Pollution Abatement in the Fruit and
Vegetable Industry
WASTEWATER TREATMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF TECHNOLOGY TRANSFER
WASHINGTON, D. C.
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Pollution Abatement in the Fruit and Vegetable Industry
Volume 3
WASTEWATER TREATMENT
IN THE
FOOD PROCESS ING INDUSTRY
U. S. ENVIRONMENTAL PROTECTION AGENCY
Office of Technology Transfer
Washington, D. C.
1975
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While the recommendations in this publication are based on scientific studies
and wide industry experience, references to operating procedures and methods,
or types of instruments and equipment, are not to be construed as a guarantee
that they are sufficient to prevent damage, spoilage, loss, accidents or injuries,
resulting from use of this information. Furthermore, the study and use of this
publication by any person or company is not to be considered as assurance that
that person or company is proficient in the operations and procedures discussed
in this publication. The use of the statements, recommendations, or suggestions
contained, herein, is not to be considered as creating any responsibility for
damage, spoilage, loss, accident or injury, resulting from such use.
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TABLE OF CONTENTS
Page
CHAPTER
I. BACKGROUND
IMPORTANT WASTE CHARACTERISTICS 1
Sampling, Testing, and Flow
Measurement 5
TYPICAL WASTEWATER CHARACTERISTICS 7
Changes in Waste Strength 11
EFFLUENT REQUIREMENTS 13
Federal Requirements 13
State Requirements 24
Local Requirements 24
COST INFORMATION AND OTHER DATA 25
II. PRETREATMENT
BACKGROUND 26
Ordinance Requirements 27
Economic Considerations 27
Production Increases 27
By-Product Recovery 28
TECHNOLOGY 29
Screening 29
Neutralization 34
Flow Control 36
Soil Removal 36
FURTHER TREATMENT 37
COMMUNICATIONS 39
III. FULL TREATMENT
DEFINITIONS 40
REQUIREMENTS 43
EPA Standards 43
Other Considerations 44
PRIMARY TREATMENT 45
Gravity Sedimentation 46
Air Flotation 49
Complete Systems 51
BIOLOGICAL SECONDARY TREATMENT 53
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AERATION METHODS 54
PONDING SYSTEMS 55
Stabilization Ponds 57
Aerated Ponds 57
HIGH RATE PROCESSES 58
Activated Sludge 58
Activated Biological Filter (ABF) 72
OTHER HIGH RATE PROCESSES 75
Rotating Biological Contactors (RBC's) 75
Biological or Trickling Filters 76
NUTRIENT REQUIREMENTS 78
TERTIARY (ADVANCED) WASTE TREATMENT 78
Chemical Precipitation and Sedimentation 80
Filtration 82
Carbon Adsorption 86
Ion Exchange 87
Reverse Osmosis 89
CH LORI NATION 90
OPERATION AND MAINTENANCE 91
IV. LAND TREATMENT AND DISPOSAL
PROCESSES 94
APPLICATION METHODS 96
SITE CRITERIA 97
PRETREATMENT REQUIREMENTS 97
LOADING CONSTRAINTS 98
Hydraulic Constraints 98
Treatment Constraints 100
SYSTEM OPERATION AND MANAGEMENT 103
COSTS OF ALTERNATIVE APPLICATION METHODS 105
V. SOLIDS DISPOSAL
SOURCES AND NATURE OF SOLIDS 107
In Plant Solids (Residuals) 107
Treatment Plant Solids 110
Screenings 110
Primary Treatment 110
Secondary Treatment 112
Tertiary Treatment 114
Solids Handling 114
DIGESTION 116
THICKENING 117
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DEWATERINC 117
Vacuum Filters 120
Centrifuges 122
Other Methods 122
Sludge Drying Beds and Lagoons 126
METHODS OF DISPOSAL 126
LAND DISPOSAL OF WASTE SOLIDS 128
Pretreatment Requirements 129
Application and Incorporation Methods 129
Site Selection Criteria 130
Application Rate Constraints 130
Management and Operation 131
Cost of Waste Solids Delivery and Application 131
LIST OF REFERENCES 133
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LIST OF FIGURES
Page
Figure 11-1 Tangential Screen 31
Figure 11-2 Silt Clarifier 38
Figure 111-1 Effect of Treatment on Solids and BOD 42
Figure III-2 Clarifier 48
Figure III-3 Dissolved Air Flotation Clarifier 50
Figure III-4 Primary Treatment Plant Diagram 52
Figure III-5 Floating Mechanical Aerator 56
Figure III-6 Activated Sludge Plant Diagram 63
Figure III-7 Activated Sludge Plant 67
Figure III-8 Activated Sludge Plant 68
Figure III-9 Package Activated Sludge Plant 69
Figure 111-10 Activated Biological Filter Tower 73
Figure 111-11 ABF/Activated Sludge Plant Diagram 74
Figure 111-12 Trickling Filter Plant Diagram 77
Figure 111-13 Pressure Filter 83
Figure V-1 Vacuum Filter
Figure V-2 Solid Bowl Centrifuge 123
Figure V-3 Disk Nozzle Centrifuge 124
Figure V-4 Basket Centrifuge 125
Figure V-5 Gravity Sludge Dewatering Unit 127
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LIST OF TABLES
Page
Table 1-1
Table I-2
Table I-3
Table I-4
Table 11-1
Table II-2
Table III-1
Table 111-2
Table 111-3
Table 111-4
Table 111-5
Table III-6A
Table Ill-SB
Table 111-7
Table 111-8
Table 111-9
Table 111-10
Table IV-1
Table IV-2
Table IV-3
Table IV-4
Table IV-5
Table V-1
Table V-2
Table V-3
Table V-4
Table V-5
Importance of Wastewater Characteristics
Typical Raw Wastewater Characteristics
Factors Contributing to Raw Waste Load
Variables
EPA Effluent Limitation Guidelines
Cost Summary:
Cost Summary:
Flow Measurement and Screening
Neutralization
Full Treatment Unit Processes
Primary Treatment Design Criteria
Cost Summary: Aerated Lagoon System
Secondary Treatment Process Comparison
Secondary Treatment Design Criteria
Cost Summary: Activated Sludge System
Cost Summary: Activated Sludge System with Aerobic
Digestion and Dewatering
Available Nutrients
Tertiary Waste Treatment Applications
Cost Summary: Filtration
Cost Summary: Chlorination System
Land Treatment and Disposal Processes
Maximum Hydraulic Loadings
BOD Loading Rates
Maximum Limits of Inorganics
Cost Summary: Land Disposal
Solid Waste Produced in Food Processing
Treatment Plant Solids Characteristics
Solids Handling Options
Solids Handling Design Criteria
Cost Ranges of Solids Hauling and Disposal
4
8
12
14
33
35
41
47
59
60
64
70
71
78
81
85
92
95
99
100
104
106
108
111
115
118
132
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Chapter I
BACKGROUND
By their nature, canneries cause special problems that are not evident
in other industries. The largest problem is the seasonal variation
of cannery wastes. Each raw product has a harvest season that varies
slightly from year to year. The quality of raw products also varies,
not only from year to year, but from field to field, and from beginning
to end of harvest. Those canneries which have their own full treatment
system are acutely aware of these variations.
No two processing plants are identical. Even plants operated by the
same corporation and producing the same product can have very different
wastewater characteristics. Therefore, wastewater quality data must
be developed for each plant. This creates a problem for new plants,
or for expansions of existing plants. For these instances, waste quan-
tities are estimated by assuming them to be proportional (on the basis
of production capacity) to the waste from other similar plants. In
determining future waste loads, expansion or product changes must
be considered.
IMPORTANT WASTE CHARACTERISTICS
Scientists and engineers have developed many tests to quantify the
pollution producing capacity of wastes. The significant tests are defined
in Technical Session A. Many measurements can be taken, but they
will only be useful in certain cases. Common measurements that are
taken are briefly described below:
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Biochemical oxygen demand (BOD)
BOD must be known to size aerators in activated sludge
treatment plants, or to determine sewer service charges
when an industry is discharging to a public treatment system.
A seed acclimated to the waste must be used in the BOD
tests. Otherwise, the test may yield a false low value.
Chemical oxygen demand (COD)
COD can be used as a fast way to estimate the BOD for most
food processing waste by empirically determining a ratio
of BOD to COD. A few cities use COD to assess sewer service
charges.
Total suspended solids (TSS)
TSS is also one factor often used to determine sewer service
charges. TSS is also needed to determine the probable
volume of waste solids from a treatment system.
Volatile suspended solids (VSS)
Volatile (as compared with total) suspended solids are needed
to determine the volume of waste solids which may be biodegraded.
Nutrients
A balance of nitrogen and phosphorus is needed for successful
biological treatment. In unusual cases, other trace elements
may also be critical nutrients. Many food processing wastewa-
ters are deficient in nutrients, so adding nutrients is often
necessary. In a joint treatment system in a city, where
cannery waste is mixed with domestic waste, the balance
may be met by nutrients naturally present in domestic
sewage, but it should still be checked.
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o pH
Local sewer ordinances almost always limit the allowable
range of pH. Extreme values or wide fluctuations of pH
may require pretreatment before full treatment.
o Alkalinity and acidity
Alkalinity and acidity must be measured to determine the
resistance of the wastewater to pH changes, to design
neutralization systems, or to determine the stability of
biological treatment.
o Temperature
Wastewater temperatures are extremely important in determining
the feasibility of biological treatment. Process stability,
even in physical-chemical systems, can be adversely affected
by wide ranges in temperature.
o Toxicity
Most waste discharge requirements have limits on toxicity.
In extreme cases, high toxicity may make biological treatment
impractical, depending on bacterial growth. The most
common causes of wastewater toxicity are excessive amounts
of free ammonia, residual chlorine from disinfection, discharges
of detergents (from cleanup) or other toxic materials like
paint and solvents.
Whether a cannery intends to discharge to a municipal treatment
system, build its own treatment system, or dispose of the waste on
land, different waste characteristics must be tested. Table 1-1 shows
the factors which must be measured for each of the three waste handling
options.
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Table 1-1
IMPORTANCE OF WASTEWATER CHARACTERISTICS
Characteristics
Discharge
to Sewer*
Discharge
to Own
Treatment
Plant
Discharge
to Land
Flow
pH
Temperature
Dissolved Oxygen
BOD
COD (use as a check or
guide for BOD)
Total Suspended Solids
Volatile Suspended Solids
Fixed Suspended Solids
Total Dissolved Solids
Nitrogen
Phosphorus
Settleable Solids
Specific Ions**
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
X
X
X
X
*These analyses are determined by the City's sewer use ordinance.
Typical requirements are shown.
**See Table IV-4.
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An Environmental Protection Agency publication, "Monitoring of Industrial
Wastewater," gives additional information on the practicalities of waste
characterization, as well as methods of sampling and analyses.
Sampling, Testing, and Flow Measurement
Selecting a laboratory for testing samples is important. Many states
require that data submitted to regulatory agencies be analyzed at
a state certified or approved laboratory. The expense of building,
staffing, and maintaining such a laboratory can be costly and can
dictate use of an outside contract laboratory for most wastewater testing.
A good program of sampling, testing, and flow measurement is important.
It provides basic information to select treatment processes, to determine
sewer service charges, and to compare the economics of in-plant
waste reduction verses "end of pipe" treatment.
Perhaps the single most important wastewater characteristic is flow.
Flow rate determines the hydraulic capacity needed for a treatment
facility. Several wastewater flow factors must be known for efficient
treatment design: (1) average flow, (2) maximum instantaneous flow,
(3) peak daily flow, and (4) peak weekly flow.
Selection of a point and method of measuring flow is also important.
Factors to consider are:
o Reliability of automatic, flow-measurement equipment
o Nonclogging characteristics
o Accuracy required
o Maintenance required
o Costs
o Accessibility of the flow-measurement station
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Obtaining valid data on waste characteristics requires careful selection
of sampling points. For example, a large sewer can have variations
in waste strength, from the top of the liquid flowing in the pipe to
the bottom of the pipe, because different constituents may differ in
weight. Therefore, samples from the surface of a gravity sewer flowing
full can give misleading results. Sampling points should be selected
where there is no stratification or incomplete mixing of several waste
sources.
Significant variations in production schedule should also be accounted
for as they affect the waste load. Samples must be taken during each
operating shift, and during different stages of the finished or raw
product runs. Flows should be monitored continuously, even during
cleanup shifts and on weekends.
The amount of testing required varies according to the cannery operation
and the purposeoof testing. For maximum accuracy, the waste for
a single product should be tested in two two-week sampling periods.
The first two-week period should be during the first half of the process-
ing season. The second period should be scheduled for the latter
half of the season.
The flows for these two-week periods should be measured and recorded
continuously. Samples should be taken hourly for each day (24 hours)
and composited according to flow. The actual time that the samples
are taken should be varied to increase the possibility of recording
and testing events that happen between sampling times.
Seasonal operation further complicates treatment plant design. In
addition to the requirements of annual startup and shutdown of treatment
facilities, there are changes throughout a processing season for most
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of the wastewater characteristics resulting from changes in the crop
being processed, process changes, etc.
Seasonal operations often affect the type of disposal to be considered.
Processing plant wastewater can be used for irrigation, but it is impracti-
cal if the waste flows are generated at a time when farmers do not
need irrigation or the climate is unsuitable.
TYPICAL WASTEWATER CHARACTERISTICS
Following is a table (Table 1-2) summarizing typical wastewater character-
istics for many fruits and vegetables.
While no plant should expect to conform completely with the values
shown, these typical characteristics can be useful in evaluating whether
a plant is high or low in waste strength. Also, they can assist laboratory
personnel in analyzing wastewater samples.
The characteristics in the table are given in unit loadings, such as
thousand gallons (or pounds) per ton of raw product. Typical concentra-
tions (mg/l) for BOD and suspended solids can be calculated from
the relationships:
concentration (mg/l) = mass (lb/d)
flow (million gal/day) x 8.34
or,
. ,. , ... mass (Ib/ton) x 120
concentration (mg/l) =
flow (1000 gal/ton)
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Table 1-2
TYPICAL RAW WASTEWATER CHARACTERISTICS
Canned and Preserved Fruits and Vegetables
Flow
1,000 gal/ton raw
Min. Mean
Apples
Apricots
Asparagus
Dry Beans
Lima Beans
Snap Beans
Beets
Broccoli
Brussels Sprouts
Berries
Carrots
Cauliflower
Cherries
Citrus
0.2
2.5
1.9
2.5
2.4
1.3
0.3
4.1
5.7
1.8
1.2
12
1.2
0.3
2.4
5.6
8.5
8.8
7.7
4.2
2.7
9.2
8.2
3.5
3.3
17
3.9
3.0
product
Max.
13
14
29
33
22
11.2
6.7
21
12
9.1
7.1
24
14
9.3
BOD
Ib/ton raw product
Min. Mean Max.
3.9
18
0.9
15
9.3
1.6
28
5.8
4.2
11
17
5.5
21
0.9
18
40
4.9
60
48
15
53
20
7.5
19
30
16
38
9.6
44
80
22
182
175
81
127
61
14
40
53
36
78
26
Ib/ton
Min.
0.4
5
4.3
2.6
4.6
0.8
7.3
4.6
2.9
1.4
4.5
2.8
1.0
0.7
TSS
raw product
Mean Max.
4.5
9.9
7.5
43
39
6.1
22
17
15
7.1
17
7.8
2.0
3.7
21
19
13
99
231
46
64
61
79
22
53
22
3.8
14
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Flow
1,000 gal /ton raw
min. mean
Corn
Crapes
Mushrooms
Olives
Onions
Peaches
Pears
Peas
Peppers
Pickles
Pimentos
Pineapples
Plums
Potato Chips
Potatoes, Sweet
Potatoes, White
Pumpkin
Sauerkraut
0.4
0.6
1.8
—
2.5
1.4
1.6
1.9
0.9
1.4
5.8
2.6
0.6
1.2
0.4
1.9
0.4
0.5
1.8
1.5
7.8
8.1
5.5
3.0
3.6
5.4
4.6
3.5
6.9
2.7
2.3
1.6
2.2
3.6
2.9
0.9
product
Max.
7.6
5.1
28
—
10
6.3
7.7
14
16
11
8.2
3.8
8.7
2.2
9.7
6.6
11
3.0
Ib/ton
Min.
12
6.4
7.7
—
57
17
19
16
5
26
39
13
6.5
17
39
42
9.2
4.6
BOD
raw product
Mean Max.
27
9.0
15
27
57
35
50
38
32
42
55
25
10
25
93
84
32
5.6
64
13
28
—
58
70
126
87
50
75
76
45
14
38
217
167
87
15
Ib/ton
Min.
3.6
1.5
5.1
—
5.3
3.4
3.6
3.8
1
3.0
4.1
5.2
0.6
22
40
39
2
—
TSS
raw product
Mean Max.
10
1.7
7.3
27
17
8.6
12
11
58
8.2
5.8
9.1
2.1
32
57
128
67
1.0
27
2.0
12
—
55
21
33
38
170
23
8.1
17
4.3
48
117
423
12
2.6
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Flow BOD TSS
1,000 gal/ton raw product Ib/ton raw product Ib/ton raw product
*
Min. Mean Max. Min. Mean Max. Min. Mean Max.
Spinach
Squash
Tomatoes, Peeled
Tomatoes, Product
Turnips
3.2
1.1
1.3
1.1
2.4
8.8
6.0
2.2
1.6
7.3
23
22
3.7
2.4
18
5.7
6.3
2.2
—
14
20
9.3
4.7
—
31
—
14
9.7
—
1.8
—
5.8
5.6
—
6.1
14
12
10
—
21
—
26
19
—
Sources: EPA Guidelines Development Document
National Canners Association Data
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Changes in Waste Strength
Many factors cause changes in waste strength, as shown in Table 1-3.
One significant factor is a change in the product being processed.
The raw product itself can change in quality throughout a season.
For a variety of reasons, each year's crop is not exactly the same
as other years'. Also, the different ways a raw product is handled
and the length of haul can greatly change waste strength.
Changes in the final product or the commodity being handled, (canned
pears to fruit cocktail, tomato paste to whole canned tomatoes, peas
to corn, etc.) will have significant impacts on waste characteristics
and treatability.
Length of season also affects the wastewater. If a crop is harvested
over a long period of time, the wastewater quality and quantity may
differ markedly from beginning to end of the season.
Changes in waste strength can also occur from shift to shift. For
example, waste flows during the cleanup shift will be different than
those from a processing shift.
Daily or seasonal shutdown and startup of a processing plant can cause
problems at a treatment plant. Biological treatment systems depend
on a regular supply of a given source of food (BOD) . If the food supply
changes greatly, the biological process may not be able to adjust
with the change. Thus, frequent shutdown and startup must be carefully
considered in design of treatment processes.
Technical Session A, on in-plant control of wastewater, has a good
discussion of the quantitative effect of these factors on waste character.
11
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Table 1-3
FACTORS CONTRIBUTING TO RAW WASTE LOAD VARIABILITIES
Raw Product Condition (Ripeness, Damage)
Raw Product Mix
Finished Product Mix
Finished Product Style
Product Conveying Systems (Countercurrent vs. Single
Pass Pluming, Dry Conveying, Pneumatic Conveying)
Process Methods (Blanching, Peeling)
Timing of In-Plant Individual Process Runs
Daily Shift Organization
Cleanup Methods (Dry vs. Wet, Detergent, Disinfection Used)
Batch Dump Frequency (Brine, Caustic)
Frequency, Duration of Shutdowns
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EFFLUENT REQUIREMENTS
In the discharge of wastewater, a cannery is concerned with the require-
ments of one or more governmental agencies: (1) Federal, (2) state,
and (3) local requirements. Requirements for each of these have
been discussed in earlier sessions; however, our discussion here
will give more background regarding these regulations and their effect
on a particular cannery.
Federal Requirements
The most significant set of standards are those set by the Environmental
Protection Agency. The "Phase I" guidelines are completed, but
they only encompass regulations for the apple, potato, and citrus
industries. Phase II is nearing completion now so that effluent guidelines
will soon be established for all canned fruits and vegetables. The
latest draft guidelines (October 1975) are given in Table I-4. These
are being reviewed now by EPA and quite possibly will be modified
before the requirements are finalized.
The guidelines affect the following parameters:
o BOD
o Total Suspended Solids (TSS)
o Crease and Oil
o pH
o Fecal Cdiform Count
Table I-4 gives the allowable mass emissions of BOD and TSS for all
fruit and vegetable processors. Effluent pH is limited between 6 and 9.5
for both 1977 and 1983 for all except the apple, citrus, and potato
13
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Table 1-4
EFFLUENT LIMITATION GUIDELINES
(POUNDS ALLOWED PER TON RAW PRODUCT)
1977
Daily Max 30-Day Avg Seasonal Avg
1983
Daily Max 30-Day Avg Seasonal Avg
Added Ingredients* 3.92
Apple Juice
Apple Products
(except juice)
2.52
1.20 1.60 0.60 0.80
2.20 2.80 1.10 1.40
1.60 —
M 5.428
L 5.428
3.418
3.418
0.40 0.40 0.20 0.20
0.40 0.40 0.20 0.20
1.600
1.600
Apricots
5.96 9.36 3.88 6.70 2.52 5.20
M 1.954 3.856 1.238 2.189 0.600 1.244
L 1.954 1.954 1.238 1.238 0.600 0.600
Asparagus
1.70 2.52 1.10 1.70 0.68 1.46
M 0.560 1.004 0.326 0.420 0.140 0.326
L 0.560 0.560 0.326 0.326 0.140 0.140
Baby Food*
2.00 3.12 1.30 2.22 0.84 1.74
M 0.848 1.636 0.534 0.888 0.250 0.528
L 0.848 0.848 0.534 0.534 0.250 0.250
Beets
1.62 3.10 1.08 2.54 0.78 1.48
*lb/ton final product
**lb/ton raw ingredients
M 0.750 1.838 0.500 1.438 0.206 0.582
L 0.750 0.750 0.500 0.500 0.206 0.206
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Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
Broccoli
Daily Max
BOD TSS
7.22 10.74
1977
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
2.68 7.30 2.94 6.24
1983
Daily Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS
M 3.278 5.930 2.040 2.774 0.862 1.926
L 3.278 3.278 2.040 2.040 0.862 0.862
Brussel Sprouts
2.50 3.70 1.62 2.52 1.02 2.16
M 3.314 5.886 2.054 2.618 0.840 1.916
L 3.314 3.314 2.054 2.054 0.840 0.840
Caneberries
1.56 2.42 1.02 1.70 0.66 1.36
M 0.434 0.83 0.274 0.442 0.126 0.268
L 0.434 0.434 0.274 0.274 0.126 0.126
Carrots
3.46 5.82 2.28 4.38 1.52 3.06
M 1.620 3.330 1.036 2.036 0.532 1.070
L 1.620 1.620 1.036 1.036 0.532 0.532
Cauliflower*
3.96 5.86 2.56 3.98 1.62 3.40
M 4.712 8.348 2.920 3.704 1.194 2.714
L 4.712 4.712 2.920 2.920 1.194 1.194
Cherries (sweet)
2.18 3.56 1.42 2.64 0.94 1.92
M 0.740 1.516 0.474 0.920 0.242 0.488
L 0.740 0.740 0.474 0.474 0.242 0.242
Cherries (sour)
3.40 5.62 2.18 4.22 0.58 3.00
*lb/ton final product
**lb/ton raw ingredients
M 1.714 3.372 1.084 1.904 0.522 1.088
L 1.714 1.714 1.084 1.084 0.522 0.522
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Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
Daily Max
BOD TSS
1977
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
1983
Daily Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS
Cherries (brined)
5.54 8.96 3.62 6.58 2.38 4.86
M 1.142 2.656 0.752 1.948 0.458 0.846
L 1.142 1.142 0.752 0.752 0.458 0.458
Chips (potato)*
6.70 11.20 4.38 8.44 2.94 5.92
M 2.808 5.568 1.784 3.192 0.872 1.792
L 2.808 2.808 1.784 1.784 0.872 0.872
Chips (corn)*
3.68 6.68 2.44 5.34 1.70 3.32
M 2.062 5.038 1.324 2.724 0.700 1.386
L 2.062 2.062 1.324 1.324 0.700 0.700
Chips (tortilla)*
5.76 9.58 3.78 7.18 2.52 5.08
M 3.196 6.238 2.020 3.466 0.962 2.014
L 3.196 3.196 2.020 2.020 0.962 0.962
Citrus
1,60 2.40
0.80 1.70
0.28 0.40 0.14 0.20
Corn (canned)
1.40 2.56 0.92 2.06 0.62 1.26
M 0.358 0.830 0.236 0.410 0.144 0.264
L 0.358 0.358 0.236 0.236 0.144 O.t44
Corn (frozen)
3.98 6.32 2.48 4.74 1.66 3.34
M 1.786 3.438 1.126 1.856 0.524 1.110
L 1.786 1.786 1.126 1.126 0.524 0.524
Cranberries
*lb/ton final product
**lb/ton raw ingredients
3.36 5.34 2.18 3.82 1.42 2.94
M 1.034 2.088 0.660 1.236 0.330 0.672
L 1.034 1.034 0.660 0.660 0.330 0.330
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
Daily Max
BOD TSS
1977
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
1983
Daily Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS
Dehydrated
Onion/Garlic
4.80 7.12 3.10 4.84 1.96 4.14
M 1.894 3.512 1.184 1.748 0.522 1.140
L 1.894 1.894 1.184 1.184 0.522 0.522
Dehydrated Vegetables 5.82 8.64 3.76 5.86 2.38 5.02
M 2.930 5.410 1.830 2.662 0.800 1.754
L 2.930 2.930 1.830 1.830 0.800 0.800
Dried Fruit
3.66 5.84 2.38 4.24 1.56 3.20
M 1.078 2.244 0.692 1.402 0.406 0.720
L 1.078 1.078 0.692 0.692 0.406 0.406
Dry Beans
4.92 7.84 3.20 5.66 2.10 4.30
M 2.386 4.456 1.494 2.252 0.664 1.444
L 2.386 2.386 1.494 1.494 0.664 0.664
Ethnic Foods*
3.48 5.40 2.26 3.82 1.46 3.02
M 1.394 2.652 0.876 1.396 0.400 0.856
L 1.394 1.394 0.876 0.876 0.400 0.400
Grape Juice (canning) 2.04 3.40 1.34 2.56 0.90 1.82
M 0.938 1.836 0.602 0.992 0.280 0.594
L 0.938 0.938 0.602 0.602 0.280 0.280
Grape Juice (pressing) 0.44 0.72 0.28 0.56 0.18 0.38
M 0.178 0.350 0.112 0.198 0.054 0.112
L 0.178 0.178 0.112 0.112 0.054 0.054
*lb/final product
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
Daily Max
BOD TSS
1977
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
1983
Daily Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS
Jams/Jellies*
0.78 1.36 0.52 1.06 0.34 0.70
M 0.372 0.808 0.240 0.540 0.134 0.258
L 0.372 0.372 0.240 0.240 0.134 0.134
Lima Beans
7.28 11.28 4.72 7.98 3.04 6.34
M 2.914 5.362 1.818 2.616 0.790 1.738
L 2.914 2.914 1.818 1.818 0.790 0.790
Mayonnaise and
Dressings*
0.68 1.20 0.46 0.94 0.30 0.62
M 0.402 0.864 0.260 0.568 0.142 0.276
L 0.402 0.402 0.260 0.260 0.142 0.142
Mushrooms
5.98 9.18 3.88 6.42 2.48 5.18
M 2.000 3.744 1.254 1.900 0.560 1.212
L 2.000 2.000 1.254 1.254 0.560 0.560
Olives
10.62 17.28 6.94 12.72 4.58 9.34
M 3.652 7.128 2.308 3.960 1.098 2.298
L 3.652 3.652 2.308 2.308 1.098 1.098
Onions (canned)
6.34 10.18 4.14 7.42 2.70 5.56
M 2.794 5.666 1.782 3.384 0.898 1.822
L 2.794 2.794 1.782 1.782 0.898 0.898
Peaches (canned)
3.62 5.86 2.36 4.30 1.56 3.18
*lb/ton final product
**lb/ton raw ingredients
M 1.612 3.154 1.020 1.760 0.488 1.018
L 1.612 1.612 1.020 1.020 0.488 0.488
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
Daily Max
BOD TSS
1977
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
Daily Max
BOD TSS
1983
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
Peaches (frozen)
1.60 2.76 1.04 2.14 0.72 1.42
M 0.554 1.126 0.514 0.626 0.282 0.548
L 0.554 0.554 0.514 0.514 0.282 0.282
Pears
3.42 5.80 2.24 4.42 1.50 3.04
M 1.182 2.418 0.746 1.510 0.390 0.776
L 1.182 1.182 0.746 0.746 0.390 0.390
Peas (canned)
5.48 8.88 3.58 6.52 2.36 4.80
M 2.044 4.222 1.308 2.606 0.678 1.356
L 2.044 2.044 1.308 1.308 0.678 0.678
Peas (frozen)
4.06 6.66 2.66 4.94 1.76 3.58
M 1.714 3.340 1.084 1.850 0.514 1.078
L 1.714 1.714 1.084 1.084 0.514 0.514
Pickles (fresh pack)
2.38 3.86 1.56 2.82 1.02 2.08
M 1.160 2.144 0.724 1.060 0.318 0.696
L 1.160 1.160 0.724 0.724 0.318 0.318
Pickles (process pack) 2.78 4.76 1.82 3.64 1.24 2.48
M 1.016 2.056 0.646 1.226 0.326 0.662
L 1.016 1.016 0.646 0.646 0.326 0.326
Pickles (salt stations) 0.40 0.86 0.28 0.76 0.20 0.38
S
M
L
0
0
0
0
0
0
0
0
0
0
0
0
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
1977 1983
Commodity Daily Max 30-Day Avg Seasonal Avg Daily Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS BOD TSS BOD TSS BOD TSS
•• —•—
Pimentos 7.91 12.70 5.16 9.24 3.38 6.94 M 4.008 7.672 2.502 4.188 1.172 2.478
L 4.008 4.008 2.502 2.502 1.172 1.172
S -
Pineapples 3.56 5.64 2.32 4.06 1.50 3.12 M 1.760 3.380 1.108 1.814 0.514 1.092
L 1.760 1.760 1.108 1.108 0.514 0.514
_
—• ___ _ _ ..
Plums 1.36 2.14 0.88 1.56 0.58 1.18 M 0.466 0.874 0.292 0.448 0.132 0.284
L 0.466 0.466 0.292 0.292 0.132 0.132
Potatoes (dehydrated) 4.80 5.60 2.40 2.80 — — 0.68 2.20 0.34 1.10
Potatoes (frozen) 5.60 5.60 2.80 2.80 — 0.68 2.20 0.34 1.10
S_
Raisins 0.82 1.44 0.54 1.10 0.36 0.74 M 0.330 0.766 0.218 0.562 0.132 0.244
L 0.330 0.330 0.218 0.218 0.132 0.132
S
Sauerkraut (canning) 0.98 1.56 0.64 1.14 0.42 0.86 M 0.450 0.900 0.286 0.526 0.142 0.290
L 0.450 0.450 0.286 0.286 0.142 0.142
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
1977
Commodity
Dally Max 30-Day Avg Seasonal Avg
BOD TSS BOD TSS BOD TSS
Sauerkraut (cutting) 0.14 0.24 0.08 0.20 0.06 0.12
Snap Beans (canned) 2.32 3.46 1.50 2.34 0.94 2.00
Snap Beans (frozen) 4.24 6.50 2.74 4.54 1.76 3.68
Soups**
Spinach (canned)
Spinach (frozen)
Squash
8.30 12.68 5.32 8.94 3.42 7.12
6.04 8:98 3.90 6.10 2.46 5.20
3.54 5.24 2.28 3.56 1.44 3.04
1.72 3.14 1.14 2.50 0.80 1.56
1983
Daily Max
BOD TSS
S
M
L
S
M
L
S
M
L
S
M
L
S
M
L
S
M
L
S
M
L
0.054
0.054
1.582
1.582
2.132
2.132
4.584
4.584
1.704
1.704
2.074
2.074
0.502
0.502
0.114
0.054
2.850
1.582
3.960
2.132
8.576
4.584
3.134
1.704
3.752
2.074
1.010
0.502
30-Day
BOD
0.034
0.034
-
0.984
0.984
1.334
1.334
2.872
2.872
1.064
1.064
1.290
1.290
0.320
0.320
Avg
TSS
—
0.074
0.017
1.320
0.984
1.978
1.334
4.350
2.872
1.520
1.064
1.754
1.290
0.594
0.320
Seasonal Avg
BOD TSS
0.018
0.018
0.412
0.412
0.588
0.588
1.280
1.280
0.462
0.462
0.544
0.544
0.158
0.158
0.036
0.018
0.926
0.412
1.284
0.588
2.778
1.280
1.016
0.462
1.218
0.544
0.324
0.158
*lb/ton final product
**lb/ton raw ingredients
-------
Table 1-4
EFFLUENT LIMITATION GUIDELINES
Commodity
1977
Daily Max 30-Day Avg
BOD TSS BOD TSS
Seasonal Avg
BOD TSS
Daily Max
BOD TSS
1983
30-Day Avg Seasonal Avg
BOD TSS BOD TSS
Strawberries
3.50 5.38 2.26 3.76 1.46 3.04
M 1.052 1.992 0.660 1.038 0.300 0.644
L 1.052 1.052 0.660 0.660 0.300 0.300
Sweet Potato
1.56 3.34 1.06 2.96 0.80 1.48 M 0.768 2.026 0.522 1.712 0.372 0.640
L 0.768 0.768 0.522 0.522 0.372 0.372
Tomatoes (peeled)
2.40 3.70 1.56 2.60 1.00 2.08
M 0.750 1.424 0.472 0.746 0.216 0.460
L 0.750 0.750 0.472 0.472 0.216 0.216
Tomatoes (products) 0.96 1.42 0.62 0.96 0.38 0.82
M 0.562 1.028 0.350 0.494 0.150 0.334
L 0.562 0.562 0.350 0.350 0.150 0.150
Tomato-Starch 3.54 5.24 2.28 3.56
-Cheese Specialties*
1.44 3.04 M 1.456 2.678 0.908 1.308 0.394 0.868
L 1.456 1.456 0.908 0.908 0.394 0.394
White Potatoes
(canned)
*lb/ton final product
**lb/ton raw ingredients
2.60 4.68 1.72 3.86 1.20 2.36
M 0.770 1.962 0.520 1.598 0.354 0.620
L 0.770 0.770 0.520 0.520 0.354 0.354
-------
processing industries. For these latter three, effluent pH limits are
between 6 and 9. All industries must disinfect by 1983 to meet an allow-
able fecal coliform count of 400 per 100 ml.
A draft oil and grease limitation of 20 mg/l has been set for the "special-
ties" category only. This limit is identical for both 1977 and 1983. Those
"specialties" industries affected are:
o Added Ingredients
o Baby Foods
o Chips (potato, corn, tortilla)
o Ethnic Foods
o Jams/Jellies
o Mayonnaise and Dressings
o Soups
o Tomato-Starch-Cheese Canned Specialties
No other industries have oil and grease limitations.
The draft guidelines for 1983 have been divided according to size of
plant—small, medium, or large (S, M, or L in Table 1-4) . "Small"
is defined as a plant that processes less than 2,000 tons of raw material
per year. "Medium" is between 2,000 tons and 10,000 tons per year.
"Large" is greater than 10,000 tons per year.
To understand the guidelines, one must realize that they are based
on what is attainable; not necessarily on what is required to protect
water quality. For 1977, the effluent standards are based on what
is defined as the "Best Practicable Control Technology Currently Availa-
ble (BPCTA) ." By 1983, the effluents are to conform to limits that
23
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are the "Best Available Technology Economically Achievable (BATEA) ."
These are both set by EPA through research by outside consultants
for the industries concerned. (6,7).
Although the EPA guidelines are written for waste discharge into receiving
waters, they also effect processors discharging into a municipal sewer.
The law requires that a\\_ industries meet the guidelines. Canners
discharging to a sewer meet their treatment obligations through the
use of the joint city-industry treatment plant operated by the city.
If the city's treatment plant does not adequately treat your waste,
it is possible that you may be forced to add intermediate treatment
facilities to make up the difference.
State Requirements
For the states that have their own pollution control programs certified
by EPA, the EPA guidelines represent the maximum permissible discharge.
The standards developed by these states are usually more stringent
than the EPA requirements. These state's standards have been set
to meet strict water quality goals for receiving streams or special
local pollution problems.
Local Requirements
Local requirements are primarily in the form of sewer ordinances
which apply to sewer users. Ordinances are written with two goals
in mind. The first goal, which was the original impetus to the ordinances,
is to prevent blockages of the collection system, hazards to workers
in the sewers and at the treatment plant, or interferences with the
treatment process. In addition, ordinances set the basis for
24
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sewer user charges and limit specific waste characteristics such as
pH and grease.
Thus, most local agencies have, or are developing, extensive charge
systems and restrictive sewer use ordinances. The effect of these or-
dinances will be explored in the section on pretreatment.
The current EPA grant program, as well as several state programs,
requires that a swereage agency establish a comprehensive sewer ordin-
ance which includes restrictions on the use of the sewer system and treat-
ment plant, limits waste characteristics, and established an equitable
system for establishing sewer user charges.
COST INFORMATION AND OTHER DATA
Where not otherwise noted, the cost information and other data presented
in the-remaining Chapters are taken from CH M HILL internal sources.
A numbered list of references is attached to the end of the report.
Costs are for October 1975 and assume competitive bids by outside con-
tractors. The estimates are "order of magnitude" estimates, which means
that the final cost, adjusted for inflation, may be from 0 percent lower to
50 percent higher. It was assumed that no significant site grading would
be required and that good soil conditions existed. No costs were included
for site acquisition or for separate fencing, yard lighting, access roads,
and laboratories. Other initial assumptions for each example are either
listed on the tables themselves or given in the text.
Generalized cost curves are also given in the two EPA effluent guide-
line development documents for the fruit and vegetable industries.
25
-------
Chapter II
PRETREATMENT
BACKGROUND
Most canneries discharging to a city sewer system use some method of pretreat-
ment. Pretreatment may be thought of as treatment processes used to remove
gross solids: trash, vines, pits, skins, or soil, or a process to control or even
out variations in pH or flow. Common pretreatment steps are screening, neu-
tralization, or flow equalization; but sometimes more extensive treatment is
needed like gravity sedimentation or dissolved air flotation.
There may be any one or more of four different reasons for employing pretreatment:
o Ordinance Requirements
o Cost
o Production Increases
o By-product Recovery
Ordinance Requirements
Pretreatment is often required by city ordinance. In cases like these, screening
is almost always a requirement, but other processes, like pH control, may
be required.
Some cities require the removal of inert materials (sand or clay). This requirement
affects canneries processing tomatoes, carrots, potatoes, or any other root
crops. Although rare, a city can also require neutralization, or reduction
of flow surges.
26
-------
Economic Considerations
The other three reasons for pretreatment come from considerations of the economics
of disposal. These include: (1) attempts to reduce city sewer fees, (2) reduction
of existing waste loads to allow production increase or cannery expansion,
and (3) recovery of by-products for sale.
Despite the apparent high rates charged by some cities for using their sewers,
it is often difficult to economically justify treatment for sewer charge reduction.
The main reason for this lack of economy is the high cost of solids disposal
and the high unit cost (cents/1000 gallons) of building and operating small
treatment plants, when compared to the unit cost of a significantly larger munici-
pal treatment plant. For example, city sewer charges now are typically in the
range of $0.20 to $1.00 per 1000 gallons. Because of the high cost of industrial
capital, the short processing season and other factors, the unit charge for treat-
ment by canners alone is considerably higher. The cast summary tables in this
and the other chapters show unit costs from $0.18 per 1000 gallons for screening
to $3.21 per 1000 gallons for activated sludge. Because of the federal grant program
regulations, industries participating in joint treatment essentially receive
a thirty-year interest-free loan for their share of the joint treatment facilities.
Production Increases
Extensive pretreatment can be required as a result of plant expansions. Canner-
ies discharging to public systems frequently reach their allocated capacity
of the public treatment plant—and because of production increases, or a plant
expansion, need additional treatment capacity—but before the public agency
can provide it. Presently the time required to expand a public treatment plant
is about 5 years. Overloading the treatment plant creates operating problems
for the public agency and may cause bad publicity (or even legal action) for
an industry.
27
-------
Limitations in the construction grants program of the Environmental Protection
Agency can result in construction of public treatment facilities with limited
expansion capability. For example, the Los Angeles area is designated as
a "critical air basin", and only limited expansion is allowed in public treatment
plants. If additional plant capacity were provided, additional growth might
occur and further degrade air quality. This type of reasoning can create problems
for industrial contributors.
Few industries can wait for the public agency to provide additional capacity.
One option the industry has is to pretreat the waste so that the cannery's contribu-
tion to the public system does not increase, even though the plant has been
expanded.
A proposed new cannery, or an existing cannery that wishes to expand its
production may not be permitted to do so by the city. However, the cannery
can be required to install an extensive pretreatment system so it will not tax
the city's plant. This requirement for pretreatment may be so strict that essenti-
ally full treatment is required. When this happens, the option of discharging
to a city sewer is less attractive.
By-Product Recovery
Presently, recovery of food processing by-products at the end of the pipe
is less than a "break-even" proposition. Since the economics do not now favor
recovery, it is usually only practical if it is in response to other requirements
for pretreatment or to help defray some of the pretreatment operating costs.
For certain products in livestock producing areas, end-of-pipe screenings
can be recovered and used in animal (cattle, poultry, hogs) feeding operations.
In these cases, the screenings are given away, or the hauler only charges
fees for trucking.
28
-------
In some cases, treatment plant sludge is used for cattle or poultry feed. Ordinarily,
these sludges do not have balanced nutrients, so they are not suitable for feeds
alone. Supplements must be added to market saleable feed.
Because of possible adulteration, wastes from the end of the pipe cannot be
recovered if domestic sewage is mixed with the process waste. This mixing
will make the waste by-products unsuitable for use as animal feed. Sanitary
waste (domestic waste) should be kept separate from other wastes if any by-
product recovery is anticipated.
TECHNOLOGY
Many processes can be used for pretreatment. The processes that are most
frequently used, as required by an ordinance, are screens, neutralization
systems, flow equalization, and soil removal. For sewer charge savings,
or for plant-expansions, the processes used can include sedimentation units,
dissolved air flotation units, or even biological treatment units (roughing trickling
filters, ponds, etc.) These later more complete units are discussed in Chapter
III on full treatment.
Screening
Screening is the most common form of pretreatment. Screens are almost always
required by city authorities. The purpose of screens is to remove large particles
that might otherwise overload and clog sewers or damage treatment plant equipment.
Although fine screens (200 to 400 mesh) may be used to remove large amounts
of suspended solids, they can also trap large quantities of water to be discharged
with the screenings. Common practical screen sizes are 20-40 mesh.
29
-------
Besides initial cost, a screen is chosen with respect to hydraulic capacity,
percent of solids captured, blinding potential, volume of screenings to be
disposed, and maintenance requirements.
Four types of screens are commonly used in the fruit and vegetable industry.
Currently, the most popular is the vibrating or oscillating screen. Two common
variations are the circular center feed one, in which solids may be discharged
in a spiral toward the center or periphery, or the rectangular, end-feed variation,
in which solids are discharged along the screen toward the lower end.
The next most common is the rotary drum screen. These screens may be designed
so that the flow is from the inside of the drum toward the outside, or the reverse.
If the flow is from the inside, then the solids are retained in the inside of the
screen and removed by augers, wash troughs or gravity. In units where the
flow is from the outside to the center, the solids are retained on the outer surface
of the drum and are removed by a doctor (or scraper) blade.
Tangential screens (Figure 11-1) are becoming more common, especially the
parabolic cross section type, where wastewater is fed at the top. The water
flows down and through the parabolic screen, but the solids are retained on
the surface of the screen and discharged intermittently to a hopper at the lower
end of the screen.
Rotating drum centrifugal screens are used when high solids capture is required.
The screens are usually of a very fine mesh, up to 400. The water is sprayed
under pressure onto the inside of the rotating drum. The water then passes
through the screening media and the solids are retained on the inside of the
drum. The solids typically have a high moisture content (and hence, high
volume); thus they are often sent through successive units (two to six) for
concentration.
30
-------
Feed
Screenings
Screened Waste
FIG. EH TANGENTIAL SCREEN (45°)
(Courtesy of Dorr Oliver)
-------
Successful application of screens depends on many variables. Data from the
literature is often confusing and contradictory. For any given screen, the
amount of removal of solids is more correlative to the amount of settleable and
floatable solids in the effluent, rather than the amount of suspended solids
alone. Screens ordinarily achieve a high removal of settleable and floatable
solids, but variable amounts (0 to 70 percent) of suspended solids. Proportional
amounts of BOD are ordinarily removed with the solids.
Elevation and location of the waste screen is very important. One option is
to collect plant waste waters in a sump below the floor level of the plant, from
which they are pumped to the screen. The screen is elevated so the solid wastes
may fall into a suitable hopper. The water then flows into the subsequent treat-
ment facility, or to the sewer.
Another option is to place the screens below the level of the plant drains (if
the elevations permit). After screening, the solid waste can be conveyed up
to the waste hopper and the water pumped into the clarifier, or other disposal
system.
Screening is the most inexpensive method of removing large solids (greater
than about 60 mesh) from wastewater. A good screen may remove the same
amount of solids cheaper than in-plant dry cleanup.
Compared to other pretreatment methods, screens require a small amount of
space and can usually be easily installed in an existing plant.
An estimate of the cost for screening is given in Table ll-l. These costs are
for October 1975 and assume a 20 mesh tangential screen. The estimate assumes
that the cannery floor drains will not have to be modified.
32
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TABLE H -1
COST SUMMARY
FLOW MEASUREMENT & SCREENING
CRITERIA
o FLOW:
• TSS-
« pH:
• SEASON^
o AMORTIZATION:
I MOD AVERAGE
2 MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
o ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
• OCTOBER, 1975 DOLLARS
SCHEMATIC
PROCESS PIPING
EXISTING
WASTEWATER
COLLECTION
SYSTEM \
SCREENS
SOLIDS STORAGE
HOPPER
FLOW MEASUREMENT
PROCESS FLOW TO
~|rv DOWNSTREAM
TREATMENT
F
>UMP STATION
RECEIVING SUMP
DISPOSAL
ASSUMPTIONS
• SOLIDS HAULING AND DISPOSAL AT
4 DOLLARS / cy
• USE OF 20- MESH SCREEN
COSTS
CAPITAL COST-
ANNUAL 0 & M
AMORTIZED CAPITAL COST
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gal.)
71 ,600
3,200
12,700
15,900
17.7
-------
Neutralization
Most cities limit the pH of wastewater discharged into the sewer. This limit
Is to protect the sewer lines and to ease any pH shocks to the treatment plant.
The most stringent pH limits are those set between 6.5 and 8.5. The most
lax are between 5 and 10.
Neutralization will normally be required for only those canneries processing
naturally acid foods (tomatoes), those using a caustic peeling process (peaches,
potatoes, etc.), or those using a brine (cherries, olives). Few neutralization
systems are now installed for canneries discharging to a municipal system.
The most reliable neutralization system uses two or three mixed tanks, in series,
to which an acid (sulfuric) or base (lime, caustic) is added. The addition
of acid or base is through electrically or pneumatically operated throttling
valves. The amount of opening of the valves is controlled by effluent pH readings.
If the flow is fairly constant, and the waste is always acidic, a simpler method
is to use a column of limestone chips. For a consistently alkaline waste, pH
can also be simply controlled through the use of carbon dioxide. The problem
of reagent dose control is simpler here, but there are two serious drawbacks:
the availability and cost of the gas itself, and inefficiency in introducing the
gas into the waste stream.
A cost estimate for a neutralization system is given in Table 11-2. The costs
are for October 1975 and include two mixed tanks, an instrumentation and control
system, and chemical storage. It was assumed that the waste is acidic and
is neutralized with caustic. Facilities for neutralization with lime or sulfuric
acid will differ only in chemical storage and delivery.
-------
CRITERIA
o FLOW:
» BOD:
o TSS =
• PH:
0 SEASON:
« AMORTIZATION
I MGD AVERAGE
2 MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
o ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
• OCTOBER, 1975 DOLLARS
ASSUMPTIONS
o NEUTRALIZATION WITH 20% NaOH AT
200 mg/l NaOH
• NaOH COST AT 165 DOLLARS PER
ANHYDROUS TON
• TANK TRUCK SHIPPING COST AT
3 CENTS/100 K> LIQUID/MILE WITH
100 MILE SHIPPING DISTANCE
0 TWO NEUTRALIZATION TANKS IN SERIES
WITH 15 MINUTE AVERAGE RETENTION
TABLE n-2
COST SUMMARY
NEUTRALIZATION
SCHEMATIC
L
NaOH STORAGE
DILUTION TANKSx
MIXER
PROCESS
FLOW
CHEMICAL FEED
PUMPS
PROCESS FLOW TO DOWN-
STREAM TREATMENT
NEUTRALIZATION TANKS
COSTS
CAPITAL COST-
ANNUAL OftM
AMORTIZED CAPITAL COST
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000gal.)
100,000
23,600
17,700
41,300
45.9
-------
Flow Control
Control of surges in effluent flow is usually not required as a pretreatment
measure. If flow variations can be smoothed out and accidental spills contained
and controlled, the size of screens required will be lessened, and the problems
of effluent pH control will be simpler.
Depending on the daily operating mode of the cannery, variations in instantane-
ous flow can be from very small to very great (a maximum of 4 times the minimum)
Each cannery is obviously different, but large variations in flow may be smoothed
with a surge tank of about ten to twenty percent of the total daily flow volume.
Settling of solids will be a significant problem in a tank of this size, so the
tank must either be stirred or some means provided for settled solids removal.
Soil Removal
Root crops; such as potatoes, carrots and beets, and machine harvested crops,
like tomatoes, introduce large amounts of field soil to a cannery waste stream
along with the raw product. Since the present incentive for field cleaning
is slight, each cannery has to handle and/or remove the soil. City treatment
plant operators commonly complain of this high soil loading. The abrasive
material wears out seals and bearings in pump stations, settles out in low-flowing
pipelines and eventually ends up in the treatment plant's solids handling system
(i.e. the sludge digester).
Many city ordinances are now being written to require a cannery to remove
a large fraction of the nonvolatile settleable solids (mostly soil), in their effluent.
Depending on space available and costs of disposal of the mud, several systems
can be used. The simplest system is to use a series of settling lagoons. These
are operated on a fill and draw basis, changing lagoons about once a month.
36
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Once the mud has dried, it can be removed with a skip loader. If few dissolved
organics are in the water, then a large settling pond can be used, which only
needs cleaning once per season. This kind of pond seems to work well when
the soil-laden water can be previously separated from the remainder of the
cannery waste flow. Because of fruit breakage during unloading, large settling
ponds, if used on tomato fluming water, will develop odors after two or three
weeks.
Where space and disposal of solids is a problem, circular clarifiers (Figure
11-2) canbbe used to settle and thicken the soil. Typically, circular clarifiers
will produce a mud two to three times thicker than could be obtained in plain
settling ponds. This means that the volume of mud to be disposed of is reduced
from two to three times.
Grit removing cyclones have also been tried at some canneries. The units
are relatively cheap, but they must be run at a constant flow to achieve their
design efficiency. Cyclones are not as efficient as a well designed clarifier,
and tend to produce a rather dilute mud. Abrasion on the cyclone can be severe,
Fine (to 400 mesh) screens have also been tried to remove soil. The application
is similar to screening. Several screens are used in series, to concentrate
the solids rejected from the previous one. These units approach the efficiency
of clarifiers, but are considerably more difficult to operate and maintain, and
are also more expensive.
FURTHER TREATMENT
If it is found that processes for the additional removal of suspended solids,
or BOD areneeded, more complex units must be used. Some of these additional
processes are listed below:
37
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Influent Screen
Underflow or Mud
to Dewatering
Influent Silt Stream
from Flumes
Effluent Returned
to Flumes
FIG.E-2 SILT CLAR1FIER
(Courtesy of CH2M HILL)
-------
o chemical coagulation and settling for increased suspended solids
removal,
o dissolved air flotation for additional suspended solids removal,
o aerated ponds to remove BOD
o biological roughing filters to remove BOD.
These processes and others are discussed in complete detail in Chapter III.
COMMUNICATIONS
The importance of good communications between processing plant staff and
a local public agency treatment plant operators cannot be over emphasized.
Treatment plant operators typically feel that they are "neglected warriors"
in the battle against water pollution. They are expected to treat anything which
comes at them through the pipe. Good communications between processing
plant staff and the treatment plant operators will improve public relations and
assist the treatment plant operators in handling occasional upsets or unusual
conditions which may result with minimal effects.
City plant operators need to know, as much in advance as possible, when the
canneries will start up or when the product mix will be changed. Early notification
of planned wastewater "dumps" of an unusual nature or immediate notification
of accidental spills can be invaluable assistance to treatment plant operators.
39
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Chapter III
FULL TREATMENT
DEFINITIONS
For the purposes of this discussion, we are defining full treatment pro-
cesses as those that are used prior to discharge of wastewater to water
or land. As was mentioned in the discussion of pretreatment earlier,
many of these "full treatment" processes can be used if extensive pre-
treatment is required.
Until quite recently, full treatment could be classified as anything from
primary treatment, through secondary treatment, up to advanced waste
treatment {tertiary treatment). The processes commonly thought of as
being under each of these three categories are listed in Table 111-1.
In so far as the treatment of food processing waste is concerned, primary
treatment is used to remove the solid material in the wastewater,
secondary treatment is used to remove the dissolved material, and
advanced, or tertiary, treatment to remove anything missed by the
first two.
Figure 111-1 is a graphical representation of how BOD and suspended
solids are removed in various levels of treatment. The length of the bars
in the figure is semi-quantitative. That is, it is representative of what
happens in treatment of an idealized food processing waste, not a
particular one. The sum of a pair of bars represents the total amount of
solids (or BOD) in the waste. The length of the BOD bars should not
be compared with the length of the solids bars. BOD is an effect, or
demand, exerted by the solids, and may not be in proportion to the
mass of solids.
40
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Table 111-1
FULL TREATMENT UNIT PROCESSES
PRIMARY TREATMENT
SECONDARY TREATMENT
TERTIARY TREATMENT
(Suspended Solids Removal,
Some BOD Removal)
BOD Removal)
(Additional Solids Removal)
Plain Sedimentation
Dissolved Air Flotation
Chemical Treatment
Stabilization Ponds
Aerated Ponds
Activated Sludge
ABF/Activated Sludge
Trickling Filters
Anaerobic-Aerobic Ponds
Chemical Clarification
Filtration
(Removal of BOD, COD)
Carbon Adsorption
(Removal of TDS)
Ion Exchange
Reverse Osmosis
-------
FIGURE m-1
EFFECT OF TREATMENT
ON SOLIDS &BOD
TOTAL SOLIDS
TOTAL BOD
ACTIVATED. SLUD
-------
REQUIREMENTS
EPA Standards
Currently, the Environmental Protection Agency is in the process of
promulgating standards for the entire fruit and vegetable processing
industry. These standards will require secondary treatment for all
plants that discharge into the nation's waterways by 1977. By 1983,
the EPA guidelines may mandate advanced treatment. The guidelines
are given in Table I-4 and the accompanying text.
For all except the apple, citrus and potato products industries, the
effluent guidelines (7) assume that the 1977 requirements will be met by one
of two kinds of secondary treatment: aerated ponds, or activated sludge.
The 1983 guidelines are to be met by reducing the load on the treatment
plants through in-plant processing changes, but large plants may have to
add multimedia filtration. All plants will be required to meet a fecal coli-
form level of less than 400 MPN per 100 ml.
The 1977 guidelines for the apple, citrus and potato processing industries
are to be met with secondary treatment as well. Exemplary secondary
treatment plants studied by EPA included the following processes:
activated sludge, trickling filter and aerated ponds, multiple aerated
ponds, and anaerobic—aerobic ponds. The potato processors that were
studied used primary clarifiers ahead of secondary treatment (6).
The 1983 guidelines are to be met through the use of in-plant controls
and the addition of more aerated lagoons or a sand filter. Fecal coli-
form standards are also set for 1983.
Thus, for the future, primary treatment alone will probably be used only
for discharge to some kind of land treatment system or for pretreatment
-------
(potatoes). Primary treatment can be productively used as a first step
in secondary treatment installations if the influent waste is high in settle-
able suspended solids (tomatoes, carrots, potatoes).
Other Considerations
Treatment may be dictated by water re-use schemes, such as agricultural
re-use, groundwater recharge, or to extend the life of a land disposal
system. The State of California, for example, is setting discharge stand-
ards for waste applied to land disposal systems.
Water used for irrigation has quality requirements which are outlined in
Chapter IV. Treatment requirements prior to agricultural re-use may be
more or less stringent than those required for discharge to a receiving water.
Minerals such as boron, sodium, and calcium play an important role in
determining the feasibility of agricultural re-use. Conversely, these
constituents are seldom considered in discharges to receiving waters.
There are problems of a seasonal nature in agricultural re-use. The
general problem is that wastewater discharged from a seasonal food pro-
cessor may come at a time when farmers are not irrigating. Thus,
there could be a need for large volumes of storage during the non-
irrigation seasons.
Even if a cannery is discharging into a city sewer system, and has only
a pretreatment requirement, an understanding of the workings of the
more elaborate full treatment processes is useful. The opening of canning
season is usually a significant day for the operators of a city treatment
plant. If a plant manager of a cannery understands the effect his waste-
water has on the operation and performance of the city plant, his cooperation
will go a long way toward forging good relations between the city and the
industrial community;
44
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The processes discussed in this section are all used in many municipal
treatment plants. In keeping with the traditional flow pattern used by
most cities in their treatment plants, the following discussions are
divided according to primary, secondary, or tertiary treatment.
PRIMARY TREATMENT
Primary treatment is used for the removal of floatable, settleable and
suspended solids from the wastewater. The removal of the solids is
accomplished by gravity (or by skimming, in the case of floatables)
and may be assisted by adding some chemicals (lime, alum or polymer)
to make the particles settle faster, or by mixing with dissolved air
and chemicals to make the solids float to the top.
In treatment of domestic waste, primary treatment usually removes 40
to 60 percent of the influent suspended solids and 30 percent removal of the
BOD. These removals are usually not achieved in food processing waste.
Typically, most of the BOD in these wastes is in a dissolved form which
will not settle. An exception, however, is potato waste, where 40 to
60 percent of BOD and 80% of suspended solids can be removed with
primary treatment.
Suspended solids reductions that are achievable in primary treatment
vary widely with raw and finished products, but seem to be mostly re-
lated to the amount of non-organic material, or soil, in the waste stream.
Hence, significant suspended soils reductions are attainable with primary
treatment in products like potatoes, tomatoes, beets, or carrots, while
very little reduction is attainable in products like peas, peaches, or pears.
45
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For example, primary treatment is seldom provided for apple juice waste,
since there are few settleable solids. The waste consists primarily of
dissolved fruit sugars. Tomato processing waste is typically high in
settleable solids from field soil, so primary treatment is effective.
In treatment of potato processing waste, the organic solids removed can be
used as an animal feed supplement in some locations, perhaps recovering
part of the cost of treatment.
Gravity Sedimentation
Primary treatment systems using gravity sedimentation are sized on the
theoretical settling or falling rate of the slowest particles to be removed.
This settling rate is expressed as gallons treated per day divided by the
surface area of the clarifier (gpd/sf). Typical values are between 800
and 1000 gpd/sf, which is equivalent to settling rates of 0.89 and 1.11
inches per minute, respectively (see Table III-2). From considerations
of settling velocity alone, a clarifier only has to be deep enough to make
sure that the slowest settling particles reach the bottom before going
out over the weirs on the side. However, clarifiers should be deeper
than this, at least 10 feet, to allow for imperfections in flow distribution,
secondary influences, and sludge storage.
Primary clarifiers also thicken the settled particles, besides just allowing
them to settle out. Ciruclar tanks with rotating rakes to thicken and collect
the sludge are most efficient in this aspect, although many cities use
rectangular primary clarifiers. To attain proper sludge thickening,
attention must also be paid to the solids loading on the clarifier. The
solids, floor loading, or mass flux, is the total mass of solids treated
divided by the surface area of the clarifier. Typical values for solids
loadings are given in Table III-2. Figure III-2 is a cross section of a
typical circular gravity operated clarifier.
-------
Table 111-2
PRIMARY TREATMENT DESIGN CRITERIA
FRUIT AND VEGETABLE WASTEWATERS
CLARIFIER TYPE
Circular or rectangular with width
equal to 1/4 to 1/3 of length.
BOTTOM SLOPE
One to 2 inches per foot for
light sludge. Three to four for
heavy sludge.
OVERFLOW RATE
Common Municipal Waste
Silt and Clay
Lime Floe
Alum Floe
880 gallons/day/sq ft (gpd/sf)
300 gpd/sf
900 to 1,000 gpd/sf
600 gpd/sf
SIDE WATER DEPTH
Ten feet minimum. Twelve feet best.
RAKE SPEEDS
Rectangular tanks: 2-4 fpm
Circular tanks: 2-4 fpm at the
tip, but should be 10-15 fpm for
silt and clay.
SCUM REMOVAL
Should be on all clarifiers. Scum
trough should be on downwind side
of clarifier.
SOLIDS LOADING
SLUDGE PIPING
Ten to 30 Ibs/sf/day for light
organics. Eighty to 100 Ibs/sf/day
for silt and clay.
Preferably 6 inches diameter. Flow
velocity should be about 2-5 fps.
-------
Scum Box
Weir
Surface Skimmer
Scum Baffle
Effluent Launder
\
Scum
influent Feed Well
zms
Solids Settle
to Bottom
Rotating Clarifier
Rake Arm
Solids Withdrawal
Scrapers Thicken and
Move Solids to Hopper
FIG. m-2 CLARIFIER
-------
Chemicals, such as lime, alum or one of the many kinds of polymers,
may be added to gravity sedimentation tanks. This increases the rate
of settling of the suspended particles by coagulating smaller particles
together into larger particles. Because of fluctuations in chemical re-
quirements, chemical coagulation systems can be extremely difficult to
operate on food processing waste effluents, especially if consistently high
removals are required.
Air Flotation
For certain wastes, dissolved air flotation clarifiers can be used effec-
tively. Here, removal of suspended solids is dependent on the attachment
of fine air bubbles to each solids particle, providing buoyancy to the
solids. The solids then rise and form a blanket, or float, on the top of
the clarifier, and are skimmed off. The heavier solids that do settle
are removed by either an auger or rake.
The most common type of air flotation is by dissolved air flotation. Here
a portion of the waste, or effluent, is pressurized and air is injected into
it. When the air and solids mixture is released into the open tank, the
air comes out of solution in the form of small bubbles which become attached
to the solids. In some units, the waste is mixed with a fraction of recycled
effluent prior to pressurization.
Dissolved air flotation units must be designed empirically from pilot
experiments for a given waste. It is necessary to examine several criteria
in the pilot studies. Chemical dose requirements, hydraulic loading, solids
loading and the air to solids ratio are the criteria needed for a successful
design. Figure III-3 shows a typical rectangular dissolved air flotation
clarifier. This one is equipped to remove solids from both the top and
bottom. Common loadings in dissolved air flotation units are given in
Table 111-2.
-------
Hopper to Collect Float
Auger to
Remove Float
Influent
Surface Skimming
Mechanism
Effluent
Recycle Pump
Pressurization Tank
Heavy Solids
Recycle Line with
Dissolved Air
Auger to Remove
Heavy Solids
FIG.m-3 DISSOLVED AIR FLOTATION CLARIFIER
( Courtesy of Envirex)
-------
Complete Systems
A schematic of a complete primary plant is given in Figure 111-4.
A summary of the important design criteria for these plants is given in
Table 111-2. In addition to the criteria that must be met in the design of
the clarifier, it is also vitally important that the sludge handling system
be well matched to the treatment system.
Unless the clarifier is oversized it will be impossible to store sludge in
it until a vacuum filter or centrifuge has a chance to handle it. If the vacuum
filter or centrifuge is undersized, the clarifier will build up with sludge.
The sludge may then become septic and pH will drop, reducing the dewater-
ability of the sludge. If solids are lost over the weirs, treatment efficiency
will suffer until sludge is somehow removed. A discussion on vacuum
filter sizing and operation is given in Chapter V.
Primary paints operating on waste from root crop processing, or other plants,
like tomato canneries, may have special problems with field soil (mud) in
the clarifier. Some clays and silts are thixotropic, which means that they
will solidify unless constantly agitated. If the sludge does solidify, it
must be manually removed from the clarifier.
Most mud will settle and thicken in clarifiers to 30% to 40% total solids
(by weight). At those concentrations, the headloss in suction pipelines is
so great that pumping is ordinarily impossible. Where sludge like this is
anticipated, the clarifier should be designed with one or more of the
following:
o Sludge pump beneath clarifier at center
o 6-inch minimum diameter for suction line
o Dilution water piped to head end of suction line
51
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Plant Effluent
Clarifier
Treated Flow to Sewer
or Secondary Treatment
Flow Measurement
-*V t A
Sludge : 4 % to
15% Total Solids
Vacuum Filter
Filter Cake : 8% to
50% Total Solids
FIG.DI-4 PRIMARY TREATMENT PLANT DIAGRAM
-------
BIOLOGICAL SECONDARY TREATMENT
While primary treatment is mostly used for removal of settelable in-
organic solid material, secondary treatment for removal of soluble
organic material (BOD) (see Figure 111-1). Biological secondary treatment
may be (1) aerobic, which means that the biochemical reactions are carried
out in the presence of oxygen; or (2) anaerobic, in which case different
biochemical reactions are carried out in the absence of oxygen.
Anaerobic systems produce considerably less sludge than aerobic systems
and are commonly used to treat sludge in municipal plants. Anaerobic
lagoons followed by stabilization ponds have also been used with some suc-
cess on citrus wastes and potato waste. These treatment systems are rare
so the remainder of this discussion will be devoted to aerobic systems.
The basic treatment unit in aerobic systems is a biological reactor
(aerated tank, pond, or trickling filter) which provides an environ-
ment for the conversion of soluble organic material into insoluble micro-
organism cells. The subsequent unit is a secondary clarifier where the
cells are allowed to settle. The settled cells, or sludge, may be either
returned to the biological reactor cell mass (the mixed liquor) or wasted
from the system (waste sludge) . Large volumes of organic solids are
generated in secondary treatment processes, as the result of cellular
growth. Usually, 0.3 to 0.6 pounds of cells are created for every pound
of BOD removed. These solids are typically very wet (0.5 to 1.0%
solids by weight), voluminous, and are difficult to dewater.
There are several different biological systems which are used to provide
secondary treatment. In all cases, the secondary treatment units must
provide an environment suitable for the growth of biological organisms
which do the actual work of waste treatment. These treatment units
53
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depend on a sufficient supply of oxygen to support aerobic decomposition
of the organic matter. Aerobic biological decomposition, if operating
correctly, is practically odorless and is capable of very high removal of
the organic matter contained in wastes (90 to 95 percent) .
Two general types of biological secondary treatment will be discussed
in this section: (1) ponding systems, and (2) high rate or "mechanical"
treatment plants.
The high rate processes discussed will include:
o Activated sludge (both air and oxygen)
o Activated biological filter
o Rotating biological contactors
o Trickling filter
A summary of design factors to be considered for each process discussed
is included at the end of this section.
AERATION METHODS
Unless stabilization lagoons or ponds are used to meet secondary treat-
ment requirements, some type of artificial aeration system is required.
These aeration systems can be classified according to two approaches:
(1) bubbling compressed air into the waste through the use of diffusers
(diffused aeration), and (2) entrainment of air in the waste through
fairly violent agitation of the surface (mechanical aeration).
Air is compressed to about 8 psig with the use of blowers in diffused
air systems. The compressed air then enters the waste through diffusers,
which are mounted close to the bottom of the aeration tank. There are
many variations in the methods diffusing the air into solution, but for all
54
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of these, the efficiency of diffusion is only about seven percent. Diffusers
are prone to clogging from particles in the waste, or with deposits built up
on the diffuser pores, so they should be mounted so they can easily be
removed for cleaning. The blowers are quite noisy and should be mounted
in a separate room. As a rule, to maintain complete mixing, 20 to 30 cfm
(cubic feet per minute) should be applied to each 1000 cubic feet of basin
volume. Diffused air systems deliver 1.5 to 1.7 pounds oxygen per horse-
power-hour at field conditions.
A typical mechanical aerator is shown on Figure III-5. These aerators may
be either rigidly mounted in a tank, or installed with floats, so they can
rise and fall with the water level, like the one illustrated. Mechanical
aerators typically deliver 1.5 to 2 pounds of oxygen per horsepower-hour
at field conditions at sea level. The amount of power to maintain complete
mixing with these units is one-half to one horsepower per 1000 cubic feet.
PONDING SYSTEMS
In general, ponding systems can be considered for use where ample land
area is available, with allowances for an ample buffer zone around the
pond. Typically, ponding systems do not achieve the high levels of
treatment provided by the high rate processes, but are considerably
easier to operate and maintain.
Two common types of ponds are stabilization ponds and aerated ponds.
The treatment process is similar in each, but for a given waste, an aerated
pond will be smaller than a stabilization pond.
55
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MOTOR (TEFC)
MOTOR
CONDENSATE
DRAIN
MARINE COUPLING
SPACER
METALLIC PUMPING CHAMBER
DEFLECTOR AND DRAFT CORE
WATER LUBRICATED SHAFT
BEARING
CERAMIC COATED SHAFT
FIG.m-5 FLOATING MECHANICAL AERATOR
Courtesy of Ashbrook
-------
Stabilization Ponds
Stabilization ponds are large, usually 3 to 6 ft. deep, and retain the
wastewater for a period of 60 days or longer. Oxygen necessary for
biological action is obtained primarily from the action of photosynthetic
algae, although some oxygenation occurs as a result of the contact between
the pond surface and the atmosphere. Depending on the degree of treat-
ment desired, waste stabilization ponds may be designed to be operated
in a variety of ways, including series and parallel operations; and in some
cases, may include tertiary ponds for algae removal prior to effluent
discharge. Air temperature has a great effect on the success of ponds as
treatment.
Because of the high strength of canning waste, BOD loading is usually
the major criterion. Loading should be kept at 20 to 40 pounds BOD
per acre per day. There are several problems with stabilization
ponds that are resulting in their being abandoned, at least in joint
treatment systems with municipalities. These are:
1. Growth of algae, causing high effluent suspended solids
2. Odors, especially during start up and shut down.
3. Large land requirement.
There are several algae removal systems under study and some under
construction; but there is no full scale, long-term operating experience.
Aerated Ponds
Aerated ponds are similar to stabilization ponds, except that additional
oxygen is artificially added either by compressed air diffusion, or by use
of mechanical agitation (Figure 111-5). Supplementation of oxygen in this
manner allows the volume of the ponds to be greatly decreased, and the
57
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depth increased (to 12 feet), thus reducing surface area and heat loss.
The biological life in an aerated pond will contain limited numbers of
algae, and will be similar to that found in an activated sludge plant.
Table III-3 gives and estimated cost of an aerated pond for a 1 million
gallon per day wastewater flow. The ponds are lined with a rubber liner
with vents. In addition to the assumptions given in the Table, the
following should be noted:
o pond depth is 10 feet
o inside side slope 3:1, outside 2:1
o mechanical aerators : 12 at 40 HP each and one at 20 HP; ail
moored to the bottom
o total area for both ponds is 11 to 12 acres.
o material used in dike construction comes from the pond excavation
HIGH RATE PROCESSES
Table Ill-tf summarizes a series of high rate processes and shows the
relative comparison of such characteristics as: area requirements,
stability, reliability, and ability to withstand shock loads. This summary
table will be a good reference for general consideration of alternative pro-
cesses.
Activated Sludge
In the activated sludge process, the waste is discharged into large aeration
basins into which atmospheric oxygen is diffused by releasing compressed
air into the waste or by mechanical surface aerators. The presence of
abundant organic food, nutrients, and oxygen is favorable to the growth
of a heavy concentration of microorganisms (mixed liquor). Ordinarily,
dissolved oxygen levels are kept at 1-2 mg/l. The organic content of the
58
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CRITERIA
• FLOW*
o BOD'
• TSS'
• pH =
• SEASON'
• AMORTIZATION--
TABLE HI-3
COST SUMMARY
AERATED LAGOON SYSTEM
SCHEMATIC
I MGD AVERAGE
2 MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
o ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
• OCTOBER, 1975 DOLLARS
AERATED
LAGOON
AERATORS
SETTLING
POND
^^ /WAU//7& \ OO
^PROCESS
FLOW
PROCESS FLOW TO
DOWNSTREAM
TREATMENT
ASSUMPTIONS
o BOTH AERATED LAGOON AND SETTLING
POND ARE LINED EARTHEN BASINS
o 30-DAY DETENTION TIME IN AERATED
LAGOON
0 400 GPD/SF OVERFLOW RATE IN
SETTLING POND
« NO NUTRIENT ADDITION
» EXCAVATION & DISPOSAL COST AT *4/cy
o POWER COST AT 2 CENTS/KW-HR
COSTS
CAPITAL COST
ANNUAL 0 a M
AMORTIZED CAPITAL COST-
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gol.)
1,160,000
16,000
205,300
221,300
245
-------
Table 111-4
SECONDARY TREATMENT PROCESS COMPARISON
(Rating: 1=Lowest, etc.)
PROCESS
STABILIZATION PONDS
AERATED PONDS
AIR ACTIVATED SLUDGE
OXYGEN ACTIVATED SLUDGE
ABF/ACTIVATED LSUDGE
ROTATING BIOL. CONTACTORS
TRICKLING FILTERS
*•"•»
_ c
ro J2
tD O *~r.
U U
1
1
3
4
4
3
2
o
0) 3
"0 1?
D 0
0) or
55 a 33
.j o a:
1
1
3
4
5
2
2
n>
+J
I!
o a
4
3
2
1
1
3
3
-------
waste is removed by the life processes of the microbes and stored as
protoplasm. The mixed liquor is then removed in sedimentation basins,
leaving a highly treated effluent. About half or more of the settled sludge
is returned to the aeration tank to maintain the mixed liquor concentration.
A schematic of an activated sludge plant is given in Figure 111-6. Design
•
criteria for activated sludge processes are given in Table III-5. Figures
111-7 and 8 are photographs of activated sludge plants treating potato wastes.
An operational problem with activated sludge plants is sludge bulking.
Sludge bulking is the inability of the activated sludge to settle or thicken
in the secondary clarifier. This is a common occurrence in plants
treating cannery wastewater containing a high percentage of carbohydrates
and is due to the formation of filamentous, or stringy, bacteria. The
effect is to considerably reduce the long term removal efficiency of the
affected plant.
There are many variations of activated sludge processes; however, all
operate basically the same. The variations are the result of unit arrange-
ment and methods of introducing air and waste into the aeration basin.
A small, compact, prefabricated activated sludge plant is shown in
Figure 111-9.
Tables IV-6 A and -6B give cost estimates for an activated sludge plant
(1.0 mgd) both with,and without,sludge digestion and dewatering.
Besides the assumptions listed in the tables, the following should be noted:
o activated sludge F/M : 0.2
o aeration basin sludge age : 6.5 days
o aeration basin mechanical aerators : 10 at 50 HP each
o two 40' diameter clarifiers
o area requirements for activated sludge alone : 2 acres, approx.
o area requirements with digestion, dewatering : 3 acres, approx.
o aerobic digestor sludge age : 15 days
61
-------
o two gravity dewatering units
o raw waste activated sludge to truck : 95,000 gal/day at 0.8% TS
o digested, dewatered, waste activated sludge to truck : 35 cubic
yards/day at 9% TS
o small building for motor control center and pumps
o small building to house dewatering units
The activated sludge process variation using high purity oxygen (HPO)
merits some discussion. This system employs covered multistage (3 to 5
stages) aeration basins into which oxygen-rich gas is fed. Oxygen util-
ization is approximately 90%. Oxygen concentration varies from above 90%
in the inlet gas to about 50% in the exhaust gas. Mechanical mixers project
through the roof to mix the basin contents and entrain oxygen. Dissolved
oxygen concentrations can be maintained at high levels (7 to 15 mg/l)
(versus 1 to 2 mg/l in conventional plants) in the wastewater flow. The
basin effluent is clarified in standard secondary clarifiers and sludge is
returned to the first stage aeration. Excess sludge is wasted as in a con-
ventional activated sludge plant.
Current knowledge of food processing waste and the high purity oxygen
activated sludge process strongly suggest that, when compared with more
conventional activated sludge systems, use of this modified process will
result in the following:
o A sludge more settleable in secondary clarifiers, resulting in
lower secondary effluent suspended solids and BOD levels. This
advantage has been observed in treatment of other high strength
carbohydrate wastewaters and is believed related to the high
dissolved oxygen concentration within the system.
o Retention of wastewater heat necessary for effective treatment in
cold climates.
o Less land area
62
-------
Floating Mechanical Aerator
Effluent
iii=niL^
From Primary Clarifier
or Cannery
^a
Illfisir \
Yjfer
\
/ Return Solids Pump
Waste Solids
AERATION BASIN
FINAL CLARIFIER
FIG. m-6 ACTIVATED SLUDGE PLANT DIAGRAM
-------
Table 111-5
SECONDARY TREATMENT DESIGN CRITERIA
FRUIT AND VEGETABLE WASTEWATERS
CONVENTIONAL ACTIVATED SLUDGE
AERATION BASIN
Mixed Liquor Suspended
Solids (MLSS)
Food Microorganism Ratio
(F/M)
Sludge Age (Days)
Aeration Time
Depth
Aeration Type
Returned Sludge
2,000 - 4,000 mg/l
0.1 - 0.5 Ib BOD removed
per Ib BOD removed
3 - 10 Ibs MLSS per Ib sludge
wasted per day
16-48 hours, but controlled
by sludge age, F/M, and
MLSS concentration
10-20 feet. 7 feet min.
Floating Mechanical Aerators
or diffused aeration
25 - 100 percent of incoming
plant flow
SECONDARY CLARIFIERS
Typical overflow rate is
400 gdp/sf. Solids or
floor loading is 25 Ib/sf/day
based on influent plus
recycle flow. Most secondary
clarifiers are circular.
-------
PURE OXYGEN ACTIVATED SLUDGE
AERATION BASIN
Mixed Liquor Concentra-
tion (MLSS)
Food/Microorganism Ratio
(F/M)
Sludge Age (Days)
Aeration Time
Depth
Aeration Type
Returned Sludge
Clarifier
AERATED PONDS
Depth
Hydraulic Retention Time
ABF/ACTIVATED SLUDGE
FILTER TOWER
Height
Configuration
3,000 - 5,000 mg/l
0.5 - 0.7 Ib BOD removed
per Ib of MLSS
6 - 10 Ib MLSS per Ib
sludge wasted per day
8-24 hours, but controlled by
by sludge age, F/M, and
MLSS concentration
15 feet
Diffused high purity oxygen
in mechanically agitated
covered tanks
25 - 100 percent of incoming
plant flow
Same as conventional activated
sludge except floor loading
can be increased to 35 Ib/sf/
day
7-15 feet
20 - 45 days
20 feet
Circular with rotating waste
distributors, or rectangular
with stationary distributor
-------
Hydraulic Loading
BOD Loading
Media Type
AERATION BASIN
CLARIFIER
1 - 2 gpm/sf of tower area
including recycle
0.15 - 0.3 Ib BOD per cubic
foot of filter media
Redwood slats or various plastic
shapes
Same criteria as an activated
sludge aeration basin. Assume
that 50-60 percent of the
influent BOD has been removed
by the tower.
Same criteria as an activated
sludge clarifier. Sludge can
be returned to both the
aeration basin and the filter
tower.
TRICKLING FILTRATION (High Rate)
TRICKLING FILTER
Depth
Configuration
Hydraulic Loadings
BOD Loading
Recirculation
Media Type
3-8 feet
Circular with rotating dist-
ributor
20 - 90 gallons/sf/day
20 - 50 Ibs BOD/1,000 cf
100 - 400 percent of influent
flow
Rock Media: 1 - 3 inches diam.
Plastic media now being
used.
-------
FIG.m-7 ACTIVATED SLUDGE PLANT
(Courtesy of CH2M HILL)
-------
FIG.m-8 ACTIVATED SLUDGE PLANT
(Courtesy of CH2M HILL)
-------
Aeration Section
Clarifier Rake
Aerobic Digester Section
FIG.HI-9 PACKAGE ACTIVATED SLUDGE PLANT
( Courtesy of Cantex )
-------
CRITERIA
• FLOWt
• B00<
• TSS«
• pH:
• SEASON:
• AMORTIZATION
I M60 AVERAGE
2 MGO PEAK
TABLE HI-6A
COST SUMMARY
ACTIVATED SLUDGE SYSTEM
SCHEMATIC
^NH4OH 8 HjP(>4
/f NUTRIENT ADDITION
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
OCTOBER, 1975 DOLLARS
(
S8XMMRY CLARFCRS
AERATION
BASIN
cLJL/ m
HASTE ACTIVATED
t SLUDGE
\ PROCESS, FLOW TO
\ DOWNSTREAM
\ TREATMENT
^PROCESS
FLOW
-RETURN SLUDGE
ASSUMPTIONS
• LINED EARTHEN AERATION BASIN WITH
2-DAY DETENTION TIME
• TWO CONVENTIONAL SECONDARY CLARIFIERS
WITH 400 GPD/SF OVERFLOW RATE
• COST OF NH4OH AT *I84/TON (IOO%
BASIS) COST OF H3PO4 AT *0.2l5/lb SOL'N.
0 POWER COST AT 2CENTS/KW-HR
« W.A.S. DISPOSAL COST AT 1.5 CENTS/gol
FOR 20-MILE HAUL
COSTS
CAPITAL COST
ANNUAL 0 a M
AMORTIZED CAPITAL COST-
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gal.)
645,000
175,000
114,150
289,150
321
-------
TABLE ffl-6B
COST SUMMARY
ACTIVATED SLUDGE WITH AEROBIC DIGESTION AND DEWATERING
CRITERIA
• FLOW:
• BOD:
• TSS:
• pH =
• SEASON:
• AMORTIZATION:
I MOD AVERAGE
2MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
• ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
• OCTOBER, 1975 DOLLARS
SCHEMATIC
NUTRIENT ADDITION
AERATION BASIN
SECONDARY CLARIFIERS>
RETURN SLUDGE
WASTE ACTIVATED SLUDGE
AEROBIC DIGESTERS—
SLUDGE
DEWATERING
UNITS
DEWATERED SLUDGE TO STORAGE HOPPER
CONVEYOR
ASSUMPTIONS
o SEE ASSUMPTIONS FOR ACTIVATED
SLUDGE SYSTEM (TABLE HL-6A)
0 DEWATERED SLUDGE TRUCKING COSTS
ATS3.70/TON DRY SOLIDS/MILE
« POLYMER ADDITION AT 6 Ib/TON SOLIDS
o POLYMER COST AT s2.25/lb
o UNIT DEWATERING RATE AT 1000 GPH
FOR DIGESTED SLUDGE
COSTS
CAPITAL COST
ANNUAL 0 a M
AMORTIZED CAPITAL COST
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gal.)
1,115,000
58,500
197,350
255,850
284
-------
The capital cost of a high purity oxygen system is usually greater than
conventional systems, but it should be considered where the need for
biological secondary treatment is indicated. Commonly used design cri-
teria for HPO processes are given in Table 111-5.
Activated Biological Filter (ABF)
Activated bio-filtration (ABF) was developed in recent years to take maximum
advantage of artificial filter media characteristics. Plastic and redwood
biological filter media have high void to total volume ratios, and high surface
to total volume ratios. These characteristics make high organic loadings
possible.
In the original ABF system, secondary clarifier underflow is combined
with the secondary plant influent and pumped to the bio-filter. Bacteria
grow on the filter media and in the wastewater flow. Portions of the bac-
terial mass continuously sluff from the media, join the bacteria growing in
the wastewater, and settle out in the secondary clarifier.
A majority of the bacterial mass settled in the secondary clarifier is
returned to the filter influent to maintain a high concentration of bacteria
in the flow through the filter. The flow has the appearance of activated
sludge, giving rise to the process name, activated bio-filtration.
A recent modification of the ABF process has been the insertion of an
activated sludge aeration tank between the ABF tower and the final clari-
fier. The effluent from the tower is sent through the aeration basin for
further treatment. The aeration basin is designed to assimilate 50 to 100
percent of the organic loading to the tower. Returned sludge from the
final clarifier is split between the tower and the aeration basins.
72
-------
FIG.m-IO ACTIVATED BIOLOGICAL FILTER TOWER
(Courtesy of CH2M HILL)
-------
Influent and
Recycle Pump
Waste from Cannery
or Primary Treatment
\
ur
T
\J~
\ \ ( k — f-*
*~1 — f—f — TT"
V V V v v \ \ \ 4
Return Solids
Rotating Distributor Mechanism
Tower Containing
Stacked Filter Media
/
Tower Effluent
Tower Effluent
Splitter Box
Recycle
ABF TOWER
I
To Aeration Basin
Floating Mechanical Aerator
From ABF Tower
Effluent
Return Solids Pump
Waste Solids
to Solids Treatment
AERATION BASIN
FINAL CLARIFIER
FIG. m-11 ABF-ACTIVATED SLUDGE PLANT DIAGRAM
-------
This ABF-Activated sludge process has shown great promise in success-
fully treating high carbohydrate wastewaters (potatoes) without developing
the sludge bulking problems of activated sludge. The process is also
resistant to shock loadings. Figure 111-10 shows a circular ABF tower oper-
ating on combined domestic and pear waste. The towers (about 20 feet high)
may also be square or rectangular. Figure 111-17 is a scematic of the ABF-
Activated sludge process. Design criteria for ABF/Activated sludge plants
are given in Table 111-5
OTHER HIGH RATE PROCESSES
Rotating Biological Contactors (RBC's)
This system consists of numerous large diameter, lightweight, discs
mounted on a horizontal shaft in a semi-circular shaped tank. The discs
are rotated slowly with the lower half of their surfaces submerged in the
wastewater. Bacteria and other microorganisms grow on the disc surfaces
and in the tank. In rotating, the discs carry a film of wastewater into
the air where it absorbs oxygen. The mixing created by the disc rotation
also transfers oxygen to the tank contents. Shearing forces cause excess
bacterial growth to sluff from the discs and into the wastewater. The
sluffed solids flow out with the treated waste to the secondary clarifier for
separation and disposal.
Rotating biological contactors have been successfully applied to municipal
and some industrial waste. Operation is simple and power requirements
are low, but the capital costs of the discs are high. Prior to the system's
application in treatment of food processing waste, a number of questions
should be answered by pilot plant testing and economic analysis. Among
these questions are: (1) effect of wastewater pH, (2) effect of wastewater
75
-------
strength, (3) BOD and suspended solids removal efficiency relationships
to BOD and suspended solids unit loadings,and (4) capital and total costs
in relation to alternative systems available.
Biological or Trickling Filters
Wastewater being treated by trickling filtration is distributed over filter
beds constructed either of rocks 2i to 6 inches in size, plastic media or
wood media. Atmospheric oxygen moves naturally through the void
spaces in the filter material. In the environment thus created, biological
slimes (consisting mainly of bacteria) flourish and colonize on the rock
surfaces. As the waste trickles over the surface of the biological slime
growths, organic matter is removed. As the slime growths become more
and more concentrated, their attachment to the media surface is weakened
and the biological growth is washed from the filter. The solids are then
removed by sedimentation as in other high rate processes. See Figure 111-12
for a diagram of this process.
There are a number of variations of the biological filter process, depending
on the waste loadings applied to the filters, the arrangment of the units, and
the number of filters employed.
Trickling filters are very stable and easier to operate than activated sludge
plants. Removals of BOD seldom exceed 80 percent, and the effluent con-
tains a higher level of suspended solids than the activated sludge process.
For this reason, no new trickling filter plants are now being designed to
meet the new EPA requirements. Common design parameters for trickling
filters are given on Table 111-5.
Trickling filters have also been used ahead of activated sludge plants as
roughing filters to cut down high strength wastes. If the sludge is re-
cycled back to the filter, the flow scheme is similar to ABF-Activated sludge.
76
-------
Rotating Distributor
Bed of Large Rock
Influent
Biological Growth
on Rock Surface
Effluent
TRICKLING FILTER
FINAL CLARIFIER
FIG. m-12 TRICKLING FILTER PLANT DIAGRAM
-------
NUTRIENT REQUIREMENTS
Besides air and waste, a biological system needs nutrients to maintain a
healthy state. Microorganisms need much the same kinds of trace minerals
that humans do, but the lack of these is rarely a serious problem in waste
treatment. The most common deficiencies in food processing waste are
nitrogen and phosphorus. The amount of these nutrients required for a
given microorganism depends on its age, while the amount of nutrients
required for a treatment process depends both on the age of the organisms
and the numbers of cells generated during the reduction of BOD. Conser-
vatively, a BOC/nitrogen/phosphorus ratio of 100: 5:1 will give an adequate
amount of nutrients. As can be seen from Table 111-7, most food processing
wastes have a nutrient deficiency.
The effects of nutrient deficiencies show up most markedly in activated
sludge plants, especially those treating wastes containing a high amount of
carbohydrates. The values in the table are taken from the EPA effluent
guidelines report and presumably are developed from analyses for total
nitrogen and phosphorus. Most of the nitrogen found in food processing
wastes is in the form of organic nitrogen which is not readily available
for microorganism growth. Thus a greater amount of supplemental
nitrogen is needed than the Table would indicate.
TERTIARY (ADVANCED) WASTE TREATMENT
With the exception of 2 or 3 rapid sand filter installations, tertiary treat-
ment is not now practiced by the food processing industry (6,7). It is
not expected that it will be necessary to meet 1977 EPA requirements, but
tertiary processes may be required for 1983. Only those processes with
78
-------
Table 111-7
AVAILABLE NUTRIENTS
FRUIT AND VEGETABLE WASTEWATERS
COMMODITY
APRICOTS
ARTICHOKES
ASPARAGUS
BEANS
BEETS
BLUEBERRIES
BROCCOLI
BRUSSELS SPROUTS
CANEBERRIES
CARROTS
CAULIFLOWER
CHERRIES
CORN
CRANBERRIES
DRY BEANS
DEHYD. ONIONS
FIGS
GRAPES
JAMS & JELLIES
LIMA BEANS
MUSHROOMS
OKRA
OLIVES
BOD/N/P
RATIO
100/1. 6/. 23
100/4. 4/. 8
100/6.5/1
100/4. 4/. 8
100/3.1/3.9
100/.9/.1
100/7.2/1
100/7. 21 . 7
100/1.8/.2
100/2. 3/. 5
100/6. 8/. 9
100/1. 7/. 2
100/2. 8/. 5
100/.7/.1
100/5. 4/. 6
100/2. I/. 004
100/1. 3/. 2
100/1.6/.1
100/.1/.01
100/5. 4/. 6
100/7/1 .9
100/5/.6
100/1. 2/.1
COMMODITY
ONIONS
PEACH
PEARS
PEAS
PICKLES
(avg. sweet
6 dill)
PIMENTO
PINEAPPLE
PLUMS
POTATO CHIPS
POTATOES
PRUNES
RAISINS
RHUBARB
SAUERKRAUT
SPINACH
SQUASH
STRAWBERRIES
SWEET POTATO
TOMATOES
ZUCCHINI
BOD/N/P
RATIO
100/3. I/. 5
100/1.4/.3
100/1/.01
100/6/.7
100/1/.2
100/2. 8/. 3
100/.6/.1
100/.6/.1
100/1. I/. 2
100/2.4/.4
100/.7/.2
100/.7/.2
100/3.0/.5
100/4/.5
100/7. 11 . 6
100/3.7/.7
100/1. 6/. 3
100/1. 3/. 2
100/4/.6
100/5/.8
Source: EPA Effluent Guidelines Development Document (7)
-------
the greatest possible applicability are discussed here. These processes
are: chemical precipitation, filtration, carbon adsorption, ion exchange,
and reverse osmosis. In the discussion, the assumption has been made
that any advanced waste treatment process will be treating effluent from
a secondary treatment plant.
Chemical Precipitation and Sedimentation
The primary application for this step as a tertiary process is the removal
of suspended solids escaping secondary treatment. The process involves
the use of a coagulant to (1) form a precipitate with the waste which settles
out, and (2) form a metal precipitate which "sweeps" out other collodial
matter. The coagulants commonly used are lime, alum, or ferric chloride.
Polymers are sometimes used as a primary coagulant, but most often as
an aid.
Simplified chemical reactions illustrating the action of these coagulants
are given below:
Lime
Ca(OH)2+Ca(HC03)2-2CaC03(*)
Alum
6HC03 *3SO4 + 2AI (OH)3(4) + 6CO2
Ferric Chloride
FeCI3 + 3H20 * Fe (OH)3 (*) + 3H+ +3Cl'
( (t) indicates a solid material or precipitate that settles out.)
80
-------
Table 111-8
TERTIARY WASTE TREATMENT APPLICATIONS
POLLUTANT TO BE REMOVED
Process
Carbon
Adsorption
Suspended Dissolved Refractory
ODD BOD Solids Salts Organics
X
X
Chem.
Precipitation
X
X
Filtration.
X
X
Ion Exchange
X X
X
X
Reverse
Osmosis
X X
X
-------
The overflow rate on the chemical clarifier can be from 500 to 2000 gpd/sf
dependent on the coagulant used. Expected solids concentration in the
sludge varies from 3 to 7 percent.
If lime is used as a coagulant, the floe is very dense and settles easily.
The use of alum increases sulfates in the water. The floe is more diffi-
cult to settle and dewater than lime. The use of iron increases the chlor-
ide concentration in the water and can cause low pH problems. Chemical
precipitation is, however, the most efficient way to prevent deterioration
of effluent during biological plant upsets.
Filtration
Filtration is used to reduce suspended solids of collodial size—those that
will not settle out. Historically, a single media was used with a filtration
rate of 0.05 to 0.13 gpm/sf. This has been termed slow sand filtration.
Rapid sand filtration, in use now, uses a filtration rate of 1-8 gpm/sf. In
addition to single media filters originally used, dual and tri-media filters
are now in use.
Filters may be classified by the following five parameters:
(1) direction of flow, (2) type of media, (3) flow rate, (4) type of
head provided, and (5) cleaning method.
The types of filters used most successfully on wastewater today are down-
flow filters using dual or tri-media. A filtration rate of 2i - 5 gpm/sf is
common. Cleaning is by hydraulic backwash, commonly at a rate of
15 gpm/sf. This backwash may be preceded by air backwash and assisted
by surface wash. Often a filtration aid like polymer or alum is added to the
feed to strengthen floe and improve solids removal. Figure III-13shows a
small package pressure mixed media filter installation.
82
-------
Filter Tanks Containing
Mixed Media
FIG.HI-13 PRESSURE FILTER
(Courtesy of Neptune Mr rofloc)
-------
Single media filters ordinarily remove only 70 percent of the influent solids
under ideal conditions. Seventy-five to ninety percent of the head loss
occurs in the first inch of depth of this media, so it is easy to see that
filtration is really a surface phenomenon. In addition, single media filters
tend to "blind off" at the surface, reducing filter runtime, and thus
necessitating more frequent backwashing.
Mixed media (dual or tri-media) filters generally give longer runs and
better removals. The media is slightly more expensive. The idea of
mixed media is to provide a constant gradation of pore size in the filter
from coarse on the surface to fine on the bottom. The gradation in pore
size allows filtration and storage of solids throughout the depth of the bed -
as opposed to a single media bed in which filtration takes place in the top.
As a rule, filters cannot be used when the influent suspended solids
exceeds 100 mg/l or when the size distribution of solids changes violently
so that selection of a single media type or mix is impossible. It is also
usually uneconomic to use filters if the required backwash volume exceeds
10 percent of the incoming flow. A better choice would be a chemical
clarifier.
A primary key to successful operation of filters is in the provision for ade-
quate backwash. There must be provision to break up surface slime and
caking. The filters should be kept wet so they do not dry out, breaking
the continuity of the media.
*
Table 111-9 gives a cost estimate for mixed media filtration of 1 mgd of
secondary effluent. It was assumed that filtration was a workable option
for additional removal of suspended solids. This is not always the case.
Secondary effluent suspended solids may be high enough to "blind off"
filters after a short run time (less than 6 hours). When this happens.
-------
CRITERIA
• FLOWs
TABLE IH-9
COST SUMMARY
FILTRATION
SCHEMATIC
• TSS«
• pH
• SEASON:
• AMORTIZATION:
I MGD AVERAGE
2 MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
ENGINEERING, LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
OCTOBER, 1975 DOLLARS
BACKWASH STORAGE
POND
SURGE
POND-
BACKWASH
WATER TO
PLANT
HEADWORKS
FILTER BACKWASH
PUMPS
CLEARWELL-
TO DOWNSTREAM^
TREATMENT
ASSUMPTIONS
o TWO PRESSURE FILTERS WITH 2.5
GPM/FT2 APPLICATION RATE
• 18 GPM/FT2 BACKWASH RATE
• LINED EARTHEN SURGE POND
0 CONCRETE CLEARWELL
COSTS
CAPITAL COST
ANNUAL 0 8 M
AMORTIZED CAPITAL COST
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gol.)
-------
filter backwash volumes become so large that the secondary plant capa-
city must be significantly increased to handle the backwash return flow.
In addition to those shown on the table, the following assumptions in the
development of the estimates should be noted:
o 2 horizontal pressure filters used
o filter rate 2.5 gpm/sf
o 150,000 gal lined earthen surge pond ahead of filters
o 60,000 gal concrete clearwell
o 60,000 gal backwash return surge pond
o polymer dose 1 mg/l
Carbon Adsorption
Carbon adsorption is employed to remove refractory organic compounds
like those causing taste and odor (tannins, lignins, and ethers). It also
removes residual COD, and BOD as well as insecticides, herbicides, and
related components. However, very few tests have been run with activa-
ted carbon treating cannery wastewater.
Carbon adsorption can be done either by granular or powered activated
carbon. The use of powdered carbon still has many problems, not the
least of which is its recovery for reuse. However, the technology of
granular activated carbon in columnar beds is well developed.
The influent to a granular carbon process must be low in BOD, COD, and
suspended solids. The effluent from carbon adsorption can go to ion
exchange, or reverse osmosis and/or disinfection.
A criterion for design is to use upflow expanded bed columns with a contact
time of 20 minutes. The hydraulic rate should be between 6 to 7 gpm/sf
and the granular carbon used should be an 8 x 30 mesh.
86
-------
Carbon adsoprtion is the only method to remove refractory organics with
the exceptions of reverse osmosis, distillation, or freezing - but these
are not competitive.
As a rule, activated carbon cannot be expected to remove reducing sugars
from food processing wastes. Organic acids can, however, be removed to
some extent.
If there are high concentrations of BOD and COD in the influent, the column
can become anaerobic and produce hydrogen sulfide. This is generally not
a problem with filtered secondary effluent. At any rate, the problem can
be solved by frequent backwashing, chlorination, or the addition of
sodium nitrate.
Ion Exchange
There are many applications of ion exchange, from the selective removal
of specific substances such as-ammonia, phosphates, or nitrates, to
the complete demineralization of water.
Ion exchange to remove calcium and magnesium from potable water is
currently practiced by many canners for boiler water treatment. Regen-
erant for these softeners is sodium chloride.
The simplified equations below show the action of a typical cationic ion
exchange resin, during both use and regeneration. R indicates the resin.
Use: RNa + Ca++ -»RCa + 2Na+
Regeneration: RCa + 2NaCI -^RNa2 + CaCI2
87
-------
Dem'liberalization of wastewater requires both cationic and anionic resins
to remove cations (like sodium) and anions (like phosphates), respectively.
These can be mixed in a single bed, but more often, they are set up in
a series of separate*beds. Pilot tests on ion exchange have been run at
Pomona, California since 1965, where carbon column effluent is used as
the feed water. The system contains four resin beds in series: two cationic
and two anionic. The cationic resins are regenerated with sulfuric acid
and the anionic with ammonia. Historically, removals have been as follows:
COD 63.0 percent
Total Dissolved Solids 86.7 percent
Thirteen percent of the volumn treated goes to waste as brine.
Pilot work by Rohm and Haas, Inc., utilizing their modified Desal Process
on disinfected secondary effluent gave the following removals:
COD ' 83.3 percent
TDS approximately 90 percent
No full-scale, long-term installations of ion exchange for dissolved
solids reduction have been operated on wastewater. Very little work has
been done on a pilot scale to test dissolved solids removal in food pro-
cessing wastewater.
Three of the largest problems in the use of ion exchange are (1) in achieving
efficient regeneration of the resin, (2) the disposal or recovery of the waste
regenerant solution, and (3) the length of the resin life.
88
-------
Reverse Osmosis
The natural process of osmosis has been known since the middle of the
eighteenth century, but it was not until the 1950's that experiments were
conducted in reverse osmosis. If fresh and saline water are separated
by a semipermeable membrane, the natural tendency is for the fresh
water to migrate through the membrane into the saline water until the
concentrations of the salts on both sides of the membrane are equal . The
driving force to accomplish this appears as a pressure differential
called osmotic pressure. In reverse osmosis, this osmotic pressure is
exceeded externally, and the flow is reversed through the membrane,
leaving the salts behind and making fresh water from saline water.
The semipermeable membrane is now commercially made of a cellulose
acetate. While reverse osmosis has found application in the reclamation of
sea water and brackish water, use on wastewaters has resulted in
severe problems due to fouling the membrane. In theory, reverse osmosis
has the capacity to remove more than 90 percent of inorganic ions, and
most organic matter.
The most extensive experience in reverse osmosis has been gained from
pilot investigations at Pomona, California. The units there achieved the
following removals from domestic activated sludge effluent:
COD 88.5 percent
92.1 percent
Twenty-five percent of the volume treated went to waste as brine, but this
fraction can be reduced to 15 percent. The flux, or flow rate, through the
membrane is on the order of 10 gpd/sf . Pressure used was 750 psi . For
reverse osmosis to become economically attractive, a flux of 20 to 40 gpd/sf
needs to be attained.
89
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Some low molecular weight organic compounds like amines, alcohols, and
acids are not removed in this process. Reverse osmosis has the greatest
potential for technological improvement of any process for removing dis-
solved solids. Currently, though, it is the most expensive process. In
addition to the need to increase the flux, the product-to=waste ratio needs
to be increased and the problem of disposal of the highly concentrated
brine solved.
CH LORI NATION
Disinfection by chlorination is widely practiced in domestic water and waste
treatment. Disinfection is required here because of the presence of disease
carrying organisms, or pathogens, in the water or waste. Chlorination
is also used in the fruit and vegetable processing industries for odor and
slime growth control in flumes and process units.
So long as sanitary or domestic waste is kept separate from processing
wastewater, there will be no need for final disinfection for pathogen re-
moval. Some food processors are, however, disinfecting the effluent from
their secondary treatment plants.
For 1983, EPA has set guidelines for effluent fecal coliform count at 400 MPN
(Most Probable Number) per 100 ml (6,7). This guideline will probably not
require chlorination if sanitary waste is not included in the processing
wastewater. Fecal coliforms do not multiply outside the intestines of
mammals. Exceptions have been noted in high carbohydrate wastewaters,
such as sugar beets.
If the effluent fecal coliform count for a plant exceeds the EPA limitation,
or if a local requirement is based on total coliforms, then disinfection will
90
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be required. A cost estimate for chlorination of 1.0 mgd of secondary
effluent is given in Table 111-10. The critical assumptions in the estimate
are given in the Table.
Chlorine also oxides BOD and some organic compounds. Thus, the additional
chlorine demand of these compounds must be satisfied before adequate dis-
infection can occur. This has proved to be a considerable problem in
stabilization pond effluent, where the algae exerts a high chlorine demand.
OPERATION AND MAINTENANCE
Regardless of the skill of the designer and the efficiency of a given treat-
ment process, no treatment plant can operate itself. While the level of
skill required varies widely depending on the process selected, every
plant requires regular care and attention.
There is increasing recognition by regulatory agencies of the need for
proper operation and maintenance. It may be a requirement in the future
that an industrial treatment plant operator be certified. In addition, the
testing laboratory performing tests to be submitted to regulatory agencies
i
may have to also be state certified.
An excellent reference for determining staffing requirements for most
treatment plants is "Estimating Staffing for Municipal Wastewater Treatment
Facilities" published in March, 1973 by the Environmental Protection
Agency.
Recognize in using this manual that it is oriented toward municipal treat-
ment facilities. Frequently, in an industrial setting, fewer operating man
hours are required. That is, the plant can be operated as one portion
91
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ITERIA
TABLE ffl-10
COST SUMMARY
CHLORINATION SYSTEM
SCHEMATIC
• FLOW*
• BOD<
• TSS'
SEASON:
AMORTIZATION
I M60 AVERAGE
2 MGD PEAK
1000 mg/l
1000 mg/l
4.5
90 DAYS
10 YEARS AT 12%
• ENGINEERING .LEGAL AND CONTINGENCY
COSTS INCLUDED AT 25% OF
CONSTRUCTION COST
• OCTOBER, 1975 DOLLARS
CHLORINE
SOLUTION
PROCESS
FLOW
CHUDRINATOR
WATER
CHLORINE CYLINDERS
CHLORINE CONTACT
CHAMBER
PROCESS FLOW
TO RNAL
DISPOSAL
ASSUMPTIONS
o CONCRETE CHLORINE CONTACT CHAMBER
WITH I HOUR DETENTION TIME AT
AVERAGE FLOW
o CHLORINE DOSAGE AT 10 mg/l
• CHLORINE COST AT 27.5 CENTS/POUND
o SMALL CHLORINATION BUILDING INCLUDED
COSTS
CAPITAL COST
ANNUAL GSM
AMORTIZED CAPITAL COST-
EQUIVALENT ANNUAL COST
UNIT COST (CENTS/1000 gal.)
38,000
2,800
6,725
9,525
10.6
-------
of the total operating plant and can use the same maintenance crews,
cleanup crews, spare parts and inventory, engineering and technical
staff, as the rest of the plant.
To achieve required removals a biological treatment plant must be
started up (about 2 to 4 weeks) before the start of the pack. Conversely,
the plant must be run for thirty days after the end of the season to com-
pletely digest and dewater the remaining sludge.
Finding adequate qualified staff can be particularly difficult in a seasonal
food processing industry. Two options to an industry's staffing its own
plant are the following:
o Use an outside consulting service with expertise in plant operation
o Contract with the local public agency for operation of the treatment
facility.
93
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Chapter IV
LAND TREATMENT AND DISPOSAL
Land disposal or treatment is the application of wastewater onto land by a
conventional irrigation procedure. Treatment is provided by natural pro-
cesses as the effluent moves through the "filter" provided by the cover
crop and soil mantle. Part of the water is lost to the atmosphere by evapo-
transpiration; part to surface water by overland flow; and the remainder
percolates to the groundwater system. The method of application, the site,
and the loading rate determine the percentage of flow to each destination.
PROCESSES
Four processes have been used successfully for land treatment and disposal of
wastewater. These four processes (described in Table IV-1) are overland
flow, irrigation, high rate irrigation, and infiltration recharge. By far, the
majority of canneries use some kind of high rate irrigation by spray nozzles.
The objective and characteristics of each of the four processes are dis-
tinctly different. The most suitable process depends upon the available
characteristics of the site and the type of waste to be applied. Overland
flow is especially suited to the treatment of wastewaters high in BOD and
suspended solids, such as from tomato processing. Removal efficiencies
greater than 90% have been reported for processing plants using overland
flow. The infiltration-percolation process is least suitable for treatment
and disposal of high BOD and suspended solids wastes because the suspended
solids are forced to infiltrate the soil, allowing little contact time with air.
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Table IV-1
LAND TREATMENT AND DISPOSAL PROCESSES
Process
Overland flow
Irrigation
High Rate
Irrigation
Infiltration-
Percolation
Objective
Maximize water
treatment. Crop
is incidental.
Maximize agri-
cultural pro-
duction.
Maximize water
treatment by
evapo transpira-
tion and perco-
lation with crop
production as a
side benefit.
Recharge water
or filter water;
crop may be grown
with little or no
benefit.
Suitable
Soils
Slow permeability
and/or high water
table.
Suitable for
irrigated agri-
culture.
More permeable
soils suitable
for irrigated
agriculture;
may use marginal
soils if coarse
texture.
Highly permeable
sands and gravels.
Dispersal
of Applied
Water
Most to surface
runoff. Some to
evapotranspi ra-
tion and ground-
water .
Most to evapo-
transpiration.
Some to ground-
water; little
or no runoff.
Evapotranspira-
tion and ground-
water; little
or no runoff
To groundwater
some evapotrans-
pi ration; no
runoff.
Impact on
Quality of
Applied Water
BOD and SS greatly
reduced. Nutrients
reduced by fixation
and crop growth.
TDS increased.
BOD and SS removed,
Most nutrients
consumed in crop
or fixed. TDS
greatly increased.
BOD and SS mostly
removed. Nutrients
reduced. TDS sub-
stantially increased.
BOD and SS reduced.
Little change in.
TDS.
-------
The irrigation process is most effective for removing the nutrients in
wastewater. The application rate is limited so that the nutrient loading
does not exceed the crop nutrient requirement. The nutrients are removed
from the site by crop harvest. Some nutrients are used by crops in over-
land flow, but most will be carried away in the runoff water. Most of the
nutrients are carried into the groundwater or subsurface drainage system
in the infiltration-percolation process. Little, if any, plants are grown
on the site for nutrient uptake.
APPLICATION METHODS
Three methods commonly used for application of wastewater are, (1) sur-
face, (2) drip (or trickle), and (3) sprinkler irrigation. With the surface
irrigation method, water is distributed in furrows or small channels or
by flooding. With drip irrigation, water is applied through small holes
(emitters) spaced along the supply line. In sprinkler irrigation, water is
sprinkled onto the land to simulate rainfall. Sprinkler and surface irri-
gation are most commonly used for wastewater application. Drip irrigation
is generally impractical for use with wastewater because of the need for
very low levels of suspended material to prevent clogging of the holes.
The selection of an irrigation method depends on soil characteristics, crop,
operation, maintenance, topography, costs, water supply, and need for
control of runoff. Each method has distinct advantages.
Surface irrigation depends on soil permeability and soil uniformity for
an even distribution of wastewater. Distribution of water by sprinkler
irrigation is controlled by the selection and design of the equipment used.
If soil conditions are suitable, surface irrigation normally offers economic
advantages in power and hardware requirements.
96
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SITE CRITERIA
Many factors must be considered in selecting a site for agricultural dis-
posal of the waste effluent:
o The soil and topography must be suitable for the disposal process
(overland flow, sprinkling, ponding).
o Areas with continual winds (greater than 10 mph) cannot be used
without great allowances for sprinkler droplet drift.
o Slopes must not exceed 15 percent.
o The site must not have shallow groundwater depths (less than
4 to 5 feet)
o The site should be a short distance from the processing plant, and
it must be easily accessible.
o The site preparation requirements must not be prohibitive
o The site should be situated to allow expansion.
PRETREATMENT REQUIREMENTS
Pretreatment of wastewater before land application is normally necessary.
Screening is often used to separate solids from the wastewater and to aid
in distribution and application of wastewater. Screens (10 to 20 mesh)
are necessary to prevent sprinkler nozzle clogging. Silt and other sus-
pended particles which may hinder operation of the distribution and appli-
cation system should be removed. The pH of the wastewater must be con-
trolled for application on land. Wastewater pH outside the range of 6.4
to 8.4 may render some nutrients (phosphorus and the micronutrients)
inaccessible by plants.
97
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LOADING CONSTRAINTS
Loading rate is subject to several constraints. The rate of water moving
into and through soil depends on its capacity for infiltration and perco-
lation. Discharge quality limits placed on deep percolation to groundwater
or return flow to surface streams may require a limited loading rate or
extensive pretreatment. A soil-crop system has a finite capacity for remo-
val of various pollutants. If this capacity is exceeded, the system will
eventually fail, odors will develop and pollution of groundwater or a
nearby stream can result.
The various constraints on loading may be classified as either hydraulic
or treatment constraints:
Hydraulic Constraints
o Infiltration capacity of the soil
o Permeabilities of the root zone
o Permeabilities of the underlying soil
Treatment Constraints
o Capacity of the soil to filter and assimilate suspended solids
o Capacity of the soil to remove and oxidize BOD
o Capacity of the soil to remove major plant nutrients (nitrogen,
phosphorus and potassium)
o Sensitivity of the soil to other wastewater characteristics such as
salt content, sodium adsorption ratio, and pH
Hydraulic Constraints
The infiltration capacity of a soil is the rate at which water can be applied
without runoff. Previous erosion or lack or a dense vegetative cover will
98
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reduce infiltration capacity and require a reduction in application rates.
The infiltration capacity of the soil will influence the choice of irrigation
methods. Infiltration rate limits the instantaneous rate of application,
but only in rare instances will it limit the total seasonal application.
The permeability of the soil will determine the total of effluent and_ pre-
cipitation that can be applied. In a year with high rainfall, the amount of
effluent which can be applied must be reduced.
Three to five feet of aerated soil is required in the root zone. To provide
sufficient treatment of the applied effluent, the natural drainage capacity of
the soil depends on the permeability, the depth of wetted materials, and
the hydraulic gradient.
If no run-off is allowed, the maximum hydraulic loading is the sum of the
soil moisture depletion by evapotranspiration, plus the quantity of waste
which can be transmitted through the root zone. Maximum hydraulic
loadings less evapotranspiration under ideal conditions for different soils
are given in Table IV-2.
TABLE IV-2
ESTIMATED MAXIMUM HYDRAULIC LOADING
OF WASTEWATER EFFLUENT FOR VARIOUS
SOIL TEXTURES (IDEAL CONDITIONS)
MOVEMENT THROUGH THE SOIL ROOT ZONE*
INCHES/DAY INCHES/YEAR
Fine sandy 15.0 300
Sandy loam 7.5 180
Si It loam 3-5 90
Clay loam 1-5 40
Clay 0-5 10
*Does not include evapotranspiration
99
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The allowable loading rate for infiltration-groundwater recharge is de-
pendent on the soil and surface geology. Recharge of a water-bearing
aquifer will also be dependent on the permeability of the aquifer itself.
If recharge of the aquifer is not an objective, then drainage will likely be
required to control percolation to the water table.
Treatment Constraints
Biochemical oxygen demand (BOD) is associated with both suspended
solids and dissolved organic material. The BOD associated with suspended
solids will remain close to the surface where the soil organisms will have
access to atmospheric oxygen to break the material down. The BOD in the
dissolved organic material will percolate through the unsaturated zone
of the soil and, under aerobic conditions, be removed during percolation.
Soils have remained aerobic under loading rates of hundreds of pounds
per acre with the percentage removals in the upper 90's. Table IV-3
lists typical BOD loading rates for various soil conditions.
TABLE IV-3
BOD LOADING RATES
Ibs/acre/hr Ibs/acre/day
Fallow soif with no fresh organics 1-2 36
Fallow soil following addition of
organic residues 2-4 72
Soil with growing plants 3-6 108
Estimated recommend maximum
BOD load to be added on well
aerated soil 100
Source: American Society of Agronomy, "Irrigation of Agriculture Lands." (1)
Installations with loading rates up to 400 pounds per acre per day have been
successful (2).
100
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Any clogging of soil is principally due to a lack of complete biological
breakdown by organisms in an anaerobic environment. Aerobic conditions
will be maintained with intermittent application of effluent, thus minimi-
zing the chance of soil clogging. In the event that a problem of mechan-
ical clogging due to other suspended particulates does occur, mixing of
the soil by harrowing or disking should effectively correct it. There
is no known instance of a soil structure being permanently damaged
by the addition of inert materials, such as clay, if periodic mixing
of the soil is practiced.
Applied loadings of organic suspended solids average about 70 pounds
per acre per day. Some installations have loaded suspended solids up
to 200 Ibs/acre/day (2).
Nitrogen and phosphorus are the two main problem nutrients in wastewater
Nitrate, the very leachable form of nitrogen, is used by crops. Removal
of the grown crops is a major method of removing nitrogen in the land
treatment process. Denitrification, the conversion of nitrate nitrogen to
nitrogen gas by anaerobic bacteria, will remove significant amounts of
nitrate if the necessary aerobic condition and carbon energy source re-
quirements are met.
Typically, the total nitrogen found in fruit and vegetable wastewaters is
mostly organic nitrogen. All of this nitrogen is not immediately available
for plant use. Generally the "mineralization rate" of organic nitrogen is
such that 20 to 30 percent of it becomes available for plant use in the
first year, 5 percent in the second, 2 percent in the third, and so on.
101
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Since the amount of total available nitrogen is low compared to the amount
of BOD, the controlling parameter in sizing a disposal site for food pro-
cessing wastewater is usually BOD, not nitrogen. Nitrogen is, thus, only
a concern when pollution of underlying groundwater with nitrates is
a possibility.
•
When groundwater quality js_ of concern , the nitrogen loading rate must
be limited so that a balance is reached between the amount of applied, the
amount removed by treatment and cropping, and the concentration allowed
to reach the groundwater. Common applications are 100-150 pounds per
acre per year of available nitrogen.
Phosphorus is removed by crops, cation exchange, precipitation, and
adsorption on iron and aluminum oxides. Little movement of phosphorus
through the soil system with the drainage water will occur as long as the
finite capacity for phosphorus removal is not exceeded. Phosphorus
removal capacity is determined by field measurement.
Caustic peeling processes used for such commodities as potatoes and peaches
produces wastes somewhat high in sodium. Wastes with high sodium con-
tent can be damaging to soil permeability. The effect of sodium on the soil
is measured by the sodium adsorption ratio, SAR, the ratio of sodium (Na)
ion to calcium (Ca) and magnesium (Mg) ions, or:
SAR =
where Na, Ca, and Mg, are measured in equivalents.
The soil SAR must generally not exceed 6.0 to 9.0 depending on the soil
Should the SAR rise to unacceptable levels, gypsum (CaSO^) can some-
times be applied to lower the SAR.
102
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Some wastewater may contain certain constituents which will retard plant
growth or be a potential health hazard. Table IV-4 lists recommended
concentration limits of these constituents for continuous irrigation on all
soils. The limits are for non-sandy, non-acidic soils.
SYSTEM OPERATION AND MANAGEMENT
The major tasks involved in operating a land treatment system include'-
(1) maintaining the proper application rate and frequency, (2) managing
the soil and cover crop, and (3) monitoring the performance of the system.
Scheduling of wastewater applications will be weather dependent. During
wet months, the amount that can be applied will depend upon the daily
precipitation. Applications will also have to be coordinated with harvest.
For the most efficient operation of the system during the wet months, irri-
gation should be scheduled on a daily basis to be able to incorporate the
daily measurement of precipitation and not exceed the application criteria.
Thus, a storage pond is often required to hold the wastewater during times
when it cannot be disposed. This pond must be adequately aerated to
prevent odors.
Experience with potato wastewaters has shown that spray irrigation facili-
ties can be operated during winter months when icing of the field occurs.
Ice is allowed to accumulate in the field, and finally melts during the
spring thaw. The thaw is usually gradual enough so that BOD loading rates
are not greatly exceeded and there are no odors. If the thaw is fast, or if
there is unseasonably warm weather, odors may develop.
Proper soil management is required to maintain the infiltration rate to
prevent erosion. Methods to accomplish this include establishment of a
healthy cover crop and utilization of general soil conservation practices.
103
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TABLE IV-4
RECOMMENDED MAXIMUM LIMITS OF INORGANIC
CONSTITUENTS FOR IRRIGATION WATER
Inorganic
Constituents
Aluminum, mg/l
Arsenic, mg/l
Beryllium, mg/l
Boron, mg/l
Cadmium, mg/l
Chloride, mg/l
Chromium, mg/l
Cobalt, mg/l
Copper, mg/l
Fluor ide, mg/l
Iron, mg/l
Lead, mg/l
Lithium, mg/l
Manganese, mg/l
Molybdenum, mg/l
Nickel, mg/l
Selenium, mg/i
Vanadium, mg/l
Zinc, mg/l
Sodium Absorption Ratio
PH
Recommended Limit
for Irrigation on All
Soils
5.0
0.10
0.10
0.50
0.01
70.0
0.10
0.05
0.20
1.0
5.0
5.0
2.5
0.20
0.01
0.20
0.02
0.10
2.0
6.0-9.0
6.4-8.4
Source: University of California, "Guidelines for Interpretation of
Water Quality for Agriculture". (17)
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Grasses and other crops keep the infiltration rate high by preventing
droplets from sprinkler irrigation from puddling and sealing the surface.
A good cover crop is also necessary to remove nutrients from the soil
treatment system. The crops must be periodically harvested and physically
removed from the site. Monitoring the wastewater characteristics, the
soil, the crop, and the runoff of groundwater, are all very important to
successful operation of a land treatment system. Monitoring these items
will give forwarning of developing problems. Failure in any part of the
system: wastewater quality, soil infiltration, crop growth, or groundwater
drainage, can quickly result in the failure of the whole treatment and dis-
posal system.
COSTS OF ALTERNATIVE APPLICATION METHODS
A comparison of costs for different types of land wastewater treatment
systems is given in Table IV-5. The characteristics of the available
sites will often dictate the type of treatment system that will be feasible.
105
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Table IV-5
Comparison of Capital
and Operating Costs for 1-mgd Spray Irrigation
Overland Flow, and Infiltration-Percolation Systems'
Cost Item
Liquid loading rate, in/wk
Land used, acres
b
Land required, acres
Capital costs
Earthwork
Pumping station
Transmission
Distribution
Collection
Total capital cost
(excluding land)
Q
Amortized cost
Annual operating cost
Spray
Irrigation
2.5
103
124
12,700
61,800
163,200
178,000
0
Overland
Flow
4.0
64
77
79,100
61 , 800
163,200
79,100
7,400
Infiltration-
Percolation
60.0
—
5
12,400
0
163,200
6,200
37,100
415,700
73,600
390,600
69,100
218,900
38,700
Labor
Maintenance
Power
Total operating cost
Total equivalent annual cost
d
Total cost, */ 1,000 gal.
12,400
24,000
7,200
43,600
117,200
130.2
12,400
14,800
7,200
34, 400
103,500
115.0
9,300
4,300
2,200
15,800
54,500
60.6
a. Updated estimate for October 1975 dollars, ENR index 2300, from 1973 ENR
of 1860.
b. 20 percent additional land purchased for buffer zones and additional capacity
c. 12%, 10 year life
d. 90-day season assumed, hence annual flow is 90 million gallons.
UPDATED FROM: Wastewater Treatment and Re-use by Land Application
Prepared for Office of Research and Development, U.S. Environmental Pro-
tection Agency, (12)
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Chapter V
SOLIDS DISPOSAL
SOURCES AND NATURE OF SOLIDS
Because of the nature of food processing, a great many solids are
generated from in-plant processing. These solids, or "residuals"
may exceed the mass of solids generated with full treatment of the
cannery effluent.
The handling and disposal of the cannery and waste treatment solids
varies not only according to the characteristic of each but also as
to the governmental classification of the solids. Currently, transportation
and ultimate disposal of waste solids from treatment plants are more
regulated than waste solids generated in the canning process.
In Plant Solids (Residuals)
It is estimated that only 20 to 30 percent of an original vegetable plant
is finally used for human consumption. Some of this residue is left
behind in the field during harvest, but a large portion is generated
in processing. Table V-1 lists estimates developed in 1971, of the
percentage of raw product that shows up as solid waste, or residuals,
in food processing. The table also shows the amount of the total solid
waste that is used as a by-product, and the amount that is finally handled
and disposed of as a solid waste. By-product utilization is primarily
for animal feed, but some is also used in the production of charcoal
and vinegar. None of the waste is reprocessed and used for human
consumption.
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Table V-1
PERCENTAGE OF SOLID WASTE
PRODUCED IN FOOD PROCESSING
Product
Apples
Beans, green
Beets, carrots
Citrus
Corn
Olives
Peaches
Pears
Peas
Potatoes (white)
Tomatoes
Vegetables (misc.)
Total Waste
Produced
28%
21%
41%
39%
66%
14%
27%
29%
12%
33%
8%
22%
Utilized as
By-Product
19%
10%
21%
38%
62%
12%
9%
9%
8%
29%
2%
9%
Handled as
Solid Waste
9%
11%
20%
1%
4%
2%
18%
20%
4%
4%
6%
13%
These are average percentages of total incoming raw product.
Source: "Waste Disposal Control in the Fruit and Vegetable
Industry" Noyes Data Corp. 1973
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The use of solid waste in livestock feed is not possible for the majority
of canneries. The great majority of solid waste used for feed is generated
by the citrus, corn, pineapple and potato industries. Because of the mag-
nitude of the total production of these four industries alone, the amount of
cannery wastes that are recovered nationwide for use in animal feed is
very high — on the order of 75 percent of the total waste generated.
In most of the other industries, solid waste is disposed in landfill opera-
tions. It is worth noting why these four industries can use their residuals
in livestock operations:
1. The waste solids are generated over a long season — up to a
year's length. The exception here is corn, but corn can be ensiled
and stored for later use. Most other commodities are processed
over a very short season, and the waste cannot be stored for any
reasonable length of time without decomposing.
2. The products are produced in regions where feeding of livestock
in quantity is common.
3. With the exception of potatoes, all the waste from these four commod-
ities are produced dry. Screenings and primary clarifier sludge
are used in the potato industry.
In theSalinas Valley of California, trimmings from the vegetables grown
there are used in primary feeding operations of cattle. Such items as
asparagus, broccoli, lettuce, and artichoke trimmings and process screen-
ings are used in the feeding operation. The final feeding is done entirely
with tailored grain mixes. The operation is, however, a rarity among
food processors of this type.
109
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Most canneries do not fit the three criteria mentioned above for the citrus,
corn, pineapple and potato industry. These canneries must resort to
some type of land disposal. Land disposal is deceptively simple. If
sites are mismanaged or improperly designed, immediate problems such
as odors and breeding of insects may develop. After some time, say five
years, other problems may develop. Pollution of ground water, the destroy-
ing of original vegetation or destroying the ability of the soil to support
any plant life are disasters in land disposal that have occurred.
Treatment Plant Solids
Depending on the processes used and the extent of treatment, solids gen-
erated in waste treatment can be quite significant. Table V-2 gives a
listing and the characteristics of the general types of solids produced in
waste treatment. There are two main categories: screenings and sludges.
Sludges are generated in primary, secondary, and, to some extent, ter-
tiary treatment processes.
Screenings
The amount of screenings vary according to the nature of the waste and
screen mesh size. Screenings are wet and will drain water if allowed to
stand. The drainage of water does not reduce the volume of screenings to
be hauled away, but makes them easier to handle and acceptable in more
landfill sites.
Primary Treatment
Primary treatment wastes are: sludge from the bottom of the clarifier;
scum from the top of the clarifier; and the float from the top of dissolved
air flotation units.
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Table V-2
TREATMENT PLANT SOLIDS CHARACTERISTICS
FRUIT AND VEGETABLE WASTEWATERS
TYPE OF TREATMENT SLUDGE CHARACTERISTIC
Primary Percent solids: 1-4 percent. A
higher percentage of inerts in the
sludge can raise the percentage of
solids to 20-40 percent with the
sludge looking thinner.
Biological Sludge 0.5-1 percent solids from the
clarifier underflow. Because of the
low specific gravity of the solids,
the sludge appears to be very thick.
Pure Oxygen Activated 1-2 percent solids.
Sludge
Lime Clarifier Sludge 7 percent solids.
(Tertiary)
-------
Scum is usually not a problem in food processing wastes. It is unsightly,
but the volumes are small because of the low amounts of oil and grease in
the waste. Dissolved air flotation float commonly has a total solids
concentration of about four to six percent, and is not particularly difficult
to pump, depending on the kind of product being run in the cannery.
Sludge from the bottom of clarifiers can be very difficult to pump, depending
on the kind of product being run in the cannery. For example, field dirt
from tomatoes and potatoes can be thickened to about 40 percent solids,
which can be pumped, but only with positive displacement pumps. This
same mud will only settle and concentrate to about 20 percent solids in a
tank or pond without a thickenting rake. Purely organic sludge from a
primary clarifier will probably not exceed a concentration of three to five
percent solids.
The actual mass (pounds/day) of sludge or float from primary treatment
will be a function of the raw product. The volume (gallons/day) that
contains this mass, however, will be a function of both the product
run and the primary treatment process used.
Secondary Treatment
The masses of sludges generated by secondary treatment processes are
a function of the treatment process used, the BOD load, and the inert
suspended solids load. The biological processes used in secondary treat-
ment all produce sludge in the reduction of BOD.
In biological treatment, dissolved BOD is transformed into microorganism
cellular matter which then settles in the final or secondary clarifier.
The largest sludge producing processes are the high rate processes descri-
bed in Chapter III. Of these, the activated sludge process produces the
most sludge. In fact, a good generalization would be: the better the
treatment obtained, the more sludge generated.
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Stabilization ponds and aerated ponds take several years to accumulate
enough sludge on the bottom of the ponds to require removal. On the other
extreme, an activated sludge plant, operating at a very high rate, requires
daily removal of a significant quantity of sludge to keep treatment effi-
ciency high.
An activated sludge plant, operating at a high rate (or low sludge age) will
require the removal of up to 0.6 pounds of microorganisms for each pound
of BOD treated. It's not difficult to see that treatment of food processing
wastes, with BOD loadings as high as ten times those of domestic waste,
leads to significant sludge handling and disposal problems.
Sludge from secondary treatment systems is still biologically active, and
if let alone will naturally putrefy. This may result in an intolerable odor
problem for a cannery. If the sludge contains no wastes of human origin,
it may be possible to spread and dry the sludge quickly on a disposal site
or agricultural land, and then plow it into the soil.
If the sludge is not handled in this manner, it must be stabilized.
The remaining organics must be oxidized, "burnt up", prior to disposal
to a landfill site or a reclamation project.
Typically, secondary sludge does not dewater as well as primary on
vacuum filters or centrifuges. Raw, undigested secondary sludge has a
total solids content of only one-half to one percent. In addition, the cellu-
lar matter itself in the sludge is only fifteen percent solids. Unless the
cells membranes are ruptured, pure secondary sludge cannot be dewatered
beyond fifteen percent solids.
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Tertiary Treatment
With the exception of chemical clarification, none of the tertiary treatment
processes discussed in the previous chapter generate a solid waste.
Reverse osmosis and ion exchange produce a waste brine or concentrate,
which is probably best handled by evaporation and disposal in a landfill.
Spent carbon in columns, if not regenerated, becomes a solid waste, but
is usually acceptable for disposal in a sanitary landfill. Backwash water
from filters is usually stored and pumped at a constant rate back to the
treatment plant headworks.
Sludge from tertiary chemical clarifiers varies in handling ability according
to the coagulants used in the treatment process. Lime sludge is quite
dense, about seven percent solids, and can be dewatered rather well on
vacuum filters or centrifuges. Lime sludge lines should be oversized to
allow for scaling in the lines and ease of cleaning. Alum sludge, on the
other hand, is quite light and gelatinous and can prove to be quite diffi-
cult to dewater. Vacuum filters seem to do best with this sludge. Ferric
chloride sludge are usually not difficult to dewater, but they are messy.
Vacuum filters are usually used with ferric sludges.
Unless a secondary plant is upset, tertiary chemical clarifier sludge will
not contain much organics, so there is usually no need to further stabilize
the sludge against putrefication. Most municipal treatment plants that use
a tertiary chemical clarifier either incinerate all the raw sludge, or
digest the biological sludge, mix it with the chemical sludge, and then
incinerate them together.
Solids Handling
Table V-3 gives a listing of the available options most commonly used in
the handling of waste solids from canneries. The options apply best to
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Table V-3
SOLIDS HANDLING OPTIONS
Digestion
Thickening
Dewatering
Disposal
Anaerobic
Aerobic
Gravity
Dissolved Air
Flotation
Centrifuge
Vacuum Filter
Centrifuge
Pressure Filter
Dewatering Belts
Drying Beds
*Use of waste activated sludge for animal feeding operation is not
approved by the U. S. Food and Drug Administration
Sanitary Landfill
Disposal on Soil
Animal Feeding*
Composting
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waste solids from waste treatment operations. Waste solids generated in
the cannery are commonly disposed in three ways: (1) disposal in a
landfill, (2) spreading on fallow agricultural lands, or (3) used in
animal feeding operations.
Solids treatment and disposal from waste treatment operations comprises
a substantial fraction of the capital cost of treatment and the annual oper-
ation and maintenance (see Tables III-6A and -6B) .
DIGESTION
There are two types of biological sludge digestion processes. Anaerobic
digestion has been practiced for many years at municipal treatment plants
across the country. The anaerobic system is sensitive and prone to upset.
It must be heated for good operation. The tanks must be covered and the
generated methane gas safely handled—either as a fuel or just burnt (flamed)
A well operating anaerobic digester will reducd about fifty to sixty percent
of the volatile, or organic fraction, in the sludge. It operates well on
domestic primary sludge alone. Few cannery sludges have been digested
without combination of domestic waste. The required retention time of
sludge in a digester is about twenty days when maintained at 90 degrees
Fahrenheit.
Aerobic digestion makes more sense for small plants (treating less than
5 mgd), or for seasonally operated plants like those treating cannery waste.
Aerobic digestion allows the metabolic processes of the microorganisms used
in treatment to continue, but in the absence of food (BOD) . The organisms
continue metabolizing at decreasing rates (termed "endogenous respiration")
in the digester. Aerobic digestion is not as efficient as anaerobic, reducing
only up to 40 percent of the volatile matter. Detention times of the sludge in
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this kind of digester is only 15 to 20 days. Enough air is supplied to the
open digester, either by diffusion or mechanical means, to satisfy the
oxygen requirements of the organisms.
Regardless of the method of digestion chosen, it should be realized that
the digester will have to be kept running for twenty to thirty days after
the end of the processing season to stabilize the remaining sludge.
THICKENING
Thickening is used to reduce the volume of sludge so a smaller dewatering
device can be built (vacuum filter), or to control sludge thickness for
optimal operation of the dewatering devices.
Three units are commonly used for thickening sludge: gravity thickeners,
dissolved air flotation thickeners, and centrifuges.
Dissolved air flotation thickeners are the same as air flotation clarifiers,
but operated at higher solids loading rates. Gravity thickeners look like
ordinary clarifiers, with the exception that the clarifier rake is changed to
rotate faster, and gently agitate the sludge. Representative design cri-
teria for thickeners are given in Table V-4.
DEWATERING
Dewatering lowers water content of sludges to facilitate disposal, whether
to landfill or to incineration. Before sludge can be hauled in open trucks,
it must be dewatered so that it no longer flows. A solid sludge is also easier
to spread in a landfill operation. Prior to incineration, sludge must be con-
centrated so that it will support combustion. The exact point of allowable
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Table V-4
DESIGN CRITERIA SOLIDS HANDLING DEVICES
FRUIT AND VEGETABLE WASTEWATERS
DIGESTION
ANAEROBIC
Retention Time
Ideal Temperature
Total Solids Reduction
Methane Production
Solids Loading
20-30 days, depending on whether
the digester is heated.
90-100 degrees Fahrenheit.
45-50 percent
8-12 cf/lb volatile solids.
Standard Rate: 0.03-0.10 Ib
volatile solids/cf/day
High Rate: 0.1-0.4 Ib volatile
solids/cf/day.
AEROBIC
Retention Time
Solids Loading
Oxygen Requirement
10-20 days, depending on the
sludge age of the activated
sludge system and the ambient
temperature.
0.1-0.2 Ib volatile solids/cf/day.
1 .5-2.0 Ibs/lb of volatile solids
destroyed.
THICKENING
GRAVITY
Solids Loading
Overflow Rates
DISSOLVED AIR FLOTATION
Solids Loading
Overflow Rates
4-15 Ibs solids/sf/day, depending
on the concentration of the
incoming sludge.
400-900 gpd/sf
1.5-2 Ibs/sf/hour
1,400-5,000 gpd/sf
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Air to Solids Ratio
Recycle Rate
0.01-0.1 Ib/lb
1-3
DEWATERING
VACUUM FILTERS
Common Yields
Cake Total Solids
Content
Chemical Conditioning
Dose
Lime
Ferric Chloride
Polymer
1-4 Ibs of dry solids/hour per
sq ft of drum area for organic
material.
8-10 Ibs/hr/sf for properly
conditioned silt and clay.
11-13 percent for waste activated
sludge. 20-70 percent for silt
or clay.
5-10 percent of the sludge dry solids
2-4 percent
1/4-2 percent
CENTRIFUGES
Cake Total Solids
Content
Solids Capture
Common Capacities
4-25 percent, depending on the
use of chemicals and type of
centrifuge. For waste activated
sludge, the solids content achieved
is
Solid bowl type: 8-10%,
Disk nozzle type: 4-5%
Basket type: 7-10%
60-70 percent without chemicals.
Up to 95 percent with chemicals.
10-300 gpm.
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moisture content for incineration must be determined separately for each
sludge and incinerator. Typically, allowable moisture contents vary from
70 to 80 percent (20 to 30 percent TS).
There are several kinds of dewatering units available. The most common
are vacuum filters and centrifuges, but filter presses and capillary action
devices may be used.
Vacuum Filters
A common type of vacuum filter is shown on Figure V-1. The sludge is
pumped into a vat or pan at the base of the filter. The sludge level is
usually high enough to submerge the filter drum to about thirty to forty
percent of the diameter of the drum. A vacuum applied to the drum (about
10 to 20 inches of mercury) picks up the sludge and forms a cake during
the time the drum is submerged. As the drum rotates out of the sludge,
air is pulled through the sludge cake, drying it so that it cracks and falls
off the filter cloth before the cloth is resubmerged.
The yield, or rate of sludge dewatering, of a vacuum filter is about 2 to
10 pounds of dry sludge per hour for each square foot of filter drum area.
To achieve this yield for most secondary sludges, and some primary ones,
the sludges must be conditioned by the addition of chemicals. Although
the addition of chemicals to the sludge can solve a lot of problems with
filtration, the key to successful filter operation is proper thickness or
dryness of the incoming sludge.
Most problems experienced with vacuum filters operating on secondary
biological sludge stem from lack of sufficient drying of the filter cake.
With insufficient drying, the cake will not discharge from the cloth, and
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Filter Cake Discharging
Vat or Pan
Containing Sludge
FIG. "2-1 VACUUM FILTER
(Courtesy of Envirex)
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is flushed off by the wash sprays. The cake is consequently recycled
to the treatment system, and may overload and cause failure of the process.
Vacuum filters have a high capital cost and are difficult to operate,
sometimes requiring one man solely assigned to the operation of the filter.
When feasible, many newly constructed secondary treatment plants are
now using centrifuges.
Centrifuges
Three types of centrifuges are now commercially available. The solid
bowl centrifuge (Figure V-2) is more suitable for the dewatering of in-
organic sludges. Disc nozzle (Figure V-3) and basket centrifuges
(Figure V-4) seem to work better on organic sludges, but the disc
nozzle type tend to clog at high concentrations of sludge, or when proper
sludge pretreatment (grit removal, screening) is not provided.
Centrifuges typically do not produce as dry a product as vacuum filters,
but they are cheaper and considerably easier to operate. They may also
be operated with wetter sludges as feed.
Other Methods
Filter presses, or pressure filters seem to be able to work extremely well
on several sludges and at several different feed moisture contents. They
are, however, quite expensive, and can be difficult to operate and maintain.
They are seldom used in waste treatment applications.
There are about three different units on the market that use a combination
gravity and capillary action to dewater sludge. These units rely on a por-
ous cloth to suck up water from the sludge as it is squeezed between rollers.
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GEAR BOX
TORQUf.
CONTROL
OVERLOAD
SWITCH
ADJUSTABLE
PLATE DAM
CONVEYOR
IMPELLERS
PILLOW BLOCK
BEARING
INSPECTION PLATE
FEED TU8E
OIL FEED
TO BEARINGS
CONVEYOR DISCHARGE
NOZZLES
OIL DISCHARGE
FROM BEARINGS
VIBRATION SWITCH
FIG. ¥-2 SOLID BOWL CENTRIFUGE
(Courtesy of Sharpies)
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Centrate
Solids
K l\ R. 1= L IE
FIG. ¥-3 DISC NOZZLE CENTRIFUGE
( Courtesy of Sharnlps
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Feed
Knife
FIG.Y-4 BASKET CENTRIFUGE
(Courtesy of Sharpies)
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These units are easy to operate, but are of low capacity. They cannot be
universally applied to different sludges, and appear to work best on
waste activated sludges from domestic treatment plants. They should be
thouroughly tested before being applied to cannery waste. A typical
unit is illustrated on Figure V-5.
Sludge Drying Beds and Lagoons
In localities with dry weather during the processing season, sludge drying
beds and sludge lagoons may be effectively used to dewater digested sludge
for disposal. Drying beds are constructed with sand bottoms and an under-
drain system to capture water that percolates down through the sludge.
Digested sludge is pumped to each bed, until the depth reaches about 18
inches, then new sludge is pumped to another bed. Water evaporates from
the sludge surface and also percolates down through the bed. The drained
water is returned to the treatment plant headworks. When sufficiently
dry, the sludge is taken out with a skip loader. So long as the sludge is
adequately digested, the drying beds will only have a slight musty odor,
which should not be a problem
Sludge lagoons differ from beds in that they are deeper (about two to
three feet), and do not have a sand blanket with underdrains. If suffi-
ciently dry, the sludge may be taken out with a skip loader, otherwise
it must be removed removed with a clamshell bucket.
METHODS OF DISPOSAL
The ultimate disposal of sludge is becoming more a problem. Most munici-
pal treatment plants are now disposing dewatered digested sludge in some
type of landfill operation. In-plant solids from most canneries are disposed
in landfill operations, usually run by a municipality. These sites are
filling, consequently canneries are being asked to go elsewhere with their waste
solids.
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FIG. ¥-5 GRAVITY SLUDGE DEWATERING UNIT
(Courtesy of CH2M HILL)
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Some canneries are now operating their own land disposal system for
cannery solids and treatment plant sludge.
Many canneries are able to dispose of some portion of their waste, usually
screenings, to animal feeding operations. Because of the relatively low
food value of cannery screenings, they must be mixed with grains or other
common feedstuffs to provide a balanced diet for animals. Because of the
specific dietary requirements of many animals and the variability of goals
of feeding (egg versus meat production for poultry, for example), feeding
studies should be performed prior to staring such a program. As a rule,
the lack of nutrients in cannery waste coupled with the seasonality of
cannery waste, does not make the use of this waste attractive to animal
feeders. Transportation costs are another factor making this option un-
attractive. Year-round operations, like potato processing for example, have
been successful in setting up operations with local feed lots to accept
screenings and primary sludge.
LAND DISPOSAL OF WASTE SOLIDS
Land application of waste solids can be grouped into two methods:
(1) fertilizer, and (2) disposal. The objective of the fertilizer method is
to maximize crop production while using the waste solids for nutrients
and soil conditioning. The loading rates are relatively low compared
to the disposal method. Any soils suitable for high-production agriculture
will generally be suitable for application of waste solids. Clayey soils
or other soils with low organic matter will receive special benefit
from this use. Loading rates are on the order of 3 to 10 tons of dry solids
per acre per year.
The objective of the disposal method is to maximize disposal by incorporating
large amounts of the waste solids into the soil. A crop is maintained mainly
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to enhance site appearance, minimize wind erosion, take up moisture, or
utilize some of the nutrients in the waste solids. Loading rates are on the
order of 5 to 50 tons per year.
Pretreatment Requirements
Waste solids from food processing vary greatly in character and pre-
treatment requirements, depending upon the type of food processed and
the method of processing. Adjustment of the pH will be required before
land application if it is much below 6.4 or above 8.4. These limits will vary,
depending on the texture and buffering capacity of the soil, and the loading
rate. The waste solids may need to be stabilized by biological treatment
so that rapid degradation and odor do not result when the waste solids
are applied to land. The solids may need to be ground up to allow better
incorporation into the soil and better operation of application equipment.
Dewatering of waste solids will generally be advantageous to a land dis-
posal system. It will result in less volume to be handled and may require
a smaller disposal site.
Application and Incorporation Methods
A waste solid can be applied to land by several different methods. As
a liquid, it can be injected or plowed under the surface, or it can be sprayed
on if it is screened to prevent plugging of nozzles. As a solid, it can be
spread by equipment such as manure spreaders. The selection of the
suitable method depends upon soil characteristics, crop, labor requirements,
maintenance, topography, and costs.
Many problems have developed regarding methods of incorporating the
waste solids into the soil. The waste must generally not be allowed to
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remain on the soil surface for a long time because of odor, insect, and wind
and water erosion problems which often result. Insect problems may
develop even when liquid waste solids are immediately incorporated into
the soil. This has been prevented by spreading the waste in a thin layer
and allowing it to remain on the surface just long enough to dry before
tilling into the soil.
Site Selection Criteria
The criteria for solids waste disposal site selection are generally the same
as those listed for a waste effluent disposal site with the following exceptions:
o Hydraulic loading will normally not be as great; therefore, the
subsurface permeability is not as important.
o Waste solids application will generally have a more adverse appear-
ance than effluent application; therefore, a more remote or conceal-
able site should be selected.
Application Rate Constraints
The waste solids application rate will be limited by several constraints.
In comparison to the limits to effluent loading,the following differences
are evident. The hydraulic loading limits, infiltration capacity, root
zone permeability, and geologic permeability are less important because
relatively minor amounts of water will generally be applied with the waste
solids. Factors such as nutrient balances and BOD will reach a maximum
before hydraulic loading does. The most common limiting factor of waste
solids application is the solids loading rate. Solids must be incorporated
into the soil as applied or very shortly thereafter. Limits exist on much
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organic solids can be physically incorporated into the soil, and the soil's
ability to decompose solids wihout causing plant toxicity problems. Other
factors such as SAR and pH may also limit waste solids application. All of the
above-mentioned factors vary greatly between types of food processed and
the method of processing and waste pretreatment. The loading rate must
be studied carefully in each case.
Management and Operation
Proper management and operation of a waste solids disposal system is as
important as for a waste effluent treatment and disposal system. A major
factor of operation is the timing of waste solids application to the land.
In a fertilizer application system where crop production is optimized, waste
solids cannot be applied and tilled into the soil while the crop is growing.
Tillage would kill the crop. The best times for waste solids application are
in the spring, before the crop is planted, and in the summer or fall,
after the crop is harvested. Cropping areas and disposal areas can be
alternated. The method of disposal used—either fertilizer or disposal—will
depend greatly on who owns the site and who operates the system. A farmer
will want to maximize crop production, and a cannery will want to maximize
waste disposal. Other practices, such as crop and soil management and
monitoring, are also important as noted in the discussion of waste effluent
treatment and disposal.
Cost of Waste Solids Delivery and Application
The cost of disposing of waste solids onto land can vary greatly depending
on the amount of liquid with the solids, on the distance of transportation,
and on the method of delivery and application. Some typical recent costs for
solids hauling are given in Table V-5. Actual costs vary considerably due
to differences in disposal sites, governmental regulations, availability of
trucking firms, and pretreatment requirements. The costs given in the
Table do not include pretreatment or site preparation costs.
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TABLE V-5
COST RANGES OF SOLIDS HAULING AND DISPOSAL
Hauling of Liquid Sludge (4-15% TS)
to Ponding Site (20 mile haul)
4 to 5 cents/gallon
includes disposal fee of
3J cents per gallon
Hauling of Liquid Sludge (4% TS)
to Farm Land (35 mile haul)
2 cents/gallon
or $3.70/ton-mile
Hauling of Screenings, Mud to
Land Fill
$4.00/cubic yard -
includes disposal fee
of $1.00/cubic yard
Hauttng, Spreading of Dewatered
Sludge to Disposal Site (5 mi haul)
$1 to $2/ton-mile
Hauling, Spreading of Liquid
Sludge to Disposal Site (5 mi haul)
$3 to $4/ton-mile
Hauling of Hazardous Waste
(acid, caustic) to Evaporation Ponds
8-10 cents/gallon
includes disposal fee
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LIST OF REFERENCES
1. American Society of Agronomy, "Irrigation of
Agriculture Lands", Agronomy Series No. 11,
Madison, Wisconsin 1967.
2. American Public Works Association, "Survey of
Faciltiies Using Land Application of Wastewater,"
July 1973.
3. Ben-Gera, I., and A. Kramer, "The Utilization of Food
Industries Wastes," Advances in Food Research, 17,
1969.
4. Environmental Protection Agency, "Aerobic Secondary
Treatment of Potato Processing Wastes." December 1970.
5. Environmental Protection Agency, "Demonstration of a
Full-Scale Waste Treatment System for a Cannery,"
September 1971.
6. Environmental Protection Agency, "Development Document
for Effluent Limitations Guidelines for the Apple,
Citrus, and Potato Processing Categories." March 1974.
7. Environmental Protection Agency, "Development Document
for Proposed Effluent Limitation Guidelines.. .for the
Fruits and Vegetable Point Source Category," October
1975. Draft.
8. Environmental Protection Agency, "Proceedings, Fifth
National Symposium on Food Processing Wastes," June
1974.
9. Environmental Protection Agency, "Proceedings, Fourth
National Symposium on Food Processing Wastes," December
1973.
10. Environmental Protection Agency, "Liquid Wastes from
Canning and Freezing and Vegetables," August 1971.
11. Environmental Protection Agency, "Treatment of Citrus
Processing Wastes," October 1970.
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12. Environmental Protection Agency, "Wastewater Treatment
and Re-Use by Land Application," August 1973.
13. National Canners Association. "Management of Solid
Residuals." 1971 Research Highlights.
14. National Canners Association, "Solid Waste Management
in the Food Processing Industry," 1973.
15. Noyes Data Corporation, "Waste Disposal Control in the
Fruit and Vegetable Industry." 1973.
16. Oregon State University Water Resources Research
Institute, "Characterization of Fruit and Vegetable
Processing Wastewaters," January 1975.
17. University of California Extension, "Guidelines for
Interpretation of Water Quality for Agriculture."
15 January 1975.
U.S. GOVERNMENT PRINTING OFFICE: 1975-21M10:S5
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