PRETREATMENT OF HAZARDOUS WASTE
By
E. Timothy Oppelt
Chief, Thermal Destruction Branch
Alternative Technologies Division
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
For Presentation At The
United States of America/Spain Joint Seminar
On The
Treatment And Disposal Of Hazardous Wastes
Madrid, Spain
May 19-22, 1986
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NOTICE
This document has been reviewed in accordance with U.S. Environmental
Protection Agency policy and approved for publication. Mention of trade
names or commercial products does not constitute endorsement or recommenda-
tion for use.
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TECHNICAL REPORT DATA
(ftttsi n*d liutnictiont on the rtvene be fort comptttintl
1. REPORT NO.
2.
. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
PRETREATMENT OF HAZARDOUS WASTE
I. REPORT OATS
N/A
S. PERFORMING ORGANIZATION CODE
N/A
7. AUTMOR(S)
I. PERFORMING ORGANIZATION REPORT NO.
E. Timothy Oppelt
N/A
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency, Hazardous
Waste Engineering Research Laboratory, Alternative
Technologies Division, Thermal Destruction Branch,
Cincinnati, Ohio 45268
10. PROGRAM ELEMENT NO.
D109
11. CONTRACT/GRANT NO
N/A
12. SPONSORING AGENCY NAME AND ADDRESS
Same .
13. TYPE OF REPORT ANO PERIOD COVERED
N/A
14. SPONSORING AGENCY CODE
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19. SUPPLEMENTARY NOTES
Paper - For presentation at the United States of America/Spain Joint Seminar on
the Treatment and Disposal of Hazardous Wastes, Madrid, Spain, May 19-22, 1986.
16. ABSTRACT
This report describes the waste applicability and performance charac-
teristics of hazardous waste pretreatment processes. Pretreatment processes
are those unit operations which must often be carried out on hazardous wastes
to make them amenable to subsequent materials or energy recovery steps, to
chemical or biological detoxification, thermal destruction or safe land dis-
posal. The pretreatment processes covered are primarily phase separation
(floatation, filtration, distillation, etc.) and component separation (adsorp-
tion, stripping, solvent extraction, etc.) techniques. Methods for selecting
the appropriate pretreatment process are provided as a function of waste
characteristics, treatment objective, technical adequacy, performance, and
cost and energy considerations. Detailed summaries are provided for the
various techniques along with relevant performance data.
t
7.
KEY WORDS AND DOCUMENT ANALYSIS
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I!PA P«n» 2220-1 («•». 4.77) PREVIOUS COITION it OMOLKTC
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FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased generation
of solid and hazardous wastes. These materials, if improperly dealt with
can threaten both public health and the environment. Abandoned waste sites
and accidental releases of toxic and hazardous substances to the environment
also have important environmental and public health implications. The Haz-
ardous 'Waste Engineering Research Laboratory assists in providing an author-
itative and defensible engineering basis for assessing and solving these
problems. Its products support the policies, programs and regulations of
the Environmental Protection Agency, the permitting and other responsibili-
ties of State and local governments and the needs of both large and small
business in handling their wastes responsibly and economically.
This report describes the waste applicability and performance charac-
teristics of hazardous waste pretreatment processes. Pretreatment processes
are those unit operations which must often be carried out on hazardous wastes
to make them amenable to subsequent materials or energy recovery steps, to
chemical or biological detoxification, thermal destruction or safe land dis-
posal. The pretreatment processes covered are primarily phase separation
(floatation, filtration, distillation, etc.) and component separation (adsorp-
tion, stripping, solvent extraction, etc.) techniques. Methods for selecting
the appropriate pretreatment process are provided as a function of waste
characteristics, treatment objective, technical adequacy, performance, and
cost and energy considerations. Detailed summaries are provided for the
various techniques along with relevant performance data.
For further information, please contact the Alternative Technologies
Division of the Hazardous Waste Engineering Research Laboratory.
David G. Stephan, Director
Hazardous Waste Engineering Research Laboratory
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ABSTRACT
This report describes the waste applicability and performance charac-
teristics of hazardous waste pretreatment processes. Pretreatment processes
are those unit operations which must often be carried out on hazardous wastes
to make them amenable to subsequent materials or energy recovery steps, to
chemical or biological detoxification, thermal destruction or safe land dis-
posal. The pretreatment processes covered are primarily phase separation
(floatation, filtration, distillation, etc.) and component separation (adsorp-
tion, stripping, solvent extraction, etc.) techniques. Methods for selecting
the appropriate pretreatment process are provided as a function of waste
characteristics, treatment objective, technical adequacy, performance, and
cost and energy considerations. Detailed summaries are provided for the
various techniques along with relevant performance data.
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TABLE OF CONTENTS
Page
Foreword iii
Abstract iv
I. Introduction 1
II. Waste Treatment 1
III. Pretreatment Processes 2
A. Phase Separation 2
1. Sett!able Slurries 4
2. Colloidal Slurries 4
3. Sludges 5
4. Volatiles 5
B. Component Separation 5
IV. Selection Of Pretreatment Processes For Given Waste Streams 6
A. Philosophy of Approach - 6
B. Pretreatment Process Selection 6
1. Nature of the Waste Stream 8
2. Treatment Objective . 11
^
3. Technical Adequacy of Pretreatment Alternatives 14
4. Economic and Energy Consideration 14
V. Waste Pretreatment Process Summaries 17
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PRETREATMENT OF HAZARDOUS WASTE
I. Introduction
. Indiscriminate dumping of industrial processing wastes can lead to ground-
water contamination, or have other adverse effects, often 40 or 50 years after
the initial waste disposal. Although methods have been explored to reduce
leaching into the groundwater, by, for example, encapsulating wastes prior to
burial, and/or placement in secure landfills it is far more certain to control
contaminants by waste minimization, reuse, treatment, or destruction.
Currently, the United States has few restrictions on wastes that are land
disposed. However, the Hazardous and Solid Waste Act Amendments of 1984 have
set in motion many new programs that increase the level of control of hazardous
wastes and, in particular, the land disposal of hazardous wastes. The Amend-
ments require the U.S. Environmental Protection Agency (EPA) to develop
regulations banning all hazardous waste from land disposal unless it is deter-
mined that land disposal of specific wastes will be protective of public health
and the environment as long as the waste remains hazardous. While it is likely
that certain wastes will continue to be land disposed, the course has been clearly
set to direct wastes to the preferred alternative methods of minimization,
treatment, reuse, or destruction.
II. Waste Treatment
Because of the many valid reasons for reducing the amount and number of
classifed hazardous wastes that can be deposited in controlled land sites, it is
important that treatment processes be identified and applied as a part of an
overall hazardous waste management system. The objective of this report is to
describe the waste applicability and performance characteristics of hazardous
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waste pretreatment processes. Pretreatment processes are those unit operations
which must often be carried out on hazardous wastes to make them amenable to
subsequent materials or energy recovery, to chemical or biological detoxifica-
tion, thermal destruction or safe land disposal. As such, pretreatment really
describes the manner in which a treatment process is applied in an overall
waste management system rather than a specific set of unit processes. Table 1
lists unit operations currently believed to be useful in hazardous waste treat-
ment. In most instances, a number of these processes would be combined to form
a complete treatment system for a particular waste stream. The number and type
of processes employed are a function of the degree of ultimate treatment re-
quired (e.g., component removal prior to land disposal versus complete detoxific-
ation).
Physical treatment processes are most often used as pretreatment steps.
Chemical steps such as neutralization, oxidation, or precipitation are also
used to pretreat wastes. These processes are covered in more detail in a
companion document on chemical and biological treatments prepared for this
Seminar and will not be discussed in detail in this report. Detailed descrip-
tions of physical treatment processes are provided in Section V of this report
along with treatment performance data.
III. Pretreatment Processes
Physical pretreatment processes typically are designed to perform one of
two functions; phase separation or component separation.
A. Phase Separation
Waste streams, such as slurries, sludges and emulsions, will often require
a phase-separation process (Table 2) before detoxification or recovery steps
can be implemented. Frequently, phase separation permits a significant volume
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TABLE 1
HAZARDOUS WASTE TREATMENT PROCESSES
Physical
Air Stripping
Carbon Adsorption
Centrifugation
Distillation
Electrodialysis
Evaporation
Filtration
Flocculation
Flotation
Freeze Crystallization
Ion Exchange
Liquid Ion Exchange
Steam Distillation
Resin Adsorption
Reverse Osmosis
Sedimentation
Liquid-Liquid Extracting of Organics
Steam Stripping
Ultrafiltration
Chemical
Chemical Stabilization
Catalysis
Chlorinolysis
Electrolysis
Hydrolysis
Microwave Discharge
Neutralization
Oxidation
Ozonolysis
Photolysis
Precipitation
Reduction
Biological
Activated Sludge
Aerated Lagoon
Anaerobic Digestion
Composting
Enzyme Treatment
Trickling Filter
Waste Stabilization Pond
TABLE 2
PHASE SEPARATION PROCESSES APPLICABLE IN HAZARDOUS
WASTE PRETREATMENT
Process Category
Settleable
Slurries
PROCESS
Colloidal
Slurries
APPLICABILITY
Sludges
Waste With A
Liquid Phase
Volatile
Common Use
Sedimentation
Filtration
Flocculation
Filtration
Solar Evaporation
Distillation
Developed But Less
Commonly Used
Centrifugation
Evaporation
Development Stage
Flotation
Ultrafiltration Freezing
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reduction, particularly if the hazardous component is present to a significant
extent in only one of the phases. Furthermore, by concentrating the hazardous
portion of the stream, sequential processing steps may be accomplished more
readily. Phase-separation processes usually are mechanical, inexpensive and
simple, and can be applied to a broad spectrum of wastes and waste components.
Emulsions are generally very difficult to separate. Heating, cooling,
change of pH, salting out, centrifugation, API separators, etc., may all be
tried, but there is no accurate way to predict what might work. Appropriate
methods can only be developed empirically, specific to any given situation.
1. Settlable Slurries
Conceptually, the simplest separation process is sedimentation, or gravity
settling. The output streams will consist of a sludge and a decantable super-
natant liquid. If the components of the sludge are at all soluble, the super-
natant liquid generally will be a solution. A closely related process and the
phase separation process in most common use is filtration. Centrifugation is
essentially a high gravity sedimentation process whereby centrifugal forces
are used to increase the rate of particle settling. Flotation is used exten-
sively in ore separation, and in fact is the single most important process that
has made it possible to recover value from lower and lower grades of metallic
and non-metallic ores. Flotation is also applicable to separation of oily or
light fractions of aqueous waste streams.
2. Colloidal Slurries
The basic concept in all the above processes for settlable slurries is to
get the solid phases to drop out of the liquid phase, through the use of gravita-
tional, centrifugal, magnetic, or hydrostatic forces. Such forces generally do
not act on colloidal suspended particles.
4
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The simplest and most commonly used colloidal separation process is
flocculation. Ultrafiltration has many industrial applications, including
waste treatment, and is expected to have many more within the next five years.
3. Sludges
The major phase separation desired in the handling of sludges is dewater-
ing. Vacuum filtration or press filtration are the processes in most common
use. Some research has been done on simple freezing, but the process is not
well developed and the work that has been done is not promising.
4. Volatiles
Sludges and slurries (colloidal or separable) in which the liquid phase is
volatile may be treated by either evaporation or distillation. Solar evapora-
tion is very commonly used although this approach is likely to be limited in
the future by pending control standards for hazardous organic compound emissions
to the atmosphere. Engineered evaporation or distillation systems would norm-
ally be operated if recovery of the liquid is desired.
B. Component Separation
Many physical processes act to segregate ionic or molecular species from
multicomponent waste streams but do not require chemical reactions to be
effective. There has been a great deal of experience developed from applica-
tion of these processes in industrial and municipal wastewater treatment.
Since a significant number of hazardous wastes generated in the United States
are aqueous streams, these processes are seeing increasing use in this emerging
field of waste treatment.
The applicability of component separation processes to various classes of
treatment functions is shown in Table 3. Complete descriptions of each unit
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process are given in Section V. In many cases component separation may be the
only treatment required to make a waste suitable for land disposal or discharge
to municipal wastewater treatment systems.
IV. Selection Of Pretreatment Processes For Given Waste Streams
A. Philosophy Of Approach
There are a variety of ways to approach the problem of selecting the appro-
priate process(es) for pretreatment of a particular waste stream. Individual
engineers, chemists, equipment manufacturers, salesmen, environmental managers,
plant managers, regulatory authorities, etc., will each have slightly different
perspectives on the problem, different data needs, and different ways of mani-
pulating the data to reach a final conclusion. No one approach is necessarily
"right" for everyone or best for any given situation. No matter how one
approaches the problem of process selection, there are two seemingly conflict-
ing criteria to keep in mind. The first is to eliminate inappropriate processes
from consideration at the earliest stage feasible. The second is to maintain
an open mind for consideration of attractive processes as long as possible.
B. Pretreatment Process Selection
The selection of hazardous waste pretreatment systems is governed by four
factors. These are:
0 nature of the waste stream
0 treatment objective
0 technical adequacy of pretreatment alternative
0 economic and energy considerations
The importance of these factors is discussed below. Also matrices are
presented which may serve as a general guide for using these factors in
pretreatment process selection.
6
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TABLE 3
COMPONENT SEPARATION PROCESSES
Process
Category
Removal Of Heavy Metal
And Toxic Anions From
Aqueous Solutions
Function Of Process
Removal Of Organlcs
From Aqueous
Solutions
Removal Of In-
Organlcs From
Liquids, Slurries
And Sludges
Solvent
Recovery
Common Use
Ion Exchange
Carbon Adsorption
Steam Stripping
Distillation
Steam
Distillation
Developed, But Less
Commonly Used
Liquid Ion Exchange
Electrodialysls
Reverse Osmosis
Ultraflltratlon
Solvent Extraction
Resin Adsorption
Air Stripping
Evaporation
Development Stage
Solvent Extraction
Freeze Crystallization
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1. Nature of the Waste Stream
For the purposes of identifying possible pretreatment processes, and
eliminating those that are not likely to prove useful, a given waste stream
is conveniently characterized with respect to three broad dimensions:
0 physical form - e.g., liquid, emulsion, slurry, solid, powder
0 hazardous components - e.g., heavy metal cations, organics
0 other properties - e.g., components by waste phase, aqueous
versus non-aqueous, concentration of pollutant
It is important to assess the nature of the waste stream for several rea-
sons. One is to determine whether the waste stream characteristics match the
feed stream requirements for various pretreatment processes. In a positive
sense, this may be of interest to select processes for further consideration;
or in a negative sense, to rule out processes that are not and could not be
made useful for the particular waste under any circumstances. Another is to
determine whether the waste stream is compatible with typical treatment process
equipment, materials of construction, pumps, throughput rates, temperature,
size of pipes, etc. A third reason is to determine whether air and water
pollution controls, or the method of waste collection used, might in fact
create a stream which is more difficult to treat than the waste originally
generated in the manufacturing operation.
For a given waste stream, characterized by physical form and hazardous com-
ponents, the matrix presented in Table 4 may be used to select potentially
applicable pretreatment processes. For example, liquid ion exchange (LIE) might
be capable of removing heavy metals from solid powders. The matrix in Table 5
focusses on processes that are inapplicable for given waste streams. It provides
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TABLE 4
Physical Form
Liquid
PRETREATMENT PROCESSES FOR HAZARDOUS COMPONENTS IN WASTE STREAMS
OF VARIOUS PHYSICAL FORMS
Treatment Processes
Heavy "Metal" Cations*
And Metal Anions**
(IE), (FC), (UF), (ED), (RO).
(LIE), (Ppt)
Emulsion (UF)
Slurry (FC), (UF)
Sludge (LIE), (FC)
Solid Powder (LIE)
Legend:
(AS) Air Stripping
(CA) Carbon Adsorption
(Dis) Distillation
(ED) Electrodialysis
Non-Metal Anions***
(CA), (LIE), (FC), (UF), (ED),
(RO)
(FC), (UF)
(FC)
(FC) Freeze Crystallization
(IE) Ion Exchange
(LIE) Liquid Ion Exchange
(Ppt) Precipitation
(RA) Resin Adsorption
*e.g., Sb, As, Cd, Cr, Hg, PB, Zn, Ni, Co, V, P, Be, Se, Mn, Ti, Sn, Ba
**e.g., chromates, arsenates, arsenites, vanadates
***e.g., cyanides, sulfides, fluorides, hypochlorites, thiocyanates
Organics
(CA), (RA), (Dis), (IE),
(AS), (SS), (UF), (SE), (RO),
(UF)
(Dis), (AS), (SS), (UF),
(Dis)
(RO) Reverse Osmosis
(SE) Solvent Extraction
(SS) Steam Stripping
(UF) Ultraflltration
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TABLE 5
APPLICABILITY OF TREATMENT PROCESSES TO PHYSICAL FORM OF WASTE
Single Phase
1. Phase Separation Processes
Filtration
Sedimentation
Flocculation
Centrifugation
Distillation
Evaporation
Flotation
Ultrafiltration
Precipitation
2. Component Separation Processes
Ion Exchange
Liquid Ion Exchange
Freeze Crystallization
Reverse Osmosis
Carbon Adsorption
Resin Adsorption
Electrodi alysis
Ai r Stripping
Steam Stripping
Ammonia Stripping
Ultrafiltration
Solvent Extraction
Reverse Osmosis
Distillation
Evaporation
Liquid
Sol
y
y
y
p
lid
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
n
Inorganic
n
n
n
n
n
n
n
n
n
y
y
y
y
y
y
y
n
n
y
y
y
y
n
y
Organic
n
n
n
n
n
n
n
n
n
y
y
y
n
y
y
n
y
y
n
y
y
Mixed
n
n
n
n
n
n
n
n
n
y
y n
n
I
y
y
n
y
y
y
y
y
Two Phases
Slurry*
y
y
n
y
y
y
y
n
n
n
y
y
y
y
n
n
n
n
y
y
Sludge
n
n
n
n
y
y
n
n
n
n
y
y
n
n
n
n
n
n
y
y
*Slurry is defined here as a pumpable mixture of solids and liquids
y = yes, workable; n = no; p = possible.
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some guidance for ruling out processes that are not likely to be technically
feasible for certain types of waste streams.
2. Treatment Objective
The output streams from any given pretreatment process may or may not be
suitable for input to subsequent reuse or treatment steps. In evaluating and
analyzing pretreatment processes that might be applicable to particular waste
streams, it is usually necessary at some stage to define the objectives of
pretreatment and the desired characteristics of the output streams from each
step in the overall process train.
For example, if the treatment objective is to convert the given waste stream
to one or more streams which can legally be discharged to a water body, the
Federal and local waste pollution control regulations will govern the character-
istics of the output streams. If the treatment objective is recovery, those proc-
esses must be sought which either lead directly to a reusable resource, or which
convert the waste to a form from which resources may be more easily recovered.
Table 6 provides some general characteristics of the output streams (end
products) from various processes to aid in assessing their capability, alone or
in combination, to meet defined objectives. Where processes are routinely or
conveniently used in combination, follow-on steps are suggested, predicated on
the assumption that the only hazardous components in the waste stream are those
that the process listed can act on. If, for example, a waste stream containing
both low-molecular-weight organic and heavy metal contaminants was treated by
reverse osmosis, only the heavy metals would be concentrated in one of the
output streams (R01), and the other output stream (R02) would have to be treated
further to remove or detoxify the organics.
11
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TABLE 6 (Continued)
GENERAL CHARACTERISTICS OF THE END-PRODUCTS OF TREATMENT PROCESSES
Treatment
Output Streams
Possible Follow-On Steps
Type
b. Organlcs
Process
Electrodlalysis
Freeze Crystalliza-
tion
Carbon Adsorption
Resin Adsorption
Steam Stripping
Solvent Extraction
Distillation
Form Characteristics
Liquid concentrated stream, 100-500 ppm salts
Liquid dilute stream
Sludge concentrated brine
Liquid purified stream, -100 TDS
Solid adsorbate on carbon
Liquid purified water
Solid adsorbate on resin
Liquid purified water, <10 ppm organics
Liquid aqueous stream concentrated in volatile
organics
Liquid dilute aqueous stream with 50-100 ppm
organics
Liquid concentrated solution of hazardous
components in. extraction solvent
Liquid purified liquid; hazardous component
concentration <10 ppm
Sludge still bottoms
Liquid pure liquid
Precipitation, Metal Recovery
To Water Treatment
Recovery
To Water Treatment
Thermal or Chemical Regenera-
tion
Discharge
Solvent Regeneration
To Water Treatment
Recovery; Incineration
Recovery of Extraction Solvent
Recycle of Discharge
Incineration
Sale
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TABLE 6 (Continued)
GENERAL CHARACTERISTICS OF THE END-PRODUCTS OF TREATMENT PROCESSES
1. Phase Filtration
Separation
Sedimentation
Centrifugation
Flotation
HGMS
Flocculation
Distillation
Evaporation
2. Component
Separation
a. Inorganics Ion Exchange
Liquid Ion Exchange
Carbon Adsorption
Reverse Osmosis
Sludge 15-20% solids
Liquid 500-5000 ppm total dissolved solids
Sludge 2-15% solids
Liquid 10-200 ppm suspended solids
Stabilized particle-bearing froth
Liquid solution
Slurry magnetic and paramagnetic particles
Liquid solution
Sludge or flocculated particulates
Slurry
Sludge still bottoms
Liquid pure solvent
Solid
Liquid condensate
Liquid concentrated solution of hazardous
components
Liquid purified water with hazardous com-
ponents at ppm levels
Similar To Ion Exchange
Solid adsorbate on carbon
Liquid purified water
Liquid concentrated solution of hazardous
components
Liquid purified solution, TDS >5 ppm
Landfill, Calcination
Component Separation
Decantation
Landfill
Skimming
Component Separation
Recovery
Component Separation
Sedimentation, Filtration,
Centri fugation
Calcination
Sale
Resource Recovery
Recovery or Disposal
Precipitation, Recycle,
Electrolysis
Discharge
Chemical Regeneration
Discharge
Precipitation, Electrolysis,
Recycle
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3. Technical Adequacy of Pretreatment Alternatives
Table 4 shows that there are a number of pretreatment alternatives for
various types of hazardous components in waste streams of different physical
form. All processes which function similarly on similar types of waste streams
are not necessarily technically equivalent, however. The available feed stream
concentrations may differ. The pretreatment efficiencies and hence concentration
of hazardous components in the output streams may differ. The degree of inter-
ference by other components in the waste stream may differ. Throughputs may
differ and the available experience with using the processes to treat hazardous
wastes may also differ.
Table 7 compares treatment processes capable of separating heavy metals from
liquid waste streams with respect to feed stream properties and output parameters.
Tables 8 and 9 provide similar comparisons for processes that separate organics
and toxic anions from liquids. Table 10 compares processes that can accept
feed streams in the form of slurries and sludges.
4. Economic and Energy Considerations
From the industry point of view, economic questions are paramount in
selecting alternative pretreatment methods for in-plant use and in choosing
a waste treatment facility. Some of the important questions which must be
considered when evaluating economic factors are:
- What are the energy requirements for process operation?
- What form(s) of energy will be used, i.e., electricity, natural gas,
oil, coal, etc.
14
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Process
Physical Removal
Ion Exchange
Reverse Osmosis
Electrodialysis
TABLE 7
COMPARISON OF PROCESSES THAT SEPARATE HEAVY METALS FROM LIQUID WASTE STREAMS
Required Feed Stream Properties Characteristics of Output Streams(s)
Con. <4000 ppm; aqueous
solutions, low SS
Con. <400 ppm; aqueous
solutions; controlled pH;
low SS; no strong oxidants
Aqueous solutions; neutral
or slightly acidic; Fe and
Mn <0.3 ppm; Cu <400 ppm
Freeze Crystallization Aqueous solutions; TDS <10%
One concentrated in heavy metals; one
purified
One concentrated in heavy metals; one
with heavy metal concentrations >5
ppm
One with 1000-5000 ppm heavy metals;
one with 100-500 ppm heavy metals
Concentrated brine or sludge; puri-
fied water, TDS--1UO ppm
TABLE 8
COMPARISON OF TREATMENT PROCESSES THAT SEPARATE ORGANICS FROM LIQUID WASTE STREAMS
Treatment Processes Required Feed Stream Properties Characteristics Of Output Stream(s)
Wrbon Adsorption
Resin Adsorption
Ultrafiltration
Air Stripping
Steam Stripping
Solvent Extraction
Distillation
Steam Distillation
Aqueous solutions; concentra-
tions <1%; SS <50 ppm
Aqueous solutions; concentra-
tions <8%; SS <50 ppm; no
oxidants
Solution or colloidal suspen-
sion or high molecular weight
organics
Solution containing ammonia;
high pH
Aqueous solutions of volatile
organics
Aqueous or non-aqueous solu-
tions; concentration <10%
Aqueous or non-aqueous solu-
tions; high organic concentra-
tions
Volatile organics, non-reactive
with water or steam
Adsorbate on carbon; usually regen-
erated thermally or chemically
Adsorbate on resin; always chemi-
cally regenerated
One concentrated in high molecular
weight organics; one containing
dissolved ions
Ammonia vapor in air
Concentrated aqueous streams with
volatile organics and dilute
steam with residuals
Concentrated solution of organics in
extraction solvent
Recovered solvent; still bottoms
liquids, sludges and tars
Recovered volatiles plus condensed
steam with traces of volatiles
15
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Process
Physical Removal
Ion Exchange
Liquid Ion Exchange
Electrodialysis
Reverse Osmosis
TABLE 9
COMPARISON OF PROCESSES THAT SEPARATE TOXIC ANIONS FROM LIQUID WASTE STREAMS
Required Feed Stream Properties Characteristics Of Output Stream(sl
Inorganic or organic anions in
aqueous solution
Inorganic or organic anions in
aqueous solution
Aqueous stream with 1000-5000
ppm inorganic salts; and pH;
Fe and Mn <0.3 ppm
Aqueous solutions with up to
34,000 ppm total dissolved
solids
Concentrated aqueous solutions
Concentrated solutions in extraction
solvent
Concentrated aqueous stream (10,000
ppm salts); dilute stream (100-500
ppm salts)
Dilute solution (~5 ppm TDS);
concentrated solution of hazardous
components
Purified water; concentrated brine
Freeze Crystallization Aqueous salt solutions
TABLE 10
COMPARISON OF PROCESSES THAT CAN ACCEPT SLURRIES OR SLUDGES
Required Feed Stream Properties Characteristics Of Output Stream(sl
Process
Calcination
Freeze Crystallization
Liquid Ion Extraction
Flotation
Hydrolysis
Anaerobic Digestion
Composting
Steam Distillation
Solvent Extraction
Waste stream with components Solid greatly reduced in volume;
that decompose by volatilization volatiles
(hydroxides, carbonates, nitrate,
sulfites, sulfates)
Low-viscosity aqueous slurry or
sludge
Solvent extractable inorganic
component
Flotable particles in slurry
Hydrolyzable component
Aqueous slurry; <7% solids;
no oils or grease; no aromatics
or long chain hydrocarbons
Aqueous sludge; <50% solids
Sludge or slurry with volatile
organics
Solvent extractable organic
16
Brine sludge; purified water
Solution in extraction solvent
Froth
Hydrolysis products
Sludges; methane and C02
Sludges; leachate
Volatile, solid residue
Solution of extracted components;
residual sludge
-------
- To what extent will credit for recovered material help offset operating
costs?
- How do projected costs for alternative pretreatments compare with each
other?
- If recovery as an objective, is there enough value in the potentially
recoverable material to be worthwhile?
- Are the technically optimal operating parameters in the proper range
for economic operation of apparently attractive processes?
- If process modifications are required, what will they cost?
- For technically and operationally acceptable processes with equal
operating costs (including capital amortization), is there any economic
reason to prefer the lowest capital cost alternative?
- What is the cost impact of any necessary environmental controls?
Questions of energy utilization are asked in order to assure that pretreat-
ment processes satisfy current national objectives of both environmental protec-
tion and energy conservation. Both the absolute quantity of energy required
and the form of the energy required are important. Energy-intensive processes
generally would be in disfavor, unless there are compensating benefits (e.g.,
materials recovery). Processes that use fuels in short supply might be parti-
cularly unattractive. The economics of pretreatment processes for which energy
costs represent a significant fraction of operating costs would, of course, be
tied to the price of fuel, which as in the recent past been quite volatile.
V. Uaste Pretreatment Process Summaries
The following pages summarize the salient features of phase separation and -
component separation processes applicable for hazardous waste pretreatment. Proc-
ess flow diagrams are included as are general descriptions of process performance.
17
-------
SECTION 2.1
GRAVITY SEPARATION
Process Description
Gravity separation is widely used as a waste treatment
process for the removal of settleable suspended solids, oil and
grease, and other material heavier or lighter than the carrying
fluid (usually water). Grit chambers, clariiers, API separators,
inclined plate settlers, and corrugated plate interceptors (CPI)
are common forms of gravity separation devices used in waste
treatment.
Various configurations are used for continuous gravity
separation. These include:
1. Rectangular sedimentation basins/API Separators
2. Circular upflow clarifiers
3. Solids Contact Clarifiers
4. Inclined tube or plate separators.
Design is based on the settling rate or rise rate of the
smallest particles to be removed, expressed as flow rate per unit
area of clarifier surface. Most applications fall within a range
of 0.2 to 1.0 gpm/sf.
Figures 2.la and 2.1b Illustrate rectangular and circular
configurations respectively. An API separator is a rectangular
gravity separator designed to remove free oil in accordance with
criteria established by the American Petroleum Institute.
Inclined plate settlers are designed to greatly increase the
available settling area per unit volume of clarifier. (Inclined
settling tube systems have generally been replaced in the past
few years by the inclined settling plate design.) A plate
settler can provide equivalent settling capacity in 20-40 percent
of the area required by a conventional clarifier. An inclined
plate settilng unit is shown on Figure 2.1c. A variation on the
plate settler, the corrugated plate interceptor, has found wide
application as an alternative to the API separator. The
corrugated plates keep separated oil and solids in separate
"tracks" as they move countercurrently along the plate surface.
Solids contact clarifiers are of two types - sludge
blanket and recirculating slurry. Both improve flocculation of
newly coagulated particulate matter by contacting the feed with a
concentrated zone of previously formed floe particles. The floe
grows in size by agglomeration of small particles so that
settling velocity is increased. Figure 2.Id illustrates a solids
contact clarifier.
• toot
-------
Gravity separation is limited to removal of settleable
solids and oils. Non-settleable material or emulsified oil will
not be removed; in these cases, pretreatment with chemicals to
enhance settleability or break emulsions or an alternate
separation process is required. Heavy, oversized materials
should be removed by screens to protect clarifier mechanisms and
prevent plugging of parallel plates, sludge piping and pumps.
Sticky materials may build up and plug parallel plates, requiring
frequent cleaning.
Gravity separation can reduce effluent suspended solids to
less than 20 to 50 mg/1. If further reduction is required, an
additional process such as filtration is needed.
Applicability to the Treatment of Hazardous Waste
The two main applications for gravity separators in the
treatment of hazardous wastes are:
1. pretreatment to remove suspended solids and oils prior
to other treatment processes
2. separation of solids generated by other treatment
processes, e.g., precipitation and activated sludge.
All of the wastes which are proposed for exclusion from
landfills can contain suspended solids or immiscible liquids.
These range from metal fragments, filings and tramp oils to
pieces of wood, plastic and rags which are simply discarded into
waste containers. Gravity separation, in combination with
screening and filtration as appropriate, is a simple and
effective process for removing these materials.
In many cases where presettling of hazardous waste is
required, simple batch holding in a tank is adequate since the
volume of waste is often small. Waste holding tanks are often
designed with conical bottoms and sludge drawoff connections to
permit removal of settled material.
This was common practice at hazardous waste treatment
facilities visited. At one large facility, surface impoundments
were used for gravity settling with the settled material removed
periodically by dredging.
Clarifiers with sludge withdrawal mechanisms are
appropriate for separation of the solids produced by biological
treatment of aqueous organic wastes or precipitation (continuous
flow) of heavy metals from aqueous wastes.
At a commercial hazardous waste treatment facility that
was visited by M&E, sludge blanket type clarifiers are used to
separate flocculated heavy metal hydroxides and sulfides from a
MCTCALP • tOOT
-------
treated aqueous waste. Underflow sludge having 1-i to 2 percent
solids is periodically pumped out to a 200,000 gallon gravity
thickening tank. This second sedimentation process, with a 1.5
day holding time, results in a 6-8 percent solids sludge which is
further dewatered in a belt filter press.
Environmental Considerations
Every sedimentation process procedures:
1. A liquid efffluent which may require further treatment
before it can be discharged..
2. Sludge or skimmings which must be further treated,
chemically stabilized and/or disposed of.
In addition, there is a potential for atmospheric release
of volatile chemicals from open-topped clarifiers and
sedimentation basins. Often a nominally inorganic aqueous waste
will be contaminated wiht hundreds of mg/1 of organic solvents.
Strong odors above clarifiers used to separate metal precipitates
from wastewater have been detected at commercial hazardous waste
treatment facilities.
MCTCAir • COO''
-------
FIGURE 2.1 a
RECTANGULAR SEDIMENTATION TANK
Feed
Sludge
Drive Unit Automatic Skimmer
Baffle /
Water Level
Rake Blade
Sludge Collection
Weir
Effluent
Source: Dorr-Oliver, Stamford, CT
-------
FIGURE 2.1b
CIRCULAR CLARIFIER
SklmmerBlade
Support Bridge
Effluent
Sump Scraper
Source: Infilco Degremont, Richmond, Virginia
Sludge
!-•—Feed
Scraper Arm
-------
FIGURE 2.1C
INCLINED PLATES SETTLING UNIT
Flow
Distribution
Orifices
Discharge
Flumes
Overflow
Box
Effluent
Lamella
Settling
Plates
Flocculation
Tank
Flash
Mix
Tank
Coagulant
Aid
Feed
Sludge
Collection
Underflow
I (Sludge)
Source: Parkson Corp., R. Lauderdale, Florida
-------
FIGURE 2.Id
SOLIDS CONTACT REACTIVATOR™
Effluent
Sludge
Blanket —
Detention
Zone
Scraper Drive
,— Reclrculatlon
/ Rate Controller
-IV
Chemical
Feed
Wastewater
Feed
Sludge Collection
Settling
Zone
Source: Ecodyne Corporation,
Graver Water Division
-------
SECTION 2.2
FLOTATION
Process Description
Flotation is a gravity separation process in which the
attachment of fine air bubbles to suspended solids or oils
decreases the effective density of the material, thereby
enhancing gravity separation.
There are two .major types of flotation processes:
1. dissolved air flotation (DAT)
2. induced air flotation (IAF)
In Dissolved Air Flotation, a portion of the waste feed
stream or an effluent recycle stream is saturated with air at a
pressure of 40 to 60 psi, then released to atmospheric pressure
in a flotation chamber. The sudden pressure reduction results in
release of microscopic (50 to 100 micron) bubbles. Figure 2.2a
illustrates a dissolved air flotation system. Induced air
flotation uses mechanical or diffused air aeration to produce
bubbles with 500 to 1000 micron diameters. An induced air
flotation system is shown in Figure 2.2b. In either case,
chemical coagulants and/or polyelectrolytes may be used to effect
particle size growth prior to aeration, thereby increasing
particle rise velocity and improving separation. Surfactants may
be used as conditioning agents to change the surface properties
of the particles so that air bubbles will more readily adhere.
In all types of flotation, the design includes appropriate
equipment for skimming and removal of the oily or sludge-like
float from the surface of the treated wastestream.
Applicability to the Treatment of Hazardous Waste
Flotation is an appropriate treatment technology where oil
or light solids must be separated from a hazardous liquid
waste. Flotation is frequently used for separation of oil from
oily aqueous waste. This is an important application because
many states regulate waste oil as a hazardous waste.
A recent technical paper discusses uses of DAF for
treatment of 50 gpm of industrial rinsewater at a plant that
manufactures latex and adhesives. This wastewater contains 1 to
4 percent organic solids. Upstream of DAF, the waste is prepared
for flotation by equalization, pH adjustment for emulsion-
breaking, coagulation with alum, and flocculation with
polyelectrolytes. The DAF unit is operated in the pressurized
• (DOT
-------
recycle mode. A float containing 4-6 percent solids is skimmed
off and subsequently dewatered to a 20-25 percent solids sludge
which is landfilled. The clarified aqueous effluent from the DAP
unit contains only 30 mg/1 suspended solids.
Environmental Considerations
Every flotation process produces:
1. a liquid effluent which may require further treatment
before it can be discharged to a municipal sewer or to
surface water.
2. a skimmed residual. In the case of simple flotation,
the skimmed free oil may be recovered for its fuel
value. Air flotation processes are more likely to
produce a sludge-like residue that is not economically
recoverable and would typically be incinerated or
landfilled.
In addition, there is the potential for atmospheric
release of volatile chemicals from open-topped flotation tanks
due to air stripping.
MCTCAL' • 100-
-------
THANSFEN
PUft*
TYPICAL SINGLE EFFECT EVAPORATOR - FALLING FILM TYPE
MEAT
•XCMAN6IM
fTVP.I
OltTlLLfO
ITIAV
CONOENSiTE
TYPICAL MULTl-EFFECT {TRIPLE EFFECH EVAPORATOR - FALLING FlLMTYPE
FIGURE 2.8 SCHEMATIC OF SINGLE AND MULTIPLE EFFECT EVAPORATORES
(METCALF & EDDY, 1979)
MfTC *L' • tOO-
-------
SECTION 2.9
DISTILLATION
Process Description
Distillation is the vaporization of one or more, usually
concentrated, volatile components out of liquid solution.
Individual components vaporize in order of their volatility so
that relatively pure products result upon condensation. Organic
products are purified or volatile chemicals are recovered. Non-
volatile residues of varying solids concentration remain behind
in the feed.
Distilling is accomplished in vessels ranging up to
40 feet in diameter and 200 feet tall. Each are equipped with a
heat source such as a steam jacket or heating coil which boils
the liquid and drives off the desired chemical. A condenser
converts the vapor to liquid which is collected in an
accumulator. The capacity of a given unit is a function of the
waste being processed, purity requirements, reflux ratio and heat
input.
Distillation can occur as a batch or continuous process
and under pressures ranging from near vacuum to several
atmospheres. Fractional distillation is a continuous process
which employs fixed trays for large scale units or packing
materials for small scale units. Tray (also called plates)
configurations vary, with representative examples including
bubble cap tray or simple perforated horizontal plate. Feed
liquids enter above the plates or packing and volatile components
are vaporized by contact with rising vapor from the boiling
liquid below. Fractionation of two or more volatiles can produce
a series of vaporized fractions of different concentration.
Figure 2.9a and 2.9b illustrate batch and fractional
distillation, respectively (Kiang and Metry, 1982).
Steam distillation employs steam as the direct carrier of
immiscible volatile compounds out of solution. Steam
distillation operates on the principle (Dalton's law of partial
pressures) that the total vapor pressure exerted upon heating
when two or more immiscible liquids are involved, is equal to the
sum of the vapor pressure of each liquid. A lower temperature
(heat input) is thus necessary to achieve complete volatilization
because less than the typical vapor pressure at which it boils
oust be reached, and distillation occurs below each of their true
boiling points. Steam distilling under a vacuum (lower pressure)
is also routinely performed to produce similar results.
Steam distilling of liquids is usually conducted in batch
or semi-batch distillation equipment retrofitted to allow
MCTCAL' • coo»
-------
bubbling of steam through the feed, or in multi-tray columns.
Carrier steam and the recovered volatile compound(s) are
condensed or redistilled if not and recovered separately. Units
handling feedstock (e.g. inks, paints, forest products) from
which polymerized materials or solid residues remain after steam
distillation require removable vessel heating equipment to allow
disposal of accumulated deposits. A steam distillation unit is
shown in Figure 2.9c. (Kiang and Metry, 1982).
Distillation products approaching 100 percent purity are
possible. Higher purities generally require increasingly higher
capital and operating expense.
Applicability to Treatment of Hazardous Waste
Distillation is very useful in reclaiming spent solvents
or purifying certain aqueous wastes.
One solvent recycler has eight batch distillation units
each consisting of a reboiler and fractionating column. The
reboilers range in size from 800 to 18,000 gallons. The columns
have diameters ranging from 2 feet to 4 ft and heights ranging
from 30 feet to 80 feet. These columns are equipped with bubble
cap trays. All columns can operate with reflux rates ranging
from zero to total reflux. These units are used to produce high
purity solvent for reuse by the waste solvent generator.
Solvents reclaimed at this facility include hydrocarbons,
chlorinated hydrocarbons, ketones, and alcohols.
A second company operates two 500 gallon glass lined steam
jacketed batch stills. Each column contains six feet of ceramic
Raschig ring packing. The stills are operated without reflux and
produce a relatively low purity product suitable for resale to
marketers of compounds like lacquer thinner and windshield washer
fluid. Waste solvents treated at this facility include acetone,
chlorinated hydrocarbons, ethanol, IPA, MEK, toluene, xylene and
mixed solvents.
A third solvent reclaimer uses continuous, rather than
batch, distillation. Batch distillation is generally preferred
by commercial waste solvent reclaimers due to its flexibility and
ease of operation. However, this firm was set up to handle large
quantities of selected solvent waste streams on a toll basis, so
continuous fractionation systems were designed to purify those
specific wastes. The largest column at this facility is a 3-foot
diameter, 110-foot tall tower with 48 valve trays. With this
column, 99.9% pure freon is recovered from a waste solvent
containing freon and 1,1,1 trichloroethane.
The limitations on the use of this process for hazardous
waste are that the waste must have a very low solids concentra-
tion to prevent fouling of the equipment. Wastes that are
MCTCA!.' • tOO»
-------
subject to producing tars or other fouling substances when heated
nay not be suitable for processing using distillation without
prior treatment. Inorganic wastes would not be accommodated by
this process.
Environmental Considerations
Distillation produces a distillate fraction and a still
bottoms fraction both of which may be resold as a raw material or
require some other treatment or disposal depending on the
material. Another residual produced by distillation is the tar
and/or sludge buildup that occurs on the reboiler steam coils.
This material must be periodically removed either by scraping
and/or washing and is usually land-filled.
• COOT
-------
FEED
BATCH
STILL
CONDENSER
PARTIAL RECYCLE
STEAM
•4^— CONOENSATE
^ BOTTOM
PRODUCT
SOURCE: AOL. 197J
ACCUMULATOR
DISTILLATION
COLUMN
DISTILLATE
VOLATILE
LIQUIDS)
PERFORATED TRAY TYPE
DISTILLATION PLATE
ACCUMULATOR
DISTILLATE
CONDENSATE
SOURCE: ADL. 1977
STILL BOTTOMS
(RESIDUE)
FIGURE 2.9* RATCII DISTILLATION
FIGURE 2.9b CONTINUOUS FRACTIONAL DISTILLATION
-------
t
n
*
n
CONDENSER
FEED
STORAGE
SUPERHEATED
CARRIER STEAM
•.STRIPPED FEED MATERIAL
RESIDUE
RECOVERED
ORGANIC PHASE
DISCHARGE
SOURCE: KIANO AND METRV. 1M>
FIGURE 2.9c BATCH STEAM DISTILLATION
-------
SECTION 2.10
DLTRAFILTRATION
Process Description
Oltrafiltration is a low pressure (10 to 150 psi) membrane
process for separating high molecular weight dissolved materials
or colloidal materials from liquids. The ultrafiltration
membrane is a semi-permeable membrane, incorporated into membrane
nodules. The semi-permeable membrane is a thin selective layer
(0.1 to 1.0 microns thick) and the membrane modules are typically
made of a spongy material. The characteristics of the thin
selective layer determine the size of the species passing through
the membrane. Generally, low molecular weight species, such as
salts, sugars, and most surfactants pass through the membrane.
Oltrafiltration membranes can retain and concentrate organic
solutes of 500 to 1,500 molecular weight.
The influent stream to the ultrafiltration membranes flows
across the membrane surface at a high velocity. This
characteristic of ultrafiltration differs from the perpendicular
flow of most filtration methods. Because of the high velocity
flow across the membrane in ultrafiltration, rather than flow
through the membrane, fewer solids build up on the filter
surface. This characteristic reduces the frequency of cleaning
and allows the flux rate of the inlet stream to remain high.
Two streams are discharged from the ultrafiltration
membrane, a concentrate stream, which contains the solute that
does not pass through the membrane and a permeate stream, which
has passed through the membrane. The permeate, which flows
continuously from the DF unit, may be suitable for reuse or may
be discharged. The concentrate stream is recycled to the process
tank until some maximum concentration is achieved and the
permeate flux rate declines. At this point the unit is shut down
for cleaning. The concentrate may be recovered for reuse or for
fuel value or may undergo further .treatment or disposal.
Dltrafiltration devices range in size from 4 feet in
length by 2 feet wide by 7 feet high to 32 feet in length by
10 feet wide by 14 feet high. These two respective devices can
handle daily capacities from 50 gallons to 45,600 gallons. Flow
through a UF system is typically 30 GPD/ft2. The motor
requirements for .these devices range from 2 HP to 115 HP.
Dltrafiltration membranes can be flat sheet, tubular,
spiral wound or hollow fiber. The two largest manufacturers of
ultrafiltration membranes are Abcor and Romicon.
MCTCAur • IDO*
-------
Pretreatment of the waste is often necessary before the
wastewater passes through the ultrafiltration membrane. If
pretreatment is not performed prior to ultrafiltration, the
membranes will need to be cleaned much more often. The membranes
normally need to be cleaned once a week. One pretreatment
requirement for ultrafiltration is the removal of free oil and
large amounts of suspended material. The equalization tank
serves this purpose. The process tank serves as the concentrate
holding tank.
An ultrafiltration schematic is presented in
Figure 2.10a. A tubular membrane is shown in Figure 2.10b.
Applicability to the Treatment of Hazardous Waste
Ultrafiltration is a practical treatment technology for
separating and, if desirable, recovering solutes of molecular
weight greater than 500 to 1000 or suspended materials from an
aqueous stream. Ultrafiltration is commonly used to remove
emulsified oils, metals, and proteins from aqueous wastes.
Studies performed using ultrafiltration for removal of
hazardous substances from aqueous wastes demonstrated 80 percent
removal of TOC from a waste in which TNT accounted for 90 percent
of the 20 ppm TOC concentration.
Ultrafiltration is often used to remove .and recover
emulsified oil from aqueous wastes. Typical metal working waste
streams contain one to two percent emulsified oil.
Ultrafiltration retains 99.9 percent of the emulsified oil and
concentrates the oil to a concentration of 40 to 60 percent.
Environmental Considerations
If not recycled for reuse, the concentrate stream must
eventually be disposed of. The spent membrane cleaning solution,
typically a detergent, is sent to the equalization tank for
treatment.
MCTCAL' • (DO*
-------
PROCESS WATER
FROM
CONCENTRATE
EQUALIZATION
TANK
ui
PROCESS TANK
O
PERMEATE
FINAL
CONCENTRATE
DISPOSAL
FIGURE 2.10a SCHEMATIC OF UI.TRAF1LTRATION
-------
•.. .- .-• •'••• LJ. .-••.. V-/7 • .- ,; /-
.-.. -i!".'.-:.^?.:-.'-' • - • -; .:\- .- •: '^^^/l^r^^Y
MEMBRANE
SUPPORT TUBE
WASTEWATER
FEED
/I
CONCENTRATE
PERMEATE OUT
HCURE 2.10b TUBULAR MEMBRANE _ ULTRAFILTRATION
-------
SECTION 2.11
REVERSE OSMOSIS
Process Description
Reverse osmosis is used to separate water from inorganic
salts and some relatively high molecular weight organics.
Pressure (typically 200 to 1200 psi) is used to force water from
a solution through a semi-permeable barrier (membrane} which will
pass only certain components of a solution (the permeate) but is
impermeable to most dissolved solids (both inorganic and
organic).
To prevent fouling, feed water must be pretreated to
remove oxidizing materials including manganese and iron salts, to
filter out particulates, to remove oil, greases and other film
formers, and to destroy microorganisms. Feedwater temperature
control may be necessary to keep the temperature within a
specified range.
The basic components of a reverse osmosis unit are the
membrane, a membrane support structure, a containing vessel, and
a high pressure pump. Reverse osmosis units can be arranged
either in parallel to provide adequate hydraulic capacity or in
series to effect the desired degree of removal. A wide range of
flows can be accomodated depending on the number of units used.
Commonly used membranes include tubular membranes, spiral-
wound membranes, and hollow fiber membranes. The tubular
membrane consists of a membrane which is inserted onto or into
the surface of a porous tube. This type of membrane is primarily
used for low volume operations. Spiral-wound devices usually use
the membrane as a flat film. Sheets of the flat membrane film
are separated by cloth and are spiral wound to form a
cartridge. A number of spiral tubes are usually connected
together and inserted into a pressure vessel. Hollow fiber
membranes consist of millions of aramid or cellulose acetate
fibers formed into a tube. Feed enters the center of one end of
the tube. The other end of the tube is blocked off to prevent
short circuiting. The hollow fiber device permits very large
membrane areas per unit volume, making this the most compact
device. Membrane materials include cellulose acetate, aromatic
polyamides, and cross-linked polyethylenimines. The three types
of commercial membranes are presented in Figure 2.11.
Applicability to the Treatment of Hazardous Waste
In the treatment of liquids containing hazardous wastes,
reverse osmosis may be used for the removal of dissolved heavy
metals and dissolved organics from aqueous wastes.
MCTCA..F • CO
-------
In one textile mill, virtually complete removal (>
99 percent) was achieved for dimethyl phthalate, di-n-butyl
phthalate, acenapthene, anthracene, and napthalene (EPA
Treatability Manual, 1981) using a cellulose acetate membrane.
Zn another textile mill study > 99 percent removal was achieved
for di-n-butyl phthalate, acenapthene, anthracene, fluoranthene
and pyrene with a cellulose acetate membrane. In both of these
cases influent concentrations were very low (0.4 to 55 mg/1).
Generally, applications for reverse osmosis include removal and
recovery of heavy metals from plating wastes, alcohols and dyes
from textile wastes, and chrornate from aqueous hazardous
wastes. A summary of removal efficiencies of toxic pollutants
from aqueous hazardous wastes is presented in Table 2-11. It
should be noted that the variation in removal of certain
compounds is significant when using different types of membranes.
Reverse osmosis has several limitations. This process is
only applicable to aqueous liquid wastes. It is not usually
applicable for use with initially highly concentrated solutions
due to the increasingly high pressure required to overcome
osmotic pressure as a solution becomes more concentrated. In
addition, the feed stream must be compatible with the membrane.
Incompatible compounds must be removed prior to treatment, or
another process must be used. This can be a problem in the
treatment of hazardous wastes since the chemical compatibility of
many constituents in the waste streams may not be known.
Environmental Considerations
Reverse osmosis produces a highly concentrated reject
stream. In some cases the constituent(s) of the reject stream
may be recovered for reuse. However, often this stream requires
additional treatment and must be disposed of.
(0
-------
TABLE 2.11. UmSB OSMOSIS - EEHOVAL EFflCIENCIES OP TOXIC ODMPOUNDS
Description of Study
Chavdcal
Classification
Alcohol*
Aliphatic*
ABlM*
AroMtle*
Ether*
Heavy Nctal*
ChesJcal
NtthMiol
Acaton*
Poraaldehyd*
Antlliw
(
Chlorobencen*
Dint robs oiene
2.4-Dtnttrophenylhydrsilns
HtiaehlorobenMn*
n>droe,ulfton* •
Bis (2-Chlorolsopropyl) Ether
Methyl Ether
Ethyl Ether
Berlin
Cadalu.
Study
Type
Batch (Ub)
Batch (Ub)
Batch (Ub)
Batch (Ub)
Ut. Bavlev
Batch (Ub)
Batch (Ub)
Ut. levlev
Batch (Ub)
Ub Seal*
Batch (Ub)
Batch (Ub)
Ub Scat*
Batch
•etch
Neat*
Type
Pure Coapound
Pure Compound
Pur* Co.pound
Pure Coetpound
Unknovn
Pur* Compound
Pur* Coepound
Unknovn
Pur* Compound
Pur* Coepound
Pur* Compound
Pur* Coapoand
Pur* Coetpound
Pur* Compound
Pure Co.pound
Influent
Concen-
tration
1000 pp.
1000 pp.
1000 pp.
1000 pp.
1 360 pp.
30 pp.
30 PP.
638 pp.
1000 pp.
1000
250 pp.
1000 pp.
1000 pp.
0.75 pp.
0.85 pp.
9.15 pp.
7.05 pp.
0.10 pp.
1.0 pp.
Effluent
Cone. (1)
786 pp.
297 pp.
851 PP.
182 pp.
780 pp.
430 pp.
1000 PP.
170 pp.
0-11 PP.
28 PP.
5.7 PP.
2* PP.
2.7 pp.
306 pp.
1000 pp.
200 pp.
0-200 pp.
1000 pp.
158 pp.
15 pp.
•05 pp.
100 pp.
0-200 pp.
< 0.10 pp.
< 0.10 p*.
0.20 pp.
< 0.10 pp.
0.001
0.011
•aenval
Efficiency
21. 4S
70. IX
I4.9S
81. BX
22S
57S
OS
81S
97-IOOX
7S
BIS
3S
9IS
52S
OS
80S
80-IOOX
ox
371
94S
9.5S
90S
80-IOOS
> 86. 7X
> 88.21
97.81
> 98.61
90X
98. 11
Hsabraac
Type (2)
CA
C-PBI
CA
C-PBI
CA
C-PEI
CA
C-PEI
Unknovn
CA
C-PBI
CA
C-PBI
Unknovn
CA
C-PEI
AP
CA
CA
C-PBI
CA
C-P81
AP
CA
CA
CA
CA
CA
CA
Chroalc Aeld
tab. Continuous Industrial
flow
ZOO pp.
10
B5X
PS
-------
TABUS 2.11 (Continued). UVCtSC OSMOSIS - REMOVAL EmciBNCIBS Of TOUC COMPOUNDS
Description of Study
Chealcal
Claaalflcatloa
ate*y Metal*
(cont'd)
Peetleldee
Cheat eel
Chroalra
Copper
uad
Hlckel
tine
AldtU
AtrMlM
Cap tea
DOB
DOT
Dlailnon
DUldrln
Heptechlor
Heptechlorcpoiilde
Study
Type
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
Batch
latch
Va*t*
Type
Pur* Coapound
Pure Compound
Pur* Coapound
Pur* Compound
Pur* Coapound
Pur* Coapound
Pur* Coapund
Pur* Coapound
Pur* Coapound
Pur* Coapound
Pur* Coapound
Pur* Coapound
Pure Coapound
Pure Coapound
Influent
Concen-
tration
12.5 ppa
0.94 ppa
8.65 ppa
9.3* ppa
12.5 ppa
0.7 ppa
6.) ppa
12.) PP-
0.95 ppa
9.3 ppa
12.) ppa
12.) ppa
10 pp.
31.8 ppa
1*2 HI
1102 M
689 Ml
M uj
•2 M
474 w
321 M
145 M
307 W
Bf fluent
Cone. (1)
0.25-1.12
0.02S
0.60
1.4
0.012)
0.03)
0.06)
0
0.00)
0.20)
0.87
0.2)
0.37)
0
0.14
0.16
0 Ml
0 Mj
176 «
24 MX
8.1 M
0 UB
0 Ml
0 UB
0 M
0 UB
0 M
0 Ug
0.3 UB
0 M
0 Ml
0.6 u«
R*ab«*l
Efficiency
91-981
971
93X
B5X
99. 9X
95t
99X
IOOX
99.51
97. 8X
93X
98X
97X
IOOX
98. 6X
99. 5X
IOOX
IOOX
84X
97. 8X
9B.8X
IOOX
IOOX
IOOX
IOOX
IOOX
IOOX
IOOX
99. 9X
IOOX
IOOX
99.81
Neahraa*
Type (2)
C-PEl
CA
CA
CA
C-PBt
CA
CA
C-PBt
CA
CA
C-PBI. pH 8
C-PCt. pH II
C-PBI. pN 8
C-PCI. pH II
CA
CA
CA
C-PCI
CA
C-PEl
CA
C-PCI
CA
C-PEl
CA
C-PBI
CA
C-PEl
CA
C-PEI
CA i C-PBI
CA * C-PBI
-------
TAiLB I.II (Continued). RBVERSR OSMOSIS - REMOVAL EFFICIENCIES OP TOXIC COMPOUNDS
Description of Study
Cheat cat
Claaelflcatloa
Peitlelde
(confd)
Phenol*
Cheat eal
Undene
Malathloo
Methyl Parathlon
Parathlon
Random
Trlfluralln
2-Chlorophenol
Phenol
Study
Type
Batch
•etch
Batch
Batch
Batch
Batch
Ut. Revlev
Batch
Haate
Type
Pure Compound
Pure Compound
Pure Compound
Pure Compound
Pure Compound
Pure Compound
Unknown
Pure Compound
Influent
Concen-
tration
506 I*
IOM M
•13 M
7*7 M
321 M
1)79 W
-
1000 ppai
Iffluea*
Cone. (1)
2.) M
i UB
a.) us
3.2 M
3.6 M
0.7 M
1.) M
91 Ug
*.« M
4.7 w
0 M
-
1000 M
23) l«
Reaoval
Efficiency
M.5X
99.01
99.21
99.71
99.61
99 .9*
99 .8t
72Z
98. 61
99. 7»
loot
66.31
Ot
76. it
Mmkrane
Type (2)
CA
C-PB1
CA
C-PBt
CA t C-PBI
CA
C-PBI
CA
C-PBI
CA
C-PBI
-
CA
C-PBI
I. Effluent concentration derived froai Influent concentration end reaoval efficiency.
2. CA - CilluloM ecetata •eabrene; C-PBI - Croaa-llnked polyethylentalna •eabrane; - AP
•eabrane.
BOUtCB: Touhlll, tchukrov and Aaaoclates. Ine.J Concentration Tachnologlea for Macardoua
Bnvlronaental Reaearch Lab, Peb. Bl.
- AroMtle polyaalde •eabrane; PB - aolybenilaldaiole
Aqueoua Waate Treatatnti Prepered for Municipal
-------
MOUM i nauLAft MOOUU
tn.
iun
iun
FIGURE 2.11 COMMERCIAL MEMBRANE CONFIGURATIONS
(BERKOWITZ, ET. AL., 1978)
i' * f oo >
-------
SECTION 2.12
ION EXCHANGE
Process Description
Ion exchange is a process which reversibly exchanges ions
in solution with ions retained on a reactive solid material
called ion exchange resin. A typical ion exchange system has a
fixed bed of ion exchange resin, where the resin has either the
ability to exchange positively charged ions (cation exchange) or
negatively charged ions (anion exchange). Depending on the
charge of the resin, anions or cations will be held by
electrostatic forces to the charged sites. Resins are
presaturated with weakly adsorbed nonovalent ions, which are
readily desorbed and replaced by feed stream ions with greater
affinity for the resin. Most commonly, the presaturant ion for
cation exchange is either hydrogen or sodium, while anion
exchange resins uses either hydroxyl ion or chloride. Generally,
divalent and trivalent ions have a higher affinity for ion
exchange than monovalent ions. Thus toxic metal cations like
divalent cadmium and nickel and anions like divalent chromate and
selenate are well-removed by ion exchange.
When the useful exchange capacity of the hydrogen cation
exchange resins are exhausted, they are regenerated with a dilute
acid solution and a dilute hydroxide solution for the cation and
anion resins, respectively.
Sodium-form cation exchangers and chloride-form anion
exchangers are regenerated with salt solutions. In all cases,
the ions removed from the waste stream end up concentrated in the
spent regenerant.
A typical process schematic for a basic two step
cation/anion ion exchange system is presented in Figure 2.11a.
The ion exchange system presented in this schematic includes
series treatment with separate cation and anion exchange
systems. These systems contain both anion and cation exchange
resin in the same vessel and are capable of producing an effluent
water of almost theoretical chemical purity.
The pressure vessels used for ion exchange typically range
in size from two to six foot diameter for prepackaged modular
systems (i.e. to handle 25 gpm to 300 gpm flowrates) on up to a
maximum custom size of twelve feet diameter (i.e. maximum
1150 gpm flowrates). The side height of these vessels vary
between six and ten feet in height to provide adequate resin
storage, distribution nozzle layout, and freeboard capacity for
bed expansion during backwashing. The nominal surface loading of
• COO
-------
ion exchange vessels typically range from 8 to 10 gpm per square
foot.
Applicability to the Treatment of Hazardous Wastes
Ion exchange is more of a "polishing" technology than a
separation technology. It is typically the final technology used
to clean a wastewater stream for reuse as process water, in
almost all applications it is necessary to pretreat a waste
stream prior to the ion exchange system for removal of suspended
solids, organics, and oxidizing agents.
The electroplating and metal finishing industry make wide
use of ion exchange typically in closed loop systems to reuse
rinse water in plating rinse tanks. Wastewaters containing
chromium, cadmium, nickel, metal-cyanide complexes, and other
dilute metals are presently treated by ion exchange. In some
cases, the metals can be recovered for recycle to a plating bath.
Anion exchange is used for the removal and recovery of
chromate, a corrosion inhibitor, from cooling tower blowdown
streams.
Weak-base anion exchange resins, which adsorb strong
acids, are now being applied to the recovery of acids like HN03,
H2S04' and HF fr°m chemical milling, etching and anodizing
solutions used in metal forging and finishing. The highly
corrosive spent solutions which contain high concentrations of
dissolved metals are pumped through a resin bed. The acid is
adsorbed while dissolved metal salts pass through the bed. The
resin is regenerated with water, recovering metal-free acid
solution for reuse. Eco-Tec Limited commercialized this
technology in 1977 and markets a skid-mounted acid purification
unit (APU). Data on a specific application of this technology
for the recovery of 50 percent (W/W) nitric acid from a nickel-
stripping process is presented in Table 2.12a. (Ref. K. Munns,
Eco-Tec, Limited).
TABLE 2.12a. DATA FOR APU
Stream
Process Solution before APU
Process Solution with APU
APU Product Stream
APU Waste Stream
Nitric Acid
(g/L)
990
670
620
50
Nickel
(g/L)
20
5-7
1-2
4-5
-------
Table 2-12b follows which summarizes the review of recent
literature in the use of ion exchange as abstracted from selected
recent issues of "Amber-Hi-Lites" published periodically by Rohm
and Baas Company as compiled by Mr. Charles T. Dickert.
Environmental Considerations
Ion exchange processes generate a concentrated regenerant
stream that must be managed. This chemical regenerant stream
volume can be as low as two percent of the feed volume if the ion
exchange system is operating efficiently. If a facility has a
precipitation/ neutralization system on-site, the regenerant
stream can be directed to this system.
MfC».' • I 0
-------
TABU 2.11. WHAT'S HAPPENING IN ION EXCHANCBT
A KBVIEM OP S.KCEKT LITERATURE
CHARUIS T. OICKBKT
The Process
The Resin
Of Significance
Where
MI.
Photoproeaaalng
irllta
1RA-400
Oranlusi
Ante*
BodluB Chlorate
IRC-84
IRA-400
HIM ley Bng. Ud.
Toronto. Ont. Cen.
HBTALB
These resins remove silver from proceea rinse water Beatman Kodak
and ahow little drop In capacity after 8 cyclea. Rochester. NT
Ag le eluted with 30X ammonium thloeulfste fro* which
Ag cen be recovered and the electrolyte recycled.
The realn la then treated with 5X HjSO4 before going
keck on stream. Alternatively, the reeln can ke
regenerated several tlwea with JX H.SO^ without
reanvlng Ag. to Increaae the Ag loading before
regenerating with thloaulfate.
The chemical consumption for acid leech circuits when
uelng NO.. Cl or HjSO^ for elutlon was evelusted. No
dreaatlc changee In equipment else and resin Inventory
ere anticipated unless new end better Ion exchange
reelns are developed. The elutlon efficiency of
H.S04 circuits could ke Improved. More concentrated
eluetee could be produced at lower chemical coneuaptIon.
Chromete was removed fro* an aqueous solution of sodium Pennwelt Corp.
chlorate by passing the stream upflow through • column
containing theae two resins. Chromete wee recovered
from the realn with a 4X H*OH/8X NeCl solution. The
resins were further treated with an 8t NaCl/4X Hd
eolutlon before treetlng more sodium chlorate aolutlon.
(The CA abstract doee not cover the role of IRC-84 In
this proceea. I aaaume It la there to remove Cr end
other metal Impurltlee. The use of HC1 with NsCl In the
second step of the regeneration could Involve removal of
these metals from IRC-84 since the NeCl by Itself ehould
be adequete to convert OH groups of IRA-400 to the
Cl form).
J. Appl. Photogr. Bog
1980. 6(1). U-18
(93:101036s)
CM Bull. 1980.
73 (814). 107-14
(93: Il308c)
Jpn. Kokal
Tokkyo Koho
79. 14). 37613
Nov. 1979
(93:
-------
TABLB 2.12 (Continued). WHAT'S HAPPRN1NG IN ION RXCMANGKt
A Review or ucewr LITERATURE
CHARLES T. DICKEHT
the Procaea
The Reeln
Of Significance
Where
Kef.
Aroaattc
Purification
trlyat I)
Uofetlt KS-IO
Clbberellealc
Acid
ttarcaatane to
dlaulfldea
irllte
KAD-4
Aariwrlyat A-21
Aery leal da
Pur If lot Ion
taberllt* It-120
lewatlt HP-42
Aaberllte IRA-4J
Aroaattc hydrocarbone when In contact wtth H^SO^ can
font compound* which are colored. Either of theae
two atrong acid realna catalyttcally converted the
laipurltlea Into volatile derivative!. The proceaa
la Improved by uelng feeda containing 50-200 ppo
H|0. The catalytic activity waa retained for at leaat
10.000 bed voluaee.
A feraantatton liquor containing 3)0 unlta of
glbberellenlc acid/liter waa paaaed through a
column of the adaorbent. The glbberellenlc acid
waa eluted with 90Z acetone In water. The yield waa
about MX which la better than la achieved with
activated carbon.
Thle weak baa* realn waa Impregnated with an aa,ueoue
aolutlon containing cobalt phthalocyanlne annoaulfata
and MaOH. After drying It can be uaed aa a eweetenlng
catalyat. In an eiaapla, a VI ppa) aulfur content In
a catalytic cracker dlatlllata waa reduced to I ffm by
contact with the realn catalyat at roo« teaperature
for 5 edn.
A 3)1 aerylratde aolutlon obtained by hydratlng acrylo-
nttrlla with e copper cdntalnlng catalyat contalna up
to 300 ppa acrylonltrtte and up to 80 pp> Cu aa
••purItlea. It la purified by paaalng the aolutlon
through the cation exchanger, the tertiary aoine weak
baae realn (NP-62) and finally the prlvary/aecondary
aaine weak baae realn (IRA-45). After drying, the
polyacrylaailde la coapletely aoluble In water and haa
good flocculating propertlea for auapended aoltda.
Inat. Cheaj.
trtem Uaraaw. Pol.
Inatytat Cheall
Prseeqralowej
UOP. IMc.
Mltaul Toatau
Cheaicali, Inc.
Prieai. Cheat. 1980,
59(11-12). 603-6
(Pol) (94: IMASIp)
•rat. Padldo PI
80 00. 883
21 Oct. 1980
(94: I I9495v)
•elg.. 882, 106
01 Jul 1980
(94: I24381n)
Car. Of fen.
3.019.555
II Dec. 1980
-------
TMLB 1.12 (Continued). WUT'S HAPPBHINC IN ION eXCHANCKf
A REV IBM Of tECCNT LITBRATUM
CHARLR9 T. OICUKT
Tna rroeeee The lea In
Mketeoe IKA-68
•••oval
Of Significance
Water la added to crotonaldehyde containing 3.781
dlketene and peeaed through the weakly baalc reetn
giving an effluent containing no dlketene. In
eqntraat. the effluent contained J.59X dlkatene
when ualng IRA-400. Water addition la 0.) mol-
equlvelent baaed on the dlketene.
where
Del eel Cheklcal
Induetrlea. Ltd.
•ef.
Jfm. Kokal
Tofckyo Koho
80 22.627
18 reb. 1980
(93: 459 7g)
mcroblclde
Hmlc Aclda
rllte IIA-400
irtlte 1M-904
Leuatlt OC-1002
Iodine wee adaorbed on thta real*. Mien thla for* of
the realn containing 42.5X I waa need at the 50 ppa
level It completely Inhibited epore germination of
AJternarla kiftucMana.
Theae highly poroalty atrongly bade realne ware
evaluated for the raaaval of huaic acid and
organic aubataneea (ro« Save River weter. Ihe OH
for* of Uwatlt OC-1002 reeoved 72.31 and 77.6X
of organic aubetaneee hmlc acid, reapectlvely.
The Cl for* of IRA-904 removed 76.8 end 86.2.
Tokyo Organic
Chemical tnduatrlee.
Ltd., Japan
Tehnol. Pak
Zagreb.
Yugoslavia
Jpn. Tokkyo Koho
80. 12. 882
04 Apr. 1980
(93: 232700b).
Frehrambe-no-Tehnol.
Rev. 1979 17(4) 161-4
(Serbo-Croatian)
(93: I378l2f)
-------
TO STORAGETANK OR
OTHER TREATMENT SYSTEM
TO STORAGE TANK OR
OTHER TREATMENT SYSTEM
INFLUENT
WASTEWATER
BACKFLUSH
WATER
ACID
REGENERANT
' f
CATION EXCHANGE
SYSTEM
TO STORAGE TANK OR
OTHER TREATMENT SYSTEM
BACKFLUSH
WATER
TREATED
WASTEWATER
CAUSTIC
REGENERANT
1
ANION EXCHANGE
SYSTEM
TO STORAGE TANK OR
OTHER TREATMENT SYSTEM
FIC.URE 2.12 SCHEMATIC OF ION EXCHANGE
-------
SECTION 2.13
CARBON ADSORPTION
Process Description
Carbon adsorption is a separation technology used to
remove and/or recover dissolved organics and certain inorganics
from single-phase fluid streams. The material used in carbon
adsorption technology is referred to as Granular Activated Carbon
(GAC). Activated carbon includes any amorphous form of carbon
that has been specially treated (i.e., activated) to increase the
surface area/volume ratio of the carbon. The surface of the
carbon is generally non-polar with a few polar sites, due to the
interaction of the surface with oxygen.
Constituents are adsorbed onto the surface via physical
forces, such as van der Waals forces, and chemical forces,
referred to as chemisorption. The adsorption forces are
comparatively weak and therefore the reverse process, desorption,
is also possible. This reversible process allows the carbon
surface to be regenerated.
The majority of carbon adsorption systems use cylindrical
pressure vessels, which contain the activated carbon. The strd
to be treated can flow through the vessel in an upward or
downward flow design mode. The velocity of the upward flowing
stream can be set so that the carbon bed is expanded and
fluidized or so that it is not expanded. The bed expansion
configuration in the GAC system upward flow design mode allows
the GAC unit to handle influents which contain suspended solids
without appreciable pressure drop. The GAC system downward flow
design mode develops high pressure drop with suspended solids
accumulation and typically requires upstream filtration as a
pretreatment step. In addition, the stream can flow through the
beds in series or in parallel. The upward flowing bed expansion
process can be supplemented by periodically pulsing new carbon
into the bed. This periodic pulsing of carbon, which replaces
the same amount of spent carbon that is rejected, allows the
carbon adsorption process to continue without scheduled downtime.
A diagram for a carbon adsorption system is presented at
the end of this section. This diagram illustrates a parallel
configured carbon adsorption system.
Applicability to the Treatment of Hazardous Wastes
Carbon adsorption processes have been used extensively to
treat industrial wastewaters containing dissolved organic
materials and certain inorganic constituents. Contaminants that
are typically removed from aqueous streams include BOD, TOC,
MCTCAL' II tOC
-------
phenol, color, cresol, polyethers, various halogenated organics,
cyanide, and chromium.
At a commercial hazardous waste treatment facility which
processes 40,000 gallons of mixed metal and organic-contaminated
aqueous waste per day, carbon adsorption is the final polishing
step in a process train that includes oxidation, precipitation,
filtration, and neutralization. The carbon system consists of
two downflow beds in series. Although TOC breaks through within
two or three days, phenol concentration is the controlling
parameter due to a stringent discharge permit limit. Phenol
breakthrough occurs in about 28 days. Spent carbon is returned
to the supplier for off-site regeneration.
Full-scale activated carbon systems are installed at
numerous facilities around the world. The design flow rate at
these facilities ranges from 5,000 gallons per day at an
explosive facility in Switzerland to 20,000,000 gallons per day
at one of American Cyanamid's facility in Bound Brook, New
Jersey. The activated carbon treatment system at American
Cyanamid's facility consists of ten 16 foot diameter carbon
columns which operate in an upflow expanded bed configuration.
Table 2.13a presents the results of applying GAC
technology to aqueous wastes containing toxic organics.
Table 2.13b presents the amenability of various organic compounds
to carbon adsorption.
Carbon adsorption is not generally used in the treatment
of non-aqueous process streams. This is because the less polar
the solvent stream, the less likely it will be that constituents
are removed from a relatively non-polar solvent to a non-polar
carbon surface.
Environmental Considerations
The activated carbon used in the carbon adsorption process
eventually reaches a point where it will no longer adsorb
material. This spent activated carbon must then be either
regenerated or discarded. The most common form of regeneration
is thermal regeneration, although various types of chemical
regeneration are used. Chemicals used for regeneration include
acids, bases, and solvents.
The amount of material removed in carbon adsorption
systems will be dependent on the characteristics of the process
stream and its constituents. Most carbon treatment efficiencies
are greater than 99 percent with influent concentrations below
1,000 ppm. At higher concentrations, removal efficiencies can
reach 99.9%.
MCTCAlF • CD
-------
TABLE 2-I1A. TO«IC COMPOUNDS REMOVED PROM WATER US IMC THE CARBON ADSORPTION
IN 1KB HAZARDOUS MATERIAL SPILLS TREATMENT TRAILER
SYSTEM
Coaeovnd
DNBP
PCI
ToMphena
Chlorwana
Beptaehlor
Aldrle
Dleldrla
Re pone
Peetecklorophenol
Nethytene Chloride
Carkon Tetraehlorlde
Benteoe
Toluene
lylene
Trtchleroetheaa
Trlchleroetkylene
location of Incident
Clarke burgh. New Jereey
Seattle. Waahlngton
Ik* Platne. Virginia
Strongatown. Pennaylvanla
Strongatown, Pennaylvanla
Strongatown. Peneaylvanta
Strongetown, Penneylvaala
•opewall, Virginia
•aver ford, Pomaylvanla
Oawego, New Tork
Oewego. New Tork
Oawego. New Tork
Oawego. New Tork
Oawego, New Tork
Oawego. New Tork
Oawego. New Tork
Quantity
treated
(gallona)
2.000.000
600.000
250.000
100.000
1.000
100.000
1.000
100.000
1.000
100.000
1.000
223.000
213.000
230.000
250.000
230.000
230.000
250.000
230.000
230.000
Contact
tie*
(•Inutea)
26
30-40
26
17
240
17
240
17
240
17
240
45.3
26
8.3
8.3
8.3
8.3
8.3
8.3
8.3
Influent
Concen-
tration
-------
TABLE 2.131. AMENABILITY OP TYPICAL ORGANIC COMPOUNDS
TO ACTIVATED CAUON ADSORPTION
Compound
Alcohol*
Methaaol
Ethanol
Propaaol
Butanol
a-Amyl alcohol
a-Hexanol
laopropanol
Allyl alcohol
laobutanol
t-Butanol
2-Ethyl butanol
2-Ethyl hexanol
Aldehyde*
Formaldehyde
Acetaldehyde
Proplonaldehyde
Butyr aldehyde
Acroltlo
Crotonaldehyde
Beasaldehyde
Paraldehyde
Dt-N-Propylamlne
Butylamine
Dl-K-Butylamlae
Allylamiae
Zthylenedlamine
Diethyleaetrlamiae
tkmethaaolamlne
Dtethaaolaaine
Triethanolamiae
Honoleopropaaolamlne
Diitopropaaolamlae
Pyridloaa A BbrmfaoUaea
Pyridioe
2-*ethyl-S-Ethyl pyridine
•-Methyl morpholioe
•-Ethyl morpholloa
Aromatic*
Beetene
Tolueae
Ethyl beaxeae
Phenol
Hydroqulaoa*
Aniline
Styreae
•Urobeaaeae
Methyl acetate
Ithyl acetate
Propylacetate
Butyl acetate
Primary emyl acetate
Molecular
Height
32.0
A6.
60.
74.
88.
102.
60.
58.
74.1
74.1
102.2
130.2
30.0
44.1
58.1
72.1
56.1
70.1
106.1
132.2
101.2
73.1
129.3
57. 1
60.1
103.2
61.1
105.1
149.1
75.1
133.2
79.1
121.2
101.2
115.2
78.1
92.1
106.2
94
110.1
•3.1
104.2
123.1
7A.1
88.1
102.1
116.2
130.2
Aqueoua
Solubility
(Z)
•
•
•
7.7
1.7
0.38
•
•
8.5
•
0.43
0.07
•
•
22
7.1
20.6
15.5
0.33
10.5
.
•
•
•
•
•
•
95.4
•
•
87
•
el.eol.
•
•
0.07
0.047
0.02
6,7
6.0
3.4
0.03
0.19
31.9
8.7
2
0.68
0.2
Concentration
Initial
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.010
1.000
1.000
1.000
700
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1,000
1.000
1.000
1.000
1.000
1.012
996
1.000
1.000
1.000
1.000
1.000
1.000
1.000
416
317
115
1.000
1.000
1.000
180
1.023
1.030
1.000
1.000
1.000
»85
Piaal
(C,)
964
901
811
466
282
45
874
789
S81
705
145
10
908
881
723
472
694
544
60
261
198
480
130
686
893
706
939
722
670
800
543
527
107
575
467
21
66
18
194
167
251
18
A4
760
495
248
154
119
Adiorbabllltv
| compound/
| carbon
0.007
0.020
0.038
0.107
0.155
0.191
0.025
0.024
0.084
0.059
0.170
0.138
0.018
0.022
0.057
0.106
0.061
0.092
0.188
0.148
0.174
0.103
0.174
0.063
0.021
0.062
0.015
0.057
0.067
0.040
0.091
0.095
0.179
0.085
0.107
0.080
0.050
0.019
0.161
0.167
0.150
0.028
0.196
0.054
0.100
0.149
0.169
0.175
Percent
(eduction
3.6
10.0
18.9
53.4
71.8
95.5
12.6
21.9
41.9
29.5
85.5
98.5
9.2
11.9
27.7
52.8
30.6
45.6
94.0
73.9
80.2
52.0
87.0
31.4
10.7
29 .-4
7.2
27.3
33.0
20.0
45.7
47.3
89.3
42.5
53.3
95.0
79.2
64.3
80.6
83.3
74.9
88.8
95. 6
26.2
50.5
75.2
84.6
86.0
-------
TABLE 2.131 (Continued). AMENABILITY OP TYPICAL ORCAtilC COMPOUHDS
TO ACTIVATED CAUON ADSORPTION
Compound
••ten
Xaopropyl sectact
laobutyl ecetatc
Tlnyl acetate
Ethylen* flyeol •oooethyl ether actcat*
Ethyl eerylate
Butyl acrylate
Ether*
Xaopropyl ether
Butyl ether
Dlehlorolaopropylene ether
Qyeola A aycol Ether*
Ethylene flyeol
Diethylene glyeol
Triethylen* glyeel
Tetraethylene flyeol
Propylene flyeol
Dipropylene flyeol
Hexylene flyeol
BthyltM flyeol •oaoeAthyl ether
Ethyleac flyeol eanoethyl ether
Ethyleae flyeol npaobutyl ether
Ethyleae flyeol •ooohesyl ether
Dlethyleae flyeol eaaoethyl ether
Dtethyleae flyeol •onobutyl ether
Kthocytrlflyeol
fmlogeaeted
tthyleoe dlehlorlde
Propyleoe diehlorlde
•etovee
Acetone
Mtthylethyl ketone
Methyl propyl ketooe
Methyl butyl ketone
Methyl teobutyl ketone
Methyl Isoeiyl ketoae
DiUobutyl ketone
Cyelohexanone
Aeetophenone
leophorone
Otfaele Acid*
Foraie eeld
Aeetle ecid
froplonle acid
Butyric ecld
Velerte eeid
Ceprotc acid
Acrylic ecid
leasole eeid
OlidM
Propyleae oxide
ftyreat oxide
Molecular
Height
102.1
116.2
•6.1
132.2
100.1
128.2
102.2
130.2
171.1
62.1
106.1
150.2
194.2
76 1
134.2
118.2
76.1
90.1
118.2
146.2
134.2
162.2
178.2
99.0
113. .0
98.1
72.1
86.1
100.2
100.2
114.2
142.2
98.2
120.1
138.2
A6.0
60.1
74.1
88.1
102.1
116.2
72.1
122.1
98.1
120.2
Aqueou*
Solubility
(t)
2.9
0.63
2.8
22.9
2.0
0.2
1.2
0.03
0.17
•
•
0.99
•
•
0.81
0.30
•
26.8
4.3
v. el. w
1.9
0.54
0.05
2.5
0.55
1.2
•
•
•
•
2.4
1.1
0.29
40.5
0.3
nt/1
Initial
1,000
1.000
1.000
1.000
1.015
1.000
1.023
197
1.008
1.000
1,000
1,000
1,000
1.000
1.000
1.000
1.024
1.022
1.000
975
1.010
1.000
1.000
1.000
1.000
1.000
1,000
1.000
»1. 988
1.000
986
300
1,000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Ploal
(Cf>
319
180
357
342
226
43
203
nil
nil
932
738
477
419
884
835
386
886
70S
441
126
570
173
303
189
71
782
532
305
191
152
146
nil
332
28
34
765
760
674
405
203
30
335
89
739
47
Adtorbablllty
g compound/
g carbon
0.137
0.164
0.129
0.132
0.157
0.193
0.162
0.039
0.200
0.0136
0.053
0.105
0.116
0.024
0.033
0.122
0.028
0.063
0.112
0.170
0.087
0.166
0.139
0.163
0.183
0.043
0.094
0.139
0.159
0.169
0.169
0.060
0.134
0.194
0.193
0.047
0.048
0.065
0.119
0.159
0.194
0.129
0.183
0.052
0.190
Percent
Reduction
68.1
82.0
64.3
65.8
77.7
.93.9
80.0
100.0
100.0
6.8
26.2
S2.3
58.1
11.6
16.5
61.4
13.5
31.0
55.9
87.1
43.6
82.7
69.7
81.1
92.9
J
21.1
46.8
69.5
80.7
84.8
85.2
100.0
66.8
97.2
96.6
23.5
24.0
32.6
59. 5
79.7
97.0
64.5
91.1
26.1
95. J
-------
ACTIVATED
CARBON
SOURCE
r
1
CARBON
ADSORPTION
COLUMN
WASTEWATER
CONTAINING ORGANIC8
CARBON
ADSORPTION
COLUMN
TREATED
WASTEWATER
CARBON
ADSORPTION
COLUMN
ACTIVATED CARBON
WITH ADSORBED ORGANICS
TO BE REGENERATED
OR DISPOSED OF
FIGURE 2.13 SCHEMATIC OF CARBON ADSORPTION
-------
SECTION 2.14
RESIN ADSORPTION
Process Description
Resin adsorption is a process by which an organic
substance is removed from an aqueous waste and can be recovered,
if desirable. The process involves adsorption of organics onto a
synthetic resin in a fixed bed. Usually the waste is fed in a
downflow mode to the resin bed, which is contained in an enclosed
cylindrical stainless steel or rubber-lined steel tank. Resin
adsorbents are used in much the same way as granular carbon.
However, in resin adsorption, the strength of the attractive
forces between the solute molecules and the resin is usually
weaker than that associated with adsorption on carbon. This
allows for easier regeneration of the resin and improved
potential for recovery of the adsorbed substances.
The adsorptive capabilities depend to a great degree on
the specific type of resin used. The chemical nature of resins
may vary significantly from one resin to another. Different
types of resins have affinities for different types of chemical
compounds.
Because the influent to the adsorption tanks must be low
in suspended solids (in some cases less than 10 ppm), filtration
units often precede the adsorption units.
In many cases, adsorption will be pH dependent, and thus,
pH adjustment will be necessary prior to treatment. Strong
oxidants, which would chemically attack the resins, must be
removed from the influent stream. This process would typically
be used as a polishing step. A resin adsorption system is shown
in Figure 2.14.
Applicability to the Treatment of Hazardous Waste
Resin adsorption is commonly used for removal of phenol
from waste streams. Full-scale installations include an Indiana
plant, which uses resin adsorption to recover phenol from its
waste stream and a plant in West Virginia, which uses a resin
adsorption system to remove phenol and high molecular weight
polycyclic hydrocarbons from a waste stream. Reportedly, a resin
adsorption system was installed at the Naval Ammunition Depot in
McAlister, Oklahoma, to remove such contaminants as TNT, 2,4-DNT,
RDX (cyclotrimethylenetrinitramine), and BMX (cyclotetra-
methylenetetranitramine) from aqueous wastes (DeRenzo, 1978).
Resin adsorption for removal of explosive materials is more
economical than carbon adsorption since the carbon cannot be
thermally regenerated once its capacity has been used up.
• too*
-------
Regardless of the source of the waste, it is necessary that the
feed stream to the resin adsorption system be a single liquid
phase.
Environmental Considerations
Spent resin regenerants, if not reused, must be disposed
of. Frequently, disposal has been either by incineration or land
disposal.
MCTCALf • tOO"
-------
•IVIIT
•AMU*
MUOUC .
•Mil
ftltlMMC
MtOMtH
•1
nuni
•UTt
Kikjcd •tan Mftfy
SOURCE: CtoRENZO. 1978)
HGURE 2.14 SCHEMATIC OF RESIN ADSORPTION SYSTEM
FOR REMOVAL AND RECOVERY OF PHENOL
HC1C*t.> • C 00 •
-------
SECTION 2.15
STEAM STRIPPING
Process Description
Steam stripping is the removal of gases or volatile
organics from a dilute wastewater. This process is identical to
steam distillation (see section 2.9, DISTILLATION) except that
the wastewater is fed at the top of the column. Reintroduction of
a portion of the recovered material into the column (reflux or
recycle) increases the removal efficiency (De Renzo, 1978). A
schematic of a steam stripper is presented in Figure 2.15.
Applicability to the Treatment of Hazardous Waste
Steam stripping is a widely used to strip hydrogen sulfide
gas (B2S) and ammonia (NH3) from refinery "sour" waste and
ammonia from coke oven gas. It also removes phenol in the first
process, and has been tested for use in removal of immiscible
volatile chlorinated organics. For the potentially banned
hazardous wastes it is applicable to phenol and immiscible,
volatile organics, whether chlorinated or unchlorinated (Kiang
and Netry, 1982.)
Removal efficiencies of 99.7 percent or better of ammonia
and hydrogen sulfide gases are possible from feed solutions
containing 0.3% NH3 and 0.7% H2S by weight. Phenol-containing
solutions retain from 150-750 ppm after stripping and may require
further treatment. (Kiang and metry 1982). Removal efficiencies
approaching 90% have been observed for feed streams containing
3,000-6,000 ppm of chlorinated hydrocarbons using a column 3 feet
in diameter with 20 feet of packing (GSRI, 1979).
At one solvent recycling facility, steam stripping is used
to recover residual solvent from aqueous still bottoms.
Steam stripping is suitable for liquids only which contain
volatile chemicals. It is not as well developed for use on
immiscible organic removal as it is for ammonia and sulfide gas
removal. Table 2.15a presents some toxic organic compounds which
can be easily steam stripped and Table 2.15b presents some
performance data for steam stripping of organics.
Environmental Considerations
The stripped liquid may require further treatment (e.g.
carbon adsorption) if the chemical of concern has not been
removed to desired levels. Since the contaminants are present in
small concentrations in the aqueous waste, still bottom residues
rarely develop.
MCTCALf • COO'
-------
TABLE 2-15A. SOME TOXIC ORGANIC COMPOUNDS WHICH CAN EASILY BE STEAM STRIPPED
Benzene Vinyl chloride
Chlorobenzene 1,2-Dichloropropane
Diehlorobenzenes 1,3-Dichloropropene
Ethylbenzene Hexachlorobutadiene
Toluene Hexachlorocyclopentadiene
Styrene Methyl bromide
Xylenes Dichlorofluoromethane
Methyl chloride Dichloroethylenea
Methylene chloride Trichloroethylene
Chloroform Tetrachloroethylene
Carbon Tetrachloride Allyl chloride
Chloroethane Tozaphene
1,1-Diehloroethane Isoprene
1,1,1-Trichloroethane Carbon disulfide
Hexachloroethane Cyclohexane
Source:Analysis of Operation and Emissions from Typical Hazardous Waste
Treatment Processes. Prep, by Water General Corp. for the Common-
wealth of Massachusetts, Dept. of Environmental Management, Bureau of
Solid Waste Disposal, Dec. 1982.
-------
TABLE 2-15B. STEAM STRIPPING PERFORMANCE
Influent Effluent Percent
Compound (mg/1) (ag/1) removal
Stripper 1
Dichlorooethane 1,430 < 0.0153 > 99.99
Carbon tetraehloride < 665 < 0.0549 > 99.99
Chloroform < 8.81 1.15 < 86.9
Stripper 2
Dichloromethane 4.73 < 0.0021 > 99.95
Chloroform < 18.6 < 1.9 89.8
1,2-Dichloroethane < 36.2 4.36 < 88.0
Carbon tetraehloride < 9.7 < 0.030 99.7
Stripper 3
Kethylene chloride
Chloroform
1 ,2-Dichloroe thane
34
4,509
9.030
< 0.01
< 0.01
< 0.01
> 99.97
> 99.99
> 99.99
Source: Jett, G.M., Development Document for Expanded Best Practicable
Control Technology, Best Conventional Control Technology, Best
Available Control Technology in the Pesticides Chemicals Industry,
Effluents Guidelines Division, U.S. EPA, EPA-440/1-82-0796, November
1982.
-------
The stripped material is concentrated in the condensed
steam overhead product. In some cases, the material may be
recovered for reuse. Where recovery is not practical, this
concentrated waste stream requires further treatment, incinera-
tion, or disposal.
MCTCAir • COO"
-------
FIGURE 2.15
STEAM STRIPPING COLUMN-
PERFORATED TRAY TYPE
Organic
Vapors
Liquid
Feed
Sieve
Tray
Cartridge
Support
Rods
Downcomer
Heat
Flow
Steam
Stripped
Effluent
Source: Pf audler, Rochester, New York
-------
SECTION 2.16
AIR STRIPPING
Process Description
Air stripping is a process that uses forced air to remove
undesired constituents from a liquid phase. This process is
ideal for aqueous hazardous waste streams containing organics
that are volatile and only slightly soluble in water. Other
factors important in the removal of organics from wastewater in
air stripping are temperature, pressure, air to water ratio, and
the surface area available for mass transfer.
There are several types of air stripping processes. These
include sprays and spray towers, mechanical aeration, diffused
aeration, and packed towers.
Packed towers can achieve up to 99.9 percent removal of
some volatile compounds from aqueous wastes while the other
aeration devices have removal efficiencies in the range of
between 50 and 90 percent. The system selected will depend on
the physical/chemical characteristics of the waste stream.
A packed tower air stripper schematic is presented at the
end of this section. Tower diameters on these units range from
one foot to 14 feet with packing heights as high as .fifty feet.
Depending on the volatility of the contaminants, air to water
volumetric ratios may range from 10 to 1 up to 300 to 1.
Applicability to the Treatment of Hazardous Wastes
Air stripping is an appropriate technology for the removal
of slightly water soluble, volatile organics from aqueous
hazardous wastes and contaminated groundwater. This technology
has only been recently used in the full-scale treatment of
hazardous waste streams, but numerous pilot studies are being
performed to determine other applications.
Packed tower air stripping has been utilized to clean up
groundwater aquifers contaminated with chlorinated hydrocar-
bons. These compounds generally have water solubilities of less
than 10,000 mg/1 and are very amenable to removal using air
stripping. Contaminant concentrations have been on the order of
0.1 mg/1 to 5 mg/1. Data from air stripping of contaminated
groundwater are presented in Table 2-16.
Air stripping is an appropriate technology for a well
characterized waste stream containing volatile organics. If the
waste stream contains other constituents, pretreatment and post-
treatment technologies may be needed. Suspended solids and
too-
-------
dissolved metals that will be oxidized to an insoluble form must
be removed before the stream enters the packed tower or fouling
will occur. It is often necessary to pilot test waste streams to
assure that air stripping is an appropriate technology. This
technology is most applicable to waste streams with concentra-
tions below 100 mg/1.
Environmental Considerations
Air stripping produces air emissions of the stripped
volatile compounds. Containment of these emissions is difficult
when using mechanical aeration or sprays, but, the off-gas from a
packed tower can be directed through a carbon adsorption unit to
clean the off-gas.
TABLE 2.16. AIR STRIPPING TREATMENT RESULTS
Results from Remedial Action of Groundwater Contamined by
Landfill Leachate
Range of Concentrations, ug/1
Parameter Untreated Treated
Chloroform
Methylene chloride
1,1-Oichloroethylene
Tetrachloroethylene
Cis-1,2-dichloroethylene
Trans-1,2-dichloroethylene
Trichloroethylene
1,1-Dichloroethane
1,2-Dichloroethane
1,1,1-Tr ichloroethane
1,1,2-Tr ichloroethane
1,2-Dichloropropane
8. -
<0.2 -
8*. -
2l! -
4. -
2*. -
38.
45.
2.0
9.
35.
13.
108.
22.
2.
13.
3!
, - 5.
- 3.
2 - <0.2
, - 2.
, - 1.
- 2.
, - 9.
, - 2.
, - 2.
reT: Wenck, T984.
MCTCALf • t30*
-------
Efflum tir with
«etotilt orpnics
i»»tni wtth
•Otetito orpnics
nGURE 2.16 SCHEMATIC OF AIR STRIPPING
MfTC*l.r • too-
-------
SECTION 2.17
SOLVENT EXTRACTION
Process Description
Solvent extraction is a process whereby a dissolved or
adsorbed substance is transferred from a liquid or solid phase to
a solvent that preferentially dissolves that substance. When the
waste to be treated is a liquid (often water) the process may be
called liquid-liquid extraction, the substance transferred is the
solute, the treated effluent is referred to as the raffinate and
the solute-rich solvent phase is called the extract. For the
process to be effective, the extracting solvent must be
immiscible in the liquid and differ in density so that gravity
separation is possible and there is minimal contamination of the
raffinate with solvent.
Solvent extraction can be performed as a batch process or
by the contact of the solvent with the feed in staged or
continuous contact equipment. The solvent and the wastewater are
agitated in one vessel (the mixer) and then transferred to
another vessel (the settler) where the phases are separated by
density differences. This operation can occur more than once so
that there are multiple mixer-settler stages. Another option,
which is depicted in Figure 2.17, is continuous countercurrent
contact in a vertical column such as a spray tower, packed tower,
or sieve plate tower.
Applicability to the Treatment of Hazardous Wastes
Solvent extraction is used to remove organic contaminants
from aqueous wastes in several industries including petroleum
refining, organic chemicals manufacturing, pulp and paper, and
iron and steel.
There has been a full-scale solvent extraction operation
for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) tested at
the Syntex Agribusiness facility in Verona, Missouri. The
2,3,7,8-TCDD was extracted from distillation bottoms at this
facility with six to eight successive hexane washes resulting in
a reduction from 340 to 0.1 to 0.5 ppm 2,3,7,8-TCDD concentra-
tions.
Aqueous and organic solvents have been tested in the
laboratory for extracting 2,3,7,8-TCDD from various soil types.
The results of these tests have been positive. Chemical Waste
Management Company has reported success with solvent extraction
of 2,3,7,8-TCDD from soil. They experienced removal efficiencies
of 99 percent. They are continuing to perform bench tests on
solvent extraction.
MCTCALF • tOOV
-------
Solvent extraction is a limited technology in that it is
almost always necessary to further treat the raffinate and/or the
extract. This technology is typically used when it is not
economical or possible to use more standard technologies. The
removal efficiency of solvent extraction depends on the solvent,
the constituent to be extracted, soil properties, if a
constituent is being extracted from soil, the liquid containing
the constituentr and the unit operation design. Typical removal
efficiencies vary from 80 percent to close to 100 percent.
Table 2.17 presents extraction removal efficiencies for a
halogenated hydrocarbon waste from a petrochemical manufacturer.
It is often possible to reuse the solvent in the solvent
extraction process. This is accomplished by using a distillation
column to remove the extracted solute molecules from the solvent
in a concentrated form and then reusing the distilled solvent.
In addition, the cost of solvent extraction is relatively
high. The high cost of solvent extraction results from initial
solvent costsr further treatment of the extract, such as
distillation, and disposal costs of the extracted constituents.
Environmental Considerations
Liquid-liquid extraction results in two streams, the
raffinate and the extract, which usually require further
treatment. If aqueous, the raffinate may be contaminated with
small quantities of both the solute and the solvent. These may
have to be removed by carbon adsorption or biological
degradation. Solvent is typically recovered from the extract by
distillation, leaving a concentrated solute-solvent waste stream
for incineration or disposal.
Solvent extraction from soil or sludges produces an
extract and a solvent-saturated solid phase. The solid may be
rendered nonhazardous by evaporation of the solvent.
MCTCAL'
-------
SCRUBBER I
FEED I
INFLUENT
WASTEWATER
1
PURE
EXTRACT
SOLVENT
SCRUBBING
SECTION
IMPURE
EXTRACT
EXTRACTION
SECTION
AAFFINATE
SOLVENT FEED
FIGURE 2.17 SCHEMATIC OF SOLVENT EXTRACTION
Mf 1C *<.' • t OO «
-------
TABLE 2.17. EXTRACTION OP AQUEOUS HALOGENATED HYDROCARBON HASTES FROM
PETROCHEMICAL MANUFACTURING WITH CIQ- C12 SOLVENT AND KEROSENE
(Solvent to Haste Ratio 7 to 1)
Kerosene C10-C13 Hydrocarbon
Influent Effluent Effluent
Organic Compound (mg/1) (mg/1) (mg/1)
Vinyl Chloride 1 1 1
Ethyl Chloride 3 1 1*
Vinylidene Chloride 13 1 1
Dichloroethylene 49 2 1+
Chloroform
Ethylene Dichloride 320 — 16
Carbon tetrachloride
Trichloroethylene 24 6 5
Trichloroethane 75 2 3
Perchloroethylene 14 2 1
Tetrachloroethane 148 7 6
Pentachloroethane 10 2
Unknown 6 _2 _1.
Total 663 43 36
Percent Removed 94 95
Solubility of Solvent
in water in mg/1 — 30 20
Ref: U.S. EPA, April, 1979.
-------
FIGURE 2.2a
RECYCLE FLOW DAF SYSTEM
Air/Solids Mix
Recycle
Source: Peabody-Welles, Roscoe, IL
—Pressurized
Air Bubbles
Liquid
Light
Solids
Heavy
Solids
(Sludge)
-------
FIGURE 2.2b
INDUCED AIR FLOTATION
Pump
fCCCI
Air
Effluent
Surface (Liquid
Skimmer Sludge)
Induced
Air
Bubbles
Fixed Eductor Unit
Heavy
Sludge
Source: U.S. Filter, Whlttler, California
-------
SECTION 2.3
CENTRIFUGATION
Process Description
Ccntrifugation is a physical process which uses
centrifugal forces created in a stationary vessel to separate
immiscible components based on their density. The centrifugal
force is created by an internal piece of equipment, such as a
bowl, basket, or disk, that is spun at a high speed. The
centrifugal force causes the components with greater density to
migrate to the outer portion of the spinning mechanism.
Centrifugal forces in centrifugation are similar to gravitational
forces in sedimentation except that the centrifugal forces are
thousands of times stronger than gravitational forces.
There are three major types of centrifuges which may be
classified by their rotating device - bowl, basket, and disk.
The continuous discharge bowl centrifuge has a solid tubular bowl
with a tapered end where final dewatering takes place. Inside
the bowl is a rotating scroll that spins in the same direction as
the bowl at a slightly slower or higher speed to remove the
separated solids. A schematic of the continuous solid bowl
centrifuge is presented on Figure 2.3a.
Similar to the bowl-type centrifuge but with a diameter
larger than its working length is the solid basket type
machine. There are two types of basket centrifuges and they are
distinguished by the axis upon which the basket rotates. The
less common basket centrifuge, which spins about a horizontal
axis, is a batch centrifuge which requires stopping the
centrifuge and cleaning the basket of sludge. The other basket
centrifuge rotates on a vertical axis. In this centrifuge the
liquid (centrate) is forced to the top lip of the basket where it
flows over a weir and is removed. The solids are forced to the
basket surface forming a cake. The cake is removed by slowing
the basket rotation and advancing a plow or other device into the
cake forcing the collected solids to fall out the bottom of the
basket. A basket centrifuge is shown in Figure 2.3b.
The disc centrifuge utilizes angled discs mounted on a
vertical axis. The feed to this centrifuge is distributed into
layers of roughly 0.05 inches thick between the conical discs.
This separation of the feed increases the ability of the
centrifuge to separate the solids. The solid particles settle
through these channels to the underside of the disc and
eventually to a sludge compaction zone.
MCTCALF • 1001
-------
Typical overall dimensions for bowl centrifuges range from
two to six feet in height by six to twelve feet in length by
three to six feet in width. The actual inside diameter of the
bowl can range from less than one foot to over two feet. These
operating dimensions are appropriate for an influent slurry rate
of between 8 gpm and 800 gpm.
Basket centrifuges have actual basket dimensions that
typically range from one foot in diameter to four feet in
diameter by two feet to three feet in depth. Basket centrifuges
can treat wastewater flow rates of between 20 and 80 gpm.
Disc-type centrifuges have typical overall dimensions of
one to three feet in diameter by four to eight feet in length.
These centrifuges have influent flow rate capacities ranging from
5 gpm to 500 gpm.
Applicability to the Treatment of Hazardous Wastes
Eazardous waste treatment applications for centrifuges
include dewatering of sludge and separation of oil from water and
solids. Centrifuges are generally better suited than vacuum
filters for dewatering of sticky or gelatinous sludges. Disc-
type centrifuges can be used to separate a three component
mixture such as oil/water/solids. In this application, the oil
(which in most instances is the least dense component) moves to
the center of the centrifuge and is discharged through an upper
spout while the water travels in the opposite direction and is
discharged from a lower spout. The solids are collected at the
outer periphery of the bowl and are automatically or manually
removed. This application is very common in the metal working
industry to recover oils or coolants for reuse, and in the oil
refining industry for slop oil recovery.
Centrifugal operations are generally limited to the
dewatering of sludges and the separation of oil from water.
Centrifuges can not generally be used for clarification because
centrifugation removes large quantities of solid material but
also fails to capture much of the solids. Typically 80-90 percent
of the influent solid material is recovered. Recovery may be
improved if a filter paper or cloth is ued to line the basket.
At a commercial hazardous waste treatment facility which
treats aqueous wastes in 500 gallon batches, a horizontal
perforated basket centrifuge with a rotational speed of 850 RPM
is used to separate precipitated metals from treated
wastewater. The basket is lined with a filter paper. Effluent
is sewered. The high solids sludge may be sent to a metal
reclaimer or landfilled.
MCTCAL' » too*
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Environmental Considerations
The centrate after sludge dewatering by centrifugation
contains 10 to 15 percent of the feed solids and must be recycled
for treatment. A sludge cake containing 10-20 percent solids can
be produced by centrifugation of metal hydroxide sludges. In
phase separation applications, the water portion contains
significant oil and/or solids and must be recycled for treatment.
This is also the potential for emission of volatile
chemicals from open topped basket centrifuges.
MCTCAI' • (DOT
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FIGURE 2.3a
SOLID BOWL CENTRIFUGE
Drive Assembly
Solids
Discharge
Source: Dorr-Oliver, Stamford, Connecticut
Rotor—i
, Drive Assembly
Clarified
Effluent
Feed
-------
FIGURE 2.3b
BASKET CENTRIFUGE
Solids
Cake
Basket Wall
Fitter Paper
(Used With
Perforated Wall)
Solids
Cake Buildup
Revolving
Basket
Frame
Source: Western States Machine Co., Hamilton, Ontario
I
Effluent
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SECTION 2.4
GRANULAR MEDIA FILTRATION
Process Description
Granular media filtration is the removal of suspended
solids from a fluid by passage of the fluid through a bed of
granular material. Several mechanisms are involved in the
removal of suspended solids by granular media filtration. They
include straining, physical adsorption and coagulation-
flocculation. A granular media filter therefore can remove
particles much smaller than the void size of the filter media.
The most efficient granular media filter utilizes the
entire bed depth, not just the surface. Accordingly, the ideal
bed would be graded from the largest to the smallest media size
in the direction of flow. Unfortunately, in the usual downflow
filter configuration backwashing to remove accumulated solids
tends to distribute the media in the reverse order, with the
smaller grain sizes on top. Two methods have been used to
approach the ideal - upflow filtration and multi-media filtration
using two or more materials with different densities. Materials
most commonly used for multi-media filters are anthracite, sand
and garnet. .
Filters may be open top with gravity feed, or enclosed in
a pressurized vessel. The range of configurations available
include many proprietary designs related primarily to
improvements in the backwashing operation. Figures 2.4
illustrates a granular media filter.
Filtration rates range from two gpm/sf for shallow beds of
fine sand to over 15 gpm/sf for deep bed filters using coarse
sand or multiple media beds. Vessels are from 2-1/2 to 20 feet
in diameter, with media depth of 1-1/2 to over 15 feet.
Applicability to Hazardous Waste Treatment
Granular media filtration would typically be used after
gravity separation processes, for:
1. additional removal of suspended solids and oils prior
to other treatment processes
2. polishing of treated wastes to reduce suspended solids
and associated contaminants to low levels.
Pretreatment by filtration would be appropriate for membrane
separation processes, ion-exchange, and carbon adsorption in
order to prevent plugging or overloading of these processes. In
• COOT
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heavy metals removal by precipitation, very low metal limits
apply to the treated effluent that is discharged to surface water
or pubicly owned treatment works. Filtration of settled waste is
often required to remove undissolved heavy metals which occur as
suspended solids to ensure meeting effluent quality requirements.
Granular media filtration should be preceded by gravity
separation or other pretreatment processes for suspended solids
concentration greater than about 100 mg/1. Otherwise, premature
plugging and excessive backwashing will occur.
Environmental Considerations
Accumulated solids and oils are removed from the granular
media bed by backflushing with water, sometimes in combination
with air. The backwash water is either recycled to a clarifier
or treated separately for concentration and dewatering of the
solids.
MCTCAl.' • tOOV
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Ififluattt Plplm
Backwath mkrt
Undwdrahi Symm
ATTOVM ImflcM* Rout*
CM B«ck«Mth
Backwash
Ellkienl
SOURCE: INFItCO OEORCMOMT. INC
FIGURE 2.4 PACKAGED GRANULAR MEDIA GRAVITY FILTER
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SECTION 2.5
VACUUM FILTRATION
Process Description
Vacuum filtration is the dewatering of sludges under
negative pressure, and generally is employed to dewater sludges
produced from precipitation and sedimentation processes. A
typical vacuum filter is a mechanically supported cylindrical
rotating drum covered by a filter medium made of cloth, coil
springs, or a wire-mesh fabric. As it rotates slowly, but
continuously, through a sludge vat, sludge in contact with the
drum is subjected to a vacuum exerted through internal
pressurized pipes. Water is drawn through the filter media,
leaves behind solids on the media surface, and is discharged as
clean filtrate from an exit port. The solids are dislodged by
positive pressure from the piping system and the action of a
mechanical scraper applied as drum sections become exposed. The
filter media is then washed to remove remaining solids deposits.
Sludges are usually chemically conditioned with poly-
electrolytes or lime, and/or ferric chloride prior to vacuum
filtering to decrease clogging and reduce solids concentrations
in the filtrate. The filter media may be coated with various
precoat materials, such as diatomaceous earth, which traps finer
particles and increases solids removal. A representative rotary
vacuum filter is shown in Figure 2.5.
Applicability to the Treatment of Hazardous Waste
Vacuum filters are very common sludge dewatering devices
for treatment of hazardous wastes from a number of manufacturing
industries such as the organic and inorganic chemicals production
and paint and dye manufacture. Dewatering of metal hydroxides
from plating and finishing waste treatment by vacuum filtration
is also commonplace.
Potentially banned wastes which are treatable with this
technology include:
. metals and cyanides bound up in hydroxide sludges
. organic and inorganic chemical sludges
While vacuum filtration is not a detoxification or
destruction technology, the process is important in reducing the
volume of hazardous sludge that must be managed.
MCTCAl.' • IDS'
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Vacuum filtration is ideally applicable to sludges of a
solids concentration between 5 to 10 percent, therefore it is
often preceded by thickening. Lower solids concentration require
an excessively large vacuum filter size and time of operation,
higher concentrations will be viscous and difficult to handle. A
filtrate with solids concentration from 100 to 5,000 mg/1 or more
is generated which must be treated prior to discharge (Kiang and
Metry, 1982).
Most sludges can be dewatered to solids concentrations
between 20-50 percent. Netal hydroxide sludges are dewaterable
usually to at least 30 percent solids and 40 percent solids or
better is not uncommon.
The applicability of vacuum filtration for the management
of hazardous wastes was confirmed during one of the visits made
to commercial facilties as part of this EPA sponsored study.
This commercial establishment employed neutralization and
precipitation for metals removal. The sludge produced from the
metals precipitation process was thickened on a clarifier. The
filter cake produced from the vacuum filter was typically
comprised of 25 percent solids, thereby reducing the metal
precipitate sludge volume requiring disposal.
Environmental Considerations
Similar to other liquid-solid separation processes, vacuum
filtration produces several residuals that must be properly
managed. These include;
1. Dewatered sludge cake
2. Filtrate
3. Drum washings
4. Vapors.
Depending on the chemical composition of the dewatered
sludge, several management options are available including reuse,
recovery and solidification/fixation. The filtrate can be
recycled back to the treatment system, discharged, or used for
process water depending upon its characteristics. Drum washings
are normally recycled back to the treatment system. The negative
pressure occurring during part of the vacuum filtration cycle can
result in the release of volatile components from the sludge.
Data is needed for all four of these residuals in order to
determine appropriate management options.
• too*
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SOURCE: CLARK. ET. AU 1»77
FIGURE 2.5 TYPICAL VACUUM FILTER
MC t C * L ' • *
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SECTION 2.6
CHAMBER PRESSURE FILTRATION
Process Description
Chamber pressure filtration is the dewatering of sludges
in mechanical filtration chambers which operate in parallel under
pressures typically about 100-200 psi. Chamber pressure filters
include pressure leaf filters, tube.element filters, horizontal
plate filters, and plate-and-frame or pressure filters. The last
is most representative of chamber pressure filters, is in widest
use, and will be the focus of this discussion.
A pressure filter (also called filter press) consists of a
collection of cloth covered plates arranged in parallel, held
vertically within a frame, and pressed together by a hydraulic
cylinder. (Figure 2.4). Sludge is pumped under pressure into
the chambers between the plates, the plates are compressed, and
water exits through the filter cloth. The concentrated solids
left behind in the chamber are periodically removed; the filtrate
is usually clear and dischargeable without further treatment.
Precoating the filter cloth with diatamaceous earth can prevent
clogging of its pores, and often the sludge is chemically
conditioned to improve filterability by consolidating fine
particles.
Dewatering of flocculated or sticky sludges by pressure
filtration can produce cake densities in the range of 40-50% dry
solids after a 1-2 hour batch pressure cycle.
Applicability to the Treatment of Hazardous Wastes
Pressure filtration is well suited to dewatering sludges
with a flocculated.or adhesive-like nature, such as metal
hydroxide sludges. It dewaters such sludges to a higher solids
concentration than is achievable with a vacuum filter, though at
a somewhat higher capital and operating cost.
At one of the commercial hazardous waste management
facilities surveyed, a plate and frame filter press was being
used to dewater metal hydroxide sludges. Various drummed and
bulk liquid aqueous wastes and mixed aqueous-organic liquid
wastes were adjusted to pR 11 with lime. The entire process
stream containing the mixed-metal hydroxide sludge was subjected
to a plate and frame filter press. The 45 percent solids filter
cake produced was landfilled, while the filtrate was neutralized
to pH 6-7 with hydrochloric acid, and subjected to treatment with
GAC prior to discharge to the municipal sewer.
• COD"
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The applications of chamber pressure filtration are
limited to systems that can tolerate batch operation. Where unit
operations, used to treat hazardous wastes are operated in a
continuous mode, sufficient sludge holding capacity ahead of the
filter must be provided.
Environmental Considerations
The use of chamber pressure filtration reduces the volume
of sludge requiring disposal and reduces the associated disposal
costs. The residuals that must be properly managed, and for
which data needs have been identified, include the filter cake,
the filtrate, and any filter washings. As mentioned in the
previous section, at least one commercial hazardous waste
facility is treating the filtrate to effect neutralization and
organics removal, while the filter cake is being landfilled.
Alternatively, the filtrate can be recycled to the treatment
process.
MCTCAL? • IOO»
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Pfc«|fct«
FIGURE 2.6 TYPICAL FILTER PRESS UNIT
AND FILTER CHAMBER ASSEMBLY
MCTC «L ' • ' °
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SECTION 2.7
BELT FILTER PRESS
Process Description
Belt filter presses employ single or double moving belts
to continuously dewater sludges through gravity and pressure
stages (Figure 2.7). Chemical flocculation is important for
consistent solids capture. Most units include a flocculating
mixer and polymers are usually added from a bulk processing
system. The conditioned sludge is introduced onto a gravity
drainage section. This section removes free water, sometimes
with a vacuum assist, and increases feed solids concentration
which improves filter performance.
Sludge is then squeezed through a series of rollers in the
pressure stage. The rollers apply increasing pressure and shear
force as the sludge moves through the press. Cake discharge is
accomplished by a discharge roller and blade. A high pressure
water spray is required to clean the belts after cake discharge.
Sludge feed is usually between 0.5 and 10 percent solids,
and should be maximized to improve performance. Dry solids
loading rates typical vary between 600 and 1500 Ib/hr/meter of
belt width. Presses are generally available in sizes ranging
from 0.5 to 3.5 meters in width though the 1.5 to 2.5 meter width
currently appears to be most practical. Solids capture for
biological sludge is usually better than 90 percent resulting in
cake solids of 12 to 44 percent with dry polymer dosages of 2 to
20 Ib/ton. Belt speed, tension and type are important operating
parameters. The flow rate for belt washing is usually 50 to
100 percent of the sludge feed flow rate, and it is applied at
100 psi or more. The wash waters are usually combined with the
filtrate resulting in suspended solids concentrations of 500 to
1000 mg/1, which are returned to the treatment process.
Applicability to the Treatment of Hazardous Waste
Belt filter presses have recently gained popularity
dewatering biological and industrial sludges because of design
changes which have resulted in improved performance.
Continuous operation yielding fairly high solids content cake
combined with low capital costs have made this a cost effective
dewatering process. It has been used to dewater metal hydroxide
sludges and is being integrated into many industrial treatment
processes. Other industrial applications include textile waste
sludges, deinkihg sludges, bauxite clays, silicon wastes, coke
water slurries, lime fluoride wastes, primary paper sludges,
chemically flocculated oil and waste sludges, aluminum oxide
slurries, and pharmaceutical waste sludges. Application usually
MCTCALf • tOO*
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requires laboratory testing of sludge samples to determine
applicability and polymer dosages. Pilot tests may be conducted
to measure performance and provide design data.
Large polymer dosages may be required for effective
operation. Operation and belt parameters are optimized for
sludge conditions. Sludges with.highly varying conditions may
require large holding capacity and blending. Different sludges
may require dewatering separately under different operating
conditions.
At one of the commercial hazardous waste treatment
facilities visited, a 1.5 meter wide continuous belt filter press
was being used to dewater mixed metal hydroxide and sulfide
sludges.
The raw sludge from the thickener contained 6-8 percent
solids and was preconditioned by adding polymer. The filter cake
from the belt filter press, containing 27-32 percent solids,
underwent solidification/fixation with quicklime. The filtrate
from the press was being returned to the treatment process.
Environmental Considerations
Belt filter presses may provide a lower cost method of
dewatering sludges. Reductions in volume will result in reduced
disposal requirements and costs. Polymer addition and reduction
of moisture content will improve sludge combustion
characteristics. The filtrate and belt wash waters contain
suspended and dissolved solids which must be recycled for
treatment. The filter cake may have to be treated further prior
to disposal. Data are needed for all of these residuals in order
to select the appropriate management options.
MCTCAL'• COO'
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FIGURE 2.7
BELT-TYPE SLUDGE PRESS
Static
Conditioner Horizontal
Drainage
.Sections
Belt Wash Station
Shear Roller Syste
Ben Wash Station
Sludge-Cake
Discharge
Source: Ashbrook-Slmon-Harttey, Houston, Texas
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SECTION 2.8
EVAPORATION
Process Description
Evaporation is the vaporization of liquid from a solution,
slurry, or sludge through the application of an energy source.
This process is practical when one component is minimally
volatile. In some instances, the liquid to be evaporated is
water and the technology is used to concentrate the nonvolatile
component. In other cases, evaporation is used to separate
solvent from nonvolatile solids, oil, or water as a first step in
the reclamation of waste solvent.
There are several process variations on the technology for
evaporation. The simplest process involves evaporation ponds
using solar energy to evaporate water and other volatiles. This
technology is appropriate when there is enough land available to
provide sufficient surface area for the evaporation process.
The other processes use a heated vessel to evaporate some
of the volatile fraction thereby concentrating the nonvolatile
bottoms. The first of these processes is the single-effect
evaporator shown in Figure 2.8. These units usually use steam to
heat the liquid to its boiling temperature. The steam is passed
through a steam coil or jacket. The vapors produced by the
boiling liquid are drawn off and condensed. Trie concentrated
liquid is pumped out of the bottom of the vessel. This process
requires about 1200 BTU/lb of water evaporated. The second
process is a series of single-effect evaporators in which the
vapor from the first evaporator is used as the heat source to
boil the liquid in the second evaporator. Boiling is
accomplished by operating the second evaporator at a lower
pressure than the first. This process can continue for several
evaporators as shown in Figure 2.8. This process is called
multiple effect evaporation and depending on the number of
effects may use only 200 BTU/lb of water evaporated.
The third process is called vapor recompression
evaporation. This process uses steam to initially boil the
liquid but once vapor is produced it is compressed to a higher
pressure and temperature. The compressed vapor is then directed
to the jacketed side of the evaporator instead of using more
steam and is used as the heat source to vaporize more liquid.
This process requires as little as 40 BTU/lb of water evaporated.
MCTCAL' • coo-
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The standard vessels used for water evaporation can vary
in size from one gallon capacity to one thousand gallons
capacity, although larger custom units are designed and
manufactured.
Single-effect mechanically-agitated or wiped thin film
evaporators are used for recovery of volatile organic solvents
from waste solvent streams that may contain high concentrations
of solids or nonvolatile oil and grease. Waste solvent is pumped
into the top of a jacketed vessel. Inside the vessel, close
clearance rotating blades continuously spread the feed over the
hot walls. The solvent boils and overhead vapors rise out the
top of the vessel into a condenser. Thin film evaporators may be
operated under vacuum so that solvents can be vaporized at
temperatures below their normal boiling points. The recovered
solvent may be acceptable for reuse or may require further
purification by distillation. The bottoms sludge, typically
containing 30-50 percent solids, may be incinerated or
landfilled.
Applicability to Treatment of Hazardous Waste
Evaporation can be used to treat a wide range of hazardous
waste streams. In industries which generate large volumes of
aqueous wastes with dilute hazardous constituents, evaporation
can be used to concentrate the waste stream for additional
treatment or shipment off site.
Solar evaporation is used to concentrate waste streams
such as metal hydroxide slurries, corrosives, acids, alkalis,
aqueous streams contaminated with organics and cyanide wastes
with less than 100 ppm cyanide. One particular site utilizes
250 acres of surface ponds for holding aqueous wastes and
rainwater runoff. This site also uses sprays to enhance
evaporation and estimates that 12 million gallons of water is
evaporated per month.
Thin-film evaporation is used at another site as the first
step in waste solvent purification. The vapor stream is
condensed and pumped to a distillation column for further
purification. Evaporation is performed to remove solids that
would otherwise foul the distillation equipment. This facility
uses two "VOTATOR" thin-film evaporators manufactured bv Cherry-
Burrel, ANCO-VOTATOR division. One unit contains 50 ft2 of heat
transfer area and produces 15 gpm of overhead product while the
other unit contains 60 ft2 and produces 20 gpm overhead product.
Vapor recompression is used in many industries. One
particular company uses this process to concentrate rinse water
from electroplating copper foil. The waste contains copper
sulfate and zinc sulfate. The evaporator operates at 150 deg. F
and 24 in. Eg vacuum, concentrates the solids ten times above
MCTC*L» • IT;-
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influent concentration and processes 17 gpm. The concentrate is
then used as plating solution make-up.
Environmental Considerations
Evaporation is an expensive technology, both in terms of
capital costs and operating costs. Solar evaporation is often
less expensive, but the use of land for evaporation is expensive
and in addition lagoons used for solar evaporation often require
bottom liners to prevent the migration of hazardous constituents
into the groundwater and will need to meet other pertinent
federal and state environmental regulations. For instance, the
state of California requires that a solar evaporation pond must
be emptied once every 12 months to be considered as a treatment
process rather than a disposal practice.
Mechanical evaporation produces a condensate and a bottoms
stream one or both of which may require further processing or
disposal.
• IOOY
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