Biofilm is a colony of microbes encased in a slime layer (EPS membrane), where the microbes make their home and multiply their numbers, protected from microbicides. According to the EPA, any microbe present in water may attach or become enmeshed in the biofilm. While chlorine effectively suppresses the growth of harmful bacteria in the bulk water stream, it does not prevent the formation of biofilm on the internal surfaces of the pipes within the water system. The biofilm on the internal pipe surfaces creates an environment where bacteria proliferate and then migrate from the biofilm into the water stream. This leads to undetected contamination, affecting the water, surfaces, food, animals, and people downstream.