► engineers • scientists • architects • constructors
►Managing Mercury Mania
Jerald O. Thaler, P.E.Fishbeck, Thompson, Carr & Huber, Inc.
Michigan Water Environment AssociationAnnual IPP SeminarSeptember 25, 2008
“Mercury 101”
►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) Bioaccumulation
►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
Mercury Sources to Lake Michigan(adapted from Frequently Asked Questions About
Atmospheric Deposition, USEPA, September 2001)
Tributaries (20%)
Atmospheric Deposition
(80%)
►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
CriterionMicrograms per liter
(μg/L)
Acute Toxicity 2.8
Chronic Toxicity 0.77
Human Health 0.0018
Wildlife 0.0013
►Effluent Monitoring
• 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,
ftp://ftp.dep.state.fl.us/pub/labs/assessment/ppt/utmsamp.ppt)
• Method 1631– Grab sample– “Clean Hands/Dirty Hands”– Quantification acceptable
for compliance testing– $90 each for 3 samples
(duplicates plus field blank)
►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
• 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
Minimization Tips and Techniques
►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
N Factor
1 6.2
2 3.8
3 3.0
4 2.6
5 2.3
10 1.7
50 1.0
►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
• 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 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
• Evaluate monitoring data via mass balance to fully assess overall system
• Example:
Identified Sources 0.05 MGD
700 ng/L Hg0.107 lb/yr Hg
Domestic/Background 1.26 MGD
50 ng/L Hg0.192 lb/yr Hg
Unidentified Sources Average Removal
1.474 lb/yr HgBy difference… 98%
2.2 mg/kg Hg1.742 lb/yr Hg
WWTP Influent
1.773 lb/yr Hg
Biosolids (6.5%)
396 T/yr
1.31 MGD 445 ng/L Hg
0.031 lb/yr Hg 7.9 ng/L Hg
1.30 MGD WWTP Effluent
Current Average
►Meaningful Monitoring
• Apply mass balance results to prioritize minimization efforts
Identified Sources 0.050 MGD
200 ng/L Hg 0.030 lb/yr Hg
Domestic/Background 1.25 MGD
50 ng/L Hg 0.190 lb/yr Hg
Unidentified Sources Average Removal
0.073 lb/yr HgBy difference… 98%
0.3 mg/kg Hg 0.255 lb/yr Hg
WWTP Influent
0.250 lb/yr Hg
Biosolids (6.5%)
396 T/yr
1.31 MGD 63 ng/L Hg
0.005 lb/yr Hg 1.3 ng/L Hg
1.3 MGDWWTP Effluent
Goal
-0.077 lb/yr
-1.401 lb/yr
►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 Studies
• Scattered sampling can be inconclusive due to high variability of mercury
• Most efficient is moving upstream via “primary/secondary” scheme
S-2
S-1
P-1 P-2
S-1' S-2'
Source
WWTP
►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
• Typical mercury generated per office0.57 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 office0.59 * (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 Dentist
• Potential impact on treatment plant Assuming 2.5 million gal/day flow
No.
Dentists
Dental Mercury
(lb/yr)
Influent
Impact (ng/L)
Domestic Background
(ng/L)
Net
Influent
(ng/L)
WWTP
Removal
Net
Effluent
(ng/L)
0 +0.0 +0 50 1.0
1 +0.1 +13 63 1.3
2 +0.2 +26 ~50 76 ~98% 1.5
4 +0.4 +53 103 2.1
8 +0.8 +105 155 3.1
►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, PresidentAmerican Dental Association
October 11, 2007
►Deal With the Dentist
• Potential impact on treatment plant Again assuming 2.5 million gal/day flow
No. Dentists
Amalgam Separator Removal
Dental Mercury (lb/yr)
Influent
Impact (ng/L)
Domestic Background
(ng/L)
Net Influent (ng/L)
WWTP Removal
Net Effluent
(ng/L)
0 +0.000 +0 50 1.0
1 +0.005 +0.7 50.7 1.01
2 95% +0.010 +1.3 ~50 51.3 ~98% 1.03
4 +0.020 +2.6 52.6 1.05
8 +0.040 +5.3 55.3 1.11
►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
►Deal With the Dentist
“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.”
►Perspective
• Justifiable concern over mercury in waterways– Air emissions need same, or greater, scrutiny as
wastewater 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:
Jerald O. Thaler, P.E.Fishbeck, Thompson, Carr & Huber, Inc.
39255 Country Club Drive, Suite B-25Farmington Hills, MI 48331
►Questions and Discussion
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