The BACTcontrol determines the concentration of E. coli, coliforms and total activity from specific enzymes in these bacteria. Each enzyme has its optimal level, requiring separate measurements. The sample enters the reaction chamber, concentrated in a ceramic filter, and is heated according to the enzyme to be analyzed. The user adjusts the volume to be filtered and pumped. Reagents are added to the tank, and incubation starts. The photodiode measures fluorescence due to enzyme activity, converted into bacterial population per 100 ml of sample. Enzymes, essential to metabolic processes, are selective and catalytic. The enzymatic activity, measured in picomole per minute, indicates the presence of bacteria. Alkaline phosphatase and beta-galactosidase, activated by specific reagents, are used to detect coliforms and E. coli. This technique, sensitive to low phosphate concentrations, is a warning system for drinking water quality. The fluorescence emitted during enzymatic hydrolysis helps measure enzyme activity.