NOVELTY - Conditioning of a mixed liquor in a membrane biological reactor (MBR) comprises adding one or more water soluble anionic polymers either before, simultaneously or after the addition of one or more water soluble cationic, amphoteric and/or zwitterionic polymers to the mixed liquor.    USE - This method is useful for preventing fouling of a filtration membrane in MBR, enhancing flux through a filtration membrane and reducing sludge formation in MBR (claimed).    ADVANTAGE - This method of MBR decreases sludge production, accelerates membrane fouling and finally increases membrane-cleaning frequency.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a method of clarifying wastewater in MBR, where microorganisms consume organic material in the wastewater to form a mixed liquor comprising water, the microorganisms, dissolved and suspended solids comprising adding one or more water soluble anionic polymers either before, simultaneously or after the addition of one or more water soluble cationic, amphoteric and/or zwitterionic polymers to the mixed liquor to form a mixture consisting water, the microorganisms, coagulated and flocculated solids; and separating the clarified water from the microorganisms and the coagulated and flocculated solids by filtration through a membrane;    (2) a method of preventing fouling of a filtration membrane and enhancing flux through a filtration membrane in MBR, where microorganisms consume organic material in the wastewater in a mixed liquor comprising water, the microorganisms, and dissolved, colloidal and suspended solids (where the clarified water is separated from the mixed liquor by filtration through the filtration membrane comprising adding one or more water soluble anionic polymers either before, simultaneously or after to the addition of one or more cationic, amphoteric and/or zwitterionic polymers to the mixed liquor, sufficient to prevent fouling of the membrane and effective flux enhancing); and    (3) a method of reducing sludge formation in MBR, where microorganisms consume organic material in the wastewater to form a mixed liquor comprising water, the microorganisms and a sludge comprises, dissolved, colloidal and suspended solids and the clarified water is separated from the mixed liquor by filtration through a membrane comprising adding one or more water soluble anionic polymers either before, simultaneously or after the addition of an effective coagulating and flocculating amount of one or more cationic, amphoteric and/or zwitterionic polymers to the mixed liquor and increasing the concentration of microorganisms in the mixed liquor and increasing the amount of time that the microorganisms remain in contact with the wastewater).