Abstract: An oxygen-enriched gas burner and method of operation thereof for incinerating and/or melting and/or vitrifying and/or performing thermal treatment and/or oxidizing ground/liquid waste materials and particularly, but not exclusively, contaminated waste materials. The burner comprises a body having annular chambers and defining an injection nozzle which is adjustable whereby to adjust the configuration of a flame and wherein the nozzle is provided, at the center thereof with an axial feed port through which the grounded solid/liquid waste material is injected within the flame. The waste material is fed axially within the flame under control pressure with the waste feed and flame configuration being adjusted independently from one another whereby the waste material is substantially incinerated without substantially affecting the combustion of the gas which would otherwise produce undesirable carbon monoxide and hydrocarbons.