Abstract: A fluid mixer includes an elongate mixing chamber having an inlet system at one end for admission of liquid and gas to be intimately mixed by passage through the chamber and an outlet for the mixture at the opposite end, wherein opposed longitudinal sides of the chamber are each defined by a surface of scallop shape having peaks and troughs, with the peaks of the two surfaces being relatively offset so as to cause the liquid and gas entering the chamber to flow along a generally sinuous path through the chamber to create a turbulent flow which promotes intimate mixing. Advantageously a UV source extends within the chamber to sterilize the liquid flowing through the chamber.