A process for monitoring the concentration of bacteria in the water of a water distribution network, wherein the process includes the following steps: measuring the concentration of bacteria in the water by means of a first sensor positioned at a first location in the water distribution network, determining a variable instantaneous value of the expected concentration of bacteria in the water at the first location as a function of a parameter characteristic of the water, comparing the concentration of bacteria in the water measured by the first sensor to the variable instantaneous value, corrective action acting on the concentration of bacteria in the water if the concentration of bacteria in the water measured by the first sensor exeeds the variable instantaneous value. A device for monitoring the concentration of bacteria in the water of a water distribution network is also provided.