MERCURY POLLUTANT MINIMIZATION PROGRAM GUIDANCE 

U.S. EPA Region 5, NPDES Programs Branch 

November 2004 

1. Background and Overview 

The following Guidance has been developed in conjunction with the Region 5 states, to address situations 

where a Pollutant Minimization Program (PMP) is required in a state-issued NPDES permit as a result of 

the permittee receiving a variance from the underlying state water quality standard for mercury. Many of 

the specific recommendations are drawn from existing guidance and practices of the Region 5 states. As 

guidance, this document does not create any obligations enforceable by any party. Both industrial and 

municipal permittees may be required to develop PMPs; however, because of the more complex and 

indirect nature of mercury contributions within these systems, the recommendations in this guidance 

pertain primarily to Publicly Owned Treatment Works (POTWs). Each POTW affected by PMP 

requirements will need to determine how it intends to comply. To the extent that other nearby POTWs 

will be faced with the same requirements, however, EPA and the States strongly encourage POTWs to 

coordinate with other POTWs in both the development of their PMP Plans, and in their implementation 

activities to identify and reduce mercury loadings from source sectors. 

While it is expected that specific permit language and conditions will vary (see Ohio sample PMP permit 

language, included in Attachment 1), there are a number of important elements for a mercury PMP. 

1.	 A Program Plan, which lays out the POTW’s commitments for: 

a.	 Identification of potential sources of mercury that contribute to discharge levels; 

b.	 Reasonable, cost-effective activities designed to reduce or eliminate mercury loadings 

from identified sources; 

c.	 Tracking mercury source reduction implementation and mercury source monitoring; 

d.	 Monitoring the POTW’s influent, effluent and biosolids, including at least quarterly 

influent monitoring; 

e.	 Resources and staffing; 

2.	 Implementation of cost-effective control measures for direct and indirect contributors; and 

3.	 An annual status report submitted to the Permitting Authority, which includes: 

a.	 A list of potential mercury sources; 

b.	 A summary of actions taken to reduce or eliminate mercury discharges to enable the 

POTW to progress toward meeting the water quality based effluent limitation (WQBEL); 

c.	 Mercury source reduction implementation, source monitoring results, and influent, 

effluent and biosolids results for the previous year; 

d.	 Proposed adjustments to the Program Plan, based on the findings of 3.c. 

The PMP is meant to be a self-revising process. Results from annual reports need to be used to make 

necessary revisions to the Program Plan and the implementation activities in subsequent years to address 

problems discovered, and investigate new areas where the pollutant might be found. The goal of the PMP 

is to move the POTW’s effluent level towards, and to achieve as soon as is practicable the level specified 

by the underlying water quality based effluent limit necessary to comply with the mercury water quality 

criteria (which will generally be 1.3 ng/l in the Great Lakes Basin and elsewhere in the Region 5 states). 

When this goal is realized, that is, when the discharger can be reasonably expected to be in compliance 

with the WQBEL, then the PMP requirements can be removed from the permit. Where a POTW believes 

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Program Guidance - November 2004 1 NPDES Programs Branch 
it has identified all known sources of mercury, and has fully implemented control strategies with respect 

to those sources, yet remains unable to meet the underlying WQBEL, it should document those findings 

in its annual reports, and revise subsequent program plans accordingly. 

Each element is discussed below. 

2. Program Plans 

2.1 Requirements to develop PMP Plans.

Requirements to conduct initial monitoring and develop a mercury PMP will be included in a POTW’s 

NPDES permit at the time of reissuance (where a variance has been granted concurrently), as a condition 

for receiving a variance from the water quality standard on which the water quality-based effluent limit 

for mercury is based, or as triggered by results showing a reasonable potential for violating water quality 

criteria, based on monitoring conducted during the life of the permit. States have generally been allowing 

six to eighteen months for development and submittal of Program Plans, depending on the extent to which 

the state requires additional data collection in support of the Plan, and the POTW’s previous experience 

with regard to mercury minimization. 

2.2 Identification of potential sources of mercury that contribute to discharge levels (to be updated 

at least annually). 

Sources of mercury within a POTW system can be identified using two basic methods: 1) review of 

existing information sources, and 2) sampling at various points within the sewer system. These activities 

can be done separately, but an initial review of types and locations of existing users within a system will 

help design a monitoring plan which focuses on the most potentially significant contributors. The 

Program Plan should therefore include a review of existing information regarding industrial, commercial 

and domestic users of a POTW system. For some source sectors, including most of those in the matrix in 

Table 1, all individual facilities should be considered likely sources of mercury. For others, such as 

manufacturing facilities or other Significant Industrial Users, review of production processes, materials 

usage and discharge information should be evaluated. Studies and other literature such as source sector 

analyses from other POTWs (see http://www.epa.gov/Region5/air/mercury/mercury.html and 

http://delta-institute.org/pollprev/mercury/mercury.php), and EPA development documents and Industrial 

Sector Notebooks on specific industrial categories can be useful sources of information. 

Existing influent, effluent and biosolids data should also be evaluated, as well as other available 

information such as storm water inputs, groundwater (Inflow & Infiltration) inputs, and wastestreams or 

sewers tributary to the treatment plant. While some States and POTWs may be interested in establishing 

a mass balance of all mercury inputs so as to be able to characterize controllable versus uncontrollable 

contributions, it is recommended that the primary focus be on information indicating community sectors 

and/or geographic locations which are the source of potentially significant contributions. 

2.3 Development of Control Strategies 

The Program Plan next should describe the POTW’s prioritized approach for development of Control 

Strategies for various source sectors, based on review of existing data and the results of subsequent 

monitoring. The Plan should also describe any other mercury reduction activities which have already 

been carried out in a community, as these activities may be substantial and will form a base for the 

additional activities that will need to be done. At minimum, the sectors in Table 1 reflect direct 

dischargers of mercury to POTWs, and should be addressed as part of a POTW’s mercury PMP. 

Consideration should also be given to addressing the sectors in Table 2. Although mercury is generally 

not directly released to POTWs from these sources, they may still pose a significant threat to a POTW’s 

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Program Guidance - November 2004 2 NPDES Programs Branch 
compliance with its mercury effluent limits. Accidental breakage of mercury-containing devices such as 

thermometers, while infrequent, may be enough to increase short-term loadings to a POTW. Where a 

POTW also receives stormwater runoff, mercury levels could be elevated if mercury-containing devices 

are left at locations such as demolition sites or scrap yards. NOTE: While we believe that all of the 

activities listed in Table 1 can be valuable tools in reducing mercury discharges, specific activities 

and performance measures chosen by a POTW may vary from those recommended below in order 

to most efficiently implement effective mercury reduction outreach or other controls. These 

recommendations are based on current information and experience. They may be reevaluated if 

sector-specific or other relevant national guidance is developed. Ultimately, activities should be 

selected by a POTW as part of its mercury control strategy based on the potential of those activities to 

reduce mercury loadings to its sewer system, and thus to its effluent and biosolids. Whatever approach is 

taken initially, progress should be monitored with respect to both participation levels and mercury loading 

reductions. This tracking may indicate the need to change course as necessary for a given sector. 

In addition to describing the proposed activities for each sector, the Plan should also include a schedule 

for implementation which identifies milestones as appropriate. 

Table 1 - Direct Contributors to Address in Mercury PMPs 

Sector Activity Performance Measure Goal 

Medical- Hospitals, -Mail AHA BMP literature Date/content -Mercury-free

clinics, nursing -Workshops Participation Reduction wherever

-Onsite visits Progress, quantity recycled practicable 

Adoption/implementation 

homes, veterinarians 

-Spill management 

-BMP requirements 

-Permits 

Dental clinics -Mail appropriate BMP Date/content -Capture and 

literature recycle mercury 

-Mtgs with dentists Participation used or generated 

-Onsite visits -Minimize mercury 

-Survey(s) discharges 

-Adherence to ADA’s BMPs Adoption/implementation 

(voluntary or mandatory) 

-Mercury recycling (voluntary or Quantity recycled 

mandatory) 

-Adoption of removal equipment Adoption/implementation 

meeting ISO standards 

(voluntary or mandatory) [Note: Certain facilities do 

-Permits not use or generate mercury, 

and some measures may not 

be applicable to them] 

Schools-Secondary -Mail BMP literature 

-Workshops 

-Onsite visits 

-Permits 

Date/content -Mercury-free 

Participation wherever 

Reduction progress practicable 

Quantity of mercury -Spill management 

recycled 

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Program Guidance - November 2004 3 NPDES Programs Branch 
Sector Activity Performance Measure Goal 

SchoolsColleges/Technical, 

laboratories 

Other industries and 

businesses with 

potential for 

mercury 

contributions 

POTWs, other 

municipal 

departments and 

agencies, hauled 

waste 

General public 

see Medical and School sectors see Medical and School 

sectors 

-Mail chemical/equipment Date/content -Phaseout of 

literature mercury containing 

-Onsite visit during Reduction progress devices and 

pretreatment inspection - Quantity of mercury chemicals 

Application of local limits recycled -Spill management 

and/or require BMPs/IU PMP 

in IU permits 

-Evaluate chemical Reduction progress -Phaseout of 

/equipment usage Quantity recycled mercury containing 

-Evaluate domestic and devices and 

nondomestic wastes hauled to chemicals 

POTW, see activities from other -Spill management 

sectors as appropriate 

-Promote mercury clean sweeps Date/contents -Reduced use of 

Quantity of mercury mercury containing 

-Displays at community events recycled products 

- Public Service -Recycling of 

Announcements Website hits mercury products 

-Outreach at schools -Spill management 

 -Establish local mercury 

website 

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Program Guidance - November 2004 4 NPDES Programs Branch 
Table 2 - Indirect Contributors to Address in Mercury PMPs 

Sector Activity Performance Measure Goal 

Thermostats- -Mail Thermostat Recycling Date/content -All captured and 

HVAC Corp. literature recycled 

Wholesalers/Contract -Workshop Participation -Spill management 

ors, Retail stores -Trade assoc. coordination 

-Onsite visits Recycling progress 

-Surveys Quantity of mercury 

recycled 

Automobile and -Onsite visits-service centers Date/content 

appliance switches -Replace hood/trunk switches -All captured and 

-Onsite visits-scrap yards Participation recycled 

-Clip & Recycle switches -Spill management 

Quantity recycled 

Dairy manometers -Mail information Date/content -All captured and 

-Promote use of non-mercury Participation recycled 

manometers Quantity recycled -Spill management 

Outside POTW see all sectors above see all sectors above see all sectors above 

boundaries 

2.3.1. Stakeholder Engagement 

To be Effective, control strategies should be tailored to the specific source sector. These strategies will 

need to include forming partnerships with stakeholders such as trade associations, industrial or 

commercial representatives, local solid and hazardous waste officials, municipal and county health 

officials, POTW treatment plant and pretreatment staff, environmental or other public interest 

organizations, technical assistance providers, academics, equipment vendors, analytical labs that run 

mercury samples, mercury recyclers and others. Participation in statewide or regional efforts (e.g. state 

dental or hospital associations, state and local school agencies and boards) will also greatly improve a 

POTW’s ability to provide outreach and education to association members within its jurisdiction. In 

addition, local recognition of successful facility or sector mercury reduction activities has proven to be a 

popular means of encouraging facility participation, and should be strongly encouraged. 

POTWs and other municipal departments can be sources of mercury, and can serve as role models for 

addressing mercury in their communities (see references under wastewater treatment plants and municipal 

departments). 

Collection programs for community residents (e.g. bulk mercury from dentists, thermometer take-backs) 

have proven effective in removing stocks of mercury from the community that could otherwise end up in 

wastewater or the solid waste stream, and serve to raise awareness for the importance of mercury 

reduction efforts. The availability of mercury recycling vendors, whether public or private, is crucial to 

the success of these collection programs as well as recycling from other sectors, and should be identified, 

and established if necessary, early in program planning and implementation. 

While existing authority should generally be adequate, legal authority issues may need to be considered 

for some of the strategies. For example, POTWs should evaluate their legal authority to ensure that they 

are able to require Industrial Users to: 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 5 NPDES Programs Branch 
• Develop mercury minimization plans; 

• Comply with narrative BMP requirements; 

• Apply numeric local limits to non-significant industrial users; and 

• Permit non-significant industrial users. 

In order to improve the efficiency of educational outreach and mercury product recycling efforts, 

municipalities should be encouraged to collaborate with others in their area in the preparation and 

implementation of Mercury PMPs, at least with respect to the control strategies. 

2.4 Monitoring of potential sources of mercury

In addition to review of existing information, PMP plans should also lay out a POTW’s plans for 

monitoring known and suspected sources of mercury. POTW monitoring of source reduction activities 

using the types of performance measures included in Tables 1 and 2 is one way for both the POTW and 

states to determine whether a POTW is meeting its PMP commitments. For example, Wisconsin has 

established a goal of schools becoming mercury-free. POTWs would be able to monitor and report their 

progress towards this goal by reporting the number of schools within their jurisdiction, the number of 

mercury assessments conducted at these schools, and the number that have become mercury free. Where 

this approach is taken, it is recommended that some spot-test or random sampling program be maintained 

to measure progress of educational programs, and to identify any odd “hot spots” that may show up. 

POTWs should consider determining the baseline level of BMP implementation for various sectors, 

which may be important in establishing the potential mercury load reductions for these sectors. 

The Water Quality Guidance for the Great Lakes System, 40 CFR 132, Appendix F, Procedure 8.D. 

requires semi-annual monitoring of potential sources of the subject pollutant, and quarterly monitoring of 

the wastewater treatment plant influent where a PMP is required due to a water quality-based effluent 

limit being below the quantification level. While the PMP and associated monitoring requirements in the 

federal Great Lakes rules are not directly applicable for state-issued mercury variances, they should 

nonetheless be considered in development of an effective monitoring plan.. Where there are large 

numbers of individual sources (like residential areas), representative sampling could be conducted to 

determine how much a given type of source adds to the system load, and to gauge the effectiveness of 

outreach efforts. In some situations, monitoring methods other than chemical analysis (such as mass- or 

materials-balance, which rely on assumptions of loadings per individual source rather than chemical 

analysis) may be appropriate, such as where there are a large number of facilities with low individual 

loadings, where individual effluent monitoring on a large scale is impractical, or for episodic dischargers 

such as dentists. In general, the plan should lay out a monitoring schedule that will allow the permittee to 

establish baseline levels, determine the effectiveness of various activities and track progress of the PMP. 

To ensure that potential sources are not missed, it is also recommended that plans include an in-sewer 

monitoring scheme that begins with sampling main sewers coming into the treatment plant, and working 

back through the system to identify particular sources. This may need to include sampling of sediments 

within sewers or drainage ditches tributary to the sewers to determine if in-place pollutants are 

contributing to the loading. 

Sampling and analytical methods used in conducting these monitoring plans may vary, based on the 

purposes for which the data will be used, and the location of the sample within the POTW. Given the 

need to compare results with variance-based limits and the underlying water quality-based effluent limits, 

methods 1669 and 1631 will need to be used for effluent monitoring. However, while these methods can 

be successfully run on Industrial User effluents and other points within a POTW, less sensitive methods 

and less-strict sampling protocol may be appropriate for some influent or collection system samples. 

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Program Guidance - November 2004 6 NPDES Programs Branch 
POTW influent levels are commonly in the 50 to 200 ng/L range. Collection system samples may be 

higher in certain parts of the system. EPA Methods 1669 and 1631 are performance based. This means 

that " alternate procedures may be used so long as these procedures are demonstrated to yield reliable 

results." Stated another way, less stringent procedures may be used as long as contamination levels are 

maintained at acceptable levels and sensitivity and other quality control requirements are maintained. 

•	 Sample contamination - Method 1631E, Section 9.4.5.2 indicates that the field blank concentration 

must be no greater than 0.5 ng/L or one-fifth the level in the associated sample, whichever is greater. 

•	 Method sensitivity - Method 1631E, Section 9.1.2.1 indicates that the Method Detection Limit 

(MDL) of the method used must be no greater than 0.2 ng/L or one-third the regulatory compliance 

level, which ever is greater. 

•	 Other quality control - Requirements in Method 1631 regarding standards, method blanks, matrix 

spikes and matrix spike duplicates must still be followed. 

•	 High concentration samples - Whenever possible, laboratories should be notified when high 

concentration samples are being submitted so they can select less sensitive procedures or perform 

necessary dilutions. Failure to identify high concentration samples may compromise the quality of 

low level results and shut down the instrument for extended periods while the laboratory 

decontaminates the system. 

•	 Use of Less Sensitive Methods - Although samples may be diluted to bring sample concentrations 

into the working range for method 1631, it is also appropriate to select less sensitive methods for 

higher concentration samples. Section 9.1.2 of method 1631E allows certain modifications of the 

method when less sensitivity is required. Laboratories may substitute the detector with a cold vapor 

atomic absorption system (CVAAS) similar to that used in method 245.1. The initial preconcentration 

on the gold amalgam may be omitted, making the method functionally equivalent to method 245.7. 

For samples expected to have concentrations in excess of 500 ng/L (0.5 ug/L), the traditional 

dilutional method 245.1 can be useful. However, be aware that the potassium permanganate used in 

the method acts as a mercury scavenger, so results may have a high bias. 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 7 NPDES Programs Branch 
Typical Mercury Concentrations and Method Options For Wastewater Sources 

[Estimates based on WDNR observations] 

Source Typical Concentration Method Options 

POTW wastewater influent 50 - 500 ng/L 1631 (dilution) 

1631 modified (245.7*) 

POTW wastewater effluent 1 - 20 ng/L 1631 

POTW sludge or biosolids 0.2 - 30 mg/Kg (dry weight) SW 846-7471B 

POTW Collection System 50 - 1000 ng/L 1631 (dilution) 

1631 modified (245.7) 

1631 modified (CVAAS) 

245.1 (optimized & dedicated 

instrument) 

Industrial Effluent -general Variable 1631 

1631 modified (245.7) 

1631 modified (CVAAS) 

Industrial Effluent - mercury Variable 1631 modified (245.7) 

process or contaminated 1631 modified (CVAAS) 

feedstock 1631 (dilution) 

245.1 

Surface Water 0.2 - 10 ng/L 1631 

Dental office discharge ** episodic discharges ranging 245.1 

from 1,000- 12,000,000 ng/L 1631 modified (CVAAS) 

1631 modified (245.7) 

** Seattle Metro 1991; Massachusetts (MWRA) 1997; Barrucci (San Francisco) 1992, 1993; Pima 

County, AZ, 1991. 

Additional details on appropriate sampling and analytical procedures are discussed in WDNR’s Guidance 

for Collecting Samples for Total Mercury Analysis to Meet Wastewater Permit Requirements in 

Wisconsin sampling guidance, (attachment 2). 

2.5 Resources and Staffing

Lastly, Program Plans need to summarize the resources and staff that will be committed to 

implementation of mercury PMPs. Specifically, Plans should indicate the source and amount of funding 

that will be available to carry them out. They should also include the number and position of Full Time 

Equivalents that will be devoted to PMP implementation. Where other POTWs, municipal agencies, or 

trade associations will be helping to plan or implement mercury reduction activities, those resources and 

staffing estimates should be included as well. 

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Program Guidance - November 2004 8 NPDES Programs Branch 
2.6 State approval of the plans

The states will be reviewing and approving POTW PMP plans to ensure that implementation moves the 

POTW towards the goal of maintaining mercury concentrations at or below the WQBEL. As indicated in 

section 2.1, POTWs will generally be required to submit proposed plans within a reasonable period of 

time (typically 6-18 months) from reissuance of the POTW’s NPDES permit, or as required by the 

permitting authority as a condition for receiving a variance. 

Proposed plans should be reviewed based on addressing the specified elements discussed above. As 

indicated above, proposing activities in the “indirect contributors” section (Table 2) should generally not 

be accepted instead of activities in the “direct contributors” section (Table 1), although the value of 

addressing those additional sectors should be considered as part of the evaluation of adequacy of the 

overall plan. Similar consideration should be given to activities that address sources outside a POTW’s 

jurisdictional boundaries. POTWs would need to address comments and make necessary revisions prior 

to state approval of the plans. Upon plan approval, implementation would be required as a condition of 

the POTW’s NPDES permit. POTWs are encouraged, however, to begin implementation activities such 

as monitoring, outreach to dischargers and internal audits prior to final approval, or prior to a PMP being 

required. 

An example of a PMP developed by a POTW in Michigan is included in Attachment 3. 

3. Program Implementation 

Upon approval of its Plan, the POTW will be responsible for carrying out and tracking implementation of 

its source reduction strategies, and conducting the specified monitoring. While U.S. EPA, the states and 

others are engaged in identifying the best approaches for addressing mercury sources in the various 

sectors, much work has been done in this area. POTWs should be encouraged to review available 

information, and to the greatest extent possible adopt approaches that others have found to be effective. 

Several of the States in Region 5 have already identified materials that can be used or revised as necessary 

for distribution to sources in several sectors; these materials are referenced in references and websites 

below. Other sources of mercury pollution prevention and waste minimization information are available 

at http://www.epa.gov/Region5/air/mercury/mercury.html. 

4. Annual status reports 

PMP reports are an important element of state approved plans, and will generally be required to be 

submitted one year after the Program goes into effect, and annually thereafter. For POTWs with 

pretreatment programs, these reports can be submitted with their Annual Pretreatment Report. Reports 

should include a summary of potential sources of the pollutant, a summary of all source control activities, 

and results of source reduction monitoring and wastewater sampling for the previous year. Proposed 

adjustments to the Program should also be included. 

4.1 Potential mercury sources

The annual report should identify individual facilities or targeted groups within the various sectors 

covered by the plan. A list of new potential sources that have been identified as a result of monitoring or 

other evaluation should also be provided. Status of these facilities with respect to the goals laid out for the 

different sectors should be provided, as described in section 4.3 below. 

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Program Guidance - November 2004 9 NPDES Programs Branch 
4.2 Summary of actions taken to reduce or eliminate mercury discharges

This section would include actions taken in response to monitoring results discussed below, and in 

furtherance of the control strategies laid out in the Plan. Progress with respect to identified goals for the 

various sectors should be discussed. If no actions were taken to address an identified source or sector, an 

explanation should be provided. Historic mercury source reduction activities, as well as recent actions 

taken in the last year, should be included in this summary. This will give the municipality credit for all 

their activities to date regarding the various sectors, and will facilitate review of the annual report. 

4.3 Source Reduction and Wastewater Monitoring results 

All mercury data collected during the previous year should be included with the annual report. This 

would include tracking of source reduction activities with respect to established sector-specific 

performance measures as discussed in section 2.4, as well as influent, effluent, biosolids data, and data 

collected from potential sources. Sampling dates, method of analysis, the laboratory name, and 

appropriate units should accompany any wastewater monitoring results. 

The Water Quality Guidance for the Great Lakes System calls for at least quarterly influent monitoring 

for POTWs implementing PMPs. Several of the states have viewed this as a minimum requirement for 

both influent and effluent, but have required additional, generally monthly monitoring, for larger POTWs 

(those with flows of greater than 5 million gallons per day). In addition, these states have generally 

required biosolids monitoring from one to four times per year, with the frequency varying based on the 

volume of biosolids generated. Collection of biosolids data is important in tracking progress in reducing 

mercury releases to the environment; tracking effluent levels alone will not fully indicate progress in 

reducing mercury releases to the environment. 

4.4 Revision of plans

Finally, the Annual Report would need to include any proposed adjustments to a POTW’s Program Plan 

where municipal activities have not been implemented as originally agreed to, source reduction 

implementation has not occurred, or source reduction implementation has occurred, but has not been 

effective in reducing mercury discharges (after accounting for sample variability). 

5. Compliance determinations under state NPDES programs

Compliance with the permit provisions for a POTW with mercury limitations based on a variance from 

the water quality standard would be determined by evaluating two components of the permit. First, the 

concentration in the POTW’s effluent would be compared to the currently achievable level as established 

through the state’s variance process. Second, the facility would need to be in compliance with the PMP 

requirements of the permit. Specifically, it would need to have developed the PMP Plan, and then 

fulfilled the commitments established and agreed to in the approved Plan. After approval of the initial 

plan, compliance would be evaluated primarily through review of the annual status report, to determine 

whether the POTW had adequately identified known and potential mercury sources, had carried out the 

activities it committed to, and had satisfied the specific source reduction and wastewater monitoring 

requirements. Evaluations for subsequent years would need to take into account revisions described in 

the previous year’s annual report. Where a POTW has coordinated with other POTWs, the reports from 

the communities should be reviewed as a group. 

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Program Guidance - November 2004 10 NPDES Programs Branch 
6. Approaches to Establishing Local Limits for Mercury

6.1 Background on local limits

Local limitations are generally developed by POTWs to implement the general and specific prohibitions 

of the General Pretreatment Regulations, 40 CFR 403, and are established to prevent discharges that 

cause pass through, interference, or which threaten worker health and safety. EPA’s Local Limits 

Development Guidance (EPA 833-R-04-002A, July 2004) identifies fifteen pollutants, including mercury, 

which are presumed to be pollutants of concern, and should be evaluated to determine whether local 

limits should be established. Where established, local limits for mercury and other pollutants are typically 

expressed as daily maximum and/or a longer term average concentration. 

The National Pretreatment Program, and the underlying General Pretreatment Regulations apply to 

Industrial Users (IU). An IU is defined as a source of indirect discharge, which in turn is defined as the 

introduction of pollutants into a POTW from any nondomestic source regulated under Section 307(b)(c) 

or (d) of the Clean Water Act (40 CFR 403.3(g)). Thus, all non-domestic users of a POTW, which would 

be considered any user except for a household or dwelling unit, are considered Industrial Users, and are 

thus subject to Pretreatment Standards and Requirements. And while many POTWs have established 

local limits for mercury, with some applying these limits to hospitals and other Significant Industrial 

Users (SIU), mercury local limits have generally not been enforced against “commercial” facilities such 

as dental clinics, schools, etc. Where these facilities have been addressed, it has generally been through 

voluntary outreach and education efforts. As discussed in this PMP guidance, promotion of voluntary 

source reduction will remain an integral part of PMPs. In order to increase participation in implementing 

Best Management Practices and other source reduction strategies to achieve the greatest possible mercury 

reductions, however, POTWs will need to consider application of local limits for these commercial users. 

6.2 Best management practices (BMPs) as local limits

Ensuring compliance by all industrial and commercial facilities within a POTW’s jurisdiction with 

uniform concentration-based mercury limits will generally not be desirable or feasible. As an alternative, 

some POTWs have established mercury limits that apply to all IUs, but then establish alternative methods 

that can be used by certain commercial or industrial sectors to demonstrate compliance with the limits. 

The issue of using requirements for Best Management Practices instead of or in addition to numeric local 

limits was addressed in EPA’s Pretreatment Streamlining Proposal (64 FR 39563, July 22,1999). As 

discussed in that proposal, the Pretreatment Regulations do not specifically address the use of BMPs as 

local limits, and are not clear as to whether BMPs can satisfy current requirements for development and 

implementation of local limits. However, as pointed out in the proposal, The Guidance Manual on the 

Development and Implementation of Local Discharge Limitations Under the Pretreatment Program (EPA 

833/B-87/202, December 1987) provides general information on the use of BMPs as local limits. 

Specifically, the guidance explains, ``The development and implementation of numeric local limits is not 

always the only appropriate or practical method for preventing pollutant pass through and interference, or 

for protecting POTW worker health and safety. Control of chemical spills and slug discharges to the 

POTW through formal chemical or waste management plans can go a long way toward preventing 

problems. A local requirement for an IU to develop and submit such a plan can be considered as a type of 

narrative local limit and can be a useful supplement to numeric limits.'' 

Recognizing that some POTWs are already using BMPs to control certain wastewater discharges where 

they found it impractical to apply a numeric effluent limit, EPA proposed to clarify that best management 

practices developed by POTWs may serve as local limits required by 40 CFR 403.5(c)(3), and that such 

BMPs would be enforceable under 40 CFR 403.5(d). While this clarification has not yet been finalized, 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 11 NPDES Programs Branch 
U.S. EPA Region 5 believes that BMPs developed by POTWs to prevent pass through and interference 

would be considered enforceable local limits under 40 CFR 403.5(c), and supports this approach. 

6.2.1 Sector-specific mercury BMPs

With respect to mercury, some cities are implementing formal regulatory programs for controlling 

mercury discharges from dental facilities, which were identified in a 2002 Association of Metropolitan 

Sewerage Agency study as the largest source of mercury to evaluated POTWs (Mercury Source Control 

& Pollution Prevention Program Evaluation (March 2002). Voluntary and regulatory programs, along 

with case studies, are discussed in the Binational Toxics Strategy Mercury Workgroup report Options for 

Dental Mercury Reduction Programs: Information for State/Provincial and Local Governments (updated 

April 2004). In general, these programs focus on implementation by dental facilities of BMPs such as 

those adopted by the American Dental Association (ADA), as well as installation of amalgam separators. 

Amalgam separators are devices that remove amalgam from wastewater before it leaves the dental clinic. 

As pointed out in a video developed by the ADA and the Naval Institute for Dental and Biomedical 

Research entitled "Dental Amalgam and Best Management Practices" 

(http://www.ada.org/prof/resources/topics/amalgam_bmp.asp), the use of amalgam separators can 

substantially reduce levels of dental mercury that reach wastewater treatment plants, and studies in several 

communities where separators have been adopted have shown marked reduction in mercury levels in 

municipal wastewater treatment plant sludge. 

To control potential mercury releases from schools, Indiana, like some other states, has adopted 

legislation prohibiting schools from using or purchasing most mercury commodities, compounds or 

equipment. Satisfaction of these state requirements or implementation of state programs for inventorying 

and elimination of mercury in schools could be incorporated into local requirements for schools. 

Likewise, hospitals and medical clinics could be required to implement BMPs adopted by the American 

Hospital Association. 

6.3 Incorporating BMPs into the technical evaluation of local limits 

As discussed in the Pretreatment Streamlining proposal: 

For BMPs to be considered local limits under 40 CFR 403.5(c), they must protect against pass 

through and/or interference. This will require the POTW to evaluate the BMPs during the 

technical evaluation of its local limits. During the technical evaluation for local limits, the POTW 

will determine the maximum allowable headworks loadings (MAHL) for pollutants of concern. 

This MAHL will then be allocated to the different contributing sectors of the service area, such as 

domestic loadings, commercial loadings, industrial loadings and a safety factor. 

Based on these considerations, the POTW will decide how to control the different contributing 

sectors in order to protect against pass through and interference. Often the POTW simply 

allocates a portion of the loading to control industrial contributions; this is considered to be the 

maximum allowable industrial load (MAIL). The MAIL is then converted into the local limit 

which is often expressed as an across-the-board concentration applicable to all industrial sources 

or all "users of the POTW." This is not the only way local limits can be developed. Another 

option available to the POTW is to apply the MAIL to all industrial and commercial sources and 

to use a mixture of BMPs and numeric limits to control industrial and commercial sources of 

pollutants. Whatever the allocation scenario, the BMPs are developed by the POTW to protect 

against pass through and interference, and are local limits." 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 12 NPDES Programs Branch 
Thus, POTWs providing for use of BMPs by certain commercial or industrial sectors as an enforceable 

alternative to numeric mercury limits will need to review the basis of their underlying numeric limits. 

What may previously have been considered “uncontrollable” loadings from commercial facilities may 

now be considered “controllable” loadings. The recharacterization would result in the shifting of loading 

from the domestic background to the MAIL. Under ordinary circumstances, POTWs using BMPs as local 

limits would be able to provide an evaluation that implementation of the numeric limit plus 

implementation of BMPs for specific sectors should result in the calculated MAIL being met. 

Available data, however, indicates that mercury local limits calculations for many Great Lakes 

dischargers would result in negative local limits. In other words, the domestic loading alone may exceed 

the MAHL, leaving no allowable loading to allocate to commercial or industrial users. This is mainly a 

function of the estimated domestic loading (the mercury loading from an “average” person multiplied by 

the number of residents), and the water quality based effluent limit (WQBEL) (A report prepared for the 

Association of Metropolitan Sewerage Agencies utilized a value of 17.2 ug/day/person (Mercury Source 

Control & Pollution Prevention Program Evaluation (March 2002)). This situation will pose a significant 

challenge to POTWs responsible for developing technically based local limits that prevent pass through 

and interference, as well as the States that must approve these limits. One option for addressing this 

situation would be to set the local limit equal to the POTW’s NPDES limit, adjusted for the mercury 

removal efficiency (which appears to be above 90 percent at most POTWs). Thus, if the WQBEL is 1.3 

ng/l, the local limit would be between 13 and 26 ng/l (1.3 ng/l /1-.9= 13 ng/l; 1.3 ng/l /1-.95=26 ng/l). 

The rationale in support of this approach is that facilities with such a limit would not be contributing to 

pass through. This approach appears to be more practical than other, even more stringent alternatives, 

and would serve as a clear incentive to meet BMPs instead of the numeric limit. Even under this 

approach, however, opportunities for reductions in mercury discharges may be very limited in some 

circumstances. Where a nondomestic user discharges above the local limit due primarily or entirely to 

mercury in sanitary waste, BMP requirements may not have an effect. 

6.4 Structuring BMP-based limits

There are a variety of ways to set mercury local limits, from establishment of uniform concentration 

limits, to setting technology-based limits based on achievability using certain practices or treatment 

technologies for different sectors. Regardless of how the numeric limit is established, the Ordinance 

could then provide users an alternative means of demonstrating compliance with the limit through the use 

of BMPs. To be considered enforceable local limits under 40 CFR 403.5(c), mercury BMPs developed 

by POTWs should include the common elements listed below. Depending on the sector being controlled, 

however, certain elements such as installation of treatment or prohibitions on practices, may not be 

applicable. 

• Specific notice to affected users of requirements and enforceability 

• Installation of treatment 

• Requirements for or prohibitions on certain practices, activities or discharges 

• Requirements for operation and maintenance of treatment units 

• Reporting and records retention for O&M activities 

• Certification and reporting of compliance 

• Re-opener for a permit and local limits to be applied at the POTW’s discretion 

• Other requirements as determined by the POTW 

As discussed above, dentists could be given the option of satisfying locally-imposed ordinance and/or 

permit requirements by installing an ISO 11143 approved amalgam separator, and complying with other 

BMPs established under the Ordinance. Compliance in such cases would be determined by review of 

certifications by facilities that they are satisfying those requirements, and/or by random inspections and 

records review by the POTW. Under this approach, those choosing not to install this equipment or follow 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 13 NPDES Programs Branch 
the BMPs should be required by the Ordinance to obtain a permit within a specified time frame, and 

monitor and report their compliance with the numeric limit. The POTW would also determine 

compliance by these facilities with the numeric limit through traditional wastewater sampling. 

Similarly, hospitals, schools and potentially even Significant Industrial Users could be allowed to 

implement BMPs specific to their sectors as an alternative to demonstrating compliance with a numeric 

local limit. 

6.5 Timing of local limit evaluations 

Normally, POTWs with Pretreatment Programs are required to conduct technical local limit evaluations 

within six to twelve months from the effective date of NPDES permit reissuance. In the case of mercury, 

the evaluation may be significantly influenced by information generated in the course of the PMP 

development process. Thus, we recommend requiring mercury local limit re-evaluations to be provided 

subsequent to submittal of PMP plans, although the plans should include the municipality’s intentions and 

a schedule for data collection and proposal of revised numeric limits. Where a POTW plans on using 

BMP-based limits, the plan should also include a schedule for revising the Sewer Use Ordinance. 

References 

1. Pollutant Minimization Programs Guidance, Ohio Environmental Protection Agency, Division of 

Surface Water, August 13, 1998, http://www.epa.state.oh.us/dsw/guidance/guidance.html 

2. The Use of Best Management Practices (BMPs) as Industrial Local Pretreatment Limits, Ohio 

Environmental Protection Agency, Division of Surface Water, August 13, 1998, 

http://www.epa.state.oh.us/dsw/guidance/guidance.html. 

3. Municipal Mercury Pollutant Minimization Program (Mercury PMP), Wisconsin Department of 

Natural Resources, Bureau of Water 

http://www.dnr.state.wi.us/org/caer/cea/mercury/index.htm. 

4. Procedure for Reviewing Pollutant Minimization Programs, Michigan Department of Environmental 

Quality, Surface Water Quality Division, August 2002. Please contact Grace Scott, Pretreatment 

Coordinator, at 517/335-4107. 

5. Mercury Source Control & Pollution Prevention Program Evaluation- Final Report, Association of 

Metropolitan Sewerage Agencies, March 2002. 

Websites 

General Mercury: 

http://www.epa.gov/Region5/air/mercury/mercury.html 

Medical Mercury: 

http://www.h2e-online.org 

http://www.michigan.gov/deq/0,1607,7-135-3585_4127_4175-35423--,00.html 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 14 NPDES Programs Branch 
Dental Mercury: 

American Dental Association Best Management Practices, and 

"Dental Amalgam and Best Management Practices" (Video), American Dental Association and the Naval 

Institute for Dental and Biomedical Research 

http://www.ada.org/prof/resources/topics/amalgam_bmp.asp 

http://www.dentalmercury.com 

Options for Dental Mercury Reduction Programs: Information for State/Provincial and Local 

Governments, A Report of the Binational Toxics Strategy Mercury Workgroup Co-Chairs 

http://www.epa.gov/region5/air/mercury/dentaloptions3.pdf 

Evaluation of Amalgam Removal Equipment and Dental Clinic Loadings to the Sanitary Sewer, 

Metropolitan Council Environmental Services and Minnesota Dental Association, December 21, 2001. 

http://delta-institute.org/pollprev/mercury/linkfiles/Separator%20Comparison%20Chart.htm 

Schools: 

http://www.mercuryinschools.uwex.edu 

General Public: 

http://www.epa.gov/mercury/ 

North Carolina Division of Pollution Prevention and Environmental Assistance 

http://www.p2pays.org/mercury/ 

General Industry: 

http://www.nwf.org/nwfWebAdmin/binaryVault/mercuryproducts.pdf 

http://www.state.me.us/dep/mercury/lcspfinal.pdf 

Dairy manometers: 

http://www.dnr.state.wi.us/org/caer/cea/mercury/program.htm#Dairy 

http://www.deq.state.mi.us/documents/deq-ead-p2-ag-richro.pdf 

Wastewater Treatment Plants: 

http://delta-institute.org/pollprev/mercury/mercury.php 

http://delta-institute.org/pollprev/mercury/selfassess.php 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 15 NPDES Programs Branch 
Auto Switch: 

http://www.dec.state.ny.us/website/ppu/p2autosw.html 

http://www.deq.state.mi.us/documents/deq-ess-p2-mercury-michiganswitchstudy.pdf 

[Note: The following attachments are intended as examples only, and are not intended to serve as models 

or templates] 

Attachment 1- Sample NPDES Permit Language Regarding Mercury PMP Requirements, Ohio 

Environmental Protection Agency, Division of Surface Water 

http://www.epa.state.oh.us/dsw/guidance/permit7.pdf 

Attachment 2- Wisconsin DNR Guidance for Collecting Samples for Total Mercury Analysis to Meet 

Wastewater Permit Requirements in Wisconsin, 2003. 

http://dnr.wi.gov/org/water/wm/ww/mercury/clean_hands.pdf 

Attachment 3- Holly, Michigan Pollutant Minimization Program, March 2003. 

http://www.epa.gov/region5/water/npdestek/MercuryHolly_PMP_4-03_final.pdf 

Mercury Pollutant Minimization U.S. EPA Region 5 

Program Guidance - November 2004 16 NPDES Programs Branch