an industrial Waste Guide to the
Wool
Processing
Industry
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
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Foreword
In the Woolen Industry, as in many other industries, control and dis-
posal of wastes is of major concern. There are two important reasons for
increased attention to these problems: First, the greatest possible recovery,
use, and reduction of wastes is necessary for most economical production
in small as well as large plants. Second, protecting the Nation's limited
water resources for maximum use is essential to our health and continued
economic growth. Stream pollution control is mutually beneficial to indus-
try, the individual citizen, and the Nation as a whole. Thus, wastes which
cannot be eliminated must be disposed of in a manner which will not impair
the usefulness of stream waters for other beneficial purposes.
This "Industrial Waste Guide to the Wool Processing Industry" is in-
tended primarily to aid operators of woolen mills and commission processors
to utilize, reduce, and otherwise suitably dispose of their wastes. The Guide
was prepared by the Stream Pollution Abatement Committee of the American
Association of Textile Chemists and Colorists, which is the technical associ-
ation of the textile wet-processing industry. It was submitted for publication
to the Public Health Service through the National Technical Task Committee
on Industrial Wastes.
The National Technical Task Committee on Industrial Wastes is com-
posed of representatives from the Nation's leading industries concerned with
solving difficult industrial-waste problems. The objective of the organization
is to perform technical tasks pertaining to industrial wastes in cooperation
with the Public Health Service and all others concerned with improving the
quality of our water resources. The preparation of this Guide was one of the
tasks assumed by the Textile Industry in carrying out this objective.
This is the third of a series of Industrial Waste Guides prepared by
the National Technical Task Committee in cooperation with the Public Health
Service.
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an Industrial Waste Guide to the
Wool
Processing
Industry
Prepared Uy the Stream Pollution Abatement Committee
oj tlte American Association of Textile
Chemists and Colorist.s
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service Bureau of State Services
Division of Sanit ary Engineering Services
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CONTENTS
INTRODUCTION 1
INSCRIPTION OF PROCESS i
Opening and Scouring 1
Spinning 2
Dyeing 2
Weaving and Finishing 2
Tin: POLLUTING EFFECTS OF WOOLEN MILL WASTES... 2
The Meaning of "Pollution" 2
Tuhlr 1—Polluting K fleets of Some Industrial Waste Components. ... .'{
Polluting Effects of Specific Woolen Mill Wastes 4
Table 2—Properties of Woolen Mill Wastes Solutions 4
METHODS OF DEALING WITH WOOLEN MILL WASTES ... r,
Waste Saving 6
Byproduct Recovery 6
Combined Treatment With Municipal Sewage 8
Treatment of Residual Waste 10
SUMMARY AND CONCLUSION 12
BIBLIOGRAPHY 13
Public Health Service Publication No. 438
U. S. GOVKRNMKNT PRINTING OFFICE, WASHINGTON : 1955
For sale by the Superintendent of Documents, Government Printing Office, Washington 25, I). C. - Price 15 cents
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on huluslrial H ash' (inidc In thv
Wool Processing Industry
Introduction
The woolcn-mill supervisor occupies a key
position in reducing the polluting effects of his
mill eflluents. He can be particularly effective in
the area of good housekeeping, which prevents
wastes at the source and reduces manufacturing
costs at the same time. This handbook is de-
signed to assist him in exercising his responsibil-
ity for waste reduction and pollution control,
and in recognizing those additional problems
which require the services of the plant chemist
and plant engineer.
With this primary purpose in mind, waste
technologists and others in the Woolen Industry
have attempted to design a concise, practical
guide for wool-plant operating and design per-
sonnel. This booklet summarizes information
made available over a period of time by many
investigators. It emphasizes the appreciable re-
duction of waste which can be accomplished by
waste-prevention measures within the processing
plant. Practical methods of carrying out such
waste-saving measures are discussed in some
detail.
The section on waste treatment is not intended
to be a comprehensive discussion of woolen-mill
waste treatment. Sufficient information is in-
cluded, however, to suggest possible solutions to
stream-pollution problems which cannot be ade-
quately corrected by waste-prevention proce-
dures. Some performance data are included on
various waste-treatment piocesses. This section
may also serve to emphasize the value of waste-
saving methods in reducing total waste-treatment
costs.
Description of Process
Wool processing consists of the following steps:
1. Opening and scouring.
2. Spinning.
3. Dyeing.
4. Finishing.
There are plants which perform each of these steps
separately, often on a commission basis, and there are
integrated mills, which carry out all of these functions
from beginning to end. The processes involved in the
steps ahove arc described briefly in the following
paragraphs:
Opening and Scouring
Shorn wool is packed in bales and shipped to scouring
plants for the removal of foreign matter. The bales
are ripened around a portable conveyor and fleeces are
put onto the conveyor, blending the wools from many
bales. The conveyor carries the wools to a series of
pronged opening machines and dusters where the fibers
are gently separated, and sand, grit, grass, etc., are
beaten out of the mass. Some of these impurities re-
main stuck to the grease on the wool.
From the dusters the wool is dropped into a continu-
ous scouring machine, consisting of a series of
rectangular bowls through which the wool is propelled
by reciprocating arms. Prongs on these arms dip into
the scouring solution and move the wool from bowl to
bowl through a series of squeeze rolls. The wool is
dried and rebaled in preparation for the next process,
or, if necessary, it is carbonized. Carbonizing is a
process of removing vegetable matter such as straw,
burs, and grass by steeping the wool for a short time
in a dilute sulfuric acid solution followed by drying
at a high temperature to dehydrate and char the vege-
388390—56
1
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tallica matter. The stock is passed through a heater
which brushes out the charred vegetable matter. The
wool is then dipped into a neutralizing bath and
rcdricd.
Spinning
Dry wool is sprayed with an emulsion of oil and
water as it passes over a conveyor bell. It is then
carded and spun into yarn.
»»«•"»«
The process of applying color to wool involves a
variety of steps. Wool may be dyed in any of three
forms: loose fiber, yarn, or piece goods. The proc-
esses are nearly the same. The wool is put into a vat
or dye kettle, commonly wood or stainless steel. The
kettle is filled with water; salt, acid, and dye are dis-
solved, added to the kettle, and the material boiled for
about an hour. The exhausted dye solution is run off,
and the material is rinsed and dried. Several vari-
ations of this dyeing process are used depending upon
the service to which the goods will be put. The above
describes the most commonly used "acid dyeing"
process. There are, in addition, neutral dyeing, which
uses practically no acid; chrome dyeing in which the
color is mordanted onto the fiber for best wash fast-
ness; and rnetalized dyeing which uses a strong acid
solution.
Dychi mscs commonly carry out certain auxiliary
processes connected with the coloring. Among these
are scouring of yarn and piece goods to remove spin-
ning oil, which would otherwise cause a resist to the
adsorption of dye. To correct errors in dyeing and
changes in orders, stripping of color from wool to pre-
pare for redycing another shade is often done. Strip-
ping involves the use of a reducing agent in an alkaline
or slightly acid solution, depending on the particular
reducing agent.
Weuvinff and Finitthinfi
Since weaving is a dry process, not producing liquid
wastes, it is not of particular concern in the prevention
of water pollution.
Finishing applies most particularly to piece goods.
The first step in finishing is fulling, in which piece goods
are soaked in a soap solution and put through a series
of roller mills until they have become felted and
shrunken to increase their body and density. The
goods are then put through a washer to remove soap
and emulsified spinning oil. They are then dried and
ready for dyeing or cutting.
There are many integrated mills which, within one
large building, carry out all of the processes described
above.
The Polluting Effects of Woolen Mill Wastes
Thf Meaning of "Pollution"
Water is said to be polluted when its character is
changed, by addition of materials or in any other man-
ner, in such a way that the usefulness of the water is
reduced.
In their natural state, most bodies of surface water
and flowing streams are relatively clear, colorless, and
contain several parts per million of dissolved oxygen
which is supplied by absorption from the air and to
some extent by plant life in the water. The dissolved
oxygen in the water is as necessary for the existence of
fish and many other desirable kinds of life in the water
as the oxygen in air is for the existence of man and
animals on land. Clarity of the water permits the
transmission of light which retards undesirable bac-
terial growth and generally contributes to a healthy
and balanced population of aquatic organisms. Fresh
waters in this kind of environment are usually suitable
for most uses—as a source of municipal and indus-
trial water supplies, for recreational bathing and
fishing, irrigation, etc.
Pollution represents any undesirable departure from
the condition described above. It can occur naturally
as well as artificially. The most common form of
natural pollution occurs when rains wash dirt from
uncovered ground and heavy streamflows stir up the
bottom. The stream is thus polluted by muddying,
which may destroy animal and plant life on the bottom,
reduce fish populations, and render the water less suit-
able for many beneficial uses. Land-use practices of
man contribute greatly to this form of pollution. An-
other source of natural pollution is the leaching of
excessive quantities of salts or harmful materials from
the formations over and through which the water flows.
The alkali waters of the Southwest are examples of this
type of pollution.
%
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Manmadc pollution results chiefly from the discharge
of wastes Iron) cities and industries. Domestic wastes
are relatively uniform in composition and in their effect
on streams. Methods of treating municipal sewage are
fairly standard. Therefore, wastes from the plant's
sanitary facilities can usually he discharged to public
sewers without special concern to the plant operator.
fn contrast, industrial wastes vary widely in charac-
ter and in their polluting effects; therefore, each type
of waste is a special waste-treatment problem.
Most organic substances undergo a more or less
gradual chemical or biological change which takes dis-
solved oxygen from the water. The extent ot oxygen
depletion depends on the rate of this oxygen demand
in relation to the reaeration characteristics of the
stream. If the dissolved oxygen is reduced below cer-
tain limits, desirable fish and aquatic life cannot exist.
Complete removal of dissolved oxygen results in a septic
stream which is characterized by obnoxious odors,
floating solids, and a generally disagreeable appearance.
Suspended organic solids may deposit on the bottom
of quiet areas in the stream, concentrating the oxygen
demand of these wastes in those areas. Waters con-
taining considerable organic material are generally un-
suitable for municipal and industrial water sources,
recreational and some agricultural uses.
The introduction of disease organisms or harmful
bacteria into the stream is another form of pollution
which is particularly harmful to uses such as drinking-
water sources, recreation and bathing. Sewage is the
principal cause of this type of pollution.
Excessive concentration of soluble inorganic salts
generally render water less suitable for industrial and
municipal water sources. Concentrations of sodium
and boron salts above certain limits cannot be tolerated
in irrigation water. A serious disadvantage of this
type of pollution is that soluble inorganic salts are not
usually removed by natural stream purification proc-
esses; therefore they may affect use of the water far
downstream from the point of entry. Acids and alka-
lies react to form salts and in addition have corrosive
effects on boats and structures in contact with the water.
A number of substances arc toxic to fish and aquatic
life. Many of the metals which may be present as
salts fall in this category. The acids, alkalies, and
numerous members of other classes of compounds may
have similar effects. Sonic substances are toxic to
humans also, if present in sufficient concentration in
water supplies.
The pollution may be in the form of the addition of
tastes, odors, and color to the water. Phenol is an
example of pollutant which results in serious taste
problems in drinking water supplies. Color in itself
is esthetically objectionable, particularly in drinking
and recreational waters. Some industrial process
waters must also be free of color.
Suspended inert matter may also have detrimental
effects on the utility of the stream. It makes the water
turbid, reduces light penetration and much of it even-
tually settles on the bottom. The turbidity increases
the cost of treatment required for municipal and in-
dustrial uses. Deposits on the bottom may harm bot-
tom-dwelling aquatic life, reduce the carrying capacity
of the stream channel, and shorten the useful life of
reservoirs. There are instances in which the deposition
of industrial wastes has increased the dredging neces-
sary to maintain ship channels.
Listed in table I are some of the principal polluting
effects of certain types of materials frequently present
in industrial wastes.
Tabi.t. 1.— Polluting effertn of name industrial waste components
Polluting ngp.nt
1. Acids, alkalies, and inorganic salts.
2. Dyes
3. Inert, matter, such as pigments, clay,
coat dust, etc.
4. Organic matter, including organic
oils, greases, and salts.
Effect
Toxic to fish and aquatic organisms. Deteriorate boals and structures in
the water. Detrimental to municipal, industrial, and irrigation uses.
Add color which is esthetically objectionable in drinking and recreational
waters.
Adds turbidity, settles on stream bottom. Reduces desirable fish population.
Increases municipal and industrial water treatment, costs. Interferes wit.li
navigation and may reduce useful life of reservoirs.
Depletes dissolved oxygen, eliminating desirable fisli populations. May add
tastes, odors, and t urbidity detrimental to industrial ami municipal water
supplies. Forms floating scums esthetically objectionable and harmful to
recreational uses such as bathing.
Woolen-mill wastes, like many other industrial
wastes, normally contain several of these kinds of pol-
luting materials, and therefore may have a number of
detrimental effects on the stream. For instance, wool
scouring wastes can render a stream turbid and alkaline
and remove all of the available oxygen. If this is al-
3
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Figure I.—Wool scouring uses 3 gallons of
water per pound of wool and produces
the most offensive of all textile wastes.
lowed to happen, fish are killed, and the stream gives
off obnoxious odors formed by the septic decomposi-
tion of the emulsified greases and other organic con-
stituents. Dye wastes together with the salt and acid
in them create almost all of the above effects except
turbidity.
fulfilling Wfei'lH of Speeitlc Woolen-Mill \\ ntttvn
We shall now examine the polluting effects of in-
dividual woolen-mill waste solutions. The following
table lists the polluting characteristics of the major
wastes. The data were taken from a number of refer-
ences and represent average values around which con-
siderable variation can be expected from mill to mill.
These differences arise from corresponding differences
in the grease content of various wools, and differences
between mills in the water-to-wool ratios in dyeing or
scouring.
Table 2 gives the characteristics of the individual
wastes. The stream usually receives a mixture the
composition of which depends on the relative amounts
of the individual types present. In one mill, for in-
stance, the total output consists of 20 percent wool
scouring waste, 30 percent dyeing waste, 30 percent
yarn washing waste, and 20 percent from all other
sources, including water softener backwash and sanitary
facilities. A plant which is primarily a scouring and
carbonizing plant will have a waste thai differs greatly
from that of a dyeing and finishing plant.
Many studies of woolen wastes have been under-
taken. One of these, conducted at Lowell Technological
Institute (ref. 46), evaluated the manner and extent
to which wool scouring liquors contribute to stream
pollution. Various methods of treatment were sur-
veyed, and it was determined that control of the scour-
ing process played an important part in the amount of
pollutional materials discharged.
Table 2. Properties of woolen-mill waste solutions
Waste
Wool scouring
Acid dyeing
Carbonizing
Piece or yarn wash
ing.
Gallons
waste per
1,000 lbs.
clean wool
8, 000
3, 000
500
5, 000
B. O. D. of waste
P. P. M.'
6,000 to 10,000___.
(Refs. 29, 13, 37.)
400 to 4,000 _
(Ref. 48.)
20 to 50
250 to 350_ _ .
Composition
0.5 percent wool grease
0.5 percent Suint salts,
grit, burs.
0.1 percent alkali.
0.1 percent mineral or
organic acid.
0.2 percent salt.
5 percent sulfuric acid..
0.2 percent spinning oil
0.1 percent alkali.
0.05 percent soap.
pH
10. 2
4. 0
1. 0
9. 5
Color
Brown -
Variable light to
strong.
None
Light brown
Odor
Foul.
Slightly
acid.
Acrid.
Soapy.
1 B. O. I).—-Biochemical Oxygen Demand, a term which signifies the amount or oxygen which will be taken out of the water in the decomposition and
stabilization of the waste. The value given in the table Is the number of parts by weight of oxygon used per million parts of waste In S days at a temperature
of 20° C.
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Another report by H. G. Baity (ref. 2) showed that
textile wastes have three primary bad effects on the
streams which receive them:
1. They are toxic to stream life.
2. They deplete the oxygen in the water.
3. They impair the stream's physical characteristics
and properties.
This report reviews waste-treatment accomplishments
in the State of North Carolina.
England has had a severe problem from wool scour-
ing wastes since long before wool processing became
a major industry in this country. Barker (ref. 3) has
noted that the Yorkshire area scours out 34,000 tons of
fat, 33,000 tons of dirt, and 11,000 tons of suint salts
per year, most of which end up in the rivers. Toward
the end of the last century, the putrefaction of these
wool scouring wastes evolved so much hydrogen sulfide
gas that it was possible for the air above the water to
burn. The Yorkshire Rivers Board has conducted de-
tailed studies (ref. 1) on the causes of pollution,
covering nontechnical phases such as the use of rented
manufacturing facilities, the contract processing of
waste, the use of joint outlets by several mills, etc.
IIow badly the receiving body of water will be
polluted also depends on the amount of water available
for dilution. Wastes from the largest textile mill, if
mixed in the ocean, would not affect the quality of such
a large quantity of water. Unfortunately, most textile
plants haven't an ocean nearby but are located on
streams with limited flows. This creates the need for
waste control.
A large river can assimiliate more wastes than a
small one; wastes which cause no pollution problem in
times of high stream How may cause serious conditions
during periods when the stream is low. The mill
operator should know the average, high, and low flow
rates of the stream into which the mill wastes dis-
charge in order to determine how much must be done
to prevent pollution under all conditions.
Methods of Dealing with WooJen-Mill W astes
When a woolen-mill operator is confronted with a
waste problem, he should consider four steps:
1. Waste saving: Waste can be reduced at the
source by carefully controlling the manufacturing
process. A simple example is the use of the least
amount of acid in dyeing that will satisfactorily do
the job, in order to minimize the amount of acid that
finally gets out into the waste.
2. Byproduct recovery: Many mills have contami-
nated streams with wastes which, on investigation,
were found to contain salable byproducts. The most
common example in the woolen industry is wool
grease.
3. Combined treatment with municipal sewage:
In communities that have adequate municipal sewage
treatment facilities, it may be feasible to discharge
the woolen-mill effluent into the municipal sewerage
system. This approach frequently requires no capi-
tal outlay and can generally be paid for on a sewer
rental basis.
4. Treatment of residual waste: After everything
possible has been done along the lines of the first
three steps above, the final recourse is to treat the
Figure 2.—Titration control with metering of detergent
and alkali to the wool, washer reduces scouring cost,
improves control and minimizes the alkalinity and
variability of the scouring affluent.
remaining waste to the extent required by the receiv-
ing stream. A number of treatment methods are
available.
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Each of these steps is discussed in the sections which
follow.
With a planned program based oil these four steps,
almost any industrial waste can be satisfactorily dis-
posed of without creating a stream-pollution problem;
and among industrial wastes, woolen-mill wastes are
not by any means the most difficult to handle. Now
let us look at each of these four steps.
Waste Sarin if
Logically, the first step in preventing stream pollu-
tion is to eliminate avoidable waste by careful control
of production operations and to modify processes so
that less harmful substances are in the plant effluent.
Among industrial waste control people, much of this
comes under the heading of good housekeeping econ-
omy, and almost invariably results in saving money.
Some very fine investigations have been made of this
approach in the textile industry.
1. Masselli and Burford (ref. 29) studied in detail
the processing at two woolen mills and reached the
following conclusions:
a. Many synthetic detergents have a much lower
B. 0. D. than soaps and the use of any of several
detergents in place of soap could lower the oxygen
demand load contributed by a woolen mill from 30
to 45 percent.
b. Mineral acids and ammonium sulfate have
much lower B. O. D. than acetic acid. The substitu-
tion of the former for the latter in dyeing can reduce
the B. 0. D. of the plant effluent from 2 to 15 percent.
2. Snyder (ref. 55) has reported that the polluting
effect of cotton slashing waste can be greatly reduced
by using certain synthetic compounds like carboxy
methyl cellulose as a partial or total replacement for
starch.
3. Stafford and Northup (ref. 56) made com-
parative B. 0. D. tests on about 175 textile chemicals
and dyes. From this list, many suggestions can be
taken along the lines of materials changes that can
improve the characteristics of a woolen mill effluent.
The above are examples of material substitution.
Equally fruitful is the field of material economy without
necessarily changing the materials used. For instance,
one mill which scoured as much as 400,000 pounds of
wool per week changed its method of alkali control
from conductivity measurements to titration and, by
the more accurate metering of alkali into the washers,
cut its soda-ash consumption from 10-12 pounds per
hundred pounds of wool down to 4. Spaced over the
period of a year this resulted in a saving of several
thousand dollars and cut the alkali in the effluent almost
two-thirds. The same has been shown to be true in acid
dyeing; pH control in the dyehouse can be used to
minimize the amount of acid put into the dye kettles,
thus keeping to a minimum the amount of acid in the
effluent.
R. H. Souther (ref. 57) has shown that the amount
of reducing agent added in vat dyeing is usually in
excess of what is actually required and that careful
control can produce perfect results with greater econ-
omy of material. Since reducing agents have a tre-
mendous oxygen consumption, this can be a very
important point for mills which use a large quantity of
vat dyes. In this connection, the Marhen process offers
a good tool for controlling reducing agent through the
measurement of redox potential.
Itnprtulnft llueovery
Whether an industrial waste is put into a municipal
sewer system or treated at the plant and put into surface
waters, the recovery of usable or salable materials
from the waste lessens the degree of treatment neces-
sary and generally reduces the cost of manufacturing
operations. Byproduct recovery is economically justi-
fied when the value of the byproducts plus the reduced
treatment costs exceed the cost of recovery.
Figure 3.—The acidity and unexhausted
color in dyehalh elilueiit can he kept to
a minimum by pH control.
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Iii the case of woolen mills, there are presently few
items which could possibly be recovered. These are
wool fibers, wool grease from scouring operations, and
fertilizer material from scouring operations. Re-
search now going on may result in cheaper ways of
recovering other materials now considered too costly
to recover, and may find markets for other components
of the waste which today are considered valueless.
The separation of wool fiber from waste is a rela-
tively simple matter. Vibrating screens of a readily
available standard design are in use for this purpose.
Such vibrating screens are common chemical engineer-
ing equipment. Another technique involving a filter
drum is described in a German publication (ref. 4).
Wool fiber disintegrates slowly and therefore has a
very extended period during which it will absorb
oxygen slowly from water. It has a more acute disad-
vantage of clogging pipes and sewage-treating equip-
ment if the waste is put into a municipal sewer system.
The recovery of short fiber is a distinct economic ad-
vantage since short fiber can be added to wool mixes
in certain percentages.
There is a large body of information and experience
on the recovery of wool grease from wool scouring
solutions, and there are several techniques for recover-
ing the grease, all of which work successfully. Wool
scouring wastes are the strongest polluting materials
in the whole textile industry and the major factor to be
considered in dealing with a waste problem at an
integrated woolen mill.
In addition to reducing the required residual waste
treatment, the chief incentive for recovering grease is
its salability, which has permitted profitable recovery
in the last 7 or 8 years. Prior to this period, however,
the wool-grease market had been noted for wide fluc-
tuation in price and there is relatively little confidence
even today in the steadiness of price for the recovered
wool grease. The Department of Agriculture is con-
ducting research (ref. 36) designed to broaden the
usage of wool grease, lanolin, and the components
thereof. Another Department of Agriculture labora-
tory project (ref. 25) involves a solvent scouring sys-
tem in which not only the grease but the suint salts can
be recovered. A report on this project has been made
by its head. Dr. Harold Lundgren. In this case, a com-
pletely new system of scouring is involved. A market
must be developed for recovered suint salts in order to
justify the process economically.
Details on the standard methods for grease recovery
are available from many sources (refs. 5, 7, 13, 14, 18,
20, 22, 38, 39, 49, 50). These standard methods are
based on two principles:
1. Continuously circulating the scouring solution
through centrifugal extractors to remove amounts of
wool grease in excess of a certain threshold concen-
tration. The extracted scouring solution is returned
to the scouring machines for buildup of grease con-
centration and cycled again through the extractors.
2. The entire scouring solution is treated in a
batch process of chemical precipitation such as by
acid cracking or the addition of calcium salts to
separate out the grease. The separated crude grease
is then put through a filter press to remove solids,
and is dried.
The relative amount of grease compared to the other
polluting materials such as suint salts, dung, urine,
dirt, grit, and burs in the scouring waste depends on
the type of wool being processed. The grease will ac-
count for about 80 percent of the oxygen required
(Biochemical Oxygen Demand) by waste from the
scouring of high grease content clothing wool. Sixty
percent of this grease can be removed by centrifugal
extractors. This will reduce the oxygen demand by 48
percent, or approximately one-half.
The centrifugal extraction process removes a smaller
proportion of the grease from low grease content waste.
Figure 4.—Efficient (lusting before scouring
reduces (lie waste load imposed on the
wool scouring solutions.
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It is therefore a much less effective pollution reduction
measure in plants processing low grease content wools.
Grease represents about one-half the oxygen demand
in wastes from scouring low grease content carpel
wools. The acid cracking process will remove prac-
tically all of this grease, which in turn reduces the
oxygen demand of such scouring wastes by one-half.
The process for grease recovery requires a consider-
able capital investment, not less than $35,000; but if
any volume of greasy wool is processed, the installation
can be amortized in less than 5 years.
After the grease is recovered, there are two remain-
ing components: the filter press cake which contains
considerable organic matter, dirt, and grit; and the
water phase of the scouring solution. The press cake
can easily be dried by spreading out on the ground, and
makes a good fertilizer. The water eflluent is still not
satisfactory for putting into a stream of high water
quality and must be treated in any of several ways
discussed later.
Two systems for solvent scouring have been tried
with a view toward eliminating the stream pollution
problem by reducing the amount of aqueous treatment
given to wool in its lengthy processing through a woolen
mill. Neither process is in use today. The first and
oldest is a batch process for degreasing wool in a kier
by circulating naphtha solvents through it. The naph-
tha with grease dissolved in it (ref. 55) was then filtered
and the solvent evaporated and recovered. The second
process was described by Oberholtzer (ref. 32) and
consisted of a continuous scouring with trichlorethyl-
ene. The processes fell into disuse because of the
following disadvantages:
1. The sale value of the recovered grease from a
solvent process is not as great as from an aqueous
scouring, since it is darker in color and contains
foreign matter which is difficult to remove.
2. Inevitable solvent losses add a cost factor to
the process which renders it noncompetitive to
aqueous scouring.
3. In spite of the solvent scouring, there remained
in the wool other foreign matter such as listed above
which had to be scoured out in an aqueous medium
after the solvent degreasing. This immediately re-
turned the stream pollution problem, although not
as severe as if the degreasing had not been done.
t'ombinetl Treatment With Municipal Seivafle
After setting up good housekeeping practices and
any possible byproduct recovery so as to minimize
waste at the source, the next possibility for mills suit-
ably situated is to consider putting the plant effluent
into the city or town sewerage system. This procedure
usually involves the least capital investment. How-
ever, it must first be determined whether the nature
of the waste will interfere with the sewage treatment
and whether local arrangements can be made to dispose
of the waste in this manner.
Several studies have been made to determine the
effects of textile-mill wastes on sewer systems. It has
been concluded that if certain conditions are satisfied,
woolen-mill waste can be added to sewer systems. The
factors which must be considered are:
1. Is the volume of mill wastes large or small in
relation to the amount of sewage?
2. What are construction materials in the sewer
lines, and will the mill wastes be harmful to the sewer
lines or the joints between sections of sewer pipes?
3. How is the sewage treated, and will the addition
of mill wastes overload or upset the operation of the
municipal treatment plant?
4. If some treatment is needed lo make the plant
effluent suitable for discharge to municipal sewers,
is such pretreatment feasible?
5. Assuming all these conditions to be favorable,
what would be the cost for utilizing city sewer sys-
tems to dispose of woolen-mill wastes?
The following paragraphs review the findings of some
studies that were made in an attempt to answer the
questions above:
4* 1
K'w.
-*> *
-»
¦SHIRKS
Figure 5.—Representative
waste treatment system
showing, (A) chemical feed
house, (li) clarifier, (C)
trickling filler. Chlorina-
tion of the wastes is sonie-
times substituted for
trickling filter treatment.
-------
1. The oldest reference (ref. 45) describes a study
in 1928 of a small German town, population 7,000,
where they successfully combined with the sewage
large amounts of waste from woolen mills which
scoured raw stock, dyed, spun, and finished woolen
cloth. In this case, the sewage treatment processes
(circulation on long shallow sand beds, Imhoff tank,
sludge drying beds) were a type for small cities only
and the quality of the final effluent would not be ade-
quate for all purposes.
2. Rudolfs reported in 1937 (ref. 35) on labora-
tory and pilot plant studies of the effect of a number
of trade wastes on high (70° C.) and low (20° C.)
temperature sewage sludge digestion processes. The
results of the tests with woolen-mill wastes generally
indicated—
a. The addition of 10 percent by volume of wool
scouring waste to digesting sewage sludge had rela-
tively little effect, but the addition of 20 percent
retarded digestion.
b. The addition of 10 percent dye wastes reduced
gas production up to 35 percent.
c. After a short period of continuous addition of
the wastes the bacteria of the digestion process be-
came adapted to the wastes to the extent that diges-
tion of the above concentrations proceeded satisfac-
torily.
3. Geyer (ref. 16) reports that in his opinion the
best method of industrial-waste disposal is combina-
tion with municipal sewage. He describes methods
for chemical precipitation, filtration, and biological
purification. This work included wool scouring and
dye wastes.
4. In Los Angeles (ref. 34) wool scouring wastes
were combined with sewage, but the sulfide content
of the scouring waste caused odor niusances and the
oxidation of the hydrogen sulfide damaged concrete
pipe joints in the sewers. The problem was over-
come by reusing the rinse water in the scouring solu-
tion and treating the rest of the waste with ferrous
sulfate. In this way, sodium sulfide was recovered,
the sale value of which exceeded the cost for its
recovery.
5. One other reference gives an excellent summary
of the whole situation. A report from the Textile
Foundation (ref. 42) discusses the pros and cons of
putting textile-mill wastes into domestic sewer sys-
tems. The general conclusion is that it can be done
providing certain principles are observed. These
principles are—
a. That the waste be made consistent in its char-
acter.
b. That the rate of feeding the industrial waste
into the sewer system should be controlled to main-
tain a relatively constant ratio of waste to sewage.
The case of one large plant which used this pro-
cedure can be cited. The woolen mill scoured and
dyed 300,000 pounds per week and put the waste into
the sewer system of a community of about 80,000
people. It was found that with usual dumping of the
equipment at the end of the day, large amounts of
highly concentrated wastes would reach the sewage dis-
posal plant and exceed the capacity of its chlorinating
equipment. The problem was solved by the construc-
tion at the woolen plant of a large concrete pit, capable
of handling all of the plant effluent for 1 day. In this
pit the dye wastes and scouring wastes partially neu-
tralized each other, and a great deal of the suspended
matter settled to the bottom. A sluice was opened
after the pit was filled so as to drain the pit slowly and
uniformly into the sewer system over a 12-hour period,
and the city sewage treatment was not adversely
affected.
An excellent survey has been written by G. J.
Sehroepfer (ref. 58) in which he describes the various
techniques for determining fair sewage service charges
for industrial wastes. There are a number of methods
by which an industrial corporation can pay the addi-
Figure ft.—Enlarged view of a
elarificr. After dosing with
coagulating chemicals the
waste is fed into a clarificr
such us this where the to-
agulatcd suspended mate-
rial settles. Sludge pumps
transfer the settled materi-
al from the bottom of the
clurifier to sand drain beds
for drying.
-------
Figure 7.—Dctiiil of trickling
filter construction. The
aerobic liaeteria living in
the slime coating on the
stones "digests" the organic
matter remaining in the
wastes coming from the
clarifier.
tional cost incurred by a city in handling their wastes
in combination with sewage. Naturally, the additional
measures to be taken to handle these wastes are de-
pendent upon the nature and volume of the waste in
relation to the equipment, daily sewage volume, and
the nature of ihe treatment at the municipal sewage
plant. Hazen (ref. 51) has also summarized the prob-
lems concerned with evaluating industrial wastes for
the determination of sewer service charges.
Tn'uimvnt of tteaidunl Wimtea
This section describes the techniques that may be
used for dealing with the residual ellluent after all of
the avenues that we have discussed above are explored.
If this effluent is put into the municipal sewer system,
nothing of course need be done. If, on the other hand,
it is put into surface waters, some further treatment
may be necessary. The nature and extent of this treat-
ment will depend upon stream conditions and the uses
to which the water will be put. Requirements estab-
lished by Slate and local governing authorities are not
the same in all areas and must be determined for each
case.
There are two references which summarize the laws
in existence on water quality standards and water pol-
lution abatement (refs. 52 and 54). Since many pol-
lution abatement laws are of recent origin, the develop-
ment of this type of legislation is to some extent
experimental. Equally important to the words of the
laws, therefore, are the interpretations given by the
administering authorities. For this reason, it is vitally
important in arranging for the disposition of an indus-
trial effluent that the plant management be in contact
with the agency administering the local laws that
govern waste disposal.
Woolen-mill wastes can be treated in a variety of
ways so as to reduce turbidity, dissolved solids,
acidity or alkalinity, oxygen depleting components,
color, and bacterial content. The prior sections have
discussed all of the steps that may be taken to recover
useful material and to eliminate waste at the source.
It is therefore the aim of the processes discussed here
to achieve their purpose at the lowest possible cost,
since these treatments are a net expense from which no
return can be obtained. Fortunately, many of the
treatments used employ very low cost chemicals.
It is a general premise that, where a mill produces
more than one kind of waste, it is easiest to combine the
various kinds of wastes and treat the combination as
one. This reduces the number of treating units and
usually results in handling a more uniform raw ma-
terial. An integrated woolen mill will have as its
major waste components the dyehouse effluent and the
wool scouring effluent. As noted in a previous section,
these wastes, if combined, partially neutralize one an-
other. We will first consider what can be done if this
practice is followed. We will then observe briefly how
treatment differs in the case of mills which have only
dyehouse effluent or only scouring effluent. Practices
for the treatment of industrial wastes in general, which
include textile wastes, are discussed in references 11,
21,40, and 47. Droszdorf (ref. 11) surveyed the situa-
tion as early as 1923 and noted that woolen-mill wastes
can be purified by simple chemical means such as coagu-
lation with lime and ferrous sulfate. He concluded that
biological means such as digesting systems and
trickling filters offered the only method for complete
purification.
Kuni and Platonova (ref. 21) studied chlorination as
a method for purifying textile-mill wastes and noted
that this precipitates much of the suspended and dis-
solved organic matter.
IO
-------
Figure 8.—A lagoon is a
cheaper substitute for the
clarifier and trickling filter,
but requires several acres
of ground to retain wastes
long enough for unassisted
sedimentation and absorp-
tion of oxygen from the air.
The Connecticut State Water Commission summar-
ized industrial waste research in 1948 (ref. 40) and
determined costs for treating woolen-mill wastes with
alum, iron sulfate, and chlorine. They noted that, as an
average, the treatment of woolen-mill effluents can be
done for 15 to 25 cents per thousand gallons.
Weston (ref. 47) described the characteristics of
woolen-mill wastes in 1939 and enumerated the prin-
cipals for systematic treatment:
a. Equalization of flow.
I). Wool-grease recovery.
c. Chemical precipitation.
d. Drying the sludge which results from the
precipitation.
e. Biological treatment of the clear liquor result-
ing from the chemical precipitation.
A number of other references (9, 10, 12, 17, 33)
deal solely with textile wastes. Coburn (ref. 9) de-
scribes a process for treating woolen-mill wastes in
which the various departmental effluents are composited
in sedimentation tanks, where sulfuric acid and alum
are added to adjust to a pH of 6. This process precipi-
tates out most of the solids which are then run off to
sludge drying beds and sand filters. A clear, almost
colorless, effluent is obtained.
Eldridge (ref. 12) reported in 1942 that 83 percent
removal of suspended solids and 72 percent removal of
15. 0. D. was accomplished by dosing a woolen-mill
waste with 1 pound of lime and 3 pounds of ferric
chloride per thousand gallons of waste. The character-
istics of the sludge and effluent arc described.
Coburn and Oberholtzer (refs. 10 and 33) describe
the system used at a carpet mill, similar to those de-
scribed above. In this case, however, the effluent is
put into small artificial lakes to permit a longer sedi-
mentation period and absorption of oxygen from the
air. The use of lagoons presupposes the availability of
adequate land area, usually several acres for the
average-size mill.
Goldlhorpe (ref. 17) reviewed in 1946 a description
of textile-waste disposition, which describes biological
treatment, sludge treatment, and pressure filters.
McCarthy reported in 1950 (ref. 26) that woolen-mill
wastes can be treated on trickling filters if pH is suit-
ably adjusted. He noted that wool dye wastes are
stronger than domestic sewage, and wool scouring
wastes slill stronger in their pollution effects.
Since wool scouring wastes are the most concentrated
in the textile industry, considerable effort has been
given to the disposition of this effluent alone frefs. 6, 8,
27, 28). Campanella (ref. 6) worked out a process
for precipitating wool scouring wastes with calcium
hypochlorite and adapted this to a continuous process.
He notes that the results in terms of solids and B. O. D.
removal are excellent.
Coburn (ref. 8) compared three methods for the
treatment of wool scouring wastes; acid-cracking, cal-
cium hypochlorite and calcium chloride with carbon
dioxide. He found the chemical cost for the first to be
cheapest and the second most expensive, and all gave a
solids removal better than 85 percent and a B. O. D.
removal better than 42 percent. He nevertheless found
that the residual B. O. D. after treatment is higher than
domestic sewage and, to be reduced, requires treatment
through trickling filters.
McCarthy (refs. 27 and 28) studied the application
of calcium chloride and carbon dioxide for the precipi-
tation of scouring waste and obtained very similar
results.
II
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If dyehouse wastes alone are involved, the treatment
must he different. The waste is acidic, contains very
little suspended mailer, and may be highly colored. In
some cases, chlorinatiori removes the color. A method
more recently developed is the filtration of the waste
through a bed of activated carbon. The carbon absorbs
the color from the solution and can be regenerated and
used over and over again. Fassina (ref. 15) recorded
a forerunner of this treatment in 1937. He suggested
neutralizing the acid in the dye waste with lime and
then passing the solution through a porous material
such as acid-treated wool to adsorb colored impurities.
He determined that this purifies the waste to the degree
that it is no longer injurious to fish life.
Thornton and Moore (ref. 43) reported in 1951 that
Fuller's earth and activated bauxite are good adsorbenls
for dyestuffs from waste water.
Thatcher (ref. 44) described an automatic method
for acid neutralization, whereby a lime slurry was fed
into a continuous stream of acid waste, controlled by an
automatic pH control unit.
Zack (ref. 48) showed that lime and ferrous sulfate
coagulation remove 70 percent of the B. 0. D. in dye
waste. If this waste is then lagooned, the B. O. D.
removed is better than 92 percent.
Sterling (ref. 53) notes that, to reduce the B. 0. D. of
acid dye wastes, the wastes can be treated by trickling
filters.
Summary and Conclusion
Controlling stream pollution has become an urgent
necessity in the United States today. Our demands for
usable water for public water supplies, industrial uses,
and other beneficial purposes are now so great that we
must reuse the same water many times as it flows from
city to city. Pollution can prevent or add greatly to
the cost of many water uses. For this reason, the wool-
processing industry, like other industries, is giving
greatly increased attention to reducing the polluting
effects of its wastes.
This Guide summarizes the sources of pollution in
the wool-processing industry, the polluting effects of
woolen-mill wastes, and information on the methods of
dealing with the waste problems of the industry. Four
separate operations of ihe industry produce liquid
wastes: opening and scouring, spinning, dyeing, and
finishing. Significant polluting characteristics of
these individual wastes include oxygen demand,
suspended solids, acidity, alkalinity, color, and grease.
The polluting effect of the wastes may be reduced by
substituting detergents for soap, mineral acids for
acetic, synthetic compounds for starch, and similar
changes. Limiting the amounts of acids, bases, and
reducing agents to the actual requirements for the
process also will reduce waste loads. Wool fibers,
wool grease, and fertilizer material all may be recov-
ered from the wastes. The wastes may be treated in
combination with domestic sewage, or they may be
treated by (1) coagulation and precipitation with
chemicals, (2) chlorination, (3) biological processes,
and (4) adsorption.
The information contained in this Guide can help
the mill supervisor carry out his increasing responsi-
bility to reduce the polluting effect of the mill wastes.
Much can be accomplished through good housekeeping
procedures which also reduce operating costs. The
plant chemist and engineer can be most helpful in de-
veloping further measures.
1»
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Bibliography on Woolen Wasles
1. Anonymous, "West Riding Rivers and Trade
Effluents," Engineering 93, 497-499, 569-570,
690-691, 739-740, 795-798.
2. Baity, H. G., "Textile Waste Treatment," Am.
Dyestuff Reporter 27 (Proc. Am. Assoc. Textile
Chem. and Colorists), 544-547 (1938).
3. Barker, A. F., "Yorkshire Rivers Purification—
Wool Manufacturer's Problem," J. Textile Sc. 2,
97-99 (1928).
4. Bublitz, —, "The Removal of Suspended Matter
From the Wastes of Woolen Mills by Babrowskis
Filter Drum," Sozial Tecknik., 11, Heft 7,
Wasser u. Abwasser 6, 217-219.
5. Cameron, A. A., "Recovery of Grease From Wool
Scouring Waste and Abatement of Stream Pol-
lution Through the Calcium Hypochlorite
Process," Am. Dyestuff Reptr. 39, 667-668
(1950).
6. Campanella, J. L., "Hypochlorite Treatment of
Wool Scouring Wastes—A Discussion," Sewage
Works J. 19,255 (1947).
7. Cherkinskii, S. N., and Leites, L. G., "Purification
of Waste Water From Wool Washing With
Recovery of Fat," Vodosnabzhenie Sanit. Tekh.,
No. 11-12,76(1939).
8. Coburn, S. E., "Comparison of Methods for Treat-
ment of Wool Scouring Wastes," Sewage Works
J. 27,84-90 (1949).
9. Coburn, S. E., "Improvements in the Operation of
a Textile Wastes Treatment Plant," Sewage
WorksJ. 7,77-79 (1928).
10. Coburn, S. E., "Modern Wastes-Treatment Plant
for Carpet Mill of James Lees and Sons at
Glasgow, Virginia," Water & Sewage Works 97,
167-171 (1950).
11. Droszdorf, W., "Wastes from the Textile Industry
in Russia," Gesundh, Ing. 46, 167-168 (1923).
12. Eldridge, E. F., "Report of Experimental Studies
and Recommendations for Waste Treatment at
Yale Woolen Mills," Michigan Eng. Expt. Sta.
Bull. No. 96, 3-18 (1942).
13. Faber, H. A., "The Hypochlorite Process for Treat-
ment of Wool Scouring Wastes and Recovery of
Wool Grease," Sewage Works J. 19,248 (1947).
14. Faber, H. A., "Wool Scouring Wastes Treated by
New Chemical Process," Water & Sewage Works
93, 467 (1946).
15. Fassina, L., "Purification of Waste Waters. 1.
Dye Houses," Chimie & Industrie 38, 840-847
(1937).
16. Geyer, J. C., "Industrial Wastes: Textile Industry,"
Indus. Eng. Chem. 39, 653-656 (May 1947).
17. Goldthorpe, H. H., "How Huddersfield Tackles the
Treatment of Textile Wastes," Synthetics & By-
products 8, 185-189 (1946).
18. Hillier, W. H,, and Campbell, S. G., "Recovery and
Processing of Wool Grease," Synthetics & By-
products 8, 329 (1946).
19. Jacobs, H. L., "Neutralization of Acid Wastes,"
Sewage and Ind. Wastes 23, 900-905 (1951).
20. Kelsey, W., "Recovering Fats From Waste
Waters," Brit. 123,848 (March 14,1918).
21. Kuni, V. E., and Platonova, M. N., "Chlorination
as a Method for the Purification of Waste
Waters," Vodosnabzhenie Sanit. Tekh. 9, 64-69
(1937); Khim. Referat. Zhur. 6, 81 (1938).
22. Leites, L. G., "The Purification of Waste Waters
and the Recovery of Lanolin From the Washing
of Wool," Sherstyanoe Delo 18, No. 8, 13-15
(1939); Chem. Zentr. 1,3438 (1940).
23. Ludwig, H. P., and Ludwig, R. C., "How To Floc-
culate Greases So They Won't Clog Sewers,"
Eng. News-Record 1.47, No. 1, 40 (1951).
24. Lumb, C., and Barnes, J. P., "Precipitation of a
Trade-Waste Sewage," J. Proc. Inst. Sewage
Purif., 82-92 (1940).
25. Lundgren, Dr. H., "Alcohol Abstraction of Wool
Scouring Wastes," Text. Res, J. 21, 540-555
(1951).
26. McCarthy, J. A., "Characteristics and Treatment
of Wool Dyeing Wastes," Sewage and Ind.
Wastes 22, 77-86 (1950).
27. McCarthy, J. A., "Use of Calcium Chloride in The
Treatment of Industrial Wastes," Sewage and
Ind. Wastes 24,473-479 (1952).
28. McCarthy, J. A., "Method for Treatment of Wool
Scouring Wastes," Sewage Works J. 21, 75-83
(1949).
29. Masselli, J. W., and Burford, M. G., "Pollution
Sources in Wool Scouring and Finishing Mills
and Their Reduction Through Process and
Process Chemical Change," New England Inter-
state Water Pollution Control Commission (June
1954),
13
-------
,")0. Maucrsbcrger, II., and Von Bergen, W., "American
Wool Handbook," Textile Book Publishers
(1948).
31. Merryfield, F., "Industrial Wastes in Willamette
Valley," Civil Eng. 6, 682-684 (1936).
32. Obcrholtzer, R. E., "Continuous Solvent Scouring
of Domestic Wool," Textile World 99, 103-107,
(1949).
33. Oherholtzer, R. E., "Treatment of Carpet Mill Wet
Processing Waste Liquors," Textile World 99,
103-107 (1949).
34. Ruwn, A. M., "Sulfide Wool Wastes Endanger
Sewer System," Sewage Works Eng. and Munic.
Sanit. J 6,491-493 (1945).
35. Rudolfs, W., and Setter, L. R., "High and Low
Temperature Digestion Experiments. III. Ef-
fects of Certain Organic Wastes," Sewage Works
J. 9, 549-586 (1937) ; Rudolfs, W., "Effect of
Trade Wastes on High and Low Temperature
Digestion," Ind. Eng. Chem., 29, 803-804
(1937).
36. Scanlon, Dr. J. T., "Woolfacts," Wool Bureau, Inc.
37. Singleton, M. T., "Experiments on Anaerobic Di-
gestion of Wool Scouring Wastes," Sewage
Works J. 21,286-293 (1949).
38. Snell, F. D., "Chemical Treatment of Trade
Wastes. V. Waste from Wool Washing," Ind.
Eng. Chem. 21, 210-213 (1929); cf. C. A. 22,
1204.
39. Sokolov, V. N., "Regenerating Fatty Substances
From Waste Waters of the Wool Industry,"
Sherstyanoe Delo 4-5, 24^-26 (1935).
40. State Water Commission of Connecticut, "Indus-
trial Waste Research," Public Works, 79, 19
(February 1948).
41. Stevenson, W. L., "The Treatment and Disposal of
Industrial Wastes," Chem. Eng. Congr. World
Power Conf. (1936), Advance Proof No. F7,
24 pp.
42. Textile Found. Inc., "Textile Wastes—What Solu-
tion?" from "Textile Waste Treatment and
Recovery," Sewage Works Engin., 17, 16-17
(Jan.1946).
43. Thornton, H. A., and Moore, J. R,, "Adsorbents in
Waste Water Treatment-Dye Absorption and
Recovery Studies," Sewage and Ind. Wastes 23,
497-504 (1951).
44. Thatcher, H. D., "Acid Neutralization Plant With
Mechanical pH Control," Inst. Swg. Purif. J. &
Proc.,161 (1943).
45. U. S. Public Health Eng. Abstracts E-637a, 52
(1928), "Experience Willi the Construction and
Operation of the Purification Plant at Kettwig,"
Technischcn Gemeindeblatt,^/, 15 pp. (1928).
46. Webber, Dr. H., "Study of Stream Pollution by
Wool Scouring Liquors," Bull, of Lowell Textile
Inst. 54,2 N (1950).
47. Weston, R. S., "The Treatment of Textile Wastes,"
Sewage Works J. 11, 657-74, cf. C. A. 33, 2258
(1939).
48. Zack, S. L., "Developments in the Treatment of
Dye House Wastes," Sewage Works Eng. 20,
129-130 (1949).
Other Mtetereaeea
49. American Chemical Paint Co., "Centrifugal Con-
centration of Grease Emulsions From Wool
Scouring Solutions," Ambler, Pa.
50. Bogren, G. S., "Disposal of Wool Scouring
Wastes," Weston & Sampson, 14 Beacon St.,
Boston 8, Mass.; Gibbs, F. S., Inc., 2300 Wash-
ington St., Newton Lower Falls 62, Mass.
51. Hazen, R., "Service Charges for Industrial
Wastes Treatment," Sewage and Industrial
Wastes 26, No. 7, 830-835 (July 1954).
52. R. S. Aries & Associates, "Industrial Water Pollu-
tion," Survey of Legislation and Regulations,
142 pp. (1951).
53. Sterling, C. I., "Treatment of Dye Wastes by Trick-
ling Filters," Lawrence Experiment Station,
Mass., Dept. of Public Health.
54. Feller, G,, and Newman, J., "Industrial Waste
Treatment," Industry and Power (June 1951).
55. Snyder D., "Cotton Slashing With Synthetic Com-
pounds as a Means Toward Pollution Abate-
ment," Plant Chemist, Crompton-Shenandoah
Co., Waynesboro, Va. Presented at S3d Na-
tional Convention AATCC, Atlanta, Ga., Sep-
tember 15-17,1954.
56. Stafford, W., and Northrup, H. J., "The B. O. D. of
Textile Chemicals," AATCC, Rhode Island Sect.
Subcommittee on Stream Pollution, to be pub-
lished in American Dyestuff Reporter.
57. Souther, R. H., "In-Plant Process Control for the
Reduction of Waste," American Dyestuff Re-
porter 42, No. 20, 656-658 (1953).
58. Shroepfer, G. J., "Determination of Fair Sewage
Service Charges for Industrial Wastes," Sewage
Works Management 23, No. 12,1493 (December
1951).
14
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