Industrial cooling water systems benefit from pure water in much the same manner as boiler systems, though the ROI is often more difficult to quantify. For example, cooling tower systems use blowdown as a means to control the solids level in system water. Using a higher degree of purity in the make-up water results in a reduction of water volumes (incoming water and discharge water). Also, since cooling water is chemically treated, a reduction in blowdown leads directly to chemical savings. Energy gains can be realized by the improved heat transfer efficiency of a clean system. Since the cooling system water is not heated, the energy gains present from reducing blowdown volume, often significant when evaluating a boiler situation, are not applicable in a cooling system evaluation. Also, the finished water quality in a cooling system application is not as stringent as that in a boiler application. In cooling towers, a water treatment system that goes beyond single-pass RO is seldom justified.
Most industrial cooling systems present specific water treatment challenges that are not present in boiler systems. Primary among these challenges is the fact that the water is typically at an ideal temperature to promote microbial growth. Moreover, unlike closed boiler systems, most cooling systems are open to the atmosphere. This allows dust, other solids, and even microorganisms to enter the cooling tower. These soil loads vary seasonally, and result in either the direct establishment of microbial colonies or act as nutrients for these colonies. To control this growth, anti-microbial chemicals are added to the cooling system water. If the level of suspended solids in the water reaches a critical level, the chemicals become exhausted before they effectively reduce the microbial counts. A simple and cost-effective method for controlling the suspended solids load in cooling systems is the installation of a media filter on a slip-stream of the cooling tower. In this manner, a sand filter can provide an excellent ROI in chemical savings alone.