EPA-905/2-81-003
GUIDANCE FOR BAT-EQUIVALENT
CONTROL OF SELECTED TOXIC POLLUTANTS
Prepared by
JAMES W. PATTERSON, Ph.D.
PATTERSON ASSOCIATES, INC,
1540 N. State Parkway
Chicago, 111. 60610
for
ENFORCEMENT DIVISION
U.S. E.P.A.
REGION V
CHICAGO, ILL. 60604
-------
CONTENTS
CHAPTER PAGE
I. INTRODUCTION 1
II. REVIEW OF BPT-EQUIVALENT CONTROL 4
III. TREATMENT TECHNOLOGIES 12
IV. BAT-EQUIVALENT CONTROL 25
V. REFERENCES 32
UtS. Environmental Protection Agency
0.1
-------
LIST OF TABLES
TABLE PAGE
1. BPT Effluent Limitations Guidelines for
Arsenic 5
Range of Thirty-Day Average BPT Values,
mg/1 6
IESAG Standards for BPT-Equivalent Control
Technology Proposed to the State of Illinois. 9
Expected Effluent Values for Application
of Good Technology (30-day Average) 10
Example Proposed and Promulgated BATEA
Effluent Limitation Guidelines - Thirty-
Day Average 26
Comparison of Selected BPT and BAT Effluent
Limitations Guidelines - Thirty-Day Average . 28
Summary of BAT-Equivalent Treatment Tech-
nologies and Effluent Pollutant Levels
Achievable on a Thirty-Day Averaged Basis ... 29
111
-------
FOREWORD
As mandated by the Clean Water Act of 1977 and the Great Lakes Water
Quality Agreement of 1978, control of toxicants being discharged to
the Great Lakes Basin and elsewhere in Region V is a continuing con-
cern of the U.S. Environmental Protection Agency and the State pollution
control agencies. This manual is intended to provide guidance to federal
and state NPDES permit and pretreatment staffs in determining appropriate
limitations for the discharge of selected toxic pollutants in the waste-
water from industrial facilities where applicable Effluent Guidelines
regulations are not available.
Funding for this project was provided by the Great Lakes National
Program Office as authorized under Section 104(b) of the Clean Water Act
and as partial fulfillment of Article VI and Annex 12 of the Great Lakes
Water Quality Agreement.
iv
-------
I. INTRODUCTION
Regulations for the control of point source industrial pol"
lutants are predicated upon the performance achievable by in-plant
control measures and/or end-of-pipe wastewater treatment techno-
logies. For the fourteen pollutants considered in this report,
Arsenic Copper Mercury
Barium Cyanide Nickel
Cadmium Fluoride Silver
Chromium-Hexavalent Iron Zinc,
Chromium-Total
end-of-pipe treatment technology performance is usually concen-
tration limited.
For example, for precipitation/solids removal treatment of a
metallic pollutant, performance in a well designed and properly
operated treatment plant is constrained to that effluent quality
achievable through the conversion (by precipitation) of the
soluble metallic pollutant to a solid form, and the subsequent
removal of that solid phase. Neither complete conversion of the
soluble pollutant to a solid, nor total removal of that solid, is
possible with existing wastewater treatment technologies. Thus,
an end-of-pipe treatment technology-based effluent limitation
must incorporate factors reflecting both the degree of conversion
possible for soluble to solid phase, and the performance of the
solids separation technology. Where in-plant control measures
are applied, mass discharges of pollutants may be reduced even
below that level achievable by end-of-pipe treatment alone.
In making the final BPJ/BAT determinations, consideration
should be given to the reduction of wastewater volumes and/or
raw waste loads that could decrease pollutant mass loadings to
the environment. Such reductions might be achieved by wastewater
recycling systems, production process modifications, or individual
process waste stream pretreatment schemes.
Many different categories of industry discharge common
pollutants, and utilize common treatment technologies in the
control of these pollutants. The best foundation upon which to
-------
develop technology based effluent limitations is the performance
of well designed and properly operated treatment systems. In
such systems, among different industries, comparable effluent
concentrations are observed for identical pollutants. The excep-
tion to this situation occurs in instances of improperly designed
or constructed, or inadequately operated systems, or where plant-
unique characteristics of a wastewater interfere with the
performance of the treatment technology.
In this latter instance, particular effort on in-plant
control, or specialized treatment methods, may be required in
order to achieve effluent quality comparable to other treatment
systems. Typically, however, technology based effluent limita-
tion values, in the absence of site-specific wastewater char-
acteristics which interfere with treatment, should be uniform
when expressed on a concentration basis (1). In fact, experience
has shown, and the removal data confirm, that even when several
of the cited pollutants are present in the same wastewater the
BPT-equivalent and BAT-equivalent final concentrations for each
still can be achieved by using treatment conditions intermediate
between those optimum for each pollutant when treated alone.
Several states, including California, Delaware, and Illinois, have
successfully applied uniform industrial effluent standards for
many years. These uniform standards have been enforced equally
for all industrial categories within such states.
The objective of this report is to identify effluent con-
centrations and associated treatment technologies representing
BPT-equivalent and BAT-equivalent end-of-pipe control of the
fourteen pollutants cited above. The conclusions presented in
this report are based upon the results of several studies on
available wastewater treatment technologies and their associated
levels of full-scale performance. The first study was initiated
in 1970, in support of the development by the State of Illinois
Pollution Control Board of uniform industrial effluent standards
(2). The results of that original study were updated in 1973
(3) and again in 1974 (4). A new study was undertaken in 1976-77
-------
on behalf of the State of Illinois, to develop a document on
industrial pollution control which reflected the accomplishments
of industry in complying with the Federal Water Pollution Control
Act Amendments of 1972 (PL 92-500), which required that industry
achieve "Best Practicable Control Technology Currently Available,"
or BPT, by 1977 (5). Concurrent with that effort, proposed and
promulgated BPT mass-discharge guidelines were reviewed, and
converted to concentrations to provide a common basis for com-
parison (6). A review of the results of this program was pub-
lished in the professional literature in July, 1977, the date for
BPT compliance set by PL 92-500 (1). Finally, during 1980-81,
these studies have again been updated and a text is in preparation
which reflects the full range of technical options and performance
capabilities for over twenty industrial pollutants, including
those considered in this report (7). Thus, while this report,
by intent, is concise, the literature base underlying it is
extensive and represents almost continuous evaluation of treatment
technology performance data, beginning in 1970. Reference 5 in
particular, which is available through the National Technical
Information Service, provides a full technical documentation for
the conclusions presented in this report.
The achievement of BAT-equivalent effluent quality, as cited
in this report, requires concurrent stringent control of effluent
suspended solids. For most existing treatment plants, this level
of suspended solids control would necessitate the addition of a
filtration device. New plants, if properly designed, constructed
and operated, might achieve an equivalent effluent suspended
solids level without filtration.
-------
II. REVIEW OF BPT-EQUIVALENT CONTROL
During 1975 and 1976, a study was undertaken on behalf
of the State of Illinois to review and .evaluate the BPT stan-
dards proposed and promulgated by the USEPA (6). This evalu-
ation revealed that there were major differences in the levels
of pollution control performance proposed by the USEPA for
like pollutants for different categories of industrial dis-
chargers. These differences were observed for pollutants com-
mon to many industries, and occurred for pollutants generally
controlled by similar types of treatment technology, irres-
pective of the industrial wastewater source. Tables 1 and 2
demonstrate these differences among industry categories and
subcategories, for several example pollutants.
Under the requirements for BPT effluent limitations
guidelines, the inorganic constituent arsenic is regulated for
four industrial categories, two of which include multiple sub-
categories for which arsenic is regulated (Table 1). The
minimum arsenic guideline (on a concentration basis) was 0.01
mg/1, for the phosphorus-consuming (phosphorus trichloride)
subcategory of the Phosphate Manufacturing category. Highest
effluent arsenic levels, at 10.0 mg/1, were allowed for two
of the three subcategories of the Nonferrous Metals industry.
The third subcategory, however, had an arsenic limitation of
only 0.1 mg/1. For all categories for which arsenic was regu-
lated, the range of limitations was 0.01 to 10 mg/1, a 1000-
fold span. Within the Nonferrous Metals category alone, there
was a 100-fold range of arsenic standards.
-------
Table 1. BPT Effluent Limitations Guidelines for
Arsenic (1).
Industry Subcategory Guideline,
mg/1
Inorganic Boric Acid-Ore 0.5
Chemicals Mined Borax
Nonferrous Primary Copper Smelting 10.0
Metals Primary Copper Refining 10.0
Primary Zinc 0.1
Ore Mining & Ferroalloy Ores 0.5
Dressing Uranium, Radium, Vanadium 0.5
Phosphate Phosphorus Consuming 0.01
Similar anomalies were observed in the guidelines for
other inorganic pollutants. Copper was regulated for six
industrial categories encompassing 11 subcategories, and guide-
line concentrations ranged from 0.03 to 1.1 mg/1, a near 40-
fold span. Although the guidelines were fairly consistent
among subcategories of each category, one Nonferrous Metal sub-
category had a low copper guideline of 0.03 mg/1, while three
other subcategories had guidelines of 0.3 mg/1, a 10-fold
difference.
Table 2 summarizes the high and low guideline values for
nine inorganic pollutants. Arsenic and copper have been dis-
cussed. The data for the remaining seven pollutants demon-
strate that BPT guideline variability was typical, for all
pollutants listed in Table 2. The range of guideline values
for total chromium is 100-fold, total cyanide and zinc are 50-
fold, and others range down to 10-fold.
-------
Table 2. Range of Thirty-Day Average BPT Values, mg/1 (1).
Pollutant
Low Industry
Lowest
Value
Highest
Value
High Industry
Arsenic
Cadmium
Chromium(T)
Copper
Cyanide(T)
Fluoride
Lead
Nickel
Zinc
Phosphate 0.01
Ore Mining & Dressing 0.05
Rubber Processing 0.05
Nonferrous Metals 0.03
Ore Mining & Dressing 0.01
Phosphate 0.7
Rubber Processing 0.1
Ore Mining & Dressing 0.1
Ore Mining & Dressing 0.1
10.0
0.50
5.0
1.1
0.5
29.0
2.1
2.2
5.0
Nonferrous Metals
Nonferrous Metals
Leather Tanning
Inorganic Chemicals
Organic & Inorganic
Chemicals
Glass
Inorganic Chemicals
Inorganic Chemicals
Nonferrous Metals
-------
Since under PL 92-500 (and subsequent federal legislation,
i.e., the Clean Water Act of 1977), BPT and other effluent li-
mitations are technology-based, the spectrum of effluent limi-
tations proposed by the USEPA was surprising. In order to
further assess this situation, the State of Illinois established
in late 1975 the Illinois Effluent Standards Advisory Group,
IESAG. The charge to the IESAG included the following:
o To review the technical basis upon which Illinois
Effluent Standards had been based (and
such additional information as may be appropriate,
in order to) ... adequately define the limits and
economics of state-of-the-art (industrial) pol-
lution abatement technology.
o To determine, to the extent that the state-of-the-
art of wastewater treatment had advanced, what
concentrations of effluent pollutants could be
technologically achieved and at what costs.
o To assess the applicability of mass discharge
standards as an alternative to, or in concert with
Illinois policy of concentration-based standards.
o To make such proposals and recommendations as per-
tained to the consideration by IESAG of the above
items for transmittal to the Illinois Pollution
Control Board (IPCB) and the Illinois Environmental
Protection Agency (IEPA).
-------
The documentation upon which the IESAG based its consid-
erations included References 5 and 6 of this report. In its
report to the State of Illinois, IESAG concluded that for
common pollutants treated by identical technologies, uniform
concentration-based standards were desirable (8). Further,
from its evaluation of the capabilities and limitations of
that technology, IESAG recommended that the State of Illinois
establish the effluent standards listed in Table 3. In
essence, these recommendations represent BPT-equivalent limi-
tations. The single exception to the BPT-equivalent basis of
performance was for mercury. Recognizing the extreme environ-
mental hazards of mercury, IESAG recommended the imposition of
a mercury standard based upon best available technology,
identified as ion exchange or coagulation treatment. Thus,
the recommended mercury standard in Table 3 is BAT-equivalent.
Technology associated with the other standards presented in
Table 3 are,
Arsenic Precipitation/Clarification
Barium Precipitation/Clarification
Cadmium Precipitation/Clarification
Chromium Chemical Reduction or Ion
(hexavalent) Exchange
Chromium (total) Precipitation/Clarification
Copper Precipitation/Clarification
Cyanide Alkaline Chlorination
Fluoride Lime Precipitation/
Clarification
Iron Precipitation/Clarification
Lead Precipitation/Clarification
-------
Table 3. IESAG Standards for BPT-Equivalent Control
Technology Proposed to the State of Illinois (8).
Pollutant
Arsenic
Barium
Cadmium
Chromium
Chromium
Copper
Cyanide
Fluoride
Iron
Lead
Mercury
Nickel
Silver
Zinc
Concentrati
on, mg/1
Thirty-Day Maximum
Averaged 2 4 -Hour Composite
(total)
(total)
(total)
(hexavalent)
(total)
(total)
(total)
(total)
(total)
(total)
(total)
(total)
(total)
(total)
0.25
2.0
0.15
0.1
1.0
0.5
0.1
15.0
2.0
0.2
0.003
1.0
0.1
1.0
0.5
4.0
0.3
0.2
2.0
1.0
0.2
30.0
4.0
0.4
0.006
2.0
0.2
2.0
-------
10
Nickel
Silver
Zinc
Precipitation/Clarification
Ion Exchange
Precipitation/Clarification
Table 4 compares these IESAG recommended BPT-equivalent
limitations with the range of BPT limitations proposed and
promulgated by the USEPA.
Table 4. Expected Effluent Values for Application
of Good Technology (30-day Average).
Pollutant
Type
Treatment
IESAG Range of
Recommended BPT Values,
Standards, mg/1
mg/1
Arsenic Coprecipitation 0.25 0.01-10.0
Cadmium Precipitation 0.15 0.05- 0.5
Chromium(T) Precipitation 1.0 0.05- 5.0
Copper Precipitation 0.5 0.03- 1.1
Fluoride Lime Precipitation 15.0 0.7 -29.0
Lead Precipitation 0.2 0.1-2.1
Nickel Precipitation 1.0 0.1-2.2
Zinc Precipitation 1.0 0.1 - 5.0
In support of the development of BAT-equivalent control
limitations for this report, the BPT-equivalent limitations
recommended by IESAG (Table 3) have been reviewed. Technical
performance data reported since the period of the IESAG study
(7) has been considered in this review. There is no data avail-
able at this time to support revision of the IESAG recommenda-
tions as BPT-equivalent limitations.
Table 3 presents BPT-equivalent standards for 30-day aver-
age and 24-hour maximum discharge. The ratio of the two values
-------
11
is 1:2. This ratio reflects the performance expected for well
designed and properly operated wastewater treatment systems.
-------
12
III. TREATMENT TECHNOLOGIES
This Chapter provides a brief synopsis of the most effec-
tive treatment technologies established in full-scale practice
for each of the subject pollutants. Detailed discussions of
these technologies have been published (4,5).
Arsenic. In aqueous systems, arsenic exists as either the
arsenite ion (AsO_ ; As ) or arsenate ion (AsO ~ ; As ).
Treatment methods for arsenic include lime' or sulfide precipi-
tation, or coprecipitation (sometimes described as precipitation/
coagulation) with iron or aluminum hydroxide. The oxidation
state of the arsenic influences the efficiency of each of these
treatment processes. Sulfide precipitation is partially effec-
tive for arsenate, but ineffective for arsenite. Lime precipi-
tation is preferred over sulfide precipitation due to higher
treatment efficiency, but has the disadvantage of high required
treatment pH (pH 12+). Caustic precipitation is less effective
than lime. Iron or aluminum coprecipitation is more effective
than is lime precipitation, but has the disadvantage of yield-
ing greater quantities of sludge, which is often more difficult
to dewater than is the lime precipitate sludge. Both iron and
aluminum coprecipitation are strongly influenced by treatment
pH, with aluminum treatment efficiency declining at pH above 7,
and iron treatment efficiency declining above pH 9. Both pro-
cesses perform better on arsenate than arsenite.
Thus, for all precipitation treatment processes for arsenic,
enhanced performance is observed when the arsenic is present
-------
13
as arsenate. Most effective treatment may require a chemical
oxidation step, to convert any arsenite to arsenate. Chlori-
nation has been used to achieve this oxidation. Each of the
precipitation processes is, in addition, influenced by the
efficiency of suspended solids removal. Clarification nor-
mally provides adequate solids removal, due to the quantities
of lime, or iron or aluminum salts required for precipitation.
Barium. Barium is infrequently encountered in industrial
wastewaters, and the treatment literature on barium is scant.
Barium sulfate precipitation has been reported, with enhanced
gravity clarification of the fine barium sulfate solids achieved
upon addition of a coagulant such as an iron salt. Barium sul-
fate is relatively soluble, but addition of a salt such as
sodium or iron sulfate in excess will reduce barium solubility
and thereby improve treatment efficiency. When coagulants are
employed, gravity clarification is effective for solids remo-
val, and little gain in effluent quality is observed through
filtration. The barium sulfate precipitation reaction appears
to reach equilibrium rather slowly, and adequate reaction time
in the treatment process is essential.
Cadmium. Precipitation is the principal treatment process
employed for cadmium. Most effective precipitation treatment
is achieved between pH 9 and 12, and close process control is
required to promote maximum precipitation. In wastewaters of
moderate to high carbonate, or to which supplemental carbonate
has been added, the extremely insoluble cadmium carbonate is
-------
14
formed, with best treatment near pH 10. Cadmium plating wastes
typically contain cyanide, and pretreatment to completely
destroy the cyanide is necessary for effective cadmium preci-
pitation. Lime precipitation appears to yield a better settling
precipitate than does caustic, and filtration of caustic treated
wastes may be required to achieve an effluent quality comparable
to that obtained with gravity clarification of a lime treated
waste. Although it has been reported that ion exchange treat-
ment yields effluent levels equal to or less than good precipi-
tation treatment, there is inadequate full scale data in the
technical literature to support this claim.
Hexavalent Chromium. Reduction of hexavalent chromium
from a valence state of plus six to plus three, and subsequent
hydroxide precipitation of the trivalent chromic ion, is the
most common method of hexavalent chromium control. Some indus-
tries utilize ion exchange for chromic acid control and re-
covery. The standard reduction treatment technique is to lower
the waste stream pH to 2.0-3.0 with sulfuric acid, and convert
the hexavalent chromium to trivalent chromium with a chemical
reducing agent such as sulfur dioxide, sodium bisulfite or
ferrous sulfate. One common source of the latter is spent pickle
liquor and, in the subsequent precipitation step the iron will
function as a coagulant at the expense of about four-fold
greater sludge production. The efficiency of conversion of the
hexavalent to trivalent chromium is interdependent upon the
allowed reaction time, treatment pH, and type and concentration
-------
15
of reducing agent used. Close process control is necessary to
achieve effective chromium reduction.
Ion exchange has been employed successfully for hexavalent
chromium control. In the ion exchange system wastewater pH is
a critical factor in successful treatment. At pH below 4, the
oxidizing power of the chromic acid attacks the resin. At pH
above 6, the ratio of dichromate to chromate increases. Since
most anion exchange resins are less selective for dichromate
than for chromate, ion exchange efficiency decreases.
Total Chromium. Total chromium is the sum of the hexava-
lent plus trivalent chromium. Where hexavalent chromium is a
precurser form converted to trivalent chromium and the conver-
sion has been ineffective, the total residual chromium may be
predominately in the hexavalent form. Thus, in chromium con-
trol by reduction-precipitation, effective treatment requires
the successful accomplishinent of three sequential steps:
hexavalent chromium reduction to trivalent chromium; precipi-
tation of the trivalent chromium; and removal of the precipitated
chromium. Treatment performance will deteriorate due to incom-
plete achievement at any one of these three stages.
Precipitation of trivalent chromium is most effective at
pH 8.5-9.5 although, due to the presence of other metals with
different pH optima in the typical metals-bearing wastewater,
an average waste stream treatment pH of about 8 is often
reported for mixed chromium-metals wastes. Lime and caustic
are the pH control chemicals of choice, with caustic being most
common in newer or upgraded treatment plants due to its ease
-------
16
of handling. In the gravity clarification stage, lime treated
wastes seem to settle better than do caustic treated wastes,
and filtration of these latter wastes may be necessary to
achieve suspended solids control equal to gravity clarification
of the lime treated wastewater. Lime sludge may be two to
three fold greater (dry weight basis) than a caustic sludge,
for treatment of the same wastewater. Thus, in precipitation
treatment while lime treatment may not necessitate filtration,
the choice may be caustic treatment plus filtration, with the
expense of the filter offset by greater ease of caustic hand-
ling, and reduced volumes of caustic sludge. These same trade-
offs apply for precipitation treatment of many metals.
Copper. The standard treatment method for copper is pre-
cipitation. Cyanide, or moderate to high concentrations of
carbonate will complex with copper, and prevent its precipita-
tion. Although most authorities agree that optimum copper
precipitation occurs between pH 9.0 and 10.3, effective treat-
ment has been observed at much lower operating pH values. Poor
performance in copper treatments seems more often to result
from insufficient solids removal than from inadequate precipita-
tion process pH control.
Both lime and caustic are widely used to precipitate cop-
per. In copper sulfate wastewaters, the addition of lime may
result in calcium sulfate formation. In this instance filtra-
tion should be avoided, since the slowly forming calcium sul-
fate will tend to cement the filter. With lime treatment,
gravity clarification can provide as effective treatment as,
-------
17
in contrast for some other metals, can caustic. The caustic
sludge yield can be significantly less than that from lime
treatment, although the caustic sludge dewatering properties
are poorer than are the lime sludges. In summary, effective
copper precipitation treatment can be achieved over a fairly
wide pH range, and close pH control is thus not critical.
Gravity clarification is effective in solids removal, and little
or no benefit is gained by effluent filtration. The result is
that BAT-equivalent control is comparable to BPT-equivalent
control, being based upon the same wastewater treatment tech-
nology.
Cyanide. Cyanide treatment results reported for full-scale
systems are among the most erratic observed for any inorganic
industrial pollutant. This is primarily due to the variety of
complexes which form with cyanide within different wastewaters,
and the extent to which these cyanide complexes differ in their
response to the standard cyanide destruction techniques. These
differences are reflected in the higher effluent limitations
normally promulgated for total cyanide than for cyanide amenable
to chlorination treatment.
Several methods of treating cyanide wastes are in current
use, although the most wide-spread is alkaline chlorination.
Most effective alkaline chlorination is through two-stage
treatment. The first stage is designed and operated to maximize
conversion of cyanide to cyanate, which is destroyed by addi-
tional chlorination in the second stage. There are reports
-------
18
that equivalent treatment can be achieved in a single stage
process, although some results suggest that the single stage
approach suffers from a lack of process stability. Close pro-
cess control, and automated pH and chlorine dosage are neces-
sary to accomplish a high degree of cyanide treatment. In the
first stage, a pH of 10 or higher, and a reaction period of
up to two hours is necessary. To avoid formation of solid
cyanide precipitate, the waste must be thoroughly agitated dur-
ing treatment. In the second stage, an operating pH of 8.0-
8.5 and reaction period of up to one hour is necessary, with
sufficient chlorine addition to force cyanate oxidation.
Other cyanide treatment processes include ozone oxidation
and electrolytic decomposition. The former has had limited
field application and the latter process is used primarily for
concentrated cyanide baths, with residual treatment by alkaline
chlorination.
Fluoride. Treatment options for fluoride are limited to
two alternative precipitation processes, with significant dif-
ferences in performance and associated sludge yield. Lime
precipitation to form calcium fluoride has been the dominant
technology for fluoride control. At the high treatment pH
required (pH 12+), and associated high lime dosage filtration
is risky, due to the tendency of the gravity clarified effluent
to cement the filter. Thus, within the solubility constraints
associated with calcium fluoride formation, most effective
treatment with lime depends upon highly efficient solids removal
by gravity clarification. The precipitated solids are reported
-------
19
to have poor settling characteristics. This lime precipitation/
clarification technology provided the basis for BPT effluent
limitation guidelines.
The second treatment alternative is fluoride removal by
alum addition; essentially a coprecipitation process. Much
lower effluent fluoride levels are achieved with alum copreci-
pitation than with lime precipitation and best removal appears
to result at pH 6-7. Treatment efficiency in this pH range
reflects the alum dosage (mg/mg fluoride), with enhanced treat-
ment at higher (200+ mg/mg) alum dosages. A major disadvantage
of the process is the voluminous sludge produced, which even at
moderate alum dosages can represent up to 40% of the original
wastewater volume treated. This sludge yield represents such
a serious problem that lime precipitation has remained the
treatment technology of choice of both regulatory agencies and
industry.
Iron. In aqueous systems, iron exists in the ferric (Fe )
or ferrous (Fe ) form, depending upon conditions of pH and
dissolved oxygen concentration. In precipitation treatment,
ferrous iron is more soluble than ferric iron. Therefore, most
effective iron precipitation treatment incorporates conversion
of any ferrous to ferric iron, before precipitation. At neu-
tral pH and in the presence of oxygen, ferrous iron rapidly
oxidizes to the ferric form, which readily hydrolyzes to the
insoluble precipitate, ferric hydroxide. Many iron wastewaters
such as pickling rinses are both highly acidic and contain pre-
dominately the ferrous form of iron.
-------
20
The principal treatment process for iron is oxidation-
precipitation-clarification. The iron wastewater is first
neutralized to pH near 7, where ferrous iron oxidation rapidly
occurs and where the solubility of ferric hydroxide is at its
minimum. Following or simultaneous with pH adjustment, the
waste is aerated to provide oxygen for the iron oxidation pro-
cess. Where iron complexing agents are present in the waste,
the rate of oxidation is slowed. Sufficient aeration time is
therefore essential in order to achieve a high degree of oxida-
tion. Freshly precipitated ferric hydroxide has a characteris-
tic low specific gravity, which makes settling difficult without
long clarifier detention time or additional treatment such as
filtration. Lime is frequently used for pH adjustment and,
where sulfuric acid is present as in a pickling waste, large
quantities of calcium sulfate are also precipitated. In some
industrial wastes, ferrous and ferric iron may exist in the
presence of cyanide. Extremely stable iron cyanide complexes
result. Such species present considerable difficulties for both
iron and cyanide treatment. No truly effective treatment method
has been reported for such wastes.
Lead. Precipitation treatment of lead is extremely effec-
tive, except in instances such as the tetraethyl lead industry
where significant concentrations of organic lead occur. Lead
in the organic form is not amenable to precipitation, and the
organic component must be destroyed by chemical means such as
chlorination, before the lead can be precipitated. Although
-------
21
the literature contains conflicting values of pH options for
lead precipitation (ranging from pH 6 to above pH 10), there
is strong evidence that best precipitation treatment occurs in
the pH range 9-10. At this high treatment pH, other metals in
the wastewater with lower pH optima may not be effectively
precipitated, however. Lead wastewaters precipitated with lime
have good settling properties, while caustic treated wastes may
require filtration to achieve an equivalent effluent lead level.
The expense of caustic plus filtration may be offset by the
lesser sludge volumes produced with caustic treatment.
Mercury. Many types of mercury treatment technology have
been described in the technical literature. Among the most
effective are the ion exchange and coagulation treatment pro-
cesses. Typically, ion exchange treatment of mercury involves
the formation of a negatively charged mercuric chloride complex
by addition of chlorine or hypochlorite (to oxidize any metallic
mercury present), or chloride salts, and removal of the mer-
curic chloride complex or an anion exchange resin. Most experi-
ence with ion exchange treatment has been with chlor-alkali wastes
which contain high background chloride levels.
Control of mercury by coagulation has been reported for
a variety of mercury-containing wastewaters. The process has
been applied with success to both organic and inorganic mercury. »
Iron and alum coagulants are reported to produce equivalent
mercury removal results, although the alum coagulant may display
poorer settling properties than the iron coagulant. In both
instances effluent filtration is necessary to achieve best
-------
22
treatment results. A disadvantage of coagulation treatment is
that large quantities of mercury-contaminated iron or aluminum
hydroxide sludge are produced.
Because of the large sludge quantities generated, activated
carbon adsorption is sometimes considered as an alternative to
coagulation. However, carbon adsorption is less effective than
ion exchange or coagulation at higher influent mercury levels,
and it appears that carbon treatment yields effluent mercury
levels comparable to ion exchange or coagulation only when
initial mercury levels are below 50 yg/1.
Nickel. In waste streams, nickel exists predominately as
the soluble ion. In the presence of complexing agents such as
ammonia, EDTA, or cyanide, nickel can form extremely stable
soluble complexed species which interfere with conventional
precipitation treatment.
Precipitation treatment is the standard practice for con-
trol of nickel in industrial wastes, although in specialized
circumstances such as for recovery in plating plants, reverse
osmosis has been utilized. This later technology, although
effective, is principally utilized for alkaline nickel wastes.
Best precipitation treatment is achieved at a pH above 9.5,
which pH level may cause deterioration of the precipitation
treatment of other metals in the wastewater having significantly
lower pH options. Even when lime is employed as the treatment
chemical, nickel hydroxide precipitates have rather poor
settling characteristics. Poor performance in nickel treatment
more often results through inadequate solids separation than
-------
23
through incomplete precipitation of the soluble nickel. Unless
extended clarifier detention time is provided, filtration
appears necessary to achieve good control of total nickel.
Silver. Treatment technology for silver is influenced
more by the value of the recovered metal than by the limitations
of discharge permits. Many treatment/recovery techniques are
employed, although the final polishing step is often ion ex-
change. Other processes include evaporation recovery, copre-
cipitation with ferric chloride, and silver chloride precipita-
tion. This latter process is least efficient. Coprecipitation
and ion exchange yield comparable results, and evaporative
treatment results in complete recovery. Evaporation is rarely
economical for dilute silver wastewaters.
Zinc. Precipitation is the standard of practice in treat-
ment of zinc wastewaters. There is a great deal of confusion
in the technical literature regarding the optimum pH for zinc
precipitation. Optimum performance has been cited at pH values
as low as 9.0 to 9.5, and as high as pH 11 and above. Zince
is an amphoteric metal, with increasing solubility at both higher
and lower pH. It is possible that constituents (such as com-
plexing agents) other than zinc in the various wastewaters may
influence zinc precipitation efficiency as a function of pH.
As with other metal wastewaters, both lime and caustic are used „
as the precipitating chemical. The effluent quality of full-
scale zinc treatment systems appears to be influenced most by
the efficiency of precipitate suspended solids removal and many
such systems employing only gravity clarification for solids
-------
24
control exhibit high effluent solids and associated high ef-
fluent zinc. Therefore, for zinc wastes, best available tech-
nology requires determination of and treatment at the best pH
value for that specific wastewater, plus efficient suspended
solids removal by gravity clarification and/or filtration.
-------
25
IV. BAT-EQUIVALENT CONTROL
Under the authority of the Clean Water Act of 1977, the
USEPA is developing BAT effluent limitations guidelines for
industrial point source dischargers. Guidelines for only a few
industrial categories have been published to date. Example
guidelines are presented in Table 5. As was the case for BPT
guidelines, a range of concentration values is observed for
each pollutant regulated. The range of guidelines for copper
is most extreme, at 200-fold.
Table 6 compares BPT guidelines for several pollutants with
the BAT values listed in Table 5, for three industry categories.
Although it might be expected that BAT performance should be
equal to or more restrictive than BPT, such is not consistently
the case, (see total chromium, fluoride). For several of the
cases presented in Table 6, BPT and BAT values are equal. For
most instances where BAT is below BPT, the reduction is fairly
modest. The exception in Table 6 is nickel, with a BPT guide-
line of 2.20 mg/1 versus a BAT guideline of 0.10 mg/1.
On the basis of the BAT information available to date, it
appears that a pattern of varying concentration based values
will result through the USEPA efforts. This Chapter of this
report presents single BAT-equivalent values for each subject
pollutant, developed through a technology performance evalua-
tion. These BAT-equivalent effluent values are summarized in
Table 7, for 30-day average performance. Based upon performance
data of full-scale systems, a 24-hour maximum discharge value
of 1.5 to 2.0 times the 30-day average (Table 7) is recommended.
-------
Table 5. Example Proposed and Promulgated BATEA Effluent Limitation Guidelines - Thirty-
Day Average.
Industry Category Document As
Inorganic Chemicals13 1*1*0/1-79/007
Chlor-Alkali Mercury Cells 0.10
Chlor-Alkali Daiphragm Cells
Hydrofluoric Acid
Sodium Bichromate
Titanium Dioxide-Sulfate
Process 0.50
Titanium Dioxide-Chloride
Process
Titanium Dioxide-Chloride
Ilmenite Process 0.50
Aluminum Fluoride
Chrome Pigments
Copper Sulfate 0.50
Hydrogen Cyanide
Free
Total
Nickel Sulfate
Sodium Hydrosulfite
Sodium Bisulfite
Cd Cr-H Cr-T
0.05
0.05
O.OU
0.05 0.32
0.15 O.lU
O.lU
0.10 0.10
o.oU
0.19 1.10
0.05 0.05
0.05
0.10
0.11
Cu CN
0.05
o.Uo
0.009
0.50
0.50
o.Uo
o.Uo
0.27
U.OO
o.Uo
0.50
F Fe Pb
0.16
0.22
33 0.06
2.50 0.30
2.1*0
2.50 0.30
30
1.1*0
0.05
0.05
0.30
0.30
Hg Ni
O.OU8 0.10
0.10
0.15
0.17
0.20
0.20
0.17
0.17
0.10
0.20
0.20
0.20
Ap; Zn
0.07 0.15
0.1*0
0.52
0.1*7
0.50
0.50
1.10
0.1+0
o.Uo
0.50
0.50
K)
-------
Table 5. (Continued).
Industry Category
Textile Mills
(all subcategories)
Gum & Wood Chemicals
Rosin Based Derivatives
Document As
l*UO/l-79/022b
UUo/l-79/078b
Cd Cr-H Cr-T Cu CN F Fe Pb Hg Ni Ag Zn
0.50 0.50 1.00
1.80
Sulfate Turpentine
Leather Tanning &
Finishing
Steam Electric Power
Pulp, Paper & Paperboarda
Range - Minimum
- Maximum
Median Value
UUO/1-79/016
Ul»0/l-80/029b
1.80
1.80
1.00
1.00
1.80
3.00
0.10 0.05 0.05 O.OU 0.009 0.50 30 1.00 0.05 O.OUB 0.10 0.07 0.15
0.50 0.19 1.80 1.80 It.00 33 2.50 l.Uo 1.80 3.00
0.50 0.10 - 0.10 0.1*0 - - 2.50 0.30 - 0.17 - 0.50
Daily maximum values reported. No standards proposed for 30-day consecutive average performance.
BAT and PSES mass discharge limitations are equal. PSES limitations were proposed on both a concentration and
a mass discharge basis. The PSES limitation values are presented in this Table.
to
-j
-------
Table 6. Comparison of Selected BPT and BAT Effluent Limitations Guidelines - Thirty-
Day Average.
Pollutant
Chromium (Hexavalent )
Chromium( Total )
Copper
Fluoride
Iron
Lead
Nickel
Zinc
Industry Category
Inorganic Chemicals
Inorganic Chemicals
Leather Tanning &
Finishing
Inorganic Chemicals
Steam Electric Power
Inorganic Chemicals
i
t
Inorganic Chemicals
Steam Electric Power
Inorganic Chemicals
Inorganic Chemicals
Inorganic Chemicals
Subcategory
Sodium Bichromate
Chrome Pigments
Sodium Dichromate
Copper Sulfate
Metal Cleaning
Aluminium Fluoride
Hydrofluoric Acid
Titanium Dioxide
Metal Cleaning
Chrome Pigments
Copper Sulfate
Chrome Pigments
BPT(Ref.6)
0.05
0.50
O.UU
1.00-
3.60
1.10
1.00
20.0
15-0
U.OO
1.00
2.10
2.20
I*. 00
BAT (Tab. )
0.05
1.10
0.32
1.80
o.Uo
1.00
30.0
33-0
2.50
1.00
1.UO
0.10
1.10
ro
oo
-------
Table 7. Summary of BAT-Equivalent Treatment Technologies and Effluent Pollutant Levels
Achievable on a Thirty-Day Averaged Basis.
Pollutant
Arsenic
Barium
Cadmium
Chromium,
Hexavalent
Chromium,
Total
Copper
Cyanide
Fluoride
Iron
BAT-Equivalent
Concentration, mg/1
0.20
1.00
0.10
0.05
0.50
o.uo
0.10
10.0
1.50
Treatment Technology
Arsenite Oxidation; Lime Precipitation, or Iron or
Alum Co-Precipitation; Gravity Clarification
Sulfate Precipitation; Coagulation; Gravity
Clarification
High pH Precipitation; Gravity Clarification, or
Filtration Where Caustic is Substituted For Lime
Acidic Reduction To Trivalent Chromium or Ion
Exchange at pH Below 6.0
Precipitation; Gravity Clarification, except
Filtration may be Required for Caustic Tr'-ated
Wastewaters
Precipitation; Gravity Clarification
Two-Stage Alkaline Chlorination
High pH Lime Precipitation; Gravity Clarification
Oxidation at Neutral pH of Ferrous to Ferric Iron;
Precipitation; Gravity Clarification or
Filtration
to
vo
-------
Table 7. (Continued).
Pollutant
Lead
Mercury
Nickel
Silver
BAT-Equivalent
Concentration, mg/1
0.15
0.003
0.75
0.10
Treatment Technology
High pH Precipitation; Gravity Clarification, or_
Filtration where Caustic is Substituted for Lime
Ion Exchange or Coagulation plus Filtration
High pH Precipitation; Gravity Clarification and/or
Filtration
Ion Exchange or FErric Chloride Coprecipitation
plus Filtration
Zinc
0.50
Optimized Precipitation pH; Gravity Clarification
and/or Filtration
-------
31
BAT-equivalent effluent quality requires both in-plant
water conservation, and maximum efficiency of operation of
well designed and properly constructed and maintained treatment
systems. In some instances, for precipitated solids removal,
clarification alone can yield an effluent quality equal to
final effluent filtration. However, these are rather rare
instances, and filtration would normally be required to achieve
the BAT-equivalent effluent pollutant levels cited in this
Chapter. An advantage of filtration is that it normally pro-
vides more consistent effluent quality than does clarification
alone, since clarifiers are prone to upset.
Arsenic. BAT-equivalent treatment technology for arsenic
can be achieved by oxidative conversion of arsenite to arsenate,
followed by either lime precipitation at pH 12 or iron copreci-
pitation at pH below 9, and gravity clarification. In a well
designed and properly operated treatment system, an effluent
arsenic level of 0.20 mg/1 is obtainable. Filtration would pro-
vide only marginal enhancement of the effluent quality.
Barium. Sulfate precipitation of barium is the only well
established treatment technology available. BAT-equivalent
treatment requires sufficient detention time to achieve equili-
brium formation of the barium sulfate solids, and the use of
a coagulant such as iron or aluminum sulfate to control suspended'
solids removal by gravity clarification. A BAT-equivalent bar-
ium effluent quality of 1.0 mg/1 is achievable.
-------
32
Cadmium. BAT-equivalent control of cadmium results through
complete destruction of cyanide where present, followed by lime
precipitation plus gravity clarification or caustic precipita-
tion plus filtration. In a closely controlled treatment plant
with highly efficient solids removal, an effluent cadmium level
of 0.10 mg/1 is achievable.
Hexavalent Chromium. Chemical reduction of hexavalent to
trivalent chromium followed by precipitation of the trivalent
chromic hydroxide is a well established technology. The pro-
cess, with adequate reaction time, and close process control of
pH and reducing agent dosage, can achieve a BAT-equivalent
hexavalent chromium concentration of 0.05 mg/1. Ion exchange
treatment, when wastewater pH is controlled to minimize forma-
tion of dichromate, can achieve an effluent hexavalent chromium
concentration equal to the chemical reduction process.
Total Chromium. BAT-equivalent control for total chrom-
ium will yield an effluent chromium level of 0.5 mg/1. This
treatment is precipitation and clarification. Where caustic is
used as the treatment chemical, effluent filtration may be
required to achieve the cited concentration.
Copper. Treatment by precipitation and gravity clarifica-
tion will yield BAT-equivalent control of copper to an effluent
level of 0.4 mg/1. Although close process pH control does not
appear to be critical, effective solids separation is necessary
to achieve this effluent quality.
-------
33
Cyanide. Alkaline chlorination treatment represents BAT-
equivalent control of cyanide, and in the absence of extremely
strong metal-cyanide complexes, can achieve an effluent cyanide
concentration of 0.10 mg/1. In recognition of the differences
in chemical forms and their associated treatability of cyanide
in different process streams, cyanide treatment must often be
evaluated for individual dischargers where BAT-equivalent con-
trol technology cannot achieve 0.1 mg/1.
Fluoride. Lime precipitation plus gravity clarification
represents BAT-equivalent control technology for fluoride.
Effective treatment requires high treatment pH and lime dosage,
as well as efficient solids removal, and can achieve an effluent
fluoride concentration of 10 mg/1.
Iron. BAT-equivalent control of iron requires efficient
oxidation of ferrous to ferric iron, followed by precipitation
and solids removal. In most instances, solids removal by
gravity clarification will yield an effluent iron concentration
of 1.5 mg/1. Rarely, filtration may be required in order to
achieve this effluent quality.
Lead. Effective treatment of lead requires precipitation
at pH near 10, plus effective suspended solids removal. Where
lime is employed as the treatment chemical and adequate clari-
fier detention time is provided, an effluent lead level of 0.15
mg/1 is achievable. With caustic used in lieu of lime, a poorer
settling precipitate results and filtration may be necessary to
achieve an effluent lead concentration of 0.15 mg/1.
-------
34
Mercury. BAT-equivalent control of mercury can be achieved
by ion exchange treatment, or by coagulation with effluent fil-
tration. At raw wastewater mercury levels below about 50 yg/1,
activated carbon adsorption will perform equivalent to the other
two processes. An effluent mercury level of 3 pg/1 is achiev-
able in well designed and properly operated treatment systems.
Nickel. Precipitation treatment of nickel is effective in
converting the soluble ion to a solid nickel hydroxide phase.
However, the precipitate appears to have poor settling charac-
teristics and effective solids removal is accomplished only
with either long clarifier detention time or by filtration.
Either approach can achieve an effluent nickel level of 0.75 mg/1,
Silver. BAT-equivalent control of silver can be accom-
plished by either ion exchange or ferric chloride coprecipita-
tion treatment. Either method will yield an effluent silver
level of 0.10 mg/1. With coprecipitation, effluent filtration
may be required to achieve this effluent silver level.
Zinc. The efficiency of precipitation treatment for zinc
is influenced by the treatment pH (with the optimum pH value
apparently varying among different wastewaters) and efficient
suspended solids removal. A BAT-equivalent effluent zinc level
of 0.5 mg/1 is achievable when these conditions are met.
-------
35
V. REFERENCES
1. Patterson, J.W., "Technical Inequities in Effluent
Limitations Guidelines," Journal, WPCF, 49:7:1586,
July, 1977.
2. Patterson, J.W., "Wastewater Treatment Technology,"
Illinois Institute for Environmental Quality, 1971.
3. Patterson, J.W., "Wastewater Treatment Technology, 2nd
Edition," Illinois Institute for Environmental Quality,
1973.
4. Patterson, J.W., Wastevater Treatment Technology, Ann
Arbor Science Publishers, Inc., Ann Arbor, MI., 1975.
5. Patterson, J.W., "Technology and Economics of Industrial
Pollution Abatement," Illinois Institute for Environmental
Quality Document No. 7622, 1977. (Available through
National Technical Information Service as NTIS Publication
PB 279 338/A5).
6. Patterson, J.W., "Directory of Federal and State Water
Pollution Standards," Illinois Institute for Environ-
mental Quality Report No. 77/06, October, 1977.
7. Patterson, J.W., Wastewater Treatment Technology, 2nd
Edition; Industrial Practice (in preparation), Ann
Arbor Science Publishers, Inc., Ann Arbor, MI. (1981).
8. Illinois Effluent Standards Advisory Group, "Evaluation
of Effluent Regulations of the State of Illinois,"
Illinois Institute for Environmental Quality Report
No. 76/21, June, 1976.
9. Additional References: Development Documents of the
Effluent Guidelines Division, USEPA.
U.S. Environmental Protection Agency '•
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th FtoOf
Chicago, IL 60604-3590
-------
TECHNICAL REPORT DATA "
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-905/2-81-003
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Guidance for BAT-Equivalent Control of Selected
Toxic Pollutants
5 REPORT DATE
May 1981
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James W. Patterson
8 PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Patterson Associates, Incorporated
1540 North State Parkway, Unit 13-A
Chicago, Illinois 60610
10 PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
Purchase Order
No. 54239NASX
12. SPONSORING AGENCY NAME AND ADDRESS
Permit Branch (5EP)
U.S. Environmental Protection Agency
230 South Dearborn Street
Chicago, Illinois 60604
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Project Contact: Jon Barney (312) 886-6109 Funding provided by the Great Lakes
National Program Office under Section 104(b) of the Clean Water Act.
16. ABSTRACT ~ ~~~ ~~
This manual is intended to provide guidance to federal and state NPDES permit and
pretreatment staffs in determining appropriate limitations for the discharge of
selected toxic pollutants in the wastewater from industrial facilities where appli-
cable Effluent Guidelines regulations are not available. From his extensive knowl-
edge and comprehensive review of the treatment technology available to industry, the
author has determined, in his best professional judgement, the final effluent con-
centrations that can be achieved using his estimate of best available technology
(BAT) for the following toxic pollutants: arsenic, barium, cadmium, hexavalent
chromium, total chromium, copper, cyanide, fluoride, iron, mercury, nickel, silver,
and zinc. It is concluded that, aside from a few extraordinary situations involving
unusual chemical interferences, the treatability levels provided in the manual should
be applicable, independent of industrial category.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Best Available Technology
BAT
Toxic pollutants
Metals
Cyanide
Wastewater
Treatment
Pollution control
NPDES
Permits
Treatability
8. DISTRIBUTION STATEMENT
19 SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
40
Unlimited
20 SECURITY CLASS (Tillspage)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
------- |