Tsuneyuki Yoshida

Mechanisms for the Aging-Induced Reduction of Lead Solubility in Scrubber Residues from Municipal Solid Waste Combustion

This manuscript elucidates the mechanisms responsible for aging-induced reduction in lead leaching from scrubber residues. Leaching tests (JLT13) were conducted on 48 types of scrubber residues and lead solubility was found to be significantly reduced independent of incinerator type or type of gas treatment method. Reaction kinetics that result in lead solubility reduction were shown to be proportional to carbon dioxide partial pressure and in many cases were limited by mass transfer to the residue. With forced gas convection through the residue and a CO2 partial pressure of 0.3%, the concentration of lead in leachate was reduced from 84 mg L-1 to < 0.5 mg L-1 in two days. Ettringite analogs (Ca6Al2(SO4)3(OH)2•26H2O) were identified by X-Ray Diffraction in the wetted scrubber residues early in the aging process; these appear to have been converted into gypsum (CaSO4•2H2O) and vaterite (CaCO3) in the aged material. All of these solid phases are believed to substitute lead into their crystal structure and evidence for this attenuation mechanism is presented.

Substance flow analysis of persistent toxic substances in the recycling process of municipal solid waste incineration residues

This study analyzes the substance flow such as heavy metals and dioxins in the process of recycling these residues containing slugs, and studies possible recycling of various residues, while making comparison with the standards for heavy metals and PCDDs/DFs regarding soil and water quality.

Heavy metal elution characteristics from municipal solid waste scrubber residue by a centrifugation method

The objective of this study is to clarify the elution characteristics of heavy metals into scrubber residue solution such as bound water and pore water. The L/S ratio of wet scrubber residue is smaller than that the L/S ratios used in elution tests such as: the one based on Notification No. 13 of the Japanese Environment Agency (Japanese official method, JLT13), the Toxicity Characteristics Leaching Procedure (U.S.A. official method) and the Availability test (Dutch official method). A centrifugation method employed to sample soil solution was adopted for use to sample two types of scrubber residue solutions, and to compare the concentrations of heavy metals in the leachates with that obtained from the JLT13 and the Availability test as well as the pH dependency test.