Evolution of Physical and Chemical Characteristics of Municipal Solid Waste Incineration Fly Ash in China Under Ultra-Low Emission Standard

Abstract

The safe disposal of fly ash has long been the focus of global solid waste management because of the release of heavy metals. This work investigated the pH values and leaching behaviors of fly ash from 24 typical municipal solid waste incineration plants in China. The pH value of the leaching solution obtained by HJ/T 300-2007 presented two different acid and alkali characteristics, where high and low alkalinity fly ash accounted for 54.17% and 45.83%, respectively. The alkali content in fly ash increased significantly after ultra-low emission standard, increasing by 18.24% compared with before the implementation of GB 18485-2014. The leaching behavior of high alkalinity fly ash showed the illusion that they could enter the landfill only by the addition of a small amount of chelating agent or even without stabilization treatment, and its long-term landfill risk is significant. The phase change of high alkalinity fly ash and pH value change of the leaching solution after carbonation were the key factors for the leaching concentration change of heavy metals. Therefore, we suggested that the leaching characteristics of high alkalinity fly ash should be evaluated before landfill disposal, to reduce the risk of heavy metal release after entering the landfill.

Keywords: High alkalinity fly ash, accelerated carbonation, ultra-low emission standard, leaching characteristics