The most frequently used method for treatment and management of MSW fly ash is stabilization /solidification followed by landfilling. While new landfill site is more and more difficult to be accepted by the public, the cost of landfilling is increasing dramatically in the past few years. In addition, landfilling does present long-term heavy metals leaching problem due to the metal chlorides dissolution potential.
MSW fly ash is classified as a hazardous waste because of its heavy metals and dioxin content. Rather than stabilization and landfilling which does not resolve the consequential issues of fracturing of solidified material and leaching of undesirable contaminants, an innovative approach has been taken in this work to stabilize and convert the fly ash into high value-added materials for market use.
This process involves fly ash washing to remove the soluble salts, stabilization by mechano-chemical reaction, and thermal treatment of the stabilized material. This material can either be blended with additives to produce high-value porous ceramic products, e.g. ceramic MBR filter, or be reused as a substitute of cement product due to its pozzolanic characteristics. Wastewater recovery is another issue since many incinerators are mandated to comply with zero effluent discharge requirements. Heavy metals can be recovered by chemical precipitation, calcium can be recovered by softening technique, and the high concentration chloride solution can be recovered as hyper chloric acid for use as disinfection agents.
A multi-year research has been undertaken in partnership with Keelung Incineration Plant and ceramic MBR suppliers, aiming to commercialize the above total recovery process. The results are encouraging and will be presented in this paper for expertise sharing and opportunities exploration.