THE TREATMENT OF DAIRY PLANT WASTES
UPGRADING DAIRY PRODUCTION AND TREATMENT
FACILITIES TO CONTROL POLLUTION
MADISON, WISCONSIN
MARCH 20 • 21. 1973
PREPARED FOR THE ENVIRONMENTAL PROTECTION AGENCY
TECHNOLOGY TRANSFER PROGRAM
COMPILED BY:
KENNETH S. WATSON
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THE TREATMENT OF DAIRY PLANT WASTES
UPGRADING DAIRY PRODUCTION AND TREATMENT FACILITIES
TO CONTROL POLLUTION
Prepared for the Environmental Protection Agency
Technology Transfer Program
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TABLE OF CONTENTS
Page
I. Current Practices in the Handling of
Dairy Wastes
Character of the Wastes 3
Disposing of the Effluent 14
Stockton, Illinois 6
Norwich, New York 15
South Edmeston, New York 22
Champaign, Illinois 29
II. The Benefits of the Joint Treatment Approach
with the City
Background 1
Wastewater Treatment Plants 14
The Joint Approach 5
The Relationship with Industry 11
Sampling and Analyses 13
Summary 17
III. How Dean Foods Handles the Waste Problem at
the Chemung, Illinois Dairy Plant
In Plant Controls 1
The Waste Treatment Plant 2
The Effluent Load per 1000 Pounds of Milk 2,3
Performance of the Treatment Plant 5,6
Costs 8
IV. Alternate Methods of Treating or Pre—treating
Dairy Plant Wastes?
Dairy Waste Compatibility in Municipal
Systems 1
Selection Objectives 7
Treatment Alternatives 11
Other Wastevater Treatment Alternatives 29
Treatment Methods — Summary 32
Case Histories 314
Kent Cheese Co. 314
Eiler Cheese Co. 36
Afolkey Coop Cheese Co. 38
V. Foreign Practice Reprints
Pre—Treatment of Dairy Effluent By the
Tower System i
Biological Treatment of Dairy Wastes 10
The Treatment of Creamery and. Yoghurt
Effluents 13
Spray Disposal of Food Waste 18
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CURRENT PRACTICES
IN THE HANDLING OF DAIRY PLANT WASTES
Kenneth S. Watson
Director of Environmental Control
KRAFTCO CORPORATION
Glenview, Illinois
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CURRENT PRACTICES IN THE HANDLING OF DAIRY WASTES
A paper prepared for presentation in the session on treatment
for the U. S. Environmental Protection Agency Technology Trasnfer
Seminar for the dairy industry.
Kenneth S. Watson
Director of Environmental Control
Kraftco Corporation
Glenview, Illinois
The laws, regulations guidelines and thus particularly the
pollution control efforts necessary in the dairy industry are rapidly
evolving so it is highly desirable to orient plant management and pro-
duction people with what Is going on. For these reasons this technology
transfer seminar for the industry should be beneficial. We are happy
to have the opportunity to participate in this seminar and hope that jointly
we can make it fully productive.
The treatment approaches and methods which have application
to dairy wastes are areas of significance to those who must operate plants
today. For these reasons this portion of the seminar will be concerned
with the treatment portion of the problem.
In addition to hearing from four speakers on various aspects
of treatment you will be supplied a brochure covering these presentations
and some reprints on foreign practice. The reprints briefly cover treat-
ment activities at dairy plants in Canada, England, New Zealand, Finland,
Czechoslovakia, Denmark and Germany.
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The Dairy Wastes Situation
The dairy industry is made up of a large number of, for the
most part, relatively small plants scattered primarily through the milk
producing sections of the nation. These plants range from single pro-
duct milk processing or cheese plants to rather complex multi-product
facilities in which milk, cottage cheese, sour cream, ice cream, yogurt,
etc., may, for instance, be produced.
Since many of the plants are small and located adjacent to
municipalities the usual practice has been to connect these plants into
municipal sewer systems. In fact almost 907. of the plants dispose of
their wastes in this manner.
Another reason for this method of waste disposal is the fact
that for the most part dairy plant wastes are biodegradable and compatible
with the wastewater present in a municipal system. Even fats, oils and
greases present in dairy plant wastes are edible and biodegradable so
municipalities need not feel the same concern for these materials as is
the case with the same constituents of petroleum origin. Since the average
size of the dairy plant rules against its being able to afford or pro-
fessionally operate a pretreatment facility the industry as a general
rule would prefer to buy this sewerage service from the City.
As has already been covered, but it probably deserves mention-
ing here again in the interest of completeness for this session, plant
people should exhaust the in-plant, short-of-treatment approach as the
soundest and simplest method of controlling a waste problem. In addition
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to coming to grips with the pollution problem such action will also re-
suit in cost reductions through improved production efficiencies,
reductions in losses and reductions in water usage.
Character of the Wastes
Further, as has been touched upon by other speakers, dairy
plant wastes consist mainly of lost raw materials, intermediate and
finished products and the cleaning materials required to clean and sani-
tize shipping containers and processing space and equipment all carried
in the process waters being discharged by the plant. In addition, whey
is a byproduct of most cheese operations and can become a significant
pollution problem. Every effort should be made to keep it out of the
sewer system when it can readily be separated from the water being used
in the plant. The usual procedure is to concentrate the whey so it can
be dried to whey powder or converted into another usable byproduct
either at the plant produced or at another location which can economic-
ally be reached from the point of production. These whey byproducts are
then used as food or feed supplements. Whey is of sufficient signifi-
cance that it will again be considered under Irrigation.
Milk plant wastes normally have a BOD concentration ranging
roughly between 500 and 4000 mg/I and a COD concentration which usually
runs 2 to 2.5 times higher. As a general rule the suspended solids in
such wastes are not high enough to be of great significance. Cleaning
compounds being used, particularly in larger plants, can be responsible
for swings of consequence in the pH of the effluent but these can nor-
mally be satisfactorily corrected by equalization by the City or the
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plant generating the wastes.
Disposin g of the Effluent
The various methods of disposing of dairy plant effluents will
next be briefly considered.
Biological Treatment
Most dairy plant wastes respond to the biological treatment
approach. The wastes are similar to municipal wastewater but considerably
more concentrated and more readily degraded. Since the biological treat-
ment approach most generally represents the best and most economical
method of treating dairy wastes to reduce the BOD and COD concentrations
to acceptable ones, it will be given consideration in this and the other
presentations in this session. Since biological treatment of dairy
wastes is widely provided in municipal treatment systems, one of the
papers will be devoted to this special subject.
A second paper will be the story of how a dairy plant uses the
biological approach to treat its wastes for stream discharge.
Irrigation
Irrigation of the process wastes as a means of disposal is a
viable approach for some dairy plants. The common methods of irrigation
are: spray fields, spreading and ridge and furrow application. The
plant has to own adequate land or have it under lease of suitable type
to take the volume of wastewater to be disposed of without runoff into
the streams of the area. Further, the irrigation land must be close
enough so it can be reached by pipeline or truck on an economical basis.
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Some isolation is necessary for a satisfactory irrigation site
so no odor nuisance conditions will be created. Further, care must be
exercised in application so ponding on the land does not take place.
Irrigation works best in areas where the winter climate is not
severe but can be used in such wintry areas if properly operated. Some
lagoon holding space, in some cases with the use of aeration, is desir-
able in conjunction with the operation of irrigation projects to provide
holding flexibility for rainy or wintry periods.
Spreading on land represents another method of discarding whey
for certain types of plants. There are a significant number of small cheese
plants which are somewhat isolated and cannot afford concentration equip-
ment and stay in operation. Further, as a result of the volume of whey
produced and the scatter of the plants in the particular region central
drying facilities cannot be justified.
Under these conditions, in order for these plants with their
vital cheese production to remain in operation, land disposal of the
whey must be practiced. In many areas a mutually beneficial arrangement
has been worked out with the farmers in the immediate vicinity of the
plant to dispose of the whey on their farms to take advantage of the
nutritional value to benefit the land.
Acknowledgements
The author wishes to express appreciation for the diligent ef-
forts of representatives of the Environmental Laboratory, the plants and
their Divisions for developing the data and assembling it, and for pro-
viding counsel in the preparation of the paper.
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TREATMENT PRACTICES IN KRAFTCO
STOCKTON. ILLINOIS
The Kraft Foods Division facility at Stockton, Illinois con-
sists of two separate operating plants — one for the manufacturing of
bulk Swiss cheese and the other for processing whey. All of the whey
from the cheese operation is condensed at the whey plant with the
majority of it being spray dried along with condensed whey received
from other Kraft manufacturing facilities in the area. The balance of
the whey is processed into several other institutional and industrial
products. The cheese plant is shown in Figure 1.
As is indicated in Table 1, the wastewater volume has
increased at Stockton from about 86,000 gpd in 1968 to 110,000 gpd at
present. Over this same period, however, the I OD load leaving the plant
has been reduced from 1950 to 900 pounds per day by in-plant process
modifications and improved housekeeping.
The existing waste treatment system has evolved over the almost
60 years that the plant has been in operation through efforts to solve
the wastes problem in the simplest and most economical manner. Summer
operation consists of pumping the total plant discharge through the
irrigation system on site summarized in Table 2. The concept here is
through the use of automatic controls to rotate the dosing of the land
through a preplanned application cycle so overdosing does not occur at
any one location and a maximum of percolation, evaporation and transpir-
ation of moisture will occur. Thirty-two nozzles are installed on site,
each having a capacity of 90 gpm, and dose in rotation. Each has the
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ability to spray roughly an acre. By the use of this approach maximum
advantage is being taken of the land and its cover crop to absorb the
total plant discharge.
En the winter time an activated sludge system is used the
basin for which is shown in Figures 2 and 3. A suimnary of information
on the activated sludge system is shown in Table 3. The basin is
operated using diffused air from a bottom diffuser normally supplemented
by two floating aerators. The discharge from the basin is passed through a
clarifier (Fig. 3A). From the clarifier, final disposal is made to a
ridge and furrow system on site. This system is on contour with an
overflow of the control gate of one trench to the adjoining trench below.
More details are supplied in Table 3.
The usable volume of the basin is 570,000 gaLlons having a
detention time of 5 days. It is loaded at about 24 pounds of BOD per
thousand cubic feet. When sludge must be removed from the system it
is drawn from the clarifier to a sludge lagoon located nearby. Sludge
is removed from the lagoon once a year in the spring and spread on
adjoining grass land.
For the plant to discharge into the small stream to which it
is tributary and meet the very stringent requirements of the Illinois
EPA, the effluent concentration would have to be less than 5 iwIL of BOD
and 4 mg/lof suspended solids. The decision was therefore reached that
necessary facilities should be installed to retain the effluent on site
and depend upon evaporation and percolation for disposal. For these
reasons two impoundment and flood control ponds were located at the
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lowest point on the property. These lagoons of 3,100,000 and 4,250,000
gallons capacity were provided to catch any runoff from the site during
either sunutnr or winter operations. One of these ponds is shown in
Figure 4.
In relating how this plant solved its problem, the point should
be made that the solution has been tailored through evolution to this
particular plant’s waste load in the particular habitat where located.
Many processes are in use here, however, which could have application to
other dairy plant wastes. The soundest and most economical solution to
a plant problem, however, will always be arrived at by tailoring the
treatment to the particular situation in question.
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Table 1
Waste Load Being Discharged by Stockton Plant *
WHEY PLANT _ CHEESE PLANT TOTAL
1968—9 1972 1968—9 1972 1968—9 1972
Volume gpd 57,000 80,000 29,000 29,000 86,000 110,000
BOB mg/i 2,900 900 2,400 800 2,700 870
BOD Load lb/Day 1,370 600 580 300 1,950 900
* Significant reduction in the BOD load due to in-plant processing
n difications and improved housekeeping.
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Table 2
The Kraft Foods Irrigation System at Stockton
SPRAY FIELD
50 acres of moderately sloping ground
32 operating sprayheads ÷ 2 standby
Volume - 90 gptn (each)
Coverage - 220 ft. diameter circle (approximately 1 acre)
MODE OF OPERATION
Automatic
16 circuits — 2 sprayheads/circuit
Potates through 16 positions
Preset at 90 minutes per position
1 bwed - every 3-4 weeks with 6 foot chopper mower
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Table 3
The Winter System for Handling Effluent at Stockton
Activated Slud&e Plant
Aeration basin : 212’ x 68’ x lot
Aerators - 3 — 40 HP blowers each delivering 400 scfm @ 4.5 psig
2 floating aerators
Volume - 570,000 gallons
Capacity — about 1.3 lb 8 . 0 2 /lb BOD applied
Clarifier : 24’ diameter x 9’ SWD - 1/2 HP sludge rake
Volume - 30,000 gallons
Detention — 7.2 hrs.
Sludge Lagoon : 100’ x 40’ x 10’
Volume - 300,000 gals.
Supernatant fed back to aeration basin
Ridge and Furrow System
10,000 lineal feet on contour
18” deep by 4’ wide furrow (trench) separated on 12’ centers by ridge
Overflow control gates at ends of adjoining trenches
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- The cheese plant at Stockton, Illinois with
spray fields in background.
FIGURE 2 - Aeration basin, air
floating aerators.
dittusion piping anu
FIGURE 1
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* :-v •
cT r 1T
I
FIGURE 3 — Aeration basin - winter operation.
FIGURE 3A - The Stockton claritier.
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FIGURE 4 - Impounding and flood control pond.
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NORWICH I NEW YORK
Coverage of this plant is included in this summary paper
because its treatment plant is new and of the biological type which
is widely used in the handling of dairy plant wastes. This Sheffield
Chemical manufacturing facility is not a typical dairy plant, but its
principal raw material is whey concentrated to 50% solids. Among the
major products manufactured by this Norwich facility: are lactose,
calcium lactate, sodium caseinate and food flavorings.
When it became apparent that the lagoon system being used
at Norwich would have to be replaced by more efficient treatment facili-
ties, agreement was reached with the State of New York that some pilot
scale work should be done to provide the basis of design for the new
treatment facilities. Consequently, a biological pilot scale unit was
designed and placed in operation in October 1970. The pilot facility
shown in the foreground of Figure 5 was, and can still be, operated on
a side stream of the discharge from the manufacturing plant. The activated
sludge facility for this pilot unit, operated on diffused air, is shown in
the background with the round final clarifier shown in the foreground.
The pilot facility was operated for about nine months under
laboratory control. During this same period, the design of the full scale
treatment facility was moved forward as was a program of in—plant, short—
of-treatment steps to better manage water and reduce the waste load.
Construction of the waste treatment facility was started in July, 197].
and it was placed in operation in February, 1972.
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The full scale facility consists of an activated sludge basin
broken into three compartments shown in the background of Figure 5, in
which the flexibility has been incorporated to permit it to be operated
using either the contact stabilization or extended aeration mode. The
biological treatment basin is followed by a final clarification stage
consisting of the two clarifiers shown in Figure 6. Alum is fed to the
aeration basin effluent to improve the flocculation in the final clari-
fier. When sludge must be drawn from the system, it is removed from the
clarifier to a sludge tank to be scavenged from the site. Figure 7 shows
the control building in which pumps, blowers, the flow recorder and the
laboratory are located. A picture of the laboratory is shown in Figure 8.
The treatment facility was designed to handle a hydraulic loading
of 250,000 gallons per day and a ROD load of 2500 pounds per day with 90%
removal of ROD anticipated. A maximum retention time of 3.2 days was
provided in the aeration basins. Additional information on sizes and
specifications of equipment is shown in Table 14. Since the level of sus-
pended solids in the manufacturing plant effluent did not appear of great
significance, no primary treatment was incorporated in the system. Since
the need for feeding nutrients to improve the operation of the system had
not been established prior to its being placed in operation ammonia is
being fed on an improvised basis into the influent end of the aeration
basin. Since the use of ammonia is beneficial, facilities are being added
to the system to permit ammonia to be fed on a permanent basis.
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The concept in use at this plant is to completely separate
the process wastes from the cooling water so the former can be put
through the treatment plant and the latter by—passed around same. Thus,
sampling locations have been provided for ahead. of, and following, the
treatment facilities. Finally, a sampling and measuring station has been
provided for monitoring the combined process and cooling water waste
stream which flows into the river.
Some feel for the operation of the treatment facilities can be
obtained by reviewing Tables 5 and 6. Operating experience, to date,
indicates that the 90% reduction in BOD for which the system was designed
can generally be met. As, is borne out by low minimum effluent, concen-
trations shown in Table 6, at times the system does go above 90% efficiency
in removal of BOD. Operating experience has further demonstrated that the
extended aeration mode of operation produces considerably better results
than does contact stabilization.
A program of relating river conditions to treatment plant opera-
tion has been launched and will be expanded. An initial look at river con-
ditions, on the basis of dissolved oxygen, is shown in Table 7. It will
be noted that as a general rule the dissolved oxygen in the stream is
higher below the plant discharge than it is above.
Just recently, the pilot facility was placed back in operation
to develop a better feel for how to upgrade the performance of the full-
scale unit.
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Table l
Sizes and Specifications of Waste Treatment Facilities at
Sheffield Chemical, Norwich
Aeration Facility
1. 3 tanks each 160 ft. long, 16 ft. wide, 11 ft. liquid depth,
28160 Cu. ft. volume.
2. Loading — 30# BOD per 1000 cu. ft. of aeration tank volume.
Air
1. l.5# O 2 per #BOd design.
2. 3 blowers each 1 o hp., 1200 cfm.
3. 300 coarse bubble air diffusers.
Settling Tank
1. 17 ft. diameter, 3600 Cu. ft. volume.
2. Retention time 2.9 hours at 1.1 mgd..
Table 5
Mean Results Obtained
From the
Sheffield Chemical Treatment
Facility at Norwich*
pH
Week
Flow
BOD
mg/i
COD
mg/l
Ending
GPD
Influent
Effluent
Influent
Effluent
Influent
10/6/72
1710 1 L0
907
80
33281
369
7.lt
10/13
222860
1200
5 )4
31014
7514
7.8
10/20
185780
1276
62
30147
2 ) 41
7.1
10/27
153200
1983
52
14075
70
6.2
11/3
180933
1639
914
5)425
312
7.14
11/10
1146120
1570
18
1588
1433
6.14
11/17
169920
1023
21
2533
61
6.2
11/2)4
15)41480
871
21
29)45
7 ) 4
6.5
12/1
1381)40
1895
9
5307
170
5.0
* Based on daily analyses (5—day week) of representative composite samples
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Table 6
BOD Results Obtained, from the Sheffield Chemical Treatment Facility at Norwjch*
Week
Ending
I nfluent
lug/i
Effluent
mg/i
* Based on daily analyses (5—day week) representative composite samples
Table 7
Dissolved
Sheffield
Oxygen Conditions in the River Receiving
Chemical Treatment Facility at Norwich*
the Discharge from the
Week
Ending
Above
D.O. mg/i
Below
D.O. m /l
* Based on daily analyses (5—day week) of grade samples
Max.
Mi
Max.
Mm.
10/6/72
1608
257
lI 2
i6
10/13
22 )i 8
791
21
10/20
1570
778
101
15
10/27
3621
12 48
75
29
11/3
2231
1253
189
16
11/10
2873
832
21
12
11/17
1279
832
140
14
11/214
1005
736
31
12
12/1
2196
11475
18
3
10/6/72
8.8
9.14
10/13
9.14
9.8
10/20
9.9
10.2
10/27
9.7
10.1
11/3
10.1
10.7
11/10
9.0
10.3
11/17
10.9
11.5
11/214
10.5
10.14
12/1
12.7
13.0
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FIGURE 5 - Pilot
plant facility in foreground - aeration
basin of main treatment facility in background.
FIGURE 6 - The two tank final clarification stage.
I
q
L
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I
L
FIGURE 7 - The control building.
FIGURE 8 - The wastewater laboratory iti Lhe conLroi
building.
‘I
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SOUTH EDMESTONI NEW YORK
This plant of the Breakstone Sugar Creek Foods Division pro-
duces yogurt and ricotta cheese. The plant effluent is treated on site
and discharged into the stream.
The wastewater effluent from the processing plant is perhaps
somewhat lover in concentration than is the case with that from many
dairy plants. From Table 8 it is apparent that the average BOD concen-
tration is 1 85 mg/l and the suspended solids l 7 mg/i. As is indicated
by the analytical characteristics, every effort is made to keep whey out
of the plant discharge.
The effluent treatment system consists of a raw wastes pumping
station, aerated lagoon, clarifier, sludge basin and chlorinator. A
flow diagram of the system is shown in Figure 9. The aeration lagoon is
shown in Figure 10 and one end of the clarifier at the edge of the basin
can be seen in this Figure. In the center of the aeration basin is
located a 20 H.P. high—speed floating aerator shown in Figure 11.
After biological treatment in the lagoon the effluent enters a
tank which is divided into two compartments and passes through the clari-
fier section, with a 2.5 hour holding capacity, which is served by a sludge
raking flight. The remainder of the tank consists of a compartment for
holding sludge which is removed from the effluent by the clarifier. This
sludge is returned to the aeration basin through the use of a sludge sump
and pump boated adjacent to the tank. The effluent is chlorinated at the
flow measuring device to comply with State. requirements because it also
carries the sanitary discharge from the plant.
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The treatment facility was designed for a BOD loading of 560
pounds per day and an effluent volume of 112,000 gpd. The design called
for removing 85% of the BOD and 90% of the suspended solids. As shown
by figures listed in Table 8, the treatment facilities are at present
somewhat underloaded. The removal of BOD is averaging about 95%
(Table 9). The removal of suspended solids is somewhat less efficient
perhaps because the concentration is not high to start with. In both
cases effluent concentrations fall well within State specifications.
As a result of operating experience the aerator, which was
sized to provide 1.5 pounds of oxygen per pound of BOD, is controlled by
a timer. It is in operation about 66% of the time which keeps the
dissolved oxygen content of the basin between 5 — 6 mg/l. Such an opera-
ting mode provides expansion capacity in the treatment facilities and
tends to improve sludge settleability over higher oxygen concentrations
being maintained in the basin.
Provisions have been made in this system for adequate sampling
and analyses to control its operation. The treatment plant influent is
sampled in a representative manner through a valve on the discharge side
of the pump delivering all the wastewater to the system. As the effluent
leaves the clarifier, the flow is recorded and totalized using the
Kenneson nozzle shown in Figure 12. The flow recorder is shown in
Figure 13.
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Figure i shows the laboratory which handles the wastewater
analyses for this plant and another located nearby. It is located
within the process plant. Tests which are run include BOO , COO,
suspended solids, total solids and volatile suspended and total solids.
Operational tests for controlling the treatment system consist of
dissolved oxygen, mixed liquor suspended solids, settleable solids
and chlorine residual.
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Table 8
Condensed Summary of Monthly Averages of the Influent to the
South Edineston Treatment Facility
Avg. Max. Avg. Mm.
Avg.
Avg.
lbs/day
BOD mg/i 552 ‘ o8
i85
0
COD mg/i 1033 955
1010
916
Suspended solids 208 128
162
11 7
Flow gal/day 1 2,758 73,880
108,778
Table 9
Condensed Summary of Monthly Averages of
South Edmeston Treatment Facility
the
Effluent
of the
Avg. Max. Avg. Mm.
Avg.
Avg.
1hs/a
BOD mg/ 1 31.8 11.5
20.8
18.9
COD mg/i 68 25
1i7.9
143.5
Suspended solids 6 17
32
29
Flow gal/day 1142,758 73,880
108,778
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RETURN
F,e.S
TREATMENT FACILITIES - SOUTH EDMESTON PLANT
BREAKST0NE.-SuGAR CREEK DIV.
WASTE
INFLUEIIT
SAN%TARY
WASTE
MEJER
SAMPLING
I . ’ ,
“I
UNADILLA RIVER
II
AERATE D
LAGOON
DUPLEX
PUMP STATION
WET WELL
PLING STATION
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FIGURE 10 - Aerated lagoon - South Edmeston.
I
FIGURE 11 - Floating aerator - South Edmeston.
- ‘ —
- — - ‘
‘ , .‘ç .:
-
S t
‘ F
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FIGURE 12 - Kenneson nozzle measuring final effluent.
FIGURE 13 - Recorder final effluent.
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I
FIGURE 14 - Wastewater laboratory in quality control
laboratory.
. 1
iiv
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CHAMPAIGN. ILLINOIS
Kraft Foods has had a margarine and salad dressings plant in
operation in Champaign since the early 1960 period. In 1968 the decision
was reached to make a major expansion at the Champaign plant.
Kraft Foods’ present production facility is shown in Figure 15.
In the foreground the right hand portion of the facility is in general
the original oil plant in which margarine, salad dressings and oil pro-
ducts are manufactured. The left portion of the facility is new,
having been placed in operation over a year ago and in which macaroni
type products, process cheeses (slices and Velveeta -type) and natural
cheeses in consumer size packages are produced. The plant immediately
behind the Kraft plant on the right is an edible oil refinery operated by
the HumKo Operation of the Corporation. It should be noted that the
close proximity of these facilities to extensive residential areas means
that all phases of environmental control must be carefully practiced.
Waste Treatment - In planning for the plant expansion, early consider-
ation was given to proper handling of the liquid wastes problem for the
expanded facility. As is the Corporation’s usual approach, it was pro-
posed to the Urbana-Champaign Sanitary District that the District provide
sewerage service for the expanded plant at Kraft’s expense since the
wastes to be discharged would be completely compatible with District
wastewater and be degraded in its professionally operated treatment system.
After considerable negotiation the District stood fast on its position
that it could accept the hydraulic load but the plant would need to
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provide treatment facilities to meet the specification of: 200 mg/i
of BOD, 200 mg/i of suspended solids and 100 mg/I of fats, oils and
greases covered in a proposed ordinance.
Since business considerations dictated that the production
capacities and mix of products already mentioned should be located at
Champaign, the only course open was to provide the same type of bio-
logical treatment facilities as those operated by the L istrict. These
facilities of course must be operated from now on. The pretreatment
facility provided is shown at the left rear of the site (Figure 15).
As a result of the configuration of the site it was necessary
to separate the primary facilities from the secondary. The design basis
for the plant is shown in Table 10. It will be noted that the facility
has been designed for a projected 1980 load.
The wastes from the cheese and oil production facilities at
Champaign are collected in lift stations and pumped to a surge tank.
The items of equipment used in the treatment system are summarized in
Table 11. The major units in the primary plant are shown in Figure 16.
The surge tank is on the left with the pump house in the center and
sludge storage (not presently being used) and grease storage tanks on
the right. The next step in the process is the flotation clarifier shown
in Figure 17. Grease skimmed from the surface of this unit is conveyed
to the grease tank already mentioned. The sludge removed from the
clarifier is passed on to the aeration basin to avoid the need for
primary sludge handling facilities.
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Next, the effluent flows to the aeration basin, the first
step in the secondary treatment portion of the system, shown in
Figure 18. The discharge from the aeration basin then passes through
the final clarifier and into the District system.
Controlling Operations - Arrangements have been made for collecting
samples at various points throughout the system. An automatic, composite
sampler is located on the final discharge so a continuous record can be
developed on the load being contributed to the District. Laboratory
control results for the operation of these treatment facilities are
run in the quality control laboratory. Figure 19 shows a temporary
laboratory setup within the pump house in which emulsion breaking
studies were carried out.
Table 12 shows the quality of the effluent being discharged
into the Sanitary District system at Champaign from the middle of Decem-
ber 1972 until the end of January 1973 based on daily analyses.
Unfortunately the plant decided to make some changes in its sampling
and analytical regime in October and had not again started running SOD
analyses on the influent to the plant during the period under consider-
ation. The monthly maximum, minimum and mean SOD results on the
influent for a three-month period ending with October were respectively
5268, 1113 and 3223 mg/i. Thus if the influent SOD had remained in the
same general range for the six-week period under consideration, SOD
reductions would have ranged between roughly 90 and 98%. It is
apparent from Table 12 that the reduction in suspended solids resulting
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from passing the effluent through the plant ranged between 85.6 and
95.9%. Further the COD reduction ranged between 93 and 97.47g.
Since the more work we do in Kraftco on the degrading of
edible fats, oils and greases in a plant effluent the clearer it
becomes that these types of materials are rather readily degradable
in biological treatment systems, as one would expect, this paper
will be concluded by looking briefly at this situation at Champaign.
Table 13 summarizes the concentration of fats, oils and greases on a
monthly basis in the influent and effluent of the treatment plant for
the last six months of 1972. The reductions from influent to
effluent across the system are accomplished by a combination of the
primary and secondary treatment processes in use. It is of interest
to note that an average of 97.4% of the fats, oils and greases were
removed or degraded by the treatment system described.
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Table 10
Kraft Foods
Champaign, Illinois
BASIS OF DESIGN FOR 1980 LOAD
Parameters Design
Average Flow gpd 500,000
gpm 350
BOD mg/i 3,640
BOD Load 1.b/day 15,000
Suspended Solids ne/i 685
Suspended Solids lb/day 2,850
Grease mg/i 3,140
Grease lb/day 13,000
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Table 11
Kraft Foods
Champaign, Illinois
ITEMS OF EQUIPMENT IN THE TREATMENT SYSTEM
PRIMARY PLANT
Lift Stations
Cheese - 2 - 225 gpm - 10.0 H.P. Pumps
Oil Plant - 2 - 250 gpm - 7.5 H.P. Pumps
Surge Tank
1 - 30’D x 20’H — 80,000 gal, with 10 H.P. agitator
and sludge rake
Minimum Detention Time - 1.5 hours (avg. flow and 6’ level)
Max. Detention Time - 4.5 hours (avg. flow - 18’ level)
Flotation Clarifier
1 - 39 t D x 1O ’H - 76,000 gal. with sludge rakes and surface
skimmer and recycle pressurization system.
At 507. recycle and avg. flow - surface settling rate = 625 gpd/ft 2
Weir overflow rate - 2450 gpd/lineal ft.; detention time = 2.45 hrs.
Primary Sludge Storage Tank
I - 30’D x 9’—6”H Covered Tank - 42,500 gal.
Grease Storage Tank
1 - l4’D x 29’H Cone Bottom, covered, heated tank - 18,000 gal.
. 34 -
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Table II (coin.)
Kraft Foods, Champaign, Illinois
Items of Equipment in the Treatment System
SECONDARY PLANT
Aeration Basin
Rectangular Basin 309 x 149 x 9’ Deep
Operation Volume - 2,270,000 Gal.
Detention Time @ avg. flow - 4.5 days
Dorrrlxika Aeration system using 4-75 HP blowers @ 8,000 scfm each
Final Clarifier
I - 49’D x 8 ’H tank - 100,000 gal. with sludge rakes and
surface sk tnmers
At avg. flow - Surface settling rate = 270 gpd/ft’
Weir overflow rate = 325 gpd/lineal ft
Detention time = 4.8 hours
Aerobic Digestor
I — 50’D x 27’H tank — 368,000 gal. with
3 - 50 H.P. Blowers - 700 ;scfia@ 7.5 Psig each
Sludge Lagoons (located at Sanitary District’s plant site)
2 - 1 acre surface x 8’D earthen tanks
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Table 12
The Effluent Being Discharged into the System
Kraft Foods, Champaign, Illinois District
FLOW BOD COD SS
mgd mg/I mg/i ing/1
Mean Max Mm Mean Mean Mean
Dec. 15—21, 1972
Influent 0.283 — — — 4397 1036
Effluent 90 45 54 157 61
Removal 96.4 94.1
Dec. 22-28
Influent 0.210 — — — 5176 1200
Effluent 221 74 125 376 93
7, Removal 92.7 92.2
Jan. 1-7, 1973
Influent 0.233 - - - 5157 1244
Effluent 113 32 73 254 92
7, Removal 95.1 92.6
Jan. 8-14
Influent 0.269 — — — 7471 1807
Effluent 82 32 58 192 74
7, Removal 97.4 959
Jan. 15-21
Influent 0.262 — — - 5434 1210
Effluent 214 54 127 337 97
7 Removal 93.8 92.0
Jan. 22-28
Influent 0.280 — - — 6225 1368
Effluent 142 99 117 438 184
7, Removal 93.0 86.5
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Table 13
Removal of Fats, Oils and Creases by the Champaign Treatment Plant of Kraft Foods, 1972
INFLUENT EFFLUENT
mg/i mg/i 7. REMOVAL
MONTh Na c. Mm. Mean Max. Mm. Mean = (100) Inf.(Mean)-Eff.(Mean )
mt. (Mean)-
July 2,780 161 1,376 98 29 47 96.6
Aug. 9,023 494 1,945 57 25 35 98.2
Sept. 1,966 416 1,176 50 27 39 96.7
Oct. 2,845 181 1,134 111 15 41 96.4
Nov. 4,002 215 1,058 108 6 21 98.0
Dec. 2,314 243 1,158 47 4 17 98.5
TOTAL 22,930 1,710 7,847 472 106 200 584.4
AVERAGE 3,822 285 1,308 79 18 33 97.4
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FIGURE 15 - Aerial view of Kraft Foods plant and surroundings.
FIGURE 16 — Primary plant (L to R) surge tank, pump house,
primary sludge storage tank, grease storage tank.
— 38 —
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FIGURE 17 - Flotation-clarifier, scum skimmer at 9 o’clock.
FIGURE 18 - Aeration basin, blower houses and air piping -
primary plant at left, beyond railroad cars.
- - PF , , , ,
4m
— 39 —
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FIGURE 19 - Inside pump house - emulsion breaking tests -
temporary laboratory setup for F.O.G.
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THE BENEFITS OF THE JOINT TREATMENT
APPROACH WITH THE CITY
Paul T. Hickman, P.E.
Hood-Rich
Architects and Consulting Engineers
Springfield, Missouri
Presented at an Environmental
Protection Agency Technology Transfer
Seminar for Dairy Industries
March 20 & 21, 1973, Madison, Wisconsin
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THE BENEFITS OF THE JOINT TREATMENT APPROACH WITH THE CITY
Paul T. Hickman, P.E.
Hood-Rich
Architects and Consulting Engineers
Springfield, Missouri
INTRODUCTION :
This presentation is a case history showing the joint munici-
pal and industrial approach to water pollution control as practiced in
the City of Springfield, Missouri over the past ten (10) years. While
it must be recognized that each city and its industries are different in
many respects, it is hoped that some of our experiences in Springfield
will in some small way assist other areas in their total program of
water pollution control.
Before discussing our approach and relationship with industry,
a brief look at the City’s background and location and its collection and
treatment systems is necessary in order to give a better understanding.
BACKCROUND :
The City of Springfield, Missouri is located in the south-
western section of the State less than 100 miles from the four-corner
area of Missouri, Kansas, Oklahoma, and Arkansas. Within this 100 mile
radius, the City of Springfield dominates the area as a growth center by
providing markets, jobs, product distribution, services, advanced educa-
tion, and cultural opportunities, among other things. The City and its
surrounding area has extensive and varied agricultural operations,
diversified manufacturing, mining, and rapidly expanding recreational
areas. In its function as a growth center the City has experienced a
rather phenomenal increase in population and commercial and industrial
activities over the past 20 years. Population has more than doubled to
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its present 125,000, with most of the industry also having been built
during this time. Although there is a wide diversification of manu-
facturing, the largest single type of wet industry in the City is that
of milk and milk product processing. Milk production being one of the
largest area agricultural activities. All of the milk produced is
funneled into the City either for processing or to transfer points for
transporting to other parts of the country. With this and other types
of wet industrial processing, wastewater collection and treatment is of
paramount importance. In addition to the basic needs for water pollution
control, Springfield in its particular location complicates this need
even further.
As mentioned previously, recreational activities are increasing
at a very rapid rate, particularly those associated with water sports,
fishing, and camping. Clear lakes and streams can be found in any
direction from the City. The physiography of the area is the reason
that these many lakes and streams abound. The City in its location is
situated on a plateau and straddles a major drainage divide. This
plateau is underlain with a layer of limestone bedrock containing many
fractures and solution channels. The wastewater treatment plant re-
ceiving streams have their beginnings either in the City or in the im-
mediate vicinity. It is with these conditions in mind that the City of
Springfield and most of the surroudning area is keenly aware of the need
in most instances for something more than conventional wastewater
handling and treatment. It is also the main reason that the joint ap-
proach to wastewater treatment is more desirable than individual indus-
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trial treatment facilities and their multiple effluent discharge
points. Recognizing this, the City in 1955 began a continuing capital
improvement program of wastewater facilities and a system of charges to
pay for the system’s operation, maintenance and debt requirements.
En order to explain the entire program I will briefly discuss
the City’s collection system and treatment process before relating our
joint approach and relationship with industry.
COLLECTION SYSTEM :
Once, while looking at the City archives, we discovered an
1886 ordinance which adopted a separate system of sanitary sewers for
use in the City. The ordinance went on to explain that due to the
general topography of the City, at that time, storm drainage could be
handled by normal surface runoff, thereby making it unnecessary to con-
struct underground storm sewer piping. Since there were no sewers of
any type constructed prior to that time, the practice of separate sewer
construction has continued until today. However, there are times when
we wonder if this is absolutely true when large flows are experienced
at the treatment plant due to illegal storinwater connections.
The first sewers were constructed in 1894 and has continued
steadily until today. There are now approximately 500 miles of City-
owned sewers serving 50 of the City’s 62 square miles. A rather major
program of trunk sewer construction is now underway to serve not only
the remaining area within the City but a large area surrounding it. When
this program is completed by 1978, the total service area wiLl be ap—
proximately tripled in order to serve both those areas that are currently
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being developed and those projected by the City’s comprehensive metro-
politan plan for development.
WASTEWATER TREATMENT PLANTS :
The City is currently seryed by two wastewater treatment
plants which utilize conventional primary treatment followed by the (raus
Modified Activated Sludge Process for secondary treatment. Both
plants also employ separate anaerobic sludge digestion. The larger of
the two plants, the Southwest Wastewater Treatment Plant, is designed to
handle peak flows of 16 MCD with a BOD population equivalent of 310,000.
(Figure 1) This plant accepts all of the industrial waste from the City
with the exception of one milk bottling plant, which is tributary to the
much smaller Northwest Plant.
Presently, the Southwest Plant is nearing both hydraulic and
BOD capacity. Plans are now being developed to double the hydraulic
capacity and to conform with recently adopted State Effluent Guidelines
which call for a maximum effluent SOD of 20 mg/i and NH 3 -N (ammonia
nitrogen) of 2 mg/i, along with disinfection, turbidity, and taste and
odor requirements. BOD removal will be done utilizing the pure oxygen
process in an altogether new facility. The existing aeration tanks and
air supply system will be used as nitrification tanks to convert am-
monia to nitrates to meet the recommended maximum of 2 mg/i NH 3 -N.
Nitrification will be followed by multi-media filters to remove excess
suspended solids. Disinfection is to be done by utilizing ozonation
which will also aid in turbidity and taste and odor removal. It is
anticipated that these improvements will be under contract in approxi-
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mately one (1) year.
THE JOINT APPROACH :
The reasons for a joint approach to the solution of water
pollution control problems are many and varied and can most certainly
be different for different areas. We feel that the more important
advantages to the joint approach in Springfield are:
1. Economy of Scales . En other words, it is good sound
economics to spread the cost base, both capital and
operating, so that everyone in the community benefits
directly or indirectly. I feel sure that everyone can
understand the soundness of this concept as long as the
costs in reality are equitable.
2. Professional Water Pollution Control Plant Operation .
Our approach to this has been that the City is in the
business of wastewater treatment. While it is quite pos-
sible that some individual industries could provide
capable operation if they were required to provide treat-
ment; however, the overall results most certainly would
be less than that provided at a single well-operated
combined plant. Conversely, continued surveillance by
City forces would be required if operation is separate,
thereby adding costs to the City’s operation.
3. Mutual Cooperation and Trust . When the joint treatment
method is approached realistically by both the govcrn-
mental agency and the industry, considerable public good
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can result. However, unless all parties work at main-
taining this mutual relationship, the whole concept can
break down with some very drastic results.
HISTORY :
During April 1955, the citizens of Springfield voted nearly
ten (10) million dollars in bond funds for some very major sanitary sewer
and treatment improvements. Included in these were replacement of sev-
eral existing trunk sewers which were in a badly deteriorated condition,
construction of several new mains, rehabilitation and enlargement of the
smalLer treatment plant, construction of the new 12 MCD Southwest Plant,
and a new 6 MCD pump station. Of the total $10 million authorized, $4.4
million was issued in the form of revenue bonds and was used exclusively
for the treatment plants and pump station. One of the provisions of the
election was the establishment of a system of sewer service charges to
(1) retire the revenue bond debt, (2) operate and maintain the sewer
system, (3) establish a one (1) year’s debt reserve ($256,000), and (4)
establish a depreciation and replacement fund of $300,000 to be used for
unusual or unforeseen experiences that might occur, and (5) to establish
a fund to receive any surplus income to use for any minor capital ex-
penditures that might be needed. This charge was established in 1956
and has been, and is, a separate fund used exclusively for the sewer
system. Prior to this time the sanitary sewer system was operated by
funds from the general revenue of the City.
In establishing the charges Council was attempting to place
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the system in a self-sustaining financial position and to distribute the
charges as equitably as possible.
In enacting the charge ordinance, which prescribed various
volume rates to be charged, Council also included the permissive pro-
vision for surcharges to be levied against those industries that dis-
charged wastewater with BOD and/or Suspended Solids contents greater
than domestic strengths. However, when the sewer service charges first
become effective in March 1956 these surcharges were not included.
In December 1959 the new 12 MCD treatment plant was placed
into operation with an ultimate design of 12 MCD nominal hydraulic
capacity, SS population equivalent of 100,000 and a BOD population
equivalent of 165,000. It was immediately seen that hydraulic and SS
capacities were in line with predictions of 1955 but the BOD was higher
than predicted. However, following several mechanical and operational
difficulties which arose during the first six months of operation, these
higher loadings of BOD were handled adequately, as the Kraus process
for handling shock loads had been incorporated into the design. Treat-
ment then proceeded at about the same level during the following two
years.
During the early part of 1962, the City was faced with exist-
ing industry expansion, continued construction of residential sewers and
accepting the waste from a chemical manufacturing plant whose production
had increased twenty fold since 1957. This waste had a soluble BOD PE
of 25,000-35,000. In view of this, it was felt that there were three
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possible solutions to the problem: 1. Increase the trea.tment plant’s
capacity much sooner than the ultimate design date; 2. Cut down the
strength of waste being received by requiring pre-treatment at certain
high strength industries, or; 3. That by enacting the surcharges for
above normal strength wastes it would provide a more fair and equitable
base for treatment costs and that once enacted, the surcharge would be
an incentive for industry to review their operation and possibly cut down
on volume and strength of wastes discharged and, if not, the additional
revenue would aid in a possible plant expansion.
After review of the situatiân, in April 1962 City Council
passed an ordinance declaring it mandatory to collect surcharges from
users that were contributing wastes with a BOD greater than 1.30 pounds
per 100 cubic feet (208 mgI) and/or SS in excess of 1.50 pounds per 100
cubic feet (240 mg/I), at the rate of .9c per pound BOD and l.2 per
pound SS. Following this, letters were sent to all businesses and in-
dustries whom it was thought had wastes of these strengths, explaining
the reasons for this action and that members of the City Administration
would be personally contacting them in the near future to work out in-
dividual details.
Considerable sampling, testing, and gauging was done in the
initial stages so that a reasonably reliable basis could be used for the
surcharge. Also, a great deal of time was spent with both management
and technical officials of all industries working out details of the
charge, explaining water pollution control terminology, and also
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assisting where possible in recommending ways that both volume and load
could be reduced. It would be presumptious on my part to say that all
things went smoothly, as there were numerous facets of the surcharge
system that needed deliberation and negotiation. However, I can say
that in all instances a spirit of cooperation and mutual trust existed.
The initial results of the program did, indeed, accomplish what
was intended in that a certain reduction in BOD and SS loads were ex-
perienced and the surcharge produced added revenue. However, faced
with steadily increasing population growth and industrial expansion, the
City decided to proceed with a minor expansion of the Southwest Plant
to increase the BOD handling capability from 165,000 to 310,000 by adding
the dual aeration process.
The surcharge program continued at the same rate until May 1971,
when the citizens again voted bonds for those major improvements to the
sewer system which were outlined in the first part of this paper. To
finance these improvements, an increase in the basic volume charge of
357. was enacted immediately; concurrently the surcharge was increased to
reflect the actual treatment cost experience averaged over the preceding
five (5) years for BOD and Suspended Solids removal, plus the additional
35%. Five (5) years were chosen in order to compensate for rising costs,
increasing plant maintenance, and reducing unit costs due to increased
quantities of BOD and Suspended Solids. The surcharge finally enacted
computed to l.5c per pound of BOD in excess of 1.3 lbs/lO0 cubic feet
(208 mg/l) and 2.5c perpound of Suspended Solids in excess of 1.5 lbs/lOU
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cubic feet (240 mg/I).
Again, as in 1962, each industry was contacted before the new
charge went into effect to explain the reason for the increase and how
it was to take place. In all cases we again experienced only the
highest type of cooperation.
The financial system we have followed has been and is one that
we feel and hope is as near equitable as we are able to make it. Ob-
viously, time, traditions, politics, and other numerous policy decisions
made over the years tend to complicate true equity. However, in at-
tempting to justify our rate structure under the EPA cost recovery re-
quirements, we have explained and feel that it is realistic thusly:
(1) The minimum charge for all users should be adequate to
cover all debt requirements somewhere midway through the
debt period. This we have maintained. The debt, of
course, pays the capital costs for trunk sewers and treat-
ment facilities. Basically these are designed and con-
structed around volume requirements.
(2) Additional volume charges pay for sewer maintenance,
administration, and the treatment of BOB and SS up to
domestic strengths. I know many people disagree with the
reduced rate theory for higher flow volumes that we have.
However, it is our feeling that approximately 907. of all
sewer maintenance and administrative matters are spent
with residential and commercial problems and not in
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industrial areas.
(3) The additional BOD and Suspended Solids charges made on
those industries whose load is above domestic strengths
is used strictly for excessive treatment costs. This is
a straight-forward charge and really the basis for most
joint approach methods, although it is only a part of
our total financial program.
The basic residential volume charge is $1.35 per month for 500
cubic feet or less. Each additional increment is 34c per 100 cubic feet.
Additionally, the residential charge is a flat rate based on the average
monthly usage for the months of January, February, and March to allow
for any summertime lawn and/or garden watering.
The basic minimum commercial and industrial volume charge is
$1.44 per month for 500 cubic feet or less. For usages greater than
500 cubic feet the rate structure is lowered in four steps from 34c per
100 cubic feet following the minimum down to lOc per hundred for all
usage over 40,000 cubic feet.
THE RELATIONSHIP WITH INDUSTRY :
Traditionally, over the years cities have provided wastewater
handling and treatment services to industries who desired such service,
sometimes at a lesser proportional cost than to the individual resident.
However, over the past fifteen to twenty years there has been a gradual
trend to equalize costs for water pollution control. This obviously has
been brought to a culmination in the newly enacted Federal amendments to
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the Clean Water Act which requires equitable cost recovery. In
Springfield we feel that such a system has beenM fully successful opera-
tion for over ten (10) years as the city-industrial relationship has
been excellent. This atmosphere obviously cannot be maintained unless
complete cooperation and trust is maintained by both parties at all
times. Oftentimes the City has had to meet and reaffirm this position
with industrial management personnel which is in most businesses periodi-
cally changed due to promotions, transfers, etc. But, summing up all
the details of a joint approach, the City has asked no more than for a
proportional part of the costs to operate the sanitary sewer system.
NUMBERS AND TYPES OF INDUSTRIES :
Although there are approximately 75 industries in Springfield
who are classified under Section D of the Manufacturing Standard Indus-
trial Classification, only nineteen (19) are subject to the industrial
waste surcharge. The numbers and types in this category are:
1. Meat Processing 6
2. Milk and Milk Product Processing 5
3. Other Food and Kindred Products 4
4. Commercial Laundries 3
5. Pharmaceutical 1
Of the total dollar volume the milk industry pays more than
557. of the surcharge receipts.
The total load that these nineteen (19) industries place on
the system and the treatment plants is:
1. Flow - 87.
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2. BOD - 487.
3. Suspended Solids— 187.
If one takes each of these equally, the average is 257.. Also,
if one looks at the total system income from sewer service charges, you
will see that these nineteen (19) industries pay 257. of the total.
Sampling and Analyses :
At the very outset of the program in 1962 a sampling
crew started a continuous collection of hourly samples from all
industries for a three month period to obtain enough background
data as was possible in order to arrive at a good average. In
order to get a reasonably good composite, four different
methods have been used.
1. Water Meter Reading Each Hour--
This is the most frequent use, especially at the
smaller industries. The total usage each hour
is computed and the sample composited accordingly.
Some doubts were raised intially about this
method; however, over the past ten (10) years the
highs and lows have tended to smooth out to a
reasonable rate.
2. Kennison Nozzle with Rate Indicator and Totalizer-—
Three of the largest industries (two of them
milk processors) installed these to measure
exactly what is discharged to the sewer. Not
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only are these meters used for monthly billing
purposes, but also for sampling and compositing.
The two milk processors also installed automatic
samplers of the Trebler type whereby the sample
is collected continuously and proportionally and
then pumped to a refrigerator for storage. Once
each month our sampling crew goes to these
plants and starts the sampling equipment. Checks
are made during the day to see that it is opera-
ting correctly and at the end of the 24-hour
period the sample is removed from the refrigerator,
half is left with the industry and the other half
taken to the wastewater treatment plant labora-
tory. Parallel tests are run in the
laboratories for comparison. Occasionally there
are some differences, but they have always been
resolved. The industry with the other Kennison
Nozzle is also sampled monthly by taking hourly
composite samples.
3. Parshall Flume with Rate Indicator and Totalizer-—-
One large milk product processing plant installed
a parshall flume to also measure directly what.
is discharged to the sewer. Compositing is done
as with the Kennison Nozzle.
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4. Manning’s Formula---
One large slaughter and packing house gets their
process water from a well which is not metered.
Their waste is also discharged unmetered through
two separate sewer lines. In order to compute
volume and to composite samples, the quantities
are measured by taking the depth and recording
the velocity. This data is then taken to the
laboratory where the chemist uses Manning’s
discharge curve to composite.
All testing is done in the wastewater treatment plant
laboratory in accordance with the latest edition of “Standard
Methods”. Multiple dilutions are set up in order to get good
BOD range coverage. Following analysis, the test results, along
with the composite data sheets, are forwarded to the administra-
tive offices where the surcharge is computed and billing in-
structions are written.
Sampling and testing frequency was altered many ways
over the first few years. Finally it was determined that the
four (4) largest firms would be tested each month, the next
six (6) were tested every other month, and all industries sampled
quarterly. The basis for this frequency was the amount of
revenue each produced.
Waste Compatibility and Pretreatment :
In a joint municipal-industrial system the possibilities
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of having a waste that is amenable to biological, physical,
and chemical treatment is quite good in comparison to
individual industrial wastes. However, there are certain
industrial wastes that require pretreatment. In Springfield’s
case practically all of the industry is of the food processing
category whose wastes are readily treatable, although shock loads
from these industries can be disasterous to a wastewater treat-
ment plant. In combating this we have had numerous conferences
with industrial management personnel to explain the conse-
quences of “shock loads” on the treatment facilities and that
should an accidental spill occur, to alert treatment plant
personnel immediately. Conversely, several industries have
taken steps to eliminate the possibilities of spills and to also
reduce BOD and SS loads by taking physical in—plant measures
and by having periodic supervisory meetings to urge operational
cooperation. To this end we are most grateful.
Two (2) large industries have wastes that require pre-
treatment prior to discharge into the sanitary sewer. One is
a pharmaceutical manufacturing waste and the other is a metal
plating waste. The pharmaceutical plant employs a large holding
basin to obtain a uniform waste mixture and also allow volatile
phenolic and other similar compounds to evaporate. Following the
holding basin the waste is neutralized with caustic soda to pU 7
and aerated for 24 hours. This process removes volatile compount1 ,,
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neutralizes and removes approximately 507. of the BOD and
COD prior to being discharged to the city system. The
second industry has a metal plating waste from the manu-
facture of small electric motors. The waste contains signi-
ficant quantities of zinc and hexavalent chromium. The metals
are removed by a very elaborate facility constructed in-
plant. The chromium is reduced to the trivalent state by
sodium bisulfite reduction, it is then removed along with the
zinc by caustic soda precipitation. The waste stream contains
less than 1 mg/i of both zinc and chromium. The metal sludge
is then removed by a metal reclaiming company.
SUMMARY :
The joint treatment approach to wastewater treatment is a
reasonable method to a water pollution control program in a great many
areas of the country if it is accomplished in the true sense, particu-
larly in this day of environmental awareness.
While it is not perfect in many respects, the program we have
in the City of Springfield works very well by producing sufficient revenue
on as nearly an equitable basis as we are able to realistically operate.
Taking all aspects into consideration, the cost sharing so that everyone
in the community benefits, is the primary reason for joint treatment.
Other benefits resulting from this are batter treatment, consequently
Less pollutional materials discharged to the receiving streams, and a
closer relationship between government and industry.
—17—
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CITY OF SPRINGFIELD, MISSOURI
WASTEWATER TREATMENT PROCESS
(KRA US)
FIGURE
I
TO RECEIVING
STREAM
WASTE ACTIVATED SLUDGE
RAW
I-
URN SLUDGE
SLUDGE DISPOSAL
-------
CITY OF SPRINGFIELD. MISSOURI
WASTE WA TER TREATMENT PROCESS
CURRENTLY IN DESIGN FOR SW PLANT
BACKWASH _______________
r
RAW PRIMARY I OXYGENATION CLARIFIERS NITRIFICATION CLAR/FIERS
SEWAGE TREATMENT [ REACTORS
RECYCLE SLUDGE RECYCLE SLUDGE
RAW
SLUDGE
WASTE SLUDGE WASTE
SLUDGE THICKENERS SLUDGE
THICKENED
SUPE WATANT SL UDGE SL UDGE MULTI -MEDL4 0 .3
DIGESTION FILTRATION IS/N FEC / ON
SLUDGE 70 RECEIVING
DISPOSAL FIGURE 2 STREAM
-------
I-low Dean Foods Bandies The Waste
Problem at the Chemung, Illinois Dairy Plant
George Muck and Ken Killam
I3 I
-------
The Dean plant at Chemung is a fluid milk plant
processing about 1.1 million pounds of milk per day. This
plant processes and bottles a complete line of fresh dairy
products including soft serve ice milk mixes. Cultured pro-
ducts, sour cream, buttermilk, and yogurt, are also manu-
factured at this location. Cottage cheese was produced at
this plant until April, 1972.
Waste control and waste water treatment have been
a part of this plant operation since 1950. This has been nec-
essary because Chemung is a very small community of only a
few homes and does not have a municipal waste disposal plant.
Throughout the years improvements for waste reduction and
segregation have been made both in the plant and in the
treatment system. The following examples are some of the prac-
tices used to recover and segregate waste inside the plant:
1) Fresh pasteurized product losses are recovered
for use in ice cream mix.
2) Product losses which cannot be reused are seg-
regated for animal feed.
3) Whey from cottage cheese manufacture was
recovered.
4) Cottage cheese rinse water was disposed of
through sprinkler irrigation.
5) Uncontaminated water is segregated for cooling
—1—
-------
tower treatment and the discharge by—passes the treatment
plant.
The unsegregated waste is discharged to the waste
treatment plant and consists of approximately 80,000 gpd and
1150 pounds of BOD 5 per day. Waste water coefficients for
the unsegregated waste load are approximately 0.6 pounds
waste water per pound of milk and 1.0 pound BOD 5 per 1000
pounds of milk. Table 1 shows the monthly averages for these
characteristics during 1971 and 1972. The daily averages and
the daily maximum and minimums are also given in this table.
The waste treatment facility consists of an acti-
vated sludge system followed by two lagoons. A flow scheme
for this system is given in Figure 1. The influent enters an
aerated waste holding tank (A) where the flow and BOD5 Is
partially equalized. Nitrogen is also added to the influent
at this point. The waste then goes into two activated siudge
aeration tanks (B) which are operated In series. The reten-
tion time in these tanks is approximately 24 hours and a BOD 5
reduction of about is obtained. The next step is two
gravity clarifiers (C) which operate in parallel with approx-
imately 80,000 gpd effluent overflow and 160,000 gpd return
sludge underflow. Activated sludge effluent receives addi-
tional treatment in two aerated lagoons (D) operated in series
with 20 days retention time to obtain an additional hOD 5
—7—
-------
DAIRY PROCESS WASTE WATER CHARACTERISTICS
Table 1.
DEAN FOODS COMPANY
CHEMUNG.
ILLINOIS
# WASTE
WATER PER
# MILK
# BOD 5
PER 1000
MILK
Daily Max.140 ,000 3400
Daily Mi 23,000 817
Estimated SS = 300 mg/i or 200 pounds per day
FLOW
MONTH aod
BOD 5
ma/i
BOD 5
POUNDS
PER DAY PH
1—71
88,000
1494
1096
7.49
0.56
0.83
2—71
93,000
2041
1583
7.87
0.55
1.13
3—71
83,000
2070
1433
7.79
0.51
1.06
4—71
91,000
1575
1195
7.02
0.59
0.93
5—71
92,000
1476
1132
7.72
0.62
0.91
6—71
98,000
2117
1730
6.87
0.75
1.58
7—71
89,000
1900
1410
6.80
0.63
1.23
8—71
98,000
1818
1486
6.60
0.72
1.30
9—71
101,000
1135
956
6.65
0.73
0.80
10—71
104,000
1609
1396
7.67
0.73
1.25
11—71
80,000
1215
811
7.90
0.57
0.69
12—71
80,000
2470
1648
7.40
0.55
1.36
1—72
64,000
1520
811
7.14
0.43
0.66
2—72
63,000
1638
860
6.52
0.49
0.80
3—72
61,000
1450
738
6.32
0.42
0.59
4—72
63,000
1430
751
7.14
0.48
0.68
5—72
63,000
1368
719
6.85
0.51
0.69
6—72
69,000
1618
930
7.00
0.59
0.95
7—72
81,000
1854
1252
6.82
0.59
1.25
8—72
90,000
2242
1683
7.30
0.68
1.53
9—72
82,000
1570
1074
6.75
0.62
0.97
10—72
70,000
1207
705
7.10
0.50
0.61
11—72
76,000
1604
1017
8.24
0.53
0.91
12—72
75,000
1962
1227
7.33
0.55
1.18
Daily
Avg.
81,400
1712
1156
7.16
0.58
0.98
2667
9.10
0.75
1.58
670
5.60
0.42
0.61
-3-
-------
A. Raw waste equalization tank
B. Activated sludge aeration tanks
C. Clarifiers
D. Aerated lagoons
E. Settling lagoon
F. Chlorinator
G. Sludge aerobic digester
DUtH
Figure 1
WASTE TREATMENT FLOW SCHEME
CRLE OF FEET
160
TREATMENT PiANT
CHLORINE.
CON TACT
AR P
E AT ION
AREA
0
c iO öO
Out fQII , i c hor- e.
c,.n4 b;4ch to P;sc.Qsqw Creek
af Vi!! € of Ch rnun
Cowii y of (lc.Henry, &ate of IJIino!5
i pp/ication J y bean Foods Company
a5Junel97t Date
SHEET 2é3
-4-
-------
reduction of about 70%. The total BOD 5 reduction is 90—95%.
A lagoon settling zone (E) of 4 days retention time achieves
a ss reduction of approximately 85%. The lagoon effluent is
chlorinated (F) and mixed with the segragated cooling water
prior to discharge to the stream. An aerobic sludge digester
(C) is used to further reduce BOD 5 and concentrate ss in
waste activated sludge. The digested sludge is applied to an
approved 21 acre irrigation site.
The effluent characteristics from the various steps
in the operation are shown in Table 2. These figures are
monthly averages for 1971 and 1972 and again the daily aver-
ages and maximum and minimums are given. The final effluent
consists of approximately 80 000 gpd chlorinated lagoon eff-
luent and 200,000 gpd cooling water discharge. The combined
effluent contains approximately 30—60 mg/i BOD 5 , 35 mg/I SS,
25 mg/i P0 4 , 5 mg/i NH 3 and 0.5 mg/i NO 3 . The effluent char-
acteristics given in Table 2 are displayed graphically in
Figures 2 and 3. Figure 2 shows the suspended solids varla—
tion monthly for the activated sludge effluent and the lagoon
effluent. Figure 3 shows the mor % ly variation in BOD 5 for
the influent , activated sludge effluent, and the lagoon eff—
luent.
The major components of the waste treatment complex
were initially installed as follows:
-5-
-------
Table 2.
EFFLUENT CHARACTERI STICS
DEAN FOODS COMPANY - CHEMUNG, ILLINOIS
MONTH — ACT. SLUDGE EFF. LAGOON EFF. FINAL EFF .
BOD5 SS BOD SS BODç SS DO
mg/i mg/i mg/ mg/i mg/I mg/i mg/i
1—7i 964 680 258 111 77 14 7.1
2—71 1001 910 247 30 148 79
3—71 602 764 201 45 98 29 7.3
4—7i 815 585 180 30 64 43 5.1
5—71 160 40 795 634 114 83 7.1
6—71 365 595 120 40 56 35 7,3
7—71 i36 268 58 25 44 i4 8.1
8—71 115 342 65 25 26 15 7.5
9—71 581 578 68 21 22 14 7.0
10—71 926 499 70 30 32 55 7.7
11—71 883 953 65 30 19 26 8.1
12—71 581 84 44 12 6.6
1—72 875 1246 135 78 49 6 8.0
2—72 540 303 129 49 103 36 12.7
3—72 744 648 109 63 15 26 7.2
4—72 46 31 36 123 35 28 7.4
5—72 129 170 137 78 23 28 8.0
6—72 114 102 100 65 33 44 9.1
7—72 825 788 84 36 8 25 6.3
8—72 325 221 104 48 45 22 8.1
9—72 165 848 80 86 ii 56 7.6
10—72 82 107 69 81 6 55 6.9
11—72 132 298 51 42 35 59 7.9
12—72 172 349 23 40 7.8
Daily Ave. 470 492 139 80 47 35 7.6
Daily Max. 2100 1300 2200 1200 260 303 16.4
Daily Mm. 20 30 40 10 1 4 3,5
-6-
-------
Figure -.
1971 I 1972
DEAN FOODS COMPANY
CHEMUNGI ILLINOIS
I
I
I I
II ft
11 II
1’
I’
II
I’ II
I I s
T L
1 11
1 1
SI UDG
I
I
1
FFLUENT
‘I
II
II
II
Ti
It
I
I’
ft
I
‘I
I
I
I
It
It
2000
1500
I
I
I
11
1000
*
I
I
500
Jan
I
“4
I’
II
I
1 .
I
I
I
I
I
/
Dec
JANUARY NOVEMBER
JANUARY - DECEMBER
-------
1) 1950 — One aeration tank and one clarifier.
2) 1961 — Second aeration tank and clarifier.
3) 1967 — Sludge digester and irrigation site.
4) 1968 — Lagoons and chlorinator.
The replacement cost of these components is esti-
mated at over $500,000. Annual operating cost is estimated
at $50,000 including personnel.
Since January 1972 a technically educated operator
has been employed to conduct waste sampling and analyses,
interpret results, and operate the treatment plant in a
scientific manner. Prior to that time the responsibility was
divided between the quality control laboratory and mainten-
ance department.
The final effluent has had little impact on the
receiving stream as shown by the upstream and downstream data
in Table 3. The final effluent of approximately 280,000 gpd
is discharged to a stream with a ten year low flow of around
890,000 gpd. Upstream and downstream BOD 5 and DO have been
nearly identical.
-8-
-------
I
DEAN FOOS
I
1
I
I
1
I
1
3000
Figure 3
1971
972
PANY
rr
-------
Table 3.
WATER QUALITY - RECEIVING STREAM
DEAN FOODS COMPANY - CHEMUNG, ILLINOIS
UPSTREAM DOWNSTREAM
MONTH BOD 5 DO BOD DO
mg/i mg/i m A mg/i
1—72 5 i3.6 5 13.5
2—72 10 14.4 11 14.5
3—72 14 10.9 12 10.2
4—72 8 12.2 6 12.2
5—72 4 14.6 2 i4.7
6—72 4 10.1 5 11.9
7—72 9 il.2 11 11.7
8—72 3 11.3 3 12.5
9—72 3 11.0 6 11.3
10—72 3 12.0 3 12.1
11—72 3 13.5 1 14.0
12—72 1 14.1 0 14.3
Avg. 6 12.4 5 12.7
Daily Max. 30 16.0 30 16.6
Daily Mm. 0 8.0 0 9.6
- 10 -
-------
ALTERNATE METHODS OF TREATING OR PRETREATING DAIRY PLANT WASTES
by
William C. Boyle and L. B. Polkowski
Polkowaki, Boyle & Associates
Madison, Wisconsin
Iv
-------
Dairy Waste Compatibility in Municipal Systems
Wastewater Characteristics — In comparing dairy vastewaters
with domestic sewage it is apparent from Table I that there are some
significant d1 ferences that have a bearing on the treatability and
the influence of dairy wastewater on municipal treatment systems. It is
apparent that dairy wastevater is a strong waste in terms of most parameters
reported when compared to domestic wastes. The BOD values are high and
vary widely, but the fact that the BOD values are high is also indicative
that the wastewater is amenable to biological treatment. Because the
values of BOD for dairy wastes are considerably higher than that of
typical strong domestic wastes, often surcharge rate structures are
applied when discharged to municipal systems. The suspended solids or
filterable solids are higher than domestic wastewater, but the solids in
dairy wastevater are too finely divided to permit separation by gravity
settling whereas for domestic vastewater there is a high fraction of
suspended solids that are settleable and, thus, amenable to primary
sedimentation treatment. Primary sedimentation practices usually provide
good removals at low operating and capital costs relative to the biological
treatment costs associated with secondary treatment. It is apparent in
Table I that the average Phosphorus and Grease content of dairy wastes
are higher than normally expected in domestic wastewater. Removal costs
in municipal treatment related to P removal may be assessed to the
contributing source thereby increasing overall treatment costs for use of
municipal systems. The range of grease concentrations encountered in dairy
wastes may exceed acceptable limits imposed by ordinances.
—1—
-------
TABLE I
Comparative Wastevater Characteristics
Dairy Wastewaters Domestic Sewage (9 )
Wastewater Harper (6 ) Numerow(10) Other
Characteristic Range Ave . ________________________ Strong Medium Weak
BOD, 5 day 20°C 450 — 4790 1885 1890 *15_4790 300 200 100
Solids, total 135 — 8500 2397 4516 1200 700 350
Dissolved, Total 3956 850 500 250
Fixed 525 300 145
Volatile 325 200 105
Suspended, Total *24 — 5700 560 350 200 100
Fixed 75 50 30
Volatile *17 — 5260 20 10 5
Settleable Solids
mi/liter 0.3—5.0(11) 20 10 5
Nitrogen, Total as N 15 — 180 76 85 40 20
Organic 73.2 35 15 8
Mmnonia 6.0 50 25 12
NO 2 0 0 0
NO 3 ——— 0 0 0
Phosphorus (Total as P) 11 — 160 50 59 20 10 6
Grease (fat) 35 — 500 209 150 100 50
pH *53 — 9.4 7.1
Note: *Industry values (6)
-------
Fats, Oils, and Greases (FOG) — In municipal treatment systems
treating domestic and industrial wastes, ordinances are usually adopted
to protect treatment works by rest ricting the concentration of FOG to
less than 100 mg/i. Discharges to the collection system in excess of
100 mg/i would be prohibited or require pretreatment. This particular
requirement has been adopted widely for municipal treatment systems largely
due to the available “Model Ordinances” which serve as a guideline for
drafting ordinances applicable to specific municipal systems.
The principal difficulty experienced with this criteria is that
the analytical methods employed do not account for the wide variety of
substances included in the determination; i.e., any material which is
hexane soluble and would be subsequently evaporated with the hexane at
100°C, and nor does it distinguish between that matter which is of
mineral origin (non polar) versus the fatty matter which may be of animal
or vegetable origin (polar). What appears to further complicate the
collective nature of the analytical method is that there is no differentiation
of the organic matter as to its physical state; i.e., whether these materials
are present in wastewater as a liquid or a solid, which may readily separate
by floatation, or whether they may be present In finely divided states,
emulsified or soluble and not be readily separable. Also, no distinction
is made as to the ability of the wastewater treatment facilities to remove
these substances with the usual type of treatment afforded.
For example, although most municipal treatment plants have devices
in primary and now, secondary settling units to remove floatable substances
by retention baffles extended below the water surface with scum movement and
—2—
-------
withdrawal provisions, very limited attention has been drawn to the fact
that fats, oils, and greases of animal and vegetable origin are treatable
biologically in both aerobic and anaerobic treatment units whereas FOG
of mineral origin are considered to be non—biodegradable. However, in
order for biological degradation to occur, the FOG of animal and vegetable
origin must be in physical states which will permit the biological
mass to be in contact with the material to be oxidized. Thus, if the
material separates, or floats on the surface of treatment units, the
opportunity for biological degradation is greatly reduced and this
phenomenon has long attributed to the desired exclusion of these substances
from municipal treatment systems. It is well known that anaerobic
treatment systems such as anaerobic digesters are particularly adaptable
to the degradation of FOG from animal and vegetable origin, and are capable
of higher degrees of volatile solids reduction and greater volumes of methane
gas production per pound of volatile solids reduced than for other organic
matter common to municipal wastewater systems. This i not so for FOG of
mineral origin wherein these substances effectively coat insoluble
surfaces and in high concentrations will effectively impair biological
treatment by interfering with the normal mass transfer functions of the
biological system.
In instances where gross oil or greases are present in wastewater
regardless of the origin whether mineral or from animal and vegetable sources,
these substances which are readily separated by traps or limited gravity
separation units, should not be discharged to a municipal collection system
where adverse effects of sewer clogging, excess accumulations in vet walls, or
—3—
-------
overloading of scum removal equipment occurs.
For the discharge of dairy wastes to a municipal system, in
that the FOG are biodegradable, the principal concern should be directed
to whether or not the greases present will readily separate, cause sewer
clogging, or excessive accumulations. Floatable greases should be removed
if these adverse affects are noted; however, FOG in highly dispersed states,
although in concentrations that may exceed the presently accepted level of
100 mg/i should not be excluded from municipal treatment systems. For
example, it would not be very practical to require biological pretreatment
of dairy wastes for the purposes of removing FOG of a dispersed nature
if the municipal system is going to utilize similar biological treatment
processes. It is expected that there will be a concentration limitation
imposed on FOG of mineral origin and FOG of all types which are readily
floatable. Likely no restrictions would be placed on FOG in dispersed
states of animal and vegetable origin.
Municipal System Discharge — As indicated by others, the practice
of discharging dairy wastewaters to municipal systems is commonplace. In
that dairy wastes are highly amenable to treatment generally, the main
concerns have been directed to the intermittant nature of the waste discharges
wherein the treatment plant may be heavily loaded or subject to large
variations for certain wastevater characteristics which may adversely
affect treatment. Because of the emphasis on establishing rate structures
which reflect the costs to the users of the system for appropriate Federal
construction grant monies, the dairy industry as with other wet industries
are becoming more waste conscious, employing in—plant waste saving devices
—4—
-------
and overall in—plant improvements to minimize waste discharges. The character-
istics of dairy waste discharges which have received some attention, the
degree of which is somewhat related to the percentage of dairy waste to
total municipal waste sources wherein a high proportion of dairy wastes
to total municipal wastes appears to highlight the following waste
characteristics:
1. The highly variable nature of dairy wastewater strength
in terms of BOD which may necessitate the employment of pretreatment in
the form of aerated holding facilities. The ability of a municipal
vastewater system to treat highly variable wastewater strengths depends
upon the dilution and attenuation of the characteristic with wastes from
other sources and of more concern is the resident times or detention times
in the treatment units. A wastewater treatment plant that employs
extended aeration having detention periods approaching 24 hours, little
to no benefit can be realized in employing equalization or holding facilities
prior to discharge to the municipal system. In other instances, where
treatment detention periods are shorter, recirculation may assist but the
overall effects must be observed and analyzed on a case by case basis.
2. Another dairy wastewater characteristic which draws considerable
attention is related to the pH variation of the wastewater particularly
when peak alkaline conditions occur during cleanup operations. In that an
upper limit of pH 9.5 has been adopted in certain Sewer Ordinances for
the discharge of wastes to a municipal system, this value can be easily
exceeded during periods of washing. Equalizing the waste discharge to
attenuate the pH variation may be recommended but not always be warranted.
—5—
-------
Whereas pH values below 5.5 may be harmful to severs because of the corrosive
nature of the wastewater, generally sewer construction of alkaline earth
materials would not be so effected by high p11 discharges. In terms of
biological waste treatment, large variations in pH over a short period
of time in the biological treatment unit would be undesirable. The variation
of pH at the source or industry discharge may have little bearing on the
pH in the biological treatment unit and, therefore, should be monitored in
the treatment unit, not the discharge to the unit, to determine the pH
range encountered. Again, in activated sludge treatment systems with long
detention periods, the pH variations are usually slight although large
variations in pH may be evident in the incoming waste stream. Regulation of
discharges to a municipal waste system and required pretreatment must be
consistent with the desired end result sought.
3. With the increased emphasis on removing nutrients such as
Nitrogen and Phosphorus from wastewaters that contribute to eutrophication
or fertilization of lakes and streams, this may place an additional burden
on contributors to the system particularly from point sources where the
use of phosphorus bearing cleaning compounds are employed. Costs for treatment
in some instances have been prorated on a per pound basis of P present in
the waste discharges to the system. The methods employed for P removal
usually result in high operating costs due to chemical additions required
for P removal and the handling of the resulting sludge with fairly nominal
annual costs associated with capital improvements related to this removal
function.
—6—
-------
Selection Objectives
In the selection of a vastewater treatment alternative, a
number of factors must be evaluated prior to making a final choice. Among
those objectives which most often dictate process selection are (a) effluent
criteria, (b) site limitations, (c) wastevater characteristics, (d) waste—
water variation, (a) expected life, and (f) cost to treat. A brief outline
of these objectives will precede a more extensive discussion of specific
treatment alternatives.
a. Effluent criteria — The requirements for effluent quality
from the dairy industry have been most recently released by U.S. EPA in
August, 1972, based upon two comprehensive studies of the dairy industry:
(1) “Study of Wastes and Effluent Requirements of the Dairy Industry” by
A.T. Kearney & Co. ( 8 ), and (2) “Dairy Food Plant Wastee Treatment Practices”
by Ohio State University (11 ). Currently,these requirements based on
“best practicable control technology currently available” cover only the
wastevater parameters of BOD and suspended solids. For new plants under
construction or existing plants now beginning abatement programs, effluent
BOD and suspended solids concentrations of 30 mg/l are expected regardless
of influent characteristics unless there are unusual or restrictive character—
istics.
Public Law 92—500, the Federal Water Pollution Control Act
Amendments of 1972, further states that even a higher level of treatment
will be required by July 1, 1977, in those areas where secondary treatment
—7—
-------
will not meet water quality standards. Water quality standards must be
achieved in all instances and every evidence indicates that these standards
will be whole body contact recreation plus fish and aquatic life standards.
It is likely, therefore, that requirements for the dairy industry will
become more stringent in years to come. Furthermore, additional water
quality parameters such as phosphorus and nitrogen will undoubtedly be added
to the list.
Restrictions on phosphorus removal have already become a reality
in many parts of the country. In Wisconsin industrial discharges in excess
of 8,750 pounds of total phosphorus per year must achieve 85% removal if
discharged to the Lake Michigan watershed. It is apparent, then, that the
dairy industry will have to be concerned about its phosphorus discharges
in the near future.
In process selection, therefore, it is important to consider
flexibility and versatility of the flowsheet in providing reliable and
consistent effluent quality. One must consider design based upon both
expansion of production and increased restriction of pollutant discharge.
b. Site limitation — In the selection of either pretreatment
or complete treatment facilities, the constraints of the site often play a
controlling role. Low first cost processes normally require substantial
land areas and may restrict development within one quarter to one—half mile
of the facility. Urban locations may be restricted by odor, noise, or
esthetic regulation. Costs to pump or otherwise transport vastewaters to
remote locations should not be overlooked.
—8—
-------
c. Wastewater characteristics — Wastewaters from dairy plant
processes normally include substantial concentrations of fats, milk proteins,
lactose, some lactic acid, minerals, detergents, and sanitizers. Normally,
a major fraction of the pollutants is in a dissolved organic and Inorganic
form not susceptible to plain sedimentation or floatation. The strength
and quality of vastevater varies widely even within plants producing the
same dairy food products. That plant management plays an important role
in these characteristics is brought out by the Ohio State Report (11 ). A
complete compilation of wastewater characteristics is presented in this
document.
The vastewaters from most dairy food operations are substantially
higher than domestic wastewaters as measured by BOD, COD, total organic
carbon and volatile solids. The carbon to nitrogen ratio of dairy food
processing vastewaters is normally higher than that of domestic waste as is
the carbon to phosphorus ratio. Thus, processes ordinarily acceptable for
handling domestic wastewaters may require considerable modification for
handling dairy process wastevaters. Furthermore, combined treatment of
dairy plant wastes with municipal wastes may be substantially influenced by
the proportion of dairy plant to municipal waste flows.
d. Wastevater variation — Discharges of dairy wastewater are
often batch or slug dumps producing wide variation in flow and quality.
Treatment processes may be sensitive to either qualitative or quantitative
shock loads caused by these variations. It is Important to evaluate
treatment performance reliability in light of these expected variations.
—9—
-------
Equalization, neutralization, or other forms of load equalization must be
considered in concert with the treatment processes which are sensitive to
widespread variation.
e. Expected life — The treatment facility being designed by
industry normally has a short design period owing to the uncertainty in
production forecasts. Currently, this policy would seem to be of considerable
advantage, especially to the small dairy operation. Yet, as mentioned
earlier, every consideration should be given to building in flexibility and
versatility even for short—term programs. Considerable advantage may
accrue to dairies considering modular construction to meet current needs
with an eye to the future.
f. Cost to treat — Of greatest impact in process selection is the
cost to treat which Includes both capital investment and operational maintenance
costs. All too often, process selection based on first cost has proved to
be the poorest choice owing to excessively high operation and maintenance
costs. Considerable care must be observed in interpreting cost data in
the literature. Hidden costs such as sludge handling and whey separation
and treatment are often neglected in these analyses. Data on municipal
treatment process costs are of little value in assessing costs to treat
dairy wastewaters.
—10—
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Treatment Alternatives
In the discussion of alternatives to dairy wastevater treatment,
no reference will be made to whey treatment or handling. The processing of
whey is extremely important in the overall waste disposal program and
should be considered separately from other wastewater disposal problems.
In the overwhelming majority of cases whey should not be treated in
combination with other dairy wastewaters. The characteristics of whey
normally lead to serious treatment plant upsets and would result in
excessively high costs to treat by most procedures currently employed.
Biological Waste Treatment
Dairy plant wastewaters are most often treated by biological
treatment processes owing to the relatively high fraction of readily
biodegradable compounds present. Since the major fraction of pollutants
in dairy wastewaters is dissolved and colloidal organic and inorganic
matter, chemical coagulation and precipitation of milk waste constituents
has met with only partial success resulting in relatively poor removal of
organic matter and producing voluminous quantities of chemical sludges.
Biological processes, then, provide the most economical process for removal
of the substances. The rate of biochemical stabilization of the organic
compounds in dairy food wastewaters is normally dictated by the rate of
degradation of milk proteins. Limitations of essential growth nutrients
such as nitrogen or phosphorus, the toxic effect of detergents or sanitizers,
or inhibition or repression of the activity of specific enzymes caused by
lactic acid or whey proteins may further exert a controlling influence on
stabilization rates. In general, however, a biological process can be
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designed that will effectively and consistently stabilize a major fraction
of the degradable waste constituents. This may be most effectively
accomplished by an assortment of processes including aerobic systems,
anaerobic systems, or combinations of the two processes in either suspended
or fixed film reactors.
The design of biological wastevater treatment processes is
dependent upon (a) the stoichiometry of the biochemical reaction, (b) the
rate at which this reaction proceeds, and (c) the dispersion of the waste
constituents within the reaction vessel. A vast literature exists in
sanitary engineering related to the modeling of biological treatment
processes. Investigators recognize the great complexity of the system and
considerable effort has been recently exerted to develop a unified concept
acceptable to the profession. Suffice it to say that such an agreement is
still a long way off.
The biochemistry of milk wastewater stabilization has been the
subject of numerous investigations since the early 1950’s. Considerable
effort has provided a general understanding of the mechanisms of milk
decomposition and some general stoichiometric relationships have been reported.
The selection of biological reactor type and the mode of
microorganism—wastewater contact are critical to the expected performance
of the treatment system. Normally, the microorganisms may be held in
suspension by aeration or mechanical mixing (suspended growth reactor) or
they may be grown on surfaces over which wastewater is directed (fixed film
reactors). The hydraulic regime produced in either reactor type will
also dictate the apparent performance of the system. Thus, flow configurations
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described as plug flow, completely mixed, partially mixed with longitudinal
dispersion, batch operation and complete—mixed—In—series are often used.
In practice, the design of biological wastewater treatment
processes Is often based upon empirical design parameters and rules of
thumb. The magnitude of these parameters or standards of design are
applicable primarily to domestic vastevater systems and should not be
employed for design of dairy plant wastewatere. A fundamental approach to
biological wastewater modelling In design for industrial wastevaters
requires some experimental study. Where funds are limited, reliance upon
Information in the literature is second best, but extreme care must be
taken to Insure that treatability of the wastewater in question is
realistically parallel to that being used as the model.
The following sections briefly describe a number of biological
processes which have been employed successfully to treat dairy vastewaters.
The performance of these processes, based upon past experience, is also
presented merely to provide some idea of the range of performances expected
under the design conditions. The strengths and weakness of each process for
dairy wastewater treatment application are also cited.
Activated Sludge Process — One of the most popular methods employed
for the treatment of dairy wastevaters is the activated sludge process.
Flowsheets of several of the activated sludge process modifications appear
in Figures la, lb, and ic. The process provides aerobic biological treatment
employing suspended growths of bacterial floc. High concentrations of
organisms, maintained by sludge return, reduce overall reactor size. The
organisms are separated from the treated effluent by means of plain sedimentation.
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Dairy wastevaters are normally treated in modifications of the
conventional process flowsheet. Experience over the years has indicated
that long hydraulic detention times, in the order of 15 to 40 hours,
produce most satisfactory process results. In addition, a completely
mixed flow regime appears most satisfactory providing an adequate dampening
effect on the wide fluctuations in wastewater flows and strengths. The
use of long detention time — completely stirred reactors (extended aeration,
Figure ic) precludes the use of special flow equalization facilities. Even
p11 fluctuations normally found in the raw wastewater stream will be
significantly attenuated in this system.
Batch fill—and—draw activated sludge systems are also quite popular
in the treatment of dairy wastevaters. These processes, too, normally
operate over long periods of detention time and provide substantial dampening
of flow and strength variations.
A very complete compilation of activated sludge performance for
dairy wastewaters appears in the Ohio State Report (ii ). A brief summariza-
tion of selected findings from both recent reports on dairy wastewaters ( 8 ,u. )
are presented in Table tI, along with ranges of design parameters.
It is apparent from examining Table II that a wide range of both
influent and effluent BOD values is reported over a considerable range of
detention times and volumetric loads. In general, superior performances
are achieved at longer detention times although conscientious plant operation
is paramount to successful performance. Two important design parameters,
sludge age (pounds of volatile suspended solids [ VSS] under aeration divided
by pounds of VSS wasted or lost per day) and loading velocity (pounds of
BOD applied per pound of VSS under aeration), are missing from this table.
It is difficult to obtain reliable data on these two parameters from the
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literature, yet they truly define process performance. The active microbial
population (often expressed as VSS in activated sludge systems) is an
important variable, too, in describing overall system response. Absence
of these values in Table II makes a clear delineation of expected
performance a difficult task.
Based on past experiences, it appears that BOD removal efficiencies
for dairy wastewaters in excess of 90 percent can be consistently maintained
in extended aeration activated sludge plants. More germaine, however, is
that effluent BOD concentrations below 30 mg/i may be difficult to achieve
consistently, even at long detention periods and sludge ages. Note that
for raw wastewater BOD concentrations of 1500 mg/i, 98 percent BOD must
be achievable. Of great importance in evaluating the consistent performance
of the activated sludge process is the settling properties of the mixed
liquor. Bulky sludge is not uncoi on in plants treating dairy vastewaters,
and the discharge of poorly settled sludge with the effluent will substantially
elevate effluent BOD values. Even with extended aeration, as much as
30 percent of the effluent volatile solids may contribute to the total
effluent BOD.
Oxygen requirements for stabilization of organic wastewaters
in activated sludge are proportional to both the active biomass and the
applied BOD removed. Laboratory or field analyses are employed to ascertain
these requirements.
Oxygen for the activated sludge process may be provided by one
of numerous types of diffused air or mechanical aeration systems. Oxygen
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TABLE II
Performance of Biological Treatment Systems
Dairy Food Wastewaters
Influent Effluent Removal of Volumetric Hydraulic Number of
T BOB BOD BOD Load Detention Plants
y Pe (mg/i) (mg/i) (%) ( LB BOD ) (Hours) Reported
1000 cuft
Selected Values 620—1620 13—290 64—99 25—130 15—50 7
Activated sludge ( )
Activated Sludge ( ) 24—99.6 100
Oxidation Ditches ( ) 410—2150 3—165 74—99 4—41 27—320 10
Aerated Lagoons C ) 1000 20 98 1
Aerated Lagoons ( ) 70—99 5
Performance of Anaerobic Treatment Processes
on Dairy Wastewaters
Influent Effluent % Removal Detention Number
Type BOD BOD BOB Time Surveyed
Septic Tanks and
Digesters 7000—500 300—400 50—87 3—10 12
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transfer rates are dependent upon the aerator selected, the geometrical
configuration of the reactor and the wastewater characteristics. This
latter information is normally obtained through experimental studies. Diffused
air requirements often quoted for dairy wastewaters are usually in excess
of 1500 cubic feet per pound of SOD removed. Coar3e bubble diffusion
devices are commonly reconmtended for dairy wastewaters as they clog less
frequently and require less maintanance than the fine bubble systems. Jet
aerators, shear devices, surface turbines, pumps, draft—tube aerators,
rotors and brushes are also popular. Oxygen transfer rates for these
mechanical devices normally range from 3 to 4.5 pounds of standard oxygen
per gross horsepower hour at standard conditions.
The production and handling of sludge from activated sludge plants
treating dairy wastewaters are not well documented in the literature. Long
aeration times (extended aeration) are recommended to destroy (endogenous
repiration) a substantial portion of the sludge solids. Nonetheless,
provision must be made to handle some sludge since a certain fraction of the
sludge is nonbiodegradable and will eventually accumulate. Disposal of
accumulated sludges from dairy wastewater activated sludges continues to be
a problem as sludge handling may be very costly. Aerobic digestion of
accumulated sludges followed by land disposal represents a desirable
relatively low cost alternative.
The activated sludge process is less sensitive to temperature
than other biological processes. Toxic effects of sanitizers and pH
variations are usually effectively reduced through the use of extended
aeration — completely mixed systems. Furthermore, the stability of activated
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sludge settling properties is more effectively enhanced in completely
mixed systems employing low BOD loading velocities. Finally, long—term
aeration employing sludge ages in excess of 10 days will normally produce
highly nitrif led effluents (a property likely to be desirable in the future
if effluent standards are adopted for ammonia discharges). The removal of
phosphorus by activated sludge systems is poor, normally ranging from
35 to 50 percent. Chemical precipitation, usually prior to final sedimentation,
employing aluminum or iron salts will effectively remove phosphorus from
final effluents and may serve to enhance settling properties of poorly
settling sludge.
Cost of the activated sludge process are summarized in Tablelilbased
on data available in the Cost of Clean Water Series — Volume III, Profile 9
( 1 ). All costs are reported as 1963 dollars. Unless otherwise noted,
costs are based on a “medium” plant size with current technology. Capital
costs are based on dollars per 1000 gallons of design flow, whereas operation
and maintenance costs are based on pounds of BOD, and 1000 gallons of
wastewater treated. Considerable caution should be exercised in placing
emphasis on these figures since construction costs continue to rise rapidly
and local conditions will fluctuate considerably from the national norm.
In addition, the level of treatment efficiency required has not been
stipulated in the compilation of these figures, but stringent effluent criteria
may substantially elevate this figure. Finally, sludge disposal costs are
often neglected in these figures, a fact which may lead to serious under-
estimates of true vastewater treatment costs for those processes generating
high sludge volumes.
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Oxidation Ditches — The treatment of milk wastewaters in oxidation
ditches has been acceptable practice for a number of years in Europe.
The oxidation ditch is an extension of the activated sludge process employing
a ring—shaped circuit or ditch usually 6 to 10 feet deep (Figure 2).
Aeration is provided by cage or brush aerators mounted at several points
along the ditch in order to circulate flow around the circuit and to
maintain sufficient velocity to keep solids in suspension. Baffling of
rectangular lagoons with appropriately located flow directors will achieve
the same effect. The oxidation ditch may operate as a continuous system or
as a batch process. If operated in a continuous mode, a clarifier is
incorporated as an integral part of the system.
Typical performance data for oxidation ditches appear in Table II
As was noted with the activated sludge process, considerable variation in
loading, detention time, and process efficiencies are apparent. There is
considerable evidence in the literature that at detention times In excess
of 50 days and at volumetric loadings less than 15 pounds BODhi000 cu ft
effluent concentrations of less than 30 mg/i are achievable. High mixed
liquor VSS, in excess of 4000 mg/l, are attainable with the configuration
when employing sludge recycle. There Is no evidence to suggest that this
particular configuration will more successfully treat dairy wastewaters
as compared with the extended aeration activated sludge processes at
similar loadings. Costs of this process are likely similar to those for
activated sludge although there Is not enough operating experience in this
country to provide reliable cost data.
Aerated Lagoons — Aerated lagoons are also an extension of the
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activated sludge process wherein no sludge return is normally practiced.
As a result, the active biomasa (VSS) in the lagoon is low, thereby requir-
ing longer periods of aeration for comparable performance.
Data in the literature on the performance of aerated lagoon systems
for dairy vastewaters is sketchy. Only three reports appear in the
comprehensive survey by the Ohio State group ( ii.), and 5 are reported
by A.T. Kearney & Co. ( 8 ). (Table II). Prom this data there is evidence
that current effluent requirements can be met by proper designed aerated
lagoon systems. Design would most definitely be predicated upon careful
pilot or laboratory scale studies. The experience of these authors is
that aerated lagoons are a satisfactory alternative for dairy wastewater
treatment. Currently a number of these systems for dairies are in successful
operation in Wisconsin. An example of two of these systems will be
presented later.
In most cases aerated lagoons are not vigorously mixed, resulting
in sedimentation of suspended solids within the lagoon itself. These
aerated lagoons, therefore, remove organic matter through
physical separation and anaerobic and aerobic stabilization. Mixing
intensities normally required to prevent sedimentation in aerated lagoons
require power inputs of approximately one order of magnitude greater than
for oxygen dispersion alone (8 HP/MG vs 80 HP/MG).
On the other hand horsepower requirements for aeration are dependent
upon the oxygen uptake rates, the required hydraulic detention time, and the
oxygen transfer characteristics of the wastewater. In most instances the
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power required for aeration is less than that required for complete
solids suspension and the engineer must determine whether the added
power costs justify this added mixing capacity. In the majority of
cases, dairies have not opted for this extra expense, a decision which
appears sensible.
Aerated lagoons are normally designed as a series system. Most
aeration is provided in the first cell, followed by a second or third
cell of quiescent settling and stabilization. Normally lagoon depths of
10 to 15 feet are desirable although shallower cells are allowable for
polishing or quiescent settling. Algal growths occurring in the quiescent
cells may cause a deterioration in effluent quality and should be avoided,
if possible, through proper outlet design, covering or filtration.
Aerated lagoons are temperature sensitive, producing poorer quality
effluents in the winter months. Most engineers size aerated lagoons based
on winter operations. The onset of warmer temperatures in the spring may
result in increased biological activity in the anaerobic zones of “facultative”
aerated lagoons. This activity often results in depletion of lagoon
dissolved oxygen causing odors and loss of efficiency. Aerator designs
should provide for this eventuality, especially in the poorly mixed lagoon
systems.
Aeration is normally provided by either surface or submerged
aeration equipment. In northern climates, surface aerators require
considerable maintenance for ice removal and in retaining effective and
consistent operation. Submerged units will not normally be effected by
cold weather but orifices may clog (as with activated sludge) and mixing
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velocities are usually low.
Land requirements for aerated lagoons are high and most states
require substantial distances be maintained between lagoons and residences.
Because of long detention times, no flow equalization is required when
employing lagoon systems. Sludge handling is relatively minor in most
lagoon systems, although some provision may be made to dewater quiescent
lagoons in the event of significant solid buildup. Anaerobic digestion
normally maintains a relatively small sludge volume on the lagoon bottom.
Nitrogen conversion to nitrate is usually complete in aerated
lagoons. Phosphorus removal is reported to range from 30 to 80 percent
depending upon season of year. Phosphorus precipitation would account for
this removal and resolubilization of precipitated phosphorus is likely to
occur during certain periods of the year.
Costs for lagoon construction and operation are presented in
Table III . Land costs were estimated at $300.00 per acre (1 ).
Stabilization Ponds — Stabilization ponds cover a variety of
lagoon systems employed for wastewater treatment. As compared with aerated
lagoons, stabilization ponds depend upon surface reaeration and photosynthesis
for oxygen supply. For dairy wastewaters with strengths in excess of
municipal wastewaters (300 mg/i BOD), lagoon surface areas or active algal
populations must be extremely large. There is no practical method
currently available in the midwest for maintaining algal cultures in the
concentrations necessary to effectively treat most dairy wastevaters.
Solar insolations are too low and winter conditions too severe for
successful operation. Surface area requirements would appear prohibitive
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TABLE III
Cost Comparisons for Wastewater Treatment — Base Year 1963+
Capital Costs — $11000 gal*
Creamery Cheese Condensed Ice Cream Milk &
Milk Cottage Cheese
Ridge & Furrow 325 366 380 375 300
Spray Irrigation 927 1070 1070 1080 850
Aerated Lagoon 540 1170 100 78 1410
Trickling Filter 2030 5050 1350 5050 4050
Activated Sludge 1360 3360 900 3380 2700
LBS BOD/d
153
66
236
2.9
502
Gal lons/d
17,200
4100
162,000
6400
19,600
Production—Lb/d
3,900
3400
46,200
890 gal/d
39,500
630
milk
cot.chs.
Operation & Maintenance**
Creamery Cheese Condensed milk Ice Cream Milk & Cot.Cheese
$/l000gal s/lb $/l000gal $/lb $/l000gal $/lb $/l000gal s/lb $/l000gal $/lb
Ridge & Furrow 0.18 0.02 0.20 0.01 0.21 0.14 0.21 0.47 0.17 0.01
Spray Irrigation 0.51 0.06 0.60 0.04 0.59 0.40 0.60 1.32 0.46 0.02
Aerated Lagoon 0.30 0.03 0.66 0.04 0.06 0.04 0.04 0.09 0.77 0.03
Trickling Filter 1.12 0.13 2.80 0.17 0.75 0.51 2.78 6.10 2.23 0.09
Activated Sludge 0.75 0.08 1.87 0.12 0.50 0.34 1.84 4.06 1.48 0.06
+ From “The Cost of Clean Water — Volume III, Industrial Waste Profile 9, Dairies, FWPCA, Washington,D.C.
June 1967 (1)
* Cost per 1000 gal design flow
** Cost per 1000 gal total waste flow or per total pounds of BOD
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for most dairy wastewaters, being approximately 15 to 20 lbs BOD/acre/d.
Thus, a dairy producing 500 lbs BOD per day would require at least 25 acres
of land for stabilization ponds. In addition, at least one-quarter mile
must be maintained between lagoon and the nearest residence.
The Ohio State Report (1]. ) represents a compilation of perform-
ance of stabilization ponds. With few exceptions, effluent BOD exceeds
that currently required by current effluent quality standards. The State
of Wisconsin has stated that, if the New Federal Water Pollution Control Act
is enforced as written, “treatment processes such as .... stabilization ponds
would no longer be permitted as the sole means of treatment”.
Based on the factors discussed above, there would appear to be
little advantage in considering this method of treatment for dairy wastevaters.
Trickling Filters — The trickling filter process in contrast
to suspended growth processes employs a fixed support medium to maintain
the active organisms within the wastewater stream. In the past this medium
has been rock, slag, or other low cost materials providing a large surface
area per unit volume with a high void volume. Recently, nmmerous types
of low weight, high specific surface plastic media have been developed for
this purpose.
Organic matter associated with the wastewater is absorbed or
adsorbed into the fixed biological film and is subsequently oxidized. Oxygen
is normally provided by natural ventilation within the fixed bed although
positive airflow may be provided to achieve more effective process operation.
Contact time of the waste in trickling filters is normally short depending
upon the application rate to the filter and the filter depth. Conventional
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filters are 6—8 feet deep whereas the plastic media filters may be
constructed as high as 30 feet. Increased contact time is provided in
some filters by recirculat ion of treated wastewater back through the
filter. The mode of recirculation varies considerably from plant to plant.
Trickling filters are followed by clarification facilities in
order to intercept and remove sloughed solids from the filter. Filter
sloughing is a natural process and must occur in order to maintain an
active biological mass on the media. Heavy accumulation of biological
growth on the media surface will lead to filter clogging and poor oxygen
transport.
There are numerous flowsheets currently employed that use the
trickling filter process. The engineer selects a flowsheet which makes
best use of the existing site and provides greatest operational flexibility
for the wastewater being treated. Filters are normally designed based
upon either hydraulic load (millions of gallons per acre per day MCAD) and
organic load (pounds of BOD per 1000 cu ft per day) and they are no nally
classified as high or low rate in accordance with these loading parameters.
Considerable controversy still surrounds the selection of the appropriate
design parameter and Its order of magnitude.
The performance of trickling filters treating dairy wastevaters
has been summarized in the Ohio State Report ( 11 ). Examination of this
extensive tabulation is confusing and of little real value to design
engineers. As with the activated sludge tabulations, wide variation exists
in both performance and magnitude of design parameters. Scatter diagrams
prepared in the report ( 11 ) would suggest that neither hydraulic load
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nor organic load control process efficiency to any great extent. Process
efficiencies range from less than 10 percent to 99 percent over ranges of
hydraulic loading of from 0.14 to 20 MGAD and organic loads ranging from
approximately 2 to 175 lb BOD/l000 cu ft day. Clearly, many of these
reports are for roughing filters employed for pretreatment only. The
A. T. Kearny & Co. Report ( 8 ) suimnarizes performance efficiencies ranging
from 35 to 99.8 percent for 48 plants reported.
It is clear from this data that trickling filters, properly
designed, may achieve current effluent quality standards. Indications are
that plants designed at hydraulic loads less than 2.0 MGAD and organic
loads less than 20 lb BOD/1000 cu ft/d may have a reasonable likelihood of
success in achieving low effluent BOD. Such generalizations, however, are
not sufficient that dairy food processors should employ them without
considerable investigation. Currently, the State of Wisconsin has not
favored trickling filtration as an effective means of secondary treatment.
Winter operation often deteriorates effluent quality and covering of existing
filters is strongly recommended in northern climates.
The proper ventilation or oxygen transfer in trickling filters
is paramount to successful performance. Dairy wastewaters exert high oxygen
demands as compared to municipal wastevater (per unit volume of waste)
thereby putting a high demand on oxygen resources in the filter. Poor air
circulation caused by heavy biological growths, clogged underdrains, and
waste channeling will result in serious odor conditions, development of
massive biological growths and deterioration in effluent quality. Positive
ventilation procedures may effectively be employed to improve operation.
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For this reason it is felt by these authors that the controlling design
parameter in the case of high strength wastes is organic loading.
Recirculation of wastewater through the filter is often
advantageous to eliminate excessive growths, reduce filter fly populations,
and reduce odor. Cooling effects of recirculation are undesirable,
however, during the cold winter months.
The use of plastic media filters for dairy wastewater treatment
may prove to be most advantageous. More uniform void volumes and high
specific surfaces will promote more effective oxygen transfer and wastewater
contact with the biomass. In addition, considerable savings may be
realized in land area when deep filters are employed.
Trickling filters handle shock loads moderately well although
effluent quality may suffer for short periods. Whey should never be
applied unless slowly added over long periods of time and filter design
should account for this addition. Nitrogen conversion to nitrates will
occur only on lightly loaded filters (usually less than 5 lb BOD/l000 cu ft/cl)
and phosphorus removals are poor, usually being less than 35 percent. Sludge
produced in trickling filters, although less voluminous than that from
activated sludge processes, must be subsequently handled. Anaerobic
or aerobic digestion of sludges followed by land disposal are most coimuonly
applied procedures.
The cost of trickling filter treatment appears in Table III.
Plastic media filtration may be more expensive than indicated in this
tabulation; however, a higher quality effluent will normally result more
consistently than with conventional rock filters.
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Rotating Biological Discs — The rotating disc process is a
modification of the trickling filter process whereby the fixed biological
film is rotated through the wastewater. First developed in Germany in 1955,
there are now over 1000 installations in Europe alone. Research in the
United States has developed a lighter, lower cost disc providing higher
surface area. A large biological surface is provided by a series of closely
spaced discs mounted on a rotating horizontal shaft. (Figure 3). The
discs are slowly rotated at approximately 2 rpm through the wastewater
while submerged to approximately 40 percent of their area. Organic matter
is sorbed by the biomase on the disc and is subsequently oxidized in the
presence of oxygen. A positive means of excess film sloughing is provided
by the shearing action caused by the rotation of the discs.
The biological discs are normally staged so that a number of
discs rotate within a given enclosed reactor cell. Wastevater passes
from cell to cell through openings in the cell walls. This separation of
reactors in series provides an advantageous development of specialized
biological cultures for the waste constituents during each phase of treat-
ment. Thus, by adding additional cells, one may achieve progressively
higher levels of oxidation Including complete nitrification of the waste—
water. This cellular structure also reduces the effect of shock loads to
the system. A clarification facility is required to remove sloughed
biological solids from the discs.
Performance data on the biological disc in treating dairy waste—
waters Is scant. An example of one such application is given later in
this paper. Design parameters currently used for the process are based
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upon a hydraulic loading (gallons per day per sq ft) and plant staging.
Sludge production in these units are normally comparable to that in
trickling filters and methods of handling and disposal parallel those
discussed earlier. Costs of this type of treatment are still preliminary
although it is apparent that operation and maintenance costs will be very
low. The only power consumed is that used to rotate the disc shaft.
Anaerobic Processes — The anaerobic treatment of dairy process
wastewaters has been practiced for many years in small dairy operations
through the use of septic tanks. During anaerobic decomposition, lactose
Is rapidly converted to lactic acid, lowering the pH. In addition, fats
and proteins are decomposed to amino acids, organic acids, aldehydes,
alcohols, and other anaerobic intermediates. This phase of biodegradation
is often referred to as acid fermentation and little BOD, COD or organic
carbon “removal” is achieved. A second phase of biochemical reactions,
methane fermentation, may also proceed, converting the organic acids to
methane and CO 2 . This gasification step subsequently “removes” BOD
from the system as a gas. At “steady state”, one reaction feeds the other
resulting in a relatively constant pH and organic acid level. If conditions
within the reactor become unfavorable for the methane bacteria (the most
sensitive of the two groups of bacteria In this reaction system), acid build
up will occur causing further deterioration of the process, a decrease in
pH and a reduction in gas production. Successful anaerobic processes,
designed for BOD removal, must develop a successful balance between these
two phases. -
Anaerobic processes normally have not been successful as complete
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treatment systems, since effluent quality is often poorer than that
required by stream standards. The process does, however, offer a successful
low cost process for wastewater pretreatment. Even if only the acidification
step is achieved in the anaerobic process, considerably higher rates of
aerobic stabilization may be realized with this pretreated effluent. More
rapid decomposition of organic acids and anaerobic intermediates under an
aerobic environment may result in smaller and more effective aerobic processes
than could be achieved without this pretreatment.
Although quiescent holding tanks (septic tanks) have been used to
treat dairy wastewatera, improvements in the anaerobic process have
resulted in considerably better overall performance. Anaerobic contact
processes, employing mixing with sludge return have proved to be successful
in accelerating the conversion of organics to methane and CO 2 . The use of
anaerobic fixed film contractors (anaerobic trickling filters and
biological discs) have also been examined.
Results of several reported experiences with anaerobic processes
appear in Table II . Little data is available on anaerobic contact processes
and fixed film reactors. The evidence indicates that approximately 50 percent
of the applied SOD can be removed in quiescent digestion systems with little
advantage gained beyond 4 days of detention time. Greater removals may be
realized through re effective contact between the biomass and wastewater.
Imboff tanks may also provide more consistent results due to the separation
of digestion and sedimentation processes.
The anaerobic process is sensitive to shock loads, temperature
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and toxic chemicals. Process efficiency may seriously suffer when temperatures
of the wastewater drop below 10°C. Certain sanitizers, high concentrations
of ammonia and numerous metal catlons are toxic to methane bacteria.
Anaerobic systems must be covered and should be ventilated adequately.
Safety precautions should be taken owing to the presence of methane.
Costs of anaerobic systems are not readily available. Precast
septic tanks range from $400 to $600 including installation up to 1500
gallon capacity. In most instances use of precast tanks in series is more
economical than larger cast—in—place tanks. Operation and maintenance costs
for anaerobic processes is dependent upon whether mixing is employed. Costs
for simple septic tank operation range from $100 to $200 per year depending
upon pumping and hauling costs. Low operation and maintenance costs are due
largely to the absence of power requirements and the infrequent need to
dispose of accumulated sludges.
Other Wastewater Treatment Alternatives
Irrigation — The use of irrigation as a treatment and disposal
method for dairy plant wastewaters is most efficacious. It represents the
best alternative if the proper type of soil is available in large enough
acreage. Details of land irrigation practices have been covered in subsequent
papers so that only a brief discussion will be presented here.
The success of irrigation methods depends upon the use of proper
application rates and the effective pretreatment of the wastewater prior to
disposal. Careful attention must be paid to the alternating of irrigation
plots and provision and maintenance of the cover crop. High sodium concentra—
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tions may seal soil particles. Wastes high in particulate matter should
be adequately screened prior to irrigation.
Recently, considerable success has been achieved by employing
the soil as a biological filter. Permeable soils are underlain by tile
fields which intercept the percolating wastewater. Nutrients are removed
by the soil and its cover crop yielding percolates of high quality. Recycling
or additional polishing of the percolate may be required prior to surface
discharge.
Ridge and furrow irrigation of dairy wastewaters has met with
little success in the upper midwest. Odor nuisance, standing water, and
maintenance difficulties are attributed to this method of land disposal.
A sumeary of irrigation practices is detailed in the Ohio State
Report ( 1]. ). Costs for irrigation methods are presented in Table ii .
Costs for land are based on a value of $300.00/acre.
Filtration — The filtration of wastewaters normally provides a
polishing step prior to final discharge. Filtration may be provided by
microscreens or granular filtration devices employing diatomaceous earth
or sand or mixed bed filters of materials such as anthracite and sand or
activated carbon and sand. The state of the art of wastevater filtration
is relatively new and considerable research continues to improve filtration
techniques. Further details may be found in Cuip and Cuip (4 ).
Slow sand filters, 12 to 30 inches deep, employ filter sand for
approximately one—half that depth underlain by coarse sand, gravel, and
an underdrain system. Application rates of up to 3 gallons/sq ft/d are
employed. Filter cleaning is employed when headlosses reach 8 to 10 feet.
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The filter is then partially dried and the top layer of sand and sludge
are removed. Clean sand is subsequently added prior to placing the filter
back in operation. In general, slow sand filters are expensive to operate,
require large areas and provide only moderate performance.
Rapid sand filters on sand or mixed bed filters are considerably
more popular for tertiary treatment processes. Application rates of 3 to
6 gal/sq ft/minute are commonly employed. Cleaning of filters is provided
by backvashing the filter with treated effluent.
In treating dairy wastewaters, the filtration step may be required
as a polishing operation to achieve the desired BOD or solids concentrations.
If the selected treatment process results in effluent concentrations high
in degradable suspended solids (lagooning or even activated sludge processes)
filtration may prove feasible. In most cases, filtration processes may
be added to most process flowaheets at a future time to improve overall
effluent efficiencies. If the treatment process achieves complete
stabilization of the wastevater or if suspended solids are mineralized,
filtration may not provide much advantage to the overall process flowsheet.
Chemical Methods — Chemical precipitation of dairy food wastewaters
is not widely practiced primarily because of its high cost and its nominal
effectiveness in organic matter removal. In some cases, wastewaters high
in fats or colloidal matter might be effectively pretreated by addition
of metal cations such as calcium, aluminum or iron or by polyelectrolyte
additions. Voluminous amounts of sludge normally result with the metal
salts requiring expensive methods of sludge handling and disposal. Poly—
—31—
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electrolytes may provide advantage heretofor not attainable with other
chemicals. Small quantities of polyelectrolytes may affect substantial
removal, of solids at a reasonable cost. To date, the state of the art
is not advanced enough to justify chemical methods as a reasonable alternative
in the majority of cases.
Membrane Processes — The use of molecular sieves, electrodialysis,
and reverse osmosis membrane systems has only begun. Considerable success
for whey treatment has been predicted. Where water reuse or product
recovery is feasible, these methods may prove successful. Costs at this time
are high and normally discourage use in most dairy wastewater treatment schemes.
Carbon Adsorption — Carbon adsorption technology in the treatment of
wastewaters has rapidly advanced over the past 5 years. Carbon adsorption
systems are becoming competitive with biological treatment processes in
the treatment of municipal wastewaters. Carbon systems are normally sized
on the basis of mass of COD removed per mass of carbon. Carbon requirements
for dairy wastewaters would be high and the cost of treatment is still not
competitive with other alternatives. As effluent requirements increase,
however, it is not inconceivable that carbon adsorption will be the
competitive choice. A detailed discussion of carbon adsorption theory and
application may be found in Culp and Cuip ( 4 ).
Treatment Methods — Suimnary
In summarizing this discussion of treatment processes, a brief
tabulation has been provided to assist the reader in a swmnary evaluation.
Table IV has been prepared to give some guidance as to each process
—32—
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TABLE IV
Comparison of Treatment Alternatives
Effluent Quality Reliabi— Cost
Type BOD/Solids Ammonia Phosp. lity Capital 0 & M Land Response Economic
_________________________ _______ ______________ Regmt. to Shock Life (Y rs)
Activated Sludge
(Ext. Aer) +++ 1-H- + +++ H H L +++ 15
Oxidation Ditch +1-f +++ + 44+ H H A 4-f- f- 15
Aerated Lagoon 4- f- I- +4-f- + 4-I - A A H +++ 20
Stabil.Pond + ++ + + L L H ++ 30
Trickling Filter + 4 - -H- 0 ++ H H A +4- 15
Biological Disc +++ +++ + +4+ H L L +1-f- 15
• Anaerobic Processes + 0 0 + L L L a + 20
‘ Irrigation +++ +4-f +++ ++ A A 11 - 14+ 20
Key:
+ 1 - I - - Excellent Ii - High
4-I- — Good A - Average
4--Fair L-Low
O - Poor
-------
characteristic.
In selecting a treatment process, the engineer must consider
carefully all alternatives open to him. The preliminary design may be
based to some extent upon values reported in the literature. Final
selection, however, should be based on treatability tests. This becomes more
critical as effluent requirements become more stringent. The data presented
in Table iv relates primarily to the effectiveness of these processes to
achieve current effluent standards (i.e., BOD of 30 mg/i consistently).
As effluent standards become more stringent, it will be more difficult to
achieve “excellent” performance from many of these processes.
The processes discussed above were considered as separate
treatment entities. In practice, it is wise to look at combinations of
these processes so that advantages may be taken of the best parts of each.
Thus, anaerobic pretreatment followed by aerobic polishing may provide a
more economical alternative than the aerobic process alone.
Table V briefly summarizes the characteristics of a number of
selected “tertiary” wastewater treatment processes. As pointed out
earlier, selection of “tertiary” or polishing processes is dependent upon
local effluent requirements, the current treatment process employed, and
the characteristics of the treated wastevater.
In the next section, a brief discussion of three case histories
are presented to give specific details of the types of design that may
be employed.
—33—
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TABLE V
Tertiary Treatment Processes
Effectiveness in Effluent Polishing
Process Effectiveness in Removing:
Susp.Solids BOD COD Nitrogen Phosphorus
Microscreening + + 0 0 0
Sand Filtration +1- (+)* 0 0 0
Granular Carbon ++ ++ ++ 0 0
Lime Clarification ++ + 0 0 ++
Lime Clarification &
Dual Bed Filtration + 0 0 ++
-I-i- Excellent 8O% *Depends op nature of Suspended Solids
+ Good - 50%
0 Poor - 50%
- 33a -
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CASE HISTORIES
1. Kent Cheese Co., Kent, Illinois — ( 3 ).
The Kent Cheese Company specializes in the production of
Ricotta, Parmesan, Roinano, and Mozzarella cheese. During the study, an
average of 13,000 pounds of cheese were produced per day (excluding Sunday)
producing approximately 17,000 gal per day of wastewater with a BOD of
270 pounds per day and a suspended solids loading of 85 pounds per day.
Sources of wastewaters were from the rinses and washes associated with
milk storage, transmission lines, vats and pasteurizer. Whey was collected
and transported to another site for recovery.
The wastewater treatment system consisted of two equal volume
aerated lagoons in series (Figure 4). Each 12 foot deep lagoon holds
955,000 gallons providing a detention time of 56 days based on design flow.
The first lagoon was provided with thirteen—6 foot long 18 inch diameter
Helixors (Polcon Corp) arranged in a pattern along the flat portion of
the lagoon bottom. Three additional aerators are arranged in a triangular
pattern near the inlet end. Tvo—240 scfm Gardner Denver rotary blowers
provided the air supply for the lagoons. Water surface elevation in the
lagoons was controlled by placement of a 4—inch cast iron riser pipe at a
fixed elevation to maintain a 12 foot water depth.
The aerators were of the submerged air—lift type insuring
operation throughout the year (Figure 5). Oxygen transfer studies conducted
during a one—year study indicated that standard transfer rates ranging
from 2.2 to 4.1 lb/HP—hr were achievable. Low mixing velocities were
—34—
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observed with the diffuser pattern and basin geometry employed in this
lagoon. Very light accumulations of sludge (less than 2 inches) were note d
after one year.
Results of lagoon performance based on BOD appear in Table VI
Wastewater temperature had the greatest effects on process performance.
An overall average removal of 97.3 percent produced an average BOD
concentration of 52 mg/i, ranging from 155 mg/i to 12 mg/i during the one
year study. Poorest performance occurred during the winter months
(Jan—Feb) but high oxygen uptake rates occurring in April through mid—July
produced zero dissolved oxygen concentration in the primary lagoon causing
odor and sludge rising problems. This unusually high activity has been
attributed to rapid anaerobic decomposition of benthal soldis accumulated
over the cold winter months.
During the one year study approximately 65 percent of the nitrogen
was removed. Highest nitrate production occurred in warm sui er months.
Effluent total nitrogen concentrations ranged from 0.2 to 10.6 mg/l
averaging 3.8 mg/i. Total phosphorus removals of approximately 50 percent
were observed resulting in an average total phosphorus concentration of
21.6 mg/i.
Total capital investment for this plant in 1970 was $49,500 or
$2900/1000 gallons of design flow. This is substantially higher than the
1963 costs estimated for aerated lagoons for cheese processes (Table II I).
Over the first year of the study the operation and maintenance costs were
approximately $6000 resulting in unit costs of approximately $0.13 per
pound BOD and $2.05 per 1000 gallons.
—35—
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Quarter
1971.
Performance
Influent
Flow
(gal / d)
TABLE VI
of Two Stage Lagoons — Kent Cheese Co.
BOD
(mg/i)
SS
(mg/i)
Pr1m.La oon Eff.
Sec.Lagoon Eff.
BOD SS
(mg/i) (mg/i)
BOD SS
(mg/i) (mg/i)
Jan-Mar
Apr-June
July— Sept.
Oct-Dec.
Average
14,900
17,300
20,000
15,200
16,900
Overall Removal
BOD
(mg/i)
1,940
2,040
1,530
2,100
1,910
U I
658
600
547
595
602
SS
(mg/i)
Temp .
DC
224
204
122
274
209
403
477
239
445
395
106
61
21
31
52
155
119
43
lii
108
94.5
97.0
98.5
98.5
97.3
734
80.1
92.1
81.3
82.0
1
17.8
21.7
9.5
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2. Eiler Cheese Company, De Pere, Wisconsin (2,7 ).
The Eller Cheese Company processes 30,000 pounds of milk per
day into 3,000 pounds of American cheddar and Colby cheese. The treatment
plant was designed to handle 3,000 gallons/day of vastewater, with a
maximum of 5400 gallons/day, and a BOD load of 90 pounds/day (2000mg/i).
About half of the milk handled is received in cans, the washings from which
constitute the major source of vastewater. The balance of wastewater
results from whey washing. Whey is separated and hauled to local farmers
as a feed.
The wastewater treatment facility consists of three septic tanks
connected in series followed by a four stage rotating disc system, a
clarifier, a chlorinator, and a polishing lagoon (Figure 6). The septic
tanks provide flow equalization, clarification of raw vastewater and
digestion of recycled biological sludge. The three cells have volumes of
6,450 gal, 5,040 gal, and 1,400 gal respectively providing detention times
ranging from 2.5 to 4.3 days. The rotating biological filters furnished
by Autotrol Corporation were located in a vault 12 feet below ground level.
The BI0—DISC (Autotrol Corp) system consisted of feed chamber, four—stage
BIODISC unit, and clarifier (Figure 3).
The feed chamber is provided with a bucket feeder attached to
the BI0—DISC shaft, thereby providing a constant feed to the biological unit.
Each of the four BI0—DISC stages contain 22 molded polystyrene discs, 10 feet
in diameter, providing a total area 13,800 square feet. The discs are
rotated at a speed of 2 rpm (peripheral velocity of 62 feet per minute).
Each stage provides a hydraulic detention time of 1.5 to 2.0 hours. The
—36—
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clarifier provides for overflow rates of 1800 to 2700 gallons/day/sq ft
with sludge removal being provided by sludge scoops rotating at 4.5 rph.
Sludge flows by gravity back to septic tank cell #1.
A 4.5 foot deep polishing lagoon with a 30 day detention time is
provided to “polish” final effluent from the BI0—DISC.
Results of the performance of this treatment system for a 12 day
period is presented in Table VII. It is apparent from examining this table
that the septic tank did not provide the treatment expected. It was
found that pH values dropped to values of 5.5 in cell 2 resulting in
inhibition of methane bacteria. It should be noted, however, that
recovery of pH did occur on the rotating biological filters and that
excellent BOD removals were still achieved. BOD removal exceeded 95 percent
on the BI0—DISC throughout the test period (12 days). It should also be
noted that the “polishing” value of 30 day lagoons is questionable.
Burying of the BIO—DISC vault provided substantial insulation
against cold winter temperatures. Minimum temperatures of the BlO —DISC
mixed liquor never fell below 40°F even though ambient temperatures as low
as —30°F were recorded. Several instances of shock loading were recorded
during the 10 months of recorded data. Increased production resulting in
peak discharges, raw milk spillage, and a whey dump were all experienced.
The BI0—DISC unit continued to provide 60 to 75 percent treatment with
full recovery after 2 to 3 days.
Capital investment for this process was $35,00c or $6,50c per
1000 gallons of design capacity. Operation and maintenance are minimal. The
operating power for the disc drive was 0.5 HP and the clarifier scraper
*Estimated based on current biomodule cost projection
—37—
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TABLE VII
Performance of Septic Tank — BI0—DISC — Eiler Cheese Plant (7)
Date Flow Raw Waste Septic Tank Eff. BI0—DISC Eff . Polishing Pond
BOD SS BOD SS BOD SS pH BOD
1971 (gal/day) (mg/i) (mg/i) ( mg/i) (mg/i) ( mg/i) (mg/i) ( mg/i )
Apr.19 3676 840 360 7.6 863 240 6.7 40 80 - 7.7 17
20 3411 720 280 7.6 810 320 6.6 32 20 7.6 27
21 362ó 780 220 7.6 640 220 6.7 21 80 7.8 32
22 4405 1700 340 7.3 675 180 6.7 29 20 7.7 22
23 4703 1240 640 7.1 955 280 6.7 54 40 7.4 53
24 1540 1100 220 7.1 1060 160 6.7 65 40 7.5 53
25 761 705 140 7.2 870 120 6.5 53 20 7.6 50
26 3477 840 460 7.1 1000 100 6.6 30 60 7.5 48
27 3030 1540 240 7.2 970 240 6.6 48 40 7.6 46
28 3825 1150 240 7.0 1120 200 6.6 48 60 7.6 17
Avg. 3245 1062 314 7.3 852 206 6.7 41 46 7.6 37
-------
was driven by a 1/6 HP motor resulting in an annual power cost of $100.00
based on $80 per horsepower year. Miscellaneous costs for septic tank
cleanout and approximately 1 hour per month for servicing would cost about
$200.00. Total annual operating costs, then, would be approximately
$300.00 or $O.035 per pound DOD.
3. Afolkey Coop Cheese Co., Afoikey, Illinois ( 5 ).
The Afolkey Coop Cheese Co. produces approximately 8000 pounds/day
of Italian Pizza cheese. Wastevater flows vary from 3600 to 9000 gallons
per day with an average DOD concentration of 3500 mg/i. Wastewaters are
generated from milk spillage and equipment washup. All milk is received
in bulk trucks. Cooling water is separately discharged and whey is hauled
to local farmers for livestock feed.
The wastewater treatment facility consists of an existing septic
tank, appropriately modified, an aerated lagoon, a quiescent lagoon, and
a sand filter (Figure 7). The existing 28,200 gallon three—celled septic
tank providing an average hydraulic detention time of 3.1 days (maximum flow)
was modified by the addition of paddle mixers placed within the first two
equal sized tanks. The slow speed mixers were operated through a timer
which regulated mixing for 15 minutes out of every two hours during times
when the plant flow was off. This agitation provides intimate contact of
anaerobic organisms with the raw wastewater. During periods of process
operation, the mixers are shut off so as to allow maintenance of high
concentrations of active biomass in the first two cells. The third cell
provides for quiescent settling prior to discharge to the aerated lagoon.
—38—
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The 10 foot deep aerated lagoon with a volume of 40,500 gallons
provides a hydraulic detention time of 4.5 days at maximum flow. Aeration
is provided by a 10 horsepower floating aerator located at the lagoon center.
Sludge, pumped from the quiescent lagoon may be returned to the aerated
lagoon to provide high bioinass concentrations if required. Although originally
uncovered, the aerated cell is now covered to reduce icing problems
during the winter season.
The 10 foot deep quiescent lagoon serves to provide for settling
and additional stabilization. This lagoon has a volume of 20,900 gallons
providing 2.3 days of detention time at maximum flow. A baffled overflow
weir is provided along the entire width at one end for effluent discharge
to the sand filter. The tank is equipped with a hopper bottom to allow
sludge collection and removal by pumping. This tank was initially covered
to eliminate excessive algal growths during the summer. (Figure 8)
The sand filter was added to provide some means of effluent
polishing. It consists of a 4 ft by 8 ft box approximately 12 inches deep.
Approximately 6 inches of “filter sand” is underlain by coarse sand and
pea gravel. Underdraln tile carry the filtered wastewater by gravity to
the receiving stream. The wastewater is applied at a maximum rate of 11.7
gallons/hr/sq ft (0.2 gallon/mm/sq ft). The filter is manually cleaned
when the headloss exceeds approximately four or five feet. A small layer
of old sand and sludge is removed and clean sand is added in this process.
Cleaning is required approximately every three or four days although shorter
periods of cleaning are required during periods of high solids overflow.
—39—
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Data on the performance of this plant is sketchy; the results of
two surveys are presented in Table VIII. The April 4, 1972, data was
obtained when the sand filter was not in use. Results of septic tank
performance are also presented in Table VII. These data were collected
prior to installation of the slow speed mixers in cells 1 and 2. There
is every indication from the data collected to date that the system will
produce a highly stabilized effluent well below the 30 mg/l BOD currently
required. It should be noted, however, that this performance is based upon
flows considerably less than maximum. The best estimate of flow during
the surveys reported was 3600 gallons per day, thereby resulting in detention
times in the treatment units as follows:
Septic Tank 7.8 days
Aerated Lagoon 11.2 days
Quiescent Lagoon 5.8 days
Sand filter 4.7 gal/hr/sq ft.
The capital investment in this plant in 1971 was approximately
$25,000 or $2780 per 1000 gallons of design capacity. Operation and
maintenance costs include approximately $1440.00 per year for power, $150
per year for septic tank pumping two or three times per year, and $10 per
day for plant maintenance. That amounts to approximately $4200 per year
or unit costs of $1.27/bOO gallons or $O.004/lb BOD based on maximum
design flow (9000 gallons per day at 3500 mg/i).
—40—
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TABLE VIII
Performance of Septic Tank—Lagoon System — Afoikey Coop Cheese Co.
April 4, 1972 October 20, 1972
Eat. Flow 3600 gal/day Eat. Flow 3600 gai/d
Eat. BOD 3500 mgIl Eat. BOD 3500 mg/i
Final Effluent — No sand filtration Final Effluent — Sand Filter
DOD 15 mg/i BOD = 6 mg/i
TSS 16 mg/i TSS 22 mg/i
pH8.i pH7.6
Nitrate N = 4.8 mg/i NH 3 —N — 0.13 mg/i
Kjeldahl—N 2.91 mg/i
Nitrate—N = 14.5 mg/i
COD 27 mg/i
Total Phosphorus—P 16.3 mg/i
Septic Tank Performance (Prior to Mixing)
BOD T.S.S. pH
mg/i mg/i
Dec. 1968
Cell 3 435 6.1
Jan. 1969
Cell 1 2070 930 5.4
Cell 2 1245 440 5.6
Cell 3 )760 370 5.6
Feb. 1969
Cell 3 815 560
- 40a -
-------
REFERENCES
1. Anon; The Cost of Clean Water , Volume III, Industrial Waste Profile No. 9 -
Dairies, Federal Water Pollution Control Administration, Dept. of the
Interior, Contract No. 14—12—102, June 30, 1967.
2. Birks, C.W. & Hynek, R.J., “Treatment of Cheese Processing Wastes”,
Proc. 26th Purdue Industrial Waste Conference, May 4—6, 1971.
3. Boyle, W.C. and Polkowski, L.B., “Treatment of Cheese Processing Wastewaters
in Aerated Lagoons”, Proc. Third National Symposium on Food Processing
Wastes, New Orleans, La., March, 1972
4. Cuip, R.L., and Culp, G.L., Advanced Wastewater Treatment , Van Nostrand
Reinhold Co., New York, 1971
5. Foy, Robt., Carl C. Crane & Assoc. Inc., Madison, Wisconsin — Engineering
Design of Afolkey Coop. Cheese Co 1 Wastewater Treatment Facilities.
6. Harper, W. James 6 Blaisdell, John L., “State of the Art of Dairy Food
Plant Wastes and Waste Treatment”, Second National Symposium on Food
Processing Wastes, March 23—26, 1971.
7. Romel, Jr., J.A. Foth, 6 Van Dyke, Green Bay, Wisconsin — Engineering
Design and Performance Analysis of Eller Cheese Plant Waste Water
Treatment Facilities.
8. A.T. Kearney and Co., Inc., “Study of Wastes and Effluent Requirements of
the Dairy Industry”, Water Quality Office, Environmental Protection Agency,
Cont. No. 68—01—0023, July, 1971.
9. Metcalf & Eddy, Inc., Wastewater Engineering , McGraw Hill, New York, 1972.
10. Nemerau, Nelson L., Theories and Practices of Industrial Waste Treatment ,
Addison—Wesley Publishing Co.
11. The Ohio State University, “Dairy Food Wastes and Waste Treatment Practices”,
Office of Research and Monitoring, Environmental Protection Agency,
Crant No. 12O6OEGU, March, 1971.
- 41 -
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Figure la
CONVENTIONAL ACTIVATED SLUDGE FLOW DIAGRAM
Figure lb
Contact Stabilization
Copied from Process Design Manual for Upgrading
Existing Plants , EPA Cont. No. 14-12-933.
RA M
IISTEUATER OR
PRIMARY EFFLUENT
Figure Ic
COMPLETELY-MIXED FLOW DIAGRAM
Copied from Process Design Manual for Upgrading
Existing Plants , EPA Cont. No. 14-12-933.
NT
Copied from Process Design Manual for Upgrading
Existing Plants , EPA Cont. No. 14-12-933.
RETURN SLUDGE
EXCESS SLUDGE
- 42 -
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Figure 2
Oxidation Ditch
MAMMOTH ROTOR AERATION
Figure 3
Rotating Biological Filter
CLARIFIER EFFLUENT
CHLORINE CONTACT
CHAMBER
SLUDGE DISCHARGE
SCOOP DRIVE
— EFFLUENT
Courtesy of Autotrol Corp., Milwaukee, Wisconsin.
Figure 4
Kent Cheese Company
Wastewater Lagoons
1€D 8UCI(ET
EEO
CHAMBER
INFLUENT
STAGES OcM D IA
SECONDARY CLARIFER
vz /
rSLUOGE SCOOP
I
CLARIFIER INLET—
2’
8 ...jq- H. .
43
-------
Figure 5
Kent Cheese Company Lagoons
Figure 6
Eilers Cheese Company
BlO-DISC Treatment Plant
SEPTIC TANKS FINAL EFFLUENT TO
AND FLOW EQUALIZATION RIVER
UNITS—, BUCKET ROTATING DISCS
FEED PUMP-, 4 STAGES CLARIFIER
S NTo®H -.fJIjJ1
BlO MODULE VAULT I
L CHLORINATION
L
SLUDGE TO PRETREATMENT UNITS
Courtesy of Autotrol Corp., Milwaukee, Wisconsin.
L
Aerator Placement
- 44 -
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Figure 7
AFOLKEY CHEESE COMPANY
MIXING
Wastewater Treatment Process
Figure 8
Afolkey Cheese Company
RAW
WASTE
STAGED SEPTIC TANK
AERATED
LAGOON
SLUDGE
RECYCLE
QUIESCENT
LAGOON
SAND
FILTER
L fT
- 45 -
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REPRINTS ON
FOREIGN PRACTICE IN TILE TREATI€NT OF
DAIRY WASTES
V
-------
FOREIGN PRACTICE IN THE TREATMENT OF DAIRY WASTES
rphe reprint information in this section of the brochure has
been reproduced with the permission of the Magazines or Journals
from which each was taken. Reprints were taken from the following
publications with the source of each article shown:
XVIII International Dairy Congress Vol. lE
International Dairy Federation
Square Vergote 141 - Bl0 1 40
Brussels, Belgium
Modern Dairy 51 #1 (1972)
Maccan Publishing Company
Box 366, Station F
Toronto, Onta±io M14Y 2L8
Journal of the Society of Dairy Technology, Vol. 25, No. 1,
January 1972
172A Ealing Road
Wembley, Middlesex, England
Food Manufacture 147 //5 (1972
Morgan—Grampian (Publishers) Ltd.
30 Calderwood Street
Woolwich, London S. E. 186 QH
England
-------
PRETREATMENT OF DAIRY EFFLUENT BY THE TOWER LU
SYSTEM
T. ft. ABUTON, A. J. OASTER
Express Dairy Co. Ltd., England
I. The high-rate biofiltration method for the treatment of trade effluents is
becoming more and more widely used in industry, but until recently there were few
installations of this type—i.e. the tower system—in dairies and creameries. Hence,
there is little experience of this method of treatment of dairy wastes or of its relative
merits compared with those of the more customary systems, which are largely based
on percolating filtration.
2. Some preliminary observations were made on three installations which are in
use in dairies in the United Kingdom.
3. At Creamery A the products manufactured were cream, milk powder, milk
. oncentr . tcs, cottage cheese and soft cheeses, at Creamery B they were milk concen-
trates, milk powder, cream and buttcr, and at Creamery C only yogurt, mainly of the
fruit-containing type, was produced. In all three installations, a 2-tower series arrange-
m nt with intermediate settling was adopted as a primary or “roughing” treatment
preceding secondary or “polishing” treatment by means of percolating filtration before
final settlement and discharge of treated effluent to a waterway. At Creameries A and
B adequate provision had been made for preliminary holding, in order to ensure as far
as possible minimum variations in HOD loading during the working day. During non-
productive hours arrangements had been made for re-cycling in order to maintain
consthnt irrigation of the system. At Creamery C, due to increased output of product,
the cipacity of the pretreated holding tank was insufficient, with the result that there
was little settlement and at times shock HOD loading of the system. Re-cycling was
also adopted in this case.
4 Data relating to the three installations is given below.
Creamery A B C
Design specification (m 3 Id) 1,140 910 546
Maximum flow rate (m 3 /hr) 47.7 38.2 54.6
Primary balancing Adequate Adequate Inadequate
Primary settlement Partial Adequate Inadequate
Operation flow rate (max) (m 3 /m 5 /hr) 0048 0062 0.070
Input BOD (ppm.) 1,200-1,800 800-1,800 1,000-1,200
Outflow ROD cx towers (p.p.m.) 250-300 70-150 200-300
Percentage reduction BOD 75-86 81-96 70-83
These summarized results indicate the comparative efficiency of high rate filtration
installations at three creameries. They illustrate that the efficiency of two installations
(at Creamery A and Creamery C) could be improved by providing adequate facilities
for settlement prior to the “roughing” treatment, and that at Creamery C there are
indications that the system will withstand shock loading.
5. The bios tower method has some merits as a first stage “roughing” process for
the treatment of dairy effluents. Some of the advantages are the comparatively low
constructional and operating costs, the relatively small ground area required and the
inert construction materials. In addition the efficiency in reducing BOD loading is
high with short recovery times after shock loading, and pending cannot occur.
9
XVIII International Dairy Congress Vol. 1E
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DISPOSAL OF DAIRY FACTORY EFFLUENT IN NEW ZEALAND A.12
R. r4. DOLBY
New Zealand Dairy Research institute, Palmerston North, New Zealand
I. Problems of waste disposal have increased in recent years duc to (a) concen-
tration of manufacture in largcr units, which has been made possible by tanker collection
and amalgamation of dairy companies, (b) more stringent regulations against pollu-
tion. A number of rivers have been “classified,” i.e. standards of water quality to be
maintaincd in each section, dcpcnding on uses, havc been laid down. The Watcr and
Soil Conservation Act 1967 required all uses and discharges of water to be registered.
Permits to discharge w stcs into classified waters or rights to dischargc elsewhere arc
subject to defined conditions designed to maintain the quality of the receiving waters.
Discharge of wastes into small streams is therefore restricted much more than that into
large rivcrs. Limitations on tcmpcraturc rise may preclude the discharge into small
streams of clean but warm water, e.g. condenser or cooling water.
2. A brief account is given of methods in use.
3 and 4. Types of wastes. Butter and milk powder factories offer only mild problems as
wastes are limited to plant washings, although hot water from drying plants may cause
problems where the volume of receiving water is limited. Whey from cheese and cascin
factories is a much greater problem. Cascin plants also discharge wash water at least
equal in volume to the milk received and containing whey equivalent to 10% of the
milk volume.
Uses Jot whey. In the Taranaki area a lactose factory processing 325,000 gal of whey
per day utilizes the whey from cheese factories in a large part of the province. Else-
where pig feeding is the principal use. The pig population however, cannot be rapidly
adjusted in numbers to correspond to the wide seasonal variation in milk production
usual in New Zealand (a peak in October-November with a fall to almost zero in May-
July). Consequently at least half the whey is surplus at the peak production period.
Very little whey is dried as the returns make the operation uneconomic except for
rennet casein whey.
Means of disposal. Only a few factories near large cities use municipal sewage facilities.
As the wastes from a large casein factory can be equivalent in B.O.D. to those from a
city of 100,000 the cost of a conventional sewage treatment plant would be beyond
the means of a dairy company. A few coastal factories arc able to discharge wastes
into the sça. For the majority the best solution is irrigation on pasture land, preferably
on a farm owned by the dairy company. A rate of application of 5,000-7,000 gal of
whey equivalent per acre once in 14 days as suggested by McDowall & Thomas (1)
has usually been found acceptable. The total volume of wastes per acre will depend
on soil permeability and rainfall. Damage to pasture has usually been attributable to
overdosing. With a well-managed system the increase in soil fertility and stock carrying
capacity of the farm makes a substantial contribution to running costs.
5. Irrigation on pastures has been found to be the most economical means of
disposal of dairy wastes in most parts of New Zealand.
Reference
(1) McDowall, F. H., Thomas, R. H.: NZ. Pollution 4th’. C un. PubI. No. 8 (1961)
10
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WATER POLLUTION BY FINNISH DAIRIES
I. Ln 1962 a new water law was passed in Finland. As a result, dairies started
active water pollution research. Measures taken included: prevention of unnecessary
discharge of milk residues or the first rinse water from butter, or whey, to the sewer,
burning of separator slime, and restriction of phosphate-containing washing material
to a minimum.
2. In 1967 the extent to which these measures had decreased the waste water
loads from dairies was investigated.
3. The study covered 52 dairies of different types, representing 16% of the
dairies and receiving about 30% of the milk produced in Finland. The studies were
undertaken during the pasture-feeding period and again during the indoor feeding
period. For sampling, the discharge pipe of the dairy was closed, and all the waste
water was measured. From it, single samples were taken, and these were blended in
proportion to the amount of waste water to give the test sample. Cooling water was
not included. The results of the investigations are given in the table.
The population equivalents (75 g BOD ) per 1000 kg milk were 16, 17 and 30 for
market milk, butter and cheese factories respectively. It appears that the measures
taken for reducing the waste water discharge from dairies have been appropriate,
especially in regard to butter and cheese dairies.
The total loading caused by dairies is about I % of the waste water load of Finland,
and the phosphorus loading corresponds to the waste water from about 60,000 inhabi-
tants.
5. Some dairies have a purifying plant of their own, and attempts are also being
made to purify most of the waste water from dairies in regional or other communal
purifying plants, reducing the phosphate as well as the organic load.
11
M. SARICKA, J. NORDLUND, M. PANKA OSKI, M. HEIKONBN
Waler Pollution Control Office, Helsinki
Vallo Finnish Co-operative Dairies’ Association, Laboratory of Valio, Helsinki, Finland
A.12
pH
Conductivity 8 /uS
KMnO 4 mg 02/I
Suspended solids mg/I
Residue on evaporation mg/I
Residue on ignition mg/I
SOD 5 mg/0 2 /1
TotalN mgN/l
Total P mg P/I
K 2 Cr 2 O 7 mgO 2 /l
Org C. mg C/I
Protein mg/I
Sugars mg/I
Detergents mg TBS/l
Milk received 1000 kg/day
Waste water, CU m/ 1000 kg milk
Composition of waste water from
Market milk dairy Butter factory Cheese factory
8.5 8.1 8.4
608 611 1090
258 340 641
271 354 306
1069 1158 2192
349 395 801
713 873 1045
52 51 52
12 13 15
1157 1316 2451
434 512 723
288 324 423
252 300 931
4.0 2.7 2.6
33.0 40.2 82.0
1.61 1.63 2.3
—3—
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COMPOSTINO OF NON-FEEDADLE WHEY AND OF SLUDGE £1.2
FROM EFFLUENT TREATMENT PLANTS
M. SYOSODA
Dairy Research Institute, Department of Water Management, Brno, C zechos lovakia.
I. Unless all whey from cheese factories can be regularly returned to farms for
feeding purposes, a surplus may be h:ld at the factory. It will deteriorate rapidly and
must be disposed of into farm dung-water (I) or into isolated quarries or sandpits or
on to pastures. There is always danger that such whey will be directed into the sewerage
system or into streams.
Disposal of sludge from effluent treatment plants is also a problem. In large plants it is
digested, or concentrated, precipitated and dried, or burnt. For small plants sludge
is digested or dewatered on sludge b ds, but digestion lowers the N content by only
40% and dewatering is slow and givcs offensive odours.
2. Studies were made of the effectiveness of disposing of old whey by composting
it on peat (2), and of the accelerated dewatering of sludge (3).
3. A site was selected which would not endanger spring- or surface-waters.
Fresh fibrous peat meal was formed into a composting bed 70 cm high. Old whey was
sprinkled over the surface. As the peat compacted the depressed crown of the bed
allowed whey to be emptied into it. This was continued as long as the compost absorbed
the whey. Absorption capacity was increased if the body of the compost was covered.
When the limit was reached the compost was re-bedded and application of whey was
eontinued.
Peat composts for dewatering effluent sludge were established in the subsoil. The sludge
was applied to a pan formed in the crown. After 3-10 days, according to the weather,
the dewatcred sludge was removed, taking some peat with it. (Roofing of the beds
increases their efficiency). This lowered the middle of the bed, leaving the sides. When
all peat was removed from the middle, the whole was it-worked.
Several such beds were used in rotation. The peat was loosened in the new surface
after every removal of sludge. The removed sludge was further composted separately.
4. By the composting, the pH of the peat was increased from 3.6 to 6.5-7.8,
total N rose from 0.62 to 0.86—2.3% (on dry matter), moisture rose from 51 to 81% ,
and absorption capacity fell from 7.6 to 1.6. Application of whey caused a drop in
temperature but after 2 days this rose to SOC.
Theft were no offensive smells. Under the conditions 1500 kg raw peat was sufficient
for 40,000 1 whey. Costs were one-sixth less than those for transporting the whey.
If the compost can be sold as fertilizer at a good price, there are economies of 60%
or more. The compost contains 0.8-3.3% N, 1.1-2.3% P 2 0 5 , 0.4-1.1% K 2 0, 57-79%
organic matter. /
5. The peat compost beds provide an effective method of treatment. Their
capital cost for a 60,000 I/day milk plant are half those for sludge digester or sludge
beds.
References
(1) Rinn, M.: Dte Molk.-Ztg. 83 (48) 1953-1955 (1962)
(2) Svoboda,, M.: Czechoslovak Patent No. 98095 (1961)
(3) Svoboda, M., Salplachta, I. : czechoslovak Patent No. 96227 (1960)
12
-4—
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PRELIMINARY RESULTS OF COMPARATIVE INVESTIGATIONS A.12
ON TREATMENT PLANTS FOR FACI’ORY EFFLUENT
B. LYTKBN, K. CHIUSTBNSBN
The Government Research Institute for the Dairy Industry. HlIIerØd. Denmark
I. In chemical and physical respects, dairy effluent differs so much from ordinary
sewage that conventional biological treatment plants are often considered unable to
purify dairy effluent in a satisfactory manner unless it is first mixed with substantial
quantities of sewage. However, in many cases this is not possible, and therefore some
dairy factories may have difficulties in ensuring satisfactory purification of their effluent.
2. In order to solve the problems of such factories, information had to be sought
on the bcst way of treating dairy effluent when unmixed with other waste waters.
3. Comparative investigations of the purification of dairy effluent were started
in October 1968 using different types of plants constructed for this purpose near the
Institutc.
The dairy effluent was collected in an open levelling tank of 250 cu m, from which
it was distributed to: (a) a recirculation filter containing 30 cu m of broken granite,
and a clarification tank of 10 cu m; (b) a plant for alternating double filtration
consisting of two filters, each containing 30 cu m of broken granite, and two clarifica-
tion tanks of 10 cu m each; (c) an activated sludge plant with an aeration tank of
100 Cu m and a clarification tank of 15 cu m; (d) a lagoon plant Consisting of an
anaerobic pond of 130 cu m followed by three aerobic ponds with a total surface of
500 sq m and a volume of 200 cu m.
4. The results of the first year wcre as follows: the average 80D 5 of the inflow
was 517 mg 02/1. During the year the hydraulic load of the recirculation filter was
increased from 24 to 39 cu rn/day, and the recirculation factor was reduced from 10
to 6. The organic load was 530 140 g BOD 5 /cu rn/day. Removal of SOD 5 gradually
increased from 70 to 90%. The hydraulic load of the alternating double filters was
gradually increased from 42 to 58 cu m/day. The organic load was 440 ± 110 g
BOD 5 /cu rn/day. The order of the filters was changed each week. In the course of the
year the removal of BOD 5 increased from 70 to 90%. The hydraulic load of the
activated sludge plant was gradually increased from 26 to 46 cu rn/day corresponding
to an increase of the organic load from 13 to 22 kg BOD 5 /day. Removal of DOD 5
remained at a constant percentage of about 95. The precipitation of the sludge was
periodically poor. Due to freezing and seeping the lagoon plant was not in regular
operation. In a few cases of organic overloading the filter plants proved more resistant
than the activated sludge plant.
5. When the sizes of the plants are taken into account it is evident that more
effluent could be treated by recirculation filtration than by alternating double filtration
with similar removal rates of BOD 5 . The latter at no time proved entirely satisfactory.
The activated sludge plant had at all times a satisfactory effect.
13
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OXYGEN UPTAKE OF FACTORY EFFLUENTS A.12
K. CHRISTENSEN
The Government Research Institute for use Dairy Industry, HiIlerØd, Denmark
I. The pollution of dairy effluent is commonly expressed by its 5-day biochemical
oxygen dcmand, BOD 6 . This is traditionally obtained by the dilution method. A new,
less laborious, method consists of direct rcspirometric measurement of the oxygen
uptake of the effluent. This principle is used in the Sapromat apparatus (J.M. Voith
G. rn b. H,) which records hourly the amount of oxygen added to maintain atmo-
spheric pressure above the surface of effluent in a flask.
2. This investigation was undcrtakcn to determine whether the dilution method
can be replaced by Sapromat-determinations for dairy effluent. The rate of oxygen
uptake of dairy effluent and its constituents was investigated to provide information for
work on treatment of dairy effluent by different methods.
3. Parallel determinations of BOD by the Sapromat-method and by the dilution
method were made on effluents from various dairies and from treatment plants for
dairy effluent. In addition Sapromat-determinations were made on various dairy pro-
ducts.
4. For effluents from various dairies, with BODa values between 70 and 1700
mg 02/1, the Sapromat-results were on the average 1.3 ± 0.2 times the results by the
dilution method.
Fresh samples of dairy effluent after 1, 2, 3 and 4 days in the Sapromat showed oxygen
uptakes of on the average 10. 50, 78 and 91% of the B0D , respectively. There was
an induction period on the first day, maximum oxidation on the second and third day
and thereafter the oxidation rate decreased. Continuation o the analyses for one week
showed an increased in the oxygen uptake of about 15%.
If samples, properly seeded and with pH adjusted to 6-8, were kept some time before
analysis a kind of maturation occurred, and the maximum oxidation rate was reached
sooner, but after 3-4 days the stored and unstored samples showed almost the same
oxygen uptake.
Sapromat-analyses on whey, skim-milk and whole milk gave average BOD 5 values of
58,000, 90,000 and 155,000 mg 02/1, respectively. Continuing the analyses for one
week showed an increase in the oxygen uptake of about 12, 15 and 18%, respectively.
As the theoretical oxygen demands arc about 2.8 g 0 2 /g fat, 1.7 g 0 2 /g protein and
1.1 g 0 2 /g lactose the results correspond quite well with the composition of the pro-
ducts. Compared with skim-milk the whey is decomposed faster and whole milk slower,
indicating that, compared with protein, lactose is decomposed faster and fat slower.
Sapromat-determinations on effluents from plants purifying dairy effluent to different
extents were on average 30% higher than the corresponding results by the dilution
method. Extending the time in the Sapromat by one week increased the oxygen uptake
by about 15%.
5. The BOD 5 values found for dairy effluent with the Sapromat were 1.3 ± 0.2
times the values found with the dilution method. The standard deviation is attributable
chiefly to the inaccuracy of the dilution method, and the Sapromat-values can be con-
sidered quite reliable, although 30% higher.
The Sapromat-determinations showed that fresh dairy effluent is not decomposed ap-
preciably by a short aeration. It is important to note that, although the oxygen uptake
during the first days was higher for stored samples than for fresh ones, the final
BOD,’s of fresh and stored samples were almost identical.
14
—6—
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BIOCENOSIS IN DAIRY WASTES PURIFICATION PLANTS A.1.2
.1. OILLAR
Dairy Research Institute, Department 0/ Water Management. Draw, Czechoslovakia
1. Several dairy waste purification methods have been successfully tested in
Czechoslovakia. These are single-stage fermentation (1, 2, 3, 4), high trickling filter
(5, 6), set of stabilization lagoons (7), assimilating (oxidation) pond (8), activated
sludge (9), and oxidation ditch. A complete study of these processes included com-
parison of their economics (10).
2. The studies here reported were concerned with the chemical and biological
aspects of the processes.
3. Analyses covering physical, chemical, bacteriological, and biocenological
aspects wcrc carried out at selected treatment plants. Results were compared and
connections established.
4. In laboratory and semi-pilot single-stage fermentations, two types of I So-
cenosis were found: yeast and flagellate. These arise and persist according to conditions
of operation, particularly concentration of effluent and pH, suggesting that control of
such factors could give higher efficiency. In full-scale plants there was also Found an
exponential relationship between the volume of introduced air and the count of
Diplostornarinne flagellates.
In high trickling filters the biological films were compact and thick but through-flow
was good. The films consisted mainly of zoogloea bacteria. Only rarely were filarnental
bacteria of the genus Beggiatoa not present, then being replaced by the mycelia of
Deuterosnycetes. Flagellates were common, particularly with heavy loading, which also
affected infusorians. Best purification is accompanied by the development of meso-
saprobic organisms, particularly infusorians.
Activated sludge in tanks or ditches typically contains the filamental bacteria Sphae-
rotihis, which disappear only with highly aerobic stabilization, flagellates increase with
heavier loading. Pcritricha are an index of good purification and low 8.0.0. of output.
The relation between numbers of infusorians of families .4nipliileptidae and Trachelidae
and the age of the sludge may be an index of the degree of aerobic stabilization of the
sludge.
Stabilization lagoons have three reservoirs, the first or bacterial zone, in which the
liquid is grey-black and putrid, is anaerobic. Biocenosis is hypersaprobic in winter,
polysaprobic in summer. The second or phyto plankton zone is coloured by the micro-
vegetation. Biocenosis is between poly- and alpha-mesosaprobity. Green algae and
cryptomonades predominate. The third or zoo plankton zone has clear water, develops
only in summer and is needed for maximum purification. The crustaceoplankton,
especially large cladocera are characteristic.
5. Study of biocenosis in waste water treatment can lead to more efficient opera-
tion.
References
(1) Svoboda, M., Salplachta, .1.: Czeclsoslovac Patent No. 96 226 (1960)
(2) Svoboda, M., Salplachta, J. etc.: Pruan. Potravin 14 (4) 193-197 (1963)
(3) Svoboda, M., el al.: Prum. Potravin 18 (7) 342-351 (1967)
(4) Gillar, I., Marvan, P.: Sc !. Pap. Inst. Chetn. Tech., Prague 8 (2) 221 (1964)
(5) Svoboda, M., et al.: XVlII mt. Dairy Congr. F 723-734 (1966)
(6) Salplachta, I., Gillar, J.: Prum. Potravin 19 (6) 324-330 (1968)
(7) Svoboda, M., et al.: XVIII 1n1 Dairy Congr. F 7 15-722 (1966)
(8) Gillar, J.: Vodni hospodarstvi, B 19 (4) 112 (1969)
(9) Bunesova, S.: Pram. Potravin 16 (10) 506 (1965)
(10) Svoboda, M., et at.: Pram. Potrav ln 28 (6) 182-188 (1969)
15
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ECONOMY OF DAIRY WASTES DISPOSAL IN CZECHOSLOVAK
A.12
DAIRY PLANTS
M. SVOBODA, J. GILLAR, J. SALPLACHTA, M. HLAVKA
Dairy Research Institute, Department o/ Water Management, Brno, Czechoslovakia
I and 2. We have tried, as far as it has been possible, to apply all methods of dairy
wastes purification that would give statisfactory results in Czcchoslovak dairy factories.
In recent years we have endeavoured to evaluate these purification plants in the
technological-economical sense (1). The aim of these studies was to find suitable
purifying methods for future application under varying conditions in Czcchoslovak
dairy factories.
3. Eleven dairy emucnt purification plants were studied during at least two
seasons. Physico-chemical, bacteriological, hydrobiologicil and economic aspects were
taken into consideration.
To make comparisons clearer, additional costs incurred because of unusual local condi-
(ions, e.g. distances, were deducted from capital expenditurcs. Operating costs were
based on the average charge for electric power. As in Czechoslovakia thc pollution of
water streams is subjcct of payment of indemnities fee, the average indemnity charges
actually paid by the factories in the period concerned served as a basis for the estima-
tion of anticipated costs if a purification plant was not installcd. In this way it was
possible to estimate the return on investment.
The methods of treatment studied wcre:—intcnsjve aeration, single stage fermentation,
stabilization lagoons, tower trickling filter, activated sludge with mechanical aeration,
assimilation pond and oxidation ditch.
4. ft was found that the operating costs in each purification plant were mostly
influenced by the cost of labour, by charges for electric power and by amortization
of equipment. All these costs varied depending on the method and type of purification
plant used. Amortization charges accounted for Ca. 50% of all operating costs.
Relatively large differences were found in costs per 1 kg SOD 5 ranging from 0.47
to 9.52 Kcs and depending mainly on different organic load and volume of wastes
actually treated.
Also depending on the method used the time for return of investment ranged from
3.5 years for the stabilization lagoons and activated sludge process with mechanical
aeration to 17.5 years for th assimilation pond.
5. The following purification processes appeared from these studies as most
economic :—stabilization lagoons, assimilation pond, activated sludge and oxidation
ditch. Which of the processes should be used depends largely on the location of the
factory and the topography of the available terrain.
The assimilation ponds and the lagoons require many hectars of surface area and the
oxidation ditches some hundreds of square metres. This limits their use to factories
situated in open country. The activated sludge process can be used, with minimal
protective hygienic zone, in partly populated localities.
Reference
(I) Svoboda, Metal: Prum. pot,’avln. 20(6)182-186(1969)
16
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8ASIS FOR THE COSTS OF SEWAGE IN PUBLIC A.L2
SEWAGE-TREATMENT
IL SCHULZ-FALKEbIHAIN
B uderich be! Dlisseldor/, Federal Republic oF Germany
I. Wasics and rain-water from dairies are often led to public sewage plants.
These may be plants for sewage diversion and for sewage-treatment. The plants for
sewage diversion consist of a network of pipelines for sewage and a similar one for
rain-water. They may also only have one network of pipelines, through which sewage
as well as rain-water is drained. Owners of these plants are communities, cities and
sewage-associations.
2. For the drainage of wastes and of rain-water into public plants the dairies
have to bear the actual costs incurred by them. This applies equally for the sewage
of all other properties including private housing. Social factors are not taken into
account. For the draining of sewage and of rain-water, annual payments, as well as
single payments and annual payments are demanded; the single payments can be
considered as annual payments in another form.
3. The costs, which result from the draining of sewage and of rain-water into
the public plants are quite different according to whether pipeline connection or
sewage-treatment is involved. With pipeline connection of waste waters, the costs are
determined mainly by the length of the pipelines and thus by the size-of the properties.
The quantity of waste water influences the costs generally only very little. The cost
for rain-water connections depend on the length of the pipelines and the size of the
properties and also on the highest quantity of rain-water drained away in a second.
The quanttty of waste water treated is of importance in determining the costs of the
sewage-treatment. When rain-water is also treated, part of the costs are attributable
to rain-water. The nature of the wastes can influence the costs of sewage-treatment.
4. The standards for the calculation of costs, which are demanded from dairies
for the connection of wastes and of rain-water to the public sewage disposal plants
are very different. In some cases, the quality of sewage treated is used as the only
standard. In most cases, a degressive cost calculation is also taken into
account. The amounts charged for connection only are calculated on the same basis.
According to these standards, the dairies are required to pay disproportionately high
amounts, compared with private householders. The costs for sewage-treatment are
of ten calculated according to the quantity of sewage. If there are additional costs
based on the nature of the wastes, this will partly be taken into account by quantity
factors.
5. Correct payments for the connection of wastes and rain-water to public
plants, based on the actual costs incurred, can be determined if the total costs for
public sewage plants are divided into the costs for waste water connection, rain-
water connection, waste-water treatment and rain-water treatment.
The size of property is a main factor for determining waste water connection costs
and the volume and nature of waste water are major factors in determining waste
water treatment costs. In the case of rain-water, the size of property as well as the
maximum quantity of rain-water drained per second are major factors. To this must
be added possibly pan of the costs of waite water treatment.
17
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Effective techniques available
Biological treatment of dairy wastes
by Harvey Mitchell, Eng.
Because of the nature of dairy
wastes, biological treatment
is more suitable than either
physical or chemical methods.
This article reviews several
alternatives available for
use in a modem dairy plant.
Thc dairy industry is a very divers-
ified one as far as size of plants and
type of products are concerned. Dairy
wastes consist mainly of various dilu-
tions of whole milk, skim milk, but-
termilk and whey, together with
washes containing detergents, nitric
acid, caustic and other chemicals as
well as sterilizers such as ammonia
and javcl water. Process washes of
cheese, cascin, butter and other prod-
ucts arc also included.
Table I shows the average com-
position of different dairy products
and Table II gives the average vol-
umes and strengths of wastes prod-
uced in different types of plants.
Dairy wastes are generally high
in dissolved organic matter and bio-
chemical oxygen demand (BOD),
which is defined as the amount of
oxygen required by bacteria while
stabilizing decomposable organic
matter under aerobic conditions. The
standard BOD test carried out in 5
days at 20°C is used to determine
the pollutional strength of wastes in
terms of watercourses in which aero-
bic conditions exist. Domestic sewage
has an average BOD of 225 ppm.
Importance of water quality
Water is extremely important to
the dairy industry and the quality of
the water used in washing milk hand-
ling equipment and in cooling dairy
products has a direct bearing on the
quality of the final products.
In order to meet the requirements
of the modern dairy system, the
water used should have the charac-
teristics shown in the accompanying
box.
The selection of a treatment plant
depends on the type, size and loca-
tion of the dairy.
Since dairy wastes are composed
of soluble organic materials, biologic-
al treatment is more suitable than
either physical or chemical methods.
The successful operation of a bio-
logical system depends on prevent-
ing the mixing of the wash waters
with soiled milk as well as by-prod-
ucts such as whey and buttermilk.
Standard practice is to recover these
by-products which are then used as
livestock feed, etc. The minimization
of chemicals and detergents is also
important, as excess alkaline or
quaternary ammonium base deter-
gents will raise the pH of the effluent
and impair biological purification.
Suspended matters contained in
TABLE I — COMPOSITION OF DAIRY PRODUCTS
the wash waters are usually removed
by a fine screen. In receiving sta-
tions, provision is made to further
remove the sand brought in by the
milk wastes, especially during the
winter and rainy season.
Because of the wide fluctuations
in the waste volume and composi-
tion, a holding and equalization tank
is necessary to stabilize the effluent
flow and pH. The retention time of
non-aerated holding tanks should be
limited to 2 hours in order to prevent
acid fermentation with a resultant
increase in BOD.
A pretreatment consisting of a
fine screen, degritter, aerated holding
tank, and sedimentation can reduce
the BOD by 15-20% and suspended
matter by 60%.
CHARACTERISTICS REQUIRED IN WATER USED BY DAIRIES
1. SufficIent quantity — enough water must be available every day through-
out the year. Failure of the supply, such as during a drought or freezing
weather, has serious consequences in milkhouse sanitation Sanitary
care of milk handling equipment is an everyday must and when water is
scarce, sanitation suffers.
2. Cleer. colourless, good taste, relatively soft — soft water requires iess
detergent and gives better cleaning. Dirty water results in dirty utensils.
Milk is susceptible to off flavours; poor tasting water does not help
3. Free from hamful bacteria, yeast, and moulds — unsafe water may
cause disease. Some bacteria cause rancid flavours in milk, while others
can cause bitter, fruity and/or other unpleasant flavours Yeasts and
moulds also contribute to flavour defects of milk products.
4. Non-corrosIve water — corrosion shortens the life of piping and water
heaters Copper and iron dissolved from piping by acid water may cause
oxidized flavours In milk products.
5. Nonscale-forming water — scale may clog pipes, faucets, boilers and
water heaters’”
• Mr. Mitt hell is manager of the Industrial
l)i%1.cion of Degremont Canada Ltd.,
hiontreal.
Water
%
Fat
%
Lactose
%
ProteIn
%
Ash
%
BOO
ing/1
Whole Milk .
90—91
3.5—4
4.7—5.2
3.2—3.7
0.8
120000
Slum MIlk . .
90-41
0.1
4.9
3.6
0,8
75,000
ButtermIlk. ...
90—91
0.3—0.5
3.9—4.4
(lactic
add-0.6)
3.5
0.7
70,000
Whey....
93—94
0.2—0.8
4.5—5
0.1—0.3
0.5—0.7
42,000
Modern Dairy 51 #1 (1972)
— 10 —
10
-------
To understand the special prob-
leni involved in biologically treating
dairy wastes, it is important to study
the metabolism of the two ferment-
able elements: lactose and proteins.
The lactose is in solution and
thcreforc cannot be eliminated by
precipitation or flocculation.
The proteins (casein, albumin,
globulin) arc in the form of sus-
pended matter or colloids and can
be eliminated by chemical treatment.
Lactose is a sugar having a form-
ula C, H 22 0 11 which is transformed
by fermentation into lactic acid ac-
cording to the following reaction:
Cl2 H22 Oil +H20—
4 CH3 — CHOH-COOH
Lactic acid is then transformed
into different end products depend-
ing on whether aerobic or anaerobic
(absence of air) conditions exist.
Under aerobic conditions, the end
products arc water and carbon diox-
ide:
CH 3— CHOH — COOH + 30 -
3C0 , + 3H ,O
Under anaerobic conditions, the
end products arc methane and car-
bon dioxide:
2CH 3 — CHOH — COOH -+
3C0 1 +3CH 4
Aerobic fermentation of proteins
results in the formation of amino
acids and ammonia, which is then
oxidized to nitrites and nitrates.
Anaerobic fermentation results in
odorous products such as amines,
ammonia, hydrogen sulfide and mer-
captans.
Difficulties faced
The formation of lactic acid re-
suits in a lowering of the pH. Be-
cause the aerobic decomposition of
proteins and lactose derivatives can
only occur at a fairly neutral pH,
waste waters, containing more than
I % lactose cannot be biologically
treated by aerobic means.
Waste waters containing 1000-
5000 ppm lactose are also difficult
to treat by classic biological methods
because the lactose induces the for-
mation of a flora essentially com-
posed of filamcntous bacteria having
a low purification capacity, and re-
sults in bulking of activated sludge
plants and blocking of trickLing
filters.
Biological treatment
The four conventional methods
generally used are irrigation, lagoons,
trickling filters and activated sludge.
Irrigation and lagooning can be
used in certain cases but, generally
speaking, they are not too economic-
al because of the land costs result-
ing from the large surface area re-
quired (1000-2000 USG/acre/day)
to handle the concentrated wastes.
Furthermore, the type of soil avail-
able and the climatic conditions may
adversely affect the selection of this
type of treatment.
The trickling filter and activated
sludge processes are similar in princ-
iple in that both depend on bio-
chemical oxidation of organic mat-
ters.
Trickling filter
The trickling filter contains a
medium, such as crushed rock or
a specially manufactured plastic,
which becomes coated with zooglca,
a viscous jelly-like substance con-
taining bacteria and other biota.
Under favourable environmental con-
ditions, the bacteria absorb and
break-down the suspended, colloidal
and dissolved organic matter from
the sewage.
Experience has shown that using
a single filter results in a large bio-
logical growth which blocks the
filter. BOD reductions of 75/80%
have been obtained with organic
loading of 40 lb BOD/l000 cu.ft/
day. However, high-rate two-stage
recirculating filters have produced
greater than 90% BOD removal.
For example, two-stage recirculat-
ing filters handling an organic load-
ing of 74 lb BOD/I000 cu. ft./day
reduced the influent BOD from 1690
ppm to 140 ppm (92% reduction).
Since the efficiency of trickling
filters is a function of the tempera-
ture of the waste, the quality of the
TA8LE It — DAIRY WASTES
Volume: Gal. per 1,000 lb. milk
Intake per day
Total solids, ppm
I /
.1
• ‘ : , .-- -
- .. — . - -. — -.
, •• ,•
- ., :....
- . . - .- 1
:
- - ‘
‘ )
. - ___
Typical oxy-conlact combined lank high-rate activated sludge system
at Si-Janvier, Quebec.
Receiving
Station__—
Bottling
Works
Cheese
Factory
1150
175
250
200
110
1
Creamery Condensery Dry Milk
1550
2400
150
2800
2400
Suspended solids, ppm
—
550
750
650
750
—
500
BOO, ppm
500
500
1000
1250
1300
pH
—
5
7
8
8
Nature of waste
Whole milk
washings
Whole milk
washings
Whey, casein,
washings
Butter-
milk, washings
Spoiled-milk
washings
Spoiled-milk
washings
Modern Dairy. January. 1972
— 11 —
11
-------
plant effluent deteriorates under
winter climatic conditions.
Although the effect of icing on
the filters can be reduced by sever-
al methods, covering the units is
considered mandatory.
Activated sludge method
Activated sludge is a proven
method of treating dairy wastes with
BOD reductions of 85-95%. The
BOD represents food for micro-
organisms which break down the
organic matter under acrobic con-
ditions into waste sludge and end
products such as CO and HO.
For small installations, a total
oxidation system can be economic-
ally used with a prolonged aeration
period minimizing the wastage of
sludge. An aeration volume of 480
USG is required for each pound of
SOD.
As the size of the plant increases,
it is less economical to consider total
oxidation and the aeration time is
therefore reduced.
For average size installations, an
aeration volume of 120 USG is used
per pound BOD. The excess sludge
is aerobically digested.
For installations larger than 450
lb.BOD per day, the aeration volume
is reduced to 60 USG per pound
BOD. Primary clarification may be
used ahead of the secondary activ-
ated sludge system. The waste sludge
from the primary and secondary
clarifiers can be anaerobically di-
gested.
The activated sludge process can
be carried in separate aeration and
settling tanks or more economically
in high-rate combined aeration-set-
tling tank units.
Government regulations
Regulations concerning d a i r y
wastes vary from province to prov-
ince. The Quebec Water Board re-
gulations of December 22, 1969
state the following:
1. It is forbidden to discharge dairy
by-products such as skim milk,
buttermilk, whey, etc. into a re-
ceiving body of water.
2. Because the BOD of the waste
waters are 3 to 5 times that of
domestic sewage, an aerated hold-
ing tank must be installed. This
tank may not be required:
a)—where the organic charge is
less than 20% of the total
organic charge discharged
into a municipal or private
sewer, or
b)—where the wastes are dis-
charged into a secondary
treatment plant.
Joint treatment
There are many advantages to the
consideration of joint sewage treat-
ment with a municipality. However
each case must be studied separately.
As an example of combined sew-
age treatment, a ‘Rapid-Bloc’ com-
bined-tank high rate activated sludge
plant was installed at Saint-Jean-dc-
Dieu, Quebec, to handle a combined
municipal and creamery waste hav-
ing the design characteristics shown
in the accompanying box.
We can see from these figures that
although the creamery wastes con-
tribute 9.3% of the total volume,
the BOD loading is 39.6% of the
total.
The average BOD of the com-
bined wastes is 305 ppm. The re-
quired effluent is 20 ppm which
corresponds to a 93.5% BOD re-
duction.
The aeration volume is 28,200
USG (equivalent to 57 USG per lb.
BOD) and theretention time at aver-
age flow was 3.4 hours.
The settling zone operates at 785
USG/sq.ft./day and has a surface
of 252 sq.ft.
Excess sludge was air-lifted to an
aerobic digester zone having a vol-
ume of 59,000 USG (10 days re-
tention time).
Air requirements are 1600 cu.ft./
lb BOD which gives 523 cu.ft./min.
based on the elimination of 471.8
lbs BOD/day.
The effluent was chlorinated in a
chlorination zone of 4150 USG (30
minutes retention time) before final
discharge.
Operating results have been satis-
factory and BOD and suspended
solid reductions of over 90% have
been obtained.
1 MerrilI E. P. and Arnold, B. L. 1963.
Farm water supplies. Co-op. Ext. Ser.,
University of Vermont, Cir. 133.
S DENMARK S ENGLAND• FRANCES HOLLAND S INDIA S ITALY S JAPAN• NEW ZEALAND S SPAIN•
Ask for Bulletin A346
APV CANADA EQUIPMENT
U ,
0
The Whole World is talking about
C
.4
I — — — — — — — — — — — — — — — — — — — — — — — —
The APV PUMA PUMP
COMPLETELY SANITARY
STAINLESS STEEL .
m
HIGH SPEED — RELIABLE z
C
LTD 103 RIveld. Road, W..ton, Ont.
5775 M.t, oIkoa Blvd., St. Loaasrd, Quo.
CHARACTERISTiCS OF ACTUAL COMBINED
SEWAGE TREATMENT PLANT
Loading:
Municipal — 1750 people x 0.17 lb BOD/person/day 297.5 lb BOD/day
Creamery — 18,000 USG/day x 1300 ppm x 10’ x 8.33 lb/USG —
195 BOD/day
Total : 492.5 lbs. BOD/day
Flow:
Municipal — 1750 people x 100 USG/person/day 175,000 USG/day
Creamery — 18,000 USG/day
193,000 USG/day
-l
N
S
0
-a
I ”
S
..a
p.-
In
12
— 12 —
-------
Eighth paper
THE TREATMENT OF CREAMERY
AND YOGHURT EFFLUENTS
BY A. J. OASTER
Technical Adviser. Express Dairy Foods Ltd.
Effluent treatment has received much publicity in
recent years. In the dairy industry there have been
technical advances in treatment systems, all point-
ing to a greater realization that pollution is very
much today’s problem. In the vast amount of
technical literature on effluent treatment there is,
however, very little information on the design and
performance of effluent plants.
This paper sets out to compare the treatment
system design of five creameries; four of which arc
concerncd with a wide range of milk processing
operations and the fifth solely with the production
of yoghurt. It is necessary at this stage to draw
distinctions between these two types of effluent for
whereas creamery effluent contains fatty matter
from operations involving milk reception, cream
production, condensing. buttermaking, cheese-
making and drying, the effluent from yoghurt
mar .ufacturc has comparatively little fat but a
larg r percentage of non-fatty solids and fruit pulp.
I have made no mention of bottling dairies or
creameries with operations outside those outlined.
e.g. casein plant.
One obvious prerequisite of any treatment
scheme is good housekeeping within the factory.
The MAMPTAC (1969) report illustrates this
quit clearly. Often the most difficult starting point
in the design of a new effluent plant is assessing the
volume and strength of the waste from the factory
with any degree of accuracy.
Another relevant factor is the cost of water, often
considcrcd to be low in comparison with the cx-
pen e of effluent saving schemes. Perhaps in the
not too distant future water will be strictly con-
trolled and the use of treated effluent to provide a
reclaimed water supply for pre-rinsing, floor wash-
ing. etc. will become commonplace (Priestly. 1970;
Anderson, 1970). There is also the associated
danj er that river authorities will ask for increas-
ingl: stringent standards which would result in a
tertiary treatment system such as sand filtration,
chlorination or even reverse osmosis becoming
necc ssary.
What then is required to provide the basic
information necessary to design a treatment
system? Experience has shown that for each gallon
of milk processed about 2’5.-4O gal effluent are
produced. the ratio for yoghurt being somewhat
higher. This will establish, within limits, the ex-
pected throughput for a particular creamery. It is
more difficult to find out useful BOD data as these
depend largely on the particular processes in-
volved. Creameries without chccsemaking opera-
tions tend to have lower average BOD. some actual
figures being shown in Table 2.
Once obtained, the data on concentration and
volume will be sufficient to give information about
the design loading, expressed together as lb BOD
or kg BOD. All other factors such as pH. tempera-
ture and maximum hourly rates are determined at
a later stage. Sometimes, as was the case in two of
the creameries under consideration, the need is not
for an entirely new treatment plant but an exten-
sion or modification of an existing system. The
ease with which the desired information can be
obtained will of course depend on the metering
and sampling facilities available. Often where an
existing plant is in trouble and River Authority
supervision has been close, the creamery will have
kept stricter laboratory control and hence more
data will be available.
It is now necessary to consider in detail the
requirements for a treatment system discharging to
a water course at Royal Commission standards.
Dairy effluents are normally treated by a biological
oxidation process whereby the pollutants are
broken down to form a sludge of oxidized matter.
leaving a comparatively clear liquor. The treatment
is usually considered in three parts: pre-treatment
(i.e. screening, fat separation, flow balancing,
aeration), the roughing stage where the major part
of the BOD load is removed, and the polishing
stage which is the finishing stage prior to discharge
to the river.
Initially the effluent discharged from the
creamery is collected in a central tank. At this point
screening of solid material will take place though
often it may be carried out in individual process
areas, e.g. curd removal in a cheese room. The
liquor will flow forward to a balance tank, the aim
of which is to distribute the daily flow evenly over
a 24 h period.
Table 1 illustrates the volumes required for each
of the 5 creameries, very approximately one third
26
Journal of the Sodely of Dairy Technology, Vol. 25, No. 1, January, 1972
— 13 —
-------
TABLE I
Coinp.rboa of a’eamery effluent planlo
S
reamery
A
B
C
D
E
Type of
rocessing
Cream, butler.
condensing,
drying
Cream, cottage
cheese, drying,
condensing
Cream, cheese,
baiter, drying,
condensing.
whey condensing
Cheese, whey
condensing,
drying
Yoghurt.
(Iruited type)
Desijn
throughput
gal/day
(n ”/day)
250,000
(1,140)
250,000
(1,140)
300,000
(1,360)
90,000
(407)
120,000
(546)
Actual
throughput
gal/day
(rn’/day)
100,000
(455)
200,000
(910)
230.000
(1,050)
100,000
(450)
120,000
(546)
Balancing
capacity
gallons
(IT’)
65,000
(296)
100,000
(453)
50,000
(227)
10,000
(46)
60,000
(273)
Roujlhing
treatment
single stage
Ilocor tower
600 yd’
(458 m’)
2-stage
flocor tower
1,050 yd’
(802 m’)
single stage
flocor tower
850 yd’
(650 m’)
4 small
filter beds
in parallel
with aeration
2-stage
Ilocor tower
770 yd’
(590 m’)
Polishing
treatment
4 filter
beds in ADF
3 240 yd’
(2470 m ’)
3 filter
beds in
single pass
4 filter
beds in ADF
2 filler
beds in
single pass
628 yd’
(480 m’)
2 filter
beds in ADF
360 yd’
(271 m’)
of the daily throughput. For most efficient opera-
tion a plant should be run continuously at its
ma :imum hourly throughput, the balance tank
being of sufficient capacity to hold any liquid in
excess of this amount. This balancing volume wilL
be determined by the individual circumstances of
each creamery and of course the times of cleaning
of ‘ ach section of plant. To obtain a constant
irrigation or wetting, which is required for bio-
logical oxidation, the balance tank can provide a
convenient point for recirculation of final effluent.
The USC of balancing facilities will also aid the
dilution of individual parts of the effluent load. e.g.
dcti rgcnt washes. In order to prevent anaerobic
conditions and the tank’s becoming septic, ade-
quate aeration should be provided (Stoves. 1966).
In the case of Creameries B and C, tanks that were
pre iously used for aeration became the balance
vessels.
it is interesting to note at this stage that in the
majority of the treatment systems being described.
pH or nutrient balance has been found to be un-
necessary. Before any such system is contemplated
the cost of adding a few gallons of this and that to
an ffluent plant each day must be borne in mind.
Klein (1966) suggests a ratio of BOD to nitrogen
and phosphorus for a waste water as approximately
100:4: 1. This can usually be achieved with dairy
waste.
The bulk of the total BOD load (lb BOD) is
removed in the roughing stage. In four of the
creameries under consideration high rate bio-
filtration is used. The comparatively recent
development of plastics packing materials has
opened a new field in the treatment of dairy
effluents. It is not necessary here to describe the
properties of this material, as Askew (1966),
Chippcrfield (1968) and the Water Pollution
Research Laboratory (Ministry of Technology,
1968) have already described them. It is interest-
ing, however, to compare the individual treatment
problems in each creamery, with reference to
Tables 1 and 2(p. 29).
Creamery A had a new plant dcsigncd to treat
250,000 gal effluent using a single-stage bioflltcr
tower containing 600 yd’ of media. Whilst the plant
is not up to its maximum loading, the applied load
is 1 5 lb BOD/yd’ under present conditions, design
allowing for an increase to 6’25 lb BOD/yd’. The
reduction in BOD is over 80 per cent and has been
as high as 95 per cent.
Creamery B had an existing installation which
included a series of 9 aeration tanks in series. The
system had become greatly overloaded due to
increase in the manufacturing capacity of the fac-
tory. A 2-stage side-by-side biofilter tower was
installed to overcome this problem and reduce the
load to the subsequent filter bed stage. The tower
contains 1,150 yd’ of media, the ratio of media in
the two stages being 25:1-0. With a throughput of
Jownoi of the SocIety of Dairy Technology, V.1.25, No.!, January, 1972
27
- 14 -
-------
250.000 gal/day, the present load is 625 lb
BOD/yd and the reduction in BOD loading
rou, hly 80 per cent.
Creamery C also had an existing plant which
was suffering from overloading. To improve this
posiion the existing roughing stage, a 30.000 gal
tank with aeration, was converted to a balance
tani: and a new single-stage high rate biofilter was
crcctcd. The plant was designcd for a throughput
of 300.000 gal/day with 850 yd of new filter
media being employed. It is a little early at this
stage to give operational figures for this installa-
tion. However, the design loading is 3 lb BOD/yd
and at present it is operating at about 85 per cent
of this figure. The BOD reduction is 60 per cent.
Tbe treatment plant at Creamery D is quite dif-
ferent from those already described. It consists of
4 small cnclosed aerated filter beds as a roughing
stage feeding 2 much larger filter beds as a polish-
ing ;tagc. There are rather inadequate balancing
faciI ties and the average load of raw effluent is
990 lb BOD. A satisfactory final effluent is
produced.
Creamery E is a factory dealing solely with
yoghurt production and again a new plant was
needed to relieve overloading at the local sewage
works. The plant was designed to treat 120,000
gal/ilay of effluent using two high rate biofilter
towers in scries. Because of the nature of the
effluunt. provision was made for settlement prior
to the roughing stage. Quite large volumes of
sludge are removed at this point, the pH often
being low due to the acidity of the fruit and
product waste.
These high rate filters have at times been sub-
jecteil to very severe overloading. For the first year
of operation, balancing facilities were very poor
but there was never any tendency for the plastics
material to pond, and recovery from overloading
was extremely rapid. The plant design loading was
in the order of 1,500 lb BOD/day giving an applied
load of 2 34 lb BOD/yd 3 day to the roughing stage.
The BOD reduction is about 75 per cent. The
queslion of whether a single or 2-stage high rate
filter is used is debatable at this time.
The second or polishing stage in the treatment
systems is relatively standard, percolating filter
beds being used in all cases. In general terms the
job cif the roughing stage is to reduce the load to
a constant level, say a BOD of 200—300. In a new
plant then, the size of the filter beds is determined
by this loading figure. For the treatment of milk
wastes the Water Pollution Research Laboratory
showed that by using two filters in series and alter-
nating the feed each week, a consistently good
effluent is produced. This method of alternating
double filtration (ADF method) has become
standard practice in the industry. The recom-
mended load is 048 lb BOD/yd day.
Creamery A has a comparatively large polishing
stage and the design is such that the BOD of the
waste from the high rate filter should be 500-600.
Creamery C is comparable to Creamery A, using
4 large filter beds in ADF. With Creamery B, the
situation is rather different; in order to modify the
system it was decided to run the existing 3 per-
colating filters as a single pass. This has proved
quite effective and, since the load at this stage has
been reduced to a satisfactory level, the beds have
recovered from their serious overloading and an
effluent is produced to Royal Commission
standards.
Creamery E has much smaller filter beds, the
greater part of the load being removed by the high
rate bioflltcr. It is not, therefore, possible to com-
pare the ratio of load taken by cach stage in the 5
creameries. What can be said is that each problem
was assessed individually and the reasons for any
particular. design, whilst not seeming to be techni-
cally correct, took into account the particular local
conditions.
In conclusion it is worth mentioning these local
conditions and to comment on the satisfactory
operation, cost, layout and room for future ex-
pansion. Creamery A discharges its waste into a
stream which feeds an important fishing river in
the West Country. Stringent conditions of maxi-
mum flow rate, temperature, pH and polluting
matter were laid down by the River Authority.
Though the capital investment in this plant was
quite large, a good reserve capacity is available
and the final effluent is consistently below 10 BOD.
Compared with this, the treatment plant for
Creamery E was built at a much lower cost and
modified a year later. This plant has been a con-
stant source of trouble, due to many failings,
particularly in civil engineering, though most of
these have now been corrected. This installation
showed above all the importance of adequate
balancing facilities, especially where the factory
has erratic load conditions. The one enormous
advantage of biofilter towers is their ability to
handle overloads without their subsequent per-
formance being impaired.
An interesting point to note here is the operation
of the distributor arms on the percolating filter
beds. Contrary to popular belief, these arms must
rotate very slowly so that sufficient of the bio-
logical growth is washed away from the media to
provide air passages (DSIR, 1959). The fact that
all the operations described in this paper are
essentially aerobic is basic to the treatment systems
employed.
Creameries B and C are very similar. In both
cases their treatment plants have been extended in
the roughing stage very successfully with the high
rate biofilter tower. The cost of both modifications
was similar and comparable results are achieved.
These then are some of the facts accumulated
from the operation of 5 creamery effluent plants.
28
Journal ol she Society of Dairy Tedrnology, Vol. 25, No. 1. January, 1972
— 15 -
-------
YA tE 2
Ce ..l.. . ef loads tea each ereamery
Crean:ery
A
B
C
D
E
DOD or
rww effluent
ppm
900
1,200—1,800
1,100—1,200
1,100
l.000t.500
Highest
BOD or
Ta’s effluent
ppm
1,200
1,800
1,500
1,800
2,400
Losdto
pliinl
lb BOD/day
(k i DOD/day)
.
900
(408)
3,750
(1,710)
2,650
(1,200)
990
(450)
1.440
(654)
Los d to
b ufilter
lb BOD(yd’ day
(ki BOD/m’day)
15
(0 89)
6 25
(3.71)
2•5-3 0
(1 49—1 78)
Not known
2 34
(I 39)
% DOD
reduction
in roughing
state
80-95
80
•
60
60—70
7545
Load to
percolating
filter beds
lb 3ODIyd’ day
(kgBOD/m’day
0035
(0026)
Not known
03
(0’17)
Not known
0 82-0 62
(028)
BOl)of
find
effluent ppm
9
>20
15—20
<20
15—25
Time precludes the mention of other problems
such as sludge disposal, smell, site layout, civil
engineering, etc. I trust the information given will
be useful, bearing in mind the limitations in the
arci of treatment considered.
Finally I would like to thank Express Dairy Co.
for allowing me to present this paper and in
particular Dr. T. R. Ashton for his advice and
assistance.
REFERENCES
Anderson, D. (1970) bid. War. Wastes. July-Aug., 1W 12.
Askew, M. W. (1966) Process Rlochem., 1,483.
Chi perfield, P. N. J. (1968) In: Effluent and Water
Treatment Manual, 4th Ed. London: Thunderbird
Enterprises.
DSIR (1959) Notes on Water Pollution Control, No. 5.
Landon: HMSO.
Klein, L (1966) River Pollution, 3. Control, p. 302,
L.,ndon: Butterworths.
MAMPTAC (1969) Dairy Effluents. Report of the Dairy
EOnluencs Sub-Committee of the Milk and Milk Pro-
ducts Technical Advisory Committee. London: HMSO.
Ministry of Technology (1968) Note, on Water Pollution
Crmtrol. No. 40.
Priestly, I. 3. (1970) Process Eng. Plant & Contr., Jait.,
p 125.
Stois,, S. A. (1966) MunicIpal Engng, 144,1731.
DISCUSSION
Dr. c. chambers: At a cheese factory where a plastics
biofilter is used as a roughing treatment we have experi-
enced great difficulty with the build u&, on the medium of
excessive deposits which interfere with cLrculation and
ultimately cause collapse of sections of the medium. Has
the speaker experienced this problem and can he suggest
possible causes?
Mr. A. I. Gaster: We have had no trouble whatsoever,
particularly in relation to our yoghurt factory which I
have mentioned. They are overloaded but there never has
been a build up. You would expect a good deposit of
slime on these plastics packings; that is what is doing the
good work. I would suggest that if you arc having
trouble, your problem is probably the water circulation
and the manufacturers of these packings are only too
helpful in providing information on these points, but you
do have to have a certain minimum wetting rate. This is
quite high: I think it is a figure of something like 30
gal/ft’/min, but I cannot be sure. Unless you get sufficient
water flow over these packings then you wilL not irrigate
them and will not wash out this mire to give room for
the air to get through.
Dr. R. Scott: With regard to Dr. Chambers’ problem, I
wonder if he is using too much chlorine?
I would like to ask what ii the final DOD of these
Journal of the Sodety of Ddry Tethnology, VoL 2 , No, I, January, 1972
29
- 16 —
-------
Socondly, we have not heard very much about the
chemical demand. This is becoming more and more im-
pod ant. Some of the dairies, who were quite happy to
disçoso effluent into rivers, arc now not quite so fortunate
whcn somc chemical firm built up-stream of the river
discharges its effluent into the river, thus affecting the
dait ernucnt disposal, because the two react together.
Eulucnt disposal is more complex as more and more
industrial concerns pour their waste into waterways
whether it be waste chemicals or simply waste heat.
Mr. A. 1. Caster: We will aim, depcnding on the size of
the biofihtcr which is the important thing, to get down to
a B OD of the order of 200—300, but one of our plants has
a much larger polishing stage — the plant is not one of
our own design — and there the BOD at the outfall of the
high rate filter is as high as 500-600, but we do in fact
have a bottling plant with high rate filters, where we
nornally expect to get down to a DOD of 200—300.
As regards your second point on the chemical nature,
I piesume you are talking about COD. I think this is very
mw:h related to DOD itself. I have gone through these
five plants very carefully and tried to assess their perfor-
matice on as few parameters as possible. We have in fact
not been able to provide information which is of much
use to us, other than by the standard 5-day BOD tests,
although the River Board does produce 4 h permanga-
nato tests and COD; we do extensive testing using COD
tcst i and try to obtain some correlation with this, because
it is a much quicker test than the DOD test, and we did
not get a very good correlation. I bçlicve in fact an article
was written in the Society’s journal on this subject and
we put this into practice but did not get a correlation.
In my cxpenencc of our creamery plants, we arc not in
gcnu :ral side by side with large chemical manufacturers,
so we are fortunate. I have not come across this problem,
although I heard mention of a brewery and a dairy get-
ting together and mixing their effluent. This is obviously
an :xcellcnt idea, if one of the effluents happens to be
defi;ient of one of the minerals needed to provide satis-
factery biological degradation. It is obviously much
cheaper if you can combine and saves using additives,
whi:h can be very expensive.
Mr. N. L. T. Garrett: Can I ask to what extent manage-
merit can be involved in solving effluent problems, for
example, introduction of automated CIP, segregation of
usel ul residues, recovery of fats, etc., and general house-
keeping discipline in the factory before it has become
effluent?
Mr. A. 1. Caster: I think it is very important indeed that
maicagement in processing is concerned with effluent
treatment and is fully aware of not today’s problems
only, but tomorrow’s problems. They tend to regard water
as a commodity which is freely available at l5—20p/gal
XI I ) ’. Most of our factories use perhaps 100 thousand
aljday, 5—6 days/week, and if you add this figure up, it
is quite astronomical. If you can talk in terms of this as a
capital cost, it helps. I think the difficulty arises in pro-
moling an effluent saving scheme when you have to be
constantly on guard in a factory area, and this is why I
would like to see some work done on tertiary treatment
systems, where we can use reclaimed effluent and possibly
chlorinated water supplies for such things as floor wash-
ing; but at present the work done does not show it to be
economical. No doubt in future years it will become so,
and then one can perhaps use water more freely. You
said CIP schemes, well I hope we all use CIP schemes.
Dr. D. B. Stewart: I have been very impressed by the
figures given by Mr. Gastcr. I would, however, like to ask
him how easy it is to obtain truly representative samples
for DOD assessments?
Mr. A. 1. Caster: It is very difficult, I think, to obtain an
accurate sample. What matters, as far as we arc con-
cerned, is that the discharge should always be less than
that asked for by the River Board. It does not matter
when they sample, if we are asked for Royal Commission
standards, because we must have a DOD at any time of
less than 20.
As regards samples of raw effluent or any stage needed,
we tend to take a multitude of samples, bulk them and
sample the bulk, and find this adequate. There are in fact
flow measuring devices on the market which operate
pyrostatic pumps at various times, say six times/h, take
a small sample from the effluent stream into a bottle,
(which could be stored) and obtain a sample again.
VOTE OF ThANKS
Dr. 1. C. Davis: Mr. President, in showing our apprecia-
tion of these excellent papers I think we should also pay
tribute to those who have organized this meeting, as we
have had a most interesting variety of subjects with some-
thing for everybody.
With regard to Mr. Booth’s paper one has to admit
that the position so far as mastitis is concerned is very
much the same as it was 30 years ago, or even worse. I
was concerned with a major investigation about that time,
when we found that a third of the cows had some form
of mastitis. More recently I was concerned with a smaller
investigation and was appalled by the deterioration in the
position of the problem generally. About two-thirds of
the cows had mastitis and I have never seen such a
variety of flora. The technique we formerly used for
getting samples was quite hopeless, nine out of ten plates
were crowded with colonies and altogether the position
was very much worse. The explanation is anybody s guess;
it may be the increasing stress on the cows, machine milk-
ing and increased yields, but personally I think that the
far too wide and irresponsible use of antibiotics is a
major cause of this deterioration. We have an interesting
parallel here in human infections, because there we have
many infections caused by Gram-negative organisms
today, which previously were regarded as quite harmless.
Mr. Ross’s subject is obviously one of much interest to
us today, because we have an industry which is 70 per
cent retail and this question of what is going to be the
container of the future is the No. 1 problem in our
industry.
I would particularly thank Mr. Gaster for his most
excellent paper, a model if I may say so, and I hope that
the Council will take note of this and perhaps arrange
that we have at least one paper by a younger member,
not forgetting the ladies, at these Conferences.
Ladies and gentlemen, would you please show your
appreciation of our excellent spcakers7 (Applause).
30
lournal ol the Society of DaIry Technology, Vol. 25, No. 1, January, 1972
— 17 —
-------
SPRAY DISPOSAL
OF FOOD WASTE
In common with other areas of the
process industries, food processors are
facing growing problems in disposing
of their unwanted wastes. Waste treat-
ment Coi.ts are rising as more stringent
effluent standards are demanded be-
fore disposs I of aqueous wastes to sur-
face waters is permitted. In these cir-
cumstances, any disposal method
which is cheap and which also avoids
the risk of pollution of water-courses
through oxygen depletion should be of
interest to food manufacturers. If the
evidence of a number of authorities is
to be accepied, such a disposal method
exists and forms the basis of many
“ecologically acceptable” waste dis-
posal installations. The method, which
takes advantage of the “natural” bio-
logical filtration processes occurring
when non-toxic liquid wastes of bio-
logical origiii percolate into the ground,
is spray dit posal.
Land dispsaI of municipal
wastes
The dispo5al of municipal waste
liquors on iii land has been practised in
Europe for many years. In the UK,
two such lewage treatment methods
were: (a) “,mad” or “surface” irriga-
tion where settled sewage was allowed
to flow ovr gently inclined ground;
and (b) “l.md filtration” where the
ground was flooded with sewage. Both
methods co’ ild be combined with the
growth of uitable food crops on the
so-called “sewage farm” though cash
crop growth was more usually associ-
ated with broad irrigation methods.
According to Southgatei, sewage
treatment by land filtration gave efflu-
ents of good quality provided the soil
was suitabli:. Porous soils — sand,
gravel etc —. allowed satisfactory treat-
ment at effluent rates as high as 30,000
gal per acre per day. Less porous soils
reduced the maximum permissible rates
to nearer 2,000 gal per acre per day,
while some ioils such as stiff clay were
unsuitable for this method of disposal.
Although land filtration needs less
space than L road irrigation, ground re-
quirements br both methods are high.
The increasing cost of land in urban
areas has, over the years, led to this
method of disposal being superseded by
the less space-demanding modern sew-
age plant. With the ever-increasing
need for satisfactory disposal of
mun:cipal waste waters interest in land
disposal has been revived. The pos-
sible disposal of municipal wastes to
forest land is under active considera-
tion. After “living” biological filtra-.
tion, as waste waters percolate through
the ground, purified water is returned
to ground-water reservoirs. Parizek et
j •2 describe such an experimental dis-
posal system capable of disposing of
450,000 gal of liquid per day.
Comparison of municipal waste
and food wastes
Although the disposal of sewage to
land has for long been practised, a rela-
tively new development is the disposal
of liquid industrial wastes by spraying
on to land. When associated with crop
growth, this disposal method is gain-
ing popularity under the banner of
“spray irrigation”. Not surprisingly,
when remembering the similarities be-
tween many food wastes and domestic
sewage, it is the food industry, particu-
larly the canning and dairy processing
sections of the industry, that has pion-
eered this seemingly straightforward
and inexpensive method of disposing of
unwanted waste liquors.
Both food wastes and domestic sew-
age are likely to be complex mixtures of
carbohydrates, proteins, fats and in-
organic nutrients. It must be reman-
bered, however, that food processing
wastes are cons:derably stronger than
domestic sewage. The former contain
large amounts of organic matter and
Table 1. Typical BOD values
Waste
BOD ,
(mgIl)
Fruit and vegetable
preparation
Canning
Dairying: whole milk
milk washing
Meat processing
Blood
Domestic sewage
500.2500
2000-4000
110,000
75-1500
200-3000
165,000
200.400
can have very high values of BOD
(biochemical oxygen demand). Although
only to be taken as indicating orders of
polluting strength and not as rigid
values, the figures in the accompany-
ing table indicate the wide range of
values of BOD encountered in some
sectors of the food industry (typical
figures for domestic sewage are in-
cluded for comparison).
If similar ground conditions to those
experienced with “land filtration” dis-
posal methods for sewage are to be ex-
pected following irrigation with food
wastes, then dilution may be neces-
sary.
Advantages of spray irrigation
According to Gurnham, the first ap-
plication of spray irrigation to indus-
trial waste disposal was in 1947, at the
Hanover Canning Company in Penn-
sylvania’. Since that time many more
spray disposal installations have been
successfully operated, although mainly
in the cann’ng and dairy processing in-
dustries. Scott° for example reports
that in 1963, in Wisconsin alone, 32
out of 107 vegetable and fruit ca1 -
neries operating in the State were us-
ing spray disposal. Reasons for adop-
tion of the method in these fields are
not difficult to find:
(a) A purpose built conventional waste
treatment plant entails high capital ex-
penditure. For ideal operation of such
a plant a requirement is the provision
of a steady flow of waste liquors of
constant strength. Furthermore, for
maximum return on the investment,
the plant should be operated at its opti-
mum capacity throughout the whole of
its life. Canning and dairy processing
are two areas of the food industry
whose production schedules are neces-
sarily remote from these idealised
conditions. By the very nature of their
raw materials, fruit and vegetable and
dairy processing operations are highly
seasonal. Under these conditions, ex-
pensive plant to be operated for short,
highly intensive periods becomes diffi-
cult to justify.
(b) Both cannery and dairy processing
installations are likely to be sited in
country areas where land is relatively
J. R. Butters
B Sc, Oup Chem Eng., C Eng. A M I Chem E. A.i F ST.
Se,, ,or Iccturer ,n Food £ng,ne.,,ng and Food Proceu.ng, Notional College of Food Technology, Weybr.dge
Given i:he right conditions, disposal of liquid wastes by spraying on to agricultural
land is an effective and cheap method. This article reviews work on this subject
and discusses requirements for success
Food anufacture 47 #5 (1972)
— 18 —
29
-------
chcap. The combined costs of land
plus spray irrigation equipment when
weighed a :ainst the costs of a pur-
pose-built waste treatment plant,
working at well below its maximum
eapauty f’u part of its lie, arc likely to
favour spriy dispu .il, even when al-
lowaiwe m idc for levelling and
draining of the site. This becomes par-
ticularly true ii it is possible to recover
part of the costs of the operation, by
expeditious use of the grass or other
crop raised on the spraying grounds.
(c) Though opinions differ, there is
some evidence that the spraying
ground L ciefits from resting periods,
when spra’iing ceases. Again it is sea-
sonal processing operat:ons that are
best suitcd to this type of operation.
First cont;ideratloris for
spray disposal
An essential prerequisite when con-
sidering spray irrigation as a possible
method for disposing of food wastes is
the availability, at acceptable cost, of an
adequate aica of land not too distant
from the factory site The area re-
quired depends on a variety of factors,
includ ng oil drainage characteristics,
nature of crop cover, climate-tempera-
ture, rainfall etc. The required area in-
creases as the volume of waste to be
disposed of increases.
The land should be relatively flat,
any slopes being less than 5-6 per cent
to avoid drain-o1 with consequent risk
of pollution to nearby watercourses.
The ground should also be even to
avoid poncling, so some initial level-
ling may lie required. Both soil and
subsoil shoild be fairly porous. Open-
structured ;andy soils permit consider-
ably higher liquor application rates
than do h ’ avier clay soils. With less
porous soi s, tile draining might be
necessary ta carry away excess water
during wet periods.
A geological survey must show the
absence of cracks and fissures in the
underlying strata that could lead to
contamination of underground water
sources. Scabrook’ however, reporting
on studies )f DOD values of percolat-
ing vegetabLe waste liquors at different
levels in ihc ground, suggests that some
96 per cent of the organic content of
the waste water is removed within the
first 4 inches of the surface. Under
these condi ions the risk of contamina-
tion of ground-water sources is slight.
Since strnng winds can carry finely-
divided lic uid droplets considerable
distances the spraying ground should
be protectel by some sort of wind-
break if windage could create a
nuisance in surrounding areas. Spray-
ing into ,voodland overcomes this
problem aed one U.S. cannery has,
since 1950, been satisfactorily dispos-
ing of some 8 million gal per day of
vegetable witste liquors in this manneK
30
importance of crop cover
Purification of waste water by land dis-
posal is considered to be predomin-
antly a biological process. The greater
proportion of the waste is subfectcd tO
biochemical action as it passes through
the soil. Besides removal of water by
percolation into the ground, some is
also lost by evaporation.
The volume of liquor that can be ap-
plied to a given area of land without
ponding or other deleterious effects can
be significantly increased by the pres-
ence of a crop cover. Besides removing
more water by transpiration and using
organic matter as a source of nutrients
in its growth cycle the crop cover also
prevents erosion of the soil Erosion,
with consequent compacting due to the
impact of water droplets from the
sprays, significantly lowers the drain-
age rate through the soil. The roots of
the crop cover may also help to main-
tain an open structure within the soil,
thus aiding percolation.
For a crop cover intended to yield
some sort of return, as opposed to
spraying into woodland, the most suit-
able cover is often said to be pasture
grass”. Agricultural crops besides being
more sensitive to over-watering and
scorching are more easily damagc d
when changing the position of spray-
ing heads. Controlled dosing over re-
gulated periods does yield saleable
crops however. Nelson 7 describes a
spray irrigation system disposing of
vegetable waste liquors on a 110-acre
farm. A crop rotation system based on
peas, sweetcorn and hay was used, the
resulting crop of peas and sweetcorn
being canned on site.
Obviously a knowledge of crop hus-
bandry is valuable when considering
spray irrigation schemes, since it may
permit the selection of crop-cover for
specific applications. When using pas-
ture grasses disagreement exists as to
whether shallow or deep-rooted grasses
are more suitable. With less porous
soils, thicker and deeper root systems
might, by maintaining an open struc-
ture to a greater depth, be expected to
aid percolation. On the other hand,
however, with open porous soils, the
thicker root system may lead to a de-
crease in percolation rate since the flow
rate of fluids through porous beds is
inversely proportional to bed thick-
ness. In this case shallow-rooted grasses
adequate to protect against impact
compaction would be more suitable.
In some spray disposal applications
striking changes in flora have been ob-
served following extended spraying.
Scabrook reports on a woodland
spraying area originally consisting of
mixed oaks with a ground cover of
mountain laurel, blueberry, blackberry,
dogwood and holly. After three years.
of irrigation the ground cover had been
replaced by a dense growth of climb-
ing hempweed, elder, nightshade and
other herbaceous plants. Some of the
plants had grown to heights and thick-
nesses several times those of the same
species in unsprayed areas. More re-
cently Sopper found that spraying
municipal sewage into woodland also
caused significant changes in herbace-
ous ground cover. Height growth, den-
sity, and dry matter production were
all significantly increased The dia-
meter growth of mixed hardwood trees
in the spraying area was not affected at
lower liquor application rates (2.5cm!
week) but was significantly increased at
higher rates (5 and 10cm/week rate). It
should be noted that 2.5cm/week is
equivalent to a volumetric discharge
rate of about 22,000 gal per acre per
week.
Equipment requirements
Relative simplicity, hence low capital
and maintenance costs for equipment,
are advantages offered by spray dis-
posal. Conventional crop irrigation
equipment and suitable land are al-
most the only requ’rements. A con-
stant rate of flow to the pump feeding
the self-activated revolving spraying
heads should be provided by using a
suitable sump tank. This tank is not a
septic tank and should be kept small to
avoid possible anaerobic decomposi-
tion and resultant odour problems.
To avoid blockage of pipe lines and
spraying heads, larger solid particles
should be removed by screening prior
to spraying. Minimum screen sizes of
20 to 40 mesh (openings per inch) are
recommended’. For small installa-
t ons, easily removed basket screens are
adequate but with larger installations
rotary or vibrating screens may be
necessary.
With some installations the solids re-
moved from food wastes are often suit-
able for animal feeding. For effective
application the position of the spray-
ing heads needs to be moved fre-
quently. Normally a fixed main line
transports waste to the irrigation site
while lateral lines are used for distribu-
tion from the main line. Lightweight
plastic or aluminium p pes should be
employed for the lateral lines. Thirty
foot lengths of aluminium pipe joined
by quick acting automatic Joints, eas-
ily dismantled, moved and reassem-
bled by one man, are used in an instal-
lation in Ireland .
Composition and strength of
waste liquors
The composition and strength of the
waste liquors must be acceptable to
both the cover and to the soil. The pH,
mineral and organic content must not
be injurious to the growth of the par-
ticular cover. The maximum rate of
application of a liquor will depend on
its strength. High concentration wastes
— 19 —
FOOD MANUFACFURE May 1972
-------
can lead to scrching and damage of
the cover whe ii sprayed for extended
periods.
Alkaline clciining agents are exten-
sively used in the food industry. Sod-
ium ions in these agents can replace
calcium in th soil by ion exchange
causing soil disintegration and com-
pacting. The porosity of the soil falls
and in conseq uence the rate of spray-
ing must be reduced if ponding is to be
avoided.
When food wastes arc to be applied
to clay soih, McKee’ 0 recommends
that the soditm concentration should
not exceed 100mg/I. To avoid any
odour nuisance the waste liquor must
be fresh and be sprayed on to the land
before anaerc bic decomposition can
take place.
Rates of application
Permissible waste liquor application
rates depend on the type of soil, the
crop cover and the climatic conditions
in the spraying area. Penetration tests
will provide :;uitable rates for specific
purposes. Fij ures published in the
literature pro ide some guide to ap-
plication rate:; actually experienced in
practice.
Work done by the U.S. Soil Con-
servation Service” suggests maxi-
mum rates of application to soil carry-
ing a crop cover varying from 2 in/hr.
(approximately 45,000 gal per acre per
hour) for thick uniform layers of
coarse sandy soils, to 0.15 in/hr. (3,400
gal per acre per hour) for heavy clays
and clay loams. These figures are re-
duced if rainfall is likely to be heavy.
Bell’ 2 reported the appl’cation of
0.33 in/day of a cannery waste on to
silt loam carrying a cover of alfalfa.
The plant operated for 180 days of the
canning season giving a total applica-
tion of 60 inches on some 40 acres of
land.
Again with cannery wastes Sea-
brook 5 suggests a rate of slightly less
than 1 in/hr for a sandy natured soil
having gravelly underlayers. He points
out that the area under the spray
nozzles receives considerably more
liquid. In penetration tests comparing
spray disposal on to tilled land with
that into unploughed woodland, Sea-
brook further found that in the for-
mer case, the ground was “saturated
and soupy” to plough depth after an
application of 2 inches of water. Mixed
oak and pine woodland on the other
hand took up 56 inches of water at a
rate of 6.5 in/hr without becoming
saturated. In these tests the woodland
area received 150 inches of water in 10
days with no sign of saturation.
Considerably lower application rates
are reported from trials in Holland’ 3
on the disposal of dairy wastes by
spraying on to pasture land. This work
suggests that sandy soils can receive 8
to 12 in/year whereas peaty soils can
accept up to 20 in/year. At these rates
high yields and improved quality of the
grassland resulted. Higher rates lead to
deterioration of the grassland and in
the case of sandy soils application of
some 33 inches of liquid per year led to
waterlogged conditions.
Work carried out in New Zealand on
the disposal of dairy effluent to pas-
ture land suggested applcation rates as
high as 12 inches per irrigation of 8
hours duration with well-drained sandy
soils”. With heavy clays the rate fell
to 0.15 inches per irrigation. This work
recommends against spraying on to
heavy clay soils during periods of
heavy rain. After spraying, a 14 day
rest period was allowed before grazing
or harvesting of the grass crop. This
was followed by a further 10 days re-
covery penod, thus spraying took place
for I day every 25 days.
Nearer home, Barfield” reports the
disposal of 18,000 gal/day of dairy
effluent on to 30 acres of land in Ire-
land. Eleven spray positions are in use,
each area being sprayed for 2 days fol-
lowed by a 22 day rest period. Though
the soil is said to be fairly heavy, ac-
cording to Barfield this volume of
waste was “easily and efficiently hand-
led by the irrigation scheme, which has
entirely solved the twin problems of
effluent disposal and pollution”.
Causes of failure
Over-dosing is a major cause of failure
of spray irrigation schemes. Crop cover
damage, the detenoration of soil struc-
ture leading to ponding and odour
problems, and contamination of
ground waters if the natural biological
filtration process is not completely
effective with over-strength liquors are
some troubles that can arise through
the application of liquors of too high a
concentration. A correctly balanced
waste liquor flow should prevent these
difficulties.
A more common cause of over-dos-
ing failure is the application of accept-
able strength liquors at too high a rate
of flow for the area of land available.
Again this can lead to cover damage,
ponding and odour problems. It can
also cause pollution difficulties due to
the run-off of liquors to nearby sur-
face water-courses. Liquor application
rates must be sensibly chosen and
maintained having regard to the fac-
tors influencing the rate of take-up of
water, namely soil conditions, crop
cover and climate. It is foolish to at-
tempt spray disposal if an adequate
area of land is not available.
Spray irrigation is a simple and rela-
tively cheap method for the ultimate
disposal of food processing waste
liquids. It does require an adequate
land area not too distant from the fac-
tory site.
Although the method has been as-
sociated with crop growth, spray dis-
posal into woodland areas is practic-
able and offers advantages. Well de-
signed and correctly operated spray
disposal installations have been satis-
factorily disposing of food waste
liquors on to land in a variety of clim-
ates for a number of years. A properly
engineered and controlled system
neither pollutes the environment nor
seriously disturbs the ecology of the
locality. In the words of the U.S. De-
partment of Health, Education and
Welfare’: “with proper equipment
and controlled application of the waste,
spray irrigation will completely pre-
vent stream pollution, will not create
odour problems, and is usually less ex-
pensive than other methods of waste
disposal.” For food processors in rela-
tively rural areas with a waste disposal
problem, it is a method worth con-
sidering.
REFERENCES
1. Southgatc, B. A, “Treatment and
disposal of industrial waste waters”,
HMSO, London, 1948
2. Parizek, R. R., at a!, “Waste water
renovation and conservation”, Penn.
State Studies, 1967, No 23, 71.
3. Gurnham, C. F, “Principles of in-
dustrial waste treatment”, John Wiley,
1955
4 Scott, R H., “Land disposal of in-
dustrial wastes”, Proc. 11th Pacific
Noi thwest Industrial Waste Con!.,
1963, 261
5. Seabrook, B L, “This woodland
spray system disposes billion gallons
of waste water annually”, Food Engi-
liecruag, 1957, 29(11), 112.
6. Fisher, W. J, “Treatment and dis-
posal of dairy waste waters a review”,
Dairy Sc,. Absi, 1968, 30(11), 567.
7. Nelson, L E, “Cannery wastes dis-
posal by spray irrigation”, Wasics
Engineer ,, ,g, 1952, 23, 398.
8. Sopper, W. E., “Disposal of muni-
cipal waste waters through forest
irrigation”, Environmental Pollution,
1971, 1(4), 263
9. Barfield, A., “Irrigation solves dairy
effluent problems”, Dairy Industries,
1966, 31(9), 736.
10. McKee, F. J., “Dairy waste disposal
by spray irrigation”, Sewage and In-
dustrial Wastes, 1957, 29, 157.
11. Anon., U.S. Soil Conservation Service
Regional Engineering Handbook, 1949.
12. Bell, J. W., “Spray irrigation for
poultry and cannery wastes”, Cana-
dian Food Industry, 1961, 32(9), 31.
13. Baars, C., ct al, “Agricultural and
technical aspects of the disposal of
dairy wastes on grassland”, Rzjks
Zuivel-Agrai ische Afvalwaierdiens:,
Arnhem, Pubi. No, 14, 1960.
14. McDowell, F H., and Thomas, R. H,
“Disposal of dairy wastes by spray
irrigation on pasture land”, New
Zealand Pollution Advisory Council
Publ. No. 8, 1961.
15. Anon., “Fruit processing industry: an
industrial waste guide”, U.S. Dept. of
Health, Education and Welfare, Public
Health Service PubI. No. 952, 1962.
32
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FOOD MANUFACTURE — May IQ7
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