Fine Dredged Material and Biosolids for Wetland … Bailey, Nathan Johnson, Daniel Engstrom, Carl Mitchell, Michael Berndt, & Jill Coleman-Wasik Background • Mercury in the environment

Fine Dredged Material and Biosolids for Wetland Creation:

Water Quality Implications

Aaron Mika Nathan Johnson

Xianben Zhu University of Minnesota - Duluth Department of Civil Engineering

Minnesota Water Resources Conference St. Paul, MN

October 15, 2013

Outline

• Material use background • Design/methods for lab experiments • Experimental results: chemistry • Modeling results: Flux to GW implications • Conclusions

Background Dredged Material

Dredged material from St. Louis River Harbor • Shipping channels must be kept open • Sorted into fines (clay-silt) and coarse (sand) • Fines supply exceed current demands • Characteristics: - Low nutrients - Environmental quality -

Erie Pier, summer 2013

Dredging operation

Background Biosolids

Western Lake Superior Sanitary District’s biosolids • Biological wastewater treatment – after anaerobic

digestion • WLSSD processes 40 MGD • Characteristics: - Nutrient rich (C & N) - Environmental quality

Background Dredged & Biosolids: Uses

Soil Type Investigators Vegetation Establishment

Water Quality Concerns

Biosolids, upland DNR, 2001 USS Minntac

Moderate Application rate limited by – Nitrate

Biosolids and Seeds






Dredged material, upland Corps, 1997

Moderate Minimal, trace metals, organics on solid phase

Biosolids and Seeds






Dredged material, upland Corps, 1997 Moderate Minimal, trace metals, organics on solid phase

Biosolids and Dredged material - Dry (upland)

Corps, WLSSD, recent

High ?

Biosolids and Seeds






Dredged material, upland Corps, 1997 Moderate Minimal, trace metals, organics on solid phase

Biosolids and Dredged material - Dry (upland)

Corps, WLSSD, recent

High ?

Biosolids and Dredged material - Wetlands

Current Study

? ?

Biosolids and Seeds

Conceptual model Dry vs. Wet

Dry Treatment (Representative of Upland)

Wet Treatment (Representative of Wetland)

Nutrients Metals Metals Nutrients

Groundwater

Dry vs. Wet

Dry Treatment (Representative of Upland)

Wet Treatment (Representative of Wetland)

Nutrients Metals Metals Nutrients

Groundwater

Conceptual model

Design Experimental Variables

Dredged: Biosolids Mixtures

100:0 90:10 80:20 50:50 0:100

Dry Wet Dry Wet Dry Wet Dry Wet Dry Wet

Time (weeks)

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

0

1

3

2

Design Lab Adaption To create controlled experiment: • Mixtures were placed into cylinders (4 replicates per mix) • Water was flushed through cylinders weekly & leachate

was collected • In between flushing:

• “Wet cylinders” stored in a tub of water • “Dry cylinders” stored uncovered with air circulation

Method Analysis

Biosolids Primary

Contributions

pH

Conductivity

Nitrate

Ammonia

Phosphate

Sulfate

Dredged Primary

Contributions

Copper Zinc

Cadmium

Cobalt Lead

Arsenic

Analytical Components

Samples collected and analyzed at 0, 1, 3, 5, 8, & 11 weeks (limited sample volume allocated to priority analyses)

All analytes were measured for each mixture

Method Permeability

• Permeability of wet treatments changed noticeably over time

• Tests were implemented to quantify change in

permeability for wet treatments

Results Wet vs. Dry Nitrogen

• Higher concentrations of total nitrogen and nitrate leached out of dry mixtures (except for 100% biosolids)

• Reducing conditions - present with biosolids - left nitrogen as ammonia • Fraction biosolids had no apparent affect on nitrogen concentration

under dry conditions, but did under wet conditions

Week 3 Nitrogen

146

MDH Standard

Results Wet vs. Dry Metals

Week 3 Metals

• Lower copper, higher arsenic concentrations in dry leachate • Concentrations not apparently related to mix ratio • Some metals show higher concentrations than water quality limit

Arsenic = 2 ug/l

Copper = 10 ug/l

Cobalt = 5 ug/l

Arsenic = 2 ug/l

Copper = 10 ug/l

Cobalt = 5 ug/l

Results Permeability

0

50

100

150

200

0 5 10 15Volu

me

Colle

cted

(mL)

Week

Wet

100: 0

90: 10

80: 20

50: 50

0: 100

0

50

100

150

200

0 5 10 15Volu

me

Colle

cted

(mL)

Week

Dry

100: 0

90: 10

80: 20

50: 50

0: 100

Dredged: Biosolids Dredged: Biosolids

• By week 5, wet mixtures with primarily dredged material mixtures (80, 90, 100%) were barely draining and almost quit by week 10

• Dry treated material continued to completely drain throughout entire experiment


• By week 5, the calculated permeabilities for the primarily dredged material mixtures (80, 90, 100%) were around 0.082 m/yr

• These mixtures are best for retaining water for wetlands

Dredged: Biosolids

Results Flux Concept Flux combines importance of effluent chemical concentrations and effluent quantity

Case 1: Case 2:

1/10 people that walked in were CE C =

1 𝐶𝐶𝐶𝐶10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

100 people walked in

10 CE

Q = 100 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

F = 𝐶𝐶𝐶𝐶 = 1 𝐶𝐶𝐶𝐶

10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝100 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

= 10 𝐶𝐶𝐶𝐶

10/10 people that walked in were CE

10 people walked in

10 CE F = 𝐶𝐶𝐶𝐶 = 10 𝐶𝐶𝐶𝐶

10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

= 10 𝐶𝐶𝐶𝐶

Q = 10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

C =10 𝐶𝐶𝐶𝐶

10 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝

This is analogous to the number of Civil Engineers that walked through the door Flux = Concentration * Flow

Results Flux Concept

• Theoretical reclamation site on side slope of tailings basin • Material is added for vegetation growth • Initially, rain water leaches through and then later, ponding begins from runoff • As material at low point becomes saturated, permeability decreases and water flows elsewhere

Corresponds to “Dry Conditions”

Corresponds to “Dry Conditions”

Corresponds to “Wet Conditions”


0.5 m

highly permeable tailings

k = highly permeable

q= 𝑖𝑖

= 0.9𝑚𝑚𝑦𝑦𝑦𝑦

F= 𝐶𝐶𝐶𝐶

𝐶𝐶 = 𝑞𝑞𝑞𝑞

= (0.9) 𝑚𝑚𝑦𝑦𝑦𝑦 (1) 𝑚𝑚2

= 𝟗𝟗𝟗𝟗𝟗𝟗 𝒍𝒍𝒚𝒚𝒚𝒚

/𝒎𝒎𝟐𝟐

=𝑚𝑚𝑚𝑚𝑝𝑝

𝑝𝑝𝑦𝑦𝑦𝑦

/𝑚𝑚2

=𝑚𝑚𝑚𝑚

𝑦𝑦𝑦𝑦 ∙ 𝑚𝑚2

Upland Site

= 0. 9𝑚𝑚3

𝑦𝑦𝑦𝑦 /𝑚𝑚2


dH = -1.0 m

dL = 0.5 m

k = 0.082 m/yr

q= −𝑘𝑘 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑

= −(0.082)𝑚𝑚𝑦𝑦𝑦𝑦

(−1) 𝑚𝑚(0.5) 𝑚𝑚

= 0.164 𝑚𝑚𝑦𝑦𝑦𝑦

F= 𝐶𝐶𝐶𝐶

𝐶𝐶 = 𝑞𝑞𝑞𝑞

= (0.164) 𝑚𝑚𝑦𝑦𝑦𝑦 (1) 𝑚𝑚2

= 0.164 𝑚𝑚3

𝑦𝑦𝑦𝑦 /𝑚𝑚2

= 𝟏𝟏𝟏𝟏𝟏𝟏 𝒍𝒍𝒚𝒚𝒚𝒚

/𝒎𝒎𝟐𝟐

=𝑚𝑚𝑚𝑚𝑝𝑝

𝑝𝑝𝑦𝑦𝑦𝑦

/𝑚𝑚2

=𝑚𝑚𝑚𝑚

𝑦𝑦𝑦𝑦 ∙ 𝑚𝑚2

Wetland Site

highly permeable tailings


Week 3 Nitrogen

146

F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑚𝑚𝑝𝑝

900 𝑝𝑝𝑦𝑦𝑦𝑦

/𝑚𝑚2 F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑚𝑚𝑝𝑝


/𝑚𝑚2

Results Flux Nitrogen Flux

When flux is considered, wet conditions leach less nitrogen than dry conditions

F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑝𝑝


/𝑚𝑚2 F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑝𝑝


/𝑚𝑚2


Week 3 Metals

F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑢𝑢𝑚𝑚𝑝𝑝


/𝑚𝑚2 F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑢𝑢𝑚𝑚𝑝𝑝


/𝑚𝑚2

Results Flux Metals Flux

• When flux is considered, wet conditions leach less Arsenic and Cobalt than dry conditions

• Copper has a similar flux comparing wet and dry conditions

F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑚𝑚𝑝𝑝


/𝑚𝑚2 F= 𝐶𝐶𝐶𝐶 = 𝐶𝐶 𝑚𝑚𝑚𝑚𝑝𝑝


/𝑚𝑚2

Conclusions • Dredged material is nearly impermeable when saturated

• Potential water quality concerns with using dredged material

and biosolids for wetland creation should consider fluxes of contaminants in the context of material permeability

• Lab comparisons suggest similar or smaller annually averaged fluxes from saturated conditions than dry conditions

• A mixture of 80% dredged material and 20% biosolids could minimize contaminant flux, maintain the wetland water level, and provide adequate nutrients (biosolids) for plant growth

Acknowledgements

• Carol Wolosz – Great Lakes Maritime Research Institute

• Kathy Hamel, Todd Macmillan – Western Lake Sanitary Sewer District

• Rich Price – USACE – ERDC • David Bowman – USACE – Detroit District

Questions


• Higher concentrations of total nitrogen and nitrate leached out of dry mixtures (except for 100% biosolids)

• Reducing conditions - present with biosolids - left nitrogen as ammonia • Fraction biosolids had no apparent affect on nitrogen concentration

under dry conditions, but not under wet conditions

Week 3 Nitrogen

146

MDH Standard


Week 3 Metals

• Lower copper, higher arsenic concentrations in dry leachate • Concentrations not apparently related to mix ratio • Some metals show higher concentrations than water quality limit

Arsenic = 2 ug/l

Copper = 10 ug/l

Cobalt = 5 ug/l

Arsenic = 2 ug/l

Copper = 10 ug/l

Cobalt = 5 ug/l


• By week 5, the calculated permeabilities for the primarily dredged material mixtures (80, 90, 100%) were around 0.082 m/yr

• These mixtures are best for retaining water for wetlands

Dredged: Biosolids

Geochemical factors influencing methyl mercury production and partitioning in

sulfate-impacted lake sediments

Logan Bailey, Nathan Johnson, Daniel Engstrom, Carl Mitchell, Michael Berndt, & Jill Coleman-Wasik

Background

• Mercury in the environment o Mercury (Hg) is a heavy metal with known adverse health

effects o Mercury pollution in soils & surface waters is predominantly a

result of atmospheric deposition of anthropogenic sources o Methylmercury (MeHg) is of particular concern, as it is a highly

potent neurotoxin that bioaccumulates in the food chain.

Background

• Effect of Sulfur on MeHg dynamics o Methylation of inorganic-Hg is primarily due to activity of

sulfate-reducing bacteria (SRBs) o Sulfide-Hg bonds can reduce the potential for methylmercury

production o Aqueous reduced sulfur may also have an effect on

methylmercury partitioning and transport

Background

• DNR effort to better understand the impact of sulfur from past, present, and future mining activity on methylmercury production and transport

• High methylmercury levels in fish have resulted in lake impairments and consumption advisories.

The Mesabi Iron Range is located in NE Minnesota, along the northern edge of the St. Louis River catchment area

Background Low Sulfate Sites High Sulfate Sites

Methods Field Sites

• Cores collected in May, July, & October 2012 to establish seasonal trends

• At wetland sites, sediment collected from open water areas

• At lakes, sampling at two locations: (1) deep-stratified & (2) shallower site

1

1

2

2 3

X

X

X

X

X

X

X

Methods Sampling Design

Hgi Hg2+ MeHg MeHg partitioning

SO42- S2-

demethylation

methylation

Solid Phase Pore-Water

Fe2+

AVS Fe(s)

DOC, DIC, NO32-, PO4

2-, Cl- Chemical Analytes slope ratio, SUVA

Site Characteristics

ρ(bulk), water content %C: Organic, Inorganic, Calcite pH, Temp, ORP

Al, Mn, Zn, Ca, K, Mg, Na, TC, TN

• Collection Method o Multiple sediment cores collected at each site o Cores extruded at defined depth intervals and composited

• Samples B & C: composites of the top 0-4 cm of sediment cores • Sample A: sub-sectioned into 0-2 cm, 2-4 cm, and 4-8 cm samples

A B C

0-4 cm

4-8 cm

2-4 cm

0-2 cm 0-4

cm

Core Sub-sectioning Schematic


• Sample Processing o After extruding cores, samples

immediately placed in glove bag with O2-free atmosphere to preserve in-situ redox conditions

o Processing and preservation of samples in glove bag

• Samples for solid phase analysis are homogenized and allocated

• Pore-water extracted through rhizon with filter size of 0.2 microns into an evacuated sample bottle


• Methylation Assays o Sediment core spiked with

mercury and methylmercury stable isotopes

o After incubation time -Mercury isotope concentrations used to calculate in-situ methylation and demethylation rates

Methods Methylation Assays

Methylation Potential 201Hg2+ Me201Hg+

Demethylation Potential Me199Hg+ 199Hg2+

Results Geochemical Setting

0

250

500

750

1000

1250

1500

Mng 1 Mng 2 McQ 2 McQ 3 LLC 1 WTR 1

Sulfi

de [µ

mol

/L]

Pore-water Sulfide

May

July

October

• Sulfate-impacted sites have corresponding high pore-water sulfide concentrations

0

10

20

30

40

50


SEM

/ A

VS

SEM/AVS Ratio

0

30

60

90

120

150

0

10

20

30

40

50


Fe [µ

mol

/L]

SEM

/ A

VS

SEM/AVS Ratio

SEM:AVS

Pore-water Fe(II)

• Iron and sulfide precipitate out of aqueous phase rapidly upon reaction

• Ratio of iron to sulfide in the solid phase encompasses long term sulfur loading

0

1

2

3

4


MeH

g [n

g/g]

MeHg (Solid)

May

July

October

0

200

400

600

800

1000


THg

[ng/

g]

THg (Solid)

May

July

October

0

2

4

6

8


MeH

g [n

g/L]

MeHg (PW)

May

July

October

0

2

4

6

8

10

12

14


THg

[ng/

L]

THg (PW)

May

July

October

Results Mercury Levels

Results Sediment Depth Profiles

• General Trends Observed: • Solid-phase THg concentrations consistent throughout the core • Decreases in MeHg concentration with depth, in both solid and pore-

water phases

0.0

0.5

1.0

1.5

2.0

May July Oct

MeH

g {n

g/g]

Mng 1 [MeHg] (Solid)

0-2 cm

2-4 cm

4-8 cm

0.0

1.0

2.0

3.0

May July Oct

MeH

g [n

g/L]

Mng 1 [MeHg] (PW)

0-2 cm

2-4 cm

4-8 cm

0

25

50

75

100

0 2 4 6 8

Cum

ulat

ive

%

Sediment Core Depth [cm]

Cumulative % of sediment core MeHg with depth

Solid Phase AvrPore-Water avr

Results Sediment Depth Profiles

• Net methylmercury production increased over the summer and into the fall, particularly in the top 0-2 cm

• May sample values likely a

reflection of low biological activity

**Values normalized to May (0-2 cm) value

0

1

2

3

4

May July OctAverage of All Sites

kmeth / kdemeth**

0-2 cm

2-4 cm

4-8 cm

We have a feel for WHAT is happening at

the sites…

but WHY is it happening?

Results MeHg Production

• %MeHg (solids) has been proposed as a proxy for long-term methylmercury production*

• Strong, positive correlation between %MeHg (solids) and methylation rates measured experimentally

0.0

1.0

2.0

3.0

0 1 2 3 4 5 6

% M

eHg

kmeth / kdemeth

%MeHg (solids) v. Net Methylation

LLCWTRWSRMngMcQ

*Drott et al. 2008

• Trends in observations depend starkly on pore-water sulfide: • Low sulfide concentrations show positive relationship with %MeHg values • High sulfide concentrations have uniformly low methylation potentials, with

no trend as sulfide increases • One hypothesis* is that above approx. 50 µM sulfide, the predominant mercury

species shifts from a neutral to a charged species, limiting production of MeHg.

0.0

1.0

2.0

3.0

1 10 100 1000 10000

% M

eHg

log Sulfide [µmol/L]

%MeHg (solids) v. Sulfide (PW)

LLC

WTR

WSR

Mng

McQ


*Benoit et al. 1999

• %MeHg (PW) is a result of net MeHg production in the sediment, but also of partitioning and transport processes

• Suggests a difference in sulfide’s influence on mercury dynamics between low and high sulfide sites

• Low sulfide sites: %MeHg in the pore-water follows a similar positive trend seen in solid phase

• High sulfide sites: pore-water %MeHg varies substantially with no clear trend

0

10

20

30

40

50

60

70

80

1 10 100 1000 10000

% M

eHg


%MeHg (PW) v. Sulfide (PW)

LLC

WTR

WSR

Mng

McQ


0

20

40

60

80

0.0 0.5 1.0 1.5 2.0 2.5

% M

eHg

(PW

)

% MeHg (solid)

%MeHg (PW) v. %MeHg (solid)

Low Sulfide (<50 umol) MudHigh-Sulfide (>50 umol) Mud

• Processes influencing pore-water %MeHg differ between the high and low sulfide sites

• Strong correlation for low sulfide sites implies that methylation potential is the primary influence in pore-water %MeHg

• At high sulfide sites there is no relationship between %MeHg in the solid phase and the pore-water


Correlation (R2): Low Sulfide = 0.902 High Sulfide = 0.008

Results MeHg Partitioning

• We define KD* as the in-situ ratio

of the MeHg concentration on the solid phase to the concentration in the pore-water

𝐾𝐾𝐷𝐷∗ = logMeHg solidMeHg PW

• Lower KD

* values correspond to more MeHg moving into the pore-water phase

• Low sulfide sites are characterized by a very narrow range of KD

*(MeHg) values

• High sulfide sites range from high to low KD

*(MeHg)

2.5

3.0

3.5

4.0

4.5

1 10 100 1000 10000

K D*


KD* (MeHg) v. Sulfide (PW)

LLCWTRWSRMngMcQ

2.5

3.0

3.5

4.0

4.5

0 5 10 15 20 25 30 35

log

K D*

DOC [mg/L]

KD* (MeHg) v. DOC

Low Sulfide (<50 umol) Mud

High-Sulfide (>50 umol) Mud

2.5

3.0

3.5

4.0

4.5

0 5 10 15 20 25 30 35

Kd

DOC [mg/L]

KD* (MeHg) v. DOC

LLC

WTR

WSR

Mng

McQ

• No relationship between sulfide and dissolved organic carbon (DOC) concentrations

• If DOC is important in binding mercury, an increase in DOC would be expected to lower log KD

* values – However, this relationship is only weakly present in the high sulfide

group, and non-existent for low sulfide sites.

Results MeHg Partitioning

• Mechanisms that influence methylmercury production and transport are different between low and high sulfur freshwater sediments

• High pore-water sulfide appears to suppress production, but may increase mobility of MeHg off the solid phase.

• Coordinated research examined the water columns, peat-lands, and inlets/outlets at these sites – This research will help shed more light on MeHg

transport into surface waters • Reports to be completed in Spring 2014

Discussion & Related Work

Acknowledgments

A big thank you to: • Minnesota DNR Iron Ore and Environmental

cooperative research program • Mine Water Research Advisory Panel (MWRAP) • University of Minnesota – Duluth • Hibbing Office of the Minnesota DNR Lands &

Minerals Division

Co-authors Nathan Johnson, Daniel Engstrom,

Carl Mitchell, Michael Berndt, & Jill Coleman-Wasik

Field and Laboratory Assistance Benjamin Von Korff, Katherine Rasley, Erin Mittag, Amanda Brennan,

Aaron Mika, Brian Beck, Nate Gieske

QUESTIONS/COMMENTS?

Documents

Fine Dredged Material and Biosolids for Wetland … Bailey, Nathan Johnson, Daniel Engstrom, Carl Mitchell, Michael Berndt, & Jill Coleman-Wasik Background • Mercury in the environment