Two-phase anaerobic digestion of source sorted OFMSW (organic fraction of municipal solid waste): performance and kinetic study

The results of a two-phase system operated in different conditions, treatin g the source-sorted organic fraction of municipal solid waste (SS-OFMSW), c oming mainly from fruit and vegetable markets, are presented. Hydraulic ret ention time (HRT) in the hydrolytic reactor and in the methanogenic reactor and also the temperature in the hydrolytic reactor (mesophilic and thermop hilic conditions) are varied in order to evaluate the effect of these facto rs. The methanogenic reactor is always operated within the thermophilic ran ge. Optimum operating conditions are found to be around 12 days (total syst em) using the mesophilic range of temperature in the first reactor. Specifi c gas production (SGP) in these conditions is around 0.6 m(3)/kgTVS. A kinetic study is also carried out, using the first and the step diffusion al models. The latter gives much better results, with fitted constants comp arable to other studies. Finally, a comparison with a one-phase system is c arried out, showing that a two-phase system is much more appropriate for th e digestion of this kind of highly biodegradable substrate in thermophilic conditions.