TAILOR-MADE PROCESSES FOR INTEGRATED
STABILIZATION-SOLIDIFICATION OF ACID,
BASIC, ALKALINE, AND ORGANIC WASTES
Philippe Pichat, Ph.D.
Groupe CdF Chimie
Paris, France
INTRODUCTION
In some cases, it is desirable to precede the landfilling of waste by a pretreatment. Let us look at a
certain number of cases where this pretreatment is required.
Landfilling sites are far away from waste production plants and the transportation of wastes
would involve heavy energy expenditures and, consequently, an unbearable cost burden for the waste
producer. From another point of view, road transportation of liquid wastes cost approximately twice
the transportation of a solid.
The cost of landfilling is high because it requires heavy investments such as in the construction of
dams in civil engineering (particularly in the case of thixotropic sludges).
Hydrogeological and physical-chemical properties of the landfill (and its components as well)
show some variations in time and space. Several wastes can increase the permeability of clay liners [1]
or synthetic linings [2].
The hydric cycle of the landfill is such that an overflow can take place.
The waste is very toxic. Nearby, a residential area is located which uses either an aqueous
underground or a stream [3].
The composition of the waste induces solidification. The waste has a particularly high water content. Its incineration is not economically feasible. The waste has a high organic content and a high
caustic content. The use of the usual incineration equipment is not adapted because of corrosion problems or the method of incineration which is available would give off an ash causing strong lixiviation.
Biological methods, mixed composting, dispersion, spraying, land farming are not plausible because
either the waste is too toxic, its biodegradable material content is low, or the natural environment is
inadequate.
HYDRAULIC BINDERS: HISTORIC REACTIONS
Experience shows that even when wastes are said to be "solid," they may contain a rather significant percentage of water (around 30% to 95%).
How can we thicken, immobilize the water, when is a carrier of pollutant elements found later in
the ground and underground?
The constituents of hydraulic binders, silica, anhydrous silicates (C2S and C3S), and calcium
aluminates (C3 A) react upon contact with water, and, if necessary, with lime to set into calcium
silicates and hydrated calcium aluminates.
In Rome, we can see the "Cloaca Maxima" (Figure 1), a sewer built around 500 years BC, which
withstood sewage for almost 2,500 years, and, of a different nature, the elegant dome of the Pantheon
(Figure 2).
In Ostia Antica, some remnants of the old harbor can be seen; its stone has been defaced whereas
its mortar is intact.
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