Analysis of Factors for Compacted Clay Liner Performance Considering Isothermal Adsorption

The concentration profiles and breakthrough curves of the 2 m thick compacted clay liner (CCL) given in the specification were compared, considering three different adsorption isotherms (upper convex, linear, and lower concave). In addition, the effects of transport parameters, sorption isotherms, and source concentrations on pollutant migration were analyzed. The results showed that the dimensionless breakthrough curves of different source concentrations considering the linear adsorption isotherm coincided with each other, as the partition coefficient of the linear adsorption isotherm was constant. For the lower concave isotherm, the migration of a large source concentration was slowest, because the partition coefficient of the lower concave isotherm increased with an increase in concentration. For the upper convex isotherm, the migration of a large source concentration was fastest, because the partition coefficient decreased with an increase in concentration. The effects of the nonlinear isotherms on the shape of the outflow curve were similar to the effects of a change in the hydrodynamic dispersion (Dh): the concentration front of the upper convex isotherm was narrower, which was similar to the effect of a reduction in Dh (i.e., PL), and the concentration front of the lower concave isotherm was wider and similar to the effect of an increase Dh (i.e., PL). Therefore, the diffusion and adsorption parameters were fitted separately in the study, in case the nonlinear adsorption behavior was mistakenly defined as linear adsorption.

Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

This paper presents research considering hydraulic as well as swelling and shrinkage characteristics of potential recycled fine particle materials for compacted clay liner for sustainable landfills. Five locally available clay soils mixed with 10% (by mass) of NaP1 recycled zeolite were tested. The performed analysis was based on determined plasticity, cation exchange capacity, coefficient of saturated hydraulic conductivity after compaction, several shrinkage and swelling characteristics as well as, finally, saturated hydraulic conductivity after three cycles of drying and rewetting of tested specimens and the reference samples. The obtained results showed that addition of zeolite to clay soils allowed reduction in their saturated hydraulic conductivity to meet the required threshold (≤1 × 10−9 m/s) of sealing capabilities for compacted clay liner. On the other hand, an increase in plasticity, swelling, and in several cases in shrinkage, of the clay–zeolite mixture was observed. Finally, none of the tested mixtures was able to sustain its sealing capabilities after three cycles of drying and rewetting. Thus, the studied clayey soils mixed with sustainable recycled zeolite were assessed as promising materials for compacted liner construction. However, the liner should be operated carefully to avoid extensive dissication and cracking.

Kajian daya dukung geologi rencana lokasi Tempat Pembuangan Akhir di Desa Botok, Magetan, Jawa Timur

Abstrak.Tempat Pembuangan Akhir (TPA) sampah Milangasri di Kabupaten Magetan telah mencapai daya tampung maksimum. Pemerintah Kabupaten Magetan berencana membangun TPA baru di Desa Botok. Penelitian ini bertujuan untuk melakukan kajian kelayakan daya dukung geologi rencana lokasi TPA baru. Kriteria daya dukung geologi mengacu pada SNI 03-3241-1994 tentang tata cara pemilihan lokasi TPA. Metode penelitian meliputi investigasi lapangan dan pengumpulan data sekunder. Penelitian lapangan meliputi pengamatan kondisi geologi, pemetaan topografi, survei geolistrik, pemboran inti dan uji permeabilitas lapangan serta pengamatan sumber air terdekat. Data sekunder meliputi informasi yang berkaitan dengan potensi bahaya geologi. Hasil penelitian menunjukkan bahwa kelulusan batuan antara 1,26 × 10-2 hingga 1,59 × 10-2 cm/detik tidak memenuhi kriteria. Sehingga secara alami, lokasi ini kurang layak dijadikan sebagai lokasi TPA. Namun demikian, rekayasa teknologi dengan memberikan lapisan kedap air pada alas TPA seperti compacted clay liner atau geosynthetic liner menjadikan area ini layak untuk TPA. Abstract.Current landfill in Milangasri nearly reach its maximum capacity. The government of Magetan regency plans to build a new landfill in Botok. This research aims to assess the land capability based on geological characteristics of the landfill location. The SNI 03-3241-1994 used as basic criteria for selecting landfill area. Research methods consist of field investigation supported by secondary data. Field investigation consist of geological observation, topography mapping, resistivity survey, core drilling and field permeability testing, and water source observation. Information of potential geological hazard collected as secondary data. The results show that the hydraulic conductivity of the quaternary deposit ranging of 1.26 × 10-2 to 1.59 × 10-2 cm/s, failed to meet the criteria. Therefore, by nature the location candidate not supported geologically as landfill location. However, application of compacted clay liner or geosynthetic liner as the base of the landfill is recommended to improve the capability.

The Breakthrough Time Analyses of Lead Ions in CCL considering Different Adsorption Isotherms

As the 2 m thick compacted clay liner with permeability coefficient of 1 × 10−7 cm/s is required in the Chinese technical specifications about landfill, the performance of this compacted clay liner was analyzed considering three different adsorption isotherms (convex, straight, and concave). The effects of source concentration, adsorption mode, and waterhead on the breakthrough curve and breakthrough time of Pb2+ were discussed. The results indicate that reducing the concentration of pollution sources is beneficial to prolonging the breakthrough time. With the waterhead of 10 m, the absolute breakthrough time, respectively, increased from 2.77 to 3.7 years (concave type isotherm), from 17.63 to 26.58 years (straight type isotherm), and from 35.43 to 59.6 years (convex type isotherm), as the source concentration decreased from 1000 mg/L to 10 mg/L. The effect of adsorption isotherm type on the performance of the barrier is very obvious: with the waterhead of 10 m, the absolute breakthrough time corresponding to the convex isotherm is more than twice that of the straight adsorption isotherm, and more than 12.8 times that of the concave isotherm. The absolute breakthrough time corresponding to 0.3 m waterhead is more than 4 times that of 10 m, and reducing the waterhead can effectively increase the breakthrough time.

Effect of competitive adsorption on the transport of multiple pollutants through a compacted clay liner

Leachate transport through municipal solid waste (MSW) landfill liners can be slowed considerably by adsorption. MSW landfill leachate contains a large variety of pollutants at very different concentrations, and there will be competitive adsorption as these pollutants are transported through the landfill’s compacted clay liner (CCL). In this study, we used batch adsorption tests and geotechnical centrifuge modelling to examine how the adsorption of pollutants commonly found in leachate changed under competitive adsorption conditions and how competitive adsorption affected the CCL breakthrough of multiple pollutants. The results showed that the adsorption of the target pollutant on clay decreased by approximately 30% when competing pollutants were added. The speed at which the pollutants were transported through a 2-m-thick CCL increased, and the breakthrough times reduced by up to 24.8%, when the competing pollutants were mixed. Competitive adsorption significantly promoted the CCL breakthrough of pollutants at low concentrations, but it had limited effect on pollutants at high concentrations.

Investigation of a decommissioned landfill barrier system containing polychlorinated biphenyl (PCB) waste after 25 years in service

The excavation and analysis of the barrier systems for four engineered containment cells, constructed from 1984 to 1987, is described. Very limited polychlorinated biphenyl (PCB) migration was observed over the 22–25 year period prior to decommissioning. PCBs were predominantly, and preferentially, retarded by the geotextiles (GTXs) and, where present, geomembranes (GMBs). The migration of PCBs in the primary compacted clay liner (CCL) during this period was limited both when used alone and with a GMB. The exhumed GMBs, from both cover and base barriers, had diffusive properties (with respect to volatile organic compounds) comparable to unaged GMBs. For cells with a CCL as the primary base barrier, the inferred PCB diffusion coefficient, De, was 1–2 × 10−10 m2/s and distribution coefficient, Kd, was 10–15 mL/g. For cells where a GMB was the primary base barrier, the inferred PCB partitioning coefficient, Sgf, was 150 000 and diffusion coefficient, Dg, was 1 × 10−14 m2/s. Modelling beyond the 25 years in service predicts no unacceptable PCB impact of the landfill on groundwater and indicates that the design of the barrier system was adequate for an indefinite period given the low service temperatures to which it was subjected. In this diffusion-governed system, small changes to the diffusive properties were found to have a large impact on migration.