EPA-600/2-78-013
February 1978
Environmental Protection Technology Series
BIOLOGICAL TREATMENT, EFFLUENT REUSE, AND
SLUDGE HANDLING FOR THE SIDE LEATHER
TANNING INDUSTRY
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-GOO/2-78-013
February 1978
BIOLOGICAL TREATMENT, EFFLUENT REUSE, AND
SLUDGE HANDLING FOR THE SIDE LEATHER
TANNING INDUSTRY
by
L. B. Polkowski
W. C. Boyle
Polkowski, Boyle & Associates
Madison, Wisconsin 53705
and
B. F. Christensen
S. B. Foot Tanning Company
Red Wing, Minnesota 55066
Grant Project 12120 DSG
Project Officer
Clarence C. Oster
Minnesota-Wisconsin District Office
U.S. Environmental Protection Agency Region V
Minneapolis, Minnesota 55423
Industrial Environmental Research Laboratory
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental
Research Laboratory, U. S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents
necessarily reflect the views and policies of the U. S. Environmental
Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
11
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollution impacts on our environment and even on our
health often require that new and increasingly more efficient pollution
control methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Ci) assists in developing and demonstrating new and
improved methodologies that will meet these needs both efficiently and
economically.
This report presents the findings of an extensive study of the side
leather tanning industry. The study was conducted to obtain information
concerning side leather tanning wastewater and the performance of an aerobic
biological treatment system upon the wastewater. Treated effluent reuse,
pressure sludge dewatering and sludge disposal were also evaluated. The
results of this study will be of interest to the entire leather tanning
industry. For further information on the subject contact H. Kirk Willard,
Chief, Food and Wood Products Branch, lERL-Cincinnati, Ohio 45268.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
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ABSTRACT
An evaluation of the treatability of unsegregated, unequal]'zed, and unneu-
tralized wastewaters from a side-leather tanning industry utilizing the hair
pulping process by primary and secondary biological treatment methods is
presented. Primary treatment consisted of screening and gravity separation
in clarifier-thickeners, whereas the secondary treatment method employed
aerated ponds and final clarifiers with the capability of recycling biological
solids. The system was operated ovsr a wide range of detention times, with
and without solids recycle, and nutrient (phosphorus) addition, and during
seasonal variation representing mean monthly air temperature variations
from -14°C to 30°C. The removal efficiencies were related to loading para-
meters associated with detention times and unit organic loading relationships
as well as temperature variations. Although the study was conducted for pur-
poses of research and demonstration, the results for various measured para-
meters were compared with Best Practicable Treatment (BPT) and Best Avail-
able Treatment (BAT) guidelines which served as a reference for the compar-
ison. The tannery effluent guidelines have been remanded to the courts with
possible revision as an outcome. Generally, the results indicated the inabil-
ity of the system to meet these guidelines during low temperature operations
and for some parameters even during warm weather periods.
The raw wastewater characteristics for this type of processing were
within the EPA guideline limitations based on kg/lOOOkg of hide processed with
the exception of oil and grease. Detailed source sampling indicated that the beam-
house operations represent by far the major source of most of the parameters
measured with the hair pulp operation as the single greatest overall contributor.
Solids removed from the wastewater treatment processes were dewa-
tered by pressure filtration wherein buffing dust (a material indigenous to
the industry) was used as precoat with lime and FeCl3 employed as the prin-
cipal conditioning agents. The dewatered cake was landfilled under test con-
ditions, singly and in combination with municipal refuse, and with and with-
out earth cover. Leachate quantities and qualities were measured, internal
temperature development was monitored, and changes in solids and mois-
ture content were recorded.
The secondary treatment effluent was reused in the beamhouse opera-
tions under test conditions to evaluate the effects of water conservation
practice on leather qualities as well as to determine the buildup of conser-
vative substances in the wastewater effluent such as chloride.
This report submitted as partial fulfillment of the contract terms No.
12120DSG by S. B. Foot Tanning Co. under the sponsorship of the U. S. Environ-
mental Protection Agency for the period August 1971 through November 1974.
IV
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CONTENTS
Abstract iv
Figures vi
Tables .3iii
Acknowledgement xvii
I. Introduction 1
II. Conclusions 8
III. Recommendations 14
IV. Wastewater Treatment Plant Flowsheet . ......... 17
V. Sludge Dewatering Flowsheet 28
VI. Characterization of Process Discharge 33
VIK Wastewater Flow Variations 40
VIII. Wastewater Characterization. . 45
IX. Primary Settling 60
X. Lagoon Analysis 80
XI. Chlorination Studies . 129
XII. Wastewater Effluent Reuse 135
XIII. Sludge Dewatering 142
XIV. Dewatered Sludge Cake Disposal 171
XV. Financial Considerations 199
XVI. References ........ V 204
XVII. Appendices 205
Appendix A: Analytical Procedures 205
Appendix B: Oxygen Uptake and Oxygen Transfer Studies . 213
Appendix C: Comments on Treatment Plant Operations . . 217
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FIGURES
Number Page
1 Primary treatment flowsheet 18
2 Primary settling tank 19
3 Primary settling tank scum collector 19
4 Biological treatment process flowsheet 21
5 Flow distribution chamber 22
6 Aerated lagoons 23
7 Lagoon effluent structure 23
8 Final clarifier inlet chamber 25
9 Final clarifiers 25
10 Final clarifer overflow weir 26
11 Chlorine contact chamber 26
12 Sludge dewatering building ' 29
13 Sludge dewatering flowsheet 30
14 Dewatered sludge cake 32
15 Process diagram of raw material, product and waste flows 34
16 Raw wastewater characteristics 38
17 Raw wastewater flow average 24-hour variation 42
18 Raw wastewater flow per unit weight of hide 43
vi
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19 Raw wastewater flow per unit weight of hide and process
formula 43
20 Raw wastewater BOD 5 of 24 -hour composites per unit
weight of hide 52
21 Raw wastewater COD of 24 -hour composites per unit
weight of hide 52
22 Raw wastewater total and volatile solids of 24 -hour
composites per unit weight of hide 53
23 Raw wastewater suspended solids of 24 -hour composites
per unit weight of hide 53
24 Raw wastewater oil and grease of 24 -hour composites per
unit weight of hide 54
25 Raw wastewater total chrome of 24 -hour composites per
unit weight of hide 54
26 Raw wastewater BODc related to process formula for
24 -hour composites per unit weight of hide 55
27 Raw wastewater BODg concentrations related to process
formula for 24 -hour composites 55
28 Raw wastewater suspended solids related to process
formula for 24 -hour composites per unit weight of
hide 56
29 Raw wastewater suspended solids . concentrations related
to process formula for 24 -hour composites 56
30 Raw wastewater and primary effluent BOD^ concentrations
for 24 -hour composites 63
31 Raw wastewater and primary effluent COD concentrations
for 24 -hour composites 63
32 Raw wastewater and primary effluent suspended solids
concentrations for 24 -hour composites 64
33 Raw wastewater and primary effluent oil and grease
concentrations for 24 -hour composites 54
vii
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34 Raw wastewater and primary effluent total chrome
concentrations for 24-hour composites 65
35 Primary sedimentation COD performance: 4-hour
composites 69
36 Primary sedimentation suspended solids performance:
4-hour composites 70
37 Primary sedimentation total chrome -.performance:
4-hour composites 71
38 Primary settling percent removal versus overflow
rate based on 24-hour composites 77
39 Lagoon performance--correlation of effluent BODs
and VSS concentrations 88
40 Lagoon performance--8005 removal versus F/M ratio 88
41 Final effluent concentrations for BOD and COD for
condition" 1 90
42 Final effluent mass ratios for BOD and COD for
condition 1 90
43 Final effluent concentrations for TSS and VSS for
condition 1 91
44 Final effluent mass ratios for TSS and VSS for
condition 1 91
45 Final effluent concentrations for BOD and COD for
-~~~ condition 2 92
46 Final effluent mass ratios for BOD and COD for
condition 2 92
47 Final effluent concentrations for TSS and VSS for
condition 2 93
48 Final effluent mass ratios for TSS and VSS for
condition 2 93
Vlll
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49 Final effluent concentrations for BOD and COD for
condition 3 94
50 Final effluent mass ratios for BOD and COD for
condition 3 94
51 Final effluent concentrations for TSS and VSS for
condition 3 95
52 Final effluent mass ratios for TSS and VSS for
condition 3 95
53 Final effluent concentrations for BOD and COD for
condition 13 96
54 Final effluent mass ratios for BOD and COD for
condition 13 96
55 Final effluent concentrations for TSS and VSS for
condition 13 97
56 Final effluent mass ratios for TSS and VSS for
condition 13 97
57 Final effluent concentrations for BOD and COD for
condition 13A 98
58 Final effluent mass ratios for BOD and COD for
condition 13A 98
59 Final effluent concentrations for TSS and VSS for
condition 13A 99
60 Final effluent mass ratios for TSS and VSS for
condition 13 A 99
61 Final effluent concentrations for BOD and COD for
condition 14 100
62 Final effluent mass ratios for BOD and COD for
condition 14 100
63 Final effluent concentrations for TSS and VSS for
condition 14 101
IX
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64 Final effluent mass ratios for TSS and VSS for
condition 14 101
65 Final effluent concentrations for BOD and COD for
condition 15 102
66 Final effluent mass ratios for BOD and COD for
condition 15 102
67 Final effluent concentrations for TSS and VSS for
condition 15 103
68 Final effluent mass ratios for TSS and VSS for
condition 15 103
69 Final effluent concentrations for BOD and COD for
condition ISA 104
70 Final effluent concentrations for TSS and VSS for
condition 15A 104
71 Mixed liquor settling curves for condition 15 117
72 Flux-concentration curve for mixed liquor condition 15 117
73 Sludge solids (total solids) accumulation (increase) or
solution (decrease) in lagoon system 119
74 Biological oxygen co.nsumption at 20°C relative to
F/M ratio 124
75 Breakpoint chlorination of primary settling 131
76 Breakpoint chlorination of settled lagoon effluent
(condition 13) 131
77 Breakpoint chlorination of FeCls coagulanted final
effluent (Condition 13) 132
78 Effect of Wastewater quality on chlorine requirement 134
79 Precoat pressures related to number of filtration
cycles and precoat material 158
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80 Sludge dewatering filtrate rate and volumes, 3/22/74,
run 1 162
81 Sludge dewatering filtrate rate and volumes, 7/22/74,
run 3 162
82 Landfill test bins 162
83 End view of landfill test bins 174
84 Landfill settlement (November 1974) 177
85 Landfill leachate production 192
86 Oxygen transfer lagoon sampling point locations 214
87 Oxygen transfer studies--alpha determination 215
88 Slope point for determination of KLa 215
XI
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TABLES
Number Page
1 Raw waste load from major tannery departments and
suboperations (kg/1000 kg hide processed) 36
2 Raw waste load from major tannery departments
expressed as a percentage of the total contribution 37
3 Sulfide use by process formula 39
4 Finishing wastewater characteristics 39
5 Twenty-four hour composite samplings of raw waste
during 1972--hourly flow percentages 41
6 Daily wastewater flow variations 44
7 Raw wastewater characteristics, 24-hour composites--
all data 46
8 Raw wastewater characteristics, 24-hour composites--
all data, no rendering 47
9 Raw wastewater characteristics, 24-hour composites--
all data, no rendering 48
10 Raw wastewater characteristics related to process
formula, 24-hour composites--all data, no rendering 49
11 Summary raw wastewater character: mean of 24-hour
composites 50
12 Summary of rendering process average waste load to the
treatment plant, March to November 1974 57
XI1
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13 Scrap waste characterization 58
14 Tannery well water supply, October 25, 1975 59
15 Primary effluent character: 24-hour composites--
all data 61
16 Primary effluent character: 24-hour composites--
all data, no rendering 61
17 Primary effluent characteristics related to process
formula: 24-hour composites--all data, no
rendering 62
18 Primary settling efficiency, August 8-9, 1972 67
19 Primary settling efficiency, September 25-26, 1972 68
20 Intensive primary settling surveys 73
21 Summary of primary removal by settling 75
22 Summary of linear regression--correlation analyses
for primary settling performance 78
23 Best practicable effluent limitations (control technology
currently available) maximum 30 day average 7/1/77 81
24 Best available effluent limitations (technology economically
achieveable) 7/1/83 81
25 Lagoon experimental design 83
26 Loading conditions of lagoon systems 85
27 Lagoon performance--effluent BOD5 86
28 Lagoon performance--condition 1 105
29 Lagoon performance--condition 2 105
30 Lagoon performance --condition 3 106
31 Lagoon performance--condition 13 106
Kill
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32 Lagoon performance--condition ISA 107
33 Lagoon performance--condition 14 107
34 Lagoon performance--condition 15 108
35 Lagoon performance --condition 15A 108
36 Mean primary effluent parameters for lagoon conditions 109
37 Lagoon performance: nitrogen analyses 113
38 Lagoon performance: coliforms 113
39 Lagoon performance: coliform die-off 115
40 Sludge accumulation in lagoons 118
41 Lagoon sludge production 121
42 Biological oxygen consumption in lagoons 123
43 Oxygen transfer studies 127
44 Chlorine demand studies wastewater characteristics 132
45 Chlorination of final effluent 133
46 Leather analysis 136
47 Leather physical properties 137
48 Chlorides in wastewater by tannery process 139
49 Chloride balance for water reuse system in the beamhouse 140
50 Primary sludge analysis 143
51 Mean sludge analyses --July to October 1974 146
52 Effect of pressure on specific resistance 148
53 Effect of scum on specific resistance 150
XIV
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54 Specific resistance of conditional biological solids 151
55 Specific resistance of chemically coagulated biological solids 151
56 Specific resistance of chemically conditioned stored sludge 152
57 Trial no. 1 -- February 6, 1974 154
58 Trial no. 2 -- July 22, 1974 154
59 Trial no. 3 -- August 21, 1974 155
60 Trial no. 4 -- September 11, 1974 155
61 Solids and volatile content of buffing dust 155
62 Filtrate volume--time and performance relationships 150
63 Multiple linear regression analysis dependent and
independent variables 164
64 Multiple linear regression analysis of pressure filter
performance related to sludge feed, cake solids and
chemical dosage 165
65 Multiple linear regression analysis of pressure filter
performance related to sludge feed, cake solids and
chemical dosage ratio 167
66 Multiple linear regression analysis of pressure filter
performance related to Jones equation 169
67 Landfill test bin contents at time of placement 172
68 Settlement measurements of solid waste 175
69 Temperature variations in bin contents with respect to
elapsed time after placement, bins 1-5 179
70 Temperature variations in bin contents with respect to
elapsed time after placement, bins 6-8 183
71 Bin solids analysis for dewatered sludge cake 188
XV
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72 Summary of analyses of bin contents for dewatered sludge
cake--covered versus uncovered 190
73 Leachate volume as percent of total rainfall 193
74 Average concentrations of leachate samples 194
75 Summary of leachate chemical analyses --total and unit
mass basis 196
76 Solid waste chromium balances for period April -
November 1974 198
77 Capital costs 199
78 Power consumption and costs 200
79 Chemical costs 1974 201
80 Operation and maintenance costs 1974 202
81 Summary of treatment costs 203
82 Oxygen uptake measurements 213
83 Oxygen transfer efficiencies, sample computation 216
xvi
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ACKNOWLEDGEMENTS
The authors are particularly indebted to Mr. William P. Martin,
Project Research Engineer, who assumed the responsibilities for the
conduct of this project, both in terms of plant operating requirements
from start-up through establishing routine maintenance procedures, as
well as supervision, participation in and evaluation of the total research
effort. Mr. Martin formed and supervised the nucleus of personnel
necessary for the conduct of the laboratory and field studies.
Excellent cooperation and assistance was provided throughout the
course of the study from S. B. Foot Tanning Company laboratory and
maintenance personnel. The studies related to the evaluation of waste -
water effluent reuse were conducted by tanning company personnel under
the direction of Mr. Richard G. Waite, Assistant Technical Director and
Mr. N. Clifford Benrud, Chief Leather Chemist. Mr. Werner Lersch,
Maintenance Engineer, provided the innovativeness and assistance essen-
tial to the modification or replacement of failing mechanical equipment
essential to the functioning of the wastewater treatment plant.
Appreciation is given to the City of Red Wing for the use of labo-
ratory space for certain analyses as well as for continuing assistance
throughout the study. The authors are particularly grateful to Mr.
Lawrence Monette and Mr. William Randall who were responsible for
the laboratory analytical work during the course of the study. Mr.
Randall is presently City of Red Wing Director of Public Utilities
having responsibilities for the continuing treatment of wastewaters
from the S. B. Foot Tannery.
Mr. George M. Osborn was the Financial Officer for the project who
provided much needed assistance.
xvn
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SECTION I
INTRODUCTION
GENERAL
This study was conducted to characterize the wastewaters and to
determine the performance of an aerobic biological treatment system for
the treatment of unequalized, unneutralized wastewater from a cattle side
leather industry. In addition, pressure sludge dewatering and dewatered
sludge disposal were evaluated along with reuse of the treated effluent in
beamhouse operations.
A principal objective of the project was to demonstrate the amena-
bility of biological treatment of side leather tannery wastewaters by aer-
ated ponds and the feasibility of reusing the treated effluent in certain of
the tanning processes. The tannery waste (beamhouse and tanyard utilizing
hair pulping) was treated in parallel aerated pond systems to obtain per-
formance information related to BOD removal, an evaluation of the impor-
tance of nutrient supplementation, oxygen requirements, transfer efficien-
cies, solids-liquid separation of the final effluent, the effect of recycle
solids concentrations in the aerated ponds, and temperature on the BOD
removal characteristics. The project demonstrated the value of the aer-
ated pond process in treating discharges from a tannery excluding the
wastewaters from finishing operations. The study was conducted during
periods when the fleshings were and were not rendered on the site. When
rendering was employed, the stickliquor resulting therefrom constituted
a part of the wastewater characterized and treated.
The applicability of pressure filtration was demonstrated in the
dewatering of tannery sludge with consideration given to the use of waste
materials indigenous to the industry as filter aids in the dewatering
process. Certain waste materials such as buffing dust and shavings
were used as conditioning agents. The results were evaluated in terms
of sludge filter abilities and yield with stability measurements of the
dewatered sludge cake by land disposal methods. The latter was eval-
uated in terms of leachate production and changes in the solid waste
material when disposed of separately or when combined with domestic
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refuse from a community.
The feasibility of the reuse of final effluent from the aerated ponds
in the hair pulp beamhouse operations in the leather making process were
demonstrated by measurements of the product important to the leather
industry. In that approximately 18 percent of the total waste volume is
derived from these processes, the reuse of water may constitute a reduc-
tion in costs associated with water pollution control.
The secondary objectives of the study included:
1) An evaluation was made of the gravity separation properties of
the tannery waste without the use of equalization and neutraliza-
tion in primary settling waste treatment processes. The studies
were conducted in two primary clarifiers used for settling and
thickening of the sludge.
2) The effect of chemical additives was evaluated on the solids-
liquid separation of the biological floe in the final clarifier.
3) The influence of biological treatment was determined on the sta-
bilization of the treated effluent with regard to the scale-forming
properties of tannery wastes.
4) The removal of other constituents of tannery wastewater such as
chromium, oil and grease, suspended solids, etc., in the various
treatment processes was determined to evaluate the effectiveness
of the treatment provided.
5) The bacterial die-off or regrowth of indicator organisms in the
treatment processes was determined.
BACKGROUND
The side leather tanning industry represents a major wet industry in
this country particularly in localized areas. The wastes from the indus-
try are highly polluted with inorganic chemicals such as lime, chrome and
sulfur compounds as well as organic substances, i.e., dyes, hair, grease,
manure, protein, and protein degradation materials.
The tanning industry has made progress in wastewater treatment
through laboratory pilot scale and a limited number of full-scale studies.
However, there is a lack of technical information available related to
the performance of such wastewater treatment facilities. Questions
regarding the appropriate design criteria for treatment of wastes can be
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answered only after full-scale treatment units are evaluated. The problems
related to scale-up of many of the unit processes used in treating tanning
waste are best resolved by large scale investigations.
The most pronounced characteristic of tannery wastes that presents
difficulty in treatment is the highly variable nature of the waste in terms
of pH, solids, and organic content. The wastes from the beamhouse are
predominantly high in pH, hair, sulfides, grease, manure and protein;
the wastes from the tanyard are low in pH, high in chromes, dyes, and
degraded proteins. Segregation of wastes from the tanyard and the beam-
house is normally recommended. Thus, wastes from the beamhouse may
be settled separately resulting in a smaller investment in primary set-
tling equipment. Since the beamhouse and tanyard wastes are consider-
ably different in character, separate treatment of each is sometimes
employed. Existing tannery process flowsheets and waste collection
systems often make segregation a complex and expensive alternative,
which makes the treatment of the combined wastewaters more attractive.
The biological stabilization of the unsegregated tannery waste by
conventional methods has proven to be feasible but costly. Frequently
biological waste treatment is more economically feasible if 'combined
and diluted with domestic wastes. Trickling filters, activated sludge
and facultative ponds are the biological processes which have been
studied to a limited extent.
There is an interest in aerated lagoon treatment of tannery wastes,
however, there is little information available for the design of lagoons.
A pilot scale study was conducted in August, 1966, at the S. B, Foot
Tanning Company, Red Wing, Minnesota, (1), wherein a 6.1x6.1x
1.68 m deep (20 x 20 x 5 1/2 ft deep) aerated pond having a volume
of 62.3 rrr (2200 ft3) treated settled tannery waste resulting from
hair-save beamhouse and tanyard operations at an average rate of
57.7 m3/d (15,250 gal/d).
The pilot study indicated a BOD reduction of 68 percent could be
achieved in an aerated pond with a 1-day detention time during the month
of August. The results indicated that biological stabilization of the tan-
nery waste without segregation, equalization and neutralization was pos-
sible. However, additional information was needed to provide sufficient
performance information such as the effects of detention time, tempera-
ture, nutrient addition and sludge recycle.
Dewatering and handling of tannery sludges were of interest. The
vacuum filter studies of sludge dewatering at S. B. Foot Tanning Co.
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(1, 2) were conducted primarily in the laboratory. Specific resistance
and filter leaf tests were made using sludges collected in continuous
flow clarifiers. Use of cationic polyelectrolytes improved the filtration
rate but not in a consistent way. The data available for the design of
vacuum filters for tannery sludges in general is inadequate.
Previous laboratory studies at S. B. Foot Tanning Co. (2) indicate
that centrifugation does not appear to be feasible The wet oxidation
of tannery sludges hold some possibilities in terms of chrome recovery
but capital and operating costs are high, and problems associated with
chrome toxicity in the filtrate make this method less desirable.
Pressure filtration of tannery sludges is not widely practiced in the
United States. Pressure filtration produces a cake of low moisture
content and a filtrate of high quality, both characteristics desirable in
sludge dewatering. The ultimate disposal by landfilling of dewatered
sludge cake is of particular interest because the practice represents the
most economical and practical procedures available.
Treatment of tannery wastes to a high degree can provide the oppor-
tunity for in-plant water reuse. Of the total water used, approximately
18 percent is used in the beamhouse when hair pulping operations are
employed. The influence of the reuse of secondary treated effluent on
the tanned hide quality and on the tannery processes has not been
previously documented but is part of the findings herein.
PROJECT DEVELOPMENT
The facilities were constructed to enhance the evaluation of the
performance of the various unit processes. The employment of piping
and associated appurtenances permitted separation of parallel operations
as well as permitted the units to operate through a wide range of condi-
tions. It was possible to vary the flow and resulting detention times
simultaneously from one day to approximately 20 days by altering the
flow and number of aerated ponds in service. The ponds were lined
with concrete, and floating surface type aeration equipment was employed.
The aerated pond effluent from each parallel system passed to a corres-
ponding clarifier provided with an inlet chamber and chemical additive
capability. The sludge collection equipment and piping permitted the
solids to be returned to the aerated ponds or to be wasted to the primary
clarifier. The combined waste effluent was discharged to a chlorine
contact tank and subsequently discharged into Hay Creek. Pumping and
piping were provided to convey the treated wastewater effluent to the
process site for the water reuse evaluation.
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The thickened sludge from the primary clarifier-thickeners, consis-
ting of primary and waste secondary sludges, was conditioned and dewa-
tered by pressure filtration and disposed as landfill.
An extensive sampling program was carried out during the study.
Sampling was keyed to the process and objectives of the study. Sampling
stations were located in the new influent, primary effluent, pond effluents,
secondary effluents and chlorinated effluent lines. Continuous, propor-
tional to flow samples were collected. Flow was measured and recorded
via a magnetic flowmeter preceding the clarifier-thickeners. Flow mea-
surement at the division box for individual pond treatments were made.
The waste was characterized at times throughout the study by intensive
24-hour surveys. Individual units were analyzed as dictated by the study.
The following analyses presented throughout report contents were
performed at unit influent and effluent locations to evaluate the perfor-
mance and provide information for the interpretive analysis:
1) BOD
2) COD
3) Nitrogens: NH3, NO3, Organic N
4) Phosphorus; total, ortho and condensed
5) Chromium
6) Solids: total, settleable, suspended; volatile and fixed
7) Oil and grease
8) Chlorides
9) Sulfides
10) pH
11) Effluent Langelier Index
12) Coliforms; total and fecal
13) Alkalinity
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14) Calcium
15) Temperature
To assist in obtaining information useful to the development of
design criteria for this method of treatment, additional measurements
were made of oxygen uptake, oxygen transfer rates, solids accumula-
tions within the pond and sludge production, and quiescent settling anal-
ysis of the pond contents. The results were evaluated to determine
relationships between removal and loading parameters in terms of deten-
tion times, organic loadings, volumetric loadings and sludge production.
Although ancillary in nature, an evaluation of indicator organism die-off
through the treatment processes was made.
Characteristics commonly associated with tannery wastes from the
beamhouse are high pH, high total solids, high calcium concentrations,
and high alkalinities. Often CO2 neutralization of the waste is practiced
to minimize the effects of high pH on subsequent biological processes.
The long detention time aerated pond systems minimize the effects of
pH variation and provide CC^ from biological respiration to produce an
effluent which is stable with respect to CaCO^ equilibrium. The effec-
tiveness of the aerated pond system under various operating conditions
concerning the effluent stability was evaluated.
An evaluation was made of the sludge handling system to obtain
information concerning the applicability of pressure filtration in tannery
sludge dewatering. The use of available waste materials indigenous to
the tanning industry as filter aids and for filter precoat was of parti-
cular interest. However, commercial chemical conditioning agents such
as lime and FeCl3 were used routinely. The effectiveness of the condi-
tioning agents was evaluated in terms of sludge filterability, specific
resistance, filter media blinding, filtrate quality, and cake moisture.
In order to evaluate cake stability, control test plots were used for
storage of the dewatered residues, both separately and in combination
with municipal refuse. The test plots were designed to permit collec-
tion of leachate resulting from cake drainage and/or natural precipitation
on the disposal site. Consolidation rates, internal temperatures and
cake moisture and solids analyses were performed to evaluate cake
stability and provide criteria for ultimate disposal of solids from the
tanning industry.
During the study period the secondary effluent was used in repre-
sentative drums of the leather making process and the results were
compared with similar operations using fresh water. Quality and
6
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production control tests were performed such as rehydration factors,
leather quality and physical strength properties of the finished product
in evaluating the applicability of reusing treated tannery waste effluents
for beamhouse operations. An engineering analysis was made to eval-
uate the applicability of water reuse on a full-scale basis and predict
wastewater treatment performance with a full-scale water reuse program
in the side leather tanning industry.
The overall study was conducted in the following general phases:
1) A study of detention times in the aerated ponds, from 1 to 20
days, conducted in parallel in the four -3600 m3 (1 M gal)
ponds. This study was conducted over a sufficiently long
period of time to obtain reliable information on BOD, solids,
chrome and sulfide reduction under a given period of aeration.
2) A nutrient study was conducted with phosphorus supplementation
to the aerated ponds. This study was conducted in parallel
aerated ponds to permit the non-phosphorus supplemented
system to serve as a control.
3) The recycle of sludge from the secondary settling tanks to the
aerated ponds was employed to determine the value of continual
reseeding particularly during low temperature operations and
short detention times.
4) Seasonal influence was evaluated throughout the study.
5) Aerated pond effluent reuse was studied during a period when
effluent qualities were typical of good performance for the
aerated pond system. The effect of the waste effluent quality
on hide processing and the effect of the reuse measures on the
treatment system were evaluated.
-------
SECTION II
CONCLUSIONS
1) In the acid chromium tanning of cattleskins, the major source
of wastewater pollutants derive from the beamhouse operations with the
exception of ammonia-nitrogen, total chrome and sulfates. With the
exception of chloride, the hair pulp operation contributed the majority
of the pollutants measured in the beamhouse.
2) Wastewater flows from this tannery varied with the process
formulations for hair pulping employed representing the season the hides
were flayed. The greatest wastewater flows per unit weight of green hide
were obtained when the summer formula was employed at 46.4 I/kg (5.56
gal/lb). Mean wastewater flows based on all flow data was 43 I/kg (5.21
gal/lb) of hide processed with a range of 32.2 to 53 I/kg (3.86 to 6.35
gal/lb). The mean flow was below the U.S. Environmental Protection
Agency's Development Document for Effluent Limitation Guidelines for the
Leather Tanning and Finishing Point Source Category for Category I of
53.4 I/kg (6.4 gal/lb) of hide processed. The study reported herein did
not include leather finishing wastes which represented 1.7 percent of the
total wastewater flow. Wastewater flow variation throughout a 24-hour
process day in this tannery produced a maximum flow approximately 130%
of the average and 200% of the minimum flow.
3) With the exception of oil and grease, the mean values for the raw
wastewater characteristics from this tannery, i.e., BODc, COD, total
solids, total suspended solids and total chromium, in terms ofkg/lOOOkg
of hide processed were lower, even when rendering was employed,, than
the values reported for Category I in the U.S. EPA Point Source Guide-
lines Document. The amount of oil and grease was higher than the Guide-
lines even when rendering was not employed. With the exception of total
phosphorus, the raw wastewater quality in terms of kg/1000 kg of hide
processed for BOD5, COD, total solids, total volatile solids, total sus-
pended solids, oil and grease and total chromium, was higher when ren-
dering was employed as compared to when rendering was not employed.
No significant difference was found in the various raw wastewater char-
acteristics representing the different seasonal process formulations.
8
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4) The results of the primary settling analysis indicate the highly
variable nature of primary tank performance in terms of percent remov-
als and the ability of this unit operation to reduce the variation of the
wastewater characteristics from raw to primary effluent. The mean
percent removals obtained for the range of overflow rates of 12 to 18
m3 d/m2 were BOD 39%, COD 45%, total suspended solids 58%, oil and
grease 67% and total chromium of 38%. The range of removals obtained
for 9, 24-hour intensive surveys with overflow rates ranging from 13.4
to 18.7 m3 d/m2 were as follows: BOD5 33-72%, COD 34-52%, total
suspended solids 43-84%, and total chromium 30-63%. No correlation
could be developed relating primary sedimentation performance to the
overflow rates experienced in this study.
5) The biological treatment of settled, unneutralized and unsegre-
gated acid chrome tannery wastewaters was studied over a two-year
period under a variety of loading conditions in four series/parallel aer-
ated lagoons followed by secondary sedimentation. Primary variables
of control included mixed liquor solids concentrations, hydraulic resi-
dence time and phosphorus addition. Uncontrolled variables included
temperature and wastewater characteristics. Based on these studies
the following conclusions can be drawn.
a) Settled, unneutralized, unsegregated chrome tannery waste-
waters are biologically treatable at long detention times or
low F/M (kg BOD applied per day/kg MLVSS under aeration)
loadings in aerated lagoons.
b) The percent removal of BODg in aerated lagoons is dependent
upon F/M loading and temperature. Greater than 90% of the
6005 in the primary treated wastewater can be removed at
F/M loadings as high as 0.25 kg/kg-D, but there is substan-
tial evidence to suggest that at the lower temperatures (less
than about 14°C) the F/M values should not exceed 0.15
kg/kg-D. The U. S. Environmental Protection Agency best
practicable treatment (BPT) guidelines for BODc effluent
values were achieved at temperatures greater man 13°C
at F/M loadings less than 0.14 kg/kg-D. The U. S. Envi-
ronmental Protection Agency best available treatment (BAT)
guidelines for BOD5 were achieved only under one lagoon
condition based on mean values, at 20°^, for an F/M loading
of 0.13 kg/kg-D.
c) Of the other parameters identified by the U.S. EPA guide-
lines for the category I tannery, total suspended solids, total
chrome, total Kjeldahl nitrogen and sulfides, the aerated
9
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lagoon treatment was not able to achieve BPT or BAT guide-
line values under the conditions tested except for sulfide. At
20°C and at a F/M loading of 0.13 kg/kg-D, total chrome was
reduced to an acceptable BPT level but the BAT level was not
achieved.
d) The addition of ferric chloride as a coagulant to the biologi-
cally treated effluent prior to secondary clarification, produced
acceptable effluent quality with respect to 6005, total suspended
solids, total chrome and sulfides for BPT and BOD^, total
chrome and sulfides for BAT. This coagulant also reduced
fecal coliform MPN below 200/100 ml without the need for
disinfection.
e) Total Kjeldahl nitrogen (TKN) reductions in the lagoons ranged
from 17-30%. Nitrification within the lagoon was significant
only at low F/M loadings (less than 0.14 kg/kg-D) under high
temperature conditions. Reductions in TKN were not high
enough to meet BAT effluent guideline, requirements for Cate-
gory I tannery wastewaters.
f) The settled secondary effluent contained substantial amounts of
finely divided suspended solids even when secondary clarifier
overflow rates and solids loadings were low, however, the
addition of ferric chloride greatly improved the removal of
these solids.
g) Solids production data from the biological lagoon system was
highly complicated by the nature of the influent solids and the
mixing regime within the lagoons. Solids deposition did occur
during the entire study period and the accumulations were
measured periodically but only rough estimates could be made
for the solids produced in the process. A range of 1.09 to
1.72 kg TSS/kg BODc removed was calculated with substantial
reduction in the solids produced during periods when phos -
phorus additions were being made.
h) The BOD/P ratio in the influent to the lagoons suggested a
deficiency in phosphorus to the biological system. Phosphorus
additions under selected lagoon conditions indicated greater
biological activity was occurring, however, no significant
improvement in effluent quality could be demonstrated over
the test period.
i) Oxygen consumption data for the aerated lagoons was estimated
10
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for selected operating conditions. Oxygen requirements of 0.9
to 2.0 kg 02/kg 6005 removed were calculated with the higher
values occurring at the lower F/M loadings. Under two condi-
tions occurring in the spring, oxygen requirements were esti-
mated to be 2.6 and 3.5 kg 02/kg 6005 removed possibly due
to more active biological conditions at the higher temperatures
after the dormant winter conditions.
6) The surface aeration of the shallow lagoons proved to be a
problem with respect to mixing of the lagoon contents. A large number
of lower powered high speed aerators rather than fewer number of
higher powered low speed aerators was found to produce the most satis-
factory mixing and oxygen transfer conditions although solids deposition
occurred throughout the test period. Estimates of aeration efficiency,
which included a correction for oxidation of sulfide to sulfate, ranged
from 2.7 to 5.9 Ib 02/hp-hr under standard conditions.
7) Chlorination of the final effluent was usually required in the
summer months to meet the fecal coliform objective of 200/100 ml.
Chlorine dose to achieve the objective was dependent upon effluent
quality and ranged from 3 to 18 mg/1 in 1973. In the following year
these levels had to be increased due to the accumulation of solids in
the chlorine contact tank.
8) The recycling of biologically treated tannery wastewater as
process water for the beamhouse operations was studied to determine
the effect of this practice on leather quality and physical strength char-
acteristics. The results of the test showed that the only adverse effect
on the treated hide properties was the production of a slightly darker
shade of leather over the controls which were processed with well water
as a supply source. The importance of this effect would be dependent
upon the individual tannery capability for water recycle and product
quality control.
9) A chloride balance was made to determine the impact of
treated effluent recycle for beamhouse operations which account for
17. 7% of the total tannery flow. The equilibrium chloride concentration
calculated when 100% recycle to the beamhouse would be practiced was
about 4700 mg/1 as compared with 3900 mg/1 without recycle. This
increase should not have serious effect on the wastewater treatment
process.
10) The tannery wastewater sludges were dewatered by the pres-
sure filtration process and studies related thereto produced the
following conclusions.
11
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a) Analyses of the primary sludge over the study period showed
the sludge to have the following characteristics: total solids
10.5% mean, range 7.0 to 16.1%; oil and grease 2.1% mean,
range 1.0 to 4.0%; volatile suspended solids 70.4% mean,
range 63-81%.
b) Buffing dust, a solid waste material indigenous to the industry,
was successfully used as a filter precoat material throughout
the study but required filter cloth cleaning after 30 to 40
cycles of operation.
c) With proper conditioning, biological waste sludges and sludge
mixtures with high proportions of oil and grease as scum were
filterable by the pressure filtration process.
d) Multiple linear regression analysis of full scale operating data
utilizing three dependent variables, filter time, mean filtration
rate, and a first order constant for the filtrate volume-time
relationship was used with independent variables of specific
resistance, sludge feed and cake characteristics and; condi-
tioning chemicals and amounts as well as with the independent
variables of the Jones equation which resulted in the following
conclusions.
1) The specific resistance values represent the consistent
single factor s^nificantly correlated to full scale filter perfor-
mance.
2) Increases in ferric chloride dose for sludge conditioning had
a pronounced effect on the improvement of filter performance
in the range of concentrations employed, 3.67 to 8.18% weight
of dry solids.
3) Increase in lime dose for sludge conditioning resulted in a
detriment to the filter performance in the range of concentra-
tions employed, 7.4 to 18.7% weight of dry solids.
4) The feed sludge solids concentration or the final dewatered
sludge cake solids did not prove to be significantly correlated
with filter performance measures.
11) Controlled studies were conducted to evaluate the effects of
landfilling dewatered tannery sludge cakes alone or in combination with
municipal refuse in covered and uncovered cells. Results of these tests
conducted over a two year period produced the following conclusions.
12
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a) The landfilling of dewatered sludge cake without earth cover
was a more desirable procedure than covering the cakes with
soil because the exposed or uncovered cake had greater oppor-
tunity to undergo aerobic decomposition resulting in higher
internal temperatures, more rapid evaporation of moisture,
greater rates of settlement and consolidation and lower quan-
tities of leachate generated. Some odors are associated with
the fresh dewatered cakes but were not considered to be signi-
ficant.
b) In the first 60 days after placement, the 100% sludge cake
cells had an initial settling rate of between 0.08 to 0.16
m/m height-month depending on whether they were covered
or uncovered. Refuse and combinations of refuse and sludge
cake produced initial settling rates substantially lower than
these values.
c) Analyses of sludge cakes approximately 3 months after place-
ment showed a reduction in volatile solids of 35.2% for earth
covered cakes and 55.7% for uncovered cakes. Percent dry
solids over this period increased by 3.6% in the covered
cakes and 23.2% for the uncovered cakes.
d) Collection of leachate from the test cells indicated that
between 20 to 23% of the total rainfall resulted in leachate
for the covered sludge cakes, whereas only 7 to 9% of the
total rainfall resulted in leachate in the uncovered cells.
Covered refuse produced about 10% of the incident rainfall
as leachate.
e) Analyses of leachate quality from the test cells indicated
that higher masses of pollutants were generated from
covered sludge cakes and lowest amounts were produced
by refuse or mixed refuse-sludge cake cells.
f) Greatest amounts of total chromium in leachate were pro-
duced from covered sludge cakes than for uncovered sludge
cakes. Approximately 0.001 g chrome/1000 kg dry cake
placed was released over the test period for covered
sludge cakes (approximately 0.04% of the total chrome
placed) as compared with a range of from 0.003 to 0.00004
g chrome/1000 kg dry cake for uncovered cakes (approxi-
mately 0.0017% of the chrome placed).
13
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SECTION III
RECOMMENDATIONS
1) In-plant efforts to reduce wastewater pollutants in an acid chrome
tannery should be directed primarily to the beamhouse operations except
for total chrome, ammonia and sulfate which come primarily from the
tanyard. The beamhouse hair pulp operation is the principal source of
sulfides and protein degradation products and efforts should be directed to
sulfide recovery and reuse as well as the employment of methods for the
removal and enrichment of the protein degradation products for subse-
quent marketing.
2) The treatment of unsegregated chrome tannery wastewater by
aerobic lagoons will provide a high degree of treatment but supplemental
treatment with chemical coagulation is necessary to reduce the finely
divided particulate matter and the pollutants associated therewith to more
acceptable levels. However, the addition of ferric chloride as a coagu-
lant to the secondary effluent did reduce the levels of fats and greases
and total Kjeldahl nitrogen to meet the requirements of Best Available
Treatment (BAT). However, these results were obtained only under high
temperature or warm weather conditions. The results from these studies
show that the nitrogen in the wastewater does not undergo transformation
and oxidation to the extent required by BAT guidelines even under the low
organic loading and high temperature conditions evaluated in this demon-
stration study. It would be necessary to provide substantially longer
sludge ages (lower F/M values) than utilized in these studies. Even under
these conditions, there is no evidence that biological processes will •
reduce the total Kjeldahl nitrogen to acceptable limits for this wastewater
and further research is needed to substantiate this process. The reduc-
tion of fats and greases to meet acceptable requirements will be likely
achievable through more effective oil and grease removals by prelimi-
nary and primary processes, such as electro-floatation techniques, as
well as by the employment of chemical assists in the secondary pro-
cesses. Further evaluation of the effectiveness of selected methods for
fat and grease removal would be desirable.
3) When aerobic lagoons are employed to treat acid chrome tan-
ning wastewaters, it is recommended that the process be designed to
14
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provide maximum flexibility. In cold climates, it is recommended that
the lagoon system be provided with and operated with sludge return so
that detention times may be reduced during cold periods to minimize the
cooling effects without seriously affecting performance. Consideration
should be given to deeper ponds and submerged aeration devices to mini-
mize the problems attendant with cold weather operation.
4) The results of the biological treatment systems represent rela-
tively brief periods of testing under a variety of operating conditions. Tt
is recommended that treatment performance be evaluated over an extended
period to fully ascertain the effects of seasonal variations on the capa-
bility of the treatment system employed and to statistically evaluate the
performance data relative to recommended effluent guidelines.
5) Research efforts should be conducted to ascertain the health
hazards associated with the discharge of unchlorinated wastewaters from
tannery processes when sanitary wastes are not included. It is unlikely
that the fecal coliform requirement currently acceptable for municipal
wastewater discharges is realistic for tannery process wastes.
6) Odor problems in tannery wastewater unit operations derive
principally from the evolution of hydrogen sulfide from the wastewater
attendant with a decrease in pH, from the presence of volatile nitrogen
bearing substances generated in the treatment of hides and through bio-
chemical reaction with hide protein, and from gaseous biochemical end-
products generated in unit operations, which are likely to be anaerobic
including sedimentation operations and sludge handling processes. The
addition of ferric chloride to the raw wastewater is recommended during
periods when sulfide bearing discharges to the treatment plant occur
which will likely enhance odor control through the precipitation of sul-
fide as the iron salt. This procedure also may provide benefits of
improved suspended solids separation through coagulation mechanisms.
In other areas of the treatment process where anaerobic conditions
may evolve or pH adjustments to sludge before dewatering, consider-
ation should be given to enclosure of the unit process with appropriate
ventilation and waste air treatment.
7) In designing treatment facilities for tannery wastes, consider-
able effort should be made to account for the peculiar properties of this
wastewater, such as wide pH fluctuations, ability to cause encrustations,
corrosivity and the presence of hair and scraps. The operational diffi-
culties that were encountered with this treatment facility and suggestions
to alleviate some of these problems, both for design and maintenance,
are provided in Appendix C of this report.
15
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8) To minimize the secondary pollutional effects in the land
disposed of dewatered tannery sludge from the pressure filtration
process (solids content from 40 to 50% by weight) it is recommended
that the cakes be placed in uncovered fill in 1 meter depths for a
12-month period before covering. It may be necessary to provide
odor control by topical applications on the freshly dewatered
disposed cakes to minimize odors for certain locations.
16
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Section IV
WASTE WATER TREATMENT PLANT FLOWSHEET
The unsegrated, unequalized, unneutralized wastewater is conveyed to
the treatment plant wetwell through a 61 cm sewer. Three main inter-
cepting sewers provide the in-plant wastewater collection system for
process waters. In addition, roof drainage, during times of rainfall,
enters the process wastewater streams for subsequent treatment. The
influent channel to the pumping station wetwell was provided with bar type
screening in the primary channel with provisions to grind the scraps in
place without the need for removal from the wastewater stream. During
periods of clogging or power outage provisions were made for flow to be
directed to a secondary channel equipped with a bar screen with 1. 59 cm
clear openings with manual cleaning. The grind in-place device was
ineffective and was replaced with a bar screen with 0.96 cm openings and
mechanical rake. The bar screen in the secondary channel was also
equipped with a mechanical raking device. Screenings were disposed of
as landfill.
The screened wastewater entered a wetwell with an operating volume
of about 18.9 m^. in addition to the raw wastewater flow, filtrate from
the sludge dewatering facility as well as waste activated sludge from the
secondary clarifiers, reentered the waste at this point. The wastewater
from the wetwell was pumped to the primary settling tanks with two vari-
able speed pumps under normal operation and one constant speed pump for
peak flows. The pumps are physically arranged in parallel and activated
by a control system for prescribed water levels in the wetwell.
The pumps discharge into a 36 cm main equipped with a magnetic flow-
meter capable of measuring and recording instantaneous flows as well as
totalized flows. The flow was divided between the two clarifiers with
roughly an equal portion passing to each, although these individuals flows
were not metered (Figure 1).
The circular primary settling units, each 10. 7 m in diameter, were
equipped with two sludge collectors and a single surface scum collector
(Figures 2 and 3). The flow was introduced through a center well 0.91 m
in diameter about 0.46 m below the liquid surface and the tanks served as
clarifiers with baffled peripheral discharge over a flat crested weir. The
17
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bo
OLD PUMPING
STATION
SLUDGE
DEWATERING
BUILDING
WASTE PUMPING
STATION
36 cm INFLUENT
20 cm FILTRATE FLOW
PUMPING
STATION
OUTLET CHAMBER
41cm
IATED LAGOONS
Figure 1. Primary treatment flowsheet.
-------
Figure 2. Primary settling tank.
Figure 3. Primary settling tank scum collector.
19.
-------
settled solids passed into a thickening zone in the lower portion of the tank
with sludge discharge through a sump 1.01 m x 1.98 m - 1.22 m deep near
the center of the settling tank. The settling tank sidewall depth of 3.66 m
provided a volume of about 327 m3. The floatable material was discharged
to a scum manhole adjacent to each tank and measured 1.52 m x 1. 52 m x
4.27 m deep with a capacity of about d. 44 m3 each. The scum was stored
and concentrated before disposal off-site. Each scum manhole was equipped
with a pump for dewatering the chamber.
The settled effluent from each clarifier passed into a weir controlled
outlet chamber before the two streams were conveyed by gravity to the
secondary treatment facilities. The outlet chambers served as sampling
points for evaluating the performance of the primary clarification.
The thickened primary settled sludge solids were conveyed through a
15 cm line to three positive displacement pumps for subsequent discharge
to the solids dewatering building as required.
The combined primary effluent was discharged to a distribution cham-
ber capable of dividing the primary effluent to the various aerated lagoons
or lagoon systems for each test condition (Figure 4). In addition, the dis-
tribution chamber received the return activated sludge from the final clari-
fier s as separate streams to be directed appropriately to the desired aer-
ated pond treatment system (Figure 5). Two parallel treatment systems
could be employed with or without return sludge as independent secondary
treatment systems (Figure 4). The primary effluent flow, pond influent
flow, was proportioned to the appropriate treatment system or individual
lagoon by use of shear gates thus providing complete flexibility.
The four aerated lagoons (Figure 6) were concrete lined with ground
level top dimensions of 99.4 m x 26.2 m, two of which were 2.13m deep
providing volumes of 3691 m6 each (lagoons 1 and 2) and a 1.83 m operating
depth for two with a 3524 m6 each (lagoons 3 and 4). The side walls were
sloped 2:1, horizontal to vertical, for bottom dimensions of 90. 8 m x 17.1
m for lagoon numbers 1 and 2 and bottom dimensions of 90 m x 16.8 m for
lagoon numbers 3 and 4. The primary effluent-return sludge mixture was
conveyed to the lagoons through a 36 cm pipe and introduced at mid-width
and depth at the influent end of the lagoon. The outlet structure was located
at the opposite end of the lagoon at mid-width and extended 3.66 m into the
lagoon providing 9.14 m of weir length. Each outlet weir controlled the
liquid depth at 2.13 m and 1.83 m for lagoons 1 and 2, and 3 and 4, respec-
tively (Figure 7).
The physical piping arrangement with associated valves and shear
gates for the four lagoons is shown in Figure 4. The flow patterns utilized in
20
-------
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36 cm
LAGOON
15 cm
10cm
30 cm
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LAGOON#I
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LAGOON
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LAGOON
INLET CHAMBERS
CHLORINE
CONTACT TANK
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HAY CREEK
36cm
Figure 4. Biological treatment process flowsheet.
-------
Figure 5. Flow distribution chamber.
22
-------
Figure 6. Aerated lagoons.
Figure 7. Lagoon effluent structure.
23
-------
the study were as follows:
A. Parallel—Equal flow was directed to each of the four lagoons with
the effluent directed to the final clarifiers.
B. Series--Equal flow was directed to each of the front lagoons (num-
bers 1 and 2) and then in series with the rear lagoons (numbers 3
and 4 respectively), the effluent from the rear lagoons to each
of the two final clarifiers.
C. Parallel-Series--Equal flow was directed to each of the front
lagoons (numbers 1 and 2). The effluent from lagoon number 2
was divided for flow into the rear lagoons (numbers 3 and 4).
The effluent from lagoon number 1 and effluents from lagoons 3
and 4 were directed to one of the two final clarifiers respectively.
The valve arrangement at the discharge end of the lagoons offered
some flexibility as to which final clarifier received the flow. By proper
arrangement at the distribution chamber, it was possible to direct the
return sludge to the second lagoon in series and bypass the first lagoon,
if desired.
Mechanical floating surface aerators were provided for the biological
oxygen requirements and to keep the solids in suspension. The original
750 kg m/sec aerators did not meet specifications regarding circulating
velocities and were replaced with 375 kg m/sec high speed aerators, 12
in each lagoon, which improved the ability to maintain solids in suspension
but did not eliminate the problem of solids separation in the aerated lagoons
completely.
The aerated pond effluent with associated biological solids were con-
ducted to an inlet chamber, 1.83 m x 1.83 m x 3.66 m deep, with a usable
volume of 12.7 m^, which served as a mixing compartment for the addition
of chemical coagulants for a test condition in September-October, 1974
(Figure 8).
The mixed liquor, after passing through the inlet chamber, entered
the 12.2 m diameter final clarifiers through a center well feed about 0.46
m below the surface and was deflected downward by a baffle. The clarified
effluent passed over a flat crested weir at the tank periphery and the settled
solids were conveyed by the sludge collector to a 1.68 m x 0.61 m x 0.91 m
deep sump located near the center of the tank for continuous removal. The
final clarifiers were not equipped with scum retention baffles or skimming
devices. Each final clarifier tank volume was approximately 282 m with
a sidewall depth of 2.44 m (Figures 9 and 10).
24
-------
Figure 8. Final clarifier inlet chamber
Figure 9. Final clarifier.
25
-------
Figure 10. Final clarifier overflow weir.
Figure 11. Chlorine contact chamber.
26
-------
The settled secondary sludge was removed from the clarifiers by three
variable speed centrifugal pumps (0-757 1/min), two of which were used to
return the sludge to the distribution chamber via a 10 cm line, one for each
clarifier and parallel treatment system. The third pump was used to waste
sludge from either clarifier to the wetwell via 10 cm line. Each pump
discharge was provided with flowmeters for process control.
The secondary clarifier effluents were combined and discharged to a
baffled rectangular chlorine contact tank 9.45 m x 5.79 m x 3.05 m deep
(Figure 11). Chlorine feed equipment apportioned the chlorine feed rate
from 0 to 90. 7 kg per 24 hours. The chlorine gas was combined with the
tannery water supply as a carrier and the solution was introduced to the
chlorine contact tank via a 2.54 cm PVC pipe. The chlorine solution,
introduced through a diffuser, and final effluent were combined in a 1.52m
x 1. 52 m section at the inlet to the contact tank. The contact time was
about 50 minutes for the flows experienced. An additional pump was
provided to return final settling tanks effluent from near the influent end
of the chlorine contact tank to various tanning operations for an effluent
reuse study.
The chlorinated effluent was discharged to Hay Creek via a 366 m, 46
cm outfall sewer.
27
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SECTION V
SLUDGE DEWATERING FLOWSHEET
The sludge from the primary settling tanks was dewatered by the pres-
sure filtration process housed in the sludge dewatering building (Figure 12),
wherein the conditioned sludge was pumped under pressures up to 15.8 kg
per cm2 into a 45 chamber, 1. 52 m x 1. 52 m by 3.18 cm thickness filter
press. The filter chambers were lined with a mono-filament nylon filter
cloth and a precoat of buffing dust, a waste-material indigenous to the
tanning industry, was applied just prior to commencement of the filtration
cycle. The system was designed to produce a filter cake of 45% solids
with a cycle time of 70 to 100 minutes, thus dewatering 1315 kg to 1406 kg
of sludge solids, with associated chemical conditioners, per cycle.
Chemical conditioning utilizing FeClS and lime in the amount of up to 227
kg per cycle was employed to aid filtration.
A schematic flow diagram in Figure 13 shows the ancillary equipment
and sidestreams associated with this dewatering process. The thickened
sludge was pumped from the primary clarifiers through a sludge grinder
to reduce the size of large pieces of hide or scrap that may interfere with
subsequent operations. The sludge passed into a rapid mixing or reaction
tank, 1.72 m^ capacity, where liquid ferric chloride and slaked lime were
added to the sludge before entering the contact tank. The contact tank, an
effective volume of about 15.9 m^ was provided with slow mixing paddles
to insure uniform mixing and serve as the sludge reservoir for pumping
sludge to the filter press. The filter press operated on a batch basis and
each filter cycle was preceded by precoating the filter cloth with a slurry
of buffing dust from the precoat tank,applying the precoat solution using a
4500 kg m/sec pump, over a 4 minute time interval. Filtrate water was
used as the makeup water for the precoat slurry as well as for wetting the
filter cloth before the precoat operation. The contents of the equalization
tank containing conditioned sludge was introduced to the filter press imme-
diately after precoating, prior to initiation of the filter feed pumps, to hold
the precoat materials in place. The filter feed pumps, two positive
displacement hydraulic powered pumps, were activated and conditioned
sludge was pumped to the filter press from the contact tank. The solids
were retained on the filter cloth and the liquid filtrate was conducted to
the filtrate storage tank to serve as makeup water for subsequent filter
runs. The excess filtrate overflowed and returned to the wetwell. The
28
-------
Figure 12. Sludge dewatering building.
29
-------
W
o
FERRIC
CHLORIDE
TANKS
60.6m3
FROM TANNERY'S
SLAKER
BUFFING
DUST FROM
TANNERY
LIME
TANK
3,03m3
f
PRIMARY
EFFLUENT
PRIMARY
SEDIMENTATIO
TANKS
THICKEN SLDG
PRIMARY &
WASTE
ACTIVATED
PRE COAT
BIN
RAPID
MIX
TANK
SLDG.
GRINDER
I
PRE COAT
TANK
rnx
CONTACT
TANK
ui:
111111111 11
PASSAVANT
• f^*f*f^^ v ^^tv • I | | [•
FILTER PRESSU-
-»-CAKE
TO LANDFILL
FILTRATE
TANK
TO WET WELL
PUMP
Figure 13. Sludge dewatering flowsheet.
-------
hydraulic powered feed pumps operated at declining rates from the start
of the filter cycle as the resistance to filtration increased, a result of the
solids deposited. The cycle was terminated when operating pressures
approached 15.1 to 15.8 kg/cm2 and the filtrate rate decreased to 19 to 53
1/min. The remaining unfiltered sludge in the piping and core of the filter
press was pneumatically forced back into the contact tank. The press was
opened so as to release one cake at a time. The cakes were dropped into
a chute equipped with three bars to break.the cakes as they were discharged
to a dump truck. The truck was capable of receiving the cakes from a
single cycle for disposal onsite. The filter cakes were dumped on the
ground. Subsequent landfilling and covering, was undertaken in one to two
week intervals (Figure 14). The press was closed and prepared for the
next operating cycle.
31
-------
Figure 14. Dewatered sludge cake.
32
-------
SECTION VI
CHARACTERIZATION OF PROCESS DISCHARGES
The waste products generated for the various manufacturing opera-
tions result from the tanning of cattleskins by the acidic chromium pro-
cess. The series of batch operations employed are shown in Figure 15
wherein "beamhouse", "tanyard", and "color and fat liquoring" are the
principal unit processes. In addition, the fleshings have been rendered
since March, 1974, by acidic heat treatment resulting in a stickliquor
which was discharged to the wastewater treatment plant. The leather,
grain sides, was not finished at a location which contributes to the treat-
ment works; however, wastewaters generated from the source were
characterized and reported herein.
Prior to 1971 the industry employed a "hairsave" operation and there-
after converted to "hair pulping". The results reported herein represent
the hair pulping operations typical of current technology in the tanning indus-
try.
The hides received for processing were 60-70% green salted and 30-
40%vprefleshed on an average. The raw waste load from the rendering
process depends heavily on the amount and nature of the flesh material
associated with the hide as received. The lime-sulfide formula used in
the beamhouse varied with the nature of the hide received, and had a
significant effect on the raw waste load. During the cold winter months
the hides received would have longer hair and, conversely, during the
summer months shorter hair, thus the hair pulping formula employed
would reflect these differences in hair length. In that hides are pur-
chased and stored before processing, the calendar periods may not
coincide with the processing formula employed.
The beamhouse and tanyard departments constitute a series of indi-
vidual scheduled batch drainages to the wastewater treatment plant. The
purpose of the beamhouse operation is to remove manure, blood, salt,
flesh and hair to prepare the hides for tanning. The tanyard converts
the hide to leather by a series of steps, principally chemical in nature,
followed by the physical process of splitting the side into a grain layer
of uniform thickness and a split layer or "splits" of variable thickness.
33
-------
PROCESS
CATTLEHIDE TANNERY - * CATEGORY # I OR # 2 ( 3 )
* HAIRSAVE PRIOR TO 1971, * HAIR PULP POST 1971
HIDES
a. 60 - 70%
GREEN
SALTED
b. 30 - 40%
PREFLESHED
BEAMHOUSE
I. PRESOAK
2. SOAK
*3 a. HAIRSAVE
3b. HAIR PULP
4. FINAL DRAIN
u
WATER
LIME,
LIME
.GREEN SALTED - WETTING AGENT
b. PREFLESHED - WETTING AGENT,
No OH ,NaHS
NaHS
3a TO
RECOVERY
RENDERING
OPERATION
FLESHING OIL
3b
SULFURIC ACID
TANYARD
I. PREBATE
2. BATE
3. PICKLE
4. CHROME
TANNING
HEAT
u
111
--WATER
-AMMONIUM SULFATE, BATING
ENZYME
-SULFURIC ACID, SALT, BACTERICIDE
-CHROMIC OXIDE, BACTERICIDE,
SODIUM CARBONATE
SPLITS ARE SOLD
.SHAVINGS ARE
•"SOLID WASTES
WATER
•CHROME
•DYE
EAT
LIQUORING
U, U
OIL
V
LEATHER GRAIN
SIDES TO
FINISHING.
WASTE WATER TREATMENT PLANT
Figure 15. Process diagram of raw material, product and waste flows.
34
-------
The splits are not processed further at this tannery. The grain layer is
subjected to a mechanical process of shaving to provide a smooth surface
and the resulting shaving residues are disposed of as a solid waste.
The color and fat liquoring operations are employed to impart the desired
color to the leather with the aid of synthetic dyes and to restore oils that are lost
in the preliminary processing step. The leather sides are dried and sub-
jected to a finishing operation wherein various substances are applied topi-
cally to the grain side to produce the desired finished leather surface.
A series of samplings were conducted of the individual drainages repre -
senting the major process operations as well as composite sampling of the
combined operations, i.e., beamhouse, tanyard, color and fat liquoring,
during the summers of 1973 and 1974, when the summer formula (short
hair) was used in the beamhouse. A summary of these results for the vari-
ous parameters are presented as kg/1000 kg of hides processed(as received)
in Table 1 and as a percentage of the total waste contribution from these
sources in Table 2.
It is noted that with the exception of ammonia nitrogen, sulfate and
chromium, that the beamhouse contribution for a given wastewater para-
meter varied from 50 to 99% with the largest percentage of waste mate-
rials resulting from the hair pulping operation. This is evident with the
exception of chloride where the major source results from the soak opera-
tion in the beamhouse (Figure 16).
It is readily apparent that efforts for in-plant reduction of wastes
should be directed principally to the beamhouse operations. Where ammo-
nia and total chrome effluent concentrations are of concern, additional
in-plant recovery or chemical substitution should be directed to the tan-
yard operations.
The beamhouse formulations employed for the hair pulping depends on
the nature of the hide, principally hair length, for the relative amounts of
chemicals used. The principal concern is associated with the sulfide usage
wherein greater amounts are employed with winter hides or hides having
longer hair. The effect of this is summarized in Table 3 with the desig-
nated formulations.
The finishing wastes were characterized separately in that the leather
finishing operations are conducted at another industrial site. A summary
of these results are presented in Table 4.
It is readily apparent that the finishing wastes represent an insignifi-
cant portion of the total wastewater characteristics.
35
-------
TABLE 1. RAW WASTE LOAD FROM MAJOR TANNERY DEPARTMENTS AND SUBOPERATIONS
(Kg/1000 Kg HIDE PROCESSED)
Parameter
Total solids
Volatile solids
Fixed solids
Suspended solids
Volatile solids
Fixed suspended
BOD5
COD
Oil and grease
Kjeldahl-N
Ammonia-N
Organic -N
Calcium Total
Dissolved
Chloride
Sulfide
Sulfate
Chromium
Beamhouse
Pre-
Soak Soak
38.2 63.4
3.3 18.0
34.9 45.4
3.6 11.7
1.0 9.6
2.6 2.1
2.5 8.9
4.3 18.1
0.4 5.0
0.09 0.34
0.02 0.11
0.07 0.23
0.19 0.18
0.11 0.13
3.2 38.2
-- 0.31
__
•» « — -•
Hair
Pulp Relime
176.1
90.7
85.4
76.9
56.9
20.0
36.7
160.0
10.8
27.1
0.16
27.0
10.6
7.7
31.5
5.5
--
""
31.1
9.3
21.8
7.9
3.3
4.6
7.3
19.1
2.0
0.85
0.07
0.78
2.78
1.23
5.2
0.57
--
_ _
Tanyard
Pre- Post
Total Bate Bate Pickle Chrome
308.8
121.3
187.5
100.1
70.8
29.3
55.4
201.5
18.5
28.38
0.36
28.08
13.75
9.17
78.1
6.38
--
""
7.9
2.1
5.8
2.3
1.2
1.1
2.1
4.2
0.6
0.38
0.10
0.29
0.91
0.37
1.54
0.06
0.54
"" ~"
14.8
7.9
6.9
2.4
0.7
1.7
3.1
6.0
0.5
0.77
0.55
0.21
0.77
0.60
0.26
--
4.6
™ "™
13.9
2.7
11.2
1.4
1 .1
0.3
1.2
4.0
0.66
0.15
0.09
0.06
0.20
0.08
5.9
--
1.7
""
50.9
7.3
43.6
3.0
2.7
0.3
1.8
6.3
1.18
0.31
0.17
0.14
--
--
13.7
--
11.8
1.4
(
Total F;
87.5
20.0
67.5
9.1
5.7
3.4
8.2
20.5
2.94
1.61
0.91
0.70
1.88
1.05
21.4
0.06
18.64
1.4
:olor &
at Liquor
140
23
117
10
5
5
12
32
5
1.5
0.5
1.0
5
4
20
--
14
0.5
Total
536.3
164.3
372.0
119.2
81.5
37.7
75.6
254.0
26.14
31.49
1.77
29.78
20.63
14.22
119.5
6.44
32.64
1.9
* Results are based on summer formula without rendering operation.
-------
CO
TABLE 2. RAW WASTE LOAD FROM MAJOR TANNERY DEPARTMENTS EXPRESSED AS A
PERCENTAGE OF THE TOTAL CONTRIBUTION*
Bearnhouse
Parameter
Total solids
Volatile solids
Fixed solids
Susp. solids
Volatile susp.
Fixed susp.
BOD5
COD
Oil & grease
Kjeldahl-N
Ammonia-N
Organic -N
Calcium Total
Dissolved
Chloride
Sulfide
Sulfate
Chromium
Pre-
Soak
7.12
2.01
9.38
3.02
1.23
6.90
3.31
1.69
1.53
0.29
1.13
0.24
0.92
0.77
2.68
--
--
™ —
Hair
Soak Pulp
11.82 32.84
10.96 55.20
12.20 22.96
9.82 64.51
11.78 69.82
5.57 53.05
11.77 48.54
7.13 62.99
19.13 41.32
1.08 86.06
6.21 9.04
0.77 90.66
0.87 51.38
0.91 54.15
31.97 26.36
4.81 85.40
__
_ — «. —
Relime
5.80
5.66
5.86
6.63
4.05
12.20
9.66
7.52
7.65
2.70
3.95
2.62
13.48
8.65
4.35
8.85
--
""" "*
Total
57.58
73.83
50.40
83.98
86.87
77.72
73.28
79.33
69.62
90.12
20.34
94.29
66.65
64.49
65.36
99.07
--
™* —
Pre-
Bate
1.47
1.28
1.56
1.93
1.47
2.92
2.78
1.65
2.30
1.21
5.65
0.97
4.41
2.60
1.29
0.93
1.65
** ""
Post
Bate
2.76
4.81
1.85
2.01
0.86
4.51
4.10
2.36
1.91
2.45
31.07
0.71
3.73
4.22
0.22
--
14.09
•" ~"
Tanyard
Pickle
2.59
1.64
3.01
1.17
1.35
0.80
1.59
1.57
2.52
0.48
5.08
0.20
0.97
0.56
4.94
--
5.21
— —
Chrome
9.49
4.44
11.72
2.52
3.31
0.80
2.38
2.48
4.51
0.98
9.60
0.47
--
--
11.46
--
36.15
73.68
Total
16.32
12.17
18.14
7.63
6.99
9.02
10.85
8.07
11.25
5.11
51.41
2.35
9.11
7.38
17.91
0.93
57.11
73.68
Color &
Fat Liquor
26.10
14.00
31.45
8.39
6.13
13.26
15.87
12.60
19.13
4.76
28.25
3.36
24.24
28.13
16.74
—
42.89
26.32
Total
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
*Results are based on summer formula without rendering operation.
-------
100
90
80
70
60
>
»
50-
40-
30-
20-
10-
0
BEAM
HOUSE
1 PRE SOAK
~2 SOAK
3 HAIR PULP
4 RE - LIME
m^^m
—
"^
4
mmm
/
x
/
^
X
2
X
X
x
/J
1
7
6
•§•
v]
I'.':
•
* «
*••
9'
?•
/.•'
•• *
•V
y.
*'l
r.
•*•<
V.
/
4
^y
/
x
x
X
x
/
x
X
x
x
x
/
/
^
X
/
X
X
X
/
X
X
X
X
x
/
x
•^
2
^^m
1
8
^
£
F
7///
~
*> s
'a'
9.
»,•
TANYARD
5
PRE - BATE
6 POST -
bAI b
7 PICKLE
4
7-
X
^
y
X
X
X
X
y
^
/
X
X
X
X
X
X
/
/
/
X
-i
2
I
!
"5
8
^^M
** •
•«*
r«
«,
>:
9'-
• ^
q "
.^
» .
, •
••.
CHROME
—
4
?"">
^
^
f
/
/
X
/
X
3'
X
X
X
X
X
X
X
X
X
X
X
x
/*
,
X
z
2
1
8"
1
b
^^^
'•f
J(
*v
* '
1^^
4
77
^
X
1
1
?
^
X
X
X
X
^
2
y
8
7
T
5"
icojiOR:
^^ • pnn, j^ ^^^^
:a::F/f
.§..•-•...
>r
• ,*
• * ,
.•;.
•"•'.
:^'
•9;
» **
• * t
".'-
tt
4
7"
^
/
X
/^
x
x
/
X
x
x
x
x
*
r
/
/
f
/
X
X
X
X
x
x
X
x
x
/
X
X
/
xxxx
/,
•p-
•81
^.
•g-
•s-
\ jv
r»;i
n
J»
4
7"
/
x
x
x
x
x
s
x
/
X
x
x
x
X
/
3'
'/
X
x
x
/
X
x
x
X
X
x
x
X
x
X
y
y
x
X
x
/
X
X
—i.
2
—
^
—
•Rl
TOTAL SUSPEN-BOD
SOLIDS DED
SOLIDS
COD 0-«-6
TKN
Figure 16. Raw wastewater characteristics.
38
-------
TABLE 3. SULFIDE USE BY PROCESS FORMULA
Season
Summer
Spring-Fall
Winter
Estimated
Hide weight
kg/hide
23.6
25.0
26.3
Sulfide
used
kg/d*
384
484'
580
Sulfide in
raw waste
kg/1000 kg hide
5.01
5.96
6.78
* Based on 3250 hides.
TABLE 4. FINISHING WASTEWATER CHARACTERISTICS
Parameter
Total solids
Suspended solids
BOD5
COD
Oil and grease
Kjeldahl nitrogen
Chromium
Sulfide
Flow, I/kg
Finishing
rwaBte load
kg/1000 kg
1.6
0.5
1.0
3.8
0.2
0.04
0.001
nil
0.762
Raw waste
load
kg/1000 Ig*
536.3
119.2
75.6
254.0
26.1
31.5
1.9
6.44
43.35
Ratio of finishing
waste to total ;raw
waste -lead ,.=%" +
0.30
0.42
1.30
1.47
0.76
0.13
0.05
--
1.73
* Includes beamhouse, tanyard, color and fat liquoring.
+ Includes beamhouse, tanyard, color and fat liquoring, and finishing
wastes.
39
-------
SECTION VII
WASTEWATER FLOW VARIATIONS
Considerable data were collected regarding the 24-hour wastewater
flows. In addition, hourly flow data were determined on numerous occa-
sions to characterize the flow variations associated with the processing
modes in the tanning operations.
Table 5 summarizes hourly flow data collected in 1972 for 24-hour
periods on the dates indicated. As one would expect, on the average the
wastewater flows were greatest for the early morning (first) shift, 6:00
a.m. to 2:00 p.m. (associated with beamhouse operations), and the
minimum flows were experienced during the third shift, 10:00p.m. to
6:00 a.m. A plot of the accumulative percent of wastewater flow versus
hour of the day from midnight for the average results obtained (Figure 17)
illustrates the relationship between peak to average rates. Maximum
flows are approximately 130% of the average day flow and approximately
200% of the minimum flow.
Further characterization of the wastewater flow variations based on 24-
hour flows and related to the unit weight of hide processed per day are
illustrated in Figure 18. The results of numerous surveys, corresponding
to days when 24-hour surveys were conducted, show the flows to range from
32.2 to 53 I/kg (3.86 to 6.35 gal/lb) with a value of 43 I/kg (5.16 gal/lb)
representing the median and 43 I/kg (5.21 gal/lb) the mean. All flows are
less than the value cited by the U.S. Environmental Protection Agency in
the Development Document for Effluent Limitation Guidelines for the
Leather Tanning and Finishing Point Source Category (3 ) QT53.4 I/kg (6.4
gal/lb) of hide for category 1. The waste flows measured do not include
finishing wastes representing 1.73% of the total flow. The resulting flows
in gallons per pound of hide processed for the various seasonal processing
formulas are presented in Figure 19 and all flow results are summarized
in Table 6.
40
-------
TABLE 5. 24-HOUR COMPOSITE SAMPLINGS OF RAW WASTE
DURING 1972
HOURLY FLOW PERCENTAGES
Time .1
Flow, m3
Flow, gal
Midnight -1 a.m.
1 a.m. -2 a.m.
2 a.m. -3 a.m.
3 a.m. -4 a.m.
4 a.m. -5; a.m.
5 a.m. -6 a.m.
6 a.m. -7 a.m.
7 a.m. -8 a.m.
8 a.m. -9 a.m.
9 a.m. -10 a.m.
10 a.m. -11 a.m.
11 a.m. -Noon
Noon-1 p.m.
1 p. m. -2 p.m.
2 p. m. -3 p.m.
3 p.m. -4 p.m.
X JL
4 p.m. -5 p.m.
JL X
5 p.m. -6 p.m.
6 p. m. -7 p.m.
JL JL
7 p.m. ~8 p.m.
JL X
8 p.m. -9 p.m.
X X
9 p.m. -10 p.m.
X Mr
10 p.m. -11 p.m.
JT Jr
11 p.m. -Midnight
First shift
(6 a.m. -2 p.m.
* X
Second shift
(2 p.m. -10 p.
Third shift
(10 p.m. -6 a.
H ebruary
23-24
2786
736000
3.1
2.6
3.5
2.5
2,9
4.1
7.3
5.9
5.9
6.4
4.2
6.1
4.9
6.5
4.4
3.4
3.7
4.1
3.8
4.5
3.3
3.3
1.9
2.0
47.1
)
30.5
m.)
22. 4
m.)
Composite sampling dates
March
7-8
2953
780000
3.1
2.7
3.3
3.2
2.8
2.4
5.5
5.4
6.2
5.1
5.8
5.8
5.3
5.9
4.6
3.7
3.5
4.0
4.9
3.1
4.2
3.0
3.8
2.8
44.8
30.9
24.3
March
23-24
2884
762000
1.6
1.7
3.7
2.5
1.8
4.2
5.8
7.3
4.6
5.8
5.0
5.4
6.6
4.6
5.5
3.7
3.9
3.8
4.3
3.7
4.7
4.3
2.5
3.3
44.7
34.0
21.3
August Sept.
8-9 25-26
3346
884000
1.7
2.7
4.0
2.9
2.9
3.2
5.2
6.7
5.2
6.6
5.4
5.0
5.4
5.7
5.0
3.7
3.5
4.5
3.1
3.1
3.6
3.8
3.6
3.5
45.2
30.3
24.5
2989
789600
2.3
2.8
3.1
2.9
2.2
4.4
6.5
5.8
4.1
6.1
3.5
4.8
6.4
4.8
4.1
3.9
4.4
6.7
4.7
2,9
4.1
3.8
3.3
2.9
41.8
34.8
23.4
Dec.
11-12
3028
Average
800000
2.1
3.4
4.8
2.0
2,6
4.1
4.3
4.8
5.4
7.5
5.0
4.3
5.8
5.6
4.0
4.1
3.4
4.6
3.0
3.1
4.5
4.4
2; 8
3.4
43.5
31.4
25.1
2.31
2.65
3.73
2.66
2.53
3.73
5.76
5.98
5.23
6.23
4.81
5.23
5.73
5.51
4.60
3.75
3.73
4.61
3.96
3.40
4.06
3.76
2.98
2.98
44. 52
31.98
23.50
41
-------
100
90
80
O
-I 70
U_
u_
O 60
tr
LU
40
LU
>
fl 30
O
O
20
10
I I I I I I
I I I
MAXIMUM
AVERAGE*1'3^
SLDPE=
MAXIMUM RATE
I I I I
12 2 4 6 8 10 12 2 4 6 8 10 12
AM TIME OF DAY PM
Figure 17. Raw wastewater flow average
24 hour variation.
42
-------
Frequency Of Occurrence.%
12 s 10
ae so 70
9O 95 98 99
Figure 18. Raw wastewater flow
per unit weight of hide.
Process Formula
o Winter
o Spring-Fall
• Summer
Frequency Of Occurrence,%
3.0'
2 S 10 30 50 70
Figure 19. Raw wastewater flow by
process formula per unit weight of hide.
43
-------
TABLE 6. DAILY WASTEWATER FLOW VARIATIONS.
Number Range
Date of days gal/lb hide*
All
Winter
Summer
Spring-Fall
52
19
10
23
3.
3.
4.
4.
86-6.
86-5.
84-6.
35-6.
35
51
23
35
Tvledian
gal/lb hide*
5.
4.
5.
5.
19
64
52
57
Mean Standard
gal/lb hide* deviation
5.
4.
5.
5.
21
73
56
45
0.
0.
0.
0.
619
450
510*
546
*Values times 8.345 give results in I/kg.
44
-------
SECTION VIII
WASTEWATER CHARACTERIZATION
The combined raw wastewater discharges were characterized by the
analyses of fifty 24-hour composited samples over the course of theproject*
The wastewater represents the process waters of a side leather tanning
industry utilizing a hair pulping operation but does not include the waste -
waters resulting from leather finishing operations. As demonstrated in
the section on characterization of process discharges, the finishing wastes
would represent only 1.73 percent of the total flow and 0 to 1.47 percent of
the total wasteload contribution (Table 4) for the parameters measured.
Consequently, the raw waste characterization was compared to those values
reported in category 1 of the U.S. Environmental Protection Agency Devel-
opment Document ( 3).
The results of the surveys were analyzed in several ways to demonstrate
the effect of rendering flesh as compared to not rendering and also initerms.
of the process formula employed for pulping representing winter, summer,
and spring-fall hides. In addition, all of the 24-hour survey data were
evaluated without regard to the employment of or lack of employment of
rendering or with regard to process formula.
The results have been summarized in various ways for easy reference.
Tabular results of each of the measured parameters have been summarized
as to concentration in mg/1 as well as in the form of kg per 1000 kg of hide
processed. For each measured parameter the range, median, mean and
standard deviations are presented for the number of sample results avail-
able.
Table 7 represents the summary of all 24-hour survey raw wastewater
data regardless of process formulation or the employment of rendering.
Table 8 summarizes the data regardless of process formulation, but when
the practice of rendering was not employed, whereas Table 9 reports
similar data during the period when rendering was employed. Table 10
summarizes the data according to hair pulping process formula during the
period when no rendering of the flesh was employed.
A summary of mean values, in terms of kg/1000 kg of hide, for the
various combinations of raw wastewater data are presented in Table H.
45
-------
TABLE 7. RAW WASTEWATER CHARACTERISTICS
24-HOUR COMPOSITES--ALL DATA*
Number c
Parameter analyses
BOD5
COD
Total solids
Total volatile
solids
Total suspended
solids
Oil and grease
Total chromium
Total phosphorus
Total Kjeldahl
nitrogen
48
50
50
49
50
37
42
33
19
)f Concentration, mg/1
Range
1093-2560
2730-9942
7200-13750
1630-5330
1470-5970
404-1604
20.8-80.0
1.52-21.4
105-582
Median
1624
4488
11080
2756
2568
728
49.8
5.6
285
Mean Standard
Deviation
1656
4523
10920
2824
2730
763
50.6
6.0
332
351.7
1070
1538
689
863
235
14.2
3.5
129
Range
38.6-115
131-487
313-625
75.8-207
61.6-232
17.0-72.3
1.09-3.95
0.07-0.81
3.55-26.8
Kg/ 1000 kg hide
Median
68.
186.
469.
116
113
29.
2.
0.
13.
8
8
2
8
32
25
5
Mean Standard-
Deviation
71.
195.
471.
122
117
33.
2.
n.
14,
8
8
0
5
22
26
,6
17.7
55.1
73.5
28.9
33.0
12.2
0.71
0.14
6.28
Includes data collected with and without rendering under all process formulations, no finishing wastes.
-------
TABLE 8. RAW WASTEWATER CHARACTERISTICS
24-HOUR COMPOSITES--ALL DATA, NO RENDERING*
Number of
Parameter analysis
BOD5
COD
Total solids
Total volatile
solids
Total suspended
solids
Oil and grease
Total chromium
Total phosphorus
29
31
31
30
31
18
24
20
Concentration, mg/1
Range
1093-2235
2730-6620
7200-13360
1628-3936
1468-5200
404-816
20.8-68.4
4.3-21.4
Median
1478
4220
10910
2472
2460
595
45.4
6.7
Mean Standard
Deviation
1501
4284
10540
2570
2579
601
46.8
7.4
296
841
1520
545
787
103
13.3
3.6
Kg/1000 kg hide
Range Median
38.6-103
131-278
313-580
75.8-161
61.6-180
17.0-36.9
1.08-3.21
0.21-0.81
60.5
176
430
103
104
24.7
1.97
0.29
Mean Standard
Deviation
63.2
182
443
108
108
25.1
2.02
0.33
14.5
37.8
63.9
19.4
27.3
5.6
0. 64
0. 14
*Includes data collected when rendering was not employed and represents all process formulations,
finishing wastes.
:-ut no
-------
00
TABLE 9. RAW WASTEWATER CHARACTERISTICS
24-HOUR COMPOSITES--ALL DATA, RENDERING *
Number of
Parameter analysis
BOD5
COD
Total solids
Total volatile
solids
Total suspended
solids
Oil and grease
Total chromium
Total phosphorus
19
19
19
19
19
19
18
13
Concentration, mg/1
Range
1308-2560
3735-9942
8836-13750
2224-5328
1872-5972
480-1604
24.5-80.0
1.52-6.73
Median
1929
4618
11490
3080
2872
898
50
3.2
Mean Standard
Deviation
1893
4913
11540
3225
2974
916
55.6
3.7
298
1296
1390
714
944
222
14.2
1.6
Kg/1000 kg hide
Range
65-115
153-487
387-625
103-207
87-232
22.3-72.3
1.10-3.95
0.07-0.26
Median
84
215
510
140
125
42.2
2.5
0.14
Mean Standard
Deviation
85
219
517
144
132
41.4
2.51
0.16
13.
70.
65.
27.
36.
11.
0.
0.
9
7
0
8
3
4
75
07
*Includes data collected when rendering was employed and represents all process formulations but no
finishing wastes.
-------
TABLE 10. RAW WASTEWATER CHARACTERISTICS RELATED TO PROCESS FORMULA
24-HOUR COMPOSITES--ALL DATA, NO RENDERING
CD
Process
Formula Number of Concentration, mg/1
& Parameter analysis
Winter
BOD5
COD
Total
Total
Total
Summer
BOD5
COD
Total
Total
Total
solids
vol. sol.
susp. sol.
solids
vol. sol.
susp. sol.
13
13
13
12
13
8
10
10
10
10
Spring -Fall
BOD5
COD
Total
Total
Total
solids
vol. sol.
susp. sol.
8
8
8
8
8
Range Median
1122-2235
3169-6619
7428-13360
1800-3936
1468-5200
1093-2109
2730-5380
7196-11252
1628-2413
1612-2606
1227-1717
3957-4800
9512-12016
2464-2879
1850-2880
1452
4671
11170
2931
2888
1360
3665
9061
2166
2144
1573
4330
11100
2636
2462
Mean
1514
4659
11280
2926
2991
1424
3730
9283
2100
2155
1558
4356
10906
2625
2442
Standard
Deviation
342
934
1516
623
1035
333
745
1157
221
294
168
321
915
150
339
Kg/1000
Range
39-94
131-278
313-560
76-162
62-180
54-103
131-244
372-498
84-111
84-115
58-87
156-264
376-580
96-138
73-137
Median
57
183
426
110
110
60
165
428
95
99
65
188
481
110
109
kg hide
Mean
59
180
435
113
114
67
174
428
97
100
67
194
473
113
106
Standard
Deviation
15.
38.
64.
24.
37.
16.
38.
40.
8.
11.
10.
36.
82.
15.
22.
2
9
5
9
2
4
9
7
5
2
0
3
3
2
0
-------
TABLE 11. SUMMARY RAW WASTEWATER CHARACTER: MEAN OF 24-HOUR COMPOSITES
Source
Rendering
Flow
l/kg(gal/lb) hide
BOD*
COD
Total
solids
T. susp. Oil &
solids grease
Total
chromium
kg/1000 kg hide
EPA Cat. 1
Cattleskin
Tannery*
0
Project data+
Formula
Winter
Summer
Spring -Fall
No
No
Yes
No
No
No
53.4(6.4)
#
--
39(4. 7)
47(5.6)
45(5.4)
95
63.2
84.9
58.6
66.8
67.1
260
182
219
180
174
194
525
443
517
435
428
473
140 19
108 25.1
132 41.4
114
99.8
106
4.3
2.02
2.51
* EPA Development Document--includes finishing wastes.
+ Finishing wastes excluded.
# A mean flow of 43.5 I/kg (5.21 gal/lb) hide was obtained for all project flow data including data for
rendering and no rendering.
-------
In addition, the values for category 1 on the U.S. Environmental Protection
Agency Development Document (3) are presented for purposes of compari-
son.
Several observations are noted:
1) For the parameter measured, with the exception of total phos-
phorus, the results during the period when the rendering operation was
employed resulted in higher mean levels than when no rendering was
employed (Tables 8 and 9).
2) With the exception of oil and grease, the mean values for all
parameters reported, i.e., BOD5, COD, total solids, total suspended
solids, and total chromium, were less than reported as category 1 in the
U.S. Environmental Protection Agency Development Document (3)(Table 11).
3) The mean value for oil and grease in the survey data even when
rendering was not employed was greater than the EPA category 1 (Table 11).
4) With the exception of total suspended solids, the winter formula
utilized during the period when the hides have the longest hair did not result
in the maximum mean value for the other reported values of flow, BODg,
COD and total solids (Table 11).
The results of the 24-hour surveys were presented graphically to
illustrate the variability of the measured parameters or qualities. These
variations are of particular significance as they may related process design
to minimize the variability of the effluent. The concentration in mg/1 or
mass kg/1000 kg hide processed for some of the parameters versus fre-
quency of occurrence (as a percent of the observations) are presented in
Figures 20 to 29. For a given level of the stated parameters, one is able
to determine the percent of time (24-hour composites) or percent of sam-
ples that were equal to or less than the stated level or the percent of sam-
ples that exceeded the stated value. It is understood that the results of
hourly composites or samples collected over shorter time intervals would
result in a greater range of values from low to high. The EPA category 1
value in terms of kg/1000 kg hide is indicated, as well as the median and
mean values. If the plotted data result in linearity on the probability plot,
the results conform to a normal rather than skewed distribution whereas
nonlinearity of the plotted data would indicate a skewed distribution of
results. The information is useful in setting guideline values.
RENDERING WASTES
A batchprocess utilizing sulfuric acid and water was employed to render
51
-------
RAW WASTEWATER BODS
No Rendering
Frequency Of Occurrence.%
90 95 98 99
1 2 5 10 3O SO 70
Figure 20. Raw wastewater BOD^ of
24 hour composites per unit weight of hide.
RAW WASTEWATER COD
No Rendering
1 2 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 21. Raw wastewater COD of
24 hour composites per unit weight of hide.
52
-------
900
800
700
600
RAW WASTE WATER SOLIDS
No Rendering
Frequency Of Occurrence,%
12 5 10
30 SO 70
9O 95 98 99
Figure 22. Raw wastewater total and volatile solids
of 24 hour composites per unit weight of hide.
200
180
160
RAW WASTEWATER SUSPENDED SOLIDS
No Rendering
; EPA Cat.I Ave. 14O
Frequency Of Occurrence,%
12 S 10
30 SO 70
90 95 98 99
Figure 23. Raw wastewater suspended solids of 24
hour composites per unit weight of hide.
53
-------
RAW WASTEWATER OIL AND GREASE
No Rendering
1 2 5 10 30 SO 70 90 95 98 99
Frequency Of Occurrence,%
Figure 24. Raw wastewater oil and grease of
24 hour composites per unit weight of hide.
m
RAW WASTEWATER TOTAL CHROMIUM
No Rendering
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
1 2 5 »0 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 25. Raw wastewater total chrome of
24 hour composites per unit weight of hide.
54
-------
120
Process Formula
o Winter
e Spring-Fall
• Summer
No Rendering
Frequency Of Occurrence.%
1 2 5 10 30 SO 70
90 95 98 99
Figure 26. Raw wastewater 6605 related to process
formula for 24 hour composites per unit weight of hide.
2,400
2,200
1,200
1,000
800
Process Formula
o Winter
e Spring- Fall
• Summer
No Rendering
Frequency Of Occurrence,^
12 5 10
3O SO 70
Figure 27. Raw wastewater BOD5 concentrations
related to process formula for 24 hour composites.
55
-------
220
200
ISO
Process Formula
o Winter
e Spring-Fall
Summer
No Rendering
EPA Category lAve. 140
Frequency Of Occurrence,%
12 5 10
30 50 70
90 95 98 99
Figure 28. Raw wastewater suspended solids related to
process formula for 24 hour composites per unit weight of hide.
Process Formula
o Winter
e Spring-Fall
• Summer
No Rendering
Frequency Of Occurrence,%
1,000
12 5 1O
30 50 70 90 95 98 9
Figure 29. Raw wastewater suspended solids concentration
related to process formula for 24 hour composites.
56
-------
the ground fleshings for the separation of oil. The remaining stick -
liquor was discharged to the wastewater treatment system and was charac-
terized as a component of the raw wastewater discharge.
The amount of fleshings processed would depend upon the relative
proportion of unfleshed (green salted) hides to prefleshed hides for the
process day. For example, a green salted hide would yield approximately
6 kg of flesh per hide; whereas a prefleshed hide would yield from 20 to
50% of that of a green salted hide.
The resulting waste characteristics of the rendering operation based
on processing 100% green salted hide are presented in Table 12.
TABLE 12. SUMMARY OF RENDERING PROCESS
AVERAGE WASTE LOAD TO THE TREATMENT PLANT
MARCH TO NOVEMBER 1974
Load, kg/1000 kg hide based on
Parameter processing 100% green salted hide
Total solids 53.5
Volatile solids 39.1
Fixed solids 14.4
Suspended solids 23.9
Volatile suspended solids 21.1
Fixed suspended solids 2.8
Total Kjeldahl nitrogen 4.1
Organic nitrogen 4.1
Ammonia nitrogen Negligible
BODs 20.5
COD 43.1
Oil and grease 15.9
SCRAP SOLID WASTES
Although the scrap loading is not generally a part of the raw wastewater
flow in that dry operations are employed for trimming, some scrap mate-
rial will enter the wastewater stream and be screened. All raw wastewater
sampling was accomplished after screening because the size of scrap would
not permit representative sampling.
Two periods of 3 and 4 weeks for October of 1973 and July of 1974
57
-------
respectively were sampled for scrap load. The results of these surveys
are summarized in Table 13. It is apparent that the waste load is small
in terms of kg of dry solids per 1000 kg of hide processed and the scrap
is disposed of as a solid waste by a private refuse contractor which does
not contribute to the wastewater flow.
TABLE 13. SCRAP WASTE CHARACTERIZATION
Item
Length of study, weeks
Barrels scrap per week
Total weight per barrel, kg (Ibs)
Density, kg/m3 (Ib/ft3)
Total volume of scrap per week,
m3 (ft3)
Dry solids, percent (range)
Dry solids per week, kg (Ibs)
Dry solids per operating day,
kg (Ibs)
Volatile solids, percent of dry
solids (range)
Dry solids, kg/1000 kg hide
Sampling Period
October 1973 July 1974
3
6 to 7
81.6 (180)
753 -961 (47 -60)
0.677 (23.9)
24 (17 to 29)
141 (312)
28.3 (62.4)
78.6(72.4-85.6)
0.4
4
13
89.8 (198)
865(54)
1.35(47.8)
24 (15 to 35)
280 (618)
55.8- (123)
81 (79.2-84.5)
0.7
Neither test period included winter hide stock, The expected scrap
loadings would be higher during the processing of winter hide stock.
PROCESS RAW WATER SUPPLY CHARACTERIZATION
The water used as process water for the tannery is obtained from the
industry's well and has the following raw water characteristics.
The water is considered to be hard and no pretreatment of the water
is provided.
58
-------
TABLE 14. TANNERY WELL WATER SUPPLY
OCTOBER 25, 1975
Constituent Concentration, mg/l"
Alkalinity 275
Calcium, Ca 95
Chloride, Q 177
Total .chrome, Cr 0.002
Nitrogen
Total Kjeldahl nitrogen 8.0
Ammonia nitrogen 5.0
Nitrate nitrogen 4.0
BODs 5.0
COD 12.0
Total phosphorus 0.04
Sulfate 190
Total solids 852
Volatile solids 144
Percent volatile solids 16.9
Total suspended solids 6
59
-------
SECTION IX
PRIMARY SETTLING
The raw wastewater from the beamhouse, tanyard, and color and fat
liquoring operations were combined and subjected to gravity separation in
two settling tanks arranged in parallel. The wastes were unequalized and
unneutralized, receiving coarse screening as the only preliminary treat-
ment. Waste biological solids from the secondary treatment system and
sludge dewatering filtrate were combined with the raw wastewater flow as
influent to the settling tanks at various times throughout the study.
The removal effectiveness of primary settling on various wastewater
characteristics were determined by the evaluation of routine 24-hour com-
posite results as well as for samples composited over shorter time inter-
vals within a 24-hour period. In the latter, sampling was conducted to
allow for the detention time in primary settling units. The results are
summarized as the primary effluent quality, percent removals of various
wastewater characteristics, and the evaluation of possible relationships
of removals with clarifier overflow rates.
PRIMARY EFFLUENT QUALITY
The results of the 24-hour composite surveys are summarized in
Tables 15 to 17 and in Figures 30 to 34.
It is apparent from Table 15 of primary effluent concentrations for all
data available for the various quality parameters measured the highly vari-
able nature of the results. The number of observations, standard deviations,
mean and median are presented for each quality parameter.
Table 16 and Figures 30 to 34 show the primary effluent concentra-
tions expressed in mg/1 for all data when no rendering operations were
employed. In addition, Figures 30 to 34 show the raw wastewater concen-
trations for the various parameters measured. The results are presented as
thenumberof measurements included in the statistic, range of values-,, median,
mean and standard deviation forBOD5, COD, total volatile solids, total sus-
pended solids, oil and grease, total chromium and total phosphor us. The
mean values when rendering is not employed are less for all quality
60
-------
TABLE 15. PRIMARY EFFLUENT CHARACTER:
24-HOUR COMPOSITES -- ALL DATA
Parameter
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
N*
42
44
44
44
32
35
27
Concentration
Range
308-1561
1490-3460
944-2412
252-1838
128-370
12.1-42.1
1.87-6.15
Median
1046
2508
1602
1097
236
21.6
3.22
» mg/1
Mean
1029
2509
1577
1133
242
23.2
3.39
Standard
Deviation
283
535
358
373
69.6
6.97
1.16
* The number of 24-hour composite results used to determine
statistics.
TABLE 16. PRIMARY EFFLUENT CHARACTER
24-HOUR COMPOSITES--ALL DATA, NO RENDERING
Parameter
N*
Concentration, mg/1
Range Median Mean Standard
Deviation
BODq
CODV
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
28
30
30
30
18
21
20
308-1286
1490-3460
944-2412
252-1838
128-282
12.4-85.7
2.05-6.15
874
2173
1328
1097
202
21.6
3.28
907
2319
1455
1091
207
28.9
3.51
235
501
335
382
50.1
19.6
1.11
* The number of 24-hour composite results used to determine
statistics.
61
-------
TABLE 17. PRIMARY EFFLUENT CHARACTERISTICS RELATED
TO PROCESS FORMULA 24-HOUR COMPOSITES
ALL DATA, NO RENDERING
Process formula
and Parameter
Winter
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
Summer
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
Spring -Fall
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
Concentration, mg/1
N*
12
12
12
12
7
8
4
8
10
10
10
4
6
9
8
8
8
8
7
7
7
Range
308-1286
1939-3460
1264-2412
589-1838
138-278
16.8-30.5
3.33-6.15
744-1078
1490-2174
944-1276
573-1384
162-282
12.1-27.6
2.05-5.60
787-1158
1895-2746
1194-1743
252-1172
128-253
12.4-25.2
2.14-3.99
Median
918
2696
1688
1341
226
21.4
4.7
832
1970
1176
1087
202
18.2
3.17
980
2235
1328
892
164
18.6
2.96
Mean Standard
Deviation
894
2692
1752
1320
230
22.5
4.72
855
1916
1161
1062
212
18.6
3.39
978
2262
1378
781
182
18.1
2.96
326
519
298
349
50.1
4.47
1.17
102
199
104
237
50.3
5.58
1.03
166
302
173
371
44.3
4.45
0.65
The number of 24-hour composite results to determine statistics.
62
-------
2,000
1,750
1,500
1,250
1,000
750
5OO
250
0
*
- •
- 4
t
l(
:l
\\
g
3=:
BE:;;;
:::;EEEEE:;;;;;;I ;1;;;;::::
Treatment Prtu^oce
• RawWastewater
e Primary Effluent
I No Rendering
;=;;:— = ===;;;;;;; Jiiii ih;;;;;
;;;;:==EEEE:;';ii:!!!:;;;;;:;:;;i;
;;lEEEE!!;:;;;;:!;;!;;;;;;iiiii'i
::::: :::: i, : : ± •••
;; •':=. Frequency Of G
liiiiirfiiiEii
J;:: :::::"jl|:::|:::: = = =
::|:||!!!!::SSi:~~
ii b' — f=
;:: ^ijiiit-'I^^EEEEEEi
;;; ;!!i;!!!!:;li|[Eiil
.-.! !:: : Median 874 -
Occurrence, % :=
i
= .
n:
s
:±
it-
±t:
12 5 10
30 SO 70
90 95 98 99
Figure 30. Raw wastewater and primary effluent
concentration for 24 hour composites.
Treatment Process
• Raw Wastewater
e Primary Effluent
No. Rendering
Frequency Of Occurrence,%
30 SO 70
90 95 98 99
12 5 10
Figure 31. Raw wastewater and primary effluent COD
concentrations for 24 hour composites.
63
-------
Treatment Process
• RawWastewater
e Primary Effluent
Frequency Of Occurrence,%
1 2 5 10
30 SO 70
90 95 98 99
Figure 32. Raw wastewater and primary effluent
suspended solids concentrations for 24 hour composites.
800
700
600
500
400
300
200
100
J
— (-
- *
]
~
~
:<
- •
' •
; •
— ,
— r -^
A
J=E = ii
SH!
SEE:;:
IQ
jttffiT
1_ ^
Tr<
•
••
t:::: —
'!;:'=;
satment Process
Raw Wastewater
Primary Effluent
No Rendering
iiliiliijij!!
nrmi™ nnwitiin'
= r!l::::!::I I ::::::: :1 ::::
=| Frequency Of
: + :f*^S;:::::^ = =
!;;:;p;:::|l^|
^Tf:t -Til ^1 - +f -M
..I...1. j.,,1 nr--?f • | M -|—
|tji|;! M«di»nS9S ,:E =
; ?. .: Wain 601 ::
!::::::::::jt • frit
::::|::;:;;; |pgEE=
y:||:::;j:.|Sl|i::5= =
::^I-!-::'5iiJg-ffEE-
i Sin ""•«''••' 202 -
tf' p::::: Mean 2O7 ;-
Occurrence,% ==-
^
- -L.
±
1 2 5 10 30 SO 70 90 95 98 99
Figure 33. Raw wastewater and primary effluent oil
and grease concentrations for 24 hour composites.
64
-------
Treatment Process
• Raw Wastewater
Primary Effluent
No Rendering
10
1 2
Frequency Of Occurrence,%
5H
5 10 30 50 70 90 95 98 99
Figure 34. Raw wastewater and primary effluent total chrome
concentrations for 24 hour composites.
65
-------
parameters except for total chrome and total phosphorus than when all
data are included as presented in Table 15. These differences are not
significant for the error variances associated with the results.
A similar summary of results are presented in Table 17 for primary
effluent when the three process formulas were employed. Also, these
results represent sampling during periods when rendering was not employed.
With the exception of BOD for the spring-fall formula, all the mean values
for the winter formula are higher than for summer and spring-fall formulas.
Although these differences are not statistically significant, the higher results
for winter hides may be expected on the basis of hair length and the relative
greater amounts of associated pollutional material attached to the hair for
winter hides.
PRIMARY SETTLING EFFICIENCY
On several occasions the performance of the primary settling tanks
was evaluated by taking effluent and influent 4-hour composite samples with
the effluent composite samples lagging by 2 hours to allow for tank deten-
tion times. This was to assess the variation of the influent and effluent for
the quality parameters measured regarding thepercent of the total daily contri-
bution for each 4-hour composite and the removal efficiencies experienced.
The results of two surveys are presented in Table 18 and Table 19 for
August 8-9, 1972, and September 25-26, 1972, respectively. Figures 35
to 37 show the influent-effluent results for suspended solids, chemical
oxygen demand, and total chrome for the August 8-9 survey. Based on
the results of the 4-hour composites and the influent flow for the composite
interval, the variations for each quality parameter aiepresented as mass
rates in pounds per hour. The percent removal of a given constitutent
varies markedly throughout a 24-hour period.
The influent variation reflects the practices of batch discharges from
various departments within the tannery depending upon the quality parame-
ters observed. For example, the high contribution of suspended solids in
the raw wastewater for midday through early afternoon reflects the batch
discharges from the beamhouse operations, similarly one may use the total
chrome values to reflect the periods for principal discharges from the tan-
yard (Figures 36 and 37). The primary effluent variation is less praioua^ed)
as one may expect but the variation in the effluent parallels influent quality
with higher values noted in the effluent when high values of a given quality
parameter are present in the influent.
Table 18 presents the percent of total mass for each 4-hour influent
composite and each quality parameter. Although the variations from hour
66
-------
TABLE 18. PRIMARY SETTLING EFFICIENCY, AUGUST 8-9, 1972'
Time
7 a.m.
9 a.m.
11 a.m.
1 p.m.
3 p. m.
5 p. m.
7 p.m.
9 p.m.
11 p.m.
1 a.m.
3 a.m.
5 a. m.
24 -hour
Sample Raw wasj,e Total solids
to 11 a.m.
to 1 p.m.
to 3 p.m.
to 5 p.m.
to 7 p.m.
to 9 p.m.
to 11 p.m.
to 1 a.m.
to 3 a.m.
to 5 a.m.
to 7 a.m.
to 9 a.m.
composite
flow nr
Raw 799
Primary
% Removal
Raw 704
Primary
% Removal
Raw 496
Primary
% Removal
Raw 473
Primary
% Removal
Raw 397
Primary
% Removal
Raw 477
Primary
% Removal
Raw 3346
Primary
% Removal
Total suspended
solids COD Total
' Cone. Percent Cone. Percent
mg/1 of total* mg/1 of total
6240 17.8
7300
+17
11680 29.1
9110
22
9390 16.1
8140
13
6510 10.6
6180
5.1
7350 9.9
7400
+ 0.7
10040 16. 5
8680
13
8565 100
7879
8
1040 9.7
820
21
5400 44. 2
1040
81
3110 17.5
1000
68
1060 5. 7
730
31
2120 9.4
786
63
2490 13. 5
580
77
2606 100
826
68
Cone.
mg/1
2070
1410
32
4290
2580
40
4190
2340
44
1700
1190
30
2240
1415
37
3360
1730
48
3005
1774
41
Percent Cone.
of total mg/1
16.8 17.0
12.5
26
30.5 9.0
4.7
48
20.5 37.5
12.7
66
7.9 56.4
17
70
8.6 69
18.5
73
15.7 28.5
11.0
61
100 31.4
12.1
61
chrome
Percent
of total
13.2
6.1
17.5
25.1
25.3
12.8
100
*Percent of total is based on concentration and flow or mass of the stated quality parameter.
-------
TABLE 19. PRIMARY SETTLING EFFICIENCY, SEPTEMBER 25-26, 1972
Waste
Time Sample flow, m
8 a.m. to noon
8a.m. Co noon
10 a. m. to 2 •-. m.
Noon co 8 p.m.
Noon co 8 p. m.
2 p.m. co 10 p. m.
8 p.m. co 2 a. m.
8 p.m. co 2 a.m.
10 p. m. co 4 a. m.
2 a. m. co 8 a. m.
2a.m. co 8 a . tn .
4 a.m. co 10 a.m.
Raw
Wasce si.
Primary
Raw
Waste si.
Primary
Raw
Waste si.
Primary
Raw
Wasce si.
Primary
Raw wasce composice
Influenc composice
Primary effluenc composite
Percenc removal
559
50
1156
100
550
75
723
75
2989
BOD.s
Cone. Percent
mg/1 of total
1160 14.3
528
852 21.1
2130 54.2
474
998 43.5
573 6.9
471
452 9.2
1550 24.6
457
705 26.2
1522
1426
795
48.1
COD
Cone. Percent
mg/1 of total
2445
1410
1750
6260
1430
2500
1270
1310
1070
3490
1300
1680
3957
3720
1895
49.0
11.6
18.3
61.2
46.0
5.9
9.2
21.3
26.4
Total siBp. sol.
Cone. Percent
mg/1 of total
1520 15.4
916
200 13.2
2515 52.6
830
320 36.9
546 5. 4
616
304 16.4
2035 26.6
624
340 33.5
1850
1748
300
84.0
Susp. vol. solids
Cone. Percent
mg/1 of total
775 10.0
448
48 7.9
1960 52.1
416
120 34.9
377 4.8
300
136 18.5
2000 33.2
280
156 38.7
1456
1356
119
91.7
Total chromium Total calcium
Cone. Percent
mg/1 of total
21.5 12.9
17.2
8.8 7.9
17.0 21.0
18.8
13.3 21.2
59.0 34.8
12.0
47.0 34.9
40.5 31.4
15.4
26.5 36.0
31.2
30.0
21.7
31.9
Cone. Percent
mg/1 of total
147
192
195
445
193
311
152
180
170
471
171
198
342
327
232
29. 2
8.1
16.6
50.4
46.4
8.2
11.8
33.3
25.2
-------
1600
1400
1200
1000
12 123456789 10 11 12 123456789 10 11 12
MID
AM
N
MID
Figure 35. Primary sedimentation COD performance: 4 hour composites.
69
-------
2000
1800
1600
1400 --.=
1200 -<5
1000
800
600
400
200
112*3456789 10 11 12 123466789 10 11 »
MID
AM
N
PM
MID
Figure 36. Primary sedimentation suspended soilds
performance: 4 hour composites.
70
-------
12 1 2 3 4 5
7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
MID AM N PM
Figure 37. Primary sedimentation total chrome
performance: 4 hour composites.
MID
71
-------
to hour or for shorter periods of time would be more pronounced, the 4-
hour interval dampens the variation as would the resident time of the waste-
water in the settling units. The percent total solids removals vary from
increases in effluent concentrations to reductions with an overall removal
for the 24-hour period of only 8 percent. The high dissolved solids and
the variation thereof as part of the total solids accounts for this apparent
anomaly. The removal of suspended solids is more indicative of the
portion of total solids amenable to gravity separation with removals ranging
from 21 to 81 percent for the 4-hour composites and an overall removal
of 68 percent.
The results of the September 25-26, 1972, primary settlirg survey
are presented in Table 19 with the compositing intervals for influent and
effluent indicated. The results also reflect the influence of wasting biolo-
gical or secondary sludge to the primary settling tanks. With few excep-
tions the concentrations of the wasted biological solids stream for the var-
ious quality parameters and composites were lower than for the corres-
ponding raw wastewater qualities. The raw wastewater flow was 2989
m^/d and the waste secondary sludge was 300 m^/d or approximately
10% of raw wastewater contribution. The influent composites for the 24-
hour period compared with the primary effluent composites were used to
determine the percent removals for the various parameters presented
in Table 19. The BOD5,suspended volatile solids, and total calcium were
included as the measured quality parameters and the relative contribution
or percent of total contribution on a mass basis for the composite period
for each parameter and for both raw wastewater and primary effluent are
presented also.
The results show, on this date, that high removals of suspended and
volatile suspended solids were experienced at 84 and 92 percent respec-
tively, whereas BOD and COD removals were 48 and 49 percent. It is
apparent that although high removals of suspended solids were experi-
enced, the removal of total calcium was only 29% indicating a high frac-
tion of dissolved or particle sizes too small to be affected by gravity
separation. Part of this calcium is indigenous to the carriage water or
process water supply.
Additional one-day surveys were conducted to evaluate theperformance
of the primary settling tanks and the results for the 24-hour composite, for
both raw and primary effluents, flows and overflow rates are presented in
Table 20. A summary of the percent removal results are presented at the
bottom of the table showing the number of values used, range, mean and
standard deviation. In addition, all the raw wastewater and primary
effluent data for the 24-hour composite surveys and corresponding percent
removals are presented in Table 21. The data were grouped according to
72
-------
TABLE 20. INTENSIVE PRIMARY SETTLING SURVEYS
Raw
Date wastewater
flow mgd
Feb. 23-24, '72 0.736
Raw
Primary effluent
Percent removal +
Mar. 13-14, '72 0.949
Raw
Primary effluent
Percent removal
Aug. 8-9, '72 0.884
Raw
Primary effluent
Percent removal
Sept. 25-26, '72 0.869
Raw
Primary effluent
Percent removal
Dec. 11-12, '72 0.800
Raw
Primary effluent
Percent removal
Jan. 16-17, '73 0.718
Raw
Primary effluent
Percent removal
May 8-9, '73 0.742
Raw
Primary effluent
Percent removal
Overflow
rate* BOD5
gal/d/ft2
351
1122
308
72.5
459
1411
929
34.2
421
423
1522
795
47.8
402
1174
711
39.4
330
1273
856
32.8
417
1478
703
52.4
COD
4510
2680
40.
3567
2173
39.
3005
1774
41.
3957
1895
52.
3169
2098
33.
4280
2712
36.
4308
2233
48.
Total
Total volatile
solids solids
6
1
0
1
8
6
2
12030
9610
20.1
10020
8039
19.8
8565
7879
8.0
9512
7482
21.3
7428
7422
0.08
11102
9429
15.1
3062
1682
45.1
2436
1417
41.8
2628
1194
54.6
1800
1264
29.8
2349
1679
28.5
Total
suspended
solids
5200
1330
74.4
2308
992
57.0
2606
826
68.3
1850
300
83.8
1468
589
59.9
1721
717
58.3
2128
1057
50.3
Volatile
suspended
solids
2700
765
71.7
1436
534
62.8
1456
119
91.8
956
271
71.6
938
224
76.1
1334
559
58.1
Percent secondary waste
solids to raw wastewater solids
Total Volatile
Total suspended suspended
chrome solids solids
58
21.
63.
31.
12.
61.
31.
21.
30.
43.
21.
51.
65.
24.
62.
2
4
5.67
4
1
5
4.06 2.49
2
7
4
5
1
5
9
5
8
1.50 1.75
(continued)
-------
TABLE 20. (CONTINUED)
Percent secondary waste
solids to raw wastewater solids
Raw Overflow
Date wastewater rate*
flow mgd gal/d/ft2
June 6-7, '73 0.697 393
Raw
Primary effluent
Percent removal
June 12-13, '73 0.779 420
Raw
Primary effluent
Percent removal
Percent removal summary
N, Number of values
Range
Mean
Standard deviation
BODs
1653
975
41.0
1635
799
51.1
8
32.8-
72.5
46.4
12.8
COD
4438
2192
50.6
4117
2060
50.0
9
33.8-
52.1
43.6 ,
6.75
Total
solids
10063
8995
10.6
9123
8710
4.53
8
0.08-
21.3
, 12.4
7.90
Total
volatile
solids
2614
1320
49.5
2215
1160
47.6
7
28.5-
54.6
42.4
Total
suspended
solids
2405
1108
53.9
1882
1080
42.6
9
42.6-
83.8
60.9
9.88 12.6
Volatile
suspended
solids
1575
520
67.0
1287
464
63.9
8
58.1-
91.8
70.4
10.4
Total
Total suspended
chrome solids
14.3
15.5
5
30.4-
63.4
53.9
14.0
Volatile
suspended
solids
11.2
10.1
* Overflow rate represents primary effluent flow rate which is equivalent to raw wastewater inflow plus waste activated sludge plus
filtrate from the solids dewatering less primary sludge withdrawal.
+ All percent removals represent raw wastewater influent to primary effluent.
-------
TABLE 21. SUMMARY OF PRIMARY REMOVAL BY SETTLING
Mean concentration, mg/1
Identification
Project data --all
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
Project data- -all — no
rendering
BOD5
COD
Total volatile solids
Total suspended sol.
Oil and grease
Total chromium
Total phosphorus
Process formula — no
rendering - -winter
BOD5
COD
Total volatile solids
Total suspended sol.
Process formula — no
render ing --summer
BOD5
COD
Total volatile solids
Total suspended sol.
Process formula --no
rendering - -spring -fall
BOD
COD5
Total volatile solids
Total suspended sol.
Raw
1656
4523
2824
2730
763
50.6
5.96
1501
4284
2570
2579
601
46.8
7.43
1514
4659
2926
2991
1424
3730
2100
2155
1558
4356
2625
2442
Primary
effluent
1029
.2509
1577
1133
242
23.2
3.39
907
2319
1455
1091
207
28.9
3.51
894
2692
1752
1320
855
1916
1161
1062
978
2262
1378
781
' Percent
removal
37.9
44.5
44.2
58.5
68.3
54.2
43.1
39.6
45.9
43.4
57.7
65.6
38.2
52.8
41.0
42.2
40.1
55.9
40.0
48.6
44. 7
50.7
37.2
48.1
47.5
68.0
75
-------
process formula, all data, and as all data when rendering was not employed.
The only major differences in percent removal between the various group-
ings of 24-hour composite data occur for the parameters of total chromium
and total phosphorus for 'project data all' and 'project data all no rendering',
with the lower removals of chrome and higher removals of phosphorus for
the 'project data all no rendering'.
PRIMARY REMOVALS VERSUS SURFACE SETTLING KATES
(OVERFLOW RATES)
Linear regression and correlation analyses of the data were performed
to determine if a relationship between percent removal or primary effluent
concentrations and clarifier overflow rate existed. Generally, one may
expect lower removals with higher overflow rates for certain of the quality
parameters measured and particularly sofor those parameters representing
particulate matter large enough to be affected by gravitational forces. The
parameter suspended solids which represents the non-filterable residue, is
frequently used to evaluate the performance of settling units. Only a portion
of the suspended solids are settleable which would be subject to separation
in the primary settling units.
The results for percent removals for BOD and total suspended solids
presented in Table 20 were plotted against overflow rate in gpd/ft2 to deter-
mine the extent to which overflow rate may affect removal for the limited
range of overflow rates experienced. These results are plotted on Figure
38. Linear regression correlation statistics, based on the intensive pri-
mary settling surveys (Table 20), were calculated for the BOD and total
suspended solids removals separately, both of which indicated that there
was a decrease in removal with an increase in overflow rate, however,
the correlation coefficients, were only -0.213 and -0.132 for per cent BOD
and total suspended solids removals respectively (Table 22). The range
of overflow rates were from 13.4 to 18.7 m3d/m2 (330 to 459 gal d/ft^)
based on primary effluent flows which reflected the raw wastewater flow
adjustments for primary sludge pumping and solids dewatering filtrate
return.
Additional linear regression and correlation analyses were performed
for the routine 24-hour composite data which permitted the evaluation to be
made over a wider range of overflow rates 13.4 to 40.9 m3d/m2 (330 to
1003 gal d/ft2) and a wide range of percent removals and primary effluent
concentrations. Also, 45 separate removals and overflow rates were avail-
able for the BOD evaluations and 48 available for the TSS evaluations.
The results presented in Table 22 show lack of correlation between percent
removals and overflow rates for both BOD and TSS with correlation coeffi-
cients of -0.139 and 0.124 respectively. The primary effluent BOD
76
-------
100
90_
80
70
1
LU60
QC
50
40
30
• TOTAL SUSPENDED SOLIDS
o BOD
+ TOTAL SUSPENDED SOLIDS
WHEN SECONDARY
SLUDGE WASTED TO PRIMARY
-§- BOD WHEN SECONDARY
SLUDGE WASTED TO PRIMARY
I I I I I I I I I I I I « I I I I I I I I I I » I I I
300
400
500
600
OVERFLOW RATE, gpd /ft (Values x 0.0407= md/m )
Figure 38. Primary settling percent removal versus overflow rate
based on 24-hour composites.
77
-------
TABLE 22. SUMMARY OF LINEAR REGRESSION-CORRELATION ANALYSES FOR
PRIMARY SETTLING PERFORMANCE
Data Source
Linear regression equation
Correlation
coefficient (r)
Table 20
Table 20
24-Hour composites,
all data
24-Hour composites,
all data
24-Hour composites,
all data
% BODr = -0.0659V0+ 72.74
Range % BOD = 32.8 to 72.5 Range Vo = 330 to 459
% TSS = -0.0423V0 + 77.94
Range % TSSr = 42.6 to 83.8 Range VQ = 330 to 459
% BOD = -0.00801V +41.66
Range % BODr = 13.2 to 72.5 Range Vo - 330 to 1003
BOD-
'PE
Range BODpg = 308 to 1561
= 0.516V0 + 733.0
Range Vo = 330 to 1003
24-Hour composites,
all data
% TSSr = 0.00925V0 + 50.23
Range % TSSr = 10.9 to 89.8 Range VQ = 330 to 1003
TSSpE = 0. 274V0 + 995. 2
Range TSSpE = 252 to 2108 Range Vo = 330 to 1003
where:
(BOD influent-BOD effluent)
% BODr = ( BOD influent )
(TSS influent-TSS effluent)
% TSSr = ( TSS influent 5
BODpE = BOD Primary Effluent, mg/1
TSSPE = TSS Primary Effluent, mg/1
V0 = Overflow rate, gal/d/ft2
100
100
-0.213
-0.132
-0.139
0.404
0.124
0.151
-------
concentrations appeared to correlate with overflow rates to a greater extent
than for TSS concentrations as evidenced by the correlation coefficients of
0.404 and 0.151 respectively. The only inconsistent result obtained from
this analysis was the apparent increase in percent TSS removal with an
increase in overflow rate for the range of overflow rates experienced. The
data were not uniformly distributed over the range of overflow rates exper-
ienced with a preponderance of data in the 12.2 to 18.3 m^d/m^ (300 to 450
gal d/ft^) range when two primary clarifiers were in operation. The high
range of overflow rates occurred when only one of the two clarifiers were
in operation.
The results of the primary settling analysis indicate the highly vari-
able nature of primary tank performance for the treatment of this waste-
water. This variability was evident both for removals over 4-hour com-
positing periods within a 24-hour period as well as for comparison of
results based on 24-hour composited samples. The relationship between
percent removal clarifier overflow rates show a lack of correlation with
no apparent indication of the overflow rate best suited for the design of
primary -clarifiers. The percent removals obtained by primary clarifi-
cation for overflow rates primarily in the range of 12 to 18 m^d/m^
(300 to 450 gal d/ft^) is best summarized in Table 21 wherein the per-
cent removals for the various parameters with the exception of total
chrome are essentially the same when all 24-hour composite data are
compared with all 24-hour composite data when rendering was not prac-
ticed. The removals obtained were 39% BOD, 45% COD, 58% total sus-
pended solids, 67% oil and grease, and 43% for total volatile solids.
Regarding total chrome, the removals were 54% when flesh rendering
was practiced, whereas, only 38% removals were obtained when all pro-
ject were included in the summary. It would appear that the chrome
is somehow associated with the particulate fractions that are subject to
separation to a greater extent when rendering is employed.
79
-------
SECTION X
LAGOON ANALYSIS
The primary objective of the lagoon studies was to evaluate the effec-
tiveness of this biological process in treating unneutralized, unequalized,
presettled tannery wastewaters. Effectiveness was defined in terms of
meeting Best Practicable Effluent Limitations (BPT) and Best Available
Effluent Limitations (BAT) requirements as established by the U.S. Envi-
ronmental Protection Agency and as set forth in the Development.Document
for Effluent Limitation Guidelines and New'Source Performance Standards
for the Leather Tanning and Finishing Point Source Category (3). The BPT
and BAT guidelines from this source are given in Tables 23 and 24. These
effluent guidelines have been remanded to the court for revision, however,
they serve for purposes of comparison for treatment performance in this
study. In addition, effective treatment was evaluated in terms of process
stability and operation maintenance. Since wide variations exist in chrome
tannery wastewaters, no attempt was made to establish a design criteria
for the industry, but rather to demonstrate whether such a process with
known loading relationships would achieve the desired level of treatment
within the range of design constraints normally employed in wastewater
treatment practice.
In designing the full-scale demonstration plant at the S. B. Foot Tan-
ning Company, design data was taken from pilot plant studies conducted in
1966 (1). Sufficient flexibility was built into the design of the lagoon sys-
tems so that a wide range of wastewater loadings could be evaluated. As
noted earlier, substantial changes in the in-plant tannery processes limited
this flexibility to some extent.
Sufficient data are available in the literature to suggest that aerated
lagoons operated at low solids concentrations are highly temperature sensi-
tive. Since this facility is located in a region of the country where wide
fluctuations in ambient air temperature occur (average monthly tempera-
ture range -14° to 25° C), it was determined that the lagoons should be
provided with recirculation capability to that high solids could be main -
tained during the cold winter months. In addition, piping was provided so
that the four lagoons could be operated in a number of different flow pat -
terns with independent clarification and sludge return. Thus two different
80
-------
TABLE 23. BEST PRACTICABLE EFFLUENT LIMITATIONS
(CONTROL TECHNOLOGY CURRENTLY AVAILABLE)
MAXIMUM THIRTY DAY AVERAGE, 7/1/77
Parameter* Subcategoryf
I 234 5
BODr
Total
Oil &
TSS
chromium
grease
4.0
0.10
0.75
5.0
4.
0.
0.
5.
6
12
90
8
3.
0.
0.
4.
8
05
75
8
1.
0.
0.
2.
6
10
25
0
4.
0.
0.
6.
8
06
90
0
2.8
0.10
0.35
3.4
* For all subcategories pH should be between 6.0 and 9.0 at any time.
+ Classification related to in-plant processes employed with all values
reported in kg/1000 kg hide.
TABLE 24. BEST AVAILABLE EFFLUENT LIMITATIONS
(TECHNOLOGY ECONOMICALLY ACHIEVEABLE), 7/1/83
Parameter* Subcategoryf
~I 2 3 1 5
BOD5
Total chromium
Oil & grease
Sulfide
TSS
TKN
1.40
0.05
0.53
0.005
1.5
0.27
1.60
0.06
0.63
0.006
1.8
0.32
1.30
0.05
0.50
0.005
1.4
0.25
0.50
0.02
0.24
0.002
0.6
0.10
1.60
0.06
0.63
0.006
1.8
0.31
0.70
0.03
0.34
0.003
0.8
0.14
* For all subcategories pH should be between 6.0 and 9.0 at any time.
For all subcategories Most Probable Number (MPN) of Fecal Coliform
should not exceed 400 counts per 100 ml.
+ Classification related to in-plant processes employed with all values
reported in kg/1000 kg hide.
81
-------
configurations could be examined simultaneously. Also chemical addition
facilities were available to provide pretreatment or post-treatment of the
wastewater.
LAGOON OPERATING CONDITIONS AND PROCEDURES
A number of process flowsheets were initially proposed for study of
the lagoon system. Preliminary investigations on the lagoons were started
in the fall of 1971. As indicated earlier in this report, difficulties were
encountered with the aeration equipment. It was late in the summer of
1973 before the appropriate aeration facilities were installed and operated.
Although some lagoon configurations were studied prior to that time, mean-
ingful data was not available until the fall of 1973. A listing of the lagoon
conditions are presented in Table 25. Four other conditions which were
operated between the fall of 1973 and early spring of 1974 are not listed
nor were they analyzed as a result of mechanical failures.
Sampling for the lagoon studies was accomplished with automatic flow
proportioned samplers on the primary sedimentation effluent and secondary
clarifier effluent, or by grab sampling of lagoon effluent proportioned to
flow. The details of the sampling procedures are discussed in Appendix A.
It should be emphasized, however, that where two lagoon configuration flow
sheets employed the same final clarifier, it was necessary to grab compo-
sites of treated lagoon wastewater effluent before discharge to the clarifier.
Samples were grabbed and composited proportionally to flow over a 12- or
24-hour period. Settling of the composite was then performed in the labo-
ratory using a 1000 ml cylinder and all settled effluents were then analyzed.
Samples settled in this manner were denoted on the data tables.
Effluent analyses included RQD$; COD; solids, total and dissolved;
chrome, total and dissolved; oil and grease; all nitrogen; total, ortho and
suspended phosphorus; total, suspended and dissolved calcium; sulfide,
sulfate, chloride and alkalinity. Analytical procedures used are outlined
in Appendix A. Measurements in the lagoon included continuous recording
of pH, temperature and dissolved oxygen, and periodic determinations of
lagoon mixed liquor solids, oxygen uptake rates, and accumulated sludge
deposits. Recycle flow rates and sludge wasting rates were also recorded.
LAGOON PERFORMANCE
Analysis of the data from,the lagoon study was performed for each
condition over a period of time selected to be representative for that condi-
tion. An allowance of about two sludge retention periods (estimated) was
normally made. All data collected after that time interval was then
82
-------
TABLE 25. LAGOON EXPERIMENTAL DESIGN
Condition
1
2
3
4
5
6
7
8
9
10
11
12
132E
145
151
15A
Dates
8/7/73-9/17/73
9/17/73-10/29/73
10/29/73-2/18/74
2/6/74-3/25/74
2/6/74-3/25/74
4/1/74-5/13/74
4/8/74-5/13/74
5/13/74-6/17/74
5/13/74-6/17/74
7/8/74-8/12/74
7/8/74-8/12/74
8/12/74-9/9/74
9/9/74-11/1/74
9/9/74-11/1/74
9/9/74-11/1/74
11/1/74-1/2/75
Mode
Single
Single
Single
Single
Single
Single
Single
Single
Series
Single
Series
Series
Single
Single
Single
Single
P addition
mg/lP
No
No
No
Yes
Yes -10
Yes -10
Yes-10
No
Yes-10
Yes-10
Yes-10
No±
No
Yes -7
Yes -7
Yes -7
Recycle
No
No
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Na
Yes
No
No
Yes
Yes
Percent
Flow*
5
10
25
25
75
50
50
50
50
33.3
33.3
33.3
30
30
30
33
Lagoon
No.t
1
1 '
3
3
2
1
4
4
1,3
4
1,3
1,3
1
3
4
4
* Percent of total tannery flow to that lagoon system.
+ See Figure 4.
± Phosphorus carryover in sludge from condition 11 was likely.
I Chemical additions were practiced during these condition as follows:
Condition 13: FeClg added to raw wastewater, CO2 added to raw wastewater;
Condition 14: FeC^ added to secondary effluent.
-------
used except in the case of the winter condition 3 when aerator freeze-up
occurred.
The results of the operational conditions for the 15 lagoon condi-
tions analyzed appear in Table 26. The design parameters employed
in this study were F/M, SQ, and 0 defined as follows:
kg BOD applied/d
ition
\r/"% 11 irv\ d
(days)
F/M = MLVSS under aeration
volume
0 = hydraulic retention time = flow rate
volume
g/1 MLVSS x flow rate
(days)
The use of solids retention time was not possible owing to the difficulties
in obtaining satisfactory solid balances on the lagoon systems. This will
be discussed more fully elsewhere.
The values estimated for these design parameters and the percent
reduction calculated were based on primary effluent data for process
days only. Very little data was collected over the weekends when only
partial processing of hides was undertaken. The best weekend data
was collected during 1974 after rendering was instituted. Based on an
analysis of weekend BODc data, it was estimated that the average daily
waste loading for a 7-day week versus an average daily loading for a
process week (used in all subsequent calculations) would be 86 percent
of the daily value for the process week. The 86 percent value repre-
sented the period prior to the employment of rendering operations
(before March, 1974, and for conditions 1, 2, and 3), and a value of
81 percent was obtained during the period when rendering was employed
(conditions 4 - ISA). Thus for the F/M ratios reported herein they
would be reduced 86 to 81 percent of those values reported if based on
a 7-day week. Corresponding reductions would be made in the
percent removal values as well.
Biochemical Oxygen Demand
Analysis of all 15 conditions with respect to BOD removal, both
total and soluble fractions, appear in Table 27. Soluble BOD values
were estimated by performing a least squares linear regression on total
BOD versus volatile suspended solids (VSS) for the effluent. The soluble
BOD 5 value obtained where the line of best fit intercepted the y-axis or
at zero VSS. One graphical example of this estimating procedure
84
-------
TABLE 26. LOADING CONDITIONS OF LAGOON SYSTEMS*
00
tn
Condition
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
15AJ
Dates+
8/7/73-9/9/73
10/5/73-10/29/73
11/16/73-12/31/73
a/8/74-3/24/74
3/8/74-3/24/74
4/19/74-5/13/74
4/19/74-5/13/74
5/21/74-6/17/74
5/21/74-6/17/74
7/26/74-8/11/74
7/26/74-8/11/74
8/30/74-9/9/74
9/20/74-11/1/74
9/26/74-11/1/74
9/27/74-11/1/74
11/1/74-1/2/75
Lagoon
Mean
20
13
4.4
7
11
16
16
19
18
21
21
15
14
14
13
8
Temp °C
Range
16-26
10-16
0-14
6-12
8-14
14-19
13-19
18-24
16-24
19-26
18-24
11-20
9-20
7-19
8-17
4-16
F/M
kg/kg
0.13
0.14
0.15
0.16
0.41
0.21
0.89
0.87-
0.23
0.10
0.26
0.05
0.34
0.34
0.12
0.09
s e
g/1 day
12.30
9.90
4.61
4.87
3.21
7.76
2.51
1.38
4.79
15.17
9.80
20.50
6.48
6,68
13.41
7.96
0
days
50.0
21.0
3.3
2.5
1.0
2.1
2.7
2,2
4.0
3.0
9.8
7.0
5.5
5.6
3.8
2.1
MLVSS
mg/1
246
474
1396
1973
3248
3733
921
644
1202
5127 -
1002
2980
1179
1187
3507
3875
Comment
Low D.O.
T rvttr r"\ /~*\
JLOW D. U.
T S +
L-i « iJ * -4-
FeCl3
L.S.
L.S.
*A11 values represent averages.
+Dates through which lagoon performance was estimated.
±L.S.'-- Lab Settled.
^Estimated values after project period.
-------
TABLE 27. LAGOON PERFORMANCE--EFFLUENT
Condition
1
2
3
4
5
6
7
8
9
10
11
12
13
13A±
14
15
ISA
BOD5
mg/1
37
51
194
171
397
171
489
293
56
169
62
8.8
67
182
107
129
34
BOD5
Removal
percent
96
93
80
85
76
85
70
70
94
87
96
99
95
85
91
88
97
Sdlublef ^005
6005 Suspended fraction
mg/1 mg BODq/mg VSS
146
320
50.0
70.4
18.9
79.8
38.4
5.8
41.8
57.1
56.9
0.30
0.51
2.40
0.82
0.54
0.65
0.33
0.36
0.54
0.26
0.31
* All values are average.
+ See, for example, Figure 37; linear least squares estimate.
± Without FeCl3 coagulation of final effluent.
86
-------
appears in Figure 39. In several instances, insufficient data were avail-
able to produce a meaningful regression analysis. The slope of the least
squares line of best fit, expressed as mg BOD/mgVSS, is also presented
in Table 27. Note that there is a trend of increased contribution of BOD
by the volatile solids fraction as the F/M ratio increases. Oxygen defi-
ciencies in lagoons (conditions 6 and 10) also produced higher BOD per
weight of VSS.
The results of the BOD analysis are presented in Figure 40 wherein
the percent removal of BOD as a function of F/M ratios is shown. Regres-
sion lines are shown for percent removal as a function of F/M ratio for
results representing temperatures less than 11°C and for the results of the
temperature range 15-21°C, both for F/M ratios ranging from 0.05 to 0.4.
It is evident that the BOD removal results are temperature dependent with
lower removals at the lower temperatures, particularly at the higher F/M
ratios which suggests that low F/M ratios be employed during winter condi-
tions. Also it can be noted the influence of D.O. deficiency on lagoon per-
formance as represented by conditions 6 and 10. The importance of chemi-
cal coagulation of the lagoon effluent is apparent from the condition 13 (see
also condition 13A--laboratory settled without FeClg addition). Finally,
the addition of phosphorus as an essential nutrient in the biological stabili-
zation of tannery waste is not clearly delineated in this analysis. The pri-
mary effluent produced a BOD:N:P ratio; averaging 100:24:0.30 suggesting
a phosphorus deficiency. Addition of phosphoric acid for selected lagoon
conditions in the amount of 10 mg/1 (7 mg/1 was added to lagoons under
conditions 14 and 15) indicated a higher oxygen uptake rate over lagoons
without phosphorus addition. This increase, in several cases, produced
an oxygen deficiency, yet examination of the data did not clearly show a
demonstratable increase in performance. Since environmental conditions
varied so much from condition to condition and since there was no effective
way to establish an absolute control, it is likely that the effect of phos-
phorus addition was obscured.
Data on the continuation of condition 15 beyond the project period into
the winter of 1974 are also plotted on Figure 40 to indicate the effective-
ness of this particular flowsheet through the colder winter months. Although
colder temperatures were experienced for condition 15A, than for condition
15, the BODc removals were higher, however, the F/M ratio was lower for
the lower temperature condition 15A. Freeze-up of some aerators by mid-
January occurred bringing about a very substantial deterioration of the pro-
cess. Similar problems occurred in the winter of 1973. Further discus-
sion of this operational problem will be presented later.
For a more detailed analysis of lagoon performance, several
lagoon conditions were selected. These conditions were used because:
87
-------
400-
«V 300
o>
E
i
m
Q
O
m
200
100
Condition 13
4l.8mg/fo
0 50 100 150 200 250 300
VSS - mg/-P
Figure 39. Lagoon performance--correlation of
effluent BOD 5 and VSS concentrations.
%R (l5-2l°c=93,6 + 2.29 F/m
100
90
0)
u
»_
0)
0.
I 80
UJ
oc.
70
m
O
O 60
CD
50
TEMR
II-I4°C A
I5-2I°C D
o«P
%R(
-------
first, there was sufficient data collected to provide a meaningful statis-
tical analysis; second, they represented a flowsheet considered to be
more acceptable for design than others; and, third, they provided a
means of comparison between different flow configurations. The condi-
tions selected were 3, 15, and ISA (the high solids systems) and 1, 2,
13, and 14 (the low solids systems). Condition 3 is contrasted with 15
and 15A to show effect of phosphorus addition. Both conditions were
operated during the early winter months. Conditions 1 and 2 were
contrasted with 13 and 14 to show the influence of phosphorus addition
in low solids operation. All four conditions were operated in the late
summer and early fall.
Results of the performance of the lagoons under these selected
conditions appear in Figures 41 through 70 and Tables 28 through 35.
Probability plots of the 24-hour composite samples taken over the test
period for each condition for BOD, COD, TSS and VSS, both in terms
of mg/1 and kg/1000 kg hide, are employed to illustrate variability of
the process. The primary influent data for the appropriate time period
for a given condition can be seen in Figures 41 through 70 and are
summarized in Table 36. The mean BOD and COD values of the
primary settled influent were considerably lower for lagoon conditions
1 and 2, than for 3, 13, 13A, 14, and 15, which can be attributed to
process formula in part and the practice of rendering (Table 36).
Although conditions 13, ISA, 14,and 15 had the benefit of FeCls addi-
tion to the raw wastewater for control of sulfides and attendant odor
problems, the primary effluent values for BOD and COD were the
highest when presumably the FeCls could serve as a coagulant to
improve primary tank performance. The differences between summer
and spring-fall process formulas, comparing conditions 1 and 2 with 3,
shows the higher values of BOD and COD for condition 3 when spring-
fall formula is used, however, the TSS concentrations do not follow.
Rendering the practices employed in conditions 13, ISA, 14, 15, as
compared to conditions 3, result in higher BOD, TSS and VSS values,
but essentially no change in COD. In reviewing the results of the
lagoon treatment, the primary influent characteristics should be noted
and are depicted on Figures 41-70.
The results of the various lagoon conditions are reported as proba-
bility plots, each point representing a 24-hour composite of the secon-
dary effluent. The BPT limits presented in Table 23 represent
discharge limitations based on a maximum 30-day average. In that the
data presented herein for each condition represented the results over a
very limited period of time, 1 to 2 months, at a given season of the
year, the interpretation of the results with reference to the BPT values
is limited. Nonetheless a comparison of the BPT limits with the results
89
-------
I Condition 1
Final Effluent ,
PE mg/l.
BOD =867
COD =1978
1 2 S 10 30 FO 70 PO 95 98 99
Frequency Of Occurrence,%
Figure 41. Final effluent concentrations for BOD
and COD for condition 1.
45
Condition 1
Final Effluent
PE mgt I.
BOD=867
C OO= 1978
1 2 5 10 30 SO 70 90 95 98 99
Frequency Of Occurrence,%
Figure 42. Final effluent maiss ratios for BOD and
COD for condition 1.
90
-------
300
200
100
1 2 5 10 3O 50 70
Frequency Of Occurrence,%
95 9899
Figure 43. Final effluent concentrations for
TSS and VSS for condition 1.
40
35
30
25
20
15
10
5
— f-
r
4
X
61
*
i
JH
>
t
{
T
#
:3l!p
y-"if
t :Ef i:::
'rl
BPT
EPA
Cat.l
SS S.O
t3 —
:5 =
^^t- —
^i: 1
::::: '
= =i::: Condition
===i Final Effli
= i-;:::::::: RE mg/l
= =i::::±:::l TSS = 117
Bii
««5i ;;;|EE:!;;§;;;;;
1 E:f 1 IjiEEEEEE
ieny^i[|pi
1 2 S. 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 44. Final effluent mass ratios for TSS
and VSS for condition 1.
91
-------
900
Condition 2
Final Effluent
PE mg/l.
800 = 867
COD=1978
200
100
1 2 S 10 3O SO 70 90 95 98 9
Frequency Of Occurrence,%
Figure 45. Final effluent concentrations for BOD
and COD for condition 2.
45 EFJ!: ;:; ;; - -EEEEE Conditic
=EESJ;| ==EEE| Final Ef
^l=ffHJlliillllil 1 f-J-iitliiiiii PE •"
::EEjjE?:: ":':': = = --"-'-':":':':. BOD=
35 =E = = :;::J::| = = = E:^:;:;;, r CODS
rr, -HJJ-TJ nirfrTTTnm
di ±+#;::±'=L = r::::::::: • ::::::::::
»
20 ^iiEHiililEEp;!;;:: ;p!!;;;;i;
^N|ilIMH!ii!pii!iii
15 ,EEE!;::::;;;i ==EEE;!;:;:::: |:=i;;!!!;
10 Ep-EEEcob— E|E? ;;;f(jlEE=P5
:;::::::;« t:::: E
ft.i4J=y:BOD|_U4|jjjt|j|)|^^
)n 2 i"| :::::::i= = = = :::
Fluent :: ::::|:" = IE
/I. ::::-"- • Tt:tff:: = = = ;:::
1978 :::::::::! i: ::::± --— E:::
::ii::::::::±:::::: St::::" ~= ::::
1 2 S 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 46. Final effluent mass ratios for
BOD and COD for condition 2.
92
-------
800
700
600
500
400
300
200
100
f=
— i
— ^
•sst
-----.-.::: COIIClitfOI
= = :::::! Final Efffl
- = ::::::::: < PE mgf 1
:::::::::; TSS 3 117
i2 i;;; :|;;;::EE =
uent Ell; |;;;!!!E =
. t;;;;;!E:! igiiEEEE1'
[
a
B
i
i
i
[
B
=:::
II
If
i
Ii
Frequency Of Occurrence.%
Figure 47. Final effluent concentrations for
TSS and VSS for condition 2.
40
35
30
25
20
15
10
5
nl
a
••
3
b
2
g
^
>
t
I
I
I
T
•
lEr::::
P"::n
» = = :::::
1PT
EPA
Jat.l
SS 5.0
•••
iiii
l::j =
••L
!=:::: Condition
EEEEi: Final Ef flu
2 •-
ent i:ii:: : :EE
12 5 10
30
50 7O
90 95 98 99
Frequency Of Occurrence,%
Figure 48. Final effluent mass ratios for
TSS and VSS for condition 2.
93
-------
Condition 3
Final Effluent
PE tag/I.
BOOB 1090
CODS 2487
1 2 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,^
Figure 49. Final effluent concentrations
for BOD and COD for condition 3.
J
•
3
!
*
^
i
s
i
:__ = ;:::: :: (JOtt
:;— EEE|:;;;;;;- "- fins
\ [|| | | | [I PE
::: =::::::::::: :::::; BO
HEEE::;;!;.:;: !!:!:;:;;;!:!
?iiHiinHiiiMiii!
rtiii iii
C= = EEE^;;;;;;:; ;;;;;ii:;;i!;
2 5 10 30
dition 3 ||j|t]T| 1 1
(Effluent iEEE-
mg/l. : |S:ff" —
0 = 1090 :g ;i;iE:EEp
D=2487 : . tt::::::p
::::::.::::::::: :ti S:::::r =
E.;;;ii;;!!;-EEEE |1^^==
:.:::: ::::.:::: : :::• \t-_: BPT
;;;;;;::;;;;iiEE;,|.:;|;;EEE EPA
50 70 90 95 98
99
90
SO
70
60
SO
40
30
20
10
Frequency Of Occurrence,^
Figure 50. Final effluent mass ratios
for BOD and COD for condition 3.
94
-------
550
500
450
400
350 —
300
250
200
150
no-
Condition 3
Final Effluent
PE ms/ '.
TSS = 737
VSS =512
12 -5-10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 51. Final effluent concentrations for
TSS and VSS for condition 3.
12
Condition 3
Final Effluent
PE me/1.
TSS = 737
VSS • 512
10
12 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 52. Final effluent mass ratios for
TSS and VSS for condition 3.
95
-------
450
400
350
300
250
200
150
100
Condition 13
Final Effluent
PE mg/l.
BOD =1256
COD = 2459
FeCI3 Coagulant used
on Effluent
I 2 5 10 30 50 70 90 9S 98 99
Frequency Of Occurrence,%
Figure 53. Final effluent concentrations for
BOD and COD for condition 13.
Condition 13
Final Effluent
PE me/I-
BOD = 1256
COD =2459
F«CI3 Coagulant used
on Effluent
1 2 5 10 30 50 70 90 95
Frequency Of Occurrence,%
Figure 54. Final effluent mass ratios for BOD
and COD for condition 13.
96
-------
450
400
350
300
250
Condition 13
Final Effluent
PE me/1.
TSS = 1152
VSS s 688
F*CI3 Coagulant u*ed
on Effluent
200
150
100
12 5 10 30 50 70 90 95 98 S9
Frequency Of Occurrence,%
Figure 55. Final effluent concentrations for
TSS and VSS for condition 13.
Condition 13
Final Effluent
1 2 5 10 30 50 70 90 95 98 99
„ ^f Frequency Of Occurrence,%
Figure 56. Final effluent mass ratios for TSS
and VSS for condition 13.
97
-------
Condition 13 A
Final Effluent
PE me/I.
BOD = 1256
COD = 2459
12 5 10
30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 57. Final effluent concentrations for BOD
and COD for condition ISA.
Condition 13 A
Final Effluent
PE mg/1.
BOO = 1256
COD a 2459
10
1 2 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,^
Figure 58. Final effluent mass ratios for BOD
and COD for condition 13A.
98
-------
900 P
800
700
600
500
400
300 1
200
100
III^H
jjjs
i'is
1
il
i:!=
::!=
h =
TS
VS!
= = E|:!i!:: I :' Condi
=EEp:;;; Final 1
= r = S::::: : :::::: PE
-U-UiliLUJU TSS
= — ;:::::::. if ::::::::: j|;:
:::::::: : ::|| :: ll: ::::
:::::::: . jj i ----T-- ----
rrrftllrtmln' m \m 1m n
m
tionlSA p EE=
Effluent ||lj||fH
IB*/I. ,: ::::: —
= 1182 1 • ||H
:::::::::::::: | :!:::::
;;;;;;;;;|!;:j||;=i!ili
:!!!:!!::::::. It ffj;::! —
nTMTInLirBi 1 ™TI IT I
::J:ll::i>::: .. ::!::::;--
:!!'::::::^pj;^ ::::::::: = =
— •(--
tLf
Am
Frequency Of Occurrence,%
Figure 59. Final effluent concentrations for
TSS and VSS for condition ISA.
45
40
35
30
25
20
15
10
E PA
Cat.l
TSS 5.0
VSS
Condition
Final Effluent
PE
TSS 31152
VSS =888
1 2 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 60. Final effluent mass ratios for
TSS and VSS for condition 13A.
99
-------
Condition 14
Final Effluent
PE me/I.
BODS1233
COD = 2517
5 10
30 50 70
90 95 98 99
Frequency Of Occurrence,^
Figure 61. Final effluent concentrations for BOD
and COD for condition 14,
1 2
so
70
60
50
40
30
20
10
t—
»~
•a-
r-
«J
o =
o =
o =
< =
cc
•• B
= EE:i| Condi
h^§JU Final 1
_:•;:::::::::.: :::: f»E ,
E = ":::!::::::ffi:::: BODS
= ;;::::::::::. :::: COD:
=-EE:E::;;;;" iii;!!;;;;;;;;
jDEEic;;;;;iii !!;;!!;;!!:;!!
tiOnl4 ::: = = =
Effluent ii \:\"-"-= — ;
HB/I. ffHtiln 1 1 1 "I m
51263 ::il :!!!!tEEEEEE !
S25I7 ::: : , :::..:±;= :
:;;^;ii;;:iji i-pEEE==;
ii;;iJ!!;;EE; ;;;:.EEEEEE=;
.::::.::::::::: :: :::::::: BPT
ii;; iiiiiiEii M:;;::!!: c«*-1
:!!;;:;;:;!EE: ; iii iii! BOD4.
t
0
5 10 30 50 70 90 95 989
Frequency Of Occurrence,%
Figure 62. Final effluent mass ratios for BOD
and COD for condition 14.
100
-------
Condition 14
Final Effluent 3
PE me/1.
TSS = 1237
VSS S 746
I 2 S 10 30 SO 70 90 95 98 99
Frequency Of Occurrence,%
Figure 63. Final effluent concentrations for
TSS and VSS for condition 14.
Condition 14
Final Effluent
PE mg/1.
TSS= 1237
VSS B 746
5 10 30 SO 70 90 95 98 99
Trequency Of Occurrence,%
Figure 64. Final effluent mass ratios for
TSS and VSS for condition 14.
101
-------
•B CO
- EEEE: Fill
800 ;:;;— EEE=E;:;;;':; :-:
1HHI 1 1 RriitimiilniT B
700 :| EEE-E-|E;;;;;:'! \~\ c
600 :;;;— E|EE:;;;: • :E|;;;:
SCO ^— =----••:•".: ::::::::::
400 m------.----:::::::: :::::::|
300 I:;- — EEEEE;:::h: ::::::::
200 ||-=EJl:;;;||iEEE:;:!
100 ;=;;--EEE|:;;;;:;;J;JEJJ;;!
® 1 2 5 10 30
ndition 15 f:;;;;;iEEEEE
lal Effluent J:;;;:EEEEE^
0 S1263 :::r: i::.|::= —
01^2517 : : :-__Ep
50 70 90 95
Si
SBSS!
i
i
ii
II
11
=*
= ',3
t— -
-" " p1-"*
98
i
if
!:
::
::
ii
11
il
!
99
Frequency Of Occurrence,%
Figure 65. Final effluent concentrations for
BOD and COD for condition 15.
Condition 15
Final Effluent
1 2 5 10 30 50 70 90 95 98 99
Frequency Of Occurrence,%
Figure 66. Final effluent mass ratios for BOP
and COD for condition 15.
102
-------
800
700
600
500
400
300
200 1
100
^H
_
: 1 I
»d
T T
rn V!
^™{:::::i:- COltd!
^.flk^M Final
- . = ::::::::::: ::::: PE
--;-.-..... - + TSS
-- — :::::::::: ::::; VSS
= = -"::::: :::::::j::'l::
= EEE::::::ili: !!:::::::: ill
BSE?!;;:;::;;: :;;;;;;:;;;:;:;
nj*^ *** =
tion 151 |;;;i|Eii
Effluent |;;|EEEE=
mexl. ^ inff ^4:
=1237 ::: {:: f::i;:iEE
=746 ::: {:: .i:::::;;1*11
::::::::::::::: :|ff|::!E = = =
::::-ii i ?•-•
;;ii.;
-------
450
400
350
••••5S3355SSS !!!••
Condition 15 A
Final Effluent
1 2 S 10 30 50 70 90 95 9899
Frequency Of Occurrence,%
Figure 69. Final effluent concentrations for
BOD and COD for condition ISA.
180
160
Condition 15 A
Final Effluent
12 5 tO
30 50 70
90 95 98 99
,-,. _„ Frequency Of Occurrence,%
Figure 70. Final effluent concentrations for
TSS and VSS for condition ISA.
104
-------
TABLE 28. LAGOON PERFORMANCE: CONDITION 1
-
Number of Concentration, mg/1
Parameter data points Mean
BOD5
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH, standard units
10
10
10
10
1
4
2
6
-
6
36.7
287.4
486.0
111.2
2.14
30
Trace
1.02
-
Standard
deviation
22.4
49.4
136.9
34.4
-
20.3
-
0.25
-
Range
15-87
218-370
208-656
76-200
-
8-62
-
0.66-1.49
-
7.6-8.3
kg/1000 kg*
Mean Standard
deviation
1.31
10.15
16.80
3.81
0.08
1.05
Trace
0.03
-
0.87
2.47
4.87
1.26
-
0.77
-
0.01
-
Range
0.41-3.16
5.94-14.24
8.51-24.72
2.07-6.64
-
0.22-2.26
-
0.02-0.06
-
Weight per weight of hides processed.
TABLE 29. LAGOON PERFORMANCE: CONDITION 2
Number of Concentration,
Parameter data points Mean Standard
deviation
BOD5
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH, standard units
9
9
9
9
6
3
1
3
-
6
51.0
476.4
530.2
171.1
3.06
65.3
Trace
0.98
-
18.8
74.0
72.1
46.8
2.09
43.2
-
0.01
-
mg/1
Range
25-89
361-569
352-608
88-252
0.64-6.38
28-126
-
0.96-0.99
-
7.8-8.1
kg/1000 kg
Mean Standard
deviation
2.09
19.41
22.06
7.15
0.26
1.14
0.009
0.043
-
1.11
6.22
5.62
3.13
0.24
0.01
-
0.004
-
Range
0.72-4.10
10.15-27.48
14.23-31.29
2.36-12.97
0.03-0.75
1.13-1.15
-
0.04-0.05
-
-------
TABLE 30. LAGOOiM PERFORMANCE: CONDITION 3
Number of
Parameter data points
BOD.
COD3
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Tota\ organic nitrogen, N
pH, standard units
10
10
10
10
8
6
5
10
-
10
Concentration,
Mean
193
893
326
238
5
84
0
1
.6
.2
.5
.0
.99
.7
.08
.14
-
Standard
deviation
64
180
120
67
2
35
0
0
.8
.1
.7
.5
.49
.3
.07
.32
-
mg/1
Range
113-322
632-1140
132-548
136-344
1.43-9.20
10-120
0.05-0.19
0.62-1.58
-
7.6-8.2
Kg/1000 kg
Mean Standard Range
deviation
7
35
13
9
0
3
<
0
.68
.41
.02
.40
.28
.65
.002
.05
-
2.84
7.82
4.94
2.91
0.12
1.59
-
0.01
-
4.
22.
5.
4.
0.
0.
0.
0.
25-13.46
78-54.37
95-18.35
61-14.22
05-0.40
44-5.33
01-<0.001
03 -0. 06
-
TABLE 31.. LAGOON PERFORMANCE: CONDITION 13*
Number of
Parameter data points
BOD5
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH, standard units
14
14
14
14
16
13
14
9
16
10
Concentration, mg/1
Mean
66.8
303.3
87.8
46.5
0.77
29.9
0.07
0.37
198.5
Standard Range
deviation
26.9
47.3
30.5
24.0
0.50
17.3
0.14
0.16
43.5
17-121
215-401
57-165
23-106
0.24-1.67
3.5-53
Tr-0. 53
0.13-0.65
80-260
6.9-7.5
Kg/iowr kg
Mean Standard
deviation
2.39
10.76
3.13
1.66
0.03
1.08
<.001
0.012
7.26
0.89
2.01
1.17
0.89
0.017
0.66
-
0.006
2.19
Range
0.69-3.91
8.75-13.93
1.49-5.66
0.80-3.64
0.01-0.07
0.12-2.43
Tr-0. 02
0.01-0.02
1.83-11.18
._
FeClo coagulation preceding sedimentation.
-------
TABLE 32. LAGOON PERFORMANCE: CONDITION ISA*
Number of Concentration, mg/1
Parameter
data points Mean Standard
deviation
Range
Kg/1000 kg
Mean Standard
deviation
Range
BOD=
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus. P
Total organic nitrogen, N 9
pH, standard units
9
9
9
9
12
2
182.4
232
90.0
728.8 237.5
415.1 131.5
297.7 94.6
6.09 2.00
67.5 16.5
33.8
17-331
190-320
7.40
215-1313 27.80
57-592 15.15
24-364 10.30
3.71-10.50 0.21
51-84 2.51
8.43
4.90
15.09
5.76
4.39
0.04
0.36
0.69-18.61
8.75-73.83
2.32-24.08
0.98-18.89
0.14-0.27
2.17-2.87
2.08 5.62-12.31
Without FeClg coagulation--laboratory settled.
TABLE 33. LAGOON PERFORMANCE: CONDITION 14
Number of
Parameter data points
Concentration,
Mean Standard
mg/1
Range
deviation
BOD5
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH, standard units
10
8
5
6
13
10
107.1
500.1
3.80
70.80
Trace
1.67
209.2
20.3
103.0
1.36
36.5
-
0.52
14.7
79-134
401-697
0.96-5.04
30-139
-
0,98-2.65
184-238
7.7-7.8
Kg/1000 kg
Mean
Standard
Range
deviation
5.89
27.43
0.20
3.50
Trace
0.08
11.31
1.35
6.58
0.07
1.93
-
0.03
1.31
3.71-8.39
18.83-43.01
0.05-0.29
1.41-7.47
-
0.05-0.13
9.05-14.27
-------
TABLE 34. LAGOON PERFORMANCE: CONDITION 15
Number of
Parameter data points
BOD5
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH, standard units
13
13
13
13
10
10
7
6
13
11
Concentration,
Mean Standard
deviation
128.8
464.1
377.5
285.2
5.73
62.2
0.05
1.90
177.1
49.7
150.7
116.7
89.9
2.59
34.8
0.05
0.55
19.9
mg/1
Range
41-197
241-793
212-624
136-448
1.42-9.19
13-124
Tr -0. 07
1.50-3.06
146-198
7.5-7.9
Kg/1000 kg
Mean Standard
deviation
7.39
25.82
20.97
12.74
0.33
3.14
<.001
0.10
9.50
2.72
9.10
8.01
5.99
0.13
1.92
-
0.03
1.48
Range
1.92-11.29
11.32-47.77
9.95-34.63
7.32-29.61
0.07-0.53
0.61-7.0
-
0.60-0.15
7.24-12.03
TABLE 35: LAGOON PERFORMANCE: CONDITION ISA*
Number of
Parameter data points
BODr
COD
TSS
VSS
Total chrome, Cr
Oil and grease
Sulfide, S
Total phosphorus, P
Total organic nitrogen, N
pH
15
15
15
15
17
17
17
26
Concentration, mg/1
Mean
34.3
236.6
74.4
36.7
0.98
31.6
-
-
204.1
7.7
Range
10-63
180-307
39-164
8-140
0.39-2.51
7-176
170-236
7.2-7.9
* After project period.
-------
TABLE 36. MEAN PRIMARY EFFLUENT PARAMETERS FOR LAGOCH CONDITIONS
Condition Dates *
1
2
3
13
13A
14
15
8/7/73-10/29/73
8/7/73-10/29/73
11/15/73-12/31/73
9/20/74-11/1/74
9/20/74-11/1/74
9/26/74-11/1/74
9/26/74-11/1/74
Process
formula Rendering
Summer
Summer
Spring-Fall
Spring-Fall
Spring-Fall
Spring-Fall
Spring-Fall
No
No
No
Yes
Yes
Yes
Yes
Coagulant addition Number Primary effluent, mg/1
to raw waste of data
None
Mone
None
FeCl3
FeCl3
FeCl3
FeC Is
14
14
9
20
20
18
18
BOD
867
867
1090
1256
1256
1263
1263
COD
1978
1978
2487
2459
2459
2517
2517
TSS
1170
1170
737
1152
1152
1237
1237
VSS
509
509
512
688
688
746
746
* Dates through which primary settling effluent was evaluated.
15 were averaged over the same periods respectively.
Data for conditions 1, 2; 13, 13A; 14, and
-------
obtained can serve to provide some relative measure of the performance
of the systems.
Biochemical Oxygen Demand and Total Suspended Solids
In viewing the BOD mass ratio plots for conditions 1 and 13 (Figures
42 and 54), it is apparent that all of the 24-hour composite samples had
values less than the BPT limitation of 4.0 kg/1000 kg. Obviously if all
effluent values are less than this limitation, the 50% or mean value of all
effluent values are less than the stated BPT value. Condition 13 repre-
sented an effluent that had received FeCl3 addition as a coagulant to the
secondary effluent. Neither condition represented a period when cold
weather conditions prevailed, therefore, the results likely do not demon-
strate performance during the poorest 30-day period corresponding to
the BPT maximum monthly average limitation reported.
For condition 2 (Figure 46), approximately 85% of the 24-hour com-
posite values was within the BOD limitations as well as the 50% of mean
value for this period. The same restrictions apply as above concerning
the season when the pond system was operated for this condition. In con-
ditions 3, 14 and 15 (Figures 50, 62 and 66, respectively), 90% of the
24-hour composite BOD values exceeded the BPT limitation and likewise
for the mean value. One can conclude that these operating conditions
would not meet the BPT limitation regardless of season. In condition
ISA (Figure 58), identical to 13 but without the benefit of FeCls coagu-
lation of the secondary effluent, 70% of the 24-hour composite BODs
exceeded the BPT limitation as well as the mean or 50% value. Although
the value of utilizing FeClg as a coagulant under operating condition 13
is evident, no inference can be made concerning the ability of the lagoon
systems to meet BPT requirements if a coagulant is employed, however,
higher removals are expected with the use of the coagulant.
With the exception of condition 13, none of the 24-hour composite
values reported meet the BPT limitation for TSS of 5.0 kg/1000 kg hide
(see Figures 44, 4g, 52, 56, 60, 64 and 68). In condition 13 (Figure 56),
85% of the 24-hour composite values were less than the 5.0 kg/1000 kg
hide limitation, as was the meaner 50% value. The limitation as applied
to the BOD results concerning cold weather operating conditions must be
applied to the TSS results as well.
Low solids systems operating during the warmer weather periods
conditions 1 and 2 can make the BPT requirement for BOD5 but coagu-
lant is definitely required to achieve the requirement with respect to
TSS. Even more significant is the fact that PBT requirements for BOD
110
-------
and TSS could not be met 100 percent of the time during the colder
months of the year (Figures 66 and 68), even with high solids operation
condition 3 (Figures 50 and 52), and condition 15 (Figures 66 and 68).
The high effluent solids from these processes and the contribution of
BOD by the VSS would suggest that proper coagulation might achieve the
BPT requirements for BOD and TSS but no long term data is available
on the stability of a coagulant dosed high solids system over the winter
months. The average FeCls dosage of 214 mg/1 to the low solids
lagoon effluent for condition 13 (Figures 53-56) did readily achieve a
vast improvement in effluent quality.
Examination of BAT effluent limitations with respect to BOD and
TSS indicate that only condition 1 (Figure 42) was able to achieve the
BOD requirement greater than 50 percent of the time. No condition
studied could achieve the TSS requirement, even with coagulant dose.
Total Chrome, Oil and Grease, TKN, Sulfide, and pH
Tables 28 through 35 summarize the effluent quality characteristics
for the selected conditions discussed above. A scarcity of data for a
number of the quality parameters precluded probability plots. Examina-
tion of these tables and the BPT effluent limitations as set forth in
Table 23 would produce the following conclusions.
With the exception of a single value reported for condition 1 (Table
28), the total chrome requirement can be met for BPT situations only
with addition of coagulant (condition 13, Table 31). All other conditions
studied produced total chrome levels in excess of 0.1 kg/1000 kg on an
average basis.
In no condition studied could the requirement on oil and grease of
0.75 kg/1000 kg hide be met, even with the addition of coagulant aid.
Significant decreases in oil and grease were achieved by chemical coagu-
lation (condition 13 -- 1.08 + 0.66 kg/1000 kg versus condition 14 --
3.50 + 1.93 kg/1000 kg). Lower values noted for conditions 1 and 2
were due primarily to lower oil and grease loadings to the lagoons
since no rendering was practiced during these operational periods.
. -OS??""
In no condition studied, could the requirement on TKN of 0.27 kg/
1000 kg of hide be achieved for BAT (Table 32). The TKN values
expressed as kg/1000 kg were excessively higher than established in the
Guidelines Report (3 ). TKN, values ranged from 7.3 to 11.3 kg/1000
kg on an average and no apparent correlation existed between this para-
meter and a chemical coagulant addition or lagoon loading rate.
Ill
-------
The data in Tables 28-35 show that sulfide levels in the lagoon
effluents will fall below BAT requirements of 0.005 kg/1000 kg of hide.
Only when aerator failure occurred (or under severe overload where
oxygen transfer rate was exceeded by uptake rates throughout the lagoon)
did sulfide appear in significant amounts in the effluent.
The pH values in the lagoon effluents were dependent upon tannery
process formula, temperature and lagoon leading conditions. As was
noted in the discussion of the raw wastewater, alkalinities and pH were
highly variable. This variation was greatly attenuated in the lagoon
effluents. Normally pH varied from 7.5 to 8.3 except for condition 13
where Feds additions lowered pH values in the range of 6.9 to 7.5.
All values of pH reported were in the range of values 6.0 to 9.0 for
BPT and BAT effluent limitations. Alkalinity was reduced through the
lagoons, likely as precipitated carbonates. Langlier Saturation Index
dropped from a range of +1.8 to +2.5 in the primary effluent to +0.3
to+0.6 in the lagoon effluents suggesting that the waste was sufficiently
stabilized against carbonate precipitation.
Fate of Nitrogen
The fate of nitrogen through the pond system is best depicted by
results obtained for conditions 13, 14, and 15 (Table 37). Scant data were
available on conditions 1, 2, and 3.
TKN reductions through the lagoon system were significant ranging
from about 17' to 30%. This reduction was likely due to adsorption and
precipitation of colloidal materials although some biological oxidation and
deamination may have occurred. Nitrification did occur to a limited
extent in a 11 three systems. The greatest degree of nitrification occurred
under condition 15 at an F/MofO.12 where the average nitrate concentra-
tion increased from 25 mg/1 to 41 mg/1. Ammonia reduction was noted
under this condition as well from-99 to 73 mg/1. At the higher F/M
loading of 0.34 (conditions 13 and 14) only slight nitrification occurred
and ammonia concentrations remained constant through the system.
Fate of Chlorides and Sulfate
As would be expected, the conservative element, chloride, did not
undergo change in the lagoon system. Effluent chloride concentrations
varied with process formula, normally ranging from 1500 to 3000 mg/1
without rendering and from 3000 to 4000 mg/1 with rendering. Sulfates
did not reduce during the process since it was normally aerobic. Oxida-
tion-reduction potentials did not drop sufficiently even in the secondary
clarifiers to allow any significant conversion of sulfate to reduced sulfur
112
-------
TABLE 37. LAGOON PERFORMANCE: NITROGEN ANALYSES
Condition
13pe*
13fe
14pe
14fe
15pe
15fe
TKN
mg/1
avg sd
251
198
251
209
251
177
90
43.6
90
14.2
90
19.9
NH3-N
mg/1
avg sd
99
104
99
102
99
73
10
10
10
8.5
10
12.9
NO3-N
mg/1
avg sd
25
28
25
29
25
41
5.8
7.5
5.8
5.1
5.8
16.6
Temp.
range
°C
9-20
7-19
8-17
*Primary effluent (pe); final effluent (settled)(fe).
TABLE 38. LAGOON PERFORMANCE: COLIFORMS
Condition
6
7
8
9
10
11
12
13
14/15
Number
of data
5
4
6
6
5
5
3
6
6 5.
0
Days
2.1
2.7
2.2
4.0
3.0
9.8
7.5
5.5
6/3.8
F/M
kg/kg
0.21
0.89
0.87
0.23
0.10
0.26
0.05
0.34
0.34/3.8
Total*
coliforms
MPN per 100 ml
561,390
582,343
133,147
112,248
13,506
1,118
1,233
855
2,411
Fecal*
coliforms
MPN per 100 ml
1,949
3,646
1,582
1,106
1,533
108
220
113
229
Geometric means.
113
-------
compounds. Effluent concentrations ranged from 1100 to 1500 mg/1 as
864 during the last year of the study when rendering was employed.
Fate of Bacteria
Bacterial studies were, conducted on the lagoons during the experi-
mental period. A detailed study on the microbiology of the lagoons was
conducted in the summer of 1972. In brief, this study found six
bacterial genera: Pseudomonas, Bacterium, Flavobacterium, Achremo-
bacter, and Alcaligenes, the first three being dominant genera during
the late summer months. Protozoa were also examined on a few occa-
sions. Flagellated protozoa were predominant with some ciliated forms
being found in low numbers. No other protozoa forms were observed
in this study.
Coliform and fecal coliform analyses were conducted throughout
the study period on lagoon effluents, chlorinated and unchlorinated.
Table 38 presents the geometric means of coliform counts from secon-
dary settling tanks for 10 different lagoon conditions. Several points
can be made from these data. The fecal coliform MPN requirement of
200/100 ml could be met in only two lagoon conditions without chlorine
addition based on geometric means. Condition 13 with FeCls precipita-
tion did achieve fecal coli reductions below 200 MPN/100 ml 85 percent
of the time. Higher coliform counts were observed at the higher organic
loading rates and/or shorter hydraulic detention times. Hydraulic
retention time may be more significant as contrasted by counts from
condition 11 (108 MPN/100 ml) versus condition 9 (1106 MPN/100 ml)
and condition 9 (1106 MPN/100 ml) versus condition 6 (1949 MPN/100
ml). One added complication in this analysis was the absence of data
on primary effluent coliforms. The higher effluent coliform might have
been influenced by higher influent coliform counts.
One- brief analysis of the die-off of coliforms in lagoons was
conducted in September and October. As shown in Table 39 there
appeared to be a very substantial increase rather than .die-off in both
total and fecal coliforms through the lagoon system. It is unlikely that
this represented real growth, but rather release of coliforms from
larger particle masses during the aeration process or the toxic charac-
teristics of the raw wastewater may have produced analytical underesti-
mates of the coliform group. The lagoon counts are about two orders
of magnitude higher than settled effluents by comparing these counts to
those of conditions 13 and 14 on Table 38.
114
-------
TABLE 39. LAGOON PERFORMANCE: COLIFORM DIE-OFF
Date
Raw Waste
Total Fecal
Coliform Coliform
MPN/100 MPN/100
Lagoon 1
(Condition 13)
Total Fecal
Coliform Coliform
MPN/10Q MPN /100
Lagoon 3
(Condition 14)
Total Fecal
Coliform Coliform
MPN/100 MPN/100
9/27/74
7anmoon
400
<50
49, 500
200
49,300
1,700
10/11/74
7am-noon 42,000
420
48,000 5,800
340,000 2,000
SVI of Mixed Liquor
The solids settling ability of the mixed liquor from the lagoons
was characterized by finely divided solids which readily carried over
the weirs even at the relatively low overflow rates and solids loading
rates employed in the secondary clarifiers. The bulk of the solids did
settle cleanly, even for the high mixed liquor conditions (5,6,12, and 15)
with SVI values always well below 100. The granular characteristics
of the sludge containing high concentrations of inert precipitated salts
likely contributed to this.
SECONDARY CLARIFIER PERFORMANCE
The solids loading to the clarifiers were normally low ranging
from 0.49 to 4.9 kg/d/m2 (0.1 to 1.0 lb/d/ft2) for the low solids
systems to values of 9.8 to 58.6 kg/d/m2 (2.0 to 12.0 lb/d/ft2) for the
high solids systems. No correlation appeared to exist between effluent
suspended solids and solids loadings within this range. Bulking was
never apparent during the study, and absence of heavy protozoan popula-
tions may have accounted to some extent for the discharge of large
amounts of finely divided solids. The effect of chemical addition on
removal of these solids is apparent from examination of condition 13
(with FeCls coagulant, Figure 55) versus condition 13A (no coagulant
added, Figure 59).
The underflow solids from the clarifiers were highly variable,
varying from 3000 to 27,000 mg/1 for the high solids system and from
115
-------
2000 to 8000 mg/1 for the low solids systems. Sampling difficulties and
operational problems led to the wide variation on these values.
Examples of settling curves for typical mixed liquor sludges for
condition 15 are depicted in Figures 71 and 72. Figure 71 shows the
zone settling interface for various concentrations of TSS with respect to
time. The rate of settling of the sludge water interface for each sludge
concentration is used to construct the flux concentration curve shown in
Figure 72. For the sludge loading on that day, 47.4 kg/d/m2 (9.72 lb/
d/ft2) the maximum underflow solids would have been 9100 mg/1 on that
date. Values as high as 27,000 mg/1 were achieved for condition 15
under solids loadings ranging from 39.1 to 58.6 kg/d/m2 (8 to 12 lb/d/
ft2).
LAGOON SOLIDS MEASUREMENTS
The estimation of biological sludge production by the lagoon
systems studied was complicated by the influent wastewater characteris-
tics and the physical characteristics of the lagoons. Efforts were made
to perform material balances on the systems studied but results were
not meaningful.
The primary effluent contained high concentrations of non-settleable
suspended solids of which 50-70 percent were volatile. A portion of
these finely divided suspended solids, such as protein substance, had
an opportunity to be precipitated with the reduction in pH within the
lagoon. Analysis of the accumulated solids within the lagoon indicated
that 55-60 percent of the solids were fixed. The organic suspended
solids may have been (1) adsorbed into these inorganic precipitates,
(2) biodegraded in suspension or within the precipitated sludge, (3)
bioflocculated, or (4) simply carried through the process.
Accumulation and Resuspension and/or Resolution of Lagoon Solids
Since the lagoons were not well mixed, accumulation or resuspen-
sion of solids was noted throughout the period of this study. Table 40
summarizes the results of lagoon accumulation studies. The measure-
ments were made according to the procedure outlined in Appendix A.
These data are presented for given lagoon conditions after the appro-
priate number and location of aerators had been established. Since
chemical and biochemical reactions are both pH and temperature
dependent, a plot of lagoon pH and temperature was made to examine
the importance of these variables in sludge accumulation. Figure 73
illustrates that, for the systems studied, accumulations were most
116
-------
1000
UJ
800
O
> 600
Q
UJ
_J
LJ
400
200-
I
I
I
CONDITION IS
SAMPLES
OCTOBER, 1974
MLSS (mg/l)
4648
6292
6764
7708
8548
SOLIDS LOADING 9.72 lb/0/ft2
SLOPE OF SETTLING CURVES
EQUALS SETTLING VELOCITY
AT EACH CONCENTRATION
I
I
I
I
456789
TIME, minutes
10
Figure 71. Mixed liquor settling curves for condition 15.
CM
60
*T 50
— 2 40
> i
O <*>.
.: 30
X u
3 < 20
c! fc
10
o
CONDITION 15
SOLIDS
LOADING 9.72 /0/ft2
2000 4000 6000 8000
CONCENTRATION ,mg/-E
9IOOmg/-e
1 I
10000
Figure 72. Flux concentration curve for mixed liquor
condition 15.
117
-------
TABLE 40. SLUDGE ACCUMULATION IN LAGOONS
Net sludge"1"*"
volume
change
Condition gal/d
3
4
8
9
10
11+
12*
13
14
15
700*
346*
1350*
505*
140*
770t
tSKQi1
700t
8W
607t
76t
60f
Sludge accumulation^*
sludge solution^
TS
Ib/d
600*
331*
1535*
442*
127*
460>
590T
46^
IDOf
457t
103t
29*
VS
Ib/d
8
278
334
250
~5T
242
51
2
COD
Ib/d
400*
209*
1083*
490*
319t
574*
66 5t
400t
75t
359t
72T
171*
TKN
Ib/d
35*
20*
107*
30*
9*
80t
I0t
40t
~T*
lOt
3*
31*
Ib/d
125*
58*
220*
54*
84*
1734
83T
159*
~Wh
223t
411-
141
Lagoon
temp
°C
4.4
7
19
19
21
24
2T
21
rs
14
14
13
Lagoon Phosphorus
pH addition
7.7
7.65
8.1
8.1
7.9
7.9
7.5
7.7
775"
7.7
7.7
7.7
No
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
Sludge
return
Yes
Yes
Yes
Yes
Yes
No
Yes
No
No
Yes
* ^Indicates deposit or accumulation of material, f indicates resuspension and/or resolution of
materials.
+ Series operations, top figure represents first lagoon in series, lower figure represents
second lagoon in series.
-H- Values represent either the net sludge volume increase or decrease as an average over
the operating period.
-------
8.1
x 79
Z
O
0
< 7.7
i
_j
7.5
7 3
9{
-
_^.^^^^M
.S ._ T
3j ^ / I5f »|4 ^
y sf^
/ 12(2)*
1 1 1 1
04 8 12 16
LAGOON TEMPERATURE
8
10 .^-n Kin
t , TSS
12(0* f Deposition
J TSS
f Solution
IK2H
1 1
20 24
- °C
Figure 71. Sludge solids (total solids) accumulation (increase) or solution (decrease)
in lagoon systems.
-------
predominant in colder temperatures or at the higher pH values. Solu-
tion of sludges or loss of solids from the lagoon sludge layer occurred
in the warmer periods and at the lower pH values.
Carbonates are less soluble at the higher pH values, accounting
for in part the sludge accumulations. The anaerobic degradation of
the accumulated organics will be more rapid at the higher temperatures
resulting in a greater loss of organic solids at the higher temperatures.
Sludge Solids Production in Secondary Treatment
The discussion above makes it clear that any effort to account for
biological solids production by employing a material balance around the
lagoon system is simply too complex and that estimates of fixed, non-
degradable solids carryover is not realistic. Crude estimates of gross
solids"production" were made in those instances where data was suffi-
cient to estimate solids "loss" from the system. In these instances,
the change in mixed liquor suspended solids plus accumulated sludge
plus wasted effluent suspended solids were employed to calculate a
gross solids "production" per unit of BOD removal. These values
appear in Table 41. There are several trends noted in this data.
Generally as F/M loading increases, net solids production increases,
a phenomenon well documented in the literature. No immediate effect
of temperature is apparent. Most significant, however, is the substan-
tial reduction in solids production with the addition of phosphorus.
Direct comparisons may be made between conditions 7 and 8 and condi-
tions 2, 3 and 4. The reduction in "produced" solids with phosphorus
addition may be attributed to more active biological respiration which
could produce higher rates of endogenous respiration. Phosphorus poor
conditions did not produce significantly poorer effluents, however, but
oxygen uptake rates were noted to rapidly increase upon addition of that
element. One might also attribute lower apparent solids "production"
in phosphorus treated wastes to greater BOD reductions in proportion
to the fixed fraction of recalcitrant suspended solids which would carry-
over. Thus the ratio of TSS to BOD removal would decrease primarily
because of the increase in the denominator.
The range of production values from 1.09 to 1.72 kg TSS/kg BOD
removal are higher than those normally reported for biological systems.
But, again, it should be emphasized that these values include carryover
of non-degradable organic and inorganic suspended solids. Since steady
state was never ideally achieved within the lagoons with respect to a
solids balance, it is not realistic to predict whether the "production"
values cited are valid over a long period of time.
120
-------
TABLE 41. LAGOON SLUDGE PRODUCTION
Lagoon
Sludge Phosphorus F /M
Condition return addition kg/kgd
2 No
3 Yes
4 Yes
5 Yes
7 No
8 Yes
12 Yes
No
No
Yes
Yes
Yes
No
No
0.14
0.15
0.16
0.41
0.89
0.87
0.05
temp. Sludge*
°C production
mean range kglSS/kg/BODr
13
4.4
7
11
16
19
15
10-17
0-14
6-12
8-14
13-19
18-24
11-20
1.42
1.35
1.09
1.26
1.15
1.72
1.27
*Determined as the sum of (1) the change in mixed liquor suspended
solids, (2) sludge accumulations in the lagoon system, and (3) sludge
solids wasted and in the settled effluent.
That these "produced" solids contain a variety of constituents
including biological solids and inorganic and organic residues that have
been carried through the process is apparent. Since all of these solids
must be handled as a sludge eventually, the source of the solids is per-
haps not critical at this point.
OXYGEN REQUIREMENTS
The consumption of oxygen in the biological stabilization of organic
matter within the lagoons was estimated by monitoring oxygen uptake rates
within the lagoon system on several occasions during each condition. In
order to most effectively estimate the oxygen requirement, it was necessary
to monitor oxygen uptake at a number of grid points within the lagoon sys-
tem over a representative period of time. Since organic loading to the
lagoon was variable throughout the day, it was very difficult to assess
oxygen consumption rates as a function of BODc removed. Because of the
time required to do these surveys properly only limited data was collected.
Extensive field studies were performed for conditions 2, 3, and 5, during a
period when oxygen transfer analyses were being made. Details of the
method employed appears in Appendix B.
In analyzing the routine data collected on oxygen uptake rates
121
-------
within the lagoons. It was determined that representative data was also
available for conditions 1, 4, 11, 14, and 15. These calculations have
been included in the subsequent analyses although it must be recognized
that the data base is not as rigorous as that for conditions 2, 3, and 5.
In assessing oxygen uptake rates, efforts were made to negate the
influence of immediate chemical oxygen demand due to the presence of
sulfides. Early uptake studies showed a pronounced break in the uptake
curves, the uptakes being very rapid initially, followed by a substantial
reduction in rate. The diphasic uptake response was due to sulfide oxi-
dation and laboratory studies verified this. Modification of the uptake
analysis was subsequently performed wherein samples collected for
uptake measurements were vigorously aerated for 15 minutes to oxidize
reduced compounds prior to actual uptake measurements. Thus, oxygen
uptake values reported herein reflect only biological consumption.
Results of the oxygen uptake studies are presented in Table 42.
The values reported are expressed in terms of mass of oxygen consumed
per mass of BODg removed. The uptake values were also corrected to
20°C for comparison purposes. The temperature coefficient, 0,
employed was 1.08 (4). Values of the uptakes reported ranged from
as high as 3.51 to 0.9 kg 02/kg BODs removed.
The effect of lagoon loading on these oxygen uptake values is
depicted in Figure 74. No trend is apparent from these few data points.
It does not appear that phosphorus addition has affected uptake rates
appreciably.
Most significant in Figure 74 are the higher uptake values reported
for conditions 4 and 5. These conditions were both operated in early
spring when lagoon temperatures began to increase. Since substantial
deposition of solids had occurred over the winter months due to reduced
biological activity in the anaerobic sludge layer and due to aerator
failure, the solubilization of biodegradable organics in the spring from
these underlying anaerobic sludge deposits likely increased oxygen demand
Consequently, the oxygen consumption per mass of BOD5 removed from
the influent would be high in comparison with values estimated for condi-
tions operated during the late summer and fall. This phenomenon is
common in incompletely mixed lagoons in the north, where sludge depo-
sition plays an important role. Supply of sufficient oxygen during the
critical spring period can be a very signficant operational problem for
such lagoons.
Long term BOD studies were performed on several occasions
122
-------
CO
TABLE 42. BIOLOGICAL OXYGEN CONSUMPTION IN LAGOONS
Condition
1
2
3
4
5
13
14
15
Dates
8/7-9/17
10/5-10/29
11/16-12/31
3/8-3/24
3/8-3/24
9/2-11/1
9/26-11/1
9/27-10/31
Recycle
No
No
Yes
Yes
Yes
No
No
Yes
Phosphorus F/M
addition kg/kg
No
No
No
Yes
Yes
No
Yes
Yes
0.13
0.14
0.15
0,16
0.41
0.34
0.34
0.12
T
°C 1
20
13
4.4
7
11
14
14
13
kg 02
kgBOD5at
2.18
0.90
0.63
1.29
1.77
0.58
0.56
1.16
^ kg O2 _ On0^*
Kg oUlJc}
2.18
1.54
2.01
3.51
2.60
0.92
0.89
1.98
* Calculated by
= k
20
>T-20.
0 = 1.08.
-------
in
o
O
oo 4.0
o"
S 3.0
LJ
<
^ 2.0
UJ
I '-0
© W/0 P
• u7 P
ww I
4« 1-15 -Condition
MHVMV
5«
©
15 ^ 3
2©
— 13©
14*
1 1 1 1 1
O.I 0.2 0.3 0.4 0.5
F/M kg/kg
Figure 74. Biological oxygen consumption at 20°C relative to F/M ratio.
-------
during the study period. The ratio of ultimate carbonaceous BOD to
BODr on primary effluent ranged from 1.42 to 2.25 averaging 1.86.
Provided that nitrification does not play an important role in the lagoon
systems, one would assume that minimum oxygen consumption per mass
of BODs removed would fall within this range. The values
recorded in Table 42 did appear to be consistent with this finding with
the exception of conditions 4 and 5 previously discussed. As noted in
Table 37, nitrification did occur to some extent in conditions 13 and 15.
The oxygen demand estimated for ammonia oxidation in these systems
amounted to less than 5% of the total oxygen demand.
The oxygen consumption values reported in this study are higher
than those for domestic wastewaters, but this is not unusual. There is
no reason to expect that such a relationship should be universal for all
wastewaters. It should be re-emphasized, as well, that one must add
to these figures the chemical oxygen demand exerted by sulfides as well
as the oxygen consumed by ammonia oxidation. The oxygen consumed
by sulfide may range from 0.75 to 2.0 kg per kg sulfide oxidized
depending upon the end product of oxidation (thiosulfate and sulfate
respectively). Oxygen demand by ammonia is approximately 4.5 kg per
kg ammonia oxidized to nitrates.
OXYGEN TRANSFER
From the beginning of the demonstration project it was apparent
that the aerators provided under the contract were inadequate in main-
taining solids in suspension. Three low speed 10 HP aerators were
provided in each lagoon providing a power input of 31 HP/mg (0.23 HP/
1000 ft^). Demonstrations, both at the manufacturers test facility and
in the lagoons at S. B. Foot Tanning Company, indicated that for these
very shallow lagoons, 1.83 m (6 ft) water depth, the low speed aerators
were totally inadequate in maintaining the solids in suspension. A
detailed report on these studies over a two year period are on file at
the S. B. Foot Tanning Company. In summary, these studies showed
that high speed aerators were more effective in mixing the shallow
lagoons. Furthermore, sarsploymemt of a large number of small aerators
was more effective than a few larger ones. The final aerator configu-
rations were installed and in operation by the late summer of 1973.
Twelve HP high speed aerators were arranged as shown in Figure 6.
These aerators were capable of providing adequate oxygen transfer
under most lagoon conditions studied, although high oxygen demands
occurring under certain lagoon conditions studied did deplete oxygen
levels to zero. At no time were the lagoons ideally mixed and accumu-
lations of sludge were evident (Table 40).
125
-------
Oxygen transfer studies were conducted on occasion from October
of 1973 through August of 1974. The studies were conducted by collecting
six samples (two per each third of the lagoon) and determining oxygen
uptake rates, oxygen transfer capacity --«-(Kla waste/Kla tap), oxygen
saturation ratio -- /3 (Cs waste /Cs tap), D.O., sulfide concentration,
temperature and mixed liquor solids. Oxygen transfer rates were esti-
mated by the following equation:
M = _N_ Cs 1.0220"T
*
where: N0 is the oxygen transferred per HP-hr at 20°C and 0.0 mg/1
D.O.;
N is the oxygen transferred per Hp-hr at lagoon conditions;
Cs is the saturation of oxygen in tap water at 20°C - 9. 2 mg/1;
Csw is the waste oxygen saturation value (/#CS); and
C is the measured D.O.
The value of N was calculated based on complete oxidation of sulfide to
sulfate.
S= + 2O2 -
plus the oxygen uptake rate at that sample point.
Values of alpha (
-------
TABLE 43. OXYGEN TRANSFER STUDIES
Date
10/4/73
10/4/73
10/4/73
10/17/73
10/23/73
12/19/73
8/6/74
Lagoon
number
2
3
4
2
1
3
3
Oxygen
uptake
Lagoon
rate Aerators volume
mg/l/hr
21.4
10.95
7.45
21.5
2.3
4.7
7.5
HP
60
60
60
60
55
60
60
mg
0.845
0.855
0.870
0.845
0.971
0.849
0.896
T
f\
°C
20
17
17
18
14
5
18
Sulfide
C oxidized
Alpha
0.74
0.78
1.0
0.75
0.91
0.86
0.74
Beta
0.90
0.90
0.90
0.90
0.90
0.90
0.97
mg/1
1.70
5.23
8.00
1.51
8.50
9.83
4.58
Ib/d
530
0
0
530
50
150
0.8
N*
LB02
HP-hr
3.26
1.29
0.90
3.26
0.43
0.76
0.95
NO+
LBO.2
HP-hr
6.22
4.77
4.88
5.88
5.60
6.40
2.58
* N is the oxygen transferred per nameplate HP-*hr at lagoon conditions.
+ No is the oxygen transferred per nameplate HP-hr at 20°C and 0.0 mg/1 D.O., assuming
consumption by sulfide.
-------
oxygen uptakes measured were pre-aerated for 15 minutes to avoid mea-
surement of sulfide oxidation, and therefore measure biological uptake
only.) More important may simply be the errors in measurement and
assumed distribution of oxygen uptake. The analysis of alpha may also
produce some error, although the values measured seem reasonable and,
if anything, may be a little high.
128
-------
SECTION XI
CHLORINATION STUDIES
Owing to the relatively high concentrations of total and fecal coli-
forms in the wastewater and the potential presence of pathogens from the
cattle hides, the plant was designed to provide chlorination of the final
effluent. No sanitary wastewaters were admitted to the facility however.
A description of the chlorination facilities appears elsewhere.
SAMPLING AND ANALYSES
Routine analyses of the final effluent for total and fecal coliforms
as well as total bacteria were performed during the months of May
through November when chlorination was required by the State of Minne-
sota Pollution Control Agency. Analyses were performed in both 1973
and 1974.. Details of the bacterial analyses are outlined in Appendix A.
During the chlorination period, routine data was also collected for
chlorine dose and effluent characteristics. Analyses for bacteria were
obtained from grab samples taken from the final effluent discharge weir
and from the two final clarifiers. Grab sampling was normally
performed in the morning. Instantaneous flow rates and chlorine dosagp
were read during the grab sampling period.
Special studies were also conducted on occasion with grab samples
collected from the primary clarifiers, the lagoons, and from the final
clarifiers.
Chlorine was analyzed by the DPD ferrous titrimetric method as
outlined in Appendix A. This method provided an accurate means of
differentiating free and combined chlorine residuals.
BREAK POINT STUDIES
Chlorine demand studies were performed on samples from the
primary sedimentation tanks, laboratory settled lagoon effluent and final
settling tank effluent receiving FeClg coagulation each representing
different degrees of treatment. Aliquots of samples, 250 ml, were
129
-------
added to 600 ml glass beakers and appropriate doses of sodium hypo-
chlorite were added. Samples were gently stirred in a Phipps-Bird gang
mixer for 15 minutes and then residuals were analyzed. Results of
these studies are depicted in Figures 75, 76, and 77. Characteristics
of the treated samples are delineated in Table 44.
Break points were visible for all three wastewaters analyzed. It
is apparent that demand increased with increased organic strength. The
primary had a break point chlorine value of 2390 mg/1 (COD = 2740) as
compared with settled final effluent with a value of 870 mg/1 (COD =
490). Ferric chloride coagulation improved this chlorine requirement
to some extent. High sulfide, NH3-N, and oil-grease concentrations
likely produced the high demand for chlorine in the primary effluent.
BACTERIAL DISINFECTION
Results of the tv\o summers of analyses on chlorination appear in
Table 45. A relationship appears to exist (as should be expected)
between chlorine dose to achieve a particular objective and wastewater
quality. A rough graphical depiction of this relationship for the 1973
data appears as Figure 78. The COD was used as the measure of
wastewater quality and the line roughly describes a condition which
achieved a total coliform reduction to less than 200/100 ml. In the
second year, 1974, heavy deposits of sludge which had accumulated
in the chlorine contact chambers decidedly changed this relationship.
No provisions were made to allow for cleaning of this tank and high
washouts of solids from the clarifiers added significantly to the chlorine
demand. As noted in Figure 78, substantially higher doses of chlorine
(greater than 10 mg/1) were therefore required during the 1974 test
period to achieve the same objective for bacterial kill as that for the
1973 test period.
As discussed earlier, certain conditions of lagoon operation, as
well as the addition of FeCls as a coagulant, often reduced the need for
chlorine at all in order to achieve the current EPA effluent value of
200 fecal coliforms per 100 ml. This level can be achieved, when
needed, by the addition (3-18 mg/1) of chlorine. Further study might
be desireable to delineate whether there is any need for chlorinating
this industrial watewater which contains no sanitary wastewaters.
130
-------
«v
V.
01
3000
2500
i
UJ
Z 2000
o:
X 1500
o
< 1000
^)
o
« 500
o:
PRIMARY EFFLUENT
23 °C
9.72
Il2mg/
E
uTiooo
OC
O
o
700
500
LJ
OC.
SETTLED LAGOON EFFLUENT (CONDITION 13)
I8.5°C
7.98
Il2mg/f as N
100
I I I I I I I I I I I I
0 200 400 600 800 1000 1200 1400 1600
CHLORINE DOSE-mg/f
Figure 76. Breakpoint chlorination of settled lagoon
effluent (condition 13).
131
-------
FINAL EFFLUENT -FeCI3COAGULATION
(CONDITION I
TEMP, i I8.5°C
pH : 7.80
NHS i H2mg/f asN
0 200 400 600 800 JOOO 1200 1400 1600 1800 2000
CHLORINE DOSE-mg/f
Figure 77. Breakpoint chlorination of FeCls coagulated
final effluent (condition 13).
TABLE 44. CHLORINE DEMAND STUDIES
WASTEWATER CHARACTERISTICS
Primary effluent*
Analysis (10/17/74)
BOD(mg/l)
COD(mg/l)
NH3-N(mg/l)
TKN-N(mg/l)
Nitrate-N(mg/l)
FOG(mg/l)
TS(mg/l)
TVS(mg/l)
SS(mg/l)
VSS(mg/l)
pH
Temp(°C)
1180
2740
112
236
22
270
10190
1700
1170
624
9.7
23.0
Lagoon effluent"7"
Condition 13
(9/25/74)
100
490
112
190
21
15
8272
584
292
176
8.0
18.5
Final effluent*
Condition 13
(9/25/74)
49
265
112
180
20
4
8072
464
75
33
7.8
18.5
* 24-hour composite from primary sedimentation tanks.
+ 24-hour composite settled in laboratory for one hour.
* 24-hour composite from final settling tank -- FeC^ dose 180 mg/1.
132
-------
TABLE 45. CHLORINATION OF FINAL EFFLUENT
CO
w
Chlorine
dose
Date mg/1 pH
7/13/73
8/8/73
8/16/73
8/23/73
8/30/73
9/6/73
9/13/73
9/20/73
9/27/73
10/4/73
10/10/73
10/17/73
10/25/73
10/31/73
5/8/74
5/16/74
5/22/74
5/29/74
6/5/74
6/l?/74
6/19/74
7/10/74
7/17/74
7/24/74
7/31/74
8/7/74
8/14/74
8/22/74
9/4/74
9/18/74
9/25/74
10/2/74
10/9/74
10/17/74
10/25/74
11.1
13.3
12.5
10.4
8.2
5.8
5.5
2.5
2.8
2.8
5.6
5.1
5.1
5.5
15.9
18.0
14.7
9.4
8.9
12.4
6.0
~6.
8.8
5.2
6.4
18.1
17.8
18.3
11.9
10.1
13.4
14.2
11.4
10.9
10.1
7.9
7.8
7.6
7.9
7.8
7.9
7.9
7.9
7.9
7.7
7.8
7.8
7.6
7.4
8.0
7.9
7.5
'7.6
7.5
7.6
7.8
7.4
8.4
7.7
8.5
7.7
7.7
7.1
7.6
7.4
7.6
7.6
7.1
7.1
7.3
Total coliforms
COD
mg/1
784
424
435
290
360
437
466
558
447
588
522
789
1054
1288
980
705
649
631
570
330
396
409
490
537
561
340
296
302
1348
1022
1474
346
282
NHs-N
mg/1
171
152
158
157
162
144
102
121
105
68
94
120
123
91
85
96
72
80
107
95
(x!03/100 ml
< i
<0. 1
<0. 1
<0. 1
<0. 1
0.2
0.4
<0. 1
21.1
<0. 1
< 0. 1
1.4
2.4
300
1300
67
30
27
<1
0.4
1.3
17
10
9.4
1.9
2.2
6.4
0.15
6.5
2.8
0.6
0.05
0.01
Fecal coliforms
xNodlxlOOl (xl03/100ml)
97
90
99
99.
97.
96.
97.
54.
99.
99.
97.
32.
88.
99.
70.
'31.
58.
>97
79.
88.
5.
46.
43.
42.
-23.
54.
97.
8.
7.
61.
94.
97.
6
4
5
1
1
5
7
9
4
1
1
2
0
5
3
5
8
1
5
8
0
8
3
1
6
4
5
2
9.0
i!s
1.4
1
<0. ?
0.08
<0.05
0.04
0.0?5
2.8
1
2. 2
0.2
0.65
1.8
<0. 1
0.12
0.4
0.1
0. 0?5
0. 005
l(^W^ x lom
-6.1
45.5
31.7
48.?
>70.6
93
>77. 8
88.?
87.0
-25.6
41.5
44
46.9
2?. 1
57.9
>61.5
58.1
20.0
47.4
67.8
98.3
'1 otal bacteria
(xlO^/mlX
.029.
. ?lxlO~3
.013
0. 4x10-3
.012
8.3x10"^
0. 023
5.8
0.029
2.0
.085
0.11
19.9
18.4
1.0
7.2
2.6
0.026
0.051
0.083
6.9
35
1.3
6.2
6.6
0.22
12
1.2
0.6
OAC
. Uo
0.8
^"-^xlOO)
99.99
99.99
99.94
99.99
99.93
99.95
99.75
77.9
99.9
91.4
98.7
98.7
69.4
75.3
96.1
90.6
73.5
99.7
89.5
99.3
-14.3
3.1
58.2
33.4
9.0
91.1
-74.4
65.6
91.3
99.5
93.9
-------
o>
E
u
CO
8
18 -
16
14
12
10
8
6
§ 4
o
O
1973 data
o —
° Key: Total Coliforms
O 1973 - > ZOO/100 mf
• 1973 -< 2007 100 mf
A 1974 ->200/IOOmf
A 1974 -<200/IOOm*
_L
I
I
0 200 400 600 800 1000
COD; mg/f
Figure 78. Effect of wastewater quality on
chlorine requirements.
134
-------
SECTION XII
WASTEWATER EFFLUENT REUSE
As part of the objectives of this demonstration study, the feasi-
bility of using wastewater treatment plant effluent for certain in-plant
process waters was to be evaluated. Preliminary analyses indicated
that the likely area for water reuse would be associated with the
beamhouse operations of soaking, hairpulping, and reliming rather than
use the well water supply. In that the water use in the beamhouse
represents approximately 17 to 18 percent of the total requirements,
the reuse of effluent could result in a signficant reduction of waste -
water volume for ultimate disposal. However, certain conservative
substances, such as dissolved mineral matter, would result in higher
wastewater effluent concentrations but would not increase the mass of
substances discharged to the environment.
Several studies were conducted to evaluate the feasibility of
effluent reuse, first from the results of experiments related to hide
processing and the quality of the product, and second, from a mass
balance of chloride concentrations buildup in the wastewater effluent
by the employment of this practice.
EFFECT ON PRODUCT
Final wastewater effluent from the secondary wastewater treatment
plant was used as process water for the beamhouse operations as com-
pared to the use of the well water supply representing normal operating
procedures.
Twenty cattle hides were sided down the backbone, numbered, and
odd left and even right sides were taken as the test and the correspon-
ding sides were taken as the control. The twenty 'test' sides were
processed with a production lot in which the wastewater treatment
secondary effluent was used as the sole water source from soaking
through reliming, whereas the twenty 'control' sides were processed to
the same point with well water which is the normal production proce-
dure. After the beamhouse operations, the two lots, test and control,
received similar treatments from tanning through finishing.
135
-------
The results for the matched sides are presented in Table 46 for
the leather analyses and in Table 47 for the standard physical tests.
All analyses and physical tests were performed by tanning company per-
sonnel by routine ASTM, Federal Test Method Standard 311 and Society of
Leather Trades' Chemists (see Appendix A).
The physical strength characteristics (Table 47) were about equal
as well as such qualitative measures as leather break and temper. It
appears that the yield figures favor the controls as well as the uptake
of chrome and fats, however, the values are not statistically signficant.
The test sides were slightly darker in shade than the controls which
represents the only adverse circumstances affecting the desirability of
recycling wastewater treated effluent. The degree to which this may
be of concern would depend on the individual tannery and product
quality control.
TABLE 46. LEATHER ANALYSIS*
As received Water free H.S. Basis"1"
Test Control Test Control Test Control
(All values expressed as percent)
Moisture 12.40
Fat 7. 54
Hide substance 67.22
Ash 5.00
Organic(bydiff.) 7.84
Cr203 3.49
pH 3.2
12.04
8.45
65.71
5.46
8.34
3.88
3.2
— _
8.61
76.74
5.71
8.95
3.98
"
w _
9.61
74.70
6.20
9.48
4.41
"™ *™
18.45
11.22
100.00
7.44
11.66
5.19
— -•
18.32
12.86
100.00
8.31
12.69
5.90
_• _i
* Test sides treated with wastewater effluent for beamhouse procedure
made in 742 Fairway. Control matched sides, well water used in
beamhouse process. Test and control sides processed together from
tanyard.
+ Hide substance basis.
CHLORIDE BUILDUP BY EFFLUENT REUSE
In that chloride concentration represents a substance unaffected by
the wastewater treatment processes employed and is a substance of high
solubility, the effect of water reuse in the beamhouse operations on the
136
-------
TAPLE 47, . PHYSICAL LEATHER PROPERTIES
% Yield
Test
1. 87.5
2. 115.1
3. 100.8
4. 98.0
5. 110.1
6. 102.9
7. 90.5
8. 91.1
9. 111.9
10. 93.9
11. 95.6
12.107.7
13. 86.4
14.103.5
15. 91.3
16.112.2
17. 89.6
18.104.0
19. 93.3
20. 98.3
Mean
99.2
Control
89.1
119.2
103.0
100.6
110.7
105.5
92.9
94.8
114.5
89.2
94.3
105.7
87.4
101.9
92.0
111.9
92.3
100.4
93.8
96.5
99.8
Satra grain crack*
force -kg/ Mullen grain*
exten-mm burst -Ibs
Diff.
T-C
-1.6
-4.1
-2.2
-2.6
-0.6
-2.6
-2.4
-3.7
-2.6
+4.7
+1.3
+2.0
-1.0
+1.6
-0.7
+0.3
-2.7
+3.6
-0.5
+1.8
-0.6
Test Control Test Control
80+/10.880+/11.5
43/9.2 40/9.3
47/9.9 39/8.6
27/8.1 39/9.3
80/11.8 62/10.4
55/10.4 47/10.6
25/7.8 18/7.7
80+/L1.9 77+/L1.0
20/8.1 16/7.2
32/8.2 37/8.7
49/9.6 46/9.4
700+
590
700+
520
700+
700+
265
700+
300
525
570
700^
700
590
635
700+
700+
325
700+
310
525
589
Tensile
strength - psi
% Tensile elong.
Test Control Diff. Test Control Diff.
T-C T-C
4590
2460
3795
2220
5495
3280
1350
3810
825
3050
3090
4480
2595
5385
2560
4055
2895
1200
4320
825
2675
4000
110
-135
-1590
-340
+1440
+385
+150
-510
0
+375
-10
38
42
50
40
47
47
35
50
31
43
42
50
45
55
55
47
49
37
47
31
45
46
-12
-3
-5
-15
0
-2
-2
+3
0
-2
-4
* Values with a superscript of + indicate the measurement was above the scale range of the
instrument.
-------
resulting wastewater effluent concentrations was of particular interest.
In addition, most of the chloride found in the wastewater effluent is the
result of the beamhouse operations with a substantial increase in
effluent concentrations even without water reuse.
Table 48 showed the contributions of chloride from the various
tanning operations with the major portion, in excess of 80%, resulting
from the beamhouse. The well water supply has a chloride concentra-
tion of 177 mg/1 but in the wastewater effluent, without recycle, the
chloride concentration would increase to about 3,900 mg/1. Table 48
summarizes the water use and the resulting chloride concentrations
and estimated pounds of chloride for each process operation. It should
be noted that chlorides result from the tanyard operations as well,
however, recycle of the effluent appears only to be feasible for the
beamhouse operations at this time.
If one considers the chloride balance with the effluent reuse only
for the beamhouse operations and the additional chlorides that would
result from the sludge filtrate returned to the wastewater stream when
using FeCls as a sludge conditioner, the wastewater effluent chloride
concentration would approach 4, 700 mg/1. This would represent the
equilibrium chloride concentration for the wastewater effluent which
would be used in the beamhouse operations rather than the chloride
levels of 3,900 mg/1 as performed in the tests on leather quality repre-
sented in Tables 46 and 47. A calculation of the chloride balances
with respect to reuse cycle are presented in Table 49. These results
are based on a water use of 534 m^/d (0.141 mgd) for the beamhouse
and a total wastewater flow of 3028 m3/d (0.8 mgd) or a 17.7% of the
total effluent water reuse in the beamhouse operations. The percent
increase in chloride concentration in wastewater treatment effluent as
a result of recycle would be 21.4% which would be representative of a
soluble conservative substance. Non-conservative substances, remov-
able by the treatment process, would not increase in the wastewater
treatment effluent to as high a degree.
Levels of chloride concentration in excess of 10,000 mg/1 in the
process water for the beamhouse operation are assumed to be unaccept-
able by tannery personnel. Consequently wastewater effluent reuse for
100% of the beamhouse operation appears to be feasible and acceptable
providing that the resulting slightly darker shades of product can be
properly adjusted. The overall increase in chloride concentration would
likely have no significant effect on the treatability of the wastewaters
so generated. Effluent limitations would require adjustment to account
for the water conservation measures realized by effluent recycle when
expressed as a concentration. However, effluent limitations expressed
138
-------
TABLE 48. CHLORIDES IN WASTEWA^EK
Department
l.Beamhouse
?.Tanyard
3. Color and
fatliquoring
and other
departments
Chloride
concentration
Process nig/1
a.Presoak
b.Soak
c. Hairpulp
drain
wash
d. Hairpulp
final drain
Subtotal
a.Pfebate
b.Bate
c. Pickle
d. Chrome
Subtotal
Total
24900
22200
21800
13440
5100
200
200
36600
6300
177*
3764+
Number
of drums
9
9
9
9
9
9
9
9
9
Estimated
Estimated Total pounds of
gallons/drums gallons chloride/day
2200
6600
1100
3600
2200
2000
4000
500
3000
19800
59400
9900
32400
19800
141300
18000
36000
4500
27000
85500
573200
800000
4112
10998
1800
3632
842
21384
30
60
1374
1419
2883
846
25113
* Chloride concentration of well water source of supply.
+ Mean chloride concentration for the process waters excluding sludge dewatering filtrate recycle.
-------
TABLE 49. CHLOfilDE BALANCE ,FOR WATER REUSE SYSTEM IN THE BEAMHOUSE
Chloride, kg/day, (pounds/day)
Number of Beamhouse Chloride % Increase in
effluent Process Final effluent cone, mg/1 chloride cone, in
reuse cycle addition reuse Other Total T. plant effluent wastewater effluent
No reuse 9700(21384) none 2060(4542) 11760(25926) 3886 2095*
1st 9700(21384) 2077(4579) 2060(4542) 13837(30505) 4572 17.65
2nd 9700(21384) 2444(5388) 2060(4542) 14204(31314) 4693 2.64
3rd 9700(21384) 2508(5530) 2060(4542) 14268(31456) 4715 0.47
4th 9700(21384) 2520(5556) 2060(4542) 14280(31482) 4718 0.06
5th 9700(21384) 2522(5560) 2060(4542) 14282(31486) 4719 0.02
* Increase percent compared to chloride concentration in water supply, all others compared to
preceding effluent quality.
Other: Tanyard, sludge filtrate, chloride level in well water for color and fat department.
Flows: Beamhouse 535 m3/d (0.1413 mgd)
Tanyard 324 m3/d (0.0855 mgd)
Color & Fat 2170 nrj/d (0.5732 mgd)
Total 3029 m3/d (0.800 mgd)
-------
in kg/1000 kg hide would be unaffected by the practice of effluent
recycle.
141
-------
SECTION XIII
SLUDGE DEWATERING
SLUDGE CHARACTERISTICS
was
The solids removed by gravity separation in the primary clarifiers
dewatered by the pressure filtration process.
The primary sludge contained settled raw wastewater solids and
biological solids from time to time wasted from the secondary treatment
system throughout the study. The sludge solids were thickened in the
lower portions of the primary clarifiers. The thickened sludge was
pumped to the sludge dewatering building where sludge grinding was
affected and the sludge solids were discharged to a contact tank for
chemical conditioning and subsequent pumping to the filter press.
The primary sludge (i.e., primary sludge and waste activated
sludge at times), was analyzed routinely prior to grinding and chemical
conditioning. The results of the analyses for various dates and opera-
ting conditions with associated chemical parameters are presented in
Tables 50 and 50A. In addition, the extent to which waste activated
sludge contributed to the number of filtered cycles per week is included
as a relative reference. The average results for the sludge analyses
for the period July to October, 1974, are shown in Table 51.
The sludge was dewatered on a 5-day basis Monday through Friday.
SPECIFIC RESISTANCE
The specific resistance measurements used in this study were after
the recommendations of Passavant Corporation, Birmingham, Alabama.
The stainless steel cylindrical specific resistance meter was capable of
operating through a wide range of pressures by the use of nitrogen gas
for the driving force. Filtrate volumes are measured with respect to
time in a fashion similar to the standard specific resistance test
operated under pressures less than 1 atmosphere.
The procedure involved the placement of 100 ml of the conditioned
142
-------
TABLE 50. PRIMARY SLUDGE ANALYSIS
Total
Date
10/16/73
10/23
10/24
10/25
10/31
11/1/73
11/2
11/6
11/7
11/8
h^ 11/13
co 11/14
11/15
11/27
11/28
11/29
12/4/73
12/5
12/11
12/12
12/12
12/13
12/18
12/21
7/9/74
7/10
7/10
Cycle
no.
3
2
2
2
3
3
3
1
2
4
Waste act.
sludge
yes
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
Extent of
waste filtered*
cycles/wk. pH
<5
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
none
8.15
7.5
7.68
9.48
7.48
10.25
10.5
10.68
9.79
7.69
10.7
7.68
8.4
8.99
8.35
7.74
6.9
8.67
9.07
9.32
7.28
8.82
6.88
7.18
Total Volatile
solids solids
mg/1 mg/1
90832 53980
129840 78800
110700 69400
125500 75500
132600 81700
79100 45600
79000 44300
110280 71280
142240 95200
117840 74880
135200 92500
116320 77920
109040 71360
158720
91520 56400
65520 38720
122160 77840
94160 57120
120720 79440
159040 105280
103680 69120
81120 52080
106640 71920
158640 115840
160920 118920
159160 114760
119000
Fixed Suspended
solids Volatile total solids
mg/1 % mg/1
51040
41300
50000
50900
33500
34700
39000
47040
42960
42700
38400
37680
35120
26800
44320
37040
41280
53760
34560
29040
34720
42800
42000
44400
60.7
62.7
60.2
61.6
57.6
56.1
64.6
66.9
63.6
68.4
67.0
65.4
61.6
59.1
63.7
60.7
65.8
66.2
66.7
64.2
67.4
73.0
73.9
72.1
77.5
116240
98300
109600
92000
60300
6500
94560
124320
100720
120700
102320
94960
144480
78960
50400
105280
78080
105360
142800
89360
69440
91200
142480
142240
135640
Suspended
Volatile
suspended
mK/1
75520
67600
72600
61000
43000
42000
68280
92320
72960
90300
76000
69440
54080
37840
75040
55280
76560
101280
66960
51120
70560
111680
115640
110400
Fixed
suspended
mg/1
40720
30700
35000
31000
17300
23000
26280
32000
27760
30400
36320
25520
24880
12560
30240
22800
28800
41520
22400
18320
20640
30800
26600
25240
Volatile
65.0
68.8
66.2
66.3
71.3
64.6
72.2
74.2
72.4
74.8
74.3
73.1
68.5
75.1
71.3
70.8
72.7
70.9
74.9
73.6
77.4
78.4
81.3
81.4
(Continued)
-------
TABLE 50. (CONTINUED)
Date
7/11
7/24
7/26
7/29
7/31
8/6/74
8/7
8/9
8/16
8/20
8/26
9/3/74
9/6
9/10
9/16
9/18
9/20
9/25
9/26
10/1/74
10/3
10/3
10/3
10/8
10/8
10/8
10/16
10/17
10/17
Cycle Waste act.
no. sludge
4
2
3
5,6,7
6,7,8
2
1
2
3
3
4
5
1
2
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
Extent of
waste filtered*
cycles /wk. pH
none 6. 52
<10 7.36
<10 7.08
<10 7.48
<10 6.68
<10 6.78
<10 7. 54
<10 7.74
<10 6.62
<10 6.82
<10 7.15
<10 7.02
<10 9.01
>10 8.26
>10 7.64
>10 7.61
>10 7.32
>10 7.3
>10 6. 99
>10 7.18
>10 7.09
>10 7.18
>10 7.16
>10 7.08
>10 7.06
>10 7.18
>10 7.20
>10 7.06
>10 7.04
Total
Total
solids
mg/1
108724
97040
110080
91160
100880
101440
123120
113520
136680
108920
125904
120040
88520
85880
105760
89640
85560
104720
77400
78320
76160
94120
81120
69600
76480
75640
87440
103840
81240
Volatile Fixed
solids solids
mg/1 mg/1
69244
65880
75760
61920
64880
65440
77680
74440
93120
69160
80856
66680
53680
54080
65520
52680
49400
68600
46760
48520
49280
58320
52760
44240
49600
44800
54080
64440
48480
39840
31160
34320
29240
36000
36000
45400
39080
43560
39760
45042
53360
34840
31800
40240
36960
36160
36120
30640
29800
33360
39400
32760
Volatile
63.7
67.9
68.8
67.9
64.3
64.5
63.1
65.6
68.1
63.5
64.2
55.5
60.4
63
62
58.8
57.7
65.5
60.4
61.9
64.7
62
65
63.6
64.9
59.2
Suspended
total solids
mg/1
89004
83560
98480
79400
88480
88640
108760
100200
120320
95150
113064
95160
77400
74480
90300
73800
69840
90360
63800
67120
64920
82000
69560
59360
64840
63720
74560
90840
69040
Suspended
Volatile
suspended
mg/1
66204
62560
72800
58240
61760
61920
73000
70760
88560
66160
78264
64160
52640
52480
62320
49920
46640
65120
43840
45800
46840
55800
49680
41800
41840
50920
61640
45960
Fixed
suspended
mg/1
22800
21000
25600
21160
26720
26720
35100
29440
31760
28960
34800
31000
24760
22000
27980
23880
23200
25240
19960
21320
23640
29200
23080
Volatile
74.4
62.7
73.9
73.4
69.8
69.9
67.7
70.6
73.6
69.6
69.2
67.4
68.0
70.5
69
67.6
67.8
72.1
68.7
68.2
72.1
67.8
71.4
70.6
65.7
68.3
67.9
66.6
-------
TABLE 50A, PRIMARY SLUDGE ANALYSES
COD Oil & grease
Date mg/1
12/21/73
7/11/74 125290
7/26/74 105272
8/6/74 126200
8/9/74 141360
8/16/74 11930
9/16/74 94600
9/18/74 90454
9/20/74 110400
10/1/74 100700
10/3/74 105600
10/16/74 81072
mg/1
46440
19120
17200
21000
20000
33000
10000
14000
16600
16000
20000
Total
Kjeldahl
nitrogen
mg/1
4700
5250
5050
7000
4450
4700
5500
5600
6100
5500
5450
6550
Ammonia
mg/1
430
--
580
1090
1070
800
950
720
680
950
920
86
Calcium
mg/1
7306
--
--
--
--
--
5790
5371
6333
7188
5890
6525
Total
chromium
mg/1
1187
1128
1153
2144
2198
2531
1906
1635
1954
1954
1104
*Extent of WAS. filtered is an estimation of cycles/week as contribution to total: 5--minor,
10--significant.
-------
TABLE 51. MEAN SLUDGE ANALYSES --JULY TQ OCTOBER, 1974
Parameter
Total solids
Suspended solids
COD
Oil and Grease
Total Kjeldahl nitrogen
Calcium
Chromium
pH, standard units
Concentration, mg/1
104, 800
86, 400
109, 100
21,200
5,500
6,350
1,685
6.5-9.1
Percent volatile
64.4
70.4
sludge into the resistance meter, tighten the cover, and supply the nitro-
gen gas at the requisite pressure. The filtrate would be collected in a
graduate cylinder or burette and the filtrate volume recorded in 1 minute
intervals after a 2 minute initial filtration period. Additional information
was recorded for the sludge such as pH, temperature, and total solids.
A plot of the filtrate volume data, wherein t/V versus V was pre-
pared where t equals elapsed time in seconds and V equals volume of
filtrate collected. The graph of t/V versus V results in a linear plot
from which the slope " b " was determined.
The specific resistance, R, of the sludge was calculated by the
following formula:
R - Kxb
K " C
where R = specific resistance
b = slope of plot t/V versus V
C = solids of the sludge, ..„, , _^s,ludge JF.^8.0^ - -
wt or sample-we siudge dry solids
K = constant, function of temperature (viscosity)
A value of 3 or less indicates the sludge is properly conditioned
for dewatering on the filter press with the lowest values representing
the more readily dewatering characteristics.
The specific resistance determination permitted the evaluation of
146
-------
the effects of various concentrations of conditioning agents and various
operating pressures.
To obtain information pertaining to the effect of pressure on the
filtration of the sludge, the specific resistance measuring device was
readily adapted to this function, wherein the specific resistance values
could be determined at various operating pressures. Table 52 presents
a summary of measurements made at normal terminating operating pres-
sure of 225 psi and for lower pressure values for a given sludge sample.
The results indicate that reducing the terminating operating pres-
sure as measured by the specific resistance test did not yield higher
or lower specific resistance values in a consistent manner.
An empirical relationship between pressure and specific resis-
tance follows:
R2 =
where: R = specific resistance;
P = pressure;
s = coefficient of compressibility.
The value s can be determined as the slope of a plot of log specific
resistance versus log pressure. An s value of 1.0 would indicate a
compressible cake, with the increase in specific resistance being
directly proportional to the filtering pressure. As the value of s
approaches zero, the specific resistance values would be more inde-
pendent of pressure or considered to be of a non-compressible nature.
On two dates, 7/16/74 and 7/25/74, the specific resistance measure-
ments were made in the range of pressures from 150 to 225 psi and
100 to 225 psi respectively (Table 52). In the first instance the
specific resistance values increase with pressure indicating the com-
pressible nature of the cake, whereas in the second instance, there is
an increase in specific resistance with pressure for 100 psi and 150
psi values, however, in the pressure range from 150 to 225 psi, no
increase in specific resistance is noted.
147
-------
TABLE 52. EFFECT OF PRESSURE ON SPECIFIC RESISTANCE
00
Date
11/27/73
1/28/73
11/29/73
12/4/73
12/5/73
12/7/73
12/11/73
12/12/73
12/28/73
12/27/73
1/2/74
1/16/74
1/22/74
7/16/74
7/25/74
9/4/74
Cycle ^Conditioning
no. kg/kg
2
2
2
4
3
5
2
2
2
5
2
3
2
3
1
2
1
1
2
3
1
2
FeCIS
0.0395
0.0468
O.C468
0.0374
0. 0297
0.0365
0.0390
0.0562
0.0395
0. 0405
0.0405
0.0389
0. 0590
0. 0520
0.0569
0.0473
0.0525
0.0577
0.0410
0. 0499
0. 0491
Sludge character
PH
Lime
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
128
144
117
0659
111
114
0641
0909
147
114
0754
0949
114
12.
12.
12.
11.
11.
11.
12.
12.
12.
11.
12.
12.
12.
12.
11.
11.
12.
12.
Temp
°C
2
0
0
8
8
9
2
2
0
95
12
12
1
1
5
6
4
2
29
25
26
21
23
25
30
26
26
27
19
23
24
24
23
23
22
14
21
26
29
26
26
Solids
%
12.
10.
10.
12.
16.
13.
12.
8.
12.
11.
11.
12.
8.
9.
8.
10,
9.
8.
9.
11.
11.
12.
12.
1
0
0
5
1
1
8
5
1
8
8
3
1
2
4
1
1
1
1
6
4
5
7
Specific resistance at different pressures
Psi/R=
175/1.5
175/1.163
175/1.45
175/1.82
135/1.57
135/2.06
135/2.06
135/1.10
100/1.10
100/1.59
100/. 79
100/1.65
175/1.77
175/1.87
175/1.77
100/. 59
100/1.53
100/.82
ISO/. 78
150/1.86
100/. 84
100/1.17
120/1.12
Psi/R= Psi/R- Psi/K-
225/1.97
225/1.047
225/1.15
225/1.95
225/1.21
225/1.56
225/1.59
22S/.85
22S/.74
200/1.36
22S/.83
225/1.25
225/1.49
225/1.87
225/1.48
225/1.65
225/2.02
225/.30
22S/.69
180/2.72 200/3.12 225/2.76
140/1.82 180/1.52 225/1.64
150/1.90 225/1.18
200/.99 22S/.72
*Expressed as weight of chemical as FeClsor Ca(OH)2 per unit weight of dry sludge solids.
-------
The specific resistance test is performed at a constant pressure
throughout the test period whereas the pressure under full-scale filter
operating conditions increase from the precoat pressure to the termi-
nating pressure of 225 psi, thus the cake so formed is subject to the
range of operating pressures rather than a constant pressure during the
filter cycle. Generally, for a given target filter cake moisture content,
the higher the terminating operating pressure the shorter the filter time
and hence greater production. This relationship is evident from the
equation developed by Jones ( 5 ).
0.321 Rnd2(Ci-Cf)2
(lOO-q)
where T = filter time, hours
7
R = specific resistant of the sludge in 10 cm per gram
H, = viscosity of filtrate, in centipoise
d = distance between cloths (chamber thickness), in inches
Cj = initial sludge moisture content, in percent
Cf = final sludge moisture content, in percent
P = filtration pressure, in Ib per sq in
In that filter time is inversely proportional to pressure, the benefit of
higher terminating operating pressures are evident. However, if
specific resistance increases with pressure in direct proportion, (i.e.,
for s value of 1.0), the benefit of increased pressures would be nulli-
fied as expressed in this equation. The filter time can- be minimized
by decreasing the moisture content of the feed sludge, the filtrate
viscosity (higher temperature) and specific resistance. The latter is
affected principally by sludge conditioning measures. The desired
moisture content of the cake Cf depends upon ability to form cakes
which will be readily released from the press and the ultimate disposal
of the cake, whether or not incineration is to be employed or the cake
placed in a landfill.
Specific Resistance Measurements of Special Sludge Mixtures
The dewatering properties of several different sludges were
evaluated by the use of the specific resistance test. It was desired
149
-------
to determine the influence of primary tank scum, principally grease, in
combination with primary sludge underflow on the dewatering properties
of the combination. Also, additional specific resistance information
was desired for the dewatering of the waste biological sludge separately
The scum sludge was conditioned with ferric chloride and lime and
added to conditioned primary sludge in various volume proportions in
accordance with Table 53.
TABLE 53. EFFECT OF SCUM ON SPECIFIC RESISTANCE
Relative volume of Equivalent scum Specific
Sample sludge,, mixtures, mis sludge per cycle Solids pH resistance
no. Contact Scum % % ^
tank sludge
1
2
3
4
5
100
100
200
200
200
100
100
50
20
10
50
33
20
10
5
15.9
14.7
13.5
11.4
13.1
11.08
10.58
12.64
12.6
11.4
0.84
1.31
0.50
1.12
0.77
The resulting specific resistance measurements indicate that the
mixture of scum sludge and primary sludge with appropriate conditioning
could be dewatered, i.e., R less than 3. The effect of continued
dewatering of a sludge with a high grease content on a full-scale filter
was not evaluated. The possible blinding of the filter cloth or weeping
of the oil bearing substances requires evaluation for extended periods.
The dewatering of waste activated sludge is usually more difficult
than for primary sludges. A combination of biological solids from an
aerobic digester and mixed liquors from high and low solids biological
treatment units were conditioned with ferric chloride and lime in the
proportions shown in Table 54. The resulting specific resistance
measurements of the conditioned biological solids are shown. The
results indicate that a properly conditioned biological sludge can be
dewatered separately.
In the third test, waste activated sludge from a low solids biolo-
gical system was flocculated with 300 mg/1 ferric chloride, settled and
thickened before the resulting sludge was chemically conditioned. The
resulting specific resistance values are reported in Table 55.
150
-------
The value of specific resistance near 3 and below indicate that the
solids so conditioned would be filterable. In that the biological sludge
solids were flocculated with ferric chloride, apparently the ferric
chloride requirement for sludge conditioning is lower than in the fore-
going test.
TABLE 54. SPECIFIC RESISTANCE OF CONDITIONED BIOLOGICAL SOLIDS
Chemical dosage, kg/kg
Sample
no.
1
2
3
4
Ferric chloride
as FeCls
None
0.047
0.081
0.082
Lime
asCa(OH>9
.None
0.12
0.25
0.18
Sludge
solids
%
3.4
12.1
8.6
12.3
pH
7.8
12.8
12.6
12.3
Specific
resistance
14.0
1.14
1.76
1.49
TABLE 55. SPECIFIC RESISTANCE OF CHEMICALLY COAGULATED
BIOLOGICAL SOLIDS
Chemical dosage, kg/kg
Sample Ferric chloride Lime
no. as FeClS
1 None
2 None
3 0.091
4 0. 100
5 0. 070
asCa(OH)2
None
0.24
0.23
0.25
0.31
Sludge
solids
%
6
6
6.3
5.7
4.6
pH
8.6
12.6
13.1
13.1
13.6
Temp
°C
15
15 J
16
16
16
Specific
resistance
38
3.2
.74
.66
2.38
Effect of Sludge Aging on Specific Resistance
The purpose of this evaluation was to determine if conditioned
sludge loses filterability, as measured by specific resistance, as the
contact time increases.
Six samples of primary sludge, 11.4% total solids including raw
and waste activated sludge solids, were conditioned by ferric chloride
and lime at 12.2 pounds of Ca(OH)2 and 4.2 pounds of FeC^ per 100
pounds of sludge solids and placed on a magnetic stirrer for agitation
for a specified time. The results are shown in Table 56.
151
-------
TABLE 56. SPECIFIC RESISTANCE OF CHEMICALLY CONDITIONED
STORED SLUDGE
Test
na
1
2
3
4
5
6
Length of mixing
after chemical
addition (hours)
Immediately
1 hr.
2 hr.
4 hr.
8 hr.
24 hr.
Sludge soils
of conditioned
sample (%)
11.7
12.7
11.4
12.3
12.2
12.7
PH
12.2
12.2
12.6
11.7
11.7
10.6
Temp
°C
17
19.5
21
22
24
23
Specific
resistance
5.4
6.2
5.0
5.2
10.3
9.8
None of the samples so conditioned had specific resistance values of
3 or less. Some deterioration in dewatering properties occurred for
the 8 and 24 hour elapsed time intervals. Usually the conditioned
sludge remains in the contact tank less than 4 hours which apparently
would not adversely affect the dewatering properties of the sludge.
SLUDGE CONDITIONING
Routinely ferric chloride and lime were used as the sludge condi-
tioning chemicals throughout the course of the experimental work.
Other materials were used on a limited basis as conditioning agents
such as, scraps and shavings, and buffing dust, both separate and in
combination with the chemical conditioners.
Ferric Chloride
Ferric chloride was received as an acidic solution having an
average FeClg content of 39.2% with an average dry weight of 4.63
pounds per gallon. The material was stored in two-8000 gallon
reservoirs located inside the sludge dewatering building.
Normally, FeClg used in conjunction with lime would form the
alkaline flocculant precipitate of Fe(OH)3 to facilitate dewatering of the
solids. The flocculant material likely serves to gather highly dispersed
fine solids which contribute to the poor dewatering properties of the
solids present. For the tannery sludge dewatered in this instance,
the ferric chloride also served to combine with the sulfide present
forming ferric sulfide, an insoluble precipitate without benefit as a
conditioning substance. However, the ferric sulfide so formed served
152
-------
to minimize secondary odors which would result from the presence of
free sulfide for the cake disposal practices employed.
The extensive use of sulfide for hair pulping operations has been
identified and presented in previous sections of this report. Although
the soluble sulfide fraction would not be removed by primary sedimen-
tation practices, a significant portion of sulfide is associated with the
insoluble fraction of the hair pulp. Additional sulfide generation can
occur in the thickening zones of the primary clarification units wherein
higher oxidized forms of sulfur are biologically reduced resulting in
additional sulfide generation. Although the sulfide contents of the
primary sludge were not measured, operating personnel estimated that
the FeCls dosages required for sludge dewatering were increased by
10 to 30% as a result of the presence of sulfide.
Lime
Slaked lime, a material extensively used in the tannery beamhouse
operations, was obtained from the industry's lime slaker for use as a
sludge conditioning agent. The lime slurry was periodically sampled
and analyzed for total and fixed solids and unit weight in kg/1 (Ib/gal).
The results of the periodic analyses of the lime slurry indicated the
following mean values:
Total solids 193,000 ppm
Total fixed solids 161,000 ppm
Density 1.10 kg/liter (9.21 Ib/gal)
Buffing Dust
The use of buffing dust as a sludge conditioning agent was tried on
a limited basis. The properties of the buffing dust are presented in
a subsequent section on filter precoat materials. Although the specific
resistance results indicated that buffing dust may have some potential
as a conditioning agent, the filter cycles of operation employing buffing
dust indicated a lighter wetter cake. (Results, August 2, 1974). Also,
the available buffing dust indigenous to this industry would be insuffi-
cient for use both as a precoat and conditioning agent.
Combinations of Conditioning Materials
Several experimental trials were made for a combination of
chemical conditioning agents, with and without buffing dust and/or
shavings, in conjunction with primary sludge and specific resistance
measurements were made of the sludge so conditioned. The results
153
-------
for several experimental trials are shown in Tables 57, 58, 59, and
60.
TABLE 57. TRIAL #1--FEBRUARY 6, 1974
Conditioning materials
Sludge
Test Ferric chloride Lime Buffing dust
no.
1
2
3
4
5
kg/kg
0.070
0.032
0.031
0.035
None
kg/kg
0.
0.
0.
0.
0.
147
123
117
133
104
kg/kg
None
0.096
0.183
None
0.326
solids
pH %
13.
13.
13.
13.
13.
1
1
1
2
2
12.
14.
15.
13.
17.
3
7
4
6
3
Temp Specific
°C
23
23
23
23
22
resistance
0.
1.
1.
1.
13.
64
01
31
20
2
Results of Trial #1 indicate that buffing dust in combination with lime
and ferric chloride conditioners did not appear to improve the dewa-
tering properties of the sludge as measured by specific resistance.
Test No. 5 did demonstrate the need for ferric chloride as one of the
conditioning agents.
TABLE 58. TRIAL #2--JULY 22, 1974
Conditioning materials
Test Ferric chloride Lime Buffing Shavings Sludge Temp Specific
no. kg/kg kg/kg dust kg/kg PH solids °C resistance
kg/kg %
1
2
3
4
5
6
7
8
0.059
0,035
0.029
0.032
None
None
None
0,134 Mqpe
0.
0.
0.
0.
0.
0.
132
110
178
172
119
128
No$2 None
None
0.029
None
None
0.031
None
None
None
None
None
0.046
0.045
None
None
None
10.
11.
11.
11.
11.
11.
10.
7.
6
0
0
5
9
5
5
6
10.
10.
13.
8.
8.
12.
11.
12.
8
9
1
1
4
1
3
8
3.
7.
2.
1.
15.
29.
17.
290
9
3
5
6
9
1
0
Results of Trial #2 (Table 58) indicate that both buffing dust and
shavings used singly improved the dewatering properties of the sludge
as measured by specific resistance. Ferric chloride as a conditioning
agent is again demonstrated as needed to facilitate the dewatering of
154
-------
the sludge. The need for lime was not evaluated in a similar fashion.
TABLE 59. TRIAL #3--AUGUST 21, 1974
Conditioning materials
Test Ferric chloride Lime Butting dust
no.
1
2
3
4
kg/kg
0.049
0.032
0.032
0,032
kg/kg
0.130
0.119
0.1.19
0.118
kg/kg
none
none
0.034
none
Sludge
Shavings solids
Specific
kg/kg pH % . resistance
none 11 11.1
none 12.7 12.1
none 12.8 12.1
0.034 12.6 12.2
2.47
2.19
2.91
3.96
Results of Trial #3 (Table 59) indicate that neither the addition of
shavings or buffing dust improved the dewatering properties of the
sludge.
TABLE 60.
TRIAL #4-- SEPTEMBER
11, 1974
Test
no.
1
2
3
Conditioning
Ferric Chloride
. kg/kg
0.028
none
0.056
materials
Lime
kg/kg
0.160
0.278
none
Buffing dust
kg/kg
none
none
0.182
pH
9.9
11.5
6.8
Sludge
solids
13.5
10.4
10.3
Specific
resistance
2.93
17.0
8.5
The results of Trial #4 (Table 60) are inconclusive but there is an indi-
cation that the combination of ferric chloride and lime is more desir-
able than lime alone on the combinations of ferric chloride and buffing
dust.
Polymer Conditioning
The possible use of polymers as a conditioning agent was consi-
dered but not evaluated. The use of polymers to replace all or part
of the lime requirements would have the advantage of dewatering less
solids, because of the solids produced as a result of lime addition.
The polymers would likely be unaffected by the sulfides present as well.
The major disadvantage would be related to the apparent loss of effec-
tiveness of polymers at high pH values, with a pH 9 to 9. 5
155
-------
representing the upper limit. The pH of the primary sludge in the
absence of waste secondary sludge may exceed this value. The use of
lime appears to be beneficial both to overcome the sticky properties of
sludge having a high grease content and to reduce the FeCL} condi-
tioning requirement, thus extensive testing would be necessary to opti-
mize the use of polymers which was not within the scope of the work
reported herein.
FILTER PRECOAT MATERIALS
Several materials are used in conjunction with the precoat of
pressure filters. Incinerator ash is most frequently used when the
sludge cake is incinerated or when other sources of ash are readily
available. If ash is not available, the use of diatomaceous earth is
frequently recommended.
As part of the objectives of this study, waste materials indigenous
to the industry were to be used for both precoating and conditioning of
the sludge. One material that showed considerable promise in the
sludge dewatering pilot studies was the use of "buffing dust" , a waste
product normally disposed of as a solid waste.
The dry buffing dust was transferred from the storage bin by an
augur to the precoat tank, the amount of weight was controlled by the
operating time and speed of the augur. Thus a predetermined amount
of precoat materials were transferred to the precoat tank for wetting
and subsequent batch use during the precoat operation.
The solids analysis of the buffing dust for the test period were
as follows (Table 61).
TABLE 61. SOLIDS AND VOLATILE CONTENT OF BUFFING DUST
Percent volatile
Date Percent solids on dry weight basis
7/10/74
7/19
7/29
8/21
8/28
9/6
9/10
9/16
86.1
90.0
93.4
88.7
90.4
89.8
89.5
95.2
(continued)
83.6
82.7
75.6
77.9
83.4
67.8
80.2
63.1
156
-------
TABLE. $1. (CONTINUED)
Percent volatile
Date Percent solids on dry weight basis
9/26
10/1
10/16
10/21
93.3
91.4
92.4
93.7
63.9
77.0
69.5
76.1
Mean = 91.2 Mean = 75.1
s = 2.56 s = 7.33
The sampling results indicate a mean percent solids of 91.2 and with a
percent volatile ccntent of 75.1 on a dry weight basis.
The buffing dust applied to the filter press per cycle during the
course of the study ranged from 136 to 244 kg (28 to 50 Ib) for the
filter surface. The filter had a total surface area of 178 m2 (1913
ft2). Depending on the number of dewatering cycles required, the
pressure filtration process utilized 50 to 90% of the buffing dust gener-
ated by the tanning process, the remainder of which was disposed of
as refuse.
The use of buffing dust as a precoat affected the filtration opera-
tion in several ways. The buffing dust tended to blind the filter cloth
material resulting in higher headless through the filter medium. This
was evidenced by the sequential increase in precoat pressures required
for subsequent filter cycles after media cleaning. Normally, the filter
medium was cleaned at the end of each operating week. The precoat
pressures for various operating periods are shown in Figure 79. It is
apparent that the precoat pressure increased with each cycle of opera-
tion after cleaning of the filter cloth when buffing dust is used as a
precoat material. Diatomaceous earth precoat material, for the limited
operating period October 2-8, 1974, did not have as pronounced
increase in precoat pressure with subsequent filter cycles. After filter
cloth cleaning the precoat pressures for the first filter cycle may vary
from 45 to 55 psi which is primarily related to the relative cleanliness
of the drainage grooves in the filter plate. This effect is evident in
Figure 79 also.
Although diatomaceous earth as a precoat material would have
demonstrated advantages, the use of buffing dust, a solid waste material,
157
-------
100
80
CO
Q.
•*
UJ
cr
60
C/)
LU
CC
Q_
O
o
UJ
40
20
PRECOAT
(D AUG. 27, 73 BUFFING DUST
•
-------
can be successfully employed with appropriate maintenance procedures.
FILTER PRESS PERFORMANCE
Over a period of 7 months, detailed information was collected on the
operating conditions and performance of the filter press. Data was col-
lected on sludge characteristics, cake solids, dosage of chemical condi-
tioning agents, cycle times, filtration rates with respect to time,
terminating filter pressures, temperature and specific resistance
measurements of the conditioned sludge. The information obtained was
used to evaluate the influence of the various factors on the dewatering
properties of the sludge in the full scale press. The performance of
the filter press and dewatering properties of the sludge can be deter-
mined from the length of the filter run or 'filter time' or from the
.average filtration rate over the length of the filter run. The shortest
filter time and the highest mean filtration rate to produce a filter cake
of desired moisture content represents the highest performance for the
filter press but would not necessarily represent optimum or minimum
costs associated with the application. Generally, chemical conditioning
costs will be higher for operating conditions which will minimize the
filter time and maximize the filtration rate. This study was not
directed to minimizing costs, but rather to determine those factors and
the relative significance of the factor in improving filter performance.
In addition to the use of filter time and mean filtration rate as
filter performance variables, the first order rate constant was deter-
mined for each of the filtrate volume versus time curves. Table 62
presents the filter data that included filtrate volume with respect to time
for filter runs throughout the 7 months period. Figures 80 and 81
show the relationships for filtration rate and cumulative filtrate volume
with respect to elapsed time from the start of the filtration cycle for
two runs on different dates. In addition, the filter time in minutes as
well as the average or mean filtration rate is indicated on each plot.
It is apparent that these two parameters only define or are related to
the terminal condition of the filtrate volume-time curve.
In this study an additional parameter was used to characterize the
filtrate volume-time curve. By the use of statistical curve fitting
procedures,both first order and second order relationships were deter-
mined for each of the runs presented in Table 62. The rate constants
determined by this procedure resulted in the minimum sums of squares
fit for each set of filtrate volume-time data. The sums of squares were
compared for the first order and second order model for each set of
data and in all but one instance the first order model resulted in the
minimum sums of squares fit and therefore was used as the third
159
-------
JTABLE 62
Date
3/7/74
3/7
3/12
3/12
3/22
3/26
3/28
4/4
4/16
4/16
4/30
5/9
5/14
5/14
5/29
5/29
6/4
6/13
Run
no.
2
6
1
4
1
3
9
6
3
7
2
3
6
8
3
8
5
7
Temp Cumulative filtrate
volume, gallons
C Elapsed filter time, minutes
20
21
20
18
19
16
(20)
21
21
20
17
27
22
17
25
25
25
23
319 711
7 12
207 434
8 13
308 542
7 10
336 729
8 13
328 868
7 12
160 242
8 10
21 136
7 9
443 727
7 10
318 387
6 7
180 378
4 6
198 665
6 11
168 360
6 9
160 480
4 8
167 558
6 11
144 626
3 8
50 278
4 6
64 342
5 7
23 104
6 7
959 1153
17 22
648 833
18 23
660 1055
12 22
1012 1238
18 23
1157 1363
17 22
542 575
18 19
448 669
14 19
1036 1244
15 20
552 750
12 17
826 1125
11 16
960 1132
16 21
602 772
13 17
830 1078
13 18
832 1028
16 21
984 1184
13 18
771 1062
11 16
893 1194
12 17
565 865
12 17
1308 1430 1524
27 32 37
986 1114 1219
28 33 38
1315 1500 1625
32 42 52
1406 1531 1636
28 33 38
1514 1625 1716
27 32 37
715 822 918
24 29 34
818 920 1005
24 29 34
1408 1508 1582
25 30 35
892 992 1064
22 27 32
1318 1460 1562
21 26 31
1266 1383 1480
26 31 36
927 1050 1160
22 27 32
1246 1381 1498
23 28 33
1179 1301 1406
26 31 36
1332 1466 1509
23 33 38
1269 1424 1537
21 26 31
1406 1557 1670
22 27 32
1093 1275 1421
22 27 32
1599 1671
42 47
1385 1454
48 53
1724 1803
62 72
1732 1812
43 48
1796 1863
42 47
1002 1078
39 44
1074 1129
39 44
1641 1686
40 45
1121 1169
37 43
1638 1696
36 41
1563 1630
41 46
1260 1354
37 42
1598 1686
38 43
1496 1573
41 46
1621 1684
36 41
1706 1820
37 42
1538 1632
37 42
1734 1787
52 57
1520 1574
58 63
1824
75
1880 1940
53 58
1915 1956
52 57
1142 1191
49 54
1172
49
1744
46
1687 1735
51 56
1432 1484
47 52
1763 1828
48 53
1635 1687
51 56
1734
44
1867
47
1712 1782
42 52
1834 1917
62 72
1659
73
1994 2079
64 74
1768
60
1938
63
1840 1890 1908
57 62 64
Filter
time min.
69.6
74.8
75.8
74.3
56.3
65.0
50.2
45.9
42.7
49.0
61.0
54.7
66.0
56.2
39.6
45.4
47.1
64.1
Mean filtr
rate gpm
27.5
22.2
24.1
28.0
34.7
22.0
23.3
36.7
27.4
37.9
29.0
27.1
29.4
30.0
38.1
38.2
39.6
29.8
. 1st order
0.035
0.020
0.032
0.031
0.042
0.017
0.016
0.049
0.046
0.047
0.038
0.026
0.036
0.030
0.061
0.037
0.036
0.024
(continued)
-------
TABLE 62 . 'CONTINUED)
Date
6/18
7/11
7/18
7/22
7/22
8/1
8/8
8/8
8/15
8/20
8/20
9/5
9/5
9/10
9/10
Run
no.
3
4
6
2
3
2
8
9
4
2
4
4
6
5
7
Temp
°C
23
27
24
24
27
27
28
26
28
27
25
22
27
27
Cumulative filtrate volume, gallons
Elapsed filter time, minutes
213 583
6 11
88 320
4 9
95 351
4 9
172 526
5 10
32 173
5 7
230 382
8 10
308 708
7 12
83 422
7 12
164 508
4 8
484 630
11 13
240 628
6 11
440 875
8 13
324 702
6 11
101 478
6 11
304 862
4 9
852 1061
16 21
533 711
14 19
599 796
14 19
771 944
15 20
476 672
12 17
702 940
15 20
998 1206
17 22
651 887
17 24
871 1136
13 18
883 1078
18 23
948 1190
16 21
1140 1330
18 23
916 1105
16 21
767 994
16 21
1192 1438
14 19
1226
26
860
24
954
24
1086
25
822
22
1130
25
1388
27
1030
29
1388
23
1242
28
1370
26
1480
28
1246
26
1175
26
1640
24
1361
31
980
29
1089
29
1210
30
948
27
1298
35
1553
32
1256
40
1613
28
1375
33
1510
31
1602
33
1354
31
1326
31
1793
29
1474
36
1086
34
1214
34
1322
35
1072
32
1424
40
1683
37
1468
50
1766
33
1468
38
1625
36
1702
38
1436
36
1456
36
1913
34
1566
41
1176
39
1300
39
1424
40
1184
37
1549
45
1798
42
1673
62
1896
38
1540
43
1785
46
1780
43
1506
41
1568
41
2010
39
1639
46
1248
44
1439
44
1522
45
1286
42
1662
50
1906
47
1808
72
2016
43
1665
53
1829
54
1845
47
1666
46
2090
44
1699
51
1308
49
1539
49
1614
50
1382
47
1764
55
1996
52
1844
75
2125
48
1752
51
2162
49
1743
55
1368
54
1631
54
1698
55
1472
52
1857
60
2078
57
2223
53
1827
56
2225
54
Filter
time mm.
1427
59
1716
59
1773
60
1552
57
1939
65
2153
62
2308
58
1893
61
2279
59
1483
64
1866
69
1846
65
1626
62
2107
75
2220
67
2448
68
1965
67
2308
62
1535 1586
69 74
1981 1990
79 80
1911 1964 2017
70 75 80
1696 1761 1846 1908
69 72 77 82
2192
85
2272
71
2640
84
55.2
75.6
82.0
81.4
85.2
81.2
70.7
75.1
82.7
53.5
53.2
46.6
40.6
67.0
62.4
Mean filtr.lst order
rategpm K --min";*
31.6
21.0
24.3
24.8
22.3
27.0
32.0
24.6
31.4
31.4
33.9
39.2
36.7
29.3
37.2
0.030
0.024
0.019
0.025
0.017
0.018
0.026
0.016
0.027
0.028
0.033
0.037
0.042
0.022
0.047
-------
3/22/74 - 1
K= 0.042
FILTRATION -
RATE = 34.3(GPM)
800.0 >
FILTER TIME =56.3
--X—X_^
10.0
50.0
20.0 30.0 40.0
TIME, minutes
Figure 80. Sludge dewatering filtrate rate and volumes, 3/22/74,
Run 1.
AVG.
FILTRATION.
RATE =23.2 _
(GPM)
FILTER TIME =85.2
min.
1600.0
- 1200.0
o
^^•B
^•*
O
«M»
UJ
ID
-800.0
-400.0 <
10.0
20.0
30.0
40.0. 50.0
60.0
TIME, minutes
Figure 81. Sludge dewatering filtrate rate and volumes, 7/22/74,
Run 3.
162
-------
parameter, K, to describe the filtrate volume-time relationships as
presented in Table 62 and in Figures 80 and 81. As would be expected
higher values of K are associated with shorter filter runs and higher
filtration rates.
In order to evaluate various factors on the filter performance as
measured by the three variables described, multiple linear regression
analyses were performed on various combinations of dependent and
independent variables. A summary of the variables used in the multiple
regression analyses and presented in Table 63 showing the range of
values used for a given variable over the test period. The independent
variables were not varied randomly over the range of values experienced
but rather, the values presented represent actual operating and perfor-
mance conditions for filter runs where the filtrate volume-time relation-
ships were available.
In the first series of multiple linear regression analyses performed
the dependent variable, one of the three filter performance measures,
was correlated with the independent variables of sludge feed concentra-
tion in percent, dewatered cake solids concentration in percent, ferric
chloride added as a percent of dry solids weight, lime added as a
percent of dry solids weight, filter cake dry weight and specific resis-
tance. The results of these analyses are presented in Table 64 wherein
the partial regression coefficient,partial correlation coefficient,and signi-
ficance level is indicated for each independent variable as well as the
multiple correlation coefficient and coefficient of determination for the
multiple linear regression. A positive partial regression coefficient for
an independent variable indicates an increase in the independent variable
results in an increase in the dependent variable and likewise a negative
partial regression coefficient for an independent variable indicates a
decrease in the dependent variable. For the three filter performance
dependent variables, low values for filter time and high values for
filtration rate and first order K are the desired objectives. The partial
correlation coefficients for the independent variables indicate the corre-
lation between the dependent factor and each independent variable elimi-
nating any tendency for the other independent variables to obscure the
relation. A partial correlation value of +1 or -1 would indicate perfect
correlation between the independent and dependent variables whereas a
value of 0 indicates the complete lack of correlation between the two
variables. The significance level is indicated for each independent
variable with two levels of confidence selected at 95%, significant,
corresponding to a significance level of 0. 05, and 99% highly significant,
corresponding to a significance level of 0.01, to denote that the regres-
sion parameter differs significantly from zero. The multiple correlation
coefficient shows the relative strength of the linear relationship between
the dependent variable and all the independent variables in the regression
163
-------
TABLE 63. MULTIPLE LINEAR REGRESSION ANALYSIS DEPENDENT AND INDEPENDENT VARIABLES
Date
3/7/74
3/7
3/12
3/12
3/22
3/26
3/28
4/4
4/16
4/16
4/30
5/9
5/14
5/14
5/29
5/29
6/4
6/13
6/18
7/11
7/18
7/22
7/22
8/1
8/8
8/8
8/15
8/20
8/20
9/5
9/5
9/10
9/10
Run
no.
2
6
1
4
1
3
9
6
3
7
2
3
6
8
3
8
5
7
3
4
6
2
3
2
8
9
4
2-
4
4
6
5
7
Sludge Dewatered Ferric Lime Filter
feed cake chloride * hydrated cake Viscosity
solids solids added to added to yield Specific of
concentration cone. dry weight dry weight dry weight resistance filtrate
% % % % pounds 107cm/g centipoise
12.5
12.7
12.3
11.4
11.4
12.8
15.3
12.7
8.7
19.1
16.2
17.2
14.1
14.2
10.1
14.6
12.6
16.5
10.9
14.1
11.2
12.4
11.7
11.4
12.^
9.7
11.8
13.4
13.6
12.1
12.5
12.2
11.9
45.4
45.8
46.2
50.0
48.9
41.3
•43.9
44.9
48.0
43.1
46.7
50.2
47.1
46.0
43.6
47.7
47.5
49.7
46.5
45.7
45.5
44.2
42.7
45.8
45.3
42.4
48.2
46.0
46.9
45.5
36.5
46.8
47.6
3.88
4.51
4.58
3.67
5.90
4.66
5.53
5.22
4.83
5.65
5.18
5.77
4.40
4.54
4.35
3.77
3.95
4.55
4.14
5.06
4.45
3.99
3.98
5.36
4.46
3.98
5.18
5.62
4.28
6.64
8.18
6.35
6.35
11.8
11.8
18.7
10.5
13.1
12.8
12.5
16.3
12.5
15.1
17.2
14.6
12.4
11.8
10.7
8.20
9.76
12.1
12.1
19.3
14.8
9.40
8.49
15.1
10.5
10.5
13.2
18.5
7.39
13.7
16.0
18.5
11.5
3042
2685
3014
3127
3198
2793
2934
2968
3229
2838
3062
3371
3313
3105
2968
3256
3185
3302
3128
2930
2918
3096
2994
3071
3048
2891
3254
3022
3155
2785
2291
2917
3056
0.46
0.62
0.84
0.80
1.41
1.50
1,10
0.64
2.18
0.75
0.65
1.38
1.53
1.59
0.75
0.84
0.76
0.79
1.03
2.25
2.56
2.82
2.46
2.59
2.15
2.01
0.89
0.75
0.95
1.20
1.10
1.20
0.81
1.0050
0.9810
1.0050
1.0559
1 . 0299
1.1111
1.0050
0.9810
0.9810
1.0050
1.0828
0.8545
0.9579
1.0828
0. 8937
0.8937
0.8937
0.9358
0.9358
0.8545
0.9142
0.9142
0.8545
0.8545
0. 8360
0.8737
0. 8360
0.8545
0.8937
0.9579
0.8545
0.8545
-------
TABLE 64. MULTIPLE LINEAR REGRESSION ANALYSIS OF PRESSURE FILTER PERFORMANCE RELATED TO SLUDGE FEED,
CAKE SOLIDS AND CHEMICAL DOSAGE
Independent variables
Dependent
variable
Filter time, min
Partial regression
Partial correlation
Significance level
Feed
solids
Number of concentration
observations Constant %
33
coefficient
coefficient
Average filtration rate, gpm 33
Partial regression coefficient
Partial correlation coefficient
Significance level
1st order K, min
Partial regression
Partial correlation
Significance level
33
coefficient
coefficient
48.51
0.209
0.2848
36.40*
0.380
0.0463
0.0285
0.147
0.4559
0.
0.
0.
-0.
-0.
0.
-0.
-0.
0.
187
035
8602
0238
Oil
9543
00147
308
1106
Dewatered
cake solids
concentration
2.841
0.336
0. 0800
-0.9517
-0. 292
0.1313
-0. 00191
-0. 272
0.1611
Ferric
chloride
added
-7.249*
-0.456
0.0148
2.982*
0.474
0. 0109
0. 00453
0.353
0. 0654
Hydrated
lime
added
•
1.000
0.233
0.2320
-0. 7397*
-0.413
0. 0291
-0. 00024
-0. 069
0. 7275
Filter
cake dry Specific Multiple Coefficient
weight resistance correlation of
pounds 10 cm/g coefficient determination
-0. 0366
-0.311
0. 1073
0.0129
0.282
0.1416
0. 000034
0.336
0. 0800
11.
0.
0.
-4.
-0.
0.
-0.
-0.
0.
0.6633
03**
535
0034
0. 7087
863**
580
0012
0.6101
00974**
550
0024
0. 4399
0. 5022
0.3722
Statistical significance:
* 95% confidence level, significant
** 99% confidence level, highly significant
-------
equation with values between 0 and 1. The coefficient of determination
which is the square of the multiple correlation coefficient represents
the fraction of total variation of the dependent variable explained by all
the independent variables in the regression equation.
In comparing the multiple correlation coefficients and coefficient of
determination for the multiple linear regression analysis presented in
Table 64, it is evident that the variation of the dependent variable,
average filtration rate, was better explained by the independent variable,
50%, than for filter time or first order K values with corresponding
values of 44 and 37%. A review of each of the independent variables
indicates that specific resistance is highly significantly correlated with
the dependent variables indicating that an increase in specific resistance
will increase filter run time and decrease filtration rate and first order
K values. This finding supports the value of utilizing specific resis -
tance measurements for the purpose of evaluating conditioning agents
and other operating conditions for expected filter performance. The
other independent variable affecting the filter performance showing
significance is the ferric chloride added as a percent of sludge dry
solids wherein an increase in ferric chloride for the range tested indi-
cates a decrease in filter time and an increase in filtration rate with
an increase in ferric chloride dosage whereas lime additions showed a
significant decrease in filtration rate with an increase in lime added
whereas the filter performance parameters of filter time and K showed
no significant effect. The independent variables feed sludge solids
concentration and dewatered cake solids concentration showed that an
increase in these independent variables resulted in an increase in filter
time and a decrease in filtration rate and K but not significantly so.
The filter cake dry weight independent variables was negatively corre-
lated to filter time and correlated positively with mean filter rate and
first order K but not significantly so.
A second series of multiple linear regression analyses were
performed between the three dependent filter performance variables and
the same independent variables with the exception that the weight ratio
of lime to ferric chloride was used rather than the two independent
variables of ferric chloride and lime as in the previous analysis. The
results are presented in Table 65.
The combination of the ferric chloride and lime variables as a
single ratio resulted in a decrease in the multiple correlation coeffi-
cients and corresponding coefficients of determination but the relative
values are in the same order as the results presented in Table 64.
As in the first series of results, the specific resistance values are
highly significantly correlated to the three filter performance values.
166
-------
TABLE 65. MULTIPLE LINEAR REGRESSION ANALYSIS OF PRESSURE FILTER PERFORMANCE RELATED TO SLUDGE FEED,
CAKE SOLIDS AND CHEMICAL DOSAGE RATIO
Independent variables
Feed
solids
Dependent Number of concentration
variable observations Constant %
Filter time, min. 33
Partial regression coefficient
Partial correlation coefficient
Significance level
Average filtration rate, gpm 33
Partial regression coefficient
Partial correlation coefficient
Significance level
1st order K, min 33
Partial regression coefficient
Partial correlation coefficient
Significance level
-15.
-0.
0.
49.
0.
0.
0.
0.
0.
76
076
6959
24**
523
0036
0708*
372
0469
-0.2290
-0.042
0.8268
-0.1586
-0. 076
0.6957
-0. 00109
-0.231
0.2289
Dewatered
cake solids
cone.
P7
/o
1.974
0.241
0. 2075
-0.3387
-0. 109
0. 5719
-0.00121
-0.176
0.3601
Filter
Ratio cake solids
lime/ weight
ferric chloride pounds
8.
0.
0.
-4.
-0.
0.
-0.
-0.
0.
247
350
0630
927**
499
0059
0032
168
3844
-0.
-0.
0.
0.
0.
0.
0.
0.
0.
0153
149
4392
00589
149
4413
0000169
193
3170
Specific Multiple
resistance correlation
lO^cm/g coefficient
11.
0.
0.
-4.
-0.
0.
-0.
-0.
0.
0.6157
0347**
518
004
0.6722
676* *
553
0019
0. 5449
00958**
525
0034
Coefficient
of
determination
0.3791
0.4519
0. 2969
Statistical significance:
* 95% confidence level, significant
**99% confidence level, highly significant
-------
Also, the independent variable lime to ferric chloride ratio was highly
significantly correlated to average filtration rate with high values of the
ratio resulting in a decrease in filtration rate. The significant level
for this ratio is 0.063 for filter time which also demonstrates the rela-
tive importance of reducing this ratio. This result reinforces in general
the value of increasing ferric chloride dosage to improve filter perfor-
mance and the negative effect of high lime dosages.
Another set of multiple linear regression analyses were performed
using the various terms of the Jones equation and sludge density as the
independent variables with each of the three filter performance measures.
The dependent variable in the Jones equation is filter time and should
represent the best correlation with the independent variables. A review
of the results presented in Table 66 shows this to be the case wherein
the largest multiple correlation coefficient 0.72 and coefficient of deter-
mination of 52% for filter time as the dependent variable as compared
to coefficients of determination of 45 and 41% for the dependent vari-
ables of first order K and average filtration rate respectively. Again
the specific resistance independent variable is significantly correlated
for filter time and highly significantly correlated with average filtration
rate and first order K dependent variables. Filtrate viscosity is signi-
ficantly correlated with average filtration rate but not so with the other
two filter performance variables wherein an increase in viscosity would
result in a decrease in filtration rate. The independent variable term
related to initial moisture content in the feed sludge, Ci, and final
moisture content in the cake, Cf, shows that a decrease in C{ should
result in a substantial decrease in filter time for a given cake moisture
content Cf in that this term is directly proportional to filter time in the
Jones equation. The results of the multiple linear regression analysis
show that there is no significant relationship between this term and
filter time or average filtration rate. A significant correlation is indi-
cated between the moisture term and the first order K value which indi-
cates that a higher moisture content in the feed solids would result in
higher first order K rates. The signs of this term are the opposite
to what one would expect for all three filter performance factors. The
terminal pressure independent variable is highly significantly correlated
with filter time and first order K dependent variables wherein an increase
in terminal pressure results in lower filter times and higher first order
K values as one would expect over the narrow range of terminal pressures
encountered. The significance level for terminal pressure as related to
average filtration rate is 0.0515 just under 95% confidence level which
represents a sizable level of significaice for this filter performance
parameter as well. The independent variable of the square of the sludge
cake density is not correlated with any of the three filter performance
factors..
168
-------
TABLE 66. MULTIPLE LINEAR REGRESSION ANALYSIS OF PRESSURE FILTER PERFORMANCE RELATED TO JONES EQUAT'ON
CD
Independent variables „
Dependent Number of
variable observations Constant
Filter time, min. 32
Partial regression coefficient
Partial correlation coefficient
Significance level
Average filtration rate, gpm 32
Partial regression coefficient
Partial correlation coefficient
Significance level
1st order K, min" 32
Partial regression coefficient
Partial correlation coefficient
Significance level
635.
0.
0.
-71.
-0.
0.
-0.
-0.
0.
32**
643
0002
474
206
2934
3224*
444
0179
Specific
resistance
107 cm/g
7.
0.
0.
-4.
-0.
0.
-0.
-0.
0.
573*
442
0187
217**
520
0045
00741**
488
0084
Filtrate
viscosity -
centipoise
21.98
0.169
0.3894
-28.077*
-0.438
0.0196
-0. 00604
-0.055
0.7822
(Ct- Cff
quoo-c^
-4.193
-0.121
0. 5404
1.696
0.109
0.5815
0.0138*
0.422
0.0254
. *i
Terminal /Sludger Multiple Coefficient
pressure \densitw correlation of
psi (lb/ft3) coefficient determination
-2.
-0.
0.
0.
0.
0.
0.
0.
0.
677**
621
0004
6079
372
0515
-0.
-0.
0.
-0.
-0.
0.
00164**-0.
491
0080
-0.
0.
0.7182
00168
027
8927
0.6383
00345
121
5397
0. 6709
00001
181
3557
0.5158
0. 4074
0. 4501
Statistical significance: * 95% confidence level, significant
**99% conficence level, highly significant
-------
The results of these multiple linear regression analyses indicate
the following:
1) The specific resistance values represent the most consistent
single factor significantly correlated to full scale filter perfor-
mance and should be used as the measure for evaluating chem-
ical conditioning and operating characteristics.
2) Increases in ferric chloride dose for sludge conditioning has a
pronounced effect on the improvement of filter performance in
the range of concentrations encountered.
3) Increases in lime dose for sludge conditioning in the range
encountered resulted in a detriment to the filter performance.
4) The feed sludge solids concentration or the final dewatered
sludge cake solids did not prove to be significantly correlated
with the filter performance measures.
5) All three filter performance variables, i.e., filtration time,
average filtration rate and first order K values, were near
equally useful as measures of filter performance for the inde-
pendent variables studied. Filter time was better suited as
the dependent variable for the Jones equation and average
filtration time for the independent variables related to sludge
feed, cake solids, and chemical conditioning dosages.
The dewatering process can be optimized by conducting statistical
studies employing evolutionary operation procedures wherein sludge
conditioning chemicals and dosage levels could be evaluated along with
certain physical operating parameters. In that the specific resistance
measurements have a highly significant correlation with the filter perfor-
mance measures utilized, initial studies should be conducted on a
laboratory scale, optimized and expanded to the full scale performance.
Economic factors should be considered in the final optimization.
170
-------
SECTION XIV
DEWATERED SLUDGE CAKE DISPOSAL
The ultimate disposal of dewatered sludge cake at this tannery was
accomplished by landfilling. Because landfilling the sludge cake singly
or in combination with municipal refuse could represent practice indus-
trywide, eight solid waste cells or bins were constructed which would
permit the monitoring of certain physical and chemical characteristics of
the material so placed. The controlled variables for the eight test bins
were (1) the composition of the solids waste placed, i.e., dewatered
sludge cake only, municipal refuse only and combinations thereof; and
(2) the presence or absence of earth cover. The response variables
included the measurements of internal temperatures at various locations
within the solid waste material placed, the settlement or consolidation
of the solid waste, the composition changes of the solid waste regarding
volatile solids and moisture content, and the characterization of the
leachate collected from each bin regarding volume and chemical analyses
such as BODg, COD, residue, pH, chromium, calcium, chloride, sulfide,
oil and grease, and alkalinity.
The placement of the refuse, cake, and refuse-cake combinations for
each experimental bin were conducted according to schedule and amounts
shown in Table 67. The municipal refuse was obtained from the City of Red
Wing, Burnside area. At the time of the study the garbage generated in this
area was part of the municipal refuse collected therefrom. The bins that
were constructed in the late summer of 1973 containing municipal refuse,
likely had a higher content of yard vegetation than those constructed in the
spring of 1974. The weight of refuse placed in each bin was obtained, but,
the composition of the refuse was not determined.
The dewatered sludge cake was obtained from the pressure filtra-
tion system and the weight of the filter cake placed was determined either
by truck weighings (August - September, 1973) or by weighing indivi-
dual cakes from the filter press (March - April, 1974). Random
samples were collected from the cakes for determination of percent
solids, percent volatile, and chromium content. Throughout the
study, buffing dust was used as a precoat material and ferric chloride and
171
-------
TABLE 67. LANDFILL TEST BIN CONTENTS AT TIME OF PLACEMENT
to
Dewatered sludge cake
Bin
no.
1
2
3
4
5
6
7
8
Date of
placement
9/14/73
9/7/73
8/16/73
8/24/73
8/30/73
4/17/74
4/10/74
3/22/74
Total Percent
Composition Earth cover weight of total
by weight 10-15cm(4-6") kg,(lb) weight
100% refuse
20% cake
80% refuse
100% cake
100% cake
50% cake
50% refuse
50% cake
50% refuse
100% cake
100% cake
yes
yes
no
yes
yes
no
yes
no
100
1311(2890) 20.2
12200(26890)100
12580(27740)100
4470(9860) 54
3000(6615) 46.4
11640(25673)100
11960(26363)100
Percent
dry solids
--
54.2
47.0
48.0
48.3
48.4
44.7
48.4
Municipal refuse
Volume of Total Total Percent
water chromium Density weight of total Density
gal kg(lb) lbs/ft3 kgclb) weight Ibs/ft3
--
159
1709
1731
596
409
1704
1631
-- 478000540^100 14.8
-- 5175(11410^ 79.8 20.2
45.6
44.4
-- 3806(8390) 46 27
7.17(15.8) -- 3461(7630) 53.6 18.7
29.8(65.6) 52
30.1(66.4) 44.5 -- -- * --
-------
lime were the conditioning chemicals.
After- placement of the bin contents, the solid wastes were com-
pacted. In those instances where cover was desired, 10-15 cm (4-6 in)
of earth were applied, compacted and sloped for surface runoff to the
front of the bin. The depth of the placement of the solid waste material
was about 5 feet to the rear of the bin to 4 feet at the front. Each bin
was 3.05 by 4.57 m (10byl5 ft) in plan with a concrete floor and trench
underdrain. Timber sides lined with plastic for waste containment were
employed, and the leachate was collected at a sample point to the front
of the bin in an individual collection well (see Figures 82 and 83).
SETTLEMENT
Measurements of the settlement of the bin contents provides infor-
mation useful for the design of landfills. Each test bin was provided
with three settlement plates placed 15 cm(6 in) below the top surface to
record the drop in elevation as a result of consolidation or settlement of
the material placed. The plates were metal, 30. 5 cm(l ft) square with
a 46 cm (18 in) length of 2. 54 cm (1 in) pipe attached to the center so
as to extend above the surface of the landfill to facilitate measurements.
The three plates for each bin were placed with one plate forward and
center of the bin with the remaining two placed on the right and left
areas at the rear of the bin.
All changes in elevation were observed with the aid of surveying
instruments wherein bench marks were established external to the site
as well as at the exposed corners of the concrete base for each test bin.
Measurements were made after the completion of the placement of the
bin contents and then, at first, thereafter at one week intervals. After
changes in elevation become less pronounced, the changes in elevation
of the settlement plates were recorded in two week, one month and two
month intervals. The last measurements were made in November, 1974,
some 14 months after placement of solid waste in bins 1 through 5 and 7
months after the placement of solid waste in bins 6 through 8.
The results of the settlement measurement are presented in Table
68 wherein the average cumulative settlement that occurred over the test
period as well as during the first two months was reported. The average
settlement in meters represents the average of the results for the three
settlement plates in each bin. The greatest settlement occurred in test
bins containing 100% dewatered sludge cake placed without earth cover
(bins 3 and 8). A comparison of bins 3 and 4 shows the settlement in
meters to be greater for 100% dewatered sludge cake uncovered (bin 3)
than for 100% cake covered (bin 4).
173
-------
SYMMETRICAL
10-0
-0
COVER
i I
! I
SAMPLE
WELL
6" VCP BRANCH
15-0
l
, GRADED SAND &
--> GRAVEL TO FLOOR
ELEVATION
I I
I I
_J L.
NOTE. ALL DIMENSIONS IN ENGLISH UNITS
Figure 82. Landfill test bins.
Figure 83. End view of landfill test bins,
174
-------
TABLE 68. SETTLEMENT MEASUREMENTS OF SOLID WASTES
Initial settlement (first 60 days)
Bin
no*
1
2
3
4
5
6
7
8
Cumulative settlement
Bin contents Average Range As percent c
percent by weight m m original heigl
100% municipal refuse 0.314
covered
80% municipal refuse 0. 354
20% sludge cake
uncovered
100% sludge cake 0. 411
uncovered
100% sludge cake 0. 323
covered
50% municipal refuse 0. 280
50% sludge cake
uncovered
50% municipal refuse 0. 344
50% sludge cake
covered
100% sludge cake 0.283
covered
100% sludge cake 0. 555
uncovered
0.241-0.421
0.302-0.399
0.329-0.466
0.247-0.445
0.235-0.311
0.287-0.369
0.215-0.320
0.543-0.576
20.3
23.0
34.4
23.6
19.0
22.2
21.6
43.8
>f Settlement
tit m
0.131
0.122
0.274
0.250
0.107
0.280
0.210
0.418
Percent
of total
settlement
42.1
34.2
66.7
77.4
38.0
81.1
74.2
75.0
Settling rate
initial m per
m/height/mo
0.04
0.04
0.11
0.09
0.04
0.09
0.08
0.16
* Bins 1 through 5 were constructed in August - September, 1973 (14 months of data).
Bins 6 through 8 were constructed in March - April, 1974 (7 months of data).
-------
The settling rate in meters per meter of initial height per month
for the first 60 days shows the rates for covered and uncovered to be
nearly the same (bins 4 and 3 respectively). However, for the sludge
cake placed in April, 1974, for covered and uncovered, bins 7 and 8
respectively, the cumulative settlement in meters for the uncorered
sludge cake and the rate of settlement for the first 60 days was two
times that for the covered cake. The settlement 60 days after the date
of placement for bins 3 and 8 represented 67. 7 and 75% respectively
of the total settlement during the test period.
The results for cumulative settlement in meters and feet over the
test period for each of the bins are shown in Figure 84. Although sani-
tary landfill practices required the placement of earth cover for muni-
cipal refuse for purposes of public health, it is apparent that the benefits
of landfill consolidation or settlement is better realized with the testbins
when no cover is provided as evidenced for the 50:50 combinations and
100% dewatered sludge cake materials. The settlement of the material
can be related to a combination of the following factors.
1) Physical compaction of the material resulting in a lower void
volume to total volume ratio (porosity).
2) Loss of water as a result of evaporation.
3) Volatilization or degradation of organic matter by biological
matter.
4) Loss of material as part of the leachate.
It was apparent from other measurements of moisture content, vola-
tile solids content and temperature development within the solid waste
material that loss of water and volatilization or degradation of organic
matter was a significant factor for the settlement of the uncovered bins
3, 6 and 8. The uncovered test bins would tend to promote aerobic
biological activity similar to compost and the attendant rapid rise of
internal temperatures discussed in the following section seem to support
this.
INTERNAL TEMPERATURE
The temperatures within the solid waste material for each bin was
monitored by the use thermocouples and a readout potentiometer. The
thermocouples were placed in a centrally located area near the back of
the solid waste bins. Initially the thermocouples were placed at several
locations with reference to the supporting concrete floor and the
176
-------
UI
_l
H-
H
UJ
O)
PLACEMENT AUG. 73 • COVERED
O UNCOVERED
PLACEMENT APR. 74 A COVERED
A UNCOVERED
100 80 60 40 20
£
K '-!
Z
UJ
-
O
UJ 0.5
e>
<
o:
UJ
S o
III!
% WT MUNICIPAL REFUSE
• A
•
1
A
0
A
• *
% WT FILTER CAKE
1 1 1 1 1
2
O
o
UJ
2
LJ
H-
0.305 UJ
(/)
UJ
O
0.152 g
UI
<
20
40
60
80
100
Figure 84. Landfill settlement (November 1974).
177
-------
material surface. As a result of settlement over the test period the
position of the thermocouples changed with respect to the supporting
floor. The locations of the thermocouples and the resulting tempera-
tures for the dates indicated and corresponding elapsed time from place-
ment are presented in Tables 69 and 70. In addition the average air
temperature and the rainfall in centimeters for the corresponding months
are indicated.
Results:
Bin no. 1 (100% municipal refuse, covered)--Internal temperatures
within a short period of time rose to between 60 and 70°C for a
period of about 3 months well above the monthly ambient air tem-
perature 17 to -7°C. The internal temperatures dropped markedly
during the winter months of January, February, March and half of
April with the lowest value of 4°C attained by the end of February
thereafter, the temperature levels rose again to a range of 40 to
60°C during the warm weather months followed by decreasing
temperatures during the fall.
Bin no. 2 (80% municipal refuse, 20% sludge cake, covered) --The
internal temperature buildup was not as great for bin no. 2 as for
bin no., 1, however, the temperatures remained more uniform over
the test period generally between the temperatures of 40 to 60°C.
The minimum temperatures were experienced during the first half
of the month of April.
Bin no. 3 (100% dewatered sludge cake, uncovered)--Although the
increase in internal temperatures did not occur as rapidly as in
bin no. 1, within 6 weeks after placement the temperatures were
in excess of 70°C. The decrease in temperatures during the
winter months was similar to that of bin no. 1, however, a temper-
ature increase from a level of low teens at the end of March to a
level of 77°C occurred during the month of April with monthly
average ambient air temperatures during the month of April of only
9.4QC. For the remainder of the test period the internal temper-
atures were in the 40 to 60°C for the most part. The high temper-
atures experienced early after placement for bin no. 3 and the
reoccurrence of high temperatures in the spring appears to be
related to the cyclic effect in moisture content wherein the initial
moisture was evaporated during the early phases. After the winter
months with the spring thaw and incident rainfall the moisture
content increased to a level which permitted accelerated biological
activity as evidenced by the rapid rise in temperature during the
month of April.
178
-------
TABLE 69. TEMPERATURE VARIATIONS IN BIN CONTENTS WITH RESPECT TO ELAPSED TIME AFTER PLACEMENT
Bin no. 1
100% municipal
covered
Date
8/16/73
8/24
8/28
8/30
9/6
9/7
9/13
9/14
9/18
9/22
I-1 9/27
«j 10/1
10/4
10/9
10/10
10/11
10/18
10/23
10/24
10/26
10/30
11/1
11/21
11/23
11/30
12/7
12/13
12/21
12/28
Elapsed
Time Days
Probe
Temp°C
Bin no. 2
20% sludge cake
80% municipal
covered
Bin no. 3
100% sludge cake
uncovered
Elapsed Probe Elapsed Probe
Time Days Temp°C Time Days Temp°C
date of
6
date of placement
12 30
21 38
Bin no. 4
100% sludge cake
covered
Bin no. 5
50% sludge cake
50% municipal
covered
Elapsed Probe 1 Probe 2 Elapsed Probe
Time Days Temp°C Temp°C Time Days Temp°C
date of placement
4 32 30
13 56 46
date of
7
placement
72
placement
48
28
46
20
64 58
14
57
date of placement
4
8
13
17
20
25
26
27
34
39
40
42
46
48
68
70
77
84
90
98
105
66
68
72
70
70
72
69
69
66
64
64
66
62
62
38
59
58
62
60
49
42
11
15
20
24
27
32
33
34
41
46
47
49
53
55
75
77
84
91
97
105
112
46
49
55
53
51
48
44
45
50
46
45
45
57
56
60
56
59
60
60
48
38
33
37
42
46
49
54
55
56
63
68
69
71
75
77
97
99
106
113
119
127
134
48
70
70
71
73
70
71
72
65
62
68
69
65
37
71
64
62
58
42
38
25
29
34
38
41
46
47
48
55
60
61
63
67
69
89
91
98
105
111
119
126
66 59
69 68
67 56
56 49
53 47
55 45
54 44
53 44
50 42
49 41
49 40
50 40
52 42
50 40
57 40
52 38
36 32
44 40
58 46
43 32
44 33
19
23
28
32
35
40
41
42
49
54
55
57
61
63
83
85
92
99
105
113
120
60
70
71
68
65
70
68
68
63
65
66
60
60
60
64
66
58
58
60
41
44
Monthly
mean
Temp °C
22.8
22.8
22.8
22.8
16.7
16.7
16.7
16.7
16.7
16.7
16.7
13.3
13.3
13.3
13.3
13.3
13.3
13.3
13.3
13.3
13.3
2.2
2.2
2.2
2.2
-7.2
-7.2
-7.2
-7.2
Rainfall
cm/mo
7.82*
7.82
7.82
7.82
6.45
6.45
6.45
6.45
6.45
6.45
6.45
4.80
4.80
4.80
4.80
4.80
4.80
4.80
4.80
4.80
4.80
5.82
5.82
5.82
5.82
2.79
2.79
2.79
2.79
Date
9/1-3
9/8
9/15-21
9/24-28
10/3
10/6
10/8-11
10/24
10/26
10/30
11/6
11/14
11/20-22
II/2§
12/5
12/9
12/14
12/18
Rainfall
cm
0.56
0.46
0.91
4.52
0.53
1.07
2.44
0.05
0.69
0.02
0.05
0.74
4. 1!
8' 41
o.'se
0.08
0.23
0.08
(continued)
-------
g
Bin no. 1
100% municipal
covered
Date
1/1/74
1/14
1/18
1/24
1/28
2/7
2/11
2/14
2/18
2/22
2/25
2/28
3/4
3/7
3/12
3/15
3/18
3/22
3/28
4/1
4/4
4/8
4/12
4/15
4/19
4/22
4/26
4/29
mapsed Probe
Time Days Temp°C
112
122
126
132
136
146
150
153
157
161
164
167
171
174
179
182
185
189
195
199
202
206
210
213
217
220
224
227
47
38
30
28
30
28
22
18
14
10
4
7
8
10
12
12
13
16
12
11
13
14
19
36
50
62
63
64
Bin no. 2
20% sludge cake
80% municipal
covered
Elapsed
Time Days
119
129
133
139
143
153
157
160
164
168
171
174
178
181
186
189
192
196
202
206
209
213
217
220
224
227
231
234
Probe
Tempt
42
44
40
44
46
45
45
48
43
46
48
46
40
40
40
39
39
41
36
38
34
30
17
39
36
42
45
46
Bin no. 3
100% sludge cake
uncovered
Elapsed
Time Days
141
151
155
161
165
175
179
182
186
190
193
196
200
203
208
211
214
218
224
228
231
235
239
242
246
249
253
256
Bin no. 4
100% sludge cake
covered
Probe Elapsed Probe 1
Temp°C Time Days Temp°C
42
45
36
25
21
11
12
7
6
10
6
4
2
6
9
9
10
12
13
28
24
36
49
62
76
72
77
77
133
143
147
153
157
167
171
174
178
182
185
188
192
195
200
203
206
210
216
220
223
227
231
234
238
241
245
248
(continued)
40
34
26
26
32
30
31
34
31
36
37
48
34
34
35
37
38
38
40
48
38
37
32
32
32
35
36
36
Bin no. 5
50% sludge cake
50% municipal
covered
Probe 'I Elapsed
Temp°C Time Days
29
26
22
24
23
26
25
24
26
19
38
29
26
26
27
38
34
30
30
30
29
28
25
25
23
24
31
•24
127
137
141
147
151
161
165
168
172
176
179
182
186
189
194
197
200
204
210
214
217
221
225
228
232
235
239
242
Probe
Temp °C
48
48
46
48
52
44
41
42
37
44
38
38
32
35
38
42
40
39
33
31
28
33
39
20
48
58
56
57
Monthly
mean
Temp °C
-10
-10
-10
-10
-10
-7.8
-7.8
-7.8
-7.8
-7.8
-7.8
-7.8
-0.6
-0.6
-0.6
-0.6
-0.6
-0.6
-0.6
9.4
9.4
9.4
9.4
9.4
9.4
9.4
9.4
9.4
Rainfall
crn/mo
0.33
0.33
0.33
0.33
0.33
2.95
2.95
2.95
2.95
2.95
2.95
2.95
3.89
3.89
3.89
3.89
3.89
3.89
3.89
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
Rainfall
Date cm
12/25-28
1/8
1/20
1/30
2/1-4
2/9
2/13-14
2/20-21
3/14-15
3/18
3/22
3/25
3/27-30
4/1-4
4/11-13
4/21-22
4/27-28
o:i
0.25
0.01
1.68
0.30
0.30
0.71
0.51
0.05
0.10
0.38
2.84
0.79
1.85
0.23
0.09
-------
TABLE 69. (CONTINUED)
00
Bin no. 1
100% municipal
covered
Date
5/2
5/6
5/9
5/13
5/17
5/21
5/23
5/28
5/31
6/3
6/7
6/10
6/14
6/17
6/21
6/24
6/28
7/1
7/3
7/8
7/11
7/17
7/19
7/22
7/25
7/29
Elapsed
Time Days
230
234
237
241
245
249
251
256
259
262
266
269
273
276
280
283
287
290
292
297
300
306
308
311
314
318
Probe
Temp°C
62
56
J8
42
38
39
44
40
45
44
44
44
42
42
44
40
45
48
48
49
48
51
48
50
55
52
Bin no. 2
20% sludge cake
80%. minicipal
covered
Elapsed
Time Days
237
241
244
248
252
256
258
263
266
269
273
276
280
283
287
290
294
297
299
304
307
313
315
318
321
325
Probe
Temp°C
43
48
44
44
44
42
43
38
44
43
46
48
42
41
38
38
44
44
44
44
44
50
48
50
54
56
Bin no. 3
100% sludge cake 100%
uncovered
Elapsed
Time Days
259
263
266
270
274
278
280
285
288
291
295
298
302
305
309
312
316
319
321
326
329
335
337
340
343
347
Probe
TempQC
50
56
46
43
47
44
48
42
48
46
42
42
42
48
48
53
56
53
52
52
53
54
52
52
53
56
Elapsed
Time Days
251
255
258
262
266
270
272
277
280
283
287
290
294
297
301
304
308
311
313
318
321
327
329
332
335
339
Bin no. 4
, sludge cake
covered
Probe 1
Temp°C
37
41
36
34
30
30
30
28
30
32
33
33
30
31
28
27
31
32
33
32
31
47
38
38
39
40
Probe 2
Temp°C
23
28
25
26
24
24
24
22
24
26
25
26
26
26
24
22
26
25
25
25
25
29
30
30
30
32
Bin no. 5
50% sludge cake
50% municipal
covered
Elapsed
Time Days
245
249
252
256
260
264
266
271
274
277
281
284
288
291
295
298
302
305
307
312
315
321
323
326
329
333
Probe
Temp°C
58
55
49
48
44
42
44
40
45
48
47
47
44
43
43
44
48
50
51
50
49
54
54
56
57
60
Monthly
mean
Temp °C
13.3
13.3
13.3
13.3
13.3
13.3
13.3
13.3
13.3
20
20
20
20
20
20
20
20
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
Rainfall
cm/mo
9.40
9.40
9.40
9.40
9.40
9.40
9.40
9.40
9.40
13.31
13.31
13.31
13.31
13.31
13.31
13.31
13.31
5.36
5.36
5.36
5.36
5.36
5.36
5.36
5.36
5.36
Date
5/2
5/7-18
5/21
5/29-30
6/3-13
6/18-20
7/1-3
7/10-12
7/18
7/25-24
Rainfall
cm
0.30
6.71
0.84
1.55
7.70
5.61
0.58
0.76
0.08
3.94
(continued)
-------
TABLE 69. (CONTINUED)
00
Bin no. 1
100% municipal
covered
Date
8/2
8/5
8/9
8/12
8/16
8/19
8/24
8/26
8/29
9/3
9/6
9/9
9/13
9/16
9/25
10/4
10/11
10/17
10/21
11/1
12/2
Elapsed Probe
Time Days Temp°C
322
325
330
333
337
340
345
347
350
355
358
361
365
368
377
386
393
399
403
414
445
49
46
48
44
48
48
54
51
48
45
42
36
49
37
32
27
24
31
41
17
19
Bin no. 2
20% sludge cake
80% municipal
covered
Elapsed Probe •
Time Days Temp°C
329
332
337
340
344
347
352
354
357
362
365
368
372
375
384
393
400
406
410
421
452
52
52
55
51
51
51
58
55
53
58
56
48
63
53
44
43
44
72
79
54
58
Bin no. 3
100% sludge cake
uncovered
Elapsed Probe
Time Days Temp°C
351
354
358
361
365
368
373
375
378
383
386
389
393
396
405
414
421
427
431
442
473
44
45
54
46
46
50
52
55
50
59
48
44
61
56
46
40
36
44
66
50
54
Bin no. 4
100% sludge
covered
Elapsecl
Time Days
343
346
350
353
357
360
365
367
370
375
378
381
385
388
397
406
413
419
423
434
465
cake
Probe 1 Probe 2
Temp°C Temp°C
38
38
38
36
34
34
42
46
41
47
38
36
45
38
32
30
30
36
48
28
61
29
30
32
29
28
26
32
35
30
38
28
30
36
32
28
26
22
27
37
18
45
Bin no. 5
50% sludge cake
50% municipal
covered
Elapsed Probe
Time Days Temp°C
337
340
345
348
352
355
360
362
365
370
373
376
380
383
392
401
408
414
418
429
460
55
53
55
52
53
56
63
64
60
66
58
52
66
58
44
40
37
58
64
37
26
Monthly
mean
Temp°C
20
20
20
20
20
20
20
20
20
14.4
14.4
14.4
14.4
14.4
14.4
11.1
11.1
11.1
11.1
1.1
-3.3
Rainfall
cm/mo
6.86
6.86
6.86
6.86
6.86
6.86
6.86
6.86
6,86
2.51
2.51
2.51
2.51
2.51
2.51
3.43
3.43
3.43
3.43
Rainfall
Date cm
8/1-3
8/9-10
8/20-21
8/30-9/2
9/9-12
10/6
10/10
10/13
10/27-31
11/10
4.14
0.38
1.32
1.14
2.39
0.36
0.56
0.25
2.24
0.99
*Rainfall for 8/15/73-8/31/73.
Probe locations: Bin no. 1: 38 cm(15") above bottom, 91 cm(36") below top of landfill.
Bin no. 2: 15 cm(6") above bottom, 109 cm(43") below top of landfill.
Bin no. 3: 10 cm(4") above bottom, 74 cm(29") below top of landfill.
Bin no. 4(1): 48 cm(19") above bottom, 84 cm(33") below top of landfill.
(2): 5 cm(2") above bottom, 127 cm(50") below top of landfill.
Bin no. 5: 51 cm(20") above bottom, 79 cm(31") below top of landfill.
-------
TABLE 70.
TEMPERATURE VARIATIONS IN BIN CONTENTS WITH RESPECT TO ELAPSED
TIME AFTER PLACEMENT
Bin no. 6
VQ watered sludge cake
50% municipal refuse
uncovered
Bin no. 7
100% dewatered
sludge cake
covered
Bin no. 8
100% dewatered
sludge cake
uncovered
Elapsed
time
Date days
Temp°C
Probe 1* Probe 2*
3/22/74
3/28
4/1
K 4/4
8 4/8
4/10
4/12
4/15
4/17 date/placement
4/18
4/19
4/22
4/23
4/24
4/25
4/26
4/29
5/2
5/6
5/9
2
5
7
9
12
15
19
22
24
38
36
32
44
38
25
26
24
49
48
54
55
60
53
48
Elapsed
time
days
Temp°C Elapsed
Probe 1* Probe 2* time
days
date/placement
2 27 16
5 34 18
9
12
16
19
22
26
29
40
38
34
30
29
32
31
22
24
25
24
26
30
30
Temp^C
Probe f Probe
date /placement
6 13
10 13
13 21
17 55
21 70
24 72
26 83
27
28
31
32
33
34
35
38
41
45
48
82
81
80
80
78
77
80
78
72
70
66
8
9
11
23
40
63
67
62
60
67
62
61
59
60
60
57
60
52
Monthly
2* mean Rainfall
temp°C cm/mo
-0.6
-0.6
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
9.5
13.3
13.3
13.3
(continued)
3.89
3.89
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
2.95
9.40
9.40
9.40
-------
TABLE 70., (CONTINUED)
Bin no. 6 Bin no. 7
50% watered sludge cake 100% dewatered
50% municipal refuse sludge cake
uncovered covered
Bin no. 8
100% dewatered
sludge cake
uncovered
Elapsed Temp"C Elapsed Temp°C Elapsed Temp"C Monthly
time Probe 1* Frobe 2* time Probe 1* Probe 2* time Probe 1* Probe 2* mean Rainfall
Date days days days temp° C cm /mo
5/13
5/17
5/21
5/23
5/28
5/31
6/3
6/7
6/10
6/14
6/17
6/21
6/24
6/28
7/1
7/3
7/8
7/11
7/17
7/19
7/22
7/25
26
30
34
36
41
44
47
51
54
58
61
65
68
72
75
77
82
85
91
93
96
99
33
46
48
42
43
36
30
39
26
22
36
37
38
40
48
42
48
40
40
36
42
49
52
52
46
42
48
48
48
48
51
50
51
54
56
57
52
53
51
54
52
54
56
33
37
41
43
48
51
54
58
61
65
68
72
75
79
82
84
89
92
98
100
103
106
31
36
36
35
37
40
40
40
41
38
38
39
38
40
38
38
38
38
44
41
44
48
33
32
32
31
29
30
32
32
32
32
32
31
30
31
30
31
32
30
34
32
35
37
52
56
60
62
67
70
73
77
80
84
87
91
94
98
101
103
108
111
117
119
122
125
64
65
64
64
49
52
52
58
54
60
48
54
63
61
56
53
55
54
53
52
52
50
49
48
48
48
40
45
43
44
42
44
43
44
46
48
48
49
50
49
48
47
49
49
13.3
13.3
13.3
13.3
13.3
13.3
20
20
20
20
20
20
20
20
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
(continued)
9.40
9.40
9.40
9.40
9.40
9.40
13.31
13.31
13.31
13.31
13.31
13.31
13.31
13.31
5.36
5.36
5.36
5.36
5.36
5.36
5.36
5.36
-------
TABLE 70. (CONTINUED)
Bin no. 6 Bin no. 7 Bin no. 8
50% watered sludge cake 100% dewatered 100% dewatered
50% municipal refuse sludge cake sludge cake
uncovered covered uncovered
Hlapsed Tern]
time Probe 1*
Date days
7/29
8/2
8/5
8/9
8/12
8/16
£ 8/19
01 8/24
8/26
8/29
9/3
9/6
9/9
9/13
9/16
9/25
10/4
10/11
10/17
10/21
11/1
12/2
103
107
110
114
117
121
124
129
131
134
139
142
145
149
152
161
170
177
183
187
198
229
32
38
33
47
41
42
39
34
30
29
16
25
23
28
18
22
16
18
10
1
20
4
[HJ
Probe 2*
56
53
49
60
55
58
57
58
56
52
54
55
46
60
51
43
38
38
55
60
48
30
elapsed
time
days
110
114
117
121
124
128
131
136
138
141
146
149
152
156
159
168
177
184
190
194
205
236
Tern
Probe 1*
45
41
38
38
36
37
35
40
41
36
38
36
33
43
34
39
30
26
37
46
24
48
p«U
Probe 2*
36
37
36
40
32
36
34
40
38
36
40
40
36
44
30
34
30
30
45
54
32
50
Elapsed Temp'-'u Monthly
time Probe 1* Probe 2* mean Rainfall
days temp°C cm /mo
129
133
136
140
143
147
150
155
157
160
165
168
171
175
178
187
196
203
209
213
224
255
51
51
38
56
62
60
58
70
62
56
59
58
50
66
58
49
47
53
76
84
76
40
58
53
52
60
59
56
56
60
61
60
66
65
55
68
51
51
40
49
77
86
65
60
24.4
20
20
20
20
20
20
20
20
20
14.4
14.4
14.4
14.4
14.4
14.4
11.1
11.1
11.1
11.1
1.1
1.1
5.36
6.86
6.86
6.86
6.86
6.86
6.86
6.86
6.86
6.86
2.51
2.51
2.51
2.51
2.51
2.51
3.43
3.43
3.43
3.43
(continued)
-------
TABLE 70. (CONTINUED)
* Probe locations:
Bin no. 6 (1) 97 cm (38 in) above bottom 36 cm (14 in) below top of landfill
(2) 28 cm (11 in) above bottom 104 cm (41 in) below top of landfill
Bin no. 7 (1) 46 cm (18 in) above bottom 71 cm (28 in) below top of landfill
(2) 20 cm (8 in) above bottom 97 cm (38 in) below top of landfill
Bin no. 8 (1) 64 cm (25 in) above bottom 46 cm (18 in) below top of landfill
(2) 33 cm (13 in) above bottom 76 cm (30 in) below top of landfill
00
05
-------
Bin no. 4 (100% dewatered sludge cake, covered)--A temperature
rise peaked within 30 days after placement with a high in the upper
60*s and a rapid decrease in temperature to the 40 to 50°C level.
During the winter months, like bin no. 2, the temperatures
remained in the 20 to 40°C range and for the most part remained
at about 30°C for the following late spring and summer. No atten-
dant secondary rise in temperature was experienced in late April
such as with bin no. 3 for the same material uncovered.
Bin no. 5 (50% municipal refuse, 50% sludge cake, covered) --The
internal temperature results for this bin were similar to the
patterns experienced for bins 1 and 3. An early rapid rise in
temperature in excess of 70°C, the decrease during winter and
attendant rise in April during the spring thaw and a somewhat
steady temperature pattern between 40 and 60°C for the remainder
of the study.
Bin no. 6 (50% municipal refuse, 50% sludge cake, uncovered)--
The results appear in Table 70 for the 7 months test period from
April-March through November of 1974. The temperature rise
to 50 to 60°C within several weeks after placement remained
essentially unchanged for the duration of the study for the deep
probe (2). The shallow probe (1) showed greater variations with
a drop in temperature occurring in early fall.
Bin no. 7 (100% dewatered sludge cake, covered)--The internal
temperatures represented by Probe 2 showed a gradual rise in
temperature to about 4QOC with temperature generally in the 30
to 40°C range throughout the study unlike the rapid temperature
rise displayed for the same material covered represented by bin
no. 4.
Bin no. 8 (100% dewatered sludge cake, uncovered)--Within aperiod
of 30 days after placement a sharp rise in temperature to values
in the high 70's with a decrease to temperature in the 50 to 60°C
range within 60 days after placement for most of the remainder of
the test. A brief secondary rise in temperature to the high 70's
level was experienced in October without apparent explanation.
The results of the internal temperature measurements demonstrate
the benefit of placing the dewatered cake uncovered in a landfill as
evidenced by the higher internal temperatures for uncovered bins 3 and
8 versus covered cake bins 4 and 7. The higher temperatures result
in greater moisture loss, consolidation and compost bacterial activity
or organic volatilization. The results of the refuse-cake mixtures are
187
-------
not as conclusive with regard to the benefits of covered or unco\ered
placement conditions when one compares the results of bin 5 covered
with bin 6 uncovered for 50% refuse-50% cake. However, the bins were
placed into service over two different time intervals. The 100% refuse
covered bin no. 1 had internal temperature development patterns similar
to the 100% dewatered cake uncovered in bin no. 3.
ANALYSIS OF DEWATERED SLUDGE CAKE BINS
The analyses of the solid wastes in the bins were performed only
for the bins containing the dewatered sludge cake. The heterogeneity
of the bins containing municipal refuse or mixtures of refuse and cake
would likely result in large variations in the results obtained making
interpretation difficult. The dewatered sludge cake was most uniform
which greatly facilitated the interpretation of the results obtained.
The bin contents were sampled with the aid of a posthole digger
wherein samples were collected from the four corners and center of
the bin at 0.152, 0.305, 0.457, 0.610, 0.762 and 0.914 meters (0.5,
1.0, 1.5, 2.0, 2.5, and 3.0 feet) below the surface for bins 3 and 4
representing uncovered and covered cake, respectively. The results of
the sampling for percent total solids and percent moisture are summa-
rized in Table 71.
TABLE 71. BIN SOLIDS ANALYSES FOR DEWATERED SLUDGE CAKE
Bin no. 3 uncovered
(placed 8/16/73;
sampled 12/28/73)
Bin no. 4 covered
(placed 8/24/73;
sampled 12/18/73)
Sampling depth
meters (feet)
Surface
Subsurface
0.152 (0.5)
0.305 (1.0)
0.457(1.5)
0.610(2.0)
0. 762 (2. 5)
0.914 (3.0)
Percent total
solids
43.5
37.5
41.3
60.0
90.3
89.0
86.8
82.8
Percent
moisture
56.5
62.5
58.7
40.0
9.7
11.0
13.2
17.2
Percent total
solids
...
31.7
—
50.1
51.2
52.2
40.4
41.4
Percent
moisture
69.3
—
49.9
48.8
47.8
59.6
58.6
It is readily apparent that bin no. 3 with the uncovered dewatered sludge
cake had a much lower moisture content than for the covered cake
188
-------
approximately 4 months after placement. The high temperature develop-
ment in the uncovered bin no. 3 is likely a contributing factor to the
evaporation or loss of moisture as well as the opportunity for the mois-
ture to be discharged to the atmosphere.
A more detailed analyses was performed for bins 7 and 8 containing
dewatered sludge cake representing covered and uncovered placement
respectively. Analyses for volatile and fixed solids as well as for mois-
ture content were made to determine the extent to which volatile solids
are reduced and determine changes in the density of the bin contents.
The bins received dewatered sludge cake on April 10 and March 22,
1974, respectively for bins 7 and 8, each receiving four cycles from the
filter press. For each cycle 9-12 samples of cake were analyzed for
percent solids and percent volatile solids. The average results indicated
that bin no. 7 had a percent total solids 44.7 and a percent volatile
solids of 57.5 whereas bin no. 8 had 48.4 percent total solids and 56.8
percent volatile solids.
The results of the analyses for the various sampling times after
material placement are presented in Table 72. Several findings are
worthy of note with reference to changes in percent dry solids, percent
volatile solids and percent reduction of volatile solids. The first indi-
cates the changes in moisture content with respect to time and the
remaining two parameters indicated the extent to which volatile or
organic solids are decomposed or converted to gaseous end products.
With appropriate accountability for organic losses in the leachate the
advantages or disadvantages of covering sludge cake can be assessed.
The results are as follows:
Bin no. 7 (cake covered)--The dry solids increased 5.4% in 3 1/2
months reflecting a moisture loss with some moisture gain by the
end of the test period for a net increase in dry solids of 3.6%.
The percent volatile solids content decreased from 57.5% to 46.8%
representing a 10.7% decrease. The reduction in volatile solids
for the test period was 35.:
Bin no. 8 (cake, uncovered)--The percent dry solids increased from
48.4% to 71.6% or a difference of 23.2% in a 3 month period
following placement. As previously stated, the internal tempera-
tures of the solid waste exceeded 70°C during this initial period.
The percent volatile solids content decreased from 56.8% to 37.1%
representing a difference of 19.7%. The percent reduction of
volatile solids was 55.2% for the test period.
It is evident that the uncovered cake bin no. 8 represented the
189
-------
TABLE 72. SUMMARY OF ANALYSIS OF BIN CONTENTS FOR DEWATERED CAKE SLUDGE
--COVERED VERSUS UNCOVERED
Bin no. 7 Bin no. 8
100% Dewatered sludge cake 100% Dewatered sludge cake
covered uncovered
parameter Date: 4/12/74 7/29/74 9/3U/74 11/4/74 a/25/74 5/2U/74
Total cake weight,kgl!645
Dry solids, % 44.7
Dry weight, kg 5220
Fixed, %
Fixed weight, kg
Volatile, %
Volatile weight, kg
Volatile reduction,%
42.5
2215
57.5
2985
7844 10254
49.9 46.8
3914 4795
56.3
2204
43.7
1710
42.7
45.9
2200
54.1
2595
13.1
8554 11971
48.3 48.4
4134 5788
53.2
2199
46.8
1935
35.2
43.2
2500
56.8
3288
7380
63.8
4707
53.0
2497
47.0
2210
32.8
7/2/74
5947
71.6
4258
58.6
2496
41.4
1762
46.4
7/2V/74
5533
70.0
3872
64.5
2496
35.5
1376
58.2
V/5U/74
5285
73.4
3879
64.4
2496
35.6
1383
57.9
11/4/74
6813
58.
3970
62.
2496
37.
1474
55.
3
9
1
2
Bin cake volume, m3 14.0 11.2 11.1 11.2 16.8 10.8 9.66 9.18 9.06 9.06
Density:
Total, kg/m'3 832 700 924 764 713 683 616 603 583 752
Dry, kg/m3 371 349 432 369 344 436 441 422 428 438
Cake water content:
6445 3929 5459 4421 6170 2673 1689 1661 1406 2843
6.44 3.93 5.46 4.42 6.17 2.67 1.69 1.66 1.41 2.84
Filter press cake
Volume, m3 10.7 -- -- -- 10.5
-------
more desirable placement procedure. Regarding loss of volatile solids
by leachate presented in the following part, only 7.7 kg as compared to
49.9 kg were lost from bin no. 8 as compared to bin no. 7 which
further supports the uncovered placement procedure. The relatively
small loss of volatile material by the leachate indicates the biological
conversion of organic matter to gaseous end products. The high temper-
ature development in the uncovered bin no. 8 indicates that a greater
opportunity for aerobic, compost-like conditions to prevail for at least
part of the time whereas the covered bin no. 7 temperature development
indicates that likely more anaerobic conditions prevail.
LEACHATE QUALITY AND QUANTITY
The liquid which percolates through the solid waste material is of
particular interest in indicating the activity within the cell and the poten-
tial for affecting subsurface groundwater quality.
A major factor that influences leachate production is the incident
rainfall assuming the landfill is above the groundwater table. Factors
such as earth cover, soil type, and sloped surface to facilitate drainage
would bear oil the amount of leachate generated. Also the development
of high internal temperatures with the opportunity for liquid evaporation
or the presence of absorptive materials which retain the moisture until
field capacity is reached would also effect the quantity of leachate gener-
ated. The inherent errors in measurement or undetected leakage also
may affect the results.
A rain gage was installed adjacent to the test bins to determine the
incident rainfall over the test period. During the 14 month test period
for bins 1 through 5, the accumulative rainfall was 78.66 cm (30.97in)
which is 13% lower than for average rainfall conditions. During the 7
month period for bins 6 through 8, the precipitation was 47.70 cm (18.78
in), some 20% below the average rainfall.
The leachate collected from the bin sampling well at the front of the
bin was monitored for volume throughout the test periods. The results
for the total volume of precipitation on a given test bin presented in
Table 73 was based on rainfall and the horizontal surface area of the
bin over the test period. The rainfall data in centimeters throughout
the test periods are presented in Tables 69 and 70. The total volume
of leachate and leachate volume as a percent of total rainfall are pre-
sented in Table 73. A graphical plot of the results are presented in
Figure 85.
191
-------
80
60
40
20
% MUNICIPAL REFUSE
20 40 60
% FILTER CAKE
Figure 85. Landfill leachate production.
192
-------
TABLE 73. LEACHATE VOLUME AS PERCENT OF TOTAL RAINFALL
Bin
number
1
2
3
4
5
6
7
8
Total
volume
of
leachate
liters
920.0
670.1
721.3
1842.3
677.3
417.7
1280.3
538.0
Total
volume
of
rainfall
liters*
9220
9280
10383
9354
9354
5438
5683
6224
Leachate
as a
percent
of total
rainfall
10.0
7.2
6.9
19.7
7.2
7.7
22.5
8.6
Period
of record
9/14/73-11/6/74
9/7/73-11/6/74
8/16/73-11/6/74
8/24/73-11/6/74
8/30/73-11/6/74
4/17/74-11/6/74
4/10/74-11/6/74
3/22/74-11/6/74
* Total volume of rainfall based on rain gage measurements on site for
the horizontal surface area of the landfill bin.
It is apparent that the covered test bins containing 100% dewatered
sludge cake produced a significantly greater amount of leachate than all
other bins. Although the uncovered 100% dewatered sludge material
would readily permit incident rainfall to penetrate the landfill, the
amount of leachate is less than for covered cake. The high temperature
development within the uncovered bins must represent the benefit of
attendant high evaporation rates. The covered bins containing municipal
refuse had leachate volumes of 7 to 10% of the incident rainfall, in the
same range as for uncovered dewatered sludge cake. High internal
temperatures in these bins were not as marked as in the bins with
uncovered cake.
The results of the chemical analyses of the leachates are presented
as concentrations (mg/1) in Table 74 and as total mass amounts in kg
and kg/1000 of material placed in Table 75. The analyses for COD and
solid residues were performed routinely whereas analyses for other para-
meters were performed less frequently but as often as time would
permit.
It is apparent from reviewing these results that the highest concen-
trations and mass amounts for the parameters measured of the leachate
are for bins 4 and 7, 100% covered, dewatered sludge cake. Bins 3 and
8, uncovered dewatered sludge cake, yielded as a group the second
greatest amount of pollutants with the remaining bins containing municipal
193
-------
refuse or combined solid wastes with lower but less definitive results.
Bins 5 and 6 contained 50% refuse and 50% sludge cake under covered
and uncovered conditions respectively indicate, that with the exception
of the parameters COD and sulfide the covered bin no. 5 had the highest
amount of pollutants in the leachate. Direct comparison of the results of
these two test bins should be qualified because of the differing elapsed
times over which these results were obtained with the longer period for
bin no. 5.
The combination of 80% municipal refuse, 20% sludge cake for bin
no. 2 compared to 100% municipal refuse for bin no. 1, both covered,
yield leachate results which are similar except for higher values of
chromium and chloride for bin no. 2 as one might expect.
A more detailed analysis was made with reference to solid material
and leachate for total solids, volatile solids and total chromium for bins
6, 7 and 8 to determine the percentage of chromium placed found in the
resulting leachate. The results are presented in Table 76 where it is
evident in comparing bins 7 and 8 that the covered bin no. 7 resulted in
the highest percentage of total solids, volatile solids and total chromium
in the leachate. It is likely that more nearly anaerobic conditions
prevail in the covered bin no. 7 whereas the opportunity for ventilation
in the uncovered bins would be greater. Under anaerobic or reducing
conditions the formation of organic acids would tend to enhance the solu-
bility and hence migration of chrome to the leachate.
TABLE 74. AVERAGE CONCENTRATIONS OF LEACHATE SAMPLES *
Parameter
Concentrations, mg/1
Bin no. 1
BOD5
COD
Total solids
T. volatile solids
T. suspended solids
Volatile susp. solids
Oil and grease
Calcium
Chloride
Sulfide
Total chromium
83
843
2700
742
205
75
68
148
392
0.04
0.17
86
993
719
4380
6130 15000
1220
140
99
71
330
1610
0.08
1.68
6780
457
231
62
1010
2930
0.73
4.76
3018
11200
18700
12500
717
476
107
271
6180
135
8.74
79
952
6900
1710
575
88
69
602
1300
0.02
4.78
59
1750
3460
939
276
124
47
326
791
—
27700
65100
51400
39200
1090
523
85
1440
4550
160
0.22 9.81
8120
15000
22100
14300
446
207
44
762
4000
5.5
0.95
194
-------
,, A . Total weight of matter (milligrams)
* Average concentration = Total V8olume of leact;ate (fiters);
for the period from placement to November, 1974.
Bin no. 1-5 placement: August - September, 1973.
Bin no. 6-8 placement: March - April, 1974.
195
-------
TABLE 75. SUMMARY OF LEACHATE CHEMICAL ANALYSES--TOTAL AND UNIT MASS BASIS
Bin no. 2
Bin no. 1 80% municipal refuse Bin no. 3
100% municipal refuse 20% sludge cake 100% sludge cake
covered covered uncovered
Bin no. 4
100% sludge cake
covered
Parameter
BOD=;
cotf
Total solids
Total volatile
solids
Suspended solids
Volatile susp.
solids
Total chromium
Oil and grease
Calcium
Chloride
Sulfide
kg*
0.765
0.776
2.49
0.683
0.189
0.064
0.000154
0.0625
0.136
0.360
0. 000035
kg/1000 kg+ kg
0.016
0.162
0.520
0.143
0.039
0.013
0. 00003
0.013
0.028
0.075
0. 000007
0.058
0.665
4.11
0.816
0.094
0.067
0.00113
0.048
0.221
1.081
0. 000056
_kg/1000 kg
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
009
102
633
126
014
010
00017
007
034
167
0000086
0.
3.
10.
4.
0.
0.
0.
0.
0.
2.
0.
kg kg/1000 kg
519
16
8
89
330
166
00343
045
729
116
000529
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
043
259
884
401
027
013
00028
004
060
173
000043
kg
5.56
20.6
34.5
23.1
1.32
0.877
0.0161
0.198
0.499
11.38
0.250
kg/1000 kg
0.041
1.63
2.74
1.84
0.105
0.070
0. 0013
0.016
0.040
0.903
0.020
^Continued)
* kg represents total mass of stated parameter over test period in kilograms.
+ kg/1000 kg represents unit mass of stated parameter based on total mass of stated parameter
divided by total mass of material placed without regard to parameter.
-------
TABLE 75. (CONTINUED)
Bin no. 5, covered Bin no. 6,uncovered Bin no. 7
50% municipal refuse 50% municipal refuse 100% sludge cake
50% sludge cake 50% sludge cake covered
Bin no. 8
100% sludge cake
uncovered
Parameter
BOD5
COD
Total solids
Total volatile
solids
Suspended solids
Volatile susp.
solids
Total chromium
Oil and grease
Calcium
Chloride
Sulfide
kg kg/1000 kg
0.053
0.645
4.67
1.16
0.389
0.060
0. 00324
0.047
0.408
0.880
0.0000118
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
006
078
564
140
047
007
00039
006
049
106
0000014
kg kg/1000 kg kg kg/1000 kg
0.025
0.732
1.45
0.392
0.115
0.052
0. 000092
0.0196
0.136
0.330
0.115
0.004
0.113
0.224
0.061
0.018
0.008
0. 000014
0.0030
0.021
0.051
0.018
35.4
83.3
65.9
50.1
1.40
0.670
0.013
0.109
1.845
5.76
0.205
3.04
7.15
5.65
4.30
0.120
0.057
0.001
0.009
0.159
0.494
0.017
4.
8.
11.
7.
0.
0.
0.
0.
0.
2.
0.
kg
37
07
88
67
240
112
00051
023
410
148
00294
kg/1000 kg
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
365
674
992
641
020
009
000043
002
034
179
00025
-------
TABLE 76. SOLID WASTE CHROMIUM BALANCES FOR PERIOD APRIL-NOVEMBER, 1974.
to
00
Solid material:
Total weight placed, kg
Total solids, %
Total weight dry solids, kg
Volatile solids, %
Volatile Solids weight, kg
Total weight chromium, kg
Percent of total weight placed, %
Dry solids, %
Leachate:
Total solids, kg
Total dry solids, %
Volatile solids, kg
Volatile solids, %
Total chromium,, kg
Percent of chromium placed, %
Bin no. 6
Municipal refuse 53.6%
Dewatered cake 46.4%
Uncovered
Placed 4/17/74
Total Sludge cake only
6461 3000
48.4
1452
66.0
958
7.18* 7.18
0.11 0.24
0.49
1.45
0.39
0. 000092*
0.0013*
Bin no. 7
Dewatered
cake 100%
Covered
Placed 4/10/74
Total
11645
44.7
5205
57.5
2998
29.8
0.26
0.57
65.9
1.27
50.1
1.67
0.013
0.044
Bin no. 8
Dewatered
cake 100%
Uncovered
Placed 3/22/74
Total
11958
48.4
5788
56.8
3288
30.2
0.25
0.52
11.9
0.21
7.67
0.23
0. 00051
0. 0017
* Assumes no chromium in refuse placed.
-------
SECTION XV
FINANCIAL CONSIDERATIONS
CAPITAL COSTS
The capital costs for the treatment facilities are summarized in
Table 77. The contracts were let for the treatment plant, associated
equipment, and engineering costs in the spring of 1970 for the amount
of $950,000. The contracts for sludge handling structures, equipment
and engineering costs were let in the springs of 1972 and 1971 in the
amount of $575,000. The total capital cost of the treatment and sludge
handling facilities was $1,525,000 and if amortized at 6% over a 20-
year period the annual cost related thereto amounts to $132,956 per
annum.
TABLE 77. CAPITAL COSTS
Treatment Plant (Bid Spring 1970)
Construction $700,000
Euipment
Primary and Final Clarifiers $35000
Aerators 42500
Mazorator 6900
Pumps 29800
Chlorine Feed 3200
Metering 6600
Mechanical Rakes 2000
C02 System 13000
Primary Sludge Pump 3000
Subtotal 142,000
Engineering 108,000
Sludge Dewatering
Construction (Bid Spring 1972) 230,000
Equipment (Bid Spring 1971) 325,000
Engineering 20,000
Total Capital Costs $1,525,000
Annual Captial Cost Amortized 6% 20 year $132,956
199
-------
POWER COSTS
Both electrical and natural gas was consumed in the operation of
the wastewater treatment facilities. The electrical energy was used to
operate all pumps, mechanical equipment, aerators, mixers and mis-
cellaneous control equipment whereas the gas was used in space heaters
for the purpose of heating treatment plant buildings. As a result of the
joint effort between the industry and the City of Red Wing, the utility
rates reflected schedules consistent with municipal services. During
the operating period from starting through the middle of March, 1974,
the electrical unit costs were 1.38 to 1.45^/KWH, thereafter for the
remainder of the project the unit costs were 1.62-1.64<£/KWH. The
natural gas costs ranged from 11 to 13<£/cu. ft.
The total energy requirements were different for winter than for
summer periods of operation. During winter operation only two of the
four lagoons were operated which reduced the electrical energy require-
ments for aerators, however, natural gas was consumed during the
winter for building heating.
Table 78 summarizes the unit costs and the monthly costs of $2300
and $3200 for winter operations and spring-summer-fall operations res-
pectively during the 1973-1974 operating period.
TABLE 78. POWER CONSUMPTION AND COSTS
Unit Power Costs
Electric 1.38-1.45<£/KWH 1972,1973,1974(3 mos)
Natural Gas 1.62-1.640/KWH 4/1974-
11-130/cu. ft.
Monthly Average Power Consumption and Cost
Winter (3 mos, 1973-1974)
Electric 120.000KWH
Gas 4,000 cu. ft.
Cost $2300/month
Spring Summer Fall (9 mos, 1974)
Electric 190,000 KWH
Cost $3200/month
CHEMICAL COSTS
Table 79 lists the chemicals used in treatment of the wastewater
200
-------
during the project period. Although facilities were provided in part for
C02 addition to the raw wastewater near the end of the project period,
C02 was not employed to facilitate separation of solids in the primary
settling units. The ferric chloride and lime was used primarily in
conjunction with sludge dewatering. Ferric chloride was also used on
occasion as an additive to the raw wastewater for purposes of controlling
sulfide losses to the atmosphere. The defoamers were used to control
foaming in the aerated ponds with weekly costs ranging from $100 to
$500. Phosphoric acid was used a nutrient supplement for certain of the
operating modes wherein dosages of 7-10 mg/1 of P were employed for
a weekly cost of $225 to $325. Chlorine obtained in 150 pound cylinders
was applied to the treated effluent from 75 to 100 pounds per day for a
weekly cost of $100 to $125.
The annual costs associated with chemical use are summarized in
Table 80.
TABLE 79. CHEMICAL COSTS 1974
Chemical Unit Cost Remarks
Ferric Chloride 8.3<£/dry Ib delivered freight 4.3^/dry Ib
(40% solution)
Lime (Dry) 1.1^/dry Ib. slaked by tannery
Defoamers 18-38<£/liquid Ib several types used
Phosphoric Acid 92^/lb phosphorus
Chlorine 12-20^/lb 150 Ib cylinders
Carbon Dioxide 4.5<£/lb not used during
study
OPERATION AND MAINTENANCE COSTS
The operation and maintenance costs summarized in Table 80
reflect power, labor and* chemical costs for the year 1974. Although
the numbers of project personnel was increased to 18 persons during
the peak of data gathering activity, the costs for salaries shown in
Table 80 represent costs for 8 and 11 persons for winter and spring-
summer-fall periods respectively. The additional personnel are
required during the spring-summer-fall period for operation of the
sludge handling facilities over extended periods to remove the excess
sludge accumulation in the aerated pond systems. The total annual
operating and maintenance cost of $257, 829 includes $192,915 for
personnel and $64,914 for equipment repair and replacements,
201
-------
supplies and disposal cf sludge cake.
TABLE 80. OPERATION AND MAINTENANCE COSTS 1974.
Item
Salaries
Power
Chemicals
$20226 *
6930
13794
Subtotal $40950
Total
Equipment Repair and Maintenance, Supplies
and Sludge Disposal
Total Annual Cost
$75240 +
28116
48609
$151965
$192915
$64914
$257829
* 8 persons.
+ 11 persons for additional sludge dewatering.
SUMMARY OF COSTS OF TREATMENT
The amortized capital cost at 6% over 20 years from Table 77 and
the annual costs for operation and maintenance from Table 80 give a total
annual cost of $390,785, as shown in Table 81.
The unit costs based on BOD and COD applied or 1000 gallons of
wastewater are presented in Table 81, at $0.263 per kg BOD ($0.119
per pound BOD), $0.0965 per kg COD ($0.0438 per pound COD), or
$0.434 per m3 ($1.645 per 1000 gallons of flow). These costs are not
additive, but merely reflect the total annual costs divided by the total
annual weight or volume of wastewater characteristic. Assignment
or allocation of costs by unit operation relative to the wastewater
characteristic is not presented.
202
-------
TABLE 81. SUMMARY OF TREATMENT COSTS.
Item
ATnortized Capital Cost $132,956
Operation and Maintenance Cost $257, 829
Total Annual Cost $390,785
Estimated Cost of Treatment
1, 485, 500 kg (3, 275,000 Ibs) BOD/year
$0.263 per kg ($0.119 per Ib) BOD applied
4,050,600 kg (8,930,000 Ibs) COD/year
$0.0965 per kg ($0.0438 per Ib) COD applied
899.320m3 (237,600,000 gals) waste water/year
$0.434 per m6 ($1.645 per 1000 gals of waste-
water flow)
203
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SECTION XVI
REFERENCES
1. Polkowski, L. B. and Boyle, W. C. An Investigation on the Biolo-
gical Treatment of Wastes from the S. B. Foot Tanning Company
Alone and in Combination with Red Wing, Minnesota Municipal
Wastewaters. November, 1966.
2. Polkowski, L. B. , Boyle, W. C. and Rohlich, G. A. Investigation
on the Treatment and Disposal of Wastes from the S. B. Foot
Tanning Company at Red Wing, Minnesota. November, 1965.
3. Development Document for Effluent Limitations Guidelines and New
Source Performance Standards for the Leather Tanning and Finishing
Point Source Category. U.S. Environmental Protection Agency.
440/1 -74 -016 -a. March, 1974.
4. Eckenfelder, W. W. Industrial Water Pollution Control. McGraw-
Hill, Inc. 149-160.
5. Jones, B. R. S. "Vacuum Sludge Filtration II Prediction of Filter
Performance." Sewage and Industrial Wastes. 29(9):1103-1115. 1956.
6. Eckenfelder, W. W. and Ford, D. L. Water Pollution Control-
Experi mental Procedures for Process Design. Pemberton Press,
Jenkins Publishing Company, Austin, Texas. 1970.
204
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SECTION XVII
APPENDICES
APPENDIX A: ANALYTICAL PROCEDURES
Sampling
The sampling of wastewaters within the plant were performed by
hand or by the use of specially designed automatic flow compositing
samplers located at the primary sedimentation tank effluent lines, the
lagoon sedimentation tank effluent lines and the final effluent line from
the chlorine contact chamber. Details on hand sampling and compositing
of samples are outlined under the appropriate study phase within this
report. The design and operational details of the automatic samplers
are presented in the following subsection.
Continuous monitoring systems were installed to measure pH,
temperature and dissolved oxygen at selected points within the plant.
Leeds and Northrup pH probes and thermocouples and Weston Stack
D.O. probes were employed. The signals were picked up by Leeds
and Northrup monitors and transmitted to multipoint recorders located
within the buildings. The monitors were located in insulated wooden
boxes equipped with 60 watt lightbulbs to maintain temperature in the
winter. Lines from the probes to the monitor and from the monitors
to the recorders were buried. Two recorder systems were employed.
System 1 picked up pH and temperature signals from the raw waste-
water and the primary effluent. System 2 detected pH, temperature
and D.O. from the lagoons as well as pH and temperature of the final
effluent from the chlorine contact chamber. Details of these monitoring
systems and operational difficulties with them appear in a following
subsection entitled'Monitoring System'.
Automatic Sampling System--
The automatic samplers were designed with the assistance of Mr.
Donald Nelson (Ph.D. candidate, Electrical Engineering, University of
Wisconsin) by Polkowski, Boyle, and Associates. The sample
consisted of a sequence of solenoid valves and timers which were actu-
ated by a signal from the magnetic flow meter. On a signal from the
205
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flow meter, a solenoid valve was opened in the sampling line and the
line was completely flushed to waste for approximately 20 seconds. Upon
closing a short pause was induced to allow for dampening of resulting
transient water pressures and then a timer controlled solenoid valve was
opened to allow the sample to flow at a prescribed time to the sampling
vessel. After the sampling, the valve closed to complete the sampling
sequence. The timer control could be set from 0 to 3 seconds in 0.05
second intervals depending upon the quantity of sample desired. In the
sampling program conducted at this plant a 0.25 second opening time
was employed producing 50 to 80 ml of wastewater per sampling interval.
The sample was collected in a 3.78 liter container placed in an insulated
chest. Ice was packed around the container to keep the sample cool
over the 24 hour storage period. (Most sampling was done over a 24
hour interval.)
Flow was monitored by a Fisher-Porter magnetic flowmeter located
in the 36 cm diameter raw wastewater line from the raw wastewater
pumps to the primary sedimentation tanks. The signal from the flow-
meter was transmitted to a recorder to indicate rate of flow. A flow
integrator was also provided to indicate total quantity of flow. A signal
to the automatic samplers was obtained by employing a Bliss Eagle prede-
termining counter which was set to store a series of signals from the
flow integrator. Thus a signal was sent to the predetermining counter
for every 1000 gallons of raw wastewater and when 10 such signals were
received (10,000 gallons) a signal was transmitted to the automatic
samplers. Over a typical process day approximately 1,000,000 gallons
would flow producing 100 signals to the samplers and yielding approxi-
mately 5 to 8 liters of waste sample.
Normally, samplers were actuated at about 7 a.m. on a selected
sampling day. By experience it was found that the 3.78 liter containers
were filled by 4 or 5 p.m. The sample collected at that time was then
transferred to a 7. 57 liter container and refrigerated. The remainder
of the sample was then collected and the two aliquots were mixed and
analyzed the following morning.
The automatic samplers were located at four points within the plant
Primary effluent was collected from the effluent line from the sedimenta-
tion tank to the outfall chamber. The sampler was located in the
primary clarifier building. Lagoon effluents were collected from the
inlet chamber to the final clarifiers. Final clarifier effluent samples
were collected in the clarifier effluent lines to the chlorine contact
chamber. Final effluent samples were collected from the effluent end
of the chlorine chambers ahead of the overflow weir. These last three
sampler systems were located within the final clarifier building.
206
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There were no operational difficulties recorded for the automatic
samplers once they were properly adjusted. Some maintenance problems
were experienced with the flowmeter system. Initially, no clean-out or
bypass had been provided around the magnetic flowmeter to allow for
cleaning. A buildup of lime and grease covered the sensors within the
throat producing erroneous results. Once provisions were made for
adequate cleaning of the meter, no other difficulties were encountered.
Because of the highly corrosive atmosphere within the pump buildings,
it was determined that the electronic components of all sensors including
the automatic samplers be sealed against the ambient environment.
Sealing proved to be effective as no failures in electronic systems due
to corrosion were recorded.
Monitoring System--
The monitoring system was designed by Leeds and Northrup in
accordance with specifications presribed by Polkowski, Boyle and Asso-
ciates. Leeds and Northrup monitors and multipoint recorders were
employed with appropriate probes to provide continuous monitoring of
selected sites.
System 1, which measured pH and temperature from the raw and
primary effluent systems, employed a six point recorder located within
the raw waste pumping station. Temperature and pH probes were
placed in the raw wastewater line and the primary effluent line from one
sedimentation tank. Analyses were made at 30 second intervals. Consi-
derable difficulty was encountered in maintaining the pH probes in the
raw waste stream. Even the placement of a baffle around the probe did
not prevent rapid fouling with hair, grease and lime scale. Therefore,
raw waste pH was continuously monitored only on days when 24 hour
raw waste surveys were conducted. During these times sufficient man-
power was available to keep the probes clean and properly calibrated.
The monitoring of pH in the primary effluent was not as difficult to
maintain. The probes were calibrated two or three times per week and
held their calibration satisfactorily. Occasional removal of scale from
the probe was practiced by soaking them in 15% of HC1. The tempera-
ture probes at both points performed satisfactorily and were cleaned
periodically to remove extraneous scale, hair and grease.
System 2 monitored pH, D.O. and temperature within selected
lagoons and pH and temperature of the final effluent at the chlorine
contact chamber. A twelve point recorder was employed using a 30
second sampling interval. The probes for the lagoons were installed on
a special hoist arrangement on the outlet structure. They were placed
below the water surface and could be easily raised and swung into posi-
tion for calibration and cleaning by the operator. Two probe systems
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were available and could be moved from one lagoon to another. Wiring
was available at all four lagoons, but only two systems could be moni-
tored at one time. The pH probes performed satisfactorily in the
lagoons and final effluent. Calibrations were checked two or three times
per week and occasional cleaning with dilute HC1 was used to remove
scale. The temperature probes were satisfactory. Considerable main-
tenance was required for the D.O. probes. They did not hold calibra-
tion as well as anticipated due primarily to the wastewater characteris-
tics--grease and solids scale. The probes were provided with mixers
to maintain adequate velocity across the probe but this action did not
prevent deposition on the membrane surface.
Analyses
The analyses performed during this study were conducted in accor-
dance with Standard Methods for the Examination of Water and Waste -
water, 13th edition, except as noted. Details of the conduct of these
analyses follow.
Chemical Methods--
Alkalinity-- Alkalinity was initially determined employing brom-
cresol green-methyl red indicator for end point detection. In July, 1973,
the potentiometric titration procedure was employed using a pH meter.
Dissolved alkalinity was estimated by filtering a sample through Whatman
42 filter paper and after January, 1974, by filtering through Whatman
GF/C glass fiber paper.
Calcium-- Calcium was determined by the EDTA titrimetric method.
In order to eliminate interference by organic matter, all samples were
fired in a muffle furnace at 550°C for 50 minutes, redissolved and
titrated. Dissolved calcium was obtained by filtering samples through
Whatman GF/C glass fiber paper.
Chloride-- Chlorides were measured by the Argentometric method.
Organic interferences were eliminated by firing samples in a muffle
furnace at 550°C for 50 minutes, redissolving and titrating. Beginning
in March, 1973, Quantab Chloride Titrators (Ames Co., Division of
Miles Laboratory, Inc., Elkhart, Indiana) were employed. Automatic
titration was accomplished through capillary action in the Quantab strip.
Comparisons with the Argentometric method indicated values within 100
mg/1 over the range of 2,000-3,000 mg/1 chloride.
Chlorine-- Chlorine was determined by the DPD ferrous titrimetric
method"!In the absence of iodide, free available chlorine reacts
instantly with the N, N, -diethyl-p-phenylenediamine (DPD) indicator to
208
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produce a red color. Subsequent addition of a small amount of iodide
ion acts catalytically to cause monochloramine to produce color. Further
addition of iodide in excess evokes a rapid response from dichloramine.
Manganese interference was removed in the procedure. The endpoint
was clearly visible for the final effluent.
Chrome-- The analysis for chrome followed the procedure of the
Permanganate-Azide method outlined in Standard Methods with modifica-
tions. Initial studies using this procedure indicated poor recoveries of
chrome added to wastewater samples. It was determined that wet ashing
was superior to dry ashing which often left black particulates. Perman-
ganate was used primarily because alternative mthods required removal
of too many interferences. The oxidation step was carried out in 0.5
N H2S04 using sodium azide to eliminate excess permanganate. Careful
pH control was essential during color development. Constant pH was
maintained on all samples and standards by use of 0.2 N HoSO,. Finally
it was found that dissolving S-diphenyl carbazide (DPZ) reagent In ethyl
acetate produced a more stable reagent giving improved performance and
shelf life over the use of ethyl or isopropyl alcohol.
Color-- Color was determined by the Spectrophotometric Method
outlined in Standard Methods. Samples were filtered through a calcined
filter aid and light transmittance was measured.
Dissolved Oxygen-- Dissolved oxygen was measured with a Yellow
Springs Instrument Company dissolved oxygen probe and meter, cali-
brated by the azide modification of the Winkler procedure.
Fats, Oils and Grease (FOG)-- FOG was measured using the
Soxhlet Extraction Method employing hexane as the solvent.
Nitrogen-- Nt^N-Ammonia was measured by the use of an Orion
moder05-10 specific ion electrode employing procedures outlined in
Standard Methods, Methods for Chemical Analysis of Water and Wastes
(U.S. EPA, 1971), and R.F.Thomas and R.L.Booth, ("Selective Electrode
Measurement of Ammonia in Water and Wastes", Environmental Science
and Technology, 1, 6, 1973).
Kjeldahl-N--The micro Kjeldahl method was employed to determine
total organic nitrogen. Ammonia collected was analyzed by use of the
Orion Model 95-10 specific ion electrode.
Nitrate-N--The aluminum reduction of nitrate to ammonia was
employed to determine nitrates. In brief the procedure was as follows:
100 ml of sample was placed in a round-bottom flask equipped with
209
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magnetic stirring bar. One ml concentrated HC1 and approximately 0. 5
g of NaF was added and stirred vigorously. To this mixture 0.1 finely
divided aluminum powder was added. After the evolution of hydrogen
(5 to 7 minutes), 1 ml of 10 M NaOH was added and the contents were
poured into a beaker for analysis of ammonia with the Orion Model 95-
10 specific ion electrode. A control sample was also run to give back-
gound ammonia levels. A recovery study in the wastewater indicated
that from 85-90% of the nitrate could be recovered by this method.
Phosphorus--
Orthophosphate -P - -Phosphates which responded to the stannous
chloride color development employing benzene-isobutanal solvent extrac-
tion, without preliminary hydrolysis or oxidative digestion were consi-
dered orthophosphates. Filtered orthophosphates were obtained by filtra-
tion through prewashed GF/C filter paper (pore size--0. 5 microns).
Condensed Phosphate-P--The phosphates obtained as the difference
between orthophosphates as measured above and the phosphate found after
mild acid hydrolysis and stannous chloride color development employing
benzene-isobutanol solvent extraction. Dissolved portions were deter-
mined as above.
Total Phosphate-P--Because of technical difficulties in the laboratory
perchloric acid digestion and sulfuric acid-nitric acid digestion methods
were not employed to determine total phosphates. A procedure employed
extensively by the State of Wisconsin Water Quality Evaluation Section
was carefully tested and found to be very satisfactory for this study.
Recoveries of added phosphates to selected wastewater streams in the
plant ranged from 90-112%. The procedure is briefly described below.
Five ml of a 15% solution of magnesium nitrate [Mg(NOg)2-6H20]
was added to 25 ml of sample. The sample was evaporated to dryness
at 103°C and then fired over a Bunsen burner for between 5 and 15
minutes until only white ash remained. The ash was completely
dissolved using strong acid solution and heat. After dissolution, stan.-
nous chloride color development, employing benzene-isobutanol solvent
extraction was used to determine the phosphorus content. Dissolved
portions were determined as above.
Residue-- Suspended solids analyses were performed using Whatman
No. 40 filter paper from October, 1971, to February, 1973. In March,
1973, Whatman GF/C glass fiber filters were employed.
Sulfide--The Methylene Blue Photometric Method was employed for
sulfide analysis. Zinc acetate and sodium carbonate were employed as
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preservatives for sulfide samples. For the very thick wastewaters
coming from the hair pulping operation, it was necessary to first dilute
the same with oxygen free water before preservation since incomplete
precipitation of zinc sulfide occurred in the undiluted sample.
Biological Methods—
Total Bacteria-- Total bacteria were enumerated on Plate Countagar
after incubation at 20°C for 72 to 120 hours. The colonies were slow
growing at this temperature so longer incubation times than prescribed
in Standard Methods used.
Total Coliforms-- Total coliforms were determined by the mem-
brane filter method using Gelman GN 6 white membrane filters. The
filters were incubated on M-Endo medium for 24 hours at 35°C.
Fecal Coliforms— Fecal coliforms were determined by the mem-
brane filter procedure employing Gelman GN 6 white membrane filters.
The filters were incubated M-FC medium for 24 hours at 44.5°C.
Sludge Accumulation Measurements
Since the aerator power in the lagoons was not sufficient to main-
tain all suspended solids in a suspended state, it was desireable to
routinely determine sludge accumulation within the lagoons so that esti-
mates could be made on sludge generation. Sludge accumulations were
monitored by the use of a 20.3 cm (2.31 in) pie pan attached to a 1.83
m (6 ft) 0.635 cm (0.25 in) diameter steel rod. The rod, graduated in
feet, weighed 1.05 kg (2.31 Ib). The pan was lowered in the lagoon
until it met resistance. The water depth was measured and the sludge
depth was obtained by difference. This procedure was satisfactory for
the heavy inorganic sludges encountered in this study but would likely
be inadequate for a lighter biological sludge. It is reasonable to assume
that the lighter material in these lagoons would remain in suspension
since mixing by the aerators did provide substantial horizontal velocities.
The lagoons were divided into sectors by describing sampling lines
across the width, intersecting each aerator and bisecting the distance
between adjacent aerators. Thus 21 width lines were established. Along
each width line, seven equidistant points were sampled producing a total
of 147 sampling points. The bottom of the lagoons occupied approxi-
mately 1672 m2 (18,000 ft2), therefore, each sample point represented
about 11 m2 (120 ft2).
Based on the survey, a cross section of each width station was
prepared. Total sludge volumes were estimated between width stations
211
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by averaging procedures.
Samples of sludge were also collected during the survey and analyzed
for percent solids , percent volatile solids, COD, TKN, andCa. These
analyses were employed to estimate changes in accumulated masses of
organic and inorganic matter within each lagoon.
Analytical Procedures Employed for the Wastewater Effluent Reuse,
Section —
The following methods were employed to determine the results pre-
sented in Tables 46, Leather Analysis, and 47, Physical Leather Properties,
in Section XII on Wastewater Effluent Reuse of this report. The standard
procedures employed are identified by determination accordingly below.
Moisture
FED STD - 311 Method 6221
(Fat) Chloroform soluble materials FED STD - 311 Method 6341
(H.S.) Hide Substance
Ash
Organic
ASTM D2868 - 70T
ASTM D2617 - 69
by difference
Chromic Oxide in Leather ASTM E>2807 - 69T
pH of Leather
ASTM D2810 - 69T
(Satra Grain Crack) Distension and SLTC S.L.P. 9
strength of grain by ball burst test
(Mullen) Grain Crack
Tensile strength of leather
Elongation of leather
ASTM D2210 - 64 (1970)
ASTM D2209 - 64 (1970)
ASTM D2211 - 64 (1970)
Test Methods Used
Federal Test Method Standard - 311 (FED STD - 311)
The American Society of Testing and Materials (ASTM)
Society of Leather Trades' Chemists (SLTC)
212
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APPENDIX B: OXYGEN UPTAKE AND OXYGEN TRANSFER STUDIES
Oxygen transfer studies were performed in selected lagoons during
the research study. Figure 86 depicts the sampling points used to conduct
this study. Samples were collected two feet below the water surface at
each sampling point. Oxygen uptake rates were then measured for each
sample collected. Analyses were also made in situ for dissolved oxygen,
mixed liquor solids temperature and sulfides'
Alpha tests were performed on mixtures of samples collected taken
in each one-third of the lagoon. The diffused aeration technique described
by Eckenfelder and Ford (6) was employed for alpha estimations. A typical
graphical calculation of alpha is shown in Figures 87 and 88.
A typical analysis for oxygen uptake rates appears in Table 82.
Average uptake rates were then used to estimate total oxygen consumption
within the lagoon system. Oxygen uptakes per unit of BODs removed were
estimated based upon BODs data for the lagoon studied during the sampling
period.
Oxygen transfer rates were estimated by averaging oxygen uptake
rates, alpha values and total sulfide oxidized during the test period. Beta
values were estimated by both measurement in the laboratory and by
calculation using a total dissolved solids correction on the depression
of the oxygen saturation value.
An example of the calculation employed to determine oxygen transfer
rates under standard conditions is given in Table 83. Values were
expressed on a nameplate horsepower basis and included sulfide oxidation
where applicable.
TABLE 82. OXYGEN UPTAKE MEASUREMENTS
November
Length
Station
0 + 14
0+50
0+63
1 + 13
1 +63
2+13
2+63
Effluent
Width
Station
0+56
0+35
0+56
0+35
0+56
0+35
0+56
D.O.
mg/1
2.6
2.8
3.8
3.3
3.8
2.5
2.4
2.2
29, 1972 -
Temp .
°C
12
12
12
12.5
12
13
12
13.5
- Lagoon #2
Oxygen Uptake
mg/l/hr
10.1
10.6
8.73
8.64
9.8
11.8
10.1
9.4
TSS
mg/1
1260
1170
1190
1100
1020
1100
1000
940
VSS
mg/1
547
503
397
413
427
453
420
347
213
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214
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TAP WATER
LAGOON 1
o>
E
§
LAGOON 1, 10/23/73
T = 20°C
BUBBLE AERATION
345
TIME - minutes
Figure 87. Oxygen transfer studies—alpha determination.
I *
o>
E
o
•o 2
0.77
La
Nk^Xs TAP WATER, Kln=0.77/min
>V
LAGOON 1
KLa S0.69/min
I 234567
DO - mg/-f
Figure 88. Slope plot for determination of KLa.
215
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TABLE 83. OXYGEN TRANSFER EFFICIENCIES. SAMPLE CALCULATION.
Test Condition 2; 10/23/73; Lagoon 1
Average oxygen uptake rate = 2.3 mg/l/hr
Volume = 0.971 mg
A era tor HP = 11 x 5 = 55
Sulfide oxidized = 50 Ib/d
Lb 02/hr = 2.3 x 8.34 x 0.971 = 18.63 Ib/hr
O2 Equivalent of sulfide = 2 x 50 = 100/d =.4'-17 lt>/fir
22. 80 Ib/hr
22.8 Ib/hr
N= - 55-^- =0.41
T = 14°C
CL = 8. 5 mg/1
= 9.33mg/l(/3=0.90)
- _ _ 1.022°-T
0 *.
_ 0.41 9.17 no20"14
"DTW x 9.33-8.5' i'U
NQ= 5.60 Ib/HP hr (nameplate basis)
216
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APPENDIX C: COMMENTS ON TREATMENT PLANT OPERATIONS
Wastewacer Pumping Station
The 61 cm influent pipe to the pumping station required annual
cleaning which was accomplished during the summer vacation period.
The material deposited in the pipe was principally grit and a fire hose
water stream was used to remove these materials. Additional cleaning
was found to be necessary at times as evidenced by the reduction of
hydraulic capacity in this 61 cm influent line.
Raw wastewater screens--In the design of the treatment plant,
a Mazorator, for grinding or cutting the larger pieces of flesh and
scraps to an acceptable smaller size, was supplied on the primary
influent channel. The problems experienced with the Mazorator
suggested a misapplication of the unit.
Pieces of flesh and scraps, especially after tanning, are
extremely tough and resistant to cutting and the unit was unable to
cope with the task. In the first eight months of operation, the
Mazorator was down 38% of the time. By October, 1972, 13
months after start-up, the Mazorator was permanently removed.
During the period when operating difficulties were experienced
with the Mazorator, a mechanical rake was provided on the secondary
channel. The rake was designed by the plant engineer and was
similar to the rake used in the old pumping station. When the
Mazorator was removed, another rake and bar screen were installed
on the primary channel. The rakes so provided were not trouble
free and would break down on numerous occasions. However, the
standby unit was available, the cost to repair was minimal and the
rake was usually back in service within a day. The rake and bar
screen units did perform adequately but not as effectively as the
Mazorator potentially offered. Problems with scraps continued
to be experienced elsewhere such as with the grinding of primary
settling tank sludge and binding of the raw wastewater pumps.
Deposits in the wet well--It was necessary to clean the wet
well three to four times a year as a result of the solids deposited
on the bottom, in the corners and the formation of a grease
layer at the surface. The deposits caused air locking of the
raw waste pumps and the grease layer formed on the surface,
became unsightly, odorous, and caused pumping problems.
217
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The wet well was cleaned by dislodging the deposits with a fire
hose stream and the resulting mixture was pumped with the raw waste-
water pumps to the primary settling tanks.
Deposits in the raw was tewater pumps--The scrap material which
passed through the bar screens caused a maintenance problem with the
raw wastewater pumps. The scrap material would become bound in
the pump impellers and substantially decrease its output. During
poorest operating periods, a pump would need cleaning by removing
the obstruction from the housing three to four times a day, but was
normally done once a day per variable speed pump.
The plugging problem was common to the two variable speed
pumps but not to the constant high speed standby pump and that the
binding of scrap material in the pump impeller occurred at low
speeds. To minimize the problem, adjustments were made in the
pump controls to increase low discharge from 1.04 m^/min to
1.89 m^/min (275 gpm to 500 gpm) with a maximum of 6.06
m^/min (1600 gpm).
Magnetic flowmeter maintenance--The raw wastewater passing
through the flowmeter caused a scale deposit to form and eventually
coated the meter electrodes. When this occurred, the unit failed and
required an extended period of factory servicing in early 1973.
Thereafter, routine removal of the meter for electrode cleaning
was needed every four to six months to insure continued performance.
The meter was selected for design flow rates of 0 to 18930 m^/day
(0 to 5.0 MGD), whereas the average daily flow during the study was
less than 3785 m^/D (1 MGD). The accuracy of the unit for the low
end of the range is subject to greater errors for the flow determina-
tions than would have been experienced at higher flow rates.
Primary Clarifiers and Pumping Station #1
Primary clarifiers--The mechanical equipment provided with the
primary tanks operated relatively maintenance free during the demon-
stration project. As part of a preventive maintenance program, each
primary tank was drained and the equipment inspected for wear at four
to six month intervals. A series of steps were used to clean and
inspect a primary clarifier.
218
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A portable gas operated pump was used to pump the liquid
remaining in the tank. Residual sludge in the tank was pumped to the
other settling tank or back to the wet well and the center feed well was
pumped to remove accumulated material.
When empty, the sludge collector mechanisms were inspected, the
walls and floors scraped to remove scale and the sludge withdrawal pipe
to the sludge pumping station was cleaned with a Roto Rooter after which
the tank was put back in service.
Routinely during each operational week, the three raw waste pumps
were operated simultaneously to put a high flow rate through the center
feed well to dislodge accumulated sediments. This procedure was used
to reduce headlosses and facilitated the equal distribution of flow to
each clarifier. The flow division to the two primary tanks should have
been 50/50 for similar influent piping and equal effluent weir levels;
however, as can be observed in the dewatering studies, the division of
flow appeared not to be equal. This cleaning procedure and the resetting
of the weirs (March, 1974) were employed to provide more effective
sedimentation operation.
Primary sludge pumps--The primary sludge pumps operated under a
heavy load and for the most part performed well. The positive displace-
ment pumps broke down when the hydraulic headlossess were high and
the sludge concentration was too high. The breakdown usually involved
shear pin breakage and within minutes the pump was back on line. A
reliable pressure gage by Ronningen Fetter (0-80 psi) was installed on
the discharge side of the pumps and through the use of water on the
suction side of the pump and by observation of the pressure gage, the
operator was able to pump the primary sludge as thick as possible to
the desired location with a minimum of breakdown.
The normal recommended maintenance on the pumps was followed
and all sludge piping was dismantled and cleaned quarterly to prevent
build up from affecting the pump performance.
Primary clarifier scum handling--In the original design and con-
struction of the treatment plant, separate lines were provided for
conveying primary sludge and primary scum to the dewatering process.
When the sludge dewatering building was designed, the entrance point of
the materials into the building was changed and these lines had to be
relocated It was decided for this relocation to combine the two lines
into one common 15.2 cm (6 in) pipe. The connection of the scum
piping to the sludge piping was made in pumping station #1. Although
this change seemed economically attractive, the reaction between the
219
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scum and the sludge in the underground line produced an adverse effect
of solidifying and blocking of the pipe.
To overcome this problem, the decision was made to keep the
sludge and scum systems separate. The lack of a separate scum line
to the dewatering building is unfortunate in that dewatering studies on a
sludge scum mixture indicated compatability.
The concentrated scum was removed from their storage tanks by a
portable gas pump used to fill private haulers trucks for subsequent
disposal off-site. Normally, the work necessitated two operators, the
truck drivers and took four to five hours to complete at monthly inter-
vals. The frequency of disposal was increased when the rendering
operation began in March, 1974.
Sludge piping maintenance--As indicated above, the maintenance of
the sludge piping, especially for the underground section was critical.
It was necessary to contract with a private company to clean the sludge
line three to four times a year. The method used was either by a high
speed cutting blade^or a high velocity water spray to remove the depo-
sited material.
In addition to this procedure, daily preventive maintenance was
performed. During the last filtration cycle for each day, the operator
would shorten the sludge contact tank make up time to flush the sludge
line with a fire hose back into the clarifiers to remove the sludge. The
underground sludge line was drained back into the pumping station to
remove any loose sediment and the line would be left dry for the next
operating day.
Various chemicals were tried to remove the pipe scale but were
unsuccessful for the most part.
Aerated Lagoons
Removal of accumulated sludge--The major maintenance required
in the lagoon area was the removal of accumulated sludge. As indicated
previously, the specifications concerning the provision for adequate velo-
cities in the lagoon were not met by the original equipment provided.
The original Sigma Pac aerators were replaced by more numerous,
lower horsepower high speed aerators. Though this replacement was an
improvement, settling of solids was not completely eliminated. This
section describes the procedure utilized to physically clean a lagoon of
settled sludge.
220
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The best results were obtained by pumping the sludge back to the
primary tanks for subsequent dewatering of the sludge using the filter
press. One primary tank was taken off-line to receive the sludge for
this purpose.
The lagoon to be cleaned was taken out of service and the aerators
were removed. The liquid contents of the lagoon was then pumped into
an adjacent lagoon by a portable gasoline pumping unit of 2.27 m3/min
(600 gpm) maximum capacity.
Upon completion of the dewatering operation, the sludge was pumped
dailv to the primary clarifier. The amount of sludge pumped was
normally equal to the volume of sludge dewatered the previous day to
minimize carryover of the concentrated liquor to the other operating
lagoons. Where the settled sludge was too thick to pump from the lagoon,
primary effluent was introduced to thin the sludge, or the operators
physically mixed the sludge at the suction point. In many instances a
front end loader was used to mix the entire lagoon contents to give a
pumpable mixture and the front end loader was used daily to move the
sludge to the suction point.
Through this procedure provided an excellent method to handle the
settled sludge, the rate of removal was limited by the capacity of the
filter press to dewater this sludge in addition to sludge resulting from
primary settling of the raw wastewater and waste activated sludge. To
increase production of the sludge dewatering system, three shifts (24
hour) of operation was employed and diatomaceous earth (DE) was used
as a filter precoat. The DE precoat material eliminated the filter
cloth washing required when buffing dust is employed.
The distribution chamber preceding the aerated lagoons was cleaned
yearly of accumulated sludge. The amount of sludge was minimal, and
was normally pumped into a lagoon.
Foam-- The control of foam in the aerated lagoons was a continual
problem throughout the project.
When uncontrolled, the level of foam reached was significant
wherein foam would accumulate and be carried out of the aerated
lagoons to deposit the trapped solids on the grounds adjacent to the
lagoons, forming nuisance conditions for the operators.
Some observations regarding the occurrence of foam formation
follow.
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(a) As the percent of the total primary effluent flow directed to the
lagoon increased, foaming tendencies increased.
(b) Foam tended to form beginning in the late afternoon and through
the night which may coincide with the discharge of the hair pulp
to the plant from noon to 7:00 p.m. and the reduction of foam
film evaporation in absence of sunlight.
(c) The accumulation of foam was more significant on weekends
rather than weekdays.
(d) As mixed liquor solids increased, the ability to control foam
without the benefit of defoamers increased.
(e) Foaming problems appeared to be more intensified when ambient
air temperatures ranged from -1.1 to 10°C (30° to 50°F).
(f) As the efficiency of the biological system increased the ability
to control foam without the benefit of defoamers increased.
(g) Extensive foaming and the associated deposition of solids around
the lagoon resulted in lowering the lagoon's mixed liquor
suspended solids concentrations.
To control foam, various defoamers were employed during the
project. All were liquids, oil based, and contained surface active agents.
Initially, pail quantities of defoamers were thrown into the lagoon each
night or when the foam was excessive. This procedure was not entirely
satisfactory, and arrangements were made to feed defoamers on a
continual basis. Defoamer feed pumps, Brunner chemical solution pump,
Model 22SP, were purchased and installed to introduce the defoamer
either at the distribution chamber as influent to the lagoons or in the
basement of pumping station #2 in the return sludge. The pumping rate
was adjustable and a time clock controlled the operation.
Through operator control, feed rates were adjusted to levels that
would contain the foam in the aerated lagoons. By continued evaluation
of various defoaming products, significant progress was made in control-
ling foam at reasonable costs.
Winter operation--The proper operation of the biological system was
hampered by winter cold weather. The effects of cold weather were
related to reduced biological activity and the failure of mechanical
floating aerators to operate continuously. The problem of aerator shut-
down was anticipated to occur but the extent to which this occurred was
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not predictable.
Both types of aerators provided experienced cold weather problems
and the circumstances of occurrence were similar. Under cold temper-
atures, and ice build-up would begin beneath the vertical mounted motor
and expand, thereby increasing the submergence of the unit, thus causing
the unit to work harder with associated high amperage draw. As a
result, the electrical heaters installed in the control box would shut the
unit down. The length of time required to cause shut-down was depen-
dent on the severity of the cold, with lower temperatures, the shutdown
would occur sooner. As a general guideline, for the Sigma Pacs to
operate without failing, air temperatures of above -12.2% (10°F) were
required. To lengthen the operating time at lower temperatures, half
of Sigma Pacs blades were removed to reduce the weight. For the high
speed aerators, an air temperature of -17.8°C(0°F) seemed to insure
continuous operation with moderate attention.
Once the aerators shut off, different procedures were required to
restart the units. With both types, first it was necessary for the oper-
ator to row out and physically remove the ice. With the Sigma Pac
aerators, the operators checked to see if the blades turned freely. With
the high speed units, the water in the narrow throat construction would
freeze if too long a period had elapsed and the aerator had to be brought
into the tannery to thaw. With both units, if the blades or propeller
turned freely the unit was restarted as soon as possible. The high
speed aerators were more reliable but it is important to restart the
aerators as soon after shutdown as possible. Operation of the floating
aerators will be a continual winter problem. Measures to conserve
heat to prevent shutdown should be employed.
Transfer of aerators--In operating the aerated lagoons, it was
necessary to transfer the mechanical aerators within the lagoon or from
one lagoon to another. The procedures necessary to accomplish this
action were: Sigma Pacs--The 750 kg m/sec (10 HP) units were not
easily adapted to transferring. The motor, gear reducer and blades
were mounted to a circular unit that was 2.44 m (8 ft) in diameter,
1.22 m (4 ft) high, and had 0.305 m (1 ft) thick walls. The ballast had
three separate compartments for water which had to be removed before
transferring the unit. A crane was used to transfer the 544 kg (1200 Ib)
aerator to its new lagoon and the ballast had to be refilled. The Sigma
Pac aerators were secured by three stainless steel wires to anchoring
posts at the lagoon edge.
High speed--The 375 kg m/sec (5 HP) units were lighter and more
easily movable because there were no water ballasts on the units. The
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scoop of a front end loader was sufficient to adequately move the aerator.
These units were secured by four guylines, two of which were tied to
other units.
Scum formation--At various times, it was visually evident that a
scum layer was formed on the surface of the aerated lagoons. Cold
weather seemed to intensify the problem and the scum blanket would be
found in areas where surface velocities were low. In the design of the
treatment plant, scum dewatering pads were provided at each end of the
aerated lagoons. These pads were inadequate since the scum was not
confined to areas near the pad.
Aside from being unsightly, there is some question as to whether
the scum blanket would impair mixing by impeding surface movement,
as well as reduce oxygen transfer. To minimize the scum blanket
formation a grease dissolving chemical was used which appeared to
alleviate the problem.
Grease balls --Wooden slotted gratings were installed across the
effluent structure to keep debris and vegetation, blown into the lagoons,
from entering the effluent piping (Figure 7). The gratings became a
catch basin for trapping grease balls formed by the rotating action of
the aerators and required almost a daily cleaning of the gratings. The
grease dissolving chemical helped to curtail the grease ball production.
Miscellaneous comments-- Pipe scaling was not observed to be a
problem in operating the treatment plant. The primary effluent had
Langlier Saturation Index (SI) values greater +2.0, while the lagoon
effluent had SI values less than +. 50. Calcium carbonate precipitation
occurred within the aerated lagoon representing a significant portion of
the sludge accumulations. Analysis of the sludge deposits showed
calcium carbonate to be 40 to 50% of the total solids on a dry weight
basis.
During the first months of plant operation, it was apparent that
regular attention was needed for floating aerators. Relocation, greasing,
ice removal were among the routine maintenance activities required.
A boat was used extensively by the operators to perform their work.
When the change was made from the Sigma Pac to the high speed
aerators, additional electrical controls were needed with the increase
from 12 to 48 aerators. Rather than locate the controls in pumping
station #2, as originally provided, panel boxes for the additional aerators
were located at the lagoons. The panel housing the electric controls
were wooden, insulated and heated, and provided an economical and
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convenient solution.
The major electrical problem experienced with the aerators was
motor burn-out. Drain holes on the aerator housing became plugged
with solids and water penetrated into the motor with the result that
the motor needed rewinding. Field modification of drilling the drain
holes larger reduced the motor burn-out problem.
Final Clarifiers, Pumping Station #2
Final clarifiers--The final clarifiers did not require as close atten-
tion as the primary clarifiers. The pumping out of the clarifier for
cleaning and inspection was performed on an annual basis.
One problem experienced with the final clarifiers was during
periods of extremely cold weather wherein the temperature of the waste
water was lowered to near freezing. Without the aid of scum scrapers
to create movement, the surface of the final clarifier would form surface
ice with a narrow opening at the weirs for effluent release. To prevent
structural damage to the clarifier the operators cleared an opening
around the center feed well and around the effluent weir. The ice would
remain until the wastewater temperature increased.
A second maintenance activity was the removal of grease and scum
from the clarifier inlet structure. This material would be contained in
the inlet and the operator would periodically scrap the scum out for
disposal.
Return and waste sludge pumps--The centrifugal pumps operated
well but two major maintenance activities were necessary. One
problem involved the pumping of too thick a final sludge. To either
clean the discharge piping of the thick sludge or to thin the sludge when
pumping, the effluent reuse pump was used. Final effluent water was
used for this purpose and the connection between the water reuse pump
and the sludge piping was made by using a fire hose. Normally the
sludge piping was flushed for a period of one to two hours only. The
chlorine system was shut off during these brief periods to insure that
the return sludge was not being adversely affected.
The second problem involved cleaning of the centrifugal sludge
pumps when they would become plugged by extraneous matter, such as
weeds, sticks, or scraps. The pumps would plug and lose efficiency
when low pumping rates, less than 0.19 m3/min (50 gpm), were
employed. The operator had to dismantle the pump and clean out the
impeller, at times as often as two to three times a day. This operating
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nuisance contributed to the employment of high pumping rates by the
operators and resulted in high recirculation rates for some biological
systems.
Chlorine Contact Tank and Chlorination System
Chlorine contact tank--With the actual flow less than half the
design flow, the chlorine contact tank was underloaded. Horizontal
velocities were very low, 0.46 m/min (1.5 ft/min) and no mechanical
mixing was provided. During process upsets and deteriorated final
clarifier effluent quality, settled sludge accumulated in the contact tank.
Periodically, it was necessary to clean the contact tank to restore
the detention time and to eliminate the chlorine demanding sludge. This
cleaning was done in the spring and the portable gas pump was used.
Each spring the flow was backed up in the lagoons by closing the
discharge valves and the contents of the contact tank were pumped by a
portable gasoline pump into a partially filled final clarifier for subse-
quent discharge to the wet well.
As indicated in the treatment plant flowsheet description, wooden
planks were added to the effluent end of the contact tank to serve as a
scum baffle to prevent discharge of this material to Hay Creek. There-
fore, it was necessary for the operators to remove the floating scum
from the contact tank for disposal as needed and varied from daily to
weekly.
Chlorination system--At the time the treatment plant was designed,
Minnesota required Chlorination from May 1 to November 1 only. During
the fall as temperatures cooled, the ability to maintain chlorine feed
rates was hampered by the cold temperature experienced in the chlorine
room. A small space heater was used to keep the 68 kg (150 Ib) cylin-
ders warm to maintain the desired feed rate.
During the initial year of operation, the weighing mechanism for the
chlorine corroded and had to be replaced. Thereafter, closer attention
was paid to maintaining the system. Due to a higher than expected
chlorine demand, the chlorine feeding capacity was changed from 0 to
45 kg (100 Ib) per 24 hours to a rate of 0 to 90.7 kg (200 Ib) per 24
hours.
Sludge Dewatering
Sludge grinder--A sludge grinder was provided in the Passavant
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dewatering system to cut or grind large peices of material in the
primary sludge. As was the case with the Mazorator, the extraneous
matter found in tannery wastes, i.e., leather scraps, fleshings, etc.,
proved to be too difficult for the sludge grinder. Unable to cut the
material, the sludge grinder plate and chamber would plug causing
increased discharge pressure on the primary sludge pumps. Before the
pressure reached a point of causing the positive displacement pump to
fail, the operators would shut off the make-up system and clean the
sludge grinder. Pressure gages on either side of the grinder indicated
when plugging was occurring.
During periods when winter hides were processed or when prob-
lems were experienced with the mechanical rakes, the maintenance
problem was more severe. Whether cutting or blocking, the sludge
grinder unit served the purpose of excluding large extraneous material
from entering the sludge dewatering process.
Sludge piping—As indicated in foregoing sections of this operations
summary, special operational procedures were performed each night to
maintain the piping between pumping station #1 and the sludge dewatering
building in operating order. Within the sludge dewatering building, the
piping between the sludge grinder and the contact tank needed an exten-
sive cleaning every two weeks. A Roto Rooter was used to clean this
piping.
The piping between the contact tank and the filter press, a contin-
uous welded section, remained clean. It was feared that a blockage in
this section would be a major problem; however, the problem never
developed. Valves on the ferric chloride lines did require some main-
tenance. Tanks such as the large surge tank, filtrate tank, precoat
tank and bin required a periodic cleaning to remove accumulated
deposits.
Filter cloth--In the original discussion with the Pasavant personnel,
the indicated life span for the 90 filter cloths was 4000 cycles (2 years).
It was determined that the porous underline media had slipped slightly
and was forming a cutting edge against the outer nylon cloth. This cut
was prevalent around the four metal bosses and center feed hole. Using
Passavant's recommendation, the underdrain media was resupported.
Studies during the project last six months showed the filtering cloths
failure rate to decrease substantially.
When a tear or rip occurred in the nylon cloths, efforts were made
to patch the cloth rather than replace it. Spare cloths were used to
supply patching material, and patches were glued on. Weekly the
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patches would loosen and new rips were found with the net result that
three to five hours were required each week on patching or replacing
the outer nylon cloths.
Odor Control
One problem that needed continual attention during the 31/2 years
of treatment plant operation was odor control. Various chemicals and
procedures were employed to affect odor control.
Sludge disposal basins--The treatment plant operated for 21 months
before the pressure filtration solids handling method was available. In
the interim, primary sludge was pumped to diked low areas. The
sludge solids were allowed to consolidate and the supernatant was
pumped into an aerated lagoon. The sludgeholding basin generated odors
and control was required.
The basic odor control procedure employed consisted of spraying a
lime slurry--orthodichlorobenzene (odorfresh) mixture onto the sludge
bed surface. The purpose was to raise the pH to discourage anaerobic
activity and secondly the chemical bactericide was intended to reduce the
number of odor causing organisms.
The depth of supernatant liquid over the sludge was maintained at
a minimum to keep the sludge as dry as possible, thereby reducing
anaerobic activity.
During the winter of 1973-74, with the dewatering system opera-
tional, the two sludge beds were covered with 15.2 cm (6 in) of dirt.
Dewatered cakes-- The odor from the disposed dewatered sludge
cakes was not considered significant. As was indicated in the section
on the solid waste study, covering the cakes did much to curtail decom-
position and drying. While the cakes were exposed to the atmosphere,
they were sprayed with an orthodichlorobenzene solution.
Aerated lagoons--At one time it was felt that the sludge deposits
formed on the lagoon's bottom contributed to the odor. While the lagoon
was in active use, little odor control was applied so as not to interfere
with the aerobic biological system. When the lagoon was removed from
service and emptied for cleaning, lime and odor-fresh was used to
control the odor.
Primary sedimentation tanks--With the prevailing alkaline pH in the
raw wastewater, odor problems were not as severe as expected. It was
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assumed that the sulfide reduction was accomplished in part by oxidation
in the lagoon.
During the summer of 1975, some discoloration was experienced
to the painted surface of homes approximately 0.8 km from the treat-
ment plant. This was similar to occurrences experienced in 1971, the
summer before the new plant was placed in operation. The discoloration
was attributed to hydrogen sulfide. Though in 1971, Hay Creek as well
as sludge lagoons may have been the source of H2S emission, studies
in the summer of 1974 traced the f^S emission to the aerated lagoons.
Under conditions of high mixed liquor solids, nutrient phosphorus
additions and operating conditions representing higher than normal organic
loadings resulted in biological respiration requirements which exceeded
the capability of the aeration system resulting in reduced oxidation of the
sulfide. This combined with the phenomena of discharging a primary
effluent of high pH, wherein the H2S remains in solution, into the
aerated lagoons of operating pH values of near 8 resulted in release of
H2S to the atmosphere.
To control the sulfide, ferric chloride was added to either the raw
waste or primary effluent. The ferric combined with the sulfide to form
a precipitate thus eliminated the problem. The amount of FeCls added
was balanced chemically to the sulfide levels. It appears that to a
great extent the odors generated at other areas were due to lower, but
not recognizable, F^S levels. Some odor generation connected with the
sludge dewatering operation may be attributed to the release of NHs
resulting from increasing the pH of the conditioned sludge to values near
11.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-78-013
2.
3. RECIPIENT'S ACCESSIONING.
4. TITLE AND SUBTITLE
Biological Treatment, Effluent Reuse, and Sludge
Handling for the Side Leather Tanning Industry
5. REPORT DATE
February 1978 (issuing date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
L. B. Polkowski, W. C. Boyle, and B. F. Christensen*
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
*S. B. Foot Tanning Co.
Red Wing, Minnesota 55066
10. PROGRAM ELEMENT NO.
1BB610
11. CONTRACT/GRANT NO.
12120 DSG
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory—Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES
L. B. Polkowski and.W. C. Boyle are with Polkowski, Boyle & Associates, Madison,
Wisconsin 53705
16. ABSTRACT
An evaluation of the treatability of unsegregated, unequalized, and unneutral-
ized wastewaters from a side-leather tanning industry utilizing the hair pulping
process by primary and secondary biological and gravity separation in clarifier-
thickeners, whereas the secondary treatment method employed aerated ponds and final
clarifiers with the capability of recycling biological solids. The system was
operated over a wide range of detention times, with and without solids recycle, and
nutrient (phosphorus) addition, and during seasonal variation representing mean
monhtly air temperature variations from -14 °C to 30°C. The removal efficiencies were
related to loading relationships as well as temperature variations. The secondary
treatment effluent was reused in the beamhouse operations under test conditions to
evaluate the effects of water conservation practice on leather qualities as well as
to determine the buildup of conservative substances in the wastewater effluent such
as chloride.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Industrial wastes
Waste treatment
Sludge disposal
Leather tannery
Waste characterization
Temperature effects
Water reuse
43
50 B
3. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport/
Unclassified
21. NO. OF PAGES
248
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
230
U. S. GOVERNMENT PRINTING OFFICE: 1978 — 757-140/1320
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