Geosynthetic Clay Research Articles

A mobile-immobile model for contaminant transport through GCL/AL composite liner: analytical solutions.

The current study focuses on developing alternative formulations (mobile-immobile model) of transient analytical modelling for organic contaminant transport in a composite of geosynthetic clay (GCL) and attenuation layer (AL) system. The Laplace transform method is adopted to derive the solution. The proposed analytical frameworks are validated by two set of benchmarks. The varied examples of organic contaminant transport in the composite liner are evaluated by the proposed solution to discuss the effects of soil properties, flow conditions, adsorption, and mass transfer in mobile and immobile zones on the overall transport of contaminants. Finally, an example case is presented to show the application prospect of the proposed model. The result demonstrated that mass transfer between mobile and immobile may increase the breakthrough time by a factor of 2. This indicates that heterogeneities of clay are a non-negligible part for the performance assessment of the liner system. Péclet number in GCL ([Formula: see text]) is used to investigate the relative importance of advection and diffusion mechanisms. Increasing [Formula: see text] from 0.1 to 1 can lead to an increase of the breakthrough time by a factor of 15. The analytical solutions presented here may also serve as the basic benchmark test tool for alternative numerical studies of contaminants transport in heterogeneous media.

Effects of pH and concentration on the capability of E. coli and S. epidermidis with bentonite clay as biosorbent for the removal of Copper, Nickel and Lead from polluted water

This paper discusses the effects of pH and concentration on the capability of E. coli ATCC29522 and S. epidermidis RP62A biofilm with bentonite in removing divalent copper, nickel and lead from wastewater. Batch adsorption study at laboratory scale was utilized to evaluate the potential use of bacterial biomass (E. coli ATCC29522 and S. epidermidis RP62A) aided with geosynthetic clay (bentonite) for the removal of Cu2+ , Ni2+ and Pb2+ . Results revealed that removal of Cu2+ , Ni2+ and Pb2+ by both types of organisms supported with bentonite were high in the first 4 hours of the experiment. This illustrates that the binding site on that particular time was abundant. Hence, the removal rate was evident at high concentration depicting the line adsorption equilibrium. It also revealed that S. epidermidis RP62A supported with bentonite had the highest affinity to Copper and Lead with Qm = 277.7 mg/g and 5.0075 mg/g, respectively. While E. coli ATCC 29522 had the highest affinity to Nickel (Qm= 58.82 mg/g). Hence, the sorption of Cu2+ , Ni2+ and Pb2+ onto E. coli ATCC29522 and S. epidermidis RP62A biofilm supported with bentonite clay occurred through monolayer chemisorption on the homogeneous surface of E. coli ATCC29522 and S. epidermidis RP62A biofilm with bentonite clay. Batch kinetics studies revealed that the sorption of Cu2+ , Ni2+ and Pb2+ onto E. coli ATCC29522 and S. epidermidis RP62A biofilm supported with bentonite clay was well described by a pseudo-second-order equation model of type 1 (R2 = 0.9999), which implies that chemisorption is the rate limiting step.

The System Dynamics Modeling of Geo-Synthetic Clay Landfill Liners

The effectiveness of geo-synthetic clay (GC) material as landfill liners using the system dynamics modeling approach is the focus of this paper. Study area is the Local Government Area (LGA) in Ogbomoso land of Oyo State, Nigeria. These five LGAs include the urban (Ogbomoso North and Ogbomoso South) and rural (Oriire, Ogo Oluwa and Suurulere). The properties of focus on the material were hydraulic conductivity, porosity, thickness and placement slope. A mathematical model was developed by applying the governing equations coded in Visual Basic Computer programming Language. This model was validated with field data collected on the study area. The interrelationship of the properties and the breakthrough times for GC liner was found through the STELLA 9.1.4 software application. It was discovered from this research that GC liners were more effective in urban than rural LGAs. The GC liner is therefore recommended for use as landfill liner in the urban LGAs of the study area.

System Dynamics Modeling of Dumpsite Leachate Control in Ogbomosoland, Nigeria

Leachate pollution from landfills is a major source of environmental hazard in many Nigerian municipalities and there is the need to mitigate its effects. The aim of this study is to examine the leachate pollution and determine the effectiveness of liner system in leachate management of dumpsites in Ogbomosoland. The method of modeling us ing principles of system dynamics was employed to determine the interrelationships of leachate generation components for 50 years. Causal loops indicating the linkage of population, economic status, waste generation per capita and weather conditions to wastes and leachate generation were developed. A set of state model equations for Gas Produced (Gp), Precipitation (Pt), Degradation water-loss (Wg), Leachate Quantity (LQn), were formulated. Leachate management strategies of liner systems were studied, and the effectiveness of Compacted Clay (CC), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Geosynthetic Clay (GC), Silt (SI), Sandy loam (SL), and Sand (SA) liners were examined. A user-friendly computer program for estimating leachate generation per time and breakthrough time for liners was then developed. The results showed that a direct relationship exists between leachate and Gp, Pt, Wg and LQn. Average leachate breakthrough times for the liners, in years, were CC (41.5), HDPE (14.0), LDPE (10.0), GC (1.1), SI (0.1), SL (0.01), and SA (0.00002). In conclusion, dumpsite leachate pollution was established as having negative effects on the groundwater resource. Compacted Clay liner is therefore recommended for use in curtailing its menace.