United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/8-80-032
Laboratory August 1980
Cincinnati OH 45268
vvEPA
Research and Development
Septage
Management
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2, Environmental Protection Technology
3. Ecological Research
4, Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the "SPECIAL" REPORTS series. This series is
reserved for reports targeted to meet the technical information needs of specific
user groups. The series includes problem-oriented reports, research application
reports, and executive summary documents. Examples include state-of-the-art
analyses, technology assessments, design manuals, user manuals, and reports
on the results of major research and development efforts.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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SEPTAGE MANAGEMENT
by
Joseph W. Rezek
Ivan .A. Cooper
Rezek, Henry, Meisenheimer and Gende, Inc.
Libertyville, Illinois 60048
Contract Number 68-03-2231
Project Officer
James F. Kreissl
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
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r
DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U. S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U. S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
11
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FOREWORD
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 pur natural environment. The complexity
of that environment and the interplay between its components re-
quire a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution and it involves defining the problem, measuring
its impact, and searching for solutions. The Municipal Environ-
mental Research Laboratory develops new and improved technology
and systems for the prevention, treatment, and management 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 pol-
lution. This publication is one of the products of that re-
search; a most vital communications link,between the researcher
and the user community.
This study represents a significant effort to document the
state of the art of the treatment, disposal and management of
septic tank pumpings in the United States. This source of
treatment residuals, often referred to as "septage", represents
a major public health and environmental hazard which is particu-
larly vexing due to its overall volume and its diffuse nature of
generation. By documenting some of the more enlightened tech-
niques of septage management employed ascertain locations, this
report represents a major contribution to those charged with
these responsibilities throughout the country.
Francis T. Mayo
Director
Municipal Environmental
Research Laboratory
Office of Research and Development
111
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ABSTRACT
This report presents state-of-the-art information for imple-
menting cost effective and environmentally sound solutions to
the nationwide problem of septic tank sludge (septage) treatment
and disposal.
Current hauler practices, septage characterization, and
regulatory control are presented. Design concepts of full scale
and pilot installations are presented for land disposal schemes,
for separate septage treatment processes in areas with suffi-
cient septage volumes to support such a facility, and for sep-
tage disposal at sewage treatment plants (STP). Actual system
costs and environmental and socio-economic acceptability for
many actual and proposed treatment schemes are detailed to as-
sist in the selection of the best treatment scheme for a parti-
cular locale at the least possible cost.
This report was submitted in fulfillment of Contract number
68-03-2231 by Rezek, Henry, Meisenheimer, and Gende, Inc., under
the sponsorship of the U.S. Environmental Protection Agency.
This report covers the period from July 1975 to April 1977, and
work was completed as of April 1977.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures .. vi
Tables ix
Acknowledgement . xi
1. Introduction . 1
2. Summary and Conclusions 3
3. Recommendations 7
4. Problem Definition 9
5. Present Practice 22
6. Septage Disposal Alternatives 37
7. Alternatives Evaluation 104
References 118
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FIGURES
Number
1
2
4
5
6
7
8
9
10
11
12
13
14
15
16
Page
Diagram of a typical domestic septic tank system . 10
Distribution of on-site domestic septic systems,
by state, in the United States 11
Hauler pumping out septic tank contents (septage)
from access manhole .... 14
Septage loading pattern, Lebanon, OH STP 16
Comparative enumeration of specific types of
microorganisms with 95% confidence limits ....... 21
Land spreading on farmland near Olympia, WA
showing area with recent discing of septage .... 44
Sludge disposal via SSI on a farmland
near Boulder, CO ,
46
Cross-section of SSI process 47
Terreator apparatus for SSI of septage ".... 47
Septage disposal trenches near Olympia, WA 49
Septage disposal lagoon in Acton, MA 50
Septage disposal in a SLF near Waretown, NJ 51
Schematic of marsh-pond system, Brookhaven
National Laboratory 52
Schematic of meadow-marsh-pond system, Brookhaven
National Laboratory 54
VSS and 6005 decay rate from a batch septage
aeration unit ,
60
Septage treatment facility flow diagram for
the town of Brookhaven, NY 62
VI
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FIGURES (continued)
Number
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Bench scale anaerobic-aerobic unit for septage
treatment
Schematic of a typical«Lebo composting facility .
Schematic diagram of a forced aeration compost
pile system
Temperatures in various locations within raw
sludge compost pile shown in Figure 19
Page
66
68
68
69
Details of Ventura, CA high dosage chlorine
oxidation system for treating septage .......... 73
Schematic of Islip and Oyster Bay chemical preci-
pitation septage treatment facilities in NY .... 73
Wayland-Sudbury, MA septage treatment alternative
II - aerobic treatment ,
76
Wayland-Subdury, MA septage treatment alternative
III - anaerobic/aerobic treatment 76
Two stage pilot plant autothermal thermophilic
aerobic digester (ATAD) system at Cornell
University, Ithaca, NY 79
Septage addition points in septage treatment
facilities
80
Schematic diagram of the Barnstable, MA septage
receiving station 81
Punch card reader at Seattle Metro's Renton STP .. 82
Septage receiving station at Renton, WA 82
Probability of reduction of solids-liquid
interface height after 30 minutes settling of
Alaskan septage samples 84
Volumes of septage addition to activated sludge
wastewater treatment plants (no equalization
facilities) ,
86
Septage addition to wastewater treatment plants
with equalization facilities 88
VII
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FIGURES (continued)
Number
33
34
35
36
37
38
39
Page
BOD5 removal from septage-sewage mixtures in
batch activated sludge process 92
Additional oxygen requirements for septage
addition to activated sludge wastewater
treatment plants 93
Unit processes - sludge processing and disposal
Aerobic digester at Bend, OR STP ,
Anaerobic digester stabilizes septage at
Tallahasee, FL STP ,
95
98
99
Islip, NY vacuum filter dewaters chemically
conditioned septage 101
Summary of a survey of septage disposal charges
at 42 United States sewage treatment,plants .,
115
Vlll
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TABLES
Number
3
4
5
6
7
8
9
10
11
12
13
14
15
Counties with More than 50,000 and Counties
with More than 100,000 Housing Units Using
On-Site Domestic Waste Disposal Systems 11
Sewage Disposal Characteristics for the United
States from 1970 Census 12
Estimated Household Septage Generation by State .. 15
Septage Characteristics 18
Septage Metal Concentrations 20
Heavy Metal Content of Septage and Municipal
Sludge 20
Estimated Hauler Charges 29
Existing State Septage Regulations 31
Fecal Coliform Counts of Stored Digester Super-
natent Exposed to Atmospheric Conditions .' 42
Disappearance of Fecal Coliforms in Sludge Cake
Covering a Soil Surface 42
Laboratory Study on Days of Storage Required for
99.9% Reduction of Viruses and Bacteria in
Sludge 43
Characteristics of Marsh-Pond System - Averages
for 13 Month Study Period 8/75 - 8/76 53
Characteristics of Meadow-Marsh-Pond System -
Averages for 13 Month Study Period 8/75 - 8/76 . 55
Land Disposal Characteristics 57
Original System Aeration Lagoon Performance at
Brookhaven, NY 63
IX
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TABLES (continued)
lumber
16
17
18
19
20
21
22
23
Comparison of Digested Sludge, Screened Sewage
Sludge Compost, and Lebo Compost Characteristics 70
Performance Data From Chemical Precipitation
Plants in Islip, Oyster Bay, Long Island, NY ... 74
Volatile Solids Reductions at Two Stage
Autothermal Thermophilic Aerobic Digestion
(ATAD) Pilot Plant at Tonowanda, NY 78
Relative Volumes of Septage Addition to Various
Plant Schemes of Identical Design Capacity 89
Performance of Huntington, NY Trickling Filter
Wastewater Treatment Facility Accepting Septage 95
Time to Loss of Septage Odor and Foam Reduction
From Batch Aerobic Digester , 97
Summary of Costs of Septage Treatment Systems
111
Ranking of Various Alternative Septage
Treatment Processes 116
x
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ACKNOWLEDGMENTS
J. W. Rezek served as Project Director for this study with
I. A. Cooper acting as Project Manager. Professional assistance
was provided by T. Bickford, R. E. Emmonsf C. J. Touhill, and A.
P. Pajak. The excellent technical assistance provided by F. J.
Bradke, N. G. Brown, G. E. Wilson, and R. W. Magnuson is espe-
cially appreciated. The secretarial and technical typing ef-
forts of Valerie J. Zilius and Cynthia Mickley Harris are grate-
fully acknowledged.
Special thanks go to various members of the staff of the
EPA's Municipal Environmental Research Laboratory in Cincinnati,
OH, particularly James F. Kreissl and Robert P. G. Bowker, Sani-
tary Engineers with the Urban Systems Management Section, Sys-
tems and Engineering Evaluation Branch, Wastewater Research Di-
vision, who provided helpful guidance throughout the program.
XI
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SECTION 1
INTRODUCTION
The use of a septic system requires periodic maintenance
which includes pumping out the accumulated scum and sludge,
called septage. Kolega (1) has reported septage volumes pumped
between 190 to 265 1 (50 to 70 gal) per capita per year in prop-
erly functioning septic systems. Some states suggest septage
accumulations ranging from 190 to 265 1 (50 to 70 gal) per capi-
ta per year in Connecticut to 3.8 1 (1 gal) per capita per day
in Massachusetts.
Various recommendations exist for time periods for septic
tank pumping, with most recommendations between 2 and 5 years.
After a hauler pumps out the homeowner's septage, this highly
offensive sludge must be disposed of in a safe, cost-effective,
and convenient manner.
An extrapolation of Vesilind's estimate for the annual vol-
ume of domestic STP sludge slated for disposal yields approxi-
mately 92 million m3 (24,300 million gal) per year of an as-
sumed 4% digested sludge in the United States. (2) Thus, the
estimate of 15.67 million m3 (4,100 million gal) per year of
septage to be disposed of annually indicates that a volume equal
to an additional 20% of the domestic treatment plant digested
sludge problem has been essentially overlooked.
Septage is generally placed on the land, in lagoons, in sa-
nitary landfills, or in wastewater treatment facilities. With
increasing public awareness of environmental pollution and
stricter regulatory enforcement of groundwater quality, leachate
control, surface water quality, and odor control, numerous dis-
posal facilities have refused acceptance of the material, focus-
ing attention on septage treatment and disposal as a legitimate
problem. In many cases, waste treatment operators have justifi-
able concerns in treating septage, since the material may have
previously created an organic overload in a treatment plant,
causing a violation of water quality standards, or added too
much liquid in a sanitary landfill creating a leachate hazard.
-1-
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The major objective of this study is to bring together mate-
rial from highly specialized technical works and the more gener-
al/ overview type management reports to form a broad background
and evaluative decision factors which provides a rational format
for design and operation of treatment facilities. This basis
should pre-empt previous practices which led to operational
problems.
The initial work to achieve the objective centered on review
of the information and laboratory research of septage treatment
and disposal. Additional information was obtained from various
levels of government including municipalities and sanitary dis-
tricts. Hauler practices complimented this area. The'majority
of the work was conducted in gathering and evaluating data from
successful installations treating septage to obtain secure de-
sign criteria and cost data. This latter information provides
the foundation for the systematic selection method for choosing
the best suited treatment or disposal option for any given situ-
ation, and is presented in Section 7. Literature search and
data collection was performed during the period of 1975 - 1977.
-2-
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SECTION 2
SUMMARY AND CONCLUSIONS
This report investigated several areas in present day sep-
tage treatment and disposal practice. The usage of septic tank
systems and generation of septage was detailed on a state by
state basis, with the majority of the 16.6 million housing units
with septic tanks located in the Northeast, the Southeast, and
the Pacific Northwest regions of the United States. The total
annual septage generation in the U. S. was estimated to be over
15.7 million m3 (4.1 billion gal).
Septage is a highly variable waste, with BOD5 and sus-
pended solids (SS) concentrations similar to wastewater. Heavy
metal content of septage is 1/2 to 2 orders of magnitude less
than STP sludge.
Septage may exhibit various offensive characteristics, such
as the ability to create vast quantities of foam when aerated, a
highly pervasive and obnoxious odor, poor settleabllity, and
poor dewaterability. These qualities make septage a less than
desirable material to treat properly.
The problems associated with septage treatment and disposal
have been addressed in detail only in the last few years. The
body of information is beginning to accumulate as political and
environmental pressure force attention on this issue.
Statewide septage disposal regulations are often missing oi:
are enacted on a case by case basis to meet immediate needs.
Often, state officials comment that septage problems are on "the
back burner". Some states are beginning to address the issue
with effective and comprehensive areawide programs. One excel-
lent example of a comprehensive statewide program is found in
Maine, where Title 30, Sections 4104 and 4105 require each muni-
cipality to provide an acceptable disposal site. This program
is backed with effective licensing, monitoring, research, and
enforcement efforts.
-3-
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Frequently 208 programs failed to identify septage disposal
problems. If these programs did address this topic, their im-
portance has usually been minimized.
Existing and proposed septage treatment and disposal options
have:been identified and evaluated, including:
Land Based Disposal
Spray Irrigation
Ridge and Furrow
Land Spreading
Subsurface Injection
Burial
Trenching
Disposal Lagoons
Sanitary Landfills
Leaching Lagoons
Marsh/Pond
Meadow/Marsh/Pond
Separate Septage Treatment Systems
Aerated Lagoons
Anaerobic/Aerobic Process
Composting
Pressure Chlorination
Rotating Biological Contactors
Wet Air Oxidation
Autothermal Aerobic Digestion
Chemical Precipitation/Stabilization
Septage Treatment at Sewage Treatment plant
Receiving Stations
Primary Treatment
Activated Sludge by Slug Addition
Activated Sludge by Controlled Addition
Attached Growth Systems
Aerobic Digestion
Anaerobic Digestion
Mechanical Dewatering
Sand Bed Drying
Under the proper conditions, direct land disposal of septage
may prove most economical.
The placement of septage into lagoon systems with filtrate
applied to infiltration beds has been shown to be a cost-effect-
ive solution, but should be applied in low density areas if
groundwater levels are known to maintain a substantial distance
below the surface. Management problems with lagoons consist of
-4-
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bucketing out very wet solids periodically for final disposal
elsewhere. Often additional dry soil is added to the lagoon
solids to obtain a truckable mixture.
In more densely populated areas, the addition of degritted
and equalized septage into a STP solids stream works well if ex-
cess digestion or solids handling capacity exists. Separate
solids treatment of septage at an STP could include liming and
sand bed drying in an STP at or near design loading. This
method, however, is more costly than utilizing existing solids
handling facilities.
Septage disposal into the liquid stream of STP can be prac-
ticed if a facility has the capacity to handle additional organ-
ic loadings fed continuously. Also, liquid stream disposal will
contribute to a larger volume of sludge for treatment than if
septage were placed in the solids stream directly, because ex-
cess waste activated sludge is typically at 0.5 to 1.0% solids
concentration, whereas septage may range from this level up to 5
to 8% solids. Foaming problems do not seem to be a drawback to
placement in an activated sludge flow; however, this precaution
would apply to aerobic digestion unless design considerations
include effective foam control.
In areas where it is not feasible to place septage in a land
based system or in a sewage treatment facility, independent sep-
tage treatment plants should be considered. Composting is one
of the most practical of these alternates when evaluated in
terms of both cost effectiveness and environmental acceptance.
Greater acceptance of this method will require additional work
in the final product marketing area.
Other separate treatment schemes include chemical coagula-
tion, lime stabilization, wet air oxidation, and chlorine (Cl)
oxidation. These methods suffer from economic drawbacks, but
all have been shown to treat septage effectively. The fate of
chemically stabilized septage is unknown. The significance and
fate of Cl compounds formed during pressure chlorination of sep-
tage needs further research.
Of all the alternatives investigated, land disposal had the
lowest associated operation and maintenance cost reported, from
less than $1.00 to $5.00 per 3.8 m3 (1000 gal), exclusive of
the cost of the land. Various lagoon systems report the cost of
treatment between $5.00 and $10.00 per 3.8 m3 (1,000 gal).
The cost of septage treatment in STPs varies widely, but typi-
cally average $15.00 per 3.8 m3 (1000 gal) with solids stream
-5-
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processing showing slightly lower costs. Composting by the Lebo
process is reported to cost approximately the same as disposal
in wastewater treatment plants. Cost for physical-chemical
treatment, such as the Purifax process or chemical stabiliza-
tion, range from those found for disposal at treatment plants to
triple that figure.
-6-
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SECTION 3
RECOMMENDATIONS
Further research or study is needed to remedy the following
problem areas in present practice or to obtain needed informa-
tion for more efficient management and design of septage treat-
ment facilities.
MANAGEMENT
*
*
*
*
*
Improved design of septic tanks to facilitate pumpout.
Contingency plans for septage disposal when small STP's
normally receiving septage are closed.
Nationwide licensing and registering of haulers after
meeting certain professional and job related education-
al requirements.
Legislative guidelines requiring septic systems to be
inspected and pumped, if necessary, on a predetermined
schedule.
Inspection and pumping, if necessary,/before a home can
be sold.
Periodic state review of existing regulations in light
of current needs.
Minimum standards for hauler equipment and annual in-
spection of equipment.
Requiring haulers maintain accurate files of date sep-
tic tank system serviced, volume transported, and dis-
posal site utilized. Haulers could report results an-
nually.
User fees for septage treatment based on capital re-
covery and operation and maintenance costs.
DESIGN
Further research needs are listed below to determine costs
and applicability for septage treatment in the following areas:
•7-
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* Innovative designs such as Marsh/Pond systems and Auto-
thermal Thermophilic Aerobic Digestion (ATAD) techni-
que.
* The fate of chemically stabilized sludge applied to the
land or to a landfill.
* Clarifier sizing on physical chemical stabilization
processes.
* Survival of viruses, ova, and cysts in limed septage.
* Market development for composted septage products.
* Treatability of dewatering filtrates and fate of sludge
cakes from different disposal schemes.
* Quality and volumes of excess sludge produced from sep-
tage addition to both liquid and solids flow streams in
STP' s.
_ Q —
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SECTION 4
PROBLEM DEFINITION
GENERAL
Major source categories of septage producers include domes-
tic, commercial, institutional, and industrial. Septage volumes
and characterizations are available for domestic septage, but
are lacking for other categories. Results of the 1970 census
informs us that 16.6 million housing units, or over 24.5% of the
total housing units in the United States, relied on septic
systems for wastewater disposal. (3) ,
The individual septic tank system is shown in Figure 1.
Wastewater enters the septic tank where heavy material settles,
while grease and scum float. The clarified liquid, or septic
tank effluent, then flows to the disposal area. The liquid is
distributed into the soil mantle by drain tile or seepage pits
for further purification, eventually entering the local ground-
water regime. In poor soil areas, other disposal options are
available following the septic tank, such as evapotranspiration
and mound systems.
GEOGRAPHICAL DISTRIBUTION
The geographical distribution of domestic septic systems,
Figure 2, shows states with over 35% usage located in New Eng-
land, the Southeast, and the Pacific Northwest. The Southwest-
ern states' usage of septic tanks is between 10% and 20%. On a
local level, Table 1 shows many counties in New Jersey, New
York, and California and other states have over 50,000 housing
units which use on-site waste disposal systems, while their
statewide usage appears less significant. Areas with over
100,000 housing units using on-site waste disposal systems in-
clude suburban New York, Los Angeles, and Miami. (4)
-9-
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Production
Well
Pretreatment
Disposal
rEvapotranspimtion
r • -r -i V Subsurface
|_ SepticTank f Disposal System
/Absorption
Soil Layers
/ \
'purification 1
Water Table
\
Figure 1. Diagram of a typical domestic septic tank system.
Table 2 presents the actual data from which Figure 2 was
created. Factors considered by the census bureau were the num-
ber of housing units and the percent of total housing units in
each state served by either sewers, septic tank - cesspool sys-
tems, or housing units lacking either of the above disposal
methods.
-10-
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OVER 35%
23% TO 35%
UNDER 25%
Figure 2. Distribution of on-site domestic septic systems,
by state, in the United States.
TABLE 1. COUNTIES WITH MORE THAN 50,000 AND COUNTIES WITH
MORE THAN 100,000 HOUSING UNITS USING ON-SITE
DOMESTIC WASTE DISPOSAL SYSTEMS
More than 50,000
Jefferson, AL
Riverside, CA
San Bernardino, CA
Pair field, CT
Hartford, CT
New Haven, CT
Broward, FL
Duval, FL
Hillsborough, FL
Jefferson, KY
Bristol, MA
Middlesex, MA
Norfolk, MA
Plymouth, MA
Worcester, MA
Genessee, MI
Oakland, MI
Monmouth, NJ
Multanannah, OR
Westmoreland, PA
Davidson, TN
King, WA
Pierce, WA
More than 100,000
Los Angeles, CA
Dade, FL
Nassau, NY
Suffolk, NY
-11-
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TABLE 2. SEWAGE DISPOSAL CHARACTERISTICS FOR THE
UNITED STATES FROM 1970 CENSUS (3)
State
AL
AK
AX
AR
CA
CO
CT
DE
DC
FL
GA
HI
ID
IL
IN
IA
KS
KY
LA
HE
MD
HA
HI
KH
MS
HO
HT
HE
NV
KB
NJ
NM
NY
NC
ND
OH
OK
OR
PA
RI
SC
SD
TN
TX
UT
VT
VA
HA
HV
HI
HY
U.S.
Ter.
PR
VI
GO
AS
CZ
Trust Tec. of the
Pacific Islands
Total U.S. and Tec.
Total Housing Units
U. S. and Tec.
Housing
on Public
Number
566,307
55,511
446,304
355,684
6,084,632
612,659
608,603
130,259
277,068
1,509,682
848,516
161,438
137,891
• 3,072,266
1,060,942
662,320
594,758
536,388
778,247
169,975
953,470
1,339,304
1,947,137
864,984
338,581
1,173,688
154,581
385,860
147,743
132,475
1,890,977
230,737
4,824,525
733,848
128,967
2,565,317
686,240
448,967
2,798,522
197,947
363,611
140,258
671,248
2,989,684
258,649
72,264
906,030
786,551
304,151
994,926
86,983
48,187,675
346,830
IU*
ID
IU
IU
IU
48,534,505
68,403,575
Units
Sewecs
% of
Total
50.80
62.69
77.11
52.85
87.22
82.47
62.82
74.44
99.52
60.61
57.85
74.78
57.87
83.20
61.97
69.35
75.52
50.57
67.90
50.11
77.23
72.83
68.43
70.92
48.56
70.47
64.21
75.44
86.07
53.26
82.03
71.60
98.34
45.32
64.32
74.41
73.17
61.04
72.13
64.41
45.18
63.30
51.76
78.49
82.93
48.23
71.02
65.28
51.31
70.26
75.94
THIS
48.87
70.95
Housing Units
with Septic
Number
385,345
18,629
114,433
220,287
853,013
113,290
354,585
39,860
454
938,352
474,455
50,558
93,146
554,603
589,794
257,889
163,918
312,856
287,481
140,409
243,728
490,365
847,433
307,441
209,115
359,278
74,198
105,320
21,988
109,015
404,241
65,781
1,289,253
687,572
53,074
779,510
203,174
275,944
985,014
107,544
334,210
62,366
457,008
654,283
49,249
68,265
408,213
403,909
187,028
371,567
23,349
16,601,792
112,595
16,714,387
Tanks
% of
Total
34.56
21.03
19.77
32.73
12.23
15.25
36.60
22.78
0.16
37.67
32.35
23.42
39.09
15.02
34.45
27.00
20.82
29.50
25.08
41.39
19.74
26.67
29.78
25.21
30.00
21.57
30.82
20.59
12.81
43.83
17.53
20.42
20.93
42.46
26.47
22.61
21.66
37.52
25.39
34.99
41.53
28.14
35.24
17.18
15.79
45.56
27.49
33.52
31.55
26.24
20.38
24.52
15.86
24.43
Housing
Units
with Othec
Number
163,139
14,423
18,013
96,999
38,324
16,689
5,633
4,870
871
42,743
143,654
3,844
7,266
65,080
61,061
34,829
28,808
211,328
80,245
28,817
37,271
9,120
50,509
47,070
149,514
132,617
11,974
20,266
1,951
7,231
10,123
25,722
44,883
197,859
18,457
102,566
48,413
10,559
96,502
1,843
106,996
18,970
168,672
164,950
3,976
9,315
170,580
14,464
101,600
49,549
4,217
2,904,375
250,308
3,154,683
* of
Total
14.63
16.29
3.11
14.41
0.55
2.25
0.58
2.78
0.31
1.72
9.79
1.78
3.05
1.76
3.57
3.65
3.66
19.93
7.01
8.50
3.02
0.50
1.78
3.86
21.44
7.96
4.97
3.96
1.13
2.91
0.44
7.98
0.73
12.22
9.21
2.98
5.16
1.44
2.48
0.60
13.29
8.56
13.00
4.33
1.28
6.21
11.49
1.20
17.14
3.50
3.68
4.30
35.27
4.61
•Information Unavailable.
-12-
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Normal maintenance of a septic tank system requires the user
to inspect periodically the buildup of sludge and scum in the
septic tank. Pumping is required when the bottom of the scum
mat is within 7.6 cm (3 in) of the bottom of the outlet tee, or
the level of. sludge comes close to the bottom of the outlet de-
vice (example: 10.2 cm (4 in) .in a 3.8 m3 (1000 gal) septic
tank with 91 cm (3 ft) liquid depth). (5) Such a condition is
present in Figure 3. The hauler has uncovered the access man-
hole to the septic tankr lowered the flexible suction pipe into
the liquid, and is ready to pump out the septic tank's contents.
If the septic tank is not pumped when the above limits are
reached, it will be unable to perform its settling and flotation
functions, allowing most of the influent SS and hexane solubles
(grease) to be carried out to the distribution field. Plugging
of the soil structure is. greatly accelerated, resulting in a
premature system failure.
SEPTAGE GENERATION
Several methods are available for obtaining the volumes and
frequency of septage to be disposed of in an area. Septage
haulers have been surveyed in the states of Massachusetts and
Oregon. Unfortunately, fewer than 50% of those contacted re-
sponded. Records of the responding pumpers have been examined
for volume and frequency of pumpings.
In Massachusetts, volumes of septage generated range from
0.190 to 0.265 m3 per capita per day (0.72 to 1 'gal per
capita per day). (6) Homes with few elderly residents in a warm
climate in Orange County, FL have been known to not require
pumping for up to 25 years. (7) In a sfcudy in Wayland, MA, 1705
residents responded that their system was last pumped out an
average of 3.24 years ago. (8) The same residents reported they
regularly have their tanks pumped at 3.21 year intervals.
Haulers report most commercial/institutional/industrial systems
receiving domestic wastes are pumped annually.
A reliable estimate of the ^annual septage generation by
state is shown in Table 3. It was estimated that each housing
unit has a 3.8 m3 (1,000 gal) septic tank pumped at an aver-
age interval of 4 years. This estimate assumes 4.0 persons per
housing unit served by a septic tank, generating 237 1 (62.5
gal) septage per capita per year. These computations result in
an annual septage generation estimate of 15.67 million nP
(4,100 million gal) of septage.
-13-
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Manhole
Cover
Outlet
Scum-/
Sewage
Sludge
Figure 3. Hauler pumping out septic tank contents
(septage) from access manhole.
This estimate of U.S. septage generation lacks considera-
tion in terms of geographical distribution by locality, as well
as daily, weekly, monthly, or seasonal variations. Patterns on
Long Island exhibit a daily variation of septage deliveries to
treatment works on Mondays and days following holidays that are
20 to 40% heavier than the average for the week, with peak days
sometimes running as high as 5 times the daily load. (9) The
New England Interstate Water Pollution Control Commission
(NEIWPCC) indicates that climate (especially precipitation),
-14-
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TABLE 3. ESTIMATED HOUSEHOLD SEPTAGE GENERATION BY STATE*
State
AL
AK
AZ
AR
CA
CO
CT
DE
DC
FL
GA
HI
ID
IL
IN
IA
KS
KY
LA
ME
MD
MA
MI
MN
MS
MO
M3/Yr
0.36
0.02
0.11
0.21
0.81
0.11
0.34
0.00
0.00
0.89
0.45
0.05
0.09
0.52
0.56
0.24
0.16
0.30
0.27
0.13
0.23
0.46
0.80
0.29
0.20
0.34
Gal Yr
(Millions)
96.3
4.7
28.6
55.1
213.3
28.3
88.6
1.0
0.11
234.6
118.6
12.6
23.3
138.7
147.4
64.5
41.0
78.2
71.9
35.1
60.9
122.6
211.9
76.9
52.3
89.8
State
MT
NE
NV
NH
NJ
NM
NY
NC
ND
OH
OK
OR
PA
RI
SC
SD
TN
TX
UT
VT
VA
WA
WV
WI
WY
Total
U. S.
Ter .
(Avail.)
PR
Total
U.S.
and
Ter.
(Avail.)
M3/Yr
0.07
0.10
0.02
0.10
0.38
0.06
1.22
0.65
0.05
0.74
0.19
0.26
0.93
0.10
0.32
0.06
0.43
0.62
0.05
0.06
0.39
0.38
0.18
0.35
0.02
15.67
0.1.1
15.78
c
Gal/Yr
(Millions)
18.5
26.3
5.5
27.3
101.1
16.4
322.3
171.9
13.3
194.9
50.8
69.0
246.3
26.9
83.6
15.6
114.3
163.6
12.3
17.1
102.1
101.0
46.8
92.9
5.8
4,141.91
28.15
4,170.06
*Based on pumping a 1,000 gal septic tank every 4 years.
-15-
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daily hours, the number of days of weekly operation, and the
home occupancy pattern (primary or secondary home), are influen-
cing factors in delivery variation. (10) Southern climatic con-
ditions seem to attenuate the estimated pumpout frequency, since
higher year round temperatures increase the organic material di-
gestion rates in the septic tank.
Septage generation is usually greater in the warmer seasons
than during the cooler time periods of the year. Ice and snow
cover, and frozen ground limit accessibility to the septic tank,
and odors indicating a failed system are frequently absent dur-
ing this period, all contributing to lower pumpout frequency in
northern climates during winter. Figure 4 is indicative of this
septage loading pattern. These data were taken from the Lebanon,
OH STP for the year 1972.
I2O
JFMAMJJASOND
Figure 4. Septage loading pattern, Lebanon, OH STP.
-16-
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SEPTAGE CHARACTERISTICS
x
Septage is a highly variable anaerobic slurry whose charac-
teristics include large quantities of grit and grease, a highly
offensive odor, the ability to foam, poor settling and dewater-
ing characteristics, high solids and organic content, and often
an accumulation of heavy metals. Table 4 presents septage char-
acterization data compiled by the U. S. EPA's Municipal .Environ-
mental Research Laboratory in Cincinnati, OH compared to extreme
values reported in the literature.
Physical and Chemical Properties
Graner (9) reports septage characteristics in Nassau and
Suffolk counties similar to medium to strong municipal waste-
water, while Goodenow (11) in Maine found some samples with
total and SS over 130,000 mg/1 and 93,000 mg/1, respectively.
Tilsworth (12) obtained some septage samples with BOD5 over
78,000 mg/1 and COD's over 700,000 mg/1 in Alaska. The EPA's
mean concentrations are good indicators of septage concentra-
tion when compared to the data of most researchers.
A significant variability in septage characteristics has
been reported by most investigators. The cause of the varia-
bility may be the result of a combination of many undocumented
factors, including user habits, tank design, and sampling pro-
cedure. Pumping equipment and hauler practices, as described in
the next section, are also elements. Time of the year, as re-
lates to seasonal groundwater, may affect septage strength.
Some haulers on Long Island, for example, report they have
, pumped out 1,500 to 2,000 gal of septage from a 1,000 gal septic
tank, the excess being groundwater pulled in from the soil ab-
sorption system or through cracks or holes in the septic tank.
The use of garbage grinders in kitchens was observed to result
in an increased rate of scum accumulation. (6) The age of sep-
tage (time between pumpings) was also found to be important.
Feng (13) reported the levels of BOD$, SS, and NH3-N varied
with age in Amherst, MA septage, as anaerobic decomposition par-
tially liquifies and gasifies the solids.
Characteristics of septage from other than domestic sources
have not been reported in sufficient detail to be analyzed.
These other residuals may be waste products of laundries, indus-
tries, restaurants, .or institutions. Any facility treating
these wastes should have an adequate sampling and screening pro-
gram to determine their characteristics prior to truck unloading
thereby avoiding serious plant upsets from unanticipated con-
stituents.
-17-
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TABLE 4. SEPTAGE CHARACTERISTICS ,
(all values in mg/1 except for where noted.)
Parameter
EPA Mean
Concentration
Minimum Maximum
Reported Reported Variability*
TS
TVS
TSS
VSS
BODs
COD
TOC
TKN
NH3-N
N02-N
N03-N
Total P
K>4
Alkalinity
Grease
pH (units)
LAS
38,800
25,300
13,300
8,700
5,000
42,900
9,900
680
160
250
9,100
6-9
160
1,132( 9)
4,500(96)
310 (12)
3,660(96)
440 ( 9)
1,500(12)
1,316(14)
66(14)
6(14)
0.1(15)
0.1(15)
20 (96)
10 (96)
522(12)
604(14)
1.5(9)
110 (14)
130,475 (11)
71,402(11)
93,378(11) .
51,500(16)
78,600(12)
703,000(12)
96,000(15)
1,900(96)
380 (15)
1.3(15)
11(17)
760(14)
170 (96)
4,190(12)
23,368(14)
12.6(9)
200 (14)
115
16
301
14
179
469
73
29
63
13
110
38
17
8
39
8
2
* Values represent ratio of maximum to minimum.
Metals
The U. S. EPA has addressed the question of septage metal
concentration in studies at Lebanon, OH and Blue Plains in
Washington, DC. Assuming all samples were from domestic
sources, metal contamination of septage probably resulted from
one of three sources: 1) household chemicals which contained
trace concentrations of heavy metals that adsorb to solids and
show increasing concentrations with time, 2) contamination of
septage in hauler trucks from a previous industrial waste load,
or 3) leaching of metal (particularly cadmium (Cd) associated
with zinc (Zi) in galvanized piping) from household piping and
joints. Table 5 shows the results of this testing, showing con-
centration, minimum and maximum observed values, and variability
of twelve metals. If the value for mercury (Hg) is deleted from
the variability column, then the order of- variability for
chemical parameters is very close to the metals variability.
-18-
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In Table 6, the geometric mean heavy metal content of resi-
dential septage from Lebanon, OH and from Blue Plains, STP near
Washington, DC, is compared to geometric means found in raw and
digested sludge from American, Danish, and Swedish STPs on a mg/
kg dry weight basis. From this table it is noted that septage
contains significantly lower concentrations of heavy metal than
does municipal treatment plant sludge. (14) This level of metal
content is of ^signif icance when consideration is given to sep-
tage application to the land. Significance of metal toxicity in
the land disposal mode is discussed in Section 4.
Bacteriological Characteristics
Bacteriologically, septage contains predominantly gram-nega-
tive nonlactose fermenters. (5) Many of these microorganisms,
such as Pseudomonas, which are considered aerobic, have been
found in septic tanks. Numerous obligate anaerobes are present,
but only spore-forming types, including Clostridium lituse-
burence and Clostridium perfringens, have been recovered. Cala-
bro was unsuccessful at isolating nonspore-forming obligate an-
aerobes because species such as Bacteriodes are exceedingly oxy-
gen sensitive, and the septic tank pumping operation may have
exposed them to incident oxygen. Figure 5 shows the comparative
enumeration of specific types of microorganisms from 12 septage
and septic tank sewage samples, with 95% confidence limits.
Septic tank sewage samples were taken from the inlet end of a
functioning septic tank at a depth of 61 to 91 cm (2 to 4 ft).
The standard plate count (SPC) per ml was determined after 48
hours of incubation under aerobic and anaerobic conditions at
24°C. When the septic tank is pumped, mixing of the bottom
sludge, intermediate wastewater and upper layer of scum occurs.
The presence of aerobic organisms in a septic tank can be ex-
plained by either the dissolved oxygen of the incoming sewage
providing sufficient oxygen to allow limited aerobic growth or
chemostatic action by displacement of effluent by the influent
furnishing a relatively constant number of aerobic microorgan-
isms. (18) It is therefore fortunate that Pseudomonas and other
similar aerobic bacteria are found in the septic tank, as they
are capable of lipid and detergent degradation.
Calabro estimated the gross relative stability of septage,
septic tank effluent and domestic wastewater using methylene
blue as a redox indicator of biological activity. Septage sam-
ples changed color in 5 hours, septic tank effluent between 6
and 21 hours, and raw domestic sewage between 17 and 21 hours.
(18)
While information on the presence and survival of viruses in
septic tank effluents was reported by many investigators (Sen-
ault, Foligate, Laurienant, and Martin, 1962, and numerous pub-
-19-
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lications by the University of Wisconsin Small Scale Waste
Management Project), little is reported on virus, bacteriophage,
ovum and cyst identication and survival in septage.
TABLE 5. SEPTAGE METAL CONCENTRATIONS
(all values in mg/1)
Metal
Al
As
Cd
Cr
Cu
Fe
Hg
— ™ 3
Mn
Ni
Pb
Se
Zn
EPA mean
Concentration
48
0.16
0.71
1.1
6.4
200.0
0.28
5.0
0.9
8.4
0.1
49.0
Minimum
Reported
2.00d4)
0.03d4)
0.05d4)
0.3d4)
0.3d5)
3.0d4)
0.0*002(14)
0.5d4)
0.2d4)
1.5d4)
0.02(14)
33.0d5)
/
Maximum
Reported
200.0d4)
0.05d4)
10.8d4)
3.0d5)
34.0d4)
750.0d4)
4.0d4)
32.0(14)
28.0d5)
31.0d4)
0.3d4)
153.0d4)
Variability*
100
17
216
10
113
250
20,000
64
140
21
15
5
* Values represent ratio of maximum to minimum.
TABLE 6. HEAVY METAL CONTENT OF SEPTAGE
AND MUNICIPAL SLUDGE (14)
(mg/kg)
Metal
Lebanon, OH
Septage
Salotto
Municipal Sludge
Other U. S. Denmark Sweden
Cd
Cr
Cu
Hg
Mn
Ni
Zn
5.
21.
28.
0.
106
28.
1,280
5
0
1
24
5
43
1,050
1,270
6.5
475
530
2,900
69
840
960
28
400
240
2,600
10
110
340
7.8
350 •
37
2,600
9
170
670
5
400
65
1,900
.8
.8
-20-
-------
0.
A-Septage
B- Septic Tank Sewage
o 8
0 7
s: e
"2 5
o
•o 4
c
2 3
(0
_j
Pj 95% Confidence Limits
r-
•f.
-
f"1
...
i
i
...
ir
-
r-i
~.
...
~
...
—
•-•
p-
f
...
A B A B A B
Aerobic Anaerobic Synthetic
A B A B
E.coli Lactose
Fermenters
A B
Non-Lactose
Fermenters
Figure 5. Comparative enumeration of specific types of
microorganisms with 95% confidence limits.
-21-
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SECTION 5
PRESENT PRACTICE
SEPTAGE HAULER
The hauler is known by different names in different regions:
"scavenger waste hauler", "septic tank cleaner", or "septage
hauler". No matter what the name/ this person usually operates
as a small independent business person owning 1 to 3 trucks, al-
though firms having as many as 20 vehicles have been identified.
There is approximately 1 septage hauler for each 3,000 septic
tanks on a nationwide basis.
The hauler is fiercely independent by nature and often sec-
retive in methods, practices, and records, which is why many
state agencies repeatedly have had poor success in obtaining vi-
tally needed planning information from them. Although haulers'
organizations exist, they are local in character and have no
national representation. Members of haulers' organizations have
repeatedly tried to raise their status by pressing state and
local agencies to require both licensing and qualifying examina-
tions. These efforts have met with limited success.
In some areas of the country, unscrupulous haulers, mostly
transients, known as "floaters" or "drifters", cause problems
when they dump septage loads in unapproved or potentially hazar-
dous sites, such as streams or roadside ditches. .In many areas,
the few floaters have given the approximately 4,000 honest
haulers a stigma.
Equipment
Discussions with state and local regulatory agencies and
private haulers about hauler equipment resulted in a basic
agreement on minimum requirements as well as preferable equip-
ment. Much of the equipment used in the field today is func-
tional, but will not meet certain state requirements, such as
Oregon's Sewage Disposal Service regulation. Recommended mini-
-22-
-------
mum requirements and preferred equipment for trucks, valves,
hoses, pumps, and other equipment are listed below.
Trucks—
Minimum Requirements— Hauler trucks should provide a water-
tight metal enclosure, with at least 3.8 m3 (1,000 gal) capa-
city, which is usually the nominal size septic tank presently
being installed. Tanks should have an access port for periodic
inspection and maintenance. A device for determining the quan-
tity of liquid in the truck, such as a sight gauge, should be
included. On each side of the tank there should be a painted
sign in contrasting colors, at least 7.6 cm (3 in) high, dis-
closing the business name, address, capacity of the truck, and
a disclaimer that the truck is to be used for cleaning residen-
tial septic tanks and not for industrial wastes. Annual or more
frequent inspections by the appropriate authority, usually ei-
ther the state or local health department, should determine if
the trucks are leakproof and in a sanitary condition. A pres-
surized washwater tank with disinfectant and cleanup implements
should be on each truck.
Preferred Equipment— Many haulers are advocates of larger
capacity trucks, since fewer non-revenue generating runs must be
made to the disposal site. A nonleaking rear door on the tank
has been reported as useful in recoating, repairing, and serv-
icing the tank. Other desirable components include a catwalk
and guard rail with hose racks.
Valves—
Trucks should have drip-tight gravity drainage valves that
can be safety locked during transportation and storage. Spread-
er type gates are not recommended.
Pumps—
Minimum Requirements— Pumping equipment on hauler trucks
should be able to provide at least a 3.2 m (15 ft) suction lift
with reversible flow. Some haulers prefer having their pumps
pull a vacuum on the truck's tank. In this case, a vacuum pump
or blower with a water trap to prevent septage aerosol disper-
sion is provided. A high level automatic shutoff control should
be included to avoid spillage and associated aesthetic and
health hazards. Other haulers prefer an in-line, self-priming
sewage pump with a high net positive suction head (NPSH) capa-
city. These open impeller or recessed impeller pumps should
have the ability to pump heavy slurries with rocks or large
solids that are frequently encountered. Annual inspection
should include verification that no leaking is occuring through,
the pump diaphragm or packing glands. Minimum pump capacity
should be about 1,500 1 (400 gal) per minute.
-23-
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Preferred Equipment— Air exhausts on vacuum pumps or air
outlets on in-line pumps should have an activated carbon filter
or other suitable devices for odor control. Combination vacuum/
pressure gauges are useful in determining system performance.
When in-line pumps are used, consideration should be given to
materials for impellers and other internal parts which are su-
perior in abrasion resistance to those commonly provided. Se-
ries pumping with twin pumps are provided by some tank truck
manufacturers for use when heavy septage slurries are encount-
ered. Some pumps used have capacities up to 4,500 1 per minute
(1,200 gpm).
Hoses —
Hoses used in pumping septage should be a minimum 7.6 cm (3
in) diameter. High pressure black rubber is expensive but works
well. Spirally wound flexible vacuum tubing is less expensive,
but haulers tend not to like this material because frequent
breakage and subsequent spills result at the couplings. Hoses
should be capable of being drained, capped, and stored without
spilling their contents. Discharge nozzles on the hauler trucks
should have either a cam lock quick coupling or threaded screw
cap and should be sealed when not in use. Haulers normally car-
ry a minimum of 100 to 150 ft of hose.
Other Equipment —
This heading includes equipment for breaking up the scum
layer, such as a long-handled shovel, rake, and manhole "spoon".
Probes are often necessary in locating buried septic tanks. A
trash container with close-fitting lid should be carried to hold
dirt, which should be scooped up if septage is spilled on it.
(19)
Hauler Practices
Pumping —
The strength of septage is often dependent on the mode of
pumpout a hauler uses. A weak, in-line pump will leave most of
the heavy matter in the tank, while a pumper who draws a high
vacuum on his tank and then opens his valve quickly will draw
almost all the heavy sludge, grit and scum from a tank. Most
haulers are cognizant of the need to leave a small amount of
septage in the tank as a starter, or seed material, for diges-
tion of future wastes. Most haulers report they leave from 5 to
10 cm (2 to 4 in) of sludge material in the tank. Washing down
and disinfecting a tank is not recommended.
The pumping procedure requires the removal of almost all ac-
cumulated bottom sludge and all top scum mat from the septic
-24-
-------
tank. The NEIWPCC recommends lowering the liquid level suffi-
ciently below the outlet to prevent sludge and scum from enter-
ing the distribution system before breaking up the scum mat for
pumping. A long-handled tool should be used to pull sections of
scum from far ends of the tank toward the pumpout hose. Follow-
ing the scum removal step, the bottom sludge and septic tank
wastewater should be pumped out. It may be necessary to back-
flush the tank by reversing the suction of the vacuum pump to
force loose the accumulated solids from the bottom of the tank.
After the required amount of septage has been pumped, the hauler
should inspect the inlet and outlet baffles and pipes for signs
of clogging or deterioration.
At the end of each workday, equipment and the exterior of
trucks should be cleaned and the washwaters disposed of as if
they were sewage.
Maintaining the Septic System—
A periodic, scheduled pumping, to prevent premature clogging
of the leaching field, is generally required to properly main-
tain a septic system. At each 3 or 6 month interval, the home-
owner should check the scum and sludge accumulation level in the
tank. The Manual of Septic Tank Practices recommends pumping
the septic tank when certain levels are reached, depending on
tank geometry. (5)
Many haulers may recommend septic tank maintenance products
to the homeowner. However, the Manual of Septic Tank Practice
reports no product has proved to be of advantage in properly
controlled tests. Many haulers report that the addition of a 2
Ib box of baking soda into the homeowner's drain each week will
provide significant buffering to the septic tank, keeping the pH
in the 6 to 8 range and resulting in less of a hard, crusty scum
layer. Other chemical additions or treatments, such as acid or
alkali treatments, may be, at best, of no value. Sometimes tem-
porary relief is seen, followed frequently by a damaged soil
structure and accelerated clogging. These products are not rec-
ommended.
Enzyme products and live microbial cultures are not neces-
sary in properly functioning septic systems, and most should be
considered of no value until proven otherwise. Many haulers and
various state agencies in Ohio, Virginia, and Michigan have used
a liquid suspension of live microorganisms to reduce the quan-
, tity of grease and scum buildup and grease-caused clogging in
leaching fields. (20)
-25-
-------
Before an individual decides to use any product in a septic
tank, a check with the local health department is highly recom-
mended .
Disposal Sites— In most states, haulers have the option of
disposing of domestic septage in an approved, privately owned
facility or in a publicly owned facility. A privately owned
site is usually a land-spreading site or disposal lagoon. The
publicly owned facility may be identical to the one privately
owned or may be a specially designed septage treatment works,
sanitary landfill (SLF), or wastewater treatment facility.
Unloading— When a hauler wishes to discharge a load at the
disposal site, the truck's gravity drain valve is opened and the
contents generally drained in 10 to 20 minutes, depending on the
size of the tank. In order to reduce unloading time, haulers
often pressurize their tanks, open drain valves, and literally
explode the septage out of their trucks. This practice often
results in splattered septage and the release of noxious odors,
and should be curtailed in all cases.
pH Adjustment— When a hauler discharges at a treatment fa-
cility, a sample often is taken and the pH checked. If the pH
is outside the acceptable range, the hauler must find another
suitable disposal site. Several haulers have overcome this by
chemical addition to raise or lower pH with recirculation of the
contents by self-contained pumps, or they have storage tanks at
their base location (John Schultz, Columbia Processors Co-Op,
Portland, OR) to blend several septage loads until an acceptable
pH is obtained.
One hauler in Massachusetts (John McNeil, Duxbury, MA) has
tried lime addition to his tanker truck for pH control and waste
stabilization. A 45 kg (100 Ib) bag of lime added to a 7,500 1
(2,000 gal) truck prior to pumping did not stabilize the con-
tents, proved difficult to mix into a slurry, tended to cake up
on the inside of the truck, and cemented the outlet. This prac-
tice is not recommended unless the tank and associated pumping
equipment has been designed for this function. Soda ash and
baking soda were found to be easier to handle, but the amounts
required are costly.
Hauler Comments
Some of the more frequently encountered recommendations and
criticisms offered by the hauler community are listed in brief
form below. Most comments tend to be general in nature and are
-26-
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divided into 3 basic categories. The first category deals with
septic system design and construction. The second class lists
desired improvements in management technique, particularly regu-
latory agency, while the last group of suggestions calls for
specific educational programs.
Design
-Poor design of septic tank openings
-Tank covers too heavy
-Tank openings difficult to locate
-Tanks should have better access for cleaning
-Tanks should be redesigned for easier cleaning
-Poor location to outlet "T" for cleaning
-Restrict fiberglass tanks to areas well above
groundwater
-Restrict use of steel tanks
-Tighter construction joints in tanks and piping
Management
-More detailed initial Health Department inspection
during site selection and construction
-Prefer area-wide tax on disposal rather than fees
-Correct lack of contingency disposal plans when small
plant normally employed for disposal are closed
-Need exists for hauler spare parts distribution
network
-Licensing and registering haulers by personal
examination
Education
-Desire more information on regulatory agency disposal
site criteria
-Desire a National Haulers Association as a means of
exchanging hauling and disposal information
-Decry the unavailability of specialized information
of Health Department inspectors, which prevents
haulers from defending inequitable applications of
existing regulations
-Desire an intensive education campaign for homeowners
which would include the following basic points
promoting existing system longevity:
1. Reduce water usage
2. Reduce use of garbage grinders
3. Proper placement of disposable diapers and sani-
tary napkins
4. Buffering of system by weekly addition of baking
soda, if local testing proves beneficial
-27-
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Hauler Charges
An estimate (shown in Table 7) was performed to determine a
reasonable charge a homeowner could expect to pay for having a
3.79 m3 (1,000 gal) septic tank cleaned, assuming the tank is
easily accessible and no additional work was needed. It was
based on a 25 km (15 mile) haul to the disposal point, 2 hours
travel time per load, vehicle depreciation and insurance of
$4,108 per year, and estimated wages. Depending on the level of
profit and a disposal cost not exceeding $15, a reasonable
charge would be in the range of $25 to $70, 1976 prices.
As of 1976, fees charged to homeowners ranged from a low of
$20 to $25 per 3.8 m3 (1,000 gal) in parts of Long Island to
around $100 per 3.8 m3 (1,000 gal) in areas of New Jersey,
Connecticut, and Oregon. Rural areas in New England had slight-
ly lower charges, $25 to $40 per 3.8 m3 (1,000 gal) , while in
most areas of the rest of the country, charges were in the range
of $40 to $60 per 3.8 m3 (1,000 gal). These charges are de-
pendent on the distance from the septic tank to the disposal
point (especially pronounced if over 15 miles) and the disposal
fee charged.
REGULATORY CONTROL
Basis for Regulations and Legislation
Regulatory and public health officials recognize that pro-
tection of the public health is of paramount importance. When
combined with the recently accepted public mandate for mainten-
ance and improvement of environmental quality, they acknowledge
that the achievement of these goals can be furthered by the en-
actment and enforcement of rules and regulations governing sep-
tic system construction and maintenance practices by various
bodies of government, ranging from local units to county, re-
gion, or state.
Existing Regulations
Regulatory decisions in the septage management area have far
reaching effects, from both economic and environmental stand-
points. These decisions may affect licensing requirements,
hauling equipment used, pretreatment requirements, allowable
disposal practices, and regulation enforcement.
-28-
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TABLE 7. ESTIMATED HAULER CHARGES
Estimated travel costs of septage hauler truck and charge home-
owner might pay for cleaning 3.8 m3 (1,000 gal) septic tank
with hauling 1 way travel distance of 25 Km (15 miles) (21)
1. Assumptions: 1500 gal (5.7 m3) truck, 7 yr life, initial
cost $20,000, travels 40,000 Km (25,000 miles) per yr.
Capital recovery factor (0.2054) x 20,000 = $4,108 per yr.
4108
40,000 = 0.103/Km
50 Km round trip
2. Fuel and lubricants $0.069/Km x 50 Km
3. Maintenance and insurance $0.038/Km x 50 Km
4.* Labor at $15.00/hr x 2 hours
5., Other costs 0.033/Km x 50 Km
6. Disposal cost at $15.00/3.8 m3
$ 5.15
3.44
1.88
30.00
1.63
15.00
$57.10
*Profit included in Labor Charge.
Permit Requirements—
Most states have some form of permit or licensing require-
ments for the septic tank cleaner. States usually license the
hauler company, while a smaller number license each truck sepa-
rately. Fees usually range from $50 to $500 per company, with
truck fees varying from nominal charges to several hundred dol-
lars per truck. A smaller number of states leave permit re-
quirements up to the county or municipal authorities. Many
states have concurrent registration codes with county or local
government agencies. Connecticut is the only state that has a
registration act which certifies individuals as competent on a
professional basis as determined from education and examination
standards. Most existing licensing requirements therefore act
as identifiers and revenue generation instruments.
-29-
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Equipment Requirements—
Few states have specific requirements for type, construc-
tion, maintenance, operation, and periodic inspection of septage
pumping and transportation equiment. Many states did, however,
cover this area in a general way by the use of phrases such as
"sanitary procedures" or "shall not create a health hazard".
Delaware, Illinois, Massachusetts, and Oregon detailed certain
requirements, but compliance is in direct relationship to the
policing effort of the responsible agency. Commonly used and
preferred equipment is detailed in the previous section dealing
with Haulers.
Disposal Requirements—
Most states require a hauler to submit disposal plans and
have them approved prior to use. Recommended disposal practices
were found to vary from state to state, but little actual varia-
tion was found on a nationwide basis. Regional factors which
influence disposal options such as precipitation, temperature,
and soils seldom entered into regulatory decisions. For exam-
ple, septage is allowed to be placed in sanitary landfills in
rainfall-abundant western Washington state.
Sewage treatment plants
lowed as disposal points if
plant's effluent will not
ments. Land disposal and
permitted if public health
protected.
and sanitary sewers are usually al-
plant capacity is sufficient and the
be degraded beyond permit require-
SLF application are also typically
and ground and surface waters are
Reporting Requirements—
Few states require haulers to keep or submit records. These
records should include the septic tank owner's name, address,
volume of tank, condition of tank, location on property, date
last pumped, and point of disposal. Those states that do have
some form of reporting have encountered very poor response.
These background data are useful in preparing disposal plans.
Contingency Requirements—
No state studied had any requirements for backup or contin-
gencies in the event that the normal disposal means (such as a
wastewater treatment facility) was not able to accept the wastes
as generated.
The matrix in Table 8 describes some of the above listed
practices in many states where septage disposal is a significant
problem.
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TABLE 8. EXISTING STATE SEPTAGE REGULATIONS
State
AL
Hauling Permit
County Health Officer
licenses hauler co.
Equipment
1.
2.
3.
Septage Disposal
Approval of local DPH
Sanitary sewers
Method of disposal
Comments
„,-
AK
AZ
CA
CO
CT
DE
FL
County licenses hauler
•co.
County licenses
hauler co.
State Dept. of
Health licenses
all operators
Regional Water Quality
Control Board (RWQCB)
licenses haulers
Local Board of Health
licenses haulers
Hauler licenses by
State Dept. of Health
1. Container to be
leakproof and
flytlght
2. Dept. of Health
licenses all
trucks
RWQCB licenses all
trucks
1. Trucks bear name
of co.
2. Watertight vehicles
In a clean condition
State permits for
haulers dumping Into
sewer or STP
State licenses hauler,
but inspected and approved
by local office
reviewed by county
health officer
Dept. of Environmental
Conservation (DEC)
requires review
County Health Dept. may
approve:
1. Community sewer system
2. Burial
3. Open dumping
RWQCB may approve:
Inspected and approved
by local office
Reluctant to allow
septage to treatment
plant because of
upsets
DEC may require
pretreatment before
STP
1. Tanks watertight 1,
2. Hoses leakproof
3. Receptacles portable 2.
4. Automatic shutoff
valves for pumping 3.
and discharge hoses
STP
Class II sanitary
landfill
a . Surface drainage
b. Leachate controlled
c. 0.0115-0. 184 m
(25 - 40 gal/cy) of
refuse In Bay area
1. Penalties for viola-
tions are $100/30 days
and revoke license
2. Record loads and
disposal and submit
reports. 3.20% to STP,
80% to land
Municipalities have
ordinances on disposal
State Division of Water
Resources prefers
septage to be placed
upstream of STP
Land spreading regulated
by counties
Municipalities r.espon- 1.
sible for providing
disposal facility -
Most don't
Local Health Dapt. site 2.
permit needed if disposal
Is offsite of septic tank
owner
State DEP closing unac-
ceptable sites and em-
phasizing new anaerobic-
aerobic digestion lagoons
Two of three counties go Sufficient capacity at STP
to STP necessary to treat septage
Other county "plows in"
- road setback 300'
Discharge not pollute
water course, water
supply, bathing
Pumper strikes and
other actions forced
one town to provide
disposal sites
Violation - $100/30
days
Sites inspected by state
Local codes may dictate
disposal practice in
area
State prefers STP, not
landfill
Revoke or deny future
hauler license for
violations
(continued)
-31-
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TABLE 8. (continued)
StQto
IL
Hauling Permit
State Health Dapt.
licenses haulers -
county may license
too
State Board of Health
licenses hauler
Equipment
State Health Dept.
has regulations for:
1. Tank
2. Vacuum pump
3. Hose
4. Nozzle
5. Self-rinsing
State Board of Health
licenses vehicles
KS
ME
County Health Depts.
licenses hauler
State licenses hauler
after local Health
Dept.
Dept. of Environmental
Protection (DEP)
Issues license plates
State Inspects
equipment and
license.
MD
Permit required by State
Dept. of Health and
Mental Hygiene (DHMH)
MA 1. State DPH
2. Board of Health
3. Local Board of
Health
MI DNR licenses haulers
and County Health
Dapt. responsible for
surveillance
Specific guidelines
for size of truck
Inspection and
approval by local
Board of Health
1. Tank
2. Hose
3. Pump
4. Venting
5. Drying and
burial - local
Board of Health
6. New seepage
lagoon
regulations
1. Separate equip-
ment
2. Display sign on
vehicle
Septage Disposal
1. IEPA and State Health
Dept. requires permits
a. Application to
farmland
b. Landfill
c. STP '
d. Sludge drying beds
2. Local codes for
dumping in sewer
system
1. State prefers STP
subject to municipal
approval
2. Written approval for
landfill as contingency
only
3. Burial in private
property with owner1 s
approval
1. Public sanitary sewer
2. Plow under in cropland
3. Sanitary landfill
4. Dewatering by vacuum
filtration
Local Health Dept.
enforcement:
1. Municipal sewers
2. Burial 200 yards from
.residences, roads
3. Property served should
be left in sanitary
condition
Disposal Is municipal
responsibility subject to
DEP approval, except
STP. Recommended
practices:
1. STP
2. Land spreading
3. Spray Irrigation
4. Lagooning
Not recommended:
1. Landfills
2. Composting
1. DHMH must approve
all sites in writing
2. Setback 200' from
any highway
1. Local Board of Health
approval required from
town pumped from and
town disposed in
2. Sanitary sewer -
approval by local
authority
Comments
1. OK to dump wastes to
sanitary sewers if they
don't harm STP
2. Hauler must file
disposal plan with
Health Dept.
3. Local codes may be
more strict under Home
Rule power
1. Minimum fine for
violation $25 - $100
2. Pumpers must be
bonded
Violations bring $100
maximum fine
1. State prefers STP but
need local approval
2. Land spreading
permitted:
a. 1,000 foot from
property
b. Written approval
of owner and
local Health Dept.
1. Minimum fines for
violations: $10 - $50
2. Confusing and
redundant local laws
requiring registering
with Boards of Health
for each municipality
septage Is transported
through, even If on
state or Interstate
highway
Violations bring:
a. $5,000 - $25,000
plus jail
b. Revoke license
(continued)
-32-
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TABtK 8. (continued)
State
MN
MO
NE
ND
NH
NT
NO
OH
OR
Hauling Permit
Permit required from
Division of Public
Health Services and
local community
No statewide rules.
Responsibility of
municipalities
No permit requirements
Permit required from
local health officer
Equipment
Regulations oh vehicle
structure and equip-
ment - inspection by
State
Septage Disposal
Comments
Equipment requires
inspection and
approval of local
health officer
Permit required from
Division of Public
Health Services
(DPHS)
Bureau of Solid Wastes
Management licenses
vehicles. Landfills
pay annual registration
fee
DEC and County Health
Board require permits.
Towns or villages may
require permits
Operator files state-
ment on transportation
and means of septage
removal
Annual inspection
Display of permit on
vehicle
Permit required from
County Health
Director
Dept. of Health'
requires permit
Dept. of Environ-
mental Quality (DEQ)
requires permit
Vehicle registered
with State Board of
Health
Permit required from
local health officer
Local requirements
only
1. Hauler files
description of
equipment
2 . Division of Health
inspects for:
a. Tank
b. Hose
c. Pump
d. Discharge
nozzle
e. Cleanup
facility
1. Local Health Depts.
regulate disposal in
• some areas
2. Shallow trench
disposal preferable
1. Spread on land
2. Burial
a. 1,000' setback
b. No surface or
groundwater
contamination
c. No contact with
livestock and
food producing
land
3. Sanitary sewer
Disposal site reviewed
by DPHS
1. Sanitary landfill
loading at 0.0046 m3/
m3 (10 gal/cy) solid
waste
2. Land disposal also used
3. STP not recommended
1. STP owner's permission
filed with hauler permit
2. Land disposal sites to
be approved by regional
DEC and County Health
Dept.
3. Special septage treat-
ment plants encouraged
4. DEC rates landfills as
last disposal option
1. Sanitary sewers
2. Landfills
3. Burials
1. Land spreading on
farmland most common
2. STP
3. Landfills
1. Disposal site to be
approved by DEQ
2. DEQ recommends:
a. STP with two
holding tanks
b. Non-overflow
lagoons
c. Land disposal
on fields
without crops
d. Plowed under
if near
habitation
State laws recently
defeated
Violations bring:
1. $100 or more in fines
or 60 days in jail
2. Permit revoked
Insufficient statewide
disposal area available
caused hauler demon-
strations
Haulers responsible
for annual report on
collection and disposal
volumes
Different level of
government have
different regulations
for disposal
Hauler must maintain
origin and disposal
records
Violations: $1,000 or
revoke license
(continued)
-33-
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TABLE 8. (continued)
State
PA
Hauling Permit
County Health Depts.
may require licenses
Equipment
Varies by county
TN
VT
State Dept. of Health
requires permit
Dept. of Public Health
requires permit
Dopt. of Public Health
recommends licensing
and regulatory practices
to local authorities
No state regulations -
Local Health Dept.
option of licensing
VA
No statewide regulations
WA
Permit required from local
Health Dept. with secondary
responsibilities shared by
Dept. of Ecology and Dept.
of Social and Health
WV
Local Boards of
Health set
standards on
vehicles,
equipment, and
operation
Dept. of Public
Health requires
equipment that
can flush, clean,
and deodorize
septic tanks
Septage Disposal
1. State Dept. of Environ-
mental Regulation
approved hauler disposal
sites
2 . State recommends STP
but land disposal most
frequent
3. Landfills, lagoons, and
trenches also permitted
1. Disposal site to be
approved by Dept. of
Health
2 . Disposal rin STP most
common
Local Health Depts. have
regulations for disposal
Comments
Lack of statewide
regulation hampers
management (5 of 62s-
counties have
regulations)
90 - 95% septage to
land, 5 - 10% to STP
Regulations being
developed to comply with
new act
1. Disposal site set back
300' from highway
unless buried or treated
2. Dept. of Public Health
encourages disposal to
STP
1. Septage prohibited from
landfills
2 . Local health officer
approves land disposal
a. Land spreading
b. Disposal trenches
3. Few STPs accept septage
State Water Control Board
requires^ septage treatment
systems to be approved as
industrial waste treatment
sites. Options include:
a. Lagooning
b. Wet air oxidation
c. Chemical treatment
d. STP
e. Land disposal
1. Disposal site to be
approved by local
health officer
2. Preferred disposal
options include:
a. STP
b. Surface spreading
c. Anaerobic lagoons
d. Sanitary landfills
1. Disposal in sewer or
STP with local approval
2. Incineration acceptable
3. Burial requires approval
of State Dept. of
Health
1. Little cooperation
among units of govern-
ment - No overall plan.
State officials estimate
percentage disposal
as follows:
15% STP
45% land
40% illegal
More local control ,
anticipated
Additional regulations
in preparation
-34-
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Suggested Regulations
Ideally, a state regulatory program should address the main-
tenance and repair of septic tanks, and the licensing of haul-
ers, as well as provide for rational disposal alternatives.
Such a program would eliminate gross local code differences and
should include the following items.
I. User-Related Regulations
1. Users should be required to have septic systems
inspected and pumped, if necessary, on a prede-
termined schedule.
2. Since the average American home is sold once every
7 years, a correlative regulation could require
each septic system to be inspected and pumped, if
necessary, before transfer of title can take
place.
II. Hauler-Related Regulations
1. Equalize local permit requirements by a statewide
hauler permit program.
2. Register all hauling vehicles.
3. Certify individual haulers by examination and levy
uniform statewide annual fee. ,
4. Establish hauler truck specifications,
5. Inspect all trucks annually.
6. Prohibit industrial waste hauling trucks from
pumping out domestic tanks.
7. .Require haulers to maintain accurate files of the
date system serviced, volume transported, disposal
site utilized, and report results annually.
III. Disposal-Related Regulations
1. Establish statewide program requiring municipali-
ties or regional governments to designate disposal
facilities and alternates in their area. This
program would eliminate the restrictive geograph-
ical area of individual governmental units, yet be
responsive to local needs. Enactment might be
similar to Maine's Regional Refuse Act.
-35-
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2. Establish user fees for public disposal facilities
based on capital and operation and maintenance
costs. Costs could be ,recovered through general
taxation of septic tank users or a combination of
fees and taxation. Disposal fee should be kept
low to discourage unregulated (illegal) disposal
practices. Taxation rebate consideration should
be applicable to the hauler who disposes, of sep-
tage privately.
3. Design and construction of disposal facilities
should be approved by state prior to use.
4. Require disposal site to maintain files on volumes
and sources of septage received., A sample should
be taken of each load for identification purposes
if the area has history of problems with indus-
trial wastes.
Less strict or less comprehensive regulations than those
listed above might be envisioned in areas with a smaller popula-
tion base served by onsite septic systems and relatively few,
problems.
-36-
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SECTION,6
SEPTAGE DISPOSAL ALTERNATIVES
LAND DISPOSAL CRITERIA
Septage disposal on the land can include surface spreading
and sub-surface injection, spray irrigation, trench and fill
techniques, lagqoning, and disposal in SLFs. Common require-
ments in all. land disposal alternatives are analyses of soil
characteristics, seasonal groundwater levels, neighboring land
use, groundwater and surface water protection and monitoring,
climatological conditions, and site protection such as signs
and fencing. ,
Land spreading requires a knowledge of land slopes, often
limited to 8%, and runoff conditions. Other requirements may
include storage facilities for times when land application is
inadvisable, crop management techniques, odor control proce-
dures, and loading criteria. Loading criteria generally are de-
termined by agricultural considerations, which result in nitro-
gen (N) and heavy metal loading rate limitations.
Loading Factors
Nitrogen—
In most agricultural areas, available existing nitrogen is
far below levels needed for optimum crop yield. As a result,
artificial sources of nitrogen are generally added, such as com-
mercial fertilizer. Nitrogen is available as a plant nutrient
in the form of the ammonium ion which is retained on negatively
charged soil particles. (22) Septage is rich in available am-
monia, about 25% of the total 0.6 to 1.0 kgN/m3 (5 to 8 Ib
N/1,000 gal) occuring in this form. Soil bacteria will
transform NH4-N to NO3-N, but much of this N may not be
available for plant use if hydraulic loadings cause the highly
soluble NO3-N to be leached below the plant root zone. Nitro-
gen may also be lost if poor drainage conditions exist, causing
ponding which provides anaerobic conditions and conversion of
nitrate to N gas.
-37-
-------
Health aspects dictate that N be applied at rates less than
or equal to plant N uptake requirements, since excess nitrate
formation could contaminate groundwater or surface water through
leaching or runoff. Since it is generally recognized that
N03~N concentrations above 10 mg/1 in drinking water may
cause health problems, particularly infant methemoglobinemia
(nitrate cyanosis) , concern is justified. Nitrate pollution in
surface waters also can lead to eutrophication, or premature
aging of lakes and streams.
The State of Maine has reported, in its Guidelines for Sep-
tic Tank Sludge Disposal on the Land, (23) that a loading cri-
teria of 585 m3/ha/yr (62,500 gal/acre/yr) on well-drained soils
and 351 m3 ha/yr (37,500 gal/acre/yr),on moderately well drained-
soils should not result in pollution caused by excess N. These
loadings result in N application rates of 560 kg/ha/yr (500 lb/
acre/yr) and 336 kg/ha/yr (300 Ib/acre/yr), respectively. Maine
officials report that monitoring wells at sites that follow these
criteria show no signs of groundwater pollution.
Phosphorous and Potassium—
Both phosphorus (P) and potassium (K) are basic requirements
for plant growth. Land application of septage usually results
in P loadings in excess of plant requirements, while K deficien-
cies will result at the same dosages. Both elements, however,
tend to become fixed in the soil and are not liable to leach
out. For this reason, N requirements usually govern the organic-
nutrient considerations in septage application rates.
Heavy Metals—
The phytotoxic metals zinc (Zn), nickel (Ni) , and copper
(Cu) are foliage-limiting factors in the amount of sludge which
may be applied to the land. Cadmium (Cd) is also of concern due
to its mobility in the plant structure and its toxicity to hu-
mans. How these metals are retained in the soil is complex and
poorly understood, but workable estimates of application limits
based on soil cation exchange capacity (CEC) have been proposed
(24).
The CEC can be estimated by a displacement procedure which
yields an exchange capacity in milli-equivalents (meq) per 100
grams of soil. A lifetime application load to any soil has been
proposed by the Wisconsin Department of Natural Resources, lim-
iting the amount of phytotoxic metal applied in terms of Zn
equivalents. Further research into lifetime metal loading lim-
its is underway, as it has been observed that some heavy metals
may become tied up in the soil structure over a period of time
-38-
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through a reversion effect linked with a solid-state diffusion
into crystalline soil structures. Attenuation of the effects of
overapplication of phytotoxic metals in sludges to the land may
be attributed to this mechanism.
The Wisconsin metal-loading criterion limits the Zn equiva-
lent to 10% of the CEC. Zinc equivalents are based on Cu being
considered twice as toxic as Zn, and Ni 4 times as toxic as Zn,
although other'researches have proposed relative toxicities in
ratios other than 1:2:4.
The calculation of permitted lifetime loading of metal from
septage, using the Wisconsin criteria, may be expressed as:
ML = (72.3(CEC)/(Zn) + 2(Cu) + 4(Ni))/l,000
where:
ML
CEC
Zn
Cu
Ni
maximum septage loading to soil, m3 septage/acre
cation exchange capacity of soil, meq/100 g
Zinc content of septage, mg/1
Copper content of septage, mg/1
Nickel content of septage, mg/1
Cadmium toxicity presents a special problem in its mobility
and its potential accumulation in the edible portions of plants.
One recommendation for Cd limits is based on work in Wisconsin
which found that application of greater than 2.24 kg Cd/ha/yr
(2 Ib Cd/acre/yr) showed a significant increase in metal concen-
tration in plants. The proposed limits are 2.24 kg Cd/ha/yr (2
Ib Cd/acre/yr), with a total lifetime loading of 22.4 kg Cd/ha
(20 Ib Cd/acre). (24) The proposed limits of phytotoxic metals
and Cd are reported to be low enough to protect reasonably well
chosen disposal sites.
Based on Lebanon, OH septage and Salotto findings (Table 6)
approximately 8 times as much septage could be applied to the
land as could municipal sludge using Cd as the limiting factor.
Using the phytotoxic metals limit, approximately 5 times more
septage could be applied as could municipal sludge. (14)
An example calculation for septage application rates, based
on a combination of phytotoxic metals and Cd, again assuming
average Lebanon, OH, septage and a soil CEC of 10 meq/100 g, is
presented.
-39-
-------
Metal Loading Calculation
Septage Concentration:
Zn = 50 mg/1
Cu = 8.5 mg/1
Ni = 1.0 rag/1
Cd = 0.5 mg/1
1. Total Metal Equivalent Loading:
72.3 x CEC = 723 kg/ha
(650 Ib/acre)
2. Septage metal equivalent per ton:
(50 + 2(8.5) + 4(1.0))/1,000 = 71/1,000 = 0.071 kg
metal equivalent per m3 septage .
3. Total lifetime loading permitted:
(723 kg/ha)/0.071 kg/m3 = 10,183.1 m3/ha
(6.65 mg/acre)
4. Yearly loading limit due to Cd:
(2.24 x 1,000)/0.5 = 4,480 m3/ha/yr (2.92 mg/acre/yr)
for 2.24 kg Cd/ha/yr
The above calculations show that in this example, this site can
receive a maximum of 10,183 m3 septage/ha (6.65 mg/acre),
(the phytotoxic limit), with a maximum yearly loading of 4,480
m3/ha/yr (2.92 mg/acre/yr), (the Cd limit). Actual loadings
should take into consideration the projected period of land use,
potential septage generation rates, capability for spreading the
material on the land, and the organic nutrient limitations as
they relate to heavy metals limits.
It is interesting to note that the yearly loading based on
Cd of 4480 m3/ha/yr (2.92 mg/acre/yr) is 33.1 times the ap-
plication rate based on the limiting N loading in this example
of 560 kg/ha/yr (500 Ib/acre/yr) , assuming a TKN of 680 mg/1.
Therefore, a well-drained site receiving this septage would have
its phytotoxic metal loading lifetime of 75 years at the N ap-
plication rate.
Pathogens—
The natural digestion process in a septic tank does not re-
sult in a pathogen-free material, as previously noted. For this
reason, care must be always taken in handling this material.
Evidence for pathogen reduction when septage is exposed to
atmospheric conditions is based on sewage sludge work performed
by the MSDGC (25) and others. (26) As shown in Table 9, only 1%
-40-
-------
of the original coliforms survived after 7 days. Table 10 shows
basically the same reduction for sludge cake applied to the
land. In a laboratory study on stored sludge, Berg determined
the number of days of storage required to reduce several viruses
and bacteria to 99.9% of the original values at different tem-
peratures. (27) The results are shown in Table 11.
Pathogens reportedly have been removed in the soil by vari-
ous mechanisms, predominantly filtration, adsorption, and die-
off. Pathogen travel is usually restricted to several feet from
point of application unless runoff or channeling occur, poten-
tially polluting surface and groundwater.
While the Guidelines for Sludge Disposal on Agricultural
Land in Wisconsin do not recommend raw sludge application with-
out prior treatment, the partially digested septage may be ap-
plied if some preventive measures are followed, such as lagoon-
ing prior to land disposal, or the immediate application of lime
to after spreading the septage. Care should be exercised in ap-
plying stored septage to the land, as cysts of protozoans and
ova of helminths, frequently found in septage, are very persis-
tent and constitute a health hazard. (22)
LAND DISPOSAL METHODS
Septage disposal techniques include surface application on
the land by spreading from septage hauler trucks (Figure 6) or
transfer vehicles such as tank wagons, spray irrigation, ridge
and furrow practices, and overland flow. Subsurface application
techniques include Plow Furrow Cover (PFC) and Subsurface Injec-
tion (SSI) alternates. Placement in trenches, lagoons, and
Sanitary Landfills (SLF) are classified as burial practices.
Land Disposal-Surface Applications
This method of septage disposal is perhaps the most fre-
quently used technique in the United States today. Future
studies should give consideration to stabilization and addi-
tional pathogen reduction before surface application of septage
on the land, as no discussion of septage health hazards in this
respect is available.
With any surface application technique, some N loss occurs
through ammonia volatilization, with the highest losses occur-
ing from spray irrigation. (98)
-41-
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TABLE 9. FECAL COLIFORM COUNTS OF STORED DIGESTER
SUPERNATENT EXPOSED TO ATMOSPHERIC CONDITIONS (25)
Days
0
2
7
14
21
35
Fecal Coliform Counts
(per 100 ml)
800,000*
20,000**
8,000
6,000
2,000
20
Percent
Survival
100.00
2.50
1.00
0.75
0.25
0.01
* Fecal coliform count just prior to lagooning.
** Fecal coliform count after lagooning.
TABLE 10. DISAPPEARANCE OF FECAL COLIFORMS IN SLUDGE
CAKE COVERING A SOIL SURFACE (26)
No. Days After
Sludge Application
1
2
3
5
7
12
No. of Fecal Coliforms/gm
Sludge Cake
(Dry Weight)
3,680,000
655,000
590,000
45,000
30,000
700
-42-
-------
TABLE 11. LABORATORY STUDY ON DAYS OF STORAGE
REQUIRED FOR 99.9% REDUCTION OF VIRUSES AND
BACTERIA IN SLUDGE (27)
Organism
•4°C
No. of Days at
20°C
28°C
Poliovirus 1
Echovirus 7
Echovirus 12
Coxsackievirus A9
Aerobacter aerogenes
Escherichlia coli
Streptococcus faecalis
110
130
60
12
56
48
48
23
41
32
—
21
20
26
17
28
20
6
10
12
14
Land Spreading—
The hauler truck which pumps out the septic tank is fre-
quently the vehicle which applies septage to the land. Consid-
eration should be given to intermediate holding facilities be-
fore application to the land. Storage is necessary during or
imminent to precipitation in order to prevent runoff of contami-
nated water. In colder climates, land application should be
limited to non-frozen surfaces to prevent runoff during thaw
conditions. Pathogen die-off with storage, presented under the
previous heading, is also a factor indicating the necessity of
storage.
With a storage facility, disposal can be performed either by
the hauler truck or by a tank wagon usually pulled by a farm
tractor. The choice between the two is one of economics. A
larger operation may choose to have its trucks on the road, with
septage spreading being performed by a separate spreading crew,
thus freeing the more expensive tank truck to perform the clean-
out functions. A smaller septage hauler may prefer to use 1 ve-
hicle to perform both tasks, thus leveling the work load by
spreading septage during slack hauling time periods. In some
instances, soil conditions may require the use of floatation-
type tires which are not suitable for long-distance highway use.
This would dictate the use of separate collection and spreading
vehicles.
-43-
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Figure 6. Land spreading on farmland near Olympia, WA,
showing area with recent discing of septage.
Spray Irrigation—
Spray irrigation of septage necessitates a storage lagoon
prior to disposal. Portable pipes and nozzle guns are used
rather than fixed or solid sets. Since the septage must be
pumped at 80 to 100 psi through 3/4 to 2 in nozzle openings, in-
stallation of a screening device at the lagoon's pump suction
is mandatory to prevent clogging at the distribution nozzles.
Since spray irrigation also offers the greatest potential for
offensive odors, knowledge of wind patterns and a well located
site are important during the planning stage.
Ridge and Furrow—
Ridge and furrow disposal methods have been used to dispose
of sludges on relatively level land, usually limited to slopes
-44-
-------
in the range of 0.5 to 1.5%. No instances ,of. this practice were
found during the course of this study. While this method can be
used to distribute septage to row crops during their growth,
care should be taken to ensure these crops are not for human
consumption.
Overland Flow—
Overland flow disposal method is used as part of an overall
septage-sewage and septage-sewage sludge treatment system at the
Brookhaven, National Laboratory in Upton, NY, and is described
under the Meadow-Marsh-Pond system in this section. The over-
land flow, field is planted with reed canary grass and has a
slope of 3%. The operator suggests future designs should limit
slopes to 1 1/2 to 2% to allow for cold weather operation. Sev-
eral yearly harvests of grass crop can be made during growing
season with multiple fields suggested. Current sizing criteria
is= 0.1 ha (0.2 acre) per 38 m-Vday (10,000 gpd) septage-sew-
age mixture.
Land Disposal-Subsurface Application
Soil incorporation techniques offer better odor and pest
control than surface spreading techniques, plus likelihood of
inadvertent pathogen contamination to humans is greatly reduced.
Disadvantages include full incorporation of all N, since ammo-
nia volatilization is eliminated, which reduces any N loading
safety factor from ammonia loss in surface spreading. Costs in-
crease over surface spreading, because a storage lagoon or tank
becomes mandatory, and additional capital is required for the
SSI equipment. A resting period of 1 to 2 weeks is required
before equipment can be driven over the waste incorporated land.
Three methods have been used to inject septage into the
land, including PFC, SSI, and a Terreator.
Plow-Furrow-Cover (PFC)—
A typical setup using this method consists of a single mold-
board plow, a furrow wheel, and a coulter. The coulter blade is
used to slit the ground ahead of the plow. Septage is applied
to the land in a narrow furrow 15 to 20 cm deep and immediately
covered with a following plow. Typical application rates were
0.012 m3/m of travel (1 gal/ft), or on an area basis, 306
m3/ha (32,700 gal/acre) in a Connecticut study. (97)
Subsurface Injection (SSI)—
This technique employs a device (Figures 7 and 8) which in-
jects a wide band or several narrow bands of septage into a ca-
-45-
-------
vity 10 to 15 cm (6 to 8 in) below the surface. Some equipment
uses a forced closure of the injection swath. Volumes injected
may be varied from 0.6 to 3.8 m3/min (150 to 1,000 gpm), de-
pending on the number of sweeps or injectors on the unit. (28,
29) One study in Connecticut found no measured increase in
groundwater pollutants. Acceptable loadings in this study were
0.025 mVlinear m (2 gal/lin ft) for a volumetric loading of
407.5 m3/ha (43,560 gal/acre).
Terreator—
This is a patented device (U.S. Patent No. 2,694,354) which
opens a 9,5 cm (3.75 in), mole-type hole with an oscillating
chisel point (Figure 9). An 11.4 cm (4.5 in) diameter curved
tube then places the septage at 50.8 cm (20 in) below the sur-
face at a rate of 24.8 1/lin. m (2 gal/lin ft). Passes are
spaced 1.5 m (5 ft) apart for an application of 163 m3/ha
(17,400 gal/acre). Kolega found that subsurface application of
49 kg/ha of N (43 Ib/acre) over 12 weeks in a well-drained soil
did not produce any noticeable groundwater quality variation with
either PFC, SSI, or Terreator methods. (30)
Land Disposal - Burial
Broad forms of septage burial include disposal in trenches,
disposal lagoons and SLFs. Foul odors are endemic to these
operations until a final soil cover is placed over the open sur-
faces of trenches or landfills. Disposal lagoon management
practices, such as inlet design, location, or liming, try to
minimize these problems.
Figure 7. Sludge disposal via SSI on a farmland
near Boulder, CO.
-46-
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CROSS-SECTION/SUB-SURFACE
INJECTION PROCESS
Injector Shank
& Hose
Cavity-
Producing
Sweep _
Initial Injection Ultimate Dispersion
Cavity Area After Injection
Figure 8. Cross-section of SSI process.
SPREADER PLATE
I
TERREATOR FRAME BY
OTHERS
CURVED
INJECTION
TUBE
SECTION
AA
Figure 9. Terreator apparatus for SSI of septage.
-47-
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Site selection is important, not only for odor control, but
also to minimize potential groundwater monitoring as an opera-
tional check.
Trenches—
Septage disposal in trenches is similiar to disposal in la-
goons, except trenches are usually a smaller scale alternative
to the lagoon. Septage is placed sequentially in One of many
trenches in small lifts, 15 to 20 cm (6 to 8 in) , to minimize
drying time (Figure 10). When the trench is filled with sep-
tage, 0.6 m (2 ft) of soil should be placed as a final covering,
and new trenches opened. An alternate management technique al-
lows a filled trench to allow as much solids to settle as pos-
sible and as much liquid to evaporate and travel laterally and
downward as possible. Then the solids are removed from the
trench for disposal at a SLP. The trench can then be reused as
long as some bottom and sidewall material is bucketed out with
the septage to allow renewed leaching out of the clogged sur-
faces. If not, subsequent usage often requires greater time
periods for liquid reduction as sides and bottoms of trenches
may become further plugged, reducing liquid leaching rates.
New York recommends trenches be a maximum of 2.1 m (7 ft)
deep. Sufficient room must be left between trenches for move-
ment of heavy equipment. The trench and fill technique is quite
often used at SLPs.
Disposal Lagoons—
Disposal lagoons (Figure 11) are usually a maximum of 1.8 m
(6 ft) deep and allow no effluent or underdrain system. These
disposal lagoons require placement of septage in small incremen-
tal lifts (0.15 to 0.30 m, or 6 to 12 in) and sequential loading
of multiple lagoons for optimum drying. Series or series paral-
lel lagoons with 2 years capacity each and a 0.6 m (2 ft) maxi-
mum depth are called for in New York State Guidelines. (31)
After drying, solids may be bucketed out for disposal in a SLF
in order to permit use of the lagoon for further applications.
Alternatively, 0.6 'm (2 ft) of soil may be placed over the sol-
ids as a final cover. Many states report odor problems with
disposal lagoons, but may be controlled by placing the lagoon
inlet pipe below the liquid level and having water available for
haulers to immediately wash any spills into the lagoon inlet
line.
Sanitary Landfills—
When a SLF (Figure 12) accepts septage, leachate production
and treatment must be investigated. For moisture absorption,
New Jersey recommends a starting value of 0.05 m3 of septage
to each m3 of solid wastes (10 gal of septage to each yd3).
-48-
-------
**£ *Fr* N' ^; ^^4*"
Figure 10. Septage disposal trenches near Olympia,
Septage should be prevented from entering landfills in areas
with over 89 cm (35 in)/yr rainfall, those without leachate
prevention and control facilities, or those not having isolated
hydrogeological underlying rock strata.
A 15 cm (6 in) earth, cover should be applied daily to each
area that was dosed with septage, with a 0.6 m (2 ft) final
cover within a week after the placement of the final lift. (10)
Many designers suggest a maximum cell height of 2.5 m (8 ft) .
At this rate, 3.79 m3 (1,000 gal) of septage could be distri-
buted on 31.6 m2 (340 ft2).
Other Land Based Systems
Leaching Lagoons—
The State of Conneticut has been advocating leaching lagoon
systems consisting of earthen anaerobic-aerobic sludge digestion
cells. Septage is discharged into a vertical manhole at the
edge of a lagoon and enters the lagoon at a point about 1/3 the
distance from the front to the rear of the cell near the bottom.
The lagoon bottom is not sealed, and at least 1/3 of the lagoon
is above ground level to facilitate liquid removal by percola-
tion and evapotranspiration. The minimum depth of the lagoon is
-49-
-------
0.9 to 1.5 m (3 to 5 ft). Sludge is periodically removed, and
the effluent from this anaerobic lagoon flows through a con-
trolled outlet to an aerobic leaching lagoon. Lime addition is
suggested to maintain pH between 6.8 and 7.2. However, it has
been observed when lime is introduced into the influent manhole
with the septage, the lime settles at the end of the anaerobic
leaching lagoon influent pipe and exerts little or no effect on
lagoon pH (Frederick Schauffler, NEIWPCC). Parallel sets of
these series lagoons are recommended. The capacity of each cell
is equal to 10% of the yearly septage influent volume, based on
0.2 to 0.26 m3 (50 to 70 gal) of septage generated per capita
of contributing population per year.
Massachusetts requires a minimum 1.8 m (6 ft) deep anaerobic
lagoon, followed by at least 6 percolation beds having 0.04
m2/m3 (1 ft2/gal) per day of design capacity. The lagoon
design requirements call for a sizing of 3.79 x 10 3 m3 (1
gal)/cap/day, with a minimum of 20 days retention at average
flow. The recommended discharge pipe located below the liquid
level has caused some problems by stirring up bottom sediments
and releasing foul odors. Acton, MA (Figure 11) now allows
haulers to discharge over rip-rap into the lagoon, which, they
report, lessens odor problems. (10)
Figure 11. Septage disposal lagoon in Acton, MA.
-50-
-------
Figure 12. Septage disposal in a SLF near Waretown, NJ.
Marsh-Pond System—
A land-based treatment system has been operating since
April, 1975 at the Brookhaven National Laboratory in Upton, NY
(Figure 13). This system treats strong blends of pretreated
(aerated and comminuted) septage and sewage into a shallow
marsh, then into a 5 foot deep stabilization pond. The marsh
is sized for 468 m3/ha/day (50,000 gal/acre/day), has a 20
mil PVC barrier over which 10 to 15 cm (4 to'6 in) of muck was
placed prior to planting cattails. The 946 m3 (250,000 gal)
pond also has a 20 mil PVC barrier and has been stocked with
carp, golden shiners, and fresh water clams. Duckweed (Lemna
mi nor) is a free floating plant often associated with cattails,
grows profusely, and keeps a high level of dissolved oxygen in
the pond. Discharge from the pond is spread over a mixed pine
and deciduous forest floor litter for infiltration to the ground
water.
-51-
-------
Various septage-sewage mixtures have been tried: 1:2, 1:10,
and 1:5. At a 1:5 septage-sewage ratio, a composite average
BODs of 210 mg/1 was achieved. The pond produces an effluent
not over 30 mg/1 8005. Recently, higher strength loadings
have been added to the system, consisting of a mixture of sep-
tage and settled sewage solids. Table 12 shows a typical influ-
ent and effluent concentrations from this marsh-pond system.
(32)
DEGRITTED AND SCREENED
RAW SEWAGE + SEPTAGE
o
9
O
9
2-6O.OOO GALLON
"AERATION PONDS
mimnn
0.2
: ACRE MARSH
, E , ,
• i
,
i 1 4
O.2
ACRE POND '
COMMINUTOR
50,OOO GALLON
AERATED POND
4" RECIRCULATING HEADER
GUTTER FEED
RECHARGE BY SPREADING
ON FOREST FLOOR
Figure 13. Schematic of marsh-pond system,
Brookhaven National Laboratory.
-52-
-------
TABLE 12. CHARACTERISTICS OF MARSH-POND SYSTEM -
AVERAGES FOR 13 MONTH STUDY PERIOD 8/75 - 8/76
(in ppm - mg/1 except for pH and as noted)
Pond
Influent
Concentration
farameter
TS
TVS
TSS
TVSS
IDS
BOD5
COD
Tot. N
TKN
NH3-N
NO2 + NOs
Tot. P
P04
Tot. coll
F. coll
PH
Turb. (JTU)
Temp. (°C)
Spec. cond.
(mho)
MBAS (ABS)
Ca'
Cl
Cr
Cu
F
K
Ug
Mn
K
Na
Zn
Average
5.62 x 102
3.35 x 102
3.53 x 102
2.35 x 102
2.08 x 102
1.70 x 102
4.95 x 102
25
19.7
8.4
5.5
7.2
4.8
*5.96 x 104
*1.56 x 103
6.8
43
10
4.R4 x 102
0.3
20
35
0.05
0.7
O.s
3.6
4.3
0.14
5
26
1.3
Maximum
5.3 x 103
3.64x 103
4.3 x 103
3.05 x 103
l.Ox 103
2.7x 103'
7.9 x 103
. 91
88
18
17
27.7
22
2. Ox 107
1.0 x 10s
8.9
4. Ox 102
22
6.6 x 103
3
72
1.1 x 102
0.5
3.2
1
20
8.5
0.75
11
52
4
Minimum
2. Ox 102
83
50
35
1.27 x 102
11
33
12
5
0.5
0.7
2.5
2
1.3 x 103
0
4.8
0.3
-4
2.5 x 102
0.02
12
25
0.01
0.2
0.2
0.8
3.4
0.06
2
18
0.3
Pond
Effluent
Concentration
Effluent Average
2.06 x 102
1.02 x 102
30 43
35
5.0 x 102 1.63 x 102
30 19
58
10 9.5
6.8
3.5
10 2.6
2.1
1,3
4 *2.0 x 103
2.0 x 102 *SO
7.4
5 8.5
11
2'.fi2 x 102
O.S 0.24
Sat. 14
2.5 x 102 30
0.05 . 0.01
1 0.03
0.6 0.4'
0.3 1.2
3.6
0.05 0.1
4-
20 25
5 0.2
Maximum
3. Ox 102
1.42 x 102
l.Ox 102
76
2.42 x 102
46
1.2 x 102
18
14
11.5
6.7
4
3
2 . 34 x 10s
1.06 x 104
9.1
74
24
3.4 x 102
1.4
26
46
0.03
0.14
0.6
5.5
6.3
0.3
9
52
0.6
Minimum
1.42 x 102
40
14
11
1.12 x 102
1
20
2.5
1.7
0.05
0.4
0.4
0.2
40
0
6.2
0.7
-6
1 .5 1 x 102
0.02
8.8
15'
0.01
0.01
0.2
0.3
2.1
0.4
0.5
15
0.03
* Geometric mean #/100 ml
-53-
-------
Meadow-Marsh-Pond System—
The meadow-marsh-pond system at the Brookhaven National Lab-
oratory in Upton, NY, (Figure 14) is similiar in concept to the
marsh-pond system described earlier except for the 0.16 ha (0.4
acre) meadow planted with reed canary grass. The meadows were
excavated, a 20 mil PVC barrier was installed and the site was
backfilled with silty loam. Three crops are harvested each year
from the meadow area. The meadow has a slope of 3%, however,
future installations should be limited to 2% to allow for more
favorable wintertime operation. The pond in this system is
stocked with catfish, fathead minnows and fresh water clams. A
desirable hydraulic limit to this system has been established at
935 m3/ha/day (100,000 gal/acre/day). (33) Pond effluent
flows into a small ditch which flows through a forested area of
mixed pine and deciduous trees before soaking into the sandy
soil. Characteristics of influent and, effluents are shown in
Table 13.
DEGRITTED AND SCREENED
RAW SEWAGE + SEPTAGE
o
9
I
O -
GALLON
"AERATION
PONDS
COMMINUTOR
60,000 GALLON
"AERATED POND
$L_4"RECIRCULATING
-'HEADER
GUTTER FEEDS
MM
O.2
ACRE
MEADOW
M M 1
O.2
ACRE
MEADOW
^ ^
w
.*. OC
z
^
* 3
0.2
ACRE
POND
C
^
-------
TABLE 13. CHARACTERISTICS OF MEADOW-MARSH-POND SYSTEM -
AVERAGES FOR 13 MONTH STUDY PERIOD 8/75 - 8/76
(all in mg/1 except pH and as noted)
Parameter.
TS
TVS
TSS
TVSS
IDS
BOD5
COD
Tot. N
TKN
NH3-N
NO2 + NOs
Tot. P
P04
Tot. co 11
F. coll
pH
Turb. (JTU)
Temp. (°C)
Spec. cond.
MBAS (ABS)
Ca
Cl
Cr
Cu
F
Fe
Mg
Mn
K
Na
Average
5.62 x 102
3.35 x 102
3.53 x 102
2.35 x 102
2 . 08 x 102
- 1.70 x 102
4.95 x 102
25.2
8.4
19.7
S.5
7.2
4.8
5.9606 x 104
1.557 x 103
6.8
42.7-
10.33
4.64 x 102
0.3
20
•35
0.5
0.7
0.5
3.6
4.3
4.9
26.4
1.3
Maximum
5.30 x 103
3.64x 103
4.30 x 103
3.05 x 103
1.00 x 103
2.70 x 103
7.90 x 103
91.1'
18
87.7
17.3
27.7
22.4
2.00 x 107
1.00 x 106
8.9
4.00 x 102
22
6.60 x 103
3.1
72
l.lOx 102
0.5
3.2
1
20.1
8.5
11
52
4
Water
Minimum Quality Criteria Average
2. Ox 102
83
50
35
1.27 x 102
11
33
12.5
0.51
5
0.68
2.5
1.6
12.5
20.0
4.8
0.26
-4
2.50 x 102
0.02
12
25
0.01
0.2
0.2
0.8
3.4
2
18.2-
0.3
l.SOxlO2
87
30 39
28
5.0 x 102 1.40x 102
30 13
48
10 5.2
1.2
3.7
10 1.5
1.6
1.1
4 *2.25xl03
2.0 x 102 *30
6.9
0.5 4.8
10.6
2.24X 102
0.5 0.3
Sat. 14 ,
2.50 x 102 29
0.5 0.02 '
1 0.04
0.6 0.3
0.3 1.5
3.3
0.05 0.1
3.1
20 22.8
Maximum
3.65 x 102
2.41x 102
1.04x 102
70
3.08 x 102
62
1.20x 102
15.6
6.8
12.6
3.2
5.3
. 4.6
1,27 x 10s
4.50 x 104
9.2
71
24
3.15 x 102
2.9
47
85
0.3
, 0.2
0.5
3.9
4.4
0.5
11
30
Minimum
89
6
13
7
69
2
16
1.3
0.04
0.7
0.2
0.3
0.1
40
0
6.1
0.6
-2
1.65.x 102
0.2
9
17
0.01
0.01
0.2
0.3
2.3
0.03
0.9
15.7
* Geometric mean.
-55-
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Comparative Land Disposal Practices
The land disposal methods previously discussed in this sec-
tion are compared in Table 14. This matrix assumes a moderately
well-drained soil, N loading limitations, and northern climatic
conditions (requiring use of holding tanks or lagoons in incle-
ment weather). In surface spreading techniques, particularly
spray irrigation, significant amounts of NH3-N (25 to 50%)
may be lost. (34, 35, 26) Although the amount of NH3-N that
may be lost is highly pH dependent, Jackson (98) has shown sig-
nificant ammonia losses through spray irrigation occur: (1) by
NH3-N volatilization while the liquid is traveling from the
sprinkler head through the air to the ground, and (2) by
NH3-N volatilization from the soil surface and from plant fo-
liage during and shortly after spraying. The amount of NH3-N
that is lost directly affects the amount of sludge which may be
added - i.e., the greater the loss, the, higher the application
rate.
SEPARATE SEPTAGE TREATMENT FACILITIES
Alternatives for treating septage at a separate treatment
facility include aerated lagoons , anaerobic/aerobic processing,
composting, high dosage chlorine oxidation (Purifax) , and chemi-
ical treatment.
Aerated Lagoon
Aerated lagoons may be employed for treating septage if the
aerators have the required oxygen transfer capacity and impart
sufficient turbulance to prevent- solids deposition.
Howley, in a laboratory-scale study (36) , reported severe
foaming problems with aeration. Measures were taken to control
foaming, including placing a chemical mixer's blade several
inches above the liquid surface to interfere with foam overflow.
Foam fractionation was used successfully and had the added bene-
fit of producing VSS and COD§ removals of 31.0% and 50.2%,
respectively of the initial concentrations. Two commercial sil-
icone defoamers and anti-foamers (Dow Corning DB-110 and DB-31)
were used at an application dose of 17 ml/1. Foaming in some
samples with defoamer added reappeared after 24 hours.
When owners of septic tanks were questioned about use of de-
tergents, there was almost a direct correlation between the
presence of foam upon aeration and the use of detergents in a
household. (36)
-56-
-------
TABLE 14. LAND DISPOSAL CHARACTERISTICS
Land Disposal Method
Surface Application
Spray Irrigation
Land Required at
37.9 mVday
(1Q,000 gpd)
Hectares (acres)
ISO 428.3) + storage
+ buffer zone
Ridge and furrow
162(32.4) t storage
Hauler truck spreading 162 (28.3) + storage
Farm tractor with tank
wagon spreading
162 (28.3) + storage
Tank truck with plow
and furrow cover
Farm tractor with plow
and furrow
170 (32.4)
170 (32.4)
Characteristics
Large orifices for
nozzle
Irrigation lines
to be drained
after Irrigation
season
Land preparation
needed
Larger volume
trucks require
flotation tires
500 to 2000 gal
trucks
Land requires
rest between
applications
800 to 3000 gal
capacity
Requires addi-
tlonal equipment
Land requires
rest between
applications
Single furrow
plow mounted
on truck
Septage discharge
Into furrow ahead
of single plow
Septage spread in
narrow swath and
immediately t
covered with plow
Advantages
Use on steep or
rough land
Low power require-
ments than spray
Irrigation
Use in furrows on.
growing crops not
for human consump-
tion
Same truck can be
used for transport
and disposal
Frees hauler truck
during high usage
periods
Minimal odor
Minimal odor
Disadvantages
High power requirements
Odor problems
Possible pathogen dispersal
Storage lagoon for pathogen
destruction and during
periods of wet or frozen
ground
Limited to 0.5 to 1.5%
slopes
Storage lagoon'
Some odor
Some odor immediately
after spreading
Storage lagoon
Slopes limited to 8%
Some odor immediately
after dispersal
Storage lagoon
Slopes limited to 8%
Slopes limited to 8%
Longer time needed for
disposal operation
Slopes limited to 8%
Longer time needed than
surface disposal
Not usable on wet or
frozen ground
(continued)
-57-
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TABLE 14. (continued)
Land Disposal Method
Sub-surface Injection
Land required at
37.9 rnVday
(lO.OOOgpd)
250 days/year
Hectares (acres)
170 (28.3) '
Characteristics
Septage placed In
opening created
by tillage tool
Advantages
Injector can mount
on rear of some
trucks
Minimal odor
Burial
Tronch
6 (15)
New trenches
opened when old
ones filled
Simplest operation
No slope limits
No citmatological
limits
Disadvantages
Slopes limited to 8%
Longer time needed for
dispersal
Keep vehicles off area for
1 to, 2 weeks after
Injection
Not usable In wet, frozen
or hard ground
Odor problems
High ground water
restriction
Vector problem
Long term land commitment
after termination of
operation
Disposal lagoon 12 (30)
Sanitary landfill 79 (195) of
working surface
Leaching lagoons 12 (30)
Marsh/pond system 0.24 (0.4)
Meadow/marsh/pond* 0.48 (0.8)
systom
lagoon Is filled
and dried, then
covered with
soil', or sludge
bucketed out to
landfill from
bottom of
septage lagoon
Septage mixed
with solid waste
at controlled
rates
Consider
leachate and
collection
requirements
Sludge bucketed
out to landfill
from bottom of
lagoon
Multiple lagoons
required
Settled water
usually flows to
percolation -
infiltration beds
Low energy and
low maintenance
type treatment
system
Greater acreage
required for
higher strength
wastes
Same as above
No slope limits
No cllmatologlcal
limits
; '
No topographic
limits
Simple operation
,
No slope limits
No cllmatological
limits
•
Winter operation
If increase freeboard
No chlorinatlon of
effluent recommended
No Odor
Simple operation
As above, but
produces better
quality effluent
Odor problems
High groundwater
restrictions
Vector problem
Odor problems
Rodent and vector problems
Limit areas less than 35
Inches yearly
Rainfall or leachate
collection or Isolate from
groundwater
Odor problems
High groundwater
restrictions
Vector problems
(
Rainfall counts as
hydraulic load
As above, but requires
additional maintenance
from harvesting 3 grass
crops annually
-58-
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Howley (36) found bench-scale removals with 1 and 5 day
aerated lagoons achieving 74 and 91% COD reductions. He found
higher oxygen uptakes by septage than sewage in this study, 54
mg/l/hr vs considerably lower 5 to 10 mg/l/hr, with soluble COD
average decay rate of 0.218 day"1. (37)
Howley also studied treatment in batch lagoon systems.
Jewell and McCarty (38) presented a first order model describing
this batch system as:
d (Total biodegradable _ (Total biodegradable organic
dt organic mass) mass, organic mass decomposed)
°r/
dt (Mo - fV = -k (M - fMo>
where M = initial mass of VS
f = refractory fraction (non-biodegradable) ="
VMo
•where M = ^the mass remaining after a long period of aera-
y tion (i.e., 1 yr)
k = reaction rate constant, day
M = total mass of VS at any time, t
Integration of this equation gives:
ln((M - fM0)/(Mo - fMQ)) = -kt
Decomposition rates may thus be determined graphically by re-
arranging the above equation in the following manner:
• ln(M - fM ) = -kt + ln(M. - fM ) 3
o • o o
which is analogous to a straight line plot on coordinate paper.
Results of a typical batch aeration unit after 45 days aera-
tion (Figure 15) by plotting the results of this unit according
to equation 3. Initial COD (total) was 74,400 mg/1, while ini-
tial COD (soluble) was 2,400 mg/1, and initial VSS was 33,000
mg/1.
After treatment, total COD was 55,000 mg/1, soluble COD was
680 mg/1 and BOD5 was 4.2 mg/1. No initial BOD,, analyses were
performed. He reported that (in a hypothetical example) a
septage addition of 18,500 gpd/million gallons of aerated lagoon
-59-
-------
design capacity, operating at 50% of the design sewage flow,
should not cause an overload condition.
9.6
g .
vss
K - 0.072 Mrs
,-1
Refractory VSS - 20600 mg/1
Refractory CODg » 680 mg/1
COD
K • 0.0711 BAYS"1
e
10 20 30
TI« (DAYS)
Figure 15.
VSS and BOD5 decay rate from a batch
septage aeration unit.
-60-
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Other studies using aerated lagoons to treat high strength
industrial waste show effective treatment. In a pulp and paper
mill (39) , surface aerators treated a waste averaging 530 mg/1
BOD5, producing ,a reduction of 91% at a retention time of 3.6
days. The lagoon was -loaded at 146 kg/m3 (9.1 lb/1,000
f t*) . in a pilot plant study for an aerated lagoon system
with sludge recycle treating vegetable processing wastes in
Washington State (40) pea, corn, and carrot processing wastes
showed between 95 to 99% reductions from influent BOD5 levels
which ranged from 1,503 to 3,550 mg/1. COD removals ranged from
92 to 98% from initial, COD levels ranging from 2,155 mg/1 to
5,450 mg/1. SS removals ranged from 83 to 97% from raw SS con-
centrations ranging from 428 mg/1 to 1,350 mg/1. Detention time
varied from 3 to 6 days.
In another study treating high strength vinegar waste in a
batch two stage aerated lagoon with recycle (41), an influent
BOD5 of 5,500 mg/1 was reduced to 194 mg/1 in the settled .ef-
fluent after 16 days. The COD was reduced from an initial 3,400
mg/1 to 646 mg/1 during the same time period.
The Town of Brookhaven, NY treats septage in an aerated la-
goon system. (42) Figure 16 shows the original installation on
top and revised present operating sequence on bottom. Table 15
shows performance of this system with sample No. 1 and 2 indica-
ting normal performance of this system, and sample No. 3 indica-
ting failure mode. The modified system has equalization facili-
ties, but the plant suffers from poor operation (Personal Com-
munications: John Esler, New York State Department of Environ-
mental Control). Grit and scum chambers and three large sett-
ling lagoons (25 m x 25 m or 80 ft x 80 ft) now buffer flow to
the 189 m3/day (50,000 gpd) septage system. The effluent
from a final settling lagoon is chlorinated and discharged to
sand rechargfe beds. Accumulated sludge is removed to a nearby
landfill.
-61-
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SEPTAGE-
AERATED
LAGOON
SETTLING
RECHARGE
ORIGINAL
SEPTAGE
SLUDGE RETURN
I •--• 1
I
I
1
c=
=>
\CL2
SCREEN GRIT SETTLE SETTLE SETTLE AERATED SETTLE RECHARGE
SCUM LAGOON
PRESENT
Figure 16. Septage treatment facility flow diagram for
the town of Brookhaven, NY.
-62-
-------
TABLE 15. ORIGINAL SYSTEM AERATION LAGOON PERFORMANCE
AT BROOKHAVEN, NY (42)
Sample
1 pH
BOD
COD
TS
TVS
SS
VSS
% TVS
% VSS
2 BOD
COD
TS
TVS
SS
VSS
% TVS
% VSS
3 pH
BOD
COD
TS
TVS
SS
VSS
% TVS
% VSS
Influent
6.0
7000
8200
10880
7800
7290
5450
72.0
74.8
9.4
5600
2749
3686
1964
2692
1426
53.3
53.0
Effluent
Aeration
Lagoon
7.2
2100
2158
1814
1274
1364
654
70.2
47.8
Effluent
Settling
Lagoon
6.15
570
840
1061
574
84
75
54
89.2
267
1116
1044
628
270
250
60
92.8
6.8
3000
3328
2382
1740
1041
498
73,0
47.9
%
Reduction
(Total)
92.0
90.0
90.5
92.5
98.7
98.5
62.5
+21
50.8
35.1
49.4
54.0
Anaerobic/Aerobic Process
The anaerobic/aerobic process, which uses an anaerobic la-
goon or digester prior to an aerated lagoon, is generally used
to reduce high strength wastes such as slaughterhouse or packing
plant wastes. Bench scale and pilot septage treatability stud-
ies using anaerobic digestion followed by aerobic treatment and
sand filtration were conducted at the University of Connecticut
(97). High rate digestion was used for the anaerobic process,
-63-
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with 15 day retention in the bench scale study and 10 day reten-r
tion for the pilot plant. Although temperatures were maintained
between 32.2°C to 37.8°C (90°F to 100°F) , the digester
contents were not mixed. The aerobic process detention time is
based on the removal requirements for BOD5. A steady state
material balance of BOD5 is: BOD5 influent (mg/day)
effluent mg/day) = BOD5 removed rag /day) , or
- CeQ = KV 4
Influent BOD5 concentration, mg/1
Effluent BOD5 concentration, mg/1
Septage flow rate per day, liters/day
where:
C =
Q =
V = Aeration tank volume, liters
K =. BOD5 removal rate, (mg/1 per day)
9 "'
Since BOD5 removal is considered to be a first order
equation, the BOD5 removal rate constant (K) is proportional
to the effluent BOD5 concentration. In a complete-mix unit,
where:
= KeC
dt e
dC = the time rate of change in BOD concentration at
dt any time, t
Ke = BOD5 removal rate constant, day"1
After equilibrium, the BOD5 removal rate (K) is equal to
If we replace K with KeCe in (4) and t = V/Q,
then:
(Ci - C )/C = Ket = Ket • 6
ts ts *
KeCe
Ce/Ci =
Ket)
where: C /C. is the fraction of BOD5 remaining
^2 JL
The percent BOD5 removed is:
R - 100 - (100/(1 + Ket)) '
The detention time t, in days, will then become:
t = R/((100 - R)Ke)
,7
-64-
-------
The researchers chose a Ke value of 0.5 for the anaerobic
digester supernatant and a 95% BOD5 removal through the
aerated unit. The theoretical detention time is then calcu-
lated to be 38 days.
In the bench scale study (97) BOD5 and COD concentrations
of over 3,000 mg/1 each were reduced by more than 96%. Sand
filter effluents were 40 mg/1 BOD5 and 100 mg/1 COD. The
NH3-N removal was 92%, and TKN removal was 94%. Overall VS
reduction averaged 36%. Increases were noticed in N03-N con-
centration due to nitrification of NH3-N in the aerobic
treatment unit. Total phosphate removal was 92%, with the ma-
jority of phosphate removal occur ing in the filtration unit.
Chemical addition was not mentioned in this study.
The pilot plant anaerobic-aerobic septage treatment unit
achieved similar removals to the bench scale unit. An initial
8005 concentration of 1,042 mg/1 showed a 96% reduction after
the aerobic treatment unit to an average effluent concentration
of 35 mg/1. Sand filter effluent 6005 concentration averaged
4 mg/1. COD removal averaged 92% through the entire treatment
scheme, including sand filtration. NE^-N was reduced 99% and
TKN showed a 96% reduction. An intermediate NH^-N increase
between the digester and the aeration unit was reported, from
influent 59 mg/1 to an effluent 80 mg/1. (97) (See Figure 17.)
N effluent concentrations averaged 72 mg/1 from the
aerobic unit and 70 mg/1 from the filtration unit. Total phos-
phate removal averaged 78% after the aerobic unit and 88% after
sand filtration. VS removal in the pilot plant study averaged
29%, compared to 65% removal in the bench scale tests, possibly
a result of considerable solids settling out in the pilot plant
storage tank prior to introduction to the treatment unit. A
2.54 cm (1 in) rigid scum mat formed on the top of the digester,
but did not interfere with its operation. (97)
Composting
Composting is an alternate septage disposal technique offer-
ing a potential for good bactericidal action and a 25% reduction
in organic carbon. (43, 44)
Aerobic composting operations mix septage with dry organic
matter for moisture control and for the addition of bulk to fa-
cilitate air penetration through the mixture to maintain aerobic
conditions.
-65-
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,Septoge
Input GQS Gullet
c" Scum i. •*•-:: -r-~—
Anaerobic Digestion Tank
Volume = 15 Gallons
Detention Time * 15 days.
Effluent
r
Diffusers
Aerobic Digestion Tank
Volume = 20,000 ml
Deterftion Time = 40 days
(ft.
11
»»
1 Final
» Fffln.
\\
Effluent
Sand Bed
Figure 17. Bench scale anaerobic-aerobic unit for
septage treatment.
Aerobic composting is generally recognized as superior to
anaerobic composting due to odor control, higher temperatures
for pathogen control, and shorter periods necessary for stabili-
zation. Two types of aerobic systems for composting septage
currently exist, namely either the Lebo Process or the Belts-
ville Process.
Process Stages—
Three stages exist in composting. In the process initiation
stage, temperatures pass from cryophilic (5°C to 10°C) to
mesophilic (10° to 40°C) regions. Active composting can
begin within days and operates in the thermophilic (40°C to
80°C) region. This temperature region tends to be self-lim-
iting by competing mechanisms. With an abundance of substrate,
bacterial populations increase, raising temperatures. Above
60°C, temperatures inhibit microbial growth, lowering popula-
tion and temperatures until the operating point where optimum
temperatures exist in balance with renewed growth. The third
stage is substrate limiting, exhibiting continuously declining
pile temperatures. This curing stage operates under two succes-
sive temperature regions, mesophilic (40°C to 10°C) and
then cryophilic (10°C to 5°C).
-66-
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Design
Composting areas should have ample room on-site for movement
of heavy equipment, as well as tankage for septage equalization
and for collection of leachate and surface water. Primary
screening for removal of larger unwanted material is advised.
After mixing with dry organic matter, compost piles are shaped
into windrows or other shapes, such as cubes or hemispheres.
Moisture control is achieved either by controlling the dry or-
ganic material/septage ratio (usually about 1.2 m3 sawdust/-
m3 septage (6 y3 sawdust/1000 gal)) or with increased aera-
tion. Pile aeration can include either natural draft, mechani-
cal mixing, forced (bottom) aeration, or by turning compost
piles.
Lebo System—
The Lebo system shown in schematic (Figure 18) has been com-
posting septage in South Tacoma, Bremerton, and Kent, WA. The
Lebo method appears promising and uses a patented preaeration
process prior to spraying septage on piles of sawdust, wood
shaving, or other dry organic material. A 1 to 2 in applica-
tion is covered with additional sawdust, until a 50 to 60% mois-
ture content is achieved. The mixture is then formed with
front-end loaders into piles to minimize heat loss. Natural
draft aeration is possible because of the bulky nature of this
mixture, eliminating the need for turning or forced aeration.
Three months of composting the material at a thermophilic pile
temperature between 40°C and 60°C greatly reduces numbers
of fecal and total coliforms and eliminates salmonella bacteria.
Pile temperatures may reach a maximum of 78°C. (43)
Beltsville System—
The Beltsville system, devised by U. S. D. A., is operating
in Washington, DC; Bangor, ME; Durham, NH; Orange County, CA;
and Johnson City, TN, on dewatered sludge. Camden, NJ will use
the Beltsville forced aeration system (Figure 19) on 8% sewage
sludge using licorice root as the bulking. The Beltsville sys-
tem usually mixes dewatered sludge with wood chips in separate
or extended piles and has piping facilities to alternately blow
and pull air through 0.66 cm (0.25 in) holes in 15 cm (6 in)
pipe covered by 30 cm (1 ft) of wood chips or screened, compost
to maintain aerobic bacterial action. (43, 44) After several
weeks, the compost can be screened, recycling the residual wood
chips for further composting. It may be necessary to dry the
compost by spreading and periodically turning the material prior
to screening. The composted material is then stockpiled prior
to preparation and distribution.
-67-
-------
Compressor
& Air Storage Tank
Aeration Tank
Figure 18. Schematic of a typical Lebo composting facility,
LONGITUDINAL SECTION
WATER
REMOVAL
R
SCREENED
COMPOST
WOOD CHIPS AND SLUDGE
SCREENED COMPOST
UNSCREENED
COMPOST
PERFORATED
PIPE
LOCATION OF MEASUREMENTS
I 3OO CM. HT. FROM BASE
2 ISO CM.HT. FROM BASE
3 40 CM. HT. FROM BASE
4 4O CM. HT. FROM BASE
AND 3O CM.FROM
SURFACE
5 ISO CM. HT. FROM BASE
AND 3O CM. FROM
SURFACE
CROSS SECTION
Figure 19.
Schematic diagram of a forced aeration
compost pile system.
-68-
-------
so
a
£
60
«r
W40
a,
20
— 40 CM. HT, CENTER OF PILE
—* 150 CM. HT, CENTER OF PILE
*~A 300 CM. HT, CENTER OF PILE
•••-«'4OCM.HT. SIDE OF PILE
2 4 6 8 IO 12 14- 16 IS 2O 22 24 26 28
DAYS
Figure 20. Temperatures in various locations within raw
sludge compost pile shown in Figure 19.
End Use—
The end use of a compost depends on several factors to suit-
ability as a fertilizer or soil enhancer, marketability, and
cost.
Compost Quality— Table 16 compares the composition of digested
sludge, screened sewage sludge compost, and Lebo process compost
from various aspects. Important considerations for use as a
fertilizer are nitrogen-phosphorus-potassium (N-P-K) contents,
the amount of heavy metals, and bacteriological quality. . Com-
post tends to be low in N-P-K, and should be considered a soil
ammendment rather than a fertilizer. Heavy metals from septage
compost are significantly lower than those found in sludge pro-
ducts.
In a study on the effect of Lebo compost in conjunction with
commercial fertilizer on sweet corn yield at Western Washington
Research and Extension Center, (45) a residual effect of the
compost caused a slightly increased yield during the second year
of the test when no compost was applied. The application rate
of 62,800 kg/ha (28 tons/acre) compost and 90 kg/ha (80 Ib/acre)
N provided a sweet corn yield of 18,800 kg/ha (8.4 tons/acre) in
year one of this experiment. Although no fertilizer or compost
was applied in the second year, a sweet corn yield of 19,700 kg/
ha (8.8 tons/acre) was harvested, thus showing a 4.7% increase
in yield.
-69-
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TABLE 16. COMPARISON OF DIGESTED SLUDGE, SCREENED SEWAGE
SLUDGE COMPOST, AND LEBO COMPOST CHARACTERISTICS
Component
Filter cake
H20
TS
Sol. frac.
Org. matter
N
H3P04
KOH
S
Ca
Mg
B**
Heavy metals
Zn**
Cd**
Cu**
Pb**
Micro-org.
Tot. coli***
Pec. coli***
S almone11ae* * *
Digested
Sludge %
80
20
50
2.5
2.7
0.6
0.9
2.9
' 1
23
2.0 xlO3
19
6.0 x 102
5.4 x 102
2.4 x 1010
2.3 x 1010
6.0 x 103
Screened
Compost '
35
65
50
0.9
2.3
0.2
0.4
2.6
0.3
27
10 3
1.0
9
2.5 x 102
3.2 x 102
9.7 x 104
3.0 x 103
0
Lebo Compost %
59
41
75
.77 - 1.37
0.3
0.05 - 0.35
3
0.075
80
4.0 x 102
10
50
60
460 -1.1 x 105
3 - 93***
* The composition of digested and composted sludge is subject,
to considerable variation. Values in the table are approx-
imate averages. Variations in composition occur because of
the different wastes discharged, chemical additions, types
and degrees of treatment, and bulking materials used.
** Parts per million.
*** Most probable number per hundred grams of sample.
Bacteriological quality is good, especially from the stand-
point of resistant pathogenic organisms, such as ova and cysts.
If the entire compost product attains a temperature of 60°C
(140°P) for 3 months or longer, these organisms do not prove
to be a biological hazard. (22) Therefore, before a Lebo com-
post pile is to be marketed, the outer layer of the pile, to a
-70-
-------
depth of 1 foot, is skimmed off and used as seed for the next
pile, since the outer layer is not exposed to the composting
temperatures of the pile interior. (46)
Marketability— In a recent, survey of the marketability of
sludge products, a strong market for such products was detailed.
(47) The range of sludge product costs ran from zero to $.20/kg
, ($180/ton), with composted products ranging from no charge at
Beltsville, MD (available only to municipalities) to $0.07/kg
($1.59/50 Ib bag) for Los Angeles composted sludge, bagged and
resold by the Kellog Supply Company. Demand for Beltsville com-
post exceeds supply, and the product is not promoted heavily.
Lebo compost has had some success at distributing their product
to golf courses in bulk with an approximate cost of $0.0022/kg
($2.00/ton).
Ettlich found successful marketing operations generally in-
clude: 1) favorable local publicity, 2) availibility of the
product for pick up or delivery, 3) offering suggestions or
guidelines for use, 4) keeping the price extremely low, and 5)
giving the product a trade name. (47)
High-Dosage Chlorine Oxidation (Purifax Process)
The BIF-Purifax process oxidizes screened, degritted and
equalized septage with dosages of Cl from 700 mg/1 to 3000 mg/1
under 308 kPa to 377 kPa (30 to 40 psig) pressure. Chlorine re-
places oxygen in organic molecules, rendering this material un-
available to bacteria as a food source and in the same process
stabilizing and deodorizing the septage. The purifaxed septage
changes color from black or deep brown to straw color. The pro-
cess initially releases CO2 gas which separates liquids and
solids quickly by imparting an effective flotation of the sol-
ids.
In domestic septage, the following compounds react signifi-
cantly with Cl; ammonia, amino acids, proteins, carbonaceous
material, nitrates, and hydrogen sulfide. The reaction time is
pH dependent, being faster at lower pH. The reactions detailed
in Feng's work, (48) verify the reduction of NH3-N, BOD, COD,
and TOC. Organic removal is generally increased with C12
concentrations and time.
Purifax treatment results in a highly acidic slurry whose pH
ranges from 1.65 to 2.02. (48) If mechanical dewatering or la-
goon separation of the liquids or solids is contemplated, chemi-
cal addition for pH control of the resultant liquid fraction
-71-
-------
must be included. At Ventura, CAf 1.7 kg (3.7 Ib) of caustic is
added per 3.785 m3 (1,000 gal) of decant to achieve a pH of
6.0. (7)
A Purifax treatment scheme, studied at Lebanon, OH, involved
a pressure-chlorination of septage followed by dewatering on
sand drying beds. Analyses of underdrainage showed LAS, COD, P
and Pe removal of 99%, BOD5 removal of 97%, Zn removal of 96%
and N removal of 83%. (14)
Only 1 to 2 1/2 days were required to dry a 15 to 30 cm (6
to 12 in) application to 30% solids. The sand bed underdrainage
was measured to be at a pH 6.8 to 7.2. (14)
Other locations treating septage or septage-municipal sludge
mixtures by the Purifax process include: Plainfield, and Put-
nam, CT; Easthampton, MA; and Ventura, CA (Figure 21) . Some
sites utilizing lagoons for liquid-solid separation have had
periodic solids separation and odor problems. Sand drying beds
appear to be the most efficient method of liquid-solids separa-
tion. Adequate ventilation of covered sand drying beds is man-
datory to eliminate operator health hazards from inhalation of
any NCls released subsequent to the Purifax process.
The EPA is currently analyzing pressure chlorinated sludge
and septage for chlorinated organics formed by this process to
determine the potential environmental impact of this form of
processing.
Chemical Precipitation
Raw septage is chemically treated with lime and ferric chlo-
ride at Islip, Long Island and, until recently, at Oyster Bay,
NY treatment facilities (Figure 22) . After screening and de-
gritting, the septage flows to a tank equipped with heavy duty
paddle mixers, designed to prevent deposition of SS in the two
day equalization tank. Operational difficulties were encoun-
tered in keeping the waste completely mixed. About 0.04 kg
lime/kg dry solids (190 Ib lime/ton ,dry solids) and 0.00021
m3/kg dry solids (50 gal/ton dry solids) of a standard
strength ferric chloride solution is flash-mixed with the sep-
tage. The solids-liquid separation step occurs in a clarifloc-
culator. An observed significant solids carryover problem in-
dicates the separation unit may have been undersized. The liq-
uid fraction is chlorinated and discharged to ground water re-
charge beds. Polymer is added to the underflow solids from the
clariflocculator which is then vacuum" filtered, with the fil-
-72-
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OCCJIBT KCVCIE
Figure 21. Details of Ventura, CA high dosage chlorine
oxidation system for treating septage.
Truck Discharga
Bar Screen
Grit Chamber
filter Cako
Tank
Olarifloeculfitor
Sand leaching Beds
Figure 22. Schematic of Islip and Oyster Bay chemical
precipitation septage treatment facilities in NY.
-7.3-
-------
trate being returned to the equalization tanks or flash mixers.
(7, 49) Long term relative stability of the lime-ferric septage
mixture is unknown.
Design parameters include clariflocculator sizing at ,30 min-
utes detention time in the flocculation zone, and an overflow
rate of 24.5 m3/day/m2 surface area in the settling zone
(600 gpd/ft2). Komline-Sanderson coil filters were based on
laboratory findings of 24.4 kg sludge cake/m2 of filter area,
but in actual experience, the yield was only between 10 to 15
kg sludge cake/m2 filter area (2 to 3 lb/ft2 filter area).
The later designed Islip plant has a 27.9 m2 (300 ft2) of
filter area to account for field experience. Long Island soil
conditions dictate at least 0.12 m3 per day/m2 (3 gpd/
'ft2) of recharge bed. (49)
Operational experience of both the Oyster Bay and Islip
plants are presented in Table 17, and include averaged test data
from Nassau County Department of Health correspondences and oth-
er sources over a multi-year period. (9)
TABLE 17. PERFORMANCE DATA FROM CHEMICAL PRECIPITATION PLANTS
IN ISLIP, AND OYSTER BAY, LONG ISLAND, NY
Plant
Parameter
PH
BOD
COD
SS
% VSS
TS
% VTS
I*
OB**
I
OB
I
OB
I
OB
I
OB
I
OB
I
OB
Influent
6.8
6.4
2,800
740
8,060
— • — .
987
1,660
80,714
47.3
Clariflocculator
Effluent
11.8
11.9
1,823
282
9,212
2,842
85
5,204
1,728
35.8
Vacuum Filter
Effluent
11.8
12.4
77
434
223
. .
4,454
58.1
6,645
3,060 -..'
;,
31.6
* Islip, NY data.
** Oyster Bay, NY data.
-74-
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Tilsworth found good liquid - solid separation only with
huge additions of chemicals; for example, either 10,000 mg/1
lime, 10,000 mg/1 ferric sulfate, 4,000 mg/1 lime and ferric
sulfate mixture, or 30,000 mg/1 of a cationic polymer. (52)
The NEIWPCC suggests (in unpublished test data) that primary
settled septage can be reduced to 50% original volume in 1 to 2
hours and to 25% original volume after 2 to 4 hours after addi-
tions of 0.08 kg lime/kg dry solids plus variable amounts of
both FEC13 and an anionic polymer.
Rotating Biological Contactors
After various septage handling schemes were analyzed for the
Wayland-Sudbury, MA area, a treatment system using rotating bio-
logical contactors (RBC) was proposed. (8, 50, 51) The scheme
using RBC's was based on a design at Ridge, NY. The Ridge de-
sign treats an equalized and screened wastewater with a BODc
of 325 to 402 mg/1 and SS of 130 to 145 mg/1 in a 2,323 m2
(25,000 ft2) disc area RBC. (54) RBC effluent characteris-
tics are BOD5 of 32 to 48 mg/1 and SS of 42 mg/1. ' The waste-
water then flows from the RBC clarifier to 0.02 m3/ min/m2
(2 gpm/ft2) sand filtration units for disposal in 0.06 m3/
day/m2 (5 gpd/ft2) sand recharge beds. Sludge is thick-
ened, then stabilized with chemical addition by ferric chloride
and sodium hydroxide and vacuum filtered at the rate of 29.3
kg/hr/m2 (6 lb/hr/ft2). Effluent to sand recharge beds
averaged 7 mg/1 BOD5 and 6 mg/1 SS.
The two alternatives suggested for Wayland-Sudbury using
RBC's are shown in Figures 23 and 24. Figure 23 shows Alternate
II, the recommended alternate. (Alternate I is the Purifax Pro-
cess) Figure 24, showing Alternate III, is a more costly treat-
ment scheme replacing chemical equalization with anaerobic di-
gestion. (8) Major unit sizing for this 95 m3/day (25,000
gpd) facility is identical to the Ridge, NY plant, except "that
the size of the rapid sand filters was doubled for the Massachu-
setts design.
Wet Air Oxidation
The wet air oxidation process has been used in Japan to
treat night soil wastes. (55, 56) Night soil is "accumulated
human wastes, stored outside homes, and pumped on a routine ba-
sis. The material has many of the same concentrations as sep-
tage, but it differs considerably from septage in that it is
much less septic (days compared to years), so it is neither
subjected to the same degree of decompositon, nor is it sub-
-75-
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jected to elutriation, as septage is. Typical parameter values
for night soil include a high ,pH (8.1 to 9.0), TS of 29,300 to
35,000 mg/1, BODc of 10,000 to 14,000 mg/1 and an NH3-N of
3,000 to 3,900 mg/1. (55) Therefore, this type of treatment may
be applicable to septage stabilization.
COAGULATION SECONDARY FINAL
MEIHCATMENt EQUALIZATION SETTLING EQUALIZATION TREATMENT FILTERING RECHARGE
SCHEMATIC
Figure 23. Wayland-Subury, MA septage treatment
alternative II - aerobic treatment.
RECHARGE
BASIN
LTANK ' SYSTEM
FH.T..H r i
I 3LUDGC {J
1
ANAEROBIC COAGULATION SECONDARY FINAL
OIOESIION SETTLINO TREATMENT FILTERINO RECHARGE
SCHEMATIC
Figure 24. Wayland-Subdury, MA septage treatment
alternative III - anaerobic/aerobic treatment.
-76-
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Wet air oxidation studies at the Chubu STP, Yokohama,-Japan,
were performed on night soil mixed with air at pressures between
5.6 x 106 pa and 8.4 x 106 pa (800 to 1,200 psig) and
heated to temperatures of 185° to 210°C (365° to 410°F)
in heat exchange tubes. The mixed oxidized material showed a
high pH, a 9 to 38.2% TS reduction, a BOD5 reduction of 13 to
39.3%, but no change in NH3-N and total N concentrations.
The oxidized material characteristically exhibits excellent s.et-
tling properties, with a supernatant pH of 7.8 to 8.5, VS of
8,000 to 17,400 mg/1, a BOD5 of 6,500 to 9,500 mg/1 and
NHo-N of 3,140 to 3,720 mg/1. The settled sludge also had a
pH of 7.8 to 8.5, a BOD5 of 8,800 to 15,600 mg/1 and VS of
;14,600 to 33,000 mg/1. The clarified liquid was then shown to
be amenable to biological treatment. After diluting the oxi-
dized waste to a maximum of 900 mg/1 BODs, Ikeda found excel-
lent BOD reductions can be expected with a 6005, loading of 80
kg BOD5/100 kg MLSS/day and 1.5 kg/m3/day loading limit on
the aeration tank. The stabilized sludge solids have a signifi-
cantly improved filtering ability, and can be dewatered on a
filter press. The tendency of the wet air unit to accumulate
scale on the exchange tubes can be counteracted by weekly flush-
ing with 5% nitric acid at operating pressure and temperature.
Treating night soil in a unit with heat exchangers of 304 stain-
less steel did result in corrosion, especially at pipe bends.
After 1,000 hours of operation, all surfaces, except titanium
materials, developed pitting, corroded holes, and cracking.
With night soil, the current material of choice in a wet-air,
oxidation unit is titanium.
Autothermal Thermophilic Aerobic Digestion
An ATAD at Cornell University is currently treating domes-
tic animal waste, and soon will test treatment of septage. The
two stage reactor system is based on pilot plant work performed
at Tonowanda, NY using pure oxygen, whereas the Cornell study is
using an air supply. Using covered, well insulated tanks, and
small gas flows of pure oxygen, reactor temperatures up to
65°C can be obtained by taking advantage of the exothermic
reactions of aerobic digestion. The lower gas volumetric flow
rate of a high purity oxygen supply (about 1% of an air flow
system) carries away much less heat in the form of E^O eva-
poration then does an air supply, allowing inherent thermal ef-
ficiencies to be realized in the oxygen system. (53)
The two stage system at Tonowanda resulted in an overall VS re-
duction of 29.1 to 41.9% at VS loadings from 12.8 to 16.0 kg
VS/day/m3 (0.032 to 0.46 Ib VS/day/ft3). (53) A two stage
system was used, as it proved more temperature stable than a one
stage reactor system. The first stage is temperature limiting
(reaction rates decrease above 65 to 70°C), while the second
-77-
-------
stage is substrate limiting. Table 18 shows results of VS re-
ductions at the Tonowanda pilot plant.
TABLE 18. VOLATILE SOLIDS REDUCTIONS AT TWO STAGE
AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION (ATAD)
PILOT PLANT AT TONOWANDA, NY (53)
Phase
I
III
III
I*
III
III
Retention
Time
Feed (days)
WAS* 2 . 1
Unox WAS 1.7
Unox WAS 2.3
and PS**
WAS 2 . 5
Unox WAS 2.0
Unox WAS 2.7
and PS
Stage 1
Temp . °C
Max/Mean
55.0/48.7
57.8/50.1
54.7/49.3
Stage
50.3/50.3
57.8/57.3
54.8/54.8
VS Load
kg VS/day/m3
(Ib VS/day/ft3
11.05 (0.69)
15.86 (0.99)
13.94 (0.57)
2
6.89 (0.43)
10.59 (0.66)
9.13 (0.57)
% VS
Reduc-
tion
27.9
22.1
26 . 9
19.5
12.5
12.5
Overall Reduction
Phase
I
III
III
Retention
Time
(days)
4.6
3.7
5.0
VS Load
kg VS/day/m3
(Ib VS/day/ft3
5.13 (0.32)
7.37 (0.46)
6,. 41 (0.40)
% VS
Reduc-
tion
41.9
29.1
36.0
* Waste Activated Sludge
** Primary Sludge
-78-
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In the unpublished Cornell University ATAD digestion study
two covered, well insulated pilot scale digesters were operated
at about 2.5 days retention period each stage (Figure 25). This
system used high efficiency atmospheric air aerators (oxygen
transfer efficiency greater than 20%) to reduce the air flow
through the units limiting evaporative heat loss so temperatures
may be maintained in the 65°C to 70°C range. Investiga-
tions claim a stabilized sludge has been produced from this unit
after 5 to 6 days retention time.
PRIMARY
TANK
AERATION
TANK/T.F.
CLARIFIER
AEROBIC
DIGESTER
ANAEROBIC
DIGESTER
SEPTAGE
ADDITION PT
SAND DRYING
OR:PURIFAX
PROCESS,
ZIMPRO
PROCESS. ETC.
NG
J
MECHANICAL
DE WATER ING
t
SOLIDS TO
LAND OR SEA
Figure 25. Two stage pilot plant autothermal thermophilic
aerobic digester (ATAD) system at Cornell University,
Ithaca, NY.
SEPTAGE HANDLING AT SEWAGE TREATMENT FACILITIES
GENERAL HANDLING PROCEDURES
Septage can be disposed of in a STP by addition to either
the liquid stream or the sludge stream. In either case, screen-
ing, degritting, and equalization are recommended.
Septage frequently is considered a high strength wastewater
and is dumped into an upstream sewer or placed directly into
various unit processes in a treatment plant (Figure ,26). In
several facilities, septage is considered a sludge because it is
-79-
-------
AERATION
TANK/T.F.
PRIMARY
TANK
CLARIFIER
AEROBIC
DIGESTER
ANAEROBI
DIGESTER
SEPTAGE
ADDITION PT.
MECHANICAL
SAND DRYING
DE WATER ING
OR:PURIFAX
PROCESS,
ZIMPRO
PROCESS, ETC.
SOLIDS'TO
LAND OR SEA
Figure 26. Septage addition points in septage treatment
facilities.
the product of an anaerobic settling/digestion tank, and it has
approximately the same total solids concentration as primary mu-
nicipal sludge. The septage application points in the solids
processing stream of an STP may include sludge thickening, sta-
bilization, and dewatering steps. The decision of where to ap-
ply the septage should be determined following a statistically
significant sampling and analysis program of a locale's septage
for at least a theatre of seasons, including:
. solids loading
. oxygen demand
. toxic substances
. foaming potential
. nutrient loading (N and P) , where required.
The above factors, combined with a plant's layout, design
capacity, present loading, and the following design criteria
provide the design professional with sufficient information to
arrive at a reasonable septage treatment scheme within a waste-
water treatment facility.
-80-
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Receiving Station
Whether septage is added to an upstream sewer or discharged
at a treatment plant in either the liquid processing stream or
the solids handling area, a suitable hauler truck discharge fa-
cility should be provided. (57) This facility should include a
hard surfaced, sloping ramp to an inlet port to accept a quick-
disconnect coupling directly attached to the hauler's truck out-
let, (7) thus reducing odor problems significantly. Washdown
water should also be provided for the hauler so spills may be
cleaned up. A recording of the time, volume, and name of the
hauler is vital for both operation and billing purposes.
A schematic of the Barnstable, MA septage receiving station
is shown in Figure 27. Portland, OR's Columbia Avenue plant
septage receiving site is shown in Figure 28, while Seattle
Metro's Renton STP septage receiving site is illustrated in
Figure 29. The latter two sites use a plastic card or magnetic-
ally enclosed card and card reader to assist in management func-
tions. The operator at the Portland facility validates a re-
ceipt with a charge card issued by the facility to each hauler
certified, to dump in that plant, while in Renton, the hauler
places his identification card in an automatic card reader which
relays information to the control center. A hard copy is re-
tained for billing purposes. In addition, a buried loop and
control circuit under the roadway at the Renton dump station
causes a signal to register at the control center alerting the
plant operator that a hauler truck has entered the dump station
area.
"HoneywagorT
Rock Sump
Hypochli
Appli
Figure 27.
Domestic (2)
Sewage
Primary Clarification
I®
Primary Effluent
Schematic diagram of the Barnstable, MA
septage receiving station.
-81-
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lij^^
DUMP SITE OPERATING PROCEDURE
1. Punch in your METRO I.D. card within 2 minutes
after arrival. The red light should go out and
the green light should come on.
2. Dial 31 or 32 on telephone if:
a) Green light fails to operate when I.D. card is
punched in.
b) Lost or no METRO I.D. card.
c) I.D. card punched more than once or
additional assistance is needed.
3. Please answer telephone if it rings.
Figure 28. Punch card reader at Seattle Metro's Renton STP.
Figure 29. Septage receiving station at Renton, WA.
-82-
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Pretreatment
Treatment plants handling septage have experienced better
operation when septage pretreatment is employed. Pretreatment
generally includes bar screens of 1.9 to ,2.54 cm (3/4 to 1 in)
opening, grit removal, and usually pre-aeration or prechlorina-
tion in aerated grit tanks along with the sewage flow for odor
control if septage is added to an aerobic process. Grit removal
by cyclone classifiers was designed into the Babylon plant and
is included in the new Bay Shore plant, both on Long Island, NY.
Separation of inorganic matter larger than 150 mesh can be
achieved with currently marketed equipment. (58, 59) Equaliza-
tion in 2 day average septage flow storage tanks and mixing ca-
pability should also be provided. To further attenuate odors,
enclosed storage tanks, ozonation, activated carbon adsorption,
or use of a soil filter to purify vent gasses exiting from per-
forated vent lines shallowly buried may be considered. The oc-
curence of odor problems is sporadic, and degree of control
should be related to proximity to dwellings, roads, other build-
ings, as well as prevailing wind patterns. Transfer pumping
equipment should be used to apply a continual adjustable small
dose of septage into the desired unit process from the storage
tanks.. Operators report slug doses or intermittent doses of
septage are not as effective as a continuous feed rate. (60)
LIQUID STREAM PROCESSING
The following liquid stream'processes were found to be ca-
pable of treating septage. They include primary treatment, slug
(random mode) dumping, controlled (or continuous) feed into ac-
tivated sludge units, and attached growth systems including
trickling filters and rotating biological discs.
Primary Treatment—;•
The report by Feige et al. for the U. S. EPA indicated that
neither natural settling, lime addition, nor polyelectrolyte
addition resulted in consistent liquid-solids septage separa-
tion. (15) Tilsworth characterized 'raw septage as relatively
non-settleable, as determined by a settleable-solids volume
test. Results -ranged from 0 to 90% settleable by volume, with
an average of 24.7%. (12)
In an unpublished study at the University of Massachusetts,
A. Tawa found septage settling characteristics could be divided
into 3 groups, types 1, 2, and 3. Type 1, from septic tanks
pumped before necessary, settled well. Type 1 septage was found
in approximately 25% of his samples. Type 2 septage, from nor-
mally operating systems, showed intermediate settling character-
istics and was found in 50% of his samples. Type 3 septage ex-
-83-
-------
hibited poor settling, was found in 25% of his samples, and was
from tanks overdue for pumping. It was generally found that
poor settling characteristics can be expected from septage. All
samples were between 1 and 6 years of age.
It is generally accepted that septage settles very poorly
without chemical addition. Tilsworth reported in his Alaskan
septage study, 50% of the samples exhibited sludge interface
height reductions of only 10% when allowed to settle for 30
minutes (Figure 30). About 1/3 of the samples are not shown in
the figure, since they settled less than 1% of the original
height. (12)
E
jo
"o
co
o>
CO
1,000
K.f\t\
DOO-
IOO-
5O-
irk
IO-
5
1
0
.01 0.1
12 5 IO 2O
Probability
j
/
/
I
/
/*
•
/
j/
S
^
~
-
4O 6O 8090959899 99.9
Of Occurrence
Figure 30. Probability of reduction of solids-liquid
interface height after 30 minutes settling of
Alaskan septage samples.
-84-
-------
Elutriation, or settling of septage in a septage-sewage mix-
ture, is reported to yield better results than attempting to
settle pure septage. Smith and Wilson report that up to 60% of
septage SS can be expected to settle in a STP's primary sedimen-
tation basins. (61) An EPA study found 55 to 65% SS removals in
a primary clarifier, while only 15 to 25% BOD removals resulted
in the same unit process. (62) An EPA sponsored septage treat-
ment project is currently underway at a Falmouth, ME STP, inves-
tigating pretreatment and liquid-solids separation techniques
by the additions of various chemicals including Cl, Fe, Mg, Al,
and acids; heat, and various combinations of these approaches.
(96)
Activated Sludge—
Septage may be added to the activated sludge process if 1)
additional aeration capacity is available, 2) the plant i.s hy-.
draulically loaded below design capacity, 3) the septage metals
content can be diluted to a sufficiently low concentration, 4)
foaming potential can be controlled by sufficient dilution and
5) excess sludge handling capacity is available. Very limited
quantities of septage may be added without changing the sludge
wasting rates.
Slug Dumping—
Slug, or random mode dumping, occurs at a majority of the
STPs which accept septage. Because of the dilution effect when
mixed with raw sewage, it is suitable only for medium to large
(2.0 mgd or greater) treatment plants. CE^M/Hill recommended
to the Forest Service that levels of septage and vault toilet
wastes that can be added to differing types of activated sludge
plants. (63) Vault toilet waste,volumes are more critical than
septage due to the effects of the 2 principal preservatives used
in vault toilets - formaline and zinc sulfate. In an acclimated
biomass, formaline may be added until an aeration basin level of
200 mg/1 is reached, however wibh slug dumps, the level should
.not be raised to higher than 50 to 100 mg/1. (63) Zinc addi-
tions, however, should be limited to an aeration basin concen-
tration of 5 to 10 mg/1 on a continuous .basis, but should be
much lower in the slug dumping mode. Formaline is biodegradable
and will not accumulate in sludge solids whereas Zn will accumu-
late rather quickly (over 90% in the first few hours) in the
sludge solids. (64) This information, modified by the author's
field investigations, is presented in Figure 31.
The use of slug dumping of septage may depend on limiting
the increase in MLSS to 10% per day to maintain a relatively
stable sludge, as seen in Figure 31. Higher loadings and wast-
ing rates than the resident aquatic biomass is acclimated to may
result in a poor settling sludge. (13) Severe temporary changes
-85-
-------
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WASTEWATER TREATMENT PLANT CAPACITY(M.G.D.)
Figure 31. Volumes of septage addition to activated sludge
wastewater treatment plants (no equalization facilities).
in loading beyond the 10 to 15% MLSS increase may cause a total
loss of the system's biomass, while loadings below this level
usually do not cause upset conditions. For example, the Weaver-
ville wastewater treatment plant in Trinity County, CA, reports
400 GPD slug dumps could be handled at a 0.5 MGD plant operating
at 40% capacity. (61)
In the slug dumping mode, package treatment plants should
not be allowed to accept any septage if their design capacity is
less than 100,000 gpd. (7) Most package plants of this size or
less do not have grit removal, and without this process, grit
accumulations in the treatment units may occur. Package treat-
ment plants can be expected to treat septage at approximately
0.1% of the plant design capacity, since many package plants
have been designed with minimal excess flow and treatment capa-
city compared to larger, built-in-place plants. This trend is
now reversing as package plants are designed on excess flow cri-
teria identical to larger plants. Modified activated sludge
-86-
-------
plants may treat septage at twice the rate of a package plant.
(63) Conventional activated sludge plants are able to treat
septage at about 4 times the rate of package plants and at about
twice the rate as modified activated sludge plants. A large
percentage of solids (25 to 60%) may be removed in the conven-
tional plant's primary settling unit, normally lacking in a
modified (contact stabilization or extended aeration) activated
sludge plant, which accounts for the increased treatment capa-
city.
Controlled Addition • . »
In plants with holding and metering facilities, septage may
be bled into the waste flow stream at considerably greater flows
than would be attainable if only 'slug dumping procedures were
available.
A U. S. EPA study fed septage at loadings of 2 to 13% of the
sewage flow to 1 of 2 activated sludge units. (62) With a con-
trol unit F/M ratio of 0.4 and a septage-sewage F/M of 0.8, ef-
fluent BOD5 and SS characteristics were similar. Effluent
COD of the unit receiving septage increased almost in direct
proportion to the rate at which septage was loaded. When a
lower F/M ratio of 0.5 to 0.6 was utilized in the septage unit,
this unit had superior performance due to control of Nocardia,
a procaryotic filamentous actinomycete, often associated with
bulking, and indigenous to the Blue Plains facility. (65)
Figure 32, showing volumetric feed rates of septage on a
controlled basis to various types of treatment facilities, was
developed from mass balances in various research reports, plus
field investigations. Again, package plants with design capa-
cities under 379 m3/day (100,000 gpd) should not be allowed
to accept septage because of their historic lack of ability to
treat flows in excess of their design flow and loading capacity.
(7) For example, the State of Maine does not allow septage ad-
dition at treatment facilities under 1,140 m3/day (0.3 mgd) .
(66) Depending on the present plant flow compared to the design
plant flow, a biological treatment reserve can be estimated
which will allow for a certain level of septage to be adequately
treated. With identical plant design capacities, the allowable
relative volumes of septage addition to various types of treat-
ment schemes flowing at various levels of design flow would be
as follows.
-87-
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ACTIVATED SLUDGE
NO PRIMARY TREATMENT
PACKAGE
PLANTS
ACTIVATED SLUDGE
WITH PRIMARY
TREATMENT
AERATED
LAGOON
SEPTAGE ADDED (I.OOOGALJPER MGD PLANT CAR
(PER DAY)
Figure 32,
Septage addition to wastewater treatment plants
with equalization facilities.
The limiting ratios of septage addition in Table 19 are
based on 1) package plants having a limited ability to treat
both flows and waste loadings'beyond design capacity, 2) acti-
vated sludge treatment facilities without primary sedimentation
treating all solids in aeration tanks, and 3) aerated lagoons
usually having a long detention time (days) with which to buffer
septage flows. (7) Figure 31 is indicative of continuous sep-
tage addition to a facility with a fully acclimated biomass. An
initial septage feed to an unacclimated system should be sub-
stantially less than shown on the graph, and on the order of 10%
of the graph values. Further gradual increases should be made
in the range of 5 to 10% of the current septage flow per day up
to the maximum amount shown in Figure 31. Dissolved oxygen must
be checked continuously and gradual changes made in sludge age
for optimum performance.
-88-
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TABLE 19. RELATIVE VOLUMES OF SEPTAGE ADDITION TO VARIOUS
PLANT SCHEMES OF IDENTICAL DESIGN CAPACITY
Package Plants
Activated Sludge (no primary treatment)
Activated Sludge (conventional)
Aerated Lagoons
1.00
2.08
4.83
6.00
In a recent study at the University of Massachusetts, feed-
ing various volumes of septage to both batch and continuous flow
complete mix activated sludge systems, the following empirically
developed relationship between biological growth and substrate
utilization were found- to be applicable. (-17)' These models can
predict volumes of septage that may be added to an existing fa-
cility if treatability studies of the service area's septage are
undertaken to determine waste loadings and utilization rates:
dX/dt = Y dF/dt - k,X
10
The rate of substrate utilization of the above expression, that
is dF/dt, can be approximated by the following equation:
dF/dt = kXS/(Ks + S) = dS/dt 11
where dX/dt = net growth of bacterial cells, mass/volume-time.
Y = growth-yield coefficient, mass of cells/mass of
substrate utilized.
dF/dt = rate of substrate utilization by bacterial cells,
mass/volume-time.
k<3 = bacterial decay coefficient, time
X = concentration of bacterial cells, mass/volume.
k = maximum rate of waste utilization per unit weight
of bacterial cells, time~l.
Ks = waste concentration at which rate of waste
utilization is one-half the maximum rate,
mass/volume.
-89-
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S = waste concentration surrounding the bacterial
cells, mass/volume, which is the waste concentra-
tion in a complete-mixing continuous flow reactor.
Dividing both side of Equation (10) by Xf gives
(dX/dt)/X = Y(dF/dt)/X - kd. 12
On a finite mass and time basis, Equation (12) becomes
(AX/dt)m/Xm = Y(AF/At)m/Xm - kd. 13
where the subscript m represents a definite mass of bacterial
cells. In Equation (13), the reciprocal of the term . (AX/d
t)m/Xm is often referred to as the "sludge age", and will
be designated as 0C.
6C = X m /AX/ At)
m
14
The term ( A F/ At)M/XM is commonly "knows as the fopd-to-
microorganism (F/M) ratio, and will be referred to as U,
U = (AF/At)m/Xm
15
Utilizing Equations (14) and (15), Equation (13).can be re-
written as:
1/6
= YU -
and Equation (11) can be rewritten as:
U = kS/(Ks + s)
16
17
By the principles of mass balance, Equations (16) and (17)
wall model both batch reactors and complete-mixing continuous
flow reactors under steady-state conditions. These are condi-
tions that will occur with continuous feed of septage to an
aeration system.
and
Solving Equations (16) and (17) for S, gives:
S = Ks (1 +kd 0C)/ 0c(Yk -kd) - 1
S = UKs/(k- U)
18
19
The kinetic coefficients Y, kd, k, and Ks, which relate
effluent substrate concentration, S to 0C and V can be de-
-90-
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termined in laboratory-scale batch reactors or complete-mixing
continuous- flow reactors.
The efficiency of waste treatment can be defined as:
E = 100 (S0 - S)/S0 " 20
where:
E = efficiency of waste treatment, percent
S0 = influent substrate concentration
S = effluent substrate concentration of waste
The rate of substrate utilization, dF/dt, can be expressed
on a time related basis as:
AF/ At = (Q/V) (S0 - S) 21
where:
Q = flow rate, volume/time
V = volume of reactor
By utilizing Equations (15) and (21) , and setting V/Q equal
to 6 , or the liquid retention time, the following equation is
obtained:
U = (S0 - S)/ 6x 22
Substituting U from Equation (22) in Equation (16) and
solving for X, gives:
x = ecY(s0 - s)/eci + -k '&0 /;.;• .23
'
which can be used to calculate the aeration system's concentra-
tion of bacterial cells. (17) With a known concentration of
septage and empirically determined degradation rates, an exist-
ing facility can be optimized for sludge age and MLSS to obtain
a U, or F/M ratio that will treat a septage-sewage mixture to
the desired effluent concentration.
Feng has shown higher sludge ages (10 days vs 4 days) re-
sults in higher percentage BOD5 removals and less sludge pro-
duction than at the lower sludge age (17) (Figure 33) . Wasting
must be adjusted gradually with increased loads to obtain a
sludge age which produces the optimum between aeration tank ef-
ficiency and good settling characteristics. A high sludge age
produces a light sludge with poor settling ability but good sub-
-91-
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strata removal characteristics.
very young sludge. (7)
The reverse is often true for a
O O
9f\
u
o
_J -» *>.
PERCENT REMOVAI
_ ro w •& u» o> -•
OQOOOOOC
...J*'
tf
r
k
JSf~
2^
-41
'•^-Z
)AY
Sr-5
\
j —
,.
N
WE
ST
V
:s=
e<
AK
RON
•SL
.^^—— •
••'
.-!(
— -•
>D/
SEPTA<
G SEPT
UDGE A
iYS
5E I
AGE
GE
•WM
,
"n=r;
30D5-I,'
BOD5-I
(FE
^JG,
>5Omg/
1,000m
975)
'I
g/i
5 IO 15 2O 25 3O 35 4O 45 50 55 6O 65 7<
PERCENT SEPTAGE
Figure. 33. BODs removal from septage-sewage mixtures
in batch activated sludge process.
Figure 34 shows the additional oxygen requirements for sep-
tage addition in activated sludge treatment plants and is modi-
fied upwards from field experience. (63) Oxygen requirements
usually exceed mixing requirements.
Because of the higher oxygen demand for septage than for raw
sewage, an additional oxygen supply for activated sludge plants
accepting septage having primary treatment would be 4.8 kg
02/m^ (40 Ib 02/1 , 000 gal) septage added. For plants
without primary treatment, an additional 9.6 kg 02/m-3 (80
Ib 02/1 , 000 gal) septage added should be provided. Package
treatment plants will have an oxygen requirement similar , to
plants without primary treatment. (63) Feng has shown similar
oxygen requirements in septage-sewage mixtures ranging from 0 to
40% septage in the mixture* At 40% septage, the mixture re-
quires 4.3 times the volume of oxygen as would an influent with
no septage in it. (17) ,
-92-
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WITH PRIMARY
TREATMENT
NO PRIMARY
TREATMENT
I 2 3 4 5 6 7 8 9 10 II 12 13 14 15
SEPTAGE ADDED, I.OOO'S GALLONS ( PER DAY)
Figure 34. Additional oxygen requirements for septage
addition to activated sludge wastewater treatment plants
At one plant in suburban Long Island, NY, septage is bled
into the liquid stream inversely proportional to the sewage
flow. This procedure takes advantage of a larger, excess aera-
tion capacity lower loading times '(7). An Orange County, PL STP
added septage proportionately with sewage flow rates to dilute
influent septage concentrations. Both plant's operators have
experienced some operational problems. When septage is added
inversely proportional to sewage flow variations, odor and
floatable solids problems have been reported, but if septage is
added proportionately to flow, an inferred oxygen deficiency can
result. (67) ,
Some odor and foaming problems have been reported in aera-
tion systems, however, the odor usually dissipated within 6 to
24 hours as freely strippable odor components of septage were
separated from the material. (48, 11) Foaming was not apparent
in all cases. Commercial defearners, decyl alcohol, heat grids,
foam fractionation, ozonation, aeration tank spray water, and
increased aeration tank freeboard have been used in various
-93-
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studies and at various treatment plants on an exploration basis
to reduce foaming with septage addition, all with limited suc-
cess. (68, 67, 36, 69, 16, 13, 70, 97)
The United States EPA is sponsoring a contract study at the
University of Lowell, MA, titled, "Monitoring Septage Addition
to Wastewater Treatment Plants" to evaluate the effects of sep-
tage addition to secondary wastewater treatment facilities. In-
formation _ to be presented includes effects of slug and continu-
ous addition of septage on unit processes and overall plant per-
formance, recommended septage loading rates to biological pro-
cesses, recommended operational control strategies for plants
treating septage, and estimates of both additional costs for
treating septage and additional operation and maintenance re-
quirements.
Attached Growth Systems—
Systems that employ attached growth aerobic treatment pro-
cesses, such as trickling filters and rotating biological con-
tactors, are usually more resistant to upsets from changes in
organic or hydraulic loadings and are suitable for septage
treatment. (54, 10, 71)
In trickling filters, additional recirculation has been
shown to adequately dilute septage concentrations and diminish
chances of plugging the media. At Huntington, Long Island, 114
m3 (30,000 gpd) of septage is treated at a 7,200 m3/day
(1.9 mgd) facility. (10) BOD5 reductions of 85 to 90% have
been observed concurrent with a SS reduction of 85%. (10)
Screening and grit removal is important to prevent plugging of
the trickling filter media. Results of treating septage in
Huntington's Plant are shown in Table 20.
Rotating biological contactqrs utilize a long detention time
and a continually rotating biological media that is reportedly
resistant to upsets. (8) At Ridge, Long, Island, a BOD5 re-
duction of 90%, COD reduction of 67%, and a TSS reduction of 70%
has been reported. This installation utilizes flow equalization
of a high strength waste. A surface loading of 0.04 m3 flow/
day per m2 surface area (1 gpd/ft2) produced these results.
SOLIDS STREAM TREATMENT
Various processes for treating septage in the solids treat-
ment area of a^STP are discussed in this section. They include
aerobic digestion, anaerobic digestion, mechanical dewatering,
and sand drying beds. These processes, along with other closely
-94-
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related treatment schemes that are applicable to a STP (but have
been practiced at another type of facility and have been dis-
cussed previously), are shown in Figure 35 by asterisk. Those*
sludge processing unit operations not investigated for septage
treatment are also shown.
TABLE 20. PERFORMANCE OF HUNTINGTON, NY TRICKLING FILTER
WASTEWATER TREATMENT FACILITY ACCEPTING SEPTAGE
Raw
Scavenger
Sample Waste
1 BOD 5400
2 pH 6.1
BOD 1130
COD
TS 1132
TVS
SS
VSS
% TVS
% VSS
Influent
Chamber
(Combined
Waste)
190
6.9
206
409
509
287
196
160
56.5
84.0
Primary
Tank Secondary
Influent Effluent
350
6.8
173
951
730
' 450
414
338
61.5
81.7
40
6.8
38
151
325
146
62
34
45
54.8
%
Reduc-
tion
88.5
76.0
84.0
55.5
67.5
. 85.0
90.0
bLUDGEJYPElTHKIKENING |STAB^LI^Tpslc«MI]TgNIINGlOEWATERINGlHEAT PR YINd REDUCTION I _F|NAL_ I
I \ Binding *| Reduction ^Stabilization "p |~ ("stabilization | Disposal ~|
SEPTAgg.*"
Figure 35. Unit processes - sludge processing and disposal,
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Aerobic Digestion —
An alternative to considering septage as a concentrated
wastewater would be to assume septage is the product of an un-
heated digester and, therefore, a sludge.
Many researchers have reported good results in both lab
scale and pilot plant scale aerobic digestion of septage or
septage-sewage sludge mixtures. Jewell reports diminished
odors, but the time required to produce an odor-free sludge
varied up to 7 days. (16)
Tilsworth reported a high degree of septage biodegradability
at a 10 day aeration time, resulting in a BOD5 reduction of
80% and a VSS reduction of 41%. (12) Chuang treated septage
first in an anaerobic unit then with an aerobic digester, re-
ported a 36% VSS removal in the aerobic portion at a 40 day
aeration time under a loading of 0.03 Kg/day/m3 (0.0016 lb
VSS day/ft3) . (7) After 22 to 63 days aeration, Howley found
a 43% VSS reduction and a 75% COD reduction. (36)
Septage-sewage mixtures are also amenable to treatment.
Cushnie showed an average 98% BOD5 removal from septage-
sewage mixtures, ranging from 0% septage to 20% septage at 6
day's aeration. -Orange, County, FL, adds septage to aerobic
digesters at the rate of 5% of the sludge flow and obtains good
reductions at a loading of 2.4 kg VS/ft3/day (0.15 lb VSS/-
f t3/<3ay) . (67) Bend, OR, obtained good removal in a mixture
containing 13% septage and 87% sludge at a loading of 0.32 kg
VSS/ft3/day (0.02 lb VSS/ft3/day) , utilizing a 15 to 18 day
aeration time. (68)
Tilsworth observed cXl and /& gas transfer characteristics
for septage and found that both &L , the ratio of gas transfer
efficiency to tap water, and /# , the ratio of O2 saturation
concentration to tap water, approached unity after 1 to 2 days'
aeration. Prior to 1 day, c*. and /ff were in the range 0.4 to
0.6. (12)
Jewell found both dewatering and settleability improved with
aeration, but the aeration time required to effect significant
improvement varied. (16) Two U. S. EPA studies are currently
investigating septage addition to aerobic digesters. An inhouse
study is underway at Lebanon, OH, and a contract stu,dy is being
performed at Falmouth, ME.
-96-
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Prior to adding septage to the aerobic digestion process,
aeration capacity, toxic metal or chemical accumulations, and
increased solids disposal should be investigated. All investi-
gators consistently have reported repulsive odors and foaming
problems (7, 67, 36, 69, 12) with foaming occuring as an in-
direct relationship with the use of detergents by the septic
tank owners. (36) Most investigators report foaming diminishes
after 24 hours.
Bend, OR (Figure 36) solved the overflow of foam from its
aerobic digester with the addition of fiberglass panels for
around the top of the digester for increased freeboard. Table
21 below shows time to change in odor and loss of foam from 11
Vermont septage samples. (24)
TABLE 21. TIME TO LOSS OF SEPTAGE ODOR AND FOAM
REDUCTION FROM BATCH AEROBIC DIGESTER (36)
Batch
Number
1
2
3
4
5
6
7
8
9
10
11
Mean
Median
Time to Odor
Change After
Initiating
Operation
(days)
4
9
4
3
10
5
5
1
No septic odor
3
3
4.7
4
Time to Loss
Of Foam
(days)
9
10
! 13
19FF
12
No ' foam
6
FF
14FF
7
11
10.9
10.5
Household
Used Washer
Detergent
Yes
Yes
Yes
Yes '
Yes
No
Yes
Yes
Yes
Yes
Yes
FF' Batch 4 was foam fractionated after 19 days, batch 8 at
start-up, batch 9 after 14 days.
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Figure 36. Aerobic digester at Bend, OR STP,
Recommendations, when considering septage addition to aero-
bic digesters, should include screening, degritting, flow equal-
ization, an analysis of excess digestion capacity, management
scheme to reduce foaming problems, and peripheral effects to
other processes such as solids handling. An initial septage ad-
dition should be limited to approximately 5% of the existing
sludge flow. Further septage additions should be gradual.
Anaerobic Digestion
Septage in Tallahassee, FL, is treated in an unheated an-
aerobic digester which operates at 20°C to 30°C (7, 72)
(Figure 37). With an influent septage concentration of 17,700
mg/1 total solids, a VS reduction of 56% was reported after an
82 day retention time at a loading of 0.16 kg VSS/m3/day
(0.01 lb VSS/ft3/day) . Large quantities of grit in the sep-
tage required draining and cleaning of the open digester after
only 3 years of operation. Leseman and Swanson analyzed the
distribution and concentrations of volatile acids in the di-
gester (72) and found volatile acid to alkalinity ratio varied
from 0.34 to 0.83. The 8 month average volatile acid concen-
tration was 703 mg/1 and ranged from 408 mg/1 to 1,117 mg/1 at
a consistent pH near 6.0. The progression of volatile acid con-
centrations in the digester, from 2 to 5 carbon acids, showed
acetic - 276 mg/1, propionic = 294 mg/1, isobutryric = 14 mg/1,
-98-
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butyric = 49 mg/1, isovaleric = 28 mg/1, and valeric = 42 mg/1.
Similar results are reported by Kolega in raw septage samples
from Litchfield, CT. He found an average total volatile acid
concentration of 807 mg/1, with acetic = 253 mg/1, propionic =
412 mg/1, isobutyric = 26 mg/1, butyric = 30 mg/1, isovalertc =
50 mg/1, and valeric = 36 mg/1. (27) Since Tallahassee's di-
gester had an open cover, gas production could not be monitored.
Supernatant from this digester is pumped to the sewage sludge
anaerobic digester. Anaerobic digestion of septage is more
likely to be successful than anaerobic digestion of night soil.
Poor results have been experienced in the Orient, relating to
scanty methane production, slow stabilization, strong superna-
tant liquid, and an odorous, poorly dewaterable product. (56)
Figure 37.
Anaerobic digester stabilizes septage at
Tallahassee, FL STP.
-99-
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Jewell reported a 45% reduction in VSS from a digester
loaded at 0.80 kg VSS/m3/day (0.05 Ib VSS/ft3/day), with a
15 day hydraulic retention time. Gas production varied from
0.26 to 0.47 m3/kg CODr (1.2 to 7.6 ft3/lb CODr) , at a
loading of 1.28 kg VSS/m3/day (0.08 Ib VSS/ft3/day), where
gas production fell off drastically, indicating, a possible poi-
soning of the system by a toxic chemical concentration of un-
known source. (16)
Chuang reported a 92% VSS removal from a heated anaerobic
digester loaded at 1.28 kg VSS/m3/day (0.08 Ib VSS/ft3/day)
with a 15 day hydraulic retention time. (7) Incoming solids
ranged from 0.3 to 8%, and total solids reduction was more than
93%. BOD reductions averaged 75%, from 6f100 mg/1 in the in-
fluent to 1,500 mg/1 in the effluent. Spohr found that when
septage-sewage sludge was added to anaerobic digesters in Anne
Arundel County, MD, no-change in digestion was apparent if total
solids in the digester were between 2 and 15%. (73)
Based on his research, Howley recommends a maximum septage
addition of 8.1 m3/day (2,130 gpd) to each 55 m3 (14,500
gal) sewage sludge added per day per 3,785 m3 (million gal)
of digester capacity, with a detention time of 30 days and a
maximum loading of 1.28 kg VSS/m3/day (0.08 Ib . VSS/ft3/
day). (36) Good operation of anaerobic digesters requires a li-
mitation on toxic materials. An inhouse U. S. EPA study on sep-
tage addition to anaerobic digesters is being performed at Leba-
non, OH, and is expected to yield more precise loading informa-
tion.
In single-stage digesters, prior treatment with screening,
grit removal, and equalization is necessary. Digesters should
be cleaned on a regular schedule, such as every 3 to 5.years, or
as required. (74)
Monitoring digester performance includes long term evalua-
tion of volatile acid/alkalinity ratios and gas production.
Mixing is vital in preventing a sour digester from the propaga-
tion of point-source failure due to a septage load containing
high volatile acid concentrations and low pH.
In systems with multiple digesters, in addition to all the
preceding suggestions, the additional practices should be fol-
lowed. Spreading the septage load to many digesters will reduce
septage concentrations. Recycling from the bottom of a secon-
dary digester or from another well-buffered primary digester at
a rate of up to 50% of the total raw feed per day has been help-
-100-
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ful. Control of temperature and mixing should also be adjusted
for maximum performance. (74) A rule of thumb in adjusting tem-
peratures says changes should not exceed 0.56C° (1F°) per
day to prevent shocking an acclimated biomass.
Mechanical Dewatering
Islip, Long Island, uses a vacuum filter (Figure 38) to de-
water 379 m3/day (100,000 gpd) of chemically conditioned,
settled septage. A design basis of 10 Ib/hr/m2 (5 lb/hr/
ft-') of surface area was used. A lime addition of about 0.1
kg lime/kg septage dry solids (190 Ib/ton of dry solids) and
0.0002 m3/ kg dry solids (50 gal/ton of dry solids) standard
concentration ferric chloride solution are added prior to set-
tling and vacuum filtration of the resultant sludge. (7)
Figure 38. Islip, NY vacuum filter dewaters
chemically conditioned septage.
-101-
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In laboratory study at Clarkson College, Crowe obtained
successful results with vacuum filtration of raw septage and
mixtures of raw septage and digested sludge with up to 20% raw
septage by volume. Chemical conditioning with 10 to 20 gm
lime/100 gm dry solids, 5 to 25 gm ferric chloride per 100 gm
dry solids, and 1 to 2 gm polymer/100 gm dry solids (Calgon
WT2640) were investigated. Dewatering characterisics of chemi-
cally treated septage and septage-sewage mixtures were observed
to be similar to the chemically treated digested sludge alone.
The filtrate contained only 5 to 10% of the raw septage COD.
(75) Attempts to vacuum filter untreated Alaskan septage met
with limited success because of media plugging problems. Poly-
propylene 24 x 21, having a plain weave 1/1 gave the best fil-
tration rates of any media tested, ranging from 4.88 to 26.07
kg/hr/m2 (1.0 to 5.34 Ib/hr/ft2). Highest filtration rates
were observed on samples with solids in the range of 0.5 tor
1.0%. (12)
Sand Drying Beds
Sand drying has been used to dewater septage, but with vary-
ing success. Anaerobically digested septage is reported to re-
quire 2 to 3 times the drying period of digester sludge. (72)
After 15 to 20 days treatment in aerated lagoons and batch aero-
bic digesters, dewatering simulation studies yielded a septage
capillary suction time (CST) of less than 50 seconds. (76) CST
values of conventional sewage sludge that can be readily de-
watered in sand drying beds vary up to a maximum of 70 seconds.
A lower CST can be correlated to a faster dewatering time.
GST's of raw septage usually range from 120 to 825 seconds, with
a mean of 200 seconds. (76) Lime addition of septage prior to
sand bed dewatering vastly improved dewatering characteristics.
Feige, et al, found that an addition of 0.09 kg lime/kg dry
solids (180 Ib lime/ton dry solids), or 3.59 kg lime/m-* (30
lb lime/1,000 gal) septage based on 40,000 mg/1 total solids,
raised the pH to 11.5 and dried to 25% solids in 6 days and 38%
solids in 19 days. (15) An application depth of greater than 8
inches is not recommended, because it slows the drying process.
The filtrate analysis (Table 22) showed that 1) most heavy
metals were tied up in the solids; 2) fecal coliform were re-
duced substantially, 3) fecal streptococci were more resistant
than fecal coliforms; and 4) odors were significantly reduced.
Some minimal filtrate treatment is necessary, however. (10)
Lime addition in this study was lower than levels recommended in
a Battelle Northwest study in which higher pathogen kills were
obtained by raising the pH above 12. (15)
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2 ? Other chemicals worked well in modifying the
n s?Pta9e to dewater. From a mean initial septage CST
of 450 seconds, a CST of 50 seconds was realized after the addi-
tion of an average of either 1,360 mg/1 ferric chloride, 1,260
or 2,480 mg/?
Crowe's laboratory study also found chemical addition great-
nLfT ?C?n few^ntering ?f septage and septage-sewage mixtures.
Doses of 10 to 20 gms lime/100 gms dry solids, 5 to 26 gms fer-
ric chloride/100 gms dry solids, and 1 to 2 gms Calgon WT 2640
polymer (cationic)/100 gms dry solids reduced initial CST of 400
seconds to less than 50 seconds. (75)
Perrin also studied the affects of freezing on dewatered
samples of . septage after treatment in aerated lagoon, or batch
aerobic digestion. Freezing lowered the CST from an initial
225 seconds to 42 seconds, an 80% improvement in dewatering
time. (76) ^
A U.S. EPA sponsored study at Falmouth, ME, will investigate
septage treatment by conditioning and dewatering of septaqe with
vacuum filters, filter presses, and centrifuges!
If _ septage is to be placed on sand drying beds, treatment to
a consistent CST range of 50 to 70 seconds is recommended. Fur-
ther treatment of underdrainage would be required in most cases
-103-
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SECTION VII
ALTERNATIVES EVALUATION
General
The purpose of this evaluation is to summarize key design
and operating data, present advantages and disadvantages for
each alternative, discuss relative economics of each process,
and combine that information in a comprehensive evaluation and
ranking of each alternative in order of preference in a socio-
economic, technical, institutional, and environmental framework.
Several methods of septage treatment and disposal have been
presented. Each of these alternatives can be assigned to one of
the following categories. -
1. Land application
2. Treatment at a septage facility
3. Treatment at a STP
LAND APPLICATION
Presently, the authors estimate well over 75% of the septage
generated in the United States is disposed of directly on the
land. Chemical constituents of concern in this mode of disposal
include heavy metals and nitrogen. Septage odors are a poten-
tial problem in determining land disposal sites, yet odors may
abate within hours after thin land applications of septage. If
nitrogen loadings to the soil are kept to level which will not
promote buildup of nitrate concentrations in underlying ground-
water, heavy metals will not be a major consideration. (78)
Transmissibility considerations for various pathogenic agents
that may be found in septage (viruses, bacteria, cysts of proto-
zoans, and ova of helminths), suggests that some pretreatment of
septage be accomplished prior to direct land disposal. (24, 22)
A partial list of available pretreatment processes could include
storage in aerated or non-aerated lagoons, lime addition to a pH
11 5 to 12, aerobic or anaerobic digestion, composting, wet air
oxidation, pressure chlorination, or possibly processes not yet
fully investigated, such as irradiation.
-104-
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Land application techniques that do not require pretreatment
processes include subsurface disposal and disposal in a sanitary
landfill. .Subsurface disposal requires more land on a N loading
basis than direct application since no volatilization losses oc-
cur, but subsurface disposal is not as sensitive to precipita-
tion events (which may lead to runoff problems) nor would odor
problems be as apparent. Capital investment and labor is
greater than direct application techniques, but savings may be
reflected in systems without pretreatment requirements. Gener-
ally, surface application techniques are more acceptable in less
densely populated regions, while subsurface disposal is prac-
ticed close to major population centers.
Septage disposal to sanitary landfills is practiced exten-
sively in NJ,_ with application rates limited to 0.05 m3
septage per nP solid waste. In order to minimize leachate
production, many landfills prohibit the introduction of wastes
with free water. Leachate collection and treatment facilities
should be provided if septage is added to a landfill, but may
not be needed if the landfill should be located so leachate
water is prevented geohydrologically from entering the ground-
water and no runoff of leachate is possible. Based on U. S. EPA
Construction Grants sludge disposal cost data, septage disposal
in landfills tends to be one of the more expensive methods en-
countered.
Lagoon disposal of septage is also one of the more common
methods of disposal. The placement of septage in terminal dry-
ing lagoons is practiced in many states including Connecticut,
New York, and Oregon. Free water will percolate through sides
and the bottom until clogging occurs. Evaporation then removes
much of the remainder of the free water. Solids are then buc-
keted to a landfill or the lagoon is covered with a soil layer.
Massachusetts and other areas use lagoons followed by infiltra-
tion beds. Lagoons are sized to handle 20 days storage at aver-
age flows at a minimum depth of 1.8 m (6 ft). At least 6 perco-
lation beds with a total effective area of 0.04 m3/m2/day
(1 gal/ftVday) follow the lagoon. Groundwater considera-
tions should be evaluated, and current requirements include the
base of a lagoon being at least 1.2 m (4 ft) above maximum high
groundwater, while the percolation beds should be at least 1.8
m (6 ft) above high groundwater level. As further protection
for potable well water quality and odor control, a lagoon system
should be a minimum of 305 m (1,000 ft) from any dwelling.
Groundwater quality should be monitored to determine if degrada-
tion is occuring.
Total disposal costs of land based systems are estimated to
be in the range of $1.50 to $5.00 per 3.8 m3 (1,000 gal). (78)
-105-
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A potential for a more cost-effective disposal system exists
with the marsh/pond and meadow/marsh pond system. Although ex-
perimental, these systems are estimated to treat septage at
about $1.00/3.8 m3 (1,000 gal). (832, 33, 77) Lagoon dispo-
sal facilities generally require site location in sparsely popu-
lated areas to provide buffer zones for odor dissipation and
aesthetic camouflaging.
Separate Septage Treatment Facility
Separate treatment facilities account for a very small per-
centage of the total disposal volume at present, but the proli-
feration of these types of facilities in the future is probable
as political forces motivate management decisions in these di-
rections. (65, 14) These systems are applicable only where suf-
ficient septage volume (over about 50 to 100 m3/day or 13 to
26,000/gal day) is available in a local area. Such facilities
will fulfill the requirements of pretreatment prior to land dis-
posal or they will include complete treatment facilities with
controlled effluents and solids disposal to the land. This
category also includes composting, which yields a useable, mar-
ketable end product.
Systems employing aerated lagoons for treating septage and
other high strength wastes followed by settling lagoons typical-
ly show BOD removals in excess of 90% with aeration retention
times over 4 days. Aerated lagoons have been shown to work bet-
ter when grit removal and buffering and equalization of at least
one days average flow are provided. Odors have been found to
dissipate within one day, but foaming is frequent and hard to
control. Various methods have been tried, including defoamer
addition, heat grids crossing the tops of the units, and sprays.
More work is needed to develop effective anti-foaming techni-
ques. Effluents from these systems may require further treat-
ment, such as application to infiltration beds or land based
disposal, such as spray irrigation. Solids may be hauled for
disposal in a sanitary landfill or diposed of on the land.
Total costs for aerated lagoon systems are in the range of $5.00
to $10.00 per 3.8 m3 (1,000 gal). (78) Costs for further
treatment must be added to these costs.
Chemical addition to septage in clarifiers will sometimes
achieve liquids-solids separation. Good results have been noted
with various combinations of lime (about 10,000 mg/1), ferric
sulfate (4,000 mg/1), ferric chloride (0.0002 m-* standard
strength solution/kg dry solids), and varying amounts of cation-
ic polymers. Previously, clarifiers based on typical sewage
overflow rates have been undersized, with significant solids
carryover occurring at 25 m3/day m2 (600 gpd/ft^). U. S.
-106-
-------
EPA sponsored research is underway at Falmouth, ME to determine
suitable overflow rates. Underflow solids have successfully
been dewatered on vacuum filters with yields of 2 to 4
kg/m2/hr (0.4 to 0.8 Ib/ft2/hr. Odor and foam are insigni-
ficant problems and operation is not affected by climatic
changes. Due to the shear bulk of chemicals needed, disposal
costs for this process can excees $30.00/3.8 m3 (1,000 gal).
(78)
An adjunct to chemical precipitation is chemical stabiliza-
tion. Enough lime (3.6 kg/m3 or 30 lb/1,000 gal) is added to
raise the pH to 11.5 to 12 to kill bacteria and stabilize the
waste. Coliforms are readily killed, but streptococi are more
resistant. Virus inactivation and ova and cyst survival need to
be addressed. Costs for chemical stabilization can be in excess
of $30.00/3.8-m3 (1,000 gal). (78).
Pressure chlorination of septage results in a material that
is easily dewatered, possesses a medicinal odor, and is stabi-
lized from further bacterial action. Chlorine consumption ac-
counts for a significant amount of the $15.00 to $50.00/3.8
HH (1,000 gal) treatment cost. (78) Typical dosages of chlo-
rine are in the range of 700 to 3,500 mg/1 chlorine at 241,000
pascals (35 psig). The occurance and significance of chlori-
nated hydrocarbons that may be associated with this technique
are being investigated by the U. S. EPA.
Composting of septage has been practiced almost exclusively
in Washington State with the Lebo process. Aerated septage is
mixed with sawdust until the mixture has a 50 to 60% moisture
content. After three months, bacterial concentrations have been
greatly reduced and organic carbon conversion has occurred. A
market needs to be further developed for the soil amendment re-
sidual of the compost process. Site preparation is necessary to
prevent runoff of leachate or rainfall runoff. The process lo-
cation need not be significantly separated from dwellings for
consideration of odors, as composting is an aerobic process and
is inherently less subject to odor problems than anaerobic pro-
cesses. Costs for composting are in the $7.00 to $30.00 range
per 3.8 m2 (1,000 gal). (78)
Autothermal thermophilic aerobic digestion (ATAD) is still
experimental, but may prove cost-effective as a digestion tech-
nique for septage as well as sludge solids. (53) Reaction time
in two stage insulated aerobic digesters is cut to 2.5 days/
unit, vastly lowering unit sizing and associated capital costs.
Foaming will be apparent, as it is in any aerobic process.
-107-
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Treatment costs may be about $15.00/3.8 m3 (1,000 gal), but
further treatment or disposal costs should be added.
Facilities have been proposed for separate septage treat-
ment using rotating biological contactors (RBC) preceded by
either anaerobic digestion or clarification. Experience with
other high ^strength waste has shown a total disc area of 24.4
m2/m3 septage applied is required. The liquid phase would
require additional treatment, such as sand filtration, while
solids would be disposed of on land after dewatering. Total
capital and operation and maintenance costs for this process are
estimated to be between $28.00 to $32.00/3.8 m3 (1,000 gal)
in 1975. (8) Solids disposal costs must be added to these
figures. If the units are enclosed, odors should not present a
problem, and foaming would be significantly less than in a
forced aeration unit.
Sewage Treatment Plant
Septage addition to a STP includes either addition to the
incoming municipal wastewater flow or to the solids processing
area. In either case, additional sludge solids will accrue from
the septage addition. For example, plant operators at the Co-
lumbia Avenue Treatment Plant in Portland, OR have found the ad-
dition of 1 m3 (264 gal) of 5% solids septage will result in
an additional 1 m3 (264 gal) of 0.5 to 1% waste activated
sludge plus an undetermined amount of primary sludge. Research
studies at the University of Lowell, MA are underway with em-
phasis on resolving both sludge production questions and what
limits of stress several types of biological systems will accept
in order to determine the consequences of varying levels of sep-
tage addition to wastewater treatment plants.
Direct addition of septage without pretreatment at a point
in the sewer upstream or at the head of a treatment facility re-
sults in potentially upsetting slug organic loads to a biologi-
cal process as well as accumulations of large volumes of grit
and extraneous material which may cause clogging and accelerated
equipment wear. Large treatment facilities (over 379,000 m-*/
day or 100 MGD) usually handle infrequent (less than 0.01% of
the daily flow) slug dumps of septage, but smaller plants ac-
cepting septage have shown a trend towards installing screening,
degritting, and blending pretreatment facilities to meter sep-
tage to the plant on a controlled basis.
The key requirement of a treatment facility is to maintain
required effluent quality. The regime which places the least
-108-
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stress on effluent quality is typically septage addition to the
solids processing system rather than the sewage flow scheme,
providing excess capacity is available. Potentially, more sep-
tage could be handled in the sludge processing system than by
addition to the liquid flow due to the tendency for septage to
be higher in solids concentration than waste activated sludge.
Septage has been shown to dewater poorly. Approximately 40
- 60% of SS can be expected to settle in the primary facilities
if septage is added to the mainstream flow. The remainder of
the solids, plus soluble BOD5 is added to the aeration units
for conversion to solids. These secondary solids are lighter
and bulkier than septage. Consequently, more incremental sludge
flow to the digesters can be expected when septage is added to
the liquid stream than when it is added directly to the solids
processing area.
The degree of septage treatment in aeration facilities de-
pends on the degradability of the waste and the excess aeration
capacity available. Present information concludes septage is
highly amenable to aerobic treatment, but excess aeration capa-
city is crucial to BOD$ removals. Slug dumping imposes heavy
organic shock loads, and should not be practiced, since the
rapid increase in sludge mass may make the sludge unstable.
The likelihood then exists for a washout of sludge solids over
the final clarifier weirs. Additional oxygen is required to
treat septage, and varies from 18 to 36 kg Oo/S.S m3 (40 to
80 Ib 02/1,000 gal).
Odor control and foaming problems are endemic to septage
treatment in aerated systems. Fortunately, various methods of
foam control are currently available, such as spray water, de-
fearners, and foam fractionation, but more work needs to be per-
formed in this area. Costs for treating septage at a STP typi-
cally are $10.00 to $20.00 per 3.8 m3 (1,000 gal) but indivi-
dual plants have reported costs significantly higher and lower
than this commonly seen range. (78)
Most treatment plants accepting septage utilize either aero-
bic or anaerobic digestion followed by sand bed dewatering or
vacuum filtration. Few used other processes, such as chemical
oxidation or wet air oxidation and incineration.
Anaerobic digestion treating septage must be closely moni-
tored, since the high volatile acids concentrations of septage
may lead to failure conditions. This method eliminates the
foaming and odor problems found in aerobic units, but high sep-
-109-
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tage loadings may introduce critical concentrations of heavy
metals,, surfactants, or toxic organic compounds (especially if
vault toilet or recreational vehicle toilet pumpings are in-
cluded) that may upset digester performance. Loadings of sep-
tage in excess of 1.28 kg VSS/m3/day (0.0816 lb VSS/ft3/
day) resulted in a drastic drop in anaerobic digester gas pro-
duction. (16) Anaerobic digestion also increased dewaterability
of septage, but it will still dewater slower than anaerobically
digested sewage sludge.
Aerobic digestion of septage has been successfully demon-
strated in various locales, but major problems stem from foam
production and to a lesser extent, odor. One successful method
of foam control is to increase available freeboard from a stan-
dard 0.5 m (18 in) to 1.2 m (48 in) or more. Aerobic digestion
of septage, demonstrated at rates from 0.48 kg VSS/m3/day
(0.03 lb VSS/ft3/day) to 20.8 kg VSS/m3/day (1.3 lb VSS/
ft3/day) , has been successful in improving dewaterability.
Costs for treating septage by anaerobic or aerobic digestion
predominantly fall in the range from $5.00 to $15.00 per 3.8
m3 (1,000 gal), including pretreatment facilities. (7)
Other methods are available for increasing the dewaterabili-
ty of septage, but they have significant drawbacks. The U. S.
EPA has successfully demonstrated liming septage to a high pH
(11.5 to 12), but costs are excessive compared to other systems
(over $26.00 per 3.8 m3 (1,000 gal)). (7)
Other additives, such as cationic polymers and ferric chlo-
ride will significantly improve septage dewatering, but their
costs, too will be excessive based partly on the high concentra-
tions of chemicals required. These methods also do not insure
stabilization, as normally would be required. Septage dewater-
ing can be drastically improved by freezing. Since no chemicals
are required, the cost is lower, but neither is stabilization
achieved nor can this method be practiced on a year round basis,
even in northern climates.
Costs
A summary of costs of various existing and proposed septage
treatment systems has been compiled in Table 22. A brief de-
scription of each process is given along with design informa-
tion, cost data, year applicable to the cost data, and system
comments. The cost data is detailed into yearly capital and
operation and maintenance costs on a 20 year amortization
schedule, discounted at 7% per year.
-110-
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TABLE 22 SUMMARY OP COSTS OP SEPTAGE TREATMENT SYSTEMS.
Process or System and Location
1. Spray irrigation center
pivot - sewage
2. Spray irrigation center
pivot - sewage
3. Spray irrigation solid
set - sewage
4. Spray irrigation solid
set - sewage
5. Spray irrigation MSB
Chicago - sludge
6. Surface spreading EPA -
sludge
7. Surface spreading EPA -
sewage
8. Surface spreading EPA -
s 1 udge
9. Surface spreading Xenia,
OH - sludge
10. Surface spreading U. S.
Navy Boardman Bombing
Range/ OR - septage
11. Land application nation-
wide sludge average
12. Subsurface disposal Tom-
kins County, NY - septage
13. Subsurface disposal Tom-
kins County/ NY - septage
14. Subsurface disposal Tom-
kins County, NY - septage
15. Subsurface disposal -
septage
16. Subsurface disposal -
septage
17. Subsurface disposal CO
State University - septage
18. Lagoon system Tomkins
County, NY - septage
19. Lagoon system Tomkins
County, NY - septage
20. Lagoon system Wayland,
MA - septage
21. Marsh/pond Upton, NY -
septage and sewage
22. Meadow/marsh/pond
23. Landfill construction
grants - sludge data
24. Landfill EPA Sludge Manual
25. Landfill various NJ sites
- septage
SEPARATE SEPTAGE TREATMENT
FACILITIES
26. Landfill Brunswick, ME -
septage
27. Aerated lagoon Douglas
County, OR - septage
28. Settling tanks/leaching
hnds Way! and, MA -
snptaqe
Design Flow Desiqn Loading Annual Costs/$3
rcyday Capital 0 & M
1137 5 cm/week 0.19 0.18
1137 10 cm/week 0.16 0.13
1137 5 cm/week o.26 0.15
1137 10 cm/week 0>19 0>12
6.8 x 1Q* o.l7 x 106 dry
wet Kg Kg/ha/yr
1137 5 cm/week o.20 0.19
1137 10 cm/week 0>17 Ojl5
23'9 1.05
43-3 0.58 2.03
16.98 13.77
, 32 10.51 6.87
32 17.12 10.99
32 21.06 9.16
19.6 30,000 PE 1.08 3.29
190 1124 - 4495 2.50 3 13
m3 ha/yr
95 674 m3/ha/yr 5>64 5_40
32 ' 5.72 5.49
32 9.57 7.78
O2?!^;:^0"
on leaching beds
945 0.19 m3/m2/day 0.26 0 50
total area
945 0.38 m3/m2/day 0 31 „ „
total area
23.38 17.13
61 cm layers 3.97 19.86
so?i! 5&a
.-I/day78
5 i/2 - ? ^ 12.69 5.40
detention in
aerated lagoon
38 1.5 day settling n co i ci
tank; 0.09 m3/ 9 °*69 *-*l
m2/day in
leaching beds
(continued)
-111-
1 79 m3
Total
0.37
0.29
0.41
0.31
5.67
0.39
0.32
4.62
2.61 ,.
8.00
30.75
17.38
28.11
30.22
4.37
5.63
11.04
11.21
17.35
0.80
0.76
1.06
"39.51
23.83
25.0 -
70.0
18.09
2.30
Cost Base
1973
1973
1973
1973
1973
1973
1973
1971
1972
1975
1976
1976
1976
1976
1972
1977
1977
1976
1976
1969
1977
1977
1976
1974
1975
1973
1972
1969
Reference
79
79
79
79
80
79
79
80
80
7
81
21
21
21
, 1
82
83
21
21
71
77
Author ' s
Estimate
81
80
7
84
85
71
-------
TABLE 22. (continued)
or Svstca and Location Design Plow Design Loading
29. Settling tanks/leaching
beds Sudbuty, MA -
septage
304 Thickener vacuua filter
Kayland, HA - septage
31. equalize clarify RBC Way-
land, Sudbucy, HA -
32. Anaerobic digestion RSC
Kayland, Sudbury, HA -
31. Thernophillic aerobic di-
gester HE - scptagc
34. Conpostlng tobo process -
septage
IS. CosposSLng Lebo process
saptage
36. Coaposltng Lebo process
Taeoaa, KA - septago
37. Cosposting Bcltsvllle
process Rehoboth, HA -
septage
38. Coopostlng Beltsvllle
process Beltsvllle, KO -
sludge
3*. Chealcsl oxidation
Brunswick, HE -
septage
40. Cheaical oxidation Ven-
tura, CA - septage
41. Chealcal oxidation Way-
land, Sudbury, KA -
septage
42. Chealcal oxidation
Babylon, MY - septage
43. Cheaical oxidation Port-
land, OR - septage
44. Cneaical precipitation
Oyster Bay, MX - septage
45. Chenlcal precipitation
lallp, HV - septage
46. Chealcal stabilization
Lebanon, OH - septage
sand drying beds
38
38
95
138
29
57
57
10.4
264
95
2500
76
455
910
2 day settling
tank 0.03 m3/
m2/day in
leaching beds
1.5 day reten-
tion in thick-
ener; 6.8 m3/
B)2/day vacuum
filter area
0.04 m3/m2
total disc area-
sand filters 59
m3/mVday;
infiltration 0."
infiltra
mVm2/da
2 stage digester
1st - 7 days,
2nd - 14 days;
0.04 nVm2
total disc area;
sand filters 59
m3/i"2/day;
Infiltration 0.2
m3/m2/day
0.2 m3/m3
digester
40,000 PE; 50 -
60% moisture in
sawdust mixture
50 - 601 mois-
ture in sawdust
mixture
0.02 sawdust
per m3 septage
1.2 m3 sawdust/
m3 septage,
3-6 months
2 day equaliza-
tion; 2 Pur ifax
units at 35 GPH
each; sand
filters 59 m3/
ra2/aay, infil-
tration beds 0.2
m3/m2/day
2 purifax units
at 35 GPM each
Sand recharge at
0.12 m3/m2/day;
vacuum filter
48.9 m3/in2/day
Sand recharge at
0.12 m3/m2/day;
vacuum filter
24.4 m3/m2/day
28.4 mVm2
septage in sand
drying beds; pH
to 11.5 - 12.0
Annual Costs/$3.79 m3
Capital o & H Total
1.62 4.60
11.38 28.14
14.71 36.20
Cost Base
1969
Reference
50
1.02 14.60 15.62
5.70 21.82 27.52
1.43
46.20
6.03
7.45
1.29 5.76 7.05
6.04 33.16 39.20
5.67
3.55 49.75
7.05 9.24 16.29
21.49 14.71 36.20
0.20 0.74 0.94
2.59 16.19 18.78
0.60 6.25 6.85
0.58 0.91 1.49
13.69 19.04 32.73
1974
1975
1976
1975
1977
1975
1973
1975
1975
1965
1971
1968
1974
1968
86
87
Western
Minerals
Letter
90
51
91
70
49
(continued)
-112-
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TABLE 22. (continued)
Process or System and Location Design Flow Design Loading
SEPTAGE ADDITION TO SEWAGE
TREATMENT PLANTS
47. Pretreatment Westport, CT
- septage
48. Pretreatment Poughkeepsie,
NY - septage
49. Pretreatment Brunswick,
ME - septage
50. Activated sludge Tomkins
County, NY
51. Activated sludge Tomkins
.County, NY - septage
52. Activated sludge Pough-
keepsie, NY - septage
53. Activated sludge Tri
Municipal Area (near
Poughkeepsie, NY) -
septage
54. Activated sludge Palo
Alto, CA - septage
55. Activated sludge South
Bend, IN
56. Activated sludge Cleve-
land, OH
57. Aerobic digestion Fort
Collins, CO - sludge
58. Aerobic digestion Bend,
OR - septage and vault
toilet wastes
59. Anaerobic digester Talla-
hassee, FL - septage
60. Anaerobic digester Japan -
night soil
61. Anaerobic digester Japan -
night soil
62. Anaerobic digester Way-
land, MA - septage
63. Anaerobic digester Way-
land, MA - septage
64. Wet air oxidation Pough-
keepsie, NY - septage
65. Wet air oxidation Ven-
tura, CA, - septage
'/day
15
190
4
32
32
190
231
16.6
1.9
114
227
20.5
13.5
30
30
25
25
190
246
0.05% flow
0.44% flow
0.05% flow
0.002% flow
0.04% flow
25 day SRT 0.43
Kg »s/mVday
15 day SRT 0.32
Kg vs/mVday
82 day SRT 0.16
Kg vs/m3/day
30 day SRT
15 day SRT
25 day SRT
vac filter 4.42
m3/nz/day
25 day SRT
leaching beds
0.13 m3/m2/
day
Capital 0 s M Total
1.81
3.27
2.50 13.50 15.50
10.49 19.23 29.72
27.47 8.24 35.71
7.25 3.95 11.20
9.87 2.73 12.60
4.48 4.76 9.24
i
30.00
5.32
1.92 2.08 4.00
7.78 6.37 14.15
1.97
0.71 0.40 1.11
0.97 0.57 1.54
5.76 1.62 7.38
3.77 1.61 5.38
6.75 3.38 10.13
4.58 5.03 9.61
Cost Base
1964
1976
1972
1976
19,76
1976
1976
1974
1976
1976
1977
1973
1976
1962
1962
1969
1969
1976
1971
Refers
59
21
11
21
21
92
92
93
7
7
83
68
7
94
94
71
71
92
95
-113-
-------
A survey of 42 sewage treatment facilities was performed in
this study (Figure 39). All processes reported were included,
including liquid stream treatment, aerobic digestion, and an-
aerobic digestion. Survey results showed that only about half
charged for septage disposal based on treatment costs. (78)
Some charge prohibitive rates to avoid septage, while others
place a minimal charge on septage to ensure against illegal
dumping at an unauthorized site. For those plants surveyed, the
average charge surveyed for septage was $15.18 per 3.8 m^»
(1,000 gal). However, an additional 20 to 30 plants contacted
either placed no charge on septage disposal or levied only a
yearly fee, most often in the range of $50.00 $300.00 per truck.
Many variables affect treatment costs, including local
funding requirements; eligibility for state or federal funds;
necessity for industrial cost recovery formats; local taxes as-
sessed in lieu of, or to offset, treatment plant expenses; level
of design; climate; present loading vs design plant capacity;
and cost of land. With this in mind, the broad range of charges
for treatment plant septage disposal is easily understood.
A summary of alternatives investigated is shown in Table 23,
with a representative range of costs for treating septage in
various alternatives shown in Figure 39. This matrix arranges
the alternatives by ordering the systems by cost effectiveness.
If a septage treatment system is desired in a particular loca-
tion, physical and environmental impacts would be evaluated for
compatability with the surroundings. If valid objections in
these areas do not arise, then this system should be chosen as
the most cost-effective solution for the problem. If the solu-
tion does not meet local requirements, investigate the following
system as the next most cost-effective answer. The procedure is
continued until a system meeting all stipulated requirements is
met.
Although research is required to answer various treatabili-
ty, design, and operation questions, sufficient detailed infor-
mation has been presented or referenced to assess the alterna-
tives listed.
-114-
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SEPTAGE DISPOSAL CHARGE AT WASTEWATER
TREATMENT PLANTS, »/I.OOQ GALLONS
42 PLANT AVERAGE CHARGE «I5.I8/I,OOO GALLONS
Figure 39. Summary of a survey of septage disposal charges
at 42 United States sewage treatment plants. (78)
115
-------
TABLE 23. RANKING OF VARIOUS ALTERNATIVE SEPTAGE TREATMENT PROCESSES*
yathod Miiabcr
10
12
13
14
17
Conditioning Method
Hatch/Pond - Meadow Harsh Pond
Surface Spreading Application
Sanitary landfill
Lagoon Systems
Subsurface Injection
Anaerobic Lagoons
Aerobic Lagoons
Aerobic Digestion
Anaerobic Digestion
Anaerobic - Aerobic Digestion
Anaerobic Digestion
Aerobic Digestion
Composting
Activated Sludge
Trickling Filter
Chemical Coagulation
Liae Stabilization
Disposal Category
Treatment
Effluent Treatment Solids
Land
Land
Land
Separate
Separate
Separate
' Separate
Separate
STP
STP
Separate
Separate
Separate
N/A
N/A
N/A
N/A
N/A
Infiltration Beds
Infiltration Beds
Infiltration Beds
Same Biological
Treatment
N/A
N/A
N/A
N/A
N/A
Dry out
Infiltration Beds Dry out
Vacuum Filter
Infiltration Beds Vacuum Filter '
Vacuum Filter
Biological Treatment Dewatering
Biological Treatment Dewatering
N/A Sell,as a
conditioner
Biological Treatment STP Solids
Stream
STP Solids
Stream
Physical - Chemical Oxidation Separate
Infiltration Beds Vacuum Filter
Infiltration or Sand drying
Biological Treatment beds
Transport STP Bio- Lagoon or Sand
logical. Treatment Drying Beds
•AsnlQiwrt r«nle determined on cost basis only.
(continued)
116
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TABLE 23. (continued)
Sensitivity of Process to Cost to Treat per 3.B m3 Estimated Use (%)
Treatment (1,000 gaTT
Method °°orE Vectors Groundwater Foaming Climate Precipitation 0 s M Capital Total present Future
117
-------
REFERENCES
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REFERENCES (continued)
25. Metropolitan Sanitary District of Chicago. U. S. EPA No-
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-------
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Third Annual Sanitary Eng. Conf., Univ. of Missouri, 1966.
Jewell, W. J., and McCarty, P. L. Aerobic Decomposition
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Amberg, H. R., Pritchard, J. H., and Wise, D. W. Supple-
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Gray, G. E., Bhagat, S. K., and Proctor, D. E. Biological
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Malhotra, S. K., and Miller, M. J. Biological Treatment
of Vinegar Plant Wastes. Proc. 28th Ind. Waste Conf.,
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Graner, W. F. Scavenger Waste Disposal Problems on Long
Island. Suffolk County Dept. of Health, 1968.
Epstein, E., Willson, G. B., Burge, W. D., Mullen, D. C.,
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Paper presented at 43rd Annual Pacific Northwest Pollution
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1976.
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-121-
-------
REFERENCES (continued)
48.
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can City, 83:2, pp. 78-79.
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for Town of Sudbury, MA. Dec., 1969.
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MA. Rosyln, NY, 1973, updated 1975. 21 pp.
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Corp., Park Ridge, NJ, 1974.
Noyes Data
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Digestion. Presented at 48th Annual W.P.C.F. Conf., Miami
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et al. Anaerobic-Aerobic Treatment of Sep-
tage (Septic Tank Pumpings)
Grant No. 17070 DKA, Phase I,
EPA Water Quality Office,
-122-
-------
REFERENCES (continued)
61. Smith, S. A., and Wilson, J. C. Trucked Wastes: More
Uniform Approach Needed. Water and Wastes Engineering,
10, March, 1973. pp. 49.
62. Bennett, S. M., Heidman, J. A., and Kreissl, J. F. Feasi-
bility of Treating Septic Tank Waste by Activated Sludge.
Environmental Protection Technology Series, EPA-600/2-77-
141, Aug., 1977.
63. CH2M/Hill Engineers. Planning Guidelines for Sanitary
Waste Facilities. Report to U. S. Dept. of Agriculture,
Forest Service, California Region, Jan., 1972.
64. Cooper, I. A. Distribution of Mercury, Cadmium and Zinc
in Activated Sludge Systems. M. S. Thesis, Northwestern
Univ., June, 1975.
65. Office of Research and Development. Papers for Discussion
at the Non-Sewered Domestic Waste Disposal Workshop. EPA
Region I, Boston, MA, April, 1975.
66. Whitman and Howard, Inc. A Study of Waste Septic Tank
Sludge. Disposal in Massachusetts, Wellesley, MA. Dec.,
1976, 65 pp plus appendices.
67. Cushnie, G. C., Jr. Septic Tank and Chemical Pumpings
Evaluation. M. S. Thesis, Dept. of Civil Engineering,
Florida Tech. Univ., 1975.
68. C & G Engineers. The Feasibility of Accepting Privy Vault
Wastes at the Bend Waste Treatment Plant. Prepared for
the City of Bend, OR, Salem, OR, June, 1973.
69. Jewell, W. J., Howley, J. B., and Perrin, D. R. Design
Guidelines for Septic Tank Sludge Treatment and Disposal.
Progress in Water Technology, 7, Feb., 1975.
70. Stevens, Thompson & Runyan, Inc. Pre-Design Report on
Septic Tank Sludge Disposal to the City of Portland, OR.,
Sept., 1971.
71. Weston and Sampson Engineers. Town of Wayland, MA Report
on Disposal of Septic Tank Pumpings and Refuse. Nov.,
1969.
72. Leseman, W. , and Swanson, J. Lab Director and Research
Chemist, respectively. Water Pollution Control Dept.,
City of Tallahassee, FL. Unpublished test data.
-123-
-------
REFERENCES (continued)
73. Spohr, G. W. Municipal Disposal and Treatment of Septic
Tank Sludge. Public Works, Dec., 1974. pp. 67 - 68.
74. Zickefoose, C., and Hayes, R. J. B. Anaerobic Sludge Di-
gestion". EPA 430/9-76-001, Municipal Operations Branch,
U. S. EPA, Feb., 1976.
75. Crowe, T. L. Dewatering Septage by Vacuum Filtration.
M. S. Thesis presented to Clarkson College of Technology,
Sept., 1974.
76. Perrin, D. R. Physical and Chemical Treatment of Septic
Tank Sludge. M. S. Thesis, Dept. of Civil Engineering,
Univ. of Vermont, 1974.
77. Small, M. M. Natural Sewage Recycling Systems. Brookha-
ven National Laboratory, Upton, NY. BNL 50630, Jan.,
1977. 103 pp.
78. Chuang, F. S. Treatment of Septic Tank Wastes by an An-
aerobic/Aerobic Process. Deeds and Data Supplement, WPCF
Highlights, July, 1976. pp. 3.
79. Environmental Protection Agency. Costs of Wastewater
Treatment by Land Application. Office of Water Programs,
EPA-430/9-75-003, Washington, DC, June, 1975.
80. Environmental Protection Agency. Process Design Manual
for Sludge Treatment and Disposal. Technology Transfer
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81. Environmental Protection Agency. Municipal Sludge Manage-
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Programs, EPA 430/9-76-009.
82. Briscoe Maphis Environmental. Sludge Management by-Sub-
surface Injection. Boulder, CO, Undated. pp. 8.
83. Houck, C. P., and Smith, J. L. Subsurface Injection - How
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84. Wright, Pierce, Barnes and Wyman Engineers. A Study for
Disposal of Septic Tank Wastes. Prepared for the State of
Main DEP, Topsam, ME, Oct., 1973.
85. Bowne, W. C. An Engineering Study of Septic Tank Content
Disposal in Douglas County, OR. County Engineers Office,
March, 1972.
-124-
-------
REFERENCES (continued)
86. Jewell, W. J. Waste Organic Recycling Services - Septic
Tank Sludge Treatment and Utilization. Proposal to.U.'S.
EPA Region 1, June, 1974.
87. Western Minerals, Inc. System Description Lebo Composting
Process. No. SD 750926. Seattle, WA, 1975.
88. Western Minerals, Inc. Engineering Report for Composting
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S. W., Tacoma, WA, Seattle, WA, 1975. 21 pp.
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90. Katsura, Y. Regional Plant Treats Septic Waste. Pollu-
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-125-
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/8-80-032
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
SEPTA6E MANAGEMENT
5. REPORT DATE
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Joseph W. Rezek and
Ivan A. Cooper
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Rezek, Henry, Meisenheimer and Gende,
P. 0. Box 40
162 E. Cook Ave.
Libertyville, Illinois 60048
Inc.
10. PROGRAM ELEMENT NO.
35B1C (DU B-124)
11. CONTRACT/GRANT NO.
68-03-2231
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Gin., OH
Office of Research and Development
U.S. Environmental Protection Agency *
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final July 1975-April 1977
14. SPONSORING AGENCY CODE
EPA/600/14
IB. SUPPLEMENTARY NOTES
Project Officer - James F. Kreissl (513-684-7614)
10. ABSTRACT
This report presents state-of-the-art information for implementing cost effective and
environmentally sound solutions to the nationwide problem of septic tank sludge
(septage) treatment and disposal.
Current hauler practices, septage characterization, and regulatory control are pre-
sented. Design concepts of full scale and pilot installations are presented for land
disposal schemes, for separate septage treatment processes in areas with sufficient
septage volumes to support such a facility, and for septage disposal at sewage treat-
ment plants (STP). Actual system costs and environmental and socio-economic
acceptability for many actual and proposed treatment schemes are detailed to assist
in the selection of the best treatment scheme for a particular locale at the least
possible cost.
A significant bibliography is presented which embodies most of the pertinent U.S.
references on the subject.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Sludge
Septic Tanks
Characteristics
Processing
Disposal
Management
Septage
Septic Tank Pumpings
Generation Rates
Treatment
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
138
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
126
U.S. GOVERNMENT PRINTING OFFICE: 1980--657-166/0149
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