2.1: Microbiology Regulations
After reading this section, you should be able to:
- Explain the Total Coliform Rule
- Compare the Groundwater Treatment Rule and Surface Water Treatment Rule
- Describe the concern with Cryptosporidium
Total Coliform Rule
The Total Coliform Rule (TCR), a National Primary Drinking Water Regulation (NPDWR), was published in 1989 and became effective in 1990. The rule sets a health goal (Maximum Contaminant Level Goal (MCLG)) and legal limits (Maximum Contaminant Levels, MCLs)) for the presence of total coliforms in drinking water.
The Environmental Protection Agency (EPA) published the Revised Total Coliform Rule (RTCR) in the Federal Register (FR) in February 2013 (78 FR 10269) and minor corrections in February 2014 (79 FR 10665). The RTCR is the revision to the 1989 Total Coliform Rule (TCR) and is intended to improve public health protection. All public water systems (PWSs), except aircraft PWSs subject to the Aircraft Drinking Water Rule (ADWR) (40 CFR 141 Subpart X), must comply with the RTCR starting April 2016, or an earlier state effective date.
Total coliforms are a group of related bacteria that are, with few exceptions, not harmful to humans. This is very important to note. The EPA considers total coliforms a useful indicator of other pathogens for drinking water. Total coliforms are used to determine the adequacy of water treatment and the integrity of the distribution system.
Key provisions of the RTCR include:
- Setting a maximum contaminant level goal (MCLG) and maximum contaminant level (MCL) for E. coli for protection against potential fecal contamination.
- Setting a total coliform treatment technique (TT) requirement.
- Requirements for monitoring total coliforms and E. coli according to a sample siting plan and schedule specific to the PWS.
- Provisions allowing PWSs to transition to the RTCR using their existing Total Coliform Rule(TCR) monitoring frequency, including PWSs on reduced monitoring under the existing TCR.
- Requirements for seasonal systems (such as, Non-Community Water Systems not operated on a year-round basis) to monitor and certify the completion of a state-approved start-up procedure.
- Requirements for assessments and corrective action when monitoring results show that PWSs may be vulnerable to contamination.
- Public notification (PN) requirements for violations.
- Specific language for CWSs to include in their Consumer Confidence Reports (CCRs) when they must conduct an assessment or if they incur an E. coli MCL violation.
Revised Total Coliform Rule
Overview of the Rule
Revised Total Coliform Rule (RTCR) 78 FR 10269, February 2013, Vol. 78, No. 30
Purpose: Increase public health protection through the reduction of potential pathways of entry for fecal contamination into distribution systems.
General Description
The rule establishes a maximum contaminant level (MCL) for E. coli and uses E. coli and total coliforms to initiate a find and fix approach to address fecal contamination that could enter into the distribution system. It requires public water systems (PWSs) to perform assessments to identify sanitary defects and subsequently take action to correct them.
The Total Coliform Rule applies to all Public Water Systems.
Implementation of the Total Coliform Rule will result in:
- A decrease in the pathways by which fecal contamination can enter the drinking water distribution system.
- Reduction in fecal contamination should reduce the potential risk from all waterborne pathogens including bacteria, viruses, parasitic protozoa, and their associated illnesses.
Requirements:
- Public Water Systems must develop a written sample siting plan that identifies the system’s sample collection schedule and all sample sites, including sites for routine and repeat monitoring.
- PWSs monitoring quarterly or annually must also identify additional routine monitoring sites in their sample siting plans.
- Sample siting plans are subject to state review and revision.
Routine Sampling Requirements
- Total coliform samples must be collected by Public Water Systems at sites which are representative of water quality throughout the distribution system according to a written sample siting plan subject to state review and revision.
- For Public Water Systems collecting more than one sample per month, collect total coliform samples at regular intervals throughout the month, except that ground water systems serving 4,900 or fewer people may collect all required samples on a single day if the samples are taken from different sites.
Repeat Sampling Requirements
Within 24 hours of learning of a Total Coliform positive routine sample result, at least 3 repeat samples must be collected and analyzed for total coliform:
- One repeat sample must be collected from the same tap as the original sample.
- One repeat sample must be collected from within five service connections upstream.
- One repeat sample must be collected from within five service connections downstream.
- The PWS may propose alternative repeat monitoring locations that are expected to better represent pathways of contamination into the distribution system.
If one or more repeat sample is Total Coliform Positive:
- The TC+ sample must be analyzed for the presence of E. coli.
- If any repeat TC+ sample is also EC+, then the EC+ sample result must be reported to the state by the end of the day that the PWS is notified.
- The PWS must collect another set of repeat samples, unless an assessment has been triggered and the PWS has notified the state.
Routine Sampling Requirements
- Each total coliform-positive (TC+) routine sample must be tested for the presence of E. coli.
- If any coliform-positive (TC+) sample is also E. coli-positive (EC+), then the EC+ sample result must be reported to the state by the end of the day that the PWS is notified.
- If any routine sample is TC+, repeat samples are required.
- Public Water Systems on quarterly or annual monitoring must take a minimum of three additional routine samples (known as additional routine monitoring) the month following a TC+ routine or repeat sample.
- Reduced monitoring may be available for Public Water Systems using only ground water and serving 1,000 or fewer persons that meet certain additional Public Water System criteria.
Assessments and Corrective Action
The RTCR requires PWSs that have an indication of coliform contamination (e.g., as a result of TC+ samples, E. coli MCL violations, performance failure) to assess the problem and take corrective action. Two levels of assessments exist (i.e., Level 1 and Level 2) based on the severity or frequency of the problem.
Purpose of Level 1 and Level 2 Assessments
To find sanitary defects at the Public Water System including:
- Sanitary defects that could provide a pathway of entry for microbial contamination
- Sanitary defects that indicate failure (existing or potential) of protective barriers against microbial contamination.
Deadline for Completing Corrective Actions
When sanitary defects are identified during a Level 1 or Level 2 Assessment, they should be corrected as soon as possible to protect public health. The Public Water System must complete corrective actions by one of the following timeframes:
- No later than the time the assessment form is submitted to the state, which must be within 30 days of triggering the assessment, or
- Within state-approved timeframe which was proposed in the assessment form.
Level 1 Assessments
Conducting Level 1 Assessments
- Performed by the PWS owner or operator each time a Level 1 Assessment is triggered.
- Upon trigger of a Level 1 Assessment, the Level 1 Assessment form must be submitted within 30 days to the state.
Level 1 Assessment Triggers
Level 1 Assessment is triggered if any one of the following occurs:
- A Public Water System collecting fewer than 40 samples per month has 2 or more TC+ routine/ repeat samples in the same month.
- A PWS collecting at least 40 samples per month has greater than 5.0 percent of the routine/repeat samples in the same month that are TC+.
- A PWS fails to take every required repeat sample after any single TC+ sample.
Level 2 Assessments
Conducting Level 2 Assessments
Performed by the state or state-approved entity each time a Level 2 Assessment is triggered.
- The Public Water System is responsible for ensuring that the Level 2 Assessment is conducted regardless of the entity conducting the Level 2 Assessment.
- (3)Upon trigger of a Level 2 Assessment, the Level 2 Assessment form must be submitted within 30 days to the state.
Level 2 Assessment Triggers
Level 2 Assessment is triggered if any one of the following occurs:
- A Public Water System incurs an E. coli MCL violation.
- A Public Water System has a second Level 1 Assessment within a rolling 12-month period.
- A Public Water System on state-approved annual monitoring has a Level 1 Assessment trigger in 2 consecutive years.
Seasonal System Provisions
The Total Coliform Rule defines seasonal systems and specifies additional requirements for these types of PWSs:
- A seasonal system is defined as a non-community water system that is not operated as a PWS on a year round basis and starts up and shuts down at the beginning and end of each operating season.
Start-up Procedures for Seasonal Systems
At the beginning of each operating period, before serving water to the public, seasonal water systems must:
- Conduct state-approved start-up procedures.
- Certify completion of state-approved start-up procedures.
- An exemption from conducting state-approved start-up procedures may be available for seasonal systems that maintain pressure throughout the distribution system during non-operating periods.
Examples of state-approved start-up procedures, which need to be completed prior to serving water to the public, may include one or more of the following:
- Disinfection.
- Distribution system flushing.
- Sampling for total coliform and E. coli.
- Site visit by state.
- Verification that any current or historical sanitary defects have been corrected.
Routine Monitoring for Seasonal Systems
- The baseline monitoring frequency for seasonal systems is monthly.
- A reduced monitoring frequency may be available for seasonal systems that use ground water only and serve fewer than 1,000 persons.
Other Provisions for the State Drinking Water Agency Special Monitoring Evaluation
The state must perform a special monitoring evaluation at all ground water systems serving 1,000 or fewer persons during each sanitary survey to review the status of the Public Water System and to determine whether the sample sites and monitoring schedule need to be modified.
Major Violations
E. coli MCL Violation
A Public Water System will receive an E. coli MCL violation when there is any combination of an E.coli positive sample result with a routine/repeat Total Coliform positive or E. coli positive sample result:
E. coli MCL Violation Occurs with the Following Sample Result Combination
Routine Repeat
EC+ TC+
EC+ Any missing sample
EC+ EC+
TC+ EC+
TC+ TC+ (but no E. coli analysis)
Treatment Technique Violation
A PWS will receive a Treatment Technique violation when any of the following occur:
- Failure to conduct a Level 1 or Level 2 Assessment within 30 days of a trigger.
- Failure to correct all sanitary defects from a Level 1 or Level 2 Assessment within 30 days of a trigger or in accordance with the state-approved timeframe.
- Failure of a seasonal system to complete state-approved start-up procedures prior to serving water to the public.
Key Points for Public Water Systems to Remember
Find and correct sanitary defects as soon as you become aware of them. This can help reduce E. coli MCL violations, which trigger a Level 2 Assessment. This can help reduce TC+ sample results, which may trigger a Level 1 Assessment.
Make sure to collect all routine and repeat samples as required. Timely and correct monitoring can help reduce triggering a Level 1 or Level 2 Assessment because:
- Failure to conduct repeat monitoring triggers a Level 1 Assessment.
- A Level 1 Assessment triggered twice within a certain timeframe triggers a Level 2 Assessment.
Surface Water Treatment Rule
The purpose of the Surface Water Treatment Rules (SWTRs) is to reduce illnesses caused by pathogens in drinking water. The disease-causing pathogens include Legionella , Giardia lamblia , and Cryptosporidium .
The SWTRs requires water systems to filter and disinfect surface water sources. Some water systems are allowed to use disinfection only for surface water sources that meet criteria for water quality and watershed protection. This combination of rules is designed to provide protection from microbial pathogens.
Simultaneously, the rules minimize health risks to the population from disinfection byproducts.
For PWSs that use surface water sources and are not required to filter, existing regulations do not require any treatment for Cryptosporidium. New survey data suggest that typical Cryptosporidium levels in the treated water of unfiltered PWSs are higher than in the treated water of filtered PWSs. Thus, Cryptosporidium treatment by unfiltered PWSs is needed to achieve comparable public health protection.
Further, results from recent treatment studies has allowed EPA to develop standards for the inactivation of Cryptosporidium by ozone, ultraviolet (UV) light, and chlorine dioxide. Based on these developments, the EPA has established requirements for all unfiltered PWSs to treat for Cryptosporidium, with the required degree of treatment depending on the source water contamination level. Additionally, the long-term rule addresses risks in uncovered finished water storage facilities, in which treated water can be subject to significant contamination as a result of runoff, bird and animal wastes, human activity, algal growth, insects, fish, and airborne deposition. Existing regulations prohibit the building of new uncovered finished water storage facilities. Under the long-term rule, PWSs must limit potential risks by covering or treating the discharge of such storage facilities. The requirements in the Surface Water Treatment Rule reflect consensus recommendations from the Stage 2 Microbial and Disinfection Byproducts (M–DBP) Federal Advisory Committee. These recommendations are set forth in the Stage 2 M–DBP Agreement in Principle.
Long-Term Surface Water Treatment Rule
Source Water Monitoring. The rule requires PWSs using surface water or groundwater under the direct influence (GWUDI) of surface water to monitor their source water (the influent water entering the treatment plant) to determine an average Cryptosporidium level. Monitoring results determine the extent of Cryptosporidium treatment requirements.
Large PWSs (serving at least 10,000 people) must monitor for Cryptosporidium (plus E. coli and turbidity in filtered PWSs) for a period of two years. To reduce monitoring costs, small filtered PWSs (serving fewer than 10,000 people) initially monitor just for E. coli for one year as a screening analysis and are required to monitor for Cryptosporidium only if their E. coli levels exceed specified trigger values. Small filtered PWSs that exceed the E. coli trigger, as well as all small unfiltered PWSs, must monitor for Cryptosporidium for one or two years, depending on the sampling frequency.
Under the long-term rule, specific criteria are set for sampling frequency and schedule, sampling location, using previously collected data, providing treatment instead of monitoring, sampling by PWSs that use surface water for only part of the year, and monitoring of new plants and sources. The long-term rule also establishes requirements for reporting of monitoring results, using analytical methods, and using approved laboratories. The rule also requires a second round of monitoring to begin approximately 6.5 years after the first round concludes in order to determine if source water quality has changed to a degree that should affect treatment requirements.
The long-term rule establishes risk-targeted treatment technique requirements to control Cryptosporidium in PWSs using surface water or GWUDI. These treatment requirements supplement those established by existing regulations. Filtered PWSs are classified in one of four treatment categories (or bins) based on the results of the source water Cryptosporidium monitoring. This bin classification determines the degree of additional Cryptosporidium treatment, if any, that filtered PWS must provide. PWSs classified in Bins 2, 3, or 4 must achieve 1.0 to 2.5-log of treatment (90 to 99.7 percent reduction) for Cryptosporidium over and above that provided with conventional treatment. Different additional treatment requirements may apply to PWSs using other than conventional treatment, such as direct filtration, membranes, or cartridge filters.
Filtered PWSs must meet the additional Cryptosporidium treatment required in Bins 2, 3, or 4 by using one or more treatment or control processes from a microbial toolbox of options. The long-term rule requires all unfiltered PWSs to provide at least 2-log (99 percent) inactivation of Cryptosporidium . If the average source water Cryptosporidium level exceeds 0.01 oocysts/L, the unfiltered PWS must provide at least 3-log (99.9 percent) inactivation of Cryptosporidium . Further, under the long-term rule, unfiltered PWSs must achieve their overall inactivation requirements (including Giardia lamblia and virus inactivation) using a minimum of two disinfectants.
PWSs with uncovered finished water storage facilities must take steps to address contamination risks. Existing regulations require PWSs to cover all new storage facilities for finished water but do not address existing uncovered finished water storage facilities. Under the long-term rule, PWSs using uncovered finished water storage facilities must cover the storage facility or treat the storage facility discharge to achieve inactivation and/or removal of 4-log virus, 3-log Giardia lamblia , and 2-log Cryptosporidium on a state-approved schedule.
The rule applies to all PWSs using surface water or GWUDI, including large and small PWSs, community and non-community PWSs, and non-transient and transient PWSs. Wholesale PWSs must comply with the requirements of the rule based on the population of the largest PWS in the combined distribution system.
Consecutive PWSs that purchase treated water from wholesale PWSs that fully comply with the monitoring and treatment requirements of the rule are not required to take additional steps for that water.
Existing Regulations for Microbial Pathogens in Drinking Water
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The Surface Water Treatment Rule (SWTR) (54 FR 27486, June 1989) applies to all PWSs using surface water or ground water under the direct influence (GWUDI) of surface water as sources (Subpart H PWSs). It established MCLGs of zero for
Giardia lamblia
, viruses, and
Legionella
, and includes the following treatment technique requirements to reduce exposure to pathogenic microorganisms:
- Filtration, unless specific avoidance criteria are met
- Maintenance of a disinfectant residual in the distribution system
- Removal and/or inactivation of 3-log (99.9%) of Giardia lamblia and 4-log (99.99%) of viruses
- Maximum allowable turbidity in the combined filter effluent (CFE) of 5 nephelometric turbidity units
- (NTU) and 95th percentile CFE turbidity of 0.5 NTU or less for plants using conventional treatment or direct filtration
- Watershed protection and source water quality requirements for unfiltered PWSs
- The Total Coliform Rule (TCR) (54 FR 27544, June 1989) applies to all PWSs. It established an MCLG of zero for total and fecal coliform bacteria and an MCL based on the percentage of positive samples collected. Coliforms are used as an indicator of fecal contamination and to determine the integrity of the water treatment process and distribution system. Under the Total Coliform Rule, no more than 5 percent of distribution system samples collected in any month may contain coliform bacteria (no more than 1 sample per month may be coliform positive in those PWSs that collect fewer than 40 samples per month). The number of samples to be collected in a month is based on the number of people served by the PWS.
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Interim Enhanced Surface Water Treatment Rule (63 FR 69478, December 16, 1998) (USEPA 1998a) applies to PWSs serving at least 10,000 people and using surface water or GWUDI sources. Key provisions established by the interim rule include the following:
- An MCLG of zero for Cryptosporidium
- Cryptosporidium removal requirements of 2-log (99 percent) for PWSs that filter
- More stringent turbidity performance standards of 1.0 NTU as a maximum and 0.3 NTU or less at the 95th percentile monthly for treatment plants using conventional treatment or direct filtration
- Requirements for individual filter turbidity monitoring
- Disinfection benchmark provisions to assess the level of microbial protection that PWSs provide as they take steps to comply with new disinfection by-products standards
- Inclusion of Cryptosporidium in the definition of GWUDI and in the watershed control requirements for unfiltered PWSs
- Requirements for covers on new finished water storage facilities
- Sanitary surveys for all surface water systems regardless of size
The interim surface water treatment rule was developed in conjunction with the Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1 DBPR) (63 FR 69389, December 1998), which reduced allowable levels of certain DBPs, including trihalomethanes, haloacetic acids, chlorite, and bromate.
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Long Term 1 Enhanced Surface Water Treatment Rule (67 FR 1812, January 2002) builds on the microbial control provisions established by the interim rule for large PWSs through extending similar requirements to small PWSs. The long-term interim rule applies to PWSs that use surface water or GWUDI as sources and that serve fewer than 10,000 people. Like the interim rule, the long-term rule established the following:
- 2- log (99 percent) Cryptosporidium removal requirements by PWSs that filter
- Individual filter turbidity monitoring and more stringent combined filter effluent turbidity standards for conventional and direct filtration plants
- Disinfection profiling and benchmarking; inclusion of Cryptosporidium in the definition of GWUDI and in the watershed control requirements for unfiltered PWSs
- The requirement that new finished water storage facilities be covered.
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Filter Backwash Recycle Rule (66 FR 31085, June 2001) requires PWSs to consider the potential risks associated with recycling contaminants removed during the filtration process. The provisions of the filter backwash rule apply to all PWSs that recycle, regardless of population served. In general, the provisions include the following:
- PWSs must return certain recycle streams to a point in the treatment process that is prior to primary coagulant addition unless the State specifies an alternative location
- Direct filtration PWSs recycling to the treatment process must provide detailed recycle treatment information to the State
- Certain conventional PWSs that practice direct recycling must perform a one-month, one-time recycling self-assessment
Introduction to Cryptosporidium
Concern with Cryptosporidium in Drinking Water
EPA is promulgating the Long-Term Surface Water Treatment Rule to reduce the public health risk associated with Cryptosporidium in drinking water.
Figure 2.1.1: Cryptosporidiosis.
Cryptosporidium is a protozoan parasite that lives and reproduces entirely in one host. Ingestion of Cryptosporidium can cause cryptosporidiosis, a gastrointestinal (GI) illness. Cryptosporidium is excreted in feces. Transmission of cryptosporidiosis occurs through consumption of water or food contaminated with feces or by direct or indirect contact with infected persons or animals. In the environment, Cryptosporidium is present as a thick-walled oocyst containing four organisms (sporozoites).
The oocyst wall insulates the sporozoites from harsh environmental conditions. Oocysts are 4–5 microns in length and width. Upon a host’s ingestion of oocysts, enzymes and chemicals produced by the host’s digestive system cause the oocyst to excyst, or break open. The excysted sporozoites embed themselves in the surfaces of the epithelial cells of the lower small intestine. The organisms then begin absorbing nutrients from their host cells. When these organisms sexually reproduce, they produce thick and thin-walled oocysts. The host excretes the thick-walled oocysts in its feces. The thin-walled oocysts excyst within the host and contribute to further host infection.
The exact mechanism by which Cryptosporidium causes GI illness is not known. Factors may include damage to intestinal structure and cells, changes in the absorption/secretion processes of the intestine, toxins produced by Cryptosporidium or the host, and proteins that allow Cryptosporidium to adhere to host cell surfaces. Upon excretion, Cryptosporidium oocysts may survive for months in various environmental media, including soil, river water, seawater, and human and cattle feces at ambient temperatures. Cryptosporidium can also withstand temperatures as low as 20 °C for periods of a few hours, but they are susceptible to desiccation.
Cryptosporidium is a widespread contaminant in surface water used as drinking water supplies. Cryptosporidium contamination can come from animal agriculture, wastewater treatment plant discharges, slaughterhouses, birds, wild animals, and other sources of fecal matter. Cryptosporidium parvum (C. parvum ) has been the primary species of concern to humans.
Cryptosporidium infection is characterized by mild to severe diarrhea, dehydration, stomach cramps, and/or a slight fever. Incubation is thought to range from 2 to 10 days. Symptoms typically last from several days to 2 weeks. In a small percentage of cases, the symptoms may persist for months or longer in healthy individuals. Symptoms may be more severe in immunocompromised persons. Such persons include those with AIDS, cancer patients undergoing chemotherapy, organ transplant recipients treated with drugs that suppress the immune system, and patients with autoimmune disorders.
Cryptosporidium oocysts are highly resistant to standard disinfectants like chlorine and chloramines. Consequently, control of Cryptosporidium in most treatment plants is dependent on physical removal processes. However, due to their size (4–5 microns), oocysts can sometimes pass through filters. Monitoring data on finished water show that Cryptosporidium is sometimes present in filtered, treated drinking water.
Certain alternative disinfectants can be more effective in treating for Cryptosporidium . Ozone and chlorine dioxide have been shown to inactivate Cryptosporidium at doses higher than those required to inactivate Giardia , which has typically been used to set disinfectant doses. Studies have also demonstrated a synergistic effect of treatment using ozone followed by chlorine or monochloramine. UV light has recently been shown to achieve high levels of Cryptosporidium inactivation at feasible doses. Other processes that can help reduce Cryptosporidium levels in finished water include watershed management programs, pretreatment processes like bank filtration, and additional clarification and filtration processes during water treatment. Further, optimizing treatment performance and achieving very low levels of turbidity in the finished water has been shown to improve Cryptosporidium removal in treatment plants.
Cryptosporidium has caused a number of waterborne disease outbreaks since 1984 when the first was reported in the United States. Data from the Centers for Disease Control and Prevention include ten outbreaks caused by Cryptosporidium in drinking water between 1984 and 2000, with approximately 421,000 cases of illness. The most serious outbreak occurred in 1993 in Milwaukee; an estimated 403,000 people became sick, and at least 50 Cryptosporidium -associated deaths occurred among the severely immunocompromised.
A PWS that begins using a new surface water source after the date the PWS is required to conduct source water monitoring under the Long-Term 2 Surface Water Treatment Rule must monitor the new source on a schedule approved by the State. This applies to new plants that begin operation and previously operating plants that bring a new source on-line after the required monitoring date for the PWS. The State may determine that monitoring should be conducted before a new plant or source is brought on-line or initiated within some time period afterward.
The new source monitoring must meet all long-term rule requirements. The PWS must also determine its treatment bin classification and comply with any additional Cryptosporidium treatment requirements based on the monitoring results on a schedule approved by the State.
Background and Analysis Monitoring requirements in the rule are designed to ascertain Cryptosporidium levels with suitable accuracy for making treatment bin classifications and in a time frame that does not delay the installation of Cryptosporidium treatment where needed. A mean Cryptosporidium concentration of 0.01 oocysts/L determines whether unfiltered PWSs are required to provide 2 or 3-log Cryptosporidium inactivation. No E. coli concentration was effective in determining whether PWSs were likely to fall above or below this level. Consequently, the rule requires all unfiltered PWSs to monitor for Cryptosporidium , unless they choose to provide 3-log Cryptosporidium inactivation.
Sampling location
The requirements in the rule for the source water sample collection location are designed to achieve two objectives:
- Characterize the influent water to the treatment plant at the time each sample is collected.
- Ensure that samples are not affected by treatment chemicals that could interfere with Cryptosporidium analysis.
The first objective is the basis for requiring PWSs that use multiple sources to analyze a blended source sample or calculate a weighted average of sources that reflects the influent at the time of sample collection. It is also the reason that PWSs are required to sample after certain pretreatment processes like bank filtration that do not involve chemical addition.
The second objective is why PWSs are generally required to sample upstream of chemical addition and prior to backwash addition (for PWSs that recycle filter backwash). However, EPA recognizes that in some situations, sampling prior to chemical addition will not be feasible and discontinuing chemical addition for a period of time prior to sampling will not be advisable. This situation could occur when a treatment chemical is added at an intake that is difficult to access. Further, some treatment chemicals may not interfere with Cryptosporidium analyses when present at very low levels. Consequently, the rule allows States to approve PWSs sampling after chemical addition when the State determines that collection prior to chemical treatment is not feasible, and the treatment chemical is not expected to interfere with the analysis of the sample. EPA believes that States should review source water monitoring locations for their PWSs.
Sampling Schedule
The requirement will help to ensure that monitoring determines the mean concentration of Cryptosporidium in the treatment plant influent. To achieve this objective, the timing of sample collection must not be adjusted in response to fluctuations in water quality, such as the avoidance of sampling when the influent water is expected to be of poor quality. EPA believes that the 5-day window for sample collection and associated allowances for sampling outside this window provide sufficient flexibility. If circumstances arise that prevent the PWS from sampling within the scheduled 5-day window, such as a weather event or plant emergency, the PWS must collect a sample as soon as feasible. In this case, feasibility includes the ability of the PWS to safely collect a sample and the availability of an approved laboratory to conduct the analysis within method specifications. In addition, the rule allows States to authorize a different date for collecting the delayed sample.
Failing to Monitor
For most monitoring and testing procedure violations under the Long-Term Rule 2, PWSs must provide a Tier 3 public notification, which is standard for this type of violation under an NPDWR. However, if a PWS fails to collect three or more Cryptosporidium samples, the violation is elevated to a Tier 2 special public notice. The reason for elevating the public notice at this point is the persistence of the violation and the difficulty the PWS will have in collecting the required number of samples for bin classification by the compliance date. The rule requires bin classification within six months following the end of the monitoring period specified for the PWS. This six-month period provides some opportunity for collecting and analyzing missed samples. The number of samples that can be made up in this period is limited, though, due to the need for samples to be evenly distributed throughout the year, as well as for PWSs and States to spend time during this period evaluating monitoring results to determine bin classification.
Failure by a PWS to collect the required number of Cryptosporidium samples for bin classification by the compliance date is a treatment technique violation with a required Tier 2 public notice. This violation reflects the inability of the PWS to determine and comply with its Cryptosporidium treatment requirements under the rule and provide the appropriate level of public health protection. The violation ends when the State determines that the PWS is carrying out a monitoring plan that will lead to bin classification.
A PWS that has already provided a Tier 2 public notice for missing three sampling dates and is successfully meeting a State-approved sampling schedule is not required to issue another public notice for missing the bin classification date. Alternatively, the PWS can choose to provide the highest level of Cryptosporidium treatment required under the rule, which is 5.5-log for filtered PWSs and 3-log for unfiltered PWSs.
Requirements for grandfathering previously collected monitoring data in the rule based on the principle that to be eligible for grandfathering, previously collected data must be equivalent in quality to data that will be collected under the rule.
The Stage 2 M–DBP Advisory Committee recommended that EPA accept previously collected Cryptosporidium data that are equivalent in sample number, frequency, and data quality (volume analyzed, percent recovery) to data that would be collected under the long-term rule to determine bin classification in lieu of further monitoring.
Ongoing watershed assessment treatment requirements under the rule are based on source water quality. Consequently, the rule requires watershed assessment and, a second round of monitoring following initial bin classification to determine if source water quality has changed to the degree that the treatment level should be modified. States are allowed to use programs other than the sanitary survey to assess changes in the watershed. The rule leverages the existing requirement for States to perform sanitary surveys on surface water PWSs. During the source water review in the sanitary survey, the rule requires States to determine if significant changes have occurred in the watershed that could lead to increased contamination by Cryptosporidium . The State can also choose to make this determination through an equivalent review of the source water under a program other than the sanitary survey, such as a Source Water Protection Assessment. If the State determines that significant changes have occurred, the State may specify that the PWS conduct additional source water monitoring or treat the potential contamination. This approach allows the PWS and State to respond to a significant change in source water quality prior to initiating a second round of monitoring or any time thereafter.
Second Round of Monitoring
A more rigorous reassessment of the source water occurs through a second round of monitoring that begins six years after initial bin classification. If EPA does not develop and finalize modifications to the rule prior to the date when PWSs must begin the second round of monitoring, then this second round must conform to the same requirements that applied to the initial round of monitoring. PWSs may be classified in a different treatment bin, depending on the results of the second round of monitoring.
Process Summary
Source water monitoring to determine additional treatment requirements for Cryptosporidium.
- Sampling parameters and frequency, sampling location, sampling schedule, monitoring plants that operate only part-year, failing to monitor, providing treatment instead of monitoring, grandfathering previously collected data, ongoing source water assessment, second round of monitoring, and new source monitoring.
The Rule requires filtered PWSs using surface water or GWUDI sources to provide greater levels of treatment if their source waters have higher concentrations of Cryptosporidium . Filtered PWSs are classified in one of four treatment bins based on results from the source water monitoring. PWSs classified in the lowest concentration bin are subject to no additional treatment requirements, while PWSs assigned to higher concentration bins must reduce Cryptosporidium levels. All PWSs must continue to comply with the requirements of the SWTR, IESWTR, and LT1ESWTR, as applicable. This section addresses procedures for classifying filtered PWSs in Cryptosporidium treatment bins and the treatment requirements associated with each bin. Microbial toolbox that PWSs must use to meet additional Cryptosporidium treatment requirements.
- Bin classification-after completing initial source water monitoring, filtered PWSs must calculate a Cryptosporidium bin concentration for each treatment plant where Cryptosporidium monitoring is required. This Cryptosporidium bin concentration is used to classify filtration plants in one of the four treatment bins.
In general, the Cryptosporidium bin concentration is calculated by averaging individual sample results from one or more years of monitoring. Specific procedures vary, however, depending on the frequency and duration of monitoring. These procedures are as follows:
- For PWSs that collect a total of at least 24 but not more than 47 Cryptosporidium samples over two or more years, the Cryptosporidium bin concentration is equal to the highest arithmetic mean of all sample concentrations in any 12 consecutive months of Cryptosporidium monitoring.
- For PWSs that collect a total of at least 48 samples, the Cryptosporidium bin concentration is equal to the arithmetic mean of all sample concentrations.
- For PWSs that serve fewer than 10,000 people and monitor for Cryptosporidium for only one year (collect 24 samples in 12 months), the Cryptosporidium bin concentration is equal to the arithmetic mean of all sample concentrations.
- For PWSs with plants that operate only part-year that monitor for less than 12 months per year, the Cryptosporidium bin concentration is equal to the highest arithmetic mean of all sample concentrations during any year of Cryptosporidium monitoring.
In data sets with variable sampling frequency, PWSs must first calculate an arithmetic mean for each month of sampling and then apply one of these four procedures using the monthly mean concentrations. PWSs may grandfather previously collected Cryptosporidium data where the sampling frequency varies (one year of monthly sampling and one year of twice-per- month sampling). Filtered PWSs serving fewer than 10,000 people are not required to monitor for Cryptosporidium if they demonstrate a mean E. coli concentration less than or equal to 10/ 100 mL for lake/reservoir sources or 50/ 100 mL for flowing stream sources or do not exceed an alternative State-approved indicator trigger. PWSs that meet this criterion are classified in Bin 1.
When determining the Cryptosporidium bin concentration, PWSs must calculate individual sample concentrations as the total number of oocysts counted, divided by the volume as saved. In samples where no oocysts are detected, the result is assigned a value of zero for the purpose of calculating the bin concentration. Sample analysis results are not adjusted for analytical method recovery or the percent of Cryptosporidium oocysts that are infectious. PWSs must report their treatment bin classification to the State for approval following initial source water monitoring. The report must include a summary of the data and calculation procedure used to determine the bin concentration. PWSs must recalculate their bin classification after completing the second round of monitoring and report the results to the State for approval. If the State does not respond to a PWS regarding its bin classification after either report, the PWS must comply with the Cryptosporidium treatment requirements of the rule based on the reported bin classification.
- Bin treatment requirements. All filtered PWSs must comply with the treatment requirements based on their bin classification.
The total Cryptosporidium treatment required for plants in Bins 2, 3, and 4 is 4.0-log, 5.0-log, and 5.5-log, respectively. Conventional treatment (including softening), slow sand, and diatomaceous earth filtration plants in compliance with the IESWTR or LT1ESWTR, as applicable, receive a prescribed 3.0-log Cryptosporidium treatment credit toward these total bin treatment requirements. Accordingly, these plant types must provide 1.0 to 2.5-log of additional treatment when classified in Bins 2–4, respectively. Direct filtration plants in compliance with existing regulations receive a prescribed 2.5-log treatment credit and, consequently, must achieve 0.5-log greater treatment to comply with Bins 2–4.
For PWSs using alternative filtration technologies, such as membranes, bag filters, or cartridge filters, no prescribed treatment credit is available because the performance of these processes is specific to individual products. Consequently, when PWSs using these processes are classified in Bins 2–4, the State must determine additional treatment requirements based on the credit the State awards to a particular technology. The additional treatment requirements must ensure that plants classified in Bins 2–4 achieve total Cryptosporidium reductions of 4.0- to 5.5-log, respectively. PWSs can achieve additional Cryptosporidium treatment credit through implementing pretreatment processes like pre-sedimentation or bank filtration, by developing a watershed control program, and by applying additional treatment steps like ozone, chlorine dioxide, UV, and membranes. In addition, PWSs can receive a higher level of credit for existing treatment processes through achieving very low filter effluent turbidity or through a demonstration of performance.
A combination of options from the microbial toolbox can be used to gather additional credit. PWSs in Bin 2 can meet additional Cryptosporidium treatment requirements by using any option or combination of options from the microbial toolbox. For Bins 3 and 4, PWSs must achieve at least 1-log of the additional treatment requirement by using ozone, chlorine dioxide, UV, membranes, bag filtration, cartridge filtration, or bank filtration.
- The rule increases protection against Cryptosporidium and other pathogens in PWSs with the highest source water contamination levels. This targeted approach builds upon existing regulations under which all filtered PWSs must provide the same level of treatment regardless of source water quality. The rule is to ensure that PWSs with higher risk source waters achieve public health protection commensurate with PWSs with less contaminated sources.
The rule establishes risk-targeted Cryptosporidium treatment requirements and sets specific bin concentration ranges and treatment requirements that apply to filtered PWSs. The IESWTR established a Cryptosporidium MCLG of zero and requires large filtered PWSs to achieve 2-log Cryptosporidium removal. The LT1ESWTR extended this requirement to small PWSs. After these rules were promulgated, advances were made in analytical methods and treatment for Cryptosporidium, and EPA collected new information on Cryptosporidium occurrence and infectivity. Consequently, EPA assessed the implications of these developments for further controlling Cryptosporidium to approach the zero MCLG. The risk-targeted approach for filtered PWSs in the rule stems from four general findings based on new information on Cryptosporidium :
- New data on Cryptosporidium infectivity suggest that the risk associated with a particular level of Cryptosporidium is most likely higher than EPA estimated at the time of earlier rules.
- New data on Cryptosporidium occurrence indicate that levels are relatively low in most water sources, but a subset of sources has substantially higher concentrations.
- The finding that UV light can readily inactivate Cryptosporidium , as well as other technology developments, makes achieving high levels of treatment for Cryptosporidium feasible for PWSs of all sizes.
- EPA Methods 1622 and 1623 are capable of assessing annual mean levels of Cryptosporidium in drinking water sources.
These findings led EPA to conclude that most filtered PWSs currently provide sufficient treatment for Cryptosporidium , but additional treatment is needed in those PWSs with the highest source water Cryptosporidium levels to protect public health. Further, PWSs can characterize Cryptosporidium levels in their source waters with available analytical methods and can provide higher levels of treatment with available technologies. Consequently, risk-targeted treatment requirements for Cryptosporidium based on source water contamination levels are appropriate and feasible to implement.
Basis for bin concentration ranges and treatment requirements. To establish the risk-targeted treatment requirements in today’s rule, EPA had to determine the degree of treatment that should be required for different source water Cryptosporidium levels to protect public health. This determination involved addressing several questions:
- What is the risk associated with Cryptosporidium in a drinking water source?
- How much Cryptosporidium removal do filtration plants achieve?
- What is the appropriate statistical measure for classifying PWSs into treatment bins?
- What degree of additional treatment is needed for higher source water Cryptosporidium levels?
- How should PWSs calculate their treatment bin classification?
The risk of infection from Cryptosporidium in drinking water is a function of exposure (the dose of oocysts ingested) and infectivity (likelihood of infection as a function of ingested dose). Primary (direct) exposure to Cryptosporidium depends on the concentration of oocysts in the source water, the fraction removed by the treatment plant, and the volume of water consumed (secondary exposure occurs through interactions with infected individuals). Thus, the daily risk of infection (DR) is as follows:
DR = (oocysts/L in source water) × (fraction remaining after treatment) × (liters consumed per day) × (likelihood of infection per oocyst dose). Assuming 350 days of consumption per year for people served by community water systems (CWSs), the annual risk (AR) of infection is as follows: AR = 1 ¥ (1 ¥ DR)350.
EPA has estimated the mean likelihood of infection from ingesting one Cryptosporidium oocyst to range from 4 to 16 percent. Median individual daily water consumption is estimated as 1.07 L/day.
Key Terms
- Cryptosporidium - a protozoan parasite that lives and reproduces entirely in one host; ingestion of Cryptosporidium can cause cryptosporidiosis, a gastrointestinal (GI) illness; cryptosporidium is excreted in feces.
- Ground Water Rule (GWR) – the purpose is to improve drinking water quality and provide protection from disease-causing microorganisms; water systems that have groundwater sources may be susceptible to fecal contamination; applies to public water systems that use ground water as a source of drinking water
- Surface Water Treatment Rules (SWTRs) – the purpose is to reduce illnesses caused by pathogens in drinking water, including Legionella , Giardia lamblia , and Cryptosporidium ; the SWTRs requires water systems to filter and disinfect surface water sources.
- Total Coliform Rule (TCR) - a National Primary Drinking Water Regulation (NPDWR), published in 1989 and became effective in 1990; sets a health goal (Maximum Contaminant Level Goal (MCLG)) and legal limits (Maximum Contaminant Levels, MCLs)) for the presence of total coliforms in drinking water
Review Questions
- What are the primary components of the Total Coliform Rule?
- What is the basis of the Total Coliform Rule?
- What is the primary requirement in the Groundwater Rule?
- List four EAP approved laboratory methods for testing for coliforms.
- What are the major provisions of the Long-Term Surface Water Treatment Rule?
Chapter Quiz
-
Total coliforms are used as a(n) _______ of the possible presence of pathogens in drinking water. Total coliforms are used to determine the adequacy of water treatment and the integrity of the distribution system.
- indicator
- model
- log removal
- alternative
-
The Revised Total Coliform Rule establishes _________for E. coli and uses E. coli and total coliforms to initiate a find and fix approach to address fecal contamination that could enter into the distribution system.
- a log removal
- a maximum contaminant level (MCL)
- a secondary maximum contaminant level (SMCL)
- a model
-
Within 24 hours of learning of a Total Coliform positive routine sample result, at least ____ repeat samples must be collected and analyzed for total coliform.
- 1
- 2
- 3
- 4
-
States are required to conduct __________ of all groundwater systems in order to identify significant deficiencies, including deficiencies which may make a system susceptible to microbial contamination.
- hydrologic studies
- microbial examinations
- a sanitary survey
- laboratory studies
-
The Surface Water Treatment Rule requires water systems to ________ surface water sources.
- filter and disinfect
- conserve
- aerate
- disinfect
-
In order not to be subject to triggered source water monitoring under the Groundwater Rule, a groundwater system can notify the state that it provides at least _______ treatment of viruses using virus inactivation, or removal, before or at the first customer.
- 2-log
- 3-log
- 4-log
- 6-log
-
The Long-Term Surface Water Rule establishes risk-targeted treatment technique requirements to control
_________
in PWSs using surface water or groundwater under the influence of surface water.
- E.coli
- Giardiasis lambdia
- Cryptosporidium
- Coliforms
-
What is the maximum allowable turbidity in the combined filter effluent?
- 0.5 NTU
- 1.0 NTU
- 3.0 NTU
- 5.0 NTU
-
EPA promulgated the Long-Term Surface Water Treatment Rule to reduce the public health risk associated with ________ in drinking water.
- Giardiasis lambdia
- Cryptosporidium
- Coliforms
- E. coli
-
_________ is a protozoan parasite that lives and reproduces entirely in one host,
- E. coli
- Coliforms
- Cryptosporidium
- Fecal streptococcus