bio-geochemical simulation for solute transport...

J. SE Asian Appl. Geol., Jan–Jun 2011, Vol. 3(1), pp. 1-11

BIO-GEOCHEMICAL SIMULATION FOR SOLUTETRANSPORT IN PIYUNGAN LANDFILL,YOGYAKARTA SPECIAL PROVINCE,INDONESIA

Keophousone Phonhalath∗1, Dwikorita Karnawati1, Heru Hendrayana1, Doni PrakasaEka Putra1, and Kenji Jinno2

1Department of Geological Engineering, Gadjah Mada University, Yogyakarta, Indonesia2Urban and Environmental Engineering Department, Faculty of Engineering, Kyushu University, Japan

Abstract

Piyungan Landfill is the largest in Bantul Regency.According to water quality sampling taken from aleachate pond, there are significant contaminant is-sues resulting from landfill leachate. The objectivesof this research were achieved by applying a two-dimensional bacteria mediated reduction numericalmodel was applied. Method of characteristic was ap-plied to solve the advection part of the solute trans-port equation. Three bacteria (X1, X2, and X3)groups were defined in the redox model. In the con-ceptual model, bacterial X1 utilizes oxygen underaerobic conditions and nitrate, NO−3 under aero-bic conditions as electron acceptors. Consequently,under aerobic conditions bacteria X2, and X3 uti-lize MnO2, and Fe(OH)3 respectively as electron ac-ceptors. In the redox model organic carbon whichwas defined as CH2O was considered as the electrondonor for all bacteria mediated reduction reactions.The results of research are to improve the under-standing of biogeochemical processes in aquifer.Keywords: landfill leachate, hydrogeological fac-tors, numerical model, redox modeling.

∗Corresponding author: KEOPHOUSONE P., Depart-ment of Geological Engineering, Faculty of Engineering,Gadjah Mada University, Jl. Grafika 2 Yogyakarta, 55281,Indonesia. E-mail: [email protected]

1 Introduction

Piyungan landfill is a dumping site of wastedisposal from human activities’ products,which has operated since 1995 and is thebiggest landfill in Bantul Regency. Day byday the wastes are increasing in Yogyakartaand dumped in Piyungan landfill that canproduce leachate (wastewater from leachate),which gives value of contaminant concentra-tion. Based on Putra et al. (2001), the researchfor two-dimensional horizontal solute trans-port had been done; the plume was extendedalong the flow which moves from southern tonorthern part (Putra, 2001).

Furthermore, the existing of sanitary land-fill still can bring a negative impact to thesurrounding environment. The problems ofgroundwater contamination from leachate leak-age always occur on the aquifer on the land-fill area. Issue of groundwater contaminationsuch as heavy metal and dissolved organic car-bon, caused by leachate leakage in PiyunganLandfill has been reported by the local commu-nities of Banyakan village (Putra et al., 2001).Banyakan village is located more or less 700 mnorthern of Piyungan landfill (Figure 1).

Beside that there are still many researchesof groundwater in Yogyakarta which are beingperformed. Some graduation papers of under-graduate and postgraduate students of Gadjah

1

KEOPHOUSONE et al.

Figure 1: Location map and tree-dimensional view of the study area (North-South)

Mada University are contributed to groundwa-ter problem in Bantul regency. Although manyresearches of groundwater had been done inthis landfill, the study about contaminant trans-port from Piyungan landfill must be continuedto give more understanding about redox reac-tion in groundwater systems.

Therefore, in order to give more understand-ing of contaminant transport from landfill, themodeling of redox from landfill will be focusedon this research works must be simulated.

2 Site condition

This study area occupies the morphology ofthe river plains of the railroad. It is the re-sult of fluvial deposition of Opak river. Thisunit spreads widely about 10.58% of the totalmapped area. As well as alluvial deposits, out-crops of this unit found along river banks ofOpak (Putra, 2001). Description and the char-acteristics of Opak fluvial deposit is as follows:spreading along the flow of Opak river, brown-

gray, clayey sand-sized further down the coarsegrain size and gravel, sorting is quite good, lay-ered with changes not clear, and below are thetuffaceous sandstones and agglomerates. Thethickness on the river bank of Opak river reachsapproximately 12-15 meters (see Figure 2).

3 Theoretical Background

Based on the research of Perera et al. (2009),the model explains the utilization of O2, NO−3 ,MnO2, Fe(OH)3 and SO2−

4 as electron accep-tors for oxidation of organic carbon in theaquifer under aerobic and anaerobic condi-tions. The conceptual model consists of threedifferent phases named as bio phase, mobilephase and matrix phase. Model parameters areadopted from literature on bacteria mediatedmulti-component modelling and bioremedia-tion processes. Monod kinetic equation is usedto formulate the bacterial growth (Perera et al.,2009). The model explains the behaviours ofaerobic and anaerobic bacteria under the avail-

2 c© 2011 Department of Geological Engineering, Gadjah Mada University

BIO-GEOCHEMICAL SIMULATION FOR SOLUTE TRANSPORT IN PIYUNGAN LANDFILL

Figure 2: Geological map of study area (re-drawn and modified from Putra, 2001)

ability of organic carbon. The redox simulationof this research focuses on the possibility of thesimulation of the formation of reduced environ-ments in groundwater aquifers which purposeto know and understand the redox reaction ingroundwater environment (Figure 3).

Bacteria group X1 uses oxygen under aero-bic conditions and NO−3 under anaerobic con-ditions as electron acceptor. Anaerobic bacterialgroups X2, X3 and X4 use MnO2, Fe(OH)3 andSO2−

4 as electron acceptors respectively (Pereraet al., 2009). Organic carbon which behaves asthe electron donor is considered as the mostimportant factor for the bacteria mediated re-duction processes (Figure 3). On the Figure 3shows the chemical species considered in the re-dox model and species exchange between dif-ferent phases. The redox model describes theinteractions between O2, NO−3 , MnO2, Fe(OH)3,SO2−

4 , organic carbon concentrations, bacterial

growth, precipitation of Fe(OH)3 in the mixingzone of the water region source.

Figure 3: Conceptualization of redox model(Perera et al., 2009)

Exchange processes considered between thedifferent model phases can be summarized as;(a) the mobile phase and the bio phase; (b) themobile phase and the matrix phase; and (c)the bio phase and the matrix phase. The re-dox model describes the biological degradationof organic carbon by different bacterial groupsand the precipitation of Fe(OH)3 and FeS (Per-era et al., 2009). Microbial mediated redox se-quences of reactions as shown in Figure 4, (aer-obic oxidation, NO−3 reduction, MnO2 reduc-tion, Fe(OH)3 reduction and SO2−

4 reduction)are modelled with four bacteria groups (X1, X2,X3, and X4).

The general form of contaminant transportequation for the mobile components in theaqueous phase with the reaction term can bewritten as follow (Perera et al., 2009):

∂Cmob∂t + u′∂Cmob

∂x + v′∂Cmob∂y =

∂∂x

(Dxx

∂Cmob∂x + Dxy

∂Cmob∂y

)+

∂∂y

(Dyy

∂Cmob∂y + Dyx

∂Cmob∂x

)+

3

∑i=1

Si

(1)

Where Cmob is the mobile phase species con-centration. u′ and v′ are the components of real

c© 2011 Department of Geological Engineering, Gadjah Mada University 3

KEOPHOUSONE et al.

Figure 4: Sequence of major biological reactions considered in the biogeochemical model (Perera etal., 2009)

pore velocities in x and y directions. Si is thesource/sink term which represents the soluteexchange between different phases.

The dispersion coefficients, dependent on thereal pore velocity, are represented as follows (inPerera et al., 2008):

Dxx = αLu′2V + αTv′2

V + τ · DM

Dyy = αTu′2V + αLu′2

V + τ · DM

Dxy = Dyx = (αL−αT)u′v′V

(2)

Where αL and αT are the microscopic disper-sion lengths related to the sand particle diame-ter, v =

√(u′2 + v′2), and DM is the fluid molec-

ular diffusion coefficient. τ is the tortuosity(Perera et al., 2008).

The source-sink term (Si) of Equation (3)describes the solute exchange between modelphases. The solute exchange driving force isthe difference between the concentrations ofthe species in different phases. The followingequations describe the solute exchange betweenmodel phases (Perera et al., 2009).

The exchange of solute between the mobilephase and the bio phase S1 is defined as:

S1 = α(1−ε0)a · θbio

√DL

θbio+θw(Cbio − Cmob)

= α′ (Cbio − Cmob)

α′ = α(1−ε0)a · θbio

√DL

θbio+θw

(3)

The exchange of solute between the mobilephase and the matrix phase S2 is defined as:

S2 = β(1−ε0)a · θmat

√DL

θmat+θw(Cmat − Cmob)

= β′ (Cmat − Cmob)

β′ = β(1−ε0)a · θbio

√DL

θbio+θw

(4)

The exchange of solute between the bio andmatrix phases S3 is defined as:

S3 = γ(1−ε0)a · θmat

√DL

θbio+θmat(Cbio − Cmat)

= α′ (Cbio − Cmat)

γ′ = γ(1−ε0)a · θbio

√DL

θbio+θw

(5)

Where Cmob, Cbio and Cmat are the concentra-tions of solute in the mobile phase, bio phaseand matrix phase respectively. α is the ex-change coefficient between bio phase and mo-bile phase. β is the exchange coefficient be-tween matrix phase and mobile phase. γ isthe exchange coefficient between bio phase andmatrix phase. α′, β′ and γ′ are the simplifiedexchange coefficients. ε0 is the initial porosity, ais the diameter of uniform soil particle and bio,mat and w are the specific volume of bio, ma-trix and mobile phases respectively. DL is thedispersion coefficient (Perera et al., 2009).

4 Methods

Finite different approximation is used to solvethe problem. The finite difference approxima-tions are derived from the fundamental defini-tion of derivative and Taylor series expansionof a function f (x). When a function f (x) and



its derivatives are single valued, finite, and con-tinuous function of x, then by Taylor’s series (inJinno et al., 2001).

The method of characteristic is one of the so-lution technique used to solve the solute trans-port in porous media. It was originally appliedby Garder et al. (1964) for calculation of miscibledisplacement in reservoir simulation

5 Results and Discussions

The some parameters to input the redox modelwere show in Keophousone et al. (2010a). Basedon Keophousone et al. (2010b), the research oftwo-dimensional groundwater flow was sim-ulated; therefore the flow modeling has beensimulated again for satisfying with parametersdata and site situation. Beside the flow simula-tion, the solute transport has been simulated ei-ther (in Keophousone et al., 2010c), and the cal-ibration of parameter were edited afterward tomake the model in reality.

The redox model was applied to the se-lected cross section under the following chem-ical species distribution which is shown in Ta-ble 1. Redox model was applied for two yearsof simulation and results are shown for bacteriagrowth, mobile phase species and matrix phasespecies along the borehole BH1 were chosen.Thus, the organic carbon supply from the ma-trix phase was kept constant and the velocityprofile was followed as done for flow simula-tion (Keophousone et al., 2010). Moreover, con-stant supplies of MnO2 are also assigned. Theorganic carbon (1.0 mg/L; Perera et al., 2009)is continuously supplied from the top soil layerwhere cocist of sandy silt. Oxygen is infiltratedfrom the ground surface at the constant con-centration of 8 mg/L with the infiltrated water(Perera et al., 2009).

On Table 1 shows the initial conditionsassigned for redox model and the assignedboundary conditions for the simulation. Theinitial bacterial concentrations for aerobic andanaerobic bacteria were kept as 0.001 mg/L.Redox model was applied for two years simula-tion and results are shown for bacteria growth,mobile phase species and matrix phase speciesalong the borehole BH1.

As shown on Figure 6 to 8, the obtainednumerical results show the formation of tworeduced zones. One reduced zone has beenformed at depths between 0.0 m and 0.7 m,and another one has been formed below 2.3 mdepth, this result can be observed by matrixphase (Figure 7). The reason for the redox zoneis obvious.

Aerobic Oxidation, Denitrification and Growthof Bacteria X1

According to Figure 6, bacteria X1 growth isdominant in the freshwater region (Figure 6)and no or less growth can be seen in the anaero-bic source region of the aquifer. The gradual de-crease of CH2O in the aerobic freshwater regionis the main reason for the decrease of bacteriaX1 growth after 30 days.

Due to the consumption of CH2O in the fresh-water region of bio phase by bacteria X1, CH2Oin the freshwater region of the matrix phaseis decreased and it is correctly simulated andshown in Figure 7. The growth of bacteria X1 inthe freshwater region is controlled by the avail-able CH2O. As a result of continuous infiltra-tion of rainwater with the 8 mg/L of O2 con-centration, there is enough O2 for bacteria X1 togrow. However, there is no constant CH2O sup-ply for the freshwater region. Therefore, whenthe available CH2O is consumed, the growthof bacteria X1 hinders. Moreover, in Figure 8,NO−3 concentration decreases gradually due tothe denitrifying (NO−3 reduce to bacteria X1)process of bacteria X1. The concentration vari-ations of O2 and NO−3 with the metabolism ofbacteria X1 imply that the redox model can sim-ulate the growth of aerobic and denitrify bacte-ria under the available CH2O appropriately.

Reduction of MnO2 and growth of bacteria X2

Formation of Mn2+ and Fe2+ could be ob-served as a result of the reduction of MnO2 andFe(OH)3 below 2.3 m. Bacteria X2 reduce MnO2to Mn2+ under anaerobic conditions. Figure 7shows the growth of MnO2 reducing bacteriaX2. The decrease of MnO2 in the matrix phase(Figure 7) corresponds well with the bacteria X2growth which is shown in Figure 6.


KEOPHOUSONE et al.

Table 1: Initial chemical species distribution for redox model

Figure 5: Initial and boundaries of chemical species distribution for redox model



Figure 6: Numerical results for aerobic and anaerobic bacterial growth (at BH1)


KEOPHOUSONE et al.

Figure 7: Numerical results for concentration variations of the matrix phase species (at BH1)



Figure 8: Numerical results for concentration variations of the mobile phase species (at BH1)


KEOPHOUSONE et al.

Figure 8 shows the concentration of formedMn2+ in mobile phase. Bacteria X2 growth issignificant in the anaerobic source region of theaquifer. Constant CH2O layer provides abun-dant electron donor environment which is fa-vorable for bacterial growth. According to Fig-ure 6 growth of bacteria X2 increases up to 2years. The reason for that is the availability ofMnO2. Bacteria X2 use available MnO2 in theorganic carbon region. Availability of CH2Oand MnO2 under anaerobic condition is favor-able for the growth of bacteria X2. Availabilityof CH2O and MnO2 in the anaerobic region arethe determining factors for bacteria X2. Redoxmodel is able to simulate the growth of bacte-ria X2 appropriately under the assigned condi-tions.

Reduction of Fe(OH)3, the growth of bacteriaX3 and precipitation of Fe(OH)3

The reduction of Fe(OH)3 occurs in the anaer-obic region due to the metabolism of bacteriaX3 in the redox model. On Figure 8 shows theformation of Fe2+ in mobile phase due to thereduction of Fe(OH)3 in the bio phase. Fig-ure 6 shows the bacteria X3 growth for tenyears while in Figure 7 shows the concentrationchanges of Fe(OH)3 in the matrix phase.

The decrease of the growth of bacteria X3 inthe constant CH2O layer is due to the consump-tion of Fe(OH)3 in the bottom of the aquifer.Therefore, bacteria X3 grows in that region untilall the Fe(OH)3 is reduced by bacteria X3. Theprecipitation of formed Fe2+ takes place in themixing zone area, where O2 is available. The re-duction of Fe(OH)3 takes place in the lower partof mixing zone and anaerobic source region ofthe aquifer at different rates according to theavailability of CH2O and Fe(OH)3. High con-centration of dissolved Fe2+ is a common wa-ter quality problem associated with groundwa-ter. Therefore, the reduction of Fe(OH)3 is animportant process to be considered in numer-ical simulations to enhance the understandingof biological involvement in groundwater.

The formed Fe2+ moves to the mixing zonewith the advective flow and meets O2 andprecipitates as Fe(OH)3. The precipitationof Fe(OH)3 is highlighted as the increase of

Fe(OH)3 concentration in the matrix zone. InFigure 7, the gradual increase of Fe(OH)3 con-centration in the mixing zone region (elevationbetween 2.1 m to 2.3 m) depicts the precip-itation of Fe(OH)3. The Fe2+ concentrationincreases around the 2.3 m elevation in themobile phase (Figure 8) is due the reductionof precipitated Fe(OH)3 in bottom edge of themixing zone.

6 Conclusions

The calculation result shows that biochemicalprocesses are important and must be taken tobe considered in groundwater quality prob-lem. The simulation results show the trendsof groundwater quality alteration such as den-itrification, MnO2 reduction and Fe(OH)3 re-duction. Therefore, due to the limitations inthe field measurements and difficulties in thebiogeochemical parameter identification, it wasimpossible to simulate the exact situation whichis prevailing in the Piyungan landfill area. Fur-ther efforts are needed to modify the redoxmodel parameters in the case where more ac-curate groundwater chemistry is needed.

Acknowledgements

This study has been supported financially byAUN/SEED-Net, JICA. The authors wouldlike to acknowledge and express their sincerethanks and appreciations to Prof. Kenji Jinno.Our gratitude is further expressed to Regencyof Bantul, Yogyakarta Special Province for theirkind supporting and kind helps during datacollection.

References

Garder, A.O., Peaceman, D.W. Jr., Pozzi, A.L. (1964).Numerical calculation of multi dimensional mis-sible displacement by the method of characteris-tics. Society of Petroleum Engineers Journal, Vol(6), pp. 175-182.

Jinno, K., Momii, K., Fujino, K., Nakagawa, K.,Hosokawa, T., Egusa, N. and Hiroshiro, Y. 2001.Numerical analysis of mass transport in thegroundwater. ISBN 4-87378-689-4. Kyushu-university publication, Japan.



Keophousone, P., Karnawati., D. Hendrayana. H.,Putra, D.P.E., and Jinno, K. (2010a), Hydrogeolog-ical factor controls on groundwater contaminantmovement from landfill leachate, Case Study:Piyungan Landfill, Yogyakarta, Central Java, In-donesia, International Symposium and The 2ndAUN/SEED-Net Regional Conference on Geo-Disaster Mitigation in ASEAN, Indonesia, pp.431-438.

Keophousone, P., Karnawati., D. Hendrayana. H.,Putra, D.P.E., and Jinno, K. (2010b), 2-D verti-cal groundwater flow simulation by using nu-merical method, Case Study: Piyungan Landfill,Yogyakarta, Indonesia, International Symposiumon a Robust and Resilient Society against Natu-ral Hazards & Environmental Disasters and theThird AUN/SEED-Net Regional Conference onGeo-Disaster Mitigation, Japan, pp. 325-334.

Keophousone, P., Karnawati., D. Hendrayana. H.,Putra, D.P.E., and Jinno, K. (2010c), Tracing ofsolute transport at Piyungan Landfill Site, Yo-gyakarta, Central Java, Indonesia, InternationalSymposium on a Robust and Resilient Societyagainst Natural Hazards & Environmental Disas-ters and the 3rd AUN/SEED-Net Regional Con-

ference on Geological Engineering Research inASEAN, Cambodia, pp 172-178.

Putra, D.P.E., Hendrayana, H., and Sukandar-rumidi. (2001), Groundwater ContaminationModeling, Case Study: Piyungan Landfill Area,D.I.Yogyakarta, 30th Annual Conference 10thRegional Congress, Yogyakarta, Indonesia.

Putra, D.P.E. (2001), Leachate Contamination onGroundwater at The Landfill and Surround-ing Area, Subresidency, Bantul Residency, Yo-gyakarta. Master thesis, Geological EngineeringDepartment, Gadjah Mada University. Unpub-lished.

Perera, E.D.P., Jinno, K., Tsutsumi, A., and Hi-roshiro, Y. (2008), Development and Verificationof a Three Dimensional Density Dependent So-lute Transport Model for Seawater Intrusion,Memoirs of the Faculty of Engineering, KyushuUniversity, Vol. 68, No.2, pp. 94-106.

Perera, E.D.P., Jinno, K., and Hosokawa, T. (2009),Simulation of Bio-geochemical processes in acoastal aquifer, Annual Journal of HydraulicEngineering, JSCE, Vol. 53.


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