Heterotrophs are a group of microorganisms that use organic carbon sources to grow and can be found in all types of water. Heterotrophic plate count (HPC) is a method that measures colony formation on culture media of heterotrophic bacteria in drinking water. Thus, the HPC test can be used to measure the overall bacteriological quality of drinking water systems. High levels of microbial growth can affect the taste and odor of drinking water. To determine HPC, pour plate method can be used as a method.

Total coliform bacteria are commonly found in the environment and are generally harmless while fecal coliform bacteria are a sub-group of total coliform bacteria. The presence of fecal coliform in a drinking water sample often indicates recent fecal contamination, meaning that there is a greater risk that pathogens are present than if only total coliform bacteria is detected. The presence of fecal contamination in aquatic environments is an indicator that a potential health risk exists for individuals exposed to this water. Multiple tube fermentation technique is often used for the determination of total and fecal coliforms.