Weir for waste water treatment systems

A weir system for decanting the upper layers of wastewater from a wastewater tank to selectively lower the water level in the tank, comprising, in combination:

• (a) a rotatably mounted header pipe extending horizontally across the wastewater tank adjacent an end of the wastewater tank below the water level in the tank for withdrawing wastewater from the tank, said pipe forming a plurality of openings through the wall thereof;
• (b) an elongate weir extending horizontally across the wastewater tank, the weir comprising a bottom forming a plurality of outlet openings therethrough, a trailing side proximate said end of the tank forming an upper trailing edge, a leading side distal of said end of the tank forming a leading edge proximate the body of wastewater in the tank, and ends closing the weir, said bottom, sides and ends defining a trough-like weir structure;
• (c) a plurality of downcomer pipes extending between the weir and the header pipe and connected to said plurality of outlet openings therein providing closed fluid communication between the weir and the header pipe through said plurality of outlet openings therein, for permitting flow into the header pipe only from the weir;
• and
• (d) positive drive means associated with the tank for selectively rotating the header pipe thereby moving the weir in an arcuate path, respectively downwardly to lower the level of wastewater in the tank and upwardly to permit the tank to fill with wastewater, the weir being so constructed and disposed that the leading edge thereof is always lower than the trailing edge thereof thus permitting wastewater to flow into the weir only over the leading edge thereof.