EPA-600/2-77-198
September 1977
TREATMENT AND DISPOSAL OF WASTES
PUMPED FROM SEPTIC TANKS
by
John J. Kolega
Arthur W. Dewey
Benjamin J. Cosenza
Robert L. Leonard
Storrs Agricultural Experiment Station
University of Connecticut
Storrs, Connecticut 06268
Grant No. 17070 DKA
Project Officer
G. K. Dotson
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
al Protection
«v,ion V, Library
iC South Dearborn Street
Illinois 60604-
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. 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.
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled land
are tragic testimony to the deterioration of our natural environment. The
complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and searching
for solutions. The Municipal Environmental Research Laboratory develops new
and improved technology and systems for the prevention, treatment, and man-
agement of wastewater and solid and hazardous waste pollutant discharges from
municipal and community sources, for the preservation and treatment of public
drinking water supplies, and to minimize the adverse economic, social, health,
and aesthetic effects of pollution. This publication is one of the products
of that research; a most vital communications link between the researcher
and the user community.
This report presents results of a study that was conducted to identify
alternative methods of treating and disposing of wastes from septic tanks.
About a third of the country's population live in homes that are not served by
sewers. Increased population density and stricter standards of environmental
protection have made old disposal methods unsatisfactory and caused the search
for more acceptable alternatives.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
111
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ABSTRACT
A multidisciplinary team was organized to identify feasible methods for
treating and disposing wastes pumped from septic tanks (septage). Biological,
chemical, and physical properties of septage were determined. Statistical
data and design curves were developed for use in the design of septage treat-
ment processes and facilities.
Two approaches were developed, tested in both laboratory and pilot
plant studies, and found feasible for treating and disposing of septage:
(1) soil injection, and (2) anaerobic-aerobic series processes. These
series processes can sustain shock loadings and reduce the concentrations
of BOD , COD, and total Kjeldahl nitrogen by at least 93 percent. Most of
the nitrogen is converted to nitrate. Consideration was given to combined
treatment of septage and sewage in a conventional biological treatment plant.
A figure of 70 gallons (265 liters) per person per year was estimated as the
volume of septage to be treated and disposed. Criteria were developed for
the design of septage-receiving facilities.
As a rule of thumb, the total cost of treating 1000 gallons (3,785
liters) of septage is approximately 18 times the cost for treating the same
amount of raw wastewater in a secondary treatment facility. Operating costs
for treating septage in 10 mgd plants are estimated to be about half the
treatment costs in 1 mgd plants or at 1972 prices, $1.80/1,000 gallons
($0.48/1000 liters) as compared with $3.24/1,000 gallons ($0.86/1000 liters).
This report was submitted in fulfillment of Grant Number 17070DKA by
the Storrs Agricultural Experiment Station, University of Connecticut, under
the partial sponsorship of the Environmental Protection Agency. This report
covers the period June 1, 1969 to May 31, 1972.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vii
Tables x
Abbreviations xii
Acknowledgments xiv
1. Introduction 1
2. Conclusions 3
3. Recommendations 6
4. Materials and Methods 8
Sampling 8
Chemical and Physical ... 9
Biological 13
Land Disposal 19
Specialized Treatment Processes: Anaerobic-Aerobic 34
Pilot Plant 37
5. Experimental Data and Results 40
Chemical and Physical Observations. . „ 40
Gas Utilization and Production 53
Prolonged Holding of Septage 56
Biological. 61
Land Disposal 75
Anaerobic-Aerobic: Bench Scale Study 85
Anaerobic-Aerobic: Pilot Plant 91
Other Aspects of Specialized Treatment of Septage 107
Septage Treatment at a Water Pollution
Control Facility (WPCF) 107
6. Septage Volume Estimates 112
Homeowner Survey 112
Statewide Septage Pumping Volume Estimates 113
7. Model Land Disposal System 118
Soil Injection Costs and Land Requirements 118
Off Season Handling of Septage 122
8. Costs for Treating Septage in Conventional Water
Pollution Control Facilities 123
Septage/Sewage Operating Treatment Cost Ratio 124
Surcharges and Total Charges 126
9. Economic and Governmental Aspects of Septage Disposal 128
Municipal Provision for Septage Disposal 128
State Policy Considerations 129
Federal Policy Considerations 130
10. Septage Receiving Stations 131
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CONTENTS (continued)
References 136
Publications 140
Appendices
A. Questionnaire Mailed to Homeowners 141
B. Questionnaire Mailed to Septic Tank Pumpers 142
C. Laboratory Analyses Summary 143
D. Nitrogen Application Calculations 144
E. Septage Land Application Data 145
F. Identification Key to Characterization of Bacteria
Isolated from Septage and/or Septic Tank Sewage 147
G. Aeration Processes 148
H. Frequency of Pumping in Relation to Size of Septic Tank .... 149
I. Septage Seminar 150
VI
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FIGURES
Number Page
1 Schematic diagram of gas collection and sampling 12
2 Protocol for biological sample assay 16
3 Characterization of bacteria isolated from septage and/or
septic tank sewage 18
4 Growth chamber for study of microbial interactions:
top view 20
5 Growth chamber for study of microbial interactions:
side view 21
6 Land disposal field plot preliminary studies 22
7 Profile of tile drain line and collection pit 23
8 Plan view of sampling area for septage microorganism study . 25
9 Experimental site layout for study of sub-soil disposal
of septage 26
10 Receiving station for land disposal of septage 28
11 Experimental tank-trailer 30
12 Terreator (U.S. Patent No. 2,694,354) for sub-soil injection 32
13 Top view of sub-sod injector (Rutgers University) 33
14 Bench scale anaerobic-aerobic unit for treatment of septage. 36
15 BOD,, septage design curve 42
16 Total solids design curve 43
17 BODp septage supernatant design curve 44
18 Volatile total solids septage design curve 45
VII
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FIGURES (continued)
Number Page
19 Fixed volatile total solids septage design curve 46
20 COD septage design curve 47
21 COD septage supernatant design curve 48
22 Total suspended solids design curve 49
23 Volatile suspended solids design curve 50
24 Free ammonia septage design curve 51
25 Organic nitrogen septage design curve 52
26 Changes in the gas production, COD, and total volatile
fatty acids contents of septage during prolonged
storage at ambient temperature 58
27 Distribution of microorganisms in composite septage .... 62
28 Comparative enumeration of specific types of microorganisms
with 95 percent confidence limits 65
29 Comparative enumeration with selected physiological
activities with 95 percent confidence limits 67
30 Comparative distribution of substrate levels with 95 percent
confidence limits 69
31 Comparative enumeration of selected physiological activities
with 95 percent confidence limits 72
32 Comparative distribution of specific types of microorganisms
and their physiological activities 73
33 Survival curves of Salmonella typhimurium in septic tank
sewage 74
34 Bench Scale: Biochemical oxygen demand reduction by system 86
35 Bench Scale: Chemical oxygen demand reduction by system. . 87
36 Bench Scale: Ammonia nitrogen of system 88
37 Bench scale: Total Kjeldahl nitrogen of system 89
38 Bench scale: Total solids reduction by system 90
Vlll
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FIGURES (continued)
Number Page
39 Bench scale: Volatile solids of system 92
40 Bench scale: Total phosphate of system 93
41 Bench scale: Nitrate nitrogen of system 94
42 Bench scale: Dissolved oxygen of system 95
43 Bench scale: pH of system 96
44 Pilot plant: Biochemical oxygen demand 98
45 Pilot plant: Chemical oxygen demand reduction by system . . 99
46 Pilot plant: Ammonia nitrogen of system 100
47 Pilot plant: Total Kjeldahl nitrogen of system 101
48 Pilot plant: Nitrate nitrogen of system 102
49 Pilot plant: Total solids reduction by system 103
50 Pilot plant: Volatile solids of system 104
51 Pilot plant: Total phosphate of system 105
52 Pilot plant: pH of system 106
53 Sampling locations for combined waste treatment study. . . . 110
54 Septage disposal in Connecticut 117
55 Septage receiving station basic layout 132
56 Septage receiving station: Scheme 1 133
57 Septage receiving station: Scheme 2 134
IX
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TABLES
Number Page
1 Septage Data Statistical Summary 41
2 Percentage Composition of the Gas Mixture in the Head
Space Over Septage, Sewage, and Digester Sludge 54
3 Changes in the COD, Fatty Acids Contents, and pH of the
East Hartford Sewage Sample 57
4 Changes in the COD, Fatty Acids Contents, and pH of the
Litchfield Sewage Sample 60
5 Characterization of Clostridial Species Isolated from
Septic Tank Sewage 63
6 Host Specificity Range of Bacteriophages Isolated from
Septage 64
7 Significance Tests (t) Comparing Septage and Septic Tank
Sewage Using 12 Paired Observations 68
8 Nitrate Concentration in Septage Tank Sewage 70
9 Reduction Time in Hours of Septage and Sewage 70
10 Methylene Blue Reduction Time and Selected Activities of
Septic Tank Sewage 71
11 Comparison of Viable Counts (SPC/g) From Septage Samples
Introduced in Soil at Point 0 on August 11, 1970 76
12 Comparison of Viable Counts (SPC/g) From Septage Samples
Introduced in Soil at Point 25 on August 11, 1970 .... 77
13 Count Distribution After Initial Septage Subsoil Injection. 78
14 Count Distribution (SPC/g of soil) on TGYE and Enumeration
of Fecal Coliform After Second Application of Septage . . 79
15 Observation Well Data for the White Memorial Foundation,
Litchfield Septage Soil Injection Experimental Site ... 81
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TABLES (continued)
Number Pa
16 Test Well Observation Data Summary 83
17 BOD , in mg/1, of Combined Wastes (Sewage and Septage)
From Direct Discharge Into Raw Sewage Inflow 109
18 Septic Tank Pumpings Reported by 44 Pumpers Classified by
Size of Pumper Operation and Disposal Outlet 114
19 Septic Tank Pumpings in Connecticut Classified by
Disposal Outlets 114
20 Septic Deliveries by Size of Tank Pumped, East Hartford
WPCF for Four Selected Months 115
21 Septage Volumes Related to Population Classified by
Areas According to Disposal Method, Connecticut 116
22 Requirements and Costs (1972) for Septage Injection at a
10-Acre Site in Litchfield, Connecticut, to Serve a
Surrounding Population of 22,000 Persons 120
23 Distribution of Operating Costs for Sewage Treatment. . . . 124
24 Concentration Ratios for Solids and BOD,, in Septage and
Sewage 125
XI
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ABBREVIATIONS
APHA American Public Health Association
AWWA American Water Works Association, Inc.
BBL Baltimore Biological Laboratories
BCP Brom creosol purple
BOD Biochemical oxygen demand
BOD^ Five day BOD
BPL Beta-propiolactone
COD Chemical oxygen demand
Cl Chloride
CTA Cystine trypticase agar
D.O. Dissolved oxygen
EPA Environmental Protection Agency
EtO Ethylene oxide
PC Fecal coliform
FID Flame ionization detector
fsl Fine sandy loam
g Gram
gpm Gallons per minute
GA Glucose-asparagine
HE Hektoen Enteric agar
1 Liter
LAS Linear alkylate sulfonate
Ib Pound
L+D Salmonella typhimurium
m Meter
mg/1 Milligrams per liter
ml Milliliter
mm Millimeter
MGD Million gallons per day
MLD Million liters per day
MLSS Mixed liquor suspended solids
min Minute
MPN Most probable number
Xll
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ABBREVIATIONS (continued)
N Normal
Nitrogen
o Ammonia nitrogen
NCU Nitrate
OF^ Oxidative fermentative
PGA Plate count agar
P-F-C Plow furrow cover
PFU Plaque forming units
pH Hydrogen ion
ppm Parts per million
PTA Phosphotungstic acid
SCS Soil Conservation Service
SIM Sulfide indol motility agar
SPG Standard plate count (Total viable count)
spp Species
S-S-I Sub-soil-injection
TC Thermal conductivity detector
TGYE Tryptone glucose extract agar
TS Total solids
TSA Trypticase soy agar
TSB Trypticase soy broth
TSI Triple sugar iron
TSS Total suspended solids
TVA Total volatile acids
M Millimicron
VS Volatile solids
VSS Volatile suspended solids
WMF White Memorial Foundation, Inc.
WPCF Water pollution control facility or facilities
Xlll
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ACKNOWLEDGMENTS
This multidisciplinary study was funded, in part, by the U. S. Environ-
mental Protection Agency (EPA) under Grant No. 17070 DKA, "Treatment
Processes—Wastes Pumped from Septic Tanks." Mr. G. K. Dotson, of the EPA
Ultimate Disposal Section, Wastewater Research Division, Municipal
Environmental Research Laboratory in Cincinnati, served as project officer.
Individuals who contributed to sections of the final written report
were Dr. Joseph F. Calabro, former Ph.D. candidate in microbiology;
Dr. Frank S. Chuang (anaerobic-aerobic treatment processes), post-doctoral
fellow in agricultural engineering; and Dr. A.F. Halim (gas chromatography
studies), post-doctoral fellow in agricultural engineering.
Research technicians, Mr. Ralph C. Gold and Mr. Randall C. May, carried
on the field operation phase of the septage land disposal study.
Mr. George F. Sweeney, District Conservationist, USDA Soil Conservation
Service, Litchfield, Ct. played an important role in the selection of the
WMF site and worked cooperatively with the University during the course
of the study. Similarly involved was Mr. Robert Shropshire, Superintendent
at the WMF. Other assistance and cooperation during the course of the study
came from Mr. Richard Gillett of the Connecticut Sewage Disposal Association,
and Mr. Theodore W. Roberg, Litchfield, Ct. Consultations were had with the
Torrington area health district in the course of the investigation. Lastly,
it was the White Memorial Foundation, Litchfield, Ct. that made the excellent
site available. The search for information about our natural environment
through organized scientific observation and experimentation and the public
dissemination of this knowledge has been one of the White Memorial Founda-
tion's guiding principles.
In the preliminary septage land disposal studies, Mr. Bryon L. Tart,
M.S. candidate in microbiology, assisted in the microorganisms soil distri-
bution study. Mr. Gerald Wolfson was the research assistant and Mr. Theodore
Roberg of Litchfield the cooperator.
The data presented on biological, chemical, and the physical properties
of septage would not have been possible without the assistance of Dr. Ashwani;
Joseph F. Calabro, doctoral candidate in microbiology; and research
assistants Jaihind S. Dhodhi, Mrs. Mahusen Halim, Tripat S. Basur, Lawrence V.
Cammarato, and Randall C. May. Mr. Ning Wang assisted with the computer
analyses of data.
Mr. Raymond Lavery and personnel of the E. Hartford, Ct. Metropolitan
District WPCF provided the necessary assistance for septage sample collection
and refrigeration. This group also obtained the information source data.
xiv
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Dr. Charles S. Shu, doctoral candidate in civil engineering, assisted
with the receiving station and combined sewage-septage treatment studies.
Cooperation in the latter investigation was received from Mr. Gregory
Satzuk and personnel at the University of Connecticut WPCF. Cooperating
from the Connecticut Sewage Disposal Association was Mr. William McKinney.
The study involved interstate cooperation between Rutgers University,
New Brunswick, New Jersey, and the University of Connecticut, Storrs Agri-
cultural Experiment Station. Prof. Charles H. Reed of the Agricultural
Engineering Department of Rutgers University was the institituonal co-
operator and participant. Collaborators from the Connecticut State Depart-
ment of Health, Environmental Health Services Division were Mr. Joseph
Kosman, Chief, Municipal Wastewater Control Section, and Mr. Ronald E.
Topazio, Senior Sanitary Engineer. Dr. Rain Laak and Prof. William C.
Wheeler, respectively, of the Univesity of Connecticut Civil and Agri-
cultural Engineering Departments were other collaborators.
Mr. George Lebetkin, formerly of the E. Hartford Metropolitan District
Commission WPCF assisted in the early years of the study. During the last
year, Mr. Wilbur L. Widmer, Professor of the University Civil Engineering
Department, provided assistance in terms of consultations and suggestions.
Prof. Ralph P. Prince, Acting Head of the University Agricultural Engineering
Department, provided assistance in critical areas when needed and made sug-
gestions on manuscript copy material prepared. The cooperation from
Dr. R. W. Wengel of the University Plant Science Department as it relates
to the use of the Technicon autoanalyzer and Kjeldahl nitrogen apparatus is
appreciated.
Use was made of the University Computer Center facilities. Data and
statistic consultations were made with Dr. Joseph Lucas, Agricultural
Experiment Station Bioiretrician.
Mr. Raymond Blanchette of University publications prepared most of the
drawings and figures with some assistance from Mr. Ranjit Roy.
One person who was invaluable throughout the three-year period was
Miss Linda Floeting, project secretary. Her secretarial competence con-
tributed significantly in the preparation of this report and in the closing
out of the project.
Special recognition should be given to agricultural publications staff
members, David W. Bechenholdt and David Kimball, for coming up with the
word, '' septage", to replace the phrase "septic tank pumpings". This word
has been received and is being used on a national and international level.
xv
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SECTION I
INTRODUCTION
This report presents the findings of a multidisciplinary team investiga-
tion for the disposal of septic tank pumpings; such pumpings are referred to
as septage. Septage is defined as the mixed liquid and solid contents pumped
from septic tanks and dry wells receiving domestic type sewage. Septage may
also include the pumpings of similar biodegradable materials obtained from
the septic tanks of schools, motels, restaurants, and similar establishments.
The primary participants in this investigation were the Storrs Agri-
cultural Experiment Station and the University of Connecticut Departments
of Agricultural Engineering, Agricultural Economics, and the Microbiology
Section of the Biological Sciences Group. Financing in part was from the
U.S. Environmental Protection Agency. Active cooperators at various stages
of the study were the Metropolitan District Commission, Bureau of Public
Works, East Hartford Water Pollution Control Facility; the White Memorial
Foundation, Inc., Litchfield; representatives of the Connecticut Sewage
Disposal Association; and the Rutgers University (New Jersey) Agricultural
Engineering Department. Serving as collaborators in the study were the
Connecticut State Department of Health,Environmental Health Services Divi-
sion; the USDA Soil Conservation Service,Litchfield Work Unit; and the
University of Connecticut Civil Engineering Department. In addition to
the University of Connecticut Agricultural Engineering Department laboratory
and pilot plant facilities, use was made as needed of the Plant Science
Department's Technicon autoanalyzer and nitrogen apparatus, and the Uni-
versity of Connecticut Computer Center Facilities.
The Manual of Septic Tank Practice (U.S. Department of Health, Rev.
1967) states that septic tanks should be inspected at least once a year and
cleaned when necessary. The necessity for pumping the septic tank depends
upon the amount of sludge and scum that has accumulated. A general recom-
mendation for homeowners is to pump the septic tank at intervals of three
to five years (Rockey, 1963). If the practice of inspecting a septic tank
is not followed, then pumping at more frequent intervals is recommended.
Another reason for more frequent septic tank pumping is poor site
selection. Poor soil acceptance capability or a seasonal high ground
water table may result in backup or overflow of household sewage. The
condition can be temporarily alleviated by emergency pumping. Frequent
pumpings may be required when septic systems have been improperly designed
or installed. To minimize septic system failures, the state and some
municipalities or the health districts of which they are members hire
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trained sanitarians to insure better compliance with the Connecticut Public
Health Code Regulations.
Few homeowners and municipal officials are knowledgeable about local
septage disposal practices. Yet, in unsewered communities, there is an
almost continuous demand for septage disposal facilities. Since this study
began, the need for developing and improving facilities for receiving and
processing septage has begun to receive more public attention.
Lack of knowledge concerning the properties of septage has hampered
both designers and operators of sewage treatment facilities. Plant operators,
unfamiliar with septage, often assume that it has different properties than
it really has. Where septage is received, plant operators are often con-
cerned with establishing working ratios for mixing septage with incoming
sewage. Thus, septage as a trucked liquid waste needs design and operational
criteria for physical handling and treatment.
When a wastewater treatment facility is not available, septage is
commonly disposed of in unacceptable ways. One such practice in Connecticut
is the use of earth excavated pits. In these pits, the septage depth varies
depending on the ground water level, the amount of land available, and the
volume of septage being handled. These pits tend to become hazardous when
they are filled and abandoned.
The research undertaken in Connecticut and reported in this study was
designed to develop information to the following questions:
1. What is the nature of septage?
2. Is septage compatible with sewage for treatment in water pollution
control facilities?
3. What special treatment methods are appropriate for handling septage?
4. What economic and governmental factors determine the design, regula-
tion, and operation of septage disposal systems?
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SECTION 2
CONCLUSIONS
1. Experimental findings have provided data for use in the design of
treatment and disposal processes for septage (the wastes pumped from
septic tanks).
This information as it relates to BOD5, COD, total solids, volatile
solids, total suspended solids, volatile suspended solids, organic
nitrogen, and ammonia-nitrogen has been presented statistically and
in the form of design curves. Related data of interest in characterizing
septage include pH, color, odor, gas utilization and production, total
volatiles, settleable solids, and detergents. For estimating the volume
of septage to be disposed of, a figure of 70 gallons (265 liters) per
capita per year was established.
2. In selecting a system for septage disposal, attention should be given
to the following types of treatment and disposal methods that can be
used singly or in combination:
(a) Treating with wastewater in a wastewater treatment facility.
(b) Land disposal.
(c) Specialized treatment process in preparation for disposal.
3. The biological, chemical, and physical properties of septage, although
different from that of incoming raw sewage, indicate that this material
can be treated in wastewater treatment facilities.
In planning to accept septage at a wastewater treatment facility,
the following factors should be considered:
(a) The need for a septage holding or storage tank.
(b) The timing and control of septage flow into the treatment
process.
(c) The volume of septage relative to the available plant capacity.
(d) Pretreatment through a bar screen followed by a grit chamber
and comminuter to remove grit before the septage enters the
main wastewater treatment processes.
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4. Soil injection of septage was demonstrated as a feasible method of
disposal without contaminating ground waters. Depending upon geographic
location, soil injection may not be a year round disposal method. Under
this circumstance, a combination of septage disposal methods will be
required, e.g., disposal in a wastewater treatment facility during the
colder seasons and soil injection during the warmer seasons.
5. The anaerobic-aerobic series processes can be used for treating septage.
Laboratory and pilot plant studies showed that these processes can with-
stand shock loadings and reduce the concentrations of 6005, COD, and
total Kjeldahl nitrogen by at least 93 percent. Most of the nitrogen
is converted to nitrate.
6. Operating costs for treating septage in a 10 mgd (37.9 mid) wastewater
treatment facility is estimated at approximately $1.80/1,000 gallons
($0.48/1,000 liters). Operating costs for treating septage in a 1 mgd
(3.8 mid) facility is estimated at approximately $3.24/1,000 gallons
($0.86/1,000 liters) at 1972 prices.
7. Disposal charges, methods of collecting charges, regulations governing
acceptance of septage, and enforcement of regulations are major factors
that affect the relative volumes of septage received at adjacent disposal
outlets.
Septage volumes received at already established outlets could
change substantially if receiving stations were established beyond a
15-mile radius of existing wastewater treatment facilities and if the
septage were then trucked from the stations to treatment facilities.
8. Intervention by state and intrastate (regional) agencies may be a
necessary step for modifying existing policies whenever the authority
and responsibility for septage disposal rests solely with municipalities.
Without intervention
(a) there may be a shirking of legislatively assigned
responsibilities;
(b) working agreements among adjacent municipalities may be
difficult to establish and maintain;
(c) incentives will be minimal for upgrading septage disposal
practices and facilities or for requiring their use when low
cost dumping pits are available; and
(d) many receiving facilities for septage at many treatment
plants will continue to be inadequate and unsanitary.
9. A comparison of microorganisms recovered from septage and those reported
for sewage showed slight variation in distribution.
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The gram negative, non-lactose fermenters were the predominant
types present in septage. A total of 474 bacterial isolates were
obtained and grouped as to genus.
10. Bacteriophage isolated from septage and septic tank sewage can lyze
cells of Citrobacter freundii and Shigella flexneri.
Host specificities range studies indicated that rough forms of
certain gram negative bacteria are sensitive to phage. This may
account for the rapid disappearance of Escherichia coli and related
forms in septage.
11. Health hazards to pumpers (presence of enteric pathogens) were investi-
gated by introducing a biological marker, Salmonella typhimurium, into
a septic tank system and observing its survival time. Results indicate
that this pathogen is unable to compete with other less fastidious
microorganisms in the system. This observation, coupled with the
inability to isolate Salmonellae from this niche previously, sub-
stantiates the view that enteric pathogens die within a relatively
short time.
12. A plexiglas multichambered tank specifically designed and constructed
to assess the interactions of predominant bacterial types present in
septage, either singly or in combination, is functional as in other
areas of biology and medicine.
For example, the original prototype tank was modified and used at
the University of Connecticut Health Center to study the interaction of
microorganisms found in the oral cavity. It has also been adapted to
ecological studies and is commonly referred to as an eco-chamber.
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SECTION 3
RECOMMENDATIONS
1. Septage should be examined for the presence of heavy metals, total
organic carbon and animal viruses.
2. Policies for the disposal of septage should be developed at municipal,
intermunicipal, state and national levels.
This information should be presented in a manner useful to indi-
vidual states in the preparation of their respective policies regarding
the disposal of septage.
3. An interagency technical advisory committee on septage should be
established to:
(a) Coordinate the overall approaches being taken towards
solution of the septage disposal problems:
(b) Determine priorities for future research if needed.
4. Because septage disposal is a problem throughout the United States, the
EPA or some other designated Federal agency should develop and sponsor
a national meeting or a series of regional meetings to discuss means
for disposing of septage.
5. Application of findings from the soil injection pilot study for septage
disposal should be demonstrated.
The purpose of this demonstration would be to:
(a) Demonstrate the adaptability of the EPA WQO project to
Grant No. 17070 DKA research findings to the public manage-
ment of septage disposal.
(b) Enchance the development of public plans and programs for
the disposal of septage.
(c) Evaluate the long-term effects of continued septage disposal
by soil injection on the ground water quality and soil permea-
bility.
(d) Determine the effects of microbial activities on crops grown.
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6. A study is needed on the feasibility of modifying pumping schedules to
conform with seasonal opportunities for soil injection. In order to
minimize the number of emergency pumpings during periods when soil
injection is not feasible, scheduled pumping would have to be accom-
panied by a program of inspection and enforced correction of defective
septic tank and drainage systems.
7. Continued research is needed to develop a better understanding of the
soil as a mechanism for use in the degradation of septage.
8. Design and construction criteria should be developed for shallow basins
or lagoons in series for the disposal of septage in areas where odor
will not be a nuisance.
9. At septage disposal sites, studies should be initiated to determine the
extent of aerosol formation and disposal.
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SECTION 4
MATERIALS AND METHODS
SAMPLING (For examination of biological, chemical and physical properties
of septage.)
Septage samples were collected primarily from vehicles carrying septage
to the Metropolitan District Commission, E. Hartford Connecticut Water Pollu-
tion Control Facility (WPCF). A 3-inch tee, with a shut-off valve, was used
in conjunction with a 10-foot section of discharge hose to collect the
sample. The collection assembly was attached to the tank discharge pipe.
The sample was collected as a side stream while the septage was being dis-
charged into a sewer. Sample collection was at the beginning, the mid-point,
and near the end of the unloading period.
A limited number of septage samples were collected from North Haven,
Ellington, and Mansfield, Connecticut. The North Haven location is a water
pollution control facility, whereas Ellington and Mansfield are pumper-owned
or leased dumping sites.
The septage samples were refrigerated until analyzed. The size of
sample was either about 500 ml or about 2000 ml depending upon the number
and type of tests to be performed. Later in the study a few 5-gallon samples
were collected. These samples were not refrigerated.
Most of the sampled septage loads (180) were from household residences.
Other sources were schools, a convalescent home, restaurants, motels, apart-
ment units, a food chain store, and light industry. For each sample col-
lected, information was obtained as to:
(1) Date
(2) Load source (name, address, and telephone number of the household
residence or commercial establishment).
(3) Estimated size of the septage load.
(4) Name of the septic tank pumper.
(5) pH of septage at the receiving station and upon arrival of the
sample at the laboratory.
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Deviations in sample collection procedure from the above, e.g.,
specialized studies, are explained as appropriate in the sections which
follow.
In addition to the septage samples, raw sewage and primary digester
sludge samples were collected from the sewage treatment plants at the
University of Connecticut, City of Willimantic, and East Hartford. These
samples were used to compare the gases produced and their quantities.
CHEMICAL AND PHYSICAL
Analytical (STANDARD METHODS)
The laboratory methods followed the procedures in 1965 and 1971 editions
of the (APHA, AWWA and WPCF) STANDARD METHODS FOR THE EXAMINATION OF WATER
AND WASTEWATER. The analyses were: biochemical oxygen demand (BODs),
chemical oxygen demand (COD), pH, settleable solids, total solids, volatile
solids, suspended solids, ammonia nitrogen and organic nitrogen. The number
of replications and simultaneous tests conducted per sample varied according
to the personnel available, day of the week, and the limitation of laboratory
facilities. Physical and visual observations were used for recording odor
and color. A limited number of samples were examined for the presence of
detergents and chlorine demand. Total volatile acids (TVA) concentration
was measured by a chromatographic technique.
Instrumentation
When a large number of samples were involved a Technicon Autoanalyzer
(Technicon Corporation, Tarrytown, N.Y.) was used for measuring COD, chloride
and nitrate-nitrogen concentrations. Nitrate-nitrogen concentrations also
were measured with a: (1) Hach DR Colorimeter (Hach Chemical Co., Ames,
Iowa); (2) specific ion electrode (Orion Research Inc., Cambridge, Mass.);
and (3) Delta Model No. 260 photometric analyser (Delta Scientific Corp.,
Lindenhurst, N.Y.). The Hach DR Colorimeter also was used for measuring
phosphate concentrations. Some chloride measurements were made with a
specific ion electrode. A Model 51 oxygen meter (Yellow Springs Instrument
Co., Yellow Springs, Ohio) was used to measure dissolved oxygen (D.O.). This
instrument was checked periodically by a chemical technique using the
STANDARD METHODS procedure.
Early in the study, known standards were not used in the colorimetric
analyses for measuring nitrate-nitrogen concentrations. However, the
nitrate-nitrogen concentrations on a select number of samples were compared
with measurements also made on the Technicon Autoanalyzer.
Gas Products and Reactants
For analyses of gases and reactants a Model 1860 Varian Aerograph
(Walnut Creek, California) gas chromatograph equipped with dual-flame
ionization detectors (FID) and a thermal conductivity detector (TC) was
used. Quantitative measurements were made by means of a Varian Aerograph
Model 480 electronic digital integrator.
-------
For the analyses of gases, a Porapak Q, 80-100 mesh, 12 feet by 1/8 inch
(3.7 meters by 0.3 cm) o.d., stainless steel column was used for the separa-
tion of air (oxygen and nitrogen), methane and carbon dioxide (Bell, 1968).
A molecular sieve 13X, 30-60 mesh, 13 feet by 1/8 inch (4 meters by 0.3 cm)
o.d., stainless steel column was used to separate the oxygen from nitrogen.
The gas chromatographic analyses conditions using either column were as
follows: (1) temperatures for the injector, TX and column were 150°C,
150°C and 52°C respectively; (2) helium flow rate was 35ml/min; and (3)
bridge current 100 mA.
A total of 21 different septage, raw sewage, and primary digester
sludge samples were collected. From each sample, one and one-half liters
were transferred to a 2-1/2 liter screw-cap flask. The screw-cap had a
circular hole (1/2 cm diam.) and was fitted with a rubber septum on the
inside. The samples were kept at ambient temperature without exposure to
any activation procedure. A 0.2 ml portion of the head space gas of each
sample was withdrawn for injection into the chromatographic column using
a 1 ml capacity gas-tight Hamilton syringe.
Total Volatiles, Including Mercaptans and Sulfides
The total volatiles including the mercaptan and sulfides were analyzed
on a Porapak Q, 50-80 mesh, 4 feet by 1/4 inch (1.2 meters by 0.6 cm) o.d.,
stainless steel column. A 1-1/2 foot (0.5 meter) section of this column was
bent into a U-shape for use as a precolumn trap. Temperature of the injector
and dual-flame ionization detectors (FID) was 250°C. The column temperature
was initially held at 135°C for 4 min., programming 135°C - 175°C, 10°C/min.;
held at 175°C for 4 min., programming 175°C - 225°C, 10°C/min.; and then held
at 225°C until the completion of analysis. The flow rates for helium, hydro-
gen and air were 25, 25, and 250 ml/min., respectively.
The total volatiles including the mercaptan and organic sulfides found
in the different liquid wastes were initially trapped in the U-shaped por-
tion of the Porapak column. The assembly and sampling procedures were
prepared according to Burnett, 1969. For the description of the odor
character of each fraction emerging from the column, a stream-splitter was
used whereby part of the fraction was vented to the sniffing port of the
gas chromatograph. Some of the organic sulfur compounds could be tentatively
identified by their characteristic odors as well as retention time data.
Prolonged Holding of Septage
Two samples were examined for determining the biochemical characteris-
tics and the changes taking place when septage was stored under quiescent
conditions for a prolonged period of time. One sample was obtained from a
trucked septage load received at the East Hartford WPCF and the second sample
came from the White Memorial Foundation, Inc. land disposal experimental
site located in Litchfield. The sample size was approximately four liters.
Each sample was collected in plastic containers and refrigerated until the
start of the experiment.
10
-------
Two different laboratory assemblies were designed. One assembly was
used for the cumulative collection and periodic analysis of the gas mixture
(Figure 1). A one-liter bottle was filled with septage up to its 4/5 mark.
The bottle was connected to a 500 ml graduated buret and the latter, in turn,
was attached to a one-liter aspirator bottle. The buret and the aspirator
were filled with acidified NaCl-saturated aqueous solution. The aspirator
functioned as a regulator for the internal pressure of the system in reference
to atmospheric pressure. Two gas-sampling ports were inserted; one at the
top of the sample bottle and the other at the top of the buret. At the
beginning of the experiment, the water level in the graduated buret was
adjusted to the zero graduation mark under atmospheric pressure by means of
the aspirator. The initial volume of the gas (100% air) trapped in the sys-
tem measured approximately 270 ml for each sample assembly. To minimize air
entry into the system, the pressure of the trapped gas was kept slightly
above atmospheric pressure. Before recording the volume of the gas evolved,
the gas components were homogeneously mixed together by rapidly moving the
water level in the buret up and down. The efficiency of mixing was further
improved by frequent withdrawing and pumping the gas through each gas-
sampling port using a 10 ml gas-tight Hamilton syringe. The system was then
returned to atmospheric pressure and the amount of gas evolved daily was
recorded. The same mixing procedure was repeated before withdrawing sample
for gas chromatographic analysis. The assemblies were placed in an
uncontrolled temperature room. However, before any gas measurement or
sampling, the room temperature was adjusted to 70° +_ 2° F. The gas
chromatographic column and conditions were the same as previously described
under the gaseous products and reactants section. For quantitative measure-
ment, volume/volume of each individual component in the gas, a calibration
chart was developed by plotting the digital integrator counts against the
volume of the gas injected. Care was taken so that all samples and reference
gases (carbon dioxide, methane, and air) were analyzed under the same chro-
matographic conditions.
The other assembly was designed to determine changes in pH, chemical
oxygen demand (COD), total volatile fatty acid (TVA) content and the relative
percentage of the individual volatile fatty acids. Eleven bottles (125 ml
capacity) were each filled with about 100 ml of the septage sample. Each
bottle was tightly closed with a rubber stopper fitted with a 15-inch
(38.1 centimeters) glass tube. The tube was shaped so that the opposite
end could be conveniently dipped into a beaker filled with water. Excess
gases were expelled through the water without allowing atmospheric air into
the sample head space. Ten sample bottles were analyzed daily within the
first 35 days, after which one sample was used for analysis every third or
fourth day. The last sample bottle was stored for an additional 2-1/2
months. This sample was then analyzed for pH, COD and TVA.
The relative percentage of individual fatty acids was measured on
50 milliliters of the liquid waste. The analytical procedure was to
(1) centrifuge at 3200 rpm for 30 minutes.
(2) transfer the supernatant to an evaporating dish.
11
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(3) adjust pH of the supernatant to between 9 and 10 with a few drops
of IN NaOH.
(4) concentrate the supernatant to about 3 milliliters on a boiling
water bath.
(5) adjust pH of the supernatant concentrate to 2 with IN H SO .
(6) transfer the supernatant concentrate to a test tube. The residue
on the evaporating dish was washed into the test tube with about
1 milliliter of distilled water.
(7) The supernatant concentrate was then saturated with anhydrous
Na2SO. (2 g) and thoroughly shaken with freshly distilled ether
(10 ml).
(8) The ethereal layer was separated and the remainder of the solvent
was removed by bubbling a slow stream of pure nitrogen gas through
the water phase.
(9) Two microliters of the ethereal extract of fatty acids were
injected into the gas chromatograph. A 5-foot (1.58 meters) by
1/8 inch (0.32 cm.) o.d. stainless steel column packed with a
neopentylglycol succinate (20%) plus phosphoric acid (2%) on fire
brick 60-70 mesh was used.
The gas chromatographic conditions were:
(1) temperature of the injector, FID and column were 265°C, 250°C
and 150°C, respectively.
(2) flow rates of helium, hydrogen and air were 30, 30 and 300 ml/min.,
respectively.
Identification of the individual acids was made by the retention time com-
parison with reference samples.
BIOLOGICAL
Media Preparation
All media, glassware, and equipment were sterilized by autoclaving at
15 psi and 121°C unless otherwise stated.
The initial pH reading of all media and solutions was adjusted to
7.2 +_ 0.1.
Sample dilutions were made in bottles containing 90 ml of sterile
phosphate buffer (STANDARD METHODS FOR EXAMINATION OF WATER AND WASTEWATER,
1965).
13
-------
Maintenance of Cultures
All isolates were maintained on trypticase soy agar (TSA) (Baltimore
Biological Laboratories, Baltimore, Md.) slants and transferred every three
months. Strict anaerobes were held in cystine trypticase agar (CTA, BBL).
Special Equipment
Liquid wastes from a septic tank were collected with a special sampling
device. The unit consisted of a cylindrical tube which could be opened or
closed at one end by a spring-action mechanism to permit sampling at various
depths.
Brewer anaerobic jars containing H2-C02 disposable gas packs (BBL) were
employed for establishing anaerobic conditions. Methylene blue served as the
oxidation/reduction indicator.
Plastic and/or glass Millipore filter holders (Millipore Corporation,
Bedford, Mass.) were used for filtration. Prefilters and membranes were
47 mm in diameter and presterilized.
Electron micrographs of bacteriophage isolated for septage were taken
with a Philips, Model 75 electron microscope.
Sample Collection
In addition to trucked septage, samples were also obtained at a depth
of two and four feet from the inlet end of a household septic tank. Each
sample was thoroughly mixed and a representative portion placed under
anaerobic conditions. Also, samples were collected from a household septic
tank for the Salmonella typhimurium survival time study and the methylene
blue reduction time test. Sample collection was made at a depth of 18 inches
using a hand operated diaphragm pump.
Isolation and Enumeration Procedures
Two methods for isolation and enumeration of microorganisms were
followed. In one procedure, samples in duplicate were serially diluted in
phosphate buffer, and aliquot portions were overlayed with plate count agar
(PCA) (Difco Laboratories, Detroit, Mich.). The standard plate count
(SPC)/ml was determined after 48 hours incubation under aerobic and anaerobic
conditions at 24°C +_ 1. Predominating types were selected and transferred
to TSA for further characterization. Strict anaerobes were inoculated into
thioglycollate (Difco) broth.
In the other procedure, 20 ml of each sample was pre-filtered to remove
gross organic matter. The prefilter pad was washed twice with sterile phos-
phate buffer and the filtrate was passed through a Millipore membrane (0.45
uM). Microorganisms were dislodged from the Millipore filter by a 15-minute
agitation in a phosphate buffer with a magnetic stirrer. This agitation step
was repeated twice using fresh buffer. The washings from the membrane were
combined and serially diluted. Membrane filters from anaerobically treated
14
-------
samples were washed under nitrogen. Spread plates were made on plate count
agar from the dilutents, and counted after 48 hours incubation, aerobically
and anaerobically, at 24°C.
Enzymic activities of microorganisms were observed when cultured on
specific differential media. Enumeration of bacteria with simple nutritional
requirements was obtained on glucose-asparagine (GA) agar. The most probable
number (MPN) method was used to detect cellulolytic bacteria in modified
medium of Kadota (1956).
To isolate and enumerate clostridial types, washed samples were
incubated at 60°C for three hours to kill vegetative forms. Spread plates
were made on Schaedler's anaerobic agar (Schaedler, Dubos, and Costello,
1965) and TGYE. The plates were incubated anaerobically at 24°C for
48 hours.
A summary of the protocol for biological assay is shown in Figure 2.
To detect bacteriophage, septage samples were centrifuged at 5,000 rpm
for 30 minutes. The supernatants were passed through a 0.22 uM membrane
filter. The filtrates were assayed for phage activity using bacterial hosts
recovered from septage. Hosts included Escherichia coli, Citrobacter
freundii, Alcaligenes sp., Pseudomonas sp., Streptococcus fecalis, and
Mima-Herellea-Achromobacter spp. In addition, laboratory strains of
Salmonella typhimurium and Shigella flexneri were also tested. Aeration
of cultures produced log phase cells in approximately three hours at 30°C
in KG broth (Hutchison and Sinsheiner, 1966). To enchance the growth of
Streptococcus fecalis and Citrobacter fruendii, 0.5 percent phytone was
added to 3 ml of KG broth. Then, 0.1 ml of each host cell was transferred
and the tubes were aerated for three to four hours to insure infection and
lysis of the particular host. The intact cells were removed by centrifuga-
tion and the supernatants were drawn through 0.22 uM membrane filter. Con-
centrates were tested for bacteriophage using the spot plate method. Petri
plates, containing KG bottom agar (Hutchison and Sinsheiner, 1966) were
divided into twelve sectors. Then, 0.2 ml of each host was added to 4.8 ml
of KG top agar (Hutchison and Sinsheiner, 1966). Overlays were made on KG
agar plates to ensure an even bacterial lawn. After the surface agar had
solidified, 0.02 ml of each enriched filtrate was added. The spots were
permitted to dry and the plates were incubated at 30°C for 48 hours. The
presence of clear zones indicate phage infection and lysis of host cells.
Morphological features of each bacteriophage were obtained with the
electron microscope. To increase the titer of phage present in the original
filtrate, 2 ml of host cells (1 x 106 cells/ml) and 3 ml of each filtrate
were transferred to flasks containing 50 ml of KG broth. The cultures were
aerated for three hours and the remaining bacteria removed by centrifugation
and filtration. Then the phage titer was estimated from the filtrates using
the double layer plaque counting method. The filtrates were concentrated by
dialyzing overnight against ammonium carbonate (ionic strength, 0.006), after
which they were centrifuged (Spinco, model L) at 93,000 G for six hours. The
precipitate was reconstituted in 0.2 ml of dialyzate, placed on 200 mesh cop-
per grids, and negatively stained with two percent phosphotungstic acid (PTA).
15
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Characterization of Isolates
Bacteria isolated from septage as previously described were subjected
to various morphological and physiological tests as described in the Manual
of Microbiological Methods (1957). The Gram reaction was performed on cells
from an 18-hour ISA slant. Flagella stains were prepared according to
Leifson's method (1960). Morpnological observations were made using bright
field and phase contrast microscopy. Colonial and cultural characteristics
were examined in Trypticase Soy Broth (TSB) and TSA. Beef Heart Infusion
(Difco) slants served to enhance pigment production. Gram negative bacteria
were initially characterized on Triple Sugar Iron (TSI) (Difco) slants.
Hydrogen sulfide production was observed in Sulfide Indol Motility Agar
(SIM) (Difco) stabs. The formation of nitrite from nitrate was visualized
in nitrate broth by adding alpha-napthol amine and sulfanilic acid. Urease
activity was detected in urea broth (Stuart, von Stratum and Rustigan, 1945).
Cytochrome oxidase and phenyalanine deaminase were observed from the methods
of Ewing and Johnson (1960). The method of Moeller (1955) was used to assay
for lysine decarboxylation. Specific reagents were added to the media to
detect indole production, pH changes, and production of acetyl methyl
carbinol. Growth in Koser's citrate resulted from the utilization of citrate
as a sole carbon source. Metabolic patterns were observed in OF basal
medium (Difco) supplemented with 1.0 percent glucose (Hugh and Leifson, 1953).
All cultures were incubated at 24°C +_ 1, and examined after 24, 48, and
72 hours.
E. coli was enumerated and characterized using the Millipore method
and elevated temperature (Geldreich, Clark, Huff, and Bert, 1965). Samples
from septage and/or septic tank sewage were filtered through a 0.22 uM
membrane. The membrane was then transferred to disposable petri dishes
containing pads saturated with m-FC (Difco) broth. The dishes were covered,
placed in plastic bags, and incubated in a water bath at 44.5°C + 0.1.
The Millipore method was also used to enumerate and characterize fecal
streptococci. Membranes were placed on m-Enterococcus agar (Difco) and
incubated at 37° for 48 hours.
A scheme for characterizing bacterial isolates is shown in Figure 3.
Conventional anaerobic techniques were employed to establish anaerobic
populations in septage and septic tank sewage. Attempts were made to isolate
non-spore-forming as well as spore-forming types.
Methylene Blue Reduction Time
Selected redox indicators were used to estimate the biological activity
in liquid waste. Methylene blue, resazurin, and indigo carmine were added
to liquid wastes in concentrations sufficient to color the suspensions.
The following liquid wastes were tested: a) Septage from a recently
pumped tank; b) Septic tank sewage from a normal operating tank; and c) Raw
domestic sewage from a local treatment plant. After the indicators were
17
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added, the samples were shaken thoroughly and incubated at 25°C. Visual
observations of color were made at 30-minute intervals.
Survival Time of Salmonella typhimurium
A study of the survival time of Salmonella typhimurium (L^) in septage
was made using Hektoen Enteric (HE) agar (King and Metzger, 1968) to select
for Salmonella. In the preparation of the inoculum, the bacterium was cul-
tured in a liter of TSB for 18 hours at 30°C. Approximately 7.0 x 108 cells/
ml were suspended in 100 ml of phosphate buffer. These were introduced into
an individual septic tank system via the household commode and mixed. Then,
using a diaphragm pump, a sample was taken at zero and designated time
intervals. Measured amounts of the diluted samples were filtered through
0.22 uM membrane filters. The filters were placed on HE agar plates and
counted after 48 hours.
Microbiological Growth Chamber
An octagonal, plexiglass growth chamber, Figures 4 and 5, was constructed
for the purpose of studying the microbial interactions of bacterial types
recovered from septage and/or septic tank sewage. The experimental growth
chamber, fitted with a cover containing sampling ports, consisted of eight
compartments surrounded by a center well. The sides adjacent to the well
were slotted and contained removable membrane filters to allow exchange of
substrates and/or end products between the compartments.
Ethylene oxide was used as the sterilant. Preliminary experiments were
performed to determine the time, temperature, and concentration necessary for
sterilization. The apparatus was placed in a plastic bag containing 200 ml
of liquid ethylene oxide (10 percent), and a swab saturated with Bacillus
cereus spores served as a sterility check. The bag was gas-tight and placed
in a 45°C incubator for six hours. Then it was aerated at room temperature
for 18 hours, to remove the residual vapors.
LAND DISPOSAL
Preliminary Site
The first land disposal experiment was conducted on a 100 feet by
208 feet (30.5 meters by 63.4 meters) field site located in Litchfield
County. The soil is a Paxton fine sandy loam type, as classified by a
USDA Soil Conservation Service Soil and Capability Map. This field site
was subdivided into two plots: 20 feet by 208 feet (6.1 meters by 63.4
meters) and 50 feet by 208 feet (15.8 meters by 63.4 meters), Figures 6 and 7.
The 20 feet by 208 feet plot was used to follow the lateral distribution of
microorganisms along the fracture line and the survival time of septage iso-
lates. The 50 feet by 208 feet plot was used to evaluate the subsoil injec-
tion method and the effects on crop growth and soil water. Also on the
50 feet by 208 feet plot two tile drain lines were installed, 4-inch
(10.2 centimeter) diameter and 50 feet (15.8 meters) long, with collection
well pits.
19
-------
Figure 4. Growth chamber for study of microbial interactions:
Top view.
20
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Figure 5. Growth chamber for study of microbial interactions
Side view.
21
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Figure 7. Profile of tile drain line and collection pit.
23
-------
For septage application, a tank truck was driven alongside the tractor,
and Terreator. The septage was discharged by gravity from the tank truck
through a 3-inch (7.6 centimeter) diameter hose connected to a 4-1/4 inch
(10.8 centimeter) diameter curved tube attached to the Terreator. The
Terreator is described on pages 31 and 32.
Before septage application, representative soil samples were examined
for microbiological types and contents.
After deposition of septage into the trench line, samples were collected
by coring after 24, 48, 72, and 144 hours. Figure 8 shows the collection
points. Soil samples collected were placed in sterile glass stoppered
bottles. One gram of soil sample was placed in 99 ml of sterile water and
subsequent dilutions were plated on TGYE. The plates were incubated at
28°C and counted after 24 hours.
Selective media, previously described, were employed to determine num-
bers of Escherichia coli and Streptococcus fecalis in treated soil and to
follow the survival of coliforms and enterococci in the soil. In addition,
microbial profiles indicated the time involved to restore the soil to normal
conditions.
Experimental Site
The pilot study experimental site, Figure 9, was a 5-acre (2 hectares)
parcel of land owned by the White Memorial Foundation, Inc. (WMF) in
Litchfield, Connecticut. This site was an abandoned field that had been
used by farmers for cutting hay. It was a cleared area surrounded by woods
located approximately one-third of a mile from a normally travelled road.
The soil where septage was injected is classified by the USDA Soil
Conservation Service (SCS) as a Woodbridge fine sandy loam. This soil is
described in the SOIL SURVEY (Gonick et al., 1970) as being moderately
well-drained, underlain by a compact layer, or pan, at a depth of about
24 inches. Soil samples also were taken at various depths during the
drilling of the observation wells. The soil profile was determined down
to bedrock.
The experimental site had two separate areas. These areas will be
referred to as the receiving or unloading area and the disposal site (the
field where septage was injected). The disposal site, Figure 9, was divided
into three areas. One area was used for the plow-furrow cover disposal
method. Another area was used to study the subsoil injection disposal
technique. A third area was reserved for special applications, such as
demonstrations for interested individuals or groups.
Receiving Area
The receiving area was approximately two acres (0.8 hectares) in size.
On the site was a storage (receiving) tank for septage; a turn-around area
for the pumper trucks; a loading area for the tractor-septage trailer unit;
a miscellaneous area for general vehicle parking, tank storage and equipment;
24
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and septage subsoil injection machinery. Fuel supplies, tools, and miscel-
laneous items needed for daily operation were stored nearby in a plywood box.
A 10,000 gallon (37,850 liters), steel reinforced, precast concrete
tank (A. Rotondo and Sons, Inc., Avon, Connecticut) 8' (2.4m) by 8' (2.4m)
by 34' (10.4m) was used to receive and hold septage, Figure 10. The liquid
depth in the tank was 7 feet (2.1 meters). The tank was set on a 6-inch
(15 centimeter) compacted gravel bed and projected approximately two feet
above the ground. The tank was made watertight after it was installed to
insure against ground water contamination.
Seprage discharge into the storage tank was by gravity. Water for
clean-up was available from a 1,000 gallon (3,785 liter) storage tank mounted
on a 4-wheel trailer. A record of septage loads brought to the site was
maintained.
A tractor power take-off driven liquid manure pump (International
Harvester No. 1150) was used to mix the septage prior to loading the septage
hauling tank-trailer. A small stationary tractor was used to drive the pump.
The liquid manure pump manufacturer's discharge rating was 500-700 gpm
(35-40 liters/sec).
Septage Field Application Area
The maximum amount of septage to be applied by the subsoil disposal
method was determined by the septage nitrogen content. A maximum of 300
pounds of nitrogen per acre in one year was selected as the limiting factor.
This nitrogen loading limit was based upon:
(1) Agricultural field practices presently used.
(2) Research studies (Wengel and Kolega, 1970) on the effects of high
poultry manure application rates on soil water.
(3) A preliminary investigation of subsurface application of septage to
a 50 feet by 208 feet (15.8 meters by 63.4 meters) experimental site
having a subsurface drainage system. Analysis of a limited number
of drain water samples showed no noticeable effect on the soil
water after approximately 10,000 gallons (37,850 liters) was
injected.
Appendix D illustrates a sample calculation for estimating the size of
a land plot needed for septage disposal based on an estimated nitrogen con-
tent. The nitrogen concentrations assumed for the septage were 92 rng/1 for
ammonia-nitrogen and 37 mg/1 for organic nitrogen. In this study only 25%
of the septage samples analyzed exceeded these assumed nitrogen levels. Thus,
this theoretical calculation approach estimates that up to 279,000 gallons
(1,053,000 liters) of septage could be applied per acre in one year under
conventional cropping practices and without detrimental effect on ground
water quality.
27
-------
Figure 10. Receiving station for land disposal of septage.
28
-------
Three pairs of six-inch (15.2 centimeter) diameter observation wells
were installed on the diagonal of the rectangular field. These wells were
used to monitor the effects on ground water quality after septage applica-
tions. One of each pair of wells went into bedrock at a depth of about
10 feet (3 meters). The other well was left in the soil water or aeration
zone. The wells were capped. Water samples were collected by means of a
hand-operated diaphragm pump (Dart Union Co., Providence, Rhode Island).
Water samples were analyzed for chloride, COD, nitrate, pH, phosphate, and
for the presence of fecal coliforms.
Land Disposal Equipment
Septage was transferred to an 800 gallon capacity tank-trailer pulled
by a Ford 4000 tractor. The material was then transported to the field site
and injected into the soil. The tank-trailer design was based upon the
earlier studies of Reed (1969). The tank-trailer was a multi-purpose unit
designed so that septage, dairy or poultry manure, or sewage sludge could be
handled in field application. The design of the equipment involved inter-
state cooperation with Rutgers University (The State University of New Jersey),
and assistance from Waymark, Inc. (Cortland, New York), the manufacturer of
the prototype tank-trailer. This concept centered around the fabrication of
a basic tank unit which could be adapted to the final intended use, i.e., a
septage trailer unit would not necessarily require an auger type agitator.
The tank-trailer unit is shown in Figure 11.
Tank-Trailer
The tank hauler was rectangular with straight sides that tapered into a
U-shaped bottom. Overall tank dimensions were 10' (3m) long by 5' (1.5m)
wide by 3-1/2' (l.lm) deep. Corten steel was used in the tank fabrication,
with No. 12 gage steel used for the sides and No. 10 gage steel for the
bottom. For filling purposes there was a 30" (76cm) by 30" (76cm) hinged
manhole cap in the tank cover.
The tank was mounted on a two-wheel trailer chassis having 17" (43 cm)
by 20" (51cm) flotation tires. The trailer chassis was adjustable to permit
changing trailer wheels to an offset position. The gooseneck tongue was an
integral part of the tank-trailer and provided ease of tractor maneuvera-
bility when it was used with subsoil injection equipment. A trailer braking
system was included.
Slurry agitation and heavy slurry unloading were aided by a nine-inch
(23 cm) diameter auger in the U-shaped trough. The auger was driven by a
hydraulic motor at a speed not to exceed 250 rpm. A hydraulic motor, 10
brake horsepower in size, was mounted on the front end of the tractor and it
was also used to operate a 12-inch (30.5cm) stainless steel knife gate valve
for septage discharge control. The position of the gate valve could be
regulated by a hydraulic piston to control the flow rate of the septage
discharge. An additional hydraulic oil reservoir tank (Gresen Mfg. Co.,
Minneapolis, Minnesota) was mounted near the seat of the tractor operator.
Hydraulic pump hoses, necessary fittings, and a flow control valve, mounted
on the gooseneck frame of the trailer, completed the hydraulic system.
29
-------
Figure 11. Experimental tank-trailer.
30
-------
Septage Application Equipment
Two basic septage application methods were tested: (1) Plow-Furrow
Cover (P-F-C), and (2) Subsoil Injector (S-S-I). Two subsoil injection
units were used: (1) subsoil and (2) Terreator. All subsoil injection
units had a standard three point hitch for attachment to a tractor. The
P-F-C and S-S-I techniques were those developed for liquid manure disposal
(Reed, 1970).
The Terreator (U.S. Patent No. 2,694,354), Figure 12, was a subsoil
injection device developed by Mr. T. Roberg of Litchfield, Connecticut. This
unit could be either hydraulically or power-take-off driven from the tractor.
A 3-3/4 inch (9.5 centimeters) diameter mole-type hole was made by an
oscillating chisel point device. Attached to the Terreator was a 4-1/2
inch (11,4 centimeters) diameter curved tube attachment for receiving the
septage and its injection into the soil. Injection with the Terreator was
to a depth of twenty inches (50.8 centimeters) at a discharge rate of about
two gallons per linear foot (24.8 liters/linear meter) of travel. Terreator
application passes were spaced 5 feet (1.5 meters) apart to give an overall
application rate of 17,424 gallons per acre (163,000 liters/hectare) during
the study.
The P-F-C technique involved the use of a 16-inch (40.6 centimeters)
single bottom moldboard plow, a furrow wheel, and a 16-inch coulter (40.6
centimeters). Septage was applied in a six to eight inch (15.2 to 20.3 cm)
deep plowed furrow and immediately covered with soil, and at the same time
opening another furrow for the next septage application. The septage applica-
tion rate was approximately one gallon per linear foot (12.4 liters/linear
meter) of travel. For one acre, the equivalent volume of septage applied
was 32,700 gallons (306,000 liters/hectare).
The subsoil method, Figure 13, consisted of two plows assembled
together to provide a 24-inch (61 centimeters) wide opening for injection
of septage six to eight inches (15.2 to 20.3 centimeters) beneath the sod
surface. It had a Category II three-point hitch (American Society of
Agricultural Engineers Yearbook, 1971). The septage application rate was
approximately two gallons per linear foot (24.8 liters/linear meter) of
travel. For one acre, the equivalent volume of septage applied was 43,560
gallons (407,500 liters/hectare).
The tank-trailer was designed so that septage discharge was either from
the side of the tank for P-F-C soil injection, or from the bottom front
center of the tank when used with the S-S-I or Terreator techniques. The
size of the tank discharge opening was six inches (15.2 centimeters). An
adapter was provided for reducing the discharge opening to four inches
(10.2 centimeters). The septage flowed by gravity into a 4 or 6 inch (10.2
or 15.2 cm) flexible hose and then into the furrow or subsoil injection
apparatus. A quick coupling attachment (Andrews Industries, Inc., Dayton,
New Jersey) was used to connect the flexible hose at the trailer discharge
point. The hose material used was corrugated plastic pipe for the four-inch
(10.2 centimeters) application, and a corrugated neoprene hose with rein-
forcing coil for the six-inch (15.2 cm) application.
31
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Figure 13. Top view of sub-sod injector (Rutgers University)
33
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SPECIALIZED TREATMENT PROCESSES: ANAEROBIC-AEROBIC
The anaerobic-aerobic series processes were selected for study to treat
septage. Factors influencing this selection were the
(1) wide variability possible among septage loads.
(2) frequency at which trucked septage loads are received.
(3) quantities of septage being pumped in different areas.
(4) process controls required for system operation and maintenance.
(5) costs relative to alternate treatment processes.
It was hypothesized that solids degradation could be achieved in the
anaerobic stage followed by the degradation of soluble organics in the
aerobic stage. Sand filtration was added as a final treatment step to
insure acceptable effluent for discharge into a stream. Another purpose
for the anaerobic stage was to improve process control for the aerobic
treatment step by reducing the effects of both shock loading and variability
of the septage properties.
High rate digestion was used for anaerobic treatment. A retention time
of 15 days was selected for the laboratory bench scale study. A retention
time of 10 days (Rich, L.G., 1963) was selected for the pilot plant study.
Digestion temperature was maintained at the mesophilic optimum of 90°F to
100°F (32.2°C to 37.8°C). In contrast to the usual practice, the digester
contents were not agitated.
The design of the aerobic stage was based upon the 6005 to be removed
which is expressed by the following steady state material balance equation:
(Influent BODs, Ibs/day) - (Effluent BODs, Ibs/day) = BODs removed, Ibs/day
when evaporation and leakage are negligible, equation may be written as:
C^Q - CeQ = KXV (1)
Where: C. = Influent BOD,, concentration, mg/1
1 O
C = Effluent BOD,, concentration, mg/1
C O
Q = Septage flow rate per day, gallons/day
V = Aeration tank volume, gallons
K = BOD,, removal rate, mg/1 (day)
J. O
BOD removal is considered to be a first order reaction. The BODs
removal rate (Kj) is proportional to the effluent BOD concentration. Assuming
complete mixing, the concentration of 6005 throughout the aerated tank is
equal to the effluent concentration, C:
34
-------
dC = K C (2)
dt 6
Where: dC = the time rate of change in BOD concentration at any time, t
dT
K = BOD,, removal rate constant, day
When the system comes to equilibrium, the BOD removal rate, Kj is equal t
K C . Substituting equation KG in (1) and letting t = V/Q, the equation
t 6 G Q Q
beco: ----
Ci -
C2
C.
= 1 (4)
i 1 + K t
e
Where: C? is the fraction of BOD remaining
^ O
cT
The percent BOD removed is
O
R = 100 - 100 (5)
1 + Ket
The detention time t, in days, can also be expressed as:
* = R (6)
(100 - R) Ke
By knowing the percent BODt; removal required, the value of Ke which can be
measured experimentally, fixes the detention time. In this study, a Ke value
of 0.5 was chosen for the anaerobic digester supernatant. Using 95 percent
BODg removal as criteria, the aerobic theoretical detention is 38 days.
The anaerobic-aerobic effluent was sand filtered prior to discharge.
The septage treatment evaluation consisted of
(1) a five-month laboratory bench scale study.
(2) a six-month pilot plant study.
Laboratory Bench Scale Unit
A schematic of the laboratory bench scale unit is shown in Figure 14.
The anaerobic digestion tank was located in a controlled environment room.
Temperature was maintained at 90°F (32.2°C) using thermostatically controlled
35
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electric space heaters. The aerobic treatment tank was operated at ambient
laboratory room temperature. Air was supplied to the aerobic digestion
tank through two stone diffusers for aeration and mixing. Septage loads
were obtained from the East Hartford, Connecticut Water Pollution Control
Facility.
Samples, 500 ml each, were taken weekly to evaluate the effectiveness of
the anaerobic-aerobic-sand filtration series processes for treating septage.
The sample points were: (1) anaerobic digester supernatant (feed to the
aerobic tank), (2) aeration tank mixed liquor two hours after the addition
of the anaerobic digester supernatant and (3) sand filter effluent. On the
first day of each operational week a 900 ml sample was removed from the
aeration tank. Five hundred milliliters was used for laboratory analysis.
The remaining 400 ml was passed through the sand filter. For the period
Tuesday through Friday, 500 ml of anaerobic digester supernatant was added
daily to the aeration tank and 400 ml was removed to make up the Monday
aeration tank volume loss. Aluminum foil was placed over the aeration
chamber to minimize evaporation losses.
The sand filter was checked periodically for clogging. If signs of
clogging were evident, the upper one-inch layer was stirred.
The excess anaerobic effluent, one gallon (3.785 liters) collected
versus 500 ml added to the aeration tank was discarded.
The following analyses were conducted on the samples collected : total
solids, volatile solids, COD, BODs, nitrate-nitrogen, ammonia-nitrogen,
organic nitrogen, fecal coliform, total phosphate, total suspended solids,
pH, and D.O. Tests for nitrogen components, COD and 6005 were begun after
collection of the samples. Other physical and chemical tests were completed
as soon as possible. Samples were refrigerated when tests could not be
completed the day samples were taken.
PILOT PLANT
The anaerobic-aerobic process components were housed in a 20-foot
(6.1 meters) metal frame building. The pilot plant components were
(1) two 1,000 gallon (3,785 liters) holding tanks.
(2) for the anaerobic digester, a steel circular tank housed in a
controlled environment room.
(3) an above ground plywood (American Plywood Association, 1970)
oxidation ditch for aerobic biological treatment.
(4) a 4-foot (1.2 meters) by 3-1/2 foot (1.1 meters) sand filter to
polish the effluent from the aerobic ditch.
For receiving and storage of septage, two buried tanks were located
outside the metal frame building. One tank used was a conventional concrete
septic tank. The other tank was made of steel. Both tanks had special
37
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openings for admitting septage. The normal inlet and outlet openings were
plugged to prevent loss of septage or entry of ground water. Septage used in
the pilot study came from the Manchester, Connecticut region.
A manually operated diaphragm pump (Dart Union Company, Providence,
Rhode Island) was used to pump septage in 100 gallon (378 liters) quantities
from the storage tank into the heated anaerobic digestion tank. This circular
digestion tank had base supports to prevent its movement. Approximate tank
dimensions were: diameter - 5 feet (1.5 meters) and length - 8 feet (2.4
meters). On top of the tank and at each end were two 18-inch (45.7 centi-
meters) access openings with gasket bolted plywood cover plates. Room temper-
ature was maintained at 95-100°F (35 to 37.8°C) using thermostatically
controlled electric space heaters. A 2-inch (5 centimeters) diameter
flexible plastic tubing was used on the suction and discharge side of the
diaphragm pump. Effluent discharge from the heated digester was by gravity
through a 4-inch (10.2 centimeters) diameter clear plastic pipe into the
oxidation ditch. Semi-circular steel baffles were located on both the
inlet and outlet ends of the heated digester.
The oxidation ditch dimensions were: length - 23 feet (7 meters); over-
all width - 6 feet 6 inches (2 meters); depth - 3 feet 10 inches (1.2 meters).
Sizing of the oxidation ditch was based on an installation used for a
poultry waste treatment study (Loehr, R.C., et al., 1971) and the size of
plywood sheets available. Having two ditches, one from the referenced study
and the other from this study, similar in size, enabled comparisons to be
made of oxidation ditch performance for treating two types of biodegradable
wastes - poultry and septage. The inside of the ditch was lined with fiber-
glass. In the fabrication of the plywood ditch, a silastic type adhesive was
used in conjunction with conventional wood fasteners. A liquid depth of
27-1/2 inches (69.9 centimeters) was maintained in the ditch during system
operation.
A horizontally mounted paddle type surface aerator (Thrive Centers, Inc.,
Monmouth, Illinois) was used to oxygenate the liquid in the oxidation ditch.
The paddle aerator rotor diameter was 27-1/2 inches (69.9 centimeters) and
its length was 34-1/2 inches (87.6 centimeters). A single phase, 2 hp motor
drove the rotor aerator at a speed of 100 rpm through a speed gear reducer and
belt driven pulleys. The rotor aerator paddle blades were rectangular in
shape measuring 2-1/2 inches (6.4 centimeters) by 6 inches (15.2 centimeters).
The paddle blade was immersed to a depth of 3-1/7 inches (7.9 centimeters).
Prior to starting the experiment, the anaerobic-aerobic process system
components were tested using water. After satisfactory system performance
was demonstrated, septage was introduced into the system at a rate of 100
gallons (378 liters) per day. The data presented in this study started with
the time period after all of the calculated water volume in the system had
been displaced with an equivalent volume of one septage throughout.
Septage was fed into the system, each afternoon, daily Monday through
Friday. This subjected the anaerobic-aerobic process to shock loading.
38
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Each morning, Monday through Friday, a general inspection was made of
the anaerobic-aerobic process system components. Measurements were made of
the dissolved oxygen, pH and temperature of the mixed liquor in the oxidation
ditch. Each Thursday approximately 1000 ml of a mixed liquor sample was
taken from the oxidation ditch for suspended solids analyses. The remainder
of the sample, 400 ml, was sand filtered with the same unit used in the
laboratory bench scale study. Also on a weekly basis, the solids volume in-
dex (SVI) of the mixed liquor was measured using a 1,000 ml graduated
cylinder. Thereafter, the rotor aerator was shut down for one hour to
settle the mixed liquor. The liquid portion was pumped (T-6 Series Sigmamotor
pump manufactured by the Sigmamotor Pump, Inc., Middleport, New York) into
the University sewer line or sand filtered (pilot unit). The sand filter
effluent was discharged into a subsurface drainage system. Provisions were
also made for chlorination of the effluent. The factor which determined the
amount pumped from the oxidation ditch was the liquid depth. The liquid depth
was maintained at 27-1/2 inches (69.9 centimeters).
While the rotor aerator was shut down, the temperature in the digestion
tank room was measured. Also, routine equipment maintenance was performed.
Samples were collected weekly on Wednesdays from four locations in the
pilot plant:
(1) feed to the anaerobic digester.
(2) influent (anaerobic digester supernatant to the oxidation ditch).
(3) grab sample from the oxidation ditch at the corner where liquid
movement was toward the rotor aerator.
(4) sand filter effluent.
The septage feed to the digester and the supernatant from the digester were
taken in the afternoon and at the beginning of the pumping sequence. The
oxidation ditch grab sample was taken in the morning after restarting the
aeration process. The wastewater analyses were the same as those described
under the bench scale unit test procedure.
39
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SECTION 5
EXPERIMENTAL DATA AND RESULTS
CHEMICAL AND PHYSICAL OBSERVATIONS
The septage pH ranged from 4.8 to 10.5, though most pH measurements
are below 7.0. The septage color varied from greyish-green, greyish-black,
greenish-black, brown-black to black. Its odor was at least equivalent to
sewage. Occasionally, the septage odor was nauseating.
Analyses of the liquid fractions (supernatant, after one hour settling
in a Imhoff cone) and the entire septage samples are shown in Table 1. Before
conducting analyses, the septage samples were mixed in a Waring blender. The
volatile total solids, volatile fixed and volatile suspended solids analyses
were made by igniting the samples at 600°C for 30 minutes in an electric
muffle furnace.
In Table 1 the weighted mean is shown because of the varying number of
sample replications of the 180 septage samples (Appendix C). A coefficient
of variation greater than 25 percent indicates a highly varying material.
For the population, the interval of a true weighted mean for a student
distribution (Steel, R.C.D. and J.H. Torrie, 1969) 95 percent confidence
level is shown in the last column of Table 1.
For the designer of septage waste treatment facilities, data which
provides flexibility in the selection of septage parameter numbers has merit.
Figures 15 through 25 show the accumulated percentages of samples analyzed
versus the physical or chemical parameter of interest. The cumulative
frequency distribution represents successive addition of the number of
observations falling within a given percentage starting with the lowest
value. The approximate vertical ordinate increment was 10 percent.
For examples of the use of Figures 15 through 25, a designer may con-
sider concentrations of a specific parameter that will include 75 percent of
the observations. Thus for 8005 a 75 percent design value is 6350 mg/1 or
less (Figure 15). A 50 percent BODs design value would include all values
approximately 2900 mg/1 or less. Comparatively, the 75 percent value for
BOD5 seems to be more than twice as large as the 50 percent value. If design
evaluations are needed for septage total solids, then Figure 16 shows that
the 75 and 50 cumulative percentages would include all samples with 3 percent
or less or all samples with 1 percent or less total solids, respectively.
The decision whether to use a statistic or design curve is left up to the
user.
40
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Table 1. SBPTAGE DATA STATISTICAL SUMMAKI
Name of Arithmetic Weighted Standard Coef . of Range of
Test Mean Mean, I Median Deviation Variation Xs
Septage U,79l* 3,81*0 2,912 1*,1*10 115.0 + 510
mg/l
Super- 1,91*8 1,860 1,528 1,2UO 66.5 1 171.5
natant, ng/1 ~
COD Septage 26,162 25,600 16,803 26,900 10l*.9 + 3*220
COD Super- 6,31*3 6,690 5,280 7,280 108,6 + 1,100
natant, *g/l ~"
Total Solids 2.21* 2.37 1.1*5 2.69 113-1* * 0.1*3
Septage, % ~
Volatile 67.8 67.5 70.5 15.1* 22.8 + 2.1*6
Solids
Septage, %
Fixed Solids, 32.2 32.1* 29.2 15.1* 1*7.6 + 2.1*6
Septage, % ~~
Total Sus- 2,350 2,530 2,302 1,1*10 55.7 * 321
pended Solids
Supernatant, rag/1
Volatile Sus- 1,819 1,880 1,31*3 1,390 73.8 + 323
pended Solids ~~
Supernatant, Jug/1
1*5.7 139.5 1 10.1*5
U1.7 58.2 + 8.55
a 955f confidence limits
Organic N
Septage fflg/1
Ammonia N
Septage ng/1
26
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32.7
71.7
12
62
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With nitrogen analyses, foaming was experienced. Therefore, 30 septage
samples were analyzed for surfactants. All 30 samples contained detergents.
The linear alklyate sulfonate (LAS) concentrations ranged from 3 mg/1 to
61 mg/1; average concentration was 23.6 mg/1. These analyses imply that
the household septic treatment does not completely decompose LAS.
GAS UTILIZATION AND PRODUCTION
Several septage samples, raw wastewater and digester sludge were taken
from different sources for head space gas composition analyses. Table 2
shows the percentage of oxygen, nitrogen, methane and carbon dioxide gases
in the head space of each sample. These samples were collected periodically
and immediately transferred to stoppered bottles. The bottles were kept
tight to prevent any immediate equilibration of trapped gases with the out-
side atmosphere. Any substantial increase of internal pressure from the
production of methane and/or carbon dioxide was followed by releasing a
limited portion of the head space gas from the bottles; e.g. samples 4 and
6, Table 2. After gas production virtually ceased (e.g. all raw wastewater
samples after the third week) equilibration with the outside atmosphere pro-
ceeded at a relatively slow rate.
The raw wastewater and digester sludge samples showed similar gas
composition patterns. However, the septage samples showed wide variation
(Table 2). Several factors may influence the chemical, physical and bio-
logical characteristics of the septage:
(1) inputs to the septic tank
(2) frequency of pumping
(3) efficiency of individual household sewage system
The production of methane was slow for most septage samples, whereas the
digester sludge produced significant amounts of the gas within 24 hours.
The raw wastewater samples did not show any detectable amount of methane
at the highest sensitivity setting of the TC detector; even with a simul-
taneous injection of as much as 2 ml of the head space gas. The utilization
of oxygen and the production of carbon dioxide proceeded at a significant
but variable rate in all samples, increasing in following order: sewage,
septage, and digester sludge.
Total Volatiles, Including Mercaptans and Sulfides
The septage material also was examined by gas chromatography for its
volatile contents; organic sulfur and other compounds. The results were
compared with those of sewage and digester sludge samples. In a preliminary
examination, the volatiles in the septage material (400 ml) were swept by
nitrogen gas through a lead acetate tube to remove the hydrogen sulfide and
then through an aqueous solution of mercuric chloride (4% w/v) (Gumbmann and
Burr, 1964) to precipitate any volatile organic sulfur present. After passing
nitrogen gas for one hour, no white precipitate or turbidity could be detected
in the mercuric chloride solution indicating that only traces of these
53
-------
Table 2. PERCENTAGE COMPOSITION OP THE GAS MIXTURE IN THE
HEAD SPACE OVER SEPTAGE, SEWAGE, AND DIGESTER SLUDGE
Sample
Identity
Septage #1
Septage #2
Septage #3
Septage #4
Septage #5
Septage #6
Septage #7
Septage #8
Sewage
(Univ. of
Conn. )
Sewage
Time
Period,
Days
2
2
1
35
42
55
84
12
19
32
61
12
19
32
61
9
16
29
58
9
16
29
58
8
15
28
57
1
8
21
50
P-2
16.70
19.97
18.89
1.10
1.32
0.77
0.76
1.11
0.09
0.87
1.01
1.08
0.59
0.58
0.54
1.38
1.62
3.95
3.90
2.36
2.57
1.12
2.40
9.82
7.22
8.17
20.28
17.67
6.62
7.30
18.01
N2
79.62
79.29
77.14
73.00
68.20
65.12
56.13
77.04
71.93
70.95
74.19
71.47
52.36
38.93
36.46
77.66
75.43
74.70
87.60
82.54
75.53
73.79
78.50
83.06
84.57
84.30
78.22
80.04
83.04
83.49
77.03
CH4
0.09
0.06
0.27
3.87
5.09
7.35
15.90
1.45
1.96
2.23
1.77
5.73
20.32
30.61
29.82
0.16
0.13
0.09
tr.
0.12
0.29
1.17
0.28
__
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--
--
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—
--
—
£P-2
3.47
0.66
3.69
22.02
25.37
26.75
27.10
20.38
25.20
25.94
23.00
21.71
26.72
30.00
33.10
20.79
22.82
20.83
8.50
14.97
21.60
23.89
17.80
7.11
8.21
7.53
1.48
2.28
10.33
9.19
4.96
54
-------
Table 2. (continued).
Time
Sample Period,
Identity Days p_2
Sewage 0.25 20.63 79.37
(E. Hart- 7 9.11 83.38 -- 7.36
ford) 20 9.78 83.18 — 7.02
49 18.60 77.89 ~ 3.51
Primary 1 8.06 38.39 28.08 25.45
Digester 2 0.30 13.44 43.17 43.09
Sludge 8 0.16 7.51 46.16 46.16
(Willi- 21 0.37 15.29 40.92 43.40
mantic) 50 0.97 40.81 23.20 35.02
Primary 0.25 20.00 76.96 0.49 2.55
Digester 1 0.89 31.07 33.46 34.58
7 0.55 12.46 45.21 41.77
10 0.66 20.70 38.17 40.45
0.90 60.45 10.86 27.78
55
-------
volatile sulfur compounds were present. Consequently, the pre-column trapping
technique (Burnett, 1969) was followed for concentrating volatiles.
While several peaks were obtained with all three classes of liquid
wastes, the dissimilarities between the classes were apparent. Raw waste-
water samples did not show any traces of mercaptans or sulfides. Digester
sludge samples showed evidence of mercaptans and sulfides with comparatively
small peaks of other nonsulfur compounds. All of the septage samples showed
several sizable peaks for both organic sulfur and nonsulfur compounds. The
following mercaptans and sulfides were tentatively identified; methylthiol,
ethylthiol, n-propylthiol, n-butylthiol, and methyl sulfide. Other unidenti-
fied sulfur compounds could be easily located on the chromatogram by their
characteristic odors.
PROLONGED HOLDING OF SEPTAGE
East Hartford Septage Sample
The East Hartford septage odor was not offensive, nor did it turn
offensive during the study. The liquid portion even after two weeks
settling, remained turbid. Table 3 shows the effect of storage on the
pH, COD, TVA and the relative percentage of individual volatile acids.
Figure 26 shows the rate of gas production and changes in the gas com-
ponents, in addition to changes in COD and TVA.
The total COD concentration (Table 3) stayed fairly constant over
five weeks. However, the supernatant COD concentration continually decreased,
and after three weeks reached a minimum level of approximately 900 mg/1, or
an average reduction of 84 percent. Thereafter, the COD concentration
stayed relatively constant for two more months.
Initially, the volume of trapped air (Figure 26) was 270 ml of which
56 ml was oxygen. Oxygen was rapidly consumed and after one week the D.O.
concentration was reduced to and maintained a relatively constant level of
7 mg/1.
From the beginning of the experiment, the total volatile fatty acids
(see Table 3, Figure 26) decreased steadily while C02 showed a parallel
increase up to the 10th day after which C02 production slowed down. There-
after, the fatty acids concentration showed a marked increase from 60 mg/1
on the 12th day to 252 mg/1 on the 15th day, after which the concentrations
decreased steadily but without any significant increase in C02 production.
The wide variation in the relative percentage of each individual fatty
acid (Table 3) was indicative of an active metabolism in the sample. However,
the data did not follow a characteristic pattern that would permit elucida-
tion of the metabolic pathways of the acids.
The production of methane was very slow at the beginning of the experi-
ment mainly because of the presence of molecular oxygen which inhibits the
activity of the methane-forming bacteria. When the oxygen content became
56
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DATE OF ANALYSIS
Figure 26. Changes in the gas production, COD, and total
volatile fatty acids contents of septage during
prolonged storage at ambient temperature.
58
-------
minimal, methane production increased rapidly and the CH4/CCL ratio increased
progressively (Figure 26).
The total gas production rate was recorded almost daily (Figure 26). A
slow but continuous increase in the nitrogen content of the gas from the very
beginning of the experiment was observed. After seven weeks, the daily
increase in total gas production volume averaged around 20 ml. After the
eleventh week, the rate of gas production slowed to only 2-3 ml/day. Conse-
quently, the last septage sample (No. 11) was analyzed for its COO and TVA
contents. Although supernatant COD remained unchanged (940 mg/1), the sample
was virtually free of any acid content. On the 14th week and thereafter, it
became evident that the biological activity in the sample almost ceased
because no additional gas was produced. The gas assembly was dismantled
after 22 weeks. The supernatant COD to concentration had decreased 443 mg/1.
The total COD was 11.128 mg/1.
Litchfield Septage Sample
During the experiment, the odor of the Litchfield septage sample
remained offensive and penetrating. In addition, the supernatant stayed
turbid. Table 4 shows the effect of storage on the pH, COD, TVA and the
relative percentage of the individual fatty acids. The total COD remained
unchanged over a period of five weeks. The reduction in the supernatant
COD over the same period was irregular.
The gas production continually increased in the first week of the
experiment. The net increase amounted to 70 ml, which comprised 4 ml methane,
50 ml carbon dioxide. After the first week, the increase in gas production
either slowed down considerably, stopped completely, or showed some decrease.
No significant changes occurred in the relative quantities of the gas com-
ponents over the next nine weeks.
During the first week the pH remained in the optimum range for active
biological reactions (Table 4, sample No. 1 and 2). However, from the second
to the fifth week, the pH dropped significantly below that range. The TVA
content (Table 4) was originally high (greater than 500 mg/1) and it
increased steadily to a maximum of 972 mg/1. This TVA increase may be due
to the inhibition of the methane-forming bacteria by the low pH, by contact
with molecular oxygen or insufficient nutrients, or breakdown of organics
to volatile acids via bacterial action and possible air leakage. Meanwhile,
the acid-forming bacteria managed to grow under these conditions producing
more acids with relatively slow changes in the percentage composition of the
different fatty acids.
Without any apparent reason the Litchfield sample after ten weeks
started to increase in gas production. Consequently, the last sample bottle
(No. 11) was examined for its pH, TVA, and COD. Its pH was within the opti-
mum range, 6.85; its TVA was significantly reduced to 372 mg/1; and its
supernatant COD showed some reduction (Table 4). After almost 24 weeks of
increased gas production, the volume of the gas exceeded 500 ml. The per-
centage composition of the gas components were then determined: 02, 2.6;
59
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N , 36.4; CH., 50; CO , 11. The supernatant COD was reduced to 1568 mg/1
and the total COD was found to be 11,600 mg/1.
The Litchfield sample reactivated itself. This could be due to air
leakage into the bottle after which the presence of 0™ plus bacteria acclima-
tion resulted in gas production increase once past the lag phase. The type
of trend discussed is also observed in sewer lines carrying raw wastewater
in which there is an increase in biological activity after the raw wastewater
is in the sewer line for a given time period.
BIOLOGICAL
During the summer of 1969, 374 bacterial isolates were obtained from 38
septage samples using conventional laboratory techniques. Throughout the
fall and winter of 1969-70, an additional 100 isolates were recovered from
septage and septic tank sewage samples using modified techniques as shown in
the protocol for sample analysis (see Figure 2).
The distribution of bacteria from the summer and fall-winter isolates,
Figure 27, shows the gram negative non-lactose fermenting bacilli were pre-
dominate. These include Alcaligenes, Pseudomonas, Mima-Achromobacter-Here1lea,
and others which are considered aerobic. Percentages found were as follows:
Alcaligenes, 62; Pseudomonas, 16; Mima-Achromobacter-Herellea, 6; Providence,
2; and others, 14. Their recovery suggests the presence of oxygen in septage.
Of the 35 anaerobic spore-formers recovered from treated septage and
samples taken from septic tanks, 24 were obligate anaerobic. Their charac-
teristics are shown in Table 5. Clostridium lituseburence and Cl. perfringens
were most frequently encountered. The fastidious nature of many of the micro-
organisms that constitute the seven remaining families may account for their
inability to compete with the resident flora in septage.
The host specificity range of bacteriophages isolated from septage is
shown in Table 6. E. coli and S. typhimurium mutants were sensitive to phage
specific for Citrobacter freundii. The wild type of S. typhimurium (Lt2) and
20 strains of E. Coli isolated from septage were smooth and insensitive to
phage infection. It seems likely that rough variants lack a portion of the
antigenic determinants which results in a loss of type specificity.
Electron micrographs of phage morphology revealed two morphological
types: short-tailed phages similar to T^ and Ty and a long-tailed phage
similar to T even phages. One type was present in the filtrate active
against C. freundii, whereas, the other types were found in filtrates active
against S. flexneri.
The results of the enumeration studies of aerobic and anaerobic
(facultative) bacteria present in septage and in a single septic tank
system are presented in Figure 28. Salmonellae and Shigellae were not
encountered, and fecal streptococci counts were less than 1 x 10^ per
ml. Cellulolytic bacteria were detected in cellulose broth and appeared
in association with other bacterial types.
61
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Table 6. HOST SPECIFICITY RANGE OF BACTERIOPHAGES
ISOLATED FROM SEPTAGE.
Bacteria Active filtrates** Variant1*
122
Escherichia coli
isolated from septage
(20 strains) - S
E. coli B + - - R
E. coli K12 + - - R
E. coli 200P * R
E. coli 3300 * R
E. coli C * - + R
Salmonella typhimurium Ltg - S
S. typhimurium R« + R
— r- 3.
S. typhimurium R^ •*• - - R
S. typhimurium R^ + R
_ c
S» typhimurium R - R
S. typhimurium R2 •*• - - R
Erwinia carotovora - S
Alcaligenes viscolactis - S
Pseudomonas aeruginosa - S
P. fluorescens - S
Proteus vulgaris - S
P. Myxofaciens - S
Serratia marcescens - S
Flavobacterium sp. - - - 3
Klebsiella penumoniae - S
Aerobacter (Enterobacter)
aerogenea - S
aFiltrates«
1 Active against Citrobacter freundii R = Rough
2,3 Active against Shieella flexneri S « Smooth
64
-------
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:. Biochemical activities of microorganisms as observed aerobically on
specific media are shown in Figure 29. The results indicate that the pre-
dominant microorganisms present in the system are able to hydrolyze a variety
of nutrients present in the tanks.
Biological characteristics of septage are not significantly different
from the characteristics of the contents of an operating septic tank except
for protease and amylase activities and for nitrogen levels, Table 7 and
Figure 30. The quantity of reducing sugar in both systems was low and not
significantly different in septage as compared with septic tank contents.
Four methods were used in the determination of nitrate levels in septic
tank sewage. The amount of nitrate present, as measured with the brucine
method, was higher and suggestive of the presence of organics in the samples
which frequently interfered with the color reaction. The data are presented
in Table 8.
Methylene blue, resazurin and indigo carmine were tested to measure
biological activity in septage and sewage samples, Table 9. Methylene blue
was the most satisfactory while rasazurin and indigo carmine were not reduced
after two weeks in at least one type of liquid waste. Perhaps with modifica-
tion, the methylene blue reduction test can be developed into a rapid precise
method for estimating the strength of septic tank sewage and the correspond-
ing relationship to the need for septic tank pumping. An active septic tank
should have a short reduction time. To supplement the methylene blue reduc-
tion time study, additional data on ammonia, organic nitrogen, pH, and SPC/ml
values were sought and are presented in Table 10.
The enumeration of specific types of microorganisms in septage and
septic tank sewage show little variation as indicated by the range given in
Figure 31. The distribution of specific types of microorganisms and selected
physiological activities is shown in Figure 32.
A comparison of septage with available literature values for untreated
sewage indicated slight differences in E. coli counts, aerobic types, B-
glactosidase, and proteolytic activities"^The streptococci counts in septage
were always lower than those reported for sewage (Gaub, 1924), and the ratio
of coliforms to enterococci was approximately 20:1 in septage. The low
numbers of enterococci are probably the result of their inability to multiply
when substrates are limiting. When sterile septage was seeded with S. fecalis,
there was no increase in the cell number after 48 hours.
An experiment was designed to determine the survival time of S. typhimur-
ium in a septic tank system. Approximately 7.0 x 10^ cells/ml were introduced
into a septic tank via the household commode. A sample was taken at zero and
designated time intervals. An examination of the growth curve (A) in Figure
33 indicates that the survival time is approximately two weeks. Similar
results were obtained when the experiment selected was repeated (B). S.
typhimurium colonies possess a distinct morphology and exhibit a black pig-
ment on HE agar. Suspicious colonies were selected, cultured on TSI, and
urea broth verified by a slide agglutination with somatic (Type 0) antisera.
66
-------
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67
-------
Table 7. SIGNIFICANCE TESTS (t)a COMPARING SEPTAGE
AND SEPTIC TANK SEWAGE USING 12 PAIRED OBSERVATIONS.
Value of t Significance
statistic at 0.95
Aerobic 0.72
Anaerobic 2.05
Synthetic 0.22
Escherichia coli 2.00
Lactose fermenters 0.49
Non-lactose fermenters 1.50
Protease 2.^5 +
Amylase 2.97 +
Lipase 2.01
Ammonia level 4.U-0 +
Organic N2 level 2.96 +
Reducing sugar level 1.4-9
Nitrate level 1.20
Significance level for t values « 2.20.
68
-------
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69
-------
Table 8. NITRATE CONCENTRATION IN SEPTIC TANK SEWAGE.
Methods Employed
Sample
1
2
3
4
5
Reductive
Hydrazine
me/1
1.3
4.4
2.2
4.9
1.8
Direct
UV
rag/1
6.0
6.6
2.2
15.2
3.2
Brucine
Sulfanilic
Acid
me/1
11.1
10.2
3.0
13.2
3.1
Nitrate
Specific Ion
Electrode
me/1
3.5
4.3
2.8
4.2
3.1
Table 9. REDUCTION TIME IN HOURS OF SEPTAGE AND SEWAGE.
Redox Indicator
Sample
Septage
Septic
Tank Sewage
Raw Domestic
Sewage
Resazurin
March April
Methylene Blue
March April
21
21
17
Indigo Carmine
March April
21
21
— indicates no reduction after two weeks.
70
-------
Table 10. METHYLENE BLUE REDUCTION TIME AND
SELECTED ACTIVITIES OF SEPTIC TANK SEWAGE.
Daily Reduction NHo Organic-N
unples
1
2
3
4
5
6
time (hours)
18
17
16
17
16
14
SPC/ml
l.SxlO5
l.SxlO6
6. 9x10 5
5.9xl05
2.5xl06
l.lxlO5
mp/1
29.4
28.0
28.2
40.7
35.0
28.6
me/1
3.8
3.5
14.7
8.9
7.0
12.2
EH
7.0
6.7
6.8
6.6
6.7
7.0
15 7.7xl05 - 11.0 6.8
71
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Comparative enumeration of selected physiologica
activities with 95 percent confidence limits.
Figure 3
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74
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Although investigators (Gaub, 1924 and Maki, 1953) have recovered
cellulolytic bacteria from various stages of sewage treatment, especially
primary digesters, these microorganisms were not isolated from septage and/or
septic tank sewage under aerobic or anaerobic conditions.
Dissolved oxygen level of the incoming wastewater when combined with
mixing at the inlet may provide conditions for growth of aerobic type bac-
teria. Another possibility exists in that the septic tank may act as a
chemostat. The displacement of effluent by influent may provide a constant
number of aerobic types. In this situation, a resident flora would exist.
Oxidative bacteria especially Pseudomonads and related forms are capable of
degrading detergents and lipids, a desirable feature of the system.
Growth chamber studies dealt with one aspect of microbiology frequently
bypassed—the study of mixed cultures. These studies were limited to the
determination of acceptable membrane filter pore sizes for bacteriological
use. Membrane filters with pore sizes of 0.22 u and 0.45 u were found to
be acceptable. The technique developed is one which may contribute to the
progress of research in this area.
LAND DISPOSAL
Preliminary Studies
In a preliminary study to determine biological effects of injecting
septage into the soil, two standard microbiological methods were selected
for rapid assessment of the land site, (1) total viable counts on TGYE and
(2) enumeration of fecal indicators. Counts were established for the control
area. Total counts (SPC/g) at the 3, 6, 12, and 20 inch (7.6, 15.2, 30.5,
and 50.8 centimeters) depths were as follows: 850,000, 330,000, 240,000,
240,000, and fecal counts were less than 20 per gram of soil.
After introducing septage, samples were collected and counts were made
at 24, 48, 72, and 144 hours. The data are presented in Tables 11 and 12.
Examination of the data show lateral and vertical movement of bacterial
population in the soil. (This was of particular interest since the advantage
of this method of injection were the fracture lines as avenues of liquid
movement and may also provide more efficient filtration of wastewater.) The
northern points exhibit greater lateral movement of septage than the southern.
Bacterial counts at the center indicate vertical seepage as well as lateral
movements. The counts obtained from samples collected at points 0 and 25
differ. The differences suggest that the loading procedure was ineffective
in delivering the septage into the soil uniformly.
Approximately two weeks later, samples were drawn at 6 and 9 inch depths
at weekly intervals. The plot was monitored by viable count and by fecal
coliform enumeration. The counts presented in Table 13 demonstrated that
the fecal coliform survival time in soil was short and both viable counts
and fecal counts decreased at lower depths and laterally. The decrease may
be attributed to the competition with normal flora, inhibitors present in
the soil, lack of essential nutrients for growth, or its filtering capacity.
75
-------
Table 11. COMPARISON OP VIABLE COUNTS (SPC/g) FROM
SEPTAGE SAMPLES INTRODUCED IN SOIL AT POINT 0 ON
AUGUST 11, 1970.
Location
Center
3"
6"
24 hrs. 48 hrs. 72 hrs. 144 hrs
1,000,000
370,000
1*3" South 3" 370,000
6" 170,000
1'6" South 3- — 540,000
6- --- 420,000
2'6" South 3" — 40,000,000
6" --- 28,000,000
3' South 3" --- --- 450,000
6" — --- 6,000,000
3'2" South 3" — --- --- 230,000
6" --- -— --- 270,000
Y1 North 3" 370,000 ~~T^
6" 160,000
1*6" North 3" — 22,000,000
6" — 3.200,000
2§6" North 3" -- 7,300,000
6" — 580,000
3' North 3" --- — 330,000
6" — — 570,000
3*6" North 3" --- --- --- 660,000
6" --- --- --- 540,000
76
-------
Table 12. COMPARISON OF VIABLE COUNTS (SPC/g) FROM SEPTAGE
SAMPLES INTRODUCED IN SOIL AT POINT 25 ON AUGUST 11, 1970.
Location 21; hrs» US hrs. 72 hrs« U|l| hrs«
Center 6" 9,UOO,000 LA^ 21,000,000 130,000,000
9" 7U,000,000 250,000,000 2UO,000,000 120,000,000
1»3" South 6" 3,200,000 ~m ~
9" 510,000
1»6" South 3" --- 900,000
6" --- 50,000
2'3" South 3" --- --- 950,000
6" --- --- 520,000
3» South 3"
6" --- --- --- 6,100,000
p North 6" 720,000 r"r: ~^~- "^
9H 3,700,000
2' North 6" 360,000
9" Ulj.0,000
1'6" North 3" --- 6UO,000
6" --- 1,300,000
216» North 3" --- 850,000
6" --- 18,000,000
3' North 3" --- --- 320,000
6" --- --- 9,000,000
3»6" North 3" --- --- --- 11,000,000
6" --- --- --- 5,700,000
(1) Laboratory accident
77
-------
Table 13. COUNT DISTRIBUTION AFTER INITIAL SEPTAGE SUBSOIL INJECTION.
Location Point 0
Sample
Location
Center 6"
9"
I1 South 6"
21 South 3"
6"
1 North 6"
9"
21 North 3"
6"
Control Area
3"
6"
9"
8/27/70
77,000,000
(230,000)
190,000,000
32,000,000
27,000,000
180,000,000
6,500,000
Viable
9/2/70
SPC/g of Soil
20,000,000
(U3,ooo)
12,000,000
(58,000)
11,000,OOC
—
1,900,000
2,000,000
Count/Gram of Soil
21,000,000
77,000,000
10,500,000
9/10/70
12,000,000 (
70,000,000
(9,000)
kf 300, 000
—
7,300,000
10,000,000
10)
Location Point 25
Center 6"
9"
I1 South 6"
9"
21 South 6"
9"
I1 North 6"
2 North 6"
9"
6,500,000
(160,000,000)
iUU,ooo,ooo
3,500,000
3,900,000
9,700,000
5,000,000
30,000,000
86,000,000
U,5DO,000
8,000,000
260,000,000
(33,000,000)
110,000,000
(10,000,000)
28,000,000
1|0,000,000
2U,000,000
50,000,000
89,000,000
15,000,000
67,000,000
11,100,000 (
56,000,000 (
6,500,000
30,000,000
—
U, 500,000
25,000,000
10)
10)
Center refers to the center of the septage deposition line. The North
and South points are measured from the center of the deposition line.
78
-------
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80
-------
Table 15. OBSERVATION WELL DATA FOR THE WHITE MEMORIAL FOUNDATION,
LITCHFIELD SEPTAGE SOIL INJECTION EXPERIMENTAL SITE.
Observation Observation Chloride COD Nitrate-N Phosphate
Period Wells ppm mg/1 p_H ppm ppm
Weeks preceding
application
6
I*
2
U
c
L
U
C
L
U
C
T
XJ
7.6
2U.6
...
7.0
2U.8
•••»•»
6.0
6.0
10.0
6.0
...
19.2
1U.2
...
19.2
15.8
7.1
7.3
...
8.7
8.2
...
8.0
8.2
...
1.5
o.U
...
1.3
1.3
_*.«-
0.3
0.3
—
O.it
1.0
__•
1.2
2.9
—
2.1
2.3
Weeks after
initial septage
application
0
2
3
6
7
8
U
c
L
U
C
L
U
C
L
U
C
L
U
C
L
U
C
L
U.7
6.0
20.8
1.5
6.U
3.2
._.
5.1
22.U
7.5
8.0
ii.O
5.5
8.S
27.0
6.5
6.5
23.0
8.1*
12.6
16.8
19.2
18.6
15.2
...
22.7
19.2
12.0
16.0
e.o
21.0
25.0
12.0
Ul.O
8.0
10.0
7.1
7.7
7.6
6.7
7.0
6.9
— —
7.0
6.9
7.1
7.6
7.7
6.3
7.7
7.S
7.U
7.8
7.8
0.3
0.1
0.1
0.5
0.3
1.0
._.
1.5
0.1
0.7
0.3
0.0
0.1
0.1
0.7
0.0
0.0
0.9
1.1
1.0
0.2
1.1
0.7
2.U
~~.
0.2
0.3
1.0
0.9
o.u
2.5
0.2
0.9
0.6
0.6
o.u
81
-------
Table 15 (continued). OBSERVATION WELL DATA FOR THE WHITZ MEMORIAL
FOUNDATION, LITCHFTELD SERFAGE SOIL INJECTION EXPERIMENTAL SITE.
Weeks after
initial septage Observation
•r-application Wells
9 U
C
T
±J
10 U
C
L
11 U
C
L
12 J
n
O
L
Chloride
ppm
6.0
6.0
3.0
5.0
11.0
3.9
7.3
12.0
3.3
6.U
10.3
COD
2§ZL
15.0
8.0
Hi.7
7.3
9.8
21.0
16.0
21.0
12.2
19.6
25. k
I
PH
7.2
7.7
7.8
8.5
8.6
7.6
8.U
7.9
7.7
8.5
8.2
tfitrate-N
ppm
0.3
0.0
o.u
0.2
0.1
0.0
0.1
0.1
0.1
0,1
0.1
Phosphate
ppm
2.6
0.6
0.5
o.k
0.1
0.8
0.7
0.3
o.5
0.7
0.3
Septage Applications Ceased
13
1!;
15
16
20
U
c
L
U
r»
v/
L
U
C
L
U
C
L
U
C
L
3.U
6.U
12.3
U.7
7.5
lii.l
5.1
9.2
13.6
5.3
7.2
12.7
8.6
8.2
11.9
18.5
18.5
1U.2
17.3
18.5
2U.O
12.0
12.7
1U.O
7.6
8.1
7.9
7.6
7.7
7.8
7.8
8.2
7.9
7.6
8.2
7.7
7.3
8.0
7.6
7.U
8.1
7.6
7.5
8.1
7.8
0.1
0.2
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.1
0.1
0.1
0.0
0.0
0.0
0.5
0.2
0.3
o.U
0.6
0.3
0.2
0.1
0.1
o.5
0.3
0.2
0.1
0.1
0.1
u - Upper wens
C - Center wells
L - Lower wells
82
-------
Generally, trends in lateral distribution were not well defined, but a
slight reduction in numbers of viable cells was observed.
An additional injection of septage at the same location rendered
essentially the same trends over one-month period. This is shown in
Table 14.
Experimental Site
During the twelve-week application period, approximately 120,000 gallons
of septage were received and injected. The nitrogen equivalent of the total
septage volume that was applied was about 43 Ibs/acre. The results shown
below are in agreement with the predicted or forecasted result that there
would not be any detrimental effect on the ground water. The field equipment
proved to be serviceable and no serious equipment problems were encountered.
Observations, Table 15, made during the summer and fall on the concen-
trations of chloride, COD, nitrate-N, phosphate and hydrogen ion (pH) in the
soil water show no significant effects of the septage applications. Concen-
tration levels fluctuated but no trends that could be related to septage
applications were observed.
Weekly checks were made for fecal coliforms on the ground water samples
during this period. Except for one sample, there were no fecal coliforms
found in the water samples analyzed throughout the entire reporting period.
This single incidence of contamination was from one of the two upper observa-
tion wells. The positive observation occurred during the second week of
septage application and may have been due to contamination picked up during
sampling.
Averages of observations for the period preceding septage application,
for the twelve weeks of application, and for the eight weeks after applica-
tion that ended in the late fall are shown in Table 16.
TABLE 16. TEST WELL OBSERVATION DATA SUMMARY
6 Weeks 12 Weeks 8 Weeks
Unit of Preceding During Subsequent to
Parameter Measure Application Application Application
Chloride ppm 11.7 8.5 8.7
COD mg/1 13.6 15.6 13.1
Nitrate-N ppm 0.6 0.3 0.1
Phosphate ppm 1.4 0.8 0.3
Averages for observations made during the following spring--chloride, 5 ppm;
COD, 21.4 mg/1; nitrate-N, 0; and phosphate, .7 ppm--showed no significant
differences that could be attributed to the earlier septage applications.
Thus, the pilot study demonstrated that soil injection of septage can
be a feasible disposal method. Further investigations are required both in
83
-------
terms of an increase in the rate of septage application and to discover any
long-term effects on ground water quality from continued application of
septage to a given plot of land. Additional information should also be
obtained on the effects on crop responses on land on which septage has been
applied. The findings in the present study provide evidence that if the
septage application rate is controlled, this recycling scheme can be used
as a means for disposing of septage or other comparable biodegradable
materials.
Land Disposal Equipment Appraisal
The equipment performance was satisfactory for experimental purposes and
demonstrated the feasibility of soil injection as an acceptable method for
septage disposal. The study was conducted under research controls and objec-
tives which are different from those that may be encountered under publicly
managed operating conditions.
The plow-furrow-cover (P-F-C) method is preferred to either of the sub-
soil-injection (S-S-I) methods. With the subsod injection method, a sod
cover is required and the frequency of equipment access to the field site
is less because of field techniques used. More corrective work on the
Terreator would be required before its performance could be evaluated.
There is uncertainty as to whether the vibrating action from the Terreator
had a beneficial effect in the septage soil injection operation. However,
the flexibility for depth control of septage application may be an advantage
of the Terreator. It also appeared that this unit might be capable of
performing under more rugged soil terrain than the P-F-C and the subsod
units. The heavier weight of the Terreator, 570 Ibs (259 Kg), may be a
disadvantage.
Instead of a research-oriented, multipurpose tank-trailer, a tank-
trailer unit should be designed specifically for the injection of septage.
Suggested modifications are as follows:
(1) A larger tank-trailer would be advantageous. An increased trans-
port tank size will decrease the number of trips necessary from
the septage receiving tank area to the land disposal area and in
turn will result in a more efficient operation. The minimum sug-
gested tank size is 1500-2000 gallons (5678-7570 liters) as com-
pared to the 800 gallon (3028 liters) unit used.
(2) Flotation tires should be used on the tank-trailer to minimize
compaction of the soil.
(3) Suggested changes in the experimental tank-trailer.
(a) The control levers on the tank-trailer unit should be
relocated on the tractor where they can be more readily
accessible to the operator. Refinements can also be made
in the overall hydraulic system.
84
-------
(b) With the P-F-C method, there was an occasional splashing of
septage on the plowed ground. This can be overcome by improv-
ing the septage hose delivery system from the tank-trailer to
the furrow.
(c) The S-S-I units could be located on the gooseneck tongue.
This would simplify the delivery of slurry from the tank-
trailer to an S-S-I unit.
(d) It was necessary to remove the initial jack provided with the
tank-trailer. A jack to permit easier connection between the
tank-trailer and hauling tractor is desirable. It is also,
perhaps, a needed safety factor in equipment design.
(e) If both the P-F-C and S-S-I units are to be used inter-
changeably, a mast having a three-point hitch to permit
mounting these units would contribute to a saving in equip-
ment changeover time.
(f) The surge braking system did not operate satisfactorily when
the tank-trailer was carrying a load. Reconstruction of the
braking system is suggested.
(g) Although one position of the trailer-axle was used for most
of the field studies conducted, the adjustment for changing
the angle of the trailer could be improved.
ANAEROBIC-AEROBIC: BENCH SCALE STUDY
The sample points were: (1) septage feed; (2) heated anaerobic digester
supernatant (feed to the aeration tank); (3) mixed liquor in the aeration
tank, and (4) sand filter effluent. Figures 34 through 43 show measurements
versus time for parameters that define the efficiency of this treatment
system.
The BOD$ and COD concentrations in the septage feeds varied considerably.
However, the BODs and COD concentrations in the digester effluents (anaerobic
supernatant) aerations tanks were relatively constant. Thus, this septage
treatment system can- apparently withstand shock loading effects. Both the
6005 and COD concentrations were reduced more than 95 percent. The 6005 and
COD concentrations in the sand filter effluents (percolate sample) were
approximately 40 mg/1 and 100 mg/1, respectively. Both BOD,, and COD concen-
trations in the septage feed were greater than 3,000 mg/1.
The changes in ammonia-nitrogen and total Kjeldahl-nitrogen concentra-
tions after each stage of treatment are shown in Figures 36 and 37. Both
ammonia-nitrogen and Kjeldahl-nitrogen concentrations decreased progressively
after each treatment stage. The total ammonia-nitrogen removal was approxi-
mately 92 percent, for total Kjeldahl-nitrogen approximately 93 percent.
The total solids content in septage ranged from 0.3 percent to 8 per-
cent, Figure 38. The total solids removed by the heated anaerobic digester
85
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was greater than 93 percent. The total solids content was reduced slightly
after aerobic treatment. However, sand filtration resulted in a further
decrease in total solid content to approximately 0.05 percent in the effluent.
Volatile solids were also removed in each treatment stage. The overall
reduction was approximately 36 percent, Figure 39.
The total phosphate removed was low until the aerobic effluent was
filtered through a one-foot (30 centimeter) tall, 4-inch diameter (10 centi-
meter) sand bed column. The total phosphate concentration was reduced
92 percent, Figure 40.
The nitrate-nitrogen concentration in septage and the digester effluent
were approximately 1 mg/1, Figure 41. The nitrate-nitrogen concentrations
after aerobic treatment and in the sand filter effluent increased to over
100 mg/1 after four weeks of operations. Simultaneously, after several weeks
of operations the D.O. concentration in the aerobic treatment increased to
and leveled off between 6 and 7 mg/1, Figure 42. Figure 43 shows that the
pH was decreased and corresponding increase in nitrate-nitrogen concentration
is due to oxidation (nitrification) of ammonia-nitrogen. One procedure for
controlling nitrate-nitrogen production would be to reduce the D.O. concen-
tration in the aerobic tank to less than 2 mg/1. This procedure would leave
a relatively high concentration of ammonia-nitrogen in the final effluent.
Another approach would be to add methanol to the sand filter influent to
promote biological denitrification in the sand filter. The latter procedure
may be preferable where the sand filter effluent is either discharged to a
stream, or percolated; and the buildup of nitrate-nitrogen or a D.O. sag in
a receiving stream would be undesirable.
The fecal coliform MPN in septage varied considerably. However, these
organisms were not detected in the final effluents. It also was observed
that a limited number of aerobic microorganisms were present in septage.
Apparently some of these microorganisms are carried over into the aerobic
treatment. To follow the movement of aerobic microorganisms, an examination
of the aerobic system was conducted. Weekly samples were taken from the
aerobic tank. Viable counts were recorded on Tryptone Glucose Yeast Extract
Agar (TGYE). During a 6-week period, the MPN ranged from 1-9 million
bacteria/ml. Heterotrophic types were selected, checked for purity and
identified using conventional microbiological techniques. The generic
distribution of 88 isolates were as follows: Alcaligenes, 52.3; Flavo-
bacterium, 4.8; Bacillus, 11.3; Enterobacter, 4.5; Pseudomonas, 2.2;
Micrococci, 15.9; Corynebacterium, Rhodotorula, 2.3; and unidentified
isolates 4.5. The majority of the microorganisms selected exhibited
proteolytic activities. The presence of nutritional microorganisms indicate
probable utilization of organics, more specifically proteins, thus paving
the way for oxidation of NH_ to NO^ and ultimately to N03 by autotrophic
microorganisms. Coliforms were absent in 0.1 ml of sample examined from the
aerobic tank.
ANAEROBIC-AEROBIC: PILOT PLANT
Comparable data observations for 6005, COD, total solids, volatile
solids, pH, nitrate nitrogen, ammonia nitrogen, total Kjedahl nitrogen, and
91
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total phosphate for the anaerobic-aerobic pilot plant study over the six-
month test period are shown in Figures 44 through 52.
The concentration of 6005 which averaged 1042 mg/1 in the septage
(Figure 44) was reduced by over 96 percent to an average aerobic ditch
effluent concentration of 35 mg/1. The BODs aerobic ditch effluent con-
centration ranged from 5 to 86 mg/1, with the higher concentrations measured
in the early part of the study. The sand filter effluent (oxidation ditch
supernatant filtered through the laboratory sand column) BOD 5 concentration
averaged 4 mg/1, with the highest concentration measured at 7 mg/1. This
represents over 99 percent BOD5 removal. COD removal by the pilot treatment
system, including sand filtration, was 92 percent, Figure 45.
Ammonia-nitrogen and total Kjeldahl-nitrogen concentrations were
reduced 99 and 96 percent, respectively (Figures 46 and 47). The heated
anaerobic digester effluent ammonia-nitrogen concentration averaged 80 mg/1,
whereas the ammonia-nitrogen concentration in the septage feed to the diges-
ter was 59 mg/1. This ammonia-nitrogen increase reflects the bacterial
conversion of unassimilated protein matter.
As also observed in the laboratory bench scale study, there was a high
amount of nitrification after the aerobic ditch and sand filtration treatment
steps. The nitrate-nitrogen concentration, Figure 48, in the oxidation ditch
and sand filter samples averaged 72 mg/1 and 70 mg/1, respectively. These
nitrate-nitrogen levels exceed the U.S.P.H.S. drinking water standard of
10 mg/1. Though not tested, the nitrate-nitrogen concentration could be
reduced by adding methanol to the sand filter influent and biologically
denitrifying on the filter.
The total solids concentrations of the septage feeds averaged 0.6 per-
cent and ranged from 0.1 to 7.2 percent, Figure 49. The septages in the
storage tank were not agitated before pumping. Therefore, the pilot plant
septage feed solid levels varied according to the liquid height and the
amount of solids that settled in the tank. The total solids concentrations
after pilot plant treatment (after the aerobic treatment step) averaged
0.16 percent. Samples of this effluent were polished by the laboratory
sand filter. The filter effluent solids concentrations showed a further
reduction to 0.1 percent. The volatile solids removal, Figure 50, in the
final sand filter effluent averaged only 29 percent as compared to an average
removal of 65 percent in the laboratory bench scale study. This lower per-
cent removal could be due to volatile solids settling in the storage tanks
and would not show up as being removed by the basic treatment system.
Total phosphate removal was 78 percent after pilot plant treatment and
88 percent after sand filter polishing, Figure 51. Phosphate removal was
also less than observed in the laboratory bench scale study.
The oxidation ditch dissolved oxygen concentration averaged 5.6 mg/1.
The D.O. concentrations ranged from 4.2 mg/1 to 6.6 mg/1. Figure 52 shows
the pH measurements for the septage feeds, digester supernatant and pilot
plant and sand filter effluents.
97
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As in the laboratory bench scale study, fecal coliforms were not
detected in the final effluent.
At the end of the pilot study, inspection of the heated anaerobic
digester showed little damage. A rather rigid scum mat, approximately one
inch thick, developed on top of the liquid. Some mold growth was observed
on top of the scum mat. In the bottom of the tank the settleable solids
accumulation buildup was two to three inches. Hair was present in the
digester tank slurry.
OTHER ASPECTS OF SPECIALIZED TREATMENT OF SEPTAGE
There are treatment methods other than the anaerobic-aerobic process
which would be considered for septage treatment. In several instances, the
investigators offered to evaluate commercially available methods, but the
offers were not accepted. For various specialized treatment units that were
evaluated in a somewhat cursory manner, the processes did not appear to lend
themselves to treatment of septage. However, by not having available
specialized treatment processes for careful test evaluation does not imply
their unacceptability for septage treatment.
The specialized treatment processes tested are used in the treatment of
domestic type sewage. They also have been used with wastes that are more.
difficult to treat than septage, e.g., certain agricultural or food process-
ing wastes. To choose a treatment system, an assumption would need to be
made concerning the maximum daily volume of septage to be treated. Some of
the criteria for evaluation of specialized treatment processes include
(a) potential for effective septage treatment; (b) costs in relation to
estimated volume of septage to be handled; (c) field performance reports
and site observation; (d) simplicity of operation and maintenance; and
(e) personnel required. For a large volume of septage, full-time personnel
working eight hours per day with plant emergency control devices for the
nonworking hours might be required.
A comparison of the treatment needs for septage and municipal sewage in
terms of detention time, the amount of oxygen required, aeration volume and
surface area needs, power requirements, and estimated costs for the conven-
tional activated sludge process and the extended aeration sludge process are
presented in Table 1 of Appendix G. Also included is a summarization of BOD
loading range and expected percent BOD removal efficiency for selected
aeration processes, Table 2 of Appendix G.
SEPTAGE TREATMENT AT A WATER POLLUTION CONTROL FACILITY
One approach is to combine septage with raw sewage for treatment in a
conventional water pollution control facility (WPCF). Septage can be intro-
duced into the raw wastewater from a tank truck, or pumped from a septage
storage tank, under controlled conditions. When using a septage storage
tank, the WPCF installation should include a grit chamber and communitor
ahead of the storage tank. Possibly, septage can be added directly to the
plant sludge digestion treatment provided that grit removal is first
available.
107
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In a preliminary survey, Kolega, J.J., in 1967, discussed combined
septage-sewage treatment in Connecticut water pollution control facilities.
The survey reported on what appears to be unwarranted objections from treat-
ment plant operators:
(1) septage is harmful to digester operations and, therefore, this
material is not acceptable for combined treatment.
(2) septage is of little value to a WPCF because of the added cost of
treating septage with no resulting benefit.
(3) as a policy, a new septage treatment plant would exclude septage
based on the advice received from other WPCF superintendents.
However, septage is a biodegradable waste even though its biological, chemical
and physical characteristics are different from raw sewage. Thus, an ade-
quately designed WPCF should be able to treat septage.
Calculations were made of the probable effects of adding septage to a
conventional WPCF. These calculations are for various combinations of
hydraulic and BOD loadings with the raw sewage for selected time periods.
Table 17 shows the results of these calculations.
The increase in the amount of solids to be handled should not adversely
affect plant operation unless the sewage treatment plant is already overloaded.
Tests on the effect of septage addition to sewage were made at the
University of Connecticut WPCF. The first test was conducted in late summer,
two weeks prior to the start of the fall term. The second test was conducted
during the two-week winter recess. These time periods were chosen because
the University's WPCF was exceeding its design capacity during the school
academic year.
A 1,000-gallon (3,785 liters) tank was placed above ground level for
storing septage. This tank was coated with Thoroseal to insure against
leakage. A diaphragm submersible pump was installed in the tank. A plastic
pipe line was installed from the pump discharge into a manhole at the sewage
influent line just outside the University's WPCF. A wood stirrer was used
for mixing the septage prior to and during pumping.
In the first test, septage was fed into the manhole in slugs of 250
gallons (946 liters) over a 4-hour period. In the second test, the septage
was fed directly from the tank truck into the raw sewage line. The estimated
raw sewage flow during both tests was approximately 0.5 mgd (1.9 mid).
Samples were taken hourly for analyses over a 16-hour period, at the four
sampling locations shown in Figure 53. These analyses were compared to the
analyses of samples taken at the same locations during plant operations with-
out septage addition.
The septage added to the raw wastewater had no significant effect on the
concentration levels of chloride, COD, nitrate-nitrogen and pH. Digester
performance was not affected. However, at the bar screen and grit chamber
108
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Septage
Post-Chlorinotion
NOTE: P - Pumping
D.B. - Distribution Box
D.C. - Dosing Chamber
Design Flow = 1.3 MGD
Flow during academic year - Ave. 1.9 MGD peak 2.1=3.0 MGD
Flow during summer = 0.5=0.6 MGD
Figure 53. Sampling locations for combined waste treatment study.
110
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locations, the labor time needed did increase slightly. Additional tests are
needed to better evaluate the effects of septage-sewage ratios on WPCF opera-
tions.
Ill
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SECTION 6
SEPTAGE VOLUME PUMPING ESTIMATES
HOMEOWNER SURVEY
A survey was made of homeowners with septic tank systems to estimate
the volume of septage pumped. Four areas in Connecticut were selected,
representing a mixture of soil types and population densities. The towns
chosen were:
(1) Harwinton
(2) Old Saybrook
(3) Tolland
(4) East Hartford (most of the unsewered parts)
In each town, one sixteenth of the single family homes (a total of approxi-
mately 565 homeowners) were randomly chosen from the city directories. Of
the 188 questionnaires returned, four were for summer residences and were
discarded. The number of times a septic tank was emptied during the three
preceding years indicated the pumping frequency. The estimated tank capacity
was reported in gallons. Also the number of people in the dwelling was
requested.
Of the 184 septic tanks reported on, 103, or 57 percent, were pumped
one or more times in the preceding three years. In total, there were 186
pumpings over the three year period. Thus, the average was 0.34 pumping per
tank, per year. The tank volume, reported by 120 of the 184 respondents,
averaged 763 gallons (2,885 liters).
An estimate was made of the volume of septage pumped, per person, per
year from the pumping frequencies, tank volumes and the number of people
using the septic tank systems. The volume pumped was assumed equal to the
septic tank size. Multiplying the average septic tank size, 763 gallons
(2,885 liters) times the average number of pumpings per year per tank, 0.34
gives an estimate of the volume of septage pumped, 259 gallons (980 liters)
per year, per residence. The average annual volume pumped per tank, 259
gallons (980 liters) divided by the average number of persons per household,
3.9, gave an estimate of the annual per capita volume of septage pumped, or
66 gallons (250 liters) per person per year. Where small sewered areas are
scattered through a generally unsewered region, commercial and public
112
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buildings would probably utilize the sewered areas. In generally unsewered
regions, allowances for nonresidential buildings and summer residences would
require that the 66 gallon per person per year estimate be modified.
The homeowner survey also provided some insight into reasons for load to
load variations in septage characteristics. Pumpings at frequent intervals
are often associated with seasonally high ground water. Volumes pumped may
be considerably larger than those indicated by tank sizes alone because of
reverse water flow from the flooded drainfields. Some tanks were pumped only
after many years of service, and this septage would presumably contain a
rather high concentration of solids.
Forty-four percent of the septic tank systems showed some form of
failure. Problems were so severe for three systems in East Hartford that
they had to be pumped a total of 34 times in three years.
STATEWIDE SEPTAGE PUMPING VOLUME ESTIMATES
Information from a statewide survey of septic tank pumpers provided
primary data for estimating the septage volume pumped in Connecticut. A
questionnaire was sent to each of the 213 septic tank pumpers listed in the
yellow pages of the telephone directories. The 44 or 20 percent of the
pumpers who replied to this initial survey reported on the number of tanks
they pumped annually and the disposal facilities they used. These pumpers
were classified, first, by type of disposal outlet they used and, then, into
one of three size groups according to the number of septic tanks pumped;
namely, more than 700 tanks per year; 300 to 700 tanks per year; and fewer
than 300 tanks per year. The average number of tanks pumped by each group
was calculated, Table 18.
A follow-up survey was made to determine the size class of non-
respondent pumpers. This survey was accomplished by supplying the names
of the nonrespondent pumpers to nearby respondent pumpers and asking them
to classify each non-respondent by size group. This second survey plus
some follow up checking provided a nonduplicative pumper population in
Connecticut, Table 19.
The total number of tanks pumped annually was determined for each
classification by multiplying the number of pumpers by the average number
of tanks pumped. The volume of septage pumped annually was estimated by
multiplying the number of tanks pumped by the average septic tank size. The
average septic tank size was 847 gallons (3,206 liters). This figure was
based on delivery slips turned in by pumpers who delivered septage to the
East Hartford WPCF, Table 20.
About 1.3 million persons, or 43 percent of Connecticut's total 1970
population of 3 million, are dependent on septic tank systems for the dis-
posal of household wastes. This estimate of the state's unsewered popula-
tion was based, in part, on an updating of the population served by sewers
in each municipality made in 1966 by the Connecticut State Health Department.
The differences between the estimated sewered population and the total popu-
lation for each municipality provided the unsewered population estimate.
113
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Table 18. SEPTIC TANK PUMPINGS REPORTED HC 1*U PUMPERS
CLASSIFIED BY SIZE OF PUMPER OPERATION AND DISPOSAL OUTLET.
Disposal Outlet
Total
Other than
Treatment Facilities Treatment Facilities
Size of Pumping
Operation
(Tanks Pumped
per year)
More than 700
tanks
300 to 700
tanks
Fewer than
300
Average No.
tanks
Pumpers pumped
8 1,350
6 U22
U 136
Average No.
tanks Average No.
pumped tanks pumped
8
11
7
1,230
1*71
153
1,290
11*7
Includes six pumpers who disposed of part of the septage at
treatment facilities.
Table 19. SEPTIC TANK PUMPINGS IN CONNECTICUT
CLASSIFIED B* DISPOSAL OUTLETS.
Disposal Outlet
Total
Other
Size of Pumping
Operation (Tanks
pumped per year)
More than 700
tanks
300 to 700
tanks
Under 300 tanks
TOTAL
WPCF
Tanks
Pumpers Pumped
26
60
36
122
35,100
25,320
1*,896
65,316
than
Pumpers
18
36
18
72
WPCF
Tanks
pumped
22,1UO
16,959
2,75U
1*1,853
Pumpers
U*
96
51*
191*
Tanks
pumped
57,21*0
U2,279
7,650
107,169
114
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Table 20. SEPTAGE DELIVERIES B* SIZE OF TANK PUMPED, E. HARTFORD
WPCF FOR FOUR SELECTED MONTHS.
Size of
Septic Tank
(gallons J
Under 350
350 to 6^0
551 to 850
851 to 950
951 to 1050
1051 to 1350
1351 to 1650
1651 to 1999
2000
2500
3500
5000
TOTAL
Class
mode
(gallons)
250
500
750
900
1,000
1,200
i,5oo
1,300
2,000
2,500
3,500
5,000
Deliveries
(number)
2
86
197
181
8U
3
6
8
6
1
1
1
576
(gallons)
500
U3,ooo
1U7,750
162,900
8U,000
3,600
9,000
il*,l*oo
12,000
2,500
3,500
5,000
1*88,150
Average * 8U7 gallons (3,206 liters), For other liter
equivalents, multiply by 3.785.
115
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With an estimated annual volume of septage pumped of 91 million gallons
(344 x 10 liters),and an unsewered population of 1.3 million, the annual
volume of septage pumped per person, per year is estimated to be 70 gallons
(265 liters). This 70 gallons per capita estimate provides a useful first
approximation for the amount of septage that may be expected from an area
where the unsewered population is known. Also, this per capita estimate is
slightly higher than that reported in the homeowner survey. The difference
could be due to the additional septage pumped from commercial, industrial,
and public sources.
TABLE 21. SEPTAGE VOLUMES RELATED TO POPULATION CLASSIFIED BY
AREAS ACCORDING TO DISPOSAL METHOD, CONNECTICUT
Total Connecticut
Septage Unsewered Septage Pumped
Area Classification Pumped Population Eer Capita
(mil. gal.) (thousands) (gallons) (liters)
WPCF disposal 55 806 68 257
Other disposal outlet 36_ 501 72_ 272
91 1,307 70 265
In Table 21, municipalities and their respective unsewered populations
were classified according to whether or not their probable septage disposal
outlet was a WPCF. Information for this classification came partly from the
initial pumper survey in which the survey respondents also indicated the
names of those municipalities in which they pumped. The classification of
municipalities by disposal outlet was also based in part on information from
an earlier survey of municipal policies regarding septage receipts. The
classification also took into account data on actual septage receipts that
were reported by the WPCF to the State Department of Health. Based upon
this, central and southwestern shoreline parts of Connecticut were presumed
to go to a WPCF, Figure 54. This is an area of high population density. Of
the approximately 1.3 million persons who must rely on septic tank systems,
approximately 60 percent live in this designated area. In the remaining
parts of the state, where the other 40 percent of the state's unsewered popu-
lation reside, septage is usually disposed of in excavated pits.
Since the research study of septage disposal was started in 1969, seven
WPCF's with septage receiving and processing facilities have been built in
areas where disposal in excavated pits has prevailed. To date, septage
disposal at these recently completed plants have been meager. This failure
to change disposal outlets can be attributed to two major reasons: (1) sep-
tage dumping fee at the WPCF is higher than the cost to pumpers who have
access to excavation pits, and (2) the lack of enforcement regulations
leading to establishing or upgrading of septage disposal outlets.
116
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117
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SECTION 7
MODEL LAND DISPOSAL SYSTEM
SOIL INJECTION COSTS AND LAND REQUIREMENTS
Soil injection is one of several feasible methods that are being
developed for septage disposal. Soil injection lends itself to recycling
a biodegradable liquid waste with a minimum of ground water pollution.
The feasibility of septage disposal by soil injection depends upon the
availability of an adequate site or sites that are acceptable to municipali-
ties, regulatory agencies, septage pumpers, and the nearby neighborhood. The
costs of soil injection must compare favorably with other available means for
treatment of septage, e.g., water pollution control facilities, other methods
of land disposal, and specialized treatment processes. In developing the
soil injection land disposal method in the study, environmental acceptability
as well as costs was considered.
In considering the soil injection approach to the treatment and disposal
of septage, the factor of heavy metals should be considered. This factor was
not investigated.
In general, land disposal of septage by soil injection is not intended
for year-round application. Instead, soil injection could be combined with
other waste treatment processes that together would constitute a year-round
septage disposal program for a designated area. If land disposal is used
for septage that would otherwise go to a WPCF, this would contribute to a
reduction in the hydraulic and organic loadings placed upon the WPCF, par-
ticularly during the warm weather period when a final effluent discharge
into a stream is being chlorinated. In winter months biodegradable rates
are slowed down because of lower temperatures. This may work against septage
addition to a WPCF.
Land requirements for the six months (Connecticut) when soil injection
can be carried out are necessarily based on the expected septage volumes. It
may be assumed that 5/7 of the total septage in the area being served will be
pumped during the six-month injection period. Thus, if the septage volume
for an area to be served is estimated to be 70 gallons (265 liters) of
septage per capita, the volume for injection would be estimated at 50 gallons
(189 liters) per capita.
An adequate site for soil injection is one with a receiving area which
is adjacent to a moderately drained soil area suitable for field cropping.
118
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The useable field area should allow for a two-year rotation, i.e., used for
injection one year and cropped the second year. Crops selected for the rota-
tion should be those which would enhance the removal of nitrates from the
soil.
With the plow-cover method of injection, septage can be applied at the
rate of one gallon (3.785 liters) per linear foot (305 cm) using a 16-inch
(41 cm) plow. Once over, this amounts to approximately 33,000 gallons/acre
(308,727 liters/hectare). With eight septage injections in the same area
over a six-month period, a total of 284,000 gallons (1,075,000 liters) would
be disposed of per acre (0.4 hectare). This rate of application is equivalent
to a nitrogen application of slightly over 300 pounds (136 kilograms).
As an illustration for estimating land requirements, a population of
10,000 that generated 700,000 gallons (2,650,000 liters) of septage annually
would need enough field area for injecting 500,000 gallons (1,893,000 liters)
of septage. At an injection rate of 284,000 gallons per acre (2,680,000
liters/hectare), this would require about 1.8 acres (0.7 hectare) of useable
field area per year or a minimum 3.6 acres (1.4 hectares) for a two-year
rotation. Land for roadways and headlands would bring the field requirement
up to at least five acres (2 hectares). In addition to the field injection
area, approximately one acre (0.4 hectare) of land is required for a septage
receiving area to provide space for temporary equipment storage, a tank truck
washing area, a turnabout for transport vehicles, and a tank for temporary
septage storage. Thus, six acres (24 hectares) of land might be the adequate
requirement for a population of 10,000.
Given a 1,000 gallon (3,785 liters) trailer tank, an injection rate of
4,000 gallons (15,140 liters) per hour is possible. Injection at this rate
for six hours of a working day would amount to 24,000 gallons (80,800 liters).
Under minimally favorable conditions whereby injection could be three days
per week, over 70,000 gallons (265,000 liters) could be injected weekly. If
the temporary storage tank proved to be inadequate during an extremely wet
period, arrangements for disposal elsewhere would be necessary.
The requirements and a representative budget for soil injection,
Table 22, were developed from the pilot study discussed in the section on
materials and methods. The dollar cost figures shown in Table 22 were pre-
pared for a grant to carry out a demonstration project on the site of the
pilot project. Those capital costs that may be spread over a period of years
are amortized at 6 percent interest. The septage storage tank, site improve-
ment and maintenance costs are amortized over ten years; and machinery
capital costs, over five years. Included among the listed requirements are
some that are not absolutely essential to the operation but which are con-
sidered to be highly desirable.
This representative injection system is considered to be adequate for
handling 1.5 million gallons (5,678,000 liters) during a season, one that
could serve a population of 30,000. More likely, systems would be designed
to serve smaller populations and handle smaller volumes of septage. Cost
adjustments would then be required for most budgeted items.
119
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Table 22. REQUIREMENTS AND COSTS (1972) FOR SEPTAGE INJECTION
AT A 10 ACRE SITE IN LITCHFIELD, CONNECTICUT, TO SERVE
A SURROUNDING POPULATION OF 22,000 PERSONS.
Costs to be Amortized Annual
Item at 6 Percent Cost
1. Land rent $ 1,000
2, Site improvement and maintenance (Amortized over 10 yrs.)
Well ;ind water pump $2,700 367
(300 feet 3 $8/ft. + $300)
(Observation wells) 1,000 136
Drainage (if needed) 750 102
Electric Power Line (1,000 ft.) 1,200 162
Establish roadway 1,000 136
Maintain roadway 200
Grade site 500 68
Planting materials 150
$ 1,321
3* Storage tank
30,000 gallon tank $3,OCO 1*08
Excavate for tank 500 68
$ U76
'4. Machinery capital costs (Amortized over 5 yrs.)
Tractor $8,000 1,900
Plow 375 90
Tank trailer 3,000 710
(Experimental model $5,000)
Septage pump w/electric motor 2,0?6 U92
$ 3,192
5. Machinery operating costs
Hardware and replacement parts 500
Lubricants, fuel, electricity 300
$ Bo75
6 . Labor
1 man © $k per hour, 26 weeks U,160
Fringe benefits 1*00
Insurance 200
RAND TOTAL $11,5U9
120
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Whether the septage disposal site is leased or owned is a factor in land
costs. If the land were owned by a municipality, the ownership costs might
take into account the resale value of the land as well as its cost or book
value. Soil injection is unlikely to adversely affect the land and it can
enhance soil enrichment. In developing the representative budget for soil
injection, land rental costs of $1,000 per year were assumed.
Necessary facilities, in addition to the common ones, may well include
two that would be unique to septage disposal. One facility is a water
supply for hosing down any spillage and for washing the trucks. A second
item would be observation wells from which ground water samples could be
drawn.
The capital cost for .constructing large, poured in place, concrete,
underground storage tanks was estimated at $100 per 1,000 gallons ($26.42
per 1,000 liters) of capacity (Casler, G.H., 1969). Contract price in
Connecticut for an equivalent size precast concrete tank, dropped in place
would be much higher.
The largest budgeted item in machinery capital costs was for the field
tractor. The tractor used in the pilot study pulled the septage field tank-
trailer as well as supplying hydraulic power. The tractor might be used
solely for septage injection work or it might be used for other work during
six months of the year.
Labor is a major operating cost. The proper amount of wages to
attribute to field injection depends on the circumstances. Because of
weather conditions and limited volumes of septage a person might not be
needed full time at the site. On the other hand, dangers associated with
the operation of machinery might mandate a two-person crew. The representa-
tive budget provided for one person full time for six months. This presumes
that a one-person equivalent during a six-month period could inject 1.5
million gallons (5,678,000 liters) of septage, maintain the equipment,
manage the site, and keep records.
Estimated total annual costs of $11,549 are divided between capital
costs of $5,989 including $1,000 for land costs, and operating costs, of
$5,560. The operating budgeted costs for 1.5 million gallons (5.7 million
liters) of septage gives an average of $3.77 per 1,000 gallons ($1.00 per
1,000 liters). Other budgets for differing septage volumes and different
operating procedures would, of course, give different budgeted cost figures.
The significance of these findings lies, first, in the listing of some-
what compatibly sized components required for the injection system that was
based on the experiences of a pilot operation. Secondly, cost of soil injec-
tion as opposed to lower cost disposal in excavated pits may be justified
because the septage is better degraded. The degradation resulting from soil
injection compares favorably to what can be achieved in a WPCF having ter-
tiary treatment.
121
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OFF SEASON HANDLING OF SEPTAGE
A dual system of septage disposal might be established that would provide
for trucking septage from the storage tank on the disposal site to a municipal
WPCF during periods when injection is not feasible. The cost of conveyance
in large trailer trucks of 4,000 gallon (15,140 liters) capacity would probab-
ly be similar to that for liquid petroleum. Rates, current in 1971, set by
the Connecticut Public Utilities Commission for trucking liquid petroleum
are as folloivs:
Trucking Rates
One-Way Distance Per 1000 Per 1000
In Miles Gallons Liters
15 $5.40 $1.43
20 6.30 1.66
25 7.10 1.88
30 8.10 2.14
35 9.10 2.40
40 9.70 2.56
Charges levied by the facility that accepted the septage, which might be in
the range of $3 to $5 per 1,000 gallons ($0.79 to $1.32 per 1,000 liters) of
septage, would have to be added to the trucking charge and the costs associ-
ated with operating the storage facility.
If all the septage pumped in an area were to be disposed of by soil
injection, additional storage would have to be built. For each 10,000
population an additional tank of 190,000 gallons (719,000 liters) would be
required for cold weather storage. If these storage costs were to be
amortized at 5 percent on a ten-year basis, this would require an additional
annual capital expenditure of $5,030.
For soil injection to be a solution by itself, implementation of new
concepts in scheduling pumping of septage could be invoked. For example,
a community might require the compulsory pumping of septic tanks on a pre-
determined calendar schedule. Off season pumping, then might be restricted
to emergency needs. Such a regulated program of pumping might be combined
with a program of inspection and enforced correction of septic tank systems
not meeting present-day health standards. The enforcement of these regula-
tions would partially affect the limitations of season (temperature) and the
weather elements. Regulated pumping, however, could disadvantage commercial
pumpers whose businesses would become even more seasonal than at present.
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SECTION 8
COSTS FOR TREATING SEPTAGE IN CONVENTIONAL
WATER POLLUTION CONTROL FACILITIES
Both experimental results and field experience demonstrate that septage
can be successfully treated in conventional water pollution control facili-
ties. The maximum quantity of septage treatable at a plant and the associa-
ted costs depend on plant size, design characteristics, and sewage flow in
relation to design capacity. While this section of the report is focused on
treatment operating costs, consideration must also be given to maximum volume
determinants for any given plant.
Available plant capacity, and the ratio of septage to sewage, must be
considered in determining the volume of septage treatable at a particular
facility. Some problems associated with septage treatment can be reduced
through use of a storage tank and pump system for introducing septage at a
controlled rate into the treatment plant. Plants receiving a small volume
of sewage, those with less than 1.0 mgd, may need a storage tank-pump system
for septage to avoid shock resulting from the rapid discharge of loads of
septage.
There is no direct way of measuring the incremental operating costs of
treating septage at water pollution control plants. Because septage relative
to sewage generally comprises such a small volume, usually less than 0.5 per-
cent of total influent, changes in septage flow do not show in operation
costs. For instance, seasonal and day-to-day variations in septage receipts
do not result in identifiable variations in operating costs. Likewise, dif-
ferences in plant design, sewage characteristics and operating practices
preclude the comparative analysis approach.
No attempt has been made to assign capital costs for treating septage.
Much of the capital costs for municipal water pollution control facilities
are now covered by federal and state grants. However, when costs are borne
locally, they should be of concern in determining charges for septage treat-
ment.
One approach to estimating septage treatment operating costs is to begin
with the average cost of treating sewage and then adjust for the relative
composition of septage and sewage. A second approach is to examine and apply
surcharges of the type used for strong industrial wastewater.
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SEPTAGE/SEWAGE OPERATING TREATMENT COST RATIO
The component parameters measured for septage are not in the same pro-
portions as are those found in sewage. However, treatment costs can be esti-
mated for the parameters which are similar for both sewage and septage. Total
solids of the septage and 8005 of the supernatant from primary settling appear
to be directly related to the economically important processes in a plant with
activated sludge, anaerobic sludge digestion and vacuum filtration.
The objective of the cost ratio analysis is to relate the costs of
treating septage to the costs of treating sewage through adjustments that
account for the relative concentrations of major waste components. The ad-
justment process involves two steps:
(1) An identification of the percentage of operating costs associated
with particular waste components, and
(2) A combination of cost distribution percentages with concentration
ratios.
Taken together, these provide an estimate of the cost relationships between
sewage treatment and septage treatment.
The addition of water alone to a system appears to increase operating
costs by only 40 percent as much as the addition of the same volume of
sewage. This estimate was derived through a simulation model (Smith, R.E.,
et al., 1968; and Leonard, current research). Thus, if 40 percent of the
operating costs can be attributed to volume, the remaining 60 percent can
be attributed to content, Table 23.
TABLE 23. DISTRIBUTION OF OPERATING COSTS
FOR SEWAGE TREATMENT
Primary phase
Volume 20%
Total Solids 30%
Subtotal 50%
Secondary phase
Volume 20%
Supernatant BOD 50%
Subtotal 50%
TOTAL 100%
The costs associated with inflow content can be further subdivided
between primary and secondary treatment phases through the following assump-
tions: (1) that costs associated with content for the primary phase
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(including preliminary treatment, sludge digestion, and solids disposal) are
in proportion to the amount of total solids in the influent wastewater; and
(2) that costs associated with content for the secondary phase (including
chlorination) are in proportion to the 8005 of the influent to the secondary
treatment phase. Available data indicate that the primary and secondary
treatment phases account for approximately equal shares of the total operating
costs (Smith, R.E., et al., 1968).
TABLE 24. CONCENTRATION RATIOS FOR SOLIDS
AND BOD5 IN SEPTAGE AND SEWAGE
Total solids in septage 23,700 mg/1
Total solids in sewage 553 mg/1
Concentration ratio 42.3 to 1
Supernatant 8005 for septage 1,860 mg/1
Supernatant BODc for sewage 120 mg/1
Concentration ratio 15.5 to 1
The septage characteristics shown in Table 24 are the weighted mean
values for the Connecticut samples analyzed. Data for sewage are mean values
for wastewater treated during 1969 at the Metropolitan District Coirtmission
Water Pollution Control Plant in Hartford, Connecticut.
These concentration ratios in combination with the estimated distribution
of costs provide a basis for estimating the cost of treating septage in rela*-
tion to the cost of sewage treatment. For any given plant, let "C" represent
the operating and maintenance costs per thousand gallons of sewage treated.
The cost per thousand gallons for treating septage can then be estimated by
components as follows:
Water, 0.20C + 0.20C = .40C
Total solids, 0.30 (42.3)C= 12.69C
Supernatant BOD., 0.30
(15.5)C = 4.65C
TOTAL 17.74C
Thus, the rule of thumb suggested by the analysis is that for a given
plant with sufficient capacity for handling septage, the cost of treating
1,000 gallons (3,785 liters) of septage is approximately 18 times the costs
of treating 1,000 gallons (3,785 liters) of sewage in that plant.
Sewage treatment costs data for the period 1965-1968 are available from
federal audits of facilities receiving federal construction grants. From
these audits, average operating and maintenance costs for activated sludge
plants were estimated at $.05/1,000 gallons ($0.01/1,000 liters) of sewage
for plants treating 10.0 mgd (37.9 mid) and $.09/1,000 gallons ($0.02/1,000
liters) for plants treating 1.0 mgd (3.8 mid) (Michel, 1970). Limited
available data indicate corresponding current costs in Connecticut might be
about twice these amounts. These adjustments would place the estimated cost
125
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of septage treatment at $1.80/1,000 gallons ($0.48/1,000 liters) in plants
treating 10.0 mgd (37.9 mid) of sewage and $3.24/1,000 gallons ($0.86/1,000
liters) in plants treating 1.0 mgd (3.8 mid) of sewage.
SURCHARGES AND TOTAL CHARGES
An increasing number of municipalities levy additional charges on
industrial firms discharging large quantities of heavily polluted wastewater
into the municipal WPCF. The usual approach is to combine a basic sewer
service charge with a surcharge for wastes exceeding limits defined for
"normal sewage." Surcharges are usually levied on one or more of the
following waste constituents: BOD, suspended solids (SS), pH, and chlorine
demand. Surcharges for BOD and SS that are discussed below may have a direct
bearing on estimating costs and setting charges for treating septage in water
pollution control facilities.
In Connecticut, municipal experience with surcharges has been limited to
a few cases of extra charges levied on an individual basis. On a national
basis surcharge levels vary widely. Averaging surcharge rates for several
municipalities would be misleading. There are variations in the combination
of factors and in the definition of normal sewage. Some rates are clearly
lower than treatment costs. In some cases, the basic sewer service rates and
surcharge rates are set to cover a portion of capital costs as well as
operating and maintenance costs. A perspective on charges for septage
treatment in relation to surcharges for industrial wastewater can be gained
from two examples where the basis of the surcharge is known.
In Charlotte, North Carolina, surcharges are levied to include a pro-
portionate share of capital cost as well as operating cost. The surcharge
is $56.43 per thousand pounds ($0.124/kg) of BOD5 in excess of 250 mg/1
(Franklin, 1969). Of this rate $23.34 is to cover capital costs, while the
remaining $33.09 per thousand pounds of BOD^ is based on current operating
costs. Application of the $56.43 rate to septage with a BODg of 3840 mg/1
(the weighted mean of the Connecticut samples tested) would result in a
surcharge of $1.69 per thousand gallons ($0.45/1,000 liters) of septage.
Major steps in the conversion are:
($.05643/lb BOD5) x (3.840 - .250) Ib BOD5/1,000 Ib
septage x (8345 lb/1,000 gal. septage) = $1.69/1,000 gal.
If only the $33.09 associated with operating cost is used in setting a
surcharge for septage, the surcharge would be $0.99 per thousand gallons
($0.26/1,000 liters) of septage.
Greensboro, North Carolina, levies a surcharge of $15 per thousand
pounds ($0.033/kg) of suspended solids in excess of 300 mg/1 and $22 per
thousand pounds ($0.048/k ) of BOD5 in excess of 300 mg/1 (Shaw, 1969).
From the explanation of water and sewer pricing, it would appear that a
small but unidentifiable share of capital costs is included in the surcharge.
Application of the Greensboro surcharge to a septage with a 6005 of 3840 mg/1
and a supernatant SS of 2530 mg/1 (the weighted mean of Connecticut samples
126
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tested) would result in a surcnarge of $0.93 per thousand gallons ($0.25/
1,000 liters) of sepcage. Inasmuch as the total solids in sepcage, 23,700
mg/1, is very high in relation to total SS in sewage, application of the
Greensboro surcnarge with total solids instead of supernatant SS appears to
be more realistic than the use of SS alone. Using total solids and BOD,, for
septage in the Greensboro surcnarge formula would result in a surcharge of
$3.58 per thousand gallons ($0.95/1,000 liters) of septage.
In both Charlotte and Greensboro, the basic sewer service charge to
which the surcnarge is added is on a declining block pricing system. For
instance, the first block rates began at $.40 per thousand gallons ($0.11/
1,000 liters) in Charlotte and $.44 per thousand gallons ($0.12/1,000 liters)
in Greensboro. These basic rates cover both the operating costs and a por-
tion of the capital costs for the sewer collection and treatment system.
The Charlotte basic sewer service charge plus the surcharge applied to
septage would result in a total charge of $2.09 per tnousand gallons ($0.55/
1,000 liters) of septage. The Greensboro basic service charge plus the
surcharge would be equivalent to a charge for septage of $4.02 per thousand
gallons ($1.06/1,000 liters).
127
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SECTION 9
ECONOMIC AND GOVERNMENTAL ASPECTS OF SEPTAGE DISPOSAL
The septic tank pumping industry is a competitive one in Connecticut.
There are about 200 privately owned firms that provide pumping services, and
almost all parts of the state are served by more than one pumper. Pumping
may be a specialized business activity or associated with septic tank-soil
absorption system installation and repair. There are no franchises for
pumping and usually no municipal licenses are required. Pumpers pay dumping
fees for deliveries made to the municipal disposal facilities. These dumping
charges are passed on to the septic tank owners in their septic tank pumping
charges.
In some parts of the state, pumpers may own or lease their disposal
sites which are usually excavated pits or trenches. These areas may or may
not be fenced. Costs associated with this method of disposal are usually
minimal. In addition to land costs, other costs include occasional bull-
dozer work for excavations and roadway maintenance.
MUNICIPAL PROVISION FOR SEPTAGE DISPOSAL
Municipalities vary widely in the provisions they make for septage
disposal. Many municipalities that operate WPCF provide for septage disposal
at such facilities. However, most pumpers feel that improvements can be made
at the septage receiving station locations.
Approximately 120 of the 169 general municipalities in Connecticut
either have no WPCF or have a facility of insufficient size or capacity for
processing septage. About 15 percent of those municipalities that are with-
out available WPCF for septage disposal provide public disposal land sites,
usually excavation pits, or have septage disposal agreements with adjacent
municipalities. A few municipalities have installed lagoons in series.
Each municipality that allows septage disposal in its WPCF establishes
the dumping charges or fees that pumpers pay and regulates the receiving of
septage. Dumping fees in 1972 for septage coming from within municipalities
and delivered to their respective WPCF varied from no charge to seldom more
than $5.00 per 1,000 gallons ($1.32 per 1,000 liters). Usual dumping charges
are not inconsistent with cost estimates for processing septage which were
discussed in the section on surcharges and total charges. Some municipali-
ties have regulations to exclude septage pumped outside the municipality.
Others may set higher dumping fees for septage brought in from adjacent
municipalities than fees for within-town septage.
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Usually, septage disposal policies are made unilaterally by each
municipality; these policies can be changed at municipal discretion. A
recent example of unilateral action was that of a city with a large WPCF
which for years had accepted at no charge the septage from adjacent munici-
palities. These were suburban municipalities without WPCF's. The city
without consultation with these municipalities announced its unwillingness
to accept such septage in the absence of intermunicipal agreements, but
later, in response to protests, established instead unusually high fees
for receiving out-of-city septage. Another example is that of a munici-
pality with a new WPCF that set sufficiently high fees for outside septage
so as to exclude it. However, setting dumping fees at exclusionary levels
or to limit septage receipts are exceptions and do not reflect representative
practices for Connecticut.
There are, of course, exceptions to unilateral municipal regulation of
septage disposal. In a few instances municipalities that have a joint sewer
system make joint provision for septage disposal. Inasmuch as almost all
municipal WPCF's are under separate municipal control, however, there are
few built-in incentives for more joint actions. In areas where excavation
pits are the disposal method, there is a growing interest in joint municipal
actions.
Positive municipal action to provide septage disposal facilities would
appear to have been mandated in a 1971 Connecticut Statute, Chapter 361a,
Solid Waste Management, Section 19-524n, which reads, in part, "Each
municipal authority shall make provisions for the safe and sanitary dis-
posal of all solid wastes which are generated within its boundaries,
including septic tank pumpings ..." (emphasis added). Municipal responses
were often not what was expected. In some municipalities where no provision
was made for septage disposal, municipal executives interpreted the law to
mean that if pumpers were able to find or provide their own disposal sites,
as they were obviously already doing, then no municipal action was required.
On the other hand, the amendment has suggested to pumpers in a few localities
that job action or the threat of job action may be a legitimate means to
force municipalities to do what would appear to be what the legislature
had in mind.
STATE POLICY CONSIDERATIONS
Developing a state policy for septage disposal in a state even as small
as Connecticut is complicated by differing physical and economic situations
such as watershed areas for public water supplies, availability of disposal
sites, distances to approved disposal sites, and extent of residential and
recreation development. Furthermore, in New England general municipal
governmental powers rest with towns of relatively small size (townships)
which in Connecticut are seldom more than 50 square miles. Municipal-
based systems might often display limitations imposed by small size, but
they would reflect the differences in the disposal problem to be solved.
Intermunicipal disposal systems that recognize municipal differences might
more than counterbalance inefficiencies associated with size and lack of
uniformity. Therefore, if varied solutions are an acceptable end product,
129
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then the planning process could be one that took local situations into
account and reacted positively to those differing situations.
A state-municipal interactive process for septage disposal is implied
in the 1971 Act on Solid Waste Management. This Act, referred to above,
requires the Department of Environmental Protection to prepare a solid waste
management plan for each solid waste planning region in the state. Because
solid waste includes septage, planning for septage disposal is being given
attention. To the maximum extent feasible, the state's regional planning
agencies are to be allowed to prepare solid waste management plans. Munici-
palities are indirectly made a part of the planning process through their
representatives on the boards of directors of the planning agencies. When
completed, each municipality is to adopt the regional solid waste management
plan and its own municipal plan. Each local plan will require the approval
of the State Commissioner and the regional planning agency.
The 1972 Session of the Connecticut Legislature appropriated funds for
the preparation of a state-wide plan for solid waste disposal. The General
Electric Company, to whom a contract to this end was awarded, has taken under
advisement how septage disposal might be made a part of solid waste disposal
activities.
Legislation alone will not insure the provision of adequate septage
disposal practices or facilities. Such measures must be accompanied by pro-
grams which encourage public responsibility for action. However, legislative
intent formulated as state policy can help guide septage disposal programming.
In so doing, the problems of municipal indifference and laggardness may be
overcome, and incidents such as unnecessary confrontations leading to pumper
strikes can be avoided.
FEDERAL POLICY CONSIDERATIONS
Septage is clearly a "pollutant" as the term is defined in Sec. 502(6)
of the Federal Water Pollution Control Act Amendments of 1972 (Public Law
92-500). Likewise, facilities for receiving and treating of septage are
within the definition of "treatment works" as the term is defined in
Sec. 212(2)(A) of the same Act. This latter definition qualifies septage
receiving and treatment facilities for Federal grants for the construction
of publicly owned treatment works. Moreover, the definition of "treatment
works" includes "... site acquisition of the land that will be an integral
part of the treatment process or is used for ultimate disposal of residues
resulting from such treatment."
130
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SECTION 10
SEPTAGE RECEIVING STATIONS
Where septage is handled for treatment at Connecticut water pollution
control facilities, the facilities provided have generally been considered
to be inadequate in terms of sanitation, aesthetics, and efficiency of septage
discharge. To effectively overcome the objections in the areas indicated,
the design and layout of a septage receiving station should be approached
from both the septage hauler and water pollution control facility point of
view. This approach was taken and a basic plan layout, Figure 55, was
developed for a septage receiving station. Suggested modifications of the
basic layout are given in Figures 56 and 57. This information can be related
as necessary to water pollution control facility sites by the designer or
engineer. In addition, a final design or layout should meet the following
criteria:
(1) From the septage hauler point of view.
(a) An easily accessible discharge point is desirable with simple
transport vehicle movement. A straight through traffic pattern
is preferred as shown in Figure 55. A turn-around drive loop
is a less desirable alternative.
(b) The point for septage discharge from the truck should be one
that little or no spillage may occur.
(c) Provision should be made for septage discharge by gravity.
(d) Water should be available for cleaning the septage transport
vehicle and any septage spillage resulting from discharge.
For cleaning purposes, a high pressure water system is pre-
ferred. The sepage hauler should be able to personally clean
up before leaving the septage receiving station.
(f) The area should be well lighted.
(g) A telephone booth at the receiving station site is a desirable
convenience item.
(2) From the water pollution control facility point of view.
(a) The locations for receiving septage should be at points where
treatment plant operators can know about and control dumpings.
131
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(b) Aesthetic consideration with regard to dumping site is impor-
tant. For example, septage discharge in front of a water
pollution control facility greatly detracts from a good public
image.
(c) The septage receiving station area should be one which easily
promotes cleanliness.
(d) Septage may be either discharged directly into the incoming
sewage or into storage tanks. If stored, septage is then
pumped into the waste treatment process in controlled quanti-
ties in order to have the least effect on the treatment
processes.
(e) Adequate inflow pipe size, no smaller than eight inches in
diameter, is suggested for handling septage discharges from
trucks.
(f) Attractive fencing enclosures may be necessary.
Keeping the above points in mind should result in the design of septage
receiving facilities in accordance with today's needs. It should be remem-
bered that septage can at times be unpleasantly odoriferous. The odors can
permeate the atmosphere to an area beyond the water pollution control
facility itself as well as penetrating within the treatment plant itself.
Proper septage receiving station design as suggested can contribute to con-
taining such odors.
Although the above criteria were developed for septage receiving stations,
a similar approach is applicable for septage discharged at land disposal sites.
135
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Research Laboratory (1968).
Steel, R.G. D., and Torrie, J.H., Principles and Procedures of Statistics,
McGraw-Hill Book Company, Inc., New York (1960).
138
-------
Stolp, H., and Starr, M.P., "Bdellovibrio bacteriovorus Gen. and Sp. N.,
A Predatory Ectoparasitic Bacteriolytic Microorganisms," Antonie von
Leeuvenhoek Journal of Microbiology and Serology, 29, pp 217-248 (1963).
Stuart, C.A., Von Stratum, E., and Rustigan, R., "Further Studies on
Urease Production by Proteus and Related Organisms," Journal of Bacteriology,
49, pp 437-444 (1945).
Terreator, U.S. Patent No. 2,694,354, Manufactured by McAdam and Sons,
8718 Main Street, Barker, New York.
Wengel, R.W., and Kolega, J.J., "Effect of High-Rate Manure Applications
on the Soil," Paper presented at the Conn.-Mass., Poultry Engineering
Seminar and New England Farm Electrification Institute (1970).
139
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PUBLICATIONS
Calabro, J.F., Cosenza, B.J., and Kolega, J.J., "Recovery of Gram Negative
Bacteria with Hektoen Agar," Journal Water Pollution Control Federation,
44, No. 3, pp 491-493 (March, 1972).
Calabro, J.F., Cosenza, B.J., and Kolega, J.J., "Bacteriophages Recovered
from Septage, "Journal Water Pollution Control Federatipn, 44, No. 12,
pp 2355-2358 (December, 1972).
Kolega, John J., "Design Curves for Septage," Water and Sewage Works, 118,
No. 5, pp 132-135 (May 1971).
Kolega, J.J., Dewey, A.W., and Shu, C.S., "Streamline Septage Receiving
Stations," Water and Wastes Engineering, 8, No. 7, (July, 1971).
Kolega, J.J., Cosenza, Dewey, A.W., and Leonard, R.L., "Septage: Wastes
Pumped from Septic Tanks," Transactions of the ASAE, 15, No. 6, pp 1124-1127
(1972).
Kolega, J.J., Dewey, A.W., Leonard, R.L., and Cosenza, B.J., "Land Disposal
of Septage (Septic Tank Pumpings)," Pollution: Engineering and Scientific
Solutions, Edited by Euval S. Barrekette, Plenum Publishing Corp. New York,
N.Y. (1973).
Kolega, J.J., Chuang, F.S., Cosenza, B.J., and Dhodi, J., "Anaerobic-Aerobic
Treatment of Septage," Proceedings of the 28th Industrial Waste Conference,
Engineering Extension Series No. 142, Purdue University, Lafayette, Ind.
(May, 1973).
Kolega, J.J., and Dewey, A.W., "Septage Disposal Practices," Proceedings of
the National Home Sewage Disposal Symposium, American Society of Agricultural
Engineers, St. Joseph, Mich., pp 122-129 (1974).
Citations
Goldstein, S.N., and Moberg, W.J., Jr., Wastewater Treatment Systems
for Rural Communities, Commission on Rural Water, Washington, D.C.,
pp 84-88 (1973).
, Planning Guidelines for Sanitary Waste Facilities,
U.S. Department of Agriculture Forest Service, California Region, pp 8-23
(January, 1972).
140
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APPENDIX A
QUESTIONNAIRE MAILED TO HOMEOWNERS
UNIVERSITY OF CONNECTICUT
Storrs, Connecticut
August 5, 1969
Dear
Your assistance will be helpful in planning for the proper disposal
of wastes pumped from septic tanks. Data from individual households in
selected areas will be used in estimating the current and future volume
of pumped wastes. A reply envelope and a summary of the major aspects
of the research project are enclosed.
Questions you may have regarding the use and management of home
sewage disposal systems will be answered to the extent that information
is available. If you have no questions and wish to remain anonymous,
tear off the name and address.
Thank you,
John J. Kolega, Associate Professor
Department of Agricultural
Engineering
When was the septic tank and drainage system installed?
When was the septic tank last cleaned? _
(a) Just prior to the last cleaning:
Was water rising to the ground surface? ____^___
Were drains from the house slow or inoperative
(b) If the system was functioning properly why did you decide to have
the tank cleaned?
How many times has the tank been cleaned in the last three years?
What is the size of the septic tank? __^___ gallons. (Known
-» estimated )",
Hew many persons use the system?
No. of adults _ . No. of children ages 12 to 18 _ . No. under 12
Is laundry water discharged into the septic tank? _
Is kitchen water discharged into the septic tank? _
Do you have a garbage disposal? _
Have you had any problems with the septic tank or drainage system not
covered by the above questions?
How long have you lived at your current address?
Your Comments or Questions (continue on back if additional space is needed),
141
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APPENDIX B
QUESTIONNAIRE MAILED TO SEPTIC TANK PUMPERS
UNIVERSITY OF CONNECTICUT
Storrs Agricultural Experiment Station
Storrs, Conn. 06268
November lit, 1969
Dear
As a part of our research study for finding better ways for dis-
posal of septage, Art Dewey and Bob Leonard of the Department of Agri-
cultural Economics, need information on the pumping of household septic
tanks. Two summary reports are enclosed on what this research study is
about. In order for us to do an adequate job, your cooperation is
needed.
If you pump septic tanks, please fill out the questionnaire below
as best you can and return it in the postage-paid self-addressed enve-
lope. If you wish to remain anonymous please tear off your name.
Very truly yours,
J. Kolega
Department of Agricultural
Engineering
1. What is the capacity of each truck you use for hauling septage?
gallons _ gallons _________ gallons gallons
2. How many household septic tanks did you pump last year?
3. How much of the household septage you pumped was handled at sewage
treatment plants? (Check one).
None _ , 1/3 _ , 1/2 _ _ , 3/h _ _, all _ .
1*. What is a reasonable maximum one-way distance for hauling septage?
5>. What problems result from dumping in fields, trenches or lagoons?
6. Do you feel that all disposal sites should be public and operated
by town governments?
7. What should a good septage dumping facility include?
142
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APPENDIX C
LABORATORY ANALYSES SUMMARY3
Total Number of
Parameter Number of Samples Test Replications
BOD5 Septage 85 28?
BOD- Supernatant 47 204
COD Septage 10? 2?1
COD Supernatant 6l 185
Total Solids 104 153
Volatile Total
Solids 104 153
Fixed Total
Solids 104 153
Total Suspended
Solids 51 77
Volatile Suspended
Solids 51 74
Organic Nitrogen 63 77
Free Ammonia 75 94
aThe total number of different septage samples analyzed
were 180.
143
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APPENDIX D
NITROGEN APPLICATION CALCULATIONS
Sample Calculations for Rate of Nitrogen-N. Application
for Land Disposal of Septage.
Free Ammonia, 75% design valuei 92 mg/1
Organic Nitrogen, " " 37 mg/1
Assumption of above summation as 129 mg/1
being equal to total Nitrogen
Free ammonia and ammonia-nitrogen are the same
in meaning.
1 ppm is equal to approximately 1 mg/1 which is equal to
approximately 8.3^ lbs/1,000,000 gallons
Ibs of Nitrogen/1,000,000 gals = 129 x 8.3** Ibs
(1,000,000 gals)
= 1075 Ibs N/1,000,000 gallons
septage (75$> design)
Selecting a maximum Nitrogen application rate of 300 Ibs/acre
Gallons Septage to be Applied = 300 Ibs N/acre
per acre 1075 Ibs N/1,000,000 gals
= 279.000 gallons septage/acre
OR
Acreage required/1,000,000 gallons of septage =
1075 Ibs N/l.000.000 gals
300 Ibs N/acre
= 3.58 acres needed for
1,000,000 gallons of sep-
tage
144
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APPENDIX E
SEPTAGE LAND APPLICATION DATA
Location: White Memorial Foundation, Inc., litchfield, Ct,
Time Period: July 20, 1971 through October 1U, 1971
Date
Trailer Estimated Cumulative
No. of Loads, 800 Septage Volume
Passes of Gallons per Volume, Injected,
Method of Injection 1*00 ft. Load (gals.) (gals.)
July 20
21
27
27
28
29
Aug. 5
5
9
10
11
Plow-Furrow-Cover 17 10 8,000 8,000
Plow-Furrow-Cover 22 11 8,800 16,800
Plow-Furrow-Cover 17 6 U,800 21,600
Sub-Sod Injector 5 5 l*,000 25,600
Sub-Sod Injector 8 8 6,1*00 32,000
Sub-Sod Injector 5 5 I*,000 36,000
Sub-Sod Injector 11 800 36,800
Plow-Furrow-Cover 1 1 800 37,600
Problem: Tractor-trailer stuck. The tractor wheel had gone
over an area where septage had been injected pre-
viously (at an earlier date).
Observations Difficulty was probably due to wet field con-
ditions. There was a fair amount of rainfall
that week.
Action taken: Delayed field application of septage (August
6, Friday, and weekend until Jfonday, August 9).
Plow-Furrow-Cover41 25 13 10,^00 1*8,000
Plow-Furrow-Cover Ik 7 5,600 53,600
Plow-Furrow-Cover 6 3 2,1*00 56,000
Problem Field conditions wetj operation stopped because of
rain.
12 Sub-Sod Injector
2,1*00
58,uoo
Problem? Field conditions wet. Septage application still
possible.
13 Terreator
800
59,200
Problem: Hydraulic oscillating mechanism did not perform
satisfactorily.
a Second septage application coverage for this area.
145
-------
APPENDIX £ (Continued)
Trailer Estimated Cumulative
Ho. of Loads, 800 Septage Volume
Passes of Gallons per Volume, Injected,
Date ffethod of Injection UOO ft. Load (gals. ) (gals.)
Aug. 16 Terreator 11 10 7,000 66,200
22 Sub-Sod Injector 11 800 67,000
22 Plow-Furrow-Cover 1 1 800 67,800
2U Sub-Sod Injector Applications made; data not entered
31 Sub- Sod Injector . 5 5 U,000 71,800
31 Plow-Furrow-Cover 16 8 6,1*00 78,200
Problem: Plow tripped three tines during P-F-C series. Wet
field conditions was the reason for changeover from
S-S-I to P-F-C method. (Tropical storm in area on
Friday and Saturday.)
Sept. 3 Plow-Furrow-Cover 22 11 8,800 87,000
Problem: Plow tripped 11 times.
8 Plow-Furrow-Cover 20 10 8,000 97,000
Problem: Plow tripped 10 times.
10 Scheduled field application, but septage not available.
16 Sub-Sod Injector 2 1 800 97,800
Reclaimed pasture area used.
Problem: Rain on weekend and during week; wet field condi-
tions which prevented septage application.
30 Sub-Sod Injector 10 10 8,000 10$, 300
Oct. h Sub-Sod Injector 3 3 2,UOO 108,200
Problem: Insufficient quantity of septage.
5
13
1U
Plow-Furrow-Cover
Plow- Furrow-Cover
Plow-Furrow-Cover
$
6
9
2.5
3
5
2,000
2,iiOO
U,ooo
110,200
112,600
116,600
Third septage application coverage for this area.
146
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APPENDIX F
IDENTIFICATION KEY TO CHARACTERIZATION OF BACTERIA
ISOLATED FROM SEPTAGE AND/OR SEPTIC TANK SEWAGE.
PD - Phenylalanine deaminase
LD - Lysine decarboxylase
CO - Cytochrome oxidase
1. Klebsiella-Enterobacter
2. Aerobacter-Serratia
3. Escherichia coli
**• Providenis sp.
5. Proteus rettgeri
6. P. morganii
7. Citrobacter sp.
8. Arizona sp.
9. P. mirabilis
10. P. vulgaris
11. Salmonella sp.
12. S. typhi
13. Shigella sp.
1^-. S. paratyphi A
15. S. cholerae-suis
16. Escherichia
1?. Mima
18. Herellea
19. Achromqbacter
20, Pseudomonas
21. Aeromonas
22. Alcaligenes
23. Mima •polvmorpha var. oxidans
147
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APPENDIX G
AERATION PROCESSES
Table 1. AERATION PROCESS REQUIREMENTS FOR TREATMENT OF
SEPTAGE AS COMPARED TO SEWAGE TREATMENT PRACTICE
Parameter
Detention time
Oxygen required
Area required
Costs
Septage
(1) 3.9 days
(2) 7.8 days
(1) 38.6 Ib. o.c./day
(2) 38.6 Ib. o.c./day
(1) 521 ft3
9' -0" x 19' -U" x 3'
(2) 10U2.5 ft3
-0" x 23' -8" x U* -0"
$ 10(123 x U7)3/U
• 6.70/1000 gal
Power required 300 hp/iagd
Sewage
(1) 0.39 days
(2) 0.78 days
(1) 3.9 Ib. o.c./day
(2) 3.9 Ib. o.c./day
(1) 52 ft3
(2) 10U ft3
$ 10(12.3 x U7)3A
• 1.20/1-000 gal
50 hp/wgd
(1) Conventional activated sludge process
(2) Extended aeration activated sludge process
o.c. " oxygenation
capacity
Table 2. FEATURES OF AERATION PROCESSES (GLOXNA, E.F. ET AL, 1968).
Process
Conventional
Activated Sludge
Extended
Aeration
Contact
Stabilization
High Rate
Activated Sludge
Loading Range 3
Population Ibs. BOD/day/1000 ft
Range Aeration Volume
Unlimited
500 - 5000
1500 to
Unlimited
10,000 to
Unlimited
25 -
10 -
25 -
100 -
50
15
75
150
Degree
of
Removal (%)
90-95
85 - 90
85 - 90
50 - 75
148
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APPEMDIX H
FREQUENCY OF PUMPING IN RELATION TO SIZE OF SEPTIC TANK
Number of tanks
15
1
"t>
rt
f
1
(8
C
1
*
1
01
1
o
i
1
1U
13
12
11
10
9
8
7
6
5
U
3
2
i
0
1
1
U
7
26
27
1
U
5
1
1
2
2
16
11
1
2
11
8
1
1
1
3
9
1
1
5
11
17
1
1
2
Unknown 200- UOO- 600- 800- 1000- 1200- 11|00+
399 599 799 999 1199 1399
Tank size (gallons)
149
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APPENDIX I
SEPTAGE* SEMINAR
University of Connecticut
College of Agriculture & Natural Resources Auditorium
Storrs, Connecticut
PROGRAM SPONSORSHIP
Storrs Agricultural Experiment Station
Cooperative Extension Service
Institute of Water Resources
Conn. State Dept. of Health Environmental
Health Services Division
Connecticut Sewage Disposal Association
January 28, 1971
9*30 - 10:00 A.M. Registration
Program Moderator for Morning Sessiont
G. Kenneth Dotson, Advanced Waste Treatment Research
Laboratory, U.S. Dept. of Interior, Federal Water
Quality Administration, Cincinnati, Ohio.
10«00 - 10»30 A.M. Biological Parameters of Septage
Micro-organisms found in septage and their distri-
bution? a comparative evaluation in terms of simi-
larities or differences to known microorganisms of
conventional water pollution control facilities;
are pathogens present?
10*30 ~ 11*00 A.M. Physical and Chemical Parameters
of Septage
The presentation of design curves and their use
based upon analyses of septage for BOD, COD, total
solids, volatile solids, suspended solids, free
ammonia, and organic nitrogen; data on odor, set-
tling rates, color, and observed pH levels.
11*00 - 11»15 A.M. Break
11*15 - 11*^5 A.M. Volumes and Implications for Dis-
posed Septage
150
-------
Estimated total and per capita septage volumes
have been developed for the state and for thir-
teen subregions. These estimates together with
information on pumper disposal requirements and
on municipal dumping regulations will be used to
define economic aspects of septage disposal
problems. The methodology for making volume
estimates will be briefly discussed.
lltV? - 12»15 P.M. Costs Associated with Septage
Treatment
Data on the content of septage will be related
to the operating and maintenance costs of parti-
cular sewage treatment processes.
12tl5 - 12«^5 P.M. Pilot Studiest Progress Report
Septage injection in soilj interstate activities!
discharging septage at water pollution control
facilities.
IjOO - 2tOO P.M. LUNCH
Program Moderator for Afternoon Sessioni
Joseph Kosman, Municipal Wastewater Control Section,
Environmental Health Services Division of the Connecti-
cut State Department of Health, Hartford, Connecticut.
2il5 - 3-.00 P.M. W. Widmer, Civil Engineering De-
partment, "A Sanitary Engineer in
Pakistan."
3«00 - 3»^5 P.M. An Economic Engineering Analysis
of Septage Disposal Systems.
Types of septage disposal systems; criteria for
their evaluation and systems evaluation.
3:^5 - *J-*14 P.M. Open Discussion
*Septage, or septic tank pumpings, is defined as the mixed
liquid and solid contents pumped from septic tanks and dry
wells used for receiving domestic type sewage.
151
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-77-198
3. RECIPIENT'S ACCESSIOt^NO.
4. TITLE AND SUBTITLE
TREATMENT AND DISPOSAL OF WASTES PUMPED FROM
SEPTIC TANKS
5. REPORT DATE
September 1977 (Issuing Date]
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS) John j_ Kolega, Arthur W. Dewey,
Benjamin J. Cosenza, Robert L. Leonard
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDfieigSji ; '•
Storrs Agricultural Experiment Station
University of Connecticut
Storrs, Connecticut 06268
10. PROGRAM ELEMENT NO.
1BC611
11. CONTRACT/GRANT NO.
17070 DKA
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal 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/600/14
15. SUPPLEMENTARY NOTES
Project Officer: G. Kenneth Dotson (513) 684-7661
16. ABSTRACT
The study identified methods of treating and disposing of septic tank sludge
(septage). Biological, chemical, and physical properties of septage were determined
and curves were developed for designing septage treatment facilities.
Two processes were tested for treating and disposing of septage. Injecting
septage in the soil appears to be practical, but is limited to periods when the
ground is not frozen. A bench and pilot process that reduced BOD , COD, and
Kjeldahl nitrogen by 93 percent or more consisted of anaerobic digestion-aeration-
sand filtration.
Consideration was given to treating septage in publicly owned wastewater treat-
ment plants with municipal wastewater. Criteria for desirable receiving facilities
were developed.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Waste treatment
Digestion
Sludge disposal
Septic tanks
b.IDENTIFIERS/OPEN ENDEDTERMS
Septage treatment
Soil injection
Septage disposal
Aerobic treatment
Anaerobic digestion
Soil treatment
COSATl Field/Group
13B
18. DISTRIBUTION STATEMENT
RELEASE T0 PUBLIC
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
168
20 SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
152
•& U S GOVERNMENT PRINTING OFflCE- 1977-757-056/6558 Region No. 5-11
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