EPA-440/l-74-006-a
Development Document for E/fluent Limitations Guidelines
and New Source Performance Standards for the
PHOSPHORUS DERIVED
CHEMICALS
Segment of the
Phosphate Manufacturing
Point Source Category
JANUARY 1974
\ U.S. ENVIRONMENTAL PROTECTION AGENCY
* Washington, D.C. 20460
-------
DEVELOPMENT DOCUMENT
for
EFFLUENT LIMITATIONS GUIDELINES
and
NEW SOURCE PERFORMANCE STANDARDS
for the
PHOSPHORUS DERIVED CHEMICALS SEGMENT OF THE
PHOSPHATE MANUFACTURING
POINT SOURCE CATEGORY
Russell E. Train
Administrator
Robert L. Sansom
Assistant Administrator for A1r and Water Program
Allen Cywln
Director, Effluent Guidelines Division
Elwood E. Martin
Project Officer
January 1974
Effluent Guidelines Division
Office of Air and Water Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Prtce «.90
-------
ABSTRACT
A study was made of the phosphate manufacturing point source
category by the General Technologies Corporation for the
Environmental Protection Agency for the purpose of developing
effluent limitations guidelines, Federal standards of
performance, and pretreatment standards for the industry, to
implement Sections 304, 306 and 307 of the Federal Water
Pollution Control Act Amendments of 1972.
For the purpose of this study, the phosphate manufacturing
industry was defined as the manufacture of the following
chemicals: Phosphorus (and by-product ferrophosphorus),
phosphoric acid (dry process only), phosphorus pentoxide,
phosphorus pentasulfide, phosphorus trichloride, phosphorus
oxychloride, sodium tripolyphosphate and the calcium phosphates.
Effluent limitations guidelines were developed as a result of
this study, defining the degree of effluent reduction attainable
through the application of the best practicable control
technology currently available and the best available technology
economically achievable which must be achieved by existing point
sources by July 1, 1977, and July 1, 1983, respectively. The
standards of performance for new sources were also defined.
The best practicable control technology currently available
allows a discharge after suitable treatment for the manufacture
of phosphorus (and ferrophosphorus) , phosphorus trichloride,
phosphorus oxychloride and food grade calcium phosphate. The
1977 limitations prohibit discharge of process waste water
pollutants for the manufacture of the remaining chemicals.
Application of the best available technology economically
achievable and best demonstrated technology would enable all the
manufacturing operations for the three subcategories to achieve
no discharge of waste water pollutants.
ill
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CONTENTS
Section Page
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 5
IV INDUSTRY CATEGORIZATION 41
V WATER USE AND WASTE CHARACTERIZATION 45
VI SELECTION OF POLLUTION PARAMETERS 67
VII CONTROL AND TREATMENT TECHNOLOGY 79
VIII COST, ENERGY AND NON-WATER QUALITY ASPECTS 105
IX EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICA-
TION OF THE BEST PRACTICABLE CONTROL TECHNOLOGY
CURRENTLY AVAILABLE, EFFLUENT GUIDELINES AND
LIMITATIONS 121
X EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION
OF THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEV-
ABLE, EFFLUENT GUIDELINES AND LIMITATIONS 133
XI NEW SOURCE PERFORMANCE STANDARDS AND PRETREATMENT
RECOMMENDATIONS 139
XII ACKNOWLEDGMENTS 143
XIII REFERENCES 145
XIV GLOSSARY 151
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TABLES
Number Page
1 Recommended Best Practicable Control
Technology Currently Available for the
Manufacture of Phosphorus (and Ferrophosphorus) ,
Phosphorus Trichloride, Phosphorus Oxychloride
and Food Grade Calcium Phosphate 4
2 U.S. Production of Phosphates 12
3 Current Selling Prices of Phosphorus Chemicals 13
H Producers of Phosphate Products 14
5 Impurities in Phosphoric Acid 21
6 Composition of Commercial Phosphate Rocks 51
7 Summary of Raw Waste from Phosphorus Manufacture 55
8 Minor Wastes from Plant 037 (PC13 and POC13) 60
9 Summary of Raw Wastes from Phosphorus Consuming 63
Plants
10 Summary of Raw Wastes from Phosphate Plants 66
11 Waste Water Constituents of Phosphate Category 77
12 Relative chemical Costs for Neutralizing Acid Wastes 37
13 Summary of Control and Treatment Techniques at
Phosphorus Producing Plants 89
14 Effluent from Plant 028 90
15 Effluent from Plant 159 91
16 Water Quality Produced by Various Ion
Exchange Systems 100
17 Treatment Alternatives 106
18 Treatment Alternatives, Cost-Effluent Quality
Comparison 107
19 Energy Requirements for Recommended Guidelines 119
20 Metric Units Conversion Table 154
vi
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FIGURES
Number Page
1 Flow of Materials in the
Phosphates Manufacturing Industry 9
2 Standard Phosphorus Process Flow
Diagram 16
3 Standard Phosphoric Acid Flow
Diagram (Dry Process) 22
4 Variations of Phosphoric Acid
(Dry Process) 24
5 Phosphorus Pentoxide Manufacture
Flow Diagram 27
6 Phosphorus Pentasulfide Manufacture
Flow Diagram 29
7 Phosphorus Trichloride Manufacture
Flow Diagram 31
8 Standard Process for Phosphorus
Oxychloride Manufacture 33
9 Alternate Process for Phosphorus
Oxychloride Manufacture 34
10 Standard Process for Sodium
Tripolyphosphate Manufacture 36
11 Standard Process for Food-Grade
Calcium Phosphates 33
12 Manufacture of Livestock-Feed Calcium
Phosphate Flow Diagram 39
vii
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SECTION I
CONCLUSIONS
For the purpose of establishing effluent limitations guidelines
and standards of performance, the phosphate manufacturing point
source category was divided into the phosphorus production, the
phosphorus consuming, and the phosphate subcategories.
Phosphorus and phosphoric acid (furnace acid) production were
included in this study because they are necessary prerequisites
to phosphate synthesis. It is also appropriate from a technical
standpoint to include these chemicals in this study rather than
in the inorganic chemical point source category. Other
phosphorus consuming chemicals such as PC13 and P£O| were
included for the same reasons. Processes that manufacture
phosphates as fertilizers are regulated by the fertilizer
manufacturing regulations.
The phosphorus-production subcategory of the industry is charac-
terized by large guantities of raw process wastes, including
highly deleterious phossy water and highly-acidic scrubber and
quenching waste waters, both containing large quantities of
fluorides, other dissolved solids, and suspended solids. Through
a combination of in-process controls and end-of-process
treatment, several plants within this segment have achieved zero
discharge of phossy water, two have achieved zero discharge of
other process waste waters, and one has achieved zero discharge
of any waste water during normal periods of rainfall. Plants now
demonstrate abatement practices resulting in 97 Percent or
greater reduction in the raw waste load before discharge, and the
total recycle of process water without any discharge has been
demonstrated using the best practicable control technology.
The phosphorus-consuming subcategory of the industry is charac-
terized by the absence of direct process waste water; the
chemicals produced are readily hydrolyzed so that the processes
are essentially dry. However, just because the products are
readily hydrolyzed, water is universally used for air pollution
abatement scrubbing of tail gases, for periodic cleaning of
reaction vessels, and for the general washing of shipped
containers, all resulting in acidic waste waters. In addition,
Sa^er is used in protecting and transferring the raw material,
elemental phosphorus, and phossy water is therefore a raw waste
from this segment. Except for the manufacture of dry-process
phosphoric acid (where in-process control has been demonstrated
to achieve zero discharge of aqueous wastes), this segment has
not vet achieved sufficient reduction of effluents. The
application, however, of currently available technology is shown
bvthis study to permit total recycle of waste waters (and so
zero discharge) for the manufacture of P2O$ and P2S£, and to
ac^eve the9 neutralization and removal of most Suspended solids
before discharge for the manufacture of PCll and POC11. The
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latter two processes are more expensive but still economically
achievable technologies and are available for treating the
chlorides so as to achieve zero discharge.
The phosphate segment of the industry, i.e., the group of
chemicals manufactured from phosphoric acid, is characterized by
acids and by finely-divided solids in the raw aqueous wastes.
Several plants have already achieved zero discharge by in-process
controls and by end-of-process treatment; and this study shows
how this segment may achieve zero discharge by applying currently
available practicable technology. Outside contamination of the
process waste water resulting from the manufacture of food grade
calcium phosphate may prevent its reuse at existing plants, and a
discharge after suitable treatment has been allowed.
The general conclusion reached is that the industry has already
solved its most serious raw waste problem; that is, the abatement
of water pollution from phosphorus-'producing facilities. The
remainder of the industry, made up of much smaller-volume plants,
has lagged behind in effluent reduction, but technology is avail-
able to make the entire industry notable.
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SECTION II
RECOMMENDATIONS
The recommended effluent limitations guidelines based on best
practicable control technology currently available are no
discharge of process waste water pollutants to navigable waters
for the manufacture of the following chemicals:
Phosphorus Consuming Subcategory
Phosphoric Acid (Dry Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphate Production Subcategory
Sodium Tripolyphosphate
Calcium Phosphates (Animal Feed Grade)
The recommended effluent limitations for this technology for
phosphorus (and ferrophosphorus), phosphorous trichloride,
phosphorous oxychloride and food grade calcium phosphate are
given in Table 1.
The above guidelines apply to the maximum average of daily values
for any period of 30 consecutive days. The maximum for any one
day is twice the consecutive 30 day average value. The pH
limitation must be met at all times. It is recommended that
noncontact cooling water be allowed to be discharged. Effluent
limitations for this waste stream are expected to be covered in
future studies. For the purposes of this report, process water
is defined as any water that comes into direct contact with any
raw material, intermediate product, by-product, or gas or liquid
that has accumulated such constituents.
The recommended effluent limitations guidelines based on best
available technology economically achievable is no discharge of
process waste water pollutants for the manufacture of the
following chemicals:
Phosphorus Consuming Subcategory
Phosphorus (and Ferrophosphorus)
Phosphorus Consuming Subcategory
Phosphoric Acid (Dry Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphorus Trichloride
Phosphorus Oxychloride
Phosphate Subcategory
Sodium Tripolyphosphate
Calcium Phosphates (Food Grade)
Calcium Phosphates (Animal Feed Grade)
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The recommended new source performance standards are the same as
the above recommended best available technology economically
achievable.
TABLE 1.
Recommended Best Practicable Control Technology Currently
Available for the Manufacture of Phosphorus (and Ferrophoshorus) ,
Phosphorus Trichloride, Phosphorus Oxychloride and Food Grade
Calcium Phosphate. (Process Water)
The recommended effluent limitations guidelines based on best
practicable control technology currently available for process
water for the manufacture of PCl.3 and POCl^ are:
Average of daily values
for thirty consecutive
days shall not exceed
Phosphorus Phosphorus
and Trichloride
F er r opho sphorus
Phosphorus
Oxvchloride
Food Grade
calcium
hsphate,
Total suspended
Nonfilterable
Solids kg/kkg
Total Phosphorus
kg/kkg
Fluoride kg/kkg
Arsenic kg/kkg
pH
0.5
0.15
0.05
6.0-9.0
0.7
0.8
0.15
0.17
0.00005
6.0-9.0 6.0-9.0
0.06
0.03
6.0-9.0
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SECTION III
INTRODUCTION
PURPOSE AND AUTHORITY
Section 301 (b) of the Act requires the achievement by not later
than July 1, 1977, of effluent limitations for point sources,
other than publicly owned treatment works, which are based on the
application of the best practicable control technology currently
available as defined by the Administrator pursuant to Section
304(b) of the Act. Section 301(b) also requires the achievement
by not later than July 1, 1983, of effluent limitations for point
sources, other than publicly owned treatment works, which are
based on the application of the best available technology
economically achievable which will result in reasonable further
progress toward the national goal of eliminating the discharge of
all pollutants, as determined in accordance with regulations
issued by the Administrator pursuant to Section 30U(b) of the
Act. Section 306 of the Act requires the achievement by new
sources of a standard of performance providing for the control of
the discharge of pollutants which reflects the greatest degree of
effluent reduction which the Administrator determines to be
achievable through the application of the best available
demonstrated control technology, processes, operating methods, or
other alternatives, including, where practicable, a standard
permitting no discharge of pollutants.
Section 304 (b) of the Act requires the Administrator to publish
within one year of enactment of the Act, regulations providing
guidelines for effluent limitations setting forth the degree of
effluent reduction attainable through the application of the best
control measures and practices achievable including treatment
techniques, process and procedure innovations, operation methods
and other alternatives. The regulations proposed herein set
forth effluent limitations guidelines pursuant to Section 304 (b)
of the Act for the phosphate manufacturing point source category.
Section 306 of the Act requires the Administrator, within one
year after a category of sources is included in a list published
pursuant to Section 306(b)(l)(A) of the Act, to propose
regulations establishing Federal standards of performances for
new sources within such categories. The Administrator published
in the Federal Register of January 16, 1973 (38 F.R. 1624), a
list of 27 source categories. Publication of the list
constituted announcement of the Administrators intention to
establish, under Section 306, standards of performance applicable
to new sources within the phosphate manufacturing source
category.
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SUMMARY OF DEVELOPMENT METHODS
The Environmental Protection Agency has determined that a rig-
orous approach including plant surveying and verification testing
is necessary for the promulgation of effluent standards from
industrial sources. A systematic approach to the achievement of
the required guidelines and standards includes the following:
(a) Categorization of the industry and determination of those
industrial categories for which separate effluent limitations and
standards need to be set;
(b) Characterization of the waste loads resulting from discharge
within industrial categories and subcategories;
(c) Identification of the range of control and treatment
technology within each industrial category and subcategory;
(d) Identification of those plants having the best practical
technology currently available (notable plants); and
(e) Generation of supporting verification data for the best
practical technology including actual sampling of plant effluents
by field teams.
The culmination of these activities is the development of the
guidelines and standards based on the best practicable current
technology.
This report describes the results obtained from application of
the above approach to the phosphate manufacturing industry,
defined for the purpose of this study as the following list of
products:
Elemental Phosphorus and Ferrophosphorus
Dry-Process Phosphoric Acid
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphorus Trichloride
Phosphorus Oxychloride
Sodium Tripolyphosphate
Calcium Phosphates (Non-Fertilizer)
The effluent limitations guidelines and standards of performance
proposed herein were developed in the following manner. The
point source category was first subcategorized for the purpose of
determining whether separate limitations and standards are
appropriate for different segments within a point source cate^
gory. Such subcategorization was based on raw material used,
product produced, manufacturing process employed, and other fac-
tors. The raw waste characteristics for each subcategory were
then identified. This included an analysis of (1) the source and
volume of water used in the process employed and the sources of
waste and waste waters in the plant, and (2) the constituents
(including thermal) of all waste waters including toxic consti-
tuents which result in taste, odor, and color in water or aquatic
organisms. The constituents of waste waters which should be sub-
ject to effluent limitations guidelines and standards of perfor-
mance were identified.
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The full range of control and treatment technologies existing
within each subcategory was identified. This included an iden-
tification of each distinct control and treatment technology,
including both in-plant and end-of-process technologies which are
existent or capable of being designed for each subcategory. it
also included an identification in terms of the number of
constituents (including thermal). The chemical, physical, and
biological characteristics of pollutants of the effluent level
resulting from the application of each of the treatment and
control technologies and the required implementation time were
also identified, in addition, the non-water quality environmen-
tal impact, such as the effects of the application of such tech-
nologies on other pollution problems, including air, solid waste,
noise and radiation, were also identified. The energy
requirement of each of the control and treatment technologies was
identified as well as the cost of the application of those
technologies.
The information as outlined above was then evaluated to determine
what levels of technology constituted the best practicable
control technology currently available, the "best available
technology economically achievable" and the "best available
demonstrated control technology, processes, operating methods, or
other alternatives." In identifying the technologies, various
factors were considered. These included the total cost of
application of technology in relation to the effluent reduction
benefits to be achieved from the application, the age of
equipment and facilities involved, the process employed, the
engineering aspects, process changes, non-water quality
environmental impact (including energy requirements), and other
factors.
The data for identification and analysis were derived from a
number of sources. These sources included EPA research infor-
mation, published literature, previous EPA technical guidance for
inorganic chemicals, alkali and chlorine industries, qualified
technical consultation, and on-site visits and interviews at
notable manufacturing plants throughout the United States. All
references used in developing the guidelines for effluent
limitations and standards of performance for new sources reported
herein are included in Section XIII of this document. Five
companies in the phosphate manufacturing industry were contacted.
A breakdown of the data base is listed below:
-------
Chemical Ntimher of Plants in Data Base
Literature Inspected sampled Permit Application
P4 132* 2
H3~P04 21* 2
P205" 1 1 1
p|s5 2 2 2
PC1-J 22 2
POctl 2 2 2
Na^PlOJLC 2 1* 1
Calcium Phosphates
(Food Grade) 1 1 1
(Feed Grade) 1 1 1
*Includes verification of plants with no discharge.
In addition much information was obtained from plant personnel at
the time of plant inspections, plant sampling, and company
discussions.
GENERAL DESCRIPTION OF THE INDUSTRY
The industry covered by this document is the phosphate
manufacturing point source category. It is more descriptively
termed the nonfertilizer phosphorus industry. The following
chemicals covered by SIC 2819 were studied:
phosphorus
ferrophosphorus
phosphoric acid (dry process)
phosphorus pentoxide
phosphorus pentasulfide
phoshporus trichloride
phosphorus oxychloride
sodium tripolyphosphate
calcium phosphates (food grade)
calcium phosphates (animal feed grade)
Other phosphorus and phosphate chemicals are expected to be
covered at a later time.
The flow of materials in the phosphate manufacturing industry is
depicted in Figure 1. This industry is almost entirely based on
the production of elemental phosphorus from mined phosphate rock.
The economics have dictated that the phosphorus production
facilities be located at the sources of the raw material, which
are in three areas in the United states: Tennessee, the Idaho-
Montana area, and Florida. The key in-plant siting decision is
the relative weights of phosphate rock, elemental phosphorus and
phosphoric acid (about 10:1:4). Hence, the rock is processed
close to the mine and the acid is produced close to its
consumption point; the relatively low-weight elemental phosphorus
is almost universally the form shipped from place to place.
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MINED
PHOSPHATE
ROCK
ELEMENTAL
PHOSPHORUS
FERROPHOSPHORUS
tRY" OR "FURNACE"
PROCESS
AGIO
ANHYDROUS
PHOSPHORUS
COMPOUNDS
SOLUBLE
PHOSPHATES
(SODIUM
TRVOtyPHDSPHATE)
MSOLUBLE
PHOSPHATES
(CALCIUM
PHOSPHATES)
PHOSPHORUS
PENTASULFDE
PHOSPHORUS
PENTOXIDE
PHOSPHORUS
TRICHLORIDE
PHOSPHORUS
OXYCHLORIOE
FIGURE I
FLOW OF MATERIALS IN THE NON-FERTILIZER PHOSPHORUS CHEMICALS INDUSTRY
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Ferrophosphorus, widely used in the metallurgical industries, is
a direct by-product of the phosphorus production process, since
most furnace-grade phosphate rock contains 2 to 6 percent iron
oxide.
Over 87 percent of the elemental phosphorus is used to manufac-
ture high-grade phosphoric acid by the furnace or "dry" process
as opposed to the wet process which coverts phosphate rock
directly into phosphoric acid. This lower-grade wet process acid
is almost exclusively used in the fertilizer industry and is
separately discussed in that report. The remainder of the
elemental phosphorus is either marketed directly or converted to
chemicals such as phosphorus pentoxide, phosphorus pentasulfide,
phosphorus trichloride, and phosphorus oxychloride. These
chemicals are chiefly used in synthesis in the organic chemicals
industry.
Much of the furnace-grade phosphoric acid is directly marketed,
largely to the food industry and to the high-grade fertilizer
industry. Phosphoric acid is also used to manufacture two basic
classes of phosphates: water-soluble phosphates used in
detergents and for water treatment, typified by sodium tripoly-
phosphate, and water-insoluble phosphates which are used in
animal feeds and in foods, typified by the calcium phosphates.
The processes involved in the non-fertilizer phosphorus chemicals
industry are very briefly as follows:
Elemental phosphorus and ferrophosphorus are manufactured by the
reduction of phosphate rock by coke in very large electric
furnaces, using silica as a flux. Very large quantities of water
are circulated for cooling the very hot equipment, for cooling
and granulating the slag, and for condensing the phosphorus vapor
from the furnace. Since water is both non-reactive and
immiscible with liquid phosphorus, water is used extensively in
direct contact with phosphorus for heat transfer, for materials
transfer, for protection from the atmosphere, and for pur-
ification. This study is concerned with manufacturing operations
subsequent to receiving washed phosphate ores at the phosphorus
production facility. Ore benefication is commonly but not ex-
clusively conducted at a separate off-site location. The huge
waste load from benefication, 7500 kg of gangue per kkg of phos-
phorus eventually produced, warrants a separate study as a seg-
ment of the mining industry.
Phosphoric acid manufactured by the "dry" or furnace process
consists of the burning of liquid phosphorus in air, the sub-
sequent quenching and hydrolysis of the P2O5 vapor, and the
collection of the phosphoric acid mistsT The operation uses
cooling water, and process water is consumed in making the
aqueous acid. Solid wastes may be generated should a plant later
purify the acid.
10
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The manufacture of the anhydrous phosphorus chemicals (P2O5,
P2Sj>, and PC13J is essentially by the direct union of phosphorus
with the corresponding element. Phosphorus oxychloride, PC1.3, is
manufactured from PC13 and air or from PC13, P205, and chlorine.
Water use is limited to cooling water, to water for transferring
elemental phosphorus, to scrubber water, and to wash water for
reaction vessels and shipping containers.
Sodium tripolyphosphate is manufactured by the neutralization of
phosphoric acid with the appropriate proportions of caustic soda
and soda ash in mix tanks. The resulting mixture of mono- and
di-sodium phosphates is dried and the crystals calcined to
produce the tripolyphosphate.
The calcium phosphates are similarly made by the neutralization
of phosphoric acid with lime. The amount and type of lime used
and the amount of water in the process determine whether anhy-
drous monocalcium phosphate, monocalcium phosphate monohydrate,
dicalcium phosphate dihydrate, or tricalcium phosphate is the
final product. Table 2 lists production tonnages for these
chemicals as reported by the U.S. Bureau of Census. As seen from
this table the industry is relatively small in relation to
numbers of plants.
Table 3 lists the current selling prices of the chemicals within
this industry. Table U lists the producers of phosphate
products.
11
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TABLE 2. U.S. Production of Phosphates
Metric Tons
495,000
110,000*
Short Tons
545,000
121,000*
1.640,000** 1,810,000**
(withheld)
54,000
50,000
28,000
945,000
536,000
(withheld)
59,000
55,000
31,000
1,040,000
592,000
Number
of Plants
10
Chemicals
Phosphorus
Ferrophosphorus
Phosphoric Acid
(Furnace Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphorus Trichloride
Phosphorus Oxychloride
Sodium Tripolyphosphate
Calcium Phosphates
*lndependently~estimated.(2)
**Estimated as 87 percent df phosphorus consumption, using
90 percent conversion, and stated as acid of 54 percent P2.O5.
The total production of phosphoric acid both wet and dry was
5,650,000 kkg (6,240,000 short tons).
25
(withheld)
5
4
4
17
7
12
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TABLE 3. Current Selling Prices of Phosphorus Chemicals
Source: Chemical Marketing Reporter, June 25,
1973
CHEMICAL
White Phosphorus
Phosphoric Acid (Furnace)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphorus Trichloride
Phosphorus Oxychloride
Sodium Tripolyphosphate
Monocalcium Phosphate
Dicalcium Phosphate
Tri calcium Phosphate
GRADE
75% Commercial & Feed
80% Commercial & Feed
85% National Formulary
Technical
Food
Anhydrous Food
'U.S.P Food
Feed
NF Precip.
SELLING PRICE
$/Metric Ton
419
164
176
194
441
299
292
270
179
270
314
286
82
315
$/Short Ton
330
149
160
176
400
271
265
245
162
245
285
259
74
286
13
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Producers of Phosphate Products
Phosphorcvs
Holmes Company 0
FKC Corporation 0
Mobil Corporation 0
Monsanto Company 0
Occidental Petroleum Corp. 0
Stauffer Chemical 0
IVA 0
01 In Corporation
Coodpasture, Inc.
American Cyananid Co.
Borden, Inc.
Eastman Kodak Co.
Farmland Industries
Int'l. Minerals & Chemical Corp.
Knox Gelatine. lac
Richardson-Merrcll, Inc.
Phosphorous Phosphorous Phosphorous Phosphorous furnace
Pentoxlde Trichloride Oxychloride Pentasulfide Acid
00 0
0 o
0000
00000
00000
0
0
Sodium Dicalciim
Tripolyphosphate Phosphate
0
0
0
0 0
0
0
0
0
0
0
Calcium
Phosphate
0
0
0
0
0
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DETAILED PROCESS DESCRIPTIONS
The following is a description of each process in this industry.
Process flow diagrams are included. In generating the following
process descriptions, emphasis has been placed on process
features which generate aqueous wastes. The details of the waste
stream character, however, have been left for discussion in
Section V.
Much of the process data in this section were acquired by dis-
cussions with industry personnel and by observation of existing
facilities. A large body of data also exists in the published
literature, and was used extensively in the following discussion.
Of particular usefulness were the publications of Beveridge and
Hill; (U) Barber, (5, 6) Barber and Farr; (7) LeMay and Metcalf(8) of
The Tennessee Valley Authority, which supplied very specific
operating details of TVA's facilities; Ellwood; (9) and Bryant,
Holloway and Silber (10) of the Mobil Chemical Company. Standard
reference books such as Faith, Keyes and Clark, (11) Kirk and
Othmer, (12) and Shreve, (13) were also useful.
THE PHOSPHORUS PRODUCTION SEGMENT
Phosphorus is manufactured by the reduction of mined phosphate
rock by coke in an electric furnace, with silica used as a flux.
Slag, f errophosphorus (from iron in the phosphate rock) , and
carbon monoxide are reaction by-products. The simplified overall
reaction may be written:
2Cal(POH)2 + 10 C + 6Si02 1250 - ISOQQc > PU + 10 CO
A typical material balance for the process is:
Raw Materials Products
6CaSiO3
Phosphate Rock
Silica
Coke
Total
10.0 kkg
1.5
1.5
J.3.0 kkg
Phosphorus
Ferrophosphorus
Slag
Carbon Monoxide
Total
1.0 kkg
0.3
8.9
2.8
The electrical power consumption is approximately 15,tOO KWH/kkg
(14,000 KWH/ton) of phosphorus produced; part of this supplies
the endothermic heat of reaction of 6,200 KWH/kkg of
The standard process, as pictured in Figure 2, consists of three
basic parts: phosphate rock preparation, smelting in the electric
furnace, and recovery of phosphorus.
Phosphate rock ores are first blended so that the furnace feed is
of uniform composition. The silica composition is important
since the overall furnace feed must have a SiO2/CaO ratio close
15
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WASHED
ORES
\£-
\/
SIZING
AND
CALCINING
KILN
PRECIPITATOR
COKE
STORAGE
SILICA
STORAGE
\L
\/
ELECTRIC
FURNACE
WATER
J,
\/_
SLAG
QUENCHING
_V
FERROPHOSPHORUS
SALE
P, CO, DUST
ELECTROSTATIC
PRECIPITATOR
WASTE
M/
TO FURTHER
SLAG PREPARATION
BEFORE SALE
DUST
CO
PHOSPHORUS
CONDENSER
SLUDGE
PROCESSING
FIGURE 2
STANDARD PHOSPHORUS PROCESS FLOW DIAGRAM
-------
to the eutectic composition for desired slag flow properties.
The blended phosphate rock is carefully pretreated by drying, by
agglomerating the particles, and by heat treatment.
After the raw phosphate rock is dried, sizing or agglomeration is
accomplished by palletizing, briquetting, flaking, or
"nodulizing,11 and pre-formed agglomerates are then calcined in a
rotary kiln. The nodulizing operation performs simultaneous
agglomeration and calcining by heating the rock to its incipient
fusion point, with subsequent crushing, sizing, and recycling of
fines. Sizing promotes the even distribution of gas flow within
the furnace and results in more efficient heat transfer and lower
total energy costs. The size of the furnaces has dramatically
increased in recent years, accentuating the needs for
stoichiometric balance and thermal homogeneity within the charge
(or "burden"). Heat treatment or calcining of the feed increases
the strength and hardness of the particles, preventing large
quantities of fines from being formed by attrition.
The calcining, at 1000 to moO°C, also liberates water of hy-
dration, organics, carbon dioxide, and fluorine at a much lower
energy cost than would be required in the subsequent electric
furnace operation. Since 25 percent of the manufacturing costs
of phosphorus are for electric power, considerable effort is made
to conserve this power. Moreover, by-product carbon monoxide
from the smelting operation is available as a source of auxiliary
energy.
The sizing and calcining operations are sources of dust and of
fluorine fumes. The dust may be electrostatically precipitated,
and the gases are scrubbed with water, removing fluorine as HF
and H2:SiF6. The dry dusts collected are normally recycled to the
nodulizing operation.
The burden of treated phosphate rock, coke, and sand is charged
to the furnace by incrementally adding weighed quantities of each
of the three materials to a common belt conveyor. The furnace
itself has a carbon crucible, carbon-lined steel sidewalls and a
two-foot-thick self-supporting cast concrete roof. In an effort
to eliminate periodic roof replacement due to excessive cracking
of the concrete, some newer furnaces have anti-magnetic (to avoid
induction heating) stainless steel roof structures. Penetrations
in the furnace are for feed chutes, for carbon electrodes, for
tap holes, for slag (upper liquid layer), for ferrophosphorus
(lower liquid layer), and for exhaust gases.
Electric furnaces for phosphorus production have been dramati-
cally increasing in size to achieve operating economies:
17
-------
Size of Largest Furnace in Operation
Year Megawatts kkg/Year Tons/Year
1950
1960
1970
25
50
65
13,600
27,200
36,300
15,000
30,000
40,000
The smallest furnaces produce 9,100 kkg (10,000 tons) of
phosphorus per year.
An appreciation of the physical size may be attained from the
fact that the largest carbon electrodes used are 1.5 to 1.8
meters (5 to 6 feet) in diameter and carry 50,000 amperes each.
The furnace is extensively water-cooled. Cooling water is used
for the electrical transformer, for the furnace shell, for the
crucible bottom, for the fume hood, for the tapholes, and for
electrode joints. Newer furnaces use telescoping water seals on
furnace electrodes; and for TVA-type furnaces with rotating
crucibles a water seal is provided between the crucible and the
stationary roof.
The 2 to 6 percent Fe2O3 in the furnace-grade phosphate rock is
reduced, with the iron recovered as the ferrophosphorus alloy:
Fe203 + 3C-*2Fe + SCO
8Fe +
The ferrophosphorus typically contains 59 percent iron and 22
percent phosphorus and is marketed for the production of phos-
phorus alloys. The vanadium content of ferrophosphorus adds to
its value. Should the marketplace be favorable for ferrophos-
phorus, iron slugs can be added to the furnace charge. Alter-
nately, should a soft market for ferrophosphorus occur, the
ferrophosphorus can be converted into high-grade metallurgical
iron and fertilizer phosphates. An important degree of freedom
is in the ore blending operation, where ores of appropriate iron
content may be selected depending on the ferrophosphorus market.
Slag and ferrophosphorus are tapped periodically. The air cooled
ferrophosphorus is sold in lumps to the metallurgical industry;
no water is involved either in ferrophosphorus cooling or in
subsequent product preparation.
The slag may typically contain 38 percent SiO2 and US percent
Caof and also contain considerable quantities (depending of
course on the ore composition) of A12O3, CaF2, K2O, and MgO, with
traces of uranium and other heavy metals. The slag may be air-
cooled, but water quenching is more typical. High-density slag
is produced by adding water to molten slag in a pit, and by
subsequently breaking it up and shipping aggregate for railroad
bed or roadbed construction. Alternately, a high-velocity water
stream may be used on the molten slag to produce a low density
18
-------
expanded or granulated slag which has a market in concrete
formulation. In either event, some of the fluorides from the
slag are captured by the quenching water, either as soluble
fluorides or as suspended solids.
There are numerous sources of fumes from the furnace operation.
The feeding operation is a source of dust, and fumes are emitted
from the electrode penetrations and from tapping. These fumes,
consisting of dust, phosphorus vapor (which is immediately
oxidized to phosphorus pentoxide), and carbon monoxide are often
collected and scrubbed.
The hot furnace gases, consisting of 90 percent CO and 10 percent
pft» pass through an electrostatic precipitator to remove the dust
before phosphorus condensation. Unless this dust was removed, it
would later be emulsified by liquid phosphorus and water, forming
large amounts of "phosphorus mud" or sludge which would be
difficult and costly to handle.
The precipitator is a most unusual piece of equipment. In the
phosphorus process, the precipitator is in the main process
stream, as opposed to its usual application in an exhaust stream.
Because of this, it is gas-tight (especially since any air would
cause phosphorus combustion). It operates at very high temper-
atures with the inlet gas approaching 5UO°C (1000°F), and its
surfaces must be maintained hot to prevent phosphorus condensa-
tion (the dew point of phosphorus is 180°C (356°F)). The pre-»
cipitator is typically a tube bundle, with the gas passing
through the tubes and with a high-voltage wire along the axis of
each tube. Both the wire and the tube are mechanically shaken to
release the dust into a hopper. In some installations, the dust
is slurried in water and pumped to a settling pond, and the
solids are recycled to the raw feed for recovery of phosphate
values (the clarified pond effluent is reused in the slurrying
operation).
The high-voltage wires may be insulated from the shell with an
oil seal. Contaminated oil is periodically replaced with fresh
oil. Alternatively, a quartz seal may be used. The entire unit
is heated either electrically or by an inert gas jacket of
by-product carbon monoxide combustion gases.
Downstream of the precipitator, the phosphorus is condensed by
direct impingement of a hot water spray, which is sometimes
augmented by heat-transfer through water-cooled condenser walls.
The liquid phosphorus (freezing point U4°C (111°F)) drains into a
water sump, where the water maintains a seal from the atmosphere.
This water is partially neutralized by addition of ammonia or
caustic to minimize corrosion, and then is recirculated from the
sump to the phosphorus condenser.
Liquid phosphorus is stored in steam-heated tanks under a water
blanket and is transferred into tank cars by pumping or by hot
water displacement. The tank cars also have a protective blanket
19
-------
of water and are equipped with steam coils for remelting at the
destination.
Despite very high precipitator removal efficiencies, enough dust
reaches the condensers to form some phosphorus mudr which is
typically 10 percent dust, 30 percent water, and 60 percent
phosphorus.
The condenser exhaust gases are mainly carbon monoxide, which is
either burned in a flare or used for heating elsewhere in the
plant.
20
-------
THE PHOSPHORUS-CONSUMING SEGMENT
Phosphoric Acid (Dry Process)
Phosphoric acid is made from elemental phosphorus in the "dry"
process, as opposed to the acidulation of phosphate rock in the
"wet" process. The wet process is discussed in a separate report
dealing with the fertilizer industry. Furnace acid, as dry-
process phosphoric acid is called, is relatively pure compared to
wet-process acid, as Table 5 indicates. Consequently, the
furnace acid is primarily used for preparing foodstuffs,
detergents, and other high-grade products, while wet acid is
primarily used for preparing fertilizers and animal feed
supplements.
TABLE 5. Impurities in Phosphoric Acid (54* P2O5)
F, wt %
S03, wt %
Al^OS, wt %
Fe£Q3, wt %
Water insolubles, wt X
Wet Process
Acid
0.6 - 1.0
2.7
0.9
1.2
0.8
Furnace
Acid
0.007
0.003
0.001
0.0007
Total Impurities, wt %
6.2 - 6.6
0.012
Density, kg/1 (Ib/gal)
a 27 °C (80«F)
Viscosity, cp » 27°C (80°F)
Color
1.72 (14.3)
85
Black
1.57 (13.1)
18
colorless
In the standard dry process illustrated in Figure 3, liquid
phosphorus is burned in air, the resulting gaseous phosphorus
pentoxide is absorbed and hydrated in a spray of water, and
the mist is collected with an electrostatic precipitator.
The standard reaction may be written:
+ 5O2
21
-------
VENT
LIQUID
PHOSPHORUS'
t
AIR WATER
1 X
COMBUSTION
FURNACE
•^
P2°5^
ELECTROSTATIC
PRECIPITATION
/
A!
r
>ES
HYDRATION
^.
J
\
f
— >DUST WASTE
NaSH
1
PURIFICATION
•^
2
FILTRATION
WATER
V >v
— " — ^
PHOSPHORIC
ACID
STORAGE
WASTE
FIGURE 3
STANDARD PHOSPHORIC ACID FLOW DIAGRAM (DRY PROCESS)
-------
Liquid phosphorus is stored under water in tanks heated with
steam coils (the freezing point of phosphorus is HH°c (111°P)).
The phosphorus may be fed to the burner by hot-water displacement
in a feed tank, or in a loop with a steam-heated displacement
water tank and water pump. Alternately, the liquid phosphorus
may be pumped directly.
There are variations in the design of the liquid phosphorus
injector. Some producers achieve fine atomization using air in a
dual-fluid injector (where the injection orifice can be large
enough to prevent plugging). To prevent freezing of the
phosphorus in upstream portions of the injector and yet to keep
the injector tip cool, intricate use of both steam and cooling
water has been simultaneously applied. Other designs have proved
successful for phosphorus atomization, including the exploitation
of extreme turbulence in a pre-combustion zone, some form of
temperature control is required, since red phosphorus formed at
combustion temperatures much higher than 1650°C (3000°F) would
color the resulting acid and would plug injector orifices.
In the combustion chamber, corrosion by P2O5 vapors and by hot
phosphoric acid (formed from the moisture~~in the air) is count-
ered by using a graphite lining. The steel shell of the com-
bustion chamber is cooled by running water down its exterior
surfaces. This mode of heat transfer is standard; pressurized
cooling water is avoided since any leaks would result in prema-
ture hydration. Recent plants have been constructed with stain-
less steel combustion chambers.
The gas exiting from the combustion chamber is typically 540°C
(1000°F), and is then hydrated with direct water sprays which
also reduce the temperature to 120°C (250°F) or less.
A variation of the standard process, illustrated in Figure 4,
uses dilute acid for hydration instead of water. In this case,
the make-up water is added in the vapor-liquid separation step.
The rationale is that P2O5 vapor is absorbed more easily as the
concentration of absorbing acid is increased. Another deviation
from the standard process, also shown in Figure H, is the use of
a high-pressure-drop venturi scrubber to complete the somewhat
difficult hydration, and a screen~type demister and separation
tower instead of an electrostatic precipitator to free the tail
gases of the persistent acid mist.
When an electrostatic precipitator is used for collection of the
phosphoric acid mist, the corrosivity requires the use of carbon
tubes and stainless steel high-voltage wires. Those plants using
a high-pressure-drop venturi scrubber and a screen-type demister
with a separation tower are of stainless steel construction.
Where dilute phosphoric acid is used in the hydrator, the make-up
water is added in the separation tower. Regardless of process
variation, phosphoric acid is made with consumption of water; no
aqueous waste streams are generated by the process.
23
-------
LIQUID
PHOSPHORUS
COMBUSTION
AIR BLOWER
COMBUSTION
CHAMBER
TO STORA6E<-
HYDRATOR
_V
PRODUCT
ACID
COOLER
PRODUCT
ACID
VENT
t
DEMISTER
V
MAKE-UP
SEPARATOR
TOWER
_y
WATER
DILUTE
ACID
FIGURE 4
VARIATIONS OF PHOSPHORIC ACID (DRY) PROCESS
-------
The product acid is pure, but for the manufacture of food grade
acid, traces of arsenic must be removed. Arsenic occurs
naturally with phosphorus in the ore (they are both Group V-A
elements) at a level of about 0.075 kg of arsenic per kkg of
phosphorus (0.15 Ib/ton). The arsenic is quantitatively carried
through into the acid and is commonly removed by treatment with a
soluble sulfide followed by filtration of the insoluble arsenic
sulfide.
25
-------
Phosphorus Pentoxide
The manufacture of solid anhydrous phosphorus pentoxide is
similar to the first stages of phosphoric acid manufacture.
Liquid phosphorus is burned in an excess of air:
Figure 5 is a flow diagram for a standard phosphorus pentoxide
manufacturing facility. A significant difference between the two
processes is that in the anhydrous phosphorus pentoxide process
the air is dried to an extremely low dew point, since any
moisture results in a lumpy and agglomerated product not suited
for its uses as a reactive drying agent and as a reactive
condensing agent in organic synthesis. Typically, the ambient
air is filtered, then refrigerated to achieve a dew point of -18
to -7<>C (0 to 20°F) r and then dried to a dew point of -46°C (*•
50 OF) with silica gel.
After reaction of liquid phosphorus with excess dried air in the
combustion chamber, the P2,O5 vapor is condensed to a solid in a
"barn," which is a room-like structure. Some installations use a
more conventional tower for condensation. Both the combustion
chamber and the barn (or tower) are cooled by an external flow of
water down the surfaces; pressurized cooling water is avoided
since any leaks would result in lumpy, unacceptable product.
Condensed phosphorus pentoxide solid is mechanically scraped from
the walls using moving chains, and is discharged from the bottom
of the barn or tower with a screw conveyor. The gases are vented
to the atmosphere through a tail gas water seal which absorbs any
P2,O5 vapor or solid carry-over. There is usually continuous
water addition and overflow for the tail gas seal.
The product particle size is sensitive to the rate of cooling and
condensation in the barn or tower. In a barn, the external
surface-to- volume ratio is small, a relatively high temperature
is maintained in the condensing unit, and rather large crystals
may grow. in a tower, heat transfer is more rapid, and the
product is very finely divided. One installation uses two towers
in series; the first has much higher heat transfer rates and
results in a coarser product than the second, and the products
from the two towers are separately packaged.
26
-------
AIR
AIR FILTER
AIR DRYER
4
\TEf
WATER
LIQUID PHOSPHORUS STORAGE
COMBUSTION
CHAMBER
BARN
WATER SEAL
.PRODUCT
P2°5
FIGURE 5
PHOSPHORUS PENTOXIDE MANUFACTURE FLOW DIAGRAM
-------
Phosphorus Pentasulfide
The standard process for the manufacture of phosphorus penta-
sulfide, shown in Figure 6, is by direct union of the elements,
both in liquid form:
The largest use of phosphorus pentasulf ide is for the manufacture
of lubricating oil additives.
Liquid sulfur (melting point 113°C (230°F)) is transferred from a
steam-heated storage tank using submerged pumps, and liquid
phosphorus (melting point 44°C (111°F) ) is transferred by hot
water displacement. The highly exothermic reaction is usually
carried out as a batch operation in stirred cast iron pots. A
"heel" of molten P2S5 (melting point 282°C (540°F)) from the
previous batch is used to absorb the initial heat of reaction.
Liquid phosphorus and liquid sulfur are incrementally added.
Since the reactants and the product are extremely flammable at
the reaction temperature, the reactor is continuously purged with
nitrogen. A water seal is used in the vent line.
The batches from multiple reactors are forced into an
electrically heated (300°C (570°F)) P2S5 holding tank by nitrogen
pressure. Some of the P2S5 is converted directly into product,
while the rest is purified? "Liquid P2S5 from the holding tank
that is to be sold is cast directly'into drums or into cones.
When the molten product contacts air during casting, it ignites,
and fumes of P2O5 and SO2 are generated. A fume hood and water
scrubber are used. The cones, after cooling, are crushed and
packaged; solid P2S5 does not auto- ignite in air. The dust from
the crushing operation is removed in a dry separation system such
as a cyclone.
The liquid P.2S5 that is to be purified may be vacuum distilled
(normal boiling point is 515°C (960°F) ) in a continuous system.
The condenser is cooled by a high-temperature heat transfer
fluid, which in turn is cooled in a water-cooled heat exchanger.
The condenser is operated between the melting and boiling points
of the product. Molten purified PJ2S5 is then cast and crushed,
sharing the fume scrubber and dust collection systems with the
impure product operation.
An alternate mode of purification is the washing of crushed P.2S5
with carbon disulfide, in which the by-products phosphorus
sesquisulfide (P4S3) and free sulfur are soluble.
28
-------
WATER VENT
N)
t
SULFUR
STORAGE
TANK
N2 PURGE
LIQUID
PHOSPHORUS
STORAGE
TANK
-
BA1
RE AC
>,
fCH
TOR
/
WATER
SEAL
HOLDING
TANK
>VENT
v.
s
PF
STILL
SCRUBBER
/
\
CASTING
1
XMXJCT
Qf\T
r(Ji
/
> WASTE
VENT
t
S rDiicuitim "u DUST
^ CRUSHING ^ COLLECTOR
1 1
V V
PRODUCT WASTE
c<
\
"MkinfMOfD • "N /*rtl n TDAH
JNUtlMbLn ^ UULU I KAr
/\
^ \/
HEAT VACUUM
EXCHANGER PUMP
FIGURE 6
PHOSPHORUS PENTASULFIDE MANUFACTURE FUOW DIAGRAM
-------
Phosphorus Trichloride
Phosphorus trichloride, used extensively in organic synthesis, is
manufactured directly from the elements:
Pl(l) + 6C!2(g)-*4PC13(l)
The standard process is shown in Figure 7. Liquid phosphorus is
charged to a jacketed batch reactor. Chlorine is bubbled through
the charge, and phosphorus trichloride product (melting point
-112°C (-173°F», boiling point 74°C (165°F) r is refluxed until
all the phosphorus is consumed. Some cooling water is used in
the reactor jacket since the formation of PC13 is exothermic.
Care is taken to avoid an excess of chlorine; otherwise,
phosphorus pentachloride is formed.
When the reaction is complete, the cooling water to the reflux
condenser is turned off, steam is supplied to the reactor jacket,
and the product of the batch distillation is condensed and coll-
ected.
A water scrubber collects hydrochloric acid and phosphorous acid,
the hydrolysis products of PC13_ vapors:
PCI3 * 3H20-»3HC1 + H3PO3
The vapor pressure of the product is sufficiently high so that
the fumes from transferring the product into shipping containers
are also collected and scrubbed.
In a variation of the standard process, the reaction is conducted
semi-continuously instead of batch-wise. The reflux condenser of
Figure 7 is tailored so that only a small fraction of the PC13 is
withdrawn as product; the larger fraction of condensed PC13
returns to the reactor and serves as the working fluid and heat
sink for the reaction, since elemental phosphorus is somewhat
soluble in PC13. Gaseous chlorine is added continuously, and
liquid phosphorus is added incrementally.
No provision is generally made for continuous or frequent with-
drawal of residue from the reactor either in the batch process or
in the semi-continuous process. Instead, the residue is per-
mitted to accumulate, and the reactor is shut down for cleanout
infrequently.
Phosphorus trichloride is corrosive and is often shipped in
returnable nickel drums. Before use, these drums are thoroughly
washed with water and steam cleaned. Some recent use has been
made of non-returnable epoxy-lined steel drums.
30
-------
CHLORINE
LIQUID
PHOSPHORUS
STORAGE
TANK
BATCH
REACTOR
>4
s
REFLUX
CONDENSER
CONDENSER
V,
J
V
HOLDING
TANK
ITATER
^
^,
S
TRANSFER
TO
CONTAINERS
VENT WATER
t 1
f 1 \1/ \
SCRUBBER
VENT
,\
SCRUBBER
-^PRODUCT
T
WASTE
WASTE
FIGURE 7
PHOSPHORUS TRICHLORIDE MANUFACTURE FLOW DIAGRAM
-------
Phosphorus Oxychloride
Phosphorus oxychloride, used in the preparation of organic phos-
phate esters and Pharmaceuticals, is manufactured by the reaction
of liquid phosphorus trichloride, chlorine, and solid phosphorus
pentoxide:
3 PC13(1) + 3 C12(g) + P205(s)-*5 POC13 (1)
The standard process, illustrated in Figure 8, is carried out in
a batch reactor and still which are very similar to the standard
phosphorus trichloride equipment. Liquid phosphorus trichloride
is charged to the reactor, solid phosphorus pentoxide is added,
and chlorine is bubbled through the mixture while the PCI3
(boiling point 74°C (165°F)) and later the POC13 (boiling point
105°C (221°F» are refluxed. When the reactibn is complete,
steam is supplied to the reactor jacket, the water to the reflux
condenser is shut off, and the product is distilled over and
collected.
An alternative process for the manufacture of phosphorus oxy-
chloride from phosphorus trichloride is also in commercial use.
As is shown in Figure 9, dried air is used as the oxidant in a
batch process. A water-cooled reflux condenser is used as in the
standard process, except that a refrigerated condenser is added
in series to ensure total reflux of the PC13 upstream of a water
scrubber for the tail gas. The significant'difference is that in
the air-oxidation process a large quantity of non-condensible gas
(nitrogen and excess oxygen) is involved.
Instead of a final distillation step, the product POC13 is fil-
tered, with periodic changing of the cartridge filter elements.
Water scrubbers collect hydrochloric acid and phosphoric acid,
the hydrolysis products of POC13 vapors, both from the reaction/
distillation equipment and from transferring operations (for
either process):
POC13 * 3H20-WHC1 * H3PO4
Like phosphorus trichloride, phosphorus oxychloride is extremely
corrosive and is shipped in returnable nickel drums. Before re-
use, these drums are thoroughly washed with water and steam
cleaned. Some recent use has been made of non-returnable epoxy
lined steel drums.
32
-------
VENT WATER
t I
SCRUBBER
T
WASTE
V V V
BATCH
REACTOR"
REFLUX
CONDENSER
V
CONDENSER
HOLDING
TANK
TRANSFER
TO
CONTAINERS
PRODUCT
VENT WATER
t i
SCRUBBER
WASTE
FIGURE 8
STANDARD PROCESS FOR
PHOSPHORUS OXYCHLORIDE MANUFACTURE
33
-------
PCI,
REFLUX
CONDENSER
REFRIGERATED
CONDENSER
AIR
1
AIR DRYER
BATCH
REACTORS
SOLID VWVSTE<
WATER VENT
SCRUBBER
4-
WASTE
WATER VENT
SCRUBBER
WASTE
FILTER
HOLDING
TANK
V
TRANSFER
TO
CONTAINERS
V
PRODUCT
FIGURE 9
ALTERNATE PROCESS FOR
PHOSPHORUS OXYCHLORIDE MANUFACTURE
34
-------
THE PHOSPHATE SEGMENT
Sodium Tripolyphosphate
Sodium tripolyphosphate is manufactured by the neutralization in
mix tanks of phosphoric acid by soda ash or by caustic soda and
soda ash, with the subsequent calcining of the dried mono- and
di-sodium phosphate crystals. Figure 10 is a flow diagram of the
standard process. The sodium tripolyphosphate product is widely
used in detergents and in water-softening applications, in the
neutralization step, the amount of raw material is measured and
controlled to yield monosodium orthophosphate and disodium
orthophosphate in a 1:2 mole ratio:
6H3PO4 + 5Na2C03-»2NaH2POU + «*Na2HPO4 + 5H2O + 5CO2,
or
9H3PO4 + SNaOH + 5Na2CO3—»3NaH2PO4 + 6Na2HPO4 + 10H2O + 5CO2
In either process variation, the final pH in the mix tank is very
carefully adjusted by small additions of either phosphoric acid
or caustic soda solution.
The mixture of sodium orthophosphates is spray dried or drum
dried and the solids calcined to produce the sodium tripolyphos-
phate:
NaH2PO4 + 2 Na2HPO4-»Na5P3OlO * 2 H2O
The product is then slowly cooled or tempered to preserve the
condensed form of the phosphates. If the product is chilled too
rapidly, it will revert to a mixture of the meta- and poly-
phosphates:
Na5P30lO-»Na3PO3 + Na2P2O7
35
-------
50%
CAUSTIC
TANK
PHOSPHORIC ^
ACID ^
(SALE)
V
SODA
ASH
SILO
SLURRY TANK
MIX TANKS
V
SEPARATOR
CO 2
RELEASE
TANK
V
SPRAY
DRYING
TOWER
V
CALCINER
PRODUCT
COOLER
(TEMPERING)
PRODUCT
MILLING
AND SIZING
V
PRODUCT
STACK
A
DEMISTER
A
SCRUBBER
FINES
<—
WATER
DUST
COLLECTOR
FIGURE 10
STANDARD PROCESS FOR
SODIUM TRIPOLYPHOSPHATE MANUFACTURE
36
-------
Calcium Phosphates
The non-fertilizer calcium phosphates are made by the neutrali-
zation of phosphoric acid with lime. Although the reactions are
chemically similar, the processes for manufacturing the different
calcium phosphates differ substantially from one another in the
amount and type of lime used and the amount of process water used
(See Figures 11 and 12).
Relatively pure, food grade monocalcium phosphate (MCP) is made
in a stirred batch reactor from furnace acid and lime slurry:
2H3PO4 + Ca(OH)2-»Ca(H2PC4) 2 . H2O + H20
An excess of phosphoric acid maintained during the batch addition
cycle inhibits the formation of dicalcium phosphate. A minimum
quantity of process water is used. The heat of the reaction
liberates some water as steam in the reactor, and the remaining
water is evaporated in a vacuum dryer, a steam heated drum dryer,
or a spray dryer. The anhydrous MCP is produced by using CaO
(quicklime) and in carrying out the reaction at 140°C (310°F) so
that water is driven off as it is produced.
Relatively pure food grade tricalcium phosphate (TCP) is made in
a similar manner to MCP, except that an excess of lime slurry
maintained during the batch addition cycle inhibits formation of
dicalcium phosphate:
2H3POU + 3Ca(OH)2-*Ca3(PC4) 2 + 6H20
Like MCP, the TCP is dried to prevent excessive product
temperatures.
Relatively pure, food grade dicalcium phosphate (DCP) is made in
batch stirred reactors, but with much more process water than for
either MCP or TCP:
H3POi «• Ca(OH) 2-»CaHP04 . 2H20
The stoichiometry for DCP manufacture is critical; any excess
H3PO4 during the batch addition cycle would result in some MCP
and any excess Ca (011)2 would result in some TCP. The excess
water in the DCP reactor is to ensure homogeneity so that the
local stoichiometry is as balanced as the overall reactor
sto ichiometry.
As a result of the excess of water used, the reaction mixture is
a pumpable slurry as opposed to the pasty consistency of MCP and
TCP. This DCP is mechanically dewatered before drying.
37
-------
LIME
WATER
1 I
X
f
MCP
MIX
TANK
\
t
SLURRY
HOLD
TANK
V
SPF
TOV
\
HOT GAS
?AY
VER
/
SIZING
1
PRODUCT
MCP
LIME
SLURRY
TANK
\
/
\
PHOSPHORIC
ACID
TANK
\
/
WATER VENT
i t
e/"
ov.
IRUBBER
WASTE
WATER VENT
1 t
SCRUBBER
\
/
t
DCP
MIX
TANK
\
f
SLURRY
HOLD
TANK
\
/
CENTRIFUGE
WASTE
N
HOT
f \
GAS
b
KILN
MILL
\
1
CYCLONE
N,
f
TCP
MIX
TANK
\
(
SLURRY
HOLD
TANK
STEAM
\l/ \
VENT
t t
DRUM
DRYER
\
/
SIZING
PRODUCT
TCP
WASTE
PRODUCT
DCP
FIGURE 11
STANDARD PROCESS FOR
FOOD-GRADE CALCIUM PHOSPHATES
38
-------
PHOSPHORIC
ACID
WATER VENT
I t
AIR
J,
SILICA LIME
I I
DEFLUORINATION
WATER
si x
VENT
/ t
SCRUBBER
•^
s
PUG
REAC
WATER
Jr V
MILL
:TOR
VENT
/ \
SCRUBBER
rVPI ONF "a «irRllRRFR
4>
WASTE
^ ROTARY v ^ PRODUCT ^
-> DRYtR > COOLER >
WASTE
PRODUCT
WASTE
FIGURE 12
MANUFACTURE OF LIVESTOCK-FEED CALCIUM PHOSPHATE
FLOW DIAGRAM
-------
Dicalcium phosphate (DCP) is also manufactured for Livestock feed
supplement use, with much lower specifications on product purity.
Hence, the reaction can be conducted without excess water, since
some MCP and/or TCP in the DCP product is perfectly tolerable.
The pasty reaction product is normally dried in a rotary dryer.
Powdered limestone, caCO3, may be used instead of lime. If
quicklime is used, the drying step may be bypassed.
Another significant process difference is that non-food grade wet
process phosphoric acid is normally used for this product. The
DCP plants defluorinate the acid unless this step was
accomplished by the acid producer. Wet process phosphoric acid
contains approximately 1 percent fluoride in various forms. The
defluorination consists of treating the heated acid with finely-
divided silica and steaming or aerating, which liberates silicon
tetrafluoride gas:
Si02 4 ilHF —>SiFU 4 2HJ20
Wet scrubbers then hydrolyze and collect this gas as fluosilicic
acid and silicic acid:
3 SiF4 4 3H20—»2H2SiF6 4 H2Si03
The hot defluorinated phosphoric acid is then charged to the
reactor to make dicalcium phosphate.
-------
SECTION IV
INDUSTRY CATEGORIZATION
INTRODUCTION
In developing effluent limitations guidelines and standards of
performance for new sources for a given industry, a judgment must
be made by the Environmental Protection Agency as to whether
effluent limitations and standards are appropriate for different
segments (subcategories) within the industry. The factors
considered in determining whether such subcategories are
justified for the phosphate category of point sources are:
wastes generated
treatability of waste waters
manufacturing process
raw materials
plant size and age
product
land availability
air pollution control equipment
WASTES GENERATED
Tables 7, 8, and 9 in section-V show the raw waste loads for the
phosphate category. Suspended solids and dissolved phosphates
are common raw waste water constituents for phosphorus, food
grade calcium phosphates, and feed grade calcium phosphates.
Dissolved solids are present in concentrations significantly
above background for all the chemicals studied. Elemental
phosphorus can be a waste water constituent common to all of the
phosphate manufacturing industry if the phossy transport water is
not returned to the phosphorus producing plant. Sulfates,
fluorides and alkalinity are constituents and parameters specific
to phosphorus production. Furthermore, the amount of waste water
(425rOOO 1/kkg of Pj£) resulting from the production of phosphorus
is several orders of magnitude greater than that generated from
any of the other processes. The chemicals H3POf*r ?2O5, P.2.SI5,
PC13, and POC13 commonly generate acidic wastes and phosphates.
TREATABILITY OF WASTE WATERS
Phosphorus production clearly stands alone on the basis of waste
water treatability. The large amount of waste water produced
(425,000 1/kkg PU) presents special problems. It is commonly
practiced within~the industry to return phossy transport water to
the phosphorus plant. Therefore, the problem of treating
elemental phosphorus is only a phosphorus plant problem or can be
so handled that it will be a problem unique to phosphorus plants.
The chemicals H3PO4, P2O5, P2S£, PC13, and POC13 present similar
treatability problems" in that acidic wastes are encountered.
PC13 and POC13 present more difficult problems because the
resultant chloride ions are difficult to remove.
-------
The calcium phosphates involve similar treatment problems
(suspended solids and phosphates). Defluorination of animal feed
grade calcium phosphates will produce fluoride wastes, but the
proposed treatment schemes will handle this waste constituent.
MANUFACTURING PROCESS
Manufacturing process is the principal factor used to determine
subcategories. Phosphorus production is an ore reduction process
involving large electric furnaces and large amounts of raw
material and slag. Ferrophosphorus is a by-product in the
phosphorus reaction and is always considered along with
phosphorus when considering effluent quality.
The chemicals H3P<34, P2O5, PC13_, and POC13 are all similar in
that a gaseous intermediate*"or product is encountered somewhere
in the reaction sequence. The synthesis of Pj2SE> resembles the
above in that water and air must be completely absent in the
whole or parts of the reaction sequence.
Sodium tripolyphosphate and the calcium phosphates are produced
by the neutralization of phosphoric acid by alkaline slurries.
RAW MATERIALS
The following raw materials are used for each process:
Chemical Raw Materials
P^ & Fe2P Phosphate Ore Coke(C) SiO2
H3P04 "" P£ 02
P205~ P<» 02
P2S5 P4 S
PCI3 P4 C12
POC13 PC13 C12 (P205)
Naj)P3010 H3P04 Na^CO3 (NaOH)
Calcium Phosphates H^PO4 Ca(OH)2!
When the nonphosphorus compounds are excluded, four subcategories
become evident on the basis of raw material. The POC13. process
is so like the PC13 process, however, that it is included in the
latter subcategory.
^LANT SIZE AND AGE
^lant size will not affect the quantities of wastes produced (kg
:>er kkg of product) to such a degree that subcategorization would
^e warranted. The same basic production processes for each
chemical are used throughout the phosphate industry. Plant age
will not affect the quantities of wastes produced to the degree
where subcategorization is warranted. Another point is that
there are no really new plants, and consequently the situation
does not exist where new technologies make older technologies
obsolete. With respect to economics it is particularly difficult
42
-------
to assess the effects of waste water treatment. The chemicals
covered by this report serve as raw materials or intermediates
for other products produced by the same company. The theoretical
profitability of a single plant may well not decide if operations
are to continue at that site. With this in mind it would be
difficult if not impossible to establish criteria based on the
economics of plant size or age for the purpose of
subcategorization.
PRODUCT
The product does have some bearing on the waste water quality
when the product or vapors from the product or intermediate come
into contact with water. This topic has already been indirectly
discussed under wastes generated. In summary, phosphorus
production is associated with elemental phosphorus, phosphates,
fluoride, suspended and dissolved solids. The production of
H3PO4,, P2O5, P4S5, PC13 and POC13 result in phosphates, dissolved
solids, and acids in the waste waters. The production of
Na2!PlOJLC and the calcium phosphates result in phosphates,
suspended and dissolved solids in the effluent.
LAND AVAILABILITY
Removal of suspended solids from raw waste waters is most easily
accomplished by use of large settling ponds. This will be the
principle concern for land availability. The plants in this
category are located, however, in rural sites where the problem
of land availability is minimized.
AIR POLLUTION CONTROL EQUIPMENT
All of the chemicals covered in this study use wet scrubbers or
water systems in the process itself which amount to scrubbers.
Therefore this is not a topic for subcategorization.
Furthermore, it is recommended that dry air pollution control
equipment either precede or replace wet scrubbers in order to
reduce scrubber water contamination. Volatilization of hazardous
substances such as fluorine from neutralization and settling
ponds is insignificant.
SUBCATEGORIES
The factors that entered into the selection of subcategories are:
wastes generated, treatability of waste waters, product, and
particularly raw material and manufacturing process. Three
subcategories were considered necessary for purposes of
establishing effluent limitations guidelines:
-------
a. Phosphorus Production
1. phosphorus
2. ferrophosphorus
b. Phosphorus Consuming
1. phosphoric acid (dry process)
2. phosphorus pentoxide
3. phosphorus pentasulfide
4. phosphorus trichloride
5. phosphorus oxychloride
c. Phosphate
1. sodium tripolyphosphate
2. Calcium phosphates
i, animal feed grade
ii. food grade
-------
SECTION V
WATER USE AND WASTE CHARACTERIZATION
INTRODUCTION
With the background of manufacturing technology discussed in
Section III, this section discusses the specific water uses in
the phosphate manufacturing industry and the raw wastes from this
industry before control and/or treatment of these wastes. Both
Section III and Section V are intended to be generally
descriptive of the industry; i.e., they outline the standard
manufacturing processes and the standard raw waste loads that are
common to the great bulk of plants in the industry, it is not
until Section VII, Control and Treatment Technology, and Section
IX, Best Practicable Control Technology Currently Available that
distinctions are made (and quantitatively supported by
independently verified sampling data of plant effluents) within
the industry, pointing out those notable plants which have
already achieved significant reduction or total elimination of
polluting discharges.
The following discussion therefore, should not be taken as
implying that the raw waste loads quoted are always actual plant
discharges. Rather, they are intended to describe the total
waste management problem originally faced by any plant in the
industry. In actuality, significant abatement steps have been
taken by some plants within the industry. By fully explaining
the total waste management problem (in terms of raw waste loads)
the control and treatment steps can be later explained and
evaluated.
SPECIFIC WATER USES
Water is primarily used in the phosphate manufacturing industry
for eight principal purposes:
Non-contact Cooling Water
Process and Product Water
Transport Water
Contact Cooling or Heating Water
Atmospheric Seal Water
Scrubber Water
Auxiliary Process Water
Miscellaneous Uses
Non-contact Cooling Water
This type of water is used without contacting the reactants, such
as in a tube-in-shell heat exchanger. If, however, the water
contacts the reactants, then contamination of the water results
and the waste load increases. Probably the single most important
process waste control technique, particularly for subsequent
-------
treatment feasibility and economics, is segregation of non-
contact cooling water from process water.
Non-contact cooling water is generally of two types in the in-
dustry. The first type is recycled cooling water which is cool eel
by cooling towers or spray ponds. The second type is once-
through cooling water whose source is generally a river, lake, or
tidal estuary, and the water is returned to the same source from
which it was taken.
The only waste effluent from the recycled water would be water
treatment chemicals and the cooling tower blowdown which gener-
ally is discharged with the cooling water. The only waste eff-
luent from the once-through cooling water would be water treat-
ment chemicals which are generally discharged with the cooling
water. The cooling tower blowdown may contain phosphates, ni-
trates, nitrites, sulfates and chromates. The water treatment
chemicals may consist of alum, hydrated lime, and alkali metals
such as sodium and potassium produced by ion exchange units.
Regeneration of the ion exchange units is generally accomplished
with sodium chloride or sulfuric acid, depending on the type of
unit employed in the plant.
Process and Product Water
The process or product water generally is that which comes in
contact with the product and stays with the product as an inte-
gral part, such as the quenching, hydrolysis and dilution water
used in phosphoric acid manufacture, or the water used as a
reaction medium in food grade dicalcium phosphate manufacture.
Transport Water
Water may be used for transporting reactants or products between
unit operations. An example is the use of water for transferring
(by displacement) liquid phosphorus. Another example is the
transfer of electrostatic precipitator dust in phosphorus
manufacture as a slurry in water.
Since intimate contact between the process materials and trans-
port water occurs, this water may generally contain dissolved or
suspended materials and so is classified as process water.
Dntact Cooling or Heating Water
lis water comes under the general heading of process water
scause it comes in direct contact with process waters. A prime
xample is the large quantity of water used to quench the slag
com phosphorus furnaces; another is the water used to condense
gaseous phosphorus after it is produced in the furnaces.
Other direct contact cooling or heating water use such as that
for contact steam heating and/or drying, steam distillation, pump
and furnace seals, etc., is generally of much lower volume than
-------
the barometric condenser water and is easier to treat for waste
effluents.
Atmospheric seal Water
Because some of the materials in this industry spontaneously
ignite on contact with the oxygen in air, the air is kept out of
reaction vessels with a water seal. Liquid phosphorus is
universally protected by storing under a water blanket. These
seal waters are considered as process waters.
Scrubber Water
Throughout this industry, water scrubbers are used to remove
process vapors and/or dusts from tail gases and from gaseous
process streams. The used scrubber water is regarded as process
water since direct and intimate contact has occurred. The
resultant solution or suspension may contain impurities or may be
too dilute a solution to reuse or recover and thus is discharged.
Auxiliary Process Water
This water is used in medium quantities by the typical plant for
auxiliary operations such as ion exchange regeneration, make-up
water to boilers with a resultant boiler blowdown, equipment
washing, storage and shipping tank washing, and spill and leak
washdown. The volume of waste water from these operations is
generally low in quantity but highly concentrated.
Miscellaneous Water Sources
These water sources vary widely among the plants originating from
floor washing and cleanup, safety showers, eye wash stations,
sanitary uses and storm run-off. The resultant streams are
either non-contaminated or slightly contaminated with wastes.
The general practice is to discharge such streams without
treatment except for sanitary waste.
-------
PROCESS WASTE CHAJ*ACTEFIZATION
The descriptions of the manufacturing processes in Section III,
and the flow diagrams included in that Section, qualitatively
discussed the sources of wastes. The following discussion is
intended to describe these waste streams both in quantity and in
composition. These waste streams are the "raw" wastes before
control or treatment (which is separately discussed in Section
VII) .
Aqueous wastes emanating from air pollution abatement equipment
are considered as process wastes in this study.
The following sections quantify the raw process wastes in each
segment of the industry. A discussion of the source, nature, and
amount of these wastes for each segment is followed by a table
summarizing the standard raw waste load.
Various plants in the industry differ significantly in the degree
of process and cooling water recirculation. Hence, the waste
water quantities and constituent concentrations quoted may be
grossly different frcx* plant-to-plant. However, the raw loads in
kg per kkg of product (Ib/ton) are dependent primarily on the
manufacturing processes and are therefore much more
representative of the entire industry.
The Phosphorus Production Subcategory
The discussion of phosphorus manufacturing technology in Section
III and the flow diagram of Figure 2 qualitatively pointed out
the following streams emanating frow the process (in addition, of
course, to the phospnorus product stream):
By-products: Slag, Ferrophoaphorus, and Carbon Monoxide
Non-contact Cooling water
Electrostatic Precipitator Dust
Cfllciner Precipitator Dust
Calciner and Furnace Fume Scrubber Liquor
Pr.ospnorua Condenser Liquor (Aqueous phase)
Phosphorus Sludge (or rud)
Slag Quench Iiouor
The following sections discuss each of the above in quantitative
detail, and identify which are typically returned to the process
and which are classified as raw waste streams from the
manufacturing operation.
Byproduct streams
The by-products of the phosphorus manufacturing operation are:
-------
kg/kkcr Ib/ton
Ferrophosphorus 300 600
Slag (CaSiO3) 8,900 17,800
CO gas 2,800 5,600
Both ferrophosphorus and slag are sold, and the carbon me oxide
is either used to generate heat in the process or is otherwise
burned on site. Hence, none of the above three materials is
considered a waste.
The quench water used for the by-product slag is separately
discussed as a waste stream.
The by-product ferrophosphorus is cast as it is tapped from the
furnace and air-cooled. The solids are then broken up and
shipped. No water is used specifically for ferrophosphorus, and
there are no wastes accountable for ferrophosphorus manufacture.
Non-Contact Cooling Water
Phosphorus production facilities generate huge quantities of
heat. The electrical power consumption is approximately 15,500
kwh/kkg (U& million Btu/ton). An additional 8,100 kwh/kkg (25
million Btu/ton) are generated by combustion of the by-product
carbon monoxide. Some of this energy, 6,100 kwh/kkg (19 million
Btu/ton), is absorbed in the endothermic furnace reaction, and
some is absorbed by the endothermic calcining operation. Other
portions of this energy are released to the atmosphere by burning
of waste carbon monoxide (that not used for calcining) and by
convection, radiation and evaporative losses from the equipment
and process materials. Still other portions are absorbed by
contact waters in the calcining process and furnace from
scrubbers, in the phosphorus condenser, and in the slag quenching
operation.
After accounting for the above energy demands, a significant
quantity of heat is absorbed by non-contact cooling water for the
furnace shell, the crucible bottom, the fume hood, the tap holes,
the electrode fixtures, the electrical transformer, and for any
indirect phosphorus condensation. The quantity of this water is
highly variable from plant to plant, and depends on the furnace
design, the furnace size, and the degree of recirculation
(through heat exchangers with other water streams or through
cooling towers), whether or not cooling water is used in series
for different requirements, the inlet temperature of the
available cooling water, and the ambient air temperature. Plant
181 uses 325,000 1/kkg of product (78,000 gal/ton); Plant 159
uses 38,000 1/kkg (9,000 gal/ton); and TVA at Muscle Shoals,
Alabama,(5) uses 130,000 1/kkg (31,000 gal/ton).
Electrostatic Precipitator Dust
-------
The high-temperature electrostatic precipitator removes dusts
from the furnace gases before these gases are condensed for
recovery of phosphorus. These dusts may contain up to 50 percent
P£O5, and therefore find value either as a fertilizer for sale or
for return to the process. In the latter case, they are
transported to the ore blending head end of the plant. One TVA
scheme slurries the dust for transport; the slurry is pumped to a
settling pond, the settled solids are fed to the ore - blending
unit, and the pond overflow is reused in the slurrying operation.
The quantity of precipitator dust is approximately 125 kg/kkg of
product (250 Ib/ton). Regardless of the method of sale or re-
use, the precipitator dust is not a waste material to be disposed
of from the plant.
Calciner Precipitator Dust
Dry dust collectors are used in the calcining operation, upstream
of wet scrubbing systems. The dry fine dusts collected are
recycled directly to the sizing and calcining operations. The
collected and recycled fines may amount to as much as 30 percent
of the net production from the nodulizing process.
There is no plant discharge of dry calciner precipitator dusts-
therefore this is not a component of the plant's raw waste load.'
Calciner and Furnace Fume scrubber Liquor
Water scrubbers are used for air pollution abatement for the
calciner exhaust stream (downstream of dry dust collection), for
furnace fumes, for ore sizing dusts, for coke handling dusts, for
raw material feeding operation dusts, and for furnace taphole
(slag and ferrophosphorus) fumes. The scrubber liquor contains
suspended solids (which are mainly SiO2 and Fe203), some
phosphates and sulfates as dissolved solids, and a large quantity
of fluorides. To explain the presence of these fluorides in the
scrubber liquor. Table 6 lists the quantities of materials in
commercial phosphate rock presented as pounds per ton of
phosphorus ultimately produced after normalizing of 26 percent
P2.°5 content. From Table 6, the average quantity of F in ore is
275 kg/kkg of P4 (550 Ib/ton). Approximately 8 percent of this
quantity of F, or 22 kg/kkg (HH Ib/ton), is volatilized in the
ore calcining operation, and is subsequently a constituent of the
scrubber liquor.
This scrubber liquor is highly acidic for three reasons: the
3Ulfur j(as SO3) forms sulfuric acid; the P2O5 forms phosphoric
acid; and the fluorine, which is released in the form of silicon
tetrafluoride, forms fluosilicic acid and silicic acid on
hydrolysis.
The quantity of scrubber liquor wasted depends on the degree of
recirculation of this liquor from a sump back to the scrubbers.
TVA at Muscle Shoals circulates approximately 21,000 1/kkg of
50
-------
TABLE 6
Composition^ of Commercial Phosphate Rocks (12)
Expressed as kg per kkg (Ib/ton) of Phosphorus Produced
constituent _
Florida Land
Pebble
Furnace Grade
kg/kkg lb/tgn'
Tennessee
Brown Rock
Furnace Grade
kq/kkq Ib/ton
P2O5 2,600 5,200
CaO*~ 3,800 7,600
MgO 35 70
A1203 125 250
Fe203 155 310
Si02~ 725 1,450
S03~ 215 430
F " 305 610
CO2 330 660
Organic Carbon 40 80
Na20 10 20
K20 10 20
2,600
3,550
75
1,230
760
3,150
50
270
150
35
35
50
5,200
7,100
150
2,460
1,520
6,300
100
540
300
70
70
100
Western
Phosphoric Acid
Low Grade
kq/kkq Ib/ton
2,600
3,150
190
810
550
3,750
260
245
550
685
205
135
5,200
6,300
380
1,620
1,100
7,500
520
490
1,100
1,370
410
270
51
-------
product (5,000 Ib/ton) with a portion bled off to control the
composition. This scrubber liquor is of the following
composition:
Constituent Concentration, %
F 3.1
SiO2 1.1
P205 0.2
Fe2O3 0.1
S ~ 1.7
If the fluoride concentration of 3.1 percent is equated to a
standard raw waste load (as previously discussed) of 22 kg/kkg
(44 Ib/ton), the quantities of other scrubber liquor components
may be calculated:
Constituent Raw Waste Load
"" kq/kkq Ib/ton
F 22 44
Si02 8 16
P 205~ 1.5 3
Fe203 0.5 1
S 12 24
The total CaCO3_ acidity of the scrubber liquor, calculated from
the above constitxaent quantities, is 60 kg/kkg (120 Ib/ton) .
Other plants do not recirculate scrubber liquor; the volume
wasted is much greater and the constituent concentrations are
much smaller, but the raw waste loads (in kg/kkg of product)
should be comparable. Plant 181 does not directly recirculate
the liquor, and uses 300,000 1/kkg (71,000 gal/ton) for
scrubbing.
Phosphorus Condenser Liquor
The furnace gases pass from the electrostatic dust precipitator
to the phosphorus condenser, where a recirculating water spray
condenses the product. The condenser liquor is maintained at
approximately 60°C (140°F), high enough to prevent solidification
of the phosphorus (freezing point 44°C (112°F)), This condenser
liquor is "phossy water", essentially a colloidal dispersion of
phosphorus in water, since the solubility at 20°C (68°F) is only
3.0 mg/1. Depending on how intimate the water/phosphorus contact
was, the phosphorus content of phossy water may be as high as
several weight percent.
The condenser liquor also contains constituents other than ele--
mental phosphorus: fluoride, phosphate, and silica. Using the
average F content of ore (from Table 6) of 275 kg/kkg, plus the
estimate that 12 percent of the F in the ore volatilizes in the
52
-------
furnace and is therefore equivalent to 33 kg/kkg (66 Ib/ton), and
by accounting for 6 kg of F per kkg (12 Ib/ton/ ton) which is
collected in the precipitator dust and in the phosphorus sludge
ash, a raw waste load of F is derived of 27 kg/kkg (54 Ib/ton) in
the condenser liquor. This condenser liquor is not acidic
despite the hydrolysis of P205 and siF4 to H3PO4, H2SiF6, and
H2SiO3 because aqueous ammonia or caustic is added to prevent
undue corrosion in the condenser.
There are other sources of phossy water within the plant. Stor-
age tanks for phosphorus have a water blanket, which is
discharged on phosphorus transfer. Railroad cars are cleaned by
washing with water. Phosphorus may be purified by washing with
water. Together, all sources of phossy water wastes amount to
about 5,400 1/kkg (1,300 gal/ton), and at a concentration of
1,700 mg/1, the quantity of phosphorus wastes amounts to about 9
kg/kkg produced (18 Ib/ton) , as reported by TVA.
At TVA, the condenser liquor is recirculated at the rate of
33,000 1/kkg (8,000 gal/ton). Other plants may differ
significantly in the quantity of phossy water circulated, but the
raw wastes (in kg/kkg of product) should be fairly uniform. For
example. Plant 181, which does not directly recirculate its
condenser water, uses 84,000 1/kkg (20,000 gal/ton), with an
additional 17,000 1/kkg (4,000 gal/ton) for phosphorus handling
and storage.
To calculate the raw waste loads of phosphate and silica in the
condenser liquor, the following TVA recirculated-liquor compo-
sition was used:
Constituent Concentration, %
F 8.3
P205 5.0
Si02 4.2
Equating 8.3 percent F with the previously-derived 27 kg/kkg of
F, the raw waste loads of P205 and siO2 become respectively 16.5
kg/kkg (33 Ib/ton) and 13.5 kg/kkg (27 Ib/ton).
Phosphorus Sludge
In addition to phossy water, the phosphorus condenser sump also
collects phosphorus sludge, which is a colloidal suspension ty-
pically 10 percent dust, 30 percent water and 60 percent
phosphorus. The quantity of sludge formed is directly dependent
on the quantity of dust that escapes electrostatic precipitation,
hence the very large investment made for highly efficient
precipitators.
Using 125 kg of dust (per kkg of product) collected by the elec-
trostatic precipitator, and assuming a 98 percent collection
efficiency, the dust reaching the condenser amounts to 2,5 kg/kkg
53
-------
(5 Ib/ton). If all of this dust became part of the sludge, the
sludge quantity would be 25 kg/kkg (50 Ib/ton) of product, and it
would contain 15 kg/kkg (30 Ib/ton) of elemental phosphorus.
This sludge is then universally processed for recovery of phos-
phorus, typically by centrifugation. A 96 percent recovery has
been reported, with the product (subsequently returned to the
process) averaging 92 to 96 percent phosphorus. The remaining 4
percent of the phosphorus in the sludge is burned in a phosphoric
acid unit, so that no wastes emanate from the plant.
Other methods for processing the sludge which also result in no
plant effluent include heating in a slowly rotating drum in an
inert atmosphere to drive off phosphorus vapor, which is then
condensed with a water spray into a sump. The solid residue
obtained is completely free of elemental phosphorus and can be
safely landfilled or recycled to the feed preparation section of
the plant.
Slag Quenching Liquor
Slags from phosphorus furnaces are mainly SiO2 and CaO, and would
also contain A1203, K2O, Na2O, and MgO in amounts consistent with
the initial ore composition. In addition to these oxides,
phosphate rock may contain 0.1-0.2 kg/kkg (0.2-0.4 Ib/ton) of
uranium in the ore, and the radiation levels of both the slag and
the quench waters must be appropriately noted. Other
constituents of the slag presenting problems for quench water
pollution control are fluoride and phosphate. Approximately 80
percent of the original F in the phosphate rock, 220 kg/kkg of PU
(440 Ib/ton), referring to Table 6, winds up in the slag. About
2.7 percent of the original P2O5 in the phosphate rock, 70 kg/kkg
(140 Ibs/ ton), winds up in the~slag.
At Plant 181, approximately 24,600 1/kkg (5,900 gal/ton) may be
used for quenching the slag, with the slag quench liquor having
the following composition and raw waste loads:
Constituent Concentration, mg/1 Raw Waste Load
kq/kkq P4~ Ib/ton PU
Total Suspended 800 20 40
Solids
Total Dissolved 1,700 42 85
Solids
Phosphates (as P) 12 0.3 0.6
Sulfate (as S) 1,000 25 50
l?e 14 0.35 0.7
:? 170 4.5 9
Total Alkalinity 230 5.5 11
54
-------
TABLE 7
Summary of Raw Wastes froyi Phosphorus Manufacture
Note: Waste water quantities and constituent concen-
trations are highly variable, depending on
degree of recirculation, but the raw waste
loads should be representative.
Phosphorus
Calciner Condenser Slag
Scrubber Plus Other Quenching Composite
Liquor Phossy Water Water Waste
Waste Water Quantity,
1/kkg 300,000 100,000 25,000 425,000
gal/ton 72,000 21,000 6,000 102,000
Raw Waste Load,
kg/kkg
TSS 8,5 13.5 20.5 42.5
P4 9 - 9
P04 2 22 1 25
S04 36 - 75 111
F ~ 22 27 4.5 53.5
Total Acidity 60 - 54.5
Total Alkalinity - - 5.5 -
Raw Waste Load,
Ib/ton
TSS 17 27 41 85
P4 - 18 * 18
P04 4 44 2 50
S04 72 - 150 222
F 44 54 9 107
Total Acidity 120 - - 109
Total Alkalinity - 11 -
Concentrations, mg/1
TSS 28 135 820 100
P4 90 21
PO4 7 220 40 59
S04 120 - 3,000 260
F " 73 270 180 126
Total Acidity 200 - - 128
Total Alkalinity - - 220
55
-------
The Phosphorus Consuming Subcategory
No direct process aqueous wastes are generated in this segment of
the industry. The raw wastes arise from phosphorus storage and
transfer, from wet scrubbing of tail gases, from vessel cleaning,
and from leaks and spills.
Phossy Water Wastes
Because phosphorus is transported and stored under a water
blanket, phossy water is a raw waste material at phosphorus using
plants as well as at phosphorus producing plants. The standard
procedure when liquid phosphorus is transferred from a rail car
to the using plant's storage tank is to pump the displaced phossy
water from the storage tank back into the emptying rail car as
practiced at Plants 037 and 192. Instead of being wasted at the
phosphorus-using plant, the phossy water is shipped back to the
phosphorus-producing facility for treatment and/or re-use.
Therefore, standard raw phossy water wastes at the phosphorus
using plants are due to surges or to anomalies in the storage
tank water level control system rather than to the direct wasting
of all displaced water.
A more insidious source of phossy water may arise at phosphorus
consuming plants. Should reactor contents containing phosphorus
ever be dumped into a sewer as a result of operator error,
emergency conditions, or inadvertent leaks or spills, the phos-
phorus would remain at the low points in the sewer line generally
as a solid (melting point 44°c (111°F)) and would contact all
water flowing in that sewer from that time on. Since phosphorus
burns when exposed to air (autoignition temperature 93°C), there
is general reluctance to clean it out. The common practice is to
ensure a continuous water flow to prevent fire.
The typical phosphorus loss for phosphorus consuming plants is 1
kg lost to phossy water per kkg consumed (2 Ib/ton). Whenever
phosphorus is tranferred by displacement, 580 liters of water are
displaced per kkg of phosphorus (140 gal/ton). These values are
equivalent to a phosphorus concentration of 1700 mg/1. For
comparison, a typical phosphorus content in phossy water at a
phosphorus producing plant has also been reported at 1700 mg/1.
Phosphoric Acid Manufacture
The production of phosphoric acid by the "dry" process from
elemental phosphorus consumes a total of about 380 liters of
water per kkg of product (92 gal/ton) for both the hydration and
the acid dilution steps. The cooling water requirements are
typically 92,000 liters per kkg of product (22,000 gal/ton); but
with recycle of cooling water, the make-up cooling water
requirement is approximately 4,600 liters per kkg of product
(1,100 gal/ton). There is no aqueous process waste from notable
phosphoric acid Plants 003, 006, 042, and 075. Despite good
housekeeping at a notable plant, however, leaks or spills of
56
-------
phosphoric acid may amount to an average of 1 kg/kkg (2 Ib/ton),
with a range of 0 to 2.5 kg/kkg (0 to 5 Ib/ton).
Where food grade phosphoric acid is produced, a standard raw
waste of 0.1 kg/kkg (0.2 Ib/ton) of arsenic sulfide is precipi-
tated by addition of a soluble sulfide (H2S, Na2S, NaHS) and
filtered out of the acid. An additional 0.75 kg/kkg "(1.5 Ib/ton)
of filter-aid material may accompany the sulfide as a solid
waste.
Phosphorus Pentoxide Manufacture
The waste water from the tail seals on the condensing towers
typically contains 0.25 kg/kkg (0.5 Ib/ton) of H3PO4 (100 percent
basis). Approximately 500 1/kkg (120 gal/ton)" of water may be
used, resulting in a concentration of 470 mg/1 for the effluent
bleed.
The inlet air dryer silica gel is regenerated often, but is
renewed very infrequently (perhaps every ten years). The wasted
material is typically landfilled.
Approximately 29,000 1/kkg (7,000 gal/ton) of non-contact cooling
water are used.
Phosphorus Pentasulfide Manufacture
The water seals on the batch reactor vent lines accumulate a
mixture of phosphorus mud and lower phosphorus sulfides. These
seals are cleaned once a week, and the residue amounts to 0.15
kg/kkg (0.3 Ib/ton). This residue is hazardous and flammable and
is typically buried.
Should any batch be aborted (a rare occurrence) because of
agitator failure, cast iron pot failure, or other reason, the
material is disposed of by incineration.
The dust collected by a cyclone from the P2S5 crushing operation
amounts to 1 kg/kkg (2 Ib/ton).
The still pot for the vacuum distillation step accumulates im-
purities, which include carbon and iron sulfur compounds and
glassy phosphates. Most important, the residues contain arsenic
pentasulfide, which is higher-boiling than the corresponding
phosphorus pentasulfide. Arsenic occurs naturally with phos-
phorus (they are both Group V-A elements) at a level of about
0.075 kg/kkg (0.15 Ib/ton) of arsenic which is equivalent to 0.05
kg of As2S5 per kkg of product P2S5 (0.1 Ib/ton). The entire
still pot residue is about 0.5 kg/kkg Tl Ib/ton). Periodically,
these residues are removed and the solids are broken up and
buried. Approximately 17,000 1/kkg (4,000 gal/ton) of non-contact
cooling water is used.
57
-------
In the casting of liquid P2S5, the fumes from burning liquid
(molten P2.S5 auto-ignited)"are scrubbed. Typically, the scrubber
water contains 1.25 kg of combined P2O5 and SO2 per kkg of pro-^
duct P.2S5 (2.5 Ib/ton) . Because both P.2O.5 and SO2 are absorbed by
a water scrubber only with difficulty, the water flow rate is
high, 30,000 1/kkg (7,200 gal/ton). These values reduce the
concentrations of PO2~3 and S03~2 in the scrubber effluent of 17
and 34 mg/1, respectively. Much lower scrubber flow rates could
be used should weak caustic or lime be used instead of water.
Phosphorus Trichloride Manufacture
The batch or semicontinuous reactor/stills accumulate residues
which are periodically but infrequently removed. These residues
contain arsenic, trichloride, which is higher-boiling than the
corresponding phosphorus trichloride. Arsenic occurs naturally
with phosphorus (they are both Group V-A elements) at a level of
about 0.075 kg/kkg (0.15 Ib/ton) of arsenic, which is equivalent
to 0.05 kg of ASC13 per kkg of product PC13 (0.1 Ib/ton). This
is about half the quantity of total residue in the stills
(exclusive of residual PC13 from the last batch or run before
shutdown).
The average non-contact cooling water requirement is 54,000 1/kkg
(13,000 gal/ton).
Water scrubbers collect PC13. vapors from the reaction, the
product distillation, the product storage, and the product
transfer operations and hydrolyze these vapors to HC1 and to
H3PO3_ (which may subsequently be oxidized to H1PO4) . The
quantity of PC13 collected is highly dependent on the efficiency
of the upstream condensers, since PC13 is highly volatile:
Temp, °c Temp, °F PC13 Vapor Pressure, mm Hg(27)
20 68 99
40 104 235
60 140 690
76 169 760
At Plant 037, sufficient heat transfer area was provided in the
condensers to limit the raw waste load to 3 kg of HC1 plus 2.5 kg
of H3P03_ per kkg of product PC13 (6 Ib/ton and 5 Ib/ton) .
Approximately 5,000 1/kkg (1,200 gal/ton) of scrubber water were
used to collect these wastes. Other smaller waste quantities of
:L:ci and H3PQ3 generated from tank car and returnable container
Cleaning operations have been included in these quantities.
hese quantities are based on the most reliable data available at
Plant 037, overall material balances of product PC13 shipped vs.
Elemental phosphorus received. These data, validated over long
periods of time for profitability purposes, show a total loss of
phosphorus trichloride of 5 kg/kkg (10 Ib/ton). An estimated
breakdown of this loss is:
58
-------
Transfer and Storage of Phosphorus, 1.0 kg/klcg (2 lb/ton)
Reactor/Still Residues, 0.1 kg/kkg (0.2 lb/ton)
Scrubber for Distillation Tail Gasesr 2,5 kg/kkg (5 lb/ton)
Transfer of PCI 3, 1.0 kg/kkg (2 lb/ton)
Other than the estimated loss of elemental phosphorus and the
reactor/still residues, the losses which become water-borne raw
wastes amount to 3.5 kg/kkg (7 lb/ton). Upon hydrolysis, this
stoichiometrically becomes 3 kg/kkg (6 lb/ton) of HCl plus 2.5
kg/kkg (5 lb/ton) of H3PO3. These material-balance data have
been used because of their long-term confirmation. Direct
measurements of waste water flow rates and of waste water
constituent analysis were not relied on in this case since
accurate flow rate measurements were not possible in the existing
plant configuration and since no statistically meaningful
analytical data had been collected. The acid wastes from washing
tank cars and tank trucks and from washing used POC13 filter
elements are very small at present. Water use data taken from
Plant 037, supplemented by an independent analysis of the waste
water, yielded the results in Table 8. Total raw waste generated
in truck-loading, in tank-car cleaning, and in filter-element
washing is 0.014 kg/kkg (0.028 lb/ton) of HCl plus 0.003 kg/kkg
(0.007 lb/ton) of total phosphates.
Phosphorus Oxychloride Manufacture
The water scrubber for the distillation operation in the standard
process (using P2O5 and C12) typically collects 1.5 kg of HCl
(anhydrous basis) and 0.25 kg of H3POU (100 percent basis) per
kkg of product PCX: 13 (3 lb/ton and 0?5 lb/ton), and the scrubber
for POC13 transferring collects about 0.2 kg of HCl and 0.15 kg
of H3.P04 per kkg of product (0.4 lb/ton and 0.3 lb/ton).
Allowing for small wastes from returnable container cleaning
operations, the standard raw waste load is 2 kg of HCl and 0.5 kg
of H3P04 per kkg of product (U lb/ton and 1 lb/ton).
Approximately 2,500 1/kkg (600 gal/ton) of water are used, so
that the raw waste concentrations are 800 mg/1 HCl and 200 mg/1
H3P04. y
The source of the above data on raw waste loads was Plant 147
records and plant personnel analysis of these records. An in-
dependent verification of these results was not judged valid
since at this plant neither an accurate determination of waste
water flow rate nor the collection of a distinct waste water
sample from each unit operation contributing to the waste load
was practical, and since statistically valid background data were
not at hand.
These waste quantities for POC13 manufacture are somewhat smaller
than for PC13 manufacture since POC13 is less volatile (boiling
point 107°C). In the batch process7 the refluxing liquid is all
PC13 at the start, but becomes increasingly richer in POC13.
59
-------
TABLE 8
Minor Wastes from Plant 037 (PC13 and POC131
Truck-Loading
Vent
Scrubber
Water Use:
1/kkg 8.8
gal/ton 2.1
Constituent Analysis, mg/1:
Chloride 340
Total PO4 260
Total Acidity 660
Raw Waste Load, kg/kkg:
Chloride 0.0030
Total PO4 0.0023
Total Acidity 0.0058
Raw Waste Load, Ib/ton:
Chloride 0.006
Total PO4 0.005
Total Acidity 0.012
Tank Car
Cleanout
.Water
10.5
2.5
715
26
0.0075
0.0003
0.015
0.001
Filter Element
Washout
Drum
0.46
0.11
6,480
590
18,200
0.0030
0.0003
0.0083
0.006
0.001
0.017
60
-------
The air-oxidation process presents a much more difficult task for
the reflux condenser, since the vapors are highly diluted with
non-condensibles. With the use of refrigerated condensers,
however, the measured raw waste load is no different for this
process. At Plant 037, data collected over three months from the
reactor/still scrubber for POC13 manufacture, which had an
estimated flow rate of 1,800 1/kkg (430 gal/ ton), had average
net values of:
Chloride 669 mg/1
CaC03 acidity 1,213 mg/1
These data reduce to a raw waste of 1.2 kg/kkg (2.4 Ib/ton) of
HC1 plus 0.35 kg/kkg (0.7 Ib/ton) of H3PO4, which are extremely
close to the corresponding values for Plant 147.
Where product POC13 is filtered, the used filter elements are
first washed to hydrolyze the residual POC13. Disposable ele-
ments are then landfilled. The quantity of filtered solids
retained on the elements is only a very small fraction of the
weight of the used element. The elements are washed in a 55-
gallon drum, so that a very small quantity of waste water (and of
acid wastes) is involved compared to the scrubber waste load.
Although there is no continuous withdrawal of residues from POC13
distillations, very little residue accumulates. Twice a year
this residue (mostly glassy phosphates) is washed out with hot
water.
The non-contact cooling water requirement for POC13 manufacture
by either the standard or the alternate method is approximately
50,000 1/kkg (12,000 gal/ton).
Variability of Raw Wastes from the Production of Phosphorus
Trioxide and Phosphorus Oxychloride
The data below indicate the variability of concentrations in the
raw waste load at Plant 037.
Pate (19731 Cacoj Acidity, niq/i
2/27 1170 560
2/28 1220 603
3/1 1720 822
tt/19 850 UU7
4/23 480 305
«/2 1340 603
5/7 1810 1000
5X8 1220 57U
5/9 1290 116
Mean 1217 687
Std. Deviation 384 208
Std. Deviation 381 208
95S Conf. Int.
(Single Day) +_?!« + 1
61
-------
In this case, there was no damping capacity; the acidity and
chloride concentrations were closely coupled to the manufacturing
process. The comparison of the 95% confidence intervals with the
daily data show only one point of 17 (for acidity) and no points
outside (for chloride).
Based on these very limited samples of data, it appears that the
classical statistics may be applied, but with extreme caution.
For the above sets of data from Plant 037, a value of (X + 3o") / x
might represent a maximum allowable daily reading as a multiple
of the mean:
Parameter (X f 3c^/ X
Acidity Concentration 1.95
Chloride Concentration 1.91
This maximum allowable value would be extremely liberal, since a
Students "t" value of 3 is equivalent to less than one reading in
100 being unduly rejected. To be even more liberal (since the
data base for this analysis is extremely skimpy), the maximum
value from the above table will be assumed, so that the effluent
limitation guideline for the manufacture of PC13 and POC13. should
be a maximum daily value no greater than twice the mean (as
represented by consecutive 30-day averages).
pH can be controlled much more closely than other parameters.
Hence, it is recommended that the pH limitation be met at all
t imes.
62
-------
TABLE 9
summary of Raw Waste from Phosphorus-Concuming Plants
Phossy Water: ?4 cone, ppm
1/kkg P4 consumed
kqPd/kkg ?4 consumed
gal /ton ?4 consumed
Ib /tori ?4 consumed
Process Hater Wasted: 1/kkg Pdt
gal /ton Pdt
Raw Waste Load, kg/kkg Pdt:
HCT
H2S03
H3P03 + H3P04
Raw Waste Load, Ib /ton Pdt:
MCI
H2S03
H3P03 + H3P04
Concen orations, mg/1: HC1
HpS03
H3P03 + H3P04
Process Water Consumed-
1/kkg Pdt.
gal /ton Pdt
Cooling Water Used: 1/kkg 'Pdt
gal /ton Pdt
Solid Wastes, kg/kkg Pdt:
As Compounds
Total Residues
Solid Wastes, Ib /ton Pdt:
As Compounds
Total Residues
H PO
3 4
(75%)
1,700
580
1
140
2
--
--
~
...
PoOr
2 5
1,700
580
1
140
2
500
120
—
--
1 0.25
--
—
2
--
--
High
oon
38(J
92
--
—
0.5
—
--
470
--
91,000 29,000
22,000
0.1
—
0.2
" —
7,000
—
—
--
"•—
D S
25
1,700
580
1
140
2
30,000
7,200
—
1
Q.5
—
2
1
__
34
17
--
16,600
4,000
0.05
0.7
0.1
1.4
PCI.
o
1,700
580
1
140
2
5,000
15?.OQ
3
_.
2.5
6
--
5
600
—
500
—
54,000
13,000
0.05
0.05
0.1
0.1
POC1,
3
« .*
—
—
--
— —
2,500
600
2
--
0.5
4
--
1
800
--
200
—
50,000
12,000
—
<0.05
--
<0.1
63
-------
The Phosphate Subcategory
The aqueous wastes from this segment of the industry arise from
the use of wet dust scrubbing equipment for the finely divided
solid products, and from processes which use excess process water
which may become a waste stream.
Sodium Tripolyphosphate Manufacture
Exemplary Plants 006, 042, and 119 have no process wastes. The
dust collected from the spray dryer gaseous effluent stream is
added to the spray dryer solid product stream. The water used
for subsequent scrubbing of this gas stream from the spray dryer
is then recycled to the mix area and is used as process water in
the neutralization step. The cooling air used for the product
tempering is vented into the spray dryer vent line upstream of
the scrubbing operation.
The neutralization step requires a total of 1,040 I/ kkg (250
gal/ton), of which 290 1/kkg (70 gal/ton) are recycled from the
scrubber. Make-up water, 750 1/kkg (180 gal/ton), is added since
water is evaporated in the product drying step. The make-up
water is softened, and regeneration of the softener combined with
boiler and cooling tower blowdowns amounts to 210 1/kkg (50
gal/ton), 70 percent of which is from water treatment
regeneration and 30 percent from blowdowns. These blowdown
wastes typically contain 1,500 mg/1 of dissolved chlorides.
Calcium Phosphates
The raw aqueous wastes from the manufacture of food grade calcium
phosphates are from two primary and approximately equal sources:
the centrate of filtrate from dewatering of the dicalcium
phosphate slurry and the effluent from wet scrubbers which
collect airborne solids from product drying operations. Both of
these sources contain suspended, finely-divided calcium phosphate
solids. It is normal practice in an integrated plant to
partially recycle the scrubber water and to partially use the DCP
centrate or filtrate as make-up scrubber water, as at Plant 003.
The total raw wastes from this system are typically 4,200 1/kkg
(1,000 gal/ton) containing 100 kg/kkg (200 Ib/ton) of solids (a
concentration of 2.4 percent). An additional 30 kg/kkg (60
Ib/ton) of dissolved solids (0.7 percent of this waste stream)
originates from phosphoric acid mists in the scrubbers and from
excess phosphoric acid in the reaction liquid.
For non-food grade dicalcium phosphate plants, the water scrubb-
srs which collect airborne solids normally operate at partial
recycle, since there is no waste from a dewatering operation, and
since dry dust collection typically precedes wet scrubbing, the
raw wastes are considerably smaller than for the food grade
operation. Dry dust collection is typical since only one or two
products are made, so that the collected solids may be added
directly to the product stream without extensive segregation.
-------
Moreover, since purity requirements are considerably less severe,
the product stream can tolerate such additions. With the above
measures, the wet scrubber wastes are typically 420 1/kkg (100
gal/ton) containing 22.5 kg/kkg (45 Ib/ton) of suspended solids
(a concentration of 5 percent.) plus U kg/kkg (8 Ib/ton) of
dissolved phosphates from acid mists (0.7 percent). At Plant
182, this bleed stream from the wet scrubber recirculation system
is charged directly to the neutralization reactor; hence, this
plant had no discharge. As an added feature, this notable plant
used cooling water blowdown as make-up to the airborne-solids
scrubbing system, thereby eliminating all aqueous discharges
(except for the effluent from regeneration of the water
softener).
For the non-food grade plants, however, acid defluorination is an
additional source of raw wastes (unless already defluorinated
acid is delivered to the plant). Wet-process phosphoric acid (51
percent P2O5) contains approximately 1 percent fluorine. Upon
silica treatment, 13.5 kg per kkg of acid (27 Ib/ton), or 10.5 kg
of silicon tetrafluoride product dicalcium phosphate dihydrate
(21 Ib/ton), are liberated. When hydrolyzed in the acid
scrubber, the raw waste contains 12 kg/kkg product (24 Ib/ton) of
combined fluosilicic acid (H2SiF£), hydrofluoric acid (HF) and
silicic acid (H2SiO3). These raw wastes are contained in a
scrubber water flow of 6,300 liters/ kkg (1,500 gal/ton), so that
the combined concentration of fluosilicic acid, hydrofluoric acid
and silicic acid is 1,900 mg/1. For any plant manufacturing
calcium phosphates of any grade, non-contact cooling water is
used in reactors and/or in dried product coolers.
Other possible sources of aqueous wastes are regeneration of
water softeners and storm water runoff (all exterior surfaces of
calcium phosphate plants become coated with fine lime and/or
phosphate dusts).
In dry product plants, a significant housecleaning effort must be
continually maintained. In non-food grade calcium phosphate
plants, the dry product sweepings (from dust, spills, etc.) are
added to the process stream. In food grade plants, however, the
sweepings (consisting of lime, lime grit, and calcium phosphates)
are wasted. Typically, this solid waste amounts to 10 kg/kkg (20
Ib/ton).
65
-------
TABLE 10
Summary of Raw Wastes from Phosphate Plants
Process Water Wasted:
1/kkg Pdt
gal/ton Pdt
Raw Waste Load,
kg/kkg Pdt:
TSS
Dissolved P04
HF, H2S1F6, H2S1O3
Raw Waste Load,
Ib/ton Pdt:
TSS
Dissolved P4
HF, H2S1F6, H2S103
Concentrations, mg/1:
TSS
Dissolved PO4
HF, H2SiF6, H2S1O3
TDS, mg/1
Solid Wastes:
kg/kkg Pdt
Ib/ton Pdt
Sodium
Tripoly-
Phosphate
0
0
Food Grade Animal Feed
Calcium Phosphates Calcium Phosphates
Solids Acid Deflu- Solids
Dewatering Scrubbing orination Scrubbing
2,100
500
50
15
100
30
24,000
7,000
2,100
500
50
15
100
30
24,000
7,000
7,000 7,000
6,300
1,500
12
24
1,900
1,900
420
100
22.5
4
45
8
54,000
7,000
7,000
0
0
10
20
66
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SECTION VI
SELECTION OF POLLUTION PARAMETERS
INTRODUCTION
Section V of this report quantitatively discussed the raw wastes
generated in the phosphate manufacturing industry. The following
were identified as being constituents of the industry's process
waste waters:
Suspended Solids
Phosphate and Elemental Phosphorus
Sulfates and Sulfites
Fluoride
Chloride
Dissolved Solids
pH, Acidity and Alkalinity
Temperature
Arsenic
Vanadium, Cadmium, and Radioactivity
The following discussion examines each of the above
and their impact on receiving waterways from
physical and a biological viewpoint. Additional
such as hexavalent chromium, iron, alkalinity,
which are of typical concern whenever blowdowns
towers, boilers and water treatment facilities are
noted here but are not discussed in detail in this
deals more specifically with the process wastes of
industry).
constituents
a chemical a
constituents
and hardness,
from cooling
involved, are
study (which
the phosphate
PROPERTIES OF THE POLLUTANTS AND POLLUTANT PARAMETERS
The following paragraphs describe the chemical, physical and
biological properties of the pollutants and pollutant parameters
that exist for this industry. The undesirable characteristics
that these parameters exhibit or indicate are stated, giving
reason to why they were selected.
TOTAL SUSPENDED SOLIDS
Suspended solids include both organic and inorganic materials.
The inorganic components include sand, silt, and clay. The
organic fraction includes such materials as grease, oil, tar,
animal and vegetable fats, various fibers, sawdust, hair, and
various materials from sewers. These solids may settle out
rapidly and bottom deposits are often a mixture of both organic
and inorganic solids. They adversely affect fisheries by
covering the bottom of the stream or lake with a blanket of
material that destroys the fish-food bottom fauna or the spawning
67
-------
ground of fish. Deposits containing organic materials may also
deplete bottom oxygen supplies and produce hydrogen sulfide,
carbon dioxide, methane, and other noxious gases.
In raw water sources for domestic use, state and regional
agencies generally specify that suspended solids in streams shall
not be present in sufficient concentration to be objectionable or
to interfere with normal treatment processes. Suspended solids
in water may interfere with many industrial processes, and cause
foaming in boilers, or encrustations on equipment exposed to
water, especially as the temperature rises. Suspended solids are
undesirable in water for textile industries, paper and pulp,
beverages, dairy products, laundries, dyeing, photography,
cooling systems and power plants. Suspended particles also serve
as a transport mechanism for pesticides and other substances
which are readily sorbed into or onto clay particles.
Solids may be suspended in water for a time and then settle to
the bed of the stream or lake. These settleable solids
discharged with man*s wastes may be inert, slowly biodegradable
materials, or rapidly decomposable substances. While in
suspension, they increase the turbidity of the water, reduce
light penetration and impair the photosynthetic activity of
aquatic plants.
Solids in suspension are esthetically displeasing. When they
settle to form sludge deposits on the stream or lake bed they are
often much more damaging to the life in water, and they retain
the capacity to displease the senses. Solids, when transformed
to sludge deposits, may do a variety of damaging things,
including blanketing the stream or lake bed and thereby
destroying the living spaces for those benthic organisms that
would otherwise occupy the habitat. Organic solids of a
decomposable nature use a portion or all of the dissolved oxygen
available in the area. Organic materials also serve as a
seemingly inexhaustible food source for sludgeworms and
associated organisms.
Turbidity is principally a measure of the light absorbing
properties of suspended solids. It is frequently used as a
substitute method of quickly estimating the total suspended
solids when the concentration is relatively low.
PHOSPHORUS
uring the past 30 years, a formidable case has developed for the
relief that increasing standing crops of aquatic plant growths,
*hich often interfere with water uses and are nuisances to man,
frequently are caused by increasing supplies of phosphorus. Such
phenomena are associated with a condition of accelerated
eutrophication or aging of waters. It is generally recognized
that phosphorus is not the sole cause of eutrophication, but
there is evidence to substantiate that it is frequently the key
68
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element in all of -the elements required by fresh water plants and
is generally present in the least amount relative to need.
Therefore, an increase in phosphorus allows use of other, already
present, nutrients for plant growths. Phosphorus is usually
described, for this reason, as a "limiting factor."
When a plant population is stimulated in production and attains a
nuisance status, a large number of associated liabilities are
immediately apparent. Dense populations of pond weeds make
swimming dangerous. Boating and water skiing and sometimes
fishing may be eliminated because of the mass of vegetation that
serves as a physical impediment to those activities. Plant
populations have been associated with stunted fish populations
and with poor fishing. Plant nuisances emit vile stenches,
impart tastes and odors to water supplies, reduce the efficiency
of industrial and municipal water treatment, impair beauty,
reduce or restrict resort trade, lower waterfront property
values, cause skin rashes to man during water contact, and serve
as a desired substrate and breeding ground for flies.
Phosphorus in the elemental form is particularly toxic, and
subject to bioaccumulation in much the same way as mercury.
Colloidal elemental phosphorus will poison marine fish (causing
skin tissue breakdown and discoloration). Also, ohosphorus is
capable of being concentrated and will accumulate in organs and
soft tissues. Experiments have shown that marine fish will
concentrate phosphorus from water containing as little as 1 ug/1.
SULFATES AND S13LFITES
Sulfites are oxidized to sulfates in streams, exerting a chemical
oxygen demand on the streams.
Sulfates are not particularly harmful, but are a major consti-
tuent of the total dissolved solids in waste waters from this
industry (and are discussed separately as such).
FLUORIDES
As the most reactive non-metal, fluorine is never found free in
nature. It is a constituent of fluorite or fluorspar (calcium
fluoride) in sedimentary rocks and of cryolite (sodium aluminum
fluoride) in igneous rocks. Owing to their origin only in
certain types of rocks and only in a few regions, fluorides in
high concentrations are not a common constituent of natural
surface waters, but they may occur in detrimental concentrations
in ground waters.
Fluorides are used as insecticides, for disinfecting brewery
apparatus, as a flux in the manufacture of steel, for preserving
wood and mucilages, for the manufacture of glass and enamels, in
chemical industries, for water treatment, and for other uses.
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Fluorides in sufficient quantity are toxic to humans, with doses
of 250 to 450 mg giving severe symptoms or causing death.
There are numerous articles describing the effects of fluoride-
bearing waters on dental enamel of children; these studies lead
to the generalization that water containing less than 0.9 to 1.0
mg/1 of fluoride will seldom cause mottled enamel in children,
and for adults, concentrations less than 3 or 4 mg/1 are not.
likely to cause endemic cumulative fluorosis and skeletal
effects. Abundant literature is also available describing the
advantages of maintaining 0.8 to 1.5 mg/1 of fluoride ion in
drinking water to aid in the reduction of dental decay,
especially among children.
Chronic fluoride poisoning of livestock has been observed in
areas where water contained 10 to 15 mg/1 fluoride.
Concentrations of 30 - 50 mg/1 of fluoride in the total ration of
dairy cows is considered the upper safe limit. Fluoride from
waters apparently does not accumulate in soft tissue to a
significant degree and it is transferred to a very small extent
into the milk and to a somewhat greater degree into eggs. Data
for fresh water indicate that fluorides are toxic to fish at
concentrations higher than 1.5 mg/1.
CHLORIDE
Dissolved chlorides are a major constituent of the total diss-
olved solids in waste waters from this industry (and are dis-
cussed separately as such).
Sodium and calcium chlorides are found naturally in unpolluted
waters, but are harmful to fish in high concentrations.
The natural salinity of river water in the Chesapeake Estuary is
9.5 to 11.0 mg/1 of chloride; and the natural salinity of ocean
water is 7,000 to 10,300 mg/1 of chloride.
DISSOLVED SOLIDS
In natural waters the dissolved solids consist mainly of
carbonates, chlorides, sulfates, phosphates, and possibly
titrates of calcium, magnesium, sodium, and potassium, with
-races of iron, manganese and other substances.
any communities in the United states and in other countries use
ater supplies containing 2000 to 4000 mg/1 of dissolved salts,
hen no better water is available. such waters are not
-alatable, may not quench thirst, and may have a laxative action
on new users. Waters containing more than 4000 mg/1 of total
salts are generally considered unfit for human use, although in
hot climates such higher salt concentrations can be tolerated
whereas they could not be in temperate climates. Waters
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containing 5000 mg/1 or more are reported to be bitter and act as
bladder and intestinal irritants. It is generally agreed that
the salt concentration of good, palatable water should not exceed
500 mg/1.
Limiting concentrations of dissolved solids for fresh water fish
may range from 5,000 to 10,000 mg/1, according to species and
prior acclimatization. Some fish are adapted to living in more
saline waters, and a few species of fresh water forms have been
found in natural waters with a salt concentration of 15,000 to
20,000 mg/1. Fish can slowly become acclimatized to higher
salinities, but fish in waters of low salinity cannot survive
sudden exposure to high salinities, such as those resulting from
discharges of oil well brines. Dissolved solids may influence
the toxicity of heavy metals and organic compounds to fish and
other aquatic life, primarily because of the antagonistic effect
of hardness on metals.
Waters with total dissolved solids over 500 mg/1 have decreasing
utility as irrigation water. At 5,000 mg/1 water has little or
no value for irrigation.
Dissolved solids in industrial waters can cause foaming in
boilers and cause interference with cleaness, color, or taste of
many finished products. High contents of dissolved solids also
tend to accelerate corrosion.
Specific conductance is a measure of the capacity of water to
convey an electric current. This property is related to the
total concentration of ionized substances in water and water
temperature. This property is frequently used in a substitute
method of quickly estimating the dissolved soldids concentration.
fig, ACIDITY AND ALKALINITY
Acidity is produced by substances that yield hydrogen ions on
hydrolysis and alkalinity is produced by substances that yield
hydroxyl ions. The terms "total acidity" and "total alkalinity"
are often used to express the buffering capacity of a solution.
Acidity in natural waters is caused by carbon dioxide, mineral
acids, weakly dissociated acids, and the salts of strong acids
and weak bases. Alkalinity is caused by strong bases and the
salts of strong alkalies and weak acids.
The term pH is a logarithmic expression of the concentration of
hydrogen ions. At a pH of 7, the hydrogen and hydroxyl ion
concentrations are essentially equal and the water is neutral.
Lower pH values indicate acidity while higher values indicate
alkalinity. The relationship between pH and acidity or
alkalinity is not necessarily linear or direct.
Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing fixtures
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and can thus add such constituents to drinking water as iron,
copper, zinc, cadmium and lead. The hydrogen ion concentration
can affect the taste of the water. At a low pH water tastes
sour. The bactericidal effect of chlorine is weakened as the pH
increases, and it is advantageous to keep the pH close to 7.
This fact is very significant for providing safe drinking water.
Extremes of pH or rapid pH changes can exert stress or kill
aquatic life outright. Dead fish, associated algal blooms, and
foul stenches are esthetic liabilities to any waterway. Even
moderate changes from "acceptable" criteria limits of pH are
deleterious to some species. The relative toxicity to aquatic
life of many materials is increased by changes in the water pH.
Metalocyanide complexes can increase a thousandfold in toxicity
with a drop of 1.5 pH units. The availability of many nutrient
substances varies with the alkalinity and acidity. Ammonia is
more lethal with a higher pH.
The lacrimal fluid of the human eye has a pH of approximately
7.0, and a deviation of 0.1 pH unit from the norm may result in
eye irritation for the swimmer. Enough irritation will cause
severe pain.
TEMPERATURE
Temperature is one of the most important and influential water
quality characteristics. Temperature determines those species
that may be present; it activates the hatching of young,
regulates their activity, and stimulates or suppresses their
growth and development; it attracts, and may kill when the water
becomes too hot or becomes chilled too suddenly. Colder water
generally suppresses development; warmer water generally
accelerates activity and may be a primary cause of aquatic plant
nuisances when other environmental factors are suitable.
Temperature is a prime regulator of natural processes within the
water environment. It governs physiological functions in
organisms and, acting directly or indirectly in combination with
other water quality constituents, it affects aquatic life with
each change. These effects include chemical reaction rates,
enzymatic functions, molecular movements, and molecular exchanges
between membranes within and between the physiological systems
and the organs of an animal.
Chemical reaction rates vary with temperature and generally
increase as the temperature is increased. The solubility of
gases in water varies with temperature. Dissolved oxygen is
decreased by the decay or decomposition of dissolved organic
substances and the decay rate increases as the temperature of the
water increases, reaching a maximum at about 30°C (86°F). The
temperature of stream water, even during summer, is below the
optimum for pollution-associated bacteria. Increasing the water
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temperature increases the bacterial multiplication rate when the
environment is favorable and the food supply is abundant.
Reproduction cycles may be changed significantly by increased
temperature because this function takes place under restricted
temperature ranges. Spawning may not occur at all because
temperatures are too high. Thus, a fish population may exist in
a heated area only by continued immigration. Disregarding the
decreased reproductive potential, water temperatures need not
reach lethal levels to destroy a species. Temperatures that
favor competitors, predators, parasites, and disease can destroy
a species at levels far below those that are lethal.
Fish food organisms are altered severely when temperatures
approach or exceed 90°F. Predominant algal species change,
primary production is decreased, and bottom associated organisms
may be depleted or altered drastically in numbers and
distribution. Increased water temperatures may cause aquatic
plant nuisances when other environmental factors are favorable.
Synergistic actions of pollutants are more severe at higher water
temperatures. Given amounts of domestic sewage, refinery wastes,
oils, tars, insecticides, detergents, and fertilizers more
rapidly deplete oxygen in water at higher temperatures, and the
respective toxicities are likewise increased.
When water temperatures increase, the predominant algal species
may change from diatoms to green algae, and finally at high
temperatures to blue-green algae, because of species temperature
preferentials. Blue-green algae can cause serious odor problems.
The number and distribution of benthic organisms decrease as
water temperatures increase above 90°F, which is close to the
tolerance limit for the population. This occurrence could
seriously affect certain fish that depend on benthinc organisms
as a food source.
The cost of fish being attracted to heated water in winter months
may be considerable, due to fish mortalities that may result when
the fish return to the cooler water.
Rising temperatures stimulate the decomposition of sludge,
formation of sludge gas, multiplication of saprophytic bacteria
and fungi (particularly in the presence of organic wastes), and
the consumption of oxygen by putrefactive processes, thus
affecting the esthetic value of a watercourse.
In general, marine water temperatures do not change as rapidly or
range as widely as those of fresh waters. Marine and estuarine
fishes, therefore, are less tolerant of temperature variation.
Although this limited tolerance is greater in estuarine than in
open water marine species, temperature changes are more important
to those fishes in estuaries and bays than to those in open
marine areas, because of the nursery and replenishment functions
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of the estuary that can be adversely affected by extreme
temperature changes.
ARSENIC
Arsenic is found to a small extent in nature in the elemental
form. It occurs mostly in the form of arsenites of metals or as
pyrites.
Arsenic is normally present in seawater at concentrations of 2 to
3 ug/1 and tends to be accumulated by oysters and other
shellfish. Concentrations of 100 mg/kg have been reported in
certain shellfish. Arsenic is a cumulative poison with long-term
chronic effects on both aquatic organisms and mammalian species,
and a succession of small doses may add up to a final lethal
dose. It is moderately toxic to plants and highly toxic to
animals especially as AsH3.
Arsenic trioxide, which also is exceedingly toxic, was studied in
concentrations of 1.96 to 40 mg/1 and found to be harmful in that
range to fish and other aquatic life. Work by the Washington
Department of Fisheries on pink salmon has shown that a level of
5.3 mg/1 of As.203 for 8 days was extremely harmful to this
species; on musselsT a level of 16 mg/1 was lethal in 3 to 16
days.
Severe human poisoning can result from 100 mg concentrations, and
130 mg has proved fatal. Arsenic can accumulate in the body
faster than it is excreted and can build to toxic levels from
small amounts taken periodically through lung and intestinal
walls from the air, water and food.
Arsenic is a normal constituent of most soils, with
concentrations ranging up to 500 mg/kg. Although very low
concentrations of arsenates may actually stimulate plant growth,
the presence of excessive soluble arsenic in irrigation waters
will reduce the yield of crops, the main effect appearing to be
the destruction of chlorophyll in the foliage. Plants grown in
water containing one mg/1 of arsenic trioxides showed a
blackening of the vascular bundles in the leaves. Beans and
cucumbers are very sensitive, while turnips, cereals, and grasses
;i:e relatively resistant. Old orchard soils in Washington that
ontained U to 12 mg/kg of arsenic trioxide in the top soil were
3und to have become unproductive.
VANADIUM
Metallic vanadium does not occur free in nature, but minerals
containing vanadium are widespread. Vanadium is found in many
soils and occurs in vegetation grown in them. Vanadium adversely
effects some plants in concentrations as low as 10 mg/1.
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Vanadium as calcium vanadate can inhibit the growth of chicks
and in combination with selenium increases mortality in ratS'
vanadium appears to inhibit the synthesis of cholesterSl and
accelerate its catabolism in rabbits. cnoxesreroi and
Vanadium causes death to cccur in fish at low concentrations.
The amount needed for lethality depends on the alkalinity of the
water and the specific vanadium compound present. The common
bluegill can be killed by about 6 ppm in soft water and 55 ppm in
hard water when the vanadium is expressed as vanadryl sulfate.
Other fish are similarly affected.
Specific conductance is a measure of the capacity of water to
convey an electric current. This property is related to the
total concentration of ionized substances in water and water
temperature. This property is frequently used as a substitute
method of quickly estimating the dissolved solids concentration.
CADMIUM
Cadmium in drinking water supplies is extremely hazardous to
humans, and conventional treatment as practiced in the United
States does not remove it. Cadmium is cumulative in the liver,
kidney, pancreas, and thyroid of humans and other animals. A
severe bone and kidney syndrome in Japan has been associated with
the ingestion of as little as 600 ug/day of cadmium.
Cadmium is an extremely dangerous cumulative toxicant, causing
insidious progressive chronic poisoning in mammals, fish, and
probably other animals because the metal is not excreted.
Cadmium could form organic compounds which might lead to
mutagenic or teratogenic effects. Cadmium is known to have
marked acute and chronic effects on aquatic organisms also.
Cadmium acts synergistically with other metals. Copper and zinc
substantially increase its toxicity. Cadmium is concentrated by
marine organisms, particularly molluscs, which accumulate cadmium
in calcareous tissues and in the viscera. A concentration factor
of 1000 for cadmium in fish muscle has been reported, as have
concentration factors of 3000 in marine plants, and up to 29,600
in certain marine animals. The eggs and larvae of fish are
apparently more sensitive than adult fish to poisoning by
cadmium, and crustaceans appear to be more sensitive than fish
eggs and larvae.
RADIOACTIVITY
Ionizing radiation, when absorbed in living tissue in quantities
substantially above that of natural background levels, is
recognized as injurious. It is necessary, therefore, to prevent
excessive levels of radiation from reaching any living organism:
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humans, fishes, and invertebrates. Beyond the obvious fact that
including they emit ionizing radiation, radioactive wastes are
similar in many respects to other chemical wastes. Man's senses
cannot detect radiation unless it is present in massive amounts.
Plants and animals, to be of any significance in the cycling of
radionuclides in the aquatic environment, must accumulate the
radionuclide, retain it, be eaten by another organism, and be
digestible. However, even if an organism accumulates and retains
a radionuclide and is not eaten before it dies, the radionuclide
will enter the "biological cycle" through organisms that
decompose the dead organic material into its elemental
components. Plants and animals that become radioactive in this
biological cycle can thus pose a health hazard when eaten by man.
Aquatic life may receive radiation from radionuclides present in
the water and substrate and also from radionuclides that may
accumulate within their tissues. Humans can acquire
radionuclides through many different pathways. Among the most
important are through drinking contaminated water and eating fish
and shellfish that have concentrated nuclides from the water.
Where fish or other fresh or marine products that have
accumulated radioactive materials are used as food by humans, the
concentrations of the nuclides in the water must be further
restricted, to provide assurance that the total intake of radio-
nuclides from all sources will not exceed the recommended levels.
In order to prevent unacceptable doses of radiation from reaching
humans, fish, and other important organisms, the concentrations
of radionuclides in water, both fresh and marine, must be
restricted.
CONCLUSION
In view of the data presented above, it is judged that all of the
mentioned waste constituents generated in the phosphate industry
should be identified as pollution parameters as defined in the
Federal water Pollution Control Act Amendments of 1972.
In the paragraphs above, the harmful characteristics are given of
all the parameters that are encountered in the phosphate
•nanufacturing point source category. Table 11 summarizes the
parameters found for each chemical.
Uthough many parameters appear in the waste streams from these
plants, only those primary parameters signified by "x" need be
jsed to set effluent standards.
The remaining parameters signified by zeros are adequately
treated if the primary parameters are so treated.
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Chemical
TABLE 11
WASTE WATER CONSTITUENTS OF PHOSPHATE CATEGORY
Parameter
TSS
SO,
POo
F
SiF6
Cl
IDS
low
PH
Heat
As
V, Cd,
Ra, U
P4 & Fe2P
H3POA
P2°5
P2S5
PC13
POC13
Na5P3010
CaHP04 (feed grade)
CaHPO^ (food grade)
X
X
X
X
0
X
0
0
0
X
X
0
X
0
0
0
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
X
X
0
0
0
0
0
0
0
0
0
0
0
0
X
0
0
0
0
0
0
0
0
I
0
0
0
X
0
0
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SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
INTRODUCTION
Section V of this report quantitatively discussed the specific
water uses in the phosphate industry and the raw wastes from this
industry before control and/or treatment of these wastes.
Section VI identified the constituents of the raw wastes which
are classified as pollutants. Table 11 summarizes the pollutant
constituents found as raw wastes in each of the three segments of
the industry.
Two major observations may be made from table 11:
1. classical sanitary engineering practices that treat effluents
containing organic material or that are aimed at reducing
biological oxygen demand are inapplicable to the phosphate
manufacturing industry, where such pollutant constituents are
usually very low and not a significant factor. Hence, control
and treatment of the wastes in this industry are of the chemical
and chemical engineering variety, and include neutralization, pH
control, precipitation, ionic reactions, filtration,
centrifugation, ion exchange, demineralization, evaporation and
drying.
2. A limited number of pollutant constituents characterizes the
entire industry, crossing the lines between segments of the
industry. Hence, the control and treatment techniques should be
similar throughout the industry.
In this section of the report, the control and treatment tech-
nology is discussed in considerable detail. Much of this dis-
cussion is based on observed actual abatement practice in the
industry and the accomplishments of independently verified
sampling data of plant effluents.
IN-rPROCESS CONTROLS
Control of the wastes includes in-process abatement measures,
monitoring techniques, safety practices, housekeeping, contain-
ment provisions and segregation practices.
Segregation of Water Streams
Probably the most important waste control technique, particularly
for subsequent treatment feasibility and economics, is
segregation.
Incoming pure water picks up contaminants from various uses and
sources including:
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1. non-contact cooling water
2. contact cooling water
3. process water
4. washings, leaks and spills
5. incoming water treatments
6. cooling tower blowdowns
7. boiler blowdowns
If wastes from these sources are segregated logically, their
treatment and disposal may sometimes be eliminated entirely
through use in other processes or recycle. In many instances,
the treatment costs, complexity and energy requirements may be
significantly reduced. Unfortunately, it is a common practice
today to blend small, heavily contaminated streams with large
non-contaminated streams such as cooling water effluents. Once
this has been allowed to happen, treatment costs, energy
requirements for these treatments, and the efficient use of water
resources have all been compromised.
In general, plant effluents can be segregated into:
1. Non-contaminated Cooling Water, Except for leaks, non-
contact water has no waste pickup. It is usually high volume.
2. Process Water. Usually contaminated but often small volume.
3. Auxiliary Streams. Ion exchange regenerants, cooling tower
blowdowns, boiler blowdowns, leaks, washings - low volume but
often highly contaminated.
Although situations vary, the basic segregation principle is
don't mix large uncontaminated cooling water streams with a
smaller contaminated process and auxiliary streams before full
treatment and/or disposal. It is almost always easier and more
economical to treat and dispose of the small volumes of waste
effluents - capital costs, energy requirements, and operating
costs are all lower.
In the phosphorus chemicals industry, many plants have accom-
plished the desired segregation of water streams, often by a
painstaking rerouting of sewer lines which have existed for many
years. Among these plants which are notable in this respect are
Plants 003, 037, 042, 075, and 182.
Recycle of Scrubber water
The widespread use of water for scrubbing of tail gases in this
industry has unfortunately led to many examples where the use of
once-through scrubber water is the method of operation. However,
there are several plants notable in this respect which recycle
scrubber water from a sump, thus satisfying the scrubber water
flow rate demands (on the basis of mass transfer considerations)
while retaining control of water usage. These notable plants are
TVA (Muscle Shoals, Alabama), and Plants 003 and 182.
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Recycle of scrubber water permits the subsequent treatment of
much smaller quantities of waste water with much higher concen-
trations of polluting constituents. Both these attributes make
waste water treatment more economical, and in some cases, more
efficient, from a removal viewpoint.
Dry Dust Collection
A drastic reduction in the aqueous waste load may be made by
replacing wet scrubbing systems with baghouses, or alternatively,
by placing cyclone dust collectors upstream of wet scrubbers.
This approach is feasible because baghouses have recently been
improved in design to the point where operation and maintenance
costs are not excessive, where solids collection efficiences
exceed those of wet scrubbers, and where operating temperature
ranges have been extended with high-temperature media develop-
ment. Dry collected solids may be returned to the product
stream, provided that a separate collector is installed for each
product. This is a change in approach for the typical multi-
product phosphate plant, since conventional practice has been to
centralize the collection and treatment functions across product
lines. With dry separate collection, the product recovered may
significantly contribute to alleviating the operating cost of the
collectors.
Plants in this industry which are notable in this respect in
having at least some dry dust collection include Plants 003, 006,
042, 119, and 182.
Housekeeping and Containment
Containment and disposal requirements may be divided into several
categories:
1. minor product spills and leaks
2. major product spills and leaks
3. upsets and disposal failures
4. storm water runoff
5. pond failures
6. vessel and container cleanout
Minor Spills and Leaks
There are minor spills and leaks in all industrial chemical
manufacturing operations. Pump seals leak, hoses drip, equipment
is washed down, pipes and equipment leak, valves drip, tank leaks
occur, solids spill and so on. These losses are not going to be
eliminated. They can be minimized and contained. In some cases
the products are valuable; in other cases, personnel safety and
prevention of corrosion may be paramount.
Reduction techniques are mainly good housekeeping and attention
to sound engineering and maintenance practices. Pump seals or
types of pumps are changed. Valves are selected for minimizing
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drips. Pipe and equipment leaks are minimized by selection of
corrosion-resistant materials.
Containment techniques employ the use of drip pans under pumps,
valves, critical small tanks or equipment, and known leak and
drip areas such as loading or unloading stations. Solids can be
cleaned up or washed down. All of these minor leaks and spills
should then go to a containment system, catch basin, sump pump or
other area that collects and isolates all of them from other
water systems. They should go from this system to suitable
treatment facilities.
Of special importance in the phosphorus consuming sutcategory of
the industry is the containment of phossy water from phosphorus
transfer and storage operations. While displaced phossy water is
normally shipped back to the phosphorus-producing facility,
current practice in phosphorus storage tanks is to maintain a
water blanket over the phosphorus for safety reasons. Make-up
water is added resulting in the overflow of excess water.
This method of level control is unacceptable since it results in
the discharge of phossy water. One way to ensure zero discharge
is to install an auxiliary tank to collect phossy water overflows
from the phosphorus storage tank; this system can be closed-loop
by reusing this phossy water from the auxiliary tank as make-up
for the main phosphorus tank. This scheme preserves the positive
safety features of the existing level control practice and also
safeguards against inadvertent large discharges resulting from
leaky or misadjusted water make-up valves.
Major Product Spills and Leaks
These are catastrophic occurrences with major loss of product,
tank and pipe ruptures, open valves, explosions, fires, and
earthquakes.
No one can predict, plan for, or totally avoid these happenings,
but they are extremely rare. Probably the most common of these
rare occurrences is tank or valve failures. These can be handled
with adequate dikes able to contain the tank volume. All acid,
caustic, or toxic material tanks should be diked to provide this
protection. Other special precautions may be needed for
flammable or explosive substances. Plant 037 is a prime example
where product tanks and transfer pumps have been systematically
diked for containment of spills.
Upsets and Disposal Failures
In many processes there are short term upsets. These may occur
during startup or shutdown or during normal operation. The phos-
phorus consuming subcategory and the phosphate subcategory of
this industry may be more vulnerable to this type of upset since
so many of the processes are batch-type operations with much more
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direct operator control then the large-scale automated continuous
processes typically found in the chemical industry.
These upsets represent a small portion of overall production but
they nevertheless contribute to waste loads. The upset products
should be treated, separated, and largely recycled. In the event
that this can not be done, they must be disposed of.
One very special problem in the phosphorus consuming subcategory
is the inadvertent spill of elemental phosphorus into a plant
sewer line. Past practice has been to let it remain in the sewer
and ensure a continuous water flow to prevent fire. There has
been general reluctance to clean it out since phosphorus burns
when exposed to air. with this practice, of course, all water
flowing in that sewer from that time on becomes contaminated with
phosphorus.
Provisions can be made for collecting, segregating and bypassing
such phosphorus spills. One method is the installation of a trap
of sufficient volume just downstream of reaction vessels, with
appropriate installations and valving to enable the bypass of
that trap after a spill has occurred and the offline removal and
cleaning of the trap (with safe disposal of the phosphorus) .
Stormwater Runoff
The phosphates segment of this industry is characterized by the
handling, storing, conveying, sizing, packaging and shipping of
finely-divided solid products. Typically, a phosphate plant has
all the exterior surface of buildings, equipment and grounds
covered with dusts. An area of concern is the pickup of these
solids by stormwater either as suspended solids or as dissolved
solids. Of course, washing down of these dusts is not
acceptable; the dry solids must be collected. Where possible,
the solids may be returned to appropriate process streams. Where
purity requirements prohibit this return, adequate means for safe
disposal of solid wastes must be provided.
Plants 003, 042 and 182 are examples of plants which have posi-
tive continual cleanup programs for solids, which minimize
stormwater runoff. Most plants (with considerable credit to air
pollution abatement practices) have also minimized the quality of
airborne dusts.
The very practice of process water segregation discussed
previously has led to the direct discharge of stormwater without
treatment. Little is known from a quantitative standpoint about
the severity of this problem in the phosphates segment of the
industry, or to what extent containment and treatment of
stormwater is required. In the phosphorus manufacturing segment
of the industry, where large quantities of dusts are handled.
Plant 159 collects approximately 10 kg/kkg (20 Ib/ton) in a
settling pond for stormwater and non-contact cooling water.
83
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Pond Failures
Unlined ponds are the most common treatment facility used by the
industry. Failures of such ponds occur because they are unlined
and because they are improperly constructed for containment in
times of heavy rainfall.
Unlined ponds may give good effluent control if dug in impervious
clay areas or poor control if in porous, sandy soil. The porous
ponds will allow effluent to diffuse into the surrounding earth
and water streams. This may or may not be detrimental to the
area, but it is certainly poor waste control. Lined ponds are
the only answer in these circumstances.
Many ponds used today are large low-diked basins. In times of
heavy rainfall, much of the pond content is released into either
the surrounding countryside, or, more likely, the nearest body of
water. Again, whether this discharge is harmful or not depends
on the effluent and the surrounding area, but it does represent
poor effluent control.
Good effluent control may be gained by a number of methods, in-*
eluding:
1. Pond and diking should be designed to take the antici-
pated rainfall; smaller and deeper ponds should be used
where feasible.
2. Control ponds should be constructed so that drainage
from the surrounding area does not innundate the pond
and overwhelm it.
3. Substitution of smaller volume (and surfaced) treatment
tanks, coagulators, or clarifiers can reduce rainfall
influx and leakage problems.
Vessel and Container Cleanout
One common characteristic of the phosphorus consuming subcategory
of the industry is the planned accumulation of residues in re-
action vessels and stills, with infrequent shutdowns to clean and
remove these residues. In many cases, the residues are washed
down with firehoses and the wastes discharged. This practice is
clearly unacceptable. One alternative is the diking of the area
with collection and treatment of the aqueous wastes, in
conjunction with an effort to minimize the quantity of washwater.
A similar situation exists with regard to the cleaning of re-
turnable containers (drums, tank trucks and tank cars) before re-
use. Since these are routine operations, procedures and
facilities must be made available for minimizing the quantity of
waste water and for the collection and treatment of this waste
water.
-------
Monitoring Techniques
since the chemical process industry is among the leaders in
instrumentation practices and application of analytical tech-
niques to process monitoring and control, there is rarely any
problem in finding technology applicable to waste water analysis.
Acidity and alkalinity are detected by pH meters, often installed
in-line for continuous monitoring and control.
Dissolved solids may be estimated by conductivity measurements,
suspended solids and turbidity and specific ions by wet chemistry
and colorimetric measurements. Flow meters of numerous varieties
are available for measuring flow rates.
The pH meter is the most commonly used in-line monitoring
instrument. Spills, washdowns and other contributions become
quickly evident. Alarms set off by sudden pH changes alert the
operators and often lead to immediate plant shutdowns or
switching effluent to emergency ponds for neutralization and
disposal. Use of in-line pH meters will be given additional
coverage in the control and treatment sections for specific
chemicals.
Monitoring and control of harmful materials such as phosphorus
and arsenic is often so critical that batch techniques may be
used. Each batch can be analyzed before discharging. This
approach provides absolute control of all wastes passing through
the system. Unless the process is unusually critical, dissolved
solids are not monitored continuously. This follows from the
fact that most dissolved solids are rather inert. Chemical
analyses on grab or composite effluent samples are commonly used
to establish total dissolved solids, chlorides, sulfates, and
other low ion concentrations.
Summary
The preceding narrative described general treatment practices and
in-plant controls. The following discusses specific abatement
measures recommended for each subcategory.
85
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TREATMENT OF WASTE WATERS IN THE PHOSPHORUS SUBCATEGORY
Neutralization of Acidic Waste waters
Virtually every manufacturing process in the phosphate industry
results in a raw waste load of significant acidity. In some
cases, advantage is taken of the availability of alkaline waste
to at least partially neutralize the acid waste streams.
At phosphorus producing plants, some neutralization of acidic
calciner scrubber liquor is achieved by the alkaline slag or by
the slightly alkaline slag quench liquor (see Table 7). At TVA,
the slag is granulated by quenching with a high-velocity jet of
calciner scrubber liquor plus process cooling water. The
granulated slag (with its large surface area) effectively
neutralizes the acidic liquors. At plants not granulating slag
(Plants 028 and 181), the slightly alkaline slag quench liquors
are mixed with the highly acidic scrubber liquors for partial
neutralization'.
Except for this one case where granulated slag is available, lime
or limestone neutralization of acid waste streams is standard
practice in this industry as observed at Plants 003, 006, 028,
159, 181, and 182. The relative chemical costs reported by
Downing, Kunin and Polliot(28), listed in Table 12, show that
limestone or lime are far and away more economical than other
neutralizing materials. Limestone is the lower cost material
(approximately $ll/kkg ($10/ton)) but suffers the disadvantages
of slower reaction and lower obtainable pH than lime. Lime costs
approximately $22/kkg ($20/ton).
With the exception of hydrochloric acid from PC13 and POC13
manufacturing facilities, every acid waste in the phosphorus
chemicals industry forms insoluble or slightly soluble calcium
salts when treated with lime:
Acid Caj.ci.um Salt Solubility^rng/l
H3P04 Ca(H2P04)2.H20, MCP 18,000
11 CaHP04.2H20,~DCP 200
" Ca3 (P04)2~ TCP 25
HF, H2SiP6 CaF2 ~ 16
H2Si03 Caslo3 95
H2S04 CaSO<*72H20 2,410
H2S03 CaS03.2H£0 43
H3P03 2 CaHP03.3H20 (Slightly Soluble)
*Between 17°C and 30°C.
It is readily apparent that lime treatment (with excess lime) not
only neutralizes acidic waste waters from the phosphate
manufacturing industry, but also demineralizes most waste waters
by precipitating calcium salts. This then produces a solid waste
which may be disposed of by landfilling.
86
-------
TAfil.F 12 Relative Chemical Costs for Neutralizing Acid Wastes
(28)
Source: Downing, Kunin and Polliot
NI.UlWI7.lNr, MATERIAL
Lump 1 linos tone, high Ca
Lump limestone, dolomitic
Pulv. limestone, high Ca
Pulv. limestone, dolomitic
Hydrated lime, high Ca
Hydrated lime, dolomitic
Pebble lime, high Ca
Pebble lime, dolomitic
Pulv. quicklime, high Ca
Pulv. quicklime, dolomitic
Sodium bicarbonate '
Soda ash
Caustic soda (50%)
Ammonia (anhyd.)
Magnesium oxide
Relative
Cost per
Pound
Alkali*
1.16
1.00
1.59
1.37
3.06
2.50
Relative Weight Alkali
Required Per Pound Acid
H2S04
110
94
no
94
79
65
2.07 TO
1 .87
2.18
1.97
20.65
13.08
9.96
5.90
3.90
54
60
54
173
119
164
35
42
HC1
148
127
148
127
107
87
80
73
80
73
233
160
220
47
56
H3P04
165
141
165
141
119
98
90
81
90
81
260
179
246
53
63
Relative Cost
Per Pound Acid
H2S04
128
94
175
129
242
162
124
101
131
106
3570
1560
1630
207
164
HC1
172
127
235
174
327
217
166
136
174
144
4810
2090
2190
277
218
H3P04
191
141
262
193
364
245
186
151
196
159
5360
2340
2450
313
246
Delivered cost including freight.
-------
The effectiveness of the control specified in the preceding
paragraphs is summarized in Table 13 for four plants (TVA, 181,
028 and 159). Data for plants 026 and 159 were taken from Tables
14 and 15, which include a complete analysis on the intake and
effluent waters.
Removal of An ions (Except Chlorides) From Acidic Wastes
Neutralization of acid waste waters with lime also precipitates
the calcium salts of all acid wastes in this industry (with the
exception of hydrochloric acid from PC13 and POC13 manufacture) .
This treatment is widespread throughout the phosphate
manufacturing industry, and represents a class of treatment
technology which has widespread validation and demonstration at
plant-scale installations.
Other technologies for removing dissolved solids (except chlor-
ides) are also presented in this section, with a somewhat lesser
degree of full-scale validation than lime treatment.
Treatment of Acidic Fluoride Wastes
Acidic fluoride wastes are generated by the phosphorus produc-
segment of the industry and by the defluorination of wet-process
acid in the manufacture of animal feed grade calcium phosphates.
These waste waters containing large quantities of hydrofluoric,
fluosilicic and silicic acids are neutralized with lime (which
breaks down H2SiF6 at high pH) to precipitate calcium fluoride
and gelatinous hydrated silica. Lime treatment is standard
operating technology at Plants 128, 159, 181 and 182.
Like lime treatment of phosphoric acid, lime treatment of acidic
fluoride wastes is enhanced by the decreased solubility of CaF£
at high pH:
CaF2(s) - >ca*« * 2F - > Ca*« * 20H * 2HF
The equilibrium is driven to the far left by the addition of
excess lime. The theoretical solubility of CaFg may be calcined
in much the same manner as outlined for Ca5(POU)2, using the
ion iz at ion constant of HF and the pure water solubility data for
CaFjJ.
There has been recent commercial interest in recovering the flu-
oride values in acidic waste waters. Two commercial processes
have been developed to manufacture hydrofluoric acid and one to
manufacture synthetic cryolite for the aluminum industry.
Removal of Suspended solids
The raw waste streams from the phosphorus producing segment and
from the phosphate subcategory of the industry contain
considerable quantities of suspended solids. Moreover, the
-------
TABLE
13
Summary of Control & Treatment Techniques at Phosphorus-
Producing Plants
(For Process Waters Other Than Phossy Water)
Raw Waste Loads (from
Sec. V)
Kg/Kkg
Ib /ton
Waste Discharged, Kg/Kkg:
TVA
Plant 181
Plant 028 (Net)
Plant 159 (Gross)
Waste Discharged, Ib /ton:
TVA
Plant 181
Plant 028 (Net)
Plant 159 (Gross)
Control & Treatment Effi-
ciency, Per Cent:
TVA
Plant 181
Plant 028
Plant 159
TSS
42.5
85
0
0
0.5
0.5
0
0
1
1
100
100
99
99
Total
Acidity
(Alkal-
inity)
54.5
109
0
0
1
(12)
0
0
3
(24)
100
100
TDS
-
0
0
4
22
0
0
9
45
100
100
Fluoride
53.5
107
0
0
0.1
0.04
0
0
0.2
0.07
100
100
99+
99+
Sulfate
in
222
0
0
2
3
0
0
4
7
100
100
98
97
Total
Phosphate
25
50
0
0
0.2
0.8
0
0
0.4
1.6
100
100
99
97
89
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TABLE 14 - Effluent from Plant 028 (Discharge No. 001)
Effluent Flowrate = 103-200 1/kkg (24,700 gal/ton)
Notes: 1. This Discharge is from Cooling Water and Dust Collector Water.
2. There is Zero Discharge of Phossy Hater and Calciner Scrubber
Water
Constituent
PH
Turbidity
Conductivity
TSS
TDS
CaCOc;
Alkalinity
Acidity
Chloride
Fii-.-oride
Sulfate
COD
Total
Hardness
Total
Phosphate
Ortho
Phosphate
Water & Wastewater Analysis
Units
-
FTU
JJHihOS
cm""
mg/1
mg/1
mg/1
mg/l
mg/1
mg/1
mg/1
S04
mg/1
mg/1
mg/1
P04
mg/1
P04
Intake
_
26
359
15
160
116
-
<0.1
0.19
6.4
2.0
116.7
1.2
1.2
Effluent
Plant
Data
7.3-9.5
32
4U3
15
202
110
-
4.1
1.14
13.8
53.5
129.7
2.4
2.4
Effluent
Ind.
Data
7.55
30
300
20
176
130
-
8
0.87
26
25
160
2.9
Net Effluent
Qty Kg/Kkg
Plant
Data
_
-
-
-
4
(-1)
-
0.4
0.10
0.8
5.3
1
0.12
0.12
Inde-
pendent
Data
_
-
-
0.5
2
1
-
0.8
0.07
2.1
Net Effluent
Qty Lb /ton
Plant
Data
_
-
-
0
9
(-D
-
0.9
0.20
1.5
2.4 10.6
4
0.18
3
0.25
0.25
Inde-
pendent
Data
—
-
-
1
3
3
-
1.6
0.14
4.1
4.8
8
0.35
90
-------
TABLE 15
Effluent from Plant 159
Notes: 1. There ts Zero Discharge of Phossy Water
2. These data are plant Data, Not Independently Verified
Effluent Flowrate * 36,100 I/kkg (8,640 gal/ton)
Constituent
PH
Turbidity
Conductivity
TSS
TDS
CaOh
Alkalinity
CaC03
Acidity
Chloride
Fluoride
Sulfate
COD
Total
Hardness
Total
phosphate
Ortho
phosphate
Water & Waste-
water Analysis
Units
-
FTU
ymhos
cm
mg/1
mg/1
mg/1
•mg/1
mg/1
mg/1
mg/1
S04
mg/1
mg/1
mg/1
P04
mg/1
P04
Treated
Intake
7.5
<1
966
11
617
358
•
50
0,84
91.5
«•
465
18.0
15.9
Effluent
8.0-8.5
11
898
15
620
323
-
53
1.01
90.0
6
468
22.4
19.3
Gross Effluent
Quantity
Kg/ kkg
_
-
-
0.54
22.4
11.7
-
1.9
0.04
3.2
-
16.9
0.8
0.7
Ib /ton
_
-
-
1.08
44.8
23.4
-
3.8
0.07
6.5
0.2
33.8
1.6
1.4
Net Effluent
Quantity
Kg/kkg
_
-
-
0.14
0.11
(-1.3)
-
0.11
0.0061
(-0.054)
0.22
0.11
0.16
0.12
Ib /ton
M
_
-
0.29
0.22
(-2,6)
-
0.22
0.0122
(-0.108)
0.43
0.22
0.32 -
0.24
91
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chemical treatment of acidic wastes described in the previous
section produced in many instances additional suspended solids.
To facilitate settling of suspended solids, large quiet settling
ponds and vessels are needed. Settling ponds are the foremost
industrial treatment for removing suspended solids. They are in
use at Plants 006, 028, 119, 159, 181 and 182. Removal of
suspended solids generates a solid waste effluent which must be
disposed of by landfilling.
The size and number of settling ponds differ widely depending on
the settling functions required. Waste streams with small
suspended solids loads and fast settling characteristics can be
cleared up in one or two small ponds; others with heavier
suspended solids loads and/or slower settling rates may require 5
to 10 large ponds. Most settling ponds are unlined, but the
technology exists for lined ponds.
Although not as widely used as settling ponds, tanks and vessels
are also employed for removal of suspended solids in the
phosphate manufacturing industry. They are in use at TVA (Muscle
Shoals, Alabama) and at Plants 003, 006, 028 and 159.
Commercially these units are listed as clarifiers or thickeners
depending on whether they are light or heavy duty. They also
have internal baffles, compartments, sweeps and other directing
and segregating mechanisms to provide more efficient performance
This feature plus the positive containment and control and re-
duced rainfall influence (smaller area compared to ponds) should
lead to increasing use of vessels and tanks in the future, espec-
ially where a plant is short of available land for settiino
ponds. y
Filtration equipment, such as plate-and-frame pressure filters
pressure or vacuum leaf filters, rotary vacuum filters, and
pressure tubular filters, has been widely used in the chemical
and waste treatment field for many years. The batch-type filters
find most use in polishing applications to completely remove
small quantities of suspended solids, since the labor-intensive
blowdown operation is dependent on cake volume. These filtra-
tions are common for collection of undesirable solid wastes, such
as arsenic sulfide from food grade phosphoric acid. Continuous
rotary vacuum filters find general applicability in dewatering
sludges with high concentrations of solids. Sand bed filtration
also finds increasingly widespread use.
Filtration is in use at Plants 006, 075 and 119. In general,
nitration is not economically attractive for huge quantities of
waste water (except for sand bed filtration). It is usually
preceded by a gravity thickening operation so that it treats the
thickened sludge which is only a small volumetric percentage of
the total waste water flow.
92
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Centrifugation, in use at Plant 003 and at the TVA installation,
is an alternative means for mechnical dewatering of relatively
low flow rate sludges, and has made major recent inroads into the
domestic waste water treatment field. The continuous solid-bowl
centrifuge, as its name implies, provides for continuous removal
of the cake, and its design reaches a compromise between solids
recovery and cake dryness. The basket solid-bowl centrifuge, on
•the other hand, discharges cake intermittently, and the
dewatering and cake-drying portions of the cycle may be
separately controlled. Perforated-bowl centrifuges are really
centrifugal filters. The solid-bowl machines offer the
significant advantage over filters that blinding of a medium is
removed as a problem area.
Dewatering of Lime-Precipitated Phosphates
Although (as previously discussed) lime can be used to effec-
tively precipitate phosphates from solution to reduce the con-
centration to 0.3 mg/1 or less (as PO4) , the lime-precipitated
phosphates do not dewater readily, but form a water-trapping gel
structure. After 24 hours of settling, clarified effluents still
may have 15 to 50 mg/1 of suspended solids. This condition can
be significantly improved by increasing the detention time to 7
days, but the suspended solids content may still be 5 mg/1 or
greater. In the phosphate manufacturing industry, settling ponds
with 7 days or longer detention times (equivalent to an overflow
rate of 420 1/day/m2 (10 gpd/ft2) at a nominal depth of 3 m (10
ft)) are used. It has been reported that the settling
characteristics are strongly dependent on the initial
concentration of phosphate ion. An initial concentration of
75rOOO mg/1 resulted in a compacted settled slurry density 3 to 5
times higher than if the initial concentration was 1,500 mg/1.
Where sufficient land area for large settling ponds is not avail-
able, average removal efficiencies of 80 to 95 percent have been
obtained with mechanically raked gravity thickeners. A typical
thickener design has a 2-hour detention time and an overflow rate
of 42,000 1/day/m2 (1,000 gpd/ft2).
Synthetic organic, water-soluble, high molecular weight poly-
electrolytes have achieved great success in flocculation and
clarification and in sludge conditioning before centrifugation or
filtration. A polymer dosage of 0.05 kg per kkg of dry sludge
solids (0.1 Ib/ton), or about 1 mg/1 of a 2 percent slurry, may
achieve 85 percent removal of suspended solids at a detention
time of 2 hours, with a 12 percent solids content in the
thickened sludge. If this thickened sludge were then vacuum
filtered, a cake of 30 percent solids could be obtained with a
solids content in the filtrate of 0.5 mg/1 of less.
The following may be a typical performance chart for an influent
sludge containing 100 liters of water:
93
-------
Volume of
Water, liters
Suspended Solids
Kg Percentage
Influent
Thickener Overflow
Thickener Underflow
Filter Cake
Filtrate
100
84
16
5.1
10.9
2.56
0.38
2.18
2.18
5 x 10~16
2.5%
0.45%
12*
30%
0.5%
The dewatered cake, containing 85 percent of the original solids,
may be landfilled. The filtrate, when combined with the thick-
ener overflow, would consist of 95 percent of the original water
quantity and would have a suspended solids concentration of 4,000
mg/1.
A much clearer effluent could be obtained, of course, if all of
the influent waste water were directly filtered. Such is the
practice at Plant 006, which achieves an average phosphate
removal efficiency of 95 percent.
Mechanical dewatering of lime precipitated phosphates by centri-
fugation was attempted, but it proved unsuccessful because the
highly thixotropic cake plugged the solids-removal screw.
Because an excess of lime is used in the precipitation of the
phosphates, the effluent from the ponds or from mechanical thick-
ening and dewatering would have a high pH, typically 10 to 11.
This effluent could be partially carbonated (with CO2) to reduce
the pH to 8.0 to 8.5 before discharge, with another" filtration
step to remove the calcium carbonate precipitate. Alternatively,
it has been shown that subsequent activated sludge treatment of
high pH waste water at municipal treatment plants lowers the pH
due to biologically-released CO2. from the oxidation of organic
material.
Treatment Alternatives
There were two treatment alternatives considered for this
subcategory. The first alternative is the treatment currently
employed by 90 percent of the industry. This includes complete
recycle of phossy water, evaporation of some process water, lime
treatment, and sedimentation of the remaining water prior to
discharge. The second alternative practiced by 10 percent of the
industry, involved 100 percent recycle of all process water.
-------
TREATMENT OF WASTE WATERS IN THE PHOSPHORUS CONSUMING SUBCATEGORY
Control and Treatment of Phossy water at Phosphorus Producing
Plants
Because of harmful effects of elemental phosphorus in small
concentrations in waste water, and because complete removal of
•the phosphorus from the water is not practical, it is a universal
practice at phosphorus-producing plants to reuse the phossy water
after treatment (which is required to remove other constituents
in the waste water which would otherwise build up to
concentration).
Barber(5) discusses several methods which have been tried
experimentally to remove elemental phosphorus from phossy water.
Among these methods were chlorination, which was tried more than
20 years ago and which was discarded at that time because
"accurate chlorinator control was found to be impractical." With
the development of chlorine analyzer-controllers for municipal
waste water treatment, however, it appears that chlorination
deserves another trial. Air oxidation was attempted, but the
reaction was far from complete, leaving 14 to 37 percent of the
original colloidal phosphorus unoxidized. Filtration of the
colloidal phosphorus was investigated but found impractical. As
a result of these discouraging results, the industry has adopted
the route of containment and re-use rather than treatment and
discharge.
At the TVA Muscle Shoals plant, a commercial flocculant, at a
concentration of 40 mg/lr is employed to settle both the phos-
phorus and the suspended solids. Using a clarifier, the system
removes 92 to 93 percent of both the phosphorus and the suspended
solids as phosphorus sludge underflow (which is only 2 percent of
-the waste water volume). The presence of suspended solids is
necessary for efficient removal by this method.
The underflow from the clarifier may be treated as other phos-
phorus muds or sludges are treated. The sludge may be gravity
•thickened and/or dewatered by centrifugation or filtration. The
sludge, thickened sludge, or sludge cake (with respectively lower
moisture contents) may then be heat-dried in an inert atmosphere
using the process byproduct carbon monoxide as fuel. Elemental
phosphorus (nominally 40 to 65 percent of the "solids" in the
sludge) are recovered. The remaining nonvolatile solids contain
no elemental phosphorus and can be safely disposed of or recycled
to the feed preparation section of the phosphorus manufacturing
plant.
The clarifier overflow, containing only 7 or 8 percent of the
original phosphorus and suspended solids, may then be recircu-
lated to the phosphorus condenser sump and to other areas where
water contacts phosphorus. However, because the phossy water
accumulates dissolved salts (mainly fluorides and phosphates, see
Table 7), about 6 percent of the clarified water must be bled off
95
-------
and discharged. In addition to suspended solids and dissolved
solids, this bleed contains 120 mg/1 of elemental phosphorus,
equivalent to 0.4 kg/kkg, or 0.08 pound per ton, of product.
At Plant 181, a different approach is taken towards phossy water
wastes. Very large lagoons not only reduce the concentration of
suspended solids in the phossy water, but also serve to slowly
oxidize much of the elemental phosphorus to phosphates.
Subsequent lime treatment of the lagoon overflow (after combining
with other waste water streams) precipitates not only the
phosphates but also the fluorides in the water, thereby reducing
the quantity of dissolved salts so that the water may be reused
without a bleed. At this plant, the waste streams may be com-
bined since all wastes are recycled without discharge.
A slightly different approach is taken at Plant 128. The phossy
water is combined in a closed treatment and recycle system with
calciner scrubber liquor. After settling of suspended solids and
partial oxidation of phosphorus in a pond, lime treatment is used
to precipitate dissolved phosphates and fluorides. Upon
subsequent settling, the clarified (but still phossy) water is
reused as calciner scrubbing water. Fresh make-up is used for
the phosphorus condenser. The key to this scheme, which results
in zero discharge of phossy water, is that the quantity of water
vaporized in the calciner scrubber (in cooling the calciner tail
gases) exceeds the quantity of phossy water in the raw waste
load, so that fresh water may be continuously added to the loop
without discharging any contaminated water.
Plant 159 achieves zero discharge of phossy water in a unique
system. The completely segregated raw waste phossy water is sent
to a clarifier in a manner similar to the TVA technique described
above. The clarifier underflow of phosphorus sludge is treated
in conventional ways, with complete return of the material to the
process. The overflow from the clarifier is not recycled (as is
the TVA practice, which requires a bleed discharge), but is sent
to an evaporation pond.
In the approaches used by Plants 028 and 159, some or all of the
phossy water is evaporated. This presents no hazard of elemental
phosphorus, since it is very rapidly oxidized to phosphate as
soon as the protective water is removed.
In summary, this study found three different ways that existing
plants are achieving zero discharge of phossy water.
Treatment of Arsenic-Rich Residues
Arsenic-rich solid residues accumulate from the purification of
phosphoric acid and of phosphorus pentasulfide. The common dis-
posal method is burial in a controlled area, as practiced at
Plants 075, 119, 1U7 and 192.
96
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The arsenic-rich liquid residue from the PC13 distillation is
more difficult to dispose of. At Plant 037 this residue is first
treated with trichloroethylene, in which PC13, is miscible but
A8C13 is not. The trichloroethylene is then water-washed to
remove the arsenic-free PC13 and the trichloroethylene is reused.
The AsCl3,-rich residue is then segregated and stored in drums for
final disposal in an environmentally safe manner.
Treatment of Phosphoric Acid Wastes
The standard treatment of these wastes is by neutralization and/
or precipitation with lime as discussed for the phosphorus
production subcategory. The final product of neutralization, in
an excess of lime and in a considerable excess of water, is
formed:
6 H3POU + 10 Ca(OH)2—>9 CaO.3 P2O5.Ca(OH)2 + 18 H2O
Although this material is very insoluble, the reaction does not
proceed to completion in practice unless a Ca/P mole ratio of at
least 1.9 is reached. Moreover, the reactivity of the lime in
precipitating the dissolved phosphate is strongly dependent on
the lime source and the slaking conditions. It has been found
that freshly slaked pebble quicklime can precipitate in excess of
97 percent of the phosphate, whereas commercial hydrated lime
(calcium hydroxide) or freshly slaked ground quicklime only
succeeded in a 73 to 80 percent precipitation efficiency under
the same conditions.
A large body of literature has been developed in the lime treat-
ment of domestic waste waters for phosphate removal. The study
performed by Black & Veatch for EPA(31) summarizes the efforts
that have been sufficiently demonstrated to be applied to current
municipal waste water treatment projects. It is pointed out that
•the average concentration in domestic raw waste water is about 10
mg/1 (expressed as elemental phosphorus) . The domestic sources
are about 1.6 kg (3.5 Ibs) per capita per year, one-third of
which are from human excretions and two-thirds from synthetic
detergents.
The existing practice achieves better than 90 percent removal of
the phosphates from domestic waste water, reducing the con-
centration (expressed as PO4) from 30 mg/1 to as low as 0.3 mg/1.
At. first glance, this seems to conflict with the fact that tri-
calcium phosphate (or hydroxylapatite) has a solubility of 25
mg/1 (equivalent to 15 mg/1 as PO4). However* in a large excess
of lime, the pH is sufficiently high (10 to 11) to reduce the
solubility of this salt of a strong base and weak acid. The
equilibrium
2H20
Ca*3(P04.)g(s) >3Ca « * POU-* >3Ca+» * 2OH- «• 2HPOU-*
is driven to the far left (reducing phosphate solubility) by the
addition of excess lime. The solubility of tricalcium phosphate
97
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may be theoretically calculated as a function of pH (or of Ca:P
ratio) using the ionization constants for H3_PO<», H2PO4-*, and
HPO4~2 in conjunction with a solubility product for tricalcium
phosphate (which may be calculated from solubility data in pure
water).
This phenomenon, substantiated by full-scale operating data as
reported by Black 6 Veatch(31), is summarized below:
Phosphate Concentration of
Filtered Effluent, mg/1
9.0 5.7
9.5 l.«
10.0 0.6
10.5 0.3
11.0 0.2
The literature is replete with details of technology to achieve
high removal efficiencies.(31-42) For example, thickened sludge
recirculation to the neutralization tank has been found to seed
the precinitation of calcium phosphate, resulting not only in
better removal of dissolved phosphates but also in the growth of
larger crystals for easier dewatering.
Although lime treatment of phosphates has been the predominant
route, ferric chloride and alum have also been extensively used.
Ferric salts are most effective in the 4 to 5 pH range and alum-
inum salts are most effective in the 5 to 6 pH range, as opposed
to the 10 to 11 range for lime. The mole ratio of Fe/P or Al/p
should be around 2.0, the same as the Ca/P ratio with lime treat-
ment.
The use of lanthanum salts has recently been demonstrated to more
effectively precipitate phosphates over a much wider pH range
than calcium, ferric ion, or aluminum. The drawback is cost; the
treatment system must recover and reuse the lanthanum.
Another process for phosphate removal is adsorption by activated
alumina with subsequent stripping with caustic acid, and then
regeneration of phosphate-free caustic by lime precipitation.
Ion exchange has also been investigated.
One interesting process for phosphate removal is borrowed from a
commercial process for HCl acidulation of phosphate rock.
Phosphoric acid is recovered by solvent extraction, using C4 and
C5_ primary alcohols such as n-butanol and isoamyl alcohol. The
chloride-free phosphoric acid is then extracted from the organic
phase by water washing, the solvent is recycled, and the pure
phosphoric acid may be concentrated by evaporation of water.
This treatment method appears attractive for application to the
food grade calcium phosphate waste streams. The suspended solids
may be dissolved by HCl addition, and solvent extraction may be
used to regenerate phosphoric acid for return to the process.
98
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Treatment of Acidic Sulfite, Sulfate, and Phosphate Wastes
These acids are components of the waste streams from the phos-
phorus-consuming subcategory of the industry; and sulfuric"acid
is also a constituent of the wastes from the phosphorus
production segment. The sulfurous and phosphorus acids may be
partially oxidized prior to treatment to sulfuric and phosphoric
acids.
The neutralization and precipitation of the slightly soluble cal-
cium salts is exactly comparable to the treatment of acidic phos-
phate and fluoride wastes. The solubilities of calcium sulfite
and of calcium phosphite are repressed by excess lime as in the
previously discussed cases, but the solubility of calcium sulfate
"(a salt of a strong base and a strong acid) is not affected by
pH.
Removal of Chlorides
Ion Exchange and Demineralization
Ion exchange and demineralizations are usually restricted in both
practice and costs to total dissolved solids levels of 1000 to
ttOOO mg/1 or less.
An ion exchange may be simply defined as an insoluble solid
electrolyte which undergoes exchange reactions with the ions in
solution. An exchanger is composed of three components: an inert
matrix, a polar group carrying a charge, and an exchangeable ion
carrying an opposite charge. The inert matrix is usually cross-
linked polymeric resin containing the needed polar groups.
There are two types of ion exchangers: cation and anion. Cation
exchangers contain a group such as sulfonic or carboxylic acid.
These can react with salts to give products such as the
following:
RS03H + Nad ?* RSO3Na + HCl
RC02H + NaCl ?* RCOjNa + HCl
The above reactions are reversible and can be regenerated with
acid.
Anion exchangers use basic group such as the amino family.
RNa30H + NaCl # RNa3Cl * NaOH
This is also a reversible reaction and can be regenerated with
alkalies. The combination of water treatment with both cation
and anion exchangers removes the dissolved solids and is known as
demineralization (or deionization). The quality of demineralized
water is excellent. Table 16 gives the level of total dissolved
solids that is achieved. Special ion exchange systems have been
developed for treating high dissolved solids content(more than
99
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TABLE 16. Water Quality Produced by
Various Ion Exchange Systems
Exchanger Setup
Strong acid cation
+ weak-base anion
Strong-acid cation
+ weak-base anion
+ strong-base anion
Strong-acid cation
* weak-base anion
* strong-acid cation
+ strong-base anion
Mixed bed (strong-
acid cation +
strong-base anion)
Mixed bed * first
or second setup
above
Similar setup as
immediately above
+ continuous re-
circulation
Residual
Silica,
mg/1
No silica
removal
0.01-0.1
0.01-0.1
0.01-0.1
0.05
0.01
Specific
Residual Resistance
Electrolytes, ohm-cm
mq/1 5> 25 C
3
3
0.15-1.5
0.5
0.1
0.5
500,000
100,000
1,000,000
1-2,000,000
3-12,000,000
18,000,000
100
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1000 mg/liter total dissolved solids), minimizing regenerant
chemicals costs.
Reverse Osmosis
The phenomenon of osmosis has its explanation in thermodynamic
equilibrium and free energy concepts. Essentially, when a semi-
permeable membrane separates a pure liquid and solution of dis-
solved material in the same liquid, there is a net migration of
the pure liquid to the solution, driven by the free energy diff-
erence between the two sides of the membrane. Equilibrium is
reached only when the liquids on each side of the membrane are of
the same composition, or sufficient additional pressure is
applied on the solution side of the membrane to counterbalance
the osmotic driving force. Application of additional pressure on
the solution side reverses the direction of osmotic flow through
the membrane and results in concentration of the solution and
migration of additional pure liquid to the pure liquid side.
This is reverse osmosis. It may be looked at as pressure
filtration through a molecular pore-sized filter.
The small pore size of the reverse osmosis membrane is both its
strength and its weakness. Its strength comes from the molecular
separations that it can achieve. Its weakness comes from the
criticalness it has to blinding, plugging, and chemical attack.
Acidity, suspended solids, precipitations, coatings, dirt, organ-
ics and other substances can make it inoperative. Membrane life
is critical and unknown in many mediums.
With these restrictions there is little wonder that its
industrial applications are few. Fortunately, the phosphorus
chemicals industry water purification needs are similar to those
of the areas where reverse osmosis has been shown to be
applicable — treatment of brackish water and low (500 mg/1 to
20,000 mg/1) dissolved solids removal. Organics are usually
absent, suspended solids are low and can be made low rather
easily, acidity is easily adjusted, and the dissolved solids are
similar to those in brackish water — sodium chlorides, sulfates
and their calcium counterparts.
Evaporation Ponds
plant 159 utilizes an evaporation pond for disposal of phossy
water from phosphorus manufacturing. They may also be reasonably
used for other waste water disposal where the waste water
quantities are not overwhelming.
The size of an evaporation pond depends on the climatic
differential between evaporation and rainfall:
101
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Evaporation-Rainfall
Differential Pond Area
0.6 m/yr (2 ft/yr) 0.060 ha/cu m/day (560 acres/MGD)
1.2 m/yr (U ft/yr) 0.030 ha/cu m/day (280 acres/MGD)
1.8 m/yr (6 ft/yr) 0.020 ha/cu m/day (190 acres/MGD)
Evaporation ponds may be either unlined or lined, and should be
diked. Use is often made of natural pits, valleys or ponds.
Conventional evaporation ponds are not, of course, among the
useful treatments in areas where the rainfall exceeds the evap-
oration. However, surface aerators (commonly used for aerated
lagoons in secondary treatment of organic wastes) can signifi-
cantly increase the evaporation from a pond by increasing the
water/air surface area.
Single-Effect and Multiple-Effect Evaporators
For the treatment of small waste streams, single-effect evapor-
ators are characterized by low equipment costs and by inherent
reliability, at the expense of high steam requirements. Conven-
tional multiple-effect evaporators, with 2 to 6 effects, have
somewhat higher capital costs, but require much less steam.
Evaporation is a technology, of course, that is aptly
demonstrated throughout the chemicals process industry (although
not extensively for the sole purpose of waste treatment), and as
such meets the requirements of being currently available.
Refrigerated Condensers for PC13 and POC13
In the standard processes for manufacturing PC13 and POC13, the
present industry practice is to use water cooled condensers to
reflux the reaction vapors and to collect the product. Because
the vapor pressure of PC13 is significantly high (boiling point
76°c (169°F)) at normal condensing temperatures, the raw waste
load in the tail-gas water scrubbers contains rather large quan-
tities of the hydrolysis products of PC13. The use of
refrigerated condensers in place of the water-cooled condensers,
or alternately, the use of cold traps downstream of the water-
cooled condensers, would drastically reduce the amount of PC13 in
the tail gas which subsequently becomes acid aqueous wastes:
PC13 Vapor Pressure,
Temperature* °C Temperature^ °F mm Hq (27)
-t»0 -UO 3
-20 -4 13
0 32 38
+20 68 99
+UO 104 235
102
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It is apparent that a condensing temperature below -20°C (-
would lower the PC1.3 vapor pressure by an order of magnitude over
normal condensing temperatures and would virtually double the
temperature driving force for heat transfer.
Refrigerated condensers are in current use (for POC13 manufacture
using air oxidation) at Plant 037.
Inert-Atmosphere Casting of P2S5
The present industry practice is to cast molten P2S5 product into
shipping containers or into conical forms. When molten P2S5 is
exposed to the atmosphere, it spontaneously ignites, forming P2O5
and SO2 which are subsequently water-scrubbed. ~"
There are various state-of-the-art techniques available for
casting either in an inert atmosphere or in vacuum, to eliminate
this source of raw aqueous waste.
Treatment Alternatives
The treatment alternatives considered for the manufacture of
phosphoric acid are additional treatment (the only discharges are
from leaks and spills) and no discharge of any process waste
water pollutants to navigable waters. The latter alternative
involves tightened housekeeping and maintenance construction of
dikes and dams around pumps, valves, and tanks; construction of
sumps and sump pumps; lime treatment of leaks and spills; and
landfill of the sludge. This is currently practiced by 10
percent of the industry.
There were two treatment alternatives considered for the
manufacture of phosphorus pentoxide: no additional treatment and
no process waste water discharge.
Three treatment alternatives were considered for the manufacture
of phosphorus pentasulfide. The first involves no additional
treatment. The second includes reduction of the volume of waste
water discharge by the recycle of scrubber water. The third
alternative includes no waste water discharge, lime treatment,
settling tanks, recycle of tank overflow back to the process, and
landfill of sludge.
Several treatment alternatives were considered for the
manufacture of phosphorus trichloride and phosphorus oxychloride.
The first alternative is no treatment. The second involves
reduction of waste water volume by recycle of scrubber water.
The third alternative includes lime treatment, settling tanks,
and landfilling of sludge. The fourth alternative involves no
discharge of process waste water pollutants to navigable waters.
103
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TREATMENT OF WASTE WATERS IN THE PHOSPHATE SUECATEGORY
Treatment of Specific Wastes
Sodium Tripolyphosphate Manufacture
As stated in Section V, two notable plants (042 and 119) achieve
no discharge of process waste waters. Airborne solids collected
in dust collectors from the spray dryer gaseous effluent stream
are added to the product. Scrubber water is used to form a
slurry with caustic in the initial neutralization step.
The manufacture of sodium tripolyphosphate is therefore a water
consuming process, requiring no waste water treatment.
Calcium Phosphates Manufacture
The amount of airborne solid wastes removed by wet scrubbers can
be minimized by preceding wet scrubbers with dry dust collection
equipment. Treatment of phosphoric acidr suspended solids, and
sludges resulting from wet scrubbing has been previously
described for the phosphorus production subcategory.
Wet phosphoric acid is frequently used for animal feed grade
phosphates. Fluosilicic, hydrofluoric and silicic acid wastes
will subsequently result from acid defluorination. Treatment of
these parameters has also been discussed previously for the
phosphorus production subcategory.
Treatment Alternatives
The only treatment alternative considered for the manufacture of
sodium tripolyphosphate is no discharge of process waste water
pollutants.
Two treatment alternatives were considered for the manufacture of
feed grade dicalcium phosphate. TJhe first, employed by at least
50 percent of the industry, involves in-process controls for
phosphate and lime dusts and phosphoric acid mists. The second
alternative includes the above plus lime treatment settling,
recycle of clarified water to the acid scrubbers and landfill of
the sludge.
Three treatment alternatives were considered for the manufacture
food grade dicalcium phosphate. No treatment is the first
alternative. in the second alternative baghouses replace wet
scrubbers with product recovery. Approximately 30 percent of the
industry is practicing this technology. In the third alternative
waste water is treated with lime, filtered, and recycled in the
process. The filter cake is landfilled. Approximately 10
percent of the industry is achieving no discharge of process
water pollutants by this technology.
104
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SECTION VIII
COSTS, ENERGY AND NON-WATER QUALITY ASPECTS
INTRODUCTION
The control and treatment technologies applicable to the raw
wastes of the phosphate manufacturing industry were discussed in
Section VII of this report. In this Section, each of these
technologies is reviewed from the following standpoints:
* The cost of applying the technology,
* The energy demands of the technology.
* The impact of the technology on air quality, solid
waste management, noise and radiation.
* The recovery and subsequent use of process materials
from raw waste streams, as a result of applying the
technology.
A representative, hypothetical plant for each chemical produced
in the industry is synthesized. Cost-effectiveness data for the
plant for the various treatment alternatives (see table 17)
appear as table 18. The cost is in terms of both investment cost
and equivalent annual cost; and the effectiveness, in terms of
pollutant quantities, is compared to the raw waste load. The
discussion of costs and benefits in this Section, however, is
formulated to be more generally useful in evaluating the
economics for any particular plant within the industry. Costs
for a specific plant may be significantly influenced by the
following factors which cannot all be incorporated into a single
hypothetical plant:
The degree of freedom, which the personnel of each plant must
retain, to choose among the alternative control and treatment
technologies presented in Section VII, to choose from
technologies not presented in this report, and to choose any
combination or permutation of these technologies.
The cost tradeoffs, which are unique for each plant, between
in-process controls and end-of-process treatments, with
material recovery being an important parameter.
The real raw waste load for each plant, which may be app-
reciably different (in either direction) from the standard
raw waste loads as presented in Section V. In particular,
much greater plant-to-plant variability was observed with
respect to production-normalized raw waste water quantities
than with respect to production-ion-normalized raw quantities
of polluting constituents.
105
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TABLE 17
TREATMENT ALTERNATIVES
Subcategory
Phosphorus
Producing
Phosphorus
Consuming
Phosphate
Producing
Chemical
P4 (Fe2P)
K,P04
P2o5
P2S5
PCI
POC13
Na5P3°10
p • UDO *
\^orir Uf I
CaHPO^
Feed grade
Alternative
A
B
A
B
A
B
A
B
C
A
B
C
D
A
B
C
D
A
A
B
A
B
Description
Existing control complete recycle of phossy water. Evaporation of some other process water.
Lime treatment and sedimentation of remaining process water prior to discharge.
Piping, pumping, and controls for 100% recycle of process wastewaters.
No treatment. (Only wastewaters orglnate from leaks, spills, etc.)
Tighten housekeeping and maintenance. Dike and dam around pumps, valves,, tanks, etc.
Provide sumps and sump pumps. Treat with lime and landfill the sludge.
No treatment.
Line treatment, settling tank, recycle of tank overflow back to process, and landfill sludge.
No treatment.
Recycle scrubber water.
Lime treatment, settling tank, recycle tank overflow back to process, landfill sludge + B.
No treatment.
Recycle scrubber water.
L1me treatment, settling tank and landfill sludge + B.
Evaporation + B + C.
No treatment.
Recycle scrubber water.
L1me treatment, settling tank, and landfill sludge + B.
Evaporation + B +• C.
Dry dust collection already in existance at exemplary plant. May be economically
justified on the basis of product recovery.
In-process controls for phosphate and lime dusts and for phosphoric acid mists, including
dry dust collection and scrubber water recycle to process.
L1me treatment, settling pond, recycle of clarified water to acid scrubbers, and landfill
sludge. + A.
Replace wet scrubbers with baghouses.
Lime treatment, filtration of slurry, recycle of filtrate, and landfill of filter cake + A.
-------
TABLE IB
TREATMENT ALTERNATIVES
COST - EFFLUEHT QUALITY COMPARISON
Chenlcal Treatment * Industry Investment
Alternative Using $1,000
Alternative
Phoaphoru a gubcategory
P4 Rav Waste
11
90
10
-
500
Annual
Operating
Costs
$1,OOO
-
228.2
Cent Wastevater TSS IDS Acidity F SOA P04
Per Italta 1/Kkg Kg/Kkg Kg/Kkg Kg/Kkg Kg/Kkg Kg/Kkg Kg/KKg H3P04 A H3PO4 HjSOj HC1 HP, H2SIP6 PH
S/Kkg H3P03 H2,Si°3
B Ks/Kk« Kg/Kkz Ke/Kke KE/kkE KE/Kka
426.000 42 - 54 54 111 25
104,000 0.5 4 1.5 0.1 2 0. i
5.07 00 0 0 0 00
Phosphorus Contimint Subcategory
H^POj. Rav Uaate (A)
B
P2O5 Rav Uaste (A)
B
P2S5 Raw Waste
-------
There is a wide variation in the existing application of
effluent control technology. Some plants have more equipment
to install than others in order to meet the effluent
limitations guidelines. In addition physical characteristics
of each particular plant will affect treatment costs such as:
* Plant age, size, and degree of automation.
* Plant layout (i.e., can in-process controls
be physically installed between existing
units?).
* Plant distances and topography (i.e., what
are the installation and operating costs of
recycle technologies?) .
* Climatic factors (temperature and evaporation/
rainfall).
* Esthetic factors (i.e., is a settling pond
locally acceptable?).
* Land availability (primarily a factor in
applying settling pond and evaporation pond
technologies).
The degree to which a plant is integrated with other pro«*
duction departments would significantly affect the cost of
applying control and treatment technologies. Can waste
materials from one department be used in an adjoining
department (i.e., mutual neutralization of acid and alkaline
wastes)? Can common treatment facilities be built (tradeoff
between economies of scale vs. reversing the principle of
segregation of wastes)? Are the waste water sewers from
adjoining departments readily separable? The feasibility and
attractiveness of joint municipal/industrial waste water
treatment, which is a highly local evaluation to be made.
Increasingly, more examples of such dual treatment are being
reported.
The local solid waste management situation. The sludges from
applying waste water treatment technologies may be landfilled
at highly different costs, depending on the local
availability of disposal sites and the distances involved.
n appreciation of all of the above factors, the discussion of
osts in this section is formulated to be generally useful in
valuating the economics for any particular plant within the
ndustry.
Definition of Representative Plants
The sizes of the representative plants were chosen so that their
capacities were approximately the averages of the data presented
108
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in table 2. Although in many cases (especially in the phosphorus
consuming segment of the industry) more than one product is made
at. a given location, each product was addressed separately in
•this supplement. Cost savings due to combined treatment
facilities are a distinct probability. The effect in practice
would be to achieve the benefits at costs lower than those
presented in this analysis.
The particular assumptions in choosing representative plants
were:
1. phosphorus Manufacture—The representative plant has already
no discharge of phossy water (as much of the industry has). It
has, in addition, achieved a level of effluent reduction
commensurate with that of plant 028 (see Tables 13 and 1U), but
still discharges 25,000 gallons of treated process water per ton
into a receiving stream. Technology HA" of Table 17, therefore,
represents effluent reduction, with respect to the raw waste
load, already achieved by the representative plant, with no
additional costs required. The effluent from technology "A" is
suitable for process re-use, and technology "B" is the
implementation of this recycle. For the representative plant, it
was assumed that the return water system traversed 1,000 yards
back to the head end of the plant and had a difference in
elevation of 60 feet. it was also assumed that the
representative plant had no severe freezing problems.
2. Phosphoric Acid Manufacture—The representative plant had no
process water discharge (including phossy water), but had not yet
performed a systematic and thorough program for minimizing,
collecting, and treating minor phosphoric acid leaks and spills.
3. Manufacture of P1O5, P2Sj>, PC13, and POC13—The
representative plants for these chemicals^had not yet instituted
any control or treatment of acid waste waters, but have already
achieved zero discharge of phossy water. As a conservative
approach for PC13 and POC13 manufacture, it was assumed that
solar evaporation for technology "C" in Table 17 was not feasible
for climatic reasons so that mechanical evaporators were
necessary. It was also assumed that refrigerated condensers
proved less economical than larger evaporators.
The representative plants for P2O5, P2sj>, PC13, and POC13 are
assumed not to have sufficient land for settling ponds, so that
mechanically raked clarifiers are used.
U. Sodium Tripolyphosphate Manufacture—The representative plant
has either of two situations: (a) Dry dust collection with return
of solids and wet scrubber liquors to the process has already
been installed, resulting in zero discharge of process waste
waters. (b) The above controls have not been installed, but can
be economically justified on the basis of product recovery.
109
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For either of these two situations (which cover much of the
industry), no additional costs (attributable to effluent
reduction benefits) are required.
5. Feed Grade Dicalcium Phosphate Manufacture—For control of
phosphate and lime dusts and phosphoric acid mists, the
representative plant has no additional required costs
(attributable to effluent reduction benefits), for the same
reasons as listed above for sodium tripolyphosphate manufacture.
It is assumed, however, that the representative plant uses wet-
process phosphoric acid and that it performs defluorination of
all acid used (in practice, a good fraction of received acid may
already be defluorinated). It is further assumed that the
representative plants have sufficient land area for on-site
settling ponds.
6. Food-Grade Calcium Phosphate Manufacture—The representative
plant is assumed to have wet scrubbers for dust-laden vent
streams. Technology A of table 17 shows the replacement of wet
scrubbers with baghouses, but the cost is justified by product
recovery. It is assumed that at this representative plant the
elimination of wet scrubbers reduces the waste load by 50
percent.
current Selling Prices
Table 3 shows the current list prices of the chemicals within
this industry. These data are useful as a yardstick for measur-
ing the economic impact of achieving pollution control.
Capital Cost Basis
For these analyses, the capital investment costs have been
adjusted to 1971 dollars using the Chemical Engineering Plant
Cost Index (1957-59 = 100; 1971 = 132.2). The capital recovery
segment of the annual costs is based on a 5-year amortization
schedule, consistent with IRS regulations concerning pollution-
abatement equipment and facilities, and on an 8 percent interest
rate. The resulting annual capital recovery factor (principal
and interest) is 0.250U6.
"Taxes and Insurance" annual cost is estimated at 5 percent of
the investment cost. "Operating and Maintenance" annual cost
includes labor, supervision, lab support, etc., and is estimated
at 15 percent of the investment cost, exclusive of chemicals,
energy and power costs (which are calculated directly for each
appropriate case), Chemical costs are included in "Operating and
Maintenance," but power is listed separately. The cost of lime
for neutralization has been assumed at $20 per ton, and the cost
of steam for evaporation has been assumed as $0.70 per thousand
pounds (or $0.70 per million ETU).
110
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In-Process Controls
The cost of these controls are perhaps the most difficult to
generalize, since they are almost wholly dependent on the
existing equipment configuration in any particular plant.
Segregation of Waste Streams
First, a plant must be surveyed to pinpoint the sources of both
process water and non-contact cooling water. At one plant, there
were numerous points where process water entered a common sewer,
but there were relatively few cooling water sources. It was much
more economical to divert the cooling water to a new and separate
collection system than to adopt the reverse strategy. The
project costs for such a retrofit would be highly labor
intensive, especially since the construction must proceed without
unduly disrupting production schedules. Other than capital
recovery and associated annual costs, the annual costs would
consist of a small maintenance cost and no costs for operating
labor, materials or power.
There would be no effect of this project on energy demands, since
plant sewers are normally gravity flow. There would be no
adverse non-water quality impacts of this project.
Recycle of Scrubber Water
The capital costs would be to provide a surge tank, a recycle
pump, and associated piping. The surge tank need not be large; a
15-minute residence time should suffice. The power costs and
energy use of the pump would not greatly exceed the corresponding
values presently utilized to provide fresh scrubber water at
comparable flow rates. in any event they are small since
scrubber flow rates are small.
Dry Dust collection
Based on data furnished by the personnel of Plant 007, the
capital cost of high-temperature baghouses for this 91 kkg/day
(100 tons/day) plant was $350,000. The annual operating and
maintenance costs, other than capital recovery, taxes and in-
surance, is estimated at 6 percent of the capital cost. A credit
to the annual cost is the value of recovered material; the
quantity might be estimated as 2 to 5 percent of the production
rate, since baghouses recover virtually all dusts. The power
requirements for the fans and shakers are small, and are usually
comparable to the pump power requirements for the liquid
scrubbing systems they replace. Since the recovered dusts are
almost always utilized in the process, there is no adverse impact
on solid waste management.
Refrigerated Condensers
111
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The condensers are standard items, and in practice the existing
condensers may be used. The refrigeration supply is standard
equipment, and rather expensive in terms of capital costs. An
added cost would be the insulation of existing coolant lines and
of the condenser. The power requirement for the refrigeration
compressor could be moderately high. There would not be impact
on non-water quality aspects.
Inert-Atmosphere Casting for P2SS
This is a relatively expensive control technique, requiring major
revisions not only of the casting equipment but also of the basic
casting procedures. There would be some small power
requirements, either for inert-gas blowers or for vacuum pumps.
The annual cost of the inert gas (assuming it is not recycled)
must be estimated.
Housekeeping and containment
Like the previously-discussed project of water segregation,
housekeeping and containment capital costs are labor-intensive
and depend to a very large extent on the existing plant con-
figuration. A point of reference might be taken from the ex-
perience of one 360 kkg/day (UOO tons/day) plant which expended.
$160,000 for isolation and containment (trenches, sewers, pipe-
lines, sumps, catch basins, tanks, pumps, dikes and curbs). The
need to attend to many small sources of leaks and spills reduces
the economies of scale. The power requirements are minimal,
limited to small sump pumps. No adverse non-water quality
impacts arise from this control technique.
112
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TREATMENT OF SPECIFIC WASTE CONSTITUENTS
Neutralization of Acidic Waste Waters and Precipitation of
Calcium Salts
A general cost factor for neutralization is 1.3 to 5.3 cents per
cu m (5 to 20 cents/1,000 gallons). However, the cost for lime
is directly dependent not on the waste water quantity but on the
total acidity. The data of table 8, with a lime cost of $22/kkq
($20/ton), can be used to calculate this cost.
Neutralization tanks are usually small, with residence time
varying from 30 seconds to 30 minutes. The installed cost of
these tanks may be approximated by:
Capital Cost = $15,000 GPP 0.2
10,000
(Note: I/day * 3.785 x GPD)
The power requirements for mixing are rather nominal. Assuming
subsequent sedimentation or other dewatering operations, the
neutralization step alone does not have any adverse non-water
quality impacts.
Treatment of Arsenic-Rich Residues
The cost of this solvent is rather nominal because the quantities
of waste involved are only a very small fraction of the
production volume, and because the solvent (trichloroethylene) is
reused, despite the high unit cost which is more than 10 cents/cu
m (40 cents/1,000 gal). There is virtually no power requirement.
There is, however, a very substantial impact on solid waste
management, since the residues are extremely objectionable and
must be disposed of in special ways. The quantity involved is
0.05 kg of AsC13 per kkg of product PC1J. (0.1 Ib/ton).
Control and Treatment of Phossy Water
Control and treatment of phossy water is a universal practice at
phosphorus-producing plants. Although several different methods
were observed, every plant prevents the discharge of virtually
all elemental phosphorus. This technology is therefore so widely
applied that costs need not be estimated; the price has already
been paid. Similarly, a discussion of energy and of non-wate^
quality aspects would be academic.
Removal of Suspended Solids
Settling Ponds
Using a detention time of 7 days and a depth of 3m (10 ft), the
calculated overflow rate is 0.42 cu m/day/m« (10 qpd/ft») . This
is equivalent to 4,200 cu m/day/hectare (435,600 gpd/acre).
113
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The capital costs for small unlined ponds, with areas from 0.4 to
2 hectares (1 to 5 acres) can be estimated as:
Capital Cost = $50,000 x Acres - $8,000 x (Acres)2
(Note: Hectares = 0.405 x Acres)
Because diking is a large portion of pond costs, and because the
dike length increases much more slowly than pond area, larger
ponds are considerably cheaper per unit area. For large unlined
ponds of 40 to 1,000 hectares (100 to 2,400 acres), the capital
cost is $2,500 to $12r500 per hectare ($1,000 to $5,000 per
acre) .
For lined ponds, the additional installed capital cost for a 30-
mil PVC liner is $21,500 per hectare ($8,700 per acre). By using
the above overflow rate and the above pond costs per unit area, a
pond cost based on waste water flow may be calculated.
Settling ponds utilize no energy. The solids do, however, coll-
ect on the bottom and must either be periodically removed
(creating a solid waste disposal problem), or the filled pond may
be abandoned and replaced with a new one (creating a land use
problem).
Mechanically-Raked Clarifiers and Thickeners
A general cost for gravity thickening is 0 to 2.6 cents per cubic
meter (0 to 5 cents per 1,000 gallons).
The installed cost of mechanically-raked clarifiers and thick-
eners with capacities of 38 to 38,000 cu m/day (0.01 to 10 MGD)
can be estimated as:
Capital Cost = $95,000 (MGD)0.4
(Note: Cu m/day = 3,785 x MGD)
Where polymeric flocculants are used, the additional cost amounts
to $4 per kg of flocculant ($1.80/lb). The dosage rate is
nominally 0.05 kg/kkg of dry sludge solids (0.1 Ib/ton).
The power requirements are nominal, since the rake has a very
long period of revolution. Additional nominal power requirements
arise from sludge pumping and clarifier overflow pumping.
This treatment has (by definition) a solid waste impact, since
its function is the removal of suspended solids. The sludge from
thickeners may be 85 to 92 percent moisture. If the quantities
are small, this sludge may be directly transported to landfills.
Alternately, it may be dewatered on sand drying beds or
mechanically (filters or centrifuges) to 60-70 percent moisture
before landfilling. The quantity to be landfilled is therefore a
114
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very strong function of the degree of dewaterinq after
thickening.
Vacuum Filtration and Centrifugation
The costs of these two mechanical dewatering techniques are com-
petitive. A general cost for either is 0 to 2.6 cents per cubic
meter (0 to 5 cents per 1,000 gallons).
The installed capital costs for either vacuum filters or cen-
trifuges are as follows:
Capacity, MGD cu in/Day Installed Cost
0.01 38 $25,000
0.1 378 25,000
1 3785 200,000
10 37850 750,000
Polymeric flocculants are often used to condition the sludge
before dewatering. These costs were discussed in the previous
paragraph.
The power requirements for vacuum filtration are moderate; they
include the sludge pump, the flocculant pump, the rotating
conditioning tank, the vacuum filter drum drive, the sludge
agitator below the filter drum, the vacuum pump, the filtrate
pump and the cake conveyor belt. Centrifuges have much larger
power requirements, since the sludge must be accelerated to
hundreds or several thousands of G«s. At high speeds, the
windage losses (air friction) of centrifuges are considerable.
Large centrifuges may require 40 to 75 Kw (50 to 100 HP) of
power. Auxiliary power is also required for sludge pumping,
flocculant pumping, centrate pumping, the cake scraper, and the
cake conveyor belt.
Vacuum filters and centrifuges have a beneficial imoact on solid
waste management. Rather than landfilling 12 percent sludge,
these devices drastically reduce the solid waste quantity by
producing a 30 to 40 per-cent cake.
Centrifuges have a moderately adverse impact with regard to noise
pollution, since they run with a characteristic high speed whine
that is annoying to the human ear. Vacuum filtration is also
noisy.
Landfilling of Solid Wastes
The disposal costs for solid wastes are highly dependent on the
hauling distance. The landfill operations alone may cost $6 or
more per kkg (or per ton) for small operations and $2 to U per
kkg (or per ton) for larger operations.
115
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Several pertinent papers have recently been published on the
subject of solid waste management in the chemical
industry. (63,64)
Solid waste hauling and the material handling operations at
landfills are energy consuming operations. Landfilling of con-
tainerized soluble solids in plastic drums or sealed envelopes is
practicable but expensive. Blow-molded plastic drums, made from
scrap plastic (which is currently one of the major problems in
solid waste disposal), could be produced for $ll-$22/kkq ($10-
$20/ton) capacity at 227 kg (500 pounds) solids/drum and a rough
estimate of $2.50-35.00 cost/drum. A more economical method,
particularly for large volumes, would be sealed plastic
envelopes, 750 microns (30 mils) thick.
At $1.10/kg (502/lb) of film, low density polyethylene costs
about 10£ per 0.0929 square meter (1 square foot). Using the
film as trench liner in a 1.8 meters (6-foot) deep trench, 1.8
meters (6 feet) wide, the perimeter (allowing for overlap) would
be approximately 7.5 meters (25 feet). At a density of 1.6
grams/cc (100 pounds/cubic foot) for the solid, costs of plastic
sheet per metric ton would be $2.00 ($1.75/ton). With sealing,
the plastic envelope cost would be approximately $2.20/kkg
($2/ton) . With additional landfill costs of $2.20/kkg ($2/ton),
the total landfill disposal costs would be about $4.40/kkg
($4/ton).
The above figures for solubles disposal using plastic containers,
bags, or envelopes are only rough estimates. Also, the technol-
ogy would not be suitable for harmful solids or in situations
where leaching contamination is critical.
Removal of Chlorides
Demineralization and Reverse Osmosis
These treatments are costly, over 10 cents per cubic meter (40
cents per 1,000 gallons).
The installed capital costs can be calculated from:
a. Demineralization, Cap. Cost = $280,000 (MGD)0.75
b. Reverse Osmosis, Cap. Cost = $480,000 (MGD) 0.75
Hence, the capital costs for reverse osmosis are nearly double
those for demineralization.
The operating costs (not including capital recovery costs) are:
a. Demineralization, 20 cents/1,000 gal 3 1,000 mg/1 TDS
40 cents/1,000 gal 3 2,000 mq/1 TDS
b. Reverse Osmosis, 38 cents/1,000 gal 3 0.01 MGD
20 cents/1,000 gal 9 0.1 MGD
1U cents/1,000 gal 3 1 MGD
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Neither demineralization nor reverse osmosis requires a great
deal of power, and neither has significant non-water quality
impact.
Solar Evaporation Ponds
The installed costs of solar evaporation ponds (on the basis of
pond area) are essentially the same as the costs for settling
ponds presented earlier. The pond area depends in this case on
the climatic differential between evaporation and rainfall:
Evaporation-Rainfall
Differential
0.6 m/yr (2 ft/yr)
1.2 m/yr (4 ft/yr)
1.8 m/yr (6 ft/yr)
Pond Area
0.060 ha/cu m/day (560 acres/MGD)
0.030 ha/cu m/day (280 acres/MGD)
0.020 ha/cu m/day (190 acres/MGD)
The power requirements and non-water quality aspects of solar
evaporation ponds are the same as for settling ponds. Since the
residue in this case is soluble, extra disposal precautions must
be taken to prevent leaching into groundwaters.
Single-Effect and Multiple-Effect Evaporators
The installed capital and operating costs for single-effect evap-
orators and for a 6-effect evaporator (all stainless-steel con-
struction) are as follows:
Installed Capital Costs O & M Costs, S/lfOOO gal
Capacity. GPP 1 Effect 6 Effects 1 Effect 6 Effects
10,000
50,000
100,000
250,000
500,000
1,000,000
8,000
28,000
45,000
80,000
146,000
267,000
177,000
373,000
665,000
1,225,000
5.
5,
5.
5.
5.
64
51
45
39
36
5.33
1.30
1.22
1.18
1.14
(Note: Liters = 3.785 x Gallons)
The energy requirements for single-effect evaporators are 555 kg-
cal per kilogram of water evaporated (1,000 Btu/lb), while the 6-
effect evaporator requires 100 kg-cal per kilogram of water
evaporated (180 Btu/lb). The non-water quality aspects are the
same as for solar evaporation ponds.
NON-WATER QUALITY IMPACT
Air Pollution
The proposed guidelines are not expected to increase air
emissions. In fact, the cited technologies should decrease air
117
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emissions in some cases where dry air pollution equipment is
suggested to precede wet scrubbers. Volatilization of hazardous
substances, such as fluorine, from ponds is not expected to
present a problem since addition of lime will precipitate most
fluorides.
Solid Waste
Solid waste disposal will be the chief non-water quality area
impacted by the proposed guidelines. Neutralization of acidic
waste streams with lime or limestone will increase the amounts of
sludge, especially when soluble phosphates and sulfates are
precipitated. Installation of dry air pollution control
equipment will reduce the water content of wasted solids. In
addition, return of collected solids to the process may be
feasible. As stated in section VII, arsenic rich solid residues
accumulate from the purification of phosphoric acid and of
phosphorus pentasulfide. Burial in a controlled area is the
standard disposal method. Special disposal methods as mentioned
previously in this section may be necessary to prevent leachate
from reaching surface or ground waters. Solid waste quantities
and constituents are listed in Tables 9 and 10.
Energy Requirements
The energy requirements for the proposed treatment technologies
are listed in table 19. For the best practicable control
technology currently available the added energy requirements are
insignificant when compared to the process energy requirements.
Except for the production of phosphorus, energy does not
significantly enter into the product cost. For best available
technology economically available, the additional energy
requirements for PC13 and POCl^ are substantial. This is due to
the assumption that solar evaporation ponds may not be possible
in a given locale and evaporators may be necessary.
Ground Water
Since settling and evaporation ponds are extensively used for
waste water treatment in the phosphate industry, it is highly
recommended that all such ponds be sealed or lined so as to
prevent any leakage of contaminated process waters to ground
waters.
Noise
No overall adverse affect on the level of noise is expected,
although individual equipment may have excessive noise levels;
e.g., pumps and centrifuges.
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TABLE 19
ENERGY REQUIREMENTS
FOR RECOMMENDED GUIDELINES
Chemical
Process Energy
Requirement
KWH/Kkg
Treatment Energy
Requirement
KWH/Kkg
Percentage Energy
Increase
H3P04
P20
P2S5
PC13 (BPCTCA)
PC13 (BATE.A*
poci3
POC13
(BPCTCA)
(BATEA)
Na5P3010
Calcium Phosphates
animal feed grade
Calcium Phosphates
food grade
15,400
48
94
9
27
27
28
28
43
7.06
0.000025
0.0126
0.75
0.13
293
0.063
146
0
0.16
0.053
0.05
0.01
0.01
8.3
0.48
1000
0.22
520
0
BPCTCA - best practicable control technology currently available
BATEA - best available technology economically achievable
119
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
INTRODUCTION
The effluent limitations which must be achieved by July 1, 1977,
are based on the degree of effluent reduction attainable through
the application of the best practicable control technology curr-
ently available. For the phosphate industry, this level of
technology is based on the best existing performance by notable
plants of various sizes, ages and chemical processes within each
of the industry's categories. In some cases where no truly
notable plants were surveyed, this level of technology is based
on state-of-the-art unit operations commonly employed in the
chemical industry.
f5™^10*?1? ??^?01 techn°logy currently available empha-
treatment facilities at the end of a manufacturing process
SS udfVhe Control technology within the process it-
* manufacturing process controls
* recycle and alternative uses of water
* recovery and/or re-use of waste water constituents
* dry collection of airborne solids instead of (or
before) wet scrubbing.
Consideration was also given to:
a. The total cost of application of technology in relation
to the effluent reduction benefits to be achieved from
that application;
b. The size and age of equipment and facilities involved;
c. The process employed;
d. The engineering aspects of the application of various
types of control techniques;
e. Process changes; and
f. Non-water quality environmental impact (including energy
requirements) .
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PROCESS WASTE WATER GUIDELINES
Process water is defined as any water coming into contact with
raw materials, intermediates, products, by-products, or gas or
liquid that has accumulated such constituents. All values of
guidelines and limitations for total dissolved solids (TDS),
total suspended solids (TSS), metals and harmful pollutants and
and other parameters are expressed as consecutive 30-day averages
in units of pounds of parameter per ton and kilograms of
parameter per metric ton of product produced except where
expressed as a concentration.
On the basis of the information contained in Sections III through
VIII of this report, the following determinations were made on
the degree of effluent reduction attainable with the application
of the best practicable control technology currently available in
the phosphate manufacturing industry.
The Phosphorus Production Subcategory
Phossy Water
Because of the extremely harmful nature of elemental phosphorus,
it is standard practice within the industry to maintain tight
control over the discharge of phossy water, as discussed in
Section VII.
It is apparent from the discussion in section VII that existing
practicable technology can eliminate the reguirements for any
discharge at the TVA plant. Lime treatment of the blowdown
followed by sedimentation of the precipitated phosphates and
fluorides would remove the materials necessitating a blowdown, so
that this treated blowdown could be recombined with the remainder
of the clarified phossy water for return to the process.
There are three examples of plants which have achieved zero dis-
charge of phossy water: Plants 159, 028, and 181.
Hence, three plants have recognized the undesirability of ele-
mental ohosphorus in any discharge and have also recognized that
no nracticabie treatment system can remove a sufficient amount of
elemental phosphorus to permit effluent discharge of phossy water
wastes. They have all solved this dilemma by evaporating
sufficient phossy water rather than by discharge. One plant uses
an evaporation pond, while two others exploit other process heat
loads for in-process water evaporation.
In view of this clear-cut demonstration within the industry, it
is recommended that the best practicable control technology
currently available for phossy water wastes be no discharge of
pollutants to navigable waters.
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Process Waters Other Than Phossy Water
The standard techniques for treating the waste waters from cal-
ciner scrubbers and from slag quenching are lime treatment and
settling ponds, which perform the following functions:
* Neutralization of acid waste waters;
* Sedimentation of much of the original suspended
solids in the waste waters (silica, iron oxide,
and others);
* Precipitation and sedimentation of much of the
phosphates, fluorides and sulfates which were
dissolved in the original waste waters;
* Dissipation of the process heat to the atmosphere
during the extended residence in the settling
ponds;
* Reduction in the waste water quantity as a result
of net evaporation during the extended residence
in the settling ponds;and
* Where phossy water is combined with these other
process waters, some oxidation of the elemental
phosphorus to phosphates is accomplished.
At Plant 181, the lime-treated water from all sources is clari-
fied in settling ponds, and the clarified water is held in re-use
water supply ponds. There is total recycle of all water at this
plant, with zero discharge. Because phosphates and fluorides are
removed by lime treatment and sedimentation, there is no
requirement to bleed off water for the control of dissolved
solids.
Under conditions of very abnormally high rainfall which would
exceed the capacity of the pond system, the only overflow would
be from the final re-use water supply ponds, thereby minimizing
the quantities of pollutants even occasionally discharged. The
recirculating water system runs at a water deficit, due to
evaporation in the process and to net evaporation in the pond
system. Hence, fresh make-up water is supplied, and can be con-
trolled to compensate for temporary swings in the pond evapora-
tion/rainfall balance.
The TVA plant at Muscle Shoals, Alabama granulates the slag by
quenching with a high-velocity jet of water which is recirculated
from a sump in the slag pit. In this TVA operation, the cooling
water and the scrubber liquors are used for make-up in slag
quenching. The granulated slag effectively neutralizes these
waters and also acts to filter out the scrubbed solids, which
become part of the slag pile to be sold. Nearly all of the
soluble phosphate and 95 percent of the fluoride is removed by
the slag, and the fluoride concentration is reduced to 30 mg/1.
Hence, TVA utilizes slag treatment instead of lime treatment
because the slag is finely divided. Sufficient waste water
treatment is obtained by TVA to enable the plant to completely
reuse this water without any discharge.
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Two other phosphorus plants which utilize lime treatment and
sedimentation for process water treatment are Plants 028 and 159.
Tables 14 and 15 list (respectively) the effluent concentrations
and quantities discharged from these plants, neither of which
recycles treated waste water. There are three significant
differences between these two plants:
* Plant 028 discharges into the same waterway as the
plant intake so that its discharge responsibility is
the net increase in constituent quantities. Plant
159 intakes ground water and discharges into surface
water so that its responsibility is the gross amount
of constituent quantities.
* It is apparent from the "Intake" columns of Tables
14 and 15 that the intake of Plant 159 contains
much more dissolved solids (and specifically Fr
PO4 and S04) than the intake of Plant 028.
* The waste water quantity percent of production
for Plant 028 is three times that of Plant 159.
The above three differences are interrelated and affect the
quantities of fluoride, phosphate and sulfate discharged by Plant
159 because the effluent concentrations are of the same magnitude
as the solubilities of the corresponding calcium salts. Hence
the effluent quantities are significantly influenced by factors
other than the treatment of the process waters.
The effectiveness of control and treatment techniques used by the
four phosphorus plants cited are summarized in Table 13. Plants
028 and 159 achieve very high (97% to 99+X) control and treatment
efficiencies and correspondingly low quantities (although not
absolutely zero) of discharged constituents.
In areas of the country where very severe and extended cold
weather prevails, total recycle of process water becomes diffi-
cult for two reasons:
1. The return water piping and pumping must be protected
against freezing. However, technology such as buried
water mains and enclosed, heated pumping stations has
been amply demonstrated in the chemical industry and in
water supply operations.
2. The settling ponds may freeze. In a total recycle
system, this circumstance would prevent the required
water from being supplied back to the process, if
auxiliary fresh water supply were provided to uncouple
the process from frequent climatic perturbations, the
pond system would have to consist of sufficient holding
capacity to prevent temporary overflow and would have
to contain sufficient evaporative capacity to prevent
long-term accumulation of water.
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Recommended Effluent Limitations Guidelines Eased Upon
Practicable Control Technology Currently Available
Best
In view of the existence of three plants (028, 159 and 181) which
have already achieved zero discharge of elemental phosphorus, in
view of the existence of one plant (181) which has already
achieved zero discharge of all process waters, and in view of two
plants (028 and 159) that are achieving exemplary performance, it
is recommended that the best practicable control technology
currently available for a period of 30 consecutive days be:
Total suspended solids
Total phosphorus
Fluoride
Elemental phosphorus
PH
0.5 kg/kkg (1.0 Ib/ton)
0.15 kg/kkg (0.3 Ib/ton)
0.05 kg/kkg (0.10 Ib/ton)
No detectable quantity
Within the range 6.0 - 9.0
Waste water from Ore Washing or Benef iciation
n contro1 technology currently available
recommended xn the previous paragraphs does not include wastes
i 10? 2r washi*9 °* phosphate rock. This
commonly but not exclusively conducted at a
~S7 S ki^fi0rU The hu9e raw waste load from
, 7.5 kkg of gangue per kkg of phosphorus eventually
produced, warrants a separate study and separate efflwnt
limitations guidelines. *
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The Phosphorus Consuming Subcategory
Phossy Water
Gross discharges of phossy water are presently avoided by pumping
displaced phossy water from the plant's phosphorus storage tank
back into the emptying rail car which brought the phosphorus, and
by transporting this displaced phossy water to the phosphorus
producing plant for treatment and/or re-use. Such is the
practice at Plants 037 and 192.
Smaller quantities of phossy water discharge may also be elimi-
nated through the use of standard engineering techniques. The
phosphorus storage tank level control system may be altered to
provide an auxiliary water overflow tank with return of the water
to the main tank. The avoidance of elemental phosphorus in plant
sewer lines can be implemented with more stringent process and
operator controls and procedures and by providing traps
downstream of reaction vessels.
In view of the harmful qualities of elemental phosphorus and in
view of the available choices from state-of-the-art control
techniques, the recommended best practicable control technology
currently available for phossy water is no discharge of
pollutants.
Phosphoric Acid Manufacture
Exemplary Plant 075 operates without the discharge of any process
water. There is no fundamental or practical reason why process
water should be discharged at all from any dry-process phosphoric
acid plant. Minor leaks and spills may be minimized, collected
and treated using control techniques generally available and
demonstrated in the industry.
The recommended effluent limitations guideline of no discharge of
process waste water pollutants applies generally, and with
special emphasis, to elemental phosphorus (i.e., phossy water)
and to arsenic residues from the purification of phosphoric acid.
Phosphorus Pentoxide Manufacture
The single raw waste constituent is phosphoric acid from water
tail-gas seals. Application of two standard techniques would
enable total recycle of this waste water:
1. Reduction in waste water quantites by using dilute
caustic or lime slurry as tail gas liquor instead
of pure water, increasing the absorptive capacity
for P.2O5.
2. Lime treatment and sedimentation to neutralize and
to remove the phosphate, permitting total recycle.
126
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In view of the straightforward application of these two tech-
niques, the recommended best practicable control technology
currently available for phosphorus pentoxide manufacture is no
Discharge of process waste water pollutants to navigable waters.
Since total recycle is practicable technology, this recommended
guideline is not affected by modest inaccuracies in the standard
raw waste as estimated in Section V.
Phosphorus pentasulfide Manufacture
The sole source of process waste water is the scrubber liquor for
fumes from casting liquid P^S5. One control technique would be
the use of inert-atmosphere casting or vacuum casting to
completely eliminate the need for scrubbing. As an alternate to
this approach, the application of three standard techniques would
permit total recycle of scrubber water:
1. Use of dilute caustic or lime slurry instead of pure
water would reduce the waste water quantities by in-
creasing the adsorptive capacity for P2OS and SO2.
2. Partial recycle of scrubber liquor from a sump would
reduce the waste water quantity by decoupling the
buildup of absorbed acids from the mass-transfer
requirements for high scrubber flow rates.
3. Lime treatment and sedimentation to neutralize and
to remove phosphate, sulfite and sulfate would per-
mit total recycle.
In view of these different practicable alternatives, the
recommended best practicable control technology currently
available for phosphorus pentasulfide manufacture is no discharge
of process waste water pollutants to navigable waters. Since
total recycle is practicable technology, this recommended
effluent limitations guideline is not affected by modest
inaccuracies in the standard raw waste load as estimated in
Section V.
This effluent limitations guideline also applies to any arsenic-
rich residues from the purification of P2S5; these solid residues
may be disposed of by burial as in Plants 147 and 192.
phosphorus Trichloride Manufacture
The acid wastes from phosphorus trichloride manufacture arise
from the hydrolysis of PC13 in scrubber water from the
reactor/still from product storage tanks, from product
transferring operations, and from container cleaning. The
scrubber water may be collected in a sump and recycled to
decrease the wasted quantity of scrubber water (while still
maintaining sufficient scrubber flow rates for effective mass
transfer) and to increase the concentration of waste
constituents.
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WOUld »«*»"«• the acids and
^
the following recommended hl/er^y Jhen be Discharged, with
currently avlillble: practicable control technology
Total Phosphorus n 8 ko/kko n « ix^ ,
Tot 1 Suspended SQlidSr 0.8 TO (1.6 Ib/ton
0.00005 kg/kkg (0.0001 Ib/ton)
p 6.0 to 9.0
based on the raw waste load as determined in Section V:
n*™, ^ ^9/kkg (6 Ib/ton)
H3P04 2.5 kg/kkg (5 Ib/ton)
6
(f^B/ton^1^?? '^ ^^^^ralization of HCl is
:3^.SW5i - pd^e^
is no more than
s
control technolgy cur rntvavi,h™inene est Practicable
treatina the Sw c^rently available is not zero discharge. In
not reduced: 5.f kg/kkfni gJtSfi q^tity °f constit^ts is
kq/kko ni a i»>y?rt«r9 ; Jb/ton) in the raw waste vs. 5.7
treatment does remov^ th^acS?* ^^K^- effluent- However, the
alkalinity? acidity' substituting for it residual
sncerchlrohven is
VII, may be applied? Y tre*tment (as described in Section
Phosphorus Oxychloride Manufacture
of applicable control and
contr"or"technoi"cSrcSrr4ntlvaavSn^?80n 5°K ^ best Practicable
are all identically parallel fnrSr?? 2g 2€r° dischar9e'
for PC13 manufacture: S^diM.^.?? l manu|a^ure as they are
_____ ~ •«-»•«.«_*, ^s. ±iie uizie r*»nr>e i o -»«« **f ______ j a_ cm«-
POC13 manufacture,
is:
128
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HC1 2 kg/kkg (4 Ib/ton)
* HJP04 0.5 kg/kkg (1 Ib/ton)
the same rationale as for PC1£ manufacture, the recommended
practicable control technology currently available effluent
limitations guideline ares
Total Phosphorus 0.17 kg/kkg (0.34 Ib/ton)
Total Suspended solids, 0.15 kg/kkg (0.3 Ib/ton)
pH 6.0 to 9.0
129
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The Phosphate subcategory
sodium Tripolyphosphate Manufacture
Exemplary Plant 042 has HO process wastes. The dust collected
from the spray-dryer gaseous effluent stream is added to the
spray-dryer solid product stream. The water used for subsequent
scrubbing of this gas stream from the spray dryer is then recy-
cled to the mix area and is used as process water in the neu-
tralization step. The cooling air used for the product tempering
is vented into the spray-dryer vent line upstream of the scrub-
bing operation.
This plant is an excellent example where a combination of in-
process ronfrnls such as dry dust collection, water re-use, and
return 2^ +£i orocess of airborne solids have been utilized to
totally avoid any aqueous wastes. Plants 006 and 119 also have
no discharge of process waters.
f this demonstration, and in view of the general apo-
in view or such techniques throughout the industry, the
licability o begt practicable control technology currently
recommended discharge of process waste water pollutants to
available is n«
navigable waters.
I^T^_1*V!»--V-— -E- f
Exemplary Plant 182 has no process wastes. Three separate water
cycles are used, and there is no effluent from any of them. The
acid defluorination scrubber water is neutralized with lime, the
solids are settled by ponding, and the pond effluent is reused as
scrubber water. The scrubber water for collection of airborne
solids from the reactor and dryer is recirculated with a bleed-
off directly into the reactor as process water. Cooling water is
recycled through a cooling tower, with the blowdown used as make-
up in the solids scrubbing system instead of being wasted.
Softened well water is used for cooling water make-up.
This plant is an excellent example where a combination of in-
process controls (dry dust collection, recycle of scrubber water
to minimize waste water quantities, return of process waste
streams to the process, and a systems approach towards water use
whereby a blowdown stream from one water cycle becomes a make-up
stream for another) in combination with a standard lime-
treatment, sedimentation and total recycle scrubber water system
results in the discharge of no aqueous wastes.
In view of this demonstration, and in view of the general app-
licability of such techniques throughout the industry, the re-
commended best practicable control technology currently available
is no discharge of process waste water pollutants to navigable
waters.
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Food-Grade Calcium Phosphates
The raw aqueous wastes from the manufacture of food grade calcium
phosphates are from two primary and approximately equal sources:
the centrate or filtrate from dewatering of the dicalcium
phosphate slurry, and the effluent from wet scrubbers which
collect airborne solids from product drying operations. Both of
these sources contain suspended, finely divided calcium phosphate
solids and phosphoric acid from acid units and from excess acid
in the reaction liquid. The total raw waste load (from section
V) is:
Process Water Wasted 4,200 1/kkg (1,000 gal/ton)
Total Suspended Solids (2.4%) 100 kg/kkg (200 Ib/ton)
Phosphoric Acid (0.7%) 30 kg/kkg (60 Ib/ton)
The first type of currently available control technology that may
be applied is the substitution of dry dust bag collectors for wet
scrubbers, as has been done at Plants 003, 042, 119, and 182.
The fact that a multi-product plant must provide a separate
fcaghouse for each product does not deny the current availability
of this technology, but rather increases the cost of such an
installation. However, Plant 003, which is a multiple-product,
food grade, calcium phosphates plant, has justified the
installation of separate baghouses on the sole basis of
profitability from product recovery.
The elimination of wet scrubbing systems would halve the aqueous
waste load so that it would then consist of 2,100 1/kkg (500
gal/ton), containing 2.4 percent of suspended solids amounting to
50 kg/kkg (100 Ib/ton) and containing 0.7 percent of phosphoric
acid amounting to 15 kg/kkg (30 Ib/ton).
Lime treatment, clarification and sedimentation (with the aid of
polymeric flocculant) may then be used to precipitate the
phosphate and remove suspended solids to 25 mg/1. The clarifier
underflow will remove the bulk of the suspended solids.
Dewatering of these solids may be required to make them suitable
for landfill. The practice at Plant 006 after lime treatment for
neutralization and precipitation of phosphate wastes is vacuum
filtration of the slurry from the clarifier underflow. The water
lost with the solids reduces the effluent flow to 1800 1/kkg (430
gal/ton) containing:
Suspended solids 0.06 kg/kkg (0.12 Ib/ton)
Total Phosphorus 0.03 kg/kkg (0.06 Ib/ton)
111
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SUMMARY OF PROPOSED BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY
AVAILABLE
No Discharge of Process Waste Water Pollutants
The proposed best practicable control technology currently
available for process waste water is no discharge of pollutants
for the manufacture of the following chemicals:
Phosphorus Consuming Subcategory
Phosphoric Acid (Dry Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphate Subcategory
Sodium Tripolyphosphate
Calcium Phosphates (Animal-Feed Grade)
Permitted Discharge
The proposed best practicable control technology currently
available for process water for the manufacture of phosphorus
(and ferrophosphorus), PC13, POC13 and food grade calcium
phosphate require that the ^average" of daily values for 30
consecutive days shall not exceed:
Phosphorus Phosphorus
and Trichloride
Ferrophos phorus
Phosphorus
Oxvchloride
Food Grade
Calcium
Phosphate
Suspended
Solids
kq/kkg
Total
Phosphorus
kg/kkg
Fluoride
kg/kkg
Arsenic
kg/kkg
oH
0.5
0.15
0.05
6.0-9.0
0.7
0.8
0.15
0.17
0.00005
6.0-9.0 6.0-9.0
0.06
0.03
6.0-9.0
The above guidelines apply to maximum averages of daily values
for any period of 30 consecutive days.
The pH range is to be maintained at all times.
The permitted maximum concentration for any one day period for
suspended and dissolved solids is twice that of the consecutive
30 day average value.
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
INTRODUCTION
The effluent limitations which must be achieved by July 1, 1983,
are based on the degree of effluent reduction attainable through
the application of the best available technology economically
achievable. For the phosphate manufacturing industry, this level
?f^ht^?hn°10gy nWaS based On the ver* best control and treatment
* SnS ?g? employed by a specific point source within the
industrial category or subcategory, or where it is readily
tra??fh^bl% £K°in1 °ne industrY P^cess to another. Best
available technology economically achievable places equal
emphasis on in-process controls as well as on control or
treatment techniques employed at the end of a production process.
Those plant processes and control technologies which at the pilot
plant, semi-works, or other level have demonstrated both technol-
ogical performances and economic viability at a level sufficient
to reasonably justify investing in such facilities were also con-
sidered in assessing the best available technology economically
achievable. This technology is the highest degree of control
technology that has been achieved or has been demonstrated to be
capable of being designed for plant scale operation up to and
including "no discharge" of pollutants. Although economic
factors are considered in this development, the costs for this
level of control are intended to be for the top of the line of
current technology subject to limitations imposed by economic and
engineering feasibility. However, best available technology
economically achievable may be characterized by some technical
risk with respect to performance and with respect to certainty of
costs. Therefore, this technology may necessitate some
industrially sponsored development work before its application.
The following factors were taken into consideration in determin-
ing the best available technology economically achievable:
a. The age of equipment and facilities involved;
b. The process employed;
C* Leng^eering asPects <* the application of various
types of control techniques;
d. Process changes;
e. Cost of achieving the effluent reduction resulting from
application of best available technology economically
achievable; and
133
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f. Non-water quality environmental impact (including energy
requirements).
PROCESS WATER GUIDELINES
Process water is defined as any water coming into contact with
raw materials, intermediates, products, by-products, or gas or
liquid that has accumulated such constituents.
On the basis of the information contained in Sections III through
IX of this report, the following determinations were made on the
degree of effluent reduction attainable with the application of
the best available control technology economically achievable in
the various categories of the phosphate manufacturing industry.
All Chemicals Except Phosphorus, Phosphorus Trichloride,
Phosphorus Oxychloride and Food Grade Calcium Phosphate
The recommended best available technology economically achievable
for process water are the same as the best practicable control
technology currently available effluent limitations guidelines,
i.e., no discharge of process waste water pollutants to navigable
water for the manufacture of the following chemicals:
Phosphorus-Consuming Subcategory
Phosphoric Acid (Dry Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphate Subcategory
Sodium Tripolyphosphate
Calcium Phosphates (Animal Feed Grade)
The Phosphorus Production Subcategory
At Plant 181, the lime-treated water from all sources is
clarified in settling ponds, and the clarified water is held in
re-use water supply ponds. There is total recycle of all water
at this plant, with zero discharge. Because phosphates and
fluorides are removed by lime treatment and sedimentation, there
is no requirement to bleed off water for the control of dissolved
solids.
Under conditions of very abnormally high rainfall which would
exceed the capacity of the pond system, the only overflow would
be from the final re-use water supply ponds, thereby minimizing
the quantitites of pollutants even occasionally discharged. The
recirculating water system runs at a water deficit, due to
evaporation in the process and to net evaporation in the pond
system. Hence, fresh make-up water is supplied, and can be
controlled to compensate for temporary swings in the pond
evaporation/rainfall balance.
134
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is therefore recommended that the best available control
technology economically achievable for phosphorous production be
no discharge of process waste water pollutants to navigable
waters.
Manufacture of Phosphorus Trichloride and Phosphorus Oxychloride
In-Process Controls
The largest contribution to the raw waste load from these pro-
cesses is from the escape of PC13 vapor from the reactor/stills.
The methods for drastically reducing this contribution are clear
cut: the substitution of refrigerated condensers for water-
cooled condensers or the addition of refrigerated condensers
downstream of water-cooled condensers. Refrigerated condensers
are already in use at Plant 037 in the manufacture of POC13 by
the air-oxidation process. ~
AS an added step, a demister can be added downstream of the re-
frigerated condenser to prevent condensed but dispersed PC13 from
escaping to the scrubber. One concept for this demister is a
short section of column packed with metal packing (for good heat
transfer) within the refrigerated condenser.
As a corollary to this principle, other sources of PC13_ and POC13
vapors could be controlled by refrigerated condensers or cold"
traps. The storage tank vent and vents for the transfer of
liquid products are included in this concept. Alternatively, the
liquid products could be maintained at low temperatures by
refrigerating coils in the storage tanks so that vapors from
storage and transfer would be minimized.
In view of the order-of-magnitude or greater reduction in the
vapor pressure of these products resulting from readily available
refrigeration levels, plus the effect on PC13 condensation from
doubling (or more) the temperature driving force for heat
transfer, a reasonable expectation is that the PC13 vapor (and
mist) losses could be cut to 10 percent of the present values.
Tne acid wastes from washing tank cars and tank trucks, and from
washing used POC13 filter elements are very small at present,
^no^iU^ 2^ kg
-------
condensible while the corresponding H3PO3 and H3P04 is retained
as reactor residue.
All in all, the above outlined in-process control techniques
could drastically reduce the raw waste load to perhaps 10 percent
of the original value, so that the estimated raw waste quantities
would then become (for either PC13 or POCl3f manufacture) :
HC1 0.3 kg/kkg (0.6 Ib/ton)
H3PO3 + H3PC4 0.25 kg/kkg (0.5 Ib/ton)
As important as the reduction in the waste water constituent
quantities would be a corresponding reduction in the quantity of
waste water generated. Tail-gas scrubbers should be very much
smaller and should require much lower water flow rates.
As an added step, the scrubber water could be recycled from a
sump, thereby decoupling the waste water quantity (blowdown from
the sump) from the mass-transfer requirements for scrubbing.
Furthermore, water use could be cascaded in the plant; for
example, the waste water from tank car washing could be used as
make-up in the tail-gas scrubber system.
End-of-Process Treatment
At the new low levels of waste water flow rates and constituent
quantities, simple lime neutralization of moderate pH (without
sedimentation) would result in the following waste water charac-
teristics:
Waste water Quantity 500 1/kkg (120 gal/ton)
Total Dissolved Solids 0.5 kg/kkg (1.0 Ib/ton)
Total suspended solids 0.35 kg/kkg (0.7 Ib/ton)
pH 6-9
Further lime neutralization and removal of suspended solids would
not appreciably reduce the quantity of total dissolved solids,
and would trade off reduction in total suspended solids for
higher pH levels.
At this point, the waste water quantity would be extremely low,
and a practicable final step would be evaporation to dry ness. An
idea of the costs of evaporation can be obtained by assuming a
plant manufacturing 59 kkg/day (65 tons/day) of total PC13. and
POC13. The waste water quantity would be 30,000 liters/day
(7,800 gal/day). Using the data of Section VIII for single-
effect evaporation,
Capital Cost -
Annual Costs: Capital Recovery = $ 1,600
Taxes & Insurance = 300
Operation S Maintenance = 14.700
(including energy) $16,600
Unit cost « $0.85/kkg ($0.77/ton)
136
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This unit cost is only 0.3 percent of the current selling price,
*295/kkg ($268/ton).
It is entirely possible that a rigorous economic evaluation might
result in a decision to dispose of the original raw waste load by
evaporation, rather than to bear the expense of the in-process
controls discussed above which minimize (but do not eliminate)
the waste. The waste water,quantity to be evaporated would be
the original quantity, 5,000 1/kkg (1,200 gal/ton), or 300,000
liters/day (78,000 gal/ton); and the costs would be:
Capital Cost = $38,400
Annual Costs: Capital Recovery = 8,900
Taxes & Insurance = 1,900
Operation S Maintenance = 147,000
(including energy)
Unit Cost = $8.10/kkg ($7.35/ton)
The most conservative approach, i.e., to evaporate all of the
waste water without any in-process control to reduce its
quantity, would cost 2.8 percent of the current selling price.
The fundamental reason is that despite the high unit cost of
evaporating water, the waste water quantities for PC13 and POC13
are very small. The conclusion is reached that the application
of this available technology is economically achievable.
The final step of total evaporation would bring the PC13 and
POC13 manufacturing processes into line with the rest of the
phosphate industry by achieving the national goal of eliminating
the discharge of all pollutants.
It is therefore recommended that the best control technology
economically achievable for PC13. and POC13 manufacture be no
discharge of process waste water pollutants to""navigable waters.
Food Grade Calcium Phosphate Manufacture
After elimination of wet scrubbers as described in Chapter IX
standard lime treatment and sedimentation may be used to
neutralize these remaining wastes, to precipitate the phosphate,
and to remove a nominal 85 percent of the suspended solids (with
the possible aid of a polymeric flocculant). At a pH of 10.5,
the remaining concentration of dissolved solids would be
approximately 0.3 mg/1. The quantity of waste water would be
approximately 85 percent of concentration of dissolved solids
with the remainder landfilled with the underflow from the
clarifier as wet sludge. The clarified overflow would than
consist of 1,800 1/kkg (430 gal/ton) containing:
Dissolved Solids 0.0005 kg/kkg (0.001 Ib/ton)
Suspended Solids 11 kg/kkg (22 Ib/ton)
137
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The demonstrated practice at Plant 006, after lime treatment for
neutralization and for precipitation of phosphate wastes, is
vacuum filtration of all of the slurry from the clarifier
underflow.
Vacuum filtration (possibly after conditioning with a polymeric
flocculant) can reduce the suspended solids content of the waste
water from phosphates to the level of 0.5 mg/1. Based on these
data and on the level of dissolved phosphates of 0.3 mg/1, the
discharge would contain on the basis of the total process water
wasted, 4,200 1/kkg (1,000 gal/ton):
Total Dissolved Solids 0.0015 kg/kkg (0.003 Ib/ton)
Total Suspended Solids 0.0025 kg/kkg (0.005 Ib/ton)
With the achievement of these extremely low levels of TDS and
TSS, or even with considerable relaxation of these levels, the
treated-waste water from the manufacture of food grade calcium
phosphate is expected to meet the U.S. Food and Drug
Administration criteria for process water and this treated water
can then be recycled back into the process. No product purity
restrictions exist any longer which had previously necessitated
discharge. In fact, once the commitment to total recycle is
made, the lime treatment step may be bypassed since the ionic
species from the dissolved solids and the phosphoric acid are
precisely those desired in the reaction vessel. However, the
problem of waste segregation is sufficiently great that for
reasons of product purity existing plants may not be able to make
the necessary changes by 1977.
It is therefore recommended that the best available control
technology economically achievable for food grade calcium
phosphate manufacture be no discharge of process waste water
pollutants to navigable waters.
.138
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SECTION XI
NEW SOURCE PERFORMANCE STANDARDS
AND PRETREATMENT RECOMMENDATIONS
INTRODUCTION
This level of technology is to be achieved by new sources. The
term "new source" is defined in the Act to mean "any source, the
construction of which is commenced after publication of proposed
regulations prescribing a standard of performance." New source
performance standards are to be evaluated by adding to the
consideration underlying the identification of best available
technology economically achievable a determination of what higher
levels of pollution control are available through the use of
improved production processes and/or treatment techniques. Thus,
in addition to considering the best in-plant and end-of-process
control technology identified in best available technology
economically achievable, new source performance standards are to
be based on an analysis of how the level of effluent may be
reduced by changing the production process itself. Alternative
processes, operating methods and other alternatives were to be
considered. However, the end result of the analysis identifies
effluent standards which would reflect levels of control
achievable through the use of improved production processes (as
well as control technology), rather than prescribing a particular
type of process or technology which must be employed. A further
determination which was to be made for new source performance
standards is whether a standard permitting no discharge of
pollutants is practicable.
The following factors were considered with respect to production
processes which were analyzed in assessing new source performance
standards:
a. The type of process employed and process changes;
b. Operating methods;
c. Batch as opposed to continuous operations;
d. Use of alternative raw materials and mixes of raw
materials;
e. Use of dry rather than wet processes (including
substitution of recoverable solvents for water); and
f. Recovery of pollutants as by-products.
139
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PROCESS WATER GUIDELINES
On the basis of the information contained in Sections III through
X of this report the following determinations were made on the
degree of effluent reduction attainable with the application of
new source standards for the various categories of the phosphate
manufacturing industry.
Since the best practicable control technology currently available
effluent limitations guidelines for all of the chemicals consid-
ered in this study of the phosphate category were no discharge of
process waste water pollutants to navigable waters, the
recommended new source performance standards are identical to the
best available technology economically achievable.
PRETREATMENT RECOMMENDATIONS
In addition to the recommendation of new source performance
standards and related effluent limitations covering discharges
directly into waterways, the constituents of the effluent
discharge from a plant which would interfere with, pass through,
or otherwise be incompatible with a well designed and operated
publicly owned activated sludge or trickling filter waste water
treatment plant were identified. A determination was made of
whether the introduction of such pollutants into the treatment
plant should be completely prohibited.
Waste Water Flow Rate
A determination must be made on an individual basis about the
impact of a plant's discharge on the total hydraulic capacity of
both the municipal collection system and the municipal waste
water treatment plant. At an extreme, hydraulic overloading will
result in overflows or by-passes as the capacities of pumping
stations (both in the collection system and the raw waste water
pumping stations at the treatment plant) are exceeded. It must
be remembered that an overflow of combined industrial/municipal
waste water has the same adverse environmental effect as an over-
flow of raw domestic sewage. At a minimum, hydraulic overloading
would result in reduced efficiency of the treatment plant
because:
* Primary and secondary clarifiers would be
operating at excessive overflow rates;
* secondary treatment units (activated sludge or trickling
filters) would be operating at a food deficiency since
the waste water from the phosphorus chemicals industry
would provide no organic material;
* Trickling filters would become flooded (and so anaerobic);
* Grit chambers would have a high linear velocity resulting
in the carry-over of grit and the subsequent adverse
effects on equipment;
* The capacity of air blowers for activated sludge second-
ary treatment may be exceeded, resulting in reduced
140
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levels of dissolved oxygen;
* The capacity of chlorinators may be exceeded, resulting
in insufficient disinfection; and
* The critical operating parameters of the activated sludge
unit may be compromised.
The domestic waste water flow rate follows a well-known diurnal
cycle; if the industrial contribution could be staggered to
provide flow equalization, the impact of the added flow rate
could be minimized. Conversely, sporadic slug discharges could
make periodic overloading more probable.
Suspended Inorganic Solids
High concentrations of suspended inorganic solids might overload
the primary sludge collectors, the primary sludge pumps, the
sludge thickener, the sludge dewatering operation, and the sludge
disposal system. In addition, since these solids provide no
organic food for secondary treatment organisms, they would reduce
the active biological-solids fraction (i.e., reduce the mixed
liquor volatile suspended solids), thereby reducing the
efficiency of secondary treatment.
Acidity
While moderate alkalinity may be tolerated since carbon dioxide
produced in secondary treatment by the microbial oxidation of
organic material will provide neutralization, free mineral
acidity normally cannot be tolerated by the organisms in the
secondary treatment biomass. The proteins in these organisms are
precipitated and coagulated at pH 4 to 5.
Another strong reason for avoiding acidic contributions to pub-
licly-owned treatment plants is that acidic wastes would dras-
tically promote corrosion of equipment.
It is recommended that the allowable pH range be set at 6 to
10.5.
Dissolved Inorganic Solids
Dissolved inorganic solids would pass through a secondary waste
water treatment plant without being removed. Hence, reliance on
publicly owned treatment plants would be no treatment at all with
respect to dissolved solids, and it would be equivalent to direct
discharge.
The pretreatment standards for dissolved inorganic solids should
be the same as the applicable or proposed effluent limitations
guidelines.
Heavy Metals or Harmful Materials
141
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Metals or harmful materials would at best, pass through a
publicly owned treatment plant, and at worst, adversely affect
the microorganisms in secondary treatment. Elemental phosphorus
(as phossy water) and enriched arsenic compounds are substances
that may be discharged into municipal sewer systems from this
industry. Special attention is brought to pretreat wastes for
removal of these materials.
It is recommended that the pretreatment standards be no discharge
of metals or harmful materials.
Dissolved Phosphates
While dissolved phosphates would generally pass through secondary
treatment plants with the waste water treatment plant effluent,
they would affect the sludge operations. Gravity-thickened
sludge (6 to 12 percent solids) is normally conditioned with
lime, ferric chloride, or alum before dewatering operations,
although polymeric flocculants are also widely used. The phos-
phates would be precipitated as the calcium, ferric, or aluminum
phosphate and would thus render the conditioning step ineffective
by partially or totally removing the active cation from solution.
A similar situation exists in tertiary treatment, in the phos-
phate removal step using lime, ferric chloride, or alum. In this
case, the chemical requirements would be increased and the sludge
handling capacity of the treatment plant could be overloaded.
While these pretreatment standards apply only to secondary
plants, precautions should be taken to avoid adverse effects when
tertiary treatment might be added in future years.
Summary of Recommended Pretreatment
Due to the nature of the process waste waters of the phsophorus
producing and the phosphorus consuming subcategories it is
recommended that these wastes not be discharged into publicly
owned treatment works. These waste waters are considered to be
incompatible with such works principally because of harmful con-
stituents such as elemental phosphorus and the possible presence
of arsenic, cadmium, uranium and like metals also present in the
phsohate ore.
The principal contaminant from the phosphate subcategory is
phosphate, which is incompatible with secondary treatment plants.
However, these wastes are considered to be compatible with
tertiary treatment plants designed, constructed and operated to
remove dissolved phosphates.
142
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SECTION XII
ACKNOWLEDGMENTS
This report was prepared by General Technologies Corporation,
Springfield, Virginia by Dr. Robert G. Shaver and Mr. Donald H.
Sargent and their staffs.
The project officer, Mr. Elwood E. Martin, would like to thank
his associates in the Effluent Guidelines Division, particularly
Mr. Allen Cywin, Mr. Ernst P. Hall and Mr. Walter J. Hunt for
their valuable suggestions and assistance.
Mr. Michael W. Kosakowski, Effluent Guidelines Division, handled
a large portion of the reorganization and rewriting of the
Development Document and the accompanying Federal Register
documents.
The members of the working group/steering committee who
coordinated the internal EPA review are:
Mr. Ernst Hall, Effluent Guidelines Division
Mr. Walter J. Hunt, Effluent Guidelines Division
Mr. Elwood Martin, Effluent Guidelines Division
Dr. Chester Rhines, Effluent Guidelines Division
Mr. Michael Kosakowski, Effluent Guidelines Division
Mr. Harry Trask, Office of Solid Waste Management Programs
Mr. John Savage, Office of Planning and Evaluation
Mr. Taylor Miller, Office of General Counsel
Mr. Srini Vasan, Region V
Dr. Edmond Lomasney, Region VI
Ms. Begina Carroll, Office of Technical Services
Dr. Robert Swank, National Environmental Research Center,
Corvalis (Athens)
Mr. Paul DesRosiers, Office of Research and Development
Appreciation is also extended to the following trade associations
and corporations for assistance and cooperation given to use in
this program:
Calgon Corporation
Chemical Separations Corporation
Dorr Oliver
Dow Chemical
Eimco
Envirogenics Company
FMC
Goslin Birmingham, Inc.
Gulf Environmental Systems Company
Hooker Chemical
International Mineral & Chemical Corp.
Manufacturing Chemists Association
Mobil Chemical Company
Monsanto
143
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Occidental Chemical Company
Office of Saline Water, U.S. Department of Interior
Resources Conservation Company
Rice Engineering and Operating, Inc.
Stauffer Chemical
Tennessee Valley Authority
Water Pollution Control Federation
Water Services Corporation
Wellman Power Gas, Inc.
Last but not least, many thanks are given to the hardworking
secretarial staff of the Effluent Guidelines Division. In
particular, recognition is given to Ms. Sharon Ashe, Ms. Linda
Rose, Ms. Kay Starr and Ms. Nancy Zrubek. Appreciation is also
given to Ms. Kit Krickenberger who coordinated the staff efforts.
144
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SECTION XIII
REFERENCES
1. Current Industrial Reports, inorganic Chemicals, U.S.
Bureau of Census, Series M28A(71)-14.
2. Arthur D. Little, Inc., Phase I Economic Impact of 1972
water Pollution control Amendments on Phosphate
Manufacturing, prepared for EPA, 1973.
3. Study of the Economic Impact of the Cost of Alternative
Federal Water Quality Standards on Ten Inorganic Chemicals,
U.S. Environmental Protection Agency, Washington, D.C.,
Dec. 4, 1972.
4. 6.S.G. Beveridge and R.6. Hill, Phosphoric Acid Process
Survey, Chem 8 Process Eng. 49., July 1968, pp. 61-66, 73
(Part I), Aug. 1968, pp. 63-70 (Part II) , 305 References
in Bibliography.
5. J.C. Barber, Waste Effluent; Treatment and Reuse, Chem
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15. Existing Practice or Data taken at Plant No. 003.
16 . ii ii n it ii it « « 006.
17. ii « it n i« ii « ti 028.
18. ii n « ii n " " ii 037.
19. n ii n n n n ii it 042.
20. " " " " " " " " 075.
2i. n n n n n ii « n 119.
22. ii ii ii " " " " ii 147.
23. it ii ii ii ii ii n ii 159.
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U7
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148
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149
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SECTION XIV
GLOSSARY
All underlined numbers within a chemical formula represent
normally subscripted numbers. Physical limitations of the
printing device make this system necessary. For Example, H20
represents water.
A room-like condensation chamber for anhydrous phosphorus
pentoxide.
Burden
The combined rock, coke and silica feed to a phosphorus electric
furnace.
Calcination
Heating of a solid to a temperature below its melting point to
bring about a state of thermal decomposition or a phase
transition other than melting. (73)
Dicalcium Phosphate Dihydrate, CaHPOU2H20.
Dry Process Phosphoric Acid
phosphoric acid made from elemental phsophorus. Also called
furnace acid.
Eutectic
The lowest or highest melting point of an alloy or solution of
two or more substances that is comprised of the same
components. (73)
Ferrophosphgrus_
A by-product iron- phosphorus alloy of phosphorus smelting,
typically containing 59 percent iron and 22 percent phosphorus.
Symbolized as Fe2P in this report.
A substance that promotes the fusing of minerals or metals or
prevents the formation of oxides. For example, metal refining
lime is added to the furnace charge to absorb mineral impurities
in the metal. A slag is formed which floats on the bath and is
run off. (73)
151
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Furnace Acid
Phosphoric acid made from elemental phosphorus. Also called dry
process phosphoric acid.
Ganque
The minerals and rock mined with a metallic ore but valueless in
themselves or used only as a by-product. (73)
Hydrolysis
A chemical reaction in which water reacts with another substance
to form one or more new substances. (73)
Immiscible
The property of one liquid being unable to mix or blend uniformly
with another.
1
liter.
MCP
Monocalcium Phosphate Monohydrate, Ca(H£POj±)2 - H£0.
Nodule
Semi-fused agglomerated and calcined phosphate rock particle.
Product .
Phosphorus
Sludge or emulsion of phosphorus, dust and water.
Phosphorus Oxych^ryle
POC13.
Phosphorus Pentasulfide
P2S5.
Phosphorus Pentoxide
152
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PJlosphorus Trichloride
Phossv Water
Water containing colloidal phosphorus.
Process Water
Any water which, during the manufacturing process, comes into
direct contact with any raw material, intermediate product, by-
product, waste product or finished product.
The fused agglomerate which separates in metal smelting and
floats on the surface of the molten metal. Formed by combination
of flux with gangue of ore, ash of fuel, and perhaps furnace
lining. The slag is often the medium by means of which
impurities may be separated from metal. (73) .
STP
Sodium Tripolyphosphate, Na^PSOIJ.
TCP
Tricalcium Phosphate, Cal(PO£)2.
Transport Water
(1) Water used to carry solids from a site in a slurry form.
(2) Water accompanying a chemical in transport which is either
immiscible with water or highly insoluble in water. The water
a?^! fS * t?la?ket Preventing contact of air or other substances
with the chemical.
wet Process
Phosphoric acid made from phosphate rock and sulfuric acid.
153
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TABLE 20
METRIC UNITS
CONVERSION TABLE
MULTIPLY (EKCLISH UNITS)
ENGLISH UNIT ABBREVIATION
acre ac
aere -feet a c f t
British Thermal
Unit BTU
British Thermal BTU/lb
Unit/pound
cubic feet/minute cfm
cubic feet/second cfs
cubic'feet cu ft
cubic feet cuft
cubic inches cu in
degree Fahrenheit °F
feet ft
gallon .gal
gallon/minute gpm
horsepower hp
inches in
inches of mercury in Hg
pounds Ib
million gallons/day mgd
ciil'e ' mi
pound/square inch psig
(gauge)
square feet sq ft
square inches sq in
tons (short) ton
yard yd
by TO OBTAIN (METRIC UNITS)
CONVERSION ABBREVIATION METRIC UNIT
hectares
cubic meters
0.405
1233.5
0.252
0.555
0.028
1.7
0.028
28.32
16.39
0.555(°F-32)*
0.3048
3.785
0.0631
0.7457
2.54
0.03342
0.454
3,785
1.609
ha
cu m
kg cal
kg cal/kg
cu ra/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu in/day
kn
(0.06805 psig +l)*atm
0.0929
6.452
0.907
0.9144
sq m
sq cm
kkg
m
kilogram-calories
kilogram calories/
kilogram'
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters.
liters/second
killowatts
centimeters
atmospheres.
kilograms
cubic neter.s/day
kilometer
atmospheres
(absolute)
square meters
square centimeters
metric tons
(1000 kilograms)
meters
* Actual conversion, not a multiplier
154
•US. GOVERNMENT PRINTING OFFICE: 1974 544-317/301 1-3
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