Abstract: A unitary, self-contained apparatus for generating microbubbles using a pipe section with a constriction device for producing a venturi effect to cause a mainstream liquid flowing under pressure in the pipe section to draw a column of additive fluid into the mainstream liquid from an aspiration tube for mixing with the liquid and a turbulence part of the pipe section immediately downstream from the constriction device. Protrusions from the inside surface of the turbulence part of the pipe section protrude to at least the theoretical interface between the column of additive fluid and the surrounding mainstream liquid and preferably beyond, where the theoretical interface is a circumference of the column of additive fluid having a radius equal to the radius of the inside surface of the aspiration tube.