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What are Heterotrophic Microorganisms?

Heterotrophs include bacteria, yeasts and molds that require an external source of organic carbon for growth.


Why Use Heterotrophic Plate Count Testing?

The HPC test is widely used to measure the heterotrophic microorganism population in water. Heterotroph levels are a good indicator for an increase in ideal bacterial growth conditions which can lead to pipe corrosion, slime growth, altered water taste, increased need for disinfection, and harbor secondary respiratory pathogens.


Who Should Use Heterotrophic Plate Count Testing?

This test is useful for piped public water suppliers, bottled water suppliers, water treatment plants, and swimming pools to monitor the levels of heterotrophs in their water.


How Can Scientific Methods Help Me?

We are a full service microbiology laboratory that provides testing and analysis services to clients throughout the US.  We can assist you in the development of your water safety plan and analyze samples.


What is the Procedure for Heterotrophic Plate Count Testing?

Our lab utilizes the pour plate method outlined in Standard Methods for HPC testing. Tempered low nutrient medium is poured into a Petri dish with the sample and then incubated for 48 hours. All colonies are then counted to determine the number of heterotrophs present.


What are the Key Regulations/Standards for HPC?

There are no regulations or standards in place that require heterotroph monitoring. Heterotrophs are not considered to be a public health issue. They are considered an indicator for increased and/or additional water treatments. However, the EPA action limit for potable (drinking) water is 500 cfu (colony forming units)/mL. It is important to note that this test is not used instead of coliform testing to determine the presence or absence of pathogens in the water.  

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