STTR Phase I: Vacuum Stripping and Absorption (VaSA) to Recover Wastewater Ammonia and Treat Digestate

"The broader/commercial impact of this Small Business Technology Transfer Phase I project is advancing efficiency of wastewater infrastructure by filling the gap of scalable technologies to cost-effectively recover ammonia in wastewater. Nitrogen is one of the primary nutrients that are essential for the normal growth of plants. Nitrogen in the fertilizers applied for food production ends up largely in wastewater. This project is to translate the innovative Vacuum Stripping and Absorption (VaSA) process into a cost-effective, scalable technology for recovery of ammonia in wastewater while upgrading the biosolids in the treated wastewater and increasing production of renewable natural gas. The proposed technology promotes efficiency by turning wastewater pollutants like ammonia into high-purity nitrogen fertilizers. It holds a great promise to substantially reduce the operational costs for water resource recovery facilities and concentrated animal feeding operations to meet regulatory requirements for discharge of treated wastewater and land application of animal manure. The recovered fertilizers and upgraded biosolids generate revenues for the facilities and operations. The VaSA process brings wastewater to boiling under vacuum at a temperature much below the normal boiling point, under which ammonia is effectively stripped out of wastewater, separated from water vapor in a demister, and absorbed to an acidic solution to form ammonium sulfate crystals. Through pilot tests using a 3-pool VaSA prototype, this project will for the first time explore the regulation of vapor-liquid equilibrium profile from the complex boiling wastewater to the water-ammonia binary system in the stripper head and demister. When scaling up the VaSA technology, vapor-liquid equilibrium evolves from the multi-pool boiling stripper throughout the demister and varies with the number of vertically mounted pools and demister configuration. Understanding the vapor-liquid equilibrium profile will derisk the multi-pool scaling-up design approach and inline production of solid fertilizers. By controlling the factors that regulate vapor-liquid equilibrium, the technology can be scaled up for continuous operation without compromise of its high efficiency for ammonia recovery while maintaining minimal energy consumption. Moreover, it is expected to prove the high efficiency of anaerobic digestion under alkaline conditions and elucidate the mechanisms of alkaline anaerobic digestion through laboratory digestion experiments coupled with a single-pool VaSA prototype. 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."