Although many laboratory experiments are available to illustrate spectrophotometric or fluorometric methods, few of them introduce the use of luminometry to students. Bioluminescence, a subtype of chemiluminescence, is produced when an enzyme-catalyzed chemical reaction gives rise to light emission. Despite the advantages of bioluminescent methods, including sensitivity and specificity, and their increasing use in experimental sciences and biomedical laboratories, their presence in courses is almost nonexistent. The luciferase-catalyzed enzymatic reaction has generated a myriad of practical applications, including those derived from the measurement of the ATP consumed in the reaction. In particular, the measurement of ATP levels in drinking or stored waters directly correlates with their bacteria content, facilitating the development of rapid methods for detecting bacterial contamination. This avoids the long waiting time associated with traditional microbiological methods, based on the growth of the microorganisms in a suitable culture medium. Over the past two years at the University of Malaga, we have implemented a new laboratory experiment for undergraduate chemistry and biochemistry students. In this experiment, students detected bacterial contamination in water by quantifying ATP with the luciferase-catalyzed reaction. The experiment was successfully implemented in two different formats, either as a full project developed by students throughout the entire duration of the academic course, or as a short protocol, carried out in a single laboratory session. Between them, a whole range of intermediate options could be arranged by educators to suit their course requirements and the learning objectives to be achieved by students.