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Managing Mercury Mania. Jerald O. Thaler, P.E. Fishbeck, Thompson, Carr & Huber, Inc. Michigan Water Environment Association Annual IPP Seminar September 25, 2008. “Mercury 101”. The Wake-up Call.

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managing mercury mania

Managing Mercury Mania

Jerald O. Thaler, P.E.

Fishbeck, Thompson, Carr & Huber, Inc.

Michigan Water Environment Association

Annual IPP Seminar

September 25, 2008

the wake up call
The Wake-up Call
  • In the 1950s and 1960s, Japan experienced an epidemic of psychotic disease and deformed/brain-damaged births
  • Traced to mercury poisoning from eating fish in Minamata Bay
  • Tons of mercury chloride was discharged by Chisso Corporation between 1931 and 1968
  • Aquatic organisms convert inorganic mercury to highly toxic methylmercury
  • Methylmercury bioaccumulates up the food chain (~106x for trophic level 5)


regulatory focus
Regulatory Focus
  • Michigan has strict, long-standing controlson mercury in wastewater discharges
  • Only recently has focus increased on air emissions, where the impact is greater

Tributaries (20%)

Atmospheric Deposition (80%)

Mercury Sources to Lake Michigan

(adapted from Frequently Asked Questions About Atmospheric Deposition, USEPA, September 2001)

discharge standards
Discharge Standards
  • Rule 57 provides protection against toxicity
  • Wildlife protection controls at 0.0013 μg/L, or 1.3 nanograms per liter (ng/L)
  • No mixing zone credit for BioaccumulativeChemicals of Concern
effluent monitoring
Effluent Monitoring
  • Method 1631
    • Grab sample
    • “Clean Hands/Dirty Hands”
    • Quantification acceptable for compliance testing
    • $90 each for 3 samples (duplicates plus field blank)
  • Method 245.1
    • Composite sample
    • Normal handling
    • Quantification inconclusive for compliance testing
    • $40-$50 each

(from Sample Collection for Ultra-Trace Concentrations of Mercury, Florida Department of Environmental Protection,

npdes permit
NPDES Permit
  • Limits generally set at Level Currently Achievable (LCA) under multiple discharger variance
    • Initially 30 ng/L
    • Recently lowered to 10 ng/L
    • Soon to change to user-specific LCA
  • Applied as 12-month moving average
  • Effluent monitoring using Method 1631
  • Mercury Minimization Program required
mercury minimization program
Mercury Minimization Program
  • Goal to achieve effluent of 1.3 ng/L
  • Formal plan approvable by MDEQ
  • Annual status report
  • Required elements
    • Monitoring of influent, effluent, and biosolids
    • Source identification
    • Source reduction
  • Recommended elements
    • Public education

Tips and Techniques

avoid the regulatory trap
Avoid the Regulatory Trap
  • Mercury in permit if potential effluent quality (PEQ) exceeds 1.3 ng/L
  • Per Rule 1211, PEQ is statistical tool to relate quality/quantity of monitoring data

where factor set by number of samples (N):

  • PEQ = CMAX * Factor
avoid the regulatory trap1
Avoid the Regulatory Trap
  • Permit application generally requires minimum of four effluent samples
  • Sometimes more samples may be better
    • If 4 samples with CMAX of 0.7 ng/L, PEQ>1.3 ng/L and permit will include mercury

PEQ = 0.7*2.6= 1.8 ng/L

    • If 10 samples with CMAX of 0.7 ng/L, PEQ<1.3 ng/L and permit may not include mercury

PEQ = 0.7*1.7= 1.2 ng/L

flexible sewer use ordinance
Flexible Sewer Use Ordinance
  • Traditional command-and-control approach: “No discharge of detectable mercury.”
  • May not be feasible for some commercial users
    • Technical limitations
    • Economic factors
  • Strict enforcement may be counterproductive to local economy
flexible sewer use ordinance1
Flexible Sewer Use Ordinance
  • Alternative case-by-case approach: “No discharge of detectable mercury, except as specifically approved.”
  • Conditions of approval
    • Periodic self-monitoring
    • Minimization program (procedures, training, source identification/reduction, treatment, etc.)
    • All reasonable and cost-effective actions
  • Promotes flexibility and cooperation
meaningful monitoring

Identified Sources

0.05 MGD

700 ng/L Hg

0.107 lb/yr Hg


WWTP Influent

WWTP Effluent

1.26 MGD

1.31 MGD

1.30 MGD

50 ng/L Hg

445 ng/L Hg

7.9 ng/L Hg

0.192 lb/yr Hg

1.773 lb/yr Hg

0.031 lb/yr Hg

Unidentified Sources

Average Removal

By difference…


1.474 lb/yr Hg


396 T/yr

2.2 mg/kg Hg

1.742 lb/yr Hg

Meaningful Monitoring
  • Evaluate monitoring data via mass balance to fully assess overall system
  • Example:

Current Average

meaningful monitoring1

Identified Sources

0.050 MGD

200 ng/L Hg

0.030 lb/yr Hg


WWTP Influent

WWTP Effluent

1.25 MGD

1.31 MGD

1.3 MGD

50 ng/L Hg

63 ng/L Hg

1.3 ng/L Hg

0.190lb/yr Hg

0.250 lb/yr Hg

0.005 lb/yr Hg

Unidentified Sources


By difference…


0.073 lb/yr Hg

Biosolids (6.5%)

396 T/yr

0.3 mg/kg Hg

0.255 lb/yr Hg

Meaningful Monitoring
  • Apply mass balance results to prioritize minimization efforts

-0.077 lb/yr

-1.401 lb/yr


productive source studies
Productive Source Studies
  • Common sources
    • Domestic sewage (25-50 ng/L)
    • Dental offices
  • Other observed sources
    • Hospitals and medical clinics
    • State prisons
    • Car washes
    • Rainwater (~10 ng/L) and snowmelt
  • Use sampling of collection system to identify significant sources and maintain neutrality
productive source studies1









Productive Source Studies
  • Scattered sampling can be inconclusive due to high variability of mercury
  • Most efficient is moving upstream via “primary/secondary” scheme
deal with the dentist
Deal With the Dentist
  • The most common controllable source of mercury
  • Mercury inherent to dentistry due to mercury-silver amalgams
  • Special challenge for smaller communities with multiple dentists
deal with the dentist1
Deal With the Dentist
  • Typical mercury generated per office

0.57 lb/yr Amalgam removal (97%)

0.02 lb/yr Amalgam placement (3%)

0.59 lb/yr Total

  • Removals for typical capture processes

~ 68% Chair-side traps

~ 40% Vacuum filters

81% Overall

  • Typical sewer discharge per office

0.59 * (1-.81) = 0.1 lb/year

(ENVIRON International Corp., Evaluation of Mercury in Dental Facility Wastewater, Ver. 3, American Dental Association, Nov. 2002)

deal with the dentist2
Deal With the Dentist
  • Potential impact on treatment plant

Assuming 2.5 million gal/day flow

deal with the dentist3
Deal With the Dentist
  • Amalgam Separator
    • >95% mercury removal for wet vacuum systems
    • Not overly complex or expensive
    • Can produce significant improvement at treatment plant
  • “…[Amalgam separator] systems work well, and we now feel comfortable including them in our best management practice recommendations."
  • Dr. Mark J. Feldman, President
  • American Dental Association
  • October 11, 2007
deal with the dentist4
Deal With the Dentist
  • Potential impact on treatment plant

Again assuming 2.5 million gal/day flow

deal with the dentist5
Deal With the Dentist
  • Proposed Legislation
    • SB-1310/HB-6307 mandate amalgam separators by December 31, 2013
    • Michigan Board of Dentistry to promulgate associated best management practices
    • However, prevents local authorities from pursuing further source reduction where warranted

“This… supersedes any local ordinance… that imposes… additional standards on dentists… including… a permit that limits the discharge of mercury… greater than that capable of being achieved by full compliance with this section.”

  • Justifiable concern over mercury in waterways
    • Air emissions need same, or greater, scrutiny aswastewater discharges
  • Tips and techniques from experience
    • Avoid the regulatory trap
    • Flexible sewer use ordinance
    • Meaningful monitoring
    • Productive source studies
    • Deal with the dentist
  • Resist legislation that, while well-intended, pre-empts local authority/control
for additional information
For additional information:
  • Questions and Discussion

Jerald O. Thaler, P.E.

Fishbeck, Thompson, Carr & Huber, Inc.

39255 Country Club Drive, Suite B-25

Farmington Hills, MI 48331