Treatment and reuse of incineration bottom ash

Waste incineration based on mass-burn technology is currently the most commonly adopted method for the thermal treatment of municipal solid waste. Waste incineration further allows the recovery of energy from the waste, thereby providing significant savings with respect to environmental impacts (Fruergaard and Astrup, 2011; Vehlow, 2012, 2015). Modern municipal solid waste incinerators are typically equipped with effective flue gasecleaning systems able to comply with the stringent air emission criteria employed in most countries (European Commission, 2006). As flue gas cleaning technologies improve, allowed air emissions can be assumed to be further lowered in the future. This renders the solid residues from the incineration processes the primary emission route for many contaminants out of the incineration plants. Consequently, the overall environmental profile of a waste incineration plant is to a large extent related to the quality and management of solid residues such as bottom ashes (BAs), fly ashes (FAs), and air pollution control (APC) residues. Of these residues, BAs are generated in the largest amounts (150e300 kg t 1 of waste incinerated, with an average of 200 kg t 1) and are at the same time the residues with technical properties most suited for use. From an environmental and management point of view, it is therefore essential to optimize BA processing to reduce landfilling of the residues and enhance utilization. Over the past 2 decades, numerous studies have addressed aspects related to understanding the technical and environmental properties of incinerator BA as well as defining the suitable conditions for recycling. Investigations have focused on the leaching behavior (Meima and Comans, 1999, 1998; Meima et al., 2002; Polettini and Pomi, 2004; van Zomeren and Comans, 2004; Johnson et al., 1995; Dijkstra et al., 2006a; Freyssinet et al., 2002; Dijkstra et al., 2008), geochemical reactions (Meima and Comans, 1997; Eusden et al., 1999; Piantone et al., 2004; Astrup et al., 2006), weathering aspects (Meima and Comans, 1999, 1998; Polettini and Pomi, 2004; Freyssinet et al., 2002; Meima and Comans, 1997a; Piantone et al., 2004; Chimenos et al., 2000; Zevenbergen et al., 1996; Zevenbergen and Comans, 1994; Zevenbergen et al., 1998), upgrading and stabilization methods (Meima et al., 2002; Meima and Comans, 1998; Cheeseman et al., 2003; Bethanis, 2004; Arickx et al., 2006; van der Sloot et al., 2001; Crannell et al., 2000; Van Gerven et al., 2007), utilization options (Aberg et al., 2006; Onori et al., 2011a; Filipponi et al., 2003; Polettini et al., 2009, 2005a; Giampaolo et al., 2002; Pera et al., 1997; Pecqueur et al., 2001; Dabo et al., 2009; Olsson et al., 2006; Vegas et al., 2008; Cioffi et al., 2011; Triffault-Bouchet et al., 2005; Tang et al., 2015; Forteza et al., 2004) and pilot/full-scale experiences (Aberg et al., 2006; Dabo et al., 2009; DeWindt et al., 2011; Hjelmar et al., 2007; Franc¸ois and Pierson, 2009). Internationally, the individual investigations to some extent reflect varying concerns and priorities in individual countries, but also provide an important knowledge base for improving BA management. Worldwide, current management of BA varies to a considerable extent: In some countries ashes are primarily landfilled without treatment and in other countries the ashes are treated extensively before use in construction works. The basic characteristics and problems related to BA and its processing are, however, generally similar across countries and regions. In this sense, huge potentials for building on existing knowledge and research experiences exist with a potential to provide improved solutions for BA management and use in the future. The current chapter focuses on both state-of-the-art and innovative techniques for the treatment and reuse/recycling of incinerator BA. Based on a review of existing research, an outline of common characteristics of waste incineration BA as well as a discussion of important BA processing options with focus on effects on leaching are presented. The chapter further outlines important environmental aspects to be considered in relation to BA management and use.