CWT 10-18
CLEAN
WATER
EFFECT OF SEASONAL CHLORI NAT I ON OF
TREATMENT PLANT EFFLUENTS ON
JAMAICA BAY COL I FORM POPULATIONS
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION • U. S. DEPARTMENT OF THE INTERIOR
HUDSON-DELAWARE BASINS OFFICE, EDISON, NEW JERSEY
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EFFECT OF SEASONAL CHLORINATION OF TREATMENT PLANT
EFFLUENTS ON COLIFORM POPULATIONS IN JAMAICA BAY*
by
R. T. Dewling, I. Seidenberg and J. Kingery**
Summary
From March through October 1968, the Federal Water Pollution
Control Administration's Hudson-Delaware Basins Office conducted a
study to demonstrate that post-chlorination of wastewater treatment
plant effluents would significantly improve receiving water bacter-
iological quality. The study area was Jamaica Bay, a shallow tidal
estuary located within the limits of the City of New York. Six
secondary treatment plants, discharging an average of 162 mgd were
involved in the study.
The eight-month investigation, separated into two phases, was
designed to determine the levels of indicator organisms prior to the
start-up, during, and after the cessation of chlorination of treatment
plant effluents. It is important to note that these discharges, based
on a daily volume, account for less than 0.5 percent of the receiving
*Presented at the annual meeting of the New York Water Pollution
Control Association, January 28-30, 1970.
**Richard T. Dewling, Chief, Laboratory and I. Seidenberg, Chief, Micro-
biology Section of the Hudson-Delaware Basins Office, Northeast Region,
U. S. Dept. of the Interior, Federal Water Pollution Control Administra-
tion, Edison, N. J. J. Kingery, Mathematical Statistician, Pollution
Surveillance Branch, Robert S. Kerr Research Center, Ada, Oklahoma.
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water volume and more than 80 percent of the fresh-water input to the
Bay. This survey program was also designed to predict how long the
effects of storm and combined sewer overflow discharges, which average
34 mgd, or about 17 percent of the fresh-water input to the Bay, could
be detected in the Bay following a storm.
Intensive sampling of Bay waters, and examination by membrane filter
techniques for total and fecal coliform were made during the non-
chlorination period and for 37 days following the start-up of chlorination
at the wastewater treatment plants. In the second phase of the study
samples were collected prior to the cessation of chlorination on September
30 and for 17 days following this date.
Analysis of the data collected during this study showed that:
(1) In most parts of the Bay there was a significant decrease in
the coliform populations following the start-up of post-chlorination of
treatment plant effluents. Correspondingly, there was an increase in
coliform counts in the Bay following cessation of effluent chlorination.
(2) The effects of combined and stormwater overflows in the Bay
were noticeable for a period of two to three days following a storm.
After this time period, coliform levels returned to their normal background
levels.
It was concluded on the basis of this investigation, that post-chlorination
of wastewater treatment plant effluents was an effective means for reducing
receiving water coliform populations, thereby improving water quality.
2
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Introduction
Quite frequently, the question regarding the need for chlorinating
efflue'nts being discharged to receiving waters not used for recreational
purposes is raised. In an attempt to answer this question a study was
undertaken to demonstrate that chlorination of wastewater treatment
plant effluents, which, by volume, represented less than 0.5 percent
of the receiving water volume, would significantly improve the bacterio-
logical quality of Jamaica Bay. This estuary was an ideal site for such
an investigation since more than 99 percent of the treated effluents
being discharged to the Bay are chlorinated on a seasonal basis only
May 15 to September 30.
This two-phase investigation, conducted by the staff of FWPCA*s
Hudson-Delaware Basins Office, Edison, New Jersey, was divided into four
periods:
Phase I - Intensive Survey: March 26 - June 28, 1968
Prior to May 15, the date for start-up of chlorination at the waste-
water treatment plants, the normal or background levels of indicator
organisms in Jamaica Bay were determined. From this start-up date until
June 28 the Bay's waters were intensively sampled so as to determine the
response time of the Bay to this additional treatment as well as to de-
termine the new levels of indicator organisms.
Phase II - Surveillance Study: September 4 - October 2k, 1968
With less frequent sampling than that which occurred in Phase I,
the surveillance program was designed to indicate that when chlorination
3
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at the plants was stopped the coliform levels inthe'.&ywciuld respond
accordingly. From September 4 to September 30, background levels of
indicator organisms were determined throughout the Bay. Following
the cessation of chlorination on September 30, samples of the Bay's
waters were collected to determine the response time of the receiving
water to this change in treatment as well as the new and higher levels
of indicator organisms.
Jamaica Bay, which for this study was defined as the area inside
the Marine Parkway Bridge (See Figure 1), receives the discharge from
six wastewater treatment plants; however, only three, those operated
by the New York City's Bureau of Pollution Control are major in magnitude.
Table I outlines the type of treatment facilities discharging to the study
area and the flows during this investigation. The three large New York
City plants plus the small Floyd Bennett Field installation practice
seasonal chlorination, while the two smaller Nassau County plants
chlorinate year-round.
Table I
Study Area Treatment Plant Discharges
Installation
Floyd Bennett Field
26 Ward, N.Y.C.
Jamaica Bay, N.Y.C.
Rockaway, N.Y.C.
Inwood, Nassau Co.
Treatment
Trickling Filter
Modified Aeration
Flow
Discharge Point
0.3 mgd Rockaway Inlet
62.2 mgd Hendrix Creek
Modified & Step Aeration 81.1 mgd Grassy Bay
18.6 mgd South Channel
Modified Aeration
High-Rate Trickling Filter 1.1 mgd* Tributary to Motts Creek
Cedarhurst, Nassau Co. High-Rate Trickling Filter 0.8 mgd Motts Creek
*Estimated, flow meter broken
4
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The location of these treatment facilities and their points of
discharge are shown in Figure 1. Also shown in this Figure, just west
of the Marine Parkway Bridge, is New York City's Coney Island Pollution
Control Facility. While this plant discharged an average of 77 mgd
during this study, its direct influence on Jamaica Bay was felt to be
.mirili'mal"..1 a since all samples were collected at low slack, or at the
end of an outgoing tide.
In addition to receiving the direct discharge from treatment
plants, which represents approximately 82 percent of the net fresh-
water inflow to the Bay, it is estimated that the study area also re-
ceives an average daily inflow of 34 mg from storm and combined sewer
discharges emanating from numerous outlets in Rockaway and six sep-
arate overflow stations along the northern border of the Bay. (See
Figure 1)
Study Area Description
Jamaica Bay, measuring approximately six miles long by four miles
wide is located, for all practical purposes, within the limits of the
City of New York. It is bounded by two of the City's largest and most
populated Boroughs - Brooklyn and Queens. (See Figure 1) Nearly 40
percent of the area of this shallow estuary, which has a mean depth of
only 16 feet, consists of islands and tidal marshes located primarily
in the central portion of the Bay.
5
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FIGURE 1
SAMPLING STATIONS, MUNICIPAL DISCHARGES, STORM & COMBINED SEWER OVERFLOWS
BROOKLYN
LEGEND
STORM AND COMBINED
MUNICIPAL DISCHARGES SEWER OVERFLOWS
1. MARINE PARKWAY BRIDGE A. FLOYD BENNETT FIELD H. PAERDEGAT BASIN
2. FLOYD BENNETT FIELD B. 26th WARD I. FRESH CREEK
3. CANARSIE PIER, EAST END C. JAMAICA J. HENDRIX
4. CROSS BAY BRIDGE, NORTH D. CEDARHURST K. SPRING CREEK
5. CROSS BAY BRIDGE, SOUTH E. INWOOD L. BERGEN BASIN
F. ROCKAWAY M. THURSTON BASIN
G. CONEY ISLAND N. ROCKAWAY
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Geographically enclosed, with its only outlet to the ocean being
through Rockaway Inlet, Jamaica Bay has no major rivers or streams
discharging into it. Major fresh-water sources include the discharge
from municipal wastewater treatment plants, combined and storm sewer
overflows and land runoff. These fresh-water inputs account for ap-
proximately 98 percent 'fcf)the net advective flow; to-vthe Bay..
Present water resources of the Bay are restricted to boating,
wildlife management, and limited fin fishing. Swimming and shellfishing
are no longer permitted because of poor water quality. Many factors,
excluding the problems associated with the discharge of treated domestic
wastes and storm and combined sewer overflows, have contributed to the
pollution problems of this estuary. Landfill and dredging operations
have increased significantly over the past years, thus altering the
hydrography and composition of the marshlands, which has affected
water quality.
Climate in the study area is typically temperate with average
monthly temperatures in the summer in the high 70's and in the winter
near freezing 32°F. Average annual rainfall for the Jamaica Bay
area is approximately 40 inches, which is distributed rather evenly
throughout the year. Average monthly air and water temperatures during
this investigation are shown in Table II. Pertinent precipitation data
for this study are shown later in this report in Table IX.
7
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Table II
Average Monthly Air-Water Temperatures
Month Air (°F)* Water (°F)
March 40.2 52.1
April 50.5 52.5
May 56.8 62.8
June 68.1 67.1
July 77.0
August 75.8
September 70.1 72.3
October 58.2 64.2
*Monthly average, JFK Airport, U. S. Department of Commerce
The hydrologic characteristics of the Bay are somewhat unusual
even though tidal variations at Rockaway Inlet and within the Bay
average five feet. The tidal prism in this estuary, or that volume
of water between low and high water, represents approximately one-third
of the volume of water in the Bay. In spite of this large hydraulic
exchange, which occurs twice daily, it has been.'dempnsfctla1^
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Tidal current patterns within the Bay are such that the mean
advective flow is through the main channels paralleling Rockaway
Beach, Floyd Bennett Field, and Brooklyn. Average maximum tidal
currents at Rockaway Inlet on an outgoing tide are 2.1 knots and
2.2 knots on incoming tides. Little net circulation occurs through-
out the Bay because of its configuration.
Study Methodology
The problem of monitoring the changing water quality in Jamaica
Bay is complicated by the tidal nature of the embayment. To eliminate
as much as possible the variability in water quality caused by tidal
fluctuations, all samples were collected at low water slack, which
theoretically is the period of poorest water quality. Several 13-hour
studies were also conducted at the five stations to determine the tidal
fluctuations of indicator organisms. Chloride analyses were also run
during all sampling periods to verify the tidal cycle phase.
During Phase I of the investigation the five selected stations
(See Figure 1) were sampled for 35 days prior to the start-up of chlor-
ination at the treatment plants, and for 37 days following the May 15
start-up date. During Phase II of the study, the Bay was sampled 11
days prior to the cessation of chlorination at the plants on September
30, and for 17 days following this period. Considering both phases of
9
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the program, plus the tidal cycle samplings, over 1,500 samples of
Bay waters were analyzed for total and fecal coliform.
In addition to sampling Bay waters, the three major treatment
plants 26th Ward, Jamaica, Rockaway were either sampled or
visited at least twice per week throughout the study to determine if
abnormalities in bacteriological quality in the Bay could be attributed
to faulty operation at the plants.
Samples were collected from bridges or piers from a 5-foot depth,
using a Kemmerer sampler. Prior to collecting the samples, the
Kemmerer was agitated up and down to flush the sampling tube adequately. 01)
All bacteriological tests were performed using membrane filter
techniques. Total coliform was determined as described in the 12th
Edition of Standard Methods for the Examination of Water and Wastewater
using Difco M-Endo broth to which 1.5 percent agar was added. Geldreich's
fecal coliform procedure (2), which uses a medium consisting of an en-
riched lactose broth base with bile salts and rosolic acid for selectivity
and an analine blue dye to indicate acid production, was used. Use of
the Hudson-Delaware Basins Office mobile laboratory made possible com-
pletion of all total and fecal coliform analyses, through inoculation
and placement in the appropriate incubator, within 60 minutes of sample
collection.
10
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Test Data Analysis
Analysis of the data collected during the two-phase study was aimed
at defining changes in water quality in the Bay prior to and after the
cessation of chlorination at the wastewater treatment plants. Other
questions to be answered were: (a) Was this change in quality measure-
able at all sampling stations, or was it only detectable in certain areas
of the Bay; (b) How long did it take the Bay to respond to the two
changes in treatment? Again, was this change detectable throughout the
Bay, or at only selected stations; and (c) Could some prediction be
made to estimate how long the effects of storm and combined sewer overflow
discharges could be detected in the Bay before the coliform levels re-
turned to their normal background levels.
Due to distances between the location of the treatment plant outfalls
and most of the sampling stations, it was assumed that some interval of
time would elapse between the start-up of chlorination and the appearance
of its effects at any one station in the Bay. Further, if coliform pop-
ulations reached a steady-state condition before and after cessation of
chlorination some time factor would be involved in the transition from
one steady-state level to another.
Figures 2 & 3 illustrate two theoretical curve shapes which might
be expected at any station in such a study. If the transport is achieved
by current only, the lag time would be dependent upon distance and current
11
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A
to
2
O
o
u
oc
<
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i/>
cs
U I
STEADYl LAG
STATE 'PERIOD
ERIOD STATE
TIME
FIG. 2 THEORETICAL CURVE FOR CURRENT TRANSPORT ONLY
t
CO
£
Q£
o
O
u
Of
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cs
u
STEADY
N H-
STATE PERIOD
PERIOD STATE
TIME ^
FIG. 3 THEORETICAL CURVE FOR CURRENT & DIFFUSION
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velocity, and the curve would have the shape shown in Figure 2. When
diffusion is an important factor in transport, the illustrating curve
would have a more gradual transition from one steady-state to another
as shown in Figure 3.
Defining Steady-State Conditions
A regression analysis between "days into the study" and log of
the coliform counts was performed with a test of the hypothesis of a
zero regression co-efficient. Because there seemed to be such a great
variation in the counts due to rainfall, this effect had to be removed
before analyzing the data for a steady-state condition.
Analysis of the information, adjusted for rainfall, failed to
reject the hypothesis of a steady-state condition during all four time
periods. A plot of the data, however, suggested that sufficient data
were not available to accept the steady-state hypothesis for any time
period except "before chlorination".
Even though we were unable to define a steady-state condition
during all phases of the study, the question regarding whether or not
there was a significant change in water quality during the four periods
can still be answered. A summary of the median and geometric mean data
(See Table III and IV) for all stations suggests that chlorination was
effective in improving water quality at most locations. To further
13
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TABLE III
MEDIAN COLIFORM COUNT/100 ML
Station
P H A S
E I
P
H A S E
II
Before
Chlorination
During
Chlorination
Early
Dur ing
Chlorination
Late
After
Chlorination
Terminated
rota I
Col if.
Fecal
Col if.
Total
Col if.
J?ecai
Colif.
Total
Col if
fc'ecal
. Colif.
Total
Colif.
Fecal
Colif.
East End Canarsie Pier
15500
3900
23000
3400
32000
15000
96000
18000
Cross Bay Bridge North
46000
8100
3100
4200
5800
2100
20000
4900
Cross Bay Bridge South
3300
690
80
30
40
20
5600
840
Marine Parkway Bridge
2900
560
500
170
3350
150
4100
1700
N.A.S. Floyd Bennett
2200
690
2000
360
3200
780
6800
3300
TABLE IV
GEOMETRIC MEAN COLIFORM COUNT/100 ML
Station
P H A S
E I
P
H A S E
II
Before
Chlorination
During
Chlorination
Early
Dur ing
Chiorination
Late
After
Chiorination
Terminated
Total
Colif.
Fecal
Colif.
Total
Colif.
Fecal
Colif.
Total
Colif
Fecal
. Col if.
Total
Colif
Fecal
. Colif.
East End Canarsie Pier
16569
3647
18353
2414
35568
10788
76574
18875
Cross Bay Bridge North
38642
7648
33^1
464
6110
1924
14563
3681
Cross Bay Bridge South
3047
712
130
36
55
22
2456
417
Marine Parkway Bridge
2257
531
606
190
507
140
3474
821
N.A.S. Floyd Bennett
1959
686
1493
467
1562
686
5274
2072
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demonstrate,the validity of these findings, a non-parametric analysis
of variance with interaction analysis (3) was used to give an insight
to the comparable question related to all four time periods.
When analyzing these data the null hypotheses established were
that there was (a) no difference in water quality at each of the
stations, (b) no difference in water quality during all four time
periods, and (c) no significant interaction between (a) and (b), that
is, all stations, during all time periods, reacted the same.
If there were no true differences in coliform counts over the
four time periods, it would be expected that about the same number of
observations (See Table V>for total number of observations) would fall
above the average median as below.
If the observed "above" and "below" distribution was greatly dif-
ferent then we could conclude that a true difference in fact did exist.
Using a chi-square distribution, we can then calculate the probability
of such a distributional occurrence.
Table VI shows the above median frequency matrix and Table VII
the below median frequency matrix from which the chi-square values and
their degrees of freedom shown in Table VIII were calculated. With the
chi-square analysis, if there was no true difference between the expected
and observed values, then the hypotheses would be correct. However, the
observed conditions differed so greatly from the expected or hypothesized
15
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TABLE V
NUMBER OF OBSERVATIONS
Station
P
H A S E
I
P
HAS E
I I
Before
Chlorinat ion
Dur ing
Chlorination
Early
Dur ing
Chlorination
Late
After
Chlorination
Terminated
Total
Col if.
Fecal
Col if.
Total
Colif.
Fecal
Colif.
Total
Colif.
Fecal
Colif.
Total
Colif.
Fecal
Colif.
East End Canarsie Pier
34
33
37
37
11
10
17
17
Cross Bay Bridge North
35
34
36
37
11
11
17
17
Cross Bay Bridge South
35
34
37
37
10
10
17
17
Marine Parkway Bridge
35
34
37
37
10
10
17
17
N.A.S. Floyd Bennett
34
32
37
37
11
11
17
17
TABLE VI
ABOVE" MEDIAN FREQUENCY MATRIX
P
HAS E
I
P
H .A S E
I I
Before
During
Dur ing
After
Chlorination
Chlorination
Chlorination
Chlorination
Early
Late
Terminated
Total
Fecal
Total
Fecal
Total
Fecal
Total
Fecal
Station
Colif.
Colif.
Colif.
Colif.
Colif.
Colif.
Colif.
Colif.
East End Canarsie Pier
32
28
33
29
11
10
17
17
Cross Bay Bridge North
32
32
14
11
8
10
13
14
Cross Bay Bridge South
12
12
2
2
0
1
12
7
Marine Parkway Bridge
9
11
9
7
1
1
8
10
N.A.S. Floyd Bennett
8
12
14
14
2
5
11
13
16
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TABLE VII
"BELOW MEDIAN FREQUENCY MATRIX
P H A
S E
I
P H A
S E II
Before
Chlorination
After
Chlorination
Early
During
Chlorination
Late
After
Chlorination
Terminated
Total
Col if.
Fecal
Col if.
Total
Col if.
Fecal
Col if.
Total
Col if.
Fecal
Col if.
Total
Colif.
Fecal
Colif.
East End Canarsie Pier
2
5
4
8
0
0
0
0
Cross Bay Bridge North
3
2
22
26
3
1
4
3
Cross Bay Bridge South
23
22
35
35
10
9
5
10
Marine Parkway Bridge
26
23
28
30
9
9
9
7
N.A.S. Floyd Bennett
26
20
23
23
9
6
6
4
TABLE VIII
CHI SQUARES AND SIGNIFICANCE
Chi
Aquares
Degrees
of
Freedom
Probability of
a Larger Value
of*2
Total
Colif.
Fecal
Colif.
Total
Colif.
Fecal
Colif.
Total
Colif.
Fecal
Colif.
Total
197,3309
~'/
175.7797
19
19
<.005
<£.005
Locations
140.0893
111.2452
4
4
<•005
<.005
Times
27.3048
38.1497
3
3
<. 005
<.005
Interaction
,¦ 30,5367
26.3848
12
12
<•005
< .005
17
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that the final probability as calculated by the chi-square was less
than 0.005. (See Table VIII) Thus, we reject the null hypotheses and
conclude that:
(a) there is a significant difference in the coliform concentra-
tions of the Bay water at the various sampling locations.
(b) there is a significant difference in the coliform concentra-
tions of the Bay water during all four time periods.
(c) there is a significant interaction between the sampling lo-
cations and the time periods. This is to say that the change in
coliform concentrations of the Bay water over time is not the same for
all sampling locations.
Because of this significant interaction term, it is necessary to
investigate the change in coliform conditions for each sampling location.
This can be best accomplished by referring back to Table III. Note that
Cross Bay Bridge North, Cross Bay Bridge South and Marine Parkway Bridge
locations indicate lower median coliform concentrations for the two
"during chlorination" time periods than the "before chlorination" and
"after chlorination" time periods. This fact tends to support the
original hypothesis of a reduction in coliform counts due to chlorination
of effluents. However, the stations located at the east end of Canarsie
Pier and the Naval Air Station at Floyd Bennett imply a steady increase
of coliform counts over the four time periods, which does not support the
above mentioned hypothesis.
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A possible explanation for the steady increase in coliforms at these
two stations could be due to increases in water temperature, coupled with
the present problem of the lack of adequate chlorination facilities at
the 26th Ward treatment plant, which is located near Canarsie pier. Floyd
Bennett samples would have been adversely influenced because of the tidal
current patterns and by the fact that all samples were collected at low
slack, thus placing the "26th Ward effluent" in the vicinity of this
station during sampling.
Since we were unable to define steady-state conditions during all
segments of the study, it is statistically impossible to state the length
of time required for the Bay to reach a new equilibrium after either the
start-up or cessation of chlorination. A cursory review of the plotted
data, however, suggests that a response time ranging from 24—4-8 hours,
depending upon the particular station and its location to the proximity
of effluent sources, is likely. This response time agrees with previous
studies (4) conducted in 1963 by this laboratory in Raritan Bay. Depending
upon the location of the station and the proximity to the outfall, response
time in Raritan Bay ranged from 6 to 50 hours.
Storm and Combined Sewer Overflow Effects
FWPCA studies in Jamaica Bay have indicated that the average daily
discharge from storm and combined sewer overflows, (See Figure 1 for
locations) based on a storm occurring at a frequency of about once every
three days, amounts to approximately 34 mg. This volume represents
approximately 17 percent of the daily fresh-water input to the Bay. It
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is also rioted that a one inch rain storm which occurred five times
during this particular investigation, results in the discharge of
approximately 250 mg of combined sewage to Jamaica Bay.
An attempt to relate rainfall and coliform data collected during
this study failed to establish a consistent statistical relationship
except for the "after chlorination" time period for all stations except
Cross Bay Bridge South. It is suspected that because of the frequency
of rainfall during this study, which averaged once very three to four
days, insufficient data were collected to establish this relationship.
Table IV provides pertinent rainfall information regarding frequency
and intensity. A plot of the coliform counts versus "days into the study"
overlayed with a plot of rainfall suggests that one or two days, depending
upon the location of the stations in relation to the overflow points, are
necessary for a decline in the increased counts following a rain storm.
Figures 4 and 5 illustrate these observations. It is important to point
out, however, that to accurately define this figure down to the nearest
hour, duration of rainfall, intensity, runoff co-efficients, as well as
time of the day the storm occurred would have to be known in order to
properly estimate recovery time of the Bay waters.
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TABLE IX
1
RAINFALL PATTERNS DURING INVESTIGATION
Month
Number
of Days
Sampled
Total
Monthly
Precip.
Greatest
Day
No. Days
Rainfall
No.Calendar
Days wit£
Rainfall
0.50 or more
1.0 or more
Precip.
Date
March
3
4.90
1.93
12
3
2
12
April
23
1.97
1.19
24
2
1
6
May
25
5.34
2.88
29
3
1
12
June
21
4.16
1.81
12
2
2
11
July
0
2.58
1.80
24
2
1
5
August
0
2.78
0.79
7
2
0
10
September
12
2.54
1.56
11
2
1
6
October
16
1.85
1 0.71
7
1
0
5
1
Data reported from JFK Airport, U. S. Dept. of Commerce
2
0.10 inch, or more
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FIGURE 4
PHASE I : 3/26 TO 6/28/68
COLIFORM COUNTS vs RAINFALL
CROSS BAY BRIDGE SOUTH
FECAL
l(oȣ .A
.COSS- •
CO
'—
O
«o
K
O
*9
CN
O
TIME INTO STUDY
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FIGURE 5
PHASE I : 3/26 TO 6/28/68
COLIFORM COUNTS vs RAINFALL
CROSS BAY BRIDGE NORTH
300,000
250,000
£ 200,000
o
o
z
3
o
u
S
oc
O
IL
o
o
150,000
100,000
50,000
3.0
2.0
< 1.0
Li.
z
< 0.5
TIME INTO STUDY
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Conclusions
Analysis of the bacteriological data collected in Jamaica Bay
during this eight-month long effluent chlorination study, which in-
volved six secondary treatment plants discharging more than 160 mgd,
has shown that:
(a) there was a significant decrease in the coliform populations
present in most parts of the Bay following the start-up of post-
chlorination of effluents at the treatment plants.
(b) there was a significant increase in coliform populations at
most Bay stations following the cessation of post-chlorination.
(c) the estimated response time of most of the Bay stations to
this change in treatment at the plants start-up and cessation of
chlorination ranged from 24 to 48 hours.
(d) the effect of the discharge of storm and combined sewer over-
flows can be detected in most of the Bay for two to three days following
a storm.
(e) post-chlorination of wastewater treatment plant effluents, even
when the daily volume of these discharges represent less than 0.5 percent
of the volume of the receiving water, is an effective means for improving
the bacteriological quality of the receiving water.
2 h
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References
1. Brezenski, F. T., "Laboratory Methods Manual - Microbiology,
U. S. Department of the Interior, FWPCA, Edison, N. J."
(December 1967)
2. Geldreich, E. E. et al., "A Fecal Coliform Medium for the
Membrane Filter Technique." JAWWA, 57, 208, (1965)
3. Wilson, Kellogg, V., "A Distribution - Free Test of Analyses
of Variance Hypotheses", Physiological Bulletin, Vol. 53,
Nov. 1 (1956)
4. De Falco, Paul, Jr., Kandle, Roscoe, P., M. D., "Effect of
Effluent Chlorination on Bacterial Populations in Raritan
Bay Waters." Presented at WPCF 1964 Annual Meeting, not
published.
25
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