;LEA
WATER POLLUTION CONTROL RESEARCH SERIES • ORD-5
Activated Sludge Treatment
of
Chrome Tannery Wastes
DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and
progress in the control and abatement of pollution in our Nation’s
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Water pollution Control Research Series reports will be distributed to
requesters as supplies permit. Requests should be sent to the
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Federal Water Pollution Control Administration, Washington, D.C. 20242.
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ACTIVATED SLUDGE TREATMENT
OF CHROME TANNERY WASTES
A PILOT STUDY OF TREATING
COMBINED CHROME TANNERY WASTES
AND DOMESTIC SEWAGE
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
by
A.C. LAWRENCE LEATHER COMPANY
SOUTH PARIS, MAINE
GRANT NO. WPRD 133-01-68
PROGRAM NO.12120
SEPTEMBER,1969
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FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration.
ii
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ABSTRACT
The A.C. Lawrence Leather Company tannery at South Paris, Maine is a
chrome side upper leather tannery. About 220 people are employed at the
tannery and about 2,500 hides are processed each day. The water use at
the tannery is about 1.0 mgd. Each day the waste discharged from the
tannery contains about 8,500 lbs of 5.-day, 20°C BOD, 70,000 lbs of total
solids, of which about 17,000 lbs are suspended and 53,000 lbs are dis-
solved. The pH of the wastewater varies from 5.0 to 12.0. The daily
waste discharge also contains about 8,000 lbs of calcium, as CaCO 3 , 300
lbs of sulfides, and 1,800 lbs of chromium .
A waste treatment process was developed and tested, in pilot plant scale,
for the treatment of the tannery wastes in combination with municipal sew-
age. The process consisted of the following steps in the order employed;
equalizing and mixing of the alkaline and acid wastes; primary sedimen-
tation; carbonation followed by upf low sedimentation; addition of screen-
ed municipal sewage; activated sludge treatment and secondary sedimenta-
tion of the mixed wastes; and chlorination. The sludges resulting from
the treatment of the wastes and sewage were dewatered by centrifuge and
were found to be suitable for burial. Design factors for the various
steps of the process were developed and are presented in the attached
report. Studies were made of the fundamental systems and reactions which
form the bases for the processes employed in the pilot plant.
The results of the pilot plant investigation indicate that by use of the
methods recommended, mixtures of chrome tannery wastes and municipal sew-
age can be treated successfully. It may be anticipated that by the em-
ployment of the methods recommended, that mixtures of tannery wastes and
municipal sewage can be treated to remove more than 90 percent of the BOD
and suspended solids together with about 65 percent of the total solids.
Furthermore, the treatment will remove or convert 99 to 100 percent of
the sulfides, remove about 97 percent of the chromium and about 65 percent
of the calcium. Chlorination of the effluent will reduce the coliform
bacteria concentration to less than 100 per 100 ml.
The processes recommended are conventional sewage treatment unit process-
es, with the exception of carbonation and solids contact sedimentation.
Modification of conventional equipment will be necessary to accommodate
the special characteristics of tannery wastes. Fine screening will be
needed to remove hair. Calcium carbonate incrustation of equipment, es-
pecially screens and carbonation equipment, will have to be considered.
Extra strength sludge collection and pumping equipment will be needed
since the sludges are large in quantity and are denser than sewage sludg-
es.
This report was submitted in fulfillment of Grant No. WPRD-l33-0l—68 be—
tween the Federal Water Pollution Control Administration and the A.C.
Lawrence Leather Company.
111
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TABLE OF CONTENTS
Page No .
ABSTRACT iii
CONCLUS IONS 1
RECOMMENDATIONS 3
Equalization Basin 3
Primary Sedimentation 5
Carbonation 5
Aeration Basin Design 7
Secondary Sedimentation 7
Sludge Dewatering 8
COST ESTIMATES 9
INTRODUCTION 11
DESCRIPTION OF THE TANNING PROCESS 13
General 13
The Tanning Process 14
The Beamhouse 14
Tanning and Coloring 16
Finishing 18
EFFLUENT SURVEYS 19
Previous Effluent Surveys 19
Present Effluent Surveys 19
Acid Waste Survey 25
Discussion of Survey Results 28
THE PILOT PLANT 29
Purpose of the Pilot Plant 29
Pilot Plant Design 31
Log of Pilot Plant Operation 37
RESULTS OF PILOT PLANT OPERATION 45
General 45
BOD Removal 46
Removal of BOD by Primary System 49
V
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TABLE OF CONTENTS
(Continued)
Page No
RESULTS OF PILOT PLANT OPERATION — continued
Removal of BOD by Secondary System 56
Secondary Sedimentation 58
Solids Removal 60
Suspended Solids Removal in the Primary System 67
Removal of Calcium 71
Removal of Sulfides 75
Removal of Chromium 76
Sludge Handling 80
Sludge Dewatering 83
SULFIDE OXIDATION 89
General 89
Apparatus 90
General Procedure 90
Analytical Procedures 91
Individual Tests 93
Further Testing 100
Conclusions 100
OXYGEN UPTAKE STtJDIES 101
General 101
Apparatus 102
General Procedure 102
Individual Tests 104
NUTRIENTS 119
FLUE GAS UTILIZATION 123
General 123
Equipment 123
Test Procedure 125
Results 126
Discussion of Results 126
vi
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TABLE OF CONTENTS
(Continued)
Page No .
CHLORINATION STUDIES 129
General 129
Procedure 129
Results 129
SULFIDE TOXICITY 135
CHRO TOXICITY 137
ACKNOWLEDGEMENT S 139
BIBLIOGRAPHY 141
APPENDiX 143
vii
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LIST OF FIGURES
Fig. No. Title Page No .
1 Effect of Equalization on Quality 4
2 Suggested Treatment Equipment 6
3 Tannery Process Flow Sheet 15
4 Flow Sheet of Pilot Plant 32
5 Section through Carbonation — Sedimentation 35
Basin
6 Chronological Record of BOD in Plant 47
Influent and Effluent
7 Chronological Record of BOD Removal 51
8 BUD Removal versus Overflow Rate, 54
Primary Sedimentation Basin
9 BUD Removal versus Overflow Rate Carbonation — 55
Sedimentation Basin
10 Removal of BUD as a Function of the Mixed 57
Liquor Suspended Solids
11 Secondary Effluent Suspended Solids as a 59
Function of Overflow Rate
12 Chronological Plot of Total Solids 61
13 Chronological Record of Suspended Solids 65
in Pilot Plant Influent and Effluent
14 Suspended Solids Removal versus Overflow 68
Rate — Primary Sedimentation Basin
15 Weight of Sludge Removed versus Overflow 69
Rate, Primary Sedimentation Basin
16 Weight of Sludge Removed versus Overflow 72
Rate, Carbonation — Upf low — Sedimentation
Basin
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LIST OF FIGURES
(Continued)
Fig. No. Title Page No .
17 Hydrogen Sulfide Test Apparatus 92
18 Oxygen Uptake Apparatus 103
19 Plot of Oxygen Uptake Versus Time 105
with Activated Sludge in the Endogenous
Phase (Test l
20 Plot of Oxygen Uptake Versus Time with 107
Fresh Activated Sludge (Test 2)
21 Plot of Oxygen Uptake Versus Time for Equal 108
Volume Mixture of Activated Sludge and
Carbonation Basin Effluent, Sludge Aerated
4.5 Hrs. Prior to Mixing (Test 3)
22 Plot of Oxygen Uptake Versus Time for Mixture 109
of 2 Parts Fresh Activated Sludge and 1 Part
Carbonation Basin Effluent (Test 4)
23 Plot of Oxygen Uptake Versus Time Before and lii
After Adding Sodium Sulfide to Fresh Activated
Sludge (Tests 5, 6, 7)
24 Plot of Oxygen Uptake Versus Time Before and 112
After Adding Sodium Sulfide to Fresh Activated
Sludge (Tests 6 and 7)
25 Plot of Oxygen Uptake Versus Time Before and 114
After Adding Phosphate to Fresh Activated
Sludge (Tests 8 and 9)
26 Plot of Oxygen Uptake Before and After Adding 116
Calcium to Mixture of 2 Parts Fresh Activated
Sludge and 1 Part Carbonation Basin Effluent
(Tests 10, 11,12)
27 Plot of Oxygen Uptake Versus Time Before 117
and After Adding 100 mg/i Chromium to
a Mixture of 2 Parts Fresh Activated Sludge
and 1 Part Carbonation Basin Effluent (Test 13)
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LIST OF FIGURES
(Continued)
Fig. No. Title Page No .
28 Flue Gas Utilization Test Apparatus 124
29 Chlorination of Pilot Plant Effluent 130
30 Chlorination of Pilot Plant Effluent 131
A—i thru A—6 Tannery Waste — Survey: April 9—10, 1968 Appendix
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LIST OF TABLES
Table No. Title Page No .
1 Summary of Previous Surveys 20
2 24 Hour Survey December 14, 1967 22
3 24 Hour Survey January 2, 1968 23
4 48 Hour Survey January 2, 1968 24
5 Composite of Tan Wheel Effluent 26
6 Composite of Color Wheel Effluent 27
7 Pilot Plant Design Factors 38, 39 & 40
8 Removal of Calcium in the Pilot Plant 74
9 Removal of Sulfides in the Pilot Plant 76
10 Removal of Chromium in the Pilot Plant 79
11 Results of High Chromium Concentration 81
on Activated Sludge
12 Weights and Volumes of Sludges as Drawn 82
13 Average Composition of Tannery Pilot Plant 84
Sludge
14 Sludge Dewatering by Centrifuge 86
15 Sludge Dewatering by Centrifuge with 87
Coagulant Aid
16 Test Results — Aeration of a Water Solution 94
of Sodium Sulfide
17 Test Results — Aeration of Solution of 96
Cotmnercial Sodium Sulfide in Activated
Sludge Mixed Liquor
xiii
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LIST OF TABLES
(Continued)
Table No. Title Page No .
18 Test Results — Aeration of Solution of 98
Commercial Sodium Sulfide in Heat Killed
Activated Sludge Mixed Liquor
19 Aeration of Acid Killed Activated Sludge 98
20 Analyses of Nitrogen, Phosphorous, and COD 120
21 Test Data — Flue Gas Utilization Tests 127
22 Results of Flue Gas Utilization Tests 128
23 Coliform Analyses of Pilot Plant Effluent 132
Al thru A25 Pilot Plant Operating Results Appendix
xiv
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CONCLUS IONS
General
The purpose of the pilot plant investigation was to determine the feasi-
bility of treating the wastes from the A.C. Lawrence Leather Company’s
tannery at South Paris, Maine by the activated sludge process or a inodi—
fication thereof. If the process was found to be technically feasible
further investigation was to determine the loading factors leading to the
design of the most economical treatment plant and method of operation re-
quired to meet the stream classification standards established by the
Maine Water and Air Environmental Improvement Commission for the Little
Androscoggin River, the receiving stream.
The unit processes investigated were:
1. Primary sedimentation
2. pH adjustment
a. With CO 2
b. With acid wastes
3. Activated sludge treatment
4. Sludge thickening
The investigation was divided into three phases. The objectives to be
accomplished in each phase are described as follows:
Phase 1
a. Determine the optimum conditions for the operation
of the carbonation—primary sedimentation stage of
the proposed wastewater treatment system.
b. Determine the removal efficiency for calcium,
chromium, sulfide, BOD and suspended solids by
pH adjustment, carbonation, and sedimentation.
c . Investigate the use of poly—electrolytes and other
coagulant aids as means of increasing the efficiency
of the carbonation—sedimentation process.
d. Build up an operating activated sludge system, using
sanitary sewage from Norway, Maine, sewerage system.
Phase 2
The objective of the Phase 2 operation was to demonstrate the
ability of the proposed waste treatment system to remove pol-
lution materials from the waste on a continuous basis and to
determine the efficiency of the treatment. Determinations of
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the operating characteristics, such as feed to mixed liquor
suspended solids ratios; excess sludge volumes; supplen ntal
nutrient requirements; and effluent cb.aracteristics were made.
An evaluation of the operating efficiency of the activated
sludge unit as related to the operational efficiency of the
carbonation—sedimentation unit were made.
Phase 3
The objectives of Phase 3 were (a) to study the operating limits
of the proposed system, (b) to determine the ultimate fate of
the pollutional materials, and Cc) to study sludge disposal by
centrifuge dewatering and burial.
The pilot plant investigation was carried out in accordance with the pur-
pose and objectives previously stated. The treatment methods are fully
described in the main body of the report. The following unit processes,
listed in order of application, were found to be essential to satisfac-
tory treatment of the wastes.
1. Equalization
2. Primary sedimentation
3. Carbonation and sedimentation
4. Addition of municipal sewage
5. Activated sludge treatment
6. Sludge dewatering by centrifuge
7. Effluent chlorination
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REC0MJ 4ENDAT IONS
On the basis of the pilot plant testing program, it is recommended that
the wastes from the A.C. Lawrence Leather Company tannery at South Paris,
be treated by the processes described below. These processes will be
applicable to the treatment of wastewaters from the tanneries employing
tanning methods similar to those described in this report.
Equalization Basin
Wide fluctuations in the rate of discharge and the quality of the wastes
discharged by a tannery render the treatment of the waste on a continuous,
as received basis, unsatisfactory. One of the first steps in the treat-
ment process should be an equalization of the wastes discharges relative
to both flow and quality. Fig. 1 is a plot of the outflow concentrations
of calcium from an equalization basin having detention times of 4 and 8
hours as compared with no equalization. From Fig. 1, it may be seen that
the maximum fluctuation in the calcium concentration from an equalizing
basin, having approximately 4 hours detention time, will be from about
about 400 mg/i to 1700 mg/i. From an 8—hour retention time in the equal-
ization basin, the maximum variation in the effluent calcium concentration
would be from about 700 mg/i to 1500 mg/i. On the basis of this study,
it is recommended that the equalization basin have a capacity of approxi-
mately 4 hours retention time, equivalent to a volume of 210,000 gallons
for a design flow from the tannery of 1.25 mgd. It is estimated that the
maximum concentration of the various constituents in the effluent from
the equalization tank will be:
Calcium 1,700 mg/i
Sulfide 190
Total Solids 19,500
Suspended Solids 4,320
Alkalinity 1,240
Chromium 460
5—day, 20°C BOD 2,100
Special designs may permit the incorporation of the equalizing function
in combination with carbonation, primary sedimentation and other process—
es. The functions which may be incorporated in a single basin is a de-
cision which will have to be made during final design when a selection is
made of the specific equipment to be used. Suggested designs are shown
later but these designs should be investigated in n re detail by the
final designer in order to develop a unified system.
The operating cycles of the tannery are such that for periods of time up
to 10 hours, the discharge of the tannery is predominantly acidic. In
order to minimize the size of the equalization basin needed to prevent
the pH of the mixed wastewaters from falling below 9.5 it is u re econo—
mical to provide a separate storage basin for the acid waste and to add
them to the equalization basin at a variable rate such that the maximum
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-J
•4%
0 ’
C.)
D
o
HOURLY VARIATION WIThOUT EQUALIZATION
2500 - - - -- ___ ___________ _______
2OOC
FOUR HOUR EQUALIZATION
_ V _________
0
0 5 10 15 20 25 30 35 40 45 48
TIME , HOURS
FIG. I EFFECT OF EQUALIZATION ON WASTEWATER QUALITY
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rate of addition of acid waste will coincide with the maximum inflow of
alkaline wastes. For this purpose, it is estimated that the size of the
acid wastes holding tank should be about 100,000 gallons. Mixing of the
wastes during equalization is considered to be essential. Mixing is par-
ticularly important when acid wastes are being added. No local areas of
low pH should be permitted to develop within the equalization basin.
Primary Sedimentation
In the pilot plant, primary sedimentation was found to be an essential
feature of the treatment process. In the pilot plant, the primary sedi-
mentation basin served two principal purposes. The first purpose was to
equalize the fluctuations in influent quality so that minute to minute
changes were ironed out. The second purpose was to remove the bulk of
the settleable solids to prevent overloading the sedimentation section
of the carbonation—upflow sedimentation basin which followed. These pur-
poses are sucessfully accomplished. Similar functions are needed in a
full—scale plant.
It is suggested that the functions of equalization and primary sedimenta—
tion may be carried out in the same basin but in different compartments.
Fig. 2 is a sketch of one possible type of basin. Alternative designs
are being investigated.
The sedimentation section of the basin should be designed with an over-
flow rate of about 700 gpd per ft. 2 Design on this basis will result
in detention times of about 2 hours.
Special design consideration should be given to the renxval of sludge from
the sedimentation basins in the primary systems.
The sludge may have a concentration in excess of 8 percent solids. The
solids will be heavy and sticky and in many respects resemble very wet
clay. Sludge renoval mechanisms should be of extra strength design.
Sludge draw—off piping would be equipped with water flushing connections
which should be used to flush out the sludge draw—off lines after each
use. If these draw—off lines are left full of sludge, the sludge Is of
such a nature that it may set up and clog the pipes preventing any fur-
ther draw—off of sludge until the pipes are cleaned.
Carbonation
The pilot plant tests show that the rate of absorption of carbon dioxide
from the flue gas is very rapid. It is estimated, therefore, that a
20 minute contact period in a basin which was supplied with flue gas will
provide an ample opportunity for full absorption of carbon dioxide by the
tannery waste. Carbonation should be preceded by equalization because
changes in the rate of flow and the quality of the various discharges
from the tannery is so rapid that adequate carbonation is not possible on
an as received basis. Carbonation might well be preceeded by primary
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EFFLUENT WEIR
EFFLUENT WEIR
F LUE NT
SETTLING MIXING
ZONE
TURBINE —
MIXER______ -
SLUDGE
SCRAPING
MECHANISM
CARBONATI ON
FIG. 2 -SUGGESTED
— FLUE GAS
ThTh- Th .
SLuDGE
LANKET
SLUDGE
DRAWOF F
SEDIMENTATION BASIN
TREATMENT PLANT EQUIPMENT
TURBINE MIXER
ALKALINE
WASTES INLET
EQUALIZATION
SLUDGE DRAWOFF
AND PRIMARY
SEDIMENTATION BASIN
I I
I I I
U
UPFLOW
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sedimentation to reu ve undissolved lime which interferes with proper
carbonation. Carbonation ahould be followed by sedimentation in order
to remove the calcium carbonate which is precipitated by the flue gas.
Inasmuch as carbonation will require only a few minutes retention time,
this process might very well be carried out in a channel located between
an equalization basin and sedimentation basin.
On the basis of the wastewater survey, it is estimated that a capacity for
adding about 1,800 lbs of carbon dioxide per day should be provided. If
it is assumed that the flue gas contains 11 percent carbon dioxide and the
efficiency of using the carbon dioxide in the flue gas is 50 percent, the
volume of flue gas required will be about 2,600,000 cu ft per day or 1,700
cu ft per minute. On the same basis, it may be computed that it will be
necessary to burn about 1,150 lbs of oil per day in order to generate the
required quantity of flue gas.
Aeration Basin Design
In the pilot plant, the aeration basin functioned in a manner normal to
the activated sludge process. The only unusual reaction of the aeration
basin was the formation of large quantities of a very stable foam. The
foam was not a continuous problem but occurred from time to time. In the
pilot plant the foam was controlled by the use of sprays and- on occasion
by anti—foaming agents.
It is recommended that the installation of the activated sludge process
on a full—scale basis include foam control sprays and a chemical feed
system for adding anti—foam agents to the spray system. In addition, sur-
face aeration devices are recommended, because less foaming would be ex-
pected to occur than with the use of gas dispersion devices located be-
neath the liquid surface.
The aeration capacity to be provided should be sufficient to introduce
about 10,000 lbs of oxygen per 24-hours into the waste. It is estimated
that this will require aerators having a total power input of about 165
horsepower. The volume of the aeration basins should be about 1,000 cu ft
for every 60 lbs of BOD treated. On this basis, the aeration basins would
have a volume of 165,000 cu ft or about 1,250,000 gallons. Basins having
a capacity of about 1,250,000 gallons would provide a 12—hour detention
period for a waste and municipal sewage flow of about 2.5 mgd. It should
be noted that this design provides for 1.25 mgd of tannery effluents and
an equal amount of sanitary sewage from the Town of Paris.
Secondary Sedimentation
The activated sludge generated by the pilot plant was very light and dif-
ficult to settle. Based, however, upon the results of the operation of
the secondary sedimentation basin in the pilot plant it is recommended
that in the full—scale plant the secondary sedimentation basin be designed
for the overflow rate of not more than 500 gpd per sq ft per day. Pumping
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capacity equal to the influent flow to the treatment plant, i.e., about
1,800 gpm should be provided to return the sludge which settles in the
bottom of the secondary sedimentation basin back to the aeration basin.
This entire capacity may seldom be used but should be available if need-
ed.
Excess sludge from the secondary sedimentation basin should be returned
to the primary sedimentation basin and resettled with the primary sludge.
The reason for this recommendation is that the secondary sludge was very
difficult to dewater alone. However, mixing the secondary sludge with
the primary sludge resulted in a mixture which dewatered readily.
Sludge Dewatering
Although the sludge dewatered readily on sludge drying beds and there was
no odor from the drying sludge, however for the following reasons it is
recommended that sludge drying not be used at the proposed treatment
plant in South Paris:
1. A large volume of sludge will be generated by
the treatment processes (about 38,000 gallons
per day). Large quantities of sludge will
accumulate in a short period of time if not
continuously removed.
2. If unfavorable drying conditions, such as occur
in the winter, persist for any extended period
of time the volume of sludge which would accu-
mulate could become overwhelming.
3. Sludge drying beds require a great deal of hand
labor in clearing and hauling away the sludge.
In view of the cost of labor, manual handling
of the sludge is not economically attractive.
It is recommended that the sludge be dewatered by the means of a solid
bowl centrifuge. Such a centrifuge will produce a cake containing about
20 to 30 percent solids and will be sufficiently dry to truck to a final
disposal site. Dewatering by centrifuge can be arranged in such a manner
that the sludge is never handled manually. chanical dewatering of the
sludge permits dewatering without regard to weather conditions. The land
space required for mechanical dewatering of sludge permits a minimum use
of land for wastewater treatment purposes.
It is recommended that the sludge be disposed of by the sanitary landfill
method. It is estimated that about 2 acres of land per year will be need-
ed if the sludge is placed in layers 6 ft deep.
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COST ESTINATES
Cost estimates have been made and are based upon design criteria set
forth in these reconm endations with flow and effluent characteristics
existing at the studied location. The total capital and operating cost
of the full scale treatment of combined tannery and municipal effluent
is estimated to be 1.6 cents per foot of leather based upon present costs.
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ENTRQDUCT ION
The A.C. Lawrence Leather Company operates a tannery in Paris Maine.
The tannery is located immediately south of the built’-up section of the
Village of South Paris on the west bank of the Little Mdroscoggin River.
The tannery processes salted cowhides to finished leather. In 1968 the
tannery processed about 97,000 lbs (2,100 hides) per day. The management
at the tannery estimates that the maximum capacity of the existing plant
is about 144,000 lbs of hides per day. The tannery operates about 23 days
per month and employs about 220 people, divided into three shifts.
The processes utilized at the tannery may be generally classified as beam—
house operations, tanning and dyeing operations, and finishing operations.
These operations are described in detail later. The waste from these op-
erations amounts to about 1 mgd (million gallons per day) which, after
partial treatment by lagoons, is discharged to the Little Androscoggin
River. The river is badly polluted as a result of these wastes, especial—
ly during periods of low stream flow.
A report of the results of an engineering investigation and pilot plant
study of the treatment of the tannery waste carried out by Camp, Dresser
& McKee, Consulting Engineers, was submitted to the A.C. Lawrence Leather
Company in June, 1967. At that time, it was recommended that additional
experimental work should be carried out to more fully explore the treat—
inent processes recommended. A FWPCA (Federal Water Pollution Control
Administration) research grant was awarded the A.C. Lawrence Leather
Company to carry out a more extensive pilot plant program.
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DESCRIPTION OF THE TAN}UNG PROCESS
General
Tanning is the process whereby the normally putrescible proteins in animal
skin are preserved. A brief outline of the histology of skin will gLve an
insight into the sources of organic load in the wastewater in the tanning
operation which derive from the skin itself.
The skin as it arrives at the tannery consists of two layers, the flesh
and the derma. Strictly speaking the flesh is not a part of the skin pro-
per. Varying amounts of flesh may be attached to the skin, depending on
the processing employed at the meat packing plant, and the skill of the
flayer who removes the skin from the carcass.
The flesh layer must be removed by the tannery in the early stages of pro-
cessing. This flesh contains muscle tissue, fat cells, blood vessels and
adipose tissue, some of which finds its way into the wastewaters from the
tannery.
The derma layer is the portion of the hide or skin which ultimately be-
comes leather. The derina is a complex material, consisting of two broad
subdivisions; the epidermis and the corium.
The epidermis is the top layer of the skin, and contains the hair, hair
follicles, and oil glands which surround the hair roots. The surface of
the ipidermis is covered with a very thin layer of non leather—making
protein. Running through the epidermis is a connecting network of colla-
gen, the leather—making protein. During the early stages of leather pro-
cessing all of these undesirable materials are removed from the skin. They
are keratin, elastin, inucoids, albumens, and other proteins and alkaloids;
and a significant amount of fat.
The corium is the major part of the skin and is composed primarily of the
protein collagen. This collagen for the most part is an interwoven net-
work of fibers and fiber bundles. It is the objective of the tanner to
cleanse the skin of as much of the non—leather making debris as possible,
and to process or ‘stan” the remaining collagen fibers to render them
strong, flexible and non—putrescible.
As can be seen from the brief description above, the chemistry of skin is
essentially the chemistry of protein. During the early stages of the
leather manufacturing process many of these proteins are hydrolyzed or
otherwise broken down and removed from the skin. Much of the colloidal
and dissolved protein breakdown products appear in the wastewater. Very
little is known about the susceptibility of these waste products to bac-
terial attack in the biochemical oxygen demand test for pollution studies.
It may be that of efficient biochemical oxidation of these proteins re-
quires an acclimatized culture containing specialized enzymes.
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The Tanning Process
In order to understand the problems involved in treating the effluent
from the South Paris, Maine, tannery it is necessary to include at this
point a description of the tanning process.
This tannery is a chrome side upper leather tannery. That is to say, cow—
hides and steerhides are converted into a leather by the process known in
the trade as chrome tanning, a distinguished from other methods such as
alum or vegetable tanning. The following is a general description of the
various steps in the process. Fig 3 is a flow diagram of the tanning op-
erations indicating the sources of the various types of wastes.
The Beamhouse
The hides are received from thyineat packer or hide broker in bundles and
have been salted or brined to preserve them. They may also have been
“prefleshed” at the packing plant. The freshly flayed hides, if they are
to be prefleshed are processed through a machine which removes the greater
portion of the flesh from the skin. Following this step the hides are
treated with sodium chloride. The common method of doing this today is
to immerse the skins in a circulating saturated brine, which also serves
to cleanse the skin of much of the manure, dirt, blood, etc., which is
associated with it. Treatment with sodium chloride dehydrates the pro-
tein and renders it less susceptible to spoilage. The hids are then
packed in bundles for shipment to the tannery.
At the tannery the bundles are opened up and the hides are cut down the
backbone into two halves or “sides”. As a consequence of the preservation
n thod the next step at the tannery consists of removing much of the salt
from skins and restoring moisture to render them flexible and receptive to
processing chemicals. This process is referred to as soaking. The sides
from the hide storage area are placed in large pits equipped with paddle
wheels which serve to circulate the contents. The pits contain water to
which a small amount of a wetting agent may be added. From time to time,
the sides are agitated by operating the paddle. Midway through the first
soak small quantities of sodium sulfide and lime are added. After about
14 hours the paddle pits are drained and refilled with fresh water, and
the stock is washed with running water for a short time.
Fleshing follows soaking. Fleshing consists of passing the sides through
a machine with rotating helical blades which remove the excess flesh from
the sides. Water runs on the blades to keep them free of debris. The
solid fleshirigs are collected in a box equipped with drain holes, the liq-
uid waste passing to the sewer.
14
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HIDE HOUSE
STORAGE
SORTING
SIDING J_ ITRIMMINGS INGS
TRIMMING
ALKALINE ’ SOAKING 1
WASHING
FLOOR
FLESHING 1 FLESHINGS
w DRAINS I
I______ _____
w
c i )
• FLOORj UNHAIRING
DRAINS WHEELS
___________NHAIR WA
-J
4
< FLOOR ’ UNHAIRING [ /1
‘ DRAINS MACHINE SHINGJ
- 4. I DETERGENT
_____________ SOLUTION
ACID J BATE—PICKLE—
WASTE TAN
____ SHAVINGS
I SPL1T/SHAVE1 SPLITS
ACID COLOR I
WASTE FATLIOUOR
LU
SPA1_
L i i
U )
a MECHANICAL 1
OPERATIONS J -i TRIMMINGS
WASHUP ’ 1
FINISH
HAIR
[ SCREENING I
. 4
FIG. 3 TANNERY PROCESS FLOW SHEET
15
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The next operation is unhairing. This operation consists of loosening
the hair by treating the sides with a chemical solution described below,
followed by mechanical removal of the hair in a machine similar to a
fleshing machine. The sides are placed in a “drum” or “wheel”, a large
cylindrical container which is rotated at a slow speed. Water, sodium
sulfhydrate, lime, and small amounts of other chemicals are added to the
drum. After a suitable length of time in this solution, the hair has been
loosened from the skin. The liquid is drained and may be passed to a
holding tank to be refortified and reused. The sides are washed with run-
ning water, dumped, and forwarded to the unhairing machines. The hair
removed in the machines is retrieved from the water and goes to a hair re-
clamation area where it is washed, dried and baled. All washings, contain-
ing small particles of protein solids, grease, sulfide and other chemicals
go into the effluent stream.
Liming follows the unhairing step. In this step the sides are immersed
in a lime suspension in a paddle and occasionally agitated to insure a
uniformity of treatment. Sodium sulfide in a small amount may be added
to the lime pit also. This operation swells the skin and opens up the
finely interwoven collagen fiber bundles. Non—leather making protein
and other undesirable debris is loosened from the skin so that it may be
removed. Following a suitable treatment time in this solution the sides
are pulled from the paddle and are passed to a scudding machine. “Scud-
ding” consists of putting the sides through a machine which scrapes the
grain surface with a dull blade. This serves to remove remaining hair
roots, epiderinal keratinous tissue and other surface debris. This debris
passes to the effluent stream.
The above described operations constitute what is known as the beamhouse
operation. The following part of the leather—making operation is known
as tanning and coloring and is described below.
Tanning and Coloring
As a result of the several processes in the beamhouse, the sides are now
in a highly swollen alkaline state. Before the collagen will accept and
react with the tanning materials, it must be made acid and the swelling
must be removed.
The first step in this process is bating and deliming. In this process
the sides are first placed in a drum and washed thoroughly. This is
followed by treatment with a proteolytic enzyme at a pH of about 9.0.
This pH is attained by the addition of aimnonium sulfate which acts as a
deliming salt. A small amount of detergent may also be added. The en-
zyme acts on the noncollagenous proteins in the grain surface of the
leather and contributes to the final soft pleasant grain character
achieved in the finished leather. Following a suitable length of time in
this solution, the stock is washed in running water to stop the bating
action and remove the solubized lime as calcium sulfate.
16
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Pickling follows and consists of lowering the pH of the stock to about
2.0 with sulfuric acid. This is done in a sodium chloride solution,
which acts to repress the swelling and keep the stock in a firm, “fallen”
state.
When the pickling has proceeded to the desired point, the tanning material
is run into the rotating drum. This consists of a complex salt of chro—
iniuni resulting from the reduction of sodium bichromate with sulfuric acid
and an organic compound such as sucrose. This tanning solution is allowed
to penetrate the skin following which the pH is slowly raised by the ad-
dition of sodium bicarbonate to a pH of about 3.5. This causes the chro—
inium salt to combine chemically with the collagen, thus producing leather.
The excess solution is drained to waste and the leather is washed in run-
ning water.
Following tanning the leather is subjected to several mechanical opera-
tions as follows. First, the leather is wrung to extract as much moisture
as possible. The leather then goes to a splitting machine, which is es-
sentially a horizontal band knife. This machine splits the leather into
the grain, or top layer and the split, or bottom layer. This bottom layer
referred to in the trade as a “blue split” or “chrome split” is not pro-
cessed further in the South Paris tannery, but is sold to custom finishers
who process it into shoe linings, insoles, slipper soles, etc. The grain
proceeds to a shaving machine, where the back is further leveled and
smoothed by shaving off any unevenness which may be present. The chrome
shavings thus produced are retrieved, baled and sold as a byproduct. A
certain amount of the fine shavings adhere to the moist, fibrous back of
the leather and are carried into the next operation which is coloring and
oiling, and eventually find their way into the effluent.
Following shaving the sides are put into the coloring and oiling or “f at—
liquoring” wheels for further processing. It is here that the leather
may be retanned with chromium salts, synthetic tanning materials (syntans),
and the fibrous structure partially filled with clay or other fillers.
These operations are all performed in a water n dium and washing usually
follows each processing step. Here also dye solutions are applied depend-
ing on the shade desired in the finished leather. The dyes are customar-
ily fixed or made fast with formic acid. Finally oils are introduced into
the drum, usually as oil—in—water emulsions. As these emulsions are brok-
en at the leather surface the oil is worked into the leather. The oils
commonly used are cod, sperm and other animal and fish oils, usually sul-
fated sufficiently to cause them to be self—emulsifiable. In some cases
additional emulsifiers and stabilizers are added.
From the above description of the coloring and oiling procedure it is ap-
parent that a great variety of both organic and inorganic pollutants find
their way into the tannery effluent from this source. The next processes
at the tannery are completed with the coloring and oiling procedure.
17
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A relatively non—polluted effluent is discharged from the pasting and oil-
ing. Pastings is the method employed to dry the leather. The sides are
affixed to smooth porcelainized steel plates which have previously been
sprayed with a water dispersible paste. The plates with the leather ad-
hered to them are passed into a heated drier where the moisture is driven
out of the leather. After the leather has been stripped from the plates,
they are passed through a washer which removes the old paste, sending it
to the sewer. A fresh paste is then applied to the surface.
After drying, the leather is subjected to a variety of dry mechanical
operations and ultimately arrives in the finishing department where the
final processing steps are performed.
Finishing
In finishing side leather for shoe uppers it is necessary to apply a pig-
ment finish to the surface of the leather to make the surface uniform in
appearance and of the shade desired. “Pigment finish” is simply pigment,
organic and inorganic, dispersed in a suitable emulsified resin binder.
It may be modified with plasticizers, waxes, etc., to give the handling
characteristics and surface feel desired. A small amount of waste, prin-
cipally machine clean—up water is discharged in this operation.
With the exception of plant clean—up water and discharges from compressor
cooling and boiler room and the above constitute the sources of waste
from the tannery.
18
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E ’FLUENT SURVEY
? yio 1s Ef
Prior to the present pilot plant study four effluent surveys had been
conducted at the tannery at South l’aris. The results of the previous sur-
veys were studied prior to undertaking the pilot plant investigation. The
results of studies and surveys which were available are listed below:
1. Surface water sampling by the State of Maine Water
Improvement Commission for 1956 and 1959.
2. Report entitled “Waste Flow Analysis, Plant and
Unit Operation Studies,” Hydroscience, Inc., Leonia,
New Jersey, July, 1964.
3. Sewerage Tests — South Paris, July 9, July 27,
August 2, 1965, Summary Report, dated October 22,
1965 to Mr. N.H. Battles from J.A. Bassett,
Technical Department.
4. Report entitled “Pilot Plant Investigation of
Wastewater Treatment at South Paris, Maine,”
Camp, Dresser & McKee, Boston, Massachusetts,
June, 1967.
The results of the waste surveys previously made were individually aver-
aged to obtain the best possible estimate of the waste discharges for the
periods investigated in 1959, 1964, 1965 and 1966. These estimates are
summarized in Table 1. The results in Table 1 show no particular trend.
The results do indicate, however, that large quantities of waste materials
are discharged from the tannery each day. The magnitude of these discharg-
es is indicated best by the total solids and the BUD value. The total
solids in the effluent amounted to about 40,000 lbs per day and the BUD
ranged from 5,000 to 8,000 lbs per day according to the past surveys.
Present Effluent Surveys
Since the last survey, in 1966, the tannery made substantial increases in
the rate of production and some changes in the processes employed. There-
fore, in connection with the pilot plant work it was considered essential
to carry out further waste surveys. Initially, two 24—hour surveys were
made , one on December 14, 1967, and one on January 2, 1968. After study-
ing the results of these 24 - .hour surveys, it was felt that the picture of
the waste discharges presented by the results of the surveys was incom-
plete. This conclusion was based upon the manner in which the tannery op—
erates. A batch of hides is started on one day and requires approximately
two to three days to pass through the entire process. Such a manner of
operation results in a two to three day cycle of changes in the effluent
19
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TABLE 1 SUMMARY OF PREVIOUS WAS TEWATER SURVEYS
ATA.C. LAWRENCE LEATHER COMPANY TANNERY,
SOUTH PARIS, MAINE
Date 1959 April 1964 June - August 1965
Source of survey Maine Water Improvement Hydroscience A. C. Lawrence Leather Co.
Commission
Flow, gpd 1,045,000 650,000
pH
Alkalinity, (as Ca Ca 3 ), lbs/day 2,488
Total solids, lbs/day 40,625 34,905
Total volatile solids, lbs/day
Suspended solids, lbs/day 13,540 7,024
Volatile suspended soflds, lbs/day
Settleable solids, gals/day 782
Calcium (As Ca C0 3 ) , lbs/day
Suif ides (as 5), lbs/day 1 ,550
Chromum (as Cr), lbs/day
BOD, 5-day, 20°C., lbs/day 5,100 6,790 5,000
COD, lbs/day 31,165 16,284
-------
characteristics. In order to overcome this deficiency in the December
and January waste surveys, a third survey was carried Out on April 9 and
April 10, 1968. The April 9—10 survey was a 48—hour survey.
The December 14, 1967 and the January 2, 1968 surveys were conducted in
the following manner. All the effluents from the tannery, both acid and
alkaline, come together into a single open flume which conducts the flow
to a series of waste retention lagoons. A section of the flume downstream
from the junction of the acid and alkaline discharges was selected for the
sampling point. At this location, a measuring weir box was installed.
The weir box consisted of a channel about 15 ft long by 3 ft wide and about
2 ft deep. The inlet to the chamber was baffled in such a manner as to
distribute the flow uniformly across the cross—section of the channel. At
the end of the channel a sharp edge rectangular weir, having a crest width
of 1 ft, was installed. The crest of the weir was approximately 1 ft above
the bottom of the channel. The downstream slope of the channel was such
that, even at the highest flows, the crest of the measuring weir was not
submerged. A measuring gage was installed in the channel approximately
2 ft upstream from the weir. Head measurements were made in a stilling
section. A weir calibration chart was drawn up and supplied to the men
collecting the samples.
Starting at 8:00 a.m. on December 14, 1967, samples were collected every
20 minutes until 8:00 a.m. on December 15, 1967. The sample procedure
was followed for the January 2, 1968 survey. The samples were taken from
the weir overflow using a dipper and ladling into a pail. Immediately
after collecting the sample, the depth of flow over the weir was measured
and the flow computed. Immediate measurements were made of the tempera-
ture, pH, alkalinity and settleable solids from each sample. The contents
of the pail were stirred vigorously and a sample was taken having a volume
proportional to the flow. The sample was composited for further analysis.
Composites representing each two hours of flow were made up in this manner.
The composite samples were analyzed for BOD, total solids, total volatile
solids, suspended solids, volatile suspended solids, and calcium. The
results of these two surveys are summarized in Table 2 and Table 3 respec-
tively.
The 48—hour survey conducted April 9 and 10, 1968 was somewhat more inclu-
sive. During the April survey, samples were collected each 15 mm and corn—
posited hourly on the basis of flow. pH and temperature were measured at
the time of collection. Tests for alkalinity, acidity, calcium, sulfide,
total solids, total volatile solids, suspended solids, volatile suspended
solids, 5—day 20°C BOD, and settleable solids, were conducted on each hour—
ly composite. Composites of flow for 2 hr periods were analyzed for chro-
mium. The results of this 48—hour survey are presented in Table A—26 arid
summarized in Table 4. The results are also presented graphically in Figs.
A-l through A—6 in the appendix.
21
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TABLE 2 SUMMARY OF 24 HOUR SURVEY
OF TOTAL WASTEWATER DISCHARGE
DECEMBER 14 TO 15, 1967
Flow (gpd) 801 ,520
pH Range 6.1 -11.7
Alkalinity to pH 8.3 as CaCO 3 (lb/day) 2,620
5 day 20°C BOD (lb/day) 7,180
Settleable Solids (gals/day) 70,810
Total Solids (lbs/day) 47,150
Total VolatHe Solids (lbs/day) 14,060
Suspended Solids (lbs/day) 11 ,260
Volatile Suspended Solids (lbs/day) 8,480
Calcium as CaCO 3 (lbs/day) 5,960
22
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TAB1..E 3 SUMMAR Y OF 24 HOUR SURVEY
OF TOTAL WASTEWATER DISCHARGE
JANUARY 2 to 3 1968
Flow (gpd) 805,920
pHRange 5.7—11.2
Alkalinity to pH 8.3 as CaCO 3 (lbs/day) 1 ,470
5 day 20°C BOD (lb/day) 6,790
Settleable Solids (gals/day) 62,540
Total Solids (lbs/day) 44,830
Total Volatfle Solids (lbs/day) 12,020
Suspended Solids (lbs/day) 11,350
Volatile Suspended Solids (lbs/day) 6,540
Calcium as CaCO 3 (lbs/day) 6,200
23
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TABLE 4 SUMMARY OF 48 HOUR SURVEY OF TOTAL
WASTEWATER DISCI-IARGEAPRIL9 TO 11, 1968
Flow (gpd)
pH Range
Alkalinity to pH 8.3 as CaCO 3 (lbs/day)
BOD (lb/day)
Settleable Solids (gals/day)
Total Solids (lbs/day)
Total Volatile Solids (lbs/day)
Suspended Solids (lbs/day)
Volatile Suspended Solids (lbs/day)
Calcium as CaCO 3 (lbs/day)
Sulfides as S (lbs/day)
Chromium as Cr (lbs/day)
Hides into soak (lbs , hidehouse wt.)
Hides into lime (Ibs, soaked, f4eshed wt.)
Hides into tan (lbs. white wt.)
Hides out of tan (lbs, white wt.)
4/9 -4/11
AVG/DAY
934,000
5.0 - 12.0
2,832
8,562
130,425
69,940
20,405
17,090
10,625
8,275
414
1 ,836
105,750
105,300
130,200
138,600
1 1506 of the total 3,936 sides were trimmed and fleshed prior to weighing.
2 6750 lbs of green, salted, untrimmed hides or 6000 lbs of green, salted, trimmed
and fleshed hides is equivo lent to 7800 lb soaked and fleshed hides and is also
equivalent to 8400 lb white weight of hides.
4/9 4/10 4/10 4/11
8:00 am - 8:00 am 8:00 am - 8:00 am
911,000 958,000
5.2 - 12.0 5.0 - 11.6
2,345 3,319
8,244
144,230
75,600
24,420
19,350
12,270
8,160
309
1 ,870
900001
109,2002
142,8002
134,4002
8,880
116,620
64,280
16,320
14,830
8,980
8,390
519
1,802
121 ,500
101,4002
117,6002
142,8002
24
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From Table 4 the summary of the 48—hour survey results, it may be seen
that the flow was relatively uniform from day to day, being 911,000 gpd
on April 9, and 958,000 gpd on April 10, with the average flow for the
two days being 934,000 gpd. The alkalinity sununarized in Table 4 is the
net alkalinity for the periods indicated. To arrive at this figure, the
total acidity was subtracted from the total alkalinity resulting in the
net alkalinity for the day as shown in Table 4. For April 9, the net
alkalinity was 3,345 lbs per day (as CaCO 3 ) and for April 10, the net al-
kalinity was 3,319 lbs per day, while the average for the 48—hour period
was 2,832 lbs per day. The BOD also appears to be quite constant from
day to day. For April 10, the BOD was 8,880 lbs. Based upon the appro-
ximate weight of 105,000 lbs of raw hides being processed per day, the
BOD amounts to 8.16 lbs of BOD per pound of hide processed. The solids
show a somewhat wide fluctuation from day to day. The average settleable
solids for the 48—hour period amounts to 130,425 gpd. The average total
solids amount to about 70,000 lbs per day with a total volatile solids
content of about 20,400. The volatile solids content is, therefore, only
29 percent. The low percentage of volatile solids is a reflection of the
high content of inorganic materials, which are predominately sodium chlo-
ride, calcium hydroxide, sodium sulfide, and the chromium compounds em-
ployed in the tannery or washed from the hides. The suspended solids
amount to about 17,000 lbs per day, of which about 11,000 are volatile.
The volatile solids content of the suspended portion of the solids amount
to about 8,300 lbs per day. The sulfide content, expressed as sulfur, is
about 400 lbs per day and the chromium content of the wastewaters, ex-
pressed as chromium is about 1,800 lbs per day. The weight of the chro-
mium in the wastewaters is equivalent to about 1.3 to 1.4 lbs of chromium
per 100 lbs of wet hides being tanned.
Acid Waste Survey
In order to gain a deeper understanding of the wastes produced by the
tanning and coloring processes, an acid wastes survey was conducted on
March 5, 1968. This particular survey was made by sampling and measur-
ing the input and output of a number of individual tanning and coloring
wheels. Samples were collected from the liquid contents of each wheel
just prior to discharge to the sewer. Samples were analyzed both sepa-
rately and as composites. The results of the acid waste survey are sum-
marized in Tables 5 and 6. The basis of the summary is the amount of
wastes which would be discharged from 15 tanning wheels and 23 color
wheels in a 24—hour period. At the time of the survey, 126,000 lbs of
wet hide were being tanned and about the same amount of wet hides were
being colored. It was found that 267,600 gallons of acid waste is pro-
duced each day. The acidity of this waste is equivalent to about 1,500
lbs of calcium carbonate each day.
The results found in the acid waste survey correspond quite closely to
those found on the 48—hour sampling. The total chromium found in the
acid wastes survey amounted to 1,610 lbs of chromium per day, which com-
pares quite favorably with the total of 1,800 lbs per day found for the
25
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TABLE 5
COMPOSITE OF TAN WHEEL EFFLUENT
Quantity Quantity
Per Wheel Per Day
Total Volume, gallons 10,020 150,000
pH 7.2 7.2
Acidity, as CaCO 3 , to pH 4.5, lbs 0 0
to pH 8.3, lbs 2.8 42.
BOD, 5-day 20°C, lbs 140 2,100
Total Solids, lbs 636 9,550
Total Volatile Solids, lbs 134 2,000
Suspended Solids, lbs 104 1 ,560
Volatile Suspended Solids, lbs 42 630
Settleable Solids, gallons 3,000 45,000
Chromium as Cr, lbs 74 1 ,110
Pounds of hides 8,400 126,000
26
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TABLE 6
COMPOSITES OF COLOR WHEELS EFFLUENT
Quantity per Wheel
Quantity
Tropic i Casco Per Day
Total Volume, gallons 5,160 5,090 117,000
pH 3.85 3.85 3.85
Acidity, as CoCO 3 to pH 4.5, lbs 0.7 0.6 14
to. pH 8.3, lbs 3.5 5.1 100
BOD, 5—day 20°C, lbs 54 32 1 ,000
Total Solids, lbs 190 224 4,850
Total Volafile Solids, lbs 92 90 2,100
Suspended Solids, lbs 46 42 1 ,000
Volatile Suspended Solids, lbs 32 30 710
Settleable Solids, gallons 340 gals 510 gals 9,800
Chromium as, lbs 24 500
27
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48—hour survey. The total BOD in the acid wastes amounts to about 3,100
lbs per day or about 3/8th of the total BOD. The total solids in the acid
wastes amount to about 15,400 lbs per day or about 21 percent of the solids
in the total tannery effluent. Analysis of these results reveal that most
of the minerals in the wastewater are derived from the salt and lime dis-
charged from the beamhouse. On the other hand, the tanning and coloring
processes use about 28 percent of the water used by the tannery.
Discussion of Survey Results
One observation which was made during the course of the surveys and the
pilot plant operation, which is not readily seen from the study of the
survey results, is the effect of mixing the alkaline beainhouse wastes
with the acid tan house wastes. Mixing of the two wastes results in a
considerable increase in the suspended solids. When the mixture contains
an excess of the alkaline wastes such that the pH of the mixture is above
about 8.5 most of the chromium which is in solution in the acid wastes,
is precipitated as chromium hydroxide. The resultant flocculant material
tends to coagulate many colloidal particles which otherwise would not
settle. The settleable solids are thereby greatly increased in the mix--
ture over that fotnid in the individual waste streams. The total amount
of settleable solids which would be obtained by a uniform mixing of the
acid and alkaline wastes is not reflected to the full extent in the 48—
hour survey because many of the acid discharges took place when an excess
of alkalinity was not present and therefore the precipitation of chromium
hydroxide did not occur at such times. However, in the pilot plant op-
eration, acid wastes were proportioned to the total flow in such a manner
that excess alkalinity was always present and the maximum effect of the
chromium hydroxide coagulation was obtained.
All analyses made during the survey, with the exception of the analysis
for chromium, was done in accordance with the twelfth edition of “Standard
Method for the Examination of Water and Wastewater.” The analyses for
chromium were performed at the central laboratory of the A.C. Lawrence
Leather Company in Peabody, Massachusetts.
Two basic methods were used for the determination of chromium in a sample.
If the sample was thought to have a high chromium concentration, such as
the various sludges or the contents of a tanning wheel, the sample was
analyzed according to the American Leather Chemists Official Method D—lO,
which consists of evaporating the sample to dryness and ashing in an
oxidizing atmosphere. The ashed sample is then fused with a mixture of
sodium carbonate, potassium carbonate, and boraz. The fusion is dis-
solved in hot, distilled water, excess potassium iodide added, and the
iodine released is titrated with sodium thiosulphate. For samples thought
to have a low concentration of chromium, such as treatment plant ef flu—
ents, the sample is oxidized with potassium permanganate and diphneylcar—
bazide is added. The resulting color is measured spectrophotometricälly
at a wavelength of 540
28
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THE PILOT PLANT
Purpose of the Pilot Plant
Tannery wastes have many characteristics which make the treatment of these
wastes extremely difficult. The pH of the wastes fluctuate widely through-
out the day, ranging from 3 to 12. The wastes have a high concentration of
sulfide (up to more than 700 mg/i), chromium concentrations of more than
500 mg/i, fungicides which very in concentration and characteristics depend-
ing upon the particular procedures being used in the tannery, and detergents
of various kinds. In general, past attempts to treat tannery wastes have
been far from satisfactory.
The documentation of treatment methods which have not been successful is
difficult, because failures are seldom published. Problems normally en-
countered include unsatisfactory treatment by primary sedimentation, clog-
ging of trickling filters by precipitated calcium carbonate, blinding of
vacuum filters dewatering sludge and odors resulting from waste lagooning.
Previous studies (1) of the tannery effluent at South Paris indicated that
supplemental nutrients might be needed to achieve successful biological
treatment of the wastes. It was felt that the addition of municipal sani-
tary sewage to the tannery would supply the necessary nutrients. Other
literature supported this viewpoint (2),(3),(4). Furthermore, joint treat-
ment of municipal sewage and tannery wastes offers a number of other ad-
vantages such as reduced overall costs and availability of state and fed-
eral aid in financing joint treatment works. Hence, one of the purposes
of this investigation was to determine the implications of this method of
treatment.
The industrial waste treatment literature contains many reports of methods
for the treatment of tannery wastes (2),(3),(4),(5),(6). Most of the
investigations reported in the literature are laboratory scale tests or
small pilot plant tests under controlled conditions. Very few experimen-
tal results are available for full—scale waste treatment works. Most full—
scale treatment of tannery wastes has consisted of primary sedimentation
or disposal to some type of lagoon system. Treatment by primary sedimen-
tation alone or by lagooning has usually resulted in the generation of ob-
noxious hydrogen suiphide odors and an effluent which was unsuitable for
discharge to high quality receiving waters. Treatment methods based on
small scale experimental investigations have not been generally adopted
because of the narrow scope of these investigations, the high cost of the
construction of the required treatment works and the uncertainty that the
final results would meet with the designer’s expectations. In view of the
general lack of knowledge concerning the treatment of tannery wastes, it
was considered essential to conduct pilot plant studies to determine the
most feasible and economic method of treating the effluent from the tannery
at South Paris.
29
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The general type of treatment to be investigated by the pilot plant method
at South Paris was determined by three considerations:
1. The degree of treatment required, because of the classi-
fication of the Little Androscoggin River, was very high,
in excess of 90 percent removal of BUD and suspended solids.
2. The nature of the tannery wastes. Surveys indicated that
the wastes were high in BOD. BOD at times exceeded
4500 mg/i. High cromium content and high sulfide con-
tent.
3. The need to develop the most economic system available.
The degree of treatment required was quite high. The only biological
treatment which appeared to offer the required degree of treatment was
the activated sludge process. Trickling filters were considered, however,
the experience of clogging of trickling filters by calcium carbonate (7)
lead to rejection of this method of treatment.
The pilot plant was, therefore, developed on the basis of utilizing the
activated sludge process. Since the activated sludge process is a bio-
logical process, it was necessary to provide such pretreatment of the
waste as might be required to reduce the concentration of biologically
toxic materials to levels tolerable to the process.
The characteristic of the waste which appeared to be the most harmful to
biological processes was the rapid and extreme fluctuation in the pH as
it was discharged from the tannery. The tannery effluent survey indicated
that the low pH acid wastes were discharged from the tanning and coloring
process and the high pH wastes were discharged from the beamhouse process.
It was obvious that the first step for reducing the fluctuations in pH
should consist of a uniform mixing of the alkaline and acid wastes dis-
charges. Chemical analysis and computations indicated however, that the
quantity of acid wastes was insufficient to neutralize completely all of
the alkaline wastes. It was therefore, necessary to effect a further re-
duction of pH before the mixed waste was acceptable for biological treat-
ment. Carbon dioxide was selected as the most satisfactory agent for the
necessary pH reduction. Carbon dioxide was selected because it will re-
act with the excess lime which is present to form an insoluble precipitate
of calcium carbonate, which may then be removed from the waste by sedimen-
tation. Carbon dioxide is available at the tannery in large quantities
in the flue gases from the power house stacks. Carbon dioxide is a safe
material to handle and does not present the hazards involved with handling
and storage of strong acids in liquid form.
Literature studies indicated that while chromium is toxic to some forms
of biological life, in particular algae and green plants (8), the organ-
isms which are active in the activated sludge process are tolerant of
chromium in concentrations of less than 50 mg/l (9). Furthermore, a study
30
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of the chemistry of chromium indicated that a great deal of chromium will
be removed from the waste during the pretreatment stage as chromium hydrox-
ide, provided the pH of the waste is maintained above 8.5 to 9.0.
It should be noted that all of the chromium encountered in the was tewater
at the tannery was in the tri—valent form.
The presence of high concentrations of sulfide in the waste created a
serious problem. If the pH of the waste mixture is reduced below 8.5, the
chemical equilibrium of the sulfide is such that hydrogen sulfide gas will
be given off in amounts that will be intolerable both from the viewpoint
of atmospheric odors and toxicity to personnel in the vicinity.
The tolerance of the activated sludge process for sulfide was not known.
Our previous studies and those of others (10) indicated, however, that an
acclimated activated sludge process will rapidly remove or alter the sul-
fide in waters containing the concentrations of sulfide comparable to those
expected under average conditions in the South Paris tannery discharges.
However, it was not known if the process would be adversely affected by
high concentrations of sulfide in the form of surges which are discharged
by the tannery.
A further purpose of the pilot plant investigation was to determine design
factors for full—scale treatment works. It was necessary to determine such
factors as the maximum rate of oxygen uptake by an activated sludge system
treating the tannery waste; the rates at which the suspended solids will
be removed by primary sedimentation and by secondary sedimentation; the
value of polyelectrolytes for assisting sedimentation; the rate and degree
of uptake by the waste of carbon dioxide in flue gas; the rates of forma-
tion and precipitation of calcium carbonate in the complex tannery efflu-
ent; the degree of BOD removal which can be achieved by the activated
sludge process; the availability of nutrients for supporting the activated
process; the volume and concentration of both primary and secondary sludge
which will be produced; the dewatering characteristics of sludge; the chlo-
rine demand of the treated effluent; and an economic evaluation of the pro-
cess applied to a real situation. The pilot plant was designed to operate
over a fairly wide range of flows in order to determine the optimum opera-
ting point for each of the unit processes involved.
Pilot Plant Design
A process flow sheet for the pilot plant is presented in Fig. 4. The
treatment units in the order of utilization in the process are an alkaline
waste storage tank, an acid waste storage tank, an alkaline waste feed pump,
an acid waste feed pump, a mixing box, a primary sedimentation basin, a
carbonation basin feed pump, a combination upflow—carbonation—sedimentation
basin, a flue gas pump, a sanitary sewage storage basin, an activated sludge
aeration basin, a foam trap, a secondary sedimentation basin, and a sludge
dewatering centrifuge (not shown on Fig. 4).
31
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FIG. 4 FLOW SHEET FOR PILOT PLANT
MEAIU INS
wEI SOX
R CIPCULATING
PUMP
ALKALI rEED
PUMP
S CONOA Y
SIDIMENT AT ION
IA SIN
CAVITL IrE AE ATOPS
TO
NLT URN SLUD*
PUMP
rLUL GAS
COMPRESSER STACK
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The waste treatment pilot plant was normally operated in the following
manner:
The alkaline waste flow from the tannery was continuous and constituted the
largest single volume of waste discharged from the tannery. The alkaline
waste was discharged from the tannery immediately following fine screening
through a drum screen. Screening was for the purpose of hair and gross
solids removal. The acid waste was discharged intermittently through a
separate outlet. The following method was used to obtain the portions of
acid and alkaline wastes used in the pilot plant.
The alkaline waste was pumped from a discharge sump, following screening,
into a piping system which circulated through the pilot plant and back in-
to the alkaline waste discharge. The circulating pumping system operated
continuously except when the tannery was shut—down on weekends. At the
pilot plant, a small progressing cavity positive displacement metering pump
pumped at a fixed rate from the recirculating line to the mixing box. Thus,
the flow of alkaline waste to the pilot plant mixing box fluctuated in
quality in a manner representative of the tannery alkaline discharge; how-
ever, the rate of flow to the pilot plant was constant. Since the flow in
the acid discharge line was intermittent, it was necessary to pump from
the acid discharge line at such times as flow was available. When there
was flow in the acid discharge line, the acid wastes were pumped to an acid
storage tank in the pilot plant. In the acid storage tank, the acid waste
was gently mixed to keep solids in suspension. Furthermore the acid waste
was adjusted to a constant strength, equivalent to the average strength of
the acid waste discharged throughout a 24—hour period. The acid waste was
then pumped from the acid storage tank to the mixing box by a positive dis-
placement metering pump. The acid feed pump was adjusted hourly on the
basis of the concentration of alkalinity in the alkaline discharge. Ad—
justments were made in an attempt to maintain a nearly constant alkalinity
in the pilot plant influent. However, it was not possible to maintain a
constant alkalinity and wide fluctuations still occurred. However, these
fluctuations were minimized as much as possible. Great care was taken,
however, to insure that the pH of the mixed waste did not fall below 9.0
and thus ge.uerate toxic H 2 S gases.
During the initial stages of the pilot plant studies, no primary sedimen-
tation was employed. However, the amounts of sludge which were encounter-
ed when the beamhouse waste was mixed with the acid tanning wastes were so
excessive as to overload the settling section of the unit and render op-
eration of succeeding units unsatisfactory. Hence, after about three
menths of initial operation, a primary sedimentation basin was installed.
Following the mixing of the acid and alkaline wastes the flow entered the
primary sedimentation basin. The primary sedimentation basin was a modi-
fied rim feed circular basin with the effluent take—off at a central weir.
The bottom of the primary sedimentation basin was conical and equipped
with scrapers to insure the movement of the sludge to a central draw—off
valve. The primary sedimentation basin was 4 ft in diameter and had a
side water depth of 3 ft and a center water depth of 6 ft 8—in. The net
surface area was 11.5 sq ft and the capacity was 355 gallons.
33
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The effluent from the primary sedimentation basin was pumped to the com-
bination upf low sedimentation—carbonation basin. Fig. 5 is a section
through the carbonation—upflow—sedimentation basin. The carbonation—sedi-
mentation basin consisted of two compartments. The inner compartment was
a square column about 6.5 ft long with an interior cross section about
10—in on each side. The column was mounted vertically at the center of
the upf low compartment. The upf low compartment was constructed in the
shape of an inverted pyramid: the top was 4 ft on each side tapering to
1 ft on each side at the bottom. The central column was supported about
1 ft from the bottom. The liquid depth of this basin was about 7.5 ft.
The total volume of the unit was 350 gallons including about 50 gallons in
the central compartment. Mounted in the central compartment near the bot—
toni was a diffuser for flue gas.
The diffuser consisted of a short length of rubber tubing with one end
closed tightly and the other end attached to the gas supply pipe. Small
slits were cut in the rubber tubing to disperse the gas. The rubber tubing
diffuser was developed after considerable trouble had been experienced from
build—up of calcium carbonate on the orifices of more conventional type dif-
fusing systems. The initial diffuser consisted of an 8.-in diameter ring
formed from 1/2—in copper tubing. The ring contained 10 1/16—in holes.
These holes soon clogged with precipitated calcium carbonate. The holes
were enlarged to 3/16—In diameter but they still clogged. Clogging oc-
curred because calcium carbonate deposites built up as small hollow cones
around each hole. As the height of the cones increased the openings be-
came smaller and the pressure needed to exhaust the flue gas increased.
Eventually It became necessary to remove the diffuser ring and clean the
holes. The problem was increased by the intrusion of waste into the dif-
fuser when the flow of flue gas was shut off. The rubber tubing served
two purposes. If calcium carbonate tended to build-up around the slits
the rubber would stretch and flex and break off the accumulation. When
the gas was shut—off, the slits would close and prevent the waste from
entering the gas lines.
The effluent from the sedimentation section of the carbonation basin was
taken of f near the surface through two horizontal parallel pipes having
1/4—in diameter holes spaced three inches on centers. Sludge removal from
the upf low basin was accomplished in a sludge concentration hopper located
on one side of the tank. The sludge overflow weir, giving access to the
hopper, was located at a distance of 5 ft from the bottom of the unit.
Sludge was also removed from the bottom of the flow through section, es-
pecially before the primary basin was installed. At times, before the
installation of the primary sedimentation basin, more sludge was found in
the flow through compartment than in the sludge hopper. In order to pre-
vent the flow from channeling through the sludge blanket, a mixing blade
was Installed near the bottom of the hopper. The mixing blade was 9—in
long by 3—in wide and was mounted on a vertical shaft which was rotated
through a speed reducer. The speed of rotation was about 100 rpm.
34
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3• —
FiG. 5 SECTION THROUGH CARBONATION SEDIMENTATION UNIT
-------
The net surface area at the water surface was 14.1 sq ft. The cross sec-
tion area of the sedimentation—carbonation unit at the level of the sludge
weir was 8.25 sq ft net.
The carbonation—sedimentation unit was operated in the following manner.
The influent flow was introduced near the top of the central column. The
flow was downward through the central column and upward through the ex-
pending section of the sedimentation portion. Carbon dioxide or flue
gas was introduced through the gas diffusion piping at a point near the
bottom of the central column. Therefore, the gas flow was upward and the
liquid flow was downward providing good contact between the gas bubbles
and the alkaline wastes. The flow was then under the bottom edge of the
central column and upward through a sludge blanket approximately 4 ft deep.
The sludge blanket provided ample contact between previously precipitated
calcium carbonate sludge and the supersaturated calcium carbonate solution
passing through it. As the level of the sludge blanket increased above
the sludge weir, the excess sludge settled into the sludge concentration
hopper. The clarified effluent was renxved near the surface of the liquid
in the basin.
From the carbonation basin, the flow was directly to the activated sludge
unit. The activated sludge unit consisted of a cylindrical steel tank
with a flat bottom. The tank was about 8 ft in diameter and had a water
depth of 4 ft. The operating volume of the tank was 1500 gallons. Aera-
tion and mixing were furnished by three mechanical aeration “cavitette”
units. These machines introduced air into the activated sludge by draw-
ing air through a hollow shaft by the cavitation created at the tips of the
impeller which was located about 39—in below the water surface. The impel-
ler served to draw in air, break—up and mix the bubbles of air into the
fluid and to stir the aeration basin contents. Each cavitette unit was
powered by a 1 HP electric u tor.
During some phases of the operation of the aeration unit, considerable
amounts of foam occurred in the aeration basin. When the foam was permit-
ted to flow into the secondary sedimentation basin, the rising foam created
convection currents and tended to float some fine solids which reduced the
efficiency of the basin. In order to overcome this difficulty a foam trap
was installed between the aeration basin and the secondary sedimentation
basin. The foam trap consisted of a 30 gallon steel drum having an inlet
near the surface and an outlet at the bottom. This device was successful
in intercepting and retaining the foam from the aeration basin. From time
to time, the foam was renxved from the surface of the foam trap and manual-
ly returned to the activated sludge aeration unit.
The secondary sedimentation basin was a cylindrical steel tank with a
conical bottom. The diameter of the tank was 4 ft and the straight side
water depth was 4 ft. The conical bottom had a slope of 1 on 1. The
basin was equipped with mechanical scrapers which prevented sludge from
adhering to the sloping bottom. Settled sludge was continuously removed
from the bottom of the secondary sedimentation basin and pumped back to
the aeration basin. The clarified effluent from the secondary sedimen-
tation basin was removed at the surface of the basin by a small overflow
weir.
36
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Sludge from the primary sedimentation basin, the combined carbonation—up—
flow—sedimentation basin, and the excess sludge from the secondary sedimen-
tation basin were removed manually as required. The volume of all sludge
removed from the sedimentation basins was measured and a sample collected
for analysis.
During the pilot plant operation, tests were made relative to the dewater—
ing of the various sludges, both singularly and in combination. Dewatering
was investigated using a standard 6—in solid bowl continuous flow centri-
fuge. Dewatering tests were also conducted using sand drying beds. The
sand drying beds were constructed by perforating the bottoms of four 30 gal-
lon steel drums and constructing the drying beds in these drums. The drying
beds consisted of a 3—in layer of 1/4—in pea stone in the bottom of each
30 gallon drum. The pea stone supported a 4—in layer of common concrete
type of sand which formed the surface of the drying bed. A 12-in layer of
each type of sludge was placed on the surface of the sand and its drainage
and drying characteristics observed.
Table 7 presents a summary of the design factors for the various units of
the pilot plant. Each unit was designed to operate at a flow rate slight-
ly less than the preceeding unit and the excess flow was discharged to
waste between units. It should be understood, however, that the pilot
plant was operated at rates of flow both above and below the design rate.
However, the same principle applied in that each unit was operated at a
flow rate slightly less than the preceeding unit. The purpose of this
step—down design was to insure flexibility of operation. Each unit could
be operated at rates of flow independent of the flow rate of the preceed—
ing units. The efficiency of the primary basin could thus be measured at
various flow rates without affecting the operation of the secondary system.
One of the purposes of the pilot plant was to demonstrate the treatment of
a mixture of tannery effluent and sanitary sewage. Since the Town of
Paris has no municipal sewerage system, sewage was obtained from the out-
fall of the Norway, Maine, municipal sewage system. Sanitary sewage was
obtained daily except Sunday, and was transported to the South Paris pilot
plant by tank truck. The sanitary sewage was stored in an elevated, 3,000
gallon storage tank from whence it was pumped and metered directly into
the activated sludge unit. The sanitary sewage had been comminuted and
was screened through a screen box having 1/4—in openings. The contents
of the storage tank were maintained in suspension by a circulation pump.
Log of Pilot Plant Operation
The following log of the operation of the pilot plant is furnished so that
a reader who wishes to study the complete analytical data of the pilot
plant results as presented in Tables lÀ through 25A may know the operating
status of the plant on any particular day.
37
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TABLE 7. A.C. LAWRENCE LEATHER COMPANY WASTEWATER PILOT PLANT
Design Factors and Operating Range
Operating
Design Range
Characteristic Factor Tested
PRIMARY SEDIMENTATION BASIN
Circular, conical bottom, rim inlet, center weir overflow.
Diameter, ft 4.0
Side water depth, ft 3.0
Center depth, ft 2 6.66
Net surface area, ft 11 .5
Volume, gals 355.0
Flow, gpm 5.0 5.25-20.0
Surface overflow rate, gpci/ft 2 625.0 660-2,500
Detention time, hrs 1.2 1.15-0.3
CARBONATJON-UPFLOW SEDIMENTATION BASIN
Square in plan, upside down pyramid, square center column for carbonation,
side sludge hopper.
CARBONATION COLUMN
Side, ft 0.92
Depth, ft 6.5
Volume, gals 41 .0
Flow, gpm 5.0 4.0-15.0
Detention time, mm 8.0 10.0— 2.7
UPFLOW SEDIMENTATION
Side length, ft 3.9
Liquid depth, ft 2
Net surface area, ft 14.1
Volume, gals 306.0
Sludge blanket depth, ft 5.0
Net surface area at top of sludge
blanket, ft 2 8.25
38
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TABLE 7. A.C. LAWRENCE LEATHER COMPANY WASTEWATER PILOT PLANT
(Continued)
Characteristic
Flow
Surface overflow rate, gpd/ft 2
Detention time, hrs
Surface overflow rate at top of sludge
blanket, gpd/ft 2
Detention time in sludge blanket, mm
5.0
510.0
1 .0
870.0
25.0
Operating
Range
Tested
4.0 -15.0
410 -1,530
1 .25-0.33
700 -2,620
31 —8.3
Diameter, ft
Liquid depth, ft
Volume, gals
Aerators, number
Horsepower, each
F low
Tannery wastewater, gpm
Sanitary sewage, gpm
Return sludge, gpm
Total, gpm
Detention Time
Based on wastewater and sanitary
sewage, hrs
Based on total flow, hrs
BOD loading, lbs/day/1,000 cu ft
Diameter, ft
Side water depth, ft
Center depth
Surface area, ft 2
Volume, gals
8.0
4.0
1,500.0
3.0
1 .0
2 .0
1 .0
1 .0
4.0
8.3
6.3
130.0
0.0—5.0
0.5-2.5
1 .0—3.0
2.0—9.5
12 .5—3 .3
8.3-2.6
6.0-300
Design
Factor
AERATION BASIN
Cylindrical, flat bottom, “Cavitette” aerators.
SECONDARY SEDIMENTATION BASIN
Cylindrical, conical bottom, center submerged baffled inlet, weir overflow outlet.
4.0
4.0
6.0
12.5
435 .0
39
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TABLE 7. A .C. LAWRENCE LEATHER COMPANY WAS TEWATER PILOT PLANT
(Continued)
Operating
Design Range
Characteristic Factor Tested
Flow
Tannery waste pius sanitary sewage, gpm 3 2.0 -7.5
Tannery waste plus sanitarys vage plus
return sludge, gpm 4 3.0 -9.5
Surface Overflow Rate, gpd/ft 2
Based on tannery waste plus sanitary sewage 345 230-865
Based on total flow plus return sludge 460 345-1 ,I0O
Detention Time, hrs
Based on tannery waste plus sanitary sewage 2.4 3.6 -0.97
Based on total waste flow plus return sludge 1.8 2.4 -0.76
CENTRIFUGE
Solid bowl, continuous flow.
Bowl diameter, in. 6.0
Speed, rpm 3,000
4,000
5, 000
Feed rote, gpm 2.0 1.94-1.48
Solids feed rate, lbs/hr 20—60
40
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December 18 through December 28, 1967 — Initial operation of the pilot
plant began on December 18, 1967. Initially, sanitary sewage was added
to the aeration tank and the aerators placed in operation. The purpose
of this action was to develop an activated sludge. Also during this
period, adjustments were being made to the carbonation tank, the tannery
waste pumping system, and the various metering pumps. At this time, there
was no primary sedimentation basin because the need for this basin was
not known. During this initial period, the operators were being trained
in their duties.
December 29, 1967 through January 23, 1968 — During this period, the
activated sludge unit continued to treat only sanitary sewage. The car-
bonation sedimentation unit was placed in operation treating the mixed acid
and alkaline tannery wastes but no C02 or stack gas was used. The purpose
of this operation was to determine the effectiveness of the basin as a
primary sedimentation unit.
January 24, through February 8,1968 — The aeration unit continued to treat
sanitary sewage. However, a small amount of the effluent from the carbona-
tion—upflow—sedimentation basin was added to the aeration basin influent.
The addition of the settled tannery wastes to the aeration unit was not
continuous because of operational problems with the carbonation system.
February 9, through February 15, 1968 — The activated sludge unit continued
to treat sanitary sewage and small amounts of effluent from the carbonation
upflow—sedimentation unit. During this period, carbonation was carried out
using a mixture of compressed air and bottled CO 2 . Also during this period
and throughout the rest of the pilot plant work, the acid waste was diluted
to a standard average strength.
February 16, through March 12, 1968 — At the beginning of this period, the
stack gas compressor was installed and placed in operation. The alkaline
feed to the carbonation upflow—sedimentation unit was therefore carbonated
using stack gas. The rate of feed from the carbonation—upflow—sedimenta—
tion unit to the aeration unit was increased.
March 13. through March 25, 1968 — A series of special tests was made on
the carbonation- upf1ow—sediznentat1on unit. The purpose of these special
tests was to determine the amount of sludge removed by this unit at dif-
ferent flow rates.
March 26, through April 2, 1968 — The plant was operated at various flow
rates to determine the best rate for good treatment. During this period
the treatment consisted of mixing the alkaline and acid wastes, carbona-
tion and upflow—sedimentation, aeration and secondary sedimentation. Foam-
ing in the activated sludge unit was an operational problem encountered
during this period.
41
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April 3. through April 5, 1968 — During this period, excess sulfide in the
form of a strong solution of technical sodium sulfide used by the tannery
was added to the flow entering the aeration tank. The purpose of this test
was to study the effect on the biological action and degree of treatment
effected by the activated sludge unit under shock loading of sodium sul-
fide.
April 6 through April 23, 1968 — During this period, the pilot plant was
shut—down, except for the aeration basin and the secondary sedimentation
basin which continued to treat sanitary sewage in order to maintain the
activated sludge mass. The pilot plant was shut down for the purpose of
installing the primary sedimentation basin and to make other alterations
in the system.
April 24, through June 1, 1968 — The pilot plant was placed back into op-
eration with the primary sedimentation preceeding the carbonation—upf low—
sedimentation basin in the flow pattern. The plant was operated at a
variety of flow rates to study the effects of detention time, overflow
rate, and mixed liquid suspended solids concentration on the efficiency
of the treatment processes.
June 2, through June 8, 1968 — Sludge dewatering by centrifuge was investi-
gated.
June 2. through June 17. 1968 — The results of the operation of the pilot
plant to date were carefully studied and rates of flow estimated to yield
the highest possible degree of treatment were applied to each unit during
this period of the testing program.
June 18. through June 23, 1968 — Studies and analyses of the waste indi-
cated that the concentration of phosphate contained therein was less
than the theoretical optimum of phosphate required for the activated sludge
process. During this period of operation, phosphate in the form of sodium
phosphate was added to the wastes entering the activated sludge unit to
determine if an increase in the phosphate concentration would, in fact, in-
crease the efficiency of treatment.
June 24, through June 28, 1968 — One of the possible causes in the foaming
In the aeration tank was the detergent used in the tannery for the purpose
of hair washings. In order to test this thesis, appropriate doses of the
detergent were added continuously to the activated sludge unit. The phos-
phate added during the previous period was continued during this time.
June 29, through JUly 8, 1968 — The plant was continued in operation at
the theoretical optimum rate of flow with the continued addition of phos-
phate. No detergent was added during this period.
42
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July 9, through July 12, 1968 — In order to determine whether or not
chromium exerted a toxic effect on the biological system, a solution of
the chromium mixture used in the tanning process was added directly to
the aeration basin. During each succeeding 24—hour period, the rate of
addition of chromium was increased. During this period of testing, the
addition of extra phosphate continued. The pilot plant was shut—down
at the end of the work period on July 12.
July 13, through July 20, 1968 — The pilot plant was drained and cleaned
out and equipment packed for storage.
43
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RESULTS OF PILOT PLANT OPERATION
General
The pilot plant was operated in four general phases. The first phase,
December 18, 1967, through February 15, 1968, was the break—in phase when
the operators were learning how to operate the plant and working out the
bugs. The second phase, February 16, 1968 through April 5, 1968, was the
initial period when operating data were being collected. During this
period, the results of the operation were not entirely satisfactory. The
plant effluent quality was higher in ROD and suspended solids than was
desired and the results were erratic. The causes of this erratic per-
formance were felt to be fluctuations in the quality of the influent
tannery wastes and difficulty in the control of carbonation because of
rapid changes in influent alkalinity.
The pilot plant was, therefore, shut—down, except for the activated sludge
which was sewage fed, from April 6, through April 23, to permit the instal-
lation of a primary sedimentation basin ahead of the carbonation—sedimenta-
tion basin. The primary sedimentation served to equalize the fluctuations
in quality as well as to remove a large proportion of the settleable solids.
On April 24, the pilot plant was placed back in full operation with the
primary sedimentation basin in the flow line. Each week during May, the
rate of flow through the plant was increased as follows:
Flows, gpm
Date
May, 1968 Primary Carbonation Activated 1
From To Influent Influent Slud&e Influent
1 11 6.25 5 5
13 18 10 7 6.5
20 25 15 10 8
27 1 20 6 9.5
Note 3 - Includes sanitary sewage and a return sludge flow of 2 gpm
The results of the operation during May became erratic when the flow to
the activated sludge unit increased above 1 gpm of sanitary sewage, 2 gpm
of tannery waste and 2 gpzn of return sludge (a total of 5 gpm). On June 1,
the flow to the processes were reduced between 5.25 and 6.0 gpm to the pri-
mary, 4.5 to the carbonation—sedimentation basin and a total of 4.5 gpin to
the secondary system consisting of 0.5 gpm sanitary sewage, 2.0 gpm return
sludge. These flows were continued throughout the remainder of the pilot
plant operation. The flows employed for testing during June and July were
selected because previous experience indicated that maximum removal of BOD
45
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and other pollutants could be obtained while at the same time maintaining
a stable system. This was demonstrated by the four weeks operation in
June, 1968, during which time the effluent SOD exceeded 50 mg/i only on
two occasions and the average BOD was 32 mg/i.
SOT) Removal
Fig. 6 is a chronological record of the rei val of SOD in the pilot plant.
The upper line in Fig. 6 represents the 5—day, 20C BOD analyses of the
pilot plant influent and the lower line represents the BOD analyses for
the pilot plant effluent. Notes on Fig. 6 are guides to the operating
procedures being followed at any particular time. The results reported on
Fig. 6 represent the analyses of 24—hour composite samples. The pilot
plant operators collected samples from the influent to the leading pilot
plant unit after the alkaline and acid wastes had been mixed. Samples
were also collected from the effluent of the primary sedimentation basin,
the effluent from the carbonation—upflow—sedimentation basin, and the ef-
fluent from the secondary sedimentation basin. The samples were collected
approximately once each hour. Since the flow through the pilot plant was
constant, equal volumes of samples were taken for making up the composite.
The results reported on Fig. 6 indicate the wide fluctuations in the qual-
ity of the pilot plant influent. The tanning influent BOB ranged from a
low of about 500 mg/l to a maximum of about 3,600 mg/i. The wide fluctua-
tions In influent BOD could not be specifically associated with any partic-
ular operations in the tannery.
The effluent SOD was dependent to a considerable extent upon the rate of
flow and the manner in which the pilot plant was operated. When only san-
itary sewage was being treated in the secondary system at the beginning
of the pilot plant work, the detention times in the aeration basin were
about 9 hours. The long aeration period resulted in a hard—to--settle fioc
and somewhat irregular results.. When the plant was x re heavily loaded
by the addition of tannery wastes starting about February 9, the effluent
SOD concentration continued to fluctuate over a wide range in a non—accep-
table manner. Following installation of the primary sedimentation basin,
the operation of the secondary system improved greatly.
Following the installation of the primary sedimentation basin, the second-
ary system was operated initially at the rate of about 3 gpzn. The influent
consisted of about 1 gpm of sanitary sewage and 2 gpm of carbonation basin
effluent. After about 2 weeks the flows were increased to 4.5 gpm main-
taining the ratio of sanitary sewage to carbonation basin effluent at 1 to
2. After about a week at this rate, the flow was increased to about 6 gpm.
After about one week at 6 gpm the flow was increased to 7.5 gpm. The re-
sults shown in Fig. 6 indicate that when the flow of sanitary and tannery
waste exceeded 3 gpm, (May 13, — June 1), the concentration of SOD in the
effluent tended to become somewhat erratic.
46
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PAGE NOT
AVAILABLE
DIGITALLY
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Throughout the months of June and July, the pilot plant secondary system
was operated at a rate of 2.5 gpm. The influent consisted of 0.5 gpm
of sanitary sewage and 2.0 gpm of carbonation basin effluent. The results
obtained during this period were excellent with the highest BOD in the
effluent during this time being 93 ing/l and the lowest 14 mg/i. The
average BOD was about 32 mg/l.
Near the end of June a non—ionic detergent used in the tannery for hair—
washing was added to the secondary system in concentrations ranging from
10 to 40 mg/i in an attempt to determine the effect of the detergent on
foam generation in the secondary system. The results on Fig. 6 indicate
the effluent BOD increased to an average about 25 mg/i. But there was
no significant increase in the foaming.
During the last week in June, solutions of chromium used in the tanning
process were added to the secondary system in an attempt to determine the
effects of high chromium concentrations on the activated sludge process.
Each day for four days, the amount of chromium added to the secondary sys-
tem was increased. As may be seen from the results on Fig. 6 for the
end of July, little if any change could be detected as a result of the
chromium addition. The toxicity of chromium to activated sludge is dis-
cussed in greater detail later in this report. Fig. 6 does not indicate
the individual processes in which BOD was removed.
Fig. 7 is a plot of the percentage removal of BUD. The upper line repre-
sents the percentage removal in the pilot plant as a whole and the lower
line represents the percentage removal in the primary system (carbonation—
upflow—sedimentation basin only before April 5; primary sedimentation basin
followed by carbonation—upf low sedimentation after April 24). The percent
removal for the plant as a whole was computed from the total weight of
BOD in the tannery waste and in the municipal sewage and from the total ef-
fluent BOD. As may be seen from Fig. 7, the percentage removal of BOD in
the primary system was erratic; however, the overall BOD removal for the
pilot plant was good, rarely falling below 90 percent, and then only when
the plant was over—loaded i.e., the middle of May.
Studies of the individual processes and their efficiency in removing BOD
is discussed in a following section of the report. We may conclude, however,
from the results shown on Figs. 6 and 7 that if the pilot plant is operated
at a rate of flow not exceeding about 3 gpm, and with a flow of sanitary
sewage of at least 0.5 gpm an extremely high degree of treatment (in excess
of 95 percent) removal of BOD can be obtained regardless of fluctuations of
the plant influent quality.
Removal of BUD by the Primary System
From February 9, 1968, to April 5, 1968, the carbonation basin served as
both a primary sedimentation and a carbonation basin. Overloading with
sludge occurred, making proper operation difficult. Furthermore, rapid
fluctuations in influent pH and alkalinity made accurate control of car-
bonation Impractical. Hence, on April 24, 1968, primary sedimentation in
49
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a separate basin was installed ahead of the carbonation basin and used
until the end of the testing period. Therefore, removal of settleable
solids and settleable BOD by the primary section of the plant took place
in a combined carbonation—sedimentation basin prior to April 5, and sub-
sequent to April 24, in a separate primary sedimentation basin followed
by the carbonation—sedimentation basin.
The results of BOD removal in the primary sedimentation basin are shown
in Fig.. 8. In Fig. 8, the “Percent Removal of BOD” is plotted as a func-
tion of “Surface Overflow Rate.” The circled points represent the analyses
of daily composite samples. The line is the line of best I it based on the
least—squares method of fitting all of the data. On a few occasions nega-
tive results were obtained, i.e., the effluent BUD was higher than the in—
fluent. The negative results were not used in fitting the line to the
data. See “Suspended Solids” on page 67 for explanation of negative re—
suits.
The data show that on the average about 30 percent of the BOD in the
tannery wastewaters will be removed by the primary sedimentation at an
overflow rate of 500 gpd/ft . The variability of the resultant removal
reflects the variability in the quality of the influent wastes and illus-
trates the need for equalization to reduce these fluctuations and there-
by improve the operation of succeeding treatment processes.
The low percentage removal of BOD by primary sedimentation at times re-
flects the periods of low settleable solids concentration in the influent
wastes. Reference is made to the waste surveys, Figs.. A—5 and A—6 which
show a range of settleable solids concentration from more than 750 mi/i
to less than 25 mi/i. Normally following primary sedimentation, the
settleable solids were less than 5 mi/i. It should be noted that the per-
cent removal is dependent upon the total influent concentration as well as
the effluent concentration, which may be a relatively constant minimum
value regardless of the influent concentration.
The results of the primary sedimentation basin studies appear to indicate
that on the average the settleable BOD comprises about 40 percent of the
total BOO in the waste from the tannery.
Removal of BOD by the combined carbonation—sedimentation basin is shown
as a function of surface overflow rate in Fig. 9. The results may be
dividied into two periods. The first was the period when the basin served
as both a primary sedimentation basin and carbonation basin and the second
period when the carbonation basin was preceded by the separate primary
sedimentation basin.
During the first period, the BOD removal was very similar to that obtained
in the primary basin as is shown by the upper line on Fig. 9. As might
be expected, BOD removal by the carbonation—sedimentation basin alone was
about 50 percent lower following the installation of the primary sedimen-
tation basin, since the bulk of the settleable solids had already been re—
53
-------
60
0
2
OVERFLOW RATE- GPO/FT
FIG. 8 BOD REMOVAL VS. OVERFLOW RATE
PRIMARY SEDIMENTATION BASIN
0
0
-J
4
>
0
U
I-
z
U
C.)
U
Q.
50
40
30
20
I0
0
500 1000 1500 2000
2500
54
-------
50
0
0
-J
4
0
w
1-
z
I d
C.)
I d
a.
40
30
20
10
0
0 250 500 750 1000 1250 500 1750
OVERFLOW RATE- GPO/FT 2
FIG. 9 BOD REMOVAL VS. OVERFLOW RATE- CARBONATION SEDIMENTATION BASiN
-------
moved. However, the overall removal of BOD by the two basins in series
was higher than for either basin alone. At an overflow rate of 500 gpd/ft
the average rate of removal of BOD in the carbonation—sedimentation basin
alone was 34 percent. The removal in the carbonation—sedimentation basin
following the primary sedimentation basin was 23 percent and the overall
BOD removal by both basins in series was 52 percent.
The overall improvement in BOD removal (i.e., more than 40 percent) is
attributed to:
1. The effects of coagulation by precipitated calcium
carbonate and chromium hydroxide.
2. Longer detention period provided by the two basins
in series.
3. The effects of equalization in the primary sedi-
mentation basin which permitted more effective
carbonation in the carbonation basin, which re-
sulted in the precipitation and removal of some
dissolved solids.
4. Smaller sludge volumes in the carbonation—sedi-
mentation basin following primary sedimentation.
These smaller accumulations of sludge reduced
the carryover from the carbonation basin.
Removal of BOD by the Secondary System
As expected the greatest removal of BOD was accomplished by the activated
sludge system. Fig. 10 sinmn r1zes the results of BOD removal by the acti-
vated sludge system alone. The results in Fig. 10 do not include any re-
movals obtained in the primary system. In Fig. 10, the percent removal of
BOD is plotted as a function of the ratio of “Mixed Liquor Volatile Suspend-
ed Solids” to the “Influent BOD.”
The activated sludge process depends upon a complex relationship between
the concentration of blota present in the system, the concentration of
organic material suitable as food for the bacteria and the time available
for the biological oxidation reactions to take place. The biomass concen-
tration may be estimated from the mixed liquor volatile suspended solids,
the available food from the BOD and the time from the ratio MLVSS to BOD.
Experience with activated sludge has shown that approximately 0.5 to 1.0
hours contact time between the waste and the activated sludge is needed
for the sludge to absorb the food. About 0.5 to 3.0 days (Could’s sludge
age) of aeration of the sludge is needed to complete the biological re-
actions. In the completely mixed system used in the pilot plant the food
absorption and oxidation phases of the reaction occur simultaneously in
the mixed liquor aeration basin. Sludge detention time is related to the
sludge concentration and BOD by a complex but largely self—regulating re-
lationship.
56
-------
RAT’O VMLSS
Inf. B.O.D.
FIG. tO REMOVAL OF B.O D AS A FUNCTtON OF MIXED LIQUOR SUSPENDED SOLIDS
0
0
-I.
4
>
0
2
w
I-
z
w
U
a.
t’f’
-------
The line on Fig. 10 is the line of best fit for detention times between
230 minutes and 375 minutes. Data for detention times less than 230
minutes were not used in plotting the line of best fit because they were
not representative of the design recommended by this report. The BOD
in the influent includes the BOD In the untreated sanitary sewage from
Norway, Maine and the effluent from the pilot plant carbonation—sedimen-
tation basin.
From Fig. 10, it may be seen that the ratio of “Mixed Liquor Volatile Sus-
pended Solids” to “Influent BOD” had little effect on the degree of removal
of BOD by the secondary treatment process over the range of values tested.
Thus, we may assume that the bacteria concentration was not a limiting fac-
tor in this range. At a MLVSS/Influent BOD ratio of 0.5 the average BOD
removal was about 93 percent. These results indicate that over a wide
range of MLVSS/Influent BOD ratios the efficiency of the process remained
at a high level.
The time of aeration appears to be more important in determining the effi-
ciency of the process. Those tests made with detention times less than
230 minutes yielded efficiencies of about 80 percent BOD removal. How-
ever, tests at these short detention times were limited to MLVSS/Influent
BOD ratios of about 0.75. Higher ratios may have yielded Increased effi-
ciencies but no operating data are available to support any conclusions in
this regard.
Data for long detention periods (i.e., in excess of 375 minutes), is limit—
ed to the start—up period of the secondary process, during which time only
sanitary sewage was being treated. The results indicate that the effi-
ciency of treatment was about 80 percent BOD removal during this time. The
relatively low efficiency was probably due to the lack of an active sludge
mass during start—up as well as to the poor settling characteristics of
the sludge. As soon as the efficiency increased, tannery waste was added
and the proposed method of tannery wastes treatment was started.
Secondary Sedimentation
The efficiency of the activated sludge is dependent to a considerable de-
gree to the efficiency of the secondary sedimentation basin. It is neces-
sary to separate the activated sludge solids from the treated waste before
the effluent may be discharged to the receiving waters. The t conditions
necessary for satisfactory separation are; a sludge which will settle read—
ily and a properly designed and operated sedimentation basin.
Fig. 11 is a plot of the concentration of suspended solids in the effluent
of the pilot plant secondary sedimentation basin as a function of overflow
rate. The range of values for any particular overflow rate reflects in
general, the settleability of the sludge on the day of the particular test,
however, some points of low settleability were due to foam carry—over from
58
-------
‘ - ‘I
E
(I )
a
-J
0
U)
a
a
z
I d
0
(n
U)
I-.
z
Id
-j
Id
0 200 400 600 800 1000 1200 400
OVERFLOW RATE, gpd/ft 2
FIG. I SECONDARY EFFLUENT SUSPENDED SOLIDS VERSUS OVERFLOW RATE
-------
The aeration basin. Fig. 13 presents the suspended solids in the plant
effluent in a chronological order. From Fig. 13 it may be seen that dur-
ing periods of good operation the average suspended solids concentration
in the effluent were generally less than 200 mg/i. This corresponds to
an overflow rate of about 500 gpm/ft 2 for the line on Fig. 11. Since the
line on Fig. 11 is a line of best fit for all of the data it is weighted
somewhat to a conservatively low overflow rate for secondary sedimenta-
tion.
It may be concluded from the results of these tests and these data that
a mixture of sanitary sewage and partially treated tannery wastes of the
type discharged at South Paris can be treated by the activated sludge pro-
cess to remove more than 90 percent of the BOO influent to the process,
if the operating conditions are maintained within the following ranges:
1. Ratio of MLVSS/Influent BOO between 0.5 to 3.0.
2. Time of aeration between 230 minutes and 375
minutes.
3. Overflow rate in the secondary sedimentation
basin less than 500 gpd/ft 2 . (Represented by
flows of 2 gpm tannery wastes, 1 gpm sanitary
sewage and 1 gpm return sludge).
Solids Removal
Effluent surveys of the tannery indicated that the wastes contain large
quantities of solids. The average settleabie solids were estimated to
be about 130,000 gallons per day, the total solids were estimated to be
about 70,000 lbs per day and the suspended solids about 17,000 lbs per
day. The average concentration of total solids, which entered the pilot
plant between February 9, 1968 and the end of May, 1968, was 6,334 mg/l,
or about 52,700 lbs per day based on a flow of 1 mgd. During the same
time interval, the average concentration of total solids in the pilot
plant effluent was about 2,200 mg/l equivalent to about 18,300 lbs per
day based upon a daily flow of 1 mgd. The overall removal of solids
through the pilot plant was therefore about 65 percent or about 34,400
lbs per day. However, it is difficult to pinpoint the unit processes in
which various portions of the solids were removed.
Fig. 12 is a plot showing total solids in the pilot plant influent as the
upper line and the total solids in the pilot plant effluent as the lower
line. As may be seen from Fig. 12, the total solids in the pilot plant
influent varied from a low of about 3,000 mg/i to a maximum of more than
10,000 mg/i. The total solids in the effluent varied from a high of about
5,000 mg/i to a minimum of slightly less than 1,000 mg/i. The total solids
in the effluent depended somewhat on the proportion of sanitary sewage to
tannery wastes. For this reason, the period prior to the installation of
60
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the primary sedimentation basin has a slightly lower total solids in the
effluent than the period following the installation of the primary sedi—
mentation basin. Prior to installing the primary sedimentation basin, the
proportion of sanitary sewage to tannery wastes was higher than during the
period following.
Part of the solids removed will be oxidized to carbon dioxide and water
while the remainder will be removed as sludge which will require dewater-
ing and disposal.
Fig. 13 is a chronological record of the suspended solids in the pilot
plant influent and the effluent. The upper line on Fig. 13 represents the
analyses of composite samples of the plant influent. The lower line repre-
sents composite samples of the plant effluent. As may be seen from Fig. 13,
the suspended solids concentration varied from more than 3,600 to a minimum
slightly less than 500 mg/i. The suspended solids in the pilot plant ef—
fluent varied in concentration from a maximum of about 600 to a minimum of
about 30 mg/i. After the primary sedimentation basin was installed and the
pilot plant was operating in a satisfactory manner, the suspended solids
in the plant effluent averaged about 200 mg/l. During the middle and the
end of May, when the pilot plant was being operated at excessively high
rates of flow the average suspended solids increased to about 250 mg/i.
The average removal of suspended solids was about 75 percent on passage
through the treatment process. The removal of suspended solids, in terms
of percent removal, increased greatly during those periods of time that
high suspended solids occurred in the pilot plant influent. It is signi-
ficant to note from a pollution abatement point of view, that it should
be possible to readily maintain a suspended solids concentration in the
effluent of less than 100 mg/l at all times. A removal to this extent
represents a removal of more than 95 percent of all of the suspended
solids in the tannery waste.
The difficulty of identifying the particular unit processes responsible
for the removal of solids from the waste arises because of the nature of
the solids being removed and the variability of their occurrence in
waste flows. The suspended solids in the waste furnish a specific example.
During those times of the day when large amounts of acid waste discharges,
the mixture of the two waste streams results in the precipitation of con—
siderable amounts of chromium hydroxide. The chromium hydroxide precipi-
tate forms gelatinous flocs which trap significant quantities of collodal
material which normally would not settle. The resulting solids do, how-
ever, settle to the bottom of the sedimentation basin and are far in ex-
cess of the amount of solids which would have resulted if the acid and
alkaline wastes were settled separately, as is the case when their dis-
charges do not coincide. Therefore even with the same waste discharges,
the amount of solids removed by sedimentation alone is quite variable
and dependent upon the chance discharges of both types of waste. Sam-
ples of the wastes were collected hourly and composited for a 24—hour
period. However, the suspended solids determined on the composite are
not representative of the actual suspended solids entering the sedimenta-
tion units. They are only representative of the suspended solids which
63
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would have occurred in a mixture of the total tannery effluent for the sam-
pling period. There are, therefore, inconsistencies in the data such as a
negative removal of suspended solids across a sedimentation unit while at
the same time an accumulation of sludge in the bottom of the unit. This
can result if the wastes passing through lose some of their suspended
solids in the sedimentation basin and the individual samples of the ef flu-
ent from the sedimentation basin react with each other in the composite to
create new suspended solids in excess of those contained in the influent
to the sedimentation basin.
Suspended Solids Removal in the Primary System
Fig. 14 is a plot of the percent removal of suspended solids versus over-
flow rate for the primary sedimentation basin. The results shown on Fig.
14 indicate that the suspended solids removal varied from 2 percent to 72
percent. The line on Fig. 14 is the line of best fit. The average removal
of suspended solids by primary sedimentation was about 38 percent as deter—
niined by a least squares fitting of the data plotted on Fig. 14.
From this example, we may draw the conclusion that the effectiveness of
the sedimentation basin cannot be truly evaluated from a study of the in—
fluent and effluent suspended solids. A similar argument may be made for
the use of the total solids test for this purpose. It is our opinion that
the best evaluation of the effectiveness of a sedimentation basin treating
the wastewaters from the tannery is the amount of sludge accumulating on the
bottom of the sedimentation basin.
Fig. 15 is a plot of the amount of sludge removed from the primary sedimen-
tation basin as a function of overflow rate. These data furnish a fairly
consistant pattern; much more so than percent solids removal.
Between the 1st and the 31st of Nay, 1968, the average amount of sludge
removed from the primary sedimentation basin was 4,300 lbs per million
gallons of waste treated. Judged on this basis, the results are equiva-
lent to a removal of 24 percent of the suspended solids entering the sed-
imentation basin. For the same period, the amount of sludge removed from
the carbonation basin amounted to 4,536 lbs per million gallons of waste
treated. The total sludge removed by the two basins operating in series
amounted to 8,836 lbs per million gallons of waste treated. This amounts
to about 50 percent removal of the suspended solids entering the system.
A further complication which enters the consideration of solids removal
efficiency is concerned with the removal of the excess lime which is used
in the de—hairing process. The lime is employed as a dilute slurry of
hydrated lime. When this dilute slurry is discharged to the sewerage sys-
tem, it consists of a saturated solution of calcium hydroxide, calcium
chloride, and calcium carbonate. When this mixture is added to the acid
wastes from the tanning processes, the high alkalinity causes a precipita-
tion of the chromium as chromium hydroxide. The interaction of all of these
compounds together with pH changes is extremely complex and variable from
67
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FIG. 14 SUSPENDED SOLIDS REMOVAL VS. OVERFLOW RATE-
PRIMARY SEDIMENTATION BASIN
U)
0
-J
0
U)
0
U i
0
z
U I
a-
U)
U)
-j
4
>
0
U I
z
UI
U
U i
0
$0
70
60
50
40
ao
I0
0
0
0
0
0
0
0
0
0
0
0
0 500 1000 1500 2000 2 0O
OVERFLOW
a
RATE- GPD/FT
68
-------
10,000
8,000
-J
6,000
0
-J
(I )
U-
0
4,000
(9
L&J
2,000
0
3000
OVERFLOW RATE - GPD/ FT.
FIG.15 WEIGHT OF SLUDGE REMOVED VS. OVERFLOW RATE
PRIMARY SEDIMENTATION BASIN
0 500 1000 1500 2000 2500
2
-------
minute to minute in the waste discharges; some of the precipitates formed
are colloidal in nature and do not settle readily. Other of the precipi—
tators are flocculant in nature and tend to coagulate and settle well. How-
ever, the waste is predominantly alkaline and is higher in pH value than is
desirable for biological treatment of the wastes. Carbon dioxide was eel—
ected as the most suitable acid for the reduction of the pH to a level satis-
factorily for biological treatment. The advantages of using carbon dioxide
for this purpose are:
1. Carbon dioxide is readily and economically available
from the flue gas in the tannery power house.
2. Carbon dioxide reacts with the alkalinity in the
wastes to form carbonates which create a strong
buffering system. This buffering system permits a
reasonable adjustment in pH to about 9.5 which is
low enough to permit biological action but not low
enough to permit the escape of H 2 S gas from the
waste.
3. Calcium carbonate which is formed is a highly in-
soluble compound of calcium which may be removed
by sedimentation.
The carbonation upflow—sedimentation basin was selected as the most suit-
able equipment for the introducing the flue gas into the tannery wastes
and for removing the calcium carbonate. The selection of the upf low sedi-
mentation type of basin was based upon the characteristics of calcium car-
bonate precipitation.
In the upflow sedimentation basin, a sludge blanket consisting of previous—
iy precipitated particles of calcium carbonate is maintained. The flow of
the treated wastes, following carbonation, is upward through this blanket
of particles. The particles in the blanket form nuclei on which freshly
precipitated calcium carbonate may deposit. In the absence of such nuclei
super—saturated solutions of calcium carbonate may be stable for consider-
able periods of time. It has been found in water softening operations that
contact with calcium carbonate particles is essential to the removal of
calcium carbonate from a saturated solution.
The carbonation basin therefore, removes both suspended and dissolved
solids from the waste flow. During the initial stages of the pilot plant
operation, the carbonation—upf low sedimentation basin acted both as a
primary sedimentation basin and as a carbonation basin. The amount of
sludge which precipitated and settled in this basin was in excess of the
sludge handling capacity of the basin and the basin failed to operate in
a satisfactory manner. Excess amounts of suspended solids were carried
out of the basin by the effluent flow. Furthermore, rapid fluctuations
in the quality of the incoming wastes, rendered the proper operation of
the carbonation process almost impossible. In order to solve these diffi—
70
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culties, a primary sedimentation basin was installed ahead of the carbon-
ation sedimentation basin. The primary sedimentation basin removed about
25 percent of the suspended solids. These solids contained a large per-
centage of lime, particularly during periods when the suspended solids
concentration was heavy. The detention period in the primary sedimentation
basin was about two hours and some mixing occurred in this basin. As a
result of this mixing and the removal of the heavier suspended solids, the
quality of the inf low to the carbonation basin became considerably more
uniform. The more uniform quality permitted a better control of the car-
bonation process since changes in quality and the necessity for adjustment
of the rate of carbonation were not rapid. The removal of solids by the
carbonation basin was quite irregular. Hence again, the results must be
judged on the amount of solids actually removed. The operating results
for the carbonation basin are shown on Fig. 16.
On Fig. 16, the upper line represents the results obtained from the car-
bonation upflow sedimentation basin at the time that this basin was being
utilized both for primary sedimentation and carbonation. After the pri-
mary sedimentation basin had been installed, the flow of solids to the
carbonation upf low basin was substantially reduced and therefore the amount
of material to be removed was reduced and the amount of sludge which ac-
cumulated in the basin was less. For an overflow rate of 1,000 gpd/ft
the removal of sludge removed was about 16,000 lbs per million gallons be-
fore the primary basin was installed. After the primary basin was install-
ed, the removal was about 2,500 lbs of sludge per million gallons of waste
treated.
Prior to the installation of the primary sedimentation basin, the total
solids flow from the carbonation basin into the activated sludge unit
averaged about 6,000 mg/i. After the primary sedimentation basin was in-
stalled, the average concentration of total solids in the carbonation
basin effluent to the activated sludge basin was about 5,170 mg/l. In
general, sanitary sewage containing about 500 mg/i of total solids com-
prised about 1/3 of the influent flow to the activated sludge unit. From
the above figures, it may be computed that the average total solids con-
centration in the influent to the activated sludge unit was about 3,610
mg/l. The effluent from the secondary sedimentation basin averaged about
2,200 mg/i for total solids. Hence, it may be seen that the activated
sludge unit, including secondary sedimentation, removed about 1,410 mg/i
of total solids, or about 39 percent of the influent solids.
Removal of Calcium
The tannery at South Paris uses between 7,000 and 8,000 lbs of hydrated
lime per day. Most of the lime is used in the de—hairing process. As
the de—hairing process is completed, the spent lime solutions are dis-
charged to the sewerage system. In addition to the lime used, the tan-
nery also uses about 300 lbs of calcium chloride each day which is also
discharged to the sewerage system. During the waste survey in April,
71
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25,000
20,000
IS 000
10,000
5,000
a
0
0 250 500 750 1000 250 1500
2
OVERFLOW
RATE— GPO/FT
FIG. 16 WEIGHT OF SLUDGE REMOVED VS. OVERFLOW RATE,
CARBONATION-UPFLOW- SEDIMENTATION BASIN
-J
L i i
C,
a
-j
C l )
0
I —
C,
L i i
750
-------
1968, the analyses of the waste samples indicated a discharge of 8,275
lbs per day of calcium expressed as calcium carbonate. The equivalent
hydrated lime, having a purity of 93 percent, would be about 6,600 lbs
per day giving a reasonably good check against the amount of lime used in
the tannery. The average concentration of calcium in the waste samples
was 1,065 mg/i expressed as calcium carbonate.
Calcium and magnesium are the two principal elements which contribute to
the hardness of a water supply. It is therefore, advisable to remove as
much as possible of these compounds from any waste prior to discharge
from an industrial operation. The most satisfactory way of removing large
amounts of calcium from water solution is by converting it into an insol—
uable compound which may be removed by sedimentation. The solubility of
some of the calcium compounds which might occur in tannery wastes are
listed below:
Calcium carbonate — 14 mg/l
Calcium sulphate — 2,000 mg/l
Calcium hydroxide — 1,600 mg/i
The solubilities listed above are solubilities of the compounds in dis-
tilled water. The actual solubility of each of these compounds depends
greatly upon the pH, the total solids content, and the total concentration
of various common ions. However, as may be seen from the above table,
calcium carbonate has the lowest solubility and offers the best opportun-
ity for the removal of calcium from the waste. In order to convert the
calcium present in the waste solution to calcium carbonate it is necessary
to supply a sufficient amount of carbonate ion to react with the calcium
present. The most economical source of the carbonate ion was found to
be carbon dioxide in the flue gas from the power plant at the tannery.
This was not the only reason for using flue gas but is one of several
reasons. Analyses of the flue gas indicated that it contained about ii
percent carbon dioxide.
Flue gas was taken directly from the stack at the power house and pumped
with a gas compressor to the pilot plant. At the pilot plant, the flow
of gas was measured with an orifice meter and diffused into the waste
flow in the manner previously described.
The resulting removal of calcium by the plant may be divided into three
parts: the removal in the primary sedimentation basin, the removal in the
carbonation upflow sedimentation basin, and the removal by the activated
sludge process. The results for the removal of calcium are presented in
Table 8.
Table 8 lists the removal of calcium into two phases. The first phase
covers the period before the primary sedimentation basin was installed,
during which time the upflow carbonation—sedimentation basin served as
both primary sedimentation and carbonation basin. The second phase
covers the period after the primary sedimentation basin was installed.
It may be seen from Table 8 that during the first phase, the average in—
fluent concentration of calcium was 1,300 nig/l. Following carbonation
73
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TABLES. REMOVAL OF CALCIUM IN THE PILOT PLANT
Analyses for Calcium (as Ca C03) mg/I
Primary Carbonation
Plant Basin Basin Plant
Dote lnfluenf Effluent Effluent Effluent
Mar. 22, 1968 595 435 222
25 742 793 198
26 1,030 836
27 1,170 1,230 395
28 880 540 410
29 1,890 1,110 518
April 1 1,090 748 202
2-3 2,050 610 195
PRIMARY BASIN INSTALLED
24 1 ,350 620 260
25 1,310 590 270
26 1,380 560 250
29 1,740 630 168
30 1,680 670 260
May 2 2,000 993 566 351
3 2,230 1,070 764 360
6 1,180 974 606 291
7 1,190 818 533 469
8 881 1 ,040 727 408
9 388 360 505 428
10 978 937 719 436
13 998 816 525 307
14 840 929 622 501
16 776 1,010 727 493
17 2,300 1,450 848 465
20 950 1,180 1,000 295
21 770 1,100 608 445
22 1,150 1,160 1,060 545
23 1,140 1,140 — 602
24 552 800 676 466
27 1,160 917 606 311
28 792 929 660 350
29 723 769 598 451
31 684 1,030 505 295
Averages
Befote Primary 1,300 - 721 280
After PrImary 1 ,085 973 677 413
Percent Removals
Before Primary 45 78
After Prmary 10 38 62
74
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and upfiow settling, the average concentration was 721 mg/i, representing
a removal of about 45 percent by carbonation and sedimentation. During
this time, the effluent concentration from the sedcondary sedimentation
basin averaged 280 mg/i of calcium, as calcium carbonate, representing an
overall removal for the pilot plant of about 78 percent. Following the
installation of the primary sedimentation basin, the average influent cal-
cium concentration was 1,085 mg/i. The effluent from the primary sedimen-
tation basin contained on the average a concentration of 973 mg/i of cal-
cium representing a 10 percent removal in the primary sedimentation basin.
For the same interval of time, the effluent from the carbonation upflow
sedimentation basin was 677 mg/i of calcium, representing an average re-
moval across the primary and the carbonation basin of about 38 percent
of the influent calcium. The average concentration of calcium in the final
plant effluent during this time was found to be 413 mg/I, representing
a removal of about 62 percent of the calcium across the pilot plant. The
difference between the 78 percent removal of calcium prior to the primary
sedimentation basin and the 62 percent subsequently are not considered to
be statistically significant.
Definite explanation cannot be offered for the fact that the overall re-
moval of calcium prior to the installation of the primary tank, was higher
than the removal following the installation of the primary sedimentation
basin. The concentration of calcium in the effluent from the carbonation
upflow sedimentation basin was lower following the installation of the
primary sedimentation basin. However, the removal in the activated sludge
unit was considerably lower during this time. One possible explanation
might be found in the rate of operation in the secondary treatment system.
Prior to May 10, the secondary system was operated at a rate of about 5 gpm
whereas, starting on Nay 13th, the rate was gradually increased until on
the 27th, 28th, and 29th, the rate of operation was 9.5 gpm. However, the
removal of between 78 and 62 percent of the calcium across the plant as a
whole compares favorably with the results obtained during a previous pilot
plant investigation in the tannery, reported in a report dated June,
1967. The cited report dealt with the treatment of only the beam house
wastes. The results of treatment of the beam house wastes indicated a
63 percent removal of calcium across the plant.
Inasmuch as the design flow for the Little Androscoggin River to which
the effluent discharges, Is about 5.4 ingd, the addition of 1.0 mgd of
flow containing about 400 mg/i of calcium carbonate will increase the
hardness of the water by about 63 mg/i. The resulting hardness is well
within the U.S. Public Health Standards for drinking water, and therefore
should be acceptable to meet the water quality standards of the Little
Androscoggin River.
Removal of Sulfides
Between May 6, 1968, and June 21, 1968, a number of analyses of the su1-
fide concentrations at various points throughout the pilot plant were made.
The results of these analyses are presented in Table 9. From Table 9, it
may be seen that the average sulfide concentration in the pilot plant in-
75
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TABLE 9. REMOVAL OF SULFIDES IN THE PILOT PLANT
Sulfide Analyses of Composite (as S), mg/I
Primary Carbonation
Plant Basin Basin Plant
Date Influent Effluent Effluent Effluent
May 6 68 78 69 0.4
8 109 88 57 0.9
14 90 82 70 6.0
16 107 79 69 0.2
21 47 73 66 1.4
23 130 70 112 4.0
27 77 134 98 2.2
29 80 85 41 1.3
June 17 64 100 52 0
18 49 61 45 0
19 46 46 33 0.2
20 70 52 55 0
21 39 39 28 3.0
Averages 75 76 61 0.76
Percent removal 0 19 99.0
76
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fluent during this period was about 75 mg/i. This concentration was some-
what higher than the concentration found during the April survey in the
total tannery discharge (53 mg/i). However, as may be seen from Table 9,
the sulfide concentration varied considerably from day to day ranging from
a low of 39 mg/i to a maximum of 109 mg/i.
The results of these analyses show that the average concentration of sul-
fide in the effluent from the primary sedimentation basin was 76 mg/l
representing no removal of sulfide from the waste in passage through the
primary sedimentation basin. The average concentration of sulfide in the
wastes discharged from the carbonation basin was 61 mg/i, which represents
a removal of 19 percent in passage through the carbonation—sedimentation
basin. These results show that if the pH of the solution which contains
the suif ides is maintained above about 9, very little of the sulfide is
lost from the solution. Laboratory tests described later showed the same
results. The loss in the carbonation—sedimentation basin may be due at
least in part to removal of protein solids and hair debris to which sodium
sulfide is chemically or physically attached.
The right—hand column in Table 9 records the results of sulfide analyses
made on the pilot plant effluent for the same period of time. These re-
sults indicate that the sulfide content In the wastes after treatment
ranged from a low of 0 to a maximum of 6 mg/i. The average concentration
of sulfide in the discharge was 0.76 mg/i which represents 99.0 percent
removal of sulfide from the wastes being treated.
As will be shown later under the section of this report entitled “Special
Tests,” the mechanism by which the sulfide was removed is definitely
a biological process, in which the suifides are oxidized to sulfate.
Removal of Chromium
Chrome tanning is essentially the reaction of the chroniic (CR+3) ion or
its complex with the proteins in the hide substance. There is no hexa—
valent chromium present in the wastewaters from the tannery. All dichro—
mate used in the tannery is reduced to the trivalent state before being
used in the processes. When chrome tanning is completed, the leather is
washed free of excess chromium solution then neutralized with a mild
alkali. The 48—hour waste survey conducted in April, 1968, showed that
the average concentration of chromium in the wastes from the tannery was
about 236 mg/i. However, inasmuch as the tanning wheels were dumped at
irregular intervals, the chromium found in 2—hour composites of the wastes
varied from about 30 mg/i to about 570 mg/i.
In order to obtain acid waste containing chromium for use in the pilot
plant it was necessary to catch the flow in the sewer when a tanning
or color wheel was dumped. The sample caught would sometimes have a
high chromium concentration and sometimes a low concentration. The only
immediate basis for judging the strength of the sample was the acidity
77
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of the sample. The acidity was not a good basis for judging the chromium
content. Analyses of composites showed that the chromium concentration
of the wastes entering the pilot plant varied from less than 1 mg/i to
more than 85 mg/i.
The results of the removal of chromium by the pilot plant are presented
in Table 10. The results in Table 10 are divided into two parts. One
part represents the results obtained before the primary basin was install-
ed, the other part after the primary basin was installed. In the testing
period before the primary basin was installed, the average concentration
of chromium in the plant influent was about 71 mg/i. During this period,
the influent went directly Into the carbonation basin. The effluent from
the carbonation basin had an average chromium content of 21 mg/i, repre-
senting a ren val of about 71 percent in the carbonation—sedimentation
basin. The effluent from the pilot plant following activated sludge treat—
ment and secondary sedimentation, had an average chromium content of 4.7
mg/i, representing a 93 percent removal of chromium across the pilot plant.
After the primary sedimentation basin was installed, the average chromium
content of the pilot plant influent was 29.8 mg/i. Following primary sedi-
mentation, the average chromium content was 20.0 mg/i representing a 33
percent removal of chromium by primary sedimentation. The effluent from
the carbonation—upf low sedimentation basin had an average chromium content
of 15.2 mg/i following installation of primary sedimentation. This repre-
sented a 49 percent removal of chromium by sedimentation in the primary
sedimentation basin and the carbonation upf low sedimentation basin operat-
ing in series. During this same time, the plant effluent had an average
chromium content of 3.6 mg/i representing an 88 percent removal of chro-
mium across the pilot plant as a whole.
In order to determine the affects of 1tLgh concentrations of chromium on
the activated sludge process, samples of chromium solution used in the
tanning process were added continuously to the activated sludge unit for
4 days starting on July 9, 1968, and extending through July 12, 1968. On
the first day, 40 mg/i of chromium was added to the influent to the aera-
tion basin. On the second day, 80 mg/i of chromium was added to the in—
fluent. On July 11, the third day, 120 mg/i of chromium was added to the
Influent, and on July 12, the fourth day, 160 mg/i of chromium was added
to the aeration basin influent. The chromium content of the mixed liquor
in the activated sludge basin was analyzed, the chromium In the return
sludge or waste sludge was analyzed, and the chromium in the pilot plant
effluent was analyzed. The results of these tests are shown in Table 11.
From Table 11, it may be seen that the chromium content in the mixed liq-
uor on the first day was about 70 mg/i. The chromium in the waste sludge
or the return sludge was 122 mg/i, while the chromium in the pilot plant
effluent was 1.5 mg/i. On the second day when 80 mg/i of chromium was
being added to the influent to the activated sludge unit the chromium con-
tent of the mixed liquor was found to be 115 mg/i and the pilot plant ef-
fluent has a chromium content of 4.3 mg/i.
78
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TABLE 10. REMOVAL OF CHROMIUM IN PILOT PLANT
Chromium Analyses (as Cr), mg/I
Primary Carbonation
Plant Basin Basin Plant
Date Influent Effluent Effluent Effluent
March 29, 1968 80.1 34 6.4
April 1 48.1 23 2.8
2-3 84.4 12 5.0
Primary Basin Installed
May 6 9.7 4.3 3.2 2.2
8 47.9 26.6 22.2 1.9
16 36.5 12.5 12.5 0.5
21 33.0 22.6 22.6 3.0
23 11.6 12.6 7.8 2.8
27 16.0 12.6 6.1 1.5
29 34.3 13.2 5.0 19.0
June17 52.5 34.0 21.8 2.1
18 32.3 28.4 21.4 1.6
19 37.1 37.3 26.8 2.0
20 22.3 21.3 19.4 2.8
21 24.8 14.6 13.6 3.2
Average before Pr imary 70.9 21 4.7
Percent Removal 71 93
Average after Primary 29.8 20.0 15.2 3.6
Percent Removal 33 49 88
79
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The test results for chromium analyses for July 11 and 12 cannot be lo-
cated. However, it can be reported that the pilot plant continued to
function with no noticeable decrease in the removal of BOD and suspended
solids as a result of the high chromium content in the mixed liquor.
As may be seen from Table 11, the chromium content of the activated sludge
unit apparently was concentrated in the sludge itself and was removed via
the waste sludge. The chromium content of the secondary sedimentation
basin effluent showed no significant increase in chromium due to the high
feed of chromium directly to the activated sludge unit.
It is apparent from the results of the chromium studies, as reported in
Tables 10 and 11, that chromium is removed during all phases of the pro-
posed treatment system. In passing through the primary sedimentation basin
and the carbonation—upflow—sedithentation basin, the chromium content of the
wastes were reduced to about 20 mg/i, more or less independently of the
influent concentration of chromium. In passing through the activated sludge
process, the chromium content of the wastes was further reduced to about
0.5 to 32 mg/i. The special tests showed that even when the chromium con-
tent of the activated sludge unit is increased beyond that which would
reasonably be expected, the concentration of chromium found in the effluent
will still be about 4 mg/i. It is, therefore, our opinion that a full scale
waste treatment plant operating on the same processes tested in the pilot
plant will reduce the chromium content of the tannery effluent to about
4 mg/i.
Sludge Handliflg
Sludges constitute the solids which are removed from the waste by the treat—
ment processes. In the proposed tannery waste treatment, sludges will be
removed from the process at three locations: the underfiow from the primary
sedimentation basin, the underfiow from the carbonation upflow—sedimenta—
tion basin, and the excess underfiow from the secondary sedimentation basin.
The last named sludge is known as excess sludge. Table 12 lists the weight
and volume of the sludges removed from the various operations during the
pilot plant testing. Table 12 is divided Into two parts; the first part
listing the sludges obtained before the Installation of the primary sedi-
mentation basin, and part two lists the sludges obtained subsequent to the
installation of the primary sedimentation basin.
From Table 12 it may be seen that the total amount of sludge obtained in
the pilot plant varied from about 14,000 lbs of dry solids per million gal—
ions of waste treated to about 11,000 lbs per million gallons of waste
treated. The volumes of the sludge varied from about 38,000 gallons per
million gallons of waste treated to about 29,000 gallons per million gal—
ions of waste treated. The volumes of the sludge, therefore, appeared to
be about 3.7 percent of the waste treated. The average solids concentra—
Uon in the sludges is about 4.5 percent. The range of concentrations of
total solids in the sludge was from 1 percent for the secondary sludge to
about 8.2 percent for the sludge removed from the carbonation basin follow—
ing the installation of the primary sedimentation basin. It is recommended
80
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TABLE 11. RESULTS OF HIGH CHROMIUM CONCENTRATION
ON ACTIVATED SWDGE
Chromium Chromium Chromium in
Chromium in mixed in mixed pilot plant
Date added, mg/I liquor, mg/I sludge, mg/I effluent, mg/I
1968
July 9 40 69.4 222 1 .5
80 115.0 378 4.3
11 120
12 160
Carbonation Pilot
Basin Plant
Chromium Effluent Effluent
Date added, mg/I BOD, mg/I BOD, mg/I
1968
July 9 40 1,380 50
10 80 755 54
ii 120 855 50
12 160
Averages 997 51
Percent removal 95
81
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TABLE 12. WEIGHT AND VOLUME OF SLUDGESAS DRAWN
Dry Weight Volume Percent
Source lbs/mg gals/mg Solids
Carbonation basin before primary installed 13,400 32,500 5
Secondary excess sludge before primary 434 5,400 1
Total sludge before primary s installed 13,834 37,900 4.2
P imary sedimentation basin sludge 4,300 7,380 7
Carbonation basin after primary installed 4,536 6,630 8 .2
Secondary excess sludge after primary 1 ,877 14,500 1 .5
Total sludge after primary was installed 10,713 28,510 4.5
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that the sludge dewatering facilities be designed to handle at least
40,000 gallons of sludge per million gallons of waste treated. The weight
of sludge for which the sludge handling facilities should be designed is
about 15,000 lbs per million gallons of waste treated.
Table 13 presents the average composition of the sludges obtained during
the pilot plant operation. From Table 13, it may be seen that the pri-
mary sludge contained,on the average, 7 percent total solids of which 46.6
percent were volatile. Based upon the dry weight of the solids in the
primary sludge, the solids contained 1.25 percent chromium, 18 percent
calcium, 0.19 percent sulfide, 0.12 percent total phosphate, as phosphor-
ous and 0.094 percent polyphosphate, as phosphorous. The carbonation
basin sludge after the primary sedimentation basin was installed, contain-
ed 8.2 percent solids of which 34 percent were volatile. The solids con-
tained 0.56 percent chromium, 39.6 percent calcium, 0.2 percent sulfide,
0.11 percent total phosphate and 0.055 percent polyphosphate. The sludge
from the secondary sedimentation basin contained on the average, 1.56 per-
cent total solids of which 64.8 percent were volatile. The solids in the
secondary sedimentation basin sludge contained 1.3 percent chromium, 14.14
percent calcium, 0.55 percent sulfide, 0.18 percent phosphate and 0.13 per-
cent polyphosphate. These results Indicate that the solids from the pri-
mary sedimentation basin and the carbonation—upflow—sedimentation basin
contained a high percentage of mineral matter (indicated by the relatively
low percentage of volatile solids) whereas the secondary sedimentation
basin sludge contained a much higher percentage of organic matter, as in-
dicated by the relatively high volatile solids content.
It is of interest to note that all of the sludges contained a relatively
high concentration of chromium, i.e. between 0.6 and 1.3 percent. On the
other hand, the sulfide concentration in the sludges was relatively low,
about 0.2 percent in the primary sludges. The average sulfide concentra-
tion for the secondary sludge was 0.55 percent. This high average result-
ed from including one unusually high value.
Sludge Dewatering
Tests were made on dewatering the sludge by the use of a solid bowl cen-
trifuge. The centrifuge used was a production imdel, 6—in diameter solid
bowl type. The liquid capacity of the centrifuge was about 2 gpm. A
series of preliminary runs were made by pumping sludge from the various
treatment units, i.e., the primary sedimentation basin, the carbonation—
upflow—sedimentation basin, and the secondary sedimentation basin. The
preliminary tests showed that the sludge from the primary sedimentation
basin and the carbonation—upflow sedimentation basin dewatered readily to
yield a relatively dry cake. The excess activated sludge from the second-
ary sedimentation basin dewatered very poorly and gave a semi-fluid sludge
having a high water content. On the basis of the preliminary tests, the
excess activated sludge from the secondary sedimentation basin was mixed
with primary sludge before the quantitative dewatering tests were made.
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TABLE 13. AVERAGE COMPOSITION OF TANNERY PILOT PLANT SLUDGE
________________ Secondary Slud 9 e
Before After
Primary Primary Primary
Sludge ________ ________ Installed Installed
7.0 0.965 1.56
46.6 61.3 64.8
1.25 1.00 1.30
18.0 14.14
0.19 0.20 0.55
0.122 0.112 0.18
0.094 0.055 0.13
Components
Total solids, percent
Volatile solids, percent
Chromium, percent dry weight
Calcium, percent dry weight
Sulfide, percent dry weight
Total phosphate, percent dry weght
Potyphosphate, percent dry weight
Carbonation Sludge
Before After
Primary Primary
Installed Installed
5.0 8.2
39.1 34.0
0.56
39.6
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Table 14 presents the results of dewatering the sludge without the use of
coagulant chemicals. In the series of tests reported in Table 14, the
centrifuge was operated at three different speeds i.e., 3,000 rpm, 4,000
rpm, and 5,000 rpm. These speeds of rotation resulted in centrifugal
forces of 750 times gravity, 1,330 times gravity, and 2,080 times gravity
respectively. The mixture of primary and secondary sludge had an initial
concentrations ranging from 4.16 percent to 5.78 percent. The total solids
in the dewatered sludge discharged from the centrifuge ranged from 19.84
percent to 21.25 percent. The liquid effluent discharged by the centrifuge
contained suspended solids ranging from 1.68 percent to 2.49 percent. The
recovery of suspended solids from the sludge ranged from 55 to 60 percent.
The dry cake was similar in nature to manure and could be trucked to a
disposal area.
The carbonation sludge tested ranged in suspended solids concentration from
2.42 percent to 2.91 percent. The resulting dewatered sludge ranged from
29.5 percent solids to 33.7 percent. The suspended solids in the liquid
effluent from the centrifuge ranged from 0.42 percent to 0.46 percent. The
recovery of suspended solids ranged from 75 percent to 86 percent. The
sludge cake was quite dry and was easily transportable by ordinary dump
trucks.
The speed of rotation of the centrifuge apparently had little influence
upon the dewatering of the sludge tested. The tests showed a very slight
increase in the total solids content of the sludges discharged as the
speed of rotation increased. The increase in solids amounted to about
1.4 percent for the primary secondary sludge mixture when the speed of
rotation was increased from 3,000 to 5,000 rpm. For the carbonation sludge
the resulting increase in solids was about 4.1 percent when the speed of
rotation was increased from 3,000 to 5,000 rpm. On the other hand, the
highest recovery of suspended solids was achieved at a speed of rotation
of 4,000 rpm.
A second series of tests for dewatering the sludge was carried out using a
synthetic polymer. This material was used in accordance with the direc-
tions of the manufacturer. It was applied to the sludge at concentrations
of 1 lb per ton of solids in the sludge, 2 lbs per ton and 4 lbs per ton.
The centrifuge was operated at 4,000 rpm which yielded a centrifugal force
of 1,330 times gravity. The results of these tests are reported in Table
15. The suspended solids in the primary secondary sludge mixture ranged
from 4.98 percent to 5.89 percent. The total solids in the dewatered
sludge ranged from 21.1 percent to about 20 percent. The recovery of sus-
pended solids ranged from 42 to 53 percent. All in all, the results showed
that the coagulant had little, if any, effect upon the dewatering of the
primary secondary sludge mixture.
The same tests were repeated using the carbonation basin sludge and the
same concentrations of coagulant. In this test, the suspended solids in
the carbonation basin sludge ranged from 2.68 percent to 2.88 percent.
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TABLE 14. SLUDGE DEWATERING BY CENTRIFUGE
WITHOUT COAGULANTS
Influent Effluent Total Removal
Speed of Centrifugal Feed Suspended Suspended Sludge of Suspended
Rotation Force Rate Solids Solids Solids Solids
( rpm) x Gravity ( gpm) ( %) ( %) ( %) ( %)
PRIMARY AND SECONDARY SLUDGE MIXTURE
3,000 750 1.94 4.46 2.01 19.84 55
4,000 1,330 1.89 4.16 1.68 20.07 60
5,000 2,080 1.67 5.78 2.49 21.25 57
CARBONATION SLUDGE
3,000 750 1.84 2.42 0.61 29.53 75
4,000 1,330 1.86 2.91 0.42 32.28 86
5,000 2,080 1.88 2.53 0.47 33.69 81
86
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TABLE 15. SLUDGE DEWATERJNG BY CENTRIFUGE,
USING RETEN 210 COAGULANT
(Speed of Rotation 4,000 rpm, Centrifugal Force 1,330 x Gravity)
Influent Effluent Removal
Coagulant Feed Suspended Suspended Sludge of Suspended
Concentration Rate Solids Solids Solids Solids
( lbs/ton of Solids) ( gpm) ( %) ( %) ( %) ( %)
PRiMARY AND SECONDARY SLUDGE MIXTURE
1.0 1.68 5.67 3.30 21.07 42
2.0 1.68 5.89 3.00 19.94 49
4.0 1.48 4.98 2.33 21.13 53
CARBONATION BASIN SLUDGE
1.0 1.77 2.73 0.36 40.96 87
2.0 1.76 2.68 0.28 37.26 90
4.0 1.71 2.88 0.19 37.76 93
87
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The solids in the cake ranged from 87 percent to 93 percent. The appli-
cation of the coagulant to the carbonation basin sludge appeared to in-
crease the removal of suspended solids by between 5 to 10 percent. The
resulting dewatered cake was also improved in that its moisture content
was about 5 to 10 percent less than a comparable cake without the coagu-
lant.
The results of the centrifuge dewatering tests indicate that the mixture
of primary sludge and secondary sludge is readily dewatered by centrifugal
forces ranging from 2,080 to 750 times gravity. Under satisfactory con-
centration for disposal by burial. The carbonation basin sludge is readily
dewaterable to a concentration suitable for disposal by burial.
The use of a coagulant does not appear to increase the dewatering charac-
teristics of the primary secondary sludge mixture to any appreciable de-
gree, furthermore, it does not appear that the carbonation basin sludge
requires the use of any coagulant aid, although the use of the coagulant
does appear to increase the dryness of the cake and the percent recovery
of suspended solids when used with carbonation basin sludge.
Further tests with coagulants appears to be warranted.
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SULFIDE OXIDATION
General
In the unhairing process, sodium sulfide (Na2S) and sodium sulfhydrate
(NaSH.2H 2 0) are used as part of the depilatory mixture. As a result,
there is a significant amount of sulfide in the plant effluent. The ionic
form of sulfide in solution is a function of the hydrogen ion concentra-
tion (pH) in accordance with the following equilibrium expressions:
H2S H + HS (1)
HS - H + S (2)
HS— ] = 1(1 (3)
[ H 2 S]
[ lrF S- ) = K 2 4
[ HSJ (
= 9.1 x 10—8
1 (2 = 1.3 x 10—12
The above equilibrium expressions are summarized in the table below indi-
cating for various pH values, the percentage of the sulfide in solution
which is in the form of hydrogen sulfide.
Percent
H2S
5 99.3
6 91.6
7 52.4
8 9.9
9 1.09
10 0.11
Hydrogen sulfide is readily released from solution to the atmosphere as a
toxic gas with an obnoxious odor. As may be seen from the above table,
if the pH f ails below 9, a significant proportion of the sulfide content
of a solution is in the form of 11 2 S. Tests have shown that sulfide con-
centrations as low as 1.0 mg/l can create unpleasant odors if the pH of
the solution is less than 7.0. Hence, it is essential that any proposed
waste treatment reduce the sulfide concentration of the waste to less than
1.0 mg/i before it is discharged.
89
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It was found that the pilot plant treatment did in fact reduce the sul-
fide concentration to minimal and acceptable values. (See pilot plant
results Table 9). It was important to establish the mechanism by which
this reduction in concentration was accomplished. Therefore, an inves-
tigation into the fate of the sulfide was conducted and is described
below.
Sulfide is a strong reducing agent which may be oxidized by various
routes to other sulfur forms. It is known, for example, that sulfides
may be converted to thiosulfate during the depilation process .(ll) Air
oxidation of sulfide may also take place with the rate of reaction depen-
dent upon the conditions of the system. Through aerobic bacterial action,
hydrogen sulfide may be oxidized to sulfate.(” )
112s + 202 Bacteria so 4 = + 2W
Each of these processes as well as the physical “sweeping out” of hydro-
gen sulfide by aeration was investigated as one of the possible mechanisms
of sulfide ren val.
Previous pilot plant studies at the South Paris tannery revealed that the
major portion of the sulfide in the waste was renoved by the activated
sludge process. Hence, the studies to determine the fate of the sulfide
were primarily limited to this process. The solutions used in making the
tests in the laboratory consisted of either distilled water solutions of
the sulfides used by the tannery or of activated sludge samples taken from
the pilot plant to which sodium sulfide was added.
Apparatus
A glass cylinder of abut 2—1/2 liters capacity was fitted with a three
hole rubber stopper. Glass tubes were passed through the holes making
air tight connections. The first tube was connected to a compressed air
supply while the opposite end was connected to a diffuser stone in the
bottom of the cylinder. In order to prevent plugging of the diffuser by
solid material or admission of oil to the liquid, a glass wool filter
was interposed in the air line between the cylinder and the air supply
(see Fig. 17). The second tube was attached at one end of this tube which
led below the base of the cylinder. The other end of this tube reached
about half way down into the cylinder. This was used to sample the con-
tents of the cylinder by siphoning. The third tube, which acted as a
vent, led to just below the bottom of the rubber stopper inside the cyl-
inder and was connected outside of the cylinder to a rubber tube. The
end of the tube was submerged in 150 milliliters of 0.1 M zinc acetate
solution.
General Procedure
The liquid to be tested, which had been previously analyzed, was placed
in the cylinder after which the cylinder was securely stoppered. Aeration
was then begun by passing air into the cylinder through the diffuser. Ex—
90
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haust air was bubbled through a zinc acetate solution. Any hydrogen sul-
fide evolved reacted with the zinc acetate to form zinc sulfide. At in-
tervals the pinch clamp on the siphon tube was opened and a portion of the
liquid under aeration was siphoned off for analysis. At the end of the
aeration period a portion of the liquid was also collected for analysis.
The zinc acetate solution was analyzed for sulfide.
Analytical Procedures
Sample Pretreatment — The sample of activated sludge mixed liquor to be
analyzed was filtered through glass wool, after which the residue and glass
woo), were washed with distilled water. The filtrate and washings were com-
bined and diluted to 500 milliliters in the volumetric flask for sulfide,
sulfate and iodine demand analyses.
Sulfide — An aliquot of the combined filtrate and washings was placed in a
500 milliliter erlenmeyer flask. The flask was fitted with a rubber stop-
per through which was passed an outlet tube and a fritted glass inlet tube.
The inlet was connected to a cylinder of compressed carbon dioxide gas.
Two 125 milliliter erlenmeyer flasks, connected in series, were joined with
the outlet tube as shown on the diagram. (Fig. 17). One hundred rnilli—
liters of 0.1 N zinc acetate solution was placed in each of the flasks and
the first 125 milliliter flask was stoppered tightly. After this, 10 milli-
liters of concentrated sulfuric acid were added to the sample in the 500
milliliter flask and the flask was immediately stoppered tightly. The acid
converted the sulfides present to hydrogen sulfide. Carbon dioxide was
bubbled through the sample mixture in the flask and swept out the hydrogen
sulfide into the receiving flasks where it was converted to zinc sulfide.
After having bubbled carbon dioxide through the acidified sample for an
hour, the sample flask was opened and the fumes were tested for hydrogen
sulfide with lead acetate test paper. If there was no further evolution
of hydrogen sulfide, the carbon dioxide was shut off and the apparatus
dismantled.
The contents of the two receiving flasks were combined. The flasks and
effluent gas tubing were rinsed with water and the rinsings added to the
combined zinc acetate solution. A sulfide analysis was made on the com-
bined rinsings and zinc acetate solutions.
Hydrogen Sulfide — The zinc acetate solution containing any precipitated
zinc sulfide was treated with an excess of standard iodine solution. Five
milliliters of hydrochloric acid (concentrated) were added to the solution
and the excess iodine was back titrated with 0.025 N phenylarsene oxide
solution. The weight of the sulfide evolved was calculated from the
amount of iodine consumed.
Sulfate — Another aliquot was treated with a solution of barium chloride
which precipitated any sulfate or sulfite present as the insoluble barium
salts. The precipitate was separated from the liquid phase of centrifug-
ing and decanting. The precipitate was washed first with hot dilute hydro-
chloric acid and then with hot distilled water. This treatment removed any
91
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SAMPLING
SIPHON—.
PINCH
CLAP4j
______________ ______ COMPRESSED AIR
ii [ _ ° WOo
--IT
SLUDGE CONTAINING SAMPLE
EXHAUST GAS
0
o 0.
0
0
ZINC ACETATE
0
L II (
J////// /////
HYDROGEN SULFIDE TEST APPARATUS
TEST SET-UP FOR ANALYSIS OF SULFIDE
FIG. 17 HYDROGEN SULFIDE TEST APPARATUS
CO 2
SAMPLE
92
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barium sulfite present and left the barium sulfate in an easily filterable
condition. The barium sulfate was filtered through a weighed Gooch cruci-
ble and washed again with hot water. The barium sulfate was then dried,
Ignited, cooled and weighed. From the weight of Ba SO 4 present the amount
of sulfate in the original aliquot was calculated.
Iodine Demand — An aliquot of the sample was treated with an excess of
standard iodine solution, acidified, and the excess iodine was back tit-
rated with standard phenylarseneoxide solution. The amount of iodine
consumed was converted to equivalent sulfide ion by calculation as in the
sulfide and H S analyses.
Individual Tests
A series of four tests was conducted to determine the extent of sulfide
removal under different conditions and to determine the fate of the sul-
fide under these conditions.
Test 1
The purpose of this test was to determine the extent of oxidation of sul-
fide in an aqueous solution by aeration alone.
Since further tests were to establish the effect of microorganisms on the
rate of sulfide oxidation, this test established a base line for the later
tests.
Procedure — A stock solution of commercial sodium sulfide in water was ad-
justed to a pH of about 9 with hydrochloric acid. A portion of the stock
solution was diluted with water and an aliquot was taken for analysis. One
liter of the diluted sulfide was introduced into the test cylinder and the
cylinder was stoppered tightly. Aeration was begun and continued for
2—1/2—hours. Throughout the aeration period the exhaust gas was passed
through a solution of zinc acetate in order to collect any hydrogen sulfide
carried out by the air flow. At various times during the aeration period
samples were collected for iodine demand tests in order to roughly follow
the rate of sulfide disappearance. After 2—1/2—hours, a sample of the
aerated solution was collected for analysis and the aeration was stopped.
The results of the test are presented in Table 16. In Table 16 Column (1)
is the time from the start of aeration until a sample was withdrawn from
the solution for analysis. Column (2) is the “iodine demand” of the sam-
ple expressed as sulfide. The iodine demand is higher than the total sul-
fide due to the presence of iodine reducing material, in addition to the
sulfide, in commercial sodium sulfide. Column (3) is the analysis of the
samples for sulfide. Column (4) is the analysis of the samples for sul-
fate expressed as sulfide. This analysis was not made on samples in Test
1 because all sulfide lost from solution was accounted for by sulfide in
the exhaust gas. Column (5) is an analysis of the sulfide contained in
the exhaust gas, expressed as mg/l in the initial solution. Column (6)
is a summation of the various forms of sulfide accounted for by the analy-
ses.
93
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TABLE 16. TEST RESULTS - AERATION OF WATER
SOLUTION OF SODIUM SULFIDE
TEST 1
Hydrogen
Aeration Iodine Sulfide Sulfide Total
Period Demand Remaining Sulfate Expelled 3,4,5 —
( mm) Mg/I as S mg/i as S mg/I as S= mg/I as S mg/I as S
(•l) (2) (3) (4) — (5) (6)
0 120 82.8 0 82.8
30 105
60 87
120 59
150 42 31.4 51.8 83.2
Note: Sulfide solution adjusted to pH 9.0 before dilution.
94
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The total amount of sulfide found in the exhaust gas was 51.8 mg/i (based
on the initial solution). For the same period of time the sulfide content
of the solution decreased by 51.4 mg/i. Hence we may conclude that the
sulfide lost from the solution was “swept out” of the solution by the air
and no sulfide was oxidized.
The iodine demand test which was used as a quick check on the extent of
sulfide removal is not specific for sulfide. Other reducing agents were
present which responded to this test. It was known from the manufacturer’s
analysis of the sodium sulfide that some sodium thiosulfate and sodium
sulfite existed in the product as impurities. No attempt was made to
determine the extent of these impurities. However, it is evident from the
decrease of 79 mg/i in the iodine demand that the sulfide equivalent of
about 28 mg/i of these impurities were oxidized by the aeration.
Test 2
The preceding test showed the extent of sulfide removal from an aqueous
sulfide solution by aeration alone. Test 2 was designed to show the
influence of microorganisms on the sulfide removal. Since the sulfide
concentration of the plant waste was reduced in the aeration tank of the
pilot plant, it appeared likely that the microorganisms present in the
mixed liquor had developed the capability of altering sulfide.
Procedure — Fresh activated sludge mixed liquor was collected from the
pilot plant aeration tank and mixed with sodium sulfide solution. Two
hundred ml of solution was prepared from the commerical sodium sulfide.
The above solution was added to 1,800 nil of the fresh mixed liquor and
the pH of the mixture adjusted to 9.2. Zinc acetate solution was added
immediately to an aliquot of this mixture in order to fix the sulfide as
insoluble zinc sulfide. Sulfate and iodine demand tests were made on
the supernatant of another portion of the mixture in which the sludge had
been permitted to settle.
As soon as the initial samples were collected, aeration of the remainder
of the mixture was started in the cylinder as previously described in
Test 1. Aeration was continued for two hours during which time two addi-
tional samples were collected for iodine demand tests. Before each of
these samples and a final sample were collected, the aeration was shut
of f for about two minutes to allow settling of the mixed liquor solids.
This was done so that the supernatant might be sampled.
Results of the test are presented in Table hA. The concentration of sul-
fide sulfur was reduced by 236.7 mg/i while sulfate sulfur increased only
146.1 mg/i. The sulfide expelled during the test was only 13 mg/l, an
amount insufficient to account for the difference. An analysis of the
decantate from the sulfate test was made to determine if some sulfur
species intermediate between sulfide and sulfate was present. This was
accomplished by treating the decantate with an excess of standard iodine
solution and back titrating with standard phenylarsene oxide solution.
Upon converting the iodine consumed to equivalent sulfide it was found
95
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TABLE 7. TEST RESULTS - AERATION OF SOLUTION
OF COMMERCIAL SODIUM SULFIDE IN
ACTIVATED SLUDGE MIXED LIQUOR
TEST 2
Aeration Iodine Hydrogen Total
Period Demand Sulfide Sulfate Sulfide 2,3,4,5
( mm) mg/I as mg/I as S mg/I as 5 mg/I as S mg/I as S
(1) (2) (3) (4) (5) (6)
A
0 209 238 84.5 0 326.4
30 53
60 29
20 3.6 2.3 230.6 13 250.8
Note : pH initial = 9.2 pH final = 7.45
On unfiltered portion of mixture
B
0 166 fl3.5 279.5
30 96 32 228
210 21 256.4 277.4
Note : pH initial 8.0
96
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that only a small portion of the iodine consumed could not be accounted
for by the sulfide present. The unaccounted for sulfur amounted to 3.9
mg/i as sulfide in the initial sulfate decantate and 2.3 mg/l as sulfide
in the final sulfate decantate. This may be a result of the presence of
thiosulfate, some other reducing agent or simply experimental error. The
result of this analysis had little, if any, bearing on accounting for the
sulfide loss. Therefore, it is necessary to seek the discrepancy else-
where.
The sulfide concentration of the original mixture was determined on the
total mixture whereas all other analysis were made on the supernatant
liquid. It appeared that some organically bound sulfide might have been
n asured in the original analysis. The test was repeated therefore, using
consistent sampling procedures, i.e., sampling of supernatant in all in-
stances. The results of the repeated test are shown in Table 17B.
An almost exact balance of sulfur species was found between start and end
of the aeration period.
Test 2 shows that the oxidation of sulfide by acclimated activated sludge
is rapid and fairly complete under the conditions of the test. In Test 2A
61.5 percent of the initial sulfide was converted to sulfate, 5.5 percent
was lost in the exhaust gas, 1 percent was unchanged and 22 percent is un-
accounted for and presumably is absorbed by the sludge. Facilities were
not available for a complete analysis of the sludge. In Test 2B in which
only the supernatant liquid was considered the conversion of sulfide to
sulfate was 86 percent with 13 percent unchanged and 1 percent unaccounted
for.
The results of Test 2 along do not demonstrate the fact that the oxidaton
is a biological process. It does not exclude the possibility of cataly-
tic air oxidation with the sludge providing the catalyst.
Test 3
The previous test indicated that the presence of activated sludge is ef-
fective in the oxidation of sulfide. However, it was not known whether
only the living organisms were responsible for this or if killed organisms
could bring about the same result. The purpose of Test 3 was to investi-
gate this feature of the process.
Procedure — Test 3 repeated essentially the same procedure used in the
previous test with one exception. The activated sludge mixed liquor from
the pilot plant aeration tank was first boiled for about five minutes
before it was used. After the boiled mixed liquor had been cooled, sodium
sulfide stock solution was added to it and the mixture was aerated as be-
fore. Samples of the supernatant liquid were collected as in previous
tests. The results of analyses of this test are presented in Table 18.
97
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TABLE 18. TEST RESULTS — AERATION OF SOLUTION OF
COMMERCIAL SODIUM SULFIDE IN HEAT KILLED
ACTIVATED SLUDGE MIXED LIQUOR
TEST 3
Aeration Iodine Hydrogen Total
Period Demand Sulfide Sulfate — Sulfide 2,3,4,5 —
( mm) mg/I as S mg/I as S mg/I as S mg/I as S mg/I as S
(1) (2) (3) (4) (5) (6)
0 217 207 114 0 321
22 22.9
40
55 106 90 36.8 257.8
115 67 24 138 46.8 208.8
- Note : pH initial 8.1 pH final 8.8
TABLE 19 . TEST RESULTS — AERATION OF SOLUTION OF
COMMERCIAL SODIUM SULFIDE IN ACID KILLED
ACTIVATED SLUDGE MIXED LIQUOR
Test 4
Aeration Iodine Hydrogen Total
Period Demand — Sulfide — Sulfate = Sulfide — 2,3,4,5
( mm) mg/I as S mg/I as S mg/I as S mg/I as S mg/I as
(1) (2) (3) (4) (5) (6)
0 127 159 0 286
30 30 150 25.6 205.6
170 13 164 33.3 210.3
Note : pH initial 8.0
98
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The amount of sulfide removed amounted to 183 mg/i. The amount of sulfur
recovered as increased sulfate and sulfide expelled amounted to 70.8 mg/i.
Thus, about 112 mg/i of sulfide removed remained unaccounted for. About
89 percent of the sulfide was removed in 115 minutes aeration. Only 12
percent was oxidized to sulfate compared to 61.5 percent in Test 2 where
live bacteria were present. On the other hand, 23 percent of the sulfide
was expelled as H 2 S gas compared with only 5.5 percent in Test 2. However,
54 percent was unaccounted for compared to 1 percent unaccounted for in
Test 2.
The above results suggest that the activated sludge solids can absorb the
sulfide but do not oxidize it to sulfate in the absence of live bacteria
or oxidize it at a slow rate. The observation that 23 percent of the
sulfide was expelled as H2S gas further suggests that the absorption is
not rapid and may not be complete.
Test 4
Boiling is one n thod of killing the activated sludge organisms. Boiling
also causes physical and chemical changes to occur to the sludge substance.
it was desirable to learn if these side effects of boiling effected the
ability of the sludge to oxidize sulfide to sulfate. Hence, another method
of inactivating the sludge was explored. In Test 4, the ability of the
activated sludge to oxidize sulfide to sulfate was tested after the sludge
had been killed with hydrochloric acid.
Procedure — To two liters of fresh mixed liquor was added 25 ml of concen-
trated hydrochloric acid. This was sufficient to reduce the pH of the
mixed liquor to 1.2. The mixed liquor was allowed to stand for two hours
in this condition with occasional mixing. After this time about 25 ml of
45 percent sodium hydroxide solution was added to bring the pH of the mix—
ture back to the original value of 7.1. Then sodium sulfide solution (ad-
justed to ph 9) was added in the proportion of 100 ml per liter of mixed
liquor.
Aeration of the mixture was started in the usual manner but because of
excessive foaming the test was stopped.
Aeration was begun agina on a reduced volume of the mixture to which was
added about 2 ml of antifoam compound.
The results of Test 4 are presented in Table 19. From Table 19 it may be
seen that 170 minutes of aeration resulted in a reduction of the sulfide
concentration from 127 mg/i to 13 mg/i, a reduction of 90 percent. At
the same time, the sulfate concentration increased by only 5 mg/i and the
hydrogen sulfide gas expelled amounted to 33.3 mg/i. The total reduction
of sulfide was 114 mg/l while the accounted for increases amounted to
38.3 mg/i. Hence it may be assumed that 75.7 mg/i was absorbed into the
activated sludge floc but not oxidized to sulfate.
99
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Further Testing
In addition to the tests reported above, in which the rate of sulfide re—
moval was studied, another series of tests was conducted which involved
added sodium sulfide. This series studied the rate of utilization of
oxygen by organisms oxidizing sulfide solutions. The description of the
apparatus and procedures will be discussed later under the heading “Oxygen
Uptake Tests.” It will be shown later that an immediate increase in the
rate of utilization of oxygen takes place upon the addition of sulfide to
a sample of mixed liquor. The oxygen used was equal to or slightly greater
than the amount required for the stoichiometric conversion of sulfide to
sulfate, according to the reaction:
S ’ +202 - S0 =
Conclusions
The organisms in the activated sludge of the pilot plant have a profound
effect in the oxidation of sulfide. It appears that an alteration of the
sulfide occurs even after the organisms have been killed. Since all of
the sulfide loss could not be accounted for as sulfate or evolved sulfide,
in the cases where the sludge had been killed, the tests suggest that the
oxidation of sulfide to sulfate is not direct. Further, it would appear
that live organisms are required to complete the oxidation of sulfate under
the conditions studied.
It Is evident, however, that aeration of the sulfide waste without acti-
vated sludge will not result in a sufficiently rapid oxidation of the
sulfide to provide a practical method for disposal of sulfides and would
probably result in sulfide odors.
Biological treatment of the waste is essential therefore, for both ren val
of organic BOD and sulfide.
100
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OXYGEN UPTAKE STUDIES
General
Activated sludge treatment is a method of utilizing a controlled biolo-
gical process for the oxidation of the putresible organic matter in wastes.
Microorganisms convert the organic matter to cellular materials, carbon
dioxide, and water. In so doing the biological reactions release energy
that can be utilized by the organisms for growth and reproductive functions.
The overall oxidation of food for growth and energy, i.e., the metabolism
of the organisms, results in a reduction in the amount of organic matter,
some of which is converted to carbon dioxide and water.
The rate of metabolism of any particular group of aerobic organisms is
dependent upon the amount of oxygen, food, nutrients, growth inhibitors
and the number of organisms present in the biological medium. The rate of
oxygen uptake is directly related to the rate of metabolism and, therefore,
provides a means of measuring the effects of the various factors limiting
metabolism. Some of these factors and their relationship to the tannery
waste are described in the succeeding paragraphs.
Oxygen uptake rates for the activated sludge system in the pilot plant
were studied under varying conditions of food addition. Included in
the tests was a test of the uptake rate during the endogenous phase of
growth. In the endogenous phase the ratio of food concentration to the
mass of the microorganisms is small.
As important as food and oxygen are to growth, nutrients are almost equal-
ly important. The nutrients Include nitrogen and phosphorous and trace
quantities of potassium, calcium, magnesium, molybdenum, cobalt, and iron.
Normal contamination of process chemicals ensures that these trace elements
will be present in adequate amounts. It is generally accepted that a
waste contains sufficient nitrogen and phosphorous to sustain bacterial
metabolism if the nitrogen is present In the ratio of 1 part to 25 parts
of COD (chemical oxygen demand) and the phosphorous is present in the ratio
of 1 part to 100 parts of COD. If the validity of these ratios is accept-
ed, it can be seen (Table 20) that the phosphorous requirement was not met
by the tannery waste. For this reason an investigation was made of the
effects of additional phosphorous on the rate of oxygen uptake.
In addition to the factors already discussed, which would tend to stimu-
late growth, some factors which might inhibit growth were also investi-
gated. Calcium, sulfide, and chroniate have been known to slow the rate of
metabolism of microorganisms. These were studied in the concentrations
which might be found in the tannery waste.
In order to investigate the effects of these chemicals, exact measurements
of oxygen uptake under controlled conditions were necessary. Such measure—
ments could not be made in the pilot plant. The tests were, therefore,
conducted on a laboratory scale with apparatus assembled specifically for
this purpose.
101
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Apparatus
Fig. 18 is a diagram of the apparatus used in the tests. Duplicate units
were used. One was used as a control and was denoted “barometer.” It
was similar in all respects to the “sample” unit with the exception that
no stirrer was required for the barometer.
Each unit consisted of a vacuum filtering flask, the sidearm of which was
connected to a 3 ft length of 6 mm O.D. glass tubing which was supported
vertically. The lower end of the tubing was immersed in a water reservoir
in order that it would serve as a manometer. The upper end of the tubing
was vented through a short piece of rubber hose provided with a pinch
clamp. Each of the flasks were immersed in a water bath to just below the
sidearm to stabilize temperature fluctuations.
The sample flask was fitted with a rubber stopper. This was used for a
support for a small cup reservoir that was suspended just below the neck
of the flask. Mixing and aeration of the contents of the sample flask was
provided for by using a magnetic stirring device with a teflon coated
stirring bar in the flask. The barometer flask was sealed with a rubber
stopper also but no reservoir was provided within the flask.
General Procedure
A sample of mixed liquor from the activated sludge unit of the pilot plant
was introduced into the reaction flask. 3 ml of a 50 percent potassium
hydroxide solution was placed in the cup reservoir. The upper inside wall
of the reservoir had been greased previously to prevent “creeping out” of
the solution over the wall. The stopper and reservoir assemblage were
carefully and securely fixed in the neck of the flask. Extreme care was
taken to prevent the slightest contamination of the sample with potassium
hydroxide.
A volume of water equivalent to the sample volume was introduced into the
barometer flask after which the flask was securely stoppered. Mixing of
the sample by means of the magnetic stirrer was begun. Then both mano-
meters were adjusted so that the water level inside and outside the mano-
meters coincided and the vents were clamped shut immediately.
As the test progressed, the oxygen dissolved in the sample mixture was
taken up by the organisms. This was replaced by oxygen from the air with-
in the flask and resulted in a pressure loss in the system. Any carbon
dioxide produced as a result of metabolism was absorbed by the potassium
hydroxide solution. At frequent intervals the pressure decrease in the
sample flask was noted from the manometer reading. At the same time, the
barometer and thermometers in the stabllizingbaths were read.
The pressure drop in the flask represented oxygen used. The an uxft of
oxygen used was computed by the ideal gas relationship:
102
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FIG. 18 OXYGEN UPTAKE APPARATUS
POTASSIUM HYDROXIDE
50% SOLUTION
WATER
MANOMETER
WATER
NETIC STIRRER
103
-------
PV = nRT
where
P = pressure in atmosphere
V — volume in liters
T = temperature in degrees Kelvin
n number of moles of gas
R = gas constant, liter—atmosphere/mole degree K.
Another formula was derived from this which takes into account corrections
for atn ,spheric pressure changes, corrections for temperature changes, the
volume of the units, and the relationship between the volume of oxygen and
its weight under standard conditions of temperature and pressure (O’C and
1 atmosphere). The formula equates the observed values directly with the
weight of oxygen consumed and is shown here:
mg 0 — 390 Vi — [ 406.8 — (mr—br)] [ Vi — 0.68 (mr—br)1
Ti 4 O 6 . 8 Tf
where
br inches of rise in barometer
mr = inches of rise in sample manometer
Vi = air volume of flask and tubing in ml
Ti = temperature of water bath at start of the test in °K
Tf temperature of water bath at time of readings in °K
By substitution of the observed values in the equation, the weight of
oxygen used during each time period could be calculated.
Ikdifications of this general procedure are described in the discussions
of the individual tests.
Individual Tests
Test 1
In order to establish a frame of reference for the tests, the first test
was carried out under the conditions existing in the pilot plant.
A fresh sample of aeration tank activated sludge was introduced into the
test apparatus within ten minutes of Its collection. Following the gen-
eral procedure already described, manometer readings were taken at definite
intervals and were recorded. A plot of oxygen uptake versus time is given
in Fig. 19. Note that the oxygen uptake is plotted as milligrams of oxygen
per milligrams of mixed liquor volatile suspended solids. This method of
reporting the results allowed for the comparison of the several tests
where different microbial populations were present.
The rate of oxygen uptake in this test was 0.264 mg of oxygen per mg of
mixed liquor volatile suspended solids per day.
104
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TIME , MINUTES
FIG. 19 PLOT OF C (YGEN UPTAKE VERSUS TIME WITH FRESH ACTIVATED SLUDGE (TEST U
0.05
0.04
0,
>
-J
0
7
w
4
I-
3
z
hi
0
x
0
0
0.
1
RATE OF
-
OXYGEN UPTAKE
1 1
0.264 MG/MG MLVSS/OAY
__
- _
.
0.01
C
0
50
15
100
(25
(50
(75
200
225
-------
Test 2
The purpose of the second test was to establish the rate of oxygen uptake
under the conditions of endogenous metabolism. The activated sludge, after
collection, was aerated for 15—1/4—hours in the laboratory without feeding
before a portion of it was put on test. The results are presented graphi-
cally in Fig. 20. The average rate of oxygen uptake under the conditions
of this test was 0.180 mg of oxygen per mg of mixed liquor volatile sus-
pended solids per day.
Test 3
In Test 3, pre—aeration of the activated sludge sample was carried out in
the laboratory for 4.5 hours. This was done to reduce the food concentra-
tion present in the mixed liquor without carrying the organisms into the
endogenous phase. At the end of 4.5 hours aeration, equal volumes of the
aerated activated sludge and carbonation tank effluent were introduced into
the test apparatus. The amount of oxygen taken up over fixed intervals
was determined and the results plotted. See Fig. 21.
In Test 3, the mixed liquor volatile suspended solids concentration was
2440 mg/i and the 5—day, 20°C BOD of the added wastewater was 900 mg/i.
Under these conditions, the average rate of oxygen utilization for a
period of two hours was about 0.55 mg/mg MLVSS/day. The oxygen uptake in
the test was equivalent to 670 mg/if day or abut 40 lbs/day/l000 cu ft of
aerator capacity. A co n figure used in the design of activated sludge
aeration basins is 30 lbs of 5—day, 20°C BOD/day/l000 cu ft of aerator
capacity. This test indicates that the tannery effluent and sewage mix-
ture falls within the range of co on experience.
Test 4
Test 4 measured the rate of oxygen uptake of fresh activated sludge with
addition of carbonation tank effluent. No aeration of the activated sludge
was carried out after collection from the aeration tank until it had been
combined in the apparatus with the carbonation effluent.
In Test 4, fresh activated sludge, containing about 1950 mg/i of mixed
liquor volatile suspended solids, was mixed with waste having about
910 mg/i of 5—day, 20°C BOD and placed in the aeration apparatus. The
volumetric ratio of activated sludge to waste was 2 to 1. The results
of oxygen uptake measurement are shown in Fig. 22. The average rate of
oxygen uptake for the first two hours of the test was equal to 1.44 mg/mg
of MLVSS/day. The extremely high rate of uptake Is no doubt due to un-
oxidized BOD contained in the sludge when it was removed from the aeration
basin. This test indicates the rapid response to the sludge when slugs
of food are added.
Translating this observation to plant design leads to the conclusic that
the aeration system should be designed to rapidly increase its rate of
106
-------
0.03
U,
>
-J
C,
• -. 0.02
C,
d
I— 0.01
0
C ,
>-
x
0 0
200
TtI4E , MINUTES
FIG. 20 PLOT OF OXYGEN UPTAKE VERSUS TIME WtTH ACTIVATED SLUDGE
N ENDOGENOUS PHASE (TEST 2)
0 25 50 75
100 25 150 175
-------
0.06
0.05
0.04
e—0_
5-DAY 20°C BOD OF ADDED WASTE = 900 MG/L
MLVSS CONC. PRIOR TO ADDING WASTES 2440 MG/L
TEMP. 23°C O.5C RISE DURING TEST
C
00
C l)
(I)
>
-J
2
2
2
I d
I .-
a.
z
I d
C,
>-
x
0
/
rn/
0.02
/
/
0.01
/
AVERAGE
RATE
OF OXYGEN UPTAKE= 0.552
MG/MG
MLVSS/DAY
/
/
0 25 50 75 tOO 125 150 175 200
TIME , MINUTES
FIG. 2.1 PLOT OF OXYGEN UPTAKE VERSUS TIME FOR EQUAL VOLUME MIXTURE OF ACTIVATED
SLUDGE AND CARBONATION BASIN EFFLUENT, SLUDGE AERATED 4.5 HRS PRIOR TO MIXING (TEST 3)
-------
U)
U)
>
-J
CD
CD
La
4
z
‘ I i
CD
x
0
200
TIME , MINUTES
FIG.22 PLOT OF OXYGEN UPTAKE VERSUS TIME FOR MIXTURE OF 2 PARTS FRESH
ACTIVATED SLUDGE AND I PART CARBONATION BASIN EFFLUENT (TEST 4)
0
50
75
00 IZ S 5O 75
-------
oxygen transfer to match the oxygen demand of slugs of high BOD, which
occur frequently in the tannery discharges, or the treatment plant should
minimize the occurrence of slugs by equalization of flow and waste quanti-
ty.
Tests 5, 6, 7
In Test Nos. 5,6 and 7 the response of activated sludge to the addition
of commercial sodium sulfide was studied. The following procedure was
used in these tests. 100 m l. of fresh activated sludge from the pilot plant
was placed in the test apparatus. The apparatus was closed and the sludge
aerated for 1.5 hours. During this initial aeration period readings were
taken of the oxygen uptake to obtain a base line. At the end of the ini-
tial period, the apparatus was opened and a few milliliters of a strong
sodium sulfide, (2.5 grams/i sulfide) adjusted to pH 8.5, were added to
the sludge. The apparatus was closed and the aeration and oxygen uptake
measurements were resumed.
In Test Nos. 5,6 and 7, sulfide additions of 2,5 and 10 ml were made re-
spectively. The sodium sulfide solution concentration was 2500 mg/l so
that based on 100 ml of sludge the concentrations used in the tests were
50, 150 and 250 mg/l of sulfide added. After sulfide addition, readings
were taken for an additional 1.5 to 17 hours. The results of Tests Nos.
5,6 and 7 are shown on Figs. 23 and 24. Fig. 23 presents the results of
the initial results and Fig. 24 shows the long term results.
From the results of the oxygen uptake measurements for Tests Nos. 5,6 and
7 shown in Fig. 23 it may be computed that the rate of oxygen uptake prior
to the addition of sulfide ranged from 0.18 mg 0 2 /mg of MLVSS/day for Test
6 up to 0.43 ing 0 2 /mg of MLVSS/day for Test 5. After the sulfide was added
the uptake rates increased sharply. The rate for Test 5 was 1.35; for Test
6 the rate was 0.95 and for Test 7 the rate was 0.82. In other words, the
addition of sulfide increased the rate of oxygen uptake 3 to 5 fold.
Furthermore, Tests Nos. 5 and 7 were carried to the point that the rate of
oxygen uptake returned to approximately that of the fresh activated sludge.
(See Fig. 24 for the end of Test No. 7). The amounts of oxygen consumed
during the time required for the uptake rates to return to re normal
levels was reasonably equivalent to the amounts needed to convert sulfide
to sulfate. These observations support the results of the tests made to
determine the fate of the sulfide in the activated sludge process.
Tests Nos. 5,6 and 7 point out the importance of preventing slugs of high
oxygen demand sulfide from entering the aeration system. The best method
of prevention is equalization which causes changes in concentration to be
gradual.
110
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FIG. 23 PLOT OF OXYGEN UPTAKE VERSUS TIME BEFORE AND AFTER ADDING
SODIUM SULFIDE TO FRESH ACTIVATED SLUDGE (TESTS 5,6 AND7)
U)
U)
CD
CD
w
I -.
a.
z
I i i
CD
0
TIME , MINUTES
-------
U)
0 )
>
-j
C,
C,
w
I-
0.
z
w
C,
0
FIG. 24 PLOT OF OXYGEN UPTAKE VERSUS TIME BEFORE AND AFTER ADDING
SODIUM SULFIDE TO FRESH ACTIVATED SLUDGE (TEST 6 AND 7)
—D
0
0.25
0.20
o.I
A
50 MG/L SULFIDE ADDED
250 MG/L SULFIDE ADDED
.-. lu
7
0.05
‘
SULFIDE
,r
ADDED
U
0
it
0 •_______
00 200 300 400 §00 600 700 800 900 1000
TIME , MINUTES
-------
Tests 8 and 9
These tests were designed to determine the effect of phosphate added to the
sludge. The procedure was the same as that used in the sulfide tests
(Tests Nos. 5,6 and 7). Phosphate was added as a solution of disodium
phosphate (Na2H P0 4 ) containing 500 mg/i of phosphorous. After establish-
ing the basic oxygen uptake rate, 1 iii]. (Test 8) and 3 ml (Test 9) of the
phosphate solution were added to the activated sludge in the apparatus.
Based on the 100 nil of sludge used this provided a phosphorous concentra-
tion of 5 mg/i in Test 8 and 15 mg/i in Test 9. The plotted results ap-
pear in Fig. 25.
From the results of Test Nos. 8 and 9, it appears that the addition of
phosphate, in the form of disodium phosphate, has little, of any, effect
on the short time oxygen uptake rates. These results indicate that al-
though the phosphate concentration in the activated sludge system is some-
what low according to generally accepted standards it is high enough to
cause the sludge to function in a satisfactory manner. This observation
is supported by the fact that no readily apparent increase in efficiency
of the activated sludge system was noted when the phosphate to the system
was supplemented for a period of several weeks. (See Figs. 6 and 7).
Short term tests such as this for phosphate may not be the best evidence
for the effects of phosphate. Additional time may be needed for the
added phosphate to be incorporated in the metabolic cycle of the bacteria.
Tests 10. 11 and 12
The influence of calcium on the rate of oxygen uptake was next studied
according to the procedure of Tests 8—12. The possibility of calcium
inhibiting oxygen uptake prompted this investigation.
One, two and three ml of a solution of calcium chloride (7500 mg/i as
Ca) were added in the established manner in Tests 10, 11 and 12, respec-
tively. Since calcium, of itself, would not create an oxygen usage by the
organisms, it was necessary to add 50 in]. of carbonation effluent to the
100 ml of activated sludge. Thus, an uptake rate would be established
and any deviation from this rate upon adding calcium would be due to the
inhibition of calcium on metabolism.
The procedure for conducting Tests Nos. 10, 11 and 12 was as follows:
1. 100 ml of fresh activated sludge were added to the
aeration apparatus.
2. 50 ml of carbonation—basin effluent were added.
3. Aeration was started and uptake measurements were
made for about 90 minutes to establish a baseline.
113
-------
0.04
0.03
>
-J
2
0
2
0.0Z
2
(U
4
I— nn
4,.
z
(U
0
0
—0.01
200
TIME MINUTES
FIG. 25 PLOT OF OXYGEN UPTAKE VERSUS TIME BEFORE AND AFTER ADDING
PHOSPHATE TO FRESH ACTiVATED SLUDGE TEST 8 AND 9)
0
50
75
I00
ITS
-------
4. A solution of calcium chloride was added and uptake
measurements continued.
The results of these tests are presented in Fig. 26.
From Fig. 26, it may be seen that the rates of oxygen uptake did not change
significantly after the addition of the calcium. Any reduction in rate
which might appear to have occurred is probably due to the gradual reduc-
tion in the initial food concentration with time.
Although calcium does not appear to have a significant short—term effect
on the activated sludge system, it is our opinion that an accumulation of
calcium carbonate in the sludge over a period of time will have a detri—
mental effect.
The detrimental effect of calcium will, in our opinion, be due to an accu-
mulation of calcium carbonate in the recirculated activated sludge increas-
ing the nonvolatile and nonactive portions of the sludge mass. At this
time it has not been determined where a balance will occur between the
added calcium and the accumulated calcium carbonate. In a full scale
treatment plant this possibility should not be overlooked when evaluating
operating characteristics.
Test 13
In this final test, the effect of chromium on the oxygen uptake was deter-
mined. As in the previous tests, carbonation effluent was added to the
sludge in the apparatus to provide food for the microorganisms. At the
start of the test readings were taken with the mixture of 50 ml carbonation
effluent and 100 ml of activated sludge. At the end of 90 minutes, 1 ml
of solution of chrome liquor (a dilution of the tannery prepared liquor)
containing 15 gm/i of chromium was added to the mixture in the apparatus.
This represented a concentration of 100 mg/l of chromium. As in previous
tests, oxygen uptake readings were taken for another 90 minutes.
The results are shown in Fig. 27.
From Fig. 27, it may be seen that no change occurred in the rate of oxygen
uptake before or after the addition of excess chromium. These observations
are in accordance with the experience of others.( 9 ) Furthermore, it should
be painted out that the chromium in the tannery liquors is completely in
the tri—valent state.
115
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0.06
0.05
0.04
0.03
0.02
0.01
0
0
U)
U )
>
-l
(D
C D
l U
4
I.-
a-
z
‘ U
0
>-
0
H
H
0 ’
25 50 75 100 25 I SO 175 200
TINE , MINUTES
9G. 26 PLOT OF OXYGEN UPTAKE VERSUS TIME BEFORE AND AFTER ADDING CALCIUM TO MIXTURE
OF 2 PARTS FRESH ACTIVATED SLUDGE AND I PART CARBONATION BASIN EFFLUENT C TEST 10, II, 12)
-------
(I )
C l ,
0
0.
IL l
I ::
200
FIGS 27 PLOT OF OXYGEN UPTAKE VERSUS TIME BEFORE AND AFTER ADDING 100 MG/L
CHROMIUM TO A MIXTURE OF 2 PARTS FRESH ACTIVATED SLUDGE AND I PART
CARBONATION BASIN EFFLUENT (TEST 13)
0.05
0.04
0 25 50 75 00 125 I SO IT S
TIME , MINUTES
-------
NUTRIENTS
The effluents from the tannery are rich in protein material, dissolved
from the animal skins. Protein matter is readily metabolized by the
organisms found in the activated sludge process. Proteins contain ade-
quate amounts of nitrogen to meet the nutritional needs of the activated
sludge organisms. However, there is some question as to the adequacy of
the phosphorous in the waste needed to meet the nutritional requirements
for this element. Table 20 presents a number of analyses of the waste in
various stages of treatment indicating the amounts of COD, nitrogen and
phosphorous present. The samples analyzed were typical of a number of
eight hour composites taken for this purpose.
From Table 20, it may be seen that the total phosphorous in the untreated
effluent varied from 4.0 to 22.4 mg/i. On passage through the primary
system the phosphorous content decreased to between 5.6 to 4.8 mg/i. The
decrease was probably due to settling out of insoluble calcium phosphate.
The primary system sludges contained about 0.12 percent phosphates, as
phosphorous.
The COD to phosphate ratio in the waste leaving the primary system varied
from 300 to 323. The amounts of phosphorous in the sanitary sewage are
not known; however it has been estimated that the concentration may be
between 4 to 9 mg/i. (12) On the basis that the sewage containing 6 mg/i
of phosphorous is mixed with the tannery waste following sedimentation and
carbonation in the ratio of 1 to 4 the resulting ratio of COD to P will be
about 75 to 1. These estimates indicate the importance of mixing sanitary
sewage with the tannery wastes in order to provide a nutritionally balanced
waste for biological treatment.
Many biologists and sanitary chemists consider that the minimum COD/P ratio
for a successful activated sludge is 100 and the minimum COD/N ratio is 25.
If one accepts the above values it is apparent that the tannery effluent
entering the activated sludge process (carbonation effluent) is deficient
in phosphorous, but adequate in nitrogen. The sanitary sewage serves to
make up the deficiency. A study of the phosphorous content of the plant
effluent indicates that the COD/P ratio decreased greatly in passage
through the plant to about 50. On the other hand, the volatile solids!
phosphorous ratio (roughly equivalent to COD/P ratio) of the sludge removed
from the secondary system was 360 (see Table 13) indicating that little, if
any, phosphorous was being extracted and retained in the sludge.
From June 18, through July 12, extra phosphate in the amount of 3.25 mg/i
P was added to the aeration basin. No significant increase in BOD removal
was noted for this period. However, the suspended solids in the secondary
effluent decreased to the lowest level observed during the pilot plant
operation. A survey of the literature on the subject indicated that low
119
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TABlE 20. ANALYSES OF TANNERY WASTEWATERS FOR
NITROGEN, PHOSPHORUS, AND COD
Primary Carbonation Plont Primary Carbonation Plant Primary Carbonation Plant
Source Untreated Effluent Effluent Effluent Untreated Effluent Effluent Effluent Untreated Effluent Effluent Effluent
Date 5/6/68 5/6/68 5/6/68 5/6/68 5/14/68 5/14/68 5/14/68 5/14/68 5/23/68 5/23/68 5/23/68 5/23/68
Total Phosphate asP, mg/I 22.4 7.2 5.20 4.8 9.6 14.0 5.6 1.2 4.0 5.6 4.8 5.2
Polyphosphate as P, mg/I 18.9 6.68 4.32 4.66 3.6 8.5 4.0 1.0 1.6 3.3 3.2 4.2
Total Nitrogen as N, mg/I 145 116 105 52 105 102 106 35.8 128 112 93.1 46.0
Ammonia as N, mg/I 14.2 16.8 16.8 12.9 18.3 16.8 17,6 25.4 7.9 10.8 10.4 3.4
Nitrates as N, mg/I 0.30 0.20 0.18 0.09 0.54 0.36 0.15 0.03 0.31 0.10 0.10 0.01
Nitrites as N, mg/I 0.003 0.003 0.003 0.13 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003
COD 3,050 1,870 1,560 118 3,060 1,930 1,810 168 1,960 2,000 1,490 215
COD/P Ratio 136 260 300 25 319 138 323 140 490 358 310 41
COD/N Ratio 21 16 15 2 29 19 17 5 15 18 16 5
Note: The “Untreated Wastes,” the “Primary Effluent” and the “Carbonbonation Effluent”
consisted of tannery wastewater. The “Plant Effluent” included municipal sewage
and tannery wastewater.
-------
COD/N and COD/P ratios in activated sludge favor the developn nt of fungi,
which do not settle well but are efficient in removal of BOD from solution.
Such was probably the cause of the results observed in the pilot plant dur-
ing periods of poor secondary sludge settleability.
On the basis of these results, it is recommended that equipment and facili-
ties be included in the full scale treatment plant to add phosphates to the
activated sludge unit as needed. The equipment should have the capacity
to add up to 15 mg/i of phosphorous. Such facilities would only be used
if needed.
121
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FLUE GAS UTILIZATION
General
The efficiency of the carbonation unit is primarily dependent upon the
rate of transfer of carbon dioxide between the flue gas and the wastes.
The amount of flue gas required to treat the waste can be computed only
with the knowledge of transfer rate of the carbon dioxide in the system.
The rate of transfer of a gas into a liquid may be expressed as:
= k a (C —C) (1)
Where
dC = rate of change of gas concentration in the liquid, C the
dt concentration of the gas dissolved in the body of the
liquid.
C = the concentration of the gas in the liquid at saturation
a = the gas—liquid interfacial area per unit volume of liquid
K 1 = the liquid—gas film coefficient
In the tests hereinafter described dC/dt, C, and a are measured. C 5 was
taken from the literature. From the above data Ki may be calculated.
Later it will be shown that when the pH of the carbonation mixture is
maintained at or above pH 9, which is a condition for which there is
essentially no dissolved carbon dioxide, C becomes zero and may be drop-
ped from the equation. The concentration of carbon dioxide in the liquid
at saturation concentration is 1495 mg/l at 25°C and 1 atmosphere pressure
for pure CO 2 over water.
Rearrangement of equation (1) gives:
1(1= a Cs (2)
dC
dt
and K 1 was determined by evaluating the other parameters.
Equipment — The tests were conducted in an 8 ft high clear plastic column
as illustrated in Fig. 28. The inside diameter of the column was 5—3/8—in.
At the bottom the column was sealed water tight using a plastic cap and
gasket arrangement while the top of the column was closed with an over-
lapping wooden cap. Ports, fitted with rubber stoppers through which tub-
ing could be passed, were located at various points on the column and in
the wooden cap.
123
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EXHAUST GAS
FIG. 28 FLUE GAS UT LIZATtON TEST APPARATUS
124
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A ring shaped piece of rubber tubing was punctured in numerous places
with a pin. This was anchored at the bottom and was connected through
the bottom inlet to the source of flue gas. The perforated tubing served
as the gas diffuser.
About half way up the column, a sampling tube was connected through one of
the ports. This allowed for sampling the liqud contents of the column.
Still further up the column, a p11 electrode was passed through a port so
that pH measurements of the liquid could be made throughout the test.
Finally a rubber tube was attached through the wooden cap to serve as an
exhaust for the wasted flue gas and to permit sampling of the exhaust gas.
An Orsat gas apparatus was employed to analyze the flue gas and the ex-
haust gas for carbon dioxide. Basically, the Orsat apparatus measures
the volume of gas before and after absorption of carbon dioxide in a
concentrated solution of potassium hydroxide. The difference in volume
represents the fraction of carbon dioxide in the gas being analyzed.
Test Procedure — A thirty liter portion of a grab sample of the tannery
waste, taken from the pilot plant influent, was placed in the column. A
smaller portion of the sample was reserved for pR and alkalinity deter-
minations. The column was capped and the flue gas was fed to the waste
in the column. A sample of the flue gas was taken at the start of carbon-
ation. Samples of the gas which had passed through the liquid were also
collected during the test. A final sample of the influent flue gas was
also taken at the end of the test.
During the period of carbonation, i.e., while the gas was bubbling through
the waste, the pH was monitored and samples of the waste were collected
for alkalinity tests. Carbonation was continued until the pH was reduced
to about 8.5.
The average carbon dioxide content of the flue gas during the test was
determined from the gas analysis. By subtracting the average carbon
dioxide of the effluent gas from that of the influent, the amount of
carbon dioxide transferred during the time of carbonation may be calcu-
lated. Thus, dC/dt is determined.
In order to determine (a) the interfacial area, it is necessary to measure
the average bubble diameter and the number of bubbles present at any time
in the column. Several pictures were taken of the bubbles rising in the
column and these pictures were enlarged to actual size. From the pictures,
it was possible to measure bubble diameters and arrive at an average dia—
meter. Knowing the diameter of the bubble, both the surface area and vol—
ume of the average bubble could be calculated. The number of bubbles was
determined as follows.
The height of a column of a known volume (30 liters) of liquid was measur-
ed. The height of the liquid column was then remeasured under expanded
conditions with gas bubbling through it. The liquid height was measured
125
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at various flow rates and was noted. The volume difference between the
expanded and unexpanded column was equal to the volume of the gas bub-
bles in the liquid. Dividing this volume by the volume of the average
bubble yielded the number of bubbles present.
Results — The test data is shown in Table 21. The diameter of the aver-
age bubble was measured to be 0.45 centimeters. The volume and surface
area of an average bubble, therefore, were 0.0477 cm 3 and 0.636 cm 2 re-
spectively. Values for the rate of carbon dioxide transfer, interfacial
area, and the liquid film coefficient are shown in Table 21.
Discussion of the Results
From Table 21 it may be seen that the efficiency of absorption of carbon
dioxide from flue gas by the waste varied from 42 percent to 100 percent
of the carbon dioxide present in the flue gas. The efficiency of the
absorption was related in a general way to the pH of the waste, i.e., the
higher the pH the higher the efficiency of absorption.
For design purposes, an efficiency of absorption of 50 percent is recom-
mended. This recommendation is based on using a carbonation basin at
least 8 ft deep as compared with 6 ft 7—in depth in the test column.
The time required to reduce the pH to about 9.5 was related to the total
alkalinity and varied from about 2 minutes for an alkalinity of 900 mg/i
to nxre than 20 minutes for an alkalinity of 6030 mg/i. The average
alkalinity for the tannery effluent from the 1968 survey (Table 4) was
about 2800 mg/i with hourly fluctuations between 0 and about 7500 mg/i.
Equalization will be necessary and will iron out the fluctuations to an
estimated range of between 1000 mg/i to 3500 mg/i on a slowly changing
basis. Hence, a 20 minute contact period will be sufficient to permit
adequate pH adjustment prior to secondary treatment.
Table 22 presents the computed rates of carbon dioxide transfer and the
liquid film coefficients. The computed liquid film coefficients ranged
from about 24 cm/hr to about 48 cm/hr. These values fail within the
range of published data(l 4 ) indicating that no particular characteristic
of the waste adversely effects the transfer of carbon dioxide from the
flue gas to the waste.
126
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TABLE 21. TEST DATA - FLUE GAS UTILIZATION TESTS
Flow % C02 Carbonation Alkalinity % C02 % Utilization
Rate in Time pH of to pH 8.3 in Effluent of C02
I/mm Flue Gas ( mm) Waste ( mg/I as CaCO3 Gas in Flue Gas
5 11.4 0 10.8 525
1.0 10.7 4.4 61
2.0 10.0
2.5 9.7 360
3.0 6.0 47
3.5 9.3 250
4.5 8.9 130 3.4 70
5 11.2 0 12.2 6,030
1.0 0 100
5.0 12.0 5,520 0 100
15 1L8 3,700 0 100
20 12.0 3,030
10 11.4 0 11.4 660
1.0 11.2
1.5 10.5 5.4 52
2.0 300
3.0 9.7
3.5 9.0 135 6.6 42
11.4 0 11.5 900
1.5 3.0 73
2 11.2 560
3.5 9.6 225 4.6 60
25 11.4 0 11.2 900
0.5 5.8 49
1.0 10.3 620
2.0 9.45 475 4.2 63
2.5 9.1 325 4.0 65
127
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TABLE 22. RESULTS OF FLUE GAS UTILIZATION TESTS
Rate of Surface Area
C02 Transfer of Bubbles/ K
Gas Flow dC/dt Unit Volume L
( I/m m) mg/l/hr) cm1 ) ______
5 1,200 0.76 24.4
10 1,640 1.06 34.9
15 3,450 1.35 41.2
25 5,100 1.92 48.2
128
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CHLORINATION STUDIES
General
In order to prevent the discharge of pathogenic organisms via the effluent
from a waste treatment plant, the effluent of the treatment plant is chlo-
rinated. Chlorine will kill pathogenic organisms in waste providing that
the chlorine dosage and the period of chlorine contact is sufficient. The
dosage and contact period are interrelated. Greater dosages of chlorine
require lesser times of contact to effect a given percentage kill of organ-
isms; with longer contact time, lesser amounts of chlorine are required.
Rowever, since the impurities in the waste will react with chlorine more
rapidly than the chlorine will kill pathogenic organisms sufficient chlorine
must always be added to satisfy this chlorine demand in addition to that
necessary for disinfection.
Grab samples of the pilot plant effluent were collected from time to time
to measure the chlorine demand of the effluent. The test procedures and
results follow:
Procedure — Sodium hypochlorite solution was added in varying amounts to
the sample of waste under test. The treated waste was set aside in the
dark for a period of time after which the chlorine residual in the waste
was measured. In some cases, the number of coliforni organisms present in
the wastes before chlorination and after the contact period were enuiner—
ated. The extent of reduction in the numbers of these organisms was
used as a measure of the effectiveness of chlorination. The analytical
procedures used for these tests are cited below:
Chlorine — standardization of the chlorine solution (sodit’n
hypochioride) and the analysis of the treated wastes for the
chlorine residual were performed by the iodimetric method as
described in “Standard Methods for the Examination of Water
and Wastewater,” using phenylarsene oxide solution and detect-
ing the end point with starch solutions.
Coliform organisms — Enumeration of coliform organisms was
performed according to Standard Methods using the Milhipore
filter techniques.
Results — Figs. 29 and 30 show the relationship between chlorine dosage
and chlorine residuals for tests on three different effluent samples.
Table 23 shows the range of coliform populations found in the tests of
the pilot plant effluent. From Table 23 it may be seen that the number
of coliforms in the samples ranged from 1,200,000 to 90,000’ per 100 ml.
The effectiveness of the chlorine was tested with chlorine doses ranging
from 5 to 15 mg/i.
129
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50
10 20 30 40 50 60
CHLORINE DOSAGE - MG/L
FIG. 29 CHLORINATION OF PILOT PLANT EFFLUENT
-J
I-
a
z
0
a
C l ,
0
In
w
I- .
I I-
4
-j
4
Cl,
L&J
U i
z
9
C)
Q
40
30
20
I0
0
0
-------
30
C.)
4
I —
z
0
I -)
U)
3
0
r
20
I0
FIG.30 CHLORINATION
OF PILOT PLANT EFFLUENT
0
0 10 20 30 40
CHLORINE DOSAGE - MG/L
0 10 20 30
CFtLORINE DOSAGE- MGIL
40
131
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TABLE 23. CQLIFORM ANALYSES OF PILOT PLANT EFFLUENT
Date 12 3 4 5
Chlorine dose, mg/I 0 5 ‘tO 10 15
Contact time, mm 0 3 3 30 30
(Numbers of coliform bacteria per 100 ml of plant effluent)
June 21, 1968 152,000
July 2, 1,200,000 8,240 1,100
July 9, 312,000 320 35
July Lj, 90,000 36(1)
(1) 8.2 mg/I chlotine residual after 30 minutes contact time,
residual after 3 hrs, 1.8 mg/I.
132
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In each test, the number of coliforms was reduced by more than 99.8 per-
cent. In the test on July 12, 5 mg/i of chlorine reduced the number of
coliforms present from 1,200,000 to 8,240 with a 3 minute contact time.
On the same sample, a 10 mg/i dosage of chlorine reduced the coliform
count to 1,100 with a 3 minute contact time. On July 9, a sample con-
taining 312,000 coliform bacteria per 100 ml was dosed with 10 mg/i of
chlorine for 30 minutes and the coliforin count was reduced to 320 per
100 ml. The same sample with a 15 mg/i dose of chlorine and a 30 minute
contact period resulted in a reduction of the coliform count to 35 per
100 ml. A similar result was observed on July 11, in which test 15 mg/i
dose of chlorine reduced the coliform count to 36 per 100 in]. in 39 minutes.
In this test, the chlorine residual was 8.2 mg/i after 30 minutes and
1.8 mg/i after three hours.
These tests indicate in general, that the effluent from the secondary
sedimentation basin has a 30 minute chlorine demand of about 10 mg/i. The
three hour chlorine demand increases slightly to between 13 and 16 mg/i.
Furthermore, it appears that a 15 mg/i chlorine dose and a 30 minute con-
tact period will result in a satisfactory reduction in the coliform con-
centration. The effluent will be suitable for discharge to the Little
Androscoggin River. The discharge of an effluent containing less than
100 coliform bacteria per iOO ml should pose no serious health hazard
downstream from the point of discharge.
133
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SULFIDE TOXICITY
General
A major constituent of the tannery effluent is sulfide. Suifides in water
are known to be toxic to fish in the 1—10 mg/i range. The study described
below was made to determine the toxicity of sulfide to the activated
sludge.
Procedure — A solution of commercial grade sodium sulfide was prepared and
fed to the aeration basin of the pilot plant. On April 2, 1968, 400 mg/i
of sulfide was added for a period of two hours. During the periods April 2
to 3, and April 4 to 5, 5, 50 and 100 mg/i respectively of sulfide were
added for 24—hour periods to the aeration basin. The dosages were based
on the effluent carbonation basin flow of 2 gpm.
In addition to the tests described above which were conducted in the pilot
plant, laboratory tests were conducted which yielded information concerning
sulfide toxicity. These laboratory tests are described in the sections
Sulfide Oxidation and Oxygen Uptake Studies — tests 5, 6 and 7.
The results of these various investigations are discussed below.
Results — The pilot plant tests showed little effect of the sulfide addi-
tions on the activated sludge. Addition of 400 mg/i of sulfide did cause
a problem of excessive foaming in the aerator. However, after the sulfide
feed was stopped and foaming had subsided, the activated sludge appeared
to have suffered no damage. The ability of the activated sludge to cope
with high sulfide dosages was indicated also in the laboratory tests.
During the oxygen uptake studies, it was shown that addition of up to
250 mg/i of sulfide caused a sharp increase in the rate of oxygen uptake
(see Figs. 23 and 24). This indicates that the sulfide was easily uti-
lized by the organisms of the activated sludge. Although the mechanisms
by which the sulfide was utilized were not determined the sulfide oxida-
tion tests showed that the micro—organisms were essential to the rapid
conversion of sulfide to sulfate.
The overall average sulfide concentration determined in the 48—hour raw
waste survey of April 9 to 11, was computed to be about 53 mg/i. The
pilot plant tests showed that at best twice this concentration fed over
a 24—hour period caused no problem. A dosage of 5 times the average con-
centration was easily handled by the organisms as evidenced by the oxygen
uptake rate.
135
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CHROHE TOXICITY
General
Chromium, one of the heavy metals, will have a toxic effect on living
organisms if it is absorbed in sufficient quantity. Since the activated
sludge process is dependent upon the living organisms in the sludge for
breakdown of the waste, and since the wastewater contains chromium, it
was necessary to determine if the concentration of chromium in the waste
might become enough to retard the biological action or kill the sludge
organisms.
Procedure — A solution of basic chrome sulfate was added directly to the
aeration basin continuously for four days. The rate of addition was held
constant throughout each full day and was increased each day. Thus, on
July 9, 10, 11, and 12 chromium was added at the rate of 40, 80, 120 and
160 mg/i respectively, based on the flow of 2 gpm of the carbonation basin
effluent. These concentrations of chromium were in addition to the chro-
mium derived from the tannery waste and already present in the carbonation
basin effluent.
Results — There was rio apparent detrimental effect on the action of the
activated sludge due to the addition of chrome in the concentration used.
The suspended and volatile suspended solids concentrations of the mixed
liquor remained relatively constant. BOD removal in the aeration basin
was good. No excess suspended solids were found to appear in the second-
ary settling basin effluent. Variations in each of these would have been
expected if the chromium had reached toxic levels.
The effect of chromium on the rate of oxygen uptake was studied in Test 13
of the section Oxygen Uptake Tests. The plot (Fig. 27) of the results of
this test shows no reduction in the rate of oxygen uptake with the addi-
tion of 100 mg/i of chromium.
Discussion — It has been demonstrated that the chromium concentration in
the activated sludge basin influent can be maintained at less than 100
mg/i by n ans of primary settling. The toxicity level of chromium to the
activated sludge appears to be considerably above this concentration.
Therefore, chromium in the concentrations normally occurring in the tan-
nery effluent should have no effect on the action of the activated sludge
system.
137
-------
ACKNOWLEDGEMENTS
The investigation and studies reported herein were jointly carried out by
the A.C. Lawrence Leather Company and Camp, Dresser & McKee, Consulting
Engineers. Mr. Joseph Bassett was the Project Director; Dr. Robert H.
Culver was Assistant Project Director; Mr. John C. Thompson was Project
Engineer and Mr. Norton G. True was Resident Engineer.
The laboratory staff of the A.C. Lawrence Leather Company made the chro-
mium analyses and the maintenance staff at the South Paris tannery per-
formed the nonroutine maintenance, made necessary equipment installations,
changes and repairs. The project was given full cooperation by the manage-
ment and the research and development sections of the Company.
The advice and assistance of Mr. N.H. Battles, Director of Research for
the Company, and Project Officer, Dr. Thomas A. Murphy of the Federal
Water Pollution Control Administration, are hereby acknowledged.
139
-------
BIBLIOGRAPHY
1. Camp, Dresser & McKee, “Report on Pilot Plant Investigation
of Wastewater Treatment at South Paris, Maine,” 1967.
2. Rosenthal, B.L., “Treatment of Tannery Wastes by Activated
Sludge,” Sanitalk 6, 7, (1957).
3. Vrooman & Ehie, “Combined Tannery and Sewage Sludge Digestion,”
Sewage and Industrial Wastes 22, 94, (1950).
4. Rosenthal, B.L., “Treatment of Tannery Waste—Sewage Mixture
on Trickling Filters,” Sanitalk 5, 21, (1957).
5. Hasetime, T.R., “Tannery Wastes Treatment with Sewage at
Williamsport, Pennsylvania,” Sewage and Industrial Wastes,
30, 65, (1958).
6. Wims, F.J., “Treatment of Chrome Tannery Wastes for Acceptance
by an Activated Sludge Plant,” Proc. 18th Industrial Waste
Conference, Purdue University Engineering Extension Service
115, 534, (1963).
7. Camp, Dresser & McKee, “Report on Improvements to the Sewage
Treatment Plant at Ayer, Massachusetts,” May 22, 1957.
8. McKee, J.E. and Wolf, H.W., “Water Quality Criteria,”
California State Water Quality Control Board (1963).
9. “Interaction of Heavy Metals and Biological Sewage Treatment
Processes,” U.S. Department of Health, Education and Welfare,
May, 1965, Public Health Service Publication No. 999—WP—22.
10. Heukelekiam, H. and Dondero, N.C., “Principals and Applications
in Aquatic Microbiology,” Page 405, John Wiley & Sons, Inc.,
(1964).
11. McLaughlin and Theis, “The Chemistry of Leather Manufacture,”
Page 193, A.C.S. Monograph 101, Rheinhold Publishing Corporation,
New York, N.Y. (1945).
12. Sawyer, C.N., “Chemistry for Sanitary Engineers,” Page 322,
McGraw—Hill Book Company, Inc., (1960).
13. Perry, John H., Chemica1 Engineers’ Handbook”, 4th Edition, P. 14—37,
McGraw—Hill Book Company (1963).
141
-------
APPENDIX
143
-------
8
1
\(
E
m
0
C)
0
C)
-S.
E
V I
200
2000
TIME OF DAY
FIG. A-i RAW WASTE SURVEY AC. LAWRENCE LEATHER COMPANY
SOUTH PARIS MAINE APRIL9IO, 1968
J 1 7
2400 0400 0800
-------
a-
AA
/ \ ,/
‘4
— I
H
Ln
ALKALINITY O 3
T Th i- 1
U)
4
E
U)
4
1600
2000
TIME OF DAY
FIG. A-2 RAW WASTE SURVEY A.C.LAWRENCE LEATHER COMPANY
SOUTH PARIS, MAINE APRIL 10 11,1968
a400
0400
0800
-------
TIME OF DAY
FIG. A-3 RAW WASTE SURVEY A.C.LAWRENCE LEATHER COMPANY
SOUTH PARIS,MAINE APRIL 9-10,1968
FLOW
2,
TOTAL SOLIDS
E
4,000
‘2,OOO
0
0 ’
E
2400
0800
-------
600
FIG. 4-4 RAW WASTE SURVEY A.C. LAWRENCE LEATHER COMPANY
SOUTH PARIS, MAI NE APRIL tO- 11,1968
1200
a-
0 ’
E
—4
2,000
01
E
0’
E
VOLATILE SUSI
ENDEI
200
2000
TIME OF DAY
2400 0400 0800
-------
U-
I ,
FLOW
I
0
0
LLrLfl
E
C-,
(I)
4
CHROMIUM
E
1800
20O P600 2000
TIME OF DAY
FIG. A-5 RAW WASTE SURVEY AC. LAWRENCE
SOUTH PARIS,MAINE APRIL 9-
2400
0400
LEATHER COMPANY
10,1968
0800
-------
a-
2
E
0
0
4
U
In
1 ]
25
E
0800
600 2000 2400 0400
TIME OF DAY
FIG. A-6 RAW WASTE SURVEY AC. LAWRENCE LEATHER COMPANY
SOUTH PARISMAINE APRIL 10-11,1968
0800
-------
SOLIDS, ‘ - I
oI co1v ED
T O M7 J 7 Oo & ‘I I
45
I,5’ 4 962 5,920 058 3
1,512 688 0988 7,320 4
I,2.,6 1,514 3,2,0 390 22
1,116 68 3,. 34 498 Ill
0
,L)
42
1,350 II 6 543
1,310 II 6 565
1,380 11,6 695
740 II 4 515
7,680 11,4 625
TABLE A-I PBIMARY SETTLING BASIN OPER,A liON AND ANALYSIS OF COMPOSITE SAMPLES
AP8II ,. l ’ 68
INF I.UE NT
‘ FLOWS, 99 ’O
‘0 6:
— .8
24 24 I 75 6 25 I I 8
25 24 3 l7 625 31 9
26 24 7’, 625 119
28
29 14 5 125 625 116
30 74 5 75 6 2 II 5
TOTAL
2
830
825 17,614 2,020
930 7,000 2.
1365 6,508 2,004
8’S 4,710 076
EFFLUENT
2,600
2,100
I 590
I, 30
810
SLUDGE
SOLIDS, o,g I
--
,
0) — —
0 -
8 & —
E 0 - -
- j - ! !
3 ,2
TOT4L S(JSPCE -40tD
DESSOLVEE)
Toial Vol To ol Vol
Toiol Vol
5,066 2,254 604 390
4,660 1,030 150 14.4
4,462 864
4,210 886
6
2
B
900
1,390
640
820
860
930
230
170
330
71,912
72,694
37,516
36,428
5,656 978 502 122
4,430 408 4 2 0
5,154 856
3,918 452
15
4
690
620
1,270
1,270
120
180
50,048
SB,738
21,P34
24,294
-------
TABLE 6-2 PRIMARY SETtLING BASIN OPERATION ANT) ANAl Os lo OP COMPOSITE SAMPLES
1 11 31 NT 0 3)004
_ _ _ _ _ _ - 0 T. ,
2, 0 ‘ 7 1 —f L I
1 (2100 _______ _ I
TOTAL 921 59 1N040 515,041l,’ “‘ 1 ’’ 3 )’
f 42 riT VICTT T I H 0L
I 24 3 29 625 7 II 6 390 5,286 094 33 1) 294 4. ,, 0’ . 2 4 4 ‘99’ 244 69,1211 5’21’l
2 24 5 I 25 625 )j 7 680 1,432 262 26 354 ‘I’” 0 ” I ) 1 , 7 9 ” “1 I I’ ) 53, dO 1,
3 24 5 29 0 65 3,394 3,020 36 64 4,429 9,1, 949 197 60 . 124 II’ ,.
24 5 I 25 61) 64 5,456 1,496 9 )4 298 5, 112 1.188 I 11 3,640 1,184 88 47 4,828 .204 44 344 4,352 840 ‘ ‘ I 74 4 4) 4 0 d2 8 19,221 /80 49 404
24 5 I 2 610 89 320 8 00 26 504 4 Ml 0 470 140 I I 8 6 40 I 00 4)1 29 0 I 037 0 II 44/7 64/1
4 24 0 I 20 625 No o,ote, 2,002 1,500 1,4% 3)2 5,594 094 1,380 881 09 479 4,032 1,012 684 340 5,340 452 1,054 3,040 49 266 120 64,396 29, 36 464 . 4 I, 115
4 24 5 I 25 620 66 No rncI’ 2,8)8 544 392 32 2,424 334 600 389 4431 No “Ne ’ 3,176 506 292 1)0 284,4 376 474 ‘ 1 4 4 84 3/, 40 24, 24
30 24 5 I 70 820 95 120 - 4,270 398 1,046 544 3,229 802 2.0 1,980 978 I39 II 9 335 j,790 1,244 646 244 5,144 3,305 04 007 907 70 67,004 73,12/
I I /0
H
13 24 8 2 10 66 II 7 630 0,310 1,313 688 344 4,622 966 33 070 990 I I 520 ),372 1,200 904 374 4,898 826 4 7 640 416 50 80,666 07, .44
14 24 8 2 10 68 I I 0 465 6,7% 1,300 736 392 6,082 908 44 1,080 846 94 08 I) 9 623 4,604 964 450 00 4,354 864 07 605 929 82 I 8 192 93,140 23,1/ 12,100 106 42)
IS 24 8 2 10 66 II 9 470 8.0 I I 4 045 0 0 120
16 24 8 2 10 I I 9 400 2,748 1,336 992 046 6,704 290 II 0 900 776 107 36.0 120 685 8,848 1,164 4 )8 232 8,230 °32 30 9 15 1,010 79 I l ‘ 90 65,179 3 1 1,44 1 11,2161 142 .‘53
1/ 24 8 2 30 121 1,760 6,324 1,604 1,180 034 0,144 1,150 140 1,380 2,334 7 I 1,000 3,966 1,444 467 304 4,904 1,179 25 1,100 1,450 “4 57,3/0 21 ,7/’
48 9)1
‘9
20 24 12 3 IS 63 11.6 483 5,150 1,142 6)2 366 4,938 776 4 0 964 750 11,8 800 6,232 1,412 9)0 478 0,434 166 2 ‘ 1 3, “0 1,160 40 40,120 24, 314
2) 24 1/ 3 IS 62 II 3 450 8,8)6 1,470 360 0 8,256 1,482 64 1,070 770 47 33 0 II 6 78011,134 2,422 1,860 1,242 3.244 1,380 36 I,”'’. 1 ,1”’ 73 /74 60 41,0171 27 ./42 15,4114 113 3 ” ?
22 14 I l 3 IS 70 I I 5 6)3 8,324 2,236 1,704 1,174 9,070 1,062 39 5 ‘ 1.0 1,150 I I / 705 5,862 1,394 916 326 .390 .266 3 ‘ 1, 16’ 120 /7, 194 72,664
23 24 I I I, 63 II 8 808 7,968 1,438 730 364 7,178 1,094 6.5 ‘, ,. 1,140 134 II 9 II I. 760 7,772 1,2/7 900 442 o1,’’ldl 4’’ 1,175 /0 I/ S 90 303,467 .0,614 ,‘5,9 1 1l 14’) 3,1)94
24 74 I l 3 0 II 0 780 3,892 1,392 834 600 3,038 702 73 SI , 332 II 564 4,900 946 488 194 4.1 ‘ 1 1/ I 4 )15 53 /4,9,4 31,161’
25 95
26
2/ 24 16 4 ,0 2 , 12.4 836 4,93 1,149 898 488 4,036 758 8 0 1,100 1,160 7, 1 9.9 11.8 423 5,0)2 1,112 304 234 ,,429 US 2 ‘ 694 9)7 I I I’ 6 115 63,244 ,,,IIl, ‘ 13 1. 040
29 14 16 4 20 9’ II 4 490 8,97 1,976 1,999 782 9,544 704 10.0 870 792 11.7 760 6,654 3,394 596 306 8,000 3,386 1 ‘ 85,525’ Id 1.0, 996 .0, . 52’
23 ‘4 36 4 20 40 11.2 470 4,006 1,136 1,092 642 3,614 534 73.0 630 723 90 34 3 17,7 675 4,752 1,038 616 3. ’I, 4,1 1’ 5 06 6 ‘ 5)4 569 5 I , 2 7 )’ 03, 140 40,33” .4 . 430 250 I , . :’
11.4 420 3,434 764 594 274 7,440 494 70 570 684 II 4 515 4,008 1,119 592 996 0,°76 550 3 ‘ 76, 1,010 II ’’ ‘ ( ‘ .1321’ 34,137
MAY, ‘968
0 , ‘- 0
—. ‘02 ,._±, 9, ! 3 i.J 5’ ! 1__ ‘70 l SOLIDS, ng I 9
0 TOTAL S O PINOEL 015 04794 —
‘c £ 2f ,52 0 2T U ’ 70o I ’ l& 9 ’ ° 0 0M ’ 1 ” ’ 0
II 3 410 ‘.022 1,274 970 630 4,344 844 8 5 1,789
32 0 3,293 9 ‘54 1,438 1,914 497 3,290 761 8 3 1,460 7,1)47
7, ,‘9’ 2,038 2,714 049 .406 1,042 1,380 2,290
30
01 24 I A 1 20
No N, II ) lolioe booed 04
-------
TABLE A-3. PRIMARY SETTLING BASIN OPERATION AND ANALYSES OF COMPOSITE SAMPLES
JUNE
INFLUENT EFFLUENT SLUDGE
‘4,-
0_C
4-
> ,c
&
C
0 FLOWS gpm
O . ._
,,,0
h .
a, E
a)
‘.
4-
- .O
0 a)
- I-
a.
2! ,C ?
‘E
==
V)
00)
E
a
-o Z
I
v, E a.
zz
J j
0
0..
a) ’
._
a
v v
c: —
00)
E
a,
o
——
c.n
-
0
0 )
a) -
EC
a)
-—
,0)
E
1
Water
20
2
Water
66
3
24
4.5 1.5
6.0
67
11.0
310
10.0
855
11.1
330
1.5
615
65
4
24
4.5 1.5
6.0
72
11.6
730
11.5
1,225
11.4
450
1.4
795
111
5
24
4.5 0.75
5.25
68
11.7
730
18.0
1,150
11.6
610
2.0
1,100
120
6
24
4.5 0.75
5.25
67
11.5
945
14.0
1,125
10.9
415
1.0
975
112
7
24
4.5 1.5
6.0
64
11.3
655
17.0
1,440
11.4
675
3.0
1,410
166
8
Water
9
Water
66
.
10
11
24
24
4.5 1.5
4.5 0.75
6.0
5.25
70
67
10.0
11.3
180
635
8.0
12.0
1,170
1,260
11.1
10.9
325
285
5.0
4.0
1,030
1,050
150
170
12
24
4.5 1.0
5.5
70
12.2
1,440
11.0
1,500
12.0
830
1.0
970
160
13
24
4.5 0.75
5.25
65
12.2
1,020
5.0
995
12.0
580
0.5
780
172
14
24
4.5 1.0
5.5
11.8
920
18.0
1,000
11.8
770
0.2
720
136
15
Water
16
Water
66
17
24
4.5 1.0
5.5
66
11.4
490
5.2
64
11.6
630
0.9
100
110
18
24
4.5 1.0
5.5
70
11.1
370
5.8
49
11.5
620
0.3
61
137
19
24
4.5 1.0
5.5
62
11.6
800
12.0
46
11.7
780
1.5
46
169
20
24
4.5 0.75
5.25
65
11.4
520
5.0
70
11.4
380
0.6
52
118
21
24
4.5 1.0
5.5
10.8
270
11.0
39
11.3
490
0.7
39
150
22
Water
23
Water
24
24
4.5 1.5
6.0
11.4
735
10.0
11.1
375
1.2
108
25
24
4.5 1.5
6.0
69
10.8
275
15,0
11.0
300
2.5
136
26
24
4.5 1.0
5.5
68
11.2
420
10.0
11.2
435
0.8
150
27
24
4.5 0.75
5.25
66
11.7
730
8.0
11.3
315
0.5
141
28
24
4.5 1.0
5.5
64
11.4
640
20.0
11.5
750
1.3
185
29
Water
30
Water
86
68
102
99
82
-------
TABLE A-4. PRIMARY SETTLING BASIN OPERATION AND ANALYSES OF COMPOSITE SAMPLES
JULY, 1968
INFLUENT EFFLUENT
________________________________________________________________________ E
a) zz
C
>°
0 FLOWS gpm —
0 0 ..D —0
0 0-
a) a) —
>SC Q)
00 0 D CD 0 E 0 Q
4 -
—
U) (I ) U) U) U) 0
1 24 4.5 1.5 6.0 11.6 950 28.0 11.4 470 0.6 79
2 24 4.5 1.5 6.0 80 11.3 450 7.4 11.3 450 0.7 141
3 24 4.5 1.0 5.5 75 11.4 415 5.0 11.5 595 2.5 120
4
5 24 4.5 1.0 5.5 73 11.7 715 6.0 11.5 660 0.5 90
6
7
8 24 4.5 1.0 5.5 80
9 24 4.5 1.0 5.5 11.4 820 15.0 11.4 675 2.5 114
10 24 4.5 1.0 5.5 68 11.6 1,170 7.5 11.4 605 0.3 77
11 24 4.5 1.0 5.5 11.5 1,340 14.0 11.3 665 0.7 150
12 12 4.5 1.0 5.5 50
-------
TABLE A-S CARBONATION BASIN OPERATION AND ANALYSES
oc COMPOSITE SAMPLES
JANUARY, 968
62 (11,704 9,554
40 (
EFFLUENT
SOLIDS, 9/l
TOTAL SUSPENDED DISSOLVED 8 - - 8 - 6
Total Vol. Total Vol. Total Vol. -
INFLUENT
-
0 SOLIDS /l 1 ‘
- - —.
o 1OTAL SUSPENDED DISSOLVED — 1
I - O
— - 2 Total Vol Total Vol. Total Vol. , ‘ 1
5 B 3 2 5 8.7 53 240 9.6 290
6 0
7 2 5 3 2 5
8 0
9 5 3 2 5
10 0
II 8 3 2 5
12 0.5 4 2 6
13 0
Ji 14 0
15 6 6 2 8
16 2.5 6 2 8
17 0
18 0
19 0
20 2 6 2 8
21 0
22 14.5 4 .75 5.75 9.5 255 9,642 928 2,190 1,040 7,452 888 30 1,105 0.7 590
23 19 4 1.75 5.75 11.3 455 9,360 2,872 1,076 1290 8,284 1,582 30 10.2 265
24 7 4 2.3 6.3 10.8 630 240 11.8 895
25 12.5 4 2.3 6.3
26 2 4 1.75 5.75 9.4 285 370 8.8 90
27 0
28 0
29 4.5 9.4 395 420
29 7 4 1.75 5.75
30 13 4 1.75 5.75 11.3 9014 1,874 2,550 1,250 6,464 624 215 1,200 l? 840
31 73 4 1.75 5.75 II 7 1,220 30 1,050 11.4 1,075
140 8
10,024 1,846 2,076 880 7,948 966 30 820 32 37,252 16,340
8,028 1,206 10 53 45,112 19,952
12 16
ID
70
40
280 42
7,662 1,640 2,122 1,034 5,540 606 85 900 182 43,985 21,098
0.5 650 144
-------
I 15 4
2 2 4
2 7 4
5 2 4
, 18 4
6 7 4
7 16 4
B 13 4
9 7 4
9 12 4
10 5.5 4
2 5 4
12 II 4
13 14 4
13 7 4
14 2 4
LI ’ 4 2 4
15 24 4
6 5 4
16 18 4
17 I 4
(8 4 4
9 IS 4
19 9 4
20 (6 4
20 8 4
21 11 4
21 (3 8
22 24 2
23 75 2
23 2
26 15 3
27 16 4
27 5 4
28 9 8
28 15 B
29 (4
9.6 220
1,305 1.8 385
28 828 9.8 180
2.5 9.4 100
559
8.9 80
10.6 350
38
16
27
68
98
64
40
148
2 132
(1.5 885 60
56
837 92 68,848 33,592
36
164
(Trace 104
136
602 84 (69,812 35,304
189 (
136
8
46
432
256 (39,172 18,512
8 (
3 24 (43,800 21,500
634
80 34,108 23,964
TABLE A-6 CARBONATION BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
FEBRUARY, (968
(NI ’ LUE NT
- > , ‘ 1
0 ‘ ‘ ‘ °‘ .5 SOLIDS, ‘i I SOLIDS, rag/I -o
j TOTAL SUSPENDED DISSOLVED TOTAL SUSPENDED DISSOLVED .i ’ 8
O £ 2 Total Vol. Tot I Vol Total Vol. ToIal Vol. ToTal Vol. ToTal Vol. 2 ,
£ F FL E N T
SLUDGE
I . 75
1 . 75
2.0
2.3
75
I 75
75
1.4
0
1.0
0
0
1.0
0
1.0
0
1.0
0
0
1.0
I .0
1.0
0
I .0
0
I .0
0
2 .L
0
0
1 .0
1 .6
(.0
0
0
iS
8,772 2046 2,370 1,220 6,402 826 00 1,286 94 43,250 22,644
(50 132
30
l ,852 3,280 3,032 2,132 7,820 1,148 240 670 — 37,272 18,700
20
960 192
2 90
56
5,4
(0
(0
5.75 9.8 215 8,160 1,840 2,372 1,260 5,788 580 210 .680 (0.8 520
5.75 (11.0 450 20 (0.9 435
6.0
6.3 (10.2 590 10,178 2,796 2,634 1,304 7,544 1,492 280 502 0.8 495
5.75 1
5.75 1,020
5.75 11.1 465 80 11.2 410
5.4
4.0
5.0
4
4 11,0 440 Trace 82
5 1
4 (8.7 55
4 11.0 695 25 9.4 180
4
4 (12.1 875
5 1
5 10.7 465 7,356 1,120
4 (10.4 685
5 (
(10.6 3,628 1,100
10
2 11.5 1,120
2 (11.4 1,410
3 1
4.6 9.1 185
5 0 (10.6 420 6,964 (.436 1,280 360 5,684 1,076
4
8 (11.2 795 6,160 1,628 1,160 592 5,000 1,036 IS
10 1
10 (0,9 510 6,072 1,216 920 572 5,152 644
7,748 944
(6,112 1,172
10.0 395
0.5 320 (6,152 628 54.4 16 5,608 612
11 I 605 (7,568 1408 580 312 6,988 1,096
(0.6 375 6,006 920 584 248 5,512 672
-------
16818 A-7 CA8SONATION SASIN OPERATION AND ANA005RO
Or COMPOSITE SAMPLES
6440091, (98$
. I
I 6 9 2 10
2 24 WoM. 2
2 74 Wo0 ’ ‘2
4 Ij 8 3 lb
5 74 I I ‘2 0
o 14 8 2 I I )
2 24 6 7 IS 64
2 24 4 I ‘, 72
7 14 Wool.
II 24 4 I 3 70
2 24 Il ‘I IS 66
Ii 24 8 1 (0 67
4 24 7 I /5 6 25 68
I, 24 2.5 75 420
(6 24 Wo .’
I? 2 70 20
(8 24 (2 3 (5 66
9 24 (2 3 5 88
20 24 Il 3 I ? 66
21 24 05 IS 7 66
11 24 55 5 7 72
23 24 Wool.. 2
24 24 W640, 2
25 10 WoO., 2
, 5 (4 0 I 6
16 84 5 I 6 70
2; 24 4 I
16 ‘14 4 I
2? 24 4 I , 66
20 24 Wool. ’ ‘2
31 24 Wool., /
II 0 470 7948 :724 7077 940 5,876 794
II 3 440 22
II 5) 340 (4
109 390 (8
IC 9 420 3,852 1256 1.184 740 2,568 316 65
II 9 1,130 7,368 1,776 1,404 816 5,964 920 8 1,500
158 310 5,440 1,164 880 468 4,560 796 8 1,110
II I 70? ,.864 2,316 1,720 1,156 4,528 1,236 (2 1,200
I I 6 620 5,716 1,476 4,416 1,388 1,380 88 (2 845
II 2 355 70
II I 430 9,3
115 485 10 1,470
II 3 565 / 1,380
120 930 5 .‘ “
(.6 490 5,056 1,436 .888 700 3,968 736 (4 1,5 7 K, 595
15,304 (.384 I, 60 928 4,644 436 /42
(09 4351 (2
II 6 /10 “, 30o 892 444 280 3,860 6(2 8 8(0 1,030
II 6 610 5,472 (.270 1,036 660 4,386 6(0 8 783 1,170 (83
II ‘2 470 0,88 1,688 1,240 804 4,649 884 8 1,770 880 (33
II 7 930 6,632 1,779 1,492 806 5,390 964 7 1,810 1,990 218 80
I I I 360 6.490 7,080 3(6 229 7,924 836
95(00 7
II 7 441, 4
‘09 260 03
06 210 3,8(2 728 644 300 2,168 428
II 0 340 5,271 1,008 628 o6 4,644 1,032 I 5 870
1038 265 4,880 1,648 3(2 (96 4, 68 052 I 1,030
(09 590 4,996 I,3 468 72 4,528 1,236 2 1,150
1 15 6(0 5,8(2 9,068 59’? (80 5,720 888 08 760
(0.9 249 T,oc
((2)60 30
114 345 6 1,063
((6723 6 1,1(0
II 8 520 1 o ,. I,(K0
I I 4 375 0,188 1,028 536 200 4,607 828 1.,, 040 435
250 Is, 21,136
364
08
252
394 43,284 21,908
360 28,760 2,491
409 32,470 8,460
7(0 07,656 11,544
136 56,400 35,116
300
80
32
(80
467
,76
270
376
6’ o e -k r-to
SOLIDS,” ? ’ ( “7 ‘
IOTAL SUSPENDED_015 50L110 - 0— _“ — 9 1C 1AL 5U5p9N)IODISSOLV 1 O - ° .- , . — —
5 Tool vol lolol /01 10001 ‘1.1 ,0 ‘°‘ ‘ ‘ 2 1olol’/ l
__________ 790
17,0 1,260 9 6 (60 /6
6(0
970
4,u2C 836 316 . 4,604 , )7r’ 79 2
11,3 4(0 5 . , 1 59 202
(0 7 325 .540 790 390 200 ,, 7) 207 boo oI7) 036 014 3,0,004 1 )60
(0 7 250 0,992 834 720 360 3,764 406 Too 1,/37 Ill 456 3,497 17, ,66
9.3 80 3,496 890 390 116 5.100 ‘7/. l’o’o 92; 590 1201 3 )6 54 , ’IO 76,167
10 4 ‘03 5,731 950 636 ‘72 ‘ ,O°P 6 6 I) ‘ I , ? ?, 1,1 17 Ill 14 109 I I’) SIT’) 17, 0 ’ )’ “‘I
2,0
94o9. III boOm. d. ,,0 . .9d 04 (9 .4 0 .
-------
TABLE A -S CAJEBON4ATION BASIN OPERATION AND ANALYSES OF COMPOSITE SAMPLES
APRIL, 1968
INFLLJE NT EFFLUENT 211100€
2 SOLIDS,o 9 1 501100,081 ‘ F
08 8 TOTAL SUSPENDED o 15503 — —— TOTAL USPENDED DISSOLJED Y — E_
04 0 .2 0 .0 .2 .0 .2 .9 To 01 Vol ToNI Vol ToNI Vol .2 .2 ,0 .2 2 10101 Vol ToNI Vol ToNI Vol °° n . 2 .2 .2 — .2
24 4 5 67 1 670 6,294 I 62 i8 682 1,336 1080 12 I 300 I 000 21 49 9 6 130 1,326 1,066 734 244 4 590 822 675 7483 20 25 424 10, 310 23, 320 I .13
2 24 4 I I II 6 945 7,784 1,992 1,364 782 0,620 3,210 9 3,228 2,050 84 92 00 4,234 718 799 368 3,436 550 4 780 630 l2 3 2 386
3 24 4 I I I 6 890 770 12.0 1,460 I 381 284 1,342
4 24 4 I 71 12 3 1,115 6_, 193 10 I 40 0 9 40 32
5 24 4 I I 60 232
Cao,ona4ion banjo 001 a op e na 60 0 No ann y .ann4n od94d 10601109 p. noon,, ,O3rling bonin.
24 4 lS,oe NoN 21 1 68 I I 6 545 6 998 820 9 7 35 Tnaoe 800 620 07,5 lIE
25 24 5 II 6 585 5,066 2,224 604 390 4,462 864 1,390 860 0,0 123 .1,272 966 452 30 3,E20 836 I 1,020 590 96 3 64 64,280 24,366
26 24 5 II 6 695 8,660 1,030 450 44 4,210 886 6 640 930 98 35 5,040 852 460 304 4,580 648 2 S 780 360 68 96 110,760 32,676
27 24 2
28 24 2
29 24 5 1 4 513 3,606 978 302 22 5,134 806 15 690 I 270 95 20 4,970 912 614 730 4,356 682 I 465 630 25 44 49,940 16,990
30 74 5 ii 4 625 4,410 498 492 0 3,918 432 4 620 1,270 104 83 4,840 536 894 218 4,236 318 I 560 670 66 60 61,316 19,018
NOI e,o VI Iodine d.,nand a, , alIjdn
121 Began a, ding efIloent of pnima n,Ill 09 baiin in loot of tan ‘oute on’,
bean, oou ,e n,jaed ,,, ,I,,
2g#nnoIaa onnob,niI,n.d1onp, .noaoy ettIingbo ,ioefIIuen4 Apnil2 o .o .
28 No t000C, p oa,te o oailoble.
-------
TASO.8 A 9. CMSO94ATIOI4 SASIN OP88ATION ANO
ANALYSIS 09 COA4POSITh SMtIS
MAY, 1941
ft.L N T
6’
‘ . — t SOLIDS, q’I
9 1 TOTAL SUSPON060 DISSOtVED .
— 2 Tot I Vol. TOP& Vol. ?ot.l Vol
24 11.6 590 5,286 094 530 294 4,756 000 2.0 010 993 9,6 135
2 24 11,7 680 5,632 I 262 5 376 5,106 886 0.5 1,000 993 205
3 24 67 5,394 I o2O 536 184 4,838 036 1,5 84$ 1,070
2 24 44 Nom.t., 4,870 1,254 476 394 4,352 M 1.0 950 974 78 4.3 NO mite,
7 24 72 11,0 565 5,740 1,016 610 278 5,130 798 I 0 1,030 881 9.7 100
9 74 70 NGpt4m.M 6,032 1,012 684 340 5,34 On 1,050 1,040 08 26.6
9 24 68 No p11 m.te, 3,176 506 292 30 2,864 326 470 360
0 74 83 11.9 535 3,790 1,2.44 646 244 5,144 1,000 0,8 500 937 10.1 300
12
13 24
14 74
IS 24
16 24
17 74
IS
19
20 24 65 11.8 600 6,252 1,412 818 426 5,434 986 20 1,000 1,180 11.3 330
21 24 62 11,6 700 11,104 2.322 1,060 1,242 9,244 1,050 3.8 1,405 1,100 73 22.6 11.0 335
22 24 62 11.7 705 5,862 1,594 676 326 5,186 1.24$ 5.0 1,100 1,100 11,4 385
23 24 61 11.8 760 7,772 1,772 800 443 6,972 834 4.0 1,000 1,140 70 12.6 11.5 .480
24 11.5 560 4,000 946 408 194 3,512 752 1.2 1,100 800 10.9 270
24 74 11.8 625 5,012 1.112 384 2 4,628 . 890 917 134 12.6 9.
t :?3 “ I is 13.2
31 74 11.6 715 4,508 1,118 582 336 3,926 7*2 3.5 765 1,030 10.4 125
2 ppm of *ot. , ,ub.titot.4 let p timo t9 l,tt 1178 beti,t •flIo.nI Ap , ,I 4,5,11,12,18, I9 ,25,24,o 4 30. Tmv.my wi.i ,ne eilibI, onth.,. do i
299 11, 69 47 SLU000
6’ . ‘ 6’
SOLIDS, “ /l . . I
TOtAL SUSPINOID DISSOLYID ‘- L. .- — _ _
Totel Vol. 7 . 1 .1 Vol. 7.1.1 Vol. 3 . t5 ”t ‘t
- 5.614 1,000 464 210 5,150 790 Ttoc. 446 36 06,062 37,702
4,012 922 510 222 4,302 700 1.0 770 566 60 118,790 43,558
4922 1,020 614 294 4. * 726 ttoc . 848 764 88 38,392 P0,972
4,136 94.4 324 32 3.812 892 0.3 770 606 69 3.2 29 54,864 0,56.4 6,200 160 226
10,81? 2,156 700 436 10,112 1,720 05 850 533 68 113,398 23,236
5,$li 958 446 - 5,434 1.04$ 820 727 57 22.2 60 48,412 5,608 14,200 279
4,360 544 492 224 3,805 320 540 505 19Q) 48 88,256 25,724
5,326 1,128 488 4,830 820 0 7 580 719 113(1) 64 102,404 29,592
25
66 11.6 525 5,312 1,200 674 374 4.698 926 4,0 640 916 10.1 145 3,926 176 410 ISO 3,516 626 0.3 420 525 32 67,960 27,556
60 11.8 625 4,804 964 450 l aO 4,354 864 0.7 655 929 82 1.8 10.5 155 4,398 842 432 144 3,966 688 0 5 630 622 70 1.7 72 110,590 36,794 48,600 120 135
66 12.0 345 33 11.5 285 1.2 60
12.0 685 8,8.48 1,164 618 232 8.230 932 3.0 915 1,010 79 12.5 11,1 230 5,964 886 536 216 5,428 670 1.8 810 fl7 69 12.5 52 109,210 39,752 48.000 162 771
12,1 1,020 5,366 444 442 334 4,904 1,190 2 0 1,110 1,450 11,2 235 4,726 1,062 670 7% 4.056 764 0.5 680 848 36 132,414 46,384
5,614 1,010 618 146 4,996 864 0.7 920 1,000 44 82,3)6 34,796
9,820 3,152 1,122 1,842 8,690 1,310 2.0 1,070 406 66 22.6 28 09,420 32,580 30,400 88 146
6,144 1,398 830 274 5,306 1,124 2.0 980 1,060 32
6,410 1,014 618 268 5,792 746 I 3 720 112 7.8 42 42,242 22,862 27,200 155 602
4,388 912 430 118 3,958 794 0.8 840 676 85,628 28,196
5.0 42,100 113 9K)
3,070 604 366 lii 2,112 46 T..c. 345 505 43 97,678 33,566
Note (I) md i .. detnond et eulfide.
-------
TABLE A-10. CARBONATION BASIN OPERATION AND
ANALYSES OF COMPOSITE SAMPLES
JUNE, 1968
INFLUENT EFFLUENT SLUDGE
_s
LU
o•— C) •-
0 0- C . . . I)
2 ‘ - -v E -a
> C ) Ca. C ). Z O O ZZ ..2
o a. 0 - •- — — - .1- — — 0 —
C =
10
2
3 24 5 11.1 330 1.5 615 8.7 55 Trace 570 26
4 24 5 11.4 450 1.4 795 8.9 80 0.1 705 48
5 24 5 11.6 610 2.0 1,100 9.5 110 0.1 910 44
6 24 5 10.9 415 1.0 975 10.2 290 1.0 735 48
7 24 5 11.4 675 3.0 1,410 11.3 530 0.2 1,125 29
8
9
10 24 5 11.1 325 5.0 1,030 8.7 50 1.3 710 40
11 24 5 10.9 285 4.0 1,050 8.8 55 Trace 900 52
12 24 5 12.0 830 1.0 970 9.6 105 0.3 870 30
13 24 5 12.0 580 0.5 780 9.2 80 0.2 450 23
14 24 5 11.8 770 0.2 720 9.2 60 1.5 440 42
15
24 5 11.6 630 0.9 100 9.6 100 0.8 510 52 26 94
18 24 5 11.5 620 0.3 61 9.0 95 Trace 870 45 44 159
19 24 5 11.7 780 1.5 46 9.5 110 1.3 1,000 33 48 147
20 24 5 11.4 380 0.6 52 9.0 80 0.8 645 55 34 170
21 24 5 11.3 490 0.7 39 8.9 60 0.3 780 28 34 122
24 24 5 11.1 375 1.2 8.8 70 0.4 1,120 30
25 24 5 11.0 300 2.5 8.5 40 0.1 835 40
26 24 5 11.2 435 0.8 8.8 65 0.2 1,300 1 29
27 24 5 11.3 315 0.5 8.8 70 0.4 510 ’ B
28 24 5 11.5 750 1.3 9.1 70 0.5 785 66
29
30 (1) 3-day BOD
-------
TABLE A-fl. CARBONATION BASIN OPERATION AND
ANALYSES OF COMPOSITE SAMPLES
JULY, 1968
— - INFLUENT EFFLUENT SLUDGE
C
o •. >. . a) • CO .— CX ) O
a . . .E -
o .. _ EC
> 00. Z ..... O •;:.-
- 4-— —o
00 ._ z = — ao °
c 0 o..u.. a. v v a. < v tn >
1 24 5 11 .4 470 0.6 9.3 85 0.3 960 34
2 24 5 11.3 450 0.7 8.6 80 1.5 960 44
3 24 5 11.5 595 2.5 9.1 75 0.2 1,000 48
4
5 24 5 11.5 660 0.5 10.5 20 0.4 44
6
7
8 24 5 992 20
9 24 5 11.4 675 2.5 11.0 435 0.2 1,380 52
10 24 5 11.4 605 0.3 10.2 160 Trace 755 52
11 24 5 665 0.7 9.5 110 0.5 855 44
12 12 5 16
Note : 2 gpm of water substituted for primary basin effluent July 4, 6, and 7.
Tannery waste unavailable.
-------
8
8 12.5
9 20
10 24
11 24
12 24
13 24
14 24
15 8
15 16
16 24
17 24
18 24
19 24
20 24
21 24
22 24
23 17
23 7
24 17
24 7
25 12
25 12
26 22
26 2
27 18
27 6
28 24
29 7
29 11
29 6
30 13
30 11
31 1
31 23
TABLE A-12. ACTIVATED SLUDGE BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
JANUARY, 1968
( ( (
(1,280 (276 (35
( ( (
(2,124 (1 o92 (60
( (
2,846 (1,594 120
FLOWS, gpm
INFLUENT SANITARY SEWAGE - MIXED LIQUOR
C
0
0 ..!E - .E
c w SOLIDS, mg/I
E .‘ 2 ’ c .o —
E; .2 2 TOTAL SUSPENDED DISSOLVED .H ._ .O _ .
=
O ______________ ___
0 Total Vol. Total Vol. Total Vol. j E — a. — E —nv v
(240 (151 (436 (133 (18 279
( ( ( ( ( 80
360 272 384 170 10.5 279 6.45 600 476 10
270 0 344 332 8.0 276 70 7.2 600 518 11
71 790
o7o (284
2 0 1 3 ( (
2 0 1 3 744 442
2 0 1 3 614 332
2 0 1 3
2 0 1 3 10
2 0 0.5 2.5
2 0 0.5 2.5 848 676 458 418 390 258 20 290 74
2 0 0.5 2.5 ( 4 ( o (174 (614 (230 (250
2 0 1 3 ( ( ( ( ( ( ( 78
2 0 1 3 786 476 276 230 510 246 3.5
2 0 1 3 640 314 150 118 490 196 4.5 201 67
2 0 1 3 576 280 62 84 514 196 3.5 221 68
2 0 1 3 6.5
2 0 1 3 496 424 38 244 458 180 4.5
2 0 1 3 618 288 532 228 2.5 185
2 0 1 3 572 202 30 600 172 0.5 201 78
2 0.5 (o90 292 (90 44 600 ( 8 0.75
2 0 1 3 io
2 0.5 1 3.5 ( 74
2 0 1 3
2 0.5 1 3.5
2 0 1 3 1 69
2 0.5 1 3.5 69
2 0 1 3 (
1 0 1 2
1 0 1 2 810 370 118 112 692 258 1.25 288 78
1 1 1 2 ( ( ( ( ( ( 83
1 0 1 2 (742 (312 (76 80 (666 (232 (2.5 385 83
2 0 1 3 ( ( ( ( ( ( 83
,124 564 358 282 766 ¶282 8.0
2 1 1 4 (T (344 72
1,020
80
1,680 1,372
1,540 906 80
1,696 1,208 120
2,188 1,672 115
1,392 1,016
1,508 1,092 80
1,364 850 56
(5 o
-------
TABLE A- 13 ACTIVATED SLUDGE BASIN OPERATION AND ANAl W,
OF COMPOSITE SAMPLES
FEBRUARY, 1968
aQws. INFLUENT SANITARY SEWAGE — MI)(ED LIQUOR
‘ —1’
SOLIDS, m9’I E I
. § ‘ c J . ‘ .— TOTAL SUSPENDED DISSOLVED . 8 !
S 4, 0 0 —
O Total Vol Total Vol Total Vol. . 2 ‘ .- —
I 15 2 1 I 4 987 322 82 122 905 200 T 235 72 3,348 1,818 120
1 9 2 0 I 3
2 24 2 0 I 3 7 7 * 4,042 1,844 120
3 IS 2 0 1 3 3.5
3 6 1 0 1 2
4 24 1 0 I 2 r 0
5 4 1 0 1 2 2,360 896 188 60 2,172 836 T 136 100
5 20 I I I 3 77
6 7 2 0 I 3 140 5,572 2,668
6 17 2 I I 4 78
7 2 0 0 I I T
7 6 2 0 I 3
7 16 2 I I 4 74
8 II 2 0 I 3
8 13 2 1 1 4
9 19 2 I I 4 71
9 5 2 0 I 3
NJ 10 51/2 2 1 1 4
10 121/2 2 0 I 3 12
10 6 1 0 1 2
11 24 1 0 1 2 7 0
12 8 2 0 I 3 24 69
12 16 2 I I
13 24 2 I 1 4 30 69
14 24 2 I 1 4 20
15 24 2 I I 4 17 72
16 8 2 1 I 4 12 473
16 16 2 2 1 5 70
17 16 2 0 I 3 II
17 & I 0 1 2
18 20 I 0 I 2 812 312 180 164 632 148 7.5 182 4,320 1,332
18 4 1 2 1 4
9 24 2 2 I 5 656 280 6.0 157 75 6.5
20 8 2 I 1 4 3.0 4,252 384
20 16 2 2 1 68
21 24 2 I I 4 420 65
22 24 11 2 I I 31/2 1 68 3,300 1,188
23 1512 2 1 I 4
23 812 2 0 I 3
24 24 I 0 1 2 10 84
25 24 1 0 I 2 2 72
26 15 2 2 1 5 4 76
26 9 I 0 I 2
27 24 2 2 1 5 1,988 260 148 136 1,840 124 64
28 24 2 2 I 5 1,260 388 312 224 948 164 67 5,228 1,500 13
29 14 2 2 I 5 712 412 344 292 368 120 3,036 828
29 ID 2 0 1 3
-------
TABLE A-I4. ACTIVATED SLUDGE BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
MARCH, 1968
C
2
C,
0,0
58
I 15 2 2
1 9 2 I
2 18 2 —
2 6 I -
3 24 1 -
4 12 I —
4 12 2 2
5 24 2 2
6 24 2 2
7 24 2 2
8 24 2 2
9 18 2 -
9 6 I -
10 19 I —
10 5 1 2
11 10 1 2
II 14 2 2
12 24 2 2
3 24 2 2
14 24 2 2
5 24 2 2
16 18 2 -
16 6 1 -
17 19 I —
7 3 I 2
17 2 0.5 2
18 8 1
18 8 1 —
18 8 1 2
T9 24 I 2
20 24 1 2
21 24 1 2
22 18 1 2
22 6 1 —
23 24 1 —
24 24 1 -
25 24 1 2
26 24 I 2
27 24 I 2
28 24 I 2
29 24 1 2
30 24 I —
31 24 1 —
INFLUENT SANITARY SEWAGE
6 SOLIDS, mgI : 2
5 O TOTAL SUSPENDED DISSOLVED 8
2 , Total Vol. Total Vol. Total Vol 9 ‘ ,!
I 5
I 4
I 3
I 2 2 64
I 2 1,460 880 826 708 644 172 16 221 66
I 2 828 452 328 296 500 156 198 70
I 5
1 5 6.9 55 7 ,5
I 5 64 13 65
1 5 59 7.2 30 13 64
1 5 57 7.1 60 756 448 292 228 464 220 13 61
I 3
1 2
1 2 63 70
I 4 68 716 428 264 228 452 200 4 72
I 4 70 72
1 5 6.4 7.6 20 836 340 284 116 552 224 12 342 69
1 5 58 7.4 20 2,672 688 512 292 2,160 396 14 292 62
I 5 56 7.7 20 1,604 648 1,328 372 1,176 276 14 345 63
2 6 55 7.5 60 1,296 464 420 312 876 152 10 270 59
2 6 54 7.6 30 12 60
2 4 57 62
2 3 58 7.4 10 61
2 3 62 1 62
2 5 65 (5.5
2 4.3 (
2 4 74 ( ( 71
2 3 (7.8 (10
2 5 (
2 5 63 7.6 30 14 135 68
2 5 64 7.7 50 9 100 71
2 5 58 8.2 - II 200 64
2 5 64 7.9 25 548 256 208 172 340 84 6 103 66
2 3
2 3 62 7.0 30 1.5 67
2 3 69 3.0 69
2 71 7.8 25 320 404 128 40 392 264 6.0 115 70
2 5 62 8.2 - 490 176 184 134 306 50 5.5 96 64
2 5 69 7.7 30 522 224 210 210 312 14 4 100 67
2 5 7.1 5 476 192 90 70 386 122 4 90
2 7.5 25 464 204 112 132 352 72 I 110
2 3 59 7.1 30 1.5 64
2 3 58 61
7.9
7.0
SOLIDS, mg/I .0
TOTAL SUSPENDED DISSOLVED -j , x
Total Vol. Total Vol. Total Vol. ‘ o
3,740 732
2,504 1,396 1,350 1,352 872 4.4
4,328 1,156 1,588 928 2,740 228
3,072 740 580 220 2,492 520
2,460 824 824 648 1,636 176
4,580 740 2,380 68 2,200 672
1,550 61.3
1,850 54.0
7.5 94
7.2 81
7.1 4,400 2,552 2,676 2,268 1,724 284 90
7.2 1,700 1,280 92 52.8
6.8 1,700 1,336 87 57.1
6.7 1,656 1,310 89 86.5
7.2 1,744 1,328 800 73 94.0
6.9 700 109 114.5
7 750 114 116.1
FLOWS, gpm
Ml)
-------
24 2
2 24 2
3 24 2
4 24 2
5 24 1 2
6 24 -
7 24 1 -
8 24 1 -
9 24 1 -
10 24 1 -
ii 24 1 -
12 24 1 -
i— ’ 13 24 I
14 24 1 -
15 24 1 —
16 24 1 -
17 24 1 -
18 24 1 -
19 24 1 -
20 24 1 -
21 24 1 -
22 24 1 -
23 24 1 -
24 24 1 1
25 24 I
26 24 I
27 24 1 -
28 24 1 -
29 24 I
30 24 I 2
5 68 7.4 20 908 354
5 61 7.7 2,124 480
5 7.1
5 60 6.9
5 62
3 62 7.0
3 67 6.9
3 75
3
3
3 4
3 4
2 56
2 59
2 58
2 56
3 6 75 25
4 52 7.5 15 734 328
4 54 7,8 15 512 208
3 54 7.0
3 54 6.6
4 58 8.0 50 510 204
5 55 7.8 15 492 180
252 236 656 118 15
488 298 636 182 15
6.0
8.0
270 65 7.1
182 66 6.7
7.3
70 7.1
72 6.9
3.5 67 6.7
9.5 69 7.0
2,072 1,510
1,400
1,984 1,538
300
1, 100
2,100
I ,000
2,820 1,750
3,362 1,320 1,100
500
1,700
1,200
3,854 1,638 1,938 1,308 1,916 130
95 105.0
112
72 50
85 35.4
93 77
98 77
114 55
108
103
110
122 66
123 93
125
120
116
110
109
97
85
97
91
75 63
81 51
95 91
93 160
80 47
89 79
97 62.5
Note: Solution of commercial sodium sulfide odded to aeration basin as follows:
4.2
4/3 - 4 /4
4, 4 — 4.’5
Time
3:00 PM - 5:00 PM
3:00 PM 3:00 PM
3:00 PM - 3:00 PM
Ppm S based on 2 pn carbonation
basin effluent
400
TABLE A-15, ACTIVATED SLUDGE BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
APRIL, 1968
FLOWS, 9pm
INFLUENT SANITARY
SEWAGE
MIXED LIQUOR
i
C S I
0
j ,
M ‘ - - -
8 — a
u ,- —
i
a.
2
SOLIDS, m9/I
8
e j
V
SOLIDS, m9/I
E
,_
TOTAL
SUSPENDED
DISSOLVED
- 8
4,
.E
TOTAL
SUSPENDED
DISSOLVED
TOtOl Vcl.
Total Vol.
Total Vol.
Total
Vol.
Total Vol.
Total Vol.
2
2
2
2
2
2
2
2
2
2
3 4
3 4 56
3 4 60
3 4 54
0.5 1.5 54
1 2
1 2
2
2
2
2
2
2,000
1,300
74
68
63
66
62
62
65
63
62
7 67 7.2
304 218 430 110 2 195 65 7.4
132 112 380 96 5.5 94 65 7.1
1.5 60 6.9
2.5 64 6.7
114 88 396 116 5.0 106 65 6.7
146 lOO 346 80 5.1) 90 62 7.1
Date
50
100
-------
TABLE A-b. ACTIVATED SLUDGE BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
MAY, 1968
2
3
4
5
6
7
8
F- 9
11
12
13
14
15
16
17
w
19
20
21
22
23
24
25
26
27
28
29
30
31
24 1 2 2
24 I 2 2
24 1 2 2
24 I 0 2
24 1 0 2
24 1 2 2
24 1 2 2
24 1 2 2
24 1 2 2
24 1 2 2
24 1 0 2
24 1 0 2
24 1.5 3 2
24 1.5 3 2
24 1.5 3 2
24 1.5 3 2
24 1.5 3 2
24 1.5 0 2
24 1.5 0 2
24 1.5 4 2
24 2 4 2
24 2 4 2
24 2 4 2
2
12 1 0 2
24 1 0 2
24 2 5 2
24 2.5 5 2
24 2.5 5 2
24 0.5 0 2
24 2.5 2
526 218 163 136 3o3
7.3 20 530 210 174 130 356
1,220 170 144 74 1,076
448 156 132 96 316
7.7 5 532 166 136 118 396
528 202 154 68 374
482 192 126 124 356
6.8 100 526 242 186 160 340
624 286 204 174 420
610 250 230 186 380
556 256 174 166 382
514 204 128 106 386
670 220 184 130 486
590 218 194 170 396
584 264 184 196 360
552 180 204 136 348
574 48 226 184 348
700 308 186 158 314
664 312 234 186 430
786 210 114 106 672
654 266 274 202 380
82
80 &.O
96
60
48 1.0
102
66
82 6.0
6.5
6.0
112 10.0
74 10.0
130 51
130 44
140
150
145
171 72
175 42
180 66
210 58
220 69
220
220
230 84
230 70
250
280
350
190
200
160 75
160 205
150 33
170 45
160 40
144 -
158 -
155 50
200 50
170 46
138 -
130 55
FLOWS,
gpm —
INFLUENT
SANITARY SEWAGE
MJ> ED LIQUOR
‘.-
O
>.
C
* °
O
2
0
2g)
0
.
.=
gw
..E
2
-g’
0 2 o
- i-
c ,
>
2
a. <
SOLIDS, mg/I
—
—
E
•°
. -t3
0
u v
_
0 o
E
,
-
D
2
-
I
SUSPENDED
SOLIDS
mg/I
— ..
-°
0
- -o
.
g
O)
,ii E
TOTAL
SUSPENDED
DISSOLVED
Total Vol
“
L V
Total Vol.
Total Vol.
Total Vol.
5 63
5 56
3 60
3
5 62
5 50
5 60
5 60
5 62
3 58
3 60
6.5 56
6.5 65
6.5 61
6.5
6.5
3.5 50
3.5 54
7.5 55
8 52
8 56
ii
9.5 58
9.5 64
2.5 59
.5 62
7.5 15
7.5 15
7.5 15
7.1 20
7.3 20
7.8 15
8.6 20
7.6 20
7.8 15
7.8 20
7.0 55
7.6 45
7.8 45
7,9 45
7.8 60
7.2 50
96 65 7.2 2,750
122 7.3 3,182 2,624
98 64 7.0 2,734 2,238
62 7.2
7.0
92 7.3 3,292 2,796
97 68 7.0 4,140 3,520
130 66 7.4 3,968 3,448
141 67 7.2 3,016 2,036
164 70 3,784 3,288
66
65 6.8
138 65 7.4 3,332 2,956
183 70 7.1 3,416 2,860
70 3,296 2,600
167
150 7.2 5,008 3,916
59 7.2
60 7.2
134 66 8.2 3,124 2,204
159 62 7.2 4,588 2,660
142 64 7.6 4,900 2,856
129 68 7.0 3,936
190 7.4 3,608 2,552
62 6.7
66 6.9
190 68 7.3 2,840 2,108
170 65 6.6 3,440 2,784
125 69 6.8 3,400
66 7.1
92 66 2,260 1,772
90
98 7.0
5.0
5.0
90 7.5
48 10.0
68 11.0
44 11.0
64 10.0
7.5
9.5
150 7.5
126 11.0
104 4.5
5.5
64 12.5
-------
TABLE A-17. ACTIVATED SLUDGE BASINI OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
JUNE, 1968
o. E
). ..
&
C
‘
>
a.
a. <2
.
Z
wo
UI U ’.
2
- -
TOTAL
. Total Vol.
SOLIDS, mg/I
SUSPENDED
DISSOLVED
E
g
- X
-o v
.-—
V I VI VI
V 0
Total Vol.
Total Vol.
INFLUENT
41
a
t
C
...- 0
1 24
2 24
3 24
4 24
5 24
6 24
7 24
8 24
9 24
I—’ 10 24
0 ’
a’ 11 24
12 24
13 24
14 24
15 24
16 24
17 24
18 24
19 24
20 24
21 24
22 24
23 24
24 24
25 24
26 24
27 24
28 24
29 24
30 24
2,084
2,412
2,444
f!.2Y ’S, gpm
C
0 ’
.- _.
.2
u
0 2
0 2
2 2
2 2
2 2
2 2
2 2
0 2
o 2
2 2
2 2
2 2
2 2
2 2
o 2
0 2
2 2
2 2
2 2
2 2
2 2
0 2
0 2
2 2
2 2
2 2
2 2
2 2
0 2
0 2
1,740
1 , 904
1,932
y I U ,
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
51
80
123
140
130
98
100
156
110
103
a
2.5
2.5
4.5
4.5
4.5
4.5
4.5
2.5
2.5
4.5
4.5
4.5
4.5
4.5
2.5
2.5
4.5
4.5
4.5
4.5
4.5
2.5
2.5
4.5
4.5
4.5
4.5
4.5
2.5
2.5
2,592 1,960 4,130 556
68
69
70
68
71
72
72
72
70
68
70
70
70
69
68
69
71
70
67
66
7.2
7.1
7.1
7.0
7.3
7.3
7,0
7.3
7.4
7.2
7.3
6.9
7.0
7.0
6.9
7.6
7.8
7.9
7.6
7.8
7.1
7,5
7.8
7,7
8.0
8.3
8.2
69 7.6
69 7.6
62 8.1
60 8.0
64 7.9
64 7.6
7.2
62 7.3
62 7.3
7.8
66 7.8
64 7.5
62 6.9
60 7.6
56 7.0
70 7.4
35 3.5
5 2.5
15 4.5
50 5.0
20 5.0
30 8.0
- 7.5
20 7.0
15 2.5
5 3.2
o 4.5
0 6.0
15 3.0
20 8.0
5 3.5
10 13.0
5 9.0
10 8.0
15 4.0
10 0.7
- 1.0
15 7.5
45 7.0
30 7.0
105 7.5
25 8.0
40 5.5
30 2.0
6,722 2,516
5,346 2,254
6,138 2,376
6,780 4,440
4,296 1,684
5,478 1,948
2,186 38
3,022 -
3,616 2,000
140
155
200
240
300
300
355
280
310
300
250
220
220
— 220
230
200
150
280
280
310
3,160
4,108
3,116
3, 164
3,216
2,404
2,592
2,780
2,820
2,956
2,260
2,112
2,312
2,612
3,120
63
70
57
81
91
79
94
127
87
97
109
113
78
88
56
74
87
136
91
75
104
93
126
93
2,416
3,128
2,408
2,440
2,412
1,744
I ,872
2,060
2,112
2, 184
I ,704
1,620
1,852
2, 124
2,564
2,892
2,658
6.7
72 6.7
72 6.7
70 6.7
70 7.0
68
69
Note: 10 ppm of phosphate (based on 2 gpm tannery waste flow) added to activated
sludge basin 12:00 M 618 - 8:00 AM 6,’24, and 4:00 PM 6/25 through 6/30.
-------
TABLE A—18.
ACTIVATED SLUDGE BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
JULY, 1968
FLOWS, gpm
SANITARY SEWAGE
..-
Q
O ..
-
)
Q
O
v
-
. —
C
g.
w
c
. —
c
- 0)
D D
c
—
0
2
?
—
T
0
-
—
—
a
SUSPENDED
SOLIDS,
0..
E m / I
Total Vol.
—
—
>
°
)<
e
0
Z7 ,
MIXED LIQUOR
1
24
0.5
2
2
4.5
76 7.5
30
5.0
78
7.0
3,212
2,584
290
100
2
24
0.5
2
2
4.5
75 7.9
45
7.5
79
6.9
3,280
2,628
310
86
3
24
0.5
2
2
4.5
74 7.1
75
4.0
76
6.7
3,268
2,624
390
134
4
24
0.5
0
2
2.5
7.0
60
3.0
6.9
290
-
5
24
0.5
2
2
4.5
8 7.9
5
1.0
70
7.0
300
—
6
24
0.5
0
2
2.5
7
24
0.5
0
2
2.5
68
70
8
9
10
11
24
24
24
24
0.5
0.5
0.5
0.5
2
2
2
2
2
2
2
2
4.5
4.5
4.5
4.5
74
8.0
70 7.7
69 7.7
40
60
45
7.0
9.0
5.0
74
75
74
6.5
6.7
6.5
2,056
2,264
2,792
2,420
1,628
1,836
2,164
1,852
260
180
170
104
62
61
12
12
0.5
2
2
4.5
6.2
1,896
70
—
Notes:
10
ppm of
phosphate
(based
on 2
gpm tannery
waste
flow) added
to
activated
sludge
basin.
Chrome liquor (tannery prepared
basic chrome
sulfate) added to activated sludge basin in the
quantities shown below.
Date
Ppm Cr based on 2 gpm carbonation
basin effluent
July
9,
1968
40
July
10,
1968
80
July
11,
1968
120
July
12,
1968
160
-------
o.
P .
.E
8 12.5 3 1
9 20 3 1
10 24 3 1
11 24 3 1
12 24 3 1
13
14
15
24 3
24 3
8 3
15 16 3
16 24 3
17 24 3
18 24 3
19 24 3
20 24 3
21 24 3
22 24 3
23 17 3
23 7 3.5
24 17 3
24 7 3.5
25 12 3
25 12 3.5
26 22 3
26 2 3.5
27 18 3
27 6 2
28 24 2
29 13 3
29 1) 2
30 13 4
3’) 11 3
31 3
31
TABLE A-19. SECONDARY SETTLING BASIN OPERATION AND ANALYSES
OF COMPOSiTE SAMPLES
JANUARY, 1968
FLOW. aom
EFFLUENT
RETURN SLUDGE
1/2
3/8
3/8
I
— I
SOLIDS, mg/I I - - > - -
TOTAL SUSPENDED DISSOLVED 0 j
Total• Vol. Total Vol. Total Vol. 2 ‘
2 838 346 392 215 4.46 131 8 246
2 570 310 164 174 406 136 Trace 127
2 346 136 * 40 34 306 102 Trace 47.5
2
2 Trace
2.5
2.6 414 252 68 - 346 288 36
2.6 (570 108 64 - 506 198 78
2 (
2 576 260 90 1)6 486 144 Trace 2,278 1,618
2 624 298 190 164 434 134 1.5 78
2 584 310 190 154 394 156 2 104 3,740 806 30
2 3.5 2,240 1,732 45
2 530 240 0 0 554 240 5.0 45
2 574 260 52 26 522 234 1 123 30
2 740 386 302 262 438 124 75 159 15
2 (640 248 344 104 396 114 13
2.5 (
2 (2.5
2.5 (
2
2.5
2 (2.5
2.5 (
2 (23 30
1 1,338 738 682 322 656 416 52 252 28
2 (1,280 276 8 120 2,068 880
1 (
3 (1,290 270 122 124 1,168 146 0 53 4,092 2,456 15
2 (
2 (Trace 34
23 4 1 3
45
-------
TABLE A-20 SECONDARY SETTLINC BA .IN OPERATION AND ANALYSES
OF CCMPC)SITE SAMPLES
FE 9UARY, 1968
EFFlUENT RET1 N SLUDGE
FLOWS , 9 pm 8
- E
SOLIDS, mg I -D
___________________________ 0
V
Ea,
- D TOTAL SUSPENDED DISSOLVED -U
0
O ‘0 - Total Vol. Total Vol. Total Vol. V 0 0 00 ,g —
v v, 8 —
I,! 4 I 3 (1,497 199 69 24 1,428 175 Trace 24 7,080 4,550 120
I 3 I 2
2 24 3 1 2 0 16,286 10,460 150
3 8 3 I 2 0 140
3 6 2 1
4 24 2 1 1 50
3 4 2 I 1 (6,784 1,088 360 48 6,424 1,040 0 53 30
3 20 3 1 2 ( 90
o 7 3 I 2 (55 15
6 17 4 I 3 ( 120
7 2 1 I 0 0
7 6 3 1 2 60
7 16 4 I 3 120
8 II 3 I 2 60
8 13 4 1 3 120
9 9 4 1 3 150
9 j 3 1 2 60
10 5.5 4 I 3 30
10 12.5 3 1 2 120
10 6 2 1 1 60
11 24 2 1 1 90
12 8 3 I 2 0 30
12 16 4 I 3 120
13 24 4 1 3 1 150
14 24 4 1 3 Trace 120
15 24 4 I I 180
I a I 3 (0.5 72 30
6 16 5 1 4 ( 120
I 2 (1.0 15
S 2 1 1
8 20 2 I I (864 160. 76 40 788 120 Trace 23 8,912 4,848
IS 4 I 3
24 1 4 3,112 3 Trace 102
0 6 4 I 3 (Trace (16,740 11,360 60
16 5 I 4 (
24 I 3 2,176 260 167 60
22 24 3 I 2.5 Trace
23 I: . 4 I 3
- ‘ - 8.5 3 I 2
24 24 2 1 I Trace
25 24 2 1 I Trace
26 (5 I -
90
26 . 1
24 I 4 3,280 256 30.: 208 2,976 48 60
28 24 . I 4 3,3o8 364 520 276 2848 10$ 12,a2 I ó 90
0 (4 . I 1 13, 1(5: :40 460 206 2644 244
-------
TABLE A-2 1 SECONDARY SETTLING BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
MARCH, 1968
EFFLUENT R(TL*N SLUDGE
—
FLOWS , m 0
TOTAL t1t DISSOLVED o- L - J— Ef H
iu Total Vol. Total Vol. Total Vol. 21 1 I 1 2. ,2,
1 15 5 1 4 47,540 29,564
93 I 2
2 18 3 1 2
6 2 I 1 0.5
3 24 2 1 1 1,104 152 188 20 916 132 Troc. 19
4 12 2 1 1
12 5 1 4 1,120 156 120 52 100 104 36 30
5 24 5 1 4 5 13,664 9,236 60
6 24 5 I 4 9
7 24 5 1 4 5
8 24 5 1 4 1,88.4 308 408 232 1,476 76 2.5 12,972 9,460 90
9 18 3 1 2
6 2 1 1 Trace 30
10 19 2 1 2
5 9 1 3 684 240 212 104 472 136 2.1 90
II 10 4 1 1,368 440 392 396 976 44 7 100 10,036 7,480
14 5 1 4
12 24 5 1 4 784 548 284 148 500 400 10 387
13 24 5 1 4 1,840 644 1,556 316 28.4 328 8 288 13,332 7,708
14 24 6 2 4 1,992 412 510 280 1,482 132 8 245 3,804 1,892
15 24 6 2 4 6.5
16 18 4 2 2 Trace
6 3 2 1
17 9 3 2 1 Trace
17 3 5 2 3
17 2 4.5 2 2.5
18 8 4 2 2 (
18 8 3 2 1 (1.5
18 8 5 2 3 (
19 24 5 2 3 11 175 30
20 24 5 2 7 110 60
21 24 5 2 3 6 155 60
22 18 2,524 372 356 252 2,168 120 4.5 88 222
23 4 3 2 1 0.5 30
24 24 3 2 I Trace
25 24 5 2 3 952 228 152 136 800 92 Trace 44 198 5,088 2,632 30
26 24 5 3 3 1,362 140 150 104 1,212 36 3.0 35 4,442 1,968 30
27 24 5 2 3 1,862 196 158 138 1,704 58 1.0 100 395 N.g. 6,408 3,456 60
28 24 S 2 3 2,320 252 224 164 2,096 88 0.5 97 410 5.7 5,792 2,838
29 24 5 2 3 3,236 276 188 190 2,048 86 1.5 81 518 5.95 6.4 4,002 2,122
24 3 2 I Trace 30
31 24 3 2 I
Note (1) Iodine demand as sulfide.
-------
TABLE A-22. SECONDARY SETTLING BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
APRIL, 1968
EFFLUENT RETURN SLUDGE
— —
a
FLOWS, gprn 0
E E E E
D
SOLIDS, mg/I E °
_ C
-a E E me
E w E , TOTAL SUSPENDED DISSOLVED 0 o
eo O ° - o o DO
Q £ , Total Vol. Total Vol. Total Vol. E U E v U E - u I- v U E
I 24 5 2 3 1,342 142 54 64 1,288 78 Trace 59 202 1.12 2.8 5,866 3,308 62
2 24 5 2 3 1,216 342 342 240 874 102 9.0 159 195 8.15 5.0 8,946 2,448 81 30
3 24 5 2 3 0.25
4 24 5 2 3
24 5 2 3
o 24 3 2 1 0
7 24 3 2 1 Trace
24 3 2 1
9 24 3 2 1
10 24 3 2 1
ii 24 4 3 1
12 24 4 3 1
13 24 4 3 1 60
14 24 4 3 1 30
15 24 4 3 1 30
16 24 4 3 1 30
17 24 1.5 0.5 1 30
18 24 2 1 1
19 24 2 1 1
20 24 2 1 1
21 24 2 1 1
22 24 2 1 1 30
23 24 2 1 1
24 24 3 1 2 0 79 260 4.4 30
25 24 4 2 2 1,978 344 68 206 1,910 138 0 49 270 Neg.
26 24 4 2 2 1,820 148 122 76 1,698 72 0 105 250 Neg. 10,484 7,166
27 24 3 2 1 Trace 30
28 24 3 2 1 Trace
29 24 4 2 2 1,100 130 66 44 1,034 86 0 54 168 Neg. 90
30 24 5 2 3 1,586 102 70 0 1,516 116 0 75 260 Neg. 10,564 7,866 60
Note (1) Iodine demand as sulfide.
-------
TABLE A-23. SECONDARY SETTLING BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
MAY, 1968
EFFLUENT RETURN SLUDGE
0 , . , I
- FLOWS, gp n —
— SOLIDS, mg/I . > E
2 J TOTAL SUSPENDED DISSOLVED -h — — — — T - — — F
c Total Vol. Total Vol. Total Vol. i 1 51 51 51’
I 24 5 2 3 2,392 348 122 54 2,270 94 79 17,394 11,725 ÔL)
2 24 5 2 3 2,776 180 50 40 2,726 140 0 80 351 7,776 4,130 90
3 24 5 2 3 2,804 134 140 76 2,664 58 61 360 11,316 7,808 60
4 24 3 2 1 30
5 24 3 2 1 0
6 24 5 2 3 1,832 192 162 102 1,670 90 38 291 0.4 2.2 10,872 7,296 194 231 60
7 24 5 2 3 3,582 184 174 74 3,408 110 0 94 469 17,392 12,084 90
8 24 5 2 3 3,794 1,048 2,108 934 1,686 114 48 408 0.9 1.9 18,81613,328 303 2.1 289 90
9 24 5 2 3 2,836 100 1,148 34 2,688 66 28 428 18,080 13,248 60
10 24 5 2 3 2,952 206 120 120 2,832 86 0 35 436 0.8 20,262 15,086 60
11 24 3 2 I 0 90
12 24 2 1 Trace 30
13 24 6.5 2 4.5 2,204 168 260 78 1,944 90 Trace 36 307 9,780 6,406 90
14 24 6.5 2 4.5 3,246 636 666 524 2,580 112 0.6 545 501 6.0 13.6 11,974 8,324 1,616 13 170 350
15 24 6.5 2 4.5 90
16 24 6.5 2 4.5 4,250 164 38 34 4,212 130 39 493 0.2 0.5 17,938 10,658 2,900 325 138 90
17 24 6.5 2 4.5 3,364 172 180 56 3,184 116 8.0 42 465 17,568 11,396 90
18 24 3.5 2 1.5 15.0 90
39 24 3.5 2 1.5 Trace 60
20 24 7.7 2 5.5 2,588 154 88 10 2,500 144 0 73 295 21,108 14,182 90
21 24 8 2 6 4,304 474 430 364 3,894 310 5.0 234 445 1.4 3.0 26,83615,438 6,850 299 145 60
22 24 8 2 6 3,680 450 202 300 3,478 350 7.5 186 545 22,848 11,794 60
23 24 8 2 6 5,106 442 402 160 4,704 282 3.2 240 602 4.0 2.8 24, 094 11,682 6,420 69 298 60
24 24 8 2 6 5,240 228 2,170 66 3,070 162 1.7 100 466 17,34410,254 90
25 32 4 2 2 Trace 90
12 3 2 1 Trace
26 24 3 2 1 Trace 0
27 24 9 2 2 1,912 208 164 78 1,748 130 Trace 73 311 2.2 1.5 17,34631,740 212 150
28 24 y.5 2 7.5 3,094 404 358 220 2,736 184 6.5 120 350 17,324 11,766 350
29 24 9.5 7 7.5 2,934 154 270 122 3,204 276 99 451 1.3 19.0 11,762 7,382 1,630 176 180
30 24 2.5 2 0.5 Trace 90
33 24 9. 2 7.5 1,726 228 48 295 7,944 5,090 60
-------
TABLE A-24. SECONDARY
OF
SETTLING BASIN OPERATION AND ANALYSES
COMPOS lIE SAMPLES
JUNE, 1968
EFFLUENT
FLOWS, gpm
‘4-
o -c
•1-
>_ C
00
-a
4)
0
0
C
4)
‘4-
C
20 2
4)2
U) LL.I
SOLIDS,
mg/I
- TOTAL SUSPENDED DISSOLVED
Total Vol. Total Vol. Total Vol.
-D
0-
4)4
— -a
4)0
V)
Oz
Om
E
c )
0
(J
F
or::
o
UE
: 2
z
. C0)
OE
-
0
0)
-
4 )0
a).
a
7I
2,958
178
246
76
2,712
102
3,058
148
186
36
2,872
112
2,896
164
190
54
2,706
110
3,444
256
354
56
3,090
200
2,092
210
46
54
2,046
156
3,664
220
182
82
3,482
138
3,148
244
96
118
3,052
126
1 24 2,5
2 24 2.5
3 24 4.5
4 24 4.5
5 24 4.5
6 24 4.5
7 24 4.5
8 24 2.5
9 24 2.5
10 24 4.5
L..) 11 24 4.5
12 24 4.5
13 24 4.5
14 24 4.5
15 24 2.5
16 24 2.5
17 24 4.5
18 24 4.5
19 24 4.5
20 24 4.5
21 24 4.5
22 24 2.5
23 24 2.5
24 24 4.5
25 24 4.5
26 24 4.5
27 24 4.5
28 24 4.5
29 24 2.5
30 24 2.5
2 0.5
2 0.5
2 2.5
2 2.5
2 2.5
2 2.5
2 2.5
2 0.5
2 0.5
2 2.5
2 2.5
2 2.5
2 2.5
2 2.5
2 0.5
2 0.5
2 2.5
2 245
2 2.5
2 2.5
2 2.5
2 0.5
2 0.5
2 2.5
2 2.5
2 2.5
2 2.5
2 2.5
2 0.5
2 0.5
435
360
360
470
400
360
435
28
35
30
23
39
24
25
34
23
14
20
15
22
24
24
93
53
50
10(1)
40
Trace
Trace
Trace
Trace
Trace
0
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
1 .5
Trace
Trace
Trace
Trace
0
0
Trace
Trace
Trace
Trace
Trace
0
Troce
0
60
150
180
180
150
150
60
120
180
180
180
180
150
30
150
180
180
120
180
120
0
120
150
150
1,620 150
150
120
60
82 66
50 40
62 47
84 63
72 56
55 49
30 28
30 28
64 57
62 56
Note (1) 3—day BOD.
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TABLE A-25. SECONDARY SETTLING BASIN OPERATION AND ANALYSES
OF COMPOSITE SAMPLES
JULY, 1968
FLOWS, gpm EFFLUENT
0
V U,
a,
V - . -s V
‘4- 4- C
0-c V V . - - -8
>..• .-a
00 - ‘4- —.-
C 4)— ‘4- 0
w >‘, .,
1 24 4.5 2 2.5 79 72 103 150
2 24 4.5 2 2.5 42 - 0 30 240
3 24 4.5 2 2.5 0 41 180
4 24 2.5 2 0.5 0 120
5 24 4.5 2 2.5 54 50 0 90
6 24 2.5 2 0.5 0
7 24 2.5 2 0.5
8 24 4.5 2 2.5 68 60 0 62 60
9 24 4.5 2 2.5 56 56 0 50 580 120
10 24 4.5 2 2.5 128 116 Trace 54 1,000 120
11 24 4.5 2 2.5 370 0.3 50 150
12 12 4.5 2 2.5 60
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RIRL 10 0RAPR IC: ACCESSION NO.
The A. C. Lawrence Leather Company, Activated Sludge Treatment of Chrome
Tannery Wastes, FWPCA Publication ORD-5
ABSTRACT: KEY WORDS:
rho A.C. Lawrence Leather Company tannery at South Paris . Maine, is a chrome Pilot Plants
side apper leather tannery. The watet one at the tannery is shoot L.O ngd. Tannery
Each day the waste discharged from the tannery roorains about 8,500 lbs of Chromium
5—day, 2i’C 500, 70,000 lbs of total solids, of which about 17,000 lbs are Sulfides
suspended and 53,000 Lbs are dissolved. The p8 of the wantewater varies from waste Treatment
5.0 to 12.0. The daily waste discharge also ccstaiss about 8,000 lbs of cal— ledustrial Wastes
aise, as CaCS 3 , 300 lbs of sulfidos, and 1,800 lbs of chromium. Maaicipal Wades
Sludge
A waste treatment process was developed and tested, is pilot plant scale, for Activated Sludge
the treatment of the tannery wastes is conbinatios with municipal sewage. The
process consisted of the following steps is the order employed; eqoalioing and
aiaisg of the alkaline aod acid wastes; prinary sedimentation; carbonation
followed by opflew sedimentation; addition of screened cunisipal sewage;
activated sledge treatment and secondary sedimentation of the mined wastes;
med chlorination. The sludges resulting from the treatment of the wastes and
sewage were dewatorod hr centrifuge amd wore found to be suitable for burial.
Design factors for the earloas steps of the protons wore dovoiopmd and are
presented. Studies wore made of the fundamental systems asd reactions which
fern the bases for the processes employed in the pilot plant.
The results of the pilot plao t isrontigatics indicate that by use of the
methods reiosinemded, niotares of chtomo ta 0 00ry Wastes and aseicipal enc-
age can ho treated succossfslly. Sr may ho astispatod that by the employ—
moot of the methods recommended, that mistures of tannery wanton and municipal
N SR I IOCRAP HSC: ACCESSION NO.
— The A. C. Lawrence Leat her Company, Activated Sladfo Treatment of Cbtome
Tansory Wastes, FdPCA Psblicatics I R A— I
ABSTRACT: KEY WORDS:
The A.C. Lawrence leather Company tannery at Sooth Paris, Maine, is a chrome Pilot Plants
• side upper leather tannery. The water use at the tannery is about 1.0 ngd. Tannery
• garb day the waste discharged frcm the tannery contains about 8,500 lbs of Chromium
S—day, 2S C 500, 70,OiO lbs of total solids, of which about 17,000 lbs are lulfidos
suspended and 53,000 lbs are dinnolnod. The p5 ni the wantowator ration from Waste Treetmeat
5.0 to 12.0. The daily waste dinchorge also ccstaiss abont 8,000 lbs of eel— Industrial Wastes
cime, as CaCl 3 , 300 lbs of sulfiden, and 1,800 lbs of chromium. Musinipal Wastes
Sludge
A waste treatment process won dovalcpod and tented, in pilot plant soalo, for Activated Sludge
the troatmest of the t assory wanton in combination with nasicipal sewage. The
process consisted of the following steps in the order enplcyed; mqwaiiaing sad
aimIng of rho alkaline and acid wastes; yrloary sodineotation; carbonation
followed by apflcw sodioontatian; additiwa oC screened nanicipal sewage;
activated sludge treatment and secondary sedimentation of the mioed wastes;
and nh lorimation. The sludges resulting from the troatuost cf the Wastes and
sewage Were dowaterod by centrifuge and worn fooed to be noitable for burial.
Design factors for the various stops nf the yroro Sn wooo developed and are
presented. Studios veto made of the fundamental nystonn and toantiess which
— form the bases for the processes onplnyod in tie pilot plant.
The results of the pilot plant iovmntigat los indicate that by use of the
metheds rocoemmmdod, sistsras of chrcue tansery wanton and municipal sew-
age ran ho treated successfully. it nay be anticipated that by the employ-
ment of tho method n rocoonoodod. that mintaros of tansory wanton aod municipal
BIBLIOGRAPHIC: ACCESSION NO.
The A. C. Lawrence Leather Company, ictinatad Sludge Treatment of Chrome
Tannery dastos, PWPCA Pablicalion ago—I
ABSTRACT: KEY WORDS:
The AC. Lawrence Leather icopas tannery at ienth Paris, Maine, is a chrome Pilot Plants
side upper loather tannery. The water ane at the tannery is about 1.0 mgd. Tannery
Each day the canto dinchargod inco the tannery cnntaims about 8,500 lbs of C0 0 0mium
5—day, 2SC 505, 70,000 lbn of total sc uds, cf which aboot 17,000 lbs are Solfides
suspended and 53,000 lbs are dissolved. The pH of the wantowater varies from Waste Troatment
5.0 to 12.0. The daily waste discharge also contains about f,000 lbs ci sal— industrial Wastes
rise. an GaGS 3 , 300 lbs of nulfiden, and 1,800 lbs of chromium. Maoieipol Wastes
iladge
P. canto troatmont yocconn wan developed and tontod, In pilot plant scale, inn Activated Sledge
the treatment ef the tannery was ton is combination with nsoicipal sewage. The
process consisted of rho fellawiof steps in the order employed; eqaalia lmg and
aiming of the alkaline and acid wastes; primary sndimcmtatinm; carbonation
gollowod by upflow sedimmntanion; addition of screened musics pa 1 sewage;
activated sludgo troatoont and secondary sedimentation of the nisod wastes;
mod shiatinaihon. The sludges nonu lring from rho treatment of the wanton and
sowago worm dewateoed by centrifuge and wore found to ho suitable for burial.
Design factors for rho various stops of rho p0000sn worm developed and arm
peosmnted. Studios worm made of the fundamental systems and reactions which
fore the bases far the procosson meploymd in ihe piiet plant.
The results of rho pilot plant investigation indicato that by arm of the
methods receom,endod, minutes of chrome tamsory wanton and municipal sow—
— age can ho treated saocessfnlly. It nay be anticipated that by the employ-
ment of rho methods recommended, that nixtures of mommy castns and municipal
-------
sewage can be treated successfully. It may be anticipated that by the em-
ployment of the methoda recommended , that nixturaa of tannery waates and
municipal aewage can be treated to remova more than 90 percent of the BOO
and suapended solids together with about 65 percent of the total aolida.
Furtheremre, the treatment will remove or convert 99 to 100 percent of
the aulf ides, remove about 97 percent of the chromium and aboot 65 percent
of the calcium. Ch lorioatioo of the effluent will reduce the coliform
becteria concentration to lean than 100 per 100 ml.
sewage can be treated successfully. It may be anticipated that by the em-
ployment of the methods recommended, that mixtures of tannery wastes mmd
eooicipal sewage can be treated to remove more than 90 percent of the BOB
mod suspended solids together with about 65 percent of the total solids.
Furthermore, the treatment will remove or convert 99 to 100 percent of
the sulfidea, remove about 97 percent of the chromium and about 65 percent
of the calcium. Chlorination 06 the effluent will reduce the coliform
bacteria concentration to less than 100 per 100 ml.
sewage can be treated successfully. It may be anticipated that by the em-
ployment of the methods recommended, that mietures of tannery wastes end
municipal sewage cam be treated to remove more them 90 percent of the BOO
and suspended solids together with about 65 percent of the total solids.
Furthermore, the treatment will removn or comvort 99 to 100 percent of
the eulf ides, remove about 97 percent of the chromium and about 65 percent
of the calcium. Chlorination of the effluent will reduce the coliform
bacteria concentration to less than 100 per 100 ml.
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