Nutrient Recovery At The F. Wayne Hill Water Resources Center: Design And Full Scale Start Up


  • Ron Latimer, Vivi Nguyen, Eddie McCallum, Paul Pitt - Hazen and Sawyer
  • Robert Harris, Tyler Richards - Gwinnett County DWR

The process schematic and sampling points of the pilot reactor setup at F. Wayne Hill.

Construction of the Pearl® reactor.

P release tank with combined primary and WAS.

Top of centrate EQ tanks with retractable covers.

The F. Wayne Hill Water Resources Center (FWHWRC) is Gwinnett County’s largest and most advanced wastewater treatment facility with a capacity of 60 mgd. The FWHWRC uses enhanced biological phosphorus removal and chemical trim to meet a stringent TP limit of 0.08 mg/L. Solids handling consists of anaerobic digestion of combined primary sludge and WAS in egg-shaped digesters.

Over the past three years, struvite precipitation has increasingly become a major issue at the FWHWRC. Plant staff have used high pressure blasting of centrate lines in the past; however, struvite deposits are now being found in the dewatering centrifuges and upstream of dewatering. Struvite control, beyond reactive blasting of centrate lines, was needed moving forward. In addition, combined primary and secondary sludge from Gwinnett County’s 22 mgd Yellow River WRF is transferred to the FWHWRC resulting in significant additional phosphorus load, and will result in more severe phosphorus recycle loads in the future.

To address the struvite issues and decrease the impacts of phosphorus recycle loads on the main liquid stream, while at the same time creating a sustainable fertilizer through nutrient recovery, Gwinnett County evaluated the OSTARA Pearl® and the Multiform Harvest nutrient recovery processes. The OSTARA Pearl® process creates controlled conditions of struvite precipitation for P and N recovery as a high quality fertilizer (Crystal Green). The Multiform Harvest process also creates a controlled struvite recovery process. Implementation of a Pearl® type process or Multiform Harvest process will provide a significant reduction of nuisance struvite formation. In addition, each process can reduce the recycle phosphorus load by up to 80-90%.

The controlled struvite precipitation in the Pearl® process can be enhanced with the addition the patented process called WASSTRIP (wasted activated sludge stripping). The WASSTRIP process combines dewatered centrate with phosphorus and magnesium-rich WAS filtrate (from a WAS P-Release Reactor) into the Pearl® process, increasing Crystal Green production and reducing struvite in solids handling.

This paper will share results from bench scale testing, pilot scale testing, as well as, start-up and operational data from the full scale facility. As of start-up on July 6, 2015, this facility is only the second full scale WASSTRIP installation in the United States. This case study will present the full-scale performance data of the WASSTRIP and nutrient recovery process and how it compares to both bench and pilot testing performed during preliminary design.

For more information or a copy of the full paper, please contact the author at

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