United States
                     Environmental Protection
                     Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
                     Research and Development
EPA/600/S2-85/015 May 1985
SER&         Project  Summary

                    Treatment Technology for
                    Pesticide  Manufacturing
                    Effluents:  Bentazon
                    Robert W. Handy, Doris J. Smith, and David A. Green
                      Laboratory studies were conducted
                     on the treatability of wastewater gen-
                     erated from the manufacture of ben-
                     tazon. The wastewater was character-
                     ized for pesticide content by high per-
                     formance  liquid   chromatography
                     (HPLC). Toxicity determinations on
                     bentazon and its major treatment pro-
                     duct  (dichlorobentazon)  were  con-
                     ducted with  Daphnia  magna.  Ben-
                     tazon was not toxic to the daphnids
                     at concentration of up to 50 ppm. The
                     major known  by-product of chlorina-
                     tion of bentazon is  dichlorobentazon,
                     which is toxic to daphnids at 50 ppm.
                      Emphasis was placed on the remov-
                     al of  bentazon from wastewater by
                     treatment  with sodium  hypochlorite.
                     The effects of variations in  the pH,
                     amount of hypochlorite,  temperature,
                     and  mode of  hypochlorite  addition
                     were  studied.  The  temperature and
                     mode of addition had little effect on
                     the removal of bentazon. It was found
                     that bentazon is most efficiently re-
                     moved by hypochlorite when the pH
                     is 2 or below and  when a 245- to
                     370-fold excess of  hypochlorite  is
                     used.
                      Based on assumed rates of process
                     wastewater production, the total cost
                     of the treatment was estimated.
                      This Project  Summary was devel-
                     oped  by EPA's Air and Energy Engi-
                     neering Research  Laboratory,  Re-
                     search Triangle Park,  NC,  to an-
                     nounce key findings of  the research
                     project that is fully documented in a
                     separate report of the same title (see
                     Project Report ordering information at
                     back).
Introduction
  This report describes a study of the
treatability of wastewater resulting  from
the manufacture of bentazon, a postemer-
gence herbicide.  The  objective  of  this
project was to conduct a bench-scale
treatability study  of bentazon  pesticide
manufacturing  wastewater  using treat-
ment with sodium hypochlorite. Pesticide
removal was  the principal  criterion for
evaluating the usefulness of each control
treatment. Wastewater  treatment oper-
ating conditions were chosen to simulate
actual commercial units in  such param-
eters as contact time and temperature, so
that meaningful treatment cost estimates
for  manufacturing processes  could be
generated.
  Under EPA's proposed Effluent Guide-
lines for Pesticides, bentazon may be reg-
ulated as part of Category 2 pesticides.
Based on  production, the allowable dis-
charge per day is 4 Ib*, or a concentration
of 2.5 ppm based on a  wastewater flow
of 135 gpm* at the specific manufacturing
plant tested.  Preliminary  studies  con-
ducted by the manufacturer have shown
that oxidation with sodium hypochlorite is
effective  in destroying   bentazon in  the
wastewater. Hypochlorite reacts with ben-
tazon as shown below.
        'CH(CH3>2
        SO,  HOO*
NCH(CH3)2
                                                        (*)lb x 0.454 = kg; gal. x 3.785 = L.

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Excess  hypochlorite  is  destroyed  with
sodium  bisulfite before the wastestream
reaches the biotreatment facility.
  The  large  excess of  hypochlorite in-
creases  the salt  content of the  waste-
water,  and free chlorine and bisulfite can
also be pollutants.  Other organic materials
may react with hypochlorite to form prod-
ucts which may be harmful.
  While the goal  of the treatment  is  to
reduce bentazon to the 4  Ib/day level,
consideration must be  given to the prob-
lems  of  the  generation  of  additional
pollutants  and  requirements   for  com-
patibility with a downstream biotreatment
plant.

Treatability Studies
  Samples  of  bentazon  manufacturing
wastewater  were  obtained   from  the
manufacturer.  Figure 1  is a diagram of the
plant   treatment   system,  showing  the
sampling  points.  Evaluation was  carried
out on the sample collected after the car-
bon unit (Sampling Point 2  in Figure 1).
  Preliminary  treatability studies  by the
manufacturer  have  shown  that  a 40:1
molar  excess  of  hypochlorite  over ben-
tazon was necessary at 24°C and pH 6.0
to achieve a 95%  reduction in bentazon
level. This  large HOCI excess was required
at both acid and alkaline pH. Since hypo-
chlorite  is  not selective  in  its  action,
wastewater containing other amine bod-
ies, by consuming additional reagent, will
require an  even larger hypochlorite excess
(90:1). Note that  the  desired conversion
was achieved at the expense of increasing
the salt content of the wastewater.
  Excess hypochlorite must be destroyed
before the  wastestream reaches the water
biotreatment facility. Sodium bisulfite has
been used  successfully in eliminating free
chlorine, although  it has been shown that
this  reagent also   regenerates  bentazon
from its N-chloro analog.
                              NCH(CH3)2
A  technique   must  be  developed  for
destroying  free chlorine which will  not
regenerate  bentazon because it interferes
with the operation of the biosystem.
  Free chlorine and excess bisulfite  can
be  pollutants.   Other  organic  materials
react with  hypochlorite to  form products
which may also be harmful. This  is  par-
ticularly true for amines which can form
                                                                          Plant
                                                                          Sources
     (*) One of three samp/ing points.

Figure 1.    Wastewater treatment system.


potentially  toxic and explosive  N-chloro
compounds.
  The bentazon  waste  stream  entering
the activated carbon  unit is  expected to
have  the following   characteristics:   pH,
1.0-2.0; temperature,  ambient; and  ben-
tazon content, 50-300 ppm.
  The carbon columns step in the current
treatment process removes 50-75% of the
bentazon  and about  95%  of the  mono-
chlorobenzene   from  the   wastewater.
Therefore,  the bentazon  content  of the
wastewater used in this  study should be
between  38 and 150  ppm, based on the
manufacturer's information.
Treatment of Standard
Bentazon  Solutions with
Aqueous Sodium Hypochlorite
  A standard  solution  containing  55.2
ppm (within  the 38-150 ppm  range ex-
pected) bentazon was made up in 1 L of
water.  This solution, in 100 ml portions,
was used for preliminary experiments. In-
itially, a 200-fold excess of hypochlorite (2
moles  hypochlorite to 1 mole bentazon)
was utilized,  timed aliquots of 10 ml were
"quenched"  in sodium bisulfite (bisulfite)
to neutralize  excess hypochlorite, and the
bentazon was determined by HPLC. Five
separate experiments were performed:
  (1) Reagent  blank  (100  ml  water).
      Treated directly with hypochlorite.
  (2)  Dilution  blank.  Bentazon solution
      with water in place of  hypochlorite
      and bisulfite.
  (3)  Neutral  pH.  Bentazon  solution
      treated directly with hypochlorite.
  (4)  Acidic  pH.   Bentazon solution  ad-
      justed to pH  4 with HCI before addi-
      tion of hypochlorite.
  (5)  Basic  pH.  Bentazon  solution  ad-
      justed to pH 10 with NaOH  before
      addition of hypochlorite.
  In all cases,  the bentazon  disappeared
within 10  min,  but  was  "regenerated"
after a period of time, slowly disappearing
again from solution.  This suggests that a
rapid   reversible reaction  occurs  which
slowly equilibrates, followed  by the  less
rapid  formation of  the  final  treatment
product.  The  disappearance  of bentazon
was more rapid  from  neutral and  acid
solutions.
  In a subsequent experiment, a 100 ml
portion of standard bentazon solution was
treated with a 333-fold  excess of  hypo-
chlorite,  aliquots were removed over time
and analyzed. No  bentazon was found in
any  of  the  aliquots  (from  just  after
hypochlorite addition up to 1 hr later).


Treatment of Bentazon-
Containing Wastewater
  Aliquots of wastewater taken after the
carbon  unit  were treated as  described
below.

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A. Hypochlorite: 333-fold excess
        Exp. No.
          BG-10
          BG-19
          BG-16
          BG-17
          BG-3
pH
 1
 2
 3
 4
 6
700
B. pH =1.5
                               Excess
                               Hypo-
                              chlorite/
                Exp. No.       Benta-
     Temp.   20-28°C  3-7°C     zon
             BG-2,10  BG-20    333:1
             BG-11             167:1
             BG-12    BG-21     83:1
              BG-13             17:1

333-Fold Excess Hypochlorite
at pH 1 and 6
  Timed aliquots were taken after the ad-
dition of hypochlorite to 100 ml portions
of the  wastewater and  quenched  in  a
slight excess of bisulfite. A second aliquot
was  taken immediately and quenched in 3
fold  amount of bisulfite to test the effect
of excess bisulfite on bentazon concentra-
tion.
  With  the use of  a 333-fold  excess of
hypochlorite at pH 1, the bentazon disap-
peared almost completely within 10 min.
The  amount of bisulfite excess made little
difference in  the  amount  of  bentazon
detected.  At  pH 6,  the bentazon disap-
peared  more  slowly: even  after 60  min,
more than 55% remained.  Some of the
samples were not analyzed on the day the
experiment was run  but  at  a later date.
The  values obtained by HPLC were higher
by about  25% for these samples.  How-
ever, in a later re-analysis of the pH 1.5
samples,  all  remained  at  zero or  low
values. It is possible that the large amount
of flocculent  material in the quenched ali-
quots may interfere in the analysis, or that
some  bentazon  is  regenerated  upon
standing under certain conditions.


333-Fold Hypochlorite Excess
at pH 2, 3,  and 4
  Timed aliquots were taken from each of
three 100-mL portions of wastewater ad-
justed to pH  2, 3, and 4 with 10N NaOH
and  then  reacted with  a 333-fold excess
of hypochlorite. All aliquots were analyzed
by HPLC  after quenching with  bisulfite.
The  results are shown in Figure 2. The
reaction at pH 2 was nearly identical to
that  at pH 1.5; i.e.,  bentazon disappeared
immediately  and  was  only  observed in
very  small amounts or not at all up to 3
                 50

               Q)
              DC

               O
               8
                 20
333-Fold Excess Hypochlorite

—^— Beginning pH = 3

	Beginning pH - 4

	Beginning pH = 2
                      5 10  20  30
                            60
                                                    120
                             180
                                                     Time, min


              Figure 2.    Bentazon-containing wastewater treated with hypochlorite at pH 2, pH 3, and pH 4.
               hr. The reaction at pH 4 was more similar
               to the previous reaction carried out at pH
               6: some bentazon disappeared early in the
               reaction  (10 min),  but about 70%  re-
               mained even after 3 hr. The pH 3 reaction
               showed the bentazon concentration drop-
               ping off rapidly at first and then decreas-
               ing at a much slower rate to a concentra-
               tion of about 20% after 3 hr. Another ali-
               quot was taken at 5 hr: the bentazon con-
               centration was  still about  19%.
                There was a distinct change in the reac-
               tion between pH 2 and  pH 3. The mech-
               anisms involved in this  treatment are  not
               known. The reaction mixture has been
               titrated at the end of 3 hr and still con-
               tained excess hypochlorite.  The physical
               appearance  and  amount  of insoluble
               material varied with time and conditions.

               Variations of Temperature and
               Hypochlorite Added to
               Wastewater
                The effects of variations in temperature
               and  hypochlorite addition  were evaluated
               in two experiments:  in  the first, 100  ml
               aliquots were treated  with a  333-fold  ex-
               cess of hypochlorite at room temperature
               and  near 0°C; and in the other, 100  mL
               aliquots were treated with a  83-fold  ex-
               cess of hypochlorite at room temperature
               and  near 0°C. When a 333-fold excess of
               hypochlorite was added, the bentazon dis-
               appeared rapidly and  was essentially gone
               in 5 to 10 min. When  this  reaction  was
                                        carried out at near zero (3-7°C), the reac-
                                        tion  proceeded  at a  slower  rate  but
                                        resulted in the nearly complete removal of
                                        bentazon.  This  indicates  that  bentazon
                                        can be removed at temperatures as low as
                                        freezing.
                                          The  low temperature reaction using an
                                        83-fold excess of hypochlorite proceeded
                                        much more slowly than the ambient reac-
                                        tion. In fact, at all points studied,  more
                                        bentazon was detected than was originally
                                        present. In trials  using a  167-, 83-,  and
                                        17-fold hypochlorite excess at room tem-
                                        perature, bentazon levels remaining in the
                                        reaction mixture were  measured at levels
                                        5 to 10 times  greater than was originally
                                        present. The early appearance of what ap-
                                        pears to be  additional  bentazon  in ex-
                                        periments  using  less than 333:1 addition
                                        of hypochlorite is striking. There is no ex-
                                        planation for this  phenomenon.
                                        Stepwfse Addition of
                                        Hypochlorite to  Bentazon-
                                        Containing Wastewater
                                          Several  additional   experiments were
                                        performed to determine more about  the
                                        nature of the hypochlorite/bentazon reac-
                                        tion. First, half the amount  necessary for
                                        complete reaction was added (167-fold ex-
                                        cess), and  the  reaction followed  for 30
                                        min. Another 167-fold  hypochlorite excess
                                        was added, and the reaction followed for
                                        another  30  min. The  same  behavior was

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observed as before—the 167-fold excess
of hypochlorite  resulted in  an apparent
300%  increase  in  bentazon  by  HPLC.
However,  the second  167-fold  addition
caused  the  reaction  to  behave as  if a
333-fold excess had been added originally;
that  is,  the  bentazon disappeared almost
completely within a few minutes.
  In   another  experiment,  hypochlorite
was  added  to  the  bentazon-containing
wastewater  in   increments   every  5
minutes. Aliquots were taken before each
new  hypochlorite addition. The bentazon
increased as expected with each addition
until  a  critical point  was reached,  then
rapidly fell off. This  point was between
245 and 370 equivalents of  hypochlorite.
Interestingly, the characteristic  purple col-
or of this experiment did not disappear
until  after the  bentazon was gone.
  100
   80
   60
 I 40
 I
 S 20
 03
                           —-— 200-fold excess hypochlorite

                           	266-fold excess hypochlorite

                           	— 500-fold excess hypochlorite
\  -,
         10  20  30
                   60
                                                     720
                                                                              780
                                                                                Time, min
Fine-Tuning of Hypochlorite
Addition  to Bentazon-
Containing Wastewater
  To  determine  more  precisely  the
amount of hypochlorite needed to remove
bentazon from the wastewater in a rea-
sonable  amount   of  time (10-30  min),
several  concentrations were  investigated
between 167-  and 333-fold excess hypo-
chlorite:  200-fold  excess hypochlorite to
correspond to 200-fold excess studied on
standard bentazon and  266-fold  excess
(20% less than 333-fold  excess). An ex-
periment was also carried out using  a
500-fold  excess  (50%  greater  than
333-fold  excess).   The experiments were
carried out just as previous experiments:
timed aliquots were taken, quenched with
bisulfite, and  analyzed  by  HPLC.  The
results of these experiments are shown  in
Figure 3.
  It  can be seen that  neither  the 200- nor
266-fold excess hypochlorite was as effec-
tive  as the  333-fold excess  in removing
bentazon from wastewater. The 500-fold
excess was,  however, quite  effective  in
removing 98% of the  bentazon in a 5 min
reaction time.
  The timed  aliquots  were  analyzed by
HPLC and also qualitatively by Thin Layer
Chromatography (TLC). At the end of the
experiment,  a  portion  of the reaction mix-
ture was extracted with methylene chlo-
ride  and  the  extract  analyzed  by TLC.
Dichlorobentazon  was seen  in  all three
reaction  mixtures, the largest amount  in
the  experiment  using  266-fold  excess
hypochlorite. This reaction also contained
the  largest variety of compounds seen by
TLC.
Figure 3.    Addition of different hypochlorite excesses to bentazon-containing wastewater.
Scaled-Up  Treatment of
Bentazon-Containing
Wastewater  with Hypochlorite
  Using  the  most favorable  conditions
from previous experiments (low pH with
addition of 333-fold excess hypochlorite),
the reaction was  scaled  up to  1  L  of
wastewater. An  aliquot was taken before
addition of hypochlorite, immediately after
hypochlorite addition, and  again after  10
and 30 min. The  entire reaction mixture
was then  quenched with bisulfite. A final
aliquot was taken 10  min after  bisulfite
addition. The  results are in Table 1.  The
removal of  bentazon from solution  was
essentially the same as the corresponding
100 mL reaction.
                                 Identification  of
                                 Dichlorobentazon as Reaction
                                 Product of Hypochlorite
                                 with Bentazon
                                   The major product of hypochlorite with
                                 bentazon was  initially  assumed  to  be
                                 dichlorobentazon based on TLC studies of
                                 the reaction.  To  positively identify  it as
                                 the reaction  product,  authentic bentazon
                                 was  treated  with hypochlorite, and the
                                 product isolated and characterized.
                                   Preliminary  experiments with  authentic
                                 bentazon showed  that under acidic condi-
                                 tions dichlorobentazon was seen 10 to 162
                                 min after hypochlorite addition.  Bentazon
                                 was  extractable with  methylene chloride
                                 from neutral  and acidic,  but  not basic.
 Table 1.    Larger Scale Treatment of Bentazon-Containing Wastewater with Excess Hypochlorite
Bentazon
Add hypochlorite





Add bisulfite



Time
min
0
1
10

30

30


40
Bentazon
Remaining, %
100
23
1.3

—

_


-
Temp
°C
25
27 to 29. 5
30

30

31


32
Reaction

Color changes
Orange, flocculant
material
Reddish material
separates out
Oil globules
adhere to flask
walls


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solutions.  After testing  on a  small-size
reaction, dichlorobentazon  was  isolated,
using an extractive procedure.
  Infrared  spectra  were generated  for
bentazon, dichlorobentazon, and isolated
product using  the  Nicholet  FT-IR.  The
lack of  resolution in  the  spectrum  of  the
product, and the complexity and similarity
of bentazon and dichlorobentazon spectra
made identification impossible.
  The same  materials were subjected to
low  and   high  resolution  mass  spec-
trometry.  The  major treatment product
was shown to be the aromatic substituted
dichloro analog  of  bentazon.  The spec-
trum so generated was compared  to  the
spectrum  of dichlorobentazone standard
(supplied by the manufacturer). A com-
mon fragmentation pattern was observed:
m/e 308 (molecular  ion), 264, 229,  and
187.  Peak-matching  the  308  signal from
the   treated   bentazon   spectrum   gave
a   mass   of  307.9787,  best   match
doHuNjOaSCU—empirical   formula  of
dichlorobentazon. Thin  layer  chromatog-
raphy and  infrared spectrometric analysis
of the HOCI-treated extract confirmed this
structure assignment.
  The presence of  a  second  treatment
product was  indicated.  This material gave
rise  to a mass signal at 282 (281.9303  -
C12H4SO2CI2). The  absence of a nitrogen
atom suggested the possibility that this
specie may be a fragment ion.
  Characterization  of other  compounds
was not undertaken.

Daphnia B/oassay
  Solutions of bentazon and dichloroben-
tazon were subjected to toxicity testing
with Daphnia magna. The test procedure
used  is  an  EPA-approved  acute  static
bioassays  procedure. The bentazon was
not toxic at the levels studied: 50,  5, and
0.5  ppm.  The  dichlorobentazon showed
toxicity at all levels,  and was quite toxic
at 50 ppm.

Cost Estimate
  A cost estimate,  prepared for the HOCI
treatment of bentazon wastewater for  the
specific site  sampled,  showed the esti-
mated capital cost  to be $1.3 million and
yearly operating costs to be $3.6 million.
  The following assumptions were used
in preparing the estimate:
  (1) 333-fold excess of  HOCI (2 HOCI/I
      bentazon)
  (2) 100 ppm .bentazon  in wastewater
  (3) 30 min residence time
  (4) Use of  NaHS03 to  neutralize half of
      added HOCI
  (5) Operate 270 days/yr
  This estimate  does not take into con-
sideration  the  manufacturer's  comment
that heat  exchangers would be  needed
that would add  $1  million  to  the  capital
costs.  Installation of  a  storage tank  for
hypochlorite  would  require  heat   ex-
changers to cool the hypochlorite to pre-
vent decomposition. Because of the cor-
rosivity of the  hypochlorite,  these  ex-
changers must  be made of carbon steel
shell with  titanium tubes.
Results and  Conclusions
  The  following  results were  obtained
from this hypochlorite treatment study of
bentazon-containing wastewater.
  (1) The analytical  HPLC method  was
     used  successfully  to  monitor ben-
     tazon levels in wastewater samples.
  (2) Assuming  a  stoichiometry  of  2
     equivalents  hypochlorite  to  1  equi-
     valent bentazon,  the  excess hypo-
     chlorite (5% aqueous  sodium hypo-
     chlorite) required for complete ben-
     tazon removal was between 245 and
     370-fold.
  (3) Bentazon  disappeared   rapidly  as
     long as the wastewater pH was 2 or
     below with the use of a 333-fold ex-
     cess of hypochlorite. A higher initial
     pH resulted in incomplete bentazon
     removal.
  (4) The effect of temperature  on the
     reaction was  of  secondary impor-
     tance  over  the  temperature range
     which  the wastewater   would  en-
     counter.  Water  temperatures
     (3°-7°C) may slow the reaction a lit-
     tle (the smaller the excess of hypo-
     chlorite, the greater the slowing ef-
     fect), but with a 333-fold  excess the
     effect was very small.
  (5) The mode  of addition   of  hypo-
     chlorite had no effect on the treat-
     ment process. As  long as the  cor-
     rect excess was added,  whether all
     at once or in portions, the  final
     result was the same.
  (6) Dichlorobentazon   was  the major
     product of the reaction of bentazon
     with excess hypochlorite in acidic
     solutions. Other products have not
     been identified.
  (7) Bentazon was essentially nontoxic
     to Daphnia magna  up  to  at least 50
     ppm.  The major treatment product
     of bentazon, dichlorobentazon, was
     toxic to Daphnia magna  at 50 ppm,
     with some toxicity  also at 5 and 0.5
     ppm.
  (8) The  estimated   unit   cost   of
     hypochlorite   treatment   was
      $0.0714/gal. Annualized costs were
      estimated at about $3.6 million/yr.

Recommendations
  The experimental findings have  led to
the following possibilities for future work.
  (1)  Other  treatment  approaches could
      lead to a system with a product less
      toxic than bentazon or upgrade cur-
      rent treatment to produce less ben-
      tazon in wastewater.
  (2)  Other  treatment  conditions  could
      reduce  the hypochlorite  excess re-
      quired for complete  bentazon  re-
      moval  (e.g., catalysis, nature of the
      acidic agent).
                                                                                   U. S. GOVERNMENT PRINTING OFFICE: 1985/559 111/10831

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     R. I/I/. Handy, D. J. Smith, and D. A. Green are with Research Triangle Institute,
       Research Triangle Park, NC 27709.
     Robert V. Hendriks is the EPA Project Officer (see below).
     The complete report, entitled "Treatment Technology for Pesticide Manufacturing
       Effluents: Bentazon," (Order No. PB 85-176 816/AS; Cost: $10.00, subject to
       change) will be available only from:
            National Technical Information Service
            5285 Port Royal Road
            Springfield, VA 22161
            Telephone: 703-487-4650
     The EPA Project Officer can be contacted at:
            Air and Energy Engineering Research Laboratory
            U.S. Environmental Protection Agency
            Research Triangle Park, NC27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
           OC0C329    PS
           U  S ENVIR PROTECTION  AGENCY
           REGION  5  LIBRARY
           230 S DEARBORN  STREET
           CHICAGO               It-   £0«04

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