Title: Interaction between Heavy Metals and Aerobic Granular Sludge

abstract

Metals play important roles in the life processes of microbes. Some metals, such as Fe, Zn, Cu, Ni, and Co are of vital importance for many microbial activities when occur at low concentrations. These metals are often involved in the metabolism and redox processes as parts of enzyme cofactors or participators in the electron transfer in microbial respiration (Zandvoort et al., 2006). However, metals at high concentrations are inhibitory or even toxic to living organisms. Essential metals in the enzymes can be displaced by toxic metals which have the similar structure, thus resulting in the enzymes inactivation or damage (Bruins et al., 2000). Heavy metals contaminants have posed great challenge to wastewater treatment. Large quantity of heavy metals are released from mineral rock weathering and anthropogenic sources such as metalliferous mining and smelting, electroplating, batteries, fertilizers, and pigments industries (Sirianuntapiboon & Ungkaprasatcha, 2007; Ong et al., 2005a). Due to their high toxicity and environmental recalcitrance, remediation of heavy metal is of urgent importance. Many techniques have been tried out to remove heavy metals from wastewater. Physicochemical methods, such as chemical precipitation, ion exchange, adsorption, electrolysis, chemical oxidation/reduction and membrane technologies, are found to be ineffective or rather expensive or generate toxic slurries (Liu et al., 2003; Pamukoglu & Kargi, 2006). Biological treatment is considered a promising technique for bioremediation of heavy metals wastewater, since it can degrade organic pollutant in the wastewater and simultaneously transform heavy metals.