...
Determining
...
the
...
Cause
...
of
...
Surface
...
Foam
...
Experiments
Experimental Set-Up
...
In
...
an
...
attempt
...
to
...
recreate
...
surface
...
foam
...
in
...
a
...
lab
...
setting,
...
similar
...
to
...
that
...
found
...
in
...
AguaClara
...
Plants
...
in
...
Honduras,
...
we
...
first
...
had
...
to
...
recreate
...
a
...
similar
...
design
...
in
...
the
...
lab.
...
We
...
did
...
so
...
by
...
first
...
having
...
a
...
tank
...
which
...
mixed
...
tap
...
water
...
and
...
clay
...
in
...
order
...
to
...
have
...
a
...
constant
...
turbidity
...
of
...
approximately
...
100
...
NTU.
...
This
...
tank
...
represented
...
the
...
incoming
...
plant
...
water.
...
Water
...
from
...
this
...
tank
...
was
...
then
...
mixed
...
with
...
Natural
...
Organic
...
Matter
...
(NOM)
...
and
...
sent
...
into
...
Tank
...
2
...
which
...
simulated
...
the
...
rapid
...
mix
...
tank
...
and
...
first
...
baffle
...
of
...
the
...
flocculation
...
tank.
...
Once
...
in
...
this
...
tank,
...
the
...
turbidity
...
of
...
the
...
water
...
was
...
once
...
again
...
measured,
...
and
...
alum
...
was
...
dripped
...
onto
...
the
...
surface
...
of
...
the
...
water.
...
The
...
water
...
in
...
the
...
rapid
...
mix
...
side
...
of
...
tank
...
2
...
was
...
mixed
...
with
...
a
...
stirrer
...
before
...
traveling
...
into
...
the
...
first
...
baffle
...
portion
...
of
...
the
...
tank.
...
It
...
was
...
here
...
that
...
the
...
water
...
was
...
able
...
to
...
settle
...
a
...
bit
...
and
...
a
...
webcam
...
took
...
pictures
...
of
...
the
...
surface
...
water
...
every
...
two
...
minutes
...
to
...
determine
...
if
...
surface
...
foam
...
was
...
created.
...
When
...
an
...
aerator
...
was
...
added,
...
it
...
was
...
placed
...
in
...
the
...
first
...
baffle
...
portion
...
of
...
tank
...
2.
...
In
...
order
...
to
...
calculate
...
the
...
energy
...
dissipation
...
rate
...
at
...
the
...
rapid
...
mix
...
due
...
to
...
the
...
tubing,
...
first
...
we
...
calculated
...
the
...
head
...
loss
...
(h)
...
of
...
the
...
tubing
...
using
...
the
...
equation,
...
Wiki Markup |
---|
{latex}
\large
$$
h = \left( {{Q \over {ka}}} \right)^2 {1 \over {2g}}
$${latex} |
...
Then
...
we
...
calculated
...
the
...
residence
...
time
...
(θ)
...
using,
Wiki Markup |
---|
{latex} \large $$ \theta = {{d_{tube} } \over v} $${latex} |
Where,
...
Wiki Markup |
---|
{latex}
\large
$$
v = {Q \over a}
$${latex} |
...
Finally
...
energy
...
dissipation
...
(ε)
...
was
...
calculated
...
using
...
the
...
following
...
equation,
Wiki Markup |
---|
{latex} \large $$ \varepsilon = {{gh} \over \theta } $${latex} |
Where:
...
h=
...
the
...
head
...
loss
...
due
...
the
...
tube,
...
Q
...
=
...
is
...
the
...
flow
...
rate
...
in
...
mL/min
...
a
...
=
...
the
...
area
...
of
...
the
...
tube
...
k
...
=
...
constant
...
magnitude
...
of
...
0.6
...
g
...
=
...
gravity
...
θ
...
=
...
the
...
residence
...
time
...
d
...
tube
...
=
...
the
...
length
...
of
...
energy
...
dissipation
...
of
...
the
...
jet,
...
which
...
was
...
estimated
...
on
...
the
...
length
...
scale
...
of
...
the
...
diameter
...
of
...
the
...
tubing.
...
V
...
=
...
speed
...
the
...
flow
...
ε
...
=
...
energy
...
dissipation
...
We
...
obtained
...
the
...
same
...
order
...
of
...
magnitude
...
for
...
energy
...
dissipation
...
as
...
the
...
AguaClara plants. Â
Wiki Markup |
---|
plants. \\ {float:right\|border=2px solid black\|width=300px} !AguaClara experiment setup.jpg|width=300px, align=center! h5. Illustration of Experimental Setup {float} |
Our
...
experiment
...
included
...
the
...
following
...
parameters:
...
Coagulant(Alum)
...
dosage,
...
concentration
...
of
...
Natural
...
Organic
...
Matter
...
(NOM),
...
location
...
of
...
alum
...
addition,
...
aeration
...
of
...
water
...
and
...
addition
...
of
...
a
...
surfactant.
...
In
...
the
...
first
...
week
...
of
...
our
...
experiment,
...
we
...
tested
...
for
...
alum
...
dosage
...
in
...
order
...
to
...
determine
...
whether
...
it
...
caused
...
foam
...
formation.
...
Alum
...
dosages
...
of
...
35
...
mg/L,
...
45
...
mg/L,
...
55
...
mg/L
...
and
...
65
...
mg/L
...
were
...
added
...
to
...
the
...
rapid
...
mix
...
chamber.
...
The
...
following
...
week
...
the
...
group
...
used
...
Humic
...
Acid
...
in
...
order
...
to
...
determine
...
the
...
effects
...
of
...
NOM
...
on
...
surface
...
foam
...
formation.
...
Varying
...
the
...
dosage
...
at
...
1mg/L,
...
2mg/L,
...
5
...
mg/L
...
and
...
10
...
mg/L,
...
Humic
...
acid
...
was
...
mixed
...
in
...
the
...
rapid
...
mix
...
chamber
...
with
...
45
...
mg/L
...
of
...
alum.
...
After
...
deciding
...
to
...
add
...
an
...
aerator,
...
we
...
kept
...
the
...
parameters
...
the
...
same
...
as
...
in
...
the
...
NOM
...
experiments,
...
however
...
we
...
added
...
an
...
aerator
...
to
...
the
...
first
...
baffle
...
portion
...
of
...
tank
...
2.
...
Finally
...
to
...
study
...
the
...
effect
...
of
...
hydraulic
...
jump
...
on
...
bubble
...
formations,
...
we
...
varied
...
the
...
height
...
of
...
the
...
water
...
fall
...
at
...
12.4cm,
...
14cm,
...
and
...
15.4
...
cm.
...
We
...
used
...
these
...
heights
...
because
...
they
...
were
...
approximately
...
equal
...
to
...
the
...
distance
...
that
...
water
...
would
...
be
...
falling
...
in
...
the
...
LFOM.
...
After
...
determining
...
both
...
the
...
cause
...
of
...
the
...
foam
...
and
...
theoretical
...
ways
...
to
...
prevent
...
the
...
water
...
from
...
aerating,
...
our
...
next
...
task
...
was
...
to
...
produce
...
designs
...
for
...
retrofitting
...
the
...
current
...
AguaClara
...
plants
...
in
...
operation.
...
Results
...
&
...
Discussion
...
Our
...
first
...
experiment
...
sought
...
to
...
determine
...
whether
...
overdosing
...
alum
...
could
...
aid
...
in
...
the
...
formation
...
of
...
surface
...
foam.
...
After
...
dosing
...
the
...
water
...
with
...
varying
...
alum
...
concentrations,
...
it
...
was
...
determined
...
through
...
observation
...
that
...
no
...
foam
...
was
...
formed.
...
Although
...
the
...
foam
...
was
...
not
...
formed,
...
this
...
information
...
was
...
crucial
...
to
...
our
...
research.
...
Not
...
only
...
did
...
it
...
minimize
...
the
...
list
...
of
...
potential
...
foam
...
formation
...
factors,
...
it
...
also
...
help
...
build
...
our
...
understanding
...
of
...
foam
...
formation.
...
As
...
a
...
result
...
of
...
foam
...
not
...
forming
...
due
...
to
...
alum
...
addition
...
at
...
the
...
surface
...
of
...
the
...
water,
...
we
...
also
...
were
...
able
...
to
...
rule
...
out
...
alum
...
addition
...
under
...
the
...
water
...
surface
...
as
...
intuitively
...
it
...
was
...
a
...
solution
...
to
...
the
...
form
...
formation.
...
Our
...
second
...
experiment
...
sought
...
to
...
determine
...
whether
...
or
...
not
...
the
...
addition
...
of
...
Natural
...
Organic
...
Matter
...
(NOM)
...
contributed
...
to
...
the
...
formation
...
of
...
surface
...
foams.
...
At
...
all
...
concentrations
...
of
...
Humic
...
Acid,
...
we
...
again
...
found
...
there
...
was
...
no
...
surface
...
foam
...
formed.
...
Although
...
the
...
NOM
...
did
...
lower
...
the
...
surface
...
tension
...
better
...
enabling
...
bubbles
...
to
...
form,
...
we
...
believe
...
they
...
did
...
not
...
form
...
due
...
to
...
a
...
lack
...
of
...
air
...
bubbles
...
which
...
naturally
...
are
...
found
...
in
...
AguaClara
...
plants.
...
As
...
a
...
result,
...
we
...
modified
...
our
...
experiment
...
to
...
include
...
an
...
aerator
...
to
...
provide
...
them.
...
In
...
our
...
next
...
experiment,
...
we
...
again
...
varied
...
the
...
concentration
...
of
...
NOM
...
but
...
included
...
an
...
aerator
...
to
...
provide
...
bubbling
...
directly
...
into
...
what
...
would
...
be
...
the
...
first
...
baffle
...
spacing.
...
At
...
concentrations
...
below
...
2
...
mg/mL
...
we
...
found
...
that
...
no
...
foam
...
was
...
formed.
...
However
...
at
...
higher
...
concentrations
...
of
...
Humic
...
Acid,
...
we
...
found
...
that
...
large
...
bubbles
...
would
...
rise
...
and
...
then
...
quickly
...
pop
...
in
...
the
...
center
...
of
...
the
...
tank.
...
In
...
the
...
meantime,
...
smaller
...
bubbles
...
would
...
form
...
around
...
the
...
edges
...
of
...
the
...
tank
...
and
...
were
...
slightly
...
more
...
persistent
...
as
...
seen
...
in
...
Figure
...
2.
Wiki Markup |
---|
{float:left\|border=2px solid black\|width=300px} !foam.jpg|width=300px, align=center! h5. Figure 2: Surface foam as a result of Humic Acid Addition {float} |
Bubbles
...
form
...
when
...
water
...
molecules
...
form
...
bonds
...
around
...
air
...
pockets.
...
A
...
surfactant
...
is
...
generally
...
an
...
organic
...
molecule
...
that
...
has
...
both
...
hydrophobic
...
and
...
hydrophilic
...
ends.
...
While
...
surfactants
...
reduce
...
the
...
surface
...
tension
...
of
...
water
...
they
...
also
...
form
...
micelles
...
in
...
water
...
which
...
helps
...
to
...
stabilize
...
air
...
bubbles
...
and
...
prevent
...
them
...
from
...
aggregating.
...
The
...
concentration
...
at
...
which
...
surfactants
...
begin
...
to
...
form
...
micelles
...
is
...
known
...
as
...
the
...
...
...
...
or
...
CMC.
...
Although
...
the
...
addition
...
of
...
humic
...
acid
...
did
...
reduce
...
the
...
aggregation
...
of
...
air
...
bubbles
...
it
...
still
...
occurred.
...
This
...
resulted
...
in
...
large,
...
non
...
persistent
...
air
...
bubbles
...
that
...
formed
...
a
...
foam
...
at
...
the
...
surface
...
of
...
the
...
water.
...
This
...
may
...
be
...
attributed
...
to
...
not
...
reaching
...
the
...
CMC,
...
however
...
using
...
higher
...
concentrations
...
of
...
humic
...
acid
...
would
...
not
...
accurately
...
replicate
...
plant
...
conditions.
...
Although,
...
a
...
surface
...
foam
...
was
...
formed
...
at
...
concentrations
...
of
...
Humic
...
Acid
...
greater
...
than
...
2
...
g/mL,
...
it
...
was
...
not
...
the
...
foam
...
that
...
is
...
found
...
in
...
AguaClara
...
plants.
...
The
...
foam
...
we
...
created
...
in
...
lab
...
contained
...
large
...
non-persisent
...
bubbles,
...
however
...
the
...
foam
...
we
...
sought
...
to
...
create
...
contained
...
small
...
persistent
...
bubbles
...
similar
...
to
...
...
...
...
...
...
...
...
.
...
At
...
this
...
point
...
we
...
began
...
searching
...
for
...
a
...
stronger
...
surfactant
...
to
...
further
...
prevent
...
the
...
aggregation
...
of
...
bubbles,
...
thus
...
replicating
...
the
...
foam
...
found
...
in
...
Honduran
...
AguaClara
...
plants.
...
In
...
order
...
to
...
support
...
our
...
hypothesis,
...
we
...
added
...
soap
...
to
...
our
...
last
...
experiment
...
with
...
Humic
...
Acid
...
simply
...
to
...
see
...
if
...
would
...
create
...
the
...
surface
...
foam
...
we
...
wanted.
...
We
...
added
...
soap
...
because
...
its
...
molecular
...
composition
...
is
...
similar
...
to
...
that
...
of
...
fatty
...
acid
...
surfactants
...
found
...
in
...
nature.
...
We
...
found
...
that
...
the
...
soap
...
caused
...
a
...
persistent
...
foam,
...
similar
...
to
...
that
...
found
...
in
...
AguaClara
...
plants
...
and
...
can
...
be
...
seen
...
in
...
Figure
...
3
...
below.
Wiki Markup |
---|
{float:right\|border=2px solid black\|width=300px} !foamwewant.jpg|width=300px, align=center! h5. Figure 3: Surface foam after the addition of Dial soap {float} |
In
...
our
...
bucket
...
without
...
holes
...
experiment,
...
we
...
found
...
that
...
at
...
heights
...
less
...
than
...
14cm
...
we
...
can
...
prevent
...
a
...
hydraulic
...
jump.
...
A
...
hydraulic
...
jump
...
normally
...
causes
...
a
...
significant
...
loss
...
of
...
energy
...
and
...
the
...
production
...
of
...
turbulence
...
often
...
resulting
...
in
...
the
...
entrainment
...
of
...
air.
...
This
...
experiment
...
helps
...
us
...
determine
...
an
...
ideal
...
height
...
for
...
our
...
cup
...
design.
...
Although
...
we
...
have
...
eliminated
...
this
...
cup
...
design
...
(see
...
...
...
...
...
...
),
...
if
...
we
...
were
...
to
...
continue
...
looking
...
into
...
this
...
theory
...
it
...
would
...
be
...
beneficial
...
to
...
start
...
by
...
testing
...
smaller
...
hydraulic
...
jumps.