Wastewater level was maintained suitable through a water
level controller in the influent tank (2). Wastewater was pumped
into the air dissolving vessel (5) where air dissolved at pressure.
The air produced by the air compressor (7) passed the air dissolving
vessel (5) through a porous diffuser at the bottom. Activated
sludge in the air dissolving vessel (5) obtained oxygen produced
by the air compressor (7) and removed pollutants in the wastewater.
Then, the mixed liquor was delivered to the contact zone (9)
and separation zone (10) of flotation tank by the pressured air flow
through the dissolved gas releaser. Within the separation zone
(10), a lot of tiny bubbles were produced whose sizes ranged from
10 to 100 mm when the pressure abruptly dropped, and attached
to activated sludge flocs which were consequently lifted to the
top of the flotation tank (8) and were returned to the mixing column
(3). Effluent water left the flotation tank (8) through the outlet
near the bottom of the tank.