In-channel screening with a drum screen

A rotating drum screen installation for screening out debris from a flow of water in a channel, comprising:

• a drum rotating on a horizontal axis, with a shaft supporting the drum for rotation, the shaft being supported on fixed structure of the channel, and a screen extending around the drum's circumference, forming the drum screen,
• the axis of the drum screen being perpendicular to the channel flow direction such that the drum has a width that occupies part of a width of the channel, leaving a remaining width of the channel for water flow, the drum screen having a diameter not greater than about 10 feet, and being a single entry drum screen, with an open side facing said remaining width of the channel and positioned to receive a flow of water from said remaining width of the channel,
• the channel having a flow direction from upstream to downstream, and said remaining width of the channel being blocked by a barrier adjacent to a downstream end of the drum screen,
• a seal plate positioned in the channel alongside the open side of the drum screen, with a flexible contact seal between the seal plate and a circular side edge of the rotatable drum screen,
• the seal plate having a water admitting opening to permit said flow of water into the drum screen from the open side,
• a diverter plate in the channel, with a downstream end of the diverter plate connected to an upstream end of the seal plate, the diverter plate having an upstream end fixed to a wall of the channel and engaged against a floor of the channel, a main portion of the diverter plate being angled so as to form a parallel flow offset to direct all water and debris flowing in the channel into said remaining width of the channel prior to entering the drum screen through said water admitting opening, and
• the drum screen installation including a debris hopper within the drum, fixed in position near a highest point of the drum, for catching debris from the screen as the drum screen rotates, and with a series of high-pressure water nozzles above the drum aimed at the hopper, to dislodge the debris from the screen into the hopper, and further including an exit trough positioned to carry away the debris and water from the hopper.