FULL SCALE BIOLOGICAL PRE- TREATMENT OF SCRUBBER WASTEWATERS FOR SELENATE REMOVAL Jeremy Driver Alabama Power Company Environmental Affairs Lab & Field Services 205.664.6188 [email protected]
F ULL S CALE B IOLOGICAL P RE - T REATMENT OF S CRUBBER WASTEWATERS FOR SELENATE REMOVAL Jeremy Driver Alabama Power Company Environmental Affairs Lab.
Dec 28, 2015
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FULL SCALE BIOLOGICAL PRE-TREATMENT OF SCRUBBER WASTEWATERS FOR SELENATE REMOVAL
Jeremy Driver
Alabama Power Company
Environmental Affairs Lab & Field Services
205.664.6188
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
Current NPDES limit on Ash Pond Discharge includes Hg12 ppt Hg
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 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
Scrubber Slurry Clarifying Pond
Biofilm Cell 3 Discharge
Iron Clarification
Pond
Primary Settling Pond
Ash PondMobile River
Ash Sluice Sump
Other Minor WW
Service Water
Scrubber
Biofilm Cell 1
Biofilm Cell 2
FeCl3
Ash Pond FeCl3 Treatment With Biofilm Pre-Treatment
Three Biofilm Cells ½ acre each
Primary Settling Pond
Iron Clarification Pond
River Discharge
ChemicalInjection
Total Flow 20 MGD<12 ppt Hg
$1M /yr Chemical cost on FeCl3 and NaOH
Successful now for over a year
Clarified Scrubber Slurry Wastewater
Ash Sluice and Other Minor Wastewater
VERTICAL FLOW SYSTEM(BIOFILM OR BIO-REDUCTION)
SeO3-2
SeO4-2
Se0
Glycerin
In-soluble
SolubleWood
Chip
s
VERTICAL FLOW SYSTEM(BIOFILM OR BIO-REDUCTION)
FULL SCALE BIOFILM TREATMENTS
2 of 3 Seasonal Treatments (completed) Fall 2011 Winter 2012 Summer 2012 (ongoing)
Flow rate 180 - 220 gpm (~ 0.3 MGD) Clarified Scrubber WW Influent
65% Diluted (unsaturated) Service Water Diluted by winter rains
Complete Chemical Analyses ICP-MS-interference correction system
EPA 200.7 Peroxide
BIOFILM PRETREATMENT RESULTS
FULL SCALE TREATMENT OF CLARIFIED SCRUBBER WASTEWATER
Season Biofilm Cells (#)
Time (d)
Avg. Flow (gpm
)
No Flow (%)
Infl. Se
(ppb)
Effl. Se
(ppb)
Se Remova
l (%)
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
Relatively Inexpensive & Robust Low capital and maintenance cost
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 Pollutant Removal
Se (mostly Selenate) , Method 200.7 (98%) Hg (82%)
Presently Being Evaluated 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
Additional physical-chemical treatment of minor waste water with pretreated Scrubber wastewater from the biofilm.
Scrubber Slurry Clarifying Pond
Biofilm Cell 3 Discharge
Iron Clarification
Pond
Primary Settling Pond
Ash Pond Mobile River
Ash Sluice Sump
Other Minor WW
Service Water
Scrubber Biofilm Cell 1
Biofilm Cell 2
FeCl3
Ash Settling Pond
FeCl3
QUESTIONS?
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