Cooling Water Treatment Problems – How to Control Them

The purpose of a cooling water treatment programme is to control the problems that I outlined in part 2. Sourcing a a water treatment service company that offers a complete range of scale and corrosion inhibitor formulations, biocides and ancillary equipment is imperative to control these problems.

Water Softeners

If the available make-up water is very hard then removal of most of the calcium, which is the principal action associated with scale formation, will reduce the tendency for scale to form. For large systems, treating all the make-up water can be too expensive and may not be required. The softened water can be blended with raw water to provide a suitable make-up water, with a reduced tendency to form scale. Removal of calcium ions is usually carried out using a base exchange water softener.

Base exchange water softeners contain ion exchange resins which, when in contact with water, replace calcium ions with sodium ions. The system is fully automated using very reliable control valves that automatically regenerate the softener, based either on the time in operation or volume of water treated. Time control is usually only appropriate for intermittently operated systems and volume control is most cost effective as the resin is only regenerated when most of its exchange capacity is exhausted. Where soft water is required continuously or there is a large demand, the softener should be a “duplex” design, having two exchange columns such that one is in operation while the second is being regenerated

Chemical Dosing

Control of scale and corrosion is most commonly achieved by using chemical inhibitors. To function correctly, these chemicals need to be maintained at the correct concentration legionella preventie in the system. However, the concentration at which they are dosed to the system has to take account of the concentration factor. Thus in a system with a concentration factor of 4, an inhibitor requiring 100ppm would be dosed at 25ppm in the make-up water. However, even if a system maintains a constant concentration, the volume of make-up water added will vary depending on ambient weather conditions and the load on the system.

Accurate dosing of inhibitors is best achieved using a system that monitors make-up water quantity (usually from a water meter signal) and signals to a pump, the volume of chemical to add.