Total Organic Carbon (TOC) in Drinking Water Information:

Properties:

Total organic carbon (TOC) measurements quantify the amount of organic carbon present in a water supply. Decaying natural organic matter (e.g. plants and other vegetation), microbiological activity, and other processes related to plant and animal life can all increase TOC.1 In general, TOC is a good measure of water quality due to the fact that raw water with high TOC requires additional treatment before it is acceptable for consumption. Organic matter can also cause problems with colour in water and may be unacceptable to consumers. 

Sources:

Organic carbon is naturally present in nearly every water source. Low, stable levels of TOC are not cause for concern and simply indicate that decaying vegetation and organic matter are present.1 Abnormal changes to TOC measurements may indicate that water treatment processes will require adjustment.

Regulations:

There may not be abnormal TOC changes in drinking water supplies.  

Health/Environmental Concerns:

High TOC levels are not necessarily harmful for human health. However, if a large amount of organic matter is reaching consumers, it is likely that the filtration and treatment systems in place are insufficient. In such cases, other chemicals or bacteria of concern may also reach the public.1 Organic matter present in raw water supplies can also compromise chlorine-based disinfection systems; the organic compounds can react with the chlorine to form THM’s, a class of carcinogenic byproducts.2

Action:

Contamination caused by organic matter in drinking water can be prevented by monitoring changes in raw water sources and can be removed through filtration.1 Disinfection and realted treatment processes may need to be adjusted if any abnormal changes in TOC measurements do occur. If you suspect that your drinking water supply is contaminated, contact your Water Service Authority. If drinking water makes you feel ill, contact a doctor right away.

1 Disinfection By-Products in Drinking Water; Advice Note No. 4 Version 2; EPA Drinking Water Guidance on Disinfection Byproducts, Environmental Protection Agency: United States. ISBN 978-1-84095-444-9.

2 Guide to the Parameters in the European Communities. What’s in your water?; S. I. No. 278 of 2007; National Federation of Group Water Schemes: Ireland.