WATER POLLUTION CONTROL RESEARCH SERIES • 17O7ODJW11/69
STATE OF THE ART
REVIEW ON PRODUCT RECOVERY
U.S. DEPARTMENT OF THE (NTERIOR»FEDERAL WATER POLLUT,ON CONTROL ADM.NISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe
the results and progress in the control and abatement
of pollution of our Nation's waters. They provide a
central source of information on the research, develop-
ment, and demonstration activities of the Federal Water
Pollution Control Administration, Department of the
Interior, through in-house research and grants and
contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Water Pollution Control Research Reports will be
distributed to requesters as supplies permit. Requests
should be sent to the Planning and Resources Office,
Office of Research and Development, Federal Water
Pollution Control Administration, Department of the
Interior, Washington, D.C. 202U2.
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STATE OF THE ART REVIEW ON PRODUCT RECOVERY
by
Resource Engineering Associates
24 Danbury Road
Wilton, Connecticut 06897
for the
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
Contract Number 14-12-495
November 1969
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FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration, nor does
mention of trade names or commercial products
constitute endorsement or recommendation for
use .
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TABLE OF CONTENTS
Table of Contents iii
Abstract iv
List of Figures v
List of Tables vi
Summary vii
Introduction 1
Economic, Technical and Philosophical Framework 3
Pulp end Paper Mills 5
Steel Industry 17
Plating and Allied Industries 25
Mining Industry 29
Coal By-Products 33
Coke end Gas Industry 33
Flue Gas Treatment 33
Petroleum Industries 37
Petrochemical Industries 37
Petroleum Refineries 38
Recovery of Oil From Waste Waters 40
Sludge Disposal end By-Product Recovery 46
Heat Recovery or Utilization 49
Miscellaneous Industries 50
Breweries and Distilleries 50
Food Industries 50
Fertilizer Industry 53
Animal Products 56
Organic Chemicals Industry 61
Textile Industry 71
Nuclear Plants 72
Milk Industry 73
Inorganic Chemicals Industry 73
Appendix I - General Methods of Treatment and Recovery 78
Appendix II - Other Chemical Reactions of Interest 81
Appendix III - Physical Methods of Treating Gaseous Wastes 86
References 88
ill
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ABSTRACT
This report on "Stote of the Art Review on Product Recovery"
covers the recovery, reuse end/or sale of materials recovered from
liquid effluents or produced as a result of the treatment of liquid
effluents. A critical and complete review of literature up to date
on product recovery in major water use industries is presented. The
economical, technical end philosophical framework which determines
the application of product recovery is presented wherever possible.
This report does not cover water renovation for reuse end product
recovery from solid wastes. However, en evaluation of the utiliza-
tion end product recovery of municipal sludge is presented. The
principal areas of discussion are: waste reduction practices in-
cluding in-plant control, recovery techniques end practices,
practical operating problems end the relationship between recovery
and treatment.
The report concludes that:
1. Product recovery is an accepted practice with
increasing usage.
2. Industry needs increasingly complex processes to
develop optimum recovery schemes.
3. By-product recovery generally results in a net cost
to industry generally of a smeller magnitude than
conventional treatment.
4. The situation is complicated by the tox exemption lews.
IV
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LIST OF FIGURES
Page
1. USEFUL RANGES OF VARIOUS SEPARATION PROCESSES viii
2. - 6. UNIT PROCESSES AND BY-PRODUCTS RECOVERED IN
THE MAJOR WATER USE INDUSTRIES ix-xiii
7. PRESENT STATUS OF RECOVERY CYCLE 6
8. PULP AND FIBER RECOVERY IN A BOARD MILL 10
9. HOLOPULPING PROCESS 13
10. RECOVERY OF SULFURIC ACID AND IRON FROM WASTE PICKLE
LIQUOR IN THE STEEL INDUSTRY 18
11. EVAPORATION - CRYSTALLIZATION (S.A. LAURICK -
STRUTHERS - WELLS CORP.) 19
12. PICKLING REGENERATION CYCLE 22
13. FLOW DIAGRAM OF BIOCHEMICAL OXIDATION AND LIMESTONE
NEUTRALIZATION PROCESS 31
14. PROCESS FLOW SHEET OF FLUE GAS TREATMENT 35
15. RECOVERY OF SOLUBLE OIL FROM RECLAIMED OIL 45
16. BASIC PROCESSES IN THE MEAT-PACKING INDUSTRY 57
17. FLOW DIAGRAM OF KEL-CHLOR PROCESS 57
18. INCINERATION - SCRUBBING SYSTEM (UNION CARBIDE) 69
V
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LIST OF TABLES
Page
I. BY-PRODUCT RECOVERY IN THE PULP AND PAPER MILL
INDUSTRIES 16
II. BY-PRODUCT RECOVERY IN THE IRON AND STEEL INDUSTRIES 24
in. BY-PRODUCT RECOVERY IN PLATING AND ALLIED INDUSTRIES 28
17. BY-PRODUCT RECOVERY IN COAL BY-PRODUCTS INDUSTRY 36
V. BY-PRODUCT RECOVERY IN THE ORGANIC CHEMICALS INDUSTRY 70
VI. BY-PRODUCT RECOVERY IN THE INORGANIC CHEMICALS INDUSTRY 77
A-1.. CHEMICAL OXIDANTS AND AREA OF USE . 80
VI
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SUMMARY
Product recovery from waste waters is an accepted practice from
an economical end pollution control point of view. In many cases,
recovery of by-products is not practiced as it is cheaper to dump the
wastes rather then to process them. But with the increasing environ-
mental control legislation and enforcement, product recovery technique
is gaining high importance.
The urgent problem facing the industries is how to recover by-
products from waste materials and what to do with them. Sophisticated
methods have been developed for the separation of products of different
sites and a chart showing the ranges of various separation processes
is presented in Figure 1. The various unit processes used in the re-
covery of by-products and the products recovered ere shown in Figures
2-6. These unit operations are typical and can be applied in the
various industries wherever applicable.
The practice of product recovery results in a net cost to the
industry, but it has been proven frequently to be cheaper than other
methods of disposal. The choice of a method of treatment depends on
the economic considerations and degree of treatment desired. Removal
of pollutants to the desired level is generally achieved through con-
ventional processes, but it should be realized that the seme degree
of treatment can be achieved either by product recovery alone or by e
combination of product recovery and conventional treatment processes.
Advantage of reducing pollutionel loed through product recovery con-
sists in the overall reduction of the cost of treatment end conservation
of natural resources.
Unfortunately, the entire thrust of taxation and regulation has
been negative with regard to by-product recovery. Too many of the
state regulations ere promulgated and permits issued with e specific
reduction in a pollutant level regardless of the amount of discharge.
Therefore, a company may eliminate e substantial quantity of pollutant
by by-product recovery and still find itself faced with the same degree
of required removal although on a smaller quantity. This has the
effect of eliminating part of the benefit of by-product recovery. Only
when recovery reaches 100% (a very unusual case) can total recovery
of waste costs be achieved.
This problem is complicated by the fact thet ell pollution control
facility tax exemption laws enacted in this country specifically ex-
clude credits for facilities which recover any product for reuse or
sale.
Thus, while it can be argued that while the social good of the
vn
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PRIMARY FACTOR
AFFECTING
SEPARATION
FIGURE I
USEFUL RANGES OF
VARIOUS SEPARATION PROCESSES
lONK
CHARGE
VAPOR
TEMP PRESSURE
SURFACE
ACTIVITY
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MKROFKTERS
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ULTRAFILTRATION
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REVERSE OSMOSIS
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DIALYSIS |
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ELECTRODIALYSIS
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; i n
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.-LI
DISTILLATION / FREEZE CONCENTRATION
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SOLVENT EXTRACTION
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FIGURE 2
UNIT OPERATIONS AND PRODUCTS
RECOVERED IN MAJOR WATER USE INDUSTRIES
iKinti if***T*n\y
INDUSTRY
PAPER AND PULP MILLS
STEEL INDUSTRY
PLATING INDUSTRY
MINING INDUSTRY
COKE 8 GAS
iNDUQTR !ES
PETROCHEMICAL
INDUSTRIES
PETROLEUM
REFINERIES
BREWERIES a
DISTILLERIES
FERTILIZER INDUSTRIES
ANIMAL PRODUCTS
TEXTILE INDUSTRY
ORGANIC CHEMICALS
INDUSTRY
NUCLEAR PLANTS
LIQUID - LIQUID f
DISTILLATION
Recovery of pine
oil from sulfate
turpentine ^Recovery
of Methenol from
evaporated black
liquor solids
Production of pig-
ment produci no
organometallic
compounds
Recovery of Argon
fT-r^m Hvdroger.
Recovers chlorine -
ted hydrocarbons ,
olefins and sol-
vents
Recovery of NH^ and
H2SO. from sour
of (NH4)2S04
Recovery of process
weter
Recovery of
ammonia
Recovery of phenol
Recovery of pluto-
nium and uranium
ADSORPTION
Recovery of B from
so2
Removal of
fluorides
Recovery of
raolybdic oxide
Recovery of HgSC^;
Recovery of Pheno]
Separation of H
from Hydro- ^
carbons • Recovery
of CS2 and CC14
Removal of fines
Recovery of
fluorides
ABSORPTION
Recovery of S
from SO2
R*eov»ry of NH
Recovery of HC1
Recovery of HCl;
Recovery of nitro-
gen oxides
CRYSTALLIZATION!
Recovery of sulfete
turpentine;Recovery
of NB2C03 end
Me:iC03
Recovery of NegSO^
Separation of
Xylene from ethyl
benzene
Recovery of
gypsum
Recovery of in-
organics
ix
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FIGURE 3
UNIT OPERATIONS AND PRODUCTS
RECOVERED IN MAJOR WATER USE INDUSTRIES
INDUSTRY
PAPER AND PULP MILLS
STEEL INDUSTRY
PLATING INDUSTRY
MINING INDUSTRY
COKE & GAS
INDUSTRIES
PETROCHEMICAL
INDUSTRIES
PETROLEUM
REFINERIES
BREWERIES 8
DISTILLERIES
FERTILIZER INDUSTRIES
ANIMAL PRODUCTS
TEXTILE INDUSTRY
ORGANIC CHEMICALS
INDUSTRY
LIQUID - LIQUID
EVAPORATION
Concentration of
1 i gnin for pheno 1
recovery
Concentration of
H3FO4 acid
Cone entret ion of
H2SOd
Drying of yeast
for cattle feed
Recovery of
gyp sura
Recovery of N«OH
NUCLEAR PLANTS I
PRECIPITATION
Production of
gypsum ;
Recovery of iron
Recovery of copper
from mine tailings ;
Removal of contam-
inating metals
Recovery of NH^
as (NH4)2S04;
Production of syn-
thetic cryolite or
aluminum fluoride
Recovery of NB
Salts
SOLVENT
EXTRACTION
Recovery of Acetic
and formic acids
from MSSC cooking
effluents
Recovery of Phenol
Recovery of phenol
with benzene
Recovery of iso-
butylene , naph-
thalenes, pere-
fins and phenols
Recovery of Phenol
Recovery of
process water
Recovery of phenol;
Recovery of oil
Recovery of pluto-
niujit from metal
scraps
DIALYSIS
Recovery of acids
H2S04, H3P04
Recovery of Ni i
Cu
Recovery of H2S04
Removal of fines
to improve the
product
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FIGURE 4
UNIT OPERATIONS AND PRODUCTS
RECOVERED IN MAJOR WATER USE INDUSTRIES
INDUSTRY
r = —
j PAPER AND PULP MILLS
STEEL INDUSTRY
PLATING INDUSTRY
MINING INDUSTRY
LIQUID - LIQUID
ELECTRO
DIALYSIS
I
1 Recovery of ligno-
| sulfonic acids,
wood sugars and
acids
Recovery of acid
end iron
ION EXCHANGE
1
Process water
recovery
able metals like
Au f Ag ; Recovery of
cyanides , chromic
acids and deminer-
Recovery of copper
uranium from leach.
ing solutions from
copper ore waste
dump; Recovery of
ULTRA-
FILTRATION
Concentrating
solutes , produc-
tion of demineral-
ized water
Recovery of de-
mineralized water
Recovery of pigment
producing orgeno-
metallic compounds
COKE 8 GAS
INDUSTRIES
Recovery of H SO^ ;
Recovery of
Chlorine from HCl
Recovery of HgSO. ;
Recovery of Phenol
PETROCHEMICAL
INDUSTRIES
PETROLEUM
REFINERIES
Recovery of amino
acids, organic
acids and alkaloids
Recovery of H^
from
petroleum effluents
BREWERIES 8
DISTILLERIES
Removal of fines
to improve the
product
Refining the
products
Refining the
products
FERTILIZER INDUSTRIES
ANIMAL PRODUCTS
TEXTILE INDUSTRY
ORGANIC CHEMICALS
INDUSTRY
NUCLEAR PLANTS
Separation of
radionuclidss
Separation of
radionuclidea
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FIGURE 5
INDUSTRY
PAPER AND PULP MILLS
STEEL INDUSTRY
PLATING INDUSTRY
MINING INDUSTRY
COKE 8 GAS
INDUSTRIES
PETROCHEMICAL
INDUSTRIES
PETROLEUM
REFINERIES
BREWERIES 8
DISTILLERIES
FERTILIZER INDUSTRIES
ANIMAL PRODUCTS
TEXTILE INDUSTRY
ORGANIC CHEMICALS
INDUSTRY
NUCLEAR PLANTS
SOLID-LIQUID_
SETTLING
Concentrating
pulp
Separation of oil
Separation of
spent hops
THICKENING
Concentre ting
Pulp
Separation of
spent hope
FILTRATION
Dewetering
Sludge
Recovery of Silica
from ferro silicon
plants
Recovery of
powdered silica
Recovery of NaOH;
Recovery of pi oceee
water
xii
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FIGURE 6
INDUSTRY
PAPER AND PULP MILLS
STEEL INDUSTRY
PLATING INDUSTRY
MINING INDUSTRY
COKE a GAS
INDUSTRIES
PETROCHEMICAL
INDUSTRIES
PETROLEUM
REFINERIES
BREWERIES 8
DISTILLERIES
FERTILIZER INDUSTRIES
ANIMAL PRODUCTS
TEXTILE INDUSTRY
ORGANIC CHEMICALS
INDUSTRY
NUCLEAR PLANTS
SOLID-LIQUID
CENTRIFUGATION
Separation of tall
oil from black
liquor; Dewatering
of paper mill sludge
Separation of oil
Removal of phenol
from ammonia
liquor
Recovery of f«t
and grease
FLOTATION
Recovery of Phenol ,
Phosphates and
heavy metals;
Recovery of oil
Recovery of fine
coals
Separation of oil
from tar sands
Separation of
radio nuclldee
EVAPORATION
Recovery of
NajCOg and Na2S;
Production of
Masonex cattle feed
Concentration of
acids > concentration
of calcium chloride
Concentrating the
waste; Concentra-
tion of H3P04 acid
Recovery of
(NH4)2 S04
Concentrating the
acid H2S04
Production of cattle
feed and vitamin
Recovery of NaOH
WET SCRUBBING
Recovery of S or
H-SO from SO,
& 4 ^
Production of
S, H2SO4 or SO2
end (NH4)2S04
Removal of C02
and Hg Streams
Recovery of Solvents
Recovery of NH
from exhauat
gas
Recovery of HC1 ,
Recovery of S ,50%
and H2S04
xiii
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country is in the direction of by-product recovery, the existing
regulations end texetion are such es to discourage by-product re-
covery by industry in piece of conventionel waste treatment
techniques. We strongly feel thet e review of reguletory end
fiscal policies should be made to encourage the use of recovery
end reuse techniques by industry in the treatment of their wastes,
The Future
It is obvious from this study thet:
1. By-product recovery already occupies en important piece in
the regular practice of American industry.
2. By-product recovery practice is dependent primarily upon
economic factors rather than technological ones.
3. A variety of technology exists and is practiced to echieve
by-product recovery in e variety of industries.
Further, it is anticipated that increased by-product recovery
will occur in the future because of tighter pollution control regula-
tions. It is not herd to justify the social desirability of by-
product recovery both on the basis of reduced pollutionel load end
beceuse of the decreased demands which would be created for our ob-
viously limited neturel resources. Thus, it is importent to note
those factors which will encourage industry to utilize by-product
recovery on an increasing scele. After numerous discussions with
industrial leaders, we feel thet the steps outlined below, if taken,
would encourage the use of by-product recovery es en enti-pollution
epproech end one of considerably more merit then ordinery pollution
control techniques currently in prectice:
1. Development of e consistent pollution control progrem with
sherply defined objectives end e sharply defined time scele
strictly enforced with controls set on discharge quantities
rether then e universal removel percentage.
2. Use of tax incentives to include treatment units where by-
product recovery is practiced. Special incentives should
be given for materiel in short supply for the reuse end
recovery of.
3. Development of additional technological tools for the removel
of pollutants in smell quentities from weter, not only on e
gross besis, but in a manner which will permit specific
seperetions to be mode.
xiv
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4. Encouragement of pretreatraent of industrial wastes prior to
admission into joint systems through surcharging programs.
It is recognized that portions of these proposed steps are under-
way and that others may be administratively or politically difficult
to undertake. However, they ere necessary for optimal socio-economic
goals. As a further note, it is important that industry recognize the
significance of building a market for by-products just as it does for
prime products. In many cases, greet quantities of by-product chemi-
cals and materials are readily available for use but the markets for
them ere simply not sufficiently developed to totally accept the
available supply. If markets have not been developed, maximum by-
product recovery will not be feasible or practiced.
Both industry and government must become attuned to a "waste not
want not" philosophy in the future in order to preserve the environ-
ment end our natural resource base.
Most industrial leaders agree that recovery and use is highly
precticel in meny circumstances because industrial wastes can be
separeted by unit (at least in newer plants) end the wastes ere
largely product, feed or by-product. The pressure for reuse will be
strongest in the case of conservative species which, when regulations
are enacted and enforced, will have to be concentrated end disposed
of in some fashion. If concentration is necessary in any case, then
recovery and reuse seems to be an economically viable approach in
handling this type of waste in the future.
xv
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INTRODUCTION
This report on the "State of the Art Review on Product Recovery"
is based on an exhaustive literature review, discussions with various
outside sources including industrial organizations actively engaged
in product recovery activities end the experience of the principal
investigator, associates and consultants of Resource Engineering
Associates.
Considerable literature already exists with regard to water
reuse and by-product recovery although no complete presentation of
the current status of by-product recovery exists in the literature.
This report was developed on the basis of an extensive literature
search based on Chemical and Engineering Abstracts as well as a com-
plete review of ell existing literature in the fields of chemical and
sanitary engineering. The reports prepared by the USPHS end FWPCA
were also reviewed end numerous contacts were made with industries
with practical experience in by-product recovery.
The report summarizes, industry by industry, the current status
of by-product recovery. In addition, the Appendix contains three
chapters which review the process technology as related to by-product
recovery.
The purpose of this report is to summarize the technical and
practical extent of by-product recovery as practiced in this country.
The concept of product recovery is gaining far more widespread
utilization then in the pest because of the press and expense of
increasingly tight environmental control legislation and regulations.
Such en approach is being encouraged by both industries and govern-
mental agencies for the following reasons:
1. A general reduction of the level of industrial pollutant
discharge.
2. The possibility of reducing overall environmentel control
expenditures.
3. Reduction in the rete of materiel utilizetion end wastage
by the economy.
It is, however, interesting to note that, in the pest, meny
recovery methods proposed have been rejected because it is cheeper
to dump the westes than to process them. With stricter enti-pollution
regulations end recovery processes making very good economic sense,
pollution abatement through product recovery, either wholly or
partially, should be promising in order that the natural resources
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of the country may be handed on to posterity undamaged and undestroyed,
Valuable by-products may include:
1. Water and other solvents for recycle.
2. A major product that is collectable in a commercial form,
e.g., iron ore dust from blast furnace gas effluents.
3. A major product collectable in a non-commercial form,
e.g., in dilute solution.
4. A M&Oeble or presently u»e»ble by-product.
5. A by-product not presently en article of commerce.
Recycled water may ultimately be the major valuable product
because of increasing water supply costs, increasing water treatment
costs and mounting charges for using municipal sewerage facilities.
As considerable work has been done and reported in the literature
on renovation and reuse of water, this subject will not be discussed.
The recovery of product fines, useable water and thermal energy are
important methods of reducing overall waste disposal costs end should
be seriously considered in every case. Recovery of products from
solid wastes is not included as it falls outside the scope of this
report. There are many products that are recovered now but there ere
many more that are not being recovered now that could be recovered
in the future by the so-called second generation recovery systems.
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ECONOMIC. TECHNICAL AND PHILOSOPHICAL FRAMEWORK
The product of waste must be considered es en integral part of
the manufacturing process and the cost of treatment of industrial
wastes must be charged against the product. The waste disposal op-
erations result in a net cost to the industry producing the waste,
but product recovery and utilization practices reduce the cost of
treatment and frequently prove to be cheaper than other methods of
disposal.
While considering treatment of a waste, the choice of a method
of treatment or process is made that gives maximum benefits or re-
turns. In many cases, the industrial wastes contain valuable products
such as high value metals, acids and other products which could be
used for producing by-products and these, when recovered, will give
high economic returns in addition to removal or pollution loed from
the waste stream. Further, in some cases, water recovered from these
wastes are of good quality and can be reused, resulting in the reduc-
tion of waste and cost of treatment. The renovation end reuse of
waste water becomes a necessity when the natural water supply source
is limited and water needs ere increasing, due to growing population
and expanding industries.
By-product recovery frequently accompanies water reuse and water
conservation. Recycled water may ultimately be the major valuable
product because of increasing water supply costs, increasing water
treatment costs, end mounting charges for using municipal sewerage
facilities.
Industrial wastes contain toxic chemicals such es cyanide, free
acids and heavy metals. Disposal of these wastes into surface waters
are objectionable because they cause fish kills, retard self purifi-
cation of surface waters. These wastes cannot be discharged into
the sewage treatment plants es they contain toxic materials. The
reduction of waste load is of major importance in the waste treat-
ment operations. Waste load reduction is achieved by removing the
spent grains in a semi-dry state, by removing the yeast from fermenters
for filtration and drying end by removing the sediment from the chill
storage tanks as a slurry for separate disposal. In many cases, these
operations have yielded a saleable' by-product which has more then off-
set the increased cost of recovery.
Frequently, waste streams can be eliminated or reduced by process
modifications or improvements. A notable example of this is the use
of save-rinse and spray-rinse tanks in plating lines. This measure
brings about a substantial reduction in waste volume and frequently
a net reduction in metal dragout.
Segregation of waste streams is a necessity at times, not from
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the product recovery point of view but from the operational point of
view. An example of this is segregation of acidic metal rinses from
cyanide streams to avoid the production of toxic hydrogen cyanide (HCN)
end thus eliminate potential safety hazards.
From the industries' philosophical point of view, the prime
requirement of waste treatment, by-product recovery end water reuse
is that the principal product or products of the plant is satisfactory
to the consumer and the secondary requirement is that the operation
of the plants be efficient end economical.
The urgent problems facing the industries ere how to recover
by-products from waste materials inherent in every industrial opera-
tion end whet to do with the by-products. Confronted with the growing
dangers of air end water pollution, the anticipation of government
reguletion, as well as loss of valuable materials through unprofitable
waste disposal methods, industries ere forced to develop sophisticated
refining methods for processing chemical and industrial by-products
end even develop markets for by-products.
The industries, in general, are becoming more and more aware of
the necessity for pollution abatement and product recovery, not only
because of its effect upon the general welfare of the public, but
also because of its own dependence upon rivers and streams for suitable
water for manufacturing processes. Industries ere also increasingly
aware of the fact that benefits accruing from pollution abatement
through product recovery may be quite significant.
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PULP AND PAPER MILLS
Recovery of chemicals from cooking liquor end process water
reuse are the two important efforts in the conservation and pollution
control in this industry end the other efforts are recovery of by-
products from spent liquor and berk.
The present status of recovery technology in this industry is
shown in Figure 7.
Cooking liquor recovery was developed in order to reduce the
cast for cooking chemicals end reduce the waste water load being
discharged to stream. In the Kraft process of pulping, economic
considerations dictate recovery end reuse of chemicals end, there-
fore, stream pollution from Kraft operation is less prevalent when
compared to other types of pulping.
In the modern technology, liquor recovery system is an essential
pert of the pulping process end the recovery technique is different
with eech type of pulping method.
1. Kraft Liquor
A major part of the chemicals in the spent cooking liquor
(block liquor) is usuelly recovered in a series of
operations: eveporetion, burning end ceusticizing. The
dissolved orgenic residues from the wood resins can be used
for heet end power generation, some soda is lost in the
washing operation and, therefore, salt coke is added to
the recovered liquor.
2. Sulfite Liquor
Sulfite liquor recovery techniques ere more complex end
difficult then those employed in the sulfate system. In
fact, the feasibility of liquor recovery is dependent on
the base involved in the sulfite liquor. It is generally
conceded that recovery is not precticel with the calcium
base. When e megnesium base is used, the spent liquor is
evaporeted and burned and'chemicals recovered for reuse.
However, for the sodium base, it is possible to recover the
inorganic chemicals with e feirly complex process. Spent
chemicels from the ammonium base sulfite pulping process can
only be pertielly recovered but the process does not eppeer
economicelly promising.
Numerous products including Torule yeest and alcohols are
produced from waste sulfite liquor by fermentation. Phenol
mey be produced by pyrolysis, vanillin by lime addition,
-------
KILN GASES
DREGS
WOOD STEAM
1 I
PULPING
(TURPENTINE
COLLECTING)
MAKEUP
LIMESTONE
CAUSTICIZING
(AND LIME
REBURNING)
BY-PRODUCTS
LIQUOR AND
COOKED CHIPS
WATER
I
WASHING
(DERBERING)
WASHED PULP
GREEN
LIQUOR
DILUTE
BLACK LIQUOR
WATER
STEAM
FLUE GAS
\1
A'R STEAM >
1 MAKEUP I /
• CHEMICALS 1 /
COMBUSTION
(AND SMELT
DISSOLVING)
EVAPORATION
(TALL OIL
SKIMMING )
CONDENSATE
BY-PRODUCTS
CONCENTRATED
BLACK LIQUOR
FIGURE 7
PRESENT STATUS OF RECOVERY CYCLE
RESOURCE ENGINEERING ASSOCIATES, INC.
6
-------
while acetic acid, formic ecid, dimethyl sulfoxide (DMSO)
and lignosulfonetes ere recoverable directly.
3. Semi-chemical Liquor
Liquor recovery in the NSSC (Neutral Sulfite Semi Chemical)
process is practiced in some independent NSSC pulp trills
using a complicated cerbonetion method. In the integrated
semi-chemical Kraft mills, the recovery system is also
integrated. The "cross recovery" method is based on the
sodium end sulfur values in the NSSC liquor that can be used
as chemical make-up in place of salt cake. The NSSC spent
liquor can be combined with Kreft liquor for evaporation end
combustion but the NSSC cooking liquor has to be made from
fresh chemicals.
The KSC spent liquor is recovered in the seme process that is
used in a regular Kreft pulping process.
Large quantities of water ere essential in the pulp end paper
manufacturing processes such as pulp processing, washing, dissolving
or mixing the various loading, sizing, and color ingredients, end
carrying the fibers through the screens end refiners to the paper-
meking machine. Weter is also used to convey by-products end undesir-
able wastes and to generate power end steam. The maximum reuse of
water becomes one of the basic epproeches in the effective reduction
of waste water quantities.
There ere definite limits in the amount of mill water which can
effectively be reclaimed end reused. Fresh water hes to be added in
certain operetions to prevent the build-up of undesirable dissolved
solids, temperetures, end slime from becteria end fungi growth.
Eech mill hes its own epproech on how best to reuse water in the
various operetions. However, the following process waters ere most
frequently collected end reused:
1. Weter from the log flumes end barkers.
2. Evaporator condensete from the liquor recovery eree.
3. Bleech plent wesher filtrete.
4. White weter from the paper mechine.
5. Wesher weter from coerse screens.
An accepted practice is the reuse of waste weter in wood handling
end storege such es in the log flumes, hot pond, hydraulic or wet drum
-------
deberker, and for the showers prior to chipping. For these applica-
tions, heeted effluents discharged from evaporators, bleach plant,
or paper machine ere preferred because the heat increases berk removal
efficiency. Recycling barker effluent, which has been cleaned end
screened, is a widely practiced water reuse procedure.
In the pulp mill, the waste water from the digester usually con-
tains the spent cooking liquor end the condensete from the digester
heat exchanger. If the cooking liquor is recoverable, the water is
evaporated end collected as condensete while chemicals ere recovered
for reuse. The condensate collected is used in steam generation,
as scrubber water for flue gas or in the brown stock washing process.
In the screening department, a large emount of waste effluent may
be reused as dilution water ahead of the screening end cleaning opera-
tion. However, since the washing operation is intended to remove the
cooking liquor from the pulp, economics dictate that a considerable
amount of the contaminated wash water be displaced by make-up water
since this reduces the pulp's chlorine demand in a later operation and
also prevents the build-up of dissolved solids which cause selting out
end foaming on the screens. The necessary meke-up water is obtained
by reusing the pulp mill condensete, condenser cooling water, paper
machine white water end certain bleech plant filtretes.
In the Kreft chemical recovery process, water can be reused in
the following operations:
1. Dregs washing.
2. Green liquor dilution.
3. Lime slaking, lime mud washing end lime kiln scrubbing.
4. White liquor filter beck washing.
5. Scrubbing of flue gases.
The primary source of water to be reused in these processes is
the evaporator condensate.
In the sulfite chemical recovery process, the evaporetor conden-
sete is used to dilute the sode ash from the furnece end to scrub the
flue gases when recovering SO . The weshing of the bleached pulp end
removal of the residue lignin requires e lerge amount of water. The
weste weters generated contain e lerge emount of color and hove e
tendency to foem requiring fresh weter meke-up. The amount of fresh
water meke-up required can be reduced by employing the following weter
reuse techniques:
1. The use of washer filtrate for dilution of stock leaving
the bleaching towers.
8
-------
2. The use of excess washer seal box waters in the preceding
seal box washing cycle.
3. The use of white water end excess cooling water to dilute
the finished bleached pulp.
4. The use of digester condensate for shower water, bleaching
tower dilution water and known stock dilution water.
The estimated percentage of the total process water reused in
the paper end pulp industry is in the range of 63 - 73%.
The installation of save-alls in paper mills to recover fiber
permits the reuse of treated water. V/hen a disk filter is employed,
the cloudy filtrate is returned to the pulpers as make-up water and
the clear filtrate is used for many purposes. The overflow is dis-
charged to the sewer. The use of flotation save-all also results in
a similar operation. A simplified scheme of two pulp and fiber
recovery systems in a paperboerd mill is shown in Figure 8.
Reverse osmosis is finding its potential use for the recovery of
deminerelized water end concentrating the solutes from pulp mill
effluents.
Deinking sludge solids contain 50 - 75% clay end these ere
particularly useful in the following applications:
1. Light-weight aggregate for building blocks.
2. Filler for asphalt tile end liquid emulsions.
3. Filler for fiberboerd and other lined board.
4. Filler for paper, rubber end other manufacturing materials.
Recovery of lime at a recovery rate as high as 97% from causti-
cizing operations in the Kraft wood-pulping process has been practiced
with advantage. The recovery process consisted of dewatering on
vacuum filters end calcining the concentrated slurry in a 1600° F. kiln.
Several organic by-products can be and are being recovered from
the spent cooking liquor resulting from various types of pulping opera-
tions. They include turpentine, tall oil, yeast, alcohols, dimethyl
sulfoxide, vanillin, etc.
Digester relief gases from both sulfate and sulfite pulping
contain significant quantities of turpentine. The turpentine recovery
procedure consists of condensing the cooking relief end decenting
the crude oil fractions. The turpentine is used as paint thinners
end in the manufacturing of insecticides. Yields very from 1.5 to
4.3 gallons/ton of pulp.
-------
TO SEWER
TO SHOWERS
AND PULPERS
6-14 Ib/IOOOgol.
PULP TO HYDROPULPER
-------
Tall oil is recovered from the black liquor by various refining
operations end the yields are 180 - 300 Ib/ton of dry pulp. Tall oil
and its derivatives are used to make adhesives, emulsions, disin-
fectants, lubricants, paints and soap.
Torula yeast is produced from spent sulfite liquor by fermen-
tation. Torula yeast contains large amounts of proteins end vitamins
and it is used as a food supplement for humans end animals. Waste
reduction resulting from yeest production is about 95% for total
solids, 20% for BOD's, end 60% for total waste water volume.
Alcohols ere attained es by-products in the fermentation of spent
sulfite liquor by using specific yeast organisms. Ethyl alcohol is
produced es a first-stage product and can be further processed to
produce glycols, ethyl acetate, ethylene dichloride end ecetaldehyde.
Dimethyl sulfoxide (DMSO) is a valuable compound extracted by a
series of complicated processes from liquor dissolved in spent cooking
liquor. DMSO can be used es en antiflemmetory agent or es a becteri-
cide.
Vanillin is generated from the calcium-bese sulfite spent liquor
by treatment of calcium lignosulphonete with sodium hydroxide under
pressure.
It has been established that berk from particular trees can be
used es a source of a saleable by-product while many types of bark
can be used directly in the manufacture of roofing felts, thermal
insulation materials end cheep wrapping paper. By-product utiliza-
tion of bark is currently being studied intensively by the industry.
Many other by-products can be and ere being generated from the
sulfite spent liquor. These include emulsions for insecticides, scal-
ing inhibitors for boilers, tenning egents, cement dispersing agents,
fertilizers, flotation ecids for separation of ores, well drilling
lubricants, extenders in storage batteries, reinforcing agents for
rubber, gradients for ceramic industry electroplating end rood binders,
In spite of the numerous fields in which the spent sulfite li-
quor con be utilized, the amount actually used is very smell. The
prospect of finding en economical use of waste liquor is questionable
et the present technological level in large pert beceuse cheaper end
better raw materials for making these products ere eveileble.
There ere various miscellaneous processes end modificetions of
conventional processes related to product recovery that are worth
reporting.
There is a new process applicable to ell acid or alkaline base
pulps that offers substantial savings . The flue gas obtained by
11
-------
burning the concentrated spent liquor gives up its heat to the incom-
ing dilute spent liquor in direct contact, supplying energy for
evaporation of the dilute liquor. Then the flue ges is scrubbed to
recover chemical values (thereby forestalling air pollution problems)
es well as additional heat. This method contrasts with conventional
processes wherein flue ges heat is used to produce steam and the steam
in turn, heats the evaporators. By eliminating the steam boiler end
steam evaporator, the new approach cuts the required liquor handling
investment by about one half.
Nuclear irradiation of geses produced at Kreft pulp mills was
found successful to make them less objectionable j also, irradiation
of sulfite-mill water pollutants was found to modify their water
solubility and make them easier to treat. Similar studies involving
sewage end liquid industrial wastes are being made by the Metropolitan
Sanitary District of Chicago.
In the Kreft pulping process, the burning of spent liquor is a
necessary step to recover heat and chemicals. This process releases
dust end sulfur-bearing gases into the air. Using a Venturi scrubbing
system , 99% of the dust is removed from flue geses and an improved
oxidation step greatly reduces the amount of H2S released to the
atmosphere.
A new selective hydrogenetion process^7 for pulping wood and
other cellulosic materials patented by Pressure Chemical Company
(Pittsburgh) converts more then 90% of the wood feed, including ligne-
ous portions, into usenble pulp. This high rate of conversion has
other advantages in addition to minimizing the stream pollution; they
ere es follows:
1. Water is used es a solvent instead of the organics.
2. The organo metellics used for cetelysis can be recovered
end recycled.
3. Hydrogen consumption is low because there is no appreciable
cleavage of carbon bond.
The limitations of this process are that the dry pulp produced
has to be bleached end cannot be fed directly to an ordinary Fourdrinier
paper-making machine.
1 Q
A radically new process , "Holopulping" , developed by the
Institute of Paper Chemistry (IPC), slashes the cost of chemicals to
pulpers by two-thirds and increases the yield by 20 to 30%. It elimi-
nates the use of sulfur and regenerates its basic pulping chemicals
and, compared to the Kreft process, greatly reduces pollution. Holo-
pulping is a selective delignification process and the process is
shown in Figure 9.
12
-------
MAKE UP I
•=£>
ELECT. |
•=£>!
AIR
WOOD
WATER
POWER
(C
a
o
set
J8
|
o
J
z
o
X
Id
I
i
x
o
<
Id
2
K
o
H
O
§
T_
X
O
»-
Id
i
T
o
5
Id
a*
'
T
FIGURE 9
HOLOPULPING PROCESS
o
e
z
SOLIDS
b=>
'GASES
.PULP
WASHINGS
I
RESOURCE ENGINEERING ASSOCIATES, INC.
13
-------
The other meJOT features are:
1. Chemical regeneration end recycle is relatively simple.
The pulping and bleaching liquors are of similar chemical
nature and they can be treated in a single stream. Also,
the recovery of products is generally very efficient end
the products can be used in the pulping operations.
2. Stream pollution is kept at a minimum by countercurrent
washing. The remaining calcium sludge waste is disposed
of without causing harmful effects. Air pollution is
greatly reduced because the organic materials are burned
and few odorous compounds are formed.
3. The process may mean a loss of markets for the chemical
industries but the advantage of holopulping is in the con-
servation of forest resources and natural environments by
producing more pulp with a smeller amount of chemicals at
the expense of electric energy.
In a herd-boerd mill , the soluble sugar in the pulp washer
water is concentrated in evaporators in stages to recover "Mesonex" -
a molasses type cettle feed - as a by-product. This product is said
to have a worldwide market as a food supplement carbohydrate or
pellet binder.
The fluidized bed processing has been applied to spent sulfite
liquor combustion by Dorr-Oliver end was found to present an economi-
eel solution to both water and air pollution abatement by converting
the spent liquor to a granular inorganic solid and a clean, dust free,
odorless exhaust gas. In most cases, complete or partial chemical
recovery is possible or e saleable product is produced so that the
operating costs associated with the operation can be offset. Even
more attractive is the fact that when chemical recovery is coupled
with other recovery devices, as high and low level heat recovery,
return on investment becomes an attainable asset.
Hydrogenation of waste liquor containing lignin yields a multi-
tude of products^*, but only phenol offers en attractive combination
of price end market volume. The solids concentration is 10& by
weight end is concentrated to 50% before feeding the liquor to the
hydrogenetion lignin reactor. The products from organic lignin ere
as follows:
Products Yield, % by wt. of organic lignin
05 - hydrocarbons 19.5
Neutrals 14.0
Phenols 37 »5
Catechols °«7
Bottoms 2.4
Water end others 23.6
14
-------
The neutral end organic liquid products ere given e by-product
value of l£/pound. Additional credits ere available from the con-
version of sugers. The bottom meterial is given e value of 21$
per million BTU, a very low value for fuel. The recovered ammonia
is valued at $30/ton.
Hydrogenation can be effectively used for the bleaching of wood
pulp and conversion of celluloslc structures to poly-hydroxyl organic
compounds of lower molecular weight by hydrocrecking seems en in-
triguing possibility.
Table I summarizes by-product recovery in the pulp and paper
mill industries.
15
-------
TABLE I
BY-PRODUCT RECOVERY IN THE
PULP AND PAPER MILL INDUSTRIES
By-Product Recovery
Process
Kraft
Sulfite
By-Product
Turpentine
Tell oil
Lime
Soda ash
Fiber recovery
Torula yeast
Various alcohols
Lignosulphonates
DMSO
Vanillin
Phenol
Acetic acid
Formic acid
Fiber recovery
Quantity
Value -
Recovered
Products
1.5-4.3 gel/ton $0.20-0.40/ton
180-300 Ibs/ton $9-15/ton
2.0 tons/ton $40/ton
1.5 tons/ton $40/ton
Not relevant
500 Ibs/ton
1500 Ibs/ton
50O Ibs/ton
$25/ton
$10/ton
$40/ton
30 Ibs/ton $3/ton
8 Ibs/ton $0.80/ton
Not relevant
Diminution
of Pollu-
tional Load
2%
95%
95%
20-70%
90%
1%
90%
4%
1%
NSSC
Debarking
operations Berk
See Kraft end Sulfite Processing
100 Ibs/ton
$100/ton
Holo-
pulping
10%
Sodium hydroxide Quantities not confirmed in full test.
16
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STEEL INDUSTRY
The disposal of waste pickle liquor is a major problem that hes
been plaguing the steel industry. The steel companies frequently find
it costs almost as much to dispose of the waste as it does to buy
the acid.
There are various methods for treatment, disposal end product
recovery for pickle liquors such as lime neutralization, evaporation-
crystallization, controlled neutralization, electrolysis end dialysis.
Lime neutralization, though very commonly used, is an expensive method
without any product recovery. When evaporation-crystallization is
practiced, only free acid amounting to half the requirement for pick-
ling is recovered. Further, even though the cost of evaporation-
crystallization is not excessive, the disposal of ferrous sulfete
(PeSO^) poses further problems because of its inadequate market.
Electrolytic schemes for complete acid recovery and plating metallic
iron are being used with advantage.
Controlled neutralization with lime (duPont process) produces a
smeller volume of sludge and easy to dewater solids^. Magnetic iron
oxide formed is easily recoverable and crystalline gypsum may be used
for wallboard or cement manufacture. If local conditions do not
justify recovery, solids may be piled as lend fill.
Recovery of sulfuric acid end iron from waste pickle liquor in
the steel industry has been technically proved feasible in the
Ruthner process^ . This recovery system is a non-paying one with
high investment. Roasting of ferrous sulfate monohydrate (crystal-
lized from pickle liquor) with carbon and air to produce iron oxide
and sulfur dioxide hes been proposed. On a large scale, this system
appeared more economical than the Ruthner process. The acid produced
here would be shipped back to the steel mills or other customers.
Iron oxide, to be of value, would have to be sintered and shipped
beck to the mills. Sulfuric acid recovered is the only significant
credit here end recovery of iron in a reedy-to-melt form, rather then
iron oxide, is very desirable.
Several electrolytic schemes have been proposed in the pest to
plate metallic iron from waste pickle liquor end one such scheme with
high efficiency of iron plating end acid formation is shown in
Figure 10.
Evaporation-crystallization hes been used in producing ferrous
sulfate crystals and the flow sheet is shown in Figure 11. Waste
pickle liquor is evaporated at 160° P. and ferrous sulfete is then
crystallized in a vacuum crystallizer and cooled down to 30° F. The
crystals ere separated from the mother liquor by centrifugation.
The mother liquor is diluted to 2596 acid, thereby reducing the
17
-------
STEEL SHEET, WIRE | PICKLING BATH
•MIM^MI
STRIP ETC.
PICKLED STEEL PRODUCT
WASTE PICKLE
LIQUOR (F«S04
+ H£S04)
WATER
1
EVAPORATOR
HEAT
i SOLID F«S04
WATER
DISSOLVER
ACID RECYCLE
TO EVAPORATOR
F«S04 SOLUTION
D.C.
VOLTAGE
ELECTROLYTIC CELL
FIGURE 10
PICKLE LIQUOR
(HtS04)
PLATED I RON
RECOVERY OF SULFURIC ACID AND IRON FROM WASTE
PICKLE LIQUOR IN THE STEEL INDUSTRY
RESOURCE ENGINEERING ASSOCIATES, INC.
18
-------
DILUTE LIQUOR
EVAPORATOR
160° F
H
VACUUM
CRYSTALLIZER
32° F
H
CENTRIFUGE
F«S04 • 7 H20
MOTHER LIQUOR
35% H, S04
6-7%F« S04
WATER
25% H2S04
4-5 % F» S04
ACID TO PICKLING
FIGURE II
EVAPORATION-CRYSTALLIZATION (FeS04- 7H20)
( S.A. LAURICK- STRUTHERS - WELLS CORP )
RESOURCE ENGINEERING ASSOCIATES, INC.
19
-------
residual ferrous sulfete to 4.5% end this solution is returned to
pickling.
Dialysis, e separation process utilizing diffusion es its driving
force, may be used for the economical recovery of acids • In the
viscose rayon industry, dialysis provided the means for recovering
the bulk of the wasted caustic soda. About 0.85 pounds of caustic
were recovered per pound of rayon produced, sufficient to have e reel
effect on the production cost. Recovery of sulfuric acid was done in
two copper refineries on full scale plant units. The economic feasi-
bility of dialysis for stainless steel pickle baths has also been
proven.
Dialysis is a simple unit operation requiring a minimum of opera-
tor attention. The operating cost is almost nil as no power or chemical
is used. However, it should be noted that dialysis alone will not
resolve a waste treatment problem, but its role to remove raw materials
and to reduce plant waste is significant. Some acid systems may allow
recovery of es much es 70 or 75% of currently wasted acid, but even
recovery of es little as 20% of the wasted acid may justify the process
from the economical point of view.
The pickling of steel in the United States is predominantly done
with sulfuric acid. The acid used is consumed and produces a waste
pickle liquor which is both uneconomical end extremely difficult to
regenerate. The waste pickle liquor is normally neutralized and/or
dumped. This method of disposal is becoming more end more difficult
to pursue. A practical answer to this problem is the use of hydro-
chloric acid instead of sulfuric in the pickling operation. Major
steel strip manufacturers in the United States have already started
the trend ^ toward hydrochloric acid due to the following reasons:
1. Hydrochloric ecid prices ere dropping while sulfuric acid
prices are rising.
2. Hydrochloric ecid pickling is faster end produces e better
quality product.
3. Most importantly, hydrochloric ecid waste pickle liquor can
be and is being regenerated economically.
Switching to hydrochloric ecid is not practical in the open-batch
pickling of wire, pipe and plate due to the production of corrosive
vapor. In the continuous strip pickling operations where hoods •and
ventilation systems are provided, the switching is relatively easy.
The vapor problem has been avoided in Europe by using enclosed tunnel
end Ottocleve picklers.
The handling of spent pickle liquor is done by the Turbulator
process^". The turbuletor process simply reverses the reaction that
20
-------
occurs in the pickling bath and, thereby, regenerating the hydro-
chloric acid and iron oxide consumed in operation.
2FeO + 4HC1 ............. ->2FeCl2 + 2H20
2FeCl2 + 2H20 * O ..... >Fe203 + 4HC1
The pickling-regeneration cycle can also be symbolized es shown
in Figure 12.
Theoretically, ell the hydrochloric acid is recovered in this
cyclical system. In practice, however, some loss does occur in the
pickling end regeneration process which makes it necessary to add a
small amount of fresh acid to the pickling system. The advantages
of the turbulator process are es follows:
1. High reaction rates resulting in small space requirements.
2. High operating flexibility in very short start-up end
shut-down times.
3. Low maintenance requirements.
.4. A system that can point to actual operating plants.
97
In a process developed by Interleke Steel Company- -duPont ,
waste hydrochloric acid pickle liquor is neutralized and discharged
rather then regenerated. In the process treating 11 million gallons
per year of acid waste, pickle liquor (spent HC1 , FeCl2 end water) is
neutralized by adding lime and ferrous hydroxide £Fe(OH)2~J end calcium
chloride (CaCl2) ere formed. The ferrous hydroxide is oxidized to
magnetite ^630^) and separated from week calcium chloride solution,
sintered and returned to furnace. Recovery will be 5000 ton/year from
waste liquor. Calcium chloride is usually diluted and discharged into
sewers or natural waters but it could be recovered by concentration.
Because of the relationship between hydrochloric acid, pickling
end regeneration as a natural complement to the other, it is believed
that the use of hydrogen chloride in the pickling operation will play
a large part in the future27. Presently in the United States, Drevo
Corporation accomplishes hydrogen chloride regeneration in a spray
roaster and in Germany, Lurgi has developed a fluid bed acid regenera-
tion process.
The elimination of phenol (CeHsOH) from coke plant ammonia liquor
has been a problem of major concern to the steel industry. Solvent
extraction process was found to have possibilities of attaining the
advantages such as high efficiency, operating charges as low es possi-
ble and lowest investment. In the solvent extraction process^®, raw
21
-------
REGENERATION
Fe205
FIGURE J2
PICKLING REGENERATION CYCLE
22
RESOURCE ENGINEERING ASSOCIATES, INC. —•
-------
ammonia liquor is contacted counter-currently with a solvent, such as
light oil, readily available in the coke plant. The solvent removes
the phenol and, in turn, is treated with a caustic soda solution for
extraction of phenol as sodium phenolate (CeHs-ONe), end then the
solvent is recycled. The caustic concentration greatly influenced the
percentage of elimination of phenol from the liquor. The more dilute
caustic used, the better the phenol elimination. A phenolate of reason-
able concentration must be produced to be saleable. This was achieved
by employing two streams of caustic of different strengths as feeds
to the reactor; the desired elimination of phenol end concentration
of product could be obtained. The removal efficiency for phenol was
reported to be about 9896. Ammonium sulfate is regularly recovered
from these waste waters by neutralization with sulfuric acid end
crystallization of the salt.
29 •
A new process developed in Japan turns pyrite (FeS2) cinder into
pellets with a high iron content, suitable for feeding to blast furnaces,
This increases the iron ore requirements as Japan develops only about
1096 of iron ore requirements domestically from sources such as pyrite
float concentrates. Process economics ere improved by the recovery
end sale of precious metals contained in the cinder. Gas produced is
treated by a wet system to recover Cu, Zn, Au, Ag and Pb. Other
main features include:
1. Purification end pelletizing are done simultaneously.
2. The removal rates of copper, zinc end bismuth are higher
than the conventional chlordizing, roasting and bleaching
process.
3. Recovery rate for silver, gold is better.
4. Residual sulfur dioxide is recovered from the gas as gypsum.
In a gray iron foundry30, briquetting was practiced to recover
flue dust end mill scale and this process can be used to save a
variety of valuable waste materials. In the steel industry, better use
of turnings and borings left over in mill operations as scrap is made
by making briquettes out of this scrap material and returning them to
make more iron.
Table Hsummarizes by-product recovery in the iron and steel
industries.
23
-------
TABLE II
BY-PRODUCT RECOVERY IN THE
IRON AND STEEL INDUSTRIES
Process
Pickle
liquor
Grey iron
foundry
By-Product Recovery
By-Product
Quantity
Value
Iron oxide
Gypsum
Sulfuric acid
Hydrochloric
ecid
Flue dust
Mill scale
25-35 Ib/ton
40-50 Ib/ton
30-40 Ib/ton
30-40 Ib/ton
$0.10-0.20/ton
$0.10-0.20/ton
$0.60-0.80/ton
$0.60-0.80/ton
Blest fur- Mill scele
nece scrub-
ber waters
25-50 Ib/ton
Diminution
of Pollu-
tional Load
100%
100%
100%
100%
60-80%
60-80%
24
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PLATING AND ALLIED INDUSTRIES
The rinse water from plating industry mostly contains some or
many of the following contaminants usually in intolerable amounts:
hexevalent chromium, sodium cyanide, complex cyanides of the heavy
metals, such as cadmium, copper, zinc, sometimes silver and gold,
soluble nickel salts, strong mineral ecids end strong alkalis. Of
these, the most toxic are hexavelent chromium end the cyanide ion.
Aquatic life is also sensitive to salts of the heavy metals.
There are several basic methods of treating this waste for final
disposal or recovery of products. The oldest is the batch treatment
method. In this method, the rinse waters ere collected for treatment
and disposal. The destruction of toxic chemicals is accomplished by
oxidation of the cyanides end reduction of chrome. Chlorine (C12) is
used to destroy cyanides (CM) end the chlorinated rinse water is
pumped into a reduction tank containing sulfuric acid end e reductent-
like ferrous sulfate (FeSO4), sodium bisulfite (NeHSOg) or sulfur
dioxide (SCU) • Chromium is reduced from its hexavalent state (Cr )
to trivelent state (Cr ) end is precipitated along with metals as
their hydroxides by the addition of lime. The clear water from the
clerifier would be reedy for discherge into e sewer end the sludge
is disposed by any convenient method.
Another method of treatment of rinse water is the continuous
flow method. To be effective end fool-proof, this requires excellent
instrumentation to monitor the flow end deliver the proper amount of
reactent. Also, such e system may not allow enough reaction time to
allow slow reactions to go to completion.
Where the volume of chromic acid end sodium or potassium cyanide
used in the industry is great enough, the system of recovery of the
cyenides and chromic acid by ion-exchange end evaporation hes obvious
economic edventages. However, when the plating operetion is split up
into several smell, different operetions involving chrome plating,
several different kinds of chrometing baths and several types of
cyenide beths, this method becomes precticel .
Lency's integrated system of treatment of cyenide end chromium
wastes is found to be suiteble for a pleting operetion split up into
several operations. The system involves countercurrent rinsing end
the basic adventege of this system is that the toxic contaminants ere
destroyed before they cen enter into the rinse weter, rether then
having to be removed leter.
When reclemetion of chemicels is desired, ion exchenge pleys en
importent role. The rinse weters are kept separete in the following
categories:
1. Herd chrome rinse weters
25
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2. Cyanide rinse waters containing silver, gold or any other
valuable metal.
3. Miscellaneous wastes such as alkaline cleaners and acids.
The hard chrome rinse waters ere passed through a cation and a
strong base anion exchanger. The contaminating metals such as copper,
nickel end trivalent chrome ere exchanged on the cation exchanger,
while the hexevelent chrome is exchanged on the enion exchanger. Upon
exhaustion of the system, the cation exchanger is regenerated with en
acid and the enion exchanger regenerated with caustic soda.
The regenerent effluent from the cation exchanger can be dis-
charged to a collection chamber for neutralization. The regenerant
effluent from the enion exchanger will contain sodium chromete end
some caustic soda. This material can then be converted to chromic
acid by passing back through the cation exchanger so that the two
exchangers may be alternated between service end conversion.
32
The ion exchange system for silver recovery would consist of a
strongly acidic sulfonic cation exchanger end a strong base enion
exchanger. The effluent from the system is de-ionized water and can
be reused in the rinsing operation. Sodium hydroxide is used as a
regenerent end the regenerant effluent contains sodium cyanide (NaCH)
and sodium hydroxide (NeOH). This solution is passed downflow through
the exhausted bed of the cation exchanger. The cation exchanger efflu-
ent contains sodium silver cyanide and NeOH. This regenerent solution
may be used in the make-up of silver bath. Otherwise, addition of 15%
sodium hypochlorite (NaOCl) solution precipitates the silver as silver
chloride (AgCl) end destroys the cyanides. The AgCl is recovered and
the supernatant liquid dumped in the sewer, cyanide free. Sodium silver
cyanide can be recovered by this method for e chemical cost of approxi-
mately 18<£/pound of silver recovered.
The rinse water frogi gold plating line contains enough gold to
make recovery economical . The recovery of gold is accomplished by
passing the rinse water through e strong base anion exchanger of the
hydroxide form. After exhaustion of the resin, the gold is recovered
by burning the resin. The residue remaining is metallic gold. One
cubic foot of anion exchange resin, when exhausted with gold cyanide,
contains approximately 125 ounces or $4,OOO worth of gold.
The rinse water in the platinum plating industry contains platinum
in the form of chlorophetinic acid. Strongly basic anion exchanger is
used end when the resin is saturated with platinum, the recovery is
achieved by burning the resin .
Nickel may be recovered from plating rinse waters by employing e
cation exchange process^. The effluent from the service cycle of the
hydrogen exchanger can be passed through a weak base enion exchanger
to obtain deionized water for plant use. Sulfuric acid is used for
26
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regeneration end the nickel is eluted from the resin as nickel sul-
fete. The capacity of the cation resin is 5.0 pounds of nickel per
cubic foot as nickel sulfete end the chemical cost for the process
would be 20$/pound of nickel sulfete recovered.
Brightening of aluminum is done by the use of concentrated
phosphoric acid (H3?04) and a smell amount of nitric acid (HMOs).
Rinse water from this operation contains aluminum and dilute
It is estimated in en industry in Illinois 3 that two to three
million pounds of H3?04 were lost each year. Cation exchanger was
used to remove aluminum and the aluminum-free solution is evaporated
in a multiple effect evaporator to obtain concentrated HsP04 (85%)
and good quality condensate. The recovery of H3P04 in this industry
provided a net savings of $8100/month above the operating expenses.
Dialysis has also been studied in the recovery process.
In the film processing industry, tons of valuable metals go down
the drain and recovery of silver alone could effect large savings.
Some private laboratories, like those processing TV film, do recover
silver but, in many cases, the quantities at any one location are very
seldom large enough to warrant recovery measures. However, the
General Services Administration and Bureau of Budget ere looking into
the feasibility of a recovery system for government generated waste
silver solutions34. Table III summarizes "by-product recovery in the
plating and allied industries.
27
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TABLE III
BY-PRODUCT RECOVERY IN PLATING AND ALLIED INDUSTRIES
By-Product Recovery
Process
By-Product
Concentre t ion
Range
(mg/1)
Value
($/1000 gel.)
Diminution
of Pollu-
tional Load
Rinse waters
Aluminum
bright dip
Nickel
Copper
Zinc
Silver
Chromium
Cadmium
Brass
Tin
Gold
Platinum
Phosphoric
acid
150-900
2-20
100-500
70-350
50-250
400-2000
50-250
(Cu) 40-250
(Zn) 10-60
100-600
10%
0.80-7.00
0.01-0.10
0.60-3.00
0.40-2.40
1.60-9.00
3.20-15.00
1.20-6.00
0.20-1.20
0.20-1.20
0.80-4.80
$4,000
80-100%
ao-ioo%
80-100%
80-100%
80-100%
80-10O%
80-100%
80-100%
80-100%
80-100%
80-100%
Film
processing
Silver
80-100%
28
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MINING INDUSTRY
Acid mine water results from the exposure of sulfur end iron-
bearing materials to processes of erosion and weathering. The drainage
is generally acidic end contains sulfuric acid, ferrous, ferric, elumi-
num end manganese salts. In addition, the mine drainage may contain
calcium, magnesium and sodium salts, carbon dioxide end silicic acid.
The volumes of coal mine drainages encountered range from a few
hundred thousand gallons/day to several tens of millions of gallons per
day. An estimate of the magnitude of the problem in the United
States is that four million tons of sulfuric ecid equivelent per
year is being discharged to inland water courses. The reguletory
agencies, in en attempt to control mine dreinege, usually stipulate
that the discharge should be alkaline with a pH range of 6.0 to 9.0
and a maximum iron content of 7 mg/1.
Recovery of sulfuric ecid has been proved uneconomical end,
therefore, there have been many processes reported for the treatment
end disposal of acid mine dreinege. These can be considered as three
classes for convenience:
1. Lime neutralization process
2. Unorthodox or alternative processes
3. Limestone neutralization processes
The principle of these processes is that lime or other strong
elkeli is mixed with the ecid mine drainage to neutralize the acids
and to precipitate the contemineting metel selts which cen be sepere-
ted by sedimentation. However, the sludge formed has a high water
content end presents e difficult disposal problem.
The ecid mine dreinage has been treated in many cases by lime to
produce water for coal preperetion plants and dust suppression pur-
poses. The costs of treatment reported in one case was $1.O9/1OOO „
gallons, equivelent to a cost of 5.2^/short ton of the coal produced
As seen from this cost figure, lime neutralizetion processes ere not
economicel, even though in some specific cases they may prove economi-
cal. Attempts to prepare marketeble by-products such as rouge from
ecid mine dreinege hove been mode without any success. Use of organo-
metallic compounds for the production of pigments from ecid mine
dreinege hove elso been reported37. The possibility of distinction
and reverse osmosis processes heve been discussed but the costs are
OQ
prohibitive °. In summery, it cen be seid that none of the alternative
processes has yet been shown to be cheeper then the lime process for
generel epplicetion, but it is possible that processes which leed to
the recovery of poteble weter might be commercially viable in districts
which ere perticulerly short of weter.
29
-------
Limestone neutralization has found wide application in the neu-
tralization of acid wastes other then those containing iron and other
precipiteble salts. Also, reegent inactivetion is e problem when
these salts ere present. It may appear that the main advantage of
using limestone would be the low cost of the reegent, but the fact
of the matter lies in the separation and dewetering of the sludge of
precipitated contaminants. Also, if an auxiliary process could be
developed for the removal of ferrous salts, the use of limestone
would be very effective. Biochemical oxidation of ferrous salts in
acid solution appeared to be the only practical method end e new
process using this technique was developed in England. Flow diagram
of such a process is shown in Figure 13.
This new process has some limitations such as:
1. The concentration of dissolved iron end total acidity es
calcium carbonate should be et least 10 end 25 mg/1,
respectively.
2. The S04 concentration should not exceed 5000 mg/1.
3. The extreme temperature limits for the process ere expected
to be 0 to 35° C., with e preferred working range of 5 to 25° C
4. Manganese salts cannot be removed.
However, it seems possible that over half of the acid coal mine
drainages of the United States could be purified by this process. The
cost of treatment employing biochemical oxidation and limestone neu-
tralization is reported ss 33^/1000 gallons end for the lime process,
it is 53^/1000 gallons. For most contaminated acid mine drainages,
the conventional lime process would be more applicable.
In en exceptional case, disposal of mine water from a mine of
Bethlehem Mines Corporation, Pennsylvania , has been made profitable.
Mine water was used es the cleaning medium for raw coal extracted
from the mine. Raw coal had about 30% CaCOg end MgC03 end provided
more than enough alkalinity to neutralize the acidic mine waste. The
pH of the waste water was raised from 3 to 7 and iron content was re-
duced from 551 mg/1 to 0.1 mg/1 range. The quality of water was,
thus, well within the local limitations end e possible financial lia-
bility of treating the acid mine discharge has been converted into an
asset.
Leeching solutions from copper ore waste dumps may be not only
a profitable source of copper but also of uranium. The solutions pick
up both metals as they percolate through piles of copper mine waste.
A study by the U.S. Bureau of Mines' Metallurgy Research Center at
30
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ACID MINE
DRAINAGE
AIR
LIMESTONE
GRIT
FLOW
BALANCING
BIOCHEMICAL
OXIDATION
LIMESTONE
NEUTRALIZATION
ACTIVE SLUDGE
oo
O
50
O
CT
m
m
TREATED
EFFLUENT
FIGURE 13
FLOW DIAGRAM OF BIOCHEMICAL OXIDATION AND LIMESTONE
NEUTRALIZATION PROCESS
O
O
-------
Salt Lake City, Utah, has shown that economic recovery of both
copper and uranium is feasible by ion exchange. The recovered
uranium concentrates are pure enough to meet government specifi-
cations and ere also suitable for nuclear power industry. It is
estimated that an annual supply up to 1000 tons of uranium oxide
could be assured by applying this process to ell domestic copper
leaching solution containing uranium compound.
Kennecott Copper Corporation has developed e process for re-
covery of copper from mine tailings vie precipitetion process. The
process is simple and works as follows: water that hes percolated
through the dump goes into e cone of precipitetor filled with iron.
In e reaction known as cementing, the iron goes into solution end
copper precipitates. The red precipitate containing 80% copper is
used as smelter feed end the weter recirculeted to the dump. This
process hes increased the production considerably (e fector of 2 to
3) because the yield from mine tailings dumps is nearly as much as
the mine itself.
A hydrometellurgicel process hes been used to recover nickel
from sulfide ore concentrates. This process is essentially en ammonia-
leach hydrogen reduction process end hes the advantage of lessening
air pollution problems because sulfur is not emitted, but rather is
recovered as ammonium sulfate fertilizer. In the process, ammonia
solution extracts Cu, Ni, and Co from mine concentrates containing
Ni (10%), Cu (2%), Co (0.4%), Fe (30%) end S (30%). Nickel end co-
balt are extracted from solution together by treatment with H2S.
Nickel and cobalt sulfide precipitates are filtered end processed
separately for recovery. The remaining solution contains diemmonium
sulfete (NH4)2SC>4 end it is recovered by evaporation. The product
processed is 40 tons/day Ni, end by-products recovered per day are
3000 pounds Co end 300 tons (NH4)2SO4.
In the coal mines, coal fines of the -48 or -100 mesh fraction
of the coal produced are being sent to settling ponds or sold at a
low cost for reason of quality. Flotation process hes been demon-
strated4^ to increase the plant realization of fine coal successfully
because of its low cost, easy adaptability end little supervision.
Clear water can be reused in the plant.
Molybdenum oxide ores ere generally discarded as plant wastes.
A new process44 developed applies acid leeching, charcoal adsorption,
emmoniation end calcining to slime fractions of sulfide end oxidi
molybdenum ores. A production output of 1.5 pounds of molybdic oxide
(MoOg) WeS achieved for every ton of ore fed.
There is e program under way on the use of wastes from zinc min-
ing and milling for steel-making industries at the University of
Wisconsin sponsored by the U.S. Bureau of Mines45. The wastes are e
possible source of burnt dolomitic lime (useful as a flux in steel
making), iron oxide sinter for blast furnaces and elemental sulfur.
32
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COAL BY-PRODUCTS
Coke end Gas Industry
Substantial by-product recovery is practiced in this industry
and the by-products from gaseous coke-oven effluents include:
ammonium sulfete, coel tars end oils, and coal gas >^ > .
Phenolic-containing liquors ere e significant disposal problem
since they impeir the taste of the receiving waters, especially if
chlorinated. Destructive dephenolization processes, biological end
chemical oxidation were found to be unsuitaoj.e due to their high opera-
ting and capital costs, especially with the phenolic concentration.
Recovery of phenol from the liquors solved the problem of pollution
control in addition to providing credit because of the velue of phenol.
Solvent extraction (with benzene), activated carbon adsorption, steam
stripping, end ion exchange heve been employed to recover phenol from
the liquors. In a tar distillation plant, Detroit, Michigan, Allied
Chemical Corporation4 recovered phenol from e waste stream contain-
ing 3000 to 10,000 mg/1 phenolics end the effluent phenol concentration
was brought down to less then 10 mg/1 at solvent to waste ratio of
1 to 1 or less. The solvents used were readily produced et the
distillation plant without any equipment changes and this resulted in
economic and efficient waste water dephenolizetion. Also, caustic
soda was used to regenerate the solvent rether than distillation.
Phenol has been recovered by distillation by the Koppers pro-
cess end the Heffner-Tiddy process, extraction with benzene end
trichloroethylene end adsorption by activated carbon. Ammonium sul-
fete and ammonia ere usually recovered by neutralization followed by
crystallization of the salt and filtration.
It is important to note that a wide variety of cyclic and aro-
matic organics such es benzene, cresols, xylenes and naphthalenes
ere produced in coke ovens and are condensed from the gas stream.
This production has formed the basis of the coel-besed chemical in-
dustry for many years before the advent of the petrochemical-based
industry of today.
Flue Gas Treatment
Sulfur end nitrogen oxides in gaseous effluents ere e problem for
the electric utility, sulfuric acid, fertilizer, metallurgical, end
pulp industries. S02 is generally recovered by wet scrubbing while
sulfuric plants catelyticelly oxidize any SC>2 in the effluent to S03
and recover H2S04 by wet scrubbing. There ere e number of processes
that ere used for recovery of sulfur oxides, es follows:
1. Simon-Carves-Cominco process, based on wet scrubbing
with emmoniacel solution to produce ammonium sulfete end
either sulfur or SCv,.
33
-------
2. The soda ash - zinc oxide process, based on wet scrubbing
with a sode ash solution that is regenerated with Zn(NC>3)2
and lime with the production of SC>2.
3. The manganese oxide process, based on wet scrubbing with a
manganese dioxide solution to produce SO2.
4. Wet oxidation, based on the oxidation of 862 to 863 using
ozone in a manganese sulfate solution. MnSCXq. is oxidized
with air end ammonia to regenerate mengenous dioxide and
to form (NH4)2S04 for sale as a by-product.
5. The adsorption processes, based on the use of activated char
in water (Peuling), multi-bed char adsorption (Reinluft),
activated char pipeline contactor (Central Electricity
Research Labs, Leatherheed, England, end USPHS), end alka-
lized alumina (U.S. Bureau of Mines end Central Electricity
Research Labs).
Flue gas from power stations are used as heat source end nutrient
supply for production of chlorelle^ . Chlorelle , rich in protein and
vitamins, is used to upgrade enimel feeder. Electric utility industry^!
in burning 281 million tons of bituminous coal to generate about 65%
of United States' total steam electric output, yields about 20 million
tons of fly ash. About 10% of this fly ash is sold commercially
leaving about 18 million tons of wastes to be dumped at costs ranging
from 50£ to $2/ton. Utilization of fly ash by the United States is
poor compered to Western European countries. Fly ash could be used
as a prime constituent and additive for construction materials. Fly
ash makes concrete stronger and less vulnerable to freezing tempera-
ture. Fly ash can be used as a soil stabilizer and as a clarifying
egent in waste woter treatment plents and es e sludge conditioner.
In the Kraft pulping process, the burning of spent liquor is
practiced to recover heat and chemicals. This practice releases dust
end sulfur-bearing gases into the eir. A venturi scrubbing system
removes 99% of the dust end the amount of HgS released to the atmos-
phere is reduced to a great extent by en improved oxidation step.
CO
In the power plents and industrial boilers, Cat-Ox process is
used to remove 100% fly ash and recover high strength sulfuric acid
(H2S04)for sale. The process flow sheet is shown in Figure lU.
Hot flue gas taken directly from the boiler et 950° F. is first
pessed through e dust removal system, a combination of mechanical separa-
tor end electrostatic precipitetor. The gas then goes into e converter
system (Figure 14) where about 90% of S02 is converted to SOs. Flue
gas from converter is cooled end high strength ^504 is obtained through
the ebsorption tower. The residual H2S04 mist contained in the flue
gas from the ebsorption tower is removed in e mist eliminetor end the
flue gas free from dust end S02 is let into the atmosphere.
Table 17summarizes by-product recovery in coal by-products industry.
34
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FLUE GAS
I
KZKZH
CO
O
O
m
m
30
CT
O
O
I-ELECTROSTATIC 2'CONVERTER 3'ECONOMIZER 4-ABSORPTION 5-MIST 6-STACK
PRECIPITATOR TOWER ELIMINATOR
FIGURE 14
PROCESS FLOW SHEET OF FLUE GAS TREATMENT
O
-------
TABLE IV
BY-PRODUCT RECOVERY IN COAL BY-PRODUCTS INDUSTRY
Process
By-Product Recovery
By-Product
Quantity
Value
Ammonium
sulfate
coa1 burnt
Diminution
of Pollu-
tions 1 Load
Coke plant
ammonia
liquor
Flue gas
scrubbing
Phenol
Ammonium
sulfate
Ammonia
Naphthalene }
Benzene ^
Xylene f
Cresols J
Sulfur "N
Sulfuric acid!
2 Ibs/ton coke
24 Ibs/ton coke
8 Ibs/ton coke
20 Ibs/ton
AH 1 V»es /^j-%r\ /-\-P
$0.20/ton
$1.00/ton
$0.25/ton
$2.00/ton
4i ?r\/-t-^-r>
40%
50%
50%
100%
O r\ i r\/-w
36
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PETROLEUM INDUSTRIES
Petrochemical Industries
Petrochemical industries have been faced with the dealing of
large amounts of organic wastes in their early stages of development.
The reduction of pollutant load has been achieved by using organic
wastes as fuel until recovery processes have been developed and a
higher market for recovered chemicals developed. This approach has
been followed in the production of almost every large volume petro-
chemical waste.
The more important recovery methods and products ere presented
below. Hydrogen is used in ammonia production, refinery operations,
such as hydrotreating and hydrocracking , end many other purposes.
Four recovery methods have so far been reported end the choice depends
upon plant size, location, feed composition and hydrogen end use.
1, Wet scrubbing: is used to remove CO£ and H£ streams in
conventional syntheses-gas plants. Scrubbing solutions include
hot, carbonate-containing aqueous solutions, ethanolamines ,
and high pressure water.
2. Adsorption: is used on molecular sieves or activated carbon
to separate hydrogen from hydrocarbons.
3. Cryogenic scrubbing: removes higher boiling impurities by
condensation from low boiling hydrogen (-252.8° C.). This
process is useful where a refrigerant, such as liquid air
or nitrogen is readily available, as in partial oxidation
synthesis gas plants.
4. Membrane permeation: is based on palladium's selectivity
in passing hydrogen and is used to recover hydrogen from
petroleum effluents.
Other petrochemical recovery processes:
1. Distillation: is used to recover chlorinated hydrocarbons
following the chlorination of methane, olefins from the
thermal production of ethylene , eceteldehyde following the
production of vinyl acetate, end solvents from rubber latexes.
2. Crystallization: is used to separate xylene from ethyl benzene.
3. Adsorption: is useful for the recovery of carbon disulfide,
carbon tetrachloride and other solvents.
37
-------
4. Extraction: is useful for the recovery of isobutylene,
naphthalenes, paraffins end phenol from a variety of wastes,
and organic dyes are extracted following adsorption on
fuller's earth.
5. Ion exchange: recovers basic amino acids, amines, alkaloids
end organic acidsc
6. Oxidation: regenerates spent caustic.
Petroleum Refineries
The recent trend in the newly constructed petroleum refineries
is full integration of in-plent procedures and multi-stage waste water
treatment combined with reuse end reclamation of purified water,
resulting in considerable progress in pollution abatement end e drastic
reduction of clean water intake requirements.
Use of hydrogenetion processes, such es hydrosulfurizetion, yields
products low in sulfur end, therefore, require minimum subsequent
treatment. Application of chemical treatment processes, especially
for gas scrubbing, allow complete regeneration end recovery of the
solvent. The amount of spent chemicels requiring treetment end dis-
posal is brought down to a low level by these processes.
Separate collection of waste water is employed in sewer systems
according to their subsequent treetment. Efficient pretreatment such
es evaporation, stripping of sour water condensetes end equalization
of flow and strength of waste waters are some of the processes used to
improve product recovery end reduce waste loed. Treated waste weter
is used es make-up weter for recirculetion cooling systems. In conse-
quence of these measures, specific water consumption end waste water
discharge per production unit has been in the remarkably low range of
9 to 22 gallons/barrel oil processed end 3 to 8 gallons/barrel of oil
processed, respectively^.
There ere many by-products thet could be recovered from petroleum
refining westes, even though ell of them mey not bring economic bene-
fit. Therefore, the concept of by-product recovery is limited to those
meteriels which, if recovered, would accrue some economic benefit, but
not necessarily enough to cover the cost of recovery.
Besed on this definition, the mejor by-product is sulfur, which is
recovered from sour weters end from the hydro-treating process. The
velue realized through sulfur recovery is expected to increase greatly
in the neer future, due to the increased demend for low-sulfur fuels
brought on by more stringent urben air pollution controls.
A number of refining process westes have been recovered or reused
38
-------
and they are as follows:
1. Recovery of H2S04 from sludges produced in the acid treatment
of oils. Hydrolysis of the sludge produces a dilute (30-6096)
black acid of rather limited utility.
2. Reuse of spent alkylation acid in the treatment of oils and
waxes, with subsequent regeneration in captive or outside
acid plants.
3. Sale of high-phenol waste caustics from treatment of
cetalytically cracked naphthas*
4. Use of sprung phenols as refinery fuels. These materials
come from acid springing of spent caustics from cracked
naphtha treatment.
5. Use of various waste acids in slop oil treatment.
6. Recovery of aluminum chloride from hydrocarbon sludges.
7. Recovery of acid oils by reaction of waste caustics with
acids.
8. Use of boiler feed water treatment sludge in the neutralization
of waste water.
9. Reuse of treated waste water to supplement normal refinery
water supply.
10. Recovery of ammonia and hydrogen sulfide from sour water
stripping for use as raw materials in the manufacture of
fertilizer grade ammonium sulfete.
Production of single cell proteins from petroleum has been shown
feasible and the proteins can be used as animal or human feed supple-
ments^. The price of a 50% protein single cell is estimated at
6 to 80/pound end hoped to be competitive as a potential animal feed
supplement* For human consumption, the protein could command a price
in the range of 30 to 40<*/pound. But it is feared that the cost of
production of proteins is likely to mount up because of the uncertain-
ties involved in additional processing. Another big hurdle will be
probably in marketing or acceptance of such products due to factors
like flavor, color, appearance, personal and cultural idiosyncrasies
of consumers.
A $5.6 million plant is going into action in 1970 for the commer-
cial production56 of protein from petroleum. The concept consists
basically of letting microorganisms grow big in bulk by nourishing
39
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themselves on hydrocarbons; the bulked product cen be processed for
foodstuff use. About 100 tons of ges oil will be needed to produce
100 tons of protein.
A single stage extraction vessel is used as a petroleum refiner's
latest weapon for taking obnoxious phenols out of water from catalytic
crecker distillate drums before it is let into the sewer. The ex-
trectant is light catalytic crecker cycle oil which is subsequently
processed to finished heating oil. Using this principle, Humble Oil
Company in Baton Rouge, Louisiana, is accomplishing a 75% reduction
in phenol.
Aluminum chloride waste results from the petroleum and petro-
chemical industries, due to the use of aluminum chloride as a catalyst,
end this cennot be discharged to stream or municipal sewer system,
due to its low pH end high dissolved solids. Spent aluminum chloride
is available in the form of about 27% aluminum chloride (32° Be1)
solution. The handling and dispose! of such inorganic salts are
troublesome end ere not in the realm of current economic feasibility.
However, such troublesome products cen be used to control or eliminate
other environmental problems. One such cese^' is the use of waste
aluminum chloride solution in the field of waste water treatment for
effective solids separation, phosphate removal end sludge conditioning.
The present estimate is that some one hundred to two hundred million
pounds/year will be available as 32° Be'solution end that more than
9O?r' of it is recoverable. At the current cost of 32^/pound of alumi-
num, the cost of 27% aluminum chloride solution is estimated at
4.40/pound end the total value of the weste aluminum chloride amounts
to 6.6 million dollars.
Recovery of Oil From V.'este Waters
Spills of oil constitute a major pollution threat to the water
resources of the nation. Both water end land-based facilities ere
sources of this danger to our streams end rivers. Much damage has
alreedy been done from accidental or indiscriminate spillege of crude
oil, petroleum end its by-products. Such spills have contaminated
weter supplies, killed fish end wild life, creeted fire hazards, end
destroyed or reduced the usage of recreational areas.
The major sources of oil pollution include: gasoline service
stations, oily weste industries, offshore oil and gas operations,
oil tankers end industrial transfer end storage of oils. Cleaning up
en oil-contemineted area is time consuming, difficult end costly. In
addition, the losses due to destruction of fish end other wild life,
damage to property, contamination of public weter supplies and any
number of other materiel end aesthetic losses ere involved. These
losses may be very ^reet and extend for months or years, sometimes
40
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for decades, depending on the quantities and kinds of oil involved.
It is estimated that about 350 million gallons of used motor
oil must be disposed of annually by the more then 210,000 gasoline
filling stations. These stations ere the key suppliers of used oil
re-refiners. Re-refined oils are used in railroad journals, to
freeze-proof coal, as dust control for rural roads and as motor oils
end industrial lubricants. In the recent years, more than half of
the re-refiners have gone out of business due to changes in labeling
requirements and in the tax laws. Also re-refining has now become s
marginal business. As the demand for used oil for re-refining dimin-
ishes, more of the waste oil will be disposed in other ways leading to
pollution of natural water courses. Therefore, it is imperative, et
this stage, that proper measures should be developed to provide in-
centives to collect and reuse these oils rather then disposing of
them. The disposal of waste mineral oils and greases, such as those
from garage and filling stations, to sewer systems are being prohibited
by ordinance due to the treatment problems end their flammebility end
potential explosive hazard.
There are about 10,000 industrial plants in this country having
significant quantities of oil in their wastes. Technology is now
available to cope with wastes having either floating or emulsified
oil. The more or less standard procedure of removing fleeting oil is
with API separator. The performance of API separator is limited to
the separation of solids and immiscible liquids which are susceptible
to gravity separation. Stable emulsions and substances in solution
cannot be separated by gravity differential principle. The use of
HoS04 for pH control and aluminum sulfate for floe formation is prac-
ticed for removal of soluble oil in metal-working plants. The skimmed
oil is sold to an outside concern who reclaims it for various commercial
uses. For emulsions, strong acid or salt may be used to de-emulsify
and then the oil is separated by conventional method. Dissolved air
flotation has also been used for removing the oil end improving the
quality of the separator effluent with the reduction of oil end free
solids content.
The Oil Pollution Act of 1924 end subsequent amraendment in 1966
require that willful or grossly negligent dischargers of oil from a
vessel remove the oil from the navigable waters end adjoining shore-
lines immediately. To minimize pollution, such as the Torrey Canyon
disaster, clean-up measures must be taken promptly and these are ex-
pensive. When the responsible parties cannot be identified immediately,
or fail to act expeditiously, the initiation of effective clean up
end recovery of clean-up cost poses a problem due to the present fiscal
and legal difficulties. Some of the leading oil-spill treatments ere
listed in' the accompanying pages.
58
A new process developed by Edgar Clarke ,under a FWPCA grant, is
said to recover high quality, fine particle carbon black (valued at
41
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(3 to 12£/pound) thet used to be a waste product. The process involves
the following steps:
1. dehydrate, neutralize oil with caustic soda,
2. dilute with light naphtha and remove solids,
3. distill, and recycle nephtha,
4. vacuum distill off products,
5. heet with activated clay; use spent clay for lend fill.
Berks Associates (Douglassville, Pennsylvania) using Clarke's
process, report thet their products obtained by re-refining used lube
oil ere fully comparable to those produced by major oil companies end
the cost of producing them is less then the 20 to 22<£/gellon reported
by the mejors. There ere recovery units in operation ranging in size
from 20,000 to 100,000 gallons of lube oil per day. Schofield end
deVries (Toronto) is marketing e process for recovering heeting oils,
end Comprino N.V. (Copenhagen) is planning to build 100,000 gellon/dey
units ecross Europe° A 150,000 gellon/dey unit is under plenning for
the reprocessing of industrial westes such es cutting oils, soluble
oils end certain rendering-house fets end oils. The end products
from this new unit will be non-lubriceting oils with e veriety of
industriel epplicetions.
Engine plants of the Ford Motor Compeny et Clevelend5^ recover end
reuse oil from weste weter. The disposel, efficient recovery end
secondary utilization of weste products presented a unique end difficult
challenge to the plents. The output of the 0.8 million gellon/dey
v/este treatment plents consists of clerified weter, e sludge slurry
end skim oil. The sludge slurry from the clerifier is trensferred to
holding legoons for disposel. Soluble oil is manufactured from the
reclaimed oil following the process shown in the accompanying flow
diagrem (Figure 15).
The performance of the reconstituted soluble oil demonstreted
it cennot only metch the performence of the proprietery soluble oils
but also excel in some quelities s-uch es rust protection, non-formation
of "leopard spots", cleenliness end odorlessness. Thus, the recovery
and reuse of what wes once considered e precticelly worthless weste
product wes shown productive end cen bring significent cesh savings.
42
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SOME LEADING OIL-SPILL TREATMENTS
J^eveloper
Alken-Murray
Corp.
New York, N. Y.
American Machine
& Foundry Co.
Stamford, Conn.
American Oil Co.
New York, N.Y.
Cabot Corp.
Boston, Mass.
Cyprus Mines
Corp.
United Sierra
Div.
Trenton, N. J,
Drew.Chemical
Corp.
Marine Div.
New York, N. Y.
Unit Cost &
Estimated
Cost/Gal.
of Oil
Treatment
$3.00/gal.
(250)
Product Name(s),
Composition Action &
Treatment Level
Alken OSD Dispersent, non-
ionic/enionic detergent
mix, in solvent carrier,
emulsifies oil.
Treatment level: 7 to 10%
by volume (higher for
heavy oil in cold seas).
Underwater injection of air
repels oil, debris & trash.
Oil, absorbed in boat- ---
mounted polyethene foem,
is squeezed out.
Ceb-O-Sil, silane-treated $2.00/lb.
silica (collodial) acts (250)
as a wick in thicker oil
spills. Treatment level:
1 to 4% by weight.
Mistron Vapor, micronic $3.50 for a
talc powder for beech 50 Ib. bag.
clean up via agglomeration.
Mistron ZSC, zinc steerete
coated grade designed for
the open see.
Where Used
Offshore dril-
ling rigs; jet
fuel spills;
loading docks
& paper mill
spills.
A Connecticut
beach.
Tests on inland
waters.
Tests on inland
& sea waters.
Ocean Eagle
spill.
Ameroid Oil Spill Emulsi-
fier #1, wetting and emul-
sifying agents in en oil-
soluble liquid.vehicle.
Treatment level: 3 to 5%
by volume.
$2.77-3.257
gal.
Torrey Cenyon,
General Coloco-
tronis
Ocean Eagle
43
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SOME LEADING OIL-SPILL TREATMENTS (Continued")
Developer
Product Neme(s)
Composition Action &
Treatment Level
Economics Lahore- Mix of non-ionic solubili-
tory zers end dispersents in a
Magnus Marine penetrating carrier.
Div. Treatment level: As low as
New York, N.Y. 1/2% by volume.
Unit Cost &•
Estimeted
Cost/Gel.
of Oil
Treatment
$2.00-2.58/
gel. (50)
Where
En jay Chemical
Corp.
Linden, N. J.
Corexit 7664, mix of
proprietary & purchased
food-grade emulsifiers.
Treatment level: As low
es 1 to 296 by volume.
Guardian Chemicel Pyrexon, liquid & powder,
Corp,
Long Island, N.Y,
$3.50-4.00/
gal. (100)
$2.90/lb
(100)
mixed with oil, promotes
burning by wicking end
catalytic oil breakdown.
Polycomplex A-ll, used to
disperse unburned oil.
Treatment level: 13 to
25% by volume.
Midland Silicones Silicone-treated flyesh is $24-36/ton
Ltd. dusted on the spill, sink- (400)
(subsidiary of ing it. Materiel bio-
chemically degrades on sea
bottom. Treatment level:
General
Colocotronis
General Coloco-
tronis, Esso
Essen (Capetown
South Africa) '
Laboratory &
field tests.
Albright &
Wilson)
Lagoon near
Aberthaw
generating
station.
Aberthew, Wales 250/6 by weight.
44
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DE-EMULSIFING
AGENT
SOLUBLE OIL
SKIM OIL
SURGE TANK ••MBW^M SKIM OIL
BATCH
TREATMENT TANK
Oil
O
3D
m
m
o
O
m
oo
PROCESS WATER TO
CLARIFIER
EMULSIFYING
AGENTS
DIRT a WATER
FIGURE 15
RECOVERY OF SOLUBLE OIL FROM RECLAIMED 01 L
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SLUDGE DISPOSAL AND BY-PRODUCT RECOVERY
Sludge handling and dispose! have often been the most trouble-
some espect of weter end waste weter treatment. Disposal of dried
sludge as a fertilizer or soil conditioner has been practiced for
many years. Preservation of organic matter in this fashion has a
greet appeal to conservationists, but the trend is to alternate meth-
ods of disposal because of economics. Usually, the value of sludge
as a fertilizer is limited because the nitrogen, phosphoric acid and
potash content is too low. The organic materiel in sewage sludge does,
however, make it e desirable soil conditioner.
Even though using sludges rather than disposing of them is en
appleudable concept, waste sludge utilization need not necessarily be
profitable, but it could be a means of reducing sludge disposal costs.
Among other factors, market value of by-product and marketing problems
that may be encountered are of prime importance while evaluating by-
product recovery. The market place determines the by-product specifi-
cations and the specifications are rigid involving product purity end
concentrations. The waste sludge processing cost to meet rigid
specifications are very high and, therefore, industries who have
attempted product recovery concluded that it is much easier to sell
or give the material to a refiner who assumes responsibility for its
ultimate disposition.
The recovery of vitamin B-12 from sewage sludge has been fre-
quently discussed in the literature because of its value as a supplement
to animal feeds. Vitamin B-12 has been successfully recovered from
dried, undigested activated sludge in pilot plant studies. Extensive
studies at Milwaukee determined that B-12 is derived, in part, from
raw sewage end pertly from biological synthesis in the activated
sludge aeration tanks. The B-12 production process at Milwaukee
started with the dried waste activated sludge (Mil orgenite) end con-
centrated liquor was extracted following multiple-effect washing .
The liquor was further concentrated to produce B-12. The pilot plent
operation indicated 308 pounds of pure vitamin B-12 could be produced
each year from 70,000 tons per year sludge supply.
The Metropolitan Sanitary District of Greater Chicago, in coopera-
tion with the University of Illinois, studied the value of heat dried
activated sludge as en additive to animal feed6^»^« After feeding
with chicks, pigs, etc., it was concluded that sludge was e success-
ful beneficial additive if limited to a smell percentage of the total
animal feed.
When sewage has a very high grease content end low alkelinity, e
process known as "Miles Acid Process" wes found to be very effective
for extrecting greese from row sewege solids64.
46
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In the case of oil-beering waste waters containing e complex
mixture of lubricating oils, cutting oils, end emulsion coolants
which are either soaps or synthetic detergents, lagooning is the
accepted practice prior to final disposal of the sludge. However,
by the use of ferric chloride and lime, sludge can be settled out as
ferric hydroxide. Recovery of iron coagulant has been shown to be
both feasible and economical65. The recovery is accomplished by re-
dissolving the iron hydroxide sludge with 66° Be1 sulfuric acid end
liberating the absorbed oil. The recovered iron coagulant is in its
sulfate form and reused in treating the waste.
It should be noted here that the cost of disposal is eliminated
by this method in addition to coagulant recovery. On the basis of e
million gallons of waste water, e net reduction in cost of $274 was
achieved by the recovery method as compared to the conventionel
method.
Within recent years, much interest has been directed to removal
of phosphate from treated sewage because of the unsitely and nuisance
growth of algae attributed to the phosphate content of sewage efflu-
ent . Alum has been found to be an effective coagulant end is in
much use by sewage treatment plants. It is anticipated that research
will be directed to recovery processes of aluminum from the hydrous
sludge with phosphate remaining in the residual sludge. By-product
recovery is greatly desired in this case because of the serious prob-
lem of disposing of the alum-floe sludge.
The disposal of sludges resulting from the clerificetion and
softening of raw water at water treatment plants has not been es much
of e problem as waste water sludge disposal, but it is becoming more
critical every dey. Disposal by dilution into surface waters is
simple, inexpensive and acceptable to many state regulatory agencies
without prior treatment. It does not have much effect on the dis-
solved oxygen content of the receiving waters but it can be a nuisance
because it produces turbidity end forms sludge banks.
The water plant sludge has been added to the municipal sewerage
system in many cases. It is believed that the sludge functioned as a
raw sewage flocculent end, thereby, improved the overall sewage treat-
ment efficiency66. However, if the dumping of water plant sludge is
not proportioned over a period of time, it may inhibit biological
treatment processes.
One discernible trend in water plant sludge handling has been the
increased use of recovery techniques. Water works sludge recovery is
generally considered as en alternative solution to disposal only where
lagooning end dilution were not feasible end heuling to distant farm
lend was not economical.
47
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The sludges removed from sedimentation basins consist of a
dilute suspension of aluminum hydroxide among other things such as
elgee end silt. Reclaiming alum from the hydrous sludge end reusing
it for rew water flocculation has been shown feasible. Investiga-
tions in England determined that sulfuric acid could be used to
convert insoluble eluminum hydroxide to aluminum sulfete which could
be reused as a f locculent^. With the decrease in pH, the alum
recovery was found to increase end at a pH of 3, the recovery was
60 to 65%.
At Tampa, Florida68 »^f it was estimated that 1180 pounds of
93% sulfuric acid were needed to produce 2000 pounds of reclaimed
alum (17% A12O3) et a 90% yield. Cost of commercial alum at $38.08
per ton and sulfuric acid et $19.48/ton, it wes estimeted that ebout
$26/ton could be seved by using reclaimed alum. The ebove cost
figures must be modified end interpreted in reletion to the overall
water treatment costs; the recovered flocculent is most likely to
have a lower efficiency than the original commercial alum end require
higher dosages. As recovery is not complete, some commercial alum
must be added.
Recovery of softening-plant sludges can reduce the overall plant
operating costs, but it involves numerous operational problems.
First, magnesium has to be excluded from the sludge and this is achieved
in the centrifuges often et the expense of solids capture efficiency.
Second, split treatment procedures cen be adopted, but neither calcium
cerbonete nor megnesium hydroxide floes settle separately. Third,
dewetering and calcining equipment requires substantial maintenance
end moderate opereting budgets. Fourth, sludge reclemetion often does
not eliminete the need for elternete sludge disposal facilities be-
cause not ell of the sludge is processed. A final disadvantage results
from changing water quality with the seesons. Verieble sludge
quality complicates calcining operations.
More end more water treatment plants ere edopting lime end elum
reclemetion processes end the cost of weter treatment hes been reduced
by verying degrees wherever reclemetion hes been in operation. For
further reduction in cost of operetion, improvement in efficiency,
additional research is needed in this field. When the reclemetion
process becomes more economical then whet it is now, ell the new
plents would be designed with reclemetion fecilities.
48
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HEAT RECOVERY OR UTILIZATION
Environmentel changes due to thermal pollution such es strati-
fied flow, the effects of temperature on the biota, end the effects
of temperature on the physical end chemical properties of our re-
ceiving water ere becoming quite criticel'^. The three major sources
of thermel pollution ere es follows:
1. Steem-genereting industries.
2. Steem and/or power-generating industries.
3. Process streems from wet process industries.
When the tempereture of the weste is very high, heat recovery is
very attractive and practical. When the temperature difference is
reletively small, heat recovery is not practical due to poor economics.
However, there ere e number of companies that have mode equipment
eveileble for the recovery of heet from low tempereture differential
wastes. Therefore, recovery of heat and utilization for more efficient
power generation is feasible and should be practiced wherever possible
in order to eliminate thermal pollution. Numerous cases of heet re-
covery to produce process steem is precticed in the organic end
inorgenic chemical industry.
The other feesible method of controlling thermel pollution is
water quality management . This involves flow regulation, discharge
outfall design and heeU storage with controlled releases. Though
this method does not bring in direct benefits, the cost involved in
weter quality menegement works would be much less then the construction
of conventionel cooling towers, ponds end so on.
The method thet offers the greatest promise for thermel pollution control
besides heat recovery is the utilization of weste heet in egriculture,
aquiculture or for miscelleneous industrial epplicetions. There ere e
number of FWPCA studies under way on this espect7^
The present trend in the thermel pollution control seems to be
thet the cooling towers end ponds must be used only where no other
solution is eveileble, end efforts to devise other more productive
methods of heet control end recovery will be underteken in the future.
49
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MISCELLANEOUS INDUSTRIES
Breweries end Distilleries
In the brewing industry, settled yeast from a previous fermen-
tation is used in the fermenting of beer to initiate fermentation in
the next batch. There is always an excess of yeest above the re-
quirements of the brewery end only pert of this yeast is satisfactory
for further use in the brewery as the yeast, while settling, carries
down some materials that are not desirable in beer. The undesirable
part of yeest is generally discharged to the sewer. Though it is not
harmful to plant operation, it has a very high BOD end becomes ob-
jectionable. This product could, however, be dried end used for
cattle feed.
Distilleries discharge their wastes from molasses fermentation
to the sewers or receiving waters. When this waste is evaporated and
dried, it was found to be en excellent source of vitamin B complex
end showed a substantial profit above the cost of evaporation end
drying for use in producing cattle feeds.
Wastes from brewery and distillery fermentation have been con-
verted to valuable by-products for many years. The two major
by-products are high-priced animal feed end brewer's yeast. Spent
grain mash used to be a serious water pollution problem, but the
distilling industries have recovered more than 9O% of their fermen-
tation residues for sale es animal feed . The residue has a high
concentretion of vitamins end protein that, when mixed with other
materials, mekes a premium cattle feed.
Residual yeest from brewery and distillery fermentation is also
valuable ss on enimal feed because it contains vitamin B complex,
protein and essential minerals. Drying stabilizes the residual
yeest by deactivating the enzymes in addition to improving the yeast's
digestebility. However, it is believed that a brewery must have at
ieast about one million pounds of yeest solids per year to justify
drying equipment.
The process of manufacturing terteric acid and terterate salts
from winery wastes during World War II is considered uneconomical
now74. The pomace portion of the waste has been used as a vineyard
soil conditioner or sometimes dehydrated and sold as a cattle feed
supplement and plant mulch.
Food Industries
The food-processing industries have been faced with the reali-
zation that both water supply end waste disposal ere limiting factors
50
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in growth, operation, end product cost. Water-saving techniques
have, in many cases, permitted increases in plant capacity without
additional burden on fixed resources. In some cases, these heve
brought significant savings in total production expense.
Where water conservation is practiced, there are concomitant
changes in waste quantity and character. With increased production,
the total organic waste load has inexorably risen end the problems
attendant to disposal have become increasingly difficult to solve.
Process advances have produced some new waste constituents end weter
economics have resulted in concentration of waste loads in certain
process streams.
Faced with a general expansion in the potential waste load
which must be treated or transferred to receiving waters, regulatory
authorities heve been forced to tighten controls end stimulete in-
dustry's critical examination of its contribution to the pollution
problem. Municipalities which receive the wastes of their allied
industries assume responsibility for augmenting treatment capecity
end impose the industries with service charges to transfer costs of
expended facilities and operation.
The seasonal character of wastes from the food-processing in-
dustries and their relatively high proportion might suggest that it
might be more economical to treat the separate components rether then
the combined flows. Industries, in seeking weys to reduce costs,
ere becoming increasingly ewere of their responsibilities in pollu-
tion control and have begun to explore the economic feasibility of
"in-plent" modifications to reduce waste end of "on-site" facilities
to provide treatment.
The state of the art in food processing plants appears to involve
continuous recirculetion of waters with limited make-up end blow-
down for a particuler subprocess. For exemple, in the conning industry,
wash waters for most produce cen be continuously recycled within en
optimum system. Final rinsing removes the residual dirty weter end
this serves es meke-up for the initial scrub washing subprocesses.
Similerly, flume weter used for the cerriege of fruits end vegetebles
is continuously recycled end builds up e high organic content. Low
pH and eppropriete bectericides cen be used es a means to control
bacterial growth.
Cooling tower recirculetion is e common method of conserving
water. The cooling tower blow-down can be used for supply water with
the verious subprocesses of the packing plant. Eveporetor waters
may be reused for processes, especielly initiel weshing, etc. The
increesing costs of weter and sewer service charges based on flow
volume and pollution content, ere ecting es incentives to optimize
the conservetion end reuse of water within the food-processing industry.
Recent surveys of eleven Californie cenneries^S indicate that weter
51
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conservation and reuse cen reduce water use per unit of product up
to 40%. The sludge from the food industries is a major concern to
the industries because of high moisture and fibre content plus a
lack of stability which complicates storage of the seasonal pro-
duction. However, the industries have shown keen interest in using
waste products to increase profits end reduce air and water pollution.
The use of waste activated sludge from the citrus industry has
been evaluated as a source of vitamin B and protein. Vitamins of
the B group contained in this sludge include: thiamin, B-12,
riboflevin end niecin^o. After the sludge is filtered, dried and
pulverized, it is used as an animal feed supplement.
Citrus pulp has been extensively used by itself as a cattle
feed. After dehydration, the pulp has been sold for $30 to $45
per ton ' . Without dehydration, citrus wastes have been sold as
cattle feed for $4 per ton or converted to molasses and sold for
$45 per ton. Pectin is also made from citrus wastes and used in
jams end jellies.
The disposal of wet solids from the canning industry has been a
major problem. Composting has been investigated end seems promising.
A portion of the total canning waste has been dehydrated and used for
animal feed'^. The total cost of producing this feed was reported to
be $47 to $53 per ton of feed. Even though there is a net cost to
the industry, the by-product utilization is cheeper than other methods
of disposal.
flo
The potato processing pulp is used es a cettle feed . Deweter-
ing end drying of pulp is difficult beceuse the solids ere hydrophilic,
In large plents, the 5 to 13% solids pulp is dewatered to 30 to 35%
solids by pressure filtration after conditioning the pulp with lime.
In en attempt to keep the peels away from weter-borne wastes, dry-
ceustic peeling process is used. In this process, potatoes are
sprayed for 50 to 100 seconds with 20% lye solution at 170° F. end
drained. Then potatoes ere subjected to infrared heet for 2 to 5
minutes following the holding at room tempereture for 5 minutes. The
peels ere removed in the rotating rolls and during tumbling. The
discorded peels ere sold es cattle feed.
Pressure on food end pulp process has generated a parede of re-
cent processes to upgrade liquid end solid westes. The impetus behind
this flurry of activity is the need to find doller incentives for
pollution prevention. Leeding emong the new processes ere those that
use yeast, bacteria and even laser beems to convert pollutant beans
into edible products. Swedish Suger Company82 hes announced a process
thet will treet e poteto-starch filled waste stream with a symbiotic
combination of endomicopsis end candide yeests. The end product
suitable as animal feed is 50% protein, a mix of 95% Candida yeast
and 5% endomicopsis.
52
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The wastes produced in this industry are largely organic end
of a highly biodegradable nature. Therefore, product recovery is
very much limited. However, solid wastes, in a few instances, have
been utilized in many ways. Tomatoes have been pressed and dehy-
drated for use as hog or cattle feed. Pee vines, corn husks end
corn cobs have also had limited sales. Citrus peel wastes may be
pressed for molasses which can be processed, dried and sold as cattle
feed. Installation of flash evaporators to produce the molasses has
significantly reduced the waste load discharged. Also, certain types
of pits end nut shells have been converted to charcoal.
Due to the low value of these by-products, the primary benefit
to the food industries at this time is the avoidance of the cost of
hauling wastes to a landfill. With the increase in cost for solid
waste disposal, it is anticipated that new by-products will be de-
veloped. It should be noted here that there is a definite indication
that many of the small firms ere herd pressed to compete and the
percentage of small firms will decrease in the future, as a result.
The principal difference between old, prevalent and newer technology
in these industries is not in the operational sequence, but rather
in the speed and efficiency of the machinery performing the opera-
tions. New production machinery is expensive and can be justified
by adequate production volume only.
Fertilizer Industry
The phosphoric fertilizer industry is faced with a difficult
task of improving its gaseous effluents. Fluoride-containing gases
are produced from the reactors and evaporators and collected by using
sprey boxes, wet impingement, wet-centrifugal sprey end wet-impingement
tray scrubbers. The fluoride content of these liquors, present as hy-
drofluosilicic acid (^SiFs), represents a problem and an opportunity.
The fluoride evolved during wet acid, phosphoric acid, superphosphate
end triple superphosphate production in the United States is equiva-
lent to the total United States production of hydrofluoric acid.
Hydrogen fluoride is the source of fluorine compounds used in the
production of aluminum, fluorocarbons end other chemicals. The availa-
bility of high grade fluorspar ore, the main source of hydrofluoric
acid, is limited and these liquors .represent an increasingly important
source of fluorine. The hydrofluoric acid, 25% in concentration, can
be used as fluorinating agent for public water supplies and may be
converted into sodium silicofluoride for both this purpose and for
ceramics end gloss menufecture. Hydrofluosilicic acid has been
suggested as a fluorinating agent end the use of strong dehydrating
and decomposing agents for producing hydrofluoric ecid from
fluosilicic ecid hes also been studied.
In the recent years, attention hes centered on conversion of
hydrogen fluoride synthetic cryolite (Na3AlF6) or aluminum fluoride (A1F3)
53
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for use in Hell cells. There ere two commerciel routes of
conversion:
1. The ecid is contacted with en elkali such es emmonie to
produce the elkeli fluoride end e filterable powdered silica
thet cen be marketed for use es e thickening agent, for
rubber end plastic additives end for other purposes. The
elkeli fluoride is reacted with en eluminum selt to produce
the elkali cryolite which may be converted to sodium cryo-
lite by fusion with e sodium selt .
2. The ecid is reacted with eluminum hydroxide {^1(OH);TJ to
produce eluminum fluoride (AlFs) end silice
In the ammonium phosphate plant, the exhaust air stream from
ammonietor contains high ammonia and, therefore, it is recovered by
using acid stream scrubbers from both economical and e pollution
control point of view. The initiel cost end opereting expenses for
such instelletions ere very high end the returns from the recovery
of emmonie are just enough to compensate for operating cost. Therefore,
fertilizer industries are generally reluctent to install such systems
thet cover only opereting expenses. However, industries do expend
lerge cepitel outleys in order to reduce compleints end improve
public reletions.
Most of the fluoride westes effluents from the fertilizer industry
ere aqueous type end some ere airborne. The eirborne fluoride com-
pounds become weterborne when they heve been scrubbed with weter or
with aqueous alkeline reegents.
When product recovery is not practiced, due to the small quantity
of waste or too low e concentretion for recovery, the waste is treated
end discharged to receiving weter course or sewer. The treatment
facilities essentially involve the following steps:
1. neutralizetion of weste water with hydreted lime at a pH
value slightly above 11, which results in the formation of
relatively insoluble calcium fluoride,
2. separation of the insoluble product of the reaction in a
continuous clerifier,
3. vacuum filtration of the sludge, end
4. acidif icetion of the clerifier effluent to lower the pH value
to within the range of seven to nine .
Clarified effluents contain less than 20 mg/1 of fluoride ion
end by allowing it to stand for several hours, post precipitation of
54
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fluoride salt occurs resulting in the further decrease in the
fluoride concentration. Where required, additional fluoride removal
may be obtained by passage of the fluoride waste through a bed of
activated alumina regenerated with sulfuric acid or through bone
char regenerated with sodium hydroxide.
The other important by-product from sulfuric acid-based phosphoric
acid plants is gypsum (CaSC>4) which has been used in wallboard end
cement and for the production of sulfur vie reduction with coal,
followed by fixing of the lime--either with silica or by reaction with
ammonia . Such practices ere in use in sulfur-short locations end
may become less attractive as the sulfur supply situation improves.
Gypsum, derived from the production of wet process phosphoric
acid poses major problems because it does not have a good market.
Storing of gypsum is practiced in some cases and this is becoming
expensive because of the increasing land value.
At 1969 production level, on en average of 5 tons gypsum/ton of
10096 phosphorus pentoxide, about 20 million tons of gypsum ere pro-
duced per year. There ere seven major plants throughout the world
which practice recovery of sulfuric acid end cement. Following this
process, it is forecasted86 that 1500 to 2000 tons of sulfuric acid per
day end about the same amount of cement can be recovered and there will
be e $25 to $30 million market per year. Such e recovery process solves
not only the gypsum disposal problem but also alleviates the pressures
of rising costs of sulfuric acid.
R7
A new process developed in West Germany involves recrystellize-
tion under controlled conditions by the addition of certain compounds.
The product can be dried and sold to e plaster of paris distributor
or directly cast as plaster board or construction blocks. The final
product from the synthetic gypsum compares favorably with most pro-
ducts made from natural gypsum. In addition, the requirements for
labor, space end utilities are very much less.
In order to conserve the sulfur or sulfuric acid, nitric acid
is used in the digestion of phosphate rock. Phosphoric acid (HsPO^),
calcium nitrate (pa(N03)^J end hydrofluoric acid (HF) are formed in
this process"^ and the unwanted calcium nitrate is precipitated as
gypsum by adding ammonium sulfate ^^4)2804] . The latter is regenera-
ted end reused by treating the gypsum with carbon dioxide and ammonia
and thus sulfe;t« recycle is accomplished. Ammonie remeins in solution
0s emmonium nitrate, e fertilizer ingredient.
Sulfur shortege hes sperkcd renewed interest in nitric acid
treatment of phosphate rock®" to produce fertilizers. There ere a
number of processes available. Nonsulfur-consuming nitrophosphete
generally involves larger investments but smeller operating costs
than the sulfur-consuming processes.
55
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Use of gypsum for sulfur production to fill the sulfur gas is
being studied^ by variations of standard ore-winning techniques or
bacteriological digestion methods. These studies are directed to
produce sulfuric acid or ammonium sulfate. In the wet process for
phosphoric acid production, production of uniform gypsum crystals
permits fast filtration, minimum seeling end modest requirements for
site space, power and maintenance. Therefore, it was possible to
cut down the capital and operating cost by 15%.
Nitrophosphate processes, which use nitric acid to dissolve
phosphate rock, are becoming increasingly popular as a result of the
current sulfur shortage. A Norwegian firm ^1 nes mede major improve-
ments in this field end is producing a wide range of fertilizers with
high water solubility.
Dorr-Oliver has come out with a process that uses sulfuric acid
eciduletion of phosphate rock without appreciable consumption of
sulfur. Instead of letting sulfur out as gypsum, the new process
converts gypsum into calcium carbonate (CeCOo) end reacts co-product
ammonium sulfate yNH4)2S04| with fluorosilicic acid vapor derived
from the phosphate rock to generate sulfuric acid for recycle to the
rock eciduletion step.
Animal Products
Meat-pecking industry is a major one in this category and includes
the following:
1. Slaughtering plant.
2. Meat-pecking plant.
3. Meat-processing plant.
A slaughtering plant is a killing end dressing plant which does
almost no processing of by-products. A meat-pecking plant is both a
slaughtering house end e meat-processing plant. Packing houses involve
cooking, curing, manufacture of sausage, rendering of inedible fats
into greases end many others. A meat-processing plent does no slaughter.
ing at all.
The fundamental industry processes ere shown in Figure 16. Blood
is one of the major sources of BOD and, therefore, the recovery of
blood is en important subprocess to the process of killing. Fail-
ure to recover blood increases the BOD by 72%. It is estimated that
about 9696 of the meet-pecking industry is practicing blood re-
covery. Blood can be concentrated or dried end utilized in feeds
56
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lUVE ANIMALS
CO
O
3D
CO
CO
O
O
KILLING
BLOOD
HIDE REMOVAL
j. .» ^ — i ^ -
HOG DEHAIRIN6
I HIDES
1
I
1
I
— **t i
EVISCERATION
BY -PRODUCTS
PAUNCH REMOVAL
I I
1
H
EDIBLE RENDERING
LARDS AND
EDIBLE TALLOWS
---- 1
i
INEDIBLE RENDER1N0
BONING AND CUTTING
SAUSAGE
INEDIBLE TALLOWS
GREASES, TANKAGE
FRESH MEAT
SCRAPS
FIGURE 16
BASIC PROCESSES IN MEAT PACKING INDUSTRY
POLLUTION
O
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92
end fertilizers .*
Hairs of hogs are removed by mechanical scrapers end they ere
sold, hauled to offsite disposal or dissolved in caustic solution.
The trend seems to be toward sale because it can be used in the manu-
facture of foam rubber and felt. In summer, when the hair and
bristles are short, they are disposed of at the incinerator as they
ere of little value.
Viscera are removed and distributed to the proper channels
depending upon whether they will become en edible or inedible product,
Rendering process is of two types: edible and inedible render-
ing. In the edible rendering, fats are converted into lard and
edible tallow. Edible rendering is applied primarily to hog fats,
but also to some beef fat. In the inedible rendering scraps,
trimmings, and inedible organs ere converted into inedible fats
which are used in soap, in the manufacture of grease end in animal
feeds. Inedible rendering also provides an outlet for those parts
of en animal which have been condemned by federal meet inspectors.
Through rendering, condemned material is sterilized and converted
into recoverable products. In recent years, the disposal of paunch
manure is a vexing problem. Paunch manure contains very little fat
and a large quantity of partially digested materiel. The paunch
content of cattle is estimated at 4O to 60 pounds per head end con-
tains about 1/3 pound of BOD93. In most cases, paunch solids ere
disposed of directly to fanners as fertilizer or as lend fill.
Scraps generated in the manufacture of sausage ere used in the
rendering process. Grease and fats recovered in meat processing are
valuable raw materials for soaps, gelatin and glue.
The wastes from industries producing fatty acids and glycerine
contain a large amount of grease. Improper design of interceptors
result in the discharge of a large fraction of grease. It was shown
in many cases that by recovering the grease through the installation
of proper interceptors that the yield can be increased by about 3S£
end the problems connected with sewer clogging, treatment process
upset ere solved satisfactorily.
In the wool pulling end wool scouring industry, valuable sheep
skins end wool fibres have been recovered by the provision of proper
screening errengement.
*If the protein values of the feed end fertilizer ingredients produced
at the plant ere higher then the requirements of the particular fer-
tilizer being produced, some quantities of lower grade materials ere
sometimes blended with these materials.
58
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The major concern in the poultry waste disposal is the high
concentration of solids end fat. Centrifugal solid separators ere
used for the recovery of high solids end fet. An approximate
materials balance of the system^ indicates that at a waste input
of 3200 gph, about 400 pounds per hour of solids ere removed and
125 pounds per hour of fet recovered. The insolubles content of the
influent wes reduced from 10,000 rog/1, or higher, to 1500 mg/1. The
fet content wes reduced from 0.9% to 0.04%. The fet, thus recovered,
is used in the dog food manufacturing process end solid matter disposed
of at locel rendering concerns. The returns from the by-products
ere ebove the opereting costs end the recovery system proved economicel.
In erees where there are no rendering firms, the by-products are
removed from the gross pollution load of the plant and are given free
in exchange for heuling them ewey.
In the leather tanning end finishing industry, very little weter
is reused. It eppeers thet the practice of weter reuse es e pollu-
tion reduction meesure has been neglected in the everege industry.
The methods thet could be used to reduce the quentity of process
weter ere es follows:
1. Use of countercurrent washing techniques.
2. Cleen-up end reuse of process weters.
3. Wash sprays instead of baths.
4. Automatic controls on process weter.
5. Dry weste disposel instead of weter cerriege.
The following chert deteils normel by-product utilizetion in e
tennery^.
59
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Item
Trimmings, bellies
and others
Hair
Fleshings
Degreosing exhaust
Drum liquors
Spent lime liquors
Pickle solution wastes
Chrome ten liquors
Spent vegetable fens
Spent ten bark
Use
Used for edible purposes, oil production
after rendering, protein feed after render-
ing and gelatin manufacture
Used in manufacturing, upholstering end
rug backing
Glues
Reuse of solvent in tanning, soap
After settling, the sludge can be mixed
with other plant wastes end sold es
fertilizer
In the past, this solution has been reused
within the tannery for pickling a number of
times. However, tendency of late has been
to omit this reuse through advent of drum
bete, pickling end chrome tenning
e) Holding end reusing in tennery
b) Precipitete chromium hydroxide n?r(OH)7],
filter redissolve chromium with sulfuric
acid. Considered economically
imprecticel
Bveporeted end sold as boiler compounds
Used es floor coverings for horse shows,
circuses, playground. Sometimes used in
peperboard manufacturing or in making
white lead
60
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Organic Chemicals Industry
In the organic chemicals industries, the wastes produced ere
high in COD and their treetability varies from treatable to most
difficult to treat. These wastes contain valuable by-products end
these ere recovered^.
New technology end process changes ere, in general, directed
towards better yield end, thereby, reduction in waste load. In cases
where the by-product is valuable, product recovery is always
practiced.
The organic chemicals industry is a complex one due to the
number of products end processes utilized in the industry. All of
these plants practice product recovery end weste reduction in one
form or the other. To include all of them will be too elaborate and,
therefore, the major ones are included here.
1. Aceteldehyde
Acetaldehyde is produced by the Wacker process end waste
discharge averages 1200 gallons per ton of product. The
waste contains primarily chlorinated aldehydes and the COD
is in the range of 10,000 mg/1. The waste is difficult to
treat biologically unless it is diluted with other waters.
Generally, several facilities handle these wastes by means
of a deep well rather then by biological treatment.
The waste discharge is reduced to 150 to 200 gellons/ton of
product by suitable changes in the still design for finel
disposal either through deep well injection or incineretion.
In the concentration process, there is no reduction in the
organic load and, therefore, the only possible means of re-
ducing the organic load is recovery end use of the chlori-
nated aldehydes, dechlorinetion of the aldehydes or
improvements in yield. The present trend seems to be in the
emphasis on the improvements in yield and recovery and it is
expected thet the average yield will reach 9796 in five years
thereby reducing organic loading by about 40%.
2. Acetic Acid end Anhydride
Light petroleum gas (LPG) oxidation results in the production
of substantial amounts of other acids such as formic and
propionic which must be disposed of by incineration, resale
or biological oxidation. Unfortunately, resale of these
materials does not appear to be practical because the markets
for these chemicals are quite limited. Waste flow from this
system is in the order of 1000 gallons/ton of product end
the organic concentrations are in excess of 30,000 mg/1. In
61
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some operations, the stream is neutralized with caustic end
the sodium salts of the acid ere recovered.
Acetic acid and other higher acids ere produced by oxidation
of eceteldehyde. Water flows are of the same magnitude,
but organic load is about 50% of the load generated by the
oxidation of LPG. The Reppe process is another process for
the production of propionic end other acids end the liquid
weste emounts to about 50 gellons per ton of product includ-
ing drains. The emounts and character of the waste would not
appeer to create serious weste treetment problems or expendi-
tures. There will be improvements in the yield picture which
will essist in reducing the waste management problems but it
is not anticipated that eny changes will radically change
the waste situation.
3. Acetylene
The key fector in weste menegement in the production of
ecetylene from hydrocarbons centers around the control of
the cracking furnaces to maximize the production of velueble
products. The efficiencies ere generelly low--in the order
of 40 to 50%--end efficiency improvements ere therefore vital
to the reduction of pollution load. Further, recoveries of
weste products in burnable form is also vital to the effective
operation of the unit. In some cases, a solvent is used to
recover the ecetylene. As solvent losses ere usuelly signifi-
cent, careful selection of the solvent end improved design of
the vacuum stripper would essist in reducing the pollutionel
load.
4. Ammonia
The raejor streems arising from en emmonie plant ere process
condensate end site drains. The weste flow is 300 gallon/ton
of product and ammonia lost in weste stream is 0.1 Ib/ton of
product. Removal of ammonia from waste streems is a necessity
to eliminate eutrophicetion problems end recovery of ammonia
has been proven practical. By air stripping of the waste
after adjusting the pH with NeOH (about 0.1 Ib/ton of product),
it wes possible to reduce the ammonia loss by about 60%. It
is possible to remove greater emounts of NHg (90 to 95%) by
increasing the eir flow in the range of 500 to 1000 scf/gal.,
but such en approach is not economical.
5. Carbon Tetrachloride and Other Chlorinated Hydrocarbons
The major weste stream results from the production of hydro-
gen chloride as a by-product of the reaction. There is a
greet need for routes to the economic recovery of chlorine
-------
from hydrogen chloride or through the reuse of hydrogen
chloride. A number of new oxychlorinetion processes have
recently been developed which enable the user to utilize
hydrogen chloride together with chlorine in a balanced
facility. As an example, for the production of carbon
tetrachloride (CC14) :
CH4 + 2C12 --------- *CC14 + 2H2
CH4 + 4HC1 + 02 ----- >CC14 + 2H20
This approach eliminates the problem of hydrogen chloride
(HC1) , but does produce about 60 gallons of waste containing
minor amounts of chlorinated methanes and HC I/ton of product.
It is anticipated that, in the future, process changes will
substantially eliminate the HC1 being generated in these
operations.
6. Cellulose Acetate
Major waste source arises from the stills used to recover
acetic acid, acetone and other solvents. In addition,
considerable amounts of degraded cellulose, phosphates (used
as catalyst) end sulfuric acid (from spills) are generated.
There are numerous opportunities for waste reduction in cellu-
lose acetate production end the more important ones ere the
following :
a) Recovery and reuse of CA fines.
b) Improvements to achieve higher yields on cellulose.
c) Improved operation of acetone end acetic acid stills.
d) Use of additional stills to improve recovery.
7 . Ethylene
In the production of ethylene, about 15 gallons of waste/ton
of product are generated and this contains 2.5% sodium hydroxide
(NaOH) , 1% sodium sulfide (Na2S) end 6.696 of phenols. Studies
are underway to recover the alkali value from the spent caustic.
There are no attempts at present for the recovery of sulfides
but sulfide oxidation is generally practiced to reduce the
immediate oxygen demand of this stream.
The process condensate stream may be reprocessed by being sent
to a stripper end stripped by live steam. This will strip
most of the non-phenol contaminants and about 20 to 2556 of
phenol. By contacting with fresh feed, it is possible to
strip out most of the phenol which can be sent with the feed
63
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to the cracking furnace. The phenol-free waste water can
be steam stripped to remove residual volatile hydrocarbons.
The water stream, free of contaminants may be reused in
steam generation in the plant.
The major products in the ethylene plants besides ethylene
are propylene, low density polyethylene end alfa olefins.
Spilled pellets end fluffs of polyethylene constitute a
major pollution problem because of its unsightliness and re-
duction in the rate of oxygen transfer. A surface drainage
separator with a basin and a baffle extending three feet
below the water surface is used to trap the polyethylene.
The trapped polyethylene is sent eventually to land fill
for disposal.
Handling of quench water which constitutes 30% of the totel
plant effluent is difficult because it contains 1000 to
10,000 mg/1 of oil in addition to finely divided coke end
heavy tars. A pert of the aromatic distillate co-produced
in the plant as a solvent is used to extract the oil. The
water is separated from the solvent-oil mixture, filtered,
degassed to remove hydrocarbon gases end sent to a surge
tank. This water is used for cooling water make-up, which
accounts for 10 to 15% of the cooling water for the plant.
8. Phenol
Major quantities of aqueous wastes containing organics end
inorganics create considerable difficulties relative to waste
treatment. A typical 100,000,000 Ib/yeer phenol plant based
on cumene produces a stream of 200,000 gpd of waste water
containing 13,200 mg/1 COD and 180 mg/1 of phenol. Inorganics
are produced at the following rates:
Sodium carbonete - 5,000 Ib/dey
Sodium formate - 500 Ib/day
Sodium bicarbonate - 500 Ib/dey
Sodium sulfete - 22,000 Ib/dey
The waste production from the direct oxidation facility might
be considerably less then the older process.
The following ere precticed to reduce the waste load:
a) Careful control and modificetion of the process involved.
b) Recovery of inorganics by crystallization.
c) Recovery of phenol by solvent extraction.
64
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As the sulfonetion and chlorinetion approaches are reduced
in importance, it is likely that the amount of waste genera-
ted per pound of phenol produced will be greatly reduced.
9. Urea
All of the major processes involve the high pressure re-
action of CO_ and ammonia. Typical wastes amount to about
120 gallons/ton of product with the following composition:
lb/ton
Ammonia (NHg) 3.6
Carbon dioxide (C02) 0.6
Urea (NHgCONH-) 0.8
Ammonium carbamate (NH^CO NH2) 0.1
Total 5.1
It is normal practice to remove about 50% of the ammonia by
eirstripping after adjusting pH with alkali. Recently, two
new processes have been developed which strip the ammonia
end carbamete by contacting with either NH3 or CO,, end
sending the overload to the reactor. This approach reduces
ammonia losses by 50% or more with a more drastic effect on
carbonate.
10. Production of Chlorine from Hydrochloric Acid
In the conventional electrolysis process for producing Cl?,
1.13 tons of NaOH ere produced for every ton of chlorine
produced. There is a greater demand for chlorine compered
to NaOH end, therefore, there exists a chlorine-ceustic im-
belence. In order to avoid the imbalance, e new process
celled "KEL-CHLOR" has been developed by the Kallogg Company
from the Deacon process and this process shows the possibility
of making chlorine compounds. Hydrochloric acid produced es
by-product in industries end not utilized mey be used for
the efficient end economic production of chlorine.
The following is e list of sources for HC1:
e) Production of HC1 from inorgenic sources.
b) Orgenic chlorinetion produces HC1 es e by-product.
c) MgClg can be hydrolyzed by hot steam to give MgO end HC1.
65
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d) Ammonium chloride, a by-product of the Solvey process,
con be dissociated to NH^ and HC1 end the two separated
by a suitable method.
e) Hergreaves process, which uses SC>2 and air instead of
H2^(-)4> could be used to produce HC1 from NaCl.
f) When KC1 is converted to potassium phosphate end nitrogen
oxides in order to eliminate plesmolysis of the plants,
HC1 is produced as a by-product.
The process is shown in Figure 17 end, in this process, HC1
is oxidized by pure oxygen in the presence of oxides of
nitrogen which act as catalysts. H2S04 is used as a catalyst
carrier to absorb water. Employing this process, the pollu-
tion problems associated with small producers of by-product
HC1 can be alleviated. The chlorine from these smell units
would be smell in amount and might not be competitive in the
market place, but it could be used internally.
The economics of the Kel-Chlor process keep improving as the
plant increases in size. Capital cost requirements go up
approximately as the six-tenths power of the capacity. The
by-product HC1 from a series of different chlorinetion steps
can be combined to provide feed for the Kel-Chlor plant. In
summary, this new process can improve the economics of making
chlorine compounds end has the possibility of making chlorine
on a large scale by non-electrolytic methods. It can also
alleviate the problem of caustic-chlorine imbalance and ad-
just caustic production to market requirements. It is also
hoped that the economics of chlorination will be considerably
improved end this should promote the use of chlorine com-
pounds in the competition of markets such as replacing glass
containers by copolymer of propylene end vinyl chlorine.
11. Anhydrous Hydrochloric Acid from Chlorinated Organic Waste
A variety of chlorinated organic residues ere left behind
as unwanted co-products after the manufacture of some big-
volume chemical products. Examples: ethylene dichloride
from vinyl chloride, benzene hexechloride from some insecti-
cides, tetrechloro-ethylene from herbicides, and dichloro-
propylene from propylene glycol, chlorinated elastomers end
nylon. The disposal of these wastes is a difficult problem
and the methods already tried include: deep-well injection
ocean dumping, burning in open pits, lagooning, and burying.
Disposal in deep wells is expensive and has hazards in some
form or the other. Because of the toxic fumes emitted,
open-pit burning of these wastes has been forbidden in several
66
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cl2(02,HCI)
ABSORBER AND
<£ OXIOIZER
FIGURE 17
FLOW DIAGRAM OF KEL-CHLQR
PROCESS
67
IESOURCE ENGINEERING ASSOCIATES, INC.
-------
states. Thus, there is a pressing problem of disposing of
the one billion pounds of waste generated each year in the
United States in the production of chlorinated orgenics.
97
Union Carbide's incineration - scrubbing system .shown in
Figure 18, is recovering 99% of the HC1 formed in the
incinerator es 18° Be". Alternatively, Carbide offers a
unit with e stripping system to convert the product acid
into anhydrous HC1. In either case, the venting gas stream
will conform to most state regulations; and with additional
scrubbing stations, its HC1 content can be slashed from
1000 mg/1 down to 50 mg/1. The operating costs are estimated
at about 10£/gal., in the upper limit of the 5 to 10£/gel.
range of conventional disposal costs. However, the system
has the advantage of producing e saleable by-product in
addition to meeting the anti-pollution requirements.
Table T summarizes by-product recovery in the organic chemicals
industry.
68
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CHLORINATED
WASTE RESIDUE
INCINERATOR
GRAPHITE
HUMIDIFYING
TOWER
PRIMARY
FALLING FILM
ABSORBER
ANYHYDROUS HCI
ENTRAPMENT
SEPARATOR
BRINE
CONDENSER
WATER
CONDENSER
FIGURE 18
SECONDARY
FALLING FILM
ABSORBER
TERTIARY
FALLING FILM
ABSORBER
t
MAKE UP LIQUOR
PRODUCT
ACID
FALLING FILM
STRIPPER
BOTTOMS
COOLER
ACID
21% STRIPPER
STORAGE
INCINERATION- SCRUBBING SYSTEM (UNION CARBIDE)
O
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TABLE V
BY-PRODUCT
RBCOVERY IN THE
ORGANIC CHEMICALS INDUSTRY
By-Product Recovery
Process
Aceteldehyde
Acetic acid
Acetylene
Ammonia
Carbon tetra-
chloride
Cellulose
acetate
Ethylene
Phenol
Urea
By-Product
Acetaldehyde
Formic & Pro-
pionic acid
Solvent
Ammonia
Chlorine
Cellulose
fines
Caustic
Sodium carbo-
nate
Sodium formate
Sodium bicar-
bonate
Sodium sulfate
Ammonia
Urea
Ammonium cer-
Quantity
5 lbs/100 Ibs
200 Ib/ton
lOlb/ton
0.1 Ib/ton
0.4 Ib/lb
0.1 Ib/lb
2 Ib/ton
2 Ib/ton
0.2 Ib/ton
0.2 Ib/ton
8 Ib/ton
3.6 Ib/ton
0.8 Ib/ton
0.1 J.b/ton
Value
$0.50
$20.00
$5.00-10.00
Negligible
1.2
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Textile Industry
The textile industry, as a whole, is e major factor in the
American economy. The finishing operation of the textile industry
produces e large amount of liquid wastes containing pollutants. Due
to the tremendous growth rate in this industry, it is anticipated that
more efficient manufacturing processes will be utilized, a larger
percentage of the waste will be treated due to the increased pressure
by regulatory agencies at all levels.
Process water reuse end recovery of by-products ere the two mejor
attempts being made in this industry in addition to process modifi-
cations to reduce pollution load end increase the economy.
The textile industry is grouped in three mejor categories for
convenience:
1. Wool weaving end finishing.
2. Cotton textile finishing.
3. Synthetic textile finishing.
In the wool weaving end finishing industry, epproximetely 5%
of its process water is reused. It is anticipated that countercurrent
scouring can reduce the amount of water required by as much as
6000 gel./lOOO Ib of wool end use of rinse waters in the wash after fulling
can reduce water requirement by 4000 gal./lOOO Ib of wool^ . By-
product recovery is limited because of the poor market for the products
recovered. It is estimated that fifty to one hundred thousand tons of
wool grease end 20,000 to 40,000 tons of suint could be recovered for
production of lanolin end potesh from wool end grease, respectively.
In the cotton textile industry, ebout 16% of the process weter is
reused. It appears that the process weter reused will increese in the
future beceuse newer machinery is often of continuous or counter-
current design. Also, beceuse process weter is becoming more expensive
in meny areas, increased emphasis for reuse of process water is made.
There is no significant by-product use of wastes in this industry.
Meny ettempts heve been mede in the pest to develop economicelly
feesible methods for recovery of the expensive dyeing compounds but
were unsuccessful. It is not hoped, in the foreseeeble future, that
eny by-product be recovered for use on eny significent scele.
About 10% of its process weter is reused in the synthetic textile
finishing industry. Even though there eppeers to be en edequete mer-
ket for westes recleimed in this industry, there ere no econoroicelly
feesible methods eveilable now. All liquid westes contain chemicels
used in the finishing itself end could be reused if recleimed. All
71
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carriers are recovered and reused. Chemicals such as spent developed
dye bath are not reclaimed as it is not economical. In the future,
thermal wastes can be reused by heat transfer method.
Mercerizing of cotton yarn (treating with concentrated solutions
of sodium hydroxide), results in a waste containing about 2% sodium
hydroxide. This represents an important loss of this valuable chemical
because of the relatively high chemical costs. Also, the alkalinity
of the waste was very high requiring increased consumption of alum.
In a textile mill in Argentine^, the waste stream containing
sodium hydroxide was segregated end sodium hydroxide recovered by
subjecting the waste to physical processes. Filtration of the waste
prior to evaporation and two-stage evaporation were found to cause
corrosion problems due to high temperatures. In the first stage of
evaporation, the unit works at atmospheric pressure and, in the second
stage at 25 in. Hg vacuum. The average concentration at the end of
each stage is 5.2 and 25.096 by weight, respectively. The concentrated
sodium hydroxide is filtered through a pressure filter and stored for
reuse. The main goal of recovery of sodium hydroxide was the economics
due to the high replacement cost of this chemical. Total amount of
sodium hydroxide recovered amounted to 140 tons/year and the net pro-
fit obtained through recovery amounted to $22,000/year. An additional
benefit resulting out of sodium hydroxide recovery is the decrease in
consumption of alum at the treatment plant.
Nuclear Plants
The recovery of uranium and other fissionable materials from
depleted nuclear-power fuels is necessary since only a fraction of the
fissionable material is consumed prior to removal from the reactor.
The fuel is dissolved in nitric acid or any other acid before
recovery. Sometimes fuels ere mechanically decladded or oxidized prior
to acid attack. The various products such as urenium, plutonium end
other products, are separately recovered by solvent extraction employing
an intricate set of pH adjustments. Efforts to recover fission products
are now commercial. Most redicisotopes are not prepared in this manner
but could be recovered from wastes,by chemical action or ion exchange.
The Canadian nuclear power industry uses heavy water reactors
fueled with natural urenium. The spent fuel contained plutonium, a
potential fuel, but the cost of recovering it was such that it was not
competitive with natural uranium which is in abundance in Canada. The
spent fuel is stored in zirconium cladding, under water at the reactor
site for final disposal. If the price of uranium rises sufficiently,
it will become profitable to recover the plutonium.
A fluoride volatility process has been developed O1»102 in which
the fuel is treated with oxygen, hydrochloric acid or chlorine. This
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removes the cledding material es the volatile chloride. Fluorine is
then added end uranium end plutonium leeve as the hexefluorides which
may be separated due to differences in their relative volatilities.
A nev; reclamation process by Isochem, Inc., extracts and
converts the plutonium content of metal scraps end sundry wastes from
nuclear plants into a high purity plutoniura nitrate solution. The
scrap is initially dissolved in hydrofluoric acid, nitric acid and
aluminum nitrate monohydrete. The dissolved plutonium is extracted
with organic solvents and the plutonium-rich organic phase is stripped
with nitric acid and concentrated to a final product having a plutonium
of 200 to 300 gm/1.
Milk Industry
In the milk industry, approximately fifteen billion pounds of fluid
whey results per yeer-^ . Because of its high COD end production of un-
desirable conditions, the whey has to be evaporated, processed end some
returned to the farmer as slops.
Cheese whey has en everege composition of about 4.896 lactose
and 0.9% protein end, therefore, many useful by-products could be
obtained. However, the demand for these by-products is not large
enough to utilize the surplus whey. Conversion of whey to yeast to
be used es a source of protein in animal nutrition is very attractive,
but the cost of production is expensive. However, the economic
factor becomes less important from the point of view of dispose1 of a
potent waste.
Inorganic Chemical Industry
It is usually quite difficult to separate, in the inorganic
chemicals industry, the practice of by-product recovery from normal
production modes since so many of the industry's products are pro-
duced from ores or brines, the treatment of which produces a variety
of materials other than the main product which is being sought. If
the subsidiary materiel is also recovered, one might say that by-
product recovery is being practiced. Speaking to someone familiar
with the industry would indicate that this is not considered to be the
case.
In addition, there ere many inorganic chemicals which ere routinely
produced es by-products end where upwerds of 9095 of the total United
States' production results from such activity. Among these are the
following:
1. Sulfuric acid is reclaimed from petroleum alkylation units
on a commercial basis and reclaimed by thermal meens.
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2. Ammonium sulfate is produced from coke oven wastes and
other sources.
3. Calcium chloride and sodium chloride are frequently the
by-product of fractional crystallization for other products
and the neutralization of acid chloride wastes. OSW has
said that Solvey process wastes can be crystallized to pro-
duce sodium and calcium chloride.
4. By-product • hydrochloric acid arises
primarily from the production of organic chemicals and
this source represents 90% of United States production.
5. Sodium sulfate is the by-product of the production of
hydrogen chloride by the Hergreeves process.
6. Fluoride salts are recovered from scrubber waters in the
fertilizer industry.
Other situations also exist in this regard. For example,
mercury is frequently recovered for reuse from the discharge of mercury
cells for the production of caustic end chlorine by extraction. The
recovery of ammonia in the production of soda ash by the Solvey process
is vital to the economics of the process and this is performed by
absorption. In the production of chemicals arising from brines such as
sodium chloride, potassium chloride, potassium sulfete, borax, etc., a
multitude of products are produced. Under some circumstances, e
variety of products are produced and, in other circumstances, only a
few of the potential products are utilized end the remaining brine is
discharged to ponda. The recovery depends upon economics although
certain materials such as the litWLum salts are largely produced as
by-products of other larger productive operations. The definition of
by-product thus becomes clouded.
Ammonia could be produced as a profitable by-product from sea
water desalting plonts^^S^ The study underway is looking at e theo-
retical three-way operation, namely, saline water conversion, power
generation and ammonia synthesis. The project would be predicated on
non-nuclear steam generators that would first produce power end
fresh water. Left-over heat would then be used for ammonia synthesis.
The recovery of chemicals from sea water, which is already practiced
in the case of sodium chloride end iodine, is under consideration
with regard to calcium and magnesium values--producing magnesium
aluminum phosphate, for example.
The inorganic chemical industry's disposal problems center on the
treatment of: sulfuric acid wastes, hydrochloric acid end hydrogen
chloride wastes, and effluent gases containing acid oxides of sulfur,
nitrogen end other elements.
Sulfuric acid wastes are common to many industries, and recovery
is an accepted practice. When the impurity level is low, falling film
eveporetors are used and when the acid is dilute, it is utilized in or
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near the plant for the preparation of sulfetes. When the solution
is contaminated, dialysis, electrodialysis, adsorption, ion exchange,
ion exclusion, ion retardation and crystallization ere routes toward
purifying end, in some cases, concentreting the ecid. When contami-
nants ere organic in nature, submerged combustion is used end S0?
end 303 may be recovered from the effluent gas.
Inorganic acids used or produced in this industry create a
serious waste disposal problem. Considerable efforts have been ex-
pended in some cases, such as in the production of vinyl chloride
end chlorinated hydrocarbon,for the use of the acids in the process
itself. Hydrogen chloride, in liquid or gaseous form, is produced
es e by-product from the production of chlorinated organics end used
in oxychlorinetion processes in place of chlorine. About 40% of waste
hydrochloric acid, amounting to several million tons per year, is used
in oil well activation, chemicel end metel production, sterch hydrolysis
end cleening applications.
By-product ecid is produced by absorbing the gaseous hydrochloric
ecid in water in e graphite, tentelum or titenium absorber. Anhydrous
hydrochloric ecid is produced by stripping end condensation. Ion
exchenge is used for the regeneretion of hydrochloric acid contaminated
with metals106.
In order to reduce the amount of weste hydrochloric ecid, several
processes have been modified or changed. One such process is the
production of carbon tetrechloride (CC14) from cerbon disulfide (CS )
rather than from methane. Recovery of chlorine from hydrochloric
ecid hes been precticed by electrolysis of hydrochloric ecid, catalytic
oxidation end e few others.
For the recovery of oxides of sulfur end nitrogen, wet scrubbing
is commonly used es discussed in the section on the treatment of
gaseous wastes. Other proposed processes to recover SO or SO,, ere:
2 >3
1. The Simon-Carves-Condnco process, besed on wet scrubbing with
emmoniecel solution to produce ammonium sulfete end either
sulfur or sulfur dioxide.
2. The soda ash zinc oxide process, besed on wet scrubbing with
e soda ash solution that 'is regenerated with zinc nittrete
(Zn NOg) end lime - SOo is the product.
3. The manganese oxide process, besed on wet scrubbing with e
manganese oxide solution to produce S02«
4. Wet oxidation, based on the oxidation of SO to SO using
ozone in e mengenese sulfete solution. ^
5. The adsorption processes, based on the use of ectiveted
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charcoel in weter, multi-bed charcoal adsorption, activated
charcoal pipeline contactor end alkalized alumina.
The recovering of nitrogen oxides from the tail gases of nitric
acid plants is accomplished by catalytic conversion to N0_ end subse-
quent absorption. Other chemicals recovered include: boric acid by
chelation from brine wastes, sodium sulfete from cracking-catalyst
production wastes by crystallization, argon from hydrogen plants by
fractional distillation, end silica from ferro silicon plants by air
filtration.
Calcium chloride is obtained commercially as a by-product of
chemical manufacture, principally the Solvey process, and from
natural brines. The estimated annual production is in the order of
one million tons. The overall equation for the production of soda
ash by the Solvay process is:
CaC03 + 2NaCl Ne2C03 + CeCl2
Most of the CeClg is wasted into the streams except in some
cases where it is evaporated and marketed for its calcium chloride
content. The main applications of calcium chloride ere in the laying
of dust on highways end in low temperature refrigeration. The pollu-
tion due to calcium chloride is becoming less end less tolerated by
the regulatory authorities end, therefore, recovery of calcium chloride
would receive due importance in the future.
The potential for recovery in the industry is vest because the
major water pollution problems of the industry relate to the presence
of conservative species which must be removed in a concentrated form
end disposed of by some means or other. As soon as tighter restric-
tions ere established, recovery of these meterials will be an obvious
epproech.
Table VI summarizes by-product recovery in the inorganic chemi-
cals industry.
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TABLE VI
BY-PRODUCT RECOVERY IN THE
INORGANIC CHEMICALS INDUSTRY
By-Product Recovery
Process
By-Product
Quantity
Value
Diminution
of Pollu-
tions 1 Load
Hargreaves
Caustic
chlorine
electrolysis
Solvay
Sea water
desalting
Brines
Solvey
Magnesium
salt pro-
duction
Sodium sulfete 0.6 ton/ton $150/ton
Mercury Varies According to Cell
Ammonia
Ammonia
Sulfuric acid
Hydrochloric
acid
8-16 Ibs/ton of
soda ash
Varies
Varies
Varies
Boric acid Depends on brines
Calcium chloride Depends on brines
Calcium chloride Depends on brines
50-70%
50-80%
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APPENDIX I
GENERAL METHODS OF TREATMENT AND RECOVERY
Many techniques ere available to treat wastes , and the applica-
tion of a particular method or combination of methods requires en
understanding, not only of each method and its limitations, but also
of the composition and nature of the waste. Many methods discussed
below are suitable for the recovery of waste products while others are
final disposal techniques that preclude the recovery of wastes other
then heat or water.
Methods of treating liquid wastes include:
1. Biological Reactions
Biological reactions include biological oxidation end re-
duction and they occur es a natural part of the cell's
metabolic cycle end involve enzymes. Bio-oxidation systems
are commonly used in waste treatment facilities in the forms
of trickling filters, activated sludge systems and oxidation
ponds. Biological oxidations are inexpensive in operation
end setisfectory for the removal of most organics. Sludge
handling and disposal problems, difficulty of control, poi-
soning of the biology and inability to remove certein classes
of orgenics are the major negative factors in this system.
Oxidetion ponds ere not often eereted end depend on oxygen
diffusion. When lend costs ere low, lagoons or oxidation
ponds represent the cheapest setisfectory form of organic
waste treatment.
Biological reduction is accomplished by eneerobic becterie
end the reduction of orgenics results in the production of
HgS, CH4 end 003. This principle is used in sludge digestion
systems for the reduction of volume of sludge end production
of sludge gas. Methane is the primary constituent of sludge
gas and may be used to heat the digestion tanks, for space
heating, for motor fuel, or may be used as a compressed gas.
Biological reactions are important for chemical recovery as
well as for waste disposal. Many industrial wastes such as
paper and pulp mill wastes, brewery and distillery wastes,
residues from the processing of corn and beet sugar ere
suitable es fermentation seeds. The products from the fer-
mentation of these westes ere useful end include the following
drugs, vitemins, animal feeds, alcohols, acetone and flavor
enhancers.
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2. Chemical Reactions
Chemical oxidation has been used to treat wastes near room
temperature but ere limited in application due to high cost
or low reactivity. The chemical oxidents and area of use
are listed in Table A-I.
Incineration is a chemical oxidation process end has been
applied to:
a. wastes containing organics in a number of contacting
devices such as fluidized beds,
b. wet oxidation of orgenics at elevated temperatures
and pressures,
c. thermal decomposition of inorganics in order to
recover valuable components, as in the reburning of
lime mud (arising in water treatment, sugar and pulp
mill wastes) to recover lime,
d. thermal treatment of inorganics to recover valuable
components, as in furnacing of kraft black liquor
to recover pulping chemicals, and
e. oxidation of organics during the regeneration of
adsorption and catalytic agents and of caustic solu-
tions .
Table A-l summarises Chemical oxidants and area of use.
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TABLE A-I
CHEMICAL OXIDANTS AND AREA OF USE
S. No. Chemical Oxident
1 Air
Area of Use
Ozone
Chlorine,
hypochlorite and
chlorine dioxide
4 Electrolytic
oxidation
5 Permanganate and
dichromate
6 Hydrogen peroxide
Nitric acid
Limited to easily oxidized pollutants
such as sulfites and ferrous salts. Air
may be used to agitate wastes and sweep
out gases.
May be used to oxidize most organics
end many inorganics, but is limited by
costs. Has been suggested for phenolic
and cyanide wastes.
Used as a pretreatment or disinfectant.
Chlorinetion has been used to treat
cyanide, phenolic, textile, tannery,
meat-packing and beet sugar wastes, and
paper mill white water.
Useful for oxidizing cyanides and for
treatment of pickle liquors.
Limited use due to high cost.
Has been suggested for laundry, phenolic
and cyanide waste.
Suggested for treatment of ammonia-
still liquors.
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APPENDIX II
OTHER CHEMICAL REACTIONS OF INTEREST
Complexing
This has been suggested as a means of treating wastes and
recovering by-products. The system has been applied to cyanide end
pickling wastes and to the removal of iron and manganese from water
supplies. The high cost of the complexing agent makes this process
prohibitive.
Reduction
Chromates arising from plating baths ere reduced with iron,
zinc, brass or sulfur.
Precipitation
Heavy metals such as iron, copper, zinc and cadmium may be
precipitated by the addition of alkalis. Chromium m«y be precipi-
tated by the addition of a soluble barium salt, such as barium
sulfide.
Neutralization
Many acidic wastes ere normally neutralized with lime and other
inexpensive alkali and alkaline wastes are neutralized by sulfuric
acid and waste hydrochloric acid.
Solids Separation
Many industrial wastes contain solids end colloids, which may be
removed for reuse or disposal by the application of grevitetionel
forces or blocking functions. Gravitational systems depend on the
tendency of particles to settle at' rates dependent both upon their
size and specific gravity differential between the particle end
fluid. This principle is applied in equipment such as sedimentation
tanks, thickeners, flocculation tanks, cyclones, centrifuges, screens,
filters and sieving membranes.
Foeming end Flotation
Foam separation is analogous to solid - liquid adsorption,
81
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replacing the solid phese with a gas phase end including the
important factor of entreinment.
In foaming, soluble surface-active agents gather at the
solvent-air interface and the presence of air bubbles produces
a foam which may be removed. If surface-active agents that com-
plex heavy inorganic ions are added, these ions may be removed
by foaming.
Foam separation technique has a greet potential in sanitary
engineering separation technology and can be used in the following:
1. Separation of ABS end organics from secondary effluents.
2. Removal of refractory materials from tertiary effluents.
3. Removal of radioactive metal ions.
4. Direct treatment of laundry wastes.
5. Removal of specific surfactants from industrial wastes,
such as refinery and petrochemical wastes.
6. Separation of phenol from refinery wastes.
7. Recovery of heavy metals, such as Cr+ in wastes from
metal-finishing industries.
In flotation, air bubbles attach themselves to solids and carry
them to the surface. This system removes both flocculated and
unflocculated solids and the addition of a flotation agent results
in better solid separation.
Adsorption
The contact between waste streams end high-surface-area commercial
adsorbents will result in the removal of solubles from the waste as
an adsorbed layer on the solids. Commercial adsorbents have large
surface areas per unit weight, unsatisfied surface bonds to effect
adsorption, and sufficiently large pores to permit diffusion of the
adsorbate to most of the surface. They must also be either low
priced or easily regenerated.
Adsorption may take place in columns, filters, agitated tanks or
pipe lines. A few adsorbents that have found widespread acceptance
include activated carbon and bone char, silica gel end activated
silica, bauxite, alumina, clays end fuller's earth. Adsorption has
been used in the treatment of organic-containing effluents from
82
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laundry, sewage, organic chemical and dye works, and in the removal
of metal ions from plating baths.
Ion Exchange
Ion exchange is the reversible exchange of ions between a solid
and liquid, in which there is no substantial change in the structure
of the solid. These systems ere usually operated by contacting the
liquid with the ion-exchange resin in a column. The process is
such that the pollutant ion may be recovered for use. Ion exchange
has found application in the following as given below:
1. Recovery of chromic acid from cooling tower effluents.
2. Treatment of cyanide westes--gives greater safety end costs
less when compared to conventional methods of treating
cyanides with chlorine.
3. Recovery and concentration of valuable metals such as silver,
gold, platinum end nickel.
4. Recovery of metals from plating baths.
5. Treatment of low and medium level radioactive wastes.
6. Recovery of isotopes from high level radioactive wastes.
7. Recovery and removal of ionized orgenics from aqueous solutions,
Membrane Processes
Membrane processes are widely applicable to waste treatment. Three
important and feasible processes are:
1. Dialysis: a separation method that utilizes diffusion as
its driving force. In some cases, the membranee acts as a
molecular filter. Dialysis has found application in the
recovery of rayon from textile wastes, acids from spent liquor
in the metal-treating wastes.
2. Blectrodielysis: uses electromotive driving force. The
ability of membranes to selectively pass either cations or
anions is used in this process. Electrodialysis is used in
the recovery of acid end iron from pickle liquor, end in the
waste water recycle for the removal of dissolved solids.
3. Reverse Osmosis, or Ultrafiltretion: uses a pressure gradi-
ent to make a separation based on the relative solubilities
83
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and diffusivities in the membrane of the various liquid
phase pomponents. Reverse osmosis is used in the tertiary
treatment end reclamation of waste water.
Solvent Extraction
Solvent extraction is not often used in waste treatment since it
is expensive end not well suited to either treat large and varying
volumes of liquid or remove trace quantities. Solvent loss is often
responsible for high costs. However, solvent extraction is applied
to ammonia-still wastes to recover phenol, wool wastes to recover wool
grease, and pulping liquors to recover acetic end formic acids.
Evaporation and Crystallization
These processes involve separations by the formation of a new
phase end are expensive when applied to dilute systems. However,
evaporation is frequently involved in thermal oxidation processes in
which organic-containing wastes are mechanically concentrated prior
to evaporation, combustion end oxidation. Evaporation is useful in
treating concentrated solutions but the application of evaporation to
dilute solutions is limited to special cases such as the concentration
of radioactive wastes.
Crystallization is involved in processes developed to treat
pickle liquors and waste brines.
Ultimate Disposal
Ultimate disposal must be used for solid or highly concentrated
liquid wastes that cannot be used or recovered. A large number of
ultimate disposal methods are available and the choice depends on
waste characteristics, economics and local regulations. A number of
carefully developed studies have been made to determine the optimum
means of disposing of wastes such as sewage effluent concentrate and
see water brine. Methods of ultimate disposal include the following:
1. Thermal oxidation - useful for organics end for stabilizing
organic-inorganic mixtures.
2. Long-term biological oxidation end reduction - often not
purposefully done but a natural consequence of other actions
such as the use of sewage sludge for fertilizer.
3. Return to soil in a stabilized form - useful for most
inorganic wastes.
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4. Disposal into the ocean - common practice for plants and
cities located near the ocean.
5. Deep-well injection - an extremely promising technique
limited only by geology.
6. Encapsulation - limited to radioactive wastes.
7. Salt cavern storage - suitable for nuclear wastes.
8. Long-term tank storage - practical only for high level
nuclear wastes.
9. Short-term legooning - useful for reducing organic,
nutrient and thermal loading but not a true ultimate disposal
method.
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APPENDIX III
PHYSICAL METHODS OF TREATING GASEOUS WASTES
Gaseous wastes generally find their way into liquid wastes through
wet scrubbing or other processes. Various methods are practiced for re-
moving solids from gas streams under a variety of conditions. The
common devices used are based on e limited number of principles such es:
Gravitational force - Simple settler
Multi-gravitational force - Cyclone
Interference - Gas filters
Contact with e liquid phase (Scrubbing) - Venturi Scrubbers, etc.
Other external forces - Electrostatic precipi-
tation, ultrasonics, etc.
Gaseous wastes are treated by taking advantage of molecular distri-
butions such es:
1. Adsorption
Gas purifications may be performed by adsorption and desorption
cycles. Activated carbon, silica gel, alumina end molecular
sieves find broad application.
2. Absorption
The liquid scrubbing of gases is widely practiced for the
recovery of S02 from power plants and sulfite mills.
3. Ion Exchange
Some resins can remove pollutants such es S02 but are
limited by temperature.
4. Membrane Permeation
Several applications have been developed and employed in the
separation or purification of gases. Use of thin silicone
rubber membranes for the purification of gas streams, develop-
ment of glass membrane end fluorocerbon membrane for the
separation of helium from natural gas end production of hydro-
gen from wastes by permeation through a palladium membrane are
some of the applications in the membrane permeation field.
86
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5. Chemical Reaction
This is practiced to produce a more valuable, more
collectable, or less harmful product. Removal of sulfur
dioxide from power plant stack gases is a classic example.
SO is converted to SO by chemical oxidation and, subse-
quently, removed. This conversion is necessary end beneficial
because of the higher solubility of SOg end the velue of
sulfuric acid. The method is expensive end difficulties ere
often encountered due to low concentrations of the pollutant.
The most direct method for the removal of a reactive pollutant
from a gas stream is to contact it with a reactive solid so
as to fix the pollutant in a permanent or semi-permanent
fashion. Use of lime, fly ash, or ferrous slag in e fixed,
fluidized or pipeline reactor has been suggested for the re-
moval of SO- but this appears to be expensive due to high
pressure drops and poor solids utilization.
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