-------
quality of the activated sludge effluent was good. Additionally, the
effluent total and fecal coliform densities were somewhat higher than in
previous runs with.effluent of similar quality.
The combination of decreased residence time and the relatively low
percent transmittance resulted in one of the lowest UV doses used during
the project. The calculated dose., Dy, during Run U8 was only about one-third
of the dose used during Run Ul through U3, and was about one-half of the
dose used during Runs U4 and U5. The dose used during Run U7 was approxi-
mately 30 percent higher than the 11,500 ywatt-sec./cm2 used during this run.
The low dose used was the reason for the decrease in disinfection efficiency.
Figures 105, 106, and 107 are time-series plots of the microbiological
data. The apparent variation in bacterial densities in the UV disinfected
effluent is approximately one log either side of the geometric mean. The
effect of the variability can be seen in the extreme-value frequency ,
distributions in Figures 108, 109, and 110. The indication is that 50
percent of the time a fecaT coliform density of about 320 per 100 ml will be
exceeded, and that a density of 400 fecal coliforms per 100 ml will be
exceeded approximately 45 percent of the time.
As in Run U7 poor correlations were observed when UV intensity was,
plotted versus observed log reductions in total and fecal coliforms. When
plotted versus log reduction of'total coliforms the equation of the line
obtained by linear regression analysis was log y = 0.048 x - 3.79. The
correlation coefficient for this line was - 0.15. When plotted versus log
reduction of fecal coliforms the equation obtained was log y = 0.035 x
- 3.83. The correlation coefficient for the line was - 0.09.
184
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190
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SECTION 8
VIRUS STUDIES
One of the objectives of the project was to evaluate the comparative
resistance of poliovirus, F2 bacteriophage, and total and fecal coliform
bacteria to ultraviolet radiation. The poliovirus strain used was an atten-
uated Type I culture obtained from Dr. 6. Berg, U.S. E.P.A., Cincinnati,
Ohio.
A total of three replicate experiments were conducted on the following
dates: (1) 22 April 1975, (2) 13 May 1975, and (3) 26 June 1975. Initial
volume of poliovirus seed was approximately 3.2 liters, containing approxi-
mately 8x1O7 plaque forming units (pfu) per ml. Bacterial virus F2 was
added to the poliovirus culture at a titer of 3xl08 pfu per ml.
Figure m illustrates schematically the flow diagram of a typical run.
Activated sludge effluent was used as a wastewater source. The virus/phage
seed was pumped into the effluent stream at a rate of 100 ml/minute on the
suction side of a centrifugal pump, where the seed became well mixed
with the effluent prior to entering the UPS UV unit. After emerging from
the UV unit the effluent flowed into chlorine contact basins, where a very
high chlorine residual was maintained to destroy any poliovirus which
might have survived the UV irradiation. Three sample taps were located as
shown in the diagram.
After collecting the control samples the UV lamps were energized and
allowed to reach their peak output. Ultraviolet intensity readings were
made with the IL 500 radiometer, and the water quality meter provided with
the UPS unit. After the warm-up time, three separate test samples were
collected for virus enumeration (1) prior to virus/phage addition (for
indigenous virus), (2) after the.pump, but before the UV unit, and (3)
after the UV unit. Three duplicate samples were collected one minute
later, and another duplicate set, one minute after that. This entire pro-
tocol was repeated at all four wastewater flow rates.
In order to protect the chemists and biologists from poliovirus exposure,
the bacteriology and chemistry samples were collected prior to addition of
the virus/phage inoculum to the wastewater, but with the UV unit at steady
state and the lamps on. No chemical analyses were .performed on the seeded
samples.
191
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192
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FIRST UV VIRUS RUN
An operating summary of the UV unit for the first virus run appears on
Table 33. The hydraulic characteristics .and start-finish meter readings are
presented for each of the flow conditions investigated.
, A summary of the chemical characteristics of the wastewater before and
after exposure to UV radiation averaged over all four flow rates is given
in Table 34. No significant change in any wastewater quality variable, ex-
cept possibly BOD, was observed. A summary of the bacteriological data is
given in Table 35. It is clear that, as wastewater flow rate decreased,
total and fecal coliform reduction increased. This was expected, since a
decrease in flow rate corresponds to an increase in residence time, and
thus, an increase in exposure time to UV irradiation. It also appears that
total and fecal coliforms displayed approximately the same relative resis-
tance to UV irradiation.
Results from the phage seeding experiments are given -in Table 36
(control sampling) and 37 (test sampling). The purpose of the control
sampling was to establish the attainment of steady-state conditions at
each flow rate prior to the test sampling. The UV lamps were turned off
during control sampling. Steady-state conditions were established when
influent and effluent titers were the same.
No F2 phages, were detected in either the Control 2 samples (before UV)
or the Control 3 samples (after UV). The phage/poliovirus seed suspension
was conveyed from a cubitainer 3 meters above the floor of the filter
gallery through a metering pump and tygon tube. The 3-meter length of
tygon tubing had been flushed with sterile distilled water prior to the run,
and was still full of the water when the virus feed pump was activated.
The virus/phage suspension had not completely displaced this water at the
commencement of the first run (4.7 I/sec.), and as a result the influent
titers were negative. This effect was not repeated in the three successive
runs, because the line was not flushed between runs.
Steady state conditions were established at 3.2 and 1.9 I/sec (Table
36). At 0.6 I/sec, two of the Control 3 samples were negative for phage.
This was presumably because the UPS UV unit had not been completely flushed
following the last test run when the phage titer had been reduced by
several logs. As a result the phage titer at the beginning of the control
run was lower than expected, and thus the phage numbers were undetected
because the dilutions were carried out too far.
Examination of Table 37 reveals that the number of indigenous phage
present in the wastewater was insignificant relative to the F2 titer after
seeding. It is also evident that F2 phage were undetected in the samples
before and after the UV unit during the 4.7 I/sec run probably for the
same reasons mentioned for the control samples. In general, it appears
that F2 bacteriophage may be slightly more resistant to UV than total or
fecal coliforms, as indicated by the mean log reduction values (Table 37).
193
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TABLE 33. OPERATING SUMMARY OF THE FIRST UV VIRUS RUN
Flow Rates, I/sec
Theoretical t, sec.
100 percent flushing time,
sec.
WQ Meter (Start), Dimension-
less units - scale (0-40)
WQ Meter (Finish), Dimension-
less units (scale 0-40)
Radiometer (Start) yw/cm
Radiometer (Finish), yw/cm
4.7
11.4
28
32
27
550
530
3.2
16.8
42
29
24
550
540
1.9
28.2
70
<20
20
550
540
0.6
85.1
210
30
25
550
540
194
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TABLE 34. RESULTS OF CHEMICAL ANALYSES OF GRAB SAMPLES AVERAGED OVER ALL
FOUR FLOW RATES IN THE FIRST VIRUS RUN.
Parameter Influent to UV Effluent from UV
COD, .mg/1
TOC, mg/1
SOC, mg/1
BOD, mg/1
TSS, mg/1
Turbidity, NTU
Color, Pt-Co units
NH3-N, mg/1
Org-N, mg/1
N02-N + N03-N
N02-N
D.O. , mg/1
pH
Sp. .Cond.
Total Alk. , mg/1
p Alk. , mg/1
TDS, mg/1
Cl~, mg/1
%Transmittance at
254 nm
46.2
15.5
10.0
10
20
2.8
30
1.8
4.4
6.0
0.3
3.4
7.4
727
131
0
522
58
67.2
47.9
15.2
10.8
4.5
22
2.8
30
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3.3
*v
7.3
750
-
-
-
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66.6
195
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TABLE 36. STEADY-STATE TITERS OF F2 BACTERIOPHAGE CONTROLS IN
FIRST VIRUS RUN.
Phage titers, pfu/ml
Detention time, sec
(Flow Rate, I/sec)
Sample
Control 2
30 sec
60 sec
90 sec
Geometri c
Mean
Control 3
30 sec
60 sec
90 sec
11.4
(4.7)
Before UV
< 2. 0x10°
< 2. 0x10°
< 2. 0x10°
2.0x10°
After UV
< 2. 0x10°
< 2. 0x10°
< 2. 0x10°
16.8
(3.2)
4.3xl04
3.6xI04
8.3xl04
S.OxlO4
5.3xl04
7.1xl04
1.2xl05
28 85
(1.9) (0.6)
1.4xl05 5.0xl04
7.6xl04 l.OxlO4
1.2xl05 4.2xl05
l.lxlO5 5.9xl04
7.8xl04 <2.0xlO°
7.1xl04 <2.0xlO°
3.9xl04 T.2xl06
Geometric <2.0x10
Mean
Control 1 SEED CULTURE
3.2x10
2.8x10
8
8
7.7x10
6.0x10
,4
<1.7xlO
197
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TABLE 37. TITERS OF F2 BACTERIOPHA6E EXPOSED TO ULTRAVIOLET
RADIATION AT DIFFERENT FLOW RATES IN FIRST VIRUS RUN.
Phage Titers,
pfu/ml
Detention Time, sec
(Flow Rate, I/sec)
Sampl e
INDIGENOUS PHAGE
0 sec
60 sec
120 sec
Geometric Mean
F2 Phage
Before UV Unit*
0 sec
60 sec
120 sec
Geometric Mean
F2 Phage
After UV Unit*
0 sec
60 sec
120 sec
Geometric Mean
Log Reduction
11.4
(4.7)
1.7xl02
2.7xl02
1.2xl02
1..8xl02
lx!03
>,lx!03
>lx!03
-
16.8
(3.2)
9.5X101
9.8X101
l.lxlO2
l.OxlO2
2.8xl04
5.9xl04
2.8xl04
3.6xl04
3.9xl02
3.6xl02
6.8xl02
4.6xl02
1.90,
28
(1.9)
4.9X101
6.3X101
6.2X101
B.SxlO1
__
4.4xl04
9.6xl04
6.5xl04
l.lxlO2
1.6xl02 ,
l.SxlO2
1.5xl02
2.63
85
(0.6)
l.lxlO2
6.5X101
.l.lxlO2
9.2X101
7.7xl05
6.0xl04
2.9xl05
2.4xl05
5.4X101
8.0x10°
l.lxlO1
1.7X101
4.15
*UV light had been on for two minutes.
198
-------
Results from the poliovirus seeding experiments are summarized in Table
38. Poliovirus was undetectable in the control samples during the 4.7 I/sec
run due to the incomplete flushing of sterile distilled water from the feed
line. It is clear that steady-state flow conditions were established<-at the
other three flow rates, as indicated by the comparable virus titers between
the Control 2 and Control 3 samples at each flow condition. Mean log
reduction of poliovirus increased with decreasing flow rate (or increasing
detention time). Also, poliovirus appears to have elicited a similar re..^
Sponse to UV inactivation as coliform bacteria. A complete summary of the
first virus run is given in Table 39.
A summary of the dose-related data for the first UV run appears in
Table 40. Dosages were calculated as enumerated in Section 7. The very
high indicated doses, Dj, were a direct result of the high intensity read-
ings. The highest doses, Dj, were obtained during this run, as well as the
best disinfection, for both viruses and coliforms.
SECOND UV VIRUS RUN
The second poliovirus run with the UPS unit was conducted on 13 May
1975. On the afternoon of 12 May, the UV unit was turned off, taken out of
service, cleaned with a proprietary cleaning solution provided by UPS, Inc.,
rinsed with tap water, and drained. Early the following morning it was
refilled and flushed again with tap water. The lamps were then turned on,
and intensity readings with the UPS water quality meter and IL 500 radio-
meter were recorded every 30 seconds for a period of 5 minutes. Figure 112
shows the responses. Maximum output was attained approximately 1.5 minutes
after startup. The lamps were then turned off for a.period of 5 minutes,
but tap water flushing continued. Then the lamps were turned on, and again
the readings were recorded, as shown in Figure 113. This time, the response
was much quicker, as the maximum output was attained after only 1 minute.
Following this, the lamps were turned off, and activated sludge effluent was
valved into the unit for the first time since the cleaning. About 1,5 min-
utes later the lamps,were turned on, and meter readings were recorded, as
shown on Figure 114. The response was significantly different from the tap
water readings. First, the UV output reached a maximum level after only
20 seconds, and the maximum output was higher than that recorded on tap
water. Then, between 2 minutes and 4 minutes the intensity declined from
110 to 100 uwatts/cm2. At the same time, the water quality meter responded
much differently, reaching a maximum value of only 10 after 30 seconds, but
remaining unchanged thereafter.
The ultraviolet intensity readings of 100 to 110 ywatt/cm2 on tap. water
were unusual in that in previous disinfection runs intensity readings of
approximately 550 uwatts/cirr on wastewater effluent had been obtained. There
are several possible reasons for the low intensity readings. First,
film build-up on the quartz sleeves might have been inadequately removed.
Second, the proprietary cleaning compound used may absorb UV light. If the
199
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TABLE 38. TITERS OF POLIOVIRUS'TYPE I EXPOSED TO UV RADIATION AT DIFFERENT
FLOW RATES IN FIRST VIRUS RUN.
Virus Titers, pfu/ml
Detention Time, sec
(Flow Rate, I/sec)
Sample
Control 2-before UV
30 sec
60 sec
90 sec
Geometric Mean
Control 3-after UV
30 sec
60 sec
90 sec
Geometric Mean
Before UV Unit* ,
0 sec
60 sec
120 sec
Geometric Mean
After UV Unit*
0 sec
60 sec
120 sec
Geometric Mean
Log Reduction
11.4 16.8
(4.7) (3.2)
0 9.2xl03
0 8.2xl03
0 7.9xl03
0 8.4xl03
0 6.0xl03
0 S.OxlO3
6 l.lxlO4
0 S.OxlO3
5.8xl03 1.2xl04
6.8xl03 l.OxlO4
8.6xl03 l.OxlO4
7.0xl03 l.lxlO4
2.8X101 9.0x10°
7.2X101 l.OxlO1
5.9X101 4.0x10°
4.9x10 7x10
2.15 3.23
28
(1.9)
1.2xl04
l.SxlO4
l.lxlO4 '
l.SxlO4
1.2xl04
1.3xl04
l.SxlO4
l.SxlO4
9.7xl03
l.lxlO4
l.SxlO4
l.lxlO4
1
0
1
<1
>4.04
85
(0.6)
3.9X104
S.OxlO4
S.lxlO4
4.6xl04
2.6xl03
,1.4xl04
,2.2xl04
9.3xl03
3.7xl04
5.4xl04
4.5xl04
4.5xl04
0
3
0
<1.4xlO°
>4.49
*UV lights had been on for 2 minutes.
Other Results:
All samples from the C12 contact basin were 0 .
All samples of indigenous virus were 0.
Control 1 (virus feed): start = 3.8xl07 PFU/ml
end = 2.9x1O7 PFU/ml
200
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TABLE 39. SUMMARY OF RESULTS FROM FIRST VIRUS RUN.
MEAN LOG REDUCTIONS
Organism
11.4
(4.7)
Total
Coliforms 2.70
Fecal
Coliforms 2.74
F2
Bacteriophage
Polio virus
Type 2 . 2.15
Detention Time, sec
(Flow Rate, I/sec)
16.8
(3.2)
3.53
2.74
1.90
3.23
28
(1.9).
5.00
4.60
2.63
4.04
85
(0.6)
>5.60
>4.81
4.15
>4.49
201
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TABLE 40. SUMMARY OF DOSE-RELATED DATA FOR THE FIRST VIRUS RUN
Flow Rate,! /sec
Theoretical Detention
Time, sec
Actual Detention
Time, sec
Transmittance @
254 nm, percent
Extinction Coefficient
cm"!
UV Intensity,
uwatt/cm2
Calculated Dose,0
Dp wwatt-sec/cm2
Indicated Dose, Dj,
ywatt-sec/cm2
4.7
11.4
10
66.9
0.41
540
11,200
48,100
3.2
16.8
15.5
66.9
0.41
545
16,500
75,200
1.9
28
25
66.9
0.41
545
27,500
121,300
0.6
85
75
66.9
0.41
545
83,400
363,800
202