Recently, numerous methods have been made to improvedewaterability of and remove heavy metals from sewagesludge. Various pretreatment approaches including ultra-sonic (Na et al. 2007), thermal hydrolysis (Neyens andBaeyens 2003), microwave (Yu et al. 2009), and chemicalconditioning such as adding FeCl3 into sewage sludge(Krishnamurthy and Viraraghavan 2005) have been used toimprove dewaterability of sewage sludge. Other attemptssuch as chelating (Mosekiemang and Dikinya 2012), ionexchange (Elektorowicz and Muslat 2008) and usingorganic or inorganic acids (Naoum et al. 2001) have beendevoted to extracting heavy metals from sewage sludge.However, high consumption of energy or chemicals, oper-ational difficulties and organic matter loss restrict theirpractical application (Kumar and Nagendran 2008; Liuet al. 2012b). Fortunately, bioleaching can mobilize metalsfrom ores or tailings (Liu et al. 2007; Baba et al. 2011). Itwas also applied to leach metals from waste electronicproducts (Xiang et al. 2010), fly ashes (Carranza et al.2009), and even from soils, sediments and sludge (Xianget al. 2000; Chen and Lin 2001; Kumar and Nagendran2007). The process enables heavy metals to be leached outfrom solid to liquid either directly by acidophilic bacteria orindirectly by the products of metabolism (Chen and Lin2004). After bioleaching, the concentration and sedimen-tation of sludge could be accelerated since the surfaceelectrochemical properties of sludge particles were changed(Li et al. 2008).
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