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Clays as natural geological barriers below landfills

Authors:

Abstract

Landfills produce a toxic, dark and smelly liquid that can pollute the surrounding areas; representing a groundwater risk. For that reason, landfill barriers that stop the migration of leachate pollutants are required. Compacted clays are normally used for the attenuation of landfill leachates. However, clays suffer from volume changes due to hydration (engineering problems). If mixing clays with non-hazardous industrial process residues, one could (1) stabilize clayey barriers, (2) improve the attenuation of landfill leachates, (3) save natural resources and (4) add value to a product with currently no market value. Here, the characterization of four natural clays is discussed to choose the ones to be mixed with non-hazardous recycled additives.
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Clays as natural geological barriers below landfills
Mercedes Regadío, Steven F. Thornton
Groundwater Protection and Restoration Group, Dept Civil and Structural Engineering
The University of Sheffield (TUOS)
What we do (overview of the project)
The project HARM is about recycling non-hazardous industrial process residues as materials to build affordable landfill barriers. Landfills produce a toxic, dark and smelly liquid that can
pollute the surrounding areas; representing a groundwater risk. For that reason, landfill barriers that stop the migration of leachate pollutants are required. If mixing clays with industrial
process residues, one could stabilize clayey barriers and improve the attenuation of landfill leachates. The most appropriate mixture will be selected after modelling leachate pollution
transport over 100 yrs. For that, two reactive transport models will be used: a geotechnical centrifuge (experimental model) and a numerical software (theoretical model).
For the first time, the retention of leachate pollutants will be studied under long-term and real conditions.
Outcomes will provide an effective and environmentally sustainable basis to control landfill pollution risks and ensure environmental protection, especially in low-income countries.
Clays suffer from volume changes due to hydration (engineering problems).
If mixing clays with non-hazardous industrial process residues:
stabilize clayey barriers and improve the attenuation of landfill leachates
save natural resources
add value to a product with currently no market value
Objective: Characterization of natural clays
that will be mixed with non-hazardous recycled additives
MATERIALS and METHODS
1. London clay
2. Oxford clay
3. Bradford clay (shallow section)
4. Bradford clay (deep section)
In situ moisture content: 1, 2> 3, 4
(10% vs. 20% wet basis)
Elemental composition (incl. CSHN)
Mineralogy (powder XRD and oriented XRD)
External SSE and porous volume (BET/BJH)
Pore water: pH, EC, Eh, soluble ions (> gypsum, > carbonate), alk, WSOC/WSIC
Exchangeable cations and CEC (pH dependent)
Geotechnical tests: Atterberg limits, OMC for compaction at MDD, permeability
RESULTS and DISCUSSION (clay specific)
HOMOGENIZATION. First challenge: breaking down 250 kg clay: contacted >24 companies/institutions, but high cost, or absence of adequate equipment for such small
quantities (when they work per tonne), or such big quantities (when they work per gram), or a long waiting list (min. four months).
Option adopted: Soil Grinder Humboldt Co: light and small (11.3 kg and 46 x 36 x 30 cm). £1,218
1) Several methods
2) Overestimation of Ex_Ca2+ and CEC because of dissolution of mineral phases (gypsum Ca(SO4)22H2O, portlandite Ca(OH)2, niter KNO3) in the extracting solution
solubility gypsum with T (but other phases may dissolve?)
solubility anhydrite & gypsum with [KCl],[NaCl] and specially
[MgCl2]. But not with [CaCl2] or with small addition of NaHCO3+
0.061 M CaCl2min. Yuexia Zhang et al. 2013
cEdmeades and Clinton 1981. A simple rapid method for the aThomas, 1982. Exchangeable cations. In: Methods of Soil Analysis, second ed.,
measurement of exchangeable cations and effective cation exch- bRhoades, J.D., 1982. Cation exchange capacity. Methods of Soil analysis,
ange capacity. Communications in Soil Sc and Plant Analysis. a, b from American Society of Agronomy, Madison
Attenuation of landfill leachate pollutants in compacted clays: dilution, dispersion,
biodegradation, filtration, redox, precipitation, sorption and ionic exchange.
Low income countries (highest amount and increment rate of trash and dump
sites): cheap protective measure (vs. high-density polyethylene geomembrane).
High income countries: additional protective measure (vulnerability of engineering
barriers and availability of pollutants to diffuse through them).
Two possibilities: in-situ clay and artificially established geological barrier (Council
Directive 1999/31/EC)
BACKGROUND (clay specific)
JUSTIFICATION and OBJECTIVE
1 2 3 4
Solubility in water Solubility in
diluted acid
Solubility in high
ionic strength…
V Carbonates &
sulphites SO
32-
are insoluble in
water except of
Na, K, NH
4+
X
Sulphates are
soluble in water
and dilute acids
except
Pb, Hg,
Ba and Ca
X
All SO32-
and CaCO3
dissolve in
acidic
solution
…chloride/acetate/
nitrate solutions:
1.6 M SrCl
2, NaAc
,
NH
4Ac, Mg(NO3)2
?
ELEMENTAL ANALYSIS:
Which gives more representative results, close
to actual content, in
Aluminum Silicates?:
1. Acid digestion + ICP OES (clays difficult to
dissolve thoroughly by aqua regia or HF
plus it is a dangerous lab practice)
2.
Pulverization into a fine powder (e.g.,
micronizing mill, others?) + hand-
held XRF
External SSE & porous volume:
Grind before analyses?
Measure duplicates aand b?
Surface
BET (m2
/g)
77K, 0.05
0.3 p/p
°
1.
271.8 305.4
2.
102.0 273.8
3.
176.8 225.6
4.
267.1 385.0
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
EUROPEAN UNION
This project has received funding from the European
Union’s Horizon 2020 research and innovation
programme under grant agreement No 743880.
Plastic limit,
PL (WC%)
1.
28
2.
29
3.
22
4.
25
OMC
≈ PL ─
2 (or 3)
10 100 1000
0.00
0.01
0.02
0.03
0.04
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
Pore volume (cm³/g·Å STP)
Pore width adsorption (Å)
London - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Oxford - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Deep - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Shallow - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Microporous Mesoporous Macroporous
Ca Fe KMg SNa Ti
0
10000
20000
30000
40000
50000
60000
70000
80000 London
Oxford
Bradford sh
Bradford dp
Conc (mg/Kg)
1. LONDON
Intensity
20000
15000
10000
5000
0
2. OXFORD
20000
15000
10000
5000
0
3. BRADFORD SHALLOW
Intensity
Angle 0 4 8 12 16 20 24 28 32 36
WATER, EG, 550 deg C
Angle
4. BRADFORD DEEP
0 4 8 12 16 20 24 28 32 36
PROPERTIES: XRD:
Kieran Nash, D Schofield and the rest of
Technical Staff (TUOS), C Fannin, Soil Hill Quarries, J Cuevas and Almudena
Ortega (UAM), GPRG members
GEOTECHNICAL
Acknowledgements:
:
E-mails: m.regadio@sheffield.ac.uk,
mregadio@mregadio.com
More in: http://mregadio.com/publications/
EXCHANGEABLE CATIONS and CEC:
10 100 1000
0.00
0.01
0.02
0.03
0.04
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
Pore volume (cm³/g·Å STP)
Pore width adsorption (Å)
London - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Oxford - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Deep - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Shallow - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Microporous Mesoporous Macroporous
10 100 1000
0.00
0.01
0.02
0.03
0.04
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
Pore volume (cm³/g·Å STP)
Pore width adsorption (Å)
London - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Oxford - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Deep - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Shallow - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Microporous Mesoporous Macroporous
10 100 1000
0.00
0.01
0.02
0.03
0.04
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
Pore volume (cm³/g·Å STP)
Pore width adsorption (Å)
London - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Oxford - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Deep - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Shallow - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Microporous Mesoporous Macroporous
10 100 1000
0.00
0.01
0.02
0.03
0.04
Average pore
widthads (Å) Total pore
volume
ads (cm3
/g)
43.0 43.4 0.319 0.357
47.9 53.6 0.152 0.298
41.8 44.4 0.165 0.202
42.5 43.1 0.257 0.362
Pore volume (cm³/g·Å STP)
Pore width adsorption (Å)
London - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Oxford - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Deep - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Shallow - Average of "Pore volume (no cum)", "Pore volume (no cum)"
Microporous Mesoporous Macroporous
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