1

2

7th International WETPOL Symposium Big Sky, Montana, USA August 21-25, 2017

Integrated Passive Biological Selenium Treatment System: Results of a 1-year Pilot Study

August 2?, 2017

James S. Bays1

Chelsea Ransom1

Robert BT Thomas1

Sarah Foster1

Patrick Mulhern2

Luis Tovar2

1 CH2M

2 Cottonwood Water & Sanitation District

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Biological Treatment Converts Oxidized Se to Reduced Insoluble Forms

CH2MHILL 2012

Org-Se

(CH3) 2Se

SeO42-

SeO32-

Se0

HSe-1

• Organics + Selenite/Selenate + N + P -> New Cells + CO2 + H2O + Se0

• Order of reduction: DO → NO2- → NO3

- → SeO32- → SeO4

2- → ClO42- → SO4

2-

• Volatilization as outcome of organic selenium formation

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Passive Biological Treatment Systems Configured to Reduce Se and Remove “By-products”

Wood Chips & Compost

Peat Gravel

Rip-rap & Cobble

Aerobic Cascade Aeration

Aerobic Filter (APC)

BOD, S- Polishing

Vertical Downflow Biochemical Reactor (BCR)

NO3, SeO4 Reduction

Vertical Upflow Anaerobic Filter Se0 Particulate

Capture

Flow 409 m3/d [Se] in 12 µg/L HRT 1 day (BCR) CAPEX $765,000 OPEX $15,000/A

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Joint Water Purification Plant (2010) to Replace Non-renewable Deep Groundwater Supply

Joint Water Purification Plant

Reverse Osmosis

Microfiltration

Colorado USA Parker CO

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Despite Supply of Renewable Best Quality Water, JWPP Discharge Limited by Concentrate Se

Discharge to surface water

Permit Violation Discharge Exceeds Selenium Aquatic

Protection Standard (4.6 µg/l)

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Pilot System Train 1: BCR>SPC>PPC>AF>APC

Head Tank

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Pilot System Train 2: BCR>AF>APC>PPC

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Pilot System Recipe

Unit Media %

BCR Wood Chips 30

Field Hay 30

Horse Manure 5

Peat 5

Limestone Sand 5

Sawdust 25

VUF Peat 75

Sawdust 25

SPC ZVI 5

Sand 95

PPC T1: Siderite 100

T2: Bold&Gold 100

BCR

APC

Sample Port

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2016 Project Schedule Extended to Support Specialized Analysis

Activity J F M A M J J A S O N D J

Phase 1

Construction

Establishment

Optimization

Verification

Phase 2

Phase 3

Autopsy

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Redox Potential Confirmed Anaerobic Condition; BOD/COD Loss Defined Establishment Period

Redox Potential

BOD

COD

-150

-150

Optimization

Establishment

13

Phase 1 Pilot: BTS Se Removal Capacity >90% and Can Achieve Se Removal Target

0

20

40

60

80

100

120

1-Feb 21-Feb 12-Mar 1-Apr 21-Apr 11-May 31-May 20-Jun 10-Jul

Tota

l Se

(µg

/L)

HT T1 T2 Table Value Standard

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Phase 2 Train 1 Pilot: No Significant Effect of Flow Variability on Se Removal

0

10

20

30

40

50

60

70

80

30-Aug 9-Sep 19-Sep 29-Sep 9-Oct 19-Oct 29-Oct

Sele

niu

m C

on

cen

trat

ion

(µ

g/L

)

Influent Train 1 Effluent Table Value Standard 30 day rolling average

75% flow 50% flow Variable flow

Baseline

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Phase 2 Train 2 Pilot: No Significant Effect of Operational Schedule on Se Removal

0

10

20

30

40

50

60

70

80

30-Aug 9-Sep 19-Sep 29-Sep 9-Oct 19-Oct 29-Oct

Sele

niu

m C

on

cen

trat

ion

(µ

g/L

)

2016

Influent Train 2 Effluent Table Value Standard 30 day rolling average

Baseline No weekend flow Weekend recirculation

Weekend recirculation with sodium nitrate

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Phase 3 Pilot: No Significant Effect of Flow Reduction on Removal But Some Se Re-oxidation By Aeration • Low Se in BTS

discharge

• Se release from polishing cells

0

5

10

15

20

25

30

35

40

45

50

12-Nov 19-Nov 26-Nov 3-Dec 10-Dec 17-Dec

Sele

niu

m (

µg

/L)

T2:HT T2:B (BCR2) T2:E (PPC Effluent) TVS

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Mass Distribution: Most Se Retained in Anaerobic Cells

0.1

1.0

10.0

100.0

1000.0

BC

R1

-To

p

BC

R1

-Mid

BC

R1

-Bo

t

SPC

-Bo

t

SPC

-Mid

SPC

-To

p

BC

R2

-Sca

le

BC

R2

-To

p

BC

R2

-Mid

BC

R2

-Bo

t

PP

C-B

ot

PP

C-M

id

PP

C-T

op

AP

C1

-To

p

AP

C1

-Bo

t

AP

C2

-To

p

AP

C2

-Bo

t

Effl

uen

t

Tota

l Se

(mg)

Train 1

0.1

1.0

10.0

100.0

1000.0

BC

R1

-To

p

BC

R1

-Mid

BC

R1

-Bo

t

BC

R2

-Bo

t

BC

R2

-Mid

BC

R2

-To

p

AP

C1

-Pe

at

AP

C1

-Ph

ase

1

AP

C1

-To

p

AP

C1

-Bo

t

AP

C2

-To

p

AP

C2

-Bo

t

PP

C-T

op

PP

C-B

ot

Effl

ue

nt

Tota

l Se

(mg)

Train 2

Anaerobic Aerobic Anaerobic Aerobic

Material Baseline Se

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Mass Balance Accounted for 78% (T1) and 87% (T2) of Total Applied Se

69.0% 75.8%

8.8%

10.0%

22.0% 13.3%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

T1 T2

Perc

enta

ge o

f To

tal S

e A

pp

lied

Anaerobic Aerobic Effluent Residual

Residual: Volatilization Aggregate Error

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Se Speciation Confirmed Reducing Conditions and Long-term Storage in Anaerobic Process Units

0

1

2

3

4

5

6

7

8

9

Se (

mg

/kg

ww

)

Train 1

0

1

2

3

4

5

6

7

8

Se (

mg

/kg

ww

)

Train 2 Salt

Adsorbed

AmorphousCrystallineSelenide

Residual

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60% Design: 1.9-ha Biological Treatment System to Treat and Polish 3.6 MLD RO Concentrate

JWPP

System Cells Area (m2)

Media Depth

(m) Downflow

Biochemical Reactor

6 10118 2.1

Anaerobic Upflow Filter

3 1295 2.3

Media Polishing Cell

2 648 2.2

Aerobic Polishing Cell

2 6475 1.3

BCR AF MPC

APC

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Conclusions, Applications and Next Steps

• Se treatable to target by passive biological system

• Other constituents are treatable to standards

• Spent media not toxic

• 20 yr media life

• Treatment train 2 adopted

• Will achieve net reduction of Se in watershed

• Revising costs

• Construction 2018

Discharge to surface water

Integrated Passive Biological Selenium Treatment System: Results of a 1-year Pilot Study

James S. Bays

Jim.Bays@ch2m.com

Grateful acknowledgement to Cottonwood Water & Sanitation District

Thanks to project team: Chelsea Ransom, Robert BT Thomas, Sarah Foster, Patrick Mulhern, Luis Tovar, Jason Rysavy

7th International WETPOL Symposium

Big Sky MT USA August 23 2017

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Calcium - Passive Precipitation Chloride – Conservative, No Removal

Calcium Chloride

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Phosphorus Removed in Aerobic Polishing Cells; Co-precipitation with CaCO3

[P]in = 0.78 mg/L Train 1: 96% 0.03 mg/L Train 2: 83% 0.13 mg/L

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All Metals Removed to BDL by Sulfide Precipitation, Sorption, Hydroxide Formation: Copper Example

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Iron Cycled Based on Internal Sources, Redox Potential and Oxygen Supply

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Active Biological Treatment Supplies Carbon, Nutrients to Fixed or Fluidized Media Beds

test

Fluidized Bed Reactor West Virginia USA Coal Mine Drainage

Flow 11,335 m3/d [Se] in 45 µg/L HRT 15 minutes CAPEX $49 MM OPEX $3.5 MM/A

ABMet Process