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Barman, P.

Kartha, S. A.

Pradhan, B.

English

Hydraulic Engineering Repository

Conference Paper, Published VersionBarman, P.; Kartha, S. A.; Pradhan, B.Landfill Leaching: an Experimental Investigation UsingColumn ApparatusZur Verfügung gestellt in Kooperation mit/Provided in Cooperation with:Kuratorium für Forschung im Küsteningenieurwesen (KFKI)Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/109858Vorgeschlagene Zitierweise/Suggested citation:Barman, P.; Kartha, S. A.; Pradhan, B. (2010): Landfill Leaching: an ExperimentalInvestigation Using Column Apparatus. In: Sundar, V.; Srinivasan, K.; Murali, K.; Sudheer,K.P. (Hg.): ICHE 2010. Proceedings of the 9th International Conference on Hydro-Science &Engineering, August 2-5, 2010, Chennai, India. Chennai: Indian Institute of TechnologyMadras.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Landfill Leaching: An Experimental Investigation Using Column Apparatus                         LANDFILL LEACHING: AN EXPERIMENTAL INVESTIGATION USING COLUMN APPARATUS  Barman P1. Kartha S.A2. and Pradhan B3.                                              Abstract An attempt is made in this study to understand the leaching mechanisms in the landfills by detailed experimental investigation using column leach apparatus. Various combinations of soil profiles are incorporated in the column apparatus. Water at a predetermined flow rate is poured from the top and the leachate is collected from the bottom at regular time intervals. Then by use of Atomic absorption spectrometer the concentration of zinc is determined in the leachate. Parametric studies are carried out to study the effect of flow rate  and liquid –solid ratio on the leaching behaviour of soil.It has been observed that with the increase of flow rate and liquid-solid ratio  there is  an increasing  trend of leaching  behaviour.However in some cases  small deviation is also observed.  Keywords: Numerical Modeling; Advection-Diffusion; Column leaching; Leachate  INTRODUCTION For the past few years there is a growing concern over contamination of groundwater resources due to various anthropogenic sources. One of the major sources of groundwater contamination is due to leaching of hazardous chemicals from the landfill site to the underlying aquifer. The mechanism of leaching of contaminants through soil is a complex process as it involves various chemical and biological processes. During the past two decades various analytical and numerical models are made all over the world to study the mechanism of leaching. Javadi and Najjar (2007) had presented a finite element model for contaminant transport in soil which incorporates the effect of chemical reaction also. Souhail et al. (2007) had investigated the leaching behavior of mineral processing waste by column experiment and batch test.Wang et al (2008) conducted column leaching test on coal and its combustion residues in Shizuishan in China. J.Islam et al (2002) presented one dimensional reactive multicomponent landfill leachate transport model which takes into account kinetic biodegradation, kinetic precipitation –dissolution and geochemical equilibrium. Abriola and Pinder (1985) developed a model which incorporates multiphase transport and the transport of organic species. Celia and Boluloutas (1990) incorporated a new numerical solution to the solution of advection-diffusion type of problem. Li et al. (1999) developed a numerical method of contaminant transport taking into account the effect of miscible contaminant transport. Kakuri and Molenkamp (1997) developed a new model for the simulation of groundwater flow and contaminant transport through multilayered saturated soil in 1-D. Parkhurst et al (1980) presented a mathematical basis for incorporation of the    1Research Student, Department of Civil Engg. Indian Institute of Technology Guwahati, Guwahati, India, Email: pjb@iitg.ernet.in 2Assistant Professor, Department of Civil Engg, Indian Institute of Technology Guwahati, Guwahati, India, Email: kartha@iitg.ernet.in 3Assistant Professor, Department of Civil Engg. Indian Institute of Technology Guwahati, Guwahati, India, Email: bulu@iitg.ernet.in  Proceedings of ninth International Conference on Hydro-Science and Engineering (ICHE 2010), IIT Madras, Chennai, India. 2 - 5  August 2010 1255Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Landfill Leaching: An Experimental Investigation Using Column Apparatus                      equilibrium reaction in solute transport analysis. Darby and Naser (2006) had presented a comparative analysis between numerical and analytical results on nitrate leaching through unsaturated soil column. Brun et al (2002) presented a biogeochemical transport code to simulate leachate attenuation and biogeochemical processes for landfill plume. Zheng and Bennet (2002)  presented their work on contaminant transport modeling consisting  of elaborate discussion on geochemical modeling. However the exact mechanism of contaminant transport through soil is complex because of the fact that it is difficult to characterize the exact physical, chemical and biological processes which occur during the migration of contaminants through soil. Therefore, an attempt is made in this paper to understand the mechanism of landfill leaching by detailed experimental investigation by use of column leaching apparatus. The main focus of this research work is to investigate the correlation of leaching behavior of various types of soil with their compositional behavior.  THEORY  Mass transport of solute into the ground water is based on mass balance concept. The governing equation is known as advective-dispersive equation (Zheng and Bennet, 2002) ( ) 1 2 kij i s s bi j iC CR D q C q C C Ct x x xθ θ λθ λ ρ⎛ ⎞∂ ∂ ∂ ∂= − + + −⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂⎝ ⎠                                                   (1) where  R is the retardation factor which is defined as R=1kb CCρθ∂+∂                                                             C   = Dissolved concentration (ML-3)       kC  =Sorbed concentration (M M-1), a function of the dissolved concentration as defined by a              sorption isotherm.       t =  Time,    θ =  Porosity of the subsurface medium.    Dij = Hydrodynamic dispersion coefficient tensor, (L2T-1    qi = Darcy velocity( LT-1)    1λ = Reaction rate constant for the dissolved phase  2λ = Reaction rate constant for the sorbed phase. bρ = Bulk density of the porous medium (ML-3)                    Experimental Investigation:    a) Experimental set-up:  The experimental set-up is shown below: It  comprises  of  a  rectangular  hollow chamber  of  size  (0.2m x 1.75m) which is  made up of  Perspex sheet. The apparatus is placed on an iron stand.  b) Experimental procedure:  Contaminated soil samples are collected from various waste disposal sites near IIT Guwahati. In the beginning a small portion of contaminated soil filled in the top of the leaching column is taken. Following ASTM D3974-81 methods, digestion of the soil sample is done to determine the initial concentration of contaminant (zinc in this case) in the top soil. The procedure is as       1256Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Landfill Leaching: An Experimental Investigation Using Column Apparatus                                                                                                                    Fig1. Column leaching set-up  follows.  The sample is crushed if any hard aggregate is formed during drying and weighed.  Then 0.4 g each of the dried samples is taken into several 250 ml beakers. An empty beaker is also included in the analysis. Afterwards 100ml of water is added to each sample and the blank beaker. 1 ml concentrated nitric acid is added to observe the presence of carbonates. A foaming reaction indicates the presence of carbonates in the soil samples. In this case the nitric acid is added slowly to the sample. Afterwards 10 ml of concentrated HCl is added. The beakers are covered with ribbed watch glasses and then heated on a hot plate at about 95oC. Each beaker is heated in the hot plate till the solution remaining in it is 10-15ml.The contents are allowed to cool at room temperature. Afterwards this solution is filtered and diluted up to 100 ml. This diluted solution is further analysed using Atomic Absorption Spectrometry and Flame photometry to determine the concentration of the concerned contaminant that is equivalent to the initial concentration of the contaminant in the soil sample. Regular water from the water supply system is used in the column leaching apparatus. It is poured from the top and allowed to drain through the soil column. After few minutes, the leached liquid starts appearing from the bottom boundary and this is collected in the beaker. The concentration of contaminant in the leached liquid at the bottom is also determined using Atomic Absorption Spectrometry and Flame photometry.   RESULTS AND DISCUSSION:  The experiment was carried out in a 60 cm soil column. It consists of 30cm sand, 25cm red soil, and 5cm contaminated soil. The variation of concentration of zinc in the leached liquid at the bottom for different cases are given in the figures below (Figures 2, 3, 4, and 5)  0.41.750.20.3Contaminated SoilOrdinary Soil Iron PerspeShee0.4 1257Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Landfill Leaching: An Experimental Investigation Using Column Apparatus                      a)  At  flow rate 10 ml/s  b) At flow rate 100 ml/s Fig2. Concentration vs Time graph for Zinc in the leached liquid at the bottom for liquid-solid ratio 0.09                                               a) At  flow rate 58.8 ml/s                                                b)     At flow rate 125 ml/s Fig3. Concentration vs Time graph for Zinc in the leached liquid at the bottom for liquid-solid ratio 0.10    Fig 4. Concentration vs Time graph  for Zinc at flow rate 71.428ml/s and liquid-solid ratio 0.048 Fig 5. Concentration vs Time graph  for Zinc at flow rate 76.92 ml/s and liquid-solid ratio 0.064  It is observed from Fig 2 that as the flow rate is increased from 10 ml/sec to100ml/sec the concentration of zinc at the start of appearance of leach liquid at the bottom increases. This suggests that the amount of leaching may be increasing partially with the flow rate. The leaching rate may also be function of flow rate in such cases. However from Fig 3 for a different solid-liquid ratio, this relation is not witnessed. In this case the concentration increases gradually then decreases between 60minute to 100minute time interval. Afterwards it again increases. Investigations are being carried out on this behavior of soil on this aspect. On increasing both the liquid-solid ratio as well as the flow rates, the concentration patterns are plotted in Figures 4 and 1258Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Landfill Leaching: An Experimental Investigation Using Column Apparatus                      5. From these figures it is observed that as the liquid-solid ratio is increased for the same flow rate, the amount of leaching is also increased. It implies that leaching rate is directly proportional to the liquid-solid ratio in the column. This result may have significance in landfill leaching sites citing that if depth of water on the top of landfill is more, greater leaching of the contaminant takes place.  CONCLUSION:   (1) With the increase of flow rate the rate of leaching increases partially. Thus a heavy rainfall may induce more leaching in a landfill site compared to a light rainfall. (2) The effect of liquid-solid ratio is vital in the leaching behavior of soil. Liquid-Solid ratio is found to be more prominent than the flow rate in the leaching behavior of soil. Thus stagnant water above a landfill site may enhance leaching. (3)  Further experimentation is also proposed by changing the pH. Also cylindrical column apparatus are proposed for future experiment.  REFERENCES  Abriola, L.and Pinder, G.F.1985. A multiphase approach to the modeling of porous media contaminated by organic compounds. 1. Equation development, Water Resour. Res. 21(1985) 11–18. ASTM D 3974,2009. Standard Practices for Extraction of Trace Elements from Sediments. Brun, A ., Engesgaard, P.,Christensen, T.H.and Rosebjerg, D.2002.Modeling of transport  and  biogeochemical processes  in  pollution  plumes: Vegen landfill ,Denmark, Journalof hydrology 256. 228-247. Celia,M.A. and Boluloutas, E.T.1990. A general mass-conservative numerical solution for the  unsaturated flow equation, Water Resour. Res. 26 (7) 1483–1496. Darby,A.A.and Nasser,G.A.2006. Nitrate leaching through unsaturated soil columns: Comparison      between numerical and analytical solutions. Journal of Applied sciences 6(4) 735-743. Islam,J and Singhal,N ,2002.A one dimensional multicomponent landfill leachate transport model, Environmental modeling & Software 17, 531-5443.                                                      Javadi,A.A and ,Najjar,M.M, 2007.Finite element  modeling  of contaminant transport in soils including the effect of chemical reactions. Journal of Hazardous materials 143.690-701 274. Karkuri, H.M.and Molenkamp, F.1997. Analysis of advection dispersion of pollutant transport through a layered porous media, in: Proceeding of the International Conference on Geoenvironmental Engineering, Cardiff, UK, pp. 193–198. Li ,X. Cescotto, S and Thomas, H.R.1999 .Finite element method for contaminant transport in unsaturated soils. J. Hydrol. Eng. 4 (3) 265–274. Souhail R Al-Abed, Jegadeesan, G,.Purandare and Allen J.D.2008.Leaching behaviour of mineral processing waste: Comparison of batch and column investigations, Journal of Hazardous materials 153.1088-1092. Wang W, Kin., Song, D and Wang, K.2008. Column leaching of coal and its combustion residues ,Shizuishan ,China, International journal of coal geology 75. 81-87. Zheng,C.and Bennet G.D.2002.Applied Contaminant transport modeling,Wiley,Newyork p108 1259

Landfill Leaching: an Experimental Investigation Using Column Apparatus

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Landfill Leaching: an Experimental Investigation Using Column Apparatus

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