Sewage treatment apparatus

Claim 1

SEWAGE TREATMENT APPARATUS COMPRISING A TANK, MEANS FOR INTRODUCING SEWAGE INTO THE TANK AND FOR REMOVING LIQUID FROM AN UPPER PORTION OF THE TANK, A TUBE COMMUNICATION BETWEEN A LOWER PORTION OF THE TANK AND AN UPPER PORTION OF THE TANK, AND AN IMPELLER DISPOSED ABOVE THE UPPER END OF THE TUBE FOR MOVING LIQUID WITH ENTRAINED SOLIDS UPWARDLY IN THE TUBE TO EXPOSE SOLIDS ACCUMULATING IN THE BOTTOM OF THE TANK TO THE ATMOSPHERE IN AN UPPER PORTION OF THE TANK THEREBY TO PROMOTE AEROBIC KDECOMPOSITON OF THE SOLIDS, THE TUBE TERMINATING UPWARDLY IN AN UPWARDLY OPEN FIXED HOWL OF A DIAMETER SUBSTANTIALLY GREATER THAN THE DIAMETER OF THE TUBE, THE IMPELLER BEING DISPOSED IN THE BOWL, THE BOWL HAVING AN OUTWARDLY EXTENDING BOTTOM THAT TERMINATES OUTWARDLY IN AN UPWARDLY AND OUTWARDLY INCLINED SIDE WALL, THE IMPELLER BEING A ROTOR MOUNTED FOR ROTATION ABOUT A VERTICAL AXIS AND HAVING A PLURALITY OF DOWNWARDLY EXTENDING VANES HAVING FREE LOWER ENDS WHICH ARE SPACED ABOVE THE BOTTOM OF THE BOWL AND THE LEADING EDGES OF WHICH ARE DOWNWARDLY REARWARDLY INCLINED, THE VANES HAVING CONVEX AIRFOIL CONFIGURATION ON THEIR RADIALLY INNER SIDES AND HAVING A PASITIVE PITCH OF BETWEEN ABOUT 5* AND 20*.