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.

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

Advances in Civil Engineering ◽

10.1155/2020/8861866 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Xing Zeng ◽

Xi Liu ◽

Yu-heng Li

Keyword(s):

Adsorption Isotherm ◽

Adsorption Isotherms ◽

Compacted Clay ◽

Breakthrough Time ◽

Clay Liner ◽

Compacted Clay Liner ◽

Adsorption Mode ◽

Technical Specifications ◽

The Absolute ◽

Source Concentration

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.

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Effect of Biocementation via Enzymatic Induced Calcium Carbonate Precipitation (EICP) on the Shear Strength of Compacted Clay Liner

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1153/1/012008 ◽

2021 ◽

Vol 1153 (1) ◽

pp. 012008

Author(s):

M U Zango ◽

K A Kassim ◽

A S Muhammed ◽

K Ahmad ◽

J Makinda

Keyword(s):

Shear Strength ◽

Calcium Carbonate ◽

Carbonate Precipitation ◽

Compacted Clay ◽

Calcium Carbonate Precipitation ◽

Clay Liner ◽

Compacted Clay Liner

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

Sustainability ◽

10.3390/su13137301 ◽

2021 ◽

Vol 13 (13) ◽

pp. 7301

Author(s):

Marcin K. Widomski ◽

Anna Musz-Pomorska ◽

Wojciech Franus

Keyword(s):

Hydraulic Conductivity ◽

Exchange Capacity ◽

Saturated Hydraulic Conductivity ◽

Clay Soils ◽

Compacted Clay ◽

Clay Liner ◽

Compacted Clay Liner ◽

Drying And Rewetting ◽

Swelling Characteristics ◽

Shrinkage And Swelling

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.

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Permeability protocol for the compacted clay liner at Metropolitan Toronto's Keele Valley Landfill

Canadian Journal of Civil Engineering ◽

10.1139/l89-085 ◽

1989 ◽

Vol 16 (4) ◽

pp. 552-559 ◽

Cited By ~ 4

Author(s):

Peter A. L. Richards ◽

Christopher D. Thompson

Keyword(s):

Quality Control ◽

Sanitary Landfill ◽

Compacted Clay ◽

Oak Ridges Moraine ◽

Preliminary Testing ◽

Clay Liner ◽

Testing Procedures ◽

Compacted Clay Liner ◽

Moisture Contents ◽

Control Procedures

The Provisional Certificate of Approval to construct a sanitary landfill for municipal waste in an old gravel pit in the Oak Ridges Moraine north of Toronto, Ontario, required that a 1.2 m thick compacted clay liner with a permeability of less than 10−8 cm/s should be placed beneath any refuse. Preliminary testing indicated that the native tills from the immediate vicinity were marginally capable of providing such a liner, as long as they were carefully selected and compacted at moisture contents just above optimum values. However, it was clear that the variability of material and (or) testing was such that some liner samples could have permeabilities greater than 10−8 cm/s. Additionally, there was concern that the sampling and testing procedures could affect the results. This paper details the trials which were carried out at the beginning of construction to establish acceptable sampling and testing techniques.These were finally determined to consist of carefully obtained Shelby tube samples, the permeability of which was tested at representative pressures in triaxial cells. The paper then presents the statistical analyses which were used to verify that the overall permeability of the liner is less than 10−8 cm/s. It also outlines other testing and instrumentation which has been undertaken to verify the liner permeability and integrity. It is concluded that, to date, the permeability testing and protocol are suitable control procedures to verify compliance with the condition of the Provisional Certificate of Approval that a liner permeability of 10−8 cm/s be achieved. Key words: clay liner, permeability, protocol, quality control, sanitary landfill, sampling, statistical analysis, testing.

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