United States
                                 Environmental Protection
                                 Municipal Environmental Research C*
                                 Cincinnati OH 45268
                                 Research and Development
                                 EPA-600/S2-82-028  Sept. 1982
Project Summary
                                 Collection  and  Treatment of
                                 Wastewater  Generated by
                                 Pesticide  Applicators
                                 Kenneth F. Whittaker, John C. Nye, Ronald F. Wukash, Robert G. Squires,
                                 Alan C. York, and Henry A. Kazimier
                                   A research project was conducted
                                 to develop a system for the control of
                                 pesticide-contaminated wastewaters
                                 generated by pesticide applicators.
                                 The problem was approached in three
                                 phases. First, the practices that are
                                 currently used to handle  pesticide-
                                 contaminated wastewaters were eval-
                                 uated, followed by the development of
                                 a system for collecting them. Finally, a
                                 treatment plant was developed to
                                 remove pesticides from the contami-
                                 nated wastewaters and to produce
                                 high-quality effluents.
                                   The treatment plant is well suited for
                                 treatment of pesticide formulations of
                                 varying  concentrations. Much of the
                                 toxic material can be removed during
                                 the  first coagulation stage, which is
                                 followed by activated carbon absorp-
                                 tion to remove most of the remaining
                                 pesticides. This low-cost,  low-tech-
                                 nology  system seems particularly
                                 appropriate for small-scale field op-
                                   This Project Summary was devel-
                                 oped by EPA's Municipal Environ-
                                 mental Research Laboratory, Cincin-
                                 nati, OH, to announce 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).

                                  The disposal of pesticide-contami-
                                 nated wastewaters has attracted na-
                                 tional attention during  the past two
                                 decades. Considerable  environmental
                                 degradation has been caused by the im-
                                 proper disposal of  pesticide-contami-
                                 nated wastes. Current Federal regula-
                                 tions on the control and disposal of toxic
                                 wastes, along with existing pesticide
                                 certification programs,  will have far-
                                 reaching impacts on how pesticide ap-
                                 plicators dispose of wash water used to
                                 clean  application equipment. In an
                                 effort to provide applicators with an
                                 alternative method for handling the
                                 wastewater, a low-cost collection and
                                 treatment system was developed.
                                   The objectives of the research were:
                                   1. To evaluate the practices used by
                                     pesticide applicators to control
                                     wastewater generated during the
                                     cleanup of application equipment
                                   2. To construct a system to collect
                                     the wastewater  generated by
                                     pesticide applicators.
                                   3. To design, construct, and evaluate
                                     a wastewater treatment plant
                                     capable of removing pesticides
                                     from  the wastewaters generated
                                     by pesticide applicators.

                                 Wastewater Control Practices
                                   Pesticide applicators  have used
                                 numerous techniques to dispose of the
                                 wastewaters that are generated during
                                 cleanup of equipment. The triple rinse
                                 procedure  for  cleaning  pesticide con-
                                 tainers, which is recommended by the
                                 U.S. Environmental  Protection Agency
                                 (EPA), is generally followed when
                                 cleaning a spray system. The 100 to 400

L of wastewater used each time a plane
is cleaned  is usually dumped in the
cleanup area. A few applicators haul the
dilute rinsewater back and spray it on
the target area.  As fuel costs increase,
this practice is seldom followed. More
common disposal practices involve
dumping  of wash water into a holding
pond  or  gravel trench. Research is
underway at Texas A&M and at Iowa
State  to provide applicators with evap-
orative disposal practices. The residue
left after evaporation of the  water
usually accumulates in the evaporative
disposal systems.  The ultimate fate of
the pesticide is  unknown.
  The cleanup practices used by aerial
applicators vary, but several consistent
practices were observed. The application
equipment is thoroughly cleaned about
once a week by most applicators. The
spray system and hoppers are usually
washed daily.  Most applicators try to
organize  their daily operations to that
insecticides  and fungicides are applied
first,  and herbicide applications are
made during the latter part  of the day.
After  herbicides are applied, the equip-
ment  must  be  thoroughly cleaned to
avoid  any carryover to the  next spray
job. This management practice allows
the applicator to minimize the amount of
wastewater  that is generated each day.

Wastewater  Characteristics
  Wastewater from an aerial applicator
at Delray Beach, Florida, was obtained
and analyzed for total suspended solids
(TSS), suspended  volatile solids (SVS),
chemical oxygen  demand (COD), and
pH. Nineteen-liter buckets were used to
collect the  wastewater.  Samples  in-
cluded the pesticide dumped out of the
hopper, the  wash water used to clean
the spray boom, the wastewater used to
clean the aircraft hopper,  the wash
water from the surface of the plane, and
a composite sample of all  the wash
water and wasted pesticides that would
be generated during the cleanup of the
equipment.  Results are presented in
Table 1.
  The highly variable concentration of
pollutants represented  a  severe prob-
lem in developing a treatment system to
handle the  wastewater. The different
types of pesticides (i.e.,  wettable
powders, emulsifiable concentrates,
granules,  soluble salts,  etc.) also
challenged most treatment options.

Wastewater Collection
  A simple wastewater  collection
system was installed at Monon, Indiana.
Table 1.    Volume and Characteristics of Wastewater Generated by Aerial Pesticidt
 Total   Soluble   pH     TSS      SVS
(mg/Li    (mg/L)         (mg/Lj   (mg/L)
Pesticide formulation
  in hopper

Rinse water used to
  clean spray boom

Wash water used to
  clean hoppe'r

Wash water used to
  clean aircraft

Composite wastewater
   5-20    60,000
 40-WO    13,000     9,600   6.5   11.600   8.90C
  20-40    88,500     5,000   7.0   18,000  14.00C
 75-200     1,200       500   7.5      600     35C
900    6.9     1,100
The existing concrete pad was modified
to divert all wastewater to one corner of
the pad, where a sump was installed
(Figure  1). Wastewater was pumped
from the sump to a steel storage tank.
  At 1980 prices, a  collection system
would cost an applicator about $1,600
for a 15- x 15-m concrete slab with a
sump, $150 for a chemically resistant
sump purnp, and $500 for a 2,000-L
above-ground storage tank. All waste-
water is stored in one composite tank
with this type of collection system. Rain
water is also collected unless provision
can be made to divert the runoff. With
this simple collection system,  a treat-
ment system is required that can handle
the wide variety of pesticides  used by
aerial applicators.

Treatment System
  Based on  the  results for  several
treatment options  analyzed  in the
laboratory, a pi lot treatment system was
developed  consisting of coagulation/
flocculation/sedimentation,  filtration,
oil coalescence, and  activated  carbon
absorption (Figure 2). After initial tests,
the filters  and oil  coalescers were
removed,  and the  pilot  plant was
mounted on a small trailer. Thef iltration
step was  discontinued because the
fabric  filter  and diatomaceous earth
filters did not significantly improve
effluent  quality, and  the oil coalescer
plugged too quickly to be practical.

Coagulation Studies

 mentation process  was  expected to
 reduce the pesticide concentration to its
 water solubility level or below. Two-liter
                 Figure 1.  Sump installed in one
                           corner of a concrete pad
                           to collect all wastewater.
                 Figure 2.  Pilot plant treatment system
                           for wastewater from pesti-
                           cide application equipment.

                 jar tests were conducted on synthetic
                 wastewater solutions containing (1
                 carbaryl (Sevin),* a widely used N-alky
                 carbamate insecticide, (2) malathior
                 (cythion), a commonly used phosphoro-
                 dithioate insecticide, and (3) metribuzir
                 (Sencor), a triazine herbicide.
                 "Mention of trade names or commercial products
                  does not constitute endorsement or recommenda-
                  tion for use

  Even though alum was chosen as the
coagulant for this study, it should be
noted that in  preliminary studies,
equivalent doses of ferric chloride were
equally  effective. When aluminum or
iron salt coagulants are used, sufficient
alkalinity  must  be present  in  the
solution to allow a complete reaction.
Approximately 0.85  mg/L of alkalinity
as CaCo3 must be present for each mg/L
of alum reacted. Sufficient  alkalinity
was maintained by adding NaOH to the
solution. Effective alum coagulation is
limited  to the pH range of 6.5 to 8.0.
Only one of the collected samples was
outside  this pH range, and  this was
easily adjusted  to the  proper level by
adding NaOH.
  After  a  series of  2-L jar tests was
conducted,  pilot-scale studies were
begun.  The pilot  plant (Figure 3)
consisted  of a  380-L  tank,  0.7 m in
diameter and 1.1 m high. Three taps
were  located on the tank: two on the
side (approximately 0.5 and 0.7 m below
the top of the tank) and one at the bottom
of the tank. The side taps were used to
draw  off supernatant after settling. A
variable-speed  mixer was  mounted
above the tank with a  10-  x 30-mm
paddle  blade mixer  inserted into the
tank to a depth of approximately 0.7 m.
Flocculation of the  suspended  solids
(SS) was achieved   by adding  alum,
alkalinity,  and an anionic polymer to
350-L  batches of  wastewater and
mixing at full speed (about 250 rpm) for
2  min.  The variable-speed mixer was
slowed to 30 rpm for 30 min to build the
large floes that would settle rapidly (in
less than  1 hr)  when  the mixer was
stopped (see Table 2).  After 1  hr, the
solids settled 0.5 m, and a transparent
supernatant was obtained. Little addi-
tional settling was observed after 1  hr.
  Since the coagulation/flocculation/
sedimentation  treatment system pro-
duced a sludge  after each treatment,
studies  were conducted to determine
the effect of this buildup of sludge solids
on the treatment of subsequent batches.
To conduct this test, wastewater was
added to the settled sludge. The solids
concentration of the mixture  ranged
from an initial 2,000 to 20,000 mg/L
TSS after 10 batches  of wastewater
were  treated. At the  higher  solids
concentration, settling took longer (up
to 90 min), but the solids concentrations
of the supernatant was less than  40
mg/L TSS. Above 15,000 mg/L TSS,
alum addition was unnecessary. Large
floe formed and settled with only the
addition of 1 mg/L anionic polymer. The
 HT\  Holding Tank

C  J  Pump
 fCV  Flow Control Valve
[WM] Water Meter

      3 Way Selector Valve                   Activated Carbon
                                          Absorption Columns
[pt~i]  pH Adjustment
      Sludge Discharge

  S   Sampling Point


  [22  Liquid Level Control

Figure 3.   Schematic diagram of the pesticide treatment plant.
 samples  tested  in  this experiment
 contained the wettable powder formu-
 lation of carbaryl.
  After the successful removal of
 wettable powder formulations such as
 carbaryl, the next phase was to analyze
 emulsion removal. Initial jar tests were
 performed on tap water solutions of
 malathion  at  a  concentration of 200
 mg/L (water solubility, 145ppm). Alum
 doses  of  100 mg/L  or greater (with
 anionic polymer) gave excellent  super-
 natant quality. The effects of varying the
 malathion dose at a constant alum dose
 (100 mg/L) and 1 mg/L anionic polymer
 are illustrated as follows:
Table 2.    Settling Rate  of Waste-
           Treated with Alum
Settling Time
  Based on these results, full-scale
tests were conducted using field samples
of wastewater mixed with previously
settled alum sludge and sufficient
malathion formulation to give 180 to
200 mg/L of the pesticide. With an SS
concentration of 24,000 mg/L, it took 60
to 90 min for the solids layer to settle 0.7
m. The supernatant malathion concen-
tration was 35 mg/L.  Studies  of  tap
*The sample taps were located 0.5 and
 0.7 m below the surface of the tanks,
 which were 1.1m deep.

water with malathion added were less
successful, yielding  a supernatant
concentration of 55 mg/L. Later  tests
on a solution with lower SS concentra-
tions showed a malathion reduction
from 400 to 41 mg/L after  1 hr of
settling. Increasing alum dosages  up to
500 mg/L did not improve performance.
As  the SS increased to near  50,000
mg/L in  the sample, so did the mala-
thion concentration of the supernatant,
reaching as high  as 81 mg/L in one
case. This solution of wastewater was
diluted to 12,000 to 15,000 mg/L SS;
200 mg/L of malathion was then added
along with alum and anionic polymer.
Settling  after  coagulation reduced
malathion concentration to 27 mg/L.
No  change in malathion concentration
was observed after 18 hr of  settling.

Subsequent coagulation studies on
solutions of widely differing SS concen-
trations showed  that the 12,000 to
15,000 mg/L concentration range was
the maximum that could be effectively
treated with our system. Higher concen-
trations did not settle below the bottom
tap after 45 to 60 min  of settling.
  Later attempts to use the  standard
alum coagulation  procedure  on  a
mixture  of wettable  powders  and
emulsions collected  at the Purdue
University farm were  completely  un-
successful, even at greatly increased
coagulant  doses,  with  and  without
polymers. Several  alternative tech-
niques, including  acid cracking of the
emulsion, were likewise unsuccessful.
The difficulties seemed to arise from the
presence of a wetting agent added to the
mixture. Addition  of calcium  salts
(approximate calcium to  wetting  agent
molar  ratio of 2:1) destabilized  the
emulsion and made it amenable to alum
coagulation. Another  field sample
collected sometime  later also required
the addition of calcium salts. In this
case, 0.5 to 1 mg/L of Ca (introduced as
CaCI2) successfully destabilized  the
  In the next series of tests, metribuzm,
a  soluble  herbicide, was added to
wastewater and mixed with resuspen-
ded alum sludge. Some dissolved metri-
buzin was removed by coagulation. This
removal  is especially  apparent in the
three lowest concentrations  shown  in
TableS. One possible explanation is that
previously settled emulsified material,
when  resuspended,  may have  con-
tributed  to  a  partial  extraction and
hence removed some  of the dissolved
organic compounds from solution. This
explanation is  consistent with the low
malathion concentrations observed
after coagulation. Since the sludge con-
tains some  emulsifying  chemicals, re-
suspending  the sludge allows them  to
extract some of the dissolved pesticides.
This conclusion was corroborated with
full-scale testing  in which metribuzin
concentrations of 200 and 264 mg/L re-
duced solids levels of 12,000 to 15,000
mg/L to 115 and 140 mg/L, respect-
ively — well below the water solubility
concentration of 1,200 mg/L.
  Based on our observations, jar testing
of solutions should be used to deter-
mine proper coagulant dose  and sub-
sequent settleability.  This  method
should provide  enough information to
indicate when solids wasting is neces-
sary or when additions of calcium salts
are required.
Effect of 200- and 500-mg/L Alum Doses on Metribuzin Removal b)
                 of Metribuzin
of Metribuzin
Carbon Absorption Studies
  The original field-collected  carbaryl
solution had a concentration of 450 to
480 mg/L after coagulation and sedi-
mentation, and  the main hydrolysis
product (naphthol) had a concentration
of 225 mg/L The high carbaryl concen-
tration indicated that a good deal of
suspended material was left in  the
supernatant,  but these tests were
conducted early in the study before the
coagulation procedure  had been opti-
mized. By passing the solution through
the carbon columns  at 3.8 L/min (90
L/mm per m2) with a contact time of 8
mm, the concentrations of both carbaryl
and naphthol were reduced to less than
1 mg/L.
  The capacity of activated carbon to
absorb  pesticides  varies with  the
pesticide  Exhaustion tests  were con-
ducted on malathion and metribuzin to
determine  this capacity. Small glass
columns that  held 25  g carbon were
used  for this test. Figure 4 shows the
breakthrough curve for malathion. The
carbon had absorbed 0.17 g malathion/
g  carbon by  the time  the  effluent
malathion  concentration reached  3
mg/L. The carbon was exhausted (that
is, the effluent malathion concentration
reached the  influent  concentration)
after  0.28  g  malathion/g carbon  had
been  absorbed.  The activated carbon
can absorb more metribuzin. In similar
studies, the exhaustion point for metri-
buzin was found to be 0.43 g  metribu-
zin/g carbon.
  By using 2 carbon columns in series,
it is possible to saturate the first column
with  pesticide before  the pesticide
concentration leaving the second column
reaches the detection limit.
                                 Initial Malathion Concentration
                                   Activated Carbon Column -
                                     25   50   75   100 125 15i
                                      Liters of Malathion Applied

                            Figure 4.  Breakthrough curve for
                                       malathion applied to
                                       activated carbon.

                               The ability of activated  carbon  to
                             absorb a variety of pesticides was tested
                             in  additional samples  in which  mala-
                             thion, carbaryl, and metribuzin were
                             added to wastewater samples that had
                             been collected in the field. Although
                             these initial tests demonstrated that the
                             pilot plant  carbon columns  would
                             absorb  the  pesticide to  below the
                             detection limits, no attempt was made
                             to  determine the exhaustion  point of
                             pilot plant columns. Additional studies
                             determined the exhaustion points for
                             mixed groups of pesticides  and  herbi-
                               The carbon columns on the pilot plant
                             were not  exhausted  in the field test
                             because each column held about 20 kg
                             of carbon. To exhaust them,  about
                             40,000  L of typical wastewater would
                             have to be treated. During our test, only
                             20,000 L of  wastewater could  be

  The pesticide treatment plant described
here  appears to be  well  suited for
treatment of  pesticide formulations of
varying concentrations. A large per-
centage of these toxic materials can be
successfully removed during the first
coagulation stage. The phase  separa-
tion process is followed by activated car-
bon, an adsorbent well known for re-
moving many types of  organic com-
pounds from aqueous solution. This
low-cost, low-technology system seems
particularly appropriate for small-scale
field operation, an area in which accept-
able treatment alternatives are notably
lacking. One possible advantage of the
system  (over and above the  obvious
benefits  of protecting wildlife, crops,
and water supplies) might be the reuse
of the treated water for mixing new
formulations or for washing theapplica-
tion equipment. Such an option would
achieve the goal  of zero discharge.
  The following conclusions are based
on  the test conducted to evaluate the
two-step process to remove  pesticides
from contaminated wastewater:
  1. All pesticide-contaminated waste-
     water that is generated during the
     cleanup of application equipment
     can be combined in one collection
     and  storage system. The widely
     varying  concentrations,  types of
     formulations, and variety of pesti-
     cides can be treated  by the two-
     stage process.
  2. Alum can be used as a flocculant
     to reduce the concentration of
     pesticide in the contaminated
     wastewater  to  below the water
     solubility of the compound. An
     amonic  polymer enhances  the
  3. Activated carbon can remove most
     other pesticides in the supernatant
     of the  first  stage sedimentation
     process. The  capacity of  the
     carbon to absorb the contaminant
     depends on  the chemical structure
     and characteristics of the pesticide.
  4. Particle size filtration and oil coa-
     lescence are not  effective in
     removing pesticides from waste-

  The disposal of the sludge and spent
activated carbon must be  considered.
These problems appear to be manage-
able,  though  more study is needed.
Approximately 20,000 L of wastewater
was treated  in  this study, with an
accumulation of  less than 200 L of
sludge.  Several techniques to encap-
sulate or fix the sludge in a concrete
mixture  were also evaluated with some
success. The carbon can be thermally
destroyed or regenerated by commercial
firms. Other techniques for disposal of
the waste sludge and carbon must also
be  found.  Currently the sludge and
carbon would be considered a hazardous
waste and would require disposal in an
approved landfill.
  The  detection  of  pesticide break-
through during carbon absorption must
also be further evaluated to ensure that
the effluent is free of trace quantities of
  The  full  report was  submitted in
fulfillment of Grant No. R805466010by
Purdue University under the sponsorship
of the U.S.  Environmental  Protection
   Kenneth F. Whittaker, John C. Nye, Ronald F. Wukash. Robert G. Squires, and
     Alan C. York are with Purdue University, West Lafayette, IN 47906; Henry A.
     Kazimier is with Aeronautic Commission of Indiana, Indianapolis, IN 46206.
   Frank Freestone is the EPA Project Officer (see below).
   The complete report, entitled "Collection and Treatment of Wastewater Gener-
     ated by Pesticide Applicators," (Order No. PB 82-255 365; Cost: $12.00,
     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:
          Oil and Hazardous Materials Spills Branch
          Municipal Environmental Research Laboratory—Cincinnati
          U.S. Environmental Protection Agency
          Edison, NJ 08837
                                                                               . S. GOVERNMENT PRINTING OFFICE: 1982/559-092/0521

United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
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