Startup of thermophilic anaerobic digestion of organic waste : one stage vs two stage -

Abstract

The anaerobic digestion of food waste is an attractive option for waste disposal. In the following study, a one stage digester was compared to a two stage digester for the treatment of food waste under thermophilic temperature. In addition, an innovative strategy for accelerating the startup of a one stage digester while using a fast incremental loading was explored. In this regard, two one-stage bench-top digesters and a two-stage digester were operated to treat food waste under thermophilic temperature in separate studies. In the first study (Appendix A and C), the one stage digester produced 30percent higher specific methane rate and exhibited better stability in terms of lower intermediate-to-partial alkalinity (IA-PA) ratio. However, the two stage digester exhibited better organic matter destruction exhibited by 52 percent lower average TCOD, 64percent lower SCOD and 5percent higher VSpercent reduction than in the one stage system. In the second study (Appendix B), a biomass acclimation strategy that involved gradual and incremental increase of inoculum and loading rate over 20 weeks was contrasted with a faster 12-week startup. Both reactors showed similar operational stability, there was a 30percent reduction in startup time with the fast startup reactor. Despite a 15percent reduction in specific methane generation, it remained within the reported values for similar waste. In addition, the reactor achieved high alkalinity, low overall IA-PA ratio and VSpercent and TCOD removal values within the recommended value.