Biogas from trade waste and sludges in Melbourne's west

Many abattoirs, renderers and food manufactures have installed screens and dissolved air flotation (DAF) units to comply with City West Water’s controlled trade waste concentration limits. The installation of screens and DAF units resulted in large quantities of screenings and sludge, which are then transported to a landfill for disposal. Hence, the aims of this Masters were to investigate the potential of different wastes for biogas production and to evaluate selected AD processes, as alternative technologies for the treatment of these wastes. The criteria for AD processes evaluation included, biogas quantity and quality, digestate and supernatant quality. Process configurations studied included batch, conventional (i.e. single stage, mesophilic), two-stage AD (TSAD) and two-phase AD (TPAD). The processes were monitored for the effect of operation factors such as organic loadings, temperature and hydraulic retention time (HRT). To conclude, AD of pre-DAF using TPAD showed biogas yield of 0.54 m3 biogas/kg VSadded, which are comparable to those obtained for degradable organic wastes. The AD of DAF-sludge using TPAD was more effective than using conventional AD. On the other hand CODt and TS removal both using TPAD and conventional AD were in the range of 19-31% and 45 to 62%, which is low. It is recommended that pre-treatment of DAF-sludge is investigated to enhance its degradability to the recommended removal rate.<br><br>