Wet Oxidation Toilet


  • Descriptive Overview
    The Wet Oxidation Toilet is an early stage technology no longer in active development. It is a household-scale hybrid system which uses hydrothermal oxidation as the core technology integrated with a (bio)catalytic polishing stage. It is designed to integrate with a conventional frontend dry toilet. Mixed feces and urine is macerated and transferred to a reactor where microwave-assisted heating is applied. Three technology alternatives are being evaluated for polishing the effluent; i) microbial fuel cells to treat and recover energy, or ii) TiO2/UV to photocatalyze the removal of aqueous carbon and nitrogen or iii) purple phototrophic bacteria that can recover protein-rich biomass for resource recovery.
  • Use Case Details
    Initially designed as a SURT for 5 users per day. Has the potential to integrate a stand-alone wet oxidation SURT with a polishing MURT 20 -100 users per day.
  • Dimensions (meters)
    L 1m x W 1m x H 1m
  • Weight (kg)
  • Use Cases
    • Single-stall Toilet
    • Multi-stall Toilet
  • Interface Type
  • Frontend Description
    Non-flush, dry front-end toilet is currently proposed.
  • Flush Water Source
  • Users per Day (Expected)
    Five users per day for SURT. There is potential to integrate a stand-alone wet oxidation SURT with a polishing MURT 20-100 users per day.
  • Users per Day (Maximum)
  • Type of Waste Treated
    Combined Stream (solids and liquids)
  • Core Processing Technology
    Wet Oxidation
  • Processing Overview
    The technology is based on the Terax process using a wet oxidation reactor to reduce biosolids, from an anaerobic ingestor, to volatile fatty acids.
  • Processing Capacity
    Batch processing with capacity of 15 L/day
  • Processing Parameters
    Wet oxidation temperatures (180-300 degrees Celcius) and pressures (20-50 bar), with air overpressure achieve complete sterilization.
  • Power Systems Overview
    Existing prototypes have used grid power.
  • Energy Balance
    Exothermic reaction heat partially offsets electricity requirements. Methods of energy efficiency are being explored. Volumetric heating via microwaves is being used to minimize heat losses.
  • Control System
    Siemens PLC and HIM mounted to test platform. Monitors temperatures, pressures, mass flow rates and tank levels.
  • Commercialization Status
    In Development
  • Intellectual Property Status
  • Intellectual Property Details
    No patents filed at this time.
  • Frequency of Emptying Outputs
    Solids will need to be emptied on a daily basis.
  • Nutrient Reuse
    There are multiple options, dependent upon the technology-mix. Volatile fatty acids produced in the anaerobic digester may have value as industrial feedstocks for chemical production. Additional value-added byproducts may include: P-based solid fertilizer, clean effluent proteinaceous biomass
  • Solid Emission Characteristics
    Resource recovery potential for fertilizer, energy, or protein.
  • Liquid Emission Characteristics
    Effluent volume is 5-15 liters/day
  • Technology Development Milestones
  • Laboratory Prototype
    TRL: 3 (2016)
    TR 3 was reached with a laboratory prototype in 2016. The technology is based on the proven large scale ‘Terax Process’ that was implemented in New Zealand. The Terax process uses the wet oxidation reactor to reduce biosolids, from a 50,000 person anaerobic digester, to volatile fatty acids that have value as an industrial feedstock for chemical production. Scion’s wet oxidation toilet technology has been under development from 2015. Laboratory testing of the wet oxidation process has demonstrated the technology’s feasibility. Early prototypes of the wet oxidation technology focused on the impacts of reducing the reaction severity (mixing, oxidant, heating) to reduce process costs.
  • Laboratory Validation
    TRL: 4 (2017)
    Laboratory trials achieved TRL 4. SCG was working towards a prototype to operate on-campus at Scion (TRL 5). Minimization of energy requirement and heat recovery is under investigation. The next stage prototype will incorporate biological or catalytic processing units for effluent polishing.
  • Linked Enabling Components
  • None linked
  • Linked Processing Technologies
  • None linked