What is Super Critical Water Oxidation?
AquaCritox® is based on super critical water oxidation.
When water’s temperature and pressure are above 3740C (7000F) and 221 bar (3,000 psi), respectively, it enters a supercritical condition or ‘fourth phase’, i.e. an additional phase to its more familiar solid, liquid and gaseous phases. Under these conditions the physical properties of water change.
Key properties of super critical water are:
- its density is less than that of the liquid;
- its viscosity is the same as the gas; and
- its diffusivity is mid-way between the liquid and the gas.
Most importantly the solubility of gases and organic compounds are increased to almost 100%, while inorganic compounds become largely insoluble. Oxygen is completely miscible in all proportions with super critical water.
When a stream containing organic material is placed under super critical condition and oxygen is introduced a rapid (,60 seconds) and complete (>99.999) oxidation reaction takes place. This oxidation reaction is exothermic and so the reaction can be auto thermal at very low levels (30,000 mg/ltr COD approx) of organic matter.
Unlike incineration, the only gaseous emissions from this process are carbon dioxide (CO2) and nitrogen (N 2).
Phosphorous and coagulant can be recovered from the inert residue.
Unlike volume reduction processes, AquaCritox® does not produce a hazardous concentrate which then requires disposal. Biological treatment processes produce a waste sludge that requires disposal., the AquaCritox® process produces an effluent liquid stream with extremely low COD values. Any inert material within the waste stream will exit the AquaCritox® process as inert residue.
Wet Air Oxidation processes typically achieve only partial oxidation of pharmaceutical wastewater, whereas in the supercritical phase, complete oxidation is achieved. As the oxidation occurs in the water phase, the process does not have the air emissions issues which as associated with incineration of high strength organic wastewater streams.