. Sand filters and multi-media filters that only remove particulate down to 10 microns do not remove the real particulate load in cooling systems. Centrifugal separators that remove particulate down to 44 micron don’t even come close. It is clear that a high efficiency submicron filter like that NuStream Filtration CT70 is the best answer for proper cooling tower filtration.


Click here to view a particulate distribution analysis comparing a cooling tower system's water before and after high efficiency filtration. The initial data shows that nearly all particulate is smaller than 5 microns. The second part of the analysis shows the water after the CT 70 filter has operated for 3 weeks as a side stream filter treating 3.5% of the recirculation flow: 99% of the particulate has been removed.

Generally, the filter is designed to provide side stream filtration of 3%-5% of the flow. If you don't know the recirculation flow, it can be estimated by muliplying the tower(s) cooling tonnage by 3.

The water treatment professional that is treating the water to control corrosion, scale formation and microbiological growth, will appreciate the particulate elimination. Particulate that interferes with their treatment regimen and particulate that combines with biofilm to interfere with heat transfer.

In summary, nominal submicron filtration improves cooling tower operation.

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NuStream Filtration

1257 Stanley Avenue

Dayton, Ohio 45404