Sewage treatment

Claim 1

IN APPARATUS FOR SEWAGE TREATMENT, THE COMBINATION WHICH COMPRISES A SETTLING TANK FOR HOLDING A POOL OF SEWAGE LIQUID UP TO A LEVEL, A BAFFLE IN THE TANK DIVIDING IT INTO PRIMARY AND SECONDARLY ZONES AND EXTENDING ABOVE AND BELOW THE LEVEL IN THE TANK, THE PRIMARY AND SECONDARY ZONES BEING IN COMMUNICATION WITH EACH OTHER UNDERNEATH THE BAFFLE, A LARGE OVERFLOW WEIR ON THE SECONDARY SETTLING ZONE FOR DISCHARGING LIQUID EFFLUENT FROM THE SECONDARY ZONE IN SUCH LARGE VOLUME THAT THE LEVEL IN BOTH SETTLING ZONES RISES BUT SLIGHTLY WITH INCREASED FLOW, MEANS FOR INTRODUCING A STREAM OF SEWAGE INTO THE PRIMARY SETTLING ZONE, A CONTROL SUMP HAVING ITS TOP ABOVE THE LEVEL OF THE POOL IN THE SETTLING TANK AND ITS BOTTOM BELOW SAID LEVEL, A CONDUIT CONNECTED FROM AN UPPER PORTION OF THE PRIMARY SETTLING ZONE TO THE CONTROL SUMP AND DISPOSED BELOW THE LEVEL OF THE POOL IN THE SETTLING TANK FOR FLOWING LIQUID BY GRAVITY FROM THE PRIMARY SETTLING ZONE INTO THE CONTROL SUMP, A BIOLOGICAL FILTER HAVING AN INLET AT ITS TOP AND AN OUTLET AT ITS BOTTOM, THE TOP BEING LOCATED BELOW THE CONTROL SUMP, A CONDUIT CONNECTING THE CONTROL SUMP TO THE INLET OF THE BIOLOGICAL FILTER AND PERMITTING GRAVITY FLOW OF LIQUID FROM THE CONTROL SUMP TO THE FILTER, A PUMP SUMP HAVING A BOTTOM LOCATED BELOW THE FILTER OUTLET, A CONDUIT CONNECTING THE FILTER OUTLET TO THE PUMP SUMP TO PERMIT GRAVITY FLOW OF LIQUID FROM THE FILTER OUTLET TO THE PUMP SUMP, A PUMP HAVING ITS INLET CONNECTED TO THE PUMP SUMP AND HAVING AN OUTLET CONDUIT WITH TWO BRANCHES, ONE BRANCH BEING CONNECTED TO THE PRIMARY SETTLING ZONE AND THE OTHER BRANCH BEING CONNECTED TO THE FILTER INLET, VALVING MEANS FOR CONTROLLING THE FLOW IN THE TWO BRANCHES, AND MEANS FOR REGULATING THE FLOW OF LIQUID FROM THE PRIMARY SETTLING ZONE TO THE CONTROL SUMP.