Transcript Plant Barry Cross Media Bromide Injection Study

FULL SCALE BIOLOGICAL PRETREATMENT OF SCRUBBER
WASTEWATERS FOR SELENATE
REMOVAL
Jeremy Driver
Alabama Power Company
Environmental Affairs Lab & Field
Services
205.664.6188
[email protected]

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Flue Gas is high in SO2
SO2 reacts with limestone to form
CaSO4 or gypsum
Additional pollutants are removed
GYPSUM SLURRY CLARIFICATION
APC PLANT BARRY BACKGROUND
INFORMATION
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Current NPDES limit on Ash Pond Discharge includes
Hg
 12
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Treatment system in place to meet this limit by
injecting FeCl3 and NaOH (Physical – Chemical
Treatment)
Potential future NPDES limits may include Se and
other elements
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
ppt Hg
Physical - Chemical treatment is not sufficient for removing
selenate, an oxidized soluble form of Se
Biological treatment is needed to reduce selenate
SCRUBBER SLURRY CLARIFICATION POND
WASTEWATER FLOW DIAGRAM
Service
Water
Scrubber
Biofilm
Cell 1
Ash Sluice
Sump
Scrubber Slurry
Clarifying Pond
Biofilm
Cell 2
Biofilm Cell 3
Discharge
Other
Minor WW
Primary
Settling Pond
FeCl3
Iron
Clarification
Pond
Ash Pond
Mobile
River
Ash Pond FeCl3 Treatment With
Biofilm Pre-Treatment
Total Flow 20 MGD
<12 ppt Hg
$1M /yr Chemical cost on FeCl3 and NaOH
Successful now for over a year
River Discharge
Three Biofilm
Cells ½ acre eachPrimary Settling Pond
Iron Clarification Pond
Chemical
Injection
Clarified Scrubber
Slurry Wastewater
Ash Sluice and Other
Minor Wastewater
VERTICAL FLOW SYSTEM
(BIOFILM OR BIO-REDUCTION)
Glycerin
SeO4-2
SeO3
-2
Soluble
Se0
In-soluble
VERTICAL FLOW SYSTEM
(BIOFILM OR BIO-REDUCTION)
FULL SCALE BIOFILM TREATMENTS
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2 of 3 Seasonal Treatments (completed)
Fall 2011
 Winter 2012
 Summer 2012 (ongoing)
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Flow rate 180 - 220 gpm (~ 0.3 MGD)
 Clarified Scrubber WW Influent
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65% Diluted (unsaturated) Service Water
 Diluted by winter rains
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Complete Chemical Analyses
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ICP-MS-interference correction system
EPA 200.7
 Peroxide
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BIOFILM PRETREATMENT RESULTS
FULL SCALE TREATMENT OF CLARIFIED
SCRUBBER WASTEWATER
Season
Biofilm
Cells
(#)
Time
(d)
Avg.
Flow
(gpm)
No
Flow
(%)
Infl.
Effl.
Se
Se
(ppb) (ppb)
Se
Removal
(%)
Water
Temp
(C)
Samples
(#)
Fall 2011
2
52
180
9
2,103
29
99
16
11
Winter
2012
2
41
213
0
590
13
98
16
13
Summer
2012
3
85
206
2
951
25
97
29
17
PRELIMINARY BIOFILM RESULTS
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Relatively Inexpensive & Robust
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Low capital and maintenance cost
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Requires carbon feed for bacteria food source
 (e.g., glycerin, 140mL/min)
Bacteria can withstand time periods with no flow
 Effective pretreatment directly integrated into existing
ash pond physical - chemical treatment system
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Pollutant Removal
Se (mostly Selenate) , Method 200.7 (98%)
 Hg (82%)
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Presently Being Evaluated
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Low volume wastewater treatment
Looking at different ways that we can integrate the
biofilm treatment system in the overall wastewater
treatment in order to achieve higher pollutant reduction
FUTURE EVALUATIONS
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Additional physical-chemical treatment of minor waste water
with pretreated Scrubber wastewater from the biofilm.
Scrubber
Service
Water
Scrubber Slurry
Clarifying Pond
Biofilm
Cell 1
Ash Sluice
Sump
Biofilm Cell 3
Discharge
Ash Settling
Pond
FeCl3
Biofilm
Cell 2
Other
Minor WW
Primary
Settling Pond
FeCl3
Iron
Clarification
Pond
Ash Pond
Mobile
River
QUESTIONS?