Methods were developed to correlate volatile suspended solids (VSS) with adenosine 5＇-triphosphate (ATP) concentrations in the treatment of cheese-processing wastewater. Two different physiological conditions where the maximum rates of acetate and butyrate production occurred, which were pH 7.01 at 36.2 degrees C (condition A) and pH 7.26 at 36.2 degrees C (condition B), respectively, were tested in batch mode. The ratios of ATP to volatile suspended solid (VSS) concentration were constant at exponential growth and decay phases for conditions A and B, which were 4.03 mg ATP/g VSS and 3.20 mg ATP/g VSS, respectively.