vvEPA
United States
Environmental Protection
Agency
Region 5
230 South Dearborn Street
Chicago, Illinois 60604
Municipal Facilities Branch - Technical Support Section
September 1988
905R88003
Ujtra Violet
Disinfection
Special Evaluation
Project
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Ultraviolet Disinfection - Region V Update
Special Evaluation Project Report
September 1988
A. Introduction
The question of toxicity to resident aquatic species from chlorine resi-
duals, with the resultant need for dechlorination systems, has fostered
increased interest in several alternative disinfection systems among
communities that currently either chlorinate their effluent or are
constructing entirely new wastewater treatment systems. One of these
alternative disinfection systems is ultraviolet (UV) disinfection.
This report will update the 1984 Region V data base on UV disinfection
of wastewater in order to analyze the effect of recent changes in the
design, operation, and maintenance of UV disinfection systems.
The data collected for this report was assembled from manufacturer's lit-
erature, various WPCF articles on UV disinfection, USEPA's design manual
on municipal wastewater disinfection, specifications for UV disinfection
from several plants in Michigan and Ohio, discussions with plant operators
in the Region who work at plants using UV disinfection, capital cost data
found in planning documents for several communities in Indiana and Ohio,
and on-site visits at various plants using UV disinfection.
B. Background
The earliest operating (1981) Region V municipal UV disinfection facil-
ity is located in Lyons, Wisconsin. Since 1984, the number of municipal
wastewater treatment plants (WWTP) that are either planning, designing,
building, or operating UV disinfection systems in Region V has approxi-
mately tripled from about 20 to 60 plants (see Tables 1 & 3). Michigan
has experienced the largest increase in plants using UV disinfection,
with Wisconsin and Ohio not far behind. Several communities in Indiana
are currently planning to use UV disinfection, but have not yet reached
the design stage. Minnesota and Illinois have a handful of plants that
employ UV disinfection systems.
C. System Description
Disinfection by UV radiation is a physical process relying on the trans-
ference of electromagnetic energy from a source (lamp) to an organism's
genetic material. The lethal effects of this energy result in the ir-
radiated cell being unable to replicate. The primary, and most widely
used, source of UV light energy is the low-pressure mercury arc lamp.
Approximately 85% of its energy output is at the wavelength of 253.7
nanometers (nm), which falls within the optimum wavelength range of 250
to 270 nm for germicidal effects. The lamps are long, thin (1.5-2.0 cm)
tubes similar to fluorescent lamps but transparent instead of opaque.
The lamps typically come in two lengths (0.75 and 1.5 m). The radiation
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is generated by striking an electric arc through mercury vapor. The
discharge of energy generated by excitation of the mercury results in
the emission of UV light.
Currently, there are two basic generic types of reactors that are in
use. The first, generally called the quartz-tube reactor, is a contact
reactor in which the lamps are submerged in the wastewater (see Fig. 1).
The lamps are sheathed in quartz jackets that are slightly larger than
the lamp. Flow can be either parallel or perpendicular to the lamps.
The contact reactor configuration may be further divided into either an
enclosed vessel system or an open-channel system. These systems consist
of, respectively, a lamp battery enclosed in a reactor shell and a lamp
battery that is capable of being dipped into a plant's effluent channel.
In the second generic type of reactor, called the teflon-tube reactor,
the UV lamps are suspended outside a transparent teflon conduit carry-
ing the wastewater to be disinfected. This type of reactor has only
this type of parallel flow configuration.
In addition to the lamp batteries and reactors, a complete UV system
must include ballasts for the lamps. The ballast is placed in series
with the lamp to provide a starting voltage and to maintain constant
current. Generally, the ballasts are held either in enclosures above
the lamp battery or in separate power panels remote from the reactor.
The instrumentation in a UV system generally includes UV intensity
monitors and individual lamp monitoring and operations circuitry, which
can be included as part of the reactor or the power panel.
A recent addition to the field of UV disinfection is the medium pres-
sure mercury arc lamp. This lamp has an energy output over 25 times
greater than the more commonly used low pressure lamps and uses a
permanent transformer instead of expendable ballasts to control current
and voltage. Although the cost of the medium pressure lamp is about
four or five times that of the low pressure lamp and the life cycle is
about half of the low pressure lamps, the reduced number of lamps neces-
sary for adequate disinfection may make this lamp more cost-effective.
More data needs to be collected regarding the medium pressure lamp in
municipal applications before definitive statements can be made. There
is currently one municipal installation of this type in Region V at
Lewisburg, Ohio that has been in operation for less than 1 year.
D. Critical Design Areas
There are three key areas that govern the design and eventual capabil-
ity of a UV disinfection system to produce an, effluent that complies
with permit standards. The first area relates to the hydraulic proper-
ties of the particular reactor that is being used. The path that an
organism in the reactor takes will determine whether it will come into
contact with strong enough UV radiation for a sufficient amount of time
to enable the radiation to render that organism sterile (i.e., unable
to replicate or non-infectious). Thus, the reactor must be designed so
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that the greatest number of organisms come into contact with the strong-
est UV radiation for the longest possible time. The ideal hydraulic
design of a UV reactor is one with plug flow and minimal axial disper-
sion. The flow should also be radially (perpendicular to flow path)
turbulent to encourage mixing in the nonuniform intensity field in the
reactor. Although early reactor designs did not consider the hydraulic
properties necessary for proper disinfection of wastewater, with the
result that many reactors exhibited shortcircuiting problems inhibiting
adequate disinfection, most recent designs and specifications have in-
cluded these design considerations so that short-circuiting is no longer
a problem.
The second area that should be considered in the design of a UV disinfec-
tion system is the intensity of the UV radiation that ultimately reaches
the target organism. The intensity will be affected by not only the age
of the lamps and their configuration, but also by the surfaces and mate-
rial that stands between the UV radiation and the target organisms. The
minimum bacterial density level that can be achieved by the UV disinfec-
tion process is a function of the suspended solids concentration and is
called the particulate bacterial density. A reduced UV disinfection
efficiency with increased dose is attributed to the aggregation or occlu-
sion of bacteria in particulate matter. UV light is unable to penetrate
this material and inactivate the bacteria. This is the reason for the
inability of the UV process to adequately disinfect wastewaters that
contain more than about 30 mg/1 of suspended solids. Presently, there is
no commercially available detector which can measure the true intensity
in a complex lamp reactor. This is because only light which is normal to
the surface of the detector, i.e., collimated light, will be fully mea-
sured. In a reactor, however, the target organisms are exposed to UV
light in a three dimensional setting, usually from more than one source.
An effective method for estimating delivered dose and system intensity in
a given reactor is the bioassay procedure. The species selected for the
assay should be one which is easy to culture, identify, harvest, and
which has a consistent and reproducible dose-response. Bacillus subtil is
spores are the most commonly used species for this assay. Using a col-
limated light device, which allows an accurate measurement of the in-
tensity directly with a commercial radiometer, equal portions of a B.
subtil is suspension are exposed to a set intensity for a series of fixed
time intervals, yielding known doses. The response is plotted against
the dose, and this relationship serves as the calibration for the subse-
quent reactor assays. The reactor to be tested is set to the desired
flow and operating conditions and the culture is injected into the in-
fluent. The effluent is then sampled at set time intervals and assayed
for the known bacterium. This is repeated with the lamps not in opera-
tion. The log survival rate for each time interval is determined and the
equivalent dose is estimated from the previous dose response calibration
curve. Plotting dose against time then yields the dose-rate or intensity.
The bioassay procedure is an independent verification of system design
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and, as such, it can be used either to verify the appropriateness and
validity of a design or to compare the performance of competing com-
mercial units during design and/or bid phases prior to installation.
^
The third area of concern in the design of UV disinfection systems
is the quantification of the various characteristics of the wastewater
that is to be disinfected. The parameters of primary concern regard-
ing the wastewater characteristics are the flow rate, suspended solids,
initial coliform density, and the UV absorbance of the wastewater.
Even though the first two parameters are set by the design of the
plant, and the coliform density and the UV absorbance of the waste-
water (commonly referred to as the UV absorbance coefficient) must be
measured prior to design, all wastewater characteristics should be
empirically measured for confirmation of actual values prior to design
of a UV disinfection system. These measurements should be collected
as grab samples during the times corresponding to peak diurnal flows
which reflect the maximum bacterial density levels and maximum loading
periods for a WWTP.
The design criteria that are applicable to the design of a UV disinfec-
tion system at a particular site should be determined by pi lot-testing
or in-place performance testing. Since the composition of the waste-
water is different from site to site, the only way to ensure that the
UV disinfection system will operate properly and enable the plant to
meet permit limits is to do this testing. Although some recent specifi-
cations include testing as a means of setting the system design para-
meters, this has not been a universal practice. Since UV disinfection
of wastewater is still a relatively new technology, there may be engi-
neers that are not fully familiar with all of the necessary aspects of
a properly designed municipal UV disinfection system (see Table 4).
A quick comparison of several similar communities in Indiana and Ohio
(see Table 5) emphasizes this point. Although more in-depth analysis
needs to be done, it is interesting to note that in those communities
with higher effluent limits (CBOD5 = 25, TSS = 25) UV disinfection was
the chosen alternative tor disinfection, while in communities where the
effluent limits were more favorable for UV disinfection (CBOD5 = 10,
TSS = 10), chlorination/dechlorination was selected. Although there
are always site-specific reasons for cost variances, the wide disparity
in present worth costs for similar communities further suggests a gap
in knowledge about municipal UV disinfection systems and application of
that knowledge to design.
E. Critical Operation and Maintenance Areas
Important components of a successfully designed UV disinfection system
are the operation and maintenance (0 & M) of that system. The 0 & M
of a UV disinfection system is geared primarily to ensure that enough
UV radiation is transmitted to the organisms to render them sterile.
Essentially, this means that the lamp, ballasts, and reactor are
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functioning at peak efficiency and that all surfaces between the UV
radiation and the organisms are clean so that maximum radiation can be
transmitted.
i
Since UV lamps will progressively deteriorate with increasing number
of starts, care must be taken not to have frequent on/off cycles that
rapidly shorten lamp life. The normally cited lamp life is about 7500
hours which is approximately equal to 1 year of use. In the field,
however, replacement of lamps has not always been practiced according to
recommendations. Some plants replace lamps three times per year (every
2500 hours), while at some plants the lamps are not replaced until they
burn out. While costs per lamp vary from $25 - $100, there doesn't seem
to be a correlation between cost and replacement frequency. For more
effective control of power outputs and lamp usage, voltage dimming, which
avoids the on/off cycling that reduces lamp life, in conjunction with
the ability to turn portions of the system on and off on the basis of
time, should be incorporated into the design of a UV disinfection system.
Adjustments can then be made on a diurnal basis to reflect the normal
variation in a plant's flow. Although some early designs incorporated
float activated switches, timers, or the ability to control lamp banks
according to flow, this was not a universal practice. It is important
to include some kind of control to prolong lamp life, since lamp replace-
ment is a major operational cost.
In order to protect the lamps from breakage and internal clogging, re-
movable screens should be placed ahead of the unit to prevent debris
from entering the system. This is especially important for quartz-tube
reactors where the tubes are in the wastewater flow. The efficiency ot
a lamp is also affected by the temperature of the lamp wall. The
optimum wall temperature is between 95 and 122° F. The reactor design
that is most conducive to control of lamp wall temperature is the non-
contact (i.e., lamps not in wastewater stream) reactor, otherwise known
as the teflon-tube reactor, where it is possible to maintain the lamps
at their optimum wall temperature by controlling the temperature of the
air surrounding the lamps. In quartz-tube reactors, newer designs pro-
vide 0-ring spacers that can be slipped over the lamps to prevent
direct contact with the cooler quartz sheath. Another consideration
for UV lamps is the type of quartz sheath that surrounds the lamp in a
quartz-tube reactor. Quartz is transparent to energy at the 185 nm
wavelength. Energy at this wavelength will ionize free oxygen to form
ozone, which is an absorber of UV energy at the germicidal wavelength
of 253.7 nm. This means that a UV lamp with a fused quartz sheath will
not produce the amount of UV energy necessary for proper disinfection.
It is appropriate, therefore, to use lamp sheaths that have a low
transmittance at the 185 nm wavelength, such"as vycor or other high
transmission glass. Most current UV lamp designs use such a sheath and
this is not a problem.
It is important to ensure that the ballasts that are used in a UV dis-
infection system are compatible with the lamps. Improperly mated lamps
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and ballasts will either not work or will have much shorter life cycles.
The ballasts should also have a mechanism that forces shutdown in case
of overheating. The life cycle of ballasts (5-7 years) is greatly
shortened by excessive heat. It is important, therefore, to have ade-
quate ventilation for the power panel that normally contains the bal-
lasts. This has been a problem in many early designs and the cause of
rapid failure of numerous ballasts. Since ballast replacement costs
($50-$70) are similar to lamp replacement costs, this can be a source
of significant unnecessary expenditure.
One of the most common causes of a UV disinfection system's non-perform-
ance is inadequate cleaning frequency. This refers to both the reactor
itself, as well as the lamp, quartz and teflon surfaces. Over time,
both the quartz and teflon-tube reactors will experience fouling of the
lamp and tube surfaces. In a quartz reactor, the outside of the quartz
sheath surrounding the lamps will become befouled. This is particularly
the case where the wastewater is from primary or secondary effluent, has
a high grease and oil content, or has a high hardness content. Compounds
of iron, calcium, magnesium and manganese, which are found in hard water,
will precipitate out on the quartz sheath and prevent the UV light from
penetrating into the wastewater. Also, an organic film will develop on
the quartz sheaths if low quality wastewater is present, or if the
wastewater has a high grease and oil content. The teflon-tube reactor
experiences similar reductions in UV transmittance with time. A film
will settle in the teflon conduit carrying the wastewater, similar to
the film on the quartz sheaths. In addition, the UV lamps will become
a place for dust to settle, thereby scattering and reducing the amount of
UV light available for disinfection.
There are several methods available to clean the fouled lamp, quartz
and teflon surfaces: chemical cleaning, mechanical wipers, ultrasonics,
and high pressure spray wash. The last three methods are meant to
augment chemical cleaning, which is the recommended means of cleaning
for both quartz and teflon-tube reactors. The most prevalent cleaning
agent in use today is citric acid, however, various other acid solu-
tions (e.g., muriatic, sulfuric, phosphoric, oxalic) are also used.
These solutions work best on inorganic depositions that are prevalent
in wastewater that has a high hardness content. Other cleaning agents
such as mild vinegar solutions and sodium hydrosulfite are also ef-
fective. Sodium hydrosulfite, in particular, is effective in closed
reactor systems. In the case of organic fouling from wastewaters with
high grease or oil content, detergents, alone or in combination with
other cleaning agents, are effective in restoring the lamp and reactor
surfaces. Often, various chemical cleaning agents must be tried in
order to find the appropriate agent for the particular wastewater. The
frequency of chemical cleaning will vary frorff plant to plant depending
on the characteristics of the wastewater. The most prevalent method
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used to determine if cleaning is necessary is visual inspection of the
UV reactor. NPDES violations of coliform levels are used by many
plant operators as an indication that cleaning is necessary, however,
cleaning should be done before a violation occurs. Thru experience,
the proper cleaning frequency can be established, however, wastewater
characteristics may experience subtle changes, where visual evaluation
and experience may not be enough. Current designs, therefore, include
either intensity monitors or radiometers, the latter of which are used
in conjunction with the UV absorbance measurements that should be part
of a plant's regular sampling program for operational control.
In order to keep the UV disinfection system operating at peak efficency,
properly scheduled maintenance is necessary. At least once a year, the
total system should be overhauled and all critical components (lamps,
ballasts, reactor, monitoring systems, etc.) should be checked to en-
sure that deterioration has not occurred and that all surfaces are
clean. The accessibility to the lamps, quartz sheaths, and Teflon tubes
is critical to the ease of maintenance. This is more of a consideration
for the enclosed vessel than the open-channel systems, however, both
types should be installed in an area that offers adequate space to per-
form all of the required maintenance tasks. This is more of a problem
in plants where another means of disinfection has been used and a UV
disinfection system is being retrofitted into existing buildings,
chlorine contact tanks, or effluent channels. A lot of early retrofit
installations, in order to take advantage of gravity-flow, have been in
cramped and tight quarters making accessibility and maintenance very
difficult. Since a lot of future UV disinfection systems are going to
be retrofit installations, design must include a consideration of ade-
quate space for proper maintenance.
Unlike chlorine, which has a measurable residual than can be used as an
indicator in monitoring system performance, UV disinfection has no such
indicator. This can lead to over-utilization of the system in an at-
tempt to simplify operations and ensure adequate disinfection. Un-
fortunately, this will also increase the costs to operate the process.
A key operational tactic is to use only that portion of the system that
is necessary to meet current performance demands. This will entail
frequent sampling and analysis. The system should be sampled several
times weekly during periods of peak diurnal flows when the maximum
bacterial density levels and maximum loading are expected. The influ-
ent to the UV system should be analyzed for suspended solids, UV
absorbance and coliform density. At the time of sampling, the flow
rate as well as the operating condition of the reactor (number of lamps
in operation, etc.) should be recorded. The effluent from the UV re-
actor should be analyzed for coliform density. Although at currently
operating municipal UV disinfection systems such analyses are not being
routinely performed, it is important to collect this data to not only
evaluate system performance under current wastewater conditions, but
also to be used as a tool in controlling the system and optimizing
operations for maximum use of^lamps and minimal use of energy. The con-
tinuous collection of this data will also aid in a rational approach to
troubleshooting a non-performing system.
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F. Conclusions
Region V will continue to see more installations of municipal UV dis-
infection systems, especially retrofit installations for plants where
chlorine residual toxicity is an issue. As such, design engineers must
be made fully aware of all of the critical aspects of a properly designed
municipal UV disinfection system. There are three key areas that govern
the design of a UV disinfection system: hydraulics, UV intensity, and
wastewater characteristics.
The hydraulic properties of a particular UV reactor must be such that
the greatest number of organisms come into contact with the strongest
UV radiation for the longest possible time. As part of their respon-
sibilities, the UV manufacturer must provide evidence (dye tests) that
there is greater than 90% plug flow and no shortcircuiting within the
reactor.
The intensity of the UV radiation that ultimately reaches the target
organisms will be affected by the condition and configuration of the
lamps, as well as the particulate bacterial density. These factors
establish the lower limit of disinfection efficiency. In order to
verify the validity and appropriateness of a particular design, a bio-
assay procedure to estimate delivered dose and system intensity must
be performed. This procedure could also be used to compare the per-
formance of competing commercial units during design and/or bid phases
prior to installation.
Wastewater characterises are site-specific and parameters such as the
flow rate, suspended solids, initial coliform density, and the UV
absorbance of the wastewater must be empirically measured for confirma-
tion of actual values prior to design. These measurements should be
taken during peak diurnal flows when a WWTP experiences the maximum
bacterial density levels and maximum loading periods.
Once a UV disinfection system has been designed and built, the opera-
tion and maintenance of that system will determine the ability of the
process to meet permit limits. The emphasis of 0 & M is to maintain
the lamps, ballasts, and reactor at peak efficiency while also ensuring
that all surfaces between the UV radiation and the target organisms are
clean for consistent kill ratios.
UV lamps have a finite lite that can be prolonged by the use of voltage
dimming. Frequent on/oft cycles will decrease lamp life. Inlet screens
will prevent large debris from entering the UV disinfection system,
clogging the reactor or breaking lamps.
Ballasts have to be protected from excessive heat which shortens their
useful life. Adequate ventilation must be provided for the power panel
that normally contains the ballasts. It is also important to ensure
that the ballasts are properly mated to the UV lamps.
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Inadequate cleaning frequency is one ot the most common causes ot a UV
disinfection system's non-performance. The surfaces of the lamps
and/or teflon tubes should be kept clean at all times tb ensure that
adequate radiation is being transmitted. There are several methods
available to clean the surfaces in a UV reactor, but a chemical clean-
ing system that is integrated with the disinfection system is necessary
regardless of what other methods are used.
Properly scheduled maintenance is
system operating efficiently. At
total system should be overhauled
also be thoroughly cleaned at the
season. In order to accomplish al
the UV disinfection system must be
room to remove and replace lamps,
ports, as well as sampling points
system.
necessary to keep the UV disinfection
lease once a disinfection season the
and checked out. The system should
beginning and end of a disinfection
1 of the necessary maintenance tasks,
accessible and there must be enough
sheaths, etc. Drains, inspection
must also be a part ot a complete
Frequent sampling and analysis (several times per week) during periods
of peak diurnal flows should be done as a tool to certify system per-
formance, as well as, to control the system and to optimize operations.
A key operational tactic and energy conserving measure is to use only
that portion ot the system that will meet current permit limits.
This report was prepared by
Valdis Aistars and Charles Pycha
Environmental Engineers
Technical Support Section
Municipal Facilities Branch
USEPA - 5WFT-TUB-9
230 S. Dearborn Street
Chicago, IL 60604
(312) 353-2144
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END VIEW
EFFLUENT LEVEL
SIDE VIEW
CONTROL BOX
* AND
POWER SUPPLY
\
UV MODULE
EFFLUENT LEVELl
V
Figure 1. Schematic of the ultraviolet disinfection unit
in the sewage treatment plant effluent channel
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Table 2
Current manufacturers of UV disinfection systems at Region V WWTP's
Aquiom'cs Incorporated
Kenton Lands Road
P.O. Box 18395
Erlanger, Kentucky 41018
Phone #: (606) 341-0710
2. Northland Technologies, Inc.
1115 Chestnut Street
Burbank, California 91506
Phone #: (818) 841-8080
3. Trojan Technologies, Inc.
845 Consortium Court
London, Ontario N6E 2S8
Phone #: (519) 685-6660
4. Ultra Dynamics Corporation
1631 Tenth Street
Santa Monica, California 90404
Phone #: (213) 450-6461
5. Ultraviolet Purification Systems, Inc.
299 Adams Street
Bedford Hills, New York 10507
Phone #: (914) 666-3355
Ultraviolet Systems, Inc.
P.O. Box 707
4902 Calumet Avenue
Hammond, Indiana 46320
Phone #: (219) 937-4500
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Ultraviolet Facilities in Region V in Design or Under Construction
Illinois (1) Chip (5)
La Moille Ashland
Hillsboro
Michigan (18) Senecaviiie
Williamsburg
Almont Wilmington
Bessemer
Blissfield Wisconsin
Clare
Flushing Beloit
Frankenmuth Casco
Imlay City Eagle River
Macomb (Village of Armada) Fish Creek
Manchester Marinette
Manistee Port Washington
Marlette
Milford
Mt. Clemens
Oscoda
Port Washington
St. Ignace
Vassar
Williamston
Wixom
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idered, in.
of a W disinfection system v
system design parameters (flow rate, TSS, BOD, wastewater temperature,
absorption coefficient (0.35-0.5), initial coliform density, etc.)
prequalification (bioassay-dose response curve and unit dosage
determination )
reduction of coliform count to NPDES limits after 7500 hours of lanp use
minimum design dosage (16,000 microwatts/cm2/sec ) at 70% of lamp output
greater than 90% plug flow and no short-circuiting (dye-test)
production of 90% of UV light at 253.7 nm
65% UV transmissivity (minimum of 50%)
rated lifetime of 7500 hours for UV lamps
no significant production of ozone
integrated chemical cleaning system
minimum contact time (5-7 seconds)
ballast cooling system
lamp temperature control system (95-122°F)
inlet screens
provision to drain reactor
easy access cleanout/inspection ports
suitable materials of construction (304 or 316 SS, resistant to UV, etc.)
light dimming capability
flow proportioning (ability to turn lamps on or off in relation to flow)
monitoring systems (UV intensity, ballast temperature, lamp conditions,
etc. )
acceptance testing (after installation, at manufacturer's cost for re-
testing)
manufacturer's representative to be on-site for verification of proper
installation, start-up, and operation
ballasts certified by manufacturer to be compatible with lamps
sampling ports at both inlet and outlet of the UV reactor
1 disinfection reason minimum warranty on system (coliform levels, minimum
dosage , operation of individual components , etc . )
-------
yr T*lmrinatinn vs. TV rtiKinfartiim for several
and CM <3p"""nlties* tJ^*** have exist ijjq phlorination
IN
JMHMBl
Facility
Ttown of
Churubusco
CBCt)5=20,25
TSS=24.30
Town of
Ferdinand
CBCD5=20,25
TSS=24.30
Kent land
City of
Greensburg
001)5=10,25
TSS=12,30
Average Design
Flow (M3D)
0.25
0.34
0.46
2.4
"includes
post aeration
i Capital
Icost
i
Cl-DeCl 170,000
i
UV (*) ! 50, 000
1
1
C1-D6C1 ! 15, 500
(*) !
i
UV i 66, 646
I
C1-D&C1 ! 92,000
|
UV (*) [82.000
* i
C1-D&C1 1204,000
1
* UV (*) |396,000
I
1
1
0,MtR
Cost
10,500
6,000
24,000
16 , 150
10.850
10.250
271^,000
113,000
Salvage
Value _,
8,215
4,929
Uf333
2.667
9,000
7,000
Present
Worth
165,300
104,300
134,514
215.379
189.864
175.921
546.000
502,000
QUID
Facility
Village of
North Baltimore
(3005=10
TSS=12 _,
City of
Van wert
CBOD5=10
OSS=J.2
Village of
Richwood
CBGD5=10
TSS=12
Village of
Jefferson
CBCD5=10
OSS=15
Average Design
Flow (M3D)
0.80
2.6
0.38
1.21
Cl-DeCl
(*)
L UV _,
C1-DBC1
(*J
UV
Cl-BeCl
<*)
UV
Cl-DeCl
(*)
UV
Total
Capital
cost
131,959
116.054
29,000
201.300
224,400
170,500
110,410
I89f?70 '
Annual
OiW Cost _
1,130
2.820
4,500
8.000
8,500
8.600
Present Wbrtfi
Of OiN
124,170
100.800
Total
Present
_Worti^
150,968
154.602
79,600
328.800
304,100
308.400
225,510
274 .520
(*) * selected alternative
* - derived from piannning documents
------- |