These are some photos of the diffuser pump mechanism that was designed and made for PAH treatment.

Apart from the off the shelf electric motor, the unit was custom designed and manufactured.
Components that would be submerged were turned from 316 L stainless steel.
The top plate was turned from food grade aluminium with the edge profile following the shape of the original lid.
This allowed firm clamping of the unit to the reactor.
All seals were PTFE and flow tubes shaped from 4 mm borate glass.

The centre image links to a screen shot of the design of the pump chamber.