CEEM Seminar Series | Ngai Yin Yip | Columbia University
Circular Nutrient Economy in Sustainable Cities: Membrane Innovations for Decentralized Nitrogen and Phosphorous Recovery from Wastewaters
The current once-through approach of nutrients utilization is unsustainable. A new paradigm is urgently needed to enable the transformation to a more sustainable circular economy model with fully realized nutrient reuse. The high population density of urban centers offers a propitious opportunity for more sustainable nutrient management practices. Urine is rich in nutrients, but is immediately diluted over 100 times by flushing and subsequent mixing with other waste streams. A more rational and forward-looking approach would be to take advantage of the favorable high concentrations by carrying out urine source-separation for decentralized nutrient recovery. In this project, we first evaluate the intrinsic energy requirements to separate and capture nitrogen and phosphorus from different anthropogenic wastestreams of raw municipal wastewater, secondary wastewater effluent, grey water, and diverted urine. We quantitatively show that nutrient recovery from urine is energetically more advantageous compared to other more dilute sources. Next, we employ the innovative membrane technique of Donnan dialysis for the sustainable recovery of orthophosphate from fresh urine. Using the high concentration of chloride ions in an aqueous brine stream to set up an electrochemical potential gradient and drive the transport of orthophosphates across an anion-exchange membrane, we demonstrate the high recovery and enrichment of P. Lastly, we present the novel technology of isothermal membrane distillation to recover ammoniacal nitrogen from hydrolyzed urine using inexpensive/free low-grade heat as energy input. The selective separation of ammonia over water across a hydrophobic microporous membrane avoided the energy penalty associated with the large enthalpy of water vaporization, thus achieving substantial savings in energy consumption. Lastly, we examine the economic and societal benefits of implementing decentralized nutrient recovery.
Ngai Yin Yip
Ngai Yin Yip is the La Von Duddleson Krumb Associate Professor of Earth and Environmental Engineering at Columbia University. He received his doctoral degree in Chemical and Environmental Engineering from Yale University. His current research is focused on advancing physicochemical technologies and innovations for critical separation challenges in water, energy, and the environment. Current projects include recovery of critical materials from waste streams, high-salinity desalination, and zero-liquid discharge using selective membranes and switchable solvents. For his research contributions, Dr. Yip has been featured as an Emerging Investigator by Environmental Science: Water Research & Technology and as a Young Talent by Frontiers of Environmental Science & Engineering. He is currently an associate editor for RSC journal Environmental Science: Advances. Additionally, Yip serves as an editorial advisory board member for ACS ES&T Engineering and as editorial board member for Desalination and Chemical Engineering Journal Advances.