United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-78-166
September 1978
Research and Development
x>EPA
Pressure and Vacuum
Sewer Demonstration
Project - Bend, Oregon
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-166
September 1978
PRESSURE AND VACUUM SEWER
DEMONSTRATION PROJECT
BEND, OREGON
by
Jessie E. Eblen
Lloyd K. Clark
C & G Engineering, Inc.
Salem, Oregon 97302
Grant No. S803295
Project Officer
James F. Kreissl
Wastewater Research Division
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Re-
search Laboratory, U, S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U. S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute en-
dorsement or recommendation for use.
11
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FOREWORD
The U. S. Environmental Protection Agency was created because of
increasing public and government concern about the dangers of pollution to
the health and welfare of the American people. Noxious air, foul water,
and spoiled land are tragic testimony to the deterioration of our natural
environment. The complexity of that environment and the interplay be-
tween its components require a concentrated and integrated attack on the
problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Labora-
tory develops new and improved technology and systems for the preven-
tion, treatment, and management of waste water and solid and hazardous
waste pollutant discharges from municipal and community sources, for
the preservation and treatment of public drinking water supplies and to
minimize the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that research; a most
vital communications link between the researcher and the user community.
iii
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ABSTRACT
A pressure sewer system collecting domestic septic tank effluent
and a vacuum system collecting raw domestic sewage were constructed
in the City of Bend, Oregon. Each of the systems collected sewage from
eleven houses and discharged into existing gravity sewer mains. Groups
of one, two and three houses were served by single collection sump/
vacuum valve or collection sump/pump combinations. The systems were
operated and monitored for a period of approximately one year. The
systems were evaluated for construction costs, operation and mainten-
ance costs, reliability, operating characteristics, and chemical charac-
teristics of collected sewage and septic effluent.
This report was submitted in fulfillment of Grant No. S803295 by
the City of Bend, Oregon under the sponsorship of the U. S. Environ-
mental Protection Agency. This report covers the period from July,
1974 to July, 1977.
IV
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CONTENTS
Disclaimer ii
Foreword iii
Abstract iv
Figures vii
Tables viii
Abbreviations and Symbols ix
Acknowledgments x
Section 1. INTRODUCTION 1
Background 1
Goals and Guidelines 3
Section 2. SUMMARY AND CONCLUSIONS 4
Summary 4
Conclusions 8
Section 3. PROJECT DESCRIPTION 9
General 9
Site Selection 9
Pressure System 11
Vacuum System 1 8
Section 4. DATA AND ANALYSIS 30
General 30
Equipment and Construction Costs 35
Operation and Maintenance 41
Operating Frequencies and Waste water Volumes 46
Energy Consumption 80
Effluent and Sewage Chemical Characteristics 86
Comparison of Pressure and Vacuum System Costs 94
Section 5. DESIGN CONSIDERATIONS 101
General 101
Low Pressure Sewer Technology 101
Vacuum Sewer Technology 102
Institutional Considerations 102
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CONTENTS (Cont.)
Feasibility of Multi-Home Service by a Single Pump
Station or Vacuum Valve 103
Alarm Systems 105
Pressure System Sump Configuration 106
Sump Covers 107
Comparison of Pressure Vacuum and Gravity Sewers 109
Bibliography 112
VI
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FIGURES
Numbe r Page
1 Project Vicinity Map, Bend, Oregon ] 0
2 Pressure Collection System Site Map 12
3 Low Pressure Pump Installation ] 3
4 Typical Pressure System Pipe and Fittings 16
5 Low Pressure System Discharge Manhole and
Monitoring Station 17
6 Vacuum Collection System Site Map 19
7 Vacuum, Collection Sump, Valve Pit, and
Valve Installation 21
8 Typical Vacuum Pipe Configuration Details for
Uphill and Downhill Waste water Transport 24
9 Typical Vacuum Collection Line Pocket
Assembly Detail 24
10 Rolled Y Fitting for Tributary Vacuum Line 25
11 Vacuum Station 26
12 Sliding Vane Pump 27
13 Ditch Witch*"1 R-100 used on Bend R &-D Project 40
vu
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TABLES
Numbe r Page
1 Schedule of Monitoring and Sampling 31
2 Vacuum Equipment Bid Summary 36
3 Pressure System Construction Cost Summary 37
4 Vacuum System Construction Cost Summary 38
5 Pressure System Operating Parameters 47
6 Pressure System Pump Operation Frequency 48
7 Pressure System Waste water Volumes 58
8 Pressure System Participating Resident Water Use 60
9 Vacuum System Operating Parameters 62
10 Vacuum System Valve and Pump Operation Frequency 64
11 Vacuum System Wastewater Volumes 77
12 Vacuum System Participating Resident Water Use 8]
13 Pressure System Energy Consumption 83
14 Vacuum System Energy Consumption 85
15 Pressure System Septic Effluent Characteristics 87
16 Vacuum System Sewage Chemical Characteristics 89
17 Comparison of Chemical Characteristics Data for
Septic Tank Effluent and Raw Sewage 91
18 Comparison of Pressure and Vacuum System Costs 95
19 Comparison of Pressure, Vacuum, and Gravity Sewer
Systems 110
Vlll
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LIST OF ABBREVIATIONS
C -- degrees Celcius
F -- degrees Farenheit
R & D -- research and development
DEQ -- Oregon Department of Environmental Quality
No. -- number
SDR -- standard pipe dimension ratio
PVC -- poly vinyl chloride
m -- meter
cm -- centimeter
gpm -- gallons per minute
TDH -- total dynamic head
hp -- horsepower
kw -- kilowatt
kwh -- kilowatts per hour
Hg -- mercury
STEP -- septic tank effluent pumping
DWV -- drain-waste-vent
MTBSC -- mean time between service calls
IX
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ACKNOWLEDGMENTS
The cooperation and assistance of the numerous people who con-
tributed to this project is gratefully acknowledged. The field survey for
design of the project facilities was done by members of the Bend Engin-
eering Department under the direction of Mr. Jack Donahue, Bend City
Engineer. Operation and maintenance of the system, collection of data
and laboratory analysis were done by members of the waste water treat-
ment plant staff under the direction of Mr. Mike Elmore, Superintendent.
The cooperation of the homeowners who volunteered their homes
for this project and endured the disturbances of the construction with
good cheer is gratefully acknowledged.
Finally, the preliminary work done by Mr. Lloyd Clark and
Mr. Wayne Taylor is acknowledged. Their interest in finding better
methods for construction of sewers in the rocky terrain of the Central
Oregon plateau provided the initial impetus for obtaining the funding
which made this demonstration project possible.
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SECTION 1
INTRODUCTION
BACKGROUND
Bend, Oregon, is a city of approximately 17, 000 population (1975
census) located in Central Oregon, east of the Cascade Mountains. The
city sits at an elevation of approximately 1, 096 meters (3, 600 feet) on a
plateau formed by volcanic eruptions and lava flows. Projecting basalt
rock formations and cinder cones are prominent features of the landscape.
Soils are generally shallow, over underlying basalt formations.
The Bend climate is arid-temperate. Precipitation averages 0.3
meters (12 inches) annually, occurring mostly during winter months.
Summers are dry and moderately hot. Winters are moderately cold.
Mean temperature in January, the coldest month, is -1.1 C(30 F); the
temperature does not rise above 0 C (32 F) an average of 12 days each
winter.
The central business area of Bend has been sewered since 1915, but
the system has not been extended into most of the residential area. Waste-
water is carried to a treatment plant at the edge of town by a gravity in-
terceptor. Several small housing areas adjacent to the interceptor dis-
charge into the interceptor. A motel complex on the north edge of the
city pumps sewage to the interceptor. Effluent from the treatment plant
is discharged into a lava sink hole near the treatment plant.
Wastewater from approximately 90 percent of Bend's population is
treated by septic tanks and subsurface disposal systems. A common
practice for septic tank effluent disposal is to drill a disposal well 0. 15
or 0.20 meters (6 or 8 inches) in diameter and up to 18 meters (60 feet)
deep. The vesicular basalt and volcanic ash geological structures are
generally capable of absorbing a great amount of water, although some
older residences have found it necessary to drill more than one disposal
well after the absorption capacity of the earlier wells deteriorated. Con-
ventional septic tank-soil absorption systems are also used in areas where
this approach is feasible.
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During the mid-1960's regulatory agencies became concerned about
the probability of contaminating groundwater by subsurface discharge of
inadequately treated wastewater. In 1969 regulations were adopted by the
Oregon Department of Environmental Quality (DEQ) which prohibit dis-
charge of untreated wastewater into waste disposal wells. The prohibition
is to become effective in 1980. The City of Bend has been directed by DEQ
to construct a sewage collection system before 1980.
Construction of a conventional gravity sewer system in Bend presents
a formidable task of rock excavation. Normal trench excavation practice
in Bend has been to remove soil overburden, then drill, return the over-
burden, blast, and re-excavate.
In addition to high costs for rock excavation, considerable liability
for damage is incurred when using explosive for excavation in developed
areas of Bend. The random nature of the conglomerate of volcanic lava,
ash and boulders makes it difficult to prejudge the effect of an explosive
charge. The probability of damage to buildings or other structures is cor-
respondingly high.
Faced with the high cost for installing conventional gravity sewers,
it was decided that funds should be sought for a research program to in-
vestigate innovative methods of sewage collection and rock excavation.
A preliminary survey indicated that the problem of installing sewer
in rock terrain is widespread. In response to the survey, 150 cities in
16 states stated that they faced similar problems.
In the late 1960's, the pressure and vacuum sewer technology was
being developed. Several systems had been installed and had been des-
cribed in technical journals. Both pressure and vacuum systems were
known to have the advantage of not requiring deep excavation to maintain
line and grade as do conventional gravity sewers.
Outcome of the search for funding was a research and development
(R & D) program to construct, operate, monitor, and evaluate small pres-
sure and vacuum sewage collection systems in the City of Bend. The pro-
gram was funded 75 percent by the U. S. Environmental Protection Agency
(EPA) Municipal Environmental Research Laboratory, 17-1/2 percent by
the Oregon Department of Environmental Quality, and 7-1/2 percent by
the City of Bend. The City of Bend supplied its portion of the cost by pro-
viding in-kind service for operating and monitoring the system.
Funding was not found for conducting research in rock excavation.
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GOALS AND GUIDELINES
Goals and guidelines for the experimental pressure and vacuum
sewer systems project are summarized as follows:
1. The pressure and vacuum sewer systems were to be of com-
parable size and configuration, for comparison to each other.
2. Funding limited the project's size to approximately 12 houses
in each system.
3. Only single family residential dwellings were to be included
in the system.
4. Homeowners were to be asked to volunteer to participate in
the project. As an incentive to volunteer, the participants
were not to be charged sewer installation costs if the experi-
mental systems were permanently incorporated into the city
sewer system.
5. Groups of one, two and three houses in each system were to
be served by a single effluent pump station or by a single-
vacuum valve.
6. The pressure system was to be of the septic tank effluent
pumping (STEP) type.
7. The vacuum system was to be a one-pipe design, collecting
raw domestic sewage generated by normal household fixtures.
8. Cost of equipment, construction, operation, and maintenance
would be recorded and compared to each other and to conven-
tional gravity sewers.
9. The system would include monitoring instrumentation to re-
cord operating characteristics of the system.
10. Samples of a sewage and septic effluent would be collected
and chemically analyzed, the principal intent being to project
the effect of mixing septic effluent with normal raw sewage.
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SECTION 2
SUMMARY AND CONCLUSIONS
SUMMARY
The purpose of this project was to construct, operate, and evaluate
pressure and vacuum sewers as alternative methods of sewage collection
which would not require deep trench cuts to maintain line and grade as do
conventional gravity sewers. Small pressure and vacuum collection sys-
tems were constructed, operated and monitored in Bend, Oregon.
Project Description
Separate sites were selected to construct the pressure and vacuum
collection systems. The pressure system consisted of six pump stations
which collected septic tank effluent from 11 homes and pumped it into a
gravity interceptor. The pressure system main line consisted of 305
meters (1,000 feet) of 5. 1-cm (2-inch) diameter, class 160, PVC pipe with
a maximum increase in elevation of 7. 6 meters (25 feet).
The vacuum system collected raw sewage to a central vacuum station
from 11 homes utilizing 8 collection sump-vacuum valve installations.
The vacuum system collection line consisted of 563 meters (1, 847 feet) of
7. 2-cm (3-inch) diameter, schedule 40, PVC pipe with a maximum lift of
4 meters (13 feet) and net-elevation change of 2. 4 meters (8 feet).
Instrumentation was included in the project design to collect data
to indicate a) frequency of operation of pressure-system pumps, vacuum
valves, vacuum pumps and vacuum-system discharge pumps; b) energy
used by the two systems; and c) water used by residents of the two sys-
tems. Wastewater volumes could be calculated from pump and valve op-
erating frequencies and sump configuration data. Equipment for collect-
ing composite samples of effluent from the two systems for chemical an-
alysis was included in the project design.
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Construction Costs--
Zquipment and construction cost data were collected during the project
bidding and construction phases. Total equipment and construction costs
reported by the general contractor (but not including profit and overhead
for the general contractor) totaled $138, 084. 00.
j___
A Ditch Witch R-100 rock trenching machine was used to cut pipe-
line trenches when rock was encountered and when the site allowed access
by the machine. The trenching machine cut 20-cm (8-inch) wide trenches
up to 1.2 m (4 feet) deep. Trenches averaged approximately 1.0m
(3.2 feet) deep, with approximately 50 percent rock, and cost an average
of $16. 84 per meter ($5. 13 per foot) to excavate. This cost can be com-
pared to the reported range of excavation costs in Bend for similar
trenches of $6. 50 to $65. 00 per meter ($2. 00 to $20. 00 per foot).
Operation and Maintenance
The pressure and vacuum systems were operated and monitored from
the spring of 1976 to midsummer of 1977. A daily log of operation and
maintenance tasks was maintained during this period.
Pressure System--
The only failures in the pressure system reported during this period
resulted from a defective check valve. After being repaired the same
check valve became clogged with debris which appeared to have fallen into
the sump during repair of the initial failure.
One complaint of malodor from a pump sump was received. After re-
pairing the sump-cover gasket and tightening the cover bolts, no further
complaints were received.
Corrosion in the septic atmosphere of the pump sump was subjectively
judged to be severe, although no failure from corrosion has yet occurred.
Grease buildup was not severe enough to be objectionable at the end of
one year of operation.
Vacuum System--
Problems with operation of the sliding-varie vacuum pumps used on
the Bend project occurred repeatedly. An excessive amount of water
condensed in the lubrication system of the pumps, possibly because of the
small size of the Bend vacuum system. Manometer-type condensate
drains installed on the vacuum pumps to reduce maintenance required to
manually drain the condensate each day allowed the pumps to lose their
oil. Bearing surfaces on one pump have been rebuilt.
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Failures of vacuum valves have resulted from malfunctions in the
valve controller, but not from malfunction of the valve itself. One valve
failed in an open position due to a small particle of debris in the pneuma-
tic circuits of the valve controller. Another valve failed because of freez-
ing of moisture in a check valve in the control circuit.
Neither corrosion nor grease buildup appeared to be excessive during
the first year of operation.
Waste water Volume s--
The volumes of wastewater collected from both the pressure and vac-
uum systems were surprisingly low, generally being in the ranges of 151
to 227 liters (40 to 60 gallons) per capita day in the pressure system and
30 to 50 gallons per capita day in the vacuum system. No significantly
different patterns of wastewater generation were observed to occur at dif-
ferent seasons of the year.
Water Use--
Bend has an abundant supply of high quality surface water. Water bills
are a flat monthly rate. Water was therefore used generously for lawn
watering during the summer; up to many thousands of liters per day for
some residences. During the winter, water use generally dropped off to
less than 1, 000 liters (260 gallons) per day per residence.
Energy Consumption--
Average energy consumption by the pressure system was approximately
0. 74 kwh per day per residence. However, approximately 0. 48 kwh per
day was used by a strip heater in each of the control boxes, which
would not be needed if the control box were located inside the house. The
0.26 kwh per day per residence used to operate the sump pumps represents
less than $. 01 per day at current electrical prices in Bend. The vacuum
system used an average of approximately 1. 36 kwh per day per residence,
representing cost of approximately $.04 per day per residence at current
electrical prices in Bend. Electrical energy was a relatively small cost
item for both the pressure and vacuum systems.
No significant change in the energy consumption of the pressure sys-
tem was observed over the course of the monitoring period. Energy con-
sumption by the vacuum pumps increased by a factor of approximately
1.4 during the year of monitoring. There also appeared to be a small
increase in energy consumption by the vacuum pumps during warmer
weather.
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Chemical Character!sties--
The averages of measured chemical characteristics of the septic tank
effluent and raw sewage sampled from the Bend pressure and vacuum col-
lection systems during the year of monitoring were as follows:
Temperature OC
OF
PH
Dissolved Oxygen mg/1
Alkalinity mg/1 as CaCO
Grease mg/1
Total Ortho Phosphate mg/lP
Total Kjeldahl Nitrogen mg/lN
Total Sulfide mg/lS
Suspended Solids mg/1
BOD mg/1
COD mg/1
Pressure
System
Septic Tank
Effluent
13.2
54.4
6.7
0.5
204.0
65.0
10.4
40.9
1.8
36.4
157.0
276.0
Vacuum
System
Raw Sewage
14.0
57.0
8.0
0.7
127.7
110.7
3.2
28.4
not measured
164. 1
187.7
363. 3
Cost Comparison--
A comparison of the costs of hypothetical pressure and vacuum sys-
tems was made, using the cost data from the Bend project. Adjustments
were made for the project monitoring equipment, for the differences in
the two sites, and for the potential number of residences the systems
could serve. Total annual capital recovery, operation, and maintenance
costs per residence estimated for the two hypothetical systems were close,
$399.00 per year per residence for the pressure system and $421.00 per
year per residence for the vacuum system.
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CONCLUSIONS
Both the pressure and vacuum system constructed and operated in
Bend collected and transported sewage successfully.
The STEP pressure system performed satisfactorily during the first
year of operation. The septic environment in the STEP pressure sump
was severely corrosive to ferrous metals. Care should be taken to de-
sign and construct STEP stations' components of corrosion-resistant ma-
terials.
The vacuum system experienced failures from malfunction of the
vacuum valve controllers. However, it was felt that the first year
of operation did not give sufficient operating data to judge long term re-
liability. The sliding vane vacuum pumps did not give satisfactory serv-
ice as used on the Bend project.
The multiple home connections to single pump stations or vacuum
valves operated without any problems and appear to be technically feasible.
However, a separate electrical distribution system to serve only the pres-
sure system pumps as installed in the Bend project is considered imprac-
tical for a non-re search project. The sump pump would be connected to
the electrical circuits of one of the homes and a formula would need
to be agreed upon by the homeowners connected to the sump as to how to
share payment for electrical energy to operate the pump.
The comparison of costs for the pressure and vacuum systems in-
stalled at Bend indicated that pressure and vacuum systems may have com-
parable total system costs. However, pressure and vacuum sewer systems
do not lend themselves to generalized statements of comparison. Each
system uses different components than the others. Application to any
specific site will require'a different design approach and a different mix
of components for each system.
Pressure and vacuum systems have unique capabilities and limita-
tions. Neither pressure nor vacuum sewers should be either totally re-
jected as not workable nor accepted as the total answer to all sewage col-
lection problems. Rather, pressure and vacuum sewers should be con-
sidered as alternative sewage collection methods to be evaluated for each
specific application.
The design engineer considering pressure or vacuum sewers for the
first time should be aware that they require a greater, or at least newer
and less well known, level of design sophistication than design of conven-
tional gravity sewers and should proceed with appropriate caution.
8
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SECTION 3
PROJECT DESCRIPTION
GENERAL
Equipment configurations used in the pressure and vacuum sewage
collection systems installed in Bend, Oregon are described in this sec-
tion. Discussion of considerations used in designing the Bend systems
are deferred to Section 5» where a discussion of general pressure and
vacuum technology is presented, along with some of knowledge and ex-
perience gained from designing, constructing and operating the Bend
system.
SITE SELECTION
Sites for the pressure and vacuum sewer systems were selected to
meet the following criteria:
1. The sites not serviceable by conventional gravity sewers.
2. Availability of an existing sewer to receive collected sewage.
3. Suitability of the sites to meet and test operating parameters
of pressure and vacuum system technology.
4. Willingness of area residents to participate in the program.
5. Suitability of the sites to meet goals and guidelines listed in
Section 1.
6. Suitability of sites to minimize cost of'construction.
7. Suitability of sites to minimize traffic disruption during con-
struction. The location of sites selected for construction of
the pressure and vacuum systems are shown in Figure 1.
9
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l PRESSURE SYSTEM ' "Jf
A r% r- A <»» i *^ i— -^t* s'.ii4i
VACUUM SYSTEM
AREA SITE
WASTEWATER
TREATMENT
-1 \\
L-»*w»-l—\V—rr-r-T—
!•.—i i"!: ;: -a r i—1 \ Mli II—I- :
«« i
\ * ff C~i lC
"""
nnan
J—:—' """"*•'"'••"" v^
e mikfrui i O, \
I ••• o —.. '"' '"-\
3nr
Figure 1. Project vicinity map, Bend, Oregon.
Existing sewer
Project sewe r
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PRESSURE SYSTEM
Site and Layout
The site selected for the pressure system (See Figure 2) was a rela-
tively new housing development. Houses were generally less than five
years old. The neighborhood could be characterized as typical upper mid-
dle class. The pressure system site was located on the toe of an old lava
flow which sloped downward to the northeast. A gravity interceptor passed
the area on the southwest corner. Sewer service was therefore available
to the area if means were provided to lift sewage into the interceptor.
Eleven homeowners volunteered to participate in the program. The
houses were divided into groups of two singles, three doubles, and one
triple. Each group is served by a single pump station, making a total of
six pump stations. The number of people usually resident in each house
is indicated on Figure 2. The total pressure system population was
approximately 34 people during the study period.
Pipe length from the farthest sump (No. 6) to point to discharge into
a manhole on the interceptor was approximately 305 meters (1, 000 feet),
and incorporated a lift of 7. 6 meters (25 feet).
House Sewer Interceptor Fitting
A "Y" fitting was installed in each house sewer between the septic
tank and subsurface disposal field. Septic tank effluent flow was thereby
diverted through one leg of the "Y" into the pump sump. The system was
designed to be failsafe, i.e., in the event of pump failure, effluent would
back up and overflow into the original subsurface disposal field, instead
of backing up into the homeowner's plumbing (See Figure 3).
Septic tank effluent was carried to pump sumps through four-inch
diameter Class 125, SDR 32.5, PVC pipe with elastomeric ring joints.
Septic Tanks
The existing septic tanks were cleaned and inspected for cracks,
evidence of leaks or other conditions which might affect test results be-
fore start-up of the pressure system.
Pump Sumps
Pump sumps (See Figure 3) were of fiberglass construction, 0.48
cm (3/16 inch) nominal thickness, nominally 0. 76 meter (30 inches) in
11
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SCALE: i"= mo'
RAVENWOOD COURT
T R E El/S
—LEGEND—
O COLLECTION-PUMP SUMP
D SEPTIC TANK
PRESSURE LINE
--- GRAVITY LINE
• MANHOLE
— —GRAVITY INTERCEPTOR
® VALVE
EXISTING INTERCEPTOR
TO TREATMENT PLANT
•r-i/ II . h
PRESSURE SYSTEM
MONITORING STATION
Figure 2. Pressure collection system site map.
12
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POWER AND EVENT
MONITORING CABLE
WORKING VOLUME
3?30 GALLONS
t
OVERFLOW
EFFLUENT FROM TO SOIL
SEPTIC TANK ABSORPTION SYSTEM
PUMP ON
PUMP OFF
CONCRETE COLLAR
Figure 3. Low pressure pump installation.
13
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diameter with a slight mold taper, and 1.4 meter (5 feet) deep. Upper
rims of the sumps were reinforced by fiberglass flanges approximately 6. 3
cm (2-1/2inches) wide by 1.9cm (3/4inch) thick. Nuts for cover screws
were imbedded in the flange.
Sump covers were 0. 63-cm (1 /4-inch) thick steel plate, painted and
coated with bituminous epoxy paint on the inside. Covers are bolted to the
sump flange. A smaller diameter steel plate bolted over a hole in each
sump cover gave access to the pump.
Inlet pipes intersected the sumps at a minimum of 0. 61 meter (2 feet)
above the bottom. Pump discharge lines intersected the sump 0.91 meter
(3 feet) below the surface. These intersecting pipes were sealed to the
sump by flexible rubber grommets.
Effluent lines had a mating flange for a pump slide-away coupling, a
PVC ball check valve on the vertical pipe run and a gate valve on the hori-
zontal pipe run. Sumps contained guide rails and lift chains for convenient
pump removal and replacement.
A sealed electrical junction box in each sump contained terminals for
the pump power, pump control, and alarm wiring.
Pumps
Each pump station for the pressure system contained a single sub-
mersible sump pump. Spare pumps were available for installation in the
event of pump failure.
Pumps were sized to deliver a minimum velocity of 0. 61 meter
(2 feet) per second through the 5. 08-cm (2-inch) diameter pressure main.
Two pump sizes were specified to meet this requirement, i. e. , 1. 57 liters
per second (25 gpm) at 6. 7 meters (22 feet) TDH and 1. 57 liters per sec-
ond (25 gpm) at 11. 34 meters (37 feet) TDH.
Pumps supplied which meet this specification were:
Pea body Barnes Model E52 (Sumps Nos. 1,2, 3, and 4).
Peabody Barnes Model SE52 (Sumps Nos. 5 and 6).
Pump motors were 0. 373 kw (1/2 hp), single phase, 230 volt, oil
filled, hermetically sealed, and submersible. The lower head pumps op-
erated at 1750 rpm and had 3.175-cm (1-1 /4-inch) diameter discharge
pipe. The higher head pumps operated at 3450 rpm and had 5. 08-cm
14
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(2-inch) diameter discharge pipe. The pumps were fitted with guides and a
slide-away discharge coupling to mate with the discharge pipe for conven-
ient pump removal and replacement.
Each pump assembly weighed approximately 80 pounds and could be
manually lifted from the sump by an attached chain. To remove the pump
from the site would have required opening the sealed electrical terminal
box to disconnect the pump power cables.
Pump Controls and High Water Alarms
Pump operation was controlled by two mercury float switches sus-
pended in the sump at selected "pump-on" and "pump-off" levels. A third
mercury float switch signaled high water condition by actuating an alarm,
in the event of pump failure. A high water alarm signal was transmitted
to the pressure system monitoring station, where it would actuate a light,
indicating the sump with high water condition. The high water alarm sig-
nal was also transmitted to the treatment plant and/or police station where
it would actuate a light, indicating a failure in the pressure system.
Pump starter switches and other electrical gear were housed in
weatherproof control boxes mounted on posts near the pump stations (See
Figure 3).
2
Pressure system pipe was 5. 08-cm (2-inch) diameter, 110-n/cm
(160-psi), SDR26, ring-joint, PVC pipe. PVC "T" fittings are used for in-
tersections of pump lines to the pressure main (See Figure 4). The pres-
sure pipe was buried at 0. 91 meter (3 feet) minimum depth, bedded and
covered by a minimum of 10. 2 cm (4 inches) of sand. Segregated native
backfill was used for backfill above the pipe zone.
A valve was installed in the main line between pump stations Nos. 3
and 4, as shown in Figure 2, the site map. The pressure pipe profile
maintained a continuous upward slope from the pump stations to the point
of discharge. Air release valves were therefore not needed.
15
-------
O-RING JOINTS
1-V or 2" SDR 26 CLASS 160 PVC PIPE
GATE VALVE
FIGURE 4 TYPICAL PRESSURE SYSTEM PIPE AND FITTINGS
Effluent Discharge Manhole
The pressure system discharged into a manhole on the existing gra-
vity interceptor line. The system discharge pipe was installed above the
high water level in the manhole and was angled so as to discharge in the
same direction as the gravity sewer flow to minimize gas release from the
septic effluent (See Figure 5).
A "T" fitting for an effluent sampling tube was incorporated into the
discharge pipe in the manhole.
Pressure System Monitoring and Sampling Equipment
Monitoring Station--
A metal enclosure was installed near the discharge manhole to
house system monitoring and sampling equipment as shown in Figure 5.
Event monitoring equipment--Signal wires from each pump control
to the pressure monitoring station, appropriate circuitry and a strip chart
recorder installed in the monitoring station permitted recording the time
each pump operated.
16
-------
MONITORING
STATION
PERISTALTIC
PUMP
SIGNAL FROM
SUMP PUMPS
STRIP-CHART
RECORDER
SAMPLE
CONTAINER
AND ICE
CHEST
DISCHARGE
MANHOLE
PRESSURE SYSTEM
DISCHARGE LINE
DIRECTION OF FLOW
GRAVITY INTERCEPTION
FIGURE 5 LOW PRESSURE SYSTEM DISCHARGE MANHOLE
AND MONITORING STATION
17
-------
Effluent sampling equipment--An effluent sampling system was in-
stalled in the discharge manhole and in the pressure system monitoring
station as shown in Figure 5.
A sampling well consisting of a 7. 62-cm (3-inch) diameter "T" fitting
was installed in the discharge line in the discharge manhole. A 0. 95-cm
(3/8-inch) diameter tube ran from the sampling well to a peristaltic sam-
pling pump in the monitoring station. The peristaltic pump, coupled with
an electrically actuated valve to prevent loss of sampling pump prime drew
effluent samples from the sampling well. Composited effluent samples
were collected in a plastic carboy sitting in an ice chest.
In order to collect a representative composited effluent sample, the
sampling pump was interconnected so that it operated during the operation
of any of the system pumps. Pumping rate of the sampling pump was ad-
justable so that any appropriately sized sample could be collected.
Energy Consumption--
Two standard kilowatt-hour meters obtained from the electric com-
pany were installed to totalize electrical energy consumption by the pres-
sure system. The kilowatt hour meters were installed in the project area
so as to minimize electrical distribution wiring. Meter No. 1 totalized
energy consumed by pump stations Noa 1, 2, 3, and the pressure system
monitoring station. Meter No. 2 totalized energy consumed by pump sta-
tions Nos. 4, 5, and 6.
Water Use--
Neptune water meters were installed to totalize water use by each
participating residence. The water meters were installed in the house
service lines so that they measured both consumptive water use and water
which was discharged into the sewage system.
VACUUM SYSTEM
Site and Layout
The site selected for the vacuum system (Figure 6) lay adjacent to
the Deschutes River. The project site was intersected by First Street, a
major city thoroughfare. The area was an older neighborhood. The houses
and their residents had a somewhat varied character. Lots abutting on the
Deschutes River had a high market value due to the aesthetically attractive
environment. Sizes of houses in the neighborhood varied; some were
rented units. Several of the houses were occupied by elderly retired
people.
18
-------
-LEGEND-
O COLLECTION SUMP
VACUUM VALVE
| 1 VACUUM STATION
— — ..VACUUM LINE
— -. — INDICATES TRAP IN VACUUM LINE
GRAVITY LINE
FORCE MAIN
VACUUM
STATION
DISCHARGE TO m .
GRAVITY INTERCEPTOR
SCALE: i"=ioo'
E S C H
U T E S
O OQ
Figure 6. Vacuum collection system site map.
-------
The area also had a semi-commercial character. The residence
served by No. 5 valve included a family-ope rated grocery store and gas
station. During the course of the project, one house (No. 7) was converted
from a single family dwelling to rented office space and was unoccupied
during most of the project. The number of people usually resident in each
house during the project monitoring period is shown on Figure 6. Approxi-
mately 23 people were generally resident in the vacuum system area during
the study period.
The immediate area did not have a sewer. Sewage collected by the
vacuum system was pumped to an existing force main, approximately 305
meters (1, 000 feet) east of the vacuum collection area, which in turn dis-
charged into a gravity interceptor.
Homes abutting on the Deschutes River could not be served by a con-
ventional gravity system, but lifts were within the operating parameters
of a vacuum collection system.
Eleven homeowners volunteered to participate in the project. They
were divided into groups of six singles, one double, and one triple. Each
group was served by one collection sump and vacuum valve, for a total of
eight valve installations.
The vacuum system incorporated a maximum pipe run of approxi-
mately 305 meters (1, 000 feet) from the vacuum station to the most dis-
tant vacuum valve (No. 1). The most critical lift (No. 3) was a total of
approximately 4 meters (13 feet), with 2. 4 meters (8 feet) net elevation
change.
House Sewer Interceptor Fittings
A "Y" fitting was installed in each house sewer line between the
house plumbing and the septic tank (See Figure 7). Sewage was thereby
diverted through one leg of the "Y" into a sewage collector sump. The
system was designed to be failsafe, that is, in the event of failure of the
vacuum system, sewage would back up and overflow into the existing septic
tank, instead of backing up into the homeowner's plumbing. Sewage was
carried to collection sumps through four-inch diameter Class 125, SDR
32. 5, PVC pipe with elastomeric ring joints.
Collection Sumps - Valve Pits
Sewage diverted from house sewer lines was collected in a sump
(See Figure 7). Sumps were of fiberglass construction, 0.48 cm (3/16
inch) thick, 0. 6 m (2 feet) nominal diameter with a slight mold taper, and
20
-------
-STEEL COVERS
FROM HOUSE
SEWER
INTERCEPTOR FITTING
1 i.. ••:-<•• 7. Vacuum, collection sump, valve pit, and valve installation.
-------
0. 9 m (3 feet) deep. The upper rim of the sumps were reinforced by fiber-
glass flanges approximately 6.35 cm (2-1/2 inches) wide by 1.9 cm (3/4
inch) thick. Nuts for cover screws were imbedded in the flange.
Sump covers were 0. 64 cm (1 /4 inch) thick steel plate, bolted to the
sump flanges.
Vacuum valves were housed in pits of similar construction to the
collection sumps, except 0. 9 m (3 feet) in diameter, 0. 9 m (3 feet) deep,
and without a sealed bottom. This was possible because high water tables
do not occur in the vacuum system area at Bend. However, in areas where
high water tables occur, a sealed bottom is normally part of the valve pit
construction.
Sewage and sensor pipes intersected the sumps and valve pits as shown
in Figure 7. Pipe intersections with the sumps and valve pits were sealed
by flexible rubber grommets.
Vacuum Valves
Vacuum valves used on the Bend project were 7. 6-cm (3-inch)
diameter valves manufactured by Airvac, as shown in Figure 7. Opera-
tion of the valve was powered by the pneumatic pressure differential be-
tween atmospheric pressure and vacuum in the collection lines. The
valve vacuum chamber was sealed from the collection line by a flexible
diaphragm which allowed the valve to open and close. Operation of the
valve was initiated by the head of sewage collected on the upstream side
of the valve. Pneumatic valves in the controller operated to switch the
vacuum chamber from atmospheric pressure to system vacuum, and vice
versa, at appropriate times.
The valve had two adjustments:
1. To operate when a preselected head of sewage, from 7. 6 to 76 cm
(3 to 30 inches) HO, had accumulated behind the valve.
£t
2. To remain open for a preselected period of time, from 3 to 30
seconds.
The following sequence of events constituted a valve cycle; The
valve was held in a normally closed position by a coil spring in the valve
vacuum chamber and by the pressure differential between system vacuum
and atmospheric pressure in the valve vacuum chamber. The pressure
head of the sewage accumulated behind the valve was transmitted to the
22
-------
sensor by air compressed in the sensor pipe. When the preselected head
was reached, a diaphragm valve in the sensor was closed. Closing of the
diaphragm valve caused switching of pneumatic valves in the controller
which introduced system vacuum into the valve vacuum chamber. The
valve was then pulled open by line vacuum. After a time interval deter-
mined by an adjustable air leak timer in the controller, pneumatic valves
in the controller switched the valve vacuum chamber back to atmospheric
pressure. The valve was again closed by force of the coil spring and the
pull of the vacuum.
The vacuum valve was fitted into the vacuum line by clamp couplings.
A short section of pipe below the valve could be removed for insertion of a
cleaning rod, if necessary.
Vacuum Pipe
Pipe used in the vacuum collection system was 7. 6-cm (3-inch)
diameter Schedule 40 PVC pipe with solvent weld joints, and was assembled
with PVC drain-waste-vent (DWV) type fittings. The pipe and its config-
uration were designed in accordance with recommendations by Airvac,
with the exception of sump No. 3 where the lift exceed Airvac's recommen-
dation.
Briefly, the vacuum pipe configuration consisted of abrupt rises
followed by gradually downward sloping runs as shown in Figure 8.
"Pockets" (See Figure 9) were installed before lifts. "Rolled Y" (See
Figure 10) were used to prevent drainage of liquid into tributary lines
during transport through the main line.
The vacuum pipe was buried at 0. 76 m (2. 5 feet) minimum depth.
Low points where standing water could be expected were buried a minimum
depth of 0. 91 m (3 feet).
23
-------
SUMP.
VALVE
PIT
(»OCK6T & CLEAN OUT
(TYPICA L)
UPHILL TRANSPORT
DOWNHILL TRANSPORT
Figure 8. Typical vacuum pipe configuration details for
uphill and downhill wastewater transport.
CLEAN-OUT COVER
FLOW
, i „
POCKET
TYPICAL POCKET
ASSEMBLY DETAIL
PROVIDE MINIMUM 2 PIPE
DIAMETER FALL TO NEXT
POCKET
FLOW
WtLL VARY AS
. NECESSARY
Figure 9. Typical vacuum collection line
pocket assembly detail
24
-------
45° ANGLE
™>
TRIBUTARY LINE
VACUUM
MAIN LINE
Figure 10. Rolled Y Fitting for tributary vacuum line.
Vacuum Collection Station
Vacuum station equipment was housed in a 5. 48-m long by 2.44-m
wide by 2.44-m high (18-ft. x 8-ft. x 8-ft. ) precast concrete vault. The
vault was installed partially below grade on a sloping bank as shown in
Figure 6. Access was through a roof hatch and stairway. A diagram of
the vacuum station equipment is shown in Figure 11.
Vacuum Pumps--
Vacuum pumps, shown in Figure 12, were sliding vane pumps:
3.73 kw (5 hp), three-phase, 460 volt, rated at 0.0354 m /second (75cfm)
manufactured by Lammert Division of Gould, Inc.
Sliding vane pumps operate on the principle of an eccentrically
placed rotor with sliding vanes, rotating in a pump cavity. Pumping ac-
tion is obtained by the changing volumes formed by the vanes and cavity
as the rotor turns.
The vanes and pump shaft bearings required oil lubrication. An oil
reservoir and coalescing unit were integral with the pump discharge. Oil
dripped onto the shaft bearing and then drained into the pump cavity and
onto the vanes. Vane lubricating oil was vaporized and carried into the
coalescing unit along with air and vapor discharged by the pump. Oil and
water vapor coalesced and condensed onto plates in the coalescing unit
and drained into the pump oil reservoir.
Condensed water drained into an oil reclaimer unit near the bottom
of the pump, and then was discharged through a manometer type drain
into the station sump. The station sump could be evacuated into the vac-
uum collection tank.
25
-------
VACUUM
PUMP EXHAUST
VACUUM RESERVE
TANK
STRIP CHART
RECORDER
PERISTALTIC
PUMP
Figure 11, Vacuum station.
SAMPLE CONTAINER
AND ICE CHEST
SIGNAL FROM VALVES
AND PUMPS
-------
TO VENT
V A
SCHEMATIC SLIDING
VANES MECHANISM
FROM SECOND PUMP
OIL RESERVOIR AND
COALESCING UNIT
WATER
CONDENSATE
TO SUMP
PUMP INLET
Figure 12. Sliding vane pump.
27
-------
The vacuum pumps were controlled by adjustable vacuum sensor
switches on the vacuum reserve tank. By Airvac recommendation, the
lead pump was set to start at 41 cm (16 inches) of Hg absolute pressure
and to shut off at 50 cm (20 inches) of Hg (absolute). The pumps alter-
nated in lead starting roles.
The low vacuum alarm was transmitted to the treatment plant and
police station if vacuum fell below 25 cm (10 inches) of Hg absolute pres-
sure.
Collection and Vacuum Reserve Tanks--
The collection and vacuum reserve tanks were two similar 1. 5-m
(400-gallon) steel tanks as shown in Figure 11. The collection tank re-
ceived sewage, while vacuum reserve tank provided larger evacuated vol-
ume to reduce vacuum pump running frequency. The vacuum reserve
tank also provided a buffer zone to protect vacuum pumps from contam-
ination by sewage.
Discharge Pumps--
Sewage was pumped from the vacuum collection tank to discharge
into the gravity interceptor by two centrifugal sewage pumps. The pumps
were PACO Model 495, vertical shaft, dry pit, nonclog sewage pumps,
5. 6 kw (7-112 hp), three-phase, 460 volts.
The pumps were controlled by mercury float switches in the sewage
collection tank. Working volumes (volume between "pump-on and "pump-
off") was set at approximately 0. 38 m (100 gallons). The pumps were
controlled to alternate lead operation roles. Both pumps would operate
if sewage level continued to rise above the lead pump start switch. An
alarm would be transmitted to the treatment plant and police station if
sewage level continued to rise above lag pump starting level.
Vacuum System Monitoring and Sampling Equipment
Monitoring equipment for the vacuum system was located in the vac-
uum collection station.
Event monitoring equipment—The vacuum chamber of each vacuum
valve was fitted with a pressure actuated switch which would momentarily
close each time the vacuum valve cycled. The switch was actuated by the
change in pressure when the valve vacuum chamber cycled from atmos-
pheric pressure to system vacuum. A signal was thereby transmitted to
a strip chart recorder via a wire each time a vacuum valve cycled.
28
-------
A strip chart, recorder and appropriate circuitry in the vacuum col-
lection station permitted recording of the time of operation of each vacuum
valve. Operation of each vacuum pump and each discharge pump could also
be recorded with the strip chart recorder.
Sewage sampling equipment—A sewage sampling system consisting of
the following components was installed in the vacuum collection station.
A 0. 95-cm (3/8-inch) diameter sampling cock and sampling Kne was in-
stalled on the discharge line of the sewage discharge pumps as shown in
Figure 11. A peristaltic pump, coupled with an electrically actuated
valve to prevent static pressure in the discharge line from causing leak-
age through the sampling pump whenever it was not operating, was used
to draw sewage samples from the discharge line. Composited sewage
samples were collected in a plastic carboy sitting in an ice chest.
In order to collect a representative composited sewage sample, the
sampling pump was interconnected to operate during operation of either of
the discharge pumps. Pumping rate of the sampling pump was adjustable,
so that any appropriate sample volume could be collected.
Energy consumption—Three standard kilowatt-hour meters, ob-
tained from the electric company, were installed in the vacuum station
to totalize energy consumed by the vacuum system. Meter No. 1 total-
ized energy consumed by the vacuum pumps; meter No. 2 totalized energy
consumed by the discharge pumps and, meter No. 3 totalized energy con-
sumed by station lighting, heating, and ventilating circuits.
Water Use—
Neptune m water meters were installed to totalize water used by
each participating residence. The water meters were installed in the
house service lines so that they measured both consumptive water use
and water which was discharged into the sewer.
29
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SECTION 4
DATA AND ANALYSIS
GENERAL,
This section presents and analyses data obtained from the Bend R&D
project. Data accumulated from the project consists of two categories.
The first is equipment and construction cost data accumulated from the
project bidding and construction phases. The contractor was required to
report actual construction costs incurred during construction. The sec-
ond category is data collected from operating and monitoring the two sys-
tems. A log of daily operation and maintenance tasks was kept to accu-
mulate maintenance and reliability data for the two systems. The two
systems were instrumented, as described in Section 3, to permit collec-
tion of the following specific operating data:
1. Point of time of operation of pressure system pumps, vacuum
valves, vacuum pumps and vacuum system discharge pumps.
2. Water use by the participating residents.
3. Energy consumption by the two systems.
4. Collection of composited sewage and septic tank effluent samples
for chemical analysis.
The period during which the systems were monitored extended from
July 12, 1976 to July 24, 1977. The dates at which monitoring and sam-
pling tasks were performed are indicated in Table 1. The intent of the
monitoring program was to collect operating data over approximately a
1-year period, with intervals of intensive monitoring during representa-
tive periods of cold winter weather, moderate spring or fall weather,
and warm summer weather. Daily temperature extremes recorded for
the Bend area on the project monitoring and sampling days are indicated
in Table 1.
30
-------
TABLE 1
SCHEDULE OF MONITORING AND SAMPLING
Date
July 12. 1976
July 13, 1976
August 9, 1976
August 10. 1976
August 16, 1976
August 17, 1976
August 18, 1976
August 25. 1976
August 26, 1976
September 9, 1976
September 27, 1976
September 28, 1976
October 11, 1976
October 12. 1976
October 13, 1976
October 14, 1976
October 15. 1976
October 18, 1976
October 19, 1976
October 20, 1976
October 21, 1976
October 22, 1976
October 23, 1976
October 24, 1976
October 25, 1976
October 26, 1976
October 30, 1976
November 1,1976
Operation
Events
Pressure
X
X
Vacuum
X
X
Energy
Consumption
Pressure
X
X
X
X
X
X
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
Water
Use
Pressure
X
X
Vacuum
X
X
X
X
X
X
X
Wastewater
Sampling
Pressure
X
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
Temperature
Degrees C
Max.
20.0
22.8
21.7
23.9
14.4
16.1
19.4
27.2
17.2
21.1
26.7
27.8
20.6
20.0
26.1
28.3
22.8
13.9
13.9
15.6
18.9
21.7
18.3
14.4
12.2
9.4
12.8
13.9
Min.
3.9
2.2
7.2
5.6
3.9
4.4
5.6
10.0
- 1.1
- 2.8
2.8
5.6
- 1.1
- 0.6
1.7
2.8
- 3.3
- 7.2
- 9.4
- 9.4
- 5.6
- 3.3
- 8.3
- 7.8
2.2
- 3.3
0.0
5.6
-------
TABLE 1 (Cont.)
Date
November 22, 1976
November 23. 1976
November 24, 1976
December 13, 1976
December 28, 1976
December 29, 1976
January 4,1977
January 5, 1977
January 12,1977
January 25, 1977
January 26, 1977
February 7, 1977
February 8, 1977
February 9, 1977
February 10,1977
February 11,1977
February 12,1977
February 13,1977
February 14,1977
February 15,1977
February 16,1977
February 17,1977
February 18,1977
February 19, 1977
February 20. 1977
February 21, 1977
February 22, 1977
February 23, 1977
March 8, 1977
March 9, 1977
March 10, 1977
Operation
Events
Pressure
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
X
X
X
X
X
X
Energy
Consumption
Pressure
X
X
X
Vacuum
X
X
X
X
X
X
X
X
Water
Use
Pressure
X
X
X
Vacuum
X
X
X
X
X
X
X
X
X
Wastewater
Sampling
Pressure
X
X
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
X
Temperature
Degrees C
Max.
17.2
10.0
16.1
12.8
10.0
7.2
2.8
3.3
3.3
7.2
0.0
4.4
0.0
10.6
12.8
16.7
16.7
18.3
16.1
18.3
21.1
18.3
18.3
18.9
21.1
6.7
7.8
6.7
10.6
11.1
6.7
Min,
- 6.1
- 5.6
- 1.1
- 2.2
-11.1
-11.1
-14.4
-15.0
- 1.1
- 7.8
-10.6
- 5.0
- 4.4
- 4.4
- 0.6
1.7
1.7
- 2.2
- 8.3
- 8.3
- 1.7
- 2.2
- 5.0
- 7.8
- 5.0
- 7.8
- 1.1
- 7.8
1.1
- 2.8
- 6.1
U)
to
-------
TABLE 1 (Cont.)
Date
March 15. 1977
March 16, 1977
April 12, 1977
April 20, 1977
April 21, 1977
April 22, 1977
April 26, 1977
April 27, 1977
April 28, 1977
May 16, 1977
May 17. 1977
May 18. 1977
June 1, 1977
June 2, 1977
June 16, 1977
June 22. 1977
June 28, 1977
June 29, 1977
June 30, 1977
July 7, 1977
July 8, 1977
July 11, 1977
July 12, 1977
July 13, 1977
July 14, 1977
July 15, 1977
July 16. 1977
July 17. 1977
July 18, 1977
July 19. 1977
Operation
Events
Pressure
X
X
X
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
Energy
Consumption
Pressure
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
X
X
X
Water
Use
Pressure
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
X
X
X
Wastewater
Sampling
Pressure
X
X
X
X
X
X
Vacuum
X
X
X
X
X
X
X
X
Temperature
Degrees C
Max.
6.1
10.6
20.0
15.6
17.2
19.4
21.1
16.7
21.7
9.4
11.7
12.8
27.2
15.6
26.7
27.2
27.2
30.0
26.7
22.2
28.3
26.1
29.4
23.9
25.6
27.8
31.1
31.1
26.7
23.9
Min.
- 6.7
- 8.9
- 3.9
- 5.6
1.7
1.7
0.0
- 3.3
- 0.6
- 5.0
0.0
- 0.6
6.7
- 2.8
1.7
6.7
5.0
6.7
3.9
1.7
6.7
6.7
7.8
0.0
5.0
5.6
7.2
12.2
12.2
1.7
to
-------
TABLE 1 (Cont.;
Date
July 20, 1977
July 21, 1977
July 22, 1977
July 23, 1977
July 24, 1977
Operation
Events
Pressure
Vacuum
Energy
Consumption
Pressure
X
X
X
X
X
Vacuum
Water
Use
Pressure
X
X
X
X
X
Vacuum
Wastewater
Sampling
Pressure
X
X
Vacuum
Temperature
Degrees C
Max.
25.6
31.7
30.6
31.1
29.4
Min.
6.1
8.9
7.2
9.4
10.0
-------
The winter of 1976-1977 was relatively mild for the Bend area and
did not provide a severe cold weather test for the systems. Average and
minimum temperatures recorded and departure from normal were:
Temperature °F
Departure
Average Minimum from Normal
December 1976 35.4 24 +2.7
January 1977 30.7 -6 +o! 5
February 1977 38.0 2 +3*2
EQUIPMENT AND CONSTRUCTION COSTS
Vac uurn^jC qu ipmenj^C osts
Vacuum system equipment was purchased separately from general
construction contract bidding. Two companies responded to the invita-
tion for bids for vacuum system equipment: Colt-Envirovac and Airvac.
Items included in bids and bid prices are summarized in Table 2.
Deduct items bid for optional items are noted. Estimated or quoted
equipment price, f.o.b. from the manufacturer, are also noted.
Pressure and Vacuum Systems Construction Costs
Costs for materials, equipment, and labor for construction of the
pressure and vacuum system are summarized in Tables 2, 3, and 4.
Materials, labor, and equipment costs are as reported by the general
contractor to have been incurred during construction, i.e., actual costs,
not contract price. Indirect overhead and profit to the general contractor
are not included in the reported costs. Material costs are the vendor
price paid by the general contractor. Costs reported for subcontracted
work is the subcontract price paid by the general contractor and include
profit and overhead to the subcontractor.
Breakdown into components of some lump costs reported by the gen-
eral contractor have been estimated. These estimated cost breakdowns
are so indicated on Tables 3 and 4. Vacuum equipment costs listed in
Table 2 are not included in Table 4.
35
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TABLE 2
VACUUM EQUIPMENT BID SUMMARY
Item
Sewage collection
and vacuum reserve
tanke
Vacuum pumps
Discharge pumps
Control package
Vacuum valves
Miscellaneous station
piping and vacuum
gauges
Total Bid Price
Colt-Envirovac
Single 600-gallon steel tank
Two Nash Model AHF 19 vacuum pumps,
horizontal base mounted liquid ring type,
with 50-gallon sealed water tank, 1.5 hp.
20 cfm at 15" hg
($7,376 deduct price for one pump)
($2,600 FOB Portland)
Two Fairbanks Morse, Model 5432BK,
nonclog, vertical, centrifugal sewage pump,
5 hp, 1750 rpm, discharge, suction, and
check valves
($2,240 deduct price for one pump)
(Estimated price one pump $2,200 FOB
Portland)
Airvac
Two similar 400-gallon steel tanks
($2,150 deduct price for vacuum re-
serve tank)
Two Lammert vacuum pumps, sliding
vane type, 5 hp, 75 cfm
($2,225 deduct price for one pump)
($1,500 FOB Portland)
Two PACA Model 495 vertical, cen-
trifugal sewage pump, 7.5 hp ,
1750 rpm
($2,500 deduct price for one pump)
(Estimated price one pump $1,300
FOB Portland)
Automatic control of vacuum and discharge pump. Pumps alternate service on each
start. High water and low vacuum alarms.
Seven each
(Proposal to use Airvac valve)
Not included
$41,388
Seven each
$500 each for additional valves
Estimated value of $2,500
$25,300
-------
TABLE 3
PRESSURE SYSTEM CONSTRUCTION COST SUMMARY
GJ
O
Scope of Work and Material
1. Excavation
a. Gravity lines from house sewer to
sump. Average 0. 76 m (2. 5 ft. )
deep, 10% rock
b. Pressure lines. Average 1.1 m
(3. 5 ft. ) deep, 35% rock
c. Excavation for sump
2. Pump Stations (include:)
4 low head pumps
1.57 I/sec @ 6.7 m
(25 gpm @ 22 ft) TDK
2 high head pumps
1.57 I/sec @ 11.4 m
(25 gpm @ 37 ft) TDK
3. Spare Pumps
low head
high head
4. Pipe and Pump Sump Installation
and Backfill
a. Gravity line, 10.2 cm (4 in. )
diameter, ring joint PVC
b. Pressure line 5. 1 cm (2 in. )
diameter, ring joint PVC
c. Sumps (installation only)
5. Electrical (subcontracted)
(includes monitoring equipment of
$6,000 estimated cost)
6. Site Clearing and Restoration
Number of
Units
247 m
(812 ft.)
305 m
(1,000 ft.)
6 ea.
6 ea.
1 ea.
1 ea.
247 m
(812 ft. )
305 m
(1,000 ft. )
6 ea.
Average
Unit Cost
$3.75/ft. •
(average
unit cost
includes
Items a
b and c)
$1,336 ea.
$166
$229
$10.66/m
($3.25/ft. )*
$11.25/m
($3.43/ft. )*
$100 ea. *
^estimates
Total Cost
Materials and
Subcontracts
$ 328
$ 7,941
$166
$229
$ 2,117
$11,869
$ 1,328
Labor and
Equipment
$ 6,480
$ 74
$ 4,549
$ 2,994
Total
$ 6,808
$ 8,015
$166
$229
$ 6,666
$11,869
$ 4,322
-------
TABLE 4
VACUUM SYSTEM CONSTRUCTION COST SUMMARY
Scope of Work and Materials
1. Excavation
a. Gravity lines from house sewer
to sump . Average 0. 76 m (2. 5 ft. )
deep, 25% rock
b. Collection sumps and valve pits
c. Receiving station (subcontracted)
d. Vacuum lines. Average l.lm (3. 5 ft. }
deep, 50% rock
e. Discharge line. Average 1.1 m (3.5 ft.)
deep, 80% rock
2. Receiving Station
a. Structure (subcontract)
b. Station piping (installation only)
3. Electrical (subcontracted)
(includes monitoring system, $4, 500
estimated cost)
4. Site Clearing and Restoration
5. Pipe, Sumps and Valve Pits (material
installation and backfill)
a. Gravity line 10.2 cm (4 in.)
diameter, ring joint PVC
b. Vacuum line 7. 6 cm (3 in. )
diameter, solvent weld PVC
c. Discharge line 10.2 cm (4 in. )
diameter a/c
d. Pressure relief valves
e. Sumps and valve pits (installation
only)
6. Sumps and valve pits (material only)
Number of
Units
117 m
(385 ft.)
8 ea.
1 ea.
563 m
(1,847 ft.)
317 m
(1,040 ft.)
1 ea.
117 m
(385ft.)
563 m
(1,847 ft.)
317 m
(1,040 ft.)
2ea.
8 ea.
8 ea.
Average
Unit Cost
$19.36/m
($5. 90 /ft.)
(average
unit cost
includes
Subitems
a, b, d,
and e)
$10. 66 /m
($3.25 ft.)*
$19.36/m
($5.90 ft.) *
$17.22 /m
($5. 25 /ft)*
$150/ea.*
$580 *
*estimates
$531
Total Cost
Materials and
Subcontracts
$ 767
(Receiving
station exca-
vation, Item c)
$ 8,653
$ 71
$14,324
$ 598
$ 9,034
'
$ 4,248
Labor and
Equipment
$19,328
$ 1,819
$ 4,920
$10,947
Total
$20,095
$10,543
$14,324
$ 5,518
$19,981
$ 4,248
l*J
CO
-------
Excavation
As noted before, the primary motivation for the Bend R & D Project
was to investigate sewer technology which would avoid the high costs of
deep excavation required to maintain line and grade for conventional gra-
vity sewers. Research of less costly methods of rock excavation was also
an accessory interest of the project.
Excavation methods utilizing conventional excavation equipment have
been used in Bend whenever soil depths permitted. Whenever rock has
been encountered, the usual excavation method has been to drill and blast.
Depending on the possibility of damage to surrounding buildings and utili-
ties, excavation by blasting has entailed the following procedures. The
soil, if present, has been excavated to rock before drilling and placement
of the charge. The trench has been refilled and/or covered with mats and
weighted cables before blasting. Deep trenches may require more than
one blasting operation.
Blasting operations may require extensive care to prevent damage
to adjacent structures. The effect of a given charge on the conglomerate
of soil, cinders, boulders, and lava flows typical of Bend terrain is diffi-
cult to predict. Cases have occurred in which force from a blast has
found a pathway to structures several hundred feet distant. Liability for
damages has been correspondingly high.
Excavation of 1. 0 to 1. 2-m (3 to 4-feet) deep trenches, such as used
on the Bend R & D Project, have cost in the range of $6. 50 to $65. 00 per
meter ($2 to $20 per foot) (1975 price), depending on percentage of rock
and care required to protect adjacent structures.
On the Bend R fa D Project, excavation was done with a backhoe
whenever soil was encountered. When rock was encountered, a Ditch
Witch m Model R-100 trenching machine was used for excavating whenever
possible (See Figure 13). However, access by the trenching machine was
not possible in several areas. In these areas, rock was broken by jack-
hammer and hand excavated.
The Model R-100 trencher is a tractor-mounted, chain-type exca-
vator. The chain has conical, carbide, drag-type, rock-cutting teeth.
Cutter bars and chains are reported by Ditch Witch sales representatives
to be available with capability to cut trenches up to 2.4 meters (8 feet)
deep and up to 0.6 meters (2 feet) wide. The chain used on the Bend pro-
ject cut a trench approximately 0. 2 meters (8 inches) wide, maximum
depths of cut were approximately 1. 2 meters (4 feet).
39
-------
Figure 13 Ditch Witch ^ ' R-100 used on Bend R & D Project
40
-------
The Ditch Witch Model R-100 was reported to cost approximately
$50,000.
Generally, the Ditch Witch required two operators. One operator
guided and controlled the machine. The second operator was needed in
the ditch to remove loose rubble and debris which tended to foul and bind
the cutter chain.
Trenching speeds up to 3 meters (10 feet) per hour were achieved.
Best results were obtained when cutting solid, unfractured rock with no
rubble to foul the chain.
Spoil from cutting lava rock consisted of chips and flakes up to 2. 5
cm (1 inch) in diameter. Generally, the rock-cutting spoil was of suitable
quality for use as backfill. However, considerable care was needed to
keep suitable rock-cutting spoil segregated from unsuitable rubble. Screen-
ing could have been effectively utilized for this purpose.
Average excavation costs of $12. 50 per meter ($3. 75 per foot) for
pressure system trenches, which contained approximately 25 percent
rock, $19.36 per meter ($5.90 per foot) for vacuum system trenches
which contained approximately SO percent rock, are listed in Tables
2 and 3. These excavation costs compare very favorably with the
$6. 50 to $65. 00 per meter ($2 to $20 per foot) cost range estimated for
conventional excavation methods in the Bend area.
Subsequent to construction of the Bend R & D project a rock exca-
vating machine of similar principle to the Ditch Witch R-100, but much
larger, has been used for excavating gravity sewer trenches in Redmond,
Oregon. Excavation costs are not available.
OPERATION AND MAINTENANCE
Operating Period
The pressure system started operating in March, 1976. The vac-
uum system started operating in May, 1976. The monitoring period ex-
tended through July of 1977. The following discussion is therefore limited
to recounting events encountered during approximately the first year of
operation. One year of operation experience does not provide adequate
background for assessment of long-term reliability. The account of op-
erating problems therefore probably includes some incidents that, in the
long run, would be classified as start-up problems rather than operating
problems.
41
-------
A daily log was kept of time spent operating, maintaining, and moni-
toring the systems. System monitoring time and effort is not included in
the following account since it would not be done on a normal operating sys-
tem.
Maintenance and Reliability
Pressure System—
Check Valves-- After start-up, Pump No. 2 was observed to be op-
erating repeatedly on about a three minute on-six minute off cycle. The
cause was diagnosed as a sticking check valve. The valve was replaced
by the contractor on August 4, 1976. The valve was found to be defective;
an improperly seated 0-ring had caused the ball to stick.
Several months later, in October, Sump No. 2 received a high-water
alarm. The cause of the high water was investigated and the check valve
was found to be partially plugged with bark chips. The top of Pump Station
No. 2 had been installed slightly below ground level and covered with bark
chips. It is speculated that bark chips fell into the sump during replace-
ment of the check valve and had taken several months to be sucked into the
pump inlet to clog the valve.
The operator noted that check valves installed in the vertical pipe
run were difficult to service. A discussion of design considerations for
convenient maintenance of the sump is included in Section 5,
Odors-- One complaint was received that a pump station produced
objectionable odors. The gasket on the sump cover was repaired and the
cover securely tightened. No further complaints were received.
Corrosion-- Immediately after start-up of the pressure system, the
corrosion problem associated with septic effluent became apparent. Any
metal surfaces in the sumps which were subject to corrosion began to cor-
rode.
Brass, stainless steel, or cadmium-plated screws and bolts had
been used; threads cut on the galvanized iron pump discharge pipe and the
steel plate cover were coated with bituminous epoxy paint. However, it
was apparent that corrosion was occurring under any break in these pro-
tective coatings.
Points noted as being particularly affected by corrosion were:
1. Welds on pump guide rails and pump guide flanges--The guide
rails were fabricated from galvanized iron pjpe with welded
42
-------
steel attachment tabs. The pump guide flanges were fabricated
from torch-cut steel plate.
2. Pump access cover nuts and bolts—The pump access covers were
attached to the sump covers by cadmium-plated bolts and nuts
welded to the underside of the sump covers (see Figure 3). The
nuts and bolts were subjected to the corrosive atmosphere from
inside the sump and physical abuse and fouling with debris when-
ever the cover was removed.
3. Sump cover plates--The steel cover plates were corroding un-
der pinholes or scratches in the protective coating.
It should be noted that when the pressure system sumps were rein-
spected after approximately a year of service, the rate of corrosion ap-
peared to have abated and stabilized considerably, i.e., initial corrosion
was more apparent by contrast, but stabilized after formation of surface
coats of corrosion materials.
The evaluation of corrosion in the sumps presented above is ad-
mittedly subjective. System compents were not disassembled and rigor-
ously inspected for corrosion effects. No failures of sump components
occurred because of corrosion.
Grease Build-Up-- After approximately one year of service, pres-
sure system sumps wei3 inspected for grease buildup on sump walls.
The pressure system sumps, which received septic tank effluent, typically
had a ring of grease near high-water level of less than . 32-cm {1 /8-inch)
thickness. No grease buildup was observed which would interfere with
operation of pump control or alarm float switches.
Vacuum System—
Vacuum pumps-- Vacuum pumps installed in the Bend system were
sliding vane pumps as described in Section 3. The sliding vane vacuum
pumps proved to be a high-maintenance, low-re liability item for this ap-
plication.
Initially the vacuum pumps were installed without water condensate
drain lines, i.e., manual draining of water condensate from the oil sump
was required. However, water condensate accumulated in the oil recovery
units at a rate that required daily draining. Consequently, manometer type
drain lines which permit condensate to overflow were installed to reduce
maintenance requirements.
43
-------
The high, rate at which water condensate accumulated was probably
due to the small size of the system load relative to vacuum pump capacity.
Each vacuum pump may have operated as little as 2 or 3 minutes per hour.
Vacuum systems in which the vacuum pumps operate frequently enough to
keep the oil coalescing unit and discharge header pipe warm are reported
by Airvac personnel to have less condensate accumulation.
On November 15, 1976, at approximately 2:00 p.m., a vacuum valve
stuck in the open position, as described in the following subsection. The
vacuum pumps were unable to re-establish vacuum, and a low vacuum
alarm was transmitted to the treatment plant. Both vacuum pumps ran at
a no-vacuum load for approximately 30 minutes until maintenance person-
nel reached the vacuum station. The vacuum pumps were found to have
lost their oil, i.e. , there was oil on the vacuum station floor, oil was not
visible in the oil level sight glasses, and the air was filled with a blue haze
of vaporized oil.
The failed valve controller was replaced. The pumps were refilled
with oil and restarted. The pumps performed satisfactorily. At the time
no damage appeared to have been done to the pumps' bearing surfaces.
On February 9, 1977, and on March 7, 1977, the vacuum pumps
again lost their oil to a level below the sight-glass indicators. Causes of
these two oil-loss occurrences were not determined.
On April 4, 1977, a low-vacuum alarm was received. The vacuum
pumps were found to be running and unable to restore vacuum. Some oil
had been lost from the vacuum pumps. The vacuum station was filled
with a haze of vaporized oil. The cause of the vacuum failure was found
to be a leak in the vacuum-tank cover gasket. The leak was closed by
tightening the vacuum-tank cover bolts. The vacuum pumps were refilled
w ith oil and service was restored.
On May 13, 1977, Vacuum Pump No. 1 had difficulty starting.
Pump No. 1 was pulled from service and Pump No. 2 was left to handle
the system. Vacuum Pump No. 1 was rebuilt with new vanes, springs,
and rod and shaft bearings and placed back in service on June 6, 1977.
Vacuum Pump No. 1 appeared to be overheating and was again pulled from
service on July 6, 1977 and the shaft bearings were honed.
The vacuum pumps were considered to have low reliability as in-
stalled in the Bend vacuum station because of the incidents described
above. Oil loss, if not promptly detected and corrected, could result
in damage to the pumps. The suspected reliability of the vacuum pumps
therefore necessitated frequent checking of their condition.
44
-------
It should be noted that the incidents cited did not give adequate exper-
ience to judge long-term reliability or maintenance requirements. Better
understanding of the cause of the oil-loss incidents might have changed the
estimate of the vacuum pumps' reliability. Installation of an oil-level
measuring device and a telemetry system to transmit a low-oil alarm sig-
nal to the treatment plant would have permitted less frequent checking of
the vacuum pumps, or a different type of vacuum pump might have been
more reliable.
A fuse for the vacuum pump No. 1 motor blew on May 4, 1977. Later
in 1978 the motor burned out the windings in two phases. The cause of the
motor failures were not identified, but it is speculated that the cause may
have been an intermittent short in the electrical system.
Vacuum valves--No failures were diagnosed which involved the valve
mechanism itself. Valve failures which occurred resulted from malfunc-
tions in the pneumatic valve control circuits.
On November 15, 1976, a low-vacuum alarm was received. Number
5 valve was found to be stuck in the open position. The controller was re-
placed, and the system was restored to operation. The effect of the open
valve on the vacuum pumps was described in the preceding subsection.
The failed controller was shipped to Airvac for repair. Pneumatic
valves in the controller were reported by Airvac to have been jammed by
a small particle of debris which prevented switching the vacuum valve
vacuum chamber back to atmospheric pressure.
On December 30, 1976, a high-water alarm was received from
Sump No. 7. Investigation indicated the failure was caused by.the check
valve (See Figure 7). Temperature lows of -11 C (12 F) had been re-
corded in the Bend area during the preceding two days; it appeared that
the check valve was frozen. The check valve was thawed and operation
of the vacuum valve resumed. The weather subsequently warmed and no
further problems with the valve occurred due to cold weather.
Corrosion— The vacuum system sumps did not contain either the
corrosive atmosphere or the metal components subject to corrosion that
were in the pressure system sumps. Sump covers did not appear to be
corroding at an objectionable rate. As with the pressure system sumps,
the cover bolts and nuts imbedded in the sump flanges were corroding and
receiving physical damage from removal and replacement of the sump
covers.
45
-------
Grease Buildup--The walls of the vacuum system sumps, which re-
ceived raw domestic sewage, were observed to have rings of grease build-
up near high-water level up to 2 cm (3/4 inch) thick.
OPERATING FREQUENCIES AND WASTE WATER VOLUMES
This subsection presents data indicating the frequency of operation
of the pumps in the pressure system and the vacuum valves, vacuum pumps
and discharge pumps in the vacuum system. Each of the systems was sub-
jected to periods of intensive monitoring to investigate operating character-
istics during cold, moderate and hot climatic conditions. The volumes of
waste water generated in each system area is estimated. Records of water
used at each residence is presented for comparison.
Pressure System
Pressure system operating parameters--Ope rating parameters for
the pressure system are presented in Table 5. The volumes evacuated
were calculated from sump configurations and the observed waste water
levels at which pump-operating cycles were initiated. The wastewater
levels at which the pumps' operating cycles were initiated were determined
by float switches in the sumps as described in Section 3. The time dura-
tion of pump-operating cycles were determined by measuring several oper-
ations and averaging the results. These time measurements were taken
with a stopwatch. The strip-chart recorder could have been used for the
time measurements but a faster chart speed than was used for recording
the time the event occurred would have been needed; the stopwatch method
was deemed more convenient. The volumes evacuated per pump operating
cycle were used to estimate volumes of wastewater generated within the
pressure system area.
Flow velocities in the pressure system main when each pump was op-
erating are noted in Table 5. The velocity achieved by Pump No. 4 did
not meet the design criteria of 0.61m /sec (2. Oft/sec). However, no prob-
lem was anticipated because the velocity to scour solids from the line
would be achieved by other pumps in the system.
46
-------
TABLE 5
PRESSURE SYSTEM OPERATING PARAMETERS
(Measured October 25,1976)
Sump Pump
Number
1
2
3
4
5
6
Volume Evacuated
Per Pump Cycle
(liter) (gal)
151.4
112.0
124.9
94.6
81.5
105.0
40.0
29.6
33.0
25.0
21.5
28.0
Pumping Time
(sec)
61.0
41.9
93.3
89.3
43.6
76.7
Pumping Rate
(liter/sec)
2.48
2.67
1.34
1.06
1.87
1.38
-------
TABLE 6
PRESSURE SYSTEM PUMP OPERATION FREQUENCY
Hour
12 - 1
1 - 2
2-3
3-4
4 - 5
5-6
6-7
7 - 8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2-3
3-4
4-5
5 - 6
6-7
7-8
8 - 9
9-10
Date
f
1
OH
sO
nt 0
t3 •— '
O
"£ ^
1»
2*
I
^E
^O
>•£;
'm ~*
C^ f~}
J^l ^^
CO
60
f
Operations per hour
Sump No. / No. of residences
'/i
1
1
1
1
1
Vz
1
1
1
1
1
3/2
1
1
1
1
1
1
3
1
1
1
1
1
1
Vz
1
1
1
1
1
2
1
1
5/i
1
1
1
1
1
1
1
1
3
6/3
1
2
1
1
1
1
4
1
2
1
2
48
-------
TABLE 6. (Continued)
Hour
6 - 7
7 - 8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4-5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4 - 5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
11 - 12
Date
-f
"
• I
T3 0^ ^
^ JQ ^
^
r^i
>.
In
s!
^ t-
>s 0s "
rrt l~l
CO .
H 0
H M*
s
^Q
CJ
T
•••
5!
s
'
Operations per hour
Sump No. /
Vi
1
1
1
1
1
2/!
1
1
1
1
1
2
1
V2
1
1
1
1
1
1
1
1
1
1
No. of residences
4/2
1
1
1
1
1
1
2
2
2
1
1
1
1
2
Vi
1
1
1
1
2
2
1
"
1
1
1
1
1
6/3
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
49
-------
TABLE 6. (Continued)
Hour
12 - 1
1 - 2
2-3
3-4
4-5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2-3
3-4
4 - 5
5 - 6
6 - 7
7 - 8
8-9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4-5
5 - 6
6 - 7
7-8
8-9
9-10
10 - 11
11 - 12
Date
•
>;
-£_
3
^ i
r-
o
r—4
rt -
!2 >* '
fa § '
».,
&
fa
V
i
3
^-t
^
fr
1—4
«J M"
i-i
3 7>^
•«-> to
W ^
43
fa
_J
•N
'
Operations per hour
Sump No. / No. of residences
'/i
1
1
1
1
1
1
V2
1
1
1
1
1
1
1
1
1
3A
1
1
1
1
1
1
1
1
1
1
1
1
1
V2
1
1
1
1
1
1
2
1
1
1
1
5/i
1
2
2
1
1
1
1
2
1
2
6/3
1
1
3
3
2
1
1
1
1
2
1
1
1
1
2
2
1
50
-------
TABLE 6. (Continued)
Hour
12 - 1
1 - 2
2-3
3 ~ 4i
4-5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2-3
3-4
4-5
5-6
6 - 7
7-8
8 - 9
9-10
10-11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4-5
5 - 6
6 - 7
7 - 8
8-9
9 - 10
10 - 11
11 - 12
Date
f«.
t-
i— i
•^ »
4~*
I
5!
3 Irs
d d
to r
JH
r-H
>-ro"
T3 *"*
C >>-
iS
g
V
fe
••
^
(^
1
Operations per hour
Sump No. / No. of residences
!/i
1
1
1
1
1
2/z
1
1
1
1
1
1
1
1
1
1
2
3/z
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4/2
1
1
1
2
1
1
1
1
1
1
1
1
1
1
2
V!
2
1
1
1
3
1
1
2
2
1
1
1
6/3
1
3
1
1
1
1
2
1
1
3
2
2
2
1
1
1
1
1
1
1
1
' 1 . .
51
-------
TABLE 6. (Continued)
Hour
12 - 1
1 - 2
2-3
3-4
4 - 5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
Date
.
t,.
^^^
i— i
•3 - ;
o £<
2 «j
,0
0)
5
*£
T3 ^
^
••>
__i
™ vO .§
fl ^ <£
-------
TABLE 6. (Continued)
Hour
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3 - 4
4 - 5
5 - 6
6 - 7
7 - 8
8-9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3 - 4
4 - 5
5 - 6
6 - 7
7 - 8
8 - 9
9-10
10 - 11
11 - 12
Date
t
S
<
t^-
f- •
i O*x
>» ~.
nJ '-'
1°"
T3 ^
£ cL
"^
S
P
t—
1s"
>. ^
•st.
LH
•m
(0 i-< ><
jj rvj <;
2 — <
7^ Lj
Oi
-------
TABLE 6. (Continued)
Hour
8 - 9
9 - 10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4 - 5
5 - 6
6 - 7
7 - 8
8 - 9
9 - 10
10 - 11
11 - 12
12-1
1 - 2
2 - 3
3 - 4
4-5
5 - 6
6 - 7
7 - 8
8 - 9
Date
%
•4
^r-
rt ON
w •""
c ~T
CD
-------
TABLE 6. (Continued)
Hour
9 - 10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3 - 4
4 - 5
5 - 6
6 - 7
7 - 8
8 - 9
9-10
10 - 11
11 - 12
12-1
1 - 2
2-3
3 - 4
4-5
5 - 6
6 - 7
9 - 10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3 - 4
4-5
5 - 6
6 - 7
7 - 8
-8 - 9
9-10
10 - 11
" - 12
Date ,
3
f- -
>, ^
03 -1
g pg
T3 ^
, o-
t? M
W co"
g N
H |
hj
I
i
I.
i
^•i
r^
r>-
rt "* 1
i
!••
w oo" S
g N ft
§
^
Operations per hour
'A
1
1
1
1
2
1
1
1
1
1
Sump No.
1
1
1
1
1
1 •
1
1
3/2
1
2
1
1
1
2
1
1
1
2
} .
1 '! ,
1
2
No. of residences
4/2
1
1
1
1
; 1
1
2
5/i
1
2
1
1
1
1
1
1
1
,i:"
i
i
6/3
1
1
1
3
1
1
1
3
2
1
2
2
2
. • . .
1
., / .1-; :.
'••••• 2
•••••• 2
i
1
1
55
-------
TABLE 6, (Continued)
Hour
12-1
1 - 2
2 - 3
3-4
4-5
5 - 6
6 - 7
7-8
8 - 9
9-10
10 - 11
11 - 12
12 - 1
1 - 2
2 - 3
3-4
4-5
5 - 6
6 - 7
7 - 8
8 - 9
9 - 10
10 - 11
11 - 12
12 - 1
1 - 2
2-3
3-4
4-5
5 - 6
6 - 7
Date
3
>c--
-------
Pressure System Waste water Volume
Volumes of wastewater collected by the pressure system are sum-
marized in Table 7. The data presented in Table 7 were derived by multi-
plying volumes evacuated per pump cycle, recorded in Table 5 times pump
operating frequencies recorded in Table 6. The data indicates surprisingly
low wastewater flows, generally in the range of 151 to 227 liters (40 to 60
gallons) per capita day. There does not appear to be any significant differ-
ence in wastewater volumes generated at different seasons of the year.
Pressure System Water Use
Water recorded to have been used by homeowners connected to the
Bend pressure system during the project monitoring period is presented
in Table 8. As noted in Section 3, the water meters were installed in the
house service lines so that they recorded consumptive water use as well
as water which was returned to the sewer system.
Bend has an abundant supply of high-quality water from surface
sources. Water use has not normally been mete red; water customers
have been charged a flat monthly rate. There has therefore been little
economic incentive for water conservation either by the City or by indi-
vidual water users. Unlimited use of city water for lawn irrigation has
been a common practice. In almost all cases the water usage indicated
in Table 8 is substantially greater than wastewater flows indicated in
Table 7. In some cases the water consumption indicated are many thou-
sands of liters per day per residence during summer periods when lawns
were being watered and dropping off to generally less than 1, 000 liters
(260 gallons) per day per residence during winter periods.
Vacuum System
Vacuum system operating parameters--Operating parameters for
the vacuum system are presented in Table 9. As with the pressure sys-
tem, the volumes evacuated were calculated from the sump and holding
tank configurations and the observed wastewater level at which vacuum
valve or discharge pump operating cycles were initiated. The wastewater
levels at which vacuum valve or discharge pump cycles were initiated
were determined by level sensors as described in Section 3. The time
duration of vacuum valve and discharge pump operations were determined
by measuring several cycles and averaging the results. The time mea-
surements were taken with a stopwatch, because the valve operating sen-
sor gave only a momentary signal and, as with the pressure system, use
of a stopwatch was considered more convenient than attempting to use the
strip-chart recorder to measure vacuum or discharge pump-ope rating
durations.
57
-------
TABLE?
PRESSURE SYSTEM WASTEWATER VOLUMES
Date/Time
Mon.,Aug.9,1976
Noon to
Tue., Aug. 10. 1976
10:00 AM (22 hrs.)
Wed., Feb. 9, 1977
6:00 PM to
Midnight (6 hrs.)
Thurs,Feb.10.1977
Fri.,Fefa7l1,1977
Sat.. Feb. 12, 1977
Sun.. Feb. 13, 1977
Won., Feb. 14. 1977
(Midnight to
10:00 AM (10 hrs.)
Units
No. Pump Operations
Volume/Residence liter
Volume/Residence gaf
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
Sump No./No. Residences
1/1
5
757
200
3
454
120
2
303
80
5
757
200
4
605
160
2
303
80
2
303
80
2/2
5
560
148
2
224
59
6
672
178
5
560
148
7
784
207
2
1,008
266
2
224
59
3/2
15
1.874
495
4
500
132
7
874
231
10
1,249
330
10
1.249
330
10
1,249
330
3
375
99
4/2
9
851
225
4
378
100
14
1.324
350
9
852
225
10
946
250
10
946
250
2
189
50
5/1
11
895
236
3
244
65
11
895
237
8
651
172
10
814
215
13
1,060
280
5
405
107
6/3
17
1,802
476
5
530
140
12
1.272
336
19
2,014
532
16
1.696
448
20
2.120
560
6
636
168
Waste*
Water
Volume
6,738
1,780
2.332
616
5,345
1,412
6,083
1,607
6,094
1,610
6,685
1,766
2,131
563
Waste-
Wat or Per
Capita
198.1
52.4
68.6
18.1
157.2
41.5
178.9
47.2
179.2
47.4
196.6
51.9
62.7
16.6
00
-------
TABLE? (Continued)
Date/Time
Tue., Mar. 15. 1977
8:00 AM to
Midnight (20 hrs.)
Wed.. Mar. 16, 1977
Wed.. April 20, 1977
, 5:00 PM to Thurs.
April 21. 1977
Noon (17 hrs.)
Wed.. June 1,1977
8:00 AM to
Midnight (16 hrs.)
Wed.. June 22. 1977
9:00 AM to Thurs.
June23,1977
7:00 AM (22 hrs.)
Tue., June 28, 1977
9:00 AM to Midnight
Midnight (15 hrs.)
Wed., June 29, 1977
Thurs. June 30, 1977
Midnight to
7:00 AM (7 hrs.)
Units
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
No. Pump Operations
Volume/Residence liter
Volume/Residence gal
Sump No ./No. Residences
V1
5
757
200
1
151
40
3
454
120
6
908
240
7
1.060
280
4
606
160
3
454
120
0
0
0
2/2
3
337
89
2
224
59
4
446
118
7
784
207
4
447
118
4
446
118
4
447
118
1
113
30
3/2
6
750
198
3
375
99
8
999
264
7
874
231
6
749
198
13
1,624
429
9
1.124
297
1
125
33
4/2
16
1,514
400
3
284
75
4
379
100
8
757
200
3
284
75
5
473
125
3
284
75
1
95
25
5/1
13
1,056
279
6
488
129
4
326
86
6
489
129
6
488
129
7
568
150
13
1,056
279
2
163
43
6/3
7
742
196
9
954
252
5
530
140
13
1.379
364
15
1.590
420
15
1,590
420
10
1,060
280
1
106
28
Waste-
l/Uo+ar
water
Volume
5.156
1,362
2,476
654
3,134
828
5,190
1,371
4,618
1,220
5,307
1,402
4,425
1,169
602
159
Waste-
water rer
Capita
151.6
40.1
72.8
19.2
92.2
24.4
152.6
40.3
135.8
35.9
156.1
41.2
130.1
34.4
17.7
4.7
-------
TABLE 8
PRESSURE SYSTEM PARTICIPATING RESIDENT WATER USE
Date
8/ 9/76
9/ 9/76
10/11/76
10/18/76
10/19/76
10/20/76.
10/21/76
10/22/76
10/23/76
10/24/76
10/25/76
10/26/76
12/13/76
a/12/77
2/ 8/77
2/9/77
2/10/77
2/11/77
2/12/77
2/13/77
Water use - liters per day (Volume in liters tiines 0. 264 equals volume in gallons)
No.
of
Days
31
31
32
7
1
1
1
1
1
1
1
1
48
30
26
1
1
1
1
1
Pump
Sta.
No. 1
5, 150
820
740
710
1,190
400
620
.1, 160
1, 730
450
680
990
820
540
680
570
590
370
790
510
Pur
N
a
5,100
2,320
1,730
590
990
930
400
570
1,330
400
930
680
620
590
540
510
480
400
480
2,010
np Sta.
o. 2
b
6, 850
3, 620
5, 720
3,990
400
- 650
400
570
60
5,490
310
2, 100
650
570
450
620
Pump Sta.
No. 3
a
11, 330
9,290
7,480
5,970
880
910
1,440
740
2, 630
2,920
1,730
790
1,420
1,930
1, 610
1,190
1,220
1,470
2, 270
13,250
b
7,500
5, 61.0
5..410
6,960
2, 100
2,320
1.870
2,940
6,060
2,520
2,580
1, 700
2,210
2,120
1,250
1,, 440
12,430
Pump Sta.
No. 4
a
5,520
3,480
2, 580
2,920
710
1,730
1, 300
1,080
2,070
230
1,080
1,670
590
710
650
510
1,080
570
620
790
b
7, 250
6, 170
3, 540
850
960
760
570
570
1, 870
250
790
340
710
480
680
820
650
790
820
820
Pump
Sta.
No. 5
8, 640
4,020
2,070
4,420
1,160
850
960
1,470
3,710
880
710
740
930
740
880
850
850
760
790
910
Pump Sta.
No. 6
a
5, 300
3, 570
4, 560
2, 630
450
680
370
540
1, 560
650
620
370
570
620
540
370
370
930
450
510
b
8,720
9, 120
5,690
5, 550
760
400
620
650
2, 770
960
590
880
820
790
850
910
540
820
1,440
5, 780
c
4,190
3, 880
3, 170
1, 270
0
540
400
450
930
310
310
570
400
400
370
310
280
250
310
250
-------
TABLE 8 (Cont. )
Date
3/10/77
4/12/77
5/16/77
6/16/77
7/18/77
7/19/77
7/20/77
7/21/77
7/22/77
7/23/77
7/24/77
Water use - liters per day (Volume in liters times 0. 264 equals volume in gallons)
No.
of
Ltys
25
33
34
31
32
1
1
1
1
1
1
Pump
Sta.
No. 1
588
695
684
571
821
1, 148
453
914
1 , 223
19
0
Pump Sta.
No. 2
a
466
2,445
4,799
3,141
8,240
2,503
6,457
9,014
9,727
5,740
540
b
__
4,050
6,338
11,336
16,120
7,888
16,037
25,095
1,216
974
Pump Sta.
No. 3
a
1,706
2,371
7,756
6,624
2,877
3,255
22,222
16,343
18,008
10,176
16,339
b
2,097
3,607
4,096
5,248
8,900
1,624
1,597
12,725
6,604
4,184
11,328
Pump Sta.
No. 4
a
596
1,640
1,611
3,095
5,685
8,719
11,875
2,462
8,436
9,364
219
b
553
1,200
5,181
5,530
10,409
7,476
15,610
10,629
26,640
9,716
8,451
Pump
Sta.
No. 5
809
1,712
3,143
3,914
7,678
6,548
9,583
7,858
10,320
3,274
963
Pump Sta.
No. 6
a
471
1,210
1,956
1,359
6,111
3,950
7,797
15,255
3,353
9,802
53
b
937
3,585
5,606
6,798
11,316
4,524
8,953
17,743
7,658
12,246
9,988
c
335
1,194
1,590
2,735
6,888
2,673
2,549
7,816
8,152
6,940
1,624
-------
TABLE 9
VACUUM SYSTEM OPERATING PARAMETERS
(Measured October 25,1976)
Vacuum Pump Operating State Hg(cm)
Vacuum Pump Off
Lead Vacuum Pump On
Lag Vacuum Pump On
Low Vacuum Alarm
50.5
40.6
35.6
25.4
Hg(inch)
19.9
16.0
14.0
10.0
Time for one pump to restore vacuum 51 second*
Vacuum Valve
Number
t
Z
3
4
5
6
7
8
Volume Evacuated
Per Valve Cycle
(liter) (gal)
61.1
62.1
44.3
41 JB
643
117.3
65.1
51 &
135
16.4
11.7
11.0
17,0
31.0
17.2
13.6
Valve Open
Time
(seconds)
11.7
7.2
8.5
7.8
6.0
6.9
5.0
5.6
Liquid Evacuation
Time
(seconds)
0.8
0.7
0.9
0.7
1.3
3.7
1.6
0-8
Liquid Velocity In 3" Pipe
(meter/sec) (ft/sec)
14.0
19.4
10.7
13.0
10.8
6.9
8.9
14.0
45.8
63.7
36.3
42.7
35.B
22.8
29.2
462
Volume evacuated by discharge pump cycle 1.5 cubic meters
100 gallons
Discharge pump operating time - 65 seconds
The vacuum valve sump level sensors and operating timers were
adjusted by Airvac personnel at the beginning of the project monitoring
period. It can be noted that the valves most distant from the collec-
tion station were set with considerably longer "open" times than recom-
mended by Airvac design literature-, which recommended that . . . "the
valve open for a total time equal to twice the time required to admit the
sewage. "
The high transport velocities that can be reached in the two-phase
flow of vacuum systems, relative to pumped systems, is indicated in
Table 9. It has been observed that the turbulence in high-velocity vacuum-
system transport disintegrates most sewage solids very effectively.
62
-------
Vacuum System Valve and Pump Operation Frequencies--
The recorded frequencies of operation of vacuum valves, vacuum
pumps and discharge pumps is presented in Table 10. As with the pressure
system it should be kept in mind that valve operations must be multiplied
by the evacuated volume of each sump, which are not the same for all
sumps, to obtain the volumes of wastewater generated.
Considerable difficulty was encountered in obtaining data that was
deemed reliable from the vacuum valve operation monitoring system. In
some cases the monitoring system would not produce the desired indicating
marks on the strip-chart recorder paper when valve operations were known
to be occurring; at other times the monitoring system appeared to be pro-
ducing spurious indicating marks on strip-chart channels which were be-
lieved to be not operating. For example vacuum valve No. 1 shows very
infrequent operation, while water use data presented later in this section
indicates that the resident was probably home during most of the monitor-
ing periods. However, because there was no basis for differentiating be-
tween good and bad data, the data is presented as it was collected.
Table 10 shows an increase in the frequency of operation of the vac-
uum pumps during the year of monitoring. Deterioration in the efficiency
of the pumps would result in the pumps running longer to re-establish va-
cuum. Leaks in the vacuum system (and possibly through the pumps)
would result in more frequent operation of the pumps.
Vacuum System Wastewater Volumes--
The volumes of wastewater collected by the vacuum system, derived
by multiplying the evacuated volume of sumps by .the number of recorded
valve operations is presented in Table 11. The volume of wastewater
evacuated by operation of the discharge pumps is also shown in Table 11.
Considering the questionable reliability of the vacuum valve operation
data, discussed above, the wastewater volumes derived from operation of
the discharge pumps is considered more reliable; The wastewater volumes
calculated from the vacuum valve
greater than volumes calculated from the discharge pump operations.
As with the pressure system the average per capita wastewater gen-
eration is surprisingly low, generally being in the range of 115 to 189
liters (30 to 50 gallons) per capita day. However, the wastewater col-
lected from individual vacuum valve installations varies considerably.
The data from vacuum valve No. 1 is not considered reliable. The resi-
dence connected to vacuum valve No. 7 was vacant during most of the mon-
itoring period. The residences connected to vacuum valves Nos. 2, 3, 4,
and 8 have low to moderate per capita wastewater generation (relative to
this project data) while the residence connected to valve No. 6 has rela-
tively high per capita wastewater generation.
63
-------
TABLE 10
VACUUM SYSTEM VALVE AND PUMP OPERATION FREQUENCY
Hour
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
Date
i
r^
CT^
i
•5 «s
_i ^^ ft .
c w
0^
^J5"
£
i
•«
H
5!
xO ^H
ri^
•8 «
W CO
0) ^
H^
^ ,
<
rl
£
|
Operations per hour
No. residences
M
z/,
'/,
Vi
5/,
6/3
%
8/2
Vacuum
pump no .
1
1
2
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
2
1
1
2
1
1
1
1
2
1
1
1
1
1
1
1
1
2
1
2
1
1
1
Discharge
pump no.
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
64
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
r-
r-
*
62 -
'
s!
"fi ^CL
° rrt
J-c
•8
tu
rH
y
2
I^H
Is"
H s»-
0)
to
•«:
•4
»
l*H
PH
1
Operations per hour
Vacuum valve No,/ No. residences
K
1
2/>
1
1
1
2
2
1
1
1
1
Vi
1
1
1
1
*A
1
1
1
1
1
1
1
1
1
2
1
1
2
1
1
5/:
1
1
1
1
1
6/3
1
1
1
2
2
1
1
1
1
1
2
1
1
1
3
1
1
3
1
1
1
1
Vi
Yz
1
1
1
1
Vacuum
pump no .
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
2
1
1
1
2
1
1
i
i
i
i
2
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
2
1
1
2
2
1
Discharge
pump no.
1
1
1
1
1
1
1
2
1
1
1
1
1
1
65
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
s
I
g
0—i
r-
>*rt
ri »
m fi
•§ »H"
j£ d
rQ
to
^
c
1
r-
i— i
•J* *
JH
"5 -"IS
3 fT*
i-fl Ctf '
jo
^
LXJ
1
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
•r-
r-
rH
T>£»
™ >>P.
3 S
,0
r
PH
•^H
*
^
^^*
C^
%
«J -1
*T
PH §
£
OJ
S
CU
Operations per hour
Vacuum valve No. /No. residences
2
3
V,
1
1
V,
1
1
1
1
'•
2
1
V,
I
3
1
1
1
1
1
3
1
2
1
1
5
1
1
1
*A
1
1
1
1
6/3
2
1
1
1
1
1
1
1
1
1
1
1
1
5
4
1
1
1
V,
1
6
1
1
1
8/2
1
1
1
1
2
2
1
Vacuum
pump no
1
1
2
1
1
1
2
1
2
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
1
1
1
2
2
1
2
2
2
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
2
2
1
1
1
1
1
1
Discharge
pump no.
1
1
1
1
1
1
1
1
>.
1
1
2
1
1
1
1
1
1
1
67
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
y
3
i^n
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8-9
9-10
10-11
11-12
Date
^
r-
i—i
>>0\
rt ^
§ Jj
fn
•s
to
2
^
ts.
r-
!•" "I
n) N_ .
'O L
rt ^*
O
h
Q
a)
h
2
ft
. '
Operations per hour
Vacuum valve No,//No. residences
2/!
1
1
2
2
Vi
1
1
1
Vi
1
1
1
1
1
1
2
2
4
5
1
1
1
V,
1
1
1
1
1
0/3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
3
3
6
1
1
1
7/i
1
1
8/2
1
1
1
1
1
1
2
1
1
1
1
1
Vacuum
pump no
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
2
1
2
2
1
1
1
1
1
1
2
1
1
1
1
2
i
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
2
1
1
1
1
1
1
1
Discharge
pump no.
1
1
1
1
1
1
1
2
1
1
1
1
1
1
69
-------
TABLE 10
( Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
><
3
(«H
[s.
r-
"""*
nT£J
03 >.
-------
TABLE 10
(Cont. )
Hour
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 1
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
5- 6
6- 7
7- 8
8- 9
9-10
10- 1
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
t
TJ r-l
CO
fl> »
a 0s
S3: *
rt
c
s
r
1<
Operations per hour
Vacuum valve No. /No. residences
'/'
2/i
1
. -
1
y.
i
i
y.
i
i
i
i
i
i
i
i
i
2
2
1
1
2
1
1
1
1
5/i
1
1
1
1
.
1
1
6/3
1
2
1
1
1
1
2
1
1
1
1
1
1
1
5
1
1
1
l
X
1
1
2
3
1
1
•^••Mi^MMI
?/l
1
1
1
1
1
8/2
1
1
1
1
1
2
1
i
A
1
1
Vacuum
pump no*
1
2
Discharge
pump no.
1
2
71
-------
TABLE 10
/ /"• „ „ t \
(Uont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 1
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
Date
'
s
r^a
CT^
rt ""
T3 .
to O
-^ •§
H ri
s.
«w IM
§
4
j
2
s-«
T3 N^Jffc
03 (\J^
A
2
2
1
1
2
1
1
Vi
1
1
2
1
5
1
1
1
"/
1
1
1
1
6/3
1
1
5
1
1
1
•
3
1
1
1
1
1
1
1
1
1
"I
1
y.
i
s/2
i
i
i
i
i
Vacuum
pump no.
I
i
i
i
3
3
1
2
1
2
1
2
2
1
2
2
1
1
2
2
Discharge
pump no .
1
1
1
1
1
2
1
1
72
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
Date
<
%
^—
<
f'
«r<^
01
a* £
-o _J
o^
~~ "
t—
rt0^
T3 ^
CO • «<
^00
-------
TABLE 10
(Gont. )
Hour
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4. 5
5- 6
6- 7
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
Date
f
<;
^
P-
r*^
^^O^
C^*""* «^
rO *^
S^" c
d***
g
t»
3^
To"1 '
fl2 "*
4) !>>
^5J
^
'
Operations per hour
Vacuum valve No. / No. residences
'/'
'/
1
1
1
1
1
1
1
3/
1
1
4/
1
5/>
1
1
1
1
6/3
1
2
1
1
2
3
1
1
1
1
1
1
1
1
1
1
1
1
1
y.
i
8/2
i
4
1
1
1
1
1
Vacuum
pump no.
1
1
3
3
5
4
4
5
5
5
4
3
4
5
4
2
4
4
4
4
3
3
4
4
4
3
4
4
4
3
2
2
3
4
4
5
4
4
5
4
4
3
5
4
4
3
3
4
3
4
3
3
5
5
2
4
3
4
4
2
Discharge
pump no .
1
1
1
1
1
1
1
2
1
1
1
1
1
74
-------
TABLE 10
(Cont. )
Hour
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
Date
S
<
ixr^n
flj 0s
fTJJ A^
m
•3 i»
H 3
r-v>!
£•
i?
Operations per hour
Vacuum valve No
'/
'/
1
'/.
1
1
4/>
i
i
i
i
i
i
i
i
2
2
1
. / No. residences
5/a
1
1
6/3
1
2
2
2
4
5
1
1
2
1
1
1
1
1
2
1
7/.
1
1
1
"'
8/2
Vacuum
pump no.
1
2
Discharge
pump no.
1
2
5- 6
6- 7
7-8
8- 9
9-10
10-11
11-12
• w .
M «^
S !U
aj _bj.
*^,
1
1
3
6
1
1
1
1
1
3
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
75
-------
TABLE 10
(Cont. )
Hour
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
11-12
12- 1
1- 2
2- 3
3- 4
4- 5
5- 6
6- 7
7- 8
8- 9
9-10
10-11
Date
i
<
<
>&'
T3'-«
«J
-a*"*
H >?
§
p*
3
c
r-
r*-
~
ft ..
k
H
3^J
£^
£
i
-f
i
Operations per hour
Vacuum valve No. /No. residences
'/
2/
y.
i
V
1
y.
i
i
i
i
i
i
i
i
2
1
y.
i
6/3
2
1
1
1
1
1
3
4
1
1
1
1
6
1
1
2
1
1
2
2
1
1
1
1
5
"2
7/
1
1
1
y.
Vacuum
pump no.
1
2
1
2
1
2
2
1
3
2
2
3
2
1
2
1
2
3
2
2
2
3
1
2
2
3
1
2
2
1
2
2
2
3
3
*»*. 2
2
2
2
1
2
1
2
2
2
2
3
2
2
1
2
2
1
3
3
2
1
3
2
2
2
2
2
1
2
2
2
2
2
3
2
3
Discharge
pump no.
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
76
-------
TABLE 11
VACUUM SYSTEM WASTEWATER VOLUMES
Date/Time
i^ieraalani
NmBQWy
February 14. 1977
12:01 PM to
11:69 PM (12 houn)
Tuesday
Primary 15, 1977
Wednesday
February 16, 1977
Thursday
February 17, 1977
Friday
February 18, 1977
Saturday
February 19, 1ST?
Sunday
February 20, 1977
Unit
No. Vstoe Operations
Volume/Residence liter
Volume/Residence gel
No. Vetw Operation!
Volume/Residence liter
Volume/Residence gal
No. Vain Operations
Volume/Residence liter
Volume/Residence gel
No. Valve Operations
Volume/Residence filer
Volume/Residence gel
No. Vahre Operations
Volume/Residence liter
Volume/Residence gel
No. Vatn Operation*
Volume/Residence liter
Volume/Residence gel
No. Vahn Operations
Volume/Residence liter
Volume/Residence gal
Vacuum Valve No, /No. Residence*
1/1
0
0
0
1
S3
14
1
53
14
2
102
27
5
256
68
0
0
0
1
53
U
2/1
7
435
115
4
250
66
4
250
66
3
186
49
1
62
16
2
124
33
>. 1
63
17
3/1
3
133
35
1
45
12
8
354
94
6
266
70
4
177
47
2
89
23
1
44
12
4/1
5
208
55
12
500
132
16
666
176
15
625
165
18
749
198
23
953
253
12
500
132
5/1
3
193
51
2
129
34
3
193
51
3
193
51
2
129
34
8
515
136
3
193
51
6/3
10
1173
310
19
2230
589
16
1878
496
15
1760
465
18
2112
558
19
2230
589
16
1878
496
7/1
0
0
0
0
0
0
0
0
o
0
0
0
6
390
103
0
0
0
1
65
17
8/2
1
51
14
3
154
41
5
257
68
5
257
68
6
309
82
IS
772
204
9
463
122
No. Valve Opera-
tions end Waste-
water Volume
29
2195
590
42
3361
888
53
3653
968
49
3388
895
60
4187
1106
69
4686
1238
44
3259
861
No. Vacuum
Pump
Operations
Z7
47
51
52
47
48
44
No. Discharge
Pump Operations
4
8
11
12
8
8
6
Wastewater
Volume from
Discharge Pump
Operatiom
1514
400
3028
800
4164
1100
4542
1200
3028
800
3028
800
2271
600
Wane water
Volume
per Capita
65.8
17.4
131.7
34.8
181.0
47.8
197.5
52.2
131.7
34.8
131.7
34.8
98.7
26.1
-------
TABLE 11. Contftiuetf
VACUUM SYSTEM WASTEWATER VOLUMES
Dan/fiim
Monday
February 21, 1977
Tuetday
February 22. 1977
Wednesday
February 23, 1977
12:01 AM to
11:00 AM (11 hours!
Tuesday
March 8. 1977
9:00 AM to '
Midnight (15 hour.)
Wednesday
March 9, 1977
Tfwndey
March 10, 1977
MMnight to
3:00 PM US noun)
Tuodiy
AprB 26. 1977
(3:00 AM to
MMmght 415 hours)
UrJt
No. Valve Operation!
Volume/Rendence liter
Volunw/Rendwm oal
No. Vain Operation
Volume/Residence liter
Vohima/Reiidenca gal
No. Valve Operations
Voluma/Reudencg liter
Volume/Residence gal
No. Valve Operation*
Volume/Residence liter
Volurw/RwkkirK* yi
No. Valve Operation)
Volume/Residence filer
Vblurne/Retidenc* gal
Mo. Value Operation!
Volume/Reaideiica liter
Vohime/Reiidence gal
Ma. Vain Operation!
Voluma/ftawtooc. liter
Volume/Residence gal
Vacuum Valva Mo./Mo. Rnjdencei
1/1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2/1
6
372
98
4
253
67
0
0
0
1
62
16
1
62
16
2
124
33
2
124
33
3/1
2
89
23
3
133
35
1
44
12
1
44
t2
2
89
23
2
89
23
8
168
44
4/1
17
708
187
20
833
220
6
250
66
15
625
166
13
541
143
10
146
110
3
125
33
5/1
4
257
68
5
322
85
2
129
34
5
322
35
3
193
51
2
129
34
2
129
34
6/3
23
2699
713
2
1995
527
6
704
186
23
2699
713
7
2347
620
10
1173
310
15
1760
465
7/1
2
130
34
17
130
34
0
0
0
5
326
86
49
195
52
1
65
17
0
0
0
a/2
9
463
122
2
360
95
4
206
54
7
352
93
360
95
5
257
68
3
195
51
tto. Valve Opera-
tkinf tndWut*-
witer Volume
53
4713
1245
7
4023
1063
19
1332
352
57
4429
1170
3785
1000
32
2252
595
33
2498
660
No, Vacuum
Pump
Operation!
47
44
17
26"
No. Oiichargt
Pump Operation*
9
8
2
6
Waste water
Volume from
Discharge Pump
Operation!
3407
900
3028
800
757
200
227t
600
Wattewater
Volume
per Capita
148.1
39.1
131.7
34.8
32.9
8.7
93.7
26.1
oo
-------
TABLE 11. Continued
VACUUM SYSTEM WASTEWATER VOLUM
tatt/Tbne
Wednesday
April 27. 1977
Thursday
April 28. 1977
Mdndhl to
11:00 AM 111 hour.)
Tuesday
May 17. 1977
9:00 AM to
Mdnight (15 houn)
Wednesday
May 18, 1977
Midnight to
1:00 I'M (1$ hounl
Thursday
July 7, 1977
10:00 AM to Friday
July B. 1977 (24 houn
MfjAnnrf-n' "'
IIVWK9DMY
July 13, 1977
6:00 PM to Thunday
July 14. 1977
5:00 PM 124 houn)
Thuretoy Jury 14. 1977
5:00 PM to Friday
July 15. 1977
11:00 AM (18 houn)
Unit
No. Valra Operations
Volurm/R«itdence liter
Volume/Rendenca gal
No. Valm Operations
Volume/Residence liter
Volume/Residence gal
No. Valve Operations
Volume/Residence liar
Volume/Residence gri
No. Valve Operations
Volume/Residence liter
Volume/Residence gal
'"
No. VaTra Operation.
Volume/Rewdenca \torn
Volume/Residence gal
No. Valv« Operationr
Votnmc/Rnidanca Mw
Vohime/RwidwHM gal
No. Vulva Operation!
Volume/Residence
Vohmw/Randmoa
S
Vacuum Vain NojNo. Reiidence*
VI
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
b
2fl
6
372
98
2
124
33
3
186
4ft
3
186
49
1
62
16
0
; o
;" 0
0
0
0
an
4
177
47
1
44
12
1
44
12
1
44
12
2
89
23
2
89
23
1
44
12
4/1
3
125
33
1
42
11
1
42
11
0
0
0
13
541
143
5
208
56
7
291
77
5/1
4
257
68
1
64
17
2
129
34.
2
129
34
2
129
34
3
193
SI
0
0
0
S/3
19
2230
589
11
1291
341
15
1760
465
8
939
248
28
3286
868
35
4107
1085
'15
1760
465
7fl
1
64
17
0
0
0
1
64
17
0
- 0
0
2
130
34
2
130
34
1
64
17
8/2
10
515
136
5
2S7
68
6
309
82
4
206
54
0
0
0
0
0
0
0
0
0
No. Vain Opera-
tions and Waste -
water Volume
47
3740
988
21
1825
482
29
2536
670
18
1503
397
48
4232
1118
4724
1248
24
2161
571
No. Vacuum
Vump
Operations
40*
16*
99
90
94
75
No. Discharge
Pump Operations
9
4
6
5
16
6
Waste water
Volume from
Discharge Pump
Operations
3407
900
1514
400
2271
600
1893
500
6057
1600
2271
600
Wastewater
Volume
per Capita
148.1
39.1
65.8
17.4
98.7
26.1
82.3
21.7
263.3
69.6
98.7
26.1
•Operation of only one vacuum pump recorded.
-------
Vacuum System Resident Water Use —
Water recorded to have been used by homeowners connected to the
vacuum system during the project monitoring period is presented in Table
12. Patterns of water use were similar to those observed in the pressure
system. There was unrestrained use of water during summer months, up
to many thousands of liters per day per residence, apparently for lawn
irrigation. In contrast during winter months water use dropped to gener-
ally less than 1, 000 liters (260 gallons) per residence.
ENERGY CONSUMPTION
Pressure System
The record of electrical energy used by the pressure system is pre-
sented in Table 13. It should be noted that Meter No. 1 totalized energy
consumed by Pump Stations Nos. 1, 2, 3, and the pressure system moni-
toring station. Meter No. 2 totalized energy consumed by Pump Stations
Nos. 4, 5, and 6. It is immediately apparent from Table 4 that Meter No.
2 indicates a relatively constant energy consumption near 2 kwh per day
with occasional values up to 5 kwh per day. In contract, energy consump-
tion indicated by Meter No. 1 varies from 2 to 17 kwh per day. The higher
energy consumption indicated by Meter No. 1 can be accounted for by the
heater and ventilating fan in the monitoring station. Increased energy con-
sumption in the monitoring station can be correlated with hot weather in
August and September and cold weather beginning in December. The heater
and ventilating fan in the monitoring station were controlled by a thermo-
stat and operated intermittently. Energy consumption by the heater and
ventilating fan cannot be separated from pump energy consumption.
No explanation is apparent for the low energy consumption recorded
by Meter No. 1 for the period September 9, 1976 to October 11, 1976.
The low energy use indicated may have been caused by an error in read-
ing the meter.
Each of the electrical control boxes contained a continuously energized
20-watt strip heater. Energy consumption of approximately 1. 44 kwh per
day should therefore be subtracted from each of the daily energy consump-
tion figures for Meter No. 2 to obtain sump-pump energy consumption.
The energy consumption data for Meter No. 2, corrected for the strip
heaters, indicated average energy consumption by each pump to be approxi-
mately . 26 kwh per day. This represents a cost of less than $0. 01 per
day at current electrical prices in Bend.
80
-------
TABLE 12
VACUUM SYSTEM PARTICIPATING RESIDENT WATER USE
Date
8/9/76
9/9/76
10/11/76
10/12/76
10/13/76
10/14/76
10/15/76
12/13/76
1/12/77
2/15/77
2/16/77
2/17/77
2/18/77
2/19/77
2/20/77
Water use - liters per day (Volume in liters times 0.264 equals volume in gallons)
No.
o£
Days
31
31
32
1
1
1
1
59
30
34
1
1
1
I
1
Valve
No. 1
14,330
10,680
5,860
1,530
7,700
1,300
11,210
1,500
850
1,020
760
1,130
1,780
7,560
9,480
Valve
No. 2
16,960
9,880
9,200
3,650
2,860
2,240
37,040
1,360
370
510
450
480
540
230
12,320
Valve
No, 3
4,220
4,050
1,760
2,270
11,270
170
570
80
200
170
140
510
420
590
200
Valve
No. 4
13,900
9,600
21,270
5,550
13,310
5,320
12,260
1,360
570
7,990
510
3,710
850
Valve
No. 5
1,780
1,470
1,300
1,420
740
1,020
1,950
960
880
760
590
740
Valve No. 6
a
4
50
130
140
260
100
100
150
390
340
500
280
350
b
3,650
2,180
1,610
910
310
450
540
310
310
280
370
340
1,360
230
340
c
960
5,780
310
170
170
140
400
HP
80
140
60
140
110
140
80
Valve
No. 7
1,190
230
110
400
200
60
230
310
1,840
230
230
200
1
Valve
a
880
1,360
620
1,810
400
620
930
760
880
790
420
540
480
510
790
Mo. 8
b
2,770
930
540
510
420
340
850
1,270
1,190
340
310
590
370
-------
Table 12 (Cont.)
Date
3/10/77
4/1Z/77
5/16/77
6/16/77
7/11/77
7/12/77
7/13/77
7/14/77
7/15/77
7/16/77
7/17/77
Water use - liters per day (Volume in liters times 0. 264 equals volume in gallons)
No.
of
Days
18
33
34
31
25
1
1
1
1
1
1
Valve
No. 1
852
3,570
6,485
10,019
17,991
19,152
— —
31,718
20,409
31,201
27,625
Valve
No. 2
395
3,651
16,027
10,640
18,418
18,971
24,967
19,178
13,798
18,804
Valve
No. -3
115
871
4,343
5,075
11,909
35,245
4,320
9,149
6,850
12,627
13,001
Valve
No. 4
2,244
2,955
20,631
19,049
15,740
26,443
5,724
31,715
2,092
20,927
22,214
Valve
No. 5
775
1,336
10,077
10,323
9,276
789
1,665
11,234
710
1,348
7,273
Valve No, 6
a
388
370
397
388
0
0
0
0
0
26
0
b
274
620
1,526
1,949
4,427
4,860
691
1,748
1,424
5,732
5,056
c
140
102
94
61
39
83
49
38
22
49
4
Valve
No. 7
148
163
169
134
113
276
83
170
0
Valve No. 8
a
-•_j —
1,015
1,392
2,718
944
2,065
1,295
1,484
986
951
789
b
357
419
1,866
2,396
552
344
400
683
525
548
306
oo
-------
TABLE 13
PRESSURE SYSTEM ENERGY CONSUMPTION
Period
Ending
8- 9-76
9- 9-76
10-11-76
10-18-76
10-19-76
10-20-76
10-21-76
10-22-76
10-23-76
10-24-76
10-25-76
10-26-76
12-13-76
1-12-77
2- 7-77
2- 8-77
2- 9-77
2-10-77
2-11-77
2-12-77
2-13-77
3-10-77
4-12-77
5-16-77
6-16-77
7-18-77
7-19-77
7-20-77
7-21-77
7-22-77
7-23-77
7-24-77
Number
of Days
31
31
32
7
1
1
1
1
1
1
1
1
48
30
26
1
1
1
1
1
1
25
33
34
31
32
1
1
1
1
1
1
Meter No. 1
Pump Stations Nos.
1,2,3, & Monitoring
Station (kwh/day)
5.77
5.39
0. 19
1.86
3. 0
4.0
3.0
3.0
7.0
3.0
3.0
4.0
7. 63
16. 16
15.38
17:0
16.0
11.0
12.0
1 1 . 0
12.0
17. 28
11.06
11.62
7.84
5.91
7. 0
5.0
5.0
5.0
4.0
4.0
Meter No. 2 1
Pump Station
Nos. 4, 5, 6
(lovtdi/flliacy)'
1.84
2.00
2.09
2.14
3.0
2.0
2.0
2.0
5. 0
3.0
2.0
2.0
2.31
2.47
2. 42
3.0
5. 0
i . ,- -
3.0
2.0
3.0
2.0
2.40
2. 30
2. 29
2,52
1.7.5 :
2.0
2.0
2.0
4.0
2.0
2. 0
83
-------
Energy consumption by the monitoring system would not be applicable
to a nonresearch project. If pump control boxes were installed indoors,
instead of outside, the strip heaters would probably be unnecessary.
Vacuum System
Electrical energy consumption by the vacuum system is tabulated in
Table 14. As noted on Table 14, Meter No. 1 recorded energy consump-
tion by the vacuum pumps, Meter No. 2 recorded energy consumption by
the discharge pumps, and Meter No. 3 recorded energy consumption by the
vacuum station fans, heaters and lights. The vacuum pumps consumed an
average of approximately 7. 5 kwh per day, with a range from 5. 0 to 13. 8
kwh per day. The period of highest energy consumption corresponds to the
period shortly before "Vacuum Pump No. 1 was rebuilt and perhaps resulted
from loss of pump efficiency. The energy consumption data in Table 14
appears to show slightly more efficient operation during colder weather
and an increase in energy consumed over the year of operation. Whether
the increase in energy consumed resulted from development of leaks in the
system or deterioration of pump efficiency was not determined.
The discharge pumps are recorded to have consumed an average of
approximately 1.16 kwh per day with a range of . 71 to 2. 0 kwh per day.
A range of energy consumption by the discharge pump could be expected
because the pumps operate against varying heads depending on the vacuum
in the system, in addition to the range of energy consumption that would
have resulted from the variation in the volume of waste water produced.
Station power consumption for fans, heaters and lights ranged from 3
to 14 kwh per day, with an average of approximately 6. 27 kwh per day.
Peaks of energy consumption by the vacuum station correspond to hot or
cold weather. Only an insignificant part of energy consumption by the vac-
uum system can be credited to the monitoring system. Station heating and
ventilating would be required whether the monitoring system were installed
or not.
Average electrical energy consumption by the vacuum system appor-
tioned between the eleven participating homeowners was approximately
1. 36 kwh per household per day. This represents an average cost of ap-
proximately $0.04 per day, at current electrical prices in Bend.
84
-------
TABLE 14
VACUUM SYSTEM ENERGY CONSUMPTION
Date
8- 9-76
9- 9-76
10-11-76
10-12-76
10-13-76
10-14-76
10-15-76
12-13-76
1-12-76
2-15-77
2-16-77
2-17-77
2-19-77
2-20-77
3-10-77
4-12-77
5-16-77
6-16-77
7-11-77
7-12-77
7-13-77
7-14-77
7-15-77
7-16-77
7-17-77
Number
of days
31
31
32
1
1
1
1
59
30
34
1
1
2
1
18
33
34
31
25
1
1
1
1
1
1
Meter No. 1
Vacuum Pumps
kwh/day
7.39
6. 10
5.97
7.0
5.0
6.0
7.0
6.42
5.63
5.23
6.0
5.0
6.0
5. 0
5.56
5.61
13.85
9.94
11,88
10.0
9.0
10.0
8.0
10.0
10.0
Meter No. 2
Discharge Pumps
kwh/ day
1.71
.71
.91
2.0
2.0
1.0
1.0
1. 20
1.37
1.06
1.0
2.0
1.0
1.0
1.44
1.09
1.09
1.16
1. 20
1.0
2.0
1.0
1.0
1.0
2.0
Meter No. 3
Station
kwh/day
5. 52
3.71
2.56
5.0
3.0
3.0
4.0
5.81
14.4
11.7
6.0
6.0
8.0
5.0
8. 28
5. 58
3. 15
3.90
6. 12
6.0
5.0
8.0
5.0
6.0
6.0
85
-------
EFFLUENT AND SEWAGE CHEMICAL CHARACTERISTICS
Chemical characteristics of septic-^ank effluent and sewage samples
collected from the pressure and vacuum systems are tabulated in Tables
15 and 16. The samples were collected by apparatus described in Section
3. As described in Section 3 the sampling pump was electrically inter-
connected to operate whenever any of the low pressure system pumps or
either of the vacuum system discharge pumps were operating, with intent
to allow collection of representative, composited samples proportioned to
wastewater flow rates.
A 24-hour composited sample was collected from each system on an
approximately monthly basis. Samples were also composited for each
system during succeeding six-hour periods over a 24-hour period during
each of three intensive monitoring periods. The 24-hour diurnal study
periods are indicated on Tables 15 and 16.
Temperature, pH, and dissolved oxygen were measured in fresh grab
samples collected at the site. The remaining chemical characteristics
were measured from composited samples, at the Bend wastewater treat-
ment plant laboratory.
The average and extreme values of some of the chemical character-
istic data from the septic tank effluent and raw sewage samples analyzed
for this project are compared in Table 17 to similar data reported for sep-
tic tank effluent by EPA - and for raw domestic sewage by Metcalf and
Eddy-.
Temperature
The temperatures of both the septic tank effluent and the raw sewage
apparently follow seasonal temperature fluctuations, which is to be ex-
pected considering that in both systems the sumps and pipes provide ample
time for heat exchange with the air through the sump covers and with the
soil. The raw sewage in the vacuum system was two to four degrees
warmer than septic effluent from the pressure system in both extreme
and average valves.
With only a few exceptions the pH of the septic tank effluent were a
few tenths of a pH unit below neutral while the pH of the raw sewage
ranged up to 1.5 pH units above neutral.
86
-------
TABLE 15
PRESSURE SYSTEM SEPTIC EFFLUENT CHARACTERISTICS
i— . DIURNAL STUDY— —
i
i
Time and Date of
Sample Collection
0900 August 17. 1976
to
0900 August 18, 1976
C9CO August 25, 1976
to
OCOO August 26. 1976
05 00 October 21. 1976
lo
11CO October 21. 1976
1100 October 21. 1976
to
1700 October 21. 1976
1700 Octooer 21, 1976
to
2300 October 21, 1976
2300 October 21, 1976
to
0500 October 22, 1976
0800 October 30. 1976
to
0800 November 1,1976
0800 November 23, 1976
to
0800 November 24, 1976
0830 December 28. 1976
to
0830 December 29, 1976
0815 January 25, 1977
to
0830 January 26. 1977
1700 February 9. 1977
to
2300 February 9, 1977
2300 February 9, 1377
to
ODOO February 10, 1977
0500 February 10, 1977
to
1100 February 10, 1977
1100 February 10. 1977
to
1700 Februwy 10, 1977
Temp
°F
62
58
56
62
56
52
56
44
38
52
52
CO
54
aturs
°C
16.7
14.4
13.3
16.7
13.3
11.1
13.3
6.7
3.3
11.1
11.1
15.6
12.2
pH
6.5
6.5
6.6
6.7
6.7
6.5
7.1
6.8
6.6
6.6
G.9
7.1
. 6.8
7.2
Dissolved
Oxygen
mg/l
0.0
0.3
0.9
0.9
1.2
0.0
0.0
0.0
1.3
0.0
0.5
5.6
0.0
0.0
Alkalinity
(as CaCOs)
mg/l
163.0
174.0
174.5
185.5
159.0
157.0
163.0
217.0
216.0
203.5
250.0
224.5
204.5
247.0
Grease
mg/l
45.6
72.6
73.9
71.6
118.3
63.5
43.8
34.3
47.6
48.5
133.7
93.8
68.4
71.0
Totsl Ortho
Phosphate (P)
mg/I
8.1
9.4
8.1
8.3
7.0
6.9
10.7
7.4
9.5
< 11.1 ,
14.7
12.3
12.2
14.0
Total Kjeldahl
Nitrogen (N)
mg/l
34.7
33.G
36.5
41.2
32.2
30.1
33.3
42.5
42.3
46.0
46.8
41.2
37.2
47.9
Total
Sulfide (S)
mg/l
.06
1.03
1.02
1.08
1.09
1.18
1.62
2.13
3.08
1.05
1.18
1.14
1.21
1.21
Suspended
Solids
mg/l
39.0
35.0
17.0
30.0
31.0
45.0
31.3
36.0
16.0
33.0
34.0
26.0
36.0
39.0
BOD5
mg/l
160.0
212.5
128.8
173.8
93.8
151.3
157.5
117.5
267.0
198.0
182.0
182.0
1430
195.0
COD
mg/l
172.3
273.8
202.6
210.9
170.5
257.8
231.0
196.5
171.6
210.0
673.5
631 5
415 3
380.4
.DIURNAL STUDY— 1
1 DIURNAL STUDY— J
00
-J
-------
TABLE 15
PRESSURE SYSTEM SEPTIC EFFLUENT CHARACTERISTICS. Continued
1
3
00 k
00 -I
-------
TABLE 16
VACUUM SYSTEM SEWAGE CHEMICAL CHARACTERISTICS
1
£
3
u
J
Z
tc.
D
EJ
'
1 ii.»'DIURNAL STUDY
Time and Date of
Sample Collection
0900 August 16. 1976
to
0900 August 17, 1976
0830 September 27. 1976
to
0800 September 28. 1976
0500 October 14, 1976
to
1100 October 14. 1976
1100 October 14. 1976
to
1700 October 14. 1976
1700 October 14. 1976
to
2300 October 14. 1976
2300 October 14, 1976
to
0500 October 15, 1976
0830 November 22. 1976
to
0830 November 23, 1976
0900 January 4. 1977
to
0900 January 5. 1977
0800 January 18. 1977
to
0800 January 19. 1977
1700 February 16, 1977
to
2300 February 16. 1977
2300 February 16, 1977
to
0500 February 17. 1977
0500 February 17, 1977
to
1100 February 17, 1977
1100 February 17. 1977
to
1700 February 17. 1977
Temperature
°f
62
63
62
62
62
60
51
48
44
45
50
44
52
°C
16.7
17.2
16.7
16.7
16.7
15,6
10.6
8.9
6.7
7.2
10.0
6.7
11.1
PH
8.3
6.6
8.0
7.9
7.3
7.5
7.7
8.5
8.3
7.8
8.T
8.5
8.1
Dissolved
Oxygen
mg/l
0.2
0.3
0.3
0.6
0.0
2.8
1.9
0.5
3.6
0.2
0.1
0.5
0.7
Alkalinity
(as CaCO3)
mg/l
123.0
148.5
123.5
89.0
108.0
81.5
148.0
120.0
113.0
,-•
10t.O
125.0
131.5
Grease
mg/l
142.0
57.3
57.0
202,0
129.5
172.4
162.5
67.0
47.S
154.5
89.4
104.3
253.5
Total Ortho
Phosphate (P)
mg/l
3.7
5.1
2.9
2.9
2.2
2.7
1.5
3.8
3.2
3.1
2.0
2.7
3.8
Total Kjetdahl
Nitrogen (N)
mg/l
32.4
29.0
34.3
28.4
18.4
25.7
16.9
32.8
26.3
23.0
20.3
31.5
28.6
Suspended
Solids
mg/l
194.0
166.0
83.0
107.0
115.0
32.0
220.0
164.0
216.0
102.0
12.0
98.0
178.0
BOD5
mg/l
255.0
225.0
147.5
183.8
162.3
180.0
135.0
163.0
150.0
251.0
158.0
183.0
228.0
COD
mg/I
342.5
382.9
196.4
296.3
303.4
229.9
253.9
286.7
317.8
611.0
355.0
429.4
881.0
DIURNAL STUDY— —1
t DIURNAL STUDY |
00
to
-------
TABLE 16
VACUUM SYSTEM SEWAGE CHEMICAL CHARACTERISTICS. Continued
>— DIURNAL STUDY |
Time and Date of
Sample Collection
0800 March 8. 1977
to
0800 March 9,1 977
0800 April 27, 1977
to
0800 April 28, 1977
0800 May 17, 1977
to
0800 May 18, 1977
0800 July 7, 1977
to
0800 July 8, 1977
1700 July 18, 1977
to
2300 July 18, 1977
2300 July 13, 1977
to
0300 July 14,1977
0500 July, 14, 1977
to
1100 July 14, 1977
1100 July 14, 1977
to
1700 July 14, 1977
Average
Temi
Of
50
62
56
65
66
65
65
72
57.0
erature
°C
10.0
16.7
13.3
18.3
18.9
18.3
18.3
22.2
14.0
pH
8.5
7.60
8.5
8.4
6.6
8.2
8.0
8.2
8.0
Dissolved
Oxygen
mg/f
2.00
0.1
0.5
0.0
0.0
0.7
0.0
0.0
0.7
Alkalinity
(as CaC03)
tng/l
144.5
140.0
125.0
127.5
137.5
122.0
160.0
185.0
127.7
Grease
mg/!
57.6
71.2
54.5
70.7
161.3
68.7
85.2
115.9
110.7
Total Ortho
Phosphate
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TABLE 17
COMPARISON OF CHEMICAL CHARACTERISTICS DATA
FOR SEPTIC TANK EFFLUENT AND RAW SEWAGE
Chemical Characteristics
Alkalinity mg/1 as CaCO
Average
Range
Grease mg/1
Average
Range
Total Ortho Phosphate as P
Average
Range
Total Kjeldahi Nitrogen as N
Average
Range
Suspended Solids mg/1
Average
Range
BOD mg/1
Average
Range
COD (unf liter ed) mg/1
Average
Range
Septic Tank Effluent Data
Bend R & D
Project
204
157 to 250
65
34.3 to 133
10.4
7.0 to 14.0
40.9
30.1 to 50.0
36.4
16 to 56
157.0
93.8 to 267.0
276.0
170.5 to 673.5
EPA Data9
-
-
14.6
11.4 to 17.7
55.3
48.9 to 61.6
54
47 to 62
158
142 to 174
360
335 to 386
Raw Domestic Sewage Data
Bend R & D
Project
127.7
81.5 to 185.0
110.7
57.0 to 172.4
3.2
1.5 to 5. 1
28.4
16.9 to 43.3
164.1
12.0 to 369.0
187.7
125.0 to 255
363.3
196.4 to 611.0
Metcalf & Eddy
100
50 to 200
100
50 to 150
10
6 to 20
40
20 to 85
200
100 to 350
200
100 to 300
500
250 to 1000
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Dissolved Oxygen
It is interesting to note that the septic tank effluent samples frequently
had a trace of oxygen content, some over 1 mg/1. The anomolous reading
of 5.6 mg/1 on February 9-10, 1977 is viewed with some skepticism. The
raw sewage in the vacuum collection tank generally, but not always, had
a measured dissolved oxygen content, ranging from zero up to 3. 6 mg/1.
Not unexpectedly, the higher dissolved oxygen content in samples from
both systems tend to occur during colder weather periods.
Alkalinity
The alkalinity of the raw sewage collected by the vacuum system
ranged from 81.5 up to 185 mg/1 (as CaCo ) with an average of 127. 7 mg/1.
The alkalinity of septic tank effluent ranged from J 57. 0 up to 250.0 mg/1
with an average of 204. 0 mg/1. Metcalf and Eddy- characterize typical
domestic sewage as having alkalinity ranging from 50 to 200 mg/1. Bi-
carbonate alkalinity of the Bend water supply was low; reported to be gen-
erally in the range of 10 to 60 mg/1 (as CaCOj). The natural waters from
the Bend water supply apparently received additional alkaline buffering
capacity from the wastewater pollutants. This phenomenon of apparent
alkalinity increase is common in anaerobic digesters due to the titratability
of volatile acids by the standard sulfuric acid. In order to determine the
actual bicarbonate alkalinity the concentration of volatile acids (as
CaCOs) must be subtracted from the apparent alkalinity concentration.
Volatile acids were not measured during this study.
Grease
Grease content in samples from the vacuum system averaged 110.7
mg/1, while grease content in septic effluent samples from the pressure
system averaged only 65.0 mg/1. Metcalf and Eddy- characterize medium
strength domestic sewage as having 100 mg/1 grease. The results should
not be interpreted to quantify a percentage of grease removal by the septic
tanks in the pressure system, since initial grease content was not mea-
sured.
Phosphate
Total ortho-phosphate in the samples of septic tank effluent collected
from the pressure system contained an average of 10.4 mg/1 (as P) with
variations from 7. 0 to 14.0 mg/1, while the samples of raw sewage from
the vacuum system contained an average of only 3. 2 mg/1 with phosphate
with variations from 1. 5 to 4. 7 mg/1. The phosphate consent in the pres-
sure system effluent is typical of domestic sewage -, and septic tank efflu-
ent-. The phosphate content in the vacuum system sewage is lower than
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typical. The only apparent explanation for the difference in the phosphate
content of the septic tank effluent and raw sewage samples appears to be
the difference in age and character of the residents of the two neighbor-
hoods. Residents of the pressure system area were generally younger
than in the vacuum system area. Housewives in the pressure system area
may have used detergents containing phosphates more generously in laun-
dering the clothing of children than housewives in the vacuum system area;
and, although per capita wastewater production was low in both areas •
Nitrogen
TotalKjeidahl nitrogen in the samples collected from the pressure sys-
tem averaged 40. 9 mg/1 (as N) with measured values ranging from 30.1 to
50. 0 mg/1, compared to a reported average total nitrogen content of 55. 3
mg/1 for septic tank effluent. The Kjeidahl nitrogen in the vacuum system
sewage samples averaged 28.4 mg/1 oitrogen with values ranging from
18.4 to 43. 3 mg/1. Metcalf and Eddy- reported typical medium strength
domestic sewage to have a total nitrogen content of 40 mg/1.
Sulfide
Total sulfide in the septic tank effluent samples was measured to eval-
uate the potential for odors and formation of sulfuric acid in gravity sewers
receiving the septic effluent discharge. Total sulfide was found to aver-
age 1. 8 mg/1 with a range of concentrations from . 06 to 5. 35. At the
slightly acid pH of the septic effluent most of the sulfide would have been
in the form of non-ionized gaseous hydrogen sulfide —. No objectionable
odors were noted near the discharge manhole. The septic tank effluent
was sufficiently diluted by the gravity sewer flow to prevent any acid
formation from hydrogen sulfide.
Suspended Solids
Suspended solids measured in the septic tank effluent samples averaged
36.4 mg/1 with a range from 17. 0 to 56. 0 mg/1, compared to an average of
54 mg/1- reported to be typical of septic tank effluent. Suspended solids
in the raw-sewage samples from the vacuum systems were measured to
average 1 64. 1 mg/1 with a range of 12. 0 to 369. 0 mg/1, or slightly less
than the average for typical domestic sewage reported by Metcalf and
Eddy-.
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BOD
The BOD of the septic tank effluent samples collected from the pres-
sure system averaged 157.0, in close agreement with the average septic
tank effluent BOD value reported by EPA . The average BOD of the raw
sewage samples collected from the vacuum system was 187.7 mg/1, 7
slightly less than the BOD of 200 mg/1 reported by Metcalf and Eddy for
average domestic sewage.
COD
The COD of the septic tank effluent averaged 276. 0 mg/1 with a
range from 170. 5 to 673. 5 mg/1.. The average was low and the extremes
wider than data reported by EPA . The COD of the raw sewage from the
vacuum system averaged 363. 3 mg/1 with values ranging from 196.4 to
611.0 mg/1. The average and both extreme values were lower than the
typical values reported by Metcalf and Eddy , again indicating that the
vacuum system sewage was dilute relative to typical average values.
COMPARISON OF PRESSURE AND VACUUM SYSTEM COSTS
The following is a comparison of estimated costs for hypothetical
pressure and vacuum sewage collection systems serving residences typi-
cal of the Bend R &t D project. The cost estimates are derived from the
Bend project data and are adjusted, as explained in the following, to allow
for differences in the two .areas served. Each home is assumed to have" their
own pump sump or vacuum valve. The cost figures derived are reduced to the
annual cost per residence, relative to 1976 cost levels. Labor is assumed
to cost $10.00 per hour. Amortization of capital costs are based on a
20-year payback period and 7 percent interest rates. The comparison of
pressure and vacuum system costs are summarized in Table 18.
Potential System Size
Both the pressure and vacuum systems constructed in Bend had the
potential to serve up to approximately 50 homes, although only eleven
homes were actually connected to each system. Costs for the hypothe-
tical systems which are applicable to the total system are therefore
apportioned among the potential systems' capacity of 50 homes.
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TABLE 18
COMPARISON OF PRESSURE AND VACUUM SYSTEM COSTS
Cost Item Pressure System Vacuum System
House Service Lines
16. 8m (55ft)/residence $ 289.00 $ 289.00
Collection Lines
39. 3m (131 ft)/residence 1,100.00 1,420.00
Pressure System Pump Station 2,114.00
Vacuum Sump-Valve Pit- Valve 1, 181. 00
Vacuum Station 845. 00
Vacuum System Discharge Line 20. 00
Pressure Pump Repair or Re-
placement at 10 years.
Present Worth 100.00
Vacuum Pump Repair or Re-
placement at 10-year Interval.
Present Worth 45.00
Present Worth of Total Capital
Cost 3,603.00 3,800.00
Annual Amortization
20 years @ 7% 340.00 359.00
Annual Operation and Mainten-
ance Costs 30.00 50.00
Energy Costs 4.00 12.00
Total Annual Cost Per Residence $ 374.00 $ 421.00
95
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Excavation
Costs for excavation of the pressure and vacuum system pipe trenches
averaged $12.30 per meter ($3.75 per foot) and $19. 36 per meter ($5. 90
per foot) respectively. Trenches for both systems averaged approximately
1.0m (3. 2 feet deep). The vacuum pipe trenches may have required extra
effort to excavate for trap assemblies and to maintain the downward slope
of the lines. However, there was no way to differentiate the extra cost for
the vacuum system configuration from the greater cost caused by more
rock encountered in the vacuum system trenches.
House Service Lines
The hypothetical pressure and vacuum systems should have house serv-
ice lines of similar average length. House service lines in the Bend pres-
sure system averaged 10.7 m (35 feet) in length; house service lines in the
vacuum system averaged 22. 6 m (74 feet) in length. The difference was
considered to be due to differences in the site's housing patterns, instead
of differences inherent in the two systems. In both the pressure and vac-
uum systems the house service lines were constructed of 10.2-cm (4-inch)
diameter PVC pipe and buried approximately .76 m (2. 5 feet) deep. The
hypothetical systems are assumed to have house service lines averaging
16. 8 m (55 feet) long costing $6. 56 per meter ($2. 00 per foot) for excava-
tion and $10. 66 per meter ($3. 25 per foot) for pipe installation for an aver-
age cost of $289.00 per residence.
Collection Lines
The pressure system in Bend averaged 28. 3 m (93 feet) of collection
line per house while the vacuum system averaged 51. 2 m (168 feet) of col-
lection line per house. As with the length of house service line, the dif-
ference in the length of the collection lines was considered to be due to
differences in the housing density rather than any inherent difference in
the two systems. The hypothetical pressure and vacuum systems will be
considered to have an average of 39. 3 m (131 feet) per house, with an
average excavation cost of $15. 81 per meter ($5.00 per foot).
The pressure system used 5. 1-cm .(2-inch) diameter, Class 160,
PVC pressure pipe, with an estimated installation cost of $9. 84 per meter
($3.43 per foot). It should be noted that the terrain in which the pressure
system was installed did not require use of air release valves, which
could have added as much as $1. 63 per meter ($. 50 per foot) if one pres-
sure relief valve had been required. The estimated price per foot in-
cludes the line isolation valve and cleanouts. Cost to the aye rage resi-
dence in the hypothetical pressure system for excavation and installation
of the collection pipe is $1, 100.00.
96
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The vacuum system used 7. 62-cm (3-inch) diameter, Schedule 40,
PVC pipe. The installation cost included piping through the collection
sumps and valve pits and five trap and cleanout assemblies. The pipe has
an estimated installation cost of $19.20 per meter ($5. 85 per foot). Cost
to the average residence in the hypothetical vacuum system for excavation
and installation of the collection pipe is $1,420. 00
Pressure System Pump Station
The pump stations for the Bend pressure system cost $1, 436. 00 each
plus an estimated $978. 00 for electrical hookup, which included the alarm
and alarm telemetry system and the power distribution system, but not the
pump operation monitoring system. An additional $300. 00 per residence
is deducted from the electrical system cost to arrive at the cost for the
hypothetical pressure system, which would receive power from house cir-
cuits and would have local alarms only. Cost per residence for pump sta-
tion for the hypothetical pressure system is $2, 114. 00.
Vacuum Sump - Valve Pit - Valve
The vacuum system sumps and valve pit combinations for the Bend vac-
uum, system cost $681. 00 each installed plus $500. 00 for each valve. Pipe-
line costs through the valve pit were included in collection pipe costs. The
high water alarm system will be included in electrical system costs.
Vacuum Station
Costs for the vacuum station in the Bend project were; $11, 310. 00 for
the station structure and piping, $25, 300. 00 for station equipment and
$8, 924.00 for the system electrical hookup, including the sump high water
alarm and alarm telemetry system, but not including the valve operation
monitoring equipment. As with the pressure system an additional $300.00
per residence is deducted from the electrical costs to arrive at estimated
costs for the hypothetical vacuum system, which does not include the ela-
borate alarm system included in the Bend project. The hypothetical vac-
uum station therefore has an estimated total cost of $42, 234. 00. As noted
before the cost of the hypothetical vacuum station can be divided among a
potential system capacity of 50 residences for an average cost of $845. 00
per residence.
Vacuum System Discharge Lines
A vacuum system will require some length of line to discharge into a
gravity sewer. The discharge line for the Bend vacuum system costs
approximately $6, 620.00. However, to make an equitable comparison of
97
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the Bend pressure and vacuum systems the cost of the discharge line should
be largely discounted because the pressure system was located adjacent to
the gravity interceptor. Assuming that the hypothetical vacuum system
has a discharge line costing $1, 000. 00 and apportioning the cost among 50
residences results in a cost of only $20.00 per residence.
Parts Repair and Replacement
Some of the equipment of the pressure and vacuum system will un-
doubtedly require major repair and/or replacement before the 20-year de-
sign period used for this analysis has passed. However, the data avail-
able is inadequate to make a very accurate forecast of the costs that will
be incurred. Specifically the length of operating experience from the Bend
project is inadequate to forecast future equipment failure problems.
The pumps in a pressure system appear to be the major equipment
item most likely to fail during the lifetime of a pressure system. Pre-
liminary results of a study of existing STEP and grinder pump systems
indicates that the mean time between service calls (MTBSC) for any single
pump ranges from three to seven years for different systems installed-.
However, most of the pumps had been installed less than ten years. The
service calls were caused by a variety of problems, many of which could
have been detected by a preventative maintenance program. Labor cost
for any major pump repair task very quickly equals the cost of a new pump.
For this analysis of the hypothetical pressure system it will be as-
sumed that pumps with the average cost of the pumps used on the Bend
project will be replaced every 10 years for a present worth cost of $100.00.
Labor costs and other miscellaneous repair will be included in the follow-
ing under the category of Maintenance.
An estimate of the life of components of the vacuum system is con-
siderably more uncertain than for the pressure system. As noted before
the sliding vane vacuum pumps have a poor record of reliability for this
application, but the Bend project has not provided sufficient experience
to judge whether the vacuum pump problems can be classified as "start-up"
problems, are due to the small size of the Bend vacuum system, im-
proper pump application, or whether the problems are typical of
vacuum systems generally. For this analysis it is assumed that
the vacuum pumps will need to be replaced at the end of 10 years. The
present worth of replacing the two vacuum pumps at the end of 10 years
divided among 50 residences is approximately $45.00 per residence.
98
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On the Bend project problems with the vacuum valves have originated
in the pneumatic controller, not in the valve itself. Airvac representatives
report that the vacuum valves operate through 200, 000 to 400, 000 cycles
before failure in laboratory tests. The vacuum valve life should be ade-
quate for a 20-year design period if the laboratory data is applicable to
field conditions. The Bend project experience to date has not indicated
that the valves and controllers will not last through a 20-year design period,
but has indicated that malfunction can be caused by any particle of debris
that may enter the controller.
Maintenance
Based on the performance of the Bend pressure system we would
recommend that the pressure system pump stations and the pumps be in-
spected annually as a preventative maintenance procedure. It may be de-
sirable to hose down grease buildup periodically although there was no
apparent need at the end of the first year of operation. Otherwise no main-
tenance service is recommended except when an alarm indicates a failure.
It is estimated that each pump station would receive one man hour per
year of routine inspection and maintenance, plus five man hours of major
repair and maintenance once every five years for an average annual cost
of $20.00 per year. The septic tank of a STEP pressure system will
need periodic inspection and cleaning, at an estimated annual cost of $10. 00
per residence.
Like the pump sumps the vacuum sump, valve pit and valve installa-
tions should receive an annual preventive maintenance inspection and hos-
ing down of grease buildup in the collection sump if needed. Otherwise
maintenance should be done when an alarm indicates failure. Three man
hours per year of routine inspection and maintenance, plus five man hours
of major repair once every five years is estimated at an annual average
cost of $40. 00 per year per vacuum valve installation.
The vacuum station should receive inspection at least twice weekly.
Approximately 50 man hours per year are estimated for maintenance of
the vacuum station. However, when the vacuum station maintenance is
apportioned among the potential system size of 50 homes only one-half hour
per year per residence results, for an estimated cost of $ 10.00.
Energy
The average energy cost for each residence in the pressure system
was less than $.01 per day if the energy consumed by the control box strip
heater was not included and approximately $, 03 per day if the strip heater
99
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energy was included. The strip heaters are not considered necessary if
the control boxes were placed inside the residence. The average energy
cost for each residence in the vacuum system was approximately $. 04 per
day. Energy costs for the hypothetical systems are estimated to be $4. 00
per year per residence in the pressure system and $12. 00 per year per
residence for the vacuum system costs.
Discussion
The cost estimates presented in Table 18 indicate that the hypothetical
pressure and vacuum systems may have approximately competitive total
annual costs. However, it should be understood that costs could vary
widely for specific site applications. For example, air release valves
would add to the cost of a pressure system if they were needed. The cost
of vacuum system collection line installation is indicated to be significantly
higher than for pressure system collection lines, and could make vacuum
system less attractive in a sparsely settled area.
A fundamental difference in pressure and vacuum systems which is not
reflected in Table 18 may be as significant as the cost estimates indicated
in Table 18. The major cost of a pressure system is the pump sump,
which does not need to be installed until the residence is ready for occupa-
tion. By comparison the vacuum station is a major cost component of a
vacuum system and must be the first item installed. Although the vacuum
station costs per residence may become relatively small when apportioned
among the ultimate number of residences connected, the initial residences
connected may bear a high capital cost load until the system potential size
is reached. Similarly a major portion of repair and maintenance costs es-
timated for the vacuum system occur in the vacuum station and can be ap-
portioned among connected residences. If a large number of residences
are connected the cost per residence may be small; if a small number of
residences are connected the cost per residence may be quite high.
The reader is warned against accepting the figures in the above cost
comparison for literal application to a proposed project of any size. The
figures are based, in part, on contractor costs which, in this case, were
the first experience of the contractor. Other figures are hypothetical
based on individual judgment. Anyone attempting a cost comparison be-
tween pressure and vacuum sewers and gravity sewers must recognize the
need for thorough study and evaluation pf the conditions peculiar to the
specific project.
100
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SECTION 5
DESIGN CONSIDERATIONS
GENERAL
There is a considerable volume of literature available which narrates
the development of low pressure sewer technology. An account of the de-
velopment of vacuum sewer technology is somewhat less readily available.
This report does not attempt to repeat or summarize the design information
that is available in the sources listed in the references and bibliography
section. This chapter discusses alternative design concepts considered and
experience gained during design, construction and Operation of 'the Bend
pressure and vacuum systems.
It should be understood that system design is a process of weighing
the relative benefits and disadvantages of a multitude of possibilities. A
rejected alternative may not necessarily be wrong but may be outweighed
by other considerations for the specific application. Conversely, the sel-
ected design is seldom able to satisfy all desired criteria.
LOW PRESSURE SEWER TECHNOLOGY
As stated before, this report will not attempt to present a compre-
hensive summary of low pressure sewer technology which is available from
sources listed in the bibliography section. The paper "Status of Pressure
Sewer Technology" by J. F. Kreissl- is probably the most current and com-
prehensive summary of low pressure sewer design information available.
Copies of the paper can be obtained from the U. S. Environmental Protec-
tion Agency Technology Transfer Program.
In approaching the design of a low pressure sewer system, there are
several preliminary decisions to be made. Included among these are:
1. Collection of raw sewage using a grinder pump or collection of
septic tank effluent using a sump pump. (STEP)
2. Type of pumps - Both centrifugal and semipositive displacement
grinder pumps are being used in low pressure sewage systems.
Most effluent pumps being used are centrifugal units.
101
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Several systems using grinder pumps have been installed, operated,
and reported upon. Data on grinder pump operation was therefore available.
One of the initial goals of the Bend project was to collect data from a low
pressure system collecting septic tank effluent. Design of the Bend pressure
system therefore focused on use of centrifugal pumps, without grinders,
collecting septic tank effluent.
VACUUM SEWER TECHNOLOGY
As with the pressure system, this report will not attempt to present
a comprehensive analysis of vacuum system technology. However, vacuum
system technology has not been as widely published as has pressure system
technology. The principal sources of information on vacuum systems have
been literature distributed by the companies selling vacuum systems and
equipment. Probably the most current and comprehensive summary of vac-
uum sewer information is in the paper "Vacuum Sewer Technology" by I. A.
Cooper and J. W. Rezek-. Copies of this paper are available from the
U. S. Environmental Protection Agency Technology Transfer Program.
At the present time, there are two major companies marketing vac-
uum systems across the United States: Colt-Envirovac and Airvac. Al-
though there are a number of differences in design concept between the two
companies, one fundamental difference concerns the valves marketed by the
two companies. Colt-Envirovac markets a descendant of the Liljendahl
toilet valve developed in Sweden. The principal feature of the Colt-Envirovac
valve is that it was developed as a toilet valve, has the potential for signifi-
cant reduction of flush water requirements, and is applicable to the separa-
tion of "black" water (containing fecal wastes) and "grey" water (not con-
taining fecal waste).
Airvac markets a 7. 62-cm (3-inch) diameter valve designed for col-
lecting raw sewage (combined black water and grey water). The Airvac
valve was specified for the Bend vacuum system.
INSTITUTIONAL CONSIDERATIONS
Pressure and vacuum systems require a departure from normal in-
stitutional relationships typical of gravity sewer systems. Gravity sys-
tems historically have an established division of responsibility. A city or
sewer district generally owns and maintains sewer lines up to private prop-
erty. Property owners generally maintain service sewers and plumbing
inside the property line, within restrictions established by plumbing, sew-
er, and building codes. The municipality has authority to enforce code re-
strictions to the degree the situation warrants. Gravity sewer systems are
102
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relatively simple in their operation, i.e., sewage flows down grade as long
as the channel is not obstructed or overloaded. Sewage lift stations are in-
stalled when needed.
In contrast, pressure and vacuum systems incorporate increased
mechanical complexity and a wider range of modes of failure. The need
for a more complex range of prompt, reliable maintenance response is
correspondingly increased. Since either pump sumps and pressure lines
or vacuum valves and lines may require installation on private property,
easements for installation and maintenance may be required.
It is not considered advisable to leave maintenance of either low pres-
sure pump stations or vacuum valves to either the homeowner or a plumber
selected at random by the homeowner. Standardized parts and repair and
maintenance procedures are considered necessary to maintain the integrity
of the system. It is considered advisable that before extensive vacuum or
pressure systems are installed, an institutional structure with responsi-
bility and authority for maintenance of the system be established.
FEASIBILITY OF MULTI-HOME SERVICE BY A SINGLE PUMP STATION
OR VACUUM VALVE
Either a minimum-sized low pressure pump station or a single vac-
uum valve installation generally have the capacity to handle much more sew-
age than generated by a single home. Therefore, it appears that consider-
able savings could be obtained by connecting several homes to one pump
station or vacuum valve.
The Bend pressure and vacuum sewer systems incorporated this con-
cept. Groups of one, two, and three homes were connected to single pump
stations or vacuum valves. These installations worked satisfactorily.
There does not appear to be any technical reason for not installing multi-
house connections to single pump stations or vacuum valves. However,
multi-home installations may encounter several problems of a nontechnical
nature.
One of the problems of a multi-house pressure-sewer installation is
how to meter and pay for electrical energy. It appears most feasible to
power the pumps through house circuits and accumulate the energy con-
sumption on the house meters. However, in a multi-house installation
energy consumed would appear on the meter of only one homeowner, and
presents the problem of how to apportion costs between the homeowners
sharing the pump station.
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A metering system which would accumulate energy consumption for
each pump would require a transformer and meter at each pump station.
Very little energy would be recorded; a large amount of effort would be
needed to reach the meters and prepare billings. Another option is to ac-
cumulate several pumps' energy consumption on a centrally located meter,
as was done on the Bend project. However, this approach requires a dis-
tribution line from the central meter to each of the pumps being served.
It does not appear feasible to meter the energy used by pumping sys-
tems other than on the meters of the house circuits. A formula for appor-
tioning the cost would need to be agreed upon by the participating home-
owners before installing a multi-home pump station.
Energy consumption by a vacuum system is localized at the receiving
station and presents a simpler problem of power metering.
Another possible problem of multi-home sewage collection sumps is
assigning charges to the responsible individual if damage occurs as a re-
sult of negligent acts, such as flushing material that will plug or damage
the system. This is not considered to be a major problem with septic tank
effluent pumping systems, which will have solids removed by the septic
tank, or with a 7. 6-cm (3-inch) diameter pipe vacuum system which has
capacity to handle most solids which can be flushed through normal plumb-
ing fixtures. The ability to assign responsibility for pump stoppage has
been recounted to be a desirable feature in a private system pumping raw
sewage with small Rumps which could be stopped by sanitary napkins or
articles of clothing - .
It is possible that if one home of a multi-home collection sump in-
stallation were installed at a lower level than the other homes and if the
pump and alarm system failed, sewage could back up into the plumbing of
the lower home. Claims by the flooded individual that damage resulted
from negligence of another homeowner or the sewer utility might result.
It should be noted that this is speculation; such an event did not occur on
the Bend project. However, as described in Section 3 the Bend project in-
corporated fail-safe overflow lines to the existing subsurface disposal sys-
tem, which might not be allowed on a nonresearch installation. Because
of the fail-safe nature of the Bend system the homeowners were largely
unaware of equipment failures that did occur and therefore did not have
any major reactions to the failures.
The discussion above of the problems that might be encountered in
operating a multi-home collection sump system is presented for consider-
ation. It is felt that there is not sufficient experience to rtiake firm rec-
ommendations.
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ALARM SYSTEMS
It is considered desirable to provide an alarm system to indicate
failure of a pressure or vacuum system to enable prompt repair action.
Most failures will result in high water in sewage collection sumps. There-
fore, the most versatile alarm system would be triggered by high water in
collection sumps. Hopefully, a high-water alarm system would permit re-
pair of any failed component before hydraulic storage capacity in the sump,
and septic tank if used, is filled and sewage backs up into house plumbing.
The smaller the available hydraulic storage volume, the more critical
would be the response time. The concept of adding additional hydraulic
storage volume in house sewer lines has been proposed on some projects.
Oregon subsurface disposal regulations require use of mercury float
switches for control of sump pumps because hermetically sealed float
switches are considered, by DEQ, to be less prone to failure from corro-
sion or grease buildup than other water-level sensors. Mercury float
switches were specified for sump pump controls and high-water alarm sen-
sors on the Bend project to be compatible with this regulation.
The Bend project incorporated high-water alarms in both pressure
and vacuum system collection sumps. Both the pressure and vacuum sys-
tems also included alarm circuitry which identified the location of each
collection sump experiencing high water conditions. This capability was
included as a part of the monitoring program for the Bend project but may
not be practical for systems serving a large number of homes. The wire
network carrying the alarm signals back to central monitoring points could
become very extensive and would be subject to failures and maintenance
costs.
A less elaborate alarm system than that used on the Bend project
could consist of a switch actuated by high water in the collection sump and
an alarm indicator light installed in a conspicuous place in the home. An
alarm light placed where it would be visible from the street would also
allow police to inform maintenance personnel in the event of failure when
the homeowner is absent.
A pressure system failed condition which might not result in a high-
water alarm can be caused by a pump discharge check valve sticking in
open position as occurred in the Bend pressure system. The sump with
the open check valve would be filled with sewage whenever any other pump
operated. The pump with the failed valve would then operate until the sump
is again emptied. If the sump pump could counter system back pressure,
high-water alarm conditions might never be reached. The frequent pump
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operation might not be noticed. It may be desirable to place a pump running
light in a conspicuous place where the homeowner can note unusually high
frequency of pump operation. Additional reliability can also be added to a
pressure system by double check valves on the pump discharge lines.
The Bend vacuum system included a high-water alarm in the main
collecting tank and a low vacuum alarm on the vacuum reserve tank. The
need for an alarm to indicate vacuum pump oil system failure was men-
tioned in Section 4.
To place the above discussion of alarm system in perspective, it
should be noted that gravity sewers can and occasionally do fail by plugging,
with the result that sewage backs up into house plumbing. No one has seri-
ously proposed alarm systems for failure of gravity sewers. It is consid-
ered that some degree of alarm capability is desirable to indicate mechan-
ical failure in pressure or vacuum systems, but attempting to achieve com-
plete assurance that sewage will never back up into house plumbing does
not appear practical. Additional operating experience is needed to define
the optimum alarm system for pressure and vacuum sewage collection sys-
tems.
PRESSURE SYSTEM SUMP CONFIGURATION
As noted in Section 4 care needs to be taken in design of pressure
system pump sump configurations to allow for repair and maintenance.
The optimum design may include trade-offs of the cost of extra repair and
maintenance effort against the cost of more elaborate equipment.
Removal and replacement of the pump appears to be the most prob-
able and most frequent repair and maintenance task. It is highly desirable
that the pump can be removed and replaced in the sump from the ground
surface and while the sump is full of liquid. However, in preliminary cost
estimating procedures for the Bend project, guide-rail and slide-away
coupling systems were quoted to cost up to $200. 00 each. It appeared
feasible to consider pumping liquid from the sumps into a container in the
event of failure and using a mechanical coupling system which would have
required maintenance personal to enter the sump to uncouple the pump.
The sump could not have been manually uncoupled from the surface because
of the 0, 91-m (3-foot) pipe burial requirement at Bend. The guide-rail and
slide-away coupling systems were placed on the project bid documents as
an optional add-deduct item. The add-deduct price for the guide-rail and
slide-away coupling systems on the beginning bid was only $50. 00 for each
sump, the guide-rail and slide-away coupling systems were included in the
constructed sump configuration.
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The guide-rail and slide-away coupling systems used at Bend have
performed satisfactorily, but devices for uncoupling sump pumps are
undergoing continued development by pump manufacturers. The systems
used at Bend have probably been superseded on the market by better and
less expensive equipment. For example, a pump coupling system which
uses an inverted U-fitting on the pump discharge pipe, which hooks into a
mating rubber gasketed fitting on the discharge line, has been advertized
on a grinder pump system by the F. E. Myers Co. —.
As described in Section 4, a check valve failed on the Bend pressure
system. The operator noted that check valves installed in the verticle
pipe run were difficult to service in that the valve could not be replaced
from the top of the sump. The flooded sump had to be emptied into another
container to prevent contamination of the ground, so that a maintenance
person could enter the sump to remove the check valve. The sump is
cramped in space and is an unpleasant place to work. These objectionable
conditions might be improved if the check valve were placed in the horizon-
tal pipe run, near the point the discharge pipe intersects the sump wall.
(see Figure 3), However, the horizontal pipe run would still be difficult
to reach from the ground surface when a 0.91-m (3-foot) deep pipe buried
is required, as at Bend, and the sump would still need to be emptied to a
level to expose the valve for service. Another design alternative is to
place the check and gate valve or valves outside of the sump in a separate
valve pit. Some systems have used double check valves, and some sys-
tems have used gate valves on both sides of the check valve. These options,
of course, add cost. Designers should consider costs and advantages of
alternatives for each application.
SUMP COVERS
Sump covers, for both pressure and vacuum systems, are items that
appear to have received little comment in available literature. However,
sump covers are a troublesome item that resists standardization and may
require unique treatment on each project.
Because the sump covers are the interface between the sump and the
outside environment, they may need to meet a variety of design criteria.
Security and strength versus ease of entry may present conflicting require-
ments. The cover should provide adequate strength for the expected traf-
fic load, which may range from foot traffic to heavy vehicle traffic in a
single project depending on where the sump is located. The cover should
also provide security against entry by unauthorized persons and against
vandalism. On the other hand the cover locking device should allow entry
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by maintenance personnel without undue effort and should resist physical
abuse and corrosion. The cover should be aesthetically compatible with
the site. And finally, as in all designs, costs must be balanced against
desirable design options.
Various sump-cover materials were considered during the design
phase of the Bend project (cast iron, steel plate, precast concrete, fiber-
glass). The sump-cover specification was written as a performance speci-
fication. The sump covers proposed and accepted were fabricated from
0. 64-cm (1 /4-inch) thick steel plate bolted to nuts imbedded in the sump
flanges, as described in Section 3. All of the sumps and valve pits were
located in lawn areas. The steel plates were satisfactory in that they pro-
vided adequate strength for lawn or light vehicle traffic. Although heavy,
the covers could be handled by one workman. And, although the pressure
system sumps were corroding under breaks in the protective coating, the
steel plate is probably thick enough to last through the design period.
Fiberglass covers are being used on sumps in another pressure sys-
tem in Bend and are reported to be giving satisfactory service.
The system of bolting the sump covers to nuts imbedded in the sump
covers to nuts imbedded in the sump flanges was less than satisfactory,
but with some modifications is the best system we have to recommend.
The bolts and imbedded nuts are simple and inexpensive to fabricate, will
provide adequate security against unauthorized entry in most applications,
and can provide sufficient closing force to contain the escape of odorous
gases. The bolts and nuts should be of at least 1. 3 cm (1 /2 inch) diameter
to withstand physical abuse and should be stainless steel to withstand cor-
rosion. The sump cover should either be keyed or the bolt pattern should
be symmetrical, to aid in easy replacement. The sump rim should be
above ground level to minimize fouling the nuts with debris.
The top elevation of the sumps in the Bend project, relative to the
ground surface, varied from below to several inches above the ground
surface. Problems occurred with sump covers which were placed below
ground level. As noted before, debris tended to foul the threads of bolts
and nuts on covers that were below ground level much more than if the
cover were slightly above grade. One pressure system sump cover was
installed slightly below grade and covered with bark chips. As described
in Section 4 this resulted in bark-chip debris falling into the sump during
a maintenance operation and subsequent plugging of the check valve.
The sumps and valve pits in the Bend project were all installed in
lawn areas. The sump covers received a variety of imaginative treat-
ments by the homeowners to minimize the aesthetic impacts. One vacuum
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sump cover and valve pit cover were incorporated into a rock garden. An
arrangement of lawn figurines was placed on another vacuum sump and
valve pit cover. A lawn table was placed on top of another sump cover. It
was concluded that with some care and imagination in placing the sumps
and incorporating them into the landscaping that they need not be aesthet-
ically detractive.
COMPARISON OF PRESSURE VACUUM AND GRAVITY SEWERS
A nonquantative comparison of pressure, vacuum, and gravity sew-
er systems is presented in Table 19. The limitation of a comparison such
as that presented in Table 16 should be understood. The three systems do
not have completely analogous components which may be compared without
some distortion of the compared categories. Any specific site would re-
quire a different design approach for each system and utilize a different
group of components for each system.
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TABLE 19
COMPARISON OF PRESSURE, VACUUM, AND GRAVITY SEWER SYSTEMS
ITEM
PRESSURE SYSTEM
VACUUM SYSTEM
GRAVITY SYSTEM
1. Capabilities and
Limitations
Permits installation on widely varying
terrain.
Lifts and length of line limited by pump
capability.
Technology still developing.
Total lift limited to less than approximately
4.5 m (15 feet) by use of atmospheric pres-
sure as motive force.
Maximum allowable length of line not well
defined by present state of technology.
Probably less than 1200 m (4000 feet).
Downhill transport only.
Lift stations required if terrain does not
permit downhill slope.
No limit on length of line.
2. Trench Requirements
Pipeline follows ground profile at depth
needed to provide mechanical and freeze
protection.
Narrow trench adequate. Pipe can be
assembled above ground.
Line and grade not critical.
Pipeline follows ground profile with series
of abrupt lifts follows by downhill slopes.
Depth of bury is to provide mechanical
and freeze protection.
Narrow trench is adequate. Pipe can gen-
erally be assembled above ground.
Line and grade not critical but lift and trap
assemblies and tributary intersection
assemblies require care in design and place-
ment.
Trench cuts must be deep enough to pro-
vide downhill grade and uniform line and
grade between manholes.
Trenches must generally be wide enough
to allow assembling pipe in the trench.
3. Pipe
Smalt diameter. Typically 3.17 to
10.16 cm (IK to 4 inch) diameter. Class
125 to Class 200 PVC.
Small diameter. 7.62 cm (3 inch) diameter.
Schedule 40 PVC recommended.
Generally 15.24 or 20.32 cm (6 or 8 inch)
minimum diameter. Variety of materials,
$5.00 to $10.00 per foot installed.
4. Pipeline Appurtenances
Air release valve assembly at high points
in line.
Ctaanowts (if deemed necessary).
Valves to isolate branch lines for service.
Lift and trap assemblies.
Cleanouts (if deemed necessary).
Manholes or cleanouts every 90 to 100 m
(300 to 400 feet).
5. Sewage Moving Force
Pump station at each house, (or group of
houses).
Sump and vacuum valve installation at each
house (or group of houses).
Vacuum station having the following
equipment:
Station housing
Vacuum pumps
Collection tanks
Discharge pumps
Standby engine generator (if required)
Gravity.
Lift stations and force mains, if needed.
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TABLE 19. (Continued)
ITEM
PRESSURE SYSTEM
VACUUM SYSTEM
GRAVITY SYSTEM
6. Sequence of Installation
Pump stations and lines
extended as area develops
Vacuum stntion must be Installed in-
itially. Sumps' vacuum waives and linos
extended as area developes.
Linos extended as area dovolops.
7. Operation and
Maintenance
Replace pump (or other components)
when failure occurs.
Recommend periodic check of pump
station.
Hosing down grease buildup periodically
may prove to be desirable.
Energy consumption to operate pumps.
Higher potential for damage by other
construction activities than gravity
system.
Leaks may go undetected and contam-
inate groundwater.
Replace vacuum valve or valve controller
when failure occurs.
Recommend daily check of vacuum
station, periodic check of valves.
Hosing down grease buildup in sump
periodically may prove to be desirable.
Energy consumption to operate vacuum
and discharge pumps.
Higher potential for damage by other
construction activities than gravity
system.
Undetected small leaks may increase
power consumption of vacuum pumps
and may be difficult to locate and repair.
Periodic cleaning of sewer.
Pump station maintenance and
operation costs if included.
If leaks develop infiltration will
increase treatment costs.
Infiltration may occur through
leaks in dry weather, possibly
causing groundwater contamin-
ation.
8. Estimated System
Life
Insufficient data for reliable estimates.
Pumps - 8 to 10 yean average life.
PVC pressure mains - 20 to 50 years.
PVC pressure lines should have a life
of 20 to 50 years.
Insufficient data for reliable estimates.
Airvac vacuum valves - 200,000 to
400.000 cycles.
Vacuum pumps -10 to 20 years.
Discharge pumps - 20 years.
PVC vacuum lines • 20 to 50 years.
Gravity sewers - 50 years or more.
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BIBLIOGRAPHY
1. Airvac "Vacuum. Sewage Transport and Collection Design Criteria
Manual. " Airvac Division of Burton Mechanical Contractors,
P. O. Box 508, Rochester, Indiana 46975.
2. Cooper, I. A., and Rezek, J. W. , "Vacuum Sewer Technology",
1977, U. S. Environmental Protection Agency, Technology Transfer
Seminar Program.
3. Cooper, I. A. Unpublished Data.
4. Environmental Protection Agency Technology Transfer Seminar
Publication, "Alternatives for small Wastewater Treatment Systems",
Vols. 1, 2, and 3.
5. Hydr-O-Matic "Pressure Sewer System Manual and Engineering
Guide", 1974. Hydro-O-Matic Pump Division, Weil-McLain Co., Inc.,
Clairmont and Baney, P. O. Box 327, Ashland, Ohio 44805.
6. Kreissl, J. F. , "Status of Pressure Sewer Technology", 1977.
U. S. Environmental Protection Agency, Technology Transfer
Seminar Program.
7. Metcalf and Eddy, Inc. , "Wastewater Engineering Collection, Treat-
ment and Disposal", 1972, Meg raw Hill.
8. Myers "SS Submersible Sump Pumps, Environmental System Pro-
ducts", Section 500 F. E. Myers Co. , a division of McNeil Corpora-
tion, 400 Orange Street, Ashland, Ohio 44805.
9. Pfeffer, J. T. , "Aerobic Lagoons - Theoretical Considerations"
Proceedings of the Second International Symposium for Waste Treat-
ment Lagoons, 1970, Missouri Basin Engineering Health Council
and Federal Water Quality Administration,
10. Sawyer, C. N. , and McCarty, P. L., "Chemistry for Sanitary En-
gineers" second edition, 1967, McGraw-Hill Book Company.
11. Ward, J. Personal communications.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-166
3. RECIPIENT'S ACCESSION'NO.
4. TITLE AND SUBTITLE
"Pressure and Vacuum Sewer Demonstration Project
Bend, Oregon"
5. REPORT DATE
September 1978 Tissuing Datel
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jessie E. Eblen and Lloyd K. Clark
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
C $ G Engineering, Inc. (for)
City of Bend, Oregon
P. 0. Box 431
Bend, OR 97701
10. PROGRAM ELEMENT NO.
C611B
11. CONTRACT/GRANT NO.
S803295
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Final - 7/74 - 7/77
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: James F. Kreissl
Phone: (513) 684-7614
16, ABSTRACT
A pressure sewer system collecting domestic septic tank effluent
and a vacuum system collecting raw domestic sewage were constructed
in the City of Bend, Oregon. Each of the systems collected sewage from
eleven houses and discharged into existing gravity sewer mains. Groups
of one, two and three houses were served by single collection sump/
vacuum valve or collection sump/pump combinations. The systems were
operated and monitored for a period of approximately one year. The
systems were evaluated for construction costs, operation and mainten-
ance costs, reliability, operating characteristics, and chemical charac-
teristics of collected sewage and septic effluent.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATt Field/Group
Sewers
Sanitary Sewers
Pressure
Vacuum
Pressure Sewers
Vacuum Sewers
Full-Scale Demonstration
13B
SOB
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (TMs Report)
Unclassified
123
20. SECURITY CLASS (TMspage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
113
* U.S. OOVF.HNMENT PRINTING OFFICE: 1978— 757-140/1430
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