Using Fluorescent Tracers for Cooling Tower Diagnostics - calculating volume.

Fluorescent tracers have long been a valuable tool in Hydrology’s inhibitor chemistry, allowing for quick, on-site testing and enabling real-time monitoring and control of inhibitor levels in water systems.

A common mistake made by many water treatment professionals is estimating the volume of a cooling system solely based on the visible size of the cooling tower.

This becomes particularly problematic when dosing non-oxidizing biocides, which require precise concentrations to be effective over long contact times.

It’s important to remember that the cooling tower itself is just the external component of a much larger cooling system. Cooling towers can vary greatly in size, but without a deep understanding of the production system the tower supports, estimating the true system volume is impossible. Cooling systems can be as simple as a plate heat exchanger or as complex as multiple machines, heat exchangers, cooling jackets with extensive piping.

To treat or shock dose a system effectively, you must first know the actual system volume. This allows for accurate dosing of chemicals to achieve the correct concentration.

In one recent case, we encountered a cooling system with severe biological fouling in its cooling tower packing. Upon investigation, we discovered that the incumbent water treatment provider had miscalculated the system volume. They had been dosing only 1 litre of biocide per dose, when in fact the system required 25 litres.

This underdosing led to substantial biological growth within the packing material, to the point where sections were completely blocked, preventing even water distribution. The situation was so severe that an emergency shutdown was required, and the pack was so heavily fouled that replacement was the only option.




At Hydrology, when system volumes are unknown, we use fluorescent tracers to carry out a diagnostic study. By introducing a known volume of traced chemical into the system, we can monitor the concentration levels and work backward to accurately determine the system’s volume. This method ensures precise chemical dosing, preventing issues like those encountered in the case above.