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Flocculation
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Gravity
Terms in this set (34)
Flocculation is the _____-_____ or gentle agitation of the destabilized particles (from the coagulation process) to form a rapid settling floc.
slow-mixing
Slow-mixing may be imparted by either ______ or ______ agitation.
mechanical; pneumatic
Factors affecting the degree of completion of the flocculation process:
a. _____ chracteristics
b. Velocity _______
c. ___________ value
floc;
gradient;
gradient*detention time
Flocculation basins are sometimes designed to provide for _____ _______ in which flow is subjected to _______ G values through the flocculation basin.
At least _____ compartments (to minimize short-circuiting) with typical Velocity Gradient values ranging from _____ to ____ to _____ sec^-1 in each
tapered flocculation; decreasing
3; 50 to 20 10
Tapered flocculation produces ______ _______ where there is a rapid buildup of a small, dense floc, which subsequently aggregates into larger, dense rapid settling particles at ______ G values.
optimum flocculation; lower
Flocculation devices utilized include ______ and vertical shaft paddle wheels, pneumatic systems, and _____ ______ ______
horizontal; solids contact units
What are two types of flocculation using horizontal shaft paddle wheels?
1. Cross Flow Pattern
2. Axial Flow Pattern
In Cross Flow patterns, paddle wheel shafts are mounted at _____ _____ to the flow
right angles
In Cross Flow patterns, a minimum of three consecutive compartments are required to minimize ______-_____ and facilitate ______ _______.
short-circuiting; tapered flocculation
Tapered flocculation in cross-flow units is accomplished by
a. Varying the _____ ____ on the various horizontal shafts.
b. Varying the number of _____ on the various horizontal shafts
c. Varying the ______ ______ of the paddle wheel on the various horizontal shafts
d. Varying the _______ ______ of the various horizontal shafts
paddle size; (biggest in 1st compartment)
paddles; (most in 1st compartment)
paddle diameter;
rotational speed (fastest in 1st compartment)
In axial flow patterns, the paddle wheel shafts are mounted ______ to the flow
parallel
In axial flow pattern, a minimum of ____ consecutive compartments are required to minimize short-circuiting and facilitate "tapered flocculation"
three
Tapered flocculation in axial flow units is accomplished by
a. Varying the _____ _____ on each paddle wheel that has a common horizontal shaft
b. Varying the _____ of paddles on each paddle wheel that has a common horizontal shaft
c. Varying the ______ of each compartment
paddle size;
number;
volume (smallest in 1st compartment)
If compartments are separated by concrete walls with orifices, then circular, stainless steel _______ ______ shall be used on both sides of the orifice to minimum ______-______ and to facilitate tapered flocculation.
series; short-circuiting
When using vertical shaft paddle wheels for flocculation, the basin compartments are arranged in ______ to minimize ______-_______ and to facilitate tapered flocculation
series; short-circuiting
Vertical paddles can also be?
angled
The power imparted to the water by paddle wheels is determined using Newton's Law for the Drag Force (Fd) exerted by a _____ moving object.
submerged
The drag coefficient (Cd) depends on the _______ of the paddle
geometry
What's the drag coefficient for the following paddle length-width ratio?
1. 5
2. 20
3. infinity
1. 1.20
2. 1.50
3. 1.90
The peripheral velocity of the paddle blades is found by what formula?
What is the range for its value?
(pi
D
n)
0.3-3.0
What's the formula for finding the velocity of the paddle wheel relative to the water?
0.75 * peripheral velocity of paddle blades
What's the limit of the total paddle blade area on a horizontal shaft?
<= 20% of the total basin x-sectional area
Velocity range of the water in orifices or ports
0.5-1.0 ft/s
______ _____ and the _____ _____ are determined from flocculation studies
velocity gradient; detention time
The value of _____ is computed to ensure it is within the acceptable GT range
Gt
Determine the ______ ______ of the basin based on the flowrate (Q) and the detention time (T)
design volume
Basin design dimensions are determined from the design ______ and the number of _______ ______ selected
volume; horizontal shafts
Determine the _____-______ and the ______ _____ of the horizontal shaft(s)
power-imparted; rotational speed
Tapered flocculation is used:
-___ for each compartment must be determined (lab or pilot studies)
-Paddle wheel _____ is assumed
-Peripheral _____ of the paddle wheels imparting the desired power is the calculated.
G;
design;
speeds
For Pneumatic Flocculation design
a. The _____ ____ is determined from lab or pilot-plant studies
b. The required _____ to be imparted to the water is calculated as previously defined
c. The "design" ______ value is then used to determine the detention time (T)
d. Basin ______ and _______ are determined from the basin detention time (T or theta) and flowrate (Q)
e. The _____ needed to impart the required power is calculated as follows
velocity gradient;
power;
Gt;
volume; dimensions;
airflow
What combines coagulation, flocculation and sedimentation into a single structural unit?
Solids-contact units
A large volume of flocculated solids is maintained in the system to enhance the number of _______ _______.
interparticle collisions
The volume of solids in the contact zone varies from __-__% of the zone volume.
5-50%
Solids-contact units are best suited for use with what kind of water? Is the water quality constant or variable? What types of water bodies is it used for?
Used for raw water;
reletively constant water quality;
Used to coagulate lake waters and soften well waters
;