On May 10th, a group of water professionals from Singapore, Thailand, Philippines, and India joined a highly engaging knowledge exchange webinar hosted by Aquarden Technologies, Access Cities and the Royal Danish Embassy in Singapore. During the webinar, CEO and founder of Aquarden Technologies, Zhuoyan Cai, shared how Super Critical Water Oxidation (SCWO) can be utilized to fully degrade hardly degradable organics. Organics such as per- and polyfluoroalkyl substances (PFAS) - a large group of ubiquitous, and potentially carcinogenic, chemicals used for a multitude of purposes including fire fighting foam.
Download presentation material from Aquarden Technologies here:
Q&A summary by Aquarden Technologies
What are the OPEX costs in terms of USD/m3 and KWH/m3?
Assuming high organic load ~100,000ppm COD:
Aqueous wastes (up to 10% w/w TSS) - 50 USD/m3, 250 kWh/m3.
Solid wastes (sludges and solids) - 500 USD/ton dry mass, < 2500 kWh/ton (may vary due to waste and water composition).
Note: in our plants, the waste acts as a fuel and generates a lot of energy in the form of hot water. This energy can be recovered.
Can SCWO simultaneously deal with high COD and high TDS?
We will typically need to add a pre-treatment process to either remove salts (e.g. evaporation, electrodialysis, nanofiltration, etc.), or use our sub-critical oxidation process that, depending on the complexity of the organics, can destroy 80-99% of the organics prior to SCWO treatment.
How should operators deal with inorganic contaminants?
We will provide a complete customized process for handling the inorganics. Inorganic contaminants will most likely be removed as a brine where the inorganics can be further concentrated or precipitated.
Can SCWO be used for sewage treatment plant (STP) effluent?
Yes. It is simply a matter of concentrating the organics in the effluent sufficiently so as to provide better economics. We can design and supply the appropriate concentration process.
What is the resulting water quality after SCWO treatment?
SCWO water is typically free of organics with minimal amounts of salt (conductivity <100 µS/cm). However, organically bound minerals may appear in the treated water as mineral acids that may have to be neutralized depending on discharge pH requirements.
Can SCWO treat pollutants in dry form?
Absolutely. The dry waste just needs to be mixed with water to form a slurry. Our plant can typically handle slurries with 10% w/w solids. We might grind the solids prior to SCWO depending on the feed particle size.
Is Aquarden equipped to test wastewater samples and what are the logistics/practicalities involved?
We offer lab SCWO tests where the client ships us a 10L sample of their wastewater. We then provide chemical analysis and a report describing the test results and our treatment recommendations based on the discharge requirements.
Growing demand for effective PFAS destruction
The PFAS group of chemicals includes more than 3000 substances such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) that have been identified with growing concern as highly carcinogenic and bio-accumulative contaminants.
In Europe, large quantities of groundwater and soil are increasingly found to be contaminated with PFAS chemicals. PFAS have been applied in many products and especially as flame retardants, and are extremely recalcitrant to conventional remediation technologies such as chemical and biological degradation.
Super Critical Water Oxidation is a proven method to destroy PFAS and other extremely recalcitrant organics
For more information:
Zhuoyan Cai
Managing Director of Aquarden Technologies
Phone: +45 4870 8588
Email: zc@aquarden.com
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