Wastewatei
Treatment
Systems
Upgradinglextile Operation
to Reduce Fbllutb
EPATechndogy Tansfer Seminar Publication
-------
EPA-625/3-74-004
WASTEWATER-TREATMENT SYSTEMS
Upgrading Textile Operations
to Reduce Pollution
ENVIRONMENTAL PROTECTION AGENCY* Technology Transfer
October 1974
-------
ACKNOWLEDGMENTS
This seminar publication contains materials prepared for the
U.S. Environmental Protection Agency Technology Transfer Program
and presented at industrial pollution-control seminars for the textile
industry.
Chapters I through V of this publication were prepared by
Metcalf & Eddy, Inc., Engineers, Boston, Mass. Chapter VI was
prepared by D. G. Hager, J. L. Rizzo, and R. H. Zanlitsch, of Calgon
Adsorption Systems, Calgon Corporation (a subsidiary of Merck &
Co., Inc.), Pittsburgh, Pa.
NOTICE
The mention of trade names or commercial products in this publication is
for illustration purposes and does not constitute endorsement or recommenda-
tion for use by the U.S. Environmental Protection Agency.
-------
CONTENTS
Page
Chapter I. The Need for Wastewater Treatment 1
Chapter II. Sources and Strengths of Textile Wastewaters 3
Cotton 3
Wool 6
Synthetics 8
General 8
Chapter III. Biological Wastewater Treatment 13
Overview 13
Treatment Methods 19
Chapter IV. Case Histories of Biological Wastewater Treatment 27
Dan River Mills, Danville, Va 27
The Kendall Company, Griswoldville, Mass 28
BRW Textiles, Bangor, Pa 31
United Piece Dye Works, Bluefield, Va 32
Chapter V. Experience with Granular Activated Carbon in Treatment of Textile Industry
Wastewaters 35
Introduction 35
Adsorption 36
Granular Activated Carbon 36
Adsorption Feasibility 36
Pretreatment Requirements 38
Adsorption Design Parameters 38
Carbon-handling Systems 40
Adsorption Experience with Textile Industry Wastewaters 41
Case Histories 42
Adsorption Economics 44
Summary 44
References 45
in
-------
Chapter I
THE NEED FOR WASTEWATER TREATMENT
The human race is indeed part of a limited ecosystem. While the population continues to
increase, the available natural resources are decreasing. Recent history has recorded periodic water
shortages in many highly populated areas. Newspaper reports of fish kills, toxic and hazardous
chemical spills, and even "rivers on fire" are not infrequent. Recognizing the need to reverse the
trend toward further environmental degradation, recent and proposed legislation is focusing on
cleaning up the water environment. Although any one wastewater effluent may not of itself serious-
ly degrade the receiving stream, as one of the aggregates of wastes, it may be "the straw that breaks
the camel's back."
Major point-source discharges encompass domestic wastewaters and industrial wastewaters.
The textile industry is composed of over 7,000 plants, with approximately 680 using wet processes
or discharging wastewater. This wastewater is treated by municipal treatment plants, treated on
site, or discharged untreated. The major pollutional parameters in textile wastewaters are solids,
biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrogens and phosphate,
temperature, toxic chemicals such as phenols, chromium and heavy metals, pH, alkalinity-acidity,
oils and grease, sulfides, and coliform bacteria.
Solids are present in textile wastewaters from process wastewater generated from fibrous
substrate and process chemicals, and as a result of biological wastewater treatment. The solids can
affect the natural aquatic environment by hindering oxygen transfer and reducing light penetration.
Solids that settle on the stream bottom can cover the flora and fauna and result in an anaerobic
sludge layer.
The BOD, resulting from organic process chemicals, varies widely. Some chemicals, such as
starch, are completely biodegradable, while others, such as refractory compounds in dyes, are
essentially nonbiodegradable. Five-day BOD values of 50 mg/1 to 3,000 mg/1 are experienced in
textile wastewaters. Effluents containing high concentrations of BOD could deplete the dissolved
oxygen (DO) concentration in the receiving stream, resulting in fish kills and objectional water
quality.
Phosphates are present in the detergents used by the textile industry. Together with nitrogen,
a proper balance is necessary for good biological treatment. Excess concentrations of either appear
in the effluent and reach the receiving stream. If nutrient concentrations in the receiving waters
become high, algal blooms can occur.
The temperatures that biological wastewater-treatment systems can tolerate predicate accept-
able effluent temperatures. Physical-chemical treatment could withstand higher temperatures, and
these treated wastewaters may require temperature reduction before introduction into the receiving
stream because the natural aquatic environment is a "living system" and could be damaged by
high temperatures.
-------
Heavy metals such as chromium, copper, zinc, and mercury can be found in many textile
process waters, especially those of wool and synthetics finishing. These, along with other toxic
chemicals, are detrimental to biological organisms and would harm the receiving stream. If
biological treatment is practiced at the mill, prevention of biological upsets will insure discharge
of nontoxic wastewaters.
In the textile industry, some processes require highly acid conditions while others are highly
alkaline. Consequently, wastewater pH can vary greatly over a period of time, and some form of
neutralization or equalization is necessary. The degree of neutralization-equalization will depend
on the extreme of the pH and the alkalinity-acidity of the wastewaters. Biological wastewater
treatment inherently provides an effluent with acceptable pH for discharge to the receiving stream.
Grease and oil are harmful to biological systems and esthetically damaging to the environment.
Concentrations in the effluent should be limited. This parameter is especially important in wool-
scouring processes.
Often sanitary waste is included in the industrial wastewaters, necessitating the control of
coliform bacteria. Chlorination may be needed with fecal coliform limits based on sanitary-system
guidelines.
The textile industry is dynamic with constantly changing manufacturing processes and resulting
wastewaters. Protection of the environment through adequate wastewater treatment will be a
continuing requirement for acceptable textile manufacturing.
-------
Chapter II
SOURCES AND STRENGTHS OF TEXTILE
WASTEWATERS
Textile-mill operations consist of weaving, dyeing, printing, and finishing. Many processes in-
volve several operations, each contributing a particular type of waste. Examples of waste-producing
operations are sizing of the fibers, kiering (alkaline cooking), desizing the woven cloth, bleaching,
rinsing, mercerizing, dyeing, and printing.
Textile wastes are generally colored, high in BOD and suspended solids, highly alkaline, and
high in temperature. The wastes are characterized by extreme variability and may contain toxic
compounds. The sources of pollution are the natural impurities extracted from the fiber together
with the processing chemicals, which are either directly discharged batchwise (as with kier liquor,
for example) or leached out during rinsing operations and discharged as waste.
The basic factors that bear on wastewater quantity and quality are as follows:
• Type of fiber
• Unit operations constituting the overall textile-finishing process
• Process chemicals
• Recycle and conservation procedures in force
While the last three factors play important roles in determining wastewater quality, it is both in-
formative and useful to "hold them constant" for the moment and attempt to characterize textile
wastes on the basis of process fiber—namely, cotton, wool, or synthetic. It must be emphasized
that the design of treatment facilities must be custom tailored to the individual mill, based on the
results of a carefully conducted wastewater survey. In discussing general characteristics, the objec-
tive is to introduce the plant engineer to the sources and problems of water pollution.
Waste constituents that present pollutional problems are those that deplete oxygen in the
receiving stream (i.e., exert an oxygen demand), those that encourage excessive aquatic growth (by
introducing nutrients), those that are toxic to aquatic life, and those that damage the esthetic nature
of receiving streams. Biochemical and chemical oxygen demand, nitrogen and phosphorus, tempera-
ture, pH, chrome, phenol, sulfide, and color are all parameters that define wastewater quality.
COTTON
Cotton processing consists of two basic processes—weaving and finishing. Each comprises
several operations, some of which use water while others do not. In the sequence of weaving opera-
tions, most of the water pollution originates with slashing. In slashing, the warp thread is sized with
-------
Table 11-1.— Pollutional loads contributed by various cotton-mill processes1
Department
Desizing2
Scouring ... . .
Dyeing
Printing
Bleaching
Mercerizing
Total ...
Process
Pressure kier 1st scour
Either pressure kier, 2d scour,
or continuous scour
Subtotal (scouring)
Color shop wastes
Wash after print, with soap
Wash after print, with detergent
Subtotal (printing)
Hypochlorite bleach
Peroxide bleach
Pounds
BOD per 1,000
pounds cloth
53
53
8
42
47
.5-32
12
17-30
7
19-32
8
3
6
125-250
Percent of
total
35
16
1
15
16
1 .5-30
7
17-30
7
15-35
3
1
1
' Part of the loadings shown are only indirectly contributed by these operations and, in fact, directly result from rinsing
operations. For example, a rinse after dyeing will remove a portion of the dyestuff. The resulting BODc is here attributed to dyeing.
2 For acid desizmg. Enzyme desizing or solvent desizing will produce different BODg loadings.
Source N. L. Nemerow, Liquid Wastes of Industry, Theories, Practices, and Treatment, Reading, Mass., Addison-Wesley, 1971.
starch or a substitute to give it the tensile strength and smoothness necessary for subsequent weav-
ing. The sizing compounds used are natural starches, modified cellulose, and synthetics, which may
exert either a short-term or long-term BOD. Conversion to synthetic sizing, such as carboxymethyl
cellulose (CMC), has often made it appear that plants were reducing BOD. In fact, while CMC and
other substitute sizes can have a very low BOD over a 5-day span (BODS, the common measure of
BOD), they can exert a substantial BOD in the longer run, for example, over a 20-day period
(BOD2 o )• In addition, a significant BOD5 can result with an acclimated biological culture.
The weaving process produces fixed cloth or gray goods containing from 8 to 15 percent slash-
ing compound. A pollutional loading occurs when the sizing is washed out during the finishing
process that follows. In addition, desizing, kier boiling, bleaching, mercerizing, printing, dyeing,
rinsing, resizing, and final finishing are all operations that may contribute waterborne waste. Table
II-l indicates typical pollution loads generated by these processes. A typical cotton-process flow-
sheet is shown in figure II-l, and table II-2 describes the overall characteristics of the mill wastewater.
The cotton-finishing mill using conventional process chemicals (no substitution for soap,
starch, or acetic acid) discharges a composite waste that is decidedly alkaline, colored by the pre-
dominant dye, with a BODS of approximately 300 mg/1 and a volume of approximately 40,000
gallons per 1,000 pounds of finished cloth.
Recent data1 indicate a trend toward lower water consumption, approximately 20,000 gallons
per 1,000 pounds, with correspondingly higher concentrations. Substitution of synthetic sizing
-------
Table 11-2.— Average character of composite waste, cotton finishing
Turbidity, ppm
Color
Total alkalinity ppm
Hydroxide alkalinity, ppm
pH
Suspended solids, ppm
Settleable solids, percent
BOD5 ppm .... ...
Total solids, ppm
Chromium, ppm ...
Volume, gal/1 ,000 Ib
1
Variable dark
10 5-11 9
500-800
30 000-40 000
2
125
Dves
500
100
9 0
100
0 25
175
Mill
3
Gray colloidal
Dyes
300-900
8-11
30-50
200-600
1 000-1 600
Up to 3 0
30 000-40 000
4
Gray colloidal
Dyes
600
10-1 1 5
40
300
1 300
2 0
70 000
Sources: 1, Lockwood Greene Engineers, Inc.; 2, Bogren, "Treatment of Cotton Finishing Wastes at the Sayles Finishing Plant,"
Sewage and Industrial Wastes. 3, "An Industrial Waste Guide to the Cotton Textile Industry," USPH; 4, Joseph W. Masselli,
Nicholas W. Masselli, and M. G. Burford, "A Simplification of Textile Waste Survey Treatment," N.E. Interstate Water Pollution
Control Comm , 1959.
WEAVING FINISHING
^ I ^
RAW
OTTO
N
~
CONVERSION
TO CLOTH
HARACTERISTICS
OF
WASTE
1
i
MERCERIZING
LOW BOD
ALKALINE
LOW SOL IDS
1
]
\-
DESIZING
SCOURING
1
1
HIGH BOD HIGH BOD
NEUTRAL PH HIGH ALKALINITY
1IGH TOTAL SOLIDS HIGH TOTAL SOLIDS
BLEACHING
HIGH BOD
ALKALINE
HIGH SOLIDS
^ HIGH TEMP.
N
j
DYEING
PRINTING
HIGH BOD
HIGH SOLIDS
EUTRAL-ALKALINE
\
1
FINISHING
Figure 11-1. Cotton-textile-finishing process flowsheet. (Rinsing operations not shown.)
-------
for starch has appeared to reduce BOD5 values as much as 50 percent. Researchers have shown,
however, that activated-sludge populations can acclimate to the synthetic sizes, resulting in higher
BOD5.2
Within the cotton industry, as within the wool and synthetics industries, variation in processing,
materials, styles, and finishes introduces substantial variability into wastewaters from mill to mill.
For the average mill, however, starch waste will constitute about 16 percent of the total wastewater
volume, 5.3 percent of the BOD, 36 percent of the total solids, and 6 percent of the alkalinity.
Caustic waste constitutes some 19 percent of the volume, 37 percent of the BOD, 43 percent of
total solids, and 60 percent of total alkalinity. Rinsing, bleaching, dyeing, and finishing generate the
remaining portion of the composite.
Cotton-finishing wastes, although amenable to biological treatment methods, have peculiarities
that may cause difficulties in biological processes. There may be toxic substances in the wastewater
originating with the application of mildew depressants (fungicides), chromates (from dyes), and
chloride or hydrogen peroxide (from bleaching). Occasionally, the waste will be deficient in nutrients
(nitrogen and phosphorus). Because of the great variation in quantity and quality during the course
of the day, owing to the batch operations involved in cotton finishing, equalization facilities may be
required. Detergents may hinder settling of suspended solids and may also cause foaming problems
in biological systems. Also, cationic detergents have been found to be bactericidal when present in
concentrations as low as 1 ppm.
All cotton-finishing wastes contain fine fibers. Some are settleable and introduce problems in
dewatering sludge. Suspended fibers can seal sand or carbon beds, clog equipment, and absorb
certain chemicals leading to delayed pH changes. They also clog trickling filters, are unsightly in
streams, and pose a long-term BOD.
High values of pH may necessitate neutralization before biological treatment. The low per-
centage of settleable solids usually makes primary sedimentation impractical. Fine screening is often
necessary to protect mechanical equipment, such as pumps and mechanical aerators.
WOOL
Wool wastes originate from scouring, dyeing, rinsing, fulling, carbonizing, and washing operations.
Practically all the natural and acquired impurities in wool are removed by scouring in a hot detergent-
alkali solution producing a waste that is oily, alkaline, and high in solids and BOD. The actual wool-
fiber content in "grease wool," as taken from the sheep's back, averages only 40 percent; the remain-
ing 60 percent is composed of natural impurities such as sand, grease, suint (dried sheep perspiration),
and burs. As a result, for every 1,000 pounds of scoured wool produced, 1,500 pounds of impurities
are discharged, which corresponds to some 200 to 250 pounds of BOD5 per 1,000 pounds of scoured
wool.
Mills that both scour and finish wool produce a composite effluent with the following charac-
teristics:
• pH, 9-10.5
• BOD5, 900-3,000 ppm
• Total solids, 3,000 ppm
• Total alkalinity, 600 ppm
• Chromium, 4 ppm
-------
• Suspended solids, 100 ppm
• Grease (for mill employing grease recovery), 100 ppm
Mills that only finish wool would be expected to produce a composite waste with much lower
concentrations of BODS, suspended solids, and grease. The waste is likely to be brown in color, and
the suspended solids are mainly colloidal. The major sources of BOD are the wool grease and suint
removed in scouring and the soap used in fulling and washing. Approximately 7,500 and 13,800
gallons of water are required to scour and finish, respectively, each 1,000 pounds of wool.1 Sedi-
mentation, a common treatment to remove solids in domestic and some industrial wastes, is ineffec-
tual in removing solids from wool wastes.
Many woolen mills in the United States are dyeing and finishing mills that purchase scoured
wool. In these mills, 24 percent of the BOD5 originates with dye operations, 75 percent with the
wash that follows fulling, and 1 percent with neutralization that follows carbonizing.
Figure II-2 presents a wool process flowsheet, and table II-3 indicates pollutional loads of the
untreated wastewaters.
PROCESS
RAW WOOL
POLLUTANTS
HIGH BOD
HIGH GREASE
HIGH ALKALINITY
STOCK DYEING
ACIDPH
HIGHLY COLORED
REL. HIGH BOD _
FULLING
CARBONIZING
PIECE DYEING
BRIGHTENING
BLEACHES
HIGH BOD LOW BOD
HIGH OIL LOW SOLIDS
110°-150° F
Figure 11-2. Wool-process flowsheet. (Rinsing operations not shown.)
Table 11-3.— Pollution loads of wool, wet process
Scouring
Dyeing
Washing
Neutralization
Bleaching
nM
pn
90-104
4 8-8 0
7.3-10.3
1 9-9 0
60
BO[
ppm
30 000-40 000
380-2 200
4 000-1 1 455
28
390
D
lb/1,000lb
104-221
9 0-34
31-94
1 7-2 1
1 4
Total solids,
ppm
1 1 29-64 448
3 855-8 365
4 830-19 267
1 246-4 830
908
Volume,
gal/1,000 Ib
5 500-12 000
1 900-2 670
40 000-100 000
12 500-15 700
300-2 680
Note.—Loads contributed from rinses are assigned to operation preceding rinse in each case.
-------
Wool grease is a source of lanolin, which may be recovered and sold. Suint is a source of
potassium salts. The combination of in-plant measures and wastewater treatment are generally
designed to treat the following waste characteristics: variability, total flow, oil and grease, pH, color,
temperature, BOD, chromium, and suspended solids. The presence of phenols, sulfides, and long-
term BOD must be considered in surveys and studies. Nutrients, toxic compounds, and foam-causing
detergents are all factors that must be dealt with before designing treatment facilities.
SYNTHETICS
Synthetic fibers are polymers derived from pure chemical compounds and have essentially no
natural impurities. For this reason, no desizing is needed, and relatively light scouring and bleaching
are all that is necessary to prepare the cloth for dyeing. The fibers and cloth are readily processed on
the conventional machinery used for cotton and wool.
At present, the major synthetic fibers are rayon, acetate, nylon, Orion, and Dacron. Scouring,
dyeing, and finishing chemicals are the sources of waste in the synthetic textile industry. These
fibers can all be considered as either cellulosic or noncellulosic. When such a distinction is made, it
is possible to present process flowsheets representative of each of the two categories. Figures II-3
and II-4 illustrate the two processes. The noncellulosic fibers assume the greater portion of the
textile market at present.
Tables II-4 and II-5 describe pollutional loads of synthetic fiber processes, and table II-6 pre-
sents qualitatively an analysis of waste associated with each of the major synthetic fibers.
Unlike wool and cotton, synthetic fibers of the same type can have different physical and
chemical properties. The producers of synthetic textiles are frequently and continually changing
their products, varying fiber blends, and investigating new finishes to keep abreast of changing
market conditions. As a result, the wastewaters generated by the synthetic fiber industry are
highly variable, and a general characterization of these wastes is useful only as an approximate
indication of their composition.
GENERAL
Special finishing techniques can contribute from 5 to 15 percent of the total BOD5 in any of
the three fiber groups. Techniques vary greatly from mill to mill. There is little information on
the toxicity of special finishing chemicals. Their purposes range from mildew proofing to impart-
ing wash-and-wear properties.
Throughout the textile industry, the wastewaters are highly variable in quantity and composi-
tion. The sources of these wastes are, first, the natural impurities present in the fibers and,
second, the process chemicals. Cotton and wool wastes are highly concentrated and primarily
originate with natural impurities in the fibers.
Process chemicals constitute most of the wasteload from synthetic-textile processing.
Industrywide, a great variety of process chemicals are used. Carriers used in synthetic dyeing
present special problems. Chromium and derivatives of phenol and sulfur are often present.
Color has become increasingly difficult to remove from wastewaters, since the market has de-
manded dyes that are increasingly more resistant to degradation. The substitution of synthetic
sizing compounds often has resulted in merely shifting BOD from the short-term, 5-day BOD to
a longer term oxygen demand. While in-plant pollution control measures can be quite effective
-------
I
YARN
-f
1 — 1-
1
\
KNIT
1
1
1
1 L_,__i
1 t
I
1
! .
/K 1 r>YF
« p |
I t
FINISHING
*1
SLASHING
t
WEAVE
1
nF<;i7F
1
SCOUR
i
WASTEWATER
RINSING OPERATIONS NOT SHOWN
Figure 11-3. IMoncellulosic synthetic-textile-finishing
process flowsheet. (Rinsing operations not shown.)
MAIN PROCESS
STREAM
SCOURING
AND
DYEING
SCOURING
AND
BLEACHING
1 1
COLOR, OILS, HIGHO
DETERGENTS, DYES, TOXIC 0
AND CARRIERS, SOME
R LOW PH,
XIDANTS,
-. B.O.D.
SALT BATH
UNCC
SALTS, D
)MMON
ETERGENT
SPECIAL
FINISH
1
LOWPH
SOME B.O.D.
POSSIBLY TOXIC
B.O.D.
Figure 11-4. Cellulosic synthetic-textile-finishing process flowsheet.
(Rinsing operations not shown.)
-------
Table I \-4.—Po/lutional load of synthetic wet fiber processes
Process1
Scour
Scour and dye . . .
Dye
Salt bath
Final scour . . .
Special finishing ....
Fiber
Nylon
Acrylic/
modacrylic
Polyester
Rayon
Acetate
Nylon
Acrylic/
modacrylic
Polyester
Rayon
Acrylic/
modacrylic
Polyester
Rayon
Acetate
Nylon
Acrylic/
modacrylic
Polyester
pH
10.4
9.7
-
8.5
9.3
8.4
1.5-3.7
-
6.8
7.1
-
-
-
-
-
—
BOD5
ppm
1,360
2,190
500-800
25-32
2,000
368
1 75-2,000
480-
27,000
58
668
650
-
-
-
-
—
lb/1 ,000
Ib
30-40
45-90
15-25
50-70
40-60
5-20
2^0
1 5-800
0-3
10-25
15-25
20
40
10
60
2-80
Total solids
ppm
1,882
1,874
-
3,334
1,778
641
833-1 ,968
-
4,890
1,191
-
-
-
-
-
—
lb/1, 000
Ib
30-50
12-20
25-35
25-39
20-34
6-9
30-200
20-200
4-12
10-50
3-100
3-100
3-100
3-100
3-100
Suspended
solids,
lb/1 ,000
Ib
20-40
25-50
5-15
0-4
1-20
2-42
5-20
-
2-6
3-7
3-50
3-50
3-50
3-50
3-50
3-50
Volume,
gal/1,000 Ib
6,000-8,000
6,000-8,000
3,000-5,000
2,000-4,000
4,000-6,000
2,000-4,000
2,000-4,000
2,000-4,000
500-1 ,500
8,000-10,000
2,000-4,000
500-1 ,500
3,000-5,000
4,000-6,000
5,000-7,000
1 ,500-3,000
1 Waste load due to rinsing attributed to operation preceding rinse.
Source: F. H. Lund, Industrial Pollution Control Handbook, New York, McGraw-Hill, 1971
Table \\-5.—Pollution loads3 from textile processes with various fibers
Fiber
Cotton
Greasy wool
Scoured wool
Rayon
Acetate . ... . .
Orion .
Nylon
Dacron
Natural
impurities
3-5
20-30
1-2
0
0
0
0
0
Sizes,
oils,
antistats
0.5-10
0.2-9
0.2-9
0.5-6
0.5-6
0.5-6
0.5-6
0.5-6
Scouring1
0.5-6
31.5-15
3 1.0-1 5
.5-5
.5-5
.5-5
.5-5
.5-5
Dyes,1
emulsifiers,
carriers,
etc.
0.2-8
0.5-10
0.5-10
0.2-5
0.2-5
0.5-10
0.2-5
0.3-60
Special
finishes
0.2-8
0.2-8
0.2-8
0.2-8
0.2-8
0.2-8
0.2-8
0.2-8
Total
4.4-37
2 21. 9-72
2.9-44
1 .4-24
1 .4-24
1 .7-29
1 .4-24
4.2-78
aPercent of fabric weight.
' Partial contribution from subsequent rinse operation.
2 Reduced by 98 percent with solvent extraction.
1 High values include soap (fulling).
Source. N. L. Nemerow, Liquid Wastes of Industry, Theories, Practices, and Treatment, Reading, Mass., Addison-Wesley, 1971.
10
-------
Table 11-6.— Significant pollutants in synthetic fiber, wet processing
Fiber
Process
Liquid waste pollutant
Rayon
Acetate
Nylon
Acrylic/modacrylic
Aery lic/modacry lie
Scour and dye
Scour and bleach
Salt bath
Scour and dye
Scour and bleach
Scour
Developed dispersed dye
Bleach
Dye
Thermosol dyeing
Bleach
Scour
Dyeing with
Scour
High temperature and
pressure dyeing
Bleach
Oil, dye, synthetic detergent, and
antistatic lubricants
Synthetic detergent and hydrogen
peroxide
Synthetic detergent, chloride, or
sulfate
Antistatic lubricants, dye, sulfonated
oils, synthetic detergent, esters,
and softeners
Synthetic detergent, hydrogen
peroxide, or chlorine
Antistatic lubricants, soap, tetra-
sodium pyrophosphate, soda, and
fatty esters
Dye, NaN02, hydrochloric acid,
developer, and sulfonated oils
Peracetic acid
Dye, formic acid, wetting agents,
aromatic amines, retarding agent,
and sulfates
Acid
Chlorite
Synthetic detergent and pine oil
Chlorobenzenes, hot water, and dye;
or phenylmethyl carbinol, dye, and
hot water; or orthophenylphenol
and dye
Antistatic lubricants, chlorite or
hypochlorite, and nonionic syn-
thetic detergent
Dye and hot water
Chlorite, NaNO2, acetic acid,
oxalic acid, nitric acid, bisul-
fite, proprietary bleaches
Note.—A source of potential toxicity and odor is dye carriers used with some of the synthetics (particularly polyesters). Examples
are orthophenylphenol, phenylmethyl carbinol, and monochlorobenzene. Sodium dichromate, used in dyeing, will contribute toxic
chrome to the wastes, but substitutes are available. Much of the pollutants contributed by these operations actually enter the waste
stream through rinses that follow the operations.
Source. H. F. Lund, Industrial Pollution Control Handbook, New York, McGraw-Hill, 1971.
11
-------
in their immediate objectives, the environmental effect in terms of long-term oxygen demand and
toxicity must be considered.
For individual mills, there is no substitute for a wastewater survey. General characteristics
are helpful in defining the nature of problems formed by an industrial process; however, the
solution of the problems encountered in any one mill is achieved only after careful analysis of
the mill wastewaters, together with determination of effluent limitations and laboratory and pilot-
plant studies of treatability. This survey must be combined with carefully considered in-plant
measures of waste reduction. Determining the most economical method of pollution control is
only possible if complete and accurate wastewater analysis has been undertaken. Pollution-control
measures, once installed, must be continually evaluated via ongoing wastewater monitoring pro-
grams. Existing wastewater-treatment facilities and effluent quality standards must be considered
before making substantial process changes or chemical substitutions. The wastewater-treatment
process should, in actuality, be considered a part of the overall manufacturing process, which be-
gins with the raw product arriving at the plant and the finished product and resulting wastewater
leaving the plant.
12
-------
Chapter III
BIOLOGICAL WASTEWATER TREATMENT
OVERVIEW
Before any decision can be made regarding the type of treatment to be used, all the basic facts
must be available for evaluation. These facts fall into two general categories, namely,
• The characteristics of the wastewater that is to be treated
• The effluent requirements of the treated wastewater
The missing link is the "black box" between the input (characteristic wastewater) and the output
(effluent characteristics).
A good approach to putting all the pieces in perspective for critical evaluation is the preparation
of a preliminary design report, which is the best means of insuring that all of the relevant facts have
been collected, placed in proper perspective, and critically examined. Since many of the failures or
malfunctions of wastewater-treatment plants are related to poor design resulting from negligence in
obtaining adequate design information, this report serves as an intermediate checkpoint in an effec-
tive wastewater-pollution-abatement program. It should be reviewed not only by the company, but
by the proper regulatory agencies.
Adequate characterization of the industrial wastewater could include the following parameters:
• Flow, variation
• Temperature, variation
• Character of wastes, variation
-pH
— Alkalinity or acidity
— BOD: raw and settled
— COD: raw and settled
— Phosphorus: inorganic and total
— Nitrogen: ammonia and organic
— Metals: particularly toxic
— Anions: chlorides and sulfates; toxic
13
-------
— Phenol and other organics of concern
— Oils and grease
— Solids: total with volatile; suspended with volatile (raw and settled); settleable
- Color
— Chlorine
Additions or exceptions to this list should be based on knowledge of the manufacturing proc-
ess and chemical use.
To obtain this information, a carefully planned and executed wastewater survey is required.
The survey should identify the sources, strength, and variation of the various process streams and
should be related to stockroom and production records as well as to the ongoing process flowsheet.
This information will be of value later for a continuous monitoring program. It should be noted
that a good in-plant survey will not only provide the necessary wastewater-treatment-plant design
information, but will also identify many in-plant measures of pollution control, such as water
conservation, reduction in chemical use, process modifications, and chemical substitution. These
measures have been highly successful in the past in reducing textile waste loads. BOD loads have
been reduced as much as 75 percent in cotton processing, by 30-70 percent in wool processing, and
up to 40 percent in synthetic processing by implementation of in-plant measures. Needless to say,
these in-plant remedial measures can have significant economic impact on the wastewater-treatment-
plant requirement.
Having characterized the input to the "black box" or the character of the wastewater that
must be treated, it is now necessary to consider the effluent standard that must be met. It could be
that effluent concentrations are governed by the EPA industrial effluent guidelines, but with pro-
jected increase in plant production in the near future, the State stream water quality standards may
become the controlling criteria. Since the proposed wastewater-treatment plant will be designed to
treat future loads as well as present ones, this must be a consideration in choosing the mode of
treatment.
Some other considerations in choosing the best method of treatment may be flexibility, since
the wastewater characteristics can change from day to day as well as over the years, and space
availability, since some methods of treatment may be precluded merely because insufficient space is
available.
The significance of the wastewater-characterization parameters as related to treatment-plant
design should be discussed briefly before considering treatment alternatives.
Flow: Measurement of flow, in particular flow variations, is highly important. Greatest
variations will occur when weekend and vacation period shutdowns are practiced. Daily variations
will be great with one- and two-shift operations or when batch operations occur. In all situations
in which significant flow variations occur, some provision must be made for equalization, either
through providing storage or by using long-detention treatment systems. Obtaining good flow data
when multiple sewer discharges occur offers a real challenge.
Temperature: The temperature of wastewaters is an important consideration in selection of
biological treatment systems. High-temperature wastes in excess of 100° F are not amenable to
short-detention systems such as conventional activated sludge or even trickling filters. Low-tempera-
ture wastes are not amenable to treatment in aerated lagoon systems in cold climates where tempera-
tures drop below freezing. Wastes that vary widely in temperature because of batch operations re-
quire equalization or long-detention treatment systems.
14
-------
Character of wastes: It is not necessary to analyze wastewaters for all the items previously
given. Some judgment should be used based on the industrial process involved, compounds used in
processing, and final disposition of the wastewater.
Variation in wastewater quality is of major concern, and judgment must be used in establishing
a sampling program. When space limitations force employment of short-term, high-rate systems, or
other reasons dictate, collection of 8-hour or shift composites is indicated. When long-term treat-
ment systems are employed, 24-hour composited samples are adequate. In any event, a sufficient
number of samples, usually at least 10, spaced to measure product variation, should be collected.
pH: In addition to determining the pH of composited samples, a continuous record of pH
should be obtained when it is known to vary widely, as with many textile wastes.
Alkalinity or acidity: Both of these items are related to pH in a qualitative manner, but
their measurement is required in making assessments of whether neutralizing chemicals are needed.
In situations in which equalization is impossible, hour-to-hour measurement is needed.
BOD: Measurement of BOD5 is usually necessary for determining the size of treatment units
and aeration devices. Determination should be made on both raw and settled waste to ascertain
need for primary clarification. The ultimate BOD (BODy, BODL, or BOD2o) is sometimes
required by regulatory authorities.
COD: The COD, as determined by dichromate, measures the total oxygen demand, including
biologically refractory materials. COD data cannot be used in design unless they can be interpreted
in terms of BOD. When laboratory or pilot-scale studies are conducted,
COD COD
TnT "EfT
To obtain reliable results, the final effluent samples should be filtered to remove biological
floes before determining COD.
Phosphorus (P) and nitrogen (N): Both of these elements are important in the nutrition of
activated sludge, micro-organisms, and other biological growths employed in wastewater treatment.
The amount required is related to the BOD and the method of treatment. The following ratios
are recommended:
BOD N P
High rate-high synthesis 100 5 1
Medium rate-medium synthesis 100 3 0.5
Low rate-low synthesis 100 2 0.3
Phosphorus and nitrogen in excess of the foregoing requirements will appear in the final
effluent and may cause a pollution problem in the receiving waters.
Metals: Of particular concern are the so-called toxic metals, or any whose discharge to
receiving waters is limited. In general, most metals do not have serious effect in biological waste-
treatment systems, provided the pH is maintained in the range of 8 or above. Under such conditions,
the metals are precipitated as the hydroxides become incorporated in the sludge, and the amount of
metal that can exist in the ionic form is negligible. The presence of the precipitated hydroxides,
15
-------
however, constitutes a serious threat. If the pH should fall, large amounts of the metals in ionic
form could be released and cause great harm to the treatment plant and stream biota.
Mercury is an exception and should be recognized. It should be removed at the source by
isolation and separate treatment.
Chromates are normally considered along with the metals. Chromates are not precipitated
at high-pH levels. Being soluble, they pass out in the effluent. Limits on the discharge of chromates
(Cr+6) are quite strict. At pH values of 6.5 or below, they become quite toxic and could be detri-
mental to wastewater treatment.
Anions: Chlorides and sulfates are normally of little concern in biological waste treatment
unless the concentration becomes high or variable. They are also of concern in receiving waters,
particularly those used for public water supply.
The cyanide ion is noted for its toxicity to fish. Essentially, complete destruction or conver-
sion to cyanate is recommended. Arsenic in the form of arsenites and arsenates are both soluble
and toxic. Rather strict regulations govern discharge to natural waters.
Phenol and other organics: Phenol is biologically degradable with an acclimated biota.
Certain derivatives of phenol (e.g., orthophenylphenol as used in the textile industry for dye
carrier) and other organic compounds are quite resistant to biological oxidation. Treatability
studies are required if such compounds occur. Physical removal by adsorption may be required.
Oils and grease: Oils and grease are a serious problem in many industrial wastewaters, such as
wool-scouring wastewaters in the textile industry. When present in significant amounts they should
be removed by pretreatment, as they tend to be a nuisance in biological treatment systems and may
even hinder purification. If oils and grease are present, final clarifiers should always be provided
with skimming devices.
Solids: Total solids analyses, including volatiles, should be run on 24-hour composited
samples.
Suspended solids analyses, with volatiles, should be run on both raw and settled wastes for the
purpose of determining benefits to be derived from primary clarification.
The settleable solids test gives a crude measure of the volume of primary sludge to be expected.
It can be interpreted in quantitative terms when it is related to suspended solids removed by settling.
Color: The color of wastes is becoming more and more important as restrictions on discharge
become tighter. Of great importance is the residual color following treatment. Color considerations
may force the use of physical-chemical methods of treatment or biological treatment with physical-
chemical polishing.
Chlorine: Chlorine is an oxidant and, as such, a biological disinfectant. Strong doses of
chlorine can be harmful to biological systems.
If the input to a treatment system, the significance of the input parameters on various systems,
and the performance requirements of a system are known, feasible alternative treatment systems
can be chosen, based on the following criteria:
• Experience—the engineer must have enough experience with the manufacturing processes
and resulting wastewaters to reliably choose workable alternative systems
16
-------
• Data available on similar situations—other similar plants may have workable wastewater-
treatment systems for comparable wastewaters
• Laboratory study—it may be necessary to screen several possible methods to determine the
acceptable alternatives
• Pilot-plant study—certain significant questions may be left unanswered after a laboratory
study or unpredictable scale-up effects may need to be investigated before workable systems
can be chosen
The choice of treatment could follow the following paths:
• Joint treatment with a municipal or regional plant
• Pretreatment at the plant site followed by joint treatment
• Treatment at the plant site
Joint treatment would involve contracts, surcharges, shared capital costs, and possibly partial
onsite treatment. If it is decided that onsite treatment of the wastewater is preferred, the addi-
tional alternatives are
• Physical-chemical
• Biological
• Combination of physical-chemical and biological
A qualified engineer can usually select a preferred treatment system from the feasible alterna-
tives based on the accumulated data, experience, and logic. Occasionally, two systems will appear
so nearly comparable that it is difficult to make a decision. Cost estimates will usually resolve the
problem. Capital, operating, and annual cost estimates should be compared. Often a preference for
capital costs versus operating costs is the deciding factor. The following discussion is concerned
with biological treatment—treating industrial wastewater by a living system.
Biological treatment of an industrial wastewater involves contacting the wastewater with a
mixed culture of micro-organisms (bacteria being the most important species) under a favorable
environment. The micro-organisms metabolize the wastewater components for energy and synthesis
of cells. In the process, the micro-organisms use DO, produce carbon dioxide, and synthesize new
cells. These reactions are continually occurring in nature, but the rate is usually limited owing to
one or more controlling parameters, such as DO, available nutrients, and microbial concentrations.
In biological wastewater treatment, the rate is greatly accelerated by providing high concentrations
of micro-organisms to feed on the wastewater, substantial mixing, adequate DO, and good agitation
for frequent contact between the "food" and the micro-organisms.
Methods of biological treatment are either aerobic or anaerobic. In the first case, degradation
of organic matter takes place in the presence of and through combination with oxygen. The oxida-
tion of glucose is an example.
C6H12O6 + 6O2 Bactena> 6CO2 + 6H2O
Since textile wastes are generally alkaline (high pH), the release of carbon dioxide in the aerobic
biological process serves to reduce alkalinity and lower the pH. It has been demonstrated that when
17
-------
wastewater contains sufficient BOD5, enough carbon dioxide is generated to convert all phenol-
phthalein alkalinity to bicarbonate.
20H~ + CO2 *- COi + H2O
CO3= $ CO2 + H2O »• 2HCO3~
High-pH wastewater is rapidly neutralized within the treatment system, at no cost, to a pH in
the range of 8.5-9.0, which is highly satisfactory for biological treatment.
Oxidation of organic matter (food) supplies energy to the microbial population. These micro-
organisms also need to synthesize new cells. They do this by again drawing upon the organic por-
tion of the waste in combination with nutrients, including nitrogen and phosphorus. Cell synthesis
may be represented simplistically as follows:
C6H12O6 + O2 + NH3 *-C5H7NO2 + CO2 + H2O (unbalanced)
organics nutrients new cells
Both synthesis and oxidation are ongoing metabolic processes within the biological reactor. In
any reactor, a complex mixture of micro-organisms specifically adapted to the conditions of their
environment (food supply, nutrient level, oxygen level, pH, temperature, etc.) will exist. Those
that are aerobic will be found in aerobic reactors where biochemical reactions similar to the preced-
ing reactions will occur. Anaerobic micro-organisms exist where there is little or no oxygen. (A
third type, facultative micro-organism, can adapt to either condition.) A simple reaction that may
typify anaerobic processes is as follows:
C6H1206 Bactem» 3CH4 + 3C02
Depending on the DO level, one can expect a certain type or mixture of micro-organisms to be
present. The same can be said of temperature, since there are temperature ranges within which
certain micro-organisms thrive and others do not. Bacteria may be psychrophilic (4°-10° C), meso-
philic (20°-40° C), or thermophilic (50°-55° C), for instance. For the population of any biological
reactor to perform well, it must be well adapted to its environment. These populations can be
"upset" by rapid or sudden changes in temperature, organic level, pH, or other factors, and the
bioreactor will suffer reduced performance. Thus, with highly variable wastes, flow equalization
or a large biological reactor may be required to treat the waste satisfactorily.
On a steady-state basis, aerobic systems suffer temperature limitations based on oxygen
solubility and micro-organism adaptability. Anaerobic systems perform better at higher temperatures.
A continuous supply of nutrients must be present in the wastes in either case. The adequacy of
available nutrients must be determined during the effluent survey.
Biological treatment has often been referred to as "secondary" treatment. It is usually
preceded by "primary" treatment, typically sedimentation. Pretreatment of textile wastes before
biological treatment could include any or all of the following: screening, sedimentation, equaliza-
tion, neutralization, chrome reduction (and precipitation), coagulation, or any of the other physical-
chemical treatments. Additional sedimentation is required following the biological reactor to remove
the suspended micro-organisms that settle as a sludge. The amount of sludge produced will depend
on the type of biological treatment, the organic loading, the temperature, and the efficiency of
sedimentation. Sludge handling is a basic consideration in biological treatment.
Phenols and sulfides can be successfully oxidized by aerobic biological treatment. The activated-
sludge process has been known to remove as much as 98 percent of the phenol present in refinery
waste.3
18
-------
Hexavalent chrome (Cr+6) may be toxic, even at low levels, to the micro-organisms of
biological treatment. While toxicity of hexavalent chrome will be dependent on pH and tempera-
ture, reported Cr+6 limits for biological treatment vary from 0.05 to 5 mg 1, with an average of
1 mg/1.4 It is advisable to remove hexavalent chrome or reduce it to the trivalent form before
biological treatment. Since biological treatment has typically produced only moderate color
removals with textile wastes, a process such as carbon adsorption, which has been shown to remove
both color and chromium, may be particularly advantageous as a pretreatment or posttreatment to
biological oxidation. Ion exchange, chemical coagulation, or other physical-chemical treatments
might also be considered.
In summary, biological treatment encompasses basically aerobic treatment and anaerobic
treatment. Aerobic processes require input of DO and temperatures below 100° F and are
characterized by nearly complete metabolism and high growth rates, while anaerobic processes are
reductive in nature, use no free DO, and can tolerate high temperature, but exhibit lower growth
rates and incomplete metabolism with resulting higher energy and products.
The biological treatment methods applicable to textile wastewater follow and are listed in
order of increasing detention time:
• Trickling filters
• Activated sludge
• Rotating biological disks
• Extended aeration
• Lagoons
TREATMENT METHODS
Trickling Filters
Trickling filters are the oldest form of biological wastewater treatment. They simulate in a
manmade system the same natural purification process that occurs in shallow streams where
pollutants are removed by attached biological slimes on rocks and stream bottom as the water
flows by. Trickling filters are employed in two capacities, as roughing filters before activated-sludge
treatment or as the major biological treatment system. The flow diagrams for these two are shown
in figure III-l.
In the early days, filters used sand as a media. These filters produced a high-quality, well-
nitrified effluent, but were plagued with clogging problems and high maintenance costs, and
required great areas of land. They are seldom used today except as "polishing" filters.
At the turn of the century (1900), rock filters became a favorite method of biological treat-
ment. These filters produced reasonably high degrees of purification and had the ability to shed
biological slimes, thus avoiding clogging problems. Clarifiers were required following the filters to
capture the sloughed biological solids. Shallow (3-4 feet) and deep (5-8 feet) filters, single and two
stage, with and without recirculation were widely used.
Today, synthetic materials are used widely as filter media. These filters are constructed of
Saran or polyvinylchloride (PVC) sheets arranged in "bundles." Being lightweight, they can be
stacked to great heights (as much as 40 feet) with intermediate supports, are capable of accommodat-
ing high hydraulic loadings, and are, therefore, extremely conservative of space. Recirculation is
19
-------
INFLUENT
PRETREAT
I
I
/ TRICKLING \
1 FILTER 1
V HIGH-RATE /
RECYCLE
FINAL SED.
1
EFFLUENT
PRETREATMENT
/ ROUGHING \
1 FILTER j
SUBSEQUENT
TREATMENT
Figure 111-1. Trickling filters.
usually desirable and is a necessity for variable pH wastewater or if toxic organics, such as phenol,
are present. Their capability to remove BODS varies with organic loading and with the character
of the wastewater.
Trickling filters exhibit variable behavior, and this is their greatest shortcoming. Whenever
trickling filters are proposed as the major biological system, a safe design should be based on pilot-
plant studies at the site or, alternatively, on operating data from a plant treating similar wastewaters.
Activated Sludge
The activated-sludge process was developed by Ardern and Lockett in England during 1912-14.
It was named for the activated sludge produced. The process involves aeration of a suspended
growth culture in the wastewater as a means of purification. During the aeration, aerobic bacteria
and other organisms grow and produce a biological floe, which, if conserved and fed back (return
activated sludge) to fresh wastewater, results in rapid rates of purification. Many modifications of
the original (conventional) activated-sludge process have been proposed since its inception. For
textile wastewaters, some form of a completely mixed activated-sludge system is usually preferred.
Detention times for a conventional system usually are 6-12 hours; however, the BOD5 loading
actually defines a conventional system. The loading is best expressed as food to micro-organism
(F/M) ratio. For diffused and mechanical aeration systems, the F/M ratio should be restricted to
the range of 0.2-0.5. Because of limitations on the amount of micro-organisms (mixed liquor
suspended solids (MLSS) or preferably mixed liquor volatile suspended solids (MLVSS) that can be
carried in a system, volumetric BOD loadings normally range from 25 to 75 pounds per 1,000 ft3/day.
Removals of BOD5 in excess of 90 percent are expected from this system. Waste solids are produced
at the rate of 0.35-0.55 pound per pound of BOD5 removed.
Turbine aeration systems employing compressed air with mechanical dispersion and systems
employing oxygen can operate at higher BOD5 loadings, namely, F/M ratios from 1 to 5. The
effluent produced, however, is high in suspended solids, and BOD5 removals are normally in the
range of 95 percent unless filtration of the effluent is incorporated. Oxygen requirements for this
high-rate modification of the conventional system are about double those of normal conventional
20
-------
systems. Approximately 10 percent of the sludge produced must be wasted compared to 5 percent
for the normal conventional system.
Having a small volume to dissipate a surge, shock loads do have an adverse effect on the system.
Therefore, the application of the activated-sludge process to textile wastewater results in the need
for pretreatment facilities such as equalization basins and neutralization equipment. Color removal
is usually less than 50 percent. High sludge production in the conventional activated-sludge system
may require substantial sludge-handling equipment, and disposal of sludge may be a costly process.
Rotating Biological Disks
Rotating biological disks are a relatively new type of biological treatment. Originally developed
in Europe, there are now some 1,000 such installations for treating domestic sewage in West
Germany, France, and Switzerland. Development has continued in the United States, where both
domestic and industrial wastes have been successfully treated.
The rotating-biological-disk system consists of large-diameter, lightweight plastic disks, which
are closely packed and mounted on a horizontal shaft located in a semicircular tank. A series of
these units treats the waste, which flows from one tank to another. The micro-organisms present
in the wastewater adhere to the plastic surfaces as they rotate through the tank. The wastewater is
picked up on the surface of the disk and the portion that is not submerged absorbs oxygen from
the atmosphere. The micro-organisms then aerobically degrade organic matter present in the
waste. As they multiply, excess micro-organisms are sloughed off the disks into the wastewater.
Mixing action provided by the disks keeps solids suspended. After treatment through a series of
rotating biological disks, a final clarifier receives suspended solids.
Biological rotating disks have been found to be flexible with respect to varying organic and
hydraulic loads, but the short detention times of each unit make them vulnerable to toxic shock
loads. Reduction in waste temperature would be slight, and high influent temperatures would
adversely affect treatment. This treatment method offers the advantage of low space requirements
and, in some instances, may be economically competitive with other methods. Four-stage treatment
by biological rotating disks has demonstrated BOD removals from 60 to 95 percent for domestic
wastewaters. The final effluent is well oxygenated. Oxidation of ammonia, sulfides, and phenols
would likely take place. Pilot installations are presently treating textile wastes in North Carolina.
In one instance, biological disks are used to further reduce the BOD of activated-sludge effluent
from an existing plant.
Extended Aeration
Another modification of the conventional activated-sludge process is extended aeration. This
process was developed primarily to serve situations in which short-term variations in BOD5 loadings
are great, such as batch operations, and, secondarily, to minimize the production of sludge, namely,
to only 0.1-0.2 pound per pound of BOD5 removed.
Although the original concept was to provide 24 hours' detention time, modern concepts
define an extended-aeration system as one in which BOD5 loadings are kept in the range of 10-15
pounds per 1,000 ft3/day of aeration tank capacity or F/M ratios of 0.04 to 0.06. A sludge-
recirculation ratio of 100 percent is common practice.
With domestic wastewater, the F/M ratio is usually satisfied with a 24-hour detention period.
For wastewaters of higher strength, such as textile waste, aeration periods of 36, 48, 60, 72, 96,
or over 120 hours may be required.
21
-------
A highly purified effluent is possible with BOD5 removals of 90 to 95 percent. Also, due to
the longer detention time and consequently larger volumes, the process is more resistant to upsets
from shock loads.
The clarifiers used in extended-aeration systems should be at least 12 feet deep and have
detention times of at least 4 hours. Surface overflow rates equal to or less than 300 gal/ft2 /day are
commonly used with textile wastewaters. The clarifiers must also have mechanical sludge removal
devices. WASTE SOLIDS
RAW WASTE
t-
LU
01
(t
UJ
DC
o.
AERATION
TANK
SED.
TANK
EFFLUENT
SOLIDS RECYCLE
* SCREENING, EQUALIZATION, NEUTRALIZATION, CHROME REMOVAL
Figure 111-2. Activated-sludge flowsheet.
Figure III-2 represents the flowsheet for both the conventional activated-sludge system and the
modified-system extended-aeration activated sludge. It is the extended-aeration form of activated
sludge that is very common to wastewater treatment of textile wastewater.
Lagoons
Lagoons may be classified as aerobic, anaerobic, or combination aerobic-anaerobic. One type
of aerobic lagoon relies on natural processes such as wave action and photosynthesis by algae.
Such lagoons are called oxidation ponds. They are very shallow and cover a large land area.
Waste-detention times are as great as several months. The BOD5 loading must be light to avoid
anaerobic conditions and the generation of odors. While means of controlling water level are
usually necessary (variable weirs, etc.), the equipment cost for such lagoons is minimal. The major
portion of this cost is for acquiring land.
Aeration basins are mechanically aerated lagoons. They require only 3-5 percent of the land
needed for oxidation ponds. They are 8-15 feet deep and have waste-detention times of 2-10 days,
although 5 days is usually appropriate if the heat loss is great. Oxygen may be supplied by air
diffusers or turbine aerators. The design of these lagoons must insure that the wastewater is well
aerated throughout. The mixing required for thorough aeration makes it unfeasible to separate
solids within the lagoon. As a result, clarifiers are required to treat the lagoon effluent. BOD5
removal in aerated lagoons is greater than in oxidation ponds. Removals of 85-95 percent BOD are
typically experienced with textile wastes. Resistance to shock loads and ability to efficiently
treat variable wastes are advantages offered by these two treatment methods. Detergents may
22
-------
cause excessive foaming problems when mechanical aerators are applied. Aerated lagoons and
particularly oxidation ponds suffer reduced performance during winter, and ice may hamper
operations.
Anaerobic lagoons are deeper than their aerobic counterparts, with depths up to 20 feet.
Wastes are stabilized by a combination of precipitation and the anaerobic conversion of organic
matter to CO2, CH4, H2S, other gaseous end products, organic acids, and bacterial cells. Detention
times are somewhat longer than those of mechanically aerated lagoons, 10 days being a typical
value.
Tables III-l, III-2, and III-3 list treatment efficiencies observed for several methods of
treatment when applied to textile wastes. Typical construction costs for the three most common
methods of biological treatment are presented in table III-4. Chapter IV presents case studies
illustrating the application of biological treatment to textile wastewaters.
Table 111-1 .—Treatment process removal efficiencies for cotton and synthetic finishing
Removal method
Screening
Plain sedimentation ...
Chemical precipitation
Trickling filter . ...
Activated sludge .... .
Oxidation pond
Aerated lagoon
Removal efficiency, percent
BOD
0-5
5-15
25-60
40-85
70-95
30-80
50-95
Suspended
5-20
15-60
30-90
80-90
85-95
30-80
50-95
Total
dissolved
solids
0
0
0-50
0-30
0-40
0-40
0-40
Source J Porter, "State of the Art of Textile Waste Treatment," study conducted for the WQO, EPA, Clemson University,
Clemson.S C., Feb 1971
Table I \\-2.-Treatmentprocess removal efficiencies for wool scouring and finishing
Treatment method
Grease recovery
Screening ...
Sedimentation
Chemical coagulation1
CaCI2 . .
Lime + CaCI2
C02-CaCl2
H2S04 + Alum . .
Urea+Alum .
H2S04 + FeC!2
FeS04
Normal reduction, percent
BOD
20-30
20-30
95
0-10
30-50
30-50
40-70
60
15-25
20
21-83
32-65
59-84
50-80
20-56
85-90
80-85
0-85
Grease
40-50
24-45
95
0
80-90
95-98
97
_
0-15
0-10
0-10
Color
0
0
0
0
10-50
10-20
75
10-30
10-30
10-30
Alkalinity
0
0
0
0
10-20
10-20
10-30
10-30
10-20
Suspended
solids
0-50
40-50
20
50-65
50-65
80-95
80-95
90-95
90-95
30-70
Source J Porter, "State of the Art of Textile Waste Treatment," study conducted for the WQO, EPA, Ciemson University,
Clemson.S.a, Feb. 1971
23
-------
I
c?0
_
.Q
ca
1 §
5 "3
•^ "°
<^ CD
1 1
OJ JI
Q_ -*
CD
i- 15 c
O > CD
o 2 £?
CJ C CD
£ d
U-
0
Q)
D
ro
OJ
Q.
1
"O "^
1 E
CD tn"
O. T3
w S
CJ)
E
d
0
m
I
d
CD
c
LL
"S
'E
«
—
CD
'£
C
"CD
_
LJ_
,2
'E
"CD
c
u_
—
^
'c
CD
(C
W
"o £
~
s
o
^
o
CD
LO
O
»—
O
o
*~
0
LO
o
§
CO
Ol
c
'x
UJ
"CD
CJ
OJ
SI
0
m
:s Carpets,
Glasgow, Vi
CD
0
°?
o
CO
8
LO
CD
C
CD
Q.
-
coagulatioi
aerated
lagoon
en
c
3 *B
o c
" 5
"o "°
g c
^- CD
0)
^~
S
^-
^-"
o
6
o
r~
o o
OJ O
<—"
6
o
q.
o
O CO
CN T-
*~ V
2
O)
c
I 5
LJ _J
C
O
O
01
03
•g
™ 2
O cu
Z <
- o
3. .2 6
SI >
H °. o- g
IS =1
r co JS CD
E S ? m
O CD
Q ^
K
CD
^
oT
ndall Co.,
Griswoldvill
OJ
O
Z.
LO
CD
O
LO
6
CO -J
CD LO
0 0
LO CM
CO CM
O O
01 O>
V V
LO LO
, — ^_
^— <-
0 0
£ E
— ij
C 75 - "D en
O CD C 0) C CD
r; TJ o ~o o o "
ro c ^ c ^ u c
M O nj CD CD V) O
•J5 x o x oj 3 1^
3 CD CD CD CD D_ ^2
CJ
LU
O
O
^
CO CO
r~ en
CO <—
-o
o
o
O
CM
CO
^
CO
CM
LO
O)
O
»-
CD
"CD
CJ
3
LL
C
g
13 CD" m
CD CT) IT
|| |
O
<
Ol •
c
!E ^^
•" ^ 3
O "- g
CD O ^
J]
O
CJ
CO
CD
•a
c
D
c:
o
c;
O
Z
O
o
V
LO
q>
G)
LO
CN
6
LO
CO
r)
O
LO
6
CD
O
CO
CN
8
•a-
CD
^.
00
^
^
en
s
CL
1
C
o
CD
^
-
=
Campbellsv
-Mi
o ^ -a "°
i- ; c x
CL S CD o
-------
Table 111-4. Construction costs: three common biotreatment methods
Method
BOD, amounts in ppm
Trickling filter cost
Activated sludge, cost
Aerated lagoon, cost
Cost, million dollars
@ 3.0 mgd
300
.90
1.05
.17
@ 3.0 mgd
450
1.15
1.30
.185
@ 3.0 mgd
700
1.50
1.70
.190
@ 1.0 mgd
450
.60
.65
.080
@ 5.0 mgd
450
1.50
1.85
.290
Note.—Each method employs 3-day equalization lagoons and final sedimentation and sludge lagoons. Land costs are not included.
Source: J. Porter, "State of the Art of Textile Waste Treatment," study conducted for WQO, EPA, Clemson University, Clemson,
S.C., Feb. 1971.
25
-------
Chaph
rerlV
CASE HISTORIES OF BIOLOGICAL WASTEWATER TREATMENT
DAN RIVER MILLS, DANVILLE, VA.
Dan River Mills is one of the largest industries in Danville, Va. The first phase of their
approach to stream pollution abatement was to undertake studies of the Dan River and of the
wastewaters from the mills while concurrent studies of in-plant measures to reduce wastes were
underway. The second phase included a detailed study of treatment methods; the third and final
stage consisted of implementing the recommendations of the first two stages.
Early stream studies indicated that the requirements of the State water-pollution-control bill
could be met by a reduction in alkalinity to meet pH requirements, together with a 50-percent
BOD5 reduction to meet DO requirements.
A moderate reduction in alkalinity was achieved by installing caustic recovery equipment with
the mercerization process, reducing caustic requirements by approximately 50 percent. The waste-
water survey had indicated that desizing operations contributed the major share of organic loading.
When synthetic sizing (CMC) was substituted for starch, BODS of the composite waste was reduced
by 45 percent. This conversion from starch to CMC, however, took 2'/2 years to complete. During
this period, polyester-cotton blends were replacing 100 percent cotton, further reducing waste load.
Still other in-plant changes produced further reductions.
At the completion of phase 1, a series of events took place altering the nature of the local
watershed. The Dan River became a spawning area for striped bass and other game fish. As a
result, the second phase recognized that greater reductions in BOD5 and alkalinity would be
required, and the need for external treatment soon became obvious.
Laboratory-scale treatability studies were conducted on composite wastewater samples.
These studies concluded that supplemental nutrients were not required for biological treatment
and indicated 90 percent BOD5 removal would be possible. Neutralization before biological
treatment was judged to be unnecessary.
Pilot studies were initiated to compare six treatment methods and develop design criteria for
full-scale operation. The six types of treatment were as follows:
• Biological:
— Aerobic lagoon
— Aerobic-anaerobic lagoon
— Conventional activated sludge
— Extended-aeration activated sludge
— Synthetic media filter
27
-------
• Physical-chemical: Lime precipitation
An 18-acre site was available for construction of the full-scale treatment plant. Due to the
location of this site, odors and noise would have to be minimal. Other considerations of the pilot
study would be cost and reliability.
The aerobic lagoon was operated at 3-, 4-, and 5-day detention times without sludge recycle.
Consistant removal of BOD5 (90 percent) and reduction in pH (to 9.0-9.5) were observed. Later
operation with a 1-day detention time and sludge recycle was equally successful. The only
operational problem during these studies was entrainment of leaves in the impeller of the surface
aerator.
The aerobic-anaerobic lagoon, operated at 4- and 5-day detention time, achieved BODS and pH
reductions equal to the aerobic lagoon. Initial operation was characterized by excessive mixing and,
consequently, very little anaerobic action. Baffles, placed along the periphery of the lagoon, cor-
rected this situation.
At conventional detention times, the activated-sludge unit performed unsatisfactorily, so
operation was converted to extended aeration. At a detention time of 24 hours, BOD5 removal
was 90 percent and effluent pH between 9.0 and 9.5. During later trials at a 16-hour detention
time, temperatures above 95° F and high alkalinities caused unstable operation and large variations
in BODS removal.
The synthetic media filter at two loading levels reduced BOD5 by 78 percent and 75 percent at
the low (51.4.pounds BOD5 /1,000 ft3/day) and high (92.5 pounds BODS /1,000 ft3/day) rates,
respectively. In both instances, the filters were operated at recirculation rates of 2:1. Effluent pH
in the former case was 9.8 to 10.0 and in the latter case, 10.0 to 10.5. Later operations used the
synthetic media filter as a cooling tower for wastes sent to the activated-sludge unit.
The results of chemical precipitation were erratic. BOD5 removal ranged from 10 to 60 percent.
Color removal was also erratic. Some of the variability was due to the design of the pilot unit.
Variation in wastewater characteristics created additional difficulties.
Reductions of color and temperature were major parameters considered, as were foaming and
solids handling. Initial conclusions and results with the two of the more promising treatment
methods are summarized below:
• The activated-sludge (extended aeration) unit would minimize land area requirements, but
indications were that it would cost more to operate than the other two most promising
treatment methods.
• The aerobic-anaerobic lagoon offered much promise as a low-cost treatment method.
• Since present processes and effluent requirements in the industry are changing, the design
of wastewater-treatment facilities must be flexible. Pilot systems allow the testing of new
processes before adoption.
• Performance of aerobic and aerobic-anaerobic lagoons are shown in table IV-1.
THE KENDALL COMPANY, GRISWOLDVILLE, MASS.
The Kendall Company, Fibre Products Division, operated a cotton-finishing mill in Griswold-
ville, Mass. This plant processes cotton and gauze hospital and sanitary products. Wastes are
produced primarily from caustic kiering, hypochlorite bleaching, and washing operations. Sizes
28
-------
Table IV-1.—Performance of aerobic and aerobic-anaerobic lagoons
Item
Raw waste
Effluent aerobic lagoon
Effluent aerobic-anaerobic lagoon
pH
11-12
9-10
29-10
Temperature,
°F
60-115
50-92
48-92
BOD5,
mg/l
'150-225
20-40
20-40
Suspended
solids,
mg/l
25-65
20-70
1 Occasionally over 300 mg/l.
2 Often exceeds 10 during winter.
and dyes may be found in the wastes on occasion. All operations are done batchwise and produce
a highly variable wasteload. The mill does not operate on Sundays. Something in excess of 2
percent of the total flow is domestic waste. Water is supplied by the North River, a class C stream.
Wastes are discharged to this river also.
Continuous flow measurement and composite sampling were begun in 1967. Average daily
flow varies from 600 to 800 gpm, with a mean of 716 gpm or 1.03 mgd. Table IV-2 summarizes
the results of composite sampling.
Table \\l-2.-Analyses of 24-hour composite samples
Item
Minimum
Mean
Maximum
pH
11 2
11.5
12.3
Total
alkalinity,
mg/l as
CaC03
520
615
890
Ammonia nitrogen,
mg/l as nitrogen
1.4
2.2
4.8
Organic nitrogen,
mg/l as nitrogen
3.2
9.9
13.2
BOD5,
mg/l
290
440
720
Suspended
solids,
mg/l
40
70
180
The concentration of inorganic phosphorus ranged from 8.6 to 9.4 mg/l, more than adequate
for biological requirements. Supplemental nitrogen in the form of ammonia would be required
to meet the nitrogen requirement of approximately 22 mg/l. On an instantaneous basis, waste
characteristics were highly variable: pH was observed to fall as low as 3.5 and rise as high as 13,
and temperatures between 40° F and 150° F were observed. The cold Massachusetts winters were
expected to affect treatment-plant performance.
Limited land area directed the pilot study toward biological treatment, employment of
short-to-moderate detention time, and a high food-to-micro-organism ratio. A detention time of
5 hours was found sufficient for equalization prior to biological treatment. Since shock loads of
chlorine and other oxidants had been released on past occasions, the equalization facility would
also reduce the possibility of upset from such chance occurrences.
Pilot studies investigated three forms of extended aeration and activated-sludge treatment
systems that differed only in their flow patterns. BOD5 removals of 88, 89, and 90 percent were
observed with these 36 liters per day pilot units. Suspended solids removals of 3, 23, and 9
percent were achieved. MLSS concentrations were highly variable in each system, and generally
lower than desired. Equipment problems and winter temperatures hampered studies. It was felt
that the 36-hour completely mixed activated-sludge process would be most capable of treating
these wastes. Subsequent studies were aimed at improving this process. It was found that the
addition of alum prior to clarification improved BOD5 and suspended solids removal to a slight
29
-------
extent, but more importantly, such addition greatly improved sludge stability. Without alum,
sludge bulking and suspended solids carryover were often observed. Efficient solids separation
was required in order to raise MLSS to adequate levels. Intermittent alum addition at a rate of
50-100 mg/1 was sufficient to provide efficient solids separation. The addition of polyelectrolyte
seemed to offer little benefit, however.
The full-scale treatment plant was designed to treat 1.1 mgd. Based on pilot studies, it was
felt that MLSS concentrations of 2,500-3,500 mg/1 could be maintained, resulting in a BOD loading
of 0.09-0.12 pound BOD5 per pound MLSS per day. Intermittent application of alum would be
required to obtain a sludge possessing good settling characteristics.
Sludge handling is a key element in the design and operation of any treatment plant. Pilot
studies indicated that odor problems would be associated with the sludge should it become septic.
Alum containing sludges was somewhat better in this respect. Aerobic sludge digestion was planned,
thereby stabilizing the sludge prior to dewatering and disposal. It was found that centrifugation
was superior to vacuum filtration for sludge thickening. A full-scale plant employing equalization,
fine screening, extended-aeration activated sludge, clarification, aerobic digestion of sludge, centrif-
ugation of sludge, and final sludge lagooning with supporting equipment could be expected to
cost $1,054,000 to construct and $57,000 to operate, given the characteristics of the Griswoldville
wastes.
The Kendall Company, after studying their processing procedures, felt that a reduction in flow
of 350,000 gpd was feasible. This made it possible to choose a more economical treatment scheme
with no expected reduction in efficiency. The new design eliminated equalization and aerobic
sludge digestion. Sludge centrifuging was considered as a future alternative, as was the aerated
sludge lagoon. Provision for sludge recycle made it possible to operate the plant as either an
aerated lagoon (no recycle) or as an extended-aeration activated-sludge process. The plant flow
diagram and cost breakdown are presented in figure IV-1 and table IV-3, respectively.
Table ^-^.—Treatment-plant capital costs1
Item
Cost
Screen building and equipment . . .
Aeration lagoon and equipment . . .
Final clarifier
Sludge pumping station
Instrumentation and electrical work
Pumping and site work
Sludge lagoons (without land costs)
Landfill site work
$176,000
158,000
70,000
85,000
90,000
70,000
63,000
40,000
Subtotal
Contingency (10 percent)
Total construction
Engineering and testing
752,000
75,000
827,000
103,000
Total project (exclusive of land, legal, and administrative costs)
930,000
1 Estimated at ENR Construction Index of 1250.
The construction contract was awarded to the low bidder at $798,000 in early 1971. The
plant was completed late in December 1971 and was operating by midspring of 1972. During the
last 8 months of 1972, removal of BOD5 averaged 96 percent. Foaming in the aeration basin,
variable MLSS, and pumping problems were encountered. Facilities were added to provide for
30
-------
RAW
WASTE
PUMPS SC
RAW
WASTE WATER
- AQUEC
AMMO
FINE
REENS now
TUBE
^-rv
)US .— LIQUID ALUM
MIA (WHEN NEEDED)
CLARIFIER
TREATED
•— - ' V I EFFLUENT
T i i
HYPOCHLORITE J SCREENINGS §
(WHEN NEEDED) £
CO
/
f
SLUDGE
f 1
I »
| RETURN | ,
SI IIDfiF 1 1 f
FLOW |
TUBS 1
^_ WASTE j— | |
i SLUDGE 1 '
LAGOONS
SLUDGE
PUMPS
Figure IV-1. Simplified-process flow diagram, Kendall Company, Griswoldville, Mass.
neutralization with sulfuric acid. The plant is presently an extended-aeration activated-sludge
system, with 3l/2 days' detention and 40 percent sludge recycle. Other parameters describing plant
operation are listed in table IV-4.
Table IV-4.—Treatment-p/antparameters
Parameter
Flow mgd . . ...
BODs influent mg/l .
BOD; effluent mg/l .
MLSS mg/l ....
F/M ratio . .
Settleability ml/l
Sludge volume index . .... ....
Average
0.80
437
16.6
1 739
0085
Range1
58-1.04
250-558
3-53
482-3,696
.036-. 31 2
190-990
107-919
' Weekly averages.
Experience at Griswoldville has indicated that superior color removal and less foaming in the
aeration basin are observed when wastes are neutralized prior to biological treatment. A continuous
alum dosage (40 mg/l) is applied at present. Color removal is variable but generally greater than
50 percent. Most recently, the plant has experienced problems with rising sludge after a 1-week
mill vacation. The sludge lagoons have proven to be an odor problem of late. Improved sludge
handling and neutralization facilities are planned.
BRW TEXTILES, BANGOR, PA.
BRW Textiles operates a knit-dyeing and finishing mill in Bangor, Pa. Wastewater
from the mill is cooled via heat exchanger, equalized, and then treated, first, biologically and
second, chemically. The raw wastes enter the treatment plant at an average rate of 0.72 mgd.
31
-------
Ammonia supplementation is provided when necessary, and the wastes are equalized in a 1-million-
gallon basin. No aeration is provided, but hydrogen peroxide is added in the mill to help maintain
an adequate dissolved oxygen level. The activated-sludge process is used for biological treatment.
Twelve hours' aeration with an MLSS concentration of 2,500-3,500 mg/1 results in 95 percent
BOD5 removal.
Raw waste is unusually high in color and high in temperature. Heat exchangers remove 20° F,
and holding for equalization results in additional cooling. The temperature in the aeration basin
averages 80° F, while raw-waste temperature averages 123° F. The biological process produces little
color removal. As a result, alum is applied at 300 mg/1 with 5 mg/1 of anionic polymer. After
rapid mixing, flocculation, and settling, the final effluent is colored to the extent of 300-400 color
units (platinum-cobalt standard). This represents 75 percent color removal with respect to the raw
waste, but State law requires additional removal to yield an effluent with 50-75 APHA color units.
Earlier tests with lime indicated that this coagulant was ineffective. The State also limits aluminum
and other phosphates. The former, contributed by alum, must be efficiently removed in the final
clarifier, and the latter, present at high levels in the raw wastes, has not been removed as efficiently
by alum addition as was hoped. Consequently, plans to construct a two-stage (2-pH level) process,
which may improve both color and phosphate removal, are in the works.
Chemical antifoaming agents have had to be added to alleviate foaming problems in the aeration
basin. Presently, solids are centrifuged and disposed of via landfill. Figure IV-2 presents the flow
diagram for wastewater treatment at BRW Textiles in Bangor.
Figure IV-2. Flow diagram, BRW Textile, Bangor, Pa.
UNITED PIECE DYE WORKS, BLUEFIELD, VA.1
The wastewater-treatment facility at the Bluefield United Piece Dye Works (UPDW) plant
originally was designed to treat 1 mgd of waste from the dyeing and finishing of woven goods.
1 Abstracted from American Dyestuff report "Treating Finishing Waste Chemically and Biologically," Randall and
King, pp. 63-66, June 1973.
32
-------
Treatment then consisted of partial equalization followed by neutralization. Over 2 years ago, the
plant installed process units for handling knit goods, and for the past 1V& years, has been processing
equal amounts of knit and woven goods. As a result, the volume of wastes has decreased from 1
mgd to about 0.7 mgd, and the organic strength of the wastes has decreased as well. The
characteristics of the wastewaters resulting from the processing of equal amounts of knit and woven
goods are presented in table IV-5. The data represent wastewater that has been neutralized and
partially equalized and are a summary of 73 routine samples taken over 1 year's time. The color
of this waste is quite variable and may change from green to red to blue to yellow over a period of
a few hours.
Table \V-5.-Wastewater characteristics: Bluefield UPDWplant
Parameter
pH
Suspended solids, mg/l
Total solids mg/l
Total volatile solids, mg/l . ....
Settleable solids, ml/ml . ....
BODS mg/l
COD mg/l .... ...
Total carbon mg/l ... .... ....
Total organic carbon . . . ...
Hue
Dominant wavelength mm . .
Luminance, percent
Purity percent
Zeta potential, mju
Concentration
Average
6.8
61
1,705
0.02
258
Range
28-120
1,138-2,584
0.01-0.04
109-463
Sample 11
6.4
96
279
292
634
228
200
Yellow
578
63.3
13
-22.6
Sample 21
10.3
125
308
264
750
252
205
Greenish-yellow
568
54.8
9
-26.2
1 Typical grab samples.
Present treatment of the industrial wastes from the UPDW Bluefield plant may be visualized
as a two-stage process. The first stage is a physical-chemical system. Equalization and neutralization
are pretreatment steps. The chemical treatment that follows consists of coagulation and flocculation,
using large quantities of lime (800 mg/l) as the primary coagulant. A high degree of color removal
occurs at this point. Following flocculation, a high molecular weight anionic polymer is added
(0.40 mg/l) to insure rapid settling of the floe in a sedimentation basin. The settled wastewater is
then neutralized by the addition of strong acid. A small portion of the lime sludge is recycled to
the influent end of the flocculation basin for particle nucleation, and the remainder is discharged
to a sludge lagoon where it is mixed with fly ash, allowed to settle, and later disposed of as landfill.
The second stage is a biological system. The neutralized wastewater passes through four aerated
lagoons operated in series. In these units, a high degree of biological treatment is accomplished.
Oxygen is provided principally through the use of seven 20-horsepower aerators. No difficulty has
been experienced in maintaining adequate DO levels in each lagoon. A flow diagram for the
treatment plant is shown on figure IV-3.
Treatment Plant Performance
Color was measured on a comparative scale developed for the Bluefield installation. Color
removal was always greater than 90 percent, both before and after the process change (from woven
to 50 percent woven and 50 percent knit raw materials). BOD5 removals were better than 85 percent
33
-------
TO LANDFILL
LIME
AIR
nrm
ACID
FLOCCULATION
CHANNEL
SLUDGE
SLUDGE
FLY ASH
LAGOON
LANDFILL
EFFLUENT TO RIVER
AERATED
LAGOON
20 H.P.
1 DAY
AERATED
LAGOON 60 H.P.
2 DAYS
Figure IV-3. Flow diagram, Bluefield UPDW treatment facilities.
during the summer months, but a combination of an upset in the neutralization facilities and cool
temperatures reduced BODS removal to a low of 75 percent during the winter. BOD5 was rarely
50 mg/1 and was usually nearer 30 mg/1. An average reduction in suspended solids of 75 percent
was observed during the 2-year period. Effluent concentrations generally fell within the range of
20-35 mg/1.
Most of the suspended solids were removed in the physical-chemical portion of the treatment
plant. Removal of organic matter averaged some 20 percent in the physical-chemical portion of
the plant, but substantially all the color removal occurred here. During the period of study, target
pH for neutralization was raised from 7.5 to 9.6 and had no apparent effect on effluent pH.
Biological production of CO2 picked up the slack in reducing the pH of this alkaline waste.
34
-------
Chapter V
EXPERIENCE WITH GRANULAR ACTIVATED CARBON
IN TREATMENT OF TEXTILE INDUSTRY WASTEWATERS
INTRODUCTION
Although many textile plants have similar operations, experience to date indicates that the
concentration and type of contaminant vary from plant to plant. Such variables would include
suspended material, lint, organic dyes, dispersed dyes, sizing agents, and carriers. It is difficult,
therefore, to design a waste-treatment process that would handle all types of textile-plant
wastewaters.
In many cases, more than one unit process will be necessary to satisfy water-quality standards
for discharge or reuse. Typical treatment systems may include such processes as screening, chemical
clarification, settling lagoons, pH adjustment, filtration, activated sludge, trickling filters, adsorption,
and ion exchange.
When examining the available alternatives, consideration must be given to capital and operating
costs of a process, land requirements, flexibility for expansion, and the ability of the process to
produce an effluent of consistent quality, regardless of changing conditions in the wastewater (i.e.,
temperature, volume, concentration). In addition, future wastewater-treatment requirements
indicate that attention should be given to water-reuse possibilities.
Although there are no cure-alls for wastewater-treatment problems, one process—adsorption
using granular activated carbon—has emerged as a practical and economical process for the removal
of dissolved organics from textile wastewaters.
ADSORPTION
Webster defines "adsorption" as "the adhesion in an extremely thin layer of molecules (as of
gases, solutes, or liquids) to the surface of solid bodies or liquids with which they are in contact."
The phenomenon of adsorption dates back to 1550 B.C. when the Egyptians used carbon to
"purify" medicines. Later, other civilizations used coconut char, bone char, and lignite char, to name
just a few materials, for processes such as odor control, decolorization, and chemical purification.
In the early 1900's, a powdered form of activated carbon found utility in the removal of
taste- and odor-causing constituents from drinking water supplies. Later, during World War II, a
granular activated-carbon product was developed for use in gas masks. Since that time, activated
carbon has been applied in almost every industry in which chemical processing plays a role. And,
in addition, it has and continues to aid in the improvement of man's environment, both on this
planet and in space.
The many uses of activated carbon are well documented in the literature; however, the
employment of granular carbon for the treatment of textile wastes is relatively new and will be
the subject of the following discussion.
35
-------
GRANULAR ACTIVATED CARBON
Granular activated carbon can be manufactured using a number of source materials, including
bituminous coal, coconut shells, and pulp mill black ash. The activated product is essentially inert.
The hardness and density varies based on the raw material employed. During the manufacturing
process, the carbon granules are permeated with a network of submicroscopic channels or pores, and
it is this network that provides the vast surface area on which adsorption can occur. The surface
area of a pound of granular carbon is equal to 125 acres, thus illustrating the magnitude of the
porosity involved.
Carbon pores may be classified two ways: macropores and micropores. The macropores are
the large pores in the carbon granule having diameters in excess of 1,000 angstrom units. These
openings are large enough to admit complex, long-chain organic molecules. The micropores have
diameters less than 1,000 angstrom units and provide most of the total surface area within the
granule.
When a wastewater containing organic chemicals passes through a bed of carbon, the chemical
molecules come in contact with the surface of the carbon and are held there by weak physical
forces called Van de Waals forces. The water continues through the bed, free or organic
contaminants.
It is important to note that when there is a mixture of organic molecules present, adsorption
selectivity becomes a prime factor in the efficiency of the unit process. That is, carbon will
preferentially adsorb some organic molecules over others. This selectivity is governed by three
properties of the molecules: molecular structure, molecular weight, and polarity of the molecule.
For example, if a wastewater contains a combination of an organic dye and a solvent, the dye,
being a larger compound with a higher molecular weight than the solvent, would be more readily
adsorbed by the carbon.
ADSORPTION FEASIBILITY
Adsorption Isotherm
An adsorption isotherm is usually run on representative samples of wastewater to determine
the feasibility of using granular carbon to remove the organics. The test consists of contacting a
fixed quantity of wastewater with varying amounts of carbon for a fixed length of time. The
amount of organic removal at varying dosages then gives an indication of the amount of carbon
required to treat this particular wastewater. This test is a very useful tool in determining the
feasibility of carbon treatment. The dosages obtained from an isotherm may be very conservative,
since they do not include the effects of biological degradation of organics during treatment.
Results of an adsorption isotherm are usually expressed in terms of the carbon's capacity for a
given adsorbate at a specified equilibrium concentration. In most cases, the Freundlich equation is
used to express the mathematical relationship between the quantity of substance adsorbed and the
quantity that is left unadsorbed (figure V-l). The unadsorbed concentration left in solution
(expressed by the symbol C) is measured directly. The adsorbed concentration on the carbon is
indicated by the symbol x/m, where x is the total quantity of substance, and m is the carbon dosage
used. Therefore, x/m is the quantity adsorbed by each unit weight of carbon.
With logarithmic plotting of data, the isotherm usually approximates a straight line when deal-
ing with a single organic component. Since most, if not all, waste streams are mixtures, the plotting
of the data results in a series of straight lines, each representing one of the components in the
mixture. The equation is usually written:
x/m = kC[/n
in which 1/n represents the slope of the isotherm.
36
-------
1,000 ,-
500
300
Q
uu
CD
cc
O
in
O
<
Q
O
O
100
50
30
10
AFTER pH
ADJUSTMENT
— TO 4.0
EASY-TO-ADSORB
MATERIAL
DIFFICULT-TO-ADSORB
MATERIALS
I
I
I
I
I
10 30 50 100 300 500 1,000
EQUILIBRIUM CONCENTRATION COD, mg/l
Figure V-1. Adsorption isotherm plot.
In review, an adsorption isotherm will provide the following useful information:
• Adsorbability
• Weight pickup
• Degree of removal
• Sensitivity to contaminant concentration
• Effect of variables such as pH, temperature, etc.
Pilot Carbon-Column Tests
The purpose of a pilot test is to obtain operating and design information. The test, which
should be carried out in conjunction with pretreatment studies, involves passing a side stream to
four columns filled with granular carbon and connected in series. The data obtained from the pilot
column study tests indicate:
• The effect of biological activity
• Performance under dynamic conditions
• Filtration characteristics
• Contact time necessary to accomplish objectives
37
-------
PRETREATMENT REQUIREMENTS
It sometimes becomes necessary to treat wastewaters prior to adsorption. Suspended solids
content above 50 mg/1, for instance, would collect in the carbon bed and create excessive head loss
across the bed. Lint can also cause premature pressure drop and problems by clogging pumps and
valves. General practices employed for suspended solids or lint removal are screening devices, sand
filters, diatomaceous earth filters, or conventional clarifiers. Adjustments in pH might also be
necessary to destabilize colloidal materials or optimize the adsorption process.
ADSORPTION DESIGN PARAMETERS
Materials of Construction Consideration
Granular activated-carbon adsorption systems can be divided into four specific functional
components:
• Granular activated carbon
• Adsorbers
• Reactivation package
• Hydraulic transport system
Granular activated carbon has been discussed in a previous section; therefore, only its effect on the
other three components will be considered here.
One item that must be considered from an engineering standpoint common to all components
is the extremely corrosive nature of the wet granular activated carbon. Wet carbon in contact with
the metal surface will set up a galvanic cell, causing severe corrosion problems. Conversely, as long
as carbon is kept moving through transport piping, corrosion is negligible.
Because of the corrosive nature of carbon in static conditions, engineering considerations
should be given to the materials of construction employed in the entire adsorption system.
Specifically, attention should be given to the following items from a corrosive standpoint:
• If pressure vessels are employed to house the carbon, then the mild steel vessels should be
lined. Satisfactory linings used for this purpose are epoxy and coal tar resins.
• In downflow adsorbers that are employed not only for the removal of dissolved organics,
but also for the removal of suspended solids, a surface wash or air scour system is usually
installed. Since the carbon comes in contact with these systems, the material of construction
should be resistant to galvanic corrosion.
• When carbon becomes exhausted, it must be removed through a hydraulic transport system.
This removal can take place directly through the bottom or sides of an adsorber. Water is
usually employed as the motive force. Since the moving carbon really does not present a
corrosion problem, mild steel piping has been successfully employed as the transport system.
To assure that no carbon remains in the pipelines, flush ports are usually installed for the
removal of carbon granules that may settle out.
• Materials of construction are also very important in the thermal reactivation unit, which is
either a multiple-hearth furnace or rotary kiln. Normally, the carbon is educted to a
dewatering screw from which it is sent to the thermal reactivation unit. The dewatering
38
-------
screw should be manufactured of stainless steel. In addition, the quench tank, into which
the reactivated carbon is quenched, should be of stainless steel. Manufacturers of the
thermal reactivation units are capable of recommending the materials of construction
employed in the units themselves. Considerations to the type of brick will be dependent
on the type and concentration of organics on the activated carbon, as well as the temperatures
employed for reactivating carbon.
Adsorbers
Either pressure vessels or common wall concrete containers may be employed to house the
carbon. The choice of adsorber types will be based on economics, land availability, and the amount
of suspended solids present in the influent to the adsorption system.
These adsorbers are similar in design to rapid sand filters found in potable water plants. Water
may be percolated through these adsorbers either upflow or downflow at surface loading rates
anywhere up to 10-12 gpm/ft2. A key consideration in all adsorbers is the type of underdrain
system employed. Experience indicates that Leopold Block, Wagner, Wheeler, and even a pipe
lateral system may be employed for the underdrain. The objective is to obtain uniform distribution.
Most underdrain systems will work effectively as long as there is about a 1-psi pressure drop through
it.
Adsorption systems configurations fall into four basic categories:
• Moving beds
• Fixed beds in series
• Fixed beds in parallel
• Expanded beds
The key feature of all adsorption design configurations is that they attempt to make maximum
utilization of the carbon. Moving bed adsorbers operate on a countercurrent basis. Water flows
upward through the bed and out the top. Once the treatment objective in the effluent has been
exceeded, exhausted carbon is removed from the bottom of the adsorber and fresh carbon added
to the top. This removal of carbon is countercurrent to the flow of water. Although this type
configuration makes maximum utilization of the carbon, it has one major drawback—it can only
handle a modest amount of suspended solids.
Fixed beds in series also attempt to make maximum utilization of the carbon. This is
accomplished by valving the adsorption system so that any adsorbers can be placed in the lead
position. When the objective is exceeded in the effluent from the last adsorber in the series, the
exhausted carbon from the first adsorber is removed and replaced with fresh carbon. This first
adsorber is then placed in the final, or polishing, position. This type of adsorber configuration
does have the capability of handling suspended solids. However, one can immediately see that the
capital investment is somewhat greater than using any one of the other designs.
Fixed beds in parallel are often employed since this design configuration has the capability
of removing suspended solids in addition to the dissolved organics. Innate in this configuration is
the ability to blend the effluent from all of the adsorbers to reach a treatment objective. Staggering
the reactivation of each of the adsorbers permits one to blend the effluent to the degree required to
reach the treatment objective desired.
39
-------
Upflow expanded beds may be employed to overcome the possibility of premature plugging
due to suspended solids in the influent. The carbon bed is normally expanded approximately
10 percent, and the solids are permitted to pass.
The choice of adsorber design configuration, therefore, will be made not only on the
economics, but also on the concentration of contaminants in the influent to the system and the
effluent objective desired.
Carbon Usage and Thermal Reactivation
When the activated carbon has become exhausted, three available alternatives may be considered:
• Throw the exhausted carbon away
• Thermally reactivate the carbon to its virgin quality and reuse it
• Have another company pick up the exhausted carbon and reactivate it for you (custom
reactivation)
The method chosen is usually a matter of economics. Naturally, the most expensive method would
be to employ the carbon on a throwaway basis. This method is usually reserved for the very small
adsorption systems, or systems in which the carbon exhaustion rate is extremely low.
If the choice is made to reactivate the carbon, then thermal regeneration equipment must be
designed and installed, based on the carbon exhaustion rate. Normally, 30-50 percent extra
capacity is designed into the thermal-reactivation unit, since the increase in economics is not
significantly greater than a unit sized to handle the specific exhaustion rate that was determined
through testing.
Both multiple-hearth furnaces and rotary kilns have been employed for thermal regeneration
of the carbon. Temperatures in the 1,600-1,800° F range are employed, with steam usually added
to the fired hearths. Approximately 6,000 Btu's are required to reactivate a pound of carbon.
During the reactivation process, the carbon is heated under controlled oxygen and temperature
conditions to effect volatilization and selective oxidation of the adsorbed contaminants. The
oxygen in the furnace is normally controlled at less than 1 percent. Carbon losses occur during
this reactivation process and are due to abrasion and burning of some of the carbon. These losses
have ranged from as low as 2 percent to as high as 10 percent. A 5-percent carbon loss is generally
an accepted standard on which economics may be based.
Since thermal reactivation equipment is a significant portion of the capital investment,
individuals may consider having someone else thermally reactivate their carbon. This approach
to reactivation is usually chosen by those persons who do not want to reactivate the carbon
themselves or to expend the capital required to purchase a thermal-reactivation unit.
CARBON-HANDLING SYSTEMS
The recommended method of carbon transport is the use of a water slurry. The ratio of
carbon to water is 1-3 pounds of carbon per gallon of water. The minimum linear velocity
necessary to prevent carbon settling is 3 feet per second. To minimize carbon attrition and pipe
erosion, the hydraulic transport system should be constructed employing long sweep bends rather
than 90° elbows.
Carbon slurries can be transported by using water or air pressure. Eductors, centrifugal pumps,
or other pumps, such as diaphragm or Moyno, may be employed. A blowcase may be employed,
40
-------
which uses air or water pressure applied in a pressure vessel. Carbon and water are slurried in a
feed tank located above the pressure vessel. The slurry falls into the vessel, the valve is closed, and
air or water pressure is supplied as the motive force. Water-jet eductors have been successfully
employed in situations where other types of mechanisms are not practical or available. They are
easy to operate and require little maintenance.
Either open or closed impeller pumps are suitable for carbon slurries, if the minimum clearance
for granule passage is maintained. The speed of the pump should be in the range of 800-900 rpm
to minimize degradation of the granules, and a rubber- or ceramic-lined impeller is recommended
for pump resistance to abrasion.
ADSORPTION EXPERIENCE WITH TEXTILE-INDUSTRY WASTEWATERS
Survey
In a recent survey conducted by Calgon Corporation, 222 wastewater samples from 68
different manufacturing operations were examined to determine the applicability of granular
carbon treatment for removal of dissolved organics. Of these, 34 samples were taken from 13
different types of textile manufacturers with specific four-digit Standard Industrial Classification
(SIC) designations, as shown in table V-l.
Table V-1 .—Textile manufacturing categories from which wastewater samples were taken
SIC number
2211
2221 . .
2231
2241
2251
2252
2254
2266
2269
2272
2281
2282
2283
Type of textile manufacturing
Broad-woven fabric mills cotton
Broad-woven fabric mills manmade fibers and silk
Broad-woven fabric mills, wool
Narrow fabrics and other smallware mills
Full-fashioned hosiery mills
Seamless hosiery mills
Knit underwear mills
Finishers of broad-woven fabrics of cotton
Dyeing and finishing textiles
Tufted carpets and rugs
Yarn-spinning mills, manmade fibers and silks
Yarn, throwing, twisting, and winding mills
Yarn mills, wool, including carpet and rug yarn
Each sample was collected by plant operating personnel from the wastewater stream of concern.
In some instances, a grab sample was used; in others, a composite sample was collected. The waste
streams, in some cases, were point-of-origin wastewaters, while other samples represented combined
wastewaters from a number of processes.
Each sample was tested for pH, suspended solids, total organic carbon (TOC), and adsorption
as received, and selective removal of color was evaluated on 29 samples. The TOC test was used on
the studies because it is a better measure of adsorption performance than either COD or BOD.
Industrial wastes often contain inorganic contaminants that are chemically oxidized and, therefore,
lead to COD values that are not associated with organic contaminants. Similarly, toxic substances
adversely affect the BOD tests, which can also lead to incorrect conclusions.
Each sample was millipore filtered prior to adsorption isotherm testing to remove suspended
material, which otherwise could be incorrectly associated with adsorption treatment. The type and
concentration of suspended material removed in this step provide preliminary indications regarding
41
-------
the desirability of pretreatment. A summary of raw-wastewater characteristics and treated water,
both filtered and adsorbed, is shown in table V-2.
Table V-2.—Textile-industry wastewater survey summary of adsorption isotherm results
Item
TOC ....
Color
Untreated wastewater
Range
9-4670
'0.02-5.40
2 50-7000
Median
290
0.56
450
Following filtration
Range
9-3335
0.02-1.64
0.3-3500
Median
183
0.29
410
Following adsorption
Range
1-440
0.005-0.09
0-15
Median
16
0.01
0
Organic reduction,
percent
Range
75-99
78-100
98-100
Median
94
98
100
'OD.
'Color units (platinum-cobalt standard).
This survey indicates that textile wastewaters contain color and other organics that are almost
universally responsive to removal by adsorption. This result is consistent with data being collected
from the installations presently treating textile wastewaters. It is apparent that pretreatment in the
form of pH control and suspended solids removal will, in many cases, allow direct application of
proven granular carbon technology to this industry, and the carbon-treated effluent will have direct
reuse capability.
CASE HISTORIES
Velvet Textile Company
Velvet Textile Company, located in Blackstone, Va., manufactures velvet cloth used in
clothing, draperies, and upholstery. Originally, the firm wove the cloth at Blackstone and then
shipped it to Glastonbury, Conn., for dyeing. Early in 1970, however, Velvet Textile decided to
combine its dyeing and weaving operations at Blackstone.
Although the physical transfer of the dyeing equipment did not present a major problem, one
drawback that did emerge was that of wastewater disposal. Under an agreement with the U.S.
Government, the city of Blackstone's domestic sewage is accepted by a treatment plant located a
few miles away at Camp Pickett. Industrial wastewaters, however, are not accepted under any
conditions. Thus, the textile firm began to examine various methods of treating its wastewater for
reuse. After examining several wastewater-treatment methods, the firm decided to install a treat-
ment system employing a combination of filtration and adsorption to remove suspended solids and
color.
Velvet Textile uses a wide variety of soluble organic direct dyes to produce the desired colors
and tones. Among these are phenamines and chloramines. The technique used to dye the fabric
involves processing the velvet through three different steps: (1) scouring the material with a
detergent, (2) dyeing the material, and (3) rinsing the excess dye from the fabric before drying.
Wastewaters from these operations are discharged to a 225,000-gallon concrete equalization basin
located below the building. Other plant wastes, such as this final rinse effluent, are also sewered
to the basin.
The wastewater is pumped from the basin at approximately 160 gallons per minute to a
diatomaceous-earth slurry mixing tank. Acid is also added to the tank to lower the pH to
approximately 4.0 to help destabilize the colloidal particles. From here, the slurry is pumped to a
diatomaceous-earth filter that has a filtering capacity of 10,000 gallons per hour. Samples of the
42
-------
wastewater are visually examined before and after filtration to monitor the efficiency of the opera-
tion. Analysis has shown these samples to contain about 90 mg/1 suspended solids and 175 mg/1
TOG.
The clarified effluent is then pumped upflow through a moving bed carbon adsorber. The
adsorber is 22 feet high and 9.5 feet in diameter and contains approximately 40,000 pounds of
Filtrasorb 300 granular activated carbon. As the carbon becomes exhausted, a measured amount is
removed from the bottom and an equal quantity of fresh carbon is added at the top. The exhausted
carbon is shipped to Calgon Corporation's reactivation facility in Pittsburgh where the organic dyes
are oxidized. The reclaimed carbon is then returned to the plant for reuse.
Effluent from the carbon column flows to an 800-gallon tank, where pH is readjusted to about
7.0. From there, it is discharged to a 100,000-gallon clear-water sump and held for reuse. Velvet
Textile presently treats about 60,000 gallons of wastewater daily and is planning to increase this to
150,000 gallons soon.
The capital cost for the total system was approximately $100,000. The adsorber, tanks, and
piping are of fiberglass construction, due to the corrosive nature of the wastewater. Operating costs
have been estimated at 70 cents per 1,000 gal. In addition, reuse of the treated water has produced
a 20-percent reduction in salt use and has eliminated both fresh-water and sewage bills.
Stephen-Leedom Carpet Company
Granular activated carbon is also being used to reclaim wastewater for reuse at a carpet
manufacturing plant in Southampton, Pa. The management of Hollytex Carpet Mills, Inc., was faced
with a serious problem when it began to plan an east coast operation. Water usage and discharge
was estimated at 500,000 gpd at the onset, with expansion planned for 1 million gpd. Existing
sewer capacity could not handle this volume of water. As a result, the municipality would have had
to install new sewer lines, and the carpet firm would have had to pay for the installation in the form
of a surcharge.
In addition, the water supply was not adequate to meet plant requirements. Costs for fresh
water and sewer charges were prohibitive. Hollytex, therefore, began to examine water-reuse
possibilities. After discussions with water-treatment specialists, it was decided to use a granular
carbon system.
Pilot studies were conducted to establish the applicability and design parameters for an
adsorption process. Subsequently, a plant was designed and constructed, and began operating in
1969.
Under an agreement with the local municipality, the carpet company would reclaim 80 percent
of its water and discharge the remaining 20 percent to the sewer. Since the municipal treatment
plant was able to handle the deep blue and red dye wastes, the carbon only treated rinse water and
pastel dye solutions. This allowed the plant to operate at a carbon-exhaustion rate of 0.55 pound
per 1,000 gallons of wastewater treated.
Wastewater from the dye becks flows into sumps through vibrating screens used to remove lint.
From the sumps, the water is pumped upflow through a moving bed carbon column containing
50,000 pounds of Calgon's Filtrasorb 400 (12 X 40 sieve size). The treated water, free of all color
and other organic materials, is then pumped through a cooling tower and stored for reuse.
Periodically, the carbon becomes exhausted and is withdrawn from the bottom of the column.
It is then hydraulically transferred to a storage tank and, subsequently, to a multiple-hearth, gas-fired
reactivation furnace. Here, the organics are oxidized and the carbon is restored to near-virgin activity.
43
-------
This plant, now owned by the Stephen-Leedom Carpet Company, has been operating
successfully since 1969.
ADSORPTION ECONOMICS
The capital and operating costs for custom-designed adsorption systems have been developed.
The capital costs were determined for an adsorption system having an overall superficial contact
time of 70 minutes. The system includes a two-stage adsorption system, a reactivation package,
including dewatering screw and quench tank, and the carbon slurry handling system.
The reactivation package also includes an air scrubber and afterburner to prevent any
air-pollution problems. In addition, it includes the initial carbon fill and a building to house the
entire system. The capital costs for a 200,000- and an 800,000-gpd plant having an exhaustion
rate of 1,500 pounds per day are $550,000 and $1 million, respectively. The capital costs for the
same plants having an exhaustion rate of 10,000 pounds per day are $720,000 and $1,250,000,
respectively.
The operating costs include the following:
• Amortization, using 7 percent interest on money over a 10-year period.
• Maintenance, insurance, and taxes at 5 percent of the capital.
• Labor costs based on one-half man per shift for a burn rate of 1,500 pounds per day and
one man per shift for the higher burn rate. The labor rate was assumed to be $7 per
hour.
• Utility costs were assumed at $1 per 1,000 pounds of steam, $1 per 1 million Btu's, and 1 cent
per kilowatt-hours.
• Makeup carbon costs were determined assuming IVz percent carbon loss and delivery price
of virgin makeup carbon at 35 cents per pound.
SUMMARY
Granular carbon is presently being employed to treat textile wastewaters. Two case histories
have been discussed; water reuse was an integral part of both.
A broad screening of adsorption applied to various types of wastewaters was shown and
indicated that textile wastewaters are almost universally responsive to treatment via granular
activated carbon.
Costs were shown and clearly indicate that the use of adsorption as a unit operation for
treatment of textile wastewaters is quite economical.
44
-------
REFERENCES
1. "Recommendations and Comments for the Establishment of Best Practicable Waste Water
Control Technology Currently Available for the Textile Industry," report for the American
Textile Manufacturers Institute, Inc., Charlotte, N.C., and the Carpet and Rug Institute, Dalton,
Ga. Institute of Textile Technology and Hydroscience, Inc., 1973.
2. Baines, Frederic C., "Biodegradation of Polyvinyl Alcohol," A.A.T.C.C. symposium, The
Textile Industry and the Environment, A.A.T.C.C., Washington, D.C., April 1973.
3. Eckenfelder, W. W., Industrial Water Pollution Control, New York, McGraw-Hill Book Co.,
1966.
4. Nemerow, N. L., Liquid Wastes of Industry, Theories, Practices, and Treatment, Reading,
Mass., Addison-Wesley, 1971.
45
-------
METRIC CONVERSION TABLES
Recommended Units
Description
Length
Area
Volume
Mass
Time
Force
Moment or
torque
Stress
Unit
metre
kilometre
millimetre
micrometre
square metre
square kilometre
square millimetre
hectare
cubic metre
litre
kilogram
gram
milligram
tonne or
megagram
second
day
year
newton
newton metre
pascal
kilopascal
Symbol
m
km
mm
l±m.
m2
km2
mm^
ha
m3
1
kg
g
mg
t
Mg
s
d
year
N
N-m
Pa
kPa
Application
Description
Precipitation,
run-off,
evaporation
River flow
Flow in pipes,
conduits, chan-
nels, over weirs.
pumping
Discharges or
abstractions,
yields
Usage of water
Density
Unit
millimetre
cubic metre
per second
cubic metre per
second
litre per second
cubic metre
per day
cubic metre
per year
litre per person
per day
kilogram per
cubic metre
Symbol
mm
m3/s
m3/s
l/s
m3/d
m3/year
I/person
day
kg/m3
Comments
Basic SI unit
The hectare (10000
m2) is a recognized
multiple unit and
will remain in inter-
national use.
The litre is now
recognized as the
special name for
the cubic decimetre.
Basic SI unit
1 tonne = 1 000 kg
1 Mg = 1 000 kg
Basic SI unit
Neither the day nor
the year is an SI unit
but both are impor-
tant.
The newton is that
force that produces
an acceleration of
1 m/s2 in a mass
of 1 kg.
The metre is
measured perpendicu-
lar to the line of
action of the force
N. Not a joule.
of Units
Comments
For meteorological
purposes it may be
convenient to meas-
ure precipitation in
terms of mass/unit
area (kg/m3).
1 mm of ram =
1 kg/m2
Commonly called
the cumec
1 l/s = 86.4 m3/d
The density of
water under stand-
ard conditions is
1 000 kg/m3 or
1 000 g/l or
1 g/ml.
Customary
Equivalents
39 37 in =3.28 ft=
1.09yd
0.62 mi
0.03937 in.
3.937 X 10'3=103A
1 0.764 sq ft
= 1.196 sq yd
6.384 sq mi =
247 acres
0.00155 sq in.
2.471 acres
35.314 cu ft =
1.3079cuyd
1. 057 qt = 0.264 gal
= 0.81 X 10'4acre-
ft
2.205 Ib
0 035 oz = 1 5.43 gr
0.01 543 gr
0.984 ton (long) =
1.1023 ton (short)
0.22481 Ib (weight)
= 7.233 poundals
0 7375 ft-lbf
0.02089 Ibf/sq ft
0.14465 Ibf/sq in
Description
Velocity
linear
angular
Flow (volumetric)
Viscosity
Pressure
Temperature
Work, energy,
quantity of heat
Power
Recommended Units
Unit
metre per
second
millimetre
per second
kilometres
per second
radians per
second
cubic metre
per second
litre per second
pascal second
newton per
square metre
or pascal
kilometre per
square metre
or kilopascal
bar
Kelvin
degree Celsius
|ou!e
kiloioule
watt
kilowatt
joule per second
Symbol
m/s
mm/s
km/s
rad/s
m3/s
l/s
Pa-s
N/m2
Pa
kN/m2
kPa
bar
K
C
J
kJ
W
kW
J/s
Comments
Commonly called
the cumec
Basic SI unit
The Kelvin and
Celsius degrees
are identical.
The use of the
Celsius scale is
recommended as
it is the former
centigrade scale.
1 joule = 1 N-m
where metres are
measured along
the line of
action of
force N.
1 watt = 1 J/s
Customary
Equivalents
3.28 fps
0.00328 fps
2.230 mph
15,850 gpm
= 2.120cfm
15.85 gpm
0.00672
poundals/sq ft
0.000145 Ib/sq in
0.145 Ib/sq in.
14.5 b/sq m.
5F
- -17.77
3
2.778 X 10'7
kwhr =
3.725 X 10 7
hp-hr= 0.73756
ft-lb = 9.48 X
10'4Btu
2.778 kw-hr
Application of Units
Customary
Equivalents
35.314 cfs
15.85 gpm
1.83 X ID'3 gpm
0.264 gcpd
0.0624 Ib/cu ft
Description
Concentration
BOD loading
Hydraulic load
per unit area,
e.g. filtration
rates
Hydraulic load
per unit volume;
e.g., biological
filters, lagoons
Air supply
Pipes
diameter
length
Optical units
Unit
milligram per
litre
kilogram per
cubic metre
per day
cubic metre
per square metre
per day
cubic metre
per cubic metre
per day
cubic metre or
litre of free air
per second
millimetre
metre
lumen per
square metre
Symbol
mg/t
kg/m3d
m3/m2d
m3/m3d
m3/s
l/s
mm
m
lumen/m2
Comments
If this is con-
verted to a
velocity, it
should be ex-
pressed in mm/s
(1 mm/s = 86.4
m3/m2 day).
Customary
Equivalents
1 ppm
0.0624 Ib/cu-ft
day
3.28 cu ft/sq ft
0.03937 in.
39.37 in. =
3.28ft
0.092 ft
candle/sq ft
-------
532
U.S. ENVIRONMENTAL PROTECTION AGENCY • TECHNOLOGY TRANSFER
------- |