### MEMORANDUM

TO: Public Docket for the Dental Amalgam Effluent Guidelines

EPA Docket Number EPA

- HQ

- OW

- 2014

- 0693

FROM: Jill Lucy, ERG

Kimberly Bartell, ERG

DATE: September 22, 2014

SUBJECT: Impacts of Amalgam Separators and Recommended Practices on Mercury

Discharges

EPA is proposing technology

- based pretreatment standards under the Clean Water Act (CWA) for discharges of pollutants into publicly owned treatment works ( POTWs ) from existing

and new dental offices that discharge dental amalgam. The proposed rule would require dental

offices to control the discharge of mercury and other metals in dental amalgam into POTWs

based on t he best available technology or best available demonstrated control technology (amalg am separators) and the use of best management practices (BMPs). This memorandum provides supplemental information on the impacts of amalgam separators and recommended practices on mercury discharges in addition to the information presented in the Technical and Economic Development Document for the Proposed Effluent Limitations Guidelines and Standards for the Dental Category (EPA 821

- R

- 14

- 006)

.

Table 1 summarizes the effectiveness of amalgam separators and BMP programs on mercury discharged to POTWs, based on several case studies. Although most of these studies show mercury reductions in PO TW influent following the introduction of BMPs and/or amalgam separators in dental offices, some studies show an increase in mercury concentrations. Thus, it is apparent that other factors can influence mercury levels and the measure of a program’s

effecti veness in reducing mercury discharges. The following are examples of additional criteria that affected the mercury reduction by BMP programs, as described in the National Association of Clean Water Agencies ( NACWA ) case studies (NACWA, 2007a):

Many progr ams are voluntary, and low participation rates affect the program effectiveness in reducing mercury discharges. Dental offices are not the only source of mercury to POTWs. The next largest sources are domestic sources (human waste, household products, and laundry graywater) and hospitals ( Larry Walker Associates , 2002)

. The time required to flush accumulated amalgam particles from the collection system is

not known

. The t ime needed for mercury reductions at POTWs to be measurable after implementation of BMPs or installation of amalgam separators is not known.

### Memorandum

September 22, 2014 Page 2

Table 1 . Impact of BMPs and Amalgam Separators on Mercury Discharges to POTWs

BMP Program Description Percent of Dental Offices Using Amalgam Separators Percent age of Mercury Loading Reduction Source Before Program After Program

California Dental

Association Voluntary installation of amalgam

separators. No information No information 78% of amalgam to POTW Condrin, 2004

Corvallis, OR Voluntary installation of amalgam

separators. No information No information 79% of POTW influent Lamperti, 2007

Springfield, MO BMP outreach program. No information No information 34% of POTW influent A a MU Extension,

2007

Springfield, MO BMP outreach program. No information No information 96% of POTW influent B b MU Extension,

2007

Madison, WI Voluntary installation of amalgam

separators. No information 22% (as of 2005) No trend in POTW influent Walsh, 2007

EBMUD Required installation of amalgam

separators. No information 96% No trend in POTW influent Walsh, 2007

Wichita, KS Voluntary installation of amalgam

separators. 60% 99% No trend in POTW influent Walsh, 2007

Milwaukee, WI Required installation of amalgam

separators. No information No information Decrease in POTW influent Walsh, 2007

Duluth, MN St. Louis River Beneficiary Group

provided a grant to purchase amalgam separators for all offices. No information 100% Decrease in POTW sludge Walsh, 2007

Palo Alto, CA Required installation of amalgam

separators. No information 96% No trend in POTW influent Walsh, 2007

Narragansett Bay,

RI Voluntary installation of amalgam

separators. No information No information No trend in POTW influent Walsh, 2007

King County, WA Voluntary installation of amalgam

separators and mandatory implementation of BMPs. No information 95% 50% of POTW biosolids (concentration

- basis) King County,

2008

### Memorandum

September 22, 2014 Page 3

Table 1 . Impact of BMPs and Amalgam Separators on Mercury Discharges to POTWs

BMP Program Description Percent of Dental Offices Using Amalgam Separators Percent age of Mercury Loading Reduction Source Before Program After Program

POTW “A” Required offices to either install

amalgam separators or demonstrate compliance with a mercury limit of 0.005 ppm. 0% 100% No trend in POTW influent NACWA, 2007b

POTW “B” Mandatory BMP program began in

2002. Installation of amalgam separators was not required. 5% 9% (out of 219 offices) 56.4% of POTW influent NACWA, 2007b

POTW “C” BMP program began in 2002. Some

BMPs were mandatory. Installation of amalgam separators was voluntary. 6% 6% (out of 18 offices) 43% of POTW influent NACWA, 2007b

POTWs “D” and

“E” Program required implementation of

BMPs by 2004 and installation of amalgam separators by 2008. 0.6% 38% (total number of offices unknown) 60.5% of influent to POTW

“D”;

22.0% of influent to POTW “E” NACWA, 2007b

POTW “F” Voluntary amalgam separator program

began in 1997. 0% 20% (total number of offices unknown) 38.0% of POTW influent NACWA, 2007b

POTW “G” Voluntary installation of amalgam

separators. 44% 100% (100 offices total) 90% increase to POTW influent NACWA, 2007b

POTW “H” Voluntary amalgam separator program

began in 2002. 60% 98% (out of ~200 offices) No trend in POTW influent NACWA, 2007b

POTW “I” Mandatory amalgam separator program

began in 2001. 94% 98% (total number of offices unknown) 27.5% of POTW influent NACWA, 2007b

POTWs “J” and

“K” Mandatory program required dentists to

meet a limit of 0.2 mg/L by July 2003. 94% 98% (total number of offices unknown) 8.9% increase to POTW “J”;

44.1% reduction to POTW “K” NACWA, 2007b

POTW “L” POTW recommends installation of

amalgam separators to dentists. No information 11% (total number of offices unknown) 50.6% of POTW influent NACWA, 2007b

a

— Northwest Treatment Plant.

b

— Southwest Treatment Plant.

### Memorandum

September 22, 2014 Page 4

References

Condrin, A.K. 2004. The Use of CDA Best Management Practices and Amalgam Separators to Improve the Management of Dental Wastewater. Journal of the California Dental

Association 32(7):583

- 592. DCN DA00024.

King County. 2008. Mercury Levels in King County Biosolids. http://dnr.metrokc.go v/wlr/indwaste/amalgdiff.pdf. DCN DA00212

.

Lamperti, L. 2007. City of Corvallis’ Comments on EPA’s Preliminary 2008 Effluent Guidelines Program Plan. December 21. DCN DA00235.

Larry Walker Associates. 2002. Mercury Source Control and Pollution Preventio n Program Evaluation, Final Report. Prepared for AMSA (Association for Metropolitan Sewerage Agencies). March (Updated July). DCN DA00006.

MU Extension (University of Missouri Extension Environmental Assistance Center). 2007. Maximizing Voluntary Reductio ns in Dental Amalgam Mercury: Reduction in Mercury Discharges. EPA#E0000127. P1

- 98765101

- 0. November. DCN DA00223.

NACWA (National Association of Clean Water Agencies). 2007a. N ACWA Comments on ELG Preliminary Plan. December. DCN DA00236

.

NACWA. 2007b. An Examination of Mercury Levels at Clean Water Agencies 2003

- 2006

. December 18. DCN DA00108.

Walsh, William. 2007. The American Dental Association’s (ADA) Comments on EPA’s Study of a Pretreatment Requirement for Dental Amalgam. Pepper Hamilton, LLP. December

21. DCN DA00 2 38.