Abstract
The aim of this work is to compare the properties of wastewater treatment sludge stabilized after 28 days and after one year. Hydraulic binders (low-energy cement, FBC-A, FBC-A with addition of Portland cement, and FBC-A with addition of gypsum) were used for stabilization/solidification of wastewater treatment sludge. As an adsorption additive, high porous carbon black (commercial product "Chezacarb SH") has been used to reduce leaching of organic substances. Also, the effects of asphalt emulsion addition and special polymer addition were tested. These additives were tested in order to form secondary matrix in sludge stabilized by hydraulic binders and increase the ability of these binders for stabilization of sludge. Specimens with different content of sludge were prepared for each binder. The effectiveness of stabilization has been evaluated by leaching of specimens in distilled water, according to Czech standards. Conductivity, pH, and DOC (dissolved organic carbon) were determined in water leachate (DOC limit is 30 mg/l for landfill of inert waste and unlimited for landfill of non-hazardous waste). Values of pH and conductivity for the different mixtures were similar or lower after one year than after 28 days. This is probably caused by continuing conversion of minerals in hydraulic binders. The addition of other additives, except Chezacarb SH, did not lead to significant improvement after 28 days. The values of DOC were higher after one year than after 28 days. However, it is possible to observe increasing effect of additives on the efficiency of waste water treatment sludge stabilization by means of fluidized bed combustion fly ash.
