Mesophilic digestion

Mesophase state, 20 78 Mesophiles, in composting, 25 873 Mesophilic digestion, 3 702 Mesophilic enzymes, 3 669 Mesoporous molecular sieves, 16 847—849 Mesostructured hybrid materials, 13 548-549... 

The environmental conditions in a waste water sludge treatment system are better controlled. It is probably for this reason that an overall 80 per cent increase of biogas productivity has been reached in a 2,500 m mesophilic digester upon inoculation with the hydrogen-producing microorganism. 

Biodegradation anaerobic degradation decreased by 30% within 238 d corresponding to a pseudo-first-order k = 1 X 10 d by sewage sludge collected from a mesophilic digester (Gerecke et al. 2005)... 

Figure 1. Experimental sequence for mesophilic digestion of caustic-treated feed...

Steady-state performance of conventional high-rate mesophilic digestion of the biomass-waste blend at the baseline loading and detention time is presented in Table I. The methane yields from replicate baseline runs ranged... 

Thermophilic (55 C) digestion of the caustic-treated feed at 0.4 lb VS/ft -day loading and a 6-day detention time showed the same methane yield of about 4 SCF/lb VS added as observed during mesophilic digestion of the pretreated feed at a 0.1 lb VS/ft -day loading and a 12-day detention time (Run 5T/24, Table II). However, the thermophilic gas production rate was 4-5 times the mesophilic rate. Also, the caustic requirement for feed pretreatment was lower for the thermophilic run owing to the recycling of the spent caustic solution. 

A recent development is the utilisation of thermophilic digestion processes, which operate at a temperature of 55°C as opposed to the more normal, mesophilic digestion which operates at 35°C. Sludge from this type of process has been foimd extremely difficult to treat, requiring high polymer doses and often the use of two polymers a polymer... 

Sandino, J., Santha, H., Rogowski, S., Anderson, W., Sung, S., Isik, F., 2005. Applicability of ultrasound pre-conditioning of WAS to reduce foaming potential in mesophilic digesters. Residuals and Biosohds Management 17, 819—835. 

Samain E, HC Dubourguier, G Albagnac (1984) Isolation and characterization of Desulfobulbus elongatus sp. nov. from a mesophilic industrial digester. Syst Appl Microbiol 5 391-401. 

Table II. Average Rates of Hydrolysis of Feedstock Polymers in Mesophilic Laboratory Anaerobic Digestion Systems (43)...

Temperature. Two temperature ranges exist for good biogas production, mesophilic and thermophilic. Most digesters are operated within the mesophilic range of 20° to 45°C (69° to 113°F). The thermophilic range is 45 to 55°C (113 to 131°F). 

Borja, R., Rincon, B., Raposo, R, Dominguez, J.R., Millan, R and Martin, A., Mesophilic anaerobic digestion in a fluidised-bed reactor of wastewater from the production of protein isolates from chickpea flour. Process Biochem., 39 (2004) 1913-1921. 

The impact of electric current on the environmental conditions and the anaerobic microbial activity in completely mixed fed-batch reactors was studied at various electric field strengths (Maillacheruvu and Alshawabkeh, 1999). Experiments were conducted in bio-electrokinetic (BioEK.) reactors, which consist of plexiglass boxes with titanium-coated mesh electrodes mounted at both ends. Electric fields of 1.5 V/cm through 6 V/cm were applied. Unacclimated anaerobic cultures obtained from a mesophilic anaerobic digester were used in these experiments. 

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