NOVELTY - The appliance comprises a biological reactor for removing organic matters and nitrogen in the injected sewage by performing removing of the organic matters using microorganisms, nitrification and denitrification and for releasing and uptaking phosphorus, a unit for separating sludge from treated water from the biological reactor by floatation separation and for inner-recycling the separated sludge to the biological reactor, and a membrane separator for filtrating remaining solid matters from the treated water from the sludge separator.    USE - The appliance is useful for treating sewage and waste water.    ADVANTAGE - The appliance is capable of efficiently treating sewage and waste water with high concentration of the microorganisms and reduced surface area by rapidly removing organic matters and nutritive salts in sewage and waste water, and reduces the concentration of the activated sludge injected into the membrane filtration tank thus minimizing the membrane fouling.    DETAILED DESCRIPTION - The appliance comprises a biological reactor for removing organic matters and nitrogen in the injected sewage by performing removing of the organic matters using microorganisms, nitrification and denitrification and for releasing and uptaking phosphorus, a unit for separating sludge from treated water from the biological reactor by floatation separation and for inner-recycling the separated sludge to the biological reactor, and a membrane separator for filtrating remaining solid matters from the treated water from the sludge separator to discharge the finally treated water to the outside of the separator and for inner-recycling the activated sludge to the biological reactor. The biological reactor includes an anaerobic tank, an anoxic tank, an aerobic tank, and an intermittent aeration tank for maximizing the removal of nitrogen and phosphorus. The sludge inner-recycled from the sludge separator is injected into the anaerobic tank or the anoxic tank. The floatation separation is performed by dissolved air floatation, an atmospheric floatation or other flotation processes. A coagulant is added to the sludge separator so that the sludge is easily floated to increase an efficiency of the floatation separation. The membrane separator is a submerged membrane separator or an external pressure type membrane separator.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of a sewage treatment appliance.