Flume Water Transport of Screenings Improves Headworks Operations

The Dallas Water Utilities Southside WWTP (SWWTP) is rated for 110 mgd influent flow. Raw wastewater enters the SWWTP at Influent Pump Station C. Six bar screen channels, split three and three around a central dumpster area, discharge into two separate East and West influent pump wet wells. Parkson Aquaguard screens with 6mm openings are installed in each channel and designed to screen up to 80 mgd each. The original headworks configuration included six washer compactors, one under each bar screen head. Three washer compactors on each side discharged onto a conveyor running to the central dumpster area. The washer compactors quickly failed due to bridging of screenings and mechanical breakdowns. These units were taken out of service and abandoned after numerous repairs. Temporary shallow inclined plywood platforms were installed under the bar screen head to catch falling screenings in the drop zone and direct them to the conveyor (See Photo 1). Heavy sidewall curtains were also added in an attempt to deflect falling objects on to the conveyor with limited success, because screened debris frequently fell on the floor (See Photo 2). From this point forward, the screenings system required frequent operator visits around the clock to hand rake the inclined wooden platforms to clear mounds of screenings. For years, unwashed feces-laced screenings were hand-raked onto long upper level conveyors which run to the center area from either side of the screening room and dump onto perpendicular lower conveyors which then drop the wet screenings into open dumpsters. Operators were required to knock down mounds of screenings to fill the dumpsters efficiently (See Photo 3). Prior to the improvements, the screenings handling system produced strong odors from the putrefying screenings which required both dumpsters to be hauled out and dumped at the landfill three times per week, involving extensive labor to keep the odors down.