The City of Fond du Lac designed and started up a sidestream deammonification process – the first in Wisconsin, the second in the Midwest, and the first in the United States to use the Paques AnammoPAQ process. We were hired by the City to complete the design and startup of this innovative project, which was selected for a State Finalist Award through the American Council of Engineering Companies of Wisconsin Engineering Excellence Awards.

The City’s Wastewater Treatment and Resource Recovery Facility (WTRRF) treats an average of approximately 8 million gallons per day (MGD) of wastewater from about 65,000 customers, including residents in the city, surrounding municipalities, and local industry. The influent loadings to the WTRRF have increased and high ammonia loadings from industrial wastes and recycled flows at the WTRRF would have required significant expansion of the facility in the near future.

The City decided to implement a process to remove ammonia nitrogen from the sidestream centrate recycle flow. Reduction of ammonia in the centrate flow will reduce oxygen demand requirements on the aeration system and save carbon to help drive the biological phosphorus removal (BPR) process later in the system.

The main benefits of the sidestream deammonification process include:

  • Reduced energy use
  • Smaller facility footprint
  • Improved quality of effluent discharged into the environment
  • Improved operations, including minimal carbon usage, which is necessary for the BPR process

Since startup, the process is consistently removing more than 90 percent of the ammonia load.