United States
Environmental Protection
Agency
Office of Water &
Waste Management
Washington DC 20460
SW-174c
May 1979
Solid Waste
s>EPA
Disposal of Dilute
Pesticide Solutions
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Prepubliaation issue for EPA libraries
and State Solid Waste Management Agencies
DISPOSAL OF DILUTE PESTICIDE SOLUTIONS
This report (SW-174c) describes work performed
for the Office of Solid Waste under contract no. 68-01-4729
and is reproduced as received from the contractor.
The findings should be attributed to the contractor
and not to the\0ffice of Solid Waste. I
Copies will be available from the
National Technical Information Service
U.S. Department of Commerce
Springfield, VA 22161
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
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This report was prepared by SCS Engineers, Long Beach, California,
under contract no. 68-01-4729.
Publication does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor
does mention of commercial products constitute endorsement by the U.S.
Government.
An environmental protection publication (SW-174c) In the solid waste
management series.
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ABSTRACT
An extensive literature search, site visits, and interviews
were conducted to evaluate disposal methods for dilute pesticide
solutions generated during pesticide application equipment wash-
ing operations. Methods were evaluated in relation to environ-
mental safety, versatility, applicability, economics, and effi-
ciency criteria.
It was calculated that over 400,000 m^ of dilute pesticide
solutions are generated in the United States annually. It was
determined that commercial agricultural applicators are the
major source of these pesticide wastes.
The disposal methods evaluated include land cultivation,
soil mounds and pits, evaporation basins, chemical treatment,
carbon adsorption, activated sludge, trickling filters, and
incineration. Given the state of the treatment method technology
and the nature of the wastes and their generation, it is con-
cluded that soil mounds are presently the most readily imple-
mentable disposal method available. Soil pits and evaporation
basins are technically available, but present air quality
problems. Adsorption is of limited utility, but is readily
implementable within its limitations. Land cultivation has
not been sufficiently studied in relation to dilute pesticide
solutions and presents potential environmental problems. Che-
mical treatment can be effective, but is not applicable to all
pesticides. Full-scale operating conditions have not been fully
determined. Biological treatment and incineration are of use
only in centralized hazardous waste management facilities.
i i i
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ACKNOWLEDGEMENTS
This report is the result of extensive cooperation between
EPA, agriculture, industry, and SCS personnel. The guidance
and assistance of Mr. Harry Trask, Project Officer, and Mr- Wendel
Miser, Assistant Project Officer, Office of Solid Waste, U.S. EPA,
Washington, D.C., are gratefully acknowledged.
The assistance of our consultants on this project --
Dr. Samuel Hart, Davis Waste Removal; and Dr. Walter J. Farmer,
Department of Soil and Environmental Science, University of
California, Riverside -- in providing useful information and
reviewing the interim and draft final reports is greatly
appreciated.
Special thanks are directed to Mr. Richard Yamaichi, Uni-
versity of California, Davis; Sargent J. Green, California
Regional Water Quality Control Board; Dr. Jack Dibble, Univer-
sity of California Horticultural Extension Service; Hamilton
Dusters, Merced, California; and the California Regional Water
Quality Control Board staff and regular meeting attendees of the
Technical Advisory Pesticide Sub-Group for their courteous assis-
tance and helpful suggestions.
SCS project participants, other than the authors, were Lata
Bhatt (researcher); Jackie Ivy (editing); James McAllister (gra-
phics); and Lona Taylor and June Faulkner (typing).
iv
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CONTENTS
List of Figures ..................... vi
List of Tables ......... . ........... vii
1. Summary and Recommendations ............ 1
2. Introduction ................... 6
3. Disposal Methods for Dilute Pesticide
Solutions .................... 17
Land Disposal ...... ........... 19
Land Cultivation .............. 25
Soil Mounds and Pits ............ 29
Evaporation Basins .............. 34
Chemical Treatment ......... ..... 46
Physical Treatment .............. 52
Reverse Osmosis .............. 54
Adsorption ................. 54
Biological Treatment ............. 58
Trickling Filters ............. 60
Activated Sludge ...... ........ 60
Incineration ................. 64
Transport and Incineration at
a Central Facility ............. 70
4. Comparative Evaluation of Methods ........ 74
5. Conclusions ................... 92
References ....................... 95
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FIGURES
Number Title Page
1 Uncontrolled runoff from pesticide appli-
cation equipment washdov/n pad ,18
2 Land cultivation site runoff control
system 27
3 Dilute pesticide solution tractor/
subsoiler land application equipment 28
4 University of California soil mounds
system 30
5 Iowa State soil pit disposal system 31
6 Flooded soil mound system 33
7 Evaporation basin 37
8 Evaporation pit system 38
9 Chemical treatment system 48
10 Carbon transfer with upflow column in
service 55
11 Pressurized downflow contactor 56
12 Trickling filter 61
13 Typical trickling filter slime layer 62
14 Activated sludge schematic 63
15 Basic incinerator schematic 67
16 Geographic distribution of hazardous waste
management facilities 72
VI
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TABLES
Number Title Page
1 Summary Table 4
2 Fifty of the Most Common U.S. Insecticides,
Herbicides and Fungicides . . . . . 8
3 Fifty Common Pesticides in the U.S. by
Type with Approximate Share of the Market ... 10
4 Pesticide Use by Type of Pesticide 11
5 Pesticide Use Distribution within Each User
Segment . 12
6 Relative Mobility of Pesticides in Soils .... 23
7 Land Cultivation Cost Estimates 35
8 Soil Mounds and Pits Cost Estimates 36
9 Evaporation Basin Cost Estimate 45
10 Some Pesticides Not Readily Degradable
by Practical Chemical Treatment 49
11 Selected Pesticides Amenable to Alkaline
Hydrolysis . 50
12 Chemical Treatment Cost Estimate 53
13 Carbon Adsorption Cost Estimate 59
14 Biological Treatment Cost Estimates 65
15 Incineration Cost Estimate 69
16 Environmental Safety 78
17 Effectiveness 81
18 Versatility of Method. 83
19 Availability 86
vi 1
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TABLES (continued)
Number T1tie Page
20 Applicator Factors 89
21 Summary Table 90
vi
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CHAPTER 1
SUMMARY AND RECOMMNDATIONS
Over 400,000 m (100 million gal) of dilute pesticide
solutions are generated in the United States each year. The
primary sources of these wastes are container and equipment
rinsing and washing. In the past, little attention has been
paid to the proper disposal of these wastes. As a result,
careless dumping often occurred resulting in water contamination,
wildlife deaths, soil contamination, etc.
Dilute pesticide solutions present several disposal
problems. Concentrations are generally less than the recom-
mended application rate, based on calculations using data
from available sources. Individual applicators typically
generate less than 2 m3 (500 gal) daily, mostly in agricultural
areas. Commercial waste treatment systems are usually designed
for higher flow. Many processing and disposal technologies
may be either uneconomical or impractical. It is likely
that future regulations will specify proper treatment and
disposal of these wastes, however.
In this study, several currently used and proposed methods
for disposal of dilute pesticide solutions were reviewed. The
methods include:
Soil mounds
Chemical treatment
Incineration
Adsorption
Soil pits
Evaporation basins
Land cultivation
Biological treatment
All of these methods advantages and disadvantages. Soil mounds
and pits for example, represent an attempt to take advantage of
the strengths of land treatment while minimizing its disadvantages.
Soil mounds and pits are small, lined systems that rely on soil
properties to degrade pesticides while containing non-degraded
pesticides or degradation products within the lined system. They
require less land area and operator time than land cultivation and
have a limited lifetime due to the buildup of pesticides in the
soil. High pesticide concentrations can inhibit natural soil de-
gradation mechanisms. Soil mounds and pits can still function as
contain-and-concentrate systems, however. The extent of pesticide
volatilization from these systems has not been fully determined
yet.
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Chemical treatment can yield virtually complete detoxi-
fication for many of the commonly used pesticides. For many
other pesticides it is ineffective or yields toxic reaction pro-
ducts. Thus, chemical treatment can be a highly useful, albeit
somewhat limited, treatment method. It requires more operator
skill and training than the methods already discussed because
of the hazardous nature of most treatment chemicals. Care must
be taken to ensure proper ratios of treatment chemical to
pesticide and proper selection of treatment chemical.
Incineration is highly effective at destroying all organic
(except metallo-organic) pesticides. However, incineration and
its support services are costly and not generally available to
individual applicators. The efficacy of incineration precludes
its being dropped from consideration, however. It might be possible
to establish numerous central hazardous waste treatment facilities
based on incineration which could be used to treat dilute pesticide
solutions.
Absorption is a very effective contain-and-concentrate method
for most organic pesticides. It is a proven technology
readily adaptable by pesticide applicators to dilute pesticide
solutions. It is ineffective'with certain oil-type and inorganic
pesticides, and the wastewaters require pretreatment to remove these
and any insoluble suspended matter (e.g., insoluble pesticides,
clays, sulfur) before treatment to prevent adsorption column fouling.
Evaporation basins also serve as contain-and-concentrate
methods. In addition, some pesticide hydrolysis and photolysis
can be expected to occur. These systems are frequently used by
pesticide formulators and applicators. They do, however, pre-
sent a hazard to local air quality due to volatilization.
Land cultivation is a simple technology, relatively inexpensive,
and readily implementable in many agricultural areas. Research
has shown that low concentrations of many organic pesticides will
degrade in or be adsorbed by soil with little pesticide migration.
However, land cultivation does not work as well with high pesticide
concentrations or with certain chemical classes of pesticides.
Migration to ground or surface water or volatilization can occur.
The environmental fates of many pesticide degradation products are
unknown.
Biological treatment can be very effective in degrading many
organic pesticides. However, it is highly susceptible to up set
from changes in flow rate, pesticide concentration, or type of
pesticide, all of which could occur with dilute pesticide solutions.
For biological treatment to be effective, sufficient contact time
and a fairly uniform waste are required, and neither condition can
be guaranteed by an applicator. Thus, biological treatment is not
considered appropriate for individual applicators.
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Table 1 presents a comparative summary of the eight treat-
ment methods. Each method has been given a total score (based
on the criteria explained in Chapter 4) and is ranked in the
table according to its potential as a dilute pesticide solution
method. The methods (i.e. soil mounds, chemical treatment, trans-
port and incineration) which have the highest score have the
highest potentials; biological treatment has the lowest. The
use of adsorption, soil pits, evaporation basins, and land
cultivation could be effective under certain conditions.
In light of the above, iJje following recommendations are
offered;\
• ifiays of reducing the volume of dilute pesticide
solution through improved application practices
should be studied ,J
• Table 1 indicates that yj.e use of a soil mound
system could be the mostj readily implementable
and \ef feet ive method] available (^or disposal of
dilute pesticide solutions.^) Before recommend-
ing such a system for immediate and widespread
use, however, soil mounds should be further
evaluated in terms of liner effectiveness,
pesticide volatilization, and expected useful
life.
• Since evaporation basins are already widely
used, research needs to be conducted into the
environmental impacts of volatilization from
these systems.
• Further research needs to be conducted into
the extent of volatilization from soil pits.
• Land cultivation may be an alternative method
for the disposal of some dilute pesticide
solutions. Further research should be directed
toward determining which pesticides (and at what
concentrations) can be treated as well as the
optimum soil conditions and loading rates
necessary for effective degradation.
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TABLE 1. SUMMARY TABLE
SCORES OF DILUTE PESTICIDE SOLUTION DISPOSAL METHODS
Criteria
Environmental
Method Safety*
Soil mounds
Chemical treat-
ment
Transport and
inciner-
ation
Adsorption
Soil -pits
Evaporation
basins
Land cultiva-
tion
Biological
Treat-
ment
45
45
39
55
35
35
30
40
Effectiveness
20
30
35
15
15
15
15
25
Pesticide
Applicability
30
20
20
15
30
25
25
15
Availability
22
25
22
25
14
17
22
15
Applicator
. Factor Total
18 135
11 131
14 130
9 119
19 113
20 112
17 108
4 99
*8ee Chapter 4, for explanation of criteria and scores.
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Further research is needed into chemical treatment
to more fully identify susceptible pesticides and
treatment conditions; research needs to be
directed toward chemical treatment of dilute
solutions of mixed pesticides.
For all of the above treatment methods, research
currently underway or planned should be expanded
to include more exhaustive analyses of the fates
of pesticide degradation products.
Since the advantages, disadvantages, and limita-
tions of carbon adsorption are largely known,
adsorption should be demonstrated on actual
dilute pesticide solutions from commercial appli-
cators.
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CHAPTER 2
INTRODUCTION
The increasing awareness of the health and environmental
problems associated with pesticides has spawned a reassessment
of all phases of pesticide production and use. One aspect of
pesticide use that has generally been overlooked in the past is
the disposal of wastewaters from pesticide container and appli-
cation equipment cleaning operations. All of these wastewaters
contain pesticides in varying concentrations but their disposal
has prompted little concern in the past because the liquors were
generally considered dilute and, therefore, innocuous.
PESTICIDE USE AND WASTE QUANTITIES
The quantities of such wastewaters are far from insignifi-
cant. These wastewaters, hereafter called dilute pesticide
solutions, are generated during several activities: pesticide
container rinsing, spray equipment tank rinsing, and general
equipment washing. They may also include unwanted dilute spray
mixtures. Estimates of the quantities of dilute pesticide
solutions produced in 1966 were:
o c
• 22,740 m (6 x 10 gal) of container rinsate
• 379,000 m3 (100 x 106 gal) of aerial application
equipment washwater
22,740 m3 (6 x 106 «.
equipment washwater (1).
3 6
• 22,740 m (6 x 10 gal) of custom application
These yield a total of 424,480 m3 (112 x 106 gal) of dilute
pesticide solutions for 1966. This quantity may have increased
substantially since 1966 because the total acreage treated with
pesticides and the quantity of pesticides applied by custom
applicators have increased significantly (2, 3). It has been
estimated that each application airplane and ground applicator
rig produces from 20 to 230 £(5 to 60 gal) of wastewater per
day (4).
There has been little research conducted to date either to
determine the concentration of these dilute pesticide solutions
or to estimate the total quantity of pesticides in the annual
production of dilute pesticide solutions. The variety of
pesticide formulations (granules, powders, soluble salts,
liquids), mixing ratios, and application methods make
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generalization very difficult. Dilute pesticide solutions are,
by definition, at concentrations equal to or below recommended
application rates. These rates vary widely; documented con-
centrations of pesticides in container rinsate range up to
as high as 14,800 ppm (5). Researchers at Oregon State
University found pesticide concentrations of 500 ppm in waste-
water from a container cleaning process (6). Application
equipment washwaters have not been sufficiently characterized
to determine average or typical pesticide concentrations.
Be that as it may, Federal guidelines specify that
pesticide container rinsate be treated as waste pesticide for
disposal purposes (Federal Environmental Pesticide Control
Act). The definition of pesticide includes pesticide-containing
wastewaters. Based on such criteria, dilute pesticide
solutions, generally dismissed as trivial in the past, become
a real and pressing hazardous waste disposal problem.
Before considering disposal alternatives, it is appropri-
ate to briefly look at pesticide users to determine who will
be faced with the need to treat or dispose of dilute pesticide
solutions, as well as what types of pesticides might be in-
volved. Table 2 lists 50 of the leading pesticides used in
the United States in 1976, production estimates, and estimates
of how use of the pesticide was distributed among the various
user groups. Since general discussions of pesticide use and
disposal usually deal more with types or classes of pesticides
(based on chemical similarities) than with individual compounds,
Table 3 breaks down the fifty pesticides into general types,
and Tables 4 and 5 break down the use of these pesticide types
by their distribution among various user groups and within
each user group.
As might be expected, the primary use of pesticides is
for agriculture, including use by both farmers and custom
applicators. Slightly more than 2/3 of all pesticides (3/4 of
the insecticides and herbicides) are used on cropland. The
next largest use, by urban, industrial, and commercial build-
ing pest control operators, comprises 18 percent of overall
pesticide use and 1/3 of the fungicide use. Home and garden
users are next, followed by the Federal government. These
figures do not agree precisely with the newest available in-
formation as presented in "Pesticide Usage Survey of Agri-
cultural, Governmental, and Industrial Sectors in the United
States, 1974," Office of Pesticide Programs, EPA, but the con-
clusion, that agricultural pesticide use exceeds all other uses,
is the same.* In fact, this latest information places the
figure at 94 percent.
*Report unavailable at this writing but contents highlighted in
Reference 10.
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TABLE 2. FIFTY OF THE MOST COMMON U.S. INSECTICIDES,
HERBICIDES, AND FUNGICIDES*
Use (%){
19/b
Production
Pesticide (103 t/yr AI)1" Agricultural
Insecticides and
Rodenticides
Aldicarb
Carbaryl
Carbofuran
Chlordane
Chloropicrin
Diazinon
Dichlorvos
Disulfoton
Endosulfan
Ethion
Fensulfothion
Heptachlor
Lindane and BHC
Mai a th ion
Methoxychlor
Methyl parathion
Monocrotophos
Naled
Parathion
Phorate
Ronnel
Toxaphene
Herbicides
Alachlor
Atrazine
Bromacil
Chloramben
2,4-D
Dalapon
Di camba
Diuron
Methanearsonics
(MSMA, DSMA)
Picloram
Propachlor
Propanil
Si 1 vex
0.5-2
22-45
2-6
6-13
2-6
2-6
0.5-2
2-6
0.5-2
0.5-2
0.5-2
2-6
0.5-2
13-22
2-6
13-22
2-6
0.5-2
6-13
2-6
0.5-6
13-22
Weighted Avg
6-13
>45
2-6
6-13
6-13
0.5-2
0.5-2
2-6
22-45
0.5-2
6-13
2-6
0.5-2
99
76
99
20
43
<1
98
85
99
99
75
70
31
10
99
99
25
99
99
20
98
74
99
96
13
99
76
15
40
37
66
35
99
99
99
Home &
Garden
<-,
14
<1
33
28
15
<1
5
<1
<1
<1
15
31
40
<1
<1
25
<1
<1
<1
<1
10
0
1
<1
<1
6
5
10
<1
8
<1
<1
<1
<1
Industrial/
Commercial
0
4
<1
43
17
70
<1
5
<1
<1
25
15
25
40
<1
<1
25
<]
<1
60
1
12
<-,
2
77
<1
12
15
40
57
21
65
<1
<1
<]
Government
0
6
<1
4
12
15
1
5
<1
<1
<1
<1
13
10
<1
<1
25
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TABLE 2 (Continued)
Pesticide
1976 use
Production Home &
(1QJ t/yr AI) Agricultural Garden
Industrial/
Commercial Government
Herbicides
Simazine
2,4, 5-T
Thiocarbamates
(Butylate, EPIC)
Trifluralin
Fungicides
2-6
2-6
13-22
6-13
20
60
75
98
Weighted Avg 74
25
1
80
40
<1
1
18
<1
<1
Benomyl
Captafol
Captan
Dodine
Ferbam
Folpet
Maneb
Metham
Pentachlorophenol
Trichlorophenol
Zineb
2-6
0.5-2
6-13
0.5-2
0.5-2
0.5-2
2-6
2-6
13-22
6-13
0.5-2
Weighted Avg
Overall Avg
70
70
62
70
50
65
79
75
<1
<1
85
46
69
30
30
37
30
50
35
21
25
3
<1
15
21
10
<1 <1
<1 <1
<1 <1
<1 <1
<1 <1
<1 <1
<1 <1
<1 <1
97 <1
99 <1
<1 <1
33 <1
18 3
* Von Rumker, R. et al. Production, distribution, use, and environmental
impact potential of selected pesticides, 1974 (7).
i
U.S. International Trade Commission. Synthetic organic chemicals
United States production, and sales, 1976 (8).
Farm Chemicals Handbook, 1978 (9).
f Metric ton per year active ingredient (AI). Production figures are
taken directly or are estimated based on information from references
7 and 8.
I Use estimates are taken directly or are estimated based on information
from references 7 and 9.
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TABLE 3. FIFTY COMMON PESTICIDES IN THE U.S. BY TYPE
WITH APPROXIMATE SHARE OF THE MARKET (S)*t
Chlorinated Hydrocarbon (12)
Chlordane
Endosulfan
Heptachlor
Lindane and BHC
Methoxychlor
Toxaphene
Carbamates (7)
Aldicarb
Carbaryl
Carbofuran
Organic Phosphorus (21)
Diazlnon
Dlchlorovos
Olsulfoton
Ethlon
Fensulfothlon
Malathlon
Methyl Parathion
Monocrotophos
Naled
Parathion
Phorate
Ronnel
Triazines (7)
Atrazine
Slmazine
Chlorophenoxy Adds (5.5)
2,4-D
2,4,5-T
Si 1 vex
Hethanearsonlcs (4.5)
Organic Nitrogen (10)
Alachlor
Benomyl
Dodine
Propachlor
PropanH
* Von Rumker, R. et al. Production, distribution, use, and environmental impact
potential of selected pesticides, 1974 (7).
Farm Chemicals Handbook, 1978 (9).
* Based on the figures in Table 2.
Benzole acid derivatives (4.5)
Chloramben
Dlcamba
Plcloram
Dinitro aromatics (2.5)
Trifluralin
Uracils (3.5)
Bromacil
Oiuron
Chlorinated alkyl acids (1)
Dalapon
Chlorophenols (6)
Pentachlorophenol
Trichlorophenol
Dicarboxamides (4.5)
Captafol
Captan
Folpet
Dithiocarbamates (5.5)
Ferbam
Maneb
Metham
Zineb
Thlocarbamates (3.5)
Miscellaneous (2)
Chloropicrin
10
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TABLE 4. PESTICIDE USE BY TYPE OF PESTICIDE (%)'
Pesticide Type Agricultural
Chlorinated hydrocarbon
Carbamates
Organic phosphorus
Triazines
Chlorophenoxy acids
Methanearsonics
Organic nitrogen
Benzoic acid derivatives
Dinitro aroma tics
Uracils
Chlorinated alkyl acids'
Chlorophenols
Dicarboxamides
Thiocarbamates
Dithiocarbamates
62
85
73
77
75
66
92
75
98
25
15
<1
64
75
74
Home &
Garden
16
9
9
<1
3
8
8
2
1
<1
5
2
35
25
25
Industrial/
Commercial
19
2.5
12
22
19
21
<1
21
1
67
15
98
<1
<1
"
Government Total
3 100
3.5 100
6 100
<1 100
3 100
5 100
<1 100
2 100
<1 100
8 100
65 100
<1 100
<1 100
<1 100
<1 100
Based on the figures in Table 2.
11
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TABLE 5. PESTICIDE USE DISTRIBUTION WITHIN EACH USER SEGMENT (%)*
Pesticide Type
Chlorinated hydrocarbon
Carbamates
Organic phosphorus
Triazines
Chlorophenoxy acids
Methanearsonics
Organic nitrogen
Benzoic acid derivatives
Dinitro aromatics
Uracils
Chlorinated alkyl acids
Chlorophenols
Dicarboxamides
Thiocarbamates
Dithiocarbamates
Total
Agricultural
10
9
24
8
6
4
14
5
4
1
<1
<1
4
5
6
100
Home &
Garden
18
6
20
<1
2
4
8
1
<1
<1
<1
1
16
9
14
100
Industrial/
Commercial
12
1
14
8
6
5
<1
5
<1
13
1
34
<1
<1
<1
100
Government
10
8
38
2
5
7
<1
3
<1
9
18
<1
<1
<1
<1
100
*
Based on the figures in Table 2.
12
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Government, and home and garden users are not considered
in evaluating the various dilute pesticide solution disposal
options in this report. The government is not a particularly
major pesticide user, shows no particular predilection for any
pesticide or pesticide type (except Dalapon) different from the
other user groups (see Table 2), and will be subject to any
disposal regulations imposed on other users. Although overall
consumption of pesticides (especially herbicides) may be sig-
nificant, use by individual households may not amount to much
over a few kilograms/household/yr. Consequently, the amount
of dilute pesticide solution generated by each home user would
be minuscule.
Urban, industrial, and commercial pest control operators
consume nearly 20 percent of the United States pesticide pro-
duction, a relatively small amount compared to the agricultural
use. Furthermore, the circumstances of urban use and waste
disposal do not lend themselves to the overall review of the
scope of this study. Consideration of urban pest controller
dilute pesticide solutions requires a different approach from
agricultural dilute pesticide solutions because the two user
segments face completely different disposal problems and con-
straints. No effort was made in this study to assess and
evaluate the disposal options available exclusively to the in-
dustrial/commercial user segment. Wherever a particular agri-
cultural disposal option may also be appropriate for an urban
pest controller, it is noted. This report concentrated on the
major pesticide use segment: agriculture.
Agricultural pesticide use is the principal source of
dilute pesticide solutions. Agricultural pesticide use
exceeds other uses combined by a 2:1 ratio (some reports put
the figure as high as 85 to 90 percent (10-11). Moreover,
larger quantities of rinse and washwater are needed because of
the application equipment involved. Consequently, the volume
of dilute pesticide solution from agricultural uses exceeds the
volume from all other sources combined by more than a 2:1
margin. Thus, on volume alone, agricultural dilute pesticide
solutions are the major problem.
PAST DISPOSAL PRACTICES
!
In the past, many agricultural applicators simply dumped
waste pesticides on the ground or into nearby water bodies
because they had no other disposal systems that could handle
dilute pesticide solutions economically (12). Such disposal
practices pose threats of pesticide contamination to ground
and surface water, air quality, public health, and livestock
and crops in the disposal area. Several fish kills have been
attributed to uncontrolled runoff from pesticide equipment wash
pads (personal communication, J. D. Linn, California Department
13
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of Fish and Game), container disposal, and runoff from fields
(4, 13-15). On the other hand, the large volume of water may
interfere with or preclude many conventional disposal methods
applicable for other waste pesticides (e.g., incineration or
encapsulation) without extensive waste stream pretreatment.
PROJECT OBJECTIVES
The overall pupose of this study is to evaluate the
state of the art of disposal methods in use or proposed for
dilute pesticide solutions. Specific objectives are to review
and evaluate present and proposed disposal methods; assess the
cost, use potential, and effectiveness of the proposed methods;
and to provide recommendations for further study and potential
demonstration. The methods addressed in this study are:
Land cultivation
Soil mounds and pits
Evaporation basins and lagoons
Chemical treatment
Physical treatment (adsorption, reverse osmosis)
Biological treatment (trickling filter, activated
sludge)
t Incineration
In addition, the report briefly covers means for reducing the
volume of dilute pesticide solutions through improved applica-
tion practices or reuse.
The following assumptions about the character of dilute
pesticide solutions are used to assess the disposal methods:
• Most dilute pesticide solutions (by volume) are
generated by agricultural applicators in rural areas.
• Approximately 90 percent of this waste is from
rinsing and washing aerial application equipment
(11, 16).
• Given a total annual volume of 424,480 m3 (112 x
10$ gal) and approximately 1,100 commercial crop
dusting and spraying establishments, the average
annual quantity of dilute pesticide solution per
applicator is 385 m3 (102,000 gal) (17). Approxi-
mately 77 percent of all commercial agricultural
pesticide applicators operate in areas where crops
are grown much of the year (the south and southwest,
year-round growing season: the plains states,
winter grains) (17). Therefore, a 10-mo working
year (225 days) is a reasonable assumption, giving
14
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an average daily dilute pesticide solution
generation rate of 1.7 nw (450 gal) per applicator-
The following criteria were used to select and evaluate
potential disposal methods:
• The disposal method must be environmentally safe
and not contribute to the degradation of air or
water quality.
0 Unless dilute pesticide solutions are collected and
stored for subsequent transport to a central pro-
cessing facility, the disposal system must be
located at or near (within 5 mi) the waste genera-
tion site.
cation
• The disposal method must disrupt normal appli
operations as little as possible.
• The disposal method should be inexpensive enough to
be feasible for the smallest application establish-
ments.
• The disposal method should be adaptable to any
climatological or geographical area in the United
States where agriculture is a major practice.
• If possible, at least one disposal method should
be amenable to application in urban settings.
• The disposal method should not require highly
skilled operators.
• The disposal method should be capable of handling
a wide range of pesticide types, formulations,
and concentrations with highly variable flow rates.
The relative weights for these criteria are discussed in Chapter
4.
One option that is not addressed as an option per se in
this report is the collection of dilute pesticide solutions
from all applicators in a given area for transport to a
central waste treatment facility or hazardous waste landfill.
The advantages and disadvantages of central facilities will
be discussed in the incineration section.
Although any of the methods discussed herein could be
employed at a central waste processing facility, the nature
of incineration (as presented in the following chapter) pre-
cludes its use by individual applicators. Thus, incineration
15
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is only suitable for use at central facilities. This should
become clearer in the following discussions.
16
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CHAPTER 3
DISPOSAL METHODS FOR DILUTE PESTICIDE SOLUTIONS
OVERVIEW
There are three basic goals in dilute pesticide solution
disposal: containment, detoxification, and volume reduction.
Detoxification is of primary importance. If a hazard-free
effluent can be produced, volume will no longer be a critical
factor. Complete detoxification is seldom achievable in
reality, so it becomes necessary to reduce the volume of
hazardous materials generated to a more manageable level and
to contain the material in a monitored disposal area.
As noted in the introduction, dilute pesticide solutions
have not always been considered hazardous. Rinsate and wash-
water were seldom collected. If they were, they were either
buried nearby or taken to a landfill or dump. Sometimes,
dilute pesticide solutions from washdown pads were allowed to
run into ditches or creeks near the pad, from which they
ultimately could contaminate water supplies (Figure 1).
Because of their unique nature (i.e. large volume, low
concentration, many generators) many disposal methods tra-
ditionally applied to hazardous solid and liquid wastes are
not always applicable. Given the immediacy of the problem,
it is imperative to identify disposal methods that are
currently available or can readily be developed and adapted
to dilute pesticide solutions without delay.
A variety of methods have been suggested, proposed, or
tested for treating dilute pesticide solutions. These run the
technological gamut from simple land cultivation to exotic
technologies such as microwave plasma destruction (18). The
most commonly discussed methods and those evaluated in this
report are:
• Land disposal (land cultivation, soil mounds and
pits)
Evaporation basins
Chemical treatment
Adsorption
Biological treatment
Incineration.
17
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Figure 1. Uncontrolled runoff from pesticide application equipment
washdown pad.
18
-------
Although all are theoretically applicable, there has been
little or no field-scale testing of most of these methods
with dilute pesticide solutions. Consequently, operating
data for evaluation are often lacking. The characteristics
of the industries generating dilute pesticide solutions,
the character of the wastes themselves, and experience with
these methods with other wastes must be used in evaluations
where actual field data are unavailable.
LAND DISPOSAL
Land disposal relies on the natural physical, chemical,
and biological properties of soil to adsorb, immobilize, and
decompose pesticides. There are several disposal techniques
which attempt to take advantage of these mechanisms (e.g.
land cultivation, soil mounds and pits).
The mechanisms of soil treatment include:
Volatilization
Photochemical degradation
Adsorption on;to clay, silt, and organic matter
Adsorption-catalyzed hydrolysis and oxidation
Microbial degradation.
Several attempts have been made to quantify the contributions
made by each of these mechanisms to the overall behavior of
pesticides in soil (19-21). None of the models thus
developed work especially well because of the wide range of
natural soil conditions and the differences in chemical
behavior among the different pesticides. However, a knowledge
of the mechanisms is useful in assessing the applicability of
land disposal in a specific situation.
Volatilization has recently been given a much greater
role in the loss of pesticides from the soil than previously
believed (22-25). Several researchers have stated that
volatilization is the major pathway of loss for certain
pesticides (23, 25). Volatilization rates from plant and
moist soil surfaces for the more volatile pesticides can
approach ninety percent within three days of application (26).
When the pesticides are placed below the soil surface,
volatilization continues, but at a much reduced rate (13, 22,
25). A detailed discussion of pesticide volatilization rates
is beyond the scope of this report, but an estimate of the
maximum volatilization fluxes is useful in assessing one of
the environmental impacts of land disposal.
When a pesticide is placed below the soil surface, loss
by volatilization involves movement of the pesticide upward
19
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to the soil-atmosphere interface and vaporization into the
atmosphere. The actual volatilization rate is dependent upon
the rate of movement of the pesticide to the soil surface
(22, 25). In the absence of evaporating water, the volatiliza-
tion rate depends on the rate of movement of the pesticide
to the soil surface by diffusion. When water evaporates from
the soil surface, an upward movement of water results, and any
pesticide not adsorbed in the soil solution moves toward the
surface by mass flow with the evaporating water. Thus, there
are two general mechanisms whereby pesticides move to the
evaporating surface: diffusion and mass flow in evaporating
water. For a soil disposal system, either or both transport
mechanism will be important depending upon the particular
pesticide and on the amount of water present in the system.
When water evaporates from the soil surface, transport
of pesticides by mass flow in the evaporating water will
usually be the dominant transport mechanism. Mass flow
processes are generally much more rapid than diffusion con-
trolled processes. Transport to the soil surface in
evaporating water is often referred to as the "wick effect."
When there is mass flow of pesticides to the soil surface,
the maximum pesticide volatilization flux can be estimated
using the following equation (22, 27):
op • cow (i)
where: J = the pesticide vapor flux in mass/area/time
C = the pesticide concentration in solution
J,, = the water flux
w
The concentration of pesticide in solution, C, is a function
of adsorption of the pesticide by the soil and of chemical
and microbial degradation. The maximum volatilization flux
from a soil mound would be expected with a persistent com-
pound and after the system had been in operation long enough
for soil adsorption processes to come to equilibrium. Thus,
for a compound like lindane, a relatively persistent insecti-
cide with a water solubility of 10 ppm, the maximum volatiliza-
tion flux that one could expect from the surface of a soil
mound would be
Jp = 10 ppm x Jw (2)
20
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or
per
water
10 ug of lindane evaporating per cm of water evaporating
cm2 of soil surface per unit time or 1.0 kg/ha/time/cm
Little or no volatilization of the parent compound would
be expected from compounds subject to rapid decomposition in
soils. For example, the organophosphate insecticide parathion
is subject to relatively rapid microbial and chemical de-
composition in soil; most of the parathion would be expected
to be degraded before reaching the soil surface. Strongly
adsorbed compounds and many compounds of low water solubility
would exhibit little volatilization flux. For instance, the
herbicides paraquat and trifluralin are both strongly adsorbed
by soil particles and would not move appreciably in
evaporating water. Study of the volatilization behavior of
pesticide degradation products has not been as thorough as
that of pesticides.
When diffusion through the soil is the mechanism control-
ling pesticide transport, the volatilization flux will
generally be lower than that due to mass flow because diffu-
sion rates are usually substantially lower than water movement
rates. Exceptions would be when the pesticide is insoluble
in water and little movement with the water would be expected.
It is difficult to present general equations predicting
volatilization flux due to diffusion controlled transport
because of the large number of soil and pesticide factors
contributing to the flux (28).
At the present time there are no Federal regulations or
guidelines concerning air emissions of pesticides from treat-
ment and disposal facilities, although establishment of such
is a distinct possibility. Based on the above calculations,
an adsorption-saturated soil disposal system containing a
persistent pesticide in an area with a high evaporation rate
(e.g., 200 cm/yr) would have emissions of approximately 200
kg/ha/yr or 6.5 mg/sec/ha. The concentration of the pesticide
in the air above the site would depend on the atmospheric
diffusion, keeping in mind that if diffusion is slight, con-
centrations will increase at the soil surface and the emission
rate will decrease. Further research is needed to establish
the emission rates of a non-persistent pesticide from a non-
saturated soil system for an expected range of evaporation
rates. Research is also needed to establish how pesticide
emissions from a disposal site in an agricultural area would
compare with normal atmospheric pesticide burdens from crop
spraying. The disposal site could represent a continuing
source of pesticides to the air as opposed to the seasonal
"slug" additions of pesticides from crop use. On the other
hand, regular emissions from disposal sites may be significantly
21
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lower than the amounts of pesticides added to the air during
agricultural operations (29-30).
Under ideal conditions, most organic pesticides are
subject to photolysis (31-32). It is doubtful, however, that
photodecomposition of pesticides in soil has much practical
significance (31). To begin with, only pesticides on the
soil surface would be susceptible. Since most other soil
degradation mechanisms are enhanced by soil incorporation, it
is usually not advisable to leave the pesticide on the soil
surface where it must compete with other substances for the
available solar energy and where there is a greater potential
for runoff. Radiant energy is strongly sorbed by soil and
thus is not always available even to surface pesticides (31).
Consequently, photolysis plays only a minor role in the
degradation of pesticides in the soil.
Adsorption, however, is the major factor in determining
whether and how far pesticides will move in the soil. Table
6 lists the relative mobilities of several pesticides in soil.
In general, nonionic pesticides are adsorbed more strongly
than anionic pesticides (32-33). Cationic pesticides
(e.g. diquat and paraquat) are strongly adsorbed by soils
(Personal communication, Dr. W. J. Farmer, University of
California to J. R. Marsh, SCS Engineers). Aside from the
chemical structure of the pesticides, soil properties also
strongly influence adsorption. Clay and organic matter
content tend to be highly correlated with pesticide ad-
sorption (24, 32). Sandy soils favor pesticide mobility.
Adsorption is also more favorable in dry than wet soil (34).
Water competes successfully with pesticides for available
adsorption sites. Research is needed to establish the effect
of the water-pesticide ratio on adsorption. The shear bulk
of the water present in dilute pesticide solutions means there
will be ample opportunity for pesticides to desorb and for
relatively large amounts of pesticide to be present in solu-
tion.
In general, adsorption appears to be a major mechanism
in pesticide retention in soils. A number of studies have
demonstrated the low mobility of many pesticides in non-sandy
soils (6, 24, 33, 35-40). Adsorption becomes especially
important when considering land cultivation as a disposal
method, because many land cultivation sites are unlined. Site
selection should be based in part on soil characteristics
which would retard the horizontal and vertical movement of
pesticides through the soil (e.g. cation exchange capacity,
percent clay, organic matter content, soil, pH).
Pesticide degradation in soils is primarily by microbial
or chemical means (32). Most studies have failed to
22
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TABLE 6. RELATIVE MOBILITY OF PESTICIDES IN SOILS*t
Immobile
Aldrin
Chlordane
DDT
Dieldrin
Endrin
Heptachlor
Toxaphene
TDE
Lindane
Heptachlor epoxide
Trifluralin
Slightly Mobile
Atrazine
Simazine
Prometryne
Azinophosmethyl
Carbophenthion
Diazinon
Ethion
Methyl parathion
Lindane
Heptachlor epoxide
Parathion
Phorate
Diuron
Monuron
Linuron
CIPC
IPC
EPTC
Pebulate
Mobile
2,4-D
2,4,5-T
MCPA
Picloram
Fenac
* Working Group on Pesticides. Ground disposal of pesticides,
1970 (41).
* Mobilities are based on soil thin-layer chromatography - mobile compounds
move between Rf 1.0 - 0.65, slightly mobile 0.64 - 0.10, and immobile
0.09 - 0.00. (Rf = "relative to fructose")
23
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differentiate between these two mechanisms and the data are
often inconclusive. Consequently, it is often difficult to
assess the relative significance of the two mechanisms. It
is obvious that both contribute significantly to pesticide
degradation (42).
Any pesticide subject to hydrolysis and oxidation in
water is susceptible to the same chemical degradation reactions
in moist soils. The reactions are often faster in soil
since the pesticides can be catalyzed by adsorption on the
surface of organic particles, clays, and iron and aluminum
oxides (34). In addition to adsorption and soil moisture,
soil pH also plays an important role; degradation of many
pesticides may be twice as rapid in alkaline than acid or
neutral soils (43).
When pesticides are initially applied to a soil system,
the natural soil microflora population may decline (1).
Repeated pesticide additions at low rates, as with dilute
pesticide solutions, tend to acclimate the microorganisms
and degradation rates increase. Some pesticides have been
considered nonbiodegradable because specific microorganisms
able to utilize those pesticides as a sole energy source have
not been isolated. Frequently, however, these pesticides can
be degraded when placed in a mixed culture of soil micro-
organisms. It is apparent that the soil microorganisms are
more versatile and complex than the limited laboratory tests
performed to date have indicated.
However, test results often indicate a need for supple-
mentary nutrients or simple energy sources in a soil system
used for pesticide disposal. These could be provided by
additions of commercial fertilizers and easily decomposable
organic amendments such as glucose or municipal wastewaters.
This last source suggests the possibility of using the same
land disposal site for dilute pesticide solutions and
municipal wastewaters. Research has not revealed any unex-
pected or uncontrollable adverse effects apart from those
normally associated with land cultivation of municipal waste-
waters (38).
All of these mechan.isms indicate that given proper site
selection and solution loading rates, most pesticides from
dilute pesticide solutions will not migrate through the soil
appreciably and will degrade on site. However, pesticides,
particularly persistent types or degradation products, can
accumulate in the soil if the application rate exceeds the
degradation rate, ultimately rendering the site useless for
effective disposal. High concentrations of pesticides in
soil (10 to 20,000 ppm) tend to retard degradation and increase
the potential for migration (44).
24
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Land Cultivation
Simply stated, land cultivation is the emplacement of
wastes within the plow layer of the soil (45). The objective
is to achieve thorough mixing of the pesticide wastes in the
plow layer where they will be subject to chemical and aerobic
microbial degradation. At the same time, movement of the pesti-
cides off site through runoff or by vectors is controlled and
minimized through proper site selection and construction and
waste application.
Land cultivation has been used for industrial and municipal
wastes for several years. However, the technology is still
developing and exact guidelines regarding site selection,
techniques, and amenable wastes are not always available. In
practice it has been a mixed success. One recent study
examined several land cultivation sites and found no evidence
of ground or surface water degradation (45). Other studies
have been more negative but, on closer examination, the sites
in these studies usually did not,strictly speaking, practice
land cultivation (46). For land cultivation to work, strict
site selection and waste application criteria must be developed
and followed. Where attempts have been made to do this, the
results have been largely positive (45).
In general, site selection is based on a number of
factors. The site cannot be in a flood plain or located so
that runoff would imperil surface water quality. The site
hydrogeology should be such that contamination of groundwater
by leachate is at least held to a minimum. Site soils should
have those characteristics (previously discussed) most favorable
to degrading or retaining the wastes on-site.
The amount of land needed depends on the quantity and
quality of dilute pesticide solutions and may have to be
determined experimentally for a given site. It might be
feasible to tie loading rates in with pesticide application
rates. For instance, dinoseb can be applied to citrus at rates
up to 10 Ib a.i./acre four times per year presumably without
adversely affecting the environment (47). A land cultivation
loading rate not exceeding this application rate (40 Ib/ac/yr)
should also be safe. Spreading rates could be based on the
types and concentrations of pesticides in the dilute pesticide
solutions. For 1.7 m3 (450 gal)/day of washwaters containing
dinoseb at 1,000 ppm, 8.5 ha (21 ac) would be needed to handle
one year's waste. Of course, this is a rough estimate based
on use rates; actual field tests could reduce the quantity
substantially.
Ideally, the land should be located near the source of the
dilute pesticide solutions, assuming other site selection
25
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criteria can be met. For aerial applicators, the unused land
along runways might be well-suited. Other applicators might be
able to use marginal land near their base or several appli-
cators could use a centrally located site. Local land avail-
ability and site suitability will determine the feasibility
of land cultivation.
To control runoff due to incident precipitation or excess
dilute pesticide solution, a series of collection ditches and
berms is usually constructed around a site (Figure 2). Such a
system prevents contaminated water from leaving the site as
surface runoff and collects it in a sump from which it can be
reapplied to the site as weather conditions warrant (45).
Equipment needs are limited to hardware to get the dilute
pesticide solution onto the soil surface and mixed into the
soil. A variety of techniques and equipment can be used to
accomplish this. The dilute pesticide solutions can be spread
on the soil surface by spray irrigation or tank truck or wagon
and then disked into the soil (44), or the wastewater can be
injected and mixed directly into the soil in one operation
(6, 45). Figure 3 illustrates one example of this operation
whereby dilute pesticide solution is pumped from the tank to
the blades or chisels of a subsoiler. The wastewater is injected
uniformly at about 30 cm (12 in) below the surface. Subsur-
face injection has an advantage over spreading in that the
pesticides are not left on the soil surface where they can readi-
ly volatilize, be blown away, wash off, or affect wildlife,
but are immediately incorporated into the soil where these
problems are minimized.
Subsurface injection requires a minimum of personnel
(1 to 2) and probably no more than an hour or two per day
during the application season, assuming the disposal site is
near the generation site. Maintenance would be limited to
routine tractor and pump maintenance. The skills required are
readily available in any farming community.
One of the questions faced in land cultivation is whether
or not to plant vegetation on the disposal site. The ad-
vantages are:
• The site is more aesthetically pleasing.
• Vegetation reduces wind and water erosion.
• Vegetation aids in water removal through
evapotranspiration.
t Vegetation tends to tie up some pesticides
through plant uptake.
26
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s/
-------
ro
oo
Figure 3. Dilute pesticide solution tractor/subsoi1er land application equipment
-------
• The land is not perpetually dedicated to dis-
posal, facilitating procurement of a disposal
site.
Disadvantages include:
• Pesticide concentrations in the soil may exceed
vegetation tolerance levels and prevent or inhibit
plant growth.
• Plowing must cease during certain growth periods,
leaving the pesticides on the soil and plant
surfaces.
• The pesticide-contaminated vegetation may be
unsafe for human or animal consumption and may
itself present a disposal problem.
In general, the advantages of vegetation do not exceed the
disadvantages sufficiently to recommend it as a routine
practice. Specific tests and evaluations would need to be
performed at each potential land cultivation site to determine
the safety of crop growth and use under the given conditions.
Soil Mounds and Pits
Soil mounds and pits are lined soil systems of limited
area which can accept higher rates of dilute pesticide
solution application than land cultivation. With a proper
liner, pesticide migration is prevented. The pesticides can
be allowed to accumulate in the system, although this entails
periodic replacement of the soil.
There are two basic configurations of soil mounds and
pits as depicted in Figures 4 and 5. Figure 4 depicts the
type currently being used and evaluated for dilute pesticide
solutions by the University of California. It consists of an
excavated pit, lined with an impermeable membrane (butyl rubber)
and backfilled with soil mounded above grade. A distribution
box and series of small leach lines are used to distribute
the dilute pesticide solutions throughout the system. The
soil pit in Figure 5 is being evaluated by Iowa State University,
It is a concrete-lined pit filled with soil and gravel.
Wastewaters are sprayed onto the pit soil surface and allowed
to percolate downward naturally into the pit.
Since research on soil mounds and pits is still not
complete, little data are available to assess their true
potential. They do have certain inherent advantages over
land cultivation:
29
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CO
o
PLAN VIEW
PERFORATED
10 CM (4 IN)
TILE LEACH
LINE
STRAW
PERFORATED
LEACH LINE
DISTRIBUTION BOX
SOIL
AND
AND FILL
60 CM
(2 FT)
SECTIONAL VIEW
BUTYL
RUBBER
LINER
Figure 4. University of California soil mound system
-------
MOVEABLE COVER
SUMP
DISCHARGE
Figure 5. Iowa State University soil pit disposal system.
-------
a Less land is required because the systems are
smaller.
• Dilute pesticide solutions are injected into soil
mounds beneath -the surface so no plowing is
necessary, and a vegetative cover can be used to
aid water loss through evapotranspiration.
• Except for some volatilization (the extent of
which is unknown) the pesticides are contained
entirely on site, and the possibility of contact
with people or animals is minimal.
t Soil mounds can be constructed in suburban areas
for use with urban applicator dilute pesticide
solutions (at least one soil mound system is in
use in suburban Orange County, California).
There are also some potential disadvantages, however, such as:
• The systems have a definite, limited life ex-
pectancy, unknown at this point but estimated
at 10 yr (Personal communication, Mr. Richard
Yamaichi, University of California, Davis).
• They are more expensive to construct than simple
land cultivation systems.
The size of the system depends on the quantity of .dilute
pesticide solutions generated. Estimates of void space in a
soil mound/pit are 10 to 15 percent of the total volume
(Personal Communication, Mr. Richard Yamaichi, University of
California, Davis). Application rates are limited by local
eyapotranspiration rates. When application rates are too
high, or during periods of high rainfall, the system can
flood and overflow (Figure 6). Consequently, any means used
to increase evapotranspiration (vegetative covers, transparent
roofs) can allow increased application rates or design of a
reduced system of size. A typical system might be 6 m
(20 ft) by 12 m (40 ft) by 0.9 m (3 ft) deep (48).
Once the system is constructed, only monitoring and
routine maintenance on feed systems is normally needed.
Periodically the system will become saturated with pesticides
or degradation products so that further adsorption or degrada-
tion is impossible. When this occurs, the contaminated soil
from the mound or pit will need to be excavated and transported
to an approved hazardous waste disposal site. Presently, the
frequency of this clean-out is unknown, but it will depend on
the types and quantities of pesticides added to the system.
The presence of a concrete pit or mound liner can reduce
32
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- .-;/- £viv.^sp?
• • .:%>•* OV-.-i * .-. .1'
r, ••>?•
5^^Vrr. - -
' " -
Figure 6. Flooded soil mound system
33
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the costs of the clean-out by making the replacement of the
liner unnecessary.' Membrane liners will inevitably be damaged
during excavation.
Although more expensive to install and operate, a con-
stant flow pump type feed system is better than gravity flow,
the potential surge problems in a gravity feed system flooded
by rainfall are avoided. Personnel and operator time require-
ments are minimal.
Economics
Table 7 presents a cost estimate for a land cultivation
system. These costs do not include the land, the major
system component. If the applicator can use airport land
adjacent to the runways or any nearby unused or marginal land,
land costs can be held to a lease fee. If the applicator
must purchase land, the costs of land cultivation could become
prohibitive. Otherwise, the major cost element is the
spreading/injection equipment. Labor costs include benefits
and overhead. (Note: in this and all subsequent sections,
labor costs reflect 1) only the hours devoted to the disposal
method operation, and 2) the level of skill or training
required.)
Table 8 presents a cost estimate for soil mounds and
pits. Again, basic land costs are not included. The major
expense is the initial construction of the mound or pit system
The annual operating cost estimate includes periodic system
clean-out and disposal prorated over a 10-yr system life.
Disposal costs assume a 30 mi transport to a disposal site at
$0.2/ton-mi and a site tipping fee of $35/ton.
Holding tank and pump costs are common to all of the
disposal methods. In general, these units consist of a
holding tank below the wash/rinse area and the pump/piping
needed to transfer the dilute pesticide solutions to the
actual treatment system. Cost estimates include costs of
laboratory services for monitoring and labor needed for
samp!ing.
EVAPORATION BASINS
Evaporation basins are open or covered basins or ponds
which reduce the volume of applied dilute pesticide solutions
by solar evaporation and treat the mass by microbial degrada-
tion, chemical hydrolysis, and sedimentation. Figures 7 and
8 show a typical evaporation basin and a conceptual wash pad/
basin system. Dilute pesticide .solutions can be discharged
into the basin as generated or placed in a holding tank for
controlled flow feed.
34
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TABLE 7. LAND CULTIVATION COST ESTIMATE1
Basis for calculations
1.7 mi? (450 gal)/day
385 md (102,000 gal)/yr
225 operating days/yr
1 hectare (2.47 ac) site
Capital Costs
Holding tank (2,000 gal galvanized steel,
underground, installed)
Pump
Tractor/subsoiler/nurse tank/pump assembly
Collection ditch and berm (9.85/m)
Runoff sump (lined)
Fencing
Yearly Operating Costs
Monitoring
Electricity
Fuel, oil
Labor (175 hr @ $9.20/hr)
Maintenance
Fixed charges (25% of capital costs)
Total
Total
$ 1,750
600
15,500
3,940
2,500
700
$24,990
$ 2,400
100
100
1,610
700
6,247
$11,157
Operating costs per m - $28.98
per gal - $ 0.11
* Material, equipment, and operating costs based on Means Building
Construction Cost Data 1978.
35
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TABLE 8. SOIL MOUNDS AND PITS COST ESTIMATES*
Basis for Calculations
1.7 m3 (450 gal)/day
385 m3 (102,000 gal)/yr
225 operating days/yr
Soil Soil
Capital Costs Mound Pit
Holding tank $ 1,750 $ 1,750
Pump 600 600
Distribution box 50
Pit, concrete liner, backfill (6m x 12m x 1m) 7,500 7,500
Leach lines 450
Gravel, soil 50 50
Roof 1,750 1,750
Fencing 700 700
Total $12,850 $12,350
Yearly Operating Costs
Monitoring $ 2,400 $ 2,400
Electricity 100 100
Labor (250 hr @ $11/hr) 2,750 2,750
Fixed charges (25% of capital costs) 3,212 3,087
System clean-up and spent soil disposal 1,240 1,240
(prorated over 10 yr)
Total $ 9,702 $ 9,577
Operating costs per m3 - $ 25.20 $ 24.88
per gal - $ 0.095 $ 0.09
Based on Means Building Construction Cost Data 1978.
36
-------
l-^-j,^-^-^-^-^^
.-Z^CJiS^wCSwg^
gg^KX^^
ji£>iS:£:*f^^
gOK
^ssssss^f^^feS
P^LiJUuok^^-^-^CKAAA-AX^Uk^yOfC^^ULs^^
i^^^^^^^^^^^^^^^^^^^^g
iS^^^^S^iM^^fe^^^^izeiiSiiiKSlgiiS
DILUTE
PESTICIDE
SOLUTION
Figure 7. Evaporation basin.
-------
CO
EVAPORATION BASIN
Figure 8. Evaporation pit system (4).
-------
Evaporation basins are a common industrial waste treat-
ment system. Thus, there are general guidelines for their
design and operation. The basins should be located close to
pesticide storage and equipment washdown areas to reduce
transport hazards and costs. There should be no effluent from
a basin to surrounding soil or underlying groundwater. Facili-
ties should have protective enclosures to keep wildlife,
domestic animals, and unauthorized persons out. Facilities
should be protected from storms and flood water to ensure that
erosion or other storm damage does not render any portion
inoperable. Any sludges, pesticide residues, or contaminated
soils taken from evaporation basins during cleanings must be
disposed of in approved hazardous waste disposal sites. A
basin must be lined to prevent any downward or lateral move-
ment of pesticides beyond the disposal site confines to
eliminate subsequent contamination of ground or surface water
supplies. Soil or membrane liners may be effective, depending
on pesticide type, liner material, and placement design. A
combination concrete-over-membrane liner is most secure and
least liable to mechanical damage.
As with land disposal, various mechanisms reduce the
volume and treat the dilute solutions applied to evaporation
basins. The primary mechanism to reduce the overall volume
of the dilute pesticide solution is evaporation. As noted in
the introduction, it is the large volume of waste that makes
dilute pesticide solutions a critical hazardous waste disposal
problem. Evaporation basins work to keep this volume low and
steady and, thus, more manageable.
Note that evaporation of water tends to concentrate the
pesticides remaining in the basin so the wastes and basin
media may be hazardous. However, there are several mechanisms
at work in the system that degrade or otherwise decrease
pesticide concentrations.
Pesticides, even with low vapor pressures, will evaporate
from open water (49-50). Thus, there is usually a distinct
pesticide odor associated with evaporation basins used for
concentrated wastes (48). It has been estimated that aldrin
and DDT have evaporative>half-1ives (the time required for
50 percent of the compound to evaporate) in clean water of
7.7 and 3.0 da-ys, respectively (49). However, little data
are available on volatilization losses from water surfaces
and no attempts have been made to obtain actual vapor loss
rates. Estimates of vapor losses can be made based on
thermodynamic considerations using data for Henry's constant
(ratio of vapor concentration to solution concentration and
usually taken as the ratio of the vapor pressure of the pure
compound to the solubility in water of the pure compound) and
39
-------
assuming that atmospheric transport away from the water sur-
face is limiting vapor loss. There has been little research
on pesticide evaporation from dilute pesticide solution
evaporation basins. Whether or not evaporation is a signifi-
cant transport method depends on whether evaporation rates ex-
ceed adsorption or degradation rates. The presence of bottom
muds or clays in the basin can greatly reduce pesticide evapora-
tion through adsorption (24). Laboratory evaluation studies do
not account for the competing degradation mechanisms (e.g.
photolysis, hydrolysis) which also act on the pesticides.
Photolysis of pesticides can be significant in any open
water system (51-54)^ However, ultra-violet radiation will
only penetrate a few millimeters into the water (53). Con-
sequently, shallow basins have an advantage over deeper systems
in regard to photolysis. Photolysis degradation rates
measured in laboratory studies indicate half-lives in terms
of a few hours for some pesticides (51). The presence of
photosensitizers can greatly enhance photolysis (51, 54).
Photosensitizers (e.g., humic acids) facilitate the transfer
of light energy into the pesticides, thus increasing the
reaction rate.
Chemical hydrolysis can also be an effective degradation
mechanism in evaporation basins (13, 51). Hydrolysis rates
can also vary, depending on other substances in the water-
Hydrolysis seems to be faster when the pesticides are adsorbed
onto clay or silt particles, suggesting it may be adsorption
catalyzed (13). The pH of the water can also significantly
influence degradation. Research with malathion has demon-
strated hydrolysis half-lives in neutral water and at pH 9
of one month and ten hours, respectively (51). Many industrial
pesticide waste evaporation basins are kept alkaline to enhance
degradation (55). Alkaline hydrolysis is not effective with
every pesticide but has been shown to work with organophosphates,
carbamates, imides, and hydrazides (55).
Microbial degradation can also play a role in reducing
pesticide concentrations in evaporation basins, although
probably not as great as the other mechanisms. To be truly
effective, microorganisms require a near neutral pH and a low
humic acid content (51). Under these conditions, chemical
hydrolysis and photolysis are minimized, because hydrolysis
generally proceeds better under alkaline conditions, and humic
acids are photosensitizers. Research is needed to determine
which approach is most effective in reducing pesticide levels
in evaporation basins, particularly in basins that receive
dilute solutions.
The major limitation to evaporation basin operation is the
evaporation-precipitation gradient (4). For the system to
40
-------
work, evaporation rates must exceed precipitation rates. In
areas of high rainfall, a transparent or semi-transparent roof
is needed to keep out rainfall although roofing may result in
slight decreases in evaporation (4, 55).
A basic consideration in designing an evaporation basin
is to ensure that the volume of incoming solution is less than
or equal to the volume of water leaving the basin via evapora-
tion, as expressed below (4):
Qw + Op £ Qe (3)
where :
o
Qw = volume of pesticide wastes (ft )
Qp = volume of precipitation
Qe volume of evaporation.
These parameters can be estimated as follows:
Qw = n"Do (Qw in ft3) (4)
7.48
where :
n = no. of vehicles to be washed
W = amount of washwater/vehicle, gal
D = no. of operating days
Qp VtD (5)
4,380
where:
q = annual average precipitation, in/yr
2
A. = top area of basin, ft
D = elapsed no. of days (usually 365)
^ Af
4,380
Qe = ^ AfD
41
-------
where:
q = annual average evaporation rate, in/yr
2
A~ = surface area of fluid, ft .
Equation (3) can then be restated as follows:
"^o + V^ ^ qaAf° (7)
7.48 4,380 4,380
2
To obtain the proper area (Af in ft ) for a vertical walled
basin,
. -1.6 nWD
Af " ——-—°- (D = 365 days) (8)
qp"qe
(Note: if qp = qe, set qp - qe - 1. Also, qp and qe should
be expressed as whole inches.) Since most basins have sloped
sides, Af ^ At. Furthermore, the top of the pit (t) should
be at least 60 cm (2 ft) above the fluid surface (f) to con-
tain a 10-yr, 24-hr storm and/or wind wave action. Con-
sequently,
At = (/7^~+ 2" )* (9)
where:
H = height of t above f
S = side slope of basin (use/run).
2
The area of the basin base (ft ) is,
where:
d = maximum depth of fluid (ft).
During evaporation, the surface area of the fluid will
change with changing evaporation rates. Thus, the average
fluid surface area must be calculated as follows:
A . Af (100-EV)(100) (
42
-------
where:
EV = evaporation variance (%)
100 Af
Substituting this in Equation 7 yields
nWDo , VtD ^ Vfa0 (12)
7.48 4,380 4,380
To compute the volume of fluid on hand in the basin at
the end of the application season, set D = D0 and solve. To
calculate if this volume will be removed during the idle
season, set the first term in Equation 7 equal to zero and
substitute D-Dp for D. If the net quantity of fluid removed
is less than the amount on hand at the end of the season, a
larger pit should be selected. A quickly converging iterative
procedure will probably be needed to arrive at the proper
si ze.
The volume contained below the computed fluid level
should be determined as follows:
V (in ft3) = 1/3 d (Af + / AfAb + Afa) (13)
This basin volume should be greater than or equal to the waste
volume on hand at the end of the application season.
For a roofed basin in a high precipitation area the
same design equations can be used by setting qp equal to
zero, or a very low number, to account for windblown incident
precipitation, and solving as above.
Evaporation basins are most frequently used by pesticide
formulating and packaging plants for their process wastewater
and washwater (55). Industrial basins range from shallow
concrete pads to earthen ponds lined with bentonite, plastic
membranes, or other impermeable liners. Small ponds (less
than about 2,500 ft2) are usually roofed (55). Some systems
add simple spray or waterfall aeration to increase evaporation.
Occasionally supplemental heat from immersion heaters is
applied.
Industrial experience has shown that evaporation basins
are simple to construct and operate. Usually only one
43
-------
person is needed,,and he must spend less than 10 percent of
his time in monitoring the basin, adding chemicals, and
maintaining the pumps (55). As noted above, most industrial
basins are kept at about pH 9 to enhance hydrolysis.
Advantages
Evaporation basins are simple systems that can be in-
stalled anywhere sufficient land is available. They require
a minimum of operating personnel and time to ensure proper
operation. Thus, the ease of operation is a major advantage.
Disadvantages
Evaporation basins do not work efficiently in areas with
low evaporation rates or long periods of freezing temperatures
(4). Water evaporates (submlimes) very slowly from a frozen
basin. Periods of freeze reduce the factor D in Equation 5.
Thus, there are some climatological limitations.
The major potential disadvantage is the possible air
quality impairment from pesticide volatilization. At this
point the extent of the problem is unknown. Further research
is needed to fully quantify the potential emissions.
Economics
Table 9 presents a cost estimate for an evaporation basin
The major cost element is construction of the basin itself.
Use of an appropriate plastic or bentonite liner instead of
concrete could reduce costs. The aeration pump system is
optional. If an applicator wishes to keep the water in the
basin at pH 9, additional chemical costs of about $250/yr
can be expected. The capital costs do not include land costs.
Summary
Overall, the concept of land disposal has both advantages
and disadvantages. Advantages include:
• Generally lower costs compared to other, more
elaborate disposal methods
• Availability of appropriate equipment and personnel
in rural agricultural areas
t Overall ease and simplicity of operation
0 The demonstrated effectiveness of some soils in
containing and degrading many pesticides.
44
-------
TABLE 9. - EVAPORATION BASIN COST ESTIMATE* :
Basis for Calculations
1.7 nrj (450 gal)/day
385 m3 (102,000 gal)/yr
225 operating days/yr
Capital Costs
Holding tank $ 1,750
Pump 600
Concrete lined basin (4.5 m x 9 m x 1 m) 3,500
Aeration pump system 1,200
Roof 1,750
Fencing 700
Total $ 9,500
i
Yearly Operating Costs
Monitoring $ 2,400
Electricity 100
Labor (250 hr & $11/hr) 2,750
Fixed charges (25% of capital costs) 2,375
System clean-out and sludge disposal 850
Total $ 8,475
per gal - $ 0.08
o
Operating costs per m - $22.01
Ferguson, T. L. Pollution control technology for pesticide
formulators and packages, 1975,(55) updated to 1978 using standard
engineering cost indices.
45
-------
Disadvantages include:
• A lack of comprehensive data on the types and con-
centrations of pesticides that are amenable to
land disposal
• The uncertainties surrounding the movement and
degradation of many pesticides and degradation
products is soil systems
• A lack of control over the ultimate fate of the
pesticides, compounded by a relative inability
to predict either causes or consequences (6).
The disadvantages are of more consequence in regard to
land cultivation than soil mounds or pits. Even with a liner,
the potentials for air and water contamination through
leaching, runoff, and evaporation are much higher with land
cultivation. Research has indicated that these transport
phenomena are concentration-related (44). Consequently, there
are circumstances under which land cultivation could be effec-
tive, but research to date has not clearly defined these
circumstances.
The major problem of environmental safety and pesticide
migration is largely eliminated with soil mounds and pits.
With proper liner selection, there is little potential for
subsurface migration. Roofs, berms, and sunken soil surfaces
serve to prevent runoff. The only remaining potential
transport pathway is evaporation and the significance of this
route has not been fully evaluated.
CHEMICAL TREATMENT
The objective of chemical treatment is to convert the
toxic constituents of dilute pesticide solutions into harmless
or less toxic forms. Under ideal conditions, the treated
dilute pesticide solution would be amenable to safe disposal
by any conventional wastewater disposal method without the
precautions necessary for hazardous waste streams. Typical
types of chemical treatment are oxidation, hydrolysis, and
precipitation. Oxidation and hydrolysis act on the chemical
structure of the pesticide, breaking the molecule down into
smaller, more biodegradable fragments or removing various
functional groups. Precipitation converts the pesticide
into an insoluble form which can be removed as a sludge. This
sludge must be treated as a hazardous waste, but the volume '
is considerably less than the original dilute pesticide
solution.
46
-------
Figure 9 shows a typical arrangement for a chemical
treatment system. Equipment requirements consist primarily
of a lined reactor (concrete, steel, or fiberglass tank;
lined basin, pond, lagoon) with a stirring mechanism
(mechanical, aerator) and chemical storage and feed equipment.
To eliminate air emissions, a closed tank is advisable. Use
of several different treatment chemicals might require several
chemical feeders or thorough cleaning between treatments.
Maintenance would be limited to periodic servicing of
mechanical feed and metering equipment and stirrers. In addi-
tion, occasional cleaning of pipelines, tanks, and reactors
would be necessary. Aside from maintenance, routine operations
would require one person to select, measure, and feed the
treatment chemicals and monitor the treatment process. Chemi-
cal treatment could be conducted concurrently with other
routine applicator operations.
No single chemical procedure exists for degrading the
entire spectrum of pesticides (56). Some pesticides are not
readily amenable to chemical treatment (Table 10). The more
commonly used pesticides are considered to be susceptible to
chemical treatment. In some cases, degradation products may
be hazardous. For instance, dimethoate can be entirely
degraded by alkaline hydrolysis. The degradation product,
mercaptoacetic acid, is almost as toxic as the dimethoate (58).
Moreover, the appropriate reagents may be exotic, expensive,
or extremely hazardous, and the degradation process may re-
quire special equipment, conditions, or skills not readily
available outside of research laboratories. While some
pesticides can be completely degraded by chemical treatment
(e.g. Def) slow reaction times make the method of questionable
value (58). The applicability of chemical treatment must
be evaluated in terms of the specific pesticides to be
treated (57).
There has been considerable research on chemical treat-
ment methods, particularly for the more concentrated solutions
of industrial pesticide wastes and waste pesticides (56-62).
Some of the results areiapplicable to dilute pesticide
solution treatment. For instance, 2,4-D and 2,4,5-T react
readily with hydrogen peroxide (56). Chlorine dioxide reacts
with diquat and paraquat under alkaline conditions (56).
Carbamates and organophosphorus pesticides are generally
susceptible to hydrolysis (Table 11). Potassium permanganate
reasily oxidizes parathion in alkaline media (63). Exhaustive
chlorindation is not recommended for nitrogen, phosphorus,
or organo-metallic pesticides because toxic by-products can
form (18).
47
-------
WASHROOM
CHEMICAL
FEED
00
^ FLOW
\ METER
TREATED
EFFLUENT—^
DILUTE
PESTICIDE
SOLUTION
LINED \
STORAGE\
TANK ^
LINFD
REACTOR
STIRRING
MECHANISM
Figure-9. Chemical treatment system.
-------
TABLE 10. SOME PESTICIDES NOT READILY DEGRADABLE BY
PRACTICAL CHEMICAL TREATMENT*
Dursban
Methyl Parathion
Maneb
Alachlor (Lasso)
Diuron
Picloram
Trifluralln
Methoxychlor
Chlordane
Toxaphene
Amiben
Pentachlorophenol
Ronnel
Dimethoate
Dyfonate
Def
EPTC
Molinate
Thiram
Propanll
Diphenamid
Chloroxuron
Cyanazine
Simazine
Amitrole
PCNB
Dinoseb
Chloropicrin
Chiorobenzi late
Endrin
D-D
BHC (Lindane)
DBCP
Dicamba
Sodium Fluoroacetate
Creosote
Warfarin
Arsenic Acid
MSMA
Shih and Dal Porto. Handbook of pesticide disposal by common
chemical methods, 1975 (57),
Lande, S. S. Identification and description of chemical deactivation/
detoxification methods for the safe disposal of selected pesticides,
1978 (58).
49
-------
TABLE 11. SELECTED PESTICIDES AMENABLE TO ALKALINE HYDROLYSIS*
Pesticide
Parathion
Methyl parathion
Ma lathi on
DDVP
Diazinon
Carbaryl
Propoxur
Phosphamidon
Alkalinity
IN. NaOH
IN. NaOH
pH 10.03
pH 8.0
pH 10.4
Alkaline
pH 10.0
pH 10
Half -Life
32 min
7.5 min
28 min
462 min
144 hr
Rapid
40 min
2.2 days
* Dennis, W. H., Jr. Methods of chemical degradation of pesticides
and herbicides, 1972 (56).
Shih and Dal Porto. Handbook of pesticide disposal by common
chemical methods, 1975 (57).
50
-------
On the other hand, much of the research has used exotic,
rare, or hazardous treatment chemicals which would not be
practical for dilute pesticide solution treatment in the field.
Examples of these include liquid ammonia with sodium metals,
chromous chloride in acetone, t-butyl alcohol and lithium metal
1n tetrahydrofuran, and lithium iodide in boiling collidine
(56, 59). In general, for a chemical treatment method to be
acceptable for dilute solutions encountered by applicators and
farmers, the reagents and solvents should:
• Be relatively common
• Be low in cost
• Produce no fire hazard
• Be non-toxic to fish and mammals under normal use
conditions
• Produce degradation products that are safe to handle
and can be disposed of in non-hazardous waste
facilities (56).
Advantages
Chemical treatment is reliable and results are reasonably
predictable (62). Under ideal circumstances, an innocuous
waste stream can be produced. Chemical treatment is largely
independent of climatic or .geographical limitations. Treat-
ment systems can be set up almost anywhere and seldom require
much land area. Wei 1-designed systems will not result in
stray water or air emissions. Chemical treatment is one of
the few systems which can be adapted for use by urban
pesticide applicators.
Disadvantages
Chemical treatment systems often do not yield complete
detoxification because (1) insufficient time is allowed or
(2) insufficient treatment chemical is used. Even when
complete degradation is readily achievable, the reaction
product may be as hazardous as the pesticide, as is the case
with dimethoate (58). Consequently, the effluent from a
chemical treatment system may be far from innocuous.
If an applicator uses a variety of pesticides, many
different treatment chemicals might be necessary, raising
problems of both original cost and storage. For instance,
fensulfothion is amenable to alkaline hydrolysis but chemical
oxidation forms toxic end-products. On the other hand,
51
-------
paraquat is not amenable to alkaline hydrolysis but is readily
susceptible to oxidation with chlorine or permanganate.
Moreover, most treatment chemicals are themselves hazardous
and require special handling, although usually within the
abilities of the applicator.
Determination of the proper stoichiometric amount of
treatment chemicals requires analysis of the dilute pesticide
solution and a knowledge of the treatment chemistry (or a
producer-supplied table of precise amounts). The amount could
be estimated based on formulation rates, but this would
generally lead to an excess of treatment chemical. If too
little treatment chemical is added, incomplete detoxification
will result; too much chemical and a new waste chemical
solution could be created. If an unskilled operator uses the
wrong combination of chemicals (e.g. sodium sulfide plus
hydrochloric acid), toxic gaseous by-products (e.g. hydrogen
sulfide) could be produced. A dilute pesticide solution
containing several different pesticides might require sequential
treatment by different methods or reagents. In any case,
knowledge of the constituents and concentrations in the dilute
pesticide solution are mandatory before treatment, requiring
on-site analytical facilities and appropriate personnel.
Economics
Table 12 presents a cost estimate for chemical treatment.
Major expenses are for treatment equipment and operations.
Chemical costs can vary widely depending on the types and
concentrations of pesticides in the dilute pesticide solutions.
For this estimate, costs are based on alkaline hydrolysis
with sodium hydroxide. Land costs are not included. Labor
costs reflect the increased skills and time required to
operate and maintain chemical treatment systems.
PHYSICAL TREATMENT
Physical treatment processes rely on solute-solvent
interactions and the physical properties of solutes and
solvents to effect pesticide removal. Their primary functions
are separation of liquid and solid phases and concentration,
removal, or recovery of dissolved contaminants. Among the
physical treatment processes that have been considered for
dilute pesticide solutions are adsorption, reverse osmosis,
distillation, electrodialysis, and liquid-liquid extraction.
Most of these processes have limited potential for treat-
ing dilute pesticide solutions, except as they might be used
as an integral step in a more complex waste treatment system.
Some have been used only in experimental or pilot operations.
52
-------
TABLE 12. CHEMICAL TREATMENT COST ESTIMATE*
Basis for Calculations
1.7 m;? (450 gal)/day
385 m3 (102,000 gal)/yr
225 operating days/yr
Capital Costs
Holding tank $ 1,750
Pump 600
Reaction tank (4,000 gal capacity, lined) 3,000
Chemical feeding and mixing equipment 2,500
Fencing 700
Total $ 8,550
Yearly Operating Costs
Monitoring $ 600
Electricity 300
Treatment chemicals 2,000
Labor (400 hr @ $12/hr) 4,800
Fixed charges (25% of capital costs) 2,137
Maintenance 1,000
Waste disposal 2,500
Total $13,337
o
Operating costs per m - $34.64
per gal - $ 0.13
Equipment, material, and operating costs are based on Means Building
Construction Cost Data 1978. Chemical costs are from chemical supply
catalogs.
53
-------
Most require highly specialized equipment and training.
Given the current state-of-the-art, only reverse osmosis and
adsorption show promise as dilute pesticide solution treatment
methods.
Reverse Osmosis
Most advanced applications of reverse osmosis (R. 0.) are
for desalination of brackish water. As a small-scale pesticide
wastewater treatment method, R. 0. is still in the experimental
stage. In recent years, there has been considerable work on
the development of small R. 0. systems for treating agricul-
tural wastewaters (64). Research with pesticides has shown
R. 0. to be very effective (99.5 percent) in removing non-
polar pesticides from solutions at concentrations ranging from
0.25 to 3 ppm (65). Conversely, R. 0. has not been as effective
in removing polar pesticides and low molecular weight organic
compounds in general (66). Membrane deterioration and fouling
continue to be problems. Consequently, several studies, while
recognizing its potential value, have relegated R. 0. to a
secondary position at present (6, 66, 73). Therefore, R. 0.
will not be discussed in any further detail.
Adsorption
Adsorption on activated carbon, adsorbent clay, and other
natural and synthetic adsorbents is an effective means of re-
moving many organic substances from dilute aqueous solutions.
It is widely used in water and wastewater treatment for the
removal of trace organics and taste- and odor-causing sub-
stances. Some pesticide manufacturing plants use activated
carbon on an experimental basis or as a waste pretreatment
or final polish method (54). There have been numerous studies
on the use of adsorption for removing pesticides from water,
and the results are generally good (65). One study used
activated carbon to treat container rinsate (approximately
500 ppm) and achieved 98 percent removal (6). The use of
pine bark dust instead of carbon was found to reduce con-
centrations of Sevin from 500 to 1 ppm at bark dust dose
rates of 3 kg/3.8 m3 (6.6 lb/1,000 gal) (6).
Adsorption units are available in either bed or column
configurations. In general, column units (Figures 10 and 11)
would be most appropriate for treating dilute pesticide
solutions. Portable units are available for seasonal users
(e.g., summer camps or resorts). In addition to the column
itself and the various pumping and metering equipment, mon-
itoring equipment and a source of make-up sorbent are needed.
Monitoring equipment will identify the breakthrough point
when the adsorbent has become saturated and must be replaced.
54
-------
IN
MAKUP
CARBON
SCREENED
OVERFLOW
PLACE TOP OF /
DRAIN BIN BELOW
HYDRAULIC GRADIENT
IN COLUMNS
SPENT
CARBON
DRAIN
BIN
WATER IN
HYDRAULIC
GRADIENT
WATER\
FLOW
CARBON
COLUMN-
CARBON
MOVEMENT
WATER
OUT—!
SPENT
CARBON
OUT
Figure 10. Carbon transfer with upflow column in service (67)
55
-------
6 FT
20 1" S ti i 1 I 1 i i II i i I • I I 1 • i 1 i gg?BOLT RING
HOLES cij;~~ ,, ,, ~,,i
•BACKWASH
WASH
WATER
CO
'/ A •
. ' ' •• s? ' ' '{' ' '/<'
'/':>X^ -:,:AV^X,
-si - -> '/,*•* • -<: :* 3,
; 'vV^'^r^^;,/
'--^^..^•m^^
, :m-;S|^H;
7
~^^'. -
^
—
-
->•-
-c.'
*•"•
CARBON CHARGE
'SURFACE WASH
•CARBON BED
SURFACE
•^•CARBON DISCHARGE
METAL SCREEN
•EFFLUENT
•BACKWASH
Figure 11. Pressurized downflow contactor (67).
-------
It would be impractical for the pesticide applicator to
regenerate spent adsorbent, so new adsorbent would be needed
regularly if such a process were used to treat a dilute pesti-
cide solution stream.
Advantages
Adsorption units are available in almost any size for
any application. They can be installed almost anywhere and,
with proper insulation, are not subject to geographical or
climatological limitations. Removal efficiencies of 98
percent and better have been attained. Little specialized
training is required to operate a simple adsorption unit,
although some types of adsorption devices demand extensive
training. Maintenance, particularly of monitoring devices,
can be a special problem. Since adsorption units are closed
systems, opportunities for spills, volatilization, public harm,
or damage to wildlife, stock, or crops are minimal. Adsorption
units could conceivably be adapted for use by urban pesticide
applicators.
Disadvantages
A disadvantage to adsorption, and, in reality, all
physical treatment processes, is that the pesticides are not
destroyed. In adsorption, this is partially overcome by the
fact that the waste is changed from a large volume, dilute
liquid waste to a small volume, concentrated solid waste.
This greatly simplifies the original hazardous waste disposal
problem. The volume of wastes will be less, but the concen-
tration will be greater. For instance, adsorption generates
a solid waste with a high pesticide content; reverse osmosis
generates a highly concentrated wastewater. It is imperative
to treat these wastes with a highly efficient destructive
treatment method or transport them to an appropriate hazardous
waste disposal site, but in either case, the costs and
problems are less than with the original wastewater.
Many pesticide formulations contain inert carriers (e.g.,
clay), other insoluble inorganic ingredients (e.g., sulfur),
insoluble pesticide powders or granules, or oil carriers
(9, 47, 68). These materials could clog an adsorption column.
Some pesticides (e.g., methoxychlor) can foul carbon beds
(6). Consequently, dilute pesticide solutions containing
these types of materials will require pretreatment before
adsorption.
Finally, even at removal efficiencies of 98 percent or
better, an influent of 500 ppm can still have an effluent
of 10 ppm. For many pesticides, this concentration is
potentially hazardous and further treatment will be necessary.
57
-------
Economics
Table 13 presents a cost estimate for a carbon adsorption
treatment system. The major cost element is the pretreatment
system, which can be eliminated if an applicator's dilute
pesticide solutions consistently contain no suspended matter,
emulsified pesticides, inorganic matter, or the few pesticide
types that can foul a carbon system. Aside from that, major
cost elements are the initial set-up and the annual operating
expenses. Costs include the disposal of the spent carbon.
BIOLOGICAL TREATMENT
Biological treatment systems rely on the microbial
breakdown of organic pesticides to innocuous compounds.
Although other treatment methods, such as land cultivation
and evaporation basins, depend at least in part on biological
degradation, the discussion in this section is limited to
biological activity in an artificially-controlled environment.
The principal methods to be discussed are activated sludge
and trickling filter. However, the basic principles and the
applicability of biodegradation to specific pesticides apply
to all biological systems.
Almost all organic compounds can be broken down biologi-
cally, given the proper environment and sufficient time (69).
Days or weeks may be required to obtain significant decomposi-
tion of some pesticides, and the breakdown of others may
proceed so slowly that, for practical purposes, they may be
considered nonbiodegradable. Pesticide characteristics that
affect biodegradability include molecular weight, configura-
tion, and bulkiness; elemental composition; and the type and
location of substituent and functional groups on the molecule
(69). Certain parts of a pesticide molecule may degrade
more readily than other parts. For instance, the toxic group
of a molecule may resist degradation, leaving a metabolite as
toxic as the parent compound.
In general, aromatic compounds are more resistant to
biodegradation than aliphatic and alicyclic compounds. The
presence of elements other than carbon in the skeletal chain
or ring may make the structure more degradation resistant.
For example, esters and acid salts are usually less susceptible
to breakdown than simpler compounds without these functional
groups (60). Halogens on an aromatic ring increase resistance
to biodegradation; chlorophenols become increasingly
resistant with increasing halogen substitution. On the other
hand, amino and hydroxy substitutions tend to increase bio-
degradabil ity (69).
58
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TABLE 13. CARBON ADSORPTION COST ESTIMATE*
Basis for Calculations
1.7 mi* (450 gal)/day
385 md (102,000 gal)/yr
225 operating days/yr
120 min contact time
227 kg (500 lb) carbon/yr
Capital Costs
Holding tank $ 1,750
Pump 470
Pretreatment tank 1,300
Filter and vacuum pump 7,000
Carbon column pump 250
Carbon column (3 m x 0.6 m) 600
Initial carbon charge 750
Installation, piping, electrical 4,450
Contingencies 1,750
Engineering 1,750
Total $20,070
Yearly Operating Costs
Monitoring $ 600
Carbon 1,200
Pretreatment chemicals 1,050
Labor (500 hr @ $ll/hr) 5,500
Utilities 250
Fixed charges (25% of capital cost) 5,018
Spent adsorbent disposal 500
Total $14,118
per gal - $ 0.14
3
Operating costs per m - $36.67
Carbon adsorption equipment costs are from Process design manual for
carbon adsorption (67) updated to 1978. With standard engineering
construction cost indices. The remaining cost elements are from
Means Building Construction Cost Data 1978.
59
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Trickling Filters
Trickling filters are beds packed with various kinds of
high surface area media upon which biological slimes develop.
Wastewaters are sprayed on top of the bed and allowed to
trickle through by gravity (Figure 12). As the wastes pass
through the bed, the organisms in the slime layers metabolize
organic matter present in the waste (Figure 13). The term
filter is a misnomer; the removal of organic material is
not accomplished through a physical filtering or straining
operation, but is the result of an adsorption process at the
biological slime surface followed by metabolization by the
slime organisms (60).
Activated Sludge
Activated sludge treatment is the biological oxidation
of organic wastes in a reactor containing a concentrated
biomass supplied with nutrients and oxygen in the proper
ratio for efficient use of the waste by the organisms
(Figure 14). Most organics, including pesticides, solvents,
and by-products, can be utilized by bacteria under proper
conditions. Utilization rate and removal efficiency vary
for each compound and class of compounds.
Both trickling filter and activated sludge systems re-
quire construction of special tanks as well as special
operating equipment. At least two operators skilled in the
theory and operation of biological treatment systems are needed
for each unit. Since dilute pesticide solutions do not con-
tain sufficient nutrients to support bacterial growth, nutrients
must be added to the system. Special monitoring devices are
needed to control temperature, pH, nutrient content, and other
factors.
Trickling filters and activated sludge are both used in
industry to treat pesticide manufacturing wastes (60, 62).
Trickling filters are generally used as a roughing filter,
since they can handle fluctuating waste loads or slug flows
with less chance of long-term upset than can other biological
treatment systems (59). There has been little research to
determine which pesticides are readily amenable to biological
treatment. Chlorinated herbicide wastes can be successfully
treated with trickling filter, while organic-phosphorus
and 2,4-D wastes are amenable to activated sludge (60).
Advantages
Under ideal conditions, biological treatment systems can
give virtually complete pesticide detoxification (69). Even
under less than ideal conditions, biological treatment has the
60
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FILTER
ROCK
FILTER
WALLS
UNDER
DRAINS
DISTRIBUTION ARMS
AND NOZZLES
NEFFLUENT
CHANNEL
Figure 12. Trickling filter.
-------
ro
jgggg?^^ LIQUID WASTE ^
Figure 13. Typical trickling filter slime layer.
-------
INFLUENT
AERATION TANK
SLUDGE RETURN
CLARIFIER
EFFLL
CO
INFLUENT
t t I
I 1 I
L L
RETURN SLUDGE
EFFLUENT
Figure 14. Activated sludge schematic.
-------
potential for reducing toxicity and organic content in dilute
pesticide solutions and eliminating pesticide residue traces
from effluents to be discharged to the environment. Well-
designed, and -operated biological treatment systems do not
have many of the environmental and public health problems
encountered with other treatment methods.
Disadvantages
Biological treatment systems are specialized, complex
units requiring specific operating conditions and especially
trained personnel. The systems are highly sensitive to
changes in temperature, pH, nutrient content, and pesticide
chemical structure (60). Consequently, the systems do not
always adapt well to cold climates or areas where frequent
and extreme temperature fluctuations are encountered. In
general, biological systems do not respond well to wide
variations in loading rates nor sudden changes in the con-
centration or type of pesticide in the waste to be treated.
Furthermore, given the toxic nature of some pesticides (e.g.,
organometal1ics), bacterial die-off and system upset are
common. Finally, degradation efficiencies and degrees of
detoxification have not been determined for most pesticides;
hence, the ultimate efficacy of biological systems, as applied
to dilute pesticide solutions, is largely unknown.
Economi cs
Table 14 presents cost estimates for biological treat-
ment systems. Roughly one-third of the capital costs are for
the pretreatment systems. Unlike adsorption systems, pre-
treatment with biological treatment is virtually unavoidable;
it is essential to ensure a fairly uniform influent. Cost
estimates do not include land.
INCINERATION
Incineration is waste processing (volume reduction)
by means of controlled combustion, so that the waste components
are converted to inorganic gases and solid ash residues.
Incineration is a basic procedure recommended by the EPA for
the disposal of waste organic pesticides (70). Research has
demonstrated that, under proper operating conditions, virtually
all of the active ingredients of organic pesticides can be
degraded by incineration (71).
Incineration is a common waste processing method for
municipal solid wastes, industrial wastes, and many hazardous
wastes. It is the favored waste disposal method among
pesticide manufacturing plant managers (60). However, most
64
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TABLE 14. BIOLOGICAL TREATMENT COST ESTIMATES*
Basis for Calculation
1.7 m3 (450 gal)/day
385 m3 (102,000 gal)/yr
225 operating days/yr
Capital Costs
Holding tank
Pump
Reaction tank
Aeration pump system
Sludge recirculation
system
Pretreatment system
Piping
Fencing
Total
Activated
Sludge
$ 1,750
600
4,500
1,500
2,500
8,300
1,750
700
$21,600
Trickling
Filter
$ 1,750
600
Trickling filter 4,000
Recirculation system 2,500
8,300
1,750
700
$19,600
Yearly Operating Costs
Monitoring
Electricity
Chemicals
Labor (1,000 hr @ $12/hr)
Fixed charges (25% of capital
cost)
Sludge disposal
Total
3
Operating cost per m -
per gal - '
$ 600
300
1,200
12,000
5,400
1,500
$21,000
$54.54
$ 0.20
$ 600
300
1,200
12,000
4,900
750
$19,750
$51.30
$ 0.19
* Equipment and operating cost are based on Means Building Construction
Cost Data 1978.
65
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industrial incineration involves waste pesticides and other
manufacturing wastes of high organic content. Incineration
of pesticide-containing wastewaters is confined to a few
chemical manufacturing complexes and contract waste disposal
services (55).
Figure 15 illustrates the basic design of a pesticide
incinerator. There are several incinerator types, differing
in configurations, efficiencies, and waste handling capa-
bilities. A few designs are capable of handling liquid wastes.
In all cases, the intent is that the waste have a high enough
organic content to make the combustion self-sustaining.
Otherwise, costly fuels must be used, which can make the
system uneconomic.
Whatever incinerator design is chosen, it must have the
following features:
t Adequate mixing of waste, oxidant, and auxiliary
fuel
• Adequate residence time in the flame (2 sec)
• Adequate temperature for complete destruction
of the pesticides and any toxic by-products
formed during combustion (1000°C) (70).
To meet air quality regulations, incinerator stacks
should be equipped with scrubbers or other air pollution con-
trol devices capable of removing at least 99 percent of the
hazardous emission components; continuous monitoring devices
should be placed on the stack to ensure that emission standards
are being met. Scrubber effluent should be retained or im-
pounded prior to release and tested to ascertain whether it
meets water discharge standards or if treatment is required.
Because of the high temperatures involved and the
corrosiveness of some of the waste gases (e.g., hydrochloric
acid from chlorinated hydrocarbons), interior incinerator
components must be replaced often if the incinerator is used
extensively. Depending on the design, frequent maintenance
may be required to keep waste feed lines and injection nozzles
clear. This may be especially troublesome with a variety of
waste types, compositions, and volumes.
Two to three operators are required. Special training
is needed to ensure efficient combustion at minimum expense.
Expertise is required to bring an incinerator to combustion
temperature without damaging the unit. Air pollution control
device and stack monitoring equipment operation also require
special training.
66
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CHARGING
DOOR
SECONDARY
COMBUSTION
CHAMBER
FLAME
PORT
PARTICIPATE
REMOVAL
STACKS
PRIMARY
COMBUSTION
CHAMBER
-DOWNPASS
SETTLING BASIN
Figure 15. Basic incinerator schematic
-------
Incineration is theoretically effective in destroying
any organic pesticide (71). However, there are over 500
different pesticides, and many have not been tested in
incinerators (18, 72). Some pesticides (e.g. nitrogen-
containing pesticides) can form toxic off-gases (e.g.
cyanide) if the 1000°C and 2 sec. conditions are not met (72).
These pesticides require special attention to ensure that the
incinerator is working properly.
Metal organic pesticides are not readily amenable to
incineration because of metal emissions; thus, incineration
of these pesticides is not recommended by the EPA. There is
a type of slagging incinerator which can recycle scrubbed or
filtered metals back into the slag (72). However, these
systems are not readily available.
Economics
Table 15 presents a cost estimate for an incineration
system. The incinerator itself is the largest single expense,
then the air pollution control equipment and chemicals. These
costs reflect typical industrial systems and may not be
indicative of a dilute pesticide incinerator. It is difficult
to estimate the cost differences, if any, because, although
dilute pesticide incinerators might be smaller and simpler,
they would represent special construction and a limited
application piece of equipment and could, accordingly, be
more expensive. Use of mobile incinerators may be possible in
a farm area. Capital cost for such a system would be at
least as much as for the stationary type costed here.
The largest operating expense element is auxiliary fuel.
As noted above, enough fuel must be used to drive off the
water and to combust the pesticides at sufficiently high
temperatures to effectively consume the material.
Advantages
Properly designed, operated, and maintained incinerators
can achieve complete destruction of organic pesticides.
Incineration is an existing, viable, wel1-developed technology
without the problems inherent in experimental or pilot scale
methods. Incinerators can handle a wide variety of pesticides.
formulations, and concentrations and are generally stable and
dependable (62). They can be installed almost anywhere,
require little land area, can be operated without interfering
with other operations, and are not readily upset by climatei
or.weather changes.
68
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TABLE 15. INCINERATION COST ESTIMATE*
Basis for Calculation
1.7 m^ (450 gal)/day
385 nT (102,000 gal)/yr
225 operating days/yr
Capital Costs
Holding tank $ 1,750
Pump 600
Incinerator (540 kg (1,200 lb)/hr) 58,200
Air pollution control equipment 29,000
Total $89,550
Yearly Operating Costs
Monitoring ~ $ 600
Fuel oil [2.7 mj (700 gal)/day (13, 78);
@ $0.25/gal] 40,000
Chemicals 10,000
Electricity 500
Labor (2,000 hr 9 $16/hr) 32,000
Fixed charges (25% of capital cost) 22,388
Ash and scrubber sludge disposal 1.000
Total $106,488
o
Operating costs per m - $277
per gal - $ 1.04
Equipment and operating costs based on Means Building Construction
Cost Data 1978 and Arthur D. Little, Economic analysis of pesticide
disposal methods (12) updated to 1978 with standard engineering
construction cost indices.
69
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Disadvantages
Incinerators, like any pie'ce of complex machinery, have
a greater tendency to malfunction than simpler systems. If
incinerators are not operated within strict observance of
acceptable operating procedures, combustion and stack gas con-
trol can become inefficient resulting in possible toxic
emissions into the air.
Most incinerators presently in use are large-volume
industrial and municipal units designed to handle low water
content solid wastes. No specially designed dilute pesticide
solution incinerators were identified during'this study. Use
of conventional incinerators would require dewatering of the
waste stream or concentration before incineration.
Even with a dewatered or concentrated waste stream, an
incinerator would require firing with auxiliary fuel to
evaporate the remaining water before the pesticide itself
could be consumed. Dilute pesticide wastes have a very low
organic content and cannot support combustion without large
quantities of auxiliary fuel. With high capital investments
for the incineration equipment and control and mo'nitoring
devices, incineration can become very expensive.
Transport and Incineration at a Central Facility
Given the current state of incinerator technology and
economics, individual applicator owned and operated in-
cinerators is not a viable alternative. Both capital and
operating costs are prohibitive. Special skills and training
are a necessity. Finally, neither the incinerators nor the
support services necessary to maintain them are readily
available to rural applicators.
However, incineration cannot be dismissed. It is a
proven technology with a high pesticide destruction potential.
One possible solution is to transport the wastewaters to a
centrally-located public incineration facility. This option
removes the burden of proper treatment and disposal from
the applicator.
A central incineration facility reduces many of the dis-
advantages of incineration. A central facility, by accepting
a large quantity and variety of wastes, could minimize
the requirements for auxiliary fuel. It could better support
the trained personnel needed than could an applicator-
operated facility. By maintaining a permanent, full-time
staff, overall supervision of the operation of the incinerator
is more certain than with an applicator who has more varied,
and to him more pressing, demands on his time.
70
-------
The concept of a central treatment facility is not
limited to incineration, although incineration of dilute
pesticide solutions is. Central facilities could employ
any appropriate treatment technology, including chemical
and biological treatment or secure landfilllng.
The advantages to the applicator include:
• Reduced need for additional treatment equipment,
personnel, or labor costs
• Lower costs, even if all the transport costs are
borne by the applicator
In terms of overall pesticide control, the fewer treatment
systems in operation, the fewer number that can break down
(although breakdowns, if any occur, would possibly be more
serious). Some applicators (e.g. Coastal Agricultural
Chemicals, Oxnard, California) currently use central hazardous
waste disposal facilities successfully.
On the negative side, there are very few such treatment
facilities nationwide, as shown in Figure 16 (73-75). Thus,
the option is not open to most applicators. Most hazardous
waste treatment facilities are located to serve industrial
clients and seldom near agricultural areas.
Even if the facilities were readily available, the
increased traffic in hazardous wastes raises the spectre
of hazardous spills (76-77). The relative degree of
hazard from spills versus applicator-operated treatment
systems has not been evaluated.
MISCELLANEOUS
As noted, most of the problems of dilute pesticide
solution disposal are due to large volume. Thus, any practice
that would serve to reduce the volume would also reduce the
severity of the disposal problem. For instance, if pesticide
containers were triple-rinsed and the rinsate mixed with the
pesticide solution to be sprayed, there would be no container
rinsate, no hazardous container disposal problem, and all of
the pesticide would be used (1). Triple rinsing is now
recommended by the EPA (70).
One proposal to eliminate the problem of excess dilute pes
ticide solutions and reduce the volume of rinsate is chemical
volume control using separate tanks for the pesticide and
the mix water (78-79). The concentrated chemical and water
are piped separately to the spray boom or to each nozzle.
Boom and nozzle rinsing at the washpad could be eliminated
71
-------
ro
.V..-
•V ».'J I'Jtr- .7.T"•
L-J \
o\ • "\ ;
/ v*«
/ IDAHO ^
! NOHTH DAKOTA
i
j
[SOUTH DAKOTA
1
I MINNESOTA
\
\
V
.—4
— j
'1 <
sr—
IjjjBarV t .. > /*"'/'^
"
^,9
V
\'
V.
•{
! !
_.j . ~\ ^ ^ENHtssec x- , *
«'«> T , OKLAHOMA ^ ^^5 ^ _ .^.^-TeMWllN^V
j • \ j*-"W^'^oBO^
i. ! / i \ \
\ AississiPP'^cg^c^-—'—
Figure 16. Geographic distribution of hazardous
waste management facilities (75).
-------
by flushing the system with water after spraying. Only one
small tank would need to be washed. The use of several tanks,
each for a specific pesticide, could reduce this need, since
any residual pesticide need not be washed out as it is now.
This procedure would still leave small volumes of rinsate
and periodic equipment washdown wastewaters. It has been
suggested that these dilute pesticide solutions could be
collected and reused later as diluent in pesticide solution
formulations (4). This may be impractical for several reasons.
Many pesticides are chemically incompatible, and, generally,
herbicides cannot be mixed with insecticides. Consequently,
separate holding tanks would be necessary for different
pesticide wastewaters. If an applicator uses many types of
pesticides, he could become the manager of a virtual tank farm,
and management problems could become unacceptable.
73
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CHAPTER 4
COMPARATIVE EVALUATION OF METHODS
The ultimate universal waste disposal methad capable of com-
plete destruction of all wastes under all conditions while
remaining safe and economical does not exist at the present time.
None of the disposal or treatment methods discussed in this report
is perfect, but one or more will probably be used to treat dilute
pesticide solutions.- All have advantages and disadvantages. The
purpose of this chapter is to comparatively evaluate the methods
against an ideal to:
• Clearly indicate which method(s) most closely approaches
the ideal
• Highlight the relative strengths and weaknesses of each
method.
In general, the ideal treatment or disposal method should:
• Not lead to impairment of air and water quality
• Not adversely affect wildlife or general environmental
quality
§ Not present hazards to operators or any nearby populace
• Be capable of reducing the toxicity of the pesticides to
safe levels through degradation, or at least be capable
of immobilization and containment
• Be applicable to all pesticides, formulations, and
concentrations
• Not be susceptible to breakdowns, upsets, or frequent
shutdowns
• Be readily available to all pesticide applicators
• Be relatively inexpensive and simple to operate.
The methods discussed in this report can be evaluated by
determining the degree to which each meets these ideals. To
74
-------
simplify the evaluation,
general criteria:
these factors can be reduced to five
Environmental Safety
Effecti veness
Pesticide Applicability
Availability
Applicator Factors.
Each of these criteria will be discussed in detail.
In the course of the evaluation, each method will be given
a numerical "score" for each criterion reflective of its relation
to the ideal. The total scores should indicate which methods have
the most promise and the individual criterion scores should indi-
cate what areas of research are most appropriate for each method.
The six criteria are not weighted equally. They are biased
in favor of environmental safety, pesticide applicability, and
effectiveness. The "perfect" score for each criterion is:
Environmental Safety - 55
Effectiveness - 35
Pesticide Applicability - 35
Availability - 30
Applicator Factors - 20
In the following discussions it should be noted that several
factors may go into determining the scoring for each criterion.
The numerical scores given each factor within each criterion bear
no relation to any factor within any other criterion. The
individual factor scores relate only to the other factors within
a criterion. Factors from different criteria should not be com-
pared, only the total value for the criteria. This should become
clearer in the following discussions.
The following assumptions, limitations, and choices regarding
the methods were used for the evaluation:
• All washdown pads are equipped with drains and holding
tanks; volume to be treated can thus be regulated to
provide a constant flow rate.
• Appropriate safety precautions (fencing, warning signs,
locked storage, safety devices) are used at each disposal
site. This does not mean that accidents will not happen,
but for this discussion the role of random accidents was
not considered.
• Proper site selection and
followed at each site.
operational procedures are
75
-------
• Standard pollution control measures (e:g., scrubbers on
incinerator stacks) are in use at all sites.
t With the exceptions noted below, all methods are located
near, and operate-d by, individual agriculture custom
applicator companies in rural areas.
• Land cultivation sites are unlined and the pesticides
are applied by means of a single tractor injection system.
• Soil mounds and pits and evaporation basins are lined with
a dual liner (concrete over plastic) and are roofed.
• In general, each method is operated as previously described
in the text.
0 Incineration is not considered feasible for individual
applicators; thus, incineration in the following evalua-
tions is based on transport of the dilute pesticide
solutions by the applicator to a central incineration
facility.
ENVIRONMENTAL SAFETY
There are four factors in determining environmental safety:
protection of water quality, protection of air quality, public
safety, and prevention of contact with domestic animals or wild-
life. Air and water quality factors are scored as follows:
20 - minimal possibility of quality impairment due to
migration of pesticide away from the treatment system
15 - some quality impairments possible under certain
conditions
10 - existing data regarding the degree of hazard incurred
when using this method with dilute pesticide solutions
contradictory or insufficient; there may or may not be
a hazard
significant movement of pesticides or degradation
product from the treatment system to the environmi
is likely with possible quality degradation.
Public safety refers to the hazards not related to air or
water quality presented by the method. In general, it refers to
such hazards as fire or explosion or hazards from accidental
contact by people. Public safety is scored as follows:
10 - closed system with no fire or explosion hazards
7 - open system with contact with pesticide dose possible
4 - treatment process may present a fire or explosion hazai
76
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Prevention of pesticide contamination of animals is scored
as follows:
5 - contact unlikely
3 - contact with burrowing animals or birds possible.
Table 16 shows the scores of the treatment methods for these
factors and the total scores for environmental safety.
There is considerable controversy over the degree to which
pesticides or pesticide degradation products will migrate in soil
during land cultivation. A number of references can be drawn
up to support both sides of the issue (22-50): (1) most pesticides
will not migrate through the soil but will degrade on-site or
(2) migration to ground or surface waters is possible (6, 19-43,
45, 80). A similar controversy exists in regard to the degree
of pesticide loss from soil through volatilization. It seems
likely that both migration and volatilization are related to
concentration of the pesticide in the soil, the type of pesticide,
the type of soil, the soil moisture content, and so forth. The
exact relationships and limitations have not been clearly defined.
Land cultivation, even at enclosed sites, is open to birds
and many burrowing animals. Should the fences be damaged, land
cultivation could present a hazard to wildlife and domestic
animals.
Soil mounds and pits do not fare equally well in terms of
overall environmental safety. Given a dual layer liner (e.g.,
plastic and concrete), both are unlikely to contaminate ground-
water supplies. In terms of air emissions, the impact of soil
mounds is unknown. The results available to date regarding air
emissions from soil mounds are not sufficient for an evaluation.
On the other hand, soil pits, with their open tops and method
of dilute pesticide solution addition present a clear air quality
hazard. The degree of the hazard is not known, but the potential
for harm is there. Soil mounds, being a closed system, are secure
from inadvertent contact with the pesticides. Soil pits, being
open, could present a minimal hazard, but surface concentrations
should be slight. The same reasoning generally holds true for
animal contact. In both cases the scores will'droo if less
secure liners, (e.g., clay o,r single layer polymer) are selected.
Evaporation basins generally do not present a water quality
hazard because the pesticide solutions are contained. However,
they present a definite air quality hazard, as evidenced from the
many residents who complain of odors from the evaporation basins.
Since they are open systems, contact with the pesticides is
possible.
Chemical treatment can be a closed system during operation,
making it essentially safe from animal contact or air emissions.
77
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TABLE 16. ENVIRONMENTAL SAFETY
CO
Air *
Method Quality
Land cultivation 10
Soil mounds 10
Soil pits 5
Evaporation basins 5
Chemical treatment 15
Biological treatment 15
Adsorption 20
Transport and
incineration 15
Score values:
20 - minimal possibility of impairment from
pesticide migration away from the system
15 - some quality impairments possible under
certain conditions
10 - existing data insufficient to evaluate
degree of hazard
5 - significant movement or quality
impairment possible.
Water *
Quality
10
20
20
20
15
15
20
15
Public.
Safety*
7
10
7
7
10
7
10
4
7
4
Animal .
Life T
3
5
3
3
5
3
5
5
Total
30
45
35
35
45
40
55
39
- closed system with no fire or
explosion hazard
- open system with contact with
pesticide dose possible
- treatment process may present a
fire or explosion hazard
_ r-nn + a/* + iml i L*a1 \/
— — - - — __-- - - . _ _ ^
3 - contact with burrowing animals
or birds possible.
-------
Since 100 percent degradation is unlikely, some contamination of
receiving waters due to residual pesticides or reaction products
is possible. Most treatment chemicals present a hazard to
untrained personnel, and the use of strong oxidizing agents can
present an explosion hazard.
Most biological wastewater treatment units are open to the
atmosphere and emissions are possible. Water quality impairment
from degradation products or refractory pesticides in the effluent
is also possible. Being open units, contact with animal life or
unauthorized persons is possible. The hazard is not generally
as great with biological treatment as with evaporation basins
because the concentration factor is not at work.
Adsorption is a completely closed process and, if operated
properly, can achieve a high degree of treatment. It appears
to have the fewest possibilities for environmental damage of
any of the methods discussed.
Transport to a central incinerator facility suffers in terms
of air and water quality, not because of the incineration, which
is highly safe on both counts, but because of the spill possibili-
ties discussed earlier. If this method becomes popular, the
hazard could even increase because of the increased number of
"pesticide miles." Spills can cause public safety problems,
but the rating for public safety is based primarily on the
explosion and fire hazards inherent in the incineration process.
EFFECTIVENESS
There are two factors involved in effectiveness: (1) extent
of degradation and (2) in the case of incomplete degradation,
containment of pesticides or pesticide degradation products.
Effectiveness takes into account the fact that "contained"
pesticides will require further treatment or disposal through
lower scores for containment than degradation. Containment in
this case means essentially no uncontrolled movement of pesticides
or products away from the treatment system. In scoring the
methods, complete degradation is also scored as complete con-
tainment. The factors are scored as follows:
Degradation 20 - 98+ percent degradation of the pesticides
and degradation products is possible
15 - a high degree (75 to 98 percent) of degra-
dation is likely
10 - 50 to 75 percent degradation is possible
5 - degradation effectiveness is unknown
0 - no degradation likely-
79
-------
Containment 15 - pesticides and degradation products totally
contained
10 - some minimal migration possible
5 - degree of containment unknown
0 - no containment likely.
Table 17 shows the scores of the treatment methods for these
factors and the total effectiveness scores.
- As noted earlier, the data on the effectiveness of land
cultivation are not sufficient to predict the outcome for many
disposal situations; neither degradation or containment has been
adequately determined. The lack of knowledge regarding the
degree of degradation also extends to soil mounds, soil pits,
and evaporation basins. Soil mounds, a closed system, represent
an attempt at total containment. Both soil pits and evaporation
basins, being open, have a possible atmospheric movement route.
Chemical treatment can achieve a very high degree of treatment,
but there can be pesticide residuals in the effluent. Biological
treatment can achieve a high degree of degradation but, again,
the possibility of residuals in the effluent is present. Adsor-
ption does not degrade pesticides (aside from whatever atmospheric
oxidation or natural hydrolysis may occur) but it does contain
them, effectively reducing the overall volume of wastes to be
dealt with later. Incineration is highly effective in destroying
organic pesticides. (Note: The effectiveness ratings for
incineration do not take into account reduced containment during
spills; this was dealt with under Environmental Safety and a
lesser rating for incineration here could be misleading as to its
true effectiveness). All of the effectiveness scores assume that
the individual treatment methods are not used to treat pesticides
which have been demonstrated untreatable by those methods.
VERSATILITY OF METHOD
The versatility of the treatment methods involve the types,
forms, and concentrations of pesticies considered treatable by
the method. Consequently, the factors used to score applicability
are pesticide chemical class, concentrations, and formulations.
Pesticide chemical class refers to the ability of the
treatment method to accept any type of pesticide into the system.
It says nothing about the degree of treatment nor does it assume
that all acceptable types can be treated to an equal extent. It
merely refers to whether some degree of treatment can be expected.
It is scored as follows
15 -
can accept virtally any pesticide with no change in
operating conditions
80
-------
TABLE 17. EFFECTIVENESS
00
Method
Land cultivation
Soil mounds
Soil pits
Evaporation basins
Chemical treatment
Biological treatment
Adsorption
Transport and
incineration
*
Degradation
10
5
5
5
20
15
0
20
Containment
5
15
10
10
10
10
15
15
Total
15
20
15
15
30
25
15
35
Score values:
20 - 98+ percent degradation of the pesticides and r!5 - pesticides and degradation products totally
degradation products is possible. contained.
15 - a high degree (75 to 98 percent) of degra- 10 - some minimal migration possible.
dation is likely. 5 - degree of containment unknown.
10 - 50 to 75 percent degradation is possible. 0 - no containment likely.
5 - degradation effectiveness is unknown.
0 - no degradation likely.
-------
10 - can accept virtually any pesticide but changes in
operating conditions necessary
5 -
several commonly used pesticides cannot be treated
by this method..
Given the assumptions made at the beginning of this section,
all methods are preceded by a holding tank which keeps the volume
feed rate constant. Because of differences in application rates
or washing procedures, pesticide concentrations may vary, however.
The effect this variable will have on operations is scored as
follows:
*
10 - changes in concentration will neither require changes
in operations nor affect the treatment efficiency
appreciably.
5 - changes in concentration can necessitate operational
changes or disrupt the treatment system.
All of the pesticides in dilute pesticide solutions are
water-borne, but not all enter the water in the same form. Thus,
the dilute pesticide solutions can indeed be solutions or they
can be suspensions or emulsions. The wastewaters can contain
oils, sulfur, or inert carriers such as clay. Whether or not
this can affect the treatment method is scored as follows:
10 - the system will continue to function regardless
of the formulation
5 - certain formulations can necessitate pretreatment
systems.
Table 18 shows the scores of the treatment methods for these
factors and the total applicability scores.
Land cultivation, soil mounds and pits, and evaporation
basins are natural systems with few adjustable variables once
system operation has commenced. In general, changes in the
quality of the dilute pesticide solutions are unlikely to
adversely affect the effectiveness of the system for any extended
period of time. However, there are a few limitations. Mixing
some incompatible pesticides can increase hazards due to toxic
gas formation. In such cases it may be necessary to alter
operating conditions.
Land cultivation spreading rates could be affected by changes
in pesticide concentrations in the wastewater. Many industrial
users of evaporation basins prefer to remove inert material to
prevent excessive sludge build-up in the basins. Certain pesti-
cides (e.g., metallo-organics or inorganics) and/or increasingly
high concentrations of pesticides in the soil or water can affect
82
-------
TABLE 18. VERSATILITY OF METHOD
00
CO
Method
Land cultivation
Soil mounds
Soil pits
Evaporation basins
Chemical treatment
Biological treatment
Adsorption
Transport and
incineration
Chemical
Classes*
10
10
10
10
10
5
5
5
Pesticide
Concentrations
5
10
10
10
5
5
5
10
Pesticide ,
Formulations'
10
10
10
5
5
5
5
5
Total
25
30
30
25
20
15
15
20
Score values:
15 - can accept virtually any pesticide with no
change in operating conditions
10 - can accept virtually any pesticide but
changes in operating conditions necessary
5 - several commonly used pesticides cannot be
treated by this method.
*10 - changes in concentration will neither require
changes in operation nor affect treatment
efficiency appreciable
5 - changes in concentration can necessitate
operational changes or disrupt the system.
10 - system will continue to function
regardless of the formulation
5 - certain formulations may necessitate
pretreatment systems.
-------
degradation rates significantly. However, since land cultivation,
soil mounds and pits, and evaporation basins also serve as con-
tainment systems, the loss in degradation efficiency does not
affect the overall operation of the systems.
The type of chemical treatment is highly dependent on the
pesticide compound to be treated. Thus, a change in compound
could conceivably require a complete shut-down, clean-up, and
change-over to another form of chemical treatment. Changes in
concentration will affect changes in chemical feed rates. Some
formulations, such as emulsions, can require pretreatment if
effective degradation is to be achieved.
Many common pesticides are highly toxic to the organisms in
biological treatment systems. Even those pesticides which are
only marginally toxic or to which the organisms have become
acclimated can cause severe upsets if the pesticide concentrations
increase suddenly. If biological treatment is to be effective,
inert carriers, oils, alkalies or acids (e.g., lime, sulfur),
and so forth will have to be removed before treatment.
Some pesticides, especially the oil-types, can foul adsorption
beds. Furthermore, oil emulsions or insoluble particulate
carriers or pesticides can clog beds, rendering them inoperative.
Consequently, pretreatment is often necessary. Concentration
changes affect the life of the bed and can necessitate changes
in flow rates.
Neither pesticide formulation nor concentration can normally
be expected to affect incineration (assuming that a supplemental
fuel source is being used). There are certain pesticides (e.g.,
metallo-organics or inorganics) for which incineration is not
recommended or is prohibited entirely. Certain metallo-organics
can be incinerated after pretreatment to remove the metal
component (40-CFR-l65).
AVAILABILITY
Availability refers both to the ability of the method to be
implemented and the reliability of the methods themselves. A
method which is in the experimental stage is not as valuable as
one that represents a proven technology. Similarly a method
which cannot be relied on is less useful than one which can.
The factors used to assess availability are status, scope, and
reliability.
Status refers to whether a method is operational or experi-
mental or if it can be readily installed and operated by indi-
vidual applicators. It is scored as follows:
10 - operational technology readily adaptable to operation
by applicators
84
-------
7 operational technology not readily available to
applicators but could be used in a central treatment
faci1ity
4 - experimental technology which could be imp!ementable
by applicators
1 - theoretical technology.
In evaluating availability, scope adds 5 points if a method
could be adopted for use in urban environments by pest control
operators.
Reliability assesses the amount of downtime which can be
expected with a method. It is scored as follows:
15 - breakdowns, shutdowns, downtime unlikely
10 - periodic, routine maintenance shutdowns required
5 - occasional long downtimes expected which could
seriously affect treatment of the dilute pesticide
solution
0 - may be liable to frequent or unexpected breakdowns.
Table 19 shows the scores for these factors of the treatment
methods and the total scores for availability.
Only soil pits and incineration are not readily available
to applicators. The soil pit system as developed by Iowa State
University is still an experimental design. Individual incin-
erators are simply too complex technologically and costly for
individual applicators. Transport and incineration is limited
by the small number of hazardous waste treatment facilities.
All of the other methods are being used in agricultural areas
either for pesticides or other wastes and could readily be adapted
to dilute pesticide solutions and applicator operation. Space
requirements and/or air pollution hazards prevent land culti-
vation, soil pits, evaporation basins, and biological treatment
from being adapted for use by individual pest control operations
in urban areas.
Only land cultivation has no inherent breakdown or shutdown
problems. Tractor maintenance could be a problem but this could
be solved by scheduling for weekends or lulls in spraying.
Severely adverse weather conditions (e.g., heavy rains or
freezing temperatures) could disrupt the operation of land
cultivation systems, but since spraying is unlikely under these
conditions, the overall reliability of the system may not be
impaired. Soil mounds and pits require occasional complete
shutdown so that the soil and residues in the systems can be
85
-------
TABLE 19. AVAILABILITY
00
Method
Land cultivation
Soil mounds
Soil pits
Evaporation basins
Chemical treatment
Biological treatment
Adsorption
Transport and
incineration
Score values:
10 - operational and
applicators
Status
7
7
4
7
10
10
10
7
readily available to
Scope
0
5
0
0
5
0
5
5
Reliability^
15
10
10
10
10
5
10
10
15 - breakdowns, shutdowns
10 - periodic routine mainl
Total
22
22
14
17
25
15
25
22
unlikely
tenance shutdowns
7 - operational but not necessarily available
to all applicators
4 - experimental but could be implemented
by applicators
1 - theoretical
5 - may be adaptable for use in urban
environments by pest control operators.
required
5 - occasional long downtimes which could
seriously affect treatment.
-------
completely removed and replaced. Biological treatment is
sensitive even under the best of conditions. Changes in pesticide
type or concentration, pH, weather, or many other factors can
upset even a properly operated system. The other systems need
routine maintenance, but in general not much downtime. Evapo-
ration basins require periodic sludge removal; chemical treatment
tanks and equipment will need cleaning; adsorbents must be
replaced; and incinerators will require periodic check-ups and
part replacements.
APPLICATOR FACTORS
Although not a factor in the usefulness of a treatment
method, taking the industry as a whole, applicator acceptance
will have a bearing on the actual effectiveness of a method. If
an applicator objects to a given method, he may find ways to
circumvent any regulations requiring its use. Consequently, a
method should be as unobjec'tionabl e to the applicator as possible
to ensure his cooperation.
It is possible to evaluate some tangibles which will have
an impact on the applicator, namely labor and economics. Labor
can be broken down into two component factors: man-hours and
skill. Man-hours refers to the actual time of operation of the
treatment method. This time will either reduce the man-hours
of crop treatment time available or will add man-hours to the
total labor requirements of the custom applicator. Skill considers
the degree of training necessary to effectively operate a treatment
method. In some cases extensive training will be needed, neces-
sitating lost time from the actual spraying operations. These
factors are scored as follows:
Man-hours: 5 - <8 man-hours weekly
3 - 8 to 24 man-hours weekly
1 - additional full or part-time people needed
to operate system
Skill: 5 - can generally be operated within the existing
skills of the applicator
3 - some training required, on-the-job training
usually sufficient
1 - extensive training required.
In the case of transport and incineration, the labor requirements
are based on filling the tank truck and driving to the disposal
facility.
87
-------
Economics is note scored like the other factors. Rather the
least costly method is given ten points and the other methods
are ranked accordingly, with scores decreasing as expenses
increase. Capital costs are converted to a cost per m figure
over a ten-yr period and added to operating costs to get a total
cost. Transport and incineration costs are incalculable because
they will depend on travel distance and incinerator fees which
could vary widely. Consequently, transport and incineration is
ranked midway to avoid biasing the totals too greatly in any
direction.
Table 20 shows the scores of the treatment methods for these
factors and the total applicator factor scores.
Evaporation basins are generally the simplest and least
costly system to build and operate. Soil pits and mounds are
equally simple to operate, but somewhat more costly. Land
cultivation requires greater skills, but these should be readily
available in an agricultural community. Chemical treatment and
adsorption require more time to operate, largely because of
pretreatment requirements and more comprehensive training.
Biological treatment is costly, can often need almost constant
attention, and requires extensive training to be operated at
optimum efficiency.
SUMMARY
Table 21 presents the totals for each criteria and the total
score for each method. A score of 175 would be perfect; no method
comes close to that score. Three methods scored higher than 130,
however: soil mounds, transport and incineration, and chemical
treatment. Based on the scores, these would appear to be the
most promising. However, all have problems. Soil mounds are
still uncertain environmentally. With further research they
could be eliminated as a potential method or moved still higher
in the ratings. Transport to a central incineration facility
is currently limited by the lack of commercial incinerator
facilities capable of accepting dilute pesticide solutions. At
present, chemical treatment suffers chiefly through its limited
pesticide applicability and expense. Further research could
correct these problems. As far as individual applicators are
concerned, only biological treatment appears to be out of the
running. „ Its high effectiveness scores suggest that it could
conceivably be used in a central treatment facility.
Adsorption certainly pssesses promise. Its most apparent
weaknesses are a low rating for effectiveness because of its
nature as a contain-and-concentrate rather than degrade method,
and its low rating for applicability. However, it is very
effective as a contain-and-concentrate method. Soil pits and
evaporation basins are in a nebulous place in the scorings -
neither good nor excessively bad. Both suffer in terms of air
88
-------
TABLE 20. APPLICATOR FACTORS
oo
10
Method Man-hours
Land cultivation 5
Soil mounds 5
Soil pits 5
Evaporation basins 5
Chemical treatment 3
Biological treatment 1
Adsorption 3
Transport and
incineration 3
Score values:
*
5 - <8 man-hours weekly
3 - 8-24 man-hours weekly
1 - additional full or part-time
people needed to operate
system
'5 - can be operated within
existing skills of the
applicator
3 - some training required;
on-the-job usually sufficient
1 - extensive training required.
Skill*
5
5
5
5
3
1
3
5
Economies'
7
8
9
10
5
2
3
6
•flO - least expensive; all
ranked in order with
decreasing as costs
Total
17
18
19
20
11
4
9
14
others
score
increase.
-------
TABLE 21. SUMMARY TABLE
SCORES OF DILUTE PESTICIDE SOLUTION DISPOSAL METHODS
Criteria
Environmental
Method Safety*
Land cultivation
Soil mounds
Soil pits
Evaporation basins
Chemical treatment
Biological treatment
Adsorption
Transport and
incineration
30
45
35
35
45
40
55
39
Effectiveness
15
20
15
15
30
25
15
35
Pesticide
Applicability
25
30
30
25
20
15
15
20
Availability
22
22
14
17
25
15
25
22
Applicator
Factors
17
18
19
20
11
4
9
14
Total
108
135
113
112
131
99
119
130
See chapter for explanation of criteria and scores.
-------
quality degradation. The experimental status of soil pits also
is a detriment. If they were to be made readily available,
their score could climb into the 120's.
The potential of land cultivation as a dilute pesticide
solution treatment method is still uncertain. Depending on the
ultimate outcome of research into the movement and degradation
of dilute pesticides in the soil, the total score for land
cultivation could range from 85 to 155. Consequently, land
cultivation cannot be dismissed out-of-hand because it may be
both effective and environmentally acceptable under certain
conditions. Its potential high score is such that further
research is almost mandatory.
91
-------
CHAPTER 5
CONCLUSIONS
The following conclusions are based on the information
gathered in this study:
t The disposal of dilute pesticide solutions is an
increasingly serious problem because of the volume of
wastewater, the pesticide content, the lack of compre-
hensive guidelines regarding DPS treatment and disposal,
and the possibility that the proper disposal of DPS may
soon be required and regulated.
• Most dilute pesticide solutions are generated by agri-
cultural pesticide applicators who should thus be the
major objective of any control program; a secondary
objective would be urban pest control operators.
• The treatment methods commonly considered most applicable
for dilute pesticide solutions are land cultivation,
soil mounds, soil pits, evaporation basins, chemical
treatment, biological treatment, adsorption, and
incineration.
• Land cultivation appears to be effective for readily
degradable or adsorbable pesticides at low loading rates,
but there are still too many environmental uncertainties
regarding rates of degradation, migration, and volatili-
zation; susceptible pesticides and concentrations; and
optimum site characteristics to recommend it unquali-
fiedly. Further research is needed to fully identify
its potentialities and limitations.
t Soil mounds and pits can be very effective at containing
pesticides and degradation products and are relatively
economic; thus, soil mounds and pits have a very high
potential. On the negative side, soil mounds have not
been extensively tested outside of California and soil
pits are still in the experimental stage. Both require ,
further research into volatilization rates and expected <
lifetimes. '
92
-------
Evaporation basins are a popular industrial pesticide
solution treatment method and are used by many Texas
aerial pesticide applicators; crude basins are used
informally in many other areas. They are subject to
pesticide volatilization of unknown severity. Otherwise
they are effective containment methods.
Chemical treatment can yield complete detoxification
for many of the more commonly used pesticides but is
either ineffective or yields toxic by-products for
many others. At the present time it is unlikely that
chemical treatment could be instituted on a very wide
scale or for very many pesticides. With additional
research into treatment chemicals and conditions, it
could become a very effective, although possibly some-
what limited, treatment method.
Biological treatment is totally inappropriate for an
individual applicator-operated treatment facility because
of the nature of the waste, the operational difficulties
encountered when working with microorganisms, and the
expense.
Adsorption is an effective method for removing most
organic pesticides from water. High removal efficiencies
can yield a relatively pesticide-free effluent which can
be disposed of by conventional means. Adsorption is
somewhat limited because of a requirement for pretreatment
to remove suspended and inorganic materials and soils.
In general, though, adsorption is sufficiently under-
stood to recommend demonstration of applicator-operated
adsorption units.
Individual applicator-operated incinerators are considered
infeasible; the systems are too expensive and require
special operator skills to ensure complete combustion
and no air pollution. On the other hand, centrally
located hazardous waste treatment facilities containing
incinerators could be a very effective, economic disposal
option. At the present time, however, there are only
a few such treatment facilities. Thus, the option is
available to only a few pesticide applicators.
Given the current state of the disposal method technology
and the nature of the dilute pesticide solutions and their
generation, only soil mounds could be widely implemented
without further extensive research and with a minimum
of environmental degradation expected. Evaporation
basins and soil pits could be readily implemented in
areas where the potential ai.r quality degradation would
be minimal. Small-scale carbon adsorption units for
93
-------
dilute pesticide solutions are considered technically
feasible and should be demonstrated. Chemical treatment
and land cultivation possess high potential as effective
treatment methods but both have severe limitations.
Further research is recommended to more fully identify
these limitations and to establish the conditions under
which each could be used most effectively and safely.
94
-------
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yal 792
SW-174C
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