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River Falls wastewater dryer nears full operation after repairs and test runs; staff to run 72-hour performance test
Summary
City wastewater staff reported that the new biosolids dryer and screw press system has had mechanical and polymer-dosing issues but is now producing near-target dry solids in tests after an oil leak repair; staff plans a 72-hour continuous performance test and said they have temporarily hauled material to West Central Biosolids as they finish commissioning.
City wastewater staff told the Utility Advisory Board on Jan. 26 that the recently installed biosolids dryer and Schwing Bioset screw press are close to full commissioning after technical issues delayed the original schedule.
According to staff, early problems included difficulty conveying sludge from the DAF (diffused air flotation) basement to the new processing building, polymer dosing that needed adjustment to raise solids from about 3% to near 20% through the screw press, and an internal oil leak the dryer manufacturer identified and repaired. The manufacturer and contractors ran multi-day short runs after repairs; staff reported successful runs (2,500 pounds throughput during testing) and said the dryer reached about 99% dry solids in a subsequent run. The project team planned a 72-hour continuous performance test with Strand and Associates and contractors to validate operation.
While commissioning continued, the city has hauled some biosolids off-site to West Central Biosolids (Ellsworth) and informed the prime contractor that the city expects the contractor to cover hauling costs incurred because of the commissioning delay; staff said they will seek reimbursement for hauling expenses not budgeted. Staff also discussed interim disposal of some test-product batches to landfill when material did not meet desired dryness.
Staff said the dryer project was scheduled to be complete earlier but noted they kept change orders small and relied on strong in-house project management. They said, when fully operational, the dryer should substantially reduce annual biosolids hauling costs and convert daily truckloads of wet sludge into a much smaller volume of dry product suitable for land application.
Next steps: staff will run the 72-hour performance test, finalize commissioning, negotiate any reimbursement for off-site hauling with the contractor, and return to the board with final operational and financial comparisons to previous hauling costs.
