Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes

This study investigated different solid retention time (SRT) on municipal solid waste (MSW) anaerobic digestion with various MSW incinerator fly ash (FA) and bottom ash (BA) addition. Results showed that biogas production rates (BPRs, ∼200 to ∼400 mL/gVS) with organic loading rate of ∼0.053 gVS/gVSreactor (Day 1–435, SRT 20 days, SRT20) at FA 1 g/d (FA1), BA 12 g/d (BA12) and BA 24 g/d (BA24) dosed bioreactors increased after adaptation. BPRs with SRT10 and SRT5 decreased while BPRs with SRT40 showed to increase compared to initial BPRs (∼200 mL/gVS) with SRT20. SRT5 operation reduced the BPRs (∼10 – ∼90 mL/gVS) significantly and only BA12 and BA24 dosed bioreactors could recover the BPRs (∼100 – ∼200 mL/gVS) after SRT20 operation (Day 613–617) compared to FA1 and FA3 and control. Released levels of Co, Mo and W at BA12 and BA24 dosed bioreactors showed most potential to improve MSW anaerobic digestion.

► Suitable MSWI ashes addition improved the MSW anaerobic digestion.
► Biogas enhancement was due to the suitable released metals levels.
► Co, Mo and W were mostly found to stimulate MSW biogas production.
► MSW anaerobic digestion favored SRT20 and SRT40 operation.