Problem: The Granite Falls (Minnesota) Wastewater Treatment Plant’s original main lift station was built in a floodplain on the Minnesota River. It lacked sufficient capacity and was in poor condition. Removal across the step screen was poor, creating maintenance issues in the pumps and introduction of inert solids into the package plant and sequencing batch reactor. The few solids removed through the step screen contained high moisture and fecal content.
Solution: The city hired Stantec to design a new higher-capacity lift station located outside the floodplain and equipped with a Parkson Corp. Aqua Guard 6 mm screen with an Aqua Wash Press.
Result: Since the Aqua Guard screen was installed, the plant has operated in a mode to flush the system of rags and inert material. “I was impressed by the volume of solids removed by the Aqua Guard,” says operator Cindy Fjermestad. “Thirty-five gallons of washed, dewatered, compacted material is now removed per week, compared with 16 gallons of wet, uncompacted material with the old screen.” Operator Jim Finken adds, “We have seen a reduction in rags in pumps and will see a reduction in the rags and inerts in the clarifiers. In addition, the Aqua Guard screen has reduced grit from our grit system by 50 percent.” 888/727-5766; www.parkson.com.