The headworks structure, together with the adjacent influent manhole, contains essentially all the pretreatment processes of the plant. The facilities have been designed to enable expansion to handle the projected ultimate flow, principally by adding additional mechanical equipment and a parallel influent pipe and flowmeter. The present increment is capable of handling peak flows of approximately 8.0 MGD. Unit processes located within the headworks are: influent flow measuring, mechanical bar screening, grit removal and washing, and communication. Prechlorination may be accomplished at the influent manhole. The primary sludge and scum pumps are located within the headworks along with controls for the primary sedimentation tanks. Flow splitting weirs to divide the flow between the primary sedimentation tanks are also located in the headworks. The headworks is designed for continuous operation during projected flooding resulting from a 100 year storm.
The influent flow meter is a 14-inch diameter magnetic flow meter designed to measure flows ranging up to 8.0 MGD with an accuracy of plus or minus 1% of range.
The mechanically cleaned bar screen has been designed to pass sewage flows up to 8.0 MGD. The bar screen can be controlled to operate either fully automatically according to a preset cycle which is variable from 1 minute to 60 minutes or manually. The material removed on the screen is mechanically lifted out of the sewage flow, deposited onto a screenings conveyor, and then dropped into a hopper which stores the screenings until they are removed and disposed of.
The grit chamber is a circular, air agitated and mechanically scraped tank. Grit and other settled matter is removed from the bottom of the tank by pumping the grit slurry from a sump up and into the grit washer located on the headworks upper deck. The grit washer separates the heavier grit particles from the lighter organic matter and the grit is then lifted by a screw conveyor-classifier into a hopper where it is stored until removal and disposal. The lighter organic matter is returned through a pipe overflow back into the grit tank.
The barminutors are mounted in separate channels leading to the flow splitting weirs and each is designed to comminute (grind) sewage screenings not removed by the bar screen at flows up to 8.0 MGD. The ground screenings are not removed from the sewage but pass through the machine to be removed in the primary sedimentation tanks. The barminutors are automatically controlled and will initiate a grinding cycle when the water surface differential across the machine exceeds a preset amount. A bar rack with 1-1 ½ inch clear openings is installed in a channel parallel to the barminutor channels for use when the barminutor is temporarily out of service.