Vortex. 1 - Waste water enters and solids broken up by coarse air bubbles. 2 - Aeration chamber - bacterial culture digests the pollutants. Needs constant flow of oxygen from diffuser at bottom of tank). 3 - Clarification Chamber separates into clear effluent and sludge. Effluent flows pass scum baffle and out of tank. Energy efficient features reduce electricity requirements. Runs when required and red air valve means can run at optimum efficiency.