New drinking water rules

The U.S. Environmental Protection Agency (EPA) released two new rules last year that will ultimately affect all water treatment facilities and distribution systems that use chemical disinfectants. These are the Interim Enhanced Surface Water Treatment Rule (IESWTR) and the Disinfectants and Disinfection Byproducts Final Rule. This is also known as the Stage 1 Disinfection Byproducts Rule (DBPR).

These new rules became effective Feb. 16, 1999. Compliance with the IESWTR and the DBPR is generally required by December 2001, unless EPA or a state establishes a different date, based upon the individual circumstances of the water system in question.

IESWTR applies to public water systems that serve a population of 10,000 or more people, and use either surface water or groundwater under the direct influence of surface water (GWUDI). The rule states that "the Stage 1 Disinfection Byproducts Rule (DBPR) applies to community water systems and nontransient noncommunity water systems that treat their water with a chemical disinfectant for either primary or residual treatment. In addition, certain requirements for choline dioxide apply to transient noncommunity water systems" (Federal Register 63:241:69390, Dec. 16, 1998).

In addition, the new rule notes that systems serving a population of less than 10,000 people are required to comply with the applicable Stage 1 Disinfection Byproducts Rule by December 2003. These rules are the first step toward future regulations that will eventually cover all public water systems, regardless of size, that use surface water or GWUDI.

The primary purpose of the IESWTR is to help alleviate the threat of microbial pathogen contamination. The principal objective of the DBPR is to help lessen the adverse effects of disinfection byproducts. The two rules are designed to work together to help balance the risk between microbial pathogens and disinfection byproducts by requiring:

  • A maximum contaminant level goal (MCLG) of zero for Cryptosporidium;
  • More stringent effluent filter monitoring requirements;
  • Sanitary surveys for all surface water systems;
  • Disinfection benchmarking; and
  • Maximum contamination levels (MCLs) and MCLGs for disinfection byproducts that may react to produce a carcinogen.

Some of the new regulations are not currently effective for small facilities (population less than 10,000), but a portion of the new rules will eventually apply to facilities in almost all communities.

Disinfection benchmarking and profiling, where necessary, is required for operators of water systems to document the impact of microbial protection with existing disinfection practices. Benchmarking will involve charting daily levels of Giardia lamblia inactivation for a period of at least one year to create a profile of inactivation performance. Benchmarking sampling is to begin by March 2000.

Since the early 1970s, U.S. health authorities have been striving to issue standards for the controls and identification of acceptable levels of trihalomethanes (THMs), which are halogenated chloro-organic compounds suspected of being carcinogenic. The increasing use of higher levels of chlorination for disinfection of raw water and the consequent formation of THMs has prompted extensive studies concerning THMs' possible toxicity and carcinogenicity. Now EPA has lowered the maximum contaminant levels for THMs from 0.1 mg/L to 0.08 mg/L.

As the water system modifies the disinfection practices in order to comply with the MCLs for total trihalomethanes (TTHM) and haloacetic acids (HAA5), the system will document whether or not progress is being made, or if the previous disinfection practices actually provided better overall results. The reasoning behind this requirement is that most microbial pathogens are rendered inactive with chlorination. As other disinfectants are used in order to meet the MCLs for TTHM and HAA5, they may produce byproducts that potentially create larger problems than they solve.

In other words, if you own, operate or maintain a water treatment facility for the purpose of producing potable water, your life is probably about to become more complicated, and your costs are likely to increase. Although many larger facilities are equipped to accommodate the new regulations, most smaller systems are not. Additional and unanticipated capital costs, as well as an increase in annual operation and maintenance expenses, will likely cause repeated reference to the hardships associated with "unfunded federal mandates."

The IESWTR provides better filter performance for surface water or GWUDI systems that use conventional treatment or direct filtration and serve a population of more than 10,000 people. This is accomplished by requiring a combined filter effluent turbidity of less than or equal to 0.3 nephelometric turbidity units (NTU) (previous rule required 0.5 NTU) in at least 95 percent of the measurements taken each month. Additionally, the combined filter effluent turbidity must not exceed 1 NTU (previous rule 5 NTU) at any time. Compliance is based upon the combined filter effluent totals, measured at four-hour intervals.

Continuous monitoring is now required for individual filter performance (facilities meeting the same requirements for combined filter performance). Under the previous rule, individual filters were not required to be monitored. Now, any individual filter that has a turbidity level of greater than 1.0 NTU (based upon two consecutive measurements taken 15 minutes apart), or a turbidity level of greater than 0.5 NTU at the end of the first four hours of operation (based upon two consecutive measurements taken 15 minutes apart), must be reported as a violation. The report must be made to the state on a monthly basis along with an explanation of why the violation occurred. A filter profile - a graphic representation to show filter performance - may be submitted as an alternative.

If the turbidity of an individual filter exceeds 1.0 NTU as described above for a consecutive three-month period, the system operator must prepare an exceptions report and conduct a self-assessment of the filter. If the turbidity of an individual filter exceeds 2.0 NTU as described above for a consecutive two-month period, the operator must prepare an exceptions report and arrange for a state or state-approved third party comprehensive performance evaluation.

The new rules provide for a MCLG of zero for the protozoan genus Cryptosporidium; and 2-log removal of Cryptosporidium in filter systems for populations of 10,000 or more. EPA data shows that if the treatment train operates under appropriate coagulation conditions and the filters meet the new requirements for filter effluent turbidity, the system should be able to comply with the 2-log removal requirement. The new filter rules are designed to help alleviate the potential for an outbreak of Cryptosporidium. Since Cryptosporidium is resistant to most disinfection practices commonly used today, EPA has decided there is a need to strengthen the physical removal of Cryptosporidium by filtration in the treatment process. This will also increase the end users' protection from other pathogens, i.e., Giardia or other waterborne bacterial or viral pathogens, thereby assisting EPA with its mandate to protect public health. EPA estimates that about 50 percent of water treatment plant s will modify their treatment practices to meet the revised turbidity requirements.

In 1993, Cryptosporidium was found in the drinking water in Milwaukee, and linked to a disease outbreak. According to EPA, this contaminant sickened nearly 400,000 residents and contributed to the deaths of at least 50 people, many of whom had compromised immune systems.

This widely publicized tragedy has spurred significant activity among federal regulatory agencies. Many water treatment plant (WTP) operators fondly remember the era when turbidity limits were 10.0 NTUs, and 2-log removal was as foreign as cholesterol, fat grams and zebra mussels. EPA's estimate that about 50 percent of WTPs will be forced to modify treatment practices to meet turbidity limits translates into millions of dollars in capital improvements and increased operating expenses. However, along with the negative effect that new technology brings, there is a life enhancement factor that may be immeasurable. If modifications to current standards actually prove to prevent the outbreak of sickness, or worse, fatality, it is not difficult to justify a reasonable expenditure.

Covers for finished water storage
All surface water and GWUDI systems that serve a population of 10,000 or more people are now required to cover all finished water reservoirs, holding tanks and other storage facilities constructed after Feb. 16, 1999. EPA is currently developing a guidance manual for uncovered finished water storage facilities. The manual will provide guidance on water quality issues for uncovered water storage facilities.

Since the vast majority of newly constructed facilities for finished water are already covered, it is anticipated that the impact of this section of the rule should not be significant.

Sanitary surveys
The states require sanitary surveys to be completed for all surface water and GWUDI systems at least every three years for community systems and at least every five years for noncommunity systems. The state has the authority to reduce the frequency of the required survey for systems with outstanding performance.

IESWTR classifies a sanitary survey as "an onsite review of the water source (identifying sources of contamination using results of source water assessments where available), facilities, equipment, operation, maintenance and monitoring compliance of a public water system to evaluate the adequacy of the system, its sources and operations and the distribution of safe drinking water. (Federal Register 63:241:61494, Dec. 16, 1998).

The survey will also review the disinfection profiles and benchmarking requirements if they are applicable to the system.

If the states perform the survey as a component of the normal review process, then the overall impact of this section of the rule should be minimal. However, if a state delegates the surveying and reporting requirements to the system operators, there are obviously increased administrative responsibilities and liabilities incurred.

Disinfection byproducts rule
This rule states, "The Stage 1 DBPR applies to public water systems that are community water systems and nontransient noncommunity water systems that treat their water with a chemical disinfectant for either primary or residual treatment. In addition, certain requirements for chorine dioxide apply to transient noncommunity water systems" (Federal Register 63:241:69390, Dec. 16, 1998). One of the purposes of the issuance of this rule was to reduce the levels of disinfectants and disinfection byproducts in U.S. drinking water. EPA estimates that an additional 20 million households will benefit from this rule by being protected from disinfection byproducts for the first time.

It was thought several years ago that the best way to prevent the formation of disinfection byproducts was to remove the precursors prior to the addition of the disinfectant. EPA studies (see EPA 1997b for more information) now suggest that "simultaneous employment of enhanced coagulation and pre-disinfection does not necessarily mean that DBP formation cannot be substantially controlled" (Federal Register 63:241:69416, Dec. 16, 1998).

If a public water system cannot meet the MCL or MRDL, the state may grant a variance if the system uses the best available technology as dictated by EPA and meets other requirements.

New alternatives
Chlorine has been the disinfection staple for potable water systems for decades because it is inexpensive, effective and readily available. As acceptable levels of DBPs become more and more stringent, systems may have to consider other alternatives for disinfection. Since the primary level of concern occurs during warm weather, when organic activity peaks, systems may elect to go to alternate methods of disinfection during these critical periods. Systems may also elect to reduce chlorine levels leaving the WTP and provide chlorine boosters within the distribution system to minimize effective contact.

EPA has acknowledged that these new rules are complicated. WTP operators should always refer to the specific rules for the requirements for specific systems. The interim enhanced surface water treatment rule and the disinfectants and disinfection byproducts final rules are available on the Web at: and, respectively.

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This article originally appeared in the 08/01/1999 issue of Environmental Protection.

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