ADVANCES ON SOLIDIFICATION/STABILIZATION OF SLUDGE DISPOSAL

Abstract

Solidification/stabilization(S/S) is an effective technique to disposal sewage sludge. It adds solidifying materials to the sludge. The solidifying materials and sludge occurs a series of physical and chemical reactions. It improves the mechanical strength and stabilizes the heavy metal pollutants in the sludge and can achieve the purpose of the safe disposal of sludge and resource utilization. It is therefore of significance to develop new technology for the treatment and disposal of sludge. This paper is based on the achievements at home and abroad for the recent years in this field and summarizes the advances of several important aspects on this topic. They include the types of sludge, species of solidifying agent, main measures of solidified sludge effect, factors that affects the solidified effect and solidifying/stabilizing mechanisms. The following important knowledge can be drawn:Sludge can be classified into river/lake sludge, municipal sludge and industrial sludge by the source. Due to the big differences of the sludge composition, the corresponding disposal methods are also different. For the widely used S/S technique, the most commonly used solidification agent can be divided into two categories:inorganic and organic agents. The dominant inorganic solidifying agent includes cement, lime, and uses some industrial slag, clay as auxiliary material.the two important indexes are the unconfined compressive strength and leaching toxicity in terms of main measure indexes. The initial moisture content, curing time, and the species of solidifying agent and ratio and the pH and Eh values are the main types of factors which affects the solidifying/stabilizing effect. Solidifying agent and its products form the skeleton in the sludge. The sludge particle is cemented and its pore is filled by the physical and chemical reactions, to achieve treatment effect. Harmful substances will be enclosed in the curing body by physical package, precipitation and absorption between solidifying agent and its products, to achieve the purpose of harmless and stabilization. Finally, based on the above understanding and current research shortages in this topic, some important research topics that should be well investigated in future are proposed. They include increasing the permeability coefficient of sludge, understanding the deformation properties of the cured body, development of new technology for multiple heavy metal ions stabilization, models for simulating and predicting the dissolution and migration of heavy metal ions and development of new solidifying agent.