What is ATP and how does ATP monitoring work?

ATP (Adenosine Triphosphate) is the primary energy carrier for all forms of life – bacteria, algae, vegetable, animal cells – all of them contain ATP. As such, the measurement of ATP concentration in a sample provides a direct measurement of biological concentration and health.

ATP is quantified by measuring the light produced through its reaction with the naturally-occurring firefly enzyme Luciferase using a Luminometer. The amount of light produced is directly proportional to the amount of ATP present in the sample. The following formula below shows the reaction that occurs with ATP in the presence of Luciferase enzyme:

formula - science of atp monitoring

Within any water sample, there will be two types of ATP:

  • Intra-cellular (or just Cellular) ATP (cATP) – ATP contained within living biological cells.  If desired, a conversion factor can be applied to approximate an equivalent microbial count*.
  • Extra-cellular (or Dissolved) ATP (dATP) – ATP located outside of biological cells that have been released from dead or stressed organisms.

The sum of these two types of ATP is referred to as Total ATP (tATP). The way that these types of ATP are isolated and measured depends on the application and thus the test protocol used:

  • For applications such as drinking water, cooling towers, or oil & gas applications, Cellular ATP is measured directly by filtering the sample to separate and measure cATP on the filter, while the dATP passes through the filter and is not measured.  cATP provides a direct indication of living biomass energy level, or in other words, total living biomass concentration.
  • For applications with non-filterable samples such as wastewater treatment, paints, or solid samples, we measure tATP and dATP separately with cATP being calculated as tATP minus dATP.  In some cases, a tATP measurement alone may be sufficient.

Want to learn more about how our solutions work?  Check out these brochures:

*Assuming that the average bacteria cell contains 1 femtogram (fg) of ATP (1fg = 10-15g).

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What is LuminUltra’s solution?

As described above, it is important to accurately measure both types of ATP as well as differentiate between the two types to get a true assessment of microbial activity and health.

LuminUltra’s microbial monitoring solutions involve more than just simple test kits. Our solutions combine revolutionary 2nd Generation ATP® testing methods with robust & portable equipment, and now cloud-based analytics plus extensive application experience via LuminUltra Cloud. All of this together provides you with a solution tailored to your specific needs.

It all starts with a rapid and portable measurement of the total microbiology in your sample. To do this, you need three things:

  • A test kit that measures the microorganisms, such as LuminUltra’s 2nd Generation Adenosine Triphosphate (ATP) test kit. Test kits are the heart of our solutions, and have been engineered to be the best-in-class balance of ease-of-use and accuracy available on the market today.
  • To get these results, you need to have a luminometer such as our PhotonMaster™ – a sensitive light-measurement device. Just getting results, however, is only half the battle.
  • You then need to interpret and act upon those results to truly achieve control through software. LuminUltra Cloud™ helps you achieve and stay in control through smart interpretation and analytical tools that are easy to use by anyone.

Through combining these products, you will have a true total measurement of all microorganisms contained in your sample within just a few minutes. Having rapid information allows you to take action at the earliest possible moment, thus saving time and money in the battle against microorganisms.

I already test for microorganisms… Why do I need this?

LuminUltra’s solutions are based on its patented 2nd Generation ATP measurement system. This style of testing represents a major upgrade over other microbiological tools for four primary reasons:

  • Fast – providing results within minutes of sampling.
  • Simple – for anyone to routinely apply and to take action from results.
  • Accurate – measuring 100% of the microorganisms 100% of the time.
  • Reliable – in the lab or in the field, backed by our highly-knowledgeable support team.

Microorganisms come in many shapes and sizes – there are millions of different types that we know about so far, and scientists are only scratching the surface!

Being in control of microorganisms in water generally starts with controlling the total population through the use of treatment mechanisms like filtration or disinfection, both of which are broad-spectrum treatments that target everything living in your process.

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2nd Generation ATP


Heterotrophic Plate Count





2nd Generation ATP

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1st Generation ATP




2nd Generation ATP

comparison - gen 2 atp_grey_hi res

Suspended Solids

comparison - turbidity



How does 2nd Generation ATP compare?

There are three types of indicators that have traditionally been used to ‘count’ the total microorganisms in a given water sample:

  • Heterotrophic Plate Count (HPC) – sometimes referred to as Total Plate Count, Total Count, or Total Flora. This test method is often thought of as a means for measuring the ‘total’ population. However, the scientific community knows today that they underestimate the total microbiological population by only counting a fraction (0.1 – 1%) of the true total microorganisms. That means 99 – 99.9% of the total fraction goes undetected, not to mention that acquiring results takes at least 24 hours, which means relying solely on this measurement results in reactive problem solving.
  • 1st Generation ATP– these tests have been commercially available for many years as a means of providing a qualitative “pass/fail” determination of surface cleanliness, and have been successfully applied in food and medical surface hygiene fields. However, these products have limited capabilities when it comes to water samples because of their low sensitivity (meaning they cannot measure low enough in water systems), propensity for false negative bias, and lack of quantitative results. So while they measure ATP – just like LuminUltra’s 2nd Generation system – they are not quantitative and hence are unreliable when used in water applications.
  • Suspended Solids – Depending on the application, Suspended Solids measurements (including Turbidity and Particle Counts) method may be effective used to detect solids to indicate overall loading (wastewater) or perhaps sediment intrusion (water), but they do not isolate microbiological content. As such, are not effective ways to investigate microbiological issues and can sometimes be misleading. 2nd Generation ATP monitoring quantifies the biological content of these samples, enabling the issue to be characterized and optimized much more effectively.

2nd Generation ATP is in fact the best combination of speed and accuracy when measuring total microorganisms in your application. But, that does not mean it is the only microbiological test you should use! To truly stay in control of microorganisms in your application, you need a toolbox of microbiological tests – rapid and complete measurements like 2nd Generation ATP, microorganism-specific tests like culture-based analyses, and high-powered tools like microscopes and genomics.

Different types of microbiological tests give different information, but being in control starts with fast, high-level information such as that obtained from the 2nd Generation ATP measurement central to LuminUltra’s microbial monitoring solutions!

Measure total microbial content to achieve total process control

Side-by-Side Comparison

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