A microbial indicator device for liquid disinfection comprises a first cavity, a source of biological activity fluidically coupled to the first cavity via a portion of a first fluidic path, a filter membrane positioned in a second fluidic path for a disinfectant, and a first coupling portion fluidically coupled to the source of biologically activity via the second fluidic path. The filter membrane has a first side and a second side, wherein the first side is in fluid communication with the first fluidic path. The filter membrane has a pore size sufficient to retain at least a portion of the source of biological activity on the first side. The device further comprises a frangible container contained in the first cavity, wherein a liquid in the container is in fluid communication with the first cavity when the container is fractured.