shore tine

chle Coofing Wir

in géton sini Discharge S.F Bay
(a Uf

ponrs Unt de Units”

~ Otructai
Y eae 1£2
N dschra. tunnel
N net 2" Paalischrg. ;
is funn | Unit d
’ Unit 3 # turbin€ aischay re,

v ' enerator| ruc:
KY i 9D ia9. Unit #
N + \| Unit # | olischarge tunne/

Cooling Wrr Ss turbine _Agnerater ; i _

invaked building \

Structure w

Units 12,43

chiprine ~—inrake tunnel
infection Units 4243
ints

Bo

chlorine
bai Wing

© SAMPLING LOCATIONS
0 50 100 160 20 FI.

Figure 4. Hunters Point Power Plant.


23 FEB 76

Figure 11. Results of decay studies conducted at the

1.8

»

M16

2 COND-IN

£14

gl?

a

LO

w DILUTION

08

b

z

§ 06

x

S04

0.2

0.0 i I I | L ! 1
() 0 20 30 40 5 60 £470

TIME, min

1.6 DOSE 4 MAR 76

=

S14

=)

iJ
(-) io 20 30 40 50 60 70

TIME, min

Potrero power plant, Unit 3 outfall.

28



a
°

UT, % of dose
+
tc)

LOSS OF TOR BETWEEN COND-IN AND O

KEY

POTRERO P.P.- UNIT 3
CONTRA COSTA RP, - UNIT 7
CONTRA COSTA PP -UNIT6

HUNTERS POINT P,P. - UNIT 4

MOSS LANDING PP. - UNITS6 47 |

o

i i ! I | ! I i] |

i 2 3 4 5 6 7 8 9
FLOW TIME - COND-INTO OUT, min

Figure 8. Percentage loss of TOR between the
COND-IN and the outfall sampling point for
various power plants.

24


€€

1S OCT 76
HI WATER 0701
LO WATER 1135
STUDY 1125-1205

0.02

27 OCT 76
HI WATER 1533
LO WATER 0939
STUDY 1350-1450

: 160000 FT? 195000 FT?
UNIT 1&2 INTAKE
i 1? NOV 76 19 NOV 76
: HI WATER O8I0 HI WATER 0929
; LO WATER 1442 LO WATER 1621
4 STUDY 0945-1020 STUDY 0930-1012
COND-IN 7:
~0.70
S 100 FT#
cure:
, 0.05
~0.24 16000 FT?
a 0} 2
4 24900 FT
4 S.F. BAY

SCALE: 1 IN<:= 200FT

Figure 15. TOR (maC1,/g) at receiving water surface at the Potrero power plant, Unit 3.



SECTION I
INTRODUCTION

Power plants require large volumes of cooling water to carry away waste
heat. Bacterial and algal slimes will attach themselves to the walls of the
piping and decrease the heat transfer across the condensers if fouling is not
controlled. The most economical method currently used to control fouling is
the addition of chlorine to the cooling water.

Chlorine presents problems when its toxic effects carry over into re-
ceiving waters. Brungs (1) conducted a comprehensive review of the litera-
ture dealing with chlorine toxicity to freshwater fish for both continuous
and intermittent treatment. Based on these studies he recommended inter-
mittent chlorine limits in the discharge of power plants that vary from
0.2 mg/2 to 0.04 mg/2 total residual for up to 2 hr per day depending on the
degree of protection desired. Basch and Truchan (2) studied the effect of
intermittent chlorination on brown trout (Salmo trutta) at five Michigan power
plants. They found the 48-hr total residual chlorine intermittent concentra-
tions lethal to 50 percent of the brown trout to range from 0.14 to 0.17 mg/2
and 0.18 to 0.19 mg/% for fish exposed to two and four 30 min chlorination
cycles, respectively. Mattice and Zittel (3) conducted a comprehensive review
of the literature dealing with the toxicity of chlorine to both freshwater and
marine organisms. Based on this research they determined both acute and
chronic toxicity thresholds and conclude that marine organisms appear more
susceptible to acute doses of chlorine whereas freshwater organisms appear
more susceptible to chronic concentrations.

The increasing awareness of the toxicity of chlorine residuals has
prompted regulatory control of chlorine discharges in power plant cooling
waters. The Environmental Protection Agency has established free chlorine
discharge guidelines of 0.5 mg/2 maximum and 0.2 mg/2 average concentration for
up to two hours per day from any one unit (4). The California Central Coast
Regional Water Quality Control Board has set daily maximum limits of 0.02
mg Cl2/% undissociated free available chlorine and 0.1 mg Cl2/% total avail-
able chlorine in power plant discharges (5). The San Francisco Bay Regional
Water Quality Control Board has set even stricter limitations of an instan-
taneous maximum chlorine residual of 0.0 mg/&% (6).

This study was conducted to determine the nature, levels, and persistence
of chlorinated compounds in the discharges of five power plants in Northern
California. In-plant studies were conducted to understand the demands for
chlorine in the cooling water system and to determine the levels reaching
the receiving waters. Decay studies conducted at the outfalls together with
measurements of oxidant residuals in the receiving water provide a base for
estimating the persistence and zone of influence of the chlorinated compounds.

1


22

2.0F

nN >

°

OXIDANT RESIDUAL, mg Cig /I
°
@

°
oo

04

0.2

-c XQ

-A—~“AS

|- CONDENSER 7-1

‘

CHLORINE INJEC ion R

-- CHLORINE DOSE
KEY: COND-IN

TOR

1410 1415

Figure 32.

1420

14s

A
{—<)

'y COND-IN «J _

A

i
TIME

CONDENSER 7-2

* 3800 Ibs /24hrs
(CALCULATED): 2.1mg/!

1435 1440 445 1450 1455

In-plant Study at the Moss Landing Power
14 July 1976, Unit 7.

61

Plant


TOR to the 0.05 mg/% TOR isoconcentration line is between 20-65 sec. The
exposure between the 0.3 mg/2 TOR discharge and the 0.1 mg/2 TOR isoconcentra-
tion line (assumed to be an average of 0.2 mg/&% TOR) is predicted to be acutely
toxic to marine organisms. Acute toxicity is not predicted according to the
Mattice and Zittel data beyond this area. Chronic toxicity to marine organisms
is predicted to exist out to the 0.02 mg/% isoconcentration line and consider-
ably further for freshwater organisms.

The 0.16 mgC12/&% maximum concentration measured at the surface of Monterey
Bay at the outfall from the No. 6 and 7 Units at Moss Landing could only have
existed for a flow time of a few seconds from the discharge pipes located at a
depth of 6.1 m (20 ft). At a distance of some 15.3 m (50 ft) from the dis-
charge, a residual of 0.09 mgC1./2 was detected. For this residual to be
acutely toxic by Mattice and Zittel's criterion, an exposure time of some 2.5
min must exist. It is questionable whether such a contact time existed between
the discharge structure and a point some 50 ft away on the surface. These
chlorine levels are above those suggested by Mattice and Zittel as chronic
toxicity threshold values for both freshwater and marine organisms.

The second approach has been investigated by Dickson et al. (22) who
studied the effects of intermittent chlorination on goldfish and on proto-
zoans obtained from attached growths. LC-50 values for goldfish were found
to be a function of total exposure time during a 24-hr period. In the tempera-
ture range of 17-22.5°C, 2-hr exposure/day resulted in an LC-50 of 1.18 mg/z
TOR; with 3-hr exposure the LC-50 was 0.71 mg/& TOR and with 4-hr/day exposure
the LC-50 fell to 0.63 mg/g TOR. These authors concluded that 2-3 exposures
of 15-30 min/day at a TOR of 0.5-0.75 mg/& would not result in lethality to the
goldfish. Concentrations in the ranges stated above were never detected in
the receiving waters at any location sampled during this study. Indeed, only
in early studies at Hunters Point and Potrero, before the reduction in chlorine
dosage by PG&E took place, were such levels detected in the outfalls. It
might, therefore, be concluded that with current chlorination practice no
lethality would result from chlorine toxicity in cooling water to fish with the
same response as goldfish.

43


DEMANDS IN COOLING WATER SYSTEM

Table 9 and Figure 8 indicate that the loss of oxidant residual in the
cooling water system was a function of flow time. The longer the cooling
water was held within the plant, the lower was the oxidant residual that
reached the receiving water. This loss of residual was due to many factors
including reaction with ammonia-nitrogen, demand by inorganic reducing agents,
reaction with organic nitrogen, and uptake by organisms living in the cooling
water system. It is difficult to say which of these are the most important.
Table 9 and Figure 8 suggests the flow time through the cooling water system
may be a good method to estimate the oxidant residual to be expected at various
locations from varying doses of chlorine.

DECAY AND RECEIVING WATER STUDIES

The decay studies (Figures 9-12, Table 10) Show that the most persistent
residual occurred at the Contra Costa Power Plant. From 50% to 52% of the
0.16 and 0.23 mg/2 TOR determined at the outfall remained after 60 min in
those samples covered to exclude sunlight. From 38% to 39% of the 0.16 and
0.23 mg/2 TOR lasted for the same time period in samples exposed to sunlight.
This persistence is likely explained by a slowly decaying combined chlorine
residual that occurred at Contra Costa.

The highest concentrations of TOR remaining after 30 and 60 min were at
Hunters Point and Potrero. However, this was due mostly to the greater
initial concentrations of 0.43-0.72 mg/2 TOR. The lowest concentrations of
TOR in decay studies were found at Moss Landing where the long flow time to
the outfall sample point produced small initial TOR’s of 0.22 and 0.20 mg
Cl,/2. These were approximately the same initial TOR's which existed at the
Contra Costa outfall, however the oxidant residual at Moss Landing decayed to
much lower values. After 60 min at Moss Landing from 0.02 to 0.05 mgC12/2
remained while at Contra Costa from 0.06 to 0.12 mg/2 remained. The major dif-
ference between the oxidant residuals is the predominance of bromine residuals
at Moss Landing which decay more rapidly than chlorine residuals (17,18,19).

The presence of sunlight appeared to speed up the rate of decay at all
plants. This effect was most noticeable during the initial 20 min of decay
at Contra Costa on 16 June 1976 when a FOR existed. After 20 min only
combined residual existed and the effect of sunlight on decay became less
pronounced. The significance of the oxidant residuals can be assessed in
two ways. The first approach is to consider the effect on an organism such as
a fish that is located at the discharge initially and then swims with a parcel
of water away from the plume. The second method is to consider the effect
on an organism that remains in one spot and is subjected to intermittent
doses of chlorine. Such a case would be representative of benthic organisms
located in the sediments overlain by the discharge.

The first approach has been addressed by Mattice and Zittel (3). Table
11 is derived from their data and shows several dose-exposure time combinations
that result in acute toxicity; the chronic toxicity threshold is also indicated
for marine and freshwater organisms. At Contra Costa the cooling water

41


13.

14,

15.

16.

17.

18.

19.

20.

21.

22.

Soloérzano, L. Determination of ammonia in natural waters by the phenol-
hypochlorite method, Limnol. and Oceanog., 14(5):799-801, Sep. 1969.

Zadorojny, C., S. Saxton, and R. Finger. Spectrophotometric determination
of ammonia, J. Water Poll. Control Fed., 45:905-912, May 1973.

Selleck, R. E., A. D. K. Laird, and H. H. Sephton. Optimization of
Chlorine Application Procedures and Evaluation of Chlorine Monitoring
Techniques. University of California. (Proposal to Electric Power
Research, Inc., Palo Alto, Mar. 25, 1976). Publication Number UCB-Eng-
4180, 80 p.

Sugam, R. and G. R. Helz. Speciation of Chlorine Produced Oxidants in
Marine Waters. University of Maryland. (Presented at Workshop on the
Fate and Effects of Chlorine on the Marine and Estuarine Environment.
Solomons, Maryland, Mar. 16-18, 1976).

Sollo, F. W., T. E, Larson, and F. F. McGurk. Colorimetric Methods for
Bromine, Env. Sci. and Tech., 5:240-246, Mar. 1971.

Johnson, J. D. and R. Overby. Bromine and Bromamine Chemistry, J. San. Eng.
Div., Proc. Amer. Soc. Civil Engrs. SA5:617-628, Oct. 1971. .

Johannesson, J. K. The Bromination of Swimming Pools, Am. J. Public
Health, 50:1731-1736, Nov. 1960.

Pacific Gas and Electric Company. An Evaluation of the Effect of Cooling
Water Discharges on the Beneficial Uses of Receiving Waters at: Contra
Costa Power Plant, Pittsburg Power Plant, Hunters Point Power Plant, and
Potrero Power Plant, San Francisco, California, Jul 1973.

Russell, P. P. and A. J. Horne. The Relationship of Wastewater Chlorina-
tion Activity to Dungeness Crab Landings in the San Francisco Bay Area.
Sanitary Engineering Research Laboratory, Berkeley, California. UCB/SERL
Report No. 77-1, Jan. 1977. 37 p.

Dickson, K. L., J. Cairons, Jr., B. C. Gregg, D. I. Messenger, J. L.
Plafkin, and W. H. Van der Schalie. Effects of intermittent chlorination
on aquatic organisms and communities, J. Water Poll. Control Fed., 49:35-
44, Jan. 1977.

47


8
|

mg Cly/1

°
@

OXIDANT RESIDUAL ,
°
an

0.4L

0.0

T
CHL

T q T T t T q T U T
ORINE INJECTION RATE: 1600-1100 Ibs/24 hrs

CHLORINE DOSE (CALCULATED): 1.7-1.2 mg/I

KEY:

TOR AT OUT® ee * COND-IN

COND-IN OUT
e Oo TOR (AMPEROMETRIC)
. o FOR (AMPEROMETRIC)

TOR AT COND-IN

OOD

Bo

O————o—— oo,

FOR AT OUT®

O-

* TWO TIMES MEASURED VALUES

“1010

lola

1018 1022 1026 1030 1034 1038 1042 1046 1050 1054
TIME

Figure 22. In-plant study at the Contra Costa Power Plant
6 Jun 1976, Unit 7, condenser #13

51



residuals were determined after 2 min. Solutions containing 0.41 mg/& NH3-N
and bromide concentrations of 3 and 25 mg/% dosed at 2 mgC12/% are interesting
because they most closely model the conditions existing in the cooling waters
studied in this investigation. Very little free bromine existed over the
entire pH range tested (4.3 to 9.0). At pH 7.4 and 25 mg/% Br a total
halogen concentration of 2.8 mg Br2/2 was detected which was significantly
Tower than the 4.5 mg Br2/% expected. The entire residual was determined to
be combined bromine and was believed to be NHBr2 whose instability might ex-
plain the lower than expected total halogen residual. At pH 7.4 and 3 mg/2
Br , ihe entire 4.5 mg Br2/&% total halogen residual was determined to be chlorine
residual.

Figure 19 after Johnson and Overby (18) shows the bromine species postu-
lated to be present after 1 to 2 min as a function of both pH and the loga-
rithm of the initial mole ratio of ammonia to bromine. These data suggest
that HOBr and NBr; would predominate after 1 to 2 min under conditions that
exist at the Hunters Point, Potrero, and Moss Landing Power Plants if a total
conversion of chlorine to bromine is assumed. NHBr, would be predominant at
somewhat higher ammonia concentrations than were measured at the power plants.
At Contra Costa both chlorine and bromine compounds are suggested with pre-
diction of individual species being difficult. It is apparent that both
chlorine and bromine residuals generally exist when chlorine is added to
estuarine and marine waters. Both the amperometric and DPD-FAS methods were
used to determine oxidant residuals. The amperometric titration method for
total residual determines all oxidant residuals whether they be chlorine,
bromine, or iodine. It is apparent from Figure 11 that the amperometric free
residual determination measures both free chlorine and bromine residual.
Since the DPD-FAS method does not distinguish between free and combined bro-
mine residual, it is possible that some combined bromine existed and was picked
up by the amperometric method as “free residual." This has been suggested by
Johannesson. (19), Palin (11), and Sugam and Helz (16). Therefore, the so-
called "free chlorine" residual measured by the standard amperometric method
in estuarine or marine water is neither totally "chlorine" nor totally "free."

CHLORINATION PRACTICES

Chlorine dosage at many of the power plants was decreased during the
course of this study. This was done both as a reaction to an awareness of
greater than expected residuals and to decrease the residual in the dis-
charge stream. Those plants using the OT method to set the chlorine dose were
often chlorinating at twice the desired level because of the inaccuracies of
the analytical method.

Total chlorine use per day for the four power plants located on.the San
Francisco Bay System averages about 0.30 metric tons/day (0.33 tons/day)
based on 1971 figures (20). This represents 1.25% of the total average daily
use of chlorine of 34 metric tons/day (37.5 tons/day) for the 1975-76 season
as estimated by Russell and Horne (21) for the waste treatment plants dis-
charging to San Francisco Bay.

39


except for Moss Landing where a 1.0 mg/g residual for a shorter duration was
used. Hunters Point was the only plant to measure a free residual and use it
as their criterion for dosing. The orthotolidine (OT) method was used at all
the plants until recently because it was the most portable and was the easiest
for the operators to learn and use. All the plants are currently using or are
in the process of changing over to the amperometric titration method.

FIELD STUDY PROCEDURES
In-Plant Studies

Field studies were conducted at four of the power plants. No studies were
conducted at the Pittsburg plant because no convenient sampling point existed
near the outfall. Studies were conducted during normal chlorination cycles
and were designed to monitor existing chlorination practices, therefore no
changes were made in chlorine injection rate, duration, or frequency of
chlorination cycles to accommodate this work.

At the beginning of the study, oxidant residuals were determined solely
by the amperometric method. During the course of the investigation, the DPD-
FAS titrimetric method was added in an attempt to distinguish between bromine
and chlorine residuals.

Cooling water samples were collected for the determinations of the water
quality parameters listed in Tables 4, 6, and 8. At the COND-IN triplicate
1-liter grab samples were taken before, during, and after chlorination, both
from a condenser being chlorinated and from one that was not. Samples were
taken at the outfalls during chlorination. A small excess of sodium arsenite
was added to all samples taken during chlorination to destroy oxidant residuals.
No interference from this procedure was found in any of the analytical methods
but there was some evidence that the sodium arsenite did not always react
instantaneously with the oxidant residual. This would probably result in
lower concentrations of NHs-N and organic nitrogen in those samples taken
during chlorination.

Decay and Receiving Water Studies

Decay studies were conducted on chlorinated cooling water collected at the
outfalls. Two 8-liter (2.1 gal } containers lined with polyethylene bags were
filled with cooling water. One container was covered to exclude sunlight.

No effort was made to keep temperatures constant. Oxidant residuals were
determined by the amperometric titration method in both containers over a
period of approximately 60 min.

Total oxidant residuals were determined in receiving waters by forward
amperometric titrations at all plants except Moss Landing where samples were
taken for later titration using the back titration method for free oxidant
residual. This was necessary because of the turbulence and wave action at
the outfall which caused the micrometer needle of the titrator to vibrate and
made the end-point very difficult to read. Receiving water samples were
generally taken at the surface although some samples were taken at depths of

1


22
2.0
1.8
6
1.4
1.2
1.0
08
06

OXIDANT RESIDUAL, mg Cl, /I

0.4
0.2
0.0,

2.0
1.8
1.6
4
12
1.0
08
0.6)

OXIDANT RESIDUAL, mg Cl,/1

0.4
0.2)
* 0.0

Dose 19 APR 76

DILUTION

1 et 1 t +—++ !

10 20 30 40 so C) 70
TIME, min

14 JUL 76

TOR (DARK)
TOR (LIGHT)

SS ____I
10 20 w» 40 50 60 70
TIME, min

Figure 12. Results of decay studies conducted at the

Moss Landing power plant, Units 6 and 7 at ISE,

29


2.2

2.0

rs

OXIDANT RESIOUAL , mg Cl, /1
° r rc
& fe] Ld

°
a

04

0.2

0.0!
1305 1310 1315 1320 1325 1330 1335 1340 1345 1350 1355 1400

T T i] 1 T T T T T T ~T
CHLORINE INJECTION RATE: 3800 Ibs /24 hrs
CHLORINE DOSE (CALCULATED): 2.1 mg/I
KEY: COND-IN  ISE 1
e © TOR CAMP.)
a 6 a O FOR (AMP.) _
ri
2 4
Ln |
yor AT 4
COND-IN
CONDENSER 6-1 CONDENSER 6-2 4
TOR
AT ISE* -
[L-
Oo
1 1 I l

TIME

« TWO TIMES MEASURED VALUES

Figure 31.

In-plant Study at the Moss Landing Power Plant
14 July 1976, Unit 6.

60


FOREWORD

Effective regulatory and enforcement actions by the Environmental Pro-
tection Agency would be virtually impossible without sound scientific data on
pollutants and their impact on environmental stability and human health.
Responsibility for building this data base has been assigned to EPA's Office
of Research and Development and its 15 major field installations, one of which
is the Corvallis Environmental Research Laboratory (CERL).

The primary mission of the Corvallis Laboratory is research on the effects
of environmental pollutants on terrestrial, freshwater, and marine ecosystems;
the behavior, effects, and control of pollutants in lake systems; and the de-
velopment of predictive models on the movement of pollutants in the biosphere.

This report adds significantly to our understanding of residual chlorine
behavior in coastal waters. From this work power plants may be able to re-
structure their disinfection programs and reduce the amount of chlorine reach-
ing the environment as well as reducing costs. Regulatory programs may be able
to use the results to improve effluent guidelines and monitoring programs.

iii


2.2 ee ee |

2.0- 4
KEY: COND-N SE
ek e © ‘TOR (AMPEROMETRIC) 4
a o FOR (AMPEROMETRIC)
A 0 FREE CLy+ BROMINES (DPD)
16r- 8 b COMBINED CL, (DPD) 4
c c BROMINES (DPO)
4b 4
N —|
Ls)
b=. —
& 12e Lc 4
- c c
a /
a COND-IN
2 ob 4
g 2r*
CONDENSER 7-2
Z 0. ac 4
x CONDENSER 7-1 —
Fad A

0.6 - A -|
wv
0.4-— 4
ISE*
0.2 4
ool_1t "1 15 WW 8 va Bow 1

.

CHLORINE INJECTION RATE: 2300 1bs/24 brs
CHLORINE DOSE (CALCULATED): 1.3 mg/

1400 1405 1410 '415 1420 1425 1430 1435 1440 1445 1450 1455
TIME

TWO TIMES MEASURED VALUES

Figure 34. In-plant Study at the Moss Landing Power Plant
5 August 1976, Unit 7.

63


22

OXIDANT RESIDUAL, mg ag/

16r

i S
T T

}
T

°
—P

OS-

a2

fete)

1300 1305 1310 1315 1320 1325 ise 1335 1340 1345 1350 1365
Ti

CONDENSER 6-1

CHLGRINE INJECTION RA

CHLQRINE DOSE (CALCULATED): 2.1

KEY: COND-IN

CONDENSER 6-2

TE: 3800 of /20 hes
mg/\

(AMPEROME FRIC)

(AMPEROME|TRIC)
CL, + BROMINES (DPD)

e TOR

a FOR
A FREE
8 COM:
c

Figure 33. In-plant Study at the Moss Landing Power Plant

INED CL5 |(DPD)

22 July 1976, Unit 6.

62



TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

1, REPORT NO, 2. 3. RECIPIENT'S ACCESSION NO.
EPA-600/3-78-032
4. TITLE AND SUBTITLE IS. REPORT DATE
"Power Plant Cooling Water Chlorination in March 1978
Northern California . w 6. PERFORMING ORGANIZATION CODE
7, AUTHOR(S) i PERFORMING ORGANIZATION REPORT NO.
S. Hergott, David Jenkins, and Jerome F. Thomas UCB/SERL No. 77-3
Ig, PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.
Sanitary Engineering Research Laboratory 1BA608
College of Engineering & School of Public Health 71. CONTRACT/GRANT NO.
University of California
Berkeley, CA 94720 R-803959
12. SPONSORING AGENCY NAME AND ADDRESS 13, TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency extramural 11/75 to 12/76
Corvallis Environmental Research Laboratory 14. SPONSORING AGENCY CODE
200 S.W. 35th Street
Corvallis, OR 97330 EPA/600/02

15. SUPPLEMENTARY NOTES.

16. ABSTRACT

A survey was conducted of chlorination practices at five power plants owned and
operated by the Pacific Gas and Electric Company. Frequency and duration of chlori-
nation varied significantly from plant to plant and was controlled analytically by
the orthotolidine and/or amperometric methods. All the plants plan to change to
using the amperometric method for future control purposes.

In-plant studies were conducted during chlorination cycles to determine oxidant resid-
uals at both the condenser inlets and at a point near the outfall. Both free and
total oxidant residuals were measured amperometrically for most studies. The DPD-FAS
method was included in later studies to gain a better understanding of the nature of
the oxidant residual. These results indicated that most of the oxidant residual at
the Hunters Point and Moss Landing power plants was bromine residual.

Decay studies were conducted at the plant sites on the chlorinated cooling water col-
lected at the outfall. The slowest decay was observed at the Contra Costa plant
where the cooling water was the freshest. The most rapid decay was at the Hunters
Point plant. The presence of sunlight increased the rate of decay at all locations.

17. KEY WORDS AND DOCUMENT ANALYSIS.

ja. DESCRIPTORS Ib. IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
chlorination cooling water effluents | Field 13
industrial wastes effluents San Francisco Bay Group 13B
electrical measurements decay studies
oxidizers

coastal waters

18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 21. NO. OF PAGES
Unclassified 78
20. SECURITY CLASS (This page) 22. PRICE
Release to public Unclassified

EPA Form 2220-1 (9-73)

65

ff U.S. GOVERNMENT PRINTING OFFICE: 1978~796-325/100 REGION 10


is mixed with excess phenylarsine oxide and pH 7 buffer. Another contributing
factor to this result was the flashing off of iodine during stirring in the
forward titration for TOR.

The DPD-FAS results indicated little or no combined chlorine residual
at the COND-IN. Some combined chlorine was indicated at ISE both by the
amperometric and DPD-FAS methods. Most of the DPD-FAS results must be re-
garded with suspicion because of the discrepancy between titrations A and C.

Cooling water at Moss Landing varied from 95% to 99% seawater. Ammonia-
nitrogen concentrations determined on samples collected at the COND-IN decreased
by up to 0.075 mg/2 due to chlorination. A decrease of organic nitrogen during
chlorination was observed in 4 of the 6 studies.

Summary

The DPD-FAS titrimetric method was added to the field studies to gain a
better understanding of the nature of the oxidant residual at the power plants.
The results of two studies that were conducted in the laboratory comparing this
method with the amperometric method are presented in Figure 7. Chlorine
(sodium hypochlorite) was added to 4-liter samples of San Francisco Bay water
and oxidant residuals were determined for a period of 40 min. A good correla-
tion between FOR determined amperometrically and titration A of the DPD-FAS
method was obtained. TOR determined by the amperometric method was equal to
or slightly less than TOR calculated from the DPD-FAS results (titration A
plus B). The discrepancy between amperometric and DPD TOR data appeared to
result from the underestimation of combined chlorine residual by the ampero-
metric method. Results of titration C indicated that most of the FOR was
bromine residual.

Table 9 summarizes the disappearance of oxidant residual observed for all
the in-plant studies. Loss of residual is expressed as a percentage of the
chlorine dose. The table does not included the decrease of oxidant residual
due to dilution immediately after the condensers. The measured TOR at the
outfalls has been doubled before the percentage loss was calculated for those
plants where such a dilution occurred. Flow times between the sampling points
at each plant are indicated. Results at Contra Costa are separated for
Units 6 and 7 because of the different flow times from the COND-IN to the
outfall.

The table shows that the disappearance of TOR generally depends on the
flow time through the system. This is especially evident from the COND-IN
to the outfall because of the wide variation of flow times that existed.
Figure 8 is a graph of the percentage loss of TOR between the COND-IN and the
outfall sampling point as a function of flow time.

DECAY AND RECEIVING WATER STUDIES
Decay studies were conducted on the chlorinated cooling water collected

at the outfalls to determine the approximate life of oxidant residuals in the
receiving waters. Oxidant residuals were measured at various locations in

22


Jan Francisco Bay

Coolirn 70
intake Welle
Unit 3

e forine

eg Warer.
dntak’ Structure
Units (fe

eC; TON |
“Bints Xs ghlorine gf CAlorine —@—
PRE Te)
Intake Pipes
tele pret _S.. 2
er
Turbine
Géne erator
Building

facie Injection
Poin

© SAMPLING LOCATIONS

\
Qunits 142 \

Turbine
enerator
atid,

Units |

Units K a ee
7 2 |\\ootscharge

\ Lub conduit

0 0 80 #0 +400FT.

Figure 5,

Potrero Power Plant.


ol

TABLE 3. SUMMARY OF FIELD STUDY RESULTS AT CONTRA COSTA POWER PLANT
UNITS 6 AND 7

CONDENSER- INLET QUTFALL MANHOLE+
DATE ne AMP, TIT. DPD-FAS* AMP. TIT. DPD-FAS*
TOR FOR A B c TOR FOR A B C,
mgC12/2 mgCl2/& mgCl2/2 mgCl2/% mgCl2/% mgCl2/2 mgCl2/& mgCl2/% mgCl2/k mgCl2/2 mgCl2/e

20 Jan 76 = 1.6 0.75 0.45 -- -- -- 0.18 0.03 -- -- --
10 Feb 76 1.6 0.50 0.10 -- -- -- 0.23 0.00 -- -- --
16 Jun 761.2 0.55 0.36 - -- -- 0.18 0.08 -- -- --
14 Sep 76 1.3 0.30 0.20 0.20 0.10 0.20 0.04 0.00 0.00 0.03 0.00

*Results of three titrations are: A

Free chlorine plus bromine residuals.
Combined chlorine residuals
Bromine residuals

B
Cc

+Chlorinated cooling water flow was diluted with an approximately equal volume of unchlorinated

water

immediately after the condenser.


ot

TABLE 2.

CHLORINATION PRACTICES AT PG&E POWER PLANTS

mower CHLORINATION SCHEDULE CRITERIA ANALYTICAL METHOD
PLANT UNIT(S) FREQUENCY DURATION COND- IN
(min) (mg Cl2/2) NOV. 1975 CURRENT/FUTURE
Ampero- .
CONTRA COSTA 6,7. —‘1/week 40 TOR,O.5 eevee Amperometric
PITTSBURG 5,6 Varies with Season TOR,O.5 OT Amperometric
Min., 1/week 30
Max., 1/day 30
HUNTERS POINT 4 4/day 30 FOR,0.5* Ampero- Amperometric
POTRERO 3 2/day 30 TOR,O.5* OT Amperometric
MOSS LANDING 6,7 1/day 15 TOR,1.0 OT OT/Amperometric

*Lowered to 0.4 mg/2 in January 1977.

OT = Orthotolidine Method.

TOR
FOR

Total Oxidant Residual.

Free Oxidant Residual.


30 30 JUN 76
S.F. BAY WATER AT SERL
- pH 7.6, CI” 16.0g/1, NH3-N 0.36mg/}}
rs} cl, DOSE 3.05m9/1, TEMP 21.0 °C
z 2.0
a
@
=
1.0
4 Sw
= e
FE a) “Erez
3 ¢c :
5 BO gt Bre 8 — 8
B— me sees)
0.0 l pS
“Oo Le) 20 30 40
TIME, min
4.0
7 JUL 76
pH7.7, NH3-N 0.45 m9/!
Cl DOSE 4.00mg/l, TEMP IZ0°C
oe
3.0 KEY: TOR (DPD- calculated)
Q e@ TOR (AMPEROMETRIC)
o @ FOR (AMPEROMETRIC)
€ A FREE Clot BROMINE (DPD)
F| 2.0 8 COMBINED Cl, (OPD)
a C  BROMINES (DPD)
FA
e he
=,
4 1.0 . ~~
g SEE
° B Cc ——s-y
ee a me
B————5 —
- 0.0 1 1 L
° 20 30 40
TIME, min
Figure 7. Laboratory comparison of DPD-FAS titrimetric

and amperometric titration methods.

23


SAN JOAQUIN RIVER

JOLING WATER
TAKE STRUCTURE
UNITS OL

- DiscHang, j
\ ale eee i
‘ H UNITSO47
TURBINE
GENERATOR
BUILDING
LES eLAN

© SAMPLING LOCATIONS

Figure 2. Contra Costa Power Plant.


22

T T TTT T_T TT T
CHLORINE INJECTION RATE: 3800 Ibs/24 hrs
CHLORINE DOSE (CALCULATED): 2.1 mg/l
2.0 KEY: COND-IN SE
e © TOR (AMPEROMETRIC)
a O FOR (AMPEROMETRIC)
18F
‘e
c
COND-IN
vel Re \ |
QS 4b CONDENSER 6-2|
ro)
o
E
1.2
7
ae
4
3 or
« CONDENSER 6-1
g
3 og
b4
fo}
a
O6- Oo
0.4-
o2-
° a i 1B 1 Bs | Bp

“1255 1300 1305 1310 1315 1320 1325 1330 1335 1340 1345 1350

TIME.

«TWO TIMES MEASURED VALUES

Figure 35.

In-plant Study at the Moss Landing Power Plant

23 Sept 1976, Unit 6.
64


1.4 T T T T T T T T T T T
\ CHLORINE INJECTION RATE: 1400-1600 Ibs /24 hrs
’ CHLORINE DOSE (CALCULATED): 1.6 mg/!
Lab KEY: COND-IN OUT am
e © TOR (AMPEROMETRIC)
a o FOR \(AMPEROMETRIC)
Lok 4
NX TOR AT COND-IN
3
oa
€
0.8 4
J
z
=]
°
g
.
Fost TOR AT OUT a”
Zz
4
2
x
ro]
.
0.4- 4
O02 4
* TWO TIMES MEASURED VALUES
o*
0.0 | 1 i 1 n n ! ! l 1
0930 0934 0938 0942 0946 0950 0954 0958 1002 1006 1010 1014

TIME

Figure 20. In-plant Study at the Contra Costa Power Plant
20 Jan 1976, Unit 6, Condenser #11.

49


Number.
25
26
27
28
29
30
31
32
33
34
35

FIGURES (continued)

In-plant study at the Hunters Point power plant,17 May

1976, unit 4... ee ee ee
In-plant study at the Hunters point power plant, 26 Aug

1976, unit 4. ee
In-plant study at the Potrero power plant, 23 Feb 1976,

unit 3, N. condenser. 2... 2 ee ee ee ee ee
In-plant study at the Potrero power plant, 4 Mar 1976,

unit 3, N. condenser... 2. 2 ee ee ee
In-plant study at the Moss Landing power plant, 12 Apr

1976, unit7......... ph ee ee ee
In-plant study at the Moss Landing power plant, 19 Apr

1976, unit 7. .....0. 2.0.2... 0 22 eee eee ee
In-plant study at the Moss Landing power plant, 14 Jul

1976, unit 6 2. ee tt et
In-plant study at the Moss Landing power plant, 14 Jul

1976, unit 7. we ee
In-plant study at the Moss Landing power plant, 22 Jul

1976, unit 6... 2. 2. ee ee
In-plant study at the Moss Landing power plant,5 Aug

1976, unit 7... ee ee ee
In-plant study at the Moss Landing power plant, 23 Sep

1976, unit 6. 1 ee et ee ee

ix

54
55
56
57
58
59
60
61
62
63
64


TABLE 8. WATER QUALITY AND TIDAL DATA AT THE MOSS LANDING POWER PLANT

02

NHa-N Org-N cI” Br” SUSE TIME OF TIDAL DATA
DATE/SAMPLE pH = sTupy, ————_______

mg/2  mg/& g/2 mg/R mg/L TIME ELEVATION
12 Apr 76
7-1 COND-IN BEF 0.096 0.20 19.0 78 19 7.9- 1240- Hi 0838 +4.7
7-2 COND-IN DUR +) 0.021 0.09 18.7 82 22 8.0 1330 Lo 1438 40.5
7-1 COND-IN DUR(-)+ 0.114 0.19 18.8 81 © 21
7-2 COND-IN AFT 0.137 0.25 18.5 82 21
19 Apr 76
7-1 COND-IN BEF 0.058 0.16 18.9 68 31 7.8 1300- Hi 1533 +41
7-2 COND-IN DUR(+)* 0.005 0.08 19.0 70. 14 1350 Lo 0840 «—-0.6
7-1 COND-IN DUR(-)+ 0.033 0.12 18.8 67 15
7 ISE DUR 0.016 0.10 19
7-2 COND-IN AFT 0.037 0.04 19.1 74 20
14 Jul 76
6-1 COND-IN BEF 0.046 0.19 186 82 12 8.1- 1300- Hi 1403 44.8
6-2 COND-IN DUR(+)* 0.000 0.19 -- -- 14 8.2 1400 Lo0720 -0.4
6-1 COND-IN DUR(-)+ 0.038 0.19 -- 9 -- 8
6 ISE DUR 0.010 0.19 -- - 12
6-1 COND-IN AFT 0.047 0.19 19.1 80 8
22 Jul 76
6-1 COND-IN BEF 0.072 0.30 18.8 78 15 8.0- 1300- Hi 0908 +3.5
6-2 COND-IN DUR(+)* 0.010 0.19 -- == 9 8.1 1350 Lo 1327 #2.8
6-1 COND-IN DUR(-}+ 0.120 0.30 -- -- 1
6-1 COND-IN AFT 0.093 0.26 189 74 10

(continued)


OXIDANT RESIDUAL, mg a, A}

1.4

1.0

2
@

°
o

04

02

0.0

TOR AT COND-IN

TOR AT OUT* LO

om

CHLORINE INJECTION RATE: 1750 Ibs /24 hrs
CHLORINE DOSE (CALCULATED): 2.0 mg/I

KEY: COND-IN OUT 4
e O TOR (AMPEROMETRIC)

Ld

*« TWO TIMES MEASURED VALUES

Lo

2100 2104 2108 212 26 2120 2124 2128 2132 2136 2140 2144

TIME

Figure 27. In-plant Study at the Potrero Power Plant
23 Feb 1976, Unit 3, N. Condenser.

56


2.0

>

v

OXIDANT RESIDUAL, mg 1/1
° -
@ °o

°
o

0.4

02

CHLORINE INJECTION RATE: 4000 Ibs /24 brs
CHLORINE DOSE (CALCULATED): 2.2 mg/t

KEY: COND-IN ISE

e O TOR (AMPEROMETRIC)
TOR =
AT

COND-IN
4
CONDENSER CONDENSER 4

TI 7-2
TOR AT ISE*
-
1 1 1 A l 1 1 : 1

0.
1240 1245 1250 1255 1300 1305 1310 1315 1320 1325 1330 1335 1340
TIME

* TWO TIMES MEASURED VALUES

Figure 29.

In-plant Study at the Moss Landing Power Plant
12 April 1976, Unit 7.

58


i
CHLORINE INJECTION RATE: 4000 lbs/24 hrs
2.9|_ CHLORINE DOSE (CALCULATED): 2.2 mg/i /
KEY
CONDAN ISE
1st oe © TOR (AMPEROMETRIC)
1. ToR
ler / a AT
COND-IN
o—e—__,!

Lae °
=
aN
[s)
e
EL2-
>
<=
a
a Lor
td
L CONDENSER 7-1 CONDENSER 7-2
Zz os}—
cS) ry

os |-TOR AT ISE*

04

02

ool_et | le el eblo | | el I

1255 1300 1305 ISO 135 1320 1325 1330 1335 1340 1345 1350

TIME

* TWO TIMES MEASURED VALUES

Figure 30. In-plant study at the Moss Landing Power

Plant,19 April 1976, Unit 7

59



Zt

TABLE 5. SUMMARY OF FIELD STUDY RESULTS AT THE HUNTERS POINT POWER PLANT
(UNIT 4) AND POTRERO POWER PLANT (UNIT 3)

Cle CONDENSER- INLET OUTFALL MANHOLE+
DOSE
CALCULATED AMP, TIT. DPD-FAS* AMP, TIT. OPD-FAS*
DATE TOR FORA B cc TOR FOR A B c
mgCl 12/2 mgCl2/& mgC12/2 mgCi2/% mgClo/& mgCl2/2 mgCl2/& mgCl2/% mgCi2/% mgCl2/% mgC1 2/2
Hunters Pt.
16 Dec 76 1.6 0.85 -- -- -- -- 0.50 = -- ~ --
17 May 76 1.6 0.72 0.72 -- -- -- 0.50 0.37 -- -- --
26 Aug 76 2.5 1.00 1.00 0.60 0.10 0.90 0.70 0.70 0.45 0.00 0.45
19 Oct 76% 1.2 0.65 0.65 -- -- -- 0.24 0.24 -- -- --
Potrero
23 Feb 76 2.0 1.3-1.5 -- -- -- -- 0.5-0.6 -- -- -- --
4 Mar 76 1.6 0.8-1.0 -- -- -- -- 0.4-0.5 -- -- -- --
15 Oct 76 0.9 0.73 -- -- -- -- 0.35 -- -- -- --
27 Oct 76 0.9 0.73 -- -- -- -- 0.28 -- -- -- --

*Results of three titrations are: A = Free chlorine plus bromine residuals.
B = Combined chlorine residual.

C = Bromine Residuals.

tHunters Point - the cooling water flows through both condensers of Unit 4 and are chlorinated simultan.
Potrero - Chlorinated cooling water was diluted with an approximately equal volume of unchlorinated
water immediately after the condensers.

Cooling water flows through the condensers were chlorinated separately for this study.


ABSTRACT

This research program was designed to determine the nature, levels, and
persistence of "chlorine" residuals in the cooling water effluents of power
plants located in and around the San Francisco Bay Area. Plants were located
at Potrero and Hunters Point (San Francisco Bay), Contra Costa (San Joaquin
River), Pittsburg (Suisun Bay), and Moss Landing (Monterey Bay).

A survey was conducted of chlorination practices at five power plants
owned and operated by the Pacific Gas and Electric Company. Frequency and
duration of chlorination varied significantly from plant to plant and was con-
trolled analytically by the orthotolidine and/or amperometric methods. All the
plants plan to change to using the amperometric method for future control pur-
poses.

In-plant studies were conducted during chlorination cycles to determine
oxidant residuals at both the condenser inlets and at a point near the outfall.
Both free and total oxidant residuals were measured amperometrically for most
studies. The DPD-FAS method was included in later studies to gain a better
understanding of the nature of the oxidant residual. These results indicated
that most of the oxidant residual at the Hunters Point and Moss Landing power
plants was bromine residual.

Decay studies were conducted at the plant sites on the chlorinated cool-
ing water collected at the outfall. The slowest decay was observed at the
Contra Costa plant where the cooling water was the freshest. The most rapid
decay was at the Hunters Point plant. The presence of sunlight increased the
rate of decay at all locations.

Receiving water studies detected maximum total oxidant residuals at the
surface. The distances from the outfall structures to the 0.02 mg/% total
oxidant isoconcentration line were determined at three power plants. Total
oxidant residuals were measured at the surface of Monterey Bay above a submerged
outfall structure. Toxicity of receiving water oxidant residual levels was
predicted.

This report was submitted in fulfillment of Grant No. R803959 by the Sani-
tary Engineering Research Laboratory under the sponsorship of the U:S. Environ-
mental Protection Agency. This report covers the period October 31, 1975 to
December 31, 1976, and work was completed as of June 30, 1977.


PREFACE

The concern for the potential toxicity of chlorinated effluents to re-
ceiving waters biota pampered the study of the nature and persistence of oxidant
residuals in power plant cooling water. The study was designed to provide field
information from operating power plants so that actual operating levels of
residual and their persistence could be defined. The investigation was directed
towards power plants close to the San Francisco Bay Area and located on estuarine
of coastal waters.

iv


COOLING WATER INT?

crcaare waren
nen sae

et CONTROL BUILDING. UwTs S48 UNITS 120 ke
> - ~
~ 1) _“ivrane conouts

; UNIT NOI2344

PLAN
| a

Figure 3. Pittsburg Power Plant,


=
wo oe NOOPWNH Ey
MS

yn © © WY KY BH FSF HF BF =F ese es es ew
fF WN |= CFS Hb ON DD FDO FF WwW HY | OC

FIGURES

Power plant locations... 2... 2 eee eee ee ee ee
Contra Costa power plant ........--.----+2ee06-
Pittsburg power plant... 2... 1 ee eee eee te ee
Hunters Point power plant. 2... 1. we eee te ee
Potrero power plant... 2... 2 2 ee ee ee ee ee we
Moss Landing power plant ..........-2-0 +0 lee
Laboratory comparison of DPD-FAS titrimetric and

amperometric titration methods .......... wee
Percentage loss of TOR between the COND-IN and

the outfall sampling point for various power plants
Results of decay studies conducted at the Contra Costa

power plant, units 6 and 7 outfall. ..........-.
Results of decay studies conducted at the Hunters Point
power plant, unit 4 outfall ...... wee ee ee

Results of decay studies conducted the the Potrero power

plant, unit 3 outfall] ........2..2....22-20-
Results of decay studies conducted at the Moss Landing

power plant, units 6 and 7 at ISE ........2..2.-
TOR (mgC12/2) at the surface of the receiving water at

the Contra Costa power plant,units 6 and7........
TOR (mgC12/2) at receiving water surface at the Hunters

Point power plant,unit 4 ... ee ee
TOR (mgC1,/%) at receiving water surface at the Potrero

power plant, unit 3). 2 2... ee ee ee ee ee
TOR” (mgC12/2) at receiving water surface at the Potrero

power plant, units 1 and2.......-++--+-e8 oe
FOR (mgC1./2) at the receiving water surface at the Moss

Landing power plant, unit6 ....... see eee
Time required for 99% conversion of free chlorine to

HOBr at 25°C and a pHof 8.3... ......-222--.-
Principal species of bromine and bromamine after 1-2 min

at various pH and ammonia to bromine ratios .......
In-plant study at the Contra Costa power plant 20 Jan

1976, unit 6, condenser #11 2.2... 1.2... ee eee
In-plant study at the Contra Costa power plant 10 Feb

1976, unit 7, condenser #14 2... 2. 2 ee ee eee eee
In-plant study at the Contra Costa power plant 6 Jun

1976, unit 7, condenser #13... ...-.-2.-2208-
In-plant study at the Contra Costa power plant 14 Sep

1976, unit 6, condenser #11 .......-.- we
In-plant study at the Hunters Point power plant, 16 Dec

1975, unit 4... 2 2 ee ee ee oe

S
WON HDoOW 2

23
24
26
27
28
29
31
32
33

35
38
40
49
50
51
52
53


1, 2, and 3m (3.3, 6.6, and 9.9 ft). Sampling point locations were determined
by reference to features on shore and in some cases by a rope attached to the
outfall structure.

ANALYTICAL METHODS AND EQUIPMENT

Oxidant.Residual Measurement

Amperometric Titration--

Oxidant residuals were determined amperometrically using Fischer and
Porter (Model 1771010) portable titrators. Total oxidant residuals (TOR)
were determined by a direct titration according to Standard Methods (7). TOR
could be determined in approximately 1.5 min by applying some suggestions
made by Manabe (8). These included the use of a graduated cylinder modified
to measure a 200 mg sample quickly and the addition of up to 90% of the titrant
before turning on the stirrer. The back titration procedure described by
White (9) for the determination of free oxidant residual (FOR) was adopted
because of an unstable end-point experienced during a direct titration. The
term "oxidant residual" has been used rather than “chlorine residual" because
the amperometric method measures bromine and iodine residuals in addition to
chlorine residuals.

DPD-FAS Titrimetric Method--

The DPD-FAS titrimetric method of Palin (10,11,12) was used to distinguish
chlorine and bromine residuals. Three separate titrations give: (A) free
chlorine plus free and combined bromine; (B) combined chlorine; (C) free and
combined bromine. The separate determination of free and combined bromine is
not possible. Some anomalous results were obtained using this method in some
of the saline waters.

Water Quality Measurement

Organic nitrogen, chloride, bromide, and suspended solids were all de-
termined according to Standard Methods (7). Ammonia-nitrogen was determined
by the phenolhypochlorite method of Solorzano (13). This method was found to
be well suited for fresh, marine, and estuarine waters by Zadorojny et al.(14).

12


EPA-600/3-78-032
March 1978 Ecological Research Series



OCEAN
WAVES

0.12

+

UNIT 6
0.16 0.06
+

A
SS 0.09
DISCHARGE STRUCTURES
+ +

UNIT 7

MONTEREY

BAY 0.00

SCALE: | IN. & 20 FT

Figure 17. FOR (mgCl2/2) at the receiving water surface at the
Moss Landing power plant, Unit 6.

35


ABBREVIATIONS AND SYMBOLS

COND-IN -- Condenser inlet sampling point
COND-OUT -~ Condenser outlet sampling point

DPD -~ N,N-diethy1-p-phenylenediamine

FAS -- Ferrous ammonium sulfate

FOR -- Free oxidant residual, mgC12/2

INJ-PT  -- Chlorine injection point

ISE -- Sampling point at International Shellfish
Enterprises, Inc.

MW -- Megawatt

oT -- Orthotolidine method

OUT -- Outfall sampling point

PAO -- Phenylarsine oxide

PG&E -- Pacific Gas and Electric Company

xi


Number

—-=2

-o ww ~~ a a> wn

TABLES

Power plant operating data... . 1... ee ee ee ee ee
Chlorination practices at PG&E power plants ee ee
Summary of field study results at Contra Costa power

plant, units 6 and7 2... 1... ee ee eee ee
Water quality and tidal data at the Contra Costa power plant .
Summary of field study results at the Hunters Point Power

plant (unit 4) and Potrero power plant (unit 3)......
Water quality and tidal data at the Hunters Point and

Potrero power plants ...... . we ee
Summary of field study results at the” Moss Landing power

plant, units 6 and7 .. 2... 2.2.2... 2 ee ee eee
Water quality and tidal data at the Moss Landing power plant .
Summary of Toss of oxidant residual within the power plant

cooling water system .... 2... 2 2c eee eee .-
Summary of decay studies. ........ oe
Acute and chronic doses of chlorine to marine "freshwater

organisms (Mattice and Ziettel) (3)............


APPENDIX I
FIELD DATA


8 JUL 76
HI WATER- 1447
LO WATER - 0837
STUDY- 1025-1050

SAN JOAQUIN RIVER

0.00 0.00
oom. 0.01
INTAKE STRUCTURE
UNITS 6 & 7 out
20.16
(UNIT 6)
UNIT 6
COND-IN
0.44 SCALE: | IN. = 200 FT

3 DEC 76

HI WATER- 1259
LO WATER-2033

STUDY - 1550-1625
PLUME BOUNDARY 0.00 113.2)

0.00 0.0! 0.02 0.02 0.02
(23.0) (22.0) (26.0) (24.0)

a |
04
. loos 9.08
(UNIT 6) (27.3)
UNIT 6 a
CONO-IN -
0.50 ( TEMP. -°C - IN PARENTHESES)

Figure 13. TOR (mgCl2/z) at the surface of the receiving water at
the Contra Costa power plant, Units 6 and 7.

31



TABLE 7. SUMMARY OF FIELD STUDY RESULTS AT THE MOSS LANDING POWER PLANT
UNITS 6 AND 7

CONDENSER- INLET ISE SAMPLING POINT+
Clz
DOSE AMP. TIT. DPD-FAS* AMP. TIT. DPD-FAS*
DATE CALCULATED
TOR FOR A B C TOR FOR A B c

mgC12/% mgC12/% mgC12/% mgC12/2 mgC12/2 mgC1p/2 mgC12/&% mgC12/& mgC12/2 mgC1p/2 mgC12/zk

6l

12 Apr 76 2.2 1.35- _ _ ee oo. _
1.65 0.18

19 Apr 76 2.2 1.45- . _ — 0.28 oo _
2.10 0.31

14 Jul 76 2.1 1.40-  1.60-  1.70- 0.00 1.80- 0.15- 0.10- | .
1.80 1.90 2.00 2.20 0.20 0.74

22 Jul 76 2.1 1.30- 1.40- 1.25- 0.00 1.60- _ oo _.
2.10 2.20 1.65 2.00 7

5 Aug 76 1.3 0.80- 0.90- 0.50- 0.05 0.70- 0.05- 0.05- 0.08 0.05- 0.03-
1.20 1.35 0.80 1.20. 0.15 0.10 0.11 0.10 0.05

23 Sep 76 2.1 1.00- 1.00- 1.10- 0.00 1.70- 0.24- 0.302 _
1.70 1.80 1.70 2.20 0.40 0.40

*Results of three titrations are: A
B
c

Free chlorine plus bromine residual.
Combined chlorine residual.
Bromine residual.

+Chlorinated cooling water was diluted with an approximately equal volume of
unchlorinated water immediately after the condensers.


The results at Contra Costa (Figure 13) show the effects of chlorine
addition to one condenser of Unit 6. The study of 8 July 1976 was conducted
during a flood tide so that no residual was detected downstream from the point
where the discharge canal meets the river. The study of 3 December 1976 shows
the effects of an ebb tide. A TOR of 0.02 mg C12/% was detected some 150m
(500 ft) down the San Joaquin River near the intake structure for Units 6 and
7. The plume boundary was clearly visible and its presence was confirmed by
both oxidant residual measurement and temperature readings.

Results at Hunters Point due to chlorine addition to one condenser of Unit
4 are presented in Figure 14. A TOR of 0.02 mg Cl2/2 was measured up to 150m
(500 ft) from the outfall structure. The dilution effect of varying tidal
stages is evident. The studies of 19 October 1976 and 3 November 1976 were
conducted at lower tides than the other two studies. Tidal effects are very
pronounced because the discharge structure is submerged at high tides but not
at low tides.

Results at Potrero are presented in Figures 15 and 16. Figure 15 shows
the effects of chlorine addition to one condenser of Unit 3. A TOR of 0.02
mgC12/2 was detected up to 168 m (550 ft) from the outfall structure and is
drawn into the No. 1 and 2 Unit intake. Tidal effects were not as evident as
at Hunters Point because the Potrero outfall structure is never fully. submerged.
Figure 16 shows the effects of chlorine addition to all condensers of Units 1
and 2. These units are very old and chlorination of each condenser separately
is not possible. A TOR of 0.02 mgC1,/% was detected up to 400 m (1300 ft)
from the outfall structure.

A study was conducted in the receiving water at Moss Landing on 23 Sep-
tember 1976 (Figure 17). It was very difficult to keep the boat in the dis-
charge plume in Monterey Bay because of the force of 37.9 m?/sec (600,000 gpm)
of cooling water reaching the surface. It was difficult at times to determine
the exact location of the plume because of waves continually moving the boat.
A maximum TOR of 0.16 mg Cl2/% was determined at the surface at a time when the
TOR ranged from 1.2 to 1.7 mg/g at the COND-IN and from 0.31 to 0.33 mg/2 at
ISE.

36


gL

TABLE 6. WATER QUALITY AND TIDAL DATA AT THE HUNTERS POINT AND POTRERO POWER PLANTS

NH3-N Org-N cr" Br- S.S. TIME OF TIDAL DATA
DATE/SAMPLE pH STUDY "27, ELEVATION
mg/& mg/& g/k mg/% mg/% TIME ft

Hunters Point

16 Dec 75

COND-IN DUR 0.06* 0.33 15.4 -- 4 - 1100-1145

17 May 76 .

COND-IN BEF 0.134 «0.18 18.2 71 27— 7.0 1040-1120 Hi 1655 +5.8
COND-IN DUR 0.047 0.08 17.7 70 #19 -- Lo 0959 -1.1
OUT DUR 0.036 0.03 -- -- «19 --

COND-IN AFT 0.119 0.14 17.9 70 «21 --

26 Aug 76

COND-IN BEF 0.128 0.34 18.7 72 31 «7.5 1040-1120 Hi 1422 +7.1
COND-IN DUR 0.037. 0.28 -- -- 28 -- Lo 0813 +1.6
QUT DUR 0.024 0.28 -- -- 28 --

COND-IN AFT 0.140 0.36 18.4 73 (27 --

Potrero

23 Feb 76

N. COND-IN BEF 0.055 0.27 16.8 67 13 -- 2100-2215 Hi 2026 +4.8
N. COND-IN DUR 0.000 0.20 16.5 70~«71 -- Lo 2509 +2.7
QUT DUR 0.032 0.21 16.5 70 «(12 --

N. COND-IN AFT 0.075 0.26 16.4 77 10 --

4 Mar 76

N COND-IN BEF 0.118 0.20 16.7 63 18 -- 2100-2215 Hi 2625 +5.7
N COND-IN DUR 0.059 0.16 16.8 64 «15 -- Lo 2000 +1.6
OUT DUR 0.077. 0.21—=—-- -- iW --

S COND-IN AFT 0.104 0

-17 16.8 66 20 --

*Determined by nesslerization.
+Ft above datum at Golden Gate Bridge.


mg Clo/1

OXIDANT RESIDUAL,

1.6 T T T T T T T T T
CHLORINE INJECTION RATE: 1500 Ibs/24hrs
CHLORINE DOSE (CALCULATED): 2.5 mg/I
Lat =
KEY: COND-IN OUT
° ° TOR (AMPEROMETRIC )
. o FOR (AMPEROMETRIC)
2 A a FREE CLj+ BROMINES (OPD) —|
8 bd COMBINED CL (DPD)
c c BROMINES (OPD)
Loe |
0.8 4
0.6;-—- 4 +
0.4-—- 4
0.2 4
0. 1__bt J 1 1 pt pt 'G \o |
1040 1044 1048 1052 1056 1100 104 los ill2 Wie 20

TIME

Figure 26. In-plant study at the Hunters Point Power
Plant, 26 August 1976, Unit 4

55


Foreword... 6 ee eee se eee

CONTENTS

Preface 2. 0 1. ee ee ee ee ee es ray
Abstract . 6 6 1 we ee ee wee eee .
Figures 2. wc ee ee ee ee ee ee ee ee ee
Tables ...... we wee eee oe wee .
Abbreviations and Symbols ..... rr rrr
Acknowledgment . 66 1. eee et ee ee ee ee
1. Introduction 2... 6 ee ee ee ee ee ee ee et es
2. Material and Methods oe oe rr se
3. Results ...-...ee ar . . .
4, Discussion ... 1... 2s Pr
5. Conclusions. ......-s we Se ee eee
References . 2... eee eee eee . se oe oe
Appendix 1 Field Data 2... 1 6 ee ee ee ee ee ee ee .

viii

xi

xii

13
37
44
46
48


DISCHARGE
STRUCTURE

INTERNATIONAL

SHELLFISH ys COOLING waTER
ENTERPRISES
INC.

(ISE)

a

© SAMPLING LOCATIONS

Figure 6.

COOLING WATER
INTAKE STRUCTURE

a * ee STRUCTURE y
% y
<a

UNITS 1TOS

Moss Landing Power Plant.


10.

i.

12.

REFERENCES

Brungs, W. A. Effects of residual chlorine on aquatic life. J. Water
Poll. Control Fed., 45:2180-2193, Oct 1973.

Basch, R. E. and J. G. Truchan. Toxicity of Chlorinated Power Plant
Condenser Cooling Waters to Fish. Environmental Protection Agency, Duluth,
Minnesota. Publication Number 600/3-76-009., Apr 1976. 105 p.

Mattice, J. S. and H. E. Zittel. Site-specific evaluation of power plant
chlorination. J. Water Poll Cont Fed., 48:2284-2308, Oct. 1976.

Federal Register, Vol. 39, No. 196, Oct. 8, 1974.

California Regional Water Quality Control Board, Central Coast Region,
Waste Discharge Requirements fo Pacific Gas and Electric Company, Moss
Landing Fossil Fuel Power Plant, Units 1-7, Monterey County, Order No.
76-09, NPDES No. CA0006254, San Luis Obispo, California, 1976.

California Regional Quality Control Board, San Francisco Bay Region, Waste
Discharge Requirements For: Pacific Gas and Electric Company-Hunters
Point P.P., Potrero P.P., Orders No. 76-60, 76-61, NPDES No. CA0005649,
CA0005657, Oakland, California, 1976.

Standard Methods for the Examination of Water and Wastewater, 14th Ed.
New York, amer Public Health Assoc., 1976.

Manabe, R. M. Measurement of Residual Chlorine Levels in Cooling Water --
Amperometric Method. Environmenta Protection Agency, Corvallis, Oregon.
Publication wumoer 660/2-73-039, Aug. 1974. 45 p.

White, G. C. Handbook of Chlorination. New York, Van Nostrand Reinhold
Comp. , 1972. 744 p.

Palin, A. T. The determination of free and combined chlorine in water by
the use of diethyl-p-phenylene diamine. Amer. Water Works Assoc., 49:
873-880, Jul 1957.

Palin, A. T. The determination of free residual bromine in water. Water
and sewage works, 108:461-462, Dec. 1961.

Palin, A. T. Current DPD methods for residual halogen compounds and ozone
in water. J. Amer Water Works Assoc., 67:32-33, Jan. 1975.

46


1.6

/! _
°

mg Cl.
°
@

OXIDANT RESIDUAL,
°o
o

9
>

0.2

KEY: COND-IN
e

T

CHLORINE INJECTION RATE: 1000 Ibs/24 hrs
CHLORINE DOSE (CALCULATED): 1.6 mg/I

OUT
°

a

T q 1 T T

TOR (AMPEROMETRIC)

TOR AT COND-IN

TOR AT OUT J

1 ! I 4

0.0
N02 106 =O | «4a

Figure 24.

Wg

N22 N26 «30 «3413842

TIME

In-plant Study at the Hunters Point
Power Plant,16 Dec 1975, Unit 4.

53


8 10 FEB 76

OND-IN
DILUTION

TOR (DARK)
5 Ge (LIGHT)
00 I T T t ~1

I
“oO 10 20 30 40 50 60 70
TIME, min

16 JUN 76

>
U

DOSE

on”

| COND-IN
DILUTION TOR (DARK)

02 FOR me a (LIGHT)
+ |

50 60 70

°
a

OXIDANT RESIDUAL, mg A,/ '
° °
a @

°
o2

TIME, nin

Figure 9. Results of decay studies conducted at the
Contra Costa power plant, Units 6 and 7 outfall,

26


DOSE 17 MAY 76

>

nv

of

[-COND-IN

08

OXIDANT RESIDUAL, mg Clp/1

ind
rs

26 AUG 76

np
fo

r oN
oa oO
f

a
T

4 b

2 pr

COND-IN
1.0 ia

O8T_out

OXIDANT RESIDUAL, mg Clg /1

TIME, min

Figure 10. Results of decay studies conducted at the
Hunters Point Power Plant, Unit 4 outfall.

27


discharge is into a canal that has an approximate residence time of 12 min. In
the canal average TOR concentrations were on the order of 0.05 mgCl2/2.
According to Mattice and Zittel, this combination of chlorine dose and ex-
posure time would not result in acute toxicity to freshwater organisms. It
is very close to Mattice and Zittel's acutely toxic level for marine organisms.
A TOR of 0.02 mgCl2/2 was detected for a distance of some 150 m (500 ft) down
the San Joaquin River. Assuming an average water velocity of 0.55 m/sec (1.8
ft/sec) this results in an exposure time of 4.6 min at this TOR concentration.
This TOR level is at Mattice and Zittel's chronic toxicity level for marine
organisms. For freshwater organisms the dose/exposure time stated to be
acutely toxic to freshwater organisms by Mattice and Zittel is 0.02 mg/2% for
min.

TABLE 11. ACUTE AND CHRONIC DOSES OF CHLORINE TO MARINE AND
FRESHWATER ORGANISMS (Mattice and Zittel) (3)

MARINE ORGANISMS FRESHWATER ORGANISMS

TOR DURATION TOR DURATION
mgC12/2 min mgC12/2 min
0.20 0.50 0.10 25
0.15 1.0 0.05 60
0.10 2.5 0.02 200
0.05 : 13 0.01 550
0.02* -- 0.0015* --

*Chronic toxicity threshold.

Current velocities in the discharge plumes have been determined by PG&E
at the Hunters Point and Potrero Plants. At Hunters Point the time to reach
the 0.02 mg/% TOR isoconcentration line is 45 sec. Assuming that the velo-
city is constant between the outfall and the 0.02 mg/% TOR isoconcentration
line, the estimated time to reach 0.05 mg/&% TOR is between 11-28 sec; with the —
same assumption, the time to reach the 0.10 mg/% TOR isoconcentration line is
7 sec. These dose/exposure times are far below the values quoted by Mattice
and Zittel to be acutely toxic to both freshwater and marine organisms. Con-
centrations of TOR exist in the receiving water that are above the chronic
toxicity threshold for both freshwater and marine organisms.

At Potrero, with an average discharge concentration of 0.3 mg/&% TOR, the
time to the 0.02 mg/2 TOR isoconcentration line is approximately 3 min. Using
the same assumptions as for Hunters Point, the time to the 0.1 mg/% TOR iso-
concentration line is estimated to be between 48-56 sec; from the 0.1 mg/%

42


Sl

TABLE 4.

WATER QUALITY AND TIDAL DATA AT THE CONTRA COSTA POWER PLANT

NHs-N Org-N CI” BrTM SoLaps TIME OF TIDAL DATA
DATE/SAMPLE pH STUDY
mg/& = mg/k mg/& mg/& mg/Z TIME ELEVATION, fts

20 Jan 1976
#11 COND-IN DUR 0.04* 0.13 50 -- 22 == 0930-1200 ‘Hi 0602 43.9
#14 COND-IN DUR OL 50 == 19 = Lo 1213 41.0
10 Feb 1976
#13 COND-IN BEF 0.11* 0.29 563 1.2 «942, == 0930-1120 Hi_1039 +4.0
#13 COND-IN DUR 0.09 0.21 648 1.6 30 - Lo 1841 40.2
#13 COND-IN AFT 0.10 0.20 901 1.9 35
16 Jun 1976
#13 COND-IN BEF 0.091 0.42 1180 3.9 111 7.5- 1010-1100 Hi 0646 43.8
#13 COND-IN DUR(+)+ 0.066 0.40 1019 3.6 118 7:7 Lo 1415 -0.2
#13 COND-IN DUR(-)¢ 0.078 0.43 -- 35) 1280

7 OUT DUR 0.082 0.41 - 3.4 «114
#13 COND-IN AFT 0.078 0.36 746218 «88
14 Sept 1976
#11 COND-IN BEF -- 0.33 © 1032,«3.9° = 34 7.7- 1030-1250 Hi 0835 43.0
#12 COND-IN DUR(+)+ 0.019 0.31 lL 37.8.0 Lo 1403 41.4
#11 COND-IN DUR(-)£ 0.012 0.33 913 3.5 34

6 OUT DUR 0.009 0.34 woe 320~CO
#13 COND-IN AFT 0.017 0.32 71 3.4 41

*Determined by nesslerization.

tSamples taken during chlorination cycle from the condenser being chlorinated.

as

Ft above datum at Golden Gate Bridge.

{pamples taken during chlorination cycle from a condenser not being chlorinated.


was detected at the outfall of Hunters Point and at a sample point 6-7
min of flow time from the condenser inlet at Moss Landing.

9. The DPD-FAS results indicated that most of the oxidant residual at Hunters
Point and Moss Landing was bromine residual.

10. The disappearance of total oxidant residual through the cooling water system
generally depended on the flow time. At Moss Landing where the total flow
time in the system was 6 to 7 min, from 16% to 27% of the oxidant input
remained at the outfall. At Potrero where the total flow time in the system
was only 1.3 min, from 54% to 78% of the oxidant input remained at the
outfall.

DECAY AND RECEIVING WATER STUDIES

11. The slowest decay at the outfall was observed at Contra Costa where 50%
to 52% of the total oxidant residual of 0.18-0.23 mg/g measured at the
outfall remained after 60 min in the samples covered to exclude sunlight.
For the samples exposed to sunlight, 38% to 39% remained after the same
time period.

12. The most rapid decay at the outfall was observed at Hunters Point where
17% to 28% of the total oxidant residual of 0.52-0.72 mg/2 measured at the
outfall remained after 30 min in the samples covered to exclude sunlight.
For the samples exposed to sunlight, only 6% to 17% remained after the same
time period.

13. Maximum total oxidant residuals were found to exist at the surface of re-
ceiving waters likely because of the natural buoyancy of the warmer ef-
fluent.

14. During the chlorination cycle at Contra Costa, an 0.02 mgCl./2% residual
was measured some 150 m(500 ft) from the point where the discharge canal
meets the San Joaquin River.

15. During the chlorination cycle at Hunters Point, 0.02 mgCl2/% residual
was measured up to 150 m (500 ft) from the No. 4 outfall and up to 168 m
(550 ft) away from the No. 3 outfall at Potrero, and up to 400 m (1300 ft)
from the No. 1 and No. 2 outfall at Potrero.

16. A maximum residual of 0.16 mgC12/2 was measured at the surface of Monterey
Bay above the outfall from the No. 6 and No. 7 Units at Moss Landing.

17. Using the approach of Mattice and Zittel, it was determined that all ef-
fluents produced receiving water oxidant residual levels that would be
predicted to demonstrate chronic toxicity to marine organisms; the re-
ceiving water from two plants (Hunters Point and Moss Landing) showed
levels that would be predicted to demonstrate chronic toxicity to fresh-
water organisms. Acutely toxic levels to freshwater and marine organisms
existed in the receiving waters at. the Potrero site.

45


4

° ° =
a o °

OXIDANT RESIOUAL, mg ci,/\

nd
>

0.2

0.0

T T

KEY: COND-IN OUT
e
|

T T T T T T T
CHLORINE INJECTION RATE: 1000 Ibs /24 hrs
CHLORINE DOSE (CALCULATED): 1.6 mg/I

C TOR AT OUT
FOR AT OUT

° TOR (AMPEROMETRIC)
Oo FOR (AMPEROMETRIC)

TOR & FOR AT COND-IN

Figure 25.

"1040 1044 1048 1052 1056 100 1104 1108 WWI2 NIG 1120

TIME

In-plant Study at the Hunters Point Power Plant
17 May 1976, Unit 4.

54


DISCLAIMER

This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publi-
cation. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does men-
tion of trade names or commercial products constitute endorsement or recom-
mendation for use. :

ii


ve

15 OCT 76
HI WATER i7II
LO WATER 1135
STUDY 1400-1530

aio

S.F. BAY

SCALE:

| IN. = 300 FT

27 OCT 76
HI WATER 1533
LO WATER 0939
STUDY 1130-1200

COND-IN ~0.69}

OUT
~050

Fiqure 16. TOR (maC12/2) at receiving water surface at the Potrero Power Plant, Units 1 and 2,



2

19 OCT 76
HI WATER 0959
LO WATER 1557

i“ + STUDY 1320-1410

3 NOV 76
HI WATER 0941
LO WATER 617
STUDY 1410-1500

STUDY 1130-1210

15600 FT?

0.08 0.05
COND-IN 2 COND-IN
~0.65 SOO FT woes 0.02
» 125000 FT?
126000 FT /
17 NOV 76 23 NOV 76
HI WATER O81 HI WATER 1228
LO WATER 1445 LO WATER 1940

STUDY 1320-1350

0
1500 FT?

0.05
2800 FT?

SCALE: | IN. = 200 FT

Figure 14.

TOR (mgC12/2) at receiving water surface at the Hunters

Point Power Plant, Unit 4,



mg Ciy/1
°

9
@

OXIDANT RESIDUAL,
°o
a

0.4

0.2

U T T T T T U T T 7 T

CHLORINE INJECTION RATE: 1400 Ibs /24 hs
CHLORINE DOSE (CALCULATED): 1.6 mg/I

KEY: COND-IN OUT
e ° TOR (AMPEROMETRIC)

TOR AT COND-IN \ i:
fo

TOR AT OUT*

nN

* TWO TIMES MEASURED VALUES
I ! {J ! 1

fel !

0.0) !
0900 0904 0908 0912 0916 0920 0924 3928 ase 0936 0940 0944

TIME (PM)

Figure 28. In-plant study at the Potrero Power Plant, 4
March 1976, Unit 3, N. Condenser

57


SECTION 2
MATERIAL AND METHODS

POWER PLANT LOCATION AND DESCRIPTION

A map showing the location of the five power plants studied is presented
in Figure 1. Water quality varied from fresh at Contra Costa to marine at
Moss Landing.

A summary of the operating data for each plant is presented in Table 1.
All the plants have the capability of burning either fuel oi] or natural gas.
The plants rarely operated at maximum capacity. Usually the newer, more
efficient units in any plant operated continuously and the older units were
used during peak demand periods and during periodic shutdowns of the other
units.

TABLE 1. POWER PLANT OPERATING DATA

Sa

COOLING WATER

POWER SRS RerTy N° NO. OF SOURCE OF FLOWRATE*
PLANT (MW) UNITS INTAKE WATER | —————_——____-
(m*/sec) (gpm)
San Joaquin

Contra Costa 1300 7 River 43.2 684 ,000
Pittsburg 2060 7t Suisun Bay 45.4 720 ,000
Hunters San Francisco

Point 400 3 Bay 18.2 288,000
Potrero 330 3 sae yronctsco 16.5 262,000
Moss Landing 2110 7 Monterey Bay 63.1 1,000,000

— ee <=

*A11 units in operation.

tUnit 7 cooled by a spray canal.


SECTION 5
CONCLUSIONS

CHLORINATION PRACTICE

1.

Chlorination frequency varied among the five power plants studied from
l/week to 4/day. Duration of chlorination varied from 15 to 40 min per
cycle.

Oxidant residual determined at the condenser inlets was the criterion
used by the power plants to determine the level of chlorine dose.

During this study the chlorine dose to produce the desired residual of
approximately 0.5 mgC12/2 at the condenser inlets was reduced. This re-
duction resulted from a more precise measurement of chlorine residuals
throughout the cooling system that was afforded by the amperometric method
used by us as compared to the OT method routinely used by power plant
personnel.

All of the plants are currently using or are in the process of obtaining
amperometric titrators due to more stringent regulations that require
accurate measurement of oxidant residuals.

IN-PLANT STUDIES

5.

Total chlorine usage per day for the four power plants located on San
Francisco Bay averaged about 0.3 metric tons/day (0.33 tons/day) based on
1971 figures. This represented 1.25% of the total average daily use of 34
metric tons/day (37.5 tons/day) estimated for 1975-76 for waste discharges
entering San Francisco Bay.

Oxidant residuals determined at the condenser inlets were often signifi-
cantly higher than the 0.5 or 1.0 mg/2 desired by plant personnel, es-
pecially at those plants using the OT method for control of chlorine
residual.

At Contra Costa, where the cooling water was the freshest, a combined
residual of from 0.10 to 0.40 mgC12/2 existed from the condenser inlet to
the outfall.

At Hunters Point, Potrero, and Moss Landing, where cooling water ranged
from 79% to 99% seawater, total oxidant residual generally equalled
free oxidant residual at the condenser inlets. Some combined residual

44


12 4
KEY: COND-IN OUT
e fo} TOR (AMPEROMETRIC)

OF -
x
WN
rs)
i-J
Fost 4
Jt
a
2
=)
n
#
+ 0.6 TOR AT COND-IN 4
Fe /
=] re
x oe © ~~. Neo “—e
° ony So O-

4 T T T T T T T + T T T
CHLORINE INJECTION RATE: 1400-1600 Ibs/24 hrs
CHLORINE DOSE (CALCULATED): 1.6 mg/l

naan ro Oo

0.4/- TOR AT OUT* 7
o2b 4
» TWO TIMES MEASURED VALUES
° [ar es a Oe [| 1
1024 1028 1032 1036 1040 i0aa 1048-1052 1056 O00 1104 1108
T

Figure 21. In-plant Study at the Contra Costa Power Plant
10 Feb 1976, Unit 7, Condenser #14.

50


Plan diagrams of the once-through cooling water systems at each of the
power plants are presented in Figures 2 to 6. Cooling water is diverted
from its source and pumped through the cooling system by circulating water
pumps located at the intake structures. The cooling water first passes
through bar racks which prevent large objects from entering the system.
Smaller objects are removed by travelling screens which rotate periodically
and are cleaned with high pressure water.

Heat exchange between cooling water and saturated steam occurs in the
condensers which consist of bundles of 22.2 mm (7/8 in.) or 25.4 mm (1 in.)
diameter aluminum-brass or copper-nickel alloy tubes. There is one condenser
per unit which is divided into two halves. The heated flows of cooling water
combine immediately after the condenser and are discharged to the receiving
water at the outfall structure.

Cooling water sampling locations are indicated for each power plant in
Figures 2 to 6. Cooling water could generally be sampled at the condenser
inlets (COND-IN), condenser outlets (COND-OUT), and at outfall manholes (OUT)
Very convenient sample taps had been set up at the COND-IN because this was
where oxidant residuals were routinely measured by plant operating personnel.
Sampling at the COND-OUT was more difficult even though taps generally existed
or were readily installed because samples had to be pumped out against a vacuum
of about 25.4 cm (10 in.) of mercury. Outfall manholes generally existed as
part of a discharge structure so that samples taken from these manholes were
representative of the water being discharged to the receiving water. At Moss
Landing, Units 6 and 7 discharged into Monterey Bay,.242 m (800 ft) off shore,
at a depth of 6.1 m (20 ft). A sampling point approximately midway between
the condensers and the outfall was furnished by the International Shellfish
Enterprises, Inc. (ISE).

CHLORINATION PRACTICES

Chlorine is injected intermittently into the cooling water flow to con-
trol slime-causing organisms. In PG&E plants, liquid chlorine is withdrawn
from one-ton cylinders, evaporated, and injected into a water line to produce
a concentrated chlorine solution. This solution flows to the point of in-
jection in a well behind the travelling screens and in front of the circulat-
ing water pumps. Oxidant residuals are routinely measured at the COND-IN
and the chlorine injection rate is adjusted to give the desired residual.
These adjustments are rarely needed on a daily basis, however the residual
monitoring is important to insure proper operation of the chlorinators which
are somewhat unreliable when subjected to the frequent startups and shutdowns
encountered in intermittent chlorination.

A summary of chlorination practices for the newest units at each of the
five PG&E power plants is presented in Table 2. The newest units were chosen
for study because they were the largest and most frequently operated. A
great deal of variation in frequency, duration, and levels of chlorination
existed. Frequency varied from 1/week to 4/day and was changed during the
year to meet changing demands. Duration of chlorination ranged from 15 to 40
min. All the plants seek to maintain a 0.5 mg/g residual at the COND-IN

4


EPA-600/3-78-032
March 1978

POWER PLANT COOLING WATER CHLORINATION IN
NORTHERN CALIFORNIA

by

S. Hergott, David Jenkins, and Jerome F. Thomas
Sanitary Engineering Research Laboratory
College of Engineering
and
School of Public Health
University of California
Berkeley, California 94720

GRANT NO R803959

Project Officer

Donald Baumgartner
Marine and Freshwater Ecology Branch
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330

CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330


TABLE 9. SUMMARY OF LOSS OF OXIDANT RESIDUAL WITHIN
THE POWER PLANT COOLING WATER SYSTEM

APROX IMATE TOR LOSS
FLOW TIME
. (%)* TOR
(min) (3)*
POWER PLANT UNIT Ing pT  COND-IN INI PT COND-IN REMAINING
TM 10 TOTAL 10 TO AT OUTFALLt
COND-IN OUTFALLt COND-IN  OUTFALL+
Contra Costa 6 1.2 1.5 2.7 55-75 8-21. 17-24
7 1.2 0.9 2.1 58-67 6-17 27-31
Hunters Point 4 1.5 0.9 2.4 44-59 10-34 24-40
Potrero 3. 0.9 80.4 1.3. 19-44 0-19 54-78
Noss Landing 6,7 0.8 6-7 7-8 10-32 41-64 16-27

*Percent loss does not include that caused by dilution immediately
past the condensers.

+ISE at Moss Landing

the receiving waters to determine the extent of the area affected by the
power plant discharge during chlorination.

‘The results of the decay studies conducted at the outfalls are presented
in Figures 9-12. The loss of oxidant residual between the point of chlorine
injection, the COND-IN, and the outfall are shown. The effect of the 1:1
dilution which occurred between the COND-IN and the outfall sampling point
is indicated by a dotted line for all plants except Hunters Point where flows
to both condensers were chlorinated simultaneously. Table 10 is a summary
of the decay studies. It should be remembered that the results are based on
field studies and that no attempt was made to keep temperature constant. In
Most cases temperature increased in the "light" experiments and decreased in
the "dark" experiments.

The results of receiving water studies are presented in Figures 13-17
in the form of isoconcentration lines of TOR at the surface. Surface TOR
was always found to be the highest compared to samples taken at various
depths. Whenever possible the 0.02, 0.05, and 0.10 mg Cl2/% isoconcentration
lines are shown together with the enclosed surface areas. These areas give
an approximation of the regions affected by various levels of TOR. The re-
ceiving water studies conducted at Contra Costa, Potrero, and Hunters Point
were for a time period greater than the normal chlorination cycles at these
plants.

25


SECTION 3
RESULTS

IN-PLANT STUDIES

Persistence and decay of oxidant residuals at the outfalls and in the
receiving waters can best be explained after the nature and disappearance of
the residual inside the plants are understood. The in-plant studies were
conducted to establish the nature of the oxidant residual and to gain an
understanding of the demands in the cooling water systems at each of the power
plants. Each plant was studied separately because of variations in water
quality, chlorine dosage, frequency and duration of chlorination, and flow
time through the system.

In-plant studies were conducted over a period of one year to be inclusive
of varying water quality conditions. Results at each of the four plants
studied are presented in Appendix 1 (Figures 20 to 35). The graphs show the
temporal variation of oxidant residual during a chlorination cycle. Also
shown is the chlorine dose calculated on the basis of the chlorine injection
rate determined by power plant personnel and the cooling water flow rate.

The calculated dose may not be precise because the chlorine injection rate
was difficult to read accurately and the only value usually known for the
cooling water flow rate was the original design value.

Contra Costa Power Plant

The results of the in-plant field studies conducted at the Contra Costa
Power Plant are summarized in Table 3. Water quality and tidal data corre-
sponding to most of these studies are presented in Table 4.

A combined residual of from 0.10 to 0.40 mg Cl2/2 formed by the time the
cooling water reached the COND-IN, (approximately 1.2 min of flow time) and
generally remained unchanged at the outfall when the dilution effect was taken
into account. It appeared that the FOR which disappeared accounted for most
of the loss of residual between the COND-IN and the outfall.

The DPD-FAS results for the study of 14 September 1976 indicated a com-
bined chlorine residual of 0.10 mg/% at the COND-IN and 0.03 mg/& at the out-
fall, both of which compare favorably with the amperometric titration results.
The FOR of 0.20 mg C12/& determined amperometrically titrates as bromine
residual by the DPD-FAS method since titration "A" equals titration "C".

Cooling water at Contra Costa varied from 0.3% to 6.1% seawater. Most
of the water quality data show the effects of tidal changes. The addition of

13


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

Environmental Protection Technology

Ecological Research

Environmental Monitoring

Socioeconomic Environmental Studies

Scientific and Technical Assessment Reports (STAR)
Interagency Energy-Environment Research and Development
“Special” Reports

Miscellaneous Reports

This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.

OMNAAAYON

This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.


SECTION 4
DISCUSSION

NATURE OF THE OXIDANT RESIDUAL

The nature of the oxidant residual at each of the power plants is im-
portant for understanding the decay and persistence in the receiving waters.
None of the methods currently available for the routine measurement of oxidant
residuals unequivocally identify the compounds that make up the residual.

This is especially true for oxidant residuals in estuarine and marine waters.

When chlorine is added to seawater that is free of amino-nitrogen, bromide
(present at a concentration of approximately 70 mg/2) is oxidized to bromine
as follows:

HOC] + Br” = HOBr + C1”

Figure 18 shows the time required (based on reported rate constants) to
convert 99% of the chlorine to bromine at a temperature of 25°C and a pH of
8.3 for varying percentages of seawater (15). The reaction proceeds to 99%
completion within 10 sec in highly saline water, but very little bromine is
formed in water containing less than 3% seawater. A similar oxidation of
iodine occurs. Total oxidation of the iodide in seawater to iodine would
account for a TOR of 0.035 mg/g as chlorine.

When ammonia-nitrogen is present in seawater, there is a competition
between the ammonia and the bromide ion for chlorine. A number of reactions
are possible, depending on pH, chlorine dose, concentration of NH3-N, salinity,
and reaction time. The formation of chloramines is generally favored by high
NH3-N, low salinity, high pH, and low chlorine dosage.

Using an equilibrium model, Sugam and Helz (16) suggest that free bromine
and bromamines predominate over the chlorine species at salinities above
approximately 0.3 g/2 with ammonia concentrations "typical" of estuarine and
marine waters. The predominant species in seawater containing 0.08 mg NH3-N/2
dosed at 1.0 mgC12/2 at pH 8.1 were tribromamine (NBr;) and dibromamine
(NHBr,). Equal amounts of monochloramine (NH2C1) and HOBr were estimated to
exist in a typical seawater of 35 g/2 salinity at pH 8 containing 0.12 mg/2
NH2-N dosed at 0.5 mgC12/2. The model for 0.3 g/2 salinity is very complicated
showing both chlorine and bromine compounds with no species in abundance be-
tween pH 6 and 8.

Sollo et al. (17) performed studies on the resulting speciation when
solutions containing both ammonia and bromide were dosed with chlorine and the

37


2

TABLE 8 (continued)

- - SUSP.
NH3-N Org-N C1 Br SOLIDS TIME OF TIDAL DATA
DATE/SAMPLE pH STUDY ELEVATION

mg/2 mg/2 g/2 mg/R mg/k TIME ft +
5 Aug 76
6-1 COND-IN BEF 0.074 0.22 18.8 73 23 8.2-  1300- Hi 0826 +3.8
6-1 COND-IN DUR(+)* 0.016 0.17 -- -- 18 8.3 1400 Lo 1307 42.7
6-2 COND-IN DUR(-)+ 0.072 0.21 -- -- 18
6 ISE DUR 0.045 0.170 -- -- 16
6-1 COND-IN AFT 0.074 0.23 19.1 70 18
23 Sept 76
6-1 COND-IN BEF 0.052 0.19 18.7 70 3 8.9 1300- Hi 1044 +5.4
6-1 COND-IN DUR(+)* 0.045 0.25 -- -- 5 1350 Lo 1656 +0.3
6-2 COND-IN DUR(-)+ 0.071 0.22 -- -- 4
6 ISE DUR 0.017. 0.16 -- -- 2
6-1 COND-IN AFT 0.103 0.30 18.6 67 4

—

*Samples taken during chlorination

+Samples taken during chlorination

aE

cycle from the condenser being chlorinated.

cycle but from a condenser not being chlorinated.

+Ft above datum at Golden Gate Bridge.


0€

TABLE 10. SUMMARY OF DECAY STUDIES
TOR AFTER
INITIAL INITIAL "DARK" 30 MIN 60 MIN TIME TO REACH
DATE POWER PLANT —TEMP TOR a Cour 0.1 mgCl2/2
°c mgCl2/2 EXPOSURE % OF % OF min
mgCl2/% INITIAL mgCl2/& INITIAL
TOR TOR
10 Feb 76 Contra Costa -- 0.23 Dark 0.14 61 0.12 52 >90
Light 0.12 52 (0.09 39 45
16 Jun 76 Contra Costa 34.5 0.16 Dark (0.09 56 0.08 50 20
Light 0.07 44 «0.06 38 8
17 May 76 Hunters Point 24.0 0.52 Dark 0.10 7 -- - 30
Light 0.03 6 -- -- 10
26 Aug 76 Hunters Point 30.0 0.72 Dark 0.20 28 0.15 21
Light 0.12 17 (0.08 | 38
23 Feb 76 Potrero 20.0 0.61 Dark 0.20 330.13 21 >90
4 Mar 76 Potrero 20.0 0.43 Dark 0.15 35 0.10 23 60
19 Apr 76 Moss Landing 24.0 0.22 Light 0.08 350.03 13 22
14 Jul 76 Moss Landing 27.0 0.20 Dark —-0.08 400.08 25 16
Light 0.05 250.02 10 8



chlorine generally caused a decrease in ammonia-nitrogen concentrations but
this was more evident at the other power plants. Compared with earlier studies
the much lower combined residual detected on 14 September 1976 is explained

by the very low NH3-N concentration.

Hunters Point and Potrero Power Plants

The results of the in-plant studies conducted at the Hunters Point and
Potrero Power Plants are summarized in Table 5. Water quality and tidal data
corresponding to these studies are presented as Table 6.

In general FOR equalled TOR both at the COND-IN and at the outfall. An
exception was the study of 17 May 1976 which detected a combined residual at
the outfall of 0.13 mg Cl2/2% which had formed during the approximately 0.9
min of flow time from the COND-IN.

The DPD-FAS results for the study of 26 August 1976 at Hunters Point
revealed a small combined chlorine residual at the COND-IN which the ampero-
metric method failed to detect. The DPD results at the COND-IN are difficult
to explain since titration C should never be greater than titration A. At
the outfall a total residual of 0.45 mg C1,/2 was identified as bromine
residual by the DPD-FAS method.

A TOR of 1.0 mg Cl2/2 was desired at the COND-IN for the studies of 23
February 1976 and 4 March 1976 at the Potrero Power Plant. This criterion
was lowered to 0.5 mg/% and was the criterion during the studies on the 15th
and 17th of October 1976. The studies of 4 March 1976 and 15 October 1976
revealed essentially no loss of oxidant residual between the COND-IN and
outfall manhole which corresponded to a flow time of approximately 0.4 min.

Cooling water at Hunters Point and Potrero varied from 79% to 96% sea-
water. Ammonia-nitrogen concentrations determined on samples collected at the
COND-IN decreased by up to 0.091 mg/2 during chlorination. A decrease in

“organic nitrogen was also evident during chlorination.

Moss Landing Power Plant

The results of the in-plant studies at the Moss Landing Power Plant are
summarized in Table 7. Water quality and tidal data are presented in Table 8.

The results generally indicate much higher oxidant residuals at the COND-
IN than the 1.0 mg/2 desired by the plant chemist. Measurements by the
amperometric and DPD-FAS methods were often on the order of two times the
value determined by the plant chemist during the OT method.

At the COND-IN, FOR was generally greater than or equal to TOR. Since
FOR can never be greater than TOR, an error (probably in the TOR measurement)
was indicated. Approximately 1 min was required to measure out a 200 me
sample, transfer it to the titration jar, add the KI and pH 4 buffer, and
perform the TOR titration. During this time the oxidant residual was
reacting with species in the water and decaying. On the other hand, the
back titration method for FOR fixes the concentration as soon as the sample

16


ACKNOWLEDGMENTS

We wish to thank numerous people at the Pacific Gas and Electric Company
who gave us their complete cooperation and much valuable assistance: the
plant superintendents - Mr. D.L. Nix, Mr. M. Samaii, Mr. J. Pridmore, Mr. R.
Puckett; the plant chemists and chemical engineers - Mr. E. Garcia, Mr. E.
Holt, Mr. S. Chun, Mr. M. Sransjo, Mr. M. Bush; and in the San Francisco
office special thanks are due to Mr. T. Casebolt, Mr. G. Sanders,. and Dr.

C. Walton.

Mr. R. Eissenger and Mr. M. Cox of the International Shellfish Enterprises,
Inc. were very helpful in allowing us to set up a sampling station for Moss
Landing power plant cooling water. Ms. P. Elliot of the California State
Marine Laboratory at Moss Landing arranged for the use of a boat for the re-
ceiving water studies. Dr. J. Elder of Tetra Tech, Inc., Lafayette, Ca.,
allowed us time during his sampling schedule for receiving water studies at
Contra Costa and Pittsburg using a boat owned by Mr. T. Glimme of Parameter
Research. Mr. J. J. Connors of the East Bay Municipal Utility District allowed
us the use of an amperometric titrator while we were awaiting delivery of new
ones. Mr. R. Sakaji, M.S. candidate in Sanitary Engineering, University of
California, Berkeley, was a research assistant on the project and contributed
greatly to its conduct.

The Environmental Protection Agency project officer was Dr. D. Baumgartner,

whose assistance and patience are gratefully acknowledged. Mr. Fred Roberts
of the Corvallis Office of EPA is thanked for ‘reviewing this report.

xii


1.4 T T T T T T T T T T T
CHLORINE INJECTION RATE: 1100-1200 Ibs/24hrs~
CHLORINE DOSE (CALCULATED): 1.3 mg/!
wae 4
KEY: COND-IN OUT
e © TOR (AMPEROMETRIC)
. a FOR (AMPEROMETRIC)
L A a FREE CL, + BROMINES (DPD)
1.0 B b COMBINED CL, (OPO) 7
S c c BROMINES (DPD)
5
é
~ O8- 4
J
¢
2
4
8
e
5 06F Two TIMES MEASURED VALUES 5
3
x
oO
O4F a AT COND-IN
_o
A
FOR AT COND-IN
o.2- am— a SOA c —~a-c ——cC 4
Von TOR AT OUT®
obo, 8, eh

0.0 4
1036 040 Tosa rote 1052 1086 100 oa 1108 m2 me "20

TIME

Figure 23. In-plant Study at the Contra Costa Power Plant
14 Sept 1976, Unit 6, Condenser #11.

52



300;--

240--

180--

iS
i]
U

8
T

a
fo}
T

8
T

x
i=}
T

TIME TO 99% CONVERSION, sec
8
T

0.5

1.0

2.0 Cin DOSE, mg/!

4 i ! 1

1 | 1
4°85 10 20 30 40 +50
% SEA WATER

Figure 18. Time required for 99% conversion .of free chlorine
to HOBr at 25°C and a pH of 8.3

38



Ov

LOGARITHM OF MOLE RATIO NH3 TO Br 2 INPUT

4 L I ! a ! J
3 4 5 6 7 8 9 10
pH
Figure 19. Principal species of bromine: and bromamine

after 1-2 min at various pH and ammonia to bromine ratios.
Lines represent equal equivalent concentrations. Hypobromous
acid separation from bromine given for 10-° M bromide.

(After Johnson and Overby 18),


POTRERO

HUNTERS
POINT

CONTRA
OAKLAND COSTA

SEESAN JOSE
PACIFIC

OCEAN

Anan?
(ewe Corey

MONTEREY
MOSS LANDING

Figure 1. Power plant locations,

SCALE: | IN=

i SACRAMENTO

20.5 MI.