Transcript Mercury Minimization Dealing with Today’s Hot

►Managing
Mercury Mania
Jerald O. Thaler, P.E.
Fishbeck, Thompson, Carr & Huber, Inc.
Michigan Water Environment Association
Annual IPP Seminar
September 25, 2008
► engineers • scientists • architects • constructors
“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 controls
on 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
• Rule 57 provides protection against toxicity
Criterion
Micrograms per liter
(μg/L)
Acute Toxicity
2.8
Chronic Toxicity
0.77
Human Health
0.0018
Wildlife
0.0013
• Wildlife protection controls at 0.0013 μg/L, or
1.3 nanograms per liter (ng/L)
• No mixing zone credit for Bioaccumulative
Chemicals of Concern
►Effluent
• Method 245.1
– Composite sample
– Normal handling
– Quantification inconclusive
for compliance testing
– $40-$50 each
Monitoring
• Method 1631
– Grab sample
– “Clean Hands/Dirty Hands”
– Quantification acceptable
for compliance testing
– $90 each for 3 samples
(duplicates plus field blank)
(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)
►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
►
PEQ = CMAX * Factor
where factor set by number of samples (N):
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 Hg
0.107 lb/yr Hg
Domestic/Background
1.26 MGD
50 ng/L Hg
0.192 lb/yr Hg
Unidentified Sources
By difference…
1.474 lb/yr Hg
WWTP Influent
1.31 MGD
445 ng/L Hg
1.773 lb/yr Hg
Average Removal
98%
Biosolids (6.5%)
396 T/yr
2.2 mg/kg Hg
1.742 lb/yr Hg
Current Average
WWTP Effluent
1.30 MGD
7.9 ng/L Hg
0.031 lb/yr Hg
►Meaningful
Monitoring
• Apply mass balance results to prioritize
minimization efforts
-0.077 lb/yr
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
-1.401 lb/yr
Unidentified Sources
By difference…
0.073 lb/yr Hg
WWTP Influent
1.31 MGD
63 ng/L Hg
0.250 lb/yr Hg
Average Removal
98%
Biosolids (6.5%)
396 T/yr
0.3 mg/kg Hg
0.255 lb/yr Hg
Goal
WWTP Effluent
1.3 MGD
1.3 ng/L Hg
0.005 lb/yr Hg
►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
Source
P-1
P-2
S-1'
WWTP
S-2'
►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 Dentist
• Typical mercury generated per office
0.57 lb/yr
0.02 lb/yr
0.59 lb/yr
Amalgam removal (97%)
Amalgam placement (3%)
Total
• Removals for typical capture processes
~ 68%
~ 40%
81%
Chair-side traps
Vacuum filters
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 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)
0
+0.0
+0
50
1.0
1
+0.1
+13
63
1.3
2
+0.2
+26
4
+0.4
+53
103
2.1
8
+0.8
+105
155
3.1
~50
Net
Influent
(ng/L)
76
WWTP
Removal
~98%
Net
Effluent
(ng/L)
1.5
►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 Dentist
• Potential impact on treatment plant
Again assuming 2.5 million gal/day flow
Dental
Mercury
(lb/yr)
Influent
Impact
(ng/L)
0
+0.000
+0
50
1.0
1
+0.005
+0.7
50.7
1.01
+0.010
+1.3
4
+0.020
+2.6
52.6
1.05
8
+0.040
+5.3
55.3
1.11
No.
Dentists
2
Amalgam
Separator
Removal
95%
Domestic
Background
(ng/L)
~50
Net
Influent
(ng/L)
51.3
WWTP
Removal
~98%
Net
Effluent
(ng/L)
1.03
►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.”
►Perspective
• Justifiable concern over mercury in waterways
– Air emissions need same, or greater, scrutiny as
wastewater discharges
• Tips and techniques from experience
–
–
–
–
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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
►Questions
and Discussion
For additional information:
Jerald O. Thaler, P.E.
Fishbeck, Thompson, Carr & Huber, Inc.
39255 Country Club Drive, Suite B-25
Farmington Hills, MI 48331
[email protected]
248-324-2090