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Comment: Migrated to Confluence 4.0

...

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.   
 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 
...
critical 
...
 micelle 
...
 concentration
...
 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 
...
natural 
...
 foams 
...
 found 
...
 in 
...
 rivers 
...
 and 
...
 lakes
...
. 
...
 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 
...
retrofit 
...
 designs 
...
 page 
...
 for 
...
 details
...
), 
...
 if 
...
 we 
...
 were 
...
 to 
...
 continue 
...
 looking 
...
 into 
...
 this 
...
 theory 
...
 it 
...
 would 
...
 be 
...
 beneficial 
...
 to 
...
 start 
...
 by 
...
 testing 
...
 smaller 
...
 hydraulic 
...
 jumps.