4. Reactor design – Reactor hydraulics and aerodynamics

Reactor efficiency is fundamentally linked to their ability to promote contact between pollutant molecules and bacteria. The reaction medium must be turbulent. The factors to be taken into account are the speed of liquid circulation in the reactor (mechanical energy expended in introducing the liquid, which dissipates in the reactor, and energy supplied by mixing equipment such as agitators or recirculation devices) and the production of biogas bubbles, which cause internal circulation movements in the liquid mass. The latter is a kind of "free energy", but its deployment is not without impact on reactor sizing, insofar as the coalescence of gas bubbles can significantly disrupt the retention of sludge in the reactor (flotation and expulsion of sludge from the top of the reactor to the outside with the liquid current).

As we saw in §