Effect of MSW Source-Classified Collection on Polycyclic Aromatic Hydrocarbons in Residues from Full-Scale Incineration in China

Municipal solid waste (MSW) source-classified collection represents an advancement in resource recycling and secondary pollution control in China. Comparative experiments were performed to assess the effect of a newly-established MSW source-classified collection system on polycyclic aromatic hydrocarbons (PAHs) in bottom ash from an incinerator (BA), fly ash from a boiler (FAB) and fly ash from a bag filter (FABF) of a full-scale MSW incinerator in China. Compared with FAB or FABF, PAHs were mainly concentrated in BA with a range of 1,961.0-2,420.2 μg/kg. Total amounts of 16 high priority PAHs in BA, FAB and FABF from the classified MSW incineration were significantly reduced by 19.0%, 42.4% and 59.8% respectively in comparison with those from the traditional mixed MSW incineration. Moreover, the toxic equivalent quantity (B[a]Peq) of carcinogenic PAHs in these three kinds of residues from the classified MSW incineration were significantly decreased, with the maximum decrease observed in FABF. As a result of source-classification with effective presorting and dewatering, plastics and metals in the MSW were lower, but combustibles and heat values of the MSW increased. Due to variations of the characteristics of the feed waste, complete combustion conditions including continuous higher incineration temperature, lower CO concentration and higher air excess ratio were observed during the process of classified MSW incineration. Incineration temperature and CO concentration showed a negative and positive correlation, respectively, with total PAHs, indicating that incomplete combustion products such as PAHs could be reduced by controlling combustion conditions directly related to properties of the feed waste. The newly established MSW source-classified collection process could be a feasible method for reducing PAHs formation and emission in residues from MSW incineration.