Chapter 9: Primary Standards

Types of Contaminants

Five types of primary contaminants are considered to be of public health importance:

1. Inorganic contaminants, such as lead and mercury;
2. Organic contaminants, which include pesticides, herbicides, THMs, solvents, and other synthetic organic compounds;
3. Turbidity, such as small particles suspended in water that interfere with light penetration and disinfection;
4. Microbial contaminants, such as bacteria, viruses, and protozoa; and
5. Radiologic contaminants, which include natural and manmade sources of radiation.

Identifying Contaminants to Be Regulated

The 1986 Safe Drinking Water Act (SDWA) required EPA to establish a priority list of contaminants that may have adverse health effects and may require regulation. The 1996 SDWA amendments retained the list of 83 contaminants developed earlier but revised the process by which contaminants are selected for regulation. Before selecting a contaminant for regulation, the EPA must now consult with the scientific community, solicit public comments, and demonstrate that the contaminant actually occurs in public water systems. For this latter purpose, the 1996 amendments required EPA to establish an occurrence database by August 1999. The database contains information concerning regulated and unregulated contaminants and the information is available to the public.

To regulate a substance, EPA must demonstrate that the contaminant meets three criteria:

1. The contaminant has an adverse effect on human health;
2. It occurs, or is likely to occur, in public water systems at a frequency and concentration of significance to public health; and
3. Regulation of the contaminant offers a meaningful opportunity to reduce health risks for people served by public water systems.

In addition to meeting these three criteria, EPA must also weigh the relative health risks of various contaminants being considered for regulation, the risk reduction that regulation would accomplish, and the costs of implementing the regulations.

Working on a 5-year cycle, the EPA is required to select at least five contaminants from its Drinking Water Contaminant Candidate List (DWCCL) and decide whether there sufficient reason exists to regulate them. The first DWCCL included 50 chemicals and 10 microbial contaminants. In June 2002, the EPA announced a preliminary finding that their research revealed no need to regulate ten of the listed contaminants. Based on public comments and continued research and evaluation, EPA will make a final determination about regulating any of these contaminants and will begin to develop proposed regulations as necessary.

Unregulated Contaminants

EPA uses the Unregulated Contaminant Monitoring (UCM) program to collect data for contaminants suspected to be present in drinking water, although they do not have health-based standards set under the SDWA. Every 5 years, EPA reviews the list of contaminants, largely based on the Contaminant Candidate List.

The SDWA Amendments of 1996 provide for the following:

• Monitoring no more than 30 contaminants per 5-year cycle
• Monitoring only a representative sample of public water systems
• serving fewer than 10,000 people
• Storing analytical results in a National Contaminant Occurrence Database (NCOD)

The UCM program has progressed in several stages. Currently, EPA manages the program directly as specified in the Unregulated Contaminant Monitoring Regulation (UCMR). EPA has established a timeline and plans for monitoring unregulated contaminants through 2015.

Under the UCMR, community water systems and non-transient non-community water systems serving more than 10,000 people are required to monitor for unregulated contaminants; smaller systems may also have to conduct monitoring if required by the state. Transient water systems are not affected by the UCMR.

Always keep in mind that EPA’s regulatory process is basically just a process. No list is permanent; regulations change frequently as new information becomes available. Water treatment plant operators must continually seek opportunities to learn about the regulations that affect the water industry. Also, operators should feel free to express their concerns regarding the regulations and the regulatory process to EPA.

Primary Standards

Inorganic chemicals are metals, salts, and other chemical compounds that do not contain carbon. The health concerns about inorganic chemicals are not centered on cancer, but rather on their suspected links to several different human disorders. For example, lead is suspected of contributing to mental retardation in children. Waters exceeding the MCL for these elements for short periods of time will pose no immediate threat to health. However, studies show that these substances must be controlled because consumption of drinking water that exceeds these standards over long periods of time may prove harmful.

Initial and Base Monitoring Sample Sites

Compliance with the Lead and Copper Rule depends on meeting the action levels during two consecutive six-month monitoring periods. All public water systems are required to collect one sample for lead and copper analysis from a number of sites depending on population during each six-month monitoring period.

If a system meets the lead and copper action levels or maintains optimal corrosion control treatment for two consecutive six-month periods, tap-water sampling for lead and copper can be reduced to once per year and half the number of sites. After three consecutive years of acceptable performance, tap-water sampling can be reduced to once every three years at the reduced number of sites listed above.

Water Quality Indicator Frequency

All large systems (more than 50,000 persons) and any small- or medium-sized system that exceeds the lead or copper action level will be required to monitor for the following water quality indicators: pH, alkalinity, calcium, conductivity, orthophosphate, silica, and water temperature. Samples must be taken from representative taps throughout the system and at entry points to the distribution system. Two tap-water samples must be collected for each applicable water quality indicator.

In addition to the sampling from representative taps, one sample must be collected every two weeks for each applicable water quality indicator at each entry point to the distribution system.

All large water systems and any small- and medium-sized system that exceed the lead or copper action levels after installing optimal corrosion control treatment must continue to collect samples as follows:

1. 2 samples for each applicable water quality indicator at each of the sampling sites (taps) every 6 months.
2. 1 sample for each applicable water quality indicator at each entry point to the distribution system every 2 weeks.
3. After meeting water quality guidelines for 2 consecutive 6-month monitoring periods, systems may reduce the number of tap samples collected, and after 3 consecutive years of acceptable performance they will be permitted to collect annual samples at the reduced number of sampling points.

Calculation of the 90^th Percentile

The action levels that trigger implementation of treatment techniques to reduce lead and copper concentrations are based on the principle that no more than 10 percent of the samples should exceed the limit. To determine whether a system meets this test, it is necessary to figure out the lead or copper concentration on the sample that falls at the 90th percentile.

To calculate the 90th percentile value, write down the results from a set of samples arranging them in order of increasing or decreasing concentration. Number each sample beginning with the number 1 for the smallest concentration. Multiply the total number of samples (which will be the same as the number assigned to the highest concentration) by 0.9. Then, use the value from this calculation to identify the sample with the same number.

The concentration of the sample whose number matches the calculated value is the 90th percentile and is used in determining compliance with the action level. For systems serving fewer than 100 people, the 90th percentile is the average of the highest concentration and the second highest concentration.

Public Education

A public education program developed by the EPA must be delivered to water system customers within 60 days whenever the system exceeds the lead or copper action levels. The information describes the harmful effects of lead in drinking water and tells customers what they can do to reduce their exposure. The education program should continue as long as the system fails to meet the lead or copper action levels. In conjunction with the public education program, the water system must offer to sample a customer’s water if asked to do so. However, the water system is not required to pay for the sampling and analysis and is not required to collect and analyze the sample.

Lead Service Line Replacement

Any water system that continues to exceed the lead and copper action levels even after optimizing corrosion control and installing source water treatment will be required to replace its lead distribution pipes within a maximum of 15 years. A lead pipeline qualifies for replacement if it contributes more than 15 parts per billion to the total tap-water lead levels. Seven percent of the lines meeting this standard must be replaced annually. Customers must be notified 45 days before replacing the lines.

Trichloroethylene (TCE)

In the Code of Federal Regulations Reference: 40 CFR 141.50, although the use of TCE is declining because of stringent regulations, it was, for many years, a common ingredient in household products (spot removers, rug cleaners, and air fresheners), dry cleaning agents, industrial metal cleaners and polishes, refrigerants, and even anesthetics. Its wide range of use is perhaps why TCE is the organic contaminant most frequently encountered in groundwater.

Purpose of Regulating Trichloroethylene: To improve public health protection.

Public Health Benefit: To prevent cancer risks; liver problems.

MCL/MCLG: 0.005 mg/L/zero

Monitoring Requirements: Four consecutive quarterly samples during first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems. These requirements apply to community and non-community water systems.

1,1-Dichloroethylene

In the Code of Federal Regulations Reference: 40 CFR 141.50, this solvent is used in manufacturing plastics and, more recently, in the production of 1,1,1-trichloroethane.

Purpose of Regulating 1,1-Dichloroethylene: To improve public health protection.

Public Health Benefit: To prevent impacts to the liver, kidneys, heart, and central nervous system

MCL/MCLG: 0.007 mg/L/0.007 mg/L

Monitoring Requirements/Comments: For VOCs: Four consecutive quarterly samples during first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems.

With the completion of source water assessments, primacy agencies are allowed to develop alternative monitoring requirements. Applies to community water systems and non-transient

Non-community water systems.

Vinyl Chloride

In the Code of Federal Regulations Reference: 40 CFR 141.50, billions of pounds of this solvent are used annually in the United States to produce polyvinyl chloride (PVC), the most widely used ingredient for manufacturing plastics throughout the world. Also, evidence exists that vinyl chloride may be a biodegradation end-product of TCE and PCE under certain environmental conditions.

Purpose of Regulating Vinyl Chloride: To improve public health protection.

Public Health Benefit: To prevent cancer in humans.

MCL/MCLG: 0.002 mg/L/zero

Monitoring Requirements/Comments: For VOCs: Four consecutive quarterly samples during first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems.

With the completion of source water assessments, primacy agencies are allowed to develop alternative monitoring requirements. Applies to community water systems and non-transient non-community water systems.

Carbon Tetrachloride

In the Code of Federal Regulations Reference: 40 CFR 141.50, carbon tetrachloride was once a popular household solvent, a frequently used dry cleaning agent, and a charging agent for fire extinguishers. Since 1970, however, carbon tetrachloride has been banned from all use in consumer goods in the United States.

In 1978, carbon tetrachloride was banned as an aerosol propellant. Currently, its principal use is in the manufacture of fluorocarbons, which are used as refrigerants.

Purpose of Regulating Carbon Tetrachloride: To improve public health protection.

Public Health Benefit: To prevent liver problems and cancer.

MCL/MCLG: 0.005 mg/L/zero

Monitoring Requirements: Four consecutive quarterly samples during first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems. These requirements apply to community and non-community water systems.

Benzene

In the Code of Federal Regulations Reference: 40 CFR 141.50, benzene is used primarily in the synthesis of styrene (for plastics), phenol (for resins), and cyclohexane (for nylon). Other uses include the production of detergents, drugs, dyes, and insecticides. Benzene is still being used as a solvent and as a component of gasoline. It is also discharged from factories and leaches from gas storage tanks and landfills.

Purpose of Regulating Benzene: To improve public health protection.

Public Health Benefit: To prevent anemia, a decrease in blood platelets, and cancer.

MCL/MCLG: 0.005 mg/L/zero

Monitoring Requirements: Four consecutive quarterly samples during first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems. These requirements apply to community and non-community water systems.

Para-Dichlorobenzene (p-Dichlorobenzene)²

In the Code of Federal Regulations Reference: 40 CFR 141.50, the principal uses of p-dichlorobenzene are in moth control (moth balls and powders) and as lavatory deodorants. It is also used as an insecticide and fungicide on crops; in the manufacture of other organic chemicals; and in plastics, dyes, and pharmaceuticals.

The major source of p-dichlorobenzene in drinking water is from surface water sources. Low levels at best since it does not dissolve easily in water and quickly evaporate into the air.

Purpose of Regulating Para-Dichlorobenzene (p-Dichlorobenzene): To improve public health protection.

Public Health Benefit: To prevent kidney/liver/spleen/circulatory system problems.

MCL/MCLG: 0.075 mg/L/0.075 mg/L

Monitoring Requirements: Four consecutive quarterly samples during the first compliance period. Compliance is based on annual average of quarterly samples. If no detections are found during the initial round, two quarterly samples are required each year for systems serving greater than 3,300; one sample is required every 3 years for smaller systems. These requirements apply to community and non-community water systems.

Total Coliform Rule

In the Code of Federal Regulations Reference: 40 CFR 141 Subpart C, coliforms are bacteria that are always present in the digestive tracts of animals, including humans, and are found in their wastes. They are also found in plant and soil material. The most basic test for bacterial contamination of a water supply is the test for total coliform bacteria. Total coliform counts give a general indication of the sanitary condition of a water supply.

Coliforms include the following:

1. Total coliforms—include bacteria that are found in the soil, in water that has been influenced by surface water, and in human or animal waste.
2. Fecal coliforms—are the group of the total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals. Because the origins of fecal coliforms are more specific than the origins of the more general total coliform group of bacteria, fecal coliforms are considered a more accurate indication of animal or human waste than the total coliforms.

Escherichia coli (E. coli) is the major species in the fecal coliform group. Of the five general groups of bacteria that comprise the total coliforms, only E. coli is generally not found growing and reproducing in the environment. Consequently, E. coli is considered to be the species of coliform bacteria that is the best indicator of fecal pollution and the possible presence of pathogens.

2012 Revised Total Coliform Rule (RTCR)

EPA has revised the Total Coliform Rule so that public water systems in the US take steps to ensure the integrity of the drinking water distribution system and monitoring for the presence of microbial contamination. Public water systems and the state and local agencies that oversee them must comply with the RTCR beginning April 1, 2016. The final RTCR requires the following:

1. Public water systems are to notify the public if a test exceeds the MCL for E. coli in drinking water
2. Public water systems that are at risk and therefore vulnerable to microbial contamination are required to identify and fix the problems, including the potential sources and the pathways of contamination
3. Criteria will be used for public water systems that are well operated to qualify for and stay on reduced monitoring, which could reduce water system burden
4. Provide incentives for better system operation, in particular small systems
5. Require additional monitoring requirements for seasonal systems such as campgrounds and state and national parks

The RTCR establishes an MCLG and an MCL for E. coli and eliminates the MCLG and MCL for total coliforms, replacing them with treatment techniques for coliforms that require assessment and corrective action. EPA has established an MCLG of zero for E. coli, which is a more specific indicator of fecal contamination and those pathogens that are potentially more harmful than total coliform. EPA has removed the 1989 MCLG and MCL for total coliforms, although the acute total coliform MCL violation under the 1989 TCR has been maintained as the MCL for E. coli under the RTCR.

Under the new treatment technique, total coliforms serve as the indicator of a potential pathway of contamination into the system’s distribution system. Public water supplies that exceed a specified frequency of total coliform occurrence must conduct an assessment to determine if any sanitary deficiencies exist; if found, they must be corrected. A public water system that experiences an E. coli MCL violation must conduct an assessment and correct any sanitary defects that are identified.

Monthly notification requirements based only on the presence of total coliforms will no longer be required. Instead, the RTCR will require public notification when an E. coli MCL violation occurs, indicating a potential health threat or when a water system fails to assess and take corrective action.

Sampling Plan

The Total Coliform Rule requires each water supply system to develop and follow a written sampling plan. Each plan must specifically identify sampling points throughout the distribution system. Sampling plans must be approved by the state regulatory agency, and it is necessary to check with the state agency to determine the details of their review process and what documents need to be submitted.

Laboratory Procedures

In the Code of Federal Regulations Reference: 40 CFR 141.21 and 40 CFR 141 Subpart C, with regard to coliform testing methodology, EPA maintains a current list of analytical methods that are approved for monitoring drinking water supplies that is published and updated in 40 CFR 141. Examples of the acceptable analytical methods for determining total coliforms include the following:

1. Multiple-tube fermentation technique (MTF)
2. Membrane filter technique (MF)
3. Presence-absence coliform test (P-A)
4. Colilert™ system (ONPG-MUG test)
5. Colisure test

Regardless of the method used, the standard sample volume for total coliform testing is now 100 ml. This volume is an increase over the past testing method using 50 mL for the MTF technique.

The multiple-tube fermentation method of testing for coliforms determines the presence or absence of coliforms by the multiple-tube dilution method. This test is a process whereby equal portions of a sample (100 mL) are added to 10 tubes containing a culture medium and an inverted vial. If gas accumulates in the inverted vial, it indicates presumptive evidence of coliform organisms and the sample is considered coliform-positive. If no gas forms in any of the vials, the sample is coliform-negative.

The membrane filter method provides for filtering a 100 mL water sample through a thin, porous, cellulose membrane filter under a partial vacuum. The filter is placed in a sterile container and incubated in contact with a special liquid called a culture medium, which the bacteria use as a food source. Colonies of bacteria then grow on the media. The coliform colonies are visually identified, counted, and recorded as the number of coliform colonies per 100 mL of sample.

The presence-absence (P-A) test for the coliform group is a simple modification of the multiple-tube procedure. Even though this simplified test uses only one large test portion (100 mL) in a single culture bottle, the results still indicate the presence or absence of coliform bacteria and thus meet the testing requirements.

The Colilert™ system is a privately developed version of the ONPG-MUG test procedure that meets the EPA’s laboratory methods requirements. The ONPG-MUG test indicates the presence or absence of coliform bacteria within 24 hours. Although the Colilert™ method can yield presence-absence results within 24 hours and is easier to perform than the Membrane Filtration (MF) method, operators should be aware of the limitations of these tests in evaluating samples for regulatory purposes. The results for the Colilert™ and MF tests are not always comparable, which may be due to the following:

1. Interferences in the sample that may suppress or mask bacterial growth
2. Greater sensitivity of the Colilert™ media
3. Added stress to organisms related to filtering
4. The fact that different media may obtain better growth for some bacteria

These test methods are approved by the EPA for reporting under the Safe Drinking Water Program. When these tests produce conflicting results, however, the safest course of action is to increase monitoring and treatment efforts until the results for each test is negative.

The Colisure test is a presence-absence test for coliform bacteria. A sample of water is added to a dehydrated medium and, after 24 to 48 hours, the medium is examined for the presence of coliforms.

Table \(\PageIndex{1}\): Total Coliform Indicator Color Chart

Water supply systems may contain various other types of bacteria besides coliforms. These organisms are nonpathogenic bacteria and are sometimes referred to as heterotrophic bacteria. During the analyses of water samples for coliforms, heterotrophic bacteria sometimes interfere with the test causing one of the following reactions:

1. MTF technique: a turbid culture with no gas production
2. P-A test: a turbid culture in the absence of an acid reaction
3. MF technique: confluent growth or a coliform colony number too numerous to count

The sample being tested can be considered invalid if any of these situations occurs and total coliforms are not detected. A replacement sample must be taken from the same location within 24 hours of receiving the laboratory results. If the replacement sample also shows heterotrophic interference but tests positive for total coliforms, the sample is considered valid.

Monitoring Frequency

The routine monitoring frequency for community water systems is based on the population served. Routine monitoring frequencies for non-community systems are based on the source of supply and, in some cases, the population served. Whenever a routine sample tests positive for total coliform, two provisions of the Total Coliform Rule take effect: repeat samples (formerly referred to as check samples) must be taken and the original coliform-positive sample must be tested for the presence of fecal coliforms or E. coli to determine whether an actual or potential violation of the coliform MCL exists.

The reason repeat samples are required is to investigate whether the original coliform-positive sample was caused by a contamination problem that exists throughout the distribution system or if it is a localized problem that exists only at that one sampling point. With this information, appropriate corrective action can be taken to eliminate the problem as quickly as possible.

The Total Coliform Rule specifies how many repeat samples must be taken, when, and from what locations. It also directs the water utility to collect a specific number of samples the following month, based on the number of routine samples ordinarily collected.

Non-community systems serving more than 1,000 people have the same requirements as community water systems. Non-community systems serving fewer than 1,000 people are required to collect one routine sample per quarter. When the routine sample tests positive, four repeat samples are required in the same quarter and five samples are required the following quarter.

Whenever a routine or repeat sample tests positive for total coliform, the water agency must collect a set of three or four repeat samples within 24 hours of receiving the laboratory results. At least one of the repeat samples must be taken from the same tap as the original coliform-positive sample; the remaining repeat samples in the set must be collected at nearby taps (within five service connections of the original sampling point), upstream and downstream of the original.

Repeat samples must be taken until no coliforms are detected or until the MCL is exceeded and the state is notified.

Determining Compliance

The MCLG for total coliforms (including fecal coliforms and E. coli) is zero. The MCL, based on the presence-absence concept, is as follows:

1. For water systems analyzing at least 40 samples per month, no more than 5.0 percent of the samples (including routine and repeat samples) may be positive for total coliforms.
2. For water systems analyzing fewer than 40 samples per month, no more than one sample per month may be positive for total coliforms.

The Revised Total Coliform Rule makes another significant change in the way compliance is calculated. All valid coliform-positive samples, routine and repeat samples, must be counted when calculating compliance with the monthly MCL. Under previous regulations, check or repeat samples were not included in the monthly MCL calculation. On a case-by-case basis, the state may declare a sample invalid for one of several reasons, including interference by heterotrophic bacteria during laboratory analysis, as previously discussed.

Total-coliform-positive samples may be invalidated by the state under any of the following conditions:

1. The analytical laboratory acknowledges that improper sample analysis caused the positive result
2. The state determines that the contamination is a local plumbing problem
3. The state has substantial grounds to believe that the positive result was unrelated to the quality of drinking water in the distribution system

Reporting and Notification Requirements

Reporting frequencies for coliform test results increase in step with the urgency of the problem. A water agency must report the results of monthly coliform testing to the state regulatory agency within the first 10 days of the following month.

Any time a water agency fails to collect a sample as required, the state must be notified within 10 days after the system learns of the violation. An invalid sample result is considered a failure to monitor and must be reported.

If the MCL is exceeded, the state must be notified no later than the end of the next business day and the public within 14 days. This requirement could occur when the water agency exceeds its monthly coliform-positive limit or when test results show the presence of fecal coliforms or E. coli in any sample.

The most critical situation exists when either of two situations occurs:

1. A routine sample tests positive for total coliforms and for fecal coliforms or E. coli, and any repeat sample tests positive for total coliforms.
2. A routine sample tests positive for total coliforms and negative for fecal coliforms or E. coli, and any repeat sample tests positive for fecal coliforms or E. coli.

These situations are considered an acute risk to health. This occurrence is a Tier 1 violation, which requires that the state and the public be notified within 24 hours.