1
Interaction of Landfill Leachate with Olivine-Treated BCS: Suitability for Bottom Liner Application

Deepak Kumar Padhi1, Udit Narayan Bhoi1, Biswajit Majhi2* and Siprarani Pradhan2

1M.Tech, Odisha University of Technology and Research, Bhubaneswar, Odisha, India

2Odisha University of Technology and Research, Bhubaneswar, Odisha, India

Abstract

Leachate is defined as any contaminated liquid that is generated from water percolating through a solid waste disposal site, accumulating contaminants, and moving into subsurface areas. Landfill leachate is characterized by high organic and inorganic pollutant concentrations and is extremely toxic to the environment. Due to its high toxicity, landfill leachate is a major threat for surface water as well as ground water. Nowadays, due to the rapid growth of population and industries, disposal of solid or industrial waste is a major issue. In landfills, leachate is a liquid that enters the landfill from external sources such as rainfall, surface drainage, etc. The leachate infiltrates through the pores of the soil from surface to ground water and makes the water contaminated. Therefore, to prevent this scenario from occurring, it is necessary to modify subsurface soils as barrier materials in waste containment facilities in order to confine municipal and hazardous waste materials from the surrounding environments as well as to stop landfill leachate from seeping into the nearby hydro-geological system. In this present work, the potential of olivine-treated black cotton soil (BCS) as a bottom liner material in landfills is examined. The BCS is treated with varying olivine percentage of 10%, 20%, 30%, 35% and 40% of the soil mass. Some laboratory tests namely: Index properties, standard proctor test, Modified proctor test, unconfined compressive strength and hydraulic conductive are conducted to evaluate the geotechnical properties of BCS treated with olivine. The findings show that olivine having 35% of soil mass used for treatment of BCS give the maximum desirable results.

Keywords: Landfill, liner material, BCS, olivine geotechnical tests

1.1 Introduction

A significant soil type in India is a dark, grey color BCS (BCS). When wet, it experiences high swelling, and when dried, it experiences high shrinkage. As a result, this soil grows and becomes slick throughout the wet season and shrinks throughout the dry time of the year, resulting in serious soil fractures. The BCS contains a lot of clay. Chemically, BCSs consist of lime, iron, magnesium, alumina, and potash; however, they are free of nitrogen, phosphorus, and organic matter. It expands in volume by 20% to 30% of the original volume when pressure is applied. It is quite challenging to maintain the soil because of its swell and drying characteristics [1-4]. Any construction should undergo high stabilization because of its unique properties. BCS is a sedimentary type of soil that is present in its original location; it does not spread from that location. BCS is a result of the particular rock's wear and tear. Black soil can only occur under mild climatic conditions and with igneous or basalt rock as the parent rock. Then, as a result of the igneous rock weathering or breaking and the lava cooling and solidifying, black soil is created. It is also referred to as lava soil because it is made of lava.

Clayey soils are widely used in waste containment facilities as barrier materials to stop the seepage of landfill leachate into the nearby geological and hydrological system as well as to keep hazardous and municipal waste products out of the environment. A barrier material must have low hydraulic conductivity, sufficient strength, and high compatibility with the percolating leachate to be effective. Clayey soils typically exhibit low permeability, but they can be impacted by temperature and moisture content changes, which can cause contraction and the subsequent development of fractures [5-8]. Due to varying settlements or loads that the liner material experiences, tensile cracks may also develop. Desiccation, differential settlements, swell-shrink, or pressures can all lead to the development of cracks, which can drastically alter the clay liners' strength and increase leachate penetration via the liner structure. Based on these limitations, researchers and engineers are looking into practical methods to enhance the technical potential of naturally clayey soils that have strong features that expand and contract before being used as lining materials.

As a result, it is now widely accepted in the building of liner that natural clayey soils can be blended with various compounds to enhance their hydro-mechanical qualities, such as the byproducts, organic compounds, and synthetic substances and prevent/minimize cracking. Many studies [9-15] have looked into the usage of waste products and other byproducts to address the instability of soil liners. Several investigations have also enhanced the hydro-mechanical characteristics of soil liners through the application of various synthetic and natural materials.

To ensure that the barrier material performs as intended during field application, it is imperative to determine whether it is chemically compatible with the leachate or percolating fluid it will likely encounter. This is because the leachate's interaction with the soil can change its hydro-mechanical characteristics. After a long period of leachate percolation, a substance is deemed suitable for the leachate if it retains structural reliability and minimal hydraulic conductivity. Therefore, utilizing tap or distilled water to assess the engineering features of soil barriers is far from realistic of real-world field situations.

To reduce leachate migration in constructed landfills, [16] one has to investigate an optimization technique to assess the marine clay combined with CO2-carbonated olivine and its hydraulic conductivity. The results demonstrate that, in order to reduce leachate migration in landfills that are intended for that purpose, hydraulic conductivity of marine clay combined with CO2-carbonated olivine is measured using an optimization technique.

The response surface methodology, which was utilized to plan the trials and analyze the data, was implemented to optimize the factors that reduced the hydraulic conductivity of the clay treated with CO2-carbonated olivine.

He [17] prepared a mixture of pond ash and a sample of BCS, mixing pond ash from various sources. To determine the strength of the mix specimen, for 7 and 28 days, he conditioned a specimen of black cotton blend. He found that when soil samples were treated with 25% class C fly ash (18.98 percent of CaO), swelling pressure dropped by 75% and 79%, respectively, after 7 and 28 days of curing. They [18] examined the impact of expansive soil on its hydraulic conductivity, plasticity, compaction, swelling pressure, FSI, and swell potential. Using fly ash values of 0, 5, 10, 15, and 20% on a dry weight basis, the FSI was reduced by about 50% by adding 20% Fly Ash to the ash-blended expansive soil. They concluded that the qualities of plasticity decrease as the fly ash content increases. Expanding soils coupled with fly ash have lower hydraulic conductivity as fly ash content rises because the maximum dry unit weight rises with fly ash level. Satyanarayana (2004) [19] investigated how adding lime and fly ash might affect expansive soil's engineering characteristics. The researcher discovered that the ideal proportion combination of the elements for building roads and embankments was 70%, 26%, and 4%. He/She [20] used bentonite to create liners for water-retention and waste-containment systems, either on its own or after being altered with natural soils. The study demonstrates how the clay liner's hydraulic conductivity is affected by the coarser fraction's size. It is known that, in addition to clay concentration, the coarser fraction's size affects the liner's hydraulic conductivity at low bentonite values. The hydraulic conductivity rises with the size of the coarser fraction for a fixed percentage of clay. He [21] investigated the stabilization of expansive soils by 0-30% using fly ash from and desulpho gypsum. The mixture of expanding soil, desulpho gypsum, and fly ash had a variable quantity of lime added (0 to 8 percent). The samples were then allowed to cure for seven and twenty-eight days. It was found that as the percentage of stabilizer in the combination increased, swelling percentage decreased by roughly 23 percent and swell rate increased. With the 25% fly ash addition and 30% desulpho gypsum, the swelling percentage was further lowered throughout the curing phase. He [22] studied the effects of fly ash and rice husk ash on soil strengthening. He advised the use of 25% fly ash concentrations to reinforce the expansive subgrade soil and 15% to combine with RHA to create a layer that reduces swell. The byproduct of burning coal in thermal power plants is a sort of industrial waste known as fly ash. According to the test results, compaction and CBR characteristics have significantly improved. Furthermore, it has been discovered that flyash is a waste product ineffective for stabilizing expanding soil. They [23] studied the geotechnical characteristics of pond ash samples at the inflow and outflow points of two Indian ash pond sites. To determine the strength properties, samples of both compacted and loose pond ash were subjected to triaxial tests (consolidated drained, and consolidated undrained) with...