The stabilization of biosolid using fly ash and slag

Stabilization effect of organic pollutants in biosolid waste co-disposed with industrial inorganic waste was investigated in the present study. Biological sludge obtained from an industrial park wastewater treatment plant was used as a model biosolid. Fly ash of a power plant and water-quenched slag of a steel plant were used as inorganic additives in the stabilization process. Leaching tests were performed to evaluate the stabilization efficiency of the additives with various dosages under controlled curing conditions. In the isotherm experiments we found that the dissolved organic carbon (DOC) in the biosolid may be adsorbed by additives. Fly ash has a larger adsorption capacity (0.903mg-DOC/g) than slag (0.461mg-DOC/g). Experimentally fly ash and slag could retard the leaching-out of organic matters, ammonium and phosphate from biosolid and the leaching ratio decreased with increasing additive/biosolid ratio. After curing the mixture of biosolid and additives for 7 days, the leaching ratio of DOC reduced to 43% as the quantity of slag added equals to biosolid. The results indicate that fly ash and slag co-disposed with biosolids can reduce the organic pollutants release rate and make biosolids more amendable to the land application.