enhanced natural removal of cyanide … · enhanced natural removal of cyanide and ammonia in...

REMTECH 2006

byBill Coedy & Ken Ashley

ENHANCED NATURAL REMOVAL OF CYANIDE AND AMMONIA IN TAILINGS LAKE AND ZONE 2 PIT LAKE AT COLOMAC, NWT

ACKNOWLEDGEMENTSScientific InterpretationJohn Chapman Roger PietersSusan Watson Greg LawrenceHedy Kling Stephen ShultzKen Hall Anne Wilson

Managerial SupportJames Edwards (INAC), Dave Bynski (PWGSC)

ACKNOWLEDGEMENTSTechnical Assistance:

Dillon Consultants (Yellowknife)Tli Cho Logistics Dean Holman, Judy Mah, Regan Fielding

Laboratory Analysis:ALS EnvironmentalTaiga Environmental

• Treatment Of Mine Water At Colomac• Description of Monitoring Programs• Results &Treatment Evaluation for

Tailings Lake and Zone 2 Pit

PRESENTATION OVERVIEW

Colomac Mine Site

Great Bear Lake

Great Slave Lake

Yellowknife

HISTORY• 1990 Mine operations begin• 1997 Ore processing & milling ceases• 1999 Water transfers begin• 1999 INAC assumes responsibility of abandoned site• 2001 Construction of diversion ditches begins• 2002 Water treatment begins• 2004 Remediation Plan approved by MWL&W Board

ISSUES• Water Management

Tailings Lake expected to exceed licenced freeboard limit by 2006

• Water QualityNatural degradation of cyanide and related compounds insufficient

Add phosphate for ENR

Divert runoff to increase storage time

2002: 11 tonnes of MAP2003: 9 tonnes of MAP

Discharge Fuscum Lake annuallyFirst discharge of TLk via north spillway : 2008 - 2009

Tailings LakeWATER TREATMENT & MANAGEMENT PLAN

WATERTRANSFER1999 – 2002

3.4 M m3 from TLk to Z2P

Diversion Ditches Construction 2001 to 2004

WATER TREATMENT OPTIONSEnhanced Natural Removal (ENR)• Preferred Option• Phosphorus Deficient• Bench Scale Tests

Pilot Plant• Alkaline Chlorination• Rotating Biological Contactor

ENR LAB BENCH TEST Oct 2001

MAP fertilizer on melting ice

Staging of MAP

MAP Addition on Zone 2 Pit

PHOSPHATE ADDED BY HELICOPTER AT BREAKUP

Zone 2.0 Pit Water Treatment & Management Strategy

Add phosphate for ENR

2002: 22 tonnes of MAP2003: 9 tonnes of MAP

If required, induce artificial circulation in 2006

Reach regulated level in 2011 Seepage to Baton 2014

Colomac Technical Advisory Committee

ENR Monitoring Program

• Physical : lake limnology(depth profiles – Temp, DO)

• Biological: algae identification, biomass and diversity

• Chemical : major ions, nutrients, metals targets: cyanide, ammonia

Challenges - TCA is filling up; water is of unacceptable quality; exposed tailings

Tailings Lake

North Station

Middle Station

TCA

Zone 2 Pit Sample Locations

Z2P-S

Z2P-NW

Pieter’s Monitoring Raft

Twice under ice

Monthly open water

0 4 8 12 16 20

0

2

4

6

8

10

12

14

Dep

th (m

)

Temperature (C)

COLOMAC Tailings Lake - All 2004 Seabird Casts

(a)


(a)


(a)


(a)


←Jul01

S

M

N

(a)


(a)


(a)


(a)


← Aug18

SM

N

(a)


(a)


(a)


← Oct06(a)

1200 1300 1400 1500 1600

0

2

4

6

8

10

12

14

Dep

th (m

)

Conductivity, C25 (μS/cm)

(b)(b)(b)(b)

← Jul01

S

M

N↓

(b)(b)(b)(b)

Aug18 →

S

MN

(b)(b)(b)

Oct06 →

(b)

05

1015

Win

d (m

/s) COLOMAC TLK-N Wind and Water Temperature 2005

Jun03 Jun23 Jul13 Aug02 Aug22 Sep11

0C 2C 4C 6C 8C 10C 12C 14C 16C 18C 20C 22C

520 540 560 580 600 620

02468

Dep

th (m

)

Jun03 Jun23 Jul13 Aug02 Aug22 Sep11

STRONG WIND

Dissolved Oxygen % vrs Depth TLK 2005

0

20

40

60

80

100

120

140

160

1.3 2.1 3.3 4.1 5.1 6.1 7 8.1 9 10.1 11.2 12 12.5

Mar18-Jun28-Jun13-Jul5-Aug27-Aug23-Sep

Physical Monitoring indicated :

• lake stratifies in summer active, warm, oxygenated epilimnioncold, anoxic hypolimnion

• strong wind can overturn or cause mixing• Mixing is important to supply P to the surface

where it is needed for SCN & NH3-N removal• lake is anoxic in winter

Biological Monitoring Component

• Physical changes in water – colour, clarity

• Algal productivity levels (biomass)• Algae identification & diversification

Algae Response to Phosphorus Addition

0

100

200

300

400

500

600

Apr-02

Jul-0

2Oct-

02Ja

n-03

Apr-03

Jul-0

3Oct-

03Ja

n-04

Apr-04

Jul-0

4Oct-

04Ja

n-05

Apr-05

Jul-0

5

chlo

ro"a

" ug

/L

0

200

400

600

800

1000

1200

OP-

P u

g/L

chloro'a'

OP-P

MAP added

Predominant algal assemblage in TLK 2003-04 (typical of wastewaters)•small flagellate and colonial Chlorophyta (top row)

•large heterotrophic flagellates (left)

Cryptophyte dominated 2005

TLK-M

ALGAL BIOMASS &

MAJOR TAXA 2004-2005

Similar biomass range Predominated by green

algae

2005 increase in flagellates (Cryptomonads)

0

5000

10000

15000

20000

25000

18-Jun 13-Jul 5-Aug 17-Aug 26-Aug 23-Sep

1m eu eu eu eu eu

bio

mas

s (u

g/L

)

DINOCRYPDIATHAPTCHRYEUGCHLORCYAN

0

5000

10000

15000

22 Jun 29 Jul 18 Aug 31 Aug

3m eu 1m 2m

bio

mas

s (u

g/L

2004

2005

TLK-M

MICROZOOPLANKTON &

HETEROTROPHS

LOWER ABUNDANCE IN 20050

250

500

750


1m eu eu eu eu eu

ug/L

HETPROTOZOA

2004

2005

TLKM

0

1000

2000

3000

4000

22 Jun 29 Jul 18 Aug 31 Aug

3m eu 1m 2m

biom

ass

(ug/

L)

First Appearance of Macrozooplankton in 2005

Daphnia pulex Cyclops vernalis

Monitoring Water Chemistry

Monthly sampling of the water column indicated:

• Trends in contaminant removal from season to season

• Greatest removal rates related to biological activity in the epilimnion(above thermocline layer)

THIOCYANATE REMOVAL in TLK

0.1

1.0

10.0

100.0

1000.0

5-Nov-01 24-May-02 10-Dec-02 28-Jun-03 14-Jan-04 1-Aug-04 17-Feb-05 5-Sep-05 24-Mar-06 10-Oct-06

Thio

cyan

ate

(mg/

L

Epilimnion Thiocyanate SCN mg/L

Hypolimnion Thiocyanate SCN mg/L

THIOCYANATE REMOVAL

SCN - + 2H2O + 5/2 O2 -> SO4-2 + HCO3

- + NH3

Biological oxidationProduces ammonia

AMMONIA REMOVAL in TLK

0.0

10.0

20.0

30.0

40.0

50.0

60.0

5-Nov-01 24-May-02 10-Dec-02 28-Jun-03 14-Jan-04 1-Aug-04 17-Feb-05 5-Sep-05 24-Mar-06 10-Oct-06

Amm

onia

-N (m

g/L

Epilimnion

Hypolimnion

5 mg/L license limit

Ammonia–N Removal : TLk Epilimnion 2002 - 2003

0

10

20

30

40

50

60

16-M

ay-02

28-Ju

n-02

26-Ju

l-02

27-A

ug-02

25-S

ep-02

07-A

pr-03

04-Ju

n-03

09-Ju

l-03

05-A

ug-03

17-S

ep-03

NH

3-N

mg/

L

0

2

4

6

8

10

12

NO

3 &

NO

2 m

g/L

NH3-NNO3-NNO2-N

AMMONIA-N REMOVAL MECHANISMS

1) DIRECT UPTAKE BY ALGAE

2) MICROBIOLOGICAL NITRIFICATION

NH4+ + 3/2 O2 -> 2H+ + H2O + NO2

-

NO2- + ½ O2 -> NO3

–

3) MICROBIOLICAL DENITRIFICATION (anoxic)Nitrate to nitrogen gas

Nutrient Recycling At Bottom 2m of TLk

0

10

20

30

40

50

60

Apr-02

Aug-02

Dec-02Apr-0

3

Aug-03

Dec-03Apr-0

4

Aug-04

Dec-04Apr-0

5

Aug-05

Dec-05Apr-0

6

mg/

L N

H4-

N

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

mg/

L TP

Ave NH3-N

Ave TP-P

Sedi trap Recovery

SEDIMENT TRAP RESULTS

Nutrient Removal From Sedimentation in TLk

0

5

10

15

20

25

30

Tot-N Tot-P VSS (%)

Tonn

es

2004 2005

Removal Of Total Phosphorus - TLk

0

0.1

0.2

0.3

0.4

0.5

0.6

Jul-0

1Oct-

01Apr-

02Sep

-02Apr-

03Sep

-03Feb

-04Apr-

04Sep

-04Mar-

05Sep

-05Mar-

06Sep

-06

TP mg/Llicence20080.22

MAP additions

Removal Of Total Metals - TLk

0

10

20

30

40

50

60

70

Oct-01

Apr-02

Sep-02

Apr-03

Sep-03

Feb-04

Apr-04

Sep-04

Mar-05

Sep-05

Mar-06

Sep-06

TCu ug/LTAs ug/L

Cu 10

As 40

Tailings Lake Discharge to North Wetlands

Discharge channel

L Shaped Lake

SUMMARY FOR TAILINGS LAKE• ENR with P addition + Water Management

was an cost effective and low risk treatment

• Water Quality of Tailings Lake has improvedto within licence limits established for discharge in 2008/09

NEXT STEPS for TLk

• Continue to monitor ENR process until discharge in 2008/09

• If necessary, supply depleted phosphorus to active algae layer from lake bottom with a pumping system

• Modify the Tailings Lake discharge wetland to optimize wetland treatment and attenuation

Zone 2 Pit - OVERVIEW

ENR processZone 2 Pit morphology and limnologyArtificial circulation optionDesign of Zone 2 Pit destratification system Preliminary resultsNext steps

COMPARISON OF TREATED LAKES

Active layeractive layer

12 m deep

4 M m3 volume

105 m deep7.9 M m3 volume

75 % 20 %

Tailings Lake Zone 2 Pit

TLk mixes completely

Z2Pit does not mix

SURFACE BLOOM IN ZONE 2 PIT

Z2P-N

ALGAL BIOMASS & MAJOR TAXA 2004 -05

Greenalgae

flagellates(Dinophyta)

0

25000

50000


1m eu eu eu eu eu

biom

ass

(ug/

L)

DINO

CRYP

DIAT

HAP

CHRY

EUG

CHLOR

CYAN

0

5000

10000

15000

22 Jun 29 Jul 18 Aug 31 Aug 21 Sep

bio

mas

s (u

g/L

)

1m euph 1m 2m 0-8int

ZONE 2 PIT - ISSUES

• SCN and NH3-N remain despite ENR• Z2P water elevation predicted to reach

Baton Lake level in 2011• Action required if water quality not

suitable when Z2P reaches 0.5 m within Baton Lake

Zone 2 Pit Morphology & Limnology• high depth to length ratio (15.7 ha)• occurrence of relatively saline water• lack of natural outlet (220 years retention time)• protection from prevailing winds• sampling data indicate the Pit rarely mixes below 50 m, usually ~ 22 m

• no oxygen in lower layers, high concentrations of ammonia and thiocyanate

• Under-ice circulation driven by salt freeze-out

0 5 10 15

0

20

40

60

80

100

120

Dep

th (m

)

Temperature (C)

FIGURE 1. COLOMAC Zone 2 Pit - All 2004 Seabird Casts

← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)


← Jul01←

Aug17←

Aug30←

Sep13←

Sep21←

Oct05

(a)

1000 1050 1100 1150

0

20

40

60

80

100

120

Dep

th (m

)

Conductivity, C25 (μS/cm)

← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)

Seabird uncertaintyHydrolab spec

← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


← Jul01← Aug17

& 30←

Sep13←

Sep21

← O

ct05

(b)


Depth profiles of SCN from Z2PNW Stn 2005

02468

101214161820

1 3 5 10 15 20 30 40 60 80 100

depth (m)

SCN

mg/

L

18-Jun-05

30-Jun-05

13-Jul-05

4-Aug-05

17-Aug-05

26-Aug-05

23-Sep-05

Hardware Of Artificial Circulation System

STAINLESS STEEL DIFFUSER

Diffusers set at 60 m depthBaton Lake

INSTALLATION OF DIFFUSER INTO RAFT

CHECKING FOR LEAKS IN THE HOSE SECTION JOINS

Circulation System in Zone 2 Pit

S Diffuser Raft

Pieter’s Monitoring Raft

NW Diffuser Raft

BATON LAKE

Startup – July 12 – Both Diffusers

STARTUP PLUME SOUTH DIFFUSER

22 DAYS AFTER STARTUP

Zone 2 Pit Sonar Transect

Preliminary Results

-Temperature-% Dissolved Oxygen saturation-SCN-NH3-N-N03-N

180 200 220 240 260 2803.25

3.3

3.35

3.4

3.45

3.5

T (°

C)

(a)

100m

60m

20m

Jun28 Jul18 Aug07 Aug27 Sep16 Oct06

Temperature from dataloggers stationed at Pieters Monitoring Raft 2005

T dataloggers, Pieters raft 2006 (UBC)

Temp change July 12 – 19, 2006 fromTemp dataloggers, Pieters Raft (UBC)

DO Profiles in Zone 2 Pit - 2006

0

20

40

60

80

100

120

0 20 40 60 80 100

Percent Dissolved oxygen

Dep

th (m

)

24-Mar

23-Jun

21-Jul

2-Aug

25-Aug

13-Sep

Zone 2 Pit – Thiocyanate Inventory

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

01-Sep-02 14-Jan-04 28-May-05 10-Oct-06 22-Feb-08 06-Jul-09 18-Nov-10 01-Apr-12 14-Aug-13

SCN

Inve

ntor

y (t

onne

s)

ActualPredicted

21July06, 6.4 mg/L

24Aug06, <0.5 mg/L

Apr06, 40.7 tonnes

Zone 2 Pit – Ammonia Inventory

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

200.0

01-Sep-02 14-Jan-04 28-May-05 10-Oct-06 22-Feb-08 06-Jul-09 18-Nov-10 01-Apr-12 14-Aug-13

Amm

onia

-N In

vent

ory

(tonn

e)

21Jul06, 17.2 mg/L

24Aug06, 17.5 mg/L

12 Sept06, 13.0 mg/L

Z2 Pit Results for NO3-N (mg/L)Depth (m) June

23/06July 21/06

Aug 2/06 Aug 24/06

Sept 12/06

1 0.036 0.51 6.16

10 0.040 0.56 8.2 (15)

20 0.040 0.54 7.7 (30)

40 0.042 0.57

60 0.042 0.57

80 0.64

95 0.043 0.52

NEXT STEPS for Z2P

•Review and analyze 2006 data•Conduct under ice sample program for DO and water chemistry

•Meet with ENR Scientific Advisory Committeeand decide on 2007 treatment schedule

enhanced natural removal of cyanide … · enhanced natural removal of cyanide and ammonia in...

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