SW-148C
                     Prepubliaation  issue for EPA  libraries
                    and State Solid  Waste Management Agencies
  I                     PHYSICAL, CHEMICAL, AND BIOLOGICAL

                   TREATMENT TECHNIQUES  FOR  INDUSTRIAL WASTES

                                Executive Summary
          This  is  the executive summary from the final report  (SW-148a)
                         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
A

*
                      U.S. ENVIRONMENTAL PROTECTION AGENCY

                                      1977

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                                                                                    I
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                   31
   4    BIOLOGICAL TREATMENT: ACTIVATED SLUDGE            41
   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             91
  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                                          Page
    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    OXIDATION, 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

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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 the 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 II plus description of current
uses and projected applications to industrial wastes
Same as Category 111

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 M 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.

     •   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 as 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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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.

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     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 biomass 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 6
                             BIOLOGICAL TREATMENT METHODS
     Process Category

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

 11.   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
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       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

-------
    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?

         —   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 more 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 8

            APPLICABILITY OF TREATMENT PROCESSES TO PHYSICAL FORM OF WASTE
1.  Phase Separation Processes
   Filtration
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   Distillation
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2.  Component Separation Processes
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   Carbon Adsorption
   Resin Adsorption
   Electrodialysis
   Air Stripping
   Steam Stripping
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   Ultrafiltration
   Solvent Extraction
   Reverse Osmosis
   Distillation
   Evaporation
3.  Chemical Transformation Processes
   Neutralization
   Precipitation
   Hydrolysis
   Oxidation
   Reduction
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   Calcination
   Chlorinolysis
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                                                   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 (RO2) 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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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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-------
                 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

-------
                              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 treat-
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

-------
                                ADSORPTION, RESIN

I. CONCLUSIONS AND RECOMMENDATIONS

     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

-------
               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 1% suspended solids have  flocculated,
biological growths continuously circulated and 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.
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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.
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                 BIOLOGICAL TREATMENT: AERATED LAGOONS

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.

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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 and 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

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     The presence of arsenate or mercury in anaerobic digesters 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.
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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

     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, Trichoderma viridi,
catalyzes the hydrolysis of cellulose to glucose.

III.  APPLICATIONS TO DATE

     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.
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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 SO 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 30^  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
biodcgradation.

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          BIOLOGICAL TREATMENT: WASTE STABILIZATION PONDS

I. CONCLUSIONS AND RECOMMENDATIONS

     Waste stabilization ponds utilize natural biodegradation 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.
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                                  CALCINATION

I.  CONCLUSIONS AND RECOMMENDATIONS

     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 l-3xl06 Btu/ton of solid
product; calcination of a sludge or slurry with  90% 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.
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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-
ploratory  work  could be useful on  catalytic  hydrogcnation and   low-temperature  air
oxidation.
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                                 CENTRIFUGATION

 I.  CONCLUSIONS AND RECOMMENDATIONS

     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.
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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.

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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 waste 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

     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 sodium 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
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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.

h. 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.

     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.
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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 vapcr 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
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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 $.50/103
gal are reported for salt reduction from 2000 ppm to 500 ppm in plants treating 106 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
might cost about $6.00/103 gal.

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.
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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.
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                                ELECTROPHORESIS

I.  CONCLUSIONS AND RECOMMENDATIONS

     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 1-20/u 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

     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

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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.
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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 wastewaier 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
fiom 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-
    rins of sludees nrinr to Hisnnsal.
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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              FLOCCULATION, 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

     Hnergy 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

     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-$800,000. 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-dntensive, 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.

     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 particle 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 + H2O	>• 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    120 Btu/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,QOO/
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.

     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-$350,000, with a substantial
investment in  resin. Operating costs might be in the vicinity of $2-8/1000 gal.

V.  OUTLOOK 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 chemical 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 the 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 could 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, sullldes,  sulfites and  other hazardous  components after biological
treatment;  reduce cyanide levels from effluent  of  a  tire  plant,  a chemical plant, and an
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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 ozone 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 contact 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, H2O,  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

     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.

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 S51,400 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 process is 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

     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 aromatic 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
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 with 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.

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

 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

     Steam stripping has  been used for many years to  recover ammonia from coke oven
 gas. It is also used to recover sulfur as H2S 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.

 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 on 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
X0% 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.

     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.
t
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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. OUTLOOK 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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