Abstract: Disclosed is a liquid waste combustion system having a burner comprising a combustion chamber and first, second and third spaced apart injectors positioned outside of the combustion chamber and arranged so as to inject separate unconfined streams of first, second and third waste liquids into the combustion chamber, the axes of the waste streams defining a substantially conical surface converging at an apex within the combustion chamber and the waste streams mixing in the area of this apex. The first waste liquid has a BTU value below that required for combustion, the second waste liquid has a BTU value at least high enough to support combustion, and the third waste liquid has a BTU value significantly greater than that of the second liquid such that the waste mixture is combustible. Means are provided for supplying combustion-supporting gas to the combustion chamber and for igniting the waste mixture within the combustion chamber.