Coagulación Floculación Presentación
Coagulación Floculación Presentación
Coagulación Floculación Presentación
Coagulacin-Floculacin
Contenido
1. Partculas coloidales y mecanismos de
coagulacin
o Origen de su carga elctrica
o Capacidad de intercambio catinico
o Teora de la doble capa
2. Fuerzas bsicas y mecanismos de
coagulacin
3. Coagulantes
4. El papel del pH y la alcalinidad
5. Floculacin
6. Prueba de jarras
Coagulation process
Destabilization of small suspended and
colloidal particulate matter
Adsorption and/or reaction of portions
of the colloidal and dissolved NOM to
particles, and
Creation of flocculant particles that will
sweep through the water to be treated,
enmeshing small suspended, colloidal,
and dissolved material as they settle
Flocculation process
To
produce
particles,
by
means
of
aggregation, that can be removed by
subsequent particle separation procedures:
sedimentation and/or filtration
Microflocculation
(perikinetic):
particle
aggregation by the random thermal motion
of fluid molecules (Brownian motion)
Macroflocculation (orthokinetic): particle
aggregation by inducing velocity gradients
and mixing in the fluid containing the
particles
and
time
for
Particle size:
In natural waters:
N
log A log(d p )
(d p )
log
distribution
distribution
Particle-solvent interactions
imperfections:
clay,
negative
(2)(1000)e N A I
10
kT
0
10
1/2
1 , mole/L
2
Z
M
Zeta potential:
v0 k z
Z
0
Z = zeta potential, mV
v0 = electrophoretic mobility, m/s, V/cm
= vE/E, in natural waters (-2 to +2)
vE = electrophoretic velocity of migrating particle, m/s,
nm/s, mm/s
E = electrical field at particle, V/cm
kz = constant that is 4 or 6 when particle is much
smaller than thickness of double layer)
= dynamic viscosity of water, N.s/m2
= Permitivity relative to a vacuum ( for water is 78.54)
0 = permitivity in a vacuum, 8.854188x10-12 C2/J.m, N/V2
When Z < 20 mV, rapid flocculation occurs
Depends on:
Repulsive electrostatic force: principal mechanism
controlling the stability of hydrophobic and
hydrophilic particulates
Microflocculation
Flocculation of small particles (<
0.1 m) by Brownian motion
Macroflocculation
Major mechanism for floculation of
particles > 1 m
Mixing causes velocity gradients
and greater number of collisions
between particles
Gentle mixing
Flocculation kinetics
Tambo and Watanabe, Japan (1979)
Odegaard, Norway (1985)
Flocculation
theory:
performance factors
Flocculation
Objective:
To simulate, to the extent possible,
the expected or desired conditions
in the coagulation-flocculation
facilities
How to conduct:
First, a rapid-mix phase (high
mixing intensity) with addition of
coagulant (Coagulation)
Then, slow-mix period to simulate
flocculation (Flocculation)
Finally time for settling (Settling)
G
values
flocculation
for
coagulation
and
Parameters to measure:
Turbidity, suspended solids
removal
Dissolved solids, DQO
DOC or UV absorbance at 254
(260) nm
Metals concentration
Residual dissolved coagulant
concentration
Sludge volume that is
Coagulation-flocculation-Mixing
Coagulation mixing
Coagulation mixing
Flocculation-Mixing
Common types flocculation
mixing systems:
1.Vertical-shaft turbine system
Flocculation-Mixing
V 1 Co
1
Q k Ct
(1)
Flocculation-Mixing
For an ideal plug-flow system and
steady-state
conditions,
the
relationship between detention time
and concentration, applying firstorder reaction kinetics, is given in Eq.
2
V L 1 C
t
ln
Ct
o
(2)
wheret, V, Q, Co, Ct are same as Eq. 1
L = length of rectangular basin
= horizontal flow velocity
Q = flow rate
P
G
V
Nd 2
NR
1x105
(3)
time:
time:
time:
time:
20 s
30 s
40 s
> 40 s
G = 1000 s-1
G = 900 s-1
G = 790 s-1
G = 700 s-1
P KN 3 d 5
P
G
V
Nd 2
Re
1x105
Turbulent regimen
P KN 3 d 5
(4)
G = Velocity gradient, s-1
P = Power of mixing input to vessel, W, J/s
V = Volume of mixing vessel, m3
K = Constant, impeller 2 or 3 wings: 1
= Water density, kg/m3
d = Propeller diameter, m
N = Propeller velocity, rps
P
N 3 d 5
Pumping
Q number
NQ
important
for
design
of
(5)
Nd 3
Hg
(Nd )
N H number
Head
2
(6)
(7)
where Np = power number, dimensionless
NQ = pumping number, dimensionless
NH = head number, dimensionless
Q = flow rate imparted by impeller, m3/s
H = head impeller imparts to impeller flow, m
Example
v
(8)
P D P r
2
Example
Example
Coarse-media
flocculators
(10)
be
determined
from
the
gH
t
(11)
where L = length of the channel, m
Coarse-media flocculators:
2
Head
porus
1 2 1the
through
1 1media
H loss
1 can
a
v b
v2
the following
3
g 3 equation:
L
d
g
be estimated by
(13)
where a,
vb = empirical coeffcients
d = size of media particles (determined by sieve
analysis), m
3
Project: Coagulation-flocculation
surface water and graywater
Three working teams
Six students each
Jar-tests:
Water Center Lab. or Chemical Engineering
Lab.
Water source: surface water and graywater
from different detergents (powder and liquid)
Objective: Determine optimum coagulationflocculation conditions for removal of
turbidity, suspended solids, dissolved solids,
TDOC, cations (Na, NH, Ca, Mg, k) and anions
(Cl, F, sulfates, phosphates, nitrates and
nitrites: pH, coagulant dosage, mixing
intensity, mixing duration, settling time
of
Project: Coagulation-flocculation
surface water and graywater
of
!
GAMBARIMASU!