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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2023)

Recovery of nitrogen and phosphorus poses one of the most significant challenges for centralized wastewater treatment processes. Precipitation of struvite, a magnesium ammonium phosphate mineral, used for the recovery of nitrogen and phosphorus, is being widely implemented across Europe and North America, particularly in some of the largest wastewater treatment plants globally. However, these projects are often expensive and require large footprints. Moreover, process controls for struvite precipitation, including the effects of inhibitors on growth rates and nucleation of fine particles, have not been optimized, posing a challenge in achieving the maximum amount of nutrients recovered from wastewater. Smaller utilities, characterized by limited access to technical expertise, limited financial resources, and lower ratepayers will struggle to implement process changes to address nutrient pollution.

Existing struvite precipitation reactors exhibit sensitivity to water quality parameters and the presence of inhibiting molecules. Consequently, the modeled conditions for optimal recovery overpredict the amount of struvite that can be recovered, potentially impacting the offset of capital investments made for installing the technology. In response to these challenges, our study focuses on understanding the effects of saturation, as well as the presence of carbonate and organic inhibitors, on the kinetic rates of struvite precipitation. Additionally, for situations in which struvite may not be the most appropriate fertilizer product for the soil, we propose an electrochemical design to develop a product that addresses the needs of the local soil.

    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2023)
    Several billion metric tons per year of durable carbon dioxide removal (CDR) will be needed by mid-century to prevent catastrophic climate warming, and many new approaches must be rapidly scaled to ensure this target is met. Geologically permanent sequestration of carbon dioxide (CO2) in carbonate minerals-carbon mineralization-requires two moles of alkalinity and one mole of a CO2-reactive metal such as calcium or magnesium per mole of CO2 captured. Chemical weathering of geological materials can supply both ingredients, but weathering reactions must be accelerated to achieve targets for durable CDR. Here, a scalable CDR and mineralization process is reported in which water electrolysis is used to produce sulfuric acid for accelerated weathering, while a base is used to permanently sequester CO2 from air into carbonate minerals. The process can be integrated into existing extractive processes by reacting produced sulfuric acid with critical element feedstocks that neutralize acidity (e.g., rock phosphorus or ultramafic rock mine tailings), with calcium- and magnesium-bearing sulfate wastes electrolytically upcycled. The highest reported efficiency of electrolytic sulfuric acid production is achieved by maintaining catholyte feed conditions that minimize Faradaic losses by hydroxide permeation of the membrane-separated electrochemical cell. The industrial implementation of this process provides a pathway to gigaton-scale CO2 removal and sequestration during the production of critical elements needed for decarbonizing global energy infrastructure and feeding the world.
      Cover page: Electrolytic Sulfuric Acid Production with Carbon Mineralization for Permanent Carbon Dioxide RemovalCreative Commons 'BY' version 4.0 license
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