Leachate attack

It is possible to make soils more resistant to chemical attack. Many of the same methods used to lower hydraulic conductivity can stabilize materials against leachate attack, including greater compaction, an increase in overburden stress, and the mixing of additives such as lime cement or sodium silicate with the natural soil materials.25... 

Calcium bentonite, as though more permeable than sodium bentonite, has also been used for soil blends. Approximately twice as much calcium bentonite typically is needed however, to achieve a hydraulic conductivity comparable with that of sodium bentonite. One problem with using sodium bentonite, however, is its vulnerability to attack by chemicals and waste leachates, a problem that will be discussed later. 

HydroZinc A biological process for leaching zinc from heaps of zinc sulfide ore. Naturally occurring bacteria attack the ore, and the leachate is then neutralized and extracted with a solvent. The metal is produced from this liquor by electrowinning. The process was developed by Teck Cominco in British Columbia and piloted between 2000 and 2002. 

Batchwise kinetic leaching is aimed at understanding both the rate and extent of TE remobilization by changes in environmental scenarios. Moreover, this tecluiique has the potential to overcome the recognized limitation of phase overlapping of several extractants (e.g., the single and sequential extractants of SM T procedures) whenever the several pools attacked feature different kinetic behavior. Contributions of readsorption phenomena to the thermodynamic leachate results may also be discerned by evaluation of kinetic data (Bermond et al., 1998). Manual fractionation protocols based on kinetic explorations are capable of... 

L/D ratio See screw length-to-diameter ratio, leach To extract a soluble component from a mixture by the process of percolation. See percolation, leachate A contaminated liquid that drains from landfills and must be treated before entering the environment. It can contain decomposed wastes, decomposition byproducts, heavy metals, or bacteria. See geomembrane, lead 1. The distance in an axial direction from the center of an element such as a screw flight at its outside diameter to the center of the same flight. See directional property. 2. A heavy metal, Pb is hazardous to one s health if inhaled or swallowed. Its use is restricted. In plastics it is found in certain products, such as additives. Pb can be used in safe environments since it has excellent performance properties, such as resisting attack by many corrosive chemicals and is impervious to x-ray and gamma radiation. See hazard x-ray. 

To be effective in either limiting liquid ingress or egress and thus help to ensure effective leachate management, landfill liners/covers should be impermeable (or demonstrate very low permeability), durable, and resistant to chemical attack and puncture. 

It has been found that clays and soils may be damaged by ions which are present in high concentrations in leachates (Landreth 1980). Leachates with pH < 3 and pH > 11 are usually the most aggressive. When a concentrated acidic solution or leachate passes through a clayey soil, hydraulic conductivity sometimes declines but then increases later (Nasiatka et al. 1981 Peterson Gee 1986 Bowders Daniel 1987 Daniel 1993). Sandy soils mixed with small percentages of bentonite are very susceptible to attack by acids as these soon dissolve the bentonite grains. 

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