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Aucjust , 1 9 8 9 .
THE SFFECTiVZ;TXSS O F TI-IE ANDCO ELECTROCHEMICAL
TREATMENT PROCESS AND I T S APPLICATION IN TEXTILE
i'r AS T Eli A T E R TR E A TI~I EN T
A T h e s i s by Xarla Kaye Weinburcj
Georcjia I n s t i t u t e of T e c h n o l o G y
2 6 7 5 c u m D c r 1 ; in ci 9 3 i i w a \ ~
S l l i t t . 2 0 0 4 t i J n t a , C e o ~ 1 1 i I ' 3 3 0
F a c s i m i l e k0.i 3 I9 7777
-- I/
4
THE EFFECTIVENESS OF THE ANDCO ELECTROCHEMICAL TREATMENT PROCESS AND ITS APPLICATION IN TEXTILE
WASTEWATER TREATMENT
A THESIS Presented to
The Academic Faculty
Marla Kaye Weinberg
In Partial Fulfillment of the Requirements for the Degree
Master of Science
Georgia Institute of Technology August, 1989.
THE EFFECTIVENESS OF AN ELECTROCHEWCAL TREATMENT PROCESS AND I T S APPLICATIONS IN TEXTILE WASTEWATER
TREATMENT
Approved:
Wayne C. Tincher, cbntrmrn.
M L . cook
Edward Chian
DEDICATION
iii
ACKNOWLEDGEMENTS
With deepest admiration and heart felt appreciation, I
would like to thank parents Milton Weinberg and Shirley
Stinard for all their love and guidance. They have always
inspired me and supported my decisions, being there for me in
my greatest times of need. I would also like to thank my
sister, Lisa, for all her encouragement and help with my
thesis.
My thesis advisor, Dr. Wayne C . Tincher, has helped me
to recognize my own capabilities. His relentless striving for
perfection has fostered a conviction for perfection in all
aspects of my work. His patience and advice throughout my
years at Georgia Tech, as both an undergraduate and graduate
student, have been deeply appreciated.
I would also like to acknowledge the help of my defense
committee, Dr. Tincher, Dr. Fred L. Cook, and Dr. Edward Chian
for all of their time, help, and advice.
Tremendous thanks to my friends, Deann Smith, Dee Ling,
Ani1 Saraf, Katherine Edman, P. Dastoor, Rajeev Maholtra and
Sukasem Tejatanalert for their unmatched support and
assistance with my thesis.
Finally, I would like to send my deepest thanks to Andco
Environmental Processes, Inc. of Amherst, NY for coordinating
iv
this study and providing a pilot unit for the experimentation.
Without their cooperation, assistance and advice this project
would not have been possible. Special thanks to Mike
Lassingher and Kevin Uhrich for their instruction on the
operation and use of the Andco pilot unit.
TABLE OF CONTENTS Pase
DEDICATION ii ............................................. iii
LIST OF TABLES ......................................... vi
LIST OF ILLUSTRATIONS .................................. X
S.Y ................................................ xii
Chapter
I . Introduction and Literature Review ............ 1
The Textile Industry .......................... 2 Wastewater Characterization ................... 4 Current Treatment Technologies ................ 11 Electrochemical Wastewater Treatment .......... 30 The Andco Treatment Process ................... 45
I1 . Research Objective and Experimental Details ... 61
Experimental Methods and Procedures ........... 61 Analytical Testing Procedures. Methods and Equipment ..................................... 67 Color Removal Study ........................... 77 Dyebath Water Reuse Study ..................... 79 Color Measurement Theory ...................... 92
I11 . Results and Discussion ........................ 105
Chemical Oxygen Demand Reduction .............. 105 Color Removal Results ......................... 119 Treated Djebath Water Rewe Results ........... 139 A Study of the Color Removal Process .......... 148 Cost Analysis ................................. 162
IV . Conclusions and Recommendations ............... 167
REFERENCES ............................................. 210
vi
Table
1-1.
1-2.
1-3.
1-4.
1-5.
1-6.
1-7.
1-8.
1-9.
1-10.
3-1.
3-2.
3-3.
LIST OF TABLES
.. Pase
EPA historical averages of wastewater 7 composition for various textile subindustries.
Percent contribution of various chemicals to 8 textile wastewater
EPA average effluent limits set for textile mills.
13
Dalton Riverbend Wastewater Treatment Plant 14 effluent limitations set for local industries including textile mills.
Electrochemical treatment BOD reduction. 50
Electrochemical treatment COD reduction. 51
COD reduction after electrochemical treatment. 53
Electrochemical treatment color removal. 56
Absorbance values before and after electro- 58 chemical treatment with percent reduction of absorbance.
Heavy metal removal with increasing levels of 59 electrochemically generated iron.
COD values and percent removal values for 107 Stainblocker Formulation l1Al1 at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
COD values and percent removal values for'. 108 Stainblocker Formulation ltBl1 at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
COD values and percent removal values for Stainblocker Formulation llC1l at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
110
3-4.
3-5.
3-6.
3-7.
3-8.
3-9.
3-10.
3-11.
3-12.
3-13.
3-14.
COD values and percent removal values for Stainblocker Formulation at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition. *Denotes sample in which-no polymer was used to achieve a floc.
v i i
1 1 2
COD values and percent removal values for 113 Irgalev A, an auxiliary chemical, at 0.6 g/1 and 0.8 g/1 sample concentrations with increasing iron addition.
COD values and percent removal values for 114 Guar Gum, an auxiliary chemical, at 0.3g/l sample concentration with increasing iron addition.
COD values for distilled water blanks treated with the Andco Process, and the corresponding polymer quantities required to produce a floc.
Average peak height, total carbon and percent removal values for Stainblocker Formulation IIDtl at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron. * Denotes samples in which no polymer was used to achieve a floc.
COD values and percent removal for the acid dye mixture at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
Required polymer (ml), COD values and percent removal values for A.R. 361 dye at 2 5 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
Required polymer (ml), COD values and percent removal values for Procion Blue MS-2G dye at 2 5 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
Average peak height and total carbon values A) before iron blank subtraction, B) after iron blank subtraction, for the acid dye mixture at 25 (mg/l) sample concentrations.
Average peak height and total carbon values A) before iron blank subtraction B) after iron blank subtraction, for A.B. 4 0 25 (mg/l) sample concentration.
Average peak height and total carbon values for the distilled water iron blanks.
116
118
1 2 1
1 2 2
1 2 3
125
126
1 2 7
viii
3-15.
3-16.
3-17.
3-18.
3-19.
3-20.
3-21.
3-22.
3-23.
3-24.
3-25.
3-26.
3-27.
Absorbance values for distilled water treated 130 with the Andco Process. The absorbance values represent the color contribution of the iron.
Acid dye mixture percent reduction values for 135 15 (mg/l) and 25 (mg/l) samples with increasing iron addition A) before iron color absorbance subtraction B) after iron color absorbance subtraction. * Represents percent increase in absorbance.
Corresponding color reduction percent for the 136 acid dye mixture at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
Absorbance and percent color reduction values for A.B. 40 25 (mg/l) sample A) before iron color absorbance subtraction B) after iron color absorbance subtraction.
137
Absorbance with percent reduction values for 138 Procion Blue MX-2G at 25 (mg/l) and 50 (mg/l) sample concentrations.
CIE LAB color matching for A.B. 277 dyeing #1 141 and A.B.277/A.R.361 purple dyeing #l.
CIE LAB color matching values for A. B. 277 142 dyeing #2. ST = Stainblocker/auxiliary spiked sample.
CIE LAB color matching values for A. R. 361 14 3 dyeing #l. ST = Stainblocker spiked sample.
CIE LAB color matching values for A. R. 361 145 dyeing #2. ST = Stainblocker spiked sample.
CIE LAB color matching values for Procion Red 146 dyeing #l.
Percent change in absorbance for Acid Blue 151 277 standards and treated samples at selected wavelengths.
Percent change in absorbance for FD&C Food 154 Yellow #5 standards and treated samples at selected wavelengths.
Percent change in absorbance for FD&C Food 157 Blue #2 standards and treated samples at selected wavelengths.
ix
3-28. Percent change in absorbance for Azobenzene 159 standards and treated samples at selected wavelengths.
3-29. Percent change in absorbance f o r Azobenz-ene 160 34 mg/L degraded with sodium hydrosulfite at se1ecte.q wavelengths and absorbances for dilute Aniline.
X
LIST OF ILLUSTRATIONS
,
Fisure
1-1.
1-2.
1-3.
1-4.
1-5.
1-6.
1-7.
1-8.
1-9.
1-10.
1-11.
1-12.
1-13.
1-14.
1-15.
1-16.
1-17.
Number of mills using various degrees of wastewater treatment of 1092 responding mills.
Chemicals used in dyeing and finishing.
Main types of dyes, their main use and associated chemicals.
Origin points of effluent wastewater from various textile processes.
An anionic polyacrylamide coagulation polymer.
Combinations of water treatment processes used most frequently in industry.
Total organic carbon vs. ozone dose to study dye destruction of Acid Blue 40 .
Schematic representation of (A) a cation exchange resin and (B) an anion exchange resin.
Useful ranges of separation processes.
Schematic diagram of a bipolar pump cell.
Schematic diagram of the Chemelec cell.
Schematic diagram of the ECO cell.
Schematic diagram of the multicathode cell.
Schematic diagram of the Swiss-roll cell.
Schematic diagram of the porous flow- through cell.
Schematic diagram of the RETEC cell.
Pase
3
5
6
10
21
23
26
27
29
33 ’
35
36
38
39
41
42
Schematic diagram of the fluidized bed c e l l . 43
xi
1-18.
1-19.
1-20.
1-21.
2-1.
2-2.
2-3.
2-4.
2-5.
2-6.
3-1.
3-30
3-31
Schematic diagram of the Andco Electro- chemical Treatment Cell.
Solubility limits of some common metal ions.
Electrochemical treatment color removal from red reactive dye mixture.
Electrochemical treatment color removal from reactive dye mixture.
Sample calculations for electrochemical iron addition.
The Andco vlM1l Cell pilot unit.
Schematic of COD test apparatus.
Schematic of an ACS Spectro Sensor I1 Spectrophotometer.
CIE LAB 1976 equations used to quantify sample differences. D = Difference.
Structures for (A) FDtC Yellow # 5 , (B) FD&C Blue #2, and (C) Azobenzene.
Absorbance vs. Iron Level (mg/l) at 610 nm for three different sets of treated distilled water blanks used to measure iron color contribution.
46
48
54
55
63
68
71
93
95
102
131
Annual and daily operating costs for a mill 163 treating 1.0 million gallons per day for different iron treatment levels. Iron sludge production is also given. Values rounded to the nearest-whole number and annual values represent 355 days.
Comparisions of A) Capital cost,B) Annual 164 Operating costC) Daily Operating cost and-.D) Annual Sludge Production for 1.0 million gallon/day treatment system with different treatment methods.
xi i
SUMMARY
The concern over the condition of the environment has
grown tremendously in recent years. Efficient use of
resources and energy is a growing trend that will hopefully
improve environmental conditions for future generations. The
commercial and industrial sectors have made great progress in
about the last 15 to 2 0 years by increasing their process
efficiency, and reducing process impacts to the environment.
Most industries use water at some point in their processes
producing wastewaters of various composition and
concentration. The textile industry is no exception, using
extremely large volumes of water for various aspects of
production. The wastewater is highly varied in composition
and concentration due to the wide range of processes involved
in fiber, yarn and fabric preparation and finishing processes.
Most large textile plants use some form of biochemical
treatment system such as oxidation ponds or aerobic sludge to
provide an intefmediate level of treatment. Most textile
wastewater is treated, sufficiently by these processes,
although color removal (from dyes) is usually pobr. This
research studies the effectiveness of an electrochemical
treatment process and its applications in textile wastewater
treatment.
xiii
The research has been divided into four primary studies
to determine: 1) If chemical oxygen demand is reduced for
stainblocker and auxiliary chemicals, 2) The extent of color
removal, 3 ) If simulated dyebath water can be reused in dyeing
after treatment, and 4 ) If dolor is removed solely by some
form of dye precipitation and/or by dye degradation /
alteration. Also, a cost analysis was performed to compare
the Andco Electrochemical Treatment Process with other
wastewater treatment processes.
The results of the study show that chemical oxygen demand
is reduced by 2 5 % to 100% depending on the chemical being
treated, its concentration and, the iron addition level being
used. Color removal was very good in the range of 70% to 100%
mostly depending on the concentration of dye in the test
solution. High iron addition levels (500-650 mg/l) were
required for COD removal of finishing chemicals, while color
removal was sufficient at much lower iron addition levels
(100-250 mg/l). The treated dyebath water reuse study
indicated that water reuse was not out of the question, but
would require full-scale dyebath testing to optimize the dyebath to achieve more conclusive results. The
experimentation studying the mechanism of dye removal
indicated that azo bond containing dyes were very susceptible
to destruction, as were those containing aliphatic carbon-
carbon double bonds. The results indicated that aromatic
amines were produced in the destruction process. Also,
xiv
to destruction as were those containing aliphatic carbon-
carbon double bonds. The results indicated that aromatic
amines were produced in the destruction process. Also,
anthraquinone dyes appeared to be removed primarily by some
form of precipitation as opposed to destruction.
The cost analysis showed that the Andco Electrochemical
Treatment Process is economically competitive with other
wastewater treatment processes having similar capabilities.
1
CHAPTER I
INTRQDUCTION AND LITERATURE REVIEW
Introduction
As technology approaches the beginning of the 21st
century, the world races to keep up with it. The 20th century
has been revolutionary as It The Age of Technology.1t However,
many problems still plague the world - nuclear weapons,
disease, hunger and, of course, the deteriorating state of the
environment. Perhaps the 21st century will bring a new age
and way of thinking - perhaps It The Age of Responsibility."
The responsibility of the planet's welfare, once left to
nature, has now been accepted by the people who inhabit it.
People are trying to make amends for the careless treatment
of the planet and its resources. This study addresses the
environmental problem of water pollution reduction. Specific
focus is placed on the reduction of textile industry
wastewater constituents using an electrochemical removal
process developed and patented by Andco Environmental
-
Processes, Inc. of Amherst, New York.
Research was conducted to evaluate the effectiveness of
the Andco Treatment Process in the following applications:
chemical oxygen demand (COD) reduction, color removal and
treated dyebath water reuse. Also, a fourth study was
2
conducted to determine if color removal was totally a
consequence of dye removal or some combination of removal and
chemical alteration. Finally, a cost comparison was prepared
to determine the economic acceptability ofthe Andco Treatment
Process compared with other water treatment systems.
Background information on the textile industry, current
treatment technologies (including other electrochemical
treatment technologies), and the Andco Treatment Process is
provided for reference and comparison.
The Textile Industrv
The textile industry encompasses a wide range of sub-
industries that produce textile products, textile processing
chemicals and specialty products. There are approximately
7,000 textile mills nationwide, 77% in the mid and south-
Atlantic regions, 10% in New England and 6% in the Pacific
region [I). Nationwide, the textile industry produces
approximately 50-75 billion dollars/year of products which are
shipped worldwide. Large digit figures are not limited to
sales only. The water consumption required to process such
huge quantities of textile products is approximately 3xi08
m3/yr [l] . But the massive amount of water required is not
always as great a concern as the ability to treat it. Textile
wastewater is highly varied in pollutant composition and
concentration making treatment of certain types of textile
wastewater very expensive and sometimes difficult.
I
3
a
a
t
z
W
4
Fortunately, a variety of treatment systems are available
which can successfully treat most combinations of textile
wastewater - each with its own advantages and disadvantages as will be discussed later in this chapter. Some mills do not
treat their wastewater. Many textile mills discharge to
local waterways or local POTWs with little or no treatment.
Of the 1,092 textile mills responding to a 1982 EPA survey,
it was found that 504 discharged to a POTW with no treatment.
Of those providing treatment, 289 discharged with preliminary
treatment while only 18 direct and one indirect discharger
used some type of advanced treatment as shown in Figure 1-1
111
Wastewater Characterization
As previously stated, the major problem involved in
treating textile wastewater is the varied composition of the
wastewater. Figure 1-2 shows the approximate categories of
chemicals used in dyeing and finishing processes [2]. Figure
1-3 shows specific dye types, their main use and other
auxiliary chemicals used with them respectively [2].
Recently, however, the use of chromium has decreased due to
EPA restrictions and more stringent regulations set by OSHA
(Occupational Safety and Health Agency) to protect workers.
Continuing, Table 1-1 shows the EPA historical averages of
wastewater composition for various textile subindustries
The values are expressed as Kg pollutant/KKG of product. Of
all the subindustries, the wool industry leads in the amount
5
Acids - i n o r g a n i c and o r g a n i c (e .g . fo rmic and a c e t i c )
Alkalis
Bleaches ( c h l o r i n e , hydrogen pe rox ide )
F l u o r e s c e n t s h i t e n i n g a g e n t s
Soaps and d e t e r g e n t s
Dye carriers and o t h e r a d d i t i v e s (e.g. o-phenyl phenol , benzo ic a c i d , phenyl methyl c a r b i n o l )
O i l s
S t a r c h o r s u b s t i t u t e (e.g. ca rboxymethy lce l lu lose )
Res ins
F i r e - , r o t , and w a t e r p r o o f i n g a g e n t s
P e s t i c i d e s
S i l i c a t e s
S u l p h i d e s
Var ious i n o r g a n i c sa l ts
Organic s o l v e n t s
Figure 1-2 Chemicals used in dyeing and finishing [ 2 ] .
. .
6
Tjpe of'dyc s l a in USC Associatcd p rwcss chemicals
Acid \Vool, n_vIon
Azoic Cotton
nasic Acylic
Direct Cotton, synthetics
Dispcrsc Polyester
Mordant \Vml
Kcaccivc Cotton, wool
Sulphur Cotton, synthctin
Vat cot ton, synthctics
Sulphun'c acid Acctic acid Sodium sulph3tc Surfactants
Metal salts Formaldehydc Sodium h5drosidc Sodium nitrire Acids
__
Acctic acid Softcning agcnt
Sodium salts Fixing agcnt hlctal salts (coppcr or chromatcr.)
Gamer Sodium hy d rosidc Sodium hxdrosulphitc
Chromium and other mctal salts Acctic acid Sodium sulphatc
Sodium chloridc Sodium hydrosidc Ethylcnc diaminc
Sodium sulphidc and othcr salts Acctic acid
Sodium hFdrosidc Sodium hFdrosulphitc and othcr salts. S u rf3ctanrs
Figure 1-3 Main types of dyes, their main use and associated chemicals [ 2 ] .
7
Table 1-1
Subcategory
EPA historical averages of wastewater composition f o r various textile subindustries Cll-
1.
2.
3.
4.
5 .
6.
7.
a.
9 .
Wool Scouring
Wool Finisbing
Low Uater Use Processing a. General Processing b . Water Jet Weaving
Woven Fabric Finishing a . Simple Processing b. Complex Processing c. Desiring
Knit Fabric Finishing a. Simple Processing b. Complex Processing c. Hosiery Products
Carpet Finisbing
Stock L Yarn Finisbiog
Nonvoven Hanufacturiog
Felted Fabric Processing
1830 6900 2703 580
150
380 120
300 350 405-
205 260 325
440
190
175
205
650
1060 180
900 1170 1260
765 835
1300
1190
685
2360
555
sc, i
220 I 25 #
60 65 80 45
160 7 0 -
60 95 so 50 80 100
65 20
4 0 25
80 . a 1 IS 30
I
0
I I
55 100 130
55 155 560
175
2$5
a
a
0
50
I I
49 180 146
108 107 62
130
172
d
* 575
a
0
R f l -
1000 500
U
390 760 450
690
5 i o
V
c ~~
I Insuff ic ient data t o report value.
fource: 308 Survey Data, Table V-11.
8
Table 1-2 Percent contribution of various chemicals to textile wastewater [ 4 ] .
Source
F i b e r F i n i s h .
Dyeing Chemicals Dyes S t a i n Blockers
Contribution
50-65% 25-35%
2-5% 5-25%
9
of conventional pollutants (BOD,, TSS) produced. The carpet
industry comes in close behind the wool industry producing
very high concentrations of nonconventional pollutants like
COD (chemical oGgen demand). Tincher reports that fiber
finish contributes the greatest amount to the COD level,
nearly 50-65% as shown in Table 1-2 ( 4 1 . Tincher also
explains that COD levels have risen recently due to the advent
of stainblocking agents. The increased use of stainblocking
chemicals, the growing use of jet dyeing, as well as, the
recent growth in the carpet industry are some of the main
facters which have resulted in an increase in water demand
from an average of 5.6 gallons per pound of carpet in 1980 to
6 . 2 gallons per pound in 1988 [ 4 ] . In addition, further
demands are placed on-treatment systems not only due to the
varied wastewater from subindustry to subindustry, but also
within each subindustry. Figure 1-4 shows an example within
given subindustries of the different wastewater producing
processes [2]. Usually, each process employs a unique set of
processing chemicals. In most cases the wastewater from each
process is mixed as it travels through piping systems to a
central exit pipe or sewer line. When the water leaves the
plant it must meet limits set by the EPA and local authorities
for direct (discharging to a waterway) and indirect
(discharging to a sewer) dischargers.
10
Synthetics
Cording Q
- Scouring
Fulling c;?
- E
rirE Scouring
L
Bleaching
F+ [q--]+ Mercer i z i n g
Knit cf7 Dyeing o n d I f in i sh ing I-- E
FE Dyeing ond f i n i s h i n g
Dyeing qE Scouring ond bleoching
IE Finishing
Figure 1-4 origin points .of effluent wastewater from various textile processes [ 2 ] .
11
Effluent Limitations
The textile industry until recently has been out of the
public eye and has received little attention concerning its
pollutant dischaege. However, recent media coverage of
chemical, petroleum, and environmentally related accidents
has lead to increased scrutiny oftextile wastewater effluents
and treatment systems [ 4 ] . Local POTWs are finding it more
difficult to treat the growing volumes of textile wastewater
along with higher COD levels. They are also beginning to find
it more and more difficult to meet their own effluent
limitations for water exiting the treatment plant. The
biological treatment systems used are also susceptible to
inhibition from textile process chemicals, Although POTWs
often fine or require a surcharge from companies discharging
excessive'volumes or wastewater over pollutant limits, they
still have a finite maximum of water they can treat. Also,
the public sector generally takes priority in that its water
must be handled first; the remainder of the POTW's capacity
can be used by industry. When this capacity is- reached the
responsibility to reduce volume and/or pollutant ccncentraticn
lies in the hands of the industry. In some cases industries
have coordinated their efforts with local POTWs by staggering
production periods to create a more even wastewater load on
the POTW. During the summer drought of 1988, Dalton Riverbend
Wastewater Treatment Plant coordinated a plan with local
industries where each was assigned a five days on two days off
12
production schedule - staggered against each other to lower water use and create a balance in f l o w over a seven day
period. The plan worked successfully to reduce the impact of
the drought for a l l parties [32]. The industries and their
materials suppliers have also worked to minimize waste at the
source by continually maximizing their processes and
reformulating chemical finishes to reduce pollutant content
and strength. By operating under such strategies, wastewater
treatment costs are generally reduced, not to mention the cost
savings associated with increased process efficiency and
materials utilization.
EPA effluent limits for the textile industry are given
in Table 1-3 [32]. The nonconventional pollutant, COD, and
the conventional pollutants, BOD and TSS have their limits
decided by local POTWs according to the EPA, which sets limits
on the other nonconventional pollutants as shown in Table 1-
3. The values given are average values which vary depending
on a company's size, water consumption, flow fluctuation,
location and position relative to other pollution souxces [I],
1301 The EPA has three main sets of regulations
corresponding to BCT, BAT and NSPS standards. The BCT - Best Control Technology standards given are the least stringent
followed by the BAT - Best Available Technology standards. The NSPS - New Source Performance Standards are the tightest standards placed on the textile industry. The previous terms
refer to the use of equipment and processes which provide
13
Table 1-3 EPA average effluent limits set for textile mills [32].
14
_.
Table 1-4 Dalton Riverbend Wastewater Treatment Plant effluent limitations set for local industries including textile mills [32].
15
necessary pollutant reduction to keep a process within the
given pollution limitations. Under such regulations, if a
company can afford and needs a given treatment system, then
the EPA requires'*.the acquisition of such technology. As
previously mentioned, local authorities may also have their
own limits and guidelines for wastewater discharge which may
be more stringent than EPA values. Table 1-4 shows
limitations set by the Dalton Riverbend Wastewater Treatment
Plant which treats large volumes of textile industry
wastewater [32]. These values are fairly representative of
treatment plants processing textile wastewater.
Current Treatment Technolosies
Before selecting a treatment system for a wastewater
stream, a thorough investigation should be made of all options
available, their respective efficiencies, disadvantages and
-
of course, the economics involved. The following section
contains summaries of long-standing treatment systems, as well
as, the latest high technology removal systems. Both
preliminary and intermediate systems are discussed, as well-
as advanced treatment systems.
Preliminary Treatment
Screeninq. Wastewater flows through a grid type screen
which may be stationary or rotating (for easier cleaning and
maintenance). Textile industry wastewater often requires some
type of screening to remove solid wastes such as fiber and
16
yarn masses which can clog pipes and j am equipment gears.
Also, much of the solid waste from carpet mills consists of
nylon fibers which are not readily biodegradable, so it is
best to screen out 'these materials before any wastewater exits
the plant [l], [2].
Neutralization. The wastewater stream is adjusted to pH
6-9 (the average pH range required by local POTWs) using NaOH,
Na,CO,, H2S0 , or by passing the flow over limestone
derivatives. Adjustment is required before the wastewater can
be released to a waterway to reduce impact to existing
biological systems which are very sensitive to pH changes.
Also, local POTWs cannot accept water out of the pH 6-9 range
because 'it will kill off or inhibit growth of their biological
treatmeht systems. Acidic waste from indirect dischargers is
the largest category requiring a neutralization process [l],
121, 1301.
Equalization. The practice of sanctioning all
wastewaters to a given holding tank or lagoon where the water
is allowed to mix and dilute. Thus, any heterogenous mixture
of pollutants becomes more uniformly mixed, and the overall
strength is decreased by dilution. Neutralization. may also
be combined with this phase of treatment. The final
wastewater is then easier to treat by more advanced methods
which are usually less efficient in processing unequalized
waste. There will also be reduced shock to biological
treatment systems if the water is to be released to a local
17
.POTW
Heat Exchanse. Large amounts of water are used at
elevated temperatures in many textile processes. Heated
wastewater emptied into a stream can have very adverse
effects; raising or lowering the temperature even 2-3OC can be
detrimental to most marine life by denaturing proteins and
enzymes, as well as, reducing the dissolved oxygen capacity
of the waterway. Higher temperatures cause increased
respiration in bacteria further reducing oxygen levels.
Warmer water also enhances algal growth which tends to kill
off other biological systems by depleting oxygen and blocking
out sunlight. To reduce biological temperature shock, the
water can be processed through a heat exchanger which can
recover some of -the heqt energy for reuse [l]., [30].
Sedimentation. Particulates, fiber waste and organic
Dissolved matter are allowed to settle out in a holding tank.
air floatation may be used to remove by-products of wool
processing like grease and oils. Lanolin is recovered from
the grease as a marketable item 111, [2].
Disinfection. In wastewater flows having a high natural
organic content such as wool or cotton processing waters, the
biological activity may be cite high. Chlorination may be
usedto reduce bacteria levels. Wastewater with high bacteria
levels can reduce the oxygen content and disrupt the bacterial
composition of the receiving stream [l], [ 2 ] , [30].
18
Intermediate Treatment
Treatment Lasoons. Also called oxidation or
stabilization ponds, treatment lagoons are generally shallow
ponds approximately 2 to 4 ft in depth. The ponds may be
aerated mechanically or simply by surface exposure to air.
The algae Chlorella pyrenoidosa also releases 0, during
photosynthesis which is used for biochemical oxidation of
waste products. Nutrients (nitrogen and phosphorous) are
usually required along with long residence times ranging from
3-8 days. Land requirements may be economically prohibitive
depending on the size of the lagoon required. Although BOD
is reduced, many toxic compounds are not reduced due to
biological inhibition, and color reduction is variable [I],
123, 131, ~273. Activated Sludse. May be carried out under aerobic or
anaerobic conditions. Aerobic sludge digestion is carried out
under vigorous aeration. Huge quantities of bacteria, as well
as, yeasts, molds and protozoa take part in breaking down
organics to highly oxidized products. Proteins and other
nitroger, compounds are broken down to amino acids and finally
to nitrates. Alcohols and organic acids are oxidized to .co,
and H,O, as are carbohydrates and fats. Many textile process
chemicals fall into the formentioned categories making them
easy targets for removal. Some chemicals like aromatic dyes
are not easily broken down by the biological systems in
-
19
activated sludge so color removal may be poor. Continuing, the
settling process involves small particals called floccules
which are formed as filamentous bacteria like Thiothrix and
Nocardia form networks among the waste aggregates and
microorganisms. Excess amounts of filamentous organisms may
cause bulking which leads to poor settling, The entire
process may take 4 to 8 hours with considerable removal of
- suspended solids and BOD ranging from 7 0 to 97 %. Extended
aeration may be needed for stronger or more complicated
wastestreams with 2 4 hour or longer retention times. Aerobic
digestion can also be combined with PAC (powdered activated
carbon). The carbon is added to the sludge to adsorb organic
compounds. Biological activity develops on the carbon as
microorganisms beg-in to feed on the adsorbed materials, The.
carbon is continually reactivated as the biological activity
reduces the organic content of the carbon allowing it to
maintain adsorption capacity. This combination of treatment
systems allows for better organic constituents removal.
Anaerobic sludge digestion is used to a lesser extent.
The wastewater is broken down to organic acids by facultative
bacteria like Enterobacter and Pseudomonas . The acids are
further degraded by anaerobes like Methanobacterium and
Methanococcus. The anaerobes degrade the acids to large amounts
of methane (60 - 70 % ) and carbon dioxide (20 - 30 % ) . The
methane can be recovered for heating and operating power.
20
Complete digestion may take 2 to 3 weeks or longer with the
final wastestream containing incompletely oxidized products
c11, [21, 133, r271
Chemical Coasulation. Lime, aluminum salts, ferric
chloride, ferric sulfate, or calcium ions are used as
coagulants to help settle out solids, Coagulation aids such
as synthetic polymers are used if needed to improve
flocculation and settling. Most polymers used in flocculation
have molecular weights greater than 200,000 and often up to
several million. Figure 1-5 [ 1 3 ] shows one monomer unit of
9 polyacrylamide anionic polymer. This polymer is closely
related to the polyacrylamide polymer used in the experiments
of this study, The x and y values represent the mole
fractions of each copolymer and n is the number of monomer
units. The x value is at least 5 0 % . The A- is an anion and
R is an alkyl group. This polymer is produced by American
Cyanamid Co. for raw water clarification. Alternatively, a
process described by American Color & Chemical Corp. [12]
causes precipitation of metals in metallized azo dyes by
addition of Fe" from finely divided iron (80 mesh) at 2% by
weight based on solution weight. Color reduction ranged from
a factor of 4 to 20. In general, coagulation processes reduce
BOD, COD, color, heavy metals and suspended solids. However,
color reduction depends on the dye class and dye process
employed. Many variables (pH, chemical addition/type) must
be controlled to achieve the best degree of coagulation and
2 1
. .
-CH,-CH I I I
- CH2 1
c=o NH
I
-
X
Figure 1-5 An anionic polyacrylamide coagulation polym*::- [ I 3 1 -
22
settling making this treatment option highly susceptible to
variation in degree of efficiency. Also, mixed wastewater is
difficult to treat as different wastes may require different
chemical coagulants. In addition, the final sediment is a
sludge which must be disposed of through a separate solid
waste system creating an additional cost 113, [2], [3], [12],
c131-
Advanced Treatment Systems
When stringent regulation levels must be met, or if water
recycling is desired, various combinations of preliminary,
intermediate and advanced treatment systems are employed.
Figure 1-6 shows a schematic of possible combinations that can
be used to attain reusable water [2]. The following are brief
descriptions of those asvanced treatment options available to
plants that need a polishing treatment system.
Granular Activated Carbon fGAC). Water is passed over
a bed of activated carbon on which organics and dyes adsorb.
The activated carbon adsorbs up to 1/3 of its weight in
contaminants before residual chemicals can be detected after
treatment. However, naturally occurring organics in water can
reduce GAC adsorption capacity according to Kavanaugh [31].
Also, high molecular weight and nonpolar compounds are most
effectively adsorbed: however, disperse dyes (a principal dye
type for polyester) adsorb poorly. When the adsorption
capacity is exhausted, the carbon must be replaced or
regenerated by furnace treatment or steam heat. GAC is an
23
Effluent I
F i g u r e 1-6
I C ) boloncing
sedimenlotion Sedimentof ion
lrcotmcnt
Oischorgc Oischorge
Comhi nations of w a t e r t r e a t m e n t processes LISP.^ most frequently in industry 121 -
24
expensive capital investment and if regeneration equipment is
used, the cost increases tremendously as can be seen in the
cost analysis section [l], [2], [ 3 ] , [ll]. -
Ozonation. .Kavanaugh points out that GAC processes
transfer pollutants from one environmental medium to another
creating further disposal requirements [31]. Oxidation
processes such as ozonation can convert toxic constituents to
innocuous by-products at costs comparable to GAC. Ozone
treatment is very efficient in oxidizing organics and killing
bacteria, only hydrogen peroxide in the presence of
ultraviolet radiation is a stronger alternative. Klien
reports that preozonation enhances flocculation, reducing
chemical coagulant requirements by as much as 1/3 and can
increase sand filtratiop rates up to 50% [lo]. Also, complete
oxidation of organics to CO, and H,O is possible but not
usually carried out due to prohibitive costs. Instead,
oxidation to carboxylic acids, ketones and aldehydes is most
cost effective. The oxidized organics can then be removed by
GAC which becomes biologically active as the products serve
as metabolites €or microorganisms, thus increasing the useful
lifetime of the carbon [lo]. In any case, ozonation requires
considerable investment as ozone must be generated on site by
passing 0, or air through a generator which produces a high
voltage electric field across the air stream. Power
consumption during generation is approximately 20-25 watts/g
ozone. Treatment tanks are needed ranging in size from 2 to
25
4 m3 with good mixing required. Ozone treatment at a level of
4 5 mg/l will decolorize dye wastes but some degradation
products may be produced as shown in Figure 1-7 [ 5 ] in which
Gould and SaunderS studied the effects of ozonation on dyes.
Also, as ozone is toxic and corrosive, it must be handled with
care and excess off-ozone must be destroyed. Lastly, heavy
metals and solids usually require separate treatment El], [ 2 ] ,
r31, [ S I , [ l o ] , 1311-
Ion Exchanse Resins. Ion exchange resins remove dyes
from wastewater at 93% removal efficiency, using a cation
cellulose exchanger followed by an anion exchange resin.
McRae [9] describes ion exchange as, Ita process in which small
ions in a first liquid solution are exchanged for other small
ions of likecharge sign from a solid or from a second liquid
insoluble in the first liquid solution.@I Two types of ion
exchange resins are shown in Figure 1-8 [ 9 ] . The fixed charge groups are the sulfonate (A) and quaternary ammonium (B)
groups which do not migrate according to McRae [9 3 . The M+
and X- counterions can migrate freely and carry -current
through the membrane. Mobile ions having the same charge as
the stationary charges do not easily permeate the membrane.
The exchangers can be regenerated by treatment with NaOH
solution. Macroreticulated resins can also be used, but
require a methanol rinse to clean the resin; the methanol can
be distilled off and recovered for reuse. A l s o , most dyes are
effectively removed except for disperse dyes. One advantage
..
26
. .
u 0 f-
0 40 . 80 120 hm 2c3C 240
Ozone a x e ( m q [-&) . .
Figure 1-7 Total organic carbon vs. ozone dose to study dye destruction of Acid B l u e 40 [ 5 ] .
27
F i g u r e 1-8 Schematic representation of ( A ) a cation exchange resin and (B) an a n i o n exchange resin [ 9 1 -
28
is that the final treated effluent can be reused for dyeing,
and that initial investment costs for an ion exchange system
are about 40% less than activated carbon with roughly 70% less
operating costs 123
Ultrafiltration - Water permeates through polymeric
membranes under pressure. The membranes usually have an
average pore size of 1 to 100 nanometers. Ultrafiltration can
be used for desalination, purification and or sterilization
according to Lanigan 163. The pore size is usually adequate
to remove large organic molecules, polymers and bacteria. The
waste stream is forced under pressure through the membrane
yielding purified water on the other side. Figure 1-9 shows
ranges of various separation processes as compared to
ultrafiltration [31]. Also shown are the primary factors
affecting separation [31] . Ultrafiltration reduces BOD, COD, and color. However, the membranes foul easily and must be
cleaned often, and they are not sufficient to remove heavy
metals 113, 123, 161, ~311.
Reverse Osmosis. Also called hyperfiltration - can remove smaller species than ultrafiltration. This process
works by the passage of impurities through a cellulose acetate
based non-porous membrane ackoss a pressure gradient. The
impurities are trapped on one side of the membrane where the
effluent begins to concentrate; on the other side emerges
purified water which can permeate through the membrane to be
reused or discharged. Organics with a molecular weight
29
PRIMARY FACTOR AFFECTING SEPARATION
I 1 1 MICROSCREENS
SIZE
I ULTRA FILTRATION 1 I I
I I
I 1 I GRANUALR MEDIA FILTRATION I I SURFACE CHARGE/ V O L T A G E
.4 .3 - 2 1 0 1 2 3 4
LOG SIZE @m)
F i g u r e 1-9 U s e f u l r a n g e s of s e p a r a t i o n processes [31].
30
greater than 100 g/mole are rejected by almost all reverse
osmosis membranes. For molecular weights of less than 100
g/mole, selectivity is based on molecular structure and the
membrane material. that is used according to Rautenbach and
Janisch [ 8 ] , Composite polymer membranes are currently being
developed. Most membranes have a lifetime of about 5-10
years, The process involves a very expensive capital
-
investment and membrane maintenance 113, [23, [ 4 ] , [ 8 ] ,
Electrochemical Wastewater Treatment
Electrochemical water treatment was developed approximately
20 years ago in response to the need for a method to remove
toxic metal ions from wastewater. Toxic metals are produced
as a waste material ,in such processes as electroplating,
battery production, photographic development, cellulose
acetate production and dye chemical production [7]. The
efficiency of an electrochemical reactor depends primarily on
the amount of specific electrode area and the mass transfer
possible. The larger both properties are, the more efficient
the reactor [7]. Also, because the concentration of metal
ions in wastewater is usually very small, the metal
electrodeposition reactions are mostly diffusion controlled
[7]. The equation governing diffusion controlled limiting
current density is as follows:
i = K v, Fc (1-1)
which gives rise to the main formula used in the design of
31
electrochemical treatment reactors:
-. p = O c M a e k c (1-2 1
which shows that f m treating low concentrations of metals in
wastewater, a high specific electrode area a, and large mass
transfer coefficient K are needed. The preceding parameters
are defined as follows:
i = current density (A/cm2) k = mass transfer coefficient (cm/sec) V,= F =
'p = a= M = a,=
c =
However, reactor
electron number (1) Faraday number (As/mole) concentrat ion (mole/cm3) space time yield (g/cm3*s) current efficiency (1) molar mass (g/mole) specific electrode area ( cm2/cm3)
performance cannot be effectively
measured unless it is studied along with wastewater properties
like inlet concentration and conversion on which it depends.
To meet this need a normalized space velocity eq?iation is
best suited to characterize the performance of the reactor and
which gives the volume of wastewater in 1.0 cm3 fo r which
impurities can be reduced by a factor of 10 during a'residence
time of 1.0 sec in a reactor volume of 1.0 cm3. The values ci
and c, represent inlet and exit concentrations while v is
equal to the'' voidage and I equal to the current (1).
32
There are three main types of electrochemical reactors
that are designed to produce a large mass transfer coefficient
and provide a high specific electrode area. Kreysa [7]
describes the reactor types as those which:
The mass transfer rate and the current density can be
enlarged by setting the electrodes in motion by using
turbulence promoters.
Have multiple cathodes or extended cathodes to create a
large surface area in a small cell volume.
Use a three dimensional electrode to achieve high mass
transfer coefficients and large specific electrode areas.
Because the use of electrochemical precipitators in the
textile.industry is a relatively new application, examples of
each type of reactor will be provided so that those with
minimum knowledge in this area may see what additional
processes are available and possibly applicable to textile
wastewater treatment.
TvDe A Cells
..
Type A reactor cells include the pump cell, the Chemelec
cell, and the ECO cell. Also included are cells with
vibrating electrodes or electrolytes.
The pump cell [19] is shpwn in Figure 1-10. It consists
of two stator disc electrodes, also acting as endplates with
electrical connections. A bipolar rotating disc electrode is
mounted on a rotating shaft which runs between the endplates.
The electrolyte or wastewater flows through the central tube
FLOW
FLOW
MAGNETICALLY DRIVEN ROTOR RUNNING ON CERAMIC SHAFT
Figure 1-10 Schematic diagram of a b i p o l a r pump ce l l [ 1 9 ) . 1
W W
34
to the outer circumference of the rotating electrode. The
rotation of the electrode creates a high mass transfer
coefficient which can be increased or decreased by changing
the rotation speed. The residence time is determined by the
radial flow rate.
The Chemelec cell [203 is shown in Figure 1-11. It uses
a fluidized bed of glass spheres (fluidized by electrolyte
flow) to promote turbulence around the numerous electrodes
increasing mass transfer. Several stationary monopolar plate
electrodes are employed along with glass spheres averaging 1.0
mm in diameter. According to Kreysa, the mass transfer can
be increased up to a factor of six compared to the same
processes using laminar flow [7]. Chemelec cells are
currently used by the electroplating industry to remove metal
ions from rinsing waters, thus maintaining a constant metal
concentration in the primary rinsing bath which is continually
..
reused.
Another cell which uses a rotating electrode is the ECO
cell shown in Figure 1-12 [21]. Many reactors can only attain
a limited degree of conversion in a single pass, butthe ECO
cell uses consecutive baffles which create mini reaction
chambers through the course of the cell. One rotating
cylinder of about 50 cm diameter acts as the cathode to all
chambers. The wastewater successively flows through each
chamber almost eliminating back mixing effects while achieving
high degrees of conversion.
35
MESH ELECJ
-INLETS I
Figure 1-11 Schematic diagram of t h e Chemelec cell [20].
36
- catholyte c a t h o l y t e :a..i-i-r r r T T
-
/ b a f f l e pl a t e s
-. --.
ro t a t ing cy1 inder cathode O Q
-.
F i g u r e 1-12 Schematic diagram of the ECO cell [21].
.-.. $0 A 1_11_1_1_LI_L-
I -
37
TvDe B Cells
Type B cells are designed to accommodate a large
electrode area in a small cell volume. The electrodes are
generally stationary, but their large surface area makes up
for lack of motion. The multicathode cell, Swiss roll cell
and the ESE cell are examples of type B cells.
Multicathode cells like the one pictured in Figure 1-13
[22] are used in gold recovery. However, multicathode
stacking is limited by the fact that ohmic losses occur inside
the stack, thus reducing the penetration depth of the current.
The thickness of the electrode stack is limited to 5-10
electrodes, any additional electrodes will have very little
electrochemical activity and thus merely serve to increase
space requirements.
Another type B cell employs an innovative design which
uses an electrode wrapped helically around a core, this cell
is appropriately named the Swiss-roll cell pictured in Figure
1-14 Metal foil sheets separated by a plastic mesh are
wrapped helically around a core. The wastewater flows along
the electrode roll axis; the metals being removed by
deposition on the cathode foil. An acid wash is used to
remove metals and regenerate the foil. Large space time
yields can be obtained due to the large specific electrode
area.
[23].
Like the Swiss-roll cell, the ESE (Extended Surface
Electrolysis) cell also uses a rolled electrode, only using
38
0- D S A mesh anode
ion exchange membrane /
I I I I I I I 1 I I 1
t
anoly te was te w a t e r
mult i-mesh cathode
Figure 1-13 Schematic diagram of the multicathode cell [ 2 2 1 -
39
F i g u r e 1 - 1 4 Schematic diagram of t h e Swiss-roll cell [ 2 3 ] .
40
mesh electrodes instead of foil. With a mesh electrode three
dimensional exposure and radial flow can be achieved.
Industrially this type of cell is used successfully to remove
copper from electcoplating wastewater [ 7 ] .
Type C Cells
Type C cells use a three dimensional electrode structure
to increase the cell capacity, the mass transfer and increase
the specific electrode areas.
One unique design shown in Figure 1-15 [ 2 4 ] depicts a
porous flow through cell which uses cylindrical packed beds
of conductive particulate matter for both the anode and the
cathode. The wastewater enters the cell between the
electrodes, and actually enters the two electrodes through
porous plastic. Operational valves are used to adjust flow
rates such that 99% of the effluent moves through the cathode
while only 1% moves through the anode. Once the cathode is
filled with waste metal, the whole unit is turned upside down
so that the loaded cathode becomes the anode. The trapped
waste metal is dissolved anodically, and the wastestream
produced is a concentrated metal salt solution. The cell can,
therefore, be continually operated. -. Another type C cell known as the RETEC cell [25] is shown
enlarged in Figure 1-16. The RETEC cell cathodes are metal
sponge electrodes with an active surface area 15 times greater
than their geometric area. It is used in closed loop rinse
water systems by the electroplating industry to maintain metal
41
inlet
1 ,( diluted product h
concentrated
€
product
Figure 1-15 Schematic diagram of the porous flow-through cell [ 2 4 ] .
42
' AIR SPARGER THE RETEC-50 CELL
F i g u r e 1-16 Schematic diagram of the RETEC cell [ 2 5 ] .
4 3
particle inlct
P Onode
cathode fecdcr electrode
CQ t holy ie oui lei
I I cat holyt c o noly te
anolyte outlet
membra t-4 e
Figure 1-17 Schematic diagram of the fluidized bed cell [ 2 6 1 -
4 4
' concentrations at a reasonably low level.
Lastly, an example of a three dimensional exposure,
fluidized bed cell is shown in Figure 1-17 [26]. This cell
was designed by Goodridge and Fleischmann. The wastewater
flows from bottom to top fluidizing the loose bed of particles
as it passes through. The particles are charged cathodically
by a feeder electrode and metal ions are deposited
cathodically on the particles. The particles grow large and
heavy as they collect metal ions, thus causing them to migrate
to the lower part of the bed where they are removed. Fresh
particles are fed into the top of the bed. So, as the inlet
water flows upward, its metal content decreases. For
hydraulic reasons, the height of the cell is usually
restricted to about 2 m. To increase residence time, the
wastewater can be recycled through the unit or several beds
may be connected in a series.
Although electrochemical wastewater treatment is
primarily used for metals removal, interest has recently been
directed toward the study of its applications in textile
wastewater treatment. Andco Environmental Processes, Inc. of
Amherst, New York has recently begun research to determine the
effectiveness of their electrochemical treatment process and
its applications in textile wastewater treatment.
45
The Andco Treatment Process
Andco’s electrochemical treatment unit is most closely
A diagram related to the type B reactors described earlier.
of the Andco reactor is shown in Figure 1-18 1141. It
contains multiple electrodes, the exact number depending on
the reactor size. Andco produces several different size
treatment units depending on an individual’s treatment needs
determined the volume of wastewater produced. The Andco
Process uses sacrificial iron electrodes to produce ferrous
ions which are continually entering the wastewater as it
passes through the reactor. The ferrous ions co-precipitate
heavy metals as metal hydroxides. If present, dyes and
pigments are also adsorbed onto the iron matrix. A small
amount of high molecular weight, high charge density anionic
polymer is added to assist in floc formation by helping to
form large particles which settle out easier. A bottom sludge
of 1-2% solids forms: this sludge requires additional disposal
cost. Sludge production and investment costs will be
discussed later.
As a type B reactor, the influent enters at the bottom
of the Andco cell and is pumped upward between the egectrodes.
As the current flows from electrode to electrode, they begin
to dissolve into ferrous ions as given in the electrochemical
reactions below:
Anode: Fe ---- > Fe” + 2e-
46
Figure 1-18 Schematic diagram of the Andco Electrochemical Treatment cell [14].
47
Cathode: 2H,O + 2e- = H, + 20H- The sum of the reactions are as follows:
Fe + 2H,O + Electrical Energy = Fe(OH), + H, ..
The Fe(OH), forms HM'Fe(OH), where HM = Heavy Metals, and
pollutant'Fe(OH),. It is observed that like the process
occurring in electroplating baths, the anode dissolves as the
current is applied; however, instead of the metals plating out
of solution at the cathode, hydrogen gas production occurs at
the cathode. The hydrogen produced is not directly involved
in the flocculation process, but may interfere with the
flocculation process if it is not allowed to escape. For this
reason a hydrogen gas vent is built into the Andco reactor
design.
Heavy metals and organics adsorb well onto the ferrous
hydroxide matrix, because it has such an active surface.
Also, the process can be carried out at one pH. The ,Andco
Process is operated with the influent wastewater adjusted to
pH 7-9. The upper limit pH is actually determined by local
regulations on pH discharge limits. Figure 1-19 [14] shows
the solubility limits of some common metal ions. The given
values are for metals in pure water so their solubilities may
vary significantly in a mixed wastewater stream. Because each
individual metal has a minimum solubility at a different pH,
pH adjustment to force one metal to precipitate may adversely
effect the precipitation of another metal [14]. Ferrous
4 8
10
1.c
2- 0 e7
0.0 I
.I 0.031
4 i
/ €e+! It -\
/ v
- I O
1 \
I
- I
Figure 1-19 Solubility limits of some common metal ions [14I
49
hydroxide, fortunately, increases the span of pH's at which
metals will precipitate. It also disrupts the equilibrium
between dissolved and precipitated metals. As the ferrous
hydroxide removes. the metals, the dissolved metals remaining
are pushed to become insoluble to meet equilibrium
requirements.
The simplicity of this process and its ability to treat
highly variable waste streams make it a formidable candidate
among the forementioned variety of treatment systems
available.
Initial testing performed by Andco Co. at several pilot
operations using the Andco Electrochemical Treatment Process
has shown that several types of textile pollutants are reduced
to various degrees depending on the operational values used.
The following data are the results which Andco Co. has
obtained to date. These values will later be compared with
test values observed in this study.
Andco Environmental Processes, Inc. has reported that
their process efficiently reduces color, BOD, COD and heavy
metals in textile wastewater. Demmin and Uhrich of Andco have
reported efficiencies of 50-70% for BOD and COD reduction,
greater than 90% for color reduction, and 80-100% for heavy
metals reduction [ 3 ] .
Specific results have shown that BOD levels were reduced
by 30-55% as shown in Table 1-5 [ 3 ] . Additionally, COD values
were reduced 50-70% as shown in Table 1-6 [ 3 ] . As observed,
50
Table 1-5 Electrochemical treatment BOD reduction [ 3 ] .
Source Description Influent Electrochemical Effluent % Reduction BOD5(mdL) Iron(mg/L) BODS(mg/L)
Nylon dye mixture 96 100 containing GJ
sulfur, Md reactive
Cotton dye mixture 108 150 of vat, disperse,
Nylon carpet Mill # I 377 acid dyes Nylon carpet Mill d 2 41 I acid dyes Nylon carpet Mill 1 3 455 acid dyes
100
100
300
38
. 78
60
28
09 19 1
190 54
2 0 0 5 2
e .
51
Table 1-6 Electrochemical treatment COD reduction 133.
Source Description
Nylon carpet Mill # 1 acid dyes Nylon carpet Mil l 112 acid dyes Nylon carpet Mill 6 3 acid dyes Nylon carpet Mill Lc4 acid dyes
Nylon carpet Mil l 115 acid dyes Nylon dye mixture containing Cu Cotton dye mixture of vat, disperse, sulfur, and reactive dyes
Influent COD(mg/L)
1012
1017
11s1
1776 .
560
9 50
E lec t rochem ica I Iron(mg/L)
100
100
IO0 300
IO0
IO0
IO0
Effluent COD(mg/L)
436
556
526 466
685
174
332
% Reduction
57
4s
54 60 . 61
69
65
57s 150 205 .64
52
these values can be compared to data from Tincher [17] in
Table 1-7. The values in Table 1-7 were acquired from the
Dalton Riverbend Wastewater Treatment Plant, and they show the
percent reduction. in COD after treatment with the Andco
Process. Reduction values average 45-60%. Reduction levels
depend on the type of chemical being removed, its
concentration and the iron (mg/l) level added. It must be
pointed out that part of the tests were performed on actual
textile mill effluents, while the remainder were performed on
laboratory simulated mixtures and isolated stock chemicals.
A Color Graph double beam spectrophotometer was used to
test for color reduction. Color removal was demonstrated in
Figures 1-20 and 1-21 [ 3 ] . These two figures represent two
different reactive dye mixtures treated from different cotton
textile manufacturer's effluents. It was observed that the
% transmittance increased as the iron treatment level
increased. An increase in % transmittance corresponds to a
decrease in color intensity. Care should be taken to observe
the % transmittance at any given iron treatment level in the
region where the dye normally has its highest absorbance (or
lowest transmittance). In this way color removal is not
confused with the normal increases in % transmittance that
occur at various points in a spectrum characteristic for each
dye or colored constituent. Table 1-8 [ 3 ] provides an
absorbance reduction % for a variety of dyes and dye mixtures.
Absorbance readings were taken at the approximate maximum
53
Table 1-7
D y e h o u s e E f f l u e n t WTP I n f l u e n t WTP F f f l u e n t
COD reduction after electrochemical treatment ~ 1 7 1 .
C h e m i c a l Oxygen '6ZEiand
Before T r e a t . A f t e r T r e a t .
1017 1 1 5 1 575
5 5 6 5 2 6 223
X Red.
4 5 54 61
54
H I
MI
V
Figure 1-20 Electrochemical treatment color removal from red reactive dye mixture [ 3 ] .
55
..
l a
Ui.1
m.0
W.0 ,
a.0
I - /
F i g u r e 1 - 2 1 Electrochemical t r e a t m e n t co lo r r e m o v a l f r o a reactive dye m i x t u r e [ 3 ] .
56
Table 1-8
Source Description
1.
2.
3.
4.
5.
6.
Nylon dye mixture containing heavy metals
Cotton dye mixture of vat, diJperse, sulfur, and reacrive dyes
Beverage product natural coloring agenrs
Brilliant blue, fiber reactive dye (1: 1000 dilution)
Brilliant red. fiber reactive dye (1:lOOO dilution)
Acid red 106
7. Basic red 2
Electrochemical treatment color removal [ 3 ] .
Influent Color: Absorbance ( n d , pr-co Units o r mg/L
0.227 (400 nm)
0.373 (400 nm) 0.318 (465 nm) 0.418 (525 nm) 0.535 (600 nm)
7412 P t C o Units (465 nm) 7412 ”
180 ”
0.695 (400 nm)
6.00 (525 nm)
5.48 (532 nm)
100 mgIL
Electrochemical Resulting K Reduction Iron (mg/L) Effluent Color in Calor
(same units)
mo
I so
104 212 200
500
208
100 200
50 SO0
0.020
0.033 0.019 0.0 It 0.023
6769 770 SO
0.026
0.0 I I
1.72 0.069
62 m g h 10 mg/l
91
91 94 96 96
‘ 9
56
96
9o
99+
69 98
38 90
57
absorbance wavelength (nm) for each respective sample. The
iron treatment levels were varied resulting in different
degrees of color reduction. In general, the highe-r the iron
level added, the.higher the color removal. Also, color was
measured in Pt-Co Units or mg/l. These values can be compared
to Tincher's 1171 values for color reduction from dyehouse
effluent, WTP influent and WTP effluent in Table 1-9. It is
observed that at a certain maximum of iron treatment the color
removal does begin to "bottom off" and further treatment
produces no further pollutant or color reduction. Iron levels
of 200-500 mg/l remove color by approximately 90-98%.
However, at high iron addition levels, large amounts of iron
sludge are produced.
The original testing of textile wastewater performed by
Andco was done to test the efficiency of heavy metal removal
from rinse water containing premetalized dyes from the
manufacture of automotive upholstery. It was during this
testing that Andco discovered its process had possible
applications in the treatment of other textile wastewater
components like BOD, COD and color. Table 1-10 [ 3 ] shows the
increasing degree of heavy metal removal of Cr, Cu and Co with
increasing levels of electrochemically generated iron. At 4 0 6
mg/l of iron, reduction values were 98%-99.9%. At very low
concentrations of the metals, analytical error increases due
to the detection limits for the metals.
58
...
Table 1-9 Absorbance values before and after electrochemical treatment with percent reduction of absorbance 1171.
Absorbance Before Treatment
6 1 0 - 5 10 - 4 1 0 - 250 220
Dyehouse E f f l u e n t WTP I n f l u e n t WTP E f f l u e n t
Dyehouse E f f l u e n t WTP I n f l u e n t WTP E f f l u e n t
Dyehouse E f f l u e n t WTP I n f l c e n t WTP E f f l u e n t
0.050 0 . 0 7 2 0 . 1 3 3 0 . 8 8 1 2 .23 0 .056 0 . 0 8 1 0 . 1 4 4 1 . 3 1 2 .80
2.85 0 . 0 5 3 0 . 0 7 9 0 . 1 4 4 1 . 2 5
Absorbance A f t e r Treatment
- 610 - 5 1 0 ' 410 - 2 5 0 - 220
0 . 0 0 0 0.000 0 . 0 1 8 0 . 3 3 1 0 . 8 6 0.031 0 . 0 5 4 0.102 0 . 8 3 0 1.71 0.006 0.016 0 . 0 3 6 0 . 5 6 2 1 . 1 9
Per Cent Reduct ion i n Adsorbance
610 - 5 1 0 - 4 1 0 2 5 0 220 ..
100 1 0 0 86 6 2 61
8 9 8 0 7 5 55 5 8 4 5 3 3 2 9 3 4 39
59
Table 1-10 Heavy metal removal w i t h increasing l e v e l s of electrochemically generated iron 131.
Table VI: Heavy metal removal with increasing levels of electrochemically generated iron
I !
Electrochemical Iron (mg/L)
0 142 174 206 273 318 406
Cr g l s m
1920 370 260 260 210 150 50
cu o l d )
820.0 2.0 3.6 3.6 4.0 2.2 1.8
co @€!A)
1090 20 10 10 4 3 2
60
Demmin and Uhrich report that the mechanism for removal
of contaminants from wastewater by electrochemical treatment
is not fully understood. It is thought that various organic
and inorganic species adsorb onto the ferrous hydroxide matrix
as it forms in the electrochemical cell. Assuming that
equilibrium is attained during treatment, Demmin and Uhrich
report that "data from adsorption phenomena often follow the
Freundlich isotherm equation1# [ 3 ] . Mathematically the
Freundlich isotherm equation is given by
q, = KFCe""
where q, is the weight of contaminant adsorbed/weight of
adsorbent (the reduction of contaminant per mg/l iron added.
Also, Ce is the final equilibrium of contaminant (the final
contaminant level), KF and n are constants.
In Ce yields a straight line relation [3].
Plotting In q, vs.
Demmin and Uhrich explain that although not all
contaminants are necessarily removed by adsorption, data
support that heavy metals are removed in this manner. They
also emphasize that to konclusively prove that adsorption is
occurring, extensive and controlled laboratory tests will need
to be performed [ 3 ] .
CHAPTER I1
RESEARCH.OBJECTIVE AND EXPERIMENTAL DETAILS
The goal of this research was to evaluate the
effectiveness of the Andco Electrochemical Treatment Process
and its applications in textile wastewater treatment. A pilot
unit was set-up in the Textile Engineering Department and test
samples were developed by using laboratory simulated textile
wastewater. The research was divided into four principal
sections. First, a study to determine how effectively the
Andco Process reduces chemical oxygen demand (COD)
concentrations for certain types of textile wastewater.
Second, a study using an absorption spectrophotometer to
determine the extent of color removal of various acid dyes.
Third, a study to determine if exhausted dyebath water can be
reused after treatment by the Andco Process. And fourth, a
study to determine whether dyes are removed by adsorption
alone, or if they are chemically altered in sdme manner by the
treatment system.
Experimental Methods and Procedures
Andco Pilot Unit (M-Cell) Operation Procedure
The M-Cell is a small portable test unit used to simulate
the operation of full scale systems. The M-Cell contains an
electrochemical cell consisting of two 1/8 inch cold rolled
62
steel plates separated by an 1/8 inch gap. The steel plates
act as electrodes which carry a current provided by a D.C.
power supply, which is connected across the end electrodes.
The current passes from electrode to electrode through the
wastewater stream that flows through the 1/8 inch gap. As the
current flows, the electrodes dissolve putting ferrous ions
into the wastewater [14]. For the duration of this study, the
wastewater was continually recycled through the unit instead
of making a single pass. This allowed greater freedom to
study efficiencies at different iron levels. The circulation
time required to achieve a given iron level was calculated
using the following equation [14]:
Time = Volume (sal) rDesired Iron Level ms/ll .2175 (min) Current (AMPS) (2-1)
Any value calculated having a decimal value such as 3.50 can
be changed to minutes and seconds by multiplying the number
following the decimal by 60 sec (ie 3.50 = 3 min 30 sec)
This value is the recirculation time required to put the ..
desired amount of iron into the sample. Care must be taken
to account for the volume loss after each sampling. One must
also remember that the iron accumulating in the sample is
additive. Sample calculations for iron levels from 50 to 650
mg/l are shown in Figure 2-1. The volumes are given in
gallons. The quantity of each sample taken is approximately
500 ml and the amperage is kept constant at 13 Amps (although
6 3
FORA C0N"OUS SERIES OF IRON IEVELS FROM 50 MG/L TO 650 MG/L IRON LZVEL
1) [( 3.16 gal )( 50 mg/Liron )( 0.2175 11 / 13 amps = 2.64 --> 2min.. 39 sec
2) [( 3.03 @)(lo0 *Limn)( 02175 )I / 13 amps = 5.07 ---> 5min.. 4 sec
3)[( 2.89gal )(lo0 mg/Liron )( 0.2175 11 / 13 amps = 4.84 -> 4min.. 51 sec
4)[( 2.79@)(100 mg/Liron)( 0.2175 )I / 13 amps = 4.62 ---> 41Ilin.. 32 sec
5)[( 2.63@)(100 mg/Liron )( 0.2175 I1 / 13 amps = 4.40 -> 4min.. 24 sec
6)[(2.5Ogal)(100mg/Liron)(0.2175)] / 13 amps =4.18 ---> 4min.. 11 sec
7)[( 237gal )(lo0 mg/Liron)( 02175 )I / 13 amps = 3.96 -> 3min.. 58 sec
nrrALTLME . 29MIN..39SEC
FORA SIN= SAMPIE WITH A RJ3QUlRED IRON UXEL OF 6!5OMG/L :
8)[(3.16gal)(650mg/Liron)(O.2175)1/ 13amps =34.37 --> 34mh.22sec
Figure 2-1 Sample calculations for electrochemical iron addition.
64
the amperage value can be changed if desired). Lowering the
value of the amperage increases the waiting time required for
each sample to reach a given iron level. The ttM1l-cell should
not be operated at a current higher than 15 Amps. The water
flows through the reactor cell from bottom to top at a rate
controlled by a flow control valve. Exiting water appears as
a muddy dark-green liquid due to the ferrous ion; however,
after exposure to air during the recirculation process, a
portion of the ferrous ion oxidizes to the ferric state giving
the water a dark black and finally a rust colored appearance.
After flocculation and clarification, the water will be clear
and the metal hydroxides will be collected as a sludge.
The amperage of the ttMtl-cell can be adjusted using the
voltage knob which is calibrated in percent of maximum output
voltage. The maximum output is 4 5 volts. An ammeter and
voltmeter are provided on the control panel so that the
current and voltage across the cell can be monitored. The
voltage at a given amperage depends on the conductivity of the
wastestream. The higher the conductivity, the lower the
voltage requirement needed to attain a given amperage. A
small amount of salt (approximately 1-3 grams) may be added
to low conductivity waste streams to reduce voltage
requirements or to attain a higher amperage. Lastly, the I 1 M 1 l
cell requires a 120 volt, 1 phase, sump power connection.
Before any samples are passed through the machine, it
Large scale units require one ten minute must be acid washed.
65
acid wash everyday; however, due to the nature of the
analytical tests being performed, the pilot unit was acid
washed between each major chemical change (ie between two
different dyes or chemicals) and tapwater rinsed between each
concentration change within 'a series of tests on any one
chemical. The acid wash consists of 15-17% hydrochloric acid
solution totaling 6.0 1 which is pumped through the machine
for 10 minutes at 13 amps. The acid wash is followed by a
tapwater rinse lasting about 2-3 minutes.
Sample Preparation for the llM1l-Cell Unit
Through the entire course of this research, the sample
volume used in each experiment was 12 liters or 3.16 gallons
unless otherwise indicated. The sample bucket which is
attached at the base of the llM1t-cell was calibrated and marked
at 12 liters for testing convenience. Each sample treated by
the unit was calculated for concentration in mg/l. Sample
chemicals were mixed directly into the 12 liters of distilled
water in the sample bucket (distilled water was used for all
samples tested except when otherwise indicated). In each
case, a small aliquot (approximately 50 ml) of stock solution
was taken as a control sample future testing and comparison
with treated samples.
The operation manual [14] suggests pH adjustment of the
sample prior to treatment in the range of pH 7-9 [14].
Caustic NaOH solution and H2S0, solution were used for pH
adjustment; for consistency of test procedures each sample was
66
adjusted to pH 8.3-8.5 before treatment. Also, in almost all
cases some salt ( ' about 1 to 3 g NaC1) was required to
increase the conductivity, and thus, achieve the desired
amperage. The flow was started and water circulated before
the voltage is applied- This allows for flow adjustment (1.5
- 2 gallons/minute was used as the procedure flow rate). A
stopwatch was used to monitor the recycle time. The start up
time actually began when the amperage was turned on and the
electrodes began to dissolve. All times were monitored
starting at this point. When the first iron level was
reached, the amperage was cut off and the water allowed to
circulate for 1 minute to create a uniform iron level in the
sample bucket. A 500 ml sample was collected in an Erlenmyer
flask directly from the exit tube. The amperage was turned
on and recycling continued until the next iron level was
attained, at which time the next sample was collect as above
and so on until samples of all desired iron levels had been
acquired-
Each flask was labeled with its sample type and iron
level. After the sample was taken from the machine, its
llexitvv pH was recorded using a digital pH meter. Also,
hydrogen bubbles created during the treatment process were
allowed to degas, occasional mixing accelerated the degassing
process.
Once no bubbles were visually present, the sample was pH
adjusted to approximately pH 8.8-9.2 before polymer addition.
67
During the course of experimentation it was found that
different chemical samples flocced best at a characteristic
pH which was determined through trial and error. The polymer
used for all samples was an anionic polyacrylamide copolymer
type 3640 manufactured by Aries Chemical, Inc. A 0.2%
solution of the polymer was used to flocculate the samples.
Roughly 0 . 2 5 to 2 . 5 ml of polymer was required to flocculate
a 500 ml sample. The amount of polymer added was not closely
monitored until it became suspect in contributing
significantly to COD and TOC measurements, after which exact
polymer additions (ml) were recorded. After polymer addition,
floc formation was usually observed followed by a settling out
process. The clear surface water was decanted into a beaker
and then filtered through glass wool to remove iron
particulates. Filtered samples were stored in glass bottles
and refrigerated until applicable tests could be performed.
Also, the machine was rinsed out with tapwater after sample
collection was complete. A- picture of the Andco 18Mt8-cell unit
is shown in Figure 2-2 [14]. -.
Analytical Testins Procedures, Methods and Equirsment
Chemical Oxysen Demand Studv -.
One of the main tests performed on almost all of the
samples was a COD or chemical oxygen demand test. This test
measures the amount of oxygen needed to oxidize any organics
or oxidizable inorganics to CO, and H,O. This is not to be
89
69
confused with the BOD or biological oxygen demand which
measures the amount of oxygen required by microorganisms to
break down biodegradable compounds in a standard time of
usually 5 days. The COD is a more comprehensive value taking
into account both biodegradable and nonbiodegradable
..
oxidizable constituents. CODtests were performed on both the
sample stock solution before treatment and the samples taken
after treatment as described earlier. COD tests were run on
stainblocker chemicals, dyes, auxiliary chemicals, distilled
water and blank samples.
The COD test is a titration experiment. Titrants of
varying degrees of strength were prepared in an attempt to be
"in range" for the variety of chemicals used and their
respective COD ranges. The COD test -method was taken directly
from the EPA manual Methods For Chemical Analvsis of Water and
Wastes [15]. For samples having high COD'S the titrants used
in the method were strengthened to increase the COD test
range. Likewise, for low COD samples, the titrants were
diluted to increase the accuracy of the volume determination.
Stainblocker chemical samples and auxiliary chemicals required
medium to high strength titrants while dyes and distilled
water required low strength titrants.
COD Method and Procedure. Organic constituents in the
sample are 'oxidized by potassium dichromate in a 50% (by
volume) silver sulfuric acid solution. Silver sulfate serves
as a catalyst and mercuric sulfate is added to remove any
70
chloride interference. The excess potassium dichromate is
titrated with standardized ferrous ammonium sulfate using
orthophenanthroline ferrous complex (ferroin) as an indicator .. 1151 .
High level COD tests were used for older stainblocker
chemicals and auxiliary chemicals. The high level test has
a maximum range of 1000 mg/l COD. The high level titrants
were prepared as follows:
1 ) Potassium dichromate titrant 0.25 N was prepared by
baking 12.84 g of K2Cr,07 at 14OoC for two hours to remove
moisture and then dissolving in a 1000 ml volumetric
flask with distilled water and mixing.
2 ) Ferrous ammonium sulfate tirant 0.10N was prepared by
adding 39.00 g of ferrous ammonium sulfate to a small
amount of distilled water in a 1000 ml volumetric flask
9
with swirling and addition of 20 .0 ' ml of concentrated
sulfuric acid. The titrant was then diluted to the mark.
COD SamDle PreDaration
1) In a clean 500 ml ground glass Erlenmyer flask was placed
U.4g Of Hg2S04 (mereuriz: Sulfate) fclllowed by 20.0 ml Of
sample water and 10.0 ml of K2Cr207 0.25 N titr'ants.
The flask was placed in'.an ice bath to reduce fuming as 2 )
3 0 . 0 ml of H2S04.AgS04 solution was added.
boileezers were added and the solution was mixed.
Several
3 ) The flask was connected to a condenser over a hot plate
as shown in Figure 2 - 3 . The solution was slowly brought
71
Outlet
. . , ,I1(.Reflux Cond I .
ensor
+Water I n J e t
\ 500 ml Erlenmyer Flask
,g Hot Plate
Figure 2-3 Schematic of COD test appara tus .
72
to a boil and allowed to reflux for 2 hours before being
allowed to cool to room temperature.
4 ) Once the oxidized solution was removed from the COD ..
apparatus, the volume was brought up to 150 ml with
distilled water.
5) Six drops of ferroin indicator was added and the sample
was titrated with ferrous ammonium sulfate 0.10 N
titrant.
blue-green to a reddish hue was recorded.
The ml needed to achieve the color change from
With each set of COD tests performed, a blank of
distilled water was tested. The blank was prepared in
the exact manner as a normal sample except that the 10.0
ml of sample volume was substituted with 10.0 ml of
distilled water. The blank was titrated and the volume
included in the final COD calculation to subtract off
background contamination. The equation used to calculate COD
concentration is given below [15]:
COD, mg/l = 1A-B) N x 8000 c2 -21 S
C .
Where
A = Milliliters of Fe(NH,),(SO,), required for titration of the blank.
B = Milliliters of Fe(NH,),(SO,), required for titration of the sample.
N = The Normality of the Fe(NH,)2(S0,)2 titrant.
S = Sample volume used in the test (ie 10.0 ml)
8,000 is a constant value
7 3
The medium level COD test used for reduced COD
stainblocker chemicals has a maximum range of 500 mg/l COD.
All sample preparation for this test is identical to the high
level test except that the titrants used are 0.05 N ..
Fe(NH,)2(S0,)2 and 0.125 N K2Cr207.
The low level COD test used for dyes and distilled water
blanks (run through the rrMrt cell with polymer addition) has
a maximum range of 250 mg/l COD. Note must be made that the
distilled water blanks run through the IrMrr cell are test
samples which are not to be confused with COD distilled water
reference blanks. As above, all sample preparation remains
the same except that the titrant strengths used are 0.025 N
Fe(NH,)2(S0,)2 and 0 . 0 6 2 5 N K2Cr20,.
The titrants were kept refrigerated and were used for no
more than two weeks before discarding and preparing fresh
titrants. A standardization of the titrants was carried out
before the titrants were used in any COD tests. ACS grade
0.025 N K,Cr,O, standard solution was used to standardize the
Lab prepared ferrous ammonium sulfate. A back titration wag
then carried out to determine the normality of the lab
prepared K,Cr,07. The normality was calculated 'using the
following relation [15]:
where N = Normality. ( 2 - 2 )
7 4
tests were run on the following samples:
Stainblocker A - 0.1 g/l, 0.3 g/l, and 0.6 g/l, solutions. The high level test was used.
Stainblocker A - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 200, 400, 500 and 650 mg/l iron addition. The high level test was used.
Stainblocker A - 1.0 g/1 stock solution and 1.0 g/1 solutions treated at 500 and 650 mg/l iron addition. The high level test was used.
Stainblocker D - 1.0 g/1 stock solution and 1.0 g/1 solutions treated at 150, 250, 350, 450, 550 and 650 mg/l iron addition. The high level test was used.
Stainblocker D - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 550 and 650 mg/l iron addition for each. The high level test was used.
Stainblocker D - 0.6 g/1 solutions treated at 550 and 650 mg/l iron addition, however, with only settling (no polymer addition to achieve floc). The high level test was used.
Stainblocker B - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 450, 550, and 650 mg/l iron addition. The medium level test was used.
Stainblocker B - 1.0 g/1 stock solution and 1.0 g/1 solutions treated at 450, 550 and 650 mg/l iron addition. The medium level test was used.
Stainblocker B - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 450, 550 and 650 mg/l iron addition. the medium level test was used.
Stainblocker C - 1.0 g/1 stock solution and 1.0 g/1 solutions treated at 450, 550 and 650 mg/l iron
Stainblocker C - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 450, 550 and 650 mg/l iron addition. The medium level test was used.
Irgalev A - 0.3 g/1 stock solution. was used.
Irgalev A - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 250, 350, 450, 550 and 650 mg/l iron addition. The high level test was used.
addition. The medium level test was used.
The high level test
75
Irgalev A - 0.9 g/1 stock solution and 0.9 g/1 solutions treated at 250, 350, 450, 550 and 650 mg/l iron addition. The high level test was used.
Irgalev A - 0 . 8 g/1 stock solution and 0.8 g/1 solutions treated at 25.0, 350, 450, 550 and 650 mg/l iron addition. The high level test was,used.
Guar Gum - 0.6 g/1 stock solution and 0.6 g/1 solutions treated at 250, 350, 450, 550 and 650 mg/l iron addition. (This test was performed twice). The high level test was used.
Guar Gum - 0.3 g/1 stock solution and 0.3 g/1 solutions treated at 250, 350, 450, 550 and 650 mg/l iron addition. The high level test was used.
Distilled Water - Distilled water treated at 50, 150, 250, 350, 450, 550 and 650 mg/l iron addition with carefully measured polymer addition (to assess residual polymer COD contribution to treated samples). The low level test was used.
Acid Dye Mixture - Acid Blue 277, Acid Red 361, Acid Orange 156, 25 mg/l stock solution and 25 mg/l solutions treated at 50, 150, 250, and 350 mg/l iron addition. The low level test was used.
Acid Dye Mixture - Acid Blue 277, Acid Red 361, Acid Orange 156, 50 mg/l stock solution and 50 mg/l solutions treated at 50, 150, 250 and 350 mg/l iron addition. The low level test was used,
Acid Red 361 25 mg/l stock solution and 25 mg/l solutions treated at 50, 100, 150, 250, 350 and 450 mg/l iron addition. The low level test was used.
Acid Red 361 50 mg/l stock solution and 50 mg/l solutions treated at 50, 100, i50, 250, 350 and 450 mg/i iron addition, The low level test was used.
Procion Blue MX-2G 25 mg/l stock solution and 25 mg/l solutions treated at 50,;100, 150, 250, 350 and 450 mg/l iron addition. The low level test was used.
Procion Blue MX-2G 50 mg/l stock solution and 50 mg/l solutions treated at 50, 100, 150, 250, 350 and 450 mg/l iron addition. The low test was used.
76
All samples were prepared from 1.0 g/1 stock solutions of the
desired chemicals. Concentrations were calculated as the
number of ml of 1.0 g/1 stock in the 12 liter volume required
for each lot to be run through the Andco "M" cell. Before
treatment, a small sample of the mixture was recovered and
stored to serve as the standard. So, for a 25 mg/l dye l o t ,
300 ml of 1.0 g/1 dye solution is diluted in the Andco bucket
to 12 1. The sample taken before treatment is approximately
25 mg/l and serves as the standard stock solution.
In addition to the COD test, the total carbon (TC) test
was run on several selected samples of stainblockers, dyes,
and blanks. The TC apparatus uses very high temperatures,
( 1600°F in this set of tests) to oxidize carbon containing
organics and inorganics to carbon dioxide which passes through
an infrared light detector similar to an IR spectrophotometer
except instead of scanning a field of wavelengths there is
only one wavelength studied. That wavelength corresponds to
the carbon dioxide stretch and so senses and quantifies the
amount of carbon present as CO,. The amount present is
proportional to the peak height and must be compared to peak
heights produced using potassium hydrogen phthalate -standard.
Peaks of the same sample that are within & 2 chart divisions
of each other denote good reproducibility within the data.
The chemicals used and the TC values obtained are given in the
results and discussion section.
77
Both stock solutions and treated samples were tested to
observe total carbon reduction with treatment.
Total carbon testing was performed on the following samples:
Acid Dye Mixture - Acid Blue 277, Acid Red 361 and Acid Orange 15 mg/l stock solution and 25 mg/l solutions treated at 50, 150, 250 'and 350 mg/l iron addition.
Acid Dye Mixture - Acid Blue 277, Acid Red 361 and Acid Orange 25 mg/l stock solution and 50 mg/l solutions treated at 50, 150, 250 and 350 mg/l iron addition.
Distilled Water run at 0, 50, 150, 250 and 350 mg/l iron addition with polymer addition.
Acid Blue 40 25 mg/l stock solution and 25 mg/l solutions treated at 50, 150, 250 and 350 mg/l iron addition.
Stainblocker D - 0.6 g/1 stock solution and 0.6 g/1 stock solutions treated at 550 and 650 mg/l iron addition, two sets were tested, one with just settling (no polymer addition) and one with floccing.
Color Removal Study
A Varian Cary 219 spectrophotometer was used to perform the
color removal evaluation tests. Only dye samples were tested
as they are the major color contributors in textile
wastewater. In addition to the dye samples, distilled 'water
blanks were run through the Andco Treatment Process following
the selected procedures. In this case, the spectrophotometer
was used to detect color contribution from the iron
hydroxides. An attempt was made to subtract off this color
from dye color measurements obtained at the same iron
treatment levels.
Absorbance values were recorded at the principal
These wavelengths used in dye detection 410, 510 and 610 nm.
78
are the maximum absorbance wavelengths of yellow, red and blue
dyes respectively. Initial testing was performed on four
different dyes, Acid Blue 277, Acid Blue 40, Acid Red 361 and
Acid Orange 156. . Standards were prepared of each dye at 5
mg/l, 10 mg/l and 20 mg/l. Using the recorded absorbance
values, a linear regression was done by computer and formulas
were developed for each dye. The formulas can be used tc
calculate the existing concentration of any one of the four
dyes in a mixture given the absorptions at the three
wavelengths. This is very useful in observing the individual
reduction percents of dyes in a mixture as they pass through
a treatment system. Alternatively, dye mixtures of the three
acid dyes were also prepared at 15, 25 and 50 mg/l
concentrations and formulas were developed to study overall
dye reduction (color removal) as opposed to individual dye
concentrations. The mixtures were run through the Andco Unit
and absorbance values were measured at 410, 510 and 610 nm.
These values were used in the previously calculated formulas
to determine remaining dye concentration in mg/l. The Acid
Blue 4 0 dye was treated separately, at 25 mg/l sample
concentration, and its own calibration curve and emation was
developed. Absorbance value's were measured at 610 nm, the
maximum absorbance for blue. The Acid Blue 40 dye was tested
individually to observe its treatment behavior with the Andco
Process because it has recently been added to the Interagency
Testing Committee Priority List [ 4 ] . Also, Procion Blue MX-
79
2G was treated in the Andco Unit at sample concentrations of
25 and 50 mg/l with varying iron levels, Lastly, through the
course of this study, several sets of distilled water blanks
were run through the Andco Unit for various comparisons of
iron color contribution. Although some of the iron levels
used in treatment varied from lotto lot, the distilled water
lots were compared to check reproducibility of iron color,
Dvebath Water Reuse Studv
In recent years the southeast has experienced record
setting droughts. Textile industries in the southeast have
experienced strains on production as they have been plagued
with water restrictions and higher pollution standards. Water
conservation and reuse pethods for all aspects of the textile
industry are being developed and put to practical use, One
possibility existing with the Andco Treatment Process is that
the treated water has reuse potential. Chemical removal with
the Andco Process ranges from about 50-100% depending on the
type or combination, as well as, the concentration of
chemicals present. Any residuai chemicals, iron or polymer
remaining in the treated water may have a significant effect
on the dyeability of process materials. This study
investigated the effects of dyeing materials with exhausted
dyebath water treated with the Andco Process. The iron
treatment levels were varied to study variation in dye uptake
and shade matching with control samples dyed in tapwater.
80
Also, some dyeings used treated dyebath water containing
residual dyes, stainblocker chemicals and other- auxiliary
chemicals, these samples were ref erred to as ltspikedll samples.
During the residual dyebath water testing, the absorbance
spectrophotometer was employed to test absorbances of the
exhausted dyebaths. The absorbances were compared to see if
the material samples had taken up equal amounts of dye from
the dyebaths. However, in most cases the exhausted dyebath
was still so concentrated with dye as to be off scale. At
this point, the most likely alternative for testing dyeing
similarity was the colorimeter. This method is more accurate,
in any case, for the type of test to be done. That is,
reflectance measurement of the material samples would be a
more accurate and direct method of color measurement than
measuring residual dyebath color. After all, dye removed from
the bath may come off the sample during rinsing. Color
measurements using an ACS Spectro Sensor I1 spectrophotometer
were taken of the samples to determine how close the
experimental materials were in shade to the standard materials
dyed in untreated tap water. Procedure *.
Two acid dyes used previbusly in this study were used for
the dyebath reuse tests, as well as one direct dye. The three
dyes were Acid Blue 277, Acid Red 361 and Procion Red MX-5B
RR-2. Stock solutions of 1.02 g/1 were prepared and 20 mg/l
solutions of each were treated with the Andco Process at
81
various iron levels. The Acid Blue 277 was treated at 197
mg/l and 283 mg/l of iron; 1800 ml samples were taken at each
iron level for the first dyeing set. A second sample of A.B.
277 was treated at'121, 207 and 287 mg/l of iron and 20 mg/l
dye concentration. Again, 1800 ml samples were taken and the
treated water was used in the second set of A.B. 277 dyeings.
The Acid Red 361 and Procion Red MX-5B RR-2 were treated at
121, 207 and 287 mg/l of iron and 1800 ml samples were taken
at each iron level. An identical sample of A.R. 361 as above
was treated at the same iron levels and the treated water was
used in the second set of A.R. 361 dyeings. Also, 100 ml
samples of each 20 mg/l dye solution were taken before
treatment as references and for absorption measurement.
Absorption data was collected on all sample stock solutions
and iron level samples at 410, 510 and 610 nm.
The Beer-Lambert equation was used to calculate the
concentration of dye present after treatment at each iron
level. The equation is given as follows:
A = abc (2-3)
Where A is the absorbance, a is the absorptivity coefficient
at a given wavelength, b is the path length (cm) and c is the
concentration of the sample. The lat value was calculated
using the absorbance value of the stock solution for each
sample at its primary absorbance wavelength which corresponds
to 510 nm for the red dyes and 610 nm for the blue dye. The
82
use of a single data point from one concentration to calculate
the absorptivity is not a standard procedure. A -chemical Is
absorbance may not increase linearly with concentration so a
single measurement at one concentration mat not be valid. ..
Therefore, there is a considerable error that may be
introduced in this particular experiment, After realizing the
procedural error, an attempt was made to determine if the
absorptivities calculated in this experiment were valid.
Solutions of 3, 10 and 2 0 mg/l of both the red and blue dyes
were prepared respectively and their absorbance values
recorded at the forementioned wavelengths. The absorptivities
were calculated using a computer generated linear regression.
The calculated absorptivities were then compared with the
original absorptivities to see how much the initial
measurement varied and how it affected the calcultions that
followed. It was found that the error in the original
measurement was off by approximately 0.1 to 0.2% which was
considered to be negligible. Given the measured absorbance
values for the treated water and using the less precisely
calculated l a o value, t h e existing concentration of residiral
dye was calculated. Knowing the existing resldual dye
concentration of the treated water allowed the development of
a reconstituted dyebath which incorporated the residual dye
with the add:ition of fresh dye and auxiliary chemicals. Nylon
6,6 270'F Superba heatset carpet yarn (5.0 t 0. lg) was used in
the experiments using the acid dyes, while scoured cotton
83
fabric (10.0 2 0.1s) was used with the Procion dye. All
dyeings were carried out in 600 ml beakers started at 60 C , with heating to 100 C and dyed for 30 minutes with stirring.
The samples were ‘.‘removed, rinsed with tapwater and labeled.
All nylon yarn dyeings had a p H of 10.2 except those that were
spiked, which had a dyebath p H of 10.4. The cotton dyeings
had a p H of 7.4. Also, all volumes were measured with
graduated pipets and/or volumetric flasks to increase volume
accuracy; however, the small dyebaths used were by nature,
very susceptible to large variance in final chemical
concentration. Even a small drop of unintentionally added
chemical or dye can greatly affect the final dyebath
concentration. Full-scale dyebaths would have been affected
much less by small differences in chemical addibon and would
have produced much more conclusive information about dyebath
reuse; however, the Andco ttM1t cell was not practical for use
in large scale testing due to its small size. The small-scale
beaker dyeings were used as an indicator to determine if
further testing and/or full-scale dyeing tests should be
pursued. The following dyebaths were prepared:
A . B . 277 Dyeinq #1
Control Dvebath.
30 : 1 Liquor Ratio for 5.0 + 0.1 g nylon 6,6 Superba
270°F heatset yarn = 150.0 total volume
4 . 0 % ammonium sulfate owf = 0.2 g = 10.0 ml of 2 0 g/1
stock soh.
84
1.0% ammonium hydroxide (28%) owf = 1.5 ml (1.0% X
150ml)
Tapwater to make 150 ml volume (= 88.5 ml)
Residual Dve.Content Calculation*. ..
Iron Level
Sample mg/l
197 mg/l : 0.0246 = (0.0095) (1 cm) (c)
c = 2.59 mg/l -->0.003 mg/ml --> .
0.003 mg/m1(88.5 ml treated water) = 0.30 mg
283 mg/l : -0221 = (0.0095) (1 cm) (c)
c = 2.33 mg/l - ->0.002 mg/ml -->
0.002 mg/m1(88.5 ml treated water) = 0.20 mg
Dve Rewired - Residual Dve = Needed Dye.
197 mg/l :
50.0 mg (=50.0 ml A . B . 277 1.0 g/1 stock soln.) - 0.30mg = 49.7 mg (=49.7 ml A.B. 277 l.Og/l stock soln.)
.
Also, 0.3 ml tapwater to make 50.0 ml dye volume.
283 mg/l :
5 0 . 0 mg (=50.0 ml A . B . 277 1.0 g/1 stock soln.) - 0.20mg = 49.8 mg (49.8 ml A . B . 277 1.0 g/l. stock soln.)
Also, 0.2 ml tapwater to make 50.0 ml dye voltrme.
* The more precisely calculated absorptivity value was 0.0076. Using this value in the above calculations resulted
in only a 022% difference in dye volumes. Consequently, the
small error in absorptivity calculation had little effect on
this experiment.
85
A.R. 361 Dveins #2
Control Dvebath.
30:l Liquor Ratio f o r 5.0 2 0.lg nylon 6,6 Superba 270'F
heatset yarn.= 150 ml
4.0% ammonium sulfate owf = 10 ml
1.0% ammonium hydroxide owf 1.5ml
1.0% dye owf = 50 ml
Tapwater to make 150 ml volume (88.5 ml tapwater)
Residual Dye Content Calculation *. Iron Level : A = abc
..
Sample
121 mg/l
207 mg/l
287 mg/l
: 0.0908 = 0.0103 (1 cm)(c)
c = 8.8 mg/l ---> 0.0088mg/ml --- >
0.0088 mg/m1(88.5 ml) = 0.8 mg
: 0.0718 = 0.0103 (1 cm)(c)
c = 7.0 mg/l ---> 0.0070 mg/l --- >
0.0070 mg/m1(88.5 ml) = 0.6 mg
: 0.0824 = 0.0103 (1 cm) (c)
c = 8.0 mg/l ---> 0.0080 mg/ml --- >
0.0080 mg/m1(88.5 mlj = 0.3 mg
Dye Rewired - Residual Dye = Needed Dye.
121 m g / l :
50 mg ( = 50 ml of AR 361 1.0 g/1 stock soln.) - 0.8 mg = 49.2Img (= 49.2 ml of AR 361 1.0 g/1 stock soln.)
Also, 0.8 ml of tapwater to make 50.0 ml dye volume
207 mg/l :
86
50 mg - 0.6 mg = 4 9 . 4 mg (=49.4 ml)
Also, 0.6 ml of tapwater to make 50.0 ml dye volume
287 mg/l :
50 mg - 0.7 mg = 4 9 . 3 mg (=49 .3 ml)
Also, 0.7 ml of tapwater to make 50.0 ml dye volume
* The more precisely calculated absorptivity value was 0.0119. Using this value in the above calculations resulted
in only a 0.2% difference in dye volumes. Consequently, the
small error in absorptivity had little effect on this
experiment.
..
Sgiked Dvebath.
The three iron level treated samples 121, 207, and 287
mg/l for A.R. 361 were each used in a spiked dyeing. Also,
for this set of dyeings, residual dye content was not taken
into consideration. The dyebath consisted of the following:
- ,
5 0 . 0 ml A.R. 361 1.0 g/1 stock solution
10.0 ml (+ 1.0 ml additional) ammonium sulfate = 11.0 ml
1.5 ml (+ 0.5 ml additional) ammonium hydroxide = 2.0 ml
25 ml Stainblocker "Btl (15 g/1 stock solution>)
Treated water to make 150 ml total volume (62.5 ml)
A.B. 277/A.R. 361 Purple Mixture Dveinq
Control Dvebath.
30:l Liquor Ratio = 150 ml total volume
4 . 0 % ammonium sulfate owf = 10 ml
1.0% ammonium hydroxide owf = 1.5 ml
87
1.0% dye owf = 50 ml (35 ml AR 361 1.0 g/1 stock solution
+ 15 ml AB 277 1.0 g/1 stock solution)
Tapwater to make 150 ml volume (88.5 ml tapwater)
Treated Water Mixture.
The 197 mg/l A . B . 277 and 207 mg/l A.R. 361 iron level
treated samples were mixed in equal volumes of 44.25 ml to
total the 88.5 ml water requirement. The 283 mg/l A . B . 277
and 287 mg/l A.R. 361 iron level treated samples were mixed
in the above proportions. The forementioned iron level
treated samples were mixed in the given manner because their
iron addition levels were considered to be approximately the
same. Previous calculations showed that the residual dye
contents were 0.0026 and 0.0023 mg/ml for A.B. 277 197 mg/l
and 283 mg/l treated water samples respectively, and 0.0069
and 0.0080 mg/l for A.R. 361 207 mg/l and 287 mg/l treated
water samples respectively.
.
Residual Dve Content Calculation*.
A . B . 277 197 mg/l: 0.0026 mg/1(44.25 ml) = 0.1 mg
--> 15 mg (715 ml AB 277 l.Og/l stock soln.) - 0.1 mg =
14.9 mg (=14.9 ml AB 277 1.0 g/l stock soinj
AR 361 207 mg/l: 0.0069 mg/1(44.25 ml) = 0.3 mg
--> 35 mg (=35 ml AR 361 1.0 g/1 stock soln) - 0.3 mg =
34.7 mg (=34.7 ml A.R. 361 1.0 g/1 stock soln)
AB 277'283 mg/l: 0.0023 mg/1(44.25 ml) = 0.1 mg
--> 15 mg (=15 ml AB 277 1.0 g/1 stock soln) - 0.1 mg =
14.9 mg (=14.9 ml A . B . 277 1.0 g/1 stock soln)
88
AR 361 287 mg/l: ).0080 mg/1(44.25 ml) = 0.4 mg .
--> 35 mg (=35 ml AR 361 1.0 g/1 stock soln) -- 0.4 mg =
34.6 mg (=34.6 ml AR 361 1.0 g/1 stock s o h )
For the AB 277 197 mg/l : A.R. 361 207 mg/l mixture,
total dye required = 34,7ml(AR 361) - 14.9ml(AB 277)
= 49.6 ml, + 0.4 ml tapwater For the A.B. 277 283 mg/l : A.R. 361 287 mg/l mixture,
total dye required = 34.6ml(A.R. 361) - 14.9ml(A.B. 277)
= 49.5 ml, + 0.5 ml tapwater
* The more precisely calculated absorptivity for A.R. 361
was 0.0119 as compared to the determined value of 0.0103. The
final difference in the dye volumes calculated for the two
absorptivity values was less than 0.1%. This small difference
in dye volumes was considered negligible. Thus, the error in
the procedure for determining the absorptivity value did not
result in a great error in the experiment.
.
Procion Red MX-5B Dveinq
Control Dvebath.
40:l Liquor Ratio for 10.0 g of scoured cotton fabric =
400 mi total volume
20% NaCl owf = 2.0g
1.0% dye owf = 0.1 g = 100 ml of Procion Red l.Og/l
stock solution
Tapwater to make 400 ml volume (300 ml of tapwater)
89
Residual Dye Content*.
Iron Level :
Sample
121 mg/l
207 mg/l
287A mg/l
287B mg/l
.
A = abc
0.0360 = 0.02 (1 cm) (c)
c = 1.8 mg/l ---> 0.002 mg/ml --- >
0.002 mg/m1(300 ml) = 0.60 mg
0.0526 = 0.02 (1 cm) (c)
c = 2.63 mg/l ---> 0.003 mg/ml --- >
0.003 mg/m1(300 ml) = 0.90 mg
0.0460 = 0.02 (1 cm) (c)
c = 2.3 mg/l ---> 0.002 mg/ml --- >
0.002 mg/m1(300 ml) = 0.60 mg
0.0540 = 0.02 (1 cm) (c)
'- c = 2.7 mg/l ---> 0.003 mg/ml -->
0.003 mg/m1(300 ml) = 0.90 mg
Dye Recruired - Residual Dve = Needed Dye.
121 mg/l:
100 mg (=lo0 ml of Procion Red 1.0 g/1 stock soh) - 0.6 mg = 99.4 mg (=99.4 ml of Procion Red 1.0 g/1
stock SOPXIj w i t h 9.6 nl tapwater = 100 AI dye volume
207 mg/l:
100 mg - 0.9 mg = 99';l mg (=99.1 ml) with 0.9 ml H20
287A mg/l:
100 mg - 0.6 mg = 99.4 ml (=99.4 ml) with 0.6 ml H20
287B mg/l:
100 mg - 0.9 mg = 99.1 mg (=99.1 ml) with 0.9 ml H20
90
* The precise absorbance was not calculated for this experiment. Hence, the error in the less precisely determined
absorbance was not known, but it was believed to be very
small ,
A.B. 277 Dveina #2
Control Dvebath.
30:l Liquor Ratio for 5 . 0 2 0.1 g nylon 6,6 Superba
270oF heatset yarn = 150 ml total volume.
4 . 0 % ammonium sulfate owf = 10 ml
1.0% ammonium hydroxide = 1.5 ml
1.0% dye owf = 50 m g = 50 ml
Tapwater to make 150 ml volume ( 8 8 . 5 ml tapwater)
Unspiked Dvebath.
Same as the control except that 8 8 . 5 ml of treated water
was used instead of tapwater.
not taken into consideration.
Also, residual dye content was
Dyebaths were prepared for 121,
207, and 287 mg/l iron level treated samples of A.B.
mg/l stock sample for a total of three unspiked samples,
277 20
Spiked Dvebath:
The spiked dyebaths used t'ne contol dyebath famulation
with the addition of some auxiliary and stahblocker
chemicals. The additional chemicals were addedto the dyebath
with water that had already gone through the treatment
process. If the chemicals had been added before treatment,
the removal levels of each chemical treated would have been
extremely complicated to determine. By adding the chemicals
91
after treatment, exact concentrations of each was known and
their affects on the dyeing were simplier to determine. It
was estimated that a mixed wastestream containing a 1.0 g/1
stainblocker concentration would contain approximately 0.3-
0.5 g/1 residual concentration of stainblocker after treatment
by the Andco Process. For this reason, each spiked sample
contained 25.0 ml of 15 g/1 stainblocker lrBlt stock solution
(0.375 9). An additional 1.0 ml of ammonium sulfate and 0.5
ml of ammonium hydroxide was added to simulate residual
process chemicals in the treated dyebath water. Again,
dyebaths were prepared for the 121, 207, and 287 mg/l iron
level treated samples.
The spiked dyebath contained the following:
50.0 ml of A . B . 277 1.0 g/1 stock solution
10.0 ml ( + 1.0 ml additional) ammonium sulfate = 11.0 ml
1.5 ml ( + 0.5 ml additional) ammonium hydroxide = 2.0 ml
25.0 ml of Stainblocker llB1l (from a 15 g/1 stock solution)
Treated water to make 150.0 ml total volume (62.5 ml)
A.R. 361 Dveins #2
The A.R. 351 dyeing #2 consisted of one con t ro l samples
three unspiked samples and three spiked samples corresponding
to 121, 207 and 287 mg/l iron level treated water samples.
The procedure and dyebaths were exactly the same as for the
A . B . 277 dyeing #2. Again, residual dye content was not taken
into consideration.
. . I , . - . , - . .. ... . - . . I . . , ’. . , -;” ’-. . . . , .
92
Color Measurement Theorv
Instrumental assessment of color (hue), saturation and
lightness components is based on the same principles as human
assessment, Both evaluate radiant energy reflected off an ..
object or emanating from a source. The instrumental
assessment converts detected radiant energy into quantifiable
numerical data in a manner similar to the way the human brain
converts radiant energy into visual perception.
For this study, visual comparison was used because the
trained human eye is still an incredibly sensitive method for
distinguishing differences between samples, However, the
visual observation was limited to the assessment of large
differences in color and shade because the observer did not
have a trained eye (in the textile industry and other
industries there are people specifically trained to
distinguish between very small differences in color) ,
i
However, convert human visualization into quatifiable
. differences an instrumental method is required. An ACS
Spectro Sensor II using the Chroma Calc Color Lab program was
employed in addition to visual observation. A schematic of
an ACS Spectro Sensor type colorimeter is shown in’Figure 2-
4 . The sample is placed in front of the sample port where it
is illuminated with light from the tungsten lamp. The
reflectancezfrom the sample passes through a rotating filter
disc to a photo detector. An amplifier receives the signal
and sends it to an IBM PS/2 digital computer system which
93
ANALOG To DIGITAL
CONVERTER - --
..
..
DATA TO COMPUTER
-
ACS SPECTRO-SENSOR SCHEMATIC
Figure 2-4 Schematic of an ACS SpectroSensor Colorimeter.
. - - . . , . . , .
94
computes the measurement data. The CIE LAB measurement system
was used to calculate the data given in the results section.
The subject of colorimetry is very extensive and many other
methods like the CZE system have been developed, each with its
own advantages. However, for the scope of this research only
the CIE LAB 1976 method was employed.
..
The CIE WIB system was developed by the Commission
Internationale de 1'Eclairage (CIE) as a method to calculate
color differences between two samples. In the CIE LAB system
the a and b values represent color differences in redness-
greenness and yellowness-blueness respectively while the L
value represents the lightness-darkness. The total color
difference is given by DE ( the change in E between two
samples), The &7 Yn', and 2, values represent tristimulus
values of the standard illwinant (typically A or DC5 CIE
standard il1uminants)under which the samples are prepared.
A set of sample calculations is given f o r comparison of two
samples in Figure 2-5. In general, it is found that dye
aciditfion tends to increase absorbance or decrease reflectance
while reducing dye concentration decreases absorbance,
therefore, increasing reflectance values. The matedal sample
itself has a great effect on measured values. Sample yarns
with many voids tend to scatter light increasing reflectance
values. Increasing the diameter of a fiber reduces light
scattering by decreasing the surface to volume ratio, this
increases absorbance therefore reducing reflectence.
95
Samrsle 1 Samrsle 2 &< Standard Illuminant
X = 6.94 X = 7.69 Y = 7.19 Y = 8.24 Z = 7.42 z = 7.93
X, = 94.825
Z, = 107.381 Y , = 100
L* = 116 L, = 116 Lz = 116 DL = 34.47 - 32.23 = 2.84
( Y / Y , ) ’ l 3 - 16 (7.19/100)1’3 - 16 = 32.23 (8.24/100)1’3 - 16 = 34.47
a* = 500 [ ( X / % ) l l 3 - 16 = 34.47 a, = 500 [(6.94/94.825)lI3 - (7.19/100.0~~~~] = 1.23 a2 = 500 [(7.96/94.825)’13 - (8.24/100)” J = 1.35
b* = 200 (Y/Y,) - jz/zn) J b, = 200 [ (7.19/100)1 - (7.19/107.381)1’3] = 1.09 b2 = 200 [ (8.24/100)1’3 - (7.93/107.381)1’3J = 3.12 DB = 3.12 - 1.09 = 2.03
D, = 1.35 - 1.23 = 0.08
C = [(a)2 + (b)2]1/2 C, = [(1.23)2 + (1.0939)2a1’2 = 1.65 C2 = [(1.35)2 + (3.12)2J1’ = 3.39 DC = 3.39 - 1.65 = 1.74
DE = [(DL)2 + (Da)2 + (Db)’]1/2 DE = [(3.02)2 + (.08)2 + (2.03)2]1/2 = 3.02
DH = [ (DE)2 - (0Ll2 - iDC)2]1’2 DH = [(3.02)’ - (2.24) - (1.75)2]1’2 = 1.04
Figure 2-5 CIE LAB 1976 equations used to quantify sample differences. D = Difference
96
Each of the samples dyed in the recycled water was
measured against the control sample which was dyed by the
conventional method. Yarn samples were tested after mounting
on white poster. board bys wrapping the surface with
approximately 2 x 2 inches of yarn. The cotton fabric samples
that were used in the Procion Red dyeing did not require
mounting and were placed directly in the porthole for color
measurement. Each sample was scanned from 400-700 nm. The
%Reflectance vs. Wavelength was obtained for each sample and
compared to see how much the samples dyed conventionally
varied with samples dyed alternatively with treated water.
This is very important because visual inspection is limited
to the color sensitivity of the eye and the ability to
distinguish between v e b minute changes in color or depth of
shade. Also, the light source used w i l l change the color
perception. The ACS Spectro Sensor I1 spectrophotometer has
the ability to provide color differences in terms of
quantifiable numerical data. Also, the differences in
lightness, saturation, and hue were measured between the
treated water samples and the control samples.
The Mechanism of Electrochemical Color Removal
The results collected in the color removal study showed
excellent color removal and in the later study on dye water
reuse results collected indicated promising reuse
capabilities. However, one concern remained - how was the color being removed? It has been suggested that the dye
97
molecules may be removed by adsorption onto the iron matrix
created as the ferrous hydroxide precipitates. The ferric
hydroxide exists in an octahedral form, forming a ladder type
matrix with other: molecules of ferric hydroxide [36]. Part
of the color removal process may involve the dye molecule
adsorbing onto this matrix by both electrostatic attraction
and physical entrapment (363. Also, the dye actually may be
complexing with the ferrous hydroxide forming ionic bonds.
However, because the reaction within the treatment cell is a
reductive process (ie hydrogen gas is produced), it is
possible that the some dye molecules are degraded by a
reduction mechanism. Particular concern is placed on the
reactions of acid dyes with azo bonds which are susceptible
to reduction [16]. The electrochemical treatment involves the
production of ferrous iron Fe” which is very unstable and
tends to quickly oxidize to ferric iron Fd3. In the treatment
unit the azo bond can act as an electron acceptor obtaining
electrons from Fe” as it oxidizes to Fe+3. Using azobenzene
as an example, upon accepting 2 e- and 2H+, hydrazobenzene is
forned, and under the hi3hly reductive environment of the
treatment system with large electron availability.from the
continual production and oxidation of ferrous iron, the
hydrazobenzene would likely be reduced further to two
molecules of aniline [16]. Generally, aniline is only
produced when ortho-para activating groups like -OH or ether
groups and other amines are present on the ring making the azo
98
bond more susceptible to complete reduction [16]. However,
given the highly reductive environment existing in the
treatment cell, it is highly likely that aniline is produced.
The aniline is veky susceptible to air oxidation, oxidizing
to various products like nitrobenzene, azobenzene, and the
aniline can even be oxidized back to azobenzene [16]. Because
the treated water is continually recirculated through the
machine, the treated solution is exposed to air which promotes
further oxidation. For this reason it seems reasonable to
assume that if aniline is produced, that it is also likely
that some of its oxidation products are also present in the
treated sample. If such degradation products are produced,
a dual system using the Andco Process followed by oxidative
aerobic sludge digestion may reduce any threat to man or the
environment by further oxidizing the reduction products,
Lastly, color removal can also take place if some of the
substituents which determine the color of the dye are altered
in some manner, Examples of substituent groups are NO,, NO,
N=N and CO groups. Other chemical groups .. which impart-dyeing
properties to a colored substance and intensify the action of
the other color contributing substituents are called
auxochromes. They are usually weakly salt forming substances:
examples of auxochromes are SO,-Na+ and COO-Na+. The absorption
spectra are laffected by acid, base and changes in solvent.
Isomerism, tautomerism and transitions between electronic
states also affect absorption spectra. A great effort can be
99
made to obtain a pure chemical to study its spectra, but the
presence of isomers can cause differences in spectra compared
to that of an isomerically pure chemical. This is because the
spectrophotometer ‘:is measuring the absorption of light by a
chemical species which is raised to a state of higher energy
[ 3 4 ] . The energy, angle and strain on a given bond may affect
how it absorbs light energy. This is why isomers of the same
chemical may produce spectra with some absorption differences
1 3 4 1
Of course, the Andco Process may remove color by any one
of the above processes or any combination of the above. An
attempt was made to determine if dyes were removed totally by
adsorption or by another process or combination of the two.
It was determined by visual observation of the residual iron
sludge, that some amount of adsorption was likely taking
place. In some cases dye color was observed to increase in
the treated water if the water was not removed from the beaker
shortly after the flocculation procedure. In one case a blue
food dye contained in the sludge of a treated sample was
observed to migrate out of the sludge back into the treated
effluent over a period of about 2 4 hours.
To determine whether 3r not processes other than
adsorption were taking place, it was suggested that high
performance ,‘liquid chromotography (HPLC) be used. HPLC has
the ability to separate different chemical species in a
mixture. Each species has its own characteristic retention
100
time and peak height for a given solvent and column system
allowing it to be compared with standards to confirm its
identity. This method would allow a more detailed elucidation
of exactly what dye degradation products are produced - if any. However, due to limited time a detailed study of dye
degradation products using HPLC was not possible and a
quicker, but more general method of analysis was employed.
Absorption spectrophotometry was used to observe the change
in characteristic absorption peaks of the treated samples as
an indication of dye molecule alteration. This method is
sufficient to determine if dye molecule alteration is
occurring and to give a general indication of what degradation
products might be produced. However, specific and decisive
information cannot be accurately determined, as many of the
degradation products have absorption peaks that overlap.
Several sets of absorption experiments were performed using
the Cary 219 absorption spectrophotometer.
..
The following samples were treated with the
elect'rochemical treatment process:
1) Acid Blue 277 at 20 mg/l solution concentration
with 121, 207, and 287 mg/l iron treatlnent
levels.
2) FD&C Yellow # 5 food dye at 30 m g / l solution
concentration with 151, 237, and 337 mg/l iron
treatment levels.
101
3) FD&C Blue #2 food dye at 28 mg/l solution
concentration with 151, 237, and 337 mg/l iron
treatment levels,
4) Azob&zene at 34 mg/l solution concentration
in approximately 3.5% methanol/water at 154 , 302 ,
and 345 mg/l iron treatment levels.
All samples were prepared in the following manner.
Sample volumes of 1800 ml were taken; the pH was adjusted to
9.0-9.1; the samples were flocculated with the 0.2% polymer
solution (about 5 ml); and, then, the samples were filtered
through Pyrex glass wool into storage bottles. Next, each
sample was p H adjusted to 6.5 to reduce the solubility of
carbonate, and each was bubbled with pure oxygen for 3-5
minutes to oxidize any.residua1 soluble ferrous Fe” to ferric
Fe+3. This would reduce errors in absorbance measurement
caused by the presence of FeiZ and carbonate, The samples were
then filtered a second time with Pyrex glass wool before
taking any absorbance measurements.
The structures of FD&C Yellow #5, FD&C Blue #2, and
azobenzene are given in Figure 2-6. The structure of A . B . 277
is proprietary and has not been released. As a result of
this, no prediction of the altered products was possible, only
observation of spectral changes was carried out. A l s o , the
A . B . 277 is a commercial textile dye of unknown purity so the
changes in solution may be masked by the existence of
impurities, which have their own absorptions at characteristic
102
F i g u r e 2-6 S t r u c t u r e s f o r (A) FD&C Y e l l o w 95, (B) FD&C B l u e #2 , and (C) Azobenzene.
103
wavelengths. For this reason, food dyes of high purity
(approximately 9 5 % ) were obtained. The selection of the
yellow and blue dyes .. was based on their structures. The
yellow dye had an'azo bond and was selected because the azo
bond is frequently found in textile dyes. The blue dye had
a carbon-carbon double bond and was selected to see how it
behaved in comparison to the azo bonded yellow dye. To
further study the azo bond, azobenzene was selected as a model
compound. The azobenzene was 9 6 . 7 % pure and was treated in
a 3.5 % methanol/water solution to achieve acceptible
solubility of the azobenzene.
Color removal would indicate either removal by
adsorption/complexing or by destruction/alteration of the azo
bond. If the color removal was accompanied by corresponding
removal in the aromatic region of the spectra, then adsorption
9
would seem the likely mechanism for color removal. However,
color removal accompanied by a smaller decrease in absorbance
in the aromatic region would indicate some type of dye
molecule alteration, as the actual chemical content of the
solution may still be present, only not producing color due
to alteration of the chromophore.
In addition to the specba run on the treated azobenzene
samples and its standards, a spectrum of dilute aniline was
also obtained. Lastly, part of the azobenzene control stock
solution (about 50 ml of 34 mg/l stock solution) was degraded
with 1.0 g of sodium hydrosulfite, and a spectrum was recorded
104
for comparison with the stock solution, the aniline and the
treated samples. Also, for each sample of dye and azobenzene,
lower concentrations of 3 and 10 mg/l were prepared. _.
Additionally, concentrations of 20, 30, 30, and 35 mg/l
corresponding to the approximate concentrations of the control
samples for A.B. 277, Food Yellow #5, Food Blue #2, and
azobenzene, respectively, were prepared, Spectra of each were
obtained to calculate the absorptivity values at the given
selected wavelengths and to simulate how spectra would appear
if the dye chemical content was actually removed with no
alterations.
Spectra were measured from 195 to 622 nm for A.B. 277,
195 to 618 nm for FD&C Food Blue #2, 195 to 520 nm for FD&C
Food Yellow #5, and 195 to 555 nm for azobenzene. The scan
rate for all spectra was 0.5 nm/sec with a 1.0 second period.
The ABS range was 0-2 for each sample except for the A.B. 277
which was 0-1. Absorptivity values were calculated at
wavelengths of interest by using the absorbance values for
each of’ the three different concentrations prepared of each
sample. The Sadtler Handbook of Ultraviolet Spectra [ 3 3 3 was
used to select wavelengths of interest. Values for absorption
maxima of possible dye alteration products were obtained from
this source.
reduce degradation.
All samples were refrigerated between tests to
105
CHAPTER I11
RESULTS AND DISCUSSION
Chemical Oxvsen Demand Reduction
One of the purposes of this section was to determine how
effectively the electrochemical treatment process reduced COD
levels for the auxiliaries involved in dyeing and the
stainblocking chemicals recently introduced to the textile
industry. Throughout the experiments in this section, three
types of COD tests were used and referred to as high, medium
and low level tests. These simply corresponded to the
strength of the titrants used for each chemical tested.
Chemicals with a high COD content (up to 1000 mg/l COD)
required the use of high strength titrants, while medium range
chemicals (up to 500 mg/l COD) used titrants with half the
strength of the high level tests. Dyes had low COD values and
so low strength titrants had to be used to increase volume
accuracy. Details on the COD experimentation are given in the
experimental section (Chapter 11).
Stainblocker Chemicals
During experimentation it was found that COD values were
reduced anywhere from 25% to 100% depending on the chemical
being tested and the iron treatment level used. Stainblocker
chemicals generally had a maximum COD reduction of 80-90%.
106
Alternatively, dye COD reduction was less well defined because
the dyes had such low COD'S to begin with compared to the
stainblockers. The low values added to the error because they
approached background levels-associated with distilled water
blanks. The stainblockers on the other hand, were usually
easy to test with consistent and expected COD values. Table
..
3-1 shows the COD test values in mg/l and
for the Stainblocker rtAtt formulation.
0.1, 0.3, 0.6 and 1.0 g/1 were tested for
the percent removal
Stock solutions of
COD values and were
found to increase linearly with concentration. Removal levels
for the 0.6 g/1 stock solution'at 550 and 650 mg/l were
slightly higher than the corresponding 1.0 g/1 samples. It
was observed that increasing the iron addition from 550 to 650
Iron mg/l did not significantly change removal levels.
addition levels less than 550 mg/l would not floc for unknown'
reasons so only treatment levels of 550 mg/l and 650 mg/l were
used. Although greater amounts of iron can be added, the
economics are prohibitive and sludge disposal costs increase.
Due to the additional strain on local POTWs from the
increasing CODs of the stainblocker chemicals, manufacturers
began to develop formulations with lower COD valugs. During
the course of experimentation one of the stainblocker
producers sent two additional lower COD formulations known as
ltBtt and ltCtt'for testing. It can be observed by comparing COD
values from Table 3-2 for Stainblocker t tBtt with the
Stainblocker trAtt values in Table 3-1 that initial COD values
107 - -
Table 3-1 COD values and percent removal values for Stainblocker Formulation tlAtt at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
0.1 g/1 stock (0) 0.3 g/1 stock (0)
0.6 g/1 stock (0) Iron Level 5 5 0
( m g / l ) - 650
1.0 g/1 stock (0) 5 5 0 650
COD (mcr/l)
112 253
693 471 471
1158 840 859
32.0 32.0
-- 27.5 25.8
108
Table 3-2 COD values and percent removal values for Stainblocker Formulation lrBrr at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
0.6 g/1 stock (0) 4 5 0 550
Iron Level 6 5 0
1.0 g/1 stock ( 0 ) 4 5 0 5 5 0 6 5 0
"/l)
COD (ms/l)
240 34 16 4 4
401 85 107 77
-- 85.8 93.3 81.7
-- 78.8 73.3 80.8
109
had been reduced by 65% for both the 0.6 and 1.0 g/1 stock
solutions. In addition, Stainblocker I I B I 1 unlike Stainblocker
I1A1@ flocced at 450 mg/l iron addition allowing for lower
treatment levels.. Furthermore, the new formulation yielded
higher removal values (Table 3-2) from 80 - 93%. Once again,
it was observed that an increase in iron level from 450 to 650
mg/ldid not significantly yield further removal. It appeared
as though once an optimal treatment level was reached, further
treatment accomplished little more than increasing treatment
costs and sludge production., The third sample tested, known
as formulation 18C11, had initial COD values reduced by only 49%
and 56% of the Stainblocker I1Al1 sample at 0.6 and 1.0 g/1
stock solutions respectively. Not only was initial COD
removal less than for Stainblocker l tBt l , but COD removal after
treatment was also less, Table 3-3 shows COD values and
percent removal for Stainblocker I1C1l. The COD values for the
0.6 g/1 sample were reduced roughly 74-79% while the 1.0 g/1
sample had poor removal at only 42-49%. The removal values
decreased with increasing iron addition past the optimum level
(450 m g / l ) , Given that removal. percent decreased only a few
percent, it seemed likely that the decrease in removal with
increased iron addition could be taken to be part of the error
within the COD test. That is, for all intents and purposes
COD values of 73 and 92 mg/l for instance, can be considered
to be essentially the same. The final stainblocker tested
was a stainblocker formulation referred to as Stainblocker
110
Table 3-3 COD values and percent removal values f o r Stainblocker Formulation rtCrt at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition.
0.6 g/1 stock (0) 450 5 5 0
I ron L e v e l 650
1.0 g/l stock ( 0 ) 450 5 5 0 650
"/l)
353 73 73 92
508 260 270 293
-- 79.3 79.4 73.9
-- 48.8 46.8 42.3
111
t rDt t . Initial COD values as shown in Table 3-4 are slightly
lower than the lowest COD for formulation tlBtl. Once again,
removal values were highest for the 0.6 g/1 stock solution
sample ranging from 60-100%. The 1.0 g/1 stock solution
sample achieved removal values of only approximately 40-55%.
A special test was performed on the Stainblocker t lDtt 0.6 g/1
stock solution sample. One set of 550/650 mg/l treated
solutions was flocced with polymer addition, the other was
allowed to settle without polymer addition. The COD removal
percents were compared in Table 3-4 and it was observed that
the polymer flocced samples achieved significantly higher
removal levels nearly 20% greater than the unflocced samples.
The degree and quality of the floc and its settling quality
appeared to have significant effects on the degree of removal
of COD and color. The process was very p H sensitive and
samples had to be adjusted to pH 8.9 - 9.1 before polymer addition to achieve any flocculation at all. In some cases
no amount of pH adjustment or polymer addition would cause a
floc and those samples that did not floc were discarded as
they were not considered representative of successful
electrochemical treatment. Problems with flocculation seemed
to plague the laboratory scale tests, but these problems were
attributed to the small sample size and the limited time
available to optimize the system to each individual chemical.
It was observed near the end of the experimentation that
larger volume samples like those used in the dyebath water
112
Table 3-4
Iron Level ( m g / l )
. I
COD values and percent removal values fo r Stainblocker Formulation **Dlf at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron addition. * Denotes sample in which no polymer was used to achieve a floc.
0.6 g/1 stock (0) * 5 5 0 * 6 5 0
5 5 0 6 5 0
1.0 g/1 stock (0) 550 650
COD (ms/l)
196 77 61
31 0
326 147 196
-- 60.7 68.9
84.2 100.0
-- 54.9 39.9
113
Table 3-5 COD values and percent removal values f o r Irgalev A, an auxiliary chemical, at 0.6 g/1 and 0.8 g/1 sample concentrations with increasing iron addition.
Iron Level (mg/l)
0.6 g/1 stock (0) 250 3 5 0 450 550 650
0.8 g/1 stock (0) 250 350 450 550 650
604 294 171 184 175 143
673 370 331 257 362 405
-- 50.0 71.6 69.6 71.0 76.3
45.1 49.1 61.9 46.2 40.0
114
Table 3-6
Iron Level “/l)
COD values and percent removal values for Guar Gum, an auxiliary chemical, at 0.3 g/1 sample concentration with increasing iron addition.
0.3 g/1 stock ( 0 ) 250 350 450 5 5 0 6 5 0
298 104 84 58 58 96
-- 65.2 71.7 80.7 80.7 67.8
115
reuse tests (volume = 1800 ml) flocced much easier than those
of the 500 ml volume size.
Auxiliarv Chemicals
A set of tests were run on Irgalev A anionic surfactant.
The CODs were very high at 600 mg/l COD for the 0.6 g/1 stock
solution and 673 mg/l COD for the 0.8 g/1 stock solutions.
A 0 . 9 g/1 sample was run but the sample would not floc and
much of the solids floated on the top. As shown in Table 3-
5 removal values were mostly consistent with approximately 70%
removal for the 0.6 g/1 stock solution sample and 40-60% for
the 0.8 g/1 stock solution. As in the past, the higher the
concentration of the stock, the lower the removal level
achieved. A sample of Guar Gum (a thickening agent) was run
at 0.3 g/1 and 0.6 g/1 stock solutions; however, the 0.6g/l
sample would not floc. A repeat test of the 0.6 g/1 sample
was conducted with the same results and had to be discarded.
Table 3-6 shows the COD values and respective removal percents
for the 0.3 g/l. Maximum removal was observed at 450-550 mg/l
iron addition giving roughly 81% removal.
Flocculation Polvmer Contribution To COD
In response to a concern that the polymer addition may
have been contributing to the sample COD, standards of
distilled water were treated at frequently used iron levels
with monitored polymer addition. A low level COD test was
performed and it was found that COD values were more or less
random from one iron level to another. Table 3-7 shows the
116
Table 3-7
Iron Level "/l)
COD values for distilled water blanks treated with the Andco Process, and the corresponding polymer quantities required to produce a floc.
5 0 150 2 5 0 3 5 0 450 5 5 0 650
Polymer (ml)
0.24 0.26 0.95 1.00 1.40 0.25 0.65
COD (ms/ll
4 0 0
109 0
23 26
1 1 7
distilled water samples’ COD values and it can be seen that
at the two highest polymer additions, the lower 1.0 ml
addition has a COD of roughly 110 mg/l while the higher
addition level, 1;4 ml, has a COD of zero. Questions still
remain on the nature of these distilled water samples, such
as whether or not the high COD values are caused by poor
flocculation or free polymer in solution. Poor flocculation
may result in the presence of more Fe” ferrous iron in
solution. This may also result in a contribution to COD as
Fe+2 oxidizes to Fe+3. Background distortion is not out of the
question as a cause of the random results, especially since
the low level COD test was used. The low level COD test
involves the use of diluted titrants used to increase the
volume accuracy when .testing chemicals with low chemical
oxygen demand values approaching the background error for the
test. In any case, the COD values for the polymer and iron
contribution should be negligible when high COD containing
chemicals like auxiliaries and stainblocker chemicals are
being tested.
Another method investigated for use in determining the
organic content of a sample was the TC - Total Carbon Analyzer. The detector measures carbon dioxide produced by
an organic, or inorganic carbon containing compounds upon
oxidation under extreme heat (1600OF) with units of mgC/1 , while chemical oxygen demand measures the oxygen necessary to
oxidize organics to CO, and H,O given in units of mgOJl.
118
Table 3-8 Average peak height, total carbon and percent removal values for Stainblocker Formulation rrDrl at 0.6 g/1 and 1.0 g/1 sample concentrations with increasing iron. * Denotes samples in which no polymer was used to achieve a floc.
Average Peak Heiqht
0.6 g/1 stock (0) 51.2
* 550 13.5 * 650 21.5
5 5 0 8.5 Iron Level 650 6.7
1.0 g/1 stock ( 0 ) 70.1 5 5 0 34.1 650 55.3
"1)
TC 0 88.6
1.2 19.7
-10 . 4 -14.6
132.4 48.9 98.1
98.6 77.8
> l o o > l o o -- 63.1 25.9
119
\
After CODs were tested for on Stainblocker oD1l, the same
sample was tested on a TC Analyzer. Table 3-8 shows the total
carbon in mgC/1 and the percent removal with increasing iron
addition. Samples were tested at 0.6 g/1 stock solution with
both flocced and settle samples, and at 1.0 g/1 with just
flocced samples. The settled 0 . 6 g/1 samples had very high
removal levels between 77-99% and the flocced samples measured
out below background levels indicating near 100% removal. The
1.0 g/1 stock solution had good removal at 550 mg/l iron
addition but that removal dropped to 26% when the iron
addition was increased to 650 mg/l. It was decided that this
method would be sufficient for future tests on high COD
materials like the stainblockers or auxiliary chemicals, but
would not be a wise choice for low COD materials whose
response tends to be obscured by background noise and CO,
naturally dissolved in water. The TC did support the COD
measurements on the Stainblocker llD1l including the observation
that polymer floccing increases organic reduction more than
settling alone as shown in Figure 3-8.
Color Removal Results
Dve COD And TC Test Results
During the beginning of this study, it was thought that
COD reduction in dye solutions would serve as an indicator of
actual dye removal and therefore color removal. However,
several attempts were made to adjust the COD test to
120
accurately determine the COD of
not very successful as the dyes
results were often masked in the
the dye solutions, this was
had such low COD values that
error range of the COD test.
The first set of ‘CODs run on dyes used the high level COD
test. The COD values and removal percents for the 25 mg/l and
50 mg/l acid dye mixtures (A0156, A R 3 6 1 , AB277) are shown in
Table 3-9. As can be seen, the numbers are scattered and
inconclusive, fluctuating and showing no linear relation with
increasing iron level as might be expected. The low level test
was employed to increase the volume accuracy of the test.
Samples of 25 mg/l and 50 mg/l Acid Red 361 were tested with
the low level COD test. The corresponding COD values in Table
3-10 showed improvement with less scattered results. The COD
was observed to increase with an increase in concentration as
expected and somewhat consistent reductions in COD were
observed at most iron levels. Polymer addition levels were
recorded to see if they had any effect on COD. Average
removals were in the 0-100% range for the 25 mg/l stock
solution and between 25 to 6.0% for the 50 mg/l stock solution.
Similar results were obtained from Procisn Blue MS-2G run at
25 mg/l and 50 mg/l sample concentrations. The amount of
polymer necessary to achieve a floc is given along with
corresponding COD values and percent removal for the Procion
Blue samples in Table 3-11. The polymer used appeared to have
no apparent bearing on the level of COD. The Procion Blue
sample at the higher concentration of 50 mg/l had the greatest
121
Table 3-9
I r o n Level
COD values and percent removal for the acid dye mixture at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
25 (mg/l) stock ( 0 ) 50
150 250 350
"/l) 50 (mg/l) stock ( 0 )
50 150 250 350
93 27 89 0
85
40 566 89 85 0
70.8 4.2
100.0 8.3
-- + + +
100.0
122
Table 3-10 Required polymer (ml), COD values and percent removal values for A.R. 361 dye at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
25 (mg/l) stock ( 0 ) 50
100 150 250
Iron Level 350 "/l) 450
50 (mg/l) stock ( 0 ) 50
100 150 250 350 450
Polvmer (ml)
-- 0.10 0.17 0.10 0.21 0.17 0.42
0.40 0.24 0.52 0.31 0.36 0.43
COD (ms/l)
10 0 2 6 2 12 0
102 ,69 94 75 43 74 67
-- loo. 0 80.0 40.0 80.0 +20.0 100.0
-- 32.4 7.8 26.5 57.8 27.5 34.3
123
. .
Table 3-11 Required polymer ( m l ) , COD values and percent removal values for Procion Blue MS-2G dye at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
25 (mg/l) stock
Iron Level “/l)
50 (mg/l) stock
( 0 ) 50 100 150 250 350 450
( 0 ) 50 100 150 250 350 450
Polymer (ml)
-- 0.4 0.4 0.6 0.5 0.4 0.4
-- 0.4 0.6 0.6 0.7 0.5 0.5
COD (ms/l)
40 32 39 30 31 19 19
64 13 33 61 31 20 46
20.0 2.5 25.0 22.5 52.5 52.5
-- 79.7 48.4 4.7 51.6 68.8 28.1
124
removal ranging from 5 to 8 0 % while the lower concentration
of 25 mg/l had lesser removal from 3 to 50%. Removal levels
fluctuated among the different iron levels, with no one iron
level appearing to be significantly better than any other iron
level. Due to the inconsistency of the results obtained, the
use of the COD test for dyes was discontinued.
The total carbon test was attempted to see if it could
be applied to the dyes, but once again, the carbon content in
the dilute (25, 50 mg/l) solutions of the dyes was below the
background noise associated with the TC test. Values came out
negative for carbon content in samples, known to have carbon
content. Tables 3-12 and 3-13 show the scattered and negative
results obtained for the 25 mg/l and 50 mg/l acid dye mixtures
and the Acid Blue 40 25 mg/l test solution respectively. An
attempt was made to subtract off TC values obtained from the
distilled water blanks treated at corresponding iron levels
(TC ttBa). However, almost all values came out negative after
subtraction, even for samples known to have residual dye from
absorption measurements. For this reason, the "puret1 values
without blank subtraction for TC of the dyes are given under
TC "Atf. In any case, the TC appeared to increase after
treatment, possibly from polymer addition. Also, the treated
water churns as it recycles through the machine possibly
increasing dissolved gases such as 0, and CO,. The values used
for iron blank subtraction are given in Table 3-14. In
addition, a negative value was observed for untreated
125
Table 3-12 Average peak height and total carbon values A) before iron blank subtraction, B) after iron blank subtraction, for the acid dye mixture at 25 (mg/l) and 50 (mg/l) sample concentrations.
25 (mg/l) stock ( 0 ) 5 0
1 5 0 Iron Level 2 5 0
"1) 3 5 0
50 (mg/l) stock ( 0 ) 5 0
1 5 0 2 5 0 3 5 0
Average Peak TC "1) Heisht A B
--- 10.8 -5.2 16.6 8.4 -24.1 18.7 13.1 -19.3 13.5 0.4 -31.0 16.7 8.5 -17.5
--- 15.6 6.1 31.9 43.8 11.3 27.9 33.6 - 3.9 27.2 32.9 '1.6 8.3 -10.9 -23.4
126
Table 3-13 Average peak height and total carbon values A) before iron blank subtraction B) after iron blank subtraction, for A.B. 40 25 (mg/l) sample concentration.
Average Peak TC “1) Heicrht A B
--- 25 (mg/l) stock ( 0 ) 10.5 -5.9 50 18.5 12.8 -19.7
Iron Level 150 21.9 20.6 -16.9
350 17.0 9.3 -16.7 “/l) 250 17.0 9.3 -22 . 0
Table 3-14
I r o n Level “/l)
Average peak height and total carbon values fo r the distilled water iron blanks.
0 5 0
150 2 5 0 3 5 0
Average Peak H e i c r h t
8 . 8 14.0 16.2 13.5 11.2
Tc tm/ 1)
-10.3 2.3 7 . 4 1.2
- 4 . 2
128
distilled water. It was decided that this method would not
be a wise choice for low COD materials whose response tends
to be obscured by background noise and CO, naturally dissolved
in water. ..
Absomtion SDectroDhotometer Color Removal Results
The COD and TC tests did not provide a very clear picture
concerning dye removal. However, the absorption
spectrophotometer (Cary 219 model) turned out to be several
magnitudes greater in sensitivity to changes in dye
concentration (actually color concentration) as an indicator
of dye behavior with the Andco Process. The absorption tests
were used to determine color removal. The color removal could
represent actual dye removal, dye alteration or a combination
of the two. This topic was studied further in the fourth
study on the mechanism of dye removal in the Andco Process.
Preliminary absorbance data were collected at absorbance
wavelengths of 410, 510 and 610 nm for the dyes used in
testing as shown in Table A-1 of the Appendices. Four
principal acid dyes were tested - CI Acid Red 361, CI Acid Blue 277, CI Acid Orange 156 and CI Acid Blue 4 0 . The CI Acid
Blue 40 was tested individually. The preliminary absorbance
values given in Table A-1 have corresponding concentration
calculation equations given in Figure A-1 of the Appendices.
The formulas can be used to calculate the concentration y of
any one of the dyes individually or in a mixture given the
absorbance x value. The formulas were not used in subsequent
129
calculations because (0,O) was used as the first point in the
linear regression which may have had a large effect on the
calibration curve. More accurate formulas were calculated for
the various dyes and dye mixtures used during the
experimentation which did not use (0,O) as a data point.
Additionally, absorbance values were recorded for
distilled water samples treated at the principal iron addition
levels , These values were used to assess the color
contribution of the iron in each sample. However, iron color
contribution was not linear as expected, Table 3-15 shows the
maximum iron color contribution at 354 mg/l iron addition
after which color contribution decreases. Also, several sets
of distilled water were treated throughout the experimentation
for the purpose of iron color subtraction, Different iron
treatment levels were used between sets to match treatment
levels used in sample testing. Figure 3-1 shows three sets
of distilled water samples treated at various iron levels and
absorbance values at 610 nm. Much fluctuation was observed
in absorbance values from set to set although color did
increase in each set with increases in iron addition to about
350 mg/l iron after which color contribution dropped o f f .
This phenomena is not understood, but it is possible that some
equilibrium is offset forcing more iron out of solution at
iron levels in excess of 350 mg/l or perhaps that flocculation
is maximized at that point decreasing the iron in solution and
therefore the color. Incidently, the ferric iron is a rust
130
Table 3-15 Absorbance values for distilled water treated with the Andco Process. The absorbance values represent the color contribution of the iron.
..
Absorbance
5 0 7 5 9 1
Iron Level 1 5 0 ( m g / l ) 3 0 0
3 5 4 450
4 1 0 n.m 510 nm
0.0094 0.0042 0.0212 0.0096 0.0297 0,0144 0.0113 0.0053 0.0476 0,0268 0.0533 0,0392 0.0428 0.0261
610 m
0.0033 0.0085 0.0075 0.0027 0.0193 0.0337 0.0188
131
0.12
0 100 200 300 4 0 0 500
IronLevel (mg)
F i g u r e 3-1 A b s o r b a n c e v s . I r o n L e v e l ( m q / l ) a t 610 nm f o r t h r e e d i f f e r e n t s e t s of t r e a t e d d i s t i l l e d wa te r b l a n k s u s e d t o m e a s u r e i r o n c o l o r c o n t r i b u t i o n .
132
color, but a mixture of ferric and ferrous is nearly black;
the proportion of each present in solution would likely have
an effect on the absorbance. This factor may be significant
as the ferrous iron is continually oxidizing to ferric iron,
changing their respective proportions in solution until all
of the ferrous iron is oxidized, which may take several days
or longer. The amount of iron in solution may also depend on
what other species are present. A dye in water may cause more
iron to precipitate or flocculate than with distilled water
alone, where the iron may stay in solution, Because the
behavior of the iron color at low iron addition levels was
mostly linear but at higher iron levels was non-linear, it was
not decided whether or not iron color subtraction would be a
valid practice. For this reason, two sets of absorbance and
percent removal values are given, one set with iron color
contribution (from Table 3-15) subtracted off and one with the
original data. Except with very pale samples, iron color
contribution could probably be considered negligible.
Betore and after iron color subtraction absorbance values
are given in Table A-2 in the Appendices for the 15 mg/l and
25 mg/l acid dye mixture (AR361, A0156, A B 2 7 7 ) . -The stock
solution absorbance value& were used to develop the
corresponding concentration calculation equations shown in
Figure A - 2 . ' These equations were used to calculate remaining
total dye concentration at each treatment level, the resulting
percent removal values are shown in Table 3-16. Percent
134 - *
reduction ranged from a few percent up to roughly 99%.
Increasing iron addition appeared to consistently increase
color removal until removal was achieved around 95% after
which further iron addition showed little improvement.
Maximum removal seemed to occur from 150 to 350 mg/l iron
addition. A second run of the acid dye mixture was made with
25 mg/l and 50 mg/l stock solutions; however, iron color was
not subtracted out as shown in Table 3-17. Once again,
maximum removal occurred around 250-350 mg/l iron addition
although with noticeably less removal than the first acid dye
mixture results had shown. Unlike COD treatment, higher
initial dye concentrations appeared to have better removal
than lower concentration samples. The Acid Blue 4 0 was tested
..
for absorbance values at 5, 10 and 20 mg/l sample
concentrations to develop a concentration calculation equation
as shown in Table A-3 in the Appendices. The absorbances were
taken only at 610 nm as it is the principal absorbance
wavelength for blue, and because the Acid Blue 4 0 was to be
tested individually. Excellent color removal was observed for - Acid Blue 40 at 250-350 m g / l iror? addition in the range of
roughly 80-97% as shown in Table 3-18. Iron colo2 was also
subtracted out revealing even higher color reduction (in the
event that iron color subtraction is valid). Another dye was
tested at 25 mg/l and 50 mg/l stock solution concentrations,
Procion Blue MX-2G. Absorbance values were recorded at 610
nm and removal percents provided as shown in Table 3-19. The
135
Table 3-16 Acid dye mixture percent reduction values f o r 15.(mg/l) and 25 (mg/l) samples with increasing iron addition ~ A ) before iron color absorbance subtraction B) after iron color absorbance subtraction. * Represents percent increase in absorbance.
Percent Reduction
A) 410 mu 510 nm
15 (mg/l) 7 5 45.9 44.0 150 58.9 48.6 300 * +29.3 18.0 450 27.0 53.3
Iron Level ( m g / l )
25 (mg/l) 9 1 4.1. 0 150 76.2 354 68.7 450 78.3
B)
15 (mg/l) 7 5 150 300 450
I r o n Level ( m g / l )
9 1 150 354 450
- 55.5 66.9 76.2 79.0
Percent Reduction
4 1 0 mu 510 nm
61.8 67.4 6.3
59.0
52.5 50.6 42.1 76.4
54.3 81.0 92.6 97.5
63.2 69.7 96.9 92.9
610 nm
* +19.0 29.7
* +15.5 25.9
26.5 68.4 55.6 65.3
610 nm
* + 1.0 35.4 25.5
** 66.2
36.0 71.8 98.8 89.3
136
Table 3-17
25 (mg/l) 50 150 250 350
Iron Level "/I)
50 (mg/l) 50 150 250 350
Corresponding color reduction percent for the acid dye mixture at 25 (mg/l) and 50 (mg/l) sample concentrations with increasing iron addition.
Percent Reduction
4 1 0 nm 510 nm
21.0 69.3 68.0 77.6
+1.0 56.8 66.2 74.0
29.4 72.0 65.6 76.5
+2.5 58.9 68.3 70.2
610
17.6 44.3 63.6 75.4
+15.0 + 8.8 44.4 42.9
137
Table 3-18 Absorbance and percent color reduction values for A . B . 40 25 (mg/l) sample A) before iron color absorbance subtraction B) after iron color absorbance subtraction.
A) 610 nm % Reduction
2 5 ( m g / l ) stock ( 0 ) 0.4044 50 0 3510
Iron Level 150 0.3302 "/l) 250 0.0960
350 0 . 0 3 0 2
- 13.0 18.3 77.6 94.2
B) 610 nm % Reduction
2 5 . ( m g / l ) stock ( 0 ) 0.4044 50 0 . 3456
Iron Level 150 0.3198 "1) 250 0.0810
350 0.0192
14.6 21.1 81.4 97.0
138
Table 3-19
Iron Level "/l)
Absorbance with percent reduction values for Procion Blue MX-2G at 25 (mg/l) and 50 (mg/l) sample concentrations.
2 5 (ms/l)
3
Stock (0) 0.1255 - 610 nm Reduction
50 0.1132 9.8 100 0,0700 44.2 150 0.0800 36.3 250 0.0536 57.3 350 0.0550 56.3 450 0.0555 55.8
50 (ms/l)
31 610 nm Reduction
0.2121 - 0.0531 75.0 0.0531 73.5 0.0580 72.7 0,0483 77.3 0.0455 78.5 0.0574 72-9
139
percent color reduction was good but not exceptional with
maximum values around 7 8 % .
Treated Dvebath Water Reuse Results
The treated dyebath water reuse tests involved the use
of both nylon heatset carpet yarn and scoured cotton fabric.
Only one set of dyeings was done with the cotton fabric, using
a Procion direct cotton dye. All other sets of dyeings used
acid dyes and the nylon carpet yarn. The carpet yarn dyeings
were done using two types of dyebath constitutions. The first
type, referred to as Wnspiked,Ir were prepared in the same
conventional manner as the control sample except that treated
water (a dye solution simulating an exhausted dyebath, treated
electrochemically to remove color such that the water can be
reused in dyeing) was used in place of the tapwater required
in the dyebath. The second type, referred to as llspiked,lt had
additional auxiliary chemicals and stainblocker chemicals
added directly to the dyebaths to simulate residual chemical
content remaining in the dyebath water after treatment.
Details on the constitution of both types of dyebaths are
given in the experimental section (Chapter 11).
Also, in the dyeings referred to as A.B. 277 dyeing #1,
A . R . 361 dyeing #1 (for unspiked samples) and the A . B . 2 7 7 /
A . R . 361 purple mixture, residual dye content in the treated
water was accounted for by reconstituting the dyebaths;
however, this did not seem to improve or effect the color
140
matching results and so was not taken into account in
subsequent dyeings. Also, the iron treatment level used
appeared to have no noticeable effect on the dyeing behavior
of the samples as::long as color removal was better than 60%.
The results of the dyebath reuse tests appeared to
indicate at best, the possibility of dyebath reuse after
treatment. Tables 3-20 through 3-24 show color matching data
for several sets of dyeings. Values are given for the control
standard and samples dyed with water treated at various levels
of iron addition (the number at the top of each column
represents the iron addition level in mg/l used to treat the
water used in that particular dyeing). A spiked sample is
denoted when the letters 88ST88 appear after the iron addition
level, and a dyeing carried out in the same manner twice is
denoted by the iron level followed by an I8Att and then a I1BI8.
The color matching values f o r each sample are L* = lightness-
darkness, a* = redness-greenness, b* = yellowness-blueness,
C* = saturation, and h = hue. The I8Dl8 values represent the
differences -in the above variables between the control
standard sample and the treated water sample, with DE being
the total color difference. Table 3-20 summariees color
matching values for the first;set of dyeings for Acid Blue 277
and the Acid Blue 277/Acid Red 361 purple dyeing. The values
of the first A.B. 277 dyeing can be compared to the values
given in Table 3-21 for the second set of A.B. 277 dyeings.
Table 3-22 gives color matching values for the first A.R. 361
141
T a b l e 3-20 CIE LAB color matching for A.B. 2 7 7 - d y e i n g 81 and A.B. 277/A.R. 361 purple dyeing #1.
A.B. 277 Dveinq
S t a n d a r d - 197 - 283
L* 41.37 40.57 37 . 70 a* -2.57 -2.87 -1.16 b* -44.45 -43 . 50 -44.37 C* 44.52 43 . 59 44 . 38 h* 266.69 266.23 268.50
DL* --- -0.79 -3 . 67 D a * --- -0.30 1 . 4 1 Db* --- 0.95 0.08 DC* --- -0.93 -0.14 DH* --- -0.36 1.40 DE* --- 1.27 3.93
Pumle Dveinq
Standard 207A
L* 31.62 34 .71 a* 28.11 26.87 b* -21 .41 -21.95 c* 35.34 34 . 69 h* 322.70 320.76
DL* --- 3.09 D a * --- -1.24 Db* --- -0.53 DC* --- -0.64 DH* --- -1.18 DE* --- 3.37
- 207B
33.32 27.30
-22.50 35.37
320.51
1.70 -0.81 -1.08 -0.04 -1.35
2.17
32.15 26.80
-23.35 35.54
318.94
0.53 -1.31 -1.93
0 . 2 1 -2.33 -2.39
142
Table 3-21 CIE LAB color matching values for-A.B. 277 ST = stainblocker/auxiliary spiked dyeing #2 .
sample.
Standard - 1 2 1
L* 4 2 . 1 9 42 .37 a* -3.19 -3.28 b* -43.70 -43 .95 C* 43 .82 4 4 . 0 8 h 265 .82 265 .74
DL* --- 0 . 1 8 'Da* --- -0 .19
Db* --- -0 .25 DC* --- 0 . 2 6 DH* --- -0 .07 DE* --- 0 .32
1 2 1ST
4 3 . 6 1 4 .22
-42 .86 4 3 . 0 7
2 6 4 . 3 7
1 . 4 3 -1.03
0 .84 -0 .75 -1.10
1 . 9 5
- 207
40 .55 -2.08
-44 .81 44 .86
267 .34
-1.64 1.11
-1.11 1.04 1.17 2 .27
207ST 287
4 4 . 9 8 42 .34 -4 .70 -3.10
-42 .71 4 4 ; 0 7 42 .97 44 .18
2 6 3 . 7 1 265 .98
2 .79 0.16 -1.51 0.09
0 . 9 9 -0.36 -0.85 0 .36 -1.60 0.12
3.33 0 . 4 1
287ST
4 3 . 9 5 -4.20
-43 .30 4 3 . 5 0
2 6 4 . 4 5
1 . 7 6 -1.01
0 . 4 0 0 .32
-1.04 2 .07
143
Table 3-22
Standard
L* 45.54 a* 54.20 b* -1.77 C* 54.23 h 358.13
CIE LAB color matching values f o r A.R.361 dyeing
121
46.71 53.86 -2.20 53.90 357 . 66
1.17 -0.34 -0.42 -0.32 -0.44 2.07
#1. ST =stainblocker spiked sample
121st
43.89 54.09 -0.52 54.09 359.45
-1.65 -0.11 1.24
-0.13 1.24 1.29
- 207
42.99 54.51 0.05
54.51 0.06
-2.54 0.32 1.82
-0.29 -1.83 3.14
207ST
46.64 53.70 -1.61 53.72
358.29
1.10 -0.50 0.16
-0.51 0.15 1.22
- 287
46.12 53.57 -1.76 53.60 358.12
-0.58 -0.62 0.01
-0.62 -0.01 0.85
2875t
45.06 54.29 -0.99 54.30
358.96
-0.48 0.09 0.78 0.07 0.78 0.92
144
dyeing including
matching values
including spiked
somewhat higher
first .
spiked samples. Table 3-23 gives color
for the second set of A.R. 361 dyeings
samples . Overall color difference was
n the second A.R. 361 dyeing than in the
The Procion Red dyed set was the only set done on scoured
cotton, all other sets used nylon 6 , 6 270°F Superba heatset
yarn. Visual observation of the samples showed that samples
had poor leveling. This was no doubt due to the small scale
beaker dyeing process in which the sample was folded or
crumpled into a ball in the dyebath. Stirring did not seem
to help dye diffusion very much. Color differences as given
in Table 3-24 were very large, although the 121 sample had a
smaller'color difference as compared to the other samples.
For the most part, samples within a given set of unspiked
samples came closest to the tapwater dyed control sample.
Spiked samples did not come nearly as close, and in most cases
were quite far from a match with the control sample. In fact,
of the ten spiked samples only one had a DE value less than
1.00 (A good color match has a DE value less than or equal to
1.00). However, within a given set of spiked samples, the
dyeing similarities were much,closer when comparing one spiked
sample to another within the same set. In fact, of all the
spiked samples, the DE values ranged from approximately 0.30
to 1.70 with an average value of about 1 corresponding to
color matches within the sets of spiked samples. One of the
145
Table 3-23 CIE LAB color matching values f o r AR 361 dyeing #2. ST = stainblocker spiked sample.
Standard 121 - 207 - 287
L* 40.43 40.82 42.05 41.56 a* 56.06 55.84 55.93 55.59 b* 2.96 2.28 1.60 1.85 C* 56.14 55.89 55.96 55.62 h 3.03 2.34 1.64 0.74
L* a* b* C* h
DL* Da* Db DC DH DE
Standard
40.43 56.06 2.96 56.14 3.03
0.39 1.62 1.13 -0.22 -0.13 -0.48 -0.68 -1.36 -1.11 -0.25 -0.19 0.52 -0.67 -1.36 -1.09 0.82 2.12 1.66
121ST
42.47 56.19 1.75
56.21 1.79
2.04 0.12
-1.21 Q.07 -1.22 2.37
207STA 207STB 2875t
43.54 55.93 0.73
55 . 94 0.74
3.11 -0 . 13 -2.24 -0.20 -2 . 23 3.84
44 . 15 56.14 0.41
56.14 0.42
3.72 0.08
-2 . 55 0.00
-2.55 ' 4.51
43.90 55.88 0.34
55.88 0.35 '
3.47 -0.18 2.62 0.26
-2. 62 4.35
146
Table 3-24
L* a* b* C* h DL* Da* Db* DC* DH* DE*
CIE LAB color matching values f o r Procion Red dyeing #l.
Standard
62.64 45.85 -4.14 46.03 354.85 ---
62.18 46.73 -4.81 46.98 354.12 -0.06 0.89 0.68 0.95
-0.59 1.12
64.25 42.80 -5.15 43.11 354.12 2.01
-3.04 -1.02 -2.92 -1.33 3.79
60.59 47.60 -5.12 47.88
353.87 -1.65 1.76
-0.98 1.84
-0.80 2.60
147
major causes of color difference between the spiked samples
and the control was probably due primarily to the stainblocker
chemical addition, as opposed to the excess auxiliary
chemicals, as the ',ispiked samples generally appeared lighter
than the unspiked samples. Of a total of ten spiked dyeings
eight were lighter and two darker than the control sample.
It was observed during the experiments that a noticeably
larger amount of dye washed off the spiked samples during the .
tapwater rinse. This would seem realistic since the
stainblocker chemical present in the spiked dyebaths very
probably competed with the dye for dye sites, reducing the
amount of dye uptake onto the fiber.
A color match may possibly be achieved by compensating
f o r the effects of the stainblocker chemical by increasing the
dye concentration in the bath. Also, the presence of a
stainblocker chemical in the dyebath may reduce the amount of
fresh stainblocker chemical needed in the finishing process.
On the other hand, the presence of stainblocker chemicals in
the dyebath may also inhibit or alter the usual uptake of
fresh stainblocker chemicals. In any case, the fact that
initial dyeings showed consistency within each set .(even if
there were no color matches) suggests that optimization of the
dyebath with chemical compensation might be all that is
necessary tox reduce color differences. If the exhausted
dyebath water is segregated from the wastewater containing the
stainblocker, the optimization of the recycled dyebath water
148
would likely be much easier. Also, the color differences
occurring in the samples may be partially due to the small
beaker dyeings which were used. Chemical concentration
differences are much more likely in the small volume beaker
dyeings than in full-scale dyeings. A one drop difference in
dye solution addition is significant in beaker dyeings and can
cause measurable color differences between samples, However,
the purpose of these experiments was not to achieve exact
color matches, but rather to observe the general behavior of
the treated dyebath water in reuse tests, and to determine if
full-scale dyeing tests would be worthwhile to attempt,
A Studv of the Color Removal Process
The purpose of this section was to determine if dyes were
removed, totally by adsorption onto the ferrous hydroxide or
by dye alteration or some combination of the two. The scope
of this research was not necessarily to determine what
degradation products were present so much as to determine if
there were degradation products. However, where ever
possible, details on’possible destruction/altered products are
given. It is also possible that if there are degradation
products that the concern for safety may be negligible as the
degradation products may further degrade at such a fast rate
as to make over concern unjustifiable. Camp [16] found that
anilines degraded by photolysis and oxidation within a few
days after preparation and weeks old samples had no measurable
149
traces of aniline or its oxidation products. Camp [16] also
indicated that sulfonated
water soluble keeping them
molecules of the hody thus
type degradation products.
An attempt was made to
degradation products were quite
from bioaccumulating in the fatty
reducing the threat of sulfanilic
calculate the actual concentration
of the remaining chemical content at each wavelength studied.
Standard solutions of known concentratiorl were measured for
absorbance values at each wavelength for each chemical tested,
and linear regression was used to develop calibration
equations. However, the use of these equations was found to
be invalid as they were only useful for calculating the
residual concentration of pure starting material (i.e. Food
'Blue #2 ) at the selected wavelengths, Unfortunately, after
electrochemical treatment the solution consisted of not a pure
starting material, but rather, a mixture of starting material
and degradation products. Because the absorptivity values
were calculated for the pure starting material, they were not
applicable to the mixture, as each degradation product would
have its own absorptivity value at each wavelength. For this
reason results are given as percent change in absorbance
relative to the absorbance o:f the starting material before
treatment (i.e. the control sample) at the selected
wavelengths and arrows indicate whether there was an increase
or decrease in absorbance. Also, the absorbance spectra for
the control, standard and treated samples of each set are
150
given in Appendix B, Figures B-1 through B-26.
Results For Acid Blue 277
The Acid Blue 277 control sample was a 20 mg/l
concentration solution treated with 121, 207, and 287 mg/l
iron addition levels. The A.B. 277 was the first sample
tested in this series of experiments, and was used to observe
the behavior of a major carpet dye with electrochemical
treatment. The structure of A.B. 277 is proprietary but is
believed to be an anthraquinone type dye. The anthraquinone
structure is not nearly as susceptible to reduction as azo
bonded structures due to the stabilized conjugated bonds in
the multiple ring system of the dye. It should show
significantly less indication of alteration and/or
destruction. The results in Table 3-25 show the percent
change in absorbance for selected wavelengths for each treated
sample and standard stock solution measured with the
spectrophotometer. The higher wavelengths, 556 and 604 nm
represent the visible region in which blue dye has its
absorption maxima. The A.B. 277 turned out to be a weak
absorber even in the blue region; however, its absorption in
this region was strong enough to show color removal with
electrochemical treatment. T.pe spectra of the 3.0 mg/l and
10.0 mg/l standards were very useful in determining what
approximate reductions at each wavelength could be expected.
The 3.0 mg/l standard was very consistent having absorption
reductions of approximately 88 to 92 % on the average (
Table 3-25 Percent change in absorbance for ACID BLUE 277 standards and treated samples at 8 deet e d wavelengths.
Wavelengths (nm)
Stimdnrds 220 254 284 332 386 556 604
3" 5. 86.7% J. 89.7% 4 91,3% 5. 97:9% 3. 91.5% L 88.2% 3. 89.1%
10mg/L J. 49.0% .L 59.9% 5. 62.0% 4 62.7% .1.47.1% $ 54.6% 5. 58.9% . --
Iron Levels ------ 121mg/L 5. 30.0% 3. 57.3% 4 50.0% 0.00% I' 3.53% L 44.0% 3. 82.1%
207mg/L 4 52.0% 4 55.5% 4 82.6% 3.1 74.2% 4 58.8% 4 92.0% \1. 94.9%
287mg/L .L 28.5% 5. 55.5% 4 46.1% 3. 6.45% .& 459% J, 60.0% 5. 66.6% '*
152
relative to the spectral absorptions measured for the A . B . 277
control solution of 20 mg/l ) . However, with an increase in
concentration to 10.0 mg/l the percent decrease in absorption
was fairly consistent values for 254, 332, 556 and 604 nm but
was roughly 10 - 12% less at 220 and 386 nm. Since this was a standard solution these observations had to be taken into
account when observing the corresponding treated samples'
spectra. In order to suggest dye alteration with some amount
of confidence, the differences between the color removal
absorption reductions and the aromatic region absorption
reductions would need to be greater than 10 to 12 % to account
forthe variabilitywithinthe standards. The treated samples
showed significantly more variability in absorption decreases
allowing for conclusions to be drawn. The 121 mg/l treatment
level shows nearly the same color removal as the 3.0 mg/l
standard but 25% less reduction at 254 nm, the maximum
absorption wavelength for benzene and 30 % less at 284 nm, the
substituted benzene region. The absorption is 50 % less at
220 nm, but the 10 to 12 % difference observed for the
standard must be taken into account. This gives an actual
difference of about 40 %. The 207 and 287 mg/l samples did
not exhibit as great a variability in absorption reduction
from wavelength to wavelength. For instance, the color
removal was 94.9% at 604 nm for the 207 mg/l treated sample
and 88.5% at 254 nm indicating a closely corresponding
aromatic content reduction. The 207 and 287 mg/l treated
153
samples had noticeably less absorbance reduction at 386 nm
ranging from 2 0 to 35%. The 386 nm is at the lower end of the
visible wavelengths corresponding to absorbance of the color
yellow. After studying the different absorbance reductions,
it was decided that adsorption/complexing was probably
predominating, but that the areas of remaining aromatic
content at high color removal levels indicated color
substituents alteration as opposed to dye molecule
destruction. It is not unlikely that the carbonyl group(s)
could have been reduced to alcohol groups causing the removal
of color without aromatic content removal (or anthraquinone
structure destruction). If the anthraquinone had been broken
into aromatic fragments a much lower or even an increase in
absorbance reduction would have been observed in the aromatic
absorption region (molecule destruction would have resulted
in a molar increase in benzene type derivatives).
Resuzts For FD&C Food Yellow #5
The Food Yellow #5 dye control sample was a 30 mg/l
concentration solution treated at 151, 237, and 337 mg/l iron
addition levels. The Food Yellow #5 was tested because of its
purity and because it had an azo bond incorporated. into its
structure. The results in Table 3-26 indicated that actual
dye destruction of some type was occurring. Again, the 3.0
and 10.0 mg/l standards were used to observe the variability
in absorbance reduction from wavelength to wavelength. The
3.0 mg/l sample was fairly consistent in percent absorbance
154
Table 3-26 Percent change in absorbance for FDBrC Food Yellow #5 standards and treated samples at selected wavelengths.
Wavelengths (nm)
standards 220 229 254 266 433
Iron ]Levels
151 q / L 4 31.3%
237 mg/L J. 39.4%
337 mg/L J. 43.8%
\t 72.3%
f 29.4%
?' 17.6%
r 9.8 yo
& 62.5% & 73.3%
4 17.7?? 4 62.3%
5. 13.6% $ 64.9%
4 23.6% 4 67.4%
.. .
4 90.0?/0
J. 68.4%
& 88.6%
6 88.9%
.L 90.00!
155
reduction, but the 10.0 mg/l standard
not exceeding 20 %. For this reason a
greater than 20 % would be needed to
showed some fluctuation
variation in absorbance
support the possibility
of dye destruction. Fortunately, there was a large difference
between color removal for each of the treated samples (89 to
90 % decrease at 433 nm yellow absorption wavelength) and the
corresponding aromatic region removal (31to 44 % decrease at
220 nm, 10 to 30 % increase at 229 nm, 14 to 24 % decrease at
254 nm and 62 to 67 % decrease at 266 nm). These values are
significantly different from the color removal values such
that they support actual dye destruction. Characteristic
absorption wavelengths for the possible degradation products
obtained from the Sadtler Handbook [33] also support the
conclusions. One likely degradation product of Food Yellow
#5 would be sulfanilic acid which has absorption maxima at 253
nm and 266 nm where 14-24% and 25-30% less reduction in
absorbance is observed respectively comparedtothat for color
removal. Also, aniline would be a likely product and it has
absorption maxima in the r-egion of 230 nm and 254 nm where an
increase in absorption is observed from 10 to 30 % and a
decrease of only 14 to 24% respectively . Also,-.residual
amines and carbonyl groups absorb strongly at 195 nm to 220
nm; the values at 220 nm would be at the beginning of this
region and they show a decrease of only 31 to 44%. Visual
observation of the treated samples showed that their color was
significantly different fromthat of dilute standard solutions
156
of Food Yellow #5. The treated samples were pale beige/tan
as compared to pale yellow for the diluted standards
(incidentally, dilute aniline appears beige/tan in color) . The data support':-that dye destruction is occurring in this
case with likely reduction of the azo bond predominating.
Results For FD&C Food Blue #2
The Food Blue #2 control sample was a 28 mg/l
concentration solution treated with 1 5 4 , 237 and 337 mg/l iron
addition levels. The Food Blue #2 was selected out of
curiosity to observe the behavior of a dye with a carbon-
carbon double bond as compared to the behavior of the azo-
bond. The results in Table 3-27 indicate dye destruction as
with the Food Yellow #5. The 3.0 and 10.0 mg/l standard
samples were very consistent in percent absorbance reduction
with no more than a 12% difference between any two
wavelengths. The treated samples were also fairly consistent
in percent absorbance reductions from wavelength to
wavelength. Color removal is given at 612 nm ranging from 78
to 90%. A 5% to 11 % less reduction in absorbance is observed
at 286 nm, another characteristic absorbance region for
aniline. At 2 5 4 nm a 59 % to 69 % reduction in absorbance
occurs corresponding to benzene, benzene sulfonic acid, and
sulfanilic acid-sodium salt (i.e. 254, 253, 252.5 nm
respectively) , all of which are possible degradation products of 'Food Blue #2. Absorption decreases at 232 nm were very low
at 3 to 28 %. Aniline has an absorption maxima at 233 nm.
157
Table3-27 Percent change in absorbance for FD&C Food Blue ff2 Seandards'and treated samples at selected wavelengths.
Wavelengths (nm)
L O e / L J, 69.6% .L 65.7% J. 61.1% .L 58.8% & 57.5%
Iron Levels
237efL & 46.0?! 28.3% .L 68.6% 5-- 81.6% 86-8om
337mg/L J. 39.0?! 5- 16.7% 4 58.6% & 70.8% J. 78.1%
158
Absorption was also found to increase at 220 nm going off-
scale in most cases by 210 nm and continuing strong to 195 nm.
As discussed earlier, amine, aldehyde, ketone and nitro groups
absorb strongly Pn this region. The data indicate the ..
production of aniline and sulfanilic acid products which would
only be possible if the carbon-carbon double bond was reduced
during the treatment process.
Results For Azobenzene
The azobenzene control sample was a 34 m g / l concentration
solution treated with 154, 302 and 345 mg/l iron treatment
levels. The azobenzene was treated in a 3.5% methanol/
distilled water solution to achieve sufficient solubility.
More supportive data could be collected by running a high
purity solution of azobenzene through the electrochemical
treatment unit for the simple reason that it has a limited
number of possible degradation products, Azobenzene in
solution is a bright yellow color which lends itself to this
type of study by allowing color removal to be compared with
aromatic content removal, Color removal, if not by
adsorption, would be caused by destruction bf the azo bond
which is the main chemical substituent responsible'for color
of the azobenzene. The results in Table 3-28 indicate azo
bond destruction, also Table 3-29 shows percent change in
absorbance r for the azobenzene degraded with sodium
hydrosulfite and absorbance values for dilute aniline. The
3.0 and 10.0 m g / l standards were very consistent in percent
Table 3-28 Percent change h .absorbance for Azobenzene standards and treated samples at selectcd wavelengths.
Wavelengths (nm)
3mg/L
IOmg/L
Iron Levcts
151mg/L
302mg/L
-------
345mg/L
J. 83.8%
5. 52.4%
'l' 85.0%
'? 197,%
'l' 69.3%
4 84.1%
-& 53.6%
'I' 150.%
'I' 149.%
1' 145,%
.I 87.6%
$. 5,8.9%
T 190.%
?' 259.%
'T' 219,%
$ 84.1%
5. 53.0%
1' 4,20%
'P 22.6%
J. 9.80%
3. 82.4% 8&5%
5. 50.6% '4 60.6%
J. 59.3% 4' 1.57%
3. 53.0% It\ 200.?40
3. 65.4% + 85.0% I
160
Table 3-29 Percent change in absorbance for Azobenzene 34 mg/L degraded w i t h sodium hydrosulfite at selected wavelengths and absorbances for dilute Aniline.
Azobenzene degraded with sodium hydrosulfite
Wavelengths (nm)
220 230 254. 285 3 s 4L9
T42.9% 1'51.1% T124Yo 452.0% +84.8% 498.2%
Anfline (unknown wnceniration - dilute)
0.67 1.18 0.14 0.20 0.00 0.00
. .
I
f
reduction of absorbance, varying no more than 10 % betwc
two wavelengths. The strongest absorption maxima f
azobenzene control sample was at 319 nm (compared with
for the Stadtler. value 1331). The percent reduct
absorbance at this wavelength (319nm) for the treated
was 53 % to 65 %.
(the same as the treated sample) reduced with
i
< The identical concentration of azo
c
rl
c
hydrosulfite, had a corresponding 85% absorbance reduc
319 nm. On the other hand, at 285 nm the 150 and 3
iron treated samples increased 4 to 23 % in abs
respectively while the 345 mg/l treated sample decrea:
10%. It also happens that aniline has an absorptior
at 286 nm being a likely cause of the absorbance inc
In addition, absorbance increased dramatically from 22
nm for all treated samples; this was also the case
azobenzene degraded with sodium hydrosulfite. The ot
absorption maxima for aniline is 233 nm which might co
to the 150% increase at 230 nm for the treated samp
addition, benzene absorbs strongly at 254 nm; where
a 190 to 250 % increase in absorption for the treated
One other supporting observation was made. The spe'c
dilute aniline was observed to be nearly superimpose;
the spectra of the treated samples and that of th
hydrosulfite reduced azobenzene. One unexplained
observed only with the treated samples was an inc
absorption at 419 nm ranging from 2 to 200 %. This
1 6 2
the aromatic absorption region and in the visible region.
This indicates a possible change in the chemical molecule
separate from destruction. This might be caused by incomplete
reduction of the..azo bond to form hydrazobenzene which may
have some color contributing characteristics. This may also
be supported by the fact that the color of the treated samples
was beige/tan as opposed to pale yellow for dilute azobenzene
and clear/transparent for the sodium hydrosulfite degraded
sample. The chemically degraded azobenzene was probably more
completely reduced as indicated by the clear transparent
color. Regardless of the actual destruction mechanism or
degree of destruction, the data do support that azo bonded
species are highly susceptible to some form of alteration
and/or destruction during the electrochemical treatment
process employed in these experiments.
Cost Analysis
Electrochemical treatment appears to have good potential
as an textile wastewater treatment system. A cost analysis
was performed to compare the Andco Treatment System's daily
annual operating costs and capital investment costs with other
wastewater treatment systems. Figure 3-30 [ 3 8 ] shows a cost
break-down that includes consumables (chemicals, iron etc.),
and power requirements. The power requirements for iron
generation, as well as, the iron used are the largest
contributors to the operating cost for the Andco Process.
The daily and annual operating costs are given for each of the
Iron Addition Level mg/l
Consumables' 150 200 250 300 350 450 550 650 $/day
1,119.315 Annual opr. cost 269.800 354,645. 439.845 524,690 609,535 78 1 ,OOO 949,270
p s p e 3-30 Annuatand W y operating costs for a mill treating 1.0 million gallons per day for Werent b n treatment levels, Iron sludge production is also given. Values rounded to the nearest whole number and annual values represent 355 days.
a Lui. 135 S1.162 9J470-17,OOo tons 2500 tans
165
standard iron addition levels most commonly used. The values
given are representative for a plant treating one million
gallons per day. Annual operating costs range from $ 270,000
for a plant using. 150 mg/l iron addition to $ 1,120,000 for
a plant using 650 mg/l iron addition. For a plant treating
dyebath water, the lower iron treatment levels would be
sufficient, thus costing less than a plant treating a high COD
wastestream containing auxiliaries and stainblockers, which
would require higher iron addition levels greater than 300mg/l
Figure 3-31 [1],[38] gives A) The capital cost, B) The annual
operating cost, C) The daily operating cost and D) The annual
sludge production in tons, for several selected water
treatment systems including the Andco Treatment Process. Each
has been calculated for plants treating one million gallons
per day. At iron treatment levels of 300 mg/l, the Andco
Process is comparable in capital investment cost to chemical
coagulation/precipitation, powdered activated carbon. with
extended activated aerobic sludge, and granular activated
carbon (without regeneration) . Although the capital costs are similar, the annual operating costs for the Andco Process are
up to twenty-five times less than chemical precipitation and
activated carbon. However, both chemical precipitation and
activated carbon have several times greater sludge production.
On the other hand, at iron treatment levels greater than
300mg/l the Andco Process is comparable in operating cost to
ozonation. Ozonation, which has considerably less annual
166
operating cost and no sludge production, would seem like the
better option, as it is very effective at destroying
wastewater constituents. Ozonation also has no sludge
disposal cost, although . I the ozone must be generated at the
treatment site, requiring its own generation equipment.
Although, the initial capital investment for ozonation is
roughly 2 to 2 1/2 times greater than for the Andco Process,
the cost differential can be recovered within about two years.
Even at lower iron addition levels, the Andco Process is still
more expensive to operate than ozone. Other than ozone, all
of the intermediate and advanced treatment systems listed are
considerably more expensive to operate than the Andco Process.
Although activated carbon and membrane systems may be the most
effective systems for actual chemical removal, in some cases
actual removal is not necessary and only adds to the expense
of wastewater treatment. For this reason, processes like
ozonation and the Andco Electrochemical Treatment Process
which destroy (and/or remove and destroy in the case of the
Andco Process) a chemical's structure may be sufficient. The
final selection of a wastewater treatment system is determined
by an individual plant's water treatment needs and available
investment and operating capital.
167
CHAPTER IV
CONCLUSIONS AND RECOMMENDATIONS
Chemical Oxysen Demand Reduction
The Andco Electrochemical Treatment Process appears to
be a potential prospect for use in textile industry wastewater
treatment. Through the first portion of this study it war
found that the Andco Process effectively removed chemical
oxygen demand levels by 25% to 95% depending on the chemical,
its concentration and the iron treatment level. The newer
stainblocker formulations achieved removal levels' averaging
80%. Industry should be applauded for the quick response time
in reformulating their stainblockers to reduce threat to the
environment and meet effluent standards. Chemical oxygen
demand values were not very conclusive as far as dyes were
concerned, as their COD values approached the background error
for the COD test. Polymer addition used in the flocculation
process was found-to contribute negligible amounts of COD to
the treated samples. However, the polymer COD in the
distilled water blanks was not easily determined. as the
results were often masked in Bhe background error for the COD
test. A better method of assessing the polymer COD would have
been to prepare more concentrated solutions of polymer and
168
determine the COD with increasing concentration. In this
manner, the COD of the dilute polymer added to flocculate a
sample could be calculated from a calibration equation
developed from the COD values determined for the higher
concentration polymer solutions. The COD contributed to the
sample could then be estimated to be no more than the COD for
the corresponding volume of dilute polymer used to flocculate
the sample. One other possible contributer to the COD of the
treated samples was the ferrous hydroxide from the
electrochemical treatment. The amount of COD contribution
would be proportional to the amount of ferrous hydroxide
present in the sample, which would depend on how fast it
oxidizes to ferric hydroxide before the COD test is performed
on the sample. A more accurate experiment would have employed
the use of treated samples bubbled with oxygen to oxidize the
ferrous iron to ferric iron before running the COD test. The
contribution to COD would probably be very small as a large
portion of ferrous iron oxidizes to ferric iron during the
electrochemical treatment, due to air exposure and constant
solr-ltior. mixingi
Also , auxiliary chemicals were reduced by about 40 %
to 70 &. Chemicals like Guar Gum were difficult to floc at
concentrations higher than 0.3 g/1 because the chemical
floated to ‘the surface away from the iron. The anionic
surfactant tested had good removal as long as the concentation
of the stock solution was less than 0.8 g/1 after which
169
flocculation became difficult due to excessive foaming of the
surfactant. The total carbon tests appeared to work best for
testing higher COD samples like stainblockers as opposed to
dyes. The TC tksts confirmed increased organic (carbon)
reduction with polymer flocculation, as opposed to settling
alone without polymer addition. The COD and TC results for the
dyes were too inconsistent and variable to draw any
conclusions on dye removal, The absorption testingturned out
to be a much better method for studying color removal.
Color Removal
The color removal study showed very high removal levels
approaching 100% in some cases, Average color removal values
ranged from 75% to 95%. Mid-range concentrations around 25
mg/l of dyes were removed the best, while concentrations that
were lower (i,e. 15 mg/l) or higher (i.e. 50 mg/l) generally
had lesser removal values. Also, iron levels from 150 mg/l
to 2 5 0 mg/l had the best removal values. Higher iron addition
did not appear to significantly increase removal percents.
In addition, iron color contribution was studied and was found
to fluctuate from one treated set to another. Iron color
contribution within a given test set was found to. increase
until an iron level of 300-3.50 mg/l was reached after which
the color level dropped off. The cause of this phenomena was
not known but thought to be a consequence of several factors.
One possibility was that at higher iron levels the iron
flocculated better removing more iron , thus reducing iron
170
color contribution. Another possiblity was that the
proportion of ferrous (greenish yellow in color) to ferric
(reddish color) iron changed significantly (for unknown
reasons) at higher ‘iron addition levels, thus causing a change
in color contribution. At higher iron levels the sample would
have been exposed to air and mixing longer allowing for more
oxidation of the ferrous iron. Dye samples reaching high
levels of removal at high treatment levels appeared to take
on the characteristic color increase and drop-offs associated
with iron blanks. The iron may also behave differently when
a chemical species (i.e. dye) is present as opposed to when
it is in a distilied water soultion, Due to the unusual
behavior of the iron color, its subtraction from dye samples
for iron color contribution may not be valid. The color
contribution of the iron was very small in relation to
absorbance values of treated samples except at very high
treatment levels and so could be considered to be negligible,
Treated Dvebath Water Reuse
The results of the dyebath water reuse study indicated
that electrochemically treated dyebath water might be
acceptable for reuse with further optimization.,’*Further
experiments using full-scale’dyeings would be necessary to
optimize the dyebath for use with treated water. Full-scale
testing wou‘ld greatly reduce the concentration errors
associated with the small beaker dyeings and give more
conclusive results as to how close a color match could be
1 7 1
obtained between control and treated samples. Also, a
treatment system set up for treated dyebath water reuse should
be positioned in the process such that it receives segregated
water coming directly from the dyebath with no further
finishing chemical content (i.e. stainblockers). A mixed
wastestream would increase the difficulty in adjusting the
recycled dyebath. Also, a company investing in such a
treatment system with water reuse capabilities would be
foolish not to use the system to its fullest potential.
Although the recent year has seen precipitation levels above
average, the trend until recently has been drought. By merely
adjusting some of the plumbing within the plant water reuse
capability would at least be available during times of water
limitations, minimizing impact on production during droughts,
even if the system was not utilized in such a capacity on a
permanent basis.
Mechanism of Dye Removal
Results of the mechanism of dye removal study showed that
dyes containing azo bonds are highly susceptible to
alteration/destruction. Depending on the exact structure of
the dye, various degradation products were indicated in the
results including: 1) aniline, 2) sulfanilic acid, 3 ) benzene
sulfonic acid, 4 ) benzene, and 5) hydrazobenzene. Also, it
appeared that dyes with carbon-carbon double bonds were also
highly susceptible to destruction at the double bond. The
anthraquinone dye that was tested appeared to be primarily
172
removed by some precipitation process, possibly adsorption or
complexin2. The anthraquinone was less susceptible to
destruction in the electrochemical treatment process most
likely due to the, stabilized anthraquinone ring structure.
To determine the exact degradation products and their
various content proportions, a further study should be
performed using a more sophisticated analytical method. One
possibility would be to use high performance liquid
chromatography (HPLC) to separate the degradation products
present in the treated water samples. Having some idea of the
identities of the degradation products from the present study,
standards of the suspected degradation products could be
prepared and run through the HPLC to determine retention times
and characteristic peak heights. This information could then
be compared with HPLC chromatograms for the mixture of
degradation products to see if there are any identical
retention times and peak heights. The HPLC could also be
combined with mass spectrophotometry (Mass Spec) which can
give the exact structure of a chemical by matching the
unknown's spectrum with a computer library of spectra,
eliminating all but a few possibilities for chemical
identification. In addition, HPLC could also be combined with
electrochemical detection as used by Camp [16] in her research
work on azo dye/degradation product identification. The HPLC
would be used to separate the mixture of degradation products
in the treated water samples. The electrochemical detection
173
would measure the reduction potential of the separated
degradation products using a mercury dropping electrode.
Although dyes may have more than one reduction potential, (due
to the existence in some cases of more than one electroactive
site where reduction occurs), usually the reduction potential
is an identification characteristic for each dye and
degradation product.
Some modification of the treatment process may be
necessary if certain known toxins are identified in the
treated wastewater. Strategically combining the
electrochemical treatment process with another complimentary
process may eliminate the threat of degradation products. As
mentioned earlier, the Andco Process could be followed by
. oxidative aerobic sludge L digestion to further degrade any
degradation products produced in the Andco Electrochemical
Treatment Process. Other more expensive options could follow
this treatment system producing approximately the' same
results. Ozonation or carbon adsorption would work well in
this capacity, but aeEobic sludge or an oxidation pond would
no doubt be the less expensive route. Also, as suggested by
Camp [16] , the dye degradation products of azo bonded dyes appear to degrade rapidly by air oxidation and photolysis.
This may make over concern unjustifiable, as they may not
exist in the environment long enough to be a threat. However,
due to the serious nature of a possible health or
environmental threat being created, further work needs to be
174
done to determine the lifetimes of the different degradation
products in the environment. Should a further study on
degradation product identification be done, a corresponding
study on the biodegradation of the degradation products (that
is, any products that should be identified) should also be
done. The biodegradation study would identify those products
which do not readily degrade in the environment.
Additionally, toxicity (and/or carcinogenity and mutagenity)
of the degradation products that do not readily degrade may
have to be determined if they are not already known, so that
assessment of the threat of such degradation products to
health and the environment may be complete,
Cost Analysis
..
The results of the costs analysis show that the Andco
Process is comparable to ozonation in terms of its treatment
capabilities. However, ozonation has considerably less
operating costs even though the initial investment may ‘be
higher.
less operating costs than the advanced treatment systems
studied. The final decision in selecting a water treatment
system depends on the degree of treatment required’and the
available investment and opedating capital. The Andco
Process would work well as a pretreatment process most likely
preceding oxidative aerobic sludge. The electrochemical
treatment would effectively remove color and reduce COD, while
the aerobic sludge would most likely further degrade any
The Andco Process still has up to twenty-five times
175
degradation products produced by the Andco Process. If future
studies show that the degradation products produced are not
a threat to health or the environment, the aerobic sludge
treatment may not.be necessary.
The Andco Electrochemical Treatment Process appears to
have definite applications in textile wastewater treatment.
Other electrochemical treatment systems as described earlier
in the introduction, may also work well treating textile
wastewater. One drawback of the electrochemical treatment
processes in general is the production of large amounts of
iron sludge, which contains various pollutants collected
during the treatment process. The iron sludge itself may need
to be studied for its leaching characteristics with textile
wastewater contaminants. Depending on these characteristics,
the iron sludge may or may not be disposable in a municipal
landfill.
176
APPENDICES
177
Appendix b
Absorbance Values and Calibration Equations f o r the Color Removal Study
178
Table A-1 Absorbance values for the prominent carpet mill dyes used in the dye removal tests.
A.B. 277 5.0 10.0 20.0
A.R. 361 5.0 10.0 20.0
A.O. 156 5.0 10.0 20.0
A.B. 40 5.0 10.0 20.0
ABSORBANCE
410 nm 510 610 nm
0.0090 0.0084 0,0457 0.0203 0.0204 0 . 0912 0,0422 0.0448 0.1802
0.0140 0,0492 -0.0018 0.0301 0.1201 0 , 0019 0.0620 0.2284 0.0026
0.0056 0,0445 -0,0006 0.2194 0.0826 0.0005 0,4175 0.1750 0.0019
0.0250 0.0235 0.0872 0.0471 0.0400 0,1673 0.0752 0.0695 0.3270
A.B. 277
179
410 nm 510 nm 610 nm
A.R. 361
410 nm 510 nm 610 nm
A.O. 156
410 nm 510 n m 610 nm
y = 0.883 + 452.461 x y , = 1.565 + 411.758 x y = -0.134 + 111.639 X
y = 0.609 + 312.638 X y = 0.475 + 84.420 X y = 9.211 + 2728.086 x
y = -0.302 + 48.359 x y = 0.218 + 113.640 x y = 8.036 + 6050.950 x
A . B . 4 0
410 nm y = -3.129 + 301.338 X 510 nm y = -2.%57 + 327.605 x 610 nm y = -0.459 + 62.561 x
Figure A-1 Dye concentration calculation equations developed from absorbance and concentration values in Table 3-15 by linear regression. x = absorbance, y = concentration ((mg/l))
180
Table A-2 Acid dye mixture absorbance ( m g / l ) and 25 ( m g / l ) samples color absorbance subtraction. color absorbance subtraction. ..
15 ( m g / l ) stock 75 150 300 450
Iron Level “/I)
25 ( m g / l ) stock 91
150 354 450
15 ( m g / l ) stock 75 150 300 450
Iron Level “/I 1
25 ( m g / l ) stock 91
150 354 450
Absorbance
values for 15 A) before iron B) after iron
4 1 0 nm 510 nm 610 rm
0,1315 0,1096 0.0474 0.0716 0.0623 0.0563 0 , 0542 0,0571 0.0332 0.1722 0,0913 0.0545 0.0969 0.0518 0.0348
0.2230 0.1889 0.0785 0,1308 0,0828 0.0578 0.0530 0.0613 0.0244 0.0692 0.0439 0.0349 0,0477 0.0385 - 0.0273
Absorbance
4 1 0 nll~ 510 nm 610 rm 0,1315 0.1096 ‘ 0.0474 0.0504 0.0527 0.0478 0.0429 0.0548 0.0305 0.1246 0.0645 0.0352 0 , 0541 0.0257 0.0160
0.2230 0.1889 0.0785 0.1011 0.0684 0.0503
0.0159 0.0047 0.0012 0.0049 0.0124 0.0085
0.0417 0.0560 0.0222
181
Acid D y e Mixture
410 nm y = 6.9 x + 112.24 x 510 nm y = 0.137 + 132.60 x 610 nm y = - 2 . 5 x + 318.30 x
Figure A-2 Acid dye mixture concentration calculation equations developed from absorbance and concentration values in Table A. x = absorbance y = concentration ((mg/l))
182
Table A-3 Concentration and absorbance values fo r A c i d Blue 40 and corresponding dye concentration c a l c u l a t i o n equation.
0 5 10 20
Absorbance 610 nm
0 0.0872 0.1673 0.3270
y = -3.3 x + ( 4 . 4 1 9 ) X
183
Appendix B
Absorption Spectra f o r the Mechanism of Dye Removal Study
i I - i
184
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185
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186
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187
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