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•?A 902/9-79-005
BIOCHEMICAL STUDIES
OF THE
POTOMAC ESTUARY—SUMMER 1978
-------
-------
EPA 903/9-79-005
BIOCHEMICAL STUDIES
OF THE
POTOMAC ESTUARY—SUMMER 1978
May 1979
Joseph Lee Slayton
E. Ramona Trovato
Annapolis Field Office
Region III
U.S. Environmental Protection Agency
-------
Table of Contents
Page
Tabulation of Figures ii
Tabulation of Tables iii
I. Introduction . . . : 1
II. Conclusions 4
III. Procedures 6
IV. C30D and NOD Kinetics in The Potomac Estuary 8
V. Oxygen Demand of Algal Respiration and Algal Decay 19
VI. Phytoplankton Elemental Analysis/Methods of TKN 25
Digestion of Algal Samples
VII. Potomac Long-Term BOD Survey Data 28
References 35
-------
Figures
Page
No.
1. Study Area 3
2. General BOD Curve: Y = L0(l-10'kt) 8
3-4. River Samples-Oxygen Depletion Curves 10-11
5. Plot of NOD2Q vs (TKN x 4-57) 15
6. STP Effluent Samples-Oxygen Depletion Curves 17
7-9. Oxygen Depletion Curves of Algal Respiration and Decay ... 20-22
-------
Tables
Page
1. Station Locations 2
2. Thomas Graphical Determinations of k-|g, L0, and r for River CBOD's . 12
3. Thomas Graphical Determinations of k-jg, L0, and r for River NOD's . . 13
4. Thomas Graphical Determinations of kio» L0, and r for STP CBOD's . . 16
5. First Order Correlation Coefficients for STP NOD's 18
6. Phytoplankton Oxygen Depletion 23
7. BOD5 Requirements for Algal Decay and Respiration 24
8. Phytoplankton Elemental Analysis 26
9. Results from Three TKN Digestion Methods 27
-------
-------
I. Introduction
During the summer of 1978 an intensive survey of the middle
reach of the Potomac River was undertaken by the A.P.O. (Table 1 ,
Figure 1). As part of this work biochemical assays were performed to:
(1) determine the carbonaceous and nitrogenous oxygen demand
rate constants for river and STP effluent samples;
(2) establish the relative contributions to the BODg of algal
respiration and the oxygen utilized in algal decay; and
(3) characterize the elemental composition of the phytoplankton
present and establish the relative digestion efficiencies
of several methods of algal TKN determinations.
The mention of trade names or commercial products in this report
is for illustration purposes and does not constitute endorsement or
recommendation by the U.S. Environmental Protection Agency.
-------
Table 1. Station Locations
Station Number
Station Name
RMI
Buoy Reference
P-8
P-4
1
1-A
2
3
4
5
5-A
6
7
8
8-A
9
10
10-B
n
12
13
14
15
15-A
16
Station Number
S-l
S-2
S-3
S-4
S-5
S-6
S-7
S-8
Chain Bridge
Windy Run
Key Bridge
Memorial Bridge
14th Street Bridge
Hains Point
Bellevue
Vloodrow Wilson Bridge
Rosier Bluff
Broad Creek
Ft. Washington
Dogue Creek
Gunston' Cove
Chapman Point
Indian Head
Deep Point
Possum Point
Sandy Point
Smith Point
Maryland Point
Nanjemoy Creek
Mathias Point
Rt. 301 Bridge
Treatment Plant Name
Piscataway STP
Arlington STP
Blue Plains STP East &
Alexandria STP
Westgate STP
Hunting Creek STP
Dogue Creek STP
Pohick Creek STP
0.0
1.9
3.4
4.9
5.9
7.6 C "1"
10.0 FLR-231 Bell
12.1
13.6 C "87"
15.2 N "86"
18.4 FL "77"
22.3 FL "67"
24.3 R "64"
26.9 FL "59"
30.6 N "54"
34.0
38.0 R "44"
42.5 N "40"
45.8 N "30"
52.4 G "21"
58.6 N "10"
62.8 C "3"
67.4
West
-------
Figure 1. Study Area
Potomac Estuary
-------
II. Conclusions
(1) The carbonaceous oxygen demand of the Potomac River samples
followed first order kinetics with an average deoxygenation
constant ke = 0.12 day "^ and standard deviation = 0.03 day"1
= 0.051 day"1)-
(2) The growth kinetics of river nitrification were more erratic
but in general were first order with an average ke = 0.10 day"'
and standard deviation of 0.06.
(3) The CBODs on the average was 58% of the BOD5 for river samples
and" therefore estimates of CBOD5 from BODs values are prone to
error unless a nitrification inhibitor is employed.
(4) The CBOD of the Potomac STP effluent samples followed first .
order kinetics with an average ke =0.16 day"' and standard
deviation of 0.05.
(5) The NOD for the STP effluent samples had a significant lag
time resulting in poor correlation coefficients for first
order fit. This lag time was probably an artifact of the
APHA dilution method, since nitrification in the receiving
waters was immediate.
(5) The NOD2o observed for river samples did not significantly
differ from the product of 4.57 and the TKM concentration
(4.57 x TKN).
-------
(7) In concentrated algal samples the average algal contribution
to the 8005 was 0.027 mg BODs/yg chlorophyll a_. The predominant
species present was the filamentous blue green algae Pseudanabaena,
(8) Phytoplankton decay represented 70% of the algal BODs and algal
respiration accounted for the remaining 30% of the five day
oxygen depletion.
(9) The average composition of the phytoplankton present in the
study area was (mg/yg):
Org C/Chlor a_ = .021 ; P04/Chlor a. = .002; TKN/Chlor a_ = .005
(10) Relative to manual digestion the Technicon continuous digestor
and Technicon block digestor recovered respectively an average
of 58% and 83% of the algal TKN.
-------
III. Procedures
Biochemical Oxygen Demand: The BOD test is outlined in Standard
Methods APHA, 14th edition1. All dissolved oxygen measurements
were made with a YSI BOD probe #5720 and a YSI model 57 meter.
The BOD of river water was determined on unaltered samples. STP
effluent samples were altered by: the addition of 1 ml of stale
settled sewage (seed); sufficient sodium sulfite (Na2$03) to
dechlorinate the samples; and dilution with APHA dilution water.
Nitrification: Formula 2533 nitrification inhibitor (Hach Chemical
Co.) was dispensed directly into the BOD bottles. Two bottles
were filled with each sample—one received the inhibitor and
represented CBOD and the uninhibited bottle expressed total BOD.
The NOD was determined by difference2.
Algal BOD Measurements; The algae in 4 to 10 liters of sample were
concentrated by continuous centrifugation (Sharpies Continuous
Centrifuge Model T-l at 12,000 rpm and 1.5-2 liters/min). The
pellet was resuspended in 500 ml of collected supernatant. The
resultant suspension was diluted in a 300 ml BOD bottle as follows:
a. 50 ml suspension + 250 ml supernatant
b. 50 ml suspension (freeze dried) + 250 ml supernatant
c. 50 ml deionized water + 250 ml supernatant
a1. 50 ml suspension + 249ml supernatant + 1 ml seed/bottle
b1. 50 ml suspension (freeze dried) + 249ml supernatant +
1 ml seed/bottle
cl. 50 ml deionized water +• 249ml supernatant + 1 ml seed/bottle
The sample composite on September 6 consisted of approximately
2 gallons each from stations: 8; 8A; 9; 10; and 10B.
The composite of September 14 consisted of about 1/2 gallon each
from stations: 8; 8A; 9; and 10. Twenty ml volumes were used
instead of the 50 ml volumes indicated above for this composite.
Freeze Drying: Samples were freeze-dried in a Virtis model 10-100
Unitrap freeze-drier. The suspension was spread as a thin sheet
and slowly frozen to avoid foaming and to shorten drying time.
Samples required 4 to 6 hours to reach the manufacturer's specified
end point.
The freeze-dried samples were washed into BOD bottles with
supernatant from centrifugation.
Elemental Analysis;
1. Sample Preparation: Samples were stored on ice and returned to
the laboratory where 4 to 8 liters were immediately concentrated
using a Sharpies T-l Continuous Centrifuge at 12,000 rpm and
1.5-2.0 liters/min. Microscopic examination revealed no
-------
apparent morphological damage to the predominant phytoplankton
species present. The pellet was resuspended in 250 ml of
clear supernatant, which had been collected during centrifugation,
Aliquots of the suspension and the supernatant were chemically
analyzed. The supernatant values were used for blank corrections,
2. Chlorophyll a: The photosynthetic pigment from 5-20 ml of
algal suspension was retained on a 0.45y Millipore filter and
extracted into 90% acetone with grinding. The extracted
solution was centrifuged and measured spectrophotometrically3.
3. Total Organic Carbon (TOC): 10 ml of algal suspension was
diluted to 100 ml in a volumetric flask using deionized water.
A blank was run using 10 ml of supernatant river water
diluted to 100 ml in deionized water. The samples and
calibration standards were then acidified by the addition of
1 ml of 6% phosphoric acid to 25 ml and purged free of
inorganic carbon with oxygen. The total organic carbon
was then determined on a Beckman 915 TOC analyzer1*.
4. Total Phosphate: 5 ml of sample and blank were diluted to
25 ml with deionized water. The sample and blank were
placed in aluminum foil covered pyrex test tubes to which
ammonium persulfate and sulfuric acid were added and auto-
el aved at 15 psi for 30 minutes. The digests were then
analyzed for total phosphate by the Techm'con automated
ascorbic acid reduction method^.
5. Algal Nitrogen: 5 ml of sample and blank were diluted to
25 ml with deionized water. The prepared solutions were
then analyzed for TKN by the following methods:
A. He!ix_: Samples and blanks were digested by a Technicon
Continuous Digester (Helix) and analyzed by the
automated colorimetric phenol ate method1*.
B. Manual : Samples and blanks were manually digested
with 10 ml aliquots placed in reflux tubes and 8.0 ml
of H2S04/K2S04 digestion solution added. The tubes
were placed over flame until boiling and reflux
stopped. The contents of the tubes were washed
into a graduated cylinder with deionized water and
brought to 50 ml. The resultant digests were analyzed
using a Technicon Continuous Digestor (Helix) and
the Technicon automated colorimetric phenol ate method1*.
C. Block: Samples and blanks were analyzed by a Technicon
Block Digestor BD-40 and analyzed by the sal icy!ate/
nitroprusside method5.
The blank carried throughout these methods was used to correct
for non-algal nitrogen.
-------
IV. CBOD and NOD Kinetics in the Potomac Estuary
Biochemical oxygen demand (BOD) is a bioassay in which the
oxygen utilization of a complex and changing population of micro-
organisms is measured as they respire in a changing mixture of
nutrients. That portion of the BOD due to the respiration of organic
matter by heterotrophic organisms is termed the carbonaceous oxygen
demand and that portion resulting from autotrophic nitrification
is termed nitrogenous oxygen demand. Nitrification is the conversion
of ammonium to nitrate by biological respiration. These BOD
components were delineated using an inhibitor to nitrification. The
inhibitor, formula 2533 of the Hach Chemical Company, has been shown
2£;7
to effectively stop the growth of Nitrosomonas . The product consists
of 2-chloro-6 (trichloromethyl) pyridine, known as nitrapyrin, plated
onto an inorganic salt. The salt serves as a carrier because it is
soluble in water. The organic component is not biodegradable* even
after 30 days of BOD incubation, and therefore does not contribute
to the measured carbonaceous oxygen demand2.
The shape of the oxygen depletion curves (Figures 2,3, and 4)
were such that the slope of the curves decreased with increased time
of incubation.
Figure 2: General BOD Curve
Curve Equation: y = L0(l-10"kt)
t = elapsed time of incubation in the dark at 20°C
y = BOD; mg/1 oxygen consumed after time t
o ! / LO = ultimate BOD; the oxygen used in the total
degradation of the substrate
k = deoxygenation constant; a constant which
reflects the rate at which a substance is
oxidized--a function of temperature, biota
and the nature of the substrate.
Time
o
-------
The rate of reaction associated with oxidation-respiration (Ay/At)
was initially rapid corresponding to an initial relatively large
substrate concentration. This rate decreased with time as the
oxidizable substrate was depleted. Other nutrients are provided
in excess and do not effect the rate of oxygen consumption in the
standard BOD test. The quantity and nature of the organic material
in the sample will limit oxygen consumption and determine the rate
of depletion. This type of reaction, in which the rate is proportional
to the amount of the reactant remaining at any time is referred to
as a "first order" reaction. In general, the first order reaction
pattern was observed for both the carbonaceous oxygen demand and the
nitrogenous oxygen demand BOD components of Potomac River samples.
Long-term BOD incubation data were used to give the best available
estimate of k-jQ and L0 using the Thomas Graphical Determination8'9'10 in
1 /^
which a plot of (t/y) ' vs. t yielded a linear relation where
k-|Q = 2.61 x (slope/intercept) and Lo = (2.3 x (intercept)3 x Iqo) •
The correlation coefficient of the linearized data was taken as a
measure of goodness of fit to first order reaction kinetics.
The CBOD results for river samples were compiled in Table 2.
The average (n=23) k-]o value for river CBOD's was 0.051 day" or
ke = 0.12 day~1 with an average correlation coefficient = 0.98 and
standard deviation = 0.03 (base e). The value of ke obtained in a 1977
Potomac study8 was 0.14 day"1 , with n = 43 and a standard
deviation of 0.02. The ratio of CBODs to BODs was found to be 0.58 in
the 1978 study.
The NOD of the river samples (Table 3) followed first order kinetics
with a correlation coefficient of 0.86 (n=22) and an average ke of 0.10
day""'. The standard deviation of ke was 0.06.
-------
Figure 3; River Samples-Oxygen Depletion Curves
01
a.
cu
o
c
o>
en
>-,
x
0
7.0-
6.0-
5.0-1
4.0-
3.0-
2.0-
1.0-
Woodrow Wilson Bridge Station 5
Sept. 11, 1978
= .054
8 10 12
Time (Days)
Ft. Washington Station 7
Sept. 11, 1978
8 10 12
Time (Days)
14 16
18
Tota'
BOD
NOt
€— CBOE
Tot
BO
CBO
-------
Figure 4 : River Samples-Oxygen Depletion Curves
en
7 -
6 -
5 -
5 4
0)
c
»
X
o
1 -
Indian Head Station 10
August 23, 1978
Total
BOD
CBOn
MOD
1 1
2 4
i
6
i
8
1
10
!
12
l
14
i
16
1.
18
1
20
Time (Days)
8 -
§ 6
cu
!•"
X
c
4 -
Ft. Washington Station 7
September 25, 1978
Total
BOD
CBOD
8 10 12
Time (Days)
16 1R
-------
Table 2; Thomas Graphical Determinations of
L, and r for River CBOD's
Date
Aug.
- Sta
14
5
7
8A
10
n
14
16
r
.931
.951
.966
.958
.991
.984
.985
(day'1)
.045
.059
.038
.057
.067
.062
.089
(mg/1 )
2.5
2.0
5.3
4.8
5.5
4.2
2.1
Calc.*
CBODs
(mg/1 )
1.0
1.0
1.9
2.3
2.9
2.2
1.4
Calc.
CBOD2Q
(mg/1)
2.2
1.9
4.4
4.4
5.2
4.0
2.1
CBOD5/BOD5
.50
.42
.50
.70
.74
.73
...
Calc.
BOD5
(mg/1)
2.0
2.4
3.8
3.3
3.Q
3.0
...
Aug. 28
Sept. 11
Sept. 25
5
7
8A
10
n
14
16
5
7
8A
10
n
14
16
5
7
8A
10
n
H
16
5
7
8A
10
n
14
16
.931
.951
.966
.958
.991
.984
.985
.993
.996
.992
.994
1.000
.990
.996
.994
.990
.987
.989
.940
.981
.997
.999
.99i6
(.931)
(.231)
(-.231)
(.126)
(.557)
.045
.059
.038
.057
.067
.062
.089
.046
.040
.039
.033
.029
.027
.056
.059
.054
.044
.044
.041
.054
.069
.079
.049
(.020)
Lag
4.5
5.7
6.5
5.2
6.7
3.4
5.8
5.0
5.9
7.9
6.7
5.1
3.5
5.5
5.4
7.2
(15.7)
r: (correlation coefficient)
n = 23
Average = .98
Std. deviation = .02 (base 10)
k10'-
n = 23
Average = ...„ c
Std. deviation = .015 day' (base 10)
CBOD5/POD5:
n = 19
Average = .58
Std. deviation = .15
.051 day'1 or ke = .12 day'1
1.8
2.1
2.4
1.7
1.9
0.9
2.8
2.5
2.7
3.1
2.7
1.9
1.6
3.0
3.2
3.1
(3.2)
3.9
4.7
5.4
4.1
5.0
2.4
5.4
4.7
5.4
6.8
5.9
4.3
3.2
5.3
5.3
6.5
(9.5)
.43
.43
.71
.51
.60
.38
.93
.39
.61
.70
.69
.49
.41
4.2
4.9
3.4
2.8
3.2
2.4
3.0
6.4
4.4
4.4
3.9
3.6
7.9
* calc. = Calculated value based u
Thomas Graphical determi:
-------
Table 3: Thomas Graphical Oetermi net ions of k
-|0
0,
and r for River MOD's
Date
Aug.
- Sta
14
5
7
8A
10
n
14
16
r
.957
.780
.939
.600
.949
.802
-.441
hOi
(day )
.077
.032
.037
.019
.037
.024
Lag
L0
(mg/1 )
1.7
4.7
5.5
5.3
3.0
3.6
Calc.*
NODS
(mg/1 )
1.0
1.4
1.9
1.0
1.0
.8
Calc.
N0n20
(mg/1 )
1.7
3.6
4.5
3.0
2.4
2.4
Potential**
NOD
(mg/1 )
2.5
2.9
2.8
1.9
2.3
1.3
( .9)
Aug. 28
5
7
8A
10
11
14
16
.600
.995
.978
.996
.989
.876
.877
.017
.067
.039
.037
.048
.049
.030
13.8
5.2
2.9
3.1
3.1
1.9
0.8
2.4
2.8
1.0
1.1-
1.3
1.5
0.2
7.4
5.0
2.4
2.5
2.7
1.6
0.5
Sept. 11
Sept. 25
5
7
8A
10
11
14
16
.974
.216
.276
.658
.727
.735
.995
.104
Lag
Lag
.022
.023
Lag
.088
r: (correlation coefficient)
n = 22
Average = .85
Std. deviation = .14 (base 10)
6.7
4.0
5.2
1.1
4.7
.9
1.2
0.7
6.7
2.5
3.4
1.1
7.2
5.1
2.5
2.4
2.3
1.5
1.4
5
7
8A
10
n
14
16
.877
.994
.628
.755
.937
-.619
-.381
.049
.098
.028
.023
.039
Lag
Lag
9.1
2.6
4.8
5.0
4.7
3.9
1.7
1.3
1.2
1.7
8.1
2.5
3. A
3.3
3.9
7.0
2.9
2.9
3.1
2.3
(1.4)
(1.4)
8.3
(5.0)
(4.3)
3.4
3.7
(3.5)
3.3
* calc. = calculated
** Potential NOD = 4.57 x TKN
n = 22
Average = .045 day" or ke
Std. deviation = .026 day'1
"''
.104
(base 10)
-------
The NOD results agreed with previous Potomac demand studies8 in which
the average NOD ke was 0.14 day""' with a standard deviation of 0.05.
The larger standard deviation observed for the NOD reflects
both the more fragile nature of nitrification11 and the method by
which it was determined—uninhibited depletion minus inhibited depletion.
The NOD20 was found not to be significantly different from the
potential NOD expressed as 4.57 x TKN (Figure 5). The critical value
of the paired t-test at a 95% confidence level was 2.08 and the
calculated value was 0.37. The 4.57 constant is the stoichiometric
conversion factor for the milligrams of oxygen consumed by the oxidation
of ammonia to nitrate.
The CBOD kinetics observed for the sewage treatment plant effluents
were first order with an average ke of 0.16 day"^ (n = 36 and standard
deviation of 0.05). The average correlation coefficient was 0.98f
(Table 4, Figure 6).
The NOD kinetics observed for the sewage treatment plants were
characterized by a lag period (Figure 6) which resulted in poor
correlation to first order reaction kinetics (Table 5). This lag
time was probably an artifact of the APHA dilution method, since
nitrification in the receiving waters was immediate. Because the
Potomac waste treatment effluents are characterized by high ammonia
levels8, the initial lack of nitrification is probably the result of
an insignificant number of nitrifying bacteria in the samples and/or
in the seed innoculum. The long term BOD oxygen depletion data is
included in Section VII.
-------
Figure 5: NOD20 (Inhibitor) vs NOD (TKN x 4.57) River Water Samples
v = 19778
• = 1978
1978
NOD9n vs (TKN) X 4.57
^n = 22
Correlation coefficient * .872
Least Squares: Slope = .886;
y-intercept = .455
Paired t test
Degrees of freedom = 21
t found = .374
t critical (a = .050;
a/2 = .025) = 2.080
10 11
NOD20 (Inhibitor)
(mg/1)
-------
Table 4: Thomas Graphical Determinations of k-jQ, L0, and r for STP CBOD's
Date - Sta
Aug. 14
S-l
S-2
S-3 E
S-3 W
S-4
S-5
S-6
S-7
S-8
Aug.
28
S-l
S-2
S-3 E
S-3 W
S-4
S-5
S-6
S-7
S-8
Sept. 11
S-l
S-2
S-3 E
S-3 W
S-4
S-5
S-6
S-7
S-8
Sept. 25
S-l
S-2
S-3 E
S-3 W
S-4
S-5
S-6
S-7
S-8
Name
Piscataway
Arlington
Blue Plains
Blue Plains
Alexandria
Westgate
Hunting Creek
Dogue Creek
Pohick Creek
Piscataway
Arlington
Blue Plains
Blue Plains
Alexandria
Westgate
Hunting Creek
Dogue Creek
Pohick Creek
Piscataway
Arlington
Blue Plains East
Blue Plains West
Alexandria
Westgate
Hunting Creek
Dogue Creek
Pohick Creek
Piscataway
Arlington
Blue Plains East
Blue Plains West
Alexandria
Westgate
Hunting Creek
Dogue Creek
Pohick Creek
East
West
ik
r
1.000
.997
.999
.997
.999
.995
1.000
.993
1.000
kio
(day-1)
.060
.032
.081
.054
.080
.053
.050
.064
.024
Lo
(mg/1)
12.8
17.3
109.4
21.1
45.9
18.3
29.3
24.7
31.4
Calc.*
CBOD5
(mg/1)
6.4
5.3
66.3
9.7
27.7
8.3
12.9
12.9
7.44
Calc.
CBOD20
(mg/1 )
12.0
13.2
106.7
19.3
44.8
16.7
26.4
23.4
20.8
East
West
ik
1.000
.997
.999
1.000
.998
.993
1.000
1.000
.998
.067
.092
.067
.067
.071
.069
.053
.060
.032
11.7
9.90
41.8
32.0
47.7
12.9
22.9
24.4
26.6
6.3
6.5
22. *
17.2
26. R
7.1
10.4
12.2
8.20
11.2
9.8
39.8
30.6
45.9
12.4
20.8
22.9
20.5
.975
.969
.982
.994
.987
.994
.988
.977
.950
.079
.094
.077
.082
.087
.078
.077
.060
.049
15.9
11.0
30.1
26.4
33.8
20.4
22.5
23.9
23.0
9.5
7.3
17.7
16.1
21.4
12.0
13.2
11.9
9.9
15.5
10.9
29.2
25.8
33.2
19.8
21.8
22.4
20.5
.885
.933
.00
.999
.991
.987
.954
.992
.964
.059
.062
.090
.071
.113
.115
.071
.095
.103
18.4
17.1
42.0
68.5
41.6
15.3
32.5
22.4
15.8
9.1
8.8
27.1
38.2
30.3
11.2
18.1
15.0
11.6
17.2
16.2
41.4
65.9
41.4
15.2
31.2
22.2
16.6
36
Average = .071 day""1 or ke = .16 day'"1
Std deviation = .021 day-T (base 10)
* calc. = calculated value based upon
Thomas Graphical determination
r: (correlation coefficient for
first-order kinetics)
n = 36
Average = .986
Std Deviation = .024
1 C
-------
Figure 6: STP Effluent Samples - Oxygen Depletion Curves
c
o
c.
CD
C
OJ
en
>,
x
O
50 -
40
30
20
10 -
Piscataway STP Station 1
August 14, 1978
r = .894
Total
BOD
N NOD
8 10 12 14
Time (Days)
CSOD
16 18 20 22
en
C
o
OJ
n.
a;
cu
X
o
90
80
70
50
50
40
30
20
10
0
Westgate STP Station 5
September 11, 1978
Total
BOD
NOD
CBOD
10 12 14
16
18
20
22
-------
Table 5: First Order Correlation Coefficients for STP NOD's
Sta.
3-1
3-2
3-3
3-3
S-4
S-5
S-6
S-7
S-8
Name
Piscataway
Arlington
Blue Plains East
Blue Plains West
Alexandria
Westgate
Hunting Creek
Dogue Creek
Pohick Creek
Aug 14
r*
-.744
.060
-.574
-.335
-.597
-.591
-.538
.957
-.722
Aug 28
r
-.863
-.995
-.886
-.892
-.905
-.902
-.582
-.993
-.982
Sept 11
r
-.629
.351
-.642
.972
-.994
-.778
-.594
-.778
-.709
Sept 25
r
-.210
.987
-.816
-.833
-.872
-.619
-.816
-.829
-.619
r - correlation coefficient
-------
V. Oxygen Demand of Algal Respiration and Algal Decay
Potomac BODs samples containing algae historically8'12 expressed
significantly high oxygen demand. The oxygen demand of such samples
was the result of: algal respiration; the decay of phytoplankton; and
the carbonaceous and nitrogenous demand of other non-algal sample
constituents. To resolve the BOD fractions of the sample, it was
assumed that algae represented the only significant particulate
contribution to the BOD of the sample. The non-algal BOD of the
sample was assumed to be associated with the soluble organic and
ammontum/nitrite fractions of the sample. The non-algal or background BOD was
measured in the supernatant which had been obtained from the
centrifugation of the algae containing samples. It was further assumed
that the BOD of freeze-dried algae corrected for seed addition and
the BOD of the dilution water (river water supernatant) represented
the biochemical oxygen demand of algal decay. Freeze-drying has been
shown to effectively kill phytoplankton without significantly altering
their physical structure13 thus providing a method of separating algal
respiration and algal decay measurements in a BOD analysis.
The results of these experiments are presented in Figures 7,8,and 9
and Tables 6 and 7. Algal decay was found to be the major contribution
to algal 6005 with an average mg algal BQDg per yg chlorophyll a_ of
0.019. Algal respiration represented about 30% of the algal BOD^
contribution with an average of £.008 mg algal BOD5 per yg chlorophyll a_.
The predominent species present in the Potomac during this study was the
-------
Figure 7: Oxygen Depletion Curves of Algal Respiration and Decay
September 14, 1978
7 -i
6 -
5 -
I 4
+j
QJ
"a.
0> -5
o 3
c
OJ
Ol
>> ?
x £
o
1 -
River water supernatant used as dilution water
Free;
Driec
O Algal suspension
X Algal suspension,
freeze-dried
* River water
supernatant
blk
= .066 day"1 L0 = 2.0
i i i
5 n 14
Time of Incubation (days)
7 -
5 -
4
^j
O)
"D.
& 3
c
o>
CT>
i H
Q
River water supernatant used as dilution water
1 ml seed/300 ml BOD bottle
Free2
Driec
'1
.966 k10 = .049 day"1 L0 = 2.3
5 11 14
Time of Incubation (days)
-------
Oxygen Depletion (rog/1}
ro
!_
Ji
_L
cn
OS
o
ro
!_
.pa
I _
ro
ro
o
r>
c.
o- _.
o> ^-4
vo
o
3
CL
0>
*<
i/>
CO
U)
00
ro
o
JO
H'
<
ro
H
s
P
rt
TO
i-S
0)
c
^3
TO
b^
~
3
P
rt
P
3
rt
o-
t— i
7?
>
H^
OQ
P
t— '
in
C
in
'D
C
3
in
(-••
O
3
rti
4
TO
TO
N
TO
1
O.
H
TO
Cu
>
HJ
OQ
P
^
in
C
in
T3
TO
3
in
H-
O
3
CO
o
x
*<
o
(D
n>
-o
ro
rt-
o
n> o
T3 C
3 ro
cr i"
ro
-s o
-h
Oi
oo
ro
to
CL
CD
O
o
CB
O
rt-
00
ro
in
-a
^u
-5
OJ
a>
3
CL
ro
o
01
-------
Oxygen Depletion (nrrg/1)
n>
rl
3
D
-5
O
-------
Table 6: Phytoplankton Oxygen Depletion
Date/Sample
Days of Incubation
Sept. 6, 1978
Algal Suspension
Algal Suspension
Freeze-Dried
River Water
Supernatant Blk
Seeded Al gal
Suspension
Seeded Algal
Suspension
Freeze-Dried
Seeded" River Water
Sept. 14, 1978
Algal Suspension
Algal Suspension
Freeze-Dried
River Water
Supernatant Blk
Seeded Algal
Suspension
Seeded Algal
Suspension
Freeze-Dried
Seeded River Water
5
9.8
6.4
3.0
10.0
9.3
2.8
5
2.4
2.2
1.4
2.6
2.0
1.1
8
12.0
8.5
3.4
12.6
10.8
3.3
11
5.0
3.8
1.2
5.0
3.5
1.4
12
13.8
9.8
3.6
14.4
12.0
3.6
14
5.1
3.6
1.7
5.3
3.2
1.8
19
16.6
11.4
9.3
17.2
14.3
4.4
25
6.7
5.0
1.9
7.0
4.8
2.1
33
19.1
13.1
5.1
19.8
16.1
5.2
0-5
-------
Table 7: BODs Requirements for Algal Decay and Respiration
Decay
'/ \ \
/ BODs - Background]x Dilution]*
((freeze- BODs / factor /
dried /
chloro a
5-Day
Algal Decay
mg 0? depletion
Date
Sept. 6
Sept. 14
Sept. 6
Sept. 14
algal
suspension)
mg/1
6.4
2.2
9.3
2.0
mg/1
3.0
1.4
2.8
1.1
6.0
15.0
6.0
15.0
yg/l
1386
810
1386
810
average
Respiration
Date
Sept. 6
Sept. 14
Sept. 6
Sept. 14
/
\ BOD5 ~
1 algal
V V suspension
\
mg/1
9.8
2.4
10.0
2.6
BODs \X
(freeze-
dried /
algal
suspension)
mg/1
6.4
2.2
9.3
2.0
\
Dilution)*
factor j
•
6.0
15.0
6.0
15.0
chloro a.
yg/l
1386
810
1386
810
average
yg cm or a_
.0147
.0148
.0281
.0167
.019
5-Day
Algal Respira
8
mg Oj depletion
yg cm or a_
.0147
.0037
.0030
.0111
.008
-------
filamentous blue-green algae Psuedanabaena. Figures 7,8,and9 also
revealed that seeding of the samples with 1 ml per bottle of stale
settled sewage1 had little effect upon the amount and rate of oxygen
depletion. This suggested that the supernatant contained sufficient
microorganisms for algal decay.
VI. Phytoplankton Elemental Analysis and Methods of TKN Digestion
of Algal Samples
The algae bloom of Psuedanabaena occurred in mid to late September
with a chlorophyll a_ peak of 159 yg/1 on September 27. The elemental
composition of the phytoplankton is compiled in Table 8. The average
elemental ratios to chlorophyll a_were: .021 mg C/vg chlorophyll a_;
.0054 mg N/yg chlorophyll a_; and .0020 mg P04/yg chlorophyll a_. It
should be emphasized that the results are based on the overall
phytoplankton standing corp. The nitrogen values reported for elemental
analysis were obtained by the automated colorimetric phenol ate procedure
employing the continuous (helix) digestor with preliminary manual
digestion. Neither the Technicon block digestor nor the Technicon continuous
digestor alone provided satisfactory digestion of algal TKN. The data
from side-by-side algal digestions are compiled in Table 9. The
average recovery relative to preliminary manual digestion for the
Technicon continuous digestor and block digestor were 58% and 83%
respectively. This suggested that 42% of algal nitrogen was refractory
to the Technicon continuous digestor. This agreed with a 50% TKN recovery
estimate suggested in a previous study.14
-------
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roro—'—'—'—'rorororo rorororo
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vo o —' O —•
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2222222222 2222 22222
ro—'rorororoooroo—' roroooro oocoooonoo
10 :o
00
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09
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00
00
-------
Table 9: Results From Three TKN Digestion Methods
Date
Sept.
Sept.
Sept.
Sept.
Station
7 5-A
8-A
9
10
10-B
11 8-A
9
10-B
11
n 8
8-A
9
10
26 8-A
9
10
10-B
11
average
std. deviation
Manual
mg/1
TKN
14.52
15.14
15.14
14.89
15.89
15.89
15.89
14.52
15.14
29.27
28.28
23.32
29.05
21.73
25.17
34.66
31.95
26.74
Block
mg/1
TKN
11.10
14.50
13.03
14.47
14.09
13.63
14.06
13.09
14.36
19.49
20.00
_ _ _
___
16.58
17.74
20.63
19.46
30.88
28.02
24.00
26.30
20.60
20.32
Helix
mg/1
TKN
9.15
9.52
9.27
9.52
9.27
9.21
8.81
8.24
8.06
12.92
12.61
11.83
11.83
13.65
16.86
22.36
22.84
18.53
Helix
Manual
.63
.63
.61
.6*
.58
.58
.55
.57
.53
.44
.45
.51
.41
.63
.67
.65
.71
.69
.58
.09
Block
Manual
.76
.96
.86
.97
.89
.86
.88
.90
.95
.67
.71
— — „
— — —
.76
.82
.82
.77
.89
.81
.75
.82
.77
.76
.83
.08
Helix
Block
.82
.66
.71
.66
.66
.68
.63
.63
.56
.65
.63
•*• •
__ —
.82
.77
.82
.87
.72
.80
.95
.87
.90
.91
-------
VII. Potomac River Long-Term BOD Survey Data - Summer 1978
Date 8/14/78
Station
5
Days of Incubation
10 15
8-A
10
n
14
16
Date 8/28/78
Station
5
8-A
T*
C*
N*
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
C
T
C
2.4
1.3
1.1
2.7
1.3
1.4
4.3
2.3
2.0
3.9
2.9
1.0
4.6
3.5
1.1
3.5
2.6
0.9
1.8
1.6
0.2
T
C
N
*T-BOD (mg/1)
*C-CBOD (mg/1 )
*N-NOD (mg/1)
3.0
1.4
1.6
4.4
1.3
3.1
6.3
2.8
3.5
5.3
3.1
2.2
5.8
4.0
1.8
4.7
2.9
1.8
2.0
1.6
0.4
3.4
2.1
1.3
4.9
1.7
3.2
8.0
3.9
4.1
6.8
4.0
2.8
7.0
4.7
2.3
5.6
3.7
1.9
2.4
2.0
0.4
Days of Incubation
7 13
4.3 9.3
2.4 3.2
1.9 6.1
6.2 8.0
2.7 3.8
3.5 4.2
4.4 6.4
3.1 4.3
1.3 2.1
21
3.8
2.2
1.6
5.3
1.9
3.4
8.7
4.4
4.3
7.2
4.4
2.8
7.3
5.0
2.3
6.2
3.8
2.4
2.9
1.8
1.1
20
10.8
3.9
6.9
9.4
4.7
4.7
7.7
5.4
2.3
-------
VII. Potomac River Long-Term BOD Survey Data * Summer 1978 (con't)
Date 8/28/78 (con't)
Station
TO
14
16
Date 9/11/78
Station
5
8-A
10
11
14
16
T
C
N
T
C
N
T
C
N
T
C
N
Days of Incubation
7 13 20
3.6 5.2 6.6
2.2 3.2 4.1
1.4 2.0 2.5
4.2 6.1 7.6
2.5 3.9 4.9
1.7 2.2 2.7
1.4 2.7 3.9
1.2 1.8 2.4
0.2 0.9 1.5
3.8 4.9 5.8
3.5 4.5 5.2
0.3 0.4 0.6
Days of Incubation
6 10 14
21
T
C
N
T
C
N
T
c
N
T
C
N
T
C
N
T
C
N
T
C
N
3.7
1.7
2.0
3.3
1.9
1.4
2.1
2.1
—
2.5
1.9
0.6
___
—
1.2
1.2
0
2.2
2.1
0.1
8.9
2.9
6.0
4.9
3.1
1.8
4.8
3.6
1.2
4.4
2.9
1.5
3.9
2.0
1.9
2.0
1.7
0.3
3.5
3.5
0
9.8
3.5
6.3
6.0
3.9
2.1
7.7
4.6
3.1
6.6
4.2
2.4
6.3
3.2
3.1
2.8
2.3
0.5
4.3
4.2
0.1
n.o
4.0
7.0
6.7
4.5
2.2
9.1
6.2
2.9
7.8
5.0
2.8
7.1
4.1
3.0
3.8
2.7
1.1
5.0
4.6
0.4
12.2
4.6
7.6
7.6
5.4
2.2
9.9
6.7
3.2
8.9
5.9
3.0
8.0
4.0
4.0
4.5
3.2
1.3
5.8
5.0
0.8
-------
VII. Potomac River Long-Term BOD Survey Data - Summer 1978 (con't)
Date 9/25/78
Station
5
8-A
10
n
14
16
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
Days of Incubation
3 7 14
6.1 8.5 11.0
2.3 3.8 4.8
3.8 4.7 6.2
2.7 6.2 8.4
2.1 3.8 5.7
0.6 2.4 2.7
2.5 7.1 10.5
2.1 4.1 7.6
0.4 3.0 2.9
2.5 7.6 11.0
2.0 6.2 9.1
0.5 1.4 1.9
2.3 5.7 11.2
1.5 3.8 8.6
0.7 1.9 2.6
0.8 2.0 4.5
0.7 1.1 2.9
0.1 0..9 1.6
1.1 1.6 2.7
0.6 0.7 1.7
0.5 0.9 1.0
Date 8/14/78
Station
S-l
T
C
N
20.1
7.2
12.9
Days of Incubation
10 15
38.7
9.6
29.1
41.6
10.8
30.8
21
43.5
11.4
32.1
S-2
S-3 (E)
T
C
N
T
C
N
21.0
6.0
15.0
81.0
75.0
6.0
22.8
9.0
13.8
157,
88,
41,
n,
29,
69.0
174
96.0
78.0
55,
13,
42,
181,
96,
85.5
-------
VII. Potomac SIP Long-Term BOD Survey Data - Summer 1978 (con't)
Date 8/14/78 (con't)
Station
S-3 (W)
S-4
S-5
S-6
S-7
S-8
Date 8/28/78
Station
S-l
S-2
S-3 (E)
S-3 (W)
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
r
N
T
C
N
T
C
N
T
C
N
Days of Incubation
6 10 15 21
21.6 60.0 73.8 77.4
10.8 15.0 18.0 18.3
10.8 45.0 55.8 59.1
36.0 72.0 87.0 92.3
31.5 36.8 40.5 40.3
4.5 35.2 46.5 52.0
14.1 41.7 59.4 72,
9.6 12.8 14.4 16.
4.5 28.9 45.0
18.6 39.9 51.3
14.7 20.0 23.6
3.9 19.9 27.7
30.6 44.4 43.5
15.2 18.0 20.7
15.4 26.4 22.8
10.2 38.7 56.4
8.7 13.1 17.4
1.5 25.6 39.0
Days of Incubation
7 13 20
9.6 43.7 71.7
7.8 9.8 10.5
1.8 33.9 61.2
12.3 22.8 46.8
7.8 8.4 8.6
4.5 14.4 38.2
28.5 79.5 148.5
27.0 36.0 36.8
1.5 43.5 111.7
24.0 67.5 117.8
21.0 27.0 28.5
3.0 40.5 89.3
6
5
56.1
55.8
25.8
30.0
46.8
22.5
24.3
75.5
21.2
54.3
-------
VII. Potomac STP Long-Term BOD Survey Data - Summer 1978 (con't)
Date 8/28/78 (con't)
Station
S-4
S-5
S-6
S-7
S-8
Date 9/11/78
Station
S-l
S-2
S-3 (E)
S-3 CM)
S-4
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
Days of Incubation
7 13 20
42.0 87.0 132.0
33.0 39.8 42.8
9.0 47.2 89.2
9.5 22.8 47.7
8.9 10.4 11.7
0.6 12.4 3F.O
19.4 42.0 47.9
13.1 17.7 20.1
6.3 24.3 27.8
25.2 41.4 53.6
15.0 20.1 21.6
10.2 21.3 . 36.0
11.7 22.4 52.4
10.8 16.1 20.4
0.9 6.3 32.0
Days of Incubation
6 10 14
21
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
11.4
7.8
3.6
28.8
6.0
22.8
13.5
13.5
0
13.5
12.0
1.5
1.8
16.5
1.5
39.0
10.2
28.8
50.4
8.4
42.0
20.3
20.3
0
22.5
18.0
4.5
27.0
24.0
3.0
52.8
11.4
41.4
68.4
8.4
60.0
34.5
22.5
12.0
49.5
21.0
28.5
46.5
27.0
19.5
62.4
13.2
49.2
70.8
8.4
62.4
69.0
24.0
45.0
78.0
22.0
56.0
76.5
27.0
49.5
63.0
15.0
48.0
87.0
10.4
76.6
79.5
28.5
51.0
90.0
24.0
66.0
99.0
31.0
68.0
-------
VII. Potomac STP Long-Term BOD Survey Data - Summer 1978 (con't)
Date 9/11/78
Station
S-5
S-6
S-7
S-8
Date 9/25/78
Station
S-l
S-2
s-3
S-3 (W)
S-4
S-5
Days of Incubation
6 10 14
21
T
C
N
T
C
N
T
C
N
T
C
N
9.0
9.0
0
9.9
9.9
0
9.6
9.0
0.6
7.8
7.8
0
14.4
13.2
1.2
15.0
15.0
0
14.4
13.2
1.2
12.0
10.2
1.8
44.4
16.2
28.2
32.4
17.4
15.0
31.8
16.2
15.6
42.6
14.4
28.2
76.2
16.8
59.4
51.6
18.0
33.6
55.8
18.6
37.2
69.0
16.8
52.2
91.2
18.6
72.6
55.2
21.0
34.2
64.2
22.8
41.4
79.8
21.6
58.2
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
T
C
N
7.8
5.4
2.4
22.8
5.4
17.4
31,
19,
12.0
63.
27.
36,
Days of Incubation
7 14
40.2 49.2
13.8 14.4
26.4 34.8
60.0 91.8
12.6 13.8
47.4 78.0
69.0 108
31.5 37,
37.5 70,
123.0 163,
45.0 60
78.0 103.5
,5
,5
,5
.0
30.0
24.0
6.0
9.0
9.0
0
52
31
21
,5
,5
.0
m,
37
73,
15.6
11.4
4.2
59.4
13.8
45.6
-------
VII. Potomac STP Long-Term BOD Survey Data - Summer 1978 (con't)
Date 9/25/78 (con't) Days of Incubation
3 7 14
Station
S-7
S-8
T
C
N
T
C
N
11.4
11.4
0
14.4
9.6
4.8
21.0
16.2
4.8
60.0
11.4
48.6
42.0
20.4
21.6
94.8
15.6
79.2
-------
References
1. "Standard Methods for The Examination of Water and Wastewater,"
14th ed., APHA, 1975.
2. Slayton, J.L. and Trovato, E.R., "Simplified N.O.D. Determination,"
34th Annual Purdue Industrial Waste Conference, Purdue University 1979,
3. Strickland, J.D.H. and Parsons, T.R., "A Manual of Sea Water
Analysis," Bulletin 125, Fisheries Research Board of Canada,
Ottowa, 1960, p. 185.
4. Environmental Protection Agency, Methods for Chemical Analysis
of Water and Wastes. 1974.
5. Gales, M.E., "Evaluation of The Technicon Block Digestor System
for Total Kjeldahl Nitrogen and Total Phosphorus," EPA-600/4-78-015,
Feb. 1978, Environmental Monitoring Series, E.P.A. Cincinnati,
Ohio.
6. Young, J.C., "Chemical Methods for Nitrification Control,"
24th Industrial Waste Conference, Part II Purdue University,
pp. 1090-1102, 1967.
7. Young, J.C., "Chemical Methods for Nitrification Control,"
J.W.P.C.F., 45, 4, pp. 637-646 (April 1973).
8. Slayton, J.L. and Trovato, E.R., "Carbonaceous and Nitrogenous
Demand Studies of The Potomac Estuary, AFO Region III, Environmental
Protection Agency, 1977.
9. Thomas, H.A., "Graphical Determination of B.O.D. Curve Constants,"
Water and Sewage Works, p. 123-124, (March 1950).
10. Moore, W.E. and Thomas, H.A., "Simplified Methods for Analysis of
B.O.D. Data," Sewage and Industrial Works, 22, p. 1343-1355, 1950.
11. Finstein, M.S., et al , "Distribution of Autotrophic Nitrifying
Bacteria in a Polluted Stream," The State Univ., New Brunswick,
N.J., Water Resources Res. Inst. W7406834, Feb. 1974.
12. Clark, L.J. and Roesch, S.E., "Assessment of 1977 Water Quality
Conditions In The Upper Potomac Estuary, E.P.A. 903/9-78-008,
July 1978.
13. Fitzgerald, G.P., "The Effect of Algae on B.O.D. Measurements,"
J.W.P.C.F., Dec. 1964, pp. 1524-1542.
14. Slayton, J.L. and Trovato, E.R., "Algal Nutrient Studies of the
Potomac Estuary", AFO Region III, Environmental Protection
Agency, 1977.
-------
-------
TECHNICAL REPORT DATA
I'li'zst: read Insir.ictio'i1; on llic re.crs? before complain,;)
flTFc ORT NO. \2'
v EPA=9Q3/q-jq=flQ5_ 1
T'TTYri: AND SUBTITLE
Biochemical Studies in The
Potomac Estuary
^^^ 0. L. SI ay ton and
E. R. Trovato
^yT^T^FOHMING ORGANIZATION NAM= AND ADDRESS 1
Annapolis Field Office, Region III
U.S. Environmental Protection Agency
Annapolis Science Center
Annapolis, Maryland 21401
12 SPONSORING AGENCY NAME AND ADDRESS
3 RECIPItN PS ACCESSION NO.
j. REPOHT DATE:
Summer 1978
6. PERFORMING ORGANIZATION CODS
3. PERFORMING ORGANIZATION REPORT
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OP REPORT AND PERIOD COVE
14. SPONSORING AGENCY COD5
Same
EPA/903/00
15. SUPPLEMENTARY NOTES
. ABSTRACT
The carbonaceous and nitrogenous oxygen demand of Potomac River and STP effluent
samples was determined during the summer of 1978. The oxygen depletion kinetics
were studied during long term incubation using an inhibitor to nitrification. The
average deoxygenation constants (ke) for the river sample CBOD and NOD were 0.12
day" and 0.10 day" , respectively. The CBOD of the Potomac STP effluent samples
followed first order kinetics with an average ke - .16 day" . The NOD for the STF
effluent samples had a significant lag time resulting in poor correlation
coefficients for first order fit. The average algal contribution to the 8005 was
0.027 mg/ug chlorophyll a^ with 70% due to decay an'd 30% due to respiration. The
average elemental composition of the phytoplankton present in the study area'was
determined to be (mg/yg chlorophyll a_): .021 TOC, .002 P04 and .005 TKN. : ;
Forty-two percent of algal nitrogen was found to be refractory to the Technicon
Continuous Digester. "•,
17. " KEY WORDS AND DOCUMENT ANALYSIS
s. DESCRIPTORS
Biochemical Oxygen Demand
Nitrification
Algal Respiration and Decay
Algal Elemental Composition
:;;. DISTRIBUTION STATEMENT
b.lDENTIFIERS/OPEN ENDED TERMS
Deoxygenation Kinetics
Lag Time
Oxygen Depletion Curve
TKN Digestion
19. SECURITY CLASS ('I Iris KeportJ
20. SECURITY CLASS { I'ldf p.iyc)
c. coSATi Field/G
?1. NO. Of- PAGES
35
22. f'RICt.
t:orr,i 2220-] (9-73)
-------
EPA 903/9-78-006
ANALYSIS OF SULFUR IN FUEL OILS BY
ENERGY-DISPERSIVE X-RAY FLUORESCENCE
January 1978
Technical Paper No. 15
Annapolis Field Office
Region III
Environmental Protection Agency
-------
Annapolis Field Office
Region III
Environmental Protection Agency
ANALYSIS OF SULFUR IN FUEL OILS BY
ENERGY-DISPERSIVE X-RAY FLUORESCENCE
E. R. Trovato
J. W. Barron
J. L. Slayton
-------
DISCLAIMER
The mention of trade names or commercial products in this report
is for illustration purposes and does not constitute endorsement or
recommendation by the U.S. Environmental Protection Agency.
-------
INTRODUCTION
Sulfur oxides have long been recognized as significant air
pollutants. With increased usage of sulfur containing fuels, an
increase in atmospheric sulfur dioxide content will become an
ever more important problem. Legislation has been passed governing
the allowable levels of sulfur in fuels in an attempt to control
this source of air pollution.
Energy-dispersive x-ray fluorescence (EDXRF) can provide a
rapid, non-destructive method of analysis of sulfur in fuel oils.
Because the EDXRF system is automated and minimal sample preparation
procedures are involved, a reduction in the time and cost of
analysis is possible.
-------
EXPERIMENTAL
Materials
Sulfur standards of: 2.14, 1.05, 0.268, and 0.211 weight
percent sulfur in fuel oil were obtained from the National
Bureau of Standards. In addition, sulfur standards prepared
by commercial sources were obtained with concentrations in
weight percent sulfur of: 2.02, 1.06, and 0.49. Actual
samples analyzed by wavelength-dispersive x-ray fluorescence
with the following weight percent sulfur concentrations were
also analyzed: 2.95, 2.10, 2.05, 2.00, 1.61, and 0.33.
Zinc, barium, and lead standards were prepared from Conostan
Metallic-Organic standards.
Equipment
A Finnigan 900 Series energy dispersive x-ray fluorescence
spectrometer and data system were used for all EDXRF analyses.
Procedure
The determination of sulfur in fuel oils follows the procedure
outlined-in ASTM D2622-671: Standard Method of Test for Sulfur
in Petroleum Products (X-Ray Spectrographic Method) with
minor changes in the procedure to accommodate the energy
dispersive equipment. A brief outline of the procedure follows:
a. Place the sample in an open cell sample cup over which
0.25-mil Mylar film has been stretched and attached
with a snap-on ring. Attach microporous film to the
open-end of the sample cup to prohibit the oil
from escaping.
-------
b. Place the samples in the x-ray beam, apply vacuum,
and allow the atmosphere in the x-ray chamber to
come to equilibrium. Instrument operating conditions
are found in Table III.
c. Determine the intensity of the SK& peak at 2.307 Kev
and make background measurements adjacent to the peak.
d. If the sample contains interfering elements in
concentrations greater than those listed in ASTM
D2622-67, dilute the sample by weight with white oil.
Calibration
a. Determine the net SIQv intensity for all standards
and samples.
b. Determine the weight percent sulfur by ratio against
the 2.14 weight percent sulfur standard reference
material using net intensities or by comparison to a
calibration curve of sulfur net intensity vs. concentration.
c. Measure a sensitivity standard at frequent intervals
and determine the net counting rate for each sample.
-------
RESULTS AND DISCUSSION
Commercially obtained standards, NBS standards, and previously
analyzed field samples were analyzed by energy dispersive x-ray
fluorescence. The accuracy results shown in Table I and precision
results shown in Table II, indicate the high degree of precision and
accuracy obtainable by this method of analysis. The average recovery
was 97^ (Table I) and a plot (Figure I) of found weight percent sul-
fur vs. known weight percent sulfur gives a correlation coefficient
of 0.999. A paried-t test applied to the data indicates that there
is no difference between the found and known values at a 95^5 confi-
dence level. An average standard deviation of 0.02 weight percent
sulfur was found over the O.l6 to 2.00 weight percent sulfur range.
A plot of the standard calibration curve (Figure II) is linear with
a correlation coefficient of 0.9997, further facilitating analysis by
this method.
The minimum detectable amount2, defined as 3x(intensity of the
background)1''2, is 0.11 weight percent sulfur; this is below the
majority of legislated limits of sulfur concentration in fuel oil in
the United States^.
The analysis of fuel oil samples by energy-dispersive x-ray
fluorescence is accurate and precise, requires minimal sample
preparation, and is non-destructive. It also simultaneously deter-
mines sulfur and its interfering elements, phosphorus, zinc, barium,
calcium, and chlorine. These factors combine to produce an overall
increase in the efficiency of analysis of sulfur in fuel oils.
-------
TABLE I
Comparison of Sulfur Results Found by Classical and EDXRF Methods
Date of
Analysis
10-28-75
8-12-76
2-11-77
2-14-77
4-27-77
Origin
Field Sample
Field Sample
Field Sample
Secondary Std.
Field Sample
Field Sample
Secondary Std.
Field Sample
Field Sample
Field Sample
Field Sample
Secondary Std.
NBS
Secondary Std.
NBS
NBS
NBS
NBS
Secondary Std.
NBS
NBS
NBS
Secondary Std.
NBS
Classical
wt. % S
2.95
2.10
2.05
2.02
2.00
1.61
1.06
2.94
2.10
2.00
1.61
1.06
1.05
0.49
0.268
0.211
1.05
0.211
1.06
1.05
1.05
0.268
0.24
0.211
correlation coefficient = .999
•
EDXRF
wt. % S
2.98
2.07
2.05
1.94
2.04
1.68
0.99
3.04
2.13
2.04
1.67
1.01
1.04
0.48
0.264
0.206
1.02
0.155
1.00
1.06
1.03
0.231
0.22
0.192
mean
s
* R*
101.0
98.6
100.0
96.0
102.0
104.3
93.4
103.4
101.4
102.0
103.7
95.3
99.0
98.0
98.5
97.6
97.1
73.4
94.3
101.0
98.1
86.2
91.7
91.0
= 97. %
= 6.7%
t-statistic = .540
degrees of freedom = 23
*R = Recovered
-------
Figure I: Plot of Found Weight Percent Sulfur vs Known Weight Percent Sulfur
3 D
>>
Found
wt. % S
2.0
r = .9990
m = 1.028
b = -0.04027
2Jl
Known wt. % S
-------
TABLE II
Results of Duplicate Analyses of Field Samples
Duplicate I
wt. % S
.16
.16
.16
.16
.16
Duplicate II
wt. % S
.17
.17
.19
.21
.17
s = .02% S
difference
Toi
.01
.03
.05
.01
0.3-1.0%
.72
.96
.99
.93
.59
.44
.72
.98
.98
.91
.58
.44
s = .01% S
0
.02
.01
.02
.01
0
> 1.0%
1.99
03
04
05
74
09
.96
1.63
,92
.01
.00
.04
.74
.08
.94
.63
.07
.02
.04
.01
0
.01
.02
0
s = .02% S
s = (I(d2) /2k)-*
where: s = standard deviation
d = difference between duplicates
k = number of samples
-------
TABLE III
Instrument Operating Conditions
Date
of Voltage Amperage Time Colliroator
Analysis Kv ma sec Path Filter diameter mm
10-28-75 10 4 500 vacuum none 1
8-12-76 10 1 500 vacuum none 6
2-11-77 10 0.8 500 vacuum none 6
2-14-77 10 0.8 1000 vacuum none 6
4-27-77 10 0.8 1000 vacuum none 6
-------
-igure II: Plot of SKa Net Intensity vs Weight Percent Sulfur
300
r = .9997
m = 144.99
b = -5.246
200:
1 0 0 h
Weight % Sulfur
-------
REFERENCES
1. ASTM D2622-67, ASTM Standards on Petroleum Products and Lubricants,
ASTM Committee D-2, September 1967
2. Bertin, Eugene P., Principles and^ Practice of X-Ray Spectrometric
Analysis, Plenum Press, Me\v York, 1975
3. Martin, Werner and Stern, Arthur C., The World's Air Quality
Management Standards, Volume II: The Air Quality
Management Standards of the United States, U.S.
Environmental Protection Agency, Office of Research
and Development, Wash., D.C., 1974, pg. 113-124
4. U.S. Environmental Protection Agency, Office of Water Programs
Operations, National Training and Operational Technology
Center, Participant's Handbook for the Drinking Water^
Chemical Laboratory Certification Course, pg. E9-20
ACKNOWLEDGEMENTS
We would like to thank: Dr. Jungers, EPA, RTP; Mr. Al Curry,
Aerospace Fuels Lab; Mr. Mac Dill, AFB, Tampa, Fla.; and Mr. Al Kewing,
Mobil Oil, Paulsboro, N.J. for providing analyzed samples and
commercial standards utilized.
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
EPORTNO 2.
IPA 903/9-78-006
ITLE AND SUBTITLE
.nalysis of Sulfur in Fuel Oils by Energy Dispersive
X-ray Fluorescence
UTHOR(S)
:. R. Trovato, J. W. Barren, J. L. Slayton
ERFORMING ORGANIZATION NAME AND ADDRESS
.nnapolis Field Office, Region III
.3. Environmental Protection Agency
.nnapolis Science Center
unnapolis, Maryland 21/401
SPONSORING AGENCY NAME AND ADDRESS
lame
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
January 1978
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
Technical Paper 15
10. PROGRAM CLEMENT NO.
8BD144
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
In House; Final
14. SPONSORING AGENCY CODE
EPA/903/00
SUPPLEMENTARY NOTES
ABSTRACT
Energy dispersive x-ray fluorescence was used to analyze for sulfur in oil in
sommercially prepared standards, NBS standards and laboratory samples. The
,echnique of energy dispersive x-ray fluorescence for sulfur was found to be
iccurate, precise, and required minimal sample preparation. In addition it
ras non-destructive, and enabled the simultaneous determination of sulfur and
ts interfering elements: phosphorus; zinc; barium; calcium; and chlorine.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
I -ray Fluorescence Sulfur Analysis
>ulfnr ;>termi nation Fuel Oil
. DISTRIBUTION STATEMENT
i'"loe;i^ 1 o in: lie
b.lDENTIFIERS/OPEN ENDED TERMS
Energy -dispersive X-ray
Fluorescence Sulfur
Analysis
19. SECURITY CLASS (This Report)
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21. NUMBER OF PAGES
Insert the total nurnbei of pages including this ont and unnumbeied pages, but exclude distribution list, if any
22. PRSCH
Insert tr..- <>iiie set b> the National technical Intoimation hi'ivke or the Government Printing Office, it known
fcPA Form 222O-I (9-/3) (Reverse)
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EPA 903/9-78-008
ASSESSMENT OF 1977
WATER QUALITY CONDITIONS
IN THE UPPER POTOMAC ESTUARY
July 1978
Leo 0. Clark
and
Stephen E. Roesch
-------
-------
EPA 903/9-78-008
TABLE OF CONTENTS
Chapter Page
List of Figures ii
List of Tables iii
I. INTRODUCTION 1
II. DESCRIPTION OF MONITORING PROGRAM 5
III. FINDINGS AND CONCLUSIONS 13
A. General 13
B. Dissolved Oxygen 15
C. Algae 37
D. Nutrients 46
E, BOD 48
F. Estuary loadings 49
G. Herbicides 52
IV. FUTURE STUDY NEEDS 55
V- APPENDIX 56
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-------
LIST OF FIGURES
Number Page
1 Secchi Disk vs. Chlorophyll a_ 14
2 DO Profile - September 8, 1977 16
3 Potomac Estuary DO Data: Rosier Bluff 23
Swan Creek (Drogue Study)
August 16, 1977
4 Potomac Estuary DO Data: Rosier Bluff 24
Piscataway Creek (Drogue Study)
August 30, 1977
5 Diurnal Transect Data: Potomac Estuary 26
at Hains Point - August 8-9, 1977
6 Diurnal DO Data - Hains Point 27
7 Diurnal Transect Data: Potomac Estuary 29
at Woodrow Wilson Bridge
August 9-10, 1977
8 Diurnal DO Data - Woodrow Wilson Bridge 30
9 Diurnal Transect Data: Potomac Estuary 32
at Fort Washington - August 10-11, 1977
10 Diurnal DO Data - Fort Washington 33
11 Chlorophyll a_, BOD, and DO Time Plots 39
12 Nitrogen - Chlorophyll Relationship 43
13 Phosphorus - Chlorophyll Relationship 44
A-l DO Isopleth: Potomac Estuary - 1977 56
A-2 Chlorophyll a^ Isopleth: Potomac Estuary 57
1977
A-3 NH3 Isopleth: Potomac Estuary - 1977 58
A-4 N02 + N03 Isopleth: Potomac Estuary - 1977 59
A-5 TP04 Isopleth: Potomac Estuary - 1977 60
A-6 Pi Isopleth: Potomac Estuary - 1977 61
A-7 BOD5 Isopleth: Potomac Estuary - 1977 62
ii
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-------
LIST OF TABLES
Number Page
1 1977 Potomac Estuary Sampling Stations 6
2 Potomac Slack Water Runs 7
3 1977 Potomac Productivity Study 18
4 Analysis of Diurnal DO Variability - 20
August 16, 1977
5 Oxygen Production - Respiration Balance 21
6 Comparison of Surface and Bottom DO - 28
Mains Point
7 Comparison of Surface and Bottom DO - 31
Woodrow Wilson Bridge
8 Comparison of Surface and Bottom DO - 34
Ft. Washington
9 Analysis of Diurnal DO Data 36
10 Relationship between Organic N&P and 41
Chlorophyll a_
11 Relationship between Inorganic N&P and 42
Chlorophyll a_
12 Summary of Sewage Treatment Plant 50
Effluent Data
A-l Summary of 1977 Potomac Estuary Data 63
m
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Chapter 1
INTRODUCTION
The water quality problems of the Potomac in the Wash-
ington area have been recognized since the days of President
Lincoln. Most of the difficulties at that time manifested them-
selves as sewage related odors which were abundant on warm summer
evenings. It was not until the 1930's that treatment facilities
were constructed to alleviate the obvious odor problems and less
obvious potential health hazards. Since that time, there has been
a continual race between expanding population and construction of
treatment works in order to adequately treat the increased waste-
loads. Needless to say, treatment facilities still lag behind
current and anticipated needs in the Washington Metropolitan Area.
A major objective of the Water Quality Act and its
amendments is to "maintain the physical, chemical and biological
integrity of the Nation's waters". In the 1950's and 60's, changes
in growth of aquatic plants in the Potomac were documented. These
biological perturbations were indicative of more basic changes
taking place in the physical and chemical environment supporting
these aquatic plants. Such biological changes serve as barometers
pointing to ecological imbalance within the supporting environ-
ment, in this case the Potomac Estuary.
Extensive field studies in the Potomac Estuary were
conducted by EPA from 1966 to 1970. These studies pointed out
the two major water quality problems existing during that period.
1
-------
These were an oxygen deficit brought about by discharge of organic
wastes and excessive eutrophication brought about by overenrich-
ment of the estuary with nutrients, particularly nitrogen and
phosphorus. These studies resulted in the publication of Technical
Report 35, which documented the scientific efforts carried out up
to that time by EPA's Annapolis Field Office (AFO).
Now, nearly a decade later, these problems are receiving
increased attention from regional planners, as attempts to find
a solution have grown more complex. The water quality problems
of the Potomac Estuary must be considered along with other local
environmental issues, such as: water supply needs incorporating
a low flow policy, pressure to rerate treatment capacity at Blue
Plains, land treatment alternatives, and other legitimate concerns
that must somehow be orchestrated into an overall regional
management plan, which is at the same time rational, cost-effective,
and meets the needs of the public.
It is within this framework of competing uses of the
Potomac and conflicting needs of the public that EPA designed a
two-year water quality study to update the available data base
and provide current information on the status of the Potomac
Estuary. Our studies will not answer the many questions raised
by the various constituencies served by the Potomac, but they will
provide factual documentation on the river's health and an indica-
tion of the water quality trends evolving. Such information is
basic to the decision maker in formulating the available options
from which a workable decision can be made. It is this foundation
-------
of scientific reality that we are attempting to investigate and
document.
This report is intended to present the information
gained from the first half of the current two-year study effort.
The field phase was performed during the summer of 1977 and the
findings and conclusions herein evolved during the data interpreta-
tion and analysis phase that followed. Tabulations of the raw
data along with numerous graphs depicting this data are contained
throughout the text and in the Appendix. The ongoing usage of this
data within the context of mathematical modeling and for updating
portions of Technical Report 35 will be documented at a later time.
The specific objectives associated with this intensive
study of the Potomac Estuary's water quality are as follows:
Principal Objective
Provide the first phase of an updated technical data
base that will be necessary to address the denitrification deferral
issue at Blue Plains.
Secondary Objectives
1. Provide data for updating the verification and
improving the predictive reliability of AFO's
existing mathematical model of the Potomac
Estuary.
2. Determine the response of the Potomac Estuary
to the upgraded treatment currently in existence
at Blue Plains.
3. Provide a basis for establishing water quality
trends with particular emphasis on a comparison
3
-------
with data collected during the critical period
of 1965 - 1970.
4. Define current point source nutrient and oxygen
demanding loads entering the Potomac Estuary
along with those being contributed from the
Upper Basin.
5. Monitor the impact of a storm event in the WMA
on the widespread quality characteristics (as
opposed to high frequency monitoring for local-
ized effects) of the Estuary.
6. Determine the magnitude of selected herbicides
entering the Estuary from upstream and signifi-
cant point sources, and their extent in the
Estuary itself.
-------
Chapter II
DESCRIPTION OF MONITORING PROGRAM
This intensive monitoring program, conducted during
the period of July 18 to September 8, was comprised of three
distinct but interrelated phases: (Each of these phases will be
discussed below.)
A. Ambient Water Quality Monitoring
During six different weeks of the study period, two
boat runs, each following a slack water tide condition, were made
from the Route 301 Bridge (river mile 67.4) to Chain Bridge (river
mile 0.0). The stations sampled enroute, along with their river
miles and station number, are presented in Table 1. Because of
time constraints, these stations were sampled only within the
main channel and near the surface (i.e. no transect type data was
obtained). Shown in Table 2 are the approximate starting and
ending times for each run, and the significant rainfall events
that occurred during the study period. As can be seen, about an
equal number of low water and high water slack conditions were
sampled.
The following is a list of parameters that were analyzed
in conjunction with the ambient monitoring. All of these parameters
were measured routinely at every sampling location (with the
exception of herbicides, which were done only twice), as well as
ultimate (20 day) BOD and phytoplankton counts, which were done
on a selective basis.
5
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TABLE 1
1977 POTOMAC ESTUARY SAMPLING STATIONS
Station
Number
P-8
P-4
1
1-A
2
3
4
5
5 -A
6
7
8
8-A
9
10
10-B
11
12
13
14
15
15-A
16
Name
Chain Bridge
Above Windy Run (opposite Georgetown
Reservoir
Key Bridge
Memorial Bridge
14th Street Bridge
Mains Point
Bellevue
Woodrow Wilson Bridge
Rosier Bluff
Opposite Broad Creek
Fort Washington (Piscataway)
Dogue Creek - Marshall Hall
Opposite Gunston Cove
Chapman Point - Hallowing Point
Indian Head
Deep Point - Freestone Point
Possum Point
Sandy Point
Smith Point
Maryland Point
Opposite Nanjemoy Creek
Mathias Point
Route 301 Bridge
RMI*
0
1.90
3.35
4.85
5.90
7.60
10.00
12.10
13.60
15.20
18.35
22.30
24.30
26.90
30.60
34.00
38.00
42.50
45.80
52.40
58.55
62.80
67.40
*Miles below Chain Bridge
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TABLE 2
POTOMAC SLACK WATER RUNS
JULY - SEPTEMBER, 1977
Date
7/17
7/18
7/20
7/21
7/25
7/27
8/01
8/03
8/05
8/14
8/22
8/24
8/29
8/30
8/31
9/06
9/08
Tide
LWS
LWS
HWS
LWS
LWS
HWS
HWS
HWS
*
HWS
HWS
LWS
Start
Time
1125
1245
1100
0855
1145
0830
1035
1130
1055
0910
1245
0930
End
Time
1700
1710
1505
1410
1610
1301
1540
1535
1512
1313
1700
1335
Remarks
Rain - .24"
Rain - .59"
Rain - .30"
Rain - 1.08"
Rain - .33"
Rain - 1.20"
Rain - 1.23". Fish kill
between Broad Creek and
Piscataway Creek
Rain - .40"
Fish kill between Broad
Creek and Piscataway
Creek
*Missed LWS
-------
Nitrogen Series
TKN
NH,
NOg + N03
Phosphorus Series
Total PCL (filtered and unfiltered)
Inorganic PO. (filtered and unfiltered)
Carbon Series
Total C
Total Organic C
Biological
Chlorophyll a_
Phytoplankton Counts & Identification
Physical
Temperature
Turbidity
Secchi Disc
Other Chemicals
PH
BOD5
BOD°ultimate
DO
Salinity
Selected Herbicides
Atrazine
Simazine
B. STP Effluent Monitoring
A 24 hour composite effluent sample was obtained from
each of the major wastewater treatment plants (collected by plant
operators) in the WMA during the same days that the slack water
boat runs were being performed. These samples were preserved on
ice and returned to the AFO laboratory for analyses. The
8
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parameters that were analyzed included the nitrogen, phosphorus, and
carbon series (as contained in the aforementioned parameter list)
along with BOD5 and BODult on a once-per-week basis. In addition,
herbicide analyses were completed on one occasion. The following
is a list of the facilities that were sampled during this study:
Arlington Fairfax Co. - Pohick Creek
Alexandria Fairfax Co. - Dogue Creek
Blue Plains Fairfax Co. - Hunting Creek
Piscataway Fairfax Co. - Westgate Creek
At the time these STP samples were collected, AFO
personnel obtained a representative flow measurement in order that
mass loading rates could be computed.
C. Special Studies
Several special studies were incorporated in this monitor-
ing program to address the eutrophication state of the Potomac and
its relationship to the prevailing DO values that were being
measured. Much of the design and methodology employed in these
special studies was for the purpose of better defining various
model inputs, as required by its representation of the DO budget.
Practically all of these studies were performed before, in the
Potomac, with a high degree of success.
1. Algal Elemental Composition Analysis
Concentrated samples of the algal cells were collected
at different times, and at different locations in order to determine
the relative quantities of carbon, nitrogen, and phosphorus actually
contained within the cellular material. This information would
-------
have value in ascertaining the nutritional requirements of the algae,
and in interpreting whether or not a nutrient limited situation existed.
2. Bioassay Experiments
Dr. George Fitzgerald, University of Wisconsin, developed
several algal bioassay procedures for demonstrating whether the
environment has supplied limited or surplus quantities of nutrients.
These tests rely on in-situ algae but can be performed in a labora-
tory by measuring surplus phosphorus uptake, the enzyme alkaline
phosphatase, and the ammonia absorption potential under dark condi-
tions. The alga] elemental composition analysis and Dr. Fitzgerald's
bioassay experiments are very complementary in assessing the impact
of nutrients on algal growth.
a. Light and Dark Bottle Studies
Both clear and opaque bottles were submerged at two
different depths (in and below the euphotic zone) and at several
different locations within the algal bloom for a period of 4-6
hours. The differences in the oxygen content of the bottles
can be used to estimate the effects of algal photosynthesis and
respiration. If one knows the ambient chlorophyll concentrations,
these P and R rates can be expressed very conveniently on a per ug
chlorophyll basis.
4. Benthic Oxygen Demand Studies
AFO had previously designed and utilized a benthic
respirometer that could be applied in estuarine environments, so long
as the water depths did not exceed 15-20 feet. This respirometer
was "planted" at several locations in the Potomac Estuary for
10
-------
at least one hour, and periodic DO readings within the
chamber were obtained. The magnitude of the DO variations as a
function of time constitutes an indication of the benthic oxygen
demand rate. One inherent assumption of this procedure is that
the benthic rate proceeds much quicker than the rate of bacterial
respiration within the water column.
5. Long Term BOD/Nitrification Rate Study
Since the characteristics of the treated wastewater
being discharged to the Potomac Estuary have changed significantly
during the past few years (particularly in the case of Blue Plains),
it was believed that previous estimates of both the carbonaceous
and nitrogenous oxidation rates may no longer be valid; therefore,
long term (i.e. 20 days) incubated bottle tests in the laboratory
were performed on a weekly basis using river samples, STP effluent
samples, and samples of the water entering the estuary at Chain
Bridge. An adequate number of DO measurements were obtained from
both inhibited and noninhibited samples to distinguish the individual
reaction rates and ultimate BOD values.
6. Diurnal Transect Sampling
Three stations were selected for cross-sectional (transect)
sampling at hourly intervals, for a total period of 24 hours. Data
of this nature is invaluable for assessing the impact of algae on
DO concentrations throughout the water column. However, since
this diurnal sampling was conducted at a fixed point, the tidal
effects had to be accounted for.
7. Drogue Studies
In order to obtain additional data related to a senri-
11
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diurnal DO cycle, but without having to consider the troublesome
tidal effects, two special studies were performed wherein a
floating drogue identifying a parcel of water was followed. Hourly
surface sampling was conducted while following the drogue with
samples being analyzed for DO and Chlorophyll.
It should be noted that separate reports, documenting
the special laboratory studies relating to algae and oxidation
rates, have been prepared and published by AFO.*
*Algal Nutrient Studies in the Potomac Estuary, Joseph Lee Slayton
& E. R. Trovato
Carbonaceous and Nitrogenous Demand Studies in the Potomac Estuary,
Joseph Lee Slayton & E. R. Trovato
12
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Chapter III
FINDINGS AND CONCLUSIONS
A. General
1. The 1977 Potomac Estuary Intensive Survey was conducted
during an extremely critical period (July 18 - September 8), as
evidenced by ambient flows and temperatures. River flows after
water supply withdrawals averaged about 1500 cfs, with the range
extending from 940 to 3600 cfs. Water temperatures averaged about
27.6°C. The maximum water temperatures (30-31°C) were as high as
any ever documented in the Estuary.
2. The water clarity of the Potomac Estuary was quite
low, as usual, particularly in the middle reach, which supports
the major algal blooms. Typical Secchi Disk readings were about
20-24 inches. Minimum values (during large algal blooms) ranged
between 7-12 inches, whereas the maximum readings in the extreme
upper reach (above Mains Point) ranged between 30-35 inches. (See
Figure 1.) Turbidity levels followed a similar pattern with respect
to water clarity.
3. An effort was made to identify rapid temporal changes
in the water quality of the Estuary based on the data collected
during slack water runs, and to relate changes to the occurrence
of storm events. No consistent pattern between these significant
changes (of which there were several for DO, BOD, and TP04) and
preceeding climatological conditions could be discerned. Even
Secchi Disk and turbidity readings could not be closely associated
13
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Figure 1
SECCHI DISK VS. CHLOROPHYLL a
POTOMAC ESTUARY - PISCATAWAY CR. TO POSSUM PT.
(1977 DATA)
38 -
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
J I
0 20 40 60
80 100 120 140 160 180 200 220 240 260 280
Chlorophyll J.-Jig/1
14
-------
with particular storm events. This is not intended to imply that
storm water and/or combined sewer overflows do not adversely affect
the Estuary, but that these effects may be masked by the various
"in-stream" reactions and transport processes taking place, or
possibly, that the sampling did not occur at the most opportune
time.
4. Numerous regression/correlation analyses were per-
formed using data (see Table A-l) for each of the major para-
meters monitored during this study. Those which yielded statistically
significant results are shown below:
Y (dependent) X (independent) r
.73
.58
.62
.66
.76
.68
.58
.54
.55
.51
1. Minimum DO concentrations measured during the twelve
slack water runs varied between 2-3 mg/1. (See Figure A-l.) These
low DO levels normally occurred in the immediate vicinity of the Blue
Plains STP. The most critical DO profile was observed on September 8.
(See Figure 2) ,_
a) BOD5
b) Chloro
c) Chloro
d) Chloro
e) Pi
f) NH3
g) N02 + N03
h) Secchi Disk
i) BOD5
j) Secchi Disk
B. Dissolved
TKN
BOD5
TP04
PH
TP04
TKN
TKN
Chloro
TP04
Turbidity
Oxygen
-------
Figure 2
DO PROFILE
POTOMAC ESTUARY
SEPT. 8, 1977
Temp = 27°C
Flow = 1100 cfs
8
10
20 30 40
Miles Below Chain Br.
16
50
60
70
-------
2. Based upon a statistical analysis of intensive type
data collected in the Potomac Estuary during 1965, 1968, 1969,
and 1970, as well as the 1977 data, it can be concluded that DO
concentrations in the critical reach downstream of Blue Plains
have, in fact, improved with time. While difficult to quantitate
because of data anomalies and limitations, it appears that on the
average, DO levels have increased by about 1.0-2.0 mg/1. All of
this data was collected at surface stations having similar algal
bloom intensities, and was taken during low flow and high tempera-
ture conditions, making the data as comparable as possible.
3. A series of light and dark bottle DO analyses were
performed at depths of 1 foot and 6 feet between Broad Creek and
Indian Head. (See Table 3.) The purpose of this special study
was to estimate representative rates of algal photosynthesis and
respiration. Although a considerable amount of variability occurred,
the data was averaged and the following rates resulted:
P - 0.0140 mg 02/ug Chloro/hr
R - 0.0015*mg 02/ug Chloro/hr
*It was estimated that about 25% of this total respira-
tion rate was attributable to bacterial respiration, producing a
net algal respiration rate of 0.0011 mg 02/ug Chloro/hr.
These rates, it should be noted, compared quite well
with the original values presented in Technical Report 35 and used
in the Dynamic Estuary Model (P = 0.012 and R = 0.0008 mg 02/ug
Chloro/hr) along with a euphotic depth of 2.0 feet.
17
-------
Table 3
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r-in co ro in «» o •— co o CM co cot)-—to en 4-csj *.
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-------
4. The oxygen production rate observed on August 16
between 0600 hours and 1200 hours was +0.0020 mg 02/ug Chloro/hr.
(See item 7) The results of a light/dark bottle study performed
during this time period within the same reach of the Potomac
Estuary was used for comoarison purposes. Assuming a water depth
of 15 feet and a euphotic zone of 2.0 feet, the P and R rates (0.014
and 0.0015 mg 02/ug Chloro/hr) translate to a net oxygen production
rate of +0.0004 mg Og/ug Chloro/hr. Assuming a water depth of
25 feet and a euphotic zone of 6.0 feet, the same P and R rates
translate to a net oxygen production rate of +0.0019 mg 02/ug
Chloro hr, which compares very favorably with the observed produc-
tion rate. (See Table 4)
5. An oxygen balance was developed utilizing the average
P and R rates obtained from the light and dark bottle studies. If
a euphotic zone of 2.0 feet is assumed, a zero net production of
oxygen is expected to occur when the water depth is about 13 feet.
Greater water depths will produce a net depletion of oxygen, whereas,
lesser water depths will produce a net addition of oxygen. The
actual quantities of oxygen added or consumed will, however, be
a function of the chlorophyll level. If a euphotic zone of 4.0
feet is assumed, and if it is further assumed that the same P rate
applies, there will be a net production of oxygen even when the
water depths are 25 feet. (See Table 5)
6. Seven measurements of the sediment oxygen demand
rate were made using a specially designed benthic respirometer.
The results are presented below:
19
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Table 4
ANALYSIS OF DIURNAL DO VARIABILITY
POTOMAC ESTUARY - AUGUST 16. 1977
(BROAD CREEK AREA)
Observed Increase in DO:
Time = 0600 - 1200 + .0020 ^/^ Ch1°r°/hr
Time - 1200 - 1700 + .0075 2/ Chl°r°/hr
Estimated Increase in DO Based on P&R Data:
Productivity Results (8/16/77)
P = 0.014 mg 02/yg chloro/hr
R = 0.0015 mg 02/ chloro/hr
Assumptions_fl_ (used in Model)
Water Depth « 15 ft
Euphotic Zone = 2 ft
.014 * yf - .0015 = +.0004 mg °2/Mg ch1oro/hr
Assumptions #2
Water Depth = 25 ft
Euphotic Zone = 6 ft
.014 * - .0015 = .0019 mg °2/yg chloro
/hr
20
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TABLE 5
OXYGEN PRODUCTION-RESPIRATION BALANCE
POTOMAC ESTUARY
P =
Depth
(ft.)
5
10
15
20
25
5
10
15
20
25
5
10
15
20
25
CHLORO A
0.014 MG 0?/U9 CHLORO/HR.
Increase in 02 Over
Water Column Due to
Photosynthesis for
12 Hours/Day
Euphotic Zone
6.72
3.36
2.24
1.68
1.34
Euphotic Zone
10.08
5.04
3.36
2.52
2.02
Euphotic Zone
13.44
6.72
4.48
3.36
2.68
= 100 yg/1
R = 0.0011 MG
Decrease in 02 Over
Water Column Due to
Respiration for
24 Hours /Day
= 2.0'
2.64
2.64
2.64
2.64
2.64
= 3.0'
2.64
2.64
2.64
2.64
2.64
= 4.0'
2.64
2.64
2.64
2.64
2.64
02/yq CHLORO/HR.
Net
(ing/ 1 /day)
4.08
0.72
-0.40
-0.96
-1.30
7.44
2.40
0.72
-0.12
-0.62
10.80
4.08
1.84
0.72
0.04
21
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Station
Key Bridge -
VA Shore
Hains Point
Bellevue -
VA Side
% mile below Wood-
row Wilson Bridge
MD Side
Rosier Bluff -
MD Shore
Fort Washington -
Mid River
Dogue Creek -
MD Side
Rate
(gr/m2/day)
3.5
2.1
3.6
3.1
Remarks
1.4
1.5
5.3
Unrepresentative - main channel
of river (almost entire width)
contained a hard bottom.
Representative.
Soft, muddy bottom - probably
representative.
Soft bottom but unrepresentative
- bottom was hard along MD side
of shipping channel from Woodrow
Wilson Bridge to near Goose
Island.
Hard bottom with clay and
gravel - representative.
Soft bottom - representative.
Soft bottom - representative.
7. Two attempts were made to track and monitor a discrete
parcel of water in the Upper Potomac Estuary between Rosier Bluff
and Piscataway Creek over a semi-diurnal period extending from
0600 hours to about 1700 hours. A floating drogue was used for
this purpose. During both occasions (August 16 and 30), tidal
conditions, weather conditions, flows, and water temperatures were
very similar.
On August 16, the DO concentration (surface) was 1.5
mg/1 at 0600 hours and increased to about 5.5 mg/1 by 1700 hours.
(See Figure 3.) The ambient chlorophyll concentration was 80
ug/1. Computed net rates of oxygen production were 0.0020 mg Op/
ug Chloro/hr between 0600 and 1200 hours and 0.0075 mg 02/ug Chloro/
hr between 1200 and 1700 hours.
22
-------
Figure 3
f
§
SMI
a
LU
< =>
t °
< O
a oc
O * K
0 * £
> Ut i-
ac UJ .
< oc CD
3 O *-
ts
o
s
o
&*.
SAAH
i
I
I
Hi
o
§
1
O
f
S
§
Ul
si
m
oc
UJ
CO
O
oc
o
O
»
x:
Q
L/SIAI
23
-------
Figure 4
SMI
00
8
(A
Ul
3
O
<
5
o
o
c
=
CO
IS
o *•
2
w
o
a.
OC
UJ
55
o
oc
8 3
i-S
*0
in
I
o
o
01
a.
~fc
O
M
SMH
01
00
c a
° E
<0
L/BIAI
24
-------
On August 30, the DO concentration (surface) varied
from 3.0 mg/1 at 0600 hours, to 11 mg/1 at 1700 hours. (See
Figure 4.) This variation translated to a net oxygen production
rate of 0.0049 mg 02/ug Chloro/hr. The ambient chlorophyll con-
centration was 135 ug/1, and the weather was again mostly sunny
and hot.
8. Diurnal (24 hour) transect sampling was performed at
three stations during the week of August 8. These stations were
Mains Point, Woodrow Wilson Bridge, and Fort Washington. The
comments relating to the observed data at each station, followed
by a general conclusions statement, based upon a detailed interpre-
tation of this data, are given below:
a) Hains Point data (surface and transect mean) showed
a classical diurnal DO pattern. (See Figures 5 and 6 and Table 6.)
The total variability of the surface data was about 4.5 mg/1 (2.5
- 7.0 mg/1), whereas the transect mean data experienced a total
variability of about 3 mg/1 (3.5 - 6.5 mg/1). Variations at the
bottom were about the same as the surface, but not in phase. The
mean bottom DO was 3.9 mg/1. The average chlorophyll level was
65 ug/1.
b) Neither the mean transect data, nor the bottom
data collected at the Woodrow Wilson Bridge demonstrated a classical
diurnal DO pattern, although both showed substantial variability
(2-7 mg/1 and 1 - 4 mg/1, respectively). (See Figures 7 and 8
and Table 7.) The surface data, on the other hand, did demonstrate
such a pattern, with DO concentrations varying from about 8 mg/1
25
-------
Figure 5
DIURNAL TRANSECT DATA
POTOMAC ESTUARY @ HAINS PT.
AUGUST 8-9, 1977
Transect
Range
. Transect
Mean
A Mid Channel, Surface
ADO * 3Mg/1
T Chloro a
TPO>i
Ebb
Ebb
12 I 234 567 89 10 II 13 I 2 3 4 5 6 7 8 9 10 11 12
8/8 Hours 8/9
26
-------
Figure 6
t
in
o
C
o
OQ
CD
in
n
CM
CT)
oo
oo
r-
CD
- oa
27
-------
Table 6
COMPARISON OF SURFACE AND BOTTOM DO
Date Time
8/08 1200
1300
1400
1500
1600
1700
1800
1900
2100
2200
2300
2400
8/09 0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
POTOMAC ESTUARY - 1977
HAINS POINT
Surface
Chloro DO
(yg/l) Tide (mg/1)
60 | 3.6
•§ 3'7
80 I 5.1
1 1
u_
60
>
85
4.0
7.2
7.1
7.3
S 6.4
70 £ 6.4
50
45
3.8
6.5
5.1
4.5
80 "g 4.1
o
C 4.0
65
80
2.9
2.7
2.7
3.8
75 ^ 4.3
f~i
^ 3.9
45
'
1 4.3
* 4.5
ADO* 4.5
Avg. 4.7
Bottom
DO Depth
(mg/1 ) (feet)
2.5 30
4.8
2.0
1.9
1.5
1.9
2.8
4.6
6.5
6.0
6.8
5.6
5.1
4.0
3.4
3.0
3.0
2.9
3.6
3.8
3.8
4.9
4.6 >'
4.5
3.9
28
-------
Figure 7
DIURNAL TRANSECT DATA
POTOMAC ESTUARY (o^WOODROW WILSON BR.
AUGUST 9-10, 1977
DO
Transect
_[ Range
0 Transect
Mean
A Mid Channel, Surface
ADO = 5 Mg/1
I2 I 2 3 4 5 6 7 8 9 10 II I2 I 2 3 4 5 6 7 8 9 10 II 12
I
-------
Figure 8
DIURNAL DO DATA
WOODROW WILSON BR.
Tidal & Diurnal Effects
in Harmony
Opposing Tidal &
Diurnal Effects
Surface
8
Smooth Approximation
Bottom
Daylight
Darkness
Daylight
11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 2 34 5 6 78 9 10 11 12
Flood I Ebb I Flood I Ebb
30
-------
Table 7
COMPARISON OF SURFACE AND BOTTOM DO
Date Time
8/09 1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
8/10 0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
POTOMAC ESTUARY - 1977
WOODROW WILSON BRIDGE
Surface
Chloro DO
(ug/1) Tide (mg/1)
60 t 4.7
1 5.5
80 1 6.9
^ 7.7
75
>
130
90
.c
.c
LL.
80
70
>
i
9.2
f 5.8
K 6.8
8.3
6.7
6.0
5.5
4.9
5.0
t
3.8
95 o 3.0
o
[I 1.7
100
90
/
80
-C
j£
U
45
>
2.0
2.4
2.4
2.5
1.8
] 2.8
0.8
3.7
ADO* 6.0
Avg. 4.5
31
Bottom
DO Depth
(mg/1 ) (feet)
1.9 15
1.3
1.7
3.4
1.1
3.8
3.0
2.2
3.0
6.5
2.1
1.1
2.3
2.0
2.5
2.4
2.7
4.0
3.3
2.8
2.2
1.5
1.0
1.0 ^
2.5
2.5
-------
Figure 9
DIURNAL TRANSECT DATA
POTOMAC ESTUARY (a) FORT WASHINGTON
AUGUST 10-11, 1977
13.0 12'4 12.7
10
8
40.-
20
1.2
1.0
.8
.6
S
T
O
R
M
Transect
J_ Range
9 Transect
Mean
A Mid Channel, Surface
ADO = 4 Mg/1
Chioro a
TPO,,
Flood
Ebb
Flood
Ebb
I 2 3 4 5 6 7 a 9 10 II 12 I 2 3 4 5 6 7 8 9 10 II 12
8/10 Hours 8/11
32
-------
Figure 10
DIURNAL DO DATA
FORT WASHINGTON
Tidal & Diurnal Effects
in Harmony
Opposing Tidal &
Diurnal Effects
Surface
Smooth Approximation
o
a
Bottom
Daylight
Darkness
Daylight
11 12 13 14 15 16 17 18 19 20 21 22 23 24 1 2 3 4 5 6 7 8 9 10 11 12
Flood | Ebb | Flood | Ebb
33
-------
TABLE 8
COMPARISON OF SURFACE AND BOTTOM DO
Date Time
8/10 1200
1300
1400
1500
1600
1700
1800
1900
2200
2300
2400
8/11 0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
POTOMAC ESTUARY - 1977
FORT WASHINGTON
Surface
Chloro DO
(wg/l) Tide (mg/1)
60 6.3
>
45
5.6
7.6
-a
§ 8.0
60 C 7.6
70
/
60
7.1
r 8.5
8.8
5.2
-Q c r
.a 0.5
1 1 i
55
>
/
45
5.0
( 5.5
5.5
-o 6.6
o
60 ° 3.5
1 1
50
-
45
6.1
5.8
7.1
4.9
5.3
-Q
40 £ 4.5
[ 3.8
Bottom
DO Depth
(mg/1) (feet)
2.4 45
3.2
3.2
3.1
4.1
5.8
3.8
4.2 1
2.9 30
3.5 45
3.6
3.8
3.9
3.3
4.2
4.8
5.2
5.0
4.5
4.1
3.8
4.3
8/30
0600
BROAD CREEK
120
ADO-
Avg.
34
3.1
4.0
6.0
4.0
2.0
4.0
20
-------
in late afternoon to about 2 mg/1 just before dawn. The mean sur-
face DO was 4.5 mg/1, and the mean bottom DO was 2.5 mg/1. The
average chlorophyll level was 80 ug/1.
c) In the case of Fort Washington, a classical
diurnal DO pattern could not be discerned in the transect mean
surface, or bottom data. (See Figures 9 and 10 and Table 8.)
The former exhibited a total variability ranging between 4-8 mg/1,
and the latter a range from 2.5-5 mg/1. The variability pattern
of both the surface and bottom data were quite similar. The mean
surface DO was 6.0 mg/1, and the mean bottom DO was 4.0 mg/1. The
average chlorophyll level was 55 ug/1.
It is important to recognize that two separate phenomena
are the major factors influencing the DO concentrations described
above: tidal action, and the algal photosynthesis/respiration cycle;
moreover, these processes, at certain times, will work in harmony
(i.e. be complementary), while at other times, they will be opposing.
An attempt was made to at least discern, if not quantitate, their
individual effects. (See Table 9.) Examination of longitudinal
DO gradients at the surface during slack water runs, and a comparison
of the observed DO variability at both surface and bottom waters (in
light of what was considered to be typical tidal variations), leads
to the conclusion that at the first two stations (1) algae produce
a large diurnal cycle in surface waters which exceeds the local
tidally influenced DO variations, and (2) this diurnal cycle is
undetectable in bottom waters where the tidal influence alone
accounts for practically all of the variability. It can be inferred
35
-------
TABLE 9
ANALYSIS OF DIURNAL DO DATA
POTOMAC ESTUARY
Station
Mains Point
Transect Mean
Surface
Bottom
Woodrow Wilson Bridge
Surface
Bottom
Fort Washington
Surface
Bottom
Rosier Bluff -
Swan Creek
Surface
Rosier Bluff -
Piscataway Creek
Surface
Summary
Chloro
(ug/1)
65
65
65
80
80
55
55
80
ADO
(mg/1)
3.0
4.5
4.5
6.0
2.5
4.0
2.0
Remarks
4.0
Algal influenced,
Algal influenced.
Tidal influenced,
Algal influenced.
Tidal influenced.
Algal influenced,
Random variation.
Algal influenced.
135 8.0 Algal influenced.
60-135 4-8
36
-------
that the vertical mixing time is of sufficient length to either
dampen out the diurnal cycle entirely, or to transmit it out of
phase with the surface at a decreased magnitude. At the third
station, it appears that tidal action constitutes the dominating
force, with respect to diurnal DO fluctuations.
C. Algae
1. Chlorophyll levels were highly variable, both over
time and space. Maximum concentrations of about 300 ug/1 were
recorded during one week in August between Gunston Cove and Indian
Head. Average values in the critical reach (between Dogue Creek
and Deep Point), were about 150 ug/1, and minimum values were less
than 100 ug/1. (See Figure A-2.)
2. Algal mats, floating on the surface of the Potomac
Estuary, were never observed during the course of this study, as
they were during the late 1960's; however, the greenish tint was
present in the high bloom areas extending from about the Woodrow
Wilson Bridge to Sandy Point. The indigenous forms of freshwater
algae this past summer appeared to be almost microscopic in size,
and well dispersed in the water column.
3. A bloom of marine algae, which imparted a "mahogany
tide" condition, was observed during the first week of the study
in the higher saline waters near the Route 301 Bridge. Chlorophyll
levels within the bloom peaked at about 400 ug/1.
4. Phytoplankton counts and species identification were
performed. During the early phase of the survey, when chlorophyll
levels were about 100 ug/1 or less, there appeared to be some
37
-------
diversity in algal populations, as both green and blue-green
varieties were observed; however, as the study progressed, and
chlorophyll levels attained their peak values, the blue-green algae
Oscillatoria became the dominant form, almost to the complete exclu-
sion of the other forms observed earlier. This behavior could
possibly be explained by the fact that Oscillatoria grow in long
strings, making it difficult for zooplankton to feed on them.
Assuming that other forms of algae are depleted due to continual
grazing by zooplankton, Oscillatoria would no longer have to compete
for the available nutrients. This would permit them to proliferate
greatly. Actual cell counts at this time were in the range of
70,000 to 90,000 per ml. Anacystis cyanea, the dominant form of
algae inhabiting the Potomac Estuary during the 1960's, was not
present to any noticeable degree.
5. An interesting situation, which warranted special atten-
tion, occurred between August 24, and September 8, when algal levels
declined drastically (as evidenced by a chlorophyll reduction of 200
ug/1). During this time period, data collected from Dogue Creek
to Deep Point showed that BOD5 concentrations increased 5-6 mg/1,
while DO concentrations decreased about 5 mg/1 (10 to 5 mg/1),
allowing for the fact that Blue Plains was exerting a greater than
usual influence upon DO on September 8,
(See Figure 11.) The effects of massive algal death and decomposition
on the DO budget may be quite significant, as indicated by this
data.
38
-------
Figure 11
8
cB
0
o
03
I
O
a
a
o
CO
10
9
8
7
6
5
4
3
2
1
0
10
9
8
7
6
5
4
3
2
1
CHLORO a, BOD, & DO TIME PLOTS
POTOMAC ESTUARY - 1977
Dogue Creek — Hallowing Point
•V
•\
A Chloro 3 200 pig/11 \
A B0D 5 6 Mg/1 | \
A 00 s*5Mq/1 1 *
Indian Head — Deep Point
pO...
V/^
—.' \?s
A Chloro = 200/zg/1 |
A B0D = 5 Mg/1 f
s»5Mg/1 |
1 I i 1 1 t
300
200
100
5
o
loi
I
-------
6. Two separate and independent methods were used to esti-
mate a relationship among nitrogen and phosphorus utilization (in-
organic forms), algal content of carbon nitrogen and phosphorus
(organic forms), and chlorophyll a_. One method was based on an
analysis of the field data which emphasized spatial differences in
nutrient levels, while the other was based on an actual composition
analysis of the algal cells in the laboratory. The conclusions drawn
were as follows:
a) The mean ratio between organic nitrogen and chloro-
phyll indicated by the field data was 0.0028 mg N/ug Chloro, with a
standard deviation of 0.0008 mg N/ug Chloro. This ratio becomes
0.0056 mg N/ug Chloro if a 50% nitrogen recovery rate is assumed
for the analytical procedure followed in the laboratory. The mean
ratio between organic phosphorus and chlorophyll, also obtained from
field data, was 0.0019 mg PO./ug Chloro, with a standard deviation
of 0.0004 mg PO^/ug Chloro. (See Table 10 and Figures 12 and 13.)
b) Compositing selected inorganic nitrogen and phosphorus
field data as a function of chlorophyll, yielded typical ratios of
0.01 mg N/ug Chloro, and 0.0011 mg PQJug Chloro, respectively.
(See Table 11 and Figures 12 and 13.)
c) Ten different laboratory analyses of the algal cells
for elemental composition provided a range of data as shown below:
OrgC: Chloro - 0.012 - 0.037
OrgN: Chloro - 0.003 - 0.013
- 0.007
Org P: Chloro - 0.001 - 0.003
(average = 0.002
40
-------
RELATIONSHIP BETWEEN
Date
7/18
7/20
7/25
7/27
8/03
8/22
8'24
8/29
8/31
9/06
3/08
Station
7
8
10
8A
9
10
10B
11
6
7
5A
6
7
8
8A
9
10
10B
6
7
8
8A
9
10
10B
11
12
5A
6
7
8
8A
9
10
108
11
12
13
6
7
8
8A
9
10
10B
11
8A
9
10
10B
11
12
13
14
10
10B
11
*Assume 50% "ecovery
ORGANIC
N & P AND
CHLORO A
POTOMAC ESTUARY
Chloro
(mg/1)
147
132
104
110
123
118
129
120
112
104
124
104
130
169
172
276
306
264
284
198
139
147
261
306
303
312
228
168
118
122
129
152
180
190
261
300
294
200
158
111
111
134
176
188
172
195
171
148
104
146
180
130
180
186
146
254
188
100
130
120
A 1
Org *
N
(mg/1 )
0.83
0.44
0.32
0.25
0.30
0.28
0.35
0.23
0.29
0.33
0.24
0.28
0.41
0.56
0.79
1.10
0.89
0.87
0.54
0.27
0.66
0.70
0.99
1.09
1.05
0.81
0.57
0.52
0.46
0.61
0.74
0.85
0.90
0.77
0.55
0.28
0.24
0.33
0.23
0.40
0.40
0.56
0.40
0.62
0.43
0.38
0.45
0.23
0.37
0.30
0.25
Org
P04
("3/1 ?
.18
.16
.23
.25
.28
.22
.25
.29
.21
.27
.29
.30
.29
.29
.30
.42
.46
.44
.42
.35
.30
.32
.39
.41
.50
.43
.35
.30
.19
.25
.23
.31
.30
.41
.49
.44
.50
--
.25
.21
.24
.32
.37
.37
.42
.40
.33
--
.19
.22
.30
.20
.34
.33
.28
.30
--
.21
.28
.24
Max
Mm
Mean
Std Dev
Ma N*
Mg Chloi
.0056
.0033
.0029
.0020
.0025
.0022
.0029
.0021
.0028
.0027
.0023
.0022
.0024
.0033
.0029
.0036
.0034
.0031
.0027
.0019
.0045
.0027
.0032
.0036
.0034
.0036
.0034
.0044
.0030
.0034
.0039
.0033
.0030
.0026
.0028
.0018
.0022
.0030
.0017
.0023
.0021
.0033
.0021
.0036
.0029
.0026
.0025
.0018
.0021
.0016
.0010
.0056
.0010
.0028
.0008
.0012
.0012
.0022
.0023
.0023
.0019
.0019
.0024
.0019
.0026
.0023
.0029
.0022
.0017
.0017
.0015
.0015
.0017
.0015
.0018
.0022
.0022
.0015
.0013
.0017
.0014
.0015
.0018
.0016
.0020
.0018
.0020
.0017
.0022
.0019
.0015
.0017
.0016
.0019
.0022
.0024
.0020
.0020
.0024
.0021
.0019
.0018
.0015
.0017
.0015
.0019
.0018
.0019
.0012
.0021
.0022
.0020
.0029
.0012
.0019
.0004
-------
TABLE 11
RELATIONSHIP BETWEEN
INORGANIC N & P AND CHLORO
Date
7/20
7/27
8/01
8/03
8/22
8/24
8/29
8/31
9/06
Reach
(Stations)
6-11
5- 9
7-11
5- 8
5-8A
8A-11
5- 7
7-10B
6- 8
4- 6
5-1 OB
5-10B
4- 7
5A-10B
5A- 8
5-10B
3- 7
5-11
POTOMAC ESTUARY
Chloro
(mg/1)
90
90
120
50
50
70
50
100
100
90
180
200
80
150
60
100
60
100
A
AN
(mg/D
.9
1.0
.8
.8
.5
1.0
1.0
1.8
1.9
1.6
1.7
1.7
AP
(mg/D
.10
.04
.06
.06
.05
.06
.05
.08
42
-------
-------
Figure 13
PHOSPHORUS — CHLOROPHYLL RELATIONSHIP
POTOMAC ESTUARY - 1977
Field Data
OrgP
x Lab Data
O Field Data - Inorg P
0 TR#35
100
Chloro a_-
44
-------
For the sake of comparison, the average values of
these ratios, which were contained in Technical Report 35 and were
based on laboratory findings, are given as follows:
0.045
0.010
mg Chloro
mg N
mg Chloro
n 003 mg P0d
u>UUi:i ug ChToro
d) The variability encountered in the 1977 phosphorus-
chlorophyll ratio data, depending upon whether the organic or
inorganic fraction is used, may be attributable to either analytical
inaccuracies or, possibly, some form of recycling process.
7. Algal bioassays that were developed by Dr. George
Fitzgerald, University of Wisconsin, were run on Potomac Estuary
samples. Phosphorus related bioassays (i.e. luxury PO^ uptake
and alkaline phosphatase) indicated that this nutrient was not rate
limiting algal growth, but rather, that a surplus might have existed,
The data obtained from the nitrogen related bioassay (i.e. ammonium
uptake rates in the dark) was somewhat inconclusive, but did indi-
cate that inorganic nitrogen was approaching a limiting situation
during the latter phase of the study.
8. A laboratory experiment (acetylene reduction) was
performed near the end of the survey to determine if the blue-green
algae in the Potomac were fixing atmospheric nitrogen (this was a
definite possibility, since inorganic nitrogen concentrations in the
water column were almost non-existent); the results of the test,
however, were negative.
45
-------
D. Nutrients
1. Maximum NhU concentrations generally varied from about
1.0 to 1.5 mg/1, and invariably occurred in the immediate vicinity
of Blue Plains. (See Figure A-3.) The dramatic decrease in NH3
to virtually undetectable levels, accompanied by a comparable increase
in N02 + N03 over a ten mile stretch of river, indicated that
nitrification was proceeding at a rapid rate because of the high
ambient temperatures.
2. The NOo + NCL nitrogen form peaked in the area of
maximum nitrification (below Blue Plains) at a level between 1.5 -
2.0 mg/1. (See Figure A-4.) Farther downstream, the concentrations
diminished greatly because of algal uptake or other biological
utilization.
3. As expected, significant quantities of both soluble and
particulate forms of organic nitrogen were present in the Upper
Potomac Estuary throughout the study period.
4. Several forms of phosphorus were measured, with the
most notable ones being total phosphorus, and filtered inorganic
(reactive) phosphorus. With the exception of the September 8 run,
TPO^ concentrations were relatively constant in the estuary down-
stream of Blue Plains varying between 0.5 and 0.8 mg/1. (The
latter figure was obtained when a maximum algal bloom was present.)
(See Figure A-5.) The filtered Pi was more variable (0.1 - 0.3 mg/1)
on a spatial basis, but did not behave as expected. Instead of
diminishing to reflect its utilization by phytoplankton, concentra-
tions generally increased in a downstream direction regardless of
46
-------
ambient algal bloom conditions. (See Figure A-6.) Data collected
by the USGS during a similar time period confirmed this distribution
of reactive phosphorus in the Upper Potomac Estuary.
5. Maximum phosphorus concentrations, occurring in the
Upper Potomac Estuary near Blue Plains, showed a substantial decrease
(>50%) in 1977 over previous years, when levels ranging between
1.5 to 3.0 mg/1 were experienced. Inorganic nitrogen, on the other
hand, did not exhibit a well defined trend in either direction
within this same reach.
6. Concentrations of total inorganic carbon generally
varied from about 20-30 mg/1, with no particular spatial or temporal
pattern evident. Even when maximum algal levels were encountered,
inorganic carbon levels persisted above 20 mg/1, leading one to
believe that this nutrient is extremely abundant in the Potomac
Estuary and does not have growth rate limiting consequences.
7. An analysis of the spatial distribution of nutrients
and chlorophyll (i.e. phytoplankton densities) in the Potomac
Estuary, indicates that the inorganic nitrogen may be limiting algal
growth in the area of maximum production (downstream of Hallowing
Point), since concentrations of both NH3 amd N03 become non-detectable
as bloom conditions progress. It is suspected that light may be
the limiting factor in the upper zone (i.e. upstream of Piscataway
Creek), where considerably lower chlorophyll levels are normally
found.
8. There is no indication, based on the observed water
quality monitoring data, that phosphorus is a rate limiting nutrient
47
-------
at the present time. The fact that inorganic (soluble) phosphorus
concentrations actually experienced an increase in areas of algal
bloom production indicates that recycling/regeneration or possible
recruitment from the benthos may be important reactions which should
be further investigated.
E. BOD
1. Maximum BOD5 concentrations in the vicinity of Blue
Plains ranged from about 8-12 mg/1. A BQD5 of 10 mg/1 was also
measured in the area of a peak algae bloom on August 29. (See
Figure A-7.)
2. Long term (e.g. 20 days) inhibited and non-inhibited
BOD analyses were performed on many of the river samples in order to
approximate the first order decay or oxidation rates for both the
carbonaceous and nitrogenous components. The mean rates provided
by this study are as follows:
CBOD - 0.14/day (base e - 20°C) (Std. Dev. = 0.023)
NBOD - 0.14/day (base e - 20°C) (Std. Dev. = 0.053)
3. The CBOD rates were also estimated for the major load
inputs to the estuary. The average value for the wastewater
effluents was 0.17/day (base e - 20°C), and that for the Chain
Bridge station was 0.13/day (base e - 20°C). The standard devia-
tions were 0.046 and 0.026, respectively.
4. A sizeable percentage of the BOD5 measurement for the
wastewater effluents was attributable to the nitrification reaction.
Consequently, the ratios of CBODult/BOD5> and CBODult/CBOD5 were
significantly different. The results of this special long term
48
-------
rate study indicated these ratios to be 1.30 and 1.75, respec-
tively.
F. Estuary Loadings
1. Blue Plains is by far the largest single point source
discharger of oxygen demanding material and nutrients in the Potomac
Estuary. (See Table 12) During the study period, it contributed
an average flow of 276 mgd, and the following average loadings:
% of Total Point Source
Parameter Average Loading Wastewater Load
BOD5 58,000 Ibs/day* 78*
TKN 36,500 Ibs/day 75
NH3 32,500 Ibs/day 76
N02 + N03 250 Ibs/day 14
TP04 12,200 Ibs/day 55
2. For comparison, the average pollutant loadings from
Blue Plains in 1970, based on an average flow of 252 mgd, were
estimated to be as follows:
% of Total Point Source
Parameter Average Loading Wastewater Load
BOD5 104,000 Ibs/day 75
TKN 46,200 Ibs/day 85
N02 + N03 2,000 Ibs/day 55
TP04 52,000 Ibs/day 75
3. The non-tidal portion of the Potomac River continues
to be a significant contributor of BOD and certain nutrients to
the estuary. This is demonstrated by the relatively high average
*0n September 8, 1977, a mechanical breakdown occurred at the Blue
Plains treatment plant, causing a BODc loading of 344,000 Ibs/day.
If this loading were included in the analysis, the average BODc load
would be 82,000 Ibs/day,which constitutes 85% of the total point
source BODr load generated by the Washington Metropolitan Area.
-------
TABLE 12
SUMMARY OF SEWAGE TREATMENT PLANT EFFLUENT DATA
Flow
(mgd)
TC
(mg/D
TOC
(mg/0
TP
(mg/1)
Pi
(nig/I]
TKN
(mg/1;
NO, + NO,
NH-j
(mg/1!
BODr
(ma/1)
BOD™
(mg/T)
Turbidity
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
Max.
Mean
Min.
'lax.
Mean
Min.
Max.
Mean
Min.
Max.
1977 POTOMAC INTENSIVE
^
ID
3
a
0
21
11.91
7.50
16.00
43.97
29.15
87.03
12.66
6.72
28.37
2.98
1.96
5.00
2.36
1.72
4.07
6.00
4.01
12.90
4.73
1.74
6.77
4.53
2.33
12.90
6.57
0
17.40
c
o
+J
en
c
•£
-------
concentrations of these pollutants measured at the Chain Bridge
station during the study period, as shown in the table below:
Parameter
BOD5
DO
TKN
Org.-N
NH
N0
TP0
Average
Concentration
(mg/1)
2.58
7 41
/ • " I
.49
.46
.03
.03
.25
.04
02
* \JL.
32.28
5.43
42.88*
Standard
Deviation
(mg/1 )
.77
4fi
. *TU
.10
.10
.03
.04
.04
.05
0?
« Uc.
2.60
3.30
23.20*
Average
Loading
(Ibs/day)
2,358
444
415
29
25
230
40
28,533
4,693
41
Inorg. PO.
Filt. Inorg. P04
TC
TOC
Chlorophyll a^
4. Storm sewer and combined sewer contributions from the
WMA were estimated (order .of magnitude type) based upon the best
available information. These loads, along with the two other major
loads to the Potomac Estuary (point source and upper basin inputs),
were translated to a total poundage for the study period and are
summarized and compared in the following table:
51
-------
Flow q
Volume (ft3)
BODr (Ibs)
Total N (Ibs)
Total P04 (Ibs)
Point Source
2.4 x 109
3.7 x 106
0.8 x 106
1.1 x 106
Upper Basin
6.5 x 109
1.0 x 106
0.1 x 106
0.1 x 106
Urban
2.2 x 109
2.0 x 106
0.3 x 106
0.5 x 106
5. On September 8, the last day of the survey, Blue
Plains was discharging a very poor quality effluent, as evidenced
by a BOD5 concentration of 132 mg/1 (344,160 Ibs/day, loading).
This BODc has since been refuted by Blue Plains personnel, but USGS
field staff sampling the Potomac has corroborated the fact that on
this date, the effluent from Blue Plains was very poor. Its impact
on the receiving water quality was considerable. The BOD concentra-
tions in the estuary near Blue Plains exceeded 11.0 mg/1 on September 8,
the highest value recorded during the survey. More importantly, the
DO concentrations on this date ranged between 1.8 and 4.0 mg/1 over
a 20 mile stretch of estuary from Bellevue to Indian Head. Other
water quality parameters, such as nutrients, were also elevated
during the September 8 run.
G. Herbicides
1. Special analyses for the herbicides atrazine and simazine
were performed on samples collected at approximately every other
station in the Potomac Estuary on July 18, and August 22. These
are widely used herbicides on corn crops, which have been identified
in other areas of the Chesapeake Bay.
52
-------
a) On July 18, a day following a rainfall event of 0.25
inches, maximum concentrations of both atrazine and simazine occurred
between the Woodrow Wilson Bridge and Dogue Creek. The levels
varied from .84 - 1.15 ug/1 and .49 - .78 ug/1, respectively. The
incoming concentrations at Chain Bridge were .46 ug/1 and .34 ug/1,
respectively.
b) On August 22, following an extended dry period,
atrazine and simazine concentrations were considerably lower in the
estuary: 0.4 - 0.5 ug/1, and 0.3 - 0.4 ug/1, respectively. Again,
maximum levels were recorded in the upper portion of the estuary near
and below Washington. Concentrations at Chain Bridge did not change
radically with atrazine being 0.38 ug/1 and simazine, 0.33 ug/1.
c) Atrazine and simazine were also monitored in the
effluents of the major sewage treatment plants and at Chain Bridge
on July 11. The results are shown in the table below:
Atrazine Simazine
Location (ug/1) (ug/1)
Piscataway STP .75 .38
Arlington STP 1.21 .54
Blue Plains STP 1.72 .55
Alexandria STP 1.08 .52
Westgate STP .26 .28
Hunting Creek STP .70 .10
Dogue Creek STP 1.06 .19
Pohick Creek STP 1.39 .52
Chain Bridge .92 .49
53
-------
The comparatively high values recorded at Chain
Bridge may have been due to a 0.43 inch rainfall which occurred on
July 9. The reason for the even higher values at most of the sewage
treatment plants has not been adequately determined.
54
-------
-------
CHAPTER IV
FUTURE STUDY NEEDS
In addition to a continued ambient monitoring program in
the Potomac, forthcoming intensive studies to be conducted by AFO
will include the following elements to rectify present data gaps:
a) Expanded drogue studies to include 24
hour sampling at both surface and bottom.
b) Improved delineation of the BOD load
to include not only the carbonacenous
and nitrogenous components,but the
algal components as well.
c) Use of a photometer/transmissometer to
better define the euphotic zone in the
Upper Potomac Estuary.
d) Further SOD studies to extend the area
of coverage and to obtain a better
resolution of the data.
Another future study need concerns an improved definition
of the phosphorus budget and the role of suspended sediment as a
contributor of and a transport media for different forms of
phosphorus. Other reactions which should be considered and inves-
tigated in more detail as part of the phosphorus budget include
recycling and remineralization, both within the water column as
well as at the water sediment interface. This study, however, is
presently beyond the capabilities of AFO.
55
-------
-------
APPENDIX
-------
-------
Figure A-l
DO ISOPLETH (Mg/1)
POTOMAC ESTUARY - 1977
_o
"3
m
I
S
55
50
45
40
35
30
25
20
15
10
16 18 202224262830 1 3 5 7 9 11 13151719212325272931 2468
July August Sept.
56
10
-------
Figure A-2
CHLOROPHYLL_a_ ISOPLETH (pg/1)
POTOMAC ESTUARY - 1977
100
16 18 202224262830 1 3 5 7 9 11 13151719212325272931 2 4 6 8 10
August Sept.
57
-------
Figure A-3
NH3ISOPLETH
POTOMAC ESTUARY - 1977
00
.£
£
u
&
I
55
50
45
40
35
30
25
20
15
10 '
5 -
i i i i
i i i i
0
16182022242628301 357 9111315171921232527293124 6 8 10
July August Sept.
58
-------
Figure A-4
N02 + N03ISOPLETH(Mg/1)
POTOMAC ESTUARY - 1977
I
i
' ' i. . ' ' '—I—I—I—I
16182022242628301 357 9111315171921232527293124 6 8 10
July August Sept.
59
-------
Figure A-5
TP»ISOPLETH(Mg/1)
POTOMAC ESTUARY - 1977
w
e
ca
Ji
55 r
20
15 -
16182022242628301 357 9111315171921232527293124 6 8 10
July August Sept.
60
-------
Figure A-6
FILTERED Pi »ISOPLETH (Mg/1)
POTOMAC ESTUARY - 1977
55
60
45
40
35
m 30
~S
m
i
25
20
10
i j i i i i i i i i i i i i i i i i i i i i i i i i I
16182022242628301 357 9111315171921232527293124 6 8 10
.AsP04 -»"'V August
61
-------
Figure A-7
BOO ISOPLETH (Mg/1)
POTOMAC ESTUARY - 1977
CO
e
1
u
3
i
5
4 V. _.
16182022242628301 357 9111315171921232527293124 6 8 10
July August Sept.
62
-------
TABLE A-l
Summary pf 1977 Potomac Estuary Data
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