FOULING OF FINE PORE DIFFUSED AERATORS:
AN INTERPLANT COMPARISON
by
C. Robert Baillod and Kevin Hopkins
Michigan Technological University
Houghton, Michigan 49931
Cooperative Agreement No. CR812167
Project Officer
Richard C. Brenner
Water and Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
Development of the information in this report has been funded in part by the U.S. Environmental
Protection Agency under Cooperative Agreement No. CR812167 by the American Society of Civil
Engineers. The report has been subjected to Agency peer and administrative review and approved for
publication as an EPA document. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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FOREWORD
Today's rapidly developing and changing technologies and industrial products and practices frequently
carry with them the increased generation of materials that, if improperly dealt with, can threaten both
public health and the environment. The U.S. Environmental Protection Agency (EPA) is'Charged by
Congress with protecting the Nation's land, air, and water resources. Under a mandate pf national
environmental laws, the Agency strives to :
formulate and implement actions leading to a compatible balance between human activities and the ability
of natural systems to support and nurture life. These laws direct EPA to perform research to define our
environmental problems, measure the impacts, and search for solutions. *
The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and managing
research, development, and demonstration programs to provide an authoritative, defensible engineering
basis in support of the policies, programs, and regulations of EPA with respect to drinking water,
wastewater, pesticides, toxic substances, solid and hazardous wastes, and Superfund-related activities.
This publication is one of the products of that research and provides a vital communication link between
the researcher and the user community. i
As part of these activities, an EPA cooperative agreement was awarded to the American Society of
Civil Engineers (ASCE) in 1985 to evaluate the existing data base on fine pore diffused aeration systems
in both clean and process waters, conduct field studies at a number of municipal wastewater treatment
facilities employing fine pore aeration, and prepare a comprehensive design manual on the subject. This
manual, entitled "Design Manual - Fine Pore Aeration Systems," was completed in September 1989 and
is available through EPA's Center for Environmental Research Information, Cincinnati, Ohio 45268 (EPA
Report No. EPA/625-1-89/023). The field studies, carried out as contracts under the ASCE cooperative
agreement, were designed to produce reliable information on the performance and operational
requirements of fine pore devices under process conditions. These studies resulted in 16 separate
contractor reports and provided critical input to the design manual. This report summarizes the results of
one of the 16 field studies. :
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
in
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PREFACE
In 1985, the U.S. Environmental Protection Agency funded Cooperative Research Agreement
CR812167 with the American Society of Civil Engineers to evaluate the existing data base on fine pore
diffused aeration systems in both clean and process waters, conduct field studies at a number of
municipal wastewater treatment facilities employing fine pore diffused aeration, and prepare a
comprehensive design manual on the subject. This manual, entitled "Design Manual - Fine Pore Aeration
Systems," was published in September 1989 (EPA Report No. EPA/725/1-89/023) and js available from
the EPA Center for Environmental Research Information, Cincinnati, OH 45268. ;
As part of this project, contracts were awarded under the cooperative research agreement to conduct
16 field studies to provide technical input to the Design Manual. Each of these field studies resulted in a
contractor report. In addition to quality assurance/quality control (QA/QC) data that may be included in
these reports, comprehensive QA/QC information is contained in the Design Manual. A listing of these
reports is presented below. All of the reports are available from the National Technical;Information
Service, 5285 Port Royal Road, Springfield, VA 22161 (Telephone: 703-487-4650).
1. "Fine Pore Diffuser System Evaluation for the Green Bay Metropolitan Sewerage District"
(EPA/600/R-94/093) by J.J. Marx
2. "Oxygen Transfer Efficiency Surveys at the Jones Island Treatment Plants, 1985-1988"
(EPA/600/R-94/094) by R. Warriner
3. "Fine Pore Diffuser Fouling: The Los Angeles Studies" (EPA/600/R-94/095) by; M.K. Stenstrom
and G. Masutani j.
4. "Oxygen Transfer Studies at the Madison Metropolitan Sewerage District Facilities"
(EPA/600/R-94/096) by W.C. Boyle, A. Craven, W. Danley, and M. Rieth
5. "Long Term Performance Characteristics of Fine Pore Ceramic Diffusers at Monroe, Wisconsin"
(EPA/600/R-94/097) by D.T. Redmon, L. Ewing, H. Melcer, and G.V. Ellefson j
6. "Case History of Fine Pore Diffuser Retrofit at Ridgewood, New Jersey" (EPA/600/R-94/098) by
J.A. Mueller and P.O. Saurer [
7. "Oxygen Transfer Efficiency Surveys at the South Shore Wastewater Treatment Plant, 1985-
1987'(EPA/600/R-94/099) by R. Warriner
8. "Fine Pore Diffuser Case History for Frankenmuth, Michigan" (EPA/600/R-94/100) by T.A.
Allbaugh and S.J. Kang
iv
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9. "Off-gas Analysis Results and Fine Pore Retrofit Information for Glastonbury, Connecticut"
(EPA/600/R-94/101) by R.G. Gilbert and R.C. Sullivan \
10. "Off-Gas Analysis Results and Fine Pore Retrofit Case History for Hartford, Connecticut"
(EPA/600/R-94/105) by R.G. Gilbert and R.C. Sullivan !
11. The Measurement and Control of Fouling in Fine Pore Diffuser Systems" (EPA/600/R-94/102) by
E.L Bamhart and M. Collins \
12. "Fouling of Fine Pore Diffused Aerators: An Interplant Comparison" (EPA/600/R-94/103) by C.R.
Baillod and K. Hopkins
13. "Case History Report on Milwaukee Ceramic Plate Aeration Facilities" (EPA/600/R-94/106) by
L.A. Ernest ' j
14. "Survey and Evaluation of Porous Polyethylene Media Fine Bubble Tube and Disk Aerators"
(EPA/600/R-94/104) by D.H. Houck !
15. "Investigations into Biofouling Phenomena in Fine Pore Aeration Devices" (EPA/600/R-94/107) by
W. Jansen, J.W. Costerton, and H. Melcer !
16. "Characterization of Clean and Fouled Perforated Membrane Diffusers" (EPA/600/R-94/108) by
Ewing Engineering Co.
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ABSTRACT
There has been increasing interest in fine pore aeration systems, along with concern about diffuser
fouling and the subsequent loss of aeration efficiency. The objective of this study was to
assess the
relative fouling tendency of fine bubble diffusers at nine activated sludge treatment plants. A secondary
objective was to relate fouling to mixed liquor and process parameters. A standardized diffuser test
header containing four removable diffusers was installed at each of the participating plants. Diffusers
were periodically removed and tested for oxygen transfer efficiency (OTE), bubble release vacuum (BRV),
dynamic wet pressure (DWP), foulant accumulation, and increase in OTE after acid cleaning.
The results of this study showed that an increase in BRV was generally accompanied'by a decrease
in oxygen transfer efficiency, an accumulation of foulant, and an increase in DWP loss through the
diffuser. The plants were classified according to their degree of fouling (as measured by BRV). The
classifications were: heavily fouling, moderately fouling, fouling, and lightly fouling. The secondary
objective was to relate fouling tendency to process parameters. Observations at individual plants
suggested that high organic loads enhanced fouling, although interplant comparison suggested a weak
association between fouling and organic load. i
This report was submitted in partial fulfillment of Cooperative Agreement No. CR812167 by the
American Society of Civil Engineers under subcontract to Michigan Technological University under the
partial sponsorship of the U.S. Environmental Protection Agency. The work reported herein was
conducted over the period of 1986-1988.
VI
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CONTENTS
Foreword i... iii
Preface iv
Abstract vi
Figures I viii
Tables i ix
Acknowledgments ; x
1. Introduction ; 1
2. Methods and Approach ', 2
Plan of Study ; 2
Diffuser Test Header 2
Measurements ; 5
Coordination 7
3. Plant Descriptions 8
Frankenmuth, Michigan , 9
Green Bay, Wisconsin .; 10
Jones Island west Plant, Milwaukee, Wisconsin 11
Madison, Wisconsin 12
Monroe, Wisconsin .' 13
North Texas, Piano, Texas ; 14
Portage Lake, Hancock, Michigan .j 14
South Shore Plant, Milwaukee, Wisconsin ....' 15
Whittier Narrows Plant, Los Angeles, California 16
4. Results 18
Data Directory 20
Diffuser test Header Behavior During Study ; 20
Comparative Analysis of Fouling After 12 to 16 Months .; 22
Discussion 26
5. Conclusions i 31
References 32
Appendices
A. Diffuser Foulant Characteristics 33
B. Influent and Plant Process Conditions During Study , 41
C. Description of Methods 45
vii
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FIGURES
Number
Page
1 Sketch of test header and accessories i 3
2 Sketch of test header and pressure monitoring box . . .! 4
3 Frankenmuth plan sketch of Cells 1-6 . .l 9
4 Green Bay Plant plan sketch of Tank 4 i 10
5 Jones Island West Plant plan sketch of Tank 6 i 11
6 Madison Plant plan sketch of Unit 3 (Tanks 22, 23 and 24) .... 12
7 Monroe Plant plan sketch of Tank 2 '. 13
8 North Texas Plant plan sketch of Tank One • 14
9 Portage Lake Plant plan sketch of Unit 2 15
10 South Shore Plant plan sketch of Tank 9 16
11 WMttier Narrows Plant plan sketch i 17
12 Trends in bubble release vacuum ' 21
13 Trends in dynamic wet pressure i 23
14 Relationship between BRV and fouling factor '.-.... 25
15 Relationship between BRV and SRT j. . 27
16 Relationship between BRV and F/M ' 28
17 Relationship between BRV and percent volatile in foulant < . . . 29
viu
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TABLES
1 Characteristics of participating plants ........ ..... 8
2 Frankenmuth Plant process summary ..... ...... '.**** 9
3 Green Bay Plant process summary ............ I.'.*.*.** 10
4 Jones Island West Plant process summary ........ <..!!! ll
5 Madison Plant process summary ............. . ! ! " ' 12
6 Monroe Plant process summary ........... !!!!'*' 13
7 Portage Lake Plant process summary . . ........ ! ! ! ! 15
8 South Shore Plant process summary ........... :. . . . ! is
9 Whlttier Narrows Plant process summary ........ '!!!!! 17
10 Portage Lake Plant summary of dlffuser fouling . . . . . * 19
11 Portage Lake Plant foulant characteristics ...... . . ! ! ! 19
12 Portage Lake Influent and process characteristics
during the study . . . . ........... . . . i ..... 20
13 Comparison of dlffuser characteristics and plant
operating data . . ............. ....;..... 24
IX
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ACKNOWLEDGMENTS ;
!
Significant effort on the part of the professional staff at the various
wastewater treatment plants examined 1n this study was required' to coordinate
the field studies and to supply operating data. Contributions of the
following Individuals are gratefully acknowledged: Lee Hauswlrth at the
Portage Lake plant, Michael Plerner, David Schauer, and Jack Boiex at the Green
Bay plant, Paul Nehm at the Madison plant, Read Warrlner at the! Milwaukee
Jones Island and South Shore Plants, Jerry Elllfson at the Monroe Plant, Dan
Geyer at the Frankenmuth Plant, M1ke Stenstrum at the Wh1tt1er Narrows Plant,
and Ed Barnhart at the North Texas Plant. ;
This study utilized dlffuser cleaning data collected by oth^r
Investigators working on the EPA - ASCE Fine Bubble Diffused Aeration Design
Manual Project. Such data and Information contributed by David; Redmon and
Lloyd Ewlng of Ewlng Engineering and William Boyle of the University of
Wisconsin are gratefully acknowledged. <
This work could not have been completed without the efforts of several
students at Michigan Tech. The contributions of Janette Lutz and Ronald Mauno
are especially acknowledged.
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SECTION 1 ;
INTRODUCTION
The activated sludge process is the most widely used method for secondary
wastewater treatment in the United States, and its popularity is increasing.
Provision of oxygen to the active organisms through aeration is'the most .
energy intensive aspect of activated sludge process operation and consumes 60%
to 80% of the total energy requirements in wastewater treatment. Moreover,
the performance of the biological treatment system is intimately linked to the
proper functioning of the aeration system.
i
Contemporary interest in effective and economical wastewater treatment
systems has resulted in an emphasis on more cost-effective aeration systems.
Fine pore aeration systems, while not a new technology, have the potential to
achieve energy savings in wastewater treatment. One perceived problem with
these systems is the uncertainty involved in estimating their maintenance
costs. In operation, the fine pore aeration devices can become fouled or
covered by a biophysical foulant or slime, and this condition has been
associated with severely reduced aeration efficiency (Boyle and Redmon, 1983).
(U.S. Environmental Protection Agency, 1985). To effectively exploit the
advantages of fine pore diffused aeration equipment, design and operating
engineers need information not only on clean and process water performance,
but also on fouling tendency and cleaning costs.
In recognition of this need, the American Society of Civil Engineers
(ASCE) and the U.S. Environmental Protection Agency (EPA) entered into a
cooperative agreement to develop design Information on fine pore1 diffused
aeration. This effort Included a significant emphasis on plant-scale field
studies conducted to fill gaps 1n knowledge relative to fouling and cleaning
of fine pore air diffusers. One aspect of this effort, and the subject of
this report, was focused on comparing the relative fouling tendencies observed
at the various wastewater treatment plants participating in the ASCE-EPA
project. The objective of this study, therefore, was to assess the relative
fouling tendency of fine bubble diffusers at the participating activated
sludge plants. This information was useful in interpreting the hesults of
other related studies being conducted at these plants. A secondary objective
was to relate fouling to mixed liquor and process parameters. i
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SECTION 2
METHODS AND APPROACH
PLAN OF STUDY
The general approach relied upon Installation of a standardized dlffuser
test header in each of the nine participating activated sludge plants.
Properties of the dlffusers and accumulated foulant were monitored over a
period of approximately 16 months. At the same time, Information on
wastewater and process operating conditions was collected. Comparisons
between the plants were then made to indicate the relative fouliing tendencies.
In addition, the data were examined for possible association of fouling
tendency with wastewater characteristics and process loading parameters.
Additional studies related to the significance of blofllms 1n the dlffuser
fouling phenomenon were conducted on the dlffuser test header stones removed
at the 12 to 16 month interval. The results of these studies are presented
elsewhere (Costerton, 1988). i
DIFFUSER TEST HEADER i
A standardized, Instrumented and removable test header containing four
San1ta1re 0.22 m. (9 in.) disk diffusers was Installed in each of the nine
participating activated sludge plants. The test header was attached to a
removable downcomer, and Instrumented so that air flow could belmeasured and
controlled. Figure 1 shows the test header and Its accessories! The section
of the header feeding Dlffuser 1 was separated from the sect1on:of the header
feeding Dlffusers 2, 3, and 4. This was because the stone in Dlffuser 1 was
replaced at four month Intervals and was expected to have less resistance to
air flow than the older stones in the other dlffusers. Consequently, to
maintain a constant air rate to each dlffuser, the air flow to Diffuser 1 was
independent of the common header feeding Diffusers 2, 3 and 4. !
Figure 2 1s a schematic of the pressure monitoring box and,and associated
tubing connected to a single diffuser. Quick disconnect fittings and valves
were employed so- that selected color coded tubes could be connected to the
pressure monitoring box. Pressure taps into the header and dlffuser plenums
allowed measurement of the pressure differential across the orifice. Air flow
was determined from a calibration curve developed for this orifice. For
example, a pressure differential of 10 cm. (4.0 in.) across the orifice
indicated an air flow of 1.7 m3/hr (1.0 cfm) to the diffuser. The air bubble
pipe terminated at the level of the diffuser so that pressure drop across the
dlffuser was equal to the differential pressure between the plenum and the
bubble pipe. This 1s known as the dynamic wet pressure (DWP). i
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PRESSURE LINES TO DIFFUSERS:
PURGE LINE
PRESSURE
MONITORING
BOX
AIR SUPPLY FROM
EXISTING SOURCE
DIFFUSER #2,
\
DIFFUSER #\ AIR SUPPLY
BUBBLER TUBE
. DIFFUSER #3
.DIFFUSER #4
Figure 1. Sketch of test header and accessories.
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BUBBLER PIPE
O
o
o
DWP
o
AIR TO
BUBBLE PIPE
LOW-DOWN
ORIFICE
PLENUM
HEADER
PLENUM •'
DIFFUSER
Figure 2. Sketch of test header and pressure monitoring box,
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The test headers were installed so that the dlffusers were at a depth of
approximately 1.5 m. (5.0 ft.) and at a position in the tank which was
meaningful for the assessment of fouling. The prescribed position was at the
end of the first grid (in a tapered system), or at the quarter point of a plug
flow tank, or anywhere in a completely mixed tank. When plant conditions made
it impractical to install the pilot header at the prescribed position, the
header was installed closer to the feed point. ;
MEASUREMENTS '•
•
The diffuser study at each plant was conducted over a period of roughly
16 months starting from the date of the test header installation. The study
period was divided into phases, with each phase approximately four months
long. Because of scheduling problems, the length of study at each plant was
not always 16 months and the phases were not always four months |in length.
Air Rates and Pressure Drops i
Air rates were controlled at approximately 1.0 scfm per diffuser. This
was accomplished by measuring and adjusting the flow rate at weekly intervals.
At the same time, the dynamic wet pressure was recorded. The procedure was
straight-forward and consisted of connecting the appropriate color-coded tubes
to the pressure monitoring box, reading the desired pressure differential,
and, if necessary, adjusting the air flow rate to the diffuser. i
i
At the conclusion of each 4 month phase, dynamic wet pressures were
measured at air rates of 1.0, 2.0 and 2.5 scfm, and the test header was lifted
from the tank for removal and characterization of stones. i
Diffuser Characterization Schedule I
The diffuser removal and characterization schedule was designed so that
the stones removed reflected both the incremental and cumulative effects of
fouling. Thus, at the conclusion of each phase except the first|, two stones
were removed, one which had operated only the previous four months, and one
which had operated since the beginning of the study. Normally, a routine
characterization was performed on each stone removed. A special • cleaning
characterization was performed on stones removed at the 12 to 16 month
intervals. This was accomplished by the schedule described below.
At the conclusion of the fourth month, the diffuser stone in Position 1
was removed and replaced by a new stone. The removed stone was subjected to a
routine laboratory characterization for dynamic wet pressure (DWP), bubble
release vacuum (BRV), foulant analysis, and flow profile. At the eighth
month, the stone in Position 1 was again removed and replaced, and the stone
in Position 2 was removed. The Position 2 air outlet was plugged. A routine
characterization was performed on both stones. At the twelfth month, the
diffuser in Position 1 was again removed and replaced, and the stone in
position 3 was removed and the outlet was plugged. A routine characterization
was normally performed on both removed stones. Finally, at the;sixteenth
month, the stones in Positions 1 and 4 were removed. A special cleaning
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characterization was performed on these stones. This consisted of a routine
characterization for DWP, BRV, flow profile, and foulant analysis plus
measurement of oxygen transfer efficiency before and after acid cleaning the
stone. Certain stones removed at the 12 to 16 month periods were also studied
to explore the influence of biofilm formation on fouling (Costerton, 1988)
Routine Diffuser Characterization ',
- , i
A routine diffuser characterization included the following;
Foulant Analysis: This consisted of scraping the foulant off the
surface and analyzing for the weight of dry solids per unit area, volatile
and non-volatile content, and acid solubility. i
Bubble Release Vacuum: This was measured by applying a vacuum to a point
on the working surface of a thoroughly wetted diffuser stone!and measuring
the vacuum required to withdraw bubbles at the specified flux rate from
the point in question. A large number of points were sampled to obtain a
distribution of BRV values and these were averaged to obtain the BRV values
reported in this study. The BRV parameter is sensitive to the the
effective pore diameter at any point on the surface of the stone.
Dynamic Wet Pressure: The dynamic wet pressure (DWP) test measured the*
pressure differential across the diffusers while operating 1n a submerged
condition. The DWP was measured in situ during operation of'the test
header as well as in the laboratory during characterization. Normally,
the DWP was reported at air rates of 1 and 2 SCFM. However, some of the
DWP tests were reported at other air rates, and this required interpolation
to obtain the DWP corresponding to the 1 and 2 SCFM.
Gas Flow Profile: The gas flow profile test measured the rate of air
captured in three concentric circular areas centered over the diffuser
stone. This was used to quantitate the uniformity of air release across
the surface of the stone. ;
Details of the routine diffuser characterization procedure are given in
Appendix C. Normally, this characterization was performed under the general
supervision of William C. Boyle at the University of Wisconsin.
Special Cleaning Characterization. j
Diffusers from the fourth phase of the study were subjected to a special
cleaning characterization. This consisted of a routine characterization plus
laboratory OTE measurement in clean water before and after cleaning. Cleaning
was accomplished by hosing, acid application, and hosing (Milwaukee Method).
In addition, the foulant ash was analyzed for elemental composition by energy
dispersive spectroscopy. Details of this characterization are described in
Appendix C. Normally, this characterization was performed undeV the
supervision of David Redmon at the Ewing Engineering Laboratoryiin Milwaukee.
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Plant Operating Data. !
Throughout the study, operating data were collected by personnel at each
participating plant. This Information Included Influent and primary effluent
wastewater characteristics, final effluent characteristics, and process
information such as food/microorganism ratio, and sludge age. !
COORDINATION \
I
The diffuser. test header was installed at the participating plants as
part; of other studies supported by the ASCE-EPA Fine Bubble Diffused Aeration
Design Project. The investigators responsible for the various s'tudies were
responsible for collection of the test header operating data and for removal
and shipment of the stones for characterization. C. Robert BaiVlod of
Michigan Technological University was responsible for coordinating the
diffuser test header studies and compiling and analyzing the data obtained
from the various plants. l
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SECTION 3 ,
i
PLANT DESCRIPTIONS
Nine municipal activated sludge plants participated in the interplant
fouling comparison. Table I lists the plants along with the wastewater
characteristics and typical operating conditions. The data from certain
plants, such as Green Bay, and Madison were more complete than the data from
other plants such as Whittier Narrows and North Texas. Appendix B summarizes
the wastewater characteristics and operating conditions experienced at each
plant during the fouling study. !
Plant
Frankenmuth
Green Bay '
Jones Island
Madison
Monroe
North Texas
Portage Lake
South Shore
Whittier
Narrows
TABLE 1.
Average
Flow *
(MGD)
1.47
40.0
58.9
13.2
2.2
14.0
2.3
98.0
12.5
CHARACTERISTICS
Annual
BODS *
(mg/L)
:====== = =
652
375
278
87
418
100
150
100
96
SRT
(d)
15.9
2.5
4.0
11.0
8.0
10.0
10.0
7.9
2.3
OF PARTICIPATING PLANTS
Process
Configuration
= s ss a: s =s= s ss =3 ==a ss =2=
CS
CS
C
C
SF
SF
CS
SF
C
* Flow and BODS values are for primary effluent except
used fine screening and Portage Lake, which used only
CS =• Contact Stabilization C = Conventional SF =
** 1 MGD = 3785 mVd
IndustM.
% Flow
45
30
11
6
17
NA
< 5
6
NA
==========
for Jones
course scr
Step Feec
Jl Contribution
% BOD8
71
50
38
38
50
NA
< 5
18
NA
5SSS
Island, which
•eening.
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FRANKENMUTH, MICHIGAN
This 5,560 m'/d (1.47 MGD) contact stabilization plant Includes four
aeration tanks, or cells. The plant receives a substantial Industrial load
consisting primarily of brewery waste. The plant recycles effluent from an
anaerobic dlgestor and filtrate from vacuum filters into the primary
sedimentation tanks. Table 2 summarizes the wastewater characteristics, and
Figure 3 shows a plan view of the aeration tanks.
TABLE 2. FRANKENMUTH PLANT PROCESS SUMMARY
Location: Frankenmuth, Michigan
Average Primary Effluent Characteristics:
Dally Flow: 5,560 rnVd (1.47 MGD)
BOD8: 652 mg/L
TSS: 310 mg/L
NHS: 10.9 mg/1 pH: 7.0
Temperature: 20 °C
Major Industrial Contributors: brewery and restaurants
Fraction of Flow: 0.45
Fraction of BOD8: 0.71
Primary Treatment: sedimentation
Typical SRT: 15 days
Tank Dimensions (each cell, L x W x D)
13.4 m (94 ft) x 6.7 m (22 ft)
x 5.01 m (16.4 ft)
j RAS
Primary
Effluent
-»
->
CEL
CEL
-\
L 2
L I
/
CEL
/
CEL
/
L 3
\
L 4
\
CELL 6
CELL 5
/S
Mixed Liquor
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GREEN BAY, WISCONSIN ,•
This plant consists of 4 parallel contact stabilization processes, each
of which Includes an aeration and reaeratlon tank. The plant ha|s a thermal
sludge conditioning system and recycles the thermal sludge conditioning liquor
to the activated sludge process. Filtrate from the sludge filters 1s also
recycled to the activated sludge process. Typical wastewater and process
characteristics are given 1n Table 3. Figure 4 1s a plan view of the contact
and reaeratlon tanks of quadrant 4 showing the location of the dlffuser test
header. I
TABLE 3. GREEN BAY PLANT PROCESS SUMMARY j
Location: Green Bay, Wisconsin ' .
Average Combined Influent Characteristics *:
Daily Flow: 151,000 mVd (40 MGD)
BOD8: 375 mg/L
TSS: 224 mg/L
NH9: 26 mg/L
pH: 7.0
Temperature: 25 °C
Thermal Sludge Conditioning Liquor and Sludge Filtrate:
Average Daily Flow: 1,890 m3/d (0.5 MGD)
Average BOD8: 7000 mg/L
Average TSS: 3400 mg/L
Major Industrial Contributors: paper mills
Fraction of Flow: 0.30
Fraction of BOD,: 0.50
Primary Treatment: sedimentation
Typical SRT: 2.5 days
Tank Dimensions (L x W x D): 74 m (245 ft) x 22 m (74 ft) x 6.4 m (21 ft)
3j3IMaiMaiWaim«B3::BMMMMMMai:m«aMMV« »aM3B»at«« 3S»aiaiSB«»»«»"«i««»»««
* Primary effluent and mill waste. !
Primary \J/.
Effluent-
REAERATIDN TANK 4
AERATION TANK 4
New
location
RAS
Mixed Liquor
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JONIES ISLAND WEST PLANT, MILWAUKEE, WISCONSIN i
The Jones Island West Plant Includes 2 batteries of 12 aeration tanks
each located north and south of the secondary clarlflers. Each tank consists
of two passes. The test header was Installed 1n the first pass ;of Tank 6.
Screened sewage 1s combined with recycled sludge before 1t flows Into the
aeration tanks. The plant recycles vacuum filter filtrate and scrubber water
from dryers back Into the activated sludge process. Characteristics of the
combined recycle flows and plant Influent are listed 1n Table 4.; Figure 5
shows a plan view of Tank 6. I
TABLE 4. JONES ISLAND WEST PLANT PROCESS SUMMARY
^9(g3BMM:3VIB3B3S33MaRVmMMMnMMMMMMHMMSMBMMHMM9M3iMXfl
Location: Milwaukee, Wisconsin
Average Screened Influent Characteristics *:
Dally Flow: 222,940 mVd (58.9 MGD)
BOD9: 278 mg/L
TSS: 232 mg/L
TKN: 32 mg/L
pH: 7.3
Temperature: 18 °C
Major Industrial Contributors: breweries, food processors, tanneries
Fraction of Flow: 0.11
Fraction of BODS: 0.38
Primary Treatment: fine screening
Typical SRT: 4 days
Tank Dimensions (each pass, L x W x D): 67.7 m (222 ft) x 6.7 m (22 ft)
x 4.6 m (15 ft)
* Includes recycle flows
Mixed Liquor
(-to clarlfler)
Mixed Liquor
|
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MADISON, WISCONSIN . j
i
This 151,000 m*/d (40 MGD) activated sludge plant 1s divided Into two
sub-plants, East and West. The West Plant, 1n turn, 1s divided Into Units 3
and 4. Each unit Includes 1 three-pass aeration tank, and the test header was
placed 1n the first pass (labeled Tank 24) of Unit 3. The plant normally runs
at a relatively high SRT and produces a nitrified effluent. Table 4 lists
some of the plants Influent and process characteristics prior tp the test
header Installation, and Figure 5 1s a plan view of the Unit 3.;
TABLE 5. MADISON PLANT PROCESS SUMMARY,
Location: Madison, Wisconsin
Average Primary Effluent Characteristics:
Dally Flow (West Plant): 50,000 m*/d (13.2 MGD)
BOD9: 87 mg/L
TSS: 67 mg/L
NH,: 15 mg/L
pH: 7.8
16 °C
Temperature
Major Industrial Contributors
Fraction of Flow: 0.06
Fraction of BOD8: 0.15
Primary Treatment: sedimentation
Typical SRT: 11 days
Tank Dimensions (each pass, L x W x D)
meat and cheese processors
80.8 m (265 ft) x 9.2 m (30 ft)
x 5.1 m (16.7 ft)
Approximate location of test iheader
Primary
Effluent
t
RAS
POOOI
TANK 24
£
TANK 23
TANK 22
^1 Mixed
: Liquor
;
-------
MONROE, WISCONSIN
This is an 8,330 m*/d (2.2 MGD) plant that Includes an aerated in-line
equalization basin between the primary clarlflers and the aerat1:on tanks. The
equalization basin was 1n operation during most of the study. T,here are 3
two-pass aeration tanks, and the test header was Installed at the end of the
first pass In Tank 2. Influent 1s fed step-wise along the first pass. The
plant receives a significant Industrial load consisting primarily of soluble
cheese processing and brewing wastes. Characteristics of total waste load 1s
given in Table 6 and a plan view of the aeration basin which contained the
test header is given in Figure 7.
TABLE 6. MONROE PLANT PROCESS SUMMARY
Location: Monroe, Wisconsin !
Average Raw Influent Characteristics: I
Dally Flow: 8,330 m'/d (2.2 MGD)
BOOB: 418 mg/L
TSS: 212 mg/L
TKN or NHS: NA
pH : NA
Temperature: NA ;
Major Industrial Contributors: breweries and dairy and food processors
Fraction of Flow: 0.17 '.
Fraction of BOD8: 0.50 i
Primary Treatment: sedimentation plus aerated, In-line flow equalization
Typical SRT: 8 days
Tank Dimensions (each pass, L x W x D): 31.1 m (102 ft) x 7.6 m (25 ft)
x 3.9 m (12.8 ft)
Mixed Liquor
-------
NORTH TEXAS PLANT, PLANO, TEXAS i
This 53,000 m'/d (14 MGD) treatment plant 1s located near Piano, Texas
and: 1s a combined trickling filter and activated sludge plant. !Lack of
Information on the division of flow between the trickling filter and activated
sludge portions of the plant hampered Interpretation of the plant operating
data. Figure 7 shows a plan view of the tank containing the test header.
RAS
Mixed Liquor
(to clarlfier)
c
cu
3
£
Q-
Ld
£
Q_
TANK #1
Catwalk
Approximate
location of
test header
Figure 8. North Texas Plant plan sketch of Tank One. i
PORTAGE LAKE PLANT, HANCOCK, MICHIGAN '
i
This contact stabilization plant consists of two separate circular
modular units, each of which includes a contact tank, reaeratloni tank,
clarlfier, and aerobic sludge dlgestor. Both units were 1n operation during
the study. This plant receives a relatively low strength and low temperature
influent, with almost no Industrial contribution to the waste load. Table 7
summarizes typical Influent and process conditions for the plant; and Figure 9
is a plan view of Unit 2, which contained the test header. i
14
-------
TABLE 7. PORTAGE LAKE PLANT PROCESS SUMMARY
Location: Hancock, Michigan
Average Raw Influent Characteristics:
Dally Flow: 8,700 mVd (2.3 MGD)
BOD,: 150 mg/L
TSS: 110 mg/1
NH3 or TKN: NA
pH: 7.4
Temperature: 16 °C
Major Industrial Contributors: none
Primary Treatment: coarse screening and preaeratlon
Fraction of Flow Treated by Aeration Basin Studied: 0.50
Typical SRT: 10 days
Tank Dimensions: Diameter of Clar1f1er: 11.9 m (39 ft)
Diameter each unit: 30 m (98.4 ft)
Depth: 4.6 m (15 ft)
Primary
Effluent
Approximate location
of test header
Activated
Sludge ft- VAS
WAS
Secondary
Effluent
Aeration Tank Volunei 340 n3
Figure 9. Portage Lake Plant plan sketch of Unit 2.
SOUTH SHORE PLANT, MILWAUKEE, WISCONSIN i
This plant has 28 single-pass aeration tanks. Primary effluent is fed at
the head and step-wise along both sides of each tank. The test header was
located in Tank 9, approximately 27 m. (90 ft.) from the head of;the tank.
Typical primary effluent and process characteristics are given lij Table 8, and
Figure 10 shows a plan view of Tank 9. i
15
-------
TABLE 8. SOUTH SHORE PLANT PROCESS SUMMARY
Location: Milwaukee, Wisconsin i
Average Primary Effluent Characteristics: •
Dally Flow: 371,000 mVd (98 MGD) \
BODS: 100 mg/L
TSS: 72 mg/L
TKN: 29 mg-N/L j
pH: 7.7 - • i
Temperature: 15 °C ;
Major Industrial Contributors: glue processors, food processors, and machine
industries \
Fraction of Flow: 0.06 ;
Fraction of BODS: 0.18
Primary Treatment: sedimentation i
Typical SRT: 7.9 days j
Tank Dimensions (each pass, L x W x D): 113 m (370 ft) x 9.1 m (30 ft)
4.6 m (15 ft) I
Primary
Effluent
t
RAS
Primary
Effluent
1
Primary
Effluent
/^BBBO TANK * 4
/ t
t
; Mixed
i Liquor
;
-------
TABLE 9. WHITTIER NARROWS PLANT PROCESS SUMMARY
Location: Los Angeles, California
Average Primary Effluent Characteristics:
Dally Flow: 47,300 mVd (12.5 MGD)
BOD,: 96 mg/L
TSS: 95 mg/1
NH3 or TKN: NA
pH: NA
Temperature: 25 °C
Major Industrial Contributors: NA
Primary Treatment: sedimentation
Typical SRT: 2.5 days
Primary . .
Effluent /
\
r— >
^
s*
Tank
Tank
Tank
fff*m
3
2
1 ,
^ Mixed Liquor
— ... ^> ^ J.Q j-^pif jer)
^ '
DA
-------
SECTION 4
RESULTS
DATA DIRECTORY
The reduced data are presented 1n three tables for each participating
plant. These tables are titled: i
IPlarvt Name) Summary of Dlffuser Fouling i
i
These tables 11st the date, elapsed time (time the characterized stone
resided in the tank), field and laboratory DWP, laboratory BRY, flow
profile (fraction of air flow collected in outer annular are'a), and
fouling factor (SOTE of a fouled stone divided by the SOTE of a new
stone). Table 10 is a summary of diffuser fouling for the Portage Lake
Plant and is given here for illustration. Corresponding tables for the
other participating plants are given in Appendix A (Tables Al, A3, A5, A7,
A9, All, and A13). i
i
(Plant Name) Foulant Characteristics
These tables list the date, elapsed time (time the characterized stone
resided in the tank), dry foulant accumulation expressed as mg/sq.cm,
percent ash in the dry foulant, percent of the ash which wasi solubilized
by hydrochloric add, and percentages of silicon, calcium, and iron
measured in the ash during a cleaning characterization. Table 11 shows
the foulant characteristics for the Portage Lake Plant and 1s given here
for illustration. Corresponding tables for the other participating plants
are given in Appendix A (Tables A2, A4, A6, A8, A10, A12, and A14).
(Plant Name) Influent and Process Characteristics During thei Study
These tables begin with the date and elapsed time followed by Influent and
process characteristics. Table 12 shows the influent and process
characteristics for the Portage Lake Plant. In these tables; the elapsed
time refers to the Incremental time prior to the listed date. In Table
12, for example, the date 1/14/87 appears with elapsed timesiof 4.0 and
8.4 months. The influent and process data listed for the 4.0 month
elapsed time pertain to the incremental 4.0 month period preceding
'L/14/87. Likewise, the data listed for the 8.4 month elapsed time pertain
to the cumulative 8.4 month period preceding 1/14/87. The cumulative
period spans the time between the beginning of the study and!the listed
date. Corresponding tables for the other participating plants are given
i
18 '
-------
in Appendix B (Tables Bl, 82, B3, B4, B5, B6, and B7). '.
TABLE 10. PORTAGE LAKE PLANT SUMMARY OF DIFFUSER FOULING
DATE
=============
NEW DIFFUSER
9/10/86
1/14/87
1/14/87
5/21/87
5/21/87
8/3/87
ELAPSED
TIME
MONTHS
=============
0.0
4.4
4.0
8.4
4.2
12.7
15.2
FLD OWP
1n
111
9 1 SCFM 9
=============
5.0
5.5
6.0
7.6
9.0
12.0
8.0
LAB DWP,
1 SCFM 9
============
5.0
8.9
6.5
7.5
6.4
7.5
NA
1n
2 SCFM
:======:
5.6
10.5
9.0
9.5
9.4
9.6
NA
DDW
DKV
In
========
5.3
14.8
13.5
18.3
13.0
19.9
18.1
FLOW ;
DDAC TIC
PROFILE
OUT/TOT
i
==33S3SS— 333=2
0.80 '•
0.50
0.70 :
0.80
0.70
0.90
NA :
FOULING
t A/^TrtQ
FACTOR
.============
NA
NA
NA
NA
NA
0.833
NA
TEST HEADER INSTALLED: APRIL 29, 1986
TABLE 11. PORTAGE LAKE PLANT FOULANT CHARACTERISTICS
DATE
NEW DIFFUSER
9/10/86
1/14/87
1/14/87
5/21/87
5/21/87
8/3/87
ELAPSED
TIME
MONTHS
0.0
4.4
4.0
8.4
4.2
12.7
15.2
MG/SQ.CM
0
22
NIL
4
3
2
NA
% ASH
NA
85
NA
78
88
65
NA
% Ac SOL ASH
NA
NA
NA
9.7
15.0
13.8
NA
%Si ASH
NA
NA
NA
NA
NA
16.4
NA
!
%Ca ASH
NA
:NA
NA
;NA
NA
'3.5
NA
%Fe ASH
NA
NA
NA
NA
NA
13.4
NA
19
-------
TABLE 12. PORTAGE LAKE INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
RAW INFLUENT PROCESS CONDITIONS
DATE
9/10/86
1/14/87
1/14/87
5/21/87
5/21/87
8/3/87
ELAPSED
TIME (mo)
4.4
4.0
8.4
4.2
12.7
15.2
FLOW
(MGD)
0.89
1.20
1.05
1.16
1.08
1.08
BOD,
(mg/L)
122
155
139
166
148
144
TSS
(mg/L)
107
109
108
120
112
112
BOD
Loading
(lb/1000
75.5
129.2
101.1
133.6
111.1
108.0
TSS pH
Loading
ft»-d)
66.2 7.4
91.1 7.4
78.7 7.4
96.8 7.6
84.3 7.4
84.3 7.4
MLVSS
1028
1463
1246
1964
1485
1514
SRT
(d)
7.7
9.4
8.5
8.7
8.6
8.5
F/M
i
0.23
0.28
0.25
0.22
0.24
0.24
DO
(mg/L)
3.5
3.0
3.2
** 3.0
** 3.2
** 2.9
TEMP
(C)
17
16
16
12
15
15
TEST HEADER INSTALLED ON APRIL 29,1986
* Unit 2 only
** DO measurements were not taken from April 9 - June 14, 1987.
*** 1 MOD = 3785 m*/d
DIFFUSER TEST HEADER BEHAVIOR DURING STUDY
Bubble Release Vacuum Trends \
• i
BRV data for the participating plants are plotted versus time in Figure
12. A general upward trend 1s evident for the more heavily fouljing plants
such as Jones Island and Frankenmuth, whereas a relatively constant pattern 1s
shown for the more lightly fouling plants such as Madison and Monroe. The
data suggest that the pl-ants can be grouped as follows: !
Heavily Fouling Plants: Jones Island and Frankenmuth. •
BRV values increased rapidly to more than 100 cm (40 1n) of water by the
12th month. These plants also tended to show high foulant accumulation
with Jones Island accumulating over 150 mg/cm2 1n 13.6 months and
Frankenmuth accumulating 95 mg/cm2 in 5.3 months.
i
Moderately Fouling Plants: Green Bay, North Texas, and Whittier Narrows.
BRV values increased gradually but perceptibly to more than 50 cm (20 In)
of water by the 12th month.
Fouling Plants: South Shore and Portage Lake.
BRV values increased somewhat but to less than 50 cm (20 in) of water by
the 12th month. Foulant accumulations were less than 25 mg/cm2 over 12
months ;
20
-------
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Lightly Fouling Plants: Madison and Monroe.
BRV values Increased to about 25 cm (10 1n) of water and then remained
relatively constant. Foulant accumulations were variable but generally
less than 10 mg/cma over 12 months.
Dyn6im1 c Wet Pressure Trends I
Dynamic wet pressure (DWP) data are plotted 1n Figure 13. A general
upward trend is suggested with the plants judged to be more susceptible to
fouling generally showing higher values for DWP. The exception to this
observation is the Jones Island plant which exhibited an average DWP even
though 1t was shown to be an extremely fouling plant by BRV and foul ant
accumulation.
Cumulative Versus Incremental Fouling |
The schedule of dlffuser removal and characterization was planned so that
incremental fouling over four month periods might be distinguished from
cumulative fouling over the entire study period. Consequently, many data
points are shown at the four month time period in Figures 12 and 13. These
represent the various stones removed from Position 1 on the test header at
four month intervals. Based on these limited data, no consistent seasonal or
incremental trend is evident. Hence, more attention was focusedi on the stones
1n the fouled condition after a cumulative period of 12 to 16 months.
i
COMPARATIVE ANALYSIS OF FOULING AFTER 12 TO 16 MONTHS !
Table 13 is derived from the Tables in Appendices A and B and compares
the characteristics of the fouled diffusers after an elapsed time of
approximately 12 to 16 months along with selected plant operating parameters
during the elapsed time period. Since this was a relatively uncontrolled
study, care must be used in Inferring cause and effect relationships from
these data. Nevertheless, it 1s useful to examine these data for reasonable
associations. i
i
Relationship between Fouling Factor and BRV |
Figure 14 shows the relationship between BRV and fouling factor, computed
from SOTE measurements made on clean and fouled stones. SeveraliSOTE
measurements were also made on stones after add cleaning and, in nearly all
cases, the stones were restored to within 5% of the SOTE for a new stone.
Figure 14 shows that the fouling factor 1s reasonably well correlated
with BRV (correlation coefficient -.- 0.88). This is understandable as it was
shown earlier that the plants which accumulated the most foulant!had the
highest BRV values. The heavily fouling and moderately fouling plants showed
fouling factors ranging from about 0.55 to 0.74 whereas the fouling and
lightly fouling plants showed fouling factors ranging from 0.83 to 0.99.
Based upon these data and reasoning, BRV can be accepted as a measure of
fouling. i
22 !
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Relationship between BRV and Loading Parameters i
i
It 1s interesting to explore the association between fouling, as measured
by BRV, and activated sludge loading, as measured by the Food/Ml'cro-organism
ratio (F/M) or solids retention time (SRT). Here, F/M 1s expressed as mass of
5 day BOD fed/day per unit mass of mixed liquor volatile suspended solids
(MLVSS), and SRT is determined as the mass of MLVSS 1n Inventory! divided by
the mass of MLVSS wasted per day. Figure 15 shows the relationship between
BRV and SRT, and Figure 16 shows the corresponding relationship between BRV
and F/M. In each case, an understandable association 1s weakly suggested by
the lines of best fit. However, the correlation coefficients are low (-0.52
for BRV vs. SRT, and 0.24 for BRV vs. F/M). In both associations, the Jones
Island and Frankenmuth plants appear to behave differently than the other
plants. The DWP/BRV ratio given in Table 13 also Indicates different dlffuser
behavior at the Jones Island and Frankenmuth plants. Both the DWP and BRV
tests measure bubble release pressure, and for a new stone the average DWP/BRV
ratio will be close to 1.0. As the stone becomes fouled, this ratio will be
less than 1.0. The DWP/BRV ratio for the Jones Island and Frankenmuth plants
at 12 months are 0.13 and 0.33, respectfully. These are the lowest ratios
among the nine plants studied, thus supporting the conclusion that these are
the heavily fouling plants. ,
Relationship between BRV and Percent Volatlles In Foulant !
Figure 17 explores the relationship between BRV and percent volatile
solids (100% - ash%) in the foul ant. Based on these data, 1t appears that
foulant high in inorganic as.h and low 1n organics 1s conducive to deleterious
fouling. It appears that a foulant low 1n organics Is a necessary, but not
sufficient condition for deleterious fouling.
i
DISCUSSION , i
The reasons for the robust fouling observed at the Jones Island and
Frankenmuth plants are not entirely clear. A possible contributing factor is
that Jones Island was receiving an undetermined amount of additional waste
activated sludge by tank truck from the South Shore plant. Th1s!could have
provided inorganic partlculates to the foulant matrix. The Frankenmuth waste
contained the highest BOD5 concentration (652 mg/1, much of which 1s soluble)
and industrial contribution (71% of BODB) of the participating plants, and
this appears to have stimulated fouling. Another possible contributing factor
was the location of the test headers at the head of the tanks. Both Jones
Island and Frankenmuth had their test headers placed, within a few meters of
the Inlet. The combination of the each plant's waste characteristics and
locating the headers at the tank inlets may have contributed to the heavy
diffuser fouling. \
Previous studies (EPA, 1985)(Reith, 1985) have observed severe fouling
problems at the Madison and Monroe plants. Yet, in this interplant
comparison, both plants showed only light fouling tendencies. Likely
contributing factors to the lessened fouling tendency at Monroe are the
incorporation of aerated In-line equalization and the addition of ammonia to
26
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improve the nutrient balance. The aerated equalization basin following
primary, treatment greatly reduced the soluble BODB load on the lactivated
sludge process (Baillod, 1988). Earlier fouling at the Madison plant appears
to have been associated with heavy loadings of dairy waste. !
30
-------
SECTION 5
CONCLUSIONS
The objective of this study was to assess the relative fouling tendency
of fine bubble dlffusers at nine municipal activated sludge planits
participating in comprehensive studies related to fouling and cleaning of fine
bubble diffusers. The results showed that an Increase in average bubble
release vacuum (BRV) was generally accompanied by a decrease in ioxygen
transfer efficiency, an accumulation of foulant, and an increase 1n the
dynamic wet pressure (DWP) loss through the diffuser. Based on ithese results,
the participating plants were classified as: I
i •
Heavily Fouling : Jones Island West and Frankenmuth, characterized by BRV
values increasing to more than 100 cm (40 in) of water and foulant
accumulation greater than 100 mg/cm2 over period of one year, i
Moderately Fouling; Green Bay, North Texas, and Whittier Narrows,
characterized by BRV values increasing to more than 50 cm (20 1ri) of water
over one year. !
i
Fouling; South Shore and Portage Lake, characterized by BRV values
increasing to less than 50 cm (20 1n) of water and foulant accumulations less
than 25 mg/cm2 over one year. . .
Lightly Fouling; Madison and Monroe, characterized by BRV values increasing
to about 25 cm (10 in) of water and remaining relatively constant along with
foulant accumulations generally less than 10 mg/cm2 over one year.
A secondary objective was to relate fouling tendency to process
parameters. Observations at individual plants suggested that high organic
loads enhance fouling. However, interplant comparisons suggested a weak
association between fouling and organic load. Thus, it appears that other
plant and waste specific factors in addition to organic load also Influence
fouling. ;
31
-------
REFERENCES
Boyle, W.C. and D.T. Redmon, "Biological Fouling of Fine Bubble Dlffusers:
State-of-Art", Jour. Env. Engr. Div. ASCE, 109(5):991-1005, 1983.
U.S. Environmental Protection Agency, "Summary Report: Fine Pore (Fine
Bubble) Aeration Systems", EPA/625/8-85/010, 1985.
Costerton, J.W., "Investigations into Biofouling Phenomena 1n Fine Pore
Aeration Devices", Draft Report Submitted to ASCE/EPA Fine Pore^Aeration
Project Committee, Cooperative Agreement No. 812167, March, 1988.
Dan'ly, W.B., "Biological Fouling of Fine Bubble Dlffusers - Phase I", M.S.
Independent Study Report, Civil and Environmental Engineering Department,
University of Wisconsin, Madison, 1984. \
Reith, M.G., "Effects of Biological Fouling on the Oxygen Transfer Efficiency
of Fine Bubble Diffusers", M.S. Thesis, University of Wisconsin-Madison, 1985.
BaiUlod, C.R., "Oxygen Utilization in Activated Sludge Plants: Simulation and
Model Calibration", Final Report, U.S. Environmental Protection Agency, Water
Engineering Research Laboratory, Cooperative Agreement CR813162-01-2, 1988.
32
-------
APPENDIX A
DIFFUSER FOULANT CHARACTERISTICS
TABLE Al. FRANKENMUTH PLANT SUMMARY OF DIFFUSER FOULING !
ELAPSED FLD DWP LAB DWP, 1n FLOW FOULING
TIME 1n _ BRV PROFILE ! FACTOR
DATE MONTHS 0 1 SCFM @ 1 SCFM @ 2 SCFM 1n OUT/TOT i
10/7/87 5.3 NA 17.3 27.1 20.2 0.50 ' NA
5/20/88 12.8 NA 19.0 42.0 57.3 NA ' 0.737
TEST HEADER INSTALLED: APRIL 28, 1987
i
TABLE A2. FRANKENMUTH PLANT FOULANT CHARACTERISTICS
ELAPSED
TIME i
°ATE MONTHS MG/SQ.CM % ASH % Ac SOL ASH %S1 ASH %Ca ASH %Fe ASH
10/7/87 • 5.3 95 95 32.0 21.0 4J8 8.6
5/20/88 12.8 96 89 NA NA NA NA
33
-------
TABLE A3. GREEN BAY PLANT SUMMARY OF DIFFUSER FOULING
— — 'saasiataisasa
DATE
10/18/86
2/24/87
2/24/87
6/19/87
6/19/87
8/3/87
10/27/87
10/27/87
TEST HEADER
==============
DATE
10/18/86
2/24/87
2/24/87
(5/19/87
(5/19/87
8/3/87
10/27/87
ELAPSED
TIME
MONTHS
4.6
4.1
8.8
3.9
12.6
14.0
4.2
2.8
INSTALLED JUN
TABLE
ELAPSED
TIME
MONTHS
4.6
4.1
8.8
3.9
12.6
14.0
4.2
FLD DWP
In
III
@ 1 SCFM
NA
5.5
11.5
12.5
25.0
14.5
9.0
5.5
IE 1, 1986
A4. GREEN
===========
MG/SQ.CM
13
10
63
NA
NA
30
33
LAB DWP, 1n . FLOW
® 1 SCFM ® 2 SCFM In OUT/TOT
10.1 14.0 15.0 0.53 !
10.5 13.3 16.5 0.48 ;
11.0 17.7 20.0 0.54 :
NA NA NA NA i
NA NA NA NA |
15.0 34.0 24'.8 NA :
15.8 22.7 13.9 0.64 |
NA NA NA NA i
i
BAY PLANT FOULANT CHARACTERISTICS \
==========================3=================
% ASH % Ac SOL ASH %S1 ASH %Ca ASH
90 14.0 11.6 17.8
88 49.0 8.7 17.9
88 51.0 4.9 16.4
NA NA NA NA
NA NA NA NA
92 37.6 NA fjlA
94 29.0 13.1 12.6
FOULING
FACTOR
NA
NA
NA
NA
NA
0.714
NA
NA
=========
%Fe ASH
6.7
6.7
6.2
NA
NA
NA
8.4
34
-------
TABLETS. JONES ISLAND WEST PLANT SUMMARY OF DIFFUSER FOULING
DATE
10/20/86
3/6/87
3/6/87
8/5/87
ELAPSED FLD DWP LAB DWP, 1n
TIME 1n
MONTHS @ 1 SCFM @ 1 SCFM @ 2 SCFM
4.1
4.5
8.5
13.6
14.1
24.0
23.4
NA
13.0
10.8
8.7
10.0
26.9
20.3
16.9
19.8
FLOW |
BRV PROFILE
In OUT/TOT
FOULING
FACTOR
19.0 0.78 : NA
34.9 0.65 ] NA
43.0 0.79 NA
75.7 NA 0.555
TEST HEADER INSTALLED: JUNE 18, 1986
TABLE A6. JONES ISLAND WEST PLANT FOULANT CHARACTERISTICS
DATE
ELAPSED
TIME ;
MONTHS MG/SQ.CM % ASH % Ac SOL ASH %S1 ASH %Ca ASH %Fe ASH
10/20/86
3/6/87
3/6/87
8/5/87
4.1
4.5
8.5
13.6
100
26
107
152
90
86
87
86
4.0
33.1
21.6
NA
14.9
18.0
11.7
9.3
io.i
111. 9
7.8
i
8.1
7.3
6.6
9.3
14.2
35
-------
TABLE A7. MADISON PLANT SUMMARY OF DIFFUSER FOULING
DATE
1/14/87
4/23/87
4/23/87
8/6/87
8/6/87
TEST HEADER
DATE
1/14/87
4/23/87
4/23/87
8/6/87
8/6/87
ELAPSED
TIME
MONTHS
4.7
3.3
7.9
4.0
12.0
FLD DWP
1n
@ 1 SCFM
3.2
5.2
9.8
NA
NA
LAB DWP, 1n
@ 1 SCFM 9 2 SCFM
5.7 6.7
5.4 6.1
8.6 11.3
NA NA
6.2 8.0
FLOW ! FOULING
BRV PROFILE FACTOR
1n OUT/TOT
12.4 0.50 \ NA
7.7 0.55 ! NA
. i
9.3 0.53 i NA
8.4 NA : NA
9.3 NA 0.989
INSTALLED: AUGUST 25, 1986 |
i
TABLE
ELAPSED
TIME
MONTHS
4.7
3.3
7.9
4.0
12.0
A8. MADISON
MG/SQ.CM !
7
5
8
NA
7
PLANT FOULANT CHARACTERISTICS :
' «
1 ASH % Ac SOL ASH
50 41.5
58 39.4
56 41.7
NA NA
48 NA
%S1 ASH %Ca|ASH %Fe ASH
10.3 16.3 4.2
5.3 11.9 2.7
11.1 9.6 2.6
i
NA NA NA
NA NA NA
36
-------
TABLE A9. MONROE PLANT SUMMARY OF DIFFUSER FOULING
DATE
12/4/86
3/9/87
3/9/87
7/10/87
:=========i:s==:3=
ELAPSED
TIME
MONTHS
4.5
3.5
8.0
12.0
FLD DWP
1n
@ 1 SCFM
NA
NA
NA
NA
LAB DWP
@ 1 SCFM @
7.2
5.2
6.5
6.9
, In
2 SCFM
8.2
6.6
8.8
8.1
QD I/
1n
8.1
7.8
8.2
9.3
FLOW '
PROFILE!
OUT/TOT;
NA ;
NA
NA j
NA
FOULING
FACTOR
NA
NA
NA
0.976
TEST HEADER INSTALLED: JULY 9, 1986
TABLE A10. MONROE PLANT FOULANT CHARACTERISTICS
DATE
12/4/86
3/9/87
3/9/87
7/10/87
ELAPSED
TIME
MONTHS
4.5
3.5
8.0
12.0
MG/SQ.CM
50
13
81
2.6
% ASH
75
45
73
45
% Ac SOL ASH
NA
NA
NA
NA
%S1 ASH
NA
NA
NA
NA
l
%Ca !ASH
HA
NA
NA
NA
«
%Fe ASH
NA
NA
NA
NA
37
-------
, TABLE All. NORTH TEXAS PLANT SUMMARY OF DIFFUSER FOULING
DATE
5/12/86
7/86
11/86
7/87
7/87
ELAPSED
TIME
MONTHS
4.4
7
11
3
18
FLD DWP
In
9 1 SCFM
NA
NA
NA
NA
NA
LAB DWP,
« 1 SCFM 0
11.0
11.9
12.4
8.7
37.0
1n
2 SCFM
14.0
13.7
15.8
9.1
40.5
QDW
1n
27.4
14.3
21.4
9.5
40.7
FLOW '<
KKUr IL&
OUT/TOT,
0.7
0.6
0.6 i
0.6
0.5
FOULING
FACTOR
NA
NA
NA
NA
NA
TEST HEADER INSTALLED: DECEMBER 30, 1985
TABLE A12. NORTH TEXAS PLANT FOULANT CHARACTERISTICS
ELAPSED
DATE
5/12/86
7/86
11/86
7/87
7/87
TIME
MONTHS
4.4
7
11
3
18
MG/SQ.CM
42
8
29
0.2
18
% ASH
95
94
96
77
88
% Ac SOL
NA
20.0
9.5
NA
40.3
ASH %S1 ASH
NA
20.4
20.7
11.7
22.8
%Ca ASH
NA
19.2
16.8
I
8.3
0.5
%Fe ASH
NA
3.3
3.5
2.1
2.3
38
-------
TABLE A13. SOUTH SHORE PLANT SUMMARY OF DIFFUSER FOULING
DATE
10/21/86
3/6/87
3/6/87
8/5/87
TEST HEADER
DATE
10/21/86
3/6/87
3/6/87
8/5/87
ELAPSED FLD DWP LAB DWP, In FLOW1 FOULING
MONTHS @ 1 SCFM ® 1 SCFM @ 2 SCFM In OUT/TOT
4-3 7.6 7.6 9.0 10.2 0.21 ! NA
I
4.5 9.8 10.1 12.5 12.3 0.65! NA
8.8 11.9 10.6 14.1 19.6 0.63 NA
13.7 NA 11.5 16.0 18.0 NA 0.994
INSTALLED: JUNE 13, 1986
I
TABLE A14. SOUTH SHORE PLANT FOULANT CHARACTERISTICS \
ELAPSED
TIME
MONTHS MG/SQ.CM % ASH % Ac SOL ASH %S1 ASH %Ca| ASH %Fe ASH
4.3 6 87 NA 10.9 10.0 10.2
4-5 5 86 50.0 10.6 11.8 9.9
8-8 7 67 44.0 7.8 8.3 8.1
13.7 23 76 NA 4.7 10.2 1.3
39
-------
TABLE_A15. WHITTIER NARROWS PLANT SUMMARY OF DIFFUSER FOULING
ELAPSED FLD DWP LAB DWP, 1n FLOW ! FOULING
TIME 1n BRV PROFILED FACTOR
DATE MONTHS 9 1 SCFM 9 1 SCFM 9 2 SCFM 1n OUT/TOT
====================================================3==»=«»=======s======3=aaa==,i-=a=-==.«=
6/28/88 * 9.6 NA 12.1 21.9 25.0 NA : 0.896
TEST HEADER INSTALLED: AUGUST 22, 1986
* Data Is for a dlffuser stone Installed on 9/9/87
TABLE A16. WHITTIER NARROWS PLANT FOULANT CHARACTERISTICS
ELAPSED
TIME
DATE MONTHS MG/SQ.CM % ASH % Ac SOL ASH SI ASH %Ca ASH %Fe ASH
6/28/87 9.6 NA NA NA NA NA
NA
40
-------
APPENDIX B
INFLUENT AND PLANT PROCESS CONDITIONS DURING STUDY
TABLE 81. FRANKENMUTH INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
I
PRIMARY EFFLUENT PROCESS^ CONDITIONS
DATE
10/7/87
*5/20/88
ELAPSED
TIME (mo)
5.0
12.8
FLOW
(MGD)
1.36
1.38
BOD,
(mg/L)
653
526
TSS
(mg/L)
322
253
BOD TSS
Loading Loading
(lb/1000 ft»-d)
116.7 57.4
95.5 46.2
PH
6.4
6.9
MLVSS
(mg/L)
4877
4720
SRT
(d)
23.6
21.8
F/M
(1/d)
0;29
0.24
DO
(mg/L)
0.97
1.03
TEMP
(C)
26.8
22.0
TEST HEADER INSTALLED ON APRIL 28, 1987
*Est1mated
TABLE B2. JONES ISLAND INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
PRIMARY EFFLUENT
PROCESS CONDITIONS
DATE ELAPSED
TIME (mo)
10/20/86 4.1
3/6/87 4.5
3/6/87 8.5
8/5/87 *13.6
FLOW
(MGD)
4.65
4.60
3.83
3.74
BOD,
(mg/L)
220
208
245
253
TSS
(mg/L)
NA
NA
NA
NA
BOD
Loading
(lb/1000
58.1
54.3
53.5
53.8
TSS
Loading
ft'-d)
NA
NA
NA
NA
PH
7.7-6.9
7.7-6.8
9.4-6.8
9.4-6.8
MLVSS
(mg/L)
1470
1443
1653
1636
SRT
(d)
3.4
3.4
3.7
3.6
! F/M
(1/d)
0.64
0.61
0.52
io.53
DO
(mg/L)
0.6
1.6
1.2
0.9
TEMP '
(C)
19.8
14.2
16.7
17.0
TEST HEADER INSTALLED ON JUNE 18, 1986
41
-------
TABLE B3. GREEN BAY INFLUENT AND PROCESS CHARACTERISTICS DURING THE!STUDY
COMBINED MILL WASTE AND 'PRIMARY EFFLUENT PROCESS CONDITIONS
DATE ELAPSED
TIME (mo)
10/18/86 4.6
2/24/87 4.1
2/24/87 8.8
6/19/87 3.9
6/19/87 12.6
8/3/87 14.0
10/27/87 4.2
FLOW
(MGD)
18.8
14.3
16.4
14.2
15.7
15.5
13.5
BOD,
(mg/L)
396
467
433
402
424
417
371
TSS
(mg/L)
220
242
228
224
227
223
167
BOD
Loading
(lb/1000
168.6
151.1
160.4
129.2
150.4
146.1 '
113.6
' TSS
Loading
ft'-d)
93.6
78.6
84.9
71.8
80.5
78.0
51.2
pH
7.1
7.2
7.2
NA
7.2
7.2
6.9
MLVSS
(mg/L)
1881
2320
2174
1890
2060
2003
1513
SRT
(d)
2.7
3.1
2.9
3.1
3.0
3.1
3.8
F/M
(1/d)
:
0.53
0.47
i
0.51
0.46
0.49
0.48
0.38
DO
(mg/L)
ISSSS3S
1.6
2.2
1.9
2.2
2.0
2.0
2.0
TEMP
(C)
28
20
24
23
24
24
28
TEST HEADER INSTALLED ON JUNE 1, 1986 ;
* pH data was not available for June and July of 1986 and March, May, June and October of
1987. :
** MLVSS was only measured one day out of each month during the study (1 to 3 samples per
sample day). Data was not available for June, July and August of 1986.
TABLE B4. MADISON INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
PRIMARY EFFLUENT
PROCESS CONDITIONS
=========
DATE
====3l = = =
1/14/87
4/23/87
4/23787
8/6/87
8/6/87
ELAPSED
TIME (mo)
= ======33=
FLOW
(MGD)
=*====: ====s====aj===
4.7
3.3
7.9
3.0
11.0
11.6
10.7
11.3
10.8
11.2
BOD,
(mg/L)
=«==S5SJ
83
83
90
99
92
TSS
(mg/L)
=======
67
67
67
68
67
===555====:
BOD
Loading
TSS pH
Loading
(lb/1000 fts-d)
a=s_0==!_==
20.0
18.7
21.2
22.5
21.2
MLVSS
(mg/L)
==.====.==== ====== ====&—
16.2 *
15.0 *
15.6 *
15.6 *
15.6 *
1851
1944
1895
1641
1826
SRT
(d)
18.5
18.5
18.5
15.8
17.7
F/M
(1/d)
0.11
0.11
0.11
0.14
0.12
DO
(mg/L)
**
**
**
**
**
TEMP
(C)
18
14
16
20
17
TEST HEADER INSTALLED ON AUGUST 25, 1986
* Average pH during the study was 7.6 (range: 7.4-7.7)
** Average DO during the study was 2.0 mg/L (range: 0.7-4.9 mg/L)
42
-------
TABLE 85. MONROE INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
EQUILIZATION BASIN EFFLUENT PROCESS CONDITIONS
E ELAPSED
TIME (mo)
FLOW
(MGD)
BOD, TSS
(mg/L) (mg/L)
BOD
Loading
(lb/1000
TSS
Loading
ft'-d)
PH
MLVSS SRT F/M DO TEMP
(mg/L) (d) ; (1/d) (mg/L) (C)
121/4/86
3/9/87
3/9/87
7/10/87
4.5
3.5
8.0
12.0
2.30
2.35
2.17
2.17
**290
**285
**283
273
104
103
120
140
85.5
85.5
78.6
75.5
30.6
30.9
33.3
38.9
8.9-6.9
8.8-7.0
8.9-7.2
9.0-7.2
1230
1150
1281
1361
6.3
5.8
- 7.5
7.4
\ 0.38
j 0.42
0.35
; 0.32
2.8 19/23
2.7 18/22
*3.4 *15/19
*3.7 *16/20
TEST HEADER INSTALLED ON JULY 9, 1986
* DO and temperature data was not available for February, March, and April of |l987.
** Primary effluent !
SRT's were estimated.
TABLE 86. SOUTH SHORE INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
PRIMARY EFFLUENT
PROCESS CONDITIONS
DATE ELAPSED
TIME (mo)
FLOW BOD,
(MGD)
TSS BOD TSS
(mg/L) Loading Loading
(lb/1000 ft"-d)
PH
MLVSS SRT : F/M DO TEMP
(mg/L) (d) ;(l/d) (mg/L) (C)
10/21/86
3/13/87
3/15/87
8/15/87
4.3
4.5
8.8
*13.7
6.00
6.20
5.51
5.69
74
77
90
90
NA
NA
NA
NA
22.5
23.7
25.0
25.8
NA
NA
NA
NA
7.9-7.6
7.9-7.6
8.1-7.4
8.1-6.8
1164 6.1
1165 6.0
1207 6.1
1140 5.8
i0.31
|0.33
!0.33
;0.36
1.3
0.9
1.1
1.1
18.4
13.4
15.9
15.9
TEST HEADER INSTALLED ON JUNE 13, 1986
43
-------
TABLE 87. WHITTIER NARROWS INFLUENT AND PROCESS CHARACTERISTICS DURING THE STUDY
PRIMARY EFFLUENT
PROCESS CONDITIONS
DATE ELAPSED
TIME (mo)
FLOW BOD. TSS BOD TSS pH
(mVd) (mg/L) (mg/L) Loading Loading
(lb/1000 ft'-d)
MLVSS SRT F/M DO TEMP
(mg/L) (d) (1/d) (mg/L) (C)
1/1/87 9.6 4.54 97 95 28.7 28.1 NA 682 2.2 0.67 2.0 24.4
TEST HEADER INSTALLED ON AUGUST 22, 1987
44
-------
APPENDIX C
DESCRIPTION OF METHODS
FOULANT ANALYSIS
An Important aspect of the characterization of the fouled cMffusers was
the analysis of the nature of the foulant on the dlffuser. Theiprocedure for
foulant analysis 1s given below:
1. Specify a certain area on the surface of a dlffuser disc.
2. Scrape the materials off the surface, divide and put them Into two
vials« '
i
3. Place each vial's contents 1n a tared evaporation dish.
4. Measure the wet weight.
5. Dry at 105°C for > 1 hour (To constant weight). ',
6. Cool, desiccate, and weigh for total solids. \
7. Put the dishes into furnace, firing them at 550°C fori20
minutes. ,
8. Cool, desiccate and weigh the dishes for fixed solids.'
9. Take one dish content for metallic 1on analysis. Place 1n a
vial. i
10. Add approximately 10 ml of 14% HC1 to the other dish and stir
gently until the formation of gas bubbles ceases.
11. Centrifuge the solution at 20,000 rpm for 15 minutes. Decant
the upper portion, add deionized water into the tube centrifuge
again and decant. Repeat once more for a total of thre;e decants.
12. Repeat the steps 5, 6, and 9 using the centrlfuged solids.
Compare the results with those of the non-acidified foulant.
45
-------
BUBBLE RELEASE VACUUM
The bubble release vacuum, as Indicated by the name, 1s a measure of the
vacuum 1n Inches of water gauge, required to emit bubbles from a localized
point on the surface of a thoroughly wetted porous dlffuser element. The test
provides a means of determining the effective pore diameter at any point on
the surface of a ceramic dlffuser, and is an Important measure 6f the relative
fouling among plants. The test apparatus consists of a probe, manometer,
vacuum source, and rotameter as shown 1n Figure C.I. j
A brief description of the BRV testing procedure is llsted'below. Danly
(1984) more thoroughly describes the test procedure. I
1. If the dlffuser 1s new, immerse 1t 1n tap water until wetted.
Remove from water just prior to test and let drain by gravity for not
more than 30 minutes. Keep diffuser in a horizontal plain while
draining. Do not soak fouled dlffusers.
I
2. Set BRV flow rate. !
3. Apply probe to BRV test location. The water surface will rise 1n
the probe while bubbles are released at the dlffuser surface. If the
water level becomes too high, discard excess water by a quick lateral
and upward movement of the probe. If water level 1s too low, apply
additional water onto the dlffuser adjacent to the probe. This 1s
especially useful when testing fouled dlffusers.
4. Equilibrium has been reached when the rate of rise of water in the
probe equals the rate of rise 1n the manometer (inches ;water gauge).
If time to reach equilibrium is excessive, it may be reduced by
operating the by-pass valve momentarily. The flux rate increases
dramatically when the by-pass valve 1s open. The large suction
force will pull foulant off a dirty dlffuser. Because Ithe loss of
foulant may effect test results, the by-pass valve should be used
judiciously. :
i
i
5. At equilibrium, read and record the manometer reading and the height
of water in the probe. BRV equals the manometer reading less the
height of water 1n the probe. !
6. Repeat steps 3 through 5 for all test locations.
i
DYNAMIC WET PRESSURE i
i
The dynamic wet pressure, DWP, 1s the pressure differentials across the
diffusion element when operating in a submerged condition, and is expressed in
inches of water gauge. In the dynamic wet pressure test, most of the pressure
differential is due to the force or pressure required to form bubbles against
the force of surface tension and only a small fraction of the total pressure
gradient is required to overcome frictlonal resistance. |
46
-------
DWP and BRV test both measure bubble release pressure. DWP measures 1t
for the whole dlffuser while BRV gives a distribution of pressure. For a new
stone, the average DWP/BRV ratio 1s close to 1.0. As a stone fouls, the
average BRV for the 12 points tested on the top surface becomes greater than
DWP. The average DWP/BRV ratio becomes less than 1.0. '
Laboratory DWP was measured each time a stone was removed from the test
header. The equipment required for measuring DWP 1n the lab Includes an air
source, rotameter, In-line mercury manometer, thermometer, dlffuser plenum
with standard orifice, water-filled manometer and aquarium. The test set-up
looks very much like Figure C.2 without manometer A and the bubbler. The
water-filled manometer (manometer B 1n Figure C.2) 1s tapped Into the plenum
at one end and open to atmosphere at the other end. The water »1n the aquarium
1s high enough so the dlffuser was covered with water. i
The following 1s a brief description of the DWP test. Consult Danly
(1984) for more Information on the test.
1. The aquarium should be filled with tap water so there will be
several cm. (1n.) of water over the dlffuser. If this 1s done the
day before testing, the water will warm to room temperature.
2. New diffusers should be wetted the same as for the BRV test. Do ndt
soak fouled dlffusers.
3. Place dlffuser securely 1n plenum.
4. Hold plenum over aquarium and turn air on. This allows water
entrained 1n the dlffuser to drain into the tank and not on the
floor. If the dlffuser 1s fouled, do not turn air flow any higher
than its operating air flow rate. \
5. Place plenum in aquarium. Adjust air flow to minimum suggested rate
of 0.85 mVhr/dome (0.5 scfm/dome). Visually inspect the flow
profile. If the dlffuser is not mounted correctly, coarse bubbling
will be evident. If this is the case, take plenum outiof the
aquarium and reseat the dlffuser. '
6. Adjust air flow to maximum allowable rate for the test'being
time for excess water to be driven out of stone. When'testing fouled
diffusers, dp not exceed the operating air flow rate. !
i
7. Perform a DWP profile. This is done by checking DWP at three or
more air flows. Typical air flows are 36.6, 73.2, 109i7, 146.3-
m'/hr/m" (2, 4, 6, and 8 scfm/ft2). A bucket catch may be performed
to check air flow rate. In line pressure and temperature readings
are taken so air flow rates can be translated to standard conditions.
8. After the last DWP reading, turn the air flow to almost zero.
Measure the static head over the dlffuser. The static ihead is
subtracted from DWP manometer readings to give true DWP| readings.
47 : .
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I
-j
BRV
PROBE
DIFFUSER
BY-PASS _ VALVE
•o-
MANOMETER
CO
VACUUM
SOURCE
ROTAMETER
Figure C.I. BRV test apparatus.
AIR SOURCE
~\ ' • • •
V' ' -. ' '
\ •••'...
AIR FLOW CONTROL
:( ORIFICE
HEADER
Figure C.2. Laboratory DWP test apparatus.
48
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9. Correct air flow data to standard conditions. Regress DWP (y) on
air flow (x). The correlation coefficient should be close to 1.0.
GAS FLOW PROFILE TEST ;
The gas flow profile test uses quantitative techniques to evaluate the
uniformity of air release across the surface of ceramic dlffusers, while
operating, rather than appraising uniformity by visual means. This 1s
accomplished by testing the element at an air rate which 1s approximately
equal to 36.6 mVhr/ma (2.0 scfm/ft2), or at the recommended design rate, with
anywhere from 5.1 - 20.3 cm. (2 - 8 1n.) of water over 1t. i
The rate of air release from selected areas 1s measured by Displacing
water from an inverted container and recording the rate of displacement of
water with a stopwatch. By combining the container area and the rate of air
discharge, a flux rate, expressed as m3/hr/m2, or other convenient units, can
be calculated. By comparing the flux rate of the selected area ;read1ngs with
one another, a quantitative measure or graphical representation of the profile
can be generated.
Flux rate Is determined by measuring the displacement of water by the
rising gas stream from a vessel Inverted over the diffuser. The vessel must
first be filled with water, covered and deftly Inverted so that the mouth of
the vessel 1s just submerged. Captured gas volume 1s measured over a time of
a few seconds taking care so that the captured volume 1s recorded at
atmospheric pressure, i.e. equal water surface levels Inside and outside of
the Inverted vessel. The flow rate 1s determined by dividing the captured
volume by the time Interval. The flux rate Is defined as flow rate divided by
the area of the capture vessel. A flow profile for a typical diffuser
requires flow measurements on each of three concentric circles as shown 1n
Figure C.3. Flow rates for the annular areas are determined by difference.
i
These measurements are made by using three vessels, each with a different
surface capture area. The large, 13.5 liter vessel captures the entire flow.
The two liter vessel captures all but the periphery flow, whereas the 1000 ml
graduated cylinder captures the flow around the washer. By subtraction, flux
rates are obtained for the outer, middle and Inner areas of the diffuser.
These flux rates are then compared to the average flux rate for the diffuser.
HOSE-ACID-HOSE CLEANING (MILWAUKEE METHOD) ;
This method has been used at the Milwaukee wastewater treatment plants
for many years. A high pressure water jet 1s applied to the diffuser surface
followed by acid spraying and hosing. The rationale is to first hose off the
easily removable foulant so that the applied acid can solubH1ze; the inorganic
precipitate inside the pores of the diffuser. A second hosing 1s then
performed to remove the solubilized foulant and residual acid. The materials
needed for this method are: high or low pressure water hosing equipment, add
spray applicator (Hudson Add Sprayer or equivalent) and 50% by volume of 18
i •
49
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1000 ml GRADUATED
CYLINDER
Figure C.3. Diffuser air flow profile
50
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Baume Inhibited muriatic add. This 1s equivalent to a 14% HC1 solution. The
procedure 1s given below:
i
1. Clean dlffuser by high pressure or low pressure hosing'with the air
on at approximately 1.7 mVhr (1 cfm) per dlffuser. ;
2. Apply approximately 50 ml of 14% HC1 to the surface of; the dlffuser
using the spray applicator. No air should be applied to the dlffuser
during the add application period.
3. Let add remain on the dlffuser for 30 minutes. Turn air on 5
minutes. :
4. Hose the dlffuser again for one minute or so to remove all the
residual add.
51
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