The flotation tank is 1.2 m (4 ft) in diameter with 0.41–0.46 m (16–18 in)
effective water depth. The system is complete with feed pump, pressure pump,
compressor, air dissolving tube, collection tank, and chemical feed equipment. The
flotation tank is equipped with a spiral scoop for collection and removal of floated
biosolids (Fig. 2.4).
The inlet, outlet, and biosolids removal mechanisms are contained in the central
rotating section. This section and the spiral scoop rotate around the tank at a speed
synchronized with the flow. The system is operated in the recycle flow pressurization
mode, whereby a portion of clarified effluent (30–40%) is continuously recycled
from the collection tank to the air dissolving tube under 400 kPa (60 psi) pressure.
After pressure release, the aerated water is mixed with the influent flow just before
the inlet to the distribution duct that moves with the same velocity, but in opposite
direction to the incoming flow, thus creating a quiescent state in the flotation
chamber. Fine bubbles generated in this manner attach to the suspended particles
and float them to the surface. The spiral scoop takes up the floated biosolids, pouring
them into the stationary center section where they are discharged by gravity.
Clarified water is removed by extraction pipes, which are attached to the moving
center section and discharged into the collection tank [8, 16, 17].
Wiper blades attached to the moving distribution duct scrape the bottom and the
sides of the tank and discharge settled biosolids into the built-in sump, for periodic
purging. The variable speed gear motor drives the rotating elements and scoop.
Electrical current for the gear motor feeds from a rotary contact mounted on the
central shaft.
The second stage FF-Cell is identical to the cell described previously in Sect. 2.
The main characteristics of the two cells are listed in Table 2.1.
For further information on the subject of flotation the reader is referred to the
literature [27–32]
Fig. 2.3 Flow diagram of two-stage flotation system [20]
58
N. K. Shammas et al.
effective water depth. The system is complete with feed pump, pressure pump,
compressor, air dissolving tube, collection tank, and chemical feed equipment. The
flotation tank is equipped with a spiral scoop for collection and removal of floated
biosolids (Fig. 2.4).
The inlet, outlet, and biosolids removal mechanisms are contained in the central
rotating section. This section and the spiral scoop rotate around the tank at a speed
synchronized with the flow. The system is operated in the recycle flow pressurization
mode, whereby a portion of clarified effluent (30–40%) is continuously recycled
from the collection tank to the air dissolving tube under 400 kPa (60 psi) pressure.
After pressure release, the aerated water is mixed with the influent flow just before
the inlet to the distribution duct that moves with the same velocity, but in opposite
direction to the incoming flow, thus creating a quiescent state in the flotation
chamber. Fine bubbles generated in this manner attach to the suspended particles
and float them to the surface. The spiral scoop takes up the floated biosolids, pouring
them into the stationary center section where they are discharged by gravity.
Clarified water is removed by extraction pipes, which are attached to the moving
center section and discharged into the collection tank [8, 16, 17].
Wiper blades attached to the moving distribution duct scrape the bottom and the
sides of the tank and discharge settled biosolids into the built-in sump, for periodic
purging. The variable speed gear motor drives the rotating elements and scoop.
Electrical current for the gear motor feeds from a rotary contact mounted on the
central shaft.
The second stage FF-Cell is identical to the cell described previously in Sect. 2.
The main characteristics of the two cells are listed in Table 2.1.
For further information on the subject of flotation the reader is referred to the
literature [27–32]
Fig. 2.3 Flow diagram of two-stage flotation system [20]
58
N. K. Shammas et al.