Side Stream Filters

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Cooling towers, by design, serve as the world’s finest air scrubbers. As part of the cooling method, these systems flush airborne contaminants into the cooling water system, where they deposit on heat exchange and condenser surfaces. Suspended matter in the cooling water also provides living microorganisms with a constant food source for sustaining life and multiplying.

Implementing a permanent medium filtration system can effectively remove these contaminants before they increase the operating costs of water-cooled equipment or cause system shutdowns. When combined with chemicals, constant side-stream filtration leads to a much cleaner system, with the chemicals ensuring ongoing suppression of microorganism growth.

Cooling water system treatment programs must address four specific control parameters for successful equipment protection: Scale, Corrosion, Biological fouling, and Airborne contaminants. Airborne dirt impacts scale control, corrosion, and biofouling, and it remains the only factor that cannot be measured accurately. No one can predict the direction of the wind or what it will carry and deposit into the system.

With side-stream filtration, a portion of the water is filtered continuously, ensuring that the entire system is filtered every 24 hours. This method works on the principle that continuous particle removal will keep the system clean. The filtration objective is to eliminate fine dirt, dust, smoke, and organic particles that accumulate in the water.

The most effective filter system for cooling towers and process water is a permanent medium filtration unit, which requires minimal attention or maintenance. The filtration medium should be finer than 50 microns to effectively capture the average airborne contaminant. Key features to seek in filter systems include self-cleaning capabilities, simplicity, compactness, and ease of operation. Additionally, screens with pore sizes down to 15 microns are vital for consistent filtration and a short manual/automatic backflush cycle.

Typically, a side-stream representing about 3-20% of the total recirculated flow is adequate for sizing purposes. For example, a circulation rate of 6000 m3/hr would require a 180 m3/hr side-stream filter. Properly sizing the filter to manage these flows ensures that the entire capacity of the cooling tower is cleaned once every 24 hours.

In summary, when you consider all the benefits, investing in permanent side-stream filtration combined with chemicals pays for itself in less than two years. No water-cooled equipment, especially cooling towers, should operate without this essential filter and chemical combination.