Anaerobic digestion process scheme

The monitoring scheme carried out on 5 Mi-scale plants, 4 demonstrative ones and an experimental one, shows high biogas yield (m3.Kg VS.d ). The anaerobic digestion process is shown to be stable, even when there are falls in digestion temperature, or breaks in the mixing and feeding process. Considerable problems were noted, however,... 

In this work, the AD model proposed and validated by Bernard et ah, 2001 is used in the development of the robust nonlinear scheme. The use of this model is justified by two facts i) this model has demonstrated to be useful in the monitoring and control of AD processes and, ii) the semi-industrial fixed-bed anaerobic digester located in the LBEhlNRA used in the validation and identification of the model will be also used in the experimental implementation of the robust nonlinear approach here proposed. Therefore, in what follows the model is briefly described. 

The sludge from the sewage-treatment process mainly contains organic materials. These are- biologically decomposed in a large, closed container called an anaerobic digestor. A simplified scheme of the overall mechanism of anaerobic digestion is shown below. 

Several bioreactor designs are used to produce bioproducts, and include, but are not limited to batch reactors, fed-batch reactors, continuous cultivation reactors, plug flow reactors, recycle bioreactor systems, immobilized cell reactors, biofilm reactors, packed bed reactors, fluidized-bed reactors, and dialysis cultivation reactors (Williams 2002). These reactor types can contain either mixed or pure cultures, and can stimulate heterotrophic and/or phototrophic cellular functions depending on the specific reactor design. Additionally, these reactor schemes can be used to produce products directly, or to harvest biomass or other products for downstream processes. Due to the complex nature of bioreactors, particularly anaerobic digesters, the use of metagenomics is helpful to understand the physiology of such systems. 

Selection of the suitable measurements The properties of a suitable measurement to be used in a control scheme are the ability to reflect the process state and its changes due to disturbances (sensitivity), as well as the time response and the simplicity of the measurement method. The most common measurements in anaerobic digesters (Table 10.3) are ... 

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