EPA-600/2-76-139
May 1976
Environmental Protection Technology Series
TREATMENT OF DENIM TEXTILE MILL WASTEWATERS:
NEUTRALIZATION AND COLOR REMOVAL
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeccnomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
EPA REVIEW NOTICE
-"'This report has been reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the
views and policy of the Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-76-139
May 1976
TREATMENT OF DENIM
TEXTILE MILL WASTEWATERS:
NEUTRALIZATION AND COLOR REMOVAL
by
Charles R. Froneberger and Michael J. Pollock
R. S. Noonan, Inc. of South Carolina
Greenville, South Carolina
for
Canton Textile Mills, Inc.
P.O. Box 827
Canton, Georgia 30114
Grant No. S800852
ROAPNo. 21AZT-006
Program Element No. 1BB036
EPA Project Officer: Thomas N. Sargent
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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CONTENTS
List of Figures jv
List of Tables yl
Acknowledgements IX
SECTIONS
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Fly Ash Adsorption of Color 19
V " Chemical Destabilization for Removal of Color 43
VI Neutralization of Caustic Wastewaters Utilizing 63
Coal-Fired Boiler Flue Gases
VII References 89
VIII Appendix 93
iii
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FIGURES
Number Page
1 Canton Textile Mills, Inc.'s manufacturing process 7
flow diagram
2 Flow diagram of indigo dyeing process 8
3 Flow diagram of sulfur dyeing process 10
4 Flow diagram of Canton Textile Mills, Inc.'s 14
existing wastewater treatment facility
5 Flow diagram of Canton Textile Mills, Inc.'s up- 16
graded wastewater treatment facility
6 Canton Textile Mills, Inc.'s upgraded wastewater 17
treatment facility
7 Fly ash adsorption isotherm with existing effluent 24
8 Fly ash adsorption isotherm with prefiltered efflu- 25
ent
9 Powdered activated carbon isotherm with prefiltered 26
effluent
10 Gravity feed, packed-bed fly ash contacting flow 27
diagram
11 Pressurized packed-bed fly ash contacting flow 30
diagram
12 Pressurized packed-bed fly ash test apparatus 31
13 Expanded-bed fly ash contacting flow diagram 33
14 Buchner Funnel test apparatus 55
15 Filter leaf test apparatus 55
16 Flow diagram of treatment system with proposed 58
chemical coagulation system addition
17 Neutralization pilot plant 68
18 Pilot plant effluent pH versus liquid/gas ratio 69
19 FMC/Link-Belt variable throat scrubber 73
iv
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FIGURES (Cont'd)
Number , Page
20 Process flow diagram of scrubber installation 74
21 Distant view of Canton Textile Mills, Inc.'s scrubber 75
installation
22 Close-up view of Canton Textile Mills, Inc.'s 76
scrubber installation
23 Percent S02 removal versus pH of scrubbing liquid
84
v
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TABLES
Number Page
1 Characterization of dye wastewaters 11
2 Typical profile of influent wastewater to the 12
treatment system
3 Profile of existing treatment system's influent- 13
effluent wastewater characteristics
4 Profile of upgraded treatment system's influent- 18
effluent wastewater characteristics
5 Typical analysis of Canton Textile Mills' fly ash 20
6 Typical adsorption isotherm data 23
7 Typical results of fly ash packed-column tests with 29
prefiltered effluent
8 Typical packed-bed fly ash test results 32
9 Results of fly ash expanded-bed test with prefil- 34
tered effluent
10 Fly ash slurry contact test results with unfiltered 36
effluent
11 Fly ash slurry test results with prefiltered- 37
effluent
12 Effect of pH on adsorption capacity of fly ash 38
13 Effect of temperature on the adsorption capacity of 39
fly ash
14 Powdered activated carbon slurry contact results 40
15 Summary of phase one jar test investigations 46
16 Average results of successful jar tests on existing 47
wastewater treatment plant effluent
17 Sludge characterization 48
18 Summary of alum sludge reduction investigations 49
vi
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TABLES (Cont'd)
Number Page
19 Typical results of alum regeneration-coagulation 50
investigation
20 Relative economics of alum regeneration 51
21 Results of filter leaf tests with sludge generated 56
from lime-Dow A-23 coagulation
22 Estimated capital costs of chemical coagulation 59
system addition to Canton Textile Mills, Inc.'s
existing biological treatment facility
23 Projected operating and maintenance costs of exist- 60
ing biological and new chemical coagulation system
24 Typical profile of existing stack gas 66
25 Wastewater characterization across pilot scrubber 71
26 Typical results of various scrubber operating con- 7,9
ditions
27 Typical wastewater characterization across full 81
scale scrubber
28 Comparative wastewater treatment characterization 83
with and without scrubber neutralization of dyeing
process wastewaters
29 Capital and operating costs of scrubber system 86
Al Design data for existing wastewater facilities 94
A2 Design data for upgraded wastewater treatment 95
facilities
A3 Packed column reactor test with unfiltered ef- 96
fluent
A4 Packed column reactor test with prefiltered ef- 97
fluent
A5 Typical jar test procedures 98
A6 Buchner Funnel test procedure 99
vii
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TABLES (Cont'd)
Number Page
A7 Results of Buchner Funnel tests with sludge gen- 100
erated from alum coagulation
A8 Results of Buchner Funnel tests With sludge gen- 101
erated with lime coagulation
A9 Results of Buchner Funnel tests with sludge gen- 102
erated with magnesium carbonate and lime coagu-
lation
A10 Results of Buchner Funnel tests with sludge gen- 103
erated with lime-Dow A-23 coagulation
All Typical coal analysis
viii
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ACKNOWLEDGEMENTS
The research reported herein is a combined effort of Canton Textile
Mills, Inc. of Canton, Georgia and R. S. Noonan, Inc. of South Carolina,
Greenville, South Carolina (Consulting Engineers).
The cooperation and assistance of Mr. T. E. Brumbeloe, Mr. J. C. Gray,
Mr. J. T. Holbrook, Mr. L. G. Hobgood, and the maintenance staff of
Canton Textile Mills, Inc., are gratefully acknowledged.
The cooperation of the FMC Corporation, the Duriron Company, Inc., and
the Allis-Chalmers Company in providing equipment for the experimental
scrubber phase of this project are gratefully acknowledged.
The technical assistance and support of the project by the United
States Environmental Protection Agency and Mr. T. N. Sargent, the
Grant Project Officer, are acknowledged with sincere thanks.
ix
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SECTION I
CONCLUSIONS
Over a forty-four month period, a study was .conducted to investigate the
use of fly ash adorption and chemical destabilization techniques of color
removal from indigo and sulfur dyeing wastewaters. This investigation
also included a feasibility study and subsequent full scale demonstra-
tion of coal-fired boiler flue gas wet scrubbing techniques for neu-
tralization of caustic wastewaters.
Based on the results of these studies conducted at Canton Textile
Mills, Inc., Canton, Georgia, the following conclusions have been
reached:
1. The fly ash generated in Canton Textile Mills, Inc.'s coal-
fired boiler is capable of adsorption and subsequent removal
of color, BOD5, and COD from the biologically treated domestic
and dyeing process wastewaters. The adsorption capacity,
however, is significantly below that of powdered activated
carbon.
2. The use of column reactors (expanded or packed-bed) for fly
ash-wastewater contacjt was found to be impractical due to
problems related to hydraulic plugging and channeling of flow
resulting from the extremely fine fly ash and the suspended
solids present in the wastewater.
3. The use of slurry fly ash contacting reactors was also demon-
strated impractical due to the volume of fly ash required in
excess of that produced at the mill to achieve a significant
color reduction of the wastewaters.
4. Chemical destabilization of the effluent from the existing bio-
logical treatment system was demonstrated to have the ability
of accomplishing removal of color and the production of a super-
natant of suitable quality to recycle.
5. Of eleven destabilizing agent combinations investigated, it was
proven that alum or lime with an anionic polyelectrolyte could
successfully accomplish removal of color and the production
of a supernatant suitable to recycle.
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6. Lime-polyelectolyte coagulation illustrated the ability of producing
a sludge with good dewatering characteristics which was amenable to
dewatering with conventional vacuum filtration techniques. The
chemical and disposal costs associated with the lime dosages re-
quired were, however, considered economically impractical for
present application.
7. Economically, the use of alum coagulation has the potential of re-
sulting in a significant savings in chemical cost over that of the
lime-polyelectrolyte coagulant cost. The economic advantage of
alum, however, is contingent upon the cost associated with that of
overcoming the poor dewatering properties of the alum sludge.
The alum sludge was not considered to be capable of conventional
vacuum filtration techniques without further proper conditioning.
8. The practicability of utilizing coal-fired boiler flue gases to
neutralize caustic wastewaters was demonstrated. Caustic waste-
waters were used in conjunction with a conventional wet scrubber to
successfully neutralize the wastewaters by carbon dioxide and sul-
fur dioxide absorption from the flue gas while simultaneously re-
ducing the particulate emissions.
9. Neutralization of the wastewaters by flue gas scrubbing appeared to
improve the efficiency of the subsequent biological treatment system
by producing a more favorable pH and alkalinity while producing
relatively insignificant other detrimental effects upon the waste-
water .
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SECTION II
RECOMMENDATIONS
1. As a result of the laboratory chemical destabilization investiga-
tions, it is recommended that future efforts in this area should
be directed into the use of alum coagulation.
2. Further investigation of alum coagulation should be concentrated
on improving the sludge dewatering characteristics. It is re-
commended that additional polyelectrolytes and suitable sludge
conditioners be investigated to improve the amenability of alum
sludge to conventional vacuum filtration techniques. Other de-
watering techniques such as the cyclone or various gravity-type
filters should also be investigated.
3. If the investigations, as recommended in 1 and 2 above, prove
successful, it is further recommended that the alum coagulation
evaluation be extended to a pilot scale study to provide in-
dicative chemical cost and operational data for a continuous
flow system. Consideration should also be given at this time
to the possible use of the scrubber installation for producing
the optimum pH levels required for alum coagulation. This
could result in a significant economic savings in a full scale
installation.
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SECTION III
INTRODUCTION
High pH and color are often typical characteristics of textile dye-
house wastewaters. In addition to the complexity of wastewater treat-
ment problems, mills presently operating coal-fired boilers or those
faced with the conversion to coal as a result of fuel shortages, are
now confronted with tasks of meeting compliance regulations related
to the control of noxious gases and particulate emissions. The
intent of this research project was to investigate an integrated solu-
tion to both of these problems. The approach was to combine dye waste-
waters and combustion by-products of coal to offset the less desirable
effects of each by utilizing the causticity of the dyehouse wastewater
and the neutralizing capacity of the scrubbed flue gases.
Included in this report are the results of a forty-four month research
project initiated jointly by Canton Textile Mills, Inc. of Canton,
Georgia and the United States Environmental Protection Agency under
EPA Grant S800852. The objectives of the research project as proposed
were as follows:
1. Investigate the practicability of utilizing the caustic waste-
waters resulting from the dyeing processes, as a scrubbing
agent in conventional scrubber equipment to accomplish a reduc-
tion of the particulate matter and noxious gases in the flue
gas while neutralizing the wastewater causticity.
2. Investigate the potential of using the residual carbon adsorp-
tion value of the fly ash generated from the combustion of coal
for the adsorption and subsequent removal of the color produc-
ing dyes from the wastewater.
3. Investigate the feasibility of utilizing the fly ash as a fil-
tration media to remove suspended solids from the wastewater
while simultaneously removing color by adsorption.
4. Utilize the treatment concepts listed in 1, 2, and 3 above in con-
junction with a conventional biological wastewater treatment system
to produce a final wastewater quality suitable for recycle to the
dyeing process.
The research project was performed in two phases. The initial phase,
including bench scale and pilot testing, was conducted to provide
design information for a full scale application. Early in the bench
'scale investigation of the fly ash adsorption of color, it was con-
cluded that this technique of color removal was impractical for this
application. As a result, the scope of the project was redefined to
include an evaluation of the feasibility of utilizing chemical desta-
bilization techniques of color removal from the dyehouse wastewaters.
-------
The second phase consisted of a demonstration of the full scale scrubber
installation as an integral part of the mill's total wastewater treat-
ment facility.
Simultaneously with the EPA Research and Demonstration Grant, Canton
Textile Mills, Inc. initiated a program to upgrade the existing biological
treatment system in order to obtain compliance with the Georgia Department
of Natural Resources' wastewater treatment regulations. This necessitated
several major modifications to the existing treatment facility. These
modifications are described within this report. Due to the time factor
involved in upgrading the existing biological system (i.e., preliminary
field engineering, submittal of plans for state approval, final design
engineering, equipment purchase, and construction), the bench scale phase
of the fly ash adsorption research was conducted concurrently with this
work. Therefore, to accomplish the bench scale fly ash investigations,
it was necessary to simulate the expected improvement in the effluent.
This was attempted by simply screening or filtering the existing system's
effluent to reduce the concentration of suspended solids.
The research reported herein is a combined effort of Canton Textile Mills,
Inc., of Canton, Georgia and R. S. Noonan, Inc. of South Carolina, Green-
ville, South Carolina, (Consulting Engineers).
PROJECT SITE
The site of the project is Canton Textile Mills, Inc.'s Mill No. 2 in
Canton, Georgia. This facility produces an average of 60,000 to 80,000
pounds of finished cotton denim fabric per day with a normal seven-day,
24-hour per day, mill production week and a 5-day per week dyehouse
production week.
Manufacturing Process Description
A number of mechanical operations have to be performed to convert cotton
fibers into fabrics. The operations performed at this facility to pro-
duce fabric are shown in the flow diagram listed as Figure 1. Although
several of these processes are wet operations, the primary contributor
in terms of pollution load and volume of wastewater is the dyeing opera-
tion. Indigo and sulfur dyeing processes are utilized at the mill.
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RAW COTTON]
j OPENING "~|
*
j PICKING I
*
j CARDING I
*
j DRAWING j
| SPINNING |
{ WINDING j
j
DYEING
| WARPING
j SLASHING j
j WEAVING |
SINGEING |
' *
I PRINTING j
| FINISHING |
Figure 1. Canton Textile Mills, Inc.'s
manufacturing process flow diagram
Due to the larger number of aqueous rinses, the indigo dyeing process is
the major contributor of wastewater in terms of volume. A flow diagram
of the indigo process is provided in Figure 2. Dry cotton warp fibers
enter a wetting out bath containing a penetrant. The warp fibers are
then rinsed with cold water and processed through a series of five indi-
go dye vats containing indigo reduced with sodium hydrosulfite and
caustic soda. Following each addition of indigo dye, the fiber is oxi-
dized in air. Once the dyeing cycle is completed, the dyed cotton fibers
are given an additional three stage wash consisting of cold, warm, and
hot water baths and dried.
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00
INDIGO
NoOH
DYE
MAKE-UP
FRESH WATER
PENETRANT
COTTON^
fc • A M^ ^ B ^^^
YARN
1
WET OUT
BATH
WASHER
\ I
DYE VATS
t \
WASHERS
t \
t \
DRYER
EFFLUENT TO SEWER
Figure 2. Flow diagram of indigo dyeing process.
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The sulfur or commonly called sulfur-black process consists of two sepa-
rate types of dye applications as illustrated in Figure 3. In this pro-
cess, the sulfur-black dye is applied in the initial vat along with a
formulation of soluble oil, penetrant, and sodium sulfite which is part
of the purchased dye. A cold water wash follows the sulfur dye vat after
which the warp enters a single stage indigo dye bath and is oxidized in
air. The indigo vat contains indigo dyestuff, sodium hydroxide, sodium
hydrosulfite and dextrose. The fiber is finally rinsed twice, once with
cold water and once with hot water, and dried. Occasionally, this dye
range is utilized for varying types of sulfur and naphthol colors with
diluted hydrogen peroxide used in oxidizing the various colors. The
relative use of the different dyes varies with production requirements.
During the latter stages of this project (in January 1975), the sulfur
dye range was modified to reverse the points of indigo and sulfur dye
applications. This was done to produce a more desirable color in the
final product. This change also significantly reduced the quantity of
sulfur dye used and as a result, altered the wastewater characteristics
somewhat. This process change had no direct bearing on the major por-
tion of the project except in evaluating the effect of scrubber neutrali-
zation. Further discussion has, therefore, been restricted to that
portion of this report.
Wastewater Characterization
The wastewaters resulting from the dyeing processes contribute a major
portion of the total volume of wastewater to the mill's treatment facil-
ity. During production periods, this wastewater stream ranges from 570
to 850 liters per minute (150-225 gpm). Normal daily production time
for each dye unit varies greatly from day to day, ranging from 10 to 24
hours. The wastewater from each of the dyeing units (indigo and sulfur)
is characterized in Table 1.
The dyeing process wastewaters combine with three additional wastewaters—
sanitary sewage from the mill and a nearby residential area (96 liters/
minute) and the discharge from a local hospital (36 liters/minute)—to
form a total average weekday volume of 1037 cubic meters (274,000 gal-
lons). Because of the mill's five-day dyehouse production schedule, the
weekend flow drops off significantly to an average of 273 cubic meters
(72,000 gallons) per day and is almost entirely domestic sewage and
hospital wastes. A profile of the typical weekday and weekend wastewater
characteristics is provided in Table 2.
Because the major portion of the total wastewater volume results from
the dyeing processes, the influent wastewater characteristics often
vary quite dramatically as a result of frequent production variations.
In addition to flow variations resulting from production trends, the
influent is influenced by apparent rainwater infiltration. This is
quite obvious from the heavy influent flow rates observed during rainy
periods.
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SULFUR BLACK INDIGO
i
DYE
MAKE-UP
FRESH WATER
COTTON „
YARN
NaOH
1
DYE
MAKE
DOWN
\ r
DYE VAT
WASHER
DYE VAT
v v
WASHER
DRYER
EFFLUENT TO SEWER
Figure 3. Folw diagram of sulfur dyeing process.
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Table 1. CHARACTERIZATION OF DYE WASTEWATERS
Parameter
Tempera-
ture
PH
Color
COD
BOD
TOC
Total
Solids
Suspended
Solids
Iron
Zinc
Calcium
Magnesium
Units
°C
Units
APHA Pt.-Co.
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
Indigo Range
40
10.5-11.5
5500-7500
750-950
400-750
150-300
2500-3300
50-300
0.10-0.5
0.05-0.10
9-13
4-7
Sulfur Range
60
10-11
24000-34000
2500-3500
900-1350
-
-
100-340
-
-
-
-
Modified
Sulfur Range3
60
10-11
-
500-1700
400-750
300-500
1600-3400
200-450
1-1.3
0.3-0.5
6-11
4-8
a Wastewater resulting from the reversal of the sulfur and indigo
dye application points. This change took place in January, 1975
at which time the fly ash adsorption and chemical coagulation
studies had been completed.
11
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Table 2. TYPICAL PROFILE OF INFLUENT WASTEWATER
TO THE TREATMENT SYSTEM
Parameter
Flow
Temperature
Dissolved Oxygen
pH
p Alkalinity
m Alkalinity
Acidity
Color
COD
BOD
TOC
Zinc
Chromium
Copper
Iron
Phosphate, Total
Nitrogen, Total
Kjeldahl
Total Solids
Total Volatile
Solids
Suspended Solids
Dissolved Solids
Units
1pm
°C
mg/1
Units
mg/1 as CaC03
mg/1 as CaC03
mg/1 as CaO>3
APHA Pt. Co.
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
Weekday
Influent3
720
25-40
2-5
10.0-11.5
150-350
400-900
-
2800-10,000
500-1800
300-500
250-400
0.2-1.9
0.1-0.4
0.05
0.7-1.8
5-8
5-30
1600-3700
400-800
80-230
600-2200
Weekend .
Influent3
190
14-18
5-8
6.0-7.5
-
50-150
10-40
400-5000
300-600
100-300
80-150
0.1-0.3
0.5-0.09
0.05
0.7-1.4
6-8
15-30
400-800
100-200
60-130
250-350
Average results of analyses performed on 24-hour composite samples.
12
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Existing Biological Treatment System
The mill's biological treatment facility, as it existed at the beginning
of the research project, is shown in Figure 4. Constructed in 1960, this
system consisted of screening, preaeration, extended aeration activated
sludge, and clarification. Flow monitoring was accomplished at an influ-
ent parshall flume. Due to the extended aeration nature of the activated
sludge process, the system relied on complete oxidation to prevent sludge
accumulation. More specific design data for this system is provided in
the Appendix in Table Al.
The results of a routine weekly influent-effluent wastewater monitoring
program conducted during the period of May 1971 through May 1973 are
summarized in Table 3. As may be observed from this data, the existing
treatment system was characterized by frequent upsets in operation
leading to poor treatment efficiencies. The instability of the treat-
ment system was attributed to large variations in flow and frequent
changes in the influent wastewater chemical characteristics (e.g., BOD,
COD, and pH).
Table 3. PROFILE OF EXISTING TREATMENT SYSTEM'S
INFLUENT-EFFLUENT WASTEWATER CHARACTERISTICS3
Parameter
BOD5
COD
Total
Solids
Suspended
Solids
PH
Units
mg/1
mg/1
mg/1
mg/1
Units
Influent @
Parshall Flume
Ave. (Std. Deviation)
429 (244)
1045 (474)
1808 (595)
230 (89)
10.3 (1.0)
Effluent (3
Clarifier Overflow
Ave. (Std. Deviation)
163 (88)
547 (339)
1071 (365)
190 (96)
7.8 (0.9)
Average
Removal
%
62
48
41
27
-
Data taken from routine weekly monitoring - May, 1971 through
May, 1973.
NOTE; This data was taken on weekdays only and does not reflect
weekend characteristics.
13
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•INDUSTRIAL WASTEWATER
•DOMESTIC WASTEWATER
• HOSPITAL WASTEWATER
SLUDGE RETURN (624LPM)
PRE-AERATION
TANK
MIXING
BOX
718 LPM 5 DAYS WK
189 LPM 2 DAYS WK
BAR SCREEN
PARSHALL FLUME
ACTIVATED
SLUDGE
AERATION
TANK
tr±3
MANHOLE
GRIT CHAMBER
LEGEND
CFR) FLOW RECORDER
LEVEL ACTUATED SWITCH
EXISTING AIRV
LIFT
LIFT STATION
CLARIFIER
SLUDGE
RETURN
--PUMP
MANHOLE
—n
DISCHARGE
TO
ETOWAH
RIVER
Figure 4. Flow diagram of Canton Textile Mills, Inc.'s existing wastewater treatment facility
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Upgraded Treatment System
In order to obtain compliance with the Georgia Department of Natural
Resources' treatment requirements, Canton Textile Mills, Inc. initiated
a program to upgrade the existing biological treatment system. At the
date of the upgrading of the existing facility, the State of Georgia's
Department of Natural Resources specified a treatment equivalent to
secondary treatment which is defined as approximately eighty-five
percent (85%) removal of the five-day Biochemical Oxygen Demand'-.
The first step in upgrading the existing treatment system was to bring
the system to its highest attainable level of operating efficiency. Dur-
ing a special maintenance period, all pipes were flushed, excess grit and
sludge were removed from tanks, .air spargers were cleaned, and adjustments
made to the clarifier weir. In addition, a daily operational log was in-
itiated so that performance trends could be observed and operational ad-
justments made if necessary.
Although the clean-up and operational changes greatly improved the ef-
ficiency of the system, it was concluded that three major modifications
would be necessary to obtain reliable treatment levels on a daily basis.
First, the flow from the grit chamber was diverted to a newly constructed
equalization pond with a nominal capacity of 3785m^ (1,000,000 gallons).
The purpose of this pond was to dampen flow fluctuations and protect the
biomass from shock organic loads resulting from the mill's production
variations. The second modification consisted of providing additional
clarification, increased sludge recycle capabilities, and provisions for
sludge wasting and aerobic digestion. Provisions were made in the selec-
tion of new clarifier and aerobic digester to allow those units to be
utilized in a future chemical coagulation system if such a system proved
feasible. The third addition to the system provided for the chlorination
of the final effluent. A flow diagram of the upgraded system is provided
in Figure 5 and a photograph of the system is provided in Figure 6 with
more specific design data tabulated in the Appendix in Table A2.
The upgrading work was completed in May, 1974. The results of a seven-
day monitoring program provided in Table 4 shows the typical treatment
efficiencies resulting from this program. The effect of equalization
is readily apparent as shown by the reduced standard deviations of the
wastewater's characteristics. The high concentration of suspended solids
in the effluent is attributed to the presence of colloidal suspensions of
dye which are not biologically destabilized.
15
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•INDUSTRIAL WASTEWATER
•DOMESTIC WASTEWATER
•HOSPITAL WASTEWATER
SLUDGE RETURN (624LPM)
SLUDGE RETURN PUMP
•AIR LIFT PUMPS
»
ACTIVATED
SLUDGE
AERATION
TANK
PRE'AERATION TANK i
7I8LPM5DAYSWK.
I89LPM 2 DAYS WK.
BAR SCREEN
BIOLOGICAL
CLARIFIER
PARSHALL FLUME
GRIT CHAMBER
_ GATES _
L3~BYPASS T I
WET WELL
SUPERNATANT
CHLORINE
CONTACT
BASIN
LIFT STATION
EMERGENCY DRAIN
AEROBIC XEMERGENCY DRAIN
DIGESTER
DIGESTED SLUDGE
LEGEND
SLUDGE
LAGOON
SLUDGE
LAGOON
EQUALIZATION
BASIN
DISCHARGE
TO
ETOWAH
RIVER
SUPERNATANT
FLOW RECORDER ,
£AS) LEVEL ACTUATED SWITCH
LEVEL TRANSMITTER
CV) AUTOMATIC CONTROLS VALVE
Figure 5, Flow diagram of Canton Textile Mills, Inc.'s upgraded wastewater treatment facility
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Figure 6. Canton Textile Mills, Inc.'s upgraded wastewater treatment facility
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Table 4. PROFILE OF UPGRADED TREATMENT SYSTEM'S
INFLUENT-EFFLUENT WASTEWATER CHARACTERISTICS3
Parameter
BOD5
COD
TOC
Alkalinity, M
Total Solids
Total Vola-
tile Solids
Suspended
Solids
Susp. Volatile
Solids
Settleable
Solids
PH
Units
mg/1
mg/1
mg/1
mg/1 as CaC03
mg/1
mg/1
mg/1
mg/1
mg/1
Units
Influent @
Parshall Flumeb
Ave.(Std. Deviation)
392 (158)
884 (266)
241 (62)
431 (168)
1880 (579)
570 (162)
129 (66)
100 (43)
-
10.0 (0.7)
Equalization
Pond Effluent
Ave.(Std. Deviation)
394 (85)
931 (38)
238 (26)
422 (33)
1930 (124)
492 (97)
171 (30)
131 (23)
-
8.6 (0.4)
Final Effluent
Ave.(Std. Deviation)
42 (14)
284 (72)
92 (29)
209 (30)
1634 (102)
254 (68)
175 (50)
181 (90)
0.1
6.9 (0.3)
Removal
%
89
68
62
-
13
-
-
-
-
-
a Data was taken during seven-day monitoring period, August 21-27, 1974.
00
To allow comparison with previous data, influent averages are for weekdays only.
-------
SECTION IV
FLY ASH ADSORPTION OF COLOR
One of the major problems resulting from the combustion of coal is the
disposal of the combustion by-product, fly ash. Due to the ever-
increasing demand for cleaner air, the quantity of fly ash recovered
from the combustion of coal in furnace - boiler systems has increased
appreciably over the recent years. The disposal of this fly ash has now
become an acute solid waste problem .
It has recently been reported that less than ten percent (10%) of the
fly ash generated in the United States is utilized to any degree3.
Efforts to utilize or at least recover disposal costs have been primarily
directed towards utilization of the pozzolanic properties of fly ash for
a constituent in concrete and concrete products . One area that has
recently gained recognition involves the utilization of fly ash as an
adsorbent material .
Due to the residual carbon value of fly ash and its relatively large sur-
face area per unit volume, fly ash exhibits many of the adsorbent charac-
teristics of activated carbon^. Fly ash has been reported in the litera-
ture to be an effective adsorbent for the removal of various chemical
constituents such as refractory organic materials^, phenols^, and color
resulting from various soluble organic materials found in polluted lake
waters-*. It is this adsorption characteristic that was used as the
basis for the investigation of fly ash as a mechanism of color removal
from the wastewaters of Canton Textile Mills, Inc.
PROPERTIES OF FLY ASH
Fly ash consists of a heterogeneous material consisting of minute par-
ticles of inert compounds and partially burned carbon particles generally
ranging in size from 0.5 to 300 microns. Chemically, fly ash consists of
unburned carbon and a variety of oxides - aluminum, magnesium and sulfur -
as well as other trace metals. The physical size and shape of fly ash
particles is largely determined by the type of coal, type of firing equip-
ment, and even the type of collection system employed.
The source of fly ash used for the research was obtained from Canton
Textile Mills, Inc.'s 27.2 metric ton per hour (60,000 pounds per hour)
spreader stoker-fired boiler (Combustion Engineering, Inc.'s C-E Verti-
cal Unit). This installation utilizes a Whirlex dust collector to re-
move approximately 34 to 45 kilograms (75 to 100 Ibs.) of fly ash per
hour. A typical analysis of this fly ash is provided in Table 5.
19
-------
Table 5. TYPICAL ANALYSIS OF
CANTON TEXTILE MILLS' FLY ASH
Chemical Composition By Weight (%)
Silica, Si02 19-72
Alumina, A1203 22.03
Iron Oxide, Fe203 or Fe304 6.00
Calcium Oxide, CaO 1.72
Magnesium Oxide, MgO 1.11
Sulfur Trioxide, 803 0.63
Loss on Ignition, Carbon 46.21
Trace Elements (By Difference) 2.58
Physical Properties By Weight (%)
Range of Particle Size, Microns 0.5-2500
Ave. % Passing No. 325 Sieve (U. S. Standard) 21
Bulk Density, gm/cc 0.47
Specific Gravity, gm/cc 2.0
LABORATORY INVESTIGATION
The objective of the laboratory investigation was to evaluate fly ash as
an adsorption media for the removal of color from Canton Textile Mill,
Inc.'s wastewaters. Over one hundred tests were performed to determine
optimum parameters for a full scale fly ash color removal system. These
tests investigated various contacting systems - batch, packed-bed, and
expanded-bed as well as the effects of pH and temperature on the adsorp-
tion capacity.
Adsorption Isotherms
Prior to initiating the investigation of the various fly ash - wastewater
contacting systems, a series of jar tests was conducted in order to de-
velop adsorption isotherms. An adsorption isotherm is simply a plot
showing the relationship between the amount of impurities (color) ad-
sorbed on a unit weight of adsorption media (fly ash) and the amount of
impurities (color) remaining in the wastewater. These isotherms are
useful in:
1. Providing a general indication of the effectiveness of the adsorp-
tion media.
20
-------
2. Predicting the maximum quantity of impurities (color) capable of
being adsorbed onto the media.
The adsorption isotherms were developed by placing various quantities of
fly ash in each of several jars containing a constant volume and concen-
tration of dye wastewaters. The jars were then shaken simultaneously for
a period of thirty minutes by a mechanical "shaker with the supernatant
color measured both before and after agitation. The adsorption capacity
was then expressed as an adsorption isotherm in accord with the Freund-
lich Equation®. The Freundlich Equation has the general form:
x/m - k CRn (01)
where x = Amount of residual color reduction due to adsorption
t- Co.
m = Mass Concentration of the Fly Ash, gm/1
k = Constant (obtained from graphical plot)
n = Constant (obtained from graphical plot)
CR= Residual Color of Adsorbate at Equalibrium Expressed in
APHA Pt. Co.
Cz= Initial Color (APHA Pt. Co.)
It is usual practice to take logarithms of both sides of the above expres
sion to obtain:
log x/m = log k + n log CR (02)
Therefore, a plot of log (x/m) vs. log (Cr) will be a straight line with
a slope of "n" and an intercept of "log k". This data was then used in
predicting fly ash requirements for single batch treatment and column sys
tems.
The isotherm plot was also used to provide an indication of the theo-
retical adsorption capacity. The adsorption capacity was determined by
entering the abscissa with the initial color concentration (Co) and ob-
taining the color reduction per mass concentration of fly ash (x/m) at
the intersection of the isotherm plot.
In the investigation, adsorption isotherms were determined utilizing the
final effluent from the mill's biological treatment facility. Three
typical isotherms are shown using the following variations:
1. Isotherm No. 1 was developed with the treatment plant's final ef-
fluent and with fly ash from the mill's coal-fired boiler.
21
-------
2. Isotherm No. 2 was derived with the final effluent prefiltered
through a 12-inch deep sand filter for suspended solids removal and
again with the mill's fly ash.
3. Isotherm No. 3 was determined utilizing the sand filtered effluent
and Westvaco's Aqua Nuchar A powdered activated carbon.
The results of these investigations are tabulated in Table 6 with the
corresponding graphical plots provided in Figures 7-9.
The results of the adsorption isotherm investigations led to the follow-
ing conclusions:
1. Fly ash was capable of removing the color constituent from the
wastewaters.
2. Removal or reduction of suspended solids appears to enhance the
ability of the fly ash to adsorb color as is observed in the in-
creased adsorbance capacity.
3. The results of the isotherm test indicate that the fly ash require-
ments to achieve an effluent color of less than 100 APHA Pt. Co.
color units will be significantly larger than the fly ash available
from the mill's boiler. By utilizing the Freundlich Equation and
the constants developed in the isotherm plots (Figures 7 - 9), it is
predicted that 61 gm of fly ash will be required per liter of unfil-
tered wastewater to reduce the color from 440 to 100 APHA Pt. Co.
Units while 23 gm of fly ash will be required per liter of the fil-
tered effluent for a similar color reduction. These values dras-
tically exceed the quantity of fly ash available from the mill's
boiler per unit volume of wastewater which is 0.8 gm/1.
4. Comparatively, powdered activated carbon exhibits a superior adsorp-
tion capacity to that of fly ash. By use of the Freundlich Equation
•and data developed in the isotherm plot (Figure 8), it is predicted
that only 2 gm of activated carbon will be required per liter of
filtered effluent to achieve an effluent with a color level of 100
APHA Pt. Co. Units. Therefore, it appears that the fly ash is only
approximately 10 percent as effective as the powdered activated car-
bon in achieving color removal.
Packed-Bed Contacting Systems
The first of the bench scale investigations of the various contacting
systems were performed with the test apparatus illustrated in Figure 10.
This system consisted of a 5.72cm I.D. (2.25 inch I.D.) plexiglass, gravity
feed column containing varying amounts of fly ash. Wire mesh screen
was used at both fly ash interfaces of the column to retain the fly ash.
A constant liquid level was maintained in the overhead feed tank through
the use of a sump pump controlled by a level switch.
22
-------
Table 6. TYPICAL ADSORPTION ISOTHERM DATA
Isotherm No. la (raw effluent and boiler fly ash)
Fly Ash Dosage (m)
(gm/liter of wastewater)
0
5
20
60
100
170
Residual Color (CR)
(APHA Pt. Co. Units)
440
400
150
125
25
5
Color Removed (x)
(X = CT - CR)
_
40
290
315
415
435
x/m
_
8.0
14.5
5.2
4.2
2.6
Isotherm No. 2b (prefiltered effluent and boiler fly ash)
Fly Ash Dosage (m)
(gm/liter of wastewater)
0
2.50
3.75
5.00
10.00
25.00
Residual Color (CR)
(APHA Pt. Co. Units)
440
400
390
370
300
60
Color Removed (x)
(X = CT - CR)
_
40
50
70
140
380
x/m
_
16.0
13.4
14.0
14.0
15.2
Isotherm No. 3° (prefiltered effluent and Westvaco's Aqua Nuchar A
Powdered Activated Carbon)
Act. Carbon Dosage (m)
(gm/liter of wastewater)
0
1.25
2.50
3.75
5.00
10.00
Residual Color (CR)
(APHA Pt. Co. Units)
420
180
30
10
0
0
Color Removed (x)
(X = Ci - CR)
m,.
240
390
410
420
420
x/m
192.0
156.0
109.0
84.0
42.0
a Refer to Figure 7 for graphical plot.
b Refer to Figure 8 for graphical plot.
c Refer to Figure 9 for graphical plot.
23
-------
N>
50
40
30
20
CO
,o
!
o
8
fe
H
1
ADSORPTION CAPACITY = 7.9
1.75
I I I I I I 11
I I I I I MM
I
1
IO
• cooo poo oooOo
— C3 K> * in <0 f-®0>
8O O O
o o
m *
esi
Cr = RESIDUAL COLOR, APHA PT-Ca UNIT
(ONE LITER SAMPLE)
Figure 7. Fly ash adsorption isotherm with existing effluent.
-------
M
Ul
^
3
u.
o
s
£
UJ
0
**
¥
I
o
u
&
£
§
i
.
50
40
30
20
10
8
7
6
5
3
2
1
1
•••MM
i«MM>
•••MBA*
•M^M*
ADSORPTION CAPACITY = 15.0 g) 0
— f ~~ |n=O.Ol"u&nT1" ^l
•wmv
••••••*
— Crs440
—
_
_ k» 14.0
MM*
•MM*
i 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 | III
CM ro «- ««>NCOO>O § g 0 gggoog | 8 | 8
Cr a RESIDUAL COLOR.APHA PT.-CO. UNIT
(ONE LITER SAMPLE)
Figure 8. Fly ash adsorption isotherm with prefiltered effluent.
-------
0>2
Cr
O
10
o o o p oog
*tf IO (0 ^* QOO^^'^
888
lO
RESIDUAL COLOR, APHA PT.-CO. UNIT
(ONE LITER SAMPLE)
Figure 9. Powdered activated carbon isotherm with prefiltered effluent.
-------
LEVEL CONTROLLER
FEED
TANK
SAMPLE
STORAGE
—STOPPER
SCREEN
ASH
PLEXIGLASS
TUBE (5.7cm)
SCREEN
STOPPER
EFFLUENT
STORAGE
Figure 10. Gravity feed, packed bed contacting test apparatus.
27
-------
The objectives of the first series of investigations utilizing the gravity
feed column were as follows:
1. Determine the adsorption characteristics of the packed-bed fly ash
column.
2. Evaluate the feasibility of utilizing the fly ash column for the
dual purpose of color adsorption and suspended solids removal.
Variables of these tests included the depth of fly ash and the type of
wastewater (raw effluent or prefiltered effluent). The prefiltered sam-
ples were obtained by passing the effluent through a 710 micron screen.
This was an attempt to simulate the expected effluent that would result
from the upgrading of the existing treatment plant. During each test,
samples were withdrawn at periodic intervals for analysis of color, total
solids, and suspended solids. A color level of less than 100 APHA Pt. Co.
units was arbitrarily established as an acceptable final effluent color.
Data taken during one of the more successful tests utilizing the prefil-
tered efffluent is provided in Table 7. Also, data representative of
the other investigations with varying filter depths on each of the waste-
water conditions (raw effluent or prefiltered effluent) is provided in the
Appendix as Tables A3 - A4. The gravity fed column tests resulted in low
and erratic flow rates leading to the conclusion that a gravity-fed fly
ash column was impractical. The columns did, however, successfully remove
the majority of the suspended solids.
To overcome the erratic flow rates, the system was modified to provide
for a pressurized feed and a sand filter pretreatment. This test appa-
ratus is illustrated in Figures 11 and 12. Data from one of the typical
tests is provided in Table 8. As may be detected from the data, the
color level after 430 minutes of operation was still below the colorless
level (100 APHA Pt. Co. Units); however, the flow rate had declined
drastically as a result of the plugging and compaction of the fly ash.
It was thus concluded that packed-bed fly ash columns appeared to be im-
practical due to the inability of the fly ash particles to maintain
their structural integrity. This resulted in a continuous increase of
head loss through the filter media. To overcome this difficulty, expan-
ded bed operation was investigated.
Expanded-Bed Contacting System
The principle of operation of the expanded-bed contacting system is to
feed the wastewater through the bottom of the column at a velocity suf-
ficient to suspend the adsorbent particles. Unlike the packed-bed sys-
tem, particulate matter (suspended solids) in the wastewater is not re-
tained in the column. Thus, due to the expanded nature of the bed, head
losses do not increase as a function of time.
28
-------
Table 7. TYPICAL RESULTS OF FLY ASH PACKED-COLUMN
TESTS WITH PREFILTERED EFFLUENT3
Test Conditions;
Fly Ash Bed Depth
Fly Ash Weight
Wastewater
Mode of Contact
Elapsed Time
(min.)
Flow Rate
l/min/m^
25.4 cm (10 inches)
318 gm (0.70 Ibs.)
Filtered Effluent
(710 micron screen)
Gravity, Downflow
Color Total Solids
(APHA Ft. Co. Units) (mg/1)
Susp. Solids
(mg/D
Effluent
Filtered
Effluent
0
30
60
90
120
150
180
210
—
33.16
21.88
13.65
13.65
13.65
12.91
9.78
7.82
2150
1895
30
20
35
50
50
60
110
310
1232
977
3974
1377
1173
1197
1240
1225
1406
1203
74
50
6
11
9
9
6
7
9
7
Total volume of effluent with color 100 APHA Pt. Co. Units = 7.6 liters
a Samples were prefiltered with U. S. Standard Seive No. 325.
29
-------
5.1cm
7.6cm
203cm 1—
FILTER
LO
O
-GRAVEL
— <7IO)im
SAMPLE
STORAGE
-»«**
•V
*-ASH
COLUMN I
w
IcLARIFlER-J
•=•.:•
". • »•*
i
COLUMN 2
EFFLUENT
STORAGE
Figure 11. Pressurized packed bed contacting test apparatus.
-------
TEST IM°
NOVEMBER 15,1372
Figure 12. Pressurized packed-bed fly ash test apparatus,
I]
-------
Table 8. TYPICAL PACKED-BED FLY ASH TEST RESULTS
Test Condition;
Fly Ash Bed Depth
Fly Ash Weight
Wastewater
Operation Mode
Column No. 1 - 25.4cm, Column No. 2 - 25.4cm
Column No. 1 - 454gm, Column No. 2 - 453gm
Prefiltered Effluent (sand filter)
Pressurized Feed, Downflow
Elapsed Time Flow Rate Color Total Solids Susp. Solids
(min.) (1/min/m2) (APHA Pt. Co. Units) (mg/1) (mg/1)
Effluent
Filtered
Effluent
0
23
53
90
160
263
430
-
81.89
70.07
63.96
54.59
58.67
52.55
1300
1150
0
0
0
0
0
0
32.59 1 30
I
3706
2952
4291
2710
2898
1145
4590
-
2960
122
15
13
15
14
12
19
13
22
To investigate this mode of wastewater - fly ash contact, a test apparatus
as illustrated in Figure 13 was utilized. The principle problem encoun-
tered with this test set-up was that the fly ash tended to form conglomer-
ated masses. These masses of fly ash then formed into packed beds at
various points within the fly ash column depending upon flow rate and re-
sulted in channeling of flow. This phenomenon, therefore, negated the
advantage of the expanded-bed mode of operation. Data from a typical
test with approximately fifty percent bed expansion is provided in
Table 9.
Due to the difficulties encountered with the* cohering properties of the
fly ash in the columns and the resulting hydraulic conditions, it was
concluded that further studies utilizing the column mode of contact were
impractical. At this time, the investigation was directed toward the
use of a slurry contacting system.
32
-------
£$
-ASH COLUMN
uil
o
LfcJ
UJ
It.
SAMPLE
STORAGE
•EFFLUENT
STORAGE
Figure 13. Expanded bed contacting test apparatus.
33
-------
Table 9. RESULTS OF FLY ASH EXPANDED-BED
TEST WITH PREFILTERED EFFLUENT
Test Conditions;
Fly Ash Bed Depth
Fly Ash Weight
Wastewater
Mode of Contact
22-28 cm (8.7-11.0 inches)
318 grams (0.7 Ibs.)
Filtered Effluent (No. 4
Whatman Paper)
Pressurized, Approximately
50% Bed Expansion
Color
Elapsed Time Flow Rate pH (APHA Pt. Total Solids
(min.) (1/min/m2) (Units) Co.Units) (mg/1)
Effluent
Filtered
Effluent
5
15
45
-
81.89
74.15
58.67
9.8
9.8
7.4
9.1
9.3
2025
1720
50
125
675
\ 1745
1430
2175
1557
—
84
62
_
-
—
Susp. Solids
(mg/1)
Total volume of effluent with color <100 APHA Pt. Co. Units = 2.84 liters
Slurry Contacting System
The slurry contacting system employs a combination of simple unit opera-
tions consisting of mixing, flocculation, and settling. The results of
the thirty minute adsorption isotherms indicated that the fly ash was
capable of removing color in slurry type systems. Also, preliminary data
obtained concerning settling characteristics of the fly ash indicated
that clarification would present no significant problems. Therefore, a
series of batch reactor investigations were undertaken to determine the
feasibility of a slurry contact system.
The bench scale fly ash slurry investigations were conducted with a 30-
liter batch reactor. After the desired contact time, the slurry was
filtered through No. 4 Whatman paper (20-25 micron pore size) to remove
the fly ash granules. The resulting filtrate was then analyzed for
residual color and
34
-------
The results of these tests are shown in Tables 10 & 11. These tests
demonstrate very conclusively that the quantity of fly ash available per
volume of wastewater is insufficient to accomplish a significant color
reduction. The results also show that the adsorption reaction is essen-
tially complete after the initial 30 minute contact time.
Further studies were conducted to ascertain the effect of pH and tempera-
ture on the adsorption properties of the fly ash. These tests, as tabu-
lated in Tables 12 & 13, show that the color adsorption is slightly
greater with increasing temperatures and acidic pH levels. The increased
adsorption capacity of the fly ash at acidic pH ranges corresponds to the
theory that the increased ionization or increased hydrogen-ion concentra-
tion results in the neutralization of the negative surface charges found
on the surface of carbon. Thereby, the hindrance to diffusion is reduced
and more active surface of the carbon is available for adsorption^.
Further discussion of the interactions of acids and bases with activated
carbons is available in the literature9»10»H. The increased color
removal accomplished with increasing temperature is believed to be a
result of an increase in the rate of adsorption rather than in the adsorp-
tion capacity. While the rate of adsorption is directly related to the
activation energy and therefore a function of temperature, the extent of
adsorption is, however, indirectly related to temperature, thus increases
with decreasing temperature . The range of temperatures investigated
within this study was concluded to be too small to alter the extent of ad-
sorption to a significant degree, therefore, the increased adsorption was
attributed to the increased rate of adsorption.
For comparative purposes, a similar series of investigations was also
performed utilizing Westvaco's Aqua Huchar A - powdered activated carbon.
During these tests, the powdered activated carbon was added in amounts
equal to the fly ash additions in the earlier investigations (23, 47, and
71 grams). This amount is equivalent to one, two and three times the
amount of fly ash produced on site per 30 liters of final effluent waste-
water discharged. Because this investigation was for comparative pur-
poses, the test period was limited to thirty minute batches only. The
resulting data from these powdered activated carbon investigations is
provided in Table 14. The results of the powdered activated carbon
slurry tests show the superiority of the activated carbon to fly ash.
Further study involving activated ca-rbon was beyond the scope of this
study.
35
-------
Table 10. FLY ASH SLURRY CONTACT TEST
RESULTS WITH UNFILTERED EFFLUENT
A. Wastewater
Fly Ash Addition
Contact Time
(Minutes)
30 liters (Final Effluent)
23 grams (Equivalent to 75 Ibs/hr at
a flow rate of 190 gpm)
Color
(APHA Pt. Co. Units)
BODc
(mg/1)
Raw wastewater
30
60
90
3400
2800
2900
2800
1099
208
130
199
B. Wastewater
Fly Ash Addition
30 liters (Final Effluent) '
47 grams (Equivalent to 150 Ibs/hr
at a flow rate of 190 gpm)
Contact Time Color BOD5
(Minutes) (APHA Pt. Co. Units) (mg/1)
Raw wastewater
30
60
90
I
2900
950
950
1000
182
29
16
12
C. Wastewater
Fly Ash Addition
30 liters (Final Effluent)
71 grams (Equivalent to 225 Ibs/hr at
a flow rate of 190 gpm)
Contact Time Color BOD5
(Minutes) (APHA Pt. Co. Units) (mg/1)
Raw wastewater
30
60
90
1900
1800
1600
700
95
59
43
40
36
-------
Table 11. FLY ASH SLURRY CONTACT TEST RESULTS
WITH PREFILTERED EFFLUENT
A. Wastewater
Fly Ash Addition
30 liters, (Final Effluent Prefiltered
with No. 4 Whatman Paper)
23 grams (Equivalent to 75 Ibs/hr @ a
Flow Rate of 190 gpm)
Contact Time Color BOD5
(Minutes) (APHA Pt. Co. Units) (own)
(Prefiltered
Wastewater)
30
60
90
1575
1225
1200
1295
75
52
42
70
B. Wastewater
Fly Ash Addition
30 liters (Final Effluent Prefiltered
with No. 4 Whatman Paper)
47 grams (Equivalent to 150 Ibs/hr @
a Flow Rate of 190 gpm)
Contact Time Color BOD5
(Minutes) (APHA Pt. Co. Units) (ppm)
(Prefiltered
Wastewater)
30
60
90
1710
1300
1310
1250
85
71
65
54
C. Wastewater
Fly Ash Addition
30 liters (Final Effluent Prefiltered
with No. 4 Whatman Paper)
71 grams (Equivalent to 225 Ibs/hr @
a Flow Rate of 190 gpm) v
Contact Time Color
(Minutes) (APHA Pt. Co. Units)
(Prefiltered
Wastewater)
30
60
90
1470
990
1100
900
BOD5
(ppm)
73
51
49
65
37
-------
Table 12. EFFECT OF pH ON ADSORPTION
CAPACITY OF FLY ASH
Test Data:
Slurry Contact Reactor
Fly Ash: 23 grams per 30 liters of wastewater (equivalent to 75 Ibs/hr
of Fly Ash and 190 gpm)
Contact Time: 30 minutes
Wastewater Profile:
Final Effluent
Color
COD
BOD5
Suspended Solids
Temperature
pH
2950 APHA Pt.
283 mg/1
136 mg/1
84
13° C
8.8
Co. Units
pH Adjustment Chemicals: Sulphuric Acid & Sodium Hydroxide
Residual
pH
Units
2.7
5.3
7.0
8.9
10.7
Color
(APHA Pt. Co. Units)
1500
1900
2200
2600
2600
COD
(mg/1)
113
140
138
145
168
BOD5
(mg/1)
72
98
63
78
85
Susp. Solids
(mg/1)
160
64
40
48
48
38
-------
Table 13. EFFECT OF TEMPERATURE ON THE
ADSORPTION CAPACITY OF FLY ASH
Test Data:
Slurry Reactor Contact
Fly Ash: 23 grams per 30 liters of wastewater (equivalent to 75 Ibs/hr
of Fly Ash and 190 gpm)
Contact Time: 30 minutes
Wastewater Profile:
Final Effluent
Color
COD
BOD5
Suspended Solids
Temperature
3900 APHA Pt. Co. Units
566 mg/1
285 mg/1
216 mg/1
13° C
Residual
Temperature
(C°)
5
11
18
25
31
Color
(APHA Pt. Co. Units)
3000
2975
2950
2900
2800
COD
(mg/1)
172
249
174
528
197
BOD5
(mB/1)
90
189
98
340
106
Susp. Solids
(m*/l)
76
76
64
' 60
64
39
-------
Table 14. POWDERED ACTIVATED CARBON
SLURRY CONTACT TEST RESULTS
A. Wastewater 30 liters (Final Effluent)
Powdered Activated Carbon Color 8005
(grams) (APHA Pt. Co. Units) (mg/1)
(Raw Wastewater)
23
47
71
220
1200
875
310
53
50
55
27
B. Wastewater
Powdered Activated Carbon
(grams)
30 liters (Final Effluent Prefiltered
with a 325 mesh screen)
Color
(APHA Pt. Co. Units)
BODs
(mg/1)
(Prefiltered Wastewater)
23
47
71
1580
1145
930
175
42
52
45
26
40
-------
SUMMARY OF CONCLUSIONS OF FLY ASH COLOR ADSORPTION STUDY
The results of the preceding fly ash investigations led to the following
conclusions:
1. Fly ash is capable of removing color, BODj, and COD from the waste-
waters at Canton Textile Mills, Inc. The adsorption capacity of fly
ash, however, is significantly below that of powdered activated car-
bon.
2. Slurry contacting investigations have shown conclusively that the
quantity of fly ash produced at Canton Textile Mills, Inc. is much
less than that necessary to accomplish the desired color reduction.
3. The adsorption capability of the fly ash can be improved in acidic
pH ranges in accordance with the dominate theory that the increased
ionization effects the surface properties of the adsorbing material.
A similar adsorption capability improvement resulting with increas-
ing temperatures was concluded to be attributable to an increased
adsorption rate rather than increased adsorption capacity.
4. Problems related to hydraulic plugging as a result of the fineness
of the fly ash particles and suspended solids present in the waste-
water, led to the conclusion that consideration of column (packed or
expanded-bed) contacting systems was impractical.
41
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SECTION V
CHEMICAL DESTABILIZATION FOR REMOVAL OF COLOR
Until recently, the typical approach utilized for treating textile waste-
waters has resulted in a treatment scheme in'which the total wastestream
was biologically treated by some oxidative process such as the activated
sludge or extended aeration processes12. Although this treatment ap-
proach is moderately successful in reducing the total organic content, it
has been relatively unsuccessful in removing color. Typically, textile
dyeing and finishing operations are also subject to interrupted schedules
and wide variations of process chemicals which in turn cause wide fluctu-
ations in the operational performance of these biological systems. The
presence of toxic dyestuffs, particularly sulfur dyes, as well as toxic
emulsifiers and leveling agents also tax the operating efficiency of
these biological systems1^. Because of the aforementioned shortcomings
of biological systems and the increasing public pressure to eliminate
color from wastewater discharges, chemical coagulation techniques are now
beginning to gain prominence.
Historically, chemical coagulation techniques have been reported in the
literature to be successfully employed in the textile industry in reduc-
ing the BOD in strong textile wastes1^, as a polishing process on bio-
logically treated effluentlS, and as a complete treatment process for
the removal of toxic materials as well as color from the dyeing and fin-
ishing wastestreamsl^. Coagulants which have been reported as effec-
tive in treating textile waste effluents include: calcium hydroxide
(lime), ferrous sulfate, ferric chloride, calcium chloride, and alumi-
num sulfate (alum)13.
CHEMICAL DESTABILIZATION
Chemical clarification or destabilization generally consists of four
steps: coagulation, flocculation, sedimentation and filtration. As a
wastewater treatment process, coagulation is defined as the addition of
chemicals (coagulants) to effect destabilization and aggregation of non-
settleable suspended materials, commonly referred to as dispersions. The
materials generally comprising these dispersions typically range in size
from 0.1 millimicrons to 100 microns and are commonly termed colloids.
The result of the chemical addition is the formation of floe particles
which have the ability to adsorb, entrap, or to aggregate the suspended
colloidal particles. Most of the flocculated material is then removed
by sedimentation with the remainder removed by filtration.
There are several dominant theories associated with the mechanics of col-
loidal destabilization and the principles governing coagulation. Discus-
sion of those theories and principles is beyond the scope of this report;
however, it can be found in the literature17'18'19'20. Likewise, a dis-
cussion of the chemistry and stoichiometry of chemical coagulation reac-
tions is also well documented in the literature18'iy»20, and has, there-
fore, been omitted from this discussion.
43
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Laboratory investigation of the applicability of various chemical coagu-
lants is typically accomplished by the use of a series of jar tests. This
test consists of a series of sample containers (typically six) which may
be mixed by individual mechanically-operated stirrers. The samples to be
treated are placed in the containers with the coagulants added while the
contents are mixed. After a period of rapid agitation to ensure complete
dispersion of the coagulant, the mixing rate is reduced and a period of
particle aggregation (flocculation) is allowed to continue. After the
flocculating period, the mixing is stopped and the floe allowed to settle
for a selected time at which the supernatant may be withdrawn for
analysis. A typical step-by-step procedure description of the jar test
methods utilized during this investigation is provided in the Appendix as
Table A5.
The jar test attempts to simulate the full scale coagulation-flocculation
process under controlled laboratory conditions. The use of the jar test
investigations affords the opportunity for taking a multitude of observa-
tions pertaining to optimization of coagulants, effective pH ranges, and
characteristics of supernatant liquids or sludges. These studies may
also be employed as a basis for treatment plant design, although final
design must feature flexibility in mixing and feeding equipment to pro-
ide for the differences between batch and continuous flow processes.
LABORATORY INVESTIGATION
The primary objective of the laboratory investigation was to evaluate the
applicability and effectiveness of several chemical destabilizing agents
for removing color from the various wastestreams of Canton Textile Mills,
Inc. The investigation was carried out in two phases. The objective of
the first phase was to determine the point within the wastewater system
at which chemical destabilization would be most effective. The objec-
tives of the second phase of the investigation was then, to select the
destabilizing agent best suited for application on the wastestream
selected. This selection was to be based upon supernatant quality,
chemical dosage requirements, as well as the various parameters associ-
ated with sludge handling and disposal (i.e., sludge volume, sludge
filterability, and chemical recycle feasibility).
Destabilization Investigations
In the first phase of the chemical destabilization investigations, four
wastewater streams were selected as potential points for chemical addi-
tion. These four points were:
1. Wastewater stream from the indigo dyeing process.
2. Wastewater stream from the sulfur dyeing process.
3. Combined wastewater stream from the two dyeing processes.
4. Effluent from the existing (prior to upgrading) biological
wastewater treatment plant.
44
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Because attention at this stage of the investigation was centered pri-
marily upon color removal, the selection of the optimum location was
based entirely upon the color quality of the supernatant, relative
chemical dosage requirements, and visual observations related to the
various sludges. Eight destabilizing agents or combinations thereof
were utilized in the initial screening series of jar tests. A series
of jar tests wasconducted with each of eleven destabilizing agent
combinations on each of the four wastewater streams to determine the
optimum color removal. Various pH ranges were also investigated for
each destabilizing agent to insure optimum chemical dosage. The re-
sults of these preliminary screening investigations are provided in
Table 15.
These preliminary investigations indicated that chemical destabiliza-
tion of the wastestreams from the dyeing processes, either separate or
combined, would be difficult. In most cases, regardless of chemical
dosage, the color concentration of these wastestreams could not be brought
below 100 APHA Pt. Co. Units. In those few cases where the level of
100 APHA Pt. Co. Units could be reached, the chemical dosages required
were economically impractical.
Chemical destabilization investigations performed on the effluent from
the existing biological system, however, demonstrated that seven of
the destabilizing agents could successfully reduce the color levels to
or below 100 APHA Pt. Co. Units. Of these seven, three — concentrated
sulfuric acid, calcium chloride, and ferric chloride — produced sludges
that were impractical to dewater due to their extreme fineness and ex-
cessive volume. Aluminum sulfate, magnesium carbonate hydrolyzed with
lime, lime, and lime with an anionic polyelectrolyte visually demon-
strated the ability to produce a supernatant with low color concentra-
tions while producing a sludge with good settling properties.
At this point of the investigation, an additional series of jar tests
was performed on the effluent from the biological treatment system with
each of the four successful coagulants. These tests were designed to
evaluate the effect of daily fluctuations of the wastewater over a week
period and to establish optimum coagulant dosages. During these tests,
the quality of the supernatant was analyzed in terms of BOD5, COD, and
suspended solids. The results of these tests as summarized in Table 16
reinforced the earlier conclusions regarding the ability of these coagu-
lants to satisfactorily remove color. They also demonstrated the
ability of the coagulants to produce a supernatant with low BOD5, COD,
and suspended solids concentrations.
Sludge Characterization
To further evaluate the respective coagulants, the investigations in-
cluded characterizing the various sludges. Sludge in sufficient
quantities for analysis was obtained through the use of a thirty-liter
batch reactor. Each of the coagulant sludges were produced by reacting
45
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Table 15. SUMMARY OF PHASE ONE JAR TEST INVESTIGATIONS
Destabilizing
Agent
Initial
H2S04(Conc.)
A12(S04)3-18H20
A12(S04)3-18H20
& Ca(OH)2
Ca(OH)2
Ca(OH)2 &
MgC03-3H20
Ca(OH)2 &
Dow A-23
Ca(OH)2 &
FeS04-7H20
Ca(OH)2 &
FeCl3-6H20
CaCl2
FeCl3'6H20
FeS04-7H20
Indigo Dyeing
Wastewater
Dosage3
-
1.0 ml
(pH=2.0)
33,COO(A1+3)
(pH adj. to 5.5)
25,000(A1+3)
5300
5300
NO TEST
NO TEST
2500
7000
NO TEST
5000
4000
30,000
Colorb
6500
3500
'
750
550
60
780
850
300
Sulfur Dyeing
Wastewater
Dosage3
-
10.0 ml
(PH=0.5)
30,000(A1+3)
(pH adj. to 5.5)
30,000(A1+3)
10,000
25,000
10,000
40
10,000
4
5000
10,000
5000
10,000
5000
5000
3500
Colorb
30,100
100
60
360
500
620
570
, 250
80
30,100
2000
1400
Combined Dyeing
Wastewater
Dosage3
-
6.0
(pH=1.0)
600 (A1+3)
(pH adj. to 5.5)
40(A1+3)
5000
4500
10,000
15
4000
4
2600
5000
3300
4000
4000
380
2000
Colorb
16,000
550
380
400
250
390
425
150
80
600
16,000
150
Biol. Treatment
Plant Effluent
Dosage3
-
40
(pH=1.0)
20(A1+3)
(pH adj. to 5.5)
SO TEST
1500
1500
15
1500
4
NO TEST
NO TEST
5000
250
1000
Colorb
1400
80
30
90
60
100
100
25
280
a Dosage as mg/1 and as destabilizing agent
b Color as APHA Pt. Co. Units
form denoted unless otherwise indicated.
-------
Table 16. AVERAGE RESULTS OF SUCCESSFUL JAR TESTS ON
EXISTING WASTEWATER TREATMENT PLANT EFFLUENT3
Parameter
Coagulant
Dosage0 (mg/1)
pH (Units)
Color (APHA Pt.
Co. Units)
BOD5/ (mg/1)
COD (mg/1)
Suspended
Solids (mg/1)
Waste-
Water
-
6.8
1216
57
165
123
A12S04-
18H?0
20(Al+3)
5.5
30
14
39
3
MgC03'3H20
& Ca(OH)?
15 & 1500
12.6
60
11
33
33
Ca(OH)9
2000
12.5
65
15
37
30
Ca(OH)2 & Anionic
Polyelectrolyte
1500 & 4
12.8
30
13
19
19
a Values within Table respresent the average of five-days of testing de-
signed to evaluate the various coagulants' effect on the wastestream's
normal daily deviation resulting from production variations.
Coagulant dosage is in form denoted unless otherwise indicated.
thirty liters of wastewater with the previously established optimum co-
agulant dosages. Upon completion of the coagulation, flocculation, and
sedimentation cycles, the supernatant was carefully decanted. The re-
maining sludge was poured into a two-liter graduate and allowed to settle
for sixty minutes. At this time, the sludge volume was noted, the super-
natant again decanted, and the remaining sludge analyzed for density and
moisture content. A minimum of three such tests were performed for each
coagulant. The average of the test results are tabulated in Table 17.
Alum Sludge Investigations
In reviewing the relative sludge characteristics, the primary disadvan-
tages associated with alum coagulation were the excessive sludge volume
and high moisture content. In an effort to produce a more favorable alum
sludge, a series of jar tests was performed to investigate the benefits
of several selected polyelectrolytes and coagulant aids. The results of
these investigations which are tabulated in Table 18 show an insignificant
improvement in sludge volume derived from the coagulant aids investigated.
It is recognized, however, that the investigation of polyelectrolytes was
somewhat limited. Although polyelectrolytes representative of the three
basic types (i.e., cationic, nonionic, and anionic)were investigated, it
must be acknowledged that there are endless varieties of polyelectrolytes
available from the various manufacturers which might prove much more
beneficial in improving the sludge characteristics.
47
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Table 17. SLUDGE CHARACTERIZATION
Coagulant
A12(S04)3-
18H20
MgC03-3H20
& Ca(OH)2
Ca(OH)2
Ca(OH)2
& DOW A-23
Sludge Volume
after 60 min.
(% of total)
5.4
2.1
1.7
1.6
—-_______—
Sludge
Density
(gm/cnH)
1.001
1.003
1.027
1.012
Moisture
(%)
99.5
97.3
97.0
95.4
Estimated
Full Scale
Sludge Volume
(m3/hr)
1.85
0.72
0.56
0.56
1
Estimated
Full Scale
Dry Sludge
(kg/hr)
9.26
19.50
17.25
26.07
Table 18. SUMMARY OF ALUM SLUDGE REDUCTION INVESTIGATIONS3
Coagulant Aid
Activated Silica
Bentonite
Dow A-23
(Anionic Poly-
electrolyte)
Dow N-20
(Nonionic Poly-
electrolyte)
Dow C-41
(Cationic Poly-
electrolyte)
Fly Ash
(From C.T.M.
Inc. 's Boiler)
Dosage
(mg/1)
_
25
25
4
5
40
930°
.Sludge
Volume
(%Tot^
5.4
4.0
5.0
5.0
b
5.0
4.0
Supernatent
Susp. Solids
(mg/1)
16
2
8
28
80
28
40
COD
(mg/1)
62
80
62
23
47
54
18
Color
(APHA Ft. Co. Units)
30
30
20
30
20
20
80
a Alum Dosage: 20mg/l as Al+3
b Resulted in partial sludge flotation.
c Dosage is equivalent toquantity of fly ash available from mills
boiler, per volume of wastewatef.
48
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Further work in this area was beyond the scope of this phase of the pro-
ject; however, additional investigation is recommended prior to pilot
scale testing.
Coagulant Regeneration
The feasibility of coagulant regeneration and reuse was investigated in
a series of bench scale tests. The procedures and the resulting conclu-
sions are summarized below:
Aluminum Sulfate (Alum) - Recovery of alum from waste sludge is simply a
reversal of the precipitation process. After preliminary thickening
and/or dewatering, the sludge, consisting mostly of aluminum hydrox-
ide, is treated with sulfuric acid. The alum is regenerated accord-
ing to the following reaction:
2A1(OH)3 + 3H2S04 —A12(S04)3 + 6H20 (03)
Stoichiometrically, by calculating the weights of each of the two
compounds, it may be determined that approximately 1.9 Ibs. of sul-
furic acid is required to regenerate each pound of aluminum hydrox-
ide. Previous studies conducted on alum recovery^, have reported
that adjustment of the pH to a range between 1.5 - 2.5 is necessary
to insure complete conversion of the aluminum hydroxide to aluminum
sulfate.
The alum recovery investigations were performed on the sludge re-
covered from 30 liter batch coagulation tests. This sludge was
collected in a two-liter graduate and acidified according to 1.9
parts concentrated sulfuric acid per each part A1(OH)3 (calculated
from the quantity of Al+3 present in the sludge) or to a minimum pH
level of 1.5. After approximately 15 minutes of agitation, the mix-
ture was allowed to settle and the resulting supernatant decanted
and analyzed for aluminum. This supernatant was then utilized for
subsequent coagulation tests. The results of the alum regeneration
investigations lead to the following discussion and conclusions:
1. Acidification of the sludges produced by alum coagulation did
release alum in sufficient quantities for reuse. The results
from one of the more successful series of alum coagulation-
regeneration investigations are provided in Table 19. These
results demonstrate the progressive loss of alum with each re-
generation. A mass balance of the aluminum ion (Al+3) present
at the various stages of the regeneration process indicated
that varying amounts of the aluminum were irreversibly tied up
in the sludge. A range from 15 to 60 percent of the initial
aluminum addition was lost with each coagulation. It is felt
that the percentage of aluminum loss to the sludge is largely
a function of raw wastewater quality (i.e., pH, hardness, color,
etc.). The degree of alum recovery for reuse in these investi-
49
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Table 19. TYPICAL RESULTS OF ALUM REGENERATION —
COAGULATION INVESTIGATIONS
Coagulant
Dosage
(mg/1 as Al+3)
20
20a
(1st Regen.)
20a
(2nd Regen.)
Total
Coagulant
Addition
(mg/as Al+3)
600
198
102
Total Coagulant
in Regenerated
Sludge Supernatant
(rag as AF"3)
297
136
87
% Alum
Recovery'3
49
22
14
Initial Wastewater
COD
(mg/1)
143
132
120
Color (APHA
Pt. Co. Units)
1650
2000
1600
Coagulant Su
PH
(units)
5.5
5.5
5.5
COD
(mg/1)
32
39
58
•r
ernatant
Color (APHA
Pt. Co. Units)
30
40
20
Ln
O
a The volume of wastewater used for each successive coagulation test was reduced to permit constant
Al+3 dosage.
b Based on quantity of Al+3) added initially (600 mg).
-------
gations was also partially influenced by the failure to com-
pletely dewater the final sludges after regeneration. This
loss was overcome by reducing the volume of each successive
coagulation test in order to maintain a constant coagulant
dosage.
2. Although the regenerated alum demonstrated the ability to re-
move color at efficiencies comparable to that of the fresh alum,
the settling properties of the sludge produced with each suc-
cessive coagulation test progressively deteriorated.
3. The final sludge remaining after recovery of the alum was visu-
ally observed to be much more gelatinous than the original alum
sludge. This might present problems in final dewatering steps.
Other potential problem areas include the buildup of impurities
in the recovered alum solution and operational problems associ-
ated with acidification.
4. In reviewing the relative economics of the chemical costs alone
as tabulated in Table 20, it appears that alum regeneration
offers a very insignificant economic advantage. It is recog-
nized that there are numerous other economic factors that
should be considered in evaluating the potential benefits of
alum regeneration. The results of the relative chemical costs,
however, indicate that regeneration of alum for this applica-
tion is at best, marginal. Further pilot scale testing is
necessary to more closely define the alum recovery, sludge de-
watering requirements, and ultimate disposal considerations.
Table 20. RELATIVE ECONOMICS OF ALUM REGENERATION
Cost/m3 Cost/1000 Gal.
Estimated Cost of Aluma without Regeneration $ 1.50 $ 5.67
Estimated Chemical Cost with Regeneration
Alum3 Cost @ 50% make-up 0.75 2.83
Sulfuric Acidb Required for Regeneration 0.42 1.59
Estimated Chemical Savings with Regeneration
a Liquid Alum (17% Al^Oa) @ $68/metric ton
b Sulfuric Acid (66°Be, 93% H2S04> @ $36/metric ton
51
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Magnesium Carbonate - Recovery of magnesium carbonate from waste sludge
is accomplished by reacting the magnesium hydroxide component of the
sludge with carbon dioxide. This solubilizes the magnesium selec-
tively as magnesium bicarbonate which may then be reclaimed from rh •
filtrate in the dewatering process and returned for reuse in the co-
agulation process^, 27,28. The basic regeneration chemical reaction
is:
Mg(OH)2 + 2C02 ~*-Mg(HC03)2 (04)
To investigate the potential application of magnesium carbonate re-
generation, a series of recovery tests was performed. These inves-
tigations utilized the sludge recovered from a thirty-liter batch,
lime-magnesium carbonate coagulation test. The sludge was collected
in a graduate cylinder and the volume brought to two-liters with
distilled water. During agitation, laboratory grade carbon dioxide
was introduced at a low rate until a pH level of 7.5 was reached.
At this point, the remaining sludge was allowed to settle for ap-
proximately three hours and the supernatant withdrawn for analysis
and reuse.
In this investigation, the magnesium source utilized was in the form
of magnesium carbonate trihydrate (HgCO^- 3H20). This is a relatively
new coagulant and is not available commercially. The basic carbon-
ate - 4MgCC>3Mg(OH)2-5H20 - which is commercially available has a
low solubility and is unsatisfactory for practical use as a coagu-
lant^S. in a full scale system, recovery of the naturally available
magnesium from the water would be required for use as a coagulant.
The results of the series of regeneration investigations indicated
that approximately 50-70 percent of the magnesium content could be
recovered through carbonation of the sludge. The remaining portion
of the magnesium was either lost in the supernatant or in the waste
sludge. The supernatant quality obtained through coagulation with
regenerated magnesium bicarbonate was found to compare very favorably
with that obtained utilizing the magnesium concentrations found in
the wastewaters (1.5 to 3.0 mg/1 as Mg4"*"). It was concluded that
magnesium bicarbonate regenerated from the sludges, could produce
sufficient quantities to sustain the optimum coagulation require-
ments. Further evaluation of the potential full scale application
led to consideration of the magnesium available as an impurity in
commercial hydrated lime. High purity reagent grade lime was
utilized in the bench scale investigation. The commercially avail-
able hydrated lime utilized by Canton Textile Mills, Inc. for fresh
water treatment has a typical magnesium oxide content of 0.73 per-
cent (by vaight). Although this content may seem insignificant, at
the lime dosages required for this application (1500 mg/1 as
Ca(OH)2), the magnesium addition from the lime (4.38 mg/1 as Mg++per
gram of lime) is adequate to meet the magnesium requirements for
optimum coagulation. Therefore, it was concluded that magnesium
bicarbonate regeneration would not be required for this application.
52
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This magnesium regeneration process, however, might prove beneficial
at other location^,
Lime - Recovery of waste lime sludges by recalcination has been practiced
successfully for many years by the pulp and paper industry. Recent-
ly, the lime recalcination process has also found application in the
recovery of wastewater treatment lime sludges28. The process of
recalcination is accomplished by heating the calcium containing
sludges to temperatures ranging between 800 and 1100°C
(1500-2000°F)30. The basic reaction is as follows:
CaC03 - „ Ca0 + C02 (05)
To evaluate the potential use of lime recovery at Canton Textile
mills, Inc., a series of batch recalcination tests was performed.
The test sludge was recovered from thirty-liter batch coagulation
tests and dewatered by oven drying at 103°C (217°F) for a period of
24 hours. The dried sludge was then ground to powder and fired at
930°C (1700°F) for a period of five minutes. Stoichiometrically, if
total recovery of the calcium were possible, the addition of one gram
of Ca(OH>2 should result in the recovery of 0.76 grams of CaO. Total
recovery is not practical and a portion of the final material after
firing would be expected to be inert material removed from the waste-
water. Based only on a weight recovery comparison, the results of
the batch recovery tests indicated that only 38 percent of the theo-
retically possible recovery could be accomplished. Considering the
fact that a portion of the recovered material was inert matter and
not CaO, it was concluded that the percentage recovery was actually
somewhat less than 38 percent. It was also noted that the super-
natant water hardness was increased from an original 50 mg/1 as
CaCC-3 to a final of 1400 mg/1 as CaC03. This indicated that much of
the original calcium addition in the lime was lost with the super-
natant rather than precipitated.
In considering the economic aspects of lime recalcination, it has
been reported at the South Lake Tahoe wastewater plant that the cost
of the lime recalcination is slightly greater than the cost of new
lime29. At this installation which has a design flow of
28,4000 m3 per day, approximately seventy percent of the required
CaO is recovered by recalcination of the lime sludges. In view of
these economic aspects, the scale of operation, and the preliminary
CaO recovery indications, consideration for recalcination was aban-
doned.
Sludge Filterability
To investigate the filterability of the various sludges, a series of
Buchner funnel tests was performed utilizing the test set-up illustrated
in Figure 14. These tests were utilized to provide an indication of fil-
53
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tration times and the effect of various vacuum pressures. Basically, this
test consisted of applying a selected vacuum (25, 38, or 51 centimeters of
mercury) to the funnel apparatus covered with two No. 4 Whatman filter
papers (prewetted to insure a vacuum seal) and containing exactly 200 mil-
liliters of the test sludge. After applying a vacuum for a predetermined
period of time, the filtrate was analyzed for volume, color, pH, and COD.
The filter cake was also analyzed for percent solids although it was
recognized that the comparative moistures of the cakes are unobtainable
due to loss of vacuum before normal drying time^O.
A more detailed description of the test procedure is provided in the Ap-
pendix as Table A6 and the results of the tests tabulated in Tables A7
through A10 also found in the Appendix.
The results of the Buchner filter tests demonstrated the ability of the
lime-Dow A23 coagulation process to produce a sludge lending itself to
dewatering by vacuum filtration. This was evident by the ability of
this sludge to form a defined filter cake in filtration times of two
minutes or less. The other coagulants showed poor cake formation at
vacuum periods less than six to eight minutes. This was important be-
cause most conventional vacuum filtration equipment is manufactured with
drum speeds of 1-10 minutes per revolution with a typical 25-35 percent
submergence. Therefore, the filter cake formation period is generally
less than 2.5 minutes-* 1. In comparing the relative filter cake solids
concentrations, the lime-Dow A23 coagulant again demonstrated the ability
to produce a filter cake having solids concentrations as high as 11 to
15% at filtration periods of two minutes and without vacuum loss. Alumi-
num sulfate produced a very poor cake at filtration times less than six
minutes with vacuum loss soon after cake formation.
Based upon these conclusions, a series of filter leaf tests was performed
with the lime-Dow A23 sludge. The purpose of these tests was to develop
design data. The test leaf as illustrated in Figure 15 has the ability to
simulate a vacuum filter in operation (i.e., submergence, drying, and re-
moval of the filter cake). Another advantage of the filter leaf is that
it is possible to use the same filter media as might be utilized on the
full scale vacuum filter. Thus, in short, the results are more representa-
tive of the operation of a plant size vacuum filter-^.
The filter leaf were performed in accordance with the following proce-
dure:
1. The filter leaf assembly was submerged in the prepared sludge and
the desired vacuum applied for a time period corresponding to the
desired form time (1 minute).
2. The leaf was then removed from the sludge and brought to the verti-
cal position for a time corresponding to the desired drying time
(3 minutes).
54
-------
9cm. BUCHNER
O-VACUUM GAUGE
_V_
at TO VACUUM PUMP
-NEEDLE VALVE
FILTER FLASK
•Figure 14. Buchner funnel test apparatus.
CLAMP-
VACUUM
GAUGE
2 LITER
BEAKER
MAGNETIC
STIRRER
FILTER
LEAF
-CLOTH
MAGNET
TO VACUUM PUMP
CLAMP
FILTER FLASK
F.igure 15. Filter leaf apparatus.
55
-------
3. After drying, the vacuum was released and the filter cake carefully
removed for analysis.
Based on the results of these filter leaf tests as tabulated in Table 21,
it was concluded that sludge resulting from lime-Dow A23 coagulation
could successfully be dewatered with vacuum filtration equipment having
a total cycle time of four minutes. The investigations also indicated
that Eimco Filter Media, Style No. PO-801RF or NY-333 is best suited for
this application.
Table 21. RESULTS OF FILTER LEAF TEST WITH SLUDGE
GENERATED FROM LIME-DOW A23 COAGULATION
Basis of Test: Sludge from Lime and Dow A-23 tests
Vacuum, cm Hg
Cycle time, min.
Form time, min.
Dry time, min.
38.1
4.0
1.0
3.0
Medium - all supplied by EIMCO
Medium
Style No.
PO-801RF
PO-802HF
POPR-854F
POPR-925F
NY-384F
NY-333
CO- 3
Initial
% Solids
5.08
7.01
7.36
6.03
5.07
4.24
6.34
Cake
% Solids
25.4
30.1
30.9
31.7
30.1
26.6
25.2
Filter Yield
Dry gm/hr/cm2
1.89
1.06
0.75
0.74
1.11
1.70
1.47
Filtrate
pH,
Units
11.5
11.3
11.3
11.5
11.4
11.5
11.4
Color,
(a )
80
10
30
210
180
120
110
COD,.
mg/1
127
93
108
100
111
203
258
a APHA Pt. Co. Units
56
-------
FULL SCALE COST PROJECTIONS
Results of the bench scale coagulation investigations indicated that co-
agulation of the wastewaters with lime and Dow A-23 polyelectrolyte was
the most feasible approach due to the sludge dewatering properties.
Based on this treatment concept, preliminary flow diagrams and cost pro-
jections were prepared for incorporating the,coagulation process into
the present wastewater treatment system. The preliminary flow schematic
as provided in Figure 16, would require the addition of lime, polyelec-
trolyte, and sulfuric acid feed and storage systems; a vacuum filtration
system; modifications to the existing clarifier and digester; and the
related instrumentation and piping changes. Preliminary estimates for
this chemical coagulation and sludge dewatering system indicate a capital
cost of $330,000 with a total operating coat (including the operation of
the existing system) of approximately 23.0$ per cubic meter of raw waste-
water treated. A breakdown of both capital and operating cost is pro-
vided in Tables 22 and 23.
In evaluating the chemical costs of the lime coagulation system, it was
concluded that the cost of lime and the subsequent sulfuric acid cost
required for final neutralization were excessive. Chemical costs alone
for the lime coagulation system would be approximately 11.9$ per cubic
meter or $35,000 per year.
In considering the use of alum coagulation, the primary disadvantages en-
countered were the excessive sludge volume and related problems of de-
watering. If a polyelectrolyte or suitable sludge conditioner could be
utilized to improve the alum sludge dewatering properties, a substantial
savings in chemical costs might be realized with alum coagulation. This
would be largely dependent on the costs associated with the sludge condi-
tioning agent. Comparatively, the estimated chemical cost of alum (at a
dosage of 20 mg/l.,as Al+3) is approximately 1.52) at an estimated cost
of 5.8$ per cubic meter. An additional chemical cost of the alum sys-
tem, however, would be that of the acid (typically sulfuric) required to
adjust the wastewater pH to the optimum coagulation range (5.0-5.5) and
the subsequent readjustment of the pH level to a range of 6.0 to 9.0 for
final discharge or reuse. The chemical cost associated with the alum
system would most likely still be significantly less than that of the
lime system which would require final pH adjustment from 12.5 to 9.0 pH
units with sulfuric acid at a cost of approximately 5.6
-------
oo
J£G£NJL
)PH CONTROLLER
)FLOW RECORDER
) LEVEL TRANSMITTER
) LEVEL ACTUATED SWITCH
MAKE-UP WATER-
WASTEWATER
•DOMESTIC WASTEWATER
-HOSPITAL WASTEWATER
PRE-AERAT10N TANK
POLYMER
DAY TANK
SLUDGE RETURN (624LPM)
DRY POLYMER
STORAGE (BAGS)
SLUDGE RET. PUMP
IR LFT PUMP
AUGER FEED
MAKE-UP WATER
LIME SLURRY
DAY TANK
ACTIVATED
SLUDGE
AERATION
TANK
718LPM5DAYSWK.
I89LPM 2 DAYS WK.
BULK ACID
STORAGE
BAR SCREEN
'FftRSHALL FLUME
GRIT CHAMBER
SLIDE GATES
IOLOGICAL
CLARIFIER
REACTOR
LARIFER
SUPERNATANT
LIFT STATION
CHLORINE
EMERGENCY DRAIN
VACUUM
"W!
EMERGENCY BYBASS
EQUALIZATION
BASIN
SLUDGE CAKE
TO LANDFILL
DISCHARGE
TOETOWAH
RIVER
SPERNATANT
Figure 16. Flow diagram of treatment system with proposed chemical coagulation addition.
-------
Table 22. ESTIMATED CAPITAL COSTS OF.CHEMICAL COAGULATION SYSTEM
ADDITION TO CANTON TEXTILE MILLS, INC.'S EXISTING
BIOLOGICAL TREATMENT FACILITY3
Modifications to Existing Clarifier & Digester $ 32,500
(Conversion to Reactor-Clarifier and Thickener)
Vacuum Filter Station 85,000
(6* Dia. x 6' Drum with accessory drive, pumps,
motors, sludge conveyor, installation, etc.)
Lime Storage and Feed System 42,850
(45 ton bulk lime storage, auger feed, day tank,
mixer, and slurry metering pump)
Polymer Feed System 4,500
(2-day tanks, mixer, and metering pump)
Bulk Acid (H2SO^) Storage and Feed system 6,000
Instrumentation 15,000
(pH and Flow)
Sludge Pumps 7,500
(Clarifier & Thickener)
Site Preparation 15,000
Housing for Vacuum Filter, Polymer, and Lime Systems 37,500
Piping and Electrical 84,150
TOTAL $ 330,000
Engineering News Record Cost Index (1913 Baseline) = 2275.'
59
-------
Table 23. PROJECTED OPERATING AND MAINTENANCE
COSTS FOR EXISTING BIOLOGICAL AND
NEW CHEMICAL COAGULATION SYSTEM3
Chemical Costs for Coagulation System
Hydrated Lime @ 38.6 $/metric ton 5.8
Dow A-23 Polyelectrolyte @ 1.10 per kilogram 0.5
Sulfuric Acid (66°Be, 93% H2S04) @ 36 $/metric ton 5.5
Power Costs (@ 2.5$/Kw-Hr)
Biological System
Coagulation System
Total Operating Personnel and Maintenance Costs
TOTAL
a Does not include cost for landfill disposal of sludge or value of
treated effluent for reuse.
SUMMARY OF CHEMICAL DESTABILIZATION CONCLUSIONS AND RECOMMENDATIONS
The results of the chemical destabilization investigations led to the fol-
lowing conclusions and recommendations:
1. Chemical destabilization of the effluent from the existing biologi-
cal treatment system was found to be the most advantageous point of
coagulant application. This conclusion was based upon the demon-
strated ability of the various destabilizing agents in accomplishing
removal of color and the production of a high quality supernatant at
practical levels of chemical addition.
2. Of the eleven destabilizing agent combinations investigated, it was
concluded that alum or lime with an anionic polyelectrolyte would be
the two coagulants most feasible for application.
3. Coagulation of the wastewaters with lime (at 1500 mg/1 as Ca(OH>2)
and an anionic polyelectrolyte (Dow A-23 at 4 mg/1) demonstrated the
ability to produce a sludge with superior dewatering characteristics
60
-------
in comparison to the characteristics of the sludge resulting from
alum coagulation. It was also demonstrated that the sludge result-
ing from lime coagulation was amenable to dewatering with conven-
tional vacuum filtration techniques. Results of filter leaf tests
indicated that vacuum filtration might be expected to produce a
sludge cake with approximately 25 percent solids and have a filter
yield of approximately 1.7 gm/hr/cm or 3.5 lbs/hr/ft2 (dry basis).
4. Coagulation of the wastewater with alum (at 20 mg/1 as Al+3) resulted
in the formation of a gelatinous sludge with poor dewatering charac-
teristics. Comparatively, alum coagulation resulted in a sludge
volume of 5.4 percent (99.5% moisture) as opposed to a sludge volume
of 1.6 percent (95.4% moisture) resulting from coagulation with lime
and polyelectrolyte. The results of Buchner filtration tests indi-
cated that the alum sludge was not amenable to conventional vacuum
filtration techniques. Several representative polyelectrolyte
(anionic, nonionic, and cationic) as well as several common coagu-
lant aids (bentonite, activated silica, and fly ash) were investi-
gated for use in conjunction with alum coagulation for improving the
sludge dewatering characteristics. These investigations proved
relatively unsuccessful.
5. The potential of coagulant (lime and alum) regeneration and recycle
was investigated. In each case, it was concluded that the percentage
of coagulant recovery was insufficient to economically justify re-
covery.
6. In examining the economic aspects of the application of a full scale
lime-anionic polyelectrolyte coagulation system, it was projected
that the capital costs for incorporating the chemical coagulation
and vacuum filtration processes into the existing biological system
would require an expenditure of approximately $330,000. The total
operating cost including chemicals, power, maintenance, and operating
personnel was estimated to be approximately 22.8
-------
It is recommended that a series of bench scale tests be conducted to
examine additional polyelectrolytes and suitable sludge conditioners
that could be utilized to improve the dewatering characteristics of
the alum sludge. Other dewatering techniques such as the centrifuge
or various gravity-type filters might also be investigated during
this phase of the investigation. If these tests prove successful,
it is further recommended that the investigation be extended to a
pilot scale study. The function of the pilot scale phase would then
be to provide indicative chemical cost and operational data for a
continuous flow svstem.
62
-------
SECTION VI
NEUTRALIZATION OF CAUSTIC WASTEWATERS UTILIZING
COAL-FIRED BOILER FLUE GASES
A common problem presently facing many industries utilizing fossil-fired
boilers is that of meeting various compliance regulations related to the
control of noxious gases and particulate emissions. Removal of these
fractions of the flue gas through wet scrubbing techniques often reduces
the air pollution problem only to create a water pollution problem. The
intent of this phase of the research project was to investigate an inte-
grated solution to this problem whereby the acidic fractions of the flue
gas might be utilized to offset the causticity of the dyeing process
wastewaters. Neutralization would, as a result, create a wastewater
more readily amenable to biological degradation.
»
The pH of a wastewater is a key factor in the growth of microorganisms
which are vital to the biological wastewater treatment process. General-
ly, the optimum pH level for biological growth lies between 6.5 and
7.5-". Most organisms cannot tolerate pH levels above 9.5 or below 4.0.
There are, however, some instances where wastewaters having pH levels
as high as 12.0 have been successfully treated biologically due to the
ability of the microorganisms to produce weak neutralizing acids. At
Canton Textile Mills, Inc., the influent to the biological treatment
system generally ranges from 10.0 to 12.0 pH units during dyehouse pro-
duction hours. The wastestreams from the hospital, a residential section,
and the domestic wastes from the mill provide much of the biological
life needed to properly seed the dyeing process wastewaters for subse-
quent treatment. Although the hospital and domestic wastestreams are
normally within the optimum pH ranges for the biological growth, the
dyehouse discharge has pH levels in excess of 10. Thus, when the three
streams are combined, the microorganisms receive a pH shock which either
kills them or greatly retards their ability to function normally. By
adjusting the pH level of the dyehouse wastewater into the proper range
thereby reducing the pH shock, it was anticipated that the entire sys-
tem's efficiency could be improved.
RESEARCH OBJECTIVES
The primary objective of the research performed in conjunction with this
phase of the project was to demonstrate the practicability of utilizing
coal-fired boiler flue gases to neutralize the causticity of Canton Tex-
tile Mills, Inc.'s dyeing process wastewaters. The secondary objectives
included the following:
1. Evaluate the effect of flue gas scrubbing on the physical and chem-
ical properties of the wastewaters.
2. Determine the effect of scrubber neutralization on the subsequent
biological treatment system.
63
-------
3. Appraise the efficiency of a conventional wet scrubber utilizing
dyehouse caustic wastewaters as the scrubbing media.
4. Investigate the feasibility of utilizing the scrubber installation
to permit the burning of low grade, high sulfur coal.
During the early stages of the project, the fourth objective concerning
the use of low grade, high sulfur coal was dropped due to the location of
the coal fields supplying high sulfur coal, the time factor involved in
rail transport, the volume required to be purchased, and the cost factor
involved in obtaining this coal.
NEUTRALIZATION PRINCIPLES
The neutralization technique investigated is based primarily upon the
same principles employed by the conventional "dual alkali" or "double
alkali" processes of desulfurization. These processes utilize soluble
sodium based alkali in the forms of sodium hydroxide (NaOH), sodum sul-
fite (Na2S03), sodium carbonate (Na2C03). or sodium bicarbonate (NaHC03)
to accomplish sulfur dioxide absorption-* . The main overall absorp-
tion reactions are described by the following equations:
2NaOH + S(>2 *-Na2S(>3 + H20 (06)
S02+ H20^ "* 2NaHS03 (07)
2S02 + H20 «- 2NaHS03 + C02 (08)
Na2HC03 + S02 —*-NaHS03 + C02 (09)
Some carbon dioxide removal is also accomplished according to the follow-
ing reactions:
2 NaOH + C02 —Na2C03 + H20 (10)
Na2C03 + C02 + H20 *-2NaHC03 (11)
The absorption of carbon dioxide results in the production of sodium
species capable of further reaction with the sulfur dioxide fractions of
the flue gas. When these subsequent reactions occur in accordance with
equations 08 and 09 previously provided, the carbon dioxide is released.
Thus, the extent of carbon dioxide absorption depends upon the efficiency
of the desulfurization process.
The desulfurization process results in the production of what is commonly
referred to as "inactive sodium" or sodium bisulfite and the oxidation ,r
pro'duct sodium sulfate. Both of these compounds cannot be further reac-
ted with the sulfur dioxide and must be either regenerated or removed
from the system. This is typically accomplished by reacting the scrub-
bing effluent with either^lime or limestone according to the following
reactions^. ' -
64
-------
Lime
Ca(OH)2 + 2NaHS03 —Na2S03 + CaS03- ^H20 4 + 3/2 H20 (12)
Ca(OH)2 + Na2S03 + %H20 *• 2NaOH + CaS02'%H2o4 (13)
Ca(OH)2 + Na2S04 + H2 0 *• CaS04• 2H20t + 2NaOH (14)
Limestone
CaC03 + 2NaHS03 + 5$H20 Na2S03 + CaS03'%H20^ + C02 + H20 (15)
Upon removal of the insoluble species resulting from the regeneration
process, the regenerated active sodium is returned to the scrubbing sys-
tem. A much more detailed examination of double alkali process is pro-
vided in the Iiterature34,35,36.
The wastewaters resulting from Canton Textile Mills, Inc.'s dyeing pro-
cess are particularly suited for use as a scrubbing solution in that they
contain "active sodium" species present in the form of sodium hydroxide
and sodium sulfite. Therefore, it would appear that utilizing these
wastewaters as a scrubbing solution could accomplish the dual purpose of
neutralization and flue gas desulfurization.
EXISTING BOILER SYSTEM
The boiler utilized for the neutralization investigations was the coal-
fired standby unit which is normally used during periods of interrupted
natural gas service. This boiler is a Combustion Engineering, Inc. C-E
Vertical Unit which was constructed in 1959. It is a 27 metric ton per
hour (60,000 Ib/hr) boiler with a maximum pressure of 14 kilograms per
square centimeter (200 psi). The boiler furnace burns 3.18cm by 0.95cm
(1-1/4" x 3/8") coal fed by a spreader stoker at an approximate rate of
44 metric tons/day. A typical coal analysis is provided in the Appendix
as Table All. The boiler is equipped with a Whirlex dust collector
which captures approximately 34 to 45 kilograms/hour (75-100 Ibs/hr) of
fly ash. A typical profile of the existing stack gases discharged to the
atmosphere is provided in Table 24.
The State of Georgia's Department of Natural Resources has established
emission standards applicable to Canton Textile Mills, Inc. for both
particulate and sulfur dioxide emissions. These standards indicate that
the maximum particulate emissions for an existing source (with a rated
heat input of 3.4 x 105 Kg-cal/min or 80 x 106 BTU/hr) shall not equal
or exceed 16.7 Kg/hr (36.8 Ibs/hr). The standards for new sources with
a similar capacity is, however, approximately 6.4 Kg/hr (14 Ibs/hr)3?.
With the definite possibility that more stringent secondary standards may
be adopted in the future, it was felt that it would be desirable for the
scrubber system utilized for neutralization to have the additional capa-
bilities of providing for a 62% reduction of particulate emissions,
thereby allowing Canton Textile Mills, Inc. to be in compliance with the
new source regulations. The maximum sulfur dioxide emissions applicable
for Canton Textile Mills, Inc. required that sulfur dioxide emission shall
not equal or exceed 56.70 Kg/hr (125 Ibs/hr). With an existing emis-
sion of 20.86 Kg/hr, it is evident that as long as the 0.8% sulfur coal
65
-------
Table 24. TYPICAL PROFILE OF EXISTING STACK GAS
Temperature, °C 274
Volume (at actual stack temperature), m3/min 1164
Volume (at standard temperature and pressure) m3/min 610
Molecular Weight of Flue Gas, grams/mole 30.02
Particulates, gm/m3 0.42
Sulfur Dioxide, gm/m3 0.57
Carbon Dioxide, gm/m3 162
Carbon Monoxide, gm/m3 3
Oxygen, gm/m3 157
Nitrogen Dioxide, mg/m3 3.38
Nitrogen Monoxide, mg/m3 10.16
Fuel Rate (at normal operating conditions), Kg-cal/min x 10° 0.22
is utilized, there should be no problem in meeting the sulfur dioxide reg-
ulations even without any further reduction within the proposed scrubber
system.
NEUTRALIZATION PILOT PLANT INVESTIGATIONS
The practicabaility of the neutralization concept was first investigated
in a pilot-scale installation. The objectives of this phase of the in-
vestigation were as follows:
1. Establish preliminary projections of the liquid-gas ratio required
for optimum neutralization of the caustic dyeing wastewaters.
2. Investigate the potential effects of flue gas scrubbing on the
characteristics of the wastewater.
3. Obtain preliminary information related to the efficiency of flue gas
scrubbing with the dyeing process wastewaters.
66
-------
Description of Pilot Plant
The pilot plant investigation was performed with a wet scrubber test model
available through Zurn Air Systems. This unit as shown in Figure 17, is a
medium-energy, impingement type wet scrubber capable of handling 56.6
standard cubic meters per minute (2000 scfm) with a pressure drop range of
5 to 24cm (water column). In this unit, the flue gas is impacted with the
scrubbing media as the high velocity gases pass through the slat between
the inlet bonnets and collecting tubes. The shearing actions of the gases
atomize the liquid into a dense spray with cyclone spinning and mixing
continuing as the gas-liquid mixture progress up the collecting tube.
Final separation of the liquid and gas is accomplished by impingement upon
the flooded surface of a deflector. The gases then continue upward,
exiting through the discharge plenum, while the liquid is returned to the
hopper through a sealed leg. The final treated liquid is discharged from
the bottom of the hopper.
. .-* •",
~*.:'
Pressure drop across the unit is automatically maintained by controlling
the liquid level in the hopper with a differential pressure switch which
activates a solenoid valve on the liquid makeup line.
,> "• • • •* > • i z
Neutralization Investigations
In the initial series of pilot scrubber investigations, the gas flow was
held relatively constant while varying the liquid wastewater flow through
the system. The pilot scrubber system was allowed to operate continuously
over a period of three to six hours for each test condition (liquid waste-
water flow rate) to assure attainment of operational equilibrium. During
the test period, the pH of both influent and effluent were monitored to
provide an indication of the degree of neutralization obtained at each
liquid to gas ratio. The degree of neutralization (expressed as the pilot
scrubber effluent pH) achieved for various liquid to gas ratios is shown
graphically in Figure 18. Two separate plots over identical liquid to gas
ratios were developed to demonstrate the changing characteristics of the
wastewater. Based on an average dyeing process wastewater flow of approx-
imately 568 liters per minute (150 gpm) and a typical gas flow rate of
1165 actual cubic meters per minute (41,130 acfm), a full scale system was
projected to have a liquid to gas ratio of approximately 0.49 1/m3. By
interpolation, it was projected that a full scale system under similar •
operating conditions might be expected to achieve a reduction of the
wastewater pH from a typical pH range of 10.5 to 12.0 units to a final pH
level of approximately 8.0 units. It was, therefore, concluded that
scrubber neutralization was feasible. Because it was felt desirable to
have the capacity of achieving a slightly greater degree of neutralization
in the full scale system, the decision was made to utilize a slightly dif-
ferent scrubber configuration allowing more efficient gas scrubbing.
67
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GAS OUTLET
SCRUBBING MEDIUM
DEFLECTOR
•TUBE SHEET
SEALED LEG
COLLECTING TUBE
INLET BONNET
SCRUBBING MEDIUM
INLET
SLURRY DRAIN
Figure 17. Neutralization pilot plant
68
-------
I
CO
CO
8.5
8.0
7.5
7.0
4
8.0
7.0
6.0
5.0
vt. L/G RATIO
©
I
JBBER INFLUENT pH'll-12 UNITS
JGAS FLOW RATE'83.5 ACTUAL
M7MIN
PRESSURE DROP' 9cm(W.C.)
TEST PERIOD'JAN.4-9,1973
I I , I
O.I 0.2 0.3 0.4 0.5 0.6
L/G (LITERS PER MIN./ACTUAL M3 PER MIN.)
pH vs. L/G RATIO
SCRUBBER INFLUENT pH-IO.5-11.5
FLOW RATE'83.5 ACTUAL
INSURE DROP' 9cm(W.C.)
TEST PERIOD* JAN.I6 - FEB.J5.I973
OH 0.2 "03 0.4 0.5
L/G (LITERS PER MIN./ACTUAL M5 PER MIN.)
Figure 18. Pilot plant effluent pH vs. liquid/gas ratio.
69
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Pilot Scrubber Efficiency Investigations
To investigate the relative scrubbing efficiencies with respect to parti-
culate and sulfur dioxide removals, a series of tests was performed to
monitorjthese parameters across the pilot scrubber. For this investiga-
tion, a liquid to gas ratio of 0.45 l/rtr was selected to closely approxi-
mate that of the full scale application. The results of these tests in-
dicated that the pilot scrubber was capable of achieving; an average of 75%
reduction of particulate matter and an average sulfur dioxide removal of
approximately 40% at a pressure drop of 9cm (w.c.). It was therefore
concluded that a conventional wet scrubber on the full scale application
would be capable of achieving in excess of the desired particulate reduc-
tion of 62% necessary to meet the new source emission standards.
" •>,,,
Effect of Flue Gas Scrubbing on Wastewater Characteristics
The potential effects of flue gas••<•<
Most of the parameters examined showed an increase in concentration ,
across the pilot scrubber. A portion of this increase was attributed to
vaporization loss in the effluent gas stream. The gas entered the pilot
scrubber(at approximately 260°C and exited at approximately 60°C at a
saturated condition";,. Several parameters concentration increases were,
however,\attributed directly to the removal of these various constituents
from the!flue gas. Both the color and suspended solids concentration
increases were felt to be the result of fly ash removal from the flue gas.
The sulfate increase was related to the oxidation of theivarious sulfite
species present in the wastestream. The COD and BOD^ increases respec-
tively were believed to be related to the organic carbon present: in the
fly ash and the production of oxidizable chemical species such as sulfites
which would result in an increased oxygen consumption thereby introducing
error into the BODq test. ?l ~~\v^ /»;
•J *-. -03
; •; ''&
Two metals, nickel and zinc, showed particularly large increases in con-
centration across the sorubber. Previous studies related to metals
present in desulfurization sludges38 at several much larger installa-
tions have not reported; similar increases in nickel and zinc. It is
postulated that a major portion of the increased concentrations might be
attributed to the. corrosion of the metals in the pilot scrubber installa-
tion. Corrosion of galvanized steel as used for much of the piping and
duct work of the pilot unit results in the liberation of zinc. Also, it
is common for a galvanic reaction to occur between dissimilar metals such
as galvanized steel of the duct and piping and stainless steel of the
pilot scrubber. This reaction could possibly release nickel. In short,
it was concluded that nickel and zinc concentration increases of these
levels were not attributed to the flue gas scrubbing.
70
-------
Table 25. WASTEWATER CHARACTERIZATION
/ACROSS PILOT SCRUBBER3
Parameter
pH, Units
Temperature, °C
Total alkalinity, mg/1 as Ca2C03
Total Hardness, mg/1
Color, APHA Pt. Co. Units
COD, mg/1
BOD5, mg/1
Suspended Solids, mg/1
Sulfates, mg/1
Metals
Cadmium, yug/1
Chromium, ^ug/1
Copper , /ig/ 1
Iron, /ig/1
Lead, ,/ug/l
Manganese , yug/ 1
Nickel, yig/1
Zinc, /ig/1
Scrubber Feed
11.2
30.0
710
35
4375
922
259
212
78
35
520
100
550
110
40
330
296
Scrubber Discharge
7.7
42.5
210
25
5187
1046
302
396
400
35
660
230
11700
110
245
1260
2570
a Data developed at a liquid to gas ratio of 0.45 1/m3 (actual)
corresponding to the possible full scale application.
71
-------
In evaluating the cummulative effects of flue gas scrubbing on the waste-
water, there seemed to be several problems associated with increased con-
centration levels of certain parameters. It was felt, however, that
these increases were insignificant and would not cause problems in the
biological treatment system.
FULL SCALE SCRUBBER INSTALLATION
In the selection of the full scale scrubber equipment, consideration was
given to operational flexibility and potential scrubbing efficency as
well as the relative economics. The medium energy, impingement type
scrubber demonstrated the ability to achieve neutralization of the waste-
waters to a pH of approximately 8.0 at the liquid to gas ratio equivalent
to the full scale application. To allow for flexibility of operation and
provide additional neutralization capacity if required, a scrubber con-
figuration more readily lending itself to gas absorption was selected for
use in the full scale application. As a result, a venturi type, medium
energy (15 to 30cm, w.c.) scrubber manufactured by the FMC/Link-Belt Cor-
poration was purchased. This system as shown schematically in Figure 19,
provides a venturi flow constriction with an adjustable wedge to control
the pressure drop and particle impaction area. The scrubbing liquid is
injected into the gas stream through spray pipes just ahead of the venturi
constriction. As the liquid-gas mixture enters the venturi constriction,
the gas is accelerated to a high velocity atomizing the scrubbing liquid
and causing numerous collisions between the liquid droplets and particulate
matter within the gas stream. The flooded elbow connecting the venturi and
liquid separator sections provides for additional collision, impaction, and
agglomeration of the gas-liquid mixture.
The incorporation of spray pipe liquid injection was of particular impor-
tance for this application due to the presence of cotton fibers in the
wastewater scrubbing liquid. By utilizing 1.3cm (% inch) diameter spray
pipes rather than small orifices or spray nozzles typical of many other
installations, it would be possible to reduce if not eliminate the poten-
tial plugging problems. Another important consideration in this scrubber
design was the operational flexibility afforded by the adjustable wedge
shaped throat insert. By raising and lowering this wedge, it is pos-
sible to maintain a constant pressure drop and subsequently a consistent
operational performance even with greatly reduced boiler loads as is
often experienced on weekends and third shifts.
The full scale scrubber process design as shown in the flow diagram pro-
vided as Figure 20 with photographs provided in Figures 21 and 22,
allowed for a potential liquid to gas ratio of 0.97 1/m-* (actual) at
the peak gas flows. This high ratio was achieved by providing the capa-
bility of scrubbing liquid recirculation. The capability of adjusting
both the percentage of recirculation and the liquid to gas ratio was pro-
vided to allow additional operational flexibility and to assure achieve-
ment of the desired degree of neutralization. Another feature incorpora-
ted into the full scale application for flexibility of operation was the
72
-------
DIRTY GAS
SCRUBBING
LIQUID
1
PARTICAL IMPACTION ON
ATOMIZED LIQUID
DROPLETS
INSERT MOVES
UP AND DOWN
FUTHER COLLISION AND
AGGLOMERIZATION OF
LIQUID DROPLETS
*-TO LIQUID GAS
SEPARATOR
Figure 19. FMC/Link Belt variable throat scrubber.
73
-------
FLUE GAS
FROM BOILER
MILL
LEGEND
PH RECORDER
LEVEL CONTROLLER
FR)FLOW RECORDER
FLOW SWITCH
DAMPER OPERATED
SOLENOID VALVE
WASTEWATER
FROM DYEING
PROCESS
WASTEWOTER
MAKE-UP FROM
EQUALIZATION BASIN
(0-1100 LITERS/MINO
ExisovE
COLLECTION
MANHOLE
TREATMENT PLANT
Figure 20. Process flow diagram of scrubber installation
-------
:
Figure 21. Distant
view of canton Textile Hill.. Inc.,s scrubber InstaUatlo,
-------
Figure 22. Close-up of Canton Textile Mills, Inc.'s
scrubber installation
-------
capability of utilizing the wastewater from the equalization basin as a
scrubbing liquid during the periods of low dyehouse production and week-
ends.
Prior to the addition of the scrubber system, fresh water was utilized
for sluicing the fly ash collected in the existing Whirlex dust collector
of the coal fired boiler. Fly ash and watea were then sent straight to
the receiving stream without treatment. In conjunction with the upgrading
work performed on the biological treatment system, this wastewater was
diverted into the waste treatment system providing for the removal of fly
ash within the equalization basin. To conserve both fresh water and re-
duce the hydraulic loading on the biological system, provisions were made
within the scrubber system to utilize the scrubber discharge wastewaters
for this purpose.
The potential need for a demister was considered, but concluded -as un-
necessary. The FMC Corporation indicated that the open design, with no
internal sieve plates, baffles, or demisters present was important in
avoiding potential plugging and scaling problems. Also, it was felt that
sulfuric acid mist would not be a significant problem for this size ap-
plication.
Upon initial system startup, several operational problems were encoun-
tered. Below is a brief outline of the basic problems and steps taken to
correct them:
1. A severe plugging problem was encountered in several of the pumps
due to the presence of cotton fibers in the wastewater. This pro-
blem was temporarily solved by placing a screen ^basket around the
initial scrubber system intake pipe in the dye collection manhole.
A more permanent solution to this problem is presently being inves-
tigated with the possible use of a hydrasieve or mechanically
cleaned screen prior to the scrubber system.
2. The presence of surface-active agents in the dyeing wastewaters
produced an unsightly foaming problem in the scrubber sump. Other
than the problem created by the overflowing foam, the foam created
a false liquid level reading by the capacitance level detector al-
lowing the sump to be pumped dry and in turn activating the safety
shower and deactivating the fan. This problem was solved by util-
izing a defoamer additive injected into the scrubber feed from the
dye retention basin.
3. In the initial design, all pH probes were equipped with ultrasonic
cleaners to prevent fouling of the probe. Even with the ultrasonic
cleaners, fouling of the various probes has been a continuous
trouble area. Another major trouble area experienced with submerged
pH probe assemblies is that of obtaining a proper liquid seal. The
instrument used for this application utilized an 0-ring pressure
seal which has failed on numerous occasions permitting liquid seep-
77
-------
age into the probe assembly. In future installations, consideration
should be given to the use of a different type of pH monitoring
equipment.
4. The initial scrubber installation utilized an existing carbon steel
stack with no mist eliminator. Sul^furic acid mist was not felt to
be problem with acid mist emissions ranging from 0.04 to 2.27 kilo-
grams per hour. A slight temperature change of the gas exiting the
stack, however, resulted in the condensation of water droplets.
These water droplets then reacted with the remaining sulfur dioxide
in the gas to form a severely corrosive liquid. To solve this pro-
blem, several alternatives are under consideration. One common
method utilized to counteract this problem is the use of a flue gas
reheater. Reheating of the flue gas is typically accomplished by
several methods consisting of direct-fire, flue-gas bypassing, steam
injection, or recuperative transfer (transfer of heat from inlet gas
to outlet gas through the use of a heat exchanger). Another alterna-
tive and the one under consideration at present is the selection of
a corrosion resistant stack. The use of a fiberglass stack compati-
ble to the material construction of the scrubber separator is felt
to offer the most economical alternative for this application.
FULL SCALE SCRUBBER EVALUATION
The full scale scrubber installation successfully demonstrated the ability
to neutralize the wastewater, reduce the particulate and sulfur dioxide
emissions, and to do so without any detrimental effect on the biological
treatment system.
Neutralization of the wastewaters was readily accomplished with the full
scale scrubber system. The scrubber demonstrated the ability of re-
ducing the wastewater pH to levels as low as 4.5 pH units. The addition-
al neutralization capacity of the venture scrubber proved, however, to be
in excess of the design expectations resulting in the over neutralization
of the wastewaters into the acidic pH ranges. Various scrubber opera-
tional conditions were tested in an attempt to produce higher scrubber
effluent pH levels. A summary of the various operational variations and
effects are presented in Table 26. The results of this testing demon-
strated that over the feasible system operating variables, it was not pos-
sible to consistently maintain a desired scrubber effluent pH of 7.5-8.0
units. Thus, it was apparent that a reduction must be made in either the
volume of gas processed with the scrubber or the volume of the wastewaters
neutralized. Because it was desirable to process the entire gas volume
to achieve a particulate reduction, the decision was made to reduce the
volume of caustic wastewater utilized for scrubbing thereby allowing a
portion of the caustic wastewaters to be used to readjust the scrubber
effluent pH. It was determined experimentally that by reducing the
wastewater volume utilized for scrubbing to 230 liters/min (60 gpm) and
by using a minimum scrubbing rate of 380 1/min (100 gpm) or a recircu-
lation factor of approximately 160%, the excess caustic wastewater was
78
-------
Table 26. TYPICAL RESULTS OF VARIOUS SCRUBBER OPERATING CONDITIONS
System
Effluent
Flow
(1/min)
756
756
756
680
680
680
529
529
529
227
227
227
Scrubbing
Liquid
Flow Rate
(1/min)
983
983
756
1096
756
567
945
756
680
983
756
378
Flue Gas
Volumetric Flow
(act. m3/min)
519
598
963
436
452
847
496
673
531
1146
836
925
L/G
(1/m3)
1.66
1.64
0.78
2.54
1.67
0.67
1.90
1.12
1.28
0.86
0.90
0.41
System
Influent pH
(units)
11.2
11.2
11.1
11.0
10.9
10.4
11.0
11.1
11.0
10.8
10.4
10.8
Scrubbing
Liquid pH
(units)
8.9
8.2
8.0
7.8
7.4
"-" 10.0
7.5
7.5
7.9
6.3
6.2
9.6
System
Effluent pH
(units)
7.1
6.6
6.3
6.5
6.6
6.6
**
6.7
6.5
6.8
5.3
4.5
6.0
System
Pressure
Drop
(cm -w.c.)
17.8
25.4
22.6
25.4
24.9
25.4
15.2
25.4
15.2
25.4
25.4
25.4
VO
-------
capable of maintaining an influent wastewater treatment system pH of 7.5
to 8.0. With these operating conditions, it was also possible to utilize
a small volume of the neutralized, equalization basin wastewaters as make-
up for the scrubber system during short periods of dyehouse non-production
and without a significant decline in the pH levels of the influent of the
biological system. It is, however, doubtful that the scrubber operation
with the equalization basin wastewaters could be utilized for periods
extending over a day without a significant decline in the pH level of
the equalization basin effluent. With the present production schedule of
the mill, the scrubber system could be operated continuously during the
five day dyehouse production period then turned off during the weekend
period of low boiler loading.
Similar to the pilot study, an evaluation of the wastewaters across the
scrubber system showed concentration increases for several parameters.
Typical profiles of the influent and effluent to the scrubber system at
two separate operating conditions are provided in Table 27. In comparing
the full scale system with the pilot results, the larger increases in
concentration were attributed to the increased recirculation rate, higher
scrubber efficiency, as well as the concentration effect resulting from
evaporation loss in the exit gas. Again, the increased concentration of
both COD and TOC was attributed to the unburned organics within the fly
ash. This conclusion is substantiated by a comparison of the soluble
values for COD and TOC. While the total COD and TOC increased considera-
bly, the soluble form (with the fly ash removed) remained relatively con-
stant. The increase in BOD concentrations were again concluded to be the
result of a high oxygen demand created by the increased sulfite concen-
tration. The fact that the soluble 8005 values across the scrubber is
relatively constant was attributed to the increased oxidation of the
wastewater during the filtration phase of the soluble test. Unlike the
results of the pilot scale scrubber, the increases in the metal concen-
trations were considerably lower. The nickel and zinc concentrations
which caused concern in the pilot application were much lower in the full
scale application. This supported the previous conclusions regarding the
release of nickel and zinc resulting from galvanic corrosion. Iron con-
tinued to show a large increase in concentrations across the scrubber;
however, these concentrations were not felt to be detrimental to the
wastewater treatment.
As expected, the full scale scrubber proved to have a much higher effi-
ciency than the pilot scrubber for both sulfur dioxide and particulate
removal. The scrubber demonstrated the ability to successfully remove
from 80 to 90% of the incoming particulate. This resulted in exit
gas particulate emission ranging from 0.9 to 3.0 Kg/hr. (2 to 6.6 Ibs/hr.)
which is well below the Georgia Department of Natural Resource's new
source standard of approximately 6.4 kg/hr (14 Ibs/hr.). Liquid to gas
ratios ranging from 2.5 to 15.4 l/m^ (actual) were evaluated as to their
effect on particulate removal; however, there seems to be no correlation
readily evident. It is estimated that the total particulate removal in-
cluding that of the Whirlex dust collector is approximately 94-98%.
80
-------
Table 27. TYPICAL WASTEWATER CHARACTERIZATIONS
ACROSS FULL SCALE SCRUBBER
Scrubber Operating Conditions
Scrubber Effluent Flow Rate, liters/min
Scrubbing Liquid Flow Rate, liters/min
Pressure Drop, en (w.c.)
605
850
23
Parameter
pH, units
Phenol. Alkalinity
Total Alkalinity
Acidity
COD
COD (soluble)
BOD 5
BOD5 (soluble)
TOC
TOC (soluble)
Total Solids
Total Volatile Solids
Suspended Solids
Suspended Volatile Solids
Calcium
Chromium
Copper
Iron
Manganese
Magnesium
Nickel
Zinc
Units
mg/1 as CaCO<}
mg/1 as CaCOj
mg/1 as CaC03
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
/ig/1
>JgA
JUg/1
Alg/1
JUg/1
/lg/1
^/lg/1
yUg/1
Scrubber
Influent
11.2
640
957
0
1338
1239
579
629
720
450
3681
614
117
1 91
8.1
-
-
527
-
3.68
—
351
Scrubber
Effluent
6.3
0
342
520
1732
1372
824
666
1167
437
4128
801
180
115
4.9
-
-
7833
-
4.43
—
332
Scrubber
Influent
10.4
260
584
0
1067
-
482
-
170
-
:;
72
158
72
9850
BDLa
58
412
40
230
70
78
Scrubber
Effluent
5.7
0
110
520
4603
-
1815
-
610
-
-
872
2347
648
11725
91
355
28175
150
370
205
378
227
378
25
a BDL - Below atonic adsorption spectrophotometer detection limit.
-------
The scrubber was capable of achieving as high as 76% sulfur dioxide re-
moval while reducing the scrubber effluent pH to a level of 4.5 to 5.0.
In order to achieve the desired neutralization effect (pH >7), it was,
however, necessary to reduce the sulfur dioxide removal efficiency to
approximately 29%. The full scale scrubber's capacity for sulfur diox-
ide removal was found to be a function of the scrubbing liquid's pH
level as shown in Figure 23 and also indirectly a function of alkalinity.
ij ^\ ^
It has been reportedjy that S02 removal is also a function of the liquid
to gas ratio. Attempts to derive a correlation between scrubber dis-
charge pH and scrubbing liquid to gas ratios as was found with the pilot
system were impractical due to the numerous variables influencing the
absorption of sulfur and carbon dioxide. Frequent variations in the
alkalinities of the wastewater resulted in a wide scrubber effluent pH
range at constant wastewater conditions. Also it was found that the
flue gas flow was subject to wide variations of both flow rate and com-
position. With the excess air of the flue gas ranging to as high as
200% (typical excess air for this type of boiler is normally 30-50%),
the concentration of both carbon dioxide and sulfur dioxide were observed
to vary quite dramatically. This variation of concentration in turn has
a quite pronounced effect on the efficiency of the absorption reaction.
Another factor contributing to the system variables is the degree of oxi-
dation of the wastewater prior to scrubbing. The concentration of one of
the "active sodium" species (^2803) is inversely related to the degree
of oxidation of the wastewaters prior to scrubbing.
Effect Of Neutralization On The Biological Treatment System
Assessment of the true effects of neutralization on the performance of
the biological treatment system was somewhat hindered by frequent incon-
sistencies of the wastewater characteristics resulting from dyehouse pro-
duction trends and the influence of heavy rainwater infiltration. Evalu-
ation of the relative effects of neutralization on a daily basis proved
erratic and relatively unsuccessful; however, when averaged over several
weeks of monitoring, it was observed that neutralization did aid the bio-
logical treatment process. The comparative averages of the monitoring
results of the system with and without neutralization as provided in
Table 28 led to the following conclusions:
1. Other than in the parameters directly related to flue gas scrubbing
(pH, alkalinity, and the various solids parameters), it appears that
the effect of flue gas scrubbing on the total influent wastewater is
relatively insignificant. In most cases, it is extremely difficult
to attribute any change of the average influent wastewater parameters
directly to flue gas scrubbing.
2. Neutralization did increase the efficiency of the biological treat-
ment system with respect to BODs, COD, and TOG removal. This in-
creased efficiency was directly related to an increased mixed liquor
volatile suspended solids concentration (MLVSS). With neutraliza-
tion, it was possible to maintain a maximum MLVSS concentration
within the aeration basin of approximately 2400 mg/1 as opposed to
82
-------
Table 28. COMPARATIVE WASTEWATER TREATMENT CHARACTERIZATION WITH
AND WITHOUT SCRUBBER NEUTRALIZATION OF DYEING PROCESS WASTEWATERS
Parameter
pH (units)
P. Alkalinity
M. Alkalinity
Acidity
Hardness
COD
BOD
TOC
Sulfate
Total Solids
Total Volatile Solids
Suspended Solids
Volatile Suspended
Solids
Dissolved Solids
Iron
Zinc
Calcium
Magnesium
Units
(mg/1 as CaO>3)
feg/1 as CaC03)
(mg/1 as CaCOj)
(mg/1 as CaCOo)
(mg/1)
(mg/1)
(mg/1)
(ng/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
(mg/1)
Influent to Treatment Plant
W/0 Scrubber*
Neutral.
9.6
172
486
0
' 50
585
305
179
53
1241
195
115
81
90
1.35
0.082
12.0
3.6
W/Scrubberb
Neutral.
7.1
0
206
86
26
696
264
191
248
992
220
256
150
736
2.34
0.09
4.44
2.52
Effluent From Equal. Basin
W/0 Scrubber
Neutral.
8.6
14
351
0
50
479
281
137
184
987
171
90
65
897
1.69
0.12
13.5
3.2
W/Scrubber
Neutral.
7.1
0
210
39
31
439
205
115
152
823
170
100
66
751
1.64
0.11
7.34
2.34
Final Treat. Plant Efflu.
W/0 Sc.rubber
Neutral .
7.4
0
220
14
29
226
87
84
482
985
125
104
68
881
0.84
0.13
13.3
3.1 '
W/ Scrubber
Neutral.
6.8
0
82
18
25
188
42
54
389
801
158
85
70
678
1.17
0.15
5.23
2.38
09
U>
Flow (liters/min)
Average Daily Indigo Dye Range Production During Sample Period
Average Daily Sulfur Dye Range Production During Sample Period
Average Daily Total Dyehouse Production During Sample Period
(Kg/day)
(Kg/day)
(Kg/day)
945
20,040
4,320
24,360
1085
18,820
8,390
27,210
All analyses were performed on 24 hour composite samples.
a Average results of dally monitoring performed during period April 9-15, 1975 on system without neutralization
b Average results of daily monitoring performed during the period March 5-18 and April 24- May 1, 1975 on system with scrubber
neutralization during 5-day dyehouse production.
-------
oo
90h
80
70
60
50
§ 40
LJ
^ 30
M
8 20
10
0
L/G*0.67*
APi25cm.(W.C.)
* LITERS/ACTUAL CUBIC
METERS PER MIN.
1
67 8 9 10
SCRUBBING LIQUID pH (UNITS)
II
Figure 23. Percent S02 removal vs. pH of scrubbing liquid.
-------
*
1800 mg/1 without. It was concluded that the neutralized wastewaters
produced a more favorable climate for biomass growth and reproduc-
tion.
3. With neutralization, the final effluent wastewaters were less buf-
fered as measured by the alkalinity and acidity. Being less buf-
fered is advantageous because this reduces the chance of influencing
tha pH level of the receiving streamf " ' ;\
4. The removal of particulates from the flue gas resulted' in elevated
suspended solids levels in the influent. These suspended solids,
however, are removed within the equalization basin and do not in-
fluence the biological system. These solids primarily consist of
fly ash which will eventually necessitate removal from the 'equali-
zation basin.
--. ' •
Scrubber Economics
The total cost of the scrubber installation was approximately $138,000
with an estimated operating cost of approximately $30,000 per year. A
breakdown of these costs is provided in Table 29. It should be pointed
out, however, that many of the material costs are somewhat depressed as
a result of cooperation among many of the equipment vendors in supplying
equipment for a research-demonstration oriented project.
SUMMARY OF SCRUBBER NEUTRALIZATION CONCLUSIONS AND RECOMMENDATIONS
The results of the scrubber neutralization, demonstration phase of this
project lead to the following conclusions:
1. The practicability of utilizing coal-fired boiler flue gases to
neutralize caustic wastewaters was proven. Caustic wastewater re-
sulting from Canton Textile Mills, Inc.'s dyeing operation were
utilized in conjunction with a conventional wet scrubber to remove
a portion of the carbon dioxide and sulfur dioxide fractions of the
c'oal-fired boiler flue gas to successfully reduce the pH level of
these wastewaters.
"•> '•-
2. Neutralization of the wastewaters by flue gas scrubbing was shown
to improve the efficiency of the subsequent biological treatment
system by producing a more favorable influent pH and alkalinity
while producing relatively insignificant effects upon the other
characteristics of the wastewater influent.
3. The scrubber installation demonstrated the ability to achieve in
excess of 80% particulate removal from the exit gas stream of a
mechanical dust collector reducing the particulate emissions to as
low as 0.9 to 3.0 kilograms per hour.
85
-------
Table 29. CAPITAL AND OPERATING COSTS
OF SCRUBBER SYSTEM
CAPITAL COSTS
Item Description $ Cost
FMC/Link Belt Scrubber System (with Fiberglass 17,000
separator and sump)
I.D. Fan and Motor 8,500
Pumps and Motors 7,500
Instrumentation , 15,000
Ductwork 16,200
Electrical 15,300
Foundations and Concrete Work 10,700
Erection 9,600
Piping 20.200
Total Capital Costs $120,000
Engineering Construction Supervision, Start-up,
and other Contingencies 18,000
GRAND TOTAL $138.000
OPERATING COSTS*
Item Description Yearly $ Cost
Power 18,500
Operating Personnel 5,500
Maintenance 10,000
Total , $ 34.000
a Does not include the cost of dredging fly ash from equalization basin
or landfill disposal.
86
-------
While it was demonstrated possible to achieve up to 76% removal of
sulfur dioxide from the flue gas, it was found necessary to optimize
the sulfur dioxide removal to achieve the desired neutralization
effect. By utilizing a sulfur dioxide removal of approximately 29%,
it was possible to produce a neutralized total dyestream having a pH
of approximately 7.2 units.
The ability of the scrubber system to acidify the entire volume of
wastewater might prove especially advantageous should the decision
be made to incorporate alum coagulation into the treatment system.
Since the optimum pH for alum coagulation occurs at a pH of 5.5
units, the scrubber system might be utilized to produce this pH
level and achieve significant savings in chemical costs. Likewise,
should the decision be made to proceed with a lime coagulation addi-
tion, the scrubber system might be utilized in the final wastewater
pH adjustment step. The excess calcium from the lime coagulation
process might, however, result in serious scaling problems. In
either case, lime or alum coagulation; economics might be signifi-
cantly improved by incorporation of scrubber neutralization. Further
investigation is recommended in this area of application.
87
-------
SECTION VIII
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v ' . • '
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• : : , •••^- / • . — - ° .-.
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-••••>,.
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89
-------
12. Kelnath, T. M. and P. D. Holcombe. Process Technology for the Treat-
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18. Stumn, W. and J. J. Morgan. Chemical Aspects of Coagulation.
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nal of American Water Works Association. 60:514-539, 1962.
22. EPA Process Design Manual for Suspended Solids Removal, EPA Tech-
nology Transfer Program 17030 GNO, Contract No. 14*12-930.
October, 1971.
23. Roberts, J. M. and C. P. Roddy. Recovery and Reuse of Alum Sludge.
Journal of American Water Works Association. 58(7):857-865, 1960.
24. Thompson, C. G., J. E. Singley, and A. P. Black. Magnesium Carbo-
nate: A Recycled Coagulant - Part I. Journal of American Water
Works Association. 64(1):11-19, 1972.
90
-------
25. Thompson, C. G., J. E. Singley, and A. P. Black. Magnesium Carbo-
nate: A Recycled Coagulant - Part II. Journal of American Water
Works Association. 64.(2) :93-99, 1972.
26. Environmental Science and Technology. Recyclable Coagulants Look
Promising for Drinking Water Treatment. Environmental Science
and Technology. 74(4):304-305, 1973.
27. South Lake Tahoe Public Utility District. Advanced Wastewater
Treatment as Practiced at South Lake Tahoe. EPA Report 17010
ELQ 80/71. 1971.
28. Evans, D. R. and J. C. Wilson. Capital and Operating Cost - AWT.
Journal Water Pollution Control Federation. 44(1):1-13, 1972.
29. Kram, D. J. Selection and Use of the Rotary Lime Kiln and Its
Auxiliaries. Paper Trade Journal. July, 1972.
30. Beck, A. J., E. N. Sakellariou, and M. Krup. A Method for Evalu-
ating the Variables in Vacuum Filtration of Sludge. Sewage and
Industrial Wastes Association. 27(6):689-701, 1965.
31. Vesilind, P. A. Treatment and Disposal of Wastewater Sludges.
Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan. 1974.
p 109-112.
32. Schepman, B. A. and C. F. Cornell. Fundamental Operating Variables
in Sewage Sludge Filtration. (A paper presented at 1955 Annual
Meeting of Pacific Northwest Sewage and Industrial Wastes Associa-
tion, Vicoria, B. C. October 27-29, 1955).
33. Metcalf & Eddy, Inc. Wastewater Engineering: Collection, Treat-
ment, Disposal. McGraw Hill, Inc., New York. 1972. p 376-377.
34. Kaplan, N. An Overview of Double Alkali Process for Flue Gas De-
sulfurization, Atlanta, Georgia. EPA-650/2-74-126-b. November,
1974. p 445-517.
35. Lamantia, C. F., R. R. Lunt, J. E. Oberhaltzer, E. L. Field, and
N. Kaplan. EPA-ADL Dual Alkali Program - Interium Results. Pro-
ceedings: Symposijm on Flue Gas Desulfurization, Atlant, Georgia.
EPA-650/2-74-126-b. November, 1974. p 549-564.
36. Elliott, T. C. S02 Removal From Stack Gases. Power. 118(9);51-524,
1974.
91
-------
37. Georgia Department of Natural Resources. Rules and Regulations for
Air Quality Control. Chapter 390-3-1. September, 1973 (Rev.).
p 203-242.
38* Rossoff, J., R. C. Rossi, and L. J. Barnstein. Disposal of By-
products from Non-Regenerable Flue Gas Desulfurization Systems.
Proceedings: Symposijm on Flue Gas Desulfurization, Atlanta,
Georgia. EPA-650/2-74-126-b. November, 1974. p 401-443.
39. Weir, A., J. M. Johnson, D. G. Jones, and S. T. Carlisle. The
Horizontal Cross Flow Scurbber. Proceedings: Symposium of Flue
Gas Desulfurization, Atlanta, Georgia. EPA-650/2-74-126-b.
November, 1974. p 357-400.
92
-------
APPENDIX
93
-------
Table Al. DESIGN DATA FOR EXISTING
WASTEWATER FACILITIES
A. Mix Box, Bar Screen & Parshall Flume
1. No mechanical or baffle-type mixing provided.
2. Bar Screen is manually cleaned.
3. Parshall Flume (6") with continuous read out flow recorder.
B. Pre-Aeration Tank
1. Modified Imhoff Tank with provisions for diffused air
2. Three sections having total volume of 42,400 gallons
(30' x 7' x 9')
3. Air delivery regulated manually with no flow measuring devices
on air lines.
C. Lift Station
1. Provides for transfer of wastewater from pre-aeration tank
to aeration tank.
2. Three pumps - 175, 275, 400 gpm capacities
D. Biological Aeration Tank
1. Volume - 272,000 gallons (90' x 27' x 15')
2. Air diffusers 3-28* headers with 14 spargers per header for
a total of 42 spargers.
3. Two (2) blowers (485 cfm @ 6 psi rated capacities)
E. Secondary Clarifier
1. Volume 39,600 gallons
2. Effluent Weir Length 54.3 feet
3. Sludge return to Aeration Basin (Pump) - 165 gpm capacity
4. No skimmer
5. Overflow Rate - 1820 gpd/ft2
NOTE; Existing System Designed by R. H. Souther, 1960.
94
-------
Table A2. DESIGN DATA FOR UPGRADED
WASTEWATER TREATMENT FACILITIES
A. Equalization Pond Lift Station '•'•
1. Two pumps - 420 gpm @ 33 feet of water (Head)
2. Mechanical alternator, float controlled
B. Equalization Pond
1. Nominal Capacity 1 million gallons
2. Dimensions - 300' x 60' (top) & 270' x 35' (bottom)
C. Biological Aeration Basin
1. Reduced air spargers from 42 to 28 to improve mixing effect.
2. Blowers - changes motor sheaves to achieve maximum rpm rating
(680 cfm @ 6 psi & 910 cfm @ 6 psi).
D. Lift Station (to No. 2 Clarifier)
1. Provides for transfer of wastewater exiting existing clarifier
to new No. 2 Clarifier,
2. Two (2) pumps - each 300 gpm @ 30 ft. head (water).
3. Mechanical alternator, float controlled.
E. No. 2 Clarifier
1. Volume - 74,800 gallons (40* dia. x 8f S.W.D.)
2. Skimmer provided
3. Design Overflow Rate - 350 gpd/ft2.
4. Sludge return to Aeration Basin (via gravity) - 0 to 300 gpm
manually controlled.
5. Weir Length - 122 feet.
F. Aerobic Digester
1. Volume 74,100 gallons (35' dia. x 10' S.W.D.)..
2. Aerator - 20 HP. (30cfm).
3. Gravity Drain to Sludge Lagoons.
G. Sludge Lagoons (2)
1. Volume - 1 @ 142,620 gallons and 1 @ 131,215 gallons.
H. Chlorine Contact Basin
T Volume - 2872 gallons (Based on 15 minute retention time @ 190
2. Chlorine solution feed (C12 gas + H20) - 100 Ibs. Cl2/day
capacity.
3. 90° V-notch weir with flow recorder and totalizer.
95
-------
Table A3. PACKED COLUMN REACTOR TEST
WITH UNFILTERED EFFLUENT
A. Test Conditions:
Fly Ash Bed Depth:
Fly Ash Weight:
Mode of Contact:
16.5 cm
200 gm ;
Gravity, Downflow
Elapsed Time Flow Rate Color (AP11A Total Solids Susp. Solids
(Min.) (1/min/m2) Pt.Co. Units) (mg/l) ' (mg/1)
Prefiltered Effl.
0
10
20
30
_
55.00
48.08
43.19
39.93
4375
85
165
1350
2000
1845
3739
1713
1659
1732
123
137
1
2
2
B. Test Conditions:
Fly Ash Bed Depth:
Fly Ash Weight:
Mode of Contact:
Elapsed Time
(Min.)
Flow Rate
25.4 cm
318 gm
Gravity, Downflow
Color (APHA
Pt.Co. Units)
Total Solids
(me/I)
Susp. Solids
(mg/1)
Raw Effluent
3
33
63
123
153
Total Volume of Ef flue
28.11.
15.28
13.73
13.73
13.73
it with color (1
3400
30
15
20
1400
1600
10 APHA Pt. Co. Unit
1939
4072
1769
1771
1763
1733 16
i = 3.59 liters
78
6
7
5
19
16
C. Test Conditions:
Fly Ash Bed Depth:
Fly Ash Height;
Mode of Contact:
Elapsed Time
(Min.)
Flow Rate
42 cm
504 gm
Gravity, Downflow
Color (APHA
Pt.Co. Units)
Total Solids
fag/1)
Susp. Solids
(mg/1)
Raw Effluent
3
33
63
93
124
159
183
213
243
Total Volume of Ef flue
15.12
14.30
12.63
11.53
11.82
12.10
11.82
10.43
7.99
it with color (1
1550
10
10
25
30
50
40
75
200
370
10 APHA Pt. Co. Unit
1654
3647
1523
1464
1468
1477
1540
1483
1506
1518
i - 7.60 liters)
50
26
24
16
13
15
16
21
21
20
96
-------
Table A4. PACKED COLUMN REACTOR TEST WITH PREFILTERED EFFLUENT8
A. Test Conditions:
Fly Ash Bed Depth:
Fly Ash Weight:
Mode of Contact:
16.5 cm
200 gm
Gravity. Downflow
Elapsed Time Flow Rate Color (APHA Total Solids Susp. Solids
(Min.) (l/min/n/) Pt.Co. Units) (me/1) frne/n
Raw Effluent
Prefiltered Effl.
0
10
20 .v
30
67,63
63.56
50.52
48.48
4375
3050
15
860
2150
2700
1845
1699
3600
1665
1615
1753
123
120
247
17
24
30
B. Test Conditions:
Fly Ash Bed Depth: 25.4 cm
Fly Ash Weight: 318 gm
""' Mode of Contact: Gravity, Down flow
Elapsed Time Flow Rate Color (APHA Total Solids Susp. Solids
(Min.) (1/min/m2) Pt.Co. Units) (mg/1) (mg/1)
Raw Effluent
Prefiltered Effl.
0
30
60
90
120
150
180
210
-
25.95
17.11
10.67 "
10.67
10.67
9.78
7.62
6.11
3400
1895
30
20
35
50
50
60
110
310
1939
977
3974
1377
1173
1197
1240
1225
1406
1230
78
50
6
11
9
9
6
7
9
17
C. Test Conditions:
Fly Ash Bed Depth:
Fly Ash Weight:
Mode of Contact:
40 gm
481 gm
Gravity, Downflow
Elapsed Time
Flow Rate
Total Solids
Susp. Solids
yru.ii. j
Raw Effluent
3
15
29
50
76
142
157
172
Total Volume of Efflut
23.88
20.82
15.60
14.10
12.87
13.16
13.49
12.55
nt with color (1
8125
10
20
20
20
20
40
100
200
310
00 APHA Pt. Co. Uni
1488
3544
1665
1404
. 1380
1385
1361
1366
1355
1366
ts - 5.6 liters
46
19
9
19
15
11
11
11
7
9
a Effluent was "filtered through 710 micron screen
97
-------
Table A5. TYPICAL JAR TEST PROCEDURE
Test Apparatus: Phipps and Bird (Six Unit) Multiple Stirrer
Procedure
1. 1.0 liter of wastewater was measured into each jar.
2. Approximately 150 ml. of the 1.0 liter total was placed in a
separate 250 beaker.
3. Dry chemicals to be added were weighed on an analytical balance.
4. Dry chemicals were slurried with portions from the 150 ml. volume.
5. Rapid mixing of the wastewater was begun.
6. Chemical slurries were added to the jar; slurry beakers were rinsed
thoroughly with the wastewater that remained in the 250 ml. beaker.
(Total wastewater volume in each jar was 1.0 liter).
7. Wastewater was rapid mixed at 100 rpm for 2 minutes.
8. Wastewater was flocculated at 20-24 rpm for 15 minutes.
9. Floes were allowed to settle for 30 minutes.
10. After settling, supernatant was siphoned off for analyses.
11. The low dosage of coagulant that yielded good results in terms of
the subject parameter (color) was selected and a second jar series
was run with the optimum dosage in all beakers. The pH level of
the coagulation was then varied by employing various dosages of
acid (H2S04) or alkali (NaOH). Similar procedure was again utilized
through the mixing, flocculation, settling steps above and the .
optimum pH range for the desired effect was selected.
98
-------
Table A6. BUCHNER FUNNEL TEST PROCEDURE
1. Thirty liters of wastewater were coagulated using the predetermined
optimum coagulant dosage. After a period of settling, the sludge
was carefully withdrawn. This procedure was repeated until a min-
imum of four liters of sludge was collected.
2. The combined sludge sample was then analyzed for percent solids.
3. The Buchner funnel apparatus was arranged as illustrated in
Figure 12 with two No. 4 Whatman Filters placed in the 9-cm funnel.
4. The filter paper was moistened, vacuum applied, and the water drawn
through the filter discarded.
5. Exactly 200 milliliters of the sludge was then poured over the pre-
pared funnel and the vacuum applied.
6. Various vacuums were then applied for selected time periods.
7. At the end of the selected filtration time or upon loss of vacuum,
the filtrate and filter cake were analyzed.
99
-------
Table A7. RESULTS OF BUCHNER FUNNEL TESTS WITH
SLUDGE GENERATED FROM ALUM COAGULATION
Test No. 1; 2.0 Minute Filtration
Initial Sludge - 200 ml @ 0.40% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min. )
10
15
20
Poor Cake
Poor Cake
Poor Cake
ma
-
**
Volume
(ml.)
102
108
120
COD
(mg/1)
1]f
-
«.
Color r (APHA
Pt.Co. Units)
-u-
-
™"
PH
(Units)
_
-
*
Test No. 2; 4.0 Minute Filtration
Initial Sludge - 200 ml @ 0.40% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
Poor Cake
Poor Cake
Poor Cake
^
-
~
Volume
(ml.)
152
156
158
COD
(mg/1)
<0>
- .
a.
Color (APHA
Pt.Co. Units)
«*'
.••* <
•»
PH
(Units)
^
: -
*™
Test No. 3; 6.0 Minute Filtration
Initial Sludge - 200 ml @ 0.29% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) {% Solids) (min.)
10
15
20
Poor Cake
Poor Cake
Poor Cake
1 1
—
. -
Volume
(ml.)
176
184
188
COD
(ffig/1)
mm
-
• -
' '.
Color (APHA
Pt.Ca. Units)
1 «• t • '
( — -d
•*•• ;' ; . '. '
• • • J 1 - ' . *'
PH
(Units)
•V
-
-
Test No. 4:
8.0 Minute Filtration
Initial Sludge - 200 ml @ 0.29% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
55.7
60.0
67.5
7.25
6.75
6.50
Volume
(ml.)
188
190
195
COD
(mg/1)
24
28
20
Color (APHA
Pt.Co. Units)
60
70
80
PH
(Units)
4.4
4.3
4.5
100
-------
Table A8. RESULTS OF BUGHNER FUNNEL TESTS WITH
SLUDGE GENERATED WITH LIME COAGULATION
Test No. 1; 2.0 Minute Filtration
Initial Sludge - 200 ml @ 2.97% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
-------
Table A9. RESULTS OF BUCHNER FUNNEL TESTS WITH SLUDGE GENERATED
WITH MAGNESIUM CARBONATE AND LIME COAGULATION
Test No. 1:
2.0 Minute Filtration
Initial Sludge - 200 ml @ 3.01% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
Poor Cake
Poor Cake
Poor Cake
_
-
"•
Volume
(ml.)
80
82
86
COD
(mg/1)
^
-
™
Color (APHA
Pt.Co. Units)
•«•
-
mm
PH
(Units)
_
_
~
Test No. 2:
4.0 Minute Filtration
Initial Sludge - 200 ml @ 3.01% Solids
Vacuum
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
Poor Cake
Poor Cake
Poor Cake
-
—
Filtrate
Volume
(ml.)
114
118
122
COD
(mg/1)
-
~
Color (APHA
Pt.Co. Units)
-
•*•
pH
(Units)
<
—
Test No. 3:
6.0 Minute Filtration
Initial Sludge - 200 ml @ 2.03% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
Poor Cake
16.4
19.8
_
-
—
Volume
(ml.)
180
182
184
COD
(mg/1)
_
46
50
Color (APHA
Pt.Co. Units)
^
10
30
PH
(Units)
_
11.5
11.5
Test No. 4:
8.0 Minute Filtration
Initial Sludge - 200 ml <§ 3.57% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
26.4
28.8
29.9
7.25
6.75
6.00
Volume
(ml.)
178
180
182
COD
(mg/1)
39
31
23
Color (APHA
Pt.Co. Units)
10
10
10
PH
(Units)
11.5
11.5
11.5
102
-------
Table A10. RESULTS OF BUCHNER FUNNEL TESTS WITH SLUDGE GENERATED
FROM LIME-DOW A-23 COAGULATION
Test No. 1:
2.0 Minute Filtration
Initial Sludge - 200 ml @ 3.84% Solids
Vacuum
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
11.1
14.9
15.7
•V
-
~
Filtrate
Volume
(ml.)
126
130
144
COD
(mg/1)
71
60
40
Color (APHA
Pt.Co. Units)
20
15
15
PH
(Units)
11.2
11.2
11.2
Test No. 2:
4.0 Minute Filtration
Initial Sludge - 200 ml @ 4.33% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg) (% Solids) (min.)
10
15
20
24.8
29.3
28.1
3.83
3.75
Volume
(ml.)
164
180
180
COD
(mg/1)
44
36
32
Color (APHA)
Pt.Co. Units)
30
20
20
pH
(Units)
11.3
11.4
11.4
Test No. 3:
6.0 Minute Filtration
Initial Sludge - 200 ml @ 6.48% Solids
Vacuum Filtrate
Vacuum Sludge Cake Break
(in. of Hg
10
15
20
(% Solids) (min.)
24.8
29.3
28.1
4.00
3.75
3.50
Volume
(ml.)
148
160
170
COD
(mg/1)
63
31
67
Color (APHA
Pt.Co. Units)
30
20
20
PH
(Units)
11.4
11.5
11.4
Test No. 4:
8.0 Minute Filtration
Initial Sludge - 200 ml <§ 5.83% Solids
Vannim Filtrate
Vacuum Sludge Cake Break
(in. of Hg'i (Z Solids') (min.)
10
15
20
•••••••^••^^•••••^••••••^^•••••A
28,2
28.0
28.4
_.._! '
5.30
4.75
4.25
___••.••—• — — —
Volume
(ml.)
156
158
164
COD
(mg/1)
56
62
59
.•••. • n ••
Color (APHA
Pt.Co. Units)
15
20
20
_— — — i— ^— — — — —
PH
(Units)
11.4
Uj
.4
nt
.4
^^•••BHH^^H^BI-^HI^^^
103
-------
Table All. TYPICAL COAL ANALYSIS
Size
Moisture
Ash (%)
Volatile (%)
Fixed Carbon
Sulfur (%)
Fusion Temperature of Ash (AST)
Grindability (Hardgrove)
Free Swelling Index (A.S.T.M.)
Coke Button
Heat Valve (as received)
;
Heat Valve (dry)
3.2cm x 1.0cm (1-1/4 x 3/8 inch)
2.76
5.98
40.39
50.87
0.80
1454°C (2650°F)
60
7562 Kg.-Cal/Kg. (13,600 BTU/lb)
7840 Kg.-Cal/Kg. (14,100 BTU/lb)
104
-------
EPA- 600/2 -76-139
4'T1TLEANOSUBT1TLE Treatment of
Wastewaters : Neutralization and Color Removal
TECHNICAL REPORT DATA
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
May 1976
6. PERFORMING ORGANIZATION CODE
Charles R. Froneberger and
MichaelJ. Pollock
8. PERFORMING ORGANIZATION REPORT NO.
R.S. Noonan, Inc. of South Carolina
P.O. Box 1388
Greenville, South Carolina 29602
1O. PROGRAM ELEMENT NO.
1BB036; ROAP 21AZT-006
1. CONTRACT/GRANT NO.
Grant S800852*
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 4/72-7/75
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES (*) Grantee is Canton Textile Mills, Inc. Project officer for this
report is T.N.Sargent, EPA, Cincinnati, Ohio 45268.
16. ABSTRACT
repOr|; des cribes a bench scale investigation using fly ash adsorption
and chemical destabilization techniques to remove color from indigo and sulfur dyeing
wastewaters from a denim textile mill. The investigation included a feasibility study
and subsequent full scale demonstration flue gas wet scrubbing techniques for neutra-
lizing caustic wastewaters. The fly ash adsorption studies demonstrated that fly ash
from a coal-fired boiler can adsorb and subsequently remove color, BOD5, and COD
from biologically treated domestic and dyeing process wastewaters. The limited
adsorbtion capacity of the fly ash and problems related to fly ash/wastewater contact
made full scale application impractical. The chemical destabilization studies inclu-
ded investigation of 11 destabilizing agent combinations , chemical recycle , and var-
ious parameters associated with sludge handling and disposal. The studies concluded
that calcium hydroxide or aluminum sulfate could successfully remove color and
produce a supernatant of suitable quality to recycle. The practicability of using coal-
fired boiler flue gases to neutralize caustic wastewaters was demonstrated on full
scale. Caustic wastewaters were used with a conventional wet scrubber to success-
fully neutralize the wastewaters by SO2 and CO2 absorption from the flue gas while
simultaneously reducing the particulate emissions.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Gioup
Pollution, Textile Processes, Textiles,
Waste Water, Neutralizing, Decoloring,
Fly Ash, Adsorption, Sulfur, Flue Gases,
Scrubbers, Sludge, Calcium Hydroxides,
Aluminum Sulfate, Sulfur Dioxide,
arbon Dioxide
Pollution Control
Stationary Sources
Denim
Chemical Destabilization
13B, 13H, HE
07A/07D
21B,07B
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified .
•1. NO. OF PAGES
114
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
105
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