Technology Summary
Traditional methods of activated or anaerobic sludge disposal, such as land spreading and incineration are becoming more unacceptable due to social pressure, increasing costs and tighter legislation.
Super Critical Water Oxidation Technology is thermodynamically more efficient than incineration. Since it eliminates the need for a drying step as required prior to combustion, it avoids the large unrecoverable loss of potential energy to latent heat of water that is unavoidable in any incineration process.
Diagram – SCWO Flow Scheme
SCWO is also commercially more attractive than anaerobic digestion or wet air oxidation due to the fact that fast reaction rates under near critical and super critical conditions, result in a small plant footprint (lower capital cost). Furthermore it is environmentally more sustainable since the process allows for recovery and recycling of valuable by-products including thermal energy, commercial/food grade CO2, recovered phosphorus or recovered coagulant.
Diagram – Phase Diagram
Technology Benefits
SCWO offers various benefits over traditional sludge processing technologies. It achieves 99.99% destruction of organic material and produces a sterile product. Significant quantities of renewable energy is produced that can be used to generate steam or electricity. This can be used as energy source for the facility where it is installed or for export to the grid.
The process is odourless and produces an inert residue which is effectively the stabilised salts that were present in the sludge or effluent. Since it is not incineration, it does not require as stringent air emission licensing. The off-gas produced is free of dioxins and SOx emissions.
Operating costs and thus also life-cycle costs are significantly reduced since it requires much less energy than incineration. The rapid reaction time results in a small reactor with efficient plant footprint.
Applications
SCWO is suitable in various industrial processes for the treatment of high COD effluents, such as pharmaceutical, petrochemical, etc.
The most relevant application in WWTP (and growing in popularity) is however for the destruction of waste activated sludge. The technology was selected in Cork (Ireland), Valencia (Spain) and San Francisco (California, USA) in this application.
A demonstration unit for testing is available.
Video
Watch a video clip on our SCWO technology:
