NOVELTY - A biologically convertible matter is treated by providing non- biodegradable supports (43) having microorganisms in biologically active condition immobilized on the supports.    USE - The invention is used for treating biologically convertible matter, e.g., manure, milk fraction or a milk derivative, solvent, organic or inorganic matter, processed food, a food by-product, heavy metal or an aqueous solution (claimed). It is also used for the treatment of gas, liquid and/or solid.    ADVANTAGE - The invented method converts biologically convertible matter into reusable or detoxified material in a cost-effective manner.    DETAILED DESCRIPTION - Treatment of biologically convertible matter, involves providing non biodegradable supports having microorganisms in biologically active condition immobilized on the supports; disposing the supports in an arrangement to enable free circulation of a gas through the arrangement; and contacting the biologically convertible matter with the supports under conditions to produce and separate a conversion material or to concentrate and fix elements of the biologically convertible material.    An INDEPENDENT CLAIM is also included for a bioreactor for treating biologically convertible matter, comprising an upper distribution chamber (12); a bioreactor chamber (14) disposed below the distribution chamber; feeding mechanism for feeding the biologically convertible matter from the distribution chamber into the bioreactor chamber; non-biodegradable supports mounted in the bioreactor chamber having microorganisms in a biologically active condition immobilized on the supports, where the supports are arranged to cause the microorganisms to contact the biologically convertible matter and convert into a conversion material or concentrate and fix elements of the biologically covertible matter; a collection chamber operatively connected to the bioreactor chamber to collect the conversion material or recover the fixed elements; mechanism for withdrawing the conversion material or fixed elements from the collection chamber.    DESCRIPTION OF DRAWING(S) - The figure is a longitudinal cross-section view of a modular bioreactor.    Distribution chamber (12)    Bioreactor chamber (14)    Supports (43)