use of ochre products for remediation of metal-contaminated soils and waters kate heal school of...
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Use of ochre products for remediation of metal-contaminated
soils and waters
Kate Heal
School of GeoSciences
University of [email protected]
Need for remediation of metal-contaminated waters and soils in UK
• Industrial and mining legacy• 27% assessed sites
contaminated by metals and metalloids
• EU WFD: England and Wales 2472 km rivers at risk; 2428 probably at risk
• Costs of contamination: remediation, loss of fisheries, ecosystems
Why ochre for remediation of metal-contaminated waters and soils?
• Expected to have fewer environmental side-effects than other treatment methods
• Sustainability advantage; avoidance of landfill
• Readily available from MWTPs close to sites of metal contamination
Metal removal in shaking experiments
Metal Concentration (mg l-1)
Start After 1 min After 24 hrs
Polk Minto Polk Minto
Fe 120 6.7 0.04 <LOD <LOD
Mn 65 65 4.4 6.9 0.36
Zn 22 22 0.57 0.81 0.22
Cu 4.4 4.0 <LOD <LOD 0.01
Ni 6.7 6.4 0.12 0.18 <LOD
Cd 5.9 5.2 0.03 0.12 <LOD
Cr 5.0 3.8 <LOD 0.03 <LOD
Zinc removal in columns of ochre pellets
0.0
1.0
2.0
3.0
4.0
5.0
18-May 28-May 07-Jun 17-Jun 27-Jun 07-Jul 17-Jul
Zin
c co
nce
ntr
atio
n (
mg
l-1)
Input
Output
(Kaiyang Zhang, University of Newcastle, 2004)
3 potential modes of ochre application
Mixed tank reactor and clarifier to remove metals from surface runoff
Contaminated soil
Soil amendment to reduce metal leaching at source Permeable
reactive barrier to treat leachates and groundwater
New project proposal(1) Identification of processes and rates
of metal removal by ochre
• Assess different forms of ochre• Batch and column experiments• Effect of pH• Column leaching experiments
with ochre-soil mixtures
Surface of ochre pellet after reaction with P solution
X 65
• SEM analysis
(2) Long-term stability of metals removed by ochre
• Standard landfill leaching tests of metal-rich ochre
• Field microcosm experiments with metal-rich ochre
• Forms of metals identified by sequential extraction
• Preparation of metal-rich ochre
(3) Field demonstrations
• Plant experiments– Soil metal availability– Plant health– Leachate quality
• Treatment of contaminated surface waters at former metal mining site
(4) Permeable reactive barrier
• Monitor performance– Water level– pH, Eh, DO, TDS– TOC– Potentially toxic metals– Fe2+/Fe3+, Mn2+/Mn4+,
SO42-/S-
• Construct PRB
• Choose ochre type
(5) Issues for industrial implementation
• Market research of end-user community• Decision tree: effectiveness of different forms of
ochre for site type and conditions• Ochre production costs• Maintenance costs (including ochre removal and
disposal)• Cost-benefit analysis framework for remediation
methods• Regulatory framework