Advances in the Use of Passive Wetland Advances in the Use of Passive Wetland Systems for Selenium Treatment of Systems for Selenium Treatment of Systems for Selenium Treatment of Systems for Selenium Treatment of Mine Mine-Impacted Water Impacted Water James Bays PWS SE James Bays PWS SE James Bays, PWS, SE James Bays, PWS, SE BT Thomas, Ph.D. BT Thomas, Ph.D. Derek Evans, P.E. Derek Evans, P.E. Tim Harrison, P.E. Tim Harrison, P.E. Tim Harrison, P.E. Tim Harrison, P.E. Copyright [insert date set by system] by [CH2M HILL Entity] • Company Confidential 9 TH TH INTECOL International INTECOL International Wetlands Wetlands Conference Conference June 3 June 3-8 2012 Orlando Florida 8 2012 Orlando Florida
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Advances in the Use of Passive Wetland Advances in the Use of Passive Wetland Systems for Selenium Treatment ofSystems for Selenium Treatment ofSystems for Selenium Treatment of Systems for Selenium Treatment of MineMine--Impacted WaterImpacted Water
James Bays PWS SEJames Bays PWS SEJames Bays, PWS, SEJames Bays, PWS, SEBT Thomas, Ph.D.BT Thomas, Ph.D.Derek Evans, P.E.Derek Evans, P.E.Tim Harrison, P.E.Tim Harrison, P.E.Tim Harrison, P.E.Tim Harrison, P.E.
Copyright [insert date set by system] by [CH2M HILL Entity] • Company Confidential
99THTH INTECOL International INTECOL International WetlandsWetlands ConferenceConferenceJune 3June 3--8 2012 Orlando Florida8 2012 Orlando Florida
Selenium is Present in Surface Coal Mine DrainageDrainage
Geology of selenium Geology of selenium– Low sulfur, fresh water coal deposits of Southern WV– Selenium concentrated in the coal & associated black shales
• pit scrapings, bone coal, organic-rich materiall d t ti i b d d t ( t b t i )• low detection in overburden sandstone (present, but minor)
– Results in neutral to alkaline drainage, but with elevated Se Sources in post-mining landscapes
– Valley fills waste rock piles “pavement” at base of backstack;Valley fills, waste rock piles, pavement at base of backstack; anywhere black (organic-rich) material located
Water Quality Control Technology Selection Choice: Passive or Active Treatment?Choice: Passive or Active Treatment?
NaturalSystems
ConventionalSystems
•Land Intensive•Capital construction cost•Natural processes
•Energy/chemical dependent•Capital construction cost•Engineered processesp
•Low O&M (not zero O&M)g p
•Higher O&M
Natural systems can be augmented (semi-passive treatment)Conventional systems can be designed for low energy/chemical
input
Post-mining landscape: the reality of long term treatment
Existing Se Passive Treatment Systems are Free Water Surface WetlandsFree Water Surface Wetlands
Area: 36 ha Flow: ~6,540 m3/d Date: since 1991 HRT: 7-10 days Se reduction: 89% Se in: 20-30 µg/L Se out: <5 µg/L Volatilization: 10 30% Volatilization: 10-30%
Chevron’s Water Enhancement Wetland Richmond CAWetland, Richmond CA
Hansen et al, 1998
Wetland Processing and Storage of Selenium
SeOSeO4422-- VolatilizationVolatilization
O i + S O 2 (CH ) S
OrgOrg--SeSe SeOSeO3322--
(CH(CH33)) 22SeSe
Organic + SeO32-→ (CH3)2Se
Volatilized from plant tissues 5-30% cumulative loss from
sediments and plantsgg 33
SeSe00
HSeHSe--11
sediments and plants
SorptionSorption Selenite sorbs to sediments and
SeSe
DissimilatoryDissimilatory ReductionReductionSeO4
2- → SeO32- → Se0 → Se2-
Distribution in wetland sediments:
soil constituents: Fe-, Mn- or Al-oxyhydroxides and organic matter
Plant UptakePlant Uptake Distribution in wetland sediments:
0:13:41:46
89-92% reduction from selenate to elemental Se in 10 - 16 days
pp Rapid uptake Tissue concentrations increase
but not detrimentalelemental Se in 10 16 days No long term storage in plants;
Se transferred to sediments
Anaerobic “Bioreactor” Wetland Demonstration Showed High Efficiency in Minimal AreaShowed High Efficiency in Minimal Area
Volume: 124 m3
Flow: 11-131 m3/d Date: 9/08-10/09 HRT: 2.4 d Se reduction: 98%
(90% winter) Se removal rate: 73 mg/d/m3
Se out: 0.5 ug/LG d J ti CO Se out: 0.5 ug/L
US Bureau of Reclamation 2010
Grand Junction CO
Functional Role of Aerobic Wetlands in Anaerobic + Aerobic CombinationAnaerobic + Aerobic Combination
FunctionsSurface Flow Wetlands Functions Treat BCR by-products
– Oxidize BOD, CODT ti l t
Surface Flow Wetlands
Victoria, TX– Trap particulates– Assimilate excess nutrients– Odor reduction
R d l– Reduce color Se polishing to trace levels
– Biological vegetation uptake, t f ti d b i ltransformation and burial
– Hydrologic attenuation to equalize possible variation in flows and concentrationsconcentrations
Passive Se Treatment in WV: Case History
Overview Location
Two outlets assigned stringent selenium discharge standard: – 4.7 ug/L monthly mean– 8.2 ug/L daily max
Conducted barrel studies to formulate ideal substrate, calibrate model
Designed two distinct systems based on landscape, space, treatment
PROJECT LOCATION
VICINITY MAPon landscape, space, treatment
First system July 2011 Second system November 2011
System A: Design Flow Set to Capture Load and Account for Inter-annual Variationand Account for Inter annual Variation
54505450
545
L; g
pm
m3d
-1
54.5
ug/L 1
5.45
Barrel Treatability Study Showed Highest Se Removal with High HRT & Organic MediaRemoval with High HRT & Organic Media
20% woodchips 35% sawdust
10% peat moss 5% limestone sand
%25% hay, 5% composted manure
24 hr HRT ~ 17 mg/d/m3 media 17 mg/d/m media
k20 ~1700 m/yr
Barrel Study Confirmed Significant Post-Startup “Byproduct” DischargesByproduct Discharges
Gravity Flow and Sequential Process Concept Balanced Area and Compliance ChallengeBalanced Area and Compliance Challenge
System Plan and Profile Design Concepts
Replace existing sediment pondp409 m3/d base flow
Four cells-in-series:1. Downflow biochemical reactor2. Anaerobic upflow wetland3. Fill-and-drain wetland
12
34
3. Fill and drain wetland4. Aerobic surface flow marsh
Passive Se Treatment in WV: Completed 2011
Cell 1 DownflowCell 1 Downflow Cell 2 UpflowCell 2 UpflowCell 2 UpflowCell 2 Upflow
Cell 3 Fill & Drain MarshCell 3 Fill & Drain Marsh
C ll 4 S f flC ll 4 S f flCell 4 Surface flowCell 4 Surface flow
Weekly samples (6/29/11 Weekly samples (6/29/11 –– 12/28/11)12/28/11)Flow rate 11Flow rate 11 381 m381 m33/d/dFlow rate 11Flow rate 11--381 m381 m33/d/dIn: 5.7 In: 5.7 –– 16.8 µg/L total Se; Out BDL (<0.1 ug/L)16.8 µg/L total Se; Out BDL (<0.1 ug/L)88% 88% -- 99% removal efficiency99% removal efficiency
Cell 1: Downflow Biochemical Reactor (BCR)
Plan Profile
TOP OF SUBSTRATE(1117.16’)
DWSE (1120.00’)
TOP OF SUBSTRATE(1117.16’)
DWSE (1120.00’)
DWSE (1120.00’)INLET WEIR
SURFACE OVERFLOW STRUCTURE
DWSE (1120.00’)INLET WEIR
SURFACE OVERFLOW STRUCTURE
CELL 1
INLET WEIR
CELL 1
INLET WEIR
POND BOTTOM (1115.00’)
ORIGINAL GRADE
FINISHED GRADE
TOP MEDIAROCK
CELL 1
POND BOTTOM (1115.00’)
ORIGINAL GRADE
FINISHED GRADE
TOP MEDIAROCK
CELL 1CELL 1
BYPASS DITCH
CELL 1
BYPASS DITCH
CELL 1CELL 1
m2 Type Media Plants Function
SURFACE OVERFLOW STRUCTURE
LIMITS OF HDPE LINER
SURFACE OVERFLOW STRUCTURE
LIMITS OF HDPE LINER
m2 Type Media Plants Function
526Downflow
biochemical t
Mixed organic None Selenium
reductionSTRUCTURESTRUCTURE reactor g
Cell 2: Upflow Anaerobic Wetland
Plan Profile
TOP OF SUBSTRATE(1119.00’)BYPASS DITCH
TOP OF SUBSTRATE(1119.00’)BYPASS DITCH
DWSE (1120.00’)
SURFACE OVERFLOW STRUCTUREDWSE (1120.00’)
SURFACE OVERFLOW STRUCTURE
SURFACE OVERFLOW STRUCTURE
SURFACE OVERFLOW STRUCTURE
POND BOTTOM (1115.00’)
ORIGINAL GRADE
FINISHED GRADE
TOP MEDIA
ROCK
CELL 2
POND BOTTOM (1115.00’)
ORIGINAL GRADE
FINISHED GRADE
TOP MEDIA
ROCK
CELL 2
m2 Type Media Plants FunctionCELL 2
STRUCTURE
LIMITS OF
CELL 2
STRUCTURE
LIMITS OF
CELL 2CELL 2
567 Upflow anaerobic Peat Sedges,
rush
Selenium reduction, Byproduct polishing
HDPE LINER
DWSE (1120.00’)
HDPE LINER
DWSE (1120.00’)
BYPASS DITCHBYPASS DITCH
Cell 3: Fill-and-Drain Polishing Wetland
Plan Profile
BYPASS DWSE (1117.00’)
ORIGINAL GRADE SURFACE OVERFLOW
STRUCTURE
CELL 3
POND BOTTOM (1113.00’)
DITCHDWSE (1117.00’)
2 T M di Pl t F ti
POND BOTTOM (1113.00’)FINISHED GRADE
GRAVEL
CELL 3SURFACE OVERFLOW STRUCTURE
LIMITS OF
m2 Type Media Plants Function
648Subsurface
fill and Limestone Cattails Byproduct HDPE LINER
648 fill and drain gravel Cattails polishing
BYPASS DITCH
Cell 4: Free Water Surface Polishing Wetland
Plan Profile
BYPASS DITCHDWSE (1114.00’)
ORIGINAL GRADE
FINISHED GRADE
SURFACE OVERFLOW STRUCTURE
SOIL
SURFACE OVERFLOW STRUCTURE
m2 Type Media Plants Function
POND BOTTOM (1110.00’)CELL 4
CELL 4445 Free water
surface
Topsoil and
pondedwater
Cattails Byproduct polishing
DWSE (1114 00’)
POND BOTTOM (1111.00’)
(1114.00’)
On Balance, Natural Systems Favored(System A example)(System A example)
Conventional
NaturalNatural
Systems•Can be made to fitNaturalNatural
SystemsSystems •Construction $MMs •Engineered processes•O&M $500K
••BCR+wetlandBCR+wetland footprint fits (just)footprint fits (just)••Construction $534KConstruction $534K••Natural processesNatural processes••O&M $15K/yrO&M $15K/yr
Conclusions
Critical water quality management issue Can combine lessons learned from treating ag
drainage mine-water municipal & stormwaterdrainage, mine water, municipal, & stormwater Pilot studies are necessary to establish removal rates
– Consistent removals at 24 hr HRT
Selenium reduced and sequestered year-round Small footprint, lower cost of wetland reactor systems
I b d l i d i Integrate by-product control into design
AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgementsThanks to all of our collaborating partners in the West Thanks to all of our collaborating partners in the West
Virginia coal mining industryVirginia coal mining industryVirginia coal mining industry. Virginia coal mining industry. Thanks to engineering and science staff at CH2MHILLThanks to engineering and science staff at CH2MHILL
[email protected]@ch2m.com
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