About the conception and design of anaerobic digesters in zootehnical farms

Anaerobic sludge fermentation is one of the main technological steps for treating the wastewater resulting from urban consumption in the food industry. Anaerobic fermentation ensures the sludge mineralization treatment and the fermentation gas (biogas) resulting from the process can be used for the production of thermal or electric energy. The fermentation process can take place in closed reinforced concrete tanks (digesters) having different structural forms: cylinder, tapering, ovoid depending on the type of fermentation: mesophilic or thermophilic and on the performance of sludge mixing and homogenization equipment. Fermentation tanks with a capacity of 1000-4000 m3 were designed in Romania so far, the most important being those of Bucharest wastewater treatment plant made of prestressed reinforced concrete having an ovoid shape. The present paper aims at presenting the issues related to designing the fermentation tanks of the water waste plants from urban consumption in the food industry and zoo-technical farms in a new concept in which the main fermentation tank is coupled with the fermenter for the fermentation gas storage. Consequently, hereinafter structural and functional requirements for this kind of structures are presented, together with design principles and methods that must be applied in order to fulfil the performance exigencies related to strength, stability, tightness and durability