The 45th Annual Scientific Meeting of Himpunan Ahli Geofisika Indonesia Surabaya, 12-15 October 2020
Resistivity Method and TDS Analysation for Leachate Seepage Potential Identification : A Case Study of Talangagung Dumpsite, Malang Regency,
Indonesia.
Chandra Gita Perwira1*, Ira Rizkillah Koswara1, Dipta Alfian Rinaldi1, Dr.Ir. Wiyono, M.Si.2
1 Graduated student of Geophysical Engineering, Department of Physics, Universitas Brawijaya, Jl. Veteran no. 01, Malang
2 Lecture of Geophysical Engineering, Department of Physics, Universitas Brawijaya, Jl. Veteran no. 01, Malang
Abstrack
Talangagung Dumpsite in Malang Regency applies the sanitary landfill system, which is the waste is piled up on a concave location, compacting it, and then filling it with soil. One of the bad impact is the potential leachate seepage from the waste which can pollute the environment around the Talangagung Dumpsite. The description of leachate seepage potential at the subsurface can be seen by interpreting the subsurface anomaly profile using resistivity method. The research was using geoelectrical method with dipole-dipole configuration on 5 lines with the lengths ranging form 120 m to 210 m with a distance of electrodes is 10 m. Data Processing using Res2Dinv and RockWork16 for resistivity method. Water samples were tested for Total Dissolved Suspend (TDS) and then correlated with 2D and 3D resistivity models. The result are known that line-1, line-2, line-3, and line-4 have low resistivity values indicated as leachate and leachate contaminated materials (resistivity values less than 10 Ωm), while at line-5 which is located in residential areas, there is no layers with low resistivity values, which means there is no leachate or leachate contaminated materials layer. Resistivity analysis is supported by TDS test of water samples, where on the lines that have a conductive anomaly or has a low resistivity value gets a very high TDS test value (SP-1=1983 ppm ; SP-2=1708 ppm ; SP-3=2594 ppm), on line where there is no low resistivity value, the TDS test values are low (SW-1= 271ppm ; SW-2= 370 ppm). Thus, water in SP-1, SP-2, SP-3 is not suitable for consumption because it is indicated to be contaminated by leachate. Leachate seepage spread dominantly to the north, northeast, and east part of Talangagung Dumpsite towards the Metro River. Leachate seepage that spread to the west from Talangagung Dumpsite is relatively small and has not yet reached the residential area.
Keywords: Resistivity, Leachate, Dipole-Dipole,TDS
1. Introduction
Talangagung Dumpsite is located in Kepanjen Distrcit, Malang Regency, East Java Province, Indonesia.
Talangagung Dumpsite has 2.5 hectare, it can receives 110 ton of trash for each day. Two hundred meters on the west side of the Talangagung Dumpsite is a densely residental area. Talangagung Dumpsite uses sanitary landfill system, which is the waste is piled up on a concave location, compacting it, and then filling it with soil.
However, the main problem encountered in this landfill system is the possibility of environmental pollution by leachate due to inadequate leachate drainage, especially in areas with high rainfall and high ground water levels.
Leachate is a liquid waste arising from the entry of external water into the landfill, dissolving and rinsing the material in the landfill. So that, it has a variety of inorganic pollutants and organic pollutants resulting from the biological decomposition process that can seep into the soil, it can pollute the soil or ground water which is around the landfill[1].
Leachate and leachate contaminated materials resistivity value are lower than 10 Ωm[2]. The spread of liquid contaminants in the soil associated with conductive fluid with conductive anomalies (resistivity less than 10 Ωm) indicates the accumulation of leachate seepage which can contaminate ground water around the soil[2]. Moreover, based on physical model seepage monitoring research in the laboratory by Ngadimin and Handayani (2009), succeed estimate conductive fluid (leachate) resistivity value, that is lower than 10 Ωm[3]. Table 1 shows leachate and material contaminated by leachate resistivity value.
To determine the potential for leachate seepage in the landfill area, it was using a resistivity method with dipole-dipole configuration. The resistivity method is based on the principle that the electrical potential
Figure 1 Survey Design of Resistivity Method and Sample Points of TDS
measured around the current electrode is affected by the electrical resistance of rocks or material that is below the surface[4]. So that the measured resistance value of each layer can be interpreted. Then the interpretation results are correlated with the results of Total Dissolved Suspend (TDS) measurements at several sample locations. Contaminated soil or water will have more conductive properties due to its high TDS content[2]. Good water quality requirements according to the Ministry of Health Regulations, has TDS level less than 500 ppm[6]. WHO classifies water quality based on the TDS values is shown in Table 2.
Table 1 Leachate and Leachate Contaminated Materil Resistivity Value[5]
Table 2 Water Qualification based on TDS Value[7]
2. Data and Methodology
Research are conducted at Talangagung Dumpsite in Talangagung Village, Kepanjen District, Malang Regency on April 28th – May 5th 2019. Resistivity data was measured by Resistivitymeter OYO McOhm. Total Dissolved Suspend (TDS) data was measured by TDS-3 Type HM Digital TDS Meter. The data measured and obtained in the form were data from the reading of the resistivity meter in the form of resistance values (Ω), coordinates and elevation data of the datum points, and TDS data of well water samples in the research area.
In data processing, the software used include: Google Earth Pro, Microsoft Excel, Res2DInv, and Rockworks.
Line Length of Line (m) Direction
1 120 Nort – South
2 150 East – West
3 140 North – South
4 210 North – South
5 210 North – South
Data was collected using a dipole-dipole configuration with 10 m of electrode spacing for the entire line and only done until the 16th datum (n) point, so the desired depth was obtained which is about 19 m from the measurement surface. Later in helping leachate analysis, samples of well water are needed around the measurement area. In this research, 5 samples of well water will be tested for the level of dissolved solids (TDS) in order to correlate with resistivity data in the case of leachate seepage.
The resistance value is changing to pseudo resistivity by calculated according to the geometrical factor in Microsoft Excel so that the apparent resistivity value is obtained and then converted to “.dat” data format, then
Well Coordinate
SP-1 671994.00 E – 9101990.00 S SP-2 672192.00 E – 9102085.00 S SP-3 672168.00 E – 9102255.00 S SP-4 671913.00 E – 9102172.00 S SP-5 671788.00 E – 9102161.00 S
Table 3 Line Profile Table 4 Sample Coordinate
converted into Res2DInv software, so that a 2D resistivity model is generated. The inversion data from the 2D cross section is used to create 3D resistivity model in Rockworks software. In the processing a 3D model, a solid model which is a resistivity in the form of a cube represents the path of a 2D cross section interpolated with another 2D cross section, in addition to the solid model, a volumetric resistivity model of the target is also obtained.
Figure 2 Research Flow Chart
3. Result And Discussion
3.1 Total Dissolved Solid Analysis
Total Dissolved Solid (TDS) was performed on five points of water well in the area around Talangagung Dumpsite. SP-1, SP- 2, and SP-3 are inside area of Talangagung Dumpsite, SW-1 and SW-2 are outside area of Talangagung Dumpsite (inside residential area). Table 5 shows TDS value in each location sample.
Referring to Tabel 2, SW-1 with the 271 ppm TDS value has excellent water quality rating and SW-2 with the 370 ppm TDS value has good water quaity rating.
SP-1, SP-2, and SP-3 wells with TDS values of 1983 ppm, 1708 ppm and 2594 ppm indicate unacceptable water quality. According to the regulation of the Indonesian Ministry of Health regarding drinking water quality standards, water in SW-1 and SW-2 is suitable for daily consumption, whereas water in SP-1, SP- 2, and SP-3 wells have indicated the presence of contamination of hazardous substances and is not suitable for daily consumption.
SP-1, SP-2, and SP-3 wells located at Talangagung Dumpsite approaching Metro River. So SP-1, SP-2, and Sp-3 have lower elevations than SW-1 and SW-2. The highest TDS value in SP-3 can be interpreted as the worst leachate contaminated area beacause the location is near the center of the garbage pile. From this analysis, it can be assumed that leachate spreads to the north and east of the dumpsite to the Metro River which is located in an area with a lower elevation.
Table 5 Analisa Nilai TDS
3.2 2D Cross Section Resistivity Analysis
The 2D cross section is displayed with the x-axis in the form of the length of the line and the y-axis in the form of depth below the surface. Leachate can be identified by observing the presence of layers with low resitivity values (less than 10 Ωm) or conductive layers indicated by MidnightBlue to DarkTurqoise colors.
Figure 3 is a 2D resistivity cross section of Line-1. The conductive layers or the layer who having a low resistivity value (less than 10 Ωm) are defined as layers containing or contaminated by leachate at measurement line distances from 45 m to 105 m with the depth about 2.5 m to 15 m. Material contaminated with leachate and leachate are considered leachate from the leachate shelter. Leachate shelter is near the measurement line at a distance of 50 m to 60 m. Distribution of leachate and leachate-contaminated layers spread to the north of the research area. That's because the north side of the research area has a lower elevation so that the leachate liquid flows north towards Metro river. This was confirmed by the results of the TDS analysis on SP-1, which stated that water quality was not acceptable, showed leachate contamination, and was not suitable for consumption.
Figure 3 2D Cross Section of Line 1
Figure 4 is the 2D resistivity cross section of Line-2. Conductive layers that have a resistivity value of less than 10 Ωm are interpreted as containing or leachate layers found on all measurement lines ranging from 15 m to 135 m with a depth of about 2.5 m to 15 m. Line-2 is located exactly southern of the dumpsite.
So, leachate that contaminates the soil layer is produced by buried waste. Leachate and leachate contaminated layers spread to northeast towards the Metro River. This is confirmed by the results of the TDS analysis on SP- 2 wells which shows unacceptable water quality, indicate leachate contamination, and are not suitable for consumption.
Figure 4 2D Cross Section of Line 2
Figure 5 is the 2D cross section of Line-3. Line-3 is located at the west part of Talangagung Dumpsite.
Figure 5 shows that in the 2D resistivity cross section there are leachate and leachate contaminated layers in the entire distance of the measurement line with depths range from 2 m to 17 m. Leachate on the 2D resistivity section of Line 3 looks more because the line is closest to the center of the garbage. This leachate spreads towards
the north of the research area which has a lower elevation towards the Metro River. This is supported by the results of the TDS analysis on SP-3 wells which stated that water quality was unacceptable, indicated leachate contamination, and was not suitable for consumption.
Figure 5 2D Cross Section of Line 3
Figure 6 shows a 2D cross section of Line-4. Line-4 is located at west part of Talangagung Dumpsite, which is citizen plantation. Low resistivity value are interpreted as leachate and leachate contaminated materials layer there are found at the distance 70 m to 80 m of the measurement line with a depth of about 12 m to 14 m.
Leachate and leachate contaminated material layer is estimated to occur due to leachate seepage originating from the dumping site on Line 3, which is located at the east of Line 4. Leachate and leachate contaminated layer on Line 4 look very little compared to Line 1, Line 2, and Line 3. That is because in Line 4 there are areas that have higher elevations compared to Line 1, Line 2, and Line 3.
Figure 6 2D Cross Section of Line 4
Figure 7 is a 2D resistivity cross section of Line-5. Line-5 is located on the western side of the research area which is a residential area. In the 2D resistivity cross section there are no conductive anomalies (low resistivity values). This is allegedly because the area in Line-5 has the highest elevation compared to other lines, so that leachate cannot spread or flow towards the area around Line-5. This is supported by the results of TDS analysis on SW-1 wells and SW-2 which states that water quality is very good and is not indicated to be contaminated with leachate.
Figure 7 2D Cross Section of Line 5
Figure 8 shows that the low resistivity values interpreted as leachate and leachate-contaminated layers are on the north, northeast and east sides of the Talangagung Dumpsite. The model is compatible with the results of the TDS well water test. Samples taken on the north side of the research area (SP-3) have very high TDS values. The distribution of the low resistivity value goes to areas that have lower elevation that is towards the Metro River.
Figure 9 is a volumetric model of low resistivity values filtered from 3D solid resistivity models that have been obtained previously. From the volumetric model it can be seen that the distribution of low resistivity values tends towards the north, northeast, and east of the research area. From the volumetric model it can also be calculated the volume of leachate and leachate contaminated materails layers (low resistivity values). The volume is around 195,730 m3.
Figure 8 3D Resistivity Solid Model Figure 9 Volumetric Model
3. Conclusion
Based on 2D and 3D resistivity cross-section, it is known that line-1, line-2, line-3, and line-4 have low resistivity values indicated as leachate and leachate contamination (less than 10 Ωm). While at line-5 which is located in residential areas, there is no low resistivity layers. Resistivity analysis is supported by TDS test of water samples, where on the lines that have low resistivity values get a very high TDS test value ((SP-1=1983 ppm ; SP-2=1708 ppm ; SP-3=2594 ppm), on line where there is no low resistivity value, the TDS test value is low ((SW-1= 271ppm ; SW-2= 370 ppm). Thus, water in SP-1, SP-2, SP-3 is not suitable for consumption because it is indicated to be contaminated with leachate. Leachate seepage spread dominantly to the north, northeast, and east part of Talangagung Dumpsite towards the Metro River. Leachate seepage that spread to the west from Talangagung Dumpsite is relatively small and has not yet reached the residential area.
Acknowledgements
In arranging this paper, many people have provided motivation, advice, and support the writer. We would like to say thankyou to Geophysical Engineering Departement of Brawijaya University, Dr. Ir. Wiyono, M.Sc. and Mr. Didik Yudianto, M.Sc. and also to all members of the Geophysical Engineering Academic Community, University of Brawijaya Malang.
References
[1] Damanhuri, E. 2008. Diktat: Landfilling Limbah. BandungInstitut Teknologi Bandung.
[2] Grandis, H.dan Yudistira, T. 2003. Pencitraan Konduktivitas Bawah-Permukaan dan Aplikasinya Untuk Identifikasi Penyebaran Kontaminan Cair. Bandung: Geoforum HAGI Bandung.
[3] Ngadimin dan Handayani, G. 2009. Aplikasi Metode Geolistrik Untuk Alat Monitoring Rembesan Limbah (Penelitian Model Fisik di Laboratorium). Jurnal Matematika & Sains 2 (6), pp. 43-53.
[4] Milsom, J. and Eriksen, A., 2011. Field Geophysics: Fourth Edition. New Delhi: A John Wiley and Sons, Ltd.
[5] Adeoti, L., Oladele, S.and Ogunlana F.O. 2011. Geo-electrical Investigation of Leachate Impact on Groundwater: A Case Study of Ile-Epo Dumpsite, Lagos, Nigeria. Journal of Applied Sciences and Environmental Management. 15 (2), pp. 361-364.
[6] Kementerian Kesehatan Republik Indonesia. 2010. Peraturan Menteri Kesehatan: Persyaratan Kualitas Air Minum. Jakarta: Kemenkes.
[7] World Health Organizattions. 2003. Total Dissolved Solid in Drinking Water. Geneva: WHO.
