Temporary Selector Operational Innovation Mitigates Wastewater Throughput Limitations at a Large Paper Mill

Operators of a 40 MGD (6,300 m3/hr) wastewater treatment plant serving a western USA paper mill were periodically chlorinating return activated sludge (RAS) streams to mitigate a recurring filamentous bacteria bulking problem. In mid-2019, chlorination requirements to prevent filament-bulking-induced throughput limitations became more frequent. Average floc size and quality gradually deteriorated. Finally, chlorination of RAS could not be employed as frequently as needed to reduce filamentous growth without causing loss of solids due to deterioration of desired floc. Wastewater treatment plant (WWTP) throughput reductions were required which in turn required some temporary paper production curtailment. An operational innovation using existing assets was employed to select against filaments, allowing for resumption of full capacity wastewater treatment.