Page 1 

"Nelson, Martina" 

<martina.nelson@metc.

state.mn.us> 

12/06/2007 08:27 AM 

To Group Ow-Docket@EPA 

cc "Hermes, Leo" <leo.hermes@metc.state.mn.us> 

bcc

Subject Attention Docket ID No. EPA-HQ-OW-2006-0771 

 

 

Mr. Johnston: 

The attached document provides MCES’ comments on EPA’s Preliminary 2008 Effluent 

Guidelines Program Plan. We have also included a summary of MCES’ Dental Mercury 

Study, which is referenced in the comments document. 

Please contact me if you have any questions. 

Martina Nelson, P.E. 

Senior Engineer 

Industrial Waste & Pollution Prevention Section 

Metropolitan Council Environmental Services 

390 N Robert St, St Paul, MN 55101 

Ph: 651-602-4728 Fx: 651-602-4730 

www.metrocouncil.org/environment/IndustrialWaste/ 
 Page 2 

December 5, 2007 

Mr. Carey Johnston 

Environmental Protection Agency 

Mailcode: 4203M 

1200 Pennsylvania Ave NW 

Washington, DC 20460 

RE: Comments Related to EPA’s 2008 Effluent Guidelines Program Plan 

Mr. Johnston: 

Metropolitan Council Environmental Services (MCES) owns and operates eight wastewater treatment 

plants and 600 miles of interceptors in the seven-county Minneapolis/St. Paul Metropolitan Area. In 

addition, MCES administers the POTW Pretreatment Program in this area, including permits for 774 

Industrial Users. 

MCES hereby provides the following responses on EPA’s request for comments regarding its 2008 

Effluent Guidelines Program Plan. 

Dental Mercury

With regard to dental mercury, MCES has chosen to comment on the following items: 

1. In state and localities that have not established dental mercury guidance or requirements, what, if 

anything do dental offices currently do to reduce mercury discharges associated with dental 

amalgam? Also, what annual costs are associated with these activities? 

MCES has administered a program in partnership with the Minnesota Dental Association 

(MDA) to have amalgam separators installed. If this program was not in place, it is likely 

that dentists in our area would have learned about and followed BMPs put forth by the 

American Dental Association (ADA). Further, some dental offices have reduced or 

eliminated the placement of new amalgam restorations. MCES does not have specific cost 

figures on this topic. Added costs may vary significantly, depending on how far along they 

are on implementing BMPs. If everything such as chairside traps and vacuum filters had 

been put in the regular office trash or rinsed down the drain, and they switch to collection 

and transport, they may see a significant increase in costs. 

2. EPA assumed that, at a minimum, all dental facilities have chairside traps and/or vacuum pump 

filters, and that they dispose of the amalgam collected in these traps/filters as solid waste (i.e., not 

subsequently rinsed down the drain). EPA solicits comment on this assumption. 

MCES surveyed Minneapolis-St Paul area dental offices in the late 1990s, and found that 

there was quite a wide variety of waste disposal methods, which involved treating these 

wastes as solid waste, hazardous waste, or infectious waste, and also disposal by sewering. 

Since state and national dental associations have promoted BMPs, MCES believes that there 

is improved management of these wastes. See WEF’s 1999 publication “Controlling Dental 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 3 

Facility Discharges in Wastewater: How to Develop and Administer a Source Control 

Program.” 

3. To what extent are the ADA recommended BMPs currently utilized in the dental industry? What 

is the cost effectiveness in reducing dental mercury associated with BMPs, and what are the 

annual costs. 

MCES does not have specific scientific data. However, based on the annual submittal of 

statements by dental offices in the Minneapolis-St Paul metropolitan area, the 

implementation of BMPs is believed to be uniform. The submittal of these statements is a 

required part of our program which promotes the installation of separators and improved 

waste management. In addition, the seven counties of the Minneapolis-St Paul metropolitan 

area, which administer RCRA rules, are currently in the process of having dental offices 

perform self audits, which are beginning to be received for review by the counties. 

4. EPA solicits data on the effectiveness of BMP or amalgam separators in reducing mercury in 

POTW influent, effluent and/or sludge. EPA is particularly interested in obtaining data from 

studies that measured mercury concentrations in POTW influent, effluent, and/or sludge before 

and after BMP or amalgam separation implementation. 

Since the implementation of an amalgam separator program in the Minneapolis-St Paul 

metropolitan area in 2003, MCES has seen a 50% reduction in mercury measured in the 

influent at MCES’ largest treatment plant, the Metropolitan Wastewater Treatment Plant in 

St Paul. Please refer to the attached Figure 1 entitled “Influent Mercury Reduction at 

Metropolitan Wastewater Treatment Plant.”

In addition, a joint MCES & MDA study performed between 1999 and 2001 measured a 29-

44% reduction in mercury concentrations in sludge at two smaller MCES WWTPs when 

dental offices installed amalgam separators. A summary of this study is included with this 

mailing. A second MCES research study was conducted with the MDA to measure the 

mercury loading coming from dental offices and the effectiveness of amalgam separators. 

This study determined that dental offices generate 234 mg/dentist/operating day of mercury, 

and amalgam separators remove 91-99% of mercury. 

As noted, MCES data show the effect of amalgam separator installation. MCES determined 

that separator installation was warranted, and therefore began a separator installation 

program right away. MCES did not have a separate phase of implementing just BMPs, and 

therefore does not have mercury reduction data on the effect of BMPs alone. 

5. EPA solicits information on the cost and burden to POTWs of implementing state or local BMP or 

amalgam separator requirements. EPA is also interested in obtaining information on how POTWs 

have implemented such standards. 

MCES spent many years researching, creating and implementing an amalgam separator 

program for dental offices in the Minneapolis-St Paul metropolitan area. Based on staff 

time and analytical services performed, MCES estimates that the cost of this effort is in 

excess of $500,000. This is a rough estimate, and includes two major research studies, 

investigating separator testing and certification commented on below, working with 

NACWA, revising the ISO 11143 Standard, etc. 

If a POTW or a state sets up a separator program by taking advantage of the tools available, 

they will greatly minimize their costs. If they are not careful, and begin a program without 

thoroughly considering all aspects, they will set themselves up for a lot of extra work, such as 

reviewing ISO test reports and ongoing evaluation of future technical changes to separator 

models. 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 4 

An extremely critical aspect of implementing an amalgam separator program deals with 

understanding laboratory testing and certification of separators. The most common way to 

test separators is by using the International Organization for Standardization (ISO) 11143 

test method. Regulators at the local and state level need to familiarize themselves with the 

basics of testing and certification PRIOR to implementing a separator program. 

The National Association of Clean Water Agencies (NACWA) published a white paper in 

January of 2006 to help POTWs and other regulators learn about setting up separator 

programs, titled “Controlling Mercury in Wastewater Discharges from Dental Clinics.” A 

link to this paper is http://www.nacwa.org/images/stories/public/2006-01dmercwp.pdf

Regulators and separator program administrators need to take advantage of the ISO tools 

currently available, such as certification, which is a quality control system to ensure that 

separators are manufactured on an ongoing basis that conform with the ISO Standard. (A 

“UL” mark on a product is an example of certification.) To learn more about the benefits of 

certification, please refer to the NACWA paper mentioned above. 

Regulators and program administrators need to understand, and even specify, what labs and 

certification bodies are acceptable, to be sure of the test reports and certificates presented to 

them. By identifying labs and certification bodies (CB), and by requiring proper 

accreditation of these labs and CBs, regulators can lay the foundation for a rigorous 

program. These steps help ensure a fair and good program for the separator manufacturers 

competing to sell in any given area. 

6. EPA solicits comment on any known interferences or pass-through problems associated with 

dental mercury discharges? 

No interferences or pass-through problems associated with dental mercury have occurred at 

any of the eight treatment plants operated by MCES. 

7. EPA solicits additional information on the effectiveness of voluntary local programs for reducing 

mercury discharges from dental facilities. 

MCES and the Minnesota Dental Association (MDA) promoted its amalgam separator 

program as voluntary and it has been extremely successful. However, there was a general 

threat that dental offices may ultimately be required to install a separator. The MDA even 

put out information indicating that there was a “deadline” to install. Therefore, the 

program could not be described as completely voluntary. 

After the majority of the dental offices installed a separator, MCES increased the threat of 

regulation to get the remaining offices to install a separator. Offices were told that they 

would have to apply for a discharge permit, meet a mercury limit, conduct semi-annual 

monitoring of their wastewater, submit self-monitoring reports, and pay an annual permit 

fee. While some dental offices did not immediately install an amalgam separator, they all 

eventually complied with the voluntary program in lieu of holding an Industrial Discharge 

Permit. 

Unused Pharmaceuticals

1. EPA solicits identification of any policies, procedures or guidelines that govern the disposal of 

unused pharmaceuticals from hospitals; offices of doctors and mental health practitioners; nursing, 

long-term care, rehabilitation, and personal care facilities; medical laboratories and diagnostic 

service facilities; and veterinary care facilities. 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 5 

MCES participates in an ongoing partnership with the Solid Waste Management 

Coordinating Board (SWMCB) and the Minnesota Pollution Control Agency (MPCA) to 

establish uniform interpretations and guidance on regulatory issues pertaining specifically to 

the healthcare industry. This partnership has developed and routinely updates a 

“Regulatory Consensus on Health Care Issues” document to help eliminate some of the 

confusion and misunderstanding that exists in the healthcare industry concerning the 

disposal of unused pharmaceuticals. A copy of this document can be viewed at 

http://www.pca.state.mn.us/publications/w-hw3-35.pdf. 

The partnership has also established policies and procedures to help the health care industry 

look for alternative methods of disposal for unused pharmaceuticals, including incineration 

where applicable. In addition, fact sheets, BMPs and training sessions for hospital and 

surgery center employees were developed and disseminated, resulting in improved 

management and reduced environmental impacts. 

2. EPA solicits information on the most likely sub-sectors within the Health Service sector that 

would accumulate unused pharmaceuticals for management and disposal. 

MCES believes that there is potential for all the above-mentioned sub-sectors within the 

Health Service sector to accumulate unused pharmaceuticals. This is especially true for subsectors that receive sample pharmaceuticals shortly prior to their expiration date. In 

addition, MCES believes that there are significant amounts of unused pharmaceuticals 

within the residential sector. 

3. When applicable, to what extent are unused pharmaceuticals disposed according to RCRA? 

Before the partnership between MCES, SWMCB and MPCA was formed, MCES believed 

that unused pharmaceuticals were not disposed of according to RCRA. The partnership has 

strongly encouraged waste minimization in the health care industry in the Minneapolis-St 

Paul metropolitan area. Waste minimization practices such as inventory reduction, product 

substitution, and reverse distribution are utilized first. Then if unused pharmaceuticals 

remain, any quantities are disposed of according to RCRA and Minnesota Lethal 

regulations. The Minnesota Lethal regulation constitutes an additional hazardous waste 

characteristic beyond RCRA. 

As for the status of sewered unused pharmaceuticals, MCES currently evaluates requests 

and may grant discharge approval of such items under RCRA on a case by case basis. 

However, as the partnership continues its efforts to provide guidance to the health care 

industry, MCES anticipates a reduction in the request for such discharge approvals. 

4. EPA solicits comment and data on: (1) the main factors that drive current disposal practices; (2) 

any barriers preventing the reduction or elimination of unused pharmaceuticals to POTWs and/or 

surface waters. In particular, EPA solicits comment on the extent that the Controlled Substances 

Act complicates the design of an efficacious solution to drug disposal? 

In general, MCES believes that regulations, costs, and the ease of disposal drives current 

disposal practices. Historically, unused pharmaceuticals were mismanaged and disposed of 

into solid waste (trash) or sewered since generators did not know about applying RCRA and 

Minnesota Lethal regulations. Currently, under the SWMCB guidance, generators of 

unused hazardous pharmaceuticals are instructed not to sewer them, but manage via an 

approved method. See the SWMCB “Regulatory Consensus on Health Care Issues”. 

Regarding DEA Controlled Substances, the main factor driving current disposal practices is 

that DEA requires that these substances be handled in a “chain of custody” manner and 

then “rendered non-recoverable”. Therefore, the simplest, most inexpensive method of 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 6 

disposal is sewering on-site. If POTWs do not prohibit such disposal, or if no new 

regulations are implemented, this method will likely continue. 

Some pharmaceuticals that have more than one active ingredient may be deemed nonhazardous, and therefore might be sewered without full consideration as to each of the active 

ingredients. This multi-active ingredient exemption may be viewed as a loophole in the 

regulations, resulting in more pharmaceuticals being sewered. Some waste handlers have 

even suggested adding active ingredients to avoid hazardous waste regulations. Wastes 

should be evaluated on the effect of all active ingredients, not simply the number of 

ingredients. 

A barrier to reducing the amount of unused pharmaceuticals being sewered is a lack of 

knowledge on the long-term overall effects of such disposal. Without this knowledge, the 

prevailing thought is that, “if it is alright to use or ingest a drug, that it must be alright to 

sewer that same drug.” 

POTWs may be able to apply the “precautionary principal” which says that “we best err on 

the side of caution.” But given that a hospital may ask to sewer hundreds of different 

pharmaceuticals, how is a POTW to know what to accept and what to reject? Maybe some 

drugs will break down, but maybe some will not. Could there be synergistic effects? 

Without good scientific data, POTWs may be under-regulating or they may be overregulating. Questions also exist as to the effect and fate of all of the antimicrobials present in 

liquid and solid soaps (triclosan and triclocarban). 

5. EPA solicits quantitative information on tracking sheets for the past year on the disposal of unused 

pharmaceuticals via the toilet, drain, or sewer. 

MCES does not have specific quantitative data. 

6. EPA solicits data on how control authorities are currently controlling disposal of unused 

pharmaceuticals via wastewater. 

MCES utilizes existing federal, state and local regulations, as well as outcomes from its 

partnership with SWMCB and MPCA, to minimize the disposal of unused pharmaceuticals 

to the sanitary sewer in the Minneapolis-St Paul metropolitan area. MCES strongly 

encourages that all unused pharmaceuticals, including residential, be made unrecoverable 

prior to disposal as solid waste. 

7. EPA solicits information on any technologies or BMPs that are available to control or eliminate 

the disposal of unused pharmaceuticals to POTWs. 

In Minnesota, the partnership between MCES, SWMCB and MPCA has developed guidance 

and recommendations for the disposal of unused chemotherapy, pharmaceutical, and 

hazardous wastes that control or eliminate such substances from entering the sanitary sewer. 

Specifically, the new practices are inventory tracking, reverse distribution, use of drug 

dispensing machines, dose control, and accepting fewer samples by clinics and hospitals. 

8. EPA solicits any studies or information on the potential for unused pharmaceuticals disposed in 

non-hazardous landfills to contaminate underground resources of drinking water. 

MCES has no comment on this issue. 

Centralized Waste Treatment

EPA requests information on the industries for which it is continuing or initiating preliminary category 

reviews of Centralized Waste Treatment. EPA will need to collect more information for the 2008 annual 

review. 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 7 

MCES currently has four permitted facilities that fall under Centralized Waste Treatment 

Pretreatment Standards. Three are subject to Subpart B - Oils Treatment and Recovery, and one is 

subject to Subpart A - Metals Treatment and Recovery. The following information pertains to the 

four facilities. 

Specifically, EPA hopes to gather the following information: 

1. What toxic pollutants are discharged from these industries in non-trivial amounts on an industry and 

per-facility basis? 

Please see attached Tables 1, 2, 3, and 4 to view data that MCES has collected on companies 

subject to CWT regulations. The tables represent all data obtained during monitoring projects 

conducted by both MCES and the Permittees since 2004. Please note that the data source of 

“MCES” denotes monitoring conducted by MCES, while “SMR” corresponding to monitoring 

conducted by the Permittee is in relation to the submittal of required, routine self-monitoring 

reports. The companies are identified as Company A, Company B, Company C and Company 

D, with these designations applying to the subsequent questions. 

2. What raw material(s) or process(es) are the sources of these pollutants? 

For the Metals Treatment and Recovery Facility the processes are as follows: 

 Company A

• Regeneration of ion exchange resins. 

• Treatment and recovery of electroplating and metal finishing plating baths and rinses. 

• Treatment and recovery of electroless nickel baths. 

• Treatment and recovery of various industrial and hazardous wastes from a variety of 

sources. 

For the Oils Treatment and Recovery Facilities the processes are as follows: 

Company B

• Underground tank pumping, cleaning, and removal. 

• Flammable Waste Trap Maintenance. 

• Spill Cleanup. 

Company C

• Fuel tank and sump bottom dewatering. 

 Company D

• Fuel pump unit servicing and fuel tank cleaning and water removal. 

3. What technologies or management practices area available (technically and economically) to control or 

prevent the generation and/or release of these pollutants? 

For the Metals Treatment and Recovery Facility the processes are as follows: 

 Company A

• Chromium reduction 

• Metal hydroxide precipitation 

• Cyanide oxidation 

• pH neutralization 

• Electrolytic metal recovery 

• Microfiltration. 

For the Oils Treatment and Recovery Facilities the pretreatment systems are as follows: 

Company B
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 8 

• Gravity oil/water separator 

• Plate oil/water separator 

• pH adjust with air sparger 

• Bag filtration 

• Fiber element filtration 

• Carbon canister for emulsified oil 

• Carbon canister for VOCs 

• Ion exchange canister for lead 

• Ion exchange canister for mixed metals. 

Company C

• Oil/water separator followed by air stripper. 

 Company D

• Dual gravity oil/water separators in series. 

Comments on Effluent Guidelines Program Plan

1. EPA solicits comment on whether EPA used the correct evaluation factors, criteria, and data sources in 

conducting its annual review and developing this preliminary Plan. EPA also solicits comment on 

other data sources that EPA can use in its annual reviews and planning biennial planning process. 

MCES has no comment on this issue. 

2. EPA solicits comment on whether, and if so how, the Agency should provide EPA Regions and States 

with permit-based support instead of revising effluent guidelines (e.g., when the vast majority of the 

hazard is associated with one or a few facilities). EPA solicits comment on categories for which the 

Agency should provide permit-based support. 

MCES in general supports efforts by EPA to provide support and guidance related to the 

industrial categories identified, rather than promulgating additional effluent limitations 

guidelines. MCES believes, however, that some revisions as stated in Item 4 below should be 

undertaken by EPA. 

3. EPA solicits comment on the methodology for grouping industrial sectors currently not subject to 

effluent guidelines or pretreatment standards for review and prioritization, and the factors and 

measures EPA should consider for determining whether to identify such industries for a rulemaking. 

EPA solicits comment on other data sources and approaches EPA can use to identify industrial sectors 

currently not subject to effluent guidelines or pretreatment standards for review and prioritization. 

MCES has no comment on this issue. 

4. EPA solicits comment on implementation issues related to existing effluent guidelines and 

pretreatment standards. 

MCES suggests that EPA consider errors and omissions in a number of existing Effluent Limit 

Guidelines (ELGs), rather than revising all parts. 

MCES again requests that EPA consider eliminating the Part 413 Electroplating Category, and 

instead bring the affected Industrial Users (IUs) under the Part 433 Metal Finishing Category. 

In addition, when EPA finalized the Streamlining of the CFR 403 General Pretreatment 

Regulations they provided a definition and adjusted requirements for Non Significant 

Categorical Industrial Users (NSCIUs). MCES strongly feels EPA should amend CFR Part 403 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 9 

to allow the NSCIUs, as defined, to be subject to POTW Local Limits only, and should be exempt 

from the applicable Categorical Pretreatment Standards. At less than 100 gallons per day of 

process wastewater discharge per day, the effect of this change on water quality would be 

minimal, and the reduction in administrative burden would be considerable. 

MCES also requests that EPA review the rationale for following existing regulations: 

• Metal Molding and Casting (Part 464) –There is a lack of a set of Pretreatment 

Standards for the casting cleaning operations in the Zinc Subcategory, whereas there is 

a set of Pretreatment Standards for casting cleaning in the Aluminum Subcategory. It 

has been MCES’s experience that most IUs that fall under the Aluminum Subcategory 

also fall under the Zinc Subcategory, and clean both types of castings in the same 

machinery. 

• Centralized Waste Treatment (Part 437) – The unusually high (and potentially 

dangerous) Pretreatment Standard for Cyanide of 500 mg/l at the end of Cyanide 

Treatment in Subpart A-Metals Treatment and Recovery. 

• Centralized Waste Treatment (Part 437) – The choice of the organic parameters of 

concern in Subpart B-Oils Treatment and Recovery, due to the difficulty in finding 

independent laboratories able to analyze for the listed parameters. 

5. EPA solicits comment on its evaluation of categories of indirect dischargers without categorical 

pretreatment standards. Specifically, EPA solicits wastewater characterization data (e.g., wastewater 

volumes, concentrations or discharged pollutants), current examples of pollution prevention, treatment 

technologies, and local limits for all industries without pretreatment standards. EPA also solicits 

comment on whether there are industrial sectors discharging pollutants that cause interference issues 

that cannot be adequately controlled through the general pretreatment standards. 

Regarding the overall Effluent Limit Guideline program, MCES feels that the use of current 

ELGs (current Categorical Pretreatment Standards) and POTW Local Limits have effectively 

reduced point source pollution. Therefore, MCES believes that EPA resources should be 

redirected towards the identification and reduction of non-point pollutant sources. This will 

result in the greatest benefit to the nation’s water environment. 

If you have immediate questions, please contact Tina Nelson at 651.602.4728 or via e-mail at 

martina.nelson@metc.state.mn.us. 

Sincerely, 

Leo H. Hermes, P.E. 

Industrial Waste Manager 

Metropolitan Council Environmental Services 

Industrial Waste & Pollution Prevention Section 

390 N Robert St, St. Paul, MN 55101 

Attachments: Figure 1: Influent Mercury Reduction at Metropolitan Wastewater Treatment Plant 

 Table 1: Analytical Results at Company A (Subject to Part 437 Subpart D – Metals 

Treatment and Recovery) 

 Table 2: Analytical Results at Company B (Subject to Part 437 Subpart B – Oils 

Treatment and Recovery) 

 Table 3: Analytical Results at Company C (Subject to Part 437 Subpart B – Oils 

Treatment and Recovery) 

 Table 4: Analytical Results at Company D (Subject to Part 437 Subpart B – Oils 

Treatment and Recovery) 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 10 Figure 1: Influent Mercury Reduction at Metropolitan Wastewater Treatment Plant 

Influent Mercury Reduction

Metropolitan Wastewater Treatment Plant

0

4080

120160200240280

2003 2004 2005 2006 2007

Median Influent Mercury, Grams/Day

50.6% Reduction 

2003 – 2007 

(through 6/12/07) 
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 11 Table 1: Analytical Results at Company A (Subject to Part 437 Subpart D – Metals Treatment and Recovery) 

Sample 

Location 

Data 

Source 

Sample 

Date 

Antimony 

(mg/L) 

Arsenic 

(mg/L) 

Cadmium 

(mg/L) 

Chromium 

(mg/L) 

Cobalt 

(mg/L)

Copper 

(mg/L)

Cyanide, 

total 

(mg/L) 

Lead 

(mg/L) 

Mercury 

(ug/L) 

Nickel 

(mg/L) 

Silv

(mg/

1/5/2005 0.007 0.041 0.001 0.014 0.004 0.038 0.33 0.003 <0.060 0.161 0.001/6/2005 0.005 0.017 0.003 0.029 0.004 0.084 0.18 0.003 0.027 0.241 0.001/7/2005 0.006 0.011 0.01 0.052 0.002 0.084 0.23 0.009 <0.024 0.157 0.002/8/2006 <0.010 0.014 <0.0008 0.031 0.019 0.092 3 0.012 0.248 0.151 0.002/9/2006 <0.010 0.014 <0.0008 0.026 0.007 0.046 0.69 0.002 <0.120 0.18 0.00

2/10/2006 <0.020 0.038 <0.0016 <0.008 0.014 0.085 0.28 <0.003 <0.6 0.498 <0.001/17/2007 0.021 0.049 <0.0004 0.02 0.006 0.148 0.42 0.003 <0.024 0.272 0.001/18/2007 0.011 0.021 <0.0004 0.018 0.031 0.076 5.6 <0.0007 <0.120 0.217 0.00

MCES 

1/19/2007 0.013 0.015 <0.0004 0.04 0.015 0.0174 ~5.6 0.002 <0.120 0.355 0.00

1/14/04 0.008 0.013 0.005 0.101 0.004 0.159 0.3 0.009 0.25 0.375 0.002/10/04 0.002 0.004 0.003 0.11 0.003 0.184 0.19 0.009 0.2 0.241 0.03/10/04 0.031 0.009 0.004 0.027 0.002 0.111 0.05 0.003 0.08 0.099 0.004/24/04 0.01 0.011 <0.001 0.221 0.002 0.459 0.27 0.004 <0.01 0.28 0.005/11/04 0.044 0.004 <0.001 0.127 0.01 0.156 <0.01 0.002 0.2 0.402 0.00

6/16/2004 0.007 0.011 0.002 0.035 0.003 0.14 0.3 0.012 0.08 0.381 0.007/27/2004 0.007 0.012 0.004 0.071 0.006 0.205 2.11 0.013 0.01 0.381 0.008/11/2004 0.069 0.003 0.002 0.041 0.003 0.093 0.56 0.008 0.01 0.593 0.009/16/2004 0.039 0.009 0.001 0.48 0.007 0.269 0.02 0.008 0.28 0.919 0.00

10/21/04 0.003 <0.001 0.006 0.093 0.001 0.177 0.21 0.008 <0.03 0.139 0.00

11/3/04 0.203 0.005 0.002 0.428 0.003 0.18 1.16 0.021 <0.01 0.44 <0.0

11/10/04 0.014 0.016 0.003 0.041 0.005 0.272 0.4 0.004 <0.01 0.664 0.0011/16/04 0.014 0.012 <0.001 0.054 0.002 0.213 0.24 0.007 0.11 0.252 0.0012/14/04 0.05 0.042 0.003 0.14 0.003 0.232 0.21 0.013 0.27 0.139 0.02

1/27/05 0.004 <0.001 0.002 0.054 0.002 0.31 0.27 0.012 0.23 0.158 0.00

2/1/05 0.004 0.004 0.005 0.083 0.003 0.201 0.37 0.008 0.35 0.229 0.002/2/05 0.013 0.001 0.005 0.51 0.002 0.275 0.56 0.005 0.19 0.501 0.02/3/05 0.027 <0.001 0.012 0.173 0.004 0.374 0.6 0.01 0.29 0.693 0.002/4/05 0.013 <0.001 0.016 0.0604 0.008 0.265 0.39 0.006 0.28 1.109 0.002/7/05 0.069 <0.001 0.015 1.155 0.004 0.304 0.58 0.006 0.23 0.455 0.002/8/05 0.018 0.019 0.006 0.312 0.003 0.269 1.33 0.004 0.19 0.481 0.002/9/05 0.007 0.009 0.002 0.052 0.003 0.133 0.98 0.004 0.13 0.102 0.0

2/10/05 0.004 0.01 0.001 0.056 0.004 0.175 0.32 0.007 0.09 0.29 0.00

10/25/2005 0.011 0.008 0.006 0.224 0.002 0.128 0.71 0.002 0.23 0.161 0.00

11/9/2005 0.008 0.004 0.002 0.029 0.002 0.096 0.07 0.002 0.13 0.257 0.00

12/16/2005 0.01 0.002 0.005 0.269 0.032 0.064 0.66 0.002 0.13 0.265 0.00

Process 

SMR* 

1/18/2006 0.013 <0.001 0.002 0.6 0.002 0.142 <1 0.003 0.32 0.259 0.02
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 12 Table 1: Analytical Results at Company A (Subject to Part 437 Subpart D – Metals Treatment and Recovery) – continued 

Sample 

Location 

Data 

Source 

Sample 

Date 

Antimony 

(mg/L) 

Arsenic 

(mg/L) 

Cadmium 

(mg/L) 

Chromium 

(mg/L) 

Cobalt 

(mg/L)

Copper 

(mg/L)

Cyanide, 

total 

(mg/L) 

Lead 

(mg/L) 

Mercury 

(ug/L) 

Nickel 

(mg/L) 

Silv

(mg/

2/15/2006 0.01 0.006 <0.001 0.25 0.003 0.094 <1 0.002 0.7 0.478 0.0

3/8/2006 0.03 0.006 0.008 0.123 0.004 0.138 <1 0.005 0.45 0.2 0.0

4/18/2006 0.009 0.004 0.005 0.094 0.024 0.291 <2 0.007 0.36 0.388 0.005/11/2006 0.006 0.02 0.005 0.066 0.003 0.119 <1 0.001 0.16 0.365 0.006/28/2006 0.022 0.098 0.004 0.08 0.02 0.263 <1 0.015 0.14 1.357 0.027/18/2006 0.022 0.019 0.008 0.098 0.057 0.576 <1 0.005 0.34 1.02 0.008/24/2006 0.008 0.007 0.004 0.055 0.003 0.079 <1 0.003 0.36 0.419 0.0

9/7/2006 0.021 0.01 0.012 0.37 0.016 0.33 <1 0.008 0.47 0.955 0.0210/17/06 0.007 0.005 0.003 0.051 0.01 0.306 0.22 0.005 0.55 0.719 0.0010/24/06 0.011 <0.001 <0.001 0.051 0.006 0.048 0.59 0.072 0.45 0.294 0.00

11/7/06 0.007 0.005 0.007 0.091 0.005 0.118 0.3 0.005 0.36 0.485 0.00

11/14/2006 0.004 0.002 0.003 0.096 0.007 0.09 <0.01 0.002 0.41 0.419 0.0011/21/2006 0.009 0.004 0.003 0.064 0.005 0.143 0.05 0.01 0.39 5.86 0.0011/28/2006 0.065 0.003 0.002 0.047 0.014 0.046 <0.01 0.002 0.34 0.299 0.00

12/7/2006 0.008 0.013 <0.01 0.051 0.013 0.125 <0.01 0.007 0.3 0.187 0.00

12/13/2006 0.055 0.033 <0.002 0.138 0.014 0.425 0.08 0.005 0.32 0.939 0.00

1/18/2007 0.006 0.02 <0.001 0.011 0.017 0.208 0.17 <0.001 0.52 0.307 <0.02/21/2007 0.006 0.01 <0.001 0.12 0.003 0.106 0.06 <0.001 0.03 0.909 <0.0

3/6/2007 0.034 0.012 <0.001 0.122 0.008 0.153 0.01 0.002 0.02 0.364 <0.0

4/18/2007 0.01 0.009 <0.001 0.028 0.003 0.194 0.09 <0.001 0.17 0.244 0.035/22/2007 0.12 0.013 0.002 0.085 0.006 0.143 0.2 0.002 0.03 0.158 <0.0

6/7/2007 0.087 0.005 0.002 0.08 0.004 0.197 <0.01 0.002 0.05 0.171 0.09

7/25/2007 0.009 <0.001 0.009 0.103 0.042 0.198 0.42 0.015 0.14 0.883 0.008/16/2007 0.014 0.032 <0.001 0.033 0.005 0.156 0.06 0.005 <0.010 0.28 0.00

Process SMR 

9/24/2007 0.07 <0.001 0.007 0.425 0.009 0.191 0.09 0.007 0.07 0.362 0.00

* SMR denotes self-monitoring conducted by Company A.
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 13 Table 2: Analytical Results for Company B (Subject to Part 437 Subpart D – Oils Treatment and Recovery 

Sample 

Location 

Data 

Source 

Sample 

Date 

Chromium 

(mg/L) 

Cobalt 

(mg/L) 

Copper 

(mg/L) 

Lead 

(mg/L) 

Tin 

(mg/L)

Zinc 

(mg/L) 

Bis-2(ethylhexyl)phthalate 

(ug/L) 

Carbazole 

(ug/L) 

Fluoran

(ug/L

8/4/04 0.1 0.01 0.227 0.1 0.003 0.934 7.48 <4.308/5/04 0.014 0.002 0.197 0.011 0.001 0.133 15.02 <4.18/6/04 0.013 0.002 0.224 0.017 0.002 0.206 62.6 <4..2

4/27/05 0.149 0.01 1.27 0.511 0.067 3.85 394.9 27.5 4/28/05 0.176 0.04 1.04 0.967 0.05 5.9 769.2 <404/29/05 0.025 0.004 0.272 0.045 <0.002 0.409 279.4 <40

10/11/06 1.6 0.001 0.048 0.025 0.004 0.302 205.92 <2 <4110/12/06 1.36 0.002 0.077 0.033 0.003 0.291 113.3 <2 <41

MCES 

10/13/06 1.12 0.003 0.08 0.008 0.0001 0.516 104 <2 <41

03/09/04 0.023 <0.032 0.231 1.27 <0.167 1.19 54 <10 <10 03/10/04 0.061 <0.032 0.34 1.99 <0.167 1.49 64 <10 <10 

11/3/04 <0.013 <0.032 0.065 <0.140 <1.00 0.046 <11 <11 <11 11/4/04 <0.013 <0.032 0.135 <0.140 <1.00 0.06 <11 <11 <11 

3/8/05 0.074 <0.032 0.248 <0.14 <0.167 0.879 29 <50 <50 3/9/05 0.032 <0.032 0.371 <0.14 <0.167 0.237 73 <20 <20 6/7/05 0.17 <0.1 0.22 6/8/05 0.13 <0.1 0.16 6/9/05 0.22 0.2 0.7 

6/10/05 0.079 0.11 0.26 6/13/05 0.04 0.03 0.11 6/16/05 0.37 0.04 0.85 6/17/05 0.29 0.04 0.31 6/20/05 0.26 0.04 0.35 6/22/05 0.18 6/23/05 0.12 6/24/05 0.37 6/28/05 0.15 6/29/05 0.36 12/7/05 <0.01 <0.005 0.029 0.18 <0.020 0.2 29 <1 <5.0 12/8/05 <0.01 <0.005 0.024 0.14 <0.020 0.2 17 <1 <5.0 12/9/05 <0.01 <0.005 <0.02 0.073 <0.020 0.1 27 <1 <5.0 4/10/06 0.02 0.02 0.074 0.13 <0.100 0.17 4.9 <40 <9.0 4/11/06 <0.025 <0.050 0.15 0.16 <0.100 0.14 6.3 <40 <9.0 10/3/06 0.026 <0.005 0.079 0.062 <0.020 0.44 <200 <1 <2010/4/06 0.047 <0.005 0.09 0.072 <0.020 0.44 <190 <1 <1910/5/06 0.46 <0.005 0.071 0.081 <0.020 0.45 <190 <1 <195/23/07 <0.01 <0.005 0.078 0.04 <0.020 0.45 <19 <19 <19 

Process 

SMR* 

5/24/07 <0.01 <0.005 0.042 0.035 <0.020 0.32 <19 <19 <19 

* SMR denotes self-monitoring conducted by Company B.
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 14 Table 3: Analytical Results at Company C (Subject to Part 437 Subpart B – Oils Treatment and Recovery) 

Sample 

Location 

Data 

Source 

Sample 

Date 

Cobalt 

(mg/L) 

Chromium 

(mg/L) 

Copper 

(mg/L) 

Lead 

(mg/L) 

Tin 

(mg/L) 

Zinc 

(mg/L) 

Bis-2(ethylhexyl)phthalate 

(ug/L) 

Carbazole 

(ug/L) 

Fl

8/31/04 <4.16 

9/1/04 0.009 0.088 0.017 <0.002 4.4 

7/28/05 0.019 0.051 0.009 <0.002 0.86 <4.16 

12/13/06 0.001 0.075 0.083 0.018 0.003 2.46 <8.0 

MCES 

10/11/07 <0.0005 0.005 0.027 <0.001 <0.005 0.451 

10/27/04 0.151 0.0217 <0.075 1.16 

6/12/05 0.0904 0.0143 <0.075 2.89 

10/17/05 <0.01 0.084 0.0072 <0.075 0.771 <0.01 <0.01 

6/14/06 0.0709 0.0082 0.585 <0.01 <0.01 

10/25/06 0.0512 0.0154 <0.075 2.99 <0.102 <0.102 

Process 

SMR* 

6/18/07 <0.010 <0.01 0.179 0.0763 <0.075 2.01 <0.011 <0.011 

* SMR denotes self-monitoring conducted by Company C.
Comments on EPA’s 2008 Effluent Guidelines Program Plan 

 Page 15 Table 4: Analytical Results at Company D (Subject to Part 437 Subpart B – Oils Treatment and Recovery)

Sample 

Location 

Data 

Source 

Sample 

Date 

Cobalt 

(mg/L) 

Chromium 

(mg/L) 

Copper 

(mg/L) 

Lead 

(mg/L) 

Tin 

(mg/L)

Zinc 

(mg/L) 

Bis-2(ethylhexyl)phthalate 

(ug/L) 

Carbazole 

(ug/L) 

Fluora

(u

11/15/06 0.003 0.008 0.037 0.078 0.004 0.244 24.44 <411/16/06 0.004 0.009 0.021 0.072 0.001 0.302 44.06 <

MCES 

11/17/06 0.005 0.012 0.042 0.158 0.002 0.453 34.78 <4

11/17/05 <0.005 <0.006 0.008 <0.015 <0.05 0.13 0.011 <0.01 <011/18/05 <0.005 <0.006 <0.005 <0.015 <0.05 0.056 0.011 <0.01 <011/19/05 <0.005 <0.006 <0.005 <0.015 <0.05 0.062 0.014 <0.01 <0

7/14/06 0.006 0.049 0.051 <0.026 0.928 0.013 <0.01 <0

11/30/06 <0.004 0.023 0.04 <0.023 0.241 0.015 <0.01 <0

Process 

SMR* 

5/4/07 0.0058 0.015 0.033 0.024 <0.020 0.3 0.083 <0.011 <0

* SMR denotes self-monitoring conducted by Company D.
Community-Wide Dental Mercury Study 

PROJECT SUMMARY December 13, 2001 

Claude T. Anderson, MCES-EPE 

Introduction 

Since the control of mercury sources is an important environmental issue for state and federal 

regulators, the regulated community, including Metropolitan Council Environmental Services 

(MCES) is continually facing increasing pressure to reduce mercury emissions to the 

environment. As a result, this study was conducted cooperatively between MCES and the 

Minnesota Dental Association (MDA). A complete project report is available from Claude 

Anderson at (651) 602-8291. 

Objectives 

The Community-Wide Study was conducted to quantify the amount of mercury discharged from 

dental clinics to MCES' wastewater treatment plants (WWTPs). This was accomplished by an 

intensive sludge sampling and analysis program at the Hastings and Cottage Grove WWTPs 

before and during the time period amalgam removal equipment was in place treating wastewater 

at the dental clinics upstream of the WWTPs.

Methods 

The Community-Wide Study was conducted in three phases; each phase included at least three 

months of data collection. The daily sludge sampling at the Hastings and Cottage Grove 

WWTPs was conducted between June of 1999 and August of 2001. The time periods and major 

activities for each phase were: 

Phase I: Establish baseline at both treatment plants. June 18, 1999 to October 14, 2000

• Baseline was established for sludge mercury concentrations and mass loadings at the 

Hastings and Cottage Grove WWTPs. 

• No amalgam removal equipment in place at any of the dental clinics. 

Phase II: Hastings test phase. October 15, 2000 to February 17, 2001.

• Amalgam removal equipment was in placed in all dental clinics in the Hastings WWTP 

service area (6 clinics). 

• No amalgam removal equipment in the Cottage Grove dental clinics. 

• Additional Cottage Grove WWTP sludge baseline monitoring. 

• At the end of this phase, amalgam removal equipment was removed from the Hastings dental 

clinics. 

Phase III: Cottage Grove test phase. April 8, 2001 to July 21, 2001

• Amalgam removal equipment was in place at all but one of the dental clinics in the Cottage 

Grove WWTP service area (7 of 8 clinics). 

• Additional Hastings WWTP sludge baseline monitoring. 
During the transition periods between Phase II and Phase III, and after Phase III, sludge 

monitoring continued at the WWTPs even though equipment was being removed or installed at 

the dental clinics. 

Results 

During the study, a 44 % reduction in mercury loading to the Hastings WWTP sludge was 

measured while the amalgam removal equipment was in place in the Hastings dental clinics. The 

mercury sludge reduction at Cottage Grove was found to be 29% while the amalgam removal 

equipment was in place in Cottage Grove. These removals are represented graphically below. 

Two possible reasons for a smaller reduction at Cottage Grove include 

(1) one clinic (with one dentist) in Cottage Grove did not participate, and (2) the grit removal 

system at the Cottage Grove WWTP removes above normal quantities of grit, which may have 

resulted in less mercury reaching the sludge. 

Based on the measured mercury sludge reductions at the wastewater treatment plants, and 

estimating the WWTP mercury grit removal rates, efficiency of the amalgam removal equipment 

in the dental offices and the number of days each clinic operated, a mercury loading from dental 

clinics was estimated. The mercury loading from dental clinics was estimated at 

120 mg/dentist/operating day for each of the Hastings and Cottage Grove WWTP service areas. 

(Note that even though the calculation for each set of clinics within each service area was done 

independently, the result of 120 mg/dentist /operating day was the same.) 

Major Conclusions and Recommendations 

• This study found that significant decreases in mercury, as measured in wastewater treatment 

plant sludge, could be realized by installing amalgam removal equipment in dental clinics. 

• The installation and operation of amalgam removal equipment in the 13 clinics did not result 

in any significant operating problems for the dental clinics during the three month installation 

period, either in terms of the amalgam removal equipment or the clinic vacuum systems. 

• During the time period that amalgam removal equipment was in place upstream of the 

WWTP, the average reduction in the mass of mercury present in the sludge was 29 % at the 

Cottage Grove WWTP and 44 % at the Hastings WWTP. The reductions were estimated 

based on sludge volumes, moisture content, and mercury concentrations. 

• Using the study data, a statistical comparison looked at the ratios of Hastings to Cottage 

Grove WWTP sludge mercury concentration and mass loadings with and without amalgam 

removal equipment in place. This comparison found that the differences observed for these 

ratios were statistically significant for both WWTPs when the amalgam removal equipment 

was in place. 
• Based on the measured mercury sludge reductions and estimated grit removal rates at the 

wastewater treatment plants, the mercury loading from dental clinics was estimated to be 

120 mg/dentist/operating day for the Cottage Grove and Hastings WWTPs. 

• It was possible to get very high participation from the dentists in this study. This was 

possible because of the extensive pre-project involvement and support from the MDA and 

the dentists, in addition to the study’s attention to minimizing adverse impacts on the 

dentists’ practice. However, since involvement in this study was voluntary, it was not 

possible to get universal participation from all the dentists in the WWTP service areas. 

• The Community-Wide Study demonstrated that significant reductions in WWTP sludge 

mercury loadings could be achieved if dental clinics treat their wastewater to reduce the 

amount of amalgam and mercury wastes prior to discharge to the sanitary sewer system. 

Therefore, it is recommended that a program to reduce dental clinic mercury be 

implemented. Development and implementation of a program should involve MCES, MDA, 

and possibly other state and local agencies. 

Overall Wastewater Treatment Plant Sludge Mercury Mass Loading

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Hastings Cottage Grove

Mercury Mass Loading (grams/day)

Baseline Test Period

44% Reduction

29% Reduction