Assessment of the response of lateritic clay component of a landfill lining system to exposure to landfill leachates BY: Mr Godwin EtonDepartment of Engineering Geology

Lateritic soils occur mostly in humid tropical climates between 30°N and 30°S latitudes. They are the product of intensive weathering that occurs under tropical and sub-tropical conditions. The are usually  rich in secondary oxides of iron, aluminium, or both.  Lateritic soils have been used traditionally as construction materials, road pavement and in earth dam embankment but its uses in landfill facilities are still very limited in application.

1.2        Overall Aim of the Project

The aim of this project is to assess the response of lateritic clay landfill lining systems from tropics, to exposure to landfill leachates and also attempt to compare the results obtained  with smectite rich clay soils of the temperate regions.

2.     DETAILED OBJECTIVE AND METHODOLOGY

2.1    Objectives

 The following set of objectives has been outlined for the project namely:

1. Identify and review the existing research in the area of landfill facilities and clay liners.
2. To obtain and analysis the composition of a natural leachate from an existing landfill site
3. To synthesis different types of leachates in the laboratory.
4. To characterise clay mineralogy of typical lateritic clay soil obtained from a site in West African tropical region and a typical smectite-rich clay soil sample from an exiting landfill site in the UK.
5. To carry out compaction tests on the two clay soils and assess their hydraulic conductivities.
6. To estimate the engineering properties of the two clay soils including their swelling potentials before and after exposure to leachates.
7. To investigate the physical and chemical changes taking place as the two clay soils are exposed to both natural and synthetic leachate and characterise the mineralogy of the two clay soils at the end of the test.
8.  To investigate the strength of the two clay soils before and after exposure to leachate interaction
9. To compare the changes that has taken place in the two clay soils at the end of the test period.
10.  To draw conclusions from the results.

2.2        Methodology:

In order to achieve the aims and objectives set out in this research the following tasks will be undertaken:

(i)        Literature search will be conducted involving review of journals, relevant text books and use of relevant web sites in order to assess the extent of work involving clay liners. Some of the literature identified so far includes but not limited to the following:

• Elliott S. and Watkins D. C., Evaluation of kaolinite-containing clay as a potential mineral liner for landfill leachate containment.  Proceedings of the Ussher Society, 9, 201 – 2004.
• Osinubi, K. J and Nwaiwu C.M.O, Design of compacted lateritic soil liners and covers. Journal of Geotechnical and Geoenvironmental Engineering. Vol 123, Issue 2, Feb. 2006, 203 – 213.
• Nwaiwu C.M.O, Osinubi, K. J and Afolayan, J. O. Statistical evaluation of the hydraulic conductivity of compacted lateritic soils. Geotechnical testing Journal. Vol 28, Issue 6, Nov. 2005, 586 – 595.
• Taha, M.R and Kibir, M.H. Tropical residual soils as compacted soil liners. Environmental Geology, Vol 47, Issue 3, Feb. 2005, 375 – 381.
• Leton, T.G and Omotosho, O. Landfill operation in the Niger Delta region of Nigeria. Engineering Geology, Vol 73, Issue 1-2, May. 2004, 171 – 177.
• Anderson, D. C., 1982. Does landfill leachates make clay liners more permeable? Civil Engineering -ASCE.  Vol 52, Issue 9, Sept, 1982, 66-69.

        Web site

http://www.pubs.asce.org

2. Natural leachate from an existing landfill will be collected on regular interval over a period of two and a half months beginning from first week of May, 2006 through second week of July, 2006. This will be analysed for pH, temperature and electrical conductivity. Each leachate sample will be filtered in the laboratory through 0.2 micron filters for analysis using ICP-AES, ion chromatography, total organic carbon and ion-specific electrode for ammonium.
3. To overcome the inhomgeneities of leachates from different sites, synthetic leachate will be prepared in laboratory. This is due to the fact that it will have a known chemical composition. This will also be used in the test to give the worst scenario as the concentration of such leachate is likely to be higher than natural leachate from site.

4. Both the lateritic clay soil  and the smectite-rich clay soil will be characterised to determine the mineralogy and the clay content using the following methods:

• X-Ray Diffraction (XRD)

This test will be used to identify and characterised the clay minerals for each of the soil samples before and after exposure to leachates. The principle is based on the diffraction of x-ray beams at it impinges on array of atoms in a mineral.

• X-Ray Fluorescence (XRF)

XRF, if available, will be used to determine the elemental oxide compositions of the clays before and after exposure to leachate.

• Scanning electron Microscopy (SEM)

Thin section of the clay soils will be made before and after exposure to leachate. These will be subjected to energy dispersion X-ray spectrometry to determine whether the leachate had affected the mineral grains of the soil samples.

• Thermogravimetric Differential Scanning Calorimetry (TG-DSC).

The purpose is to check the introduction of foreign molecular ionic material between the layers of the clay mineral (Giese, 1990). This test will be carried out to determine the presence or absence of calcite in the clay samples before and after exposure to leachate. The presence of calcite alters the engineering properties of the clay liner.

5. The lateritic clay soil and the smectite-rich clay soil will be subjected to compaction test using the BS 1377: part 4: 1990: 3.3. The main purpose of the compaction test is to impede the flow of liquids, and hence reduce hydraulic conductivity. The general requirement for a clay landfill liner is put as < 1 x 10 -9 m/s under 1m head of leachate (DOE, 1990). Hydraulic conductivity will carried out on the clay soils using BS 1377: part 6: 1990: 6.

6. The following engineering properties of clay soils are very vital for their use as landfill liner as they all affect hydraulic conductivity and will be characterised before and after the clay exposures to leachates to assess the changes that has taken place.

• Particle size distribution using the BS 1377: part 2:1990 approach.
• Natural moisture content using the BS 1377: part 2:1990: 3.2.
• Atterberg limits test using BS 1377: part 2:1990:4.3, 5.3 and 5.4.
• Soil density using BS 1377: part 2: 1990: 8).
• Swelling potential using BS 1377: part 2: 3.4.

7. About 10 – 20 g of each sample will be added to 250ml polyethene conical flasks. About 15ml of the leachate will be added to each clay sample. The addition of leachate to clay will be carried out under nitrogen, in a sealed environment to prevent oxygen from reaching the leachate. The test will be maintained at a prescribed controlled temperature. At three weeks interval, a portion of the leachate say 2ml will be removed and analysed as before. At the end of the experiment, the clay is removed from the flask, air dried and analysed as before.

8. The strength of the two clay soil samples before and after exposure to leachate interaction will be assessed in the laboratory using shear strength test by laboratory vane in accordance with BS 1377, part 2: 1975; test 18. This will be carried to assess the effect of the leachate interaction on the strength of the clay liner.

9. At the end of the test period, the result obtained from both the lateritic clay soil and the smectite-rich clay soil will be compared and the influence factors for each sample noted.

10. Final conclusions will be drawn as to the differences in the response of two clay soils to exposure to both natural and synthetic landfill leachates.

2.3        Expected conclusions

It is expected that the findings of this research will be of assistance in the design, construction and management of a landfill lining system in tropical climatic zones in which lateritic clays form over 95% of the overburden.

3.0        RISK ASSESSMENT

The following potential risks have been associated with this project are identified and appropriate mitigations taken to reduced or control them.

3.1        General Risk / Logistics Risk

        

- Continued -

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3.2        Health  Safety and Environment  Risk (HSE)

3.        Others

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4.0        WORK PROGRAMME

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5.0        REFERENCES

ACAR, Y. B., & SEALS, R. K. 1984. Clay barrier technology for shallow land waste disposal

         facilities. Hazardous waste.1, 167 – 181. 

ANDERSON, D. C., 1982. Does landfill leachates make clay liners more permeable? Civil

 Engineering -ASCE., 52, 66-69.

ANDERSON, D. C., & JONES, S.G. 1983. Clay barrier-leachate interaction. National

         Conference on Management of Uncontrolled Hazardous waste sites, Washington,

         D. C., Occtober, 31-November, 1983.

DANIEL, D. E., & LILJESTRAND, H. M. 1984. Effects of landfill leachates on natural liner

         systems.  Report by Geotechnical Engineering Centre, University of Texas.

ELLIOTT S. AND WATKINS D. C., 1997. Evaluation of kaolinite-containing clay as a potential

mineral liner for landfill leachate containment.  Proceedings of the Ussher Society,

           9, 201 – 204.

ENVIRONMENTAL AGENCY. 1999. Monitoring of lanfill sites. Guidelines on monitoring

         of landfill leachate, groundwater and surface water. Main guidelines document –

        draft for external consultation. August 1999 –version 8.

LETON, T.G., 1990. Waste management Part II (Solid wastes). In: Leton, T.T., Ed, 1990.

             Pollution Control in the Oil Industry, Short Course by PCE Unit, CORDEC, University

             of Port Harcourt, Port Harcourt, Nigeria.

LETON, T.G AND OMOTOSHO, O. 2004. Landfill operation in the Niger Delta region of

 Nigeria. Engineering Geology, 73, 171 – 177.

NWAIWU C.M.O, OSINUBI, K. J & AFOLAYAN, J. O. 2005. Statistical evaluation of

the hydraulic conductivity of compacted lateritic soils. Geotechnical testing Journal.

 28, 586 – 595.

OLA. S.A., 1983. Geotechnical properties and behaviour of some Nigerian lateritic soils.

           In   Tropical Soils of Nigeria in Engineering Practise, S. A. Ola, Ed., A.A. Balkema,

          Rotterdam, pp 61-84.

OSINUBI, K. J AND NWAIWU C.M.O, 2006. Design of compacted lateritic soil liners and

        covers. Journal of Geotechnical and Geoenvironmental Engineering. 123, 203 – 213.

QUIGLEY, R. M., FERNANDEZ, F. & ROWE, R. K. 1988.  Clay barrier assessment for

         impoundment of domestic waste leachate (southern Ontario) including clay

        leachate compatibility by hydraulic conductivity testing. Canadian Geotechnical

        Journal. 25,  574 – 581.

TAHA, M.R & KIBIR, M.H. 2005. Tropical residual soils as compacted soil liners.

 Environmental Geology, 47, 375 – 381.

YANFULL, E. K., HAUG, M. D., & WONG, L. C. 1990. The impact of a synthetic leachate on

         the hydraulic conductivity of a smectitic till underlying a landfill near Saskatoon,

         Saskatchewan. Canadian Geotechnical journal. 27,  507 – 519.

YONG, R. N & SHEREMATA, T. W., 1991. Effect of chloride ions adsorption of cadmium

          from a landfill leachate. Canadian Geotechnical Journal, 28,  378 – 387.