Monitoring a fast thermophilic re-start-up of a digester treating the organic fraction of municipal solid waste

Experimental data concerning a fast re-start-up of a digester treating the organic fraction of municipal solid waste at thermophilic conditions (55°C) is analyzed according to a classical approach (evolution of mass balance and stability parameters) and a new approach, put forward here, based on the interpretation of the biogas production profiles obtained after feeding the digester. Gas production, H2 pattern in the biogas and volatile fatty acids in the digester content are the most suitable parameters using the classical approach. Using the evolution of the biogas production profiles the start-up and normal digester operation can be monitored in a satisfactory and much simpler way. This approach could assume special importance for industrial-scale digesters. © 1993 Taylor and Francis Group, LLC

Influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste

A laboratory-scale experiment was carried out to assess the influence of temperature fluctuation on thermophilic anaerobic digestion of municipal organic solid waste (MOSW). Heating failure was simulated by decreasing temperature suddenly from 55 °C to 20 °C suddenly; 2 h time is needed for temperature decrease and recovery. Under the conditions of 8.0 g/(L·d) and 15 d respectively for MOSW load and retention time, following results were noted: (1) biogas production almost stopped and VFA (volatile fatty acid) accumulated rapidly, accompanied by pH decrease; (2) with low temperature (20 °C) duration of 1, 5, 12 and 24 h, it took 3, 11, 56 and 72 h for the thermophilic anaerobic digestion system to reproduce methane after temperature fluctuation; (3) the longer the low temperature interval lasted, the more the methanogenic bacteria would decay; hydrolysis, acidification and methanogenesis were all influenced by temperature fluctuation; (4) the thermophilic microorganisms were highly resilient to temperature fluctuation