Prepublication issue for EPA libraries
             and State Solid Waste Management Agencies
                PHYSICAL, CHEMICAL, AND BIOLOGICAL

            TREATMENT TECHNIQUES FOR INDUSTRIAL WASTES

                         Executive Summary
   This is the executive summary from the final report (SW-148c)
                  which describes work performed
          for the Federal solid waste management program
                   under contract No. 68-01-3554
         and is reproduced as received from the contractor
 Volumes I and II examine 47 unit engineering processes for- their
applicability to the task of treating hazardous industrial wastes.
         Copies of both volumes will be available from the
              National Technical Information Service
                    U.S. Department of Commerce
                   Springfield, Virginia  22161
              U.S. ENVIRONMENTAL  PROTECTION AGENCY

                               1977

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This report was prepared by Arthur D. Little, Inc., Cambridge,
Massachusetts, under Contract No. 68-01-3554.

Publication does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor
does mention of commercial products constitute endorsement by the
U.S. Government.

An environmental protection publication (SW-148c) in the solid waste
management series.

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                                    FOREWORD

     There is a strong need for treatment processes which can detoxify, destroy, or apply
resource recovery principles to industrial wastes. This study examined 47  unit engineering
processes for their applicability to the task of treating hazardous industrial wastes.

     Of these unit processes,  10 can be applied for phase separation, 3  are basically for
pre-processing of bulk solids  or tars, 12\react chemically to destroy  or  detoxify  the
hazardous components, while 25 can be used to separate specific components within the
waste  stream. Some of these unit processes are commonly used  for  industrial waste
treatment while others require further  R&D efforts before they will become commercially
attractive. Four (dialysis, electrophoresis, freeze drying and zone refining) were found not
to be applicable to waste treatment.

     Part Two of this report presents comprehensive  descriptions of each of the  unit
processes, including  information on the basic principles,  areas of application, economics,
energy  and environmental considerations, and an outlook for future use on industrial
wastes. Thus, Part Two is  in essence an up-to-date reference textbook on potential treat-
ment processes.

     A major problem is how to make all of the information in Part Two  readily available
and useful. Section IV of Part One focuses  on that problem, and is organized as a series of
reference tables to be used when screening  processes for application to an individual waste
stream. These tables  will provide a method of screening out processes that do not have any
potential for the waste in question.
                                         in

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                                     PREFACE

                           BASES FOR COST ESTIMATES
     All capital cost estimates were prepared .on the basis of equipment and construction
costs for a time period of early 1976.  The bases used were either the Chemical Engineering
Plant Cost Index of 188 or a Marshall and Swift Equipment Cost Index of 450, (Refer-
ence - Chemical Engineering March 29,1976) for all of the processes except those based on
biological activity. For the biological  processes, the cost basis was the Engineering News
Record Construction Cost Index (ENR March 18, 1976) of 2300.

     Operating  labor costs were taken as  $12.00/hour which was assumed to  include
supervision and overhead charges. Annual maintenance (labor and material) was taken as a
fraction of investment and was varied according to the estimated severity of the operations.
Chemicals were charged at unit prices  derived from Chemical Market Reporter. Electricity
was charged at $0.02/kwh.

     The  annualized costs  of capital were established on  the  basis of a  10-year capital
recovery factor with money borrowed at  10 percent interest. This method of annualizing
capital costs has been widely used in pollution control cost estimating and  is equivalent to
off-the-books financing that  might  be obtained through  the use  of industrial pollution
control  bonds.  The capital recovery factor for these cost estimates is  0.16274, i.e., the
annual cost of capital is 16.274 percent of the total capital investment.

     If cost estimates are to be prepared for different capacities, the following exponential
scaling factors based on capacities are suggested.

Capital Investment

              All processes except biological                     0.7
              Biological processes                              0.5
Operating Labor                                               0.3
Utilities and chemicals                                           1.0
                                        IV

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                        TABLE OF CONTENTS
                             Volume I
                                                        Page
PART ONE - SUMMARY
List of Tables
   I.   BACKGROUND                                     1
   II. .  SCOPE OF THE STUDY                                3
        A.  OBJECTIVES                                    3
        B.  APPROACH                                     4
  III.   TREATMENT PROCESSES INVESTIGATED                  7
        A.  PHASE SEPARATION    •                          8
        B.  COMPONENT SEPARATION                         10
        C.  CHEMICAL TRANSFORMATION                      10
        D.  BIOLOGICAL TREATMENT                         10
  IV.   SELECTION OF TREATMENT PROCESSES FOR GIVEN WASTE
        STREAMS               '                          15
        A.  PHILOSOPHY OF APPROACH                        15
        B.  BACKGROUND QUESTIONS FOR TREATMENT PROCESS
            SELECTION                                     15
        C.  EXAMPLES OF PROCESS SELECTION PROCEDURES       19
   V.   WASTE TREATMENT PROCESS SUMMARIES                35
PART TWO - TREATMENT TECHNIQUES
   1    ADSORPTION, CARBON                              1-1
   2    ADSORPTION, RESIN                                2-1
   3    BIOLOGICAL TREATMENT: OVERVIEW                  3-1
   4    BIOLOGICAL TREATMENT: ACTIVATED SLUDGE           4-1
   5    BIOLOGICAL TREATMENT: AERATED LAGOON            5-1
   6    BIOLOGICAL TREATMENT: ANAEROBIC DIGESTION        6-1
   7    BIOLOGICAL TREATMENT: COMPOSTING                 7-1
   8    BIOLOGICAL TREATMENT: ENZYME TREATMENT          8-1
   9    BIOLOGICAL TREATMENT: TRICKLING FILTER            9-1
  10    BIOLOGICAL TREATMENT: WASTE STABILIZATION        10-1
  11    CALCINATION                                    11-1
  12    CATALYSIS                                      12-1
  13    CENTRIFUGATION                                13-1
  14    CHLORINOLYSIS                                  14-1
  15    DIALYSIS                                       15-1

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                    TABLE OF CONTENTS (Continued)
PART TWO - Continued
    16    DISSOLUTION                                       16-1
    17    DISTILLATION                                       17-1
    18    ELECTRODIALYSIS                                   18-1
    19    ELECTROLYSIS                                      19-1
    20    ELECTROPHORESIS         ,                          20-1
                              Volume II
    21    EVAPORATION                                       21-1
    22    FILTRATION                                         22-1
    23    FLOCCULATION, PRECIPITATION, AND SEDIMENTATION      23-1
    24    FLOTATION                                         24-1
    25    FREEZE-CRYSTALLIZATION                            25-1
    26    FREEZE-DRYING                                      26-1
    27    FREEZING, SUSPENSION                                27-1
    28    HIGH-GRADIENT MAGNETIC SEPARATION (HGMS)           28-1
    29    HYDROLYSIS                                        29-1
    30    ION EXCHANGE                                      30-1
    31    LIQUID ION EXCHANGE                                31-1
    32    LIQUID-LIQUID EXTRACTION OF ORGANICS                32-1
    33    MICROWAVE DISCHARGE                               33-1
    34    NEUTRALIZATION                                    34-1
    35    QXIDAJJON. CHEMICAL                                35-1
    36    OZONATION                                         36-1
    37    PHOTOLYSIS                                         37-1
    38    REDUCTION, CHEMICAL                                38-1
    39    REVERSE OSMOSIS                                    39-1
    40    STEAM DISTILLATION                                 40-1
    41    STRIPPING, AIR                                      41-1
    42    STRIPPING, STEAM                                    42-1
    43    ULTRAFILTRATION                                   43-1
    44    ZONE REFINING                                      44-1
                                 vi

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                                 LIST OF TABLES

Table No.                                                                  Page

   1       Treatment Processes Identified   (                                   5
   2       Categorization of Processes by Effort Needed                         5
   3       Phase Separation Processes                                         9
   4       Component Separation Processes                                   11
                                         *
   5       Chemical Transformation Processes                                 12
   6       Biological Treatment Methods                                     13
   7       Treatment Processes for Hazardous Components in Waste Streams
           of Various Physical Forms                                         21
   8       Applicability of Treatment Processes to Physical Form of Waste        22
   9       General Characteristics of the End-Products of Treatment
           Processes                                                        24
  10       Comparison of Processes that Separate Heavy Metals from
           Liquid Waste Streams                                             27
  11       Comparison of Treatment Processes that Separate Organics from
           Liquid Waste Streams                                             28
  12       Processes that Destroy Organics                                    29
  13       Comparison of Processes that Separate Toxic Anions from
           Liquid Waste Streams                                             30
  14       Comparison of Processes that Can Accept Slurries or Sludges          31
  15       Comparison of Processes that Can Accept Tars or Solids              32
  16       Approximate Treatment Costs                                     34
                                         vii

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PART ONE




SUMMARY

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                                 I.  BACKGROUND

     A typical manufacturing establishment takes in raw materials, adds value through one
or more processing steps, and produces one'or more products for sale. It is seldom possible
to convert 100% of the raw materials into salable products, so there almost always is some
waste or residual. In addition, there are usually gaseous and aqueous emissions, but recent
air and water  pollution  control  regulations  limit the release  of potentially hazardous
materials  in effluent water and gas streams.  Water treatment and air pollution control
systems usually act to remove rather than to detoxify hazardous materials. Potentially toxic
or hazardous materials removed from air and water streams, or generated as waste  in the
course of  normal industrial production, are 'not currently subject to Federal regulation; and
most frequently these residual waste materials are dumped on land.

     Indiscriminate dumping of industrial processing wastes can lead to groundwater con-
tamination, or other adverse effects,  often 40 or 50 years after the initial waste disposal.
Although  methods have been explored to reduce leaching to groundwater, by, for example,
encapsulating wastes prior to burial, and/or securing sanitary landfills, the amount of land
available for dump sites still is decreasing, while the volume of residuals requiring disposal is
increasing.

     As a normal course of events, large industrial plants are constantly seeking ways to
convert process residuals into profitable by-products that can  either be returned to the raw
material stream within the plant, or marketed outside. The success of such resource recovery
efforts is  governed  almost entirely  by  economics.  The  net  costs of recovery (actual
treatment costs minus credits  for  the recovered resource) must be less than the costs of
alternative waste  management  methods.  As long as  the  alternative of land  dumping at
$2-3/ton remains,  the economically  allowable investment in waste treatment is severely
restrained. Clearly,  however,  continued  release  or  re-release  of contaminants into the
environment via leaching to groundwater, surface water run-off, or airborne dusts from land
burial sites cannot be permitted. As land disposal costs begin to increase in  response to
pressures for protecting the environment, other hazardous waste management alternatives
can become more attractive.

     For the management of industrial processing wastes  from the  point of generation to
the point  of ultimate (and environmentally adequate) disposal, three technically desirable
alternatives to immediate land burial are:

     •    resource recovery (materials or energy),
     •    detoxification, and
     •   volume reduction, coupled with disposal.

The resource recovery alternative is obviously attractive not only from the point of view of
conserving materials supplies  now beginning  to be  recognized as finite, but also as a
potential  means  of  reducing the quantity of hazardous  material requiring disposal. The

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detoxification alternative interposes a step prior to disposal that makes the waste stream
innocuous, so that lowest-cost disposal methods become applicable. The volume-reduction
alternative simply reduces the magnitude of trie waste disposal problem, permitting efficient
utilization of available secured chemical landfill sites.

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                             II.  SCOPE OF THE STUDY

A. OBJECTIVES

     The objectives of this study are to identify physical, chemical, and biological treatment
methods with potential  utility  for the design and implementation of resource recovery,
detoxification,  and/or volume-reduction  systems.  This  study is  not meant  to  provide
detailed designs of such  systems for specific waste streams;rather, it aims to provide back-
ground  information that will aid subsequent systems designers in selecting relevant treat-
ment processes.

     For each  potentially applicable treatment method identified, Part Two of this study
addresses, in depth, the:

     •   Technical characteristics

     •   Underlying physical, chemical, and/or biological principles,

     •   Operating characteristics
         —   Physical and chemical properties of suitable feed streams
         -   Mode of operation
         —   Physical and chemical properties of the output streams

     •   Operating experience             .
         —   Principal current applications (including waste treatment)
         —   Potential applications for treatment of hazardous wastes

     •   Capital and operating costs (including credits for products recovered)

     •   Environmental  impacts
         —   Waste streams or residues associated with the treatment process
         —   Pollution control  or further treatment requirements

     •   Energy requirements
         —   electricity
         —   fossil fuels

     •   Outlook for industrial waste treatment
         -   current state-of-the-art
         —   factors favoring and inhibiting widespread use
         —   development needs

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     To increase the utility of the information provided on individual treatment processes,
Part One of this report  presents general guidelines for selecting those treatment processes
which are potentially applicable to wastes of'particular characteristics.

B. APPROACH

1. Literature Search

     An  extensive  literature  search  on potentially  useful  processes  was initiated. The
Hazardous  Waste Management Division (HWMD) of  the EPA made information available
from its files, and conducted a computerized search of the SWIRS (Solid Waste Information
Retrieval System) data bank  for pertinent articles. Prior HWMD contractor reports(1>2'3)
and  the  Division's  Report to Congress^ ;were reviewed. An independent search of the
general literature and patent  literature was performed and trade and professional organiza-
tions and government agencies, industries, and universities were contacted.

     By the  time of this  report, 47 treatment processes had been identified (Table 1).
(Incineration and encapsulation processes are excluded, as they are the subjects of other
U.S. EPA studies.) At least two processes were assigned to each of 12 ADL technical staff
specialists for in-depth investigation, thus the study team was  able to  develop a high level
of technical  and professional expertise on  all processes of real potential applicability to
industrial wastes.

2. Interview Program

     The processes identified in the  Literature Search were subdivided into the five cate-
gories  defined  in  Table 2. These categories were  set  up  to guide the amount of  effort
required by the contractor for each process'. A site visit and personal interview program was
planned to obtain first-hand  information and expert  opinion or advice on the processes in
each category.

     In addition to hundreds of telephone .contacts, each expert made two  to seven site
visits for each identified Category II-V process. The visits covered commercial and industrial
waste treatment facilities,  equipment suppliers; industrial laboratories; government labora-
tories;  and/or experts. In all instances, each specialist gathered information for other team
members as appropriate.

3. Analysis of Information

     a. Mini-Reports

     On  the basis  of the initial  Literature Search,  each technical  specialist prepared  a
preliminary state-of-the-art report on his/her  assigned  processes. These reports, generally
5-10 pages in length,  were used  to help assign processes to categories (Table 2); to identify
key information gaps for investigation in the Interview Program; and to report progress to
date to EPA.                              4

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                                           TABLE 1
                             TREATMENT PROCESSES IDENTIFIED
Physical

Air Stripping
Suspension Freezing
Carbon Adsorption
Centrifugation
Dialysis
Distillation
Electrodialysis
Electrophoresis
Evaporation
Filtration
Flocculation
Flotation
Freeze Crystallization
Freeze Drying
High Gradient Magnetic Separation
Ion Exchange
Liquid Ion Exchange
Steam Distillation
Resin Adsorption
Reverse Osmosis
Sedimentation
Liquid-Liquid Extracting of Organics
Steam Stripping
Ultrafiltration
Zone  Refining
Chemical

Calcination and Sintering
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

Pretreatment of Bulk Solids of Tars

Crushing and Grinding
Cryogenics
Dissolution
                                            TABLE 2
                    CATEGORIZATION OF PROCESSES BY EFFORT NEEDED
No.     Category Description

  I.     Process is not applicable in a useful way
        to wastes of interest to this program
 II.     Process might work in 5-10 years, but
        needs research effort first
III.     Process appears useful for hazardous
        wastes, but needs development work
IV.     Process is developed but not commonly
        used for hazardous wastes
 V.     Process will be common to most industrial
        waste processors
Work Effort for Each Process

Enough to justify category assignment

Same as Category I, plus description of what
questions need to be answered by future effort
Same as Category 11 plus description of current
uses and projected applications to industrial wastes
Same as Category III

Description of how used, where, for what, including
economics, environment, energy, etc.

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     b. Final Report

     After an extensive field Interview Program, each Mini-Report was revised and expanded
into  comprehensive final treatment  process reports (Part Two). The results on individual
processes are summarized and compared herein.

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                   III. TREATMENT PROCESSES INVESTIGATED

     Most  of the 47  processes identified in  this study (Table 1) are  unit  processes or
operations, several of which would normally have to be linked in series to form a complete
treatment system for a particular waste stream. Four of the processes, however, were found
to have little or no potential utility in a hazardous waste management system; that is:

     •   Dialysis, while it does separate  high-molecular-weight molecules from low-
         molecular-weight salts, results in; two output streams, both of which are
         more dilute than the original stream but not suitable for direct disposal.

     •   Electrophoresis  could in  principle be  used  to remove suspended colloidal
         matter (1-20 /i particle size) from.any aqueous or organic medium, provided
         that the colloidal particles were charged relative to the liquid phase.  How-
         ever, the process is  not only underdeveloped, but also unpromising. There
         are  no  scientific or practical guides upon  which to base  a  development
         program, so there is some question  that high removal efficiencies could be
         achieved. Suitable equipment is  not available. Furthermore,  in any working
         unit, electrode reactions would  have to be suppressed, the conductivity of
         the  waste stream might  have  to be below 300 microhms/cm,  turbulent
         mixing  would  have  to be avoided,  and potential  problems of membrane
         plugging would have  to be solved.
                                                                    i
     •   Freeze  drying is an  operationally difficult,  expensive and energy-intensive
         dewatering  process  whose use  would not  appear to be justified in  the
         treatment of any real waste streams.

     •   Zone refining is a slow, costly,  energy-intensive process for purification of
         solids. It can only be operated in batch, on samples weighing  less than 10 kg,
         which are relatively  pure. It is impractical for the complex mixtures which
         are typical of waste streams.

     Thus,  of the initial 47, this left 43 as1 potentially useful processes to be investigated.
These processes fall naturally  into four classes: (1) phase separation processes, potentially
useful  in  volume reduction  or resource  recovery; (2) component separation processes,
capable of  physically segregating particular ionic or  molecular species from  multicom-
ponent, single-phase waste streams; (3) chemical transformation processes, which promote
chemical reactions to detoxify, recover, or reduce the  volume of specific components in
waste streams; and (4) biological treatment methods,  which involve chemical transforma-
tions brought about by the action of living  organisms.

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A. PHASE SEPARATION

     Waste streams, such as slurries, sludges, and emulsions, which are not single phase, will
often require a phase-separation  process (Table 3) before detoxification or recovery steps
can be implemented. Frequently, phase separation permits a significant volume 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 supernatant liquid. If the com-
ponents of the sludge are at all soluble, the supernatant 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 extensively  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. It has not been
extensively studied  for hazardous waste applications. High-gradient magnetic separation is a
relatively new process that appears  to have potential for separating magnetic and paramag-
netic particles from slurries.

2. Colloidal Slurries

     The basic  concept in all the above  processes for  settable slurries is to  get the solid
phases to  drop out of the  liquid phase,; through the  use of gravitational, centrifugal
magnetic, or hydrostatic forces.  Such forces generally do not act on colloidal suspended
particles.

     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.  Further  development effort is required,
however, to demonstrate its full potential.

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                                                               TABLE 3

                                                   PHASE SEPARATION PROCESSES
                                                                       Type of Waste to Which Process is Applicable
           Process
          Category1

 V.       Common in Waste Treatment
IV..       Developed but not commonly
          used in Waste Treatment
III.       Need further development
          for Waste Treatment
Settlable
Slurries2
Sedimentation
Filtration
Centrifugation
Colloidal ,
Slurries2
Flocculation


Any Wastes With a
Sludges3 Volatile Liquid Phase
Filtration Solar Evaporation

Distillation
Flotation

High-Gradient
Magnetic Separation
Ultrafiltration
Freezing
                                                             (with solvent recovery)
                                                             Evaporation
1.  Described in more detail in Table 2.
2.  A slurry is defined as a pumpable solid-liquid mixture. It is settlable if the phases separates on standing, and colloidal if they do not.
3.  A sludge is defined as a non-pumpable solid-liquid mixture.

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3.  Sludges

     The major phase separation desired in the handling of sludges is dewatering. 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 evaporation is very commonly used.
Engineered evaporation or distillation systems would normally be operated if recovery of
the liquid is desired.

B.  COMPONENT SEPARATION

     The many physical processes which act to  segregate ionic or molecular species from
multicomponent waste streams (Table 4) do not require chemical reactions to be effective.
None are so commonly used as to be classified in Category V, but there has been a great deal
of experience with most of them in the water treatment field. The majority of Category IV
processes act only on aqueous solutions.

C.   CHEMICAL TRANSFORMATION

     The relatively few processes which involve  chemical reactions (Table 5) are the  only
processes which we found are potentially capable of detoxifying hazardous components in
waste streams (in addition to recovering resources or reducing volume for land disposal). By
far the  two most common processes are neutralization and precipitation.  Since there is
usually a pH range  where the solubility of heavy metal precipitates is at a minimum,
neutralization (interpreted broadly as pH adjustment)  and precipitation are in  fact often
used together.

D. BIOLOGICAL TREATMENT

     Biological  Treatment methods (Table 6) are only effective  in aqueous media, and are
only capable of breaking down organic components. The four Category V processes are  used
essentially in polishing of  soluble  organics. The feed streams must be low in solids (<1%),
free  of oil and grease, and non-toxic to the active microorganisms (e.g., heavy metal content
less than 10 ppm). The processes yield a bibmass sludge for disposal which contains heavy
metals and refractory organics not decomposed by the biologically active species present.

     The Category IV processes,  anaerobic digestion and composting, are useful for more
concentrated waste streams and will tolerate solid contents of 5-7% and 50%, respectively.
Composting will decompose oils, greases, and tars, yielding a concentrated metal sludge and
a leachate containing partially decomposed organics.
                                        10

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                                                               TABLE 4
                                                COMPONENT SEPARATION PROCESSES
IV.
 Process
Category

Developed, but not commonly
used in Waste Treatment
III.
Needs further development
for Waste Treatment

Needs further research
                                                                                  Function of Process
Removal of heavy metal
and toxic anions from
aqueous solutions
Removal of 'organics
from aqueous
solutions
Removal of in-
organics from
liquids, slurries
and sludges
Solvent
Recovery
Liquid Ion Exchange
Electrodia lysis
Reverse Osmosis
Ion Exchange
                                             Ion Flotation
Ultrafiltration
Solvent Extraction
Carbon Adsorption
Resin Adsorption
Steam Stripping
Air Stripping
Distillation
Steam
   Distillation
                                                  Freeze crystallization •
                                                  High-Gradient
                                                  Magnetic Separation

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                                                     TABLE 5




                                       CHEMICAL TRANSFORMATION PROCESSES




                                                     Treatable Components and Waste Streams
IV.
III.
 II.
Process
Category
Common in Waste
Treatment
Developed but not
commonly used in
Waste Treatment
Requires further
development for
Waste Treatment
Needs further
research
Cyanides, phenolics,
sulf ides, sulfites, and
organics in aqueous
solution

Oxidation
Ozonation
UV/Ozonolysis
UV/Chlorination

Photolysis
Catalysis
Nitrates, carbonates,
sulfates, hydroxides,
in sludges, tars, and Heavy metals in
solids aqueous solution
Precipitation
Calcination Reduction
Electrolysis
Precipitate
Flotation
Organic liquids,
sludges, slurries Organic
tars and solids Acids and Bases liquids
Neutralization

Hydrolysis Chlorinoly:
Catalysis Microwave

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                                          TABLE 6

                             BIOLOGICAL TREATMENT METHODS
     Process Category

 V.   Common in Waste Treatment
IV.   Developed but not commonly
     used in Waste Treatment

 II.   Needs further research
                                                     Functions of Process
Decomposition of soluble
organics in dilute aqueous
       streams

Activated sludge
Aerated Lagoon
Trickling Filter
Waste Stabilization Pond
Enzyme Treatment
Decomposition of
  hydrocarbons
(non-chlorinated)
                               Composting
                               Anaerobic Digestion
       Enzyme treatment has been shown to be effective for phenols and some hydrocarbons,
   but the waste stream must be of constant composition and free of inorganic contamination.
                                             13

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    IV. SELECTION OF TREATMENT PROCESSES FOR GIVEN WASTE STREAMS

A.  PHILOSOPHY OF APPROACH

     There are a variety of ways  to  approach  the problem of selecting the appropriate
process(es)   for treatment 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 manipulating the data to reach a final conclusion. No  one
approach  is "right" for everyone.  The sequence  of  steps that to  one individual seems
necessary and immutable, may to another seem irrelevant or illogical.

     Within the scope of this report we cannot duplicate the thought processes of the many
different kinds of individuals who  might  be involved in the selection of waste treatment
alternatives. We also cannot impose our own thinking — no matter how logical it may seem
to us - on individuals'who approach the problem differently. To resolve this dilemma, we
have  chosen  first to  pose some of the questions  to  which  various  people might require
answers before even beginning to match wastes with  treatment processes. Next, we have
provided a number of examples of possible  steps in process selection for  some typical
wastes. We leave it to the individual  reader to decide what questions he must have answered,
and in what sequence, in order to be able to develop a procedure that meets his needs for
choosing the treatment processes applicable to  particular waste streams. No matter how one
approaches the problem of process  selection,' there are two seemingly conflicting 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. BACKGROUND QUESTIONS FOR TREATMENT PROCESS SELECTION

     •   Nature of the Waste

         —   What are the characteristics of the waste stream?

         —   Is it a liquid, an emulsion, a slurry,  a sludge, a solid powder, or a bulk
             • solid?

         —   What is its chemical composition?

         -   Which components are potentially hazardous for land disposal; or more
              generally, what is the problem?

         —   What are the physical properties of the waste stream — e.g., viscosity,
              melting point, boiling  point, vapor pressure,  Btu  content,  specific
              gravity, etc.?
                                       15

-------
         —   Is the waste stream corrosive?

         -   Over what range will the typical physical and chemical properties vary?

         —   What  is the volume or mass of waste that will require treatment from a
              typical plant and/or region?

         —   Where does the waste stream originate and at what points could it be
              intercepted for treatment?

     Questions on the nature of the waste, stream are  asked for several reasons. One is to
determine whether the waste stream characteristics match the feed stream requirements for
various treatment 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 equip-
ment, materials of construction, pumps, throughput rates, temperature, size of pipes, etc. A
third, reflected  in  the last  question, 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.

     •   Objectives  of Treatment — Desired Characteristics  of the Output Stream

         —   What  is the present treatment/disposal  method and why is this unac-
              ceptable?

         —   What  are the objectives or goals of treatment, in order of priority, i.e.,
              purification, resource recovery, detoxification, volume reduction,  safe
              disposal to land, safe disposal to water, compliance with regulations ?

         —   What  are the air, water and other environmental quality regulations
              which must be complied with?

         —   What  must be removed to make the waste stream amenable to disposal?
              What  level of removal is necessary; i.e., what are the maximum allow-
              able concentrations in the output stream(s)?

         —   What  are the  chemical and physical property requirements for recycle
              or reuse of the output streams?

         —   What  are the physical and chemical property requirements for disposal
              to land or water?
                                         16

-------
     Questions on the desired characteristics of the output streams are asked to: (1) clarify
the objectives of a treatment process, (2) explicitly learn what regulatory standards must be
met, (3) help establish criteria for judging the usefulness of various treatment alternatives in
meeting the objectives;  and (4) establish a bench mark for improvement by identifying
current practice.

     •    Technical Adequacy of Treatment Alternatives

          -   What processes, alone or in combination, are capable of meeting the
              treatment objectives?

          —   If a  sequence of processes is  needed,  are the processes  technically
              compatible?

          —   Can the key  process  selected for meeting the objectives  handle the
              waste stream in its existing form? If not, can the waste  stream be put
              into a form amenable to the process?

          —   What key processes are really attractive technically?

          —   Are  there  any components of the waste  stream  that  would inhibit
              application of an otherwise  technically attractive  key  process? Can
              these potentially inhibiting effects be minimized or eliminated?

          —   If no process, as presently conceived, can meet the objectives, can any
              process be modified to do the job?

          —   What function can each process perform, and how can the processes be
              grouped to achieve the objectives?

          —   Are there any processes that must be eliminated on technical grounds?

     Questions about technical adequacy are asked  to  help distinguish processes that are
technically feasible for use on the waste from those that are totally infeasible treatment
alternatives.

     •    Economic Considerations

          —   What  are the capital investment requirements for process implementa-
              tion?

          -   What are the operating costs?
                                         17

-------
         -   To what extent will credit for recovered material help offset operating
              costs?

         —   How do projected costs for alternative treatments compare with current
              costs of disposal and with each other?

         —   If recovery was 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?

     From  the industry point of view, economic questions are paramount in selecting
alternative treatment methods for in-plant use and in choosing a waste treatment contractor.

     •   Environmental Considerations

         —   Will air pollution control devices be required to clean up effluents?

         —   Will  output  streams require  clean-up  prior to discharge into water
              bodies?
                                         i. i.
                                         t •
         —   Will  secured chemical landfill areas be necessary  for solid  residue(s)
              from process?              ;',  '

     Waste treatment processes,  like any manufacturing process, almost always result in
some residue for disposal. Environmental questions are directed towards tracing the fate of
the hazardous components present in the waste  feed stream to the  point  of ultimate
disposal.

     •   Energy Considerations

         —   What are the energy requirements for process operation?

         -   What form(s) of energy will be used, i.e., electricity, natural gas, oil,
              coal, etc.?
                                          18

-------
          —    Are estimated energy costs niore than 10% of operating costs?

     Questions of energy utilization are asked in order to assure that treatment processes
satisfy current national objectives of both,.environmental protection and energy conserva-
tion. 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 natural gas, which is in
short supply,  might be particularly unattractive. The economics of treatment processes for
which energy costs represent a significant fraction of operating costs would, of course, be
tied to the price of fuel, which has in the recent past been quite volatile.

     •    Overall Evaluation

          —•    What factors are most important in selecting a treatment process?

          -    Are there any standard, state-of-the-art processes that can be used for
               baseline comparisons?      ;

          —    Are costs "reasonable"?

          -    Does  any process have clearly desirable (or  undesirable)  features that
               make  it attractive (or  unattractive)  for treating a particular waste
               stream?

     The  final choice of a  treatment system, or treatment process  sequence,  for a given
waste stream  involves engineering judgment, which  is always highly subjective.  The indi-
vidual faced with the choice must not only establish his/her own selection criteria, but also
weight those criteria in accordance with personal priorities.  Questions asked in an attempt
to make an overall evaluation, therefore, are directed towards a determination of the degree
to which the objective features of alternative treatment systems meet subjective needs.

C.  EXAMPLES OF PROCESS SELECTION PROCEDURES

1. Selection Based on the Nature of the Hazardous Wastes

     For  the  purposes of identifying possible  treatment processes,  and  eliminating those
that are not likely to prove useful, a given waste stream is conveniently characterized with
respect to three broad dimensions:

     (a)   Physical form - Is the waste stream as generated a:

          •    liquid?
          •    emulsion?
          •    pumpable slurry?
                                         19

-------
              -    colloidal or non-colloidal?
         •    non-pumpable sludge?
         •    tar?
         •    bulk solid?
         •    powdered solid?

     (b)  Hazardous components - Does the waste stream contain:

         •    heavy "metal" cations (Sb, As; Cd, Cr, Hg, Pb, Zn, Ni, Cu, V, P, Be, Se,
              Mn, Ti, Sn, Ba, etc.)?

         •    heavy metal anions (chromates, chromites, arsenates, arsenites, etc.)?

         •    non-metallic toxic anions (cyanides, sulfites, thiocyanates, etc.)?

         •    organics (hydrocarbons, organic acids,  organic peroxides,  esters, alco-
              hols,  aldehydes, phenols, chlorocarbons,  amines,  anilines, pyridines,
              organic sulfur compounds, organic phosphorus  compounds, alkaloids,
              sterols, etc.)?

     (c)  Other properties - For example,

         •    Is the liquid phase primarily aqueous or non-aqueous?

         •    What is the concentration of each of the hazardous components in each
              of the phases present?

         •    What are the non-hazardous components in each phase?

     For a given waste stream, characterized by physical form and hazardous components,
the matrix presented in Table 7 may be used to select potentially applicable treatment
processes. For example, liquid ion exchange  (LIE) might be capable  of removing heavy
metals from solid powders. The matrix in Table 8 focusses on processes that are inapplicable
for given waste streams. It provides some 'guidance for ruling out  processes  that are not
likely to be technically feasible for certain types of waste streams.

2. Process Selection Based on Desired Characteristics of the Output Streams

     The, output streams from any given treatment process may or may not be suitable for
reuse or amenable to  disposal without  further treatment. In evaluating and  analyzing
treatment processes that might be applicable to particular waste streams, it is usually
necessary at some stage  to define the objectives of treatment and the desired characteristics
of the output streams.
                                         20

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                                                             TABLE 7

             TREATMENT PROCESSES FOR HAZARDOUS COMPONENTS IN WASTE STREAMS OF VARIOUS PHYSICAL FORMS

                                                                       Treatment Processes*
Physical Form

Liquid


Emulsion
Slurry

Sludge

Tar
Bulk Solid
Solid Powder
Heavy "metal" cations*
  and metal anions**

(IE), (FC), (UF), (ED), (RO),
(Red),(LIE),(Ppt),(E1)

(UF)
(FC). (UF), (Red), (HGMS)

(LIE), (FC), (Red)

(Cal)
(Cal)
(LIE)
    Non-metal anions***

(CA), (LIE),(FC),(UF), (ED),
(Oz), (RO), (Ox),(E1)
(FC), (UF), (Ox)

(FC), (Ox)

(Cal)   .
(Cal)
(Cal)
Legend:
(AS) Air Stripping
(CA) Carbon Adsorption
(Cal) Calcination
(CD Chlorinolysis
(Dis) Distillation
(ED) Electrodialysis
(E1) Electrolysis
(FC) Freeze Crystallization
                (HGMS) High-Gradient Magnetic Separation
                (Hy)    Hydrolysis    -
                (IE)    Ion Exchange
                (LIE)   Liquid Ion Exchange
                (MW)   Microwave Discharge
                (Ox)    Oxidation
                (Oz)    Ozonation
                (Ph)    Photolysis
       Organics

(CA), (RA). (Dis). (IE),
(AS), (SS), (UF), (SE), (RO), (Ox),
(Oz).(Hy). (C1),(MW),(Pb),(UF)


(Dis), (AS), (SS). (UF),
(Oz), (Hy)
(Dis), (Cal), (Oz),
(Hy). (Ox)
(Cal), (Hy)
(Cal)
(Cal), (Hy)
                       (Ppt) Precipitation
                       (RA) Resin Adsorption
                       (Red) Reduction
                       (RO) Reverse Osmosis
                       (SE) Solvent Extraction
                       (SS) Steam Stripping
                       (UF) Ultrafiltration
   *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

-------
                                              TABLES

            APPLICABILITY OF TREATMENT PROCESSES TO PHYSICAL FORM OF WASTE
1.  Phase Separation Processes
   Filtration
   Sedimentation
   Flocculation
   Centrifugation
   Distillation
   Evaporation
   Flotation
   Ultrafiltration
   HGMS
   Precipitation
2.  Component Separation Processes
   Ion Exchange
   Liquid Ion Exchange
   Freeze Crystallization
   Reverse Osmosis
   Carbon Adsorption
   Resin Adsorption
   Electrodialysis
   Air Stripping
   Steam Stripping
   Ammonia Stripping
   Ultrafiltration
   Solvent Extraction
   Reverse Osmosis
   Distillation
   Evaporation
3. Chemical Transformation Processes
   Neutralization
   Precipitation
   Hydrolysis
   Oxidation
   Reduction
   Ozonolysis
   Calcination
   Chlorinolysis
   Electrolysis
   Microwave
   Biological
   Catalysis
   Photolysis
Single Phase
Liquid
Solid
n
n
n
n
n
n
n
n
P
n
s
n
V
n
n
n
n
n
n
V
y
n
P
n
n
n
W6S
n
n
P
n
n
n
y
n
n
n
n
n
n
Inorganic
n
n
n
n
n
n
n
n
n
n
y
y
y
y
y.
y
y
n
n
V
y
y
v
n
y
y
Y
n
Y
Y
y
Y
n
y
n
n
Y
n
Organic










Y
Y
Y




y
V

y
y

y
Y
y
y
Y
y
y
Y
Y
Y

y
y
y
Y
n
n
n
n
n
n
n
n
n
n



n
n
n
n


n


n










n




Mixed
n
n
n
n
n
n
n
n
n
n
Y
n
n
y.
Y
Y
y
Y
y
n
Y
Y
y
Y
Y
y
y
y
y
y
y
y
y
y
y
Y
Y
Y
                                                                                     Two Phases
Slurry
y
y

Y
y
Y
y




y
y




y
Y




Y
y
Y

y



y



y


*


n




n
n
n
n


n
n
n
n


n
n
n
n



n

n
n
n

n
n
n

n
n
Sludge
n
n
n
n
y
Y
n
n
n
n
n
Y
Y
n
n
n
n
n
n
n
n
n
n
Y
Y
y
n
y
n
n
n
y
n
n
n
Y
n
n
 "Slurry is defined here as a pumpable mixture of solids and liquids.
 y = yes, workable; n = no; p = possible.
                                                   22   .

-------
     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 water
 pollution control regulations will govern the characteristics of the output streams.  If the
 treatment objective is recovery, those processes 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 9 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
 were treated by reverse osmosis, only the heavy metals would be concentrated in one of the
 output streams (RO1), and the other output stream (R02) would have to be treated further
 to remove or detoxify the organics.

 3. Selection Based on Technical and Operational Adequacy of Treatment Alternative

     Table 7 shows  that there are a number of treatment alternatives for various types of
 hazardous components in waste streams of different physical form. Tables 4-6 show further
 that several of the alternatives function similarly; i.e., they remove or detoxify certain types
 of hazardous components. All processes which function similarly  on similar types of waste
 streams are not necessarily technically  equivalent, however.  The allowable feed stream
 concentrations may differ. The treatment efficiencies and hence concentration of hazardous
 components in the output streams may differ. The degree of interference by other com-
 ponents in the waste stream may differ. Throughputs may differ and the available experi-
 ence with using the processes to treat hazardous wastes may also differ.

     Table 10 compares treatment processes  capable'of separating heavy metals from liquid
 waste streams with respect to feed stream properties, output parameters and state-of-the-art.
 Tables 11-13 provide similar comparisons for processes that separate organics from liquids
 and  toxic anions from liquids. Table 14 compares processes (other than phase separation
 processes) that can accept feed streams in the form of slurries or sludges. Table 15 compares
 processes that can accept feed streams in the form of tars, bulk solids or solid powders.

     It is clear that the vast majority of processes considered in this program operate mainly
 on liquids. Some have potential for handling slurries and sludges, but in most real cases, a
liquid/solid separation would precede treatment and/or disposal. None of the  processes can
 directly treat bulk solids contaminated by heavy metals, such as slags from the metallurgical
industries (an enormously large  waste stream in  the aggregate).  Few processes can  work
directly on tarry or even powdered solid feeds. Unfortunately, water treatment sludges, still
bottom tars, powdered particulate from air pollution  control devices and oil-contaminated
solids account for a larger fraction of the wastes destined for land disposal than do liquids.

                                         23

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                                                             TABLE 9
                         GENERAL CHARACTERISTICS OF THE END-PRODUCTS OF TREATMENT PROCESSES
             Treatment
Type
Process
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
                                              Output Streams
                                       Possible Follow-On Steps
                                                                                       Landfill, Calcination
                                                                                       Component Separation

                                                                                       Decapitation

                                                                                       Skimming
                                                                                       Component Separation
                                                                                       Recovery
                                                                                       Component Separation
                                                                                       Sedimentation, Filtration,
                                                                                       Centrifugation  "
                                                                                       Calcination
                                                                                       Sale
                                                                                       Resource Recovery
                                                                                       Recovery or Disposal
                                                                                       Precipitation, Recycle,
                                                                                       Electrolysis
                                                             with hazardous components  Discharge
                                                at ppm levels
Code No.
F 1
F2
S1
S2
FI1
FI2
H 1
H2
Fc
Dis1
Dis2
E1
IE1
IE 2
Form
Sludge
Liquid
Sludge
Liquid
Stabilized
Liquid
Slurry
Liquid
Sludge or
Slurry
Sludge
Liquid
Solid
Liquid
Liquid
Liquid
Characteristics
15-20% solids
500-5000 ppm total dissolved
2-1 5% solids
10-200 ppm suspended solids
particle-bearing froth
solution

solids


magnetic and paramagnetic particles
solution
flocculated participates
still bottoms
pure solvent
condensate



concentrated solution of hazardous
components
purified water with hazardous componer
                      Similar to Ion Exchange
                      CA1       Solid
                      CA 2      Liquid
                      RO 1      Liquid
                                     JRO 2
                                 Liquid
adsorbate on carbon
purified water
concentrated solution of hazardous
components
purified solution, TDS >  5 ppm
Chemical Regeneration
Discharge
Precipitation, Electrolysis, Recycle

To Water Treatment

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                                                                  TABLE 9 (Continued)
to
         	Treatment	
         Type            Process
                         Electrodialysis
                Freeze Crystallization

 b. Organics     Carbon Adsorption

                Resin Adsorption

                Steam Stripping


                Solvent Extraction


                Distillation

3. Chemical
   Transformation
                Neutralization
                Precipitation
                         Oxidation
                         Ozonation
                         Reduction
Output Streams
Code No.
ED1
ED 2
FC1
FC2
CA1
CA2
RA1
SSI
SE 1 >••-••
SE2
Dis1
Dis2
N
Ppt1
Ppt2
Form
Liquid
Liquid
Sludge
Liquid
Solid
Liquid
Solid
Liquid
Liquid
Liquid
Liquid
Liquid
Sludge
Liquid
Unchanged
Sludge
Liquid
Characteristics
concentrated stream, 100-500 ppm
dilute stream
concentrated brine
purified stream, ~ 100 TDS
adsorbate on carbon
purified water
adsorbate on resin
purified water, < 10 ppm organics

salts



aqueous steam concentrated in volatile
organics
dilute aqueous stream with 50-100 ppm
organics
concentrated solution of hazardous- - - •
components in extraction solvent
purified liquid; hazardous component
concentration < 1.0 ppm
still bottoms
pure liquid
stream of altered pH
supernatant with concentrations



                                        o
Liquid

Slurry
governed by solubility of precipitate
CO2, H20 and other  oxidation products

heavy metals and residual reducing agent
                                                        Possible Follow-On Steps	

                                                        Precipitation, Metal Recovery
                                                        To Water Treatment
                                                        Recovery
                                                        To Water Treatment
                                                        Thermal or Chemical Regeneration
                                                        Discharge
                                                        Solvent Regeneration
                                                        To Water Treatment
                                                        Recovery; Incineration

                                                        To Water Treatment

                                                        Recovery of Extraction Solvent •--

                                                        Recycle or Discharge

                                                        Incineration
                                                        Sale
Component Separation
Landfill, Calcination
Depends on Product Stream
Composition
Depends on Product Stream
Composition
Filtration

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                                                          TABLE 9 (Continued)
             Treatment
                       Output Streams
                                                         Possible Follow-On Stream
Type Process
Calcination
Hydrolysis
Electrolysis
Photolysis
Microwave Discharge
Code No.
Call
Cal2
Hy
EM
El 2
P
M
Form
Solid
Gas
Liquid .Slurry
or Sludge
—
Liquid
Gas
Characteristics
oxide and/or other residue
volatiles (CO2 , NOX, SOX, hydrocarbons,
fine particulates)
mixture of products that may or may not
be toxic '
cathode reaction products
anode reaction products
solution of photodecomposition products
similar to incinerator emissions

Landfill or Recovery
Wet Scrubbing
Resource Recovery
Often a Recovered Metal
Depends on Nature of Products
Depends on Nature of Products
Wet Scrubbing
4. Biological
   Treatment
                Catalysis
                Activated Sludge

                Aerated Lagoon
                Trickling Filter
                Waste Stabilization
                 Pond
                Anaerobic Digestion

                Composting
Depends on Reaction Catalyzed
AC1
AC 2
W
An1
An 2
Com 1
Com 2
Liquid
Sludge
Liquid
Sludge
Gas
Sludge
Liquid
clean water
heavy metals and refractory organics
clear water

CO2, methane
concentrated in metals
leachate solution of partially degraded
organics
Discharge  •
Calcination
Discharge
Incineration
Fuel Recovery
Calcination or Recovery
Component Separation

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                                                                      TABLE 10

                            COMPARISON OF PROCESSES THAT SEPARATE HEAVY METALS FROM LIQUID WASTE STREAMS
        Process

        Physical Removal
           Ion Exchange

           Reverse Osmosis
           Electrodia lysis
State-of-the-Art
Used but not common (Cat. IV)
Cat. IV
Cat. IV
Required Feed Stream Properties     Characteristics of Output Stream(s)
^         Liquid Ion Exchange     Cat. IV
           Freeze Crystallization    Needs development (Cat. Ill)
        Chemical Removal
           Precipitation
           Reduction
           Electrolysis
Common (Cat. V)
Cat. IV
Cat. Ill
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
Aqueous solutions; no con-
centration limits; no surfact-
ants; SS< 0.1%
Aqueous solutions; TDS < 10%
Aqueous or low viscosity non-
aqueous solutions; no con-
centration limits

Aqueous solutions; concen-
trations of heavy metals < 1 %;
controlled pH
Aqueous solutions; heavy metal
concentrations < 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

Extraction solvent concentrated in heavy
metals; purified water or slurry

Concentrated brine or sludge; purified
water, TOS ~ 100 ppm
Precipitated heavy metal sulfides, hydr-
oxides, oxides, etc.; solvent with TDS
governed by solubility product of
precipitates
Acidic solutions with reagent (oxidized
NaBH4 or Zn); metallic precipitates

Recovered metals; solution with 2-10 ppm
heavy metals

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                                                                      TABLE 11

                     COMPARISON OF TREATMENT PROCESSES THAT SEPARATE ORGANICS FROM LIQUID WASTE STREAMS
to
oo
        Treatment Process

        Carbon Adsorption

        Resin Adsorption
State-of-the-Art

Used but not common (Cat. IV)

Cat. IV
   Required Feed Stream Properties      Characteristics of Output Stream(s)
Ultrafiltration
Air Stripping
Steam Stripping
Solvent Extraction
Distillation
Cat. IV
Cat. IV
Cat. IV
Cat. IV
Cat. IV
        Steam Distillation
Cat. IV
  Aqueous solutions; concen-
  trations < 1 %; SS < 50 ppm
  Aqueous solutions; concen-
  trations < 8%; SS < 50 ppm;
  no oxidants
I  Solution or colloidal suspension
  of high molecular weight organics
  Solution continuing ammonia;
  highpH
'f Aqueous solutions of volatile
  organics

f Aqueous or non-aqueous
  solutions; concentration < 10%
  Aqueous or non-aqueous
  solutions; high organic con-
  centrations
  Volatile organics, non-reactive
  with water or steam
Adsorbate on carbon; usually regenerated
thermally or chemically
Adsorbate on resin; always chemically
regenerated

One concentrated in high molecular weight
organics; one containing dissolved ions
Ammonia vapor in air

Concentrated aqueous streams with
volatile organics and dilute stream with
residuals .
Concentrated solution of organics in
extraction solvent
Recovered solvent; still bottom liquids,
sludges and tars

Recovered volatiles plus condensed steam
with traces of volatiles

-------
K>
Process

Biodegradation

Oxidation


Ozonation

Calcination

Hydrolysis

Photolysis


Chlorinolysis



Microwave Discharge
                                    State-of-the-Art

                                    Cat. V

                                    Cat. IV


                                    Cat. IV

                                    Cat. IV
               TABLE 12

PROCESSES THAT DESTROY ORGANICS

                Required Feed Stream Properties      Characteristics of Output Stream(s)

                Dilute aqueous streams with soluble   Pure water
                organics
                Dilute aqueous solutions of phenols.   Oxidation products in aqueous solutions
                organic sulfur compounds, chlor-
                inated hydrocarbons, etc.
                Aqueous solutions; concentrations     Oxidation products in aqueous solutions
                                    Needs development (Cat. Ill)
                                    Needs research (Cat. II)
                                    Cat. Ill
                                    Cat.
                Organics and inorganics that de-
                compose thermally
                Aqueous or non-aqueous streams;
                no concentration limits
                Aqueous streams; transparent to
                light; components that absorb
                radiation
                Chlorinated hydrocarbon waste
                streams; low sulfur; low oxygen;
                can contain benzene and other
                aromatics; no solids; no tars
                Organic liquids or vapors
Solid oxides; volatile emissions
Hydrolysis products
Photolysis products
Carbon tetrachloride; HCI and phosgene
Discharge products; not accurately
predictable

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u>
o
                                                                      TABLE 13

                             COMPARISON OF PROCESSES THAT SEPARATE TOXIC ANIONS FROM LIQUID WASTE STREAMS
        Process

        Physical Removal
           Ion Exchange

           Liquid Ion Exchange

           Electrodialysis


           Reverse Osmosis
State-of-the-Art


Cat. IV

Cat. IV

Cat. IV


Cat. IV
          Freeze Crystallization     Needs development (Cat. Ill)
        Chemical Removal
          Oxidation


          Ozonation

          Electrolysis
Cat. III-IV


Cat. IV

Cat. Ill
Required Feed Stream Properties     Characteristics of Output Stream(s)
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   ,
Aqueous salt solutions
Aqueous solutions of cyanides,
sulf ides, sulf ites etc.; concen-
trations <1%
Aqueous solutions of cyanides;
concentrations < 1 %
Alkaline aqueous solutions of
cyanides or concentrated HCI
solutions (>20%)
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
Oxidation products
Cyanate solutions

Cyanides to ammonium and carbonate
salt solutions; HCI to CI2 gas

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                                                                TABLE 14
                                COMPARISON OF PROCESSES THAT CAN ACCEPT SLURRIES OR SLUDGES
Process
Calcination


Freeze Crystallization

HGMS

Liquid Ion Exchange

Flotation
Hydrolysis
Anaerobic Digestion

Composting
Steam Distillation

Solvent Extraction
State-of-the-Art
Used but not common (Cat. IV)


Needs development (Cat. Ill)

Needs research (Cat. II)

Cat. IV

Cat. Ill
Cat. II
Cat. IV

Cat. IV
Cat. IV

Cat. IV
Required Feed Stream Properties
Waste stream with components
that decompose by volatilization
(hydroxides, carbonates, nitrates,
sulfites, sulfates)
Low-viscosity aqueous slurry or
sludge
Magnetic or paramagnetic particles
in slurry
Solvent extractable inorganic
component
Flotable particles in slurry    .
Hydrolyzable component
Aqueous slurry; < 7% solids;
no oils or greases; no aromatics
or long chain hydrocarbons
Aqueous sludge; < 50% solids
Sludge or slurry with volatile
organics
Solvent extractable organic
Characteristics of Output Stream(s)
Solid greatly reduced in volume; volatiles


Brine sludge; purified water

Particles adsorbed on magnetic filter

Solution in extraction solvent

Froth '.•-.'.
Hydrolysis products
Sludges; methane and CO2

Sludge; leachate
Volatile, solid residue

Solution of extracted components; residual
sludge

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                                                                        TABLE 15

                                           COMPARISON OF PROCESSES THAT CAN ACCEPT TARS OR SOLIDS

         Process                    State-of-the-Art                       Required Feed Stream Properties     Characteristics of Output Stream(s)

         Calcination                Used but not common (Cat. IV)         Tars or solids that can be volatilized   Volatiles; char and/or metal oxides

         Hydrolysis                 Needs development (Cat. 111)           Tars or solid powders                Hydrolysis products

         Steam Distillation           Cat. IV                               Solids contaminated with volatile     Purified solids; condensed organics
                                                                        organics

         Dissolution                Cat. IV                               Tars, solids, or solid powders that     Liquid solution for further treatment;
                                                                        will dissolve in some reagent          solid residue

         Crushing and Grinding       Cat. IV                               Bulk solid                          Powdered solid

to       Cryogenics                 Needs research (Cat. II)                 Tar, bulk solid                      Reduced particle size

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Crushing  and grinding,  and dissolution  are therefore likely to play  important roles in
subsequent design of alternative hazardous waste treatment systems. Tars, which are often
neither easy to crush and grind nor to dissolve, might be reduced to smaller particle size by
cryogenic cooling. The smaller particles thus formed should dissolve more rapidly than the
bulk tar removed from the reactor.

4. Selection on the Basis of Economic Considerations

     Processes performing similar  functions are  compared with  respect to  capital  and
operating costs in Table 16. The bases for the cost estimates are summarized in the Preface
to Part Two. For more  detailed descriptions of the types of waste streams assumed in
developing the costs in Table 15, refer to the individual process reports. In deriving costs of
alternative treatment systems (generally a sequence of processes) for any given waste stream,
operating parameters specific to the particular  situation should be taken into  account; the
costs  in  Table 16  and  the economic analyses given in Part  Two only provide general
guidelines.
                                         33

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                                                                         TABLE 16

                                                         APPROXIMATE TREATMENT COSTS
Process
Phase Separation
Sedimentation
Vacuum Filtration
Cent rifugat ion
Freeze Crystallization
Evaporation
Annual Volume or Mass
of Waste Stream Treated
     (typical), gpd
       5,000,000
          36,000
          36,000
          50,000
      20,000,000
Metal Removal From Liquids
Precipitation      .                400,000
Electrodialysis              •'       9,000
Ion Exchange                      80,000
Liquid Ion Exchange                80,000
Reduction                          2,000
Reverse Osmosis                     3,000
Electrolysis                        20,000
Organic Removal From Liquids
Carbon Adsorption                100,000
Resin Adsorption                   67,000

Solvent Extraction
Steam Stripping

Steam Distillation
Distillation
Hydrolysis
Oxidation
Ozonation
Other
Neutralization                   1,000,000
Calcination                       156,000
Chlorinolysis                       20,000
  Capital Costs
$  200,000
$  140,000
$  280,000
$1,300,000
                        $  300,000
                        $   24,000
                        $  40Q.OOO
                        $  300,000
                        $  230,000
                        $   12,000
                        $   31,000
                        $1,200,000
                        $  720,000
100,000
720,000

750
i;ooo
30,000
1,000
800,000
$
$

$
$
$
$
$
400,000
500,000-
850,000
130,000
230,000
320,000
100,000
330,000
                        $1,050,000
                        $2,900,000
                        $5,500.000
Operating Costs
$0.10-0.50/1000 gal
$5-7/1000 gal
$5-7/1000 gal
$6-12/1000 gal
$1-2/1000 gal
                     $1-2/1000 gal
                     $5-7/1000 gal
                     $4-6/1000 ga)
                     $3-5/1000 gal    :
                     $150-200/1000 gal
                     $9-11/1000 gal
                     $1-2/1000 gal
                     $5-20/1000 gal
                 (high figure with regeneration)

                     $11-13/1000 gal

                     $4-6/1000 gal
                     ~$10

                     $0.25-0.90/1000 gal
                     $264/1000 gal
                     $20-30/1000 gal
                     $229/1000 gal
                     $0.40-1.00/1000 gal
                    $2-3/1000 gal
                    $15-20/1000 gal
                    $3000/1000 gal
      Fraction of Operating Costs Attributable to:
Labor       Energy         Materials       Other*
   45
   35
   52
    3
                              47
                              62
                              36
                              24
                              32
                              29
                                                                           24
                                                                                                   11
                                                                           53
                                                                           14
                                                                           57
                                                                           44
                                                                           26
                              15
                              10
                               1
4
5
16
92
2
3
2.
"1
21
6
10-35
5-25
(high with thermal
regeneration)
40
1
17
—
— . .
5
7
46
12 '
15
—
—
15


Regenerating
50
43
32
5
46
28
- 16
63
32
65
—
36-56



Solvent recovered
                                         72

                                          6
                                         12
                                         17
                                          4
                                         20
             1.5
              26
               4
                             15
                                                        59
                                                        88
21

41
74
26
37
54
24.5
64
 7
•Capital amortization, water, maintenance, etc.

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                 V. WASTE TREATMENT PROCESS SUMMARIES

    The following pages summarize briefly the salient features of each of the treatment
process considered. More complete process descriptions are provided in Part Two.
                                    35

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                              ADSORPTION, CARBON

I.  CONCLUSIONS AND RECOMMENDATIONS

     Carbon adsorption should be given serious consideration  whenever it is desirable to
remove  mixed organics, or to recover select organic  or inorganic  species from aqueous
waste streams with adsorbate concentrations less than 1%.

II. PROCESS DESCRIPTION

     A large variety of organic solutes, and a more limited number of inorganic solutes can
be removed from aqueous waste streams by  adsorption onto activated carbons with a high
absorptive surface area (500-1500  m2/g).  Adsorption of organic  solutes is commonly
followed by  thermal regeneration of the carbon and simultaneous destruction of  the absor-
bates. In a few cases, the carbon may be regenerated and the adsorbate recovered by treat1
ment with acid, base, steam, or solvent.

III. APPLICATIONS TO DATE

     There are about 100 full-scale carbon adsorption systems currently in use for industrial/
municipal wastewater treatment. In general, the process works best with chemicals that have
a low water solubility, high molecular weight, low polarity, and low degree of ionization.
The concentration of adsorbates in the influent should be less than  1%, and suspended solids
must be low (^50 ppm) for most systems. Recovery is possible if the adsorbate may be
easily volatilized  or dissolved off the carbon. Thermal regeneration (with organic adsorbates)
is economical if the carbon usage is above about 1000 Ib/day.

IV. ENERGY, ENVIRONMENT. ECONOMICS

     Energy  requirements  include electricity: for pumps  and fuel  for  the regeneration
furnace.  Energy  costs  may  be around 25%  (or higher) of the total  operating costs where
concentrated waste streams are being  treated and the carbon is thermally regenerated.
Energy  may constitute no more than 5% of total operating costs if regeneration is accom-
plished by non-thermal means.

     Capital  costs for a 100,000-gpd facility would be in the neighborhood of $1,000,000.
Total operating costs would  be in the range of $5-20/1000 gal.

     If spent carbon is not regenerated, it presents a problem for disposal. If it is thermally
regenerated,  the  regeneration  furnace will usually require an afterburner, a scrubber, and
perhaps a dust filter.

V. OUTLOOK FOR WASTES

     For aqueous waste streams containing up to 1% of refractory or toxic organics, carbon
adsorption is an excellent,  proven process.  For more concentrated  waste streams, solute
removal would be even more efficient, but the more frequent regeneration required would
significantly  increase costs.  Development of new  methods of regeneration, particularly
ones  that allow  recovery of the adsorbate,  could greatly expand  potential applications of
the process.
                                         37

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                                ADSORPTION, RESIN

I.  CONCLUSIONS AND RECOMMENDATIONS
                                         i1* •
     Resin adsorption, like carbon adsorption, is  a useful process for extraction of organic
solutes from  aqueous waste  streams. Resin adsorption will generally be preferred when it
is  desirable to recover the adsorbate.  Carbons are usually thermally regenerated with de-
struction of the adsorbate. Resins are always chemically regenerated (with caustic or organic
solvents).

II. PROCESS DESCRIPTION

     Resin adsorption uses synthetic resins (which can vary significantly in their chemical
and  physical  nature)  to  extract and  recover,  if desired, dissolved organic solutes  from
aqueous waste streams. Resins with  either (or mixed) hydrophobic or hydrophylic  natures
are available,  and can be used to extract, respectively, hydrophobic or hydrophylic  solutes.
Resins are always chemically regenerated. When organic solvents are used as the regenerant,
solute recovery is generally via distillation.

III. APPLICATIONS TO DATE

     Current  industrial waste treatment applications include:  phenol recovery; color  re-
moval; and fat removal  from aqueous waste streams. The phenol concentration can  be  as
high  as 8% by weight in the feed.

     Proposed waste treatment applications (near-term) include removal of toxic chemicals
from munitions facilities' effluents; removal of pesticides from aqueous streams; carcinogen
removal from laboratory waste waters; and removal of phenolics; and removal of chlorinated
hydrocarbons.                            ' ;

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements  are small when the regenerant is not recycled. When both solvent
and solute are recovered, the steam requirements  for distillation (up to three stills required)
will be significant. If the regenerant is not recycled, it must be disposed of. If the regenerant
is recycled (e.g., by distillation), the still bottoms must be disposed.

     Capital costs are moderately large; while no furnace is needed for regeneration (an
expensive item with carbon  systems), resins costs are high. Operating costs may be below
$1/1000 gal in some  applications, but may reach $5-20/100 gal when concentrated waste
streams  are treated and the solute recovered. Credit for recovered solute can allow a system
to operate at a profit in favorable cases.

V. OUTLOOK FOR WASTES

     Resin adsorption is particularly attractive for removing organics from aqueous waste
streams  when material recovery is desirable, and when the waste stream contains high levels
of dissolved inorganic salts: Applications appear to be expanding.

                                         38

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               BIOLOGICAL TREATMENT:  ACTIVATED SLUDGE

  I. CONCLUSIONS AND RECOMMENDATIONS

     Activated sludge treatment  is extensively  used in industry, and is probably the most
cost-effective method of destroying organics present in an aqueous waste stream. Neutraliza-
tion and equalization of the  waste  stream,- as well as suspended solids removal, should
precede the activated sludge system. It is a safe and reliable  process which is relatively
uncomplicated to operate and relatively inexpensive. Improved understanding of activated
sludge microbiology and enzyme catalysis will improve process operating efficiencies in the
future.

 II. PROCESS

     Aqueous organic waste streams having less  than \% suspended solids have  flocculated,
biological growths continuously circulated  arid  contacted in the presence of oxygen. Since
the process was introduced  at  the  turn  of the  century  it has been modified through
improved methods of maintaining aerobic conditions under varying organic loadings.

    The process involves an aeration step, followed by solids-liquid separation, with recycle
of a portion of the solids. The basic system has an open tank for the mixture of the active
biomass with influent wastewater and air, followed by a clarifier. Bacteria in activated
sludge systems serve to perform hydrolysis and oxidation reactions.

 III.  APPLICATIONS TO DATE

    The activated sludge process has been applied extensively  to treat wastewater from
municipal sewage plants, canneries, paper  and  pulp mills,  refineries, breweries,  and steel,
textile,  petrochemical, pharmaceutical,  and timber processing plants. It has also been
applied to photo processing wastes and to  the propylene glycol wastewater from polyvinyl
chloride production.

IV. ENERGY, ENVIRONMENT, ECONOMICS

    The activated sludge system is energy-intensive, with over 10% of total operating cost
based on energy needed for pumping, aeration and clarification. The system is basically
environmentally sound; no chemicals are added and natural degradation takes place.

    Capital costs are about 10^ per 1,000 gallons for a 10 mgd facility. These costs increase
to over $1 for facilities handling  less  than  1 mgd. Processes handling dilute wastewaters are
reported to have total costs of 10-40^  per 1,000 gallons.
                                        39

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 V.  OUTLOOK FOR WASTES

    Activated  sludge systems are  employed in at least two facilities for treatment of
hazardous  wastes. The system is environmentally sound because it employs natural micro-
bial metabolic processes; no chemicals are added.
                                       40

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                BIOLOGICAL TREATMENT: AERATED LAGOONS
                                       a
I.  CONCLUSIONS AND RECOMMENDATIONS

     The aerated lagoon biological  treatment process decomposes organics in wastewater
containing  less than  1% solids, employing  essentially the same microbial reactions as
activated sludge. The  aerated  lagoon, however, does not have a sludge recycle system for
continuous circulation of microorganisms, and microbial strains do not acclimatize to the
same  extent.  BOD removal efficiencies range from  60 to 90%. The process is not as
attractive for industrial waste treatment as the activated sludge process; removal efficiencies
are not as  high and the process is  less flexible in maintaining effluent limitations under
varied influent loading.

II. PROCESS

     The aerated  lagoon  technique  developed from adding artificial aeration to existing
waste stabilization ponds. Usually the lagoon is an earthen basin with sloping sides and
about 6-17 feet depth. For the  treatment of industrial wastes, it may be necessary to line
the basin with  an impermeable material. Because wastewaters in aerated lagoons are generally
not as well mixed as  those in activated sludge basins, a low level of suspended  solids is
maintained. If mixing  and aeration are not complete, a portion of the solids settles to the
bottom and undergoes anaerobic microbial decomposition. Retention times are slightly
longer than for activated sludge; and where anaerobic decomposition is encouraged,  the time
is even longer.

III. APPLICATIONS TO DATE

     The process has been successfully used for petrochemical, textile, pulp and paper mill,
cannery, and refinery wastewaters.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     For comparable treatment efficiency, energy requirements are comparable to those for
activated sludge treatment; but generally the aerated lagoon employs less energy for aeration
and longer retention periods.  Chemical requirements are essentially limited to addition of
nutrients.  As in activated sludge treatment, the effluent is a clarified liquid and a biomass
sludge residue; the biosolids are more difficult to flocculate and settle from the mixed liquor
because of the  longer retention time.

     Total costs range from 10 to  30(^/1000 gallons of dilute influent; if basin lining and
high aeration is required, treatment costs may be nearly $2/1000 gallons.

V. OUTLOOK FOR WASTES

     The process is not as attractive as activated sludge treatment for a wastewater influent
with highly variable organic and metal concentrations.

                                       41

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              BIOLOGICAL TREATMENT:  ANAEROBIC DIGESTION

  I. CONCLUSIONS AND RECOMMENDATIONS
                                        .;.
     Anaerobic digestion is a biological treatment process for the degradation of simple
organics in an  air-free environment. Part of the carbon substrate is used for cell growth and
the other is converted to methane and carbon dioxide gas. The microbiology is complex and
still not well understood. Two types of interdependent organisms are present, and steady-
state environmental conditions must be maintained to keep them balanced. Because of this
delicate balance, the process is not suitable for treatment  of most industrial processing
sludges. Oil, fat, and grease are also troublesome.

 II. PROCESS                         . ;

     The organic  sludges and  biomass sludges from primary  clarification and biological
treatment  are processed to reduce  their volume and improve their stability. In the conven-
tional process,  the  waste  stream  is fed into: the middle  zone of a closed tank with no
agitating mechanism. The solids are digested by the  organisms, gas rises, bringing scum to
the surface,  and the gas is collected from the;roof of the tank.  Usually this gas is used to
maintain the temperature of the installation arid sometimes to heat other parts of the plant.
The digested sludge settles to the bottom of the tank after 30 to 60 days. There is only a
small volume of digested sludge, which is stable and  inert and can be disposed of for land
reclamation or by ocean  dumping.  The bacteria are sensitive to pH, temperature, and the
composition of the waste, but usually with time the system will achieve its  own balance.
Modifications have been made for  some installations, usually involving agitation or heating,
shortening the  process to several days to two weeks.

 III.  APPLICATIONS TO DATE

     Most  installations have been  for the digestion of sewage sludge, as the final step in a
complete  municipal waste  treatment  facility. Boston  and Chicago both use anaerobic
digesters:  Boston disposes of the waste by.ocean dumping; Chicago, whose plant is the
world's largest, treating  a  billion gallons of wastewater per day,  uses the waste  for land
reclamation. In the past 20 years, the system, has been studied for meat packing wastes, and
there are several plants operating commercially. It has also been studied  for cotton kiering
liquor, brewery wastes and alcohol  distillery wastes.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy  demands are relatively low; some electric power is needed to mix the reactor
contents, recycle some of the effluent  sludge to the reactor and heat the incoming sludge.
Essentially all  of the  power  for  the  heat exchanger is provided through production of
methane gas.
                                        42

-------
     The presence of arsenate or mercury in anaerobic digestors could lead to formation of
toxic compounds.

     In municipal wastewater treatment plants, costs for anaerobic digestion are difficult to
segregate. Estimates for a facility treating 100,000 gal/day of sludge with 5% solids would
be: capital  investment, $1.25 million,annual fixed costs would be $219,000, and variable
costs $171,000. The cost for treating 103 gallons would be $10.69.

 V. OUTLOOK FOR WASTES

     There  seems to be  a potential for disposal of feed lot wastes, culture material  from
pharmaceutical processing, and food processing wastes. For industrial processing sludges, the
method may be suitable if there is a steady volume and flow, oil and grease are removed,
and soluble metal content is low.
                                         43

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                    BIOLOGICAL TREATMENT:  COMPOSTING

  I. CONCLUSIONS AND RECOMMENDATIONS

    Composting provides a means of achieving  aerobic digestion of organic wastes by
microorganisms inthepresenceoftheirownreleasedheat.lt is the only  biological treatment
process relatively insensitive to toxicants and it encourages adsorption of metals. Costs are
higher than for other biological processes, but lower than for incineration.

 II. PROCESS

    Composting basically involves piling ground waste in windrows and aerating the piles
by periodic turning. All  that need be done is scheduling of spreading and turning with
earthmoving equipment, adding some nutrients and alkalis if necessary, and providing for
collection of leachate and runoff water to protect groundwater. There are over 30 process
modifications involving rotating drums, forced aeration, etc. Complete digestion of most
organic wastes take place in three or four months, although refinery wastes or other difficult
organics may take up to a year.

 III. APPLICATIONS TO DATE

    Systematic composting has been widely(used in Europe, where there is a ready market
for composted waste as an organic soil conditioner. Most of the demonstration projects in
the United States have closed for lack of a market for humus,  but  some cities use this
cost-effective disposal technique for municipal refuse and give the compost away. Chicago
uses the system to dispose of high-strength organic sludges, and several petroleum refineries
use it for refinery wastes. It has also been used for cannery solids, pharmaceutical and meat
packing sludges.

IV. ENERGY, ENVIRONMENT, ECONOMICS
                                        i
    Energy demand is low, limited primarily  to fuel costs to operate earthmoving equip-
ment and pumps.

    The only emissions  from composting are carbon dioxide,  steam,  a liquid effluent
containing partially  oxidized organics and a barnyard smell indicative of healthy microbial
activity.

    Costs for composting are about  $30/thousand  gallons of influent, exclusive of land
acquisition or further treatment of collected leachate. The capital expenditure to handle
100,000  gpd would be  $1.5  million;  fixed costs $275,000 annually and variable costs
$802,500.
                                       44

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V.  OUTLOOK FOR WASTES

    Composting is applicable to high-organic wastes, including oils and tars and industrial
processing sludges.
                                      45

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               BIOLOGICAL TREATMENT: ENZYME TREATMENT

I.  CONCLUSIONS AND RECOMMENDATIONS

     Enzyme  treatment of industrial  processing  wastes is totally impractical. Enzymes
catalyze specific reactions and  cannot adapt.well to the varying composition of typical
waste streams. Furthermore, enzyme production is very expensive.

II. PROCESS DESCRIPTION

     Enzymes are highly selective chemical catalysts which act on specific molecules. The
urease  enzyme, for example, breaks  down urea  into carbon dioxide and ammonia.  A
hydrolase enzyme derived from yeast has been shown to oxidize phenol to carbon dioxide
and  water.  The cellulose enzyme, produced by a stream of fungus, Trichodenna viridi.
catalyzes the hydrolysis of cellulose to glucose^

III. APPLICATIONS TO DATE            f'.

     There are no known full-scale applications of enzyme treatment processes in hazardous
waste management. There  are commercial applications in  meat tenderizing, de-hairing of
hides prior  to  tanning,  cheese-making, pharmaceutical  manufacture,  and  detergent
production.                             ;

     The Army's Natick Research and  Development Command is operating a 1000 Ib/mo.
pilot plant to convert waste paper into glucose. A number of Government, university, and
industrial laboratories are investigating the use of lactose for recovery of monosaccharides
from cheese whey. Groups at Oak  Ridge National Laboratories and the  University of
Pennsylvania have studied the enzyme decomposition of phenol.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Due to the specificity of enzyme  reactions and the fact that current waste treatment
applications are limited in number and lab  scale, no useful generalizations  can be made
about energy, economics, or potential environmental impacts.

V. OUTLOOK FOR WASTES

     Enzyme treatment  may be useful for specialized  industrial applications, particularly
in  cases where salable reaction products result. Enzymes have little or no potential in
general waste treatment.
                                      46

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                BIOLOGICAL TREATMENT:  TRICKLING FILTERS

I.  CONCLUSIONS AND RECOMMENDATIONS

     The trickling filter process is a proven technology for the decomposition of organics in
waste streams with less  than  1% suspended solids. The  process brings the wastewater in
contact with aerobic microorganisms by  trickling the water over media supporting  the
microorganisms. BOD removal efficiencies range from 50 to 85%. The  process is used in
industry  to accept wastewater loading variations and provide a relatively uniform effluent
for treatment by other biological processes, such  as activated sludge.

II. PROCESS

     Wastes  are sprayed through the air  to absorb oxygen, and then allowed to trickle
through a bed of rock or synthetic media coated with a slime of microbial growth. Process
modifications employ various media and depths to retain the microorganisms under varying
hydraulic and effluent recycle conditions. The primarily metabolic processes are aerobic, and
the microbial population is similar to the activated sludge population. However, because of
the relatively short contact time, the percentage removal of organics is not as great.

     The process involves open tanks or towers to house the filter packing, followed by
effluent clarifiers.  Recycle pumps may be used to recirculate filter effluent. A rotating spray
dosing system feeds influent wastewater to the filter surface.

III. APPLICATIONS TO DATE

     Trickling filters have been extensively used in sewage treatment and in treatment of
refinery wastewaters containing oil, phenol, and sulfide. They are applicable to the same
industrial waste streams as the activated sludge process, including cannery, pharmaceutical,
and petrochemical wastes.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy  demands are low, as little as one-tenth that of activated  sludge treatment.
Dilute wastewater is treated  at a total cost between  10  to 30tf  per  1000 gallons;  for
concentrated  waste requiring filter recycle the cost may be $2 per 1000 gallons. The process
effluents are a liquid wastewater from which a major portion of the dissolved organics have
been removed and a biomass sludge.

V. OUTLOOK FOR WASTES

     The process  could  be used  in  sequence  with other  biological treatment,  such as
activated sludge, but it  is not generally  efficient enough  to use as the  sole  method of
biodegradation.

                                       47

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          BIOLOGICAL TREATMENT: WASTE STABILIZATION PONDS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Waste stabilization ponds utilize natural bibdegradation reactions in wastewaters con-
taining less than 0.1% solids with low concentrations of organics. The process is more
sensitive  to  concentrations of inorganics  and suspended solids than any of the  other
biological treatments discussed in this report. It is suitable for industrial wastes only where
preliminary treatment has removed most contaminants and final effluent polishing is needed
before discharge to  a receiving water.      !

II. PROCESS                       •    : .     .

     Waste stabilization ponds are large shallow basins where wind action provides aeration
and a mixed autotrophic and heterotrophic microbial population provides decomposition of
organics  over a long retention time. Deep: ponds, more than 4 feet  deep, may promote
anaerobic decomposition of settled sludge.

III. APPLICATIONS TO DATE

     Waste stabilization ponds have been widely used  for sanitary sewage and dilute
industrial wastes, mostly  to provide final  effluent polishing. Industries using the method
include meat and poultry packing, canneries, dairies, iron  and steel works, paper and pulp
mills, textile mills, oil refineries and petrochemical plants.

IV. ENERGY, ENVIRONMENT,  ECONOMICS

     Large land acreage is the principal capital cost; energy and chemical requirements are
insignificant. Total  costs for treating dilute wastewaters in unlined basins range  from 5 to
15^ per 1000 gallons; for more concentrated waste streams in clay-lined basins, the cost is
about $1.70 per 1000 gallons.  Energy is  needed only for pumping. A  polished liquid
effluent and some biomass sludge are the end-products.

V. OUTLOOK FOR WASTES

     The process can  be employed only  where substantial land acreage is available and
where climate is suitable. Toxic inorganics must be  removed before waste  stabilization
ponding because of the system's  high sensitivity to inhibitors. The use of the method for
final polishing provides extra insurance that final effluent  guideline limitations will be met.
                                       48

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                                  CALCINATION

I.  CONCLUSIONS AND RECOMMENDATIONS
                                         f
     Calcination is  a well established process, and one of the few  that can satisfactorily
handle sludges. Calcination is recommended as a one-step process for treatment of complex
wastes containing organic and/or inorganic components. The organics are destroyed; the
inorganics are generally reduced in volume and converted into a form of low leachability
suitable for landfill.

II. PROCESS DESCRIPTION

     Calcination is a thermal decomposition .process, generally operated around 1000°C at
atmospheric pressure.  It can be applied to aqueous solutions, slurries, sludges, and tars to
drive off volatiles and to produce a dry powder or sintered solid.  Typical calciners include
the open hearth, rotary kiln, and fluidized bed.

III. APPLICATIONS TO DATE

     Industrial  applications include  production of cement,  lime, magnesia,  titania,  and
wall  plaster, and smelting of sulfide  and  carbonate ores. Waste treatment applications in-
clude recalculation of lime sludges from water treatment plants; coking of heavy residues and
tars  from petroleum refining  operations;  concentration and volume reduction of liquid
radioactive wastes;  and treatment of mixed refinery sludges containing hydrocarbons,
phosphates, and compounds of Ca, Mg, K, Na,  S, Fe, and Al.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements  are generally high, but depend on the water and organic content
of the waste stream. Calcination  of dry material requires about 1-3x106 Btu/ton of solid
product; calcination of a sludge or slurry with  ^0% water requires about 20x106 Btu/ton of
solid product. If this waste stream contains a combustible  organic fraction, the energy re-
quirements are reduced.                   ;

     In general, calcination systems will require fairly extensive air pollution control equip-
ment, including particulate-removal devices, • wet scrubbers, and possibly final gas adsorp-
tion systems.

     Capital investment costs  for a calciner are in the range of $10,000-$30,000/ton of
throughput daily. Operating costs are highly variable, depending on the water and organic
content of the waste stream, and the possibilities for resource recovery credits.

V. OUTLOOK  FOR WASTES

     Calcination has been used widely in industrial and waste treatment applications. Its use
is likely to expand, particularly in the treatment of tars, sludges,  and other residues which
present particularly difficult problems for disposal.
                                         49

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                                   CATALYSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Whenever a waste stream can usefully be treated by a chemical transformation process,
the possibility of catalyzing the reaction should be considered. In general, if a transforma-
tion can be successfully catalyzed, operating .costs and energy requirements will be reduced.

II.  PROCESS DESCRIPTION

     Catalysis is not a process in itself, but rather a modification of the rate or mechanism
of chemical reaction processes through the use of catalysts, which are themselves unchanged
at the end of a reaction.

III. APPLICATIONS TO DATE

     The  industrial applications of catalysts in the petroleum refining, chemical,  phar-
maceutical, and textile industries are legion.

    In the field of waste treatment, catalytic oxidation is used quite widely as an alternative
to incineration in the decomposition of waste organics. A number of catalytic processes
have been investigated in the laboratory for destruction or detoxification of chlorinated
pesticides, oxidation of cyanides, sulfides, and phenols, decomposition of sodium hypo-
chlorite solutions, and conversion of mixed carboxylic acid waste streams to fumaric acids
for recovery.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     In general,  a catalytic process  operates  at a much lower temperature than the equiva-
lent non-catalytic process and hence consumes less energy.

     Environmental impacts  are generally the' same as those  of the non-catalytic process.

     Catalytic processes may be higher in capital costs than non-catalytic processes in some
cases. However, the less severe operating conditions (lower temperatures and/or pressures)
almost always result in lower overall operating costs.

V.  OUTLOOK FOR WASTES

     As the use of chemical processing  in waste treatment increases, the effort to develop
catalytic  processes  should  be increased  as well. A  great deal of work is needed to demon-
strate the commercial practicality of catalytic  reactions tested in the laboratory, and ex-
ploralory  work  could  be useful on catalytic  hydrogcnation and   low-temperature  air
oxidation.
                                         50

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                                CENTRIFUGATION

 I.  CONCLUSIONS AND RECOMMENDATIONS
                                         l ' .
     Centrifugation is a  well-developed liquid/solid  separation process  being used in a
variety of full-scale applications for material processing and  waste  treatment. In treating
hazardous wastes, centrifugation can be used., to  greatest advantage to increase the solids
concentration, and thereby reduce the volume, of a high concentration liquid/solid mixture
(sludge) by partially separating the liquid and solid phases ("sludge dewatering")-

     Centrifugation is generally technically and economically competitive with other sludge
dewatering processes  (e.g., vacuum  filtration  or  the  use of filter presses)  and should be
considered as a potential process for concentrating hazardous waste sludges and slurries.
Equipment is commercially available in a large variety of sizes and configurations.

II. PROCESS                            '

     Centrifugation is a physical process whereby the components  of a fluid  mixture are
separated mechanically by the application  of centrifugal force, applied by rapidly rotating
the mass of  fluid within the confines  of a; rigid vessel. Centrifugal forces acting on the
revolving mass of fluid cause the solids suspended in the fluid to migrate to the periphery of
the vessel where they  can be  separated. The particles are removed as a liquid/solid mixture
significantly more concentrated than the original liquid.

III. APPLICATIONS TO DATE            :

     Some common applications of centrifugation are in separating oil and water mixtures;
clarification of viscous gums and resins; classification and removal of oversize particles and
unground pigment from  lacquers, enamel and dye paste; clarification of essential  oils,
extracts,  and food products, such  as homogenized milk and  fruit juices; separation of
micro-organisms from fermentation broths, .recovery of finely divided metal such as silver
from film scrap and platinum from spent catalyst; separation  of acid sludges from the  acid
treatment of petroleum;  recovery of crystalline solids from  brine;  dewatering of fibrous
solids such as paper pulp and  chemical fibers; dewatering and removal of starch from potato
fibers,  etc. Probably the main  application for centrifuges at  present is the dewatering of
waste sludges. •

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Power requirements for centrifugation are typically 0.3-1.2 horsepower per gallon per
minute of inlet  waste  feed. Power consumption is equal to or slightly greater than for other
sludge dewatering processes.
                                         51

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     For most sludge dewatering purposes, centrifugation is generally cost-competitive with
other dewatering processes such as vacuum filtration or press filtration.

     A conveyor bowl type centrifugation system capable of dewatering 6 tons per day of
sludge (dry basis) will have an installed capital cost of approximately $140,000 and a total
operating cost  (including amortization)  of $34.50 per ton of solids dewatered. In most
applications, costs range from $20-$45/ton.

V. OUTLOOK FOR WASTES

     The major application of centrifugation to waste treatment is the dewatering of waste
sludges generated by water pollution control systems. Centrifuges have for many years been
used on biological sludges from municipal treatment plants and from pulp and paper mills.
Some expect the technique to replace vacuum filtration as the most common dewatering
technique, especially for sticky or gelatinous sludges. It  will also find further application in
removing soluble metals from wastewater, as  from the  wet scrubbers used in the steel
industry, to dewater sludges generated from sulfur dioxide air pollution control systems,
etc.

     Because it is capable of totally closed operation, centrifugation  is particularly well
suited to treating liquids that are volatile, flammable, or otherwise pose health and/or safety
hazards to operating personnel.
                                          52

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                                 CHLORINOLYSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Chlorinolysis is capable of converting most liquid chlorinated hydrocarbons completely
to carbon tetrachloride. It is not really a rwaste treatment process, but a manufacturing
process  that uses chlorocarbon waste streams and residuals as feedstocks. The process has
excellent resource recovery  potential  (sufficient wastes are generated in the Gulf Coast
region to support at least one 25,000 ton/yr chlorinolysis plant) if there is a market for the
carbon tetrachloride. There may be, however, legal and institutional problems that might
hinder transfer of wastes from generators to an operating chlorinolysis unit.

II. PROCESS

     At temperatures around 500°C and pressures of about 200 atm in the presence of
excess chlorine, the carbon-carbon bonds of hydrocarbons can be broken, and the molecules
recombined to react with chlorine to form carbon tetrachloride.  Because liquid chlorine is
highly reactive, reactors and piping must be high-purity nickel,  surrounded by  a stainless
steel jacket. The organic feedstock and preheated chlorine are introduced to the reactor,
which is heated to initiate chlorinolysis; subsequently the process provides its own heat. At
the end of the process, the pressure is  released and the products  are cooled and drawn off.
Subsequent processing by distillation yields carbon tetrachloride, the principal product for
sale.

III. APPLICATIONS TO DATE
                                        j .
     This is not a waste treatment process, but a production process that can utilize waste
streams. A semicommercial plant to produce 6000-8000 tons/year has  been  operating in
Germany and a 50,000 ton/year plant is planned for the same site.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Electricity and fuel requirements per ton of carbon tetrachloride are relatively small —
135kWh and  794 Btu,  respectively. Chlorinolysis offers the opportunity of resource re-
covery,  but the process involves hydrochloric acid and phosgene gas effluents. Neutraliza-
tion of the effluent streams will produce spdium hypochlorite, which is toxic to aquatic life.

     Capital and operating costs for a  plant processing 25,000 metric tons/year of mixed
chlorinated hydrocarbon wastes are estimated at $19,700,000/year; the process could
produce carbon tetrachloride at 10.24 per Ib, and the selling price is now 19^.

V. OUTLOOK FOR WASTES

     Chlorinolysis is  an  efficient, cost-effective process for recovering carbon  tetrachloride
from  chlorinated hydrocarbon waste streams.  The outlook  for the  process depends on the
future demand for carbon tetrachloride, and the  availability of  a continuing supply of
suitable  wastes.

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                                    DIALYSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Dialysis is one of the earliest membrane processes. It can separate salts and low mole-
cular weight  organics from colloids and high molecular  weight solutes in aqueous waste
streams. However, both  of the output streams are more dilute than the feed stream, and
neither is likely to be more suitable for disposal or recovery than the feed stream. Hence,
dialysis has little or no potential for general waste treatment applications.

II. PROCESS DESCRIPTION

     A solute-containing feed stream  is passed across one free of a semi-permeable mem-
brane and a higher volume wash stream is passed  across the opposite face.  Small solute
molecules  are transferred to the wash stream by diffusion  across the  membrane. Larger
molecules and colloids are retained in the feed stream.

III. APPLICATIONS  TO DATE

     The best known current  application of dialysis is hemodialysis, which removes salts,
urea, and  other wastes from the blood of people  suffering from chronic kidney failure.
Since the 1920's, dialysis has been used in the rayon industry to separate caustic soda from
hemicellulose wastes.  There are also other smaller scale applications in pharmaceutical and
biochemical  laboratories for special production  and purification. Dialysis equipment is
available commercially.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements are low,  being limited to  the pumping of feed and wash streams.
                                        y-
     The two diluted product streams could' prevent difficult disposal  problems if not
reusable.                                 :

     Capital  costs depend more on the amount of material to be separated than on the
waste stream  throughput. A commercial dialyzer separating 1000 Ib/day of  solute would
cost about $3000.
                    ' '                                       *•
V. OUTLOOK FOR WASTES

     Dialysis is a mature technology; no major new developments are expected which would
make the process at all useful for hazardous waste treatment.
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                                   DISSOLUTION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Dissolution is a first step that removes major or minor constituents from solids. The
process is applicable to  any solids that can be wetted by a suitable liquid. We recommend
that more emphasis  be placed on more  complete characterization of solids to aid  in
specification  and testing of possible dissolution processes. Efforts should also be made  to
utilize lower quality or waste reagents where possible.

II.  PROCESS

     Dissolution may be defined as the  complete or partial transfer of one or more
components from a solid to a liquid phase in contact with the solid. The reaction involves
some degree  of chemical transformation, such as solvation, ionization,  or oxidation. The
solids are contacted by  the reagent in a mixer, following which the slurry is separated. Heat
may be applied to speed the process and provide increased solubility. Solids can be treated
sequentially with different reagents to remove components selectively. The products are a
wastewater stream that  requires further treatment, and  residual solids that may be suitable
for disposal, reuse, or further treatment.

III. APPLICATIONS TO DATE

     Dissolution has been widely  used in metallurgy  since the early  1800's and in the
synthetic chemical industry since its beginning. Many of these applications (e.g., separation
of metals from ores) are closely related to treatment of inorganic wastes, but there appears
to be little large-scale application to waste treatment. One installation involves production
of chemicals  for agriculture and other use from galvanizing wastes and flue dust. Another is
used for recovery of metallic copper from.scrap,  and a semi-commercial plant  is being
considered for recovery  of metal from plating slimes. Several pilot and laboratories studies
are now going on.

IV. ENERGY,  ENVIRONMENT, ECONOMICS

     Energy requirements are limited to electricity  for mixing and pumping, and heat, if
required. Emissions to water are not harmful if the liquors used and produced are conveyed
to the next process step without inadvertent losses. No land disposal problems are antici-
pated if leached solids are adequately washed to remove leach liquor. Emissions to air will
be significant only when gas is evolved in the process, or where an unintended reaction takes
place (e.g., reaction of traces of sulfides in water to give off hydrogen sulfide).

     The  diversity of materials potentially suitable for dissolution and the circumstances of
reaction  vary considerably. The process is especially sensitive to chemical and labor costs.
                                        55

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An approximate cost for dissolving a hypothetical metal finishing sludge waste using fresh
sulfuric acid reagent would be: $61 per ton of input solids or $300 per ton of desired metal
removed; the cost of sulfuric acid is $24 per input ton.

V. OUTLOOK FOR WASTES

     Further applications for waste  treatment depend on  cost-sensitive factors, such as
utilization of waste reagents,  and  on  better understanding of composition of sludges and
mixed metal compounds.
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                                  DISTILLATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Distillation is a unit operational process that is  fully developed commercially and is
often employed to separate or purify liquid.organic product streams. It is a non-destructive
process, and practical limitations are primarily economic. With more stringent limitations on
air, liquid effluents, and land  site disposal, and with the rising cost of organic chemicals,
distillation could become  more  competitive with other methods for recovery of useful
materials from waste streams.

II. PROCESS

     The basic principle of distillation is as simple as it is old:  when a mixture of liquids is
boiled, the vapor usually differs in composition from the liquid  that remains. Only since the
19th century,  however, has distillation been conducted  on a  large scale  as a steady-state
operation.

     In general, a feedstock is charged to a large vessel  (still) which is heated, and vapors are
removed  as they are formed, and then condensed. There are a  number of variations on this
basic process.

III. APPLICATIONS TO DATE

     Distillation has wide industrial application in petroleum fractionation,  organic chemical
purification, organic chemical intermediate manufacture, solvent recovery, and cryogenic air
separation to produce oxygen, nitrogen, and argon.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Because of the variables involved, there  is no such thing as a typical cost on a unit
product or unit feed basis.                  ;

     Distillation creates no air or liquid effluent problems.

     An economic analysis  of a  system  that might be used for different types of organic
liquid waste streams was made, based  on  a  capacity  of 8000 Ib 20% acetone in water
waste/day. The solvent recovery cost in this system would be 4.2^/lb acetone.

V. OUTLOOK FOR WASTES

     Hazardous wastes that can be economically treated by distillation (for organic chemical
or solvent recovery) include liquid organic mixtures, such as  solvent mixtures recovered
from curbon air adsorption units, paint wastes, organic-containing plating  wastes, and lube
                                        57

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oil. The process is not suitable for treatment of thick, polymeric materials, slurries, sludges,
or tars that can cause operational problems. The types and quantities of organic solvent and
chemical wastes that are treated by distillation will increase as effluent regulations become
more stringent.
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                                ELECTRODIALYSIS

 I. CONCLUSIONS AND RECOMMENDATIONS

     Electrodialysis has not been employed  on a full-scale basis for any hazardous waste
 problem, per se. Nevertheless, it may have applicability where it can be tied into further
 concentration or reuse schemes. It will profit by the fact that it is a mature technology with
 well-known performance characteristics and price, and therefore can be easily evaluated as a
 potential component of any multi-process treatment being considered.

 II. PROCESS

     The general principle of electrodialysis  is the separation of an aqueous  stream under
 the action of an electric field into two streams, one enriched and one depleted. Success
 depends on synthetic membranes, usually based on ion-exchange resins, which are permea-
 ble only to a single-charge type of ion. Cation exchange membranes permit passage of only
 positive ions, while anion membranes permit only negatively charged ions to  pass through.

     The feed water passes through compartments formed by the spaces between alternating
 cation-permeable and anion-permeable membranes held in a stack. At each end of the stack
 is an electrode having the same area as the membranes. A d-c potential applied across the
 stack causes the positive and negative ions to migrate in opposite directions. Feed material is
 first filtered to remove suspended particles that could clog the system. An operating plant
 usually contains many recirculation, feedback and control loops and pumps to optimize the
 concentrations and pH at different points for most efficient operation.

 III.  APPLICATIONS TO DATE

     Electrodialysis has been used for desalination since the 1950's. The largest number of
 installations is  in the production of potable water from brackish well or river water.
 Hundreds of such units, some of which can;handle more than  one million gallons per day,
 are in use throughout the world.

     In the food industry, electrodialysis is used for desalting whey and de-ashing sugar. The
 chemical industry uses the technique for enriching or depleting solutions, and for removing
 mineral constituents from product streams.

.IV.  ENERGY, ENVIRONMENT, ECONOMICS

     Electrical requirements vary, but conventional systems take about 5 kWh of energy for
 each 1000-ppm  reduction of salt in each 1000 gal. purified product water and up  to 3 kWh
 to pump each 1000 gal. products.

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     The product streams must be recycled, sold, or otherwise disposed of. Electrodialysis
may generate low levels of toxic or flammable gases that might present a hazard in an en-
closed space.

     The capital costs for electrodialysis are .modest, about 20-25% of the total  cost of
water treatment. Both capital and direct operating costs are dependent on the volume of_
water treated and on the salts removed. Total water production costs of less than $.50/10 3
gal are reported for salt reduction from 2000 ppm to 500 ppm in plants treating 10*  gal/day
or more. Other plants may have higher costs or may receive significant credits for reclaimed
material.

     A typical  electrodialysis system  to  treat rinse tanks from an acid nickel plating line
mighTcost about $6.00/163 gal.
                                         t
V.  OUTLOOK FOR WASTES

     Pilot operations have  been carried  out in the desalting of sewage plant effluent,
sulfite-liquor recovery, and acid mine  drainage treatment. Treatment of plating wastes and
rinses, particularly to salvage chromium, may have some potential.
                                         60

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                                  ELECTROLYSIS
                                        *
I.  CONCLUSIONS AND RECOMMENDATIONS

     Electrolytic processes may be considered for reclaiming heavy metals, including toxic
metals from concentrated aqueous solution and for polishing dilute metallic wastewaters.
They are not generally useful for dissolved- organics, organic  waste streams or viscous and
tarry liquids.

II.  PROCESS

     Electrolysis refers to the reactions of .oxidation or reduction that take place at the
surface  of  conductive electrodes  immersed in an  electrolyte, under the  influence of an
applied potential.

III.  APPLICATIONS TO DATE           !

     Electrolysis, including electroplating and anodizing, has been an important process of
industrial chemistry for many years. Chlorine production, for example, depends on elec-
trolysis, and many commercial metals are refined by electrolytic processes. Metals may be
obtained from primary ores, and magnesium and aluminum are processed by electrolysis in
molten salt baths. Electrolysis for waste treatment  has been employed to a limited extent
depending  largely  on costs.  The most frequent  application  is the  partial removal  of
concentrated metals such as copper from waste streams for recycle or reuse. Other applica-
tions which have been successfully piloted include  oxidation  of cyanide wastes and separ-
ation of oil-water mixtures.

IV.  ENERGY, ENVIRONMENT, ECONOMICS

     Electrical energy costs range from  10  to 35% of total operating costs, with treatment
of concentrated metals at the low end,  and dilute streams or  cyanide treatment at the high
end.                                    ;

     Gaseous emissions may exist; some may be vented to  the atmosphere, others may have
to be scrubbed or otherwise treated. The process wastewater may be reusable or disposable,
or may have to undergo further processing.

     Costs  are highly  dependent on the  concentration  and  nature of  the undesirable
material.  Electrolysis may offer significant trade-offs between capital and  operating costs,
depending on chemical and economic variables.
                                        61

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                               ELECTROPHORESIS

I.  CONCLUSIONS AND RECOMMENDATIONS
                                        r       •                  •
     No suitable equipment for electrophoretic treatment of hazardous wastes is available.
Many critical problems would have to be solved before such equipment could be developed,
and even if the design problems were solved, there is no assurance that the process would be
operationally  practical. Further consideration  of electrophoresis  cannot  therefore  be
justified.

II. PROCESS DESCRIPTION

     Electrophoresis is the transport of electrically charged particles under the influence of
a DC electric field. The charged particles (generally colloids in the  l-20/i size range)
migrate to a collecting membrane for subsequent removal.

III. APPLICATIONS TO DATE

     Electrophoresis is used extensively as a laboratory tool in the analysis and separation of
proteins, polysaccharides, and nucleic acids. It .has also been used commercially for creaming
of rubber latex, and  for fractionation of animal sera for veterinary vaccines. Numerous
proposed applications have been researched and shown to be  technically feasible. These in-
clude deposition of paints, polymers, ceramics, and  metals. The process has also been con-
sidered for water purification (e.g.,  for separation  of emulsions, and for color,  virus, and
algae removal).                            :

IV. ENERGY, ENVIRONMENT, ECONOMICS

     In  aqueous systems,  the electrical energy requirements are of the order of 7  kWh/
1000 gal.

     The process may evolve gases from electrode reactions.  Both the concentrated sludge
and the "treated" liquid may require subsequent disposal.

     Capital costs would be lower than the costs for electrodialysis.  Operating costs might
be in the range of $0.50-2.00/1000 gal, depending on the application.

V. OUTLOOK FOR WASTES

     At least 5-10 years of effort would be required to develop electrophoresis equipment
for waste treatment. In view of the lack of scientific and practical guides available, and the
very significant problems of controlling electrode reactions, pH,  conductivity, flow, tem-
peratures, and membrane  plugging,  there is even some question  whether  an R&D effort
would be successful.
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                                  EVAPORATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Evaporation  is a well-defined well-established process, used throughout industry. It is
capable of handling liquids, slurries, sludges,  both organic and inorganic, containing sus-
pended or dissolved solids or dissolved liquids where one of the components is nonvolatile.
It is energy-intensive, and specialized equipment can be expensive.

II. PROCESS

     The process  and equipment for applying heat to the solution are similar to that for
distillation, except that the vapor is not separated. Open, direct-fired pans or solar evapora-
tion  from ponds  are still used in some applications, but most evaporators are heated by
steam condensing on metal tubes, through which the solution flows. Usually the steam is at
low  pressure and the boiling  liquid is under a moderate vacuum. There are numerous
variations on equipment and processes, depending on the application.

III. APPLICATIONS TO DATE              .

     In the chlor-alkali industry, evaporation is  used to concentrate  caustic soda and to
produce  calcium  chloride. Evaporation  of saline water to provide fresh water is well
established; U.S. plants have a  capacity  of about  67 million gpd. Concentration of sulfuric
and hydrochloric acids, citrus fruit juice, phosphates, and milk whey; crystallization of salts,
sugar; dehydration of Glaubers salt,  sulfur sludges are all well established.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements  vary considerably within a range of 100 to 1100 Btu/lb liquid
evaporated, with the average closer to the lower figure.

     There are generally no pollution problems with evaporation vapors. Where the vapors
contain organics,  the liquid is  condensed  and either disposed of or recovered by another
process, such as distillation.

     Economic  analysis of an  operation to concentrate 100,000 gallons per hour of kraft
black liquor shows capital investment  of $1.3 million.  Yearly operating costs would be
$1.06 per 1000 Ibs of water.

V. OUTLOOK FOR WASTES
                                        i
     Evaporation  is  already used in  the treatment of radioactive wastes, and is very effective
where  suspended  solids content is high and other methods are difficult. A combination of
evaporation and  simultaneous combustion  is used to  dispose of  TNT wastes.  Other

                                        63

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applications  include photographic chemicals, papermill  wastes, molasses distillery wastes,
and pickling liquors. Evaporation is not suitable for tars, solids, dry powders, or gases.
                                           64

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                                   FILTRATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Filtration  is a  well-developed liquid/solid separation process currently applied to the
full-scale treatment  of many industrial wastewaters and waste sludges. For the treatment of
hazardous wastes, filtration can be used to perform two distinctly different functions:

     1)  Removal of suspended solids from a liquid (usually aqueous) waste stream
         with the objective of producing a purified liquid.

     2)  Increasing the  solids concentration, and thereby reducing the volume, of a
         high concentration liquid/solid mixture (sludge) by removing liquid from the
         mixture ("sludge dewatering").    ;

     As a wastewater treatment process, filtration is usually most applicable when following
some form of flocculation and/or sedimentation.  As a sludge dewatering process filtration is
usually technically and economically competitive with other dewatering processes.

     We  recommend that filtration be considered as a  potentially applicable process for
hazardous waste treatment applications requiring the separation of liquid and solid phases.

II. PROCESS

     Filtration is a physical process whereby particles suspended in a fluid are separated by
forcing the fluid through a porous medium. As  the fluid passes through the medium, the
suspended particles  are trapped on the surface of the medium and/or within the body of the
medium. Filter  media can be a thick barrier of a  granular material, such as sand, coke, coal,
or porous ceramic; a thin barrier, such as a filter cloth or screen; a thick barrier composed of
a disposable  material such as powdered diatomaceous earth  or waste ash.  The pressure
differential to  move the  fluid  through the medium can be induced by gravity, positive
pressure, or vacuum. The intended application  has a great influence on both the type of
filter and its physical features.

III. APPLICATIONS TO DATE

     The inorganic  chemicals industry  employs various forms  of filtration to separate
precipitated product from waste  material. They  are commonly used in the manufacture of
titanium  dioxide, sodium  dichromate,  aluminum  sulfate, and magnesium. The organic
chemicals industry also employs filter techniques, e.g., removal of acetylene carbon particles
from aqueous quench streams, and removal of dye particles from the reaction bath. Rotary
vacuum filters are used to remove impurities in the processing of sugar. Vacuum filtration is
often used to  remove  impurities  from  lube oils. Boiler feed water and  many types of
industrial process water have stringent specifications on suspended solids. Filtration is often

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used in conjunction with precipitation, flocculation, and sedimentation to remove these
solids.  Filtration  is also  used as the final step in many industrial wastewater treatment
plants.                                   ;

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements for filtration  are .relatively low. A  vacuum  filtration system
capable of dewatering 36,000 gal/day of sludge containing 6 tons of solids will have a power
requirement of only 25 horsepower.

     The cost of treatment for both vacuum filtration and press filtration is usually within
the range of $20-$45/ton of solids treated (dry basis). For liquid purification the cost of
filtration by granular media filters usually varies from $0.10-$0.50 per 1000 gallons of
wastewater treated.

V. OUTLOOK FOR WASTES

     Major applications are and will be in the removal of suspended solids from wastewater
streams and in the volume reduction (dewatering) of waste sludges and slurries. As more and
tighter restrictions are placed on wastewater discharge, filtration will often be used after
precipitation, flocculation, and sedimentation.

     Decreased  availability  of solid waste disposal  sites will further encourage  the de-
watering of sludges prior to disposal.

     Non-aqueous liquids can be subjected to filtration for removal of suspended solids, but
highly viscous semi-liquids such as tars are generally not amenable to filtration.
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              FLOCCULATIOIM, PRECIPITATION, AND SEDIMENTATION

 I.  CONCLUSIONS AND RECOMMENDATIONS

     Flocculation, precipitation, and sedimentation are fully-developed processes currently
 used in a wide variety of industrial, processing and waste treatment applications. While
 flocculation, precipitation,  and sedimentation are individual process steps, they are inter-
 related, and are often combined into a single overall treatment process. They can be quite
 readily  applied to a variety of aqueous hazardous wastes  for the removal of precipitable
 substances, such as  soluble heavy metals and for the removal of solid particles suspended in
 the liquid. We recommend that these processes be given serious consideration for removal of
 heavy metals and/or suspended solids from an-aqueous waste stream. Although the process
 theoretically  can be used  to  treat non-aqueous liquids, such applications are very rare.
 Precipitation,  flocculation, and sedimentation are generally unsuitable for treating heavy
 slurries, sludges, and tars.

 II.  PROCESS

     Flocculation is the process whereby small, unsettleable particles suspended in a liquid
 are made to  agglomerate into larger more settleable particles. Precipitation is a physico-
 chemical process where some or all of a substance in solution is removed from the solution
 and transformed into a second (usually solid) phase. Sedimentation is a purely physical process
 whereby particles suspended in a liquid are made to settle by means of gravitational and
 inertial forces acting on both the particles suspended in the liquid and the liquid itself.

 III. APPLICATIONS TO DATE

     The processes have long been widely used for a variety of industrial applications, such
 as in the manufacture of many organic chemicals, the preparation of metal ores, and the
 preparation of sugar.
                                         ^
     Practically every industry that discharges a process wastewater stream contaminated
with suspended and/or precipitable pollutants employs some form of precipitation, floccula-
 tion and/or sedimentation.  Examples are:  removal of heavy metals from  iron and steel
 industry wastewater; removal of fluoride from aluminum production wastewater; removal of
 heavy metals, from wastewaters from copper smelting and refining,  and from the metal
 finishing industry.

 IV. ENERGY, ENVIRONMENT, ECONOMICS

     linergy consumption is very low compared to other processes. The processes produce a
waste sludge, which  can often present a serious disposal problem.

     A large (over 5 million gallons per day) system  employing only sedimentation with no
flocculating  chemicals  will typically treat  wastewater  at a cost of $0.10-$0.50 per  1000
gallons treated.

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     A  moderate  size  (0.5-5  million gallons per day)  system employing precipitation,
flocculation, and  sedimentation and using moderate dosages of precipitating/flocculating
agents will usually treat wastewater at a cost of $0.50-$3.00 per 1000 gallons.

     Small,  especially  designed  systems (less  than  0.5  million gallons per day) using high
dosages of precipitating/flocculating agents can have costs that are higher, but these will
rarely exceed $6.00 per 1000 gallons.

V. OUTLOOK FOR WASTES

     Precipitation,  flocculation,  and  sedimentation are generally practical, effective, and
relatively  low-cost processes for the  removal of precipitable  soluble substances and sus-
pended  particles from  aqueous waste streams.The processes are particularly suitable for the
treatment of high volume/low concentration waste streams.

     In  determining the applicability  of precipitation,  flocculation, and sedimentation to
specific waste streams, true research and development is usually unnecessary. Past experi-
ence and simple laboratory treatability tests are usually all that is necessary in determining
applicability.
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                                   FLOTATION

 I. CONCLUSIONS AND RECOMMENDATIONS

     Flotation is a physical-chemical method of separating solid particles suspended in a
 liquid, when the valuable products to be separated constitute less than 10% of the total
 solids. Although flotation has found only limited application outside the mineral industry, it
 is our belief that, with further research  and development,  the technique could be used to
 separate many types of components from mixtures of solids.

 II.  PROCESS DESCRIPTION

     The material is crushed or ground, mixed with water and reagents into a slurry or pulp,
 and agitated. Air bubbles carry the selected materials to the surface to form a stabilized
 froth,  which is then skimmed off, while the waste materials remain. By using the correct
 reagents, it is possible  to  separate similar  materials from each other. Some installations
 separate only one valuable component from waste;  others separate two, three, or even four
 products.

 III.  APPLICATIONS TO DATE            :
                                         5

     Although  flotation has been applied  principally to  mineral processing  to  separate
 valuable ore from tailings, a few other applications seem to have potential. When cellulose is
 recycled from paper,  flotation can be used to remove ink, pigments, and coatings. A few
 years ago three plants in the United States treated about 25,000 tons of paper per year in
 this manner.

     Other possible applications outside the mineral industry, though there are no commer-
 cial plants, are as a means of removing cyanide from solutions or mixed suspensions. In one
 test, about 95% of the cyanide could be removed. Research also shows that microorganisms
 can be floated, concentrated, and removed from a  suspension.

 IV. ENERGY, ENVIRONMENT, ECONOMICS

     The typical conventional flotation plant is a relatively large consumer of  energy,
averaging about 15 kWh/ton milled. Only  about  15% of the total  is  consumed in the
flotation step, with most of the energy used for crushing and grinding.

     Air emissions are not significant, since  flotation is a wet process. Dust emissions occur
at the ore crusher and at conveyor transfer points but are controlled with collecting hoods
and  water  sprays. The  waste  effluent goes  to a tailings dam from which water may  be
recycled, especially in arid areas.

     Costs  depend on the size and nature of the process. Operating costs for sulfide ore
flotations vary from $4/ton ore processed for a 500T/day plant to $1.50/ton fora 10,000
T/day plant.

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V.  OUTLOOK FOR WASTES

     The best application for the flotation process would be for separating a hazardous solid
from one that is not. Another application would be to separate all solid materials in a slurry;
however, it is difficult to see any reason for doing it this way, when the simpler process of
thickening and filtration would accomplish :the same purpose. Heavy metal ions (copper,
nickel, cadmium) and cyanides might be amenable to removal by this process, as well as
such inorganics as carbonyls and fluorides. As far as we know, however, no work has been
done to utilize the process.

     On the  other  hand, some of  the  reagents commonly used  for mineral and  ore
processing are  themselves hazardous and, if used carelessly, may appear in the tailings. Care
must be exercised in their use and control.
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                           FREEZE-CRYSTALLIZATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Freeze-crystallization  has been successfully tested for desalination of brackish waters
in  pilot plants. It has been demonstrated in the laboratory for hazardous waste treatment,
and is expected to find commercial applications in the near future.

II. PROCESS DESCRIPTION

     Freeze-crystallization  involves formation  of "pure"  ice crystals from a solution, and
concentration  of dissolved solutes in a residual brine. The ice crystals  may be separated
mechanically from the brine, washed, and melted to yield fresh water (or solvent). The brine
must be treated further, or otherwise disposed of.

III. APPLICATIONS TO DATE

     A number of freeze-crystallization processes were developed for desalination, but none
have become  commercial. Waste treatment applications tested in the laboratory include:
sulfite liquors; plating liquors; paper mill bleach solutions; arsenal redwater; solutions con-
taining acetic acid, methanol and  aromatic acids; ammonium nitrate wastes; and cooling
tower blowdown.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Electrical energy requirements are in the  range of about 60-75 kWh/1000 gal of pro-
duct water.

     The major environmental problem is associated with  further  treatment, or disposal
of the brine. Some emissions of refrigerant (e.g., butane or freon) are possible.

     Capital costs are estimated to be in the range of $600,000-5800,000. Operating costs
might be in the range of $6-12/1000 gal of product water.

V. OUTLOOK FOR WASTES

     Freeze-crystallization appears to be a very promising process for treatment of aqueous
waste streams containing 1-10% TDS. Commercial applications are certainly anticipated
within the next five years. Applications to some non-aqueous waste streams could probably
be developed.
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                                FREEZE-DRYING

I.  CONCLUSIONS AND RECOMMENDATIONS

     Freeze-drying (lyophilization) has no apparent potential for treating hazardous indus-
trial wastes. Although freeze-drying is used; commercially  for desiccating biological and
sensitive materials, it does not appear adaptable to economical waste processing on a large
scale. The process is slow, costly, and energy-dritensive, with limited use for removing water.

II.  PROCESS DESCRIPTION             [

     Freeze-drying is  a process for subliming frozen water from a material under high
vacuum. Basic equipment consists of a vacuum chamber, a vacuum source, and appropriate
refrigeration and heating equipment. Suitable feeds include wet solids, sludges, and slurries.

III. APPLICATIONS TO DATE

     The largest current use of this process is,in the preparation of freeze-dried coffee which
commands a premium price in the marketplace. It is also used in the manufacture of phar-
maceutical and biological preparations.      I.1"

     There are no known applications to waste treatment, and none is under development.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Freeze-drying is energy-intensive and costly to operate. Capital  equipment costs range
from $300,000-500,000. Its pollution potential is low, except for secondary effects of energy
generation.

V.  OUTLOOK FOR WASTES

     Freeze-drying development aimed at waste treatment is unknown  and will probably
remain so due to the serious limitations of the process.
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                             FREEZING, SUSPENSION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Freezing of sludges can aid in  the agglomeration of suspended particles, which then
tend to separate rapidly on thawing, leaving a clean supernatant.  There are no practical
applications at this time.

II. PROCESS DESCRIPTION

     Suspension or simple freezing (dewatering) of sludge causes the  suspended solids to
agglomerate and form relatively large floe particles which are more easily removed. Freezing
is accomplished naturally outdoors or through use of a refrigerant. Flocculants may be used
to accelerate coalescence of suspended solids during freezing. Separated solids are screened
or filtered off, and the water is further treated if necessary.

III. APPLICATIONS TO DATE

     No commercial  suspension freezing or freeze dewatering  applications exist. Freezing
alum sludges typical of waste water treatment plants has been  the center of interest in the
laboratory. Development of freezing for other materials is not being advanced.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements for natural freezing outdoors are small. Mechanical refrigeration
requires large energy  expenditures.  Suspension  freezing is essentially a phase separation
process, and both the separated  solids and the supernatant liquid would generally require
further treatment prior to disposal.

     Reliable cost data are not available, but are expected to be relatively high.

V. OUTLOOK FOR WASTES

     Unless energy considerations are proven to be acceptable  and  a broader usage of sus-
pension freezing can be found, it will remain limited in application to sludge dewatering.
Its value as a viable waste treatment process remains to be demonstrated on a commercial
scale.
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                HIGH-GRADIENT MAGNETIC SEPARATION (HGMS)

I.  CONCLUSIONS AND RECOMMENDATIONS

     High-gradient magnetic  separation  (HGMS) should be  considered for removal  of
magnetic materials, or recovery of certain high-value, nonmagnetic materials, from waste
streams. The  process is particularly  attractive for  high-volume applications. Aqueous  or
non-aqueous liquids, slurries, solids, and dry powders may be treated.

II. PROCESS DESCRIPTION

     HGMS is a technique for separating magnet or weakly paramagnetic particles and other
nonmagnetic materials (down to colloidal p'article size) from slurries, sludges, and (after
chemical treatment) from solutions. The feed stream is passed through a fine ferromagnetic
filter which, when magnetized, collects the magnetic material. The filter is periodically
cleaned, with the magnetic material  then recovered by  a simple wash procedure. The re-
moval of nonmagnetic material requires the feed  to be treated with a magnetic seed (e.g.,
magnetite).

III. APPLICATIONS TO DATE

     Current applications include clay whitening (removal of a small colored  magnetic
fraction), and upgrading of low-grade iron ore.

     Applications currently being investigated,: but not yet commercial, include: beneficia-
tion  of other ores, coal desulfurization, removal of  flue dusts in air streams from blast
furnaces, and wastewater treatment (including municipal wastes and steel mill wastewaters).

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy  requirements may be relatively large, especially  if high magnetic  fields are
required. Electromagnets, used to generate fields of up to  20 kOe, have power ratings of
around 400 kW for the  larger machines.  Disposal  of the  filter wash solution, if the material
is not recovered, and additional treatment of .treated  stream may also be required.

     Capital costs may  be as high as $800,000, if  high magnetic fields are required; they
may  be as low as $5,000, if the material being removed is  ferromagnetic. Operating costs
for high-volume  applications are expected to be  around 10-50^/1000 gal  for removal of
ferromagnetic materials, and of the  order of $1-5/1000 gal for removal of weakly para-
magnetic materials.

V. OUTLOOK FOR WASTES

     HGMS has attractive possibilities for the removal of ferromagnetic and paramagnetic
particulates from liquids or slurries (where seeding  is not required). When other non-
magnetic particles are present, the magnetic material should  constitute only  a small fraction
of the total solids; total solids, however, may be as  high as  10-15% by volume of the waste
stream. Economics are probably favorable only for large-volume streams. The time frame for
development is of the order of 5-10 years.

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                                  HYDROLYSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Hydrolysis is potentially applicable to a wide range of waste forms and compositions.
There are currently very few  actual waste treatment applications, but the process does
appear promising for detoxification and recovery of organics. Expanded R&D activity is
recommended.

II. PROCESS DESCRIPTION              .:

     Hydrolysis generally refers to double decomposition reactions  with water of the type:
XY + H2 O	>• HY + XOH. The reactions are usually carried out at elevated temperatures and
pressures, often with acid, alkali, or enzyme catalysts. Suitable feed streams include aqueous
or non-aqueous solutions, slurries, sludges, or tars.

III. APPLICATIONS TO DATE

     The oldest application of hydrolysis is in the production of soap from heated  fats in
the presence of caustic (known as saponification). Hydrolysis is also used commercially for
the manufacture of a  variety of organics (e.g., production of phenol from chlorobenzene;
production of ethylene oxide from ethylene glycol or ethylene chlorohydrin).

     Waste treatment applications are not widespread. However, in the petroleum industry,
the sludge from acid treatment of light  oils is often hydrolyzed to recover sulfuric acid for
reuse; the other  product,  a  tarry acid oil, may  be concentrated  and burned as fuel.
Hydrolysis has also been used  for  detoxification of waste streams  containing carbamates,
organophosphorus compounds,  and other pesticides.

     Hydrolytic  waste treatment processes that have shown promise in the laboratory
include acid  hydrolysis of waste paper to sugar; conversion of organic sludge to animal feed;
and decomposition of polyurethane foam to toluene diamine and a polyol.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy  requirements vary considerably with the application,  but are generally high.
Steam requirements for production of  fatty acids approximate   120Btu/lb of  product.
Production of TiO2 from Ti(SO4)2 requires about  1500  Btu steam/lb of TiO2 produced.

     The products of hydrolysis of a complex waste stream are not readily predictable and
may  be toxic.

     The capital investment and operating costs are highly dependent on the specific process
details. Capital  investment figures for different processes range from about $2500-20,000/
ton of material handled daily. Operating costs might range from 0.3-1.5^/lb.
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V. OUTLOOK FOR WASTES

     Although not in widespread use as a waste treatment process, hydrolysis presents no
fundamental problem. Handling  of strong acids and alkalies requires care, and performing
reactions at high temperatures and pressures necessitates close control and monitoring.
                                        i
     For hazardous wastes, hydrolysis can be adapted to handle liquids, gases, or solids. It
does not appear  promising for  inorganic materials, but is suitable for a wide range of
aliphatic and aromatic organics.
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                                 ION EXCHANGE

I.  CONCLUSIONS AND RECOMMENDATIONS

     Ion exchange is well suited for general and selective removal of heavy metals and toxic
anions from dilute aqueous waste streams. The  upper  concentration limit for efficient
operation  is about 4000 mg/1. Research on the use of polymer beads impregnated with
liquid ion exchange materials has some promise for extending the concentration limits.

II. PROCESS DESCRIPTION

     Ion exchange involves the interchange of ions between an aqueous solution and a solid
material (the  "ion exchanger")-  After removal  of the solution, the exchanger is then
exposed to a second aqueous  solution of different composition which removes the ions
picked up by the exchanger. The process is most frequently carried out by pumping the
solutions through one or more fixed beds of exchanger.

III. APPLICATIONS TO DATE

     Full-scale operations include cleanup of dilute solutions from electroplating and other
metal-finishing operations, recovery of effluents from  fertilizer manufacturing, and indus-
trial  deionization. Promising applications include removal of cyanides  from mixed streams
and use of newer exchangers for selective removal of heavy metals.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements are low, consisting primarily  of electricity for pumping solutions.

     The dilute purified product stream is dischargeable to sewers. The regenerant stream
requires further treatment for  recovery or disposal. Minor  amounts of exchange  materials
will require disposal occasionally.

     Capital costs are expected to be in the range of $200,000-$3 50,000, with a substantial
investment in resin. Operating costs might be in the vicinity of $2-8/1000 gal.

V. OUT LOOK FOR WASTES

     Ion exchange is a well developed process, which promises to be used more widely for
recovery of heavy metals, and removal of both heavy metals and cyanides.
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                             LIQUID ION EXCHANGE
                                        ;
I.  CONCLUSIONS AND RECOMMENDATIONS

     Liquid ion exchange (LIE) is a process with demonstrated potential for removal of
heavy metals and hazardous anions from aqueous waste streams. It covers a much wider
concentration range than conventional ion exchange. Development of new applications and
reagents for waste treatment may require special economic incentives, since historically such
research has been stimulated principally by high-volume hydrometallurgical applications.

II. PROCESS DESCRIPTION

     Liquid ion exchange  involves, first,  the  extraction of inorganic species (principally
ionic) from an aqueous stream into an immiscible organic stream containing special reagents
to facilitate the extraction, and then subsequent transfer of the species to a second aqueous
stream of different composition from the feed. Process equipment is that commonly used
for liquid-liquid extraction: mixer-settlers, differential columns, or centrifugal contactors.

III. APPLICATIONS TO DATE

     Full-scale commercial  operations  include  removal of molybdenum and  acids from
metal pickling  baths,  zinc  from textile production  effluents, and copper  from various
streams. Promising applications include  removal of cyanides and treatment  of hydroxide
slimes from electroplating.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     The LIE process has very low energy consumption, consisting principally of electricity
for pumping and mixing.
                                        /. ;
     The cleaned feed  stream will contain 10-50 mg/1 of the organic extraction solvent. The
regenerative solution into which hazardous components are stripped  from the extraction
solvent will require further treatment.

     Capital costs depend upon the application. Values in the literature range from $10,000
(almost certainly too low) to $600,000. Total costs for treating dilute streams are estimated
to be around  $4/1000 gal. For concentrated stream, costs are highly variable, ranging from
$0.20-$3.00/lb of metal removed.

V. OUTLOOK FOR WASTES

     This method is well-developed, and particularly applicable to recovery of high-value
metals from waste streams.
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                   LIQUID-LIQUID EXTRACTION OF ORGANICS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Liquid-liquid extraction should be considered for the recovery of organic solutes from
fairly concentrated aqueous and non-aqueous solutions.

II. PROCESS DESCRIPTION

     Liquid-liquid extraction is the separation  of the constituents of a liquid solution by
contact with another (immiscible) liquid. If .the substances comprising the original solution
distribute themselves differently between the two liquid phases, a certain degree of separa-
tion  will result. This may be enhanced by the use of multiple contacts. A total recovery
process based on  liquid-liquid extraction usually requires the use of other unit processes,
such as stripping or distillation for solvent and solute recovery.

III. APPLICATIONS TO DATE

     Current actual or proven areas of applicability include:

     1.   Extraction and recovery from aqueous solution of:

         •    phenol;
         •    acetic acid, and other aliphatic organic acids;
         »    salicylic and other hydroxy aromatic acids; and
         •    oils.

     2.   Extraction, (without recovery) of:

         •    phenol from foul waters near a refinery.

     3.   Extraction and recovery from organic solvents of:

         •    methylene chloride (from isopropyl alcohol);
         •    freons (from oils and acetone, or alcohols); and
         •    mixed chlorinated hydrocarbons (from acetone or alcohols).

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements are usually quite small for just the extraction  step. Where solute
and solvent recovery require  stripping  or distillation, steam requirements  will be significant.

     The only  major environmental  issues  relate  to (1) possible need  for  disposal  of
recovered solutes if such are not reusable, (2) the probable need for a polishing treatment  on

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the raffinate, following extraction from water, and (3) the possible need for disposal of
unwanted fractions following extraction of organic solutions.

     Costs cannot be  generalized  usefully. However, capital  investment  might be  in the
vicinity of $1 million. Total operating costs (without credit for resource recovery) might
range from well under $1/1000 gal to more than $5/1000 gal.

V. OUTLOOK FOR WASTES

     The process is most attractive for treatment of concentrated,  selected, and segregated
waste streams where material recovery is possible and desirable. Organic solutes, of almost
any  nature, may  be economically removed if concentrations are in the range of a few
hundred  ppm to a few percent from aqueous  waste streams. Organic solutions containing
water-soluble and  non-water-soluble components may be economically separated by extrac-
tion  with water.
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                            MICROWAVE DISCHARGE

I.  CONCLUSIONS AND RECOMMENDATIONS

     Microwave  discharge  treatment of hazardous wastes is currently  in the  research
stage. Early  results are very promising.


II. PROCESS DESCRIPTION

     High-frequency microwave power is used to establish a plasma or gaseous discharge in
which neutral molecules are partially decomposed into metastable, atomic, free radical and
ionic species. The decomposition products typically recombine to form a variety of stable
molecules, some of higher molecular weight and of higher toxicity than this feed. Plasmas
may  be initiated in  low-pressure gases of all kinds, and  solids and liquids exposed to the
reactive species in plasmas generally undergo chemical  change. Toxic vapors and liquids
introduced into an oxygen plasma undergo reactions similar to those of incineration, but at
much lower temperatures.

III. APPLICATIONS TO DATE

     Commercial microwave discharge instruments are used in analytical chemistry, particu-
larly  for plasma  or  low-temperature ashing: The only  large-scale  applications are for
photoresist removal and plasma etching in semiconductor device fabrication. Most research
has been concentrated on  polymer  film deposition and organic synthesis. Lockheed is
currently investigating the use of microwave plasmas, particularly oxygen plasmas for the
treatment of organic vapors and liquids characteristic of waste streams.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Line power requirements  for microwave discharge treatment are  estimated  as roughly
14 kWh/lb of waste treated.

     In an oxygen plasma, organic waste components are converted to products similar to
those of complete combustion.

     Capital  costs for a 100  Ib/hr facility might be in the neighborhood of $100,000.
Operating costs are estimated to be on the order of $1.00/lb.

V. OUTLOOK FOR WASTES

     The process should be considered for small quantities of highly toxic materials that
cannot be handled by any other means, or for recovery of high-value components.
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                                NEUTRALIZATION

I.  CONCLUSIONS AND RECOMMENDATIONS
                                        ' ' !-
     Neutralization (or more generally pH control) is a technically and economically proven
process, currently in full-scale use in many ^industries. It has wide applicability to waste
streams of diverse physical and chemical compositions, and would have to be available in
almost any waste treatment facility.

II. PROCESS DESCRIPTION

     Neutralization is a liquid-phase chemidal reaction between an acid and a base which
produces a neutral solution. It may be carried out in batch or continuous flow. It requires
reaction tanks, agitators, monitoring and control capability, pumps, and ancillary equipment
for handling solids and/or liquids, and  storage facilities. The treated  stream undergoes no
change in physical form,  other than  solids dissolution (or precipitation) or gas evolution.
The process can be used on aqueous and non-aqueous, liquids, slurries, and sludges.

III. APPLICATIONS TO DATE

     The process is in full-scale use throughout many industries, e.g., pulp and  paper,
petroleum refining, and inorganic chemicals. It is used to treat acid exhausts, pickle liquors,
plating wastes, and acid mine drainage. It can be used on almost any stream requiring pH
adjustment.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements  are  primarily for -electricity  used to run pumps and stirrers.
Treated streams may  contain  precipitated solids which require additional  handling. The
solids must be recovered or sent for disposal as a solid waste. There is the possibility of toxic
gas being evolved, particularly if sulfides or cyanides are present in the  waste stream. Capital
investment requirements are highly variable,  depending upon the size of the stream to be
treated. Operating costs range from $0.20/1000 gal to $4/1000 gal.

V. OUTLOOK FOR WASTES

     Neutralization is and will continue  to be a routine and  accepted part of industrial
processing waste management.
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                              OXIDATION; CHEMICAL

I.  CONCLUSIONS AND RECOMMENDATIONS

     Chemical oxidation and the technology for its large-scale application are well estab-
lished. Oxidation-reduction, or "Redox" reactions are those in which the oxidation state of
at least one reactant is raised while that of another is lowered. We recommend that chemical
oxidation be  considered for dilute aqueous streams containing hazardous substances or for
removing residual traces of contaminants after treatment. Chemical oxidation should be
considered as a first treatment  step when  trie waste contains cyanide, when it  contains
constituents not amenable to other treatment methods, or as a final step to remove traces
of contaminants after other treatment.

     A more exhaustive study should be made of the potential for treatment of waste
containing hazardous  materials.  Most of the literature deals only with very dilute waste
streams, or with the preparation of materials.from basic raw materials via chemical oxidative
techniques, and little has  been published relative to treatment of concentrated hazardous
wastes.

II. PROCESS

     The  first step  of the chemical oxidation process  is adjustment of the  pH of  the
solution. The oxidizing agent is added gradually and mixed thoroughly. The agent may be in
the form of  a gas  (e.g.,  chlorine), a liquid (e.g., hydrogen peroxide), or a  solid  (e.g.,
potassium  permanganate).  Because some  heat is  liberated, concentrated solutions may
require cooling, or may require careful measurement and handling to avoid violent reactions.

III. APPLICATIONS TO DATE

     Application to industrial wastes is well developed for cyanides and for phenols, organic
sulfur  compounds,  etc., in dilute  waste streams.  The  primary application has been in
converting and destroying cyanides from plating and metal finishing operations.

     The chlor-alkali industry uses chemical oxidative techniques to  remove mercury from
ores,  as  well as from  cell wastes.  Mercury removal rates of over 99% are  claimed  for
concentrated  ores, and  residual mercury  levels of less than 0.1 ppm for chlor-alkali sludge.

     The  technique is  also used to remove organic residues from  drinking water,  or to
remove  residual chlorine after chlorine  treatment.  Gases have been treated by scrubbing
with oxidizing solutions to destroy odorous substances. Chemical oxidation is also used for
odor destruction in the  manufacture of kraft paper and in the rendering industry.
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IV. ENERGY, ENVIRONMENT, ECONOMICS

     Total energy consumption is low; the only requirements are for pumping and mixing.

     A disadvantage of chemical oxidation for waste treatment is that it introduces new
metal ions  into  the  effluent  that  might require further treatment. The only waste that
appears troublesome is the sludge that can develop in the oxidation treatment of cyanides
when iron and some other ions are  present. A facility for chemical oxidation of 103 gpd of
highly concentrated cyanide waste from a plating operation, using batch alkaline chlorina-
tion would  require a capital investment  of $100,000. Fixed costs  would  be $18,300
annually and variable costs $36,700, giving a unit cost of $229.20/103 gal. For a less highly
concentrated waste (100 ppm copper cyanide and 100 ppm sodium cyanide), the operating
cost would be about  $170/103  gal. Costs coiild be lowered if the daily flow rate were to
increase and the treatment operation could be continuous rather than batch.

V.  OUTLOOK FOR WASTES

     In addition to the already-established applications for removal of hazardous substances,
chemical  oxidation may be used to remove chlorinated hydrocarbons  and pesticides from
dilute  streams. Laboratory and pilot studies  have demonstrated the potential for this
application.

     The extent to which the technique can be used to remove hazardous substances from
industrial sludges may  be limited because of inefficiency and incompleteness of the reaction.

     The  use of chemical oxidation for concentrated wastes should have careful evaluation
for reasons of economics, process safety, and the addition of chemicals that may add to the
pollutant load.
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                                   OZONATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Technology for large-scale ozone application is well developed. Feasibility has been
demonstrated  for treatment of cyanides and phenols, and laboratory  and pilot studies
indicate potential for chlorinated hydrocarbons, polynuclear aromatics, and pesticides.

     We  recommend that ozonation be considered  for treatment of aqueous or gaseous
waste streams  containing less than 1% oxidizable hazardous components and as a prelimi-
nary treatment for more concentrated wastes not  amenable to other techniques. We also
recommend ozonation as a final treatment process  where more complete removal of
oxidizable substances is required.         ':..

     A more exhaustive study should be made of the literature on the susceptibility of
various compounds to ozonation. Laboratory studies are needed to evaluate the effectiveness
of treatment of pollutants of current concern. Additional research and development aimed
at more efficient ozone generation and ozone/water mixing should be supported.

II. PROCESS

     Since ozone is a powerful oxidizing agent and an extremely reactive gas that cannot be
shipped or stored, it must be generated on site immediately prior to use. Ozone generated at
a concentration  of  <2% and a pressure of <15 psi from a stream  of  air or oxygen
previously dried to  a dewpoint of -50°C or lower is introduced into a contact chamber
designed  to ensure  good mixing  with  the  waste stream.  For  aqueous wastes, a venturi
injector, a porous diffuser, or an impeller is used to mix  ozone and  liquid at high velocity
for 10 minutes or more. Liquid depth is at least 15 feet, and two or  more reactors are
frequently employed. For gaseous waste streams, a porous diffuser is used if ozonized air is
generated at positive pressure; at atmospheric pressure, a wet scrubbing process is used, with
a fine mist of ozone-saturated water sprayed into a contact chamber. Contact times for
gaseous streams is 5-60 seconds.

III. APPLICATIONS TO DATE

     Ozone, besides being a powerful reducing agent, has antibacterial and antiviral proper-
ties.  This disinfecting  power has been responsible for most large-scale applications. The
process is widely used in Europe to purify and improve drinking water, and there have been
a number of installations in the  United States for  treatment of municipal sewage plant
effluents. It has  also been used to remove  sulfide and other odors from rendering plant
effluent;  fermentation  odors from a pharmaceutical plant; treatment  of liquid effluent
containing  cyanides, siillides,  sulfites and  other hazardous components after biological
treatment;  reduce cyanide levels  from  effluent  of a lire plant, a chemical plant, and an
                                       85

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electroplating facility. In combination with activated carbon adsorption, ozonation has been
used to remove color from waste dyeing water. Oxidation of phenols in coke oven wastes,
wood products waste and biologically treated refinery waste.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Ozonation can be expensive, but may  be economically competitive for treatment of
dilute  waste streams. Generation of ozone1 is the dominant cost component in terms of
capital and power. With air feed, energy requirements are from 7.2 to 9.0 kWh/lb of ozone
generated. Power requirements are half this figure if oxygen is used for feed. Any improve-
ment in ozone demand or efficiency would improve economics; the catalytic effect of UV
light can extend the effect of ozonation dramatically and can reduce ozone demand by a
factor of two. Labor and space requirements are low.

     Concentrations of ozone leaving the  cohtact chamber are carefully monitored; some-
times the  ozonized air  is cycled to provide pretreatment of incoming aqueous waste. The
waste stream effluent is also monitored,  and the dosage increased  if necessary. Gaseous
effluent is discharged directly to the atmosphere; aqueous effluent may be discharged to a
sewer or natural body of water where the oxygen-rich water is beneficial.

V. OUTLOOK FOR WASTES

     Complete oxidation to CO2 can sometimes be achieved; in  other  cases, oxidized
intermediates may be formed that resist further ozonation. Whether a  given  degree of
oxidation constitutes satisfactory treatment depends on the criteria for the particular waste
stream  or disposal site.  Slurries,  tars, sludges and solutions in oxidizable liquids are
generally not suitable for ozonation. Although ozone itself is a toxic substance, the risk of
exposure to toxic levels is small.
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                                   PHOTOLYSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Technology for large-scale application of photolysis to wastes is not highly developed.
Further laboratory studies of photolysis of selected candidate waste streams (for example,
pesticide contaminated solvents) should be conducted. Pure photolysis is not likely to be a
practical industrial  waste  treatment process', within the next 5-10 years, but UV-assisted
ozonation and chlorination are promising in the near term.

II. PROCESS DESCRIPTION              :

     In  photolysis,  chemical bonds are broken under the influence of UV or visible light.
Products of photodegradation vary according to the matrix in which the process occurs, but
the complete conversion  of an organic contaminant to CO2, H2 O, etc., is not probable.
Equipment required includes a source of UV/visible radiation, such as a mercury arc. Re-
actor geometry  and materials of construction must allow adequate penetration  of the light
into  the waste.

III. APPLICATIONS TO DATE

     Pure photolysis has been investigated only in laboratory-scale studies. Combined UV/
ozonolysis and  UV/chlorination have been used in pilot and full-scale applications in the
hazardous waste area.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Any photolysis process is relatively energy-intensive.  There are not sufficient data  to
allow estimation of either process economics or environmental issues. In general, the process
effluent is a stream with physical characteristics similar to those of the  input stream, but
with different chemical characteristics. Organic hazardous  components are not completely
degraded and the residues may still pose hazard.
                                         »
V. OUTLOOK  FOR WASTES

     Applications are probably highly specialized, detoxification of pesticide-contaminated
solvents is one possibility. However, pure photolysis requires research and testing at labora-
tory  and pilot-scale to demonstrate applicability to hazardous waste.
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                              REDUCTION, CHEMICAL

I.  CONCLUSIONS AND RECOMMENDATIONS

     Reduction reactions  are  among  the  most common chemical processes;  reduction-
oxidation or "Redox" reactions are those!in which the oxidation state of at least  one
substance is raised while  another is lowered/ The technology for large-scale reduction of
some industrial wastes, sometimes allowing recovery of metals, is well developed.  We believe
that the process could well be adapted to remove hazardous substances from dilute wastes,
to pretreat wastes that have constituents not  amenable to other methods, and  to remove
traces of contaminants.

II.  PROCESS
                                        if
     The  equipment for  reduction  processes  is simple:  only  storage,  metering, mixing,
pumping and instrumentation, with the major  cost for reducing chemicals. The  economics
vary with the substance being treated. Introduction of foreign ions into the stream is a  real
or potential disadvantage;  otherwise it is straightforward.

III. APPLICATIONS TO DATE

     The application to industrial wastes is already well established for dilute waste streams,
especially those containing chromium  (VI),". and other  hazardous substances, such as lead
and mercury. In addition to detoxifying hazardous substances, the process sometimes allows
recovery  of metals. The plating and tanning  industries use the process to reduce highly toxic
chromium (VI), to chromium  (III), which is  less hazardous and  can be precipitated for
removal.

     The process also finds application in the :chlor-alkali industry for removal of mercury
from  effluents. It appears to have potential for removing other hazardous substances, e.g.,
cadmium and antimony, in diluted streams.  ;:
                                        • t ;:
IV. ENERGY, ENVIRONMENT, ECONOMICS

     Total energy consumption is low; the only requirements are for pumping and mixing.

     A disadvantage of chemical reduction for waste treatment is that it may introduce new
ions into  the effluent that  might necessitate further treatment.  Air emissions are  not
significant. There may be problems with  land disposal or residues, especially  those  sus-
ceptible to acid leaking. A facility  for chemical reduction of  2,000 gpd of chromium (VI)
waste from a plating operating, using batch  sulfur dioxide treatment would require a capital
investment of  $230,000.  Variable operating  costs would be $51,400 and fixed costs
$41,600 annually. Unit costs would be $193.80/103 gal. Costs could be lowered if the daily
flow rate  were  to increase and the treatment  operation could be continuous rather than
batch.

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V. OUTLOOK FOR WASTES

     We believe there should be a more exhaustive  study of the potential for reduction
processes for concentrated hazardous wastes. .It should certainly be considered as a treat-
ment step whenever chromium VI is a constituent of the effluent. It may be a method for
treating wastes  that  have constituents  not amenable  to other treatment, and as a final
polishing step for removing traces of contaminants.
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                               REVERSE OSMOSIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     Reverse osmosis (RO) should be considered  for treatment of aqueous waste streams
containing organic and inorganic species in solution. Total dissolved solids in  the feed
stream may be as high as 34,000 ppm.

II. PROCESS DESCRIPTION

     The heart of the reverse osmosis processes a semipermeable membrane which is per-
meable to solvent, but impermeable to most dissolved species, both organic and inorganic.
Separation is brought about by means of an applied pressure gradient. To protect the mem-
branes for chemical attack and plugging, oxidants, iron and manganese salts, and oils and
greases are generally removed prior to application of RO.

III. APPLICATIONS TO DATE
                                        •' i
     There are about 300 full-scale plants worldwide using reverse osmosis for desalination
of sea or brackish water. Reverse osmosis has been used very successfully in the treatment of
electroplating rinse waters, not only to meet.effluent discharge standards, but also to re-
cover concentrated metal solutions for reuse. A limited number of other full-scale uses can
be found in the treatment of sulfite streams from the paper industry and in food processing.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Energy requirements are of the order of 10 kWh/1000 gal of product water.

     The concentrated  brine or solute  solution  presents a problem  for  disposal, if not
recoverable.

     Capital costs range from about $0.50-4/gpd of purified water output, depending on the
volume of waste to be treated. Total operating costs are in the range of $1-5/1000 gal.

V. OUTLOOK FOR WASTES

     Use of RO for industrial waste treatment is growing rapidly. The process is particularly
useful for concentrating waste streams containing dissolved  organics  or inorganics, to
facilitate recovery, or to reduce volume.
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                              STEAM DISTILLATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Steam distillation is  a  proven process for removing water-immiscible, volatile com-
pounds from process or waste streams. It can be applied to any stream that can be contacted
with steam or water without reaction or decomposition. It can be used with liquids, slurries,
sludges, and solids.

II. PROCESS

     Steam distillation takes advantage of the unique vapor pressure relationship of two
immiscible liquids. The additive vapor pressures allow distillation at lower temperatures. It is
usually conducted  as  a  batch operation:  the  still is charged, the charge is heated  to
temperature, and  the distillation conducted by bubbling steam through the liquid phase. In
semi-batch operation,  the charge containing a., high ratio of volatiles to non-volatiles is fed to
the still continuously for a given period while the volatile component is steam-distilled from
the mixture.

III. APPLICATIONS TO DATE
                                        : ;

     The widest application  is in  the  petroleum industry where steam and feedstock are
introduced into a multi-tray distillation column to produce gasoline, lube oil,  or naphtha.
Without the use of steam or steam and vacuum together, the high distillation temperature
would result  in decomposition. The process is also used for removing low boiling compo-
nents from a  mixture. In the soap industry, glycerine is recovered from spent  soap lye; in
the naval stores industry turpentine and gum rosin are recovered from pine gum; fatty acids
and  tall oil rosin are  obtained from  crude tall oil, a by-product of sulfate wood  pulp
production. A solvent extraction process removes organics from paper before the wood fiber
can be reused; through steam distillation the solvent is recovered. In the production of coke
from .coal, quantities of aromatic hydrocarbons are also produced. The wash oils from the
ovens are steam stripped to recover the aroma'tic hydrocarbons.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     The major energy requirement is  for steam. In one application, the steam requirement
would total 29,200 Ib per 3,000 gal of treated degreasing waste, or per 1,000 gal recovered
perchlorethylene. Power requirements would be 30 kWh per 3,000 gal waste.

     The wastewater from condensed  steam in the steam  distillation process  will contain
traces of volatile organics, and may have to be steam-stripped before disposal.

     The  fixed capital investment  (new  equipment) for a steam distillation  unit with a
capacity of 3,000 gal/week degreasing solvent would be about $130,000. Operating  costs
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would be $1,424. Credits for perchlorethylene at $2/gal and $0.05/gal for the oil/grease
mixture used for boiler fuel would more than offset treatment cost.

V. OUTLOOK FOR WASTES             ;  ,'

     Numerous industrial wastes are treated, by contract disposal  companies using steam
distillation to recover valuable components or reduce waste volumes. With the  increase in
value of hydrocarbon  solvents and  increasingly  strict regulations regarding landfill with
sludges containing these solvents, the use of steam distillation is expected to increase.
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                                STRIPPING, AIR

I.  CONCLUSIONS AND RECOMMENDATIONS
                                      '  •!
                                        '! •<
     Air  stripping  of ammonia from  biologically treated domestic wastewater is being
                                        1* »-
developed as a means of reducing nitrogen content before discharge. It is suitable only for
dilute solutions, since the emission level of ammonia from a concentrated  solution would be
too high. Furthermore, steam stripping would permit recovery of the ammonia from more
concentrated  solutions. Application  of air [stripping to other gaseous compounds would
depend on the environmental impact of the resulting emissions.

II. PROCESS
                                        ?• ;
     Holding  ponds, with or without surface agitation, and spray ponds  have been investi-
gated, but the packed tower appears to be'the most compact and efficient means of air
stripping. Removal efficiencies of over 90% have been obtained in pilot tests with wastewater
containing 60 ppm nitrogen. The wastewater .containing ammonia and a lime slurry (lime
added for phosphate removal) are fed to a  rapid mix tank, and thence to a settling basin,
where the calcium phosphate and calcium carbonate settle out. The clarified wastewater is
pumped to the top of two towers packed wi.tli a  series of horizontal pipes. Air is drawn up
through the  tower  against the falling wastewater by  large  fans.  After the  ammonia is
removed, the wastewater flows.into the recarbonation basin where compressed carbon
dioxide-rich gas from  the lime recalcining furnace is bubbled through to precipitate and
recover calcium carbonate, for calcination and recycle of lime to .the system.

III. APPLICATIONS TO DATE

     Full-scale packed towers have been used at two locations in California for treating
domestic wastewater.
                                        I

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Electric power requirements for treating "15  million gpd  are in the range from 1600 to
1800kWh/hr. The recalciner requires about 8 million  Btu (8000ft3) natural gas/ton of
feed, or 192 million Btu/day.

     When the  ammonia  concentration is .about 23 ppm  and the  air-to-water ratio is
500 ft3 /gal, the concentrated ammonia  in the saturated air leaving the tower is about
6 mg/m3, well below the odor threshold. Disposal of about 25 tons/day of sludge requires a
significant amount of land, but does not pose an environmental hazard.

     The capital investment would be about $7.8 million; fixed costs would be $1,420,000,
and variable operating costs would be $940,000/year.
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V. OUTLOOK FOR WASTES




    It is unlikely that many other applications of air stripping will be found.
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                                STRIPPING, STEAM
                                         t
I.  CONCLUSIONS AND RECOMMENDATIONS

     Steam stripping should  be considered whenever it is  desirable  to  remove volatile
components (e.g., organics, H2S, NH3) from aqueous waste streams.

II. PROCESS DESCRIPTION               ;

     Steam stripping may be considered a form of fractional  distillation. Live steam is
injected into the bottom of the  distillation column,  and carries dilute volatile components
with it. There are two aqueous output  streams, one  a concentrated solution of the volatile
organics and the other a dilute  stream containing only residual traces of volatile organics.

III. APPLICATIONS TO DATE             !.
                                        ' c-
     Steam stripping has  been used  for many years to recover  ammonia  from coke oven
gas. It is also used to recover sulfur as H2 S -from refinery raw waste. Other applications
include phenol  recovery, vinyl  chloride monomer  removal  from PVC suspension resins,
and removal of organics and sulfur from Kraft mill condensates. Research work is in pro-
gress  for steam stripping of light chlorinated hydrocarbons  from industrial waste water.
                                         t
IV. ENERGY, ENVIRONMENT, ECONOMICS

     The primary energy requirements are for steam. Between 0.5 and 2.5 pounds  of
steam are required per gallon of waste  water. The concentrated stream containing the bulk
of the volatile organic components is  processed for recovery or incinerated. If the incin-
erated stream contains sulfur, emission of SO2 must be considered.  The impact  of dis-
charging the treated dilute stream depends'din the nature and  residual concentration  of
the volatile organics of the waste water.
                                        ;' •
     Capital investment for a new 200-gpm, .single-stage (one column) "sour water" steam
stripper would be between $500,000 for mild steel and $850,000 for stainless-steel con-
struction. Treatment cost by this system would be about $10/1000 gal. A capital investment
closer  to $1,700,000, would  be required  for a two-stage, two-column, 200-gpm system
that would recover NH3 and H2 S for  credits.

V. OUTLOOK FOR WASTES

     The use of steam stripping  for industrial waste  treatment is growing. The most attrac-
tive  applications are those that permit byproduct recovery,  thus  to offset fairly high
operating costs. The process is  energy-intensive, with  steam costs amounting to close  to
80% of operating costs.
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                              ULTRAFILTRATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     Ultrafiltration is a membrane filtration; process that separates high molecular weight
solutes or colloids from their surrounding media. The process has been successfully applied
to both homogeneous solutions and to colloidal suspensions that are difficult to separate by
other techniques. Commercial use has been focused on aqueous solutions.
                '• • •  .                      J ;/
     Retained solute or particle size is one characteristic distinguishing ultrafiltration from
other filtration processes.  It filters out particles as small as 10~3 to 10~2 microns. Where
solutes are being separated  from solution, .the process can'serve as a concentration or
fractionation process for single-phase streams. .It competes with adsorptive and evaporative
processes, and has  the potential for broader applicability than  conventional filtration.
Usually the concentrate requires further processing if a pure solute is to be recovered.

II. PROCESS

     Ultrafiltration  membranes have  an extremely thin selective layer supported  on a
thicker spongy substructure, and  it is possible to tailor membranes with a wide  range of
selective  properties.  A solution  containing molecules too small  to be retained by the
membrane  and larger molecules that  will be  100% retained is  passed in a pressurized
stream. The larger molecules are collected from the upstream side and the smaller molecules
downstream.

III. APPLICATIONS TO DATE            ',

     Ultrafiltration is used for electrocoat paint rejuvenation and rinse water recovery,
protein  recovery  from cheese whey,  and  metal machining oil  emulsion treatment, with
capacity  to handle approximately 100 million; gallons per year for each application. There
are also smaller (on the order of 10 million gpy) plants for treatment of textile sizing waste
and wash water from electronics  component manufacturing, and for production of sterile
water for pharmaceutical manufacturing.

IV. ENERGY, ENVIRONMENT,  ECONOMICS

     Electrical energy for pumping to  maintain flow at operating pressures may be as much
as 30% of total direct operating costs.

     Ultrafiltration  residues  are  typically  a concentrate  of the undesirable or hazardous
components and usually require further processing unless valuable by-products can be re-
covered.
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     Capital and operating costs are dependent on the specific application and the capacity
of the system.  For large plants, capital costs may be $l-$4/gpd; operating  costs may be
$5-$ 10 per 103 gal. Coupled with the economies of reuse of salvaged materials, these costs
are often acceptable.

V. OUTLOOK  FOR WASTES

     There are a number of other applications where ultrafiltration may become commercial
within the next five years. These include: treatment of dye waste, pulp-mill waste, industrial
laundry waste,  and recovery of sugar from orange-juice pulp, protein  from soy  whey,
products from pharmaceutical and fermentation industries, and purification of power-plant
boiler feedwater and water for beverages.

     Application to hazardous wastes is already well advanced,  since many of the aqueous
solutions treated present severe sewage problems.
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                                 ZONE REFINING

I.  CONCLUSIONS AND RECOMMENDATIONS

     Zone refining is unlikely to be useful  for treatment of hazardous wastes.  Although
zone refining is an effective purification technique, it has inherent limitations which make
its use for broad treatment of large quantities of waste unlikely in the near future. Zone
refining is a  slow and costly operation, energy-intensive, and, at present, suitable for opera-
tion up to only about 10 kg batches.

II. PROCESS DESCRIPTION

     Zone refining is a fractional crystallization technique in which a rod of impure material
is purified by heating it so as to cause a molten zone to pass along its length. Basic equip-
ment consists of a material support or ingot holder to contain the sample; a feed or travel
mechanism;  and  a source of heat. The process may include a cooling step. It can be used on
solids, liquids, and mixtures such as  slurries. High viscosity and reactive materials are not
suitable.

III. APPLICATIONS TO DATE             '

     Zone refining is  used to  purify elements, metals, semiconductor materials, oxides,
salts, and organic materials in the laboratory. Its primary commercial use is in purification
of semiconductor materials.
                                                             *
     It is used on relatively pure materials.  It is  not now used for hazardous wastes,  and
there are no  known proposed applications for hazardous waste.

IV. ENERGY, ENVIRONMENT, ECONOMICS

     Zone refining is an energy-intensive process and therefore expensive to operate.

     Its pollution potential is low. Equipment costs are not presently available, most equip-
ment being engineered on a custom basis.

V. OtiTLOOK FOR WASTES

     Zone refining, at  present, is only useful  for processing small quantities (up to 10 kg) of
relatively pure material.  Processing rates are under  10 cm/hr. The process is not practical
for the complex mixtures that characterize most waste streams. Even for specialized applica-
tions, the process is only operationally feasible if the distribution coefficients permit segre-
gation of impurities.

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