Draft
Supplement to Development Document
For Effluent Limitations Guidelines
And New Source Performance Standards
For the
Phosphorus Derived Chemicals
Segment of the
Phosphate Manufacturing
Point Source Category
Contract No 68-O1-3289
Prepared For
Effluent Guidelines Division
Office of Water and Hazardous Materials
U.S. Environmental Protection Agency
Washington, D.C. 20460
OCTOBER, 1977
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NOTICE
The attached document is a DRAFT CONTRACTOR'S REPORT. It includes technical
information and recommendations submitted by the Contractor to the United States
Environmental Protection Agency ("EPA") regarding the subject industry. It is being
distributed for review and comment only
The report, including the determinations and recommendations, will be undergoing
extensive review by EPA, Federal and State agencies, public interest organizations, and
other interested groups and persons during the coming weeks. The report and in particular
the Contractor's determinations and recommendations are subject to change in any and
all respects
The regulations to be published by EPA under Sections 301, 304(b), and 306 of the
Federal Water Pollution Control Act, as amended, will be based to a large extent on this
report and the comments received on it. However, pursuant to Sections 301, 304(b),
and 306 of the Act, EPA will also consider additional pertinent technical and economic
information that is developed in the course of review of this report by the public and within
EPA. EPA is currently performing an economic impact analysis regarding the subject
industry, which will be taken into account as part of the review of the report. Upon
completion of the review process, and prior to final promulgation of regulations, an EPA
report will be issued setting forth EPA's conclusions concerning the subject industry and
effluent I imitations guidelines applicable to the industry. Judgments necessary for
promulgation of regulations under Sections 301, 304(b), and 306 of the Act, of course,
remain the responsibility of EPA Subject to these limitations, EPA is making this draft
contractors report available in order to encourage the widest possible participation of
interested persons in the decision-making process at the earliest possible time.
This report shall have standing in any EPA proceeding or court proceeding only to
the extent that it represents the views of the Contractor who studied the subject industry
and prepared the information and recommendations. It cannot be cited, referenced, or
represented in any respect in any such proceedings as a statement of EPA's views
regarding the subject industry.
U.S. Environmental Protection Agency
Office of Water and Hazardous Materials
Effluent Guidelines Division
Washington, D.C. 20460
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DRAFT
SUPPLEMENT TO DEVELOPMENT DOCUMENT FOR
EFFLUENT LIMITATIONS GUIDELINES
AND NEW SOURCE PERFORMANCE STANDARDS
FOR THE
PHOSPHORUS DERIVED CHEMICALS
SEGMENT OF THE
PHOSPHATE MANUFACTURING
POINT SOURCE CATEGORY
Contract No: 68-01-3289
Prepared for
Effluent Guidelines Division
Office of Water and Hazardous Materials
U.S. Environmental Protection Agency
Washington, DC 20460
OCTOBER, 1977
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ABSTRACT
This document presents the findings of an extensive study of the phosphorus
derived chemicals industry for the purpose of revising effluent limitations
guidelines, Federal standards of performance, and pretreatment standards
to implement Sections 301, 30-4, 306, and 307 of the "Act". The study
was conducted in response to the technical issues raised by the U.S.
Court of Appeals for the Second Circuit in its opinion of April 28,
1976 (74-1683 and 74-1687). Certain portions of the effluent regulations
for the phosphorus derived chemicals industry were remanded by the Court
in its decision.
The determinations and recommendations contained herein set forth the
degree of effluent reduction attainable through the application of the
best practicable control technology currently available and the degree
of effluent reduction attainable through the application of the best
available technology economically achievable, which must be achieved by
existing point sources by July 1, 1977, and July 1, 1983, respectively.
The achievable effluent levels for new sources contained herein set
forth the degree of effluent reduction that is achievable through the
application of the best available demonstrated control technology,
processes, operating methods, or other alternatives.
Supporting data and rationale for development of effluent limitations
guidelines and standards of performance are contained in this report.
This report was submitted by Sverdrup & Parcel and Associates, Inc.,
in partial fulfillment of Contract #68-01-3289 under the sponsorship of
the Effluent Guidelines Division, Environmental Protection Agency.
111
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TABLE OF CONTENTS
Section Page
I Conclusions 1
II Summary of Achievable Effluent Levels 3
III Introduction 7
IV Industry Categorization 53
V Water Use and Waste Characterization 57
VI Selection of Pollutant Parameters 87
VII Control and Treatment Technology 105
VIII Costs, Energy, and Non-Water Quality Aspects 161
IX Effluent Reduction Attainable Through the
Application of the Best Practicable Control
Technology Currently Available 187
X Effluent Reduction Attainable Through the
Application of the Best Available Technology
Economically Achievable 205
XI Effluent Reduction Attainable at New
Plants and Pretreatment Considerations 217
XII Acknowledgments 223
XIII References 225
XIV Glossary 231
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DRAFT:
TABLES
Number Page
1 Annual U.S. Production of Phosphorus
Derived Chemicals 18
2 Current Posted Selling Prices of
Phosphorus Derived Chemicals 19
3 Producers of Phosphorus and Phosphorus
Derived Chemicals 20
4 Impurities in Phosphoric Acid 34
5 Composition of Commerical Phosphate Rock 64
6 Summary of Raw Wastes from Elemental Phosphorus
Manufacture 70
7 Minor Wastes from Plant 11 (PC13_ and POC13) 77
8 Raw Waste Loads from PC13_ and POC13 Manufacture 78
9 Summary of Raw Waste Loads from Phosphorus
Consuming Plants 81
10 Summary of Raw Wastes from Phosphate Plants 86
11 Waste Water Constituents of Phosphorus Derived
Chemicals Category 103
12 Summary of Control and Treatment Results at
Elemental Phosphorus Plants 132
13 Effluent Data from Plant 9 134
14 Effluent Data from Plant 5 135
15 Water Quality Produced by Various Ion
Exchange Systems 153
16 Treatment Alternatives 162
17 Treatment Alternatives, Cost - Effluent
Quality Comparison 166
18 Energy Requirements for Achievable
Effluent Levels 185
19 Metric Units Conversion Table 234
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FIGURES
Number Page
1 Flow of Materials in the Phosphorus
Derived Chemicals Industry 15
2 Elemental Phosphorus Plant Locations 23
3 Phosphoric Acid (Dry Process) Plant
Locations 2-4
4- Phosphorus Derivative Plant Locations 25
5 Sodium Phosphate Plant Locations 26
6 Calcium Phosphate Plant Locations 27
7 Standard Phosphorus Process Flow Diagram 29
8 Standard Phosphoric Acid Flow Diagram
(Dry Process) 35
9 Variations of Phosphoric Acid (Dry)
Process 37
10 Phosphorus Pentoxide Process Flow Diagram 38
11 Phosphorus Pentasulfide Process Flow Diagram -40
12 Phosphorus Trichloride Process Flow Diagram 42
13 Standard Phosphorus Oxychloride Process Flow
Diagram 45
14 Alternate Phosphorus Oxychloride Process
Flow Diagram 46
15 Sodium Tripolyphosphate Process Flow Diagram
(Food and Non-Food Grade) 48
16 Food-Grade Calcium Phosphates Process Flow
Diagram 49
17 Feed-Grade Calcium Phosphate Process Flow
Diagram 51
18 Plant 31 Waste Treatment Process 145
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 producing, 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 P205 were included for the same reasons. Processes that
manufacture' phosphates as fertilizers are regulated by the fertilizer
manufacturing regulations.
The phosphorus producing subcategory of the industry is characterized by
large quantities 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, seven of the nine plants within this segment have
eliminated discharge of phossy water. The other two plants discharge
treated phossy water only in the event of excessive rainfall.
Three elemental phosphorus plants have no discharge of phossy water,
process waste waters, or other waste waters, including storm water
runoff. Six plants anticipate no discharge of phossy water or other
process waste waters even in the case of excessive rainfall conditions.
Two of these plan to install additional facilities to achieve complete
recycle. The total recycle of process water without any discharge has
been demonstrated as practicable using control technology currently
available.
The phosphorus consuming subcategory of the industry is characterized by
the absence of direct process waste water; the processes are kept essen-
tially dry because the chemicals produced are readily hydrolyzed.
However, water is universally used for air pollution abatement scrubbing
of tail gases, for periodic cleaning of reaction vessels, and for the
general washing of shipping containers, all resulting in acidic waste
waters. In addition, water 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
eliminate discharge of aqueous wastes), this segment has not yet achieved
significant reduction of pollutants.
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The application of currently available technology may not achieve total
recycle of process waste waters from P2S5_, PC13, and POC13_ manufacture.
Nevertheless, technologies for the treatment of" these process waste
waters and other waste waters are transferable from other industries to
permit substantial reduction in the quantities of pollutants discharged.
Transferable technologies include precipitation with lime, clarification,
sludge dewatering, filtration, neutralization, recycle of scrubber and
other process waste waters, segregation of uncontaminated storm water,
treatment of contaminated storm water, the use of cooling towers for
reducing the volume of contaminated cooling water, and alkaline chlorina-
tion. The universal practice for the handling of phossy water is shipment
back to the phosphorus producer. Thus, "no discharge" of phossy water
is being achieved at phosphorus consuming plants, but discharge of other
waste waters without adequate treatment to control pollutants is a
common practice at this time.
The phosphate segment of the industry (chemicals manufactured from
phosphoric acid) is characterized by acids and by finely-divided solids
in the raw aqueous wastes. Several plants already operate without
discharge of process waste water by in-process controls and by end-of-
process treatment, and this study shows how this segment may operate
without discharge of process waste water by applying currently available
practicable technology. Outside contamination of the process waste
waters resulting from the manufacture of food grade sodium tripoly-
phosphate, other food-grade soluble phosphates, and food-grade calcium
phosphates may prevent their reuse at existing plants, and discharge after
suitable treatment may be required.
The industry has indicated that elemental phosphorus and total phosphorus
originating from raw materials, intermediates, and products have been
detected in storm water runoff in all three subcategories of this industry.
Methods such as storm water containment, segregation, diversion, impound-
ment, treatment, and analytical monitoring can be cited from each of the
phosphorus derived chemicals industry subcategories. These methods are
applicable for controlling site storm water runoff to avoid any significant
unmonitored or uncontrolled discharge of process waste water pollutants
to navigable waterways.
Similarly, some plants from all three subcategories report incidental
contamination of noncontact cooling water by process waste water pollutants.
Some plants in this segment use cooling towers and some recycle blowdown
to the processes. This study revealed the need for discharge or treatment
and discharge of incidentally contaminated storm water runoff, incidentally
contaminated noncontact cooling water, and other incidentally contaminated
waste water.
The elemental phosphorus production subcategory generates the highest
waste loads and volumes within the industry, but most plants have solved
their major problems. The remainder of the industry, made up of much
smaller-volume plants, has lagged behind in effluent reduction, but
technology is available to provide uniform pollution control throughout
the industry.
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SECTION II
SUMMARY OF ACHIEVABLE EFFLUENT LEVELS
Average achievable effluent levels for the various subcategories of the
phosphorus derived chemicals industry are summarized below. These
levels were determined for the best practicable control technology
currently available (BPT or 1977 technology), for the best available
technology economically achievable (BAT or 1983 technology), and for new
sources.
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
The best practicable control technology currently available, when
applied to the phosphorus producing, phosphorus consuming, and phosphate
subcategories, can achieve the following average levels of waste water
pollutants (all figures except pH are in kg of pollutant per kkg of
product or lb/1,000 Ib):
Elemental
Phosphorus
Phosphoric
Acid
Phosphorus Phosphorus
Pentoxide Pentasulfide
Phosphorus
Trichloride
Total Phosphorus
Suspended Solids
Fluoride
Arsenic
Elemental Phosphorus
Sulfide
pH
0.15
0.5
0.05
N.D.**
0.044
0.004
2.6 x 10'
N.D.
-5
0.024
0.011
N.D.
0.039*
0.018
N.D.
0.01
Within the range 6.0 to 9.0 for all subcategories
0.05
0.025
2.5 x 10'
N.D.
-5
Sodium Tripolyphosphate
(and Other Soluble Phosphates) Calcium Phosphates
Total Phosphorus
Suspended Solids
Fluoride
Arsenic
Elemental
Phosphorus
Sulfide
PH
Phosphorus
Oxychloride
0.05
0.025
_
Food
Grade
0.018
0.008
_
Non-food
Grade
0.0044
0.002
_
Food
Grade
0.17
0.072
_
Feed
Grade
0.026
0.012
0.01
2.5 x 10 '
N.D. - -
Within the range 6.0 to 9.0 for all subcategories
* Achievable level is for orthophosphate (as P).
** Not detectable; as of this writing, 0.5 ppb (ug/l) of elemental phosphorus
in water is considered detectable in a manufacturing plant.
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Okar!
Plants that manufacture PC13_ or POC13_ may need to reduce the level of
chlorine in their waste waters prior to discharge. Circumstances vary
from plant to plant, and evaluations will be required on an individual
plant basis. This is discussed further in Section IX, and available
technologies for dechlorination are discussed in Section VII.
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
For elemental phosphorus manufacture, the best available technology
economically achievable can eliminate discharge of pollutants to navigable
waterways.
The best available technology economically achievable, when applied to
the phosphorus consuming and phosphate subcategories, can achieve the
following average levels of waste water pollutants (all figures except
pH are in kg of pollutant per kkg of product or lb/1,000 Ib):
Phosphoric
Acid
Phosphorus
Pentoxide
Phosphorus Phosphorus Phosphorus
Pentasulfide Trichloride Oxychloride
Total Phosphorus
Suspended Solids
Fluoride
Arsenic
Elemental
Phosphorus
Sulfide
PH
3.6 x 10
3.6 x 10
"3
~3
1.7 x 10
1.7 x
~3
1.5 x 10
1.5 x 10"
0.0011
3.3 x 10
-5
3 x 10
3 x 10
-5
-5
2.6 x 10
N.D.
-5
N.D.
N.D.
5.5 x 10
N.D.
-7
N.D.
5 x
Within the range 6.0 to 9.0 for all subcategories
Sodium Tripolyphosphate
(and Other Soluble Phosphates)
Total Phosphorus
Suspended Solids
Fluoride
Arsenic
Elemental
Phosphorus
Sulfide
PH
Food
Grade
0.0021
0.0021
Non-Food
Grade
0.0012
0.0012
Calcium Phosphates
Food
Grade
0.011
0.011
Feed
Grade
2 x 10
2 x 10
6 x 10
-3
-3
-3
Within the range 6.0 to 9.0 for all subcategories
As discussed above for best practicable technology (BPT), dechlorination
may be required for PC13 and POC1_3_ waste waters. The need for this
additional treatment should be determined on a plant-by-plant basis.
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EFFLUENT REDUCTION AT NEW SOURCES
It was determined that the achievable effluent levels for new plants are
identical to those that can be achieved at existing plants employing
best available technology economically achievable (BAT). These levels
are summarized above for each product in the phosphorus derived chemicals
industry.
PRETREATMENT
It was determined that discharge of waste waters from elemental phosphorus
production to municipal treatment systems would be environmentally
undesirable. These waste waters contain objectionable pollutants, and
are best handled by treatment and recycle at the manufacturing plant.
For the phosphorus consuming subcategory, pretreatment is recommended
before discharge to publicly owned treatment works. The technologies
recommended for BPT and BAT are applicable for pretreatment and will
provide control of elemental phosphorus, arsenic, fluoride, and sulfide.
In all cases, pH can be held between 6.0 and 9.0.
The principal pollutant from the phosphate manufacturing subcategory is
phosphate, which is incompatible with secondary treatment plants.
Phosphate is compatible with tertiary treatment plants designed to
remove phosphate, and pretreatment might not be necessary if the municipal
plant is capable of accepting and removing the waste load from a phosphate
manufacturing plant.
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SECTION III
INTRODUCTION
The United States Environmental Protection Agency has the responsibility
of issuing regulations limiting the discharge of pollutants from the
phosphorus derived chemicals segment of the phosphate manufacturing
industry point source category. Regulations for this industry were
originally promulgated on February 20, 1974 (Federal Register, vol. 39,
pp. 6579-6588). The final Development Document for Effluent Limitations
Guidelines and New Source Performance Standards (EPA-4<40/l-74-006a) was
published in January, 1974.
The United States Court of Appeals for the Second Circuit decided on
April 28, 1976, to set aside certain portions of the regulations and
remand them to EPA for further study. The Court ordered EPA to restudy
areas where the record was ruled to be inadequate. The present document
and revised regulations are the result of this restudy.
PURPOSE AND AUTHORITY - GENERAL
Section 30l(b) of the Act requires achievement by not later than July 1,
1977, of effluent limitations for point sources, other than publicly
owned treatment works, that 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 30l(b)
also requires achievement by not later than July 1, 1983, of effluent
limitations for point sources, other than publicly owned treatment
works, that are based on application of the best available technology
economically achievable. The 1983 technology must 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 304(b) of the Act. Section 306
of the Act requires achievement by new sources of a standard of perform-
ance providing for control of the discharge of pollutants reflecting the
greatest degree of effluent reduction that the Administrator determines
to be achievable through application of the best available demonstrated
control technology, processes, operating methods, or other alternatives.
This includes, where practicable, a standard permitting no discharge of
pollutants.
Section 304(b) of the Act requires the Administrator to publish within
one year of the enactment of the Act, regulations providing guidelines
for effluent limitations setting forth the degree of effluent reduction
attainable through application of the best control measures and practices
achievable including treatment techniques, process and procedure innova-
tions, 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.
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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
(vol. 38, p. 1624), a list of 27 source categories. Publication of the
list constituted announcement of the Administrator's intention to estab-
lish, under Section 306, standards of performance applicable to new
sources within the phosphate manufacturing point source category.
SUMMARY OF DEVELOPMENT METHODS FOR THE REGULATIONS PROMULGATED IN 1974
The Environmental Protection Agency determined that a rigorous approach
was necessary for the promulgation of effluent limitations for industrial
sources. This approach included the following:
(l) Categorization of the industry and determination of those
industrial categories for which separate effluent limitations and
standards needed to be set;
(2) Characterization of the waste loads resulting from discharge
within industrial categories and subcategories;
(3) Identification of the range of control and treatment technology
within each industrial category and subcategory;
(4) Identification of those plants having the best practical
technology currently available (exemplary plants); and
(5) Generation of supporting verification data for the best practical
technology, including actual sampling of plant effluents by field teams.
The culmination of these activities was the development of the guidelines
and standards promulgated on February 20, 1974.
For the purpose of the study, the phosphorus derived chemicals industry
was defined 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 were
developed in the following manner. The point source category was first
subcategorized to determine whether separate limitations and standards
were appropriate for different segments within a point source category.
Such categorization was based on raw material used, product produced,
manufacturing process employed, and other factors. The raw waste character-
istics for each subcategory were then identified. This included an
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analysis of (l) 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 pollutants and substances causing taste, odor, and color in water
or aquatic organisms. The constituents of waste waters that should be
subject to effluent limitations guidelines and standards of performance
were identified.
The full range of control and treatment technologies existing within
each subcategory was identified. This included an identification of
each distinct control and treatment technology, including both in-plant
and end-of-process technologies that were existent or capable of being
designed for each subcategory. It also included an identification of
the effluent level resulting from the application of each of the treatment
and control technologies, including the amounts of constituents (including
thermal) and the chemical, physical, and biological characteristics of
pollutants. The required implementation time was also identified. In
addition, the non-water quality environmental impact was identified,
including effects of application of such technologies on pollution
problems such as air, solid waste, noise, and radiation. The energy
requirement of each control technology was identified as well as the
cost of application.
The information 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
such 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 such application, age of the
equipment and facilities involved, process employed, engineering aspects,
process changes, non-water quality environmental impact (including
energy requirements and solid waste disposal), and other factors.
The data for identification and analysis were derived from a number of
sources. These sources included EPA research information; published
literature; previous EPA technical guidance for inorganic chemicals,
alkali, and chlorine industries; qualified technical consultation; and
on-site visits and interviews at selected manufacturing plants throughout
the United States. References used in developing the original guidelines
for effluent limitations and standards of performance for new sources
are listed in Section XIII of this document. Five companies in the
phosphorus derived chemicals industry were contacted, representing about
80 percent of the industry in terms of production. A breakdown of the
data base is listed below:
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p. •' -.
L-'i »,
Chemical Number of Plants in Data Base
NPDES Total
Inspected Sampled Application Plants
P^ 3 2* 2 10
H3P04 2 1* 2 23
P?05_ 111 3
P2S£ 222 7
PC12 222 6
POC13 222 4
Na5P3010 2 1* 1 17
Calcium Phosphates
(Food Grade) 111 4
. (Feed Grade) 111 9
* 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.
AUTHORITY FOR RESTUDY
On April 28, 1976, the Second Circuit Court of Appeals set aside certain
parts of EPA's phosphorus industry regulations promulgated February 20,
1974, and remanded them to the EPA for further study, as follows.
Definition of_ "Process Waste Water"
The Court remanded the regulation defining "process waste water" so the
EPA might assess the relationship of this definition to rainfall runoff,
and to leaks and spills.
1977 Limits for Phosphorus Manufacturing
The only defect found by the Court was that there is "no provision for
excess rainfall or discharge after storms which will assertedly increase
the discharge flow and hence the pounds of pollutants discharged."
1983 Limits and New Source Standards for Phosphorus Manufacturing
The Court found the same "rainfall" defect as it did in the 1977 regulation.
Additionally, the Court determined that EPA, in setting a limit of "no
discharge of process waste water pollutants", did not adequately consider
the availability and costs of cold weather adjustments. According to
the Court, a "practical consideration of costs" is needed. The main
problem cited by the Petitioners was that freezing of settling ponds
could occur.
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r i
1977 Limits for Phosphorus Pentasulfide
The technology proposed by EPA for "no discharge of process waste water
pollutants" included inert or vacuum casting of P2S5_ and total recycle
of waste water. EPA agreed to a voluntary remand to reassess the tech-
nology upon which it based the 1977 limits because they were based
solely on fundamental changes in the basic manufacturing process. The
Court concurred, setting aside the regulation and remanding to EPA for
further study. The Court agreed with EPA's view that no "in-process
changes can be mandated for 1977 unless they may be considered normal
practices within the industry." However, the Court indicated that it
was permissible for EPA to identify as best practicable technology
certain in-plant controls if they may, by simple modifications, enable
the phosphorus pentasulfide industry to achieve the objectives of the
1977 limits.
1983 Limits and New Source Standards for Phosphorus Pentasulfide
The same technology for "no discharge" was proposed by EPA for 1983 and
new sources as for the 1977 standard, namely, inert gas or vacuum casting
of P2S^ to avoid or reduce evolution of sulfur dioxide fumes, which
require water scrubbing, and the total recycle of scrubber waste water
with neutralization. The Court concluded that EPA's record did not
support the technology transfer of inert or vacuum casting in that no
explanation was given as to how this technology used in other chemical
industries could be adapted to P2S5 manufacture. The Court also concluded
that EPA's record did not support" ""total recycle" of waste water inasmuch
as EPA failed to adequately explain how the problem of scaling by sulfite
and sulfate precipitates in the recycle system could be avoided without
periodic "blowdown." Additionally, the Court found that the EPA had
neglected the problem of eliminating the discharge of waste water other
than that produced in the "casting" part of the production process. For
these reasons, the 1983 regulation for P2S5 was set aside and remanded
to the EPA for further study. However, the~Court stated that EPA may
adhere to a no discharge limit if the record supports it.
1983 Limits and New Source Standards for Phosphorus Trichloride and Oxychloride
'In establishing limitations, EPA assumed the principal source of waste
water pollutants was water scrubbing of PC1_3_ and POC13_ vapors. Technolo-
gies proposed to achieve "no discharge" were reduction in PC13 or POC13
vapor load by use of refrigerated condensers, recycle of scrubber liquors,
lime treatment, settling, landfilling of sludge, and evaporation of the
treated effluent. The Petitioners challenged EPA's conclusions that
refrigerated condensers would reduce PC13 or POC13_ vapor loads by the 90
percent assumed, that 90 percent reduction in waste water generated
would result, and that evaporation of the final treated effluent was an
"available" technology. Petitioners .also claimed that energy and cost
factors were miscalculated or ignored, and that solid waste pollution
caused by consumption of fuel for evaporation was not addressed. EPA
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agreed to reassess the limitations because energy requirements were not
adequately evaluated. EPA still contended that a basis for the regulation
existed in the record and that the standard of no discharge was achievable.
1977, 1983, and New Source Limits for Food Grade Sodium Tripolyphosphate;
1983 Limits and New Source Standards for Food Grade Calcium Phosphates'
Petitioners' basic argument was that stringent purity requirements for
food grade phosphate products prevent total recycle of waste waters as
proposed for the achievement of "no discharge." The EPA agreed to a
voluntary remand to reassess the position urged by Petitioners.
SUMMARY OF DEVELOPMENT METHODS USED FOR THE REMAND STUDY
The present remand study makes use of existing data for the industry
from the EPA files, including the 1974 Development Document, the Court
record, and a 1975 sampling study requested by the EPA.
Data on manufacturers, plant locations, and products were validated and
updated. Seventeen phosphorus industry on-site plant visits and inter-
views were conducted during the period from August, 1976 to February,
1977. A data collection portfolio (DCP) was developed for distribution
by the EPA to 45 plants in the segment. The DCP was distributed in
January, 1977, and replies were received between March and June, 1977.
EPA received and reviewed 38 replies. Literature searches for several
aspects of the investigation were conducted. Development Documents for
related industries were reviewed for possible transfer of technology,
including the following: Fertilizer Manufacturing, Phase II of Phosphate
Manufacturing, Steam Electric Power Generation, Iron and Steel Manufactur-
ing, Nonferrous Metals Manufacturing, Organic Chemicals Manufacturing,
Inorganic Chemicals Manufacturing, Ore Mining and Dressing Industry,
Leather Tanning and Finishing Industry, Pulp Paper and Paperboard Mills,
and Ferroalloy Manufacturing. EPA Process Design Manuals for Phosphorus
Removal and for Sulfide Control in Sanitary Sewerage Systems were reviewed
for possible technology transfer.
Data were available from the industry for several plants in responses to
an EPA request for 30-day sampling studies. Requests were made to six
phosphorus derivative plants, five of which performed sampling studies
and provided data. In addition, one company provided estimated data on
food grade phosphate operations at three of its plants. These data were
received by EPA during the period May to September, 1975.
All published references used in the remand study are listed in Section
XIII of this document.
For the purposes of the remand study, sodium tripolyphosphate and calcium
phosphate (non-fertilizer) were subdivided as follows:
12
-------
\F
Sodium Tripolyphosphate (Food Grade)
Sodium Tripolyphosphate (Non-Food Grade)
Calcium Phosphates (Food Grade)
Calcium Phosphates (Animal Feed Grade)
In at least one instance, a plant noted they had combined all sodium
phosphates and reported as an equivalent amount of sodium tripolyphosphate
for the purpose of the original study (1974 Development Document).
During the remand study, specific information was solicited for other
soluble phosphates manufactured from furnace grade acid because some are
manufactured in significant quantities. These soluble phosphates include
sodium, potassium, and ammonium phosphates. In most cases, these phosphates
are produced in a manufacturing complex that does or did produce sodium
tripolyphosphate, and the wastes are comparable to but not segregated or
handled separately from sodium tripolyphosphate wastes. In this report,
pollutant quantities are expressed in terms of total quantity of finished
product (e.g., kg of pollutant per kkg of phosphates produced).
A breakdown of the remand study data base follows:
Chemical Number of Plants in Data Base (1976-1977)
_
P205
P2S5
PClJ
POCl.3
Na5P3010
(Food Grade)
(Non-Food Grade)
Calcium Phosphates
(Food Grade)
(Feed Grade)
Other Sodium
Phosphates
Potassium Phosphates
Ammonium Phosphates
Plant
Inspection
2
1
3
5
5
(3)
3
1
(2)
2
0
1
1
0
1975 NPDES
Sampling Permit
Study Applic.
1
5
4
1
3
(1)
1
Total
Plants
9
21
3
7
7
6
12
5
7
13
4
9
11
7
2
Data, narrative, figures, and tables published in the original 1974
Development Document were used where not found at fault by the Court or
when found to be clear, accurate, and logical as far as could be deter-
mined by the remand study and by best engineering judgment.
13
-------
GENERAL DESCRIPTION OF THE INDUSTRY
The industry covered by this document is the phosphorus derived chemicals
segment of 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
ferropho sphorus
phosphoric acid (dry process)
phosphorus pentoxide
phosphorus pentasulfide
phosphorus trichloride
phosphorus oxychloride
sodium tripolyphosphate
calcium phosphates (food grade)
calcium phosphates (animal feed grade)
As previously mentioned, sodium tripolyphosphate has now been split into
food grade and non-food grade. Other soluble phosphates (sodium,
ammonium, potassium) were also studied. Other phosphorus and phosphate
chemicals are expected to be covered in more detail as BAT is periodically
updated to utilize novel technological improvements.
The flow of materials in the phosphorus derived chemicals 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 to plant siting decisions 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.
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. Other
by-products of elemental phosphorus production include furnace slag and
electrostatic precipitator dust. Some phosphorus furnace slag is sold
as aggregate for road building, in structural concrete block, and in
roof construction. Its use in these ways, however, may be limited by
its radioactivity, depending upon the source of the phosphate ore and
the availability of other aggregate sources. Some furnace electrostatic
precipitator dust has been sold for its content of rare metals.
Approximately 90 percent of the elemental phosphorus produced is used to
manufacture high-grade phosphoric acid by the furnace or "dry" process.
About 15 to 20 percent of phosphoric acid produced in the country is
made by this "dry" process. The remaining 80 to 85 percent is made by
14
-------
•DRY" OR "FURNACE1
PROCESS
PHOSPHORIC
ACID
SOLUBLE
PHOSPHATES
(SODIUM. POTASSIUM
AND AMMONIUM)
INSOLUBLE
PHOSPHATES
(CALCIUM
PHOSPHATES)
FIGURE 1
FLOW OF MATERIALS IN THE PHOSPHORUS
DERIVED CHEMICALS INDUSTRY
-------
the "wet" process, which converts phosphate rock directly into phosphoric
acid by reaction with other acids and does not utilize elemental phos-
phorus. This lower-grade wet process acid is primarily used in the
fertilizer industry and is separately discussed in that report. Defluorin-
ated wet process phosphoric acid is discussed in the "Other Non-
Fertilizer Phosphate Chemicals" segment of the Phosphate Manufacturing
industry.
The elemental phosphorus not converted into acid is either marketed
directly or converted to chemicals such as phosphorus pentoxide, phos-
phorus 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. Phos-
phoric acid is also used to manufacture two basic classes of phosphates:
water-soluble phosphates used primarily in detergents, for water treat-
ment, and for food uses, typified by sodium tripolyphosphate; and water-
insoluble phosphates that are used primarily in animal feeds and in
foods, typified by the calcium phosphates.
The processes involved in the non-fertilizer phosphorus chemicals industry
are very briefly summarized below:
Elemental phosphorus and ferrophosphorus are manufactured by the reduction
of phosphate rock by coke in large electric furnaces, using silica as a
flux. Large quantities of water are circulated for cooling the very hot
equipment, for cooling 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 purification. This study is concerned with
manufacturing operations subsequent to receiving washed phosphate ores
at the phosphorus production facility. Ore benefication is commonly but
not exclusively conducted at a separate off-site location. The huge
waste load from benefication, 7500 kg of gangue per kkg of phosphorus
eventually produced, warrants a separate study as a segment of the
mining industry.
Phosphoric acid manufactured by the "dry" or furnace process consists of
the burning of liquid phosphorus in air, the subsequent quenching and
hydrolysis of the P205_ vapor, and the collection of the phosphoric acid
mists. The operation uses cooling water, and process water is consumed
in making the aqueous acid. Solid wastes may be generated if the plant
later purifies the acid.
The manufacture of the anhydrous phosphorus chemicals (P205_, P2_S5_, and
PC13) is essentially by the direct union of phosphorus with the corres-
ponding element. Phosphorus oxychloride, POC13, is manufactured from
16
-------
PC13 and air or from PC13, P205_, and chlorine. Water uses are limited to
cooling, transferring elemental phosphorus, wet scrubbing, and washing
of reaction vessels and shipping containers.
Sodium tripolyphosphate is manufactured by the neutralization of phos-
phoric 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.
Other soluble orthophosphates of sodium, potassium, and ammonia are
manufactured by the neutralization of phosphoric acid with the appropriate
proportions of caustic soda, soda ash, caustic potash, or ammonia in mix
tanks. The resulting slurries or solutions are usually dried directly,
although crystallization and centrifugation steps may precede the drying
operation. The condensed or hydrolyzable phosphates (poly, meta, or
pyro) of sodium or potassium may be produced by calcining the appropriate
dried orthophosphate or orthophosphates, or by a combined drying-
calcining step for the mix tank solution or slurry to achieve the required
molecular dehydration.
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 anhydrous monocalcium
phosphate, monocalcium phosphate monohydrate, dicalcium phosphate di-
hydrate, or tricalcium phosphate is the final product. The condensed or
hydrolyzable phosphates of calcium are made by adding a calcination step
or by the use of a combined drying-calcining step.
Table 1 lists 1975 production tonnages for phosphorus derived chemicals
as reported by the U.S. Bureau of Census (l). As seen from this table
the industry is relatively small in relation to numbers of plants.
Table 2 lists the current selling prices of the chemicals within the
industry. Table 3 lists the producers of phosphorus products.
Figures 2 through 6 indicate plant locations within the phosphorus
derived chemicals industry. Figure 2 shows elemental phosphorus plants,
Figure 3 shows phosphoric acid (dry process) plants, Figure 4 indicates
phosphorus derivative plants (P205_, P2S5_, PC13_, POC13), Figure 5 indicates
sodium phosphate plants, and Figure 6 shows the locations of calcium
phosphate plants.
17
-------
TABLE 1
ANNUAL U.S. PRODUCTION OF PHOSPHORUS DERIVED CHEMICALS
Chemicals Metric Tons Short Tons Number of Plants
Phosphorus
Red and White 408,000 450,000 9
Phosphoric Acid
from Phosphorus 710,000 782,000 24
Phosphorus Pentoxide 7,000 8,000 3
Phosphorus Pentasulfide 56,000 61,000 6
Phosphorus Trichloride 75,000 82,000 6
Phosphorus Oxychloride 31,000 35,000 4
Sodium
Tripolyphosphate 699,000 770,000 15
Calcium Phosphates
Animal Feed 1
Other Grades Except > 473,000 522,000 9
Fertilizer J
Notes: 1. All figures are for year 1975.
2. Source - Industrial Reports, Inorganic Chemicals,
U.S. Bureau of Census, Series M28A (75)-14.
3. Phosphorus pentoxide figures are independently estimated.
4. Animal feed grade calcium phosphate is actually not an
elemental phosphorus derived product, since wet process
phosphoric acid is used as the raw material.
18
-------
TABLE 2
CURRENT POSTED SELLING PRICES OF PHOSPHORUS DERIVED CHEMICALS
Chemical Grade
White Phosphorus
Phosphoric Acid 75% Commercial & Technical
(Furnace) 30% Commercial & Technical
85% Commercial & Technical
Phosphorus Pentoxide
Phosphorus Trichloride Tanks
Phosphorus Pentasulfide Drums
Tote bins
Phosphorus Oxychloride
Sodium Tripolyphosphate Tech bags
Bulk hopper cars
Food
Monocalcium Phosphate Monohydrate Food
Anhydrous Food
Dicalcium Phosphate Feed
USP Food dihydrate
USP Food anhydrous
Dentrifice
Selling :
$/Metric Ton
1345
320
384
1102
728
871
772
816
480
452
628
461
596
90
553
285
285
Tricalcium Phosphate
503
$/Short Ton
1220
290
312
348
1000
660
790
700
740
435
410
570
418
541
82
502
259
259
456
Notes: 1. Food grade phosphoric acid prices are $40/short ton
above technical grade.
2. Source: Chemical Marketing Reporter, May 30, 1977.
-------
»
TABLE 3
PRODUCERS OF PHOSPHORUS AND
PHOSPHORUS DERIVED CHEMICALS
Company
Elemental Phosphorus
Electro-Phos Corporation
FMC Corporation
Hooker Chemicals & Plastics
Mobil Chemical Company
Monsanto Company
Stauffer Chemical Company
Dry Process Phosphoric Acid
FMC
Hooker
Mobil
Monsanto
Stauffer
Plant Location
Pierce, Florida
Pocatello, Idaho
Columbia, Tennessee
Nichols, Florida
Columbia, Tennessee
Soda Springs, Idaho
Mt. Pleasant, Tennessee
Silver Bow, Montana
Tarpon Springs, Florida
Carteret, New Jersey
Green River, Wyoming
Lawrence, Kansas
Newark, California
Columbia, Tennessee
Dallas, Texas
Jeffersonville, Indiana
Charleston, South Carolina
Fernald, Ohio
Augusta, Georgia
Kearny, New Jersey
Long Beach, California
St. Louis, Missouri
Trenton, Michigan
Chicago, Illinois
Chicago Heights, Illinois
Morrisville, Pennsylvania
Nashville, Tennessee
Richmond, California
Silver Bow, Montana
South Gate, California
20
-------
TABLE 3
(cont)
Company
Phosphorus Derivatives
FMC
Hooker
Monsanto
Stauffer
Mobil
Sodium Tripolyphosphate
FMC
Monsanto
Hooker
Olin Corporation
Stauffer
Plant Location
Nitro, West Virginia
(PC13, POC1_3)
Columbus, Mississippi
(P2S5_)
Niagara Falls, New York
(P205_, P2S5_, PC12, POC13_)
Anniston, Alabama
(P2S5_)
Sauget, Illinois
(P2S5, PC12, POC12)
Gallipolis Ferry, West
Virginia
(PC12, POC12)
Mobile, Alabama
(PC13.)
Morrisville, Pennsylvania
(P205_, P2S5, PC12, POC12)
Mt. Pleasant, Tennessee
(P2S5_)
Nashville, Tennessee
(P205_, P2S5_)
Charleston, South Carolina
(PC13, POC13)
Carteret, New Jersey
Green River, Wyoming
Lawrence, Kansas
Newark, California
Augusta, Georgia
Kearny, New Jersey
Long Beach, California
St. Louis, Missouri
Trenton, Michigan
Dallas, Texas
Jeffersonville, Indiana
Joliet, Illinois
Chicago, Illinois
21
-------
D'/AFT
TABLE 3
(cont)
Company
Calcium Phosphates
American Cyanamid
Borden
Eastman Gelatine Corporation
Farmers Chemical Company
International Minerals & Chemical
Monsanto
Occidental Chemical Company
Stauffer
Texasgulf Company
Plant Location
Alden, Iowa
Hannibal, Missouri
Weeping Water, Nebraska
Plant City, Florida
Peabody, Massachusetts
Joplin, Missouri
Bonnie, Florida
Augusta, Georgia
St. Louis, Missouri
Davenport, Iowa
Chicago Heights, Illinois
Nashville, Tennessee
Weeping Water, Nebraska
22
-------
c.
FIGURE 2
ELEMENTAL PHOSPHORUS PLANT LOCATIONS
-------
FIGURE 3
PHOSPHORIC ACID (DRY PROCESS) PLANT LOCATIONS
-------
X)
FIGURE 4
PHOSPHORUS DERIVATIVE PLANT LOCATIONS
-------
C.
• FOOD GRADE
O NON-FOOD GRADE
O
i FIGURE 5
SODIUM PHOSPHATE PLANT LOCATIONS
;— f
-------
• FOOD GRADE
O FEED GRADE
FIGURE 6
CALCIUM PHOSPHATE PLANT LOCATIONS
-------
DRAFT
DETAILED PROCESS DESCRIPTIONS
The following is a description of each process in this industry. Process
flow diagrams are included. In generating the following process descrip-
tions, emphasis has been placed on process features that generate aqueous
wastes. The details of the waste stream characteristics, however, have
been left for discussion in Section V.
Much of the process data in this section were acquired by discussions
with industry personnel, by observation of existing facilities, and from
DCP replies. A large body of data also exists in the published litera-
ture, and was used extensively in the following discussion. Of particular
usefulness were the publications of Beveridge and Hill (2); Barber (3>
4), Barber and Farr (5), and LeMay and Metcalfe (6) of the Tennessee Valley
Authority, which supplied specific operating details of TVA's facilities;
Ellwood (7); and Bryant, Holloway, and Silber (8) of the Mobil Chemical
Company. Standard reference books such as Faith, Keyes, and Clark (9),
Kirk and Othmer (10), and Shreve (11) were also useful. The 1974 Develop-
ment Document descriptions were revised only where necessary.
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, ferro-
phosphorus (from iron in the phosphate rock), and carbon monoxide are
reaction by-products. The simplified overall reaction may be written:
2Ca3(P04)2 + IOC + 6S102 1250 - 1500°C _ P4 + 10CO + 6CaSi03.
"""* "™ *"^ ^™ • ' '"'- — ~~^™~^^^ ^" ™""
A typical material balance for the process is:
Raw Materials Products
Phosphate Rock 10.0 kkg Phosphorus 1.0 kkg
Silica 1.5 Ferrophosphorus 0.3
Coke 1.5 Slag 8.9
Carbon Monoxide 2.8
Total 13.0 kkg 13.0 kkg
The electrical power consumption is approximately 15,400 kwh/kkg (14,000
kwh/ton) of phosphorus produced; part of this supplies the endothermic
heat of reaction of 6,200 kwh/kkg of P4.
The standard process, as pictured in Figure 7, consists of three basic
parts: phosphate rock preparation, smelting in the electric furnace,
and recovery of phosphorus.
28
-------
VENT
WATER
WASTE WATER
LIME
WASTE
WATER
PHOSPHATE ORES:
• ROCK
• SAND
• PEBBLE
• CONCENTRATE
(SOME WASHED)
SILICA
STORAGE
1
TAPHOLE FUME
SCRUBBER
AMMC
FUME SOD
WASTE
WATER
SODA ASH WATER
ELECTROSTATIC
PRECIPITATOR
L
SLAG SOLD
TRANSPORT
WATER
DUST
RECYCLED
OR
SOLO
PHOSPHORUS (P.)
PRODUCT
*• TO
CONSUMERS
WASTE
WATER
P. RECYCLED OR WASTED
»• SLUDGE SOLIDS RECYCLED OR WASTED
*• WASTE WATER
FIGURE 7 -—•»
STANDARD PHOSPHORUS PROCESS FLOW DIAGRAM
-------
E1? "'" 4 •''""
'WA
Phosphate rock ores are first blended so that the furnace feed is of
uniform composition. In some cases ores are blended simply by stratifying
into storage piles and cross sectioning the piles when shoveling out.
The silica composition is important since the overall furnace feed must
have a Si02/CaO ratio close to the eutectic composition for desired slag
flow properties. The blended phosphate rock may be pretreated by drying,
agglomerating the particles, and/or by heat treatment.
Sizing and/or agglomeration is accomplished by screening, pelletizing,
briquetting, and/or flaking, and the ore may then be calcined in a kiln.
This calcination is commonly termed "nodulizing" and the calcined ore
termed "nodules." Rotary kilns are commonly used. Nodules are air-
cooled after calcining.
The nodulizing operation performs simultaneous agglomeration and calcining
by heating the rock to its incipient fusion point; subsequent operations
include crushing and sizing of the nodules, with recycle 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 L400°C, also liberates water of hydration,
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 for calcining.
Some Florida phosphate pebble is charged to electric furnaces without
calcining or nodulizing. The air and additional moisture contained in
this uncalcined pebble contribute to inefficient operation by creating
higher furnace off-gas velocities and entraining more dust, resulting in
more dust or sludge handling problems. Also, more oxidation and hydration
of phosphorus vapor occur, contributing to corrosion problems because of
acid formation.
The sizing and calcining operations are sources of dust and fluorine
fumes. The dust may be dry collected by cyclones or other means, and
the gases are scrubbed with water, removing fluorine as HF and H2SiF6_.
The dry dusts collected are normally recycled to the nodulizing operation.
Coke drying is usually performed on site. The coke dryer off-gas and
fines from coke handling are usually water scrubbed. The off-gas may
contain traces of phenols, cyanides, and other substances associated
with coke manufacture. At least one plant also dries silica on-site
before introduction to the furnace burden.
30
-------
The burden of treated phosphate rock, coke, and sand (silica) is charged
to the furnace by incrementally adding weighed quantities of each of the
three materials to a common belt conveyor. The furnace 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 provided for feed
chutes, carbon electrodes, tapholes, slag (upper liquid layer), ferro-
phosphorus (lower liquid layer), and exhaust gases.
Electric furnaces for phosphorus production have been dramatically
increasing in size to achieve operating economies:
Size of largest Furnace in Operation
Year Megawatts" kkg/Year Tons/Year
1950 25 13,600 15,000
1960 60 27,200 30,000
1970 65 36,300 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.
At most plants the furnaces are 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
shoes. Newer furnaces use telescoping water seals on furnace electrodes.
Some furnace shells and/or bottoms are air-cooled.
The 2 to 6 percent Fe203 in the furnace-grade phosphate rock is reduced,
with the iron recovered~as the ferrophosphorus alloy:
Fe203
The ferrophosphorus typically contains 59 percent iron and 22 percent
phosphorus and is marketed for the production of phosphorus alloys. The
vanadium content of ferrophosphorus adds to its value. Should the
marketplace be favorable for ferrophosphorus, iron slugs can be added to
the furnace charge. Alternately, 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.
31
-------
DK.-.FT
Slag and ferrophosphorus are tapped periodically from the furnace. The
air-cooled ferrophosphorus is sold in lumps to the metallurgical industry.
No water is normally involved either in ferrophosphorus cooling or in
subsequent product preparation, although at least one producer follows
air cooling with water cooling.
The slag typically contains 38 percent SiO£ and 48 percent CaO, and also
contains considerable quantities (depending on the ore composition) of
A12Q3_, CaF2_, K20, 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 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. Some producers
have instituted prolonged air cooling of slag to reduce fluoride fumes
before a final quench with water.
There are numerous sources of fumes from the furnace operation. The
burden 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 collected and scrubbed with water.
The hot furnace gases, consisting of 90 percent CO and 10 percent P^,
may pass through an electrostatic precipitator to remove the dust before
phosphorus condensation. Dust not removed by precipitation is later
emulsified by liquid phosphorus and water, forming "phosphorus mud" or
sludge. Some producers prefer to process larger quantities of sludge
rather than to operate and maintain an electrostatic precipitator. One
producer indicated that the source of the phosphate ore and the extent
of furnace feed preparation influence the economics. Some electrostatic
precipitator dust is marketable for rare metals values contained. In
other cases, the dust may be returned to the nodulizer or else disposed
of as solid waste.
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 temperatures with the inlet gas approaching 540 C
(1000 F), and its surfaces must be maintained hot to prevent phosphorus
condensation (the dew point of phosphorus is 180 C (356 F)). The
precipitator 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. The high-voltage wires may be insulated from the shell
with an oil seal. Contaminated oil is periodically replaced with fresh
32
-------
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 <4<4°C (lll°F)) drains into a water sump, where the water
maintains a seal from the atmosphere. This water may be partially
neutralized by addition of ammonia, soda ash, 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 of water and are equipped
with steam coils for remelting at the destination.
Despite very high precipitator removal efficiencies, where used, enough
dust reaches the condensers to form some phosphorus mud or sludge. Some
producers process this sludge in "roasters" or evaporators, vaporizing
most of the elemental phosphorus, which is then condensed and processed
with the main stream phosphorus. A dry sludge residue high in P2p5_
remains, which may be recycled to the kiln or furnace. Gravity settling
and centrifugation are also used for sludge processing. Some sludge
becomes solid waste, which is commonly disposed of in on-site ponds.
The condenser exhaust gas is mainly carbon monoxide, which is normally
used as fuel for phosphate ore calcining. Excess carbon monoxide is
flared.
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 4 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.
33
-------
TABLE 4
IMPURITIES IN PHOSPHORIC ACID (54$ P205)
F, wt %
S03, wt %
Al]&3, wt %
Fe203, wt %
Water insolubles, wt %
Total Impurities, wt %
Density, kg/1 (ib/gal)
g 27DC (80°F)
Viscosity, cp % 27°C (80°F)
Color
Wet Process
Acid
0.6 - 1.0
2.7
0.9
1.2
0.8
6.2 - 6.6
1.72 (14.3)
85
Black
(2)
Furnace
Acid
0.007
0.003
0.001
0.0007
0.012
1.57 (13.1)
18
Colorless
In the standard dry process illustrated in Figure 8, 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:
-2P205 + 6H20
•4H3P04
Liquid phosphorus is stored under water in tanks heated with steam coils
(the freezing point of phosphorus is 44 C (ill F)). 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. Alter-
nately, 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 tempera-
tures much higher than 1650 C (3000 F) would color the resulting acid
and would plug injector orifices.
In the combustion chamber, corrosion by P205 vapors and by hot phosphoric
acid (formed from the moisture in the air7 Ts countered by using a
graphite lining. The steel shell of the combustion chamber is cooled by
34
-------
LIQUID
PHOSPHORUS
PHOSPHORIC
ACID
STORAGE
WASTE
FIGURE 8
STANDARD PHOSPHORIC ACID FLOW DIAGRAM (DRY PROCESS)
-------
running water down its exterior surfaces. This mode of heat transfer is
standard; pressurized cooling water is avoided since any leaks would
result in premature hydration. Recent plants have been constructed with
stainless steel combustion chambers.
The gas exiting from the combustion chamber is typically at a temperature
of 540°C (1000 F), and is then hydrated with direct water sprays that
also reduce the temperature to 120°C (250°F) or less.
A variation of the standard process, illustrated in Figure 9, uses
dilute acid for hydration instead of water. In this case, the makeup
water is added in the vapor-liquid separation step. The rationale is
that P205_ is absorbed more easily as the concentration of absorbing acid
is increased.
Another deviation from the standard process, also shown in Figure 9, 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 separation tower are of
stainless steel construction. Where dilute phosphoric acid is used in
the hydrator, the makeup 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.
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).(l2) 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. This waste material is normally disposed
of to landfill, although some plants discharge arsenic wastes to municipal
sewer systems.
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:
2P205( s)
Figure 10 is a flow diagram for a standard phosphorus pentoxide manufactur-
ing facility. The phosphorus pentoxide process differs from the manu-
facture of phosphoric acid in that the air is dried to an extremely low
dew point. This is done because 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
36
-------
PRODUCT
ACID
VENT
t "
/ DEMISTER V
SEPARATOR
TOWER
DILUTE
ACID
. MAKEUP
WATER
FIGURE 9
VARIATIONS OF PHOSPHORIC ACID (DRY) PROCESS
-------
AIR
J_
ou
AIR FILTER
AIR DRYER
LIQUID PHOSPHORUS STORAGE
*
WATER
COMBUSTION
CHAMBER
WATER SEAL
PRODUCT
P,0,
FIGURE 1O
PHOSPHORUS PENTOXIDE PROCESS FLOW DIAGRAM
-------
ambient air is filtered, refrigerated to achieve a dew point of -18
to -7°C (0 to 20°F), and then dried to a dew point of -46°C (-50°F)
with silica gel.
After reaction of liquid phosphorus with excess dried air in the com-
bustion chamber, the P205 vapor is condensed to a solid in a "barn",
which is a room-like structure. Some installations use a more conven-
tional 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 conyeyor. The gases are vented to the atmosphere
through a tail gas water seal that absorbs any P2_<35_ 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.
Phosphorus Pentasulfide. The standard process for the manufacture of
phosphorus pentasulfide, shown in Figure 11, is by direct union of the
elements, both in liquid form:
P4(l) + 10S(1) »-2P2S5(l)
Phosphorus pentasulfide is used for the manufacture of lubricating oil
additives, insecticides, flotation agents, and other organic chemicals.
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 (lll°F)) is transferred by hot water displacement or direct
pumping. The highly exothemic reaction is usually carried out as a
batch operation in stirred cast iron or stainless steel reactors. A
"heel" of molten P2S_5 (melting point 232°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 or carbon dioxide. A water seal is
sometimes used in the vent line.
39
-------
WASTE WATER
. 1
en en
".
3<"
5"-
CRUSHING,
GRINDING,
SIZING,
STORAGE
/ \
CONTAINER
FILLING
CASTING:
DRUMS OR CONES
PRODUCT
- CAST
IN DRUMS
POWDERED
PRODUCT IN
- DRUMS AND
RETURNABLE
BINS
WASTE
" WATER
O
FIGURE 11
PHOSPHORUS PENTASULFIDE PROCESS FLOW DIAGRAM
-------
Depending on purity requirements, the P2S5_ may be purified by distillation.
At least one manufacturer uses a vacuum dTstillation in a continuous
system. (The atmospheric boiling point is 515°C (960°F)). The condenser
is cooled by a high-temperature heat transfer fluid, which in turn is
cooled in a water-cooled heat exchanger.
Transfers of liquid P2S5_ are made by inert gas (N2_ or C02_), pressure
transfer, submerged pump, or gravity. ~
Some liquid P2S5_ is cast directly into small drums and some is cast into
cones. These operations are performed under fume hoods. The hot P2S5
normally auto-ignites at the surface, producing P205_ and S02_ fumes.
Unburned P2S:5_ can also hydrolyze, producing P205_ and" H2S fumes. Scrubbers
are normally used for air pollution control.
P2S5 can also be solidified continuously, using belt or drum type
flakers or screw conveyor type coolers with chilled flights. Some
manufacturers use one or more of these solidification methods. These
operations are commonly enclosed and inert gas purged, so burning does
not occur.
Cast cones are crushed, and the flakes or chunks from the crusher or
from the continuous solidification devices may be sized and/or milled
before filling final product containers. Powdered product is commonly
shipped in returnable aluminum bins and nonreturnable drums. Dust
control is usually required for filling powdered material, and dry
collectors and/or water scrubbers may be used for air pollution control.
An alternate mode of purification is the washing of crushed P2S5_ with
carbon disulfide, in which the by-products phosphorus sesquisulfide
(P4_S_3_) and free sulfur are soluble.
Phosphorus Trichloride. Phosphorus trichloride, used extensively in
organic synthesis, is manufactured directly from the elements:
P4(l) + 6C12(g) »*4PC13(1)
The standard process is shown in Figure 12. Liquid phosphorus and a
heel of PC13 are charged to a jacketed reactor. As additional phosphorus
is fed continuously, chlorine gas is continuously bubbled into the PC13
layer. Elemental phosphorus is somewhat soluble in PC13_, and the reaction
is more easily controlled by minimizing direct contact between the
heavier liquid phosphorus layer and the chlorine gas. Also, as additional
PC13_ forms, the exothermic heat of reaction causes PC13_ vaporization,
because the reaction is conducted at the PC13_ boiling point, 74 C
(165°F). In this way, the PC13_ serves as the" working fluid and heat
sink for the reaction. Additional elemental phosphorus continuously
dissolves in the PC13 layer via the horizontal interface.
41
-------
WATER
EMPTY
TANK CARS AND
WATER TANK TRUCKS
CLEAN
CONTAINERS
TO FILLING
PHOSPHORUS
WASTE
WATER
PRODUCT IN
TANK CARS,
TANK TRUCKS,
AND DRUMS
WATER
WASH
WATER
*• PCI. TO IN-PLANT USES
CARTRIDGES
TO
SOLID
WASTE
o
, FIGURE 12
PHOSPHORUS TRICHLORIDE PROCESS FLOW DIAGRAM
-------
The vapors typically are removed through a column, counter-current to
refluxed PC13 condensate. The column serves to reduce the amount of
reactor entrainment and high boiling impurities present in the PC13
product withdrawn. High boiling impurities that may be present in~~the
reactor include elemental phosphorus, arsenic trichloride, coke dust,
phosphorus oxychloride, thiophosphoryl chloride, and iron compounds.
Some cooling water is used in the reactor jacket. Care is taken to
avoid an excess of chlorine; otherwise, phosphorus pentachloride is
formed. Most reactors are iron or carbon steel. Condensers and other
process equipment may be steel, nickel, lead, or stainless steel.
A water scrubber collects hydrochloric acid and phosphorous acid, the
hydrolysis products of PC13 vapors:
PC13_ + 3H20 »-3HCl + H2P03_
The vapor pressure of the product is sufficiently high so that 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 by incremental rather than continuous phosphorus addition.
In another variation, enough phosphorus is charged to the reactor in a
single batch to permit a prolonged chlorination without further addition.
In this variation, chlorination continues until almost all of the phos-
phorus batch is consumed, but avoiding phosphorus pentachloride formation.
The PC13 formed is totally refluxed without product takeoff until the
batch of" chlorination is complete, with the PC13 accumulating in the
reactor. Steam is then supplied to the reactor Jacket, and the product
of the batch distillation is condensed and collected.
No provision is generally made for continuous or frequent withdrawal of
residue from the reactor either in the batch process or in the semi-
continuous process. Instead, the residue is permitted to accumulate,
and the reactor is shut down for cleanout infrequently.
PC13 is normally filtered before filling into shipping containers.
Phosphorus trichloride product is considered corrosive, principally
because of the acids formed by hydrolysis when in contact with water
vapor in the air. Therefore, it is shipped in lead-lined or plastic-
lined tank cars, stainless steel or nickel tank trucks, and in plastic-
lined (phenolic or epoxy) nonreturnable drums. Plastic-lined, nickel, or
glass lined storage tanks are typical.
Phosphorus Oxychloride. Phosphorus oxychloride is a common industrial
chemical widely used as an intermediate in the preparation of plasticizers,
motor fuel additives such as tricresyl phosphate (TCP), insecticides,
extraction solvents such as tributyl phosphate, and other organic phos-
phate esters.
-------
•1 4
The standard process, illustrated in Figure 13, uses dried air and/or
gaseous oxygen as an oxidant to convert liquid PC13_ in reactors or
columns to POC13. A catalyst will increase the reaction rate appreciably.
2PC12( 1) + 02( g) *- 2POC12C1)
Heat of reaction is removed by circulation of the reaction mixture
through a heat exchanger and/or by jacketing the reactors. Unreacted
oxygen and other noncondensables pass through a condenser for removal of
PC12 and POC13 vapors before venting. The condensed liquid is recycled
to the process. In at least one instance, this vent gas is then passed
through refrigerated condensers for recovery and recycle of additional
PC13. A small quantity of dissolved POC1_3_ may also be recovered.
Further purification of the POC13 product may be achieved by filtration
or distillation, depending somewKat on the type of impurities to be
removed. One plant uses cartridge-type filters.
An alternative process for the manufacture of phosphorus oxychloride may
be carried out in a batch reactor-still and column that are very similar
to the standard phosphorus trichloride equipment. This alternate is
illustrated in Figure 14. Liquid phosphorus trichloride is charged to
the reactor, solid phosphorus pentoxide is added, and chlorine is bubbled
through the mixture while the PC13 (boiling point 74°C (165 F)) and
later the POC13 (boiling point 105°C (221 F)) are refluxed. When the
reaction 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. Depending on the purification acheived and product
purity requirements, additional purification by distillation may be
performed. This distillation step may be designed for stripping of
noncondensables and low boilers (such as chlorine and PC13_)> which are
vented via a condenser, and for removal of high boilers that accumulate
in the still bottoms.
Water scrubbers collect hydrochloric acid and phosphoric acid, the
hydrolysis products of POC13_ vapors, both from process equipment vents
and from transferring operations (for either process):
POC12 + 3H20 ^3HC1 + ItfPOA
Like phosphorus trichloride, phosphorus oxychloride is extremely corrosive,
particularly because of hydrolysis products. It is therefore shipped in
nickel, nickel-clad, lead-lined, or plastic-lined tank cars or tank
trucks; nickel returnable drums; or plastic-lined nonretumable drums.
POC13 process equipment is typically nickel, stainless steel, or lead.
Storage tanks are typically nickel, plastic-lined, glass-lined, or lead-
lined.
44
-------
VENT
WASTE
WATER
WASTE
WATER
POCIi PRODUCT IN
TANK CARS. TANK TRUCKS. DRUMS
WATER FOR
STILL CLEANOUT
WASTE CARTRIDGES TO
WATER SOLID WASTE
STORAGE VENTS
FIGURE 13
STANDARD PHOSPHORUS
OXYCHLORIDE PROCESS FLOW DIAGRAM
—I
-------
VENT
VENT
POCIi PRODUCT IN
TANK CARS,
TANK TRUCKS,
DRUMS
WASTE
WATER
WASTE
' WATER
I FIGURE 14
! ALTERNATE PHOSPHORUS
IOXYCHLORIDE PROCESS FLOW DIAGRAM
-------
T
Phosphate Segment
Sodium Tripolyphosphate . Sodium tripolyphosphate is widely used as a
builder in detergent formulations, in water softening, and in cleaning
compounds. A food-grade form is used for treating meats.
The manufacture of sodium tripolyphosphate begins with the neutralization
of phosphoric acid by soda ash in reactors or mix tanks. Some manufactur-
ers also add caustic soda as a source of part of the sodium. In this
neutralization step, the amount of raw material is measured and controlled
to yield monosodium orthophosphate and disodium orthophosphate in a 1:2
mole ratio:
_ + 5Na2C02 - ^ 2NaH2PQ4 + 5H20 + 5C02_, or
9H2PQ4 + 5NaOH + 5Na2C03 - ^3NaH2P
-------
VENT
VENT
CO
SODA
ASH
J
SILO
PHO
1
WATER
1
SCRUBBER
CO,
SPHORIC
tCID
CAUSTIC
SODA
(OPTION)
1 M -
SLURRY
TANK
SCRl
LIQ
TORS
IBBEF
UOR
f
CYCLONE
FINES
i
DRYER
SCRUBBERS
VENTS
1
t
CYCLONE
FINES
'
CALCINER
PRODUCT
(TEMPERING)
DRY
DUST
COLLECTORS
PRODUCT
MILLING
AND SIZING
»-PRC
o
FIGURE 15
' SODIUM TRIPOLYPHOSPHATE PROCESS FLOW DIAGRAM
(FOOD AND NON-FOOD GRADE)
-------
WATER FOR
CALCIUM PHOSPHATES
WASTE _
WATER
STEAM
AND/OR HOT GAS
FIGURE 16
FOOD-GRADE CALCIUM
PHOSPHATES PROCESS FLOW DIAGRAM
-------
Relatively pure, food grade monocalcium phosphate (MCP) is made in a
stirred batch reactor from furnace acid and lime slurry:
SItfPCK + Ca(OH)2_ ^Ca(H2P04)2_.H20 + 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 by carrying out the reaction at
HO C (310 F) so that water is driven off as it is produced.
Relatively pure food grade tricalcium phosphate (TCP) is made in a
similiar manner to MCP, except that an excess of lime slurry maintained
during the batch addition cycle inhibits formation of dicalcium phosphate:
2H3P04 + 3Ca(OH)2_ *-Ca3_(P04)2_ + 6H20
Like MCP, the TCP is dried by methods that prevent excessive product
temperatures. The TCP slurry may be spray dried, drum dried, or flash
dried. Filtration may precede the drying of filter cake solids.
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:
H3P04 + Ca(OH)£ ^CaHP04.2H20
The stoichiometry for DCP manufacture is critical; any excess H3P04_
during the batch addition cycle will result in some MCP and any excess
Ca(OH)2_will result in some TCP. The excess water in the DCP reactor
ensures homogeneity so that the local stoichiometry is as balanced as
the overall reactor stoichiometry. As a result of the excess water
used, the reaction mixture is a pumpable slurry as opposed to the pasty
consistency of MCP and TCP. This DCP slurry is mechanically dewatered
before drying.
Much of the food grade calcium phosphate produced is used in dentrifrices.
Dicalcium phosphate (DCP) is also manufactured for livestock feed supple-
ment 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. Figure 17 shows the
manufacturing process for feed-grade calcium phosphate. The pasty
reaction product is normally dried in a rotary dryer. Powdered limestone,
CaCO^, may be used instead of lime. If quicklime is used, the drying
step may be bypassed.
50
-------
(OPTION)
DEFLUORINATED
PHOSPHORIC ACID
AIR SILICA
PHOSPHORIC
ACID
DEFLUORINATION
SCRUBBER
LIMESTONE
PUG MILL
REACTOR
WATER
VENT
SCRUBBER
WASTE WASTE
CYCLONE
ROTARY
DRYER
WATER VENT
SCRUBBER
*
WASTE
PRODUCT
COOLER
-PRODUCT
FIGURE 17
FEED-GRADE CALCIUM PHOSPHATE PROCESS FLOW DIAGRAM
-------
v''.H f\ FT
^tw'ir I
Another significant process difference is that non-food grade wet process
phosphoric acid is normally used for the feed-grade product. The feed-
grade DCP plants defluorinate the acid unless this step was accomplished
by the acid producer. Wet process phosphoric acid contains approximately
one 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_ + 4HF »» SiF4 + 2H20
Wet scrubbers then hydrolyze and collect this gas as fluosilicic acid
and silicic acid:
3 SiF4_ + 3H20 *• 2H2S1F6 + H2S103.
The hot defluorinated phosphoric acid is then charged to the reactor to
make dicalcium phosphate.
52
-------
SECTION IV
INDUSTRY CATEGORIZATION
INTRODUCTION
In developing effluent regulations for a given industry, a judgment must
be made by the Environmental Protection Agency as to whether effluent
limitations and performance standards are appropriate for different
segments (subcategories) within the industry. The factors considered in
determining whether such subcategories are justified for the phosphate
manufacturing category of point sources are:
1. wastes generated
2. treatability of waste waters
3. manufacturing process
4. raw materials
5. plant size and age
6. finished products (product mix)
7. land availability
8. air pollution control equipment
WASTES GENERATED
Tables 6, 9, and 10 in Section V show the raw waste loads for the phos-
phorus derived chemicals segment of the phosphate manufacturing category.
Suspended solids and dissolved phosphates are common raw waste water
constituents for elemental phosphorus, food grade calcium phosphates,
and feed grade calcium phosphate production. Dissolved solids are
present in concentrations significantly above background for all the
chemicals studied. Elemental phosphorus can be a waste water constituent
common to the phosphorus producing and consuming categories if the
phossy transport water is not returned to the phosphorus producing
plant, or if leaks or spills are not adequately contained. Alkalinity
is a constituent or parameter common to the elemental phosphorus and
phosphate production subcategories. Sulfate is a common waste water
constituent in the phosphorus and P2S5_ production subcategories.
Fluoride is a constituent specific tb~~elemental phosphorus production.
Production of the chemicals E3PO^, P205_, P2S5_, PC13, and POC13 commonly
generates acidic wastes and phosphates. Arsenic is present in phosphate
ore and in elemental phosphorus. Chemically, it is similar to phosphorus.
For these reasons, waste waters containing phosphates or other phosphorus
derived chemicals are expected to contain arsenic as a constituent,
which sometimes is detectable.
TREATABILITY OF WASTE WATERS
Elemental phosphorus production clearly stands alone on the basis of
waste water treatability. The large amount of waste water produced
presents special problems. It is a common practice within the industry
-------
to return phossy transport water to the phosphorus plant. Therefore,
the problem of treating elemental phosphorus is principally a phosphorus
plant problem or can be so handled that it will be a problem unique to
phosphorus plants.
The chemicals E3P04_, P205_, P2S5_, PCl^, and POC13_ present similar treat-
ability problems in that~acidic" wast¥s are encountered. PC12 and POC13
present more difficult problems because the resultant chloride ions are
difficult to remove.
The calcium, sodium, and ammonium phosphate subcategories involve
similar treatment problems (suspended solids and phosphates). Defluorina-
tion of animal feed grade calcium phosphates will produce fluoride
wastes, but the proposed treatment schemes will handle this waste constitu-
ent.
MANUFACTURING PROCESS
Manufacturing process is the principal factor used to determine sub-
categories. Elemental 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 H3P04_, P205_, PC13, and POC13_ are all similar in that a
gaseous intermediate or product is encountered somewhere in the reaction
sequence. The synthesis of P2S5_ resembles the above processes 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
P4 and Fe2P Phosphate Ore Coke (C), Si02_
HJP04 P4. 02, H20
P205 P4 0?
P2S7 Pi S
PC13 P? C12_
POCT3 P£L3_ C12_, (P205_), (02_)
Na5P3010 H3P04 Na2C03, (NaOH)
CarcTunTPhosphates H3P07 Car"OHT2
-------
••*, 4 r~
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 sub-
category. ~
PLANT SIZE AND AGE
Plant size will not affect the quantities of wastes produced (kg per kkg
of product) to such a degree that subcategorization would be warranted.
The same basic production processes for each chemical are used throughout
the phosphorus derived chemicals industry. Plant age will not affect
the quantities of wastes produced to the degree that subcategorization
is warranted. Another point is that the only really new plant uses
technology similar to that used in older plants; consequently the
situation does not exist where new technologies make older technologies
obsolete. With respect to economics, it is particularly difficult 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 whether 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.
FINISHED PRODUCTS
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, and suspended and dissolved
solids. The production of EJPO^, P205_, P2S5, PC12, and POC12 results in
phosphates, dissolved solids, and acids in the waste waters. The
production of Na5P3010 and the calcium phosphates results in phosphates
and suspended ancT dissolved solids in the effluent.
LAND AVAILABILITY
Removal of suspended solids from raw waste waters is most easily accom-
plished by use of large settling ponds. This will be the principle
concern for land availability. However, most of the plants in this
category are located in rural sites where-the problem of land availability
is minimized. Treatment options such as mechanical clarifiers are
available to plants with limited land area.
AIR POLLUTION CONTROL EQUIPMENT
All of the chemicals covered in this study use wet scrubbers or water
systems in the process itself that amount to scrubbers. Therefore, this
is not a topic for subcategorization. Furthermore, it is recommended
55
-------
that dry air pollution control equipment either precede or replace wet
scrubbers when possible in order to reduce scrubber water contamination.
Volatilization of potentially hazardous substances such as fluorine from
neutralization and settling ponds is insignificant as far as can be
determined at this time.
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 con-
sidered 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
i. industrial grade
ii. food grade
2. calcium phosphates
i. animal feed grade
ii. food grade
3. Other phosphates
(including sodium, potassium, and ammonium)
56
-------
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 phosphorus
derived chemicals industry and the raw wastes from the industry before
control and/or treatment of these wastes. Both Section III and Section
V are intended to be generally descriptive of the industry; the sections
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 plant effluent sampling data)
within the industry, pointing out those exemplary plants that 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 many 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 phosphorus derived chemicals industry for
the following purposes:
1. Process Water
a. Product Water
b. Solvent Water
c. Transport Water
d. Contact Cooling Water
e. Atmospheric Seal Water
f. Scrubber Water
g. Auxiliary Process Water
2. Noncontact Cooling Water
3. Miscellaneous Water Uses
4. Potable and Sanitary Uses
Process Water
One of the principal water uses in the phosphorus derived chemicals
industry is process water. Direct use of water in the process normally
57
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results in the discharge of process waste water. The term "process
waste water" means any water that, during manufacturing or processing,
comes into direct contact with or results from the production or use of
any raw material, intermediate product, finished product, by-product, or
waste product.
Process water uses include product water, solvent water, transport
water, contact cooling water, atmospheric seal water, scrubber water,
and auxiliary process water.
Product Water. Product water is water added to a product during manufacture.
Product water comes in contact with the product and remains with the
product as an integral part.
An example of product water is the quenching, hydrolysis, and dilution
water used in phosphoric acid manufacture. The product water added in
phosphoric acid manufacture remains in the product.
Solvent Water. Solvent water is water added to a reaction system to
facilitate manufacture. Solvent water comes in contact with the product
and is later usually driven from the product in terminal dehydration
processes. Some of the solvent water may remain in the finished product,
as a hydrate for example.
An example of solvent water is the water used as a reaction medium in
food grade calcium phosphate and sodium phosphate manufacture. Phosphoric
acid is reacted with various bases in an aqueous solution. Reaction
product water is formed when an acid reacts with a base, and this reaction
water blends with and is dealt with the solvent water.
Transport Water. Water may be used for transporting reactants or
products between unit operations. Intimate contact between the process
materials and transport water usually occurs. Since transport water is
used to facilitate manufacture, it is considered a type of process
water. Transport water commonly picks up reactants or products in the
suspended or dissolved form. These materials are pollutants when discharged
with waste water streams.
An example of transport water 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.
Contact Cooling Water. Contact cooling water comes under the general
heading of process water because it is utilized in manufacture and makes
direct contact with process chemicals or materials. Contact cooling
water commonly becomes contaminated with reagents, product, and by-
products.
-------
"T
A prime example of contact cooling water is the large quantity of water
used to quench slag from phosphorus furnaces; another example is the
water used to condense the gaseous phosphorus after it is produced in
the furnaces. Other direct contact cooling water uses include furnace
electrode seal water and pump or compressor seal water. These latter
two uses require much lower water volumes than slag quenching or phosphorus
condensing.
Atmospheric Seal Water. Because some of the materials in this industry
spontaneously ignite on contact with the oxygen in air, the air is
sometimes kept out of reaction vessels with a water seal. For example,
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 dusts from stacks, tail gases, and gaseous
process streams. The used scrubber water is regarded as process water
since it was utilized in the manufacturing process. The resultant
solution or suspension usually contains impurities or may be too dilute
a solution to reuse or recover product or by-products and thus is discharged
as contaminated process waste water.
Auxiliary Process Water. Auxiliary process water is used in medium
quantities by the typical plant for auxiliary operations such as ion
exchange regeneration, makeup water to boilers with a resultant boiler
blowdown, equipment washing, storage tank and shipping container washing,
and spill and leak washdown. The waste water from these operations is
generally low in volume but highly concentrated.
Noncontact Cooling Water
The term "noncontact cooling water" means water used for cooling that
does not come into direct contact with any raw material, intermediate
product, waste product, or finished product. If the water is used without
contacting the reactants, such as in a tube-and-shell heat exchanger,
the water will not be contaminated with process waste water pollutants.
For this reason, the single most important process waste control technique,
particularly for subsequent treatment feasibility and economics, is
probably segregation of noncontact cooling water from process water.
Noncontact cooling water is generally of two types in the industry. The
first type is recirculated cooling water that is cooled by cooling
towers or spray ponds. The second type is once-through cooling water
whose source is generally a river, lake, or tidal estuary, where the
water is returned to the same source from which it was taken.
Recirculating cooling water systems normally produce cooling tower
blowdown as a waste water effluent. The term "blowdown" means the
minimum discharge of recirculating water for the purpose of discharging
materials contained in the water, the further buildup of which would
59
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"TP
9
J
cause concentration in amounts exceeding limits established by best
engineering practice. The blowdown contains the raw water constituents
in a more concentrated form, plus any chemicals used to treat the
recirculating water. Contaminants may include phosphates, nitrates,
nitrites, sulfates, and chromates. The only contaminants discharged in
once-through noncontact cooling water would be any water treatment
chemicals that might be added. However, the Agency is under great
pressure to eliminate once-through cooling systems because of their
damaging actions on surface water fauna. Aquatic organisms are commonly
destroyed at the intake screens and are killed by agitation, added
chemicals, and rapid temperature changes from the system.
Miscellaneous Water Uses
Miscellaneous water uses vary widely among the plants and include safety
showers, eye wash stations, and equipment cleaning for maintenance
purposes. The resultant discharges will vary from noncontaminated or
slightly contaminated waste water to highly contaminated waste water.
Potable and Sanitary Uses
Water used for drinking and sanitary purposes becomes sanitary waste
water. Most plants in the industry either segregate this waste stream
and provide separate on-site treatment, or discharge sanitary waste
water to a municipal treatment system.
PROCESS WASTE CHARACTERIZATION
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 from
plant to plant. However, the raw waste 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.
60
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The Phosphorus Production Subcategory
The discussion of elemental phosphorus manufacturing technology in
Section III and the flow diagram of Figure 7 qualitatively pointed out
the following streams emanating from the process (in addition, of course,
to the phosphorus product stream):
1. By-products: Slag, Ferrophosphorus, and Carbon Monoxide
2. Noncontact Cooling Water
3. Electrostatic Precipitator Dust (Sometimes sold as a by-
product )
4. Calciner Precipitator Dust
5. Calciner and Furnace Fume Scrubber Liquor
6. Phosphorus Condenser Liquor (Aqueous phase)
7. Phosphorus Sludge (or mud)
8. Slag Quench Liquor
The following discussion describes each of the above in quantitative
detail, and identifies which are typically returned to the process and
which are classified as raw waste streams from the manufacturing operation.
Figures given for the TVA elemental phosphorus plant reflect data gathered
in 1973. The facility, which is located at Muscle Shoals, Alabama, was
shut down in June, 1976.
By-product Streams. The by-products of the phosphorus manufacturing
operation are: (2,7,8)
kg/kkg Ib/ton
Ferrophosphorus 300 600
Slag (CaSi02) 8,900 17,800
CO gas 2,800 5,600
Both ferrophosphorus and slag are sold, and the carbon monoxide 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 normally is air-cooled. The solids are then broken up and shipped.
Except for one plant, no water is used specifically for ferrophosphorus,
and there are no wastes accountable for ferrophosphorus manufacture.
Noncontact Cooling Water. Phosphorus production facilities generate
huge quantities of heat. The electrical power consumption is approx-
imately 15,400 kwh/kkg (48 million Btu/ton).(7,8) An additional 8,100
kwh/kkg (25 million Btu/ton) of heat are generated by combustion of the
by-product carbon monoxide. Some of this energy, 6,100 kwh/kkg (19
61
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-
I
million Btu/ton), is absorbed in the endothermic furnace reaction, and
some is absorbed by the endothermic calcining operation. Other portions
of the 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 calciner and furnace
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 noncontact cooling water for the calcining kiln, the
furnace shell, the crucible bottom, the fume hood, the tapholes, the
electrode shoes, 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, 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. Cooling water usage at
elemental phosphorus plants is summarized below:
COOLING WATER PER UNIT P£ PRODUCTION
Plant No. 1/kkg gal/ton
1 800 . 200
3 77,000 18,500
4 7,900 1,900
5 30,000 7,200
6 97,000 23,000
7 45,000 10,900
8 72,000 17,300
9 80,000 19,000
TVA 130,000 31,000
The low water usage figures for Plants 1 and 4 in the above summary
reflect the use of cooling towers in the furnace and kiln areas of the
plants. The above figures do not necessarily reflect fresh water usage,
since some plants use recycled water for certain cooling needs.
Electrostatic Precipitator Dust. The high-temperature electrostatic
precipitator, when used, removes dusts from the furnace gases before the
gases are condensed for recovery of phosphorus. These dusts may contain
up to 50 percent P205_, and therefore find value either for return to the
process or for sale as fertilizer. In the former case, they are transported
to the ore blending head end of the plant. Some precipitator dust is
sold for its content of rarer metals.
The quantity of precipitator dust is approximately 125 kg per kkg of
product (250 lb/ton).(7) Regardless of the method of sale or reuse, the
precipitator dust is not a waste material to be disposed of from the
plant.
62
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Calciner Dust. Dry dust collectors are often 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.(S)
There is no plant discharge of dry calciner 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 (mainly Si02_ and Fe£03_), 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 5 lists the
quantities of materials in commercial phosphate rock presented as pounds
per ton of phosphorus ultimately produced after normalizing to 26
percent P205 content. From Table 5, the average quantity of fluoride in
ore is 275" kg/kkg of P4_ (550 Ib/ton). Approximately 8 percent of this
quantity of fluoride, or 22 kg/kkg (44 Ib/ton), is volatilized in the
ore calcining operation(5) and is subsequently a constituent of the
scrubber liquor.
The scrubber liquor is highly acidic for three reasons: the sulfur (as
S03_) forms sulfuric acid; the P2_05_ 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 liquor back to the scrubbers. When it was operating, the TVA plant
at Muscle Shoals circulated approximately 21,000 1/kkg of product (5,000
gal/ton), with a portion bled off to control dissolved solids buildup.
This scrubber liquor had the following average composition:(5)
Constituent Concentration, %
F 3.1
Si02_ 1.1
P205 0.2
Fe203 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:
63
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TABLE 5
COMPOSITION OF COMMERCIAL PHOSPHATE ROCK (10)
Constituent
Florida Land
Pebble
Furnace Grade
Tennessee
Brown Rock
Furnace Grade
Western
Phosphoric Acid
Low Grade
kg/kkg Ib/ton kg/kkg Ib/ton kg/kkg Ib/ton
pi°l
CaO
MgO
A1203
Fe2p2
Si02_
S02
F
C02_
Organic Carbon
Na20
K20
2,600
3,800
35
125
155
725
215
305
330
40
10
10
5,200
7,600
70
250
310
1,450
430
610
660
80
20
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
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
Note: All figures expressed as kg per kkg (Ib/ton) of phosphorus
produced.
64
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Constituent Raw Waste Load
F
Si02
P205
Fe203
S
"\iTCT / \T\TCf
-iVf-. / J\-lVtl
22
8
1.5
0.5
12
Ib/ton
44
16
3
1
24
The total CaCO_3 acidity of the scrubber liquor, calculated from the
above constituent quantities, is 60 kg/kkg (120 Ib/ton).
The extent of scrubber liquor recirculation by elemental phosphorus
producers varies widely, as indicated in the following table:
SCRUBBER LIQUOR VOLUMES PER UNIT P4_ PRODUCTION
Water Usage Scrubber Waste Water
Plant No.
1
3
4
6
7
8
9
1/kkg
7,500
117, 000
12,000
40,000
9,700
365,000
32,000
gal/ton
1,800
28,000
2,900
9,500
2,300
87,600
7,600
1/kkg
4,200
117,000
-
40, 000
3,800
363,000
32,000
gal/ton
1,000
28,000
-
9,500
900
87,000
7,600
Phosphorus Condenser Liquor. The furnace gases pass from the electrostatic
dust precipitator (when used) 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. This condenser liquor is "phossy
water", essentially a colloidal dispersion of phosphorus in water, since
the solubility of phosphorus at 20°C (68°F) is only 3.0 mg/1. Depending
on how intimate the water/phosphorus contact is, the phosphorus content
of phossy water may be as high as several percent by weight.(3)
The condenser liquor also contains constituents other than elemental
phosphorus, including fluoride, phosphate, and silica. Using the
average fluoride content of ore (from Table 5) of 275 kg/kkg, plus the
estimate that 12 percent of the fluoride in the ore volatilizes in the
65
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. .. , .,--.
.-.iMi L
furnace (2,5) and is therefore equivalent to 33 kg/kkg (66 Ib/ton), and
by accounting for 6 kg of fluoride per kkg (12 Ib/ton) that is collected
in the precipitator dust and in the phosphorus sludge, a raw waste load
for fluoride is derived at 27 kg/kkg (54 Ib/ton) in the condenser liquor.
The condenser liquor is not always acidic despite the hydrolysis of P205_
and SiF4_ to H[3P(X, H2SiF£, and H2SiCl3 because aqueous ammonia, caustic,
or soda ash is added by some producers to prevent corrosion in the
condenser.
There are other sources of phossy water within the plant. Storage tanks
for phosphorus have a water blanket, which is discharged upon 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 in 1969.(3)
At TVA, the condenser liquor was recirculated at the rate of 33,000
1/kkg (8,000 gal/ton).(6,7) Other plants differ significantly in the
quantity of phossy water circulated, as shown below, but raw wastes (in
kg/kkg of product) should be fairly uniform:
PHOSSY WASTE WATER VOLUMES
Plant No. 1/kkg P^ gal/ton P^
2 Phossy Water to Treatment 163,000 39,000
4 Phossy Water to Treatment 48,000 11,500
5 Phossy Water from 6,000 1,400
Clarification
6 Condenser Water - 55,900 13,400
Recirculation
6 Phossy Water to 6,000 1,400
Clarification
7 Condenser Water to Treatment 3,400 800
7 Total Phossy Water to Treatment 7,100 1,700
8 Condenser Water - 28,000 . 6,600
Recirculation
8 Phossy Water From 24,000 5,700
Clarification
9 Phossy Water to 2,900 700
Clarification
66
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To calculate the raw waste loads of phosphate and silica in the condenser
liquor, the following TVA recirculated-liquor composition was used:(5)
Constituent Concentration, %
F 8.3
P205 5.0
Si02 4.2
Equating 8.3 percent fluoride with the previously derived 27 kg/kkg of
fluoride, the raw waste loads of P2Q5_ and Si02 become respectively 16.5
kg/kkg (33 Ib/ton) and 13.5 kg/kkg (27 Ib/tonJ.
Phosphorus Sludge. In addition to phossy water, the phosphorus condenser
sump also collects phosphorus sludge, which is a colloidal suspension
typically 10 percent dust, 30 percent water, and 60 percent phosphorus.(6)
The quantity of sludge formed is directly dependent on the quantity of
dust that escapes electrostatic precipitation. This consideration
justifies the very large investment made for highly efficient precipitators
by some manufacturers.
Using 125 kg of dust (per kkg of product) collected by the electrostatic
precipitator,(7) and assuming a 98 percent collection efficiency,(8) the
dust reaching the condenser amounts to 2.5 kg/kkg (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.
Another source of sludge is phosphorus filtration, which is widely
practiced in the industry. Diatomite filter aid is often used. The
filters are backwashed to remove the sludge and filter aid. In some
cases, filtration is preceded by a separation step or steps such as
gravity settling in tanks or other means to remove most of the sludge
layer. The sludge separated from these operations still contains elemental
phosphorus and may be further processed by "roasting" (evaporation),
centrifugation, or other methods.
Roasting or evaporation is the heating of the sludge 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 recycled to the feed
preparation section of the plant or safely landfilled.
At least one plant uses centrifugation to process its phosphorus sludge.
Solids recovery was reported as 90 to 95 percent. Recovered solids are
returned to the furnace, and centrate is discharged to the plant's
phossy water system.
67
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t..- - U"a i
Slag Quenching Liquor. Slags from phosphorus furnaces are mainly Si02_
and CaO, and also contain A12Q3_, K20, and MgO in amounts consistent with
the initial ore composition. In addition to these oxides, phosphate
rock may contain 0.1 to 0.2 kg/kkg (0.2 to 0.4 lb/ton)(2) of uranium in
the ore, and the radiation levels of both the slag and the quench water
must be appropriately noted. Florida and Western phosphate ore deposits
contain appreciable uranium, but the Tennessee rock is practically free
of uranium.(10) Other constituents of the slag presenting problems for
quench water pollution control are fluoride and phosphate. Approximately
80 percent of the original fluoride in the phosphate rock, 220 kg/kkg of
P4 (440 Ib/ton), referring to Table 5, ends up in the slag. About 2.7
percent of the original P205_ in the phosphate rock, 70 kg/kkg (140
Ib/ton), also ends up in the slag.
At Plant 4 prior to 1974, approximately 24,600 1/kkg (5,900 gal/ton) of
water were used for quenching the slag. Data gathered at that time
indicated the following composition and raw waste loads for the slag
quench liquor at Plant 4:
Concentration Raw Waste Load
Constituent mg/Tkg/kkg P4 Ib/ton P4
Total Suspended Solids 800 20 40
Total Dissolved Solids 1,700 42 85
Phosphate (as P) 12 0.3 0.6
Sulfate (as S) 1,000 25 50
Iron (as Fe) 14 0.35 0.7
Fluoride (as F) 170 4.5 9
Total Alkalinity 230 5.5 11
The quantity of water used in slag quenching varies widely from plant to
plant depending upon the amount of air cooling used, the final slag bed
temperature achieved, and the method of contacting the slag bed. The
following are data reported in 1977 DCP submittals:
SLAG QUENCHING WATER
Water Usage Evaporation
Plant No. 1/kkg gal/ton 1/kkg gal/ton
5 3,500 800
6 51,000 12,000
7 4,200 1,000 4,100 980
8 124,000 30,000 5,000 1,200
9 11,000 2,600 1,300 320
68
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Plant 5 has no discharge of waste water from its slag pit; the quench
water either evaporates or seeps into the ground. Plant 9 has installed
slag handling facilities that will also eliminate discharge of waste
water.
Summary. Table 6 is a summary of the major raw waste loads from elemental
phosphorus manufacture. Volume figures were derived by averaging
available current data from existing plants. It should be noted that
all waste waters from elemental phosphorus production are not included
in the table. Sources of these additional waste streams can include air
pollution scrubbers other than the calciner scrubber (to control emissions
from handling of materials such as nodules and coke, to control taphole
and other furnace fumes, to control nodule cooler emissions, etc. );
cooling of the transformers, furnace, and calciner; and contaminated
storm water runoff.
69
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.!••<"
v.1 U
TABLE 6
SUMMARY OF RAW WASTES FROM
ELEMENTAL PHOSPHORUS MANUFACTURE
Waste Water Quantity,
1/kkg
gal/ton
Raw Waste Load, kg/kkg
TSS
P4
PIT/;
so"
F "
Total Acidity
Total Alkalinity
Calciner
Scrubber
Liquor
93,000
22,000
8.5
_
2
36
22
60
-
Phosphorus
Condenser
Plus Other
Phossy Water
37,000
9,000
13.5
9
22
-
27
-
-
Raw Waste Load, Ib/ton
TSS
P4
PT34
S04
F
Total Acidity
Total Alkalinity
Concentrations, mg/1
TSS
P4
P04
sot
F
Total Acidity
17
_
4
72
44
120
-
93
_
22
392
240
654
27
18
44
-
54
-
' -
360
240
586
-
719
-
total Alkalinity
Slag
Quench
Water
33,000
8,000
20
1
75
4.5
5.5
40
2
150
9
11
600
30
2,248
135
165
70
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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
operating 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 10, 11, 13, 14, 16, 17, 18, 19, 24, and 31. No other practice
has been reported to be in current usage, except where a change to this
method is currently underway. This procedure results in the shipment of
the phossy water back to the phosphorus-producing facility for treatment
and/or reuse, instead of disposal as waste water at the phosphorus-using
plant. Therefore, typical 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 phosphorus would remain at the low
points in the sewer line generally as a solid (melting point 44 C
(ill F)) and would contact and contaminate all water flowing in that
sewer for a long period of time. Since phosphorus burns when exposed to
air (ignition temperature 45 C (113 F)), 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 lb/ton).(13) Whenever phosphorus is
transferred by displacement, 580 liters of water are displaced per kkg
of phosphorus (140 gal/ton). These values are equivalent to an elemental
phosphorus concentration of 1,700 mg/1. For comparison, a typical
phosphorus content in phossy water at a phosphorus-producing plant has
also been reported at 1,700 mg/l.(3) Phosphorus concentrations in
phossy water can vary widely, however.
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 typi-
cally 92,000 liters per kkg of product (22,000 gal/ton); but with recycle
of cooling water, the makeup cooling water requirement is approximately
4,600 liters per kkg of product (1,100 gal/ton).(14)
71
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f" ~s. f\ r—T-
k-;t '»/-»r 1
There is no aqueous process waste from phosphoric acid Plants 4, 24,
27, and 31.(2,14,15,16,17) Despite good housekeeping at a plant, leaks
or spills of 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).(14,16,17)
Where food grade phosphoric acid is produced, a standard raw waste of
0.1 kg/kkg (0.2 Ib/ton) of arsenic sulfide is precipitated by addition
of a soluble sulfide (H2S, Na2S, NaHS) and subsequent filtration. (14,17,18)
An additional 0.75 kg/kkg (1.5 Ib/ton) of filter-aid material may accompany
the sulfide as a solid waste.
Leaks of phosphoric acid into noncontact cooling water have been estimated
as 0.05 to 0.17 kg/kkg (0.1 to 0.34 Ib/ton) on an average.
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
H3P04 (100 percent basis).(13) Approximately 500 1/kkg (120 gal/ton) of
water may be used, resulting in a concentration of 470 mg/1 in 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 noncontact cooling water
are used.(13)
Phosphorus Pentasulfide Manufacture. The water seals sometimes used 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.(13,19)
Should any batch be aborted (a rare occurrence) because of agitator
failure, cast iron pot failure, or other reason, the material is either
incinerated, recycled to the process, or disposed of as solid waste at a
landfill.
The dust collected by a cyclone from the P2S5_ crushing operation may
amount to 1 kg/kkg (2 Ib/ton).(13,19)
The still pot for the distillation step and in some cases the reactor
accumulate impurities, including 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 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 As2S5_ per kkg of product P2S5_ (0.1 Ib/ton).
72
-------
The entire still pot residue is about 0.5 kg/kkg (l Ib/ton). Periodically,
these residues are removed, drummed, and disposed of to landfill. One
plant burns the residue in a phosphoric acid unit to recover the phosphorus
values.
Noncontact cooling water usage varies from 890 Ifkkg (214 gal/ton) to
17,000 1/kkg (4000 gal/ton), depending upon the extent of cooling water
recirculation, distillation requirements, and the extent of air cooling
utilized.
Variable quantities of inert gas (nitrogen and/or carbon dioxide) are
emitted from the reactor, still, holding and storage equipment, condensers,
and continuous solidification equipment. These vent streams may be
saturated in P2S5_ vapor or may contain P2S5_ fumes or dusts. Depending
upon composition, these vented streams may be diluted with air and
exhausted through water scrubbers for air pollution control. In the
casting of liquid P2S5, the fumes from burning liquid (molten P2S5,
auto-ignited) may be water scrubbed, although at least one plant does
not have a scrubber. When filling powdered P2S.5 into containers (commonly,
returnable aluminum bins), hoods and wet scrubbers may be used to control
P2S5_ dust.
Returnable containers sometimes require washing. In contact with water
or water vapor, the P2S_5_ hydrolyzes to phosphoric acid and hydrogen
sulfide gas:
P2S2 + 8H20 *-2H3P04_ + 5H2S
Process equipment is sometimes washed with water. Dilute caustic may be
used to prevent equipment corrosion and to reduce hydrogen sulfide
fumes, which are highly toxic:
P2S5 + 9NaOH »-2Na2HP04_ + 5NaHS + H20
(In the presence of excess water)
The composition of scrubber waters and other waste waters from the
phosphorus pentasulfide processes will vary somewhat depending on the
amount of oxidation of the P2S5_ that occurs before scrubbing. Air
oxidation yields P205_ and S02_, which hydrolyze to H3P04- and H2S03_ in the
waste water. Hydrolysis alone without oxidation produces H3P04 and H2S.
The combined waste waters from P2S5 manufacture are reported to contaTn
0.3 to 3.0 kg/kkg (0.6 to 6.0 Ib/ton) of phosphate (as P), 0.11 to 10
kg/kkg (0.22 to 20 Ib/ton) of sulfate, and 0.3 to 2.6 kg/kkg (0.6 to 5.2
Ib/ton) of chloride. One firm reports sulfide as 0.44 kg/kkg (0.88
Ib/ton). Another reports hydrolyzable phosphate as 0.09 kg/kkg (0.18
Ib/ton). (Hydrolyzable phosphates may result from incomplete hydrolysis. )
Total waste water volumes vary from 335 to 30,000 1/kkg (80 to 7400
gal/ton). Sulfides may be oxidized to elemental sulfur or sulfate by
oxygen in the air or absorbed from the air by the waste waters. H2S02
may be oxidized to sulfuric acid (sulfate) from the same oxygen sources.
73
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Scrubber waste water volumes also depend upon the extent of recirculation
and whether caustic neutralization is practiced. Scrubbers used in P2S5_
manufacture produce 200 to 12,000 1/kkg (4-8 to 2900 gal/ton) of waste
water. The higher volume reflects use of once-through scrubber water.
Waste water volumes for scrubbers on recirculating water systems vary
from 200 to 400 1/kkg (48 to 100 gal/ton).
Available data on waste water flow from P2S5_ manufacture are summarized
below:
P2S5_ WASTE WATER FLOWS
Plant No. Waste Stream Flow
1/ldcg gal/ton
10 Total 3,186 764
13 Total 334 80
14 Scrubber 12,100 2,900
14 Noncontact Cooling 16,640 3,990
14 Total 30,860 7,400
17 Scrubber 390 94
18 Scrubber 200 48
18 Total 1,430 342
19 Scrubber 300 72
Available data on P2S5_ waste water constituents include the following:
Plant No.
13 14 17
Constituent (Total) (1973 Data) (Scrubber)
pH 1-2 7.15 9.4
Temp (°C) 20
COD, kg/kkg - 26 0.8
Ib/ton - 52 1.6
TSS, kg/kkg - 3.4 0.03
Ib/ton - 6.8 0.06
74
-------
TDS, kg/kkg 0.4 41* 13.5
Ib/ton 0.8 82 27.0
Acid hydrolyzable
phosphate as P,
kg/kkg - - 0.09
Ib/ton - - 0.18
Total P as P, kg/kkg - 3 0.3
Ib/ton - 6 0.6
Sulfide, kg/kkg 0.44
Ib/ton 0.88
Elemental Sulfur,
kg/kkg o -
Ib/ton o -
Sulfate, kg/kkg 0.11 22* 3.4
Ib/ton 0.22 44 6.8
Chloride, kg/kkg - 15* 0.3
Ib/ton - 30 . 0.6
^Figures are gross values; net values are TDS - 3.4 kg/kkg,
sulfate - 5 kg/kkg, chloride - 1.3 kg/kkg.
Phosphorus Trichloride Manufacture. The reactor/stills accumulate
residues that must be periodically removed. Frequency of reactor cleanout
varies from three times a month to about once a year, depending on the
manufacturer. These residues contain arsenic trichloride, which is
higher-boiling than the corresponding phosphorus trichloride. The
arsenic occurring naturally with phosphorus is equivalent to 0.05 kg of
AsC13 per kkg of product PC12 (0.1 Ib/ton). Other reported constituents
in the reactor residue include phosphoric acid, hydrochloric acid,
carbonaceous material, elemental phosphorus, phosphorous acid, coke
dust, thiophosphoryl chloride (PSC12), and POC13.
During a typical PC13 reactor cleanout procedure, the heel is chlorinated
to use up unreacted elemental phosphorus, as much PC13_ is recovered by
distillation as possible, and the residue is drained to drums (55-gal)
for disposal as solid waste. Estimates of residue quantities range from
10 to 12 drums per cleanout. Trichloroethane or trichloroethylene may
be used to wash out the remaining residue. This waste is also drummed
and disposed of as solid waste, resulting typically in an additional
five drums. A final water wash ("drown" water) of the reactor/still
normally follows. Most plants discharge this final rinse water rather
than collect it in drums. Plant 11 reports the following average
arsenic levels in wastes from reactor cleanout:
6,000 ppm arsenic in heel residue
600 ppm arsenic in trichloroethane mixture
116 ppin arsenic in "drown" water
75
-------
The ratio of total heel residue to trichloroethane mixture to drown
water is about 5.1:1:8.7 on a mass basis. Plant 13 reports 30 to 260
ppm arsenic in chlorinator heels, 60 to 157 ppm arsenic in raw phosphorus,
and 62 to 160 ppm arsenic (per unit P4_) in product PC1_3_. Plant 16
reports that if all the arsenic present in the elemental phosphorus
distilled over into the PC13 product, arsenic content of the product
would be 11 ppm. Actual analysis of the product has shown 10 ppm arsenic;
the remainder is lost in reactor residues and elsewhere. Based upon
available data, arsenic lost to solid waste is estimated as 0.006 kg/kkg
(0.012 Ib/ton).
The average noncontact cooling water requirement for PC13 manufacture is
31,000 1/kkg (7,500 gal/ton).
Water scrubbers collect PC12 vapors from the reaction, product distilla-
tion, product storage, and product transfer operations and hydrolyze
these vapors to HC1 and H3P03 (which may subsequently be oxidized to
H3_P04_). The quantity of FClJ collected is highly dependent upon the
efficiency of the upstream condensers, since PC1_3_ is highly volatile:
Temperature
_C ^F PC13 Vapor Pressure, mm Hg(20)
20 68 99
40 104 235
60 140 690
76 169 760
At Plant 11, sufficient heat transfer area was provided in the condensers
to limit the raw waste load to 2.3 kg of HC1 plus 1.8 kg of H3P02 per
kkg of products in the combined waste waters from the PC1_3 and POC13_ pro-
cesses (4.6 Ib/ton and 3-6 Ib/ton, respectively). Approximately 2,700
liters/kkg (650 gal/ton) of scrubber water were used to collect these
wastes. These data are based on a 1975 sampling study. Data on waste
quantities from only the PC13 process are generally not available, since
six of the seven plants that~produce PC13 also produce POC13. These
plants generally use scrubbers that serve" both the PC1_3_ and~~POCl_3 pro-
cesses, thus generating a combined waste water.
The acid wastes from washing tank cars and tank trucks and from washing
used POC12 filter elements are very small. Water use data taken from
Plant 11 Tn 1973, supplemented by an independent analysis of the waste
water, yielded the results in Table 7. Total raw waste generated in
truck loading, in tank-car cleaning, and in filter-element washing was
0.014 kg/kkg (0.028 Ib/ton) of HC1 plus 0.003 kg/kkg (0.007 Ib/ton) of
total phosphates. Where product PC13_ is filtered, the used filter
elements are first washed to hydrolyze the residual PC12- Disposable
elements are then landfilled.
Table 8 is a summary of available data on raw waste loads from PC13_ and
POC1_3 manufacture. Sources of data include 30-day sampling studies
conducted in 1975 and DCP responses submitted in 1977. The PC1_3 data
in Table 9 that follows are an average of data from Plants 14 and 16,
since these data relate to the PC13 process rather than to a combined
waste water. ~~
76
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TABLE 7
MINOR WASTES FROM PLANT 11 (PC13 AND POC13)
Truck-Loading
Vent
Scrubber
Tank Car
Cleanout
Water
Filter Element
Washout
Drum
Water Use: 1/kkg
gal/ton
Constituent Analysis, mg/1:
Chloride
Total P04
Total Acidity
Raw Waste Load, kg/kkg:
Chloride
Total PC4
Total Acidity
Raw Waste Load, Ib/ton:
Chloride
Total P04
Total Acidity
8.8
2.1
340
260
660
0.0030
0.0023
0.0058
10.5
2.5
715
26
0.0075
0.0003
0.46
0.11
6,480
590
18,200
0.0030
0.0003
0.0083
0.006
0.005
0.012
0.015
0.001
0.006
0.001
0.017
77
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TABLE 8
RAW WASTE LOADS FROM PC13
Parameter
(Daily Averages)
Flow, gal/ton
PH
BOD5, Ib/ton
COD, Ib/ton
TSS, Ib/ton
TDS, Ib/ton
Acid Hydrolyzable
Phosphate
as P, Ib/ton
Total P as P,
Ib/ton
Elemental P,
Ib/ton
Sulfate, Ib/ton
Chloride, Ib/ton
Arsenic, Ib/ton
Iron, Ib/ton
13
( Combined )
7,760
-
-
19.2
0.44
50.8
1.4
3.8
0.0001
-
20.4
0.006
-
11
( Combined )
652
2.0
-
0.66
0.015
4.2
0.003
1.36
-
-
4.52
8x10" 5
-
AND POC13 MANUFACTURE
Plant No.
14 14 14 17
( POC13 ( Combined
(PC13) (POC13) Drum wash) Scrubber)
424 1,420 16 126
1.5-2.5 1.2-3.9 - 4.5
_
0.16 0.24 0.001 2.8
0.016 - 0.06
0.78 4.04 0.1 60
0.2
0.22 1.88 0.16 3.4
_ _ _
0.16
1.04 6.6 0.06 31.6
2xlO~6 . 1.4xlO~5
0.004
16 16 16
( 1975 ( 1977 ( 1977
PC13 ) PC13 ) POC13 )
300 322 974
1.8 1.0
0.04 0.06 0.016
1.2 2.74 0.28
0 - -
9.0 29.2 57.6
0.24
1.8 1.34 6.26
_ _ _
_ _
4.8
» - •*.—
- _ _ — -•-•
•MJQUJ
-------
Phosphorus Oxychloride Manufacture. The standard process (using air
and/or oxygen) may present a difficult task for the reflux condensers,
because the vapors are highly diluted with noncondensables. The use of
air alone instead of pure oxygen increases the noncondensable load
several fold. Even using air, however, if refrigerated vent condensers
are used, the measured raw waste load is less for this process than for
the alternate process that uses P2_0_5_ and C12_ for oxidation.
Data from Plant 11, which uses air oxidation and refrigerated condensers,
•M ]ur;traten that the raw waste load is less than for the alternate
process. The data were collected over a three-month period in 1973 from
the reactor/still scrubber for POC13_ manufacture, which had an estimated
flow rate of 1,800 1/kkg (430 gal/ton). The following average net
values were found:
Chloride 669 mg/1
CaC03_ acidity 1,213 mg/1
These data reduce to a raw waste load of 1.2 kg/kkg (2.4 Ib/ton) of HC1
plus 0.35 kg/kkg (0.7 Ib/ton) of HJPCW. These values are lower.than
corresponding values measured at PTant" 14, which uses the alternate
process.
Where product POC1_3_ is filtered, the used filter elements are first
washed to hydrolyse" the residual POC13. Disposable elements 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 some plants do not have continuous withdrawal of residues from
POC12 distillations, very little residue accumulates. Reactor cleanout
frequency varies from about once a month to very infrequently, depending
on the manufacturer. Some plants do not require POC13 reactor cleanout
except for maintenance purposes.
The water scrubber used for the distillation operation in the alternate
POCOJ process (using P205_ and Cl£) typically collected 3.4 kg of HC1
(anhydrous basis) and 3.0 kg of H3P04 (100 percent basis) per kkg of
product POC13 (6.8 Ib/ton and 6.0~lb7ton, respectively). The scrubber
also received fumes from PC13 and POC13 storage tank vents. Water from
P205_ and POC13 drum washing adds to this to give 3.4 kg of HC1 and 3.2
kg of H3P04_ per kkg of product (6.8 Ib/ton and 6.4 Ib/ton, respectively).
Approximately 6000 1/kkg (1440 gal/ton) of water are used. The source
of these data for the alternate process was a 30-day sampling study
conducted in 1975 at Plant 14.
The noncontact cooling water requirement for POC13_ manufacture by the
standard process is approximately 7900 1/kkg (1900 gal/ton), and by the
alternate process averages 220,000 1/kkg (53,000 gal/ton).
79
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r:;v.;-T
The data for POC12 given in Table 9 are a simple average of 1973
data from Plant 11 and 1975 data from Plant 1-4.
Summary. Table 9 is a summary of raw waste loads from phosphorus-consuming
plants. The table includes figures for dry process phosphoric acid,
phosphorus pentoxide, phosphorus pentasulfide, phosphorus trichloride,
and phosphorus oxychloride.
80
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TABLE 9
SUMMARY OF RAW WASTE LOADS FROM PHOSPHORUS CONSUMING PLANTS*
Phossy Water:
P4 cone . , ppm
1/kkg P4 consumed
kg P4/kkg P4 consumed
gal/ton P4 consumed
Ib/ton P4 consumed
Process Water Wasted:
1/kkg
gal/ton
Raw Waste Load,
kg/kkg: HC1
H2S03
H3P03 + H3P04
Raw Waste Load,
Ib/ton: HC1
H2S03
H3P03 + H3P04
Concentrations , mg/1 : #*
HC1
H2S03
H3P03 + HlPOZ"
Process Water Consumed:
1/kkg
gal/ton
Cooling Water Used:
1/kkg
gal/ton
Solid Wastes, kg/kkg:
Arsenic Compounds
Total Residues
Solid Wastes, Ib/ton:
Arsenic Compounds
Total Residues
H3P04
(7550"
1,700
580
1
HO
2
—
—
—
—
1
—
—
2
—
—
High
380
92
92,000
22,000
0.1
—
0.2
—
P205 P2S5
1,700 1,700
580 580
1 1
140 140
2 2
500 3,380
120 810
1.5
5.7
0.25 5.2
3.0
11.4
0.5 10.4
444
1,686
470 1,534
—
— —
29,000 6,500
7,000 1,560
0.05
0.7
0.1
1.4
PC13
1,700
580
1
140
2
1,500
360
1.5
—
1.3
3.0
—
2.7
1,000
—
870
—
—
31,000
7,500
0.006
1.4
0.012
2.8
POC13
—
—
—
—
—
3,900
930
2.3
—
1.8
4.6
—
3.6
590
—
460
—
—
7,900
1,900
—
0.05
—
0.1
* Waste loads are expressed in quantity of pollutant per quantity of
product (e.g., kg/kkg) unless otherwise indicated
** Based upon average kg/kkg pollutant and average 1/kkg process waste water
81
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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,
from processes using excess process water that becomes a waste stream,
and from miscellaneous sources such as wash downs, leaks, and spills.
Sodium Tripolyphosphate Manufacture. Plants 25, 27, and 31 have no
process wastes. The dust collected by cyclones from the gaseous dryer
effluent stream is added to the dryer solid product stream. The water
used for subsequent scrubbing of this gas stream from the dryer is then
recycled to the mix area and is used as process water in the neutrali-
zation step.
The neutralization step requires a total of 1,040 1/kkg (250 gal/ton),
of which 290 1/kkg (70 gal/ton) are recycled from the scrubber. Makeup
water, 750 1/kkg (180 gal/ton), is added since water is evaporated in
the product drying step. The makeup 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.(17)
Several plants have estimated the amount of fugitive dust escaping from
dust collectors and scrubbers (Plants 20, 21, 22, 23, 24, 25, 26, 27,
28, 29, 31, and 32). Significant fractions of these dusts are estimated
to become local accumulations. Based on the estimates of Plants 21, 23,
24, 25, 26, and 31, the average dustfall that may become a waste water
pollutant via storm water drainage is 0.85 kg/kkg (1.7 Ib/ton).
Some plants have indicated that leaks of phosphates from sodium phosphate
process equipment into noncontact cooling water can occur (Plants 24,
31, and 36). A combined noncontact cooling water stream at Plant 31
contains an estimated 0.06 kg phosphate (as P) per kkg of products (0.12
Ib/ton) that was not present in the raw water. Sodium tripolyphosphate,
phosphoric acid, and other soluble phosphates are produced at Plant 31.
Leaks from the processes are evidently the cause. For sodium tripolyphos-
phate plants, cooling water usage is highly variable, ranging from 0 to
6,700 1/kkg (0 to 1,600 gal/ton). The average cooling water usage for
the 11 plants that provided data is about 2,000 1/kkg (480 gal/ton).
Water usage depends on the extent of air cooling used as well as the
extent of cooling water recycle.
Plant 31> which recycles all process scrubber waters and other direct
process contact waste waters, generates about 400 1/kkg .(100 gal/ton) of a
combined waste water, excluding noncontact cooling water. This waste
water includes floor washings from production and shipping areas, leaks
and spills, equipment washout waters, area runoff (including roof and
site drainage), lab wastes, and safety and fire waters. This waste
82
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water contains about 2.7 kg/kkg (5.4 Ib/ton) of phosphates (as P) before
treatment, and cannot be recycled to the processes because of good
manufacturing practice. The plant makes food grade soluble phosphates,
and the wastes are based on all phosphates produced. Non-process wastes
such as leaks and spills can be totally recycled at technical grade
sodium tripolyphosphate plants such as Plants 21, 26, and 29, but not at
food grade plants, if contaminated, unless first purified.
Plant 23 estimates an achievable raw waste level of phosphates (as P) in
plant effluent attributable to food grade sodium tripolyphosphate to be
about 5.1 kg/kkg (10.2 Ib/ton). This is as raw, untreated effluent that
includes leaks, spills, housekeeping effluents, equipment washwater,
startup and shutdown process waste water, dustfall, rainwater runoff,
and blowdown from wet scrubbers.
Raw process waste.waters from the manufacture of soluble phosphates,
such as sodium tripolyphosphate, other sodium phosphates, potassium
phosphates, and ammonium phosphates, are not expected to contain suspended
solids to a significant degree.
Phosphate spills and cleanings can be recycled to non-food grade processes.
Only non-contaminated spills or cleanings can be recycled to food-grade
processes. In food-grade phosphate plants, contaminated solid wastes
are disposed of to landfill or sold for non-food grade uses.
Calcium Phosphates. Waste waters from the manufacture of food grade
calcium phosphates may include centrate or filtrate from dicalcium
phosphate slurry dewatering (or thickener overflow from lime treatment
of this effluent), wet scrubber effluent, leaks, spills, equipment
washwater, safety and housekeeping washings, startup and shutdown
process waste water, and storm water runoff. Plant 36 achieves total
recycle of centrate from the DCP process after lime treatment and
thickening. Plant 24 lime treats and thickens the centrate but discharges
the thickener overflow. At Plant 24, a scrubber is used for MCP but
only dry dust collection is used for DCP and TCP. The scrubber effluent
is recycled to the process when running. Plant 36 uses only dry dust
collection for the calcium phosphate processes, not wet scrubbers.
Plant 19 uses only a small scrubber for MCP. Blowdown is disposed of as
solid waste.
Plants 24 and 36 both report that leaks may occur from calcium phosphate
processes into noncontact cooling water. Plant 36 reports that cooling
towers are used and there is no blowdown from this operation. Plant 24
discharges cooling water to the sewer. For food grade calcium phosphate
operations, cooling water usage ranges from 0 to 385 1/kkg (0 to 92
gal/ton). Plants 19 and 36 report no cooling water discharge.
Plant 19 estimates the total raw waste load from a food grade MCP pro-
cess to be 400 to 700 1/kkg (100 to 160 gal/ton) and the phosphate (as
P) to be about 3.6 kg/kkg (7.3 Ib/ton). A phosphate level of 2.5
83
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kg/kkg (5.0 Ib/ton) was considered achievable by in-process controls
without end-of-pipe treatment.
The raw waste from an integrated calcium phosphate facility, excluding
the DCP centrate or filtrate, is estimated as 600 1/kkg (130 gal/ton)
containing 16 kg/kkg (32 Ib/ton) of suspended solids, including 4
(8 Ib/ton) of phosphate (as P) in solution and/or in the solids. This
includes allowances for leaks and spills, washdowns, and storm water
runoff. (Note that these estimates are higher than actual levels
achieved by Plant 31, an integrated soluble phosphate facility. )
For the manufacture of only food grade DCP, it was assumed that the DCP
centrate or filtrate discharged would be comparable to the clarifier
overflow at Plant 24. The rationale is that significantly higher phos-
phate losses (in Ib per ton of product) can be reduced to Plant 24
levels based on cost savings through reuse of recovered phosphate. In
fact, Plant 36 completely recycles DCP centrate. The standard raw waste
load from food grade DCP manufacture is the sum of the DCP centrate or
filtrate and the raw waste from an integrated calcium phosphate facility.
The raw waste load attributable to the DCP centrate or filtrate waste
water is taken as 3,000 1/kkg (730 gal/ton) containing 14 kg/kkg (28
Ib/ton) of suspended solids, including 0.75 kg/kkg (1.5 Ib/ton) of
phosphate (as P). These figures are based on data from Plant 24.
For non-food grade dicalcium phosphate plants, the water scrubbers that
collect airborne solids normally operate at partial recycle. Since
there is no waste from a dewatering operation, and since dry dust collec-
tion 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 five percent) plus 4 kg/kkg (8 Ib/ton) of dissolved phosphates from
acid mists (0.7 percent). At Plant 41, this bleed stream from the wet
scrubber recirculation system is charged directly to the neutralization
reactor; hence, this plant has no discharge. As an added feature, this
exemplary plant uses cooling water blowdown as makeup to the airborne-
solids scrubbing system, thereby eliminating all aqueous discharges
(except for the effluent from regeneration of a water softener).(21)
For non-food grade calcium phosphate plants, acid defluorination is an
additional source of raw wastes (unless defluorinated acid is used as a
raw material). Wet-process phosphoric acid (54 percent P205_) contains
approximately one percent fluorine. Upon silica treatment, 13.5 kg per
kkg of acid (27 Ib/ton), or 10.5 kg of silicon tetrafluoride per kkg of
product dicalcium phosphate dihydrate (21 Ib/ton), are liberated. When
hydrolyzed in the acid scrubber, the raw waste contains 12 kg/kkg product
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(24 Ib/ton) of combined fluosilicic acid (H2S1F6), hydrofluoric acid
(HF), and silicic acid (H2SiO_3_)- These raw wastes are contained in a
scrubber water flow of 6,300 1/kkg (1,500 gal/ton), so that the combined
concentration of fluosilicic acid, hydrofluoric acid, and silicic acid
is 1,900 mg/l.(2l)
Of the five non-food grade calcium phosphate plants for which data are
available, four use no noncontact cooling water. One plant uses 900
1/kkg (220 gal/ton) of noncontact cooling water.
The dustfall at non-food (feed) grade calcium phosphate plants is
expected to be comparable to that in food grade calcium phosphate plants.
Dustfall at calcium phosphate plants originating from dry or wet collectors
that could become a waste water pollutant via storm water drainage is 3
kg/kkg (6 Ib/ton), based on estimates from six plants. The range of the
estimates was 0 to 10 kg/kkg (0 to 20 Ib/ton).
In dry product plants, a significant housecleaning effort must be contin-
ually 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). The range of values
reported was 2.5 to 28 kg/kkg (5 to 56 Ib/ton). Plant 19 reports that
28 kg/kkg are reused in another plant for the production of elemental
phosphorus.
At least one dicalcium phosphate plant (Plant 45) uses an acidic solution
containing MCP and phosphoric acid derived from hydrochloric acid diges-
tion of animal bone as the phosphate source. Precipitation with lime,
filtration, and drying are then performed similarly to the standard
food-grade DCP process. This filtrate cannot be recycled without blowdown,
however, because of the high calcium chloride concentration (estimated
chloride: 20,000 to 30,000 ppm). Waste water volume from this plant is
about 25,000 1/kkg (6000 gal/ton). Phosphate in plant effluent (as P)
is 0.4 kg/kkg (0.8 Ib/ton), or about 16 mg/1.
Summary. Table 10 is a summary of raw waste loads from phosphate plants.
Waste load figures are given for sodium tripolyphosphate, food grade
calcium phosphates, and feed grade calcium phosphates.
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T.
TABLE 10
SUMMARY OF RAW WASTES FROM PHOSPHATE PLANTS*
Food Grade
Sodium Calcium Phosphates
Tripoly- DCP"Other Waste
Phosphate Dewatering Waters
600
130
16
12
32
24
27,000
20,000
Animal Feed
Calcium Phosphates
Acid Deflu-Solids
orination Scrubbing
6,300
1,500
Process Water Wasted:
1/kkg 400 3,000
gal/ton 100 730
Raw Waste Load,
kg/kkg:
TSS - 14
Dissolved P04 8.4 2.3
HF, H2S1F6, H2S102 - 12
Raw Waste Load,
Ib/ton:
TSS - 28
Dissolved P04_ 16.8 4.6
HF, H2SiF£, H2S10.3
Concentrations, mg/1:
TSS - 4,500
Dissolved P04_ 20,000 730
HF, H2SiF6_, H2S103 - 1,900
TDS - 1,900
Solid Wastes:
kg/kkg - 10**
Ib/ton - 20**
Cooling Water Used:
1/kkg 20,000
gal/ton 480
24
420
100
22.5
4
45
8
54,000
7,000
7,000
* All waste loads are expressed as quantities of pollutant per quantity
of product (e.g., kg/kkg) unless otherwise indicated
** These figures are solid waste estimates for total food grade calcium phosphate
plants.
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p.;~j , p._
'• • *• vi f~ I
i.*; .'M j
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
INTRODUCTION
Section V of this report quantitatively discussed the raw wastes generated
in the phosphorus derived chemicals industry. The following were identi-
fied as being constituents of the industry's process waste waters:
Acidity, Alkalinity, and pH
Chemical Oxygen Demand
Dissolved Solids
Radioactivity
Suspended Solids
Heat (Indicated by Temperature)
Ammonia
Arsenic
Cadmium
Chloride
Cyanide
Fluoride
Phenols
Ortho and Condensed Phosphates and Elemental Phosphorus
Sulfates and Sulfites
Sulfides
Vanadium
RATIONALE FOR SELECTION OF POLLUTANT PARAMETERS
The following discussion examines each of the above constituents and
their impact on receiving waterways from a chemical, physical, and
biological viewpoint. The chemical, physical, and biological properties
of the pollutants and pollutant parameters are described, and the unde-
sirable characteristics that these parameters exhibit or indicate are
stated, giving reason to why they were selected. Additional constituents
such as hexavalent chromium, iron, alkalinity, and hardness, which are
of typical concern whenever blowdowns from cooling towers, boilers, and
water treatment facilities are involved, are noted here but are not
discussed in detail in this study.
Acidity, Alkalinity, and pH
Although not a specific pollutant, pH is related to the acidity or
alkalinity of a waste water stream. It is not a linear or direct measure
of either; however, it may properly be used as a surrogate to control
both excess acidity and excess alkalinity in water. The term pH is used
to describe the hydrogen ion-hydroxyl ion balance in water. Technically,
pH is the hydrogen ion concentration or activity present in a given
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solution. pH numbers are the negative logarithm of the hydrogen ion
concentration. A pH of 7 generally indicates neutrality or a balance
between free hydrogen and free hydroxyl ions. Solutions with a pH above
7 indicate that the solution is alkaline, while a pH below 7 indicates
that the solution is acid.
Knowledge of the pH of water or waste water is useful in determining
necessary measures for corrosion control, pollution control, and dis-
infection. Waters with a pH below 6.0 are corrosive to water works
structures, distribution lines, and household plumbing fixtures. Such
corrosion can add constituents to drinking water such as iron, copper,
zinc, cadmium, and lead. Low pH waters not only tend to dissolve metals
from structures and fixtures but also tend to redissolve or leach metals
from sludges and bottom sediments. The hydrogen ion concentration can
affect the "taste" of the water, and at a low pH, water tastes "sour".
Extremes of pH or rapid pH changes can exert stress conditions or kill
aquatic life outright. 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.
For example, metallocyanide complexes can increase a thousand-fold in
toxicity with a drop of 1.5 pH units. Similarly, the toxicity of ammonia
is a function of pH. The bactericidal effect of chlorine in most cases
is less as the pH increases, and it is economically advantageous to keep
the pH close to 7.
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. Appreciable
irritation will cause severe pain.
Acidity is defined as the quantitative ability of a water to neutralize
hydroxyl ions. It is usually expressed as the calcium carbonate equiva-
lent of the hydroxyl ions neutralized. Acidity should not be confused
with pH value. Acidity is the quantity of hydrogen ions that may be
released to react with or neutralize hydroxyl ions, while pH is a
measure of the free hydrogen ions in a solution at the instant the pH
measurement is made. Certain types of solutions, called buffers, can
resist change in acidity or alkalinity. A buffer solution contains
either a weak acid and its salt, or a weak base and its salt. The
components of a buffer solution minimize changes in pH by neutralizing
added acids or bases.
Highly acid waters are corrosive to metals, concrete, and living organisms,
exhibiting the pollutional characteristics outlined above for low pH
waters. Depending on buffering capacity, water may have a higher total
acidity at pH values of 6.0 than other waters with a pH value of 4.0.
* The term toxic or toxicity is used herein in the normal scientific
sense of the word and not as a specialized term referring to Section
307(a) of the Act.
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«•>—-ir-
Alkalinity is defined as the ability of a water to neutralize hydrogen
ions. It is usually expressed as the calcium carbonate equivalent of
the hydrogen ions neutralized.
Alkalinity is commonly caused by the presence of carbonates, bicarbonates,
hydroxides and to a lesser extent by borates, silicates, phosphates, and
organic substances. Because of the nature of the chemicals causing
alkalinity and the buffering capacity of carbon dioxide in water, very
high pH values are seldom found in natural waters.
Excess alkalinity as exhibited in a high pH value may make water corrosive
to certain metals, detrimental to most natural organic materials, and
toxic to living organisms.
A variety of titration procedures are available for alkalinity and
acidity measurements. The quantity of acid required to restore an
alkaline waste water to the upper permissible pH limit is the preferred
value of alkalinity. The quantity of base required to restore an acidic
waste water to the lowest permissible pH limit is the significant acidity
value.
Chemical Oxygen Demand
Organic and some inorganic compounds can cause an oxygen demand to be
exerted in a receiving body of water. Indigenous microorganisms utilize
the organic wastes as an energy source and oxidize the organic matter.
In doing so their natural respiratory activity will utilize the dissolved
oxygen.
Chemical oxygen demand (COD) is a purely chemical oxidation test devised
as an alternate method to the BOD test for estimating the total oxygen
demand of a waste water. Since the method relies on chemical rather
than biological oxidation, it is more precise, accurate, and rapid than
the BOD test. The COD test is widely used to estimate the total oxygen
demand (ultimate rather than 5-day BOD) to oxidize the compounds in a
waste water. It is based on the fact that organic compounds, with a few
exceptions, can be oxidized by strong chemical oxidizing agents under
acid conditions with the assistance of certain inorganic catalysts.
The COD test measures the oxygen demand of compounds that are biologically
degradable and of many that are not. Pollutants that are measured by
the BOD5 test will be measured by the COD test. In addition, pollutants
that are" more resistant to biological oxidation will also be measured as
COD. COD is a more inclusive measure of oxygen demand than is BOD5_ and
will result in higher oxygen demand values than will the BOD_5_ test.
The compounds that are more resistant to biological oxidation are becom-
ing of greater and greater concern, not only because of their slow but
continuing oxygen demand on the resources of the receiving water, but
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CT
!« I
also because of their potential health effects on aquatic life and
humans. Many of these compounds result from industrial discharges, and
some have been found to have carcinogenic, mutagenic, and similar adverse
effects, either singly or in combination. Concern about these compounds
has increased as a result of demonstrations that their long life in
receiving waters - the result of a slow biochemical oxidation rate -
allows them to contaminate downstream water intakes. The commonly used
systems of water purification are not effective in removing these types
of materials, and methods of disinfection such as chlorination may
convert them into even more hazardous materials.
Thus the COD test measures organic matter that exerts an oxygen demand
and that may affect the health of the people. It is a useful analytical
tool for pollution control activities. It also provides a more rapid
measurement of the oxygen demand and an estimate of organic compounds
that are not measured in the BOD5 test.
Dissolved Solids
In natural waters the dissolved solids consist mainly of carbonates,
chlorides, sulfates, phosphates, and possibly nitrates of calcium,
magnesium, sodium, and potassium, with traces of iron, manganese, and
other substances.
Many communities in the United States and in other countries use water
supplies containing 2,000 to 4,000 mg/1 of dissolved salts, when no
better water is available. Such waters are not palatable, may not
quench thirst, and may have a laxative action on new users. Waters
containing more than 4,000 mg/1 of total salts are generally considered
unfit for human use, although in hot climates such higher salt concentra-
tions can be tolerated whereas they could not be in temperate climates.
Waters containing 5,000 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 acclimati-
zation. 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.
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vr
Dissolved solids in industrial waters can cause foaming in boilers and
cause interference with cleanliness, 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. Specific conduct-
ance is frequently used as a substitute method of quickly estimating the
dissolved solids concentration in water.
Radioactivity
Ionizing radiation, when absorbed in living tissues 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, including humans, fishes,
and invertebrates. Beyond the obvious fact that 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 radio-
nuclides 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 radionuclides 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.
Total Suspended Solids (TSS)
Suspended solids include both organic and inorganic materials. The
inorganic compounds include sand, silt, and clay. The organic fraction
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p,r> F\ :•• r-
Ut>'« '(i '. * I
includes such materials as grease, oil, tar, and animal and vegetable
waste products. These solids may settle out rapidly, and bottom deposits
are often a mixture of both organic and inorganic solids. Solids may be
suspended in water for a time, and then settle to the bed of the stream
or lake. The 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.
Suspended solids in water interfere with many industrial processes and
cause foaming in boilers and incrustations on equipment exposed to such
water, especially as the temperature rises. They are undesirable in
process water used in the manufacture of steel, in the textile industry,
in laundries, in dyeing, and in cooling systems.
Solids in suspension are aesthetically displeasing. When they settle to
form sludge deposits on the stream or lake bed, they are often damaging
to life in the water. 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. When of an organic nature,
solids use a portion or all of the dissolved oxygen available in the
area. Organic materials also serve as a food source for sludgeworms and
associated organisms.
Disregarding any toxic effect attributable to substances leached out by
water, suspended solids may kill fish and shellfish by causing abrasive
injuries and by clogging the gills and respiratory passages of various
aquatic fauna. Indirectly, suspended solids are inimical to aquatic
life because they screen out light, and they promote and maintain the
development of noxious conditions through oxygen depletion. This results
in the killing of fish and fish food organisms. Suspended solids also
reduce the recreational value of the water.
Turbidity of water is related to the amount of suspended and colloidal
matter contained in the water. It affects the clearness and penetration
of light. The degree of turbidity is only an expression of one effect
of suspended solids upon the character of the water. Turbidity can
reduce the effectiveness of chlorination and can result in difficulties
in meeting BOD and suspended solids limitations. Turbidity is an indirect
measure of suspended solids.
Heat (Indicated by 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
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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 physio-
logical 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 decompo-
sition 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
temperature increases the bacterial multiplication rate when the environ-
ment 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 32°C (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 tempera-
tures. 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 32 C
(90 F), which is close to the tolerance limit for the population. This
occurrence could seriously affect certain fish that depend on benthic
organisms as a food source.
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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 aesthetic value of a water-
course.
In general, marine 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 of the estuary that can be adversely affected by
extreme temperature changes.
Ammonia (NH3)
Ammonia occurs in surface and ground waters as a result of the decompo-
sition of nitrogenous organic matter. It is one of the constituents of
the complex nitrogen cycle. It may also result from the discharge of
industrial wastes from chemical or gas plants, from refrigeration plants,
from scouring and cleaning operations where "ammonia water" is used,
from the processing of meat and poultry products, from rendering opera-
tions, from leather tanning plants, and from the manufacture of certain
organic and inorganic chemicals. Because ammonia may be indicative of
pollution and because it increases the chlorine demand, it is recommended
that ammonia nitrogen in public water supply sources not exceed 0.5
mg/1.
Ammonia exists in its non-ionized form only at higher pH levels and is
most toxic in this state. At low pH levels, ammonia is converted to the
less toxic ammonium ion. Ammonia, in the presence of dissolved oxygen,
is converted to nitrate (N03>) by nitrifying bacteria. Nitrite (N02_),
which is an intermediate product between ammonia and nitrate, sometimes
occurs in quantity when depressed oxygen conditions permit. Ammonia can
exist in several other chemical combinations, including ammonium chloride
and other salts.
Nitrates are considered to be among the objectionable components of
mineralized waters. Excess nitrates cause irritation to the gastroin-
testinal tract, causing diarrhea and diuresis. Methemoglobinemia, a
condition characterized by cyanosis and that can result in infant and
animal deaths, can be caused by high nitrate concentrations in waters
used for feeding. Ammonia can exist in several other chemical combina-
tions, including ammonium chloride and other salts. Evidence exists
that ammonia exerts a toxic effect on all aquatic life depending upon
-------
the pH, dissolved oxygen level, and the total ammonia concentration in
the water. A significant oxygen demand can result from the microbial
oxidation of ammonia. Approximately 4.5 grams of oxygen are required
for every gram of ammonia that is oxidized. Ammonia can add to eutrophi-
cation problems by supplying nitrogen to aquatic life.
Arsenic (As)
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 sometimes used for hardening and improving the sphericity of
shot, as a constituent in some electroplating baths, and is finding an
increasing use as a doping agent for solid state devices, especially
transistors. It is also found as an ingredient in dyes and in the
smelting and refining of some metals, particularly lead and zinc.
The major use of arsenic is as an insecticide and poison for pest control
in the home and in industry. Recently, arsenicals have found some
usefulness in livestock production, mainly as a biostat in poultry
feeding or in "dip" solutions for animals. Up to 5 mg/1 of sodium
arsenate in drinking water functions in some way to reduce selenium
poisoning in farm animals.
Severe human poisoning can result from injection of as little as 100 mg
of arsenic, and less than 130 mg has proven fatal. Arsenic can accumulate
in the body faster than it is excreted and can build to toxic levels
from small amounts taken periodically through the respiratory and in-
testinal walls from air, water, and food. Surface water criteria for
public water supplies have set a permissible level of arsenic in those
waters at 0.05 mg/1.
Arsenic in forms such as lead arsenate, calcium arsenate, and paris
green (copper acetoarsenite) have been used as insecticides, with the
most toxic of these substances being paris green. Since the advent of
DDT and other insecticides, these compounds have been largely replaced.
Cadmium (Cd)
Cadmium is a relatively rare element that is seldom found in sufficient
quantities in a pure state to warrant mining or extraction from the
earth's surface. It is found in trace amounts of about 1 ppm throughout
the earth's crust. Cadmium is, however, a valuable by-product of zinc
production.
Cadmium is used primarily as a metal plating material and can be found
as an impurity in the secondary refining of zinc, lead, and copper.
Cadmium is also used in the manufacture of primary cells of batteries
and as a neutron adsorber in nuclear reactors. Other uses of cadmium
are in the production of pigments, phosphors, semi-conductors, electrical
contactors, and special purpose low temperature alloys.
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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 that might lead to mutagenic or teratogenic effects. Cadmium
is known to have marked acute and chronic effects on aquatic organisms
also.
Toxic effects of cadmium on man have been reported from throughout the
world. Cadmium is normally ingested by humans through food and water
and also by breathing air contaminated by cadmium. Cadmium in drinking
water supplies is extremely hazardous to humans, and conventional treat-
ment, as practiced in the United States, does not remove it. Cadmium
accumulates 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.
The allowable cadmium concentration in drinking water is set as low as
0.01 mg/1 in the U.S. and as high as 0.10 mg/1 in Russia.
Cadmium acts synergistically with other metals. Copper and zinc subs-
tantially increase its toxicity. Cadmium is concentrated by marine
organisms, particularly mollusks, 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.
Chloride
Dissolved chlorides are a major constituent of the total dissolved
solids in waste waters from this industry and are discussed 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.
Cyanide (CN)
Cyanide is a compound that is widely used in industry primarily as
sodium cyanide (NaCN) or hydrocyanic acid (HCN). The major use of
cyanides is in the electroplating industry, where cyanide baths are used
to hold ions such as zinc and cadmium in solution. Cyanides in various
compounds are also used in steel plants, chemical plants, photographic
processing, textile dying, and ore processing.
Of all the cyanides, hydrogen cyanide (HCN) is probably the most acutely
lethal compound. HCN dissociates in water to hydrogen ions and cyanide
ions in a pH dependent reaction. The cyanide ion is less acutely lethal
96
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than HCN. The relationship of pH to HCN shows that as the pH is lowered
to below 7, there is less than one percent of the cyanide molecules in
the form of the CN ion and the rest is present as HCN. When the pH is
increased to 8, 9, and 10, the percentage of cyanide present as CN ion
is 6.7, 42, and 87 percent, respectively. The toxicity of cyanides is
also increased by increases in temperature and reductions in oxygen
tensions. A temperature rise of 10 C produced a two- to threefold
increase in the rate of the lethal action of cyanide.
In the body, the CN ion, except for a small portion exhaled, is rapidly
changed into a relatively non-toxic complex (thiocyanate) in the liver
and eliminated in the urine. There is no evidence that the CN ion is
stored in the body. The safe ingested limit of cyanide has been estimated
at something less than 18 mg/day, part of which comes from normal environ-
ment and industrial exposure. The average fatal dose of HCN by ingestion
by man is 50 to 60 mg. It has been recommended that a limit of 0.2 mg/1
cyanide not be exceeded in public water supply sources.
The harmful effects of the cyanides on aquatic life are affected by the
pH, temperature, dissolved oxygen content, and the concentration of
minerals in the water. The biochemical degradation of cyanide is not
affected by temperature in the range of 10 C to 35 C, while the toxicity
of HCN is increased at higher temperatures.
On lower forms of life and organisms, cyanide does not seem to be as
toxic as it is toward fish. The organisms that digest BOD were found to
be inhibited at 1.0 mg/1 and at 60 mg/1, although the effect is more one
of delay in exertion of BOD than total reduction.
Certain metals such as nickel may complex with cyanide to reduce lethality,
especially at high pH values. On the other hand, zinc and cadmium
cyanide complexes may be exceedingly toxic.
Fluoride
Fluorine is the most reactive of the nonmetals and is never found free
in nature. It is a constituent of fluorite or fluorspar, calcium fluoride,
cryolite, and sodium aluminum fluoride. Due to their origins, fluorides
in high concentrations are not a common constituent of natural surface
waters; however, they may occur in hazardous concentrations in ground
waters.
Fluoride can be found in plating rinses and in glass etching rinse
waters. Fluorides are also used as a flux in the manufacture of steel,
for preserving wood and mucilages, as a disinfectant, and in insecticides.
Fluorides in sufficient quantities are toxic to humans, with doses of
250 to 450 mg giving severe symptoms and 4.0 grams causing death. A
concentration of 0.5 g/kg of body weight has been reported as a fatal
dosage.
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•" - P A <7T
»„•'i \r~il I
There are numerous articles describing the effects of fluoride-bearing
waters on dental enamel of children; these studies lead to the generali-
zation 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.
The recommended maximum levels of fluoride in public water supply sources
range from 1.4 to 2.4 mg/1.
Fluorides may be harmful in certain industries, particularly those in-
volved in the production of food, beverages, Pharmaceuticals, and medi-
cines. Fluorides found in irrigation waters in high concentrations (up
to 360 mg/1) have caused damage to certain plants exposed to these
waters. Chronic fluoride poisoning of livestock has been observed in
areas where water contained 10 to 15 mg/1 fluoride. Concentrations of
30 to 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 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 concen-
trations higher than 1.5 mg/1.
Phenols
Phenols, defined as hydroxy derivatives of benzene and its condensed
nuclei, may occur in domestic and industrial waste water and in drinking
water supplies. Chlorination of such waters can produce odoriferous and
objectionable tasting chlorophenols that may include o-chlorophenol; p-
chlorophenol; and 2, 4-dichlorophenol.
Although described in the technical literature simply as phenols, the
phenol waste category can include a wide range of similar chemical
compounds. In terms of pollution control, reported concentrations of
phenols are the result of a standard methodology that measures a general
group of similar compounds rather than being based upon specific identi-
fication of the single compound, phenol (hydroxybenzene).
Phenols are used in some cutting oils and in the molding of plastics.
Cutting fluids can contain phenolic compounds, since these materials are
normal constituents of hydrocarbon mixtures. In addition, phenolic
compounds are added to oils as preservatives or for odor control. They
also are found in the waste waters from the petroleum industry and from
certain products of the organic chemical industry.
Phenolic compounds may adversely affect fish in two ways: first, by a
direct toxic action, and second, by imparting a taste to the figh flesh.
The toxicity of phenol towards fish increases as the dissolved oxygen
level is diminished, as the temperature is raised, and as the hardness
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is lessened. Phenol appears to act as a nerve poison causing too much
blood to get to the gills and to the heart cavity and is reported to
have a toxic threshold of 0.1 to 15 mg/1.
Mixed phenolic substances appear to be especially troublesome in imparting
taste to fish flesh. Chlorophenol produces a bad taste in fish far
below lethal or toxic doses. Threshold concentrations for taste or odor
in chlorinated water supplies have been reported as low as 0.00001 to
0.001 mg/1. Phenols in concentrations of only one part per billion have
been known to affect water supplies.
The ingestion of concentrated solutions of phenol by humans results in
severe pain, renal irritation, shock, and possibly death. A total dose
of 1.5 grams may be fatal. Phenols can be metabolized and oxidized in
waste treatment facilities containing organisms acclimated to the phenol
concentration in the wastes.
Ortho and Condensed Phosphates and Elemental Phosphorus
Phosphorus occurs in natural waters and in waste waters in the form of
various types of phosphate. These forms are commonly classified into
orthophosphates, condensed phosphates (pyro-, meta-, and polyphosphate),
and organically bound phosphates. These may occur in the soluble form,
in particles of detritus, or in the bodies of aquatic organisms.
The various forms of phosphates find their way into waste waters from a
variety of industrial, residential, and commercial sources. Small
amounts of certain condensed phosphates are added to some water supplies
in the course of potable water treatment. Large quantities of the same
compounds may be added when the water is used for laundering or other
cleaning, since these materials are major constituents of many commercial
cleaning preparations. Phosphate coating of metals is another major
source of phosphates in certain industrial effluents. Condensed phos-
phates present in waste water from certain industries may interfere with
precipitation and clarification operations unless first hydrolyzed to
orthophosphate.
The increasing problem of the growth of algae in streams and lakes
appears to be associated with the increasing presence of certain dissolved
nutrients, chief among which is phosphorus. Phosphorus is an element
that is essential to the growth of organisms, and it can often be the
nutrient that limits the aquatic growth that a body of water can support.
In instances where phosphorus is a growth limiting nutrient, the discharge
of sewage, agricultural drainage, or certain industrial wastes to a
receiving water may stimulate the growth, in nuisance quantities, of
photosynthetic aquatic microorganisms and macroorganisms.
The increase in organic matter production by algae and plants in a lake
undergoing eutrophication has ramifications throughout the aquatic
ecosystem. Greater demand is placed on the dissolved oxygen in the
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water as the organic matter decomposes at the termination of the life
cycles. Because of this process, the deeper waters of the lake may
become entirely depleted of oxygen, thereby destroying fish habitats and
leading to the elimination of desirable species. The settling of particu-
late matter from the productive upper layers changes the character of
the bottom mud, also leading to the replacement of certain species by
less desirable organisms. Of great importance is the fact that nutrients
inadvertently introduced to a lake are, for the most part, trapped there
and recycled in accelerated biological processes. Consequently, the
damage done to a lake in a relatively short time requires a many-fold
increase in time for recovery of the lake.
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 such 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 aesthetic 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 is subject
to bioaccumulation in much the same way as mercury. Collidal elemental
phosphorus will poison marine fish (causing skin tissue breakdown and
discoloration). Also, phosphorus 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 Sulfites
Sulfites are oxidized to sulfates in streams, exerting a chemical oxygen
demand on the streams. Sulfates are not particularly harmful, but are a
major constituent of the total dissolved solids in waste waters from
this industry (and are discussed separately as such).
Sulfides
I
Sulfides are oxidizable and therefore can exert an oxygen demand on the
receiving stream. Their presence in amounts that consume oxygen at a
rate exceeding the oxygen uptake of the stream can produce a condition
of insufficient dissolved oxygen in the receiving water. Sulfides also
impart an unpleasant taste and odor to the water and can render the
water unfit for other uses.
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Sulfides are constituents of many industrial wastes such as those from
tanneries, paper mills, chemical plants, and gas works; but they are
also generated in sewage and some natural waters by the anaerobic decompo-
sition of organic matter. When added to water, soluble sulfide salts
such as Na£S dissociate into sulfide ions that in turn react with the
hydrogen ions in the water to form HS or H2S, the proportion of each
depending upon the resulting pH value. Thus, when reference is made to
sulfides in water, the reader should bear in mind that the sulfide is
probably in the form of HS~ or H2S.
Owing to the unpleasant taste and odor that result when sulfides occur
in water, it is unlikely that any person or animals will consume a
harmful dose. The thresholds of taste and smell were reported to be 0.2
mg/1 of sulfides in pulp mill wastes. For industrial uses, however,
even small traces of sulfides are often detrimental. Sulfides are of
little importance in irrigation waters.
The toxicity of sulfide solutions toward fish increases as the pH value
is lowered, i.e., the H2S or HS~ appears to be the principal toxic agent
rather than the sulfide~"ion. In water containing 3.2 mg/1 of sodium
sulfide, trout overturned in two hours at pH 9.0, in 10 minutes at pH
7.8, and in four minutes at pH 6.0. Inorganic sulfides have proved
fatal to sensitive fishes such as trout at concentrations between 0.5
and 1.0 mg/1 as sulfide, even in neutral and somewhat alkaline solutions.
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.
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 cholesterol and accelerate its catabolism in
rabbits.
Vanadium causes death to occur 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.
CONCLUSION
In view of the data presented above, it is judged that all of the
mentioned waste constituents generated by the phosphorus derived chemicals
industry should be identified as pollutant parameters as defined in the
Federal Water Pollution Control Act Amendments of 1972.
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In the paragraphs above, the harmful characteristics are given for all
the parameters that are encountered in the phosphorus derived chemicals
industry. Table 11 summarizes the parameters found for each chemical
product.
Although many parameters appear in the waste streams from these plants,
only those primary parameters signified by "x" need be used to set
effluent standards. The remaining parameters signified by zeros are
adequately treated if the primary parameters are so treated.
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TABLE 11
WASTE WATER CONSTITUENTS OF PHOSPHORUS DERIVED CHEMICALS CATEGORY
Parameter
Chemical
P4 & Fe2P
K3P04
P205
P2S5_
PC13
POC13
Na5P3010
TSS
X
X
X
X
X
X
X
F
Total P Total S SiF6 TDS
X 0X0
X 0
X 0
X 0
X
X
X 0
Low
pH
0
0
0
0
0
0
0
Heat
0
0
0
0
0
0
0
P4
X
0
0
0
0
0
0
V, Cd,
As Ra, U
0 0
0
0
0
X
0
CaHP04.
( feed grade )
X
( food grade ) X
0
X
0
0
0
0
0
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 phosphorus derived chemicals industry and the raw wastes
from the industry before control or treatment. Section VI identified
the constituents of the raw wastes that are classified as pollutants.
Table 11 in Section VI 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 phosphorus derived chemicals
industry, where such pollutant constituents are usually very low and not
a significant factor. Hence, control and treatment techniques in this
industry are of the chemical and chemical engineering variety, and
include neutralization, pH control, precipitation, ionic reactions,
oxidation, 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 technology is
discussed in considerable detail. Much of this discussion is based on
observed actual abatement practice in the industry and on plant effluent
sampling data.
IN-PROCESS CONTROLS
Control of waste waters in the phosphorus derived chemicals industry
includes in-process abatement measures, monitoring techniques, safety
practices, housekeeping, containment 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 raw water picks up contaminants from various uses and sources,
including:
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1. noncontact 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 through recycle. In many instances, the treatment costs,
complexity, and energy requirements may be significantly reduced through
segregation. Unfortunately, it is sometimes a practice today to blend
small, heavily contaminated streams with large noncontaminated streams
such as cooling water effluents. Once this has been allowed to happen,
treatment costs, energy requirements for treatment, and the efficient
use of water resources have all been compromised.
In general, plant effluents can be segregated into:
1. Noncontact Cooling Water. Except for occasional leaks, noncontact
cooling water has no waste pickup except heat. It is usually high
volume.
2. Process Water. This water is usually contaminated but often small
volume.
3. Auxiliary Streams. These streams include ion exchange regenerants,
cooling tower blowdowns, boiler blowdowns, leaks, and washings. The
volumes are low but the streams are often highly contaminated. These
streams are usually considered to be process waste water.
Although situations vary, the basic segregation principle is to not mix
large uncontaminated cooling water streams with 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 operation costs are all lower.
In the phosphorus derived chemicals industry, many plants have accomplished
the desired segregation of water streams, often by painstaking rerouting
of sewer lines that have existed for many years. Among the plants
notable in this respect are Plants 4, 11, 24, 27, and 41..
Recycle o£ 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 many
plants notable in this respect that recycle scrubber water, thus satisfy-
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ing the scrubber water flow rate demands (on the basis of mass transfer
considerations) while retaining control of water usage. These plants
are Plants 2, 3, 4, 5, 6, 13, 14, 16, 17, 20, 21, 22, 23, 24, 26, 29,
and 32.
Recycle of scrubber water permits the subsequent treatment of much
smaller quantities of waste water with much higher concentrations of
polluting constituents. Both these attributes make waste water treatment
more economical, and in some cases, more efficient, from a removal
standpoint.
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 efficiencies exceed those of wet scrubbers, and where
operating temperature ranges have been extended with high-temperature
media development. 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 collec-
tion, the product recovered may significantly contribute to alleviating
the operating cost of the collectors.
Plants in this industry that are notable in having at least some dry
dust collection include Plants 2, 3, 4, 5, 6, 7, 8, 22, 24, 25, 26, 27,
29, 31, 32, 36, 39, 40, 41, 42, 43, and 44.
Housekeeping and Containment
Containment and disposal considerations may be divided into several
categories:
1. minor spills and leaks
2. major product spills and leaks
3. upsets and disposal failures
4. storm water runoff
5. pond and lagoon control
6. vessel and container cleanout
Minor Spills and Leaks. There are minor spills and leaks from time to
time 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
cannot be entirely eliminated. However, 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.
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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 drips. Pipe and equipment
leaks are minimized by selection of corrosion-resistant materials.
Containment techniques include 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. Spills of dry solids can be collected by
sweeping or vacuuming, thus reducing pollutant loads and minimizing the
use of water for wash downs. Plants that have installed vacuum cleaning
equipment for dry spill collection include Plants 24, 25, 31, and 32.
All minor leaks and spills should then go to a containment system, catch
basin, pump sump, 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 subcategory 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. Makeup 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 no discharge is to install
an auxiliary tank to collect phossy water overflows from the phosphorus
storage tank; this system can be made a closed loop by reusing the
phossy water from the auxiliary tank as makeup 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 makeup valves.
Facilities that have installed closed loop phossy water systems include
Plants 14 and 16.
Major Product Spills and Leaks. Major product spills and leaks are
catastrophic occurrences with major loss of product. Causes of such
occurrences may include 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 occur-
rences is tank or valve failures. Such occurrences 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.
Plants 5 and 11 are prime examples where product tanks and transfer
pumps have been systematically diked for containment of spills. At
Plant 24, phosphoric acid facilities are diked for spill containment.
At Plant 16, curbs have been constructed around PC13 and POC13. facilities
for the same purpose.
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Upsets and Disposal Failures. In many processes there are short-term
upsets. These may occur during startup or shutdown or during normal
operation. The phosphorus 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 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 in a proper manner so as not to
endanger life or damage the environment.
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 spills remain in the sewer and ensure a continu-
ous water flow to prevent fire. There has been general reluctance to
clean spills out since phosphorus burns when exposed to air. With this
practice, of course, all water flowing in that sewer for long periods of
time becomes contaminated with phosphorus.
Provisions should 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 off-line removal and cleaning of the trap
(with safe disposal of the phosphorus).
Storm Water Runoff. Storm water runoff may present pollution control
problems whenever the runoff receives incidental contamination from
production processes or process waste waters, or when it contacts
stockpiles of ore, by-products, or solid wastes. Facilities should be
designed to treat or to contain this contaminated runoff. The volume of
contaminated storm runoff should be minimized through segregation and
the prevention of contamination.
Storm runoff from outside the plant area, as well as uncontaminated
runoff, should be diverted around the plant or contaminated areas in
order to discharge without the necessity of treatment. Plants 1 and 8
divert uncontaminated storm runoff from outside the plant around their
process water treatment systems.
Plants 1, 5, 9, and 31 segregate storm water that is or may be highly
contaminated with process pollutants. Plant 5 collects this storm water
in an evaporation pond. Plants 1, 3> and 9 treat this storm water with
other waste waters and reuse it in the process. There is no discharge
of contaminated storm water runoff from these plants. Plant 31 combines
storm water runoff with other contaminated waste water and treats the
combined stream before discharge. At Plants 5, 9, and 31 > the remaining
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storm water is not chemically or biologically treated before discharge
but is combined with noncontact cooling water, noncontact ancillary
waste water, and other waste water, monitored, sampled, and discharged.
Plant 1 diverts the remaining storm water to avoid contamination by
process pollutants. Plants 22, 25, and 41 divert storm water to prevent
its entrance into contaminated waste water ponds. This is achieved by
curbing, diking, and the use of drainage ditches.
If there is adequate evaporative capacity in a plant process waste water
reuse system to accept all contaminated storm water runoff without
discharge, even in the case of excess rainfall, then this runoff may be
combined and handled with process waste water. If there is insufficient
evaporative capacity, then the excess contaminated storm water runoff
should be separately collected so that it may be treated, evaporated,
used, and/or discharged. If discharge is necessary, maximum effluent
contaminant reductions are attainable by segregating the initial and
most highly contaminated portion of runoff during a rainfall event from
the remainder of the runoff and by treating both streams separately.
The most highly contaminated portion of runoff during a heavy rainfall
usually occurs in the first 10 to 20 minutes.
All site storm water runoff should be sampled to the extent required by
the monitoring authority to assure that good practices are observed in
storm water runoff management.
Lagoons or ponds used for containment of contaminated or treated waste
water should be diked to prevent the uncontrolled influx of uncontaminated
or minimally contaminated storm water runoff. Production areas or
storage areas where contamination potential is high should be isolated
by drainage ditches and dikes to reduce the volume of possibly highly
contaminated storm water runoff requiring treatment or containment.
A system for handling excess contaminated storm water runoff should
include an impoundment or holding pond, with valving to permit either
impoundment or direct discharge. The impoundment effluent pipe should
be valved to permit diversion either to a treatment system or to direct
discharge. The impoundment should be sized to allow sampling and
analysis time before direct discharge, if uncontaminated. If contami-
nated, it would be impounded and held for natural evaporation, treatment,
or recycle to process uses. The system should be arranged so that only
slightly contaminated or uncontaminated water is discharged during
periods of excessive rainfall. Systems that allow flushing out of
highly contaminated ponds should be avoided. Automation of the diversion
facilities may be feasible, utilizing level and flow controls. Continuous
conductivity monitoring of the storm water runoff may reduce the need
for immediate laboratory analysis of samples, although verification
sampling and analysis should be done to prove the efficiency and continued
success of such a system.
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In the elemental phosphorus industry, storm water may become contaminated
from phosphorus and phossy water spills, dusts and mists escaping from
dust collectors and scrubbers, ore, slag, electrostatic precipitator
dusts, pond dredgings, and the dustfall from any of these sources that
become airborne. Plants 6, 7 and 9 use riding-type street sweepers on
paved areas for removal of dusts. Plant 5 collects approximately
10 kgof solids per kkg of production (20 Ib/ton) in a settling pond for
storm water and noncontact cooling water.
The phosphates segment of this industry is characterized by the handling,
storing, conveying, sizing, packaging, and shipping of finely divided
solid products. A phosphate plant typically has dust accumulations on
the exterior surfaces of buildings, equipment, and grounds. If not
removed, these solids will be picked up by storm water either as suspended
or dissolved solids. Plants 24, 27, and 41 have positive continual
cleanup programs for solids that minimize pollution of storm water
runoff. Plants 21, 23, 24, 25, 26, and 31 estimate an average on-site
dustfall of 0.85 kg/kkg product (1.7 Ib/ton), even though many of the
product dust collectors achieve 99 percent collection efficiency. The
range of estimated dustfall values reported was 0.2 to 1.8 kg/kkg (0.4
to 3.6 Ib/ton). In some cases, dust collector efficiencies can reach
99.5 to 99.9 percent removal, thus significantly reducing the amount of
dust that can become a storm water pollutant.
Some plants may find that periodic removal of phosphate dusts from paved
areas (using riding-type sweepers) and from roofs (using vacuuming
equipment) may be more economical than collection and treatment of storm
water contaminated by these wastes. Plants 24, 25, 31, and 32 use
vacuum cleaning equipment for removing dry accumulations in process and
storage areas. Extension of centralized vacuum cleaning systems for
removal of roof accumulations should be considered. Paved areas and
roofs may also be washed down with less waste water generation and
better pollution control than by relying upon the variabilities of storm
water runoff, (it should be noted, however, that Plant 9 changed to dry
dust sweeping equipment for control of fugitive dusts on paved areas
that had been washed down previously. The reason was to reduce waste
water volumes generated. ) Labor-saving can be achieved by use of
commercial street-flushing equipment and by the use of portable or
permanently installed spray headers.
Spray headers are presently used for spray cooling roofs on many air
conditioned buildings to reduce heat loads. This technology can be
modified to permit flushing of accumulated solids. Sewers may have to
be modified to prevent the dilution of these waste waters by uncontamin-
ated waste waters.
Pond and Lagoon Control. Ponds or lagoons are extensively used for
sedimentation, evaporation, collection of waste water, treatment,
equalization, and cooling in the phosphorus derived chemicals industry.
Ponds are used for contaminated process waste water, cooling water, and
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storm water. Sedimentation ponds are used at Plants 1, 2, 3, 4, 5, 6,
7, 8, 9, 16, 17, 20, 22, 23, 25, 31, 36, 41, and 43. Evaporation also
occurs in these ponds. Oxidation of phosphorus occurs in ponds at
Plants 1, 2, 3, 4, 6, 7, 8, and 9. Water is lime treated in ponds at
Plants 3, 4, and 8. Evaporation and drying occur in ponds at Plants 1,
5, 6, and 7. Plant 3 uses water recycled from ponds as the sole source
for all plant cooling water, including transformer cooling water, in a
no discharge recirculating system. The ponds at Plant 3 also receive
all treated waste waters from the plant for reuse and recirculation.
Makeup is essentially all provided by storm water runoff.
Unlined ponds are most common, although lined ponds are used at Plants 1,
5, 7, 20, 25, 31, and 36. Rubber-impregnated nylon, EPDM rubber, bentonite,
concrete, gunnite, and compacted clay are used for linings. Ponds at
Plant 23 are dug in clay. Old tailings ponds, which have clay sediment
bottoms, are used at Plants 8 and 9. Some plants rely upon natural
sedimentation and compaction of precipitates from lime treatment to seal
the ponds.
Pond failures may occur in several ways. Dikes may fail because of
structural design inadequacy, inadequate monitoring and control of
seepage, saturation and long-term plastic flow, or because of leaching
of structural or lining materials by corrosive substances, such as
acidic waste waters. No structural failures of dikes were reported for
the phosphorus production segment of this industry. Dike seepage at
Plant 4 is collected and returned to the terminal pond. The last dike
leak at Plant 9 was over 10 years ago. A carefully designed dam for a
large sedimentation pond at Plant 9 is routinely monitored to assure
that unacceptable deformation or saturation does not occur and for
seepage control. In the fertilizer industry, contaminated water pond
dikes are typically surrounded by a seepage ditch, then a secondary low
dike and then a surface water or "fresh" water ditch. The surface water
ditch permits diversion and discharge of uncontaminated storm water.
The seepage ditch collects pond seepage and contaminated storm water
runoff for return to the pond.
The potential for seepage of process pollutants from unlined ponds or
pits into groundwater systems exists. Wells are monitored at Plants 3,
7, and 9 for possible process waste water contaminants. Local spring
water has been sampled for the same reason near Plant 7.
Good designs for lined pond systems include an underbed drainage network
in a porous material underlying the pond, for seepage detection.
Alternatively, electrical resistance networks can be used for seepage
detection. Plant 5 uses underbed drainage networks for detection and
recycle of leakage.
Process waste water ponds and diking should be designed to hold the
anticipated rainfall and should be constructed so that drainage from the
surrounding area does not inundate the ponds and cause overflow. In
some cases it may be necessary to provide separate ponds or collection
facilities for noncontact cooling water and also for storm water runoff
in order to accomplish this.
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In those cases where discharge of waste water from the terminal pond in
a waste water treatment and reuse system is permitted by regulation, the
following factors should enter into the determination of the surge
capacity:
1. The required surge capacity of a pond system must be able to hold
50 percent of the heaviest expected 24-hour rainfall in a 10-year period
(25-year period after July 1, 1983). The volume of this 24-hour rainfall
is computed as the sum of the rain volume falling on the ponds plus the
drainage from the plant battery limits.
2. Once the surge capacity has been reached:
a. Treatment must be started and treated water discharged
until the total surge capacity has been restored;
b. All surface water drainage must be diverted from the
pond;
c. Noncontact cooling water that is uncontaminated must be
diverted from the pond.
Diligent application of steps (b) and (c) above may eliminate the need
for a terminal lime treatment system at some plants. If terminal pond
discharge is permitted after water level rises into the "surge capacity",
the monitoring authority should specify a treated waste water discharge
rate that will reduce pond water level to restore the surge capacity in
a reasonable time period. If treatment is delayed or conducted at an
unreasonably slow rate, overflow will occur from rainfall considerably
below the heaviest expected rainfall in a 10 or 25 year period.
Personnel concerned with monitoring recirculation and cooling water
lagoons may find it prudent to define several stages of freeboard that
relate to control of surge capacity and to the hazard of breaching the
lagoon capacity:
1. The spillway level capacity, as established by the elevation of the
spillway, should be clearly defined.
2. A crest should be provided around the pond above the spillway
elevation. This is essential to prevent breaching of the structure by
wave action in windy weather. The height of this crest should be
related to wind problems at the lagoon site.
3. A maximum permissible operating level to avoid breaching in periods
of excessive rainfall should be established. Operational experience
should be recorded to provide data for reconsideration if excessive
breaching is noted in operation under the promulgated regulations.
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Monitoring authorities should require a report on all waste water streams
discharged to the process waste water system. Problems may arise at
plants discharging waste water from processes other than phosphorus or
phosphorus derived chemicals manufacturing.
Vessel and Container Cleanout. One common characteristic of the phosphor-
us consuming subcategory of the industry is the planned accumulation of
residues in reaction vessels and stills, with infrequent shutdowns to
clean and remove these residues. In many cases, the residues are
washed down with hoses 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 returnable
containers (drums, bins, tank trucks, and tank cars) before reuse.
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 waste water.
Plant 13 reuses scrubber water for washing returnable containers but
does not recirculate container washings. No fresh water rinse is needed.
Recirculation and neutralization of container and equipment washings
with blowdown will provide a means to reduce the volume of waste water
that must be treated. When necessary, a brief fresh water rinse following
the recirculation wash could be used. This rinse would serve as makeup
to the container recirculating wash system or as scrubber water makeup.
In any case, where removal of vessel and container cleanings as solids
for reuse or disposal as solid waste can be done, this is preferred to
the generation of contaminated waste water. Vacuum cleaning systems
should be considered.
Monitoring Techniques
Since the chemical process industry is among the leaders in instrumentation
practices and application of analytical techniques 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 by 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
-------
<'•.,-» A :'
: b
additional coverage in the control and treatment sections for specific
chemicals.
Monitoring and control of harmful materials such as phosphorus and
arsenic are 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.
At Plant 9, small aquariums containing native fish are used to continuously
monitor several streams, including the river above and below the plant.
In addition to flowing through the aquariums, the pH, temperature,
turbidity, and dissolved oxygen of the sample streams are continuously
monitored and recorded. Because fish are extremely sensitive to low
concentrations of elemental phosphorus, this monitoring system provides
an indirect method of monitoring elemental phosphorus and other hazardous
pollutants. Fish kills reported to the state include any fish that die
in these aquariums. Isom (22) reported that water containing 25 ppb of
elemental phosphorus killed sunfish in 160 hours during LD50 toxicity
testing.
Summary
The preceding narrative described general treatment practices and in-
plant controls. The following section discusses specific abatement
measures recommended for each subcategory.
TREATMENT OF WASTE WATERS IN THE PHOSPHORUS PRODUCTION SUBCATEGORY
Control and Treatment of Phossy Water
Phossy water, or water containing elemental phosphorus in the colloidal
and/or dissolved form, is generated at phosphorus producing plants.
Sources include phosphorus condenser water, phosphorus and phosphorus
sludge treatment steps, furnace electrode seal water, and the transfer
of phosphorus by displacement. If electrostatic precipitation dust is
slurried with water, this water becomes phossy. Carbon monoxide compressor
(Nash pump) seal water is phossy. Additionally, a tank car of phossy
water generated in a phosphorus derivatives (phosphorus consuming) plant
is typically returned to the phosphorus producer for each tank car of
phosphorus shipped. Noncontact cooling waters for furnace cooling, dry
condensers, and phossy water coolers may also receive incidental contamin-
ation with elemental phosphorus.
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lAr i"
Because of harmful effects of elemental phosphorus in small concentra-
tions in waste water, and because methods for complete removal of the
phosphorus from the water have not been fully developed, it is a universal
practice at phosphorus producing plants to reuse the phossy water after
treatment. Lime treatment is required to remove other constituents that
would otherwise build up to concentration in the waste water.
Barber (5) discusses several methods that have been tried experimentally
to remove elemental phosphorus from phossy water. Among these methods
was 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." Substantial chlorine residuals in natural waters
must be avoided because of chlorine's toxicity to marine life. With the
development of chlorine analyzer-controllers for municipal waste water
treatment, however, it appears that chlorination deserves another trial.
Additionally, equipment is available to reduce or eliminate chlorine
residuals in waste waters. Dechlorination with sulfur dioxide has been
practiced successfully in a potable water treatment plant since 1926.(23)
At least one phosphorus producer is investigating the use of chlorination
for reduction of elemental phosphorus concentrations in the parts per
billion range, but completion and report of the investigation will not
be available until late 1977.
Barber (5) also reported that air oxidation was attempted, but the
reaction was far from complete, leaving 14 to 37 percent of the original
colloidal phosphorus unoxidized. Plant 4 reduces elemental phosphorus
concentrations to 30 to 70 ppb in the terminal pond of a pond system
that includes sedimentation, natural air oxidation, liming, and dilution.
About one-third of the terminal pond influent is treated phossy water.
Before treatment, 20 to 30 ppm of elemental phosphorus are present.
Bullock (24) reports decomposition of elemental phosphorus in water in
the presence of air with P4 half-lives of 80 hours at 30°C (86 F) and
240 hours at 0°C (32°F). lore recently, laboratory tests were made at
Pine Bluff Arsenal, Arkansas, to evaluate the destruction of elemental
phosphorus by aeration of phossy water. A forthcoming report is expected
to show elemental phosphorus in water reduced from about 200 ppb to
about 0.5 ppb in 5 to 15 days, depending upon pH and temperature. Some
phosphine gas is present in the effluent air.
Barber (5) also reported that filtration of phossy water for removal of
colloidal phosphorus was investigated but found to be impractical.
As a result of experience, economics, and the current knowledge about
phossy water treatment, the industry has adopted the policy of containment
and reuse of phossy water rather than treatment and discharge.
At the TVA Muscle Shoals plant, a commercial flocculant, at a concentration
of 40 mg/1, was employed to settle both the phosphorus and the suspended
solids. Using a clarifier, the system removed 92 to 93 percent of both
the phosphorus and the suspended solids as phosphorus sludge underflow
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(which is only 2 percent of the waste water volume). The presence of
suspended solids was necessary for efficient removal by this method.
The underflow from a phossy water clarifier may be treated as other
phosphorus muds or sludges are treated. The sludge may be gravity
thickened and 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
by-product carbon monoxide as fuel. Elemental phosphorus (nominally 40
to 65 percent of the "solids" in the sludge) is 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. These operations are termed "roasting" or sludge
evaporation.
At TVA, the clarifier overflow, containing only 7 or 8 percent of the
original phosphorus and suspended solids, was recirculated to the phos-
phorus condenser sump and to other areas where water contacted phosphorus.
However, because the phossy water accumulated dissolved salts (mainly
fluorides and phosphates - see Table 6), about 6 percent of the clarified
water was bled off and discharged. In addition to suspended solids and
dissolved solids, this bleed contained 120 mg/1 of elemental phosphorus,
equivalent to 0.04 kg per kkg (0.08 Ib/ton) of product.
At Plant 4, large lagoons are used to reduce the concentration of suspended
solids in the phossy water and 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) precipi-
tates 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 blowdown. At Plant 4, the waste streams are combined
and all wastes are recycled without discharge, except when influx of
site storm water runoff causes the terminal pond to overflow.
At Plant 9, 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 makeup is used for the phosphorus condenser.
The key to this scheme, which results in no 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 5 achieves total containment of phossy water in a system similar
to the one at Plant 9. 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
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conventional ways, with complete return of the material to the process.
The overflow from the clarifier is combined with calciner scrubber and
other scrubber effluents, limed, and clarified. Underflow from the
clarifier is dried in ponds, and the solids are recycled to the process.
The overflow from the clarifier is recycled to the calciner scrubber and
other scrubbers where further oxidation of phosphorus occurs in a no
discharge system.
Plant 3 utilizes phossy water sedimentation and oxidation ponds with
subsequent lime treatment in a system similar to that at Plant 4.
Notably, Plant 3 has large pond areas for evaporation relative to storm
water runoff acreage. Additionally, phossy water is aerated by spraying
to achieve additional phosphorus destruction. Also, no fresh water is
required as makeup cooling water because the same terminal recycle ponds
achieve adequate evaporative cooling. For these reasons, the waste
streams are combined and all waste waters are recycled without discharge.
At Plant 6, phossy water is handled in a recirculating closed system.
Excess phossy water is clarified and the underflow returned to the
phosphorus condenser water system. Overflow is evaporated in the slag
pits. Excess slag pit water is sent to recycle ponds. Water from the
ponds is used for scrubber makeup and slag quenching; there is no
discharge from the ponds. In the closed portion of the phossy water
system, hydroclones are used for clarificaion with clarified water used
for condenser sprays. Total containment of phossy water is achieved.
At Plant 8, excess phossy water is clarified and the underflow processed
in sludge evaporators for phosphorus recovery. Overflow is combined
with other waste waters, limed, and sent to the plant's process water
recycle pond. Pond water is reused as process water in the plant.
There is no discharge from the pond, although water is accumulating
because of the use of fresh water for scrubbing and cooling uses in
excess of pond and process evaporation.
At Plant 1, phossy water is sent to clarifiers for solids recovery.
Underflow is pumped to evaporators for phosphorus recovery, while overflow
is limed and sent to phossy water ponds. Pond overflow is reused in the
phosphorus condensing and handling system. Excess pond water can be
transferred to the slag pits for evaporation or to retention/evaporation
ponds. There is no discharge to surface waters from the phossy water
ponds, slag pits, or retention/evaporation ponds, so phossy water is
totally contained.
Plant 2 transfers all excess phossy water to a series of ponds where
oxidation and evaporation occur. There is no discharge from the ponds
except when excessive rainfall occurs. When discharge does occur, pond
overflow is sent to a scrubber water pond system. Overflow from the
scrubber ponds receives lime treatment before discharge.
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•'^A|;
•w« W'u
At Plant 7, excess phossy water is sent to a series of settling and
evaporation ponds. Phossy solids are allowed to accumulate, and ponds
are covered when they fill with solids. All water evaporates or seeps
into the ground, and there is no discharge from the ponds.
In summary, all phosphorus production plants are evaporating phossy
water in ponds or scrubbers to achieve total recycle and/or no discharge
under normal circumstances. Phosphorus is removed by sedimentation and
recycle to the process or by oxidation to phosphates and other phosphorus
compounds in ponds and scrubbers. Some phosphorus accumulates with
other sediments as pond solids that are presently in the form of on-site
solid wastes.
A standard, plant-scale chemical engineering unit operation known as
"solvent extraction" is potentially applicable for the removal of elemental
phosphorus from water suspensions or solutions. A number of solvents
can be used to extract elemental phosphorus from waste water. The
process would require costly experimental and developmental work to
determine cost-effectiveness, however, and cannot yet be considered
demonstrated or available technology.(25)
In spite of recent improvement and more careful attention to the control
of phossy water, a substantial number of fish kills have been associated
with phosphorus production in the State of Tennessee. Phossy water
spills and overflows were assumed to be the cause and in certain cases
were verified. Some of these kills occurred in 1976, although most of
them were considered "minor".(26) There have been no recent reported
fish kills associated with elemental phosphorus producers in Idaho,
Montana, or Florida. Only 1975 and 1976 information was available for
Florida.(27, 28, 29)
Neutralization o£ Acidic Waste Waters
Neutralization of acidic phossy water by addition of aqueous ammonia,
caustic, or soda ash is practiced at some phosphorus plants to reduce
corrosion of phosphorus condensers and other equipment. Some neutrali-
zation of acidic calciner scrubber liquor is achieved by alkaline slag
or by the slightly alkaline slag quench liquor (see Table 6). At TVA,
the slag was 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 neutralized the acidic liquors.
Partial neutralization of acidic waste water is achieved by mixing it
with the slightly alkaline slag quench water at Plants 3, 4, 6, and 8.
Lime neutralization of acid wastes is standard practice in the phos-
phorus production industry, as observed at Plants 1, 3, 4, 5, 6, 7, 8,
and 9. Liming is done for calciner scrubber water at Plants 1, 3, 4, 5,
6, and 7. It is applied at treatment ponds of Plants 1, 3, 4, and 8.
Many of the anions present are also precipitated by lime treatment, as
described later.
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In-process neutralization of acidic wastes is done to reduce corrosion
of equipment and to reduce the vapor pressure of volatile acids (hydro-
fluoric, sulfurous, hydrochloric), thereby improving scrubber efficiencies
and reducing air pollution. Also, acidic substances may leach pond
bottoms, causing seepage or leakage.
Limestone or lime is much more economical than other materials for
neutralizing acidic wastes, including soda ash, caustic soda, and ammonia.
Limestone is the lower cost material (approximately $15/kkg ($14/ton))
but suffers the disadvantages of slower reaction and lower obtainable pH
than lime. Lime costs approximately $31/kkg ($28/ton).
Lime Precipitation o£ Anions
With the exception of minor amounts of hydrochloric acid that may be
present, every acid waste in the phosphorus production subcategory forms
insoluble or slightly soluble calcium salts when treated with lime.(20,30)
Acid Calcium Salt Solubility*, mg/1
H3P04 Ca(H2P04)2.H20 (MCP) 18,000
" CaHPp4.2H20 TDCP) 200
" Ca3(P04.)2 (TCP) 25
" Ca5(Pq4)3(OH) (Hydroxyapatite) 4.3 (Max.)
H5P3010 CaT(P3010)£ (Calcium tripolyphosphate) 28 (@ 60 C)
H4_P2p7~ Ca2P207rTCalcium pyrophosphate) 28
HP02 C&TPQ3j2_ (Calcium metaphosphate) Insoluble
HF, H2SiF6 CaF2 16
H2Si02 CaST03 95
H2S04 CaS04.2H20 2,410
H2SOI CaSOl.2H2p 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 phosphorus derived chemicals
industry, but also demineralizes most waste waters by precipitating
calcium salts. This then produces a solid waste that may be disposed of
by landfilling.
Fluoride Removal with Lime. Acidic fluoride wastes are generated by the
phosphorus producing 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 H2S1F6 at high pH) to precipitate calcium fluoride and gelantinous
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hydrated silica. Lime treatment for fluoride removal is standard operating
technology at Plants 1, 3, 4, 5, 6, 7, 8, 9, and 41.
H£SiF6 - *-2H+ + SiF6~2
SiF6~2 + 2H20 - »Si02(s) + 4H+ + 6F~
Caustic or lime addition drives both of these reactions to the right.
The equilibrium is calculated using: (31)
(Si02(s)) (H*)4 (F")6 s 1>6 x 1Q-27
Furthermore:
(SiF6 2) (H20)2
Ca+2 + 2 F" >-CaF2(s)
The calcium from the lime drives this reaction to the right, precipitating
the fluoride.
The equilibrium is calculated using:
(Ca+2) (F~)2 = 4 x 10"11 (at 26°C)
The higher pH resulting from lime addition assures that the concentration
of un-ionized HF remains low,
HF - +• H+ + F~
driving the above equation to the right by removing acidity. The
equilibrium is calculated using:
'H*) '""' . 5.3 x ID'3
(HF)
The effectiveness of lime treatment for fluoride removal that has been
practicably achieved in other industries is shown in the following table
as summarized by Patterson (32).
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SUMMARY OF FLUORIDE TREATMENT PROCESSES AND LEVELS
OF TREATMENT ACHIEVED
Fluoride Concentration (mg/1)
Treatment Process Initial. Final pH
Lime Addition - 10 -
Lime Addition 1000-3000 20
Lime Addition 1000-3000 7-8 (after 24-hr
settling)
Lime Addition 500-1000 20-40
Lime Addition 200-700 6 (16-hr settling)
Lime Addition 45 8 -
Lime Addition 4-20 5.8(avg.)
Lime Addition 590 80
Lime + Calcium Chloride - 12 7-9
Lime Addition 200 3 (19-hr reaction >12
time)
Higher removal efficiencies generally reflect higher lime dosages. Up
to 1400 mg/1 excess calcium ion at the pH > 12 was required to achieve 3
mg/1 fluoride. The addition of calcium chloride was done to maintain
high calcium ion concentrations to suppress the calcium fluoride solubility,
even at neutral pH values.
Phosphate and Sulfate Removal with Lime. Phosphoric acid wastes are
generated by the oxidation of elemental phosphorus in phossy water, but
may also result from the hydrolysis of P205_ in taphole fume scrubbers or
elsewhere and from the action of sulfuric" acid and sulfurous acids on
nodule or rock dust in calciner off-gas scrubbers. P205_ from the oxidation
of elemental phosphorus present in carbon monoxide burned in the calciner
is also hydrolyzed in the calciner scrubber.
The standard treatment for phosphate-bearing waste waters is precipitation
with lime. As the pH increases when lime is added, the calcium phosphates
formed become less soluble, and less phosphate remains in solution at
equilibrium. The primary removal mechanism when lime is used is the
formation of hydroxyapatite, Ca5(OH)(P04_)3_.
A large body of literature has been developed on phosphorus removal from
waste waters with lime.(33-38) The average phosphorus concentration in
domestic waste waters is about 10 mg/1 as P. Lime treatment of these
waste waters to pH 9.5 has produced effluent phosphorus concentrations
of less than 1 mg/1.(39)
The following laboratory and plant data were reported for the fertilizer
industry for the treatment of acidic wastes from the acidulation of
phosphate ore. The same pollutants are present as in phosphorus production
except for elemental phosphorus. The figures shown are final concentrations
of total phosphorus and fluoride after lime treatment at various pH
values. (40)
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pH Phosphorus (mg/l) Fluoride (mg/l)
Laboratory Plant Laboratory Plant
5.5 - - - 17
6.0 42 14
6.5 - 24 - 12.5
7.0 500 18 13 12.5
7.5 330 14 8.5 12.5
8.0 200 12 6.8 12.5
8.5 120 8 5.8 12.5
9.0 20 6 5.2 12.5
9.5 3 3 4.8 12.5
10.0 1.2 1.2 4.6 12.5
Although the starting concentrations are either arbitrary or specific to
that plant only, the data do show significant phosphorus and fluoride
removal at high pH.
Additional data from the fertilizer industry showed total phosphorus
reduced to 9 mg/l (as P) at pH 6.4 and to 3.6 mg/l (as P) at pH 8.3 when
a 46-hour retention time was used. Long term in-plant data from double
lime treatment indicated effluent phosphorus levels of 10 to 40 mg/l at
pH 5 to 7. Double liming in that industry permits initial precipitation
and separation of a calcium fluoride-rich fraction at pH 3.5 to 4.0
followed by precipitation and sedimentation of a calcium phosphate-rich
fraction at pH 5 to 7.
Substantial amounts of sulfuric acid are present in calciner scrubber
liquor. Calcium sulfate is also precipitated by lime treatment. Al-
though data for sulfurous acid in calciner scrubber liquor are lacking,
a significant amount of sulfurous acid or sulfites may be present.
Sulfurous acid and sulfites are converted to sulfuric acid and sulfates
by air oxidation. This can occur in scrubbers and ponds, but the oxidation
is not instantaneous. In the power industry, recycling scrubber systems
utilizing lime treatment can be designed and controlled to precipitate
primarily either calcium sulfate or calcium sulfite, depending upon
preferences. The presence of sulfurous acid or sulfites will result in
COD. A concentration of 10 mg/l sulfite has a COD of 2 mg/l.
Data on recycle pond water after lime treatment at several phosphorus
production plants are presented below. All parameters except pH are
given in mg/l. Sources of data for these figures include DCP responses
for Plant 3; trip report (a), DCP responses (b), and a telecon (c) from
Plant 4; trip report (a) and DCP responses (b) from Plant 8.
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C
,' ;. „ (••• s
L, i u' ,i
Total
Fluoride pH Phosphorus Sulfate Calcium
Plant 3 6 6.9 32 92 < 76
Plant 4(a) 101 7.9 69
Plant 4(b) 271 7.7 277
Plant 4(c) 205 6.4 80
Plant 8(a) 40 7.0 4.4 1,000 560
Plant 8(b) 70 5.4 17 1,650 670
At Plant 3, recycle water is used for all noncontact cooling, including
transformer cooling, as well as for all other process uses. Most of the
lime treatment and sedimentation in ponds occur before mixing with spent
cooling water in the cooling ponds. Recycle pond water is softer than
well water supplies at the plant.
Plant 4 recycle pond water is reused for furnace shell cooling and other
process uses (such as scrubbers), but not for other noncontact cooling
services. City water is used as makeup for the other noncontact cooling
uses. Spent furnace shell cooling water dilutes other process waters
before lime treatment and sedimentation. Excessive rainfall can cause
discharge from the terminal recycle pond at Plant 4. Lime usage is
about 192 kg/kkg product.
At Plant 8, pond water is recycled primarily to scrubbers. The process
waste water discharged to the pond receives little dilution from noncontact
cooling water or storm water runoff. Lime usage is about 230 kg/kkg
product (460 Ib/ton) at the plant. The pH range of 6 to 8 results in
good suspended solids removal in the pond while maintaining adequate
fluoride removal for calciner off-gas scrubbing. The plant reported
that pH levels of 10 or more can cause scaling problems in the calciner
scrubbers.
Alternate Fluoride Removal Methods
Fluoride reductions achievable by lime treatment were previously discussed
in this section. Fluoride removal has also been accomplished commercially
by alum treatment. At an optimum pH of 6 to 7, this appears to be a co-
precipitation phenomenon of aluminum fluoride plus aluminum hydroxide
floe. Lime precipitation followed by alum and superphosphate addition
was used industrially to produce 1.5 mg/1 fluoride.(32) In the phosphorus
production industry, Plant 4 has done in-plant testing using a combined
lime-alum treatment of process waste water, but details are not presently
available. A preliminary conclusion is that the combined treatment is
more effective than lime alone.(41)
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Activated alumina adsorption beds have been used for many years in
municipal water treatment plants for removal of fluoride ion. Regeneration
is done with sodium hydroxide followed by sulfuric acid neutralization.
Fluoride is also adsorbed by hydroxyapatite (calcium phosphate).
The preferred method for treating process wastes to achieve low final
fluoride concentrations seems to be lime treatment followed by alumina
adsorption.
The effectiveness of these alternate fluoride removal methods is summarized
in the following table:(32)
Fluoride Cone entrat ion, mg/1
Current
Treatment Process Initial Final Application
Lime + Alum - 1.5 industrial
Alum 3.6 0.6-1.5 municipal
Alum 60 2 lab scale
Hydroxyapatite Beds
Synthetic . 12-13 0.5-0.7 municipal
Synthetic 10 1.6 municipal
Bone char 6.5 1.5 municipal
Bone char 9-12 0.6 municipal
Alumina Contact Beds 8 1 municipal
Alumina Contact Beds 9 1.3 industrial
(lab scale)
Alumina Contact Beds 20-40 2-3 industrial
(pilot scale)
There has also been commercial interest in recovering the fluoride
values in acidic waste waters. Two commercial processes have been
developed to manufacture hydrofluoric acid (42) and one to manufacture
synthetic cryolite for the aluminum industry.(5)
Alternate Phosphate Removal Methods
Although lime treatment of phosphates has been the predominant route,
ferric chloride and alum have also been extensively used to precipitate
phosphate. Ferric salts are most effective near pH 5 and aluminum salts
are most effective near pH 6, as opposed to the 10 to 11 pH range for
lime. For alum treatment, an A1:P ratio of 1:1 to 2:1 is required.
Anionic polyelectrolytes are useful in settling the floe. Settling
alone is reported to reduce the residual phosphorus to about 1 mg/1
after treating a municipal secondary effluent with alum. Filtration
achieves reduction of residual phosphorus to 0.1 mg/1. (40)
125
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QAFT
/»\rU !
In the phosphorus production industry, a preliminary conclusion from
Plant 4 is that a combined lime-alum treatment is more effective in
total phosphorus reduction than lime treatment alone.(41)
The use of lanthanum salts has been demonstrated to precipitate phosphates
more effectively than calcium, ferric, or aluminum salts over a much
wider pH range. The drawback is cost; to be cost-effective, the treatment
system must recover and reuse the lanthanum.(43)
Another process for phosphate removal is adsorption by activated alumina
followed by stripping with caustic soda. Regeneration of phosphate-free
caustic is accomplished by lime precipitation.(44, 45, 46) Ion exchange
has been investigated. Adsorption by magnesium oxide has also been
studied. (47)
Cyanide and Phenol Removal
Plant 3 reports that coke drying is a potential source of cyanide and
phenols, and that the phosphorus condensers are a source of cyanides. A
groundwater study at the plant was recently completed to determine
whether cyanide and phenols (as well as other substances) in process
waste water were migrating into the groundwater system from ponds. At
Plant 4, effluents from a coking operation operated by others on the
premises are discharged into the phosphorus production plant process
waste water sump before lime treatment. Coke plant wastes are a potential
source of cyanide, phenols, ammonia, and other pollutants.
Current analyses for cyanide and phenols in phosphorus plant waste
waters have not been reported, but 1971 Corps of Engineers plant effluent
data were as follows: cyanide - less than 0.01 mg/1 to 1.7 mg/1; phenol
- less than 1 ug/1 to 23 ug/1. In the iron and steel industry, alkaline
chlorination treatment of waste waters achieves 0.25 mg/1 cyanide and
0.5 mg/1 phenol in effluents. This should be considered currently
available technology for treatment of coke dryer or coking operation
effluents before dilution with other waste waters..
Removal o£ Suspended Solids
The raw waste streams from the phosphorus producing and phosphate subcategories
of the industry contain considerable quantities of suspended solids.
Moreover, the chemical treatment of acidic wastes described in the
previous section produces additional suspended solids in many instances.
As mentioned previously, settling ponds are used at all nine plants in
the phosphorus production subcategory for removal of suspended solids.
At Plant 4, sedimentation ponds following lime treatment of combined
waste waters achieved 18 mg/1 total suspended solids in the effluent.
The data were recorded in late 1976. Pond acreage after lime treatment
is estimated as 2 to 2.5 acres per million gallons per day of combined
waste water recycled at Plant 4.
126
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Pond solids containing recoverable phosphate values are dug or dredged
for reuse in phosphorus production at Plants 4, 5, and 9. Pond solids
at other plants are either kept in place as solid waste or dug and moved
to a solids disposal area, usually on-site.
Tanks and vessels, including clarifiers and thickeners, are also used
for sedimentation of waste waters in phosphorus production. Clarifiers
are used at Plants 1, 5, 6, 8, and 9 for recovery of elemental phosphorus
values from phossy water. Clarifiers are also used to reduce the volumes
of lime treated waste waters that require further sedimentation at
Plants 1, 5, and 6. Clarifier overflow is reused as process water.
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.
Continuous rotary vacuum filters find general applicability in dewatering
sludges with high concentrations of solids. Sand bed filtration also
finds increasingly widespread use, and is economically attractive even
when handling huge quantities of waste water, as in municipal water
purification. At Plant 3, a unique type of wire wound tubular filter is
used for clarifying treated combined waste water from a recycle pond
prior to reuse for transformer cooling. Plant 31 uses filters to polish
the effluent from its phosphorus removal treatment process.
Centrifugation was used at TVA for producing a recoverable phosphorus
sludge from the phossy water clarifier underflow. Plant 7 uses centrifu-
gation in phosphorus recovery operations, and Plants 24 and 36 use
centrifugation for thickening and clarifying calcium phosphate slurries.
Centrifugation is an alternative means for mechanical 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 a significant advantage over filters in that blinding of a medium
is removed as a problem area.
Hydroclones offer an alternative method of clarifying or thickening
waste waters. Hydroclones are used for separating phosphate ore from
claylike tailings in ore beneficiation. The ore is in the underflow
stream. Hydroclones are also widely used for separating, thickening,
and clarifying in the corn wet milling industry. In that industry,
these separations were performed by gravity sedimentation in tanks and
on "tables" and later with centrifuges, until the development of hydroclone
127
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T
' |fll» •
technology made a change practicable. In that industry, hydroclones rou-
tinely separate starch particles (having about 10 micron average diameter
and 1.5 specific gravity) from water and gluten particles (l.l specific
gravity). Centrifuges are still used for those separations not adaptable
to hydroclone technology. Hydroclones are used at Plant 36 for lime
slurry thickening, at Plant 8 for nodule dust handling, and at Plant 9
for phossy water processing.
Operation o£ Waste Water Treatment and Recirculation Systems in_ Severe
and Extended Cold Weather
In areas of the country where very severe and extended cold weather
prevails, total recycle of process water becomes difficult for two
reasons:
1. The return water piping and pumping must be protected
against freezing.
2. The settling ponds may freeze, necessitating special provisions
to recycle water from the ponds.
At phosphorus producing Plant 8, located in the Idaho-Montana area,
total recyle of all waste waters is presently achieved, even in extremely
cold weather, by:
1. A deep canal for return of treatment pond waters to the recycle
pumping station. The depth is about 20 feet and the length is
1,400 feet. Ice forms on the surface but does not impede
water flow.
2. Adequate pond depth. Water depth is estimated at 10 to 12
feet. Ice forms on the surface but does not prevent proper
sedimentation in the pond, in spite of the somewhat decreased
retention time.
3. Although not cited specifically as a method for acheiving
total recycle in cold weather, noncontact cooling water is
recirculated through a cooling tower system at this plant.
This reduces the amount of fresh water required for cooling
and therefore reduces the amount of spent cooling water that
reaches the treatment pond. In cold weather, less evaporation
occurs, so less makeup or blowdown is required. (Plant 7
operates a cooling tower year-round and no blowdown is required
in winter.)
The capital cost of changing from a once-through pond system, having
waste water discharge, to total recyle of waste water for Plant 8 was
about $3,000 per kkg of daily phosphorus production ($2,700/per daily
ton), in 1977 dollars.
128
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The current operating cost for the recycle system at Plant 8 is about
$11.71/kkg ($10.64/ton) of phosphorus production. Over half of this is
estimated as lime purchases, most of which would be required even without
total recycle. Some of this capital and operating cost would have been
required for total recycle even in a warm climate.
Burial of water mains and the use of enclosed, heated pumping stations
for freeze protection have been amply demonstrated in the phosphorus
production subcategory, in water supply operations, and in the chemical
industry. Uninsulated or insulated above-ground piping, without heat
tracing, is and may be used in many instances when flow is continous and
sufficiently high for the expected temperatures and pipe lengths involved.
In such cases, provision should be made for prompt draining of untraced,
exposed sections when flow ceases. Alternatively, exposed water lines
may be insulated and traced electrically or with steam. Plant 5 uses
steam tracing for certain recycle water lines.
Plants 5 and 7, also in the Idaho-Montana area, report that extreme cold
weather does not interfere with the proper operation of their waste
water treatment and handling systems. Both plants discharge only noncontact
cooling water.
A defluorinated rock plant has been operating a recycle pond system in
Montana.(48) Recyle ponds operated in the winter are deep enough to
permit adequate retention time even with a thick ice layer on the surface.
Reduction of Cooling Water Volume and Contamination
In the phosphorus production segment, a considerable quantity of process
waste water is evaporated in scrubbers, particularly the calciner scrubber.
Noncontact cooling water used is either once-through or is recirculated
through cooling towers or ponds. Excepting Plant 3, which uses a filtered,
treated combined process and cooling pond water for all cooling require-
ments, all phosphorus production plants use fresh water for transformer
cooling water makeup. If once-through transformer water were handled in
a closed system with direct discharge, this would be an uncontaminated
noncontact cooling water no different from those in other industries.
In the phosphorus production segment, however, this spent transformer
cooling water is reused, and even some of the reuse as noncontact cooling
water is subject to contamination.
Plants 4 and 7 report that noncontact cooling water is subject to
contamination by leaks from the process. Plant 5 discharges a noncontact
cooling water stream that contains detectable elemental phosphorus, a
process derived pollutant. Plant 9 does not classify furnace shell
cooling water as "noncontact" because contamination of furnace shell
cooling water is known to take place. For this reason, Plant 9 totally
recycles furnace cooling water as if it were contaminated with elemental
phosphorus. Furnace shell cooling contamination potential at other
phosphorus producing plants is comparable to that at Plant 9, based on
observation.
129
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•i E'-'T*
•At \
Noncontact cooling tower systems may receive contamination via process
dusts or mist that enter the cooling tower. Whether this is significant
will depend on the location of the tower in relation to equipment and
surfaces that generate dusts or aerosols. Slowdown can be analyzed and
compared to makeup water analysis to determine whether it contains
process pollutants, if direct discharge as uncontaminated noncontact
cooling water is desired. Elemental phosphorus, fluoride, or phosphate
from processing may pollute cooling tower water.
If fresh water is used for cooling or cooling tower makeup and spent
cooling water or blowdown is combined with other process wastes, this
adds to the total volume of waste water that needs to be treated and
evaporated and to the quantity of dissolved and suspended solids that
needs to be removed or recycled. In a recirculating cooling tower
system, the percent blowdown depends largely upon economics, including
the cost of makeup water, treatment chemicals and equipment, materials
of construction and corrosion, blowdown disposal capacity, blowdown
temperature, scaling, and fouling. In other industries, blowdown is
typically 0.5 to 5 percent, and concentration of soluble salts in
blowdown is typically 2 to 6 times that in the makeup water. Recirculation
with non-brackish fresh water makeup to levels of 1,000 to 1,800 ppm
chloride and 600 to 700 ppm sulfate concentrations in the recirculating
tower water is not unusual (49), when using effective tower water treatment.
Recirculation of sea water in tower systems may require careful selection
of materials of construction. Plant 6 uses zeolite softened water for
cooling tower water makeup and operates with no blowdown from these
recirculating tower systems. (It is assumed that dissolved solids are
lost by drift and minor leaks.)
Plants that do not recirculate transformer cooling water in cooling
tower systems report noncontact cooling water usages of 24,000 to 138,000
liters per kkg of product (7,000 to 40,000 gal/ton). The variation
depends upon the extent of use of cooling tower systems, the extent of
planned and incidental air cooling, climate where the plants are located,
the temperature rise in once-through systems, and other factors.
Plants 1 and 6 require about 690 to 1,380 liters per kkg of product (200
to 400 gal/ton) of noncontact cooling water makeup for their cooling
systems. Blowdown is 0 to 345 liters per kkg of product (0 to 100
gal/ton), and represents practicable technology for elemental phosphorus
plants. Plant 4, which uses municipal water without further softening
in a recirculating cooling tower system for transformer cooling, uses
6,600 liters of noncontact cooling water per kkg of product (1,900
gal/ton). Reductions achieved in noncontact cooling water usage and of
blowdown to contaminated water systems allow the contaminated water
system to accept more contaminated storm water runoff without the
necessity of direct discharge.
The conversion of noncontact cooling systems so that treated process
water can be used provides another way to reduce the amount of fresh
water requiring evaporation by process heat. This is practiced at Plant
3. Spent cooling water is cooled in the terminal ponds of a process
130
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L'
waste water treatment and settling pond system. The terminal pond water
is soft enough to use for transformer or other cooling uses, but is
filtered prior to use to reduce fouling of heat transfer surfaces.
Contaminated process waste water is oxidized, limed, and settled in
ponds before mixing the treated effluent with spent cooling water in the
cooling ponds. This practice, plus the planned influx of storm water as
makeup to the terminal ponds, assists in reducing the calcium concentration
to produce "soft" water (in this case, less than 80 ppm calcium). The
terminal ponds for this plant are used for evaporative cooling instead
of using cooling towers. Where sufficient site is available for cooling
ponds, this provides a practicable alternative to the use of cooling
towers.
Evaporative cooling of noncontact cooling water may be done in conven-
tional (evaporative) cooling tower systems, cooling ponds, or spray
ponds. In plants with limited site area for cooling ponds, the use of
spray ponds, using recirculating sprays, may provide sufficient evaporative
cooling to avoid the installation of cooling towers for achieving maximum
reduction in achieving maximum reduction in fresh water usage.
Another alternative to cooling towers, cooling ponds, or spray ponds is
an air-cooled heat exchanger. Typically, a fan circulates ambient air
through a finned tube heat exchanger to cool the noncontact cooling
water. Because there is no evaporation, there is no blowdown. Disad-
vantages are that cooling is limited by the dry bulb air temperature,
and first cost is substantially higher than for a cooling tower system.
If air cooling of the heat exchanger is assisted by cooling sprays, this
becomes an evaporative cooler. There would be blowdown required for the
spray water.
Summary
The effectiveness of the control methods specified in the preceding
paragraphs is summarized in Table 12 for the nine phosphorus production
plants. Data labeled (b) for Plants 5 and 9 were taken from Tables 13
and 14, which include complete analyses of the intake and effluent
waters. Raw waste loads were taken as the sum of the waste loads
tabulated in Table 6, Section V. Percent reductions in Table 12 were
based on Table 6 raw waste loads.
131
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TABLE 12
SUMMARY OF CONTROL AND TREATMENT
Waste Discharged, kg/kkg
Plant 1
Plant 2 (gross) (a)
Plant 3
Plant 4 (gross)
Plant 5 (gross) (b)
Plant 5 (gross)
Plant 6
Plant 7 (gross)
Plant 8
Plant 9 (net) (b)
Waste Discharged, Ib/ton
Plant 1
Plant 2 (gross) (a)
Plant 3
Plant 4 (gross)
Plant 5 (gross) (b)
Plant 5 (gross)
Plant 6
Plant 7 (gross)
Plant 8
Plant 9 (net) (b)
Control and Treatment
Efficiency, Percent
Plant 1
Plant 2 (gross) (a)
RESULTS AT ELEMENTAL PHOSPHORUS PLANTS
Total
Acidity
TSS (Alkalinity) TDS
0 0
4.9
0 0
0.5 (pH 7.7)
0.54 (12)
0.33 (pH 8.3)
0 0
0.04 (pH 8.2)
0 0
0.5 1
0 0
9.8
0 0
1.0 (pH 7.7)
1.1 (24)
0.66 (pH 8.3)
0 0
0.08 (pH 8.2)
0 0
1.0 2
100 100
88
0
-
0
13.9
22
-
0
-
0
4
0
-
0
27.8
44
-
0
-
0
8
100
_
Fluoride
0
21.9
0
0.79
0.04
0.028
0
0.004
0
0.1
0
43.8
0
1.6
0.08
0.056
0
0.008
0
0.2
100
59
Total
Sulfate Phosphate
0
-
0
-
3
-
0
0.93
0
2
0
-
0
-
6
-
0
1.9
0
4
100
_
0
0
0
2.5
0.8
0.38
0
0.16
0
0.2
0
236
0
5
1.6
0.76
0
0.32
0
0.4
100
0
132
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TABLE 12 (Continued)
Total
Acidity Total
TSS (Alkalinity) TDS Fluoride Sulfate Phosphate
Plant 3 100 100
Plant -4 (gross) 99
Plant 5 (gross) (b) 99
Plant 5 (gross) 99+
Plant 6 100 100
Plant 7 (gross) 99.9
Plant 8 100 100
Plant 9 (net) (b) 99
100
100
100
100
99
99.9
99.9
100
99.9+
100
99.8
100
-
97
-
100
99
100
98
100
90
97
98
100
99+
100
99+
Notes: All discharge data are from 1977 DCP submittals except as noted.
(a) Excludes noncontact cooling water.
(b) Pre-1974 data.
133
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DhttfT
TABLE 13
EFFLUENT DATA FROM PLANT 9
Constituent
pH
Turbidity
Conductivity
TSS
TDS
CaC03
Alkalinity
CaC03
Acidity
Chloride
Fluoride
Sulfate
COD
Total
Hardness
Total
Phosphate
Ortho
Phosphate
Notes: 1.
2.
3.
(DISCHARGE NO. 001)
Water & Waste Water Analysis
Effluent Effluent
Plant Ind.
Units Intake Data Data
- 7.3-9.5 7.55
FTU 26 32 30
umhos 359 408 300
cm
mg/1 15 15 20
mg/1 160 202 176
mg/1 116 110 130
mg/1 -
mg/1 <0.1 4.1 8
mg/1 0.19 1.14 0.87
mg/1 6.4 13.8 26
S04
mg/1 2.0 53.5 25
mg/1 116.7 129.7 160
mg/1
P04_ 1.2 2.4
mg/1
P04_ 1.2 2.4 2.9
Net Effluent
Qty, kg/kkg
Inde-
Plant pendent
Data Data
-
-
-
0.5
4 2
(-1) 1
-
0.4 0.8
0.10 0.07
0.8 2.1
5.3 2.4
1 4
0.12
0.12 0.18
These are pre-1974 data.
Effluent flow rate was 103,200 1/kkg (24,700 gal/ton),
This discharge included only noncontact cooling water
Net Effluent
Qty, Ib/ton
Plant
Data
-
-
-
0
9
(-1)
-
0.9
0.20
1.5
10.6
3
0.25
0.25
Inde-
pendent
Data
-
-
-
1
3
3
-
1.6
0.14
4.1
4.8
8
-
0.35 .
»
and some
dust collector water.
4. There was no discharge of phossy water or calciner scrubber water.
134
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TABLE 14
EFFLUENT DATA FROM PLANT 5
Water & Waste
Water Analysis
Constitutent
PH
Turbidity
Conductivity
TSS
TDS
CaC03
Alkalinity
CaC03
AcidTty
Chloride
Fluoride
Sulfate
COD
Total
Hardness
Total
Phosphate
Ortho
Phosphate
Notes: 1.
2.
3.
4.
Units
-
FTU
umhos
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_
These
Treated
Intake
7.5
<1
966
11
617
358
-
50
0.84
91.5
-
465
18.0
15.9
are pre-1974
Effluent flow rate
This
There
Effluent
8.0-8.5
11
898
15
620
323
-
53
1.01
90.0
6
468
22.4
19.3
plant data
was 36,100
discharge included only
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
-
-
-
0.29
0.22
(-2.6)
-
0.22
0.0122
(-0.108)
0.43
0.22
0.32
0.24
, not independently verified.
1/kkg (8,
640 gal/ton).
excess noncontact
cooling water.
was no discharge of phossy water.
135
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TREATMENT OF WASTE WATERS IN THE PHOSPHORUS CONSUMING SUBCATEGORY
Phossy Water Wastes
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 that brought the phosphorus, and by transporting
this displaced phossy water to the phosphorus-producing plant for treatment
or reuse. Such is the practice at Plants 10, 11, 13, 14, 16, 17, 18,
19, 24, and 31.
Smaller quantities of phossy water discharge may also be eliminated
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 accomplished
with more stringent process and operator controls and procedures and by
providing traps downstream of reaction vessels. Curbed or diked areas
provided with sumps should be used for containment of phosphorus and
phossy water spills.
Another potential source of phossy water is leakage of below-ground
phosphorus storage tanks. In 1961, below-grade concrete tanks (pits)
for phosphorus storage were found to be leaking at Plant 9 and were
retired from service. Phossy groundwater is still seeping from an
excavation cut nearby and is collected and processed with other phossy
water in the phosphorus production plant. Good modern practice for
storage of elemental phosphorus would include:
1. Above-ground storage tanks (steel tanks are typical).
2. Concrete dikes surrounding storage tanks with concrete paving in
the diked area. Alternatively, use concrete lined pits under the storage
tanks. The dikes and paving or concrete pit should be monolithically
cast. The volume of the diked area or pit should be large enough to
hold the volume of the storage tanks plus several inches of water blanket.
3. There should be no bottom drains in pits or diked areas. A small
depressed portion or sump and an eduction pipe will aid removal and
salvage by authorized personnel.
4. Pits or diked areas should be kept dry or filled with a minimum
amount of fresh water (a few inches) to blanket spills. If water is
used, damage caused by freezing must be prevented. Spills and phossy
water should be promptly removed. Phossy water becomes acidic with time
and may cause pit leakage or seepage and possible damage to tank founda-
tions or supports, or, if deep enough, may externally corrode the phos-
phorus tanks.
5. A source of fresh water for blanketing should be piped to the pit
or diked area and protected from freezing.
136
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r
Plant 5 uses dry pits below phosphorus storage tanks. Other plants
using diked areas or pits to contain phosphorus storage tank spills or
leaks include Plants 2, 3, 6, 7, 8, 13, 16, 17, and 2-4.
Phossy water resulting from spills may be sand filtered, neutralized,
and stored for use as makeup water for phosphorus blanketing and transfer.
Plant 13 sand filters phossy water that may contain colloidal and suspended
phosphorus and debris. The contaminated sand is disposed of as solid
waste.
Treatment of_ Arsenic-Rich Residues
Arsenic-rich solid residues accumulate from the purification of phosphoric
acid and phosphorus pentasulfide. The common disposal method is burial
in a controlled area, as practiced at Plants 4, 13, 14, 16, 18, 21, 23,
25, 26, and 29. Arsenic sulfide is held as pond solids at Plant 31 but
will eventually be disposed of as solid waste. Solid residues from P2_S5_
manufacture are incinerated at Plant 17 and the gases scrubbed to recover
phosphoric acid.
The arsenic-rich liquid residue from the PC13 distillation is more
difficult to dispose of. Typically, this reFidue is chlorinated to
convert any remaining phosphorus to PC1_3_, and as much PC13_ is recovered
by distillation as possible. At Plant 11, this arsenic-rich heel is
then drained to drums. The still is washed with trichloroethane, and
this layer is drained to drums. Any remaining residue is water washed,
producing process waste water. The drummed residues are disposed of by
a contractor. At Plant 16, the arsenic-rich heel is first diluted with
trichloroethylene and the mixture drained to drums for disposal by an
industrial waste disposal firm. Any remaining residue is water washed,
producing process waste water. An estimated one percent of the arsenic
in the arsenic-rich heel becomes a process waste water contaminant. At
Plant 17, the arsenic-rich heel is diluted with water, and this aqueous
slurry is drummed for disposal to landfill.
Recycle and Neutralization of Scrubber Liquors
At Plant 17, recycle and caustic neutralization of P2_S5_ scrubber water
to pH 9 to 9.5 is practiced for reduction of waste water discharge
volume, for reduction of hydrogen sulfide vapor released to the air, and
for ease of operation. This pH range also reduces sulfur dioxide released
to the air. This same plant practices recycle and caustic neutralization
of PC1_3_ and POC13_ scrubber water to pH 4.5 for reduction of waste water
volume, reduction of hydrochloric acid vapor and chlorine gas released
to the air, and for ease of operation. Extent of recycle and caustic
neutralization of scrubber liquor is limited principally by the solubili-
ties of the dissolved salts and dissolved gases contained, and to some
extent by the materials of construction used in the scrubber systems.
Subsequent plans for treatment of the blowdown, temperature, and the
need for cooling are also factors.
137
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,—•»«.••.••»
!«. 8
I
The following are the solubilities of sodium salts that may be present
in phosphorus derivative scrubber water after neutralization with caustic,
Salt solubilities usually increase with an increase in temperature.
Sodium Salt Solubility, mg/1 Temperature, °C
NaH2_P04_.H2p 1,103,000 20
Na2HP04_.12H20 . 874,000 34
Na2P04.12H20 258,000 20
Na2HP03_. 5H20 (soluble) (cold)
NaH2P02.2jH20 560,000 0
Na2S04_.10H20 927,000 30
Na2S03 125,400 0
NaHS03. (very soluble) (cold)
Na2S . 154,000 10
NaHS (very soluble) (cold)
NaCl 357,000 0
NaOCl (soluble) (cold)
NaHC03. 96,000 20
Na2C03 215,000 20
The following are the solubilities of dissolved gases that may be pollu-
tants present in phosphorus derivative scrubber water. These solubilities
are in pure water, and in all cases add acidity to the waste water.
Caustic neutralization results in formation of one or more of the above
salts, permitting more gas to dissolve. Gas solubilities decrease with an
increase in temperature.
Gas Solubility, mg/1 Temperature, °C
SQ2_ 54,100 40
H2S 2,361 40
HCl 633,000 40
C12_ 4,510 40
Based upon the sodium salt solubilities alone and the total process raw
waste loads reported in Section V, the following blowdown volumes result:
Slowdown
Process Blowdown 1/Ickg Pdt gal/ton Pdt
P2S5 2.3$ 80 19
PClI 1.6* 24 6
POCT3_ 0.1% 28 7
138
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'! \f 11 t
Evaporation takes place in scrubbers. Sodium salt concentration in
recycled scrubber water should be kept far enough below saturation to
avoid crystallization or scaling in the scrubber caused by evaporation.
Alternatively, fresh water makeup can be sprayed into the scrubber inlet
gas stream to saturate it before it contacts the concentrated recycling
stream.
Caustic purchases may be minimized if the blowdown is lime treated to a
high pH (11 to 12.5) with removal of the insoluble calcium salts by
sedimentation and/or filtration. The filtrate will contain regenerated
caustic (sodium hydroxide) that could then be recycled in lieu of using
makeup water and fresh caustic. In the steam power plant industry, large
scale operational "dual-alkali" treatment systems are in use for S02
removal from stack gases. The same principal is utilized.(50,51,52T
Lime treatment is followed by soda ash softening to reduce the calcium
in the recycled caustic. In that industry, waste phosphate is not
available for softening.
There is no fundamental problem that would prevent the use of existing
scrubbers with recycle, caustic neutralization, and blowdown, while
still avoiding scaling or plugging. Use of scrubber recycle with minimum
blowdown and with caustic neutralization minimizes the volume of waste
water requiring subsequent treatment and therefore minimizes the subsequent
treatment costs. It also minimizes the total mass of pollutants that
would be discharged in an effluent after subsequent treatment to practi-
cable or economically achievable minimum concentrations.
Recycle and direct neutralization of P2_S5, PC12> or POCX3 scrubber
waters with lime or limestone slurry is also feasible. Calciner off-gas
scrubbers in the phosphorus production subcategory are operated with
slaked lime addition to the scrubber water at Plants 3, 4, 5, 6, and 7.
This is done to minimize air pollution from HF, S02_, and particulates;
to neutralize the resulting acids; and to precipitate fluorides, phosphates,
and other anions. At Plant 8, clarified water at pH 6 to 8 and containing
600 to 700 mg/1 calcium is used for calciner off-gas scrubbing with no
calcium salt scaling problems. Scaling occurs if pH 10 clarified water
is used. At Plant 4, lime slurry is injected into the calciner off-gas
scrubber water inlet to maintain pH 6 to 6.5 in the scrubber effluent.
Some scaling from calcium salts occurs and must be periodically removed.
After lime treatment at the scrubbers, the precipitated calcium salts
are settled in ditches, ponds, or clarifiers. The clarified effluents
are reused at Plants 3> 4, 5, 6, and 7. Buildup of dissolved solids in
the recycle effluent does not prevent reuse in the scrubbers.
In the steam power plant industry, large scale operational lime slurry
and limestone slurry scrubbing and treatment systems are in use for S02_
removal from stack gases.(50) In these systems, lime or limestone
slurry is added to the recirculating scrubber liquor. A portion of the
scrubber effluent, containing precipitated calcium sulfite and sulfate,
is bled off to a thickener or settling pond for solids removal. Clarified
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,, ? A
effluent is returned as makeup water and for making limestone slurry or
for slaking lime, in a no discharge system. In these power plant scrubbers,
some scaling and plugging is expected, and provisions for control of
these problems are included in the designs. The presence of phosphates
in waste waters from P2_S5_, PC13> and POC12 scrubbing is expected to
produce a softer, more easily removed scale than results from calcium
sulfate alone. The "dual alkali" systems avoid the scaling problems in
the scrubbers, but require more treatment steps.
Recycle, Reuse, and Neutralization of_ Equipment and Container Washings
At Plant 13, P2_S5_ scrubber water is reused for product bin washing. At
Plant 17, alkali is occasionally used for product bin washing, avoiding
an excess to avoid reaction with the aluminum. Collection of equipment
and container washings from P2S5_, PC13_, and POC13_ processes, neutralization
with caustic, and storage for reuse in recirculating systems will reduce
the volume of waste water generated and the size of subsequent treatment
equipment. Minimum blowdown should be based upon the solubilities of
the sodium salts, as explained for recycle of scrubber water. A pH
above 9 should be avoided for washing aluminum bins. If needed, makeup
water can be added to the system by use of a final fresh water wash.
Alkaline Chlorination of_ Phosphorus Pentasulfide and Phosphorus Trichloride
Waste Waters
Alkaline chlorination is widely practiced in plating and other industries
for cyanide waste destruction. Commercial equipment and controls for
alkaline chlorination for waste treatment have been in regular use for
over 20 years. The use of alkaline chlorination for sulfide destruction
is also a practicable technology currently available. The reaction
between sulfide and chlorine is "immediate".(53)
Chlorine reacts with sulfide in the presence of alkalinity to form
predominantly free sulfur or sulfate, depending upon conditions (at
constant pH):
HS~ + C12_ + OH~ *-S(s) + 2C1~ + H20
This reaction occurs in the pH range 5 to 9, optimum 5.(54) The pre-
cipitated sulfur may be present as a colloid. For each part sulfur,
2.22 parts_chlorine and 1.75 parts sodium hydroxide are consumed.
Sulfide, S~, exists predominantly as HS" at pH 7 to 15, and predominantly
as H2_S below pH 7. _At low pH values, 3.5 parts sodium hydroxide are
consumed per part S present as H2S.
Using higher chlorine dosages and more sodium hydroxide results in the
following reaction:
HO
-------
HS~ + 4C12_ + 90H~ ».S04 + 8Cl" + 5H20
This reaction occurs in the pH range 6 to 9, optimum 9.(54). For each
part sulfide, 8.88 parts chlorine and 15.75 parts sodium hydroxide are
consumed. Other compounds, including thiosulfate, trithionate, and
sulfite are produced when the degree of oxidation is intermediate between
sulfur and sulfate.
In the iron and steel industry, alkaline chlorination is used to treat
effluents from some iron blast furnace operations to destroy cyanide,
phenol, and sulfide.(55) After chlorination, the undiluted effluent
contained an equivalent 1.86 mg/1 sulfide. Before chlorination, 45 to
50 mg/1 was present.
In the Los Angeles County Sanitation District, chlorination of sewage
achieved reduction of sulfide to 0.43 mg/1.(53) This required a chlorine
dosage of 12 mg/1, which was 6.5 to 10.5 mg/1 in excess of the dosage
consumed by the sulfide destroyed. Because other substances in sewage
also consume chlorine, the free chlorine residual required to produce
this sulfide level was less than 6.5 to 10.5 mg/1 chlorine. (Chlorine
dosage equals chlorine demand plus chlorine residual.)
Calcium hypochlorite or sodium hypochlorite may be substituted for
chlorine. One part chlorine is equivalent to 1.01 parts Ca(OCl)2_or
1.05 parts NaOCl. These hypochlorites also add alkalinity, reducing
sodium hydroxide requirements.
Alkaline chlorination will also oxidize sulfite to sulfate,
SOjf + C12_ + 20H +* S04f + 2C1~ + H20
and will oxidize phosphite to phosphate,(20)
_ _ 'P0i= + cl~ + Hi°
Although phosphite is a strong reducing agent, it reacts slowly with
most oxidizing agents. At Plant 14, a new scrubber system is in use for
scrubbing PC13_, POC13_, and PC15 (phosphorus pentachloride) fumes from
those manufacturing processes. Excess free chlorine is present in the
fumes from POC13 and PC15 manufacture. Scrubber water is recycled while
neutralizing with caustic". The extent of recirculation is limited only
by the solubilities of the sodium salts formed (phosphates, phosphites,
and chlorides). Free chlorine, a. strong oxidant, is present in a portion
of the scrubber effluent. Thus, the conditions of alkaline chlorination
exist, and conversion of phosphite to phosphate and arsenite to arsenate
may occur. (Phosphite conversion may be a slow process.)
P2S5 has also been destroyed by direct reaction with calcium hypochlorite
in the laboratory.(56) Sodium hypochlorite has been used to convert
phosphite to phosphate in the laboratory.(57) These are both examples
of alkaline chlorination.
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.-.A r
L-' I) •»/'*» I
Thus, alkaline chlorination is a practicable currently available technology
for destruction of sulfides and sulfites present in P2_S5_ waste waters.
Conversion to sulfate is recommended.
Alkaline chlorination is also an achievable technology for conversion of
phosphites in PC13. waste waters to phosphates. Chlorination may also
oxidize elemental phosphorus, if present in these wastes, to phosphate.
As previously mentioned for the phosphorus production segment, destruction
of elemental phosphorus by chlorination has been done and is being
studied in the industry.
Alternative Oxidation Methods for Phosphorus Pentasulfide and Phosphorus
Trichloride" Waste Waters
Sulfides may also be destroyed by aeration:
HS" + 202_ + OH" >- S04_= + H20
2HS~
HS"
2HS~ + 02! + 2H+ *• S + 2H20
In the iron and steel industry, sulfides are presently reduced to 0.26
mg/1 using biological oxidation.(55)
Sulfites are oxidized to sulfates at a 94 to 95 percent level by aeration
of waste water in the inorganic chemicals industry.(58) In the steam
power plant industry, extensive oxidation to sulfate also occurs because
of aeration that occurs in stack gas scrubbers.
Several references have reported oxidation of sulfide to sulfate using
other common oxidants, including hydrogen peroxide(H20£), ozone (03.),
permanganates (KMn04_, HMn04_), chlorates, peroxysulfates, and chromates.(59)
Patented catalyzed air oxidations have also been reported (60).
Phosphites and elemental phosphorus would also be expected to be oxidized
to phosphate by these same oxidants, based upon known oxidation-
reduction potentials. Phosphites react slowly with most oxidizing
agents, however. The mechanism of phosphite oxidation by ozone has been
studied.(61)
The advantage of using air, hydrogen peroxide, or ozone for these
oxidations is that only water, hydrogen, or hydroxyl ions are added to
the waste waters.
Lime Treatment of Contaminated Waste Waters
Phosphoric acid is present in raw waste waters from H3P04, P205_, P2S5_,
PC13, and POC13 manufacture. Hydrogen sulfide, sulfurous acTd, and
1-42
-------
sulfuric acid are present in raw waste water from P2S5 manufacture.
Phosphorous acid is present in raw waste water fronTPCi3_manufacture.
Hydrochloric acid is present in raw waste water from PC13_> POC1_3_> and
sometimes from P2S5 manufacture (for this last product, this may be
because of ehlorTdes in fresh water, and concentration from evaporation
in the scrubber). Arsenous and arsenic acids are also present in waste
water from PC13_ still cleanouts. All of these acids are neutralized by
lime treatment. All of the anions except sulfide and chloride can be
precipitated as their calcium salts by lime treatment. The precipitation
of phosphate, sulfate, and sulfite was described in detail earlier in
this section. Hydrolyzable phosphates (meta, pyro, poly) are also known
to be present in some waste waters from P2S5, PC13_, and possibly POC1_3_
manufacture. The solubilities of typical~calcium salts of condensed
phosphates are also tabulated previously in this section.
Data presented previously in this section (phosphorus production)
showed that Plant 8 achieved 4-4 to 17 mg/1 total phosphorus in clarified
•pond water at pH 7.0 to 5.4 with 560 to 670 mg/1 calcium present, after
lime treatment. Other data for lime treated waste waters from the
fertilizer industry and from sewage treatment plants would predict:
pH Total Phosphorus, mg/1
9.0 1.8 to 2.0
9.5 0.5 to 3.0
10.0 0.2 to 1.2
10.5 0.1
The lower values are for filtered effluents from operations in sewage
treatment plants. Calcium ion concentration data were not available.
Sodium ion concentrations are not known, but are believed to be low.
In the presence of significant concentrations of sodium ion, pH is an
insufficient indicator of whether enough lime has been added to precipitate
all of the phosphate. Plant 31, which produces phosphoric acid and
soluble sodium and ammonium phosphates, lime treats a waste water contain-
ing sodium salts and polyphosphate pollutants. The process provides
some information on treatment problems, but may not be considered exemplary
or best practicable technology. A major problem is the extremely high
pH of the treated effluent.
The raw waste water from Plant 31 contains an estimated 4,000 to 7,000
mg/1 of sodium ion (average 5,600 mg/l) and a significant fraction of
hydrolyzable phosphates. These include poly, pyro, and meta phosphates.
The raw waste water contains an average of about 5,000 mg/1 total phos-
phorus, and ammonia nitrogen ranges from 3 to 178 mg/1 as N (average 69
mg/l). Lime treatment is preceded by retention in a pond for one month.
The pH is 7 to 8, and there is algae growth in the pond. Over 99 percent
of the total phosphorus leaving the pond is in the ortho form. Lime
treatment equipment includes a lime slaker, primary reactor, and secondary
reactor.
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L.-1'
A combined block flow diagram of the treatment system at Plant 31 is
attached as Figure 18. About 15 percent of the raw waste water is used
for lime slaking in an agitated tank at about 70 C. Slaked lime overflows
to the agitated primary reactor, where it mixes and reacts with an additional
40 percent of the raw waste water. This reactor overflows to the agitated
secondary reactor, where the water mixes and reacts with the final 45
percent of the raw waste water. The water is pumped from the secondary
reactor to a clarifier with a 24-hour retention time. Clarifier underflow
is sent to a rotary vacuum filter for dewatering, and clarifier overflow
is discharged to a river via two surge ponds. A polishing filter and a
pH adjustment step for the effluent have recently been added to the
system. The filter cake, primarily hydroxyapatite and containing 35
percent dry solids, is trucked to an approved sanitary landfill. Filtrate
from the vacuum filter is returned to the secondary reactor.
In the treatment process, quicklime is added at a Ca/P mole ratio of
1.85 or 1.9 to 1. (Hydroxyapatite has a Ca/P mole ratio of 1.67 to 1).
During a recent 22-month period, the average effluent phosphorus concentra-
tion was 44 mg/1 (as P), with an average 99.4 percent removal efficiency.
Total suspended solids in the effluent averaged 20 mg/1, without filtration.
The pH before acid neutralization is 12 to 13. Use of a one-micron
retention polishing filter is projected to produce 20 mg/1 maximum
suspended solids in the effluent. No polyelectrolytes or other floccu-
lating agents are used in this system.
Finely divided suspended algae are present in the clarifier, clarified
effluent, and hydroxyapatite filter cake. Colloidal material is known
to be present in the effluent. It is believed that only 1 to 10 mg/1 of
the total phosphorus in the effluent is in solution and the remaining 34
to 43 mg/1 is present as suspended and colloidal solids.
In the steam power industry, calcium sulfite and calcium sulfate are co-
precipated by lime or limestone in acidic or caustic neutralized slurries.
The sulfite to sulfate ratio varies substantially from plant to plant.
These slurries are sometimes thickened in conventional thickeners or
clarifiers, and the thickened slurries are filtered to produce filter
cakes containing 50 percent moisture. Thickener underflow feeding the
filter is kept below 20 percent solids for ease of operation.(52) In
the "dual-alkali" treatment system, sodium concentrations may be 0.9 to
3.2 moles/liter.
In the phosphorus production subcategory, phosphate, sulfate, and fluoride
are co-precipitated with lime and settled in ponds and mechanical clari-
fiers. Lime treatment, clarification, thickening, and filtration of
waste waters containing phosphates, sulfites, and sulfates from P2_S5_
manufacture should be considered practicable technology transferable
from other segments of the phosphorus industry and from the steam power
plant industry. It is assumed that sodium ion will be present from
recycle and caustic neutralization of waste water. Plant 31 provides
information on expected concentrations of phosphate and suspended
144
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RAW WASTE WATER
FROM HOLDING POND
NONCONTACT-
COOLING
WATER
FIGURE 18
PLANT 31 WASTE TREATMENT PROCESS
14 i-
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solids in treated effluents in the presence of comparable amounts of
sodium ion, colloidal material, and algae at high pH values.
Lime treatment, clarification or thickening, and filtration of waste
waters containing phosphates and chlorides from POC13_ manufacture should
also be considered practicable technology, based on Plant 31 treatment
data for phosphate and suspended solids removal. It is assumed that
sodium ion will be present from recycle and caustic neutralization of
waste waters.
Lime treatment, clarification or thickening, and filtration of waste
waters containing phosphates, arsenates, arsenites, and chlorides from
PC13 manufacture is comparable to the treatment of other waste waters
containing phosphate, sulfate, sulfites, or fluoride. The solubility of
the slightly soluble phosphite is repressed by high concentrations of
both calcium and hydroxyl ions from slaked lime. Phosphorous acid is a
weak acid.
Ca+2 + HPCXT2 + 3H20 - »- CaHP03_. 3H20( s )
The calcium from the lime drives this reaction to the right, precipitating
the phosphite. Solubility product formulae would apply at a given
temperature :
(Ca+2) (HP03_~2) (H20)3 = constant
Also, the following ionizations take place:
+
+ HP03
Caustic or lime addition drives both of these reactions to the right. 2
At pH 8, over 99.9 percent of the phosphite would be present as HP02~ .
Subsequent sedimentation in a clarifier, with the use of polymeric
flocculant, should effectively remove 90 percent of the suspended solids
as a sludge. This sludge could be vacuum filtered as at Plant 31 before
disposal. The clarified filtrate can also be filtered for further reduc-
tion of suspended solids as at Plant 31, or, alternatively, the entire
lime treated slurry may be filtered without use of a clarifier. This
may be practical if the recycled, caustic neutralized scrubber water and
other waste waters are concentrated and low in volume.
Laboratory tests of lime treatment of PC13_ reactor cleanout waste water
from Plant 11 were made by that firm. Lime treatment to pH 11.5 followed
by filtration resulted in 99.6 to 99.7 percent removal of arsenic, to
final concentrations of 0.015 to 0.135 mg/1 arsenic. The same treatment
achieved 74 to 97.7 percent total phosphorus removal to final concentra-
tions of 68 to 83 mg/1 total phosphorus. Other lime treatment tests by
the same firm were made, using a synthetic waste comparable to a combined
PC13 and POC13 scrubber waste water. At pH 11.6, 99 percent removal of
146
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both arsenic and phosphorus was obtained, with less than 0.01 rag/1 and
16 mg/1, respectively, remaining in the filtrate. In another test by
the same firm with reactor cleanout waste water, arsenic and total
phosphorus removal efficiencies were greater than 99.7 percent and 95.0
percent, respectively, to 0.226 mg/1 and 138 mg/1 in the filtrate,
respectively. These data simply illustrate that oxidation of phosphate
to phosphite and arsenite to arsenate may not be necessary to achieve
high removal efficiencies and low treated effluent concentrations for
arsenic and total phosphorus removal by lime treatment. Also, hydrolyz-
able phosphates are known to be present in PC13 waste water and probably
in POC13 waste water. Their presence did not pFevent high total phosphorus
removal efficiencies. Information is not available on phosphorus removal
efficiency when the condensed phosphates have been completely hydrolyzed.
Additionally, the Plant 11 waste water tests tend to confirm arsenic
removal efficiencies reported by Patterson for lime treatment.(32) At
pH 12, 95 percent arsenic removal was acheived for either arsenite or
arsenate.
Recycle of Lime Treated Waste Water for Reduction of Slowdown
In the steam power plant industry, in the "dual alkali" process, stack
scrubbers remove S02 using recirculating scrubber water with caustic
addition. The scruFber blowdown is lime treated, clarified, and the
thickened slurry filtered for removal and disposal of the calcium sulfite-
calcium sulfate cakes. The clarified effluent, containing regenerated
sodium hydroxide and some sodium sulfite (an alkaline salt), is softened
by carbon dioxide or soda ash addition. The calcium carbonate sludge is
recovered by thickening and is reused to reduce lime requirements for
scrubber effluent treatment. The softened regenerated sodium hydroxide
(caustic) is then reused in the stack scrubber. No scaling occurs.
Sodium ion and hydroxide ion are lost with mother liquor in the calcium
sulfite-calcium sulfate filter cake. There is no blowdown.
The same system is applicable to the scrubbing of fumes from the P2S5_,
PC1_3> and POC13_ processes. For these waste waters, however, sodium
chloride will build up in the regenerated caustic recycle stream. The
sulfide present in the P2S5_ waste water would be converted to sulfate by
alkaline chlorination or~~other oxidation before lime treatment.
In the case of P2S5 waste water, when the recycling sodium chloride
builds up to 12 tb~15 percent in solution, this salt will leave the
recycling system as a dissolved solid in the hydroxyapatite, calcium
sulfate, calcium sulfite filter cake at the same rate it is generated by
the P2S5_ process, based on the raw waste loads given in Section V.
This assumes at least 50 percent moisture in the filter cake. However, the
previous alkaline chlorination step adds sufficient additional chloride
to prevent total recycle without blowdown. (if alkaline chlorination
could be economically replaced by air or H202_ oxidation, total recycle of
waste water would be acheivable, as originally proposed for this product.)
Enough fresh caustic must be supplied at the scrubber to replace sodium
ion lost in the filter cake. Lime addition must be controlled to avoid
high calcium concentrations in the scrubber, thereby avoiding scaling.
147
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Under conditions, of total recycle, sulfate, sulfite, and possibly
phosphate would be allowed to build up to much higher concentrations in
the lime treated filtrate (regenerated caustic) than if this filtrate
were discharged.
In the case of PC13 and POC13_ waste waters, sodium chloride would be
allowed to build up almost to its solubility, i.e. 35 percent. With no
filter cake washing, some of this will leave the recycling system as a
dissolved solid in the hydroxyapatite or calcium phosphite cake, but
some blowdown would also be required. If sodium chloride were only
allowed to build up to 200 g/1 in the recycled filtrate, filtrate
blowdown for the "dual-alkali" treated recycling waste waters would be
less than 12 1/kkg for the PC12 process and less than 18.5 1/kkg for the
POC13_ process. These compare to raw waste water loads of 1500 1/kkg and
3900 1/kkg, respectively. These estimates are based upon the raw waste
load reported in Section V. If other factors require makeup to the
associated scrubbers or other associated recylcing waste water systems
in excess of evaporation plus this blowdown, then more blowdown will be
required.
Dechlorination of_ Waste Waters
Chlorine may be present in waste waters from POC13_ and PC15_ manufacture.
If alkaline chlorination of waste waters from P2S5 manufacture is done
to achieve less than 1 mg/1 sulfide, as much as~ir mg/1 of chlorine
residual may remain. Because free chlorine in fresh water is harmful to
fish, dechlorination of waste water may be desirable.
At Plant 14, dechlorination is practiced for a portion of the alkaline
waste water resulting from scrubbing of PC13, POC1_3_, and PC15_ vents and
exhaust gases. This is done by heating the solution in the presence of
a copper sulfate catalyst. Sodium hypochlorite (the active chlorine
compound in this alkaline chlorination) is converted to common salt and
oxygen.
2NaOCl »-2NaCl + 02_
The influent contains an estimated 60,000 mg/1 NaOCl (equivalent to
57,000 mg/1 C12_).
Dechlorination using automatic S0£ addition has been used at the Toronto
water works since 1926.(23) Chlorine is reduced from an initial 3 ppm
minimum to 0.9 ppm by this treatment. Other plants reported 0.5 to 0.75
ppm chlorine after treatment.
Other Methods for Arsenic Removal
Coagulation and precipitation with iron salts at pH 6.0 will remove
arsenic. A ferric hydroxide floe is produced that ties up the arsenic
and carries it from solution. This process has consistently yielded
arsenic levels of 0.05 mg/1 or less.(49)
148
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In pilot plant tests, precipitation with alum at pH 7.0 or ferric sulfate
at pH 5.5 to 8.5, followed by dual media filtration, each resulted in
effluent concentrations of 0.003 to 0.005 mg/1 arsenic. Arsenic removal
efficiencies were 85 to 92 percent and 98 to 99 percent with alum and
ferric sulfate, respectively. Chlorination before coagulant addition
was required to remove arsenite at these efficiencies.(32)
Inert - Atmosphere Casting o£ P2S5
Although Plants 13, 14, and 18 still cast some molten P2S_5_ product into
small drums for shipment, or into cones followed by crushing, it appears
that P2S5 casting is being phased out in this industry in favor of
continuous flakers, chill wheel solidification, and hollow screw flight
types of solidification conveyors or mixers. The use of these continuous
solidifiers (62) permits solidification in an inert-gas atmosphere,
substantially reducing P2_S_5_ losses that become waste water contaminants
in fume scrubbers for the" P2S5 process. When molten P2_S_5_ is exposed to
the atmosphere, it spontaneously ignites, forming P205~and S02_. Wet
scrubbers are commonly used to remove these pollutants. The inert gas
blanket prevents this ignition and limits losses in solidification to
the P2S^ vapor contained in the small quantity of purge gas used. There
are other reasons for use of continuous solidification instead of
casting:
1. Higher reactivity of the product P2_S5_. Rapid solidification
in thin layers or in stirred equipment results in higher P2S5_
reactivity.
2. Controlled and uniform reactivity. The solidification rate in
continuous flaking or agitated solidification equipment is
more uniform than in casting.
3. Lower labor costs. Casting requires labor to be continuously
present during the pouring and for positioning and transporting
the small casting drums or cones.
4. Safety. In casting, air is present. If unburned P2S5_ vapor
or fume accumulates in hoods or ductwork, an explosion can
occur from spontaneous ignition originating at a new pour.
5. Disposal of containers. Drums used in casting must be
cut open and become a solid waste disposal problem for the
user.
Thus, the preferable alternative for reduction of waste water
contaminants from P2S_5_ casting is to replace casting equipment with
continuous, enclosed^ and inerted solidification equipment.
A second alternative would be to provide enclosed, inert gas purged casting
hoods. One plant tried such a hood but abandoned it because of
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,T -••- -,r
.L' I W'''U" J
an explosion resulting from the ingress of air during casting. Design
of a safe system would be expensive, and inert gas usage could be high.
Refrigerated Condensers and Other Equipment for PC13 and POC13
In the standard process for manufacture of PC13_ and the alternate process
for manufacture of POC13, the present industry~practice is to use water-
cooled condensers to reTlux the reaction vapors and to collect the
product. Additionally, in the standard POC13_ process, all but one
manufacturer use water-cooled vent condensers. 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 quantities 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 that subsequently becomes acid aqueous wastes:
PC13_ Vapor Pressure,
Temperature, C Temperature, F ~ mm Hg(20)
-40 -40 3
-20 - 4 13
0 32 38
+20 68 99
+40 104 235
The melting point of PC13_ is -112°C (-173°F) and of POC13_ is 2°C (36°F).
The vapor pressures of POC13_ are about one-third of PC13_ vapor pressures.
Lowering the final condenser vent temperatures to -20°C (-4°F), for
example, would lower the PC13_ vapor pressures by a factor of about 10,
as compared to an assumed vent gas temperature of 29 C (84 F) for a
water-cooled condenser. Plant 13, however, operates with vent tempera-
tures of 45 to 60 C for PC13_. As compared to a 50 C vent temperature,
316 mm vapor pressure, the factor would be about 24-fold. PC13_losses
would be proportional to the vapor pressures.
Refrigerated condensers are in use for control of PC13_ vapors from
POC12 manufacturing at Plant 11. Vent temperatures are -15 C (5 F)
to -30 C (-22°F). Raw waste water from PC13_ and POC13_ processing at
Plant 11 contains only about 20 percent of the chlorides (per kkg product
basis) and 18 to 36 percent of the total phosphorus (per kkg product
basis) found at similar plants, or 14 to 59 percent of the chlorides and
40 to 60 percent of the total phosphorus found at plants using the
alternate POC1_3_ process.
The reason that product losses to waste water are not even lower at
Plant 11 is that no refrigerated vent condensers are used for the PC13_
process, for any storage tank vents, or for tank car and container
filling.
150
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Vent condensers for pure POC13 vapors should be kept above 2 C ( 36 F ) to
avoid freezing POC13. If PClJ is also present, it acts as a solvent for
POC13 and lowers the" freezing~~point.
Vapor losses for PC13 and POC13 can be reduced by the use of refri-
gerated vent condensers and refrigerated vents for storage tanks and
product filling operations, as previously mentioned. Liquid product
refrigeration in storage will also help, particularly if air movement
across wet surfaces cannot be avoided. The use of inert gas blanketing
or air dryers for makeup air will avoid unwanted hydrolysis of the
products.
One plant has done preliminary design for refrigerated PC13_ condensers
utilizing liquid chlorine as the refrigerant. Chlorine is normally
stored as a liquid and used as a gas. Because chlorine must be used to
manufacture PC13 and is used in the alternate POC13 process, the use of
PC1_3_ vent condensers refrigerated by liquid chlorine would provide some
of the heat that is required for chlorine vaporization. The following
are the normal boiling points of chlorine and common refrigerant gases:
Chemical Boiling Point
Chlorine -3-4.6 -30.3
Refrigerant 12 -29.7 -21.6
Refrigerant 22 -40.7 -41.4
Ammonia -33.3 -28
Carbon Dioxide -70 -94.1 (at 5.2 atm)
Sulfur Dioxide -10 -14.0
Removal of_ Chlorides and Other Soluble Anions
Ion Exchange and Deminerali zation . Ion exchange and demineralization
are usually restricted in both practice and costs to total dissolved
solids levels of 1,000 to 4,000 mg/1 or less.
An ion exchanger may be simply defined as an insoluble solid electrolyte
that 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 a crosslinked 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:
151
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. T
ArS03H + NaCl >• ArS02Na + HC1
ArC02H + NaCl *• ArC02Na + HC1
The above reactions are reversible. Therefore, cation exchangers can be
regenerated with acid.
Anion exchangers use basic groups such as amino groups.
ArNR'3pH + HC1 ^ArNR'3Cl + H20
This is also a reversible reaction. Therefore, anion exchangers can be
regenerated with alkalis, which consume the free acid, leaving the amine
form of the exchangers. 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 15 gives the level of total dissolved solids that
can be achieved. Special ion exchange systems have been developed for
treating high dissolved solids content (more than 1000 mg/1 total dissolved
solids), minimizing regenerant chemical costs.
As can be seen from Table 15, ion exchange provides a means to produce
extremely low cation and anion concentrations in an effluent. The
required periodic regeneration, however, produces a waste water containing
the same ions in a much more concentrated form. Therefore, ion exchange
would be used only to produce this low volume regenerant waste concentrate
for further treatment or disposal. If evaporation is subsequently used,
the volume of waste water to be evaporated will be drastically reduced.
Reverse Osmosis. The phenomenon of osmosis has its explanation in
thermodynamic equilibrium and free energy concepts. Essentially, when a
semipermeable membrane separates a pure liquid and solution of dissolved
material in the same liquid, there is a net migration of the pure liquid
to the solution, driven by the free energy difference 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 susceptibility to blinding,
plugging, and chemical attack. Acidity, suspended solids, precipitates,
coatings, dirt, organics, and other substances can make it inoperative.
Membrane life is critical and unknown in many mediums.
152
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TABLE 15
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
Residual
Silica,
mg/1
No silica
removal
0.01-0.1
0.01-0.1
0.01-0.1
0.05
Residual
Electrolytes,
3
3
0.15-1.5
Similar setup as immediately 0.01
above + continuous recirculation
0.5
0.1
0.005
Specific
Resistance
ohm-cm
@25 C
500,000
100,000
1,000,000
1-2,000,000
3-12,000,000
18,000,000
153
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With these restrictions there is little wonder that industrial applications
of reverse osmosis are limited. Fortunately, the phosphorus chemicals
industry waste water treatment needs are similar to those of areas where
reverse osmosis has been shown to be applicable — treatment of brackish
water and low (500 mg/1 to 20,000 mg/l) dissolved solids removal.
Organics are usually absent, suspended solids are low or can be made low
rather easily, acidity is easily adjusted, and the dissolved solids are
similar to those in brackish water — sodium chlorides and sulfates and
their calcium counterparts.
The blowdown from reverse osmosis equipment contains all of the ions
excluded from the purified effluent. Thus, reverse osmosis provides
another way to produce a low volume concentrated waste water for evapora-
tion or disposal.
Evaporation Ponds. Plants 5, 6, and 7 utilize evaporation ponds for
disposal of phossy water and scrubber solids from phosphorus manufacturing.
Evaporation to dryness occurs in these ponds. Ponds may also be reasonably
used for other waste water disposal where the waste water quantities are
not overwhelming. Evaporation in ponds also takes place at Plants 1, 2,
3, 4, 6, 8, 9, 16, 17, 20, 22, 23, 25, 31, 41, and 43.
The size of an evaporation pond depends partially on the climatic
differential between evaporation and rainfall:
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 (4 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.
Evaporation from ponds can be substantially greater than published
climatic figures for lake or pan evaporation if the ponds receive waste
water warmer than pond water. For industrial ponds, this is almost
always the case. Data in Perry's handbook (63) simplify the calculations.
As previously described for reduction of cooling water volume, spray
ponds provide a means for increasing the evaporation and greatly reducing
the area required in comparison with a cooling pond. An alternative
method of achieving pond size reduction would be by the use of surface
aerators (commonly used for biological treatment of organic wastes).
There is no fundamental reason that would prevent the adaptation of a
cooling tower to the evaporation of process waste water, provided that
waste water to the tower is treated to prevent plugging, scaling, and
corrosion. The purpose would be to minimize evaporation pond area.
154
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Single-Effect and Multiple-Effect Evaporators. For the treatment of
small waste streams, single-effect evaporators are characterized by low
equipment costs and by inherent reliability, at the expense of high
steam requirements. Conventional multiple-effect evaporators, with 2 to
6 effects, have somewhat higher capital costs, but require much less
steam.
Evaporation is a technology that is aptly demonstrated throughout the
chemical process industry (although not extensively for the sole purpose
of waste treatment), and as such meets the requirements of being currently
available.
A variation of the single-effect evaporator is one wherein the evaporated
water vapor is mechanically compressed and reused as the steam source
for the evaporation. This is termed thermocompression. Thermocompression
permits recovery and reuse of the latent heat of evaporation of the
vapor. Any impurities carried over with the vapor will be present in
the steam condensate discharged. Thermocompression evaporators have
been in use for desalination of seawater for over 30 years and for
concentration of fruit juices and Pharmaceuticals for over 20 years.
Commercially available evaporators provide a means for concentrating
soluble salts almost to their limit of solubility, thereby reducing the
volumes of waste water requiring subsequent disposal or treatment. It
should again be noted that process scrubber water can be recycled using
effluent treatments to achieve essentially the same result by reducing
makeup water requirements and by evaporation in the scrubber.
155
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-u
TREATMENT OF WASTE WATERS IN THE PHOSPHATE SUBCATEGORY
Sodium Tripolyphosphate Manufacture
As stated in Section V, all direct contact process waste waters and
scrubber waste waters are recycled at Plants 25, 27, and 31. At Plant
31, a combined waste water from all soluble phosphate production and
shipping areas includes floor washings, leaks and spills, equipment
washout waters, area runoff (including roof and site drainage), lab
wastes, and safety and fire waters. Because Plant 31 produces food-
grade sodium tripolyphosphate and other soluble food grade phosphates,
this waste water cannot be recycled to the processes. Therefore, the
waste water is lime treated on the site. Clarified effluent is discharged,
and sludge is dewatered for contractor disposal. Details were described
previously in this section, and a diagram was also presented (Figure
18). This treatment process represents current practice at one plant
manufacturing food grade sodium tripolyphosphate and other soluble
phosphates.
Effluent flow from the Plant 31 treatment facility is 370 1/kkg pdt (90
gal/ton). The effluent contains 0.008 kg/kkg (0.015 Ib/ton) total
suspended solids and 0.018 kg/kkg (0.035 Ib/ton) total phosphate on an
average basis. These pollutant quantities are based on the total produc-
tion of soluble phosphates and phosphoric acid at Plant 31. Based upon
soluble phosphates only, the kg/kkg pdt figures should be multiplied by
1.4. Average effluent concentrations are about 20 mg/1 total suspended
solids and 44 mg/1 total phosphorus. Some of this may be in the hydrolyz-
able form. Average effluent pH is 13.1, but sulfuric acid addition
facilities recently installed will reduce this to 11.5. Sulfuric acid
(93 percent) will be used at an estimated rate of 4 1/kkg (0.95 gal/ton)
to achieve the desired pH. The present effluent from the plant cannot
be regarded as satisfactory, particularly because of the high pH.
As mentioned in Section V, noncontact cooling water may also be generated
in the food-grade sodium tripolyphosphate category, and is subject to
contamination by leaks. An estimated 0.06 kg/kkg pdt total phosphate is
present in untreated noncontact cooling water discharged by Plant 31.
The plant uses once-through noncontact cooling water in its phosphoric
acid and food grade phosphate processes. The average concentration of
total phosphorus in the cooling water discharge is about 1.4 mg/1.
Treatment to remove phosphorus at this low concentration may not be
cost-effective. Reduction in total phosphorus discharged in noncontact
cooling water must center on design of heat exchangers, sumps, and
systems to minimize contamination from leaks and spills, and on instrumen-
tation, such as pH monitoring instruments, for detection of leaks so
that equipment can be promptly repaired. The use of recirculating
cooling tower systems and similar systems, as described elsewhere in
this section under reduction of cooling water volume, should also be
considered. Sodium tripolyphosphate Plants 20, 23, 26, and 27 report no
discharge of spent cooling water. Plant 20 uses 1800 1/kkg (440 gal/ton)
156
T
-------
and Plant 27 uses 50 1/kkg (12 gal/ton) of noncontact cooling water
makeup. By extensive recycle in cooling tower systems, waste water
volumes will be reduced and phosphate concentrations may build up to
levels where treatment for removal is economical.
In the non-food grade sodium tripolyphosphate subcategory, Plants 25 and
27 discharge no waste water except for storm water runoff and, at Plant
25, noncontact cooling water. Although there are no detailed data for
the volume of storm water runoff from production and storage areas, it
would be reasonable to assume that it is no greater than at food-grade
Plant 31 and contains no more total phosphorus. Therefore, the Plant 31
treatment system would be applicable for any storm water in excess of
what can be used in the process.
Reduction of total phosphorus in an effluent from plants producing
sodium and other (potassium, ammonium) phosphates to levels below the 44
mg/1 average attained at Plant 31 can be achieved. This requires methods
that take into account the possible presence of sodium, potassium, and
ammonium ions; colloidal material; and hydrolyzable phosphates.
Sodium hydroxide is generated when sodium phosphates are precipitated by
lime treatment:
3Na(H2P04) + 5Ca(OH)£ »-Ca5(P04_)30H( s) + 3NaOH + 6H20
3Na2HP04_ + 5Ca(OH)2_ ^ Ca5( P04 )30H( s) + 6NaOH + 3H20
3Na3P04_ + 5Ca(OH)2_ »-Ca_5jP04_T30H( s) + 9NaOH
2Na5P3010 + 5Ca(OH)2_ ^ Ca5(P3010)£( s) + lONaOH
Similar equations apply to lime treatment of potassium phosphates.
The above equations are actually aqueous ionic reactions. Although high
concentration of sodium ion will increase the solubility of certain
calcium phosphates somewhat, this effect is not very large.(64) However,
the effect of the hydroxyl ion can be substantial principally because of
its effect upon the concentration of free calcium ion in solution. This
calcium ion reacts with phosphate to precipitate the phosphate. At 20 C
(68 F), calcium hydroxide has a solubility of about 1650 mg/1 in pure
water, yielding less than 803 mg/1 calcium ions and less than 682 mg/1
hydroxyl ions, because dissolved calcium hydroxide is less than 90
percent ionized. Theoretically, the pH would be less than 12.6. Because
the theoretical solubility product, Ksp, equals the product: (Ca )
(OH ) , doubling the hydroxyl ions in solution by addition of sodium
hydroxide will increase the pH to about 12.9, but this will reduce
calcium ion concentration by a factor of four to about 170 mg/1.
Because the solubility product of hydroxyapatite is
Ksp = (Ca)5 (PO-4)3 (OH),
this means that the total phosphorus in solution at equilibrium increases
by a factor of eight because of the presence of the excess hydroxide
from sodium hydroxide.
157
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r' i'1""*., .1 »>""-*|i»*
LsSifri" I
Two alternatives are considered available technology to prevent the
suppression of free calcium ion in the presence of sodium hydroxide:
1. Lime treat to a pH value of less than 11 to 12. Add additional
calcium as calcium chloride to achieve sufficiently high
calcium concentrations. Calcium chloride is used industrially
at one plant to supplement lime for the precipitation of
fluoride. (32) The use of calcium chloride increases the
calcium ion concentration without increasing the pH. This
technology is transferable to lime treatment systems used for
precipitating phosphates.
2. When the pH reaches 11 or 12, begin the addition of sulfuric
acid to prevent further increase in pH while adding lime. Acid
addition is a routinely practiced technology used to neutralize
excess hydroxide.
Plant 31 has indicated that suspended and colloidal solids in the
clarifier overflow are believed to be the source of most of the total
phosphorus in the effluent from their treatment plant. These solids
consist of algae and probably insoluble hydroxyapatite solids. Other
insoluble phosphates may be present. Thus, further reduction of total
phosphorus becomes a matter of removal of the suspended and colloidal
solids. Laboratory testing by the firm showed that up to 20 mg/1 suspended
solids still remain after filtration using one-micron retention media.
Removal of colloidal material from waste waters can be accomplished by
conventional sedimentation and filtration techniques if preceded by a
coagulation or flocculation step that agglomerates the colloidal particles
into large aggregates.
Flocculation is a routine treatment step used in municipal water treatment
to produce clear potable water from extremely turbid surface waters
containing large amounts of colloidal solids. Calcium ion is reported
to be about 100 times as effective as sodium ion in destabilizing aqueous
colloids.(65) Destabilization is a necessary step in the flocculation
process. Thus, the use of calcium chloride or acid neutralization as
previously described for increasing calcium in concentration may help to
destabilize the colloidal material. Flocculation using synthetic poly-
electrolytes is widely used. Iron chloride added to water produces a
ferric hydroxide flocculation over a wide pH range. Alum added to water
produces an aluminum hydroxide flocculation within the pH range 5.7 to
7.5. These flocculants are all widely used for colloid removal.(66)
Flocculation followed by filtration can achieve 0 to 2 mg/1 total suspended
solids, commercially.(66,67)
Supplementing lime treatment with calcium chloride addition or acid
addition to raise the concentration of free calcium ion in solution is
expected to reduce the total phosphorus in solution by precipitation of
hydrolyzable or condensed phosphates present. Data presented by Schmid
and McKinney(68) showed reduction of total soluble phosphorus from an
158
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initial 16 mg/1 to a final concentration of about 1.3 mg/1 by treatment
with 200 mg/1 calcium at pH 9.0. The initial 16 mg/1 contained 50
percent polyphosphates and 50 percent orthophosphate. Polyphosphate
alone was reduced to only 8 mg/1 by the same treatment in the absence of
orthophosphate. Thus, orthophosphate must be present to achieve adequate
removal of polyphosphate. If calcium in solution is present at insuffi-
cient concentration, it will be complexed or chelated by polyphosphate,
pyrophosphate, or other condensed phosphates present. This calcium is
then unavailable for precipitation of orthophosphates. Complexes of
tripolyphosphate and pyrophosphate contain Ca:P ratios of 1 to 2.33 and
1 to 1.55 by weight, respectively.(69) Thus, no phosphate precipitates
form with calcium concentrations equal to or less than these ratios.
Calcium tripolyphosphate precipitates form, however, if the Ca:P ratio
is equal to or greater than 1 to 1.16 by weight at total phosphorus
concentrations greater than 7.4 mg/1. Similarly, calcium pyrophosphate
precipitates form if the Ca:P ratio is equal to or greater than 1 to
0.78 at total phosphorus concentrations greater than 7 mg/1. Thus, the
presence of adequate calcium ion and orthophosphate ion at sufficiently
high pH values results in precipitation and removal of hydrolyzable
phosphates.
One-month retention in a pond at neutral pH in the presence of algae, as
at Plant 31, resulted in a waste water with less than one percent of the
total phosphorus present as hydrolyzable phosphate. This is another way
of avoiding the possible difficulties in the precipitation of polyphosphates,
Condensed (poly- or hydrolyzable) phosphates are also completely hydrolyzed
by acidification to 0.1 normality (-4,900 mg/1 excess sulfuric acid plus
40 mg/1 nitric acid, approximate pH of 1.0) and holding 90 minutes at
100 C (212°F) or 30 minutes at 121°C (250°F).(70) Acidification and
heating are state-of-the-art technologies in the process industries.
Energy requirements may be minimized by use of a countercurrent flow
heat exchanger utilizing the hot, hydrolyzed effluent to heat the cooler
raw waste. Materials of construction would require special consideration.
Sodium tripolyphosphate is also readily hydrolyzed to orthophosphate by
calcium hydroxide.(71)
It must be noted that, based on data presented by Schmid and McKinney
(68), maximum polyphosphate removal efficiencies are obtained in the
presence of orthophophates. Thus, an alternative to hydrolysis of
polyphosphates or direct precipitation would be to add orthophosphate to
the waste water. Performance as reported by Schmid and McKinney(68)
would be expected when the total phosphorus components in a waste water
from polyphosphate and orthophosphate are made equal.
Calcium Phosphates Manufacture
The amount of air-borne solid wastes entering waste water streams can be
minimized by preceding or replacing wet scrubbers with dry dust collection
159
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equipment. Plants 24 and 36 have already totally replaced wet scrubbers
for DCP and TCP with dry collectors. Treatment of phosphoric acid,
suspended solids, and sludges resulting from wet scrubbing has been
previously described for the elemental phosphorus production subcategory,
and elsewhere in this section.
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 pollutants has also
been discussed previously for the phosphorus production subcategory.
The DCP filtrate can be lime treated and clarified. Both the underflow
and overflow can be recycled, as at Plant 36, or there may be a discharge
of clarifier overflow, as at Plant 24. Technology for reduction of
total phosphorus in this overflow to 44 mg/1 has been described for
Plant 31, above. Other waste waters can be similarly treated as described
for Plant 31. No plant presently treats a separate noncontact cooling
water stream before discharge, but these cooling waters may be handled
as described for sodium tripolyphosphate and elsewhere in this section.
160
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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 phosphorus derived chemicals industry were discussed in Section VII
of this report. In this section, each of these technologies is reviewed
from the following standpoints:
1. The cost of applying the technology.
2. The energy demands of the technology.
3. The impact of the technology on air quality, solid waste
management, noise, and radiation.
4. 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 was synthesized. The various treatment alternatives for each
subcategory are summarized in Table 16 and are described in detail later
in this section. Cost-effectiveness data for each plant for the various
treatment alternatives appear in Table 17. 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.
However, the discussion of costs and benefits in this section 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 that cannot all be incorporated into
a single hypothetical plant:
1. The personnel of each plant must retain the degree of freedom
to choose from the alternative control and treatment technologies
presented in Section VII, to choose from technologies not
presented in this report, and to choose any combination of
these technologies.
2. There are cost tradeoffs, which are unique for each plant,
between in-process controls and end-of-process treatments,
with material recovery being an important parameter.
3. The actual raw waste load for each plant may be appreciably
higher or lower than the average raw waste loads presented in
Section V. In particular, much greater plant-to-plant variability
was observed with respect to production-normalized raw waste
water volumes than with respect to production-normalized raw
quantities of polluting constituents.
161
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TABLE 16
TREATMENT ALTERNATIVES
Subcategory
Phosphorus
Producing
Chemical
Alter-
native
Phosphorus
Consuming
H3P04
B
P205
A
B
P2S5
A
B
Description
Existing control: Complete recycle of phossy
water. Evaporation of some other process
water. Lime treatment and clarification of
remaining process water prior to discharge.
Incomplete control of storm water runoff.
Storm water diversion and collection ditches,
dikes, storm water lagoon, pumps and piping,
to prevent excessive influx into treatment
ponds, plus technology "A". Only cooling
water is discharged.
Reduction of cooling water makeup by use of
cooling towers, makeup water treatment and
softening, total recycle, cold weather
protection, plus technologies "A" and "B".
Cooling water blowdown is treated and recycled
with other process waste water.
No treatment. No phossy water discharge.
Waste waters only originate from leaks, spills,
etc.
Collect contaminated storm water. Lime
treatment, settling, neutralization, and
filtration before discharge, plus technology
"A". Dewatering and landfill of sludge.
Reduction of contaminated cooling water
volume by use of a cooling tower. Treatment
of combined waste water as in "B" (including
cooling tower blowdown), flocculation to
reduce total phosphorus. Treatment of
cooling water makeup.
No treatment. No phossy water discharge.
Collect contaminated storm water. Lime
treatment, settling, neutralization, and
filtration before discharge. Dewatering and
landfill of sludge.
Same as "B", plus flocculation step before
filtration to reduce total phosphorus.
No treatment. No phossy water discharge.
Recycle and neutralize scrubber water using
caustic. Treat blowdown with alkaline
chlorination (using caustic), lime addition,
clarification, neutralization, and filtration.
Dewatering and landfill of sludge.
162
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TABLE 16 (continued)
Subcategory
Chemical
Alter-
native
PC13
A
B
POC13
A
B
Phosphate
Producing
Na5P3010
(Food Grade)
Description
Same as "B", except recycle and blowdown of
a volume that is nearly saturated with sodium
chloride after chlorination. Alkaline
chlorination using lime. Flocculation before
filtration.
No treatment. No phossy water discharge.
Recycle scrubber water with partial caustic
neutralization. Treat blowdown with lime
addition, clarification, neutralization, and
filtration. Dewatering and landfill of sludge.
Reactor heel and trichloroethane wash are
landfilled, final reactor wash water is lime
treated. Landfill sludge and combine overflow
with scrubber blowdown for further treatment.
Technology "B" with less scrubber blowdown
volume, combined lime and calcium chloride
treatment, less acid addition, and flocculation
before filtration.
No treatment. No phossy water discharge.
Recycle scrubber water with partial caustic
neutralization. Treat blowdown with lime
addition, clarification, neutralization, and
filtration. Dewatering and landfill of sludge.
Technology "B" with less scrubber blowdown
volume, combined lime and calcium chloride
treatment, less acid addition, and flocculation
before filtration.
Existing control includes no discharge of
scrubber water but no treatment of other
contaminated waste water.
Collection, retention, lime addition,
clarification, neutralization, filtration,
and discharge of waste water. Dewatering
and landfill of sludge. No treatment of
contaminated noncontact cooling water.
Includes technology "A".
Same as technology "B", except: recycle
contaminated cooling water through a cooling
tower and treat blowdown with other waste
waters, supplement lime treatment with calcium
chloride addition, reduce acid addition, and
add flocculation. Treat cooling water makeup.
163
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TABLE 16 (continued)
Subcategory
Chemical
Other Food-
Grade Soluble
Phosphates
Alter-
native
A)
B)
O
Na5P3010
(Non-Food Grade)
Other Non-
Food Grade
Soluble
Phosphates
Calcium
Phosphates
(Food Grade)
A)
B)
O
B
Description
Technologies are identical to those for food-
grade sodium tripolyphosphate. (Average plant
size is larger and includes sodium tripoly-
phosphate if produced.)
Existing control includes no discharge of
scrubber water. Leaks, spills, and washings
are recycled to the process. Contaminated
storm water runoff and cooling water are
discharged without treatment.
Collection, retention, lime treatment,
clarification, neutralization, and filtration
of contaminated storm water runoff before
discharge. No treatment of contaminated
cooling water. Includes technology "A".
Same as technology "B", except: recycle
contaminated cooling water through a cooling
tower and treat blowdown with other waste
waters, supplement lime treatment with calcium
chloride addition, reduce acid addition, and
add filtration.
Technologies are identical to those for non-
food grade sodium tripolyphosphate. (Average
plant size is larger and includes sodium
tripolyphosphate if produced.)
Existing control includes dry dust collection,
so no scrubber waste water is produced. A
partially treated and clarified DCP centrate
is discharged. Other contaminated waste
water is not treated.
Collection of contaminated storm water runoff
from production and shipping areas. Treatment
of DCP centrate, storm runoff, and other
waste water with lime addition, clarification,
neutralization, and filtration. Dewatering
and landfill of sludge. No treatment of
contaminated noncontact cooling water.
Includes technology "A".
Same as technology "B", except: recycle
contaminated cooling water through a cooling
tower and treat the blowdown with other waste
waters. Add flocculation to treatment scheme.
Treat cooling water makeup.
164
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TABLE 16 (continued)
Subcategory
Chemical
Calcium
Phosphates
(Feed Grade)
Alter-
native
A
B
C
D
E
Description
No treatment.
Replace wet scrubbers with baghouses.
Lime treatment, filtration of slurry, recycle
of filtrate, and landfill of filter cake,
plus technology "B".
Collect contaminated storm water runoff from
production and shipping areas, treat with
other waste waters as in technology "C";
plus technology "B".
Same as "B" plus "C" and "D", plus flocculation
before filtration to reduce total phosphorus.
165
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TABLE 17
TREATMENT ALTERNATIVES
COST - EFFLUENT QUALITY COMPARISON
Chemical Treatment % Industry
Alternative Using
Alternative
Phosphorus
Phosphorus
H3P04
P205
P2S5
PC1J3
POC13
Investment Annual Cost
$1,000 Operating Per Units
Costs $/kkg
$1,000
Producing Subcategory
Raw Waste
A
B
C
90
33
33
-
740
1,226
-
355
635
-
7.14
12.76
Waste
Water
426,000
104,000
104,000
0*
TSS Total Fluoride Elemental Arsenic Sulfide pH S04 Acidity
kg/kkg Phosphorus kg/kkg Phosphorus kg/kkg +~ kg/kkg
(as P) kg kg/kkg S03 (as
kkg kg7kkg( CaC02)
42
0.5
0.5
0
8
0.15
0.15
0
54 9 ,
0.05 4.5x10 4
0.05 N.D.
0 0
< 6.0
7.3-9.5
7.3-9.5
-
111 54
2 2
2 2
0 0
Consuming Subcategory
Raw Waste(A)
3
C
Raw Waste(A)
B
C
Raw Waste(A)
B
C
Raw Waste(A)
B
C
Raw Waste(A)
B
C
90
5
0
100
0
0
100
0
0
100
0
0
100
0
0
_
625
1,570
_
410
U2
_
663
515
_
707
595
_
498
404
_
320
888
_
200
216
_
416
314
_
369
311
_
255
208
.
4.13**
11.46
_
83.28
89.94
_
37.90
28.66
_
29.65
24.99
_
39.41
32.15
4,800*
4,800*
1,200*
550
550
550
3,380
890
50
1,500
500
11
3,900
500
10
_
0.004
3. 6x10" J
_
0.011
0.0017
_
0.018
1.5xlO"4
_
0.025
3. 3x10" P
_
0.025
3x10
0.33
0.044 .,
3. 6x10" J
0.11
0.024
0.0017
1.6
0.049 ,
1.5x10 *
0.5
0.05
0.0011
0.57
0.05 ,
3x10
_
N.D.
N.D.
_
N.D.
N.D.
_
N.D.
N.D.
__
N.D.
N.D.
(N.D.)
N.D.
N.D.
2.6x10"^ < 6.0
2.6x10"' 6-9
2.6x10 6-9
< 6.0
6-9
6-9
(0.44) <6.0
0.01 6-9
5x10 4 6-9
4xlO~5 , <6.0
2.5x10 , 6-9
5.5x10"' 6-9
< 6.0
6-9
6-9
1
0
0
0.4
0
0
5.6*** 15
0
0
3.6
0
0
5
0
0
*Includes contaminated noncontact cooling water blowdown.
**Unit costs based on kkg of product as 85* H3P04.
***Includes sulfide and sulfite expressed as sulfate.
-------
TABLE 17
(Continued)
Chemical Treatment % Industry Investment Annual Cost Waste
Alternative Using $1,000 Operating Per Units. Water
Alternative Costs S/kkg 1/kkg
31,000
TSS Total Fluoride Elemental Arsenic Sulfide pH S04 Acidity
kg/kkg Phosphorus Kg/k]£g Phosphorus kg/kkg +~ kg/kJcg
(as P) kg kg/kkg S03 (as
kkg kg/Ekg (CaC03)
Phosphate Producing Subcategory
Na5P3010
(Food Grade)
?:a_5F20ic
( Kon-Focd
Grade )
Food-Grade
Soluble Phos-
phates
( Generally )
Non-Food
Grade Soluble
Phosphates
( Generally )
Calcium
Phosphates
( Food-Grade )
Calcium
Phosphates
(Feed Grade)
A
B
C
A
B
C
A
D
C
A
P
C
A
D
LJ
C
A(Raw
B
C
D
E
100
20
0
85
0
0
C K
-- S
10
0
yp
n
w
0
90
0
0
V.'aste ) -
60
14
0
0
_
916
1,413
_
522
335
„
1,435
2,235
_
567
907
„
1,005
1,300
_.
**
307
449
534
_
535
795
_
271
445
_
925
1,362
_
295
487
_
595
749
_
**
215
298
339
_
9.13
13.65
,_
4.04
6.65
_
7. 1C
10.46
_
3.S4
6.33
_
12.32
15.49
_
**
2.44
3.3S
3.85
400
375
675*
ICC
°c
39? *
400
375
675*
100
93
398*
3,600
3,600
3,700*
7,300
6,900
600
600
600
0.
0.
0.
0.
C.
r\
\j .
0.
0.
25
25
3
0.
-
008
0021
_
002
0012
_
008
0021
_
002
0012
15,
2x10 J
2.
0.
0.
0.
0.
0.
2.
0.
0.
0.
0.
0.
4.
0.
0.
1.
0.
0.
0.
7
018
0021
22
0044
0012
7
013
0021
22
0044
0012
7
17
Oil
84 7.7
5 '7.7
5 (No data)
03 o 0.01 ,
2x10 J 6x10 J
_
6-9
6-9
_
6-9
6-9
_
6-9
6-9
_
6-9
6-9
_
6-9
6-9
_
-
6-9
6-9
6-9 r
*Includes contaminated noncontact cooling water blowdown.
**Use of dry dust collection and product recovery will cover the cost
of this alternative, therefore, no costs were listed.
o
§
~n
-------
.
\. 1
4. There is a wide variation in the existing application of
effluent control technology. Some plants will have more
equipment to install than others in order to attain the achievable
effluent levels outlined in Sections IX and X. In addition,
physical characteristics of each particular plant will affect
treatment costs, including:
a. Plant age, size, and degree of automation.
b. Plant layout (e.g., whether in-process controls can be
physically installed between existing units).
c. Plant distances and topography (e.g., installation and
operating costs of recycle technologies).
d. Climatic factors (temperature and evaporation/rainfall).
e. Aesthetic factors (e.g., local acceptability of a settling
pond).
f. Land availability (primarily a factor in applying settling
pond and evaporation pond technologies).
5. The degree that a plant is integrated with other production
processes will significantly affect the cost of applying
control and treatment technologies. Factors that might be
considered include use of waste materials from one department
in an adjoining department (such as mutual neutralization of
acid and alkaline wastes), use of common treatment facilities,
and the feasibility of separating waste water sewers from
adjoining departments. The feasibility and attractiveness of
joint municipal/industrial waste water treatment is a highly .
local evaluation. Increasingly, more examples of such dual
treatment are being reported.
6. The local solid waste management situation will affect treatment
costs. The sludges resulting from waste water treatment
technologies may be landfilled at highly different costs,
depending on the local availability of disposal sites and the
distances involved.
In appreciation of all of the above factors, the discussion of costs in
this section is formulated to be generally useful in evaluating the
economics for any particular plant within the industry.
REPRESENTATIVE PLANTS AND TREATMENT ALTERNATIVES
The sizes of the representative plants were chosen so that their capacities
were approximately the averages of the data presented in Table 2 in
Section III. Although in many cases (especially in the phosphorus
168
f
-------
.'FT
consuming segment of the industry) more than one product is made at a
given location, each product was addressed separately. 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 used in choosing representative plants and
the alternative treatment technologies are discussed in detail below.
Phosphorus Manufacture
The representative plant was assumed to have no direct discharge of
phossy water during normal operations, as all plants now currently
achieve. In addition, the plant has achieved a level of effluent
reduction commensurate with that of Plants 5 and 9 (see Tables 13, 14,
and 15), but still discharges 104>000 liters of treated non-phossy
process water per kkg of product (25,000 gal/ton) into a receiving
stream. Most of this volume is cooling water. Incidental contamination
of waste water by elemental phosphorus is not detectable. It was
further assumed that the influx of storm water into treatment ponds
occasionally results in the discharge of treated phossy water into the
receiving waterway. The average level of elemental phosphorus is
assumed to be the same as at Plant 4. Technology "A" in Table 17,
therefore, represents effluent reduction already achieved by the representative
plant, with no additional costs required. The effluent from technology
"A" is suitable for process reuse.
Technology "B" assumes that uncontaminated storm water runoff from not
over 0.4 hectares per kkg (0.9 acres/ton) of phosphorus production per
day must be diverted to prevent its influx into treatment ponds. Based
on a hypothetical site, 9,100 m (30,000 ft) of drainage ditches and
1,000 m (3,300 ft) of dikes and associated facilities were included in
the estimate for an average 136 kkg per day (150 ton/day) phosphorus
plant. Only cooling water is discharged.
Technology "C" assumes that the effluent from technology "A" is totally
recycled for process and cooling uses. The cost of total recycle under
extreme cold weather conditions is included, using Plant 8 as an example.
Technology "B" is also included to assure no pollution because of excessive
rainfall. Reduction of water usage by use of cooling towers is included
to assure all waste water is treated and recycled by the process waste
water treatment system. Makeup water treatment is included. Slowdown
from the cooling tower system is 350 1/kkg (84 gal/ton). The reduced
volume of blowdown and the reduced influx of uncontaminated storm water
permit total recycle with no waste water discharge.
Phosphoric Acid Manufacture
The representative plant has no process water discharge (including
phossy water), but leaks and spills can enter storm water runoff. This
169
-------
is Technology "A". The raw waste consists of 200 1/kkg (48 gal/ton) of
contaminated storm water runoff and 4,600 1/kkg (1,100 gal/ton) of
contaminated cooling water blowdown. The storm water contains 1.0
kg/kkg of H3P04 spillage and leakage. The cooling water contains 0.11
kg/kkg of HjPOT leakage. These wastes contain 0.35 kg/kkg total phosphorus.
Arsenic contained in allrSpillage and leakage, at 0.075 kg/kkg of total
phosphorus, is 2.6 x 10" kg/kkg of product.
Technology "B" assumes diversion and ponding of contaminated storm water
runoff from the phosphoric acid production and storage area, lime treatment,
clarification, sludge filtration, neutralization, effluent filtration,
and discharge. Dewatered sludge is landfilled. The volume of lime
treated storm water is about 200 1/kkg (48 gal/ton). Contaminated
cooling water blowdown, 4,600 1/kkg (1,100 gal/ton), is also discharged
without treatment. Treated wastewater is discharged containing 44 mg/1
of total phosphorus and 20 mg/1 of total suspended solids. The cooling
water discharged contains 0.11 kg/kkg of H3P04_ leakage. These wastes
contain 0.044 kg/kkg of total phosphorus and 0.004 kg/kkg total suspended
solids. Arsenic is no greater than 2.6 x 10~ kg/kkg of product.
Technology "C" includes "A" and "B", but reduces the volume of cooling
water discharged by the use of cooling towers and treats this waste as
in "B". A flocculation step is introduced to reduce total phosphorus
and suspended solids in the combined effluent to 3 mg/1 each. Cooling
water makeup is treated. The combined lime treated waste consists of
200 1/kkg (48 gal/ton) of storm runoff and 1,000 1/kkg (240 gal/ton) of
cooling water blowdown. Therefore, total phosphorus content and total
suspended solids are 0.0036 kg/kkg. Lime treatment can also reduce
arsenic to 0.05 mg/1 or 6 x 10 kg/kkg, but control of leaks and spills
of phosphoric acid to less than 1.11 kg/kkg as HJP04_ results in only 2.6
x 10" kg/kkg arsenic in the effluent.
Phosphorus Pentoxide Manufacture
The representative plant has not yet instituted any control or treatment
for phosphate removal, but has already eliminated discharge of phossy
water. Thus, "no treatment" is Technology "A". Technology "B" assumes
collection of contaminated storm water runoff from the phosphorus pent-
oxide production and storage areas, lime treatment, clarification,
sludge filtration, neutralization, effluent filtration, and discharge.
Dewatered sludge is landfilled. Technology "C" is "A" plus "B", plus a
flocculation step before final filtration to reduce total phosphorus to
3 mg/1. The raw waste consists of 500 lAkg (120 gal/ton) from tail gas
seals and 50 1/kkg (12 gal/ton) of contaminated storm water runoff.
These same volumes are discharged after treatment by technologies "B"
and "C". The raw waste contains 0.25 kg/kkg P205_ or 0.11 kg/kkg total
phosphorus. Technology "B" achieves 44 mg/1 (0.024 kg/kkg) total phosphorus
and 20 mg/1 (0.011 kg/kkg) total suspended solids. Technology "C"
achieves 3 mg/1 or 0.0017 kg/kkg of total phosphorus and suspended
solids.
170
-------
Phosphorus Pentasulfide Manufacture
The representative plant has not yet .instituted any control or treatment
for phosphate, sulfide, or sulfite removal, but has already eliminated
discharge of phossy water. Thus, "no treatment" is technology "A". The
raw waste consists of 3,380 1/kkg (810 gal/ton) of process waste water
containing 1.5 kg/kkg HC1, 5.7 kg/kkg sulfur (expressed as H2_S03_) and
5.2 kg/kkg H3P04_, as noted in Section V. Some of the sulfur is present
as sulfide. One plant reported 0.44 kg/kkg sulfide.
Technology "B" includes recycle and caustic neutralization of scrubber
water, alkaline chlorination, lime treatment of blowdown, clarification,
sludge filtration, neutralization, effluent filtration, and discharge.
Dewatered sludge is landfilled. The volume of recycled scrubber and
container washing waste waters is 890 1/kkg (210 gal/ton) after lime
treatment. Technology "B" produces 44 mg/1 (0.039 kg/kkg) total phosphorus,
20 mg/1 (0.018 kg/kkg) total suspended solids, and 10 mg/1 (0.009 kg/kkg)
sulfide in the effluent.
Technology "C" is the same process as "B" but with less blowdown from
the scrubber. The lower volume will be almost saturated with sodium
chloride after chlorination. Lime is used instead of caustic to maintain
pH during chlorination. No clarifier is used. A floceulation step is
added before effluent filtration. For technology "C", recycled effluent
volume is 50 1/kkg (12 gal/ton). Total phosphorus and total suspended
solids are 3 mg/1 (1.5 x 10~ kg/kkg), each, and sulfide is 10 mg/1 (5 x
10 kg/kkg). Other contaminated non-process waste waters are negligible
in volume and pollutant load and can easily be handled by the scrubber
and container washing recycle and treatment systems.
Phosphorus Trichloride Manufacture
The representative plant has not yet instituted any control or treatment
for phosphate, phosphite, or arsenic, but has already eliminated discharge
of phossy water. Thus, "no treatment" is Technology "A". The raw waste
consists of 1,500 1/kkg (360 gal/ton) of process waste water containing
1.5 kg/kkg HC1 and 1.3 kg/kkg phosphorus expressed as H3P03., as noted in
Section V. Arsenic is also typically present at 0.075 kg/kkg total
phosphorus.
Technology "B" includes recycle and partial caustic neutralization of
scrubber and other waste water, lime treatment of blowdown, clarification,
sludge filtration, neutralization, effluent filtration, and discharge.
Dewatered sludge is landfilled. Reactor heel and trichloroethane reactor
wash are drummed and landfilled. Reactor wash water is lime treated,
settled, sludge is drummed and landfilled, and clarified effluent is
combined with scrubber blowdown for treatment. Areas subject to spillage
are curbed and the spillage washdown collected and combined with other
waste waters in recycled systems before treatment. The recycled scrubber,
reactor rinsing, spillage washdown, container washing, and tank car
171
-------
washing waste waters have a volume of 500 1/kkg (120 gal/ton) after
treatment. Technology "B" produces 100 mg/1 (0.05 kg/kkg) total phosphorus,
50 mg/1 (0.025 kg/kkg) suspended solids, and 0.05 mg/1 (2.5 x 10
kg/kkg) arsenic after treatment.
Technology "C" is the same as "B" with the following changes: a lower
volume of blowdown from the scrubber and other waste water systems,
almost saturated in sodium chloride; a combined lime and calcium chloride
treatment to pH 9.5 to 12; no clarifier; less acid addition required to
achieve an acceptable pH; and addition of a flocculation step before
effluent filtration. The recycled combined waste waters have a volume
of about 11 1/kkg (3 gal/ton) after treatment. Technology "C" produces
about 100 mg/1 (0.0011 kg/kkg) total phosphorus, 3 mg/l_^3.3 x 10
kg/kkg) total suspended solids, and 0.05 mg/1 (5.5 x 10~ kg/kkg) arsenic
after lime treatment.
Phosphorus Oxychloride Manufacture
The representative plant has not yet instituted any control or treatment
for phosphate removal, but has already eliminated discharge of phossy
water. Thus "no treatment" is technology "A". The raw waste consists
of 3,900 1/kkg (930 gal/ton) of process waste water containing 2.3
kg/kkg HC1 and 1.8 kg/kkg phosphorus expressed as H3P04_, as noted in
Section V.
Technology "B" includes recycle and partial neutralization of scrubber
water with caustic, lime treatment of blowdown, clarification, sludge
filtration, neutralization, effluent filtration, and discharge. Dewatered
sludge is landfilled. Areas subject to spillage are curbed and the
spillage washdown collected and combined with other waste waters in
recycle systems before treatment. The recycled scrubber, container
washing, tank car washing, and spillage washdown waste waters have a
volume of 500 1/kkg (120 gal/ton) after treatment. Technology "B"
produces about 100 mg/1 (0.05 kg/kkg) total phosphorus and 50 mg/1
(0.025 kg/kkg) total suspended solids after treatment.
Technology "C" is the same as "B" with the following changes: a lower
volume of blowdown from the scrubber, almost saturated in sodium chloride,
a combined lime and calcium chloride treatment to pH 9.5 to 12; no
clarifier; less acid addition required to achieve an acceptable pH; and
addition of a flocculation step before effluent filtration. The recycled
combined waste waters have a volume of about 10 1/kkg (2 gal/ton) after
treatment. Technology "C" produces about 3 mg/1 (3 x 10" kg/kkg) of
total phosphorus and total suspended solids.
Food Grade Sodium Tripolyphosphate Manufacture
The representative plant recycles scrubber waste waters under normal
circumstances. Spills are disposed of as solid waste whenever possible.
Other spills and leaks are sewered, as are wash downs of area and equipment.
172
-------
Contaminated storm water runoff from production and shipping areas is
discharged without treatment. This represents technology "A". The raw
waste consists of 400 1/kkg (96 gal/ton) of process and non-process
waste water containing 8.4 kg/kkg P04_ (2.7 kg/kkg as total phosphorus).
A flow of 2,000 1/kkg (-480 gal/ton) of potentially contaminated cooling
water blowdown is also discharged.
Technology "B" assumes that these contaminated waste waters are collected
and treated. Treatment includes holding in a surge pond, lime addition,
clarification, sludge dewatering, neutralization, and effluent filtration.
Incidentally contaminated cooling water is not treated. The treated
effluent has a volume of 400 1/kkg (96 gal/ton). Total phosphorus is 44
mg/1 (0.018 kg/kkg) and total suspended solids is 20 mg/1 (0.008 kg/kkg).
Technology "C" is the same as "B" except that lime treatment is supplemented
with calcium chloride addition to lower the pH, thus reducing acid
addition. Also, a flocculation step is included before effluent filtration.
Contaminated cooling water is recycled over a cooling tower, and the
blowdown is treated with other waste water. Cooling water makeup is
treated. The recycled volume of cooling water is 300 1/kkg (7$lgal/ton),
which when combined with 400 1/kkg (96 gal/ton) of other waste water,
becomes about 700 1/kkg (170 gal/ton) after treatment. Total phosphorus
and total suspended solids are 3 mg/1 (0.0021 kg/kkg) after treatment.
Food Grade Soluble Phosphate Manufacture
This subcategory includes sodium, potassium, and ammonium phosphates
produced from furnace acid. Technologies "A", "B", and "C" are identical
to the technologies described above for food grade sodium tripolyphosphate.
Non-food Grade Sodium Tripolyphosphate Manufacture
The representative plant recycles scrubber water under normal circumstances.
Leaks, spills, and washdowns are recycled to the process. Contaminated
storm water runoff from production and shipping areas is discharged
without treatment. This represents technology "A". Waste water volume
and contaminant quantities are less than those for food grade plants.
The raw waste consists only of about 100 1/kkg (24 gal/ton) of storm
water runoff from production areas, containing about 0.22 kg/kkg total
phosphorus from dustfall, primarily. A flow of 2,000 1/kkg (480 gal/ton)
of potentially contaminated cooling water blowdown is also discharged.
Technology "B" adds treatment of contaminated storm water runoff by the
same "B" technology described for food grade plants. Technology "C"
adds the same treatment steps as technology "C" for food grade plants.
The treated effluent from technology "B" has a volume of about 100 1/kkg
(24 gal/ton) and contains 44 mg/1 (0.0044 kg/kkg) total phosphorus and
20 mg/1 (0.002 kg/kkg) total suspended solids. Cooling water is also
discharged. For technology "C", the recycled volume of cooling water is
300 1/kkg (72 gal/ton), which, when combined with 100 1/kkg (24 gal/ton)
173
-------
D:^i .r r"T
i \t\\~ I
of other waste water becomes about 400 1/kkg (96 gal/ton) after treatment.
Total phosphorus and total suspended solids are 3 mg/1 (0.0012 kg/kkg)
after treatment.
Non-food Grade Soluble Phosphate Manufacture
Technologies "A", "B", and "C" are identical to the technologies defined
above for non-food grade sodium tripolyphosphate.
Food Grade Calcium Phosphates
Current technology for DCP and TCP utilizes dry dust collection, so no
scrubber waste is produced. A partially lime treated and partially
clarified DCP centrate is discharged without further treatment. The
representative plant was assumed to be a DCP plant because the volume of
waste water and quantity of pollutants discharged are greater than for
other calcium phosphates and represent the most difficult case from a
treatment standpoint. Spills are disposed of as solid waste wherever
possible. Other spills, leaks, and washdowns are sewered. Contaminated
storm water r,unoff from production and shipping areas is discharged
without treatment.
Technology "A" assumes no further treatment of the partially treated DCP
centrate or other waste water. The raw waste consists of 3,000 1/kkg
(720 gal/ton) of partially treated DCP centrate containing 0.75 kg/kkg
total phosphorus and 14 kg/kkg total suspended solids, and 600 1/kkg
(144 gal/ton) of other process and contaminated waste water containing
3.9 kg/kkg total phosphorus and 16 kg/kkg total suspended solids. An
assumed 400 1/kkg (96 gal/ton) of potentially contaminated cooling water
blowdown is also discharged.
Technology "B" includes collection of the contaminated waste waters in a
surge pond, lime treatment of the DCP centrate and these other waste
waters, clarification, sludge dewatering, neutralization, effluent
filtration, and effluent discharge. Incidentally contaminated cooling
water is not treated. The treated effluent has a volume of 3,600 1/kkg
(860 gal/ton). Total phosphorus is 44 mg/1 (0.16 kg/kkg) and total
suspended solids is 20 mg/1 (0.072 kg/kkg).
Technology "C" provides recycle of contaminated cooling water in a
cooling tower. Blowdown is combined with other waste waters and treated
as per technology "B", except that lime treatment is supplemented with
calcium chloride addition to lower pH and thus reduce acid addition. In
addition, a flocculation step is added before effluent filtration.
Cooling water makeup is treated. The recycled volume of cooling water
is 100 1/kkg (24 gal/ton), and, when combined with 3,600 1/kkg (860
gal/ton) of other waste water, becomes about 3,700 1/kkg (890 gal/ton)
after treatment. Total phosphorus and total suspended solids are 3 ng/1
(0.011 kg/kkg) after treatment.
174
-------
Feed Grade Calcium Phosphates
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 no discharge of process waste
waters; (b) the above controls have not been installed, but can be
economically justified on the basis of product recovery. Therefore, for
control of phosphate and lime dusts and phosphoric acid mists, the
representative plant has no additional required costs attributable to
effluent reduction benefits.
It is assumed that the representative plant uses wet-process phosphoric
acid and that it performs defluorination of all acid used (in practice,
a good fraction of acid received may already be defluorinated). It is
further assumed that the representative plant has sufficient land area
for on-site settling ponds. "No treatment" is Technology "A". The raw
waste consists of three components: solids scrubber water, acid defluorination
scrubber water, and contaminated storm water runoff, as delineated in
Section V. The solids scrubber water has a volume of 420 1/kkg (100
gal/ton) and contains 4 kg/kkg phosphate (1.3 kg/kkg total P) and 22.5
kg/kkg total suspended solids. The acid defluorination scrubber water
has a volume of 6,300 1/kkg (1,510 gal/ton) and contains 12 kg/kkg
H2SiF6 (7.7 kg/kkg as fluoride). The contaminated storm water runoff
contains 3 kg/kkg total suspended solids (containing 0.54- kgAkg total
phosphorus) based on dustfall, as discussed in Section V. This contaminated
runoff is estimated at 600 1/kkg (144 gal/ton). (In many cases the
volume will be much less, depending on the site and effectiveness of air
pollution controls.)
Technology "B" assumes that wet scrubbers for dry dusts are replaced
with baghouses, and phosphoric acid mist scrubber liquor is recycled to
the process. Both are assumed to be justified by cost savings. Technology
"B" eliminates the 420 1/kkg (100 gal/ton) of solids scrubber waste and
the waste load of 4 kg/kkg phosphate and 22.5 kg/kkg total suspended
solids.
Technology "C" assumes fluoride scrubber liquor is lime treated and
filtered with recycle of filtrate. The filter cake is landfilled.
Technology "C", by eliminating the acid defluorination waste, leaves
only the contaminated storm water runoff, 600 1/kkg (144 gal/ton),
containing 3 kg/kkg total suspended solids (0.54 kg/kkg total phosphorus).
Some fluoride is also present, but not enough to affect the cost or
method of treatment.
Technology "D" assumes collection of contaminated storm water runoff
from production and shipping areas for treatment with the fluoride
scrubber wastes. The effluent from technology "D" is 600 1/kkg (144
gal/ton) containing 44 mg/1 (0.026 kg/kkg) total phosphorus, 20 mg/1
(0.012 kg/kkg) total suspended solids, and 15 mg/1 (0.009 kg/kkg) fluoride.
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Technology "E" assumes treatment with "B", "C", and "D" plus a flocculation
step using a polyelectrolyte before final filtration. The effluent from
technology "E" is still 600 1/kkg (144 gal/ton), but contains only 3
mg/1 (0.002 kg/kkg) total phosphorus, 3 mg/1 (0.002 kg/kkg) total suspended
solids, and 10 mg/1 (0.006 kg/kkg) fluoride.
COST DATA BASES
Current Selling Prices
Table 3 in Section III shows the current list prices of the chemicals
within this industry. These data are useful as a yardstick for measuring
the economic impact of achieving pollution control.
Capital Cost Basis
For these analyses, the capital investment costs have been adjusted to
mid-1977 dollars using one or more of the following cost index numbers:
1977 Basis-Year
Index Number Index = 100
Chemical Engineering Plant Cost Index 201.2 1957-59
CE Pipe, Valves & Fittings Cost Index 246.5 1957-59
M£S Equipment Cost Index-Process Industries 507.2 1926
IM Construction Cost Index 2575 1913
Index numbers for earlier years were taken from CE's "Economic Indicators"
(72), a CE summary (73) and the ENR "cost roundup" (74).
In general, capital costs for this section were estimated by preliminary
sizing of equipment, ponds, long runs of piping, and drainage ditches
and the use of readily applicable estimating data. (75, 76, 77) The
cost of piping, concrete, steel, instruments, electrical insulation, and
painting materials were related to purchased equipment cost by standard
estimating factors whenever appropriate. Purchased material overhead
was taken at 5 percent times material cost, construction overhead at 18
percent of equipment cost plus material plus direct labor. Engineering
was estimated as 12 percent, contingency as 20 percent, and contractor's
fee as 10 percent of physical plant cost, including overheads.
Annual Operating Costs
Bulk chemical prices were taken from the Chemical Marketing Reporter
(July, 1977) or obtained by supplier contacts: pebble lime at $28 per
ton, 50 percent caustic at $140 per ton, sulfuric acid at $50 per ton,
hydrochloric acid at $52 per ton, and calcium chloride at $24 per ton.
A figure of $20 per ton was added for use of bagged lime. A figure of
$50 per ton was added for use of drummed acid. (Bags and drums were
used only for small quantities not justifying bulk storage.) Heating
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was assumed to be by steam at $3-30 per 1000 Ib. Electric power was
estimated at $0.03 per kwh.
Other annual operating and maintenance costs, including labor, supervision,
laboratory support, and overheads were estimated at 15 percent of the
capital investment cost. This is in addition to chemical, steam, and
power costs estimated separately. Annual cost of taxes and insurance is
estimated at 8 percent of the investment cost. 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 0.25046.
IN-PROCESS CONTROLS
The cost of in-plant controls are perhaps the most difficult to generalize,
since they are almost wholly dependent on the existing equipment configura-
tion in any particular plant.
Segregation Of Waste Streams
First, a plant must be surveyed to pinpoint the sources of both process
water and noncontact 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 rather 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 o_f_ Scrubber Water
The capital costs for scrubber water recycle 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.
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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 ton/day) plant
was $350,000 (pre-1974 data). The annual operating and maintenance
costs, other than capital recovery, taxes, and insurance, are 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
Refrigerated 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 Solidification for Phosphorus Pentasulfide
Casting of phosphorus pentasulfide is becoming obsolete. Continuous
solidification equipment with inert gas blanketing may possibly be
justified on the basis of lower production costs and higher price of the
higher quality product produced. Some, continuous solidification equipment
is used by 85 percent of the industry.
Alternatively, P2S5_ may be cast in an enclosed hood purged with inert
gas. Design of a safe hood would be relatively expensive. Inert gas
usage and costs would be high. There would be some small power requirements
for inert-gas blowers. 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 configuration. A point of reference
might be taken from the experience of one 360 kkg/day (400 ton/day)
plant that expended $160,000 (pre-1974 data) for isolation and containment
(trenches, sewers, pipelines, 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.
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TREATMENT OF SPECIFIC WASTE CONSTITUENTS
Estimates for specific wastes and alternates for Tables 17 and 18 were
made as previously described in this section under "Capital Cost Basis".
Error range for these study-type estimates is estimated as plus or minus
30 percent. (63)
Additional cost information included in the following is updated to 1977
costs (1971 cost times 1.52) based on 1971 costs presented in the January,
1974 Development Document, except where otherwise noted. (78)
Neutralization of_ Acidic Waste Waters and Precipitation of_ Calcium Salts
The cost for lime or caustic for neutralization is directly dependent on
the total acidity. Neutralization of acidity does not assure complete
precipitation of insoluble calcium salts, however, and chemical cal-
culations are required.
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 = $23,000 ( gpd ) °*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 PC13 Reactor Residues
The capital cost for treatment of these residues includes holding tanks
for fresh trichloroethane, PC1_3_ heel, used trichloroethane, and final
wash water. These tanks enable the reactor to be promptly returned to
productive service. Trichloroethane is not reused but is drummed and
landfilled, as is the PC13 heel. The final wash is pretreated with
lime, settled, and the thickened slurry drummed for landfill. The
clarified effluent is bled off to the scrubber water treatment system
for further treatment. /Trichloroethane cost is $2.66 per gallon (July,
1977). The cost of drums and landfilling was estimated as $150 per ton
of waste. Heel residue was taken as 1.2 kg/kkg, trichloroethane residue
as 0.2 kg/kkg, and final wash water as 2.2 1/kkg. (All figures are per
kkg of product PC13_). These residues are extremely objectionable and
must be disposed of" by special means. A very substantial impact on
solid waste management results.
There is virtually no power requirement for disposal of these residues.
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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-water quality aspects would be academic.
Removal o_f Suspended Solids
Settling Ponds. Using a detention time of 7 days and a depth of 3 m (10
ft), the calculated overflow rate is 0.42 cu m/day/sq m (10 gpd/sq ft).
This is equivalent to 4,200 cu m/day/hectare (435,600 gpd/acre). Ponds
used for hydrolysis of sodium tripolyphosphate and other soluble hydro-
lyzable phosphate wastes were assumed to have 30 days detention.
The capital costs for small unlined ponds, with areas from 0.4 to 2
hectares (l to 5 acres) can be estimated as:
Capital Cost = $76,000 x Acres - $12,000 x (Acres)0
(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 $3,800 to
$19,000 per hectare ($1,500 to $7,600 per acre).
For lined ponds, the additional installed capital cost for a 30-mil PVC
liner is $33,000 per hectare ($13,000 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. However, the solids collect on the
bottom and must either be periodically removed (creating a solid waste
disposal problem), or the filled pond must 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 thickeners with
capacities of 38 to 38,000 cu m/day (0.01 to 10 mgd) can be estimated
as:
Capital Cost = $144,000
(Note: Cu m/day = 3,785 x mgd)
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Where polymeric flocculants are used, the additional cost amounts to $6
per kg of flocculant ($2.75/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, sludge
may be dewatered on sand drying beds or mechanically (filters or centrifuges)
to 60-70 percent moisture before landfilling. The quantity to be land-
filled is therefore a very strong function of the degree of dewatering
after thickening.
Vacuum Filtration and Centrifugation. The costs of these two mechanical
dewatering techniques are competitive. A general cost for either is up
to 4 cents per cubic meter (7.6 cents per 1,000 gallons).
The installed capital costs for either vacuum filters or centrifuges are
as follows:
Capacity, mgd cu m/day Installed Cost
0.01 38 $ 38,000
0.1 378 $ 38,000
1 3,785 $ 300,000
10 37,850 $1,500,000
Polymeric flocculants are often used to condition the sludge before
dewatering. Costs for polymers are discussed above.
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 4-0 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 impact on solid waste
management. Rather than landfilling 12 percent sludge, these devices
drastically reduce the solid waste quantity by producing a 30 to -40
percent cake.
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\ : •••*T*
Af I
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 filters are not noisy, but associated
vacuum pumps may be noisy.
Landfilling of Solid Wastes
The disposal costs for solid wastes are highly dependent on the hauling
distance. The landfill operations alone may cost $9 or more per kkg (or
per ton) for small operations and $3 to $6 per kkg (or per ton) for
larger operations.
Several pertinent papers have recently been published on the subject of
solid waste management in the chemical industry. (79,80)
Solid waste hauling and the material handling operations at landfills
are energy consuming operations. Landfilling of containerized soluble
solids in plastic drums or sealed envelopes is practicable but expensive.
The cost of drums for this use was estimated as $55/kkg ($50/ton). Two
alternatives have been suggested that would substantially reduce the
container cost: the use of blow-molded plastic drums made from scrap
plastic, and sealed plastic envelopes, 750 microns (30 mils) thick.
Landfill and hauling costs for solid wastes from the phosphate segment
and from POC13_lime treatment were estimated at $44/kkg ($40/ton) dry
substance. Plants 31 and 41 report costs of $39 to $40/kkg ($35 to
$36/ton) dry substance. For more noxious solid wastes, landfill and
hauling costs were estimated at $110/kkg ($100/ton) based on data from
Plant 19.
Removal of Chlorides
Demlneralization and Reverse Osmosis. Ion exchange and reverse osmosis
are costly technologies, over 10 cents per cubic meter (40 cents per
1,000 gallons). The installed capital costs can be calculated from:
a. Demineralization, Cap. Cost = $426,000 (mgd)
0 75
b. Reverse Osmosis, Cap. Cost = $730,000 (mgd)
Hence, the capital costs for reverse osmosis are nearly double those for
deminerali zation.
The operating costs (not including capital recovery costs) are:
a. Demineralization, 30 cents/1,000 gal § 1,000 mg/1 TDS
60 cents/1,000 gal @ 2,000 mg/1 TDS
b. Reverse Osmosis, 58 cents/1,000 gal @ 0.01 mgd
30 cents/1,000 gal @ 0.1 mgd
21 cents/1,000 gal @ 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. Power
requirements for reverse osmosis are about 6 kwh/1,000 gal at 400 psig
pumping pressure.
Evaporation Ponds. The installed costs of 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 Pond Area
0.6 m/yr (2 ft/yr) 0.060 ha/cu m/day (560 acres/mgd)
1.2 m/yr (4 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)
The power requirements and non-water quality aspects of 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.
The influx of waste water warmer than pond water can substantially
increase the evaporation per unit pond area. As the pond becomes
saturated in soluble salts, the evaporation rate will decrease. Addition
of sprays will also substantially increase evaporation per unit pond
area.
Single-Effect and Multiple-Effect Evaporators. The installed capital
and operating costs for single-effect evaporators and for a six-effect
evaporator (all stainless-steel construction) are as follows:
Installed Capital Costs 0 & M Costs, $/l,000 gal
Capacity, gpd One Effect Six Effects One Effect Six Effects
10,000 $12,000 - 8.57
50,000 43,000 - 8.38
100,000 68,000 $269,000 8.28 1.98
250,000 122,000 567,000 8.19 1.85
500,000 222,000 1,010,000 8.15 1.79
1,000,000 406,000 1,860,000 8.10 1.73
(Note: Liters = 3-785 x Gallons)
The energy requirements for single-effect evaporators are 650 kg-cal per
kilogram of water evaporated (1,170 Btu/lb), while the six-effect evaporator
requires 133 kg-cal per kilogram of water evaporated (240 Btu/lb), The
non-water quality aspects are the same as for solar evaporation ponds.
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F ' I*1 "»\ -r » * •**••
I ' 'j
L'' r \ ) ": 'I I
NON-WATER QUALITY IMPACT
Air Pollution
The proposed guidelines are not expected to increase air emissions. In
fact, the cited technologies should decrease air 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. As mentioned
previously in this section, special disposal methods may be necessary to
prevent leachate from reaching surface or groundwaters. 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 phosphorus consuming subcategory, the
percentage increases in energy requirements are insignificant when
compared to the process energy requirements. Except for the production
of phosphorus, process and treatment energy requirements do not enter
significantly into the product cost. Even the addition of 60 kwh/kkg of
energy only adds $0.00l8/kg to the product cost. Power is consumed
principally by pump and mixer motors, but is also required for treatment
facility building lighting. A nominal amount of steam is used to maintain
constant lime slaking temperatures and for building heating. In Table
19, 1 lb of steam is taken as 1,000 Btu and 1 kwh as 3,413 Btu.
Groundwater
Since settling and evaporation ponds are extensively used for waste
water treatment in the phosphorus derived chemicals industry, it is
highly recommended that all such ponds be sealed or lined so as to
prevent any leakage of contaminated process waters to groundwaters.
Groundwater quality is monitored at Plants 3, 7, and 9 to ensure that
pollutants from unlined ponds do not cause contamination. Adequately
diked, above-ground storage tanks for elemental phosphorus storage are
considered existing technology in most of the industry, so no additional
18-4
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r
11
TABLE 18
ENERGY REQUIREMENTS
FOR ACHIEVABLE EFFLUENT LEVELS
Chemical
Process Energy
Requirement
kwh/kkg
P4_ 15,400
H3_P04_ 48
P2p_5_ 94
P2S5_ (BPCTCA)** 9
P2S_5 (BATEA)*** 9
PC12( BPCTCA) 27
PC12 (BATEA) 27
POC13 (BPCTCA) 28
POC12 (BATEA) 28
Na5P3pl£ 43
(Food Grade)
Na5P3pl£ 43
(Non-Food Grade)
Calcium Phosphates
(Food Grade)
Calcium Phosphates
(Feed Grade)
Treatment Energy
Requirement
kwh/kkg*
0.44
4.6
57
36
39
32
35
51
51
8.2
7.7
9.0
9.4
Percentage Energy
Increase
0.003$
9.6 %
60 %
400 %
436 %
118 %
129 %
183 %
183 $
19 $
18
* Building heating and lighting included
** BPCTCA - best practicable control technology currently available
*** BATEA - best available technology economically achievable
185
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T
costs were estimated to achieve this technology. Some plants may need
to upgrade phosphorus storage and handling areas to assure that groundwater
does not become contaminated.
Noise
No overall adverse affect on the level of noise is expected, although
individual equipment, such as pumps and centrifuges may have excessive
noise levels.
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SECTION IX
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF THE
BEST PRACTICABLE CONTROL TECHNOLOGY CURRENTLY AVAILABLE
INTRODUCTION
The effluent limitations that must be achieved by July 1, 1977, are
based on the degree of effluent reduction attainable through the appli-
cation of the best practicable control technology currently available.
For the phosphorus derived chemicals industry, this level of technology
is based on the best existing performance by exemplary plants of various
sizes, ages, and chemical processes within each of the industry's
categories. In some cases, where no truly exemplary plants were sur-
veyed, this level of technology is based on state-of-the-art unit
operations commonly employed in the chemical industry, or on transfer of
treatment technology for the same pollutants from other industries.
Consideration was 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 processes 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).
Best practicable control technology currently available emphasizes
treatment facilities at the end of a manufacturing process, but includes
control technologies within the process itself when the latter are
considered to be normal practice within an industry. Examples of in-
process control techniques that are used within the industry are:
manufacturing process controls, recycle and alternative uses of water,
recovery and reuse of waste water constituents, and dry collection of
airborne solids instead of (or before) wet scrubbing. A further consider-
ation is the degree of economic and engineering reliability that must be
established for the technology to be "currently available." As a result
of demonstration projects, pilot plants, and general use, there must
exist a high degree of confidence in the engineering and economic
practicability of the technology at the time of commencement of construc-
tion or installation of the control facilities.
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•RAFT
ACHIEVABLE EFFLUENT LEVELS
Specialized Definitions
Except as provided below, the general definitions, abbreviations, and
methods of analysis set forth in 40 CFR 401 shall apply to this section.
The term "process waste water" shall mean any water that, during manufactur-
ing or processing, comes into direct contact with or results from the
production or use of any raw material, intermediate product, finished
product, by-product, or waste product. The term process waste water
does not include contaminated non-process waste water, as defined below.
The term "contaminated non-process waste water" shall mean any water
that, during manufacturing or processing, comes into incidental contact
with any raw material, intermediate product, finished product, by-
product, or waste product by means of (l) precipitation runoff, (2)
accidental spills, (3) accidental leaks caused by the failure of process
equipment and which are repaired or the discharge of pollutants therefrom
contained or terminated within the shortest reasonable time, which shall
not exceed 24 hours after discovery or when discovery should reasonably
have been made, whichever is earliest, and (4) discharges from safety
showers and related personal safety equipment, and from equipment washings
for the purpose of safe entry, inspection, and maintenance; provided
that all reasonable measures have been taken to prevent, reduce, eliminate,
and control to the maximum extent feasible such contact and provided
further that all reasonable measures have been taken that will mitigate
the effects of such contact once it has occurred.
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 phosphorus derived chemicals
industry.
The Phosphorus Production Subcategory
The determinations of this section are applicable to the discharges re-
sulting from the production of elemental phosphorus and ferrophosphorus
by smelting of phosphate ore.
The following average waste water pollutant levels are achievable by
application of the best practicable control technology currently available:
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Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.15 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.5 kg/kkg (lb/1,000 Ib)
Fluoride 0.05 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity*
pH Within the range 6.0 to 9.0
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.
Seven of the nine existing plants in the phosphorus production subcategory
have no discharge of phossy water: Plants 1, 3, 5, 6, 7, 8, and 9. The
other two plants (Plants 2 and 4) only have discharges in the event of
excessive rainfall, and the waste water receives lime treatment before
discharge in both cases. Hence, most plants have recognized the undesira-
bility of elemental phosphorus in any discharge and that recycle and
reuse systems provide the most effective treatment. Evaporation processes
have played a major role in these recycle systems. Evaporation has been
achieved by the use of evaporation ponds and by in-process evaporation
through reuse in phosphorus condensation, slag cooling, and process
scrubbers.
Process Waters Other Than Phossy Water. The standard techniques for
treating the waste waters from calciner scrubbers and from slag quench-
ing are lime treatment and settling in ponds or clarifiers, which
perform the following functions:
1. Neutralization of acidic waste waters;
2. Sedimentation of much of the original suspended solids in the
waste waters (silica, iron oxide, and others);
3. Precipitation and sedimentation of much of the phosphates,
fluorides, and sulfates that were dissolved in the original
waste waters;
4. Dissipation of process heat to the atmosphere during the
extended residence in settling ponds;
As of this writing, 0.5 ppb (ug/1) of elemental phosphorus in water
is considered detectable in a manufacturing plant.
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DRAFT
5. Reduction in waste water quantity as a result of net evapor-
ation during the extended residence in settling ponds and "by
use in scrubbers; and
6. Where phossy water is combined with these other process
waters, some oxidation of the elemental phosphorus to phosphates.
Plants 1, 3, 6, and 8 all report no discharge of both process and non-
process waste water from the site, including storm water runoff. Plant
3 is studying the feasibility of installing a pumping station to prevent
excessive off-site runoff from entering their treatment ponds and possibly
causing overflow, although no overflow has yet occurred. Rainfall on
plant sites seeps into the soil, is used, contained, or evaporated at
Plants 1, 3, 6, and 8, although Plant 1 and 8 report a net accumulation
of waste water from all sources in their pond systems. Cooling towers
are used at Plants 6 and 8 to permit reuse of cooling water. Cooling
ponds are used at Plants 3 and 8 for the same reason. Plants 3, 6, and
8 lime treat acidic scrubber water and utilize sedimentation, evaporation,
and clarification operations for process waste water, including the use
of ponds.
Plants 5 and 7 discharge only non-process waste water streams, consisting
of noncontact cooling water and ancillary waste water. Ancillary waste
water includes boiler blowdown, softener regeneration wastes, steam
condensate, fire protection water, and water from safety showers. No
direct or indirect process contact waste waters are discharged at these
plants. Sanitary and potable wastes are handled separately, with no
discharge. The remaining process contaminated waste waters are clarified
and reused in the process. Lime treatment is used at kiln scrubbers or
in recycle water treatment facilities before clarification. This treatment
removes phosphates, fluorides, and other substances as insoluble calcium
salts and increases pH to improve scrubbing efficiency. The use of lime
treated, or lime treated and clarified water in phosphorus plant scrubbers
is a routine practice. Storm water at Plants 5 and 7 seeps into the
soil, is contained, or is evaporated. Plant 7 utilizes a recirculating
cooling tower system for one noncontact water stream, but Plant 5 uses
no cooling towers. Neither plant uses ponds for cooling, but ponds are
used for sedimentation and evaporation.
Plant 2 currently discharges noncontact cooling water and site runoff
directly to a stream without treatment. The plant is installing facilities
to collect furnace area runoff, which will be pumped to the phossy water
treatment system.
Plant 9 discharges noncontact cooling water, coke dust collector waste
water, nodule dust collector water, storm water runoff from remote
portions of the site, water treatment waste, and boiler blowdown. The
dust collector waste waters are sent through settling ponds before
discharge. Storm water runoff from the furnace, phosphorus, and calcining
areas is collected and reused in the process waste water recycle system.
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All other direct and indirect process waste waters are lime treated,
settled, clarified in a pond, and totally recycled to the process.
Specifically, Plants 5 and 7 are achieving less than 0.5 kg/kkg (lb/1,000
Ib) total suspended solids, less than 0.15 kg/kkg (lb/1,000 Ib) total
phosphorus (as P), and less than 0.05 kg/kkg (lb/1,000 Ib) fluoride on
an average basis by discharging only noncontact cooling water and noncon-
tact ancillary waste water. These figures are based on 1976 data. (A
small amount of site runoff may be included in the Plant 5 effluent. )
Plants 1, 3, 6, and 8 achieve no discharge of pollutants by containing,
recycling, and evaporating all waste water.
Plant 5 discharges 2.4 x 10~ kg/kkg (lb/1,000 Ib) of elemental phosphorus
in its noncontact cooling water and noncontact ancillary waste water.
Plants 1, 3, 6, and 8 have eliminated discharge of elemental phosphorus
by containing and recycling all waste water.
An important factor in waste water management at phosphorus plants
appears to be careful segregation of noncontact cooling waters, ancillary
waste waters, and uncontaminated storm water runoff to prevent contact
with process materials and contaminated waste waters. This segregation
is not as critical if in-process evaporation, in-process cooling (cooling
towers, etc. ), and pond evaporation and cooling are sufficient to prevent
any discharge of the combined effluents. Thus, the method for preventing
increased pollutant discharges during excessive rainfall is to divert
uncontaminated storm water runoff around impoundments containing process
waste water contaminants. This is currently practiced by a number of
facilities, and the practice is being expanded.
In areas of the country where very severe and extended cold weather
prevails, the following good operating practices can be instituted to
provide for effective recycle of process waste water to and from a
settling pond:
a. The return water piping, pumps, and ancillary equipment must
be protected against freezing.
b. Intake or return pump suction pipelines need to be placed
below the pond surface to prevent freezing and blockage by
ice.
c. Settling ponds must be made-deep enough to continue functioning
with thick surface ice.
A further discussion of cold weather protection measures currently in
use appears in Section VII.
Waste Water from Ore Washing or_ Beneficiation. The achievable effluent
levels discussed in the previous paragraphs do not apply to wastes from
the beneficiation or washing of phosphate rock. This beneficiation is
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commonly but not exclusively conducted at a separate off-site location.
The huge raw waste load from beneficiation, 7.5 kkg of gangue per kkg of
phosphorus eventually produced, is covered by appropriate separate
effluent limitations guidelines and standards of the Mineral Mining and
Processing Industry.
The Phosphorus Consuming Subcategory
The determinations of this section are applicable to the discharges
resulting from the manufacture of products in the phosphorus consuming
subcategory.
Phossy Water Wastes. 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 that brought the phosphorus,
and by transporting this displaced phossy water to the phosphorus
producing plant for treatment or reuse. Such is the practice at Plants
10, 11, 13, 14, 16, 17, 18, 19, 24, and 31.
Smaller quantities of phossy water discharge may also be eliminated
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 accomplished
with more stringent process and operator controls and procedures (such
as curbing around process reaction vessels) and by providing traps
downstream of reaction vessels. The receiving and handling of white
phosphorus can be managed so that there is no discharge of phossy water.
Phosphoric Acid Manufacture. The following average levels of waste
water pollutants are achievable by application of the best practicable
control technology currently available:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.044 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.004 kg/kkg (lb/1,000 Ib)
Elemental Phosphorus No detectable quantity
Arsenic 0.000026 kg/kkg (lb/1000 Ib )
pH Within the range 6.0 to 9.0
Plants 9, 20, and 31 operate 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 can be minimized, collected, recycled, and treated
using control techniques generally available and demonstrated in the
industry.
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As discussed in Section VII, Plant 31, which produces phosphoric acid
and food grade soluble phosphates, collects and treats a combined waste
stream. This waste stream includes storm water runoff from phosphoric
acid and phosphate production areas, but does not include noncontact
cooling water. Treatment results are reported in Section VII.
Plant 23, which produces phosphoric acid and sodium phosphates, reports
no detectable elemental phosphorus in its effluent. No other reports
were received, although the potential for elemental phosphorus to be
present in waste waters exists because of possible phosphorus or phossy
water spills or leaks, including heat exchanger leaks.
Some arsenic may escape in waste water from phosphoric acid manufacture
(and from other phosphorus derived products) if phosphates are discharged
in the waste water. Arsenic is always associated with phosphorus,
commonly at a level of 0.075 kg/kkg (lb/1,000 Ib). Sulfide precipitation
of arsenic is the common removal process for phosphoric acid and for
salts derived from phosphoric acid. Lime precipitation retains calcium
arsenate in solid wastes where lime precipitation of phosphate is practiced,
and limits soluble arsenic discharge.
Phosphorus Pentoxide Manufacture. The following average waste water
pollutant levels are achievable by application of the best practicable
control technology available:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.024 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.0011 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
The single raw waste constituent from phosphorus pentoxide manufacture
is phosphoric acid from water tail-gas seals. This waste water may be
combined with other process waste water, including contaminated storm
water runoff, for treatment and discharge. The same rationale for
treatment and discharge of contaminated storm water runoff applies to
phosphorus pentoxide manufacture as described previously for phosphoric
acid manufacture.
Phosphorus Pentasulfide Manufacture. The following average waste water
pollutant levels are achievable by application of the best practicable
control technology available:
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-,, ^ ir"*"ir
i .' .- (; "' t' \
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Ortho-phosphate (as P) 0.039 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.018 kg/kkg (lb/1,000 Ib) '
Elemental phosphorus No detectable quantity
Sulfide 0.01 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
Significant treatment of waste water from phosphorus pentasulfide
manufacture has not been reported. Because the industry is generally
providing inadequate treatment, transfer of technology is appropriate.
There are practicable technologies transferable from other industries
for the treatment of sulfide, sulfite, sulfate, and phosphate wastes
from phosphorus pentasulfide manufacture.
Best practicable technology for this subcategory includes recycle and
caustic neutralization of scrubber and container washing waste waters,
alkaline chlorination of blowdown to oxidize sulfide and sulfite, lime
treatment for precipitation of phosphate, filtration, sludge disposal in
controlled landfill, and neutralization of effluent with acid. Elemental
phosphorus can be controlled by strict segregation of phossy waste water
from phosphorus shipment and storage to avoid contamination of other
streams with phosphorus.
Recycle and neutralization of scrubber water with sodium hydroxide to pH
9.0 to 9.5 is practiced at Plant 17. Advantages of this process include
reduction of waste water volume requiring discharge, suppression of
hydrogen sulfide evolution, and ease of operation. Recycle with about
890 1/kkg (213 gal/ton) of blowdown would be required in order to produce
a sodium ion concentration comparable to that at Plant 31 before lime
treatment. Container wash water can be similarly recycled and neutralized.
Fresh water makeup can be introduced either at the scrubber inlet to
saturate the air entering the scrubber, or as a final rinse water for
containers. Blowdown from the scrubber system can be reused for initial
wash water for containers, or the container washing recycle system can
be blown down to the scrubber system, depending on relative sulfide
concentrations.
Alkaline chlorination is widely used in industry for waste destruction,
as described in Section VII. Commercial equipment and controls for
alkaline chlorination in waste treatment have been in regular use for
over 20 years. The reaction between sulfide and chlorine is "immediate."
A pH of 9.0 is optimum for conversion of sulfide to sulfate by chlorination.
Sulfites would also be converted to sulfate under these conditions. In
the iron and steel industry, alkaline chlorination is practiced to treat
effluents from some iron blast furnace operations to destroy cyanide,
phenol, and sulfide. Sulfide destruction to a level of 10 mg/1 sulfide
can be readily attained, which would avoid the creation of a chlorine
residual in the effluent but would still remove an estimated 99 percent
of the sulfide.
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Lime treatment, sedimentation, sludge filtration, and effluent filtration,
as practiced at Plant 31 to achieve 20 mg/1 TSS and 44 nig/1 phosphate
(as P) at pH 11 to 12, can then be performed. At these conditions, most
of the sulfate present would also be precipitated and removed as calcium
sulfate, simultaneously precipitated with phosphate as the hydroxyapatite.
Although sulfate is not normally considered a particulary harmful substance
to fish, and relatively high concentrations can be tolerated for many
potential uses in natural waters, it is a pollutant and its partial
removal is an incidental benefit obtained by the use of the recommended
process. In the fossil fuel power plant industry, the dual alkali
process is used at several power plants for removal of sulfur dioxide
from stack gases using caustic addition at the scrubber followed by lime
treatment for precipitation of calcium sulfate or calcium sulfite. In
the elemental phosphorus industry, lime treatment of calciner scrubber
effluent is used in total recycle systems for precipitation and removal
of phosphate, fluoride, and sulfate as calcium salts. Some calcium
sulfite precipitate is typically present. At Plant 4, based on data
reported prior to 1974, the ratio of total phosphorus to sulfate (total
sulfur as sulfate) to fluoride in this combined precipitate is estimated
as 1:13.5:6.5. In other words, simultaneous precipitation and removal
of phosphate, sulfate, sulfite, and other calcium salts is practicable
technology.
Some hydrolyzable phosphate is present in the phosphorus pentasulfide
raw process waste water. Plant 17 reported 230 mg/1 or 30 percent of
the total phosphorus to be present as hydrolyzable phosphate (as P).
Hydrolyzable phosphate remaining after lime treatment will not be analyzed
as orthophosphate nor will it affect achievable pollutant levels. Most
likely, the hydrolyzable phosphates will be precipitated as calcium
salts and will be proportionately removed as co-precipitates, adsorbed
precipitates, or as adsorbed ionic species with the calcium phosphate
and calcium sulfate. This is principally because of the high calcium to
phosphorus ratio in the recommended treatment process. This is an
incidental benefit to be expected for the recommended treatment process
and is explained in detail in Section VII. Achievable levels for hydro-
lyzable or total phosphate are not stated, however, because of insufficient
available data for comparable industrial effluents from lime treatment
systems in use in the phosphates, fertilizer, or other related industries.
Good manufacturing practice can minimize or prevent incidental contamina-
tion of non-process waste water. Workover of spills and leaks is an
available technology, as discussed in Section VII.
Phosphorus Trichloride Manufacture. The following average waste water
pollutant levels are achievable by application of the best practicable
control technology currently available:
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r."
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.05 kg/kkg (lb/1,000 lb)
Total suspended solids 0.025 kg/kkg (lb/1,000 Ib)
Arsenic 0.000025 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
There is no available information that would indicate that process waste
water pollutants from the manufacture of phosphorus trichloride are
being treated in an adequate manner at this time. However, there are
practicable technologies transferable from other industries, including
the phosphate industry and municipal potable and waste water treatment
plants. This technology includes lime treatment and removal of anions
such as phosphate, phosphite, arsenate, and arsenite that are present in
waste waters from phosphorus trichloride manufacture.
Available technology for this industry includes recycle and caustic
neutralization of scrubber and container washing waste waters, lime
treatment of the blowdown, filtration, filter cake disposal, and neutral-
ization of the filtrate with acid.
Recycle and caustic neutralization of scrubber water to pH 4.5 is
practiced at Plant 17. Adequate control of HC1 vapor is achieved at
this pH. Recycle and caustic neutralization of scrubber waters to an
estimated pH 11 (after mixing) is practiced at Plant 14. (High pH
values are used to aid in absorbing and treating the chlorine present).
Recycle and caustic neutralization with about 520 1/kkg (125 gal/ton)
blowdown at pH 5 would produce a sodium ion concentration comparable to
that at Plant 31 before lime treatment. Container wash water can be
similarly recycled and neutralized. Fresh makeup water can be introduced
either at the scrubber inlet to saturate the air to the scrubber or as a
final rinse water for containers. Recycling decreases the quantity of
waste waters and increases the concentration of waste pollutants.
Lime treatment of the blowdown to pH 11.5 or higher will neutralize the
remaining acidity and will precipitate the phosphate, phosphite, arsenate,
and arsenite as their calcium salts. Once these precipitated salts have
settled out, the supernatant will need to be neutralized to an acceptable
pH level prior to being discharged to receiving waters. Lime treatment
for precipitation of calcium phosphate and various other anions is
practiced at Plants 1, 3, 4, >5, 6, 8, 9, and 31. The slurry can then be
filtered, reducing total phosphorus to less than 100 mg/1, suspended
solids to less than 50 mg/1, and arsenic to less than 0.03 mg/1. Lab
data for Plant 11 project even lower total phosphorus and arsenic levels.
The filter cake can be hauled to landfill for disposal. The suspended
solids removed will consist principally of CaHP02.3H20, Ca2(P04)£, or
Ca5(P04)30H. Raw waste loads are assumed to consist of 1.5 kg/kkg HC1,
I.I kg/kkg H3P03, and 4 x 10-5 kg/kkg arsenic.
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Final neutralization of the effluent with hydrochloric or other suitable
acid can be used to reduce the pH below 9.0. Some sodium and calcium
chloride will remain in the effluent. A portion of the hydrochloric
acid may be replaced with sulfuric acid to reduce cost, but if only
sulfuric acid is used, some calcium sulfate scaling in effluent piping
may occur and some increase in suspended solids may result. Calcium
sulfate will not precipitate or scale when the product of calcium
concentration (in ppm) times the sulfate concentration (in ppm) is less
than 192,302.(81) This can be accomplished by control of calcium or
sulfate addition or by dilution after treatment by other available waste
waters that are permitted to be discharged. Reuse of a portion of the
alkaline lime treated filtrate as caustic and water makeup for the PC13_
scrubbers is an alternative to acid neutralization of the entire filtrate.
Although some hydrolyzable phosphates are present in PCI3_ waste water,
they are expected to co-precipitate and be adsorbed on tEe orthophosphate
or phosphite precipitates, as explained in Section VII for the phosphate
segment. Test data from Plant 11 tend to confirm this. In any event,
the relatively high level of 100 mg/1 total phosphorus is based on a
treated waste water that typically contains some hydrolyzable phosphates.
The arsenic-rich reactor/still residues can be drummed for disposal as
solid chemical waste. This can be done with the aid of trichloroethane
or trichloroethylene, which act as solvents for any elemental phosphorus
that may remain. If a final water rinse is used, it is advisable to
lime treat and clarify the rinse water to remove 90 percent of the
remaining total phosphorus and arsenic as a thickened slurry for drum-
ming and solid waste disposal. The clarified, lime-treated rinse water
can then be combined with scrubber blowdown for final lime treatment.
The rinse water volume will not add a significant surge load if metered
into scrubber blowdown over a long period of time. This rinse water
treatment assures that the scrubber and container waste water treatment
system is not upset by the high arsenic content of the raw rinse water.
Chlorine may be present in treated waste water (as hypochlorite) because
of excess chlorine in reactor vent gases. Estimates from Plant 14
indicate this can be as much as 0.45 kg of chlorine per kkg of product
or 900 mg/1 (based on 500 1/kkg or 120 gal/ton blowdown). Because
existing PC13 facilities are all parts of larger organic and inorganic
manufacturing complexes, reducing substances from the other waste waters
will, in most cases, consume the excess chlorine. Plant 14 does treat
this waste water for chlorine removal, as described in Section VII.
There are no available analytical data reported for chlorine levels in
raw wastes or plant effluents, so the need and cost for treatment could
not be determined. Some plants may find treatment for chlorine removal
necessary, but the determination should be made on an individual plant
basis. Technology for dechlorination is described in Section VII.
In view of the presence of chlorine in PC13_ reactor vents, it is assumed
that no elemental phosphorus reaches waste water from this source and
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T
the criteria of no discharge of phossy water still applies. The process
can be operated to avoid discharge of aborted batches. (Elemental
phosphorus is present in incomplete reaction mixtures. ) Good manufacturing
practices can minimize or prevent incidental contamination of non-
process waste water. The use of diking, diversion, and workover of
spills and leaks are available technologies, as explained in Section
VII.
Phosphorus Oxychloride Manufacture. The following average waste water
pollutant levels are achievable by application of the best practicable
control technology currently available:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.05 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.025 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
There is no available information that would indicate process waste
water pollutants from the manufacture of phosphorus oxychloride are
being adequately treated at this time. However, there are practicable
technologies transferable from other industries, including the phosphate
industry and municipal potable and waste water treatment plants. This
technology includes lime treatment and removal of phosphate anions (some
phosphite may also be present). Available treatment technologies for
this industry include recycle and caustic neutralization of scrubber and
container and equipment washing waste waters, lime treatment of the
blowdown, filtration, filter cake disposal, and neutralization of the
filtrate with acid.
Recycle and caustic neutralization are presently practiced at Plants H
and 17. About 500 1/kkg (120 gal/ton) of blowdown at pH 5 are required
to produce a sodium ion concentration comparable to that at Plant 31
before lime treatment. Container and equipment wash water can be similarly
recycled and neutralized. Fresh makeup water can be introduced either
at the scrubber inlet to saturate the air to the scrubber or as a final
rinse water for containers and equipment. Recycling decreases the
quantity of waste waters and increases the concentration of waste pollu-
tants .
Lime treatment of the blowdown to pH 11.5 or higher will neutralize the
remaining acidity and will precipitate the phosphates as hydroxyapatite
and possible other calcium phosphates (or phosphites). Calcium phosphates
and other anions are precipitated with lime at Plants 1, 3, 4, 5, 6, 8,
9, and 31. The slurry can then be filtered, reducing total phosphorus
to less than 100 mg/1 and suspended solids to less than 50 mg/1. (Note
that Plant 31 projects 47 mg/1 phosphorus and 20 mg/1 suspended solids
in its effluent after final effluent filtration. Also, Plant 11 laboratory
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K- »- . -v-
UvAr F
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.018 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.008 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
Plant 31, which produces food-grade sodium tripolyphosphate and a variety
of soluble, food-grade phosphates (sodium and ammonium), recycles most
of its process waste waters. The plant treats and discharges a combined
waste water that includes storm water runoff, as discussed in Section
VII. The total phosphorus limitation assumes treatment of this waste
water as at Plant 31 by retention in a pond for hydrolysis, lime treatment,
clarification, effluent filtration, and landfill of sludge. The clarifier
overflow can be acidified to reduce the pH below 9.0 before discharge.
Total phosphorus is reduced to 0.018 kg/kkg (0.035 Ib/ton) average or
less by this treatment, and suspended solids are reduced to 0.008 kg/kkg
(0.016 Ib/ton) average or less. Cooling water subject to contamination
by equipment leaks is discharged without treatment. Most of the Plant
31 treatment system has been in operation since 1969.
Hydrolysis of polyphosphates and other hydrolyzable phosphates can be
done by a hot acidic treatment rather than in a pond, as described in
Section VII. This would reduce land requirements. The need to hydrolyze
polyphosphates and other hydrolyzable phosphates may be avoided by the
introduction of a coagulation step after lime treatment and, if necessary,
the use of pre-coat filtration or larger filters. Laboratory data
showed that polyphosphates may be reduced to 8.5 mg/1 as total phosphorus
by lime treatment and adequate separation of solids, as discussed in
Section VII. Routine water treatment plant techniques can produce clear
filtrates. Polyphosphate levels are reduced even further in the presence
of orthophosphates during lime treatment. Thus, addition of orthophosphate
to waste waters containing only polyphosphates may improve lime treatment
efficiency.
Plant 31 routinely treats storm water runoff from the site. Significant
amounts of phosphate from dustfall can be present in runoff. Frequent
adequate removal of dust accumulations and spills in production and
shipping areas, including roofs, may avoid the necessity of impoundment
and treatment of runoff. Additional paving may be required at some
plants to accomplish this.
Non-Food Grade Sodium Tripolyphosphate and Other Soluble Phosphate
Manufacture. The following average waste water pollutant levels are
achievable by application of the feesL available Lfc&linolugy economically
Q yo J
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Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.0044 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.002 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
The same rationale applies for non-food grade plants as for food-grade
sodium tripolyphosphate and other phosphate plants. The principal
difference is that non-food grade plants can totally recycle process
waste water, except for storm water and noncontact cooling water. Total
recycyle has been achieved at Plants 25 and 27. For this reason, the
volume of waste water from a non-food grade plant is less than that from
a food grade plant on a 1/kkg (gal/ton) basis. Otherwise, the practicable
treatment for non-food grade plant waste water is identical. Some non-
food grade phosphate plants may find that they can totally recycle
contaminated storm water runoff and cooling tower blowdown to the
process without the need for lime treatment or discharge.
Food-Grade Calcium Phosphates Manufacture. The following average waste
water pollutant levels are achievable by application of the best practicable
technology currently available:
Effluent Achievable Average Level of
Characteristics Pollutant in Effluent
Total phosphorus 0.17 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.072 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
Current technology for dicalcium phosphate (DCP) and tricalcium phosphate
(TCP) manufacture utilizes dry dust collection, so no scrubber wastes
are produced. Plant 36 lime treats, clarifies, and recycles all DCP
centrate. Plant 24 also lime treats and clarifies the centrate, but
discharges the overflow. Total recycle would be an in-process change,
but lime treatment for removal of orthophophates, even in the presence
of some polyphosphates, is a technology that has been practiced at Plant
31 since 1969. Lime treatment facilities and clarifiers at existing DCP
plants probably are not large enough to produce satisfactory effluent
levels. In certain cases, the DCP overflow probably could not be totally
recycled because of the buildup of soluble proprietary additives.
Treatment of DCP clarifier overflow may require lime treatment to pH 11
or greater, as at Plant 31. Clarification, sludge dewatering, effluent
filtration, and disposal of filter cake to landfill may be required for
satisfactory effluent. Acid addition to the effluent may be required to
reduce the pH below 9.0. A retention pond for hydrolysis should not be
needed because no polyphosphates are present.
No direct process contact or scrubber wastes are generated by TCP manufac-
ture. Monocalcium phosphate (MCP) operations produce small or intermittent
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discharges from scrubbers. These may contain phosphates and suspended
solids and may require lime treatment as described above for the DCP
clarfier overflow.
Some calcium phosphate plants generate other waste waters from floor
washing, leaks and spills, equipment washdown, area runoff in production
and shipping areas (including roof drainage), and other sources. This
waste water can be collected and treated as described above for DCP
filtrate. Plant 31 (a soluble phosphates plant), has collected and
treated this type of waste water since 1969.
Thus, a DCP production raw waste will consist of 3,000 1/kkg (730 gal/ton)
of partially clarified centrate plus 600 1/kkg (130 gal/ton) of other
contaminated waste water requiring treatment. Waste water from other
calcium phosphate production would consist of the 600 1/kkg (130 gal/ton)
only, which is liberal enough to include the small or intermittent MCP
scrubber effluent. Both waste waters can be handled in the same treatment
facility. Calcium cation is present instead of sodium, potassium, or
ammonium cations. No regeneration of sodium hydroxide or suppression of
calcium cation is expected.
Storm water runoff from production, storage, and shipping areas normally
is contaminated by dustfall and spills. The 600 1/kkg (130 gal/ton) of
raw waste water includes this rainfall runoff. Plant 31 routinely
treats all site runoff from production, storage, and shipping areas, and
several plants have indicated that site runoff is potentially contaminated
with phosphates from the manufacturing operations.
Contamination of noncontact cooling water in calcium phosphate plants by
equipment leaks and spills is less than in sodium or potassium phosphate
plants, because solubilities of calcium phosphates are less and there is
a lower concentration of phosphate ion in calcium phosphate solutions
and slurries.
Feed Grade Calcium Phosphate Manufacture. The following average waste
water pollutant levels are achievable by application of the best practicable
technology currently available:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.026 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.012 kg/kkg (lb/1,000 Ib)
Fluoride 0.01 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
Plant 41 has no process wastes. Three separate water cycles are used,
with no discharge of effluent. The acid defluorination scrubber water
is neutralized with lime, the solids are settled by ponding, and the
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pond effluent is reused as scrubber water. The scrubber water for
collection of airborne solids from the reactor and dryer is recirculated,
with a bleedoff directly into the reactor as process water. Cooling
water is recycled through a cooling tower, with the blowdown used as
makeup in the solids scrubbing system instead of being wasted. Softened
well water is used for cooling water makeup.
Plant 41 is an excellent example where a combination of in-process
controls and end-of-process treatment results in no discharge of waste
water. In-process controls used include dry dust collection, recycle of
scrubber water, return of waste streams to the process, and a systems
approach towards water use whereby a blowdown stream from one water
cycle becomes a makeup stream for another. Standard lime treatment,
sedimentation, and a total recycle scrubber water system are also compo-
nents of the control technology at Plant -41.
Lime treatment of contaminated storm water runoff from storage and
production is practicable by transfer of technology from sodium tripoly-
phosphate manufacture, as described for food-grade calcium phosphates.
Fluoride which may be present in plants performing defluorination, will
also be removed by lime treatment.
Alternative technologies for contaminated storm water treatment include:
impoundment and reuse for cooling and process uses, impoundment for
evaporation in ponds, and reduction of contamination by improved dust
collection efficiency and cleanup of spills and dust accumulations for
return to the processes. Well-managed site drainage practice includes
collection and reuse or treatment of highly contaminated runoff, with
direct discharge of large volumes of uncontaminated site drainage water.
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SECTION X
EFFLUENT REDUCTION ATTAINABLE THROUGH THE APPLICATION OF
THE BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE
INTRODUCTION
The effluent limitations that must be achieved by July 1, 1983, are
based on the degree of effluent reduction attainable through the applica-
tion of the best available technology economically achievable. This
control technology is not based upon an average of the best performance
within an industrial category, but is determined by identifying the very
best control and treatment technology employed by a specific plant
within the industrial category or subcategory, or readily transferable
from one industry process to another.
The following factors were considered in determining the best available
technology economically achievable:
a. the total cost of application of this control technology
in relation to the effluent reduction benefits to be
achieved from such application;
b. the size and age of equipment and facilities involved;
c. the processes employed;
d. the engineering aspects of the application of various
control technologies;
e. process changes;
f. non-water quality environmental impact (including energy
requirements).
Best available technology economically achievable places equal emphasis
on in-process controls as well as end-of-process control and treatment
techniques. Those plant processes and control technologies that at the
pilot plant, semi-works, or other level have demonstrated both technologi-
cal performance and economic viability at a level sufficient to reasonably
justify investing in such facilities were also considered. This control
technology is the highest degree 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 the top-of-the-line of
current technology subject to limitations imposed by economic and engineer-
ing feasibility. However, this control technology may be characterized
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by some technical risk with respect to performance and with respect to
certainty of costs. Therefore, this control technology may necessitate
some industrially sponsored development work prior to its application.
ACHIEVABLE EFFLUENT LEVELS
Specialized Definitions
Except as provided below, the general definitions, abbreviations and
methods of analysis set forth in 40 CFR 401 shall apply to this section.
The term "process waste water" shall mean any water that, during manu-
facturing or processing, comes into direct contact with or results from
the production or use of any raw material, intermediate product, finished
product, by-product, or waste product. The term "process waste water"
does not include contaminated non-process waste water, as defined below.
The term "contaminated non-process waste water" shall mean any water
that, during manufacturing or processing, comes into incidental contact
with any raw material, intermediate product, finished product, by-
product, or waste product by means of (l) precipitation runoff; (2)
accidental spills; (3) accidental leaks caused by the failure of process
equipment and which are repaired or the discharge of pollutants therefrom
contained or terminated within the shortest reasonable time, which shall
not exceed 24 hours after discovery or when discovery should reasonably
have been made, whichever is earliest; and (4) discharges from safety
showers and related personal safety equipment, and from equipment
washings for the purpose of safe entry, inspection, and maintenance;
provided that all reasonable measures have been taken to prevent,
reduce, eliminate, and control to the maximum extent feasible such
contact and provided further that all reasonable measures have been
taken that will mitigate the effects of such contact once it has occurred.
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 phosphorus derived chemicals industry.
The Phosphorus Production Subcategory
Achievable Pollutant Reductions. The determinations of this section are
applicable to the discharges resulting from the production of elemental
phosphorus and ferrophosphorus by smelting of phosphate ore.
It has been determined that no discharge of waste water pollutants can
be accomplished by the application of the best available technology
economically achievable.
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Rationale for BAT. Plants 1, 3, 6, and 8 all report no discharge of all
waste waters originating from the site under normal circumstances. This
is achieved by:
1. Phossy water treatment, reuse, and evaporation utilizing
ponds and mechanical clarifiers. This is also practiced
at Plants 4, 5, 7, and 9.
2. Lime treatment of calciner scrubber waters and other
contaminated process waste waters, sedimentation of waste
water in ponds and mechanical clarifiers, and recycle of
clarified effluents for reuse as process and cooling
water. These techniques are also practiced at Plants 4,
5, and 9.
3. Evaporation of process water within the manufacturing
process, principally at scrubbers, and evaporation in
ponds. Both types of evaporation occur at all phosphorus
producing plants.
4. The use of cooling towers and cooling ponds to reduce the
usage of fresh water and the volume of waste water to be
evaporated or otherwise disposed of. Cooling towers are
also used at Plants 4, 7, and 9. Ponds are also used for
evaporative cooling of cooling water at Plants 4, 5, and
9.
5. Containing, using, or evaporating contaminated storm
water runoff from plant sites, or allowing runoff to seep
into the soil, thus eliminating discharge. This is also
the case at Plants 5 and 7.
Uncontaminated storm water runoff is prevented from entering process
waste water treatment and recycle systems at Plants 1, 5, 6, and 9 by
use of dikes and diversion ditches. This means for avoiding discharge
of contaminated storm water runoff is also part of the best available
technology economically achievable.
In phosphorus producing plants, noncontact cooling waters may be subject
to incidental contamination by elemental phosphorus, and, in some cases,
by fluoride and phosphate. The discharge of cooling water can be
eliminated by recycling in cooling tower systems with minimum blowdown,
which also minimizes makeup water requirements. Blowdown can be sent to
the process waste water treatment system, or it can be treated separately
for recycle to the cooling tower system, reducing net blowdown to the
process waste water treatment system even further. A reasonable antici-
pated blowdown volume from a well-designed system is 350 1/kkg (84
gal/ton) of product. This is based on a conservative heat load and
makeup water analysis for a typical plant. In support of this, it is
noted that Plant 6 has no blowdown, and Plant 1 has 417 1/kkg (100
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gal/ton) blowdovm. Makeup to the cooling tower system can be softened
or deionized and filtered, further reducing net blowdown volumes and
makeup water requirements. Buildup of soluble salts in the process
waste water treatment and recycle system will reach an equilibrium
because of their removal as dissolved solids in the moisture adhering to
insoluble settled precipitates in pond sediments. Thus, the maximum use
of recirculating cooling towers, with makeup water treatment and blow-
down to the process waste water treatment system, is part of the technology
recommended for eliminating waste water discharge. This technology
dramatically reduces the use of fresh water for cooling and the volume
of spent cooling water to be discharged, treated, or reused.
Even after completion of the foregoing, the process waste water recycle
system may have to be modified to assure continued operation in extremely
cold weather. Methods to accomplish this include the use of heated
pumping stations; deeper return canals and ditches; buried, insulated
and heated pipelines; and increased water recirculation. These types of
methods have been used for years in cold climates to prevent water
supplies in production areas from freezing, and are applicable in waste
water treatment and recycle systems. Plant 8, located in an extremely
cold climate, was used as the model for the costs required for cold
weather protection. Cooling operations in cold climates are generally
more feasible and economical than in warm climates. For example,
smaller cooling ponds and less cooling water recycle in cold climates
will effect the same cooling as larger ponds and more recycle in warm
climates.
The Phosphorus Consuming Subcategory
Phossy Water Wastes. It has been determined that the best available
technology economically achievable for phossy water wastes is no discharge
of elemental phosphorus in detectable quantities from any phosphorus
consuming plant. The rationale is explained in Sections VII and IX.
Phosphoric Acid Manufacture. It has been determined that process and
contaminated non-process waste water from phosphoric acid manufacture
can be treated to achieve the following average levels of pollutants by
the application of best available technology economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.0036 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.0036 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity*
Arsenic 0.000026 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
* As of this writing, 0.5 ppb of elemental phosphorus is considered
detectable
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The technical procedures available for achieving BPT at phosphoric acid
plants are also available for BAT treatment operations. For BAT operations,
in-process improvements are also essential. There are plants that have
no waste water discharge, while other plants discharge only contaminated
storm water runoff and cooling water. Plant 31 treatment technology has
been pointed out as an example because it has been in routine use since
1969 to treat a combination of process waste water and storm water
runoff. Much of Plant 31 technology is applicable for BAT: lime treatment,
clarification, sludge dewatering, effluent filtration, and acid neutrali-
zation. Additionally, by maximizing the use of cooling towers, cooling
water blowdown potentially subject to contamination from leaking equipment
can be reduced to 1,000 1/kkg (24-0 gal/ton) or less. The use of cooling
towers is state-of-the-art technology for reducing water usage, waste
water volume, and heat rejection to waterways and is used at plants
within each subcategory of the phosphorus derived chemicals industry.
Cooling water blowdown can be combined with contaminated storm water
runoff and lime treated. A flocculation step utilizing a polyelectrolyte
or other flocculation agent can be added before filtration to remove
colloidal phosphates and other colloidal solids. Achievable levels of
phosphate (as P) and suspended solids are 3 rag/1, based on transfer of
technology from municipal waste treatment systems and on laboratory test
data for similar wastes.
Frequent adequate pickup of spills and leaks in production, storage, and
shipping areas may avoid the generation of contaminated storm water
runoff and the necessity of impoundment and treatment. Improved house-
keeping and maintenance, and additional paving, dikes, curbs, and sumps
may be required to do this. Uncontaminated storm water runoff can be
diverted around contaminated areas. Small acid spills can be neutralized
with dry lime, shoveled up, and disposed of to landfill.
At plants where non-food grade phosphates are also produced, it may be
possible to avoid discharging the lime treated effluent. The effluent
can be filtered and reused as makeup water for calcium phosphate manufac-
ture, or filtered and softened for reuse in soluble phosphate manufacture.
At Plants 20, 21, 26, 27, and 36, cooling water blowdown is totally
reused as makeup water without lime treatment.
Phosphorus Pentoxide Manufacture. For phosphorus pentoxide manufacture,
it has been determined that process and contaminated non-process waste
water can be treated to achieve the following average levels of pollutants
by the application of best available -technology economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.0017 kg/kkg (lb/1,000/lb )
Total suspended solids 0.0017 kg/kkg (lb/1,000/lb)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
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' U
:j
Best available technology economically achievable for phosphorus pentoxide
manufacture includes neutralization, lime treatment, and recycle of tail
gas seal water; and lime treatment and discharge of contaminated storm
water runoff, using treatment technology similar to that used at Plant
31.
A flocculation step is added prior to effluent filtration to remove
colloidal solids. Achievable levels of phosphate (as P) and suspended
solids are 3 mg/1, based on transfer of technology from municipal waste
treatment systems and on laboratory test data for similar wastes.
All P205_ presently produced in the United States is manufactured at
plants where phosphoric acid and other phosphorus derived chemicals are
produced. Combination of the P205_ waste waters with waste waters from
these other processes before lime~~treatment will drastically reduce the
annualized treatment cost chargeable to P205_.
Phosphorus Pentasulfide Manufacture. It has been determined that process
and contaminated non-process waste water from phosphorus pentasulfide
manufacture can be treated to achieve the following average levels of
pollutants by the application of best available technology economically
achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.00015 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.00015 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
Sulfide sulfur (as S) 0.0005 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
The rationale for BPT also applies for BAT. The recommended technology
for 1983 includes recycle and caustic neutralization of scrubber and
container wash waters, followed by alkaline chlorination, lime treatment,
sludge dewatering, effluent filtration, acid neutralization, and discharge
of the blowdown. Alkaline chlorination is transferable from industries
such as iron and steel making and electroplating.
In addition, more recycle and less blowdown for scrubber and container
washing waste waters are used. Lime is used as the alkali for chlorination
to reduce regeneration of sodium hydroxide and to avoid large acid
requirements for final neutralization. There is no clarification step
used before the cake filtration because the slurry is high in suspended
solids, but a flocculation step is added prior to filtration. Achievable
levels of total phosphorus (as P) and suspended solids by lime treatment
are 3 mgA> based on transfer of technology from municipal waste treatment
systems and based on laboratory test data for similar wastes. Some of
these data show that hydrolyzable phosphates are co-precipitated with
other phosphates to total phosphorus levels well below 3 mg/1. A
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sulfide level of 10 mg/1 is readily achieved by alkaline chlorination
without the necessity of large net chlorine residuals. Some plants may
find that treatment for chlorine removal is necessary. Circumstances
will vary for individual plants, as discussed in Section IX. Technology
for dechlorination is described in Section VII.
Phosphorus Trichloride Manufacture. For phosphorus trichloride manufacture,
it has been determined that process and contaminated non-process waste
water can be treated to achieve the following average levels of pollutants
by the application of best available technology economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.0011 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.000033 kg/kkg (lb/1,000 Ib)
Arsenic 5.5 x lO'7 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
The 1983 technology for phosphorus trichloride manufacture includes
recycle and caustic neutralization of scrubber and container waste waters,
followed by lime treatment, cake filtration, effluent filtration, acid
neutralization, and discharge of the blowdown. As for BPT, the arsenic-
rich PC1_3 still residue and trichloroethane wastes are drummed. Still
wash water is lime treated, with drumming of sludge. These drummed
wastes are then disposed of in an appropriate manner as solid wastes.
The clarified effluent is combined with scrubber and container washing
waste waters for further lime treatment.
In addition, more recycle and less blowdown are used for BAT than for
BPT. Lime is supplemented with calcium chloride to reduce regeneration
of sodium hydroxide and to avoid large acid requirements for final
neutralization. There is no clarification step used before the cake
filtration step because the slurry is high in suspended solids, but a
flocculation step is added prior to effluent filtration. The achievable
levels of total phosphorus (as P) and arsenic after lime treatment are
100 mg/1 and 0.05 mg/1, respectively, based on effluent tests at Plant
11. The achievable level for total suspended solids is 3 mg/1, based on
transfer of technology from municipal waste treatment systems.
Phosphorus Oxychloride Manufacture. It has been determined that process
and contaminated non-process waste water from phosphorus oxychloride
manufacture can be treated to achieve the following average levels
of pollutants by the application of best available technology economically
achievable:
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| , r ... T,..—,
I,, , < vf I.
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.00003 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.00003 kg/kkg (lb/1,000 Ib)
Elemental phosphorus No detectable quantity
pH Within the range 6.0 to 9.0
The 1983 technology for phosphorus oxychloride manufacture includes
recycle and caustic neutralization of scrubber and container waste
waters followed by lime treatment, cake filtration, effluent filtration,
acid neutralization, and discharge of the blowdown. In addition, more
recycle and less blowdown are used for BAT than for BPT. Lime is supple-
mented with calcium chloride to reduce regeneration of sodium hydroxide
and to avoid large acid requirements for final neutralization. There is
no clarification step used before the cake filtration because the slurry
is high in suspended solids, but a flocculation step is added prior to
effluent filtration. Achievable levels of total phosphorus (as P) and
suspended solids by this treatment are 3 mg/1, based on transfer of
technology from municipal waste treatment systems and based on laboratory
test data for similar wastes. Some of these data show that hydrolyzable
phosphates are co-precipitated with ortho-phosphates, yielding total
phosphorus levels well below 3 mg/1 (as P).
Treatment for chlorine removal may be necessary at some plants, as
discussed in Section IX. Chlorine removal technology is described in
Section VII.
The Phosphate Subcategory
Food-Grade Sodium Tripolyphosphate Manufacture. For food-grade sodium
tripolyphosphate manufacture, it has been determined that process and
contaminated non-process waste water can be treated to achieve the
following average levels of pollutants by the application of best available
technology economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.002 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.002 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
Best available technology for food grade sodium tripolyphosphate manufac-
ture includes the controls defined for BPT. There are plants that
recycle most of their process waste waters and only discharge washdown
wastes, storm water runoff, and noncontact cooling water. Plant 31
treats all of its waste water except spent cooling water. Waste waters
treated include washdown wastes and contaminated storm water runoff.
Plant 31 lime treatment technology was determined to be applicable for
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BPT because it has been in routine use for many years. Much of this
technology is also recommended for BAT: retention for one month in a
pond for hydrolysis, lime treatment, clarification, sludge dewatering,
effluent filtration, and acid neutralization of effluent. In addition,
maximum use is made of cooling towers to reduce the volume of potentially
contaminated spent cooling water to 300 1/kkg (72 gal/ton) or less.
Cooling towers are used at several sodium tripolyphosphate plants. This
reduced volume is then combined with other waste waters, including
contaminated storm water runoff, and is lime treated. Also for BAT,
lime treatment is supplemented with calcium chloride to reduce regeneration
of sodium hydroxide and to avoid large acid requirements for effluent
neutralization, and a flocculation step is introduced before the filtration
to remove colloidal phosphates, algae, and other colloidal solids, if
present.
Achievable levels of total phosphorus (as P) and suspended solids by
this treatment are 3 mg/1, based on transfer of technology from municipal
waste treatment systems and based on laboratory test data for similar
wastes. Some of these data show that hydrolyzable phosphates are co-
precipitated with orthophosphates, yielding total phosphorus levels well
below 3 mg/1 (as P).
Section VII identifies the many operating techniques available to reduce
the amount of total phosphorus that potentially could become a storm
water contaminant. Effective cleanup programs may negate the need for a
storm water holding pond. Generally, the quantity of contaminated storm
water runoff and cooling water generated is a measure of the adequacy
and quality of equipment maintenance and of the sophistication of or
dedication to an adequate program of housekeeping.
Hydrolysis of polyphosphates and other hydrolyzable phosphates can be
done by a hot acidic treatment as described in Section VII, to reduce
the need for site space required by a retention pond. Preliminary
testing is recommended to be sure that a hydrolysis step such as ponding
or acid hydrolysis is necessary. The recommended flocculation and final
filtration may possibly avoid the need for hydrolysis. As discussed in
Section VII, laboratory data show polyphosphates in filtrates may be
reduced to 9 mg/1 as total phosphorus by lime treatment and adequate
separation of solids. The same data show total phosphorus is reduced to
less than 1.5 mg/1 (as P) after lime treatment and filtration of a
solution containing polyphosphates. The tests were conducted at pH 9 or
higher in the presence of adequate calcium ion, adequate orthophosphate,
and with sodium ion present.
The determinations of this section are equally applicable to other food-
grade soluble phosphates. No hydrolysis step is needed when only ortho-
phosphates are present in the raw waste.
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Non-Food Grade Sodium Tripolyphosphate Manufacture. For non-food grade
sodium tripolyphosphate manufacture, it has been determined that process
and contaminated non-process waste water can be treated to achieve the
following average levels of pollutants by the application of best available
technology economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.0012 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.0012 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
For BAT, the same rationale applies for non-food grade plants as for
food-grade sodium tripolyphosphate and other soluble phosphate plants.
The principal difference is that non-food grade plants can, and currently
do, totally recycle contaminated waste water, as at Plants 25 and 27.
For this reason, the volume of waste water from a non-food grade plant
is less than from a food-grade plant, on a 1/kkg (gal/ton) basis.
Otherwise, the recommended treatment for non-food grade plant waste
water and food-grade plant waste water is identical. For a non-food
grade plant, contaminated cooling tower blowdown can be reduced to 300
1/kkg (72 gal/ton) before lime treatment, and contaminated storm water
runoff is estimated at 100 1/kkg (24 gal/ton). Some non-food grade
phosphate plants may also find that they can totally recycle contaminated
storm water runoff and cooling tower blowdown to the process without the
need for lime treatment or discharge.
The determinations of this section are equally applicable to other non-
food grade soluble phosphates, including those of sodium, potassium, and
ammonia.
Food Grade Calcium Phosphate Manufacture. It has been determined that
process and contaminated non-process waste water from food grade calcium
phosphate manufacture can be treated to achieve the following average
levels of pollutants by the application of best available technology
economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.011 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.011 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
The 1983 technology for food grade calcium phosphate manufacture is
identical to the 1977 technology. BAT includes lime treatment, clarifi-
cation, sludge dewatering, effluent filtration, neutralization of
filtrate to pH 9.0 or less, and disposal of sludge to landfill. In
addition, maximum use is made of cooling towers to reduce the volume of
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contaminated spent cooling water to 100 1/kkg (24 gal/ton) or less.
This reduced volume is then combined with other process waste waters,
including contaminated storm water runoff, and lime treated. Also, for
BAT, a flocculation step is added prior to effluent filtration.
Achievable levels of total phosphorus (as P) and suspended solids by
this treatment are 3 mg/1, based on transfer of technology from municipal
waste treatment systems and based on laboratory test data for similar
wastes.
Section VII identifies ways to reduce the amount of total phosphorus
that becomes a storm water contaminant. Effective cleanup programs may
negate the need for a storm water holding pond.
The waste water volume discharged was assumed not to exceed that from
DCP manufacture: 3,000 1/kkg (730 gal/ton) of clarified centrate, plus
100 1/kkg (24 gal/ton) of cooling tower blowdown, plus 600 1/kkg (130
gal/ton) of other contaminated waste waters.
The reason for considering treatment of contaminated storm water runoff
in developing achievable effluent levels is because Plant 31 routinely
treats this waste water and because significant amounts of phosphate
from dustfall can be present in runoff. Frequent adequate removal of
dust accumulations and spills in production and shipping areas, including
roofs, may avoid the necessity of impoundment and treatment of runoff.
Additional paving may be required at some plants to accomplish this.
The need for control of pollution by dusts, spills, and leaks reaching
plant effluents via storm water runoff is almost identical for both
soluble and calcium phosphate plants. The methods of control and treatment
are also very similar.
Feed Grade Calcium Phosphate Manufacture. For feed grade calcium phosphate
manufacture, it has been determined that process and contaminated non-
process waste water can be treated to achieve the following average
levels of pollutants by the application of best available technology
economically achievable:
Effluent Achievable Average Level of
Characteristic Pollutant in Effluent
Total phosphorus 0.002 kg/kkg (lb/1,000 Ib)
Total suspended solids 0.002 kg/kkg (lb/1,000 Ib)
Fluoride 0.006 kg/kkg (lb/1,000 Ib)
pH Within the range 6.0 to 9.0
The rationale for BPT for feed grade calcium phosphate manufacture also
applies for BAT. There are plants that have no waste water discharge,
while others discharge only contaminated storm water runoff. BAT
includes treatment of contaminated storm water runoff from process and
storage areas with lime precipitation, clarification, sludge dewatering,
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U:t''..:' »t" I
effluent filtration, neutralization of effluent to pH 9.0 or less, and
disposal of sludge to landfill. It is assumed that the representative
plant already has total recycle of cooling water blowdown. In addition,
a flocculation step is added prior to final effluent filtration.
Achievable levels of total phosphorus (as P) and suspended solids by
this treatment are 3 mg/1, based on transfer of technology from municipal
waste treatment systems and based on laboratory test data for similar
wastes. Fluoride, which may be present in plants performing defluorination,
will also be removed by lime treatment. Contaminated storm water runoff
from storage and production areas was assumed to be no greater than 600
1/kkg (144 gal/ton). A fluoride concentration of 10 mg/1 or less is
achievable by lime treatment, as discussed in Section VII.
Alternative technologies for contaminated storm water treatment include:
impoundment and reuse for cooling and process uses, impoundment for
evaporation in ponds, and reduction of contamination by improved dust
collection efficiency and cleanup of spills and dust for return to the
processes.
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r
SECTION XI
EFFLUENT REDUCTION ATTAINABLE
AT NEW PLANTS AND PRETREATMENT CONSIDERATIONS
INTRODUCTION
The level of technology discussed in this section 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 determining what higher
levels of pollution control are available through the use of improved
production processes and treatment techniques. Thus, in addition to
considering the best in-plant and end-of-process control technology, 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
are to be considered. However, the end result of the analysis identifies
effluent standards that 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 that must be employed. In the development of these performance
standards, consideration must be given to the practicability of a standard
permitting "no discharge" of pollutants.
The following factors were considered with respect to production processes
that were analyzed in assessing new source performance standards:
a. The type of process employed and process changes;
b. Operating methods and in-plant controls;
c. Batch as opposed to continuous operations;
d. Use of alternative raw materials and mixes of raw ma-
terials;
e. Use of dry rather than wet processes (including sub-
stitution of recoverable solvents for water); and
f. Recovery of pollutants as by-products.
ATTAINABLE POLLUTANT REDUCTIONS
On the basis of the information contained in Sections III through X of
this report, the following determinations were made on the degree of
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effluent reduction attainable with the application of new source treatment
technology for the various categories of the phosphorus derived chemicals
industry.
It has been determined that the achievable waste water pollutant removal
level for new source facilities manufacturing elemental phosphorus (and
ferrophosphorus) is identical to the determination made for the application
of best available technology economically achievable, namely, no discharge
of process or contaminated non-process waste water pollutants to navigable
waters.
It has also been determined that the achievable waste water pollutant
removal level for new source facilities manufacturing the following
phosphorus chemicals is identical to the determination of best available
technology economically achievable, as delineated in Section X:
Phosphoric Acid (Dry Process)
Phosphorus Pentoxide
Phosphorus Pentasulfide
Phosphorus Trichloride
Phosphorus Oxychloride
Food Grade Sodium Tripolyphosphate (and other Food Grade
Soluble Phosphates Manufactured from Dry Process
Phosphoric Acid)
Non-Food Grade Sodium Tripolyphosphate (and other Non-Food
Grade Soluble Phosphates Manufactured from Dry Process
Phosphoric Acid)
Food Grade Calcium Phosphates
Feed Grade Calcium Phosphates
The rationale for these determinations is described in Sections IX and X.
PRETKEATMENT CONSIDERATIONS
In addition to the determinations of effluent reductions covering discharges
directly into waterways, the constituents of the effluent discharge from
a plant that would interfere with, pass through, or otherwise be incompatible
with a well-designed and operated publicly owned waste water treatment
plant were identified. A determination was made as to whether the
introduction of such pollutants into the treatment plant should be and
could be completely eliminated.
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 bypasses as
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.".•-"..FT
the capacities of pumping stations are exceeded. It must be remembered
that an overflow of combined industrial/municipal waste water has the
same adverse environmental effect as an overflow of raw domestic sewage.
At a minimum, hydraulic overloading would result in reduced efficiency
of the treatment plant because:
1. Primary and secondary clarifiers would be operating at
excessive overflow rates;
2. 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;
3. Trickling filters would become flooded (and thus anaerobic);
4. Grit chambers would have a high linear velocity resulting
in the carry-over of grit and the subsequent adverse
effects on equipment;
5. The capacity of chlorinators might be exceeded, resulting
in insufficient disinfection; and
6. The critical operating parameters of an activated sludge
unit might be compromised.
The domestic waste water flow rate follows a well-known diurnal cycle;
if the industrial contribution could be staggered to provide flow equal-
ization, the impact of the added flow rate could be minimized. Con-
versely, 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.
219
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Another strong reason for avoiding acidic contributions to publicly-
owned treatment plants is that acidic wastes would drastically promote
corrosion of equipment.
It was determined that a pH range of 6 to 9 is achievable.
Heavy Metals or_ Harmful Materials
Metals or other similar 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 have been
discharged into municipal sewer systems from this industry. The waste
water management and control practices described in Section VII include
procedures that exclude phossy water, elemental phosphorus in aborted
batches and spills, and arsenic concentrates from the waste waters of
the phosphorus consuming and phosphate manufacturing subcategories.
Effluents containing arsenic, heavy metals, or other similar harmful
materials are amenable to pretreatment by lime precipitation and such
other methods as demonstrated in Section VII, IX, and X. Achievable
reductions in levels of arsenic, fluoride, and sulfide are delineated in
Sections IX and X.
Dissolved Phosphates
While dissolved phosphates would generally pass through secondary treat-
ment 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 phosphates would be precipitated as calcium, ferric,
or aluminum phosphates 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 phosphate
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
problems apply only to secondary plants, precautions may be necessary to
avoid adverse effects when tertiary treatment is added in the future.
Summary o£ Pretreatment Determinations
Due to the nature of the process waste waters from the phosphorus
producing subcategory, it would be environmentally undesirable to
discharge these wastes into publicly owned treatment works. These waste
waters are considered to be incompatible with such works principally
because of potentially objectionable levels of harmful constituents such
220
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3 T
as elemental phosphorus, arsenic, cadmium, uranium, and like metals also
present in the phosphate ore.
It has teen determined that process waste waters from the phosphorus
consuming subcategory can be pretreated with lime and as otherwise
specified in Sections VII, IX, and X before discharge to publicly owned
treatment works. The following parameters can be controlled to the same
maximum values as determined for the corresponding treatment levels in
Sections IX and X: elemental phosphorus, arsenic, fluoride, and sulfide.
(Sulfide is readily oxidized in biological treatment systems, but can
cause problems in sanitary collection systems.) For PC12 manufacture,
total phosphorus can also be controlled to the values specified in
Sections IX and X. In all cases, pH can be held within the range of 6
to 9.
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.
Additionally, for feed-grade calcium phosphate plants that perform
defluorination of acid used, fluoride can be controlled to the values
indicated as attainable in Sections IX and X.
221
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T
SECTION XII
ACKNOWLEDGMENTS
This report was prepared under Contract #68-01-3289 by Sverdrup & Parcel
and Associates, Inc., St. Louis, Missouri. The preparation and writing
of this document was accomplished through the efforts of Mr. C. Alan Carter,
Project Engineer, Mr. Alfred A. Cook, and their staff.
The many drawings contained within were provided by Mr. Donald J. Curran
of the Sverdrup Publications Group, under the supervision of Mr. Paul J. Svezia.
The support of the project by the U.S. Environmental Protection Agency
and the guidance provided by Mr. Walter J. Hunt, Chief, Inorganic
Chemicals and Service Industries Branch and Project Manager, and Dr.
Chester E. Rhines, Project Officer, are acknowledged with grateful
appreciation.
Appreciation is extended to the many people in the phosphorus derived
chemicals industry who cooperated in providing information for this
study. Special mention is given to company representatives who were
particularly helpful in this effort:
Mr. John M. Clarke of the Electro-Phos Corporation;
Mr. Ernest C. Ladd, Mr. R. L. Pellissier, Mr. Neil H. Sheffield,
Mr. C. D. Holmes, Mr. J. R. Matulis, Mr. Richard Gerst, and
Mr. Michael Hambor of FMC Corporation;
Mr. Edward F. Smith, Mr. Frank Lee, Mr. Ted Garrett, Mr. Bernard Carreno,
Mr. Jay Cull, Mr. Ferd Machmer, Mr. Vernon Lloyd, and
Mr. Norman Bedziner of Hooker Chemicals & Plastics Corporation;
Mr. Samuel M. Lane, Mr. William Griffin, Mr. William Furlong,
Mr. George Allen, Mr. Hilton Hattaway, Mr. Stewart H. Miller,
and Mr. J. Herman Schulte of the Mobil Chemical Company;
Mr. Garth F. Fort, Mr. M. L. Mullins, Mr. John Tingling, Mr. John Merz,
Mr. Frank Basile, Mr. Wayne Krull, Mr. Emory Kimball, Mr. Glynn Davis,
Mr. Walter Scruggs, Mr. David Haines, Mr. Chuck Davis, Mr. Kent Lott,
Mr. Perry Warner, Mr. John G. DePagter, Mr. David Tai, Mr. James
McPhail, Mr. John Niedhart, Mr. William Hemmings, and Mr. J. Ronald
Condray of Monsanto;
Mr. Edgar L. Conant, Mr. Thomas J. Sayers, Mr. Henry Johnson,
Mr. Dick Harry, Mr. Charles Stager, Mr. Frank Pecht, Mr. Richard L.
Pottkotter, Mr. Ronald Dilks, Mr. James Eads, Mr. C. A. Hendrickson,
and Mr. John Stark of Stauffer Chemical Company.
Acknowledgment and appreciation are also given to Mrs. Ruth Bodapati for
library assistance, and to Mrs. Darlene McMahon, Mrs. Glenna Weaver, and
Mrs. Betty Johnson of Sverdrup & Parcel for their efforts in typing of
drafts, necessary revisions, and final preparation of this document.
223
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j?. r* w« """T
I m>,.r I
1.fcw- ' •' ' ^
SECTION XIII
REFERENCES
1. Current Industrial Reports, Inorganic Chemicals, U.S. Bureau of
Census, Series M28A(75)-14.
2. Beveridge, G. S. G., and Hill, R. G. , "Phosphoric Acid Process
Survey", Chemical and Process Engineering, Vol. 49, pp. 61-66, 73,
July, 1968 (Part iTTpp. 63-70, August, 1968 (Part II), 305 refer-
ences in bibliography.
3. Barber, J. C., "Waste Effluent; Treatment and Reuse", Chemical
Engineering Progress, Vol. 65, No. 6, pp. 70-73, June , 1969 .
4. Barber, J. C., "The Cost of Pollution Control", Chemical Engineering
Progress, Vol. 64, No. 9, pp. 78-82, September, 1968.
5. Barber, J. C., and Farr, T. D., "Fluoride Recovery from Phosphorus
Production", Chemical Engineering Progress, Vol. 66, No. 11, pp.
56-62, November, 1970.
6. LeMay, R. E., and Metcalfe, J. K., "Safe Handling of Phosphorus",
Chemical Engineering Progress, Vol. 60, No. 12, pp. 69-73, December,
__
7. Ellwood, P., "Electric-Furnace Phosphorus", Chemical Engineering,
Vol. 72, pp. 54-56, February 1, 1965.
8. Bryant, H. S., Holloway, N. G., and Silber, A. D., "Phosphorus
Plant Design-New Trends", Industrial and Engineering Chemistry,
Vol. 62, No. 4, pp. 9-23, April, 1970.
9. Faith, W. A., Keyes, D. B., and Clark, R. L., Industrial Chemicals,
3rd Edition, Wiley, New York, 1965.
10. Kirk, R. E., and Othmer, D. F., Encyclopedia of Chemical Technology,
Interscience, New York, 1966.
11. Shreve, R. N., Chemical Process Industries, McGraw-Hill, New York,
1967.
12. Stow, S. H., "Occurrence of Arsenic and the Color-Causing Components
in Florida Land-Pebble Phosphate Rock", Economic Geology, Vol. 64,
pp. 667-671, September, 1969; Discussion, Vol. 65, pp. 64-66,
January, 1970.
13. Data from Plant 14.
225
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DRAFT
14. Data from Plant 4.
15. Data from Plant 24.
16. Data from Plant 31.
17. Data from Plant 27.
18. Data from Plant 25.
19. Data from Plant 18.
20. Lange, N. A., Handbook of Chemistry, 10th Edition, McGraw-Hill, New
York, 1961.
21. Data from Plant 41.
22. U. S. Environmental Protection Agency, "Quality Criteria for
Water", EPA-440/9-76-023, p. 354, Washington, 1976.
23. White, G. C., "Chlorination and Dechlorination: A Scientific and
Practical Approach", Journal of the American Water Works Association,
pp. 540-561, May, 196F!
24. Bullock, E., "Decomposition of Phosphorus in Water", Proc. Conf.
Pollut., pp. 23-24, 1969 (Chemical Abstracts, Vol. 757~24~949"r7~
1971J.
25. Addison, R. F., and Ackman, R. G., "Direct Determination of Elemental
Phosphorus by Gas-Liquid Chromatography", Journal of Chromatography,
Vol. 47, pp. 421-426, 1970.
26. Private Communication with Tennessee Department of Public Health,
Water Quality Control Division, Nashville, January 18, 1977.
27. Private Communication with Idaho Fish and Game Department, Boise,
May 4, 1977.
28. Private Communication with Montana Department of Health and Environ-
mental Services, Office of Water Quality, Helena, June 13, 1977.
29. Private Communication with Florida Department of Environmental
Regulations, May 4, 1977.
30. Weast, R. C. (ed.), Handbook of Chemistry and Physics, 52nd Edition,
The Chemical Rubber Co., Cleveland, 1971-1972".
31. Simons, J. H., Fluorine Chemistry, Vol. 1, p. 132 et al, Academic
Press, New York, 1950.
226
-------
nor
32. Patterson, J. W., Wastewater Treatment Technology, pp. 3, 5, 103-
111, et al, Ann Arbor Press, 1975.
33. Goodman, B. L., and Mikkelson, K. A., "Advanced Waste Water Treatment",
Chemical Engineering Deskbook Issue, pp. 75-83, April 27, 1970.
34. Tofflemire, T. J., and Hetling, L. J., "Treatment of a Combined
Waste Water by the Low-Lime Process", Journal Water Pollution
Control Federation, Vol. -45, No. 2, pp. 210-220, February, 1973.
35. Dickerson, B. W., and Farrell, P. J., "Lab and Pilot-Plant Studies
on Phosphate Removal from Industrial Waste Water", Journal WPCF,
Vol. 41, No. 1, pp. 59-62, January, 1969.
36. ATbertson, 0. E., and Sherwood, R. J., "Phosphate Extraction
Process", Journal WPCF, Vol. 41, No. 8, p. 1469, August, 1969.
37. Schussler, R. G. "Phosphorus Removal: A Controllable Process", CEP
Symposium Series, Vol. 67, No. 107, pp. 536-540, 1971.
38. Shindala, A., "Evaluation of Current Techniques for Nutrient Re-
moval from Waste Waters", Water Resources Bulletin, Vol. 8, No. 5,
pp. 987-1005, October, 1972.
39. U.S. Environmental Protection Agency, Process Design Manual for
Phosphorus Removal, EPA 625/1-76-OOla, pp. 8-7, 9-1, et al, April,
1976":
40. U. S. Environmental Protection Agency, "Development Document for
the Basic Fertilizer Chemicals Segment", EPA-440/l-74-001a, p. 100,
March, 1974.
41. Private Communication with Plant 4, February 2, 1977.
42. Anon., "Phosphate Plant Waste Looms as Hydrofluoric Acid Source",
Chemical Engineering, pp. 46-48, May 4, 1970.
43. Anon., 'Water-Pollution Conclave Airs New Treatment Schemes",
Chemical Engineering, p. 40, September 7, 1970.
44. Ames, L. L., and Dean, R. B., "Phosphorus Removal from Effluents in
Alumina Columns", Journal WPCF, Vol. 42, No. 5, part 2, R161-172,
May, 1970.
45. Anon., "Phosphate Users Regroup", Chemical Engineering, p. 66,
August 10, 1970.
46. Anon., "Sorption Wins Phosphoric Acid from Finishing Wastes,
Chemical Engineering, Vol. 79, p. 60, June, 1972.
227
-------
DRAFT
47. Carter, C, A,, "Phosphorus Removal with Magnesium Oxide", M, S,
Thesis, Washington University, St. Louis, December, 1973.
48. U. S. Environmental Protection Agency, "Development Document for
Other Non-Fertilizer Phosphate Chemicals", EPA-440/l-75-043a, p.
61, June, 1976.
49. U. S. Environmental Protection Agency, "Development Document for
the Steam Electric Power Generating Point Source Category", EPA-
440/l-74-029a, pp. 220, 256-287, et al, October, 1974.
50. Noll, K. E., and Davis, W. T. (eds.), Power Generation, Chapter 22:
"Status of Sulfur Dioxide Removal Systems for the Electric Utility
Industry", pp. 310-312, 320, 322, 323, et al, Ann Arbor Press, 1976.
51. Beychok, M. R., "Coping with S02", Chemical Engineering, pp. 79-85,
October 21, 1974. "~
52. Anon., "Second Generation SO^ Scrubbing System Leads the Way for
Industrial Power Plants", Power, pp, 26-29, November, 1974.
53. U. S. Environmental Protection Agency, Process Design Manual for
Sulfide Control in Sanitary Sewerage Systems, October, 1974.
54. Information from Wallace & Tiernan, I960,
55. U. S. Environmental Protection Agency, "Development Document for
the Steel Making Segment of the Iron and Steel Manufacturing Point
Source Category, EPA-440/l-74-024a, p. 177, Fig. 23, p. 203, Fig.
41, pp. 284, 287, 379, 392, 393, et al, June, 1974.
56. Chemical Abstracts, Vol. 67, 102603z, 1967.
57. Chemical Abstracts, Vol. 75, 40890v, 1971.
58. U. S. Environmental Protection Agency, "Development Document for
Major Inorganic Products Segment", EPA-440/l-74-007-a, pp. 191,
203, et al, March, 1974.
59< Chemical Abstracts, Vol. 83, 2107629q, 1975; Vol. 80, 19176k, 1974;
Vol. 80, 124419q, 1974; Vol. 80, 40713t, 1974.
60. Chemical Abstracts, Vol. 83, 197599v, 1975; Vol. 82, 47429e, 1975;
Vol. 79, P96672a, 1973.
61. Chemical Abstracts, Vol. 83, 103902p, 1975.
62. United States Patents: US 2568128, US 2794705, US 3183062, US
3282653, US 3023086.
228
-------
63. Perry, R. H., Chilton, C. H., Kirkpatrick, S. D., Perry's Chemical
Engineer's Handbook, 4th Edition, pp. 15-19 through 15-23, et al,
Me Graw-Hill, New York, 1963.
64. Griffith, E. J., et al (eds.), Environmental Phosphorus Handbook,
p. 206 et al. Wiley Interscience, New York, 197JT
65. Weber, W. J., Jr., Physicochemical Processes for Water Quality
Control, p. 68 et al, Wiley Interscience, New York, 1972.
66. U.S. Environmental Protection Agency, Process Design Manual for
Suspended Solids Removal, EPA 625/l-75-003a, pp. 4-4, 9-13, 9-14,
9-15, et al, January, 1975.
67. Vadovic, J. P., "Industrial Water Treatment", Plant Engineering,
pp. 135, 137, December 9, 1976.
68. Schmid, L. A., and McKinney, R. E., "Phosphate Removal", Journal
WPCF, Vol. 41, No. 7, pp. 1259-1276, July, 1969.
69. Bailar, J. C., The Chemistry of Coordination Compounds, pp. 772-
775, Reinhold, New York, 19567"
70. American Public Health Association, American Water Works Association,
and Water Pollution Control Federation, Standard Methods for the
Examination of_ Water and Wastewater, 14th Edition, p. 473, Washington,
D. C., 1975.
71. Chemical Abstracts, Vol. 79, 45437v, 1973.
72 "Economic Indicators", a bi-weekly summary of index numbers in
Chemical Engineering magazine.
73. Ricci, L. J., Assistant Editor, "CE Cost Indices Accelerate 10-Year
Climb", Chemical Engineering, pp. 117-118, April 28, 1975.
74. "First Quarterly Cost Roundup", Engineering News Record, pp. 63-
72, March 24, 1977.
75. Richardson Engineering Services, Inc., "Process Plant Construction
Estimating Standards, Vol. 1, Sitework", Division 2, 1975.
76. Guthrie, K. M., H. R. Grace and Co., "Capital Cost Estimating",
Chemical Engineering, pp. 114-142, March 24, 1969.
77. Marshall, S. P., and Brandt, S. L. (Dow Chemical), "Installed Cost
of Corrosion-Resistant Piping", Chemical Engineering, October 28,
1974.
229
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D,n n r~T
nnr I
78. U. S. Environmental Protection Agency, "Development Document for
the Phosphorus Derived Chemicals Segment of the Phosphate Manufacturing
Point Source Category", EPA-440/l-74-006-a, pp. 113-117, January, 1974.
79. Bender, R. J., "Solid Waste Disposal in Chemical Plants", Power,
Vol. Ill, No. 65, March, 1967.
80. Chiagouris, G. L., "Analyzing the Cost of Solid Waste Disposal",
Plant Engineering, Vol. 26, No. 82-5, March 23, 1972.
81. Kunz, R. G., Yen, A. F., and Hess, T. C., "Cooling Water Calculations",
Chemical Engineering, p. 68, August 1, 1977.
82. Hawley, G. G. (revisor), A Condensed Chemical Dictionary, 8th
Edition, Van Nostrand Reinhold, New York, 1971.
230
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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.
1. Barn
A room-like condensation chamber for anhydrous phosphorus pentoxide.
2. Burden
The combined rock, coke, and silica feed to a phosphorus electric furnace.
3. 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. (82)
4. DCP
Dicalcium phosphate dihydrate, CaHP04_. 2H20.
5. Dry Process Phosphoric Acid
Phosphoric acid made from elemental phosphorus. Also call furnace acid.
6. Eutectic
The lowest or highest melting point of an alloy or solution of two or
more substances that is comprised of the same components. (82)
7. Ferropho sphorus
A by-product iron-phosphorus compound from phosphorus smelting, typically
containing 59 percent iron and 22 percent phosphorus. Symbolized as
Fe2P in this report.
8. Flux
A substance that promotes the fusing of minerals or metals or prevents
the formation of oxides. For example, in metal refining, lime is added
to the furnace charge to absorb mineral impurities in the metal, A slag
is formed that floats on the bath and is run off. (82)
231
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9. Furnace Acid
Phosphoric acid made from elemental phosphorus. Also called dry process
phosphoric acid.
10. Gangue
The minerals and rock mined with a metallic ore but valueless in themselves
or used as a by-product. (82)
11. Hydrolysis
A chemical reaction in which water reacts with another substance to form
one or more new substances. (82)
12. Immiscible
The property of one liquid being unable to mix or blend uniformly with
another.
13. MCP
Monocalcium phosphate monohydrate, Ca(H2P04_)2.H20
14. Nodule
A semi-fused agglomerated and calcined phosphate rock particle.
15. Phosphorus Mud
A sludge or emulsion of phosphorus, dust, and water.
16. Phosphorus Oxychloride
POC12-
17. Phosphorus Pentasulfide
P2S5_.
18. Phosphorus Pentoxide
P205_.
19. Phosphorus Trichloride
PC13.
232
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20. Phossy Water
Water containing or contaminated with elemental phosphorus. (3, 8)
(Depending upon phosphorus concentration, colloidal phosphorus and
turbidity may be present, visible P20^ fumes may be emitted in air, and
a characteristic odor may be present).
21. Process Waste Water
Any water that, during manufacturing or processing, comes into direct
contact with or results from the production or use of any raw material,
intermediate product, finished product, by-product, or waste product.
22. Slag
The fused agglomerate that separates in metal smelting and floats on the
surface of the molten metal. Formed by combination of flux with gangue
of ore, ash or fuel, and perhaps furnace lining. The slag is often the
medium by means of which impurities may be separated from metal. (82)
23. STP
Sodium tripolyphosphate, Na5P3_010.
24. TCP
Tricalcium phosphate, Ca_3_(P04_)2_.
25. Transport Water
(l) Water used to carry solids from a site in a slurry form.
(2) Water accompanying a chemical in transport that is either immiscible
with water or highly insoluble in water. The water acts as a blanket,
preventing contact of air or- other substances with the chemical.
26. Wet Process Phosphoric Acid
Phosphoric acid made from phosphate rock and sulfuric acid.
233
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,:r
TABLE 19
METRIC UNITS
CONVERSION TABLE
MULTIPLY (ENGLISH UNITS)
TO OBTAIN (METRIC UNITS)
ENGLISH UNIT ABBREVIATION CONVERSION ABBREVIATION METRIC UNIT
acre ac
acre - feet ac ft
British Thermal
. Unit BTU
British Thermal BTUAb
Unit/pound
cubic feet/minute cfm
cubic feet/second cfs
cubic feet cu ft
cubic feet cu ft
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/ mgd
day
mile mi
pound/square inch psig
(gauge)
square feet sq ft
square inches sq in
tons (short) ton
yard yd
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
(0.06805 psig +1)
0.0929
6.452
0.907
0.9144
ha
cu m
kg cal
kg c
cu m/min
cu m/min
cu m
1
cu cm
°C
m
1
I/sec
kw
cm
atm
kg
cu m/day
km
atm
sq m
sq cm
kkg
hectares
cubic meters
kilogram-calories
kilogram calories/
kilogram
cubic meters/minute
cubic meters/minute
cubic meters
liters
cubic centimeters
degree Centigrade
meters
liters
liters/second
kilowatts
centimeters
atmospheres
kilograms
cubic meters/day
kilometer
atmospheres
(absolute)
square meters
square centimeters
metric tons
(1000 kilograms)
meters
*Actual conversion, not a multiplier.
234
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