Chapter Three - Heavy Metals and Recycling of Bottom Ash

Abstract

Determination methods and contents of total heavy metals, speciation analysis, heavy metals contents in different particle sizes, leaching toxicity, acid neutralizing capacity (ANC), leaching behavior with different sizes and leaching time, environmental safety evaluation system are fully provided. Treatment of livestock wastewater using a bottom ash (BA) bioreactor is described, and the different separation pretreatment technologies of BA are presented. Fe, Al, Zn, Cu, Ba, Pb, Cr, As, Ni, Co, Be, and Hg, together with precious metals and nonferrous metals, are present in the BA. However, both HVEP and TCLP tests demonstrate that the BAs have no toxicity at different leaching conditions. Moreover, the BAs have an ANC of 1.8–2.0mol/kg and thus can resist the pH change and decrease the leachability. BAs possess a stable property and long-term safety when exposes to the environment. On the other hand, BA performs well for phosphorus removal in organic wastewater via adsorption and chemical reactions with a bioreactor which shows excellent capacity of phosphorous and COD removal. Meanwhile, nitrification for wastewater is also reliable with appropriate hydraulic load and wet–dry ratio. Moreover, different separation pretreatment technologies, such as mechanical separation, magnetic separation, crushing, wet treatment process etc. must be adopted prior to the resource recovery of BA with different intentions.