National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring

Federal RegisterJan 22, 2001

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 141 and 142

[WH-FRL-6934-9]

RIN 2040-AB75

National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

Today EPA is establishing a health-based, non-enforceable Maximum Contaminant Level Goal (MCLG) for arsenic of zero and an enforceable Maximum Contaminant Level (MCL) for arsenic of 0.01 mg/L (10 μg/L). This regulation will apply to non-transient non-community water systems, which are not presently subject to standards on arsenic in drinking water, and to community water systems.

In addition, EPA is publishing clarifications for monitoring and demonstration of compliance for new systems or sources of drinking water. The Agency is also clarifying compliance for State-determined monitoring after exceedances for inorganic, volatile organic, and synthetic organic contaminants. Finally, EPA is recognizing the State-specified time period and sampling frequency for new public water systems and systems using a new source of water to demonstrate compliance with drinking water regulations. The requirement for new systems and new source monitoring will be effective for inorganic, volatile organic, and synthetic organic contaminants.

DATES:

This rule is effective March 23, 2001, except for the amendments to §§ 141.23(i)(1), 141.23(i)(2), 141.24(f)(15), 141.24(h)(11), 141.24(h)(20), 142.16(e), 142.16(j), and 142.16(k) which are effective January 22, 2004.

The compliance date for requirements related to the clarification for monitoring and compliance under §§ 141.23(i)(1), 141.23(i)(2), 141.24(f)(15), 141.24(f)(22), 141.24(h)(11), 141.24(h)(20), 142.16(e), 142.16(j), and 142.16(k) is January 22, 2004. The compliance date for requirements related to the revised arsenic standard under §§ 141.23(i)(4), 141.23(k)(3), 141.23(k)(3)(ii), 141.51(b), 141.62(b), 141.62(b)(16), 141.62(c), 141.62(d), and 142.62(b) is January 23, 2006. For purposes of judicial review, this rule is promulgated as of January 22, 2001.

ADDRESSES:

Copies of the public comments received, EPA responses, and all other supporting documents are available for review at the U.S. EPA Water Docket (4101), East Tower B-57, 401 M Street, SW, Washington DC 20460. For an appointment to review the docket, call 202-260-3027 between 9 a.m. and 3:30 p.m. and refer to Docket W-99-16.

FOR FURTHER INFORMATION CONTACT:

The Safe Drinking Water Hotline, phone: (800) 426-4791, or (703) 285-1093, e-mail: hotline.sdwa@epa.gov for general information about, and copies of, this document and the proposed rule. For technical inquiries, contact: Jeff Kempic, (202) 260-9567, e-mail: kempic.jeffrey@epa.gov for treatment and costs, and Dr. John B. Bennett, (202) 260-0446, e-mail: bennett.johnb@epa.gov for benefits.

SUPPLEMENTARY INFORMATION:

Regulated Entities

A public water system (PWS), as defined in 40 CFR 141.2, provides water to the public for human consumption through pipes or “other constructed conveyances, if such system has at least fifteen service connections or regularly serves an average of at least twenty-five individuals daily at least 60 days out of the year.” A public water system is either a community water system (CWS) or a non-community water system (NCWS). A community water system, as defined in § 141.2, is “a public water system which serves at least fifteen service connections used by year-round residents or regularly serves at least twenty-five year-round residents.” The definition in § 141.2 for a non-transient non-community water system (NTNCWS) is “a public water system that is not a [CWS] and that regularly serves at least 25 of the same persons over 6 months per year.” EPA has an inventory totaling over 54,000 community water systems and approximately 20,000 non-transient non-community water systems nationwide. Entities potentially regulated by this action are community water systems and non-transient non-community water systems. The following table provides examples of the regulated entities under this rule.

Table of Regulated Entities

Category

Examples of regulated entities

Industry

Privately owned/operated community water supply systems using ground water, surface water, or mixed ground water and surface water.

State, Tribal, and Local Government

State, Tribal, or local government-owned/operated water supply systems using ground water, surface water, or mixed ground and surface water.

Federal Government

Federally owned/operated community water supply systems using ground water, surface water, or mixed ground water and surface water.

The table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. This table lists the types of entities that EPA is now aware could potentially be regulated by this action. Other types of entities not listed in this table could also be regulated. To determine whether your facility is regulated by this action, you should carefully examine the applicability criteria in §§ 141.11 and 141.62 of the rule. If you have any questions regarding the applicability of this action to a particular entity, consult the general information contact listed in the section listing contacts for further information.

Abbreviations used in this rule

<—less than

≤—less than or equal to

>—greater than

≥—greater than or equal to

±—plus or minus

§ —section

σ—σ, Greek letter, in statistics represents standard deviation

μg—Microgram, one-millionth of a gram (3.5 × 10

−

of an ounce)

μg/L—micrograms per liter

AA—Activated alumina

AIC—Akaike Information Criterion

ACWA—Association of California Water Agencies

AMWA—Association of Metropolitan Water Agencies

APHA—American Public Health Association

ARARs—Applicable or relevant and appropriate requirements

As (III)—Trivalent arsenic. Common inorganic form in water is arsenite

As (V)—Pentavalent arsenic. Common inorganic form in water is arsenate

ASDWA— Association of State Drinking Water Administrators

AsH

—Arsine

ASTM—American Society for Testing and Materials

ATSDR—Agency for Toxic Substances and Disease Registry, U.S. Department of Health & Human Services

AWWA—American Water Works Association

AWWARF—American Water Works Association Research Foundation

BAT—Best available technology

BV—Bed volume

CCR—Consumer Confidence Report

CERCLA—Comprehensive Environmental Response, Compensation, and Liability Act administered by EPA for hazardous substances

C/F—Modified coagulation/filtration

CFR—Code of Federal Regulations

CSFII—Continuing Survey of Food Intakes by Individuals

CWA—Clean Water Act administered by EPA for surface waters of the U.S.

CWS—Community water system

CWSS—Community Water System Survey

DMA—Dimethyl arsinic acid, cacodylic acid, (CH

)

HAsO

DNA—Deoxyribonucleic acid

DWSRF—Drinking Water State Revolving Fund

EA—Economic analysis

EDR—Electrodialysis reversal

EEAC—Environmental Economics Advisory Committee

e.g.—

exempli gratia,

Latin for “for example”

EPA—U.S. Environmental Protection Agency

et al.—

et alia,

Latin for “and others”

FACA—Federal Advisory Committee Act

FR—Federal Register

FRFA—Final Regulatory Flexibility Analysis

FSIS—Federalism Summary Impact Statement

GDP—Gross Domestic Product

GFAA—Graphite furnace atomic absorption

GHAA—Gaseous hydride atomic absorption

GI—Gastrointestinal

GW—Ground water

GWR—Ground Water Rule

HRRCA—Health Risk Reduction and Cost Analysis

ICP-AES—Inductively coupled plasma-atomic emission spectroscopy

ICP-MS—Inductively coupled plasma mass spectroscopy

ICR—Information collection request

i.e.—

id est,

Latin for “that is”

IOCs—Inorganic contaminants

ISCV—Intra-system coefficient of variation

IX—Ion exchange

L—Liter, also referred to as lower case “l” in older citations

—The dose of a chemical taken by mouth or absorbed by the skin which is expected to cause death in 50% of the test animals

LS—Modified lime softening

LT1/FBR—Long Term 1 Enhanced Surface Water Treatment and Filter Backwash Recycling Rule

MCL—Maximum contaminant level

MCLG—Maximum contaminant level goal

MDL—Method detection limit

mg—Milligrams, one-thousandth of a gram, 1 milligram=1,000 micrograms

mg/kg—Milligrams arsenic per kilogram body weight or soil weight

mg/L—Milligrams per liter

MHI—Mean household income

MMA—Monomethyl arsenic, arsonic acid, CH

ASO

NAOS—National Arsenic Occurrence Survey

NAS—National Academy of Sciences

NAWQA—National Ambient Water Quality Assessment, USGS

NCI—National Cancer Institute

NCWS—Non-community water system

NDWAC—National Drinking Water Advisory Council for EPA

NIRS—National Inorganic and Radionuclide Survey done by EPA

NODA—Notice of Data Availability

NOMS—National Organic Monitoring Survey done by EPA

NPDES—National Pollutant Discharge Elimination System for CWA

NPDWR—National primary drinking water regulation

NR—Not reported

NRC—National Research Council, the operating arm of NAS

NTNCWS—Non-transient non-community water system

NTTAA—National Technology Transfer and Advancement Act

NWIS—National Water Information System of USGS

OGWDW—Office of Ground Water and Drinking Water in EPA

OMB—Office of Management and Budget

PE—Performance evaluation, studies to certify laboratories for EPA drinking water testing

pH—Negative log of hydrogen ion concentration

PNR—Public Notification Rule

POE—Point-of-entry treatment devices

POTWs—Publicly owned treatment works, treat wastewater

POU—Point-of-use treatment devices

ppb—Parts per billion

ppm—Parts per million

PQL—Practical quantitation level

PRA—Paperwork Reduction Act

psi—Pounds per square inch

PT—Performance testing

PUC—Public utilities commission

PWS—Public water systems

QALYs—Quality adjusted life years

RCRA—Resource Conservation and Recovery Act

REF—Relative exposure factors

RFA—Regulatory Flexibility Act

RIA—Regulatory Impact Analysis

RO—Reverse osmosis

RUS—Rural Utilities Service

RWS—Rural Water Survey

SAB—Science Advisory Board

SBAR—Small Business Advocacy Review

SBREFA—Small Business Regulatory Enforcement Fairness Act

SD—Standard deviation

SDWA—Safe Drinking Water Act

SDWIS—Safe Drinking Water Information System

SEER—Surveillance, Epidemiology, and End Results

SM—Standard Method for Examination of Water and Wastewater

SMF—Standardized monitoring framework

SMRs—Standardized mortality ratios

SO4—Sulfate

SOCs—Synthetic organic contaminants

STP-GFAA—Stabilized temperature platform graphite furnace atomic absorption

SW—Surface water

TBLLs—Technically based local limits

TC—Toxicity Characteristic, RCRA hazardous waste

TCLP—Toxicity Characteristic Leaching Procedure, tests for hazardous waste

TDS—Total dissolved solids

TMF—Technical, managerial, financial capacity

TOC—Total organic carbon

UMRA—Unfunded Mandates Reform Act

URTH—Unreasonable risk to health

U.S.—United States

USDA—US Department of Agriculture

USGS—US Geological Survey

UV—Ultraviolet

VOCs—Volatile organic contaminants

VSL—Value of statistical life

VSLY—Value of statistical life year

WHO—World Health Organization

WS—Water supply

WTP—Willingness-to-pay

Table of Contents

I. Background and Summary of the Final Rule

A. What Did EPA Propose?

B. Overview of the Notice of Data Availability (NODA)

C. Does This Regulation Apply to My Water System?

D. What are the Final Drinking Water Regulatory Standards for Arsenic (Maximum Contaminant Level Goals and Maximum Contaminant Levels)?

E. Will There be a Health Advisory?

F. What are the Best Available Technologies For Removing Arsenic From Drinking Water?

1. BAT technologies

2. Preoxidation

3. Factors affecting listing technologies

4. Other technologies evaluated, but not designated as BAT

5. Waste disposal

G. Treatment Trains Considered For Small Systems

1. Can my water system use point-of-use (POU), point-of-entry (POE), or bottled water to comply with this regulation?

2. What are the affordable treatment technologies for small systems?

3. Can my water system get a small system variance from an MCL under today's rule?

H. Can My System Get a General Variance or Exemption from the MCL Under Today's Rule?

I. What Analytical Methods are Approved for Compliance Monitoring of Arsenic and What are the Performance Testing Criteria for Laboratory Certification?

1. Approved analytical methods

2. Performance testing criteria for laboratory certification

J. How Will I Know if My System Meets the Arsenic Standard?

1. Sampling points and grandfathering of monitoring data

2. Compositing of samples

3. Calculation of violations

4. Monitoring and compliance schedule

K. What do I Need To Tell My Customers?

1. Consumer Confidence Reports

a. General requirements

b. Special informational statement

2. Public Notification

L. What Financial Assistance Is Available for Complying With This Rule?

M. What is the Effective Date and Compliance Date for the Rule?

N. How Were Stakeholders Involved in the Development of This Rule?

II. Statutory Authority

III. Rationales for Regulatory Decisions

A. What is the MCLG?

B. What is the Feasible Level?

1. Analytical measurement feasibility

2. Treatment

C. How Did EPA Revise Its National Occurrence Estimates?

1. Summary of occurrence data and methodology

2. Corrections and additions to the data

3. Changes to the methodology

4. Revised occurrence results

D. How Did EPA Revise Its Risk Analysis?

1. Health risk analysis

a. Toxic forms of arsenic

b. Effects of acute toxicity

c. Non-cancer effects associated with arsenic.

d. Cancers associated with arsenic

e. How does arsenic cause cancer?

f. What is the quantitative relationship between exposure and cancer effects that may be projected for exposures in the U.S.?

g. Is it appropriate to assume linearity for the dose-response assessment for arsenic at low doses given that arsenic is not directly reactive with DNA?

2. Risk factors/bases for upper- and lower-bound analyses

a. Water consumption

b. Relative Exposure Factors

c. Arsenic occurrence

d. Risk distributions

e. Estimated risk reductions

f. Lower-bound analyses

g. Cases avoided

3. Sensitive subpopulations

4. Risk window

E. What are the Costs and Benefits at 3, 5, 10, and 20 μg/L?

1. Summary of cost analysis

a. Total national costs

b. Household costs

2. Summary of benefits analysis

a. Primary analysis

b. Sensitivity analysis on benefits valuation

c. SAB recommendations

d. Analytical approach

e. Results

3. Comparison of costs and benefits

a. Total national costs and benefits

b. National net benefits and benefit-cost ratios

c. Incremental costs and benefits

d. Cost-per-case avoided

4. Affordability

F. What MCL Is EPA Promulgating and What Is the Rationale for This Level?

1. Final MCL and overview of principal considerations

2. Consideration of health risks

3. Comparison of benefits and costs

4. Rationale for the final MCL

a. General considerations

b. Relationship of MCL to the feasible level (3 μg/L)

c. Reanalysis of proposed MCL and comparison to final MCL

d. Consideration of higher MCL options

e. Conclusion

IV. Rule Implementation

A. What are the Requirements for Primacy?

B. What are the Special Primacy Requirements?

C. What are the State Recordkeeping Requirements?

D. What are the State Reporting Requirements?

E. When does a State Have to Apply for Primacy?

F. What are Tribes Required To Do Under This Regulation?

V. Responses to Major Comments Received

A. General Comments

1. Sufficiency of information and adequacy of procedural requirements to support a final rule

2. Suggestions for development of an interim standard

3. Public involvement and opportunity for comment

4. Relation of MCL to the feasible level

5. Relationship of MCL to other regulatory programs

6. Relation of MCL to WHO standard

7. Regulation of non-transient non-community water systems (NTNCWSs)

8. Extension of effective date for large systems

B. Health Effects of Arsenic

1. Epidemiology data

2. Dose-response relationship

3. Suggestions that EPA await further health effects research

4. Sensitive subpopulations

5. EPA's risk analysis

6. Setting the MCLG and the MCL

C. Occurrence

1. Occurrence data

2. Occurrence methodology

3. Co-occurrence

D. Analytical Methods

1. Analytical interferences

2. Demonstration of PQL (includes acceptance limits)

3. Acidification of samples

E. Monitoring and Reporting Requirements

1. Compliance determinations

2. Monitoring of POU devices

3. Monitoring and reporting for NTNCWSs

4. CCR health language and reporting date

5. Implementation guidance

6. Rounding analytical results

F. Treatment Technologies

1. Demonstration of technology performance

2. Barriers to technology application

3. Small system technology application

4. Waste generation and disposal

a. Anion exchange

b. Activated alumina

c. Reverse osmosis

5. Emerging technologies

G. Costs

1. Disparity of costs

a. What is EPA's response to major comments on the decision tree for the proposed rule?

b. What is EPA's response to comments on system level costs?

c. What is EPA's response to comments that state the report “Cost Implications of a Lower Arsenic MCL” (Frey et al., 2000), be used as a basis for reflecting more realistic national costs than EPA's estimates?

2. Affordability

3. Combined cost of new regulations

4. Projected effects of the new standard on other regulatory programs.

H. Benefits of Arsenic Reduction

1. Timing of benefits accrual (latency)

2. Use of the Value of Statistical Life (VSL)

3. Use of alternative methodologies for benefits estimation

4. Comments on EPA's consideration of nonquantifiable benefits

5. Comments on EPA's assumption of benefits accrual prior to rule implementation

I. Risk Management Decision

1. Role of uncertainty in decision making

2. Agency's interpretation of benefits justify costs provision

3. Alternative regulatory approaches

4. Standard for total arsenic vs. species-specific standards

J. Health Risk Reduction and Cost Analysis (HRRCA)

1. Notice and comment requirement

2. Conformance with SDWA requirements

VI. Administrative and Other Requirements

A. Executive Order 12866: Regulatory Planning and Review

B. Regulatory Flexibility Act (RFA), as Amended by the Small Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5 U.S.C. 601 et seq.

C. Unfunded Mandates Reform Act (UMRA) of 1995

a. Authorizing legislation

b. Cost-benefit analysis

c. Financial assistance

d. Estimates of future compliance costs and disproportionate budgetary effects

e. Macroeconomic effects

f. Summary of EPA's consultation with State, Tribal, and local governments

g. Nature of State, Tribal, and local government concerns and how EPA addressed these concerns

h. Regulatory alternatives considered

i. Selection of the regulatory alternative

D. Paperwork Reduction Act (PRA)

E. National Technology Transfer and Advancement Act (NTTAA)

F. Executive Order 12898: Environmental Justice

G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks

H. Executive Order 13132: Federalism

I. Executive Orders 13084 and 13175: Consultation and Coordination with Indian Tribal Governments

J. Plain Language

K. Congressional Review Act

L. Consultations with the Science Advisory Board, National Drinking Water Advisory Council, and the Secretary of Health and Human Services

M. Likely Effect of Compliance With the Arsenic Rule on the Technical, Financial, and Managerial Capacity of Public Water Systems

VI. References

List of Tables

Table I.F-1.—Best Available Technologies and Removal Rates

Table I.G-1.—Treatment Technology Trains

Table I.G-2.—Baseline Values for Small Systems Categories

Table I.G-3.—Available Expenditure Margin for Affordable Technology Determinations

Table I.G-4.—Design and Average Daily Flows Used for Affordable Technology Determinations

Table I.G-5.—Affordable Compliance Technology Trains for Small Systems with population 25-500

Table I.G-6.—Affordable Compliance Technology Trains for Small Systems with populations 501-3,300 and 3,301 to 10,000

Table I.I-1.—Approved Analytical Methods (40 CFR 141.23) for Arsenic at the MCL of 0.01 mg/L

Table III.C-1.—Summary of Occurrence Databases for the Proposed and Final Rules

Table III.C-2.—Alaska PWS Inventories: Baseline Handbook and Corrected

Table III.C-3.—National Occurrence Exceedance Probability Estimates

Table III.C-4.—Parameters of Lognormal Distributions Fitted to National Occurrence Distributions

Table III.C-5.—Regional Occurrence Exceedance Probability Estimates

Table III.C-6.—Statistical Estimates of Numbers of Systems with Average Finished Arsenic Concentrations in Various Ranges

Table III.C-7.—Estimated Intra-System Coefficients of Variation

Table III.C-8.—Comparison of National Arsenic Occurrence Estimates

Table III.D-1.—Life-Long Relative Exposure Factors

Table III.D-2(a).—Cancer Risks for U.S. Populations Exposed At or Above MCL Options, after Treatment

1,2

(Without Adjustment for Arsenic in Food and Cooking Water)

Table III.D-2(b).—Cancer Risks for U.S. Populations Exposed At or Above MCL Options, after Treatment

1,2

(With Adjustment for Arsenic Exposure in Food and Cooking Water)

Table III.D-2(c).—Cancer Risks for U.S. Populations Exposed At or Above MCL Options, after Treatment

(Lower Bound With Food and Cooking Water Adjustment, Upper Bound Without Food and Cooking Water Adjustment)

Table III.D-3.—Annual Total (Bladder and Lung) Cancer Cases Avoided from Reducing Arsenic in CWSs and NTNCWS

Table III.E-1.—Total Annual National System and State Compliance Costs

Table III.E-2.—Mean Annual Costs per Household

Table III.E-3.—Estimated Benefits from Reducing Arsenic in Drinking Water

Table III.E-4.—Sensitivity of the Primary VSL Estimate to Changes in Latency Period Assumptions, Income Growth, and Other Adjustments

Table III.E-5.—Sensitivity of Combined Annual Bladder and Lung Cancer Mortality Benefits Estimates to Changes in VSL Adjustment Factor Assumptions

Table III.E-6.—Sensitivity of Combined Annual Bladder and Lung Cancer Mortality Benefits Estimates to Changes in VSL Adjustment Factor Assumptions

Table III.E-7.—Estimated Annual Costs and Benefits from Reducing Arsenic in Drinking Water

Table III.E-8 Summary of National Annual Net Benefits and Benefit-Cost Ratios, Combined Bladder and Lung Cancer Cases

Table III.E-9 Estimates of the Annual Incremental Risk Reduction, Costs, and Benefits of Reducing Arsenic in Drinking Water

Table III.E-10. Annual Cost Per Cancer Case Avoided for the Final Arsenic Rule—Combined Bladder and Lung Cancer Cases

TABLE V.F-4.1 Treatment Trains in Final Versus Proposed Arsenic Rule Decision Tree

Table V.F-4.2 New or Revised Treatment Trains

Table VI.B-1. Profile of the Universe of Small Water Systems Regulated Under the Arsenic Rule

I. Background and Summary of the Final Rule

A. What Did EPA Propose?

On June 22, 2000, the

Federal Register

published EPA's proposed arsenic regulation for community water systems and non-transient non-community water systems (65 FR 38888; EPA, 2000i). EPA proposed a health-based, non-enforceable goal, or Maximum Contaminant Level Goal (MCLG), of zero micrograms per liter (μg/L) and a Maximum Contaminant Level (MCL) of 5 μg/L. The Agency also requested comment on alternate MCL levels of 3 μg/L, 10 μg/L, and 20 μg/L. (In the proposed rule EPA expressed arsenic concentration in milligrams per liter (mg/L) or parts per million, which matches the units of the former and current standard for arsenic. Except as noted, the Agency will refer to arsenic concentration in micrograms per liter (μg/L) in this preamble.)

EPA based the June 2000 proposal on extensive analysis including a careful consideration of the following issues: a nonzero MCLG; occurrence of arsenic in public water systems; our approach for estimating national occurrence and co-occurrence; acceptance limits used to establish the practical quantitation level (PQL); rounding of measured values for compliance purposes; extending compliance by two years for systems serving under 10,000 people in order to add capital improvements; dates for reporting changes in the consumer confidence reports and public notification; appropriateness of the national affordability criteria; affordable technologies for small systems; implementation issues for point-of-use (POU) and point-of-entry (POE) treatments; appropriateness of non-hazardous residual costing; our overall analysis of costs; adjusting benefits estimates (

e.g.

, for factors such as latency); our approach for considering uncertainties that affected risk; use of the authority to set an MCL at a level other than the feasible MCL; expression of the MCL as total arsenic; approaches to regulation of NTNCWSs; State program revisions; selenium levels as an attenuation factor in arsenic toxicity; impacts on small entities; use of consensus analytical methods; methods to address environmental justice concerns; and comments on use of plain

language. We asked commenters to submit data and comments on these issues, as well as any other issues raised in the proposal.

The proposal reflected several types of technical evaluations, including analytical methods performance and laboratory capacity; the likelihood of different size water systems choosing treatment technologies based on source water characteristics; and the national occurrence of arsenic in drinking water supplies. Furthermore, the Agency assessed the quantifiable and nonquantifiable costs and health risk reduction benefits likely to occur at the treatment levels considered, and the effects of arsenic on sensitive subpopulations.

The proposed MCL was consistent with the Agency's use of the new benefit/cost provisions of the Safe Drinking Water Act (SDWA), as amended in 1996 (see section II. of this preamble for additional information about this provision). EPA proposed 3 μg/L as the feasible MCL, after considering treatment costs and efficiency under field conditions as well as considering the appropriate analytical methods. Because EPA determined that the benefits of regulating arsenic at the feasible level would not justify the costs, the Agency proposed an MCL of 5 μg/L, while requesting comment on MCL options of 3 μg/L (the feasible level), 10 μg/L, and 20 μg/L.

We based our estimates of large system compliance costs primarily on costs for coagulation/filtration and lime softening, although we consider several other technologies to be appropriate as best available technology (BAT) technologies. (See Table I.F-1.) For small-system (systems serving 10,000 people and less) compliance costs, we considered the costs for ion exchange, activated alumina, reverse osmosis, and nanofiltration. EPA proposed extending the effective date to five years after the final rule issuance for small community water systems and maintaining the effective date at three years after promulgation for all other community water systems. EPA proposed that States applying to adopt the revised arsenic MCL may use their most recently approved monitoring and waiver plans or note in their primacy application any revisions to those plans. EPA proposed that NTNCWSs monitor for arsenic and report exceedances of the MCL.

The Agency also clarified the procedure used for determining compliance after exceedances for inorganic, volatile organic, and synthetic organic contaminants in §§ 141.23(i)(2), 141.24(f)(15)(ii), and 141.24(h)(11)(ii), respectively. Finally, EPA proposed that new systems and systems using a new source of water be required to demonstrate compliance with the MCLs using State-specified time frames. The clarified new source and new system compliance regulations require that States establish initial sampling frequencies and compliance periods for inorganic, volatile organic, and synthetic organic contaminants in §§ 141.23(c)(9), 141.24(f)(22), and 141.24(h)(20), respectively.

B. Overview of the Notice of Data Availability (NODA)

In the proposed rule, EPA quantified the risk reduction and benefits of avoiding bladder cancer and noted that a peer-reviewed quantification of lung cancer risk from arsenic exposure would probably be available in time to consider for the final rule (65 FR 38888 at 38899; EPA, 2000i). Relying upon a discussion in the National Research Council (NRC) report (NRC, 1999, pg. 8) about the qualitative risks of lung cancer (65 FR 38888 at 38944; 2000i), EPA provided a “What-If” estimate of lung cancer benefits (65 FR 38888 at 38946, 2000i) in the proposed rule. On October 20, 2000, the

Federal Register

published EPA's Notice of Data Availability (NODA) containing a revised risk analysis for bladder cancer and new risk information concerning lung cancer (65 FR 63027; EPA, 2000m), and identified a correction to Table 4 on October 27, 2000 (65 FR 64479; EPA, 2000n). The NODA also provided information concerning the availability of cost curves used to develop the costs published in the proposal.

EPA used new risk information for lung and bladder cancer from a peer-reviewed article written by Morales

et al.

(2000). In the NODA, EPA explained that the authors used several alternative statistical models to estimate cancer risk. EPA explained its reasons for selecting “Model 1” with no comparison population for further analysis. We used daily water consumption (EPA, 2000c) reported by gender, region, age, economic status, race, and separately for pregnant women, lactating women, and women in childbearing years combined with weight data to derive exposure factors for the U.S. We used these exposure factors, our occurrence estimate (EPA 2000g) of populations exposed to arsenic at different concentrations, and the risk distributions from the Morales

et al.

(2000) paper in Monte Carlo simulations to estimate the upper bound of risks faced by the U.S. population. The NODA compared the bladder cancer risks derived for the proposal against the bladder cancer risks derived from the Morales

et al.

(2000) study. EPA also derived lung cancer risks using the same approach and the risk model contained in the Morales

et al.

(2000) study.

EPA also used the newly calculated risks to estimate a lower bound risk in the U.S. This calculation took into account the amount of additional arsenic people in Taiwan were likely to have ingested from water used in food preparation. EPA showed the effects on risks for the U.S. population at both the mean and 90th percentile levels for various arsenic levels in drinking water. Based on the revised risk assessment, we updated our assessment of the relative risk of lung cancer as compared to bladder cancer. The NODA indicated that instead of being 2 to 5 times as many fatal lung cancer cases as bladder cancer cases (as was cited in NRC's Executive Summary, NRC, 1999, pg. 8 as a qualitative estimate), the combined risk of excess lung and bladder cancer were thought to be only about twice that of bladder cancer risk. EPA noted that, while the new risks were higher than the bladder cancer risk in the proposal, the monetized benefits of lung cancer would fall within the lung cancer benefits range estimated using the “What-If” analysis (

e.g.

, $19.6 million—$224 million yearly for an MCL of 10 μg/L) in the proposal (65 FR 38888 at 38959; EPA, 2000m).

In the NODA, EPA also explained that the docket for the proposed rule had the November 1999 version (EPA, 1999o) of “Technologies and Costs for the Removal of Arsenic from Drinking Water” rather than the April 1999 version of the document that was the primary source for the treatment technology cost equations used to generate the national cost estimate. The national cost estimate was presented in the “Proposed Arsenic in Drinking Water Rule Regulatory Impact Analysis” (EPA, 2000h). The NODA therefore announced the availability of the “Technologies and Costs for the Removal of Arsenic from Drinking Water,” dated April 1999 (EPA,1999b). The NODA also noted that commenters interested in reproducing the waste disposal curves should consult the “Small Water System Byproducts Treatment and Disposal Cost Document” (EPA, 1993a) and “Water System Byproducts Treatment and Disposal Document (EPA, 1993b).” In addition to placing these documents in the docket, the NODA also specified that an electronic copy of the treatment technology and waste disposal equations used in the development of the RIA could be found in the docket.

EPA made the April 1999 version of the document, “Technologies and Costs for the Removal of Arsenic from Drinking Water” (EPA,1999b) available on its arsenic webpage.

The cost methodology and cost estimates were clearly stated and explained in the proposal for public review and consideration. Through a technical oversight, we incorrectly attributed the source for the cost curves to the November version of the document placed in the docket (EPA, 1999o). As a result, people could not replicate the precise analysis we did, should a commenter desire to do so. More specifically, although the inputs, assumptions, and model methodology were clearly explained, we incorrectly cited the sources of an intermediate step of deriving specific cost curves from those assumptions. Based upon the proposal's detailed discussion of inputs, assumptions and associated methodology, EPA believes the public was fully able to review, understand, and comment on the Agency's estimate of potential impacts. EPA discusses the cost curves further in section III.E.1 of this preamble.

C. Does This Regulation Apply to My Water System?

The final regulation on arsenic in drinking water promulgated today applies to all CWSs and NTNCWSs. The regulation not only establishes an MCLG and MCL for arsenic, but also lists feasible technologies and affordable technologies for small systems that can be used to comply with the MCL. However, systems are not required to use the listed technologies in order to meet the MCL.

D. What are the Final Drinking Water Regulatory Standards for Arsenic (Maximum Contaminant Level Goals and Maximum Contaminant Levels)?

In today's rule, the MCLG is 0 μg/L, and the enforceable MCL is 0.01 mg/L, which is the same as 10 micrograms per liter (μg/L) or 10 parts per billion (ppb). EPA based the MCL on total arsenic, because drinking water contains almost entirely inorganic forms, and the analytical methods for total arsenic are readily available and capable of being performed by certified laboratories at an affordable cost.

E. Will There be a Health Advisory?

A health advisory for arsenic is not part of today's rulemaking. EPA will be considering whether or not to issue a health advisory after evaluating the recommendations of the Science Advisory Board (SAB) (EPA, 2000q). The purpose of an advisory would be to provide useful information to water providers between issuance and implementation of this rule.

F. What are the Best Available Technologies For Removing Arsenic From Drinking Water?

Section 1412(b)(4)(E) of the Safe Drinking Water Act states that each National Primary Drinking Water Regulation (NPDWR) which establishes an MCL shall list the technology, treatment techniques, and other means that the Administrator finds to be feasible for purposes of meeting the MCL. Technologies are judged to be a best available technology (BAT) when the following criteria are satisfactorily met:

(1) The capability of a high removal efficiency;

(2) A history of full-scale operation;

(3) General geographic applicability;

(4) Reasonable cost based on large and metropolitan water systems;

(5) Reasonable service life;

(6) Compatibility with other water treatment processes; and

(7) The ability to bring all of the water in a system into compliance.

EPA identified BATs in this section using the listed criteria. Their removal efficiencies and a brief discussion of the major issues surrounding the usage of each technology are also given in this section. More details about the treatment technologies and costs can be found in “Technologies and Costs for the Removal of Arsenic From Drinking Water” (EPA, 2000t).

1. BAT technologies

EPA reviewed several technologies as BAT candidates for arsenic removal, e.g., ion exchange, activated alumina, reverse osmosis, nanofiltration, electrodialysis reversal, coagulation assisted microfiltration, modified coagulation/filtration, modified lime softening, greensand filtration, conventional iron and manganese removal, and several emerging technologies. The Agency determined that, of the technologies capable of removing arsenic from source water, only the technologies in Table I.F-1 fulfill the requirements of SDWA for BAT determinations for arsenic. The maximum percent of arsenic removal that can be reasonably obtained from these technologies is also shown in the table. These removal efficiencies are for arsenic (V) removal.

Table I.F-1.— Best Available Technologies and Removal Rates

Treatment Technology

Maximum Percent Removal

Ion Exchange (sulfate ≤ 50 mg/L)

Activated Alumina

Reverse Osmosis

>95

Modified Coagulation/Filtration

Modified Lime Softening (pH > 10.5)

Electrodialysis Reversal

Oxidation/Filtration (20:1 iron:arsenic)

The percent removal figures are for arsenic (V) removal. Pre-oxidation may be required.

2. Preoxidation

In water, the most common valence states of arsenic are As (V), or arsenate, and As (III), or arsenite. As (V) is more prevalent in aerobic surface waters and As (III) is more likely to occur in anaerobic ground waters. In the pH range of 4 to 10, As (V) species (H

AsO

−

and H

AsO

−

) are negatively charged, and the predominant As (III) compound (H

AsO

) is neutral in charge. Removal efficiencies for As (V) are much better than removal of As (III) by any of the technologies evaluated because the arsenate species carry a negative charge and arsenite is neutral under these pH conditions. To increase the removal efficiency when As (III) is present, pre-oxidation to the As (V) species is necessary.

As (III) may be converted through pre-oxidation to As (V) using one of several oxidants. Data on oxidants indicate that chlorine, potassium permanganate, and ozone are effective in oxidizing As (III) to As (V). Pre-oxidation with chlorine may create undesirable concentrations of disinfection byproducts and membrane fouling of subsequent treatments such as reverse osmosis. EPA has completed research on the chemical oxidants for As (III) conversion, and is presently investigating ultraviolet light disinfection technology (UV) and solid oxidizing media. For POU and POE devices, central chlorination may be required for oxidation of As (III).

3. Factors affecting listing technologies

Ion Exchange

(IX) can effectively remove arsenic using anion exchange resins. It is recommended as a BAT primarily for sites with low sulfate because sulfate is preferred over arsenic. Sulfate will compete for binding sites resulting in shorter run lengths. Due to much shorter run lengths than activated alumina, anion exchange must be

regenerated because it is not cost effective to dispose of the resin after one use. Column bed regeneration frequency is a key factor in the cost of the process and affects the volume of waste produced by the process. The proposed rule preamble noted that anion exchange may be practical up to approximately 120 mg/L of sulfate (Clifford, 1994). The upper-bound sulfate concentration for the final rule is 50 mg/L. The selection of this upper bound is based on several factors, including cost and the ability to dispose of the brine stream.

The proposed rule listed three mechanisms to dispose of the brine stream used for regeneration. The options were: sanitary sewer, evaporation pond, and chemical precipitation. Many comments on the proposed rule were based on the assumption that the waste streams generated would be considered hazardous waste. Waste streams containing less than 0.5% solids are evaluated against the toxicity characteristic directly to determine if the waste is hazardous. Arsenic in the regeneration brine will likely exceed 5 mg/L for most systems with arsenic above 10 μg/L and sulfate below 50 mg/L. Since the brine stream would likely be considered hazardous, EPA eliminated the evaporation pond and the chemical precipitation options from the decision tree as options for disposal of anion exchange wastes. The Agency retained discharge to a sanitary sewer because domestic sewage and any mixture of domestic sewage and other wastes that pass through a sewer system to a publicly owned treatment works (POTW) for treatment is excluded from consideration as solid waste (40 CFR 261.4). Domestic sewage means untreated sanitary wastes that pass through a sewage system. Discharges meeting the previously stated criteria are excluded from regulation as hazardous waste. However, these assumptions were reviewed to substantially reduce projections of brine wastes going to POTWs from those that were used in support of the proposed rule.

Discharge to a sanitary sewer can be limited by technically based local limits (TBLLs) for arsenic or total dissolved solids. Since anion exchange is regenerated more frequently than activated alumina, the total dissolved solids increase can be significant. Many comments indicated that significant increases in total dissolved solids would be unacceptable, especially in the Southwest where water resources are scarce. Salt is used for regeneration of anion exchange resins. The upper bound of 50 mg/L sulfate for anion exchange is based on projected increases of total dissolved solids using the quantity of salt needed for regeneration and the frequency of regeneration (based on sulfate). The sulfate upper bound for the final rule is significantly lower than the upper bound from the proposed rule. Due to the potential for an increase in total dissolved solids, anion exchange would be favored in areas other than the Southwest where the volume of brine is very small relative to the total volume of wastewater being treated at the POTW. Systems that need to treat only a few entry points or can blend a significant portion of the water to meet the MCL may produce a smaller brine stream to allow the brine to be discharged to a POTW. Water systems should check with the POTW to ensure that the brine stream will be accepted before selecting this option.

Activated Alumina

(AA) is an effective arsenic removal technology; however, the capacity of activated alumina to remove arsenic is very pH sensitive. High removals can be achieved over a broad range of pH, but shorter run lengths will be observed at higher pH. Activated alumina can be operated in one of two ways. The activated alumina can either be disposed of or regenerated after the media is exhausted. Under the regeneration option, strong acids and bases are used to remove arsenic from the media so that it can be used again to remove arsenic. Because arsenic is strongly adsorbed to the media, only about 50-70% of the adsorbed arsenic is removed. The brine stream produced by the regeneration process then requires disposal. The proposed rule listed discharge to a sanitary sewer as the disposal mechanism for the brines. Many comments on the proposed rule noted that TBLLs for arsenic or total dissolved solids might restrict discharge of brine streams to the sanitary sewer. Since activated alumina run lengths (i.e., number of bed volumes (BV) per run) are much longer than anion exchange, the arsenic concentrations in the brine stream would likely be much higher. Regeneration of activated alumina media is not recommended for larger systems because: (1) Disposal of the brine may be difficult, (2) the regeneration process is incomplete which reduces subsequent run lengths, and (3) for most systems it will be cheaper to replace the media rather than regenerate it. The option of replacing the spent media with new media is called disposable activated alumina.

The disposable activated alumina option can be operated both at the optimal pH of 6 and at higher natural water pH values. It is expected that larger systems would adjust pH to take advantage of the longer run lengths. EPA developed several disposable activated alumina options for the final rule. Two options were based on operating the process at the natural pH of the water (no pH adjustment). These options are intended primarily for smaller systems, although larger systems may also be able to operate at the natural pH if it is low enough to get sufficiently long run lengths. Two options where the pH was adjusted to pH 6 were also examined. The longer run length is based on using sulfuric acid to lower the pH. However, sulfate can compete for adsorption sites with arsenic. It was recommended that hydrochloric acid be used to obtain a longer run length (Clifford et al., 1998). When pH is adjusted to pH 6, post-treatment corrosion control will be necessary.

In our analysis, we assumed that spent media could be safely disposed of in a non-hazardous landfill. The preamble to the proposed rule described results from testing of activated alumina media used to remove arsenic in drinking water systems with arsenic above 50 μg/L. The results from the Toxicity Characteristic Leaching Procedure (TCLP) on these samples was typically less that 50 μg/L. The current toxicity characteristic (TC) regulatory level for designating arsenic as a hazardous waste under the Resource Conservation and Recovery Act (RCRA) is 5 mg/L (5000 μg/L) and is listed in 40 CFR 261.24(a). The TC regulatory level is one hundred times higher than the results from the activated alumina samples.

Reverse Osmosis

(RO) can provide removal efficiencies of greater than 95% when operating pressure is ideal. Water rejection (on the order of 20-25%) may be an issue in water-scarce regions and may prompt systems employing RO to seek greater levels of water recovery. Water recovery is the volume of drinking water produced by the process divided by the influent stream (product water/influent stream). Increased water recovery is often more expensive, since it can involve recycling of water through treatment units to allow more efficient separation of solids from water. This can also produce more concentrated solid wastes. However, the waste stream will generally not be as concentrated as anion exchange brines, so it should be easier to dispose of. Based on the cost of the process, it is unlikely that reverse osmosis would be installed solely for arsenic removal. Blending a treated portion with an untreated portion and

still meeting the MCL would make reverse osmosis more cost effective. If blending is not an option, post-treatment corrosion control would be necessary. Since a large portion of the water is wasted, water quantity could be an issue, especially in the Western U.S. It should be noted that while reverse osmosis is listed as a BAT, it was not used to develop national costs because other options are more cost effective and have much smaller waste streams.

Modified Coagulation/Filtration

(C/F) is an effective treatment process for removal of As (V) according to laboratory, pilot-plant, and full-scale tests. The type of coagulant and dosage used affects the efficiency of the process. Below a pH of approximately 7, removals with alum or ferric sulfate/chloride are similar. Above a pH of 7, removals with alum decrease dramatically (at a pH of 7.8, alum removal efficiency is about 40%). Other coagulants are also less effective than ferric sulfate/chloride. Systems may need to lower pH or add more coagulant to achieve higher removals.

Modified Lime Softening

(LS), operated within the optimum pH range of greater than 10.5 is likely to provide a high percentage of As removal. Systems operating lime softening at lower pH will need to increase the pH to achieve higher removals of arsenic.

Coagulation/Filtration and Lime Softening are unlikely to be installed solely for arsenic removal. Systems considering installation of one of these technologies should design the process to operate in the optimal pH range if high removal efficiencies are needed for compliance.

Electrodialysis Reversal

(EDR) can produce effluent water quality comparable to reverse osmosis. EDR systems are fully automated, require little operator attention, and do not require chemical addition. EDR systems, however, are typically more expensive than nanofiltration and reverse osmosis systems. These systems are often used in treating brackish water to make it suitable for drinking. This technology has also been applied in the industry for wastewater recovery and typically operates at a recovery of 70 to 80%. Since a large portion of the water is wasted, water quantity could be an issue, especially in the Western U.S. It should be noted that while electrodialysis reversal is listed as a BAT, it was not used to develop national costs because other options are more cost effective and have much smaller waste streams.

Oxidation/Filtration

(including greensand filtration) has an advantage in that there is not as much competition with other ions. Arsenic is co-precipitated with the iron during iron removal. Sufficient iron needs to be present to achieve high arsenic removals. One study recommended a 20:1 iron to arsenic ratio (Subramanian et al., 1997). Removals of approximately 80% were achieved when iron to arsenic ratio was 20:1. When the iron to arsenic ratio was lower (7:1), removals decreased below 50%. The presence of iron in the source water is critical for arsenic removal. If the source water does not contain iron, oxidizing and filtering the water will not remove arsenic. When the arsenic is present as As(III), sufficient contact time needs to be provided to convert the As(III) to As(V) for removal by the oxidation/filtration process. An additional pre-oxidation step is not required for this process as long as there is sufficient contact time. In developing national cost estimates, EPA assumed that systems would opt for this type of technology only if more than 300 μg/L of iron was present. The Agency assumed a removal percentage of 50% when estimating national costs because the 20:1 ratio could not be verified due to limitations in the co-occurrence database. However, EPA assumed a removal percentage of 80% as part of a sensitivity analysis. At proposal EPA indicated that oxidation filtration was not being listed as BAT because it has a low removal efficiency, which might not be appropriate for an MCL of 5. However, the Agency also noted that this technology may be appropriate for systems that do not require high arsenic removal and had high iron in their source water. Because this is an inexpensive technology that is particularly effective for high-iron, low-arsenic waters, EPA is listing oxidation/filtration as a BAT with a footnote that the iron-to-arsenic ratio must be at least 20:1. Systems with greater than 300 μg/L of iron will also see benefits in the aesthetic quality of the water as the iron can be reduced below the secondary standard. EPA's inclusion of oxidation/filtration as a BAT in today's final rule is based upon further evaluation of all available information and studies as well as on public comments.

4. Other technologies evaluated, but not designated as BAT

Coagulation Assisted Microfiltration.

The coagulation process described previously can be linked with microfiltration to remove arsenic. The microfiltration step essentially takes the place of a conventional gravity filter. The University of Houston recently completed pilot studies at Albuquerque, New Mexico on iron coagulation followed by a direct microfiltration system. The results of this study indicated that iron coagulation followed by microfiltration is capable of removing arsenic (V) from water to yield concentrations that are consistently below 2 μg/L. Critical operating parameters are iron dose, mixing energy, detention time, and pH (Clifford, 1997). Coagulation and microfiltration as separate processes have both been installed full scale, but the combined coagulation/microfiltration process does not have a full-scale operation history. Since a full-scale operation history is one of the requirements to list a technology as a BAT, it is not presently being listed as one. It could be designated as such in the future if the technology meets that requirement. EPA used this option in developing the national cost estimate because we believe coagulation/microfiltration is an appropriate technology that will be used by certain water systems to comply with this rule, even though it is not currently listed as BAT for the reasons mentioned.

Granular ferric hydroxide

is a technology that may combine very long run length without the need to adjust pH. The technology has been demonstrated for arsenic removal full scale in England (Simms et al., 2000). A pilot-scale study for activated alumina was also conducted on that water and showed run lengths much longer than observed in pilot-scale studies in the United States. Due to the lack of published data showing performance for a range of water qualities, granular ferric hydroxide was not designated a BAT. In addition, there is little published information on the cost of the media, so it is difficult to evaluate cost. Granular ferric hydroxide is being investigated in several ongoing studies and may be an effective technology for removing arsenic. Systems may wish to investigate it and other adsorption technologies such as modified activated alumina and other iron-based media. Many of these other new adsorptive media are also being investigated in several ongoing studies.

5. Waste disposal

Waste disposal will be an important issue for both large and small drinking water plants. Costs for waste disposal have been added to the costs of the treatment technologies (in addition to any pre-oxidation and corrosion control costs), and form part of the treatment trains that are listed in Tables I.G-1, I.G-5, and I.G-6.

The preamble to the proposed rule summarized toxicity characteristic leaching procedure (TCLP) data on residuals from different arsenic removal

technologies. The arsenic concentrations in TCLP extracts from alum coagulation, activated alumina, lime softening, iron/manganese removal, and coagulation-microfiltration residuals were below 0.05 mg/L, which is two orders of magnitude lower than the current TC regulatory level. The TCLP data for iron coagulation were mixed—the residuals from an arsenic removal plant were below 0.05 mg/L, but the residuals from another iron coagulation plant were above 1 mg/L. However, this is still below the TC regulatory level of 5 mg/L. Based on these data, EPA does not believe that drinking water treatment plant residuals would be classified as hazardous waste. The TCLP data also indicate that most residuals could meet a much lower TC regulatory level. Options where the brine stream could be hazardous were eliminated from the final decision tree. For the purposes of the national cost estimate, it was assumed that solid residuals would be disposed of at nonhazardous landfills.

G. Treatment Trains Considered For Small Systems

1. Can my water system use point-of-use (POU), point-of-entry (POE), or bottled water to comply with this regulation?

Section 1412(b)(4)(E)(ii) of SDWA, as amended in 1996, requires EPA to issue a list of technologies that achieve compliance with MCLs established under the Act that are affordable and applicable to typical small drinking water systems. These small public water systems categories are: (1) population of more than 25 but less than or equal to 500; (2) population of more than 500, but less than or equal to 3,300; and (3) population of more than 3,300, but less than or equal to 10,000. Owners and operators may choose any technology or technique that best suits their conditions, as long as the MCL is met.

The technologies examined for BAT determinations were also evaluated as small system compliance technologies. Several other alternatives that are solely small system options were also evaluated as compliance technologies. Central treatment is not the only option available to small systems. One of the provisions included in the SDWA Amendments of 1996 allows the use of POU and POE devices as compliance technologies for small systems. SDWA stipulates that POU/POE treatment systems:

shall be owned, controlled and maintained by the public water system or by a person under contract with the public water system to ensure proper operation and maintenance and compliance with the MCL or treatment technique and equipped with mechanical warnings to ensure that customers are automatically notified of operational problems (§ 1412(b)(4)(E)).

Whole-house, or POE treatment, is necessary when exposure to the contaminant by modes other than consumption is a concern; this is not the case with arsenic. Single faucet, or POU treatment, is preferred when treated water is needed only for drinking and cooking purposes. POU devices are especially applicable for systems that have a large flow and only a minor part of that flow directed for potable use such as at many NTNCWSs. POE/POU options include reverse osmosis, activated alumina, and ion exchange processes. POU systems are easily installed and can be easily operated and maintained. In addition, these systems generally offer lower capital costs and may reduce engineering, legal, and other fees associated with centralized treatment options. However, there will be higher administrative costs associated with POU and POE options. For POU options, the trade-off is lower treatment cost since only 1% of the water is treated, but higher administrative and monitoring costs occur. Centrally managed POU options, even with the higher monitoring and administrative costs, are less expensive than central treatment for populations up to 150 to 250 people depending upon the technology and number of households.

Using POU/POE devices introduces some new issues. Adopting a POU/POE treatment system in a small community requires more record-keeping to monitor individual devices than does central treatment. POU/POE systems may require special regulations regarding customer responsibilities as well as water utility responsibilities. The water system or person under contract to the system is responsible for maintaining the devices in customers' homes. This responsibility cannot be delegated to the customer. Use of POU/POE systems does not reduce the need for a well-maintained water distribution system. Increased monitoring may be necessary to ensure that the treatment units are operating properly. Monitoring POU/POE systems is also more complex because compliance samples need to be taken after each POU or POE unit rather than at the entry point to the distribution system to be reflective of treatment.

EPA examined three technologies as POU and POE devices for the proposed rule. EPA assumed that systems would more likely choose to use POU activated alumina (AA) or reverse osmosis (RO), and POE AA in the proposed rule. POU and POE ion exchange (IX) and POE RO were considered, but not included as compliance technologies in the proposed rule. Activated alumina and ion exchange units face a breakthrough issue. If the activated alumina is not replaced on time, there is a potential for significantly reduced arsenic removal. However, if the anion exchange resin is not replaced or regenerated on time, the previously removed arsenic can be driven off the resin by sulfate. Tap water arsenic concentrations can be higher than the source water. This is called chromatographic peaking. Due to the potential for chromatographic peaking and run lengths that would typically be less than six months, anion exchange was not listed as a compliance technology in the proposed rule. POE ion exchange also may present problems with total dissolved solids since the resin would need to be regenerated. Since all sites within the system would need treatment, the total dissolved solids increase from a centrally managed POE ion exchange system would be similar to that from a central treatment ion exchange system. EPA did not list POE RO units as compliance technologies because it could create corrosion control problems. In addition, water recovery would be no higher than central treatment, so water quantity issues associated with central treatment reverse osmosis would be applicable to POE RO.

The proposed rule included POE AA as a small system compliance technology. Arsenic removal by AA is very sensitive to the pH. The finished water pH will typically be higher than the optimal pH of 6 to meet the corrosion control requirements of the lead and copper rule. A finished water pH for many systems would be in the range of pH 7 to pH 8. Using data on activated alumina run length and pH, it was determined that viable run lengths were likely only when the finished water pH was at or below pH 7.5 (Kempic, 2000). Even in this pH range, the media may need to be replaced more frequently than once a year, which would make the option very expensive especially compared to the POU AA option. The run length data used for this analysis were from a site with very little competing ions (Simms and Azizian, 1997). Studies at other sites with higher levels of competing ions have much lower run lengths (Clifford et al., 1998). Based on the limited finished water pH range where POE AA might be effective and the fact that the POU media needs replacing much less frequently due to lower water demand, POE AA has not been listed as a compliance technology

in the final rule. POE devices utilizing media that are less sensitive to pH adjustment may be listed as compliance technologies in the future once data on their performance are generated.

The effect of pH was also examined on POU AA. Under the POU AA option, the volume of water requiring treatment is much smaller. The unit will be installed at the kitchen tap and only the water being used for cooking and consumption is being treated for arsenic removal. Since the ratio of the daily volume of water being treated to the size of the unit is much smaller, POU units can be operated for longer periods of time before the media needs to be replaced. The replacement frequency assumed for the costs is every six months. Viable run lengths for the POU option were greater than one year up to pH 8 (Kempic, 2000). This analysis assumed a large daily usage volume of 24 liters per day. The average consumption per person per day is just over 1 liter. Even if competing ions reduced the run length significantly, systems with tap water at or below pH 8 should meet the MCL of 10 μg/L using a six-month replacement frequency for the media. POU AA is a compliance technology when the tap water pH is at or below pH 8.

POU RO was listed as a compliance technology in the proposed rule and it is being listed as a compliance technology in the final rule as well. Several comments indicated that water rejection would be an issue with POU devices. Since only about 1% of the total water used in the household is being treated, POU RO is unlikely to create water quantity problems. If the water rejection rate was 10:1, this would only increase the total household water demand by about 10 percent. Where availability of additional water is limited, systems may want to consider other alternatives to meet the MCL.

In order to be consistent with 1996 SDWA Amendments, EPA issued a

Federal Register

notice on June 11, 1998 (EPA, 1998f) that deleted the prohibition on the use of POU devices as compliance technologies. This prohibition was in 40 CFR 141.101. This section now states that public water systems shall not use bottled water to achieve compliance with an MCL. Bottled water may be used on a temporary basis to avoid unreasonable risk to health. Therefore, bottled water cannot be used as a compliance technology for the arsenic rule.

Likely treatment trains are shown in Table I.G-1. These trains represent a wide variety of solutions, including BATs, that small systems may consider when complying with the proposed arsenic MCL. Not all solutions may be viable for a given system. For example, only those systems with coagulation/filtration in place will be able to modify their existing treatment system. The treatment trains include BATs, waste disposal, and when necessary, pre-oxidation and corrosion control. While systems could install lime softening at pH > 10.5 or optimized coagulation/filtration solely for arsenic removal, EPA does not view this as a likely option. Reverse osmosis and electrodialysis reversal are also not included in this table because other options are more cost effective for arsenic removal and do not reject a large volume of water like these two technologies. RO and EDR may be cost-effective options if removal of other contaminants is needed and water quantity is not a concern.

Table I.G-1.— Treatment Technology Trains for Consideration by Small Systems in Complying With Final Rule Including BATs

Train #

Treatment Technology Trains for Consideration by Small Systems

Add pre-oxidation [if not in-place] and modify in-place Lime Softening (pH > 10.5) and modify corrosion control.

Add pre-oxidation [if not in-place] and modify in-place Coagulation/Filtration and modify corrosion control.

Add pre-oxidation [if not in-place] and add Anion Exchange and add POTW waste disposal. Sulfate level ≤ 20 mg/L.

Add pre-oxidation [if not in-place] and add Anion Exchange and add POTW waste disposal. Sulfate level: 20 mg/L < sulfate ≤ 50 mg/L.

Add pre-oxidation [if not in-place] and add Coagulation Assisted Microfiltration with corrosion control and add mechanical dewatering/non-hazardous landfill waste disposal.

Add pre-oxidation [if not in-place] and add Coagulation Assisted Microfiltration with corrosion control and add non-mechanical dewatering/non-hazardous landfill waste disposal.

Add Oxidation/Filtration (Greensand) (20:1 iron: arsenic) and add POTW for backwash stream.

Add pre-oxidation [if not in-place] and add Activated Alumina and add non-hazardous landfill (for spent media) waste disposal. pH 7 ≤ pH < pH 8.

Add pre-oxidation [if not in-place] and add Activated Alumina and add non-hazardous landfill (for spent media) waste disposal. pH 8 ≤ pH ≤ pH 8.3.

Add pre-oxidation [if not in-place] and add Activated Alumina with pH adjustment (to pH 6) and corrosion control and add non-hazardous landfill (for spent media) waste disposal. Run length = 23,100 BV.

Add pre-oxidation [if not in-place] and add POU Reverse Osmosis.

Add pre-oxidation [if not in-place] and add POU Activated Alumina. (Finished water pH ≤ pH 8.0)

Pre-oxidation costs are given as a separate component because they will be incurred only by some systems. In estimating national costs, it was assumed that only systems without pre-oxidation in place would need to add the necessary equipment. It is expected that no surface water systems will need to install pre-oxidation for arsenic removal and that fewer than 50% of the ground water systems may need to install pre-oxidation for arsenic removal. Ground water systems without pre-oxidation should ascertain if pre-oxidation is necessary by determining if the arsenic is present as As (III) or As (V). Ground water systems with predominantly As (V) will probably not need pre-oxidation to meet the MCL.

2. What are the affordable treatment technologies for small systems?

The 13 treatment trains listed in Table I.G-1 were compared against the national-level affordability criteria to determine the affordable treatment trains. The Agency's national-level affordability criteria were published in the August 6, 1998

Federal Register

(EPA, 1998h). In this notice, EPA discussed the procedure for affordable

treatment technology determinations for the contaminants regulated before 1996.

The preamble to the proposed arsenic rule described the derivation of the national-level affordability criteria (65 FR 38888 at 38926; EPA, 2000i). A very brief summary follows: First an “affordability threshold” (

i.e.

, the total annual household water bill that would be considered affordable) was calculated. The total annual water bill includes costs associated with water treatment, water distribution, and operation of the water system. In developing the threshold of 2.5% median household income, EPA considered the percentage of median household income spent by an average household on comparable goods and services and on cost comparisons with other risk reduction activities for drinking water such as households purchasing bottled water or a home treatment device. The complete rationale for EPA's selection of 2.5% as the affordability threshold is described in “Variance Technology Findings for Contaminants Regulated Before 1996” (EPA, 1998l).

The Variance Technology Findings document also describes the derivation of the baselines for median household income, annual water bills, and annual household consumption. Data from the Community Water System Survey (CWSS) were used to derive the annual water bills and annual water consumption values for each of the three small system size categories. The Community Water System Survey data on zip codes were used with the 1990 Census data on median household income to develop the median household income values for each of the three small-system size categories. The median household-income values used for the affordable technology determinations are not based on the national median income. The value for each size category is a national median income for communities served by small water systems within that range. Table I.G-2 presents the baseline values for each of the three small-system size categories. Annual water bills and median household income are based on 1995 estimates.

Table I.G-2.—Baseline Values for Small Systems Categories

System size category

(population served)

Annual household consumption

(1000 gallons/yr)

Annual water bills

($/yr)

Median household income

($)

25-500

$211

$30,785

501-3,300

184

27,058

3,300-10,000

181

27,641

For each size category, the threshold value was determined by multiplying the median household income by 2.5%. The annual household water bills were subtracted from this value to obtain the available expenditure margin. Projected treatment costs will be compared against the available expenditure margin to determine if there are affordable compliance technologies for each size category. The available expenditure margin for the three size categories is presented in Table I.G-3.

Table I.G-3.—Available Expenditure Margin for Affordable Technology Determinations

System size category

(population served)

Available expenditure margin

($/household/year)

25-500

559

501-3,300

492

3,301-10,000

510

The size categories specified in SDWA for affordable technology determinations are different than the size categories typically used by EPA in the Economic Analysis. A weighted average procedure was used to derive design and average flows for the 25-500 category using design and average flows from the 25-100 and 101-500 categories. A similar approach was used to derive design and average flows from the 501-1000 and 1001-3300 categories for the 501-3300 category. The Variance Technology Findings document (EPA, 1998l) describes this procedure in more detail. Table I.G-4 lists the design and average flows for the three size categories.

Table I.G-4.— Design and Average Daily Flows Used for Affordable Technology Determinations

System size category

(population served)

Design flow

(mgd)

Average flow

(mgd)

25-500

0.058

0.015

501-3,300

0.50

0.17

3,301-10,000

1.8

0.70

Capital and operating and maintenance costs were derived for each treatment train using the flows listed previously and the cost equations in the Technology and Cost Document. Several conservative assumptions were made to derive the costs. The influent arsenic concentration was assumed to be 50 μg/L, which was the MCL for arsenic prior to this rule. The treatment target was 8 μg/L, which is 80% of the MCL. Thus, little blending could be performed to reduce costs. Capital costs were amortized using the 7% interest rate preferred by OMB for benefit-cost analyses of government programs and regulations rather than a 3% interest rate.

The annual system treatment cost in dollars per year was converted into a rate increase using the average daily flow. The annual water consumption values listed in Table I.G-2 were multiplied by 1.15 to account for water lost due to leaks. Since the water lost to leaks is not billed, the water bills for the actual water used were adjusted to cover this lost water by increasing the household consumption. The rate increase in dollars per thousand gallons used was multiplied by the adjusted annual consumption to determine the annual cost increase for the household for each treatment train. Several comments on affordability presented household cost increases that were

derived by dividing the annual system cost by the number of households. That is an inappropriate method because residential customers would not only be paying for the water that they use, but also all the water used by non-residential customers of the system..

Of the 13 treatment trains in Table I.G-1, the ones identified in Table I.G-5 are deemed to be affordable for systems serving 25-500 people as the annual household cost was below the available expenditure margin. The two trains using coagulation-assisted microfiltration are not affordable for this size category. All 13 treatment trains are deemed to be affordable for systems serving 501-3,300 and 3,301-10,000 people and are presented in Table I.G-6. Centralized compliance treatment technologies include ion exchange, activated alumina, modified coagulation/filtration, modified lime softening, and oxidation/filtration (e.g. greensand filtration) for source waters high in iron. In addition, POU and POE devices are also compliance technology options for the smaller systems.

Table I.G-5.— Affordable Compliance Technology Trains for Small Systems With Population 25-500

Train No.

Treatment Technology Trains

Add pre-oxidation [if not in-place] and modify in-place Lime Softening (pH > 10.5) and modify corrosion control.

Add pre-oxidation [if not in-place] and modify in-place Coagulation/Filtration and modify corrosion control.

Add pre-oxidation [if not in-place] and add Anion Exchange and add POTW waste disposal. Sulfate level ≤ 20 mg/L.

Add pre-oxidation [if not in-place] and add Anion Exchange and add POTW waste disposal. Sulfate level: 20 mg/L < sulfate ≤ 50 mg/l.

Add Oxidation/Filtration (Greensand) (20:1 iron: arsenic) and add POTW for backwash stream.

Add pre-oxidation [if not in-place] and add Activated Alumina and add non-hazardous landfill (for spent media) waste disposal. pH 7 ≤pH < pH 8.

Add pre-oxidation [if not in-place] and add Activated Alumina and add non-hazardous landfill (for spent media) waste disposal. pH 8 ≤ pH ≤ pH 8.3.

Add pre-oxidation [if not in-place] and add POU Reverse Osmosis.

Add pre-oxidation [if not in-place] and add POU Activated Alumina. (Finished water pH ≤ pH 8.0)

Table I.G-6.— Affordable Compliance Technology Trains for Small Systems With Populations 501-3,300 and 3,301 to 10,000