COLLECTION AND TREATMENT OF
WASTEWATER GENERATED BY PESTICIDE APPLICATORS
by
Kenneth F. Whittaker
John C. Nye
Ronald F. Wukash
Robert G. Squires
Alan C. York
Purdue University,
West Lafayette, IN 47906
Henry A. Kazimier
Aeronautic Commission of Indiana
Indianapolis, IN 46206
Grant No. R 805 466010
Project Officer
Frank Freestone
Hazardous Spills Research Division
Industrial Environmental Research Laboratory
Edison, NJ 08817
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does men-
tion of trade names or commercial products constitute endorsement or recommen-
dation for use.
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FORWARD
The U.S. Environmental Protection Agency was created because of increas-
ing public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled land
are tragic testimonies to the deterioration of our natural environment. The
complexity of that environment and the interplay of its components require a
concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solution
it involves defining the problem, measuring its impact, and searching for
solutions. The Municipal Environmental Research Laboratory develops new and
improved technology and systems to prevent, treat, and manage wastewater and
solid and hazardous waste pollutant discharges from municipal and community
sources, to preserve and treat public drinking water supplies, and to minimize
the adverse economic, social, health, and aesthetic effects of pollution.
This publication is one of the products of that research and provides a most
vital communications link between the researcher and the user community.
Pesticide contaminated wastewater presets a threat to the environment
when it is dumped after the cleanup of application equipment. A
coagulation/flocculation/sedimentation process followed by activited carbon
adsorption treatment system was developed and demonstrated under the research
project. The results verify the acceptability of this process.
Francis T. Mayo, Director
Municipal Environment
Research Laboratory
111
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ABSTRACT
Through the cooperative work of the Environmental Protection Agency, the
Aeronautics Commission of Indiana, and Purdue University a research project
was conducted to develop a system for the control of pesticide contaminated
wastewaters generated by pesticide applicators. This problem was approached
in three phases. First, the practices that are currently used to handle pes-
ticide contamination wastewaters were evaluated followed by the development of
a system that could be used to collect the pesticide contaminated wastewaters.
Finally a treatment plant was developed to remove pesticides from the contam-
inated wastewaters and produce a high quality effluent.
During the initial phase of the project it was determined that pesticide
applicators have between 4 and 20 L of pesticides left in the application
equipment when they ave completed a spraying operation. In addition, the wash
water used to clean the application equipment has a high concentration of pes-
ticides. The combined wastewater has as much as 20,000 ing/liter total
suspended solids and 15,000 mg/liter total Chemical Oxygen Demand. Between
100 and 200 L of wash water are generated with the cleanup of pesticide appli-
cation equipment.
In the second phase of the research an existing concrete pad, used by an
aerial applicator, was modified to control and collect all the runoff from the
pad both during the cleaning of the application equipment and following a
rain. All wastewater collected on the pad was pumped into a storage tank.
This storage tank could then be emptied periodically for treatment with the
pilot plant.
A pilot plant was developed to treat the collected wastewater from pesti-
cide applicators. Initially laboratory tests were done to evaluate 3 physical
chemical treatment options. First, a flocculation/coagulation/sedimentation
step was evaluated using alum as the coagulant. Additional studies were done
using filtration and coalescence. A final activated carbon polishing was also
evaluated. The results of this work indicated that flocculation/
coagulation/sedimentation could be used to remove a high percentage of the
pesticides. This step would bring the concentration to the water solubility
of the particular pesticide. It was also found that the filtration and
coalescence steps were much less effective than the flocculation. The super-
natant from the first step was then passed through activated carbon columns.
A hydraulic loading rate of .5L/s-m was determined to be adequate with a
residence time of approximately 15 minutes. Using this design the capacity of
the carbon was approximately 200 mg of pesticide per gram of carbon. The con-
centration of the pesticides in the clear effluent was usually less than 1
mg/liter.
iv
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CONTENTS
Forward iii
Abstract iv
Figures vii
Tables viii
Acknowledgment x
1. INTRODUCTION 1
1.1 OBJECTIVES 1
2. CONCLUSIONS 2
2.1 COLLECTION OF PESTICIDE WASTE WATER 2
2. 2 TREATMENT OF WASTEWATER 3
2.3 SYSTEM DESIGN 3
3. RECOMMENDATIONS 4
4. BACKGROUND 6
4.1 TYPES OF PESTICIDES 6
4.1.1 Pesticide Usage 6
4.1.2 Complexity of Pesticidal Formulation 7
4.2 DISPOSAL OF PESTICIDE WASTE 10
4.2.1 Current Regulations Affecting Disposal of Pesticide
Residues 10
4.2.2 Consideration of Disposal Techniques 13
4.2.2.1 System Requirements 13
4.2.2.2 Practical Considerations 14
4.3 SELECTION OF TREATMENT ALTERNATIVES 14
4.3.1 Thermal Treatment Alternative 16
4.3.2 Biological Treatment Methods 18
4.3.3 Chemical Treatment 19
4.3.3.1 Chemical Oxidation 19
4.3.3.2 Chemical Reduction 21
4.3.3.3 Acid or Alkaline Hydrolysis 21
4.3.3.4 Photolysis 22
4.3.4 Physical Treatment Methods 24
4.3.4.1 Resin Adsorption 24
4.3.4.2 Reverse Osmosis 25
4.3.4.3 Coagulation/Flocculation 26
4.3.4.4 Activated Carbon Adsorption 29
5. SAFETY CONSIDERATIONS 34
6. REVIEW OF EXISTING PRACTICES 37
7. CLEANUP AND COLLECTION SYSTEM 43
8. LABORATORY STUDIES 46
8.1 WASTEWATER CHARACTERISTICS 46
8. 2 LAB EVALUATION OF WASTEWATER TREATMENT TECHNIQUES 48
9. PROTOTYPE SYSTEM 56
9.1 TREATMENT OF FIELD COLLECTED WASTEWATER 59
v
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9. 2 TREATMENT OF FIELD COLLECTED WASTEWATER 68
9.2.1 Flocculation/Sedimentation Treatment of Malathion...68
9.2.2 Full Scale Flocculation/Coagulation/Sedimentation
Studies of Malathion 71
9.2.3 Carbon Studies 72
9.3 TREATMENT OF METRIBUZIN CONTAMINATED WASTEWATER 72
10. SYSTEM ECONOMICS 77
10.1 PLAN 1 — INDIVIDUAL TREATMENTS PLANTS 78
10.2 PLAN 2 — SIX MOBILE TREATMENT STATIONS SERVING 7-9
AERIAL APPLICATORS 80
10.3 PLAN 3 — ONE MOBILE TREATMENT SYSTEM TO SERVE THE 46
AERIAL APPLICATIONS 82
10.4 PLAN 4 — CENTRALIZED TREATMENT FACILITY 83
10.5 SUMMARY OF TREATMENT OPTIONS 85
REFERENCES 86
APPENDIX 91
VI
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FIGURES
Number Page
1 Vinyl sheet used to collect washwater from aircraft in initial
phases of study 44
2 Concrete pad at pesticide mixing area of Garwood Airport in
Monon, Indiana 44
3 Modification in collection pad included installation of a sump
and diversion of all washwater to one corner of the pad 44
4 Langmuir Isotherm plots of the adsorption of carbaryl following
alum coagulation 52
5 Langmuir Isotherm plots of the adsorption of carbaryl following
hydroxide coagulation 52
6 Langmuir Isotherm plots of the adsorption of malathion following
alum coagulation 53
7 Langmuir Isotherm plots of the adsorption of malathion following
hydroxide coagulation 53
8 Langmuir Isotherm plots of the adsorption of alum coagulated
malathion samples on Filtrasorb-400 and WV3 54
9 Carbon adsorption of malathion on columns of Filtrasorb-400
and WV3 54
10 Schematic diagram of pesticide treatment plant 57
11 Pilot plant with mixing tanks, filters, and-carbon columns 58
12 Cuno cartridge filters with 5 and 25 micron filters 58
13 Fabric basket filter with 1 micron screen 58
14 Cartridge coalescers operating at 10 psi pressure drop 58
15 Mixing tanks used for coagulation, flocculation and sedimentation..60
16 Control panel for mixers and pumps 60
17 Frame for filters and pumps in the pilot plants 60
18 Carbon adsorption of malation in 25 gm column of Filtrasorb 400....73
19 Simplified system for treating pesticide contaminated wastewater...92
20 Detail dimensions of float for treatment system 92
21 Collection of pesticide contaminated wastewater in above ground
tank 97
22 Collection of pesticide contaminated wastewater in below ground
tank 97
23 Pesticide wastewater control system 98
24 Pesticide wastewater treatment center 98
via.
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TABLES
Number Page
1 Pesticide Usage (USDA, 1977) 7
2 Pesticide Classification Scheme (Lande, 1978) 8
3 Commonly Used Formulation of Carbaryl and Malathion 9
4 NACA Triple Rinse and Drain Procedure (Shin and Del Porto, 1976)...12
5 Pesticide Oxidation by Ozone 20
6 Removal of Chlorinated Presiticides by Reverse Osmosis 26
7 Effect of Coagulation/Flocculation on DDT Removal (Carrolo, 1945)..27
8 Feric Sulfate as a Coagulent for Pesticide Removal (El-Dib and
Aly, 1977) 28
9 Absorption of herbicides on activated column 30
10 Activated carbon adsorption of chlorinated pesticides 31
11 Carbon adsorption of organophosphate and chlorinated insecticide...32
12 Toxicities of Selected Organophosphate and Carbamate Pesticides....35
13 State Regulations Affecting Aerial Applicators 39
14 Characteristics of Wastewater Samples Collected in Florida 47
15 Hydroxide Coagulation of Wastewater Samples Collected in Florida
Initial COD was 1200 mg/L 49
16 Alum Coagulation of Wastewater Samples Collected in Florida.
Initial COD was 1200 mg/L 49
17 Hydroxide Coagulation of Malathion. 50
18 Hydroxide Coagulation of Carbaryl 50
19 Effect of Alum as a Coagulant for Cerberyl Removal 61
20 Full Scale Treatment of Carbaryl" and Sump Water Using Alum as a
Coagulant 62
21 Flocculation/coagulation/sedimentation for removal of solids
using resuspended sludge 64
22 Pesticide Removal by Pilot Plant Using Aim and Anionic Polymer 64
23 Flocculation/coagulation/sedimentation as a means of a paraquat
removal 66
24 Carbaryl removal by absorption on activated carbon columns
(influent carbaryl concentration 475 mg/L) 67
25 Activated carbon columns for removal of pesticides from sump
water 68
26 Jar test results for malathion 69
27 Jar test evaluating the effect of solids concentration on
malathion removal 70
28 Jar test evaluation of flocculation/sedimentation to remove
various concentrations of malathion 70
Vlll
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29 Jar test evaluation of alum dosage on malathion removal 71
30 Carbon column exhaustion study for malathion 73
31 Jar test evaluation for flocculation/sedimentation removal
of metribuzin 74
32 Effect of alum dosage on metribuzin removal by flocculation/
sedimentation 74
33 Effect of using suspended solids on metribuzin removal by
flocculat ion/sedimentation 75
34 Carbon column exhaustion study for metribuzin 76
35 Distribution of aerial applicators 78
36 Economics of installing and operating a treatment plant for each
applicator 80
37 Economic evaluation of a regional mobile treatment plant 81
38 Economic evaluation of state wide mobile treatment plant 83
39 Economic evaulation of a central treatment plant 84
40 Summary of Alternative Systems for Treatment of Wastewater
from Pesticide Applicators 85
IX
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ACKNOWLEDGMENTS
This work could not have been completed without the cooperation of
numerous pesticide applicators. The personnel of the Southern Crop Service,
Inc. in Delray Beach, Florida were especially helpful in supplying initial
wastewater samples and in explaning the problems facing pesticide applicators
in the Southeastern region of the U.S. ADI Ag Aviation at Monon, Indiana was
extremely helpful in allowing us to modify there facilities and collect waste-
water samples. Their leadership in ag aviation in Indiana enhanced the pro-
ject greatly.
The analytical work on this project could not have been completed without
the help of Cheryl Towell and Marianne Arbuckle. The assistance we received
from the Indiana State Pesticide Office in quality control of pesticide
analysis was crucial in evaluating the process.
The completion of this project would have have been possible without the
dedicated efforts of Karen Adams and her colleagues of the clerical staff of
the Agricultural Engineering Department, Connie Harth, Roxandra Evans and Lisa
Houston.
x
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SECTION 1
1. INTRODUCTION
Pesticide applicators are currently faced with a serious problem created
by the management and disposal of the wastewater generated during the cleanup
of application equipment. Most treatment systems such as infiltration pits,
holding ponds, and evaporation ponds, do not provide adequate safeguards to
the environment. Furthermore, no attempt is made to monitor the degradation
of specific pesticides. Several elaborate disposal and detoxification
processes are currently being evaluated, including incineration and other
thermal destruction processes. In order for these more elaborate disposal and
detoxification processes to be effectively utilized a concentrated waste would
be desirable.
1.1 OBJECTIVES
The purpose of this research project was to develop a field applicable
system for containing, concentrating, and removing pesticides from the waste-
water that arises during the cleaning and draining of pesticide application
equipment. In order to achieve this goal, the following objectives were iden-
tified.
1. Evaluation of existing handling, mixing, cleanup and disposal methods
in use by commercial agricultural applicators.
2. Development of an acceptable system to prevent spillage during mixing
and cleaning of application equipment.
3. Development of an economical wastewater treatment system that could
be operated by non-technical personnel and allow for reuse of the
treated effluent.
4. Demonstration of the washing and treatment system for wastewater col-
lected from pesticide applicators.
5. Evaluation of the feasibility and economics of such a treatment sys-
tem.
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SECTION 2
2. CONCLUSIONS
Based on the results of this study it was concluded that the collection
and treatment of pesticide contaminated wastewater generated by aerial and
ground applicators is feasible.
2.1 COLLECTION OF PESTICIDE WASTE WATER
The following conclusions were drawn about the two techniques used to
collect pesticide wastewater.
1. All pesticide waste/ rinse, and wash water can be collected in a sin-
gle storage system. Segregation of the waste into dilute and concen-
trated portions is not necessary for the proposed treatment system.
2. The wash water from the surface of the aircraft does not contain suf-
ficient quantities of pesticide to warrant inclusion in the collec-
tion system/ this minimizing the volume of wastewater storage that is
required.
3. Most pesticide applicators can adequately rinse out the spray system
and wash out the tanks with 100-200 L (25-50 gal) of wash water. The
use of high pressure sprayers makes it possible for smaller quanti-
ties of water to be used in the cleaning of the equipment.
4. The volume of residue left in the tank of pesticide application
equipment may vary from 4-20 L (1-5 gal) depending on the type of
application equipment. These residues cannot be pumped out of the
tank because of current tank, pump, and piping configurations.
5. Rain water which falls on the collection pad should be diverted away
from the storage system. Inclusion of rain water would more than
double the amount of wastewater that would need to be stored and
treated.
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2.2 TREATMENT OF WASTEWATER
A physical/chemical treatment system was developed and demonstrated. The
first step in the system is flocculation, coagulation, and sedimentation. The
supernatant produced from this step is passed through activated carbon to
remove the remaining pesticide. The following conclusions can be made.
1. The sludge that accumulates during the sedimentation phase of the
flocculation, coagulation, and sedimentation process can be suspended
and reused for subsequent wastewater treatment, however the solids
concentration of the mixture should not exceed 15,000 mg/L.
2. Depending on the type of formulation, the physical treatment process
can remove up to 95 per cent of the pesticide material.
3. Activated carbon columns effectively remove the residual pesticides.
The capacity of the carbon is approximately 200 mg of pesticide/g of
carbon. The hydraulic loading rate on the column should be approxi-
mately .6 L/S-m2 (1 gal/min-ft2). Residence times of about 15
minutes are required for pesticide adsorption.
4. The pesticide treatment plant developed in this project is capable of
removing essentially all pesticide from the wash and rinse water.
Residual pesticide concentrations in the water are usually less than
1 mg/L and can be considered safe for reuse as wash water for clean-
ing the application equipment.
2.3 SYSTEM DESIGN
Based on the research described in this report, the following conclusions
can be made:
1. On-site storage of wastewater would require a 3800 L (1000 gal. tank)
for bi-weekly treatment or 11000 L (5000 gal) for annual treatment.
2. The low technology system can be operated by a semi-skilled worker
with approximately eight hours of training.
3. For aerial applicators a mobile treatment plant that could service
all applicators in the state would be the least expensive option. A
central plant could be used if all pesticide applicators are
included.
4. On-site treatment in a small dedicated treatment plant is possible.
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SECTION 3
3. RECOMMENDATIONS
Although the treatment system is well suited for handling pesticide waste
generation from a limited scale agricultural spraying operation, further
evaluations must be made before widespread application of the system can be
expected. The collection and storage of wastewater must be investigated. The
cost of the system and means of financing should be considered. Special funds
for airport improvement might be used for construction of the washing pad and
storage tank. The ground applicator should be able to obtain low cost loans
for installation of a system.
One problem that must be studied is the effect of highly mixed pesticide
solutions on activated carbon adsorption, particularly for large central
treatment facilities where a variety of different pesticide wastes could be
expected. One of the most important phenomena to be studied in this regard is
the displacement, if any, of some pesticides by other more adsorbable ones.
Based on general knowledge of the influent composition, it may be feasible to
predict which compound would be discharged first and test for that specific
compound. Detailed information on the behavior of carbon with combinations of
widely used pesticides will be required before such a method for detecting the
exhaustion of the carbon columns could be used.
Another operational aspect, directly related to the above, is the
development of a simple, low-cost technique for determining effluent quality.
Gas chromatographic investigations may be suitable for laboratory tests, but
such technology is not feasible for field application. Bioassay tests and
spectrophotometrie techniques should be investigated.
No studies have been performed on alternative techniques to dispose of
the treatment plant effluent. Irrigation, discharge to streams or publicly
owned sewage treatment works are possibilities for the central treatment
facility although such means would require careful evaluations of effluent
quality and toxicology. Two options which are particularly attractive for
on-site treatment both involve water re-use, either as a diluent in the make-
up of new pesticide formulations, or as wash water for application equipment.
Although our initial studies indicate that the effluent could be used for
rinsing purposes, evaluations with a number of other pesticides would have to
be carried out before such an alternative could be recommended. Of particular
concern in water re-use as a diluent would be herbicide residue. Minor herbi-
cide contamination during an insecticide application could cause crop damage.
Hence, water re-use would require meticulous quality control.
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Another major problem that must be addressed is disposal of the concen-
trated residues generated during treatment operations, in particular, the set-
tled alum-pesticide sludge and the spent activated carbon. The most suitable
disposal method at this time appears to be containerization of this material
and burial in an approved landfill site. However, there are alternate possi-
bilities that are especially applicable to the operation of a large treatment
facility. In particular, thermal regeneration of the carbon may be possible.
Although it is unlikely that on-site regeneration would be feasible due to the
relatively small amount of carbon used. Several manufacturers are now enter-
ing into contractual arrangements for carbon pick-up and delivery, with subse-
quent thermal regeneration. Such an arrangement should be actively pursued.
Furthermore, thermal destruction of the contaminated alum sludge may be possi-
ble in combination with sewage sludge destruction in multiple hearth furnaces.
Finally, the system must be acceptable to small and large pesticide
applicators. Every effort should be made on the part of regulatory officials
to aid in the implementation of such a system. As a result of recent federal
regulations concerning hazardous waste generation and disposal it is likely
that many operators will cooperate in installing such treatment facilities,
but they must be made aware of their existence and the ease with which they
can be used. In the case of a centrally located treatment facility, the rela-
tively minor effort required for cooperation can be emphasized, while the
advantages of compliance with federal regulations and general environmental
protection should be stressed.
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SECTION 4
4. BACKGROUND
4.1 TYPES OF PESTICIDES
Pesticides are broadly defined as any chemical compound used to destroy
organisms which are considered to be "pests" to man. These chemicals are bro-
ken down into a number of subcategories, usually on the basis of target organ-
ism such as algicides, defoliants, dessicants, fumigants, fungicides, herbi-
cides, insecticides, lampreycides, larvacides, miticides (acaricides), mollus-
cicides, nematocides, plant growth regulations, repellents, rodenticides,
sterilants and synergists. However, this broad chemical spectrum is usually
divided into the three dominant pesticide categories, herbicides, insecticides
and fungicides.
4.1.1 Pesticide Usage
According to the USDA (1977) aerial application of pesticides in 1977
accounted for 65 per cent of all pesticides used on agricultural and forest
lands, a percentage that has been consistent over the past seven years. The
pesticide application industry has sustained an annual growth rate of approxi-
mately 12% during the time period between 1971 through 1977. About 8650 agri-
cultural aircraft were in operation at the end of 1977, treating roughly 180
million acres. Helicopters accounted for 12% of the total number of aircraft,
with the remaining being fixed wing aircraft of various types. The overall
cost of agricultural spraying operations in 1977 was approximately 475 million
dollars, of which the following breakdown can be made:
51.3 per cent for weed control
39.3 per cent for insect control
5.4 per cent for pathogen control
1.8 per cent for nematode control
The volume of pesticide usage for the years 1975 through 1977 is shown in
Table 1.
It should be noted that U.S. sales of synthetic organic pesticides
reached a record high in 1974, which probably contributed to the elevated 1975
usage levels.
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Table 1. Pesticide Usage (USDA, 1977).
Fungicides
Herbicides
Insecticides
1975
1000 's Ibs
126,829
644,575
545,916
per
cent
9.6
48.9
4.5
1976
1000 's Ibs
132,648
557,873
502,083
per
cent
11.1
46.8
42.1
1977
1000 's Ibs
133,364
584,504
545,134
per
cent
10.5
46.3
43.2
4.1.2 Complexity of Pesticidal Formulation
The term "pesticides" encompasses a large class of compounds covering a
broad range of different functions and target organisms. In fact, according
to Lawless et al. (1972) there were, as of 1971, over 550 different pestici-
dal chemicals produced or sold in the United States, and these could be
broadly classified in seven major categories and 40 subcategories (Table 2).
Furthermore, the problem of disposal of excess solutions of these compounds is
further compounded by the number of different formulations in which they are
sold. As of 1976 there were approximately 24,000 different pesticide formula-
tions available for interstate shipment and sale, although this number may now
be somewhat lower in light of current Federal regulations and restrictions on
certain pesticides (Wilkinson, et al. 1978). Furthermore, this does not
account for the large number of formulations that are registered solely for
in-state sale (approximately 2000 in the state of California alone).
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Table 2. Pesticide Classification Scheme (Lande, 1978).
Pesticide Class
1. Phosphorus-Containing Pesticides
Phosphates and Phosphonates
Phosphorothioates and
Phosphonothioates
Phosphorodithioates and
Phosphonod i thioates
Phosphorus-Nitrogen Compounds
Other Phosphorus-Containing
Pesticides
2. Nitrogen-Containing Pesticides
Carbamates
Thiocarbamates
Di thiocarbamates
Anilides
Imides and Hydrazides
Amides
Ureas and Uracils
Triazenes
Heterocyclic Amines
Quaternary Ammonium Compounds
Aromatic Nitro Compounds
3. Halogen-Containing Pesticides
DOT Related Compounds
Chlorophenoxy Compounds
Aldrin-Toxaphene Group
Aliphatic and Alicyclic
Chlorinated Compounds
Aliphatic Brominated Compounds
Dihalogenated Compounds
4. Inorganic and Organometallic
Pesticides
5. Miscellaneous Pesticides
Representative Pesticides
Moncrotophos, Phosphamidon
Fensulfathion, Ronnel, PennCap-M
(microencapsulated methyl)
parathion
Dimethoate, Disulfoton, Dyfonate,
Phorate
Methamidophos
Def
Carbofuran, Aldicarb, Methomyl
EPTC, Molinate
Thiram
Propanil
Captafol
Diphenamide
Chloroxuron
Cyanazine, Simazine
Amitrole
Paraquat
PCNB, Dinoseb
Chlorobenzilate
2, 4, 5-T
Endrin
D-D, BHC (Lindane)
DBCP
Dicamba
Arsenic Acid, MSMA
Sodium fluoroacetate, Creosote,
Warfarin
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Formulations may differ not only in the physical state of the pesticide
(such as emulsifiable concentrates, wettable powders, dusts, or granules), as
evidenced by a listing of the most common formulations of carbaryl and
malathion in Table 3, but also in the concentration of active pesticide
ingredients. Formulations vary, depending on its target organism and manner
of application. For example, cotton insecticides are usually applied as emul-
sifiable concentrates whereas granular formulations are preferred for corn.
Furthermore, two or more pesticides, of varying concentration can be included
in a single formulation, and currently there are about 500 of these "mixed
formulations" available. When the variety of solvents, emulsifiers, and syn-
ergists commonly used in these formulations are also taken into consideration,
the situation becomes complex.
Table 3. Commonly Used Formulation of Carbaryl and Malathion.
Carboryl - Sevin
80% S -
50% WP -
5% Bait -
Sevin 4 Flowable
Sevimol
Sevin 4-Oil
10% dust
Malathion - Cythion
95%
80.5% EC
57% EC
51% EC
25% WP
5% Dust
4% Dust
— sprayable powder
— wettable powder
— apple pomace
— aqueous dispersion
— molasses dispersion
— oil dispersion
— Malathion ULV concentrate
— Emulsifiable concentrate
— Emulsifiable concentrate
— Emulsifiable concentrate
— Wettable powder
It would indeed be highly impractical, if not impossible, to attempt to
develop a waste treatment system that would be applicable for the
detoxification/decontamination of all formulations or wastewaters containing
the types of pesticides shown in Table 2. Rather, the best approach is to
concentrate on the major pesticide classes and/or dominant chemical species.
For this purposes of this research, it was decided to concentrate on two of
the major pesticide species used in aerial application, carbaryl (Sevin), a
widely applied N-alkyl carbamate insecticide of the nitrogen-containing class,
and malathion (Cythion) a representative and commonly used phosphorodithioate
insecticide of the organophosphate class. The testing of these compounds was
justified by the following considerations:
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1. Both are widely used in aerial application.
2. Both have relatively low toxicity so as to minimize individual hazard
during these introductory stages of plant design and operation.
3. Analytical techniques are relatively simple and thus rapid determina-
tion of treatment efficiency is possible.
4. Important subgroups (in terms of possible environmental hazard) of
the two major classes of pesticides most commonly used in aerial
application would be represented.
Treatment of pesticides in the other five classes could not be stressed
because time and people power limitations, and these compounds were not con-
sidered to pose as serious a threat to the environment as the nitrogen- and
phosphorous-containing compounds. In particular many of the inorganic and
organometallic compounds have been banned for use because they contain highly
toxic elements (e.g. arsenic, cadmium, and mercury) that cannot be completely
detoxified and present significant disposal hazards. The botanical and micro-
biological pesticides represent only a small fraction of total pesticide usage
and are, for the most part, non-toxic to man (although highly toxic to fish).
The halogenated compounds represent a wide variety of chemical types, but as a
result of their long-term environmental persistence, many have been banned or
are under consideration for registration suspension (e.g., 2,4, 5-T). One
notable exception is the chlorophenoxy compound 2,4-D, which is still in
widespread use. Its persistence is much lower than the highly chlorinated
cyclopentadienes and related compounds (aldrin-toxaphene group). Sulfur com-
pounds do not pose a serious environmental or toxicity hazard, and there is no
otherwise unclassified pesticide used in sufficient volume in aerial applica-
tion to justify consideration.
4.2 DISPOSAL OF PESTICIDE WASTE
Pesticide contaminate wastewater, when improperly disposed can lead to a
number of undesirable consequences. First and foremost is the danger to pub-
lic health, most notably in the form of groundwater pollution arising from
leaching through contaminated soil, or through direct contamination via sur-
face faults in areas with high water tables. Such contamination is of immedi-
ate concern since half of all drinking water is supplied from groundwater and
contamination of groundwater poses a threat to public health. Ground surface
contamination can pose a threat to children and livestock, while surface
runoff can lead to crop damage, poisoning of aquatic life, and contamination
of surface water supplies.
4.2.1 Current Regulations Affecting Disposal of Pesticide Residues
The initial legislation for the control of pesticides was the Federal
Insecticide, Fungicide, and Rodenticide Act of 1972, which altered and
broadened the original 1947 act to address problems of disposal and storage of
excess pesticide and pesticide containers, along with regranting the authority
for the registration, classification, and cancellation of pesticides. The
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administrator of the EPA is required under Section 19 of the Act to "establish
procedures and regulations for the disposal and storage of excess amounts of
such pesticides/ and accept at convenient locations for safe disposal a pesti-
cide, the registration of which is cancelled under section b(c), if requested
by the owner of the pesticide." Furthermore, "notification of cancellation of
any pesticide shall include specific provisions for the unused quantities of
such pesticides."
These recommendations, first published on May 1, 1974, provided a general
approach to the problem of the disposal of pesticides classified by the EPA as
highly or moderately toxic (LD^ < 500 mg/kg). Exceptions included containers
for home or garden use, or tnose used in farm applications when single con-
tainers were to be disposed (usually by open-field burial with due regard to
the protection of surface and subsurface water supplies). Recommendations
included: (1) recovery of material for further use if large quantities are
involved, (2) return to the manufacturer for reprocessing, or, (3) in some
cases of cancelled products, export to other countries where use is desired
and legal. Export of cancelled products is no longer acceptable. If such
alternatives were not viable, incineration of organic pesticides (except those
containing mercury, lead, cadmium, and arsenic compounds) was suggested.
Burial in an acceptable landfill was suggested if incineration facilities were
not available. Soil injection and chemical degradation methods were not urged
without the advice of the regional EPA administrator. Similar procedures were
suggested for metallo-organic (except organic mercury, lead, cadmium, or
arsenic compounds) pesticides. Incineration was considered appropriate after
physical and chemical treatment that removed and recovered the heavy metals.
Organic mercury, lead, cadmium, arsenic, and all inorganic pesticides were to
be treated by chemical deactivation techniques in order to convert the pesti-
cide to non-hazardous products, or if such procedures are not available,
encapsulation and landfilling was suggested. Storage in suitable containers
was allowed if all other options were not feasible. These recommendations
were announced on October 15, 1974, when EPA proposed regulations prohibited
the "worst acts" of pesticide disposal.
A far more comprehensive program for the management of pesticides and
other hazardous wastes has since been established. This program stems from
the authority granted to the administrator of the EPA under the Solid Waste
Disposal Act, was amended by the Resource, Conservation, and Recovery Act
(RCRA) of 1976 (PL 94-580). In particular, subtitle C of the act creates a
"cradle to grave" management control system for hazardous wastes.
Sections under this subtitle relevent to commercial pesticide applicators
include: (a) Section 3002, which addresses the mechanics of the manifest sys-
tem that will track hazardous waste transported from the point of generation
to its ultimate disposal, (b) Section 3003, which authorizes standards for
transporters of hazardous waste to insure careful handling, (c) Section 3004,
which establishes design and operation criteria for hazardous waste treatment,
storage, or disposal facilities (TSDF), (d) Section 3005, which discusses the
permit granting procedure for facility owners and operators, and (e) Section
3010, which establishes procedures for notifying state or federal regulatory
officials of hazardous waste ownership or treatment.
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Under the federal regulations (USEPA, 1980) farmers received an exemption
if they triple rinse containers (see Table 4) and "dispose of pesticide resi-
dues on his own farm in a manner consistent with disposal instructions on the
pesticide labels." The exemption does not include commercial agricultural pes-
ticide applicators. Such an individual is considered a hazardous waste gen-
erator if the waste generated in one month accumulates to more than "100 kg of
any residue/" of any chemical listed in the regulation. The list includes
numerous pesticides.
Table 4. NACA Triple Rinse and Drain Procedure.
(Shih and Dal Porto, 1976)
1. Ehipty container into spray tank. Then drain in vertical posi-
tion in 30 seconds.
2. Add a measured amount of rinse water (or designated spray car-
rier) so container is 1/4 to 1/5 full. For container size less
than 1 gallon, add an amount of rinse solution equal to 1/4 of
the container volume. For a 1 gallon container, add 1 quart of
rinse solution. For a 5 gallon container, add 1 gallon of
rinse solution. For 30 and 55 gallon containers, add 5 gallons
of rinse solution.
3. Replace closure. Shake container or roll and tumble to get
rinse on all interior surfaces. Drain rinse solution into
sprayer or mix tank. Continue draining for 30 seconds after
drops start.
4. Repeat the above steps for total of 3 rinses. One gallon and 5
gallon steel containers should be punctured before draining the
third rinse. It is recommended that the container be punctured
in the top near the front sprout to allow for complete drainage
of the third time.
5. For 30 and 55 gallon steel containers, replace closures and
secure tightly and send the containers to an approved drum
reconditioner (check with State Department of Agriculture for
list) or recycle as scrap into a steel melting plant. For 1
gallon and 5 gallon steel containers, crush immediately and
recycle for scrap to a steel melting plant. For glass con-
tainers, break or crush into large container (such as 55 gallon
open headed drum with cover) and recycle for scrap to a glass
melting plant. If the above preferred container disposal
method cannot be accomplished, the container should be crushed
and buried at an approved dump site. Do not reuse containers.
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That effect of these extensive regulations on the disposal of commercial
spraying pesticide residues is uncertain, especially in regard to the choice
between on-site or centrally located off-site facilities, independent of
economic considerations. On-site treatment will require compliance standards,
established in Sections 3004, 3005 and 3010, while probably easing the respon-
sibilities under Section 3002. Off-site transport is directly affected by
Sections 3002 and 3003.
It is not the purpose of this report to address the applicability of the
design or operation of the proposed treatment system to current federal regu-
lations. These details can only be clarified over time. Nevertheless, it is
almost a certainty that pesticide applicators will, in the near future, have
to provide for an acceptable method of detoxification of excess pesticides and
contaminated wash waters. The proposed system should be in accordance with
the established goals of effective hazardous waste decontamination / detoxifi-
cation and the minimization of potential environmental insult.
4.2.2 Consideration of Disposal Techniques
A wide variety of destruction, detoxification, or disposal techniques for
excess pesticide and contaminated solutions currently exists. These tech-
niques cover a wide spectrum of technical expertise and equipment expense,
ranging from highly complex processes, such as microwave plasma destruction to
simple alkaline hydrolysis by caustic addition. Despite the wide availability
of differing but applicable field disposal technologies, the types of formula-
tions of pesticides that must be treated are so complex that the problem is
not finding an applicable disposal technique, but rather finding a technique
that will be suitable for a wide range of materials, and within the economic
and technical reach of the people who must use it.
In particular, for this research, the development of a treatment system
that was suitable for use by aerial applicators, ground applicators and farm-
ers was desired. In designing this system, the following guidelines as
adapted from Lawless et al. (1972) were considered.
4.2.'2.1 System Requirements
1. The system must minimize the potential for damages to water quality.
2. The system must make minimal contributions to problems of air pollu-
tion and solid waste disposal.
3. The system must degrade the pesticide, ideally to a biologically
inactive form, or at least convert the material to a less hazardous
form.
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4.2.2.2 Practical Considerations
1. The layman has only limited equipment and/or financial resources.
2. Treatment chemicals should be readily available and reasonably
priced.
3. The layman has limited, if any, experience in treatment chemistry and
hazardous waste disposal.
4. Personal hazard should be minimized and the hazards associated with
treatment should be no more and preferably less, than those associ-
ated with exposure to the pesticide. Generation of dangerous chemi-
cal environments (i.e. explosion hazard) must be avoided.
5. The system must be suitable for the variety of different formulation
types with which the operator is expected to deal.
6. Treatment must be carried out and completed within a suitably short
period of time.
7. The system must be efficient in terms of cost, time, manpower, and
pesticide destruction.
8. The system should be, if possible, applicable to existing operation
and decontamination procedures and facilities and should not inter-
fere, to any great extent, with application operations. That is,
nonproductive time associated with cleanup must be minimized.
4.3 SELECTION OF TREATMENT ALTERNATIVES
Most work dealing with the degradation of pesticides arising from agri-
cultural operations has dealt with loss of toxicity under exposed field condi-
tions. In particular, studies on the rate of microbial breakdown by soil
organisms, or soil sorption and subsequent breakdown by bacteria (or various
environmental factors) have dominated this area or research (Sandborn et al.
1977). However, the large number of variables present during soil disposal
research (such as temperature, pH, soil composition, and moisture) tends to
make each research approach unique.
The majority of pesticide disposal research projects have been limited to
one of four areas. The first, treatment of industrial wastewaters arising
from the manufacture of various pesticides, can give some indication of
acceptable alternatives. However, such studies often apply to large volumes
of relatively dilute waste streams, that contain a variety of reaction inter-
mediates in combination with generally small amounts of product pesticide. A
second major area of research has dealt with the removal of pesticides from
drinking water supplies. Most of this work has been concerned with the remo-
val of sub-milligram per liter quantities of chlorinated insecticides. A
third course of research has been the development of laboratory-scale facili-
ties for the treatment of "pure" pesticides. However, such data does not
accurately describe actual field disposal problems. The fourth research area
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has dealt with the disposal of "empty" container rinsing and, probably, most
closely resembles actual field disposal problems.
The choice of an acceptable disposal method depends on a number of cri-
teria. One of the most fundamental questions to be considered is the total
amount of waste that must be disposed. In the case of the aerial applicator,
there is not set volume of water which becomes contaminated during tank rins-
ing and spraying operations (Day, 1976). The volume resulting from equipment
washing is difficult to estimate because rinsing procedures and equipment
differ with each applicator. Day (1976) estimated that aerial applicators,
overall, use 0.4 x 10 m /yr. for equipment washing operations. Approximate
values can be estimated in light of experience gained in the course of this
research. Discussions with Indiana aerial applicators in 1977 yielded sug-
gested that on the average, aircraft are washed about once a day, and occa-
sionally more often when the applicator changes pesticide chemicals. The
volume of water and waste generated during cleaning was found to vary from 100
to 2000 L (30 to 600 gal.). However, 190 L/wash (50 gal/wash) appears to be
adequate. The amount of excess pesticide left in spray tanks and the method
of its disposal was also found to vary, since some operators dispose of the
material by spraying on the target field others divert wastewater to a gravel
drainage field. The disposal of dilute rinse waters, as opposed to concen-
trated excess pesticides, will greatly affect the concentration of the overall
wash water to be treated and hence the choice of an acceptable treatment
method. Other factors which will affect the choice of a treatment procedure
will be the permissable pesticide discharge levels, the type of formulation
used, and the comparitive costs of equally effective systems.
According to Paulson (1977), the fundamental criterion for determining
the manner of hazardous waste disposal is the concentration of the waste
stream. Options for disposal of "concentrated waste" include only three
alternatives: storage, incineration, and wet air oxidation. A wider variety
of options are available for the treatment of "dilute" wastes, including eva-
poration, reverse osmosis, biological treatment, chemical degradation, ozone
(and other oxidants), or adsorption. As can be seen, several of these options
do not detoxify the waste but merely concentrate it so that concentrated waste
disposal procedures can be used. With the exception of adsorption techniques
these options, despite possible applicability to high volume industrial waste
treatment facilities, are not feasible for small-scale disposal.
A more detailed list of possible treatment methods for pesticide solu-
tions is given by Lawless, et al. (1972). The specific procedures discussed
were concerned with the disposal of small amounts of unwanted pesticides (less
than 10 Kg or 200 L (5 Ib. or 50 gal.) so that the alternatives evaluated
appear to be applicable to this research. A complete listing of conventional
disposal alternatives can be derived. These included:
1. Thermal methods — pyrolysis, incineration, and wet air oxidation
2. Biological methods — activated sludge, trickling filters, lagoons,
anaerobic treatment methods
3. Chemical treatment methods — pH adjustment acidification, alkaliza-
tion or neutralization, oxidation (with air, halogens, czone, etc.),
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reduction and photochemical methods (with sunlight or ultraviolet
radiation)
4. Physical treatment methods — adsorption (on clays, activated carbon,
or synthetic resins), coagulation and flocculation, precipitation,
liquid-liquid extraction, and foam infractionation.
Other more recently developed treatment methods include molten salt processes,
microwave plasma technology, catalytic ozonation, immobilized enzyme systems,
chlorolysis, and metallic couple reduction.
Many of the techniques involve complex and expensive equipment, require
highly trained personnel, and cannot be used in a field disposal system, (Wil-
kinson, et al. 1978). Consequently, not all disposal alternatives were
reviewed. Rather, only those processes that were felt to be acceptable for
small scale treatment systems were evaluated.
It should be noted that Avant and Bowmer (1979) describe several of the
techniques that are currently used to handle wash and rinse water. They con-
cluded that the evaporation pit was the most practical system for the indivi-
dual applicator. However, this system requires that the evaporation rate in
the area be greater than the rainfall or the evaporation pits must be covered.
In most regions of the Midwest and Southeast, where large amounts of pesti-
cides are used, rainfall exceeds evaporation.
4.3.1 Thermal Treatment Alternative
For the disposal of pure pesticides and their formulations, incineration
is usually the method of choice. High temperature combustion not only
represents the most advanced disposal technology commercially available, but
also provides the most effective means of destruction. A description of vari-
ous types 'of high temperature incinerators suitable for pesticide disposal was
given by Wilkinson et al. (1978).
Wet air oxidation has been found to be capable of hazardous waste detox-
ification. Reductions in COD from 50 to 95% have been achieved by this method
in the treatment of industrial manufacturing wastes. The effluent can be
further treated by biological or biophysical polishing (e.g. activated sludge
with powdered activated carbon addition) (Wilhelmi 1975).
Studies of thermal destruction of excess pesticides have been conducted
by the military. Thermal destruction of 14 chlorinated pesticides under con-
ditions of a 0.4 sec residence time at temperatures of greater than 1000°C
(1845°F) and 45-60 percent excess air have proven successful (Shih et al.
1975), and destruction of tonnage quantities of the herbicide "Agent Orange"
remaining from the Viet Nam War era, has been carried out by combustion at sea
on the M/T Volcanus.
Smaller-scale studies on commonly used agricultural pesticides have been
carried out by Kennedy et al. (1969, 1972). In their studies, thermal degra-
dation of 20 pesticides (including carbaryl and malathion) was analyzed. With
very few exceptions, temperatures at or near 1000°C were found to be
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sufficient to degrade most commercial pesticide formulations, although it was
demonstrated that some materials, such as dicamba, atrazine, paraquat, and
bromacil may yield volatile products upon incineration, including such toxic
gases as C12, HC1 and H~. Some materials (atrazine, carbaryl, bromacil, and
dalapon) left about 10 percent uncombustible residue. The authors cautioned
that some toxic residues may remain in the ash.
Wilkinson et al. (1978) claimed that current research indicates that a
two sec. residence time at 1000°C should result in 99.99 percent destruction
of pesticides. However, such technology is not applicable for field disposal
systems because of cost. Hence, incineration is usually limited to manufac-
turing wastes. Furthermore, problems of feed system clogging and corrosion
resulting from high salt formulations may be of concern, along with the
spreading of dangerous aerosols containing heavy metals that result from the
combustion of organometallic pesticides. Hence, effluent gas scrubbing is
essential.
According to Paulson (1977), municipal refuse incinerators cannot be used
because:
a. Operating temperatures are not high enough for complete combustion.
b. Residence time in the combustion zone is insufficient.
c. Gas scrubbing is inadequate.
d. High concentration mixtures may not support combustion.
However, a recent study has shown that 99.97 percent or greater destruc-
tion of DDT and greater than 99.99 per cent destruction of 2,4,5-T can be
achieved in a multiple hearth sludge incinerator when the pesticide is mixed
(2 to 5 percent on a dry weight basis) with sewage sludge, (Whitmore, 1975).
Such an option may be applicable to the sludges generated by the treatment
plant developed in this research.
Putman et al. (1971) have investigated the means for better combustion
of pesticides and their containers for the purpose of developing a practical
field disposal method. A variety of oxidants were tested for their ability to
lower oxidation temperatures, along with various organic binders to prevent
the volatilization and sublimation of the pesticides before decomposition. It
was found that oxidants were unnecessary in the presence of binding agents and
that 99 percent or more of the pesticides tested may be destroyed at the tem-
peratures normally achieved by burning wood, paper, cardboard or plastics.
The addition of a mineral oil binding agent to either carbaryl, aldrin, PCB,
or DDT significantly aided decomposition at 300°C. Even though mineral oil
addition had no effect on diazinon, malathion, or atrazine at 300°c, these
pesticides were largely degraded by heat along. Furthermore, only small or
negligible amounts of intermediate products of combustion were formed. A
variety of potentially toxic combustion gases may be given off, including CO,
HC1, Cl , and phosgene. Packaging and subsequent melting with heat from
polyethylene containers can serve as a suitable substitute for mineral oil.
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4.3.2 Biological Treatment Methods
Biological systems including activated sludge, trickling filters, aerated
lagoons, and stabilization ponds have been, and continue to be extensively
used in the treatment of pesticide manufacturing wastes. However, such sys-
tems are subject to rapid upset by a number of different factors, such as
"shock" loadings of toxins and rapid pH changes. Furthermore, treatment of
pesticide waste often requires nutrient additions and special cultures must
frequently be developed for specific types of pesticides.
There are a large number of factors that can affect the biodegradability
of a pesticide. Probably the most important of these is the solubility of the
compound, since this directly affects its susceptibility to microbial attack.
Emulsified forms or highly insoluble material would be expected to be very
slowly degraded. The molecular size of the compound can also affect biodegra-
dability, since large bulky molecules may inhibit enzyme approach and hence
reduce the rate of breakdown. Furthermore, some chemical structures (e.g.,
rings) are resistant to biological attack.
Schwartz (1967) illustrated the success of acclimated cultures in the
degradation of CIPC in an aqueous system. The maximum concentration of CIPC
tested was 5.4 mg/L, and the degradation of the isopropyl side chains was
"rapid" with 95 percent degradation in 20 days. A large proportion of the
rings and some identified breakdown products of unknown toxicity remained in
the system for other two months, although a second culture was capable of com-
plete ring breakage. In the same study, 2,4-D was found to be extremely
resistant to biological degradation.
At the present time biological treatment cannot be considered feasible
for small-scale systems. First, the quantities of waste are not extensive
enough to support an aerobic system, such as activated sludge, while anaerobic
systems are especially susceptible to upset by shock loadings. Furthermore,
the number of different types of pesticide formulations would indicate the
near impossibility of maintaining a suitable acclimated bacterial culture.
According to the recommendations of Wilkinson et al. (1978) such methods can-
not be endorsed at present because more information is needed on sludge and
effluent toxicity (especially in cases of incomplete pesticide degradation)
along with the fact that further studies on the volatilization of pesticides
in aerobic treatment systems must be done.
However, one biological processes that may in the future be applicable to
field disposal systems is the micropit.
Work on micropit disposal was initiated at Iowa State University in early
1977, (Johnson and Baker, 1980) and tests are being conducted to determine the
soil biodegradability of atrazine, alachlor, 2,4-D, butoxy ethanol ester, tri-
fluralin, carbaryl, and parathion at relatively low concentrations (0.05 and
0.025 percent). This study was primarily directed toward the development of
pesticide disposal methods for fanners and applicators. The study consists of
segregating individual pesticide types or classes into separate galvanized
metal-lined disposal pits filled with alternate layers of sand and gravel, and
monitoring the biological degradation of the pesticide by soil microorganisms.
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The results of this research may help many pesticide applicators since
soil microflora have the capability to degrade a wide range of pesticide
types.
4.3.3 Chemical Treatment
More research has been carried out in the field of chemical disposal and
detoxification of pesticides than for any other disposal means. This situa-
tion undoubtedly arises from the fact that chemical disposal combines two
major advantages that no other disposal procedure offers. That is, chemical
treatment can be easily applied to small batches of pesticide waste, and
actual detoxification (rather than segregation and concentration) can often be
achieved without resorting to expensive capital equipment, such as incinera-
tors. However, chemical disposal is also prone to some major disadvantages.
Specific chemical disposal techniques are usually only applicable to specific
types of pesticide wastes. Procedures of more widespread applicability gen-
erally require conditions too hazardous for field application. Also, chemical
procedures do not always result in complete reaction of all species involved
and, furthermore, many possibly toxic functional groups may remain unchanged.
As such, the chemical products of a reaction must be characterized and their
toxicity evaluated before the proposed reaction can be recommended. Unfor-
tunately data on reaction products is often incomplete or entirely lacking.
At the present time, there does not appear to be any one chemical method
that is applicable for the detoxification of all pesticide types, although
some techniques appear to be broadly applicable to many pesticide classes.
The chemical methods investigated for possible field use were oxidation,
catalyzed reduction, acid or alkaline hydrolysis, and photochemical degrada-
tion.
4.3.3.1 Chemical Oxidation
Oxidation can be used to detoxify certain pesticides, although many pes-
ticides have been found to be resistant to a variety of oxidants. In general,
chlorinated pesticides have been found to be resistant to chemical oxidation,
while carbamates and organophosphates are more amenable. The extent of reac-
tion varies with conditions and concentrations of oxidant dosage.
Faust and Aly (1964) found various forms of 2,4-D to be highly resistant
to the oxidizing effects of chlorine gas (Cl ) or potassium permanganate
(KMNO.) although KMNO. was found to be quite successful in the oxidation of
2,4-dfchlophenol (1.25 ppm of KMnO. per 1 ppm of 2,4-DCP caused 100 percent
oxidation in 15 min. at pH 7). Cohen, et al. (1960) found that rotenone
could be reduced from 0.1 to 0.005 ppm by chlorination. However, high
chlorine dosages were required (38.5, 29.5, and 11 mg/L of chlorine were
required to complete the oxidation in 15, 60, and 180 minutes, respectively).
Chlorine dioxide was found to be much more effective oxidant but, as would be
expected, toxaphene was found to be inert to oxidation by chlorine.
According to Robeck, et al. (1965), neither 8 nor 50 mg/L of chlorine
caused any detectable oxidation of dieldrin or lindane. Parathion was 97 per-
cent removed at 7 ppm but the more toxic intermediate, paraoxon, was produced
19
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as a result of this oxidation. Studies with potassium permanganate showed
that dosages as high as 40 ppm produced less than a 10 percent reduction of 10
ppb levels of dieldrin, lindane, 2,4-D and 2,4,5-T. A 17 percent reduction in
parathion concentration was observed. Studies were also performed using
ozone. Table 5 shows that only limited removal of the chlorinated compounds
occurred at high and impractical concentrations of oxidant, although parathion
was much more responsive to oxidation. Chlorinated pesticide breakdown pro-
ducts were not characterized.
Table 5. Pesticide Oxidation by Ozone,
Compound
Lindane
Diedrin
DOT
Parathion
Ozone dose
38
36
36
10
Percent
decrease
35
50
94
94
Beuscher, et al. (1964) studied three chlorinated pesticides, with con-
centrations of 1 to 10 mg/L for Lindane and 0.1 mg/L of aLdrin and dieLdrin.
It was found that lindane was oxidizable by ozone, partially oxidizable by
KMnO and unaffected by chlorine and peroxides. Oxidation of dieldrin was
limited to ozone. Aldrin was attacked by everything but peroxides. This
study suggested that volatility might be used as an indication of oxidizabil-
ity, since aldrin was the most volatile of the species tested.
Leigh (1969) tested the removal of lindane, heptachlor, DDT, and entrin
with chlorine, hypochlorite, potassium permanganate and potassium persulfate.
Hypochlorite and permanaganate were found to have no effect on lindane and
endrin. Hypochlorite was more effective on DDT than was permanganate, but
permanganate was much more effective in the oxidation of heptachlor.
Currently there are three pesticide detoxification methods using ozone
gas and some form of catalysis. These methods include combinations of ozone
and ultraviolet light, chemical catalysis of ozone, and ozone with sonoca-
talysis (Wilkinson et al. 1978). At present, only the first method, ozone/UV
is used on a large scale, and promising results have been obtained. Mauk et
al. (1970) have reduced initial concentration of 50 mg/L of PCP, malathion,
metham, and baygon to <0.5 ppm and have reduced 58 ppb of DDT to <0.5 ppb in
90 minutes. It has been claimed that the system is only 10 percent more
expensive than activated carbon treatment (when replacement costs are con-
sidered) although capital cost is at least twice as high (Prengle and Mauk,
1976).
Ed-Dib and Aly (1977a) investigated the oxidation efficiency of chlorine,
with and without UV light catalysis, and chlorine dioxide. Solutions of 8 to
10 mg/L of the pesticide were treated with approximately equal concentrations
of oxidants. Phenylcarbamates (IPC and CIPC) were generally unaffected by
chlorination, showing a maximum removal of only 10 percent. Greater
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efficiency, ranging from 23 to 70 percent destruction was attained with vari-
ous anilide and phenylurea pesticides. As in other studies, chlorine dioxide
was found to be a more effective oxidant, with the phenyl carbamates showing
30 percent degradation while 40 to 80 percent was seen with anilides and
phenylureas. However, the amide linkage, which is responsible for a number of
undesirable effects, was largely unaffected and, therefore, post oxidation
aniline derivatives may impart some of the same toxic effects as the parent
pesticides.
4.3.3.2 Chemical Reduction
Rsnedy et al. (1972) applied a sodium biphenyl reducing agent to 20 major
pesticides to test the degree of degradation. Analytical interferences lim-
ited product determination to only five species. It was found that triflura-
lin and paraquat showed greater than 90% and 95% degradation respectively.
However, it was noted the biphenyl reagent is unstable above 0°C and hence its
use is not recommended because of safety considerations. Metallic sodium or
lithium in liquid ammonia was also tested with great success. Sixteen pesti-
cides showed complete degradation, while carbaryl and paraquat showed greater
than 90 percent destruction. However, these reagents create a hazardous reac-
tion environment and are not recommended for field use.
A method of reductive degradation of a variety of chlorinated compounds
has been recently developed (Anon, 1976). Amenable compounds include cyclo-
diene pesticides (aldrin, endrin, etc.), DDT and related materials, chlori-
nated camphenes (toxaphene), lindane, and chlorinated phenoxy acetic acid
derivatives. The process uses a catalyzed iron reducing agent in a sand bed
matrix. Costs of treatment, based on a 100-gpm (378L/m) unit, are in the
vicinity of 72 cents per 1000 gal. (19 cents/1000 L) treated.
4.3.3.3 Acid or Alkaline Hydrolysis
Hsieh et al. (1972) discussed alkaline hydrolysis kinetics and efficiency
for treatment of rinsing arising from various emptied containers of parathion,
and showed that degradation did not follow the expected first order (with
respect to hydroxide) kinetics. This unexpected kinetic pattern may have
resulted from the presence of emulsifiers as well as the low water solubility
of parathion, that interfered with nucleophilic attack. Addition of methanol
to increase pesticide solubility greatly increased the degradation rate.
Wolfe et al. (1977) gave a detailed description of pathways and products for
acid and alkaline hydrolysis of malathion and showed that acid hydrolysis
results in a slow degradation rate. Cowart et al. (1971) discussed the degra-
dation by hydrolysis of dilute (<2 mg/L) solutions of seven organophosphate
pesticides in natural aqueous systems and found that the hydrolysis rate
increases with decreasing sulfur content. El-Dib and Aly (1976) found that
phenyl carbamates were readily susceptible to alkaline hydrolysis, while ani-
lides were less reactive and phenyl ureas were the least reactive. All the
pesticides tested were stable for at least 4 months in the pH range of 6 to 9.
The rate of hydrolysis increased 2 to 3 times for each 10°C rise in tempera-
ture.
Although the susceptibility of the organophosphate pesticides and some
members of the nitrogen-containing class to alkaline hydrolysis has been well
documented, such a technique cannot be indiscriminately applied to all members
of these classes. Based on production volume, toxicity, soil persistence,
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mobility, and chemical structure, Shih and Dal Porto (1976) chose twenty key
pesticides from the major classes of the nitrogen-containing, phosphorus-
containing, and halogenated insecticides for evaluation of chemical disposal
techniques. Alkaline hydrolytic degradation was recommended for only seven of
v'the twenty compounds: naled, diazinon, guthion, malathion, carbaryl, captan,
and atrazine. No practical disposal method was found for the remaining pesti-
cides — dursban, methyl parathion, maneb, alachlor, diuron, picloram, triflu-
ralin, methoxychlor, chlordane, toxaphene, 2,4-D, amiben, and pentachloro-
phenol. Pesticides were determined to be unsuitable for chemical detoxifica-
tion if; 1) the extent of reaction was incomplete of unknown, 2) expensive or
hazardous chemicals were required, and/or 3) hazardous end products were gen-
erated. Although all the compounds that were hydrolyzable were either organo-
phosphates, carbamates, imides, hydrazides, or triazines, not all members of
these classes could be hydralyzed. The authors stated that because the hazard
of the end product is dependent on specific functional groups, each chemical
must be judged on an individual basis. However, the unsuitability of alkaline
hydrolysis for one member of a class can often given warning for other members
as well. For example, diuron yields a more toxic 3,4-dichloroaniline product,
while closely related monuron produces an aniline product. Stewart et al.
(1967) and Bender (1969) discussed the toxicity of hydrolysis products of car-
y/ baryl and malathion.
Alkaline hydrolysis is not recommended for the halogenated pesticides
because of the difficulty in replacing halogen atoms, and the fact that the
degradation products are almost always unknown (Shih and Dal Porto, 1976).
These considerations apply to other forms of chemical treatment as well, where
reagents are often compound-specific, hazardous, and expensive.
Shih and Dal Porto (1976) found a variety of pesticides to be unsuitable
for acid hydrolysis. Slow reaction rates were seen for atrazine, malathion,
and methyl parathion, (which also gives rise to toxic P-nitrophenol). Com-
pounds resulting in toxic products or products of unknown toxicity include
maneb, alachlor, diuron, trifluralin, and ambien. Captan is unaffected by
acid treatment.
Hydrolysis can sometimes be used as a treatment after chemical oxidation
for the removal of toxic intermediates. Goman and Faust (1972) have shown
this to be true for parathion degradation.
The work of Shih and Dal Porto (1976) was continued by Lande (1978) who
s/ chose forty pesticides. Only eleven pesticides were recommended for disposal
by alkaline hydrolysis, including three carbamates, seven organophosphates and
one imide. Rejected compounds included four organophosphates, two thiocarba-
mates and two triazines.
Kennedy et al. (1969) tested alkaline hydrolysis on a number of pesti-
cides using NaOH and NH4OH. Neither method was found to give complete erac-
tion of the compounds tested.
4.3.3.4 Photolysis
A variety of pesticides have been shown to exhibit a number of chemical
changes upon exposure to ultraviolet radiation or natural sunlight (Abdel-
Wahab and Casida 1976, Weldon and Timmons 1961, Jordan et al. 1964, Crosby et
22
-------
al. 1965, Eberle and Gunter 1965) although these changes may result in more
toxic forms of the parent pesticides. For example, more toxic photodieldrin
and photoaldrin may be formed when dieldrin and aldrin are exposed to sunlight
(Robinson et al., 1966, Rosen and Sutherland, 1967, and Plimmer, 1978).
In order to undergo photo decomposition, light energy must first be
absorbed. Since most of the ultraviolet radiation emitted by the sun is
absorbed in the ozone layer, only pesticides adsorbing above 285 nm can be
expected to undergo natural photolysis. Such considerations are, of course,
not meaningful when an artificial ultraviolet light source is utilized.
Absorbed light energy may cause a variety of reactions within the pesti-
cide molecules. Frequently, free radicals that may cause isomerization, sub-
stitution, or oxidation may arise. The reaction is heavily dependent on the
chemical environment in which it takes place. One advantage to photochemical
breakdown is that it also may lead to enhanced susceptibility to biodegrada-
tion.
Many compounds require a photo-sensitizing agent or a hydrogen donor that
serves to capture light energy and transfer it to the pesticide. Examples of
this include acetone for the cyclodiene pesticides (Plimner 1978) or the use
of olive oil for TCDP decontamination (Crosby 1978).
Aly and El-Dib (1971) studied photochemical breakdown of three carbamate
pesticides, carbaryl, baygon, and pyrolan. The effects of pH were found to
vary. The primary result of irradiation appeared to be cleavage of the ester
linkage although Crosby et al. (1965) reported that photodecomposition of car-
baryl yielded, in addition to 1-naphthol, several other compounds having an
acetyl cholinesterase inhibition potential, thus indicating carbamate ester
group integrity.
Mitchell (1966) tested the effect of ultraviolet light on 141 different
pesticides. Thirty were found to undergo little or no degradation, while com-
plete or practically complete degradation was seen for 32 pesticides with a 60
minute exposure time. Based on these findings, the procedure appears to be
well suited for the partial or complete breakdown of organophosphorous pesti-
cides, but the identity and toxicity of the products were not determined.
It must be remembered that most of these studies have been performed in
the laboratory and/or in actual soil application procedures where small
amounts and thin layers of material have been involved. The necessity for
providing adequate light penetration and contact time for the larger batches
of concentrated materials expected from field operations severely limits the
practicality of photochemical degradation treatment processes.
At this time, there is no chemical disposal of detoxification technique
that can be pursued for application in a field disposal system. Although,
many such techniques can be effective, most of these are limited to relatively
few pesticides and hence have no broad range of applicability. Many of these
techniques are only partially effective and give rise to hazardous products,
the toxicity of which has yet to be determined. Since many of the proposed
techniques require hazardous chemicals and reaction conditions with which the
layman is often inexperienced, chemical disposal practices for field pesticide
23
-------
decontamination cannot be recommended at this time.
4.3.4 Physical Treatment Methods
A variety of physical treatment methods can be applied to the control of
pesticide wastes. Most of the research in this area has been concerned with
the removal of pesticides from relatively "clean" water. Because it is often
more difficult to achieve significant percentage removals of compounds from
dilute solutions than from concentrated waste streams, it would appear that
the technology used for water treatment would be equally or more effective for
the treatment of pesticide contaminated wastewater for aerial applicators.
Physical treatment methods do not result in destruction or detoxification
of the hazardous materials, but rather in the removal and subsequent concen-
tration of materials through phase separation procedures. Therefore, other
means are required to achieve ultimate decontamination of the waste. The phy-
sical treatment methods most commonly used are coagulation/flocculation and
adsorption (on resins or activated carbon). Only one study dealing with the
treatment of several chlorinated pesticides by foam fractionation was found to
be applicable to pesticide cleanup applications (Whitehouse 1971) and, hence,
that technology was not considered.
4.3.4.1 Resin Adsorption
Depending upon the individual chemical considered, pesticides can be
removed on one of three types of synthetic resins used in water and wastewater
treatment, that is anionic and cationic exchange resins as well as more
recently developed hydrophobic resins. Because the number of pesticides that
will respond to cationic resins (for example, positively charged, highly solu-
ble compounds such as paraquat and diquat) or anionic resins (such as the ion-
ized acidic pesticides of the chlorophenoxy acid class) are very limited when
compared to the total number of commonly used non-ionic or weakly charged pes-
ticides, ion-exchange resins were not considered to be a viable treatment
alternative for all classes of pesticides. For the same reason, the use of
clays with high cation exchange capacity (CEC), such as montmorillonite or
kaolinite, were not considered to be acceptable treatment alternatives except
when specific pesticides such as diquat or paraquat are in the wastewater.
However, hydrophobic resins, such as Amberlite XAD-2 and the more recently
developed, higher capacity XAD-4 resin, appear to have potential application
for the treatment of most pesticides.
Kennedy (1973) examined the removal of chlorinated pesticides on hydro-
phobic resins in laboratory scale columns (1.77 on i.d.). At a flow rate of
0.125 gpm/ft and an influent pesticide concentration of 33.5 mg/L, no pesti-
cide breakthrough was reported after 120 bed volumes had passed through the
column. Breakthrough was seen almost immediately in a similarly operated
activated carbon column. The carbon effluent contained about 1 mg/L of pesti-
cide after 70 bed volumes and was essentially exhausted after 110 bed volumes.
Performance of the resin after regeneration of both beds with isopropanol and
methanol was also found to be superior to the carbon, with the resin showing a
capacity of approximately 1.5 times that of the carbon bed with significantly
less leakage of pesticide in the early stages of operation. It should be
noted that the great majority of pesticides were recovered from the resin with
24
-------
two bed volumes of isopropanol regenerant. Acetone gave superior regeneration
performance but was dismissed because of its flammability.
Leenheer (1970) found excellent removals of carbaryl and parathion on
XAD-2 resin. A large scale industrial application of hydrophobic resin
adsorption of pesticide manufacturing wastes is currently being conducted at
Velsicol Chemical Company in Memphis, TN (Wilkinson et al. 1978).
Although resin adsorption appears to hold great promise for the treatment
of pesticide-bearing wastewaters, the hazards associated with the use of sol-
vents and the recovery of volatile regenerant chemicals make the system
uneconomical and impractical for small-scale applications at this time.
Furthermore, the problems of disposal of concentrated pesticides remaining
solvent recovery still remain.
4.3.4.2 Reverse Osmosis
The process of reverse osmosis (R.O.) has been used to treat many dif-
ferent pesticides. Edwards and Schubert (1974) evaluated three different mem-
branes for the treatment of water supplies containing 2,4-D waste. For cellu-
lose acetate, cellulose triacetate, and polyelectrolytic membranes, maximum
retention of the sodium salt formulation of 2,4-D never exceeded 65 percent
and in most cases ranged from 1 to 51 percent although it was noted that
treatment of the ester compounds was more successful.
Chian et al. (1975) tested the removal of 13 major pesticides on two R.O.
membrane types, conventional cellulose acetate and a cross-linked polyethylene
imine with m-tolulene 2,4 diisocyanate. Excellent separation was obtained,
although values were only in the 1 mg/L or less concentration range (Table 6).
In many cases, removal was largely due to pesticide adsorption on the mem-
brane. Hinden et al. (1969) also obtained high percentage removals for
several chlorinated pesticides (84 percent for lindane, >99.5 percent for DOT
and ODD and 52 percent for BHC), but only dilute solutions (
-------
Table 6. Removal of Chorinated Pesticides by Reverse Osmosis
Pesticide
Aldrin
Lindane
Heptachlor
Heptachlor
epoxide
DDE
DDT
Dieldrin
Diazinon
Randox
Trifluralin
Atrazine
Captan
^
Membrane
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
NS-100
CA
Amount of
Origional
feed
142.3
506.4
157.5
145.1
306.9
69.0
42.0
321.3
473.7
913.1
1057.8
747.3
326.8
1578.9
1101.7
688.9
Pesticides (mg/L)
Reten-
tate Permeate
6.9
29.1
440.2
2.5
5.4
28.1
25.6
71.5
4.2
13.6
2.4
N.D.
14.9
75.7
273.5
334.7
542.1
496.9
647.0
739.9
363.2
412.5
286.0
253.7
530.0
560.0
956.5
851.4
437.0
314.7
N.D.C
N.D.
5.3
346.4
N.D.
N.D.
0.5
0.7
N.D.
N.D.
N.D.
N.D.
N.D.
0.4
56.6
8.3
4.0
4.1
3.7
8.9
1.3
0.9
4.7
91.4
0.1
4.1
24.0
176^0
N.D.b
8.4
in solutions
Adsorbed
calcda
135.4
113.2
60.9
99.51
139.7
117.0
280.8
234.7
64.9
55.4
39.6
42.0
306.4
245.2
143.6
130.7
370.6
412.1
407.1
309.1
382.8
333.9
36.1
18.3
1048.8
1014.7
121.2
74.3
252.4
440.1
%
removal
100
100
98.95
68.40
100
100
99.84
99.77
100
100
100
100
100
99.88
98.05
98.25
99.56
99.55
99.65
99.16
99.83
99.88
98.56
72.03
99.99
99.74
97.82
84.02
100
97.78
%
adsorp-
tion
calcdb
95.15
79.55
12.03
96.28
80.63
91.50
76.47
94.06
80.29
94.29
100
95.36
76.31
30.31
27.59
40.59
45.13
38.49
29.22
51.22
44.68
11.05
5.60
66.43
64.27
11.00
6.74
36.64
63.88
caica = pesticides present in the original reed less tnat
determined in the retentate and permeate.
^(Pesticides adsorbed calcd)/(pesticides in original feed) x 100%.
'N.D. = nondetectable.
4.3.4.3 Coagulation/Flocculation
There are different interpretations in the technical literature of the
terms "coagulation" and "flocculation" especially in regard to wastewater
treatment. For the purpose of this discussion, coagulation will refer to the
overall process of particle aggregation to achieve larger, more settleable
masses or "floes" while flocculation will be used to describe the transport of
these materials by gentle stirring or agitation in order to accomplish parti-
cle aggregation.
26
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Perhaps the earliest study of pesticide removal from water was carried
out by Carollo (1945) in response to post-war concern about DDT contamination.
Ferric chloride and alum (aluminum sulfate) were used as coagulants for DDT-
contaminated water. Treatment consisted of coagulant addition, flocculation
for 30 minutes and subsequent filtration or sedimentation. Only low dosages
(7.4 to 8.5 ppm) of coagulant were applied. Results are summarized in Table
7.
It should be noted that the pesticide contaminant was suspended in
tion and that treatment probably did not remove any dissolved material.
solu-
Table 7. Effect of Coagulation/Flocculation on DDT Removal (Carrolo, 1945)
Coagulant
alum
alum
alum
alum
ferric chloride
ferric chloride
ferric chloride
ferric chloride
Coagulant
Dose
mg/L
7.4
7.4
8.5
8.5
7.4
7.4
8.5
8.5
DDT Cone.
(initial)
mg/L
.1
1-10
.1
1-10
.1
1-10
.1
1-10
settled 1 hr
settled 1 hr
filtered
filtered
settled 1 hr
settled 1 hr
filtered
filtered
% Removal
DET
40%
50%
84%
95%
60%
80%
80%
91%
Robeck et al. (1965) demonstrated the effectiveness of coagulation and
filtration for the removal of a number of pesticides from water. Solutions of
DDT, parathion, dieldrin, 2,4,5-T ester and endrin were prepared by forming
emulsions of these materials in concentrations ranging from 1 to 25 ppb. With
the use of these conventional water treatment practices, removal from dilute
solutions could be expected to be 80 percent for parathion, 55 percent for
dieldrin, 65 percent for 2,4,5-T esters, 25 percent for endrin, and 100 per-
cent of DDT. Lime-soda softening with an iron salt coagulant did not produce
significantly different results than were observed with alum coagulation/
except that somewhat poorer removals were seen for EOT and dieldrin. The
variety in the measured degree of removal was probably accounted for by
differences in solubility and affinity for surfaces.
Whitehouse (1971) used nine different coagulation/flocculation methods,
including combinations of alum, five different polyelectrolytes, ferric sul-
fate, clay and activated carbon for the removal of malathion. Pure solutions,
not formulations, were used for these studies, therefore, the solubility of
the material was probably much greater than would be expected in a powder or
emulsifiable concentrate-based solution. Results were not encouraging for the
removal of malathion. Coagulants alone accomplished less than 10 percent
removal while the introduction of polyelectrolytes showed little effect.
Solution concentrations ranges from 100 to 180 mg/L (note the water solubility
27
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of malathion is 145 mg/L). Alum coagulation failed to remove dilute concen-
trations of toxaphene (0.14 mg/L) and rotenone (0.17 mg/L) with applied coagu-
lant dosages as high as 100 mg/L.
Schwartz (1962) studied the removal of 2,4-D in natural waters. Alum and
ferric sulfate achieved about the same degree of removal as that resulting
from the settling of the natural silt in water, that is 3 to 6 percent.
Dosages of the pesticide ranged between 3-15 mg/L.
El-Dib and Aly (1977a) tested alum and ferric sulfate coagulation on a
variety of pesticides. Solutions were prepared from pure (non-formulated)
pesticides to a concentration of 8 to 10 mg/L. Alum dosages of 20 mg/L were
completely ineffective while dosages of 100 mg/L accomplished only 10 percent
or less removal of pesticide. Ferric sulfate was slightly more effective, and
the results can be summarized in Table 8. Note that greater coagulant dosages
gave consistently greater removals.
Table 8. Feric Sulfate as a Coagulent for Pesticide Removal
(El-Dib and Alyf 1977)
Pesticide % Removal of Pesticide
50 mg/L 100 mg/L
IPC
CIPC
Monvron
Diuron
Linvron
Nebvran
Stam
Karsil
Dicryl
Vitavax
0
10
5
8
10
11
0
10
0
10
5
21
15
20
30
22
8.6
20
5
20
Initial inspection of the literature would appear to show that coagula-
tion is an ineffective means of accomplishing pesticide removal. However, two
factors must be kept in mind in the interpretation of these results. First,
most studies have been performed on dilute pesticide solutions. Secondly, the
majority of studies have dealt with solutions prepared from pure pesticides.
As such, the results do not necessarily model those that might be expected
from treatment of aerial application waste where formulated pesticides will be
treated and relatively high pesticide concentrations are expected.
Consequently, it was decided to investigate coagulation and flocculation
as a treatment alternative as well as to evaluate filtration and oil coales-
cense. The latter processes are not substantially different from coagulation
but merely differ in the manner used to achieve physical separation.
28
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4.3.4.4 Activited Carbon Adsorption
Numerous studies during the past fifteen years have shown activated car-
bon to be an effective means for the removal of pesticides from water. White-
house (1971) found activated carbon to be the most effective treatment method
for malathion, 2/4-D, DDT, aldrin, and dieldrin. Activated carbon use in a
field treatment system for pesticide disposal is attractive from a number of
standpoints. This material has long been known as an effective adsorbent for
ring compounds and other slightly soluble materials (a characteristic shared
by many pesticides) and the high adsorption capacities exhibited by carbon,
along with the relatively low purchase price ($1.50Ag) makes its use economi-
cally attractive. Furthermore, the efficiency of the adsorbent in the removal
of low concentrations of material indicates the possibility of producing a
high quality effluent. Even though the performance of activated carbon may
vary under differing conditions of temperature and pH, such conditions are not
expected to undergo a great deal of variation in actual field situations.
However, one factor that may have significant effect on performance is the
highly mixed nature of adsorbates arising from the mixing of a variety of wash
solutions, many of which may be in sufficient quantity to cause competition
and displacement on the carbon.
A detailed study of the mechanics of activated carbon adsorption of a /"
variety of pesticide types was carried out by Weber and Gould (1966). The
pesticides studied included a number of dinitrophenols and chlorophenoxy acids
along with carbaryl and the highly toxic phosphorothioate, parathion. Adsorp-
tion parameters were determined by a batch shaking technique using a commer-
cially available activated carbon of specified size.
Within the classes of compounds studied, the rate of removal was found to
be fairly consistent, that is, the rate of pesticide removal was relatively
independent of the type of compound. Changes in adsorption rate caused by
concentration changes were also found to be consistant, in that increased con-
centrations of pesticides led to increases in the adsorption rate in a
predictable manner. The data were found to fit a Langmuir isotherm and com-
parison of "b" values, a measure of the energy adsorption, showed similarity
for all the compounds tested with the exception of parathion, whose high value
indicated exhaustion capacity could be achieved at low pesticide concentra-
tions. The authors stated that removal of low concentrations of pesticides
would likely be more efficient than that indicated by the isotherm graph.
These findings indicate the broad applicability of carbon adsorption to pesti-
cides of various classes. Exhaustion capacities of the carbon were found to
range from 387 mg/g (38.7 percent) for 2,4-D to 530 mg/g (53 percent) for
parathion.
Hyndshaw (1962) conducted studies on carbon adsorption of a number of
chlorinated hydrocarbons, chlorophenoxy acids and organophosphates. Dosages
of 29 mg/L or less of activated carbon produced a 90 percent or greater reduc-
tion for solutions containing as much as 50 mg/L of pesticide.
Schwartz (1967) tested the effectiveness of removing CIPC with activated
carbon. At a pH of 6.9 and 20°C, 5 mg/L of CIPC was reduced by 90 percent
within 2 hours and 98 percent removal was observed within 22 hours with 100
mg/L additions of powdered activated carbon (PAC). Under similar conditions
25 and 50 mg/L PAC removed 56 percent and 95 percent of CIPC, respectively, at
29
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initial concentrations of 10 mg/L. Approximately 90 percent of the adsorption
occurred within the first four hours. Adsorption data were found to follow a
Freundlich isotherm, although a Langmuir isotherm was found to be equally
applicable in the higher concentration ranges. The ultimate capacity of the
carbon ranged from 29.1 to 33.4 percent by weight. Adsorption was independent
of pH in the range of 4.8 to 9.3. Other work by Schwartz (1962) showed PAC to
be effective in the removal of 2,4-D. A concentration of 10 mg/L was reduced
60 percent by the addition of 100 mg/L PAC and greater than 99 percent removal
of 0.1 mg/L was achieved with carbon at 50 mg/L. Optimum pH was found to be
3.
Ward and Getzen (1970) studied adsorption of three related herbicides:
2,4-Df dicamba, and ambien, in order to determine the influence of pH. Their
results correlated well with those of Schwartz (1962) in showing that a reduc-
tion in solution pH from 7 to 3 increased the extent of adsorption, indicating
that sorption of the molecular species is favored over the ionic form. Sharp
increases in adsorption were noted in the pH range of 6 to 4, apparently
because of increased hydrogen ion adsorption onto the carbon, which enhanced
the removal of negatively charged acidic herbicides. Ward and Getzel (1970)
also observed that increased chlorination of the ring structures led to
increased adsorption on the carbon. These results are in agreement with those
of Leopold et al. (1960), who showed substitution of chlorine atoms on phenoxy
acetic acid rings lowered water solubility and increased adsorption. When the
relative adsorptions of the herbicides were compared, it was found that the
least soluble herbicides, monuron, CIPC, and IPC were the most high adsorbed
(Table 9). Note that the acidic nature of the poorly adsorbed compound.
Table 9. Absorption of herbicides on activated column.
Herbicide Chemical Name % Adsorption
Monuron 3-(p- chlorophenyl) 1,1 diethyl urea 98
CIPC. isopropyl N(3-chlorophenyl) carbamate 98
IPC isopropyl N-phenyl carbamat 96
Naptalam (NPA) N-1-naphthyl phthalamic acid 82
2,4,5-T 2,4,5 Trihloro acetic acid 65
2,4-D 2,4 dichloro phenoxy acetic acid 49
TBA Trichloro benzoic acid 32
TCA 'frichloro acetic acid 13
However, Leopold et al. (1960) disagrees with the results of previous
studies in stating that no effect was seen in the adsorption of 2,4-D in the
pH range of 2.2 to 8. Aly and Faust (1965) also performed laboratory studies
on removal of 2,4-D and its derivatives by conventional water treatment tech-
niques, including activated carbon, which was found to be the most effective
method for removing 2,4-D, 2,4-DCP, and the odor-producing substances in the
formulations. The 2,4-D adsorption data were found to follow a Freuendlich
isotherm and in keeping with previously discussed studies, an inverse rela-
tionship between adsorbability and solubility was noted. The ester forms of
the pesticide required significantly less carbon dosages than the correspond-
ing ionizable salt.
30
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Activated carbon has been evaluated with a variety of other chlorinated
•compounds. Bernardin and Froelich (1975) performed a number of studies with
powdered FS-300 (Filtrasorb) carbon. Data were found to fit a Freundlich
isotherm and are summarized in Table 10. Note that the low capacities are a
direct result of the low pesticide concentrations applied and do not reflect
exhaustion capacity. Among other studies Greve and Witt (1971) have shown
endosulfan to be amenable to activated carbon treatment.
Table 10. Activated carbon adsorption of chlorinated pesticides.
Initial cone. Final cone. Capacity (by weight)
Pesticide (mg/L) (mg/L) carbon at initial cone.
Aldrin
Dieldrin
Endrin
DDT
DDD
DDE
Toxaphene
19
52
41
41
56
38
155
1.0
.08
.07
.15
.14
1.0
1.0
3.0
1.5
10.0
1.1
13.0
.9
4.2
Although Carollo (1945) showed DDT removals by flocculation, signifi-
cantly better removals were observed when activated carbon was included in the
treatment process. Concentrations of 1 mg/L of DDT were completely removed
with the addition of 7.4 mg/L alum, filtration and mixing with 1.65 mg/L of
activated carbon. Cohen, et al. (I960) found carbon to be successful in the
removal of the fish poisons rotenone and toxaphene. The data were found to
fit a Freundlich isotherm, from which the following information could be
predicted; 9 mg/L of activated carbon could reduce 0.14 mg/L toxaphene to .014
mg/L, 5 mg/L could reduce this concentration to 0.058 mg/L and an effluent
concentration of 0.085 would be expected with a carbon dose of 3 mg/L.
Whitehouse (1971) worked with activated carbon for the treatment of a
variety of pesticides. Solutions of 50 mg/L of 2,4-D required 1 gram of car-
bon to achieve complete removal in 1 hour whereas 100 percent removal of
dieldrin and DDT was obtained with carbon dosages of 100 mg/L in 3 hours. In
keeping with previous findings, 2,4-D adsorption was enhanced by dropping the
pH. Of particular interest are detailed studies by Whitehouse (1971) on car-
bon adsorption of malathion. In batch shaking tests of two hour duration, 100
percent removal of 5 to 10 mg/L malathion was accomplished with carbon dosages
of 80 mg/L, while the complete removal from a 25 mg/L malathion solution was
accomplished with 140 mg/L of carbon. Such high capacities shown for batch
equilibrium studies seem to promise highly successful operation of a carbon
column.
Prometone, 2,4-D, paraquat, and diquat adsorption were all found to fol-
low a Freundlich isotherm (Weber et al., 1968). The inverse relationship
between solubility and adsorbability appeared to hold since prometone was the
most strongly adsorbed of the four compounds. Paraquat was found to be more
strongly adsorbed than diquat, results that correlate with those of Faust and
Zarins (1969). Here, as well, results could be described by a Freundlich
31
-------
isotherm. Paraquat and diquat removal by activated carbon addition was found
to be feasible with a contact time of 30 to 60 minutes, but the required car-
bon dosages were high when compared to other pesticides. This is not surpris-
ing since paraquat and diquat exist in water as ionic, soluble species. In
particular, reduction of 10 mg/L of diquat down to 0.1 mg/L required 900 mg/L
of carbon, while similar reductions in paraquat required 450 mg/L at a 30-
minute contact time. A reaction time of 60 minutes reduced the required car-
bon dosage to 629 mg/L and 456 mg/L respectively. No attempt was made to
evaluate carbon column operation.
Coffey (1969) used a root growth bioassay technique to evaluate adsorp-
tion efficiency. Contrary to the results of previous investigators, he found
activated carbon incapable of paraquat adsorption, although cation exchange
resins were well-suited to its removal. A number of compounds were tested
and, the order of adsorption efficiency was CIPC > trifluralin > 2,4-D >
diphenamid > DNBP > Amiben.
Studies with various phenylamide pesticides showed rapid and efficient
adsorption by powdered activated carbon (El-Dib and Aly, 1977b). Again,
adsorption conformed to a Preundlich isotherm and equilibrium conditions were
found to be established within 15 minutes of initial contact. Adsorption for
the phenylcarbamates followed the order: CIPC > IPC, for the phenyl ureas the
order was: diuron > linuron > neburon > monuron > fenuron, and for the
anildes: Karsil > Stam > Vitava. The general solubility/adsorbability pattern
was followed here as well. Adsorption was affected by steric hindrance, such
as those arising from the extended side chain of neburon or the "bulkiness" of
the Vitavax molecule. Further studies by Sigworth (1965) showed the amenabil-
ity of some organophosphate and chlorinated insecticides to activated carbon
treatment. Results are summarized in Table 11.
Table 11. Carbon adsorption of organophosphate and
chlorinated insecticide
Pesticide
parathion
malathion
lindane
2,4-D 23.5%
2,4-D 11.7%
chlorodane
DDT
initial
cone. (mg/L)
10
25
2
6
1
50
5
final
cone. (mg/L)
2.6
.08
.25
1.38
*
*
*
carbon dose
(mg/L)
10
5
10
20
10
10
2
Eichelberger and Lichtenberg (1971) demonstrated the efficiency of
activated carbon in "scrubbing out" low concentrations or organophosphate pes-
ticides by column application. Bidrin, ethion, azodrin, parathion, fenthion,
DBF, trithion, malathion, and methyl-parathion were all reduced from 3 mg/L
(ppb) to less than 25 mg/L (ppt) by passage through a lab scale column. A
number of chlorinated compounds were reduced to levels less than 10 ppt.
32
-------
El-Dib et al. (1973) used a 0.6/mm and 1.2/mm Dcro granular activated
carbon to determine the adsorbability of two carbamate insecticides, carbaryl
and baygon in both batch tests and down-flow columns. The results were shown
to follow both Fruendlich and Langmuir isotherms. Monolayer capacity for car-
baryl was found to be 800 moles/g on l.2/mi granules and 1250 moles/g for the
0.6/ntOsize. Capacity was independent of particle size for Baygon. Both
sizes had a capacity value of about 500 moles/g.
For column operation, contact time was a critical parameter. Increasing
the contact time from 0.5 to 3.75 minutes (influent carbaryl concentration of
20 mg/L) increased the number of bed volumes passed before breakthrough
(chosen as 0.1 mg/L) from 15 to 425. The effect was nearly as remarkable for
Baygon, which showed almost immediate breakthrough at the 0.5 minute contact
time while 273 volumes were successfully treated during a 3.75 minute contact.
At the higher contact time, almost complete adsorption capacity was realized,
independent of bed depth.
El-Dib et al. (1973) stated that the difference in the adsorption
behavior of the two pesticides could be explained by molecular structure
differences. The side chains of the carbaryl molecule all lie within the same
plane, while the 2 methyl groups in the isopropyl chain of baygon lie in a
different plane with respect to the ring. Hence, steric hindrance in entrance
into the carbon micropores may have resulted, along with the fact that the
molecule may have had weaker adhesion to the carbon because of lower surface
coverage and attachment area.
Based on these studies, especially those that illlustrate the great
effectiveness of carbon for the removal of organophosphates and various nitro-
gen containing pesticides, it appears that activated carbon represents a
viable treatment alternative for field disposal systems. Additional advan-
tages include the ability to remove most chlorinated compounds, along with the
fact that carbon adsorption appears to be applicable for achieving the goal of
water reuse, since a high quality effluent is obtainable. The broad applica-
bility, economy, and efficiency of this treatment method present distinct
advantages not found in any other treatment schemes.
33
-------
SECTION 5
5. SAFETY CONSIDERATIONS
Individual safety is of primary concern in handling pesticides or pesti-
cide contaminated waste. Pesticide toxicity is often compared on the basis of
LD5Q (the amount of material in mg per kilogram of body weight, that will
result in the death of 50 percent of the test animals). Dermal toxicity is of
equal or greater practical concern for the pesticide applicator or treatment
plant operator. This is especially true in cases where organophosphate pesti-
cides, that are easily absorbed through the skin, are involved. Comparisons
of oral and dermal toxicity data are given in Table 12. The risk of oral poi-
soning can, of course, not be neglected and the standard safety procedures of
not smoking, eating or drinking when handling these chemicals should always be
observed.
It should be noted that any treatment system containing open tanks, pumps
and hosing is susceptible to leaks, gasket failures, vapors, and spillage.
This is especially true for hose connections that, when periodically operated
under conditions of moderate to high pressure, may separate and leak. As a
result, the following safety procedures were recommended for the operation of
the designed pilot plant.
1. Employees should never work alone
2. The treatment plant should be kept in a well ventilated area
3. The treatment plant should be enclosed to maintain equipment life and
minimize runoff
4. The area around the treatment system should be diked and, if possi-
ble, a sump pump should be installed to collect spills
5. Only individuals experienced in the handling of pesticides should be
in charge of plant operation
5. The operator should be aware of the usual symptoms of pesticide poi-
soning. These symptoms include headache, giddiness, nervousness,
blurred vision, weakness, nausea, and cramps. Signs of poisoning
include profuse sweating, tearing, salivation and other excessive
respiratory tract secretions, and vomiting. In later stages,
cyanosis, papilledema, uncontrolled muscle twitches, convulsions,
coma, loss of reflexes, and loss of sphincter control may occur.
34
-------
Table 12. Toxicities of Selected Organophosphate and Carbamate Pesticides
Label Accepted
Common Name
phorate
dementon
none
none
none
none
ethyl
parathion
none
none
methyl
parathion
carbophen-
othion
none
phosphamidon
none
dioxathion
ethion
famphur
DDVP
none
none
none
none
phosalone
none
none
di.methoate
fenthion
naled
malathion
ronnel
carbofuran
methomyl
none
none
none
none
carbaryl
Some Trade
Names
Thimet
Systox
Di-syston
Phosdrin
Sulfotepp, Dithio
Dasanit
Thiophos, Ortho-
phos, Phaskil
Guthion
Dyfonate
Dalf, Metron
Trithion
EPN
Dimecron
Co-Ral
Delnav
Nialate
Warbex
Vapona
Meta-Systox-R
Diazinon
Methyl Trithion
Ciodrin
Zolone
Dursban
Imidan
Cygon, De-Fend,
Rogor
Baytex
Dibron
Neguvon
Cythion
Korlan, Trolene
Nankor
Furadan
Lannate
Zectran
Dimetilan
Baygon
BUX
Sevin
Acute Oral
LD50 mg/kg*
2.3
2. 56-6. 2
2.3-6.8
3.7-6.1
5
2-11
3-13
11-13
16
14-24
10-30
8-36
23.5
9
23-43
27-65
35-62
56-80
65-76
76-108
98-120
125
82-205
97-276
147-216
215
215-245
250
560-630
1000-1375
1250-2630
8.1-14.1
17-24
25-37
64
95-104
7
500-850
Acute Dermal
LD50 mgAg*
3-6
8-14
6-15
4-5
8
3-30
7-21
220
319
67
27-54
25-230
107-143
860
63-235
62-245
1460-5093
75-107
250
455-900
190-215
385
2000+
2000
3160
400-610
330
800
2000+
4444+
5000
885
1500+
1500-2500
600+
1000+
400
4000+
Purchase
Permit
Requi red
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
No
No
No
No
* The range in LD,. numbers is due
between male and females, between
and between different carriers of
to differences in susceptibility
different strains of test animals,
the pesticide.
35
-------
7. A change of clothing and, if possible, shower facilities should be
nearby. Clothing should always be washed (but never with the family
wash) before re-wearing.
The chemicals required for treatment plant operation should be handled
carefully. Although aluminum sulfate (alum) is not considered a particularly
hazardous chemical, its acidic action can cause irritation of eyes, skin, and
mucous membranes. Sodium hydroxide is highly corrosive while polymer solu-
tions, although not irritating to exposed areas, are usually viscous and slip-
pery and can be dangerous, if spilled. Consequently, the following procedures
are recommended:
1. Only relatively small volumes of chemicals should be transferred at
any one time.
2. Volume measurement should be done away from the treatment facility.
3. Soap and water should be on hand for washing and flushing of skin and
eyes.
4. Plastic labware (graduated cylinders, beakers, etc.) should be used
to minimize the hazards of breaking glass.
In order to minimize personal risk, the following safety equipment should
be worn at all times when handling pesticides. Note that most household
gloves deteriorate when handling organophosphates and, therefore, should not
be used. Wearing of leather shoes is discouraged. This list of safety equip-
ment is adapted from Lande (1978) and is applicable to all individuals who
handle pesticides.
1. Impervious or rubber head covering.
2. Protective eye goggles (preferred) or safety glasses.
3. Organic vapor respirators — cartridge type, as approved by U.S.
Department of Agriculture
4. Washable work clothing.
5. Natural rubber gloves.
6. Latex rubber apron, ankle length (for plant operation) or rain suit
for outside washing operators.
7. Rubber workshoes or overshoes.
36
-------
SECTION 6
REVIEW OF EXISTING PRACTICES
In order to obtain more information concerning pesticide disposal prob-
lems encountered by commercial pesticide applicators around the country, State
Aviation Associations were contacted. Information from 36 agencies is shown
in Table 13. This table identifies the regulatory agency that is responsible
for registration of aerial applicators, the registration requirements, any
problems encountered by applicators in the hauling or usage of pesticides, and
the types of pesticides commonly used in each state. Ten states indicated
that aerial applicators face several specific problems. A range of problems
range were mentioned, including spillage during loading and unloading, runoff
from the site, container disposal, and collection of pesticide wastewater.
The state of Nebraska indicated that pesticide applicators are required to
contain all wash and rinse water used in cleaning pesticide application equip-
ment. The collected wastewaters are treated either with acid or alkali to
hydrolyze the pesticide before disposal.
Some states, specifically California, require closed-loop mixing systems
for the loading of pesticide application equipment. This type of system
minimizes the problems associated with container disposal and spillage during
the loading and unloading operations. However, the closed-loop system does
not eliminate the need for a system to treat the wastewater generated when the
application equipment is cleaned.
In addition to contacts with state regulatory agencies, numerous aerial
applicators have been interviewed. Most of these applicators describe two
basic problems. First, many operate at several airport locations. Normally,
any large application that requires more than one load of pesticides and is
located more than 16 Km (10 miles) from the operator's airport will be ser-
viced from a private landing strip. These small landing strips are isolated
and have no cleaning facilities. The pesticides are usually mixed on a ser-
vice truck and then pumped into the application equipment. Occasionally, the
application equipment is rinsed out at these remote locations, although nor-
mally the cleaning of the aircraft occurs at the central airport location.
The second major problem is the large, fixed capital cost required for
treatment facilities. Most of the applicators are unwilling to depreciate a
facility over a 5-year period, since their longevity at a particular location
is unknown. Most of the applicators do not own the airport and are working on
a yearly lease basis with the local airport authority and, hence, the question
of who should be responsible for any large capital outlay is of great concern.
37
-------
These responses from the regulatory agencies and from the applicators
indicate that there is a great need for a coordinated effort in the develop-
ment of the pesticide collection system. The state regulatory agencies must
be made aware that this is a problem faced by all applicators. They must be
willing to work with applicators in order to insure that the cost of the col-
lection and treatment system is equitably distributed between the pesticide
applicator and his/her clients. In addition, the implementation of closed-
loop mixing and transfer system should be emphasized, because this system
eliminates the spillage problem during the mixing and transfer of pesticide
solution and thereby greatly reduces the need for the collection system at
each of the remote locations that the applicator may use so long as the appli-
cators avoids cleaning his/her equipment at remote locations. All of the
waste pesticide, wash, and rinse water from the application equipment should
be collected at a central location.
Since most of these criteria are currently in the form of proposed or
implemented regulations either from state or federal government agencies, it
would appear that it is only a matter of time before there will be a uniform
policy across the country for the collection and containment of the pesticide
wash water.
38
-------
Table 13. State Regulations Affecting Aerial Applicators
STATE
AL
AK
AR
AZ
CA
CT
DE
FL
REGULATORY
AGENCY
Comissioner
of Ag &
Industries
Bureau of
Land Mgmt.
State Plant
Board
Board of
Pesticide
Control
Dept. of
Food & Ag
Pesticide
Compliance
Unit of the
CT Dept.
of Envir.
Protection
Dept. of Ag.
Dept. of Ag.
& Consumer
Services
REQUIRE-
MENTS OP
REG.
written
exams
premises,
license
permit,
records,
license
exam,
records
permit
PROBLEMS
spillage
in loading
& unloading
None
rinse con-
tainer Avia-
tion adding
rinsates to
mix tanks
yes
None
None
None
ORGANIZED
GROUP
AL Ag.
Aviation
Ass'n.
None
AR Ag.
Aviation
Ass'n.
AZ Ag.
Ass'n.
AG Aircraft
Ass'n.
None
None
None
PESTICIDES USED
End r in, toxaphene,
chlordane, thiodan,
2,4-D; 2,4-T
numerous
Carbaryl, malathion
methoxychlor, diazion,
thiodan, naphthalen-
eacetic acid, cygon,
captan, maneb-zineb
2,4,5-T, polygram
ferbam, metasystox R,
difolatan, casoron
granular
numerous
Carbaryl, lannate
benlate, mocap, CDEC,
sulfur
GA Dept. of Ag.
None
GA Ag. Bravo, duter, benlate,
def, folex, paraquat,
dynap, dynitro, 6-3
mix, atrazine,
toxaphene, methyl
parathion, azodrum,
methomyl
39
-------
Table 13. (Continued)
HI
None
None
IL
IN
KY
ME
MD
MA
MS
MO
Dept. of Ag.
Dept. of
Natural
Resources
& EPA
None
None
None
None
None
MI Dept. of Ag.
None
Ag. Aviation license disposal
Board exam, of unused
residency containers
Dept. of Ag.
NH Dept. of Ag.
yes
None
KY Ag.
Aviation
Assn.
None
None
None
Aviation
Ass'n.
MS Ag.
Aviation
Ass'n.
Urea, ammonium
phosphate, TSP super
phosphate, potash,
polaris, paraquat,
amatrine, DCMU, weed
killers, dalapon,
atrazine, gibberilic
acid
Paraquat, benlate,
parathion, sevin,
lannate, malathion
Tordon 101, captan,
guthion, sistox,
cyprex, pollyram
Unknown
Parathion, systox,
guthion, various
herbicides,fungicides,
bisdithioca rbona tes,
methylmyl, lannate,
carbaryl, malathion,
abate, chloropyrofs,
methoxychlor
parathion, atrazine,
dinitrol, monitor
most used for
cotton, soybeans,
& rice
MO Aerial most herbicides &
Applicators most all herbicides
Ass'n.
None
Malathion, tordon 101,
lannate,manzate,sevin,
thiodan, dipel, abate,
2,4,5-T; methoxychlor
40
-------
Table 13. (Continued)
NJ
NM
NY
ME
ND
OK
OR
PR
SC
SD
TN
Dept. of exam,
Envir. Prot. permit,
records
Dept. of Ag.
Dept. of exams
Aeronautics
ND Aeronautic
Commission
Dept. of Ag.
Dept. of Ag.
FAA
SC Aeronautic permit
Commission
Dept. of Ag.
Dept. of Ag.
None
Used pest-
icide
containers
None
Concrete
applicator
aprons are
used for
loading &
unloading
spillage;
failure to
clean out
when chang-
ing
None
None
None
None
Runoff;
vapor drift
None
N.E. Ag.
Aviation
Ass'n.
None
NE
Aviation
Trades
Ass'n.
ND
Aviation
Ass'n.
J.L. Putnam
OR Aviation
Trade
Ass'n.
None
SC Ag.
Aviation
Ass'n.
SD
Aviation
Trade
Ass'n.
TN Aerial
Applicators
Ass'n.
Many
Primarily carbamates
& organophosphates &
toxaphene
Carbaryl, furidan,
parathion, atrazine,
disyston, banuel,
2,4,5-T; 2,4-D;
to rdon , sul fur , ramrod ,
bladex
Numerous
Pesticides &
fertilizers
Diazinon, dipel
lannate
2,4-D; sevin,larathion,
dicamba, malathion,
super acide
methyl parathion, lasso,
lannate, treflan,
2,4-D; paraquat
UT
None
None
toxaphene, galacron
fundal
Parathion, mitasystox,
dursban, diazanon,
disiston
41
-------
Table 13. (Continued)
VA
WA Dept. of
Ag
None
yes
VA Pest-
icide
Ass'n.
Ag. Appli
cators
WI
WY Dept. of Ag.
None
None
Reabe
Flying
Service
None
Dessicants, phenoxy-
Hormone type; banvel,
phosdrin, phosvel,
parathion, methyl
parathion, sevin,
lannate, linidon,
diazinon
Parathion, paraquat,
dithene, sevin
2,4-D; malathion,
parathion, sevin
42
-------
SECTION 7
CLEANUP AND COLLECTION SYSTEM
In order to implement a control system for treating the wastewater that
is generated when application equipment is washed, a cleanup and collection
system must be designed. In the preliminary phases of this project a portable
system was used to collect wastewater samples for analysis and characteriza-
tion of the wastewater. This portable collection system consisted of a 12.2 m
x 13.4 (40 ft. x 44 ft.) vinyl sheet, which was spread under the application
equipment. After the aerial application equipment was washed the wastewater
was diverted to one corner of the sheet, and pumped into appropriate con-
tainers. A high pressure sprayer was used for the washing of the aircraft. A
boiler on the high pressure sprayer made it possible to use hot water for
cleaning both the pesticide application system and the surface of the air-
craft.
This collection system was first taken to the Southern Crop Service at
Del Ray Beach, FL where it was used to collect samples from aircraft as shown
in Figures 1. Samples were taken from the residue left in the application
equipment, wash and rinse water from the pesticide spraying system and wash
water from the surface of the plane. Approximately 25 gallons of water were
needed to clean the spray systems on these planes. Results of the analysis
from these various samples is reported in Section 8.
Although the portable system was useful in collecting the initial sam-
ples, the amount of labor required to divert the wastewater to the corner of
the vinyl sheet was too great for use in a practical treatment collection sys-
tem. As a result, a permanent modification was made to an existing pads at
the Garwood Airport in Monon, IN. This installation is shown in Figures 2 and
3. The existing concrete pad had previously been crowned so that the pad
would drain to the gravel pit located around the outside perimeter. A diver-
sion was built around the outside of the concrete pad to collect and channel
the water to one corner, where a small sump was constructed and a submersible
sump pump was installed. The wash and rinse water was pumped into a 3790 L
(1000 gal.) storage tank that was located on the site. This system worked
quite well and allowed for the continuous collection of wash and rinse water
from the aerial applicator.
Experience with the system has shown that it is unnecessary to segregate
the wastewater into separate fractions. Although the concentration of pesti-
cides is highly variable, the treatment system developed is capable of han-
dling these variations. The complexity of segregating the wastewater into
fractions of decreasing concentration would complicate the system
43
-------
Figure 1. Vinyl sheet used to col-
lect wash water from aircraft in in-
itial phases of study.
Figure 2. Concrete pad at pesti-
cide mixing area at Garwood Airport
in M^non, Indiana.
Figure 3. Modification in collection
pad included installation of a sump
and diversion of all wash water to one
corner of the pad.
44
-------
unnecessarily. All of the wash water, rinse water, and excess pesticide for-
mulation can be dumped onto a concrete pad and drained into a central sump.
This same pad could be used for mixing and loading of the application equip-
ment. This technique would insure that all of the pesticide contaminated
waste would be contained and could be treated with the proposed system.
Two alternative techniques for the collection and storage of the
pesticide-contaminated wash water would be possible. One alternative would be
to install and underground tank directly below the pad. This underground sys-
tem would provide the "neatest" appearance for the applicator. However, there
are several problems associated with below grade storage. Sludge accumulation
in the bottom of the tank could be difficult to remove and leaks in the tank
could go unnoticed for a period of time and result in significant groundwater
contamination. Earth excavation and tank placement would represent a sizable
fixed investment for the operator with limited salvage value if the applicator
moves to a new site.
An above ground tank would eliminate several of these problems. Sludge
accumulation in the bottom of the tank could be easily prevented by mixing and
flushing from the tank. Any leakage would be readily noticeable and correct-
able. Further advantages of above ground storage are lower cost, along with
greater flexibility in location of the storage structures. Two notable disad-
vantages would be that such a storage tank could interfere with traffic around
the collection pad and that a pump would have to be used to move wastewater
from the sump to the above ground tank.
Some safeguards should be provided to prevent rain water from entering
the collection system since this would increase the volume and dilute the
wastewater to be treated. Although the treatment plant is capable of handling
a wide variety of wastewater concentrations it is always preferable to minim-
ize the volume treated. A cover over the collection pad is recommended. Such
covers are readily available for covering athletic fields and could be easily
implemented on a relatively small-scale.
At this time, it appears unnecessary to have the collection pad enclosed
in a building. Enclosures would inhibit the accessibility of the pad to the
applicator for the filling and mixing of pesticides. The applicators who have
evaluated the system concur with this opinion and would prefer to use an open
pad. The drift of pesticides away from the pad does not appear to be a signi-
ficant problem. This system could be employed on most currently existing
applicators' facilities. The cost of such a system is projected in Section
10. The success of the treatment system requires a simple and inexpensive
method of collecting the wastewater.
AWBERC LIBRARY U.S.
EPA
45
-------
SECTION 8
LABORATORY STUDIES
Data is extremely limited on the concentrations and amounts of
pesticide-contaminated wash water generated during the cleanup of agricultural
aircraft. In fact, since there are no standardized cleaning or disposal pro-
cedures for this industry, the problem of finding reliable data is compounded.
8.1 WASTEWATER CHARACTERISTICS
Faced with such a lack of information, the investigators in this project
felt that the only viable alternative for obtaining relevant data was to visit
an actual site. Approximately 758 L (200 gal.) of wastewater and rinse water
were collected at the Southern Crop Service Headquarters in Del Ray Beach,
Florida. Samples were drawn from a number of sources including tank drainage,
rinse water, and wash water. A high pressure sprayer was used to wash both
Piper Pawnee and Weatherly Ag Tractor aircraft. Dry powders or dust and
liquid formulations were obtained. In addition, samples were taken from an
on-site holding pond that had been used for the storage of pesticide wastewa-
ter for several years.
Because of the highly mixed nature of the waste, analyses were limited to
gross parameters such as COD, pH, and solids determination. During the ini-
tial stages of the study there was no necessity of determining specific pesti-
cide concentrations.
The samples from Southern Crop Service were returned to West Lafayette,
IN for analysis. Analytical data and source information are summarized in
Table 14. Samples designated as A were obtained by direct drainage of excess
pesticide left in the plane hoppers after spraying had been completed. The
A-l sample contained parathion, M-75 fungicide and 20-20-20 foliage fertil-
izer, while sample A-2 contained toxaphene, lannate, 20-20-20 foliage fertil-
izer, A-3 contained M-75 fungicide, parathion and lannate while A-4 contained
thiodan, guthion and M-75. Samples designated at "B" were taken from the on-
site, earthen holding pond. Sample "C" was pumped from an on-site well used
to provide wash water. Samples D-9 thru D-16 were taken from a Pawnee air-
craft after it had finished spraying a solution containing M-45, nutri-leaf
cygon, toxaphene and parathion. All other D samples were taken from another
airplane spraying a solution containing 57 L (15 gal.) of Toxaphene, 38 L (10
gal.) of phosdrin, 38 L (10 gal.) of cygon, 91 Kg (200 Ibs.) of urea, 23 Kg
(50 Ibs.) of M-45, 9.5 L (2.5 gal.) parathion, and 9.5 L (2.5 gal.) lannate.
The "E" samples were drawn from a Weatherly ag tractor that had sprayed a
46
-------
solution of M-45, dithane, methyl-ethyl parathion, toxaphene, nutri-leaf, and
20-20-20 foliage fertilizer.
Table 14. Characteristics of Wastewater Samples Collected in Florida
Sample
A-l
A-2
A-3
A-4
B
C
D-l
D-2
D-3-
D-8
D-9-
D-15
D-16
D-17
E-l
E-2
E-3
E-4
E-5
E-6
E-7
E-8
E-9-
E-ll
Source
Tank drainage
Tank drainage
Tank drainage
Tank drainage
Holding lagoon
Well water
First rinse-
pesticide tank
(after 15 gal.)
First rinse-side
loading lock
Aircraft surface
wash
Aircraft surface
wash
with detergent
Detergent wash with
bottom sediment
Bottom first rinse
Initial tank rinse
water
Last of first rinse
water
Last of first rinse
water
First rinse-side
loading rack
First rinse boom
(Note following samples
taken at 5 gal increments)
Third rinse boom
Fourth rinse boom
Fifth rinse boom
Composite
COD
Total
81,500
59fOOO
66,600
23,500
6,700
45
375
3,000
1,200
1,200
750
3,000
40,000
55,000
8,000
8,500
14,000
13,000
3,500
2,000
450
1,200
COD
Sol.
189
2,326
500
500
200
1,048
25,500
16,800
5,130
5,020
6,454
9,600
650
205
166
904
pH
7.3
7.4
7.5
7.5
7.5
6.7
7.1
6.0
7.4
7.0
6.4
6.5
6.8
6.8
7.4
6.9
TSS
130
950
600
600
550
3000
2,100
24,000
7,000
18,000
5,400
11,600
3,200
1,000
110
1,140
SVS
85
350
350
300
1,000
1,600
19,400
14,000
4,200
8,900
2,300
980
90
950
47
-------
Because samples D and E represented the type of waste that would be
treated by our proposed facility, a more thorough analysis was performed. COD
determinations along with pH, total and volatile suspended solids were suffi-
cient to adequately characterize the waste for the proposed treatment system.
An attempt was made to determine total solids on several samples, but pungent
fumes were released into the laboratory due to the high volatility of the
waste. The total solids determinations were discontinued for safety reasons.
All samples, with the exception of C, were noted for a striking
greenish-yellow color along with a sizeable amount of settleable material,
forming a "mud" on the bottom of the sample containers.
These collected samples covered a wide range of solids concentrations,
while the pH was relatively consistant with values in the range of 6.4 to 7.5.
The composite sample of the wash and rinse water collected provided the most
realistic sample of the wastewater. These samples, D-3 through D-15 and E-9
through E-ll had a COD of approximately 1000 mg/L. Consequently, a pesticide
concentration sufficient to give a chemical oxygen demand of approximately
1000 mg/L was used for initial lab scale testing of various treatment alterna-
tives.
8.2 LAB EVALUATION OF WASTE WATER TREATMENT TECHNIQUES
The representative sample, E-9 through E-ll was used for initial lab
testing. Approximately 57 L (15 gal.) of this sample were available, so a
\rari a^\r nf t-oct-c \jjora narfnfme^
l«WW\»*A *^ . f 1Ł*[*^ WA AllKtfl v»v«^ JT ^1 «•• \^W
wide variety of tests were performed.
Due to the high suspended solids content of the waste (approximately 1100
mg/L). Preliminary coagulation/flocculation/sedimentation procedure were used
to reduce the COD concentration. A series of tests was set up to analyze the
effects of coagulant types and dosages.
f
First, sodium hydroxide was tested as a flocculant. The dosages were
adjusted so as to cover a range of pH values. Here, as in all further test-
ing, samples were rapidly mixed for two minutes, slow mixed from 10 to 15
minutes to promote particle agglomeration, and allowed to settle for 25
minutes. Floe characteristics were noted and the efficiency of the operation
was measured by determining the COD of the supernatant. A summary of the data
is present in Table 15.
48
-------
Table 15. Hydroxide Coagulation of Wastewater Samples Collected
in Florida. Initial COD was 1200 mg/L.
pH Final COD Floe Characteristic
9.0
10.5
11.6
12.2
12.6
12.9
360
260
262
271
292
327
Very Turbid
Very Turbid
Slightly Turbid
Slightly Turbid
Clear
Clear
Alum was also evaluated as a coagulant. It should be noted that the
efficiency of alum coagulation is dependent on whether there is sufficient
alkalinity in the wastewater to allow formation of the aluminum hydroxide pre-
cipitate. Alkalinity determinations on sample E-10 and the well water gave
identical values at 273 mg/L as CaCC- . Sufficient alkalinity was present to
react with dosages of alum up to 200 mg/L. A summary of the alum floccula-
tions data is presented in Table 16. The final pH of the treated solutions
were between 6 and 8, the effective range for alum coagulation.
Table 16. Alum Coagulation of Wastewater Samples Collected
in Florida. Initial COD was 1200 mg/L.
Alum
(mg/1) Final pH Final COD Floe Characteristics
50
100
150
200
250
300
6.9
6.6
6.4
6.4
6.3
6.1
352
318
322
286
306
300
Turbid
Clear
Clear
Slightly Turbid
Turbid
Turbid
Based on these studies, hydroxide coagulation was most effective at pH
11, while optimum alum dosage was around 200 mg/L.
Ferric chloride was also evaluated as a coagulant and results were very
similar to those of alum. The degree of COD removal was found to be indepen-
dent of pH in the range of 4.3 to 8, as might be expected from the wide effec-
tive pH range of the iron salts, and supernatant COD values were essentially
the same as those for alum at equivalent coagulant doses. The quality of the
supernatant measured in terms of COD did not correlate with the visual appear-
ance of the samples. Part of the reason for this phenomena may have been due
to the fact that percentage differences between COD values were small and are
not significant in light of the errors inherent within the COD procedure.
49
-------
Solutions of carbaryl and malathion prepared in the laboratory were also
evaluated. Tests showed that carbaryl dosages of 500 mg/L and malathion
volumes of 5 ml/L produced COD values closely approaching those found for
solutions E-9 through E-ll, these solutions were used for all further labora-
tory equation studies. A pH of 11 was again found to be optimum for hydroxide
coagulation. The results of flocculation/cougulation studies on these syn-
thetic solutions are summarized in Tables 17 and 18.
Table 17. Hydroxide Coagulation of Malathion
pH Initial COD Final COD % Removal Floe Characteristics
10
10.
11.
12.
12.
8
8
3
6
671
684
669
605
676
285
269
375
384
431
57.
60.
44
37
36
2
7
Turbid
Clear
Clear
Clear
Clear
with
with
with
floating
floating
floating
solids
solids
solids
Table 18. Hydroxide Coagulation of Carbaryl
pH Initial COD Final COD % Removal Final Characteristics
8.5
9.3
10.1
11.2
11. 9 '
12. 3
mm
—
660
663
636
650
^
-
567
360
360
373
—
-
14
45.7
; 43
42.6
No effect
No effect
Turbid
Slightly turbid
Very clear
Very clear
Tests using alum on synthetic solutions produced similar results, that
is, approximately 200 mg/L of alum were required to obtain maximum COD remo-
val. Only minor differences in COD removal occurred with alum dosages of 100
to 300 mg/L.
Test solutions were filtered to compare filtration to flocculation and
settling. A carbaryl solution of 831 mg/L was filtered through Whatman #1
cfilter paper (11 M pore size) to produce a solution with a COD of 200 mg/L,
giving a 75 percent COD removal, slightly better than the removals observed
during flocculation. Filtration of malathion solutions only reduced COD from
approximately 920 mg/L to about 700 mg/1, indicating that these emulsions can-
not be successfully treated by filtration. \-^\~-f , ^ -,r '\ , ~,v .... '- t , * i ^
The next step in the laboratory study was to evaluate activated carbon
adsorption. Five different brands of carbons were received from three
manufacturers, and each was evaluated for its ability to remove carbaryl and
malathion. This evaluation was performed by conducting isotherms studies for
each carbon. Different amounts of carbon were added to 100 mL, of the sample.
50
-------
Samples were placed on a shaker table and allowed to equilibrate for two
hours. All pesticide solutions for the isotherm studies were prepared by
first flocculating the samples with either sodium hydroxide or alum and then
filtering through a millipore filter. Carbon was then added and after the 2
hr. equilibration, the carbon was removed by filtration through a millipore
filter. , .
-••"•-•. i , • I '. ... ~ .•_•;>, ~
A graph of the data according to a Langmier equation is provided were q
is equal to the milligrams of pesticide (expressed as COD) adsorbed per gram
of carbon and represents the final equilibrium concentration of the pesticide.
The carbon giving the line with the least slope is the best adsorbent. 7
\ "
Figures 4 and 5 show that the Darco HD-3000 is the preferred adsorbent
for carbaryl, and that the hydrolysis that occurs from hydroxide coagulation
produces a more readily absorbed product. This result is suprising in light
of the findings of other researches. However, the situation is quite dif-
ferent with malathion as is illustrated in Figures 6 and 1. The alum floccu-
lated effluent is adsorbed more efficiently than the hydroxide products, and
that the Nuchar WV-L 12 x jUl4nesh_is the better adsorbent. Other isotherm
studies were run of (Filtrasorb^400, and it was found to b^ inferior to the
Nuchar WV-L for all cases although the isotherms were fairly close for the
alum coagulated malathion as shown in Figure 8.
At this point, a decision had to be made as to which carbon to use in the
pilot plant. Unfortunately, this decision was not clear. The best carbon for
carbaryl removal was not best for malathion removal. The carbon contact unit
was designed for malathion removal. The basis behind this decision was that
carbaryl is more amenable to removal by pretreatment filtration or coagulation
since it is used preliminary as a solid formulation. Therefore, maximum life
of the carbon bed could be achieved by maximizing malathion removal.
Tn order to test the isotherm data, column studies on the removal of
malathion were begun with Nuchar WV-L 12 x 40 mesh carbon and Filtrasorb 400.
Two six-inch high, 1-inch diameter columns were constructed and fed floccu-
lated and settled malathion solution at a rate of 1.4 L/s-m (2 gpm/ft. ).
For the Filtrasorb, leakage of 3-5 mg/L COD appeared immediately, and
this increased to 20 mg/L after 12 liters, about 20 mg/L after 30 liters, 30
mg/1 after 36 liters and so on as shown in Figure 9. Operation of the column
stopped at 71 liters, where the COD concentration reached 140 mg/L. It should
be noted that the feed solution had a COD of 220 mg/L.
For the Nuchar carbon, better results were obtained, as predicted by the
isotherms. No significant leakage occurred until almost 30 liters had passed
through the column. Nearly 44 liters passed before 5 mg/L COD was found in
the effluent. This response is also illustrated in Figure 9. The column was
shut down after 142 liters had passed with an effluent COD of 105 mg/L.
The capacity of the Nuchar before breakthrough (chosen to be 5 mg/L) was
calculated to be 220 mg COD/gram carbon. At 10 percent breakthrough (20 mg/L)
the capacity of the carbon was approximately 360 mg COD gram carbon, a very
favorable degree of adsorption.
51
-------
7
.022 •
.017 •
.012 •
.007
.002
Figure 4. Langrauir Isotherm plots of the adsorption of carbaryl
following alum coagulation.
.04 •
.03
at
.01
Ol
JOS
.0
Figure 5. Langmuir Isotherm plots of the adsorption of carbaryl
following hydroxide coagulation.
52
-------
.024
.016
008
.01
.05
.10
Figure 6. Langmuir Isotherm plots of the adsorption of mlathion
following alum coagulation.
022 •
on
.02 •
O07-
.002
HO-300O
(DARCO)
.01
-02
-4-
J04
Figure 7. Langmuir Isotherm plots of the adsorption of malathion
following hydroxide coagulation.
53
-------
.015
.01
COS
VnM 12x40 MESH
(NUCHAR)
Figure 8. Langmuir Isotherm plots of the adsorption of alum co-
agulated malathion samples on Filtrasorb-400 and WVG.
coo
FILTlWSORe-«X>
KM&3N)
100
Figure 9. Carbon adsorption of malathion on columns of Filtra-
sorb-400 and WVG.
54
-------
Based on these results, a pilot plant with an initial filtration, fol- ./
lowed by flocculation and settling, followed by coalescence and carbon adsorp- ""s
tion should provide good removal for both carbaryl and malathion. In the
pilot plant both Filtrasorb and Nuchar carbon were used to provide further
comparisons of adsorption efficiency.
ft
55
-------
SECTION 9
PROTOTYPE SYSTEM
The pilot treatment plant was designed to analyze the effect of various
treatment options on the removal of pesticides from actual and synthetic
wastewaters generated by pesticide applicators. Based on the success of
several treatment options in the laboratory, both coagulation /
flocculation/sedimentation and activated carbon adsorption were included in
the final design. Filtration and oil coalescence were added to the pilot
plant since these processes are phase separation procedures fundamentally
similar to coagulation/flocculation, and presented possible advantages in
overall convenience of operation. The system was designed to be a collection
of unit operations. All connection between these individual units were made
by flexible hose with screw-type fittings. This arrangement allowed for
evaluation of various sequences of unit operations. A schematic diagram of
the system is presented in Figure 10.
The pilot plant (Figure 11) was tested in both field generated and syn-
thetic pesticide solutions. Solutions derived from field washing operations
were collected (collection system is described in Section 7) and pumped to a
1890 L (500 gal.) holding tank secured on the bed of a small truck. These
field generated samples were returned to the Agricultural Engineering building
at Purdue University, where it was transferred to holding tanks. These hold-
ing tanks also served as a reaction vessel for the first unit operation of
coagulation/flocculation/sed indentation.
The filtration systems were tested for their efficiency in the removal of
suspended solids. Two of the systems, a Cuno cartridge filter and the
Ronnigen-Petter fabri-basket filter were chosen for their operating conveni-
ence and for the wide range of pore sizes available. The Cuno filter con-
sisted of a diatomaceous earth type cartridge seated in a stainless steel
housing. Cartridges with filtration pore size of 25 and 5 microns were chosen
for study and are shown in Figure 12. The second filtration unit, the fabri-
basket filter consisted of a nylon "sock" fitted into a perforated metal
basket support. Again, media of different pore size are available, although
the 1 micron size was chosen for this research (Figure 13).
Despite the fact that these two units were considered to be adequate for
the removal of solid formulations, such as dusts or granules, they cannot be
expected to be effective against emulsified formulations. Consequently, a
Balston filter tube coalescer, consisting of a hollow fiberglass type tube
supported within a clear plastic housing, was included within the treatment
system (Figure 14). Flow to all these filtration and coalescence units was
56
-------
ui
-4
INFLUENT-
•^^^
0
s
I
SYMBOLS
HOLDING TANK
PUMP
FLOW CONTROL VALVE
WATER METER
3 WAY SELECTOR VALVE
pH ADJUSTMENT
SLUDGE DISCHARGE
SAMPLING POINT
MIXER
LIQUD LEVEL CONTROL
/
SH
3F
<=
m
c=>
-Sh
s
<$-
FLOCUL
CEN
@—
ATION
TER
^
CTD
C^>
EFFLUENT
FOR -«-
RECYCLE
FCV>
S-
S
ACTIVATED CARBON
ABSORPTION COLUMNS
Figxare 10. Schematic diagram of pesticide treatment plant.
-------
Figure 11. Pilot plant with mixing
tanks, filters, and carbon columns.
Figure 12. Cuno cartridge filters
with 5 and 25 micron filters.
Figure 13. Fabric basket filter with
1 micron screen.
Figure 14. Cartridge coalescers op-
erating at a 10 psi pressure drop.
58
-------
measured by a rotameter. Effluent from these units could be directed either
to the activated carbon columns or to 378 L (100 gal.) storage tanks to await
further treatment.
Two variable speed (0-1800 rpm) mixers were used for chemical mixing and
solids flocculation. These mixers were supported on steel frame as shown in
Figure 15. for anchoring the mixer. Mounted on this frame was a liquid level
control switch to shut -off the pump during filling of the tanks. All electri-
cal controls were centralized on a portable electrical panel that was mounted
on one of the frames. The control system is shown in Figure 16.
Each 378 L (100 gal.) tank had three outlets, one approximately .5m (29
inches) below the top of the tank, the second tap approximately .23 m (9
inches) below the first, and a third tap installed at the apex of the spheri-
cal tank bottom. Ball valves were installed at each of these taps.
The mixers were delivered with propeller type mixers. These propellers
were adequate for rapid chemical mixing, but the shear forces introduced dur-
ing batch flocculation hindered the formation of a dense, good setting "floe."
A special flat bladed paddle, .3m (12 inches) long and .15 m (6 inches)
high, was constructed and used for both chemical mixing and flocculation.
Two epoxy lined, stainless steel activated carbon columns were used in
the pilot plant. The columns had a diameter of approximately .25 m (10 in.)
and a height of 1.2 m (4 ft.). _ u .^^'^ - ^ w _ A I?1"* *- • :.v-_ i_ - -„
'
v_
The pumps filtration units and activated carbon columns were mounted on a
single frame as shown in Figure 17.
v^ V"\ * " ' ' ' -•
9. 1 TREATMENT OF FIELD COLLECTED WASTEWATER
The finished pilot plant consisted of four 378 L (100 gal.) ployolefin
tanks, two variable speed Lightning mixers, two Balston coalescers, one
Ronnigen-Peter fabric-basket filter, one Cuno filtration unit with variable
filter media, and two 5 gpm Jabsco pumps. A variety of pesticide mixtures
from two sources were analyzed and used to test the effectiveness of the plant
in pesticide removal. The first source of wastewater was a small agricultural
airport at Monon, Indiana, where the collection system described in Section 7
was installed. The second source of pesticide waste was the Purdue University
O'Neil farm.
The samples that were collected contained a wide variety of different
types of materials. The treatment of actual field samples gave an indication
of the range of possible problems that would be encountered during field test-
ing of the unit.
The first sample obtained for treatment in the pilot plant contained
sevin wettable powder and aircraft wash water. This sample was obtained after
a very thorough washing of the aircraft. Approximately 5 gallons of excess
solution was left in the aircraft and combined with the equipment wash water.
59
-------
Figure 15. Mixing tanks used for co-
agulation, flocculation and sedimen-
tation.
Figure 16.
and pumps.
Control panel for mixers
Figure 17. Frame for filters and pumps
in the pilot plant.
60
-------
Initial jar tests were conducted to determine the settling behavior of
the wastewater. The initial characteristics of the sample were: pH 7.7, COD
50,000 mg/L, alkalinity 360 mg/L as CaCO., and suspended solids of 33,000 mg/L.
Initially, the wastewater settling characteristics without chemical addition
was studied. Although some settling occurred, the high suspended solids con-
centrations indicated that some form of coagulant addition or filtration would
be necessary to achieve efficient solids separation. Separation of solids by
filtration through Whatman filter paper reduced the COD from 50,000 mg/L to
810 mg/L.
As a consequence, a large number of jar tests were performed in order to
determine coagulants and dosages that would be successful in clarifying this
material. Alum was used as the coagulant due to its availability and ease of
handling. Possible problems may occur because of the relatively narrow pH
range in which alum is effective (pH 6.5-8.0).^ However, only one solution
tested fell outside this pH range, and the pH is easily adjusted to acceptable
range.
Excellent removal of suspended solids was achieved with an alum dose of
350 mg/L and a settling time of 45 minutes to one hour. Higher dosages of
alum produced only slightly better solids removal. In order to achieve this
marginally improved removal, additional alkalinity had to be added to the
solution (in the form of NaOH) to insure sufficient alkalinity for complete
aluminum ion reaction (1 mg/L of alum reacts with approximately .85 mg/L of
alkalinity). The results of one such alum coagulation study are listed in
Table 19. Samples were taken from the 2 L beakers at the 1 L depth.
Table 19. Effect of Alum as a Coagulant for Cerb4ryl Removal
Alum dose
(mg/L)
250
300
350
400
450
Settling time
(min)
30
60
30
60
30
60
30
60
30
60
Suspended solids
(mg/L)
124
78
260
96
56
44
52
40
50
40
Further studies were carried out on a wastewater sample collected during
construction of the collection system. Wastewater was drawn directly from the
gravel drainage area surrounding the concrete pad. The highly colored, turbid
wastewater was within a few inches of the gravel surface, and illustrated the
inadequacy of gravel infiltration ditches as a means of waste pesticide dispo-
sal. This material was identified as sump water, and its characteristics were
61
-------
COD of 4100 mg/L and suspended solids of 1100 mg/L. No attempt was made to
determine the actual pesticides present.
Because alum coagulation was so successful in bench-scale jar testing,
full scale tests, that is 378 L (100 gal.) batch experiments, were begun on
the carbaryl solution and sump water. Full scale treatment consisted of a
chemical addition followed by two minutes of rapid mixing, and approximately
20 minutes of slow flocculation at about 30 rpm, after which time the material
was allowed to settle without agitation. Table 20 presents typical results
with an alum dose of 350 mg/L for carbaryl wastewater and 375 mg/L for the
sump wastewater.
Table 20. Full Scale Treatment of Carbaryl and Sump Water Using
Alum as a Coagulant
Settling Time Sample Suspended
(min) Tap* Solids (mg/L)
Carbaryl contaminated wastewater
30 Top 205
Bottom 225
45 Top 25
Bottom 52 v „ '
60 Top 16 .
Bottom 42
Sump wastewater
r . * '
, --f-
30 Top 28
Bottom 22
60 Top
Bottom 6
Overnight
(14 hrs) Top
Bottom 2
Flocculation and sedimentation, although a relatively simple and effec-
tive treatment, could present some problems to pesticide applicators in deter-
mining optimum chemical dosages and purchasing the chemicals. For these rea-
sons, filtration of pesticide wastewaters was evaluated. Three different
types of filters were analyzed. The first was a disposal cartridge type
filter with 25 n and 5 ^ pore sizes. The second filter consisted of a 1 jj
pore size fabric mesh supported by a porous metallic basket enclosed in a
stainless steel housing. The third filter was a coalescer which consists of
fiberglass tubes inserted within a clear plastic housing.
The 25 micron Cuno filter was tested first. The influent to the filter
was a carbaryl solution with a suspended solids concentration of 1182 mg/L. A
rapidly increase in the pressure drop across the filter was observed with
62
-------
littler reduction in suspended solids. The pressure drop increased from 41 to
104 Kpa (5 to 15 psi) in 15 minutes. The suspended solids concentration of
the effluent from the filters was over 1000 mg/L.
The 25 ;a filter was also used to treat a dilute solution of alum coagu-
lated sump wastewater with a suspended solids concentration of 32 mg/L. The
suspended solids concentration was reduced to 29 mg/L during filtration.
A 5 p filter was then used on the same supernatant, but at two different
flow rates. Again a slight decrease in suspended solids concentration from 29
to 25 mg/L was noted.
Further tests on the applicability of the 5 jj filters were performed on
different material. This sample was collected at the Monon airport and pri-
marily consisted of the herbicide paraquat. Sample characteristics were COD
4400 mg/L and suspended solids of 1490 mg/L. Tne material underwent a signi-
ficant drop in suspended solids on passage through the filter, along with a
sizeable decrease in COD, but the filter was almost immediately blinded,
suffering a pressure drop oŁ over 20 psi after operating less than one minute
at a flow of one gpm. The effluent had a suspended solids concentration of 25
mg/L and a COD of 1400 mg/L.
Since rapid "binding" was experienced with filters of a larger pore size,
the fabric-basket filter was only used with solutions that had been previously
coagulated. The treated sump water had a suspended solids concentration of 50
mg/L. The 1 u fabric basket filter reduced the concentration to 46 mg/L.
These results appear surprising in light of the 1 p pore size of the filter.
Three possible explanations of this phenomenon are possible: (1) Either there
was an imperfection in the filter media, such as a puncture or weak seam, (2)
the non-coagulated particles were less than 1 micron in size (highly
unlikely), or (3) the particles were broken up during passage through the
filter. Because some leakage around the seam of this unit was observed, the
first hypothesis appears the most likely.
The coalescers were considered next. These units were plagued with
operational problems from the beginning, most notably leakage around the tubes
during high pressure operation. Even though some filtration occurred, since
there was a thick layer of solids on the inside of the filter, and the pres-
sure drop reached 270 KPa (40 psi) after treatment of 150 gallons, the leakage
around the coalescer tubes precluded the collection of any valid data. Conse-
quently, these units were dismissed from further consideration.
The next step was to evaluate flocculation/sedimentation. Actual field
operations would require repeated flocculation-sedimentation in the same tank,
with the settled solids building up slowly as each supernatant was drawn off.
Therefore, the effect of resuspending and settling the settled solids on
solids removal was evaluated. Studies were conducted at both the full-scale
and jar-test level. An alum addition of only 50 to 100 mg/L was found to be
sufficient to promote good re-settling, as illustrated in Table 21 where alum
dosage was 100 mg/L. Alkalinity was added in each case to insure complete
reaction of the added aluminum.
63
-------
Table 21. Flocculation/coagulation/sedimentation for removal
of solids using resuspended sludge
Settling
time
(min)
15
30
45
30
45
60
Sample
Tap
Top
Bottom
Top
Bottom
Top
Bottom
Top
Bottom
Top
Bottom
Top
Bottom
Solution
Type
Carbaryl
Carbaryl
Carbaryl
Carbaryl
Carbaryl
Carbaryl
Sump Water
Sump Water
Sump Water
Sump Water
Sump Water
Sump Water
Suspended
solids
(mg/L)
134
2042
16
142
6
10
4
2496
0
3134
0
454
Three coagulant aids, anionic polymer Purifloo A-23 and cationic polymer
C-31, both manufactured by Dow Chemical and an anionic polymer 1255 from Wat-
con were then tested to determine if greater solid removal could be achieved.
Both Dow compounds were powders that were difficult to dissolve in water while
the Watcon product was a liquid anionic polymer. The pesticide contaminated
wastewater from the Purdue O'Neil Farm was treated with 100 mg/L of alum and 1
mg/L of anionic polymer. This treatment was sufficient to reduce the
suspended solids concentration from 230 mg/L to 5-20 mg/L in approximately 30
minutes of settling. The degree of pesticide removal achieved by
flocculation/sedimentation is summarized in Table 22. , , ,,, , ,.,_\ , *
Table 22. Pesticide Removal by Pilot Plant
Using Aim and Anionic Polymer
Removal of Indicated Pesticide in\ Percent
Treatment Monitor Lannate Carbaryl
Settled 3 days w/o chemicals
Alum addition - settling time 30 min.
Alum + polymer addition
settling time 30 min.
19%
64%
i '
90%
82%
89%
\ ' '
50%
43%
,_
56%
T ..
Another sample was collected from Monon that contained a wide variety of
compounds. This wastewater was jar tested and then treated full-scale>by
adding 100 mg/L FeCl (roughly equivalent to 50 mg/L of alum) and 1 mg/L of
anionic polymer. NO significant improvement in supernatant quality was seen
when dosages as high as 400 mg/L FeCl , were applied as long as 1 mg/L of
64
-------
anionic polymer is provided. It was observed, as expected, that when the new
solution was mixed with settled solids removed from previous treatments, a
clearer dividing line between solids and supernatant was seen, along with a
slightly faster settling rate.
At this point, all the settled solids from previous treatments were com-
bined into a single tank. The purpose of this test was to determine the
settleability of previously flocculated and settled solids. When this solu-
tion was mixed, a thick suspension was obtained with a suspended solids con-
centration of about 17000 mg/L. When 1 mg/L of anionic polymer was combined
with 100 mg/L of alum, a supernatant with excellent clarity was produced.
The next sample of pesticide contaminated wastewater from the Purdue
O'Neil farm presented some serious problems. The methods of coagulation that
had been used were completely unsatisfactory. To solve this problem several
techniques were evaluated. Acid cracking of the emulsion with varying dosages
of sulfuric acid was unsuccessful. The problem was that 300 mg/L of a wetting
agent had been added to coat the leaves of cabbage plants with the insecti-
cide. Review of industrial waste treatment literature indicated that calcium
precipitation of wetting agents has been used with success. For this particu-
lar sample, which had a pH of 5.85, the pH was raised to 10 with lime (CaOH ),
yielding a calcium to surfactant ratio of approximately 2:1 on a molar basis.
Rather than drop the pH down to an acceptable range for subsequent alum addi-
tion ferric chloride was used as the coagulant. Dosages of about 600-800 mg/L
of ferric chloride with anionic polymer were needed to achieve good clarity in
the supernatant during jar tests. However, when the material was diluted to a
concentration similar to equipment wash water it was only necessary to raise
the pH to 9.5 with lime addition and to add 200 mg/L of ferric chloride and 1
mg/L of anionic polymer to achieve good clarity.
At this point, a technique that had been studied in the Environmental
Engineering Department of Purdue University to clarifying thick suspensions of
clay material was tested. This procedure involved addition of a powdered
activated carbon (PAC) and a cationic polymer. The addition of calcium
hydroxide and about 5 g/L of PAC, 1 mg/L of cationic polymer alone was suffi-
cient to clarify the material. Due to the "messy" nature of working with
powdered activated carbon and the added expense of using PAC on a full scale
basis this method was not compared to an activated carbon adsorption of pesti-
cides.
Treatment of this wastewater demonstrated the need for the addition of
calcium salts to clarify surfactant bearing materials. Because many pesti-
cides release highly toxic intermediates upon alkaline hydrolysis, and also to
preclude the possibility of raising the pH above the acceptable range for alum
addition, calcium chloride is now being used in preference to lime.
The next batch of wastewater collected at the Monon airport contained
paraquat. The original characteristics of the waste were COD 4400 mg/L,
suspended solids 1490 mg/L and pH 7.58. The wastewater was mixed with previ-
ously settled solids, 100 mg/L of alum and 1 mg/L anionic polymer. The
results are presented in Table 23. The large reduction in suspended solids
would indicate that this wastewater is amenable to the
flocculation/sedimentation treatment.
65
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Table 23. Flocculation/coagulation/sedimentation as a means
of a paraquat removal
Settling Time Sample Tap COD (mg/L) Suspended Solids (mg/L)
45 minutes
90 minutes
Top
Bottom
Top
Bottom
3,650
55,000
2,975
295
24,360
36
Previous tests indicated that increased concentrations of solids can lead
to better settling behavior and decreased polymer dosages. Therefore, the
settling rates of a tank that contained a bottom solids concentration of
95,000 mg/L with a solids layer of approximately .50m (20 in.) was determined.
When the solids were suspended the concentration was approximately 20,000
mg/L. The second tank had a resuspended solids concentration of 7500 mg/L.
Resuspension took place by mixing with the wastewater from the Monon airport.
The first tank was first treated solely with 1 mg/L of anionic polymer, and it
took approximately 90 minutes for the solid-liquid interface to fall below the
bottom tap. Supernatant suspended solids were 36 mg/L. A replicate of this
test, but with 100 mg/L alum added as well, gave essentially the same results,
indicating that coagulant addition provides no measurable improvement when
highly concentrated solutions are involved. The supernatant COD was 2400
mg/L.
The final sample collected at Monon had a COD of only 600 mg/L and
suspended solids of 172 mg/L. Jar test treatment showed that conventional
alum and polymer treatment did not produce a good quality supernatant. How-
ever, addition of .5 to 1 gm/L of calcium, introduced as calcium chloride,
allowed for good clarification. This indicated the presence of some surfac-
tant material which was further evidenced by the formation of a surface foam
upon mixing. Where jar testing is not possible before treatment, calcium
addition as a matter of course would perhaps be desirable. ~2> C-M- CT 7
(V> -„ "*, -, u o u f> r? _ ,-, ' "7
. <*•* p fv» » -, ^(Ł /„-!• ^
Next activated carbon adsorption of pesticides was evaluated. "Table 24
illustrates carbon adsorption of the carbaryl in wastewater. The wastewater
was passed through the carbon columns twice. The first pass, at approximately
11 L/m (3 gpm) (4.2 L/s-m ) did not achieve acceptable effluent quality, so a
second pass at 3.8 L/m (1 gpm) was made. This flow rate of 3.8 L/m has been
maintained for all further studies and gives an approximate contact ime of 8
minutes in each bed. The two columns were used in series, with the first
column containing approximately 37 Kg (80 Ibs.) of Filtrasorb 300 (Calgon Cor-
poration) while the second contained an approximately equal amount of Nuchar
WV-G (Westavco Chemical.Division). Samples were first contacted with the Fil-
trasorb. Analysis of carbaryl concentration on both carbon effluents were
performed. The Nuchar effluent represented the plant's final effluent. Obvi-
ously, slowing down thexflow rate made a dramatic difference in the degree of
pesticide removal.
66
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Table 24. Carbaryl removal by absorption on activated carbon columns
(influent carbaryl concentration 475 mg/L).
Sample Carbaryl (mg/L)
First pass - 3 gpm
Filtrasorb effluent
75 gallons 48
100 gallons 26
125 gallons 21
150 gallons 20
Nuchar effluent (final product)
35 gallons 16
65 gallons 10
100 gallons 28
125 gallons 11
150 gallons 6
Second Pass - 1 gpm
Filtrasorb effluent
50 gallons <1
Nuchar effluent
25 gallons <1
50 gallons <1
Carbon studies were also run on the sump water after coagulation and sed-
imentation. The results are summarized in Table 25. Since the wastewater
contained several different compounds the results are expressed as percent
removals based on the reduction in peak height using gas chromatographic
analysis. \ •
In most cases 90 percent or better pesticide removal was obtained from
second (Nuchar) column.
87
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Table 25. Activated carbon columns for removal of pesticides from sump water
Sample
Removal of Indicated Peak (percent of influent)
1234
Filtrasorb effluent
100 gallons
150 gallons
175 gallons
200 gallons
225 gallons
250 gallons
275 gallons
^ ' - A -•. i . ---^i- ~
89.4
92
90
87
87.9
93.8
77.7
91
91
97
89
96
97
91
Nuchar effluent
25 gallons
30 gallons
100 gallons
125 gallons
175 gallons
200 gallons
225 gallons
250 gallons
275 gallons
74.2
94.5
98.0
53.8
70
79.1
94.7
95
49.3
87.2
93.5
91.5
63.1
89.5
77.8
92.6
95.6
76.9
93.7
97.5
96.4
83
91
84
95.2
—
90.1
79
88
—
—
94
93
97
99
96
9.2 TREATMENT OF MALATHION CONTAMINATED WASTEWATER
Malathion contaminated wastewater was also used to evaluate the treatment
process. These studies were limited to synthetic solutions only, that is,
malathion, as an emulsifiable concentrate, was added to either tap water or
previously collected aircraft wash water samples, to test the process on emul-
sified formulations.
2._2._1 Flocculation/Sedimentation Treatment of Malathion
As a first step, sedimentation without chemical addition was evaluated.
A 45 percent malathion emulsifiable concentrate was added to 378 L (100 gal.)
of pesticide solution with associated solids from re-suspension of pre-settled
alum floe to give a malathion concentration of 180 mg/L. A supernatant con-
taining only 90 mg/L was obtained after approximately 1 hr. of sedimentation.
Allowing the material to settle overnight did not yield any significantly
greater reductions in malathion concentration. Apparently, settling of the
suspended solids present from previous alum flocculation provided a filtering
action so that the emulsion droplets were carried down along with the floe.
The supernatant was quite turbid, indicating that more complete solids removal
could be accomplished by adding a coagulant.
To test the efficiency of flocculation/coagulation/sedimentation on emul-
sified malathion, a series of jar tests were set-up. Initial tests were per-
formed on a solution of malathion and tap water. As with previous jar tests,
68
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commercially available alum, sufficient alkalinity, and Dow Anionic Polymer
A-23 were used. Malathion concentration was 180 to 200 mg/L. Table 26 shows
the results for the first series of jar tests.
Table 26. Jar test results for malathion
Chemical dose
Alum
mg/L
0
50
100
200
400
Polymer
mg/L
0
1
1
1
1
Final Malathion
Concentration
mg/L
90
69
39
41
41
Several observations can be made from these tests. Alum dosages of 100
mg/L or greater appear to give a maximum pesticide removal. The presence of
floating solids for the highest dosages of alum may be an artifact of hindered
settling behavior within the small volume jars (2 liter beakers). At this
dilute malathion concentration, polymer alone is insufficient.
The order and timing of chemical addition to the pesticide solution was
found to affect the resulting supernatant quality. In particular, polymer
addition was found to be ineffective unless added as the final step. The
optimum chemical addition was found to be as follows. However,
1. Add alum; allow 30 seconds for mixing
2. Add hydroxide (or other source of alkalinity), allow one minute for
mixing
3. Add polymer, and allow 45 seconds for mixing
4. Flocculate material for approximately 10 minutes at 30 rpm.
Jar testing of wastewater samples were then performed to determine the
effect of initial suspended solids concentration. Table 27 shows typical
results. Initial malathion concentration was 180-200 mg/L.
69
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Table 27. Jar test evaluating the effect of solids concentration
on malathion removal
Chemical dose
Alum
mg/L
100
300
0
100
300
0
Polymer
mg/L
1
1
1
1
1
1
Malathion
Initial
mg/L
200
200
200
200
200
200
concentration
Final
mg/L
21
26
81
28
19
75
Suspended solid
mg/L
24000
24000
24000
2400
2400
2400
The conclusion drawn from these studies was that the solids concentration
had little effect on emulsion removal. The higher suspended solids concentra-
tion did remain turbid after flocculation. By diluting the wastewater to a
suspended solids concentration of approximately 12,000 to 15,000 mg/L a clear
supernatant could be produced by alum coagulation, polymer addition and sedi-
mentation. Concentrations above this point gave murky solutions even at high
coagulant dosages. All further jar test evaluations were done on solutions
whose suspended solids had been adjusted to between 12000 and 15000 mg/L.
The concentration of malathion was also varied. A series of tests
yielded the data shown in Table 28. All solutions had a suspended solids of
12,000 mg/L, with 200 mg/L alum and 1 mg/L A-23 polymer added to each.
Table 28. Jar test evaluation of flocculation/sedimentation
to remove various concentrations of malathion.
Malathion Concentration
Jar Initial Final
mg/L mg/L
1
2
3
4
5
10
30
75
150
300
9-14
9-11
11-13
15-18
20-25
By adjusting the suspended solids concentration to 1200 mg/L supernatant
quality was improved. Reductions of malathion concentration to 25 mg/L or
less are consistently achievable when good supernatant clarity is obtained.
As in all other cases, final sludge volume was approximately 25 percent of the
original solution volume after 30 to 45 minutes of settling.
70
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A number of additional coagulant polymers were also evaluated. WATCON
Inc. provided three chemicals: a liquid anionic polymer, a cationic polymer
and a nonionic polymer. For the removal of solids, the anionic was again
found to be the most effective, although for emulsion removal both the
cationic and anionic appeared to be equally effective. The anionic was used
for further testing because of its broad applicabilty to all formulation
types. Optimum liquid polymer dosage was found to be approximately
A final set of jar tests for malathion removal was conducted to test any
effects of varying alum dosages while adding .4 mL/L WATCON Anionic polymer.
The results shown in Table 29 were obtained when field collected pesticide
solutions were mixed with pre-settled solids, diluted to approximately 12,000
mg/L, and "spiked" with malathion and then treated with various doses of alum.
Effluent quality was dependent on the initial malathion dosage, and was essen-
tially independent of coagulant dose.
Table 29. Jar test evaluation of alum dosage on
malathion removal
Alum dose
mg/L
200
500
200
500
200
500
Malathion
initial
mg/L
20
20
200
200
500
500
Concentration
final
mg/L
10-16
10-13
43-58
42-56
43-61
38-51
9._2._2 Full Scale Flocculation/Coagulation/Sed imentat ion Studies of_ Malathion
During full-scale testing of the flocculation procedure, 1 to 1.5 hrs.
were required for complete settling. When a sample with an initial suspended
solids concentration of 24000 mg/L was spiked with 200 mg/L malathion and
treated the supernatant contained only 35 mg/L malathion. Studies with spiked
tap water showed a supernatant concentration of 55 mg/L. These results con-
firmed jar test results. Identical tests were later performed with more
dilute solutions. Even though one of these pesticide solutions was spiked
with as much as 400 mg/L of malathion, supernatant levels were measured at 41
mg/L malathion after 1 hr. of settling. Increased alum dosages did not pro-
duce significantly better pesticide removal from tap water solutions, as 500
mg/L of alum reduced a 200 mg/L malathion solution down to 30 mg/L. As the
solids built up after repeated coagulation and sedimentation, the clarity of
the supernatant decreased. Concentrations of malathion as high as 84 mg/L
were observed. However, dilution of this material to between 12,000 to 15,000
mg/L suspended solids, spiking with 200 mg/L of malathion and coagulation with
200 mg/L alum, produced a supernatant malathion concentration of 27 mg/L. No
change in this value was observed after 18 hrs. of settling.
71
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J9^2._3 Carbon Studies
Full-scale carbon column studies were conducted by pumping 1500 L (400
gal.) of this treated malathion contaminated wastewater through the two
columns. No malathion was detected in the effluent. Since about 15000 L
(4000 gallons) of wastewater would have to be treated to exhaust the full-
scale columns the carbon exhaustion studies were performed on two laboratory
columns. The columns were 2.54 cm (1 inch) inside diameter and held 25 grams
of activated carbon. The carbon was first washed with distilled water to
remove "fines" then dried overnight at 103 C before weighing. The feed solu-
tion of malathion was continuously fed to the column by means of a constant
head tank arrangement and effluent samples were taken at convenient intervals.
Each column was equipped with fine mesh screens in the inlet and outlet to
prevent carbon loss. Approximately 10 to 12.5 cm (4 to 5 inches) of glass
beads of graduated size were placed at the inlets to provide for flow distri-
bution. The columns were run in the up-flow mode.
Malathion solutions were made up by adding 100 mg/L of emulsifiable con-
centrate malathion to distilled water. The solution was allowed to settle for
approximately 12 hrs., and a sample was refrigerated for later analysis. The
remainder of the solution was fed to the column. Near the end of each batch
of pesticide, a second sample was taken for analysis to determine any changes
in concentration. The pH was adjusted to prevent hydrolysis. The concentra-
tions of solutions fed to columns were between 59 and 64 mg/L.
A summary of results can be found in Table 30 and the exhaustion curves
are plotted in Figure 18. Ultimate capacity was found to be quite close for
the Filtrasorb and Nuchar adsorbents. The adsorption capacity of Filtrasorb
at a 3 mg/L breakthrough concentration was computed to be 17.1 percent by
weight while that of Nuchar was found to be 18.8 percent. Exhaustion capacity
where influent and effluent concentrations are equal, was determined as 28.4
percent by weight for Filtrasorb and 27.3 percent for Nuchar.
9.3 TREATMENT OF METRIBUZIN CONTAMINATED WASTEWATER
Since triazine herbicides are heavily used throughout Indiana and the
Midwest for the control of broadleaf weeds and annual grasses, tests of the
efficiency of the treatment system in removing metribuzin were initiated.
Metribuzin was chosen for analytical convenience since a distinct peak
appears from the gas chromatograph using an electron capture detector. The
molecular structure of this herbicide is similar to the other triazines, but
the capacities of the system would be severely tested because of the high
water solubility of metribuzin (1220 mg/L) as opposed to other triazines, such
as atrazine (water solubility of 33 mg/L) and prometryne (water solubility of
48 mg/L).
It is important to note that synthetic metribuzin solutions differed in
one important aspect from the other solutions previously treated. In the case
of metribuzin, pure pesticide was used for solution make-up rather than formu-
lations. Whereas previous removals, at least during the
72
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Table 30. Carbon column exhaustion study for malathion
Liter passed Effluent
through column cone absorbed
(mg/L) (mg)
25
42
47
60
66
76
90
100
116
136
150
165
0
0
0
2
3
3
5
12
17
45
45
62
1500
2520
3500
4030
4280
4630
5130
5490
6060
6680
6890
7110
Total weight
cone absorbent
(mg/L) (mg)
0
0
0
2
2
4
4
8
11
42
58
60
1550
2620
3625
4370
4720
5180
5520
5760
6140
6740
6820
6825
50
40
30
MALATHION
CONCENTRATION
mg/l 20
10
0
INITIAL MALATHION CONCENTRATION
100 mg/l
ACTIVATED CARBON COLUMN-
25 gm
25
50 75 100
LITERS OF MALATHION APPLIED
125
Figure 18. Caj±ion adsorption, of malation in 25 gm coluim of
Filtrasorb 400.
73
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flocculation/coagulation/sedimentation procedures, were primarily a result of
removing wettable powders granules or emulsified droplets, no such behavior
could be expected with metribuzin.
Jar test procedures were used on a metribuzin contaminated wastewater.
An alum dosage of 200 mg/L with .4 mg/L of WATCON anionic polymer, was used.
The results are summarized in Table 31.
These results demonstrated that suspended pesticide, above the water
solubility, was removed, while the dissolved material was unaffected.
Table 31. Jar test evaluation for flocculation/sedimentation
removal of metribuzin
Metribuzin Concentration
Initial Final
(mg/L) (mg/L)
100 100
250 260
750 600-675
2000 1000
2500 1000-1025
4000 1176
The effect of alum dosage on metribuzin removal was evaluated with the
next series of jar tests. The results are summarized in Table 32.
Table 32. Effect of alum dosage on metribuzin removal by
flocculation/sedimentation
Alum dosage
mg/L
200
500
200
500
200
500
200
500
200
500
200
500
Metribuzin Concentration
Initial Final
mg/L mg/L
93
93
310
310
930
930
1550
1550
1940
1940
3100
3100
91
90
300
330
975
975
1250
1125
1068
1000
74
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A repeat of these tests was performed on actual resuspended pesticide wastewa-
ter that had been "spiked" with metribuzin. These results, shown in Table 33,
are consistent with previous studies. No attempt was made to determine the
removals of other components that may have been in the wastewater.
Table 33. Effect of using suspended solids on metribuzin removal
by flocculation/sedimentation
Metribuzin Concentrate
alum Initial cone. Final cone.
(mg/L) (mg/L)
200
500
200
500
200
500
200
500
200
500
200
500
100
100
500
500
750
750
1250
1250
2000
2000
3000
3000
81
90
330
315
585
585
1050
1000-1125
996
982
920
1000
Full scale flocculation/coagulation/sedimentation tests were performed to
check the validity of applying jar test data to large-scale operations. By
mixing resuspended pesticide waste with 200 mg/L of metribuzin, then adding
200 mg/L alum and associated chemicals, the supernatnat metribuzin concentra-
tion was reduced to be 115 mg/L. A repeat of this test with 264 mg/L metri-
buzin produced a supernatant concentration 140 mg/L. The 85 to 120 mg/L of
metribuzin that was removed is consistent with the results of the jar test.
The supernatant from these settling tests was then passed through the two
activated carbon beds. When the solution was first contacted with Nuchar car-
bon, the metribuzin level showed an almost immediate breakthrough of 6 mg/L, a
value that was steady for the 190 L (50 gals.) of solution treated. No pesti-
cide was found in the effluent from the second column containing Filtrasorb
carbon. When the order of carbon contact was reversed, as before, no pesti-
cide was found in the Filtrasorb effluent. As both carbons were relatively
fresh, differing response of the carbons were most probably due to differences
in relative affinity for this particular herbicide.
As in the case of malathion, capacity determinations for metribuzin
adsorption were made on laboratory scale columns. All conditions are the same
as those previously described, although the concentration of pesticide was
much higher. Influent to the Nuchar carbon contained 980 mg/L while Fil-
trasorb, due to limitations in the amount of pesticide available, received an
influent of 800 mg/L. The data is presented in Table 34.
75
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Table 34. Carbon column exhaustion study for metribuzin
Nuchar
effluent
Liters metribuzin cone.
(mg/L)
Filtrasorb
weight effluent weight
absorbed metribuzin cone. absorbed
(mg) (mg/L) (mg)
4
6
12
13
14
15
17
18
20
<1
5
220
430
515
740
982
3912
5864
7600
10,172
10,648
10,948
<1
40
160
183
216
392
515
737
782
3200
4760
6160
8680
10,000
11,280
12,219
12,256
Nuchar was found to have an overall capacity of 43.8 percent while Fil-
trasorb showed a slightly better value of 48.8 percent.
It should be noted that the computed capacity of the carbons do not
necessarily reflect the adsorption capacity to be expected during actual field
operations. Although using carbon columns in a series operation would allow
realization of high capacities, that is, the first column in the series could
be driven to exhaustion while later columns could be used to "scrub" the
effluent, influent concentration and the presence of other pesticides can
affect the adsorption efficiency of a carbon type for a particular pesticide.
76
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SECTION 10
SYSTEM ECONOMICS
Implementation of a system to handle the disposal of the wash and rinse
water from pesticide applicators would require a coordinated approach by regu-
latory agencies. Since commercial pesticide applicators are registered and
are required to recertify periodically by attending educational programs, it
is relatively simple to instruct pesticide applicators on the availability of
a treatment and disposal system. Implementing the treatment system for all
commercial applicators may be more difficult. Four alternative techniques
were proposed. The four possible treatment schemes are: 1) an on-site treat-
ment plant to handle all waste water from the applicator, 2) several mobile
treatment plants to service aerial applicators in a region on a routine basis,
3) a mobile system that would serve all aerial applicators in the entire state
of Indiana, and 4) a centralized treatment plant that would receive the waste-
water from all ground and aerial applicators in the state. Since aerial
applicators appear to have the greatest demand for such a treatment technique,
alternatives 1 and 2 were evaluated on the basis of handling only the aerial
applicators. Plans 3 and 4 could include additional pesticide applicators in
the state.
Practical considerations dictate that the treatment system or storage
facilities must be adequate to handle the peak demands of the applicator.
During the peak of the season the aircraft may be washed as many as four times
a day and operate for 5 days a week. This would require 20 washes per week,
giving a total wastewater generation of approximately 1900 L (500 gal.) per
week. The seasonal demand by these aerial applicators would be much lower.
The operator sprays for only 5 months of the year and because of weather and
other constraints, usually only half of these days are suitable for aerial
application. The average annual wastewater production was estimated to be two
washes per day during the 75 days of operation for a total of 150 washes per
season or approximately 4,000 gallons of wastewater. The same volumes of
wastewater were assumed for ground applicators.
Of the approximately 2,000 registered applicators in Indiana there are
only 46 aerial applicators and only 482 commercial ground applicators that
work primarily in agriculture. These registered applicators were located on
the state map of Indiana. It was found that the 46 aerial applicators were
located in 37 counties. These applicators could be subdivided into six
regional areas, with each region serviced by one mobile treatment plant.
Table 35 illustrates how these areas could be subdivided.
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Table 35. Distribution of aerial applicators
Max. vol. of Total annual
No. of waste generated waste water
Counties Applicators per week produced
(nO (nT)_ __
Newton, Jasper, White
Cass 7 13 106
St. Joseph, Eklhart,
LaGrange, Dekalb,
Noble, Kbsciusko 7 13 106
Wabash, Wells, Howard,
Grant, Delaware, Jay,
Randolph, Union 9 17 136
Sullivan, Vigo, Parke,
Fountain, Montgomery,
Tippecanoe 7 13 106
Clinton, Hamilton, Hancock,
Hendricks, Marion,
Shelby, Decatur 9 17 136
Jackson, Jefferson
Harrison,, Gibson,
Posey, Vanderburgh,
Warrick 7 13 106
TOTAL 46 86 696
If all agricultural related applicators in the state of Indiana were
included the total number of applicators would be increased by 482 to a total
of 528. The total amount of waste generated in one year would then be about
7560 L (2 x 106 gallons).
10.1 PLAN 1 — INDIVIDUAL TREATMENT PLANTS
Because aerial applicators are already trained in handling pesticides
and, concurrently, operate a high technology application system, it would seem
reasonable to expect that these applicators would be capable of managing a
waste treatment facility to treat the pesticide contaminated wash and rinse
water from their equipment. Numerous applicators appear to be interested in
constructing the type of system used at Garwood Airport in Monon, IN and are
quite wiling to take the responsibility of training an individual to manage
the system. Since our proposed treatment plant is a fairly low technology
operation, it should pose no great operating difficulties. However, a few
78
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safety features should be included in such a system as discussed in Section 5.
The treatment system would be composed of two flocculation/sedimentation tanks
and three activated carbon columns. The applicator would send a sample of the
wastewater through the first carbon column to a laboratory each month. The
two additional columns would be used to insure a clean effluent so that the
spent carbon column would be removed before pesticides were discharged to the
environment. Table 36 illustrates the cost of such a system. It is estimated
that the annual cost to the applicator would be about $6000/year.
The main advantage of this type of treatment system would be that the
aerial applicators could operate the plant when they had an adequate volume of
wastewater. A 1900 L (500 gal.) tank would be used to store the pesticides
until an adequate volume to justify the operation of the treatment plant had
accumulated. Treatment could be done once a week during heavy application
schedule and less frequently during the rest of the year. Another advantage
in such a system would be the increased chance of acceptance by the applica-
tor. Most aerial applicators want to manage the system on their own site.
The major disadvantage of such a treatment system would be the inability of
the local applicator to handle severe problems. Based on this research, the
additions of caustic, alum, calcium salt and organic polymer has successfully
coagulated all types of pesticide wastewaters. Activated carbon acts as a
safeguard to insure the removal of water soluble and unsettled materials
through both adsorption and filtration mechanisms. The applicator would have
to be responsible for proper disposal of the sludge and carbon. Once-a-year
collection of the spent activated carbon and sludge by a commercial disposal
firm could alleviate this problem.
79
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Table 36. Economics of installing and operating a
treatment plant for each applicator
State
Individual Wide
Capital Cost
Utility~BuTlding 1000 46000
Treatment Plant
Tanks 400
Pumps 400
Mixer 900
Columns 1200
Contingency 600
Treatment Plant Subtotal 3500 161000
Collection system 2000 92000
Total Capital Cost 6500 299000
Annual Cost
Depreciate, interest, repairs 1650
taxes, and insurance
Salaries and labor 350
Chemicals 200
Disposal of Sludge and Carbon 2500
Lab analysis 300
Contingency 750
Total annual cost 57500 264500
Annual cost per applicator 5750
10.2 PLAN 2 — SIX MOBILE TREATMENT STATIONS SERVING 7-9 AERIAL APPLICATORS
The second alternative that should be considered in the implementation of
a statewide system is the use of mobile treatment systems to service various
regions. The mobile treatment plants could be transported to a particular
applicator site on a truck or trailer. If the system was sized to handle 7 to
9 applicators in a two-week period, the capacity would have to be at least .25
L/s (4 g/min.). This calculation is based on the assumption that each appli-
cator would have a 3780 L (1000 gal.) storage tank for collection of the
wastewater and that the entire tank volume and would have to be treated in 5
hours. This scheme would presumably allow sufficient time for round trip
travel to the site and complete wastewater treatment within a single day. The
treated wastewater would be returned to the applicator for possible re-use.
describes the cost of such a treatment system. The applicators could be
expected to pay approximately $7000 per year.
80
-------
The major advantage of this type of treatment plan would be that an
experienced individual could be hired to operate the treatment plant. The
treatment plant could also be used in a southern state during the winter and
returned to the midwest during the summer. Year-round use of the system would
reduce the cost. The second advantage of this system is that since the treat-
ment plant would come to the site every 2 weeks the potential problems arising
in the treatment of highly mixed pesticide wastes could be minimized.
The major disadvantage of this type of system is the additional cost of
having six mobile stations. In addition, the periodic nature of the wastewa-
ter generation could possibly create a difficulty in managing the routing of
these mobile stations. It would also be more difficult for the treated waste-
water to be reused by the applicator for dilution of additional pesticide sam-
ples, as an additional storage tank would have to be installed for storing
water that was returned to the applicator after the wastewater had been
treated.
Table 37. Economic evaluation of a regional mobile treatment plant
Capital Cost
Truck & Trailer
Treatment Plant
Tanks
Pumps
Mixer
Columns - 2000
Construction
Contingency
Treatment Plant Subtotal
Collection System
Total Capital Cost
Mobil
Unit
35000
1200
600
1000
3000
1000
1000
7800
16100
58900
State
Wide
210000
46800
105800
362600
Annual Cost
Depreciation, interest, repair
taxes and insurance
Salaries
Chemicals
Disposal
Lab analysis
Transportation
Contingency
Total Annual Cost
Annual Cost Per Applicator
15000
15000
1000
10000
2250
1250
7000
51500
7400
91000
90000
6000
60000
10000
7500
42000
307500
6700
81
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10.3 PLAN 3 — ONE MOBILE TREATMENT SYSTEM TO SERVE THE 4fi AERIAL APPLICATORS
If the size of the mobile treatment system was increased it would be pos-
sible to handle all aerial applicators Indiana on a once-a-year basis. The
individual applicators would have to have the capacity to store at least 5,000
gallons of wastewater. The treatment facility would have to be capable of
treating and processing the wastewater in a 1-day period, necessitating a flow
rate of approximately .7 L/s (11 gal/min). Table 38 describes the cost of
such a treatment facility. These costs are divided into two categories. The
first column shows the cost if only aerial applicators are involved. Each
applicator would have to pay $4000 per year. If the system were used to treat
a total of 150 applicators the cost would be reduced to $2500 per year.
The major advantage of this treatment alternative would be the capability
of hiring a highly trained operator and of providing some analytical capabili-
ties on the treatment unit. Again, as in Plan 2, a large tank would have to
be installed at each site to store both wastewater and treated water, if it
were to be reused.
The major drawbacks of such a system would be the lack of backup equip-
ment if any problem occurred with the mobile treatment truck. A small mechan-
ical failure could cause delays in the servicing of the sites. Furthermore,
routing to achieve maximum efficiency of the vehicle would be difficult.
82
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Table 38. Economic evaluation of state wide mobile treatment plant
_ Aerial ibt) pesticides
Applications applications
Capital Cost
Truck and Trailer
Treatment Plant
Tanks
Pumps
Mixer
Columns
Construction
Contingency
Treatment Plant Sub Total
Collection system
Total Capital Cost
50000
2000
3000
1800
6000
5000
2700
20500
115000
185500
50000
20500
375000
445500
Annual Cost
Depreciation, interest, repairs
taxes, insurance
Salaries
Chemicals
Disposal
Lab Analysis
Transportation
Contingency
Total Annual Cost
Annual cost per applicator
56000
60000
6000
20000
10000
7500
22400
171900
3800
111000
90000
18000
60000
30000
22500
50000
381500
2500
10.4 PLAN 4 — CENTRALIZED TREATMENT FACILITY
The last alternative to consider would be the construction of a central
treatment plant. This alternative might be attractive if all pesticide appli-
cators in the state were required to treat their wastewater. The capacity of
the treatment works would have to be at least 2 L/s (35 gal/min.) if all pes-
ticide applicators were involved. Each applicator in Indiana would install a
1900 L (5,000 gal.) storage tank which would be emptied once each year by a
tank truck. By operating three tank trucks it would be possible to wait until
the tanks at the individual sites were full thus enabling the individual
applicators could call for pick-up and subsequent treatment. The proposed
budget for such a system is shown in Table 39. If only aerial applicators are
involved the cost of the service would be about $5000 per year. With all
applications involved the cost would be $2000 per year.
83
-------
The major advantage of this treatment alternative would be the reduced
cost per applicator. The major disadvantage of such a system would be the
inability to return the water to the applicator. This effluent would have to
be discharged to a publicly owned waste treatment plant or possibly used as
irrigation water near the treatment plant. Furthermore, public acceptance of
such a facility may be difficult to obtain, with associated problems with pub-
lic relations and land availability.
Table 39.Economic evaluation of a central treatment plant
Capital Costs
Trucks
Land
Building
Treatment Plant
Tanks
Influent
effluent
flocculat ion/sedimentation
Pumps
Mixers
Columns
Construction
Contingency
Treatment Plant Subtotal
Collection System
Total Capital Cost
Annual Cost
Depreciation, interest, repairs
taxes and insurance
Salaries
Chemicals
Disposal
Lab analysis
Transporation
Electricity
Contingency
Total Annual Cost
Annual cost per applicator
Aerial
Applicators
50000
10000
75000
10000
10000
2000
3000
3600
6000
15000
7500
57100
115000
307100
77000
90000
5000
20000
5000
7500
1200
30000
231200
5026
All
Applicators
150000
15000
100000
20000
10000
4000
4000
5400
18000
25000
13000
99400
1320000
1684400
421000
140000
50000
200000
50000
75000
2400
134000
1027400
2000
-------
10.5 SUMMARY OF TREATMENT OPTIONS
The four systems are summarized in Table 40. Based on the reaction of
most pesticide applicators a simplified version of option 1 with individual
treatment plants is most likely to be accepted. Appendix 1 describes how such
a simplified system might be installed.
Table 40. Summary of Alternative Systems for Treatment of Wastewater
from Pesticide Applicators
Plan 1 Plan 2 Plan J
Individual Six On Mobile
Plants Mobile Aerial 150
Only Applica-
tors
Plan 4
Central
Aerial All
Only Applica-
tors
Investment
collection
treatment
Annual Cost
Transport of
wastewater
Transport of
sludge
Train applicator
Energy consumption
Reuse of effluent
Potential for
discharge
Expertise of
operator
2000
4500
5750
no
2300
43800
6700
no
annually yes
2500
70500
3800
no
yes
2500
70500
2500
no
2500
192100
5000
yes
2500
364400
2000
yes
yes annually annually
yes no no no no no
low medium medium medium high high
easy possible possible possible no no
high med. high medium medium low
low med. low medium medium high high
85
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90
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APPENDIX
Numerous pesticide applicators have requested information on how to treat
the wastewater produced during cleanup of equipment. Through the financial
support of the U.S. Environmental Protection Agency and the North Central
Regional Pesticide Impact Assessment Program we were able to develop a system
that would remove pesticides from wastewater. This system was quite simple
and we believe it to be applicable to many small applicators. The procedure
outlined has been used on about 30 different classes of insecticides and her-
bicides and so far no serious problems have appeared. There are numerous
other possible mixtures which may present more severe questions. It is nor-
mally very simple to observe when the system is malfunctioning. The effluent
from the carbon columns should be odorless and colorless. If either odor or
color are present you should contact us for advice.
The procedures described in the bulletin can be used by a small scale
applicator that would only need to treat 50 gallons of wastewater at a time.
The treatment plant can be enlarged to handle larger volumes. The same recipe
can be followed with proportional increases in each ingredient.
With regard to the manufacturers and suppliers mentioned as sources of
equipment, chemicals and supplies, no endorsement is being made. Any other
source of equipment would be acceptable. The list is included only as a guide
to you in obtaining the necessary equipment.
A. Procedure for Treating Pesticide Contaminated Wastewater (See Figure 19)
1. Pump 50 gallons of wastewater into a 55 gallon drum.
2. Add 300 ml of Alum followed by 150 ml of Sodium Hydroxide solution,
then add 25 ml of an anionic polymer. Mix rapidly for 2 minutes
with a variable speed motor mounted on the drum. Reduce the mixer
speed to slowly stir the contents at about 30 rpm for about 10
minutes. Turn off the mixer. If wastewater contains paraquat or
diquat bentonite clay should be added before the alum is added.
About 1 liter of clay should be added to 50 gallons of wastewater.
3. Allow the solids in the drum to settle to the bottom. This should
take place in 30 minutes to 1 hour. The supernatant in the tank
should be discolored but transluscent. If you cannot see through a
glass full of the supernatant you should add 200 ml of the Calcium
Chloride solution and repeat step 2.
4. Pump the transluscent supernatant from the 55 gallon drum through
the activated carbon columns. The carbon columns can be made by
91
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VARIAI
SPEED
MIXER
PESTICIDE
CONTAMINATED
WASH WATER
15 GALLON TANKS
55 GALLON DRUM PUMP
PRIMARY
CARBON
COLUMN
<» s>
SECONDARY
CARSON
COLUMN
-
POLISHING
CARBON
COLUMN
Figure 19. Simplified system for treating pesticide contaminated wastewater.
12"
®
- -•«="
THREADED ROD
-12"
2" STYROFOAM
HOSE
28 GAUGE SHEET METAL
Figure 20. Detail dimensions of float for treatment system.
92
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putting 60 Ib. of activated carbon in a 15 gallon drum. Spigots can
be placed in the top and bottom and apposite side as shown in Fig-
ure 19. The flow c?n be controlled by the spigot on the first tank
to reduce the flow to about .5 gal/min.
5. The effluent from the carbon column can be sprayed on grass or
placed in a container and used to wash the application equipment.
B. Procedure for Preparing Chemicals to be used to Treat Wastewater
Sodium Hydroxide (3N)
Slowly add 5 Ib of Sodium Hydroxide to 5 gallons of water in 5 gal-
lon LPE Carboy. Caution: This solution will become very warm when
mixed. Small amounts of Sodium Hydroxide pellets should be added
periodically and allowed to dissolve. It will take about 1 hour to
prepare this solution.
Aluminum Sulfate (Alum)
Add 5 Ib of Aluminum Sulfate to 5 gallons of water in 5 gallon LPE
Carboy. It is necessary to vigorously mix this solution for several
minutes.
Calcium Chloride
Add 5 Ib of Calcium Chloride to 5 gallons of water in 5 gallon LPE
Carboy.
C. Chemicals (Amounts are based on treating 15000 gallons of wash water,
about 2 years for the typical ag applicator.)
Aluminum Sulfate (Alum)
Cat. No. 598-11652*
2 - 5 Ib bottles @ $40.00 $ 80.00
Calcium Chloride
Cat. No. 68-19302*
1 - 5 Ib bottle 0 $48.00 $ 48.00
Sodium Hydroxide
Cat. No. 630-67802*
1 - 5 Ib bottle @ $17.00 $ 17.00
*Catalogue numbers refer to:
G. Frederick Smith Chemical Co.
867 McKinley Ave.
Columbus, OH 43223
614-224-5343
93
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Bentonite Clay
Volclay HEW-20
American Colloid Company
5100 Suffield Court
Skokie, IL 60076
312-966-5720
No endorsement of these companies is intended. Any chemical supplier can
supply these products. You should check with local supply for best price
and service.
Activated Carbon (115 Ib 0 $0.70/lb) $130.00
Filtrasorb 300 or Nuchar
Calgon Corporation Westavco Chemical Div.
Environmental System Div. Carbon Department
Filtrasorb Department Covington, VA 24426
P. 0. Box 1346 703-962-1121
Pittsburg, PA 15230
412-923-2345
Anionic Polymer (Watcon 1255) or equivalent
15 gal @ $3.85/gal $ 57.75
Watcon, Inc.
2215 S. Main St.
South Bend, IN 48613
219-287-3397
Total Chemicals $332.75
D. Equipment
1. Tank for flocculation/sedimentation
A. 55 gallon drum (can use a pesticide shipping container)
B. Mixer - air drive mixer with regulator - requires 1 HP air
compressor with tank - or equivalent variable speed mixer.
Cat. No. 4318-40*
1 air drive mixer drum lip mounting $196.00
Cat. No. 4318-49*
1 regulator, filter and lubricator $ 77.00
94
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2. Pump - 1/12 HP Polyethylene centrifugal pump
Cat. No. 7001* $ 96.95
2 - Service Kits @ $3.65
Cat. No. 7001-60* $ 7.30
3. Activated Carbon Columns
Cat. No. 6321-21* (15 gallon)
3 - polyethylene tanks with spigot cover @ $46.00 $138.00
Cat. No. 6314-20*
3 - drain assembly kits @ $13.55 $ 40.65
Total Equipment $555.60
E. Miscellaneous Supplies
Conical Graduates - 1000 ml
Cat. No. 6135-45*
2 - ia $7.45 $ 14.90
Rectangular Carboy with spigots (5 gallons)
Cat. No. 6066-50
3 - @ $32.02 $ 96.06
Total Miscellaneous $110.96
Total Cost $999.31
*Catalog numbers refer to:
Cole-Parmer Instrument Company
7425 North Oak Park Ave.
Chicago, IL 60648
800-323-4340
Nb endorsement of Cole Partner is intended. Any supplier of such equip-
ment, including local plumbing or hardware stores, should be considered.
F. Caution
When treating the wash water protective clothing should be worn. This
material should be handled with the same precautions one would take in
handling pesticides. The treatment unit can be housed in a small utility
building to protect equipment from weather, but during operation the
shelter should be opened to allow ventilation of the interior.
The carbon columns may support anaerobic bacterial growth. If the
columns are not going to be used for several weeks the tanks holding the
carbon should be drained. At the end of each year the first of the car-
bon columns should be emptied and refilled with new carbon. The column
with new carbon should be moved to the polishing column position, the
polishing column should be moved to the 2nd column position and the 2nd
column should be moved to the primary position.
The flocculation/sedimentation tank will accumulate sludge during succes-
sive treatments. The sludge should be allowed to build up in the tank
until the settled sludge reaches about 1/4 the height of the tank. In
other words, for a 55 gallon drum settled sludge should be removed from
-------
the tank when the sludge blanket reaches a height of 10 inches. A float-
ing intake to the pump would be used to remove the supernatant from the
tank. This float can be made as shown in Figure 20. It is important to
support the inlet to the pump about 2 inches above the sludge blanket. A
piece of flat sheet metal will keep the float from settling into the
sludge.
When the sludge blanket in the bottom of the tank reaches a depth of 10
inches, you should remove about half the sludge and store the waste in
suitable containers such as those used to ship pesticides. Current
research into techniques to encapsulate the sludge is underway.
Currently both the sludge and the used activated carbon would be con-
sidered hazardous waste. These types of waste can be disposed of by con-
tracting with a hazardous waste disposal facility to remove the waste
from your site.
If you produce more than 50 gallons of wastewater when you clean your
equipment you may want to purchase a larger tank for the
flocculation/sedimentation tank. These are available from various
sources. A schematic of a larger treatment plant is shown in Figure 21.
G. Collection of Wastewater
Of course, before the treatment system can be used a means of collecting
the wastewater must be developed. Figure 22 illustrates a modification
that could be made in an existing concrete pad. The wash water was
diverted to one corner by nailing 2x4 to the concrete pad with a nail gun
and constructing a sump in one corner. The wastewater can be pumped from
the sump into any type of above ground tank, or an underground tank could
be located adjacent to the pad and the wash water diverted to the tank.
If you do not have an existing concrete pad and you may want to build a
slightly more elaborate facility as shown in Figures 5 and 6. The volume
of wastewater can be greatly reduced by covering the pad. Either a vinyl
cover can be rolled over the pad when not in use or a building can be
constructed over the washing pad as shown in Figures 6 and 7. This
building could be used for pesticide equipment storage and would provide
an all weather working environment for storing and maintaining your
equipment.
Summary
The system described in this article will remove pesticides from wastewa-
ter. It is very important that the receipe presented is followed closely.
The major cost of the treatment will be the disposal of the cost. Commercial
facilities for such disposal are limited. Before constructing the washing
station or purchasing the treatment system, you should contact your state pes-
ticide office and the solid waste disposal authorities so that a practical
plan can be used to dispose of the sludge. The volume of sludge that will
have to be handled is variable but you can expect to have 15 to 30 gallons of
sludge for each 1000 gallons of wastewater that you treat.
96
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5000 gallon storage
tank for wastewater
Vinyl cover to prevent rain
water from entering storage
Water supply
Tank for mixing
pesticides
Sump for pump to transfer
wastewater to storage tank
Concrete pad for collection
of washwater
Figure 21. Collection of pesticide contaminated wasterwater in
above ground tank.
Tank for mixing
pesticides
Water supply
Vinyl cover to prevent rain
water from entering tank
Below grade tank far
storing wastewater
Concrete pad for collection
of wastewater
Figure 22. Collection of pesticide contaminated wastewater in
below ground tank.
97
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Figure 23. Pesticide wastewater control system.
Applicatior Equipment Washing Area
War* • •••*
Carbon Column* LI
T
H—'Cl««n Blflu«nt
Pesticide Treatment Centar
Figure 24. Pesticide wastewater treatment center.
98
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AWBERC LIBRARY U.S. EPA
TECHNICAL REPORT DATA
(Please read Instructions on [he reverse before completing)
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Collection and Treatment of Wastewater Generated
by Pesticide Application
5. REPORT DATE
September 1981
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
K.F. Whittaker, J.C. Nye, R.F. Wukash, R.J. Squires,
A.C. York, H.A. Kazimier
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
Purdue University, West Lafayette, Indiana 47906
and
Aeronautic Commission of Indiana
Indianapolis, Indiana 46206
11. CONTRACT/GRANT NO.
R805 466010
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Edison, New Jersey 08837
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Frank Freestone, Project Officer (201-321-6632)
16. ABSTRACT
Methods for control of pesticide contaminated wastewater were studied. Evaluation
of practices that are currently used to handle pesticide contaminated wastewaters
was followed by development of a system that could be used to collect the pesti-
cide contaminated wastewaters. Then a treatment plant was developed to remove
pesticide from contaminated wastewaters and produce a high-quality effluent. Three
physical-chemical treatment options were evaluated. A flocculation/coagulation/
sedimentation step was evaluated using alum as the coagulant. Additional studies
were done using filtration and coalescence. Flocculation/coagulation/sedimentation
removed a high percentage of the pesticides. The filtration and coalescence steps
were less effective. The supernatant from the first step was then passed through
activated carbon columns. A hydraulic loading rate of .5L/s-m2 was determined to
be adequate with a residence time of approximately 15 minutes. The concentration
of the pesticides in the clear effluent was usually less than 1 mg/liter.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pesticides, Wastewaters, Treatment,
Flocculation, Coagulation, Sedimentation,
Alum, Activated Carbon
Pesticide applicators
Aerial spraying
Decontamination
Treatment apparatus
3. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS {ThisReport!
Unclassified
21. NO. OF PAGES
109
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
99
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