United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-152 Sept. 1981
Project Summary
Ultraviolet Disinfection of a
Secondary Wastewater
Treatment Plant Effluent
0. K. Scheible and C. D. Bassell
Ultraviolet (U.V.) disinfection of a
full-scale secondary effluent was
investigated during a 13-month field
study at Waldwick, NJ. The experi-
mental program was designed to
demonstrate the feasibility of achieving
a fecal coliform density of 200
MPN/100 ml by U.V. irradiation; to
determine the efficiency of U.V.
disinfection relative to dosage, power
consumption, and effluent water
quality; and to assess the utility of the
full-scale unit relative to operation and
maintenance (O&M) requirements.
The impact of photoreactivation was
investigated during the field program.
Uniform procedures for the calculation
of dose and the sizing of U.V. systems
were also developed.
Second order dose-response rela-
tionships were developed and were
found to provide a rational expression
of the microbial response to U.V.
dose. The U.V. absorbancecoefficient,
k (cm~1), was found to be an excellent
parameter for use in the dose expres-
sion and in the design sizing of U.V.
systems. Photoreactivation was ob-
served and was significantly dependent
on temperature. The phenomenon
could result in an order of magnitude
increase in coliform density at a
temperature of 20°C.
In operation, the process was
flexible and simple, requiring minimal
maintenance. Estimated costs ranged
between 1.2 and 0.80/m3 (4.5 and
3.0 C/1000 gal) for typical secondary
treatment plants with flows between
0.044 and 4.4 mVsec (1 and 100
mgd), respectively.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully documented
in a separate report of the same title
(see Project Report ordering informa-
tion at back).
Introduction
Public health and the protection of
aquatic and human environments are
the overriding considerations that
determine disinfection practices in this
country. The widespread application of
chlorine disinfection technology to
water supplies has resulted in a
dramatic decrease in waterborne disease
outbreaks and a general improvement of
the public health.
Results of recent studies of chlorina-
tion, however, are raising serious
questions about the environmental
impact of chlorine: the aquatic toxicity of
residual chlorine, the resistance of
viruses to chlorine, and the potential
formation of chlorinated organics which
may be carcinogenic. Certainly the
benefits and contributions of chlorina-
tion to public health cannot be denied,
nor should the hasty elimination of
chlorination as a disinfection practice
be considered. In light of the adverse
impacts and uncertainties associated
with chlorination, however, a search for
alternative disinfection practices is
warranted.
-------
Disinfection of wastewaters by irradi-
ation with U.V. light is a viable alternative
to chlorine disinfection. Although U.V.
light had been an accepted disinfection
technique for potable, or high-grade
waters, its application to lower-grade
waters (such as secondary effluents)
has not been widely practiced, primarily
because of a lack of efficient system
design. Recent improvements, however,
in U.V. lamps and U.V. system designs
have made the U.V. process a viable
alternative to chlorination for the
disinfection of wastewater treatment
plant effluents. These advances have
prompted a serious reconsideration of
U.V. disinfection of secondary effluents.
This report summarizes the results of
a full-scale U.V. disinfection demonstra-
tion project conducted at the Northwest
Bergen County Water Pollution Control
Plant (NW Bergen) in Waldwick, NJ. the
prototype full-scale U.V. system was
tested on a conventional activated
sludge plant effluent to determine the
system's reliability in achieving desired
coliform levels. Other project objectives
included defining the system's O&M
requirements and the process costs
relative to alternative disinfection
procedures.
Equipment Installation and
Specifications
The NW Bergen facility is a conven-
tional, air-activated sludge plant with a
design capacity of 30,000 mVday (8
mgd), and an average yearly flow, at
present, of approximately 18,900 m3/
day (5 mgd). One of the plant's dual
chlorine contact chambers was inactive
because of low-flow input to the plant.
This inactive chamber provided an ideal
location to install the gravity flow U.V.
disinfection system.
A cutout view of the chlorine contact
chamber (Figure 1) shows the installa-
tion of the U.V. lamp battery in the
chamber. Two concrete webs were
installed to provide the support. The
lamp battery itself was supported by two
steel bulkheads set into the concrete
webs.
The U.V. system was a prototype
model PWS SE-7.5 manufactured by
Pure Water Systems, Inc.,* of Fairfield,
NJ. The lamp battery contained 400
85W germicidal lamps, each with a
rated output at 253.7 nm of SOW and an
effective arc length of 142 cm. Each
lamp was enclosed in a quartz sleeve
that had a 2.3-cm outer diameter. The
nominal incident intensity at the quartz
sleeve surface was estimated to be
27,000 yuw/cm2 at full power.
The U.V. unit was equipped with lamp
battery shutoffs in one-sixth increments
and a variac to permit the adjustment of
applied voltage between 40% and
100%. The estimated total power
requirement was 40 kW at 480 volts.
The physical size of the lamp battery
was 76 x 76 x 152 cm, and the void
volume was 0.49 m3. Exposure time in
the lamp battery was 2 seconds at the
normal operating flow of 21,000 mVday.
The headless experienced at this flow
was approximately 15 cm.
The system was equipped with a
continuous mechanical cleaning system
consisting of a manifold of replaceable
elastomeric glands (similar to wiper
blades) fitted over each quartz sleeve.
The manifold was passed over the
quartz at a prescribed stroke rate. The
cable driving this system was powered
by a pneumatic cylinder (see Figure 1).
The lamps, placed to simulate what
the manufacturer describes as the
"thin-film" design, were in even rows
with 3.55 cm centerline spacings, both
horizontally and vertically. The mini-
mum spacing between any two quartz
surfaces was 1.25 cm. Flow was
perpendicular to the lamps.
Ultraviolet Dosage
Because the U.V. disinfection units
are, in effect, bundles of lamps totally
Stainless Steel
Bulkhead
Wiper Drive
Piston
Influent
Existing C/2
Contact
Chamber „
'Mention of trade names or commercial products
does not constitute endorsement by the U.S.
Environmental Protection Agency.
- Reinforced
Concrete
Support Walls
Figure 1. Ultraviolet disinfection
unit installation.
immersed in the fluid, problems are
posed in accurately expressing or
measuring the U.V. intensity and,
conseqeuntly, the applied U.V. dosage.
The average intensity in the lamp
battery is not readily determined in such
closely packed banks of lamps. The
intensity at one point in the system is
influenced by radiation of the surround-
ing lamps, with the zone of influence
dependent on the nominal lamp intensity,
the lamp spacing, and the water quality.
A uniform methodology for determin-
ing the average U.V. intensity and
dosage within a U.V. lamp battery was
developed as a part of this study. Albeit
preliminary, the procedure attempts to
include all factors inherent in the true
dosage application, thus providing a
rational parameter for U.V. system
design.
Traditionally, the dosage has been
defined as the product of I and t, where t
is the exposure time and I is the average
U.V. intensity in the fluid. For the NW
Bergen application exposure time, te,
was computed as:
te = Vv/Q
where Vv = void volume (m3),
Q = flow (mVsec).
The average intensity in a lamp
battery, as stated earlier, cannot be
directly measured. Thus, the dosage
computation procedure used for this
study uses a computed average intensity
based on water quality (U.V. absorbs nee),
lamp rating (nominal incident intensity),
and lamp placement (spacing).
The nominal incident intensity of a
single lamp, I0, can be computed from
the physical dimensions of the quartz
surface and the U.V. output rating of the
lamp. At NW Bergen, the nominal
incident intensity at the quartz surface
was estimated to be 27,000 fAN/cm3.
The U.V. intensity of a lamp will
attentuate as the distance from the
energy source increases. This attentua-
tion occurs by two mechanisms. The
first is simply the dissipation of the
intensity described by the ratio of
surface areas. This reduces to the ratio
of the radii:
r + x
where:
r = radius of the lamp (cm),
x = distance from the surface of the i
quartz (cm). "
-------
The second relates to the absorptive
properties of the wastewater. The
absorption of U.V. radiation in a waste is
commonly defined by the absorption
coefficient — a measure of the unit
absorbance of a beam of light passing
through a known liquid depth, described
by Beer's Law, as follows:
where:
k = adsorption coefficient (cm"1),
x = distance, or depth of the fluid (cm).
These attentuation factors, the dissi-
pation and absorption of energy, com-
bined to define the intensity at any point
relative to the nominal intensity of a
lamp. The intensity at any point from
one lamp is defined as:
tion coefficient and the lamp spacing.
With the development of these relation-
ships, the average intensity can be
determined for a specific unit (known
lamp spacing) for any water quality
(absorption coefficient) experienced.
The exposure time, as described earlier,
is known from the flow and the hydraulic
characteristics of the systems. Conse-
quently, the U.V. dosage can be com-
puted at any instant or sampling.
Experimental Program
The 13-month experimental program
investigated the effectiveness and the
utility of U.V. disinfection. The primary
elements of the study were developing
dose-response relationships; evaluating
seasonal variations in disinfection
efficiency; and assessing the unit's
long-term performance capabilities, its
O&M requirements, and the impact of
the photoreactivation phenomenon.
The analysis of these elements yielded a
U.V. system design procedure and an
estimate of the costs associated with
U.V. disinfection.
The wastewater characteristics were
those of a well-treated secondary
effluent. The geometric mean total
coliform density was approximately
200,000 MPN/100 ml and the mean
fecal coliform density was 50,000
MPN/100 ml. Suspended solids and
turbidities were typically low; solids
average 6.5 mg/L, and turbidity averaged
4 NTU. The parameter specific to the
design and control of the U.V. system,
the ultraviolet absorption coefficient,
averaged 0.39 crrf1.
where:
I = the intensity at the point of interest,
(/M//cm2),
I0 = the nominal incident intensity at
the lamp surface, (/M//cm2).
Where multiple lamps exist, the inten-
sity at the point of interest is the sum of
the attenuated intensities contributed
from each lamp in the system.
A compounding factor, F, was defined
to facilitate calculating the average
intensity,in a multiple lamp system and
describes the intensity at any point
within a cross-sectional plane of the
lamp battery relative to the nominal
incident intensity. F was computed for a
number of points in a representative
segment in the cross sectional plane.
This procedure allowed the construc-
tion of isointensity lines, which by
graphical integration gave an estimate
of the average F factor.
Figure 2 displays the isointensity
lines computed for the symmetrical
lamp placement used at NW Bergen.
The nominal lamp spacing was 1.25 cm
(defined as the minimum distance
between any two quartz surfaces), and
the absorption coefficient was 0.4 cm'1.
The average F factor, determined by
graphical integration, was 1.78. The
nominal incident intensity for the lamps
used in this system was estimated to be
27,000 /uW/cm2. The average intensity
can therefore be estimated (based on
the' average F of 1.78) at 48,000
AfW/cm2.
The average intensity can thus be
computed as a function of the absorp-
2.05-
•2.0
2.0 —-^ ^— 2.05
Figure 2. Example of computed isointensity lines in lamp quandrant.
3
-------
Dose-Response
The dose-response relationship is
basic to U.V. analysis and system
design. Given an accurate measure of
dose and a measured response in terms
of bacterial kill, reasonable judgements
of design requirements can be made to
achieve a desired bacterial density.
Typically the dose-response has been
described by first order kinetics, which
will show a marked tailing as the log
surviving fraction is reduced to low
levels (the range of coliform densities
where disinfection processes normally
operate). It is suggested that the dose-
response relationship at these levels is
better characterized by a model that
assumes 2nd order kinetics with respect
to density:
dN -
dt
= YNZI
that, when integrated, becomes:
1 1
-= Ylt,
where:
N = the coliform density at time t,
NO = the influent coliform density,
Y = the rate constant,
I = the average ultraviolet intensity
in the exposure chamber,
t = the exposure time.
If the initial coliform density, N0, is
assumed to be much greater than the
final density, N (which is typically the
case with municipal effluents), the term
1/No becomes insignificant and the
expression can be reduced to:
1
-ft
= Ylt
The results showed excellent correla-
tions when linear regressions of the log
effluent coliform density and the log
dosage were constructed. Figure 3
displays the least squares regression of
the log effluent fecal coliform and the
log dose. The observed data represent
approximately 350 samplings conducted
throughout the 1 -year pilot program.
The correlation coefficient for this
regression was 0.66, indicating that
approximately 44% of the variance in
the data was explained by the relation-
ship. The regression equation repre-
sented on Figure 3 is:
Effluent fecal coliform = (1.26 x 1013)
Dose"227.
As an example, to achieve a fecal
coliform level of 200 MPN/100 ml,
which is a widely accepted guideline,
the dosage requirement predicted by
the regression would be 60,000 pW-
sec/cm2.
Multiple regression analyses indicated
that temperature or other measured
water quality parameters were not
significant to the dose-response rela-
tionship. The significance of water
quality is, of course, implicit in the
dosage expression, which accounts for
the U.V. absorption characteristics of
the wastewater.
Photoreactivation
A portion of the experimental program
was devoted to investigating photoreac-
tivation, a phenomenon associated with
U.V. disinfection. Photoreactivation is
the ability of a cell to repair U.V.-induced
Carnage when it is subsequently exposed
to energy wavelengths in the visible
light range between 310 and 500 nm.
Thus, simple exposure to sunlight can
provide the catalyst to this repair
mechanism.
A static bottle test was the primary
procedure used to measure photoreac-
tivation. An irradiated sample would be
immediately split to an opaque (or dark)
bottle and a translucent (or light) bottle.
These samples were then exposed to
sunlight for 1 to 1.5 hours at the
ambient water temperature. Coliform
density was again measured. No signi-
ficant differences were noted between
the densities in the dark bottle and the
densities measured immediately after
ultraviolet irradiation. Thus, any in-
crease in the light bottle density was
attributed to photoreactivation.
1
8
*-.
|
i,
.*•«
<0
Q
|
"5
o
u
k*.
&\j\j, \j\jv
200,000 <
100,000
50,000
20,000
10,000
5,000
2,000
1,OOO
500
200
100
50
20
10
5
2
1
.
™ 0 9
Fecal Coliform
Eff FC = (1.25 x /O13) D~227
r = 0.66
.
.
. • *. .
*. • • ' •
% •• • •
^ • • •
^^ • • • • • * •
. • \!X J •• • .
• . VM« « V. .
"• ".*£*£•'••".'
- • •^••^k«» M •
*f» "^ • • •
•• • •• ^.M ••
• • ^^^
• t^-'^v.
* •• . r: %
-.- \
V
_ • • »mm» ^
l 1 I 1 t I I \ i I l lilt
Figure 3.
10 20 4O 60 80 100 200 400 600 800
Ultraviolet Dosage (103tiW-sec/cm2)
Second order dose-response relationship for facal coliform.
-------
The results of the photoreactivation
analysis for fecal coliforms are shown
on Figure 4. The regression lines are
based on approximately 170 samplings
taken through the term of the field
study. A step-wise multiple regression
analysis indicated photoreactivation
significantly depends on temperature.
The regression equation is:
Effluent Fecal Coliform (at 1 hr) =
1.35x101310007T'mpDose-23i
where temperature is in °C. The
correlation was excellent, with a
correlation coefficient of 0.80 (64% of
the variance explained). The observed
data presented on Figure 4 are differen-
tiated as to the two major temperature
periods of the study. The regression
lines are solutions at 10°C, 15°C, and
20°C.
Temperature was not significant in
the regression for the dark bottle data;
thus the lower line on Figure 4 repre-
sents all temperatures. The regression
equation in this case was:
Effluent Fecal Coliform = 1.91x1012
Dose'207.
At 10°C, a two-fold increase in den-
sity is predicted due to photoreactiva-
tion. At 20°C, a 10-fold increase is
predicted. The implication of photoreac-
tivation is that a higher dosage would be
required if photoreactivation were to be
accounted for in effluent criteria. Thus,
for a required effluent fecal coliform
density of 200 MPN/100 ml, a three-
fold increase in dosage would be
necessary at 20°C if the impact of
photoreactivation were to be considered.
Unit Performance
The U.V. system was continuously
monitored during this study, not only to
investigate the germicidal efficiency of
U.V. radiation, but also to evaluate the
system under long-term operation (13
months in this instance). Highlights of
the more significant O&M results are:
• The average lamp service was
6900 to 7200 hours. This is close to
the average life expectancy report-
ed by the lamp manufacturers. A 9-
to 10-month lamp replacement
cycle is recommended for mainten-
ance purposes.
• The mechanical wiper was in
service approximately 7200 hours.
There was no wiper-related effi-
ciency loss or visible wear on the
quartz sleeves. Some wear was
s
01
Q
<0
I
I
1.000,000
600,000
400,000
200,000
100,000
60,000
40,000
20,000
10,000
6,000
., 4,000
* 2,000
? 7,000
i 600
b 400
200
700
60
40
20
10
6
4
2
1
Fecal Coliform
June 5 - August 15
Avg. Temp. = 20.7° C
Range = 18° to 24°C
Feb. 5 - April 17
Avg. Temp. = 11.2°C
Range = 9.5° to 14.5°C
Photoreactivated
Sampl
~ Nan Photoreactivated
Samples
I
I I I I I I I I
I I I
10
20
Figure 4.
40 60 80 100 200 400 600 1000
Utraviolet Dose (103 uW-sec/cm2)
Photoreaction of fecal coliform.
noted on the wiper drive cable and
the wiper glands. A 12-month
replacement cycle is recommended
for the glands. A 4-year replace-
ment cycle may be required for the
quartz sleeves, depending on the
rate of solarization (increasing
opacity).
No signs of corrosion were noted
on the stainless steel unit.
Prescreening is recommended in
some situations to prevent an
accumulation of fibrous material in
the unit and to prevent lamp
breakage from any debris that
might inadvertently be present at
the disinfection influent channel.
At the NW Bergen facility, algae
would slough from the walls of the
secondary clarifiers and would drift
to the U.V. system as fibrous
clumps. These clumps would catch
on the lamps and be wiped to the
sides by the automatic wiper
mechanism. This caused no effi-
ciency loss, but did cause a main-
tenance problem in that the accu-
mulated material had to be manu-
ally cleaned from the unit periodi-
cally.
• Generally, the operation of the
system was marked by its flexibility,
its simplicity, and by what was
considered a reliable consistent
performance.
System Design
By analyzing the system and the
results of the field study, a rational
design procedure based on dosage
requirement, effluent criteria, and plant
effluent characteristics was developed.
Effluent coliform criteria are typically
written as a maximum 30-day geometric
mean and a maximum 7-day geometric
mean coliform density. The design
-------
requirement for a U.V. system would be
to achieve and maintain the dosage
required to meet these criteria at the
critical conditions of flow and U.V.
absorbance (i.e., the maximum 30-day
and 7-day occurrences). This critical
period would occur when variations in
the flow and water quality (absorption
coefficient) combine to require maxi-
mum output.
Recall that the dosage has been
expressed as a function of the incident
intensity, the lamp spacing, the void
volume, the flow, and the absorption
coefficient. The lamp spacing, incident
intensity, and void volume can be set by
the physical design of the system.
Therefore, the critical design condition
(i.e., sizing) will be dictated by the
maximum combined impact of the flow
and the U.V. absorption coefficient.
The 30-consecutive-day coliform
requirement was found to control the
design at the NW Bergen facility. The
critical 30-consecutive-day, average
U.V. absorption coefficient was 1.8
times the annual average coefficient.
Over this same 30-day period, the
average fjow was 1.15 times the annual
average flow. An analysis of the
combined flow and U.V. absorption
effects indicated that this combination
controlled the critical 30-consecutive-
day dosage.
A series of design curves was devel-
oped. These curves are shown (Figure 5)
for a fixed unit lamp spacing (1.25 cm)
and a fixed lamp rating (incident
intensity of 27,000 //W/cm2). The
values describe the unit used at the NW
Bergerv facility. A different series of
curves can be developed for an alterna-
tive configuration.
Figure 5 presents the total design
power requirement to meet a specified
dosage under the controlling 30-day
effluent conditions. The limiting effluent
criterion was that the maximum 30-
consecutive-day, geometric mean fecal
coliform density not exceed 200 MPN/
100 ml. Recalling Figure 3, the dosage
required to achieve this is 60,000 /uW-
sec/cm2. The design is related to the
annual average flow at various annual
average absorption coefficients. The
design requirement under these condi-
tions was 2.1 x the annual average
requirement. Thus, atan annual average
flow of 38,000 mVday (Figure 5) and a
annual average absorption coefficient
of 0.4 cm"1, the design power require-
ment would be 70 kW, although the
annual average use would be approxi-
mately 30 to 35 kW. The design curves
presented on Figure 5 do not include a
dosage adjustment to compensate for
photoreactivation.
Ultraviolet Disinfection Costs
Estimates were made of the capital
and O&M costs associated with the
application of the U.V. disinfection
process to secondary wastewater
treatment plant effluents. These costs
are based on the information derived
from the NW Bergen study and address
the installation and operation of a new
permanent facility. Retrofitting to an
existing plant has not been considered.
although the capital outlay would b
lower in such a case.
The costs of a particular applicatioi
are highly sensitive to the specific sit
characteristics such as flow and wate
quality variability and physical sit
conditions. As such, the estimate
provided herein must be considered a:
preliminary when used to estimate th<
cost of a particular application. Thi
estimates also provide a perspectivi
when comparing the U.V. process t<
alternative disinfection procedures.
Equipment costs were estimated or
the basis of information (1979) providec
I
•§
!
^
I
•I
W>
11)
Q
3,000
2,000
1,000
500
200
100
50
20
10
2
1
0.5
0.3
1.25 cm Spacing •
I0 = 27.000 (jtW/cm2
Annual
Average
Absorbance
Coefficient
k (cm"1)
Design
Power Requirement
2.1 x Annual Average Requirement
I I I I I I III
I I
I I 11II
I I I I I III
0.01 0.02 0.05 0.1
\ I
0.2 0.5 1.0 2.0
(m3/sec)
5.0 10.0
I I
1.0 10.0
(mgd)
Annual Average Flow
Figure 5. Ultraviolet system design example.
100.0
-------
by Pure Water Systems, Fairfield, NJ,
manufacturers of the system utilized at
NW Bergen. The number of units
installed depends on the peak design
requirement and the degree of replication
appropriate to the particular application.
For purposes of this analysis, a conser-
vative approach was taken in sizing the
system. The degree of replication is
considered high; with full-scale applica-
tions and operating experience, the
system design will be refined and may
result in lower sizing requirements.
Structural costs included concrete
tankage, access ways between each
lamp battery, influent and effluent
channels, a building to house the entire
unit operation, and ancillary equipment
such as overhead cranes, grating, and
utility hookups. Engineering was esti-
mated at 10% of the structural and
installation costs, and a contingency
cost was estimated at 30% of the
structural capital costs. Installation was
estimated to be 20% of the equipment
costs and included the electrical supply.
The U.V. system is relatively simple
and should require minimal labor for
O&M. Given the prototype nature of
large scale U.V. systems and the lack of
significant full-scale operating experi-
ence, a conservative estimate of approx-
imately 0.5 man-year was considered
appropriate. Material costs included
lamps, quartz enclosures, ballasts,
wiper rings, and miscellaneous expend-
able equipment parts. The system is
assumed to use germicidal lamps with a
replacement rate of 9 months. A
replacement cycle of 25% per year is
assumed for the quartz sleeves, as well
as the lamp ballasts. The rings, based on
the pilot study evaluation, should be
replaced each year. The miscellaneous
materials (repairs, etc.) were assumed
to be 0.5% of fixed capital. Power costs
were estimated on the basis of the
annual average power requirement.
The capital and O&M costs derived for
the U.V. disinfection process over a
range of 10 to 1000 kW systems are
summarized (Table 1). The capital costs
are amortized over 20 years at a rate of
6%. The total estimated annual costs
were determined to range between
$16,000 and $1,119,000/year, for
system sizes between 10 and 1000 kW.
This is equivalent to a unit cost of 1.2 to
0.8C/m3 (4.5 to 3.0C/1 OOOgal), respec-
tively.
As indicated by Table 1, .the capital
cost accounts for approximately 43% of
the annual costs. Power accounts for
approximately 12% to 17%, and labor
represents 6% to 14%. Materials ac-
count for a major share of the annual
costs, ranging between 28% and 35%.
Comparison of Costs for
Alternative Disinfection
Processes
The U.V. disinfection unit costs have
been compared with those reported for
alternative disinfection processes (Table
2). These costs, derived from a variety of
sources, have been adjusted to 1979
based on the EPA national index(1979 =
330). In certain cases, a wide range in
cost estimates was found for a specific
process (this was particularly the case
for ozonation). The values presented on
Table 2 represent an approximate
average of the various estimates.
Because the costs from the various
sources may differ in assumptions for
labor, power, etc., caution is warranted
in any direct comparisons.
U.V. disinfection appears to be
particularly competitive at the lower
flow levels. As the design flow increases,
U.V. disinfection is estimated to be
comparable in cost to chlorination,
chlorobromination, and chlorination/
dechlorination, and considerably less
than ozonation.
The full report was submitted in ful-
fillment of Grant No. R-804880 by
HydroQual, Inc., Mahwah, NJ 07630
(formerly Hydroscience, Inc., West-
wood, NJ) under a project funded jointly
by the U.S. Environmental Protection
Agency and the Northwest Bergen
County Sewer Authority.
Table 1. Capital and Operation and Maintenance Costs Associated with U. V. Disinfection Process
Design
Requirement
(kW)
10
100
1.0OO
Equivalent"'
Annual Flow
(mgd) (nf/sec)
1
10
1OO
0.044
0.44
4.4
Capital
Costs
(dollars)
80,000
700.000
5,200,000
Annual O&M Costs
(dollars)
Labor Materials Power
2.500
10.500
70,000
4.50O
43.000
400.000
2,000
19,700
197,000
Total
O&M
900
7,320
66.700
Amortized™
Capital
Costs
7.000
60.000
451,400
Total
Annual Unit Costs
Costs C/1OOO gal C/m3
16,000
134,000
1.119.0OO
4.5
3.6
3.0
1.2
0.95
0.8
111 Assumes: *= 0.5 cm"1 (average); peaking factor = 2.7; 700% replication at 10 kW. 50% at 1OO kW, 25% at 1000 kW; 1.25 cm spacing; max 30-day
mean fecal coliform density not to exceed 200 MPN/1OO ml.
" 20 years at 6% (CFR = 0.087;.
-------
Table 2.
Process
Unit Costs Associated with Alternative Disinfection Processes
Unit Cost (C/m3) for Design Flow (m3/sec)
0.044
0.44
4.4
Ultraviolet Irradiation
Chlorination
Chlorination/Dechlorination (SOi)
Ozonation (from air}
Chlorobromination
1.2
1.7
2.2
3.4
1.6
0.95
0.74
0.82
2.0
0.61
0.8
0.58
0.60
1.45
0.35
O. K. Scheible and C. D. Basse!/ are with HydroQual, Inc., Mahwah, NJ07630.
Albert D. Venosa is the EPA Project Officer (see below).
The complete report, entitled "Ultraviolet Disinfection of a Secondary Waste-
water Treatment Plant Effluent," (Order No. PB 81-242 125; Cost: $14.OO.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
US GOVERNMENT PRINTING OFFICE; 1981 —757-012/7343
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
Third-Class
Bulk Rate
LUU « TlLLtY
REblUiM V tPA
LIBRARIAN
<>3u S UEAKbOKN S]
JLL 50604
------- |