TOP® - Wet Air Oxidation for Spent Caustic

Spent caustic liquors from ethylene manufacturing and petroleum refining are some of the nastiest wastewater the industry must deal with. These liquors are odorous, highly colored and contain sodium sulfides, mercaptans, phenols and emulsifed hydrocarbons, so they do not respond to traditional treatment.

The most effective on-site treatment of spent caustic is TOP® - Wet Air Oxidation for Spent Caustic which can achieve the oxidation of pollutants as sulfide to soluble thiosulfate, sulfite and sulfate. The treated stream is then suitable for bio treatment in the plants wastewater treatment system.

Wet Air Oxidation is a proven technology currently being used by numerous olefin plants.


The TOP® technology is best known for treating liquid wastes in the following manner:

  • During the wet phase heavy organic molecules are oxidized by air at high temperature and high pressure levels creating a process similar to a flame less burning.
  • Complex organic molecules are oxidized and become simple, biodegradable molecules.
  • Odor and color will be permanently removed

International Recognition:


  • 1990 Best Reparative Technology award from ENEA (the EU delegate for Italy)
  • 2006 BAT (Best Available Techniques) award from the EU-IPPC for O.F.C.s (Organic Fine Chemicals)



Our TOP® - Wet Air Oxidation technology for Spent Caustic:

  • Has been extensively tested on an industrial scale
  • Is able to reduce COD levels by approximately 70%. The remaining COD is detoxified, fully decolored and almost entirely biodegradable, allowing it to be further processed in a biological plant