Preliminary treatment facilities include an enclosed screw pump
station, two catenary bar screens, a raw sewage pumping system, grit removal.
the raw wastewater pumping system consists of four horizontal centrifuge pumps,
an influent wet well, an ultrasonic flowmeter and a variable frequency drive
unit. The lead pump is a 2800gpm variable speed pump and the remaining three
pumps are 1900 gpm constant speed pumps. The V.F.D. matches the speed of the
lead variable speed pump with the level of the wet well. When the lead pump
reaches capacity, the system will put on line additional lag pumps until the
level of the wet well returns to normal. Influent flows are pumped into an
aerated grit chamber for grit removal. Remove grit is pumped to a hydrocyclone
grit declassifier for dewatering and collection.