EMISSION CHARACTERISTICS OF HEAVY METALS AND ORGANIC POLLUTANTS FROM THE COMBUSTION OF SEWAGE SLUDGE

摘要

In this study, a bench-scale fluidized bed combustor (FBC) was used to investigate the partitioning of 9 heavymetals (Cd, Co, Cr, Cu, Mn, Ni, Pb, V, Zn) and organic hazardous air pollutants including aliphatics, monoaromaticcompounds, cyclic hydrocarbons and PAHs, in the gas and solid phases of emissions from combustion of 7 sewagesludge samples. The concentrations of heavy metals (HMs) in two main ash streams (bottom ash and fly ash) weredetected by inductively coupled plasma–optical emission spectroscopy (ICP–OES). It was found that the concentrationof zinc was the highest in bottom and fly ashes, ranging from 1600–1900 and 2200–2900 mg/kg, respectively. Theaverage concentrations of heavy metals analysed in bottom ashes followed the order of Zn > Cu > Mn > Cr >Ni > Pb >V > Cd > Co. Co and Cu were mostly found in bottom ashes while Pb and Zn in fly ashes, other HMs almost equallydistributed between bottom and fly ashes. Organic pollutants in flue gas trapped onto the XAD resin and in fly ash wereextracted with dichloromethane and analyzed using gas chromatography–mass spectrometry (GC–MS) analyzer. Theresults showed that PAHs were more likely emitted in flue gas than in fly ash, and the concentrations of PAHs both influe gas and in fly ash of sludge combustion were in a reasonably comparable range, with a maximum concentrationreached 0.03 mg/L. Aliphatics were mainly recovered from fly ashes (>70%) while monoaromatic compounds werefound in both flue gases and fly ashes, and cyclic hydrocarbons were undetectable for most of sludge samples. The totalamount of HAPs in the flue gases increased most likely with respect to the increasing H/C ratio of the sludge samples.