Column flotation has been introduced for waste paper de-inking to take advantage of low capital cost and excellent separation performance. Bubble generation employs a. variety of systems; broadly,divided into two types: internal and external. An external in-line static mixer sparger was tested against an internal porous stainless steel sparger. They were compared in an industrial de-inking facility using a 10 cm diameter column. Operating conditions were defined and the effect of gas rate, retention time, wash water rate, and froth height on de-inking was investigated. Both spargers gave similar ink recovery and fiber loss as a function of bubble surface area flux. However, the static mixer gave stable operation while the porous sparger showed evidence of plugging over a 6h test. Combined with some ability to control bubble size overall the in-line static mixer gave superior performance.