DISSOLVED ATP: A NEW PROCESS CONTROL PARAMETER FOR BIOLOGICAL WASTEWATER TREATMENT

ATP (Adenosine Triphosphate) is the primary energy molecule in all living cells. Numerous researchers have concluded that ATP monitoring of biological processes has the potential to be valuable for process improvement and troubleshooting. However, most studies have not used methods that distinguish between extracellular or “dissolved” ATP and the ATP contained only within microorganisms. While developing ATP assay reagents and protocols that facilitate easy analyses and that have been optimized specifically for wastewater treatment, it was discovered that samples from several biological wastewater treatment systems contained significant levels of dissolved ATP. A survey of seven different treatment sites conducted during routine operations found that dissolved ATP content ranged from 0.7 to 73% of the total sample ATP. A stress index was formulated based of the ratio of dissolved ATP to total ATP, referred to as the Biomass Stress Index. It was found both in laboratory and full-scale reactors that as stresses such as sub-optimal pH, anoxia, toxicity, and nutritional deficiencies were applied to the microbial populations, the stress index increased. The stress index can be used to solve problems and enable continuous process improvement. For accurate estimation of viable biomass, dissolved ATP measurement is essential. After correction for dissolved ATP content, ATP can be used more effectively for process control such as in adjusting food to microorganism ratio, sludge age, and nutrient additions.