PCDD/Fs environmental impact from anaerobic digestion treatment

The presence of mechanical-biological treatment (MBT) plants for municipal solid waste (MSW) in a territory could result in significant contamination by dioxins and furans (PCDD/Fs). This study points out the importance of carrying out a preliminary environmental impact assessment for MBT plants. A preliminary investigation was carried out with reference to the anaerobic digestion (AD) of MSW. A dispersion model was applied to an MBT plant. The AD process was analysed as a treatment of the filtrate, i.e., the putrescible fraction (undersieve), of screened residual MSW, before a post-biostabilisation (BS) step. A comparison with the BS of the oversieve alone, i.e., the coarse fraction of residual MSW, was made too. A conventional biofilter and a regenerative thermal oxidiser (RTO) were also compared to emission control solutions. Thanks to the increased dilution by the RTO, lower impacts are expected on the surroundings. In addition, coupling AD with post-BS results considerably lower PCDD/Fs emissions with respect to BS alone.