Reactor and method of use

A reactor for introducing a gas into a fluid comprising, a mixing tank for the fluid, a partition means for dividing that tank into at least two chambers and for allowing the fluid to flow between the chambers, a first pump means located in one of the chambers for circulating the fluid downwards in one chamber and then upwards in the other chamber, an aerator assembly located in an upper region of the tank for separating and thereafter aerating a sidestream of fluid from the circulating fluid in the tank and introducing the aerated fluid into the tank for mixing the aerated fluid with the circulating fluid in the tank, the aerator assembly comprising a venturi aerator for the fluid and a second pump means for circulating the sidestream of the fluid from the tank through the aerator.

A method of aerating a fluid circulating in a mixing tank with air in an aerator assembly comprising:

• (a) a plurality of venturi aerators arranged side by side, each venturi aerator defining a region of reduced fluid pressure which is elongate in a section transverse to the direction of flow of the fluid through the region of reduced fluid pressure, and
• (b) a plurality of air delivery channels positioned between the venturi aerators for delivering air to the regions of reduced fluid pressure,
• the method comprising pumping a sidestream of the fluid through the regions of reduced fluid pressure at a linear velocity in the range of 1 to 10 meters/second, and aerating the fluid by introducing air into the fluid in the region of reduced fluid pressure at a volume ratio of air flow rate to fluid flow rate of at least 0.1.