Addressing E. coli in water

May 29, 2015

BIRMINGHAM — In Water Technology’s May issue, Technical Editor Dr. Joseph Cotruvo writes about E. coli and other fecal bacteria.

BIRMINGHAM — In Water Technology’s Contaminant of the Month featured in the May issue, Technical Editor Dr. Joseph Cotruvo writes about E. coli and other fecal bacteria in drinking water. Cotruvo discusses what they are, the potential health effects, available water treatment, analyses and regulation.

Named after Theodor Escherich, who discovered them in 1885, E. coli (Escherichia coli) are a subgroup of fecal coliforms and are gram-negative, rod-shaped bacteria, explains Cotruvo.

Cotruvo continues that E. coli are the most important indicator bacteria for relatively recent fecal contamination because they are more numerous than fecal pathogens, can survive in the environment and are similarly subject to water treatment.

Risks of E. coli are associated with exposures to recreational water, drinking water and sewage/sanitary contaminated milk and food, adds Cotruvo, and they are good indicators for potential bacterial and viral contamination in water.

“Certain pathogenic strains can cause diarrhea and illnesses such as gastroenteritis, urinary tract infections, neonatal meningitis, hemolytic-uremic syndrome, peritonitis, septicemia and some pneumonia,” states Cotruvo. “Shiga toxin-producing strains such as E. coli 0157:H7 cause hemolytic-uremic syndrome, which has many serious health outcomes and often death.”

In the article, Cotruvo also lists the following water treatment options for E. coli and other fecal bacteria:

  • E. coli are effective treatment indicators for bacteria and viruses but not protozoa.
  • Standard disinfection with chlorine, hypochlorite, chlorine dioxide, ozone and ultraviolet (UV) are effective in minutes in low turbidity water, as well as chloramines with much longer concentration x time values.
  • Protozoa are not as susceptible to disinfection as are E. coli and bacterial and viral pathogens, thus filtration is necessary for removal, although UV is also effective; boiling will eliminate all pathogens.
  • POU carbon filters do not remove pathogens. If they contain silver, it is only to reduce microbial regrowth on the filter and not to disinfect the water.
  • POU is not permitted for meeting microbial drinking water standards in public water supplies.
  • Appropriate POE systems can be used for decentralized compliance.

“The current drinking water regulations have an MCL of < 1/100 ml only for E. coli or fecal coliforms,” notes Cotruvo. “Analyses for total coliforms are still required, but they are used primarily to indicate whether there are sanitary flaws in the system that should be corrected. If E.coli are verified and not corrected immediately, there is the potential for a boil water notice to be issued because of the connection with sewage contamination.

You can find May’s Contaminant of the Month on E. coli and fecal bacteria here.

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