Environmental Aspects Of Chemical Use In Rubber Processing Operations Conference Proceedings


  EPA-560/1-7 5-002
5
         ENVIRONMENTAL ASPECTS
              OF CHEMICAL USE
                       IN
            RUBBER PROCESSING
                 OPERATIONS
          (MARCH 12-14, 1975, AKRON, OHIO)
  CONFERENCE PROCEEDINGS
     I
  OFFICE OF TOXIC SUBSTANCES
  ENVIRONMENTAL PROTECTION AGENCY
  WASHINGTON, D. C. 20460
  JULY 1975

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This report has been reviewed by the Environmental Protection Agency
and  approved for publication.  Approval  does  not signify that the
contents  necessarily reflect the views and policies of the Agency, nor
does  mention of  trade  names  or commercial  products  constitute
endorsement or recommendation for use.

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                           FOREWORD

The  proceedings  for the  conference  on  "Environmental Aspects  of
Chemical  Use in  Rubber  Processing Operations,"  is the first of three
reports each  on a different conference, to be submitted under Contract
No. 68-01-2928 to the Office of Toxic Substances for the Environmental
Protection Agency. The  conference was held at th" "  '-'ersity of Akron,
Akron, Ohio, on 12-14 March 1975.

The  objective  of this  conference  was  to cover  and  discuss current
chemical  usages, functions of chemicals  in the  operations, byproducts
likely to be  introduced, known health or environmental effects from
chemicals  used,  and measures  used or available for  use  to control
environmental contamination.  More  specifically, papers were presented
and  discussions  held that covered  industrial emissions  and effluent
surveys,  chemicals  and  their  effects,  reclamation  and  disposal  and
academic programs.

Dr.  Farley   Fisher,  Chief,  Early Warning Branch,  Office  of Toxic
Substances, Environmental Protection Agency, Washington, D.C., was the
Project Officer and General Chairman  of the  conference.

Mr. Franklin A. Ayer, Environmental Technology Department, Center for
Technology Applications,  Research Triangle Institute,  Research Triangle
Park,  North Carolina, was the Conference Coordinator and Compiler of
the proceedings.
                               in

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                                       Table of Contents

                                      (* indicates speaker)

                                                                                         Page

12 March 1975

Opening Session  	1

  Welcome and Introductory Remarks  	3
     Farley Fisher, Ph.D., General Chairman

  Keynote Address:
     Current Trends in the Control of Chemicals  	5
     Glenn E. Schweitzer

Session I:  INDUSTRIAL EMISSIONS AND EFFLUENT SURVEYS	15
     Robert C. Niles, Session Chairman

  Odor Sources in Rubber Processes and Their Control	17
     Robert E. Kenson, Ph.D., *
     Peter W.  Kalika, and
     Samuel Cha

  Liquid Effluents - Emission Points  From Rubber Manufacturing Processes	37
     David C. Day, Ph.D.

  Secondary Treatment of Wastewater From Synthetic Rubber Production   	60
     Frederick G. Troppe
Session II: CHEMICALS AND THEIR EFFECTS	87
    William E. McCormick, Session Chairman

  Toxicology of Acrylonitrile	89
    C. Boyd Shaffer, Ph.D.

  Alteration Products of SubstitutedjJ-Phenylenediamines	99
    Henry C. Hollifield, Ph.D.,* and
    Pasquale Lombardo

  Halogenated  Hydrocarbons in Rubber Processing	108
    Walter D. Harris, Ph.D.

  Panel:  CARBON BLACK

    Health Studies Relating to Carbon Black	118
       Carl  A. Nau, M.D.

    Carbon Black and Ecology  	130
       Harry J. Collyer

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                                   Table of Contents (con.)

                                                                                       Page

    Carbon Black Adsorbates: A New Carcinogen and Oxygenated Polycyclics	137
      Avram Gold, Ph.D.
13 March 1975

Session II:  CHEMICALS AND THEIR EFFECTS (con.)
    William E. McCormick, Session Chairman

  Elastomers in the Health Industries	167
    Samuel Koorajian, Ph.D.

  The Identification of Effluents From Rubber Vulcanization  	185
    Stephen M. Rappaport, Ph.D.

  Panel: ENVIRONMENTAL DEBRIS FROM TIRES

    Airborne Particulate Debris From Rubber Tires  	217
       William R. Pierson, Ph.D.,* and
       Wanda W. Brachaczek

    Rubber Dust From the Normal Wear of Tires	274
       Mark  L. Dannis
Session III:  RECLAMATION AND DISPOSAL	313
    J. R. Laman, Session Chairman

  Panel:  RECLAIMING AND RECYCLING RUBBER

    Environmental Aspects of Reclaiming and Recycling Rubber   	315
       Bobby D. LaGrone* and
       Edward A. Gallert

    Environmental Aspects of Rubber Reclaiming and Recycling (Manufacturing)	349
       Robert C.  Reinhardt

  Panel:  TIRES USED AS A FUEL

    Shredded Tires as an Auxiliary Fuel  	361
       Robert H. Taggart, Jr.

    The Tire-Fired Boiler	371
       William L. Cox
       (Delivered by Joe M. Smerglia*)

  Scrap Tires and Fishery Resources   	381
    Richard B. Stone
                                                VI

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                                    Table of Contents  (con.)

                                                                                         Page
14 March 1975
Session IV: ACADEMIC PROGRAMS   	389
     Louis S. Beliczky, Session Chairman

   Rationale, Scope, and Sponsorship of Academic Programs  	391
     Louis S. Beliczky

   University of North Carolina Occupational Health Studies Program	396
     Robert L. Harris, Jr., Ph.D.

   The Rubber Workers Study at the Harvard School of Public Health	413
     William A. Burgess, *
     John M. Peters, and
     Richard R. Monson

Session V:  CONFERENCE SUMMATION   	427
     Farley Fisher, Ph.D., General Chairman

   Panel:  SESSION CHAIRMEN COMMENTS   	429
Submitted Papers-Not Presented at Conference	435

  Toxicology and Physiological Effects of Phillips Oil Furnace Carbon Blacks  	437
     Lucian E. Renes

  An Economic Evaluation of the Use of Cryogenics in Rubber Tire Reclaiming	442
     S. L. Fredericks
                                              VII

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12  March  1975
                             Opening Session

                           Farley  Fisher, Ph.D.*
                             General Chairman
   *Chief, Early Warning Branch,  Office  of Toxic Substances, Environmental Protection
Agency, Washington, D.C.

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                 WELCOME AND INTRODUCTORY REMARKS
                       Farley Fisher, Ph.D.
                         General  Chairman
Icome to this conference on environmental  aspects of chemical  use in
 processing operations.   This is the first conference of this  type
red by the Office of Toxic Substances, and we hope it is the proto-
or conferences on a number of other industrial operations as well.
r object here is to discuss the use of chemicals in rubber process-
o analyze where these materials may have an effect on the environment,
 because of the substances used in the process or because of the
of products produced therein.  We are definitely doing this with an
de of exploration and debate, and we wish  for the conference to be
.  In no sense are we trying to restrain people from expressing
views.  We have allowed for a large number of question and answer
s, and I hope that you will avail yourselves of the opportunity to
estions and make comments.
r keynote speaker for this meeting is Mr.  Glenn Schweitzer, who
en Director of the Offfee of Toxic Substances for about 2 years
During that period of time, Mr. Schweitzer has been actively
ed in the Toxic Substance Program at EPA.

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               CURRENT TRENDS IN THE CONTROL OF CHEMICALS
                          Glenn E. Schweitzer*

The Rapid Growth of Chemical Problems
     During the last several years, the number and frequency of harmful
incidents involving toxic chemicals have increased dramatically.  Hardly
a week goes by without a new chemical emerging as an immediate health
or environmental problem, and the public outcry over carcinogenesis and
other chronic effects of exposure to chemicals seems to have literally
exploded.
     All levels of government are taking steps in response to the demands
for action to clarify and reduce the risks attendant to chemical exposure.
No longer are pollution problems viewed simply in terms of esthetics,
inconveniences, or ecological degradation; they are now tied more closely
than ever before to very personal human health concerns.  No longer are
the long drawn-out timetables acceptable for corrective steps with regard
to toxic chemicals.  No longer will the public accept the philosophy
that chemicals must be assumed safe until  proven hazardous.  No longer
are latent problems, such, as the mutagenic effects of chemicals that
may appear only in future generations, to be ignored.  No longer are
chemicals the unique concern of the manufacturers, the distributors,
and their employees, for the Chemical Age of the Seventies has engulfed
our entire society.
     I need not review for this audience the unsettling chain of events
triggered by the linkages established last year between cancer of the
liver and exposure to vinyl  chloride.  Many of the companies represented
here have been deeply involved from the outset of this very tragic develop-
ment, a development rooted in the environmental complacency of the industry
during the forties, the fifties, and the sixties.  We have all become
painfully aware of the difficulties in assessing the risks associated
with very low levels of exposure to this chemical and in taking corrective

     *Director> Office of Toxic Substances, Environmental Protection
Agency, 401 "M" Street, SW,  Washington, D.C.  20460

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actions to reduce these risks.   I  am sure that all  agree  that we can
and we must do better in the future in preventing these types of tragedies—
and particularly in identifying and assessing problems  before the fact
rather than after the damage is done.
     Already tens of thousands of chemicals are'in commerce, and the
number is increasing every year.  Little attention has  been given to
the environmental properties of many of these chemicals.   Constantly
evolving research and analytical techniques are revealing that the potential
effects of many others are much more extensive than previously suspected.
In short, during the years ahead all of us will be exposed to many more
chemicals in many more situations, and the list of chemicals known or
believed to pose a threat to man or the environment will  be greatly expanded.
     Our market forces are not designed to insure environmental equity,
and the risks and benefits associated with chemicals are not evenly distrib-
uted throughout our society.  The archaic concept of voluntary exposure
to chemicals—that we have a choice as to whether we want to come into
contact with chemicals--has been replaced with the hard reality that
in fact the individual citizen has little control over the chemicals
to which he is exposed.  Thus, governmental involvement in the chemical
arena will undoubtedly increase to keep pace with the growing chemical
burden in the environment.

The Development of^the Legislative Basis
for Controlling Toxic Chemicals
      For many years the Federal Government has been deeply involved in
chemical regulation through the activities of  the Food & Drug Administration;
more  recently it has become involved  in controlling pesticide use.  The
Clean Air Act and  the Federal Water  Pollution  Control Act have special
provisions directed to toxic and hazardous chemicals in addition  to their
broader provisions, which  also  encompass  chemical pollutants.   Indeed,
these  activities have to a  large extent established the framework for
the current spread of programs  throughout the  industry directed  to  product
safety and environmental control.
      During the  past several years,  the Department of Transportation,

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the Occupational  Safety and Health Administration (OSHA)  of the Department
of Labor, and the Consumer Product Safety Commission have 'significantly
expanded their efforts directed to toxic chemicals.   Of particular interest
to EPA and OSHA is the close interrelationship between concerns over
chemicals in the workplace and the possible discharges of these same
chemicals directly or indirectly into neighborhoods  near industrial
facilities as the result of air emissions or liquid  effluents.   In many
cases a large share of these nearby residents are the workers who may
be exposed to the same chemicals on and off the work premises.   Also3
we are concerned that in dealing with persistent chemicals, the longstanding
approach of better ventilation does not appear to be an acceptable solution
to meeting workplace standards.
     In December the Safe Drinking Water Act was somewhat unexpectedly
enacted.  The rapid congressional action on this legislation was prompted
by reports of trace amounts of organic chemicals—including several
possible carcinogens—found in several drinking water supplies, and particu-
larly in New Orleans.  This legislation, which calls for establishment
and enforcement of maximum contaminant levels in nationwide drinking
water supplies, has far-reaching implications for industry.  It seems
unlikely that municipalities will invest large sums  of money in removing
chemical contaminants from their water supplies without first attempting
to identify and control the sources of these contaminants.   In  many cases
the sources of concern will undoubtedly be industrial dischargers.
     The proposed Toxic Substances Control Act offers an unusual opportunity
to improve the soundness and the fairness of regulatory decisions concerning
toxic chemicals.   The heart of this proposed legislation is the acquisition
of more authoritative information concerning both the risks and the benefits
associated with chemical activities^  Special emphasis is placed on better
test information that is predictive of the behavior  of chemicals in the
environment.  A second aspect of this proposed legislation  is provision
for controlling serious toxic chemical problems that cannot be  adequately
addressed under other existing authorities.
     An improved information base is critical to better decisions concerning
Governmental intervention in chemical activities under a variety of regula-
tory authorities.  At the present time, decisions are being made on the
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basis of very sparse data.  Even in the absence of such information,
decisions will continue to be made, for action in this field cannot be
delayed.  In this regard, the lack of hard data concerning chemical behavior
should not be considered a license for continued production and use of
the chemicals any more than we can assume that activities should cease
until they are proven to be absolutely safe.

Intercepting the Problems at the Outset
     A main feature of the Toxic Substances Control Act is the emphasis
on identifying problems early in the commercial lifetime of chemicals —
before there has been irreversible environmental  damage and before major
economic investments are in place.  At present we find ourselves constantly
reacting to problem chemicals that are already widely dispersed throughout
our economy--chemicals which have already caused environmental problems
and which represent substantial  investments for suppliers, manufacturers,
and distributors.  Corrective measures invariably mean substantial economic
dislocations.
     With 500 to 700 new chemicals being introduced into commerce every
year, it is only sensible to make the extra effort to insure that these
new products are not going to cause problems later in their lifetime.
The extent of the research and testing needed to reach a judgment as
to potential environmental problems will vary among chemicals and among
uses of the chemicals.   However, the ground rules for early assessment
of chemicals need sharper clarification and greater acceptance by all
concerned.   In my view, the recent report of the National Academy of
Sciences Principles for Evaluating Chemicals rn_ tjre Env'ironment has
been a major step forward in this regard.   Further development of the
concepts set forth in this report, and particularly relating these concepts
to practical problems,  needs priority attention.
     Of course,  any governmental intervention during the premarket phase
must be sensitive to the financial realities of R&D activities.   Particu-
larly important is the  need to avoid additional delays due to uncertainty
as to governmental actions.  Also, the cumulative effect of actions
directed to Individual  chemicals can dampen the overall  climate for research.

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Finally, protection of the confidentiality of activities  directed to
new chemicals is of critical  importance.
     Unfortunately, this approach of early identification and prevention
of environmental problems and economic dislocations  will  not help in
addressing chemicals currently in large-scale production.  It is  indeed
unfortunate that this "pay now and save later" philosophy was not adopted
many years ago.  As problems  continue to  arise with  high-volume chemicals,
the short-term economic adjustments will  undoubtedly be severe.

Cost/Risk/Benefit Considerations
     Recently the government  has significantly increased its efforts
1;o not only assess but also to try to balance the costs,  the risks,  and
the benefits involved in regulating toxic chemicals  in the environment.
To the extent possible, regulatory activities should be judged on the
basis of their total impact on society—impact on the standard of living,
effective resource utilization, and preservation of  social as well  as
environmental values.
     This change in direction in approaching regulatory decisions has
in large measure resulted from a reorientation in the nature of some
of the legislative authorities under which EPA operates.   For example,
the'new Safe Drinking Water Act and the proposed Toxic Substances Control
Act are very explicit in their requirements to take  into account  economic
as well as health and environmental considerations.   On the other hand,
certain provisions of the Clean Air Act and Federal  Water Pollution  Control
Act are far from clear as to  the weight,  if any, to  be given to economic
considerations.  In a related development, recent court action concerning
the feasibility of the workplace standard for asbestos has had a  considerable
impact on the approach of OSHA.
     Despite growing sophistication in the approach  to controlling  toxic
substances, rigorous cost/risk/benefit analyses will  seldom be possible;
for adequate time, data, or resources will usually not be available  to
satisfy a purist.  However, we can certainly do better than we have  in
the past.
     Many of us have had direct experience in attempting  to draw  conclusions
from biological data that are invariably  "soft."  At the  same time,

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pragmatic economists tell  us  that their'data on benefits  may be even
softer—and probably characterized by uncertainty,  incompleteness,  and
perishability.    They are  particularly reluctant to provide estimates  of
the societal benefits to be derived from the use of chemicals that
contribute to improved health and living conditions, to greater personal
conveniences, to new recreational and esthetic opportunities, and
to maintenance of national defense.  Often, they are even less willing
to speculate as to how the marketplace will react if a specific chemical
is removed or if its price is increased as the result of environmeatal
controls.  In shorts the economists can provide a shopping list of
some of the factors to be  considered in -regulatory decisionmaking,
but they provide relatively little guidance as to how these economic
factors are to be weighted or integrated or how they are to be meshed
with other considerations.
     Several points related to costs seem to be clear, however.  If
there are increased costs  involved in environmental controls these
costs will be eventually passed on to the consumer.  Secondly, there
will probably be local impacts attendant to specific types of regulatory
activities, and particularly to limitations on the manufacture or use
of chemicals.  These local impacts can include business setbacks, employment
dislocations9 and even depressed real estate values.  Finally, the
market is in general sufficiently flexible and our innovative capacity
sufficently high to fill promptly the vacuum caused by the loss of
a single product witii alternative products or approaches to providing
a similar service.
     In view of the critical importance of cost/risk/benefit assessments
to responsible decisionmaking, we have recently launched several major
efforts to refine the methodologies that can illuminate in advance
the implications of regulatory decisions.  It is particularly important
that value judgments not be disguised in manipulating the data base
and that the bases  for decisions be structured in such a way that the
public can  understand the rationale that is used.

The Special  Responsibilities of  Industry
     In  recent years, many segments of industry have made very significant

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investments to control  the discharge of effluents  and emissions  into
the environment.  These steps have been taken in large measure in response
to governmental requirements at the Federal, State, and local  levels.
There seems to be little doubt that such actions have had a dramatic
effect in slowing the rate of degradation of our environment.   However,
all will agree that we still have a long way to go in cleaning up our
air and water and in preserving our landscape.
     Similarly, industry has over the years expanded its efforts to insure
the safety of its chemical products--safety as viewed from the perspective
of the worker, of the housewife, and of the general population.   Such
efforts have been spurred to a great extent by governmental regulations,
in some cases by the latent threat of lawsuits, and at times simply by
good business practices.  For many years, direct acute effects of chemicals
have, of course, been of major concern; and more recently, complementary
efforts have been directed to the more long-term and subtle health and
ecological effects.
     In some cases industry has gone far beyond the requirements laid
down by government for pollution control levels to be achieved and for
safety requirements.  For example, one major chemical company has adopted
the near-term goal that all new plants be designed to achieve zero discharge
with regard to process liquid waste effluents.  Some companies have signifi-
cantly expanded their staffs of toxicologists to address health problems
beyond those of immediate interest in governmental regulations.   Other
companies are conducting ecological effects tests  on chemicals which
by regulation are only required to be tested for their health effects.
However, our general impression is that most companies are not moving
much faster on the environmental front than the rate at which they are
required by legally enforceable regulations.
     Industry has a special responsibility to know what chemicals are
released during its manufacturing activities and during the use of its
products.  Further, industry has a responsibility to know the levels
of human and environmental exposure to chemicals resulting from such
releases.  Industry has a responsibility to know the likely hazards,
if any, associated with such exposures and to insure that the public
is aware of these hazards.  Finally, industry has  the responsibility
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to take all possible steps to minimize these hazards.
     These are societal responsibilities that transcend legal  obligations
imposed by Federal, State, or local  regulations.   In the years ahead,
these responsibilities must be given equal  weight with product performance
in judging a company's contribution  to society.
     To accept these types of responsibilities implies new dimensions
in corporate activities, particularly with  regard to physical  monitoring
and to studies of health and environmental  effects of chemicals.   However,
I am optimistic that the industrial  leadership of this country will  respond
to the challenge—that this leadership will show  restraint in  foregoing
attractive commercial activities when necessary  in the face of environmental
uncertainties, that it will expand its search for less hazardous  products,
and that it will reward its management for  contributions to the health
of the Nation and to the conservation of ecological  resources  with as
much enthusiasm as it rewards employees for increasing sales.

A New Departure Towards Common Understanding
     This Conference signals a new departure in  our efforts to better
understand the character, scope, and implications of problems  associated
with chemical activities.  As additional activities  in this field are
contemplated by government, industry, labor, and  other interested groups,
it. seems imperative that we have an  authoritative examination  of where
we are today—the effect and implications of environmental actions already
instituted by government and industry and their  future plans and programs.
Hopefully, with a common base of understanding,  deliberations  within govern-
ment, industry, and labor will be more rational,  better balanced, and  more
objective.  In the absence of this common point  of departure,  there will
only be a spiralling of confusion, suspicion, and acrimony on  the part
of all concerned.
     This session, which draws on the expertise  and insights of repre-
sentatives of many of the concerned  organizations, is  designed to help
establish the baseline as to the current situation.   Hopefully, the formal
program represents but a small portion of the exchanges that will take place
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during the next 2-1/2 days.  We are very encouraged by the large industrial
participation in this meeting.  Of particular interest to us are the
steps being taken by industry.  For example, we know that massive R&D
efforts are underway to correct the problems associated with PVC activities.
To what extent are similar efforts being extended to the rubber processing
activities of these same firms that have been so involved with PVC during
the past year?
     The industry's concern oyer chloroprene, styrene, and acrylonitrile,
for example, have been well publicized.  Similarly, government's concerns
over gross pollution effects (e.g., BOD, COD, TSS, criteria air pollutants)
are being reflected in water effluent permits and in air emission controls.
While we should understand these actions, which are important not only
in themselves but also as either successful or unsuccessful case histories,
probably of even more importance at this Conference is to look ahead
into future areas of possible concern—for we all share an overriding
interest in substituting preventive for corrective actions.
     I am pleased to note that the formal program calls for an examination
of progress in pollution control, a review of the characteristics of
specific chemicals, a discussion of innovative uses of waste products,
and an assessment of the role of epidemiological studies.  All of these
topics are central to current efforts in controlling toxic chemicals.
It seems clear that in the future:
     •Pollution control  requirements will give much greater emphasis to
      limiting discharges of selected chemicals;
     •The environmental  behavior of many more chemicals will be examined
      in detail;
     •Productive uses of waste products will  become more and more of a
      reality; and
     •Epidemiological studies to correlate exposure to chemicals with human
      health effects will expand considerably.
     We give high importance to this Conference—which is the first of
several  such meetings directed to various aspects of chemical  usage.
This  effort is enthusiastically supported by  the Administrator of EPA
and by the Chairman of the Council  on Environmental  Quality.   We are
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hopeful  that it will  make  a major contribution to wiser decisions by
government and by industry—decisions that can have a significant impact
on the price we pay for the fruits of this Chemical Age.
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12 March 1975
                            Session I:

          INDUSTRIAL EMSSSSOWS AND EFFLUENT SURVEYS

                          Robert C. Miles*
                         Session Chairman
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           ODOR SOURCES IN RUBBER PROCESSES, AND THEIR CONTROL
           Robert E. Kenson, Peter W. Kalika, and Samuel Cha*
Abstract
     The processing of rubber employs many chemicals which are potential
sources of odor emissions.  Solvents, adhesives, antioxidants, and other
chemical additives required to manufacture the final rubber products may
be odorous in themselves.  Additionally, their decomposition products
from the rubber processing may be odorous.  It is imperative that -the
difference between potential and actual odor sources in rubber processing
be determined.  Control technology that abates 90 percent of the air
pollution emissions from each process step can be very costly, and yet it
may have little or no impact on local community rubber processing odor
levels.
     Identification and quantification  (by dilution to threshold tech-
niques) of odor emission sources in rubber processing and the use of an
odor diffusion model can predict which of these sources have significant
impact on detectable odors beyond the plant boundaries under the pre-
vailing meteorological conditions. +.The model, after adjustment so that
the predicted and actual community odor surveys are in agreement, can be'
used to determine the extent of control for each odor source required to
make rubber processing odors undetectable in the community.
     These techniques can thereby be used to develop a cost-effective
odor control system for rubber processing operations.   The extent of con-
trol required and the nature of the odorous emissions (chemical identity)
helps to define the most desirable control technique.

1.0  INTRODUCTION
     This paper deals with the subject of odor sources in rubber processing
and also describes a basic methodology that can be applied successfully
to the definition and solution of odor problems in almost any processing
     *Robert E. Kenson and Samuel Cha, Research Scientists; Peter W.
Kalika, Senior Project Engineer; The Research Corporation of New England,
Wethersfield, Connecticut  06109.
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industry.  .The paper will briefly outline the methodology, and as an
example of its application, we will discuss the odor problems at a tire
manufacturing plant.
     The processing of rubber employs many chemicals which are potential
sources of odor emissions.  Solvents, adhesives, antioxidants, and other
chemical additives required to manufacture the final rubber products may
be odorous in themselves, and their decomposition products from the
rubber processing may be odorous.  Control technology which abates 90
percent of the air pollution emissions from each process step can be very
costly, and yet it may have little or no impact on community odor levels
from rubber processing.  Thus, it is imperative that the difference
between potential and actual odor sources in rubber processing be
determined.

2.0  ODOR IDENTIFICATION
     Odor pollution problems do not generally have a counterpart in other
                                                                        *
forms of pollution whose manifestations are clearly measurable by physical
or chemical means.  For example, concentration of particulates in the
ambient air is measurable directly as a unit of weight per cubic meter of
    r-	
air.yjkior pollution involves the response of the human olfactory system
to chemical stimuli and the degree of the pollution is related to many
subjective factors, including psychological, emotional, and socioeconomic
(ref. 1).  Thus, if an odorant is detectable in minute concentrations and
is offensive, an odor pollution problem certainly exists.  On the other
hand, large concentrations of certain materials may not be detectable,
or if they are, they may have a relatively pleasant odor, and not consti-
tute an odor problem.  Therefore, because odors are effects, each odor
problem is unique, j If plant management attempts to apply a successful
solution for one odor problem to what appears to be a similar problem,
merely by scaling up or down as required to fit the design to the new
source, the intended solution may not solve the problem at all or may cost
much more than it should.
     While each odor problem is unique, a consistent approach can be used
for a solution.  The key to effective odor control  is always proper defi-
nition of the problem.

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2.1   Methodology
     Most current odor regulations are of the nuisance type which ban the
release of objectionable odors but which seldom define how objectiona-
bility is to be determined (ref. 2).  Therefore,- to solve the odor
problem, it is usually necessary to achieve essentially zero detectable
odor from plant emission sources in the community beyond the plant
boundaries.  The following steps are designed to achieve this objective:
     (a)  Conduct an odor survey in the community.
          This involves the recognition of odor quality (or characteristic
     smell) and odor level under different meteorological  conditions.
     This is accomplished by trained observers operating beyond the plant
     boundaries.
     (b)  Collect odor samples.
          Odor level and standard flow rate measurements are made at each
     potentially odorous plant emission source.  This is done by trained
     observers within the plant.
     (c)  Evaluate the effects on community odor levels of specific
     individual potential odor sources.
          This aspect of the program is best done by means of simulation
     modeling.
     These problem definition steps would identify the sources that need
to be controlled and what degree of control is needed to eliminate the
detectable odors in the community.

3.0  ODOR QUANTIFICATION
     An important part of the solution of an odor problem is the quanti-
fication of the odor levels.  Since odor quantification must always
involve the human nose, there are many factors which will  affect the
results of such quantification.  These factors have been grouped into the
following two categories:
     (a)  Sampling - Factors such as sampling container materials, pre-
     conditioning of the container surfaces, storage time of the sample,
     and condensation of moist emissions are the major parameters that
     have significant effects on the odor sample collection.  Details of
                                      19

-------
     these effects have been studied by TRC under a Federal Environmental
     Protection Agency contract and results of this study have been
     reported (ref. 3).
     (b)  Dilution-to-threshold measurement techniques—There are many
     such techniques used, the most widely known (and unfortunately the
     least reliable) being the ASTM D 1391-57 syringe technique (ref. 4).
     Recently, TRC was asked by the Division of Air Pollution Control of
     the State of Illinois Environmental Protection Agency to evaluate
     the ASTM D 1391-57 technique along with three other dynamic tech-
     niques (IITRI olfactometer, Hemeon odor meter, and Misco olfacto-
     meter).  Other types of devices have recently been reported in the
     literature (ref. 5).
     Whichever dilution technique is used, the measurement involves making
successive dilutions of an odorous sample with odor-.free air, and pre-
senting the diluted sample to selected odor panelists until the panelists
report a detectable odor (ref. 6).  The dilutions should be presented in
an ascending order, i.e., the most dilute first.  Figure 1 shows a diagram
of the TRC odor laboratory system.  Panel size and panel selection and
training are additional parameters which will affect the odor measurement.

3.1  Odor Correlation
     Once the potential odor source emissions and the community odor
levels have been quantified, they must be correlated.  This means that we
must assure that the odor levels and types found in the community and
those determined for the suspected sources can be related.  This is
generally done by modeling, either by computer simulation or by wind
tunnel  modeling techniques.  If we cannot relate the sources emissions to
the community odors, this could mean that the odor source system is more
complex than originally anticipated, or that a significant contribution to
the community odor problem has been neglected, or incorrectly represented
in the model.  For example, building downwash effects could convert a
stack emission source into a ground level source.
     Figure 2 illustrates the downwash effects and how the most effective
stack height was determined by physical modeling (by means of smoke) of a
potential odor source.

                                      20

-------
                          Firs^DMution Stage	      Second Dilution Stage
                         Sx bleed off      Sample inlet      Bleed-off  Exhaust
          Figure 1.  Schematic of TRC dynamic dilution  odor
                            measurement system.
Centerline travel path of material
from roof top release
Centerline travel path of material
from intermediate height release
Centerline travel path of material
from the highest release investigated
              Figure  2.  Wind tunnel studies  with smoke
                  of  effective stack height modeling.

                                    21

-------
     Computer simulation modeling involves the application of physical
equations describing.the diffusion of contaminants in the atmosphere
(ref.  7).  There are equations available to describe a number of physical
situations, including  both elevated stack emissions (stacks generally 2
to 2.5 times higher than adjacent buildings) and low level emissions
(ground level and elevated line and area configuration sources).
     The^computer simulations can produce maps of odor concentrations such
as those shown for figure 3.  These maps show contours of constant odor
concentrations (isopleths) in the community that were predicted for
different values of stack heights.  The example shown is a rubber proces-
sing operation.  The existing configuration was successfully modelled,
then from this result the required stack height to abate the odor problem
was determined by adjustment of the stack height parameter input to.the
computer.

4.0  ODOR CONTROL
     When a proper identification of the problem has been made, we are
now in a position to determine how this problem can be solved in a cost-
effective manner.  There is an important decision point here, which
requires that we examine the problem carefully to see if either process
change or better dispersion of the odorant would be more feasible and -
cost-effective solutions to the problem when compared to control equipment
installation.

4.1  Process Change/Better Dispersion
     Process change can often be the most cost-effective method of odor
control.  Even if complete control of the odor is not possible, this may
lead to  improved operations (e.g., plugging leaks, closing windows, rede-
signing  hoods) which better confine the odorous emissions and/or reduce
total ventilation air volume and thereby lower control costs.  As discussed
in section 3.1, and shown on figure 3, better dispersion  is,another poten-
tially viable  and cost-effective method.  The stack height that meets the
criterion of no detectable community odors may, however,  not always be in
                         s~
the reasonable cost realm  (table 1).
                                       22

-------
     Odor detectable zone
                                          Odor Isopleths
                                            3 oven sources combined
                                            Existing configuration
                                            Wind speed - 2 meters/sec.
                                                                  Oven stacks
                                           Odor Isopleths
                                                3 oven sources vented to
                                              a new 20 meter stack
                                                Wind speed - 2 meters/sec.
Odor detectable zone
  Odor detectable zone
                                                                  Oven stacks
                                    Odor Isopleths
                                         3 oven sources vented to
                                       a new 40 meter stack
                                         Wind speed - 2 meters/sec.
                                                                  Oven stacks
Figure  3.  Odor isopleths for various plant stack'heights,
                                     23

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            Table 1.  Cost estimates for small diameter  tall stacks
                   for odor control at one  client  location*
Height
50 ft
100 ft
200 ft
300 ft
Construction
Guyed-on structure
Guyed-on structure
Self-supported
Self-supported
Cost (approx.)
$ 6,400
$ 12,800
$250,000
$380 ,000
        *These are specific to the case and are meant to show relative
   costs only.  Each odor problem must be treated in the context of
   the specific emission rates, flow, and meteorological conditions.
4.2  Control Technology
     If odor control by other than process change or better dispersion is
required, we must first consider the chemical and physical nature of the
odorants and other constituents of the gas stream emitted.  In many cases,
the odorant is a hydrocarbon and the technology of hydrocarbon emission
control should be pursued (ref. 8).  If the odorant is a water-insoluble
hydrocarbon, for example from rubber processing, wet scrubbing may remove
particulate matter (e.g., ground rubber) from the gas, but will not control
the odor.  If instead, we use a carbon bed which is effective for control
of the odor, the particulate matter may plug and damage the bed.  It is,
therefore, apparent that a control technology for one source cannot readily
be applied to another source without careful study of the emissions.  The
uniqueness of each odor problem makes odor control a challenge to the
ingenuity of the investigator.   Off-the-shelf solutions may be poor and/or
costly applications to the problem.  Creative design by those experienced
in odor control can lead to more cost-effective solutions which will
solve the problem without hampering process operations.
     The basic control technologies which could be considered for appli-
cation to solution of odor problems are:
                                     24

-------
      (a)  Oxidation
          (1)  Chemical
          (2)  Thermal
          (3)  Catalytic
      (b)  Condensation
      (c)  Absorption
      (d)  Adsorption.

4r2vl  Oxidation
      Oxidation is a technique which  can  solve  a wide  variety  of odor
 problems.  Chemical oxidation,  for instance, can  be used  to remove  HLS
 odors from rubber-processsing offgases by  oxidation to  less odorous S02
 using an aqueous scrubber  solution.   Permanganate or  hypochlorite solu-
 tions are among the more effective oxidizing agents.  Oondensible partially
 oxygenated hydrocarbons  (e.g.,  some  types  of paint oven emissions)  can be
 controlled in this manner.
      Thermal oxidation  is  extremely  effective  in  controlling  odors  from
 organic-based odorants.  Total  combustion  (>90 percent)-of the  odorants
 to C02 and water is achieved at about 1200° -  1400°F  for  most hydrocarbon-
 based odor sources.   It  is  also an extremely costly solution, especially
 at current fuel prices,  and may be at times the last  resort answer  for
 rubber processing hydrocarbon odors  if all 'else fails, (irefs.  VHT3}.
      Catalytic oxidation promotes the rate of  oxidation to allow use of
 lower operating temperatures and thus saves fuel  costs  as compared  to
 thermal oxidation.  Installed costs  are  about  equal to  thermal  oxidation,
 but operating costs should  be lower.  This method should  be considered
 for hydrocarbon-type  emissions  such  as those found in  tire manufacturing.
 It is important to insure  that  heavy metals and sulfur-containing com-
 pounds are virtually  absent from the treated gas  stream,  since  these are
 virulent catalyst poisons.

 4.2.2  Condensation
      For concentrated,  hot, and odorous  vapors that exist as  liquids
 under ambient conditions,  condensation may be  a feasible  technique.
 Condensers can be readily  applied as  off-the-shelf control technology,
                                      25

-------
but it must be cautioned that they may transform an air pollution problem
into a water pollution problem when contact condensers are used.  Con-
densers may also be considered as preliminary cleanup devices ahead of
more sophisticated control systems such as activated carbon adsorbers.

4.2.3  Absorption
     Water-soluble odorants can be removed by water scrubbers using this
principle.  Generally, the scrubbing liquor will contain an oxidant or
reactive reagent to convert the odorant to a nonodorous state.  Otherwise
the odor problem is transferred to the sewer system discharge point or
exchanged for a water pollution problem.  Organic solvents of low vapor
pressure might also be used as a method of concentrating the odorous
material, but a recovery or secondary disposal system (e.g., afterburner)
will be required.

4.2.4  Adsorption
     Organic odorants can be readily adsorbed on porous high internal
surface adsorbents such as activated carbon (ref. 14).  In the case of
high concentrations of hydrocarbons in gas streams, the hydrocarbons can
be recovered and recycled into the process.  This is a very common odor
control method.
     There are, of course, problems.  If, as previously mentioned, par-
ticulate matter is present in the gas stream bed, plugging can occur.
Aside  from this problem, pressure drop characteristics of the bed can
cause  certain design  limitations  (figure 4).  The regenerability and
cycle  time between steam regenerations should be carefully examined
before activated carbon is selected for odor control.  Figure 5 shows a
typical system.  Carbon adsorption control systems are a viable tech-
nology for application to odorous hydrocarbon emissions from rubber pro-
cessing, especially for solvents.

5.0  RUBBER  PROCESSING ODOR SOURCES AND CONTROL
     The odors which  can be associated with rubber processing are  in many
cases  detectable beyond the plant boundaries.   While  the objectionability
of  such odors can  be  debated, since this  is a subjective response  of

                                     26

-------
                    10
             30   40  50 60 70  90

                              80 100
Linear Velocity (ft. per min)
Figure  4.   Pressure  drop vs now  rate through  granular carbon  beds.
      Odorous
      air
        Steam
                                                     -^ Top phase liquid


                                                 Decanter


                                                     -t*- Bottom phase liquid
                                            Odor-free air
Figure  5.   Two-unit fixed bed activated carbon absorber (unit  1  in
            operation;  unit 2 being  stripped).
                                     27

-------
individuals to the odors, the detectability itself indicates a potential
community odor problem.  In some States, the regulations do not permit
any detectable.odor; therefore, such odors may already be a nuisance law
violation.
     If we examine a typical tire plant flowsheet (figure 6), the
potential emissions, including odors, occur at several different process
locations.  They can be emitted through stub stacks, roof monitors,
windows, or tall stacks.  These potential odor sources in the process,
even if they consist of high concentrations of odorous substances and are
emitted at a high flow rate, may not produce the odors finally detected
in the community.  A community odor survey needs to examine the odor
levels and the characteristics of the odor detected in order to relate
these to the potential odor sources in the tire manufacturing process.
     In the tire plant flowsheet, the plastication of the natural rubber
after heating and cutting is a potential odor source, since odors from
rubber and probably the plasticizer are detectable at the work station
involved.  In other plants, this operation is sometimes bypassed, and
therefore, the Banbury mixer (next operation) is a potential odor source.
The odors are basically hydrocarbon (gas and particulate) but also may
include gaseous sulfur compounds and oxygenated organic vapors.  Another
potential odor source is the curing press, where the basic tire is
formed and heat-cured with  steam.  Opening of the press results -in
release of odorous vapors and gases.  This odor is probably a complex
mixture of many odorants.   They include sulfur compounds  (hLS and organic
thiols/sulfides), hydrocarbons (gases and particulates),  and oxygenated
hydrocarbons (esters, alcohols, aldehydes).

5.1  Other Potential Odor Sources
     The other potential sources of odor in the tire-making process  are
fabric drying ovens (part of the fabric to rubber bonding process) and
tire-finishing operations.  These odorants probably include vapors of
the solvents and cement as  well as the rubber itself.  Other potential
odor sources not so indicated on the flowsheet are any sources where
significant quantities of hydrocarbons are emitted or where sulfur-con-
taining  compounds are  used.

                                     28

-------
       Potential
       •mission*
                                        Hydrocarbon
                                           ( Illght)
                             Part culetes
                                                               Hydrocarbon*  Hy< rocarbon*
                                                      Paniculate*
                                                        t ilight )
                                                                                                      Hydroc*rbont
        Process
        step

Primary-
Mattarbatch
Mixing

_», i Saeondary
| Mixing
^[ MllllnB|-
[Trtad &
Sldewail

	 »

4 	 	

Fabric to K^
Rubbar


Cement-
NV^^' Ing ^
\ •
- — \
| taxiing |
W 1


Cement
H House


	 a>

(con.
below)
        Process
        equipment
        category
        EmlMlon
        source*
                 Plastlcaton   B anbury f
            Fuma hoods,  Banbury
            Oanaral      Ventilation
            ventilation
        Mills       Tubrr*
        (thaatino.
         bland Ing,
         haating,
         cooling,
         lubrication)

        Fuma hoodi  Camant
                   tfpray
                   hood*,
                   General
                   ventilation
                                                                            Calendars,
                                                                            Drying
                                                                            ovan*
   Fuma hood*,
   camant dryer,
   fabric dryer
                                                                                           Cementing
                                                                                           stations
         General
         ventilation
Potnttlal
amlatloni
     Procaia
                       Hydroe«rbont     Hydrocarbons     Partlcutaia

                                               Odors
                        Particulatat  Hydrocarbon!    Partieulatai
                                    (•light)         (Might)
                                                                               Tlra
                                                                               Rapalr
Whlta
lldawall
Qrlndlng
-+
Mhlta
Sldawall
Coating


,,*
Black Sldawalli
     equipment
      EmleHon
      sources
               8-v.c.
               ublM A
               nuchlnM
                                 spray
                                 Booth
                            Spray
                            Booth
«nulp-t

          Alr-v«vlnq
Qwwal    ol
vwmiMlon  trimming*
                                                                                     iprav
                                                                                     •tatlon
Alr-v«ylnQ
°<           Fum«
grinding!      hoodi
                                                   Forca
                                                   variation
                                                   machlnat
Fuma
hoodt
Figure  6.    Process  flow diagram  of  a  tire  manufacturing  plant
                   showing  odor and  other emission  sources.
                                                        29

-------
                    Table 2.  Threshold detection values for
                       potential rubber process odorants
                Compound                       Odor threshold (ppm)*
              Styrene                        0.05
              Xylene                         0.08
              Toluene                        0.17
              1-3 Butadiene                  0.45
              H2S                            0.017 (TRC studies)

             *Ref. 6.  Concentrations at which 50 percent of the odor
        panel observed an odor in the working fountain.
5.2  Nonobvious Potential  Odor Sources
     If we confined our source identification to the inplant detectable
odor sources, we still might miss the most significant sources of com-
munity odor.  Hydrocarbons, that may have a low threshold of detection
but are emitted from the tire plant at high rates, may contribute
less to the overall community odor levels than more potentially objec-
tionable odorants, which are emitted at low rates (table 2).  Another
potential source which cannot be ignored is that due to misoperation of
air pollution control equipment.  One example would be a thermal incinera-
tor operating at too low a temperature or too short a residence time.  The
result could be the emission of a high level of partially oxygenated
odorous hydrocarbon, which may be more odorous than the original uncon-
trolled emissions.
     The evaluation of potential odor sources must be accomplished close
to the point of release to the atmosphere, and odor source measurement
programs must  include all those potential sources whose odor character
can be detected in the community or is suspected to be a contributor to
the community  odor character.  Potential odor sources to be measured
may include:
                                     30

-------
     (a)  Open plant doors and windows;
     (b)  Roof monitor and local ventilation ducts;
     (c)  Stub stacks of local hoods;
     (d)  Main process stacks;
     (e)  Stacks and vents from air pollution control equipment.

5.3  Odor Source Inventory
     If it is complex enough, an inventory of odor sources may be required.
Table 3 shows odor emission data from a hypothetical plant that was used
to help define the sources of odor in relation to the principal processes
carried out in the plant.
     It should be emphasized that odor problem identification begins in
the community but requires correlation of community odor survey data with
potential plant odor sources.  A plant odor source not detected in the
community is not an odor problem.
          Table 3.  Odor source inventory for a hypothetical  process
Source
Stack #1
Roof vent A
Roof vent B
Roof vent C
Stack #2
Stack #3
Roof monitor
Storage
Odor level
(Odor units/CF)
400
5,000
150
350
1,000
10
50
10,000
Source
flow rate
SCFM
200,000
5,000
5,000
5,000
20,000
50,000
80,000
200
Odor units
emissions
(Odor units per minute)
80,000,000
25,000,000
750,000
1,750,000
20,000,000
500,000
4,000,000
200,000
       Dilutions with pure air required to make source odor undetectable.
       Odor level * SCFM source flow rate.

                                    31

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5.4  Rubber Process Odor Control
     When considering the control of a given odor problem, the following
approaches should be considered in the order listed.  In most cases, this
would be the order of increasing costs:
     (a)  Process change;
     (b)  Better dispersion;
     (c)  Control technology.
     Under control technology, adsorption should be given preference when
economical solvent recovery can result from its use.  Oxidation (chemical
or catalytic) would be the next preferable technology to be considered.
Thermal oxidation (incineration) should generally be considered as a last
resort, since installation and operating costs, assuming that fuel is
available, are high.  Under special circumstances, the extensive use of
heat recovery techniques such as recuperative heat recovery within the
incinerator, makeup air heating, and oven or other process heat, may
make incineration a viable alternative.
                               REFERENCES
 1.  A. Turk, J. W. Johnston, and D. G. Moulton, Human Responses to
     Environmental Odors, Academic Press (1974).
 2.  G. Leonardos, "A Critical Review of Regulations For the Control of
     Odors," J. Air Pollution Control Association, May 1974.
 3.  R. A. Duffee, J. P. Wahl, W. A. Marrone, and J. S. Nader, "Defining
     and Measuring Objectionable Odors," presented at International
     Pollution Engineering Congress, October 22-25, 1973, Philadelphia,
     Pennsylvania.
 4.  R. A. Duffee., "Appraisal of Odor Measuring Techniques," J. Air
     Pollution Control Association, July 1968.
 5.  A. Dravnieks and W. H. Prokop, "Source Emission Odor Measurement
     by a Dynamic Forced-Choice Triangle Olfactometer," J. Air Pollution
     Control Association, January 1975.
 6.  T. M. Hellman and F. H.  Small, "Characterization of the Odor
     Properties of 101 Petrochemicals Using Sensory Methods," J. Air
     Pollution Control Association, October 1974.
 7.  F. Pasquill, "Atmospheric Diffusion," Van Nostrand (1962).
 8.  P. W. Kalika, "Hydrocarbon Emissions - Classification, Regulation,
     Measurement and Control," RMA Environmental Conference and Workshop,
     October 29-30, 1973, Chicago, Illinois.
                                     32

-------
 9.  A. Turk, "Industrial Odpr Control," Chemical  Engineering, Deskbook
     Issue, April 27, 1970.
10.  R. A. Duffee and J.  E. Yocom,  "Controlling Industrial  Odors,"
     Chemical Engineering, June 15, 1970.
11.  G. M. Hein and R. A. Duffee, "Odor Control -  Combustion Methods,"
     ASHRAE Systems and Equipment Guide, Chapter 63 (1967).
12.  0. E. Yocom, "Incineration of Gases and Vapors,"  AIHA Air Pollution
     Manual. 1968.
13.  D. E. Waid, "Thermal Oxidation or Incineration,"  presented at The
     State of the Art of Odor Control  Technology Conference, March 7-8,
     1974, Pittsburgh, Pennsylvania.
14.  R. Poltorak and W. D. Lovett,  "The Use of Activated Carbon for
     Controlling Odorous  Air Pollutants,"  presented at The State of The
     Art of Odor Control  Technology Conference, March  7-8,  1974,
     Pittsburgh, Pennsylvania.
DISCUSSION
DR. C. BOYD SHAFFER (American Cyanamid Company,  Wayne,  N.JJ:   There
     was a great deal  of information exchanged here about chemicals and
     the related problems.   One of the problems  is the  odor definition—
     one of the chemical standbys such as hydrogen sulfide or  hydrogen
     cyanide.   My question  is, do you think it would be feasible to
     develop a standard set of descriptions of odors, and if feasible,
     do you think it would  be worthwhile?
DR. KENSON:  I think it would be feasible in the long run, but the
     problem is that you may not be defining the odor problem  at all.
     If it is  an industrial odor problem; it is  a mixture of odors.  A
     mixture of odors is not always described and defined.  There is an
     interaction of more than one odor.   You may have very definite rele-
     vance to  the choice of sources to apply to  a certain chemical, and
     this is based on the industrial studies.  You cannot describe the
     odors sufficiently to  say they are from certain chemicals "x."
     There may be very much of a mixture.
DR. ABDUL QASI (Union Carbide, South Charleston, W.Va.'):   First, what
     odor are  we talking about?  Secondly,  have  you done any studies
     working at changing the stack height?   If so, what happened and wnat
     is the extent of the odor when you have a wind speed of zero and
     when the  stack height  is changed?
                                     33

-------
DR. KENSQN:  We are talking about the community odor as detected.   This is a
     very simplistic view, but it is one which can be had by measurement
     techniques and. by models.  Zero wind speed is something that  is just
     about never achieved in real situations.
DR. QASI:  I mean, under stagnant conditions we have temperature inversion
     and no movement of air, and the density of warm air increases.
DR. KENSON:  This type of problem would cause odors which generally are
     not odor sources because of the intensified problem.effect.  In fact,
     in Los Angeles they found that, during the stagnation period, there
     were suddenly odor problems and some drastic ones concerning  indus-
     tries, when stagnant air temperature started inversions.  In  the
     animal-processing industries, the standards were based upon problems
     that were not recognized until  very stagnant conditions occurred.
DR. QASI:  By oxidation of chemicals, is it true that at the same  time
     oxidation would be a worse problem than you have in the given
     situation?  Suppose you have C2H5OH.  When it oxidizes to a very high
     extent, it then odorizes more?
DR. KENSON:  I agree with you.  We have encountered situations, for instance,
     where an incinerator malfunctioned, causing worse problems. The
     second implies chemical oxidation.  Before we install such equipment,
     a pilot test should be run, and the odor should be no worse than what
     we are trying to solve.
DR. QASI:  I would like to ask one question.  From the studies that you
     did on the odor emission survey on the tire plant, did you determine
     that the major principal source of odors came from the application
     of natural rubber?
DR. KENSON:  Basically we find that the first step is to find the primary
     odor source, but the problem at each plant is to some extent unique.
     For instance, the ventilation system is different in different plants.
     This source may be quite different from the one I showed in the
     hypothetical plant.  The source, which is from a tall stack,  may be
     the highest odor-potential emission, may not be an odor source in
     the community.  The one coming out of the roof vent gets downwashed
     and may be the most severe odor problem.  So if I try to generalize
                                    34

-------
     I may get into trouble here, because the specific odor problem is
     different from the first plant.
MR. KEN CAMINSKY (B. F. Goodrich Chemical Co., Cleveland, Ohio):  After
     listening to the various nuggets from you I am still not sure that
     an odor problem exists.  For example, in the State of Connecticut,
     they have adopted odor regulations in the State agency.  They have
     one odor, or a concentration of one odor.  You can put your subjec-
     tion in the order of regulations.  I think that, even in -the City of
                                                                     /
     Cleveland, the indicated odor concentration of 7, 8, 9, and 10 would
     be acceptable.  However, would you give me your opinion, based on
     current odor technology, as to what a company should have or act on
     the odor problem?  For example, say there is an odor concentration of
     50 units, would it be acceptable in order for the company to take any
     action about that?
DR. KENSON:  Basically, you should be in compliance with the law first.
     Now I presume the public nuisance regulations say that, if someone
     objects to an odor, there is a problem, which is a violation of the
     law.  The other laws are involved with the various techniques in
     specifying odors or odor units from the emission source.  So the
     basic statement I first gave is to comply with the'law.  However,
     sometimes the law can be subject to the very interpretation given to
     it..  The practical limit of odor detection is odor units in the range
     of somewhere around 5 to 8, because, when you talk about odor units,
     you are talking about a trained panelist.  But at the same time,
     there is always going to be somebody possibly objecting to the
                                                             i
     odor and smell. 'So my answer is deliberately vague because there
     is a law to be obeyed.
DR. QASI:  Do you believe the time has arrived that we should have a
     little more sophisticated workman's point of view?  The health of
     the citizen may not be at stake in the criteria, but if we stay  .
     below certain levels, you can live with it.  We have shown this was
     not to be adverse to health--s.omething in this regard?  What I am
     saying in this regard is, in other words, that it is possible for a
     very small amount of odor to cause a few citizens in the community
                                      35

-------
     to precipitate a very large  expenditure  on  an  odor  problem, and  I
     think simply this means  a  large regulatory  criteria.
DR. KENSON:  This is usually  the  case.   It's  like anything  under the
     frequency-of-distribution  people,  as  far as why  the odor-processing
     problem is unique.   If you try to  say yes,  a detectable  odor  is
     tolerable, instead of saying it is unique and  detectable,  it  becomes
     so subjective at this time.   People are  trying to develop  this
     criteria, and they have  not.
DR. QASI:  One last question—many of the  odors  associated  with the rubber
     companies in general  are due to aerosols.  We  have  found where the
     classical dilution-type  techniques and other chemical  tests are  not
     appropriate in determining the odor content of an aerosol.  Are
     there any investigative  activities currently under  way which  will
     allow us to determine accurately the  amount of odor in an  aerosol?
     For example, in engineering  techniques and  other types of  techniques,
     they simply adhere to the  inside of the  container in which you
     accumulate the sample?
DR. KENSON:  Basically, you are addressing a  problem  I am aware of.   First
     of all, an aerosol odor  is a rather short-range  impact.   It is very
     difficult to model.  Secondly, it  can only  be  measured in  situ;  it
     cannot be stored—the odors  cannot be stored,  I  agree.  Now that
     odor is actually vapor,  the  odor carrier, however,  can be  an  aerosol.
     But basically, the dilution  technique must  be  done  at  the  source; you
     cannot store a sample, you cannot transfer  a sample, and we also
     have to be careful in our  modeling in that  we  do not overestimate
     the transport of any odors.
                                     36

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                     LIQUID EFFLUENTS-EMISSION  POINTS  FROM
                         RUBBER MANUFACTURING PROCESSES
                               David C.  Day,  Ph.D.*

Abstract
     During development of the recent effluent limitations  guidelines,
all significant sources of liquid process  effluents from the major
segments of the rubber-processing industry were  studied.  Wastewater
characteristics3 treatabilities,  and applicable  control and treatment
technologies were evaluated.   Based on such factors as  these* it was
determined that the rubber processing industry could be categorized:
     •Tires and inner tubes;
     •General molded and fabricated products;
     •Reclaimed rubber;
     •Synthetic rubber;
     •Latex-based fabricated products.
     Process wastewaters from the tire and inner tube industry are   \
principally caused by spills  and leakss  and contamination is by tramp
machinery oil and miscellaneous solid materials.  Accordingly oil
and suspended solids are the  major Wastewater parameters.
     Similarly3 in the general molded and fabricated product sectors
of the industry, most liquor effluents are produced by  spills and
leaks, and the principal parameters are oil and  suspended solids.
However Wastewater volumes and contaminant loadings differ  from those
found in the tire and inner tube industry.  Potentially,  lead is an
additional contaminant of the hose industry.
     Based on process methods and effluent characteristics, the rubber-
reclaiming industry requires  further sub categorization:  CD wet
digestion reclaiming, and (2) dry reclaiming.  The  Wastewater sources
and characteristics from dry  reclaiming processes are similar to those
from the tire and inner tube  industry.   However,  the wastewaters
       Project Manager, Southwest Region, Roy F. Weston, Inc.,
 Houston, Texas.
                                      37

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generated by wet digestion plants result primarily from the digestion
unit process itself and can be characterized by high COD and BOD
loadings in addition to higher levels of oil and suspended solids
than found in the tire industry.   Furthermore in some older plants,
zinc concentrations are significant.
     The principal products of the synthetic rubber industry fall  -into
three sub categories:  (1) emulsion crumb3 (2) solution crumb,  and  (3)
latex.   The principal sources of process wastewaters are monomer and
solvent recovery operations, crumb coagulation and washing steps,
equipment cleanouts, and area washdowns.  The significant parameters '
are COD, BOD, suspended solids, o-il,  and pH.
     Although the latex-based products industry is diverse,  one common
factor is the use of latex as a raw material and consequently wastewater
contamination by latex.   Equipment aleanout,  product washing,  and  area
washdowns are the major effluent sources, and COD,  BOD,  suspended  solids,
oil, and pH are principal parameters.  In some cases chromium and  zinc
levels are significant.

Introduction
     Effluent limitations guidelines  and new source performance standards
have been promulgated by the U.S. Environmental Protection Agency  for
the major segments of the rubber-processing industry (refs. 1,2).
Briefly, the guidelines identify applicable wastewater control and
treatment technologies and propose minimum levels of effluent quality for
distinct manufacturing categories within the rubber industry:
     •Tires and inner tubes;
     •General molded and fabricated products;
     •Reclaimed rubber;
     •Synthetic rubber;
     •Latex-based fabricated products.
For reasons of consistency and maximum correspondence with the guidelines,
it  is convenient to discuss the liquid effluents produced by the rubber-
processing industry in terms of the above categories.
                                      38

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     The guidelines apply only to process  effluents;  that  is  those  liquid
effluents generated directly by product processes.  However,  in  ord&r  to
adequately cover the subject of the industry's  liquid effluents,  it is
necessary here to discuss briefly other types of effluent  generated by
the industry; namely, utility and laboratory wastes.
     The intent is to describe rubber industry  effluent  types"affd character-
istics.  Since control  and treatment technologies applicable  to  the industry
are diverse and involve many considerations, discussion  of the industry's
effluent treatment practices is deemed outside  the  scope of this  paper.

Tires an'd Inner Tubes
     The tire and inner tube industry is responsible  for the  manufacture
of a diverse list of products, which includes automobile tires,  truck  and
bus tires, aircraft tires, and "off-the-road" vehicle tires,  camelback,
and inner tubes.  In spite of this fact many of the raw  materials,
processing operations,  and wastewater types are common throughout the
industry.  Furthermore, most tire and inner tube plants  manufacture a  mix
of products encompassing several  of the above product types.
     Table 1 presents the waste characteristics of  some  individual  process
effluents from typical  tire and inner tube plants,  and a simplified block
flow diagram of a typical tire and camelback production  facility  is il-
lustrated in figure 1.
     Briefly, process effluents from a typical  tire and  inner tube  plant
be grouped as follows:
     •Spills and leaks  of process materials and lubricants;
     •Intentional washdowns and cleanup wastes;
     •Unintentional cooling water and steam condensate discharges;
     •Air pollution control equipment effluents.
     The more significant spills  and leaks normally arise  in  storage areas
and compounding buildings where oils, compounding materials,  and  antitack
agents are handled and used.  In  addition, cement and sprays  can  potenti-
ally be spilled in the  building and painting areas.   If  not contained  or
removed by "dry" methods, such spillages are frequently  flushed  to  the
sewer system by washdowns or leaking cooling water.
                                     39

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            Table 1.   Typical  characteristics  of process
              effluents from tire and inner tube plants
Effluent type
Curing press
Tread cooling
Tread cooling
Wet collector
Wet collector
Inside drains

area8


tank overflow9
tank overflow0
(painting
(sidewall
e
area)
grinding

Fl,ow
(gpm)
31b
155
155
177
area)a 2
0.25
COD .
(mg/1)
2,160
40
10
188
860
216
Suspended
solids
(mg/1)
546
9
30
14
312
15
Oil
(mg/1)
836
2
_
24
65
6
 For a plant consuming 18,500 Ib/hr of raw materials.
Vlow includes water spills and leaks as  well  as  steam condensate leaks.
•»
'For a plant consuming 11,000 Ib/hr of raw materials.
 For a plant consuming 28,000 Ib/hr of raw materials.
Tor a plant consuming 22,000 Ib/hr of raw materials.
     Although there are few instances  in  a  tire or inner tube plant where
water washdown or cleanup operations are  necessary,  the practice is employed
to some degree in most plants.   Spilled process oils and solid materials
or lubricating oils and greases  normally  contaminate washdown and cleanup
effluents.
     Owing to the nature of the  industry  and  the equipment used, cooling
water usage by the industry is high.   In  old  plants, once-through cooling
water systems are common, whereas  newer plants generally employ cooling-tower
systems.  Although contamination of cooling systems  by foreign materials,
such as oil, is not a major problem, cooling  water leakage in the vicinity
of process machinery is relatively common and normally results in flushing
contaminants, such as spilled oil  or solids,  to the sewer system.  'Con-
densate leaks at curing presses  are common  to the  industry.  In most cases,
the leaking condensate picks up  tramp  hydraulic oil.  Although the volume
of leaked condensate is relatively low for  we11-maintained presses, the
accumulated leakage nevertheless requires drainage or periodic removal.
                                   41

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     In addition to noncontact cooling water used to cool  machinery,
contact cooling water is used to cool  extruded tread and camelback
rubber.  The flow of such tread cooling water is relatively low and
contamination insignificant.   In cooling the tread rubber* the temper-
ature of the discharged cooling water is raised approximately 10°F
above that of the supply water.
     Air emission control devices are normally required for the compounding,
spraying, and grinding areas  of tire and inner tube plants.  Particulates
are emitted by the compounding and grinding operations, and three types
of control devices, wet scrubbers, bag-house collectors, and cyclones
are common to the industry.  Bag-houses and cyclones are preferred
from a wastewater standpoint but, in some applications, are inappropriate
due to binding problems and wet scrubbing devices must be employed.
Although it is generally possible to recirculate part of the scrubbing
water, some water must be discharged as effluent in order to purge
accumulating solids from the system.
     The painting or spraying operations of a tire or inner tube
plant frequently generate hydrocarbon emissions which are generally
difficult or costly to control.  Many tire plants are able to use wet
scrubbing equipment.  Such devices produce an organicsladen effluent.
Generally the organic phase is separable and can be removed prior
to discharge of the aqueous effluent.  Newer technologies, used frequent-
ly in other industries, include carbon absorption and thermal or cataly-
tic in cineration and potentially have application 1n the tire industry.
Wastewater effluents from these technologies are normally lower in
volume or less troublesome than those produced by wet scrubbing.
     In summary, suspended solids and oil are the only significant
characteristics of the liquid e'ffluents from tire and inner tube
plants.  Liquid effluents are produced by spills and leaks, washdowns
and cleanups, and air pollution control discharges.

General Molded and Fabricated Products
     Rubber products made by molding processes are diverse in size,
shape, and end-use.  Principal products include hose, footwear, belting,
                                    42

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seals and gaskets, and coated fabrics.  Processes employed by this
industry can typically include compounding, milling, fabrication, molding,
and vulcanization.
     Although the product mix and number of processes can vary in
this industry from plant to plant, most process liquid effluents can
be  described as:
     •Spills and leaks of process and lubricating materials;
     •Intentional washdowns and cleanup wastes;
     •Unintentional cooling water and steam condensate discharges;
     •Air pollution control equipment effluents.
Individual process effluents produced by typical plants in the general
molded and fabricated products industry are characterized in table 2.
     Spills and leaks from this industry sector are similar in origin and
characteristics to those generated by the tire and inner tube industry.
Oil and suspended solids are the major constituents.  In addition to oil
and solid material spillage, latex leaks and spills are a potential
problem in both the rubber footwear and coated materials industries where
rubber latexes are used as adhesives and coating aids.  Latex wastes are
usually characterized by suspended solids, COD, and color.  The latex
spill potential is magnified by the fact that in many cases latex is
transported and used throughout the plant in small quantities and by manual
methods.  Process effluents caused by spillage and leakage should be
contained and cleaned by "dry" methods.  Latex spills are best coagulated
in situ and removed as a solid.
     As discussed for tire and inner tube plants, water washdowns and
cleanup methods are generally unnecessary, although they are frequently
practiced.  The most difficult problem created by such practices involves
areas where latexes are stored, transported, or used.  Ideally all "wet"
wash and cleaning methods should be reduced or eliminated completely.
     The industry in general has high cooling-water usage supplied by
once-through or recirculating systems.  In both cases if adequate water
segregation or equipment maintenance is not carried out, oil  contamination
of cooling water or oil pickup by leaking cooling water frequently results.
Similarly, leaking steam condensate can be contaminated by tramp oil.  The
hydraulic oil systems on the compression and transfer molding machines
                                    43

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         Table 2.  Typical characteristics of process effluents from
        	general molded and fabricated products plants
Effluent type
Product type
Flow     COD
(gpm)   (mg/1)
         Suspended
           solids
           (mg/1)
          Oil
         (mg/1)
Spills, leaks,'
washdown, and
runoff
Spills, leaks,
washdown, and
runoff
Spills, leaks/
washdown, and
runoff
Miscellanepus
Miscellaneous
Miscellaneous
  16
  52
         182
180
180
            216
122
145
Vulcanizer
condensate
Vulcanizer
condensate
Hose (lead
sheath cure) 1
Cement-dipped
goods and hose
(cloth wrap
cure) 1 823
63
10
63
uFor a plant consuming 5,000 Ib/day of raw materials.
 For a plant consuming 20,000 Ib/day of raw materials.
 For a ptant consuming 100,000 Ib/day of raw materials.

  used in the industry lead to a  high  incidence of oil  leaks  and spills.
       Hose manufacture normally  produces  a curing-oven condensate  which  is
  contaminated by organics or lead,  depending  on whether a cloth-wrapped  or
  lead-sheathed curing method is  used.   In either case  the condensate  volume
  is low and the contribution of  such  effluents to the  plant's  overall
  effluent is minimal.  The organics are leached from the rubber through
  the cloth wrapping, and presumably small  quantities of lead are scoured
  from the lead sheath by the steam, condensate.
       Air pollution control devices are used  by the industry in the rubber-
  compounding areas.  These can be either wet-scrubber or bag-house type
  devices.  With few exceptions bag-house equipment is  successful and
  scrubber effluents can be avoided.  Since product painting  and spraying
  with organic compounds is not practiced in this industry as much  as  in
  tire and inner tube plants, "wet"  air pollution control devices for  this
  type of service are seldom encountered.
       In some plants, such as hose-manufacturing facilities, water is used
                                     44

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to hydraulically or pressure test the hose product.  In cases where good
housekeeping is practiced, little contamination of the test waters.-occurs.
However, if the test water is spilled or poorly drained after use, con-
tamination by tramp solids or oil can occur.  Test waters can also be
recycled, and the discharge can be eliminated or its volume significantly
reduced.
     In summary, oil and suspended solids are the principal character-
istics for the industry as a whole.  Latex solids are an additional
constituent in liquid effluents from plants utilizing latex solutions
in fabrication processes.  Although most suspended solids and oils can
be removed by gravity separation, latex effluents require coagulation
                                  i
treatment or ideally should be containerized prior to contract dis-
posal .

Reclaimed Rubber
     From a wastewater standpoint, the rubber-reclaiming industry can
be subcategorizeds
     •Pan* mechanical, and dry digester processes^
     •Wet digester process.
     The manufacturing operations occurring at most rubber-reclaiming
facilities can be described by:
     •Scrap grinding and separation;
     •Depolymeri zati on;
     •Final processing.
It is in the depolymerization step that the wet digester process
differs significantly from the other reclaiming methods.
     The wet digester, pan, and mechanical reclaiming processes are
presented in simplified block flow diagram form in figure 2.  Liquid
effluents typically generated by rubber-reclaiming facilities are
characterized in table 3.
     The operations occurring in the grinding and separation areas are
essentially common to all reclaim processes and can be classified as
mechanical and "dry" in nature.  The principal  liquid effluents result
from cooling water leaks and water washdowns.  The significant character-
istics are oil (machinery lubricants) and suspended solids (rubber fines
and particles).
                                    45

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to
d)
V)
t/)
0)
u
o

E
•I—
10

u
O)
10
0)
o>
I
-o
c
id
(O
0)

-------
Table 3. Typical characteristics of.process effluent
from rubber-reclaiming plants
Suspended
Flow COD BOD solids Oil
Effluent type (gpm) (mg/1) (mg/1) (mg/1) '(mg/1)
Pan, mechanical, and drya
digester processes
Spills, leaks, washdown,
and runoff 26 110 27 287 154
Vapor condensate from air
pollution control devices 2 340 160 -8 65
Wet digester process
Spills, leaks, washdown,
and runoff 32 HO 27 287 240
Vapor condensate from air
pollution control devices 17 240 70 70 480
Dewatering liquor (chemical
defibering) 24 3,910 790 106,650° 10,770
Dewatering liquor (mechanical
defibering) 24 3,910 790 585 10,770

?For a plant producing 100,000 Ib/day of reclaimed rubber.
°For a plant producing 123,000 jb/day of reclaimed rubber.
This value is an estimate and represents a maximum loading assuming, all
scrap fibers converted to suspended solids.
Depolymerization by the wet digester method is essentially a chemical
process and the principal effluent occurs at the dewatering step where
the depolymerized rubber solids are separated (dewatered) from the
digestion liquor. Since the digestion agents include various oils,
organic sulfides, thiols, and amino compounds, the dewatering liquor is
characterized by high COD, BOD, suspended solids, and oil.
If the rubber scrap is defibered mechanically prior to digestion,
improvements can be made to the digestion and dewatering processes and
a significant fraction of the dewatering liquor can be recycled to the
digester with makeup of depleted ingredients. Excess liquor is "blown
down" from the system, but the net result is reduced levels of COD, BOD,
suspended solids, and oil in the effluent.
On the other hand, if the rubber scrap is not defibered mechanically,
47
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chemical degradation of the fibrous components must also be accomplished
in the digestion step, and this normally requires the addition of caustic
soda and calcium chloride to the digester. Accordingly, in such cases
the dewatering liquor exhibits alkalinity and extremely large amounts of
suspended solids from the fibrous materials and in addition is not
suitable for recycle to the digester.
Vapors produced during the digestion process require control. Normally
this involves condensing and decantation. With some modification to the
digestion process, the decanted organics can be recycled to the digester
for reuse, and the need for a wastewater discharge is eliminated.
The pan, mechanical, and dry digester processes are, for the most
part, "dry" processes, and most liquid effluents are produced indirectly.
Spills, leaks, and washdowns are the major sources and can be characterized
by oils and suspended solids. Vapors liberated during the depolymerization
process necessitate emission control equipment. Condensation or scrubbing
can be used resulting in a liquid effluent characterized by COD, BOD, and'
oil.
The final stage in all reclaiming processes involves compounding and
milling the reclaimed rubber with the required additives. The processing
methods are essentially "dry" in nature, and effluents are produced by
spills, leaks, and washdowns as well as air control equipment wastes.
Spills, leaks, and washdowns are characterized by oil (lubricant) and
suspended solids (additives, fines, and soapstone solids) and the ef-
fluents from air control devices contain suspended solids produced by
scrubbing of particulates and hydrocarbons.
In summary,jthe effluents produced by the grinding/separation and
final processing operations in all reclaiming plants are essentially
similar to those produced in tire and inner tube plants and can be
characterized by oil and suspended solids. The wet digestion process
itself produces a significant liquid effluent containing high levels of
COD, BOD, suspended solids, and oil. Chemical defibering, where used,
contributes additional suspended solids and some alkalinity.
48
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Synthetic Rubber
Based on the nature of the manufacturing processes, effluent chara-
cteristics, and treatabilities, most synthetic rubber production facilities
can be subcategorized:
•Crumb rubber;
•Latex rubber.
Owing to several basic processing similarities, it is convenient to
discuss jointly the liquid effluents generated by plants producing crumb
rubber via emulsion polymerization and solution polymerization processes.
The two classes of crumb rubber produce wastewater by analogous operations
and, in many cases, in common plant areas:
•Monomer recovery;
•Rubber coagulation;
•Crumb dewatering;
•Equipment cleanout;
•Area washdown.
Monomer recovery and reuse is practiced by the industry in the
interests of both process economics and product quality. In most cases
this is carried out via steam and vacuum stripping followed by decantation
and distillation. Decantation generally produces a monomer-rich layer and
a water layer. The water layer is discharged and usually contains dis-
solved and entrained monomer. Distillation frequently leads to a light
monomer cut, a middle water cut, and an organic bottom cut. The bottoms
should not be discharged to the sewers since the organic loading is nor-
mally very high. It should be incinerated or blended into a compatible
organic chemicals feedstock stream. The middle water layer contains
moderate loadings of dissolved organics and can be discharged as a waste-
water. Solution crumb plants generally combine the solvent and monomer
recovery operations. The solvent and monomers are stripped from the
rubber product in the stripping-coagulation process. The solvent-monomer-
steam overhead stream is decanted and organic layer passes to a
distillation unit for separation of the solvent and monomers. The liquid
effluents from the distillation and decantation steps are similar to
those described above. Monomer and solvent recovery wastes, depending
on the nature of the recovery process and on the organics involved, exhibit
49
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varying levels of BOD, COD, and oil and grease, the monomer recovery
effluents produced by emulsion crumb rubber plants generally contain
higher levels of organic loading than those generated at solution crumb
facilities.
The coagulation of emulsion crumb rubber is different from that of
solution crumb rubber. In the former case, coagulating agents, normally
sulfuric acid and brine, are added to the latex rubber producing
solid crumb rubber, which is screened from the coagulation liquor. The
liquor is returned to the coagulation unit with makeup and a purge stream
of the liquor is discharged. This effluent contains acid, brine, dis-
solved organics, and suspended rubber crumb fines and exhibits low pH,
COD, and suspended and dissolved solids. In some cases coagulant mixtures
other than acid and brine are used, such as acid-polyamine blends. In
such cases, the discharged coagulant liquor contains higher COD and BOD
levels and, in addition, has a high nitrogen content.
Solution crumb rubber is generally coagulated during steam stripping.
Water and live steam are added to the rubber solution, the monomers and
solvent are stripped off, and the coagulated crumb rubber remains. Sur-
factants are usually added to the stripping-coagulation unit as a means
of controlling crumb size. The rubber crumb is screened from the
coagulation slurry. The majority of the screened slurry water is returned
to the stripper as makeup hot water and the remainder is discharged as
a purge stream. The effluent contains dissolved and separable organics,
surfactants, and suspended rubber crumb fines and can be characterized
by COD, BOD, suspended solids, and surfactants. The strength of the
coagulation effluent from solution crumb plants in terms of COD and BOD
is considerably lower than the excess coagulation liquor discharged from
emulsion crumb facilities. In plants where carbon-extended masterbatch
crumb is produced, the coagulation effluent has a significant black color.
After coagulation and the associated screening operation, the rubber
crumb requires washing to remove entrained contaminants, such as monomer,
coagulation agents, etc. The rinse water is screened and recycled to the
wash operation with makeup. A purge stream must be discharged. This
effluent contains dissolved organics as well as suspended and dissolved
50
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solids and can be characterized by COD, BOD, and suspended solids. In
addition, emulsion crumb rubber rinse wastes exhibit some acidity (plus
low pH) and solution crumb rinse wastes generated by the two classes of
crumb rubber are relatively similar.
Since solution polymerization must be carried out in water-free
equipment, virtually no water is used for equipment cleanout purposes.
Any equipment cleaning that might be necessary is generally done with
solvent. The solvent is then recovered and reprocessed. In emulsion
crumb plants, however, considerable quantities of wastewater are generated
by equipment cleaning operations and in most cases contamination by latex
emulsion results. One major source of cleanout wastes is the stripping
•columns which must be periodically cleaned of accumulated rubber solids.
In most instances cleanout effluents contain dissolved and separable
orqanics and suspended and dissolved solids, and they have a milky colora-
tion caused by the rubber latex content. Cleanout wastes can be character-
ized by COD, BOD, and suspended solids.
Area washdowns occur in all parts of crumb rubber plants but are more
common in emulsion crumb facilities than in solution plants. Common*
contaminants are orgam'cs and rubber crumb solids. Latex spills are
frequently washed down in emulsion crumb plants. Washdown effluents
contain all the major wastewater characteristics including COD, BOD, oil
and grease, and suspended solids. Storm-water pickup from contaminated
areas is similar to washdown effluents, although contaminant concentrations
generally will be lower.
Three additional sources of effluent contamination that should be
mentioned are baler hydraulic oil, extender oil, and carbon black. Leaking
hydraulic oil is a common problem in the baling area. Without adequate
containment and handling, this oil can reach the plant sewer systems.
Extender oil, added to the rubber during the coagulation step, can carry
over with the coagulation purge streams and contribute to the effluent oil
and grease content. Carbon black storage and handling facilities are
generally difficult to keep clean. Storm runoff picks up tramp carbon
black, resulting in increased effluent suspended solids and color (black).
In order to prevent premature polymerization during transport and
storage, much of the butadiene used by the crumb rubber industry is
51
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shipped containing an inhibitor. Prior to processing, the inhibitor is

scrubbed from the butadiene using a strong caustic solution. The caustic

soda picks up the inhibitor and eventually must be purged from the system

as a waste discharge. This effluent has an extremely low average flow

rate with high pH, alkalinity, and color (reddish-purple).

Liquid effluents generated in typical emulsion crumb and solution

crumb rubber plants are summarized in table 4. Figure 3 is a simplified

process flow diagram of an emulsion crumb rubber "production facility