PFI-TT: Developing a vacuum stripping and absorption system for value-added ammonia removal from wastewater

The broader impact/commercial potential of this Partnerships for Innovation - Technology Translation (PFI-TT) project is to promote the shift of wastewater treatment from costly ammonia removal to resource recovery. Nitrogen discharge limits are increasingly added to wastewater discharge permits and have become more stringent in the National and State Pollutant Discharge Elimination Systems.

This vacuum stripping and absorption process provides an economical, scalable, efficient ammonia recovery technology. It can be scaled up at concentrated animal feeding operations to upgrade biosolids and recover ammonia in animal manure and anaerobically digested manure, thus providing land application of animal manure. Meanwhile, the technology can efficiently recover ammonia in anaerobically digested sewage sludge, raising the utility of biosolids separated from sludge and improving sludge dewaterability, reducing operating costs and adding revenue streams at wastewater resource recovery facilities.

This PFI-TT project will establish partnerships with wastewater generators, technology vendors, and a cooperative field station to promote technology commercialization. The project will also train a postdoctoral researcher and graduate and undergraduate students in innovation and entrepreneurship in environmental technology.

This project is to advance the recently invented vacuum stripping and absorption technology through the proof-of-concept stage for value-added treatment of ammonia-rich wastewater. To scale up from a vacuum stripper that employs single pool boiling, a 125-gallon stripper configured vertically with 3 boiling pools will be operated with landfill leachate, sludge digestate, pressate of sludge digestate, dairy manure, and manure digestate to validate the multi-pool boiling design and optimize this upscaling approach.

The pilot tests will also tune the designs of a demister and absorption column for effective reflux of water vapor and recovery of ammonia as granular ammonium sulfate. The enhancement of vacuum-assisted thermal treatment under the vacuum stripping conditions on solids solubilization, reduction of biosolids pathogens, and digestate dewatering will be evaluated along with ammonia recovery kinetics in the pilot tests to facilitate scale-up design and economic analysis of commercial applications.

The enhancement of solids solubilization and ammonia recovery for high-rate, stable anaerobic digestion will be assessed at a small scale. To facilitate certification of the recovered salt as a fertilizer, especially for organic farming, dual absorption of the stripped ammonia and carbon dioxide in biogas will be explored for benign production of ammonium bicarbonate granules.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.