Roundtable Discussion: E. coli (Escherichia coli)

May 29, 2018

About the author: Wendi Hope King is the editor of Water Quality Products magazine.


Escherichia coli, a.k.a. E. coli. A terrible, but familiar word to the public suggests sewage or animal waste contamination. E. coli 0157:H7 is considered the worst strain of the hundreds of strains of E. coli bacteria, causing severe symptoms such as diarrhea and abdominal cramps as well as hemolytic uremic syndrome (kidney failure) in children under five and the elderly. It is both foodborne and waterborne.

In 1999, E. coli-contaminated drinking water, contaminated by a dormitory septic system from a private well on New York fairgrounds, caused two deaths and hundreds ill. More recently, seven Walkerton, Ontario, Canada, residents died and 1,000 were stricken ill after the town’s water supply became contaminated with E. coli from severe flooding.

With such severe outcomes, E. coli leaves consumers desperately seeking solutions. Joining in this discussion are Lou Smith, the water quality consultant for the Canadian Water Quality Association (CWQA); Alan Leff, managing director of QUASI LLC; and Cynthia Dougherty, director of the U.S. Environmental Protection Agency’s (EPA) Office of Groundwater and Drinking Water.

Water Quality Products: How have recent outbreaks affected the water equipment market?

Lou Smith: It increased attention to the point-of-use/point-of-entry (POU/POE) industry. Consumers’ views on water became more and more suspect. The more water problems from source water supplies that are exposed, the more consumers turn to POU/POE equipment and bottled water.

WQP: Is E. coli considered a wide-spread problem?

Smith: Yes, for water contaminants in general. With the increase of factory farming (livestock manure), the threat of E.coli contamination is increasing. Concern for Crytosporidium, Giardia lambia and other outbreaks also are on the rise.

Alan Leff: We have certainly seen more reports regarding waterborne outbreaks. However, this does not mean there are more outbreaks. Outbreaks also have occurred from foodborne sources or other animal contaminations.

Cynthia Dougherty: According to the Centers for Disease Control and Prevention (CDC), E. coli O157:H7 was first recognized in 1982. It lives in the intestines of healthy cattle, and most illnesses from this pathogen are associated with eating undercooked, contaminated ground beef. A handful of E. coli outbreaks have been associated with drinking water. One of the first outbreaks of E. coli O157:H7 associated with a drinking water system occurred in Cabool, Mo., in 1989. Subsequent outbreaks have been reported in Alpine, Wyo., Washington County, N.Y., and Walkerton, Canada.

The geography of E. coli outbreaks indicates that this pathogen is widespread. The CDC estimates E. coli O157:H7 causes 73,000 cases of infection and 61 deaths in the United States each year. However, most outbreaks are not associated with drinking water.

WQP: How can E. coli outbreaks be prevented?

Smith: Chlorination, filtration and testing of source water is mandatory for both pre- and post-delivery.

Leff: Bottled water must be E. coli-free. Proper sanitation procedures and ozone can prevent coliform contamination.For municipal water, again, proper sanitation and disinfection must be used by the water treatment facilities. However, distribution systems also are a major source of coliform bacteria contamination. Residual disinfectant levels must be high enough to keep the consumers at the ends of the distribution systems at low risk from coliform contamination.

Dougherty: According to the CDC, consumers can prevent E. coli 0157:H7 infection by the following steps: thoroughly cooking ground beef and using proper food handling techniques with raw meat; avoiding drinking milk, juice or cider that has not been pasteurized; washing fruits and vegetables thoroughly; drinking municipal water treated with chlorine or other disinfectants.

Water treatment plants also can prevent E. coli outbreaks by ensuring that the water is not subsequently contaminated in the distribution system (e.g., cross connections, seepage, low pressure, main breaks).

WQP: Are POU/POE systems effective against E. coli?

Smith: Yes, with reservation. Chlorination is the prescribed treatment method. While other products will kill the bacteria, they are not certified medical devices.

Leff: In general, POU/POE systems are more effective against chemical (metals and organic compounds) contamination. However, microfiltration, reverse osmosis, chlorination, ozonation and ultraviolet treatments are effective, and each unit is becoming more common in POU/POE systems.

Dougherty: Actually, many POU/POE systems are not effective against E. coli. Unless the POU/POE has been certified by a reputable testing organization to effectively remove and/or disinfect bacteria, it should not be used for this purpose. POU/POE filters that use membrane filtration (e.g., ultrafiltration, reverse osmosis) or which use disinfectants such as ozone, bleach, iodine or ultraviolet may be effective.

WQP: What do municipalities do to prevent contamination?

Smith: Continual testing and the use of chlorination/filtration under strict supervision is a major requirement. The province, municipality, town or hamlet sets Canada’s testing frequency in accordance with the provincial requirement, which requires zero E.coli. However, the lack of provincial inspectors leads to difficulties.

Leff: In cases of high input conditions or system upsets, there are greater chances of microbiological contamination. Furthermore, old distribution systems contribute to a much greater extent to the risk of E. coli contamination. Biofilms on the insides of the pipes are extremely difficult to eliminate.

Dougherty: Outbreaks can be prevented by educating consumers about causes and prevention of E. coli infection.

In regard to drinking water, municipalities can minimize the likelihood for contamination by complying with regulations designed to limit microbial contamination. Under the Surface Water Treatment Rule (SWTR), all public water systems that use surface water or groundwater under the direct influence of surface water are required to disinfect and, in most cases, filter the water.

Under the Total Coliform Rule (TCR), public water systems must test water in the distribution system for the presence of total coliforms. The frequency of testing depends on the number of people served, ranging from one sample/year for the smallest systems to 480 samples/month for the largest. Total coliforms are a group of related bacteria that historically have been used as an indicator of water treatment deficiencies and distribution system contamination. The TCR stipulates that if a sample is total coliform-positive, it must collect a set of repeat samples. The system must test both the original positive sample and any of the repeat samples that are coliform-positive for the presence of E. coli or fecal coliforms. If E. coli or fecal coliforms are present, the system must notify the state quickly. Any fecal coliform- or E. coli-positive repeat sample, or any total coliform-positive repeat sample following a fecal coliform- or E. coli-positive routine sample constitutes a violation of the maximum contaminant level for total coliforms, requiring immediate public notification.

WQP: Is there anything water equipment dealers need to do to inform their customers about E. coli?

Smith: Our recommendation is that dealers leave this subject to the provincial authorities.

Leff: There is a much greater risk for E. coli contamination outside of North America and Europe. In Asia, Latin America and Africa, as well as other poor developed regions of the world, the same water is used for bathing, drinking and sewage removal. This makes surface water a great risk for contamination.

In the United States, municipalities must produce consumer confidence reports. Equipment dealers should have this information on hand. Microbiological testing is best done by a certified laboratory.

Dougherty: If customers are not connected to a public water system, they periodically should test their source water for E. coli. If customers are served by a public water system that disinfects the water, no further steps are necessary. However, dealers could inform customers regarding other sources of E. coli risk. Customers should be aware that not all POU/POE units will remove or kill E. coli.

WQP: How can dealers help improve city efforts for prevention?

Smith: Homeowners could boil water continually for consumption, which is unrealistic. They have to rely on local authorities to provide water that meets the federal "Guidelines for Canadian Drinking Water Quality."

Leff: Municipalities always will have a risk. A properly maintained POU/POE system reduces the risk.

Dougherty: Water equipment dealers can educate consumers about sources of E. coli and ways to prevent infection. Public water systems that comply with the TCR and SWTR (as updated) and, following promulgation, Groundwater Rule (GWR), should not have E. coli of any type in their waters.

WQP: Are there specific regulations regarding E. coli?

Smith: "Zero tolerance." While surface water must be disinfected, it is up to local authorities to govern the disinfection of groundwater.

Leff: Whether the source of municipal water is surface water or groundwater affects only the required treatment, not the treated water standards. There is an acceptable level of coliform other than E. coli (less than 4 cfu/100ml). However, I agree, there is zero tolerance for E. coli at the discharge of the treatment plant.

Dougherty: As I stated previously, the TCR specifically addresses E. coli. Also, the SWTR requires all surface water systems to disinfect. Currently, EPA regulations do not require systems using groundwater to disinfect, but some states do. However, under the proposed GWR, systems using groundwater that do not disinfect would be required to monitor their source water for fecal contamination. If fecal contamination were present, the system would have to either disinfect or use another means. (EPA anticipates finalizing the GWR in late 2000 or early 2001.)

WQP: Does disinfection guarantee elimination?

Smith: If properly inspected and chlorination/filtration equipment is working 100 percent efficiently, then yes. If not, then no. Walkerton was employing disinfection equipment but it was not being properly tested. Also, the chlorination system was not working properly. E.coli was present in their water supply over a period of time. A build-up of the bacteria became encrusted in their water mains The mains eventually had to be dug up and replaced.

Leff: Disinfection only reduces the risk. Municipal plant design and operation is defined to provide the required log reduction of contaminants. If the load of contaminants is high, there is still a risk of contamination.

WQP: What is your organization doing to reduce fears and educate water professionals and consumers?

Leff: QUASI is committed to help bottled water manufacturers worldwide understand the sources of microbiological contamination for their sources and product water. Producers are trained in identifying the risks and how to minimize the probability of contamination. These issues are addressed through trade associations, trade journals and media reports.

Dougherty: EPA has taken an active role in providing information to drinking water professionals and the general public on safety. At our website ( we have posted the National Primary Drinking Water Regulations, proposed regulations and information on source water protection. The recently published Public Notification Rule requires water suppliers to alert consumers immediately if a serious problem exists (e.g., boil water conditions). In addition, the Consumer Confidence Reports now are required every July. This information, provided by water suppliers to their customers, will supplement public notification and provide an annual snapshot of the overall quality of their drinking water.