Fecal coliforms
Encyclopedia
A fecal coliform is a facultatively-anaerobic
, rod-shaped
, gram-negative
, non-sporulating
bacterium. Fecal coliforms are capable of growth in the presence of bile salts
or similar surface agents, are oxidase negative
, and produce acid and gas from lactose
within 48 hours at 44 ± 0.5°C.
Coliform bacteria
include genera
that originate in feces
(e.g. Escherichia
) as well as genera not of fecal origin (e.g. Enterobacter
, Klebsiella
, Citrobacter
). The assay is intended to be an indicator of fecal contamination; more specifically of E. coli
which is an indicator microorganism for other pathogen
s that may be present in feces. Presence of fecal coliforms in water
may not be directly harmful, and does not necessarily indicate the presence of feces.
, a break in the integrity of the distribution system, or possible contamination
with pathogens. When levels are high there may be an elevated risk of waterborne gastroenteritis
. Tests for the bacteria are cheap, reliable and rapid (1-day incubation).
s through direct discharge of waste from mammals and birds, from agricultural and storm runoff
, and from human sewage
. However, their presence may also be the result of plant material, and
pulp
or paper mill
effluent
.
can allow coliforms in the effluent to flow into the water table
, aquifer
s, drainage
ditches and nearby surface water
s. Sewage connections that are connected to storm drain
pipes can also allow human sewage into surface waters. Some older industrial cities, particularly in the Northeast and Midwest of the United States
, use a combined sewer system to handle waste. A combined sewer carries both domestic sewage and stormwater. During high rainfall periods, a combined sewer can become overloaded and overflow to a nearby stream or river, bypassing treatment
.
s, can contribute to fecal contamination of surface waters. Runoff from roads, parking lots, and yards can carry animal wastes to streams through storm sewers. Bird
s can be a significant source of fecal coliform bacteria. Swan
s, geese, seagulls, and other waterfowl
can all elevate bacterial counts, especially in wetland
s, lake
s, pond
s, and rivers.
to graze near water bodies, spreading manure
as fertilizer
on fields during dry periods, using sewage sludge biosolids and allowing livestock watering in streams can all contribute to fecal coliform contamination.
, typhoid fever
, viral and bacterial gastroenteritis, and hepatitis A
. The presence of fecal coliform tends to affect humans more than it does aquatic creatures, though not exclusively.
that contains fecal coliform can be harmful to the environment. Aerobic decomposition of this material can reduce dissolved oxygen levels if discharged into rivers or waterways. This may reduce the oxygen level enough to kill fish
and other aquatic life. Reduction of fecal coliform in wastewater
may require the use of chlorine and other disinfectant chemicals. Such materials may kill the fecal coliform and disease bacteria. They also kill bacteria essential to the proper balance of the aquatic environment, endangering the survival of species dependent on those bacteria. So higher levels of fecal coliform require higher levels of chlorine, threatening those aquatic organisms.
and other countries, water quality
is monitored to protect the health of the general public. Bacteria contamination is one monitored pollutant. In the U.S., fecal coliform testing is one of the nine tests of water quality that form the overall water-quality rating in a process used by U.S. EPA. The fecal coliform assay should only be used to assess the presence of fecal matter in situations where fecal coliforms of non-fecal origin are not commonly encountered. EPA has approved a number of different methods to analyze samples for bacteria.
as they multiply which may grow large enough to be seen. By growing and counting colonies of fecal coliform bacteria from a sample of water, the amount of bacteria originally present can be determined.
Membrane filtration
is the method of choice for the analysis of fecal coliforms in water. Samples to be tested are passed through a filter of particular pore size (generally 0.45 micrometre
). The microorganisms present in the water remain on the filter surface. When the filter is placed in a sterile petri dish
and saturated with an appropriate medium
, growth of the desired organisms is encouraged, while that of other organisms is suppressed. Each cell develops into a separate colony, which can be counted directly, and the results calculated as microbial density. Sample volumes of 1 ml and 10 ml will be used for the water testing, with the goal of achieving a final desirable colony density range of 20 to 60 colonies per filter. Contaminated sources may require dilution to achieve a "countable" membrane.
A 100 ml volume of a water sample is drawn through a membrane filter (0.45 µm pore size) through the use of a vacuum pump. The filter is placed on a petri dish containing M-FC agar
and incubated for 24 hours at 44.5 °C (112.1 degrees F). This elevated temperature heat shocks non-fecal bacteria and suppresses their growth. As the fecal coliform colonies grow they produce an acid (through fermenting lactose) that reacts with the aniline dye in the agar thus giving the colonies their blue color.
Newer methods for coliform detection are based on specific enzyme substrates as indicators of coliforms. These assays make use of a sugar linked to a dye which, when acted on by the enzyme beta-galactosidase
, produces a characteristic color. The enzyme beta-galactosidase is a marker for coliforms generally and may be assayed by hydrolysis of the sugar glucoside o-nitrophenyl-beta-D-galactose. Assays typically include a second sugar linked to a different dye which, when acted on by the enzyme beta-glucuronidase, produces a fluorescent product. Because E. coli produces both beta-galactosidase and beta-glucuronidase, a combination of these two dyes makes possible the unique ability to use one test to differentiate and quantify coliforms and E. coli.
s. The testing requirements for drinking water under the TCR are markedly increased over previous requirements and thus are more thorough. Not only is the number of routine coliform tests increased, especially for smaller water utilities, but the regulation also requires automatic repeat testing from all sources that show a total coliform positive (known as triggered source water monitoring).
As of 2009, EPA is working on revisions to the TCR. Issues being considered by the Agency include sampling locations, sampling frequency and timing, analytical methods and corrective actions to be taken by public water systems.
Facultative anaerobic organism
A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation...
, rod-shaped
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...
, gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, non-sporulating
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
bacterium. Fecal coliforms are capable of growth in the presence of bile salts
Bile
Bile or gall is a bitter-tasting, dark green to yellowish brown fluid, produced by the liver of most vertebrates, that aids the process of digestion of lipids in the small intestine. In many species, bile is stored in the gallbladder and upon eating is discharged into the duodenum...
or similar surface agents, are oxidase negative
Oxidase
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
, and produce acid and gas from lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...
within 48 hours at 44 ± 0.5°C.
Coliform bacteria
Coliform bacteria
Coliform bacteria are a commonly used bacterial indicator of sanitary quality of foods and water. They are defined as rod-shaped Gram-negative non-spore forming bacteria which can ferment lactose with the production of acid and gas when incubated at 35-37°C...
include genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
that originate in feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
(e.g. Escherichia
Escherichia
Escherichia is a genus of Gram-negative, non-spore forming, facultatively anaerobic, rod-shaped bacteria from the family Enterobacteriaceae. In those species which are inhabitants of the gastrointestinal tracts of warm-blooded animals, Escherichia species provide a portion of the...
) as well as genera not of fecal origin (e.g. Enterobacter
Enterobacter
Enterobacter is a genus of common Gram-negative, facultatively-anaerobic, rod-shaped bacteria of the family Enterobacteriaceae. Several strains of the these bacteria are pathogenic and cause opportunistic infections in immunocompromised hosts and in those who are on mechanical ventilation...
, Klebsiella
Klebsiella
Klebsiella is a genus of non-motile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. It is named after the German microbiologist Edwin Klebs...
, Citrobacter
Citrobacter
Citrobacter is a genus of Gram-negative coliform bacteria in the Enterobacteriaceae family.The species C. amalonaticus, C. koseri, and C. freundii use solely citrate as a carbon source...
). The assay is intended to be an indicator of fecal contamination; more specifically of E. coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
which is an indicator microorganism for other pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s that may be present in feces. Presence of fecal coliforms in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
may not be directly harmful, and does not necessarily indicate the presence of feces.
Basics of fecal coliforms
In general, increased levels of fecal coliforms provide a warning of failure in water treatmentWater purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
, a break in the integrity of the distribution system, or possible contamination
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
with pathogens. When levels are high there may be an elevated risk of waterborne gastroenteritis
Gastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
. Tests for the bacteria are cheap, reliable and rapid (1-day incubation).
Potential sources of fecal coliform bacteria in water
The presence of fecal coliform in aquatic environments may indicate that the water has been contaminated with the fecal material of humans or other animals. Fecal coliform bacteria can enter riverRiver
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s through direct discharge of waste from mammals and birds, from agricultural and storm runoff
Urban runoff
Urban runoff is surface runoff of rainwater created by urbanization. This runoff is a major source of water pollution in many parts of the United States and other urban communities worldwide.-Overview:...
, and from human sewage
Sewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
. However, their presence may also be the result of plant material, and
pulp
Pulp (paper)
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
or paper mill
Paper mill
A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags and other ingredients using a Fourdrinier machine or other type of paper machine.- History :...
effluent
Effluent
Effluent is an outflowing of water or gas from a natural body of water, or from a human-made structure.Effluent is defined by the United States Environmental Protection Agency as “wastewater - treated or untreated - that flows out of a treatment plant, sewer, or industrial outfall. Generally refers...
.
Human sewage
Failing home septic systemsSeptic tank
A septic tank is a key component of the septic system, a small-scale sewage treatment system common in areas with no connection to main sewage pipes provided by local governments or private corporations...
can allow coliforms in the effluent to flow into the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
, aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s, drainage
Drainage
Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
ditches and nearby surface water
Surface water
Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....
s. Sewage connections that are connected to storm drain
Storm drain
A storm drain, storm sewer , stormwater drain or drainage well system or simply a drain or drain system is designed to drain excess rain and ground water from paved streets, parking lots, sidewalks, and roofs. Storm drains vary in design from small residential dry wells to large municipal systems...
pipes can also allow human sewage into surface waters. Some older industrial cities, particularly in the Northeast and Midwest of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, use a combined sewer system to handle waste. A combined sewer carries both domestic sewage and stormwater. During high rainfall periods, a combined sewer can become overloaded and overflow to a nearby stream or river, bypassing treatment
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...
.
Animals
Pets, especially dogDog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s, can contribute to fecal contamination of surface waters. Runoff from roads, parking lots, and yards can carry animal wastes to streams through storm sewers. Bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s can be a significant source of fecal coliform bacteria. Swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...
s, geese, seagulls, and other waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
can all elevate bacterial counts, especially in wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s, lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s, pond
Pond
A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...
s, and rivers.
Agriculture
Agricultural practices such as allowing livestockLivestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...
to graze near water bodies, spreading manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...
as fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
on fields during dry periods, using sewage sludge biosolids and allowing livestock watering in streams can all contribute to fecal coliform contamination.
Human health hazards
Large quantities of fecal coliform bacteria in water are not harmful according to some authorities, but may indicate a higher risk of pathogens being present in the water. Some waterborne pathogenic diseases that may coincide with fecal coliform contamination include ear infections, dysenteryDysentery
Dysentery is an inflammatory disorder of the intestine, especially of the colon, that results in severe diarrhea containing mucus and/or blood in the faeces with fever and abdominal pain. If left untreated, dysentery can be fatal.There are differences between dysentery and normal bloody diarrhoea...
, typhoid fever
Typhoid fever
Typhoid fever, also known as Typhoid, is a common worldwide bacterial disease, transmitted by the ingestion of food or water contaminated with the feces of an infected person, which contain the bacterium Salmonella enterica, serovar Typhi...
, viral and bacterial gastroenteritis, and hepatitis A
Hepatitis A
Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus , an RNA virus, usually spread the fecal-oral route; transmitted person-to-person by ingestion of contaminated food or water or through direct contact with an infectious person...
. The presence of fecal coliform tends to affect humans more than it does aquatic creatures, though not exclusively.
Effects on the environment
Untreated organic matterOrganic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
that contains fecal coliform can be harmful to the environment. Aerobic decomposition of this material can reduce dissolved oxygen levels if discharged into rivers or waterways. This may reduce the oxygen level enough to kill fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and other aquatic life. Reduction of fecal coliform in wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
may require the use of chlorine and other disinfectant chemicals. Such materials may kill the fecal coliform and disease bacteria. They also kill bacteria essential to the proper balance of the aquatic environment, endangering the survival of species dependent on those bacteria. So higher levels of fecal coliform require higher levels of chlorine, threatening those aquatic organisms.
Removal and treatment
Fecal coliform, like other bacteria, can usually be inhibited in growth by boiling water or by treating with chlorine. Washing thoroughly with soap after contact with contaminated water can also help prevent infections. Gloves should always be worn when testing for fecal coliform. Municipalities that maintain a public water supply will typically monitor and treat for fecal coliforms.Public health risk monitoring
In waters of the U.S., CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and other countries, water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...
is monitored to protect the health of the general public. Bacteria contamination is one monitored pollutant. In the U.S., fecal coliform testing is one of the nine tests of water quality that form the overall water-quality rating in a process used by U.S. EPA. The fecal coliform assay should only be used to assess the presence of fecal matter in situations where fecal coliforms of non-fecal origin are not commonly encountered. EPA has approved a number of different methods to analyze samples for bacteria.
Analysis
Bacteria reproduce rapidly if conditions are right for growth. Most bacteria grow best in dark, warm, moist environments with food. Some bacteria form coloniesColony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
as they multiply which may grow large enough to be seen. By growing and counting colonies of fecal coliform bacteria from a sample of water, the amount of bacteria originally present can be determined.
Membrane filtration
Microfiltration
Microfiltration is a membrane technical filtration process which removes contaminants from a fluid by passage through a microporous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometres...
is the method of choice for the analysis of fecal coliforms in water. Samples to be tested are passed through a filter of particular pore size (generally 0.45 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
). The microorganisms present in the water remain on the filter surface. When the filter is placed in a sterile petri dish
Petri dish
A Petri dish is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells or small moss plants. It was named after German bacteriologist Julius Richard Petri, who invented it when working as an assistant to Robert Koch...
and saturated with an appropriate medium
Growth medium
A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....
, growth of the desired organisms is encouraged, while that of other organisms is suppressed. Each cell develops into a separate colony, which can be counted directly, and the results calculated as microbial density. Sample volumes of 1 ml and 10 ml will be used for the water testing, with the goal of achieving a final desirable colony density range of 20 to 60 colonies per filter. Contaminated sources may require dilution to achieve a "countable" membrane.
A 100 ml volume of a water sample is drawn through a membrane filter (0.45 µm pore size) through the use of a vacuum pump. The filter is placed on a petri dish containing M-FC agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
and incubated for 24 hours at 44.5 °C (112.1 degrees F). This elevated temperature heat shocks non-fecal bacteria and suppresses their growth. As the fecal coliform colonies grow they produce an acid (through fermenting lactose) that reacts with the aniline dye in the agar thus giving the colonies their blue color.
Newer methods for coliform detection are based on specific enzyme substrates as indicators of coliforms. These assays make use of a sugar linked to a dye which, when acted on by the enzyme beta-galactosidase
Beta-galactosidase
β-galactosidase, also called beta-gal or β-gal, is a hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. Substrates of different β-galactosidases include ganglioside GM1, lactosylceramides, lactose, and various glycoproteins...
, produces a characteristic color. The enzyme beta-galactosidase is a marker for coliforms generally and may be assayed by hydrolysis of the sugar glucoside o-nitrophenyl-beta-D-galactose. Assays typically include a second sugar linked to a different dye which, when acted on by the enzyme beta-glucuronidase, produces a fluorescent product. Because E. coli produces both beta-galactosidase and beta-glucuronidase, a combination of these two dyes makes possible the unique ability to use one test to differentiate and quantify coliforms and E. coli.
EPA testing requirements
The 1989 EPA Total Coliform Rule (TCR) imposed major monitoring changes for public water systemPublic water system
The US Safe Drinking Water Act and derivative legislation define public water system as an entity that provides "water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days a year."The...
s. The testing requirements for drinking water under the TCR are markedly increased over previous requirements and thus are more thorough. Not only is the number of routine coliform tests increased, especially for smaller water utilities, but the regulation also requires automatic repeat testing from all sources that show a total coliform positive (known as triggered source water monitoring).
As of 2009, EPA is working on revisions to the TCR. Issues being considered by the Agency include sampling locations, sampling frequency and timing, analytical methods and corrective actions to be taken by public water systems.