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Key ATP Terms

Adenosine Triphosphate (ATP) Testing

ATP testing is an advanced analysis for thoroughly evaluating a biological treatment system. Because this testing is not commonplace there is a lot about this analysis that is poorly understood. In this section the key terms used in ATP testing are defined.

ATP Graphic

Key ATP Terms

ATP (adenosine triphosphate) is the primary energy carrier for all life forms and is only found in and around living cells.

The ATP concentration in the mixed liquor suspended solids (MLSS) provides a direct measurement of the microorganism population and the health of that population.

  • Intra-cellular ATP is the ATP contained within living cells.

  • Extra-cellular ATP is the ATP located outside of living cells released when microorganisms die.

Cellular ATP (cATP) – represents ATP from living microorganisms and therefore is a direct indication of the living population. This value guides inventory management and process optimization.

Total ATP (tATP) – the total ATP analysis measures ATP from both living and dead cells.

Dissolved ATP (dATP) – the dissolved ATP analysis measures ATP from only dead cells.

Biomass Stress Index (BSI) – represents the stress level experienced by the microbiological population. This value indicates the presence of inhibitory compounds in the bioreactor and upstream processes. Additional sources of stress in the bioreactor (activated sludge basin) include low oxygen concentrations, high/low pH, high organic loading, high temperature, low macronutrients (ammonia nitrogen and/or phosphorus).

Active Biomass Ratio (ABR) – represents the percentage of bioreactor solids that are active microorganisms. Maximizing the ABR enhances sludge quality and improves settling.

Specific Floc-Bulking (s-fbATP) – represents the quantity of ATP from bulking floc relative to microorganisms. This measurement provides an early-warning of bulking conditions, allowing operators to proactively mitigate bulking conditions in the secondary clarifiers.

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