Pollution Abat
tflTltfll
t
in the Fruit and
Vegetable Industry
In-Plant Control of
Process Wastewater
EPATechndogy Transfer Seminar Publication
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EPA—625/3-77-0007
POLLUTION ABATEMENT IN THE
FRUIT AND VEGETABLE INDUSTRY
In-Plant Control of
Process Wastewater
ENVIRONMENTAL PROTECTION AGENCY
Environmental Research Information Center • Technology Transfer
July 1977
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ACKNOWLEDGMENT
This seminar publication contains materials prepared for the
United States Environmental Protection Agency Technology Trans-
fer Program and presented at industrial pollution-control seminars
for the fruit and vegetable processing industry.
The Technology Transfer Program extends its appreciation to the
Food Processors Institute and the National Canners Association
for their work in preparing the publication.
NOTICE
The mention of trade names or commercial products in this publication is for
illustration purposes, and does not constitute endorsement or recommendation for use
by the U.S. Environmental Protection Agency.
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CONTENTS
Page
Chapter I. Introduction 1
Chapter II. Data Accumulation 2
The In-Plant Survey 2
Monitoring Program 3
Flow Measurement 3
Sampling Procedures 17
Sample Preservation 20
Analytical Program 21
Data Analysis 23
Chapter III. Factors Influencing Waste Generation 25
Commodity 25
Raw Product Condition 25
Harvest And Transport 25
Preparation Procedures And Equipment 27
Chapter IV. In-Plant Modifications and Effects 32
A. Water Conservation Techniques 32
Guidelines For Water Use 33
Beneficial Results From Water Conservation 33
The Cost Of Water 34
Product Washing And Rinsing 34
Potential Uses Of Water 40
Water Recirculation Systems 42
The Counterflow Water Reuse System 45
Special Water Reuse Systems 50
pH Control Of Recirculated Water 53
B. Disinfection 58
Chlorine And Chlorine Compounds 58
In-Plant Chlorination 62
lodophors 66
Ozone 68
Comparative Effectiveness of Selected Germicides 72
Other Chemical And Physical Germicidal Agents 72
C. Waste Prevention 76
In-Plant Handling Of Solid Wastes 76
Residuals From Specific Operations 77
Example 1 — Peeling of Table Beets 82
Example 2 — Cling Peach Peeling 83
Example 3 — Peeling of Tomatoes 83
Example 4 — Infrared Dry-Caustic Process 86
Additional Dry Peel Removal Studies 87
Product Conveying ,98
Plant Cleaning 100
in
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CONTENTS
Page
References 103
Appendix A. Approved Test Procedures 107
LIST OF FIGURES
II-l Propeller-type flow meter 5
II-2 Common forms of weir plates 7
II-3 Flow over sharp-crested weir g
II-4 Dimensions and capacities of the Parshall measuring flume,
for various throat widths, W(4) ;Q
II-5 Flow curves for Parshall flumes ^2
II-6 Various shapes of Palmer-Bowlus flumes 15
II-7 Measurement of X and Y dimensions for open-pipe
flow measurements lg
II-8 Operating principle of the electromagnetic flow meter 17
III-l Generated wastewater, average and 95% limits 26
III-2 Generated BOD, average and 95% limits 26
III-3 Tomatoes, peeling and BOD generation, with 95% limits 28
III-4 Effect of immersion and cutting on pollution 30
IV-1 Recommended placement of sprays 37
IV-2 Reuse of final rinse water 38
IV-3 Chlorination of can cooling water recycled over a cooling tower 43
IV-4 Diagram of water flow in a flume system 44
IV-5 Barometric condenser water 45
IV-6 General plan for counterflow reuse of flume water in a
pea cannery 47
IV-7 Plan of counterflow reuse system designed to eliminate undesirable
features of flume system shown in figure IV-4 47
IV-8 Plan for counterflow reuse of water in a pea cannery where line
arrangements require extensive fluming operations 48
IV-9 Triple duty water reuse system 51
IV-10 Diagram of charcoal filtration water recovery system 52
IV-11 Effect of pH control on the growth of bacterial cells 55
IV-12 pH control system 55
IV-13 Break-point curve 59
IV-14 The process of ozone generation 68
IV-15 Germicidal activity of ozone and chlorine 70
IV-16 Toxicity of ozone • 72
IV-17 Comparative effects of the sporicidal properties of
chlorine, iodophor and ozone 73
IV
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LIST OF FIGURES (Continued)
Page
IV-18 Dry handling solid wastes 77
IV-19 Pilot scale cleaning line 79
IV-20 Schematic of dry-caustic peeler 84
IV-21 Pilot scale peeling line 85
IV-22 Individual quick blanching unit 89
IV-23 Schematic diagram of vibratory blancher cooler 93
IV-24 One ton per hour vibratory blancher cooler 97
IV-25 Negative air conveying system 100
LIST OF TABLES
II-l Discharge over 90 V-notch weir 9
II-2 Cross-sectional area of water in pipes at various
depths of flow 14
II-3 Commercial laboratory fees for significant food processing
wastewater parameters 22
II-4 Major wastewater parameters (fruit and vegetable
processing industry) 23
III-l Wastewater and generated pollution loads by commodity 27
IV-1 Use of water in washing fruits and vegetables 36
IV-2 Effectiveness of washing in removing extraneous matter 37
IV-3 Water-economy check list 41
IV-4 Comparison of total numbers of bacteria in flume waters 46
IV-5 Effect of water recovery system on water usage in
canning green beans 54
IV-6 Characteristics of fruit pumping water
(24 hours of operation) 56
IV-7 Citric acid consumption at various fresh water flow rates 56
IV-8 Comparison of control & test systems 57
IV-9 Comparison of killing power of hypochlorites and gaseous chlorine 60
IV-10 The effect of temperature on sporicidal properties
of calcium hypochlorite solutions 61
IV-11 Solubility of chlorine in water at different temperatures 61
IV-12 Effect of organic matter on concentration of free
chlorine residual in water 62
IV-13 Effect of chlorine treatment on flavor of canned foods 63
IV-14 Effect of chlorine on metal and other surfaces 64
IV-15 Effect of temperature on the germicidal action
of iodine solutions at pH 7.5 67
IV-16 Germicidal action of ozone against E. coli, S. marcescens, and Ps. aeruginosa in
tap water 69
IV-17 Methods suitable for in-plant handling of food residuals 78
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LIST OF TABLES (Continued)
Page
IV-18 In-plant handling methods for fruit and vegetable residuals 78
IV-19 Soil, total bacterial count, and mesospore count on tomatoes at
selected points in cleaning operations 80
IV-20 Commercial dry-caustic peeling of root crops in 1974 82
IV-21 Water usage and properties of effluent waste flow in two
different peeling operations of beets 83
IV-22 Hydraulic versus mechanical peel removal for cling peaches 85
IV-23 Average water usage and peeler effluent characteristics 86
IV-24 Caustic peeling of peaches — reduction of peeling
wastes with Magnuscrubber 87
IV-25 Peach canning — reduction of total plant wastes
with Magnuscrubber 87
IV-26 Caustic peeling of tomatoes — reduction of peeling
wastes with Magnuscrubber 88
IV-27 Tomato canning — reduction of total plant wastes
with Magnuscrubber 88
IV-28 Effect of pre-conditioning treatments on blancher effluent and
product yield for 3/8 inch carrot cubes 90
IV-29 In-plant hot gas blanching of vegetables 91
IV-30 Reductions due to use of hot gas blanching of vegetables 92
IV-31 Typical operating conditions 94
IV-32 Comparison of yields and solids loss in effluent for green
beans between combined blanching and cooling vs conventional
blanching and flume cooling 95
IV-33 Comparison of effluent from green beans for combined blanching
and cooling and conventional blanching and flume cooling 95
IV-34 Comparison of operating parameters for the blanching and
cooling of green beans 96
VI
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Chapter I
INTRODUCTION
The use of water is inherent to processing operations associated with the preparation and
preservation of fruits and vegetables.
• Water is in intimate contact with most foods during their preparation and processing.
It is universally used for washing raw commodities and is used as an ingredient in
formulation of many foods, often serving as the sole or principal packing medium.
• Water is the vehicle for transfer of power and heat. It is used to transport raw
materials to and from unit operations. Vegetables are immersed in hot water or
exposed to live steam in blanching to inactivate enzymes and to wilt leafy vegetables
to facilitate their filling into suitable containers.
• Water is the primary agent used for cleaning and sanitizing processing equipment;
these steps are essential to assuring the production of nutritious and wholesome foods.
With the exception of the water used in steam production and used as the packing medium
for canned products, all other uses result in the generation of wastewaters containing various con-
centrations of pollutants which are largely organic in nature.
Pollution control of all industrial wastewaters has been legislated on the national level by the
Federal Water Pollution Control Act Amendments of 1972 (FWPCA), and on the state level by
numerous laws enacted before and since the FWPCA. These laws, as well as the myriad of regula-
tions precipitated thereby, necessitate careful management of industrial wastewaters, beginning
with minimization of pollutant generation, followed by proper collection and handling, and
ultimately concluding with adequate treatment and disposal.
The following chapters of this volume deal primarily with measures which can be used to
reduce water consumption and minimize pollutant generation through proper management of food
processing operations; that is, pollution controls within food processing plants. Pollution controls
through treatment and proper disposal are discussed in a separate volume. These chapters are •
intended to serve as guides for planning and implementing pollution abatement programs.
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Chapter II
DATA ACCUMULATION
Planning and implementation of effective water conservation and/or waste treatment and
disposal programs necessitate the availability of factual data accumulated from each step in the
fruit and vegetable processing plant. The accumulation of this necessary information can be assured
only through a well-planned and carefully executed water-wastewater survey program. Some items
of information which must be developed during such surveys are:
• The locations of both fresh water and wastewater flows within the plant.
• The volumes of water utilized and discharged by each unit operation.
• The pollutional load generated by each unit operation.
• The hydraulic and organic load (raw waste load) of the plant effluent for each product
or product combination.
THE IN-PLANT SURVEY
The information collected during an in-plant survey is especially useful for two purposes:
1. For use in an in-plant pollution control program. The survey should be designed to
critically evaluate each processing unit with the objective of reducing waste loads at the
point of generation. Operations in which water is being excessively used will be quickly
identified, enabling corrective measures to be taken to reduce these obvious contributions
to the hydraulic load. Further reductions in water consumption, and hence, wastewater
generation, will be possible through water reuse systems which can be efficiently designed
with the data collected during the survey program.
2. For use in the design of a treatment facility which will adequately reduce all waste loads
to the level required for discharge to a receiving stream. The data collected during the
survey should include the physical and chemical characteristics of each waste stream.
Relatively clean wastewater sources can then be identified, and segregation for separate
disposal or reuse can be considered. Waste streams containing high concentrations of
pollutants can be characterized and appropriate treatment systems designed for their
disposal; users of municipal facilities will be able to predict their sewer service charges
with appropriate data.
The survey program is an intensive data-collecting project which can be accomplished during
the course of a single season. Suggested procedures for such a program are outlined below. Details
pertaining to each of these steps may be found in the remaining sections of this chapter.
1. Draw a map of the plant, indicating all water supply lines and wastewater flows.
2. Select appropriate methods of flow measurement. Install measuring devices where
necessary.
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3. Select sample collection sites and establish a sampling schedule. The survey program
should be designed to develop data which reflect changes in waste characteristics that
inherently occur throughout the season.
4. Determine laboratory analyses to be made. Review test procedures to determine
chemicals and equipment required.
5. Proceed with development of data.
6. Correlate production records (tons of raw product processed or cases of finished product
produced) to water flows and to laboratory results. The accumulated data can then be
used to predict estimated effects of subsequent operational changes, such as equipment
modifications, production changes, and water conservation measures.
MONITORING PROGRAM
The primary purpose of a wastewater monitoring program is to provide information by which
the operating efficiency of pollution control programs can be evaluated. As a minimum, continuous
monitoring of the plant effluent stream(s) and treatment system discharge(s), when applicable,
should be conducted. The in-plant survey previously described may indicate additional desirable
monitoring points.
Since monitoring information is continuously gathered and should be routinely recorded, it is
convenient to provide permanently installed equipment for measuring and recording flows, and for
collecting representative samples of wastewater for laboratory analysis. Various types of equipment
are discussed in the ensuing sections.
Although the purpose of a monitoring program differs somewhat from that of a survey pro-
gram, the basic information collected is essentially identical. Suggested procedures are outlined
below. Details of each step are described in the remaining sections of this chapter.
1. Revise the map drawn for the in-plant survey to reflect any modifications which may
have been made to the water and wastewater flows. Expand the map to include existing
wastewater treatment/disposal facilities.
2. Select appropriate monitoring points for each wastewater stream being discharged from
the plant, as well as appropriate points in the existing wastewater treatment facility.
3. Install suitable flow measuring and recording devices at appropriate locations. If prac-
tical, also install suitable automatic sampling equipment at these locations.
4. Establish a sampling schedule which will assure the collection and analysis of samples at
frequencies sufficient to detect and avert potential major water pollution problems.
5. Keep permanent records of all collected data, including corresponding production
records and waste treatment/disposal costs.
FLOW MEASUREMENT
An essential part of the survey or monitoring program is the collection of flow data. A variety
of flow measuring methods and devices are available. Selection of an appropriate method for the
measurement of water used by unit operations or of flows in in-plant waste streams will be influ-
enced by the physical arrangement of each system and by the desired degree of data accuracy.
Some methods for measuring flows in various types of systems are discussed in this chapter.
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Emphasis has been placed on methods which yield reliable estimates without necessitating expen-
sive apparatus. These methods will prove satisfactory for in-plant surveys. However, for continuous
monitoring programs, permanent flow measuring and recording installations are recommended1
VOLUMES TO UNIT OPERATIONS
In-plant waste collection systems are often inaccessible or are arranged in such a manner that
it is virtually impossible to segregate flows originating from separate operations. Under these con-
ditions, the easiest means to determine the volume contribution from each operation to the com-
posite plant effluent is to measure the volume of water used by each. However, caution should be
exercised in the determination of flows by this method. Any portion of water from a unit operation
which is reused in a separate operation must be noted and properly accounted for.
Container and Stopwatch
The simplest and least expensive method for measuring flows is by the container and stopwatch
technique. Although this method is rather crude when compared to the sophisticated equipment
and devices which are available, reasonable estimates can be obtained. Flows are determined by
recording the time required to fill a container of known volume. For greater accuracy, the follow-
ing should be observed:
1. A stopwatch, rather than an ordinary clock, should be used.
2. Containers which require more than 10 seconds to fill should be used to minimize
observational errors.
Calculate the capacity of rectangular or cylindrical containers by the following formulae:
1. Volume (gallons) of , ., ,„,,. . ,,. ,_,. , ,, ,„. » „ Ar,
rectangular box = length (ft) X ™dih (ft) x depth (ft) x 7'48
or
length (in) x width (in) x depth (in)
231
2. Volume (gallons) of ,,. , .,,,9 , ,, ,„,, _ ori
, • H = (diameter, ft) zx depth (ft) x 5.87
or
(diameter, in) 2 x depth (in)
If an irregular -shaped container, such as a bucket, is used, its capacity may be determined as
follows:
1. Weigh the empty container.
2. Fill the container with water and weigh again.
3. Calculate the capacity by:
filled weight (Ibs) — empty weight (Ibs)
Volume (gallons) = -- g^34
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If water to an operation is from a single pipe, a container can readily be placed to collect the
influent stream. If, however, the influent water is difficult to collect in a single container, as in the
case of a bank of sprays, a suitable catch basin can be used to initially collect the water flow. The
collected flow can then be diverted to the measuring container. Determine the flow in the follow-
ing manner:
1. If a catch basin is required, place it in a suitable position taking care that water will not
be lost over its sides.
2. Turn on the water supply to the operation. Be certain that flow rates are as close to
operating conditions as possible.
3. Place the container in position to collect all the water from the catch basin. Simultane-
ously start the timer (stopwatch).
4. When the measuring container has filled to capacity (or to a predetermined level),
immediately stop the timer.
5. For greatest accuracy, repeat the procedure several times and use the average interval to
calculate the flow.
6. Calculation:
^ „. . „ . , , , volume of container (gal) cn
Q, flow in gallons per minute (gpm) = r. :—-3-7—...„ , , > x 60
6 K time required to fill (seconds)
Water Meters
For convenience and greatest accuracy, the installation of in-line meters on influent water lines
is recommended. A wide variety of flow meters, rate indicators and other devices for observing or
recording flows in pressurized pipes are commercially available. Due to the widespread use of these
devices and the ready availability of detailed information from numerous manufacturers, only the
commonly-used, propeller-type flow meter is included in this discussion.
The propeller-type flow meter, schematically illustrated in figure II-l, consists of a propeller,
or a similar rotor, placed within a pipeline. The propeller turns in direct relation to the velocity of
fluid flow in the pipe. By means of calibrated gears, the rotations are converted to volumes which
are visually observable on the dial (or register) normally contained in the unit. Flow rates can be
obtained by using a stopwatch while observing the meter dial.
Register
Propeller
Figure 11-1. Propeller-type flow meter.
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Accurate measurements with propeller-type meters require the maintenance of close tolerances
between the propeller blades and the inside surface of the pipe or meter casing. This requirement
precludes the use of these meters in pipelines carrying large solid material. However, these meters
are excellent for measuring and recording the volume of water entering the plant and the volumes
utilized by individual operations within the plant. Meter accuracy should be protected by regular
maintenance and ascertained by periodic calibration.
FLOWS IN OPEN CHANNELS
Open channels are commonly used in fruit and vegetable processing plants. These include
flumes and gutters used for the hydraulic transport of product within the plant as well as flumes,
gutters and ditches used for the collection and transport of liquid waste streams within and away
from the plant. The flow of water in these systems can be:
1. Estimated by measuring the depth and velocity of flow in the channel, or
2. Measured with the use of a suitable device, such as a weir or Parshall flume.
Depth and Velocity of Flow Method
A reasonable estimate of the flow in an open channel can be derived from observation of the
velocity, or rate of flow, within the channel and measurement of the cross-sectional area of the
water. Close approximation of actual flow can be obtained by using 85 percent of the measured
surface flow. The rate of flow is estimated by recording the time required for a floating object to
travel between two points of the channel.
The accuracy of results obtained by this method is improved when:
1. The flow in the channel is constant, and
2. The bottom and walls of the channel are smooth and of even dimensions along the
section where the measurements are taken.
Measure the cross-sectional area (A) of the channel in one of the following ways:
1. For rectangular channels:
A - width x depth
2. For trapezoidal channels:
. (w + b)
A = ^—=—'- x depth
where:
w = width of channel at water surface
b = width of channel at the bottom
d = depth of channel
3. For triangular channels:
. _ width x depth
A
,1 1
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Determine the flow in the following manner:
1. Select a straight portion of the channel, if possible, of sufficient length to require at
least 10 seconds for a float to traverse the distance.
2. Place a marker at each end of this stretch. Measure the distance between the two points.
3. Calculate the cross-sectional area of the channel as outlined above. If the dimensions of
the channel are irregular, make several measurements along the selected length and use
the average for calculation.
4. Place a float (a piece of wood or cork or an empty, sealed can) on the water at a distance
slightly upstream from the first marker.
5. Using a stopwatch, time the interval required by the float to traverse the distance between
the markers. Repeat several times and use the average for calculation.
6. Calculation:
._ , , area (ft^) x length (ft) , Ar. „ or
Q (gpm) = 1 (seconds) X 449 X °'85
= area (in^) x length (in)
V6K ; t (seconds)
Weirs
A weir is an inexpensive device for measuring flows in open channels. As illustrated in figure
11-2, it is simply a barrier or dam containing a recess or notch, through which water flows to fall
freely to a level below the bottom of the recess or notch. The height of the water passing over the
weir varies with the volume of water flowing in the stream. Thus, flows are determined by measur-
ing the head (i.e., the depth of the stream between the bottom of the recess and the water surface)
at an appropriate distance behind the weir (figure II-3).
Various shapes are used in the construction of these devices. The more common forms are
V-notch, rectangular, and trapezoidal. Selection of a weir shape is determined by the flow rate and
the dimensions of the channel. Flow rates over a 90° V-notch weir are provided in table II-l. Tables
for other weir configurations are available in several references, including the EPA's Handbook for
Monitoring Industrial Wastewater1 and in the Guide for Waste Management in the Food Processing
Industry 2 published by the National Canners Association. By referring to these tables, a properly
designed weir can be constructed in the following manner:
1. Estimate the maximum waste flow that can be expected. The depth-velocity or con-
tainer and stopwatch methods are useful for this purpose.
V-notch
Rectangular
Trapezoidal
or Cipoletti
Figure 11-2. Common forms of weir plates.
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Figure 11-3. Flow over sharp-crested weir.
2. Select one of the weir types and find the head over the weir corresponding to the
estimated maximum flow by referring to the appropriate table.
3. The total depth for maximum flow should be at least 3.5 times H, the head, as found in
Step 2.
4. Compare this to the actual depth of the channel in which the flows are to be measured.
Allow at least two inches to insure against flooding caused by back-up of water in the
gutter.
5. Check the lateral dimensions to see if the channel width fulfills the specifications for the
type of weir selected:
(a) For a 90° V-notch weir, the width
of each end contraction, a, must —
be at least 1.5 times H. Thus, the
width of the channel should be at
least 4 times H.
(b) For a standard rectangular weir,
the width of each end contraction,
a, should be greater than 2.5 times
H. Thus, w > 5H + L.
(c) For rectangular weirs with modified end (trapezoidal) contractions, the width of
each end contraction need only be large enough to permit the free passage of air
between the walls of the channel and the flow of water passing over the weir.
The rectangular weir with modified end contractions appears to be the best design for general
use since most gutters and flumes in fruit and vegetable processing plants are too narrow to permit
the use of a V-notch weir. However, this latter type is excellent for measurement of small flows.
Observation of the following points will increase the accuracy of all weir measurements:
1. The weir plate must be vertical and the top must be level.
2. The sides and bottom of the plate should be sealed to prevent leakage.
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Table 11-1 .—Discharge over 9(f V-notch weir
Note — Total width of two end contractions = 2a = 1.5L
where "a" = width of each contraction
"L" = width of water flowing over weir
Head (H)
inches
1
1/4
1/2
3/4
2
1/4
1/2
3/4
3
1/4
1/2
3/4
4
1/4
1/2
3/4
5
1/4
1/2
3/4
6
1/4
1/2
3/4
7
1/4
1/2
3/4
8
1/4
1/2
3/4
Discharge
gallons per minute
(gpm)
2
4
6
9
12
17
24
30
37
45
53
65
76
88
100
114
129
149
166
183
204
225
247
276
300
332
354
383
413
451
486
520
Head (H)
inches
9
1/4
1/2
3/4
10
1/2
11
1/2
12
1/2
13
1/2
14
1/2
15
1/2
16
1/2
17
1/2
18
1/2
19
1/2
20
1/2
21
1/2
Discharge
gallons per minute
(gpm)
555
594
632
684
725
815
910
1040
1130
1250
1380
1520
1650
1810
1970
2120
2310
2480
2670
2880
3080
3290
3530
3760
4000
4250
4500
4770
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3. The weir can be of wood or metal. A metal plate bolted to the upstream side of a wood
section will make a satisfactory weir. The crest should be 1/8" to 1/4" thick and sharp-
edged. If the weir is thicker, the top should be beveled to this dimension on the down-
stream face.
4. The crest height, P, should be at least 2.5 times the maximum expected head, H. Settle-
able solids, which may accumulate behind the weir, may change this dimension, thereby
introducing errors in observed flows. Therefore, the channel must be regularly cleared of
settleable material.
5. The head should be measured at a point upstream from the weir at a distance of at least
4 times that of the maximum expected head. A staff gauge or rule (the zero mark of
which is level with the crest of the weir) can be attached to the wall of the channel for
this purpose.
Parshall Flume
The Parshall flume is a convenient device for measuring the flow in existing waste flows and
consists of three parts: a converging section, a throat section, and a diverging section. The dimen-
sions and capacities of Parshall flumes are shown in figure II-4. The level of the floor in the con-
verging section is higher than the floor in the throat and diverging sections. The head of the water
surface in the converging section is a measurement of the flow through the flume.
The elevation of the water surface should be measured back from the crest of the flume at a
distance equal to 2/3 of the length of the converging section. The crest is located at the junction
of the throat and converging section. The head should be measured in a stilling well instead of in
the flume itself as sudden changes in flow are dampened in a stilling well. The size of the Parshall
flume should be determined during the preliminary survey. The general formula for computing the
.free discharge from a Parshall flume is as follows:
Q = 4WHn
where:
Q = discharge, cfs
W = throat width, ft
H = head of water above the level floor in ft in the converging section
n = 1.522 ^0.026
The flume may be built of wood, fiberglass, concrete, plastic or metal and can be installed at
convenient locations, such as a manhole. The Parshall flume is used for sewer lines where continu-
ous-flow measurements are desirable. The main advantage of the Parshall flume over a weir is the
self cleaning properties of the flume. Accurate measurements can be made even if the flow is sub-
merged as shown by the water levels in figure II-5.
The flow can become submerged due to high water elevations downstream. If the flow is
submerged, a velocity reduction in the flow occurs. The degree of submergence must be determined
in order to measure the flow accurately since the flume is calibrated for free flow conditions. The
condition of submerged flow is evidenced by a ripple or wave formed just downstream from the end
of the throat. A reduction in the velocity of the water leaving the flume may lessen the effects of
erosion downstream. In order to determine the degree of submergence, a stilling well must be built
10
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Ft In.
In.
E F G K
-*—•
Ft In. Ft In. Ft In. In.
N Ft M P X
In. Ft In. Ft In. Ft In. In.
Free-Flow
Capacity
(Second-Foot*)
Mini- Maxi-
In. mum mum
0
0
0
1
1
2
3
4
5
6
7
8
3
6
9
0
6
0
0
0
0
0
0
0
1
2
2
4
4
5
5
6
6
7
7
8
6-3/8
7/16
10-5/8
6
9
0
6
0
6
0
6
0
1
1
1
3
3
3
3
4
4
4
5
5
1/4
4-5/16
11-1/8
0
2
4
8
0
4
8
0
4
1
2
2
4
4
4
5
5
6
6
7
7
6
0
10
4-7/8
7-7/8
10-7/8
4-3/4
10-5/8
4-1/2
10-3/8
4-1/4
10-1/8
0
1
1
2
2
3
4
5
6
7
8
9
7
3-1/2
3
0
6
0
0
0
0
0
0
0
0
1
1
2
3
3
5
6
7
8
9
11
10-3/16
3-5/8
10-5/8
9-1/4
4-3/8
11-1/2
1-7/8
4-1/4
6-5/8
9
11-3/8
1-3/4
2
2
2
3
3
3
3
3
3
3
3
3
0
0
6
0
0
0
0
0
0
0
0
0
0
1
1
2
2
2
2
2
2
2
2
2
6
0
0
0
0
0
0
0
0
0
0
0
1
2
1
3
3
3
3
3
3
3
3
3
0
0
6
0
0
0
0
0
0
0
0
0
1
3
3
3
3
3
3
3
3
3
3
3
2-1/4
4-1/2
4-1/2
9
9
9
9
9
9
9
9
9
1
1
1
1
1
1
1
2
2
2
2
2
4
4
4
8
8
8
8
0
0
0
0
0
1 0
1 0
1 0
1 3
1 3
1 3
1 3
1 6
1 6
1 6
1 6
1 6
2
2
3
4
5
6
7
8
10
11
12
13
6-1/4
11-1/2
6-1/2
10-3/4
6
1
3-1/2
10-3/4
1-1/4
3-1/2
6
8-1/4
1
2
2
2
2
2
2
2
2
2
2
2
1-1/2
3
3
3
3
3
3
3
3
3
3
3
0.03
0.05
0.09
0.11
0.15
0.42
0.61
1.3
1.6
2.6
3.0
3.5
1.9
3.9
8.9
16.1
24.6
33.1
50.4
67.9
85.6
103.5
121.4
139.5
"Equals 1 cu ft per sec.
Legend:
W Size of flume, in inches or feet.
A Length of side wall of converging section.
2/3 A Distance back from end of crest to gage point.
B Axial length of converging section.
C Width of downstream end of flume.
D Width of upstream end of flume.
£ Depth of flume.
F Length of throat.
G Length of diverging section.
K Difference in elevation between lower end of flume and crest.
N Depth of depression in throat below crest.
R Radius of curved wing wall.
M Length of approach floor.
P Width between ends of curved wing walls.
X Horizontal distance to H, gage point from low point in throat.
Y Vertical distance to H, gage point from low point in throat.
Source: ORSANCO (1952).
Figure II-4. Dimensions and capacities of the Parshall measuring flume, for various throat widths,
-------
GPM
1 ,000,000
800,000
600,000
400,000
300,000
200,000
100,000
80,000
60,000
40,000
30,000
20,000
10,000
8,000
6,000
4,000
3,000
2,000
GPM
1,000
800
Q
CO
£ 400
3)
> 300
3
* 200
3
I
100
80
60
40
30
20
FLOW
10
8
MGD
r 3000
2000
'- 1000
800
600
300
200
: 100
80
60
40
30
20
10
8
6
5
4
3
2
- 1.0
OS
0.6
0.4
0 3
0.2
I MGD
0.1
0.08
0 06
0.04
i- FLOW
0.02
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-------
in the throat section. The crest elevation in the throat section is H^ and the head in the converging
section is Ha. The ratio Ha/Hb is a measurement of the submergence. The stilling well used to
measure H^ should be located near the downstream end of the throat section and the datum for
Ha and H\) is the level floor of the converging section.
FLOWS IN PARTIALLY FILLED PIPES
Measurement of flows in partially filled pipes can 'be taken by several methods depending upon
physical convenience. Where sections of pipe are exposed, a segment can be removed and substituted
with a Parshall flume or weir box as previously discussed. If a straight nonconstricted run of pipe is
accessible at both ends, flow estimates can be obtained by the depth-velocity methods. For this
purpose, table II-2 lists cross-sectional areas of water at various depths for several pipe diameters.
Calculation of flow is the same as for open channel flow measurement.
For round-bottom channels or pipelines accessible through manholes or other openings, the
Palmer-Bowlus metering flume is an inexpensive and easily installed device. The Palmer-Bowlus
flume may be nothing more than a level section of floor placed into a waste flow, which is a major
advantage over the Parshall flume. The length of the floor should be approximately the same as the
diameter of the conduit. The flume is positioned at the bottom of the conduit. It provides a slight
restriction or throat which creates an upstream head of water.
Figure II-6 shows a few possible forms of the Palmer-Bowlus flume. The materials used to
build the flume may be cast iron, stainless steel, fiberglass or concrete. This type of flume is easily
installed in existing waste flows as no drop in head is required. The critical depth will be at the top
of the level floor. The flow through a Palmer-Bowlus flume may be represented by the following
equation:
At critical flow:
Q2 AC3 FC2 AC dc
-J = ~b md ^ = 26 - T
where:
Ac = area at the critical depth, ft^
dc = critical depth, ft
Vc = critical velocity
b = width of flume
No field calibration is necessary for this type of measuring device and its accuracy is comparable
to that of a Parshall flume. A reasonably accurate measurement of flow can be obtained with up-
stream depths as great as 0.95 of the pipe diameter, provided sensitive instrumentation is used and
flows upstream to and through the unit are not turbulent.
FLOWS FROM OPEN-END PIPES
In most cases where pipes are used for in-plant transport of wastewater, the only practical
point for flow measurement is at the discharge end of the system. Several methods and devices are
suitable for use at this point.
13
-------
Table 11 -2.—Cross-sectional area of water in pipes at various depths of flow
Depth of
tlow (a)
inches
2
1/4
1/2
3/4
3
1/4
1/2
3/4
4
1/4
1/2
3/4
5
1/4
1/2
3/4
6
1/4
1/2
3/4
7
1/4
1/2
3/4
8
1/4
1/2
3/4
9
1/4
1/2
3/4
10
1/4
1/2
3/4
Cross sectional area — square feet (sq ft)
Diameter of pipe (D) — inches
6
.06
.07
.08
.09
.10
.11
.12
.13
.14
.15
.16
.17
.17
.18
.19
.19
.20
8
.07
.08
.09
.11
.12
.13
.15
.16
.17
.19
.20
.22
.23
.24
.26
.27
.28
.29
.30
.31
.32
.33
.34
.35
.35
10
.08
.09
.11
.12
.14
.15
.17
.19
.20
.22
.24
.26
.27
.29
.31
.32
.34
.36
.38
.39
.41
.42
.44
.45
.47
.48
.49
.51
.52
.53
.54
.54
.55
12
.09
.10
.12
.14
.15
.17
.19
.21
.23
.25
.27
.29
.31
.33
.35
.37
.39
.41
.43
.45
.48
.50
.52
.54
.56
.58
.59
.61
.63
.65
.67
.68
.70
.71
.73
.74
15
.10
.12
.13
.15
.17
.20
.22
.24
.27
.29
.31
.33
.36
.38
.41
.43
.46
.48
.51
.54
.56
.59
.62
.64
.67
.69
.72
.74
.77
.79
.82
.84
.87
.89
.92
.94
14
-------
End view
Longitudinal midsections
Vertical
Horizontal
c
)
•^
fff
/{{////
w^
(^
Figure II-6. Various shapes of Palmer-Bowlus flumes.
Container and Stopwatch
If the flow to be measured can be readily captured in a container of practical dimensions, the
container and stopwatch technique (as previously described) can be employed. To minimize
observational errors, the container should be large enough to require at least 10 seconds to fill.
Coordinate Method
This method can be used when the water discharges freely from the end of an open pipe. The
calculation is derived from the physics principle of trajectory which relates the distance of a particle
from a point to the velocity of that particle at the point of origin.
As illustrated in figure II-7, the position of the water after it has left the pipe is measured by
the horizontal distance (X) and the vertical distance (Y) from the end of the pipe. Y must be a
vertical distance and X must be parallel to the slope of the pipe.
With these measurements, the flow can be calculated as follows:
„ _ 1800 AX
** ~ i
where:
Q = flow in gallons per minute
A = cross-sectional area of the fluid in the pipe in square feet
X = the distance in feet, measured parallel to the pipe, between the end of the pipe and
the vertical gauge
Y = the vertical distance in feet from the water surface at the end of the pipe to the
intersection of the vertical gauge and the falling water surface.
15
-------
Adjustable nut so that
x axis is parallel to sewer
and y axis is vertical
I— Depth in sewer _"^
Distance from inside bottom
of pipe to surface of falling
liquid (depth of flow)
For sloped sewers or pipes
Figure 11-7. Measurement of X and Y dimensions for open-pipe flow measurements.
To determine the cross sectional area, A:
\. Cylindrical pipe, refer to table II-2.
2. Rectangular or other configuration, refer to the section Flows in Open Channels.
Measuring Devices
A variety of devices are available for measuring open-end discharges.1 These are constructed
for direct attachment to the end of a pipe and are designed and calibrated to enable direct visual
observation of flows. Automatic recording instruments are available as accessories for many of
these commercial models. Alternatively, open channel extensions may be constructed and fitted
with a weir, Parshall flume, or Palmer-Bowlus flume.
PIPES UNDER PRESSURE
Flow measurement in pressurized pipes necessitates installation of in-line meters. Most meters
rely either upon rotating indicators to detect flow or upon orifices to detect pressure differentials
across a constricted section of pipe. Although these devices are satisfactory for metering water
flows, the normally high concentration of particulates in food processing wastewaters generally
precludes their use for metering waste streams. However, one type of in-line meter, the electro-
magnetic flow meter, is useful for this purpose.
16
-------
The electromagnetic flow meter is a relatively recent development in flow measuring devices.
The operating principle of this meter is based upon Faraday's law of electromagnetic induction,
which (simply stated) says:
"The voltage induced across any conductor as it moves at right angles through a
magnetic field is proportional to the velocity of that conductor."
Figure II-8 illustrates how this principle has been applied to the flow meter. A uniform mag-
netic field is created around a section of pipe with electromagnets. As the fluid conductor (water)
moves through the magnetic field surrounding the pipe, a voltage is generated at the electrodes.
The magnitude of this induced voltage is measured by a suitable instrument and converted to
measurements of flow.
The operation of an electromagnetic flow meter is not affected by changes in liquid viscosity,
density, line pressure, presence of solids, or turbulence of flow. Furthermore, the inside diameter
of the pipe is free from constrictions or protuberances which might impede the flow of fluid in the
pipe. Flows in water pipes, hydraulic conveying systems and waste pumping lines can all be moni-
tored with such meters without concern for loss of head, solids build-up, clogging, or other problems
associated with the other types of meters. These features render this meter extremely attractive for
use in fruit and vegetable processing plants.
Electromagnet
Electrode
Flow tube
Flow tube liner
Electrode
Electromagnet
Figure 11-8. Operating principle of the electromagnetic flow meter.
SAMPLING PROCEDURES
The type of information desired will dictate the method utilized for obtaining wastewater
samples. Analysis of grab samples collected during the course of a day's operation will reveal
temporary fluctuations in the physical and chemical characteristics of the waste, whereas the daily
average values can be obtained with a minimum of analytical work from composite samples.
The type of sample, whether grab or composite, should also be selected on the basis of the
stability of the constituent to be measured, and the degree of accuracy desired in the results. Below
are listed some specific tests under the type of sample most suitable for its determination. How-
ever, most of these determinations can be made on either type of sample and in a routine +o^;~
program, this is frequently done.
17
-------
Grab Sample Composite Sample
pH Biochemical Oxygen Demand
Total acidity Chemical Oxygen Demand
Total alkalinity Total solids
Chlorine residual Suspended solids
Dissolved oxygen Dissolved solids
Settleable solids Ammonia nitrogen
Orthophosphate phosphorus
Regardless of the method used, the importance of representative sampling cannot be over-
emphasized. Serious errors in waste load calculations will occur if appropriate precautions are not
observed. For example, since heavy particles will rapidly settle to the bottom of a container, errors
in solids concentrations may occur when water samples are transferred from one container to
another. Therefore, the samples should be well-mixed whenever such transfers are made.
GRAB SAMPLES
Grab samples are individual portions of material taken from each collection point. For in-plant
surveys, grab samples should be taken several times per shift. Hourly samples will yield a more
complete profile of waste fluctuations occurring within each survey period. Fluctuations in char-
acteristics between individual grab samples are expected and reflect normal variations caused by
changes in raw product volume and quality, style of pack and other influencing factors which are
discussed later.
The equipment required for taking grab samples are:
1. A one-gallon capacity pail (plastic or stainless steel).
2. A large funnel.
3. A container-carrying rack.
4. Containers.
5. A simple dipper, fashioned from an enamel-lined can attached to a long pole, will
facilitate obtaining samples from difficult-to-reach areas.
An inexpensive and useful container for grab sample collection is a one-quart, wide-mouth
plastic bottle or mason jar with a screw cap (available in most supermarkets and hardware stores).
Wastewater samples collected for chlorine residual, hydrogen sulfide, dissolved oxygen, or
phosphate determinations should be collected in screw-cap glass jars with airtight closures. These
jars should be completely filled to avoid entrapment of air. Glass containers must be used for all
samples which are to be analyzed for oil and grease.
Procedure
When collecting grab samples, the following precautions should be observed:
1. One to four quarts of sample should be taken at each sampling, the volume determined
by the number of parameters which are to be recorded. Care should be exercised to
insure that the samples are free of large pieces of suspended material, such as sticks,
stems or other pieces of product which would normally be removed by an effluent
screen. If large particles are unavoidable, waste water samples should be passed through
a 20-mesh (or equivalent) laboratory sieve prior to analysis.
18
-------
2. When it is necessary to sample wastewater at different levels in a tank, a weighted bottle
with a stopper in place may be lowered to the desired depth and the stopper removed by
means of an attached string. The bottle should be held in place until bubbles cease to
rise. For routine sampling from large storage tanks, selection of the proper depth should
be made with care; skimming the liquid surface must be avoided. A sampling point of
one-third to one-half of the liquid depth is recommended.
3. The discharge from pipes, weirs and flumes should be sampled in such a manner that
turbulence in the sampling device does not concentrate the heavier solids at the bottom
while floating away suspended matter. This can be avoided by collecting the sample
without overflowing the pail or dipper.
4. The containers should be clearly labeled with sampling point, date and time of collection.
Sampling points throughout the plant should be designated by a code (such as a letter) to
identify the product being packed and by numbers to identify the sampling sites. A
convenient way of labeling glass containers is to write directly on the surface with a felt-
tip marking pen containing permanent ink (available from Esterbrook Pen Company,
Carters Ink Company, and others). Masking tape may be affixed to plastic containers for
labeling purposes.
COMPOSITE SAMPLES
A composite sample consists of measured portions, or aliquots, of wastewater collected at
frequent regular intervals. The individual aliquots are combined into a single container to form the
composite sample. The sampling may cover any convenient time period, such as a shift or a 24- s
hour operation. A composite sample has the disadvantage of not revealing fluctuations in waste
characteristics which occur during the sampling period. However, this procedure is most convenient
for determining the average characteristics of a waste stream over a period of time.
The equipment required for manually composited samples is identical to that used for obtain-
ing grab samples. Additionally, a large collection container with a capacity of 2 to 3 gallons should
be provided.
Procedure
If the rate of waste discharge is fairly constant, a composite sample may be made up of individ-
ual samples of the same volume, each collected in the manner described for taking grab samples. If,
however, the rate of discharge varies, as is usually the case, a weighted (proportional) sample is of
greater value.
To obtain a proportional composite sample, the rate of waste flow must be known and the
individual aliquots constituting the composite sample should be proportional in volume to the rate
of waste flow at the time the sample is collected. For example, if the rate of flow at one sampling
time is 500 gpm, the sample at the time could be 50 ml or some multiple of that amount. If the
rate of flow increases later to 1,000 gpm, the sample at that time would be 100 ml or some multiple
of this amount. However, abnormal surges in the flow should be disregarded. The size of the
individual portions should be such that the volume of the composite sample will be 1 to 2 gallons.
Automatic Composite Samplers
A wide variety of automatic sampling devices are commercially available. These devices col-
lect and composite wastewater samples over a predetermined period, thereby releasing an individual
from the responsibility of having to manually obtain periodic samples. Such samplers are available
for almost all situations, whether samples are to be drawn from a sump or tank, a flume or a pipe.
19
-------
Current prices range from about $300 for a simple device to more than $3,000 for a refrigerated
proportional sampler. Selection of a suitable model will be determined by the requirements of
each situation. Manufacturers should be consulted for recommendations. When selecting a sampling
device, the following points should be considered:
1. Will the sampler obtain representative samples? Be certain there are no hoses or tubing
which will contain a static volume of wastewater that will later be added to the composite
sample.
2. Be certain that aU valves and/or other orifices are of sufficient size to preclude clogging
by particulate matter which might be present in the waste stream. This factor is impor-
tant in sampling fruit and vegetable wastes.
3. If the volume of liquid flowing in the waste stream varies frequently, does the sampler
take proportional samples? Or, can the sampler be readily adapted to do so? Can the
sampler be used at the low flow rates sometimes encountered in fruit and vegetable
processing?
4. Does the unit provide refrigerated storage for the composite? If not, will the sampler
readily deliver aliquots of wastewater to a collecting container placed in a refrigerator?
(See the following section, Sample Preservation.)
5. Is the construction of the sampler such that the device can be readily cleaned without
tedious dismantling? Periodic cleaning is especially important for pipes, tubing and other
parts which come in contact with the liquid waste.
The less expensive composite samplers collect aliquots on a fixed time-fixed volume (TpVp)
basis. Although this procedure is satisfactory for constant flows, TpVp samples will yield only
approximations for most food processing wastewater streams. However, these samplers are portable
and convenient for use in in-plant surveys. Representative analytical results can only be obtained
with flow-proportional composite samples. Two basic types of automatic samplers are available for
collecting such samples, as described below.
Some flow-proportional samplers are designed to collect aliquots of varying volume at fixed
time intervals (TpVy). The volume of each aliquot is determined by the flow at the time of collec-
tion. Tp Vy samples are satisfactory for all moderately variable flows.
The greatest accuracy is obtained by analyzing samples which have been collected on a "per
unit flow" basis (TyVp). Automatic samplers designed to composite samples on this basis require
flow measuring devices capable of signaling the sampler at appropriate intervals, generally whenever
each 1,000 gallons of wastewater has flowed through the meter. Thus, each aliquot is a fixed volume
and represents a unit volume of wastewater. This method is the only satisfactory one for highly
variable flows and is recommended for routinely monitoring wastewater discharges.
SAMPLE PRESERVATION
Most food processing wastes are relatively unstable because bacterial growth and chemical
reactions can cause significant changes in a short time. For example, samples stored for one day at
room temperature may be 10 to 40 percent lower in BOD than the fresh waste. The rate of change
is influenced by temperature, pH of the sample, and the concentration of dissolved components.
Any attempt to inhibit bacterial growth by the addition of bacteriostatic agents may hasten chemical
changes or alter some physical characteristic of the waste. Immediate analysis is the best insurance
against significant errors in the use of grab samples. However, this is not always practical, especially
20
-------
when samples are collected from points quite distant from the laboratory. Furthermore, composite
samples must often be stored for as long as 24 hours. To minimize compositional alterations in
these samples, some means of preservation must be used.1' 3
PRESERVING SAMPLES IN THE FIELD
When collecting samples in the field, delays are often encountered before the samples can be
delivered to the laboratory. Under such circumstances, the samples should be stored in ice. Insu-
lated ice chests are convenient for this purpose, providing an inexpensive and portable means for
assuring minimal changes in the waste. Collection containers should be sealed, placed into the ice
chests and packed with crushed ice. Samples can be held in such a manner for several hours in even
the warmest climates. Storage duration can be prolonged by periodically draining the chest and
repacking it with more ice. Care should be exercised to assure that water from the melting ice does
not enter the containers, thereby diluting the waste samples.
REFRIGERATION
Refrigeration at 4° C (39° F) is the preferred and most common method for temporary preser-
vation of wastewater samples, especially for storage of composite samples during the period of
collection. Refrigeration retards bacterial growth, chemical reactions and physical changes. In
situations where the interval between sample collection and analysis is long enough to produce
changes in the physical and chemical characteristics, the preservation practices listed in EPA's
manual entitled Methods for Chemical Analysis of Water and Waste3 are recommended.
FREEZING AND THERMAL PROCESSING
In situations where analysis of wastewater samples will be unavoidably delayed, the samples
may be preserved by freezing or thermal processing. Samples for freezing should be placed in
flexible containers with sufficient space left in the containers to allow for ice expansion. Thermal
processed samples should be placed in enamel-lined cans with a 1/2-inch headspace provided and
processed for 25 minutes at 240° F (or equivalent). However, significant changes will occur in the
chemical and physical characteristics of samples so preserved. Therefore, these procedures should
be used only in emergencies; the analytical results should be considered as approximations.
ANALYTICAL PROGRAM
Companies implementing either in-plant survey or wastewater discharge monitoring programs
must decide the most cost-effective procedure for developing the required analytical data. Such
data may be obtained through contractual services of commercial laboratories or by establishing
in-house analytical capabilities. The economics of either will be primarily dictated by the frequency
of sampling, the number of samples, and the number of parameters which will be evaluated for each
sample.
COMMERCIAL LABORATORIES
For monitoring programs requiring minimal data accumulation, commercial laboratories
generally offer the most economical and convenient means to obtain necessary information. Lab-
oratories with capabilities for analyzing wastewater samples are numerous and geographically
widespread. Typical costs for measuring significant food processing wastewater parameters are
listed in table II-3.
21
-------
Table I \-3.-Commercial laboratory fees for significant food processing wastewater parameters8
Parameter
Biochemical Oxygen Demand (6005)
Chemical Oxygen Demand (COD)
pH 2.00- 5.00
Settleable solids
Suspended solids
Total dissolved solids
Total solids
Cost/sample
$10.00-20.00
7.50-10.00
3.00- 5.00
5.00
5.00
5.00
aBased on survey of several laboratories. Discounts are generally available for multiple samples.
When selecting a commercial laboratory, consideration should be given to the following:
1. Recognition by regulatory agencies. Several states have certification programs for
commercial laboratories. Where this is the case, certified laboratories should be employed
(check with the local agency for a list of such laboratories). In areas where no certification
program exists, ascertain that the selected laboratory follows recognized analytical pro-
cedures. See Appendix A.
2. Convenience of sample delivery. Although it would be ideal to have a commercial lab-
oratory in sufficiently close proximity to enable personal delivery of all samples, this
situation is infrequently encountered. Normally, some means of shipment must be
arranged. It is important that minimal delays occur in transit, preferably no more than
24 hours. Bus lines provide convenient intrastate and intercity sample transportation.
3. Rapid "turn-around." The selected laboratory should assure that samples will be quickly
analyzed upon receipt and the results reported immediately.
4. Other services and amenities. Most laboratories will provide detailed instructions on
sample preparation and shipment. Some provide specially designed containers to insure
against breakage and resultant loss of sample. Reputable laboratories willingly provide
advice in selecting appropriate analyses and are cognizant of the need to preserve bio-
degradable samples.
IN-HOUSE CAPABILITIES
Analytical capabilities at the fruit and vegetable processing plant offer the major advantage of
rapid results, an essential factor for controlling treatment systems and wastewater discharges. The
costs for establishing this capability will vary widely. Major influencing factors are (1) availability
of a technician(s) capable of performing the analyses, (2) the type of tests which are desired, (3) the
availability of basic analytical equipment, and (4) the availability of a sufficiently spacious working
area with appropriate laboratory fixtures.
22
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Analytical Equipment
The analytical equipment required for in-house analyses will be determined by the parameters
to be measured. The equipment and apparatus required for each test are described in References 2,
3, and 4. However, a basic need for all quantitative analyses is an analytical balance capable of
weighing to 0.1 mg.
Laboratory Facilities
The work area for laboratory analyses should be in a well-ventilated room. Minimum furniture
requirements for performing rudimentary analyses and physical measurements are (1) a sink, prefer-
ably one specifically designed for laboratory use (or an old fashioned stone laundry tub) equipped
with PVC or glass traps resistant to acids; (2) a laboratory bench with a chemical resistant surface
and at least 4-feet long; and (3) an under-counter cabinet and/or a set of drawers. Minimum require-
ments for utilities are hot and cold tap water and electricity (110 -120 V). When capabilities for
additional analyses are desired, additional pieces of furniture (such as increased bench space, addi-
tional cabinets and drawers, and a laboratory fume hood) will be required with additional utilities
(such as air, vacuum and gas lines) desirable. The basic laboratory should also be equipped with a
refrigerator for storing wastewater samples and a distilled or demineralized water source (purchased
bottled water will suffice when needs are minimal).
MAJOR WASTEWATER PARAMETERS
The major wastewater parameters for the fruit and vegetable processing industry are categorized
in table II-4. The significance of each is discussed in volume 1. Details of EPA-approved test pro-
cedures may be found in the EPA's Methods for Chemical Analysis of Water and Wastes3 and in
Standard Methods for the Examination of Water and Wastewater4 published by the American
Public Health Association (also see Appendix A of this volume).
Table I \-4.-Major wastewater parameters (fruit and vegetable processing industry)
Basic
pH
Temperature
Settleable solids
Significant
BOD5
COD
Dissolved oxygen
Suspended solids
Total dissolved solids
Total solids
Desirable/optional
Acidity & alkalinity
Chlorides
Nitrogen, organic
Oil & grease
Phosphorus, total
Turbidity
DATA ANALYSIS
Permanent records should be maintained for all information developed during in-plant surveys
and wastewater discharge monitoring programs, preferably on a daily basis. Information noted in
the records should include date, time of sampling, sample identification, flow, summary of analytical
results, and production data. Analytical worksheets should be kept on file in the event that ques-
tionable results occur. The use of bound notebooks with tear-out carbon inserts avoids the loss of
data or questions arising from "altered" data. Information developed during well planned surveys
will identify the major water-consuming and pollutant-generating operations. This information is
essential for implementing in-plant pollution controls, such as water conservation techniques and
process modifications. Surveys conducted subsequent to process changes will enable evaluation of
the effectiveness of those changes and their future operational control.
23
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The most important information to be obtained from a waste survey is the identification of
waste load variability and peak loadings which are associated with all of the operations at the plant.
This information is vital to the designing of successful waste treatment facilities. Therefore, survey
programs implemented to accumulate these data must be conducted through a minimum of one
entire processing season.
Data developed through monitoring programs can be used to establish raw waste loads (that
is, the quantity of pollutants per ton of raw product) for each commodity and commodity-mix
processed at the plant. The raw waste load (RWL) can be calculated as follows:
T>TITT / j ii ^ total flow (gal) x 8.34 x pollutant concentration (mg/1)
RWL (pounds/ton) = 1,000,000 x tons of raw product "^
This calculation should be made for at least BOD and/or COD and total suspended solids using the
daily average concentrations. The results should be recorded in the permanent log. If several sam-
ples are collected and separately analyzed during each day, calculation of the range (highest and
lowest values) will be useful.
By plotting RWL's and pollutant concentrations on a daily basis, waste profiles can be devel-
oped for the plant. Such profiles are useful for establishing normal variabilities which can be
expected in the processing wastewaters. Thus, "unusual" results will generally indicate a need for
investigation of cause and possible remedial action.
24
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Chapter III
FACTORS INFLUENCING WASTE GENERATION
Factors which affect the generation of wastes in processing fruits and vegetables are considered
in this section under several overlapping headings. Inplant survey programs should be designed to
elicit these data for each plant.
COMMODITY
On the average, wide ranges of discharged water flows and of generated pounds of pollutants
are found per ton of different commodities. Examples are plotted in figures III-l (wastewater)
and III-2 (BOD). Other data are found in table III-l. Although the average differences are large
and significant, the variability among plants processing the same commodity is much greater than
the variability of the averages from one commodity to another. This is shown by the probability
limits of the data, the upper and lower values expected to enclose the per ton generation of 95% of
the plants processing each commodity. In spite of the large average differences, the distributions
of all of the commodities overlap one another. In most instances, generation of wastes varies more
than twenty-fold within commodities and is sometimes much more variable than this. Some of the
reasons for the wide variability within commodities are the raw product condition, method of har-
vest and transport, and preparation procedures and equipment.
RAW PRODUCT CONDITION
It is widely understood in the industry that the quality of the raw commodity, as influenced
by maturity, injury, harvest conditions, and weather, affects the generation of wastes from process-
ing. However, quantifications of this effect are sparse. No studies have yet been identified which
assess the quality of the raw commodity. A measure of the effect of commodity quality upon gen-
eration of wastes is found in the records of BOD generation at a tomato plant. Average amounts
were 6.0, 5.5 and 11.9 pounds of BOD per ton of tomatoes in 3 consecutive years. The generation
doubled in the absence of plant changes that could account for the differences. Similarly, in 2-year
records, the BOD generated per ton varied two-fold between years at both an apricot and a pea
plant. Suspended solids per ton varied more than four-fold at the apricot plant and three-fold at
both the pea and a lima plant. In all these cases, there were no implant changes that would explain
the differences. Variations in the condition of the raw product may have accounted for them.
HARVEST AND TRANSPORT
The methods and conditions of harvesting and transporting raw commodities affect the
generation of waste. Machine harvesting and subsequent transportation of tomatoes may double
the amount of visible damage and may increase field soil from a trace to as much as 2% of the weight
of product. Mechanical harvesting also increases the field soil on snap beans and bruises on tree
fruits. Transportation of various commodities in bulk containers may increase damage by pressure.
In addition to the direct wastes from the soil and from leaching and culling damaged product,
more water is needed for washing away the soil. Therefore, both the volume and the strength
of the wastewater are affected.
25
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WASTEWATER, 1000 gal. per ton
o ui o 01
F^ Average (_] 95% limits
^
' *//
%
//,
'&
't
I
I
I
I
150
100
Q
O
CD
50
Kraut Corn Pear Snap bean Apricot
Tomato Peach Potato Peas
COMMODITY
Figure 111-1. Generated wastewater, average and 95% limits.
\/A Average
t t j
^ s /
c
^
] 95% limits
\,
1
\
I
I
I
Kraut Snap bean Peas Apricot Potato
Tomato Corn Pear Peach
COMMODITY
Figure III-2. Generated BOD, average and 95% limits.
26
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Table 11 Mr-Waste water and generated pollution loads by commodity
Apple
Apricot
Asparagus
Dry bean
Snap bean
Beet
Berry
Broccoli
Cauliflower
Carrot
Cherry
Citrus
Corn
Grape
Lima
Mushroom
Okra
Onion
Pea
Peach
Pear
Peppers
Pickle
Pineapple
Plum
Potato
Pumpkin
Sauerkraut
Spinach
Sprouts
Squash
Sweet potato
Tomato
Turnip
Wastewater
1000 gal Ions/ton
ave 95% limits
3.2 .2 17
4.9 1.1 14
8.6 1.4 31
9.8 1.1 44
4.7 1.1 14
4.0 .8 12
3.5 .4 16
8.8 1.6 32
11 (1.7 23)a
4.0 .8 13
4.8 .4 27
4.3 .4 16
1.9 .3 6.2
2.8 .3 13
7.3 1.4 24
9.6 1.7 33
5.0 1.3 15
6.8 (.2 17)a
4.7 1.2 13
3.0 1.1 6.8
3.9 1.5 8.4
4.6 .9 16
4.6 .8 19
1.7
4.9 .4 23
4.3 1.2 11
2.9 .4 11
1.4 .1 6.9
7.3 1.5 23
10.1 (4.8 20)a
6.0 1.1 22
4.0 .3 23
1.7 .4 5.2
7.3 2.4 18
BOD
pounds/ton
ave 95% limits
22 4.4 64
45 17 98
5 .6 26
75 16 238
20 .7 116
44 5 217
24 5.2 77
16 2.1 54
18 (2 49)a
31 9.6 80
15 2.4 75
16 (1 45)a
27 4.8 91
58 6.0 240
20 8.8 40
38 13 88
45 13 116
44 8.6 147
32 (5 50)a
16 7.4 31
11 (3 19)a
52 19 120
32 9.2 87
6.0 .9 24
13 3.5 37
25 (5 75)a
20
60 24 130
8.6 2.0 26
TSS
pounds/ton
ave 95% limits
6.3 .5 30
9.9 4.0 22
7.5 4 13
59 (2 130)a
7.0 .3 63
26 2 116
16 (1 57)a
17 2.0 72
.8 (.5 1)a
6.0 (2 10)a
12 2.1 44
50 2.7 332
10 4.2 22
12 1.3 67
9.1 1.8 30
8.7 1.7 29
58 (1 170)a
9.9 3.5 24
4.4 (.3 11)a
44 3.8 250
6.7 (2 12)a
.6
4.6 1.7 11
14
34
8.4 .3 66
Temp.
ave
54
76
70
63
79
77
70
72
92
65
79
pH
ave
5.6
8.0
6.8
7.3
7.9
8.7
6.5
5.6
6.0
9.6
7.0
6.8
6.8
6.3
6.4
7.9
a "Limits" in parentheses are reported maxima and minima.
PREPARATION PROCEDURES AND EQUIPMENT
PRODUCT STYLE
The kind of products made from a given commodity influences the amount of wastewater
and the generation of pollutants. An example of this influence is found in figure III-3, in which
the generation of BOD is compared to the percentage of peeled style tomatoes; on the average,
the more peeling, the more BOD. The relationship is highly significant in spite of the wide
probability limits. In a recent study, slicing apples, slicing snap beans, peeling tomatoes, and
27
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40
30
20
Q
O
CD
10
20
40
60
80
100
PERCENT PEELED TOMATOES
Figure III-3. Tomatoes, peeling and BOD generation, with 95% limits.5
cutting beets and carrots generated significantly greater amounts of BOD, compared to other styles.
In data from eight commodities, 21% of the variability among plants in the generation of BOD was
accounted for by style. Extra operations added to the preparation steps, such as slicing, require
extra water. Cooking and cooling canned products takes more water on the average than condensing
for frozen products. On the other hand, frozen but not canned corn must be blanched, requiring
more water and generating additional pollutants.
TYPES OF EQUIPMENT
Most of the steps in preparing foods for preservation can be done in more than one way and the
difference in the generation of wastes is one of several factors considered in choosing a preparation
method. Peeling and blanching are such steps. For those commodities which are peeled, from 30
to 60% of the total plant pollutant load is commonly contributed by peeling; for blanched commod-
ities, from 10 to 60% of the load commonly conies from blanching. Low-waste-producing equip-
ment has been developed for both procedures. Dry caustic peeling is reported to reduce the
wastewater flow from the peeling operation by 80 to 90% and the pollutant load from peeling by
60 to 90% in processing potatoes, beets, and peaches. The dry caustic equipment is more expen-
sive than conventional peelers. Modified blanching methods have reduced the blanch wastewater
by two-thirds to almost 100% and the generation of pollutants in the blanching operation by about
the same for peas, limas, corn, snap beans, and spinach. However, higher costs and product loss
can be problems. In a recent industry study, about 12% of the BOD generation and 9% of the
suspended solids generation at apple, beet, carrot, pear, and tomato plants were associated with the
type of peeling equipment in use.5
28
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Other differences in preparation equipment go with the style of the product. For example,
pitters may or may not be used in processing such fruits as cherries, plums, and olives; a variety of
cutters and slicers are used in some plants for peaches, pears, apples, snap beans, spinach, root
crops, and other commodities; size graders are needed for efficient preparation of some commodities;
specific gravity quality graders may be used on peas and limas; and mechanical corers are needed for
some styles of apples. All of these alternative preparation steps use water and generate pollutants to
some degree.
WATER USE
Water is both recycled within the same piece of equipment (for example, returned from the end
to the beginning of a flume) and reused from one piece of equipment to another, typically from a
later to an earlier step in the preparation process. Cooling, chlorinating, or other renovation pro-
cedures may occur between uses. Fruit and vegetable processors are estimated to get 64% of their
water from such reuse (180 billion gallons from 280 billion gallons per year of gross applied water).
The percentage of reused water varies among plants from little or none to more than 90% and tends
to increase on the average with increasing plant size. About 40% of the plants separate their rela-
tively clean wastewater (typically cooling or condensing water) from that with a higher pollutant
load and dispose of the two streams separately. The clean water is also a source of water for reuse.
Water is commonly used to transport the product between preparation steps. Water transport
is both economical and advantageous in maintaining sanitation. The amount of water transportation
varies widely among plants and somewhat, on the average, among commodities. The contribution
of water transportation to the pollutant load depends on the stage in preparation at which it occurs.
Among commodities with a fairly high degree of exposure to leaching from this source are asparagus,
snap beans, broccoli, cauliflower, carrots, mushrooms, okra, pears, potatoes, and soft squash; among
those with a low degree of exposure are berries, grapes, pickles, pineapple, plums, pumpkin and
sauerkraut.
The quantity of organics leached from the product is a function of the duration of immersion
and the size of the food particle. Figure III-4 shows this for timed immersions of pieces of pears
from unpeeled halves to diced.6 The measured concentrations are of total oxygen demand, propor-
tional to BOD in this instance. The pollutant strength increases sharply with both immersion time
and decreasing size of cut.
Solid residuals from food processing (culls, peels, pits, etc.) may be removed from the plant
in a water stream or by a dry transportation method. The degree of water conveyance of residuals
varies widely among plants processing the same commodity but fairly consistently among commod-
ities on the average. The most solid residuals removed have been reported in apricot, asparagus, dry
bean, berry, pepper, pickle, potato, pumpkin, soft squash and turnip plants; the least in apple, cauli-
flower, citrus, corn, mushroom, okra, pineapple and sauerkraut plants.
Leaching from solid residuals would be similar to that from the food product, a function of
time and particle size. However, water transportation of either the food or the residuals explains
only a tiny fraction of the plant to plant differences in pollutant generation. Industry data indicate
that only 1% of the variation in wastewater volume is associated with either factor; and 4% of the
variation in BOD generation is associated with water transport of the product.7
PERCENT OF USED CAPACITY
Food processors commonly use about 80% of a plant's design capacity, sometimes much less.
The unused capacity is needed for glut conditions within a season and for bumper crops which
could occur any year. The proportion of the capacity used varies widely from day to day within a
plant. Both wastewater flow and BOD generation per ton increase as the proportion used decreases.
29
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3500
2500
c
o
1500
500
Pears
Dices
1.0 2.0 3.0 4.0
IMMERSION TIME, min.
5.0
Figure III-4. Effect of immersion and cutting on pollution.
One reason for this strong negative relationship is that the flow of water cannot be reduced in some
equipment to match a reduced flow of product; and so, more water leaches more BOD. Other
factors could be partly responsible. For example, larger tonnages may force a shift in the propor-
tions of product styles because of equipment bottlenecks.
HOUSEKEEPING
Many operations in food processing which are incidental to the principal steps in preparing
the product affect both the quantity and the strength of wastewater. Some of these practices are
described here briefly and discussed in detail in the following chapter.
WATER USE
Water running in unused equipment is a source of waste. Examples are cleanup hoses between
periods of use, and flumes, washers, or graders which are empty of product.
CLEANUP
Sweeping (instead of hosing) and dry conveying of solid residuals save water and reduce pol-
lutant generation. High pressure-low volume systems permit plant cleaning with efficient water
use. The continuous application of chlorinated water to belts and other suitable equipment makes
subsequent cleanup easier and more efficient. Clean-in-place systems can be designed to clean
30
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pipes, tanks, and other equipment automatically and without wasting water. Prompt removal of
residues preventing a buildup of food deposits where water is running avoids excessive leaching.
Food processing demands sanitation. Whatever is done to conserve water and abate pollution
takes a second place to maintaining sanitary conditions in a food plant and its equipment.
SPILLAGE
Spilled products, especially juiced commodities and syrup, are a strong source of BOD and
suspended solids. If spills are unavoidable, the product should at least be kept out of the waste-
water stream.
31
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Chapter IV
IN-PLANT MODIFICATIONS AND EFFECTS
A. WATER CONSERVATION TECHNIQUES
Today, as always before, the fruit and vegetable processing industry is entirely dependent on
an adequate supply of good quality water. Automation cannot completely replace the need for
water. There are no mechanical or chemical substitutes for its use in certain operations.
Because of increased concern about chemical and biological contaminants on foods, and more
rigid definitions of cleanliness, the effective use of water is more important today than ever before.
In 1974 the canning and freezing industry processed some 35 million tons of fruits and vegetables.
Over 100 billion gallons of water were discharged by the industry, with some 180 billion gallons of
water being reused.
Today water is becoming an expensive commodity and it must be used efficiently and effec-
tively. Water and waste costs may appear to be a small percentage of gross sales, but become
significant when compared to the small profit obtained from sales. As a matter of economic
necessity coupled with recognition of responsibility in matters of public concern, the food industry
is giving increasing emphasis to water conservation and stream pollution abatement.
Historically, the reuse of water in the food industry was discouraged because of the problem
of bacterial contamination. Prior to the development of effective water chlorination procedures,
any reuse of water in contact with the product was considered to be hazardous. Even now, the
recovery of water from one operation for reuse in the same or other operation, will require con-
sideration of the effect of this water-saving procedure on the quality of the final product, on
general sanitation of the plant, and, especially, consideration of the effect on the sanitary condi-
tion of the unit operation in which the water is to be reused. Indiscriminate reuse of water can
result in unexpected and undersirable conditions. Where chlorination of the reused water is relied
upon to prevent bacteriological problems, the capabilities and limitations of chlorine as a germicide
must be understood.
Water reclaimed for use in contact with the food product in its final stages of preparation
must be low in total bacteria count, free of microorganisms having public health significance,
and free of materials which could constitute adulteration of the product. In flumes for convery-
ing and preliminary washing of raw unpeeled or uncut products (such as whole pumpkins, beets,
asparagus, whole fruits, etc.), water of lower quality, with regard to bacterial count, may be used.
In the past, it. was always the practice that partially or finally-prepared products such as washed or
blanched peas, beans, asparagus, cut fruits, etc., should be conveyed or washed in fresh water.
Today there are necessary and desirable exceptions to this general rule.
The economics of food processing have brought about development and widespread use of
bulk-handling methods in preparing foods for canning and freezing. Within the plant, bulk-hand-
ling consists of hydraulic pumps for receiving raw foods and hydraulic systems for conveying foods
to and from operations which prepare them for final processing. The excessive water demand of
these hydraulic systems creates situations of concern to industry and the public in areas where
water shortages exist. An allied concern in all areas of the nation is the necessity to treat the
correspondingly large volumes of fluid wastes.
32
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GUIDELINES FOR WATER USE
The principal conditions governing the use of reclaimed waters in contact with food products
are the following:
1. That the water be free of microorganisms of public health significance.
2. That the water contain no chemicals in concentrations toxic or otherwise harmful to man.
3. That the water be free of any materials or compounds which could impart discoloration,
off-flavor, or off-odor to the product or otherwise adversely affect its quality.
4. That the chemical and physical quality of the water be acceptable for its intended use.
Compliance of reused water with these conditions would not always mean that it meets the
standards for potable water as defined by proposed drinking water standards (PL92-523). Because
of the economic infeasibility, impracticality from an operational standpoint, and the lack of sig-
nificant need for one-pass use of fresh water at all points in food canning, the National Canners
Association objected to Section 128.07 of the Food and Drug Administration's proposed "Good
Manufacturing Practice" regulations (21CFR 128 April 1974). Section 128.7 of the draft regula-
tions included this statement:
"Water used for washing, rinsing, or conveying food products shall be of potable quality
and shall not be recirculated unless suitably treated to assure its potability."
The Association filed the following statement in reference to the above proposed regulation:
"Water used in the washing of raw products is in many cases, recycled and chlorinated
but it is far from potable in that it is not drinkable. The product as it leaves this water
is cleaner than when it entered, which is the desired result. The same thing is true of
the counterflow systems for using water throughout a cannery."
A counter proposal was offered and a compromise reached for the reuse of water. The current
regulation now states:
"Raw materials shall be washed or cleaned as required to remove soil or other con-
tamination. Water used for washing, rinsing or conveying of food products shall
be of adequate quality, and water shall not be reused for washing, rinsing or conveying
products in a manner that may result in contamination of food products."
The Association believes that this compromise will allow a continuation of water conservation
practices now in use which have been shown to have no adverse effect on the quality and whole-
someness of the finished product.
BENEFICIAL RESULTS FROM WATER CONSERVATION
Water recycling is beneficial for the following reasons:
1. Water is no longer a free commodity nor is it available in unlimited quantities.
2. There are economic considerations in the purchase of water and in the disposal of
water.
3. Reductions in the volume of water used result in corresponding reductions in the
volume of wastewater to be treated.
33
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In some instances the total organic load may not be significantly reduced by water conserva-
tion. However, the containment of the organic load in fewer gallons of water will result in significant
advantages such as:
1. Hydraulic overloads on treatment systems can be alleviated.
2. Treatment of concentrated wastewaters is more economical and efficient than the treat-
ment of dilute wastewaters.
3. By increasing the concentration of organic matter in water, the potential for recovery or
by-product utilization is enhanced.
THE COST OF WATER
The cost of water provided by a municipal system may vary from 15 cents to $2.50 per
thousand gallons. In some areas where water is least expensive, it is generally of high quality,
requires minimal treatment and minimal pumping. The higher costs for water are usually associated
with poorer quality water which has to have extensive treatment and must be transported over long
distances.
Often it is suggested that a company should drill its own well. This may or may not be a good
suggestion. It depends on whether or not one is fortunate to obtain water at a reasonable depth
which is also adequate in quantity and quality. The following is one example of costs associated
with obtaining water from a well. Assume that the well delivers 500 gallons per minute and the
first cost for the drilling, casing, pump, distribution system and controls is $40,000. If con-
sumptive use is 400 gallons per minute and it is in operation for 8 hours and 200 days per year,
some 40 million gallons of water per year will be withdrawn. With a 10-year straight line depreci-
ation, the cost will be $4,000 or 10 cents per 1,000 gallons. Maintenance is usually more than
anticipated and involves replacement of casing, replacement of screens and replacement of pump
impellers. If $2,000 is allocated for this purpose, then maintenance will be 5 cents per 1,000
gallons. The electrical costs will be $1,470 per year of 3.7 cents per 1,000 gallons. Interest
charges are calculated at 9 percent or 9 cents per 1,000 gallons. The total costs of obtaining water
are tabulated as follows:
Depreciation
Maintenance
Power
Interest
Taxes, insurance & misc.
Per thousand gallons: 28.7
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3. Insect eggs and fragments.
4. Chemical residues, such as insecticidal dusts and sprays.
5. Organic debris, such as leaves and stems or product fragments.
6. Peel, especially following chemical peelers.
The volume of water used for washing varies widely, not only from one commodity to another,
but also within each commodity from one processing plant to another. Some reported quantities
of water used (gallons per raw ton or gallons per finished case) and characteristics of the wastewater
produced by washing fruits and vegetables are summarized in table IV-1. Washing and rinsing oper-
ations are the major source of the hydraulic load associated with many products. The reduction of
various contaminants by washing potatoes and tomatoes has been reported with the results being
summarized in table IV-2.
TYPES OF WASHERS
Washing methods vary according to the product. Commonly used washers include:
1. Sprays positioned over belts, elevators, or other conveyors.
2. Flood-type washers, consisting of immersion or soak tanks in which the product is moved
forward by angled sprays and/or by recirculated water. Flumes are also used for washing
in a similar fashion.
3. Rotary or reel washers, consisting of sprays situated within a perforated metal or screen
cylinder.
4. Brush washers, consisting of revolving brushes which scour the exposed product surface.
Two or more types of washers arranged in series are generally most effective; various combinations
are used for most commodities.
Spray Washers
Sprays are used extensively for washing raw products. They may be used alone or in conjunc-
tion with other types of washers. The primary function of sprays is to apply water in such a
manner as to physically and efficiently remove undesirable materials from the raw product.
Therefore, how water is used (as dictated by the type of spray nozzles and their physical arrange-
ment) is most important. The quantity of water used is of secondary importance.
The cleansing action of water is a function of the amount of energy imparted by the water on
the raw product surface. Water impinging on a surface at a high velocity effects greater cleansing
efficiencies than a large volume of water simply cascading onto the same surface. To obtain maxi-
mum cleansing efficiency of water used in spray washing equipment, careful consideration must be
given to the choice and placement of spray nozzles.
1. Spray nozzles which deliver a small volume of water at high velocity are preferred.
Nozzles which deliver a flat, fan-shaped spray are quite suitable and most effective
when arranged in banks (see figure IV-1).
2. The nozzles should be of a design which minimizes clogging. This is especially impor-
tant for sprays in recirculated water systems.
35
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Table IV-1 .-Use of water in washing fruits and vegetables8
Product
Beans, green
Beets
Carrots
Corn
Cranberry
Fruits
Peaches
Peas
Potatoes
" (dehydrated)
Tomatoes
Function
wash
primary wash flume
primary wash flume
husked corn washer
washer & silker
skimmer & washer
spray
spray
lye peel rinser
flume
clipper mill & wash
wash
spray
spray & soak
peel & wash
spray
slicer-washer
primary wash flume
wash
rinse after dump
lye peel removal
spray
lye peel rinse
lye peel rinse
Water used
ga I/ton a
100
90
103
212
1440
385
360 (gal/min)
707 (gal/min)
1028 (gal/min)
706
432
2500
640
468
960
1540
70
1320
1186
504
gal/case a
25.5
712
1274
790
Effluent load
BOD
lbs/tona
0.8
0.5
2.5
15.0
36.5
12.0
4.0
20.0
10.7
2.2
5.1
40.0
0.5
SS
lbs/tona
20.0
2.0
1.0
4.0
15.0
5.5
0.5
30.0
21.0
2.2
2.7
49.7
2.0
aTon of raw product or case of finished product.
3. The discharge rate of the selected nozzle must be adequate to meet the needs of each
particular application. The nozzles must be operated within the design water pressure
range. Operating pressures which are either too high or too low for the selected nozzles
will decrease their effectiveness.
4. If the nozzles are positioned too high above the product, energy in the water will be
partially dissipated and a less effective job of cleaning will result.
5. The nozzles must be spaced along each header so that the sprays do not overlap excessively,
thereby resulting in excessive use of water.
6. The nozzles on the ends of each header should not be placed so close to the end as to
cause waste of unused water along the sides of the washer.
36
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Table IV-2.—Effectiveness of washing in removing extraneous matter8
Product
Potatoes (dehydrated)
Tomatoes
Function
presoak & wash
wash
chlorinated wash
Item
surface contamination
soil
organic debris
bacterial spores
Drosophila eggs
bacterial spores
lactic bacteria
mold
bacteria
spores
Reduction %
0.5-12
33-80
30-64
6-79
10-70
75-95
75-96
76-92
90
92
Figure IV-1. Recommended placement of sprays.
37
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The type of conveyor used in spray washing equipment influences the cleansing efficiency.
Roller conveyors are most effective. The revolving rollers turn the raw product, thereby exposing
all surfaces to the sprays while permitting leaves, stems, and other debris to be flushed through the
rollers. The conveyor of second choice is constructed of steel-mesh belting and the belting with
the largest permissible openings should be used. Sprays should be positioned above and below the
mesh belt. Use of solid belting should be avoided in spray washing equipment.
One of the problems in washing is the unavoidable variation in amount of product going over
a line, depending on the schedule of deliveries from the field. Regardless of whether the line is
loaded heavily or lightly, the washers operate with the same amount of water. Under constant
conditions of water flow such as these, the cleanliness of the washed product is directly related to
the quantity of product per unit volume of water. Wherever possible, the rate of product through-
put should be as even as physically possible and held at that rate which yields maximum cleaning
efficiency.
In some situations, consumption of water for spray washing and rinsing can be minimized by
dividing the spray headers into two sets (see figure IV-2). Fresh water is used initially through the
final set of nozzles. This rinse water can then be collected and pumped to the first set of nozzles,
thereby reducing the total volume of water by a half. The wash water may be discharged as waste-
water or may be collected and used for other purposes. This arrangement is especially effective
when sprays are used in conjunction with other types of washers or as a final rinse prior to canning
or freezing. It may be necessary to screen or filter the water before reuse to prevent the plugging
of spray nozzles.
The results of NCA studies on product washers emphasize the importance of the final spray
wash. It is here that the final cleanliness of the product is established. Pluming and soaking are
only a preparation for the final wash. The use of proportionately large volumes of water in tanks
or flumes does not lessen the need for a vigorous spray wash.
pooooo oooooo
Product
flow
Wasted or
further reuse
Figure IV-2. Reuse of final rinse water.
38
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Flood Washers
Flood-type washers include dump tanks, immersion tanks, flumes, and flotation washers.
These are especially suited for washing leaf vegetables, easily bruised fruits, small particles such as
peas and dry beans, and soil-encrusted, mechanically harvested tomatoes. Cleansing is achieved by
agitation of the product in water. This action is normally created by recirculating water within the
unit. Sand, stones, and other settleable materials are removed periodically through bottom drains
or continuously by constant water flow or by mechanical means, depending upon equipment de-
sign. In flotation washers, the leaves, stems, and other floatable materials are either skimmed from
the water surface or discharged from the unit by a constant overflow.
In all flood washers, soils and other suspended matter are flushed from the unit by the con-
stant addition of clean water. Product cleansing dictates that the rate of clean water addition be
sufficient to prevent build-up of contaminants within the system. Water conservation and waste
reduction dictate that the rate be carefully adjusted to prevent excessive use of clean water.
Washing efficiencies are greatly enhanced when sprays are used to rinse the raw product as it
is conveyed out of a flood-type washer. An arrangement similar to that depicted in figure IV-1 is
recommended. Effluent from the rinse sprays may be used in the flood washer to further the use
of water.
Reel Washers
Reel washers are revolving cylinders of perforated metal, screening, or metal rods. Such
washers are suited for cleaning root vegetables, as well as a variety of fruits and other vegetables.
Generally, reel washers are tailored to handle specific products. Cleansing action is facilitated by
the raw product units rubbing against each other as they tumble through the reel. A row of spray
nozzles placed within the cylinder provides water to lubricate the raw product and to wash away
soil and other extraneous debris.
Since the cleansing efficiency of reel washers is dependent upon the use of water, proper
selection of spray nozzles is important. High pressure nozzles, either with fan-shaped or solid
cone patterns, are recommended. These nozzles are most effective and use less water than flood-
type nozzles. To maximize cleansing, attention must be given to the height and spacing of the
nozzles within the reel. Product feed rates should be constant; overloading must be avoided.
Brush Washers
Brush washers are suitable for scrubbing root vegetables, especially if the vegetables have
been previously soaked. The bristles effectively remove mud from the product surface. Asparagus
is also cleaned with this equipment.8 The brushes must be cleaned continuously with water
sprays to prevent recontamination of the product. Minimum water usage requires selection of
suitable spray nozzles. High pressure, low volume nozzles are recommended. These should be
positioned over the brushes to aid in cleaning the raw product and to cleanse the bristles of mud
and other debris.
Combination of Washers
Most commodities will require washing by a combination of two or more methods, such as
soaking and flood washing, or soaking and reel or brush washing. Washing or rinsing operations
may also be required at several intermediate points in the processing line, such as after peeling or
cutting. For all washing and rinsing operations, cleaning efficiencies must not be equated to the
quantity of water applied, but rather to the methods in which water is used. In every case a
spray rinse will greatly enhance product cleanliness. Careful consideration and proper installation
39
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of spray nozzles, as previously discussed, will contribute significantly toward maximizing washing
efficiencies while minimizing water consumption.
WASH WATER TEMPERATURE
Washing efficiencies are greatiy enhanced when warm water (up to 140° F) is used. However,
warm water may detrimentally affect the quality of some raw products. Furthermore, warm
temperatures (above 80°F) favor the reproduction of food spoilage organisms.
Cold water is recommended for use in immersion washers (dump tanks, soaking tanks, flumes
and flood washers). When bacteriological contamination is of concern in such systems, chlorination
may be employed. Only that rate of clean water addition which will maintain a sanitary condition
within the system will thus be required.
Warm water may be used to wash raw products if appropriate precautions are observed.
• Since the organic matter contained in the wash water will provide a good medium for
bacterial growth, the wash water should be discharged as wastewater after use.
• Chlorination becomes less effective with higher temperatures. When warm water is used
in immersion washers, dilution by a high rate of clean water addition must be provided
to control microbial populations.
USE OF DETERGENTS
Detergents aid in the removal of soil and other debris from surfaces by increasing the wetability
of the contaminants. The effectiveness of detergents is generally increased by using warm water.
Detergent baths are effective for washing such products as root vegetables, asparagus, and mech-
anically harvested tomatoes. The quantity of water required to rinse presoaked commodities will
be substantially less when detergents are used in the soaking tanks.
Detergent formulations are widely varied with many being manufactured for specific applica-
tions. Only those detergents which have been approved by the Federal Food and Drug Administra-
tion for use in food processing operations must be used. Adequate rinsing must follow the
application of detergents to assure that no residue is carried into the filled product containers.
POTENTIAL USES OF WATER
Reclaimed water can be used in one of two ways. It can either be reused within the system
from which it was recovered (i.e., recirculated) or it can be used in some other operation. Its
suitability for use in any operation is dictated by the quality of water required in that operation.
Water quality requirements are less stringent for intermediate and preliminary steps with the final
operations requiring water of high quality. Water used to convey waste materials can virtually be
of any quality aesthetically acceptable. A check list indicating some potential uses of water from
various unit operations is provided in table IV-3.
Several methods whereby water may be recovered and reused are described in detail in this
chapter. Since water reuse offers the most practical means to significantly reduce hydraulic waste
loads, implementation of suitable reuse systems is strongly recommended.
40
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Table IV-3.—Water-economy check lisfi
Operation or equipment
1. Acid dip for fruit
2. Washing of product
A. First wash followed by
2nd wash
B. Final wash of product
3. Flumes
A. Fluming of unwashed or
unprepared product
(peas, pumpkin, etc.)
B. Fluming partially prepared
product
C. Fluming fully prepared
product
D. Fluming of wastes
4. Lye peeling
5. Product-holding vats; product
covered with water or brine
6. Blanchers — all types
A. Original filling water
B. Replacement or make-up
water
7. Salt brine quality graders
followed by a fresh water wash
8. Washing pans, trays, etc.
A. Tank washers-original water
B. Spray or make-up water
9. Lubrication of product in
machines such as pear peelers,
fruit size graders, etc.
10. Vacuum concentrators
11. Washing empty cans
12. Washing cans after closing
13. Brine and syrup
14. Processing jars under water
15. Can coolers
A. Cooling canals
1. Original water
2. Make-up water
B. Continuous cookers where
cans are partially immersed
in water
1. Original water
2. Make-up water
May
recovered
water
be used?
Yes
Yes
No
Yes
Yes
No
Yes
Yes
No
No
No
Yes
No
No
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
May water from
this equipment
be reused else-
where in plant?
No
Yesa
Yesa
Yesa
Yesa
Yes
No
No
No
No
No
Only in this
equipment
No
No
Yesa
In this equipment
after cooling and
chlorination
No
Yesa
Food processing
Source of
water for
reuse in
equipment
Can coolers
Can coolers
Can coolers
Any waste
water
Can coolers
Can coolers
Can coolers
Can coolers
& processing
waters
Water from these coolers may be reused
satisfactorily for cooling cans after
circulating over cooling towers, if careful
attention is paid to proper control of re-
placement water, and to keeping down
bacterial count by chlorination and
frequent cleaning.
41
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Table IV'-3.-Water-economy check!'/st9 (continued)
Operation or equipment
15. Can coolers (continued)
C. Spray coolers with cans
not immersed in water
D. Batch cooling in retorts
16. Cleanup purposes
A. Preliminary wash
B. Final wash
17. Box washers
May
recovered
water
be used?
Yes
Yes
Yes
No
Yes
May water from
this equipment
be reused else-
where in plant?
Source of
water for
reuse in
equipment
This water may be reused in other
places as indicated.
Yesa
No
No
Can coolers
Can coolers
aA certain amount of water may be reused for make-up water and in preceding operations if the counterflow principle
is used with the recommended precautions.
WATER RECIRCULATION SYSTEMS
The use of water in some systems may be extended by recirculating the water in a cyclic, or
closed-loop, fashion. Once such systems are filled, water consumption will be limited to the volume
required to maintain a proper level or acceptable water quality within the units. To enable reuse
of water in this manner, treatment procedures may be required. Generally, this disadvantage will be
more than offset by the benefits accrued through reduced water usage and wastewater generation.
There are three principal operations which readily lend themselves to water recirculation.
These are (1) can cooling or freezer compressor cooling waters, (2) raw product fluming water,
and (3) product concentrator or evaporator water. Although only these are discussed in this chapter,
the principles and procedures which are described may be applied to other special situations.
CAN COOLING WATER
Water is used to cool containers after thermal processing. To prevent the possibility of spoilage
due to recontamination, chlorination of can cooling water is recommended. Regardless of the type
of cooling equipment used, the water must be continuously replaced to maintain the proper tempera-
ture to accomplish the designated task. A constant overflow of relatively clean, warm water results.
If the temperature of this effluent stream is reduced, the water may be reused to cool additional
containers.
Cooling towers are being successfully and advantageously used to reduce the temperature of
cooling waters (see figure IV-3). When cooling towers are used, the following precautions should
be observed:
1. Chlorination: Sufficient chlorine should be added to the water after it has passed over
the tower to maintain a residual of approximately 0.5 ppm at the end of the cycle. Since
this amount is not adequate to prevent all growth of microorganisms, the chlorine
residual should be increased to 4-5 ppm for a short time about every two weeks.
2. Screening: It is advisable to screen all water before passage over the tower to remove
any large pieces of foreign matter.
42
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Cans in
f
1 Cooker
r
^^
i
To sa
tower
-n-
Cooler
0
f
»
nitize
?) Chic
I
1
rine
i
I I
-
~ tower ~
X^ Sump ,Xx
^^jf ^- ^r- ^SjS
1
Water
make-up
4 1
Return to tower
Figure IV-3. Chlorination of can cooling water recycled over a cooling tower.
3. Can washing: Ml cans must be thoroughly washed preferably with hot water after closing
and before entering the cooker, to prevent syrup, oil, or other adhering food material
from contaminating the cooling water.
4. Replacement water: Sufficient replacement water should be added to prevent concentra-
tion of minerals (salts) to the point where spotting of containers becomes a problem.
Can cooling water may also be recovered and used in other operations, thereby reducing the
volume of water consumed by the total plant operation. Can cooling water may be used directly
in washers or cooled and used for product rinsing or as make-up water in flumes.
COMPRESSOR COOLING WATER
Although the volume of water used to cool freezer compressors may be relatively minor when
compared to other effluent streams, the quantity annually consumed for this purpose is generally
significant. The quantity of water required to cool compressors can be drastically reduced by.
collecting, cooling and recycling the warm effluent. Cooling towers can be advantageously used to
lower the temperature of the water.
Since compressor cooling water does not contain organic contaminants, only minimal chlorina-
tion of the water will be required prior to passage over a cooling tower. The sole purpose of chlorina-
tion is to control algal growth in the tower. The water replacement rate may generally be limited to
that which is required to maintain the necessary water level within the system. In situations where
extremely hard water results in rapid and problematic concentration of salts, chelating agents may
be used to minimize the volume of fresh water otherwise required for dilution.
PRODUCT PLUMING WATER
The state of the raw product being conveyed largely determines the quality of water which is
required in a flume. Flumes for conveying and washing raw products (such as beets, tomatoes,
and other unprepared fruits and vegetables) do not require fresh water. On the other hand, partially
prepared products (such as blanched vegetables and cut fruits) should be flumed in water of good
sanitary quality. In all cases water may be recirculated in flumes provided that clean water, with or
without chlorination, is added at a rate sufficient to maintain satisfactory conditions within each
system.
43
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An undesirable feature of recirculating flume water is the inherent tendency for developing
relatively high concentrations of organic matter within the system. Each successive contact of the
water with raw product adds to the total dissolved solids and organic content until equilibrium is
reached. Furthermore, the temperature of recirculated water tends to increase, thereby creating a
favorable environment for the reproduction of microorganisms. The resulting increase in spore loads
aggravates the potential spoilage hazard for low-acid foods. Another matter of concern with
recirculation systems is the potential for accumulation of pesticides and other chemicals.
Conservation of flume water in pea canneries, for example, has been accomplished by re-
circulating water within unit systems as illustrated in figure IV-4. In the usual arrangement of such
a system, the peas are fed into the hopper of an elevating pump for which water is supplied from a
tank. At the end of the pump line, the peas are discharged into a dewatering reel and are delivered
to the next operation. The water is collected in a pan under the reel and returned to the supply
tank. Usually the water is returned through the screen of a scavenger reel to remove larger solid
particles. Fresh make-up water is added to the system continuously through an adjustable valve and
intermittantiy upon demand through a float-controlled valve. The sanitary condition of the water
is largely determined by the amount of fresh water added to the system.
Buildup of particulate matter in a recirculated system can be minimized by incorporating a
trash screen in the return line, as depicted in figure IV-4. Carryover of bacteria from the system
can be minimized by rinsing the product with fresh or clean water. The rinse water can then be
added to the system for make-up and/or dilution.
Reused flume water
Continuous addition of fresh water
Figure IV-4. Diagram of water flow in a flume system (with recirculated water in two
operations and reused water from a third operation to flume peas to the
inspection belts).
44
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Controlling the concentration of organic matter and bacterial numbers in recirculating flumes
by dilution would require the addition of clean water at a variable but high replacement rate. Al-
though this practice will greatly reduce wastewater volumes compared to single-use fluming systems,
the resultant waste load will still be considerable. Waste generation and bacterial numbers can be
more effectively controlled by counterflow reuse and chlorination of water. When fluming peaches,
apples and other high-acid products, bacterial numbers can be controlled with minimal dilution by
controlling the pH of flume waters to 4.0 or less.
EVAPORATOR WATER
One type of evaporator widely used to concentrate tomato and fruit juices, fish solubles, and
other food products employs a barometric leg to create a vacuum in the unit in order to condense
vapors emanating therefrom (figure IV-5). Cold water injected into the barometric leg condenses
water vapor and volatile organics while absorbing the heat of vaporization. Since the exit tempera-
ture of the water is one of the parameters which determines the efficiency of operation, cold water
injection rates are closely controlled.
Condenser
Cold water in
Evaporator
Hot well
Barometric leg
Hot water out
Figure IV-5. Barometric condenser water.
A multi-effect evaporator can consume a large quantity of water (in excess of 1,000 gpm).
Because the effluent is warm (generally around 120° F) and may contain traces of organic matter,
the water is often wasted. However, this water is suitable for reuse. Since the effluent volume
is large, cooling and recycling offer the greatest potential for reducing the wastewater volume.
Cooling towers are being advantageously used for this purpose. Although the thermodynamics
will differ, the application is similar to the recovery of can cooling and freezer compressor waters.
Fresh water additions may be required to control concentrations of minerals and organic matter.
The resultant overflow from the system can be readily used elsewhere in the plant.
THE COUNTERFLOW WATER REUSE SYSTEM
Preparatory operations in food processing are designed to assure the delivery of clean, whole-
some products to the final packaging operation. Water is used at various stages to separate and
remove undesirable materials, such as leaves, soil, immature and overripe products, and bacterial
45
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contaminants. To assure product cleanliness, water used in final washing and rinsing operations
must be of highest sanitary quality, whereas water used in preceding operations need not neces-
sarily meet such stringent sanitary requirements. This premise is the basis upon which counterflow
water reuse systems have been developed.
Counterflow water systems are designed to minimize the quantity of water required to effective-
ly prepare clean foods, thereby minimizing waste loads associated with food processing. Basically,
most of the fresh water is used in the final operation, collected and reused in a previous operation,
and recollected and reused in this manner one or more additional times. Since the water always
passes counter to the flow of the product, the product comes into contact with subsequently
cleaner water and is finally washed or rinsed with fresh water. Although the following discussion
concerns counterflow reuse in pea processing, the principles may be applied to the processing of
any commodity.
The sanitary condition of water is normally evaluated by measuring the bacterial population in
the water. The sanitary condition of raw product is directly influenced by the bacteria count of the
water with which it comes in contact. The condition of pea fluming waters was monitored during
a study in which recirculation was compared to counterflow reuse with different chlorination
practices.9 The results are summarized in table IV-4. The comparative bacteria counts clearly
indicate the effectiveness of product cleansing by counterflow reuse of water.
Table IV-4.—Comparison of total numbers of bacteria in flume waters reused by recirculation and by
counterflow methods, and comparison of the effect of varying the extent of chlorination in these waters9
Method of water reuse and extent of chlorination in each plant:
Plant A — Water recirculated; in-plant chlorination only.
Plant B — Counterflow reuse; no chlorination at any point.
Plant C — Counterflow reuse; in-plant chlorination only.
Plant D — Counterflow reuse; in-plant chlorination plus rechlorination.
Use of water
sampled
Water used to flume
peas from
quality graders to
inspection belts
Water used to pump
or flume peas
from blanchers to
quality graders
Water used to flume
peas from size
graders to
blanchers
Water used to flume
peas from washers
to size graders
Plant
A
B
C
D
A
B
C
D
A
B
C
D
A
B
C
D
Bacteria count3 per ml of water
High
23,000,000
350,000
14,500
3,500
1,800,000,000
1 ,900,000
220,000
21,000
78,000,000
2,900,000
190,000
130,000
52,400,000
1 1 ,000,000
130,000
140,000
Low
27,000
13,000
2,300
400
590,000
77,000
14,000
700
98,500
50,000
10,000
2,300
91,000
350,000
14,000
3,500
Average
4,729,000
65,200
6,300
1,300
365,590,000
611,000
58,760
6,250
15,752,000
837,200
40,140
22,470
13,752,300
1,780,000
47,180
31,610
aBacteria counts represent the numbers of colonies growing on glucose-tryptone agar plates inoculated with unheated flume
water and incubated for 48 hours at 86° F
46
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Rechlorination Unit
Figure IV-6. General plan for counterflow reuse of flume water in a pea cannery.
In-plant
chlorinator
Fresh chlorinated water
Reused flume water
1 Chlorine solution line
Automatic valve for make-up water
Gate valve for flow control
Figure IV-7. Plan of counterflow reuse system designed to eliminate undesirable
features of flume system shown in figure IV-4.
47
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Cooling flume
In-plant chlorinator
9
.i
Rechlorination
unit
o
Automatic valve for make-up water
Fresh chlorinated water
Reused flume water
Chlorine solution line
Gate valve for flow control
Figure IV-8. Plan for counterflow reuse of water in a pea cannery where line
arrangements require extensive fluming operations
A FOUR-STAGE REUSE SYSTEM
A general plan for counterflow reuse of flume water in a pea cannery is shown in figure IV-6.
In this plan most of the fresh water enters the system as flume water for conveying peas from the
quality graders to the inspection belts. This is the final washing of the peas before they are filled
into the cans. The water separated from the peas at the inspection belts is collected and used for
the second time in fluming peas from the blanchers to the quality graders.
The water is used for the third time in fluming peas from the size graders to the blanchers,
and for the fourth time to pump peas from the washers to the size graders. At the size graders,
the water is separated from the peas by means of a reel. From this point it may be used in the
first washing of the peas or may be diverted to flumes which remove wastes from beneath the
cleaners. Figures IV-7 and IV-8 show counterflow reuse schemes for different arrangements of
equipment. (Figure IV-7 may be compared with figure IV-4 to illustrate the differences between
recirculation and counterflow reuse of water.) In each case rechlorination of the water is recom-
mended after each use. As indicated by the results summarized in table IV-4, rechlorination will
effectively reduce and control bacterial populations in reused water.
INSTALLATION OF COUNTERFLOW SYSTEMS
The amount of water which can be saved by a counterflow reuse system will depend primarily
on the degree of balance obtained between the rate of fresh water addition to the system and the
amount of water required to adequately carry out the different operations. If the system is to
be water-saving, there must be no appreciable wastage of water other than that which may be
required to maintain aesthetically acceptable conditions within the system. In order to obtain
maximum benefits with minimum supervision, the system should include collection tanks,
screens, and appropriate water valves.
48
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Collection Tanks
After each use, the water should be collected in a tank from which it may be delivered by
pump or gravity to the next operation. Ordinarily the water used in the same fluming operation
on all of the canning lines should be brought into one collecting tank. For example, in figure IV-6,
all of the water used to flume peas from quality graders to inspection belts would be collected in
Tank No. 1. It is important that water from a later stage in the reuse system not be added to this
tank. The tank should have sufficient capacity to contain, without overflowing, all of the water
which would be delivered to it when all lines are in operation.
Screens for Reused Water
To prevent the accumulation of particulate matter in reused water, fine mesh screens should
be provided at each collection tank. Removal of particulates will extend the reusability of re-
claimed water. Dry systems to collect and transport the accumulated solids should be provided.
Automatic Valves for Fresh Water Make-Up
Fresh water lines, equipped with float-controlled valves, should be provided at each collecting
tank. These valves will eliminate the possibility of the tank becoming empty, thereby protecting
the pump and assuring that an adequate supply of water is available for the subsequent operation.
Control of Flow Rates
Minimization of water usage by the counterflow reuse method depends entirely upon
maintaining balances between the several component subsystems. Water withdrawn from any
collection tank must not exceed that volume which is required by the next operation. In addition,
the withdrawal rate from any collection tank should not greatly exceed the previously used water
supply rate.
Careful planning is a definite prerequisite to successful implementation of counterflow reuse
systems. Control of such systems will be facilitated by the use of variable speed pumps for
adjusting all flow rates. Alternately, gate valves, installed in the lines immediately after the pumps,
can be used to regulate the water withdrawal rate from each tank to correspond to the water
requirement in the next operation. In either case, periodic adjustments may be required to
assure maintenance of appropriate balances and maximum efficiencies.
Cooling and Washing Requirements
In the usual arrangement of the counterflow system for peas, the second use of water is for
fluming or pumping peas from blanchers to quality graders. This fluming operation requires more
careful attention than the other. The peas are discharged from blanchers at an average tempera-
ture of 200° F and are covered with varying amounts of foam and blanch water high in organic
solids. In some cases the blanchers may be contaminated with thermophilic flat-sour bacteria, the
spores of which will be on the peas. If these peas are discharged into the flume while still hot, the
sanitation of the third and fourth stages of the reuse system may be greatly impaired. Warm water
will favor rapid microbial growth which can cause excessive slime growth on equipment.
Of more serious consequence, however, is the increased potential for flat-sour spoilage in
canned peas. Studies have shown that blanched peas not previously cooled before entering the
flumes to the quality grader may reach the grader with a temperature still above 100°F. Elevated
temperature in water which has a high concentration of organic matter will be favorable to the
growth of thermophilic bacteria in the flumes. Furthermore, failure to adequately wash
blanched peas can result in an accumulation of thermophilic spores in the quality grader brine.
49
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Impairment of water quality due to factors attributable to blanchers can be prevented or
greatly minimized by cooling and washing blanched vegetables in a separate operation. Equipment
which can be used for this purpose (listed in the order of preference) include air coolers, vibrating
screens with overhead sprays, reel washers and hydrocooling flumes. Sprays used with vibrating
screens or reel washers should be supplied with cold, chlorinated water. Since the volume of water
used by these units is relatively small, the wash water can be wasted without contributing significantly
to the total plant effluent. Discharging of the wash water will enable more extensive reuse of the
large volume of water in the counterflow system by minimizing heat input and by preventing
excessive amounts of organic matter and bacteria from accumulating within the reuse system.
Water Saved
Under average conditions, it has been estimated that the installation of a counterflow reuse
system will reduce the total water consumption by approximately 50 per cent of the volume which
would otherwise be used if fresh water is used in all operations. However, the amount of water
which can be saved by installing a counterflow system depends upon the unit operations within
each plant. Estimations of potential water savings and waste load reductions can be made by
surveying the processing plant and monitoring each wastewater flow.
SPECIAL WATER REUSE SYSTEMS
Variations in plant layouts, processing operations, types of equipment, and varying urgencies
to conserve water and/or reduce waste loads, not to exclude variable waste characteristics, are but
a few of the many reasons that detailed discussion of specific water reuse systems are of limited
value. Instead, coverage of general principles which can be adapted to a variety of situations have
been attempted in the preceding sections. However, some unique situations offer potentially wide-
spread applications as solutions to common problems. For this reason, the following special
systems are described.
"TRIPLE DUTY" WATER REUSE SYSTEM
An advanced type of water reuse system in a specialty foods plant has recently been reported.10
This system has been designed not only to conserve water, but also to conserve heat energy. As
depicted in figure IV-9, the system consists of two parallel closed loops and a third open-ended leg.
The main feature of the closed loop circuits is the sterilization tank. Make-up water added to the
system at this tank is recovered air compressor cooling water and condensate from cereal drum
dryers and building heaters. The water is treated with ozone, pumped through a vertical cartridge-
type filter heated to 190° F in a shell-and-tube heat-exchanger, and supplied to the two closed
loop systems.
Water in the first loop is used to wash empty jars. The wash water is collected in a sump,
pumped through a filter and returned to the sterilizing tank. In the second loop, the water is used
to fill retorts. Effluent from the retorts is collected in two separate sumps. Water with a tempera-
ture above 150°F is collected in one sump, while water below 150°F is collected in the other. The
hot water is filtered and returned to the sterilization tank, thereby completing the second circuit.
By segregating and recycling only the hot water, less energy is required to reheat water from the
sterilization tank, thus resulting in a conservation of heat and fuel. Water below 150°F from the
retorts is used in the final leg of the system. This water is used for flushing gutters and cleaning
floors in processing areas and is discharged thereafter to waste.
SEDIMENTATION - CARBON FILTRATION WATER RECOVERY SYSTEM
A treatment and recovery system was designed to remove suspended and dissolved solids and
to reduce the bacterial load from green bean processing wastewater.11 A simplified diagram of the
50
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system is shown in figure IV-10. The special feature of the water recovery operation is the
sedimentation and carbon filtration treatment system which clarifies the used water sufficiently
for recycling through the canning operations.
The Water System
The water reservoir may be considered the starting point of the cycle. It is divided into two
compartments, one containing 40,000 gallons of fresh water and the other a 20,000-gallon mixture
of recovered water and fresh water. In this way, a supply of fresh water is readily available in the
event of system malfunction. Air is bubbled through the recovered water compartment to increase
dissolved oxygen. Chlorine in the form of hypochlorite is added periodically to the reservoir.
Filter
Non-potable
water surge
tank
Pump
To gutter flush
Pump
Cleanup
Figure IV-9. Triple duty water reuse system.
51
-------
en
Figure IV-10. Diagram of charcoal filtration water recovery system.
-------
Water is pumped from the recovered water compartment to the first chlorinator, where suffi-
cient chlorine is added to give 1 ppm free residual. From the chlorinator, some water is sent to the
rotary can cooler and the remainder is sent to the can cooling canal. The water from the rotary
cooler is sprayed cooled, filtered through sand, chlorinated, and added to the can cooling canal. The
water overflow from the cooling canal is used in three ways: for product washing after blanching,
for initial product washing, and in the plant drains to carry out solid wastes. Water used for both
product washing operations is combined with the plant drain water and channeled to the treatment
area for screening. Particles larger than 1/2 inch are removed by passing the wastewater stream through
a mesh belt conveyor. Waste particles smaller than 1/2 inch are removed by a 48-mesh, 60° tangential
screen. The screened wastewater is divided into three portions. One portion is pumped directly into
the plant to flush the floor drains. Another portion is piped into the water recovery system. The re-
mainder of the liquid waste is discharged.
The Treatment System
The recovery system consists of coagulation, sedimentation, and filtration treatments. When
operating properly, the system is designed to remove all traces of suspended matter, including col-
loidal particles. Under ideal conditions, the filter effluent will be almost free of bacteria. Caustic
soda, aluminum sulfate, and a polyelectrolyte (flocculent aid) are added to the screened wastewater
in a flash mixing tank. After a 3-minute detention period, the mixture is delivered to two flocculat-
ing tanks, each of which provides a 10-minute detention. Air is injected into the tanks to provide agi-
tation and facilitate flocculation. Flocculated solids are removed as a sludge from the settling tank
and are discharged to a lagoon. The clarified water is filtered at the rate of 50 gpm through a 5-foot
bed of activated carbon and is returned to the water reservoir.
Treatment Results
The reduction in fresh water consumption achieved with the reuse treatment system is shown in
table IV-5. The recovery system resulted in an 18.4% reduction in fresh water consumption by the
canning plant during the first year and a 25.4% reduction during the second year. The hydraulic load-
ing on the waste disposal system was thus reduced by a corresponding proportion.
It should be emphasized that the data are derived from wastewater resulting from a single
product operation, green bean canning. This water recovery system works well for this plant and
for this particular product. Water from multi-product operations may be more difficult to treat;
each system should be considered individually. However, the results indicate that wastewater recla-
mation and reuse is feasible without undue risk of canned product spoilage.
pH CONTROL OF RECIRCULATED WATER
The use of hydraulic conveying systems by food processors is extensive in view of the advantages
which such systems offer. These advantages are as follows: water is a convenient and efficient trans-
port medium; hydraulic systems are generally more compact than dry conveyors; little attention is
required for operation of hydraulic systems; and maintenance of product appearance is enhanced
by the gentle handling imparted by water. To maintain acceptable aesthetic and sanitary conditions
within hydraulic conveying systems, a large volume of water is generally added continuously, thereby
resulting in a continuous overflow from the system. By dilution in this manner, food particles
and product juices which are washed or leached from the conveyed commodity are maintained at
low concentrations within the system; microbial populations are likewise minimized. Where hydraulic
conveying systems are used, the organic matter which is continuously discharged from each system
is a major source of the total organic load associated with the processing operations. The water
discharged from each system is a major contributor to the total hydraulic load of the plant effluent.
Measures to reduce the waste loads from hydraulic conveying systems must include consideration
of the sanitary condition of the water within the systems.
53
-------
Table IV-5.—Effect of water recovery system on water usage in canning green beans
10
Date
8-7-67
8-9-67
8-11-67
8-29-67
8-31-67
Average
1967 Season3
1968 Season3
Gals/case
fresh water only
22.9
26.5
32.9
27.2
24.3
26.8
25.5
20.8
Gals/case
using recovered water
16.4
18.2
22.2
20.3
19.3
19.3
20.8
15.8
Percent
decrease
28.4
31.3
32.5
25.4
20.6
28.0
18.4
25.4
For periods when recovery system was used.
It is well established that the pH of water affects the growth rate of microorganisms. The
optimum pH for most bacteria is in the neutral range (pH 6.5 to 7.5). As the pH of the medium
is made more acidic or more basic, microbial growth rates decline. Under very acidic or very basic
conditions, bacteriostatic effects are evidenced. The growth responses observed in a simulated flume
system are graphically illustrated in figure IV-II.12 These results are the basis for the use of pH control
to maintain the sanitary condition of recirculated water. This control methodology is especially
well suited for systems conveying naturally acid products (such as tree fruits and tomatoes) and may
be used for potatoes and other vegetables.
EXPERIMENTAL RESULTS
A demonstration project was conducted to confirm on a commercial scale the findings of the
earlier laboratory study.13 Two identical pumping systems were used for this investigation. In each
of these systems, cling peach halves were discharged into tanks and pumped to the filling operation.
The peaches were dewatered and delivered to can fillers. The water was then returned to surge tanks
for recycling. Fresh water could be added to each system as required. In one system, pH control
capabilities were provided, as graphically depicted in figure IV-12. Citric acid, an edible acid which
naturally occurs in fruits and tomatoes, was used to acidify and maintain the water at pH 4.0. The
parameters monitored for each system included the volume of water consumed, bacterial counts on
representative samples, temperature, pH and BOD. The quantity of acid used in the test system was
also measured.
The amount of fresh water added to each system and the quantity of BOD generated by each are
summarized in table IV-6. In this case, the acidified pumping system used only 25 percent as much
fresh water and generated only 70 percent as much BOD as did the unacidified control system.
The quantity of citric acid required to maintain pH 4 within the system will be dictated by the
rate of fresh water addition, as well as the pH and buffering capacity of the raw water and commodity
being transported. Citric acid consumption in relation to the volume of water added to the system
(averaged over several days of operation under the test conditions described) is summarized in
table IV-7.
54
-------
til
o
cc
tu
LU
CC
O
o
cc
800
700
600
500
400
300
200
100
pH 7.0
O pH 6.0
234
NUMBER OF HOURS
Figure IV-11. Effect of pH control on the growth of bacterial cells.
12
Dewatering
screen
Citric
acid
tank
Recorder —
Controller
Solenoid
valve
pH
'probe
n
Pump
Fresh
water
Meter
HL^~~TM
\ se /J
Peaches after
final inspection
Overflow
Figure IV-12. pH control system.
55
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Table \\l-Q.-Characteristics of fruit pumping water
(24 hours of operation)
Measurement
Water make-up, gpm
Total water volume used, gallons
Average BOD, ppm
Total BOD discharged, pounds
Acidified
5
6,720
2,034
118
Control
20
26,520
742
170
Table \\J-l.-Critic acid consumption at various fresh water flow rates
Flow in gallons per hour
Lbs citric acid added per hour
65
160
220
330
420
560
700
2.1
2.3
2.4
2.8
3.1
3.2
3.6
Results of tests performed on samples collected from the two systems are summarized in table
IV-8. The relative bacterial count was obtained by reducing the total plate count to a common
denominator. Results are reported for samples taken at 2-hour intervals over a 24-hour period.
Almost without exception, the bacterial count in the acidified system was equal to or lower than
the count in the control system.
Use of the pH control system resulted in reduced consumption of water required to maintain
sanitary conditions in the recirculated water system. The acidified system was operated at the make-up
rate equal to 25 percent of the control system. The second principal benefit of using less water is the
resultant reduction in the volume of effluent. Using the current water charges in one California
community, the reduced intake of fresh water would pay for the citric acid used in controlling the pH
of the water. A water savings of 20,000 gallons per day would reduce the water bill by $6.00. Using
an average of 2.5 pounds of citric acid per hour at 10 cents per pound, the cost of the acid would be
equal to the savings in the smaller volume of water used. There would be a net savings in sewer ser-
vice charges for the reduction in the volume of effluent and pounds of BOD discharged.
The pH control system was operated continuously for only 24-hour periods. It is very possi-
ble that even longer periods of operation could be used and the consumption of fresh water further
reduced. This would result in even greater savings in water and citric acid, with fewer pounds of BOD
discharged. Had recirulation of the acidified water extended beyond 24 hours, there may have been
an even greater increase in the soluble solids content of the recycled water. In this case, the osmotic
exchange between product and water would decrease. This would mean less leaching from the
product and a further reduction in the BOD load of the recycled system.
Fresh water addition into the system should be controlled by a properly installed float-actuated
valve. If continuous addition of water is deemed desirable, the rate of addition should be minimal.
In some situations, product fragments and other debris may tend to accumulate within the system.
A screening device incorporated into the return water line will facilitate removal of such objection-
able materials and extend the usability of the recirculated water.
56
-------
Table \M-ft.—Comparison of control & testsystems
Time of
sampling
6 a.m.
8 a.m.
10a.m.
12 noon
2 p.m.
4 p.m.
6 p.m.
8 p.m.
10p.m.
12 midnight
2 a.m.
4 a.m.
Total count x 1010
Test
system
0.5
63
72
39
84
61
97
41
67
13
2
17
Control
system
6
138
226
106
137
111
60
82
80
22
59
9
pH
Test
system
4.4
4.1
3.9
3.8
3.9
4.0
3.9
3.8
3.9
3.8
3.8
3.8
Control
system
7.6
7.2
7.3
7.4
7.4
7.4
7.7
7.4
7.2
7.5
7.4
7.3
Temp. F
Test
system
67
72
75
72
74
76
76
75
76
75
74
75
Control
system
67
70
72
70
70
72
70
71
72
69
69
71
Foaming may be encountered in recycled systems as a result of the accumulation of soluble
organic matter. This can be controlled by the addition of an approved anti-foam substance or by
the installation of fine mist sprays in the area where the foam accumulates.
Although microbial growth can be effectively controlled in an acidified system, it is important
to insure that the system does contain "dead ends" or blind spots which may provide favorable
harbors for microorganisms.
57
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B. DISINFECTION
The disinfection of water supplies has been employed for many years as a safeguard against
waterborne disease. In recent years industrial water chlorination has become common practice in
fruit and vegetable processing plants to improve plant sanitation. With the increasing ecological
desirability of conserving water, the economic necessity of reducing the volume of wastewater
requiring treatment and disposal, and the added emphasis on plant sanitation, the use of disinfectants
has become an even more important factor in the continued assurance of producing wholesome,
quality foods.
The cost and effectiveness of various germicides vary widely. Selection of appropriate com-
pounds will require knowledge of the relative advantages and limitations of each. The following
sections describe chlorine and chlorine compounds, as well as other germicides, and their application
in water reuse systems and waste prevention programs in food processing plants.
CHLORINE AND CHLORINE COMPOUNDS
GASEOUS CHLORINE
Chlorine is prepared commercially by the electrolytic decomposition of sodium or potassium
chloride solution. It can be used as a gas or as one of its compounds. Under ordinary atmospheric
pressure, chlorine is a greenish-yellow gas about two and one-half times heavier than air. Due to
this greater density, it will flow to the lower levels of a room or building. Chlorine is nonflammable
and nonexplosive. However, it reacts chemically with many substances and may cause a fire or
explosion when in contact with combustible materials. In the presence of moisture, it is very cor-
rosive to common metals. Chlorine is only slightly soluble in water, the maximum solubility being
about 1% at 49.2°F. As the temperature increases, the solubility decreases until it is zero at the
boiling point of water. Chlorine combines with water below 49.2° F to form crystalline hydrates
commonly called chlorine ice.
Gaseous chlorine containers range from 150 pounds to 30 tons, or tank car, capacity. For
industrial use where the daily requirements are less than 50 pounds per 24 hours, 150-lb. cylinders
are suggested. At plants having greater requirements than this, there is generally an advantage in
purchasing chlorine in one-ton cylinders.
HYPOCHLORITES
Calcium and sodium hypochlorites are extensively used for chlorination of industrial waters.
Sodium hypochlorites are sold as liquids, while calcium hypochlorites are marketed in the powdered
form. They are prepared by treating the respective alkalis with chlorine gas. The degree of chlorina-
tion determines the percent of available chlorine. In the case of calcium hypochlorites, a tendency
for powders to cake is attributed to impurities in the lime.
CH LOR AMINES
Chloramines, formed by the reaction of chlorine with ammonium nitrogen in an aqueous
solution, are more stable and much less corrosive than the hypochlorites. Formation of chloramines
is a reversible reaction, resulting in the formation of undissociated HOC1 in low concentration when
chloramine is dissolved in water. The dichloramine is the most effective disinfectant.
Action of chloramines is slower but longer lasting than that of hypochlorites. They are par-
ticularly useful in situations where a long contact time can be provided. Their germicidal action is
too slow, however, to be of much value for in-plant chlorination.
58
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CHLORINE DIOXIDE
Chlorine dioxide (C1O2) is usually prepared by injecting chlorine gas into an acidified solution
of sodium chlorite. A yellow-green solution of chlorine dioxide will result and can then be metered
into water systems. The solution is not stable and must be used shortly after generation. Recently
a manufacturer has made available a stable 10 percent solution of chlorine dioxide.14 This improve-
ment may enhance future uses of chlorine dioxide.
Chlorine dioxide does not combine with ammonia to form amines, nor does it combine with
phenol type compounds. Instead, chlorine dioxide will oxidize phenols, as well as manganese,
iron and other taste or odor producing compounds. It is a vigorous and effective oxidizing agent,
greater than chlorine. Chlorine dioxide is regarded as being similar to chlorine in its efficiency in
the destruction of bacteria and other microorganisms. It appears that chlorine dioxide will main-
tain a residual in the presence of organic matter for longer periods than chlorine.15
BREAK-POINT CHLORINATION
When small amounts of chlorine are added to water under controlled conditions, the first in-
crements of chlorine are used up in satisfying the chlorine demand of the water. At the same time,
chlorine loosely combines with nitrogenous matter present to form chloramines or other chloro-
nitrogen compounds. As additional chlorine is added, a free residual appears. This residual gradually
increases until it reaches an apparent maximum concentration, determined by the physical and
chemical nature of the water. Beyond this point, oxidation reactions occur between further
incremental additions of free chlorine and the chloro-nitrogen compounds. The measurable free
chlorine residual will decrease by the amount necessary to completely oxidize the chloro-nitrogen
compounds. Further additions of chlorine beyond this point will result in a second rise in free
chlorine concentration which increases almost in direct proportion to the rate of chlorine applica-
tion. It is this persisting residual which makes in-plant chlorination of value. The point after the
first rise in concentration at which the free residual reaches its lowest level is known as the "break-
point" (see figure IV-13). Break-point chlorination, then, is the practice of maintaining chlorine
residuals beyond this point.
CHLORINE AS A GERMICIDE
Chlorine hydrolyzes in dilute water solutions as follows:
C12 + H2O ^ HC1 + HOC1 (Equation 1)
Break point
Increasing chlorine dosage
Figure IV-13. Break-point curve.
59
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Hypochlorous acid (HOC1) readily dissociates to form hydrogen ions and hypochlorite ions:
HOC1 - H+ + OC1- (Equation 2)
It is this undissociated hypochlorous acid that is primarily responsible for the destruction of
microorganisms. Therefore, the germicidal properties of gaseous chlorine, calcium hypochlorite
and sodium hypochlorite are attributable to the formation of HOC1 when these compounds are
dissolved in water. Generally, the rate at which organisms are killed is directly proportional to the
concentration of hypochlorous acid. The proportion of HOC1 which exists in solution is, in turn,
determined by the pH, temperature and organic content of the water being chlorinated. Each of
these factors has an effect on the equilibrium of Equations 1 and 2.
Effect of pH
At levels below pH 2, the reaction depicted in Equation 1 shifts to the left and most of the
dissolved chlorine exists as C12. Between pH 2 and pH 7, the predominant form is HOC1. Above
pH 7, the equilibrium of Equation 2 shifts to the right until almost all of the chlorine exists as
OC1~ at pH 8.5. This latter form of chlorine is a poor germicide.
Under practical conditions, the first reaction (Equation 1) goes to completion; that is, all the
chlorine reacts to form the acids. Therefore, the critical consideration is the concentration of
hypochlorous acid as determined by the pH, especially within the range of 7.0 to 8.5.
When chlorine gas reacts with water, both hydrochloric and hypochlorous acids are produced
(Equation 1). The net result is a decrease in the pH as chlorine dosages are increased. However,
when calcium hypochlorite is dissolved in water, the reaction products are hypochlorous acid,
calcium chloride and calcium hydroxide. Similarly, dissolution of sodium hypochlorite produces
hypochlorous acid, sodium chloride and sodium hydroxide. The amount of hypochlorous acid
produced by the reactions of the hypochlorites is only sufficient to neutralize half the alkali formed
so that free alkali results. This free alkali raises the pH and in turn reduces the amount of HOC1 pro-
duced, thus lowering the germicidal power. This effect is clearly demonstrated by investigative
results which are summarized in table IV-9. The results show that a sodium hypochlorite solution
which contains 5 ppm total residual chlorine requires 2-1/2 times as long to kill all the yeast cells
as does a 5 ppm chlorine gas solution. The pH factor becomes critical as the concentration of
hypochlorite is increased to high levels. For example, a calcium hypochlorite solution of 25 ppm
has a pH of 9.35, a 100 ppm solution has a pH of 9.75, and a 1,000 ppm solution has a pH of 11.10.
At these high pH levels, the concentration of HOC1 produced in relation to chlorine dosage is
negligible.
Table \V-9.-Comparison of killing power of hypochlorites and gaseous chlorine^8
Chlorine
compound
Chlorine gas
Calcium hypochlorite
Sodium hypochlorite
Total residual
chlorine
(ppm)
5.00
5.00
5.00
PHa
7.0
7.4
7.6
Time required
to kill 99.9%
of cellsb
1 minute
2 minutes
2.5 minutes
aThe pH of the unchlorinated water was 7.2.
^"est organism was a nonsporulating yeast.
60
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Effect of Temperature
It has been generally found that the time required for a given chlorine concentration to kill
99% of the bacterial cells in a solution is reduced by about 50% for each 18°F (10°C) rise in
temperature. This is illustrated in table IV-10.
Table IV-10.—The effect of temperature on sporicidal properties of calcium hypochlorite solutions^6
Type of Cl. botulinum
spores used8
62 A
213B
Saratoga E
Time to destroy 99.99%, min.b
25°C
6
6
4
15°C
15
20
10
5°C
35
40
24
a1 x 104 spores/ml.
^4.5 ppm free available chlorine, pH 6.5 (buffered).
Temperature also affects the solubility of chlorine in water as shown in table IV-11. This is unim-
portant for normal in-plant chlorination practices since chlorine is theoretically soluble to the extent
of 2,200 ppm at 176°F. However, chlorine is rapidly reduced to an ineffective level as the tempera-
ture approaches the boiling point.
Table IV-11 .—Solubility of chlorine in water at different temperatures17
Temperature
°C
0
10
20
30
40
50
60
70
80
90
100
°F
32
50
68
86
104
122
140
158
176
194
212
Maximum %
chlorine
dissolved
1.46
0.98
0.72
0.56
0.45
0.39
0.32
0.27
0.22
0.12
0.00
Effect of Organic Matter
Small amounts of certain organic compounds in the water rapidly reduce the free residual
chlorine, as shown in table IV-12.' The type of organic matter is an important factor. Dissolved
sugars and starches apparently have little effect on the free chlorine residual, while proteins and
other nitrogenous compounds definitely reduce it and thus decrease its germicidal effect. The re-
action between chlorine and nitrogenous organics produces chloro-nitrogen compounds, most
significantly the chloramines. These are measured as combined residual chlorine. As previously
noted, chloramines exert germicidal activity, but with greatly reduced effectiveness. Filtering re-
used water in a pea cannery to remove suspended matter only slightly reduces the chlorine demand
of the water indicating that in this case, the soluble organic matter was responsible for the loss of
61
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Table \V-12.-Effect of organic matter on concentration of free chlorine residual in water
.18
Time in
minutes after
chlorine added
1.0
3.0
6.0
9.0
12.0
Concentration of free chlorine ppm
No organic
matter
5.00
4.95
4.95
4.92
4.90
0.5 ml tomato
juice per liter
of water
4.20
3.70
3.45
3.20
3.00
1.0 ml tomato
juice per liter
of water
3.45
2.65
1.95
1.60
1.50
free residual chlorine. Suspended matter may, however, protect bacterial cells from chlorine contact,
thereby indirectly reducing the germicidal effectiveness of the solution.
IN-PLANT CHLORINATION
In-plant chlorination is defined as break-point chlorination of all water entering the plant, as
well as water reused within the plant, to a degree where a persisting residual occurs. This practice
provides a continuous application of germicidal chlorine to food preparation equipment, with the
result that bacterial counts are reduced, slime formation is prevented, odors are avoided, and the
time required to accomplish a satisfactory cleanup is shortened.
RECOMMENDED CHLORINE LEVELS
Free chlorine residuals of 2-7 ppm, measured at the point of water application to equipment,
are recommended. If the operations are light, such as with only one shift, satisfactory control may
be maintained by the lower concentrations, whereas during heavy or continuous operation higher
concentrations may be required. An increase to free chlorine residuals of 10-20 ppm is recommended
for cleanup purposes. This serves to give an effective germicidal treatment to all equipment in the
plant.
EFFECT ON FOOD QUALITY
The effects of chlorine on the flavor of fruits and vegetables have been studied, and the results
are summarized in table IV-13. Of the products tested, the flavors of apples, pears, cling peaches,
figs, strawberries and yams were most susceptible to chlorine. However, when unchlorinated water
was used for syrups and brines, off-flavors did not develop at chlorine concentrations recommended
for in-plant chlorination. Tests on these products showed that a chlorine concentration of 5 ppm
has no effect on color or ascorbic acid content.
EFFECT ON CANS AND EQUIPMENT
Chlorine is corrosive to common metals as shown in table IV-14. However, at low concentra-
tions such as are used for in-plant chlorination (2-5 ppm), it does not noticeably corrode either
cans or equipment under ordinary conditions. This conclusion is based on years of experience by
many canners using in-plant chlorination. Although chlorine effectively prevents slime formation,
corrosion does occur in this situation and is most severe under slime deposits. Even the high con-
centrations (10-20 ppm) used for cleanup do not generally produce significant corrosion because
the contact time is short. However, while corrosion attributable to chlorination is not normally a
problem, its possibility should not be completely ignored. If can cooling water contains sulfates
62
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Table IV-13.—Effect of chlorine treatment on flavor ofcanned foods19
Product
Applesauce, Rome Beauty3
Applesauce, Gravenstein3
Apricots, halves unpeeled
Apricots, whole peeled
Asparagus, all green
Beans, green cut
Beans, green limas
Beans, with pork (recanned)3
Beets, red sliced
Carrots, sliced
Carrots, pureed3
Cherries, Royal Anne
Corn
Figs, whole Kadota
Grapefruit juice (recanned)3
Orange juice (recanned)3
Peaches, clingstone halves
Peaches, Elberta halves
Peas
Pears
Pineapple juice (recanned)3
Potatoes, sweet, solid pack3
Pumpkin, solid pack8
Prunes, Italian
Spinach
Strawberries, whole
Tomato juice3
Vegetable juice cocktail (recanned)3
Yams, syrup pack
Lowest concentration which
produced off-flavor when 2, 5, 10 and 50 ppm
of chlorine were added
Partial
treatment.
Chlorination of
all water except
brines & syrups
Chlorine, ppm
10
(None at 50)
(None at 50)
(None at 50)
50
50
50
-
50
(None at 50)
(None at 50)
(None at 50)
—
50
—
—
(None at 50)
(None at 50)
—
50
-
(None at 50)
(None at 50)
(None at 50)
50
(None at 50)
—
—
—
Complete
treatment.
Chlorination of
all water including
brines & syrups
Chlorine, ppm
5
10
50
50
50
10
10
50
10
10
50
50
(None with 15)
5
50
50
5
10
(None with 10)
2 to 5
10
50
50
10
10
5 to 10
10
5
5
aChlorine added directly to the product.
63
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or chlorides, the addition of chlorine increases the tendency toward can corrosion. In this instance,
the addition of a corrosion inhibitor may be necessary.
Table I V-14.—Effect of chlorine on metal and other surfaces
Material
Glass, earthenware, silver3, tantalum,
most precious metals, bitumastics
(tar), hard rubber
Soft gum rubber, fabrics, concrete
Wood
Iron, steel, stainless steel, copper,
brass, aluminum, tin
Effect of chlorine solutions
5 ppm
None
None
None
None
100 ppm
None
None
None
Corrodes6
1 ,000 ppm
None
Disintegrates
Corrodes
Protection of silver is due to formation of silver chloride and if this is removed by abrasion, corrosion will result.
Corrosion occurs if application is continuous. A periodic application of a few minutes contact may have very little
effect. The lower the pH, the more corrosion will result.
COOLING WATER CHLORINATION
When cooling water is reused or has a high bacterial content, chlorination is advisable. The use
of chlorinated water in can coolers will help to prevent spoilage associated with recontamination.
When cans are to be processed in retorts or continuous cookers, the cans should be washed or rinsed
after filling and sealing to reduce the amount of organic matter which might be carried into the
cooling system, thereby minimizing the chlorine demand.
Cooling Towers
Reclaimed water that is cooled by passage over a cooling tower may become highly contaminated
with microorganisms and rechlorination will usually be necessary. Sufficient chlorine should be
added as the water leaves the tower for use in the plant such that a free residual of approximately
0.5 ppm is measurable in the water as it drips from the tower at the end of the cycle. This treat-
ment should be accompanied by screening to remove any large foreign materials. The cooling tower
should be subjected to direct chlorination at 4-5 ppm for a few hours every week or two to eliminate
more resistant microorganisms which may gradually develop (see figure IV-3).
Tank, Canal, and Rotary Continuous Coolers
Bacterial counts may rapidly build up to high levels in tank, canal or continuous rotary coolers
unless the water is chlorinated. A free chlorine residual of at least 0.5 ppm at the discharge end of
the cooler is recommended. When in-plant chlorination is practiced, the 5 ppm residual carried in
the cooler inlet water is often sufficient to maintain the necessary 0.5 ppm at the discharge end of the
cooler without additional chlorination.
Application of Chlorine Compounds
Chlorination of cooling water may be accomplished with either gaseous chlorine or hypochlorites.
Either automatic or manual feed equipment may be used, but precise control of chlorine feed rates
64
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is possible only with automatic chlorinators. The same precautions apply for these installations as
described under in-plant chlorination with gaseous chlorine.
For cooling canals and open coolers, hypochlorites are frequently used. These may be metered
into the system with a chemical solution feed pump or, if no other means are available, by a drip feed
mechanism. Drip feed equipment is satisfactory for applying sodium hypochlorite solutions. How-
ever, calcium carbonate deposits which form from calcium hypochlorites may clog drip feed equip-
ment, thereby impairing controlability. Calcium hypochlorite solutions should be mixed several
hours before use to allow the carbonate deposits to settle out. Pumps are advisable for addition of
calcium hypochlorite solutions.
CHLORINATION OF WATER REUSED FOR OTHER THAN COOLING
When reusing water in food preparation departments, the best and safest method is the counter-
flow principle, with successive uses of the water in reverse order to the flow of the product through
the plant. Fresh water is used for the final washing or fluming of the product prior to canning. The
second or third uses may be for fluming or washing at intermediate stages in the preparation, and
the last use for washing or pumping the raw product as it enters the preparation lines. The exact
details of such a system must be worked out for each cannery since no two plants handle a given
product in exactly the same manner. Guidelines were previously discussed in the section titled
The Counterflow Water Reuse System.
In a counterflow system, water is collected in a separate tank after each use and should be re-
chlorinated at this point prior to reuse. Since the chlorine demand of the water will vary after each
use, different amounts of chlorine must be added to each tank. One of two rechlorination systems
may be used.
1. Small, cylinder-mounted chlorinators may be provided at each collection tank of the counter-
flow system. Each chlorinator may then be independently adjusted to provide the chlorine
feed rate required to maintain the desired chlorine residual concentration. This system is
also suitable for chlorination of water recirculation systems.
2. A single chlorinator, separate from the fresh water in-plant chlorinator, may be used to
provide a concentrated chlorine solution for the counterflow system. The chlorine gas
may be injected into a header pipe to generate the concentrated solution which can then
be distributed to the collection tanks. The chlorine solution should be supplied to each tank
through individual adjustable valves, thereby providing control of feed rates and chlorine
residuals within each tank. A period of experimentation will be necessary to determine the
appropriate feed rates for each valve and for the chlorinator.
All components of this arrangement must be constructed from chlorine-resistant materials
which are available from chlorine manufacturers. The concentrated chlorine solution
supplied to each tank must be added below the water surface within the tank to prevent
liberation of chlorine gas into the atmosphere around the equipment.
A minimum chlorine residual of 5 ppm should be maintained in fresh water added to a reuse
system. However, the chlorine will combine with the organic matter present in the system, thereby
necessitating rechlorination prior to reuse. Experience has shown that the most economical yet
effective chlorine dosage for reused water is that which produces a free residual of 0.10 to 0.50 ppm
when measured at the end of the subsequent use by the orthotolidine flash method. This assures
complete satisfaction of the chlorine demand of the water and provides a fairly high total residual.
Because of the extended period in which the water is used, the total residual exerts enough
germicidal activity to prevent the reproduction of microorganisms.
65
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IODOPHORS
Chemically, iodine is one of the halogens, along with chlorine, fluorine and bromine. It is a
heavy, bluish-black solid at room temperature, in contrast to yeUow, gaseous chlorine. It has a high
vapor pressure and sublimes readily, with vapors showing a characteristic violet color. It is only
slightly soluble in cold water (one part in 3450 at 20°C), but its solubility increases as the tempera-
ture of the water rises. In contrast, chlorine is more soluble but unlike iodine, its solubility de-
creases as the temperature increases. Aqueous solutions of free iodine show a characteristic yellow-
ish color when dilute, and reddish-brown when concentrated.
FORMULATION AND PROPERTIES
An iodophor is a mixture of iodine and a carrier. The carrier is a compound that greatly in-
creases the solubility of iodine in aqueous systems while decreasing its chemical reactivity with
materials other than microorganisms. Surface-active agents (surfactants) or water-soluble polymers
may serve as carriers. A number of anionic, cationic and non-ionic surfactants solubilize iodine.
The various agents differ from each other in their ability to solubilize iodine and in their stability,
reactivity in terms of the amount of iodine liberated, viscosity, foaming, detergency, wetting action
and other properties of the resulting iodophor.
Reeves and Tilley20 reported that commercial iodophors today are almost exclusively complexes
of iodine and non-ionic surfactants. Non-ionics display their activity in hard waters and under a
wide range of pH conditions which usually render ionic compounds ineffective. Moreover, these
compounds are electrically neutral and thus compatible with electrolytes and other surfactants.
These characteristics are of great value under conditions encountered in practical applications.
Of the non-ionics available, members of the alkylphenoxypolyglycol ether group are in widest use.
GERMICIDAL ACTIVITY
Mode of Action
Studies by various workers indicate that free iodine, in the diatomic form I2, is the agent
responsible for the germicidal action of the iodophors. Russell21 reported that Allawala et al have
found that the time required to achieve a 99% reduction of bacterial cells and spores was a function
of the concentration of free iodine, despite the presence or absence of added surfactant. Bogash22
reported that the time required to destroy M. tuberculosis was reduced by 50% when the concentra-
tion of available iodine was doubled (from 25 to 50 ppm). Others have found that when the
chemical reaction occurring between iodine and E. coli was studied, only 10% of the absorbed
iodine was found to be retained by the cells. The other 90% reappeared as iodine in the supernatant
fluid. This was interpreted as indicating the occurrence of an oxidative reaction. It was not possible
to decide which of these two types of reactions was responsible for the lethal effect of iodine.
Trueman16 suggested that both probably play a part.
The Effect of pH
In aqueous solutions, iodine can exist in several forms as a result of a hydrolysis reaction with
water. Unlike chlorine solutions, it is the free element (I2) which is responsible for the germicidal
action of iodine solutions. The pH of the solution determines the form of iodine present. Con-
sequently, iodophors (as with chlorine) exhibit maximum germicidal activity at an acidic pH. For
this reason, suitable buffering agents and certain acids are used in the formulation of most iodophors
to maintain the proper pH and provide a more stable product, especially in the presence of organic
impurities.
66
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Iodine in neutral aqueous solutions is present almost completely as the effective, diatomic
molecule. Therefore, increasing the acidity can increase the iodine concentration only slightly by
favoring the equilibrium. It seems unlikely that this small quantity would significantly influence
the overall germicidal efficiency. It has been speculated that acid may increase the penetrability
or reactivity of free iodine with the organic matter of the microbial cell.23
Excess alkalinity tends to lower the germicidal efficiency of iodine solutions. When low con-
centrations of available iodine are used, solutions will have little or no germicidal activity at pH
levels higher than 8.0. At such high pH levels, available iodine will be converted to the inactive
iodide and iodate forms.
Effect of Organic Matter
The effect of organic matter on the germicidal properties of both chlorine and iodine solutions
was studied by several workers. Evans24 and Wilson23 reported that the inhibitory action of organic
matter was significantly less in iodine solutions than in chlorine solutions. Parker25 indicated that
in the presence of 5% skim milk and at 45°C, the destruction of Staphalococcus aureus within 30
seconds required 10 ppm of available iodine, compared to 35 ppm of available chlorine (hypochlorite).
Iodine does not combine with ammonia to form iodamines, but rather oxidizes the ammonia.
It also oxidizes phenols rather than combine with them to form objectionable organic compounds.
Consequently, it has been concluded that in the presence of organic matter, low iodine residuals should
be more stable and therefore persist longer than corresponding residuals of any of the other halogens.
Effect of Temperature
The germicidal efficiency of iodophors increases as the temperature increases. It is reported that
the concentration of available iodine required to kill a suspension of Staphalococcus aureus within 30 sec-
onds was 5 ppm at 45° C and 20 ppm at 5°C. Table IV-15 shows results reported by Wilson23 in
terms of ppm of free iodine required to kill a number of different organisms at two different
temperatures at pH 7.5.
CORROSIVITYOF IODOPHORS
The corrosive effect of elemental iodine on many metals is reported to be greatly reduced when
iodine is complexed in iodophors. At the recommended concentrations, iodophors have no cor-
rosive effect on tinned and stainless steel surfaces. However, iodophors will tarnish silver, silver
plate and copper. When iodophors are used to sanitize aluminum contact surfaces, gradual darkening,
but no pitting, may also be observed.
Table IV-15.-£/fecf of temperature on the germicidal action of iodine solutions at pH 7.523
Test
organism
E. coli C-36
A. aerogenes
S. typhosa P-10
S. sonnei I P-9
S. feca/is E-40
Average ppm 1 2 required to kill
organisms in 1 min.
At 2-5°C
2.0
0.9
0.87
2.47
2.37
At 20-26° C
0.69
0.6
0.4
0.6
0.7
67
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POTENTIAL USE FOR THE DISINFECTION OF CAN COOLING WATER
Unlike chlorine and chlorine-containing compounds, iodophors have not been considered for
the disinfection of potable water until very recently. Therefore, practical experience relative to
their use in can cooling systems is extremely limited. Only in. recent publications are references
given indicating the advantages of iodine-liberating compounds as disinfectants or sanitizers in
restaurants, bottling plants, dairy farms and plants, and fruit and vegetable packing and canning
plants.
A recent article indicated that a specially-formulated iodophor was used by a cannery in lieu
of chlorine for the disinfection of can cooling water and in can-sealing operations26. It was re-
ported that this treatment achieved the required sanitary conditions in the cooling water and pro-
duced bright and shiny cans free of rust and water spots. In this experiment, a proportioning feeder
was used to furnish a constant level (0.1 to 0.3 ppm) of available iodine in the discharge exit of the
can cooler. These results were confirmed in a study at another plant.27
OZONE
Ozone has a characteristic pungent odor, thought by some to be refreshing in low concentra-
tions. It is colorless at room temperature and condenses to a dark blue liquid. Liduid ozone is very
unstable and will readily explode. Concentrations of ozone in air-oxygen mixtures above 30% are
also easily exploded. Ozone may react with activated carbon to form explosive end products.
Ozone is considered one of the most powerful oxidizing agents, attacking almost all organic com-
pounds. It has an oxidation-reduction potential of 2.07 volts, compared to 1.49 for hypochlorous
acid and 0.75 for chloramine.
The density of ozone is 1.5 times that of oxygen and is about 10 times more soluble in water.
However, because of a much lower available partial pressure, it is difficult to obtain a concentration
in water of more than a few parts per million under normal conditions of temperature and pressure.
Ozone is unstable in water, having an effective half-life of about 20 minutes. Its decomposition is
accelerated by neutral salts and hydroxyl ions. Therefore, it must be produced on the site where it
is to be applied.
Ozone can be produced by one of three techniques: (I) electrical discharge, (2) electrolysis
of perchloric acid, or (3) ultraviolet irradiation. Of these, electrical discharge is the only practical
and economical method for large scale ozone production. The process, as shown in figure IV-14,
involves the passage of dry air (or oxygen) between two electrodes across which an alternating high-
voltage potential is maintained. To insure the conversion of an optimum part of the oxygen into
ozone, a uniform blue-violet glow discharge is maintained by inserting a dielectric material between
the electrodes.
Electrode
Dielectric
Electrode
Figure IV-14. The process of ozone generation.
68
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GERMICIDAL ACTIVITY
In a recent investigation, Haufele and Sprockhoff28 studied the germicidal effect of ozone on
the vegetative cells of a number of bacterial species. E. coli, S. marcescens, Ps. aeruginosa and Staph.
auerus (ATCC 6538) were used. They reported that complete destruction of these microorganisms
required between 0.05 and 0.7 ppm ozone, depending upon the density of the test organism and
the contact time. The only exception was the Staphylococci which required 3-5 ppm ozone for the
complete inactivation. It is believed that the cluster-like growth of the Staphylococci affects the pene-
trability of ozone. The results of this part of the study (table IV-16) correlate with those cited in
several other reports, especially those cited for E. coli.
Higher ozone concentrations and longer contact times are required for the destruction of
bacterial spores. Venosa29 reported that in water containing Cl. perfringens at a concentration of
2 x 103 spores per milliliter, and maintained at pH 6.0 and a temperature of 24°C, complete kill of
the spores was achieved after a contact time of 15 minutes with 0.25 ppm ozone, or after 2 minutes
with 5 ppm. Broadwater30 found the spores of B. cereus and B. megaterium, which exhibit the
same degree of resistance, were from 10 to 15 times more resistant to ozone than were their vege-
tative cells. Based on the widely accepted theory of protoplasm oxidation, he explained that the
greater resistance of spores probably is a result of the protection afforded the protoplasm by the
spore's thick, multilayered cortex and the exosporangium, whereas the protoplasm of the vegetative
cell is protected only by a cell wall.
The germicidal efficiency of ozone in aqueous solutions is influenced by several factors includ-
ing the presence of impurities, concentration of ozone in solution, contact time, pH and temperature
of the solution, and the initial microbial load of the water. The magnitude of influence, however,
differs significantly among these factors. For example, it has been reported by many research
workers that ozone disinfection is mainly a function of the concentration of ozone, contact time,
and the presence or absence of impurities, either organic or inorganic. Few investigators have added
temperature to these three factors.
Table IV-16.—Germicidal action of ozone against E. coli, S. marcescens, andPs. aeruginosa in tap water28
[Temperatures between 11.7°C and 13.5°C]
Organism
E. coli
S. marcescens
Ps. aeruginosa
Initial load
per 100 ml.
3x 107
4x 107
1.2 x 107
O3, ppm
0.16
0.13
0.08
0.02
0.70
0.52
0.38
0.22
0.38
0.29
0.18
0.12
Count/100 ml. after
3 min. 1 hr.
0 0
2 0
11 6
- Not Counted -
2 0
6 1
16 3
N.C. 9
0 0
2 1
6 1
138 96
69
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The Effect of Concentration
One of the major differences between chlorine and ozone disinfection is the correlation be-
tween the concentration of the agent used and the germicidal efficiency exhibited. As shown in
figure IV-15, the germicidal efficiency of chlorine is directly proportional to its concentration,
whereas with increasing concentration of ozone, there is little improvement until a critical concen-
tration or dose is reached. Subsequent to this critical or "threshold" dose, as it is sometimes
designated, the germicidal action is very rapid and is proportional to the concentration of ozone
in the water. Broadwater30 obtained similar "all or none" results for vegetative and spore cells.
The ozone threshold for spore destruction was much higher than for vegetative cells.
The Effect of Impurities
The critical concentration of ozone in an aqueous solution is a function of the ozone demand
of the water. The demand of the water must be satisfied before the solution exhibits a significant
(-
o
CC
C3
Z
>
IT
D
CO
0.2 0.3 0.4
CHEMICAL DOSAGE, mg/1
Figure IV-15. Germicidal activity of ozone and chlorine.30
0.5
0.6
70
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germicidal action. Because of its extremely high oxidation potential, ozone reacts rather readily
with many inorganic and organic substances present in the water. Therefore, large doses of ozone
may be required in solutions that contain oxidizable constituents before acquiring a germicidally-
active ozone residual. However, ozone does not readily oxidize all compounds. Some easily oxidiz-
able substances (such as simple carbohydrates) do not react readily with ozone. Yet ozone causes
complete destruction of phenolic compounds present in water.30 Destruction of phenol by ozone
has been reported to require a dose of about 1.2 ppm for each 0.2 ppm of phenol. Ozone treat-
ment also results in complete oxidation of ammonia and other nitrogenous compounds.
The Effect of Temperature
The germicidal properties of ozone are generally reported to be insignificantly affected by
temperature changes. However, Bringmann31 observed that the time required to achieve 100% kiU
of 6 x 104/ml. E. coli by 0.1 ppm ozone in water was reduced from 5 seconds to less than one
second when the temperature of the water was increased from 22°C to 37°C. Venosa29 reported
that Gabovich in Russia had recently studied the effect of physico-chemical properties of water on
the germicidal effectiveness of ozonation. It was pointed out that the attainment of a desired
bactericidal effect for an increase in water temperature from 4-6°C to 18-21°C resulted in a 60%
and 20% increase in gross and net ozone consumption, respectively. These findings support those
of Fetner32 and others; that is, the decomposition of ozone to oxygen is temperature dependent
and, therefore, the lower the ambient temperature, the greater the effectiveness of ozone.
CORROSIVITY OF OZONE
In a pilot plant study conducted by Kirk et a/,33 a variety of materials were used in manufac-
turing the reactors, tanks, pumps and pipes carrying both the dry gas and the wet spent gas. Mild
steel, aluminum, stainless steel, and polyvinyl chloride (PVC) were used. After nine months of con-
tinuous operation, no corrosion problems had become evident with any of these materials. Diaper34
also claims that when ozone is used for taste and odor control, it appreciably reduces the carbon
dioxide content of the water with the side effect of reducing corrosiveness.
If the moisture content of the air used in ozone production exceeds a certain limit (dew point
of -50°C), not only will ozone yield be reduced, but corrosion problems will also be encountered.
It has been pointed out that at higher moisture content, higher concentrations of nitrogen oxides
(especially N2O5) are produced by the reaction between ozone and the nitrogen present in the gas
stream. Nitrogen pentoxide (N2O5) combines with moisture to form nitric acid, which is highly
corrosive to metal surfaces and causes extensive damage to the dielectrics of the generator. For
this reason, drying of air is one of the most important steps in ozone production.
PHYSIOLOGICAL EFFECTS OF OZONE
One objection that has been raised to using ozone is its toxicity and potential danger. While
ozone is definitely toxic, there are factors which reduce the immediate danger to individuals work-
ing with it. A Maximum Allowable Concentration (MAC) over a period of time has been established
by the American Council of Governmental Industrial Hygienists as 0.1 ppm by volume of air for
continuous exposure under normal working conditions. As shown in figure IV-16, exposures at
higher concentrations can be tolerated for shorter periods. The clinical effects immediately
recognized from inhaling ozone range from headaches and dryness of the mucous membranes
of the mouth, nose and throat, to more serious changes such as functional derangements of the lung,
pulmonary congestion and edema when exposure to ozone continues.
The threshold odor level of ozone is 0.01-0.02 ppm. This means that a person working near
an ozone handling area should be able to detect the presence of ozone at concentrations far below
the MAC. Since ozone is generated at the site of application and is not stored under pressure, any
leakage from the system can be quickly stopped by simply turning off the electrical supply.
71
-------
E
a
a
O
I-
DC
I-
LLJ
O
O
O
O
N
O
10,000
1,000
100
10
0.1
Irritant
Non-symptomatic region
Non-toxic
region
Fatal region
Permanent
toxic region
Temporary
toxic
region
Symptomatic
0.1
10
100
1,000
10,000
EXPOSURE TIME, minutes
Figure IV-16. Toxicity of ozone.
COMPARATIVE EFFECTIVENESS OF SELECTED GERMICIDES
A laboratory study was conducted to develop information on the comparative germicidal (or
more specifically, the sporicidal) effectiveness of various compounds which might be useful in can
cooling systems. The organisms utilized in this study were B. stearothermophilis (NCA 1518), a
thermophilic aerobe; B. macerans, a mesophilic aerobe; and putrefactive anaerobe 3679 (NCA).
The study was limited to comparing the germicidal properties of various concentrations at two pH
levels, pH 6.5 and pH 3.5, and at two temperatures, 25°C and 55°C. In all cases the sporicidal
efficiencies of the tested compounds were enhanced by raising the temperature or by lowering the
pH. Significant differences in effectiveness were noted between the selected germicides (figure
IV-17).35 For destroying B. macerans spores, ozone was found to be most effective with equal
efficiencies at both pH levels. Chlorine's efficiency was increased at the lower pH with chlorine
being an effective sporicide under all test conditions. lodophors displayed the greatest dependence
on pH and temperature. At the higher pH level or at the lower temperature, the iodophors were
ineffectual in destroying spores of B. macerans. Similar results were noted for the other test
organisms.
OTHER CHEMICAL AND PHYSICAL GERMICIDAL AGENTS
There are a number of chemical and physical agents, other than those described above, which
possess germicidal properties. However, most of these are, for various reasons, unsuitable for use
as water disinfectants. Briefly discussed below are a few chemicals (quaternary ammonium com-
pounds, bromine and heavy metals) and physical processes (ultraviolet and ionizing irradiations)
which may have application for this use.
72
-------
B. macerans
O
CC
V)
LU
Q
90
99
99.9
99.99
2 ppm 03
pH 3.5 and 6.5
(25°C)
2.5
7.5
10
TIME, min.
Figure IV-17. Comparative effects of the sporicidal properties of chlorine, iodophor and ozone.33
QUATERNARY AMMONIUM COMPOUNDS (QUATS or QAC's)
Quaternary ammonium compounds are cationic surface-active disinfectants having a general
chemical structure as follows:
Cl or Br"
73
-------
where R± represents the long chain (C8 — C18) alkyl or alkylaryl groups or their derivatives; and
R2, R$, and E4 represent hydrogen, alkyl, aryl, or heterocyclic groups. A large number of com-
pounds of this general class have been manufactured and their germicidal properties evaluated.
The mode of germicidal action of the quats is still a matter of controversy. Some investigators
have reported that they interfere with the respiration system by inhibiting the enzymes of carbo-
hydrate metabolism. Others have claimed that they cause leakage of the cellular constituents by
lysis. Denaturation of cell cytoplasm and splitting of lipoprotein complexes throughout the cell
(with the result that autolytic enzymes are able to act freely and uniformly with it) have also been
indicated. Quats are effective against gram-positive and gram-negative bacteria. However, studies
with B. subtilis spores indicate that quats are sporistatic, not sporicidal.
With the majority of the quats, the effect of pH on the germicidal activity is generally opposite
that for chlorine and hypochlorite; that is, the activity increases with increasing alkalinity of the
solution. In the presence of a moderate amount of organic matter, their action is affected to a lesser
degree than that of hypochlorites and several other germicides. However, their effectiveness is
sharply reduced in hard waters and by a number of incompatible compounds such as anionic wetting
agents. Most of the difficulties encountered in hard water supplies can be avoided where quats are
combined with nonionic wetting agents, sequestering agents, and alkaline detergent salts in detergent
sanitizers. Generally, quats are heat stable and their effectiveness is increased with increasing tempera-
ture. They are relatively ineffective in very cold solutions.
The U.S. Food and Drug Administration, while not approving or disapproving the use of quats
in sanitary practice, considers any food product containing these compounds to be adulterated under
the provisions of Section 402(a)(l) of the Federal Food, Drug and Cosmetic Act. Bitter tastes are
imparted to many food products contacted by quats.
BROMINE
Bromine is a heavy (Sp. Gr. = 2.94) dark reddish-brown liquid which melts at -7.3°C, boils at
58.78°C, and dissolves readily in water. It exhibits chemistry in water qualitatively similar to that
of chlorine. It hydrolyzes to hypobromous acid (HOBr), ionizes to hypobromite ion (OBr~ ), and
reacts with ammonia to form monobromamine (NH2Br) and dibromamine (NHBr2), but does not
form a stable tribromamine. The same degrees of ionization for HOBr occur at pH values about one
pH unit greater than those of HOC1.
There are no known applications of bromine as a drinking water disinfectant. Because of the
germicidal properties of bromamines, bromine has been used, on a limited scale, for the disinfection
of swimming pool waters and certain industrial wastes. The strong tendency of bromine to form
irreversible compounds with organic matter of unknown physiological effects, the high costs and
difficulty of handling, and the toxicity and corrosivity of bromine are major factors deterring the
use of bromine for purification of drinking water and wastewaters.
HEAVY METALS
Silver, copper, mercury, cobalt and nickel have been found to have significant germicidal prop-
erties. However, silver is probably the only heavy metal with any reasonable degree of efficacy, and
probably the only one used for the disinfection of potable water. The use of silver for this purpose
has been more popular in Europe than in the United States. The major disadvantages of employing
silver for the disinfection of water are the high costs, the extensive water pretreatment required, the
long contact time necessary, the resistance of certain microorganisms to the action of silver and'the
significant adverse effects of certain anions, low pH and low temperatures.
74
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According to Section 141.11 of the interim drinking water standards (PL 92-523 Safe Drinking
Water Act), the presence of silver in concentrations above 0.05 ppm shall constitute grounds for
rejection of that supply as a source for drinking water.
ULTRAVIOLET IRRADIATION (UV)
Ultraviolet or short wavelength irradiation is customarily produced by low pressure mercury
vapor lamps which emit a narrow band of radiant energy at 2537 A (angstrom). At this wavelength,
only 85% of the maximum germicidal effect on most bacteria, fungi and viruses occurs (maximum
destruction occurs at 2560 A). The germicidal action of UV radiation has been linked to the
absorption of the energy by the nucleic acids in the cells which are consequently destroyed.
Spores, cysts, and viruses are normally more resistant to UV inactivation than are vegetative bac-
terial cells.
The main disadvantages of UV disinfection of water are that the water to be disinfected must
be thoroughly pretreated to remove all the organic and inorganic impurities; color and turbidity
sharply reduce the efficiency of the treatment; no residual disinfecting capacity is provided; and
treatment efficiency is not readily measurable.
IONIZING IRRADIATIONS
Ionizing irradiations, such as gamma and X-radiation, have been suggested as a potential means
of water disinfection. However, little information is available on these applications. Gamma rays
were found to be nearly one million times as powerful as UV radiation, which explains their
greater penetrating capability and their high degree of effectiveness against spores and viruses.
Their germicidal action is attributable to the direct ionization of the cell molecules, leading to
death, and to the interaction of the radiation with the water producing unstable atoms and free
radicals which may chemically react with organic molecules or cause secondary radiation effects
in viable cells.
Complete disinfection of a wastewater may require dosages as high as several million rads. At
such high dosages, a number of undesirable side effects may occur. This, together with the care
required in applying this method of disinfection, would seem likely to restrict its use to items of
high value per unit weight. Low dosages in the range of 50,000 to 1,000,000 rads are used to
"pasteurize" surfaces of certain foods, and to inhibit the sprouting of potatoes and onions in
storage.
75
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C. WASTE PREVENTION
The preparation of fruits and vegetables for preservation by freezing, canning or dehydration
generates enormous volumes of liquid wastes and solid residuals. The previous sections of this
chapter dealt with water conservation techniques which can be employed to reduce the volume of
fresh water taken into the plant and, subsequently, the hydraulic load discharged. But this does
not solve the problem of organic pollutant production as the result of raw materials contacing water.
To prevent this generation of waste, one must prevent raw materials from contacting water. Com-
plete elimination of water is impossible, since fruit and vegetable processing operations inherently
require the use of water. Therefore, one can only reduce the organic load in the discharge by
minimizing product-water contact wherever possible.
The reduction of product-water contact can be achieved by varying the operating practices
and by the use of newly developed food processing equipment. In recent years, the design of
new equipment has included consideration of not only high rate of production, product quality,
and ease of sanitation but also pollution abatement and energy demand.
Research and development work on food processing equipment of radically different con-
cept and design has received increasing attention in the past five years. The long range goal of
these programs is to develop equipment which will provide final products of acceptable quality
and safety with substantially reduced generation of liquid wastes and/or with solid by-products
generated in more manageable or utilizable form.
The following discussions identify some operating practices and process modifications
which can be utilized with relative ease to prevent or minimize the generation of pollutants.
IN-PLANT HANDLING OF SOLID WASTES
Solid wastes from food canning and freezing operations generally fit into two categories:
non-food refuse and food residuals. The first includes damaged cans or containers, packaging
materials, broken glass, discarded paper, broken pallets, and other similar inert materials. The
second category, which represents the major quantity of solid waste, includes all non-usable
items of raw materials procured for processing, such as damaged and culled whole fruits and
vegetables, seeds, stems, leaves, skin or peel, and other degradable materials which are removed
in processing. Procedures for handling fruit and vegetable residuals significantly influence the
characteristics of the plant effluent. Therefore, emphasis in the following paragraphs is placed
on methods for handling fruit and vegetable wastes within a plant in a manner that will minimize
the generation of water pollutants.
HANDLING METHODS
In-plant handling of fruit and vegetable processing residuals is not unlike the handling of
raw products. As in the case of raw products, the residuals may be handled or transported in
containers, by mechanical or pneumatic conveyors, hydraulically in flumes or, unlike raw pro-
ducts, in floor gutters. Containers which are commonly used include pans, barrels, bins or boxes,
and portable metal hoppers. Mechanical conveyors include belts, vibrating troughs or tables,
drag chains, and screw or auger conveyors. Pneumatic conveyors, which have recently been
improved to handle bulk items are available either as positive or negative pressure systems.
76
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The properties of solid waste (as determined by the size of particles, density, fluidity and
quantity), as well as the physical layout of the processing plant, determine the method best
suited for handling waste materials. In the interest of minimizing wastewater loads, hydraulic
systems should be avoided whenever possible. Where such systems are unavoidable, reclaimed
water (never fresh water) should be used. Alternate methods for handling residuals from various
processing operations (figure IV-18) are discussed in the next section and summarized in table
IV-17.
RESIDUALS FROM SPECIFIC OPERATIONS
In a recent survey of the canning and freezing industry,36 information regarding current
practices for in-plant handling of fruit and vegetable residuals was elicited (table IV-18). The
frequency of handling food residuals in water was almost twice that of dry handling. Although
residuals from some operations physically necessitate wet conveying (such as mud from washers
or peel from chemical peelers), solid wastes from many sources can readily be handled dry.
CLEANING
Fruits and vegetables for processing are initially cleaned to remove soil, dust, microbial
contaminants, and extraneous matter such as leaves, stems, and stones. The cleaning techniques
include one or more of the following: dry screening, pneumatic cleaning, agitated water baths,
water flumes or sprays. Mechanical means in cleaning fruits and vegetables may be limited by
the inability to handle different sizes of material or by excessive damage to the product. The
methods are described in the sections that follow.
Sort-out into containers
Sweep-up prior to hose-down
Handle trimmings and fragments dry
Figure IV-18. Dry handling solid wastes.
77
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Table IV-17.- Methods suitable for in-plant handling of food residuals
Source of residuals
Dry cleaning
Washing
Initial sort
Size grading
Trimming
Cutting, slicing, dicing
Peeling
Pitting
Final sort
Pulping, pressing
Plant cleaning
Handling procedures
Container
X
X
X
X
X
X
X
X
X
X
Conveyors
Belt
X
X
X
X
X
X
X
X
X
X
Mesh
X
X
X
X
Drag
X
X
X
X
X
X
X
X
Screw
X
X
X
X
X
X
X
X
X
X
Vibrate
X
X
X
X
X
X
X
X
X
Pneumatic
X
X
X
X
X
X
X
X
X
Hydraulic3
X
separate pumping system
Table IV-18.— In-plant handling methods for fruit and vegetable residuals
Waste source
Dry cleaning
Washing
Initial sort
Size grading
Trimming
Cutting, slicing,
dicing
Peeling
Quality grading
Pitting
Final sort
Pulping, pressing
In-plant handling method3
Containers
27
13
35
15
16
11
0
7
7
29
16
Dry convey
36
0
17
40
38
42
9
0
15
8
39
West convey
7
12
11
10
12
7
6
7
78
8
6
Gutter
33
82
48
36
37
40
85
86
7
63
51
Percent each category reportedly used. Since two or more methods are used in many plants, the totals
exceed 100%.
78
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Dry Cleaning
Many products are initially "dry cleaned" to remove readily separable extraneous materials
which are inadvertently mixed with the delivered produce. Equipment used for this purpose in-
clude revolving or vibrating coarse screens to remove sand from spinach and other leavy greens
and dirt clods from root vegetables, roller conveyors to separate leaves from tree fruits, and air
cleaners to remove loose husks and leaves from corn and vines from green beans and peas.
Materials removed in dry cleaning operations can readily be handled dry. When the quantity
of material removed is relatively small, containers such as bins or portable hoppers can be used
to accumulate the solid waste. If the material quantity is large, equipment should be provided
to continuously remove the waste from the operation and to convey it to an appropriate on-site
storage area. Belt, screw, and drag chain conveyors, as well as pneumatic systems, are quite
suitable for most types of wastes removed in this operation. Provisions for dry handling these
materials eliminate the need for transport water and will reduce the organic load (primarily the
settleable and suspended solids content) which would be generated by hydraulic conveying.
In the case of tomatoes, a rubber disc unit?7 replaces the flumes and sprays used in con-
ventional processes to remove tightly adhering smear soil (figure IV-19). This step supplants the
long exposure to the turbulent action of water with a short exposure to the vigorous mechanical
wiping action of soft rubber discs. The action of the discs moves the tomatoes through the unit,
loosens and wipes off the soil, and throws the heavy soiled water into a tray located beneath the
device.
Average wastewater characteristics using the rubber disc unit range from 1.8 to 3.2 tons
of tomatoes per hour. COD from the dump tank (1.1 pounds/ton) was significantly larger than
that from the disc cleaner (0.5 pounds/ton). The average residence time of tomatoes in the
dump tank was 1-2 minutes, while the average residence time on the disc cleaner was 15-25
seconds. Table IV-19 gives data for several typical runs, for which only the final rinse sprays
were used with the disc cleaner. Percent removals were obtained by measuring soil, total
count and mesospores found on tomatoes sampled after the dump tank and after the disc
cleaner, and comparing these values to those found on tomatoes sampled from the harvest bin.
Cleaning
Sorting
Water
sprays
Live roller
conveyor
Effluent
Effluent collection
collection
IOOOOOOOOOOOQ
f
Discarded
tomatoes
Elevator
to caustic
dipper and
disc peeling
Figure IV-19. Pilot scale cleaning line.
79
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Table IV-19.- So/7, total bacterial count, and mesospore count on tomatoes
at selected points in cleaning operations3
Feed rate
(tons/hr)
2.7
2.5
2.8
3.1
2.9
Location
Harvest bin
After dump tank
After disc cleaner
Harvest bin
After dump tank
After disc cleaner
Harvest bin
After dump tank
After disc cleaner
Harvest bin
After dump tank
After disc cleaner
Harvest bin
After dump tank
After disc cleaner
Soil
ppm
70
20
0
190
50
10
510
60
0
790
210
10
2,990
150
10
% Reduction
71
100
_
74
95
—
88
100
_
73
99
—
95
99+
Total count/ml
(X104)
7,000
1,500
130
2,400
1,300
120
400
220
40
12,800
2,100
188
78,000
12,800
4,800
% Reduction
79
98
_
46
95
—
45
90
_
84
99
—
84
94
Mesospore count/ml
(X104)
2,400
1,000
32
1,300
300
20
27,000
7,400
1,900
2,800
1,400
67
8,500
2,400
84
% Reduction
—
58
99
—
77
99
-
73
93
-
50
98
-
72
99
Final rinse sprays over disc cleaner only
Cleaned tomatoes appeared free of contaminants, and industrial representatives stated that
they compared well with tomatoes cleaned conventionally. No significant difference could be
found between round and pear-shaped varieties of tomatoes in contaminant removal. Total
soil removal was consistent over the feed range of 1.8-4.5 tons per hour and an initial soil load
range of 70-2,990 ppm. Total count and mesospore removal were likewise consistent.
WASHING
The initial washing of raw product is primarily to remove dust and dirt adhering to the
product. These become mixed in the water as settleable or suspended solids and can be trans-
ported from the operation only in water. However, other extraneous materials (such as leaves
and vines) often accumulate as floating debris in wash tanks and flumes. These waste materials
should be skimmed from the water, either manually or by mesh belt or other skimming devices,
and deposited into large containers. Preventing these materials from entering the gutter system
will minimize the volume of water required to transport wastes generated at this operation.
Intermediate and final washing of prepared product are normally provided to remove frag-
ments and unwanted components (such as peel and seeds) from the primary product flow. The
materials removed in such operations are frequently transported in the washwater generated at
these points. However, when the water from these operations is recovered for reuse, removal of
these materials from the water is desirable. Screens may be used for this purpose. When solid
materials are so separated, dry handling procedures should be provided thereafter. Containers
are generally suitable since only small quantities of solid wastes are removed; mechanical or
pneumatic conveyors may also be used. Use of dry handling procedures eliminates the need
for water and prevents contributions to the organic load which may result from further leaching
of soluble matter.
80
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Sorting (Inspecting), Trimming
Sorting and trimming operations involve manual removal of unusable materials from the
product flow. In the sorting operation (sometimes referred to as inspecting or picking), cull and
other unusable whole units are removed. In the trimming operation, only blemished, bruised or
overripe segments are manually cut from whole units.
Solid residuals from both operations will contribute significantly to the organic load if placed
in water. Therefore, these materials should be handled dry. When belt conveyors are used to
convey the raw products as they are being inspected, the lower return belt is frequently used to
transport the rejected materials or trimmings away from the processing area. Alternatively, these
materials may be manually placed into hoppers of a pneumatic conveying system or into con-
tainers such as pans, boxes or barrels.
When the product being inspected consists of relatively small particles (such as peas, cut
corn and diced produce), specially-designed pneumatic equipment is available to assist in remov-
ing unusable material. This equipment is similar to a hose and nozzle of a home vacuum cleaner.
The system will transport removed materials to an outside storage facility.
PEELING
Several types of equipment are used to peel a variety of fruits and vegetables. The peelers
are classified as: (1) steam peelers, which are used mainly for carrots and other root vegetables;
(2) mechanical peelers, such as mechanical knives for fruits and abrasive peelers for root crops;
(3) chemical peelers for fruits and vegetables; and (4) dry-caustic peelers to soften the skin
prior to mechanical removal.
Steam and Conventional Chemical Peelers
Steam peelers produce finely divided particles of solid waste which are difficult to separate
from water. The solid wastes from conventional chemical peelers, where water sprays are used
to remove peel material, are also finely divided. In both of these situations, the peel material
must be discharged with the liquid effluent, thereby offering no alternative by which the organic
load may be reduced.
Mechanical Knife Peelers
Mechanical knife peelers, which may be equipped with coring devices, are widely used to
pare apples and pears. The peel material is removed as large discrete particles; the cores as
cylindrical "plugs." These materials are normally separated from the peeled fruit by the ma-
chines and can readily be collected and transported on a separate conveyor. Since these ma-
terials contain soluble organic matter which will be readily leached into water, use of hydraulic
systems should be avoided. Maximum yields for by-products, especially with apples, will be
realized by dry handling these materials.
Abrasive Peelers
Abrasive peelers generate a slurried waste material, the consistency of which is largely
dependent upon the quantity of water used in the peeling equipment. Such slurries have ex-
tremely high BOD and suspended solids content. Elimination of these materials from discharged
wastewater will result in a measurable reduction in the organic load.
81
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1'he peel slurry can be collected in a hopper or a catch pan situated below the peeler. The
consistency of the slurry will enable pumping of the collected materials to the waste storage
area. By mxiing the peel slurry with other food residuals, the free moisture content of the
blend will still enable disposition of the materials by normal means. However, the consistency
of the peel material should be maintained as thick as practicable by minimizing water usage in the
peelers, thereby minimizing the quantity of free mositure in the residual blend.
Dry-Caustic Peelers
The U.S. Department of Agriculture dry-caustic peeling system uses mechanical energy from
rotating studded rubber rollers to abrade softened peel from the caustic treated raw product. This
system was developed by the Western Regional Research Laboratory of the USD A in the late 1960's
as an alternative to the hydraulic removal of peel. This system involves the removal of peel softened
by treatment with hot solutions of sodium hydroxide with high pressure water sprays.
The commercial application of dry-caustic peeling has been primarily for root crops, but re-
cently it has been used for non-root crops such as peaches. It has been used most extensively for
white potatoes and less for red beets, sweet potatoes and carrots. Table IV-20 summarizes the re-
ported installations of dry-caustic peelers for root crops up to midyear 1974.
Table IV-20.- Commercial dry-caustic peeling of root crops in 197438
Commodity
White potatoes
Sweet potatoes
Red beets
Carrots
No. of units
121
5
11
8
Total production, ton/hr.
1,100
40
67
55
Example 1—Peeling of Table Beets
Lee et a/39 presented results of experiments that adapted the dry-caustic process for peeling
beets. The major source of pollution load in the processing of beets is the peeling operation.
The waste effluent generated from conventional peeling is highly alkaline and contains consider-
able amounts of dissolved organic matter. This waste represents approximately 50% of the total
plant effluent and more than 90% of the total plant solid waste.
In the conventional peeling operation of a typical beet processing plant, solid and liquid
waste generated from the peeling line pass through a 20-mesh screen to remove the gross solids.
Then the liquid is pumped to a lagoon or delivered to a waste disposal system. The gross solids
are usually removed to a landfill. However, the very fine organic particles pass through the
screen and contribute to the major wastewater BOD and COD.
A pilot plant dry-caustic unit at the New York State Agricultural Experimental Station was
compared to a commercial scale peeler installed at a local processing plant. The results of these
two peeling operations are shown in table IV-21.
In processing 80 tons of fresh beets per day, the volume of water used in conventional
peeling in both the tumble peeler and the abrasive peeler is around 48,000 gallons per day. When
the tumble peeler is replaced with a scrubber, the water consumption volume is reduced to 12,000
gallons per day (75% reduction). Convention peeling generates 10,200 Ibs. of total solids, while
82
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Table IV-21 .—Water usage and properties of effluent waste flow in two
different pee/ing operations of beets
Measurement3
Raw beets input, ton/day
Water flow rate on peeling line, gal/day
Total solids, Ib/day
Suspended solids, Ib/day
COD, Ib/day
BOD, Ib/day
Conventional
peeling
80
48,000
10,200
340
6,500
2,670
Dry caustic
peeling
80
12,000
1,050
40
390
190
Average of 4 composite samples.
dry-caustic peeling produces only 1,050 Ibs. of total solids. Therefore, more than 85% of the
total solid waste is collected and segregated from the main plant effluent. Suspended solids were re-
duced from 340 Ibs. to 40 Ibs. per day by the dry-caustic peeling operation. The dry-caustic peeling
operation affected more than 90 percent reduction in both COD and BOD.
Example 2—Cling Peach Peeling
The dry-caustic process was also applied to cling peach halves with a mechanical peel removal
system during the 1972 season at Del Monte, San Jose, California. The soft fruit (and tomato) peel
removal units consist of a manifold of rotating rubber discs which convey the fruit and wipe off
softened peel simultaneously. The initial demonstration of the cling peach peelers was in a commer-
cial cannery40 with the first commercial utilization of dry-caustic peeling of cling peach halves in
1971.41 This first commercial installation was operated during the 1971-1973 processing seasons.
Figure IV-20 is a schematic of a commercial mechanical peel removal unit having a capacity
of 12 to 15 tons/hour of cling peach halves.
Table IV-22 summarizes overall results of commercial dry-caustic peeling of cling peaches
and compares the conventional (hydraulic) system with the dry-caustic (mechanical) system for
peel removal. The water use is reduced 90% and the BOD generation is reduced 50-60% when
the dry-caustic system replaces the hydraulic system. The reduced cost of liquid waste treat-
ment resulting from use of dry-caustic peeling is partially offset by the cost of disposal of peel-
ing sludge (approximately 50 Ib./ton of raw peaches peeled). The peeling sludge from dry-
caustic peeling of peaches has been disposed of by sanitary land fill or by land spreading and
cover. In the future, if all cling peaches canned in California were dry-caustic peeled, the
estimated 17,000 tons of sludge produced would probably be utilized as an animal feed com-
ponent.41 The number of commercial dry-caustic peeling units currently used in peach canning
is five with a total production of 70 tons per hour.
Example 3—Peeling of Tomatoes
Hart et a/42 described results obtained from a pilot scale study (2 to 4 tons per hour) using
rotating rubber discs to remove the peel from caustic treated tomatoes. Figure IV-21 is a
schematic drawing of the pilot system.
83
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Troughed
conveyor
Pitted
fruit
00
Dry peeler
disc section
(cup-up)
Rinse water
to biological
treatment system
Sodium
hydroxide
peeler
tank
To cup-up
shaker and
inspection belt
Sample
Timer
Sample bottle
(refrigerated)
Figure IV-20. Schematic of dry-caustic peeler.
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Table \\J-22.-Hydraulic versus mechanical peel removal for cling peached
[per ton of raw peaches] a
Water use, gallons
BOD, pounds
SS, pounds
Peeling loss, %
Hydraulic
850
6.7
5.1
6.45
Mechanical
90
2.7
1.9
7.35
Data from 1971 season which was confirmed in the 1972 and 1973 seasons.
Lye treating
Peeling
Rinsing
^
To
collectors
and/or
plant
processing
line
Ferris wheel Slitter
caustic dipper
Effluent
Effluent collection
collection
Rinsing
bath
Figure IV-21. Pilot scale peeling line.
Tomatoes were normally immersed in the caustic dipper (18% caustic) at 220° F for 30
seconds. Following this, the skins were slit by passing the tomatoes over a series of rotating blades
that extended about 0.10 inches above the surface. The peeler consisted of a series of shafts hous-
ing flexible rotating rubber discs. The speed of rotation was 300 to 400 rpm. Above the disc bed
were a number of sprays to wash and aid in removing caustic from the tomatoes. After the disc
peeler, tomatoes were given an additional wash and rinse.
The volume of fresh water used for peeling varied with the feed rate but averaged 74 gallons
per ton of sorted tomatoes when the peeler was being operated at, or near, capacity (table IV-23).
This is a substantial reduction compared to the usual 300 to 500 gallons per ton for conventional
lye peeling.
Most runs generated only 70-80 gallons of effluent per ton of sorted tomatoes because of the
low volume of fresh water. The effluent carried approximately 18 pounds (dry weight) and the
screenings 5-6 pounds (dry weight) of solids per ton of sorted tomatoes. The low volume and
relatively high concentration of effluent enabled it to be handled more efficiently by conventional
treatment. Thus, the process should show savings in both water and treatment costs.
85
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Table IV-23.-Average water usage and peeler effluent characteristics3
Water usage
Effluent
Volume
Concentration
COD
Total solids
Total volatile solids
Suspended solids
Volatile suspended solids
pH
Screenings
Total solids
Wet weight
74 gal /ton
74 gal/ton
2.9% total solids
17.5lb/ton
17.6lb/ton
10.0 Ib/ton
2.5 Ib/ton
2.2 Ib/ton
11.9
5.1 Ib/ton
33.9 Ib/ton
Based on feed weight of sorted tomatoes
The relatively high concentration of the effluent presents a possible alternative to the usual
sewage disposal. At an average concentration of about 3% solids, it may be economically feasible
for a canner to concentrate the effluent, recover the water and then dispose of the concentrated
waste. Concentration might be done by settling and centrifuging of the suspended solids or by
evaporation. In either case, the recovery costs would then be balanced against the conventional
disposal costs in order to determine feasibility of this procedure.
Example 4—Infrared Dry-Caustic Process43
The infrared dry-caustic peeling process for potatoes involves several steps. Wet-washed pota-
toes are immersed in a hot dilute lye solution. The excess lye is drained and the potatoes stand
for about 5 minutes to allow the caustic to penetrate. Following the holding period, the potatoes
are subjected to infrared heat for 1 or 2 minutes. The infrared heat activates the caustic and
dries the surface layer of the potato. After conditioning by the heat, the potatoes are placed
in a rubber-tipped mechanical peeler which removes the treated outer surface of the potato.
Finally the potatoes are brush washed to remove a very small amount of soft sticky residue
from their surfaces.
The gas-fired infrared heaters are of the type commonly used for space heating. Combus-
tion takes place just in front of a ceramic mantle which radiates at 860° to 890° C (1550° to
1600°F). A nichrome wire screen protects the mantle from contact with the potatoes.
Peeling losses are about 8 to 10% with fresh potatoes of regular shape and few blemishes.
They run up to 20% and over with old potatoes that have many blemishes. All potatoes could
be peeled satisfactorily. The risk of producing a partially cooked translucent superficial layer
("heat ring") can be avoided provided the lye treatment is not preceded by any heating and the
mechanical peeling takes place immediately after the infrared irradiation.
Part of the peel is abraded off during the irradiation and dries as a result of the heating, but
without charring. About one half of the peel solids are thereby removed. This residue has a
sodium hydroxide content of about 3% with 30% ashes, 9/10 of which are sodium carbonate.
It can be burned, buried for land disposal, or wetted to 35-40% solids, submitted to bacterial
action so as to lower its pH, and mixed with animal feeds. The residual peel material from the
peeler has a solids content of 23-28%, a sodium hydroxide content of about 13%, and an ash
content of 18% on a dry basis.
86
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The potatoes leaving the peeler have a small amount (about 0.5%) of soft semisticky tissue
which is readily removed with a small amount of water. The potatoes were essentially free of
caustic, except in deep eyes and cracks.
In light of these results, three 9-ton/hour lines were installed in 1970 in one plant.44 In
addition to a savings of about 80% in the consumption of sodium hydroxide and of a reduction
of 1/3 of the peeling losses, the savings in water exceeded 95%. Moreover, there was no longer
any wastewater to dispose of because the residues (solid material plus water) were collected as
a thick slurry of 12-15% solids which could be fed to cattle after neutralization. However, due to
increased energy costs, these units are not currently used.
Additional Dry Peel Removal Studies
A dry peel removal machine, entirely different in design and operation, has been recently
tested on peaches and tomatoes. Known as a Magnuscrubber Model HC, the machine is circular
in design rather than the flat bed type. The soft rubber discs are assembled in a circular re-
volving cage with a feed screw through the center. The feed rate is controlled by this central
screw conveyor. The product flow is parallel to the roll axis and perpendicular to the surfaces
of the discs. On a flat bed machine, the orientation of the product is just the opposite.
In one study, surveys were made at three peach and tomato processing plants.5 This study
concentrated on determining the reductions obtained by this new dry scrubber for the peel re-
moval operation and the impact of this on the total plant effluent. Data presented in tables
IV-24 through IV-27 have been extracted from the study report.
Table IV-24.—Caustic peeling of peaches — reduction of peeling
wastes with Magnuscrubber
Parameter
Water flow
BOD
COD
Suspended Solids
Peel
Spray washer
(Per 1000
694 gals.
8.6 Ibs.
12.6 Ibs.
2.3 Ibs.
removal method
Magnuscrubber
Ibs. of canned peaches)
13 gals.
0.3 Ibs.
0.9 Ibs.
0.2 Ibs.
Reduction with
Magnuscrubber
98%
97%
93%
91%
Table \V-25.-Peach canning - reduction of total plant
wastes with Magnuscrubber
For total plant
Water
BOD
COD
Suspended Solids
Peel
Spray washer
(Per 1000
1470 gals.
13.6 Ibs.
25.2 Ibs.
6.5 Ibs.
removal method
Magnuscrubber
Ibs. of canned peaches)
789 gals.
5.3 Ibs.
13.5 Ibs.
4.4 Ibs.
Reduction with
Magnuscrubber
46%
61%
46%
32%
87
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Table IV-26.—Caustic peeling of tomatoes — reduction of
pee/ing wastes with Magnuscrubber
Parameter
Water flow
BOD
COD
Suspended Solids
Peeling
Water washing
(Per 1000lbs.
604 gals.
6.0 Ibs
10.2lbs.
2.2 Ibs.
removal method
Magnuscrubber
of canned tomatoes)
14.5 gals.
2.4 Ibs.
3.1 Ibs.
0.5 Ibs.
Reduction with
Magnuscrubber
98%
60%
70%
77%
Table \V-27.-Tomato canning - reduction of total plant
wastes with Magnuscrubber
For total plant
Water flow
BOD
COD
Suspended Solids
pH of water waste
Peel
Water washing
(Per 1000
3750 gals.
49.3 Ibs.
93.2 Ibs.
45.3 Ibs.
9.4
removal method
Magnuscrubber
Ibs. of canned tomatoes)
2690 gals.
31. 4 Ibs.
44.5 Ibs.
-
6.2
Reduction with
Magnuscrubber
28%
36%
52%
-
-
In another study completed in 1975, a Magnuscrubber was evaluated over an entire cling
peach season.7 Particular attention was devoted to development of data on yield losses. Some of
the findings of that study are as follows:
• Caustic concentration
Water peel: 2.0- 2.7%, average 2.4%
Dry peel: 1.5 - 2.3%, average 1.8%
Savings: 25% less caustic with dry peel
Yield loss
Water peel:
Dry peel:
Savings:
7.1%
6.1%
1% increase in product yield
There was some limited data to indicate the dry peel process left less skin on the peaches than
the conventional system. The appearance of the peaches was better with the dry peel process than
with the conventional process.
88
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BLANCHING
Vegetables which are preserved for long-term storage by freezing, dehydration, or canning
receive a treatment (known as blanching) with hot water or steam. The purpose of blanching
is to deactivate enzymes and to remove tissue gases. In addition, blanching frequently accom-
plishes or facilitates removal of juice, soil, insects and other debris from the vegetable pieces.
Present methods for the blanching of vegetables prior to freezing, dehydration or canning
use large volumes of water or steam, resulting in effluents heavily loaded with organic material
which constitute a major source of pollution. The National Canners Association has estimated
that if waste strength were reduced by 50% for the seven major processed vegetables (peas, corn,
tomatoes, green beans, spinach, white potatoes, carrots), the suspended solids in wastewaters from
plants could be reduced by 40 million pounds (20,000 tons), and the BOD by 70 million pounds
(35,000 tons). Conventional blanching has also the disadvantage of extracting nutrients, mineral
salts, water soluble vitamins, and sugars.
Steam blanching will partially avoid these difficulties; however, in order to obtain the needed
capacities, the products are distributed in thick layers on the belts conveying them through the
blanching tunnels, and submitted to long exposures to steam so as to inactivate the enzymes in
the center of the largest pieces deepest in the beds. Surface sloughing and non-uniform texture
may result.
Two-Step Quick Blanching (Individual Quick Blanch)
In the blanching process developed by the Western Regional Research Laboratory,45
blanching is carried out in two steps. In the first step, the product is spread in a thin layer and
is rapidly brought to the desired temperature. In the second step, the product is discharged as
a deep bed onto another conveying belt moving slowly through an insulated chamber, so as to
let the temperature equilibrate in each piece and act upon the enzymes for a time sufficient to
inactivate them. Figure IV-22 shows schematically how this process called Individual Quick
Blanching (IQB) is carried out.
Monolayer
Curtain
' . ^ \S^\
Multiple
layer
Heating section
Fast belt
(live steam heat)
Holding Cooling section
section (optional)
Slow belt (chilled air)
(insulated, adiabatic)
Figure IV-22. Individual quick blanching unit.
89
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For 3/8-inch dices of carrots, 25 seconds in the steam at 100°C, followed by a holding time
of 50 seconds, are adequate to give a peroxidase inactivation equivalent to that obtained by con-
ventional blanching.
Lund46 reported on the application of IQB to vegetables prior to canning. In that study, peas,
corn, lima beans and green beans were blanched by: (1) the IQB process, (2) the IQB process with
predrying, and (3) pipe blanching. Compared to pipe blanching, the IQB process reduced waste-
water generation by up to 99%. The study also revealed that although predrying to greater than a
6% weight reduction would further reduce wastewater generation, product quality was adversely
affected.
Concerning the volume of effluent, its solid load and the yield of the product, the experiments
that were carried out compared conventional steam blanching (about 4 pounds/sq. ft. of conveying
belt) to the new method (1 pound/sq. ft.). Effluent volume can be decreased by not wetting the
surface of carrot dices, and even by drying it slightly, before the exposure to steam (see table IV-28).
Superficial drying is obtained by submitting the diced carrots to warm (150°F-66°C) air for
5 to 8 minutes. Table IV-28 shows that by simply not wetting the diced carrots, the effluent is
already appreciably reduced. The reduction reaches almost 95% when the new blanching process
is applied to diced carrots pre-conditioned so as to evaporate surface moisture.
The equilibration of the temperature of the carrot dices after the heating phase has been the
object of a mathematical study.46 The solution of the differential equation which has been
developed allows us to calculate the temperature gradients as a function of time inside a cube of
carrot and to establish the conditions for perodidase inactivation. The mathematical calculations
have been confirmed experimentally, and present a wider interest in that they apply to all reactions
in which the temperature acts according to Arrhenius' equation.
The blanching process just described is more appropriate prior to freezing or dehydration than
to canning, in which blanching performs other functions than merely enzyme inactivation.
Table IV-28.—Effect of pre-conditioning treatments on blancher effluent and
product yield for 3/8 inch carrot cubes
Pre-
conditioning
treatment
Wet
Not wet
Not wet
Pre-evaporated to a
5.8% product weight
loss
Pre-evaporated to a
10.5% product weight
loss
Blanching
method
Conventional
Conventional
IQB
IQB
IQB
Effluent
volume
total
flow
15.3
11.1
6.6
2.8
0.8
Effluent
total
solids
%
-
5.4
4.2
5.8
5.3
Product
yield
%
103.4
102.1
106.2
102.2
99.8
90
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Hot Gas Blanching
Comprehensive surveys of waste generation in food canning operations made by NCA have
established blanching as a major source of strong liquid wastes in vegetable preservation.8 Commer-
cial blanching with hot water is a primary source of BOD in the processing of many vegetables.
Steam blanching produces much lower wastewater volumes. A highly desirable replacement system
for vegetable blanching would produce little or no wastewater. Microwave blanching is effective
for many vegetables and produces small wastewater volumes. However, it requires large volumes of
water to the cooling equipment. This, together with the high equipment costs and large energy
requirement for microwave blanching, makes it economically unattractive for a seasonal vegetable
processing operation.
During the period of 1971 to 1973, the Western Research Laboratory of NCA explored the
use of hot gases to blanch vegetables. The concept of treating vegetables (to deactivate enzymes
and expel cellular oxygen) using the heat content of combusted hydrocarbons directly was tested
in a prototype unit with a design capacity of 500 Ib/hr. The experimental hot gas blancher was an
insulated box containing a 125,000 BTU/hr. natural gas furnace at one end. The furnace had an
external air supply turbine. Combustion gases were circulated with a blower. Steam was injected
through a single opening in the blower inlet duct to increase heat exchange rates and to minimize
dehydration losses from the high water content vegetables. The vegetables were conveyed through
the heated zone on a wire mesh belt. Schematic drawings of the hot gas blancher have been
published.47 48 The installation of the hot gas blancher included electrical, gas, and steam flow-
meters to develop information on operational costs of commercial size units. Recent work with
the hot gas blancher involved in-plant studies using commercially prepared vegetables for blanching.49
Numerous short duration experiments were conducted to establish good operating conditions and
to demonstrate that hot gas blanched material could be returned to production with no loss in final
product quality. The loading rates and operational conditions for in-plant hot gas blanching of
vegetables are summarized in table IV-29.
The data in table IV-29 illustrate the light loading, long residence time, and high steam require-
ments for corn-on-cob and beets, due to their large size and slow rate of heat penetration. The
corn-on-cob was preserved by freezing and it was necessary to blanch until all enzyme activity in
the cob was destroyed. The use of hot gas blanching for large-piece-size vegetables does not look
promising at the present time due to equipment and operational costs. The most promising
commodity for hot gas blanching is cut green beans. It was possible to use heavy loading, short
residence times and low steam injection to achieve the partial enzyme deactivation necessary to
avoid skin separation (sloughing) in the final canned product. Hot gas blanching appears to hold
promise for smaller-piece-size or thin vegetables due to the high potential for almost complete
elimination of wastewater generation.
Table \\J-2Q.-ln-plant hot gas blanching of vegetables49
Commodity
Green beans
Corn-on-cob
Beets
Spinach
Green peas
Loading
Ib/hr.
1,580
240
245
320
610
Residence
time min.
1.3
14
25
1.8
3.5
Temp.
°F
185
220
245
225
230
Steam
Ib/min.
0.63
6.3
4.2
0.5
2.2
91
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Table IV-30 demonstrates the percentage reductions in wastewater volume, weight of BOD,
and weight of suspended solids which result when hot gas blanching replaces steam or hot water
blanching.
Table IV-30.—Reductions due to use of hot gas blanching of vegetables 49
Commodity
Green beans
Corn-on-cob
Red beets
Spinach
Green beans
Wastewater
volume
99.9
33.3
(2.2)a
99.9
94.2
BOD
99.9
28.8
47.5
99.8
91.4
SS
99.9
18.7
37.0
99.5
93.0
a Increase in wastewater volume.
Quality examination of final products from hot gas blanching of vegetables has shown no
significant difference from commercially blanched (steam or hot water) samples. With a few
isolated exceptions, the retention of vitamins and minerals is similar for commercially blanched
and hot gas blanched vegetables. No significant difference in trace levels of polynuclear aromatic
hydrocarbons could be found in samples of hot water and hot gas blanched cut green beans. Thou-
sands of cases of canned products containing hot gas blanched vegetables have been sold with no
adverse consumer reaction.
Several equipment supply companies have working drawings of hot gas blanchers prepared for
potential customers. To date, no commercial size hot gas blancher has been constructed. Deter-
rents to commercial utilization of hot gas blanching of vegetables are the high estimated equipment
costs and the uncertain supply of natural gas or propane in future years. The hot gas blancher is
more complex than a hot water blancher due to burners, blowers, gas and mandatory safety devices.
The trade-off of the higher cost of a hot gas blancher against the lower cost for water and waste
disposal will need to be estimated for each potential application of hot gas blanching. Fossil fuel
energy sources will be in short supply for the period of 1974-1980. The reasons for the potential
shortage of such fossil fuels as natural gas are the high growth rate of energy consumption (4% per
year) and reduction in the U.S. reserves-to-production ratio. The predicted shortage of natural gas
may cause potential users of hot gas blanching to postpone use of this new system. Fortunately,
the hot gas blancher can be operated with liquified propane as a fuel. Under the allocation program
in effect since May 1974, food processing is one of the categories listed as priority customers (some
others are residential uses, agricultural production and mass transit vehicles). Therefore, it is likely
that vegetable processors using hot gas blanching could get adequate supplies of propane.
Vibratory Blanching and Cooling
Bomben et a/50 conducted a study to design, construct and demonstrate a steam blanching
system capable of processing 1 ton/hour of vegetables in which the effluent was to be used as a
fog spray for cooling blanched vegetables prior to freezing. This study incorporated the Individual
Quick Blanching (IQB) principle with a vibratory cooling system. Figure IV-23 shows a schematic
of the resultant vibratory blancher cooling system.
92
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Heater
CO
co
fv-'v •::•:::••;
kv. ;:;.•.;.::•;
te #?&
Vibrator
Holder
Cooler
Air blower
Figure IV-23. Schematic diagram of vibratory blancher cooler.
-------
Solid surface vibrating conveyors were chosen for the heat transfer surfaces in the heater and
cooler. This type of equipment can be more easily cleaned than wire mesh belts used in most steam
blanchers. Spiral vibratory conveyors provide a very compact design as they can be stacked close
together and do not have a return section. The vegetables can be used to form a product seal at the
entrance and exit from the equipment which will reduce heat losses.
An electromagnetically-driven, variable amplitude, Syntron circular conveyor was used in the
heater. The conveyor operated at a frequency of 3600 cycles/minute, causing the product to move
in an upward and forward motion. The residence time in the heater is controlled by varying the
feed point and the amplitude of vibration. The cooler was a spiral vibratory elevator. Like the
heater, it has a frequency of 3600 cycles/minute. The 36-inch high elevator (with five 4-inch wide
flights of 14-5/8 inch diameter) gives the cooler an effective length of 17 feet. Blowers, connected
to the plenum, delivered air over the product concurrently. Condensate from the heater was
atomized into the cooler at the blower entrances.
Table IV-31 summarizes typical operating conditions used in these experiments.
Table IV-31 .—Typical operating conditions^®
Commodity
Green beans
Carrots
Heating
time
(sec)
45
25
Holding
time
(sec)
45
60
Feed rate
(Ibs/hr)
190
145
Excess
steam3
(%)
12
24
Cooling
time
(sec)
45
60
Cooler
product
Temp. (°F)
100
105
a Equals percent over theoretical steam consumption. Theoretical steam consumption for 60° F initial temperature and a
195°F final mass average temperature is 13.8 lb/100 Ib feed.
The vibratory spiral conveyor used in the cooler conveyed both the carrots and the green beans
uniformly and continuously. When the conveyor was tried with cut cauliflower and broccoli spears,
the 4-inch conveyor was too narrow to convey these vegetables well, but they did move up the
length of the spiral.
It was found that the spiral conveyor required a product velocity of approximately 17 feet/min.
to give a uniform steady flow of product. This product velocity gave a residence time of only
1 minute with green beans and carrot dice. The resulting product temperature of 100° to 105°F is
higher than the 70° to 80°F usually achieved before freezing in a commercial process. A conveyor
twice as long would provide a 2-minute residence time, which would give adequate cooling.51
The lower gross yield of green beans for combined blanch-cooling as shown in table IV-32 is
characteristic of air cooling.51 The condensate sprayed on the product is only partially reabsorbed,
and it does not completely compensate for evaporation of moisture into the air stream. In flume
cooling, there is no evaporative weight loss, but the higher yield is accompanied by twice as much
solids lost from the product. Since frozen vegetables are sold on the basis of weight, a lower yield
means less production and can be justified economically only if the value of lost product is balanced
by the cost of increased waste disposal and increased quality of the final product.
94
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Table IV-32.-Comparison of yields and solids loss in effluent for green beans between combined
blanching and cooling vs conventional blanching and flume cooling^
Process
Combined vibratory
blanch-cool
Conventional steam blanch
flume cool
Conventional water blanch
flume cool
Gross yield3
(%)
88
95
96
Effluent
solids loss6
(%)
2.6
5.7
6.1
Reference
This work (51 )
(8)
(8)
a Gross yield
Wt. of cooled product
b Effluent solids loss
Wt. of feed to blancher
% solids in effluent x wt. of effluent
> solids in feed x wt. of feed
The results in table IV-33 show the large difference in volume of effluent between conventional
processing and the combined blanch-cooling.51 Most of this volume (96%) is due to the flume cool-
ing. Assuming a product temperature out of the blancher of 195°F and cooling water temperature
of 60° F, it requires 5.8 Ib. of water per Ib. of product to obtain an 80° F product temperature. This
amount of flume water when added to the blancher effluent results in twice the amount of COD
and 70 times the volume of effluent from combined blanching and cooling.
Table IV-33.—Comparison of effluent from green beans for combined blanching
and cooling and conventional blanching and flume cooling^
Process
Combined vibratory
blanch-cool
Conventional steam blanch
flume cooling
Conventional water blanch
flume cooling
Effluent
(lb/100lbfeed)
7.0
500
520
COD
(Ib/IOOIbfeed)
0.17
0.35
0.32
Reference
This work (51)
(8)
(8)
If no change is made in the way frozen vegetables are marketed, then air cooling of any kind
suffers a large cost disadvantage. Table IV-34 gives a comparison of the approximate operating
costs of three different kinds of blanching. The basis for this cost estimate is taken from Brown
et a/.51 It must be emphasized that these costs are approximate, and they are shown merely to
make a comparison. It is obvious that the cost of lost green beans (at $0.20/lb) due to reduced
yield is overwhelming in comparison to other costs. Even though the combined vibratory blanch-
cooler can give substantial savings in steam and effluent costs, and a product with more retained
solids, these will not balance the cost of product lost through evaporation.
95
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Table IV'-"^.-Comparison of operating parameters for the blanching and
cooling of green beans5^
Water and effluent
gals/ton
$/ton
Ib/ton
$/ton
Electricity ($/ton)
Steam ($/ton)
Product loss ($/ton)a
Total cost ($/ton)
Combined vibratory
blanch-cool
140
0.06
3
0.06
0.06
0.31
28
28.43
Conventional steam
blanch-flume cool
1200
0.48
7
0.14
0.007
0.55
0
1.17
Conventional water.
blanch-flume cool
1250
0.50
6.4
0.13
0.007
0.8
0
1.43
a Frozen green beans at $0.20/lb.
Design of Large Scale Vibratory Blanch-Cooler
To evaluate fully the technical feasibility of the combined blanch-cooling approach to process-
ing frozen vegetables, it is necessary to work with larger scale equipment. Figure IV-24 is a
schematic diagram showing the configuration and the dimensions of a 1 ton/hr. vibratory blanch-
cooler. The heater and cooler would have adjustable feed points to accommodate the different
residence times needed for different products. The holder would be a live bottom bin with an
automatic level control, which could be adjusted to maintain different holder residence times. The
cooler would use the same type of conveyor as in the heater, but the central column of the spiral
could be used to direct the air flow. The cooler spiral conveyor would have to be much longer to
accommodate up to 5-minute residence time for large vegetables such as broccoli and Brussels
sprouts.
Blancher modifications are still in the research and development stage. All of the studies
discussed were supported, in part, by grants from the Environmental Protection Agency. As indi-
cated in the discussions, some look promising while others have problems. There is still a need to
develop these and other approaches towards solving blancher effluent problems and to evaluate the
most promising methods on a commercial scale.
CUTTING, SLICING, DICING
Many products are cut or otherwise reduced in size by highly automated equipment. For
example, green beans are snipped, cut or sliced; fruits are sliced or diced; and root vegetables are
sliced into several styles or diced. Each of these operations produces undesirable fragments of
product which are normally separated from the desired material. The small bits and pieces are most
frequently removed by rotating or vibrating screens, often with the aid of water. The high percent-
age of exposed surface of inner tissues in cut pieces results in rapid leaching of soluble organic
matter into water. Therefore, when cut fragments are hydraulically conveyed, the resulting waste-
water will contain a very high organic load. For this reason, it is highly desirable to handle such
materials in containers or with mechanical or pneumatic conveyors.
96
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Enlarged cutaway
section of heater
CD
-J
Steam
Feed bin and
elevator
Air blower
with filter
Air & condensate
Cooler
Air
Enlarged cutaway
section of cooler
Figure IV-24. One ton per hour vibratory blancher cooler.
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PITTING
Automated pitting machines are used to destone such fruits as apricots, cherries, olives, peaches
and plums. The pits removed by this equipment generally have fruit flesh adhering. If placed into
water, this material will contribute significantly to the organic load. Some pitters separately dis-
charge the stones and the fruit. In such situations, the pits should be collected either in large con-
tainers or, preferably, on a separate conveyor and transported to the waste storage area. When the
pitting equipment does not separate materials, the pits are generally separated from the fruit by
revolving or shaker screens. The pits removed by the screens should then be handled as above.
PULPING, EXTRACTING
Pulping, juice extracting, and finishing equipment are used to produce fruit and vegetable
nectars, purees, and juices by mechanically compressing raw products against screens or perforated
plates. The waste material ejected from these types of apparatus is called roughage or pomace,
consisting of stems, skin, seeds, fiber and other coarse components of the raw product.
Although much of the liquid is extracted by these processes, the ejected materials still contain
soluble organic matter. When these materials are placed into water, the soluble organic matter
creates a high pollution load. A study conducted with tomato pomace revealed that the BOD load
generated by placing this material into water was equivalent to three percent of the wet weight of
the pomace (3 pounds of BOD for each 100 pounds of pomace).52 Therefore, it is mandatory that
these materials be handled dry.
Pomace from pulpers, extractors and finishers can easily be collected and transported on belt,
drag or screw conveyors. Pneumatic conveyors have also been successfully employed. When the
quantity of ejected material is relatively small, the material can be collected in bins or portable
hoppers situated at the waste discharge end of the equipment. Any of these waste handling pro-
cedures will prevent the creation of a significant organic load.
PRODUCT CONVEYING
Methods which are used to transport raw commodity within the plant can be classified into
four general categories: manual, mechanical, hydraulic, and pneumatic. Except for limited situa-
tions, technological development of food processing plants has eliminated in-plant manual handling
from all except visual inspection operations whereby culls and blemished pieces of commodity are
removed. Pneumatic conveying systems are relatively recent developments. Mechanical and hydraulic
conveying systems are most widely used. In the following discussions, emphasis is placed on reducing
waste loads emanating from these systems.
MECHANICAL CONVEYING SYSTEMS
Mechanical conveyors in widespread use include belts (both solid belting and steel-mesh),
vibrating or oscillating conveyors, live rollers, buckets, screws or augers and drags. The type of
conveyor used is limited by the nature (dry, fluid, whole, cut, etc.) of the commodity being handled.
Hence, the quantity of water used and the waste loads generated in relation to the different types
of conveyors vary accordingly.. Although water usage by mechanical conveying systems is normally
minor, care must be exercised to prevent these systems from becoming significant sources of waste
loads.
Screw conveyors are most frequently used to transport dry materials such as flour and granu-
lated sugar, or solid waste materials. In either situation, buildup of bacterial populations is not of
urgent concern. Water usage is generally limited to cleanup operations. Drag conveyors are used
most frequently to transport whole product from delivery areas into the plant or to transport solid
98
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residuals away from the processing areas. Again, water usage is generally limited to periodic cleanup.
In these situations, waste loads can be minimized by using high pressure-low volume cleaning
equipment.
Belts, vibrating or oscillating conveyors, live rollers, or bucket conveyors are used at numerous
points within all plants. Since these are used to transport raw product in various stages of prepara-
tion, sanitary considerations are of primary concern. To maintain an acceptable degree of equip-
ment sanitation, water is generally applied continuously. As in the case of raw product washing,
the degree of cleanliness is determined more by how water is used rather than by the quantity of
water that is used. Continuous cleaning of conveying equipment is normally accomplished with
sprays. Maximum efficiencies can be obtained by using high pressure-low volume spray nozzles
and water which has been chlorinated to 5 ppm. Since a continuous application of water is not
generally required to maintain acceptable sanitary conditions, the quantity of water used can be
significantly reduced by intermittent use of the cleaning sprays. Cleaning cycles can be controlled
manually or by use of appropriate timers and solenoid valves.
In addition to sanitation requirements, belts and oscillating conveyors may require a small
volume of water for surface lubrication. Fogging nozzles, or other low volume mist sprays, can be
advantageously used for this purpose. Use of chlorinated water, if practicable, will further retard
bacterial growth and reduce the required frequency of cleaning.
HYDRAULIC CONVEYING SYSTEMS
In-plant handling of raw products in hydraulic systems (pump and pipe systems and flumes)
is now widely practiced in fruit and vegetable processing plants. Hydraulic conveying systems offer
the advantages of gentle product handling, additional washing of commodities, less space for
vertical transport, and ease of maintaining equipment sanitation. The major disadvantages are the
relatively large volume of water required and the significant organic load generated by these systems.
The organic load associated with water in hydraulic conveying systems results from the wash-
ing and leaching of soluble organic matter from the commodity being transported. The organic
matter is leached from the commodity because of the osmotic difference between the transport
medium and the product tissue. The quantity of organic matter (the organic load) is a function of
the duration of immersion and the size of the particles. The longer a piece of product is in water,
the more material will be leached into the water. Smaller particles provide greater exposed surface
areas resulting in more rapid loss of solubles.
PNEUMATIC CONVEYING SYSTEMS
Among the many innovations in fruit and vegetable processing technology designed to curtail
water pollution, pneumatic conveying systems offer a means to significantly reduce waste loads
associated with the processing of several commodities. Where hydraulic conveyors have been
replaced by pneumatic systems, both the hydraulic and organic loads have been markedly diminished.
Pneumatic systems may be designed to convey materials by either positive or negative air pressure.
Such systems offer the additional advantage of requiring very little floor space. A typical negative
air system is illustrated in figure IV-25.
Although most types of solid wastes can be readily handled, pneumatic systems are currently
able to satisfactorily handle only certain types of raw commodities. Limitations are imposed upon
the size and density of the material to be transported, the distance, and the ability of the material
to withstand rough handling without incurring physical damage. Commodities which are being suc-
cessfully conveyed in pneumatic systems include peas, green beans, cut corn, lima beans, and
carrots.53 Solid wastes from numerous commodities are being handled pneumatically.
99
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Transport pipe
Intake
hopper
Vacuum pump
(blower)
Centrifugal
separator
Rotary
air lock
Discharge
Figure IV-25. Negative air conveying system.
PLANT CLEANING
The procedures normally followed for plant cleanup consume large volumes of water. Much
of the water is used simply to flush solid waste materials from equipment and floors into the gutter
system. Additional quantities of water may then be required to transport the solid materials to the
waste storage area. This practice not only adds to the hydraulic load of the plant effluent, but also
adds to the organic load by the leaching of soluble matter from the waste materials. Wastewater
loadings attributable to plant cleanup can be minimized by altering the cleanup procedure.
Prior to the use of detergents and water to clean the processing equipment and floors, food
residuals should be manually placed into suitable receptacles. Materials which tend to accumulate
in equipment should be brushed or scraped away. Materials on the floor should be swept and
shoveled into containers. Alternatively, pneumatic conveying systems may be equipped with spe-
cial attachments which can be used to vacuum clean processing areas. A dry pre-cleanup procedure
is an essential part of a successful waste reduction and prevention program.
Maintenance of cleanliness in the fruit and vegetable plant may require frequent or continuous
cleanup in addition to that at the end of each shift. Large volumes of water are often used to wash
processing equipment, inspection tables, conveyors, walls, floors, and drains. Water is also used for
cleaning areas outside the plant and for washing trucks, storage vats, produce conveyors, bins, plat-
forms, and other equipment.
Continuous in-plant cleaning operations are conducted to keep wastes from accumulating dur-
ing the operating day, thereby improving sanitation and reducing the time required for end-of-shift
cleaning. In continuous cleaning, wastes may be brushed from equipment or washed away with
water. The dry method is recommended whenever practicable to reduce the amount of solids
carried away in water.
100
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To maintain adequate cleanliness in the fruit and vegetable plant with minimum use of water,
careful consideration must be given to the design and construction of individual pieces of equipment.
Recommendations preferred by the Special Committee on Sanitation of Canning Equipment are
outlined in the NCA Laboratory Manual.54 The following discussion is limited to those procedural
practices which influence the generation of waste loads attributable to plant cleaning operations.
PRELIMINARY STEPS
The contribution to the organic load by small fragments of product cannot be overestimated.
As previously described, large amounts of soluble organic matter are washed or leached from the
product whenever water is applied. To reduce the organic load attributable to cleanup operations,
cleanup periods must be initiated by sweeping spilled material from the floors. The quantity of
water then required to finish the cleanup operation will be substantially less. This is evident when
one observes employees in plants where water is used exclusively during cleanup periods. So much
water is expended to chase a few fragments several feet across the floor to the nearest drain!
Secondly, the use of mechanical (brushes, scrapers, squeegees) and chemical (detergents)
cleaning aids, when properly used, can greatly reduce the time and increase the efficiency of cleanup
operations. The quantity of water required for cleaning may be significantly reduced by using
cleaning aids, especially when foods or other contaminants tenaciously stick to equipment surfaces.
Cleaning aids are also discussed in detail in the NCA Laboratory Manual.
WATER HOSES
When continuous cleaning is practiced, care must be especially taken to avoid wasting water
from unattended hoses. Hoses should be equipped with automatic shutoff valves to save water and
to avoid spraying the rest of the plant. To maximize the effectiveness of water, valve outlets should
be constructed so that nozzles of various types can be connected rapidly. The following inter-
changeable nozzles are suggested: a small jet type for cleaning deep cracks, a fin type for cleaning
flat surfaces, a bent type for cleaning around and under equipment, and a spray head-brush com-
bination type for cleaning surfaces where combined brushing and washing is needed.
SPECIAL CLEANING EQUIPMENT
The cleaning efficiency of water is influenced by the temperature and the pressure under which
it is applied. Hot water applied under high pressure is generally most efficient, thereby requiring
smaller volumes to accomplish specified tasks. Numerous cleaning devices are available whereby
water can be heated, pressurized, and, if desired, mixed with cleaning chemicals at controlled rates.
Such devices are available as portable units which may be used in various areas within a plant or as
a stationary unit with high pressure lines piped to various outlet stations.
SAVINGS FROM EFFICIENT CLEANUP
Substantial savings can be realized by reducing cleanup labor since this constitutes the greatest
part of cleanup costs. Labor reductions can most readily be achieved by reducing the time required
for adequate cleaning. An added benefit will be the availability of additional time for production.
However, this must be accomplished without compromising the sanitary standards which have been
established for each operation.
The key to minimizing the time required for plant cleanup lies in proper design of the facility
and in the use of efficient equipment and procedures. The results of installing high pressure hydraulic
101
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cleaning units and training employees in their use were documented in one plant.55 Comparison
of the labor expenditures before and after installation showed the following reductions in cleanup
man-hours in a tomato cannery:
Pulper and Finisher Department 84%
Filler and Seamer Combinations 78%
Raw Fruit Belts and Related Equipment 65%
Tomato Product Bottle Lines Over 50%
Concrete Floor Areas 40% - 60%
Holding Tanks, Catch Pans, Floor Drains, Walls, etc. 65% - 75%
Any manager would be pleased with such savings that more than justify the investment in
equipment and training, and with the benefits of utilizing experienced cleanup workers. This is
particularly true when the savings can be accomplished without any sacrifice of sanitation standards.
Management can usually be convinced of the desirability of budgeting money for equipment, sup-
plies and training provided reasonable estimates can be made for return on the investment.
PERSONNEL
Cleanup will only be as good as the people directly and indirectly involved. Management must
be involved if cleaning of the plant is to be a success. Management has the final decisions on alloca-
tion of funds, men and materials, sets the policy for the plant and delegates the implementation to
supervisors of authority.
It is the cleanup supervisor that then has the responsibility of achieving management's policy.
The supervisor must have a good knowledge of cleanup equipment and materials. He should have
the authority for the repair, alteration and relocation of cleanup equipment. The supervisor should
have responsibility in crew selection and discipline authority. Cleanup crews put into practice what
they have been trained to do. If they are well trained, well equipped and motivated, then chances
are good that cleanup will be done in an efficient manner.
102
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REFERENCES
1Handbook for Monitoring Industrial Wastewater, U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1973.
"Section 3: Monitoring Liquid Waste Flows," Guide for Waste Management in the Food
Processing Industry, National Canners Association, Berkeley, Calif., 1969.
o
"Methods for Chemical Analysis of Water and Wastes," U.S. Environmental Protection Agency,
EPA-625-/6-74-003, Cincinnati, Ohio, 1974.
^Standard Methods for the Examination of Water and Wastewater, (14th ed.), American Public
Health Association, New York, N.Y., 1976.
5Wilson, J. "Properties of Wastes from Conventional Peeling of Peaches and Tomatoes." CH2M
Hill Project Report No. F 8736.0, San Francisco, Calif., 1975.
6Katsuyama, A.M., "Waste Generation and the Dollar Costs," Proceedings, 1971 Research
Highlights Meeting, National Canners Association, D2490, Berkeley, Calif., Nov. 1971.
7 Ritchie, D.A., Personal Communication, Oct. 1975.
8 "Liquid Wastes from Canning and Freezing Fruits and Vegetables," National Canners Asso-
ciation, Western Research Laboratory, D-2459, Berkeley, Calif., Aug. 1971.
9Townsend, C.T., and Somers, I.I., "How to Save Water in Canneries," Food Industries, 21;
W11-W12, 1949.
10Leavitt, P., and Ziemba, J.V., "At Gerber - Water Does Triple Duty," Food Engineering,
41:(9),p. 90,1969.
11 Cook, R.W., Wang, J., Daugherty, P., Farrow, R.P., and Rhoads, A.T., "Changes in Water
Quality Factors During Recycling Through a Water Recovery System While Canning Green Beans,"
National Canners Association, Western Research Laboratory, No. 1-69, Berkeley, Calif., 1969.
12Mercer, W.A., and Rose W.W. "Integrated Treatment of Liquid Wastes from Food Processing
Operations," National Canners Association, Western Research Laboratory, D-3015, Berkeley, Calif.,
Mar. 1968.
13"Waste Reduction in Food Canning Operations," U.S. Environmental Protection Agency,
EPA 12060--08/70, Cincinnati, Ohio, Aug. 1970.
14 Lovely, C.F., "The Use of Stable Chlorine Dioxide in Water Treatment," Paper presented to
the New Jersey Section, American Water Works Association, Atlantic City, N.J., October 6,1966.
15Welch, J.L., and Folinazzo, J.F., "Use of Chlorine Dioxide for Cannery Sanitation and Water
Conservation," Food Technology, 13 (3), p. 179,1959.
16Trueman, J.R., "The Halogens," Inhibition and Destruction of the Microbial Cell, Academic
Press, New York, N.Y., 1971.
103
-------
17Hodgman, Handbook of Chemistry and Physics, 1947.
18Mercer, W.A., "Chlorination Studies on Reused Water in Pea Canneries," Meeting of Northern
California Section, Institute of Food Technologists, 1971.
19Somers, I.I., "Studies on In-Plant Chlorination," Food Technology, 5 (2), 1951.
20Reeves, E., and Tilley, N., "An Improved lodophor — Its use for the Cold Cleaning of Milk
Collection Tankers," Dairy Industry, July 1972.
21 Russell, A.D., "The Destruction of Bacterial Spores," Inhibition and Destruction of the Micro-
bial Cell, Academic Press, New York, N.Y., 1971.
22Bogash, R.C., "A New lodophor Disinfectant-Survey and Evaluation," The Bulletin Amer. Soc.
Hosp. Phar., 12,1955.
23 Wilson, J.L. et al, "Iodine Disinfectants," Soap and Chemical Specialties, Sept. 1956.
24Evans, F.L., "Ozone Technology: Current Status," Ozone in Water and Wastewater Treat-
ment, Ann Arbor Science, 1972.
25Parker, A.C., "The Inhibition and Destruction of Cocci," Inhibition and Destruction of the
Microbial Cell, Academic Press, New York, N.Y., 1971.
26"Sanitizing System Aids Conner's Retort and Can-Seam Operations," Conner Packer, 141 (5),
1972.
27Smith, H.W.N., "The Saga of Shiny New Cans at Green Giant," Conner Packer, 142 (10),
1973.
28H"aufele, A., and Sprockhoff, H., "Ozon als Desinfektionsmittel gegen Vegetative Bacterien,
Bazillensporen, Spilzeund Viren in Wasser," 361 Bakt, Hyg., Abt. Org., B175,1973.
29 Venosa, A.D., "Ozone as a Water and Wastewater Disinfectant," Ozone in Water and
Wastewater Treatment, Ann Arbor Science, 1972.
30Broadwater, W.T., Hoehn, R.C., and King, P.H., "Sensitivity of Three Selected Bacterial
Species to Ozone," Applied Microbiology, 26 (3), Sept. 1973.
31Bringmann, G., "Determination of the Lethal Activity of Chlorine and Ozone on E. coli,"
Z. Hyg. Infektionskronkh, 130,139, 333,1954.
32Fetner, R.H., and Ingols, R.S., "Bactericidal Activity of Ozone and Chlorine Against E. Coli
at 1°C, "Adv. Chem. Series, 21, 1959.
33Kirk, B.S., McNabney, R., and Wynn, C.S., "Pilot Plant Studies of Tertiary Wastewater
Treatment with Ozone," Ozone in Water and Wastewater Treatment, Ann Arbor Science, 1972.
34Diaper, E.W.J., "Practical Aspects of Water and Wastewater," Ozone in Water and Waste-
water Treatment, Ann Arbor Science, 1972.
104
-------
35"The NCA Research Laboratories in 1975 — Review of Technical Issues and Research
Progress," National Canners Association, Berkeley, Calif., 1976.
36Katsuyama, A.M., Olson, N.A., Quirk, R.L., and Mercer, W.A., "Solid Waste Management in
the Food Processing Industry," U.S. Environmental Protection Agency, SW 42C-73 NTIS No. PB
219-019,1973.
37Krochta, J.M., Graham, R.P., and Rose, W.W., "Cleaning of Tomatoes Using Rotating
Rubber Discs," J. Food Technology, 28, Dec. 1974.
38Graham, R.P., Huxsoll, C.C., Hart, M.R., Weaver, M.L., and Morgan, A.I., "Dry Caustic
Peeling of Potatoes," Food Technology, 23,1969.
39Lee, C.Y., Downing, D.L., Hang, Y.D. and Russell, P.H., Jr. "Waste Reduction in Table Beet
Processing," Proceedings, Fourth National Symposium on Food Processing Wastes, U.S. Environ-
mental Protection Agency, EPA-660/2-73-031, Dec. 1973.
40 "Dry Caustic Peeling of Tree Fruit for Liquid Waste Reduction," U.S. Environmental Pro-
tection Agency, 12060 FQE 12/70, Dec. 1970.
41 Stone, H.E., "Caustic Peeling of Clingstone Peaches on a Commercial Scale," U.S. Environ-
mental Protection Agency, EPA-660/2-74-092, Dec. 1974.
42Hart, M.R., Graham, R.P., Williams, G.S., and Hanni, P.P., "Lye Peeling of Tomatoes Using
Rotating Rubber Discs," Food Technology, 28 (12), Dec. 1974.
43Smallwood, C., Jr., Whitaker, R.S., and Colston, N.V., "Waste Control and Abatement in
the Processing of Sweet Potatoes," U.S. Environmental Protection Agency, EPA-660/2-73-021,
Dec. 1974.
44"Commercial Infrared Peeling Process," Food Processing, 31 (1), 1970.
45Lazar, M.E., Lund, D.B., and Dietrick, W.C., "A New Concept in Blanching - IQB," Food
Technology, 25, 1971.
46Lund, D.B., Bruin, S., Jr., and Lazar, M.E., "Internal Temperature Distribution During
Individual Quick Blanching," U.S. Department of Agriculture, Western Marketing and Nutritional
Research Division, Berkeley, Calif., 1971.
47Rails, J.W., and Mercer, W.A., "Low Water Volume Enzyme Deactivation of Vegetables
Before Preservation," U.S. Environmental Protection Agency, EPA-R2-73-198, May 1973.
48Rails, J.W., Maagdenberg, H.J., Yacoub, N.L., Homnick, D., Zinnecker, M., and Mercer,
W.A., "In-Plant, Continuous Hot Gas Blanching of Spinach," J. Food Science, 38, 1973.
49 Rails, J.W., and Mercer, W.A., "Continuous In-Plant Hot Gas Blanching of Vegetables,"
U. S. Environmental Protection Agency, EPA-660/2-74-091, Dec. 1974.
50Bomben, J.L., Brown, G.E., Dietrich, W.C., Hudson, J.S., and Farkas, D.E., "Integrated
Blanching and Cooling to Reduce Plant Effluent," Proceedings, Fifth National Symposium on
Food Processing Wastes, U.S. Environmental Protection Agency, EPA-660/2-74-058, June 1974.
105
-------
51 Brown, G.E., Bomben, J.C., Dietrich, W.C., Hudson, J.S., and Farkas, D.F., "A Reduced
Effluent Blanch-Cooling Method Using a Vibratory Conveyor," J. Food Sci., 39, 1974.
52 Rose, W.W., and Katsuyama, A.M., "In-Plant Water and Waste Management," Proceedings,
1972 Research Highlights Meeting, National Canners Association, Berkeley, Calif., Nov. 1972.
53Wolford, E.V., "Negative Air Pressure Conveying," Food Technology, 26 (2), Feb. 1972.
54 "Food Plant Cleaning," Laboratory Manual for Food Canners and Processors, National
Canners Association, Vol. 2, AVI Publishing Co., Westport, Conn., 1968.
55Hyams, R.F., "High Pressure Cleaning Provides Sanitation, Speed and Savings," Modern
Sanitation and Building Maintenance, Vol. 11 (9), 1959.
106
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APPENDIX A
LIST OF APPROVED TEST PROCEDURES
Appendix A contains reprints from:
• The Federal Register, Vol. 41, No. 232,
pp. 52780-52786, Dec. 6,1976
• The Federal Register, Vol. 42, No. 12,
pp. 3306-3307, Jan. 18,1977.
107
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Title 40—Protection of Environment
CHAPTER (-ENVIRONMENTAL
PROTECTION AGENCY
SUBCHAPTER D-WATER PROGRAMS
[FRL 630-4]
PART 136-GUIDELINES ESTABLISHING
TEST PROCEDURES FOR THE ANALYSIS
OF POLLUTANTS
Amendment of Regulations
On June 9, 1975,\proposed amendments
to the Guidelines Establishing Test Pro-
cedures for the Analysis of Pollutants (40
CFR 136) were published in the FED-
ERAL REGISTER (40 FR 24535) as re-
quired by section 304(g) of the Federal
Water Pollution Control Act Amendments
of 1972 (86 Stat. 816, et seq., Pub. L.
92—500, 1972) hereinafter referred to as
the Act.
Section 304(g) of the Act requires that
the Administrator shall promulgate guide-
lines establishing test procedures for the
analysis of pollutants that shall include
factors which must be provided in: (1) any
certification pursuant to section 401 of the
Act, or (2) any permit application pursuant
to section 402 of the Act. Such test
procedures are to be used by permit ap-
plicants to demonstrate that effluent dis-
charges meet applicable pollutant discharge
limitations and by the States and other
enforcement activities in routine or random
monitoring of effluents to verify compli-
ance with pollution control measures.
Interested persons were requested to
submit written comments, suggestions, or
objections to the proposed amendments by
September 7, 1975. One hundred and
thirty-five letters were received from com-
menters. The following categories of
organizations were represented by the com-
menters: Federal agencies accounted for
twenty-four responses; State agencies
accounted for twenty-six responses; local
agencies accounted for seventeen responses;
regulated major dischargers accounted for
forty-seven responses; trade and profes-
sional organizations accounted for eight
responses; analytical instrument manu-
facturers and vendors accounted for seven
responses; and analytical service labora-
tories accounted for six responses.
All comments were carefully evaluated
by a technical review committee. Based
upon the review of comments, the follow-
ing principal changes to the proposed
amendments were made:
(A) Definitions. Section 136.2 has been
amended to update references: Twenty
commenters, representing the entire spec-
trum of responding groups pointed out that
the references cited in §§136.2(f), 136.2(g),
and 136.2(h) were out of date; § § 136.2(f),
136.2(g), and 136.2(h), respectively, have
been amended to show the following edi-
tions of the standard references: "14th Edi-
tion of Standard Methods for the Examina-
tion of Water and Waste Water;" "1974 EPA
Manual of Methods for the Analysis of Water
and Waste;" and "Part 31, 1975 Annual
Book of ASTM Standards."
(B) Identification of Test Procedures.
Both the content and format of § 136.3,
"Table I, List of Approved Test Pro-
cedures" have been revised in response to
twenty-one comments received from State
and local governments, major regulated
dischargers, professional and trade associa-
tions, and analytical laboratories.
Table I has been revised by:
(1) The addition of a fourth column of
references which includes procedures of the
United States Geological Survey which are
equivalent to previously approved methods.
(2) The addition of a fifth column of
miscellaneous references to procedures
which are equivalent to previously ap-
proved methods.
(3) Listing generically related param-
eters alphabetically within four subcate-
gories: bacteria, metals, radiological and
residue, and by listing these subcategory
headings in alphabetic sequence relative to
the remaining parameters.
(4) Deleting the parameter "Algicides"
and by entering the single relevant algicide,
"Pentachlorophenol" by its chemical name.
(C) Clarification of Test Parameters.
The conditions for analysis of several
parameters have been more specifically
defined as a result of comments received by
the Agency:
(1) In response to five commenters
representing State or local governments,
major dischargers, or analytical instrument
manufacturers, the end-point for the
108
-------
alkalinity determination is specifically
designated as pH 4.5.
(2) Manual digestion and distillation are
still required as necessary preliminary steps
for the Kjeldahl nitrogen procedure.
Analysis after such distillation may be by
Nessler color comparison, titration, elec-
trode, or automated phenolate procedures.
(3) In response to eight commenters
representative of Federal and State govern-
ments, major dischargers, and analytical
instrument manufacturers, manual distilla-
tion at pH 9.5 is now specified for am-
monia measurement.
(D) New Parameters and Analytical Pro-
cedures. Forty-four new parameters have
been added to Table I. In addition to the
designation of analytical procedures for
these new parameters, the following modi-
fications have been made in analytical
procedures designated in response to com-
ments.
(1) The ortho-tolidine procedure was
not approved for the measurement of
residual chlorine because of its poor ac-
curacy and precision. Its approval had been
requested by seven commenters repre-
senting major dischargers, State, or local
governments, and analytical instrument
manufacturers. Instead, the N,N-diethyl-p-
phenylenediamine (DPD) method is
approved as an interim procedure pending
more intensive laboratory testing. It has
many of the advantages of the ortho-
tolidine procedure such as low cost, ease of
operation, and also is of acceptable pre-
cision and accuracy.
(2) The Environmental Protection
Agency concurred with the American Dye
Manufacturers' request to approve its pro-
cedure for measurement of color, and
copies of the procedure are now available
at the Environmental Monitoring and Sup-
port Laboratory, Cincinnati (EMSL—CI).
(3) In response to three requests from
Federal, State governments, and dis-
chargers, "hardness," may be measured as
the sum of calcium and magnesium
analyzed by atomic absorption and ex-
pressed as their carbonates.
(4) The proposal to limit measurement
of fecal coliform bacteria in the presence of
chlorine to only the "Most Probable Num-
ber" (MPN) procedure has been withdrawn
in response to requests from forty-five
commenters including State pollution con-
trol agencies, permit holders, analysts,
treatment plant operators, and a manufac-
turer of analytical supplies. The membrane
filter (MF) procedure will continue to be
an approved technique for the routine
measurement of fecal coliform in the
presence of chlorine. However, the MPN
procedure must be used to resolve con-
troversial situations. The technique selected
by the analyst must be reported with the
data.
(5) A total of fifteen objections, repre-
senting the entire spectrum of commenters,
addressed the drying temperatures used for
measurement of residues. The use of differ-
ent temperatures in drying of total residue,
dissolved residue and suspended residue
was cited as not allowing direct inter-
comparability between these measure-
ments. Because the intent of designating
the three separate residue parameters is to
measure separate waste characteristics (low
drying temperatures to measure volatile
substances, high drying temperatures to
measure anhydrous inorganic substances),
the difference in drying temperatures for
these residue parameters must be preserved.
(E) Deletion of Measurement Tech-
niques. Some measurement techniques that
had been proposed have been deleted in
response to objections raised during the
public comment period.
(1) The proposed infrared spectrophoto-
metric analysis for oil and grease has been
withdrawn. Eleven commenters repre-
senting Federal or State agencies and major
dischargers claimed that this parameter is
defined by the measurement procedure.
Any alteration in the procedure would
change the definition of the parameter. The
Environmental Protection Agency agreed.
(2) The proposed separate parameter for
sulfide at concentrations below 1 mg/1, has
been withdrawn. Methylene blue spectro-
photometry is now included in Table I as
an approved procedure for sulfide analysis.
The titrimetric iodine procedure for sulfide
analysis may only be used for analysis of
sulfide at concentrations in excess of one
milligram per liter.
(F) Sample Preservation and Holding
Times. Criteria for sample preservation and
109
-------
sample holding times were requested by
several commenters. The reference for
sample preservation and holding time
criteria applicable to the Table I parameters
is given in footnote (1) of Table I.
(G) Alternate Test Procedures. Com-
ments pertaining to § 136.4, Application
for Alternate Test Procedures, included
objections to various obstacles within these
procedures for expeditious approval of
alternate test procedures. Four analytical
instrument manufacturers commented that
by limiting of application for review and/or
approval of alternate test procedures to
NPDES permit holders, § 136.4 became an
impediment to the commercial develop-
ment of new or improved measurement
devices based on new measurement prin-
ciples. Applications for such review and/or
approval will now be accepted from any
person. The intent of the alternate test
procedure is to allow the use of measure-
ment systems which are known to be
equivalent to the approved test procedures
in waste water discharges.
Applications for approval of alternate
test procedures applicable to specific dis-
charges will continue to be made only by
NPDES permit holders, and approval of
such applications will be made on a case-
by-case basis by the Regional Adminis-
trator in whose Region the discharge is
made.
Applications for approval of alternate
test procedures which are intended for
nationwide use can now be submitted by
any person directly to the Director of the
Environmental Monitoring and Support
Laboratory in Cincinnati. Such applications
should include a complete methods write-
up, any literature references, comparability
data between the proposed alternate test
procedure and those already approved by
the Administrator. The application should
include precision and accuracy data of the
proposed alternate test procedure and data
confirming the general applicability of the
test procedure to the industrial categories
of waste water for which it is intended. The
Director of the Environmental Monitoring
and Support Laboratory, after review of
submitted information, will recommend
approval or rejection of the application to
the Administrator, or he will return the
application to the applicant for more in-
formation. Approval or rejection of appli-
cations for test procedures intended for
nationwide use will be made by the Ad-
ministrator, after considering the recom-
mendation made by the Director of the
Environmental Monitoring and Support
Laboratory, Cincinnati. Since the Agency
considers these procedures for approval of
alternate test procedures for nationwide
use to be interim procedures, we will
welcome suggestions for criteria for ap-
proval of alternate test procedures for
nationwide use. Interested persons should
submit their written comments in triplicate
on or before June 1, 1977 to: Dr. Robert
B. Medz, Environmental Protection Tech-
nologist, Monitoring Quality Assurance
Standardization, Office of Monitoring and
Technical Support (RD—680), Environ-
mental Protection Agency, Washington,
D.C. 20460.
(H) Freedom of Information. A copy of
all public comments, an analysis by param-
eter of those comments, and documents
providing further information on the
rationale for the changes made in the final
regulation are available for inspection and
copying at the Environmental Protection
Agency Public Information Reference Unit,
Room 2922, Waterside Mall, 401 M Street,
SW., Washington, D.C. 20460, during
normal business hours. The EPA informa-
tion regulation 40 CFR 2 provides that a
reasonable fee may be charged for copying
such documents.
Effective date: These amendments
become effective on April 1, 1977.
Dated: November 19, 1976.
JOHN QUARLES,
Acting Administrator,
Environmental Protection Agency.
Chapter I, Subchapter D, of Title 40,
Code of Federal Regulations is amended as
follows:
1. In § 136.2, paragraphs (f), (g), and
(h) are amended to read as follows:
110
-------
§ 136.2 Definitions.
(f) "Standards Methods" means
Standard Methods for the Examination of
Water and Waste Water, 14th Edition,
1976. This publication is available from the
American Public Health Association, 1015
18th Street, N.W., Washington, D.C
20036.
(g) "ASTM" means Annual Book of
Standards, Part 31, Water, 1975. This
publication is available from the American
Society for Testing and Materials, 1916
Race Street, Philadelphia, Pennsylvania
19103.
(h) "EPA Methods" means Methods for
Chemical Analysis of Water and Waste,
1974. Methods Development and Quality
Assurance Research Laboratory, National
Environmental Research Center, Cincin-
nati, Ohio 45268; U.S. Environmental Pro-
tection Agency, Office of Technology
Transfer, Industrial Environmental Re-
search Laboratory, Cincinnati, Ohio 45268.
This publication is available from the
Office of Technology Transfer.
2. In § 136.3, the second sentence of
paragraph (b) is amended, and a new
paragraph (c) is added to read as follows:
§ 136.3 Identification of test procedures.
(b) * * * Under such circumstances,
additional test procedures for analysis of
pollutants may be specified by the Re-
gional Administrator or the Director upon
the recommendation of the Director of the
Environmental Monitoring and Support
Laboratory, Cincinnati.
(c) Under certain circumstances, the
Administrator may approve, upon recom-
mendation by the Director, Environmental
Monitoring and Support Laboratory,
Cincinnati, additional alternate test pro-
cedures for nationwide use.
3. ,Table I of § 136.3 is revised by
listing the parameters alphabetically; by
adding 44 new parameters; by adding a
fourth column under references listing
equivalent United States Geological Survey
methods; by adding a fifth column under
references listing miscellaneous equivalent
methods; by deleting footnotes 1 through 7
and adding 24 new footnotes to read as
follows:
TABLE I.—List of approved lest procedures'
1.
2.
3.
Parameter and units
Acidity, as CaCO1 , milli-
grams per liter.
Alkalinity, as CaCO\
milligrams per liter.
Ammonia (as N), milli-
grams per liter.
Method
Electrometric end point
(pH of 8.2) or phenol-
phthalein end point.
Electrometric titration
(only to pH 4.5) manual
or automated, or equiva-
lent automated methods.
Manual distillation4 (at
pH 9.5) followed by
nesslerization, titration,
electrode, Automated
phenolate.
1974
EPA
methods
1
3
5
159
165
168
References
14thed. (pagenos.) Qther
standard p» 01
methods 1975
ASTM
273(4d) 116
278 111
410
412 237
616
approved
USGS methods
40 3(607)
41 3(607)
116 3(614)
BACTERIA
4. Coliform (fecal)', num-
ber per 100 ml.
5. Coliform (fecal)' in
presence of chlorine,
number per 100 ml.
6 Coliform (total),' number
per 100 ml.
7. Coliform (total)' in
presence of chlorine,
number per 100 ml.
^ Fecal streptococci,'
number per 100 ml.
MPN;" membrane filter
. . do." '
922
937
922
928,937
'(45).
. . . do."
MPN;" membrane filter
with enrichment
MPN;" membrane filter;
plate count.
916 ..
928 . .
916
933 . .
943 . .
944
947 . .
'(35)
7(50).
Ill
-------
q
in
11.
12.
1 3
14
15.
IB.
17.
18
19.
20.
21.
22.
23.
Parameter and units
Benzidine milligrams per
liter
Biochemical oxygen de-
mand, 5-d (BOD, ),
milligrams per liter.
Bromide, milligrams per
liter . .
Chemical oxygen demand
(COD), milligrams per
liter
Chloride milligrams per
liter . .
Chlorinated organic com-
pounds (except pesticides),
milligrams per liter.
Chlorine — total residual,
milligrams per liter.
Color, platinum cobalt units
or dominant wave length
hue: luminance, purity.
Cyanide, total,1 J milligrams
per liter
Cyanide amenable to
chlorination, milligrams
per liter.
Dissolved oxygen, milli-
grams per liter.
Fluoride, milligrams per
liter . .
Hardness— Total, as CaCO3 ,
milligrams per liter.
Hydrogen ion (pH), pH
units.
Kjeldahl nitrogen (as
N), milligrams per
liter.
Method
Oxidation — colorimetric6
Winkler (Azide modifica-
tion) or electrode
method
Titrimetric, iodine-iodate .
Dichromate reflux
Silver nitrate" mercuric ni-
trate; or automated
colorimetric- ferricyanide
Gas chromatographv1 : ...
lodometric titration, amper-
ometric or starch-iodine
end-point; DPD colori-
metric or Titrimetric meth-
ods (these last 2 are interim
methods pending laboratory
testing).
Colorimetric; spectrophoto-
metricjor ADMI pro-
cedure.11
Distillation followed by
silver nitrate titration
or pyridine pvrazolone (or
barbituric acid) colori-
metric.
.... do
Winkler (Azide modifica-
tion ) or electrode method.
Distillation4 followed by ion . .
electrode; SPADNS;or
automated complexone.
EDTA titration ; automated
colorimetric; or atomic
absorption (sum of Ca . .
and Mg as their respective
carbonates).
Electrometric measurement.
Digestion and distillation
followed by nesslerization,
titration, or electrode;
1974
EPA
methods
14
20
29
31
35
36
39
40
49
51
56
65
59
61
68
70. . .
239
175
165. .
182. . .
References
14th ed. (pagenos.)
standard D, Q1
methods ^*£ USGS
ASTM methods'
543 ' (50)
323 58...
550 472 124
303 267
304 265
613 . . "(46)
318
322 278
332
329
64 82. . . .
66
361 503 85
376 505
443 368 126
450
389
391 307 93 . .
393 305. . .
614
202 161 94
460 178 129
437 122
Other
approved
methods
10(17)
'(610)
(17 )
'(610)
10(22)
'(609)
3 (617)
3 (606)
3(612)
METALS
24. Aluminum—Total, milli-
grams per liter.
25. Aluminum—Dissolved,
milligrams per liter.
26. Antimony-Total,
milligrams per liter.
27. Antimony—Dissolved,
milligrams per liter.
28. Arsenic—Total, milli-
grams per liter.
29. Arsenic—Dissolved,
milligrams per liter.
30. Barium—Total, milli-
grams per liter.
31. Barium—Dissolved,
milligrams per liter.
automated digestion auto-
mated phenolate.
Digestion followed by
atomic absorption" or by
colorimetric (Eriochrome
Cyanine R).
0.45 micron filtration17 fol-
lowed by referenced
methods for total
aluminum.
Digestion15 followed by
atomic absorption."
0.45 micron filtration1' . .
followed by referenced
method for total antimony.
Digestion followed by silver
diethyldithiocarbamate;
or atomic absorption.'" 1B
0.45 micron filtration11 . . .
followed by referenced
method for total arsenic.
Digestion" followed by
atomic absorption."
0.45 micron filtration1" . . .
followed by referenced
method for total barium.
92
152. .
171 . .
"(19)
94
9
95
285.
283.
159
"(31)
"(37)
97
152 .
52
112
-------
Parameter and units
Method
References
1974 14th ed. (pagenos.)
EPA standard
methods methods
p,
ASTM
approved
USGS methods
methods2
32. Beryllium—Total, milli-
grams per liter.
33. Beryllium—Dissolved,
milligrams per liter.
Digestion15 followed by
atomic absorption" or ...
by colorimetric (Aluminon)
0.45 micron filtration17
followed by referenced
method for total beryllium.
Colorimetric (Curcumin)
99
152.
177
53 ...
34. Boron—Total, milligrams Colorimetric (Curcumin) 13 287
per liter.
35. Boron—Dissolved, milli- 0.45 micron filtration11 fol-
grams per liter. lowed by referenced
method for total boron.
36. Cadmium—Total, milli- Digestion" followed by 101 148 345 62 3(619)'°(37)
grams per liter. atomic absorption" or 182
by colorimetric (Dithizone).
37. Cadmium—Dissolved, 0.45 micron filtration" fol- ....
milligrams per liter. lowed by referenced
method for total cadmium.
38. Calcium—Total, milli- Digestion" followed by 103 148 345 66
grams per liter. atomic absorption; 189
or EDTA titration.
39. Calcium—Dissolved, 0.45 micron filtration11
milligrams per liter. followed by referenced
method for total calcium.
40. Chromium VI, milli- Extraction and atomic ab- 89,105 .... 76
grams per liter. sorption; colorimetric 192. ... 75 ...
(Diphenylcarbazide).
41. Chromium VI—Dissolved, 0.45 micron filtration" . . . .
milligrams per liter. followed by referenced
method for chromium
VI.
42. Chromium—Total, milli-. Digestion15 followed by 105 148 345 78 3(619)
grams per liter. atomic absorption" 192 286 77
or by colorimetric
(Diphenylcarbazide).
43. Chromium—Dissolved, 0.45 micron filtration"
milligrams per liter. followed by referenced
method for total chromium.
44. Cobalt—Total, milligrams Digestion15 followed by 107 148 345 80 '"(37)
per liter. atomic absorption."
45. Cobalt—Dissolved, milli- 0.45 micron filtration"
grams per liter. followed by referenced
method for total cobalt.
46. Copper—Total, milligrams Digestion1 s followed by 108 148 345 83 '(619) '"(37)
per liter. atomic absorption" or by .... 196 293
colorimetric (Neocuproine).
47. Copper—Dissolved, milli- 0.45 micron filtration" fol- . .
grams per liter. lowed by referenced
method for total copper.
48. Gold—Total, milligrams Digestion15 followed by
per liter. atomic absorption."
49. Iridium—Total, milligrams Digestion15 followed by
per liter. atomic absorption "
50. Iron—Total, milligrams Digestion15 followed by 110 148 345 102 '(619)
per liter. atomic absorption"
or by colorimetric 208 326 ....
(Phenanthroline).
51. Iron—Dissolved, milli- 0.45 micron filtration"
grams per liter. followed by referenced
method for total iron.
52. Lead—Total, milligrams Digestion15 followed by 112 148 345 105 '(619)
per liter. atomic absorption "
or by colorimetric ... 215
(Dithizone).
53. Lead—Dissolved, milli- 0.45 micron filtration1"
grams per liter. followed by referenced
method for total lead.
54. Magnesium—Total, milli- Digestion1' followed by 114 148 345 109 '(619)
grams per liter. atomic absorption, or 221
gravimetric.
55. Magnesium—Dissolved 0.45 micron filtration" . .
milligrams per liter. followed by referenced
method for total
magnesium.
56. Manganese—Total milli- Digestion" followed by 116 148 345 111 '(619)
grams per liter. atomic absorption" or . . 225,227 ....
by colorimetric (Persul-
fate or periodate).
113
-------
Parameter and units
Method
1974 14th ed.
EPA standard
methods methods
References
(page nos.)
Pt. 31
1975
ASTM
USGS
methods'
Other
approved
methods
57. Manganese—Dissolved 0.45 micron filtration1 '
milligrams per liter. followed by referenced
method for total
manganese.
58. Mercury—Total, milligrams Flameless atomic 118 156 338 "(51)
per liter. absorption.
59. Mercury—Dissolved, milli- 0.45 micron filtration11
grams per liter. followed by referenced
method for total mercury.
60. Molybdenum—Total, Digestion" followed by 139 350
milligrams per liter. atomic absorption'6
61. Molybdenum—Dissolved, 0.45 micron filtration' ....
milligrams per liter. followed by referenced
method for total
molybdenum.
62. Nickel—Total, milligrams Digestion" followed by 141 148 345 115
per liter. atomic absorption ' *
or by colorimetric
(Heptoxime).
63. Nickel—Dissolved, milli- 0.45 micron filtration17
grams per liter. followed by referenced
method for total nickel.
64. Osmium—Total, milligrams Digestion" followed by
per liter. atomic absorption.1''
65. Palladium—Total, milli- Digestion" followed by
grams per liter. atomic absorption."
66. Platinum—Total, milli- Digestion" followed by
grams per liter. atomic absorption."
67. Potassium—Total, milli- Digestion" followed by 143 134 '(620)
grams per liter. atomic absorption, 235 . .
colorimetric (Cobalti- 234 403
nitrite), or by flame
photometric.
68. Potassium—Dissolved, 0.45 micron filtration1"
milligrams per liter. followed by referenced
method for total
potassium.
69. Rhodium—Total, milli- Digestion" followed by
grams per liter. atomic absorption.'"
70. Ruthenium—Total, milli- Digestion" followed by
grams per liter. atomic absorption.1"
71. Selenium—Total, milligrams Digestion" followed by 145 159
Per liter. atomic absorption." '"
72. Selenium—Dissolved, 0.45 micron filtration1"
milligrams per liter. followed by referenced
method for total selenium.
73. Silica—Dissolved, milli- 0.45 micron filtration1" 274 487 398 139
grams per liter. followed by colorimetric
(Molybdosilicate).
74. Silver—Total,:" milligrams Digestion" followed by 146 148 142 )(619)'°(37)
per liter. atomic absorption1'' or by 243
colorimetric (Dithizone).
7."i. Silver—Dissolved,-'" milli- 0.45 micron filtration1" fol-
grams per liter. lowed by referenced
method for total silver.
76 Sodium--Total, milligrams Digestion" followed by 147 143 M621)
Per liter. atomic absorption or "by ' 250 403
flame photometric.
77. Sodium—Dissolved, milli- 0.45 micron filtration1"
grams per liter. followed by referenced
method for total sodium.
78. Thallium—Total, milli- Digestion" followed by 149
grams per liter. atomic absorption."
79. Thallium—Dissolved, milli- 0.45 micron filtration"
grams per liter. followed by referenced
method for total thallium.
80. Tin—Total, milligrams per Digestion" followed by 150 "(651
liter. atomic absorption."
81. Tin—Dissolved, milligrams 0.45 micron filtration"
per liter. followed by referenced
method for total tin.
82. Titanium—Total, milli- Digestion" followed by 151 .
grams per liter. atomic absorption."
83. Titanium—Dissolved, 0.45 micron filtration"
milligrams per liter. followed by referenced
method for total titanium.
114
-------
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
Parameter and units
Vanadium— Total, milli-
grams per liter.
Vanadium— Dissolved ,
milligrams per liter.
Zinc — Total, milligrams
per liter.
Zinc — Dissolved, milli-
grams per liter.
Nitrate (as N), milligrams
per liter.
Nitrate (as N), milligrams
per liter.
Oil and grease, milligrams
per liter.
Organic carbon; total
(TOC), milligrams per
liter.
Organic nitrogen (as N),
milligrams per liter.
Orthophosphate (as P),
milligrams per liter.
Pentachlorophenol, milli-
grams per liter.
Pesticides, milligrams per
liter.
Phenols, milligrams
per liter.
Phosphorus (elemental),
milligrams per liter.
Phosphorus; total (as P),
milligrams per liter.
RADIOLOGICAL
Alpha— Total, pCi per
liter. . . .
Alpha— Counting error,
pCi per liter.
Beta— Total, pCi per
liter
Beta— Counting error,
pCi per liter.
(a) Radium— Total, pCi
per liter.
(b) 22'Ra, pCi per
liter
RESIDUE
Total, milligrams per
liter
Total dissolved (filter-
able), milligrams per
liter.
Total suspended (non-
filterable), milligrams
per liter.
Settleable, milliliters per
liter or milligrams per
liter.
Total volatile, milligrams
per liter.
Specific conductance,
micromhos per
centimeter at 25: C.
Sulfate (as SO., ), milli-
grams per liter.
1974
Method EPA
methods
Digestion'5 followed by 153
atomic absorption" or .' ....
by colorimetric (Gallic
acid).
followed by referenced
method for total vanadium.
Digestion15 followed by 155
colorimetric (Dithizone).
followed by referenced
method for total zinc.
Cadmium reduction; 201
brucine sulfate; automated 197
cadmium or hydrazine 207
reduction.21
Manual or automated 215
colorimetric
(Diazotization).
Liquid-liquid extraction with 229
trichloro-trifluoro-
ethane-gravimetric .
Combustion— Infrared 236
method.22
Kjeldahl nitrogen minus 175,159
ammonia nitrogen.
Manual or automated 249
ascorbic acid reduction. 256
Gas chromatography ' 2
Hr> "
Colorimetric, (4AAP) 241
Persulfate digestion followed 249
by manual or automated 256
ascorbic acid reduction.
counter.
do
do
do
Gravimetric, 103 to 105"C .... 270
Glass fiber filtration, 180'' C . . . . 266
Glass fiber filtration, 103 to 105'C 268
Wheatstone bridge conductimetry. 275
automated colorimetric 277
14th ed.
standard
methods
152
260
148
265
423
427
620
434
515
532
437 . .
481
624
555
582
476,481
624 . .
648
648
648
648
661
667
91
92
94 .
95
95 .
71
493
496
References
(pagenos.) Other
p ql approved
1Q7K USGS methods
ASTM methods'
441 " (67)
345 159 3(619) 10(37)
358 119 3(614) 10(28)
121
467 " (4)
122 3(612,614)
384 131 3(621)
529 23(24)
545
384 133 3(621)
591 " ls(75+78)
594 " (79)
601 " 25(75+78)
606 " (79)
661
11 (81) •
120 148 -'(606)
424 3 (624)
425 3 (623)
115
-------
111.
112
113
114
1 1 -i
Parameter and units
Sulfide (as S), milligrams
Sulfite (as SO ) milli-
grams per liter.
per liter.
Turbiditv, NTU .
Method
Titrimetric— Iodine for levels
greater than 1 mg per liter'
Methylene blue photometric.
Colorimetric (Methvlene blue)
thermometer.
Nephelometric .
1974
EPA
methods
284
285
157
286
295
14th ed.
standard
methods
505
503
508
600
125
132
References
(page nos.)
^31 USGS
AS™ methods'
.... 154 ...
435
494 "(11).
"(31)
223 156 . . .
Other
approved
methods
1 Recommendations for sampling and preservation of samples according to parameter measured may be found in
"Methods for Chemical Analysis of Water and Wastes, 1974" U.S. Environmental Protection Agency, table 2, pp.
viii-xii.
2 All page references for USGS methods, unless otherwise noted, are to Brown, E., Skougstad, M. W., and Fishman,
M. J., "Methods for Collection and Analysis of Water Samples for Dissolved Minerals and Gases," U.S. Geological
Survey Techniques of Water-Resources Inv., book 5, ch. Al, (1970).
3EPA comparable method may be found on indicated page of "Official Methods of Analysis of the Association of
Official Analytical Chemists" methods manual, 12th ed. (1975).
4 Manual distillation is not required if comparability data on representative effluent samples are on company file to
show that this preliminary distillation step is not necessary; however, manual distillation will be required to resolve any
controversies.
5 The method used must be specified.
6 The 5 tube MPN is used.
'Slack, K. V. and others, "Methods for Collection and Analysis of Aquatic Biological and Microbiological Samples:
U.S. Geological Survey Techniques of Water-Resources Inv. book 5, ch. A4 (1973)."
6 Since the membrane filter technique usually yields low and variable recovery from chlorinated wastewaters, the
MPN method will be required to resolve any controversies.
' Adequately tested methods for benzidine are not available. Until approved methods are available, the following
interim method can be used for the estimation of benzidine: (1) "Method for Benzidine and Its Salts in Wastewaters,"
available from Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency, Cincinnati,
Ohio 45268.
10American National Standard on Photographic Processing Effluents, Apr. 2, 1975. Available from ANSI, 1430
Broadway, New York, N.Y. 10018.
1 ' Fishman, M. J. and Brown, Eugene, "Selected Methods of the U.S. Geological Survey for Analysis of Wastewaters,"
(1976) open-file report 76-177.
15 Procedures for pentachlorophenol, chlorinated organic compounds, and pesticides can be obtained from the En-
vironmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268.
13 Color method (ADMI procedure) available from Environmental Monitoring and Support Laboratory, U.S., En-
vironmental Protection Agency, Cincinnati, Ohio 45268.
For samples suspected of having thiocyanate interference, magnesium chloride is used as the digestion catalyst. In
the approved test procedure for cyanides, the recommended catalysts are replaced with 20 ml of a solution of 510 g/1
magnesium chloride (MgCl, -6H3 O). This substitution will eliminate thiocyanate interference for both total cyanide and
cyanide amendable to chlorination measurements.
1 5 For the determination of total metals the sample is not filtered before processing. Because vigorous digestion
procedures may result in a loss of certain metals through precipitation, a less vigorous treatment is recommended as
given on p. 83 (4.1.4) of "Methods for Chemical Analysis of Water and Wastes" (1974). In those instances where a
more vigorous digestion is desired the procedure on p. 82 (4.1.3) should be followed. For the measurement of the noble
metal series (gold, iridium, osmium, palladium, platinum, rhodium and ruthenium), an aqua regia digestion is to be
substituted as follows: Transfer a representative aliquot of the well-mixed sample to a Griffin beaker and add 3 ml of
concentrated redistilled HNO3. Place the beaker on a steam bath and evaporate to dryness. Cool the beaker and
cautiously add a 5 ml portion of aqua regia. (Aqua regia is prepared immediately before use by carefully adding 3
volumes of concentrated HC1 to one volume of concentrated HNO3.) Cover the beaker with a watch glass and return to
the steam bath. Continue heating the covered beaker for 50 min. Remove cover and evaporate to dryness. Cool and
take up the residue in a small quantity of 1:1 HC1. Wash down the beaker walls and wash glass with distilled water and
filter the sample to remove silicates and other insoluble material that could clog the atomizer. Adjust the volume to
some predetermined value based on the expected metal concentration. The sample is now ready for analysis, .
1 6 As the various furnace devices (flameless AA) are essentially atomic absorption techniques, they are considered to
be approved test methods. Methods of standard addition are to be followed as noted in p. 78 of "Methods for Chemical
Analysis of Water and Wastes," 1974.
1 'Dissolved metals are defined as those constitutents which will pass through a 0.45 fim membrane filter. A pre-
filtration is permissible to free the sample from larger suspended solids. Filter the sample as soon as practical after
collection using the first 50 to 100 ml to rinse the filter flask. (Glass or plastic filtering apparatus are recommended to
avoid possible contamination.) Discard the portion used to rinse the flask and collect the required volume of filtrate
Acidify the filtrate with 1:1 redistilled HNO3 to a pH of 2. Normally, 3 ml of (1:1) acid per liter should be sufficient to
preserve the samples.
1 8See "Atomic Absorption Newsletter," vol. 13,75 (1974). Available from Perkin-Elmer Corp Main Ave Nonvalk
Conn. 06852.
116
-------
Method available from Environmental Monitoring and Support Laboratory, U.S. Environmental Protection Agency,
Cincinnati, Ohio 45268.
Recommended methods for the analysis of silver in industrial wastewaters at concentrations of 1 mg/1 and above
are inadequate where silver exists as an inorganic halide. Silver halides such as the bromide and chloride are relatively
insoluble in reagents such as nitric acid but are readily soluble in an aqueous buffer of sodium thiosulfate and sodium
hydroxide to a pH of 12. Therefore, for levels of silver above 1 mg/1 20 ml of sample should be diluted to 100 ml by
adding 40 ml each of 2M Na2S,O3 and 2M of NaOH. Standards should be prepared in the same manner. For levels of
silver below 1 mg/1 the recommended method is satisfactory.
An automated hydrazine reduction method is available from the Environmental Monitoring and Support Lab-
oratory, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268.
A number of such systems manufactured by various companies are considered to be comparable in their perform-
ance. In addition, another technique, based on combustion-methane detection is also acceptable.
23Goerlitz, D., Brown, E., "Methods for Analysis of Organic Substances in Water": U.S. Geological Survey Tech-
niques of Water-Resources Inv., book 5, ch. A3 (1972).
R. F. Addison and R. G. Ackman, "Direct Determination of Elemental Phosphorus by Gas-Liquid Chroma-
tography," "Journal of Chromatography," vol. 47, No. 3, pp. 421—426, 1970.
25The method found on p. 75 measures only the dissolved portion while the method on p. 78 measures only
suspended. Therefore, the 2 results must be added together to obtain "total."
2'Stevens, H. H., Ficke, J. F., and Smoot, G. F., "Water Temperature—Influential Factors, Field Measurement and
Data Presentation: U.S. Geological Survey Techniques of Water Resources Inv., book 1 (1975)."
4. In § 136.4, the second sentence of
paragraph (c) is amended by deleting the
word "subchapter" immediately following
the phrase "procedure under this" and
immediately preceding the word "shall"
and replaced with the phrase "paragraph
c;" and § 136.4 is amended by adding a
new paragraph (d) to read as follows:
§ 136.4 Application for alternate test
procedures.
(c) * * * Any application for an alter-
nate test procedure under this paragraph
(c) shall: * * *
(d) An application for approval of an
alternate test procedure for nationwide use
may be made by letter in triplicate to the
Director, Environmental Monitoring and
Support Laboratory, Cincinnati, Ohio
45268. Any application for an alternate
test procedure under this paragraph (d)
shall:
(1) Provide the name and address of the
responsible person or firm making the
application.
(2) Identify the pollutant(s) or para-
meter^) for which nationwide approval of
an alternate testing procedure is being
requested.
(3) Provide a detailed description of the
proposed alternate procedure, together
with references to published or other
studies confirming the general applicability
of the alternate test procedure to the
pollutant(s) or parameter(s) in waste water
discharges from representative and
specified industrial or other categories.
(4) Provide comparability data for the
performance of the proposed alternate test
procedure compared to the performance of
the approved test procedures.
§ 136.5 [Amended]
5. In § 136.5, paragraph (a) is amended
by inserting the phrase "proposed by the
responsible person or firm making the
discharge" immediately after the words
"test procedure" and before the period
that ends the paragraph.
6. In § 136.5, paragraph (b) is amended
by inserting in the first sentence the phrase
"proposed by the responsible person or
firm making the discharge" immediately
after the words "such application" and
immediately before the comma. The
second sentence of paragraph (b) is
amended by deleting the phrase "Methods
Development and Quality Assurance Re-
search Laboratory" immediately after the
phrase "State Permit Program and to the
Director of the" at the end of the sentence,
and inserting in its place the phrase "En-
vironmental Monitoring and Support
Laboratory, Cincinnati."
7. In § 136.5, paragraph (c) is amended
by inserting the phrase "proposed by the
responsible person or firm making the
discharge" immediately after the phrase
"application for an alternate test pro-
cedure" and immediately before the
comma; and by deleting the phrase
"Methods Development and Quality
117
-------
Assurance Laboratory" immediately after
the phrase "application to the Director of
the" and immediately before the phrase
"for review and recommendation" and
inserting in its place the phrase "Environ-
mental Monitoring and Support Labora-
tory, Cincinnati."
8. In § 136.5, the first sentence of
paragraph (d) is amended by inserting the
phrase, "proposed by the responsible
person or firm making the discharge,"
immediately after the phrase, "application
for an alternate test procedure," and im-
mediately before the comma.
The second sentence of paragraph (d) is
amended by deleting the phrase, "Methods
Development and Quality Assurance Re-
search Laboratory," immediately after the
phrase, "to the Regional Administrator by
the Director of the," and immediately
preceding the period ending the sentence
and inserting in its place the phrase, "En-
vironmental Monitoring and Support
Laboratory, Cincinnati."
The third sentence of paragraph (d) is
amended by deleting the phrase, "Methods
Development and Quality Assurance Re-
search Laboratory," immediately after the
phrase, "forwarded to the Director," and
immediately before the second comma and
by inserting in its place the phrase, "En-
vironmental Monitoring and Support
Laboratory, Cincinnati."
9. Section 136.5 is amended by the
addition of a new paragraph (e) to read as
follows:
§ 136.5 Approval of alternate test pro-
cedures.
*****
(e) Within ninety days of the receipt by
the Director of the Environmental Monitor-
ing and Support Laboratory, Cincinnati of
an application for an alternate test pro-
cedure for nationwide use, the Director of
the Environmental Monitoring and Support
Laboratory, Cincinnati shall notify the
applicant of his recommendation to the
Administrator to approve or reject the
application, or shall specify additional in-
formation which is required to determine
whether to approve the proposed test
procedure. After such notification, an alter-
nate method determined by the Adminis-
trator to satisfy the applicable require-
ments of this part shall be approved for
nationwide use to satisfy the requirements
of this subchapter; alternate test pro-
cedures determined by the Administrator
not to meet the applicable requirements of
this part shall be rejected. Notice of these
determinations shall be submitted for
publication in the FEDERAL REGISTER
not later than 15 days after such notifica-
tion and determination is made.
[FR Doc. 76—35032 Filed 11—30—76; 8:45 am]
Title 40—Protection of Environment
CHAPTER I-ENVIRONMENTAL
PROTECTION AGENCY
SUBCHAPTER D-WATER PROGRAMS
PART 136-GUIDELINES ESTABLISHING
TEST PROCEDURES FOR THE
ANALYSIS OF POLLUTANTS
Amendment of Regulations; Corrections
In FR Doc. 76—35032 appearing at
pages 52780 to 52786 in the FEDERAL
REGISTER of Wednesday, December 1,
1976, the following changes should be
made:
§ 136.3 [Amended]
1. On Page 52783, for parameter
number 62, Nickel—Total, add "232" to
the page references in the column under
the 14th edition of Standard Methods
opposite the colorimetric method desig-
nation.
2. On page 52784, for parameter
number 89, change the parameter desig-
nation from "Nitrate" to "Nitrite."
3. On page 52784, for parameter
number 96, Phenols, delete the present
method designation, "Colorimetric,
(4AAP)," and replace it with the meth-
od designation, "Distillation followed
by colorimetric, (4AAP)"; delete the
page reference in the column under the
14th edition of Standard Methods,
"582," and replace it with page number
"574."
Dated: January 10, 1977.
WILSON K. TALLEY,
Assistant Administrator for
Research and Development
[FR Doc. 77--1453 Filed 1-17—77:8:45 ami
118
-------
METRIC CONVERSION TABLES
Recommended Units
Description
Length
Area
Volume
Mass
Force
Moment or
torque
Flow (volumetric)
Unit
meter
kilometer
millimeter
micrometer or
micron
square meter
square kilometer
square millimeter
hectare
cubic meter
litre
kilogram
gram
milligram
tonne
newton
newton meter
cubic meter
per second
liter per second
Symbol
m
km
mm
Mm or^
m2
km2
mm2
ha
m3
1
kg
g
mg
t
N
N-m
m3/s
l/s
Comments
Basic SI unit
The hectare (10,000
m2) is a recognized
multiple unit and will
remain in interna-
tional use.
Basic SI unit
1 tonne = 1,000 kg
The newton is that
force that produces
an acceleration of
1 m/s2 in a mass
of 1 kg.
The meter is mea-
sured perpendicular
to the line of action
of the force N.
Not a joule.
Customary
Equivalents*
39.37m = 3.281 ft =
1.094yd
0.6214 mi
0.03937 in
3.937 X 10'5in=l X104A
10.76 sqft=1.196sq yd
0.3861 sq mi = 247.1 acres
0.001550 sq in
2.471 acres
35.31 cuft= 1.308 cu yd
1. 057 qt= 0.2642 gal =
0.8107 X 10"4 acre ft
2.205 Ib
0.03527 oz = 15.43 gr
0.01 543 gr
0.9842 ton (long) =
1.102 ton (short)
0.2248 Ib
= 7.233 poundals
0.7375 Ib-ft
23.73poundal-ft
15. 850 gpm =
2,119cfm
15.85 gpm
Description
Velocity
linear
angular
Viscosity
Pressure or
stress
Temperature
Work, energy.
quantity of heat
Power
Application of Units
Description
Precipitation,
run-off,
evaporation
Flow
Discharges or
abstractions.
yields
Usage of water
Unit
millimeter
cubic meter
per second
liter per second
cubic meter
per day
cubic meter
per year
liter per person
per day
Symbol
mm
m3/s
l/s
m3/d
m3/year
I/person/
day
Comments
For meteorological
purposes, it may be
convenient to meas-
sure precipitation in
terms of mass/unit
area (kg/m2).
1 mm of rain =
1 kg/m2
1 l/s = 86.4 m3/d
Customary
Equivalents*
35.31 cfs
15. 85 gpm
0.1835 gpm
264.2 gal/year
0.2642 gcpd
Description
Density
Concentration
BDD loading
Hydraulic load
per unit area,
e.g., filtration
rates
Air supply
Optical units
Recommended Units
Unit
meter per
second
millimeter
per second
kilometers
per second
radians per
second
pascal second
centtpoise
newton per
square meter
or pascal
kilo newton per
square meter
or kilopascal
bar
Celsius (centigrade)
Kelvin (abs.)
joule
kilojoule
watt
kilowatt
joule per second
Symbol
m/s
mm/s
km/s
rad/s
Pa-s
Z
N/m2
or
Pa
kN/m2
or
kPa
bar
°c
°K
J
kJ
W
kW
J/s
Application
Unit
kilogram per
cubic meter
milligram per
liter (water)
kilogram per
cubic meter
per day
cubic meter
per square meter
per day
cubic meter or
liter of free air
per second
lumen per
square meter
Symbol
kg/m3
mg/l
kg/m3/d
m3/m2/d
m3/s
l/s
Comments
1 |0ule = 1 N-m
measured along
the line of action
of force N.
1 watt = 1 J/s
of Units
Comments
The density of water
under standard
conditions is 1,000
kg/m3 or 1,000 g/l
or 1 g/ml.
If this is converted
to a velocity, it
should be expressed
in mm/s (Imm/s =
86.4 m3/m2/day).
lumen/m2
Customary
Equivalents"
3.281 fps
0.003281 fps
2,237 mph
9.549 rpm
0.6722 poundal(sl/sq ft
1.450 X 10'7 Reynl/u)
0.0001450 Ib/sq in
0.14507 Ib/sq in
14.50 Ib/sq in
(°F-32I/1.B
"C + 273.2
2.778 X 10 7
kw-hr =
3.725 X 10'7
hp-hr = 0.7376
fl-lb = 9.478 X
10-" Btu
2.778 X ID'4 kw-hr
44.25 ft-lbs/min
1.341 hp
3.412 Btu/hr
Customary
Equivalents"
0.06242 Ib/cu ft
1 ppm
0.06242 Ib/cu ft/day
3.281 cu ft/sq ft/day
0.09294 It candle/sq ft
•Miles are U.S. statute, qt and gal are U.S. liquid, and oz and Ib are avoirdupois.
U.S. GOVERNMENT PRINTING OFFICE: 1977-757-056/61(48 Reg ion No. 5-11
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