By
Ethan Brooke and M. Collins
1
A Solution for Small Systems

Particularly useful for concurrent
systems

Do not have control over water quality

Can not control residence time

Alternative to precursor removal
2
Diffused
Aeration
Surface
Aeration
Spray
Aeration
3
Aeration Kinetics
Equilibrium is the driving force for all forms of
Aeration!
4
Forms of Henry’s
Constant
5
Forms of Henry’s
Constant
6
An “Intuitive Feel” for Henry’s Constants
Henrys Constant
Hcc With Respect to Percent of Constituent
in Aqueous Phase
20
Henrys Constant Hcc
18
16
14
12
10
8
6
4
2
0
0
20
40
60
80
100
Percent of Constituent in Aqueous Phase
7
Henrys Constant Hcc of Oxygen, Methane,
and Carbon Dioxide With Respect to
Percent of Constituent in Aqueous Phase
Henrys Constant Hcc
35
oxygen
30
methane
carbon dioxide
25
20
15
10
5
0
0
20
40
60
80
100
Percent of Constituent in Aqueous Phase
8
Factors Affecting
Henry’s Constant
pH
Complex Mixtures: Co-solvents and Co-solutes
Ionic Strength: Dissolved Salts
Suspended Solids
Dissolved Organic Matter
Surfactants
Temperature
9
Factors Affecting
Henry’s Constant
10
Temperature Correction Factors
11
Temperature Correction Factors
A Critical review of Henrys Law Constants for Environmental Applications
Jeff Staudinger and Paul Roberts, Critical Reviews in Environmental Science
And Technology, 1996
12
Henrys Constants and Temperature Correction
Factor for TTHMs at 20⁰ C and 1⁰ C
THM Species
Chloroform (CF)
Bromodichloromethane
(BDCM)
Chlorodibromomethane
(CDBM)
Bromoform (BF)
Hcc 20⁰ C Hcc 1⁰ C
B
0.127
0.047
183
0.076
0.024
2130
0.035
0.010
2273
0.018
0.006
2120
13
Henrys Constants for Halo Acetic Acids at
20⁰ C
Haloacetic Acid Species
Monochloroacetic Acid
Dichloroacetic Acid
Trichloroacetic acid
Monobromoacetic Acid
Dibromoacetic Acid
Hcc 20⁰ C
0.000000378
0.000000343
0.000000553
0.000000267
0.000000181
14

The Tendency of a system to seek equilibrium is the
driving force for all forms of Aeration!


Equilibrium is expressed by Henrys constant
Temperature has a large effect on Henrys Constant

Haloacetic acids are not volatile enough to strip
effectivly
15
Diffused Aeration
16
17
Diffused Aeration Apparatus
18
Diffused Aeration Apparatus
19
Diffused Aeration Apparatus
20
Diffused Aeration Apparatus
21
Bench Scale Variables
•
•
•
•
•
4º C and 20º C
Air Temperature
Water Temperature 4º C and 20º C
Air Flow Rate 1L/Min and 3L/Min
Number of Diffusers 1 and 4
THM Concentration 100 ug/L and
• Contact Time
400 Ug/L
40 Min and 80 Min
22
Experimental design and analysis
23
Re sponse Pe rce nt TTHM Remove d
Parameter Estimates
Term
Estimate Std Error t Ratio Prob>|t|
Intercept
68.225 1.429209 47.74 <.0001*
Air Tem p[20C]
-0.7125 1.429209
-0.50 0.6301
Water Tem p[1C]
-12.2125 1.429209
-8.54 <.0001*
Concentration[100ug/L]
0.475 1.429209
0.33 0.7472
Air Flow Rate[1.5 L/m in]
-9.1625 1.429209
-6.41 0.0001*
Number of Diffus ers [1]
0.4125 1.429209
0.29 0.7794
Aeration Time[45 min]
-4.975 1.429209
-3.48 0.0069*
Air Tem p[20C]*Water Temp[1C]
-0.025 1.429209
-0.02 0.9864
Air Tem p[20C]*Concentration[100ug/L]
1.1625 1.429209
0.81 0.4370
Air Tem p[20C]*Air Flow Rate[1.5 L/m in]
-0.1 1.429209
-0.07 0.9457
Air Tem p[20C]*Num ber of Diffusers[1]
1.725 1.429209
1.21 0.2582
Air Tem p[20C]*Aeration Time[45 min]
-2.0375 1.429209
-1.43 0.1877
Water Tem p[1C]*Concentration[100ug/L]
-1.2125 1.429209
-0.85 0.4182
Water Tem p[1C]*Air Flow Rate[1.5 L/min]
-1.35 1.429209
-0.94 0.3695
Water Tem p[1C]*Number of Diffus ers [1]
1.35 1.429209
0.94 0.3695
Water Tem p[1C]*Aeration Tim e[45 m in]
-2.5375 1.429209
-1.78 0.1096
Concentration[100ug/L]*Air Flow Rate[1.5 L/min] -1.2875 1.429209
-0.90 0.3911
Concentration[100ug/L]*Number of Diffusers[1]
0.4125 1.429209
0.29 0.7794
Concentration[100ug/L]*Aeration Tim e[45 m in]
0.65 1.429209
0.45 0.6600
Air Flow Rate[1.5 L/m in]*Number of Diffusers[1]
-1.6 1.429209
-1.12 0.2919
Air Flow Rate[1.5 L/m in]*Aeration Tim e[45 m in]
-2.0875 1.429209
-1.46 0.1781
Number of Diffus ers [1]*Aeration Time[45 m in]
-1.2875 1.429209
-0.90 0.3911
24
Re sponse Pe rce nt TTHM Remov ed
Parameter Estimate s
Term
Estimate Std Error t Ratio Prob>|t|
Intercept
67.738426
1.22682 55.21 <.0001*
Water Tem p[1C]
-12.69907
1.22682 -10.35 <.0001*
Air Flow Rate[1.5 L/m in]
-8.675926
1.22682
-7.07 <.0001*
Aeration Time[45 min]
-4.488426
1.22682
-3.66 0.0011*
Air Flow Rate[1.5 L/m in]*Aeration Tim e[45 m in] -2.574074
1.22682
-2.10 0.0458*
25
Bench Scale Conclusions

Water temperature and air to water ratio
have a significant effect on removals

Air Temperature and initial concentration
did not have a significant effect on
removals

Bubble size does not have a significant
effect on overall removals
26
Diffused Aeration
Minimum Air to Water
Ratio
27
Percent removal vs. air to water ratio for
THMs at 25º C
Chloroform
Bromodichloromethane
Chlorodibromomethane
Bromoform
50
40
30
20
10
95%
90%
85%
80%
75%
70%
65%
60%
55%
50%
45%
40%
35%
30%
25%
20%
15%
10%
0
5%
Air to water ratio
60
Percent removed
28
29
30
Field Scale Evaluation By
Sherant, Yeuell and Xie

Penn State Harrisburg
31

Receive finished water from wholesale
systems

No direct control over water quality

Minimal ability to manage hydraulic flow and
storage
 Difficult to reduce residence time
32
32
33
33

Consecutive system in Western PA

Violation for TTHMs
 Running Annual Average – 107 µg/L (Sept. 07)
 Must go 1 year (4 quarters) below MCL

Currently working to remove THMs
 Aeration field study October 2007
34
34
Nant-Y-Glo Water Treatment Plant
Cardiff Tank (1,000,000 gallons )
Vintondale Tank (300,000 gallons)
End of Blacklick Distribution System
35
35
C onc entration (µg /L )
THM Concentrations
120
100
80
60
40
20
0
nt
a
N
l
G
-Y
o
In l e
T
F a ll
t
R
n
i
w
s
k
c
o
Winte r
k
n
a
T
to
n
i
V
l
a
d
n
e
k
n
a
T
S pring
fS
o
d
En
em
t
s
y
S um m e r
36
36
Speciation of
THMs
TTHM
Cl3CH
BrCl2CH
Concentration (μg/L)
140
120
100
80
60
40
20
0
n
Na
l
G
t-Y
o
t
e
l
n
I
ock
R
in
Tw
an k
T
s
to
Vin
nda
ank
T
le
En
fS
o
d
em
t
s
y
37
37

75,000 gal tank
 35 days
 16 days of aeration
 Water flows
 Min -11,000 gpd
 Max - 109,000 gpd
 Avg - 63,000 gpd
 Temp 15-19°C
38

4- FlexAir
 -7.5 cfm fine bubble

16 -PermaCap5
 -1.5 cfm-fine bubble

PVC piping
39

3.5 HP

3-Phase

63 CFM
40
40
 Capital
costs
 Operational
 Blower
○ $5600
 Electrical
○ $760
 Diffuser Setup
○ $140
costs
 Blower 2.08 Kw hours
 4320 hours (June – November)
 13 cents per Kw hour
 Total
 Other set up costs
○ Varies
power cost
$1170 / 6 months
 Total
capitol cost
$6,800
41
Results at the Tank
System Inlet
Concentration (µg/L)
160
Twin Rocks Tank
120
80
40
0
0
2
4
6
8
10 12
Time (days)
14
16
18
20
42
42
Distribution System Results
Twin Rocks
Vintondale Pump Station
Concentration (µg/L)
160
120
80
40
65 µg/L
65 µg/L
0
0
2
4
6
8
10
12
14
16
18
20
Time (days)
43
43
Aeration Modeling
Same Daily Water Flow
Smaller Tank
3 Hour Tank Refill
250
Chloroform ( μg/L )
200
200
Constant Air Flow :
70 cfm
160
150
100
MCL
50
0
0
1
2
3
4
5
6
7
8
9
Tim e (days)
75,000 gallon tank, @ 70,000 gpd (total)
44
44
Aeration Modeling
“Smoothed” Water Flow
9 Hour Tank Refill
250
200
Chloroform ( μg/L )
200
Constant Air Flow :
70 cfm
160
150
Water Off 2:00 PM
100
MCL
50
Water on 5:00 AM
0
0
1
2
3
4
5
6
7
8
9
Tim e (days)
175,000 gallon tank , @ 70,000 gpd (total)
45
45

A simple air diffuser can be placed in a storage tank for THM
removal

Effective for small system THM compliance

No removal of HAAs

Most effective for Chloroform
 Dominant species in most chlorinated water

Most effective during warm weather months
 THMs highest
46
Surface Aeration
47
Spray Aeration
48
Spray Aeration Pilot
49
50
Assessing mass transfer coefficients
and interfacial surface area
51
Assessing mass transfer coefficients
and interfacial surface area
52
Pilot Goals

Assess the role of pressure in determining KLa
 Compare KLa of different shower heads at different pressure settings

Assess the influence of atmosphere venting on THM
removal from a storage facility

Evaluate the role of temperature on spray aeration removal
rates

Create a spreadsheet based model to relate percent
removal of THM to flow through shower head
53
Percent of THM removed
Percent of flow aerated
vs percent of THM
removed
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0%
20%
40%
60%
80%
100%
Percent of flow spray aerated
54
Conclusion

Aeration provides a way to remove DBS after they
have formed with a minimal capital investment

DBS most amenable to removal are THMS

HAAs could be removed by Biodegradation (data not
shown)
55
Biodegradation of Disinfection ByProducts
GAC for THM removal
(McGuire & Suffet)
57
BAC filtration on HAAs
Haloacetic Acid Concentration (µg/L)
50
Monochloroacetic acid
Dichloroacetic acid
Trichloroacetic acid
Monobromoacetic acid
Dibromoacetic acid
40
30
20
10
0
Influent
Effluent
58
BAC filtration on DBPs
60
Four trihalomethanes
Six haloacetic acids
Chloral hydrate
DBP Concentration (µg/L)
50
40
30
20
10
0
BAC Influent
BAC Effluent
59
DBP removal

GAC adsorption
 Low carbon capacity

Membranes
 RO filtration; excellent for HAAs; OK for
THMs

Biofiltration
 Biologically active carbon; HAAs not THMs

Aeration
 THMs, especially chloroform
60
Questions?
61