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Upgrade Produces Exceptional Effluent Quality

The City of Eau Claire operates an 11.5-mgd regional wastewater treatment facility. Donohue worked collaboratively with the City through planning, design, and construction of a complete replacement of the secondary treatment system with a biological phosphorus removal activated sludge system. The project included an overhaul of the anaerobic digestion system, biogas conditioning system, biogas utilization system (combined heat and power), primary and secondary settling improvements, a supplemental alkalinity system, an odor control system, and biosolids handling improvements.

The upgrades also included a new automation system intended to minimize operator attention and change staffing from 24/7 to daytime only, odor control with efficient and low cost bio-filters, new water and updated wastewater laboratories, site dewatering wells with controls, updated sludge pumping and piping, and improved ventilation and electrical systems to meet the NFPA code.

Donohue’s construction cost opinion was $44M. The low bid was awarded at $40M. Construction phase change orders were less than 0.2% of the contract amount.

The activated sludge system consistently produces exceptional effluent quality. The facility achieved 90% ammonia removal and effluent phosphorus concentrations below the 1 mg/L effluent limit after only five days of operation. The plant regularly achieves BOD and TSS removal efficiencies above 97% and average effluent total phosphorus concentrations of 0.5 mg/L.