COSMOS-rice technology abrogates the biotoxic effects of municipal solid waste incinerator residues

Bottom ash derived from municipal solid waste and sewage sludge co-incineration: First results about characterization and reuse

This paper reports a complete characterization of the lowest fractions of bottom ash derived from co-combustion of municipal solid waste with sewage sludge (COBA), with the aim to suggest suitable reuse strategies of this by-product. X-Ray Microanalysis is coupled with mineralogical characterization, based on X-Ray Diffraction and Rietveld refinement, to extract information about COBA crystalline and amorphous phases. The composition of different particle size fractions shows that amount of amorphous increases with the increase of fractions sizes. In particular, the finest COBA size fraction (<300 μm) shows more leachable heavy metals (i.e. Pb, and Zn) compared to the investigated fraction with the highest sizes (1400 µm). On the basis of their composition, lowest particle size fractions show a better hydraulic behavior compared to bottom ash obtained from incineration of only municipal solid waste, suggesting possible attractive COBA applications, as for example, Portland cement substitution. In addition, COBA with size fractions in the range of 1000-1400 μm are proposed to be used to produce glass and ceramic. Finally, due to its high amount of reactive amorphous phase (about 73% for fraction size of 1400 μm) COBA is used, in combination with other by-products (coal fly ash and flue gas desulphurization residues), to stabilize municipal solid waste incinerator fly ash produced at the same incinerator plant, following the azure chemistry principle of use a waste to stabilize another waste.

Stabilization of Municipal Solid Waste Fly Ash, Obtained by Co-Combustion with Sewage Sludge, Mixed with Bottom Ash Derived by the Same Plant

This study presents an innovative stabilization method of fly ash derived from co-combustion of municipal solid waste and sewage sludge. Bottom ash, obtained from the same process, is used as a stabilizing agent. The stabilization method involved the use of two other components—flue gas desulfurization residues and coal fly ash. Leaching tests were performed on stabilized samples, aged in a laboratory at different times. The results reveal the reduction of the concentrations of heavy metals, particularly Zn and Pb about two orders of magnitude lower with respect to fly ash. The immobilization of heavy metals on the solid material mainly depends on three factors—the amount of used ash, the concentrations of Zn and Pb in as-received fly ash and the pH of the solution of the final materials. The inert powder, obtained after the stabilization, is a new eco-material, that is promising to be used as filler in new sustainable composite materials.

Sewage sludge ash recovery as valuable raw material for chemical stabilization of leachable heavy metals

This paper proposes, for the first time, the use of sewage sludge ash (SSA), obtained by sludge combustion for the stabilization of fly ashes containing heavy metals as Pb and Zn. In particular, the proposed method aims to take advantage of valuable raw materials present in SSA, such as phosphate, silica, and alumina. The stabilization has been explained by the synergic phosphate, carbonation, and pozzolanic reactions together with the Friedel's salt formation. This method to sewage sludge management allows the complete recovery of valuable raw materials otherwise destinated for lanfill. This is virtuous example of the use of waste materials for de-pollution processes.

Municipal solid waste (MSW) incineration fly ash as an important source of heavy metal pollution in China

Incineration has overtaken landfilling as the most important option for disposal of the increasing volumes of municipal solid waste (MSW) generated in China. Accordingly, disposal of the incineration fly ash, which is enriched with a range of heavy metals, has become a key challenge for the industry. This review analyzes the temporal and spatial trends in the distributions of As, Cd, Cr, Cu, Ni, Pb, Zn, and Hg in MSW incineration fly ash between 2003 and 2017, and estimates the inventories of heavy metals associated with the fly ash and the average levels of heavy metals in Chinese MSW based on their mass flow during MSW incineration. It was estimated that MSW incinerators in China released approximately 1.12 × 10², 2.96 × 10³, 1.82 × 10², 3.64 × 10⁴, 1.00 × 10², 7.32 × 10³, 2.42 × 10², and 1.47 × 10¹ tonnes of Cd, Pb, Cr, Zn, Ni, Cu, As, and Hg, respectively, with the fly ash in 2016. Due to the much greater fly ash generation rate, the incinerators based on circulating fluidized bed combustor (CFBC) technology released more heavy metals during incineration of MSW compared to those based on grate furnace combustor (GFC) technology. Results of mass-flow modeling indicate that the geometric mean contents of Cd, Pb, Cr, Zn, Ni, Cu, As, and Hg in Chinese MSW were 3.0, 109, 101, 877, 34, 241, 21, and 1.7 mg/kg, respectively, which are comparable to those in the MSW from other countries. To protect the environment from the significant potential ecological risk posed by heavy metals in the mismanaged fly ash, strict regulation enforcement and compliance monitoring are necessary to reduce the heavy metal pollution brought by improper disposal of MSW incineration fly ash, and more research and development efforts on advanced technologies for stabilization of heavy metals in fly ash and its environmentally sound reuse can help mitigate its environmental risk.

Beyond waste: new sustainable fillers from fly ashes stabilization, obtained by low cost raw materials

A sustainable economy can be achieved only by assessing processes finalized to optimize the use of resources. Waste can be a relevant source of energy thanks to energy-from-waste processes. Concerns regarding the toxic fly ashes can be solved by transforming them into resource as recycled materials. The commitment to recycle is driven by the need to conserve natural resources, reduce imports of raw materials, save landfill space and reduce pollution. A new method to stabilize fly ash from Municipal Solid Waste Incinerator (MSWI) at room temperature has been developed thanks to COSMOS-RICE LIFE+ project (www.cosmos-rice.csmt.eu). This process is based on a chemical reaction that occurs properly mixing three waste fly ashes with rice husk ash, an agricultural by-product. COSMOS inert can replace critical raw materials (i.e. silica, fluorspar, clays, bentonite, antimony and alumina) as filler. Moreover the materials employed in the stabilization procedure may be not available in all areas. This paper investigates the possibility of substituting silica fume with corresponding condensed silica fume and to substitute flue-gas desulfurization (FGD) residues with low-cost calcium hydroxide powder. The removal of coal fly ash was also considered. The results will be presented and a possible substitution of the materials to stabilize fly ash will be discussed.