Page 116 -

MIXING, COAGULATION, AND FLOCCULATION 6.7

TABLE 6.2 Guidelines for Mixer
Detention Times
Temperature, °C Detention time factor
0 1.35
5 1.25
10 1.15
15 1.07
20 1.00
25 0.95
30 0.90

• Hydraulic methods
• Air mixing
• Induction mixing

Mechanical Mixers. Propeller- or paddle-type mechanical mixers in a dedicated basin
are the most commonly used rapid mix system in water treatment plants. A typical arrange-
ment for this type of rapid mixer is illustrated in Figure 6.1. Another mixer arrangement
without stators and with a turbine-type blade is illustrated in Figure 6.2.

RT. ANGLE GEAR-.~
MOTOR
6"
CHEMICAL FEED TYP-~ [
~

/ - :C.

-- DOWNFLOW
'7" PROPELLERS
O
t
!
i , i
STATOR / *
TYP. (4)

, .>a, • - I
FIGURE 6.1 Propeller-type mechanical flash mixer.