Water Requirements 

of the Aluminum 

Industry

By HOWARD L. CONKUN

WATER REQUIREMENTS OF SELECTED INDUSTRIES

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1330-C

A study of manufacturing processes with 

emphasis on present water uses and 

future water requirements

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale hy the Superintendent of Documents, U. S. Government Printing Cilice 

Washington 2>>, I). C. - Price 20 cents (Paper cover)
PREFACE

This report is one of a series describing the water requirements of selected industries that are of national importance. It 

was prepared at the request of and in consultation with the Water 

and Sewerage Industry and Utilities Division, Business and Defense Services Administration, Department of Commerce, and is 

designed to serve the dual purpose of providing basic information 

for national defense planniag and at the same time rendering a 

valuable service to business and industry in their development of 

water resources for present and future use.

The officers of Aluminum Company of America, Kaiser Aluminum and Chemical Corp., and Reynolds Metals Co. gave the writer 

permission to visit their plants to determine the water requirements of each plant, the manner in which water is used, and all 

conditions peculiar to each plant that would account for the use of 

water in a manner that differs from the usual practice in the industry. Grateful acknowledgment is made to these officials and to 

the management of each plant visited for the courtesies and cooperation extended to the writer in the course of this investigation.

Ill

CONTENTS

Page

Abstract...................................................................................................................................... 103

Introduction................................................................................................................................. 104

Purpose.................................................................................................................................... 104

Scope......... .................................................................................................................. 104

History and growth of the industry....................................................................................... 106

Use of aluminum in industry................................................................................................. 108

Occurrence of aluminous ores............................................................................................... 108

The methods of producing primary aluminum.......................................................................... 110

Producing alumina from bauxite........................................................................................... 110

Bayer process,.................................................................................................................... Ill

Combination process.......................................................................................................... 112

Pedersen process............................................................................................................... 115

Producing aluminum by electrolytic reduction of alumina................................................ 115

Hall process........................................................................................................................ 115

Soderberg process.............................................................................................................. 117

Heroult process.................................................................................................................. 117

Methods used in the United States...................................................................................... 118

Effect of variations in plant operation on water requirements............................................ 118

Factors affecting location of plants........................................................................................ 119

Alumina plants........................................................................................................................ 119

Reduction works..................................................................................................................... 120

Findings of the survey.............................................................................................................. 121

Sources of water..................................................................................................................... 121

Effect of size of plant on water requirements................................................................... 122

Plant uses of water.............................................................................................................. 123

Consumptive use of water..................................................................................................... 126

Quality of water..................................................................................................................... 128

Treatment of water...... ................................................................................................... 129

Treatment and disposal of waste water............................................................................... 130

Pollution from process waste............................................................................................... 131

Summary of plant water-use data............................................................................................. 132

Alumina plants........................................................................................................................ 132

Reduction works.. ................................................................................................................. 133

Water use per unit of product................................................................................................. 134

Conclusions................................................................................................................................. 135

Selected references.................................................................................................................... 137

Index........................................................................................................................................... 139

ILLUSTRATIONS

Figure 19. Map shoving location of plants surveyed for water requirements.................. 105

20. Raw materials and processes required to produce 1 pound of

aluminum ingot.................................................................................................... Ill

21. Flowsheet for Bayer process............................................................................... 113

22. Flowsheet for Combination process.................................................................... 114

23. Percentage of lotal water intake for various plant uses................................ 126

TABLES

Table 1. Production of primary aluminum in the Unitec1 Stetes,....................................... 107

2. Sources of water, alumina plants and reduction works, 1952........................ 122

3. Quantity and percent of water from various sources used at alumina

^plants, 1952.......................................................................................................... 122

4. Quantity and percent of water from various sources used at reduction

v-orks. 195Z.......................................................................................................... 122

5. Uses of water in alumina plants, 1952................................................................ 124

6. Uses of water in reduction works, 1952.............................................................. 124

7. Kinds of water treatment.......................... ........................................................... 129

8. Treatment and disposal of waste wtter at alumina plrmts............................... 141

9. Treatment and disposal of waste water at reaction works............................. 131

10. Summary of water-use data for alumina plants, 1952........................................ 133

11. Summary of water-use data for n-duction works, 1952...................................... 134

V

WATER REQUIREMENTS OF SELECTED INDUSTRIES

WATER REQUIREMENTS OF THE ALUMINUM INDUSTRY 

By Howard L. Conklin

ABSTRACT

Aluminum is unique among metals in the way it is obtained from its ore. The first step 

is to produce alumina, a white powder that bears no resemblance to the bauxite from which 

it is derived or to the metallic aluminum to which it is reduced by electrolytic action in a 

second step. Each step requires a complete plant facility, and the plants may be adjacent 

Dr separated by as much as the width of the North American continent. Field investigations 

sf every alumina plant and reduction works in the United States were undertaken to deternine the industry's water use. Detailed studies were made of process and plant layout so 

:hat a water balance could be made for each plant to determine not only the gross water 

.ntake but also an approximation of the consumptive use of water.

Water requirements of alumina plants range from 0.28 to 1.10 gallons per pound of alumila; the average for the industry is 0.66 gallon. Water requirements of reduction works vary 

:onsiderably more, ranging from 1.24 to 36.33 gallons per pound of aluminum, and average 

L4.62 gallons.

All alumina plants in the United States derive alumina from bauxite by the Bayer process 

>r by the Combination process, a modification of the Bayer process. Although the chemical 

>rocess for obtaining alumina from bauxite is essentially the same at all plants, different 

>rocedures are employed to cool the sodium aluminate solution before il enters the precipi<- 

.ating tanks and to concentrate it by evaporation of some of the water in the solution. 

Vhere this evaporation takes place in a cooling tower, water in the solution is lost to the 

atmosphere as water vapor and so is used consumptively. In other plants, the quantity of 

solution in the system is controlled by evaporation in a multiple-effect evaporator where 

>ractically all vapor distilled out of the solution is condensed to water that may be reised. The latter method is used in all recently constructed alumina plants, and some older 

)lants are replacing cooling towers with multiple-effect evaporators.

 All reduction works in the United States use the Hall process, but the variation in water

 equirements is even greater than the variation at alumina plants, and, further, the total 

laily water requirement for all reduction works is more than 9 times the total daily requirenent of all alumina plants. Many reduction works use gas scrubbers, but some do not. As 

zas scrubbing is one of the principal water uses in reduction works, the manner in which 

wash water is used, cooled, and reused accounts in large measure for the variation in waer requirements.

Although the supply of water for all plants but one was reported by the management to be 

ample for all plant needs, the economic factor of the cost of water differs considerably 

among plants. It is this factor that accounts in large measure for the widely divergent 

slant practices. Plant capacity alone has so little effect on plant water requirements that 

jther conditions such as plant operation based on the cost of water, plant location, and 

he need for conservation of water mask any economy inherent in plant size.

103
104 WATER REQUIREMENTS OF SELECTED INDUSTRIES

IKTRODUCTION

PURPOSE

This report, one of a series on the water requirements of important industries, presents a summary of basic data on water 

use in the production of primary aluminum from bauxite. This 

kind of information is presented to aid the planning of the over=all 

development of specific areas and the most effective use of our 

water resources. If defense mobilization should be necessary, 

the results of this survey would be especially helpful in locating 

new plants using large amounts of water so that they will be assured adequate water supplies of suitable quality and at the same 

time will not interfere with the requirements of other industries 

with which they must share the water.

SCOPE

Field investigations, which were carried out during the first 

half of 1952, included visits to every alumina plant and reduction 

works then in operation in the United States. Production of secondary aluminum by remelting aluminum scrap is not included in 

this investigation. Plants at which a water-use survey was made 

are shown in figure 19.

Detailed studies were made of process and equipment at every 

plant visited so that a water balance could be made to determine 

the gross water intake, the reuse of water, and a close approximation of the consumptive use of water.

Information was sought on the source of water, its adequacy, 

the need for treatment, the manner of disposal of waste water, 

and changes in process or plant practice that would indicate a 

trend in water use.

Subjects of primary interest throughout the investigation were: 

the quantity of water required for the operation of each plant; the 

chemical quality of water required; differences, from plant to 

plant, in operating practices; the extent to which those differences 

are explicable in terms of interplant variations in plant size, 

geographical location, and availability of water; and the effect 

these various conditions have on the quantity of water required by 

each plant and on the necessity to reuse water.

Because steam is essential to the production of alumina by 

chemical process from bauxite, boiler-feed makeup is included 

in the plant water balance as a process use of water.
Figure 19. Map showing location of plants surveyed for water requirements.
106 WATER REQUIREMENTS OF SEIECTED INDUSTRIES

Reduction works present a more complicated situation in the 

consideration of the quantity of water required to produce electric 

power, which is essential for the process of electrolytic reduction of alumina to aluminum. Of the 14 reduction works in operation at the time this survey was made, 8 works purchased all 

the electric power required forpotlines and other plant uses from 

federally owned power pools such as TVA and Bonneville; 2 operated company-owned hydroelectric generating plants and purchased supplemental power from privately owned utility companies; 2 generated all electric power at the plant, using internalcombustion engines as prime movers; 1 used internal-combustion 

engine generator sets for 2 potlines and purchased power for the 

other 3 potlines; and 1 plant operated 2 potlines by gas-diesel 

engine generator sets and 6 potlines from a steam turbogenerator 

plant. The condenser-cooling water required for the steam plant 

is estimated to amount to as much as 500 mgd (million gallons 

per day), approximately 16 times as much as all other water requirements of this reduction works.

In view of the fact that steam is not used in the electrolytic 

process and because 11 of the 14 works purchase power, part 

of which is produced by hydroelectric generators and part by 

standby steam powerplants, the purpose of this survey is best 

served by considering electric power used in reduction works as 

a purchased raw material. The water requirements for generating 

electric power by internal-combustion engines is insignificant. 

However, the quantity of condenser-cooling water required by the 

one reduction works at which electricity is generated by a steam 

powerplant distorts the water balance of that plant.

Water-use values in this report, therefore, do not include: the 

quantity of water required for the generation of electricity for the 

potlines, either in hydro or steam plants; the water requirements 

of plants not in operation at the time the survey was made; 

changes in process uses of water contemplated but not in operation at that time; and the quantity of water used for fabricating 

aluminum pigs, ingots, and billets into finished products such as 

castings, sheets, or extruded forms.

HISTORY AND GROWTH OF THE INDUSTRY

As little as 70 years ago aluminum was a rare and costly curiosity. In the span of one lifetime the aluminum industry has risen 

to fifth place, in tonnage produced, of all metal industries. Measured by volume rather than weight, aluminum production exceeds 

tiiat of copper, lead, and zinc and is second only to iron.
ALUMINUM INDUSTRY 107

The first sample of impure aluminum was extracted from clay 

in 1825 by Hans Christian Oersted, a Danish chemist. Frederick 

Wohler, a German chemist, succeeded in making metallic particles and in 1845 was the first to determine the physical and chemical properties of the metal.

The commercial history of aluminum dates from 1886 when two 

scientists, Charles Martin Hall in the United States and Paul L. T. 

Heroult in France, working independently, simultaneously developed essentially the same process of reducing alumina (aluminum 

oxide, A12 O3 ) to metallic aluminum (Al) by passing an electric 

current through alumina dissolved in cryolite. Two years later 

Karl Josef Bayer developed a chemical process for the production 

of refined alumina from bauxite. The processes of Bayer and Hall 

made possible the aluminum industry, the growth of which has 

been so spectacular.

From 1886 until 1910 growth of the new industry, in regard to 

tonnage produced, was slow. However, during that interval the 

price was reduced from 5 dollars per pound of ingot aluminum to 

22 cents. In 1910, when the total United States output was only 

20,000 tons, a period of phenomenal expansion began; total United 

States production increased to almost 1 million tons in 1952, a 

47-fold increase of production. (See table 1.)

Table 1. Production of primary atuninur* in the United States

[Data for 1910-50 compiled by First Boston Corp. (1951), for 1951 by Office of Defense 

Mobilization (1952aXand for 1952 by Lutjen (1953)]

Year

1910..................

1915..................

1920..................

1925..................

1930..................

1935..................

Thousand of

metric

tons

..........................20

..........................50

..........................75

..........................77

........................139

..........................75

Year

1940.................

1945.................

1950.................

1951.................

1952.................

Thousand of

metric

tons

............................187

............................445

............................653

............................836

............................937

Peacetime uses for aluminum have enabled the aluminum industry to retain its tremendously expanded wartime volume of production. The utilization by industry of the total aluminum plant 

capacity has been brought about by new applications of the metal 

induced by a practically stable price.
108 WATER REQUIREMENTS OF SELECTED INDUSTRIES 

USE OF ALUMINUM IN INDUSTRY

A conservative estimate indicates that there are today at least 

4, 000 end uses of aluminum. There are two general classifications of end products: wrought products, which develop from a 

change in shape of the metal by mechanical working of the billet; 

and castings, which utilize the molten metal of pigs or ingots.

Wrought products include sheet, extruded shapes, foil, rods 

and wire, and forgings made by hammering or by pressing the 

billet, which usually is cast in cylindrical form from remelted 

pigs.

Castings have become one of the largest outlets for aluminum. 

They are made by plaster, sand, and iron mold, and by die 

casting.

The year-by-year requirements of aluminum by the various industries fluctuate to such a degree that it is difficult to adjudge 

what is normal demand. Consider, for example, the aviation industry. In 1943 that industry was allocated approximately 90 percent of the total aluminum production in the United States (each 

B-29 required 25 tons of aluminum). In 1948, however, the aviation industry used only about 4 percent of the aluminum production. Owing to the rapidly expanded military program, nearly 9 

percent of the 1949 production went into aircraft, and in 1951 it 

was approximately 25 percent.

The cumulative effect of expanding capacity, of broadening 

consumer acceptance, of development of new applications, and of 

an improving competitive position is becoming increasingly evident in sharp gains in peacetime consumption. All things considered, therefore, the aluminum industry confidently expects that 

production and consumption over the next 10 years will double, as 

it has during each decade in the past.

OCCURRENCE OF ALUMINOUS ORES

Of all the elements in the earth's crust the element aluminum 

(Al) is third in abundance, exceeded only by oxygen and silicon. 

It is the most abundant metallic element, constituting approximately one-twelfth of the earth's crust, whereas iron constitutes 

only about one-twentieth. Although aluminous ores are widespread, the element never has been found free in nature. Aluminum is found everywhere combined chemically with other elements in more than 100 combinations, generally in the form of an 

oxide. Alum, a double sulfate of aluminum, is the common styptic
ALUMINUM INDUSTRY 109

pencil. Rubies and sapphires are compounds of aluminum to which 

ferrous impurities give their beautiful and distinctive color.

Bauxite, an amorphous mixture of two hydrates, A12O3 'H2 O and 

Al 2Cv3H2O, is the ore used for all commercial aluminum produced in the United States. High-grade bauxite ore is found principally in Arkansas, where some deposits are high in aluminumoxide content and low in impurities of silica and iron. Bauxite 

deposits of somewhat lower quality but economically usable are 

located in Georgia and Alabama. Domestic sources of high-grade 

bauxite are being depleted, and an increasing percentage of the 

total ore used in the United States is shipped from deposits in 

Surinam (Dutch Guiana), British Guiana, Jamaica, and Haiti. 

Samuel W. Anderson, formerly Deputy Administrator for Aluminum, Defense Production Administration, reported (1953) that the 

estimated quantity of high-grade bauxite in the United States is 

approximately 9 million tons, and that there are about 50 million 

tons of low-grade bauxite in the Arkansas area. Deposits in Surinam are estimated to contain approximately 50 million tons of 

bauxite, and the deposits in the islands of the Caribbean are estimated to total over 350 million tons.

Cryolite, sodium aluminum fluoride (3NaF-AlF3 , formerly written Na3 AlF$), is another aluminum compound required in the process used in the United States for producing alumina from bauxite. 

The only known commercial source of natural cryolite is one mine 

in Greenland. Synthetic cryolite is considered equally suitable as 

a solvent of alumina in the electrolytic reduction process, although it is claimed that natural cryolite has greater stability 

which makes starting a potline somewhat easier. Natural cryolite 

is concentrated to somewhat higher purity than synthetic cryolite, 

but the difference is small. Cryolite also is reclaimed from the 

old linings of pots, a process carried out at three reduction works.

A joint investigation by the Bureau of Mines and the Geological 

Survey (1948) indicates that domestic reserves of high-grade 

bauxite are very small; however, there are virtually unlimited 

quantities of low-grade sources of aluminum such as alunite, anorthosite, certain types of clays, and other aluminum silicates.

Utilization of low-grade bauxite with high silica content is made 

possible by the Combination process. This process is in operation at two alumina plants now in operation.

For many years the Bureau of Mines has conducted laboratory 

and pilot-plant research to find methods of recovering alumina 

from low-grade materials. The Government-owned demonstration plant at Laramie, Wyo., begun in World War II but never
110 WATER REQUIREMENTS OF SELECTED INDUSTRIES

completed, was transierred Dy the Surplus Property Board to the 

Bureau of Mines to determine the equipment requirements, process techniques, and economics of producing alumina from anorthosite. This aluminum-bearing rock is found in enormous quantities in the Laramie Range, in Wyoming, and elsewhere in the 

United States.

THE METHODS OF PRODUCING PRIMARY ALUMINUM

There are two separate and distinct steps in the production of 

aluminum from ore. Aluminum differs from most other major 

metals in this respect as they are reduced directly from their 

ores. Each step, as shown in figure 20, requires a complete plant 

facility for the production of its end product. The requirements 

may be carried on in adjacent plants or they may be separated by 

as much as the width of the North American continent.

The first step is the production from bauxite of anhydrous aluminum oxide, a gritty white powder known as alumina (AljOj). 

The second step is the production of aluminum from alumina by 

electrolytic reduction, the molten metal being cast into pigs or 

billets.

PRODUCING ALUMINA FROM BAUXITE

Many detailed discussions of the Bayer and other processes 

for the production of alumina are contained in the literature. The 

following brief descriptions constitute a resume of the work on 

this subject (see the bibliography) but are not taken from any one 

source.

Several detailed descriptions of the various processes for refining alumina from bauxite and other source materials have been 

made by other governmental agencies, such as the report to the 

Off ice of Defense Mobilization by the U. S. Bureau of Mines (1953). 

A similar report on the reduction of alumina to primary, or virgin, 

aluminum was made to the same office by the U. S. Department 

of Commerce (1956).

In this report it is deemed necessary to discuss the various 

processes and the chemistry involved only sufficiently for the 

reader to be able to identify the equipment when reference is 

made to the use of water or its extraction from the liquor cycle. 

The Deville-Pechiney "dry" process is not used in the United 

States.
ALUMINUM INDUSTRY 111

MetacoUkegiCa ' Tar ^Ib Pitch >/. Ib

8 4tf^ PR

Raw cryolite !/25 Ib Fluorspar Sulfur

RakoH rarhnn »/ Ih jf'Y'^-' .'^^^-X ;"~ VX ^ i-x ,/ 11. Aluminum Baked carbon /10 Ib ^Sks^^^J^^iA^ Cryolite 3/50 lb fluoride V25 It

Furnace lining

Figure 20. Raw materials and processes required to produce 1 pound of aluminum ingot. 

(Copyrighted material reproduced with the permission of the First Boston Corp. )

BAYER PROCESS

Bauxite, finely ground in a ball mill, is fed from a weighing 

hopper into a mixer where it is thoroughly mixed with hot ©austic 

soda solution from a previous cycle to which sufficient lime and 

sodium carbonate have been added to bring the solution to standard
112 WATER REQUIREMENTS OF SELECTED INDUSTRIES

concentration. The thin muddy liquid, called slurry, is pumped 

into digester tanks, where it is heated by live steam at about 50 

pounds per square inch pressure and agitated, causing the aluminum oxide in the bauxite to be dissolved or digested in the caustic 

solution as sodium aluminate. The insoluble residue of impurities 

is separated in open-top iron settling tanks where the sediment is 

drawn from the bottom and the relatively clear liquor is drawn off 

the top. In recently constructed plants the contents of the digester 

tank are passed through blowoff tanks and filter press to separate 

the insoluble residue known as red mud from the sodium aluminate 

solution. The red mud containing iron oxide, aluminum oxide 

combined with silica as aluminum silicate, and other impurities 

in the bauxite is an insoluble waste residue. It is transported to 

the red-mud lake by water pumped from the lake. Makeup water 

added to the red-mud lake to compensate for evaporation is an 

important water use at alumina plants. The clear sodium aluminate solution, dark brown in color but usually referred to as 

"green liquor" by plant personnel, is cooled and pumped to vertical 

precipitating tanks as tall as a six-story building, where it is 

seeded with alumina trihydrate from a previous cycle to accelerate 

precipitation. Alumina trihydrate, or aluminum hydroxide as some 

metallurgists prefer to designate it, is gradually formed by the 

hydrolysis of sodium aluminate in the presence of the crystalline 

seeds and settles to the bottom. The granular aluminum hydroxide 

crystals are drawn from the bottom of the precipitator. The 

crystals are classified and separated in thickeners, washed and 

filtered, and calcined at a temperature of approximately 2, 000°F 

in long gas-fired rotary kilns where free water and chemically 

combined water of hydration are driven off, leaving pure anhydrous aluminum oxide, known as alumina.

The Bayer process flowsheet shown in figure 21 is obsolete in 

some particulars, such as the use of autoclaves and triple-effect 

evaporators. All recently constructed plants use digesters in 

which live steam is introduced into the liquor to raise its temperature, whereas the autoclave has a steam jacket to raise the temperature without in-creasing the volume of the liquor. Modern 

practice calls for the use of sextuple-effect evaporators to reduce 

the volume of liquor in the cycle rather than evaporating towers 

or the triple-effect evaporator shown in the flowsheet. The flowsheet is included as a historical item which may serve to show 

the various steps in the process.

COMBINATION PROCESS

The Combination process employs a sintering operation as a 

cyclic step in the Bayer process and is intended to recover some
ALUMINA <Bayer Process)

Recovered Na OH

Triple effect 

^,-evaporator 

Steam

Finishing parr

Fout thickeners

Bauxite (55-60% A/2 0,> 2,600 Ib. Steam

Nc!OHmoike-up<76%> 80 Ib. Electricity

Water 6,300 gal. Direct labor

"H Y I Y M

L V \. >niCglcinerjn >

""-Four thickeners' 

15,000 Ib' 1 w-hr >

loin-hr J

180 kw-hr [ Per ton dry hydrate, Al,0,- 3H? 0 

3.8 Moin-l ' Z 3 2

Figure 21. Flowsheet for Bayer process. (Copyrighted material reproduced with the permission of McGraw-Hill Publishing Co., Inc.)
114 WATER REQUIREMENTS OF SELECTED INDUSTRIES

of the aluminum oxide lost as aluminum silicate with the red-mud 

residue. The flowsheet for this process is shown in figure 22.

RED MUD MIXED WITH

GROUND LIMESTONE AND

SODA ASH

BAUXITE DIGESTED WITH CAUSTIC

SODA SOLUTION AND STEAM

UNDER PRESSURE

SLURRY SEPARATED 

BY SETTLING AND FILTRATION

SODIUM ALUMINATE

ALUMINUM TRIHYDRATE SODIUM ALUMINATE

Figure 22. Flowsheet for Combination process. (Copyrighted material reproduced with the 

permission of American Institute of Mining and Metallurgical Engineers, Inc. )

When high-grade bauxite, containing from 3 to 7 percent of silica, 

is used in the Bayer process, the amount of aluminum oxide converted to aluminum silicate that can be recovered is insignificant. 

However, the supply of high-grade ore in the United States is 

rapidly being depleted, and low-grade ores, with silica content as 

high as 15 percent, of necessity must be used. Since 1 pound of 

aluminum oxide and 1 pound of soda are lost in the red-mud residue for each pound of silica in the bauxite, the loss is appreciable 

when ores high in silica are used.

The Combination process has made practicable the utilization 

of the large reserves of ores not amenable to economic treatment 

by the Bayer process because of high silica content, but richer 

in alumina than clay or other available low-grade ores.

By making possible the utilization of low-grade ores, the Combination process has been of inestimable value in extending the Nation's commercial bauxite reserves and providing a source of supply 

of ore during a war emergency when foreign sources might be cut
ALUMINUM INDUSTRY 115

off to an even greater degree than was the case in World War II. 

An over-all recovery of as much as 94 percent of the alumina in 

high-grade bauxite has been achieved by the Combination process. 

Yields of 90 percent of the total alumina in low-grade ores having 

a high silica content are economically extracted by this process. 

Normal recovery by the Bayer process from high-grade bauxite 

is 80 to 85 percent, and the amount of alumina recovered when 

bauxites high in silica are treated is 70 percent or less.

PEDERSEN PROCESS

The Pedersen process is used advantageously with bauxite ores 

that contain a high percentage of iron as an impurity. In this 

process bauxite is smelted with limestone and coke in electric 

furnaces. The iron compounds are drawn off and poured as pig 

iron of high quality. The slag, containing the aluminum as calcium 

aluminate, is pulverized and treated with soda solution. As in the 

Bayer process, the aluminum is dissolved, forming a solution of 

sodium aluminate. The silica and other impurities form an insoluble mud. The solution of sodium aluminate is treated with 

flue gases from the smelting operation, causing aluminum hydrate 

"mud" to precipitate and settle to the bottom of the precipitating 

tank where it is drawn off, filtered, and calcined. The soda solution remaining in the tank is ready for reuse, without concentration by evaporation, for the treatment of new slag. The loss 

of soda is low. Alumina obtained \by the Pedersen process has 

about the same purity as the product of the Bayer process and is 

as well suited for reduction in the electrolytic pots.

The Pedersen process is in use on a commercial scale in 

Norway, Sweden, and Russia in which countries the bauxite ores 

available contain a high iron content. It has been tried in the 

United States on an experimental scale in a pilot plant which 

yielded a good product, but the cost of production was too high to 

compete with the Bayer process using bauxite ores available to 

 United States producers. It is expected that further development 

will result in lower costs of production.

PRODUCING ALUMINUM BY ELECTROLYTIC REDUCTION OF ALUMINA

HALL PROCESS

The American aluminum industry is founded on the process 

invented by Charles Martin Hall in 1886. It is a continuous electrolytic process in which alumina is dissolved in molten cryolite 

and then electrolyzed by direct current into its components,
116 WATER REQUIREMENTS OF SELECTED INDUSTRIES

oxygen and aluminum. The oxygen ion migrates to and combines 

with the carbon anode to form carbon monoxide or carbon dioxide, 

thus liberating the aluminum at the cathode as pure molten metal. 

Approximately 2 pounds of dry alumina are required to make 1 

pound of aluminum.

The electrolytic cell, or pot as it is usually called, in which 

this process is carried out, is a rectangular steel box lined with 

firebrick and carbon blocks or carbon casing in which is imbedded 

the cathode connection to the negative or return bus bar. The 

anode may be either a prebaked carbon block or a Soderberg selfbaking electrode. A prebaked carbon block is about 12 to 14 inches 

square and 12 inches long and is made of a mixture of petroleum 

coke and coal-tar pitch. As-many as 24 prebaked anodes are used 

in each pot, each connected by copper bar to the positive bus bar. 

The anodes are so arranged that they may be lowered into the pot 

as the carbon is consumed and withdrawn individually when replacement of the electrode is necessary. The carbon lining of the 

pot does not combine with the released oxygen from the alumina, 

but it does deteriorate and wear out, requiring replacement about 

every 2| years.

Carbon thus becomes an important factor in aluminum production. About two-thirds of a pound of carbon in the form of petroleum coke and coal-tar pitch, is consumed for every pound of 

metallic aluminum produced.

The size of the pot varies. Some plants built during World War 

II have pots whose outside dimensions are approximately 12 by 15 

by 3 feet high. Other plants use a pot that is 20 feet long and 8 

feet wide. A pot of either size has a capacity of about 500 pounds 

of aluminum every 24 hours. The trend, however, is to larger 

units. This is revealed in comparing the 18,000-ton (per year) 

capacity potlines built during World War II with the 54, 000-ton 

capacity of at least one potline now under construction (Lutjen, 

1953).

A potline usually consists of approximately 100 electrolytic cells 

arranged in series. Direct current is used, and the voltage drop 

is approximately 6 volts per cell. The size of the cells determines 

the amperage that will be required at the bus bars of a potline. 

Current characteristics commonly used are 600 volts d-c at 60,000 

amperes. Some recently built potlines, however, operate at 

100, 000 amperes. Approximately 10 kilowatt-hours of electric 

power is required to produce 1 pound of aluminum. An itemized 

tabulation of the total power requirements for electrolytic reduction of 1 pound of pig aluminum at a representative plant is as 

follows:
ALUMINUM INDUSTRY 11 7

Kilowatt-hours

General plant purposes............................................................................ 0.8

Conversion loss a-c to d-c....................................................................... .4

Electrolysis.......................................................................................... 8.3

Total per pound of aluminum................................................................ 9.5

Cryolite, either natural or synthetic, to which aluminum fluoride 

has been added, is maintained in molten state at a temperature of 

about 1, 800°F by the flow of an electric current passing from the 

anode through the bath of cryolite to the cathode. Alumina is 

dropped onto the surface of the molten cryolite, and the crust of 

solidified cryolite is broken periodically. The alumina is quickly 

dissolved and electrolytically reduced to its components oxygen, 

which combines with carbon of the anode to form carbon monoxide 

and carbon dioxide, and pure aluminum. The released aluminum 

remains in the molten state and settles to the bottom of the pot. 

Pure molten aluminum is siphoned from the pot into a ladle from 

which it is poured into pigs weighing up to 50 pounds or into billets 

weighing as much as 1, 000 pounds or more.

SODERBERG PROCESS

This improvement of the Hall process avoids the frequent changes 

of prebaked anodes by the use of continuous electrodes. The 

Soderberg type of anode is continuously formed and baked in place 

in a consumable aluminum sleeve on top of the reduction cell as 

the anode functions.

Pots equipped with Soderberg electrodes can be completely enclosed for collecting gases from the reduction process. The gases 

are conducted by ducts and headers from the pots togas scrubbers.

HEROULT PROCESS

At about the same time that Hall invented his process, a French 

metallurgist, Paul L. T. Heroult, made the same basic discovery. 

Heroult filed a patent application in France that antedated by 

several months the application filed by Hall with the U. S. Patent 

Office in July 1886. This interference was resolved when Hall 

proved that he had reduced his invention to practice in February 

1886, thereby taking priority over Heroult's patent application.
118 WATER REQUIREMENTS OF SELECTED INDUSTRIES 

METHODS USED IN THE UNITED STATES

All plants in the United States now engaged in the production of 

alumina on a commercial scale employ the Bayer process with 

the exception of two plants which use the Combination process.

One of the problems confronting the aluminum industry is to 

perfect processes for beneficiating clays and other domestic 

materials at a cost comparable with the Bayer treatment of highgrade bauxite for the production of pure aluminum oxide.

Various processes have been investigated at Government-owned 

pilot plants, including one using alunite and a lime-sinter process 

using clay. Costs of producing alumina by the process using 

alunite and the Pedersen process using high-iron bauxite are 

approximately 50 percent higher than by the Bayer process. 

Further development work at pilot plants is expected to result in 

lower production costs.

The Hall process for the production of aluminum by electrolytic 

reduction of alumina is used in all reduction works in the United 

States.

EFFECT OF VARIATIONS IN PLANT OPERATION ON WATER REQUIREMENTS

Although all alumina plants in the United States operate on the 

same basic process, it was recognized that local conditions ca.used 

wide variation between plants in the quantity of water used. Field 

investigations were undertaken to determine the manner in which 

each plant used water for plant and process requirements, the 

conditions peculiar to each plant that would account for the variation in water requirements, and all other pertinent water-use 

factors. For example, even though the chemical process for obtaining aluminum oxide from bauxite is essentially the same at 

all alumina plants, different procedures are employed to cool the 

sodium aluminate solution before it enters the precipitating tanks 

and to concentrate it by evaporation of some of the water in the 

solution. When this evaporation takes place in a cooling tower, 

water in the solution is lost to the atmosphere as water vapor 

and so is used consumptively. In other plants the quantity of 

solution in the system is controlled by evaporation in a multipleeffect evaporator where practically all of the vapor distilled out 

of the solution is condensed to water which may be reused. The 

latter method is used in all recently constructed alumina plants, 

and some of the older plants are replacing cooling towers with 

multiple-effect evaporators. This one variation of plant practice 

will make a significant difference in total water requirements of
ALUMINUM INDUSTRY 119

the plant, increasing the average daily water intake at one plant 

from 1.6 to 52.0 mgd but decreasing the consumptive use of water.

The variation in water requirements among reduction works is 

even greater than among alumina plants. As gas scrubbers are 

one of the principal water users in reduction works, this variation 

is largely accounted for by whether or not gas scrubbers are used 

and, if so, whether the wash water is reused. Of the 14 reduction 

works visited in the course of this water-use investigation, all 

but 3 works use gas scrubbers to wash the fumes before they are 

released to the atmosphere. Ducts convey the gases from the reduction pots of the gas scrubbers where the gases are washed by 

sprays of water which absorb fluorine gas. This gas, if passed 

to the atmosphere, constitutes a nuisance because of its toxic 

effect on vegetation. At some works where prebaked electrodes 

are made, fumes from the carbon plant also are scrubbed. When 

wash water is reused it must be cooled, and the method employed 

to cool it makes a considerable difference in the quantity of water 

lost to the atmosphere by evaporation. Several reduction works, 

having an abundance of low-cost water available, find it more 

economical not to reuse water from the gas scrubbers. The 

quantity of water used per pound of aluminum produced at such 

works is high, and the percentage of the total water intake used 

for gas scrubbing also is high. At one reduction works where the 

water from the gas scrubbers is not reused, approximately 95 

percent of the total intake of 30. 9 mgd is used for gas scrubbing.

The total water intake for each reduction works, its production 

of alumina or pig aluminum, and the quantity of water required 

per unit of product are facts readily obtainable. The objective of 

this report encompasses the broader purpose of determining the 

unit quantities of water used under present conditions for each 

process and plant use and the minimum requirements under 

adverse conditions.

As the manner in which each plant is operated is dictated in 

some degree by conditions over which the management has m> 

control, there is included a summary of the observations that 

were made at each plant. This summary is intended to show not 

only how water is used but also facts pertaining to why such 

practice is followed.

FACTORS AFFECTING LOCATION OF PLANTS

ALUMINA PLANTS

The quantity of raw materials required by the aluminum industry 

is enormous. Production of alumina in 1952 was approximately
120 WATER REQUIREMENTS OF SELECTED INDUSTRIES

2 million tons, and the unit quantity of materials needed to produce a similar unit of aluminum is shown graphically in figure 20.

The two most important elements of cost in the production of 

alumina and its delivery to the smelter are bauxite and transportation. Taken together they account for 30 to 40 percent of net 

mill costs of primary aluminum and approximately 20 percent of 

its selling price.

Prior to the first great expansion of the industry resulting from 

World War II, most of the alumina produced was derived from 

domestic bauxite. As the chief domestic high-grade ore deposits 

are in Arkansas, it was logical to locate the alumina plants near 

the source of supply of the principal raw material.

In recent years more and more bauxite is being imported, 

principally from the Guianas and the West Indies. Alumina plants 

built to utilize ores from these sources are located on deepwater 

channels where ore carriers can dock alongside the plants.

REDUCTION WORKS

The largest cost item involved in the smeltering of aluminum 

is electric power. The power consumption in 1952 for the production of aluminum was more than 13 billion kilowatt-hours. 

Low-cost production is dependent upon low-cost electricity. As 

it takes approximately 10 kilowatt-hours of electric power to produce 1 pound of aluminum in the electrolytic cell, a variation in 

power cost of as much as 0. 1 mill per kilowatt-hour has a significant effect upon production costs. With power costs at the remarkably low average of approximately 2 mills per kilowatt-hour, 

the percentage of net plant costs per pound of aluminum for power 

is from 16 to 21 percent.

When the aluminum industry began its first great emergency 

expansion program to meet World War II needs, most of the new 

reduction works were built near the great hydroelectric powerplants in the Pacific Northwest. Plants so located, constituting 

about 30 percent of the total United States plant capacity, are the 

reduction works at Troutdale, Oreg. , and at Tacoma, Spokane, 

Vancouver, Wenatchee, and Longview, all in Washington. However, power shortages and higher freight rates on alumina and 

pig aluminum have reduced the advantage of low-cost electric 

power.

So urgent was the need for rapidly expanded production of 

aluminum that cost of production became a secondary consideration.
ALUMINUM INDUSTRY 121

Some reduction works were located by necessity near existing 

sources of electric power even though the cost of that power was 

greater than the industry could afford to pay under normal conditions of competition. Such high-cost producers became unprofitable when the wartime needs of the military decreased. 

Some of them were dismantled and are not included in this report. 

Others, such as the plants at Massena, N. Y. , and Badin, N. C. , 

were retained as marginal operators and were put back in operation to ease the shortage while new plants were being constructed to meet the industry's second great emergency expansion 

program, which started in 1951.

The more recently built plants have been located in the Gulf of 

Mexico area, nearer to the source of supply of alumina. There 

the electric power required to operate the potlines, whether 

purchased from a utility company or produced at the plant, is 

generated principally by natural gas used as fuel burned either in 

a steam powerplant or in internal-combustion engines. The most 

recent plant, at Rockdale, Tex. , will use power developed by 

steam turbogenerators in a plant in which charred lignite is the 

fuel.

Expansion of the industry is likely to occur either in areas unattractive to general industrial development, such as Alaska, or 

in areas likely to have reliable long-term cheap power through the 

use of natural gas, lignite, and coal.

FINDINGS OF THE SURVEY

SOURCES OF WATER

Water for the plants surveyed is obtained from both surfacewater and ground-water sources and is supplied to the plants by 

both municipal and company-owned waterworks. Brackish wateris used in two reduction works, principally for fume scouring. 

Several plants obtain water from more than one source.

A summary of the sources of water for 6 alumina plants and 14 

reduction works is shown in table 2. The quantity of water and 

the percent of total intake from the various sources used at 

alumina plants and reduction works are shown in tables 3 and 4, 

respectively.
122 WATER REQUIREMENTS OF SELECTED INDUSTRIES

Table 2. Sources of water, alumina plants and reduction works, 1952 

[Compiled from data obtained at the plants]

Source

Total....................................................................................

Number of plants

Alumina 

plants

4 

1 

1

0

6

Reduction 

works

7 

4 

1 

2

14

Table 3. Quantity and percent of water from various sources used at alumina plants,

1952

Source Thousands 

of gallons

18, 326

3,475

 o

11,801

Percent of 

total intake

70.5

29.5

0

100.0

*An additional 50.4 mgd is planned to be used for barometric condenser-cooling water.

Table 4. Quantity and percent of water from various sources used at reduction works,

1952

Source Thousands 

of gallons

X65, 685

35, 842

2,996

104, 523

Percent of 

total intake

62.8

34.4

2.8

100.0

An additional 500 mgd is used for condenser-cooling water at thermoelectric generating 

plants.

EFFECT OF SIZE OF PLANT ON WATER REQUIREMENTS

The six alumina plants fall into two general sizes; those having 

a capacity of approximately 2 million pounds per day and those 

having approximately double that capacity. Each of the three 

smaller plants used more water per pound of alumina produced 

than did any of the three larger plants. Furthermore, there was 

considerable uniformity in the water requirements of the three 

smaller plants. The one that had the highest unit water requirement used about one-third more water per pound of alumina than 

did the small plant that had the lowest unit requirement. The
ALUMINUM INDUSTRY 123

variation iu unit water needs in the group consisting of the three 

larger plants was far greater than that in the smaller plants; the 

highest unit water requirement was 2^ times the lowest.

The largest use of water at alumina plants is for makeup water 

to the red-mud lake to compensate for losses due to evaporation. 

If the capacity of a given plant were doubled and the areal extent 

of the red-mud lake were not increased, it follows that the surface 

evaporation would remain approximately the same as it formerly 

was and the unit loss from this cause for the enlarged plant would 

be less per pound of product. This assumption is borne out in 

general by the data obtained in the course of the survey, but the 

wide variation in unit water use between plants of similar size 

indicates that other factors have a greater effect on the water requirements for a given plant. For example, the annual quantity of 

precipitation added to the red-mud lake varies by plant location 

and has a significant effect on the quantity of water added to the 

lake as makeup.

The 14 reduction works visited do not have even this slight degree of conformity of economy based upon plant capacity. There 

is not sufficient uniformity in capacity of the individual plants to 

permit grouping them by size. Neither is there any apparent relationship between plant size and unit water requirements. The 

plant that has the lowest water requirements per pound of pig aluminum is next to the smallest in plant capacity. The second-best 

plant in water economy is next to the largest of all reduction 

works, having a capacity more than three times that of the plant 

having the highest water economy. The plant having the smallest 

daily production uses more than 13 times as much water per 

pound of aluminum as does the second smallest.

It is concluded, therefore, that plant capacity, in itself, has so 

little effect on plant water requirements that other conditions 

such as plant operation based on cost of water, plant location, and 

need for conservation of water mask any economy inherent in 

plant size.

PLANT USES OF WATER

Although the chemical process is essentially the same in all 

alumina plants located in the United States, the manner in which 

various plants are operated differs sufficiently to make direct 

comparisons difficult. For example, in some plants water from 

the distribution mains is added to the cycle as hydrate wash water 

and is charged as such in the plant water balance. At other 

plants, the condensate from the evaporators is used for hydrate
124 WATER REQUIREMENTS OF SELECTED INDUSTRIES

wash, and water for this purpose does not appear in the water 

balance as a charge against water intake. At others, wash water 

is taken from the red-mud lake, and the water thus used is charged 

as lake makeup.

Table 5 shows how the total daily plant intake of water is charged 

to the various plant and process uses at alumina plants. The water 

intake is tabulated in gallons per day and in percent of total plant 

intake for the industry.

Table 5. Uses of water in alumina plants, in gallons per day and percent of total intake,

1952

[Compiled from data obtained at the plants]

Use

Red-mud lake makeup......................................................

Thousands of 

gallons per day

984

3,591

550

6,676

11,801

Percent of 

total intake

8.4

30.4

4.7

56.5

100.0

Water requirements of the electrolytic process used in reduction works are entirely different from the water uses at alumina 

plants. Table 6 shows the quantity of water used per day for various purposes at reduction works and the percentage of the total 

water intake charged to each water use.

Table 6. Uses of water in reduction works, in gallons per day and percent of total intake,

1952

[Compiled from data obtained at the plants]

Use Thousands of 

gallons per day

1,168

714

8,682

416

1,420

13, 524

78,599

1,357

104, 523

Percent of 

total intake

1.1

.7

8.3

.4

1.4

13.0

75.1

1.3

100.0

Several reduction works are equipped to cast aluminum in 

billets and pigs by the rotary-cast method. Both of these processes use water consumptively for quenching by direct chill. The 

production of the industry, as shown in this report, is stated in
ALUMINUM INDUSTRY 125

terms of production of pig aluminum even though some of that 

tonnage is cast in billets. The additional water used when billets 

are cast by the direct-chill method is included in the water balance 

of the plants so equipped.

The unit quantity of water required for cooling transformers 

and rectifiers ranges from zero to 9. 28 gallons per pound of pig 

aluminum. The plants that use no cooling water for this purpose 

generate electric power by internal-combustion engines at 600 

volts d-c for direct connection to the bus bars of the potlines. 

Even when high-voltage a-c electric current is purchased, the 

quantity of water used for conversion or rectification to d-c 

current ranges from 0. 72 gallon to 9. 28 gallons per pound of 

aluminum. At the plant having the lowest unit water use, the 

cooling water from the rectifiers is recirculated in a closed 

system through air-cooled heat-transfer units. Water must be 

conserved at this plant, and the low water requirement for rectifier cooling justifies the first cost and maintenance of the equipment necessary to effect this saving of water. The plant having 

the highest unit use of water for current rectification is so located 

that there is no economy in plant operation to be gained through 

recirculation of cooling water.

The quantity of water required by the sprays in gas scrubbers 

is the largest water use at reduction works, accounting for 75 

percent of the total water intake of all such works. Three of the 

older reduction works are not equipped with gas scrubbers; all 

recently built plants are so equipped to eliminate or considerably 

lessen air pollution. At one plant, where water is available in 

abundance, as much as 95 percent of the total plant intake is used 

for gas scrubbing; this amounts to 28. 50 gallons of water per 

pound of aluminum. At the other extreme is a plant that uses 

purchased water for gas scrubbing. By the use of cooling ponds, 

makeup water for gas scrubbing is only 3 percent of plant intake, 

equivalent to 0. 04 gallon of water per pound of product. The 

variation in use of water between these two plants, both accomplishing the same degree of protection against air pollution but 

differing in the need to conserve water, is about 700 to 1. It is 

such wide variations in the quantity of water used for similar 

purposes at different plants, but operating under different economic compulsion to save water, that makes it difficult to state categorically the quantity of water required in the necessary processes for the production of aluminum.

As indicated by the foregoing observations, the total water requirements of alumina plants and of reduction works differ greatly. 

Despite the fact that the process in alumina plants is a chemical
126 WATER REQUIREMENTS OF SELECTED INDUSTRIES

one in which an enormous quantity of liquid recirculates through 

the various stages of the Bayer process, the total daily water requirements of all such plants is only about one-ninth of the total 

required by all reduction works; ll.Smgd as compared to 104 

mgd.

The percentage of the total daily water intake of all alumina 

plants and of all reduction works that is used for various plant 

and process requirements is shown in figure 23.

ALUMINA PUNTS

5 percent sanitary and plant services 

19 percent red-mud lake makeup

22 percent process

54 percent cooling water

REDUCTION WORKS

percent air-compressor cooling

percent engine cooling

percent electrode plant 

V 4 percent boiler-feed water 

^8 percent sanitary and plant services

12 percent rectifier and transformer cooling

72 percent gas scrubbers

Figure 23. Percentage of total water intake for various plant uses.

CONSUMPTIVE USE OF WATER

With but one exception all alumina plants and reduction works 

were reported by the plant managements to have an adequate 

supply of water for plant and process needs. Only one plant is 

handicapped by a source of water that is seasonally deficient for 

the plant water requirements. This plant obtains all its water 

directly from a stream, the flow rate of which at times is less 

than the water requirements of the plant. As the water of the 

creek cannot be impounded, the plant has been designed with an 

exceptionally large brown-mud lake which is depleted at times of 

low flow and refilled when the flow of the stream is in excess of 

plant requirements.
ALUMINUM INDUSTRY 127

^u the supply of water for all other plants is ample for 

all plant needs, the economic factor of the cost of water differs 

considerably between plants. It is this factor that accounts in 

large measure for the widely divergent plant practices in the use 

of water.

For example, consider two previously discussed alumina plants, 

both of which buy all water for plant requirements from municipal 

waterworks. Because the cost of this water is higher than the 

average cost of water pumped by company-owned plants from 

surface-water sources or from wells, the management of each of 

these plants makes complete utilization of the water intake by 

reuse. No water is discharged from either of these plants as a 

liquid, and the entire plant intake is used as makeup to compensate 

for water lost to the atmosphere as water vapor. Thus the water 

requirement for the above-mentioned plants is reduced to an 

absolute minimum, and the entire plant water intake is used consumptively. On the other hand, another plant obtains its water for 

process use from wells on the property at low pumping cost and 

will pump cooling water from a river for the barometric condenser 

to be used with the sextuplet-effect evaporator now being constructed. It is more economical for this plant merely to use the 

cooling water once and discharge it to the river than it would be 

to reuse the water by means of a spray pond or cooling tower and 

furnish only enough to make up for the water consumptively used.

Production costs similarly dictate the degree of utilization of 

water used in reduction works. Low-cost water is obtained at five 

reduction works either directly from a river or from wells hydraulically connected to the river. At all these works water is 

used but once. At one works, water is available in abundance, 

but it is relatively costly owing to the required water treatment. 

Because of this fact, it is desirable to reuse water in the interests 

of decreasing plant costs. Two works use water furnished by a 

municipal source; the supply for both works is ample, but the cost 

is high. At both works utilization of water is carried out to such a 

degree that practically all the water taken into the distribution 

mains leaves it as water vapor.

Of six alumina plants in operation, three use the entire plant 

water intake consumptively. It would seem, therefore, that when 

conditions require it, the water requirement for an alumina plant 

can be reduced to the quantity of water used consumptively.

No reduction works achieve 100 percent consumptive use, although one reported only 2 percent of the total water intake was 

discharged as waste water. Two plants reported about 80 percent 

consumptive use of water.
128 WATER REQUIREMENTS OF SELECTED INDUSTRIES

When the supply of water is inadequate, economy of water must 

of necessity be practiced. When the cost of utilizing water one 

time is higher than the cost of reusing it, the highly competitive 

status of the aluminum industry can be depended on to bring about 

a greater degree of reuse in order to lower production costs.

QUALITY OF WATER

The necessity of furnishing pure water for the health protection 

of employees is the same for alumina plants and aluminum reduction works as obtains in manufacturing plants in general. Water 

used for plant purposes such as drinking, washhouses, sanitary 

fixtures, cafeterias, and kitchens is chlorinated at all but 2 of the 

20 plants covered by this report. The source of supply of water 

for these two plants is ground water pumped from deep wells. 

Periodic examinations of water samples for bacteria are made, 

which to date have indicated no need for chlorination. Water is 

furnished to some plants from municipal waterworks and is treated 

for domestic use before entering the distribution mains. Other 

plants have their own sources of supply, pumping water from wells 

or rivers. The entire plant intake from such sources is chlorinated at the pumps. Additional treatment, consisting of coagulation and filtration, is given to the water at all plants where 

river water is used for process.

Water of good quality for process use is a prerequisite for 

alumina plants because impurities introduced by process water entering the liquor cycle as hydrate wash tend to accumulate in the 

caustic soda solution and to impair its function. The water, pumped 

from deep wells, which is used at one alumina plant requires no 

treatment other than chlorination for bacteria control and control 

of algae growth in the mains. Cooling water used at this plant is 

obtained from a river adjacent to the plant. Ground water, pumped 

from eight company-owned wells located on the plant site, is used 

for process at another alumina plant. As this water has a total 

hardness of 16. 7 grains per gallon, that portion of process water 

which enters the liquor cycle is softened by cation exchange. The 

remaining four alumina plants all use river water,-and in three of 

these plants all plant intake water has been chlorinated, coagulated, and filtered prior to delivery to the plant. At the fourth 

plant, which obtains its water from a stream, the only water 

treated is that used for such plant uses as drinking, washhouses, 

and sanitary lines. Process water is not treated. The explanation 

of this departure from normal procedure lies in the fact that this 

plant uses the Combination method, and the brown-mud lake is 

exceptionally large to provide storage when the flow of the stream 

is deficient. Its 200 acres of surface permits the brown-mud lake
ALUMINUM INDUSTRY 129

to act effectively as a cooling pond. At this plant, and others 

similarly equipped with sextuplet-effect evaporators, most of the 

process water is used as cooling water. Condensate from the 

evaporators is used as hydrate wash and, as such, enters the 

liquor cycle free from objectionable impurities in solution. The 

increasing use of multiple-effect evaporators in the liquor cycle, 

therefore, in addition to improving over-all efficiency, has the 

important advantage of enabling alumina plants to utilize water of 

inferior chemical quality without as complete treatment as would 

be required were that water introduced directly into the liquor 

cycle as hydrate wash.

The quality of water for some plant uses at aluminum reduction 

works is of great importance, but the quantity of water required 

for those uses is a relatively small percent of the total plant intake. The quality of water used as boiler-feed makeup is important, and because reduction works, unlike alumina plants, do not 

have condensate water as a byproduct of process, all boiler-feed 

makeup water is given such treatment as is necessary. At one 

plant, brackish water is evaporated, and the condensate is used 

for boiler-feed water. The principal use of water at reduction 

works is for wash water at the gas scrubbers, and for this the 

quality of the water used is unimportant. Brackish water is satisfactorily used at one plant in the gas scrubbers. The relative unimportance, quantitatively, of the quality of water required for 

aluminum reduction works is shown in figure 23. The average 

amount of water used for gas scrubbers is 72 percent of the total 

water intake. Thus it is seen that reduction works can be so designed that even brackish water can be used for a major portion 

of its total water intake. Water of high quality, required for boiler 

feed, averaged only 4 percent of total plant intake.

TREATMENT OF WATER

Table 7 indicates the frequency of occurrence of various kinds 

of water treatment given to all or part of the plant intake.

Table 7. Kinds of water treatment

Alumina plants 

(6)

6 

5 

5 

3 

1

Reduction works 

(14)

12

7 

7 

5 

5
130 WATER REQUIREMENTS OF SEUECTED INDUSTRIES

Water used for drinking and sanitary purposes at all six alumina 

plants is chlorinated. Five of these plants obtain water for all 

purposes from surface-water sources, either municipal waterworks or company-owned .pumping plants. All these plants treat 

further all or part of the water intake by coagulation and filtration. Three plants find it necessary to condition the water further 

by pH adjustment. Only one alumina plant obtains its supply of 

water entirely from ground-water sources. At that plant the water 

pumped from wells located at the plant site is chlorinated before 

entering the distribution mains.

Of the 14 aluminum reduction works visited, all but 2 chlorinate 

all or part of the plant water intake, and these 2 exceptions obtain 

their entire supply from ground-water sources. The water at all 

seven plants that use surface water requires further treatment by 

coagulation and filtration either at the municipal waterworks or at 

company-owned pumping plants. The electrolytic process at reduction works does not provide condensate from evaporators as 

does the chemical process of extracting aluminum oxide from 

bauxite, so that boiler-feed water is a matter of concern to the 

management even though the quantity for this use is an extremely 

small percent of total plant intake. Ten reduction works, of the 

total of fourteen, treat boiler-feed water further either by pH adjustment or by zeolite softening.

TREATMENT AND DISPOSAL OF WASTE WATER

The problem of disposing of sanitary sewage at alumina plants 

and reduction works is the same as that which confronts the 

management of any other kind of industrial plant or the adjacent 

municipalities. Disposition of sanitary waste water at three 

alumina plants is made to the red-mud lake, either treated or 

raw, in order to effect economy of water. Because aluminum reduction works have no such opportunity to reuse sanitary waste 

water, all 14 works discharge the waste from sanitary sewers 

into a river or the sea; sewage is given the Imhoff treatment in 

all but three.

The disposition of waste process water at alumina plants presents no problem. Although the supply of water is adequate, its 

cost at three such plants is high, so that it is desirable in these 

plants to return all waste process water to the red-mud lake. 

Because the supply of water at one alumina plant is inadequate at 

times, the supply available is supplemented by returning all waste 

water to the brown-mud lake. At the other two alumina plants, 

waste process water is dumped, untreated, into the river.
ALUMINUM INDUSTRY 131

Waste ,'iuiest; water is recirculated at five reduction works. 

The quantity of water used at these works for all plant uses other 

than sanitary service reflects the quantity lost to the atmosphere 

as water vapor. The remaining nine reduction works discharge 

waste process water into a stream or bay.

Tables 8 and 9 summarize how sanitary sewage and plant process water is disposed of at alumina plants and reduction works, 

respectively, and indicate whether the waste water is treated.

Table 8. Treatment and disposal of waste water at alumina plants

Method of disposal

Frequency of occurrence

Sanitary sewage

1 

2 

1 

1 

1

6

Process water

0 

4 

0 

2 

0

6

Table 9. Treatment and disposal of waste water at reduction works

Sanitary sewage

8

3

2

0

1

0

14

Process water

1

7

1

0

0

5

14

Frequency of occurrence

POLLUTION FROM PROCESS WASTE

There is no pollution problem involved in disposing of waste 

process water at alumina plants. The principal use for water 

which leaves the plant in liquid form is for cooling purposes and 

as such is not contaminated. Water added to the caustic soda 

solution in the chemical process used at such plants is removed 

from the solution either directly as water vapor as in the 

case of cooling towers or as condensate from evaporator and 

after condenser.
132 WATER REQUIREMENTS OF SELECTED INDUSTRIES

Pollution is more serious at reduction works. Fumes given off 

by the electrolytic action in the cells contain fluorine which destroys vegetation for a considerable distance from the plant and is 

harmful to cattle grazing in the affected area. All the reduction 

works constructed in recent years have overcome this nuisance 

by scrubbing the flue gases. Particles of aluminum oxide and 

carbon are removed, in some instances by mechanical separators, 

and the gases are scrubbed with a water spray which removes 

fluorine by absorption and the particles too fine to be removed by 

mechanical means.

At those plants where the waste water from the gas scrubbers 

is discharged directly into a river the acid formed by the absorbed 

gases, principally fluorides, undoubtedly would cause stream 

pollution were the flow of the stream not sufficient to render them 

harmless by dilution. To avoid stream pollution from this source 

two plants discharge the waste water from the gas scrubbers to 

settling ponds where lime is added to neutralize the acids. The 

sludge resulting from precipitation is removed and safely disposed 

of by burying.

SUMMARY OF PLANT WATER-USE DATA

The following water-use data were obtained from the water 

balances of the individual plants as reported by the plant managements. The water-use data are based on operating conditions obtaining at the time the plants were visited in 1952.

Important changes in plant operation were beingmade at several 

alumina plants and reduction works. These changes will affect the 

water-use data at those plants and the averages for the industry.

ALUMINA PLANTS

A summary of the water-use data of 6 alumina plants indicates 

that the industry was using approximately 11.8 mgd in order to 

produce 17. 9 million pounds of alumina per day.

The unit water use ranged from -0. 28 gallon to 1.10 gallons of 

water per pound of alumina. The average over the industry was 

0. 66 gallon per pound of alumina.

A sextuplet-effect evaporator was under construction at one 

alumina plant, the last stage of which will consist of a barometric 

condenser taking condensing water from a river and returning it 

to the river on a once-through-to-waste cycle. The maximum
ALUMINUM INDUSTRY 133

quantity of water that will be required for this operation is estimated to be 50. 4 mgd.

This single modification of plant operation will increase the 

total quantity of water used by the industry for the production of 

alumina from 11. 8 to 62. 2 mgd. The range of unit water use between plants will be increased from 0. 28 1. 10 gallons of water 

per pound of alumina to 0. 28 26. 00 gallons per pound. The average for the industry also will be greatly changed when this evaporator is put in operation, increasing the average unit water use 

from 0. 66 gallon to 3. 48 gallons per pound of alumina.

Table 10 is a summary of water-use data of alumina plants, as 

operated at the time the survey was made and as they are expected 

to be after the barometric condenser has been put in operation.

Table 10. Summary of water-use data tot alumina plants, 1952

[Compiled from data obtained at the plants]

Alumina plants

Unit water use, gallons per pound;

Present use

11, 801

17, 936

.28

1.10

.66

After plant changes

62, 201

17, 936

.28

26.00

3.48

REDUCTION WORKS

A compilation of water-use data from 14 reduction works shows 

that the total water intake was approximately 104. 5 mgd to produce 7. 1 million pounds of pig aluminum per day.

The unit water use varied even more between reduction works 

than it did between alumina plants, ranging from 1. 24 to 36. 33 

gallons of water per pound of aluminum. The average for the industry was 14. 62 gallons per pound.

The proposed installation of additional gas scrubbers at one 

plant will nearly double its total water intake, adding approximately 10 mgd to the present plant intake.

A summary of water-use data for reduction works is given in 

table 11. This table, as does the preceding one, shows daily intake and average unit water use for the industry under operating
134 WATER REQUIREMENTS OF SELECTED INDUSTRIES

conditions found when the plants were surveyed and as they are 

expected to be after plant changes in the use of water are effected.

Table 11. Summary of water-use data for reduction works, 1952 

[Compiled from data obtained at the plants]

Reduction works

Unit water use, gallons per pound;

Present use

104, 523

7,148

1.24

36.33

14.62

After plant changes

1114,523

7,148

1.24

36.33

16.05

^00 mgd of condenser cooling water for thermoelectric power generation is not included.

These several examples illustrate the profound effect major 

changes in plant operation have on total water intake and unit 

water use, not only of the plants involved but on water requirements for the industry. Any comparison of water-use data, therefore, must take into account the dates of the comparative data, the 

plant practices obtaining at those times, and the water uses 

included.

\PATER USE PER UNIT OF PRODUCT

The average for all alumina plants in the United States of the 

quantity of water required for all plant and process uses for the 

chemical production of 1 pound of alumina from bauxite, as determined when the plants were surveyed in 1952, was 0. 66 gallon.

On the same basis the average quantity of water required for 

the production of 1 pound of aluminum from alumina by electrolytic 

reduction was 14. 62 gallons.

However, if the information sought is the average quantity of 

water required to produce 1 pound of aluminum from bauxite, not 

only must the water requirements for alumina production be taken 

into consideration but also the fact that approximately 2 pounds of 

alumina are needed to produce 1 pound of pig aluminum, making a 

total water requirement of 15. 94 gallons.

Average water use, in gallons, to produce 2 pounds of alumina,..................................... 1.32

Average water use, in gallons, for reduction to 1 pound of aluminum............................. 14.62

Total average water use, in gallons, per pound of pig aluminum from bauxite.......... 15.94
ALUMINUM INDUSTRY 135

CONCLUSIONS

When economic conditions demand it, the water requirements 

of plants engaged in the production of virgin aluminum from 

bauxite can be reduced to an exceedingly low quantity per unit of 

product. The gross plant intake, however, assumes significant 

volume because of the large production capacity of these plants.

Alumina plants and aluminum reduction works are designed and 

built as a complete unit. When unforeseen circumstances require 

rapid expansion of plant capacity such as occurred during World 

War II and again more recently, any increase in the size of existing plants was made in large increments, frequently doubling 

their capacity. Plant growth in the aluminum industry is not 

achieved by small additions here and there to take care of constantly increasing demand for product. The water requirements 

of the completed plant therefore can be designed for a known production by a known process with which the management is familiar 

from experience.

The range of the quantity of water required at alumina plants, 

from a minimum of 0. 28 gallon of water per pound of alumina to 

a maximum of 1. 10 gallons, is considerable but not nearly as great 

as that at aluminum reduction works at which the gallons of water 

per pound of pig aluminum range from 1. 24 to 36. 33. As the size 

of the plant has a relatively minor effect upon the unit water use, 

other local conditions must of necessity be the principal controlling factors.

Meteorologic phenomena such as local precipitation, air temperature, relative humidity, and wind have some effect on plant 

water intake. The following observations illustrate the effect of 

climatic conditions on total plant water requirements of two 

plants. All the water used by each of them is purchased from a 

municip'al supply. Both plants are operated in such a manner that 

water is used to the best economic advantage; the first plant uses 

consumptively 92. 5 percent of the total water intake, the second 

approximates 100 percent consumptive use. Despite the fact that 

both plants are operated to use water most economically, the unit 

water requirement varies in the extreme. The first plant uses 

0. 28 gallon of water per pound of alumina, the lowest unit water 

use of all alumina plants; the other has a total unit water use of 

1. 10 gallons, which is the highest of all. This disparity is attributed largely to different rates of evaporation from the redmud lakes and partly to differences in replenishment of the redmud lakes by precipitation. The annual precipitation (U. S. 

Weather Bureau, 1953a), in the area of the first plant is 67. 21
136 WATER REQUIREMENTS OF SELECTED INDUSTRIES

inches; that at the second plant, subjected to a strong, steady 

breeze, is estimated to be 25. 44 inches (1953b).

The aluminum industry is highly competitive, not only between 

major producers within the industry but also with the older metallic industries (such as steel and copper). Aluminum plants are 

operated at a high degree of efficiency, and the management is 

alert to effect economy of operation. It can be taken for granted 

that production cost is a "major factor in determining the plant 

water requirement. At plant locations where the supply of water 

is abundant, pumping costs are low, and the quality of water is 

such that little if any treatment is required, it may be cheaper to 

use water once and waste it rather than to pump the waste water 

to some distant part of the plant for reuse. At most of these plants 

the water available would be lost to the sea if not utilized. A study 

of their water balance shows that they are among the plants having 

a high unit water use.

Variations in the manner in which details of a basic process are 

carried out account in part for the range in unit water use between 

plants. It is basic in the Bayer process that the quantity of the 

caustic soda liquor in the cycle be held constant. For that reason 

water added to the liquor as hydrate wash water must be compensated for by the removal of an equal amount of water at some 

point in the cycle. This is accomplished by evaporation. At one 

alumina plant, for example, the spent liquor now is passed through 

cooling towers where it is concentrated by evaporation, the water 

vapor passing into the atmosphere. The majority of alumina plants 

achieve this end by sextuplet-effect evaporators, the final stage of 

which is a barometric condenser. An evaporator of this kind is 

being erected at the above-mentioned plant to take advantage of its 

higher efficiency as compared to evaporation effected in a cooling 

tower. Cooling water for the condenser will be taken from a nearby river and returned to it unchanged except for a slight rise in 

temperature. It is estimated that as much as 35, 000 gpm will be 

required when the temperature of the river water is 90°F, the 

highest temperature on record. This one change in plant procedure 

will increase the average water intake of this plant approximately 

twentyfold and will triple the total quantity of water used by all 

alumina plants, It should be borne in mind that, were the large 

volume of river water not available, this plant probably would 

follow the practice of reusing the cooling water by recirculating 

it, thereby reducing the quantity of water utilized but increasing 

the quantity used consumptively.

Reduction works also differ in details of plant operation even 

though all reduction works employ the Hall process. Water used 

to scrub the gases rising from the rows of electrolytic cells
ALUMINUM INDUSTRY 137

constitutes a principal water use. This nuisance-abating improvement was used in all but 3 of the 14 plants in operation at the time 

this water-use survey was made. The increasingly insistent demand for elimination of fluorine from the gases given off to the 

atmosphere will tend to further the use of gas scrubbers, thereby 

increasing the gross plant intake of water by the industry and the 

unit quantity of water required per pound of pig aluminum produced.

SELECTED REFERENCES

Anderson, Samuel W., 1953, Aluminum industry expands for war and peace: Jour. Metals,

v. 5, no. 3, p. 388-394. 

Bray, J. L., 1947, Nonferrous production metallurgy: 587 p., 2d ed., New York, John Wiley

& Sons, Inc. 

Budgen, N. F., 1947, Aluminum and its alloys: 369 p., Id ed. London, Pitman & Sons,

Ltd.

Carr, C. C., 1952, Alcoa, an American enterprise: 292 p., New York, Rinehart. 

Chemical and Metallurgical Engineering, 1947, Chemical Engineering flowsheets: 4th ed.,

p. 7.

Chemical Engineering, 1951, Lignite process hits the mark: v. 58, no. 9. p. 219. 

Civil Engineering, 1953, Aluminum industry sets production record in 1952: v. 23, no. 2,

p. 71.

Defense Production Administration, 1951, Bureau of Mines plans to run alumina plant: Defense Production Record, v. 1, no. 31, p. 2. 

Edwards, J. D., 1945, Combination process for alumina, in Metals technology, v. 12, no.

5: Am. Inst. Min. and Metall. Eng., Tech. Pub. 1833. 

Edwards, J. D., Frary, F. C., and Jefferies, Jay, 1930, The aluminum industry: 870 p., v.

1, 2, 1st ed.. New York, McGraw-Hill Book Co., Inc. 

Electrical World, 1953, Aluminum industry sets output record in 1952: v. 139, no. 4, p.

264. 

Encyclopedia of Chemical Technology, 1947, Aluminum: v. 1, p. 602, New York, The

Interscience Encyclopedia, Inc.

Engle, N. H., Gregory, H. E., and Mosse, Robert, 1945, Aluminum, an industrial marketing appraisal: 494 p., Chicago, Inland Press. 

First Boston Corp., 1951, Aluminum, the industry and the four North American producers:

New York, 79 p.

Fortune, 1951, The great aluminum farce: v. 43, no. 6, p. 93, Time Inc. 

Frary, F. C., 1949, The light metal picture: Metal Progress, v. 56, no. 2, p. 204. 

Kaiser Aluminum and Chemical Corp., 1951, Brochure on company's aluminum activities,

Oakland, Calif., 48 p.

Lutjen, G. P., 1953, Aluminum: Enc,. and Min. Jour., v. 154, no. 2, p. 88-89. 

Metal Progress, 1950, Alcoa's new plant at Point Comfort, Texas: v. 58, no. 1, p. 5b-59. 

National Association of Manufacturers and The Conservation Foundation, 1950, Water in

industry: New York, 51 p. 

Office of Defense Mobilization, 1952a, Aluminum expansion will double 1950 production:

The Battle for production, Fourth quart, rept. to the President, p. 15.

 1952b, Aluminum capacity will rise by over 400,000 tons in 1952: Strength for the

long run, Fifth quart, rept. to the President, p. 17.

Reynolds Metals Co., 1950, The A-B-C's of Aluminum: 96 p., Louisville, Ky. 

U. S. Bureau of Mines, 1953, Materials survey: Bauxite; rept. prepared in cooperation

with U. S. Geological Survey, for the Office of Defense Mobilization, 305 p. 

U. S.. Bureau of Mines and U. S. Geological Survey, 1948, Mineral resources of the United

States: Washington, D. C., Public Affairs Press. 

U. S. Dept. of Commerce, 1956, Business and Defense Services Admin., Aluminum and

Magnesium Div., Materials survey on aluminum (in press). 

U. S. Surplus Property Board, 1945, Aluminum plants and facilities: 131 p., rept. to

Congress. 

U. S. War Assets Administration, 1947, Aluminum plants and facilities: 51 p., First supp.

rept. to Congress. 

U. S. Weather Bureau, 1953a, Climatological data, v. 58, no. 13.

 1953b, Climatological data, v. 59, no. 13.

Weldon. J. D. C., 1953, Special study of the aluminum industry: Mag. of Wall Street, v. 91,

no. Iffi p. 530. 

Western Metals, 1953, Alcoa operates western reduction plant: v. 1, no. 10, p. 24.

INDEX

Page 

Acknowledgments................................. iii

Aluminous ores, abundance................... 108

distribution of bauxite....................... 109

distribution of cryolite.......................109

possible use of anorthosite............ 109-110

reserves of bauxite............................109

use of synthetic cryolite.....................109

Bayer process.........................111-113, 114

Brackish water, percent of total water

used..................................... 122

quantity used...................................122

works using.............................. 121, 122

Combination process............... 112, 114-115

Conclusions..................................135-137

Consumptive use of water, differing need

for economy.......103, 127-128, 136

factors affecting.........................126-128

Electric power, amount required....... 116-117

effect on plant location............... 120-121

item in cost of aluminum...................120

source............................................ 106

voltage drop....................................116

Field investigations, factors involved.......106

subjects of study........................104, 106

Ground water, percent of total water

used..................................... 122

plants and works using....................... 122

quantity used...................................122

Growth of industry........................ 106, 107

Hall process................................. 115-117

Heroult process................................... 117

History of industry......................... 106-107

Location of plants, alumina plants.......... 120

reduction works near alumina supply...,.121 

reduction works near electric power

source.............................120-121

Manufacturing methods, general........... 110,

111. 118 

See a/so particular processes.

Pedersen process..................................115.

Process water, quality.................... 128-129

Production of alumina............. 119-120, 133

Production of aluminum.................107, 134

Purpose of report................................. 104

Quality of water, for domestic plant

purposes................................ 128

Page

Quality of water Continued 

process use at reduction works............. 129

treatment at alumina plants.........129, 130

treatment at reduction works........129, 130

Red-mud lake, effect of size on

evaporation............................123

function......................................... 112

Scope of report............................ 104, 106

Selected references.............................. 137

Soderberg process................................ 117

Surface water, percent of total water

used..................................... 122

plants and works using....................... 122

quantity used...................................122

Unit water use, alumina production.......J.03,

132, 133, 135 

aluminum production....103, 133, 134, 135

effect of planned operational

changes....................132-133, 134

for 1 pound aluminum from bauxite....,.134

Use of aluminum, classification of end

products................................ 108

future demand................................. 108

industry requirements........................ 108

Waste water, disposal..........*..........130, 131

pollution avoidance........131-132, 136-137

treatment................................130, 131

Water requirements, alumina

plants............................. 132-133

effect of meteorologic

conditions........................13 5-136

plant size, effect at alumina

plants............................. 122-123

effect at reduction works................. 123

reduction works..........................133-134

variations, from cooling procedures.... 103,

118, 136 

from evaporating procedures........... 103,

118-119, 136 

from gas scrubbers................ 103, 119,

136-137

Water use, at alumina plants...122-124, 126,

132-133 

at reduction works....122, 124-126, 133-134

boiler-feed makeup.......................... 124

chilling of billets....................... 124-125

consumptive..............................126-128

gas scrubbing.............................124, 125

hydrate wash......................123-124, 136

red-mud lake makeup....................... 124

sanitary..........................................124

transformer andrectifier cooling....124, 125

139

S. GOVERNMENT PRINTING OFFICE. 1956 O 395701