Q. What is E. coli?
A. Escherichia coli, or E. coli, are a group of bacteriological organisms that normally live in the digestive tracts of humans and warm-blooded animals. When found in drinking water, its presence indicates that the water may be contaminated with human or animal wastes. Although most strains of E. coli are harmless, several are known to produce toxins within the human body. One particular E. coli strain, known as O157:H7, can cause severe kidney damage, which could potentially lead to death.
Q. Who does E. coli affect?
A. Anyone of any age can become infected with E. coli, but it may pose a special health risk for infants, young children, some of the elderly, and people with severely compromised immune systems.
Q. What are the symptoms of an E. coli infection?
A. Drinking water that is contaminated with E. coli can cause short-term effects, such as diarrhea, cramps, nausea, headaches, or other symptoms. Some infected people may have mild diarrhea or no symptoms at all. Most identified cases develop severe diarrhea and abdominal cramps. Blood is often seen in the stool. Usually, little or no fever is present. Symptoms generally appear three to four days after exposure, but can take as long as nine days to appear. Persons experiencing these symptoms should immediately contact their physician.
Q. How does E. coli get into drinking water?
A. E. coli is not naturally found in groundwater. Therefore, in order for it to be present in a drinking water sample, it must have been introduced through a defect in the water system itself. For example, a hole in a storage tank can allow a rodent to gain entry. If the animal falls into the stored water, it will not be able to escape, and will eventually drown. The remains of the rodent will begin to decompose and expose the E. coli in its digestive tract to the water, thus contaminating the system. 95% of the drinking water in Monterey County comes from groundwater sources.
Some water systems have a surface water source (for example, a creek or river) that supplies the drinking water. Other systems have shallow wells or springs that may be vulnerable to surface water influence. E. coli (and other potentially harmful organisms) can be introduced at any point along the waterway, since it is completely exposed to the surrounding environment. Only 5% of the drinking water in Monterey County comes from surface water or surface water influenced sources.
Q. How many drinking water systems are regulated by Environmental Health's Drinking Water Protection Services?
A. Currently, Environmental Health's Drinking Water Protection Services regulates 1,251 drinking water systems, ranging from two to 199 service connections. The California Department of Health Services (CA-DHS) regulates water systems that have 200 or more service connections. Single-connection water systems (a drinking water source supplying only one single family dwelling) are not regulated by EHD.
Q. How often are these systems tested for E. coli?
A. The bacteriological monitoring frequency depends upon the number of service connections or the number of users on the system, and ranges from monthly to annual sampling:
· A Community Water System (CWS) is defined as a public water system which serves at least 15 service connections used by yearlong residents or regularly serves at least 25 yearlong residents. A CWS is primarily residential in nature, and a licensed water system operator is responsible for the collection of monthly bacteriological samples, to be analyzed by a certified laboratory. Currently, there are 127 CWS regulated by Environmental Health.
· A Nontransient-Noncommunity Water System (NTNC) is defined as a public water system that is not a community water system and that regularly serves at least the same 25 persons over 6 months per year. An example of an NTNC would be a school or place of business. A licensed water system operator is responsible for the collection of monthly bacteriological samples, to be analyzed by a certified laboratory. Currently, there are 95 NTNC water systems regulated by Environmental Health.
· A Transient-Noncommunity Water System (TNC) is defined as a public water system that is not a community water system or a nontransient-noncommunity water system. An example of a TNC would be a gas station or a public park. A TNC is responsible for the collection of quarterly bacteriological samples, to be analyzed by a certified laboratory. Currently, there are 63 TNC regulated by Environmental Health.
· A State Small Water System is defined as a system for the provision of piped water to the public for human consumption that serves at least five, but not more than 14, service connections and does not regularly serve drinking water to more than an average of 25 individuals daily for more than 60 days out of the year. State Small Water Systems are required to have bacteriological samples collected on a quarterly basis for analysis by a certified laboratory. EHD does the majority of sampling for State Small systems. Currently, there are 282 State Small Water Systems regulated by Environmental Health.
· A Local Small Water System is defined as a system for the provision of piped water for human consumption that serves at least two, but not more than four, service connections. Local Small Water Systems have their annual bacteriological samples collected and analyzed by EHD. Currently, there are 684 Local Small Water Systems regulated by Environmental Health.
Drinking water systems that are regulated by California State's Department of Health Services (CA-DHS) may have more frequent monitoring, depending upon the population served, ranging from one sample per month up to 120 samples per week. Single-connection water systems are not tested by Environmental Health, but are encouraged to periodically self-monitor their drinking water's quality.
Q. What is the testing method used to detect bacteria in drinking water?
A. The method used by the Monterey County Health Department's Public Health Laboratory is a present/absent test called Colilert®, from IDEXX Laboratories. This process involves adding a reagent powder to a 100 mL sample and incubating for 24 hours. After incubation, a color change to yellow indicates a positive result for total coliform bacteria (a group of normally benign organisms commonly found in plant and soil material, that act as an indicator for potentially hazardous organisms, such as E. coli). Once a total coliform positive result is confirmed, the sample container is then taken to a darkroom where it is exposed to UV light. If the sample fluoresces, then it is also present for E. coli bacteria. No color change, after the 24-hour incubation period, indicates an absent result for both total coliform and E. coli. This testing method does not identify individual strains, nor does it calculate a number to indicate the severity of the contamination. The Colilert® test only determines if bacteria is present or not. There are other bacteriological tests, which are able to identify strains and provide a count of organisms found, but the Colilert® method is used because it is both accurate (shows a positive at one total coliform or E. coli organism in a 100 mL sample) and economical.
Q. Can any laboratory analyze drinking water samples?
A. Environmental Health will only accept drinking water sample analysis results that are conducted by an Environmental Laboratory Accreditation Program (ELAP) certified laboratory. A list of local ELAP-certified laboratories is available on this website, or from any Environmental Health office.
Q. How common is E. coli bacteria found in the drinking water systems that are regulated by Environmental Health?
A. In the 2005-06 Fiscal Year (FY), the EHD Drinking Water Protection Program sampled 943 Local and State Small Water Systems (670 Local Smalls and 273 State Smalls). Out of these systems, only 21 (2.23%) tested positive for E. coli (19 Local Smalls and two State Smalls).
In 2005, a total of ten E. coli positives were detected in water systems that collect their own samples, or have a licensed operator collect the system's samples. Six of these samples were found in CWS (which are tested monthly), three were found in NTNC water systems (which are tested monthly) and the remaining one was detected in a TNC water system (which are tested quarterly).
In short, the occurrences of E. coli positives in the water systems regulated by Environmental Health are very infrequent. Out of the thousands of bacteriological lab results received by the Environmental Health Drinking Water Protection Program each year, less than 1% show a positive for E. coli.
Q. What should a water system operator do if E. coli is found in their bacteriological sample?
A. First and foremost, every user on the water system must be notified that the water is contaminated with E. coli, and that they should immediately begin using bottled water for all their drinking and culinary needs, or vigorously boil their water for a minimum of one (1) minute before using for drinking or culinary purposes. (Due to other water quality issues, using bottled water may be the preferred interim measure put into effect until the water is deemed to be free of E. coli. For example, if a water system has nitrate levels near the Maximum Contaminant Level (MCL), boiling the water will cause some water to be released as steam while the nitrate stays in the liquid that is left behind. This will actually increase the nitrate concentration. Therefore, boiling water with high levels of nitrate could cause it to exceed the MCL (45 mg/L), making it unsuitable for human consumption.)
The water system operator needs to work closely with Environmental Health to investigate and resolve the E. coli contamination. The investigation includes a water system inspection to determine if there are deficiencies in the water system (e.g. openings in the well head and unscreened openings or foreign objects in the storage tank). The investigation also includes determination if there have been:
1) Recent main repairs or well work conducted without disinfection
2) A system pressure loss of less than 5 psi
3) Potential cross connectionm, or
4) Person(s) becoming ill with a suspected waterborne disease.
Any deficiencies found in the water system must be corrected. Following repairs to the water system a disinfection procedure (such as chlorination) is then performed to eliminate contaminating bacteria. It is important to correct any deficiencies before the disinfection process, or the E. coli contamination may reoccur. After the disinfection process is completed, at least one repeat sample is required to be collected in order to ensure that the procedure was successful. The number of repeat samples required is determined by the water system's classification which was previously discussed.
The water system operator must also assure that operational practices are improved as needed to help prevent future E. coli contamination. It is important that the system is disinfected after any maintenance, that pressure is maintained and that any cross-connections are eliminated. Environmental Health will assist the system operator to implement a cross-connection control program.
Most of the larger drinking water systems are required to employ a licensed water system operator who oversees the day-to-day operations of the system, including water quality monitoring. If E. coli contamination is detected, it is the water system operator who is tasked with issuing notification to the system's users, locating the origin of the contamination and following the regulations set forth by California State's Department of Health Services and Monterey County's Environmental Health to resolve the problem.
Q. What if I am served by surface water or surface water influenced source?
A. Since surface water systems are more susceptible to E. coli contamination, they are equipped with a device that provides automatic chlorination before the water is distributed to the service connections. However, surface water systems are also vulnerable to other pathogens that may be resistant to chlorine, and further treatment methods may be required (e.g. filtration) to remove these health threats, such as protozoa (e.g. giardia and cryptosporidia) and viruses. Such systems are required to do additional water quality monitoring to make sure that their treatment device(s) are working properly.
