Continuous fermentation process and apparatus

Abstract

A deep tank reactor is utilized for fermentation of waste liquid or other liquid in a biological reaction resulting in a solid cellular material. The resulting solid material, which is in suspension, is initially separated from the bulk of the liquid by a gaseous flotation process, using the dissolved gas in the liquid as the source of gaseous bubbles for flotation purposes.

Having described my invention, I claim: 
     
       1. In a continuous fermentation process involving transfer of gaseous constituents to a liquid material or suspension for biological reaction purposes to produce a cellular material and related metabolic products in suspension, the improvement comprising the following steps: directing incoming liquid material or suspension to the interior of a .[.tall reactor.]. .Iadd.deep .Iaddend.tank exposed to atmospheric pressure;   introducing an oxygen containing gas to the lower interior of the .[.reactor.]. .Iadd.deep .Iaddend.tank at a rate equal to or greater than that required for consumption of oxygen by the biological reaction process, whereby excess gas is dissolved in the liquid phase and solid phase components of the resulting supension and whereby the resulting suspension is .[.contantly.]. .Iadd.constantly .Iaddend.agitated by incoming bubbles of the excess gas;   maintaining the liquid and gaseous components within the .[.tall reactor.]. .Iadd.deep .Iaddend.tank for a residence time sufficient to complete the biological reaction process.[., whereby excess gas is dissolved in the liquid phase and solid phase components of the resulting suspension and whereby the resulting suspension is constantly agitated by incoming bubbles of the excess gas;   maintaining the liquid and gaseous components within the tall reactor tank for a residence time sufficient to complete the biological reaction process.].;   and removing liquid suspension from the .[.reactor.]. .Iadd.deep .Iaddend.tank at a pressure greater than atmospheric pressure and directing the liquid suspension to a flotation tank exposed to atmospheric pressure, the liquid suspension being suddenly depressurized upon introduction to the flotation tank to thereby cause the dissolved gas to bubble through the liquid suspension and effect separation of the suspended solid materials by flotation.   
     
     
       2. A process as set out in claim 1, wherein the incoming material or suspension is wastewater and wherein microorganisms capable of feeding upon the carbonaceous materials in the wastewater are maintained within the .[.tall reactor.]. .Iadd.deep .Iaddend.tank. 
     
     
       3. A process as set out in claim 1 wherein a portion of the separated solids after flotation are returned to the interior of the .[.tall reactor.]. .Iadd.deep .Iaddend.tank to maintain an effective operational balance for the biological reaction. 
     
     
       4. A process as set out in claim 1 wherein the hydrostatic pressure of the liquid suspension drawn from the .[.reactor.]. .Iadd.deep .Iaddend.tank is at least 13 p.s.i.g. 
     
     
       5. An apparatus for continuous fermentation processes involving transfer of gaseous constituents to a liquid material or suspension for biological reaction purposes to produce a solid cellular material and related metabolic products, comprising: a .[.tall reactor.]. .Iadd.deep .Iaddend.tank exposed to atmospheric pressure;   input means for supplying incoming liquid material or suspension to the interior of the .[.reactor.]. .Iadd.deep .Iaddend.tank;   outlet means for discharging treated liquid suspensions from the interior of the .[.reactor.]. .Iadd.deep .Iaddend.tank at a hydrostatic pressure of at least 13 p.s.i.g.;   a flotation tank exposed to atmospheric pressure and having an inlet;   means operatively connecting the outlet means of the .[.reactor.]. .Iadd.deep .Iaddend.tank and the inlet of the flotation tank for suddenly depressurizing the liquid suspension as it is introduced to the flotation tank.[.;.]..Iadd.. .Iaddend.   
     
     
       6. An apparatus as set out in claim 5 further comprising: outlet means at the flotation tank for respectively discharging the separated liquid and solid components therein, including bypass means for directing a portion of the separated solids back to the .[.reactor.]. .Iadd.deep .Iaddend.tank.