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ATP – An Index of Fouling and Fouling Rates

A key method to monitor fouling in a water system and the progress of a chemical treatment involves measurement of ATP, adenosine triphosphate, a chemical which is present in all living organisms. Microorganisms are a significant portion of fouling deposits along with other organic and inorganic materials. The ATP method can be used to analyze both surface deposits and bulk water. Although surface fouling is the real problem to be controlled, microbial populations and thus ATP in the bulk water generally correlate with the amount of surface fouling. ATP analysis is rapid and convenient for field work. We highly recommend that ATP testing should be used as part of a water system’s routine monitoring program to assess fouling and fouling rates in the system, and therefore the effectiveness of any chemical treatments.

How ATP testing is used

ATP graph1 ATP graph2 ATP graph3

The three representative figures above demonstrate the value in monitoring ATP concentrations in the bulk water in systems as they are being treated with a chemical. The figure on the left shows typical ATP levels during treatment of a relatively fouled system. Note that after each chemical treatment, ATP levels initially increase indicating that microorganisms that were previously bound to the surfaces in the water system are now being dispersed into the bulk water. ATP levels then decrease as the microorganisms in the bulk water are removed by blowdown or as the cells die and their ATP is naturally degraded. This pattern (ATP increase after application of an effective deposit remover, followed by gradual ATP decrease) will continue until the microorganisms and deposits are cleared from the system.The two figures on the right show ATP levels in a relatively clean system in which an effective chemical treatment is routinely used. Occasional spikes or upward trends in ATP concentration indicate problems and suggest that higher levels of treatment chemical or other modifications to the treatment program be implemented. In addition to analyzing bulk water, it may also be useful to monitor deposit buildup directly by swabbing the surface. Changes in the deposit mass before and after chemical treatment or during routine operation are readily measured by ATP testing. More detailed descriptions of ATP testing to guide operation of industrial water systems can be found in a case history study. It is important to note that different ATP values may be measured for different systems that are effectively under control. The important values are the changes over time. Is ATP increasing or decreasing?


  • Rapid results on-site
  • Detects all bacteria – no bias due to growth media as in other methods
  • Understand operation of your system
  • Be proactive rather than reactive
  • Be in control
  • Predict problems
  • Reduce costs: chemicals, maintenance, downtime