United States
Environmental Protection
Agency
Off tee of
Research and Development
Washington, DC 20460
j£A/600/K-93/001
' January 1993
Technology Transfer
Seminars
Low-Cost Wastewater
Collection for Small
Communities
February 8-9,1993Towson, MD
February 11-12, 1993Springfield, MA
March 8-9, 1993Chicago, IL
March 11-12,1993Kansas City, MO
March 22-23, 1993Albuquerque, NM
March 25-26, 1993Portland, OR
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Notice
The U.S. Environmental Protection Agency (EPA) strives to provide accurate, complete, and useful information. However,
neither EPA nor any person contributing to the preparation of this document makes any warranty, expressed or implied,
with respect to the usefulness or effectiveness of any information, method, or process disclosed in this material. Nor does
EPA assume any liability for the use of, or for damages from the use of, any information, methods, or process disclosed in
this document.
Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
Printed on Recycled Paper
-------
Table of Contents
Speakers 1
Overview/Residential Wasfewaler Characterization 3
James F. Kreissl
Case Study Notes 17
Alternative Gravity Sewers 21
Richard J. Otis
Wiom C. Boyle
Pressure Sewers - Part 1 71
K. PaulFanell, h.
Pressure Sewers - Part II 83
William C. Borne
Vacuum Sewers 97
Richard Naret
Supplemental Information
Appendix A - Two Decades of Experience with Pressure Sewer Systems A-l
Appendix B - Vacuum Sewer SystemsTypical Questions & Answers B-l
Appendix C - Operation & Maintenance InformationLabor & Power Costs C-l
Appendix D - Operation & Maintenance InformationEquipment Replacement D-l
Appendix E - Simplified Sewers: A Review of Brazilian Experience D-l
s Environ^ Protection Agency
fe5j^£Sia
Chicago, IL 60604-3590
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Speaker Biographies
William C. Bowne Consulting Engineer, Eugene, OR
Mr. Bowne is a consulting engineer specializing in pressure sewers for the past 20 years. He authored the chapter on
pressure sewer systems in Alternative Wastewater Collection Systems and was a major contributor to the Water Pollution
Control Federation manual Alternative Sewer Systems.
He has prepared over 50 technical papers on aspects of alternative sewers and has worked on several hundred pressure
sewer systems. He is licensed as a registered professional civil engineer in Oregon, as well as in Washington, Idaho, and
California.
William C. Boyle Professor, Department of Civil & Environmental Engineering, University of Wisconsin, Madison, Wl
On the staff of the University of Wisconsin since 1963, Professor Boyle has pursued his interests in research and technology
in biological waste treatment, oxygen transfer, onsite waste disposal, and disinfection. He has been involved in onsite
waste disposal research since 1972 as a member of the University of Wisconsin Small Scale Waste Management Project.
He has presented numerous EPA seminars and short courses on the subject. Current research interests are in biological
nutrient removal, oxygen transfer, odor control with soil filters, clean manufacturing technology, and foundry solid waste
management.
Professor Boyle has published over 100 technical peer-reviewed papers and is the recipient of five research medals from
professional organizations. He also received the Gordon Fair medal from the Water Environment Federation for
accomplishments in training environmental engineers. He is a registered professional engineer in Wisconsin and Ohio, and a
member of the American Academy of Environmental Engineers.
R. Paul Farrell, Jr.
Senior Consultant, Environment/One Corporation, Schenectady, NY
Mr. Farrell has devoted the past 25 years to the technology of grinder pumps and pressure sewer systems. He devebped
the first prototype grinder pump under contract to the American Society of Civil Engineers and the Water Pollution Control
Administration (now U.S. EPA). Later, he served as project engineer on a 13-month, full-scale demonstration of pressure
sewers in Albany, New York, sponsored by U.S. EPA and the New York State Department of Environmental Conservation. At
the Environment/One Corporation, founded in 1969, he directed the development, product design, and early application of
the company's semi-positive displacement (progressing cavity) grinder pump.
He is an electrical engineering graduate of the Virginia Polytechnic Institute and State University; a registered professional
engineer in New York, Kentucky, Ohio, and Pennsylvania; an active member of the Water Environment Federation since
1958; and holds twelve U. S. patents on inventions used in home appliances, wastewater treatment, and pressure
collection.
James F. Kreissl Environmental Engineer, U.S. Environmental Protection Agency, Cincinnati, OH
Mr. Kreissl has been the U.S. EPA's technical leader in small community wastewater research for more than 20 years.
Throughout this period he has been involved in the development, demonstration, and monitoring of low-cost alternative
collection systems and technology transfer of the resulting information.
His nearly 30 years of federal service include experience in water conservation, water treatment, municipal solid waste
management, and pollution prevention technology transfer.
-1-
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Richard Karet Branch Manager, AIRVAC, Tampa, FL
Mr. Naret graduated from Pennsylvania State University in 1977 with a B.S. in Civil Engineering. Since his graduation he
has been active in the wastewater industry, with an emphasis on collection systems. From 1978 to 1980 he worked for
the West Virginia Department of Natural Resources in a regulatory capacity in association with the U.S. EPA's Construction
Grants Program. From 1980 to 1990 he was employed by Cerrone & Associates, Inc., a consulting firm in Wheeling,
West Virginia. In 1990, Mr. Naret joined AIRVAC, a manufacturer of vacuum sewer components.
Prior to joining AIRVAC, Mr. Naret worked extensively with vacuum sewer technology. His experience includes planning,
design, and construction management of about 20% of the operating vacuum systems in the United States. This
experience includes startup, troubleshooting, and operation of these systems.
In his present capacity, he is involved in oil aspects of virtually every vacuum system that is proposed in the United States.
This includes educating interested parties on vacuum sewer technobgy, preparing cost estimates for prospective projects,
and working closely with consultants during the design of new projects.
Richard J. Otis Vice President, Environmental Management, Ayres Associates, Madison, Wl
Mr. Otis has been research director and project manager of wastewater facility projects since 1970. His primary emphasis
has been the development and implementation of low-cost technological and institutional solutions to wastewater
problems in unsewered areas. He served as project coordinator of the University of Wisconsin's Small Scale Waste
Management Project for 10 years. Since 1980, he has been in private consulting. He was the principal contributing
author to several manuals published by U.S. EPA, including "Onsite Wastewater Collection Treatment and Disposal
Systems" (1980), "Alternative Wastewater Collection Systems" (1991), and "Wastewater Treatment/Disposal for Small
Communities" (1992). He also was a principal author of two Water Environment Federation Manuals of Practice,
"Alternative Sewer Systems" (1986) and "Natural Systems for Wastewater Treatment" (1989). Mr. Otis currently is a
member of the Water Environment Federation's Small Community Outreach Committee.
-2-
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Overview/Residential Wastewater
Characterization
U.S. Environmental Protection Agency
Cincinnati, OH
I. WASTEWATER SOURCES A. Relative Flow Contributions
B. Relative Conventional Pollutant Contributions
C. Daily Distribution by Constituent
D. Toxic Organics
E. Metals
F. Sources of Toxics and Metals
II. SEPTIC TANK FUNCTIONS A. Treatment Performance
B. Flow Attenuation
C. Production of Odorous/Corrosive Compounds
III. TREATMENT CONSIDERATIONS A. Biodegradability
B. Odor/Corrosion Control
C. Process Requirements
-3-
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£EPA
U.S. Environmental Protection Agency
Office of Technology Transfer and
Regulatory Support
Center for Environmental Research Information
Cincinnati, OH 45268
Technology Transfer
Products
Seminars Capsule Reports
Workshops ER&T Reports
Handbooks ORD BBS
Design Manuals Reports
Summary Reports Dissemination
OTTRS - CERI
Small Community Tech Transfer Activities
Seminar Series on Low-Cost
Alternative Sewer Systems (FY93)
Decision-Makers Guide on Integrated
Environmental Management (FY93)
Seminar Series on Small Community
Environmental Management
Responsibilities, Self-Assessment,
and Implementation (FY94)
-5-
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OTTRS - CERI
Small Community Tech Transfer Activities
Expert System to Evaluate Municipal Solid
Waste Options and Costs (FY92)
Expert System to Evaluate Existing
Municipal Solid Waste Facilities to Assess
Planning Needs (FY94)
Summary Report with Case Studies of
Drinking Water and Wastewater Cooperative
Seminars (FY93)
Field Guide to Septage Treatment and
Disposal (FY93)
U.S. Wastewater Systems by Size
Distribution
SIZE
(POPULATION
SERVED)
UNSEWERED
100.000-
KO
*
5,983
3,920
M70
J.C7
446
%Of
TOTAL
POTW
0
31
26
17
16
3
POPULATION
SERVED
(MILLION)
69
1
9
18
75
80
*
POPULATION
25
1
4
7
29
34
NATIONAL 15J91
TOTAL
23i10" Sep* link/nil ibsorptioo lyacou
Monthly Cost of Gravity Sewers
-6-
-------
Seminar Goals
Local Conditions Most Suitable
for Application
Key Design Elements
Information on Construction
and Costs
Operation and Maintenance
Requirements
Wastewater
Characterization
Typical Residential Water Use by Activity
Activity
Toilet Flushing
Bathing
Clothes Washing
Dish Washing
Garbage Grinding
Miscellaneous
Gal/Use
4.3
4.0-5.0
24.5
21.4-27.2
37.4
33.5-40.0
8.8
7.0-12.5
2.0
2.0-2.1
NA
Uses/Cap/D
3.5
2.3-4.1
0.43
0.32-0.50
0.29
0.25-0.31
0.35
0.15-0.50
0.58
0.4-0.75
NA
GPCD
16.2
9.2-20.0
9.2
6.3-12.5
10.0
7.4-11.6
3.2
1.1-4.9
1.2
0.8-1.5
6.6
5.7-8.0
TOTAL
NA
NA
45.6
41.4-52.0
-7-
-------
Average Daily Flow Pattern from
11 Rural Households
GALLONS PER CAPITA PER HOUR
Average Flow, 42.6 gal/cap/d
3-
T Toilet
L Uundty
B Bath or Shower
D Dish Wither
O Olher
WS Water Softener
12 3
PM AM
TIME OF DAY
Characteristics of Typical
Residential Wastewater*
Total Solids
Volatile Solids
SS
VSS
BOD5
Total N
Ammonia
Total P
Phosphate
Gm/Cap/D
115-170
65-85
35-50
25-40
35-50
6-17
1-3
1-2
0.3-1.5
mg/L
680-1,000
380-500
200-290
150-240
200-290
35-100
6-18
6-12
2-9
No Garbage DItpoMI (Add 25-50% to BOD, 50*% to SS & 10% to N with G.D.)
Hourly Distribution of BOD5
TIME OF OKI
-8-
-------
Hourly Distribution of Suspended
Solids
T TdLET
L LAUNDRY
. B BATH w SHCWEN
-------
Residential/Commercial Wastewater
EPA (1991)
Pollutant Detections
Methylene Chloride
Tetrachloroethene
Chloroform
1,1-Dichloroethene
BIS (2-Ethylhexyl) Phthalate
Total Endosulfan
Fluoranthene
Total BHC
Pyrene
7
5
21
2
5
3
2
3
2
Samples
30
29
30
29
5
3
5
3
3
Avg. Cone.
(mg/L)
0.027
0.014
0.009
0.007
0.006
0.002
0.001
0.001
0.0002
Comparison of Residential/Commercial
Monitoring Data for Metals
Cadmium
Chromium
Copper
Lead
Nickel
Zinc
Arsenic
Mercury
Silver
Cyanide
1987
0.003
0.05
0.061
0.049
0.021
0.175
0.003
0.0003
0.004
0.041
1991
0.008
0.034
0.109
0.116
0.047
0.212
0.007
0.002
0.019
0.082
Residential Toxic
Sources
Pesticides
Drain Cleaners
Toilet Bowl
Cleaners
Degreasers
Detergents
Cosmetics
Gasoline/Oil
Paints/Solvents
-10-
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System Comparison
WW Main
Type O/S Holdup Type Ventilation
GP Min Raw No
STEP Max STE No
SDG Max STE Yes
Vacuum Min Raw Yes*
'Effectively, owing to high turbulence and periodic air aluga.
Septic Tank Functions
Removal of Settleable and
Floatable Particulates
Flow Equalization
Precipitation/Coagulation of
Certain Constituents
Production of Odorous and
Corrosive Compounds
Typical Septic Tank Performance
Constituent
BOD5
SS
Grease
N
P
Toxic ORGs
Heavy Metals
Effluent (mg/L)
120-200
40-100
10-25
30-80
4-5
Low
Low
% Removal
40-50
60-80
75-90
0-20
0-20
0-50
0-50
-II-
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Flow Attenuation in a Septic Tank
Wastewater
Flow Rate,
GPH
Curve 3
(Leaving Septic Tank)
Time of Discharge
Odor and Corrosion
Considerations for SDG and
Pressure Sewers
Offgas Control and Treatment
Corrosion-Resistant
Construction Materials
Smooth Transitions and
Discharges
Drop Inlets
Outside Drop
Incoming _f_
Sewer 1 '
Drop Inlet J
ll
^
nh
F
(-a
9t
i
ow
i* LT
««
.'
IfcX
*- Discharge
Suspended
Level Control
Sensors
Submersible
"Sewage Pump
"Si>3
Ir
side Drop Inlet
','/.
\
J-
I
'/
f
'//
'
-------
Treatment
Considerations
All Are Easily Treatable by
Conventional Methods
SDG and STEP Do Not Require Grit
Removal Or Primary Sedimentation
Vacuum Does Not Require Special
Odor and Corrosion Control
-13-
-------
General Purpose Governments
in the U.S.
3.6%
>so,ooo jijSByjjujSEji/ 1,22?
Population
Number of
Governments
r
Question: What Percentage of
Land Area in the U.S. Is Under
Their Jurisdiction?
97% of the^and
Mass of the United
States Is Classified^
as "Rural"
Employees of Local
Governments
ZEG'S
1/3 of All U.S. Governments Have
No Employees at All*
Major Part of Work Gets Done by
Volunteers or Part-Timers
'Norton* AiMCMtton ol Towni »nd TowntMpi
-14-
-------
Number of People Living
in Small Jurisdictions
Under 10,000 in Population
90 Million People
Under 2,500
74 Million People
Rules ... What We Found Out
Reviewed 14 Volumes of the Code of Federal
Regulations (CFR). List Was Ver.f.ed and
Edited by Program Offices.
. 400 Separate Subsections of the CFR
Regulate Local Government
. 400 Subsections Require Local
Governments to Be the Regulator
Distribution of Rules
Area
Water*
Solid Waste
Air
Pesticides and Toxics
Grants
General
Subtotal
Effluent Standards
TOTAL
L
Total
142
131
49
26
44
27
419
374
793
Regulated
138
127
23
23
32
18
361
361
Regulator
2
2
12
2
18
371
389
Both
2
4
24
3
7
40
3
43
-15-
-------
SMAIJLXQMML!NICOS£AIM£NT SYSTEMS
USEPA Needs Survey (1988)
Total Treatment Facilities
1.0 MGD
With Water Quality or public
health problems
15.591
12.569 (81%)
> 10.000
\
/ 199Z.ERQJECTEP PQLLUT!QN_CQNTRQL_EXPEN >^
Cost ol Clean Report - OPPE (1990)
% by Media
W Water
L Land
A Air
O - Other
Total -
1.9% of Tota
U.S. Capita
Investment
90% of water investment water quality
10% = drinking water
\pnly burdensome in small communities"
I 6 8 10
POPULATION DENSITY, (wnom \m acrt
-16-
-------
Cose Study Notes #'**-
X
*-* G>
>*«-
V
E ,
x
^ >
V <> '
<~ **
«/
-17-
-------
Case Study Notes
-18-
-------
Case Study Notes
-19-
-------
Case Study Notes
-20-
-------
/.V5 /
Alternative Gravity Sewers
TYPES AND DESCRIPTION OF
ALTERNATIVE
GRAVITY SEWERS
SMALL DIAMETER GRAVITY
SEWERS (SDGS)
III. FLAT GRADE SEWERS
IV. SIMPLIFIED SEWERS
V. SDGS DESIGN EXAMPLE
A. Small Diameter Gravity Sewers
1. Uniform Grade
2. Variable Grade
3. Hybrid
B. Flat Grade Sewers
C. Simplified Sewers
A. Application
1. Extent of Use
2. Typical Applications
3. Advantages and Disadvantages
B. Design of SDGS
1. Components
2. Layout
a. Pipe Location and Alignment
b. Appurtenance Location
3. Component Design
a. Sizing
b. Materials
4. Hydraulic Design
a. Flow Estimates
b. Hydraulic Computations
C. Odor Control
D. Construction
1. Methods
2. Unit Costs
E. Operation and Maintenance
1. Routine Maintenance
2. Troubleshooting
A. Application
B. Design
A. Application
B. Design
.... RichardJ.Otis
Ayres Associates
Madison, Wl
William C. Boyle
University of Wisconsin
Madison, Wl
.$
-21-
-------
Alternative
Gravity Sewers
Richard J. Otis, P.E.
Ayras Associates
Madison, Wisconsin
William C. Boyle, Ph.D., P.E.
University of Wisconsin
Madison, Wisconsin
III!
....
«
1
!__,
1
I
-|
h
s
*
..
Ji
s
..
s
«
...
"
\
\
1
\
...
s
NX
| '
4 _
m
\
\
i
*;,
\
\
.......
^
...
t
Sewer
Lenath Per
Capita vs.
Population
Alternative Sewers
Strategies for Reducing
Construction Costs
Reduce Excavation
Eliminate Lift Stations
Improve Construction/Materials
Change Motive Force
Change Wastewater
Characteristics
-23
-------
Types of Gravity Sewers
Raw Wastewater Settled Wastewater
Conventional Small Diameter
"Flat" Grade Uniform Grade
Simplified Variable Grade
Gravity/Pressure
Hybrid
Small Diameter Gravity Sewers
SDGS
Small Diameter Gravity Sewer
Solids
Effluent
-24-
-------
SDGS Synonyms
Common Effluent Drains
Small Bore Sewers
Australian Sewers
Septic Tank Effluent Drains
Variable Grade Sewers
Application of SDGS
Low Density
Residential/Commercial
Developed Areas with High
Restoration Costs
Adverse Soil/Rock Conditions
New Developments with Slow
Build-Out (Deferred Construction)
SDGS
Extent of Use
Australia
First Application
Used Since 1960
Over 500 Miles with More Than
26,000 Connections
-25-
-------
SDGS
Extent of Use
United States
First Applications
Mt. Andrew, AL 1975
Westboro, Wl 1977
Currently Over 200 Systems
Excellent Experience
SDGS Installations
Name
Mt. Andrew, AL (1975)
Westboro, Wl (1977)
Badger, SD (1980)
Avery,ID(1981)
Maplewood,WI(1981)
S. Corning, NY (1983)
Pop
100
200
105
90
150
2,000
Length
2,500
18,850
6,615
6,690
5,800
45,525
Ft/
Conn
81
217
125
122
95
70
New Castle, VA (1982) 190 6,955 109
SDGS Installations
Name
Miranda, CA (1982)
Gardiner, NY (1982)
Lafayette, TN (1983)
West Point, CA (1985)
Zanesville, OH (1986)
Muskingham Co. (1986)
Pop
300
500
1,500
430
1,180
2,150
Length
9,615
19,330
45,310
18,000
61,360
89,750
Ft/
Conn
96
177
89
116
86
117
-26-
-------
Advantages of SDGS
Reduced Excavation
Reduced Material Needs
Reduced Maintenance
Requirements
Reduced I/I
Reduced Water Requirements
Reduced Treatment Costs
r
Disadvantages of SDGS
High Cost for Interceptor Tanks
Appurtenances on Private
Property
Odor
Corrosion
I/I at Interceptor Tank and Building
Sewer
SDGS Components
Building Sewer
Interceptor Tank
Service Lateral
Collector Main
Air/Vacuum Release Valves
Lift Stations
-27-
-------
SDGS System Layout
Dendriform or Branch
Beside Pavement in R/W or Behind Homes
Horizontal Alignment May Bend to Avoid
Obstructions
Gradient Need Not Be Uniform, But
Overall Gradient Must "Fall"
Line Summits Must Be Below Upstream
Gravity Connection Elevations
SDGS Profile
SDGS
Plan
Westboro, Wl
-28-
-------
SDGS Appurtenance Location
Manholes/Cleanouts
Manholes at Major Junctions Only
Cleanouts at:
Upstream Termini
Junctions of Mains
Changes in Main Diameter
Intervals of 120-300 M
Drops in Grade
SDGS Appurtenance Location
Valves
Air/Vacuum Release Valves at
Summits (Inflective Grades) -
Odor Control Filter as Needed at
Air Release Points
Check Valves at Service
Connections Where Potential for
Surcharge Exists
SDGS Appurtenance Location
Lift Stations
Individual Connections below
Hydraulic Grade Line (Step Unit)
Collector Mains to Lift to
Another Drainage Basin
-29-
-------
SDGS DESIGN
SDGS Recommended Design
Guidelines
Design Flow
(Per Connection)
Pipe Diameter
Slope
Flow Velocity
Open Channel Flow
Pressure Flow
Pipe Roughness Coeff.
Alignment
0.1-0.4 GPM
(0.006-0.025 L/S)
4 In. Typical
2 In. Minimum
No Minimum
No Minimum
0.5FPSMin.(0.15M/S)
0.015 (Mannings "n")
Curvilinear (Horiz/Vert)
SDGS Pipe Diameter
Building Sewer/
Service Laterals
Building Sewer
Service Laterals
Slope/Alignment
Connection
Check Valves
4-6 In. Typical
(100-150 mm)
Slope >1%
No Larger Than Collector
No Requirement
Wye or Tee
Near Main Connection
(If Needed)
-30-
-------
SDGS
Collector Main Depth
Dependent on:
Interceptor Tank Outlet Invert
Frost Depth
Trench Loading
Optimum Depth
Minimize Total Construction Cost
Excavation
.STEP Installations
SDGS
Collector Main Depth
Minimum Depth: 30 in. w/o
Traffic or Pavement
Manufacturers
Recommendations
Frost Depth
SDGS Pipe Diameter
Collector Mains
Estimate in Hydraulic Analysis
Minimum Diameter - 2 In. (50 mm)
Use Flow Control Devices to Limit
Peak Flow
Use Check Valves to Prevent
Backflow/Flooding
Most Common Minimum - 4 In.
(100 mm)
-31-
-------
SDGS Pipe Materials
Plastic (PVC or ABS) Most Common
Standard Dimension Ratio (SDR) 35
Road Crossings - SDR 26
. Within 3 M of Water Line - SDR 26
. Deep Burial - SDR 21
> Step Installations - SDR 26 or 21
Joints
Elastomeric (Rubber Ring)
. Solvent Weld < 3 In. (75 MM)
HOPE
Joints - Heat Fusion
SDGS Valves
Air/Vacuum Release
Material - 316 Stainless or Plastic
Installed in Meter or Valve Box
Set Flush to Grade
Odor Filter Required for Vented
Gases
SDGS
Typical Combination Cleanout and
Air Release Valve Detail
Collector Trench
Sealed Lid
Air Relief Valve
2" PVC Ball Valve
Polyrlbbed Vault
~~ 7
-32-
-------
SDGS Valves
Check
Objective to Prevent Backflow During
Surcharging
Specifications:
Large, Unobstructed Passageway
Resilient Seats
Wye Pattern Preferred in Horizontal Position
Alternatives:
Overflow to Abandoned Drainfield
Australian Boundary Trap
- Vent (Mcwqulto Proof)
Reinforced Cover and Block
«_L Compacted
sand
SDGS
Australian
Boundary
Trap
SDGS Cleanouts
Upstream Termini
Junctions of Mains
Changes in Main Diameter
Intervals of 400 -1,000 Ft
(120-300 M)
Drops in Grade
-33-
-------
Ground Level
Heavy Duty
Water Line
Casting
SDGS
Typical
Cleanout
45° Bend
Compacted Stone or Sand
45° Bend
SDGS
Typical
Cleanout
SDGS
Ventilated Cleanout
Fit End with 8 Mesh Qa.
Stainless Steel Screen
Concrete Pad
%8f/jL^-~ ComPacted Stone or Sand
Direction of
'Flow
2'-0" (Mln)
-34-
-------
Septic Tank Profile
Precast Concrete Cover
ln»pectlon Port
SDGS Interceptor Tank
Purposes
Remove Settleable/Floatable
Solids
Storage of Removed Solids
Flow Attenuation
SDGS Interceptor Tank
Construction
Size
Inlet/Outlet
Material
Access
1,000 Gal. Min. (3,780 L)
Baffled
0.25 Ft Drop Across Tank
Reinforced Concrete
Plastic
Fiberglass
Manhole Over Inlet
Water/Gas-Tight Cover
-35-
-------
SDGS Interceptor Tanks
Location
Install One for Each
Connection
Locate for Easy Access for
Pumping
SDGS
Locations
for
Interceptor
Tanks
SDGS Interceptor Tanks
Design
Size
Residential:
Commercial:
1,000 Gal (3,785 L)
>24 Hr Detention
Time at 2/3 Full of
Solids
-36-
-------
SDGS Interceptor Tanks
Design
Inlet/Outlet Baffles
Inlet - Open at Top for Venting
Outlet - Standard Septic Tank
Outlet
Gas Deflection Baffles
Air Vent -
Flow Una
Row
Line
Outlet KV-.
Scum Baffle n
Flow Line' I
Gas
Deflection
Baffle
Tank
Outlet
Pipe
Gas Deflection Baffle
-37-
-------
SDGS Interceptor Tanks
Design
Flow Control
Surge Chambers
Plugging
Odor
Headloss
In Situ Devices
Attenuation by Tank
SDGS
Surge Chamber Detail
j* Ji tk !* It .tA tUilil.]
SDGS
Attenuation
Box
-38-
-------
Interceptor Outlet Flow Control Device
Screened Overflow
Vault
Polyethylene Screen
1-1/4" Dla. PVC Pipe
Orifice
(CDUrtoyORENCO)
Screened Overflow
Drain Port
Septic Tank Flow Attenuation (Jones, 1975)
Wastewater
Row Rate
Rate
Entering
Septic
Tank Rate
Leaving
Septic
Tank
Time of Discharge
Flow Attenuation by
Septic Tanks
(Jones, 1975)
Storage Volume (Gal)
for Surface Area (Ft?)
24
3
6
9
15
32
4
8
12
20
40
5
10
15
25
Depth Above
Invert (In)
0.2
0.4
0.6
1.0
Discharge Rate (GPM)
for Outlet Dia. (In.)
2
0.15
0.58
1.3
3.2
4
0.21
0.75
1.7
4.2
-39-
-------
SDGS Interceptor Tanks
Design
Miscellaneous
Watertightness
Inspection Manhole
Solids Removal Access
r
SDGS Interceptor Tanks
Materials
Reinforced Concrete
Fiberglass
HOPE
Cautions
Structural
Water Tightness
Quality Control
Joints
SDGS Hydraulic Design
Flow Estimates Per Connection
Eleven Rural Homes (UW, 1978)
Family Size
Water Use
Peak Water
Use
Mean
4.6
42.6 GPCD
0.31
GPM/Conn
Range
3-7
25.4-56.9
0.14-0.41
-40-
-------
TIME OF MY
Household
Water Use
Rates -
Family of 4
Max. Flow Rate =
0.4 GPM
TIME OF MY
Household
Water Use
Rates -
Family of 6
Max. Flow Rate =
0.35 GPM
SDGS Hydraulic Design
Flow Estimates
Recommended
0.1-0.4 GPM/Connection (Peak Hour
Neglecting Flow Attenuation)
I/I
Building Sewer
Interceptor Tank
Foundation Drains
Roof Leaders
-41-
-------
SDGS Hydraulic Design
Flow Velocities
Interceptor Tank Removes Raw
Solids
Slime Growths or Neutral Buoyancy
No Minimum Flow Velocity Required
Maximum Velocities <13-16 FPS
(4-5 M/S) to Avoid Air Entrainment
SDGS Hydraulic Design
Hydraulic Equations
Manning's or Hazen Williams
Roughness Coefficients
n = 0.015
C = 90
Design Depth - No Requirement
Depressed Sections, Surcharging
Acceptable
SDGS Hydraulic Design
Inflective Grades/Surcharge
Pressure Flow
Vmin (Depressed Sections) = 0.5 FPS
(0.15 M/S)
Check Hydraulic Grade Line at Peak
Flow If Connections below Grade Line:
Lower Main Invert Elevations
Increase Pipe Diameter
Provide Check Valve
Install STEP Unit
-42-
-------
Cover,
Quick
Electrical Junction Box Gate Valve
* V s-
PVC
. Discharge
Piping
Discharge
Check Valve
Pump Off
STEP
Lift
Station
SDGS Odor Control
Causes
Turbulence at:
Lift Stations
Hydraulic Jumps
SDGS Odor Control
Escape Points
Lift Station Vents
Lift Station Hatch Covers
Manhole Lids
House Plumbing Stack Vents
-43-
-------
SDGS Odor Control
Control Measures
Odor Elimination
Soil Odor Filters on Vents
High Stack Vent
Carbon Filters
Incoming
Sewer
SDGS
Drop
Inlet
(External)
Suspended Level
Control Sensors
Submersible
Sewage Pump
with Lifting Cable
SDGS
Drop
Inlet
(Internal)
-44-
-------
SDGS
Drop
Manhole
SDGS Odor Control
Control Measures
Avoid Turbulence
Drop Inlets at Lin Stations
Eliminate Hydraulic Jumps in Sewers
Seal Air Leaks
Gas-tight Lids and Covers
Caps on Interceptor Tank Outlets
Running Traps on Service Laterals
Comparison of Design Criteria
Parameter
Design Flow
Design Depth
of Flow
Minimum Flow Velocity
Min. Pipe Diameter
Slope
Manning's n
Alignment
Conventional
200-400 GPCD
1/2 Full
2FPS
8 In.
Obtain Vn*,
0.013
Straight
SDGS
0.1-0.4 GPM/
Connection
N/A
None/0.5 FPS
2-4 In.
No Min
0.015
Curvilinear
-45-
-------
SDGS Construction
General
Shallow
No Strict Requirements on
Alignment
Significant Portion on Private
Property
Two Contracts:
Mains
Service Connections
SDGS Construction
Mainline
Minimize Restoration Costs
Alignment Control
Grade Control
Trench Construction:
Backhoe/Trencher
Select Backfill
Warning Tape
SDGS Construction
Service Connections
Building Sewer - User
Interceptor Tank - Utility
Service Lateral - Utility
STEP Unit - Utility
-46-
-------
SDGS Construction
Interceptor Tank
Existing Versus New
Easy Access for Pumping
Bedding, Inlet/Outlet
Connections
Flotation Collars
Record Drawings
r
SDGS Construction
Testing for Watertight ness
Piping (Building Sewer, Service
Lateral, Mainline)
Criteria for Conventional Sewers
Interceptor Tanks
Vacuum Test - <1 In. Hg in 5 Min. @
4 In. Hg
Hydrostatic Test - <1 In. H2O in 24 Hr
(Overfilled)
SDGS Costs
(12 Systems, 1991 $)
Construction Costs
Average Range
Cost/Connection $5,353 $1,823-$8,909
Cost/Foot of Main $50.44 $20.52-$92.64
-47-
-------
SDGS Construction Costs
Unit Costs
Main Diam
(In)
2
3
4
6
8
$/R
(1991)
8.70
17.74
12.19
13.44
19.98
Avg Depth
(«)
3.5
6.3
7.4
7.2
9.0
SDGS Construction Costs
Unit Costs (1991 $)
Manholes $1,660
Cleanouts $290
Interceptor Tanks
750 Gal $1,388
1,000 Gal $1,315
Service Lateral $9.08/Ft
Individual STEP Unit $4,143
SDGS Construction Costs
Unit Costs/Ft of Pipe (1991 $)
In-place Pipe
Manholes
Cleanouts
Lift Stations
Force Main
Building Sewers
Interceptor Tanks
Service Connections
$15.10/Ft
$1.42/Ft
$0.79/Ft
$4.95/Ft
$1.66/Ft
$3.22/Ft
$11.70/Ft
$7.13/Ft
-48-
-------
SDGS Construction Costs
Unit Costs/Ft of Pipe (1991 $)
Street Repair $4.34/Ft
Crossings $3.45/Ft
Site Restoration $2.12/Ft
Miscellaneous $2.01/Ft
Total Project $57.89/Ft
$5,353.00/Conn
r
SDGS Construction Costs
Component Cost as Percent of
Total Cost
In-Place Pipe 26%
Interceptor Tanks 20%
Service Connections 15%
LHt Stations 9%
Building Sewers 6%
Manholes 2%
Cleanouts 1%
Repair/Restoration/Misc. 29%
SDGS
Operation/Maintenance
Administration
Utility District
Entire System from Inlet to
Interceptor Tanks
Perpetual Easement
O/M Manual
-49-
-------
SGDS
Operation/Maintenance
Staff
No Special Qualifications
Basic Plumbing Skills
STEP Unit Servicing
Safety
Equipment
No Special Qualifications
Truck Mounted Centrifugal Pump
Hose
SDGS Maintenance
General
Preventative
Emergency
Spare Parts Inventory
Pipe and Fittings
STEP Unit Components
SDGS Maintenance
Interceptor Tanks
Septage Pumping - 3-5 Years
(7-10 Typical)
Tank Inspection
Commercial Facilities -
Grease/Solids
Septage Handling - Usually
Private Contractor
-50-
-------
SDGS Maintenance
Collector Mains
Excellent Performance Reported
Periodic Inspection and Cleaning
Flushing
Pigs - Not Recommended for
SDR 35
Flat Grades Where V < 0.5 FPS
SDGS Maintenance
Lift Stations
Daily or Weekly Inspection
Record Running Time Meters
Check Pumps, Alarms, Switching
Functions
Pump Calibration - Yearly
SDGS Emergency Calls
Mainline Obstructions
Construction Debris
Excavation
By-pass Pump to Downstream Cleanout
Lift Stations
Power Outage
Passive Lift Station Storage
Truck-Mounted Pump
Emergency Generator
-51-
-------
1 0*lv*niiBd Vint Pip*
^ Iff Mln. Height Above Grade
-iToCon*olP*n*l
Control
Switch**,
SDGS
Mainline
Lift Station
with
Emergency
Storage
StaHon** >\J
SDGS
Emergency
Pumping
Manhole
SDGS Troubleshooting
Odors
Lift Stations
Drop Inlets
Soil Odor Filters
Gas-tight Covers
Carbon Filters
Plumbing Stack Vents
Seal/Cap Sanitary Tee on Outlet
Pea or Running Trap on Service Lateral
-52-
-------
SDGS
Soil Odor Filter Detail
Valve Box
SDGS Troubleshooting
Corrosion
Lift Stations
Non-ferrous Hardware
Dry Wei I
Manholes
Corrosion Resistant Coatings
Corrosion Resistant Fittings
SDGS Troubleshooting
Infiltration/Inflow
Inspection/Replacement of
Interceptor Tanks
Inspection/Replacement of
Building Sewer
Removal of House Drains/Sump
Pumps
Tightness Testing
-53-
-------
"Flat" Grade
Sewers
"Flat" Grade Sewers
Comparison to Conventional Sewers
Flat Grade
Conventional
Win 0.1% Slope
Min 0.4% Slope
0.4 D
0.2 mis
Depth of Flow
(200 Homes)
Velocity
0.20
0.3 mis
"Flat" Grade Sewers
Principles
Reduced Gradients
Elimination of Lift Stations
Consideration of Improved
Construction
Consideration of Improved
Cleaning Equipment
-54-
-------
Simplified
Sewers
Simplified Sewers
Principles
Tractive Force Versus Minimum
Velocity
Reduced Depth
Consideration of Improved Materials
Consideration of Improved
Construction
Consideration of Improved Cleaning
Equipment
Simplified Sewers
Minimum Depths of Sewers
Street 1/3 Street
Width
Residential Streets
Sidewalk
Trench
-55-
-------
Simplified Sewers
Tractive Force
Maintain Sufficient Velocity to
Remove Solids Throughout Project
Life
Maintain Depth of Flow Between
0.20 and 0.75 D
Minimum Pipe Diameter of 100 mm
Velocity Not to Exceed Critical
Velocity
Simplified Sewers
Tractive Force
"Threshold of Movement" for 1 mm
Sand Particle
T = rxRxl
Where
1 = 0.1 kg/m2
r = Specific Weight of Water
R = Hydraulic Radius
I = Slope
Simplified Sewers
Residential Connection
r Collector
Main
Sewer Utility
Baffled Box
Connection Box
Property Owner
-56-
-------
Simplified
Sewers
Condominial
Sewer
System
To Street Sewer
Simplified
Sewers
Condominial
Sewer
System
Alternative 2.
... Alternative 1
OCIeanouU - . -
QBurled Junction Boxes
Layout of a
Simplified
Sewer
System
-57-
-------
Simplified Sewers
Cross-Block Connection
Sewer ^ Building Sewer
Une
Simplified Sewers
Terminal Cleanout
Sand Bedding
Concrete
Simplified Sewers
Junction/Inspection Cleanout
( . f II O\11 '"1nTnT \ »ana
^;,r.,',..i,,.,,J|LT^^~^^g^X~ Bedding
-58-
-------
Trench Limits
_\^
Pfen
A
Ur
A
-. i
Section B-B
Simplified
Sewers
Buried
Box for
Change in
Slope/
Direction
Comparison of Conventional and
Simplified Manholes
Conventional
0.6 m
Simplified
0.6 m
1.5m
Simplified Sewers
Design Procedure
Compute lmin
Compute Qfjna/l0 5
Select Dmjn Where d/D < 0.75
Compute V/Vcritjcal
Increase Pipe Size If V/VC» 1.0
d/D > 0.2 at Qinjtja,
-59-
-------
Simplified Sewers
Minimum Slope
lmin = 0.0055 0*2, (metric)
Simplified Sewers
Comparison to Conventional
Pipe
Dia. Velocity (M/s)
(mm) Slope Initial Final
Conventional 375 0.0016 0.56 0.58
Simplified 450 0.0009 0.54 0.58
Simplified Sewers
Cost Comparison
Conventional Simplified
Cost Cost %of
Quantity ($M) % Quantity ($M) Conv'l.
Excavation 2038 m3 2.4 14.5 721 m3 0.05 3.5
Piping 1530m 5.9 35.4 1510m 3.4 20.9
Manholes 27 2.1 12.8 18 1.0 6.2
Connections 258 6.1 36.7 258 2.4 14.4
Other 0.08 0.5 0.47 3.1
TOTAL $16.5M $7.3 M 48.1
(Com In 1008 Columbian DoHurt (1 US J - 335 Columbian S)
-60-
-------
SDGS
Design Example
SDGS
Design Example
SDGS
Design Example
!«000 J-HXJO
LCN2TH OF SEKK {METERS.
-61-
-------
2»000 3*000
LENGTH OF SEWER [METERS!
SDGS
Design
Example
SDGS
Hydraulic Design
Manning's Equation (metric)
V--
n
»2/3 gV2
m m
V = Flow Velocity
R = Hydraulic Radius
S = Slope
n = Roughness Coefficient
SDGS
Hydraulic Design
Hazen-Williams Equation (metric)
V = 0.8493CR°i63S°;54
V = Flow Velocity
R = Hydraulic Radius
S = Slope
C = Roughness Coefficient
-62-
-------
ew-ooo i+ooo
LENGTH Of SEWER (METERS)
SDGS
Design
Example
SDGS Design Example
Station 1+000 - Station 1+375
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
0+000 0+750 159 2.54 4.00 50 4.94
100 0.77 0.74 0.40
0+750 1+375 154 2.46 0.75 50 10.09
100 1.59
150 0.54 Full 0.26
0+750 1+475 154 2.46 1.75 100 1.12
0+750 1+375 154 2.46 2.00 100 0.97 Full 0.32
0+000 0+750 159 2.54 3.5 100 0.83 0.77 0.39
Hydraulic-Elements Graph for
Circular Sewers
-63-
-------
(HOOO H-000
LENGTH OF SE*CH (METERS)
SDGS
Design
Example
SDGS Design Example
Station 1+000 - Station 1+375
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
0+000 0+750 159 2.54 4.00 50 4.94
100 0.77 0.74 0.40
0+750 1+375 154 2.46 0.75 50 10.09
100 1.59
150 0.54 Full 0.26
0+750 1+475 154 2.46 1.75 100 1.12
0+750 1+375 154 2.46 2.00 100 0.97 Full 0.32
0+000 0+750 159 2.54 3.5 100 0.83 0.77 0.39
OtOOO WOOO
LENGTH OT SEWER (METERS!
SDGS
Design
Example
-64-
-------
SDGS Design Example
Station 1+000 - Station 1+375
STA STA NO. WW
FROM TO CONN FLOW
ELEV PIPE
DIFF DIA Q/Q, d/D
0+000 0+750 159 2.54
0+750 1+375 154 2.46
0+750 1+475 154 2.46
0+750 1+375 154 2.46
0+000 0+750 159 2.54
4.00 50 4.94
100 0.77 0.74 0.40
0.75 50 10.09
100 1.59
150 0.54 Full 0.26
1.75 100 1.12
0.97 Full 0.32
2.00 100
3.5 100
0.83 0.77 0.39
O+OOO 1+000
LENGTH OF SEWER (METERS)
SDGS
Design
Example
SDGS Design Example
Station 1+000 - Station 1+375
STA STA NO. WW
FROM TO CONN FLOW
ELEV PIPE
DIFF DIA Q/Q, d/D V
0+000 0+750 159 2.54
0+750 1+375 154 2.46
0+750 1+475 154 2.46
0+750 1+375 154 2.46
4.00 50 4.94
100 0.77 0.74 0.40
0.75 50 10.09
100 1.59
150 0.54 Full 0.26
1.75 100 1.12
2.00 100 0.97 Full 0.32
0+000 0+750 159 2.54 3.5 100 0.83 0.77 0.39
-65-
-------
o+ooo h-ooo
LENGTH OF SEWER IMETERS1
SDGS
Design
Example
SDGS Design Example
Station 1+000 - Station 1+375
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
0+000 0+750 159 2.54 4.00 50 4.94
100 0.77 0.74 0.40
0+750 1+375 154 2.46 0.75 50 10.09
100 1.59
150 0.54 Full 0.26
0+750 1+475 154 2.46 1.75 100 1.12
0+750 1+375 154 2.46 2.00 100 0.97 Full 0.32
0+000 0+750 159 2.54 3.5 100 0.83 0.77 0.39
SDGS
Design Example
-66-
-------
SDGS Design Example
Station 1+375 - Station 5+000
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
1+375 1+850 149 2.38 4.00 50 3.68
100 0.58 0.62 0.47
1+850 3+500 145 2.32 0.75 100 2.43
150 0.82 Full 0.16
1+850 4+000 2.50 100 1.52
3+500 5+000 134 2.14 1.25 100 1.66
150 0.56 0.88 0.19
SDGS
Design Example
SDGS Design Example
Station 1+375 - Station 5+000
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
1+375 1+850 149 2.38 4.00 50 3.68
100 0.58 0.62 0.47
1+850 3+500 145 2.32 0.75 100 2.43
150 0.82 Full 0.16
1+850 4+000 2.50 100 1.52
3+500 5+000 134 2.14 1.25 100 1.66
150 0.56 0.88 0.19
-67-
-------
2*000 3+000 4*000
LENGTH OF SE»ER [METERS)
SDGS
Design
Example
SDGS Design Example
Station 1+375 - Station 5+000
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
1+375 1+850 149 2.38 4.00 50 3.68
100 0.58 0.62 0.47
1+850 3+500 145 2.32 0.75 100 2.43
150 0.82 Full 0.16
1+850 4+000 2.50 100 1.52
3+500 5+000 134 2.14 1.25 100 1.66
150 0.56 0.88 0.19
4fO
LE
_ TT "7 y v *? ^
NTERCEPTOA TANK
ResCCHTML LfT STATION
©
00 5*0
NGTH OF SEWER (METERS)
00
SDGS
Design
Example
-68-
-------
SDGS Design Example
Station 1+375 - Station 5+000
STA STA NO. WW ELEV PIPE
FROM TO CONN FLOW DIFF DIA Q/Q, d/D V
1+375 1+850 149 2.38 4.00 50 3.68
100 0.58 0.62 0.47
1+850 3+500 145 2.32 0.75 100 2.43
150 0.82 Full 0.16
1+850 4+000 2.50 100 1.52
3+500 5+000 134 2.14 1.25 100 1.66
150 0.56 0.88 0.19
SDGS
Design Example
-69-
-------
Pressure Sewers - Part I
I. INTRODUCTION
II. HISTORY
STATE OF THE ART
IV. EQUIPMENT REVIEW
V. DESIGN
VI. ECONOMICS
R. Paul Farrell, Jr.
Environment/One Corporation
Schenectody, NY
A. Definition of Pressure Sewers
B. Applicability of Pressure Sewers
C. Advantages of Pressure Sewers
}. Improved Economic Feasibility
2.Less Environmental Damage
S.EIiminates Infiltration/Inflow
A. ASCE Combined Sewer Separation Project
1.Gordon M. Fair's Idea
2.Sampling Stations
B. U.S. EPA Sponsored Demonstrations in Albany, NY
A. Present Extent of Use
B. Typical Applications
A. Pumps
1 .Grinder
a. Centrifugal
b. Progressing Cavity
2.H-Q Curves
3. Treatment of Solids
a. PretreotmentandSeptoge Removal
b. Grinding and Pipeline Transport
4. Grease
A. Flow
B. Velocity
C. Friction Loss
D. Other Factors
1. Odor and Corrosion
2. Electric Service
E. Design Guides Available
A. Capital Cost
B. Operation and Maintenance
l.Reliability-MTBSC
2. Facilities
3. Personnel
4. Service Procedures
5. Costs of Repairs, Replacements, Power
C. Present Worth Analysis
VII. DISCUSSION
-71-
-------
Stylized Comparison of Gravity and
Pressure Sewer Systems
COSt VS. Depth - 8" VC Gravity Sewer
8 10 12 14 18 18 20 22 24 26
Wetwell and
Pump Hydraulic
Characteristics
GRINDER PUMP MODEL 210
-73-
-------
GP210 Hydrograph-Laundry
Vi=32, Qi=30 sec @ 35 gpm, Qo=11
RATES- GPM ft VOLUMES - GAL
Cumulative # GPs Installed
Environment/One Progressing Cavity Type
0
Jun
Msy'90
Some Existing Large-Scale Pressure
Sewer Systems, 1991
Location
Port St. Lucie, FL
Saw Creek, PA
Horseshoe Bay, TX
Kingsland, TX
Anne Arundel County, MD
Buckeye Lake, OH
Ottawa County, OH
Bloomingdale/Pooler, GA
Pierce County, WA
Palm Coast, FL
Homes Served
3,000
1,800
1,700
1,600
1,500
1,500
1,000
1,000
850
650
-74-
-------
OLD/FAILING
TILE FIELD SYSTEM
NEW SYSTEM
CAN BE INSTALLED ANYWHERE
WITH SUITABLE SOIL CONDITIONS
(BAND nLn» CAN M INCtUCCD)
Typical STEP Package with Internal
Pump Vault
Cover
JunctlonJ3ox Cover Gate Valve
Discharge
Quick Coupling
Flexible Discharge
Hose
Alarm
Pump On
Pump Off
Check Valve
'Vault
Typical
Centrifugal
GP
Package
with Pump
Suspended
from Basin
Cover
-75-
-------
Basic Components of a Progressing
Cavity Grinder Pump
Internal Pressure Switching
Inlet
High-Level Alarm '
Sensing Tube
Motor
On-Olf Sensing
Tube
1.25* MaleNPT
-FRP Tank
Anti-Siphon &
'Check Valve
Assembly
Pump Stator
Pump Rotor
Grinder Elements
0ISTEP
Pump
2-2HPC*ntriluo«IGP
S- 1/2 HP Con&vtugal STEP
4 -1/2 HP Prograiinw Cavity
Pump
5 -1 HP Ptogroiiw Cavity GP
or STEP
« - 1/2 HP 7-Skg« Subm«t.iW«
WabcWdlSTEP
Head-
Discharge
Curves for
Typical GP
and STEP
Systems
^^
HEAD (FEET)
1«0
140
120
100
SO
60
40
2O
\
\
\
\
\
\
\
- . \
0 10 20
DISCHARGE (GPU)
Typical
Progressing-
Cavity Pump
H-Q Curve
-76-
-------
FLOW (GPU)
300 -
0 20 40 GO
EQUIVALENT DWELLING UNITS
00 100
Design
Flows
-77-
-------
Circuit Diagram of a Basic 120-Volt
Control Panel
) Thermal Overload
Protection
Audible Alarm
Average Installed Unit Costs (Mid-1991) for
Pressure Sewer Mains and Appurtenances
Item Unit Cost ($)
2-in. Mains 7.50/LF
3-in. Mains 8.00/LF
6-in. Mains 11.00/LF
Extra for Mains in A.C. Pavement 5.00/LF
2-in. Isolation Valves 250/each
3-in. Isolation Valves 275/each
6-in. Isolation Valves 400/each
Automatic Air Release Stations 1,500/each
Average Unit Costs (Mid-1991) for Grinder
Pump Services and Appurtenances
Item
2-HP Centrifugal Grinder Pump
-List Price
-Quantity Price
Simplex GP Package
-List Price with 30-in. Vault
-Quantity Price with 30-in. Vault
-Installation
4-in. Building Sewer
1.25-in. Service Line
Abandon Septic Tank
Unit Cost ($)
1,200/each
600/each
4,100/each
1,800/each
500-1 ,500/each
16/LF
6/LF
400/each
-78-
-------
Reliability
Environment/One Grinder Pumps
MTBSC- YEARS
11
10
6
7
5
4
3
2
1
f- '*p
. |m . W«ct>l"|
-
NVm HOm CTm
NYO """ OHP
EPA I I I II I
"Tnl II II I
""
JunVl M«r7» S«p7» Dtclt Itar'ao Sop 'no Jim '11
DATA DATE
Jun'M
M«r'8t
Annual O&M Costs - Grinder Pumps
at Fairfield Glade, TN (1990 Dollars)
Niaber
SOURCE Obi.
STFP Bend, Oregon
EPA-600/2 II
Grinder Pmp
Albmy, MY
HVHU-72-OT1
OtEASE (concentration - ng/1)
in. MX. average
31
133
140
65
71
CONCLUSICN: There ii no statiitically lignificant difference
in tttut concentration between these two sources.
-79-
-------
Mean Time Between Service
Calls (MTBSC) Equation
# Pumps in Service (P) x Years in Service (T)
MTSBC(Yrs) = -
Total # of Service Calls in T Yrs (S)
MTBSC Example Problem
Pierce County,
System Contains 836 Pumps:
Data Is for a 14-Month Period
1988-89:
During This Period There Were
96 Pump-Related Service Calls: S = 96 Calls
P = 836 Pumps
T= 14/12 = 1.1667 Yrs
836 X 1.16667
MTBSC = =10.2 Years
96
Electric Power Consumption
Grinder Pump
Grinder Pump
B&WTV
0 50 100 150 200 250 300 350 400 450 500
Power Consumption - KwHr/Yr
-80-
-------
Analysis of O&M Costs for
Environment/One Grinder Pumps
A«»umlng«V,%lnt»re«
20-Year Period
1. Power Cost 200 kwhr/yr 6 $0.08/kwhr = $16/Year.
2. Overhauls Assume That Half the Units Require
Complete Teardown and Rebuild After 10
Years at an Average Cost of $900.
3. Minor Repairs Assume MTBSC Is 5 Years, and Average
Cost Is $75.
4. Salvage Value Assume That it Is $0, Although in Actual
Practice the Tank, Motor, and Many Other
Components Would Certainly Last More
Than 20 Years.
Analysis of O&M Costs for
Environment/One Grinder Pumps
Present Worth Calculation
1. Power Cost s 16 88 = 16 (9-3778) = $150.05
2. Overhauls = (0.5) (900) (^ ) 8"5/8 = 450 (0.43722) = $1 96.75
^Service =75(f )«« + 75 (f )
/».». VF/5 \F/1
= 75(1.57871) = $118.40
TOTAL PRESENT WORTH $465.20
r
Analysis of O&M Costs for
Environment/One Grinder Pumps
Equivalent Annual Cost
Present Worth x (£) 8"5/8 = 465.20 (.10664) = $49.61/YR
-81-
-------
Pressure Sewers - Part II
I. INTRODUCTION
II. OPERATION
AND MAINTENANCE
III. DESIGN CRITERIA
William C Borne
Consulting Engineer
[ugene, OR
A. External Pump
B. Internal Pump
C. KovarikPump
D. Unitary Design/Dry Pit Pump
E. Pump Curves
A. Causes for Maintenance
B. Service Calls
C. Cost Accounting
A. Zoning
B. Scum and Sludge Design
C. Pump Installation
D. Water Flow
E. Design Examples
F. Soil Beds
-83-
-------
Septic Tank Effluent Pump (STEP) System
Electrical Junction Box
Quick
Coupling >
Discharge
Hoae
Assembly
date Valve
Discharge
STEP
Pump In
External
Vault
STEP System with
External Pump Vault
Reserve
Scum
Clear
"Space
Sludge
-85-
-------
STEP System with
Internal Pump Vault
STEP System with Kovarik Pump
Dry Pump Vault-
Mercury Float Switches ,
-Suction
-Vault
Screen
STEP System with Unitary Design-Dry Pit Pump
Dry Pump Vault
-86-
-------
I HEAD (FEET Of WATER)
1 - 2 HP Centrifugal STEP
2-2 HP Centrifugal GP
1 - 1/2 HP Centrifugal STEP
4 -1/2 HP Pro-Cav Pump
5 -1 HP Pro-Cav GP or STEP
6 -1/2 HP 7-Shge Submeraible
Wei STEP
0 10 20 30 40
DISCHARGE (OPM)
Head-
Discharge
Curves for
Typical GP
and STEP
Systems
0 20 «
DISCHARGE (GPM)
Effective
Pump
Curve
[HEAD
-------
Distribution of Causes for Call-Out
Maintenance On Selected Grinder
Pump Pressure Sewer Projects
Category Percent of Occurrences
Electrically Related 25-40
Pump Related 20-25
Miscellaneous 20-30
Pum p Vau It Related 5-15
Piping Related 5-15
Distribution of Causes for Call-Out
Maintenance on Selected STEP
Pressure Sewer Projects
Category
Electrically Related
Pump Related
Miscellaneous
Tank Related
Piping Related
Percent of Occurrences
40-60
10-30
20-40
1-5
5-10
r
Electrically Related Service Calls
for 500 Pump STEP System
(Assuming MTBSC = 4 Years)
Floats
J-Box
Breaker Off
Breaker Tripped
Bugs In Contactor
Noise In Panel
Miscellaneous
TOTAL
20
8
6
4
3
3
10
54
-88-
-------
Pump Related Service Calls
for 500 Pump STEP System
(Assuming MTBSC = 4 Years)
Clogging
Iron Sulfide
Miscellaneous
TOTAL
^-
4
4
4
12
-^
Tank Related Service Calls for
500 Pump STEP System
(Assuming MTBSC = 4 Years)
Riser Adjustments
Vault Failure
l&l
TOTAL
3
1
2
6
Piping Related Service Calls
for 500 Pump STEP System
(Assuming MTBSC = 4 Years)
Broken Service Line 6
Clogged Building Sewer 4
TOTAL 10
-89-
-------
Miscellaneous Service Calls
for 500 Pump STEP System
(Assuming MTBSC = 4 Years)
Air Problems 20
No Problem Identified 13
Special P.P. 5
Other 5
TOTAL
43
O&M Cost Accounting Records for
the Glide, Oregon Pressure Sewer
System ($1,000)
Item Overhead WWTP Collection Services Total
Labor 28.6 56.7 2.3
Materials 2.1 24.3 0.6
Total 30.7 81.0 2.9
% 22 57 2
Average Cost* ton 888 and 1989.
^
16.3 103.9
11.3 38.3
27.6 142.2
19 100
^>
Zoning of a STEP System Interceptor Tank
Showing Scum and Sludge Accumulation
-90-
-------
Sludge and Scum Accumulation at
Glide, Oregon
(186 1,000-Gal Tanks)
Time Occupants
(yr) (No.)
Mean
S. Dev.
Min.
Max.
8.2
0.7
7,2
9.1
2.75
1.18
1
6
Sludge
(gai)
195
98
20
530
Scum
(gal)
92
60
0
300
Total
(gal)
289
114
60
650
Scum and Sludge
Design Criteria
1. Estimate Annual Combined Sludge Plus
Scum Accumulation (33 Gal/Home for Glide).
2. Scum Comprises about 1/3 of the Combined
Volume of Sludge Plus Scum.
3. About 1/3 of the Scum Lies above the Water
(Effluent) Level.
4. Pump Vault Inlet Ports Should Normally Be
Located at about 1/3 of the Depth below the
'Pump Off' Level.
Cross Section at Pump Installation
Pump Is Located Higher than HGL of Main
Air Fills This Portion
of the
Service Line
Static Hydraulic
Grade Line
Pump
Main
Higher -fhan
Static HGL
Service Line
-91-
-------
Air Bound Hydraulic Gradient
ELEVATION
100
ReMivoIr
Air Bound Hydraulic Gradient
Profile of Pipeline Showing Uphill Flow
"Uphill" Flow. All Parts of Collection System Are Lower than
the Point of Discharge to Atmosphere
STATION
Profile of Pipeline Showing
Uphill and Downhill Flow
"Downhill" Flow in Portions Shown
ELEVATION
Downhill Flow
Downhill
Row
Discharge
Elevation &
Static HGL
STATION
Direction of Flow
-92-
-------
Enlargement
of Profile at
Summit
Showing Water Surface
Profile during Flow.
Water Seals Off Air Release at
Summit
Enlargement
of Profile
Near Static
Pool
Direction
of Flow
Showing Hydraulic
Jump, Air Bubbles, and
Pockets That Require
Ventilation.
Orifice
Wastewater-
Type Air
Release
Valve
-93-
-------
FLOW (0PM)
300 "
% 100 200 300
EQUIVALENT DWELLING UNITS
400 BOO
Design
Flows
Example Pressure Sewer Design
A) PLAN VIEW
Example Pump Location
Line A 9
Row
Point of Discharge
LineB
rn 9 E-"*"
Point of
DUcharge
3«K«L£
i£r"
LinoB
wv Local ton
1 Lira A 17 + 75 » 1
LJneB 0 + 00 |
at .«
o.r-
-0*3^
U**A iT.n-
«>«M
0
k
Example
Pressure
Sewer
Design
-94-
-------
Soil Bed for Odor Absorption
Plan View
Soil Bed for Odor Absorption
.Soil Bed
Section View
Air
/^Release
Valve
Perf Pipe
-95-
-------
Vacuum Sewers
I. INTRODUCTION
II. SYSTEM COMPONENTS
III. MAJOR DESIGN ISSUES
IV. DESIGN EXAMPLES
V. MAJOR CONSTRUCTION
ISSUES
VI. ADVANTAGES
A. Vacuum Station
B. Collection Piping
C. Services
A. Line Layout
6. Line Sizing
C. Hydraulic Considerations
D. Station Component Sizing
A. Line Layout
B. Line Sizing
C. Hydraulic Considerations
D. Station Component Sizing
A. Construction Materials
B. Testing Requirements
C. Inspection
D. Historical Problems
A. Cost Savings
B. Environmental Impact
C. Operational Improvements
VII. OPERATION & MAINTENANCE A. Personnel
B. Special Tools & Equipment
C. Spare Parts
VIM. COSTS A. Capital Costs
l.Line
2.Valve Pit
S.Appurtenance
4.Station
B. Operation and Maintenance Costs
1 labor
2.Power
S.Equipment Replacement
Richard Naret
AIKVAC
Jompo, FL
-97-
-------
VACUUM SEWERS (continued)
IX. APPLICABILITY A. Screening Factors
1.Topographic Considerations
2.Ground Conditions
S.Type of Development
B. Applicability
X. EVALUATION OF A. Problems with Early Systems
OPERATING SYSTEMS B. Operating Data
C. Trend
-98-
-------
Vacuum Sewer
System
Vacuum Station
Collection Piping
Services
Vacuum Main #2
9\9 9
66 6
6 A 6 6
3" Vacuum Service Line
Vacuum Main #3
Division Valve
Branch Line
STP
Vacuum Station
Vacuum Main #1
Vacuum Station
Vacuum Pumps
Reserve Tank
Collection Tank
Standby Generator
Sewage Pump
Control Panel
-99-
-------
Vacuum Pump Exhaust
Control Panel
Vacuum
Pumps (2)
Equalizing
Lines (2)
Force Main to
Treatment or *
Interceptor
Discharge
Pumps (2)
Vacuum Pump Exhaust
Vacuum Pumps (2) DUcharoe Pumps (2) Sewa9e
Collection Tank
Collection Piping
Main Lines
Branch Lines
Service Lines
-100-
-------
Collection Piping
n
u
Service Line (3')
-0 Branch Line (4" or 6')
Main Line (4", 6", 8* or 10")
Services
Vacuum Valve
Valve Pit
Sump
Vent
,Vent
Vacuum Valve , Valve Pit
Building Sewer
Sump
Service Vacuum
Line
Main
-101-
-------
Major Design Issues
Line Layout
Line Sizing
Hydraulic Considerations
Station Component Sizing
Line Layout
Multiple Branches
Minimize Lift
Minimize Length
Equalize Branches
0.2% Slop*
m*^^mm
Upgrade Transport
Vacuum Main
45° Elbows
Level Grade Transport
0 2% Slop*
Flow
Vacuum Main
Downgrade Transport
-102-
-------
Flow vs. Pipe Size
Pipe Maximum Recommended
Diameter Flow Design Flow
(in.) (gpm) (gpm)
~~4 55 40
6 150 105
8 305 210
10 545 375
r
# Homes vs. Pipe Size
Pipe
Diameter
(in.)
4
6
8
10
Maximum
#
Homes
70
260
570
1,050
Recommended
Design #
Homes
40
170
380
700
Hydraulic
Considerations
» Available Lift
ft Static Loss
Friction Loss
-103-
-------
Lift Capability
Vacuum
Pump
I
Normal Operating Range |
18' Total Available Lift
;_5 Required for Valve Operation
13' Available for Sewage Transport
-3' Typical Friction Low
10' Available for Static Lift
'm^t-^'-'\. ^\
30" HG = 34' H2O
20" HG = 23' H20
16" HG = 18'H2O
*"f I 'NX 'VI VS^*
Static Lift
f Lift
Static Height
1 I
[Static Lift = Lift HeightPipe Diameter |
Friction Loss
Use Friction Loss Tables
Empirically Derived
Formula
Properly Sized System:
<3 ft Loss
-104-
-------
f S
Station Component Sizing
Component Sizing Function Of:
Vacuum Pumps Pipe Volume and Flow
Sewage Pumps TDH and Flow
Collection Tank Flow
Component Sizes
Large Vacuum Station
# Connections 750-1,000
Vacuum Pumps 25 hp
Sewage Pumps 30 hp
Collection Tank 5,000 gal
A
Component Sizes
Small Vacuum Station
# Connections
Vacuum Pumps
Sewage Pumps
Collection Tank
100-200
10 hp
5hp
1,000 gal
-^
-105-
-------
Line Layout - Multiple Branches
i
# Homes vs. Pipe Size
Pipe
Diameter
(in.)
4
6
8
10
Maximum
#
Homes
70
260
570
1,050
Recommended
Design #
Homes
40
170
380
700
»-. -j
Line Sizing
-106-
-------
Static Loss
Lift* (8" Pipe): 1.51
Lltt» (6-Pipe: 1.5'
Lifts (4" Pipe): 1.0'
Static Los* = 1 £ - 0.67 = 0.83'
Static Loss = 1.5 - 0.50 = 1.00'
Static Loss = 1.0 - 0.33 = 0.67'
Friction Loss
Flow
(gpm)
Head Loss
(ft/100 ft)
40
50
60
0.0407
0.0616
0.0862
Example: 2,000 ft - 6", Q = 50 gpm
Head Loss =0.0616x20
= 1.23 ft
Friction Loss
Friction LOM
Cunuhto* from the
Station towmrd the
End*
-107-
-------
Total Head Loss
Vacuum Station
Component Sizing
Calculate
Row
p
»
Size
Vacuum
Pump
Size
Pump
Size
Collection
Tank
Calculate check
» Pipe -* ..,
Calculate Check
TDH NPSH
Example wilh All
Formulas Shown in
EPA Manual. Table 5-4
Major Construction
Issues
Construction Materials
Testing Requirements
Inspection
-108-
-------
Construction Materials
Pipe 4", 6", 8" PVC
Pipe Joints Solvent-Weld or 0-Ring
Valve Pits Fiberglass
Testing Requirements
Collection System Daily
Vacuum Station Upon Completion
Entire System Upon Completion
Inspection
Proper Grade
Proper Installation
System Tightness
-109-
-------
/
Historical Problems
Problem
Glued Fittings
Pit Settlement
Line Leaks
Solution
Use of Gasketed
Pipe
Proper Pit
Compaction
Daily Testing
Vacuum Sewer
Advantages
Cost Savings
Environmental Impact
Minimized
Ease of Operation
Cost Savings
Less Excavation
Smaller Pipe
Ease in Making
Field Changes
-no-
-------
Environmental Impact
Minimized
Minimal Infiltration
No Exfiltration
Minimal Surface
Disruption
Ease of Operation
Odor and Corrosion
Minimized
No Line Blockages
Minimal Exposure to Raw
Sewage
Only One Source of Power
Operation & Maintenance
Personnel
Special Tools &
Equipment
Spare Parts
-in-
-------
Personnel Required
» Operator: Full Time
» Assistant: Part Time
*For Typical System of 200-500 Connections
See Section 3.8.3.1 to Estimate Person/Hrs/Yr
Operator Qualifications
Mechanical Aptitude
Conscientious &
Dependable
Attitude
Operator Training
Inspection During
Construction
Manufacturer's
Training School
On-the-Job Training
-------
Special Tools &
Equipment
Portable Vacuum
Pump
Portable Chart
Recorder
Test Box
Spare Parts
Valves & Controllers
Rebuild Kits
Level Control
Components
Cost Factors
Capital Costs
Operation and
Maintenance Costs
-113-
-------
Line Costs
Line Size
4"
6"
8"
Installed $$
$11.00/LF
$14.00/LF
S17.00/LF
Valve Pit Costs
Type of Pit
Standard Setting
Deep Setting
Single Buffer Tank
Dual Buffer Tank
Installed $$
$2,300/EA
$2,500/EA
$3,000/EA
$4,000/EA
Appurtenances Costs
Item
Installed $$
Division Valves S550/EA
Lifts $ 50/EA
Vent $ 50/EA
Anti-Flotation Collars S100/EA
-114-
-------
Package Station Costs
# Connections Installed $$
10-25 $ 95,000
25-50 $130,000
50-150 $160,000
Custom Station Costs
# Connections
150-300
300-500
>500
Installed $$
$210,000
$250,000
$320,000
fc- -*
Operation and
Maintenance
Labor
Power
Equipment Replacement
-115-
-------
Routine Maintenance
System Component Mrs. Required
Vacuum Station 0.5-1.0 Mrs/Day
Piping None
Vacuum Valve None
r \
Preventive Maintenance
System Component Hrs. Required
Vacuum Station 60-100Hrs/Yr
Piping 20-40 Hrs/Yr
Vacuum Valve 0.3-1.0 Hrs/Yr/Valve
Service Calls
System Component Hrs. Required
Vacuum Station 20-40 Hrs/Yr*
Piping 20-40 Hrs/Yr*
Vacuum Valve 0.2-1.0 Hrs/Yr/Valve
"For Typical System of 200-500 Connections
-------
Power
Low
High
Ave
Consumption
KwHr/Yr/Conn
160
460
250
$/CONN/MO
e$0.06/KwHr
0.80
2.30
1.25
$/CONN/MO
O$0.08/KwHr
1.07
3.07
1.67
Equipment Replacement
Vacuum Station
Cost Expected
Range ($) Life(yrs)*
Vacuum Pumps (2)
Sewage Pumps (2)
Collection Tank
Control Panel
Misc. Equip.
10,000-30,000
6,000-12,000
10,000-13,750
13,750-25,000
2,000-3,000
15-20
15-20
25-50
20-25
15-20
Annual R&R
(Vyr/staUon)
500-2,000
300-800
200-550
550-1,250
100-200
According to Equipment Manufacturers. More Conservative
Rgures May be Used for Planning Purposes.
Equipment Replacement
Vacuum Valve
Rebuild
Cost Frequency Annual R&R
Range ($) (yrs) ($/yr/valve)
Vacuum Valve
Controller
Misc. Parts
15.00-17.50
32.00-35.00
10.00-12.50
10-20
5-8
10-20
0.75-1.75
4.00-7.00
0.50-1.25
-117-
-------
Screening Factors
» Topographical
Considerations
» Ground Conditions
i Type of Development
Topographical
Considerations
Flat Terrain
Rolling Hills with Many
Small Elevation Changes
Many Stream Crossings
Ground Conditions
Rock
High Water Table
Unstable Soils
-118-
-------
Type of Development
> Urban Development in
Rural Area
> Restricted Construction
Conditions
»Existing Utilities Present
States Having Vacuum Systems
Vacuum System
Other Countries Using
Vacuum Sewers
Japan
Australia
United Kingdom
France
Holland
Canada
-119-
-------
Applicability
Existing Community
Urban Development in Rural
Areas
Existing Utilities
Flat/Rolling
Rock/High Water
Unstable Soils
Problems with Early
Vacuum Systems
Low Levels of Vacuum
Frequent Valve Failures
O&M Intensive
Factors Responsible for
Early System Problems
Lack of Hydraulic Information
No Design Standards
Insufficient Inspection
No Established O&M
Guidelines
Component Defects
-120-
-------
Systems Visited
Ocean Pines
Westmoreland
Ohio County
Lake Chautauqua
Central Boaz
White House
Startup
1970
1979
1984
1986
1988
1988
#STA
12
4
1
4
1
2
# Valves
1,500
490
200
900
180
260
#CONN
3,500
540
250
2,500
350
360
^ x
Operational Data
Ocean Pines
Westmoreland
Ohio Co PH I
Lake Chautauqua
Ohio Co PH IIA
Central Boaz
White House
Ohio Co PH MB
Startup
1970
1979
1984
1986
1987
1988
1988
1990
Power
KwHr/yr/conn
570
460
160
190
160
230
180
160
Service Calls
#/yr/1 00 valves
100
10
12
5
8
17
9
5
^ _^s
Factors Contributing to
System Improvements
Better Understanding of Hydraulics
Design Advancements
Experienced Construction
Inspection
Establishment of O&M Guidelines
Improved Components
-121-
-------
System Reliability Trend
MTBSC MTBSC
Years (Range) (Ave)
Early Systems 1960-1975 1-8yrs >4yrs
Recent Systems 1975-Present 6-22 yrs 10yrs
Summary
Action
Result
More Conservative
Design
New Hydraulic
Approach
Improved
Components
Increased
Reliability
Lower Power
Cost
Fewer Service
Calls
-122-
-------
Appendix A
Two Decades of Experience with Pressure
Sewer Systems
A-l
-------
This article was reprinted from the following journal
with permission from the New England Water
Pollution Control Association:
VOL. 26, NO. 1
MAY 1992
OF THE NEW ENGLAND WATER
POLLUTION CONTROL ASSOCIATION
Published by
New England Water Pollution
Control Association
85 Merrimac Street
Boston, Massachusetts 02114
ISSN 0548-4502
A-3
-------
TWO DECADES OF EXPERIENCE
WITH PRESSURE SEWER SYSTEMS
BY R. PAUL FARRELL*
[PRESENTED AT WINTER 1992 MEETING]
INTRODUCTION
It is always a pleasure to address the New England Water Pollution Control
Association because you are the heirs of a proud sanitary engineering tradition which
goes back to the Lawrence Experiment Station and such giants as the late Gordon
Maskew Fair. It is no exaggeration to say that American sanitary engineering had
its beginning here in New England. This region continues to this day to make material
contributions to the science and practice of what we now call environmental
engineering.
Through a fortuitous series of events, I became deeply involved in the
development of grinder pumps and the pressure sewers which they make possible.
This, now mature technology, was in its infancy when first I spoke to NEWPCA
at its 1971 meeting'.
The idea of pressure sewers was the brainchild of Dr. Gordon M. Fair, then
professor emeritus of Sanitary Engineering at Harvard. His vision and the clarity
of his thought process is obvious on Figure 1, a 1965 drawing from his United States
patent for "a sewer within a sewer"2. It was hoped this would offer one solution to
the Combined Sewer Overflow, (CSO) problem. This conceptual drawing includes
the following elements:
inlet connection to standard gravity household plumbing
storage tank
sewage grinder on inlet side ahead of pump
pump (sketch shows conceptually a positive displacement-type pump such
as a gear pump)
a tank vent to atmosphere
discharge under pressure
discharge through small diameter plastic tubing
backflow prevention (in this sketch the positive displacement pump pro-
vides the function)
Each of the above elements, along with many subtle refinements, have been
incorporated into today's commercially available grinder pumps.
*P.E., Senior Consultant, Environment/One Corp.
A-4
-------
R.P. FARRELL
//
Figure 1. CONVERTED SEWER SYSTEM
The development of early prototype grinder pumps was done under sponsor-
ship of ASCE and the Federal Water Pollution Control Administration. Dr. Fair
visited our engineering laboratory at the, then fledgling, Environment One Corporation
near Schenectady, NY at about that time. This was a memorable experience for me,
both personally and professionally, because Dr. Fair had been my father's revered
mentor and teacher at Harvard years earlier when I was a mere lad of ten. He was
highly complimentary of our pioneering work and predicted that the use of pressure
sewers would someday become commonplace.
A-5
-------
PRESSURE SEWER SYSTEMS
GROWTH 1971 TO 1991
Twenty years ago a thirteen-month-long, highly successful field demonstration
of pressure sewers had just been completed. The number of commercial units sold
at that time numbered a few dozen at most. The substance of my paper to this group
then was that pressure sewers was a viable concept that had been thoroughly
developed and demonstrated and was about to become a commercial reality.
From an estimated 50 units in 1971, the cumulative number of grinder pumps
produced and shipped by Environment One grew, slowly at first and more rapidly
in recent years, so that about a year ago we shipped pump number fifty thousand!
This growth in installed base is shown graphically on Figure 2. In the meantime,
several domestic pump companies including Hydr-O-Matic, Peabody Barnes and
F.E. Myers joined in, offering their variations on the basic theme. By 1991, annual
industry shipments were estimated3 to be almost 19,000 units.
From a single grinder pump at a marina on Lake George in 1970, the industry
has grown to the point where projects using hundreds of pumps are commonplace,
and systems with a thousand pumps or more are no longer unusual. This data, partly
from our own records and partly from a newly-released EPA manual on alternative
collection systems4, illustrates this point:
NUMBER OF INSTALLED ENVIRONMENT/ONE GRINDER PUMPS
50000 -r
0000
1965
1970
1975
1980
1985
1990
YEARS
Figure 2. NUMBER OF-INSTALLED ENVIRONMENT/
ONE GRINDER PUMPS ,
A-6
-------
R.P. FARRELL
Some Existing Large Scale Pressure Sewer Systems 1991
Location Homes Served
Port St. Lucie, FL
Saw Creek, PA
Horseshoe Bay, TX
Kingsland, TX
Anne Arundel County, MD
Buckeye Lake, OH
Ottawa County, OH
Bloomingdale/Pooler, GA
Pierce County, WA
Palm Coast, FL
3,000
1,800
1,700
1,600
1,500
1,500
1,000
1,000
850
650
CAPITAL COST
A few pressure sewer jobs installed in New England during recent years are
shown in the following table:
Prices for Pressure Sewer System Components
(low bid to furnish and install)
Description Bid Price
Simplex GP* 60 gal. 1-1/2 to 8-1/8' $3800-4300
1 1/4" PVC service line $12/lin. ft.
1 1/2" PVC pressure main $12/lin. ft.
Simplex GP* 120 gal. 4' a'way $5000
Duplex GP* 120 gal. 4' a'way $12500
1 1/2" PE pressure main $14/lin. ft.
2" PE pressure main $14/lin. ft.
Auto air & vac release valve $3500
Simplex GP* 60 gal. & SVC Conn $6940
3" PVC press main in pav'mt $14.30/lin. ft.
Simplex GP - 30" a'way $2300-5600
1-1/4" PVC service line $6/lin. ft.
2" PVC pressure main in pav'mt $7-12/Iin. ft.
3" PVC pressure main in pav'mt $8-13/Iin. ft.
4" PVC pressure main in pav'mt $9-14/lin. ft.
6" PVC pressure main in pav'mt $ll-16/lin. ft.
Auto vac & air release valve $1500
*Simplex grinder pump (GP) includes: 1 hp 1725 rpm thermally protected, capacitor start
motor; integral level controls and check valve, separate control panel with alarm and custom
features as specified by engineer, redundant check valve, heavy duty custom molded
reinforced fiberglass tank, accessway length as specified, lid and lock, integral shut-off valve
and tank vent. No field assembly or tank wall penetrations required.
A-7
Name-Date-Size
Bourne, Mass
Feb '90
>200 pumps
Town of Derry, NH
Beaver Lake area
Nov '89, 50 pumps
Palmer, Mass
Nov. '86, 50 pumps
National (Typical)
US EPA4
October '91
-------
PRESSURE SEWER SYSTEMS
These prices, as would be expected, tend to reflect the size of the job, as well
as the competitive situation in the construction industry at the time of bid. These
are all systems using positive displacement grinder pumps by the author's company,
but are believed to be representative of competitively bid prices for high quality
equipment from any of several active manufacturers. The range of prices compares
well with some "typical national" cost estimates, contained in the recently published
EPA manual of "Alternative Collection Systems", which are also shown in the table.
OPERATING AND MAINTENANCE EXPERIENCE
Equipment Maintenance Requirements
From the beginning, most engineers had little difficulty accepting the idea that
a pressure collection system would work, and that under the right circumstances it
offered the opportunity for dramatic savings in capital cost. Most reservations were
based on uncertainly about the long-term reliability and operating cost of a
technology which in 1971 had literally no "track record".
Let's see what we have learned since then. From the beginning we have kept
track of the mean Time Between Service Calls (MTBSC) on as many projects as
possible. This number is an accurate measure of the overall service call rate on a
group of pumps and is very useful for staffing and cost estimating purposes. It is
calculated as follows:
# pumps in service (P) x years in service (T)
MTBSC (yrs) = _ _'
Total # of service calls in T yrs (S)
EXAMPLE from Pierce County, WA
System contains 836 pumps: P = 836 pumps
Data is for a 14-month period 1988-89: T = 14/12=1.1667 yrs
During this period there were 96
pump-related service calls: S = 96 calls
836 x 1.6667
MTBSC = = 10.2 years
96
Here are some other MTBSC data collected and published in various places over
the years:
Date Project MTBSC-yrs
1971 Albany, NY Demonstration Project 0.9
1978 Country Knolls South, NY 2.8
1978 Weatherby Lake, MO 3.0
1978 Lake Mohawk, OH 3.0
1980 Cuyler, NY 4.3
1980 Weatherby Lake, MO 4.3
1989 Pierce County, WA 10.2
1991 Groton (Noank),-CT 4.4
1991 Fairfield Bay, AK 11.1
1991 Quaker Lake, PA 10.7
A-8
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R.P. FARRELL
Figure 3 shows that this reliability measure has improved by an order of
magnitude since 1970. The current figure-at Groton, reflects reliability levels when
the project was built and is reasonable since the occasional pumps still being installed
there are from the original stock shipped over ten years ago5.
MEAN TIME BETWEEN SERVICE CALLS
CO
- v
50
100 150
MONTHS SINCE 1/1/71
200
250
Figure 3. MEAN TIME BETWEEN SERVICE CALLS
Operating and Maintenance Costs
Another measure of reliability is the annual Operation and Maintenance (O&M)
costs expended. Fairfield Glade, Tennessee offers an excellent example because they
have done their own maintenance with a dedicated crew and have kept accurate and
detailed records. This project has grown from 20 pumps in 1978 to 821 in 1990.
The average annual cost for O&M currently is running about $30 per pump6. Further,
as shown on Figure 4, the average cost has been declining for the past 8 years; even
as the average age of the entire pump population is increasing. This is attributed
to numerous small, but continual, improvements made in the pump, along with the
fact that the maintenance force has become more efficient with experience. When
this project was in the planning stage during the middle seventies, my company
estimated $40 to $50 per year for pump O&M. It is gratifying to have the owner
tell us 13 years later, that our estimate was reliable and on the conservative side.
Quaker Lake, Pennsylvania, a beautiful community of older summer homes, was
experiencing serious degradation of water quality as a result of failing septic tanks.
A pressure sewer system, built in 1976 and serving 118 homes, has restored the lake
A-9
-------
PRESSURE SEWER SYSTEMS
Annual Operation and Maintenance Costs
(in 1990 dollars)
QL
E
a.
co
In
c
O
C
"re
c
c
$0
1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Year
Figure 4. FAIRFIELD GLADE, TENNESSEE
GRINDER PUMP O&M STATISTICS
water quality and increased property values7. A sinking fund of $42 per pump per
year was originally established for O&M. Because actual O&M costs were far lower
than predicted, a significant surplus accumulated in this maintenance and replace-
ment fund and the capital debt was retired several years early.
EFFECTS ON TREATMENT WORKS
Pressure sewers are primarily a transport system, and accomplish little in the
way of treatment. However, another legitimate question properly asked by every
engineer considering this technology is, "How will this pressure transported
wastewater affect the treatment works?" By now there are numerous examples of
pressure collected wastewater being successfully treated by all normal processes.
These include all those shown in the following table:
Types of Discharge Points for Pressure Sewers
In Current Use 1991
gravity manhole
pumping station wetwell
force main
community septic tank and soil absorption system
A-10
-------
R.P. FARRELL
aerated lagoon
secondary treatment of all types
surface aerators
rotating biological contactors
diffused air
Many Low Pressure Sewers discharge into larger systems where the effect is
not measurable because of dilution. A lesser number either pump into a dedicated
treatment facility or represent a significant fraction of the total flow arriving at the
plant.
Pressure collected wastewater differs from that delivered by a conventional
gravity system in two principal ways:
1. Gross solids have been ground prior to transport to a particle size which
generally is in the range of 1/4- to 1/2-inch maximum dimension.
2. Because of the watertight joints and absence of manholes, there is the
potential for dramatic reduction in extraneous flows, or Infiltration and
Inflow (I/I).
It was shown early on that the grinding had no deleterious effect on settleability
as compared to wastewater transported by conventional gravity8. An excellent example
of elimination of extraneous flows was brought to my attention this past summer
during a visit to a new plant serving the Towns of Sharpsburg and Keedysville,
Maryland. Historic Antietam Creek, site of the bloody civil war battle, flows through
the area and was plagued by raw sewage overflows and failing septic tanks. A
completely pressurized collection system using grinder pumps was constructed two-
and one-half years ago and has restored the area to a semi-rural beauty and serenity
appropriate to such a historic site. There are 731 connections presently on the system,
with a few more scheduled for the future. The pressure collection system consists
of 60,690 lineal feet of SDR-21 PVC pipe varying in diameter from 1-1/2 to 6-inches
and buried at an average depth of 4 feet. All the wastewater is delivered to a new
treatment works through the 100 percent pressure system. Both the plant operator
and Executive Director of the sewer district have stated that wet and dry weather
flows are identical. Metered water flow averages between 124 and 150 gpd/DU.
Measured wastewater flow is about 2 percent less than water con-sumption in winter,
and 10 percent less in summer. There is no infiltration/inflow!!!
Similar findings were made at the original Albany Demonstration project where
sewage and water flow were essentially identical and averaged about 35 gpcd8. It
is always comforting to have research conclusions confirmed by real world operating
experience. Any operator who has suffered through the shock hydraulic loads caused
by storm flows into an old leaky collection system can appreciate the significance
of predictably lower, nearly steady flows on both removal efficiencies and operating
costs. Most operators would consider it "a dream come true."
EQUIPMENT REVIEW
Grinder pumps are available from a number of reputable companies. Each
A-ll
-------
PRESSURE SEWER SYSTEMS
manufacturer has executed a product design in his own particular way, and any brand
on the market today has the generic features envisioned by Dr. Fair. My company's
product has several unique and significant features, which I sincerely believe have
contributed to its widespread use and our dominant market position. However, rather
than discuss those details at this time, I am sure that you will review the available
equipment, its features and performance record, and make an informed choice. There
are several well-qualified manufacturer's representatives who are surely eager and
able to answer your questions.
CONCLUSIONS
A. In the 25 years since Gordon Fair's conceptual description of "a sewer within
a sewer", grinder pumps and pressure sewers have:
been custom developed and thoroughly demonstrated
become eligible for construction loans and grants
been accepted by nearly all government jurisdictions
become a routine alternative considered by most engineering firms
formed the basis for a viable, mature industry with its own association
solved difficult technical and economic problems throughout the United
States, Canada and Scandinavia
begun spreading rapidly around the globe
B. Capital cost savings are significant in the right situations in the right
situations including: shoreline properties, rocky areas, high water tables, low-
density housing, and a variety of sites sensitive to the environmental trauma
so often necessitated by conventional deep gravity sewer construction.
C. There have been few serious operating problems with pumps, pressure lines
or treatment works, and those few which have been encountered, such as H2S
generation, are amenable to a variety of well-known control techniques. The
complete elimination of I/I has been demonstrated in several locations served
exclusively by pressure sewers.
D. Highly reliable equipment and systems are operating routinely in New
England and all over the country. Operating and maintenance procedures and
histories are available from a variety of installations with years of satisfactory
experience. Those now considering this technology for the first time can
benefit from the collective experience of many fellow operators and engi-
neers. Pressure sewer systems can be planned which will operate reliably into
the foreseeable future, within budget, and with few surprises.
REFERENCES
1. Farrell, R. Paul, Jr., "Pressure Sewers and the Grinder Pump Which Makes
them Possible", Journal of the New England Water Pollution Control
Association, vol. 6, no. 2, November 1972.
A-12
-------
R.P. FARRELL
2. Fair, G.M., US Patent 3,366,339, "Converted Sewer System", filed Nov 26,
1965, issued June 30, 1968 assigned by the inventor to the public.
3. Submersible Wastewater Pump Association industry data for 1990
(unpublished).
4. Bowne, William C. et al, "Alternative Wastewater Collection Systems".
EPA/625/1-91/024; US Environmental Protection Agency; October 1991.
5. Almquist, Carl; Chief Operator, Town of Groton, CT; December, 1991
personal communication
6. Gray, Donald D., "TN Community's Grinder Pumps Provide Positive O&M
Statistics"; in "Small Flows", published by Small Flows Clearing House,
West Virginia University; October 1991.
7. Milnes, Thomas R. et al, "Community Action at Quaker Lake A Low
Pressure Sewer System with Aerated Lagoons", Water Pollution Control
Association of Pennsylvania Magazine, November-December 1978.
8. Carcich, Italo G. et al, "A Pressure Sewer System Demonstration", EPA-R2-
72-091; November 1972.
A-13
-------
Appendix B
Vacuum Sewer Systems
Typical Questions & Answers
Richard Narel.P.E.
B-1
-------
E»ROJECT QUESTIONS
1. How many vacuum systems are there in the U.S.?
There are more than 50 communities utilizing about 100
vacuum stations. Because the piping network connected
to each vacuum station is hydraulically unique to that
station, it can be said that there are about 100
operating systems in the U.S.
2. How many vacuum systems are there in the world?
An additional 50. (brings the total to 100 to 150).
3. What other counties have vacuum systems?
France, England, Holland, Italy, Canada, Mexico, Japan,
Australia.
4. What is the typical size of the vacuum systems
installed to date?
1 station, 150 valves, serving 200-250 customers.
5. What is the largest system in operation?
Queen Annes County, MD : 12 stations, 1450 valves,
serving 4000 customers. An additional 1000 customers
(1 station & 325 valves) are scheduled to be added in
1992.
What is the smallest system in operation?
Spyglass, MD: 1 station, 19 valves serving 160 units
(apartments)
B-3
-------
VACUUM STATION QUESTIONS
1. Where is the break point between using a package
station and a custom station?
250 gpm (peak flow). At 75 gpcd, 3.5 per/hse, and a
peak factor of 3.5, this equates to about 400 houses,
2. How many customers can be served by 1 station?
Package station : 400 customers
Custom station : 1500 customers
3. What is the largest vacuum station in operation?
Sanford, Fl (1200 residential & 300 commercial)
4. For the typical vacuum station serving 200-250
customers, what size vacuum and sewage pumps are used?
174 cfm, 10 hp vacuum pumps; 100-200 gpm, 5-15 hp
sewage pumps.
5. What are the physical dimensions of a custom station?
Typically 24' x 24'
6. What are the typical building materials of a station?
Engineer's preference.
8-4
-------
7. Is there any odor at the station?
Typically not. (None inside, very infrequently
outside). Although there are nearly 100 vacuum
stations currently in operation, only 2 or 3 are fitted
with odor filters (more of a perceived problem rather
than an actual one).
8. Do the vacuum pumps run constantly to maintain vacuum
on the system?
No. Vacuum pumps are sized in a similar fashion to
sewage pumps (2 pumps; one lead and 1 lag with each
sized to handle 100% peak flow on its own). The vacuum
pumps are designed for a run time of 4-6 hours a day.
9. What type of vacuum pumps are used?
Sliding vane or liquid ring, although sliding vane is
preferred (more efficient in the normal operating range
of 16" to 20' hg).
10. What type of sewage pumps are used?
Engineer's preference. Usually non-clog horizontal
pumps. NPSH is a consideration.
B-5
-------
F»XF»XNG QUESTIONS
1. What is the hydraulic limit in terms of lift?
Presently about 15 feet, but new Air Admission Valve
developed by AIRVAC will allow for greater lift (about
25 to 30 feet).
2. What is the practical limit on length of a single
branch?
10,000 feet for a completely flat area (longer when
there is some grade working for you and shorter if
there is some grade working against you).
3. What are the typical line sizes?
Usually 30% of 4" and 70% of 6". (Some larger systems
use 8" and 10"),
4. What kind of pipe is used?
SDR 21 or Schedule 40 PVC.
5. What type of pipe joints are used?
Solvent weld or gasketed, although gasketed is
preferred.
6. What are the typical flow velocities?
15-18 fps.
7. Why is the saw tooth profile needed?
1) more efficient flow transport 2) allows for greater
levels of vacuum at the valve pits.
B-6
-------
I*XT
1. Is power required at the valve pit?
No, operation of valve is entirely pneumatic.
2. How many customers can be connected to one valve pit?
Four (4) homes can be connected to one valve pit. A
buffer tank can handle larger flows (as many as 35
homes in one buffer tank).
3. What about sewage backup in the event of a valve
failure in a pit sharing situation?
99% of valve failures to date have been in open
position (ie-service to homes is uninterrupted). If
still worried, use backflow preventers on service
lines.
4. Why is a 4" vent needed?
For hydraulic purposes (1" larger than 3" AIRVAC
valve). Without this vent, the traps inside the house
would be pulled dry.
5. What is the typical valve cycle?
Two (2) seconds of liquid followed by 1 or 2 seconds of
air (total cycle time = 3-4 seconds).
6. What is the hydraulic rating of the AIRVAC valve?
30 gpm.
7. Why aren't there odors at the 4" vent?
Small cycle volume (10 gallons). This small volume 1)
is not of a sufficient quantity to allow any
significant amount of sewer gas to be generated and 2)
does not stay in the sump long enough for gas to be
generated.
B-7
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QUTE s T x oxsr s
A. VACUUM STATION ISSUES
1. How much time is involved in the O&M of a vacuum
station on daily basis?
1/2 hour a day per station.
2. How many hours a day do the vacuum pumps run?
4-6 hours.
3. How many hours a day do the sewage pumps run?
1-2 hours.
4. What is the expected life of the station equipment?
Vacuum pumps: 15-20 years
Sewage pumps: 15-20 years
Collection tank: 25-50 years
5. How does the operator know of any kind of problem at
the station?
Auto-telephone dialer calls to report various kinds of
faults (low vacuum, high sewage level, power outage,
etc).
6. What kind of technical background does a system
operator need?
Operator only needs to be mechanically inclined. Any
person capable of working for the water department can
easily operate a vacuum system. Only 1 Or 2 (of 50 +)
operators have education beyond high school.
B-8
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B. COLLECTION PIPING ISSUES
1. How is a line break located?
There have been very few line breaks reported to date.
(ie-has not been considered to be a problem). Should a
line break occur, normal isolation procedures should be
followed:
Start at station. With multiple branches
typically connected to the station, one can
quickly eliminate a major portion of the system.
For example, with four major branches connected,
an operator can eliminate 75% of the system with
60 seconds by systematically opening and closing
the isolation valves on the incoming lines.
Once the problem is isolated to a major branch,
the operator goes into the field and uses a
systematic approach to further isolate the break
(go half way and determine if problem is above or
below this point, etc). AIRVAC's recently
designed gage tap (a tap adjacent to the division
valve) allows for an immediate reading of vacuum
level at that point.
2. How does a line break affect system performance?
Run time of the vacuum pumps will increase.
Only that part above the break will affected (ie-can
isolate break and keep rest of system unaffected)
3. Have any line blockages been reported?
None to date (15-18 fps velocity plays a major role)
B-9
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C. VALVE PIT ISSUES
NOTE: Answers in this section refer only to the
AIRVAC valve.
1. What kind of daily maintenance is required?
None.
2. What kind of preventive maintenance is required?
Check controller timing once a year.
See AIRVAC O&M Manual for other specifics.
3. What is the historical "reliability rate" of the vacuum
valves?
On average, 5 to 10 service calls per year per every
100 valves has been reported. More than 1 million
cycles will occur with 100 valves in 1 year.* This
equates to 1 service call for every 100,000 to 200,000
cycles, or a reliability rate of 99.999%.
* @ 150 gpd/home and 2 homes per valve
4. Has this rate improved with the more recent systems?
Yes. The EPA study of 1991 has historical data which
shows this improvement over the years. There has been
a dramatic improvement from the "early" years (1960's &
70's) to the present.
5. What causes a valve to fail?
Physical obstruction prevents valve from closing.
(Usually corrects itself)
Water in the controller (broken seal in breather)
6. What is the typical valve failure mode (open or
closed)?
Virtually every valve failure reported to date has
failed in the open position. This means 1)
uninterrupted service for the customer and 2) automatic
alarm (due to low vacuum) to the system operator.
B-10
-------
How do you locate a valve that is hung open?
Start at station and isolate the major branch losing
vacuum. Go into field and use gage taps at isolation
valves to further isolate problem area. Once problem
is isolated, operator can visit each valve pit.
Problem is usually evident by listening for rushing air
at the 4" vent.
8. How long does this take?
About 20-30 minutes after arriving at station.
9. Have there been any problems with valve blockages?
Construction debris (stones, pieces of pipe, etc) from
the lateral tie-in has prevented some valves from fully
closing (short-term problem). Should this happen, it
is easily corrected.
Presently, only AIRVAC has a 3" valve. This 3" opening
is larger than the 2 -7/8" throat opening of a standard
toilet. Any thing that passes through the toilet will
pass through the valve.
10. What is the expected life of a valve?
There are 2 or 3 parts of the valve that should be
replaced every 10-20 years (parts: $7.00, 45 minutes
labor). The controller should be rebuilt every 5-8
years (parts: $25.00, 1 hour labor).
Purdue University performed a 100,000 cycle test on an
AIRVAC valve (equivalent to 10 years of use) and found
minimal wear on the parts (Report available). AIRVAC
attempted to cycle a valve until failure occurred, but
the testing equipment failed before the valve did I!
Number of cycles completed at that point: 3,000,000.
11. Are the valves tested prior to shipment?
Every valve is cycled 100 times prior to shipment.
Every controller is cycled 50 times prior to shipment.
B-ll
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Appendix C
OPERATION & MAINTENANCE INFORMATION
LABOR & POWER COSTS
A study on Alternative Collection Systems (ACS), including vacuum sewers, was
done by the US EPA in 1989 and 1990. Part of this effort included visits to
operating systems in order to obtain information on operation and maintenance
costs.
The results of the site visits are shown on the following charts. It is important
to note that a wide variety of projects were visited, including some of the earliest
systems built, as well as systems that utilized design concepts and system
components of manufacturers that are no longer active in the industry.
As one would expect, the earliest vacuum systems have the higher O&M costs.
Design advancements coupled with component improvements have led to vacuum
systems that are operated and maintained at much lower unit costs and at much
higher levels of reliability than those of 20 years ago.
With proper design, installation and maintenance, the figures at the lower
end of the cost range can be achieved. However, more conservative figures
may be used for planning purposes.
C-1
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OPERATION & MAINTENANCE INFORMATION
LABOR
ROUTINE
PREVENTIVE
SERVICE CALLS
VACUUM
STATION
0.5 - 1.0 hr/day
60 - 100 hr/yr
20 - 40 hr/yr
PIPING
NONE
20 - 40 hr/yr
20 - 40 hr/yr
VACUUM
VALVES
NONE
0.3 - 1.0 hr/yr/valve
0.2 1.0 hr/yr/valve
TYPICAL RANGE | 210 - 400 hr/yr f 40 - 80 hr/yr| 0.5 - 2.0 hr/yr/vaiver
C-2
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OPERATION & MAINTENANCE INFORMATION
TYPICAL
POWER COSTS
PROJECT
LAKE MANITOU, IND.
WHITE HOUSE, TENN.
OHIO COUNTY, WV.
CEDAR GROVE, MD.
LAKE CHAUTAUQUA, NY.
CENTRAL BOAZ, WV.
UPPER FAIRMOUNT, MD.
YEAR*
1989
1989
1988
1988
1989
1989
1989
#OF
STATIONS
3
2
5
1
4
1
1
#OF
CUSTOMERS
700
360
700
160
2,500
350
250
ANNUAL
POWER COST
$7,400
$3,900
$5,500
$1 ,500
$27,500
$4,800
$3,750
COST PER
CUST/MO
$0.88
$0.90
$0.65
$0.78
$0.92
$1.14
$1.25
TYPICAL RANGE $0.65 - $1.25 /CUST/MO
Year the power costs were obtained, not the year the system began operation.
Adjusted for inflation, the typical range for 1993 would be about $0.80 - $1.50/Cust/Mo
C-3
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Appendix D
OPERATION & MAINTENANCE INFORMATION
EQUIPMENT REPLACEMENT
The following information is provided for maintenance of equipment used in
a typical vacuum sewer system, along with life expectency of
the components.
The life expectencies shown are based on manufacturer's recommendations.
With proper installation and maintenance these life expectencies can be obtained.
However, more conservative figures may be used for planning purposes.
D-l
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OPERATION & MAINTENANCE INFORMATION
EQUIPMENT REPLACEMENT
VACUUM STATION
VACUUM PUMPS (2)
SEWAGE PUMPS (2)
COLLECTION TANK
CONTROL PANEL
MISC. EQUIP.
COST
RANGE *
10,000 - 30,000
6,000 - 12,000
10,000 - 13,750
13,750 - 25,000
2,000 - 3,000
EXPECTED
LIFE
15 - 20 yrs
15 - 20 yrs
25 - 50 yrs
20 - 25 yrs
15 - 20 yrs
ANNUAL R&R
($/yr/station)
500 - 2,000
300 - 800
200 - 550
550 - 1,250
100 - 200
TYPICAL RANGE
* Function of equipment size
$1 ,650 - $4,800 /yr/station
EQUIPMENT REPLACEMENT
VACUUM VALVE
VACUUM VALVE
CONTROLLER
MISC. PARTS
COST
RANGE
15.00 - 17.50
32.00 - 35.00
10.00 - 12.50
REBUILD
FREQUENCY
10 - 20 yrs
5 ~ 8 yrs
10 - 20 yrs
ANNUAL R&R
($/yr/valve)
0.75 - 1.75
4.00 - 7.00
0.50 - 1.25
TYPICAL RANGE
$5.25 - $10.00 /yr/valve
D-2
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Appendix E
Simplified Sewers:
A Review of Brazilian Experience
E-l
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SIMPLIFIED SEWERS: A REVIEW OF BRAZILIAN EXPERIENCE1
Alex Bakalian, Technology Specialist, The World Bank
Richard Otis, Vice President, Environmental Management, Ayres Associates
Albert Wright, Senior Sanitary Engineer, The World Bank
Jose Azevedo Neto, Consultant
1. Introduction
Inadequate sanitation is one of the major environmental problems facing
urban areas in developing countries today. This inadequacy stems from non-
engineering as well as engineering failures. Non-engineering failures may
include: failure of the market system to coordinate supply and demand for
sanitation services, deficiencies in institutional structures for regulating
supply and demand, and inadequacies in internal institutional capacity for
managing the supply of services. These failures are exacerbated by the
unprecedented rate of population growth, by declining economic performance,
and by poverty. Engineering failures include the frequent use of high cost
conventional sewerage and undue reliance on "supply side" factors in
sanitation planning, without adequate consideration of what users want and are
willing to pay for. One of the main reasons for such engineering failures is
lack of adequate information about alternatives to conventional sewerage. This
paper is about one such alternative.
2. Strategies for Sewerage Cost Reduction
Concern about the high cost of conventional sewerage has prompted
attempts at developing lower-cost alternatives in various parts of the world.
Such attempts usually focus on those elements in sewerage systems that
influence cost the most. Among such key cost-determining factors are: the
average diameter and depth of sewers; the number and depths of manholes; and
such other factors as total sewer length, population density, set-up costs,
and excavation in rock£. Consequently, sewer cost reducing measures have
invariably been directed at modifying one or more of these cost-determining
factors. The wide range of technological options that can be produced through
this process are collectively known as intermediate sewerage or intermediate
sanitation systems.
The processes that have been used to reduce the cost of sewerage fall
under two broad categories; one involves changes in technology and the other
changes in design standards.
Changes that have been made in sewerage technology have usually involved
the introduction of special ancillary appurtenances which make it technically
feasible to use shallow, smaller diameters. An example is the introduction of
a solids interceptor tank between house sewers and laterals. The tank captures
and stores the incoming solids, attenuates the flow, and allows the settled
sewage to flow out by gravity. The absence of solids and the attenuation of
flow makes it possible to use small diameter sewers laid at flat gradients,
resulting in shallow sewers. Developed in Australia, this modification of
conventional sewerage is known as a solids-free or small diameter gravity
sewer system (Otis, 1986). Another example is the STEP (or septic tank
effluent pump) sewerage system which is like the solids-free sewerage system
except that the settled effluent is pumped, again making it possible to use
shallower and smaller diameter sewers. Other examples are grinder pump
sewerage and vacuum sewerage (Kreis.1, 1987).
1 Acknowledgements: The information provided in this paper has been in
part collected during discussions with the engineering staff of the state
water companies of Sao Paulo (SABESP) and Parana (SANEPAR).
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Changes in design standards to produce lower-cost sewerage have been
based on hydraulic theory, advances in technology, satisfactory experience and
acceptable risk. There is a wide range of possibilities; and differences
between alternatives reflect differences in the number or types of design
parameters that have been changed. One example is flat grade sewerage which
was developed some 80 years ago in Nebraska (Gidley, 1987). Based on changes
in design standards affecting only the minimum diameters and minimum slopes or
self-cleansing velocities, its use in the flat terrain and high ground water
table areas in Nebraska results in significant cost savings not only during
construction phases (savings in the cost of: deeper sewers, deeper manholes,
dewatering during sewer laying, and pumping stations), but also savings during
the operational phases (savings in pumping costs). Another example is the
condominial sewer system developed in Brazil; it is the product of changes in
design parameters for minimum depth, minimum diameter, minimum slopes, and
rules for connecting private property to public sewers. A third example is
simplified sewerage, which is the subject of this paper.
3. Origin and Development of Simplified Sewerage
The simplified sewerage system was developed in Brazil. It is the
outcome of changes in several design parameters, including the standards for
minimum diameters, minimum slopes, minimum depths and the spacing and location
of manholes. In addition, it makes use of design periods that are considerably
shorter than those used in conventional sewerage.
The key impetus for its development was the realization that the
application of the conventional design standards was making it difficult to
expand coverage to middle and lower income communities. This led to a review
of all design criteria used in Brazil for conventional sewerage. The review
showed that the prevailing design criteria were very similar to (and in some
cases even more stringent than) those used by Waring in his design of the
first separate sewer system in the USA in 1880 which consisted primarily of
150mm pipes laid at constant slopes (Otis, 1986).
The 1880 sewer system had been designed to carry peak flows at the
minimum velocity of 0.60m/s. Waring argued that if that velocity was reached
at least once a day the system would perform without any problems. But to
ensure complete removal of deposits, flush tanks were installed at the head of
each sewer line. Ventilation was provided through manholes with open grates
spaced at a minimum of 300m (1000 ft) apart. Waring's system had worked very
well, the only problems he reported being obstructions caused by objects such
as ".. a splinter of wood, a carpenter's rule, a bottle, a bone... and they
occurred primarily in areas near schools and shops". It is interesting to note
that most of these criteria and appurtenances had survived intact (or became
more conservative) in Brazil, with very few exceptions such as the flush tanks
and the open grate manholes which have long disappeared. The idea of self
cleaning sewers had become the central design criterion. Unfortunately the
costs of sewer systems based on these century-old criteria had become too high
for many cities, prompting engineers in Brazil to question their applicability
in the context of their cities.
Consequently, a thorough critical review of the basis for conventional
sewerage design standards was mounted. The review led to one of the most
sweeping changes in conventional sewer design standards. The changes were
based on a variety of factors such as findings of recent research in
hydraulics, satisfactory experience, and redundancy. The outcome of these new
standards is a lower-cost sewer system with smaller, flatter, and shallower
sewers with fewer and simpler manholes.
4. Key Characteristics of Simplified Sewerage
The key characteristics of simplified sewerage are as described below.
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Design period. In conventional design, it is common to design trunk sewers and
interceptors for the projected peak flow expected during a 50-year period (or
for the saturation population of the area). The use of such long design
periods make it possible to capture economies of scale in sewerage systems.
However, this has to be balanced against other factors, such as the
opportunity cost of capital, uncertainties in predicting future directions of
growth in developing country cities (a factor which may lead to a possible
mismatch of future supply and demand of sewerage services), and the high cost
of maintaining large sewers with low flows. The use of shorter design periods
avoids such problems, and reduces the lumpiness of investment in sewerage
systems, thereby facilitating financing or enhancing the prospects of
achieving greater coverage with a given amount of investment. With shorter
design periods, coupled with construction by phases, the effects of errors in
forecasting population growth and their water consumption could be minimized
and corrected. For such reasons, the Brazilian Code for simplified sewerage
recommends the use of design periods of 20 years or less.
Wastewater flow. Where water use information is available, the wastewater
contribution per capita is based on a return factor of 0.8. However, where
water usage information is not available, the Code on simplified sewerage
recommends that a minimum flow of 1.5 1/s b<= used. Infiltration is assumed to
be 0.5 to 1.0 1/s per kilometer of pipe. Tne design flow is femwoKr based on
this returned flow factor and a specified peak factor. A peafc /actur of 1.82
has been used in the simplified sewerage projects.
Slope Computation: the tractive force approach. Many authors (Machado, 1985;
Paintal, 1977; Yao, 1974, 1976) have proposed the use of the tractive force
approach for determining the minimum slope of sewers. They advocate the use of
the tractive force corresponding to the "threshold of movement" or that
required to cause the resuspension of deposited particles. While the common
practice uses the minimum velocity of 0.6 m/s as a surrogate for the force
required to dislodge a given particle, it is argued that the tractive force
approach is based on the use of the force itself. For design of sewers, the
Brazilian code suggests the use of 1^ = 0.0055 Qj~°-47 where ! is the minimum
slope of the sewer and Q; is the initial flow. This equation is derived for a
tractive force of 1 Pa (0.1 kg/m2 which is sufficient to transport a 1mm
particle. A fuller discussion of this design approach is given by Bakalian et
al. (1991).
Minimum diameter. A minimum diameter for sanitary sewers is usually specified
in order to avoid clogging of systems by large objects that pass through house
connections. In conventional systems, the house connections are usually 150mm
in diameter; but smaller sizes have also been used. Therefore, for
conventional sewerage, the minimum diameter commonly specified for street
sewers in many countries has been 200mm. In the US some authorities permit
150mm (which was used in late 19th century), but the commonly adopted minimum
size is 200mm. In the simplified system, smaller sizes are recommended because
in the upper reaches of a system where flow is low, the use of smaller
diameter sewers results in greater depths of flow and higher velocities;
experience in Latin America and elsewhere (e.g. Nebraska) shows that 150mm
street sewers do not present any additional maintenance problems, compared to
conventional sewerage. In Brazil, 100mm laterals or branch sewers are being
used in residential areas for a maximum length of 400 meters. These 100mm
pipes are usually located under the unpaved streets of periurban communities.
Connections. In Brazil, as in many developing countries, the connection of
basements to street sewers would necessitate increasing average sewer depths
2 This factor is the product of two ratios: a) the ratio of the maximum
day flow over the average day flow (equal to 1.2) and b) the maximum hour flow
over the average hour flow (equal to 1.5); in other words the maximum sewage
flow will be the hourly maximum, or the peak rate of the maximum day (plus the
maximum infiltration)
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to serve relatively few houses. Consequently, in simplified sewerage, basement
connections are avoided. Apart from the considerable increase in costs, there
is the serious potential of basement flooding as a consequence of clogging
downstream.
Depth of sewers. At the starting point of laterals the minimum depth at which
pipes are laid should suffice to: a) make house connections and b) have a
layer of soil over the crown to protect the pipe against structural damage
from external loads and frost. In conventional design, there is no one method
to determine the minimum depth of sewer as long it satisfies the above
criteria. However some rules of thumb suggest that 1) the top of the sanitary
sewer should not be less than 1m below the basement and 2) in case there is no
basement, the invert of the sanitary sewer should not be less than 1.8m below
the top of the house foundation. In the simplified system, typical minimum
sewer depths are 0.65m below sidewalks, 0.95m to 1.50m below residential
streets, depending on the distance from the street centerline and amount of
traffic, and 2.5m below heavily travelled streets. Building elevations are not
considered in setting the invert elevation of the sewers. If buildings along
the mains are too low to enter the sewer by gravity, it is the responsibility
of the property owner to find other means of making a connection. In some
cases, where topography permits, it may be possible to connect on the other
side of the block if easements can be obtained from the neighboring owners.
Manholes. Manholes constitute an expensive component of a sewer system (about
25 percent of the total construction costs). Although manholes are now among
the most familiar features of a sewer system, they were not used extensively
on early sewers. Their use came with the combined systems where they were
provided to facilitate the removal of grit. It appears that with time the
criteria for manhole use have gradually become more conservative and have been
contributing significantly to the high cost of sewerage.
In the early sewerage systems, some simple appurtenances such as
lampholes were used. Presently some variations of these earlier systems are
being reintroduced in Brazil: the inspection tube and the terminal cleanout.
The first is similar to the old lamphole and the terminal cleanout is an
appurtenance that replaces manholes at the upstream termini. The present
requirement of placing manholes at 100m apart was introduced when sewers were
cleaned using rods and canes. The availability of modern cleaning equipment
calls for a review of manhole location guidelines.
In conventional systems, manholes are generally located at: i) the upper
ends of all laterals ii) changes in direction and in slopes, iii) pipe
junctions, with the exception of building connections, and iv) at intervals
not greater than 100m for pipes of 600mm diameter or less, and at less than
120m for sewers between 700mm and 1200mm of diameter. In the UK the distance
between manholes has been changed from 110m to 180m (Escritt and Haworth,
1984); however as little as 30m distance between manholes has been proposed
for the Cairo sewerage project in the late 70s.
In light of the accumulated experience in Brazil, the simplified system
is designed with the following guidelines:
i) where possible, conventional manholes are replaced with "simplified"
manholes, cleanouts or buried boxes. Manholes are only used at major
junctions; simplified manholes are similar to conventional manholes except
they are reduced in size from 1.5m diameter to 0.6m-0.9m; they can be reduced
in size because the need to enter the manholes by maintenance personnel is
eliminated due to the shallower depths and to the availability of modern
cleaning equipment; for small sewers, and where infiltration is not a major
concern, manholes can be built with precast elements, such as concrete pipes
or concrete rings with precast slabs and bottoms.
ii) manholes at changes of direction or slope are replaced by underground
boxes or chambers;
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iii) house connections are adjusted to serve as inspection devices; in this
respect, a small box is built under the walkway and the connection to the
sewer is made with a curve of 45 degrees and a "Y" (the cleaning rod is
introduced through this box);
These guidelines on the design of manholes reduce considerably the costs
of the system (as much as 25 percent) especially since up to 90 percent of
them are never opened. In 1881, Waring wrote "it seems to me decidedly
advantageous to use inspection pipes, or even lampholes on 6" and 8" sewers,
rather build manholes and inspection chambers".
There are situations, however, where manholes should not eliminated;
examples are where there are: i) very deep sewers (more than 3.0m), ii) slopes
smaller than required, iii) sewers with drops, iv) points of connections from
certain commercial and industrial establishments and v) points of sampling and
flow measurements. The guidelines followed in the manhole replacement are
summarized in Table I.
Table I. Use of manholes and other simplified appurtenances
situation solution
starting point of a sewer inspection & cleaning terminal
long strait sewer intermediate inspection tube
horizontal curve of 90 deg. two separate 45 degree curves
insertion of a sewer into another Y branch and one 45 deg. curve
change of diameter underground concrete box
change of slope underground concrete box
5. Costs
Simplified sewers have been predictably shown to cost significantly less
than conventional systems. In many places, cost savings ranging from 20 to 50
percent have been reported. In the State of Sao Paulo, Brazil, the first
projects have shown a reduction of construction costs of 30 percent but after
about 8 years of experience, the reduction is estimated to be more around 40
percent. The cost reduction in sewage collecting systems in the city of Sao
Paulo is reported to be 35 percent by SABESP, the water and sewerage utility
of the State of Sao Paulo.
SABESP estimates the following average construction costs (1988 prices)
for small towns (not including the per capita costs of treatment and house
connection which are estimated to be about 40 and 50 US$ respectively):
Conventional systems 150-300 US$/capita
Simplified systems 80-150 US$/capita
Table II provides a summary of cost information on some of the systems
reviewed for this paper. The cost per person is shown to range between US$ 51
and 151.
Furthermore, analyses carried out in the course of project preparation
indicate that the savings are dependent on the number of design of criteria
that have been modified. For example, in a sensitivity analysis on costs of
different design considerations carried out in Egypt, costs savings of up to
23% were seen to be achievable (see Table III). In another project, in Bogota,
Colombia, it was estimated that the cost saving would be about 50 percent.
The total amount of savings that these modifications generate will
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Table II. Costs of selec
SAO
Total Cost of coll. $1
system
Average cost per
meter of sewer
Average cost/person
(Note: assume 6 persons
ted projects
PAULO CARDOSA CORAODOS
,897,000 $48,125 $68,194
$76 $13 $8
$151 $51 $87
per household)
TOLEDO
$3,762,066
$21
$59
Table III. Sensitivity analysis on costs of individual design variations
(figures are percentages of the total cost of alternative a)
(source: Gakenheimer and Brando, 1984)
ALTERNATIVE
A
B
C
D
E
Conv. stds.
Houses connected
to sewer lines
(instead of manholes)
Manhole spacing 50%
larger than conv.
Lighter manhole covers
(80 and 175 kg instead
of 285)
No manhole at upstream
end of branch
B+C
C+D
B+C+D
B+C+D+E
BENI SUEF
NO CONN. WITH CONN.
(1) (2)
100 100
100 92.41
95.38 97.75
95.37 96.08
91.66 NA
93.47 86.89
90.79 93.88
89.12 83.21
82.09 77.27
NOTES:
(1) costs of house connections are not included in
(2) costs of house connections are included in the
KAFR EL SHOKR
NO CONN. WITH CON
100 100
99.56 90.27
96.23 98.02
95.25 96.1
94.45 NA
90.69 82.99
93.88 94.56
83.21 80.13
82.52 76.29
the cost calculation
cost calculations
therefore be a function of the number of modifications that are deemed
E-8
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feasible in a particular project given factors such as population density,
topography, geology, soil/water conditions, etc.
6. Operational experience
Although simplified sewerage systems were first implemented in Brazil
(Sao Paulo 3 and Parana), they have subsequently been applied in Bolivia
(Cochabamba and Oruro), in Colombia (Bogota and Cartegena) and in Cuba
(Matanzas). Although specific data on operational problems are not readily
available, it is nevertheless known that no significant problems have been
reported. In the city of Sao Paulo, it has been estimated that there are about
75 obstructions per 1000km of sewers each month. This infrequent occurrence of
obstruction gives further support to the policy of minimizing the number of
manholes. Engineers in SABESP reckon that it would be economical to install
only a few manholes initially, with the intention of building additional ones
as the need arises (i.e. at points of frequent obstructions).
Similarly no problems related to excess hydrogen sulfide generation
have been reported from field surveys.
7. Discussion
As stated above, the present conventional engineering practice in sewer
design was introduced more than a century ago and has since undergone
relatively few significant changes. Engineers in Brazil who more than a decade
ago took a serious look at the rationale for the various design criteria have
found ample room for change and simplification without jeopardizing the
operational integrity and safety of the system.
It is common knowledge that engineering design is not conceived
exclusively on the basis of rigid and exact scientific facts; it is also
heavily based on empirical data supplemented with probabilistic and risk
criteria. The factors of safety which have been embedded in many design
criteria (design flow, minimum diameter, depth of sewers, etc.) need not be
the same at all times everywhere in all situations. For example, there is no
valid basis to apply the same conservative standards in business districts
(where breakdowns and repairs could create heavy economic losses and great
inconveniences) as in the outskirts (where the impact of similar breakdowns is
less severe). In addition to economic aspects, the probability of breakdowns
should be a prime consideration in design of a sewerage system. While
Gakenheimer and Brando (1983) suggest additional research on uncertainty as it
relates to infrastructure standards, they argue that there is enough evidence
to move away from the stringent standards that have been adopted from
industrialized countries; they contend that "when resource limited countries
are using conservative standards, risk is lowered in one locality at the cost
of fully exposing another".
8. Conclusions
The objective of this paper has been to present information on
simplified sewerage which provides a new cost-saving approach to the design of
sewer systems based on Brazilian experience. It is based mainly on rational
changes in long-standing traditional sewer design standards. With this
approach, depending on the prevailing "engineering culture" and codes, the
project engineer still retains the option to apply all or some of the
suggested modifications. The review shows that:
3 As of 1988, in the State of Sao Paulo alone, this technology has been
adopted in 26 cities and towns, and plans were made for at least 36 others.
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i) the simplified sewerage technology is being successfully applied, and
it constitutes a viable lower-cost alternative to the conventional system;
ii) the design modifications that have been introduced in the simplified
sewerage systems are based on sound engineering principles;
iii) the new design approach does not create a substandard level of
service; it rationalizes some design standards without sacrificing level of
service;
iv) the simplified sewerage system costs a fraction of the conventional
system thus freeing up funds that could be used to extend the service coverage
to larger segments of unserved populations.
Unfortunately information on the system has not been spread much beyond
that country's immediate vicinity. It is hoped that in time, engineers in
other parts of the world will become more familiar with it as increasing
operational experience is accumulated and disseminated 4. Already a growing
number of cities are finding the simplified system attractive and are
implementing projects using the modified criteria with considerable savings.
4 Relatively, very little information on these systems has been made
available outside their immediate area of application; the reader is referred
to a publication by UNCHS/HABITAT on the design aspects of "shallow sewers".
E-10
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References
1. American Society of Civil Engineers and Water Pollution Control
Federation (1982), "Gravity Sanitary Sewer Design and Construction"
2. Associacao Braziliera de Normas Technicas (1988), "Projeto de Redes
Coletoras de Esgoto Sanitario", NBR 9648
3. Australian Water Resources Council (1988), "Low Cost Sewerage Options
Study", Water management Series No. 14
4. Bakalian, A., A. Wright, R. Otis (1991), "Sewer Design: the Tractive
Force Approach", (forthcoming)
5. DHV Consultants, "Minimum Shear Stress Approach for Self-cleaning
Capacity of Sewers", Amersfoort, Netherlands, (date unknown)
6. Escritt, L.B. and W.D. Haworth (1984), "Sewerage and Sewage Treatment",
International Practice, J. Wiley and Sons Ltd.
7. Gakenheimer, R. and C.H.J. Brando (1984), "Infrastructure Standards", in
Shelter and Development, edited by Lloyd Rodwin, Allen and Unwin, Boston
8. Gidley, J.S., (1987) "Case Study Number 11: Ericson, Nebraska Flat Grade
Sewers", Small Flow Clearinghouse, West Virginia University, Morgantown,
West Virginia
9. Kreissl, J. (1987), "United States Experience with Alternative Sewers",
United States Environmental Protection Agency
10. Machado, J.G.O. Neto and Tsutiya, M.T. (1985) "Tensao Trativa: urn
Criterio Economico para o Dimensionamento das Tubulacoes de Esgoto",
Revista Dae, (March)
11. Otis, R. (1986), Small Diameter Gravity Sewers: an alternative
wastewater collection method for unsewered communities,
USEPA/600/S2/86/022
12. Paintal, A.S. (1977), "Design Sewers to be Self Cleaning", Water and
Wastes Engineering, (January)
13. United Nations Center for Human Settlements/Habitat (1986), "The Design
of Shallow Sewer Systems", Nairobi, Kenya
14. United Nations Development Programme/World Bank, (1985) "Manual de
Saneamiento: Redes de Alcantarillado Simplificadas", unpublished
document
15. Water Pollution Control Federation (1985), "Operation and Maintenance of
Wastewater Collection Systems", Manual of Practice, No. 7
16. Yao, K.M. (1974) "Sewer Line Design Based on Critical Shear Stress",
Journal of the Environmental Engineering Division, American Society of
Civil Engineers (April)
17. Yao, K.M. (1976) "Functional Design of Sanitary Sewers", J. Water
Pollution Control Federation (July)
E-l 1 i'U.S. GOVERNMENT PRINTING OFFICE' 1993 - 750-068/60007
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