MEND Treatment and Sludge Management...
Transcript of MEND Treatment and Sludge Management...
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