Sources of Oxygen Demand in the
Lower San Joaquin River, California
P. W. Lehman,
J. Sevier, J. Giulianotti & M. Johnson
California Department of Water Resources
122 20’ N
122 00’ N
121 40’ N
121 20’ N
Sacramento
CALIFORNIA
38 20’ W
38 00’ W
Carquinez straight
Antioch
Stockton
Mossdale
San Francisco Bay
Current situation:
There has been little change in
dissolved oxygen concentration in the
channel despite enhanced management
and a decrease in phytoplankton biomass
Percent
Frequency of values below 5 mg l-1
100
90
80
70
60
50
40
30
20
10
0
Aug
Oct
1970 -1979
Sep
Nov
1980 - 1989
Aug
Oct
1990 - 1999
Chlorophyll a decreased over time in the
channel
Chlorophyll a µg l
-1
80
Rough and Ready Island
70
60
50
40
30
20
10
0
70
75
80
85
year
90
95
2000
Question:
What are the primary sources of
oxygen demand in the Deep Water
Channel near Stockton?
Study Methods
biweekly or monthly sampling
July - November 2000 & 2001
discrete variables:
Primary productivity : in situ dissolved oxygen
light and dark bottle technique
Nutrient concentrations
chlorophyll a and phaeophytin concentration
BOD tests
continuous variables
vertical profiles with YSI 6600 sonde
continuous flow
continuous water quality
MC DONALD
ISLAND
121o 20’ N
TC
80o 00’ W
STOCKTON
San Joaquin River
Deep Water Channel
RR
L48
TB
CP
ROBERTS
Water Treatment
Plant
Rough and Ready
Island
ISLAND
Middle River
N
MD
4 km
TC Turner Cut
RR Rough and Ready Island
L48 Navigation Light 48
TB Turning Basin
CP Channel Point
MD Mossdale
VN Vernalis
San Joaquin River
VN
Findings
Dissolved oxygen in DWSC
mg/L
15
2001
10
5
0
1-Jun
1-Jul
31-Jul
30-Aug
Date
29-Sep
29-Oct
Dissolved oxygen upstream
MD
mg/L
15
2001
10
5
0
01-Jun
01-Jul
31-Jul
30-Aug
Date
29-Sep
29-Oct
Oxygen depletion was not caused by
stratification
Dissolved Oxygen mg/L
Temperature oC
20
2
4
6
8
10 12 14
22
24
Specific Conductance
mS/cm
26
0
0
0
0
2
2
2
4
8
6
Depth m
6
4
Depth m
Depth m
4
8
6
8
10
10
10
12
12
12
14
14
18-Jul
14
0.5
1
Oxygen demand was not caused by
phytoplankton respiration
net oxygen demand
oxygen demand mg/L
0.80
phytoplankton
bacteria
0.40
0.00
-0.40
-0.80
26-Jun
18-Jul
16-Aug
29-Aug
Date
14-Sep
3-Oct
Oxygen demand was caused by
nitrification
2001
mg/L oxygen
8
TBOD
NBOD
CBOD
6
4
2
0
26-Jun
25-Jul
16-Aug
Date
5-Sep
3-Oct
Pearson Correlation Coefficients
(n=103)
TBOD & NBOD
0.86
NBOD & ammonia
0.93
NBOD & organic N
0.34
TBOD & ammonia
0.78
TBOD & CBOD
0.62
TBOD & chlorophyll
0.59
Stepwise Regression
Dissolved ammonia + carbonaceous BOD
60%
30%
Year
n
R2
2000
100
0.91
2001
85
0.73
185
0.83
2000 + 2001
Where does the
ammonia come from ?
NBOD was correlated with ammonia load
from treatment plant
Ammonia load RWCF kg/day
4500
r = 0.74
4000
3500
3000
2500
2000
1500
1000
500
0
0
1
2
3
NBOD
4
5
6
NBOD at Rough and Ready varied with the
ammonia load from the treatment plant
6
5000
5
4000
4
3000
3
2000
2
1
1000
0
4-Jun
0
4-Jul
3-Aug
Date
2-Sep
RWCF NH4-N
(lbs/day)
NBOD10 mg/L
Rough and Ready
2-Oct
RR
RWCF
Total nitrogen load was higher from
upstream
Mossdale (MD)
waste treatment plant
3000
TKN load kg d
-1
2500
2000
1500
1000
500
0
June
July
August
Month
September
October
Mass Balance
Model
Object: Determine the largest source of
dissolved ammonia in the channel
Simple mass balance model
Daily dissolved ammonia load into the ship channel
from the treatment plant and upstream
=
1) daily load of dissolved ammonia from each source
+
2) daily load of dissolved ammonia from the oxidation
of the organic nitrogen load from each source
+
3) daily load of dissolved ammonia from the oxidation
of residual organic nitrogen from previous day from
each source
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
chlorophyll a ug l
-1
200
150
100
50
0
0
5
10
15
Day
20
25
30
ammonia mg l
chlorophyll a
ammonia
Log. (ammonia )
-1
Ammonification rate
Upper boundary condition:
all organic nitrogen oxidized at ammonification rate for
chlorophyll (highest rate)
Median percent
Waste treatment plant
Mossdale
70
60
50
40
30
20
10
0
1
5
10
15
Residence time days
20
25
percentage
Chlorophyll was a small percent of the
organic nitrogen load
45
40
35
30
25
20
15
10
5
0
27-Jun
18-Jul
25-Jul
1-Aug
16-Aug
date
29-Aug
14-Sep
3-Oct
Lower boundary condition:
only the organic matter associated with live chlorophyll
was oxidized
Median percent
Waste treatment plant
Mossdale
70
60
50
40
30
20
10
0
1
5
10
15
Residence time days
20
25
Summary
• Oxygen demand in the channel was primarily caused
by nitrification
• The treatment plant could be the primary cause of
nitrification in the channel on a daily basis even though
it had a small ammonia load because it was a direct
source of dissolved ammonia for bacterial oxidation
• The relative contribution of ammonia from the
treatment plant and upstream to ammonia in the
channel was a function of residence time,
ammonification rate, direct loads and load composition
Take home message
The oxygen demand produced from the direct load
of dissolved ammonia from the treatment plant
could have a greater impact on daily oxygen
demand in the channel than the oxidation of
organic nitrogen from upstream because of the
slow oxidation rate and low reactivity of upstream
organic matter
Net transport of phytoplankton mass
decreased downstream
80
Mossdale
Channel Point
chlorophyll ug l
-1
70
60
50
40
30
20
10
0
18-Jul
1-Aug
16Aug
29Aug
Date
14Sep
3-Oct
chlorophyll a
Net
Percent
transport retention
kg d -1
%
organic nitrogen
Net
Percent
transport retention
kg d -1
%
ammonia
Net
Percent
transport retention
kg d -1
%
total BOD
Net
Percent
transport retention
kg d -1
%
Week
3-Jun
49
91
903
50
-61
-17
7489
61
10-Jun
25
89
988
64
72
20
6287
69
1-Jul
8
19
-389
-37
8
1
-206
-1
12-Aug
8
27
-181
-11
418
32
-1166
-11
19-Aug
28
85
1054
77
787
69
8025
73
9-Sep
13
51
791
37
333
44
4166
37
16-Sep
41
77
1226
49
782
50
4638
34
7-Oct
32
47
1112
47
3056
84
10186
52
median
27
64
946
48
375
38
5462
44
10th
percentile
8
19
-389
-37
-61
-17
-1166
-11
90th
percentile
34
86
1068
54
783
55
7623
63
Model
residence
MD
10th
90th
WTP
10th
90th
Significant sample
time
median percentile percentile median percentile percentile difference
size
day
percent
percent
level
n
1
38
16
52
62
0
72
< 0.01
102
5
49
40
56
51
18
56
ns
20
10
55
42
57
45
29
49
< 0.02
10
15
61
45
61
39
35
46
< 0.04
7
20
58
50
62
42
33
46
< 0.04
5
25
58
56
59
42
38
43
ns
4
1
34
6
47
66
0
83
< 0.01
102
5
38
15
47
62
35
70
< 0.01
20
10
43
26
45
57
46
69
< 0.01
10
15
42
31
46
58
46
64
< 0.02
7
20
38
35
45
62
48
63
< 0.05
5
25
41
34
44
59
49
61
ns
4
Run 1
Run 2