Abstract: The invention concerns a procedure for recovery of soluble carbohydrates present in wood, in connection with the alkaline cellulose digesting process. According to the invention, recovery of carbohydrates takes place at the initial phase of the cellulose digesting process, where the digesting solution contains dissolved polysaccharides in abundance, while the content of polymeric lignin in the solution is low. A situation like this exists at the stage when the digesting solution has not yet reached the temperature at which the digestion process mainly takes place. As taught by the invention, the carbohydrates are recovered by conducting digesting solution to an ultrafilter, which separates the carbohydrates therefrom, and by returning the filtered solution to the cellulose digestion. The carbohydrates that are obtained may be used e.g. in the manufacturing of sugar alcohols, or as raw materials for biotechnical processes.

Abstract: A biofilter for treatment of waste waters and gases, comprising a bed of coniferous tree barking residue containing microorganisms and where the waste water to be treated can be uniformly conducted upon the barking residue bed and from below the barking residue bed oxygen containing gas can be blown against the waste water flow. The barking residue bed has been partly placed in a depression provided liquid and gas tightly in the ground, and that on the bottom of the depression there is a pipe system for draining the waste water that has traversed the barking residue bed and for conducting oxygen containing gas into said bed.