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Nolan wastewater staff report improved treatment but warn of wipes, ozone and storm impacts
Summary
City wastewater staff reported plants met permit limits in March, described removal of 22,500 pounds of rags from a basin, outlined polymer trials that improved sludge solids, and detailed continuing ozone-system problems that contributed to a coliform exceedance during a weekend of heavy rain.
Scott Murphy, project manager for wastewater at the City of Fayetteville, told the Water & Sewer Committee on April 8 that both treatment plants were in compliance for March but that heavy rain in April strained systems and produced operational challenges.
Murphy said crews found and removed 22,500 pounds of rags and debris from one basin during cleaning of a 3.7-million-gallon basin. “This is the dreaded flushable wipe that we all hate in the utility business,” Murphy said, adding that rags damage pumps and aerators and are costly to remove.
The committee heard that a new jet-aeration unit has been installed to reduce mechanical problems tied to rag buildup. Murphy said the jet aerator uses pumped water to induce air through a venturi, providing mixing energy and dissolved oxygen without the same rag-binding blades used on older shafts.
Murphy described successful polymer trials at the Nolan plant and at Westside: after seven days in a drying house, trial polymer produced 38% solids and the belt dryer produced 96% solids in a single pass, outcomes he called “really good.” He said additional trials with competing manufacturers are scheduled.
On ozone disinfection, Murphy said plant staff have had to limit access to areas around ozone equipment for employee safety because of leaks and that third‑party analysis shows the facility’s ozone destruct units are undersized. “By his calculations and our calculations, we really need, like, 6–655 CFM,” Murphy said, summarizing the consultant’s report attached to the monthly packet. Interim solutions include a fogging/spray neutralizer using sodium thiosulfate and pursuit of a larger ozone‑destruct unit.
Murphy also said Nolan experienced a single fecal coliform test failure during the storm period when flows overwhelmed disinfection capacity. He said staff are pursuing ultraviolet (UV) disinfection options and other operational fixes to restore reliable disinfection at high flows.
The report included smaller maintenance items: replacement of a VFD, repair and inspection of RAS pumps (estimated at about $70,000 each for replacement parts), demolition of concrete footings at an influent pump station using a product called Dexpan, and a schedule to set a new influent pump within about a week. Murphy noted crews completed several other in-plant jobs while a crane was on site.
Tim Nundgren, utilities director, and Murphy answered committee questions about whether new equipment would reduce rag-related outages; Murphy said the new impeller and venturi configuration has a larger pass-through and staff are optimistic it will reduce—but not eliminate—clogs.
Why it matters: staff said improved screening and headworks will reduce wear and failures in downstream equipment, lower maintenance costs, and reduce the risk of permit noncompliance during storm events or high flows.
Looking ahead, Murphy said crews will continue polymer trials and ozone remediation work, and that staff plan to split biological basins when mixed liquor suspended solids reach targeted levels to maintain biological performance.
