United States
                    Environmental Protection
Municipal Environmental Research
Cincinnati OH 45268
                    Research and Development
EPA-600/S2-82-099  Feb. 1983
&EPA         Project  Summary

                    Physical  Properties  and  Leach
                    Testing  of  Solidified/Stabilized
                    Industrial  Wastes
                    Environmental Laboratory, U.S. Army Engineer Waterways Experiment
                     A study was conducted to investigate
                    a  new  waste  treatment  and
                    containment technology involving the
                    solidification  and stabilization  of
                    hazardous  industrial wastes.  Small-
                    scale laboratory tests were conducted
                    to  determine the  physical properties
                    and chemical leaching  characteristics
                    of five industrial wastes that had been
                    chemically  solidified or stabilized  by
                    one or more of four processes. Basic
                    data are provided to help estimate the
                    potential for environmental pollution
                    from disposal of these industrial wastes
                    and to define the strength and durability
                    of the treated materials.
                     Results suggest  that  in  some cases
                    solidification/stabilization  may be a
                    useful  technique for  reducing
                    environmental  pollution  from  these
                    wastes. But a great deal of work must
                    be   done  to  optimize  treatment
                    procedures   for each  waste  being
                    disposed,  and  additional  work  is
                    required to  understand the behavior of
                    treated industrial wastes under actual
                    field conditions.
                     This Project Summary was developed
                    by  EPA's  Municipal  Environmental
                    Research Laboratory. Cincinnati. OH,
                    to  announce  key findings of  the
                    research project that is fully documen-
                    ted in a separate report of the same title
                    (see Project Report ordering informa-
                    tion at back).

                     As industry produces  ever increasing
                    amounts of  diff icult-to-handle hazardous
                    wastes, the need for finding solutions to
                    its  disposal  will become more and more
critical. In response to that need, this
study addresses a new waste treatment
and  containment technology involving
the  solidification and stabilization of
hazardous industrial wastes. Small-scale
laboratory  tests were  conducted to
determine the physical properties and
chemical leaching characteristics of both
untreated and chemically solidified or
stabilized industrial  wastes.  Basic data
are  provided  to  help  estimate the
potential for  surface  and groundwater
pollution from industrial waste disposal
and to define the strength and durability
of the treated materials.

Types  of Hazardous  Wastes

  Those wastes that are classed as
hazardous because  of their  organic or
inorganic constituents can be dealt with
by  somehow altering the  offending
compound to produce a new, less toxic
material before  disposal.  But  those
containing toxic  or  hazardous
constituents of an elemental nature pose
a very different  problem since, short of
nuclear  transmutation,  no  secondary
treatment can alter  them. With such
wastes,  the  toxic elements must be
contained within the disposal facility
forever or, at least, losses must be kept so
low that the environment is not harmed.
The  most  common   elemental
constituents of sludges in this category
are the heavy metals, many of which are
toxic in  very small quantities. A second
type  of waste  with  elemental
contaminants is that which contains very
high levels of moderately soluble to very

soluble  inorganic  salts.  Such  wastes
often contain substantial  levels  of toxic
heavy metals as well.

Types of Waste Containment

   Waste constituents can be contained
on several different levels. For example,
wastes  can  be  placed  unaltered  in a
containment  vessel or buried directly so
that the landfill itself ultimately provides
the containment. Or, on a smaller scale,
the wastes can be mixed with material
that will   coat  or encapsulate  each
separate  particle  or  grain  with  an
impervious, inert coating -- often termed
microencapsulation. Another  method is
to mix the waste with a binder that bonds
the waste particles together  without
necessarily  coating  each  grain.  The
smallest-scale containment systems use
the production of new,  inert, insoluble
crystal  lattices  that   bind   the  toxic
elements into a durable,  solid material.
Techniques  for  embedding  wastes  in
concrete or pozzolan concrete are well
established and commercially available.
Macroencapsulation involves  fusing an
impervious polymer coating to  a large
block of solidified waste.

 Methods and Materials
  Four  solidification/stabilization
techniques were selected for this study
as  representative of those technologies
currently available commercially or under
extensive   development.  These
techniques   are:  (1)   a  lime-flyash,
pozzolanic cement process that yields a
solid  microencapsulation system, (2) a
cement/soluble-silicate treatment
process that produces a soil-like product,
(3) an  organic  polymer system that
produces a hard, rubber-like solid, and (4)
a  microencapsulation   process  that
solidifies the  waste and then bonds it in a
polyethylene jacket.
  Five  sludges  were  selected  for
treatment by the solidification/stabiliza-
tion  techniques: electroplating sludge,
nickel-cadmium battery sludge,  pigment
production sludge, chlorine production/
 sludge, and glass etching sludge. All are
 inorganic sludges with dangerous levels
of  toxic,  heavy  metals  and/or  other
 leachable ions, but with only traces of
 organic materials. Furthermore, all are
difficult  to   dewater   and  represent
problems  for  disposal.  High  U.S.
 production levels and lack of reclamation
facilities place these wastes in a  category
of  problem  sludges.  Their  production
 rates also make them prime candidates
for large-scale commercial solidification/
 stabilization processes.
  Four waste processors agreed to take
part  in the test  program to  evaluate
and/or treat the selected sludges. They
are identified only by letter to protect their
anonymity. All were furnished a sample
of the test sludges to optimize their
treatment systems for each waste. After
these  preliminary  evaluations, the
participating  vendors  treated   sludge
samples  for laboratory evaluation and
physical   testing  at  the  U.S.   Army
Waterways  Experiment  Station   in
Vicksburg, Mississippi.

Results and  Conclusions

   Data from these investigations can be
used to evaluate the pollution potential of
the  wastes  studied when  they  are
disposed  of  in  standard landfills  or
shallow land burial. But the conditions in
such  a  landfill  would  favor  the
containment of the treated wastes more
than did the conditions used in this study.
The  small sample size and  continuous
submersion in CO2-saturated  leaching
solution  used  in  this  study appear to
represent  very  rigorous  leaching
conditions. Most  landfill operations  on
the  other hand, would allow the use of
much larger blocks of treated sludge and
would have only  intermittent saturated
conditions occurring in the fill. This study
may thus overestimate  the  leaching
losses that might  be expected  under
actual disposal  conditions.

Results of Various
Treatment Processes

   The  treatment processes used in this
study produced final products with a wide
array of physical properties varying from
moderate-strength solids  to a  soil-like
granular material. Process A, which was
the  lime-flyash pozzalonic solidification,
produced a  solid  soil/cement-like
product with good structural integrity but
poor  durability.  Concentrations  of
hazardous elements in  leachates from
this  treated product were actually higher
in about half the cases than they were in
leachates  from  similar  untreated
material. The net benefit of treatment by
this  method was marginal.
   Process B, the cement/soluble-silicate
treatment  process,  produced  a  semi-
friable material with low strength and a
soil-like  consistency. This  process
produced more consistent containment
of hazardous  elements with 60 to  70
percent of the constituents having lower
levels  in the  leachate from the treated
sludge than in the  leachate from the
untreated  control  columns.  Physical
property tests typical of structural solidi
could not be run on this material.
  Process C  attempted to contain  th<
industrial wastes in  a plastic matrix b\
polymerizing  the  waste  directly in  c
urea-formaldehyde  monomer  prepara-
tion. Only two wastes were treated by this
process -- the electroplating waste  anc
the  paint  production sludge. Both  losi
most constituents at much higher rates
than the  control  columns,   possibly
because of the acidification and resulting
dissolution  of  the  sludge  that  was
required to produce the polymerization
reaction   used  in  this  process.
Urea-formaldehyde as used here appears
to be counterproductive as a containment
  Process  D,  the  macroencapsulation
process that solidifies the waste and then
bonds it  in a  polyethylene jacket, gave
excellent containment of all constituents
but cadmium. The high costs for material,
equipment, and labor associated with this
method probably preclude its use for all
but the most hazardous wastes, however.


  Replicates of the leaching tests showed
remarkable   repeatability  between
columns  using  different samples from
one treatment batch of a particular sludge.
But the patterns of constituent loss from
different   sludges  treated  by  one
treatment  process  were  not  similar.
Since the sludges are  primarily metal
hydroxide  wastes, it would be assumed
that each treatment process would be
similarly  effective  in  containing  a
particular  contaminant  in most of  the
sludge types  tested. Results indicate,
however, that  complete leaching tests
might be required for  each new waste
even though similar constituents of other
wastes might  have been contained by a
particular treatment system.
  As might  be expected, the  same
variability was  found  for  constituent
losses from samples of a single sludge
that was subjected to different treatment
processes.   Thus,  no  generalizations
could be made concerning the probable
loss of a  particular constituent, either
from different sludges  treated  by  one
process or from a single sludgetreated by
different  solidification/stabilization

Patterns of Constituent Loss

  Two distinct  patterns of constituent
loss from leaching emerged in both the
treated and control columns.

   First, when constituent concentrations
 in  the sludge greatly  exceeded their
 solubilities in the leaching medium (e.g.,
 calcium, nickel,  lead,  and sulfate), their
 concentrations were relatively constant
 in the leachates collected over the entire
 span  of  the test period.  For  these
 constituents, the rate of loss depended on
 the volume of leachate produced not on
 the  length of  time  over  which  the
 leaching took place.
   The  second  leaching  pattern  was
 observed for those constituents whose
 solubilities  were large  compared with
 their  concentrations  in the  sludge
 (chloride,  for  example).  These
 constituents had very high  concentra-
 tions  in the  initial  leachate  samples,
 followed  by  an  asymptotic  drop  in
 concentration  as  the   element  was
 depleted  from  the  sludge   that  was
 exposed to the leaching  medium.
   Channelization of the leachate flow in
 the control  columns resulted in a rapid
 decline in  the concentration of soluble
 constituents in the leachate.  The reason
 was that this process decreased the area
 of sludge that came in contact with  the
 leaching medium.
   A third, less common leaching pattern
 showed low initial concentrations  in the
 early  leachate  samples  and  slow
 increases as the  experiment progressed.
 This  pattern  was  observed  for
 constituents in  which a  common  ion
 effect limited concentrations  at first and
 permitted them to increase as the  levels
 of interfering  ion were depleted. This
 pattern was also evident  for constituents
 whose solubility increased later because
 of changes in  pH or redox conditions in
 the   leachate.   The  loss   of  such
 constituents would be missed completely
 in short-term  leaching  tests,  but they
 might  be  of great consequence in  the
 evaluation of the waste for land disposal.


  This  study  has  indicated  that
solidification/stabilization of  potentially
hazardous industrial wastes may reduce
the losses of undesirable constituents to
environmental waters  when the wastes
are disposed of by landfilling with proper
engineering techniques.  But much more
study  involving  long-term, large-scale
operations, is  required before the
behavior of treated  industrial  wastes
under  actual  field  conditions can  be
adequately  understood.  Such  an
understanding is  necessary  before the
disposal  of industrial wastes can  be
carried  out with  confidence  that  no
environmental degradation will  occur
over the long term.
  The  full  report was  submitted  in
fulfillment of Interagency Agreement No.
EPA-IAG-D4-0569 by  the U.S.  Army
Engineer Waterways Experiment Station
under  the  sponsorship   of  the  U.S.
Environmental Protection Agency.
  Environmental Laboratory is at the U.S. Army Engineer Waterways Experiment
    Station, Vicksburg, MS 39180.
  Robert E. Landreth is the EPA Project Officer (see below).
  The complete report, entitled "Physical Properties and Leach Testing of Solidified/
    Stabilized Industrial Wastes," (Order No. PB 83-147983; Cost: $ 14.50, subject
    to change) will be available only from:
          National Technical Information Service
          52.85 Port Royal Road
          Springfield, VA 22161
          Telephone: 703-487-4650
  The EPA Project Officer can be contacted at:
          Municipal Environmental Research Laboratory
          U.S. Environmental Protection Agency
          Cincinnati, OH 45268
                                                                •feUS  GOVERNMENT PRINTING OFFICE;  1983	659-O17/O893


United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
                                                                                                        EPA 335
Official Business
Penalty for Private Use $300

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