MEND Treatment and Sludge Management Survey

Janice Zinck and Wesley GriffithJanice Zinck and Wesley GriffithNovember 28, 2007November 28, 2007

14th Annual BC/MEND - Metal Leaching/Acid Rock Drainage Workshop

Introduction• Treatment and sludge management are two

important facets of mine site environmental control practices

• Most sites employ some form of chemical treatment to address acid drainage issues. • varies from site to site

• No single, comprehensive database containing treatment and sludge management information for mine sites

Methodology

• A questionnaire was developed • Mining companies, federal, territorial and

provincial governments were contacted• Information compiled in an interactive database• Focussed mainly on Canadian sites.

• Data on sites in the US and globally will also be collected

• The surveys were completed thoroughly. Quality of the data is generally very good.

The Survey

• The survey collected information on • Site background and history• Acidic drainage characteristics

The Survey• Type of treatment used

(e.g. basic neutralization, mechanical solid/liquid separation, high density sludge, passive treatment, others • Reagents• Costs• Solid/liquid separation • Treatment issues

The Survey• Sludge management practices (e.g. sludge

pond, with tailings or other wastes, in mine working, landfill, in pit, reprocessed, etc.• Sludge composition • Sludge management issues

Sites by Contacted by Region

0

24

68

10

1214

1618

20

BC MB NB NL NS NU

NWT

ONT

QCSAS

K YTUS/w

orld

Freq

uenc

y

Completed Surveys by Region

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

BC MB NB NL NS NU

NWT

ONT QC

SASK YTUS/w

orld

Perc

enta

ge C

ompl

eted

Type of Operation

0

5

10

15

20

25

30

35

Base Metal Coal PreciousMetal

Uranium Other

Freq

uenc

y

e.g. Sb

Operation Status

0

5

10

15

20

25

30

35

Abandoned Closed Operating

Freq

uenc

y

Average Influent pH

0123456789

10

0 10 20 30 40 50 60

Site #

pH

Neutral

Acidic

Average Flow Rate

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 10 20 30 40

Site #

Flow

Rat

e m

3/ho

ur .

Peak Flows

• Maximum flows typically 2- 4 times greater than average flows.

Courtesy of B. Price

Other Information Collected

• Mine drainage composition• Temperature, TDS, TSS, turbidity,

conductivity, Eh, acidity• Receiving environment• Expected length of treatment

• 9 months to in perpetuity

Source of Acidic/Neutral Drainage

0

5

10

15

20

25

30

35

Tailings Waste Rock Mine Workings Other

Num

ber o

f Site

s

• ~30% sites treat other waste streams with their AD/ND

Treatment Process Details

0

5

10

15

20

25

30

Basic

Neutra

lizatio

nReac

tors

Aeratio

nAcid

ificati

onPas

sive Trea

tmen

tMec

hanic

al L/S

Floccu

lation

Ferric

Sulp

hate

HDS

Membra

ne S

epara

tion

Sludge

Rec

ycle

Settlin

g Pon

ds

Other

Num

ber o

f Site

s .

Flow Equalization

• Holding/collection ponds • pH controller on lime pH

feed line • Buffer pond and water

management• Feed pumps• Pump from surge pond• Pump and level control

Capital Costs

0

5

10

15

20

25

0 5 10 15 20 25 30Site #

$ M

illio

ns

Some Planned Upgrades• Rebuild/replace clarifier and steel tank• Addition new reactor tanks• Expand and winterize facilities pending

government approval • Sludge handling improvements• Reconfiguration• Slaker replacement • Replacement with newer unit with higher flow

capacity• Spiral rakes in the clarifier• Preventive maintenance

Reagents

0

5

10

15

20

25

Nutrien

tsFe2

(SO4)3 CO2

BaCl2

NaOH

Limes

tone

Hydrat

ed

Quicklim

eSlak

ed lim

e Fr

eque

ncy

~15% Paste, 85% Slurry Slakers

Other Reagents

• Sulphuric acid• Ferric chloride• Hydrogen peroxide• Aluminum chloride hydrate sulphate

(coagulant)• Sodium Hypochlorite• Sodium metabisulfide

Flocculant

0123456

Ameriflo

c 300

Flomin

(Cie

SNS)

Golden

Wes

t 188

3A

Mag

naflo

c 101

1

Magna

floc 1

0Mag

naflo

c

Magna

floc 1

55

Magna

floc 1

56 (E

10)

Magna

floc 2

4

Magna

floc 3

38

Polyflo

c 110

3

Polyflo

c AE 11

25

Powerf

loc 30

56 SH

Super

Floc A

110

Freq

uenc

y

Dose ~ 1-6 mg/L

Solid/Liquid Separation

Solid/Liquid Separation

0

5

10

15

20

25

Thickener LamellaClarifier

VacuumFilter

GritRemoval

Sand Filter SettlingPond

Freq

uenc

y

Treatment Issues• Gypsum scaling – most common problem• Suspended solids• Lime handling and mixing• Sludge density, settling, dredging disposal • Winter related

• Metal dissolution under ice cover (ponds)• Pipeline freeze ups • Polymer mixing during winter

• Other• Algal blooms in collection ponds• Seepage water corrosive to pumps

Treatment Costs

0.00

0.50

1.00

1.50

2.00

2.50

0 5 10 15 20 25

Site #

$/m

3

Average

Operating Cost Breakdown

05

101520253035

Reage

nts

Labo

urPow

er/Utilit

iesTra

nspo

rtatio

nSlud

ge M

anag

emen

tMain

tenan

ce

Other

Aver

age

Per

cent

age

•Sampling•Roads•Analyses•Etc.

Annual Sludge Production

0

5000

10000

15000

20000

25000

0 5 10 15 20 25 30 35

Site #

Slud

ge p

rodu

ctio

n dr

y t/a

135,000 t/a

Sludge Disposal

02468

10121416

Sludge

pond

Mixed w

ith ta

ilings

On exis

ting t

ailing

s

Dredge

d slud

ge on

tailin

gs

Mine w

orking

s

With w

aste

rock

Under

water c

over

PitBac

kfille

dLa

ndfill

Reproc

esse

dSmelt

ed

Other M

ethod

(Deta

ils)

e.g. Heap leach piles

Annual Sludge Disposal Costs

0

20000

40000

60000

80000

100000

120000

0 2 4 6 8 10 12 14 16

Site #

Annu

al S

ludg

e Di

spos

al ($

/a)

Sludge Management Issues• Sludge desiccation and dusting – difficult to

manage• Some sites have limited sludge disposal capacity

and are looking at off site disposal for the future• Difficulty in dredging sludge, high disposal costs,

pH spikes in ponds • Presence of cadmium over permissible leachate

limits • Dewatering NaOH sludge

more difficult than lime based sludge

Next Steps

• Will continue to take surveys up until January 2008• All sites encouraged to participate• More international sites to be included

• Final report to be completed by March’08• Database to be updated on a regular

basis – working document

Acknowledgements

Beaver Brook Antimony Mine Inc.

Thank YouMerci

jzinck@nrcan.gc.ca