Chemical fractionation of heavy metals and nutrients in sludge and waste water generated by Coca-Cola soft drink industry

Abstract

Coca-Cola soft drinks industry generates three sludge types, viz., water treatment sludge (WTS), effluent treatment plant sludge (ETPS) and filter cake sludge (FCS), and two waste waters, viz., effluent and influent. Total nitrogen (TN), phosphorus (TP), potassium (TK) and sulfur (TS) concentrations were significantly higher in ETPS than in WTS and FCS, indicating that Coca-Cola sludge is a good source of macronutrients. Among micronutrients, total iron (T-Fe) and copper (T-Cu) concentrations were significantly higher in ETPS, and total zinc (T-Zn) and manganese (T-Mn) concentrations were significantly higher in WTS compared with other sludge types. Among heavy metals, total cadmium (T-Cd) and arsenic (T-As) concentrations were significantly higher in ETPS, and total mercury (Hg) and nickel (T-Ni) concentrations were significantly higher in WTS than other sludge types. Speciation of micronutrients/heavy metals in sludge performed by using sequential extraction showed their predominance as crystalline and specifically adsorbed components. Only a small portion of each micronutrient/heavy metal was retrieved in readily exchangeable {water soluble (WS) + exchangeable (EXCH)} form. The existence of micronutrients/heavy metals in organic matter (OM) and oxide {manganese-oxide (MnOX) + amorphous iron and aluminum oxide (AMPOX) + crystalline iron and aluminum oxide (CRYOX)} bound fractions revealed very restricted release potential of sludge in soil solution.