CWQA Position Statement

Microbial Growths in Activated Carbon & Ion Exchange Resin Used in Home Water Treatment Equipment

CWQA Position:

The Canadian Water Quality Association concurs with the conclusion reached by federal government studies that the heterotrophic organisms found in water from home water treatment equipment presents no adverse effects on the health of people. All waters contain bacteria and these ubiquitous can multiply when water, in the absence of a disinfectant, is retained in any container such as pipes, plumbing fittings, water heaters, bottles or treatment equipment. Enteric, pathogenic or disease causing organisms even when present in drinking water do not compete effectively with naturally occurring and harmless heterotrophic organisms and do not grow disproportionately in water treatment units. Potable drinking water that is further treated with activated carbon and ion exchange resin in home water treatment equipment remains microbiologically safe.

Summary:

Many kinds of bacteria thrive in all aspects of our personal environment such as the air around us, our skin and our food. The following table of ‘Typical Microbiological Guidelines and Occurrences" shows the high level of bacteria that are tolerated in ordinary foods. For example, twenty thousand such micro-organisms per millilitre are commonly found in pasteurized milk. Fruits, vegetables, frozen dinners and meats may contain millions of heterotrophic bacteria per gram and still be fresh, pleasing and health to eat. One may inhale tens of thousands of heterotrophic organisms per breath from normal air. Health skin hosts hundreds of thousands per square inch and in the health human mouth, each millilitre of saliva contains as many as 150 million heterotrophic organisms.

Typical Microbiological Guidelines and Occurrences

PRODUCT	STANDARD AEROBIC PLATE COUNT	COLI FORM BACTERIA
Regular Milk2	<20 000/millilitre (ml)	<10/ML
Delicatessen foods4	<1 x 105/gram	<1 x 102/gram
Ready-to-eat, precooked and frozen foods4	<5 x 104/gram	<50/gram
Ground Beef4	1 x 106/gram
Municipal tap water after 1-10 days quiescence	up to 1 x 106/ml

 

The municipal tap water standard aerobic plate count of up to 1 x 106 organisms per millilitre is an occurrence documented in reference number one.

Numerous such harmless bacteria are found in chlorinated city water supplies. In fact, these organisms are in abundance almost everywhere but aren’t to be confused with disease causing bacteria which generally do not effectively compete and grow in water treatment equipment where normal amounts of heterotrophic bacteria are present. The point remains that while inspection and testing of our water supplies to ensure the absence of disease-causing bacteria that typically colonize in drinking water, plumbing and treatment units does not have significant health effects.

The U.S. Environmental Protection Agency (EPA) - sponsored Gulf South Research Institute study established an average one log increase in heterotrophic bacteria content of drinking waters because of the use of POU devices containing activated carbon. In a subsequent study, the Yale University School of Medicine Study found that, while bacteria levels increase in water treated by faucet-mounted and under-the-sink granular activated carbon filters, there is no significant health risk associated ‘with this increase. A second study, by the same research group in the same community involving larger point-of-entry units has resulted in the same finding: no associated health risk.

Therefore, when water treatment equipment using activated carbon or ion exchange resin is installed on centrally disinfected or microbiologically safe water supplies, the concomitant increase in general heterotrophic bacteria should not cause public health concerns. Disease causing bacteria are virtually eliminated by central treatment and the residential disinfectant effect that is normally present in the distribution system. Granular activated carbon, ion exchange and other POU/POE treatment of potable water has not been shown to add concentrate or propagate enteric pathogens of harmful organisms in drinking water.

In addition, the claim that a high level of heterotrophic bacteria in water suppresses the detection of coli form bacteria remains unproven. Coli form organisms are easily enumerated in other waters such as sewage effluent even though exceedingly high levels of non-coli form heterotrophs are present.

 

REFERENCES: s

1. Geldreich, Edwin E., American Water Work Water Quality and Treatment. A Handbook of Community Water Supplies. Chanter 18.Microbiological Quality Control in Distribution Systems. Fourth Edition, 1990, pp. 1113-1158.

2. "Statement of Canadian Water Quality Association in Response to Information Letter No. 601: Point-of-Use Water Treatment Devices, September 8,1981.

3. WQA Opposition to Petition (CPSC,CP 78-19) November 16,1978.

4. Food Technology magazine, January 1978, pp. 64-65.

5. CPSC Denial of Petition, August 23, 1979.

6. Department of Health and Welfare Canada, Information Letter 601 and CWQA Opposition.

7. Canadian water Quality Association Voluntary Guidelines for Carbon Filters Sales Promotional Claims.

8. December 13, 1983, Testimony to EPA.

9. Science Advisory Committee Recommendation.

10. EPN YaIe School of Medicine Filter Study.

11. WQA Testimony to EPA dated December 30,
1985, February 11, 1986, May 4,1987 and May 15, 1987.

12. Federal Register (USA), Volume 50, No. 219,
November 13,1985.