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REMOTE SENSING OF MUNICIPAL WASTEWATER
MARINE DISCHARGES
DEMONSTRATION PROJECT
Remote Sensing Operations Branch
Remote Sensing Division
Environmental Monitoring and Support Laboratory
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
DECEMBER 1978
HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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REMOTE SENSING OF MUNICIPAL WASTEWATER
MARINE DISCHARGES
INTRODUCTION
The Environmental Monitoring and Support Laboratory in Las Vegas, Nevada has developed
a remote sensing system consisting of an airborne multispectral scanner (MSS) and an aerial
camera that can address many environmental monitoring requirements of the EPA. In particu-
lar, this survey system is useful for detecting, locating, and mapping industrial, municipal,
and agricultural wastewater point and nonpoint source discharges into rivers, streams, lakes,
and harbors. The multispectral scanner is sensitive to visible, near infrared, and thermal
infrared radiation from the ground surface, thus it is capable of mapping the surface tem-
peratures and relative turbidity levels of the discharged waters and their associated plumes.
The aerial camera, with standard color reversal film, is sensitive in the visible portions
of the electromagnetic spectrum thereby providing the ability to locate and map turbid waste
discharges.
To test and demonstrate this technique for remote monitoring of municipal wastewater
marine discharges, the Laboratory acquired airborne MSS imagery and color aerial photography
over two municipal waste treatment sites in Boston Harbor, from an altitude of 1981 meters
(6500 feet) above ground (sea) level on July 25, 1978. The two sites were: the Deer Island
Treatment Plant in Winthrop, Massachusetts and the Nut Island Treatment Plant in Quincy,
Massachusetts (see the Boston Harbor map and Figures 1 and 2).
DISCUSSION
The two color aerial photographs (Figures 1 and 2) show the location and mixing zones of
the active wastewater discharges. Figures 3 and 4 present two multispectral scanner images
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showing surface water temperature patterns produced from the scanner's thermal channel
{8-14um), and relative turbidity levels in the harbor waters using a "green sensitive"
channel (0.50-0.55um). Table 1 briefly describes the principal characteristics of the
plant discharges shown in the previous images.
To produce the thermal image, land and water areas were separated in the digital pro-
cessing using the MSS channels 10 (0.92-1.10um) and 11 (8.00-14 .OOum). Water surface tem-
peratures were level sliced and color-coded, while land surface areas were colored in shades
of gray. Relative temperatures are displayed in 0.5°C increments. No absolute temperature
can be inferred as all temperatures are relative to the coldest water surface in the image
area at waste water discharge points 001 through 004 at the Deer Island Treatment Plant.
The temperatures at these reference points were arbitrarily labeled 0°C and color-coded dark
blue. Ambient surface temperatures of the harbor waters appear to be 1.5 C to 2.0 C warmer
than at the 001-004 discharge points.
Surface temperature patterns associated with the wastewater discharges are readily
apparent in the thermal image. The areal extent and surface mixing zone from the Deer Island
discharges are vividly displayed. The three active discharges (101, 102, 103) from the Nut
Island Plant display somewhat warmer surface temperatures (+0.5 to +1.5 C) than the Deer
Island discharges, and as a result are less readily discernible in this thermal image as
they are nearer ambient harbor temperatures. Nevertheless, the overall mixing zone of the
combined discharges can be seen in this image. Due to the lower temperatures and apparent
greater volume, the mixing zone of the Deer Island discharges is much more well defined.
The scanner image displaying relative turbidity levels (Figure 4) was produced using
the same basic digital processing as used in the thermal image. Land and water areas in the
imagery were separated using channel 10 data and then, the water areas were level-sliced to
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1
1
1
1
^B
1
TABLE 1. DESCRIPTION OF MUNICIPAL WASTE TREATMENT DISCHARGES
Deer Island Treatment Plant
DISCHARGE
PERMIT
NUMBER
001
002
003
004
005
DESCRIPTION
Plant Outfall #1
Plant Outfall #2
Plant Relief #1
Plant Relief #2
Plant Relief #3
DISCHARGE
STRUCTURE
SIZE
9 by 10 ft.
6 by 6.5 ft
9 ft. D
9 ft. D
6 ft. D
DISCHARGE
DEPTH BELOW
MEAN LOW WATER
50.0 ft.
50.0 ft.
10.3 ft.
3.0 ft.
2.0 ft.
(a)
RELATIVE^ '
SURFACE
TEMPERATURE
0.0°C
n
o.o°c
o.o°c
o
0.0 C
+1 . 0°C
(b)
RELATIVE1 ;
SURFACE
TURBIDITY
5
5
4
4
4
Nut Island Treatment Plant
•
™
1
1
1
DISCHARGE
PERMIT
NUMBER
101
102
103
104
105
Relative
004 happened
(b) Relative
DESCRIPTION
Plant Outfall #1
Plant Outfall #2
Plant Outfall #3
Emergency Relief
Sludge Outfall
to the coldest water
to be the coldest in
DISCHARGE
STRUCTURE
SIZE
5 ft. D
5 ft. D
5 ft. D
5 ft. D
1 ft. D
surface in
the image;
to the least turbid water in the
DISCHARGE
DEPTH BELOW
MEAN LOW WATER
30.8 ft.
24.8 ft.
24.3 ft.
5.1 ft.
23.4 ft.
RELATIVE ^
SURFACE
TEMPERATURE
r\
+0.5°C
+1 . 5°C
+1 . 0°C
+1 . 0°C
+2 . 0°C
the image. Surface temperatures over
thus these points were
scene on an arbitrary
labeled O^C.
scale of 0 to
RELATIVE* ^
SURFACE
TURBIDITY
12+
12+
12+
4
1
points 001-
12.
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identify different surface turbidity levels and color-coded using MSS channel 4 (0.50-0.55um)
which is sensitive to the green portion of the visible spectrum. Land areas were colored in
shades of gray. Turbidity levels were less discernible in the blue, red and near-infrared
data. Since a quantitative measure of turbidity could not be made, a subjective scale for
relative levels of turbidity was established, i.e., low turbidity (0-3) moderate turbidity
(4-8), and high turbidity (9-12). The least turbid waters within the imaged area were
assigned to level 0 and colored dark green. Differentiation of the constituent suspended
materials within the waste discharges, be they organic or inorganic solids, cannot be made.
Nevertheless, the multispectral scanner is capable of detecting and locating those discharges
with varying loads of suspended materials.
In the scanner image of relative turbidity, the three operating discharges (101, 102,
and 103) from the Nut Island Plant are clearly visible and well defined. However, at the
Deer Island discharges, only a low-to-moderate level of turbidity was discernable. The
accompanying aerial photographs also show a significantly higher level of turbidity in the
Nut Island discharges; however, the turbid plume at Deer Island is more clearly defined in
the color photograph.
Analysis of the two scanner images and the aerial photographs indicates only the primary
plant outfalls appear to be in operation at the time of the aircraft overflight.
CONCLUSION
With the capability of simultaneously sensing both temperature and relative turbidity
levels in discharged waters, the multispectral scanner is a versatile monitoring system for
detecting and locating marine discharges and mapping the resultant plumes and mixing zones.
Aerial photography provides a clear picture of discharge waters with moderate-to-high levels
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of suspended materials, but would be ineffective for detecting relatively clear discharges,
even though they may be significantly cooler or warmer than the receiving water.
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Location Of
MUNICIPAL WASTE TREATMENT DISCHARGES
Boston Harbor, Massachusetts
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X 001 - Discharge Permit Number
KILOMETERS
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BOSTON HARBOR
MARINE DISCHARGES
u s
EPA
Figure 3
THERPIflL DEMONSTRATION
EMSL/LV PROJECT R80 767S
flCQUIRED 7/25/78 10:51 EOT
niTITUOE 1981 METERS A6L
J _ I I I
I I I I
KILOMETERS
RELfiTIVE TEMPERRTURF
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u s
BOSTON HfiRBOR
MflRINE DISCHflRGES
Figure 4
E P fl
TURBIDITY DEMONSTRRTION
EMSL/LV PROJECT RSO 7875
flCOUIRED 7/25/78 iO'Sl EfiT
flLTITUDE »98! METERS rtiiL
LEVELS OF TURBIDITY
8
J I I I I I I I I
KILOMETERS
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WASTE WATER DISCHARGES
Deer Island Treatment Plant
Winthrop, Massachusetts
TREATtf|KIT PtANT £
1000 2000
—
FEt I 1 Appiox.l
0 :;
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WASTE WATER DISCHARGES
Nut Island Treatment Plant
Quincy, Massachusetts
1000 2000
FEET ( Approx.)
305 610
-J "C
METERS I Approx.)
DATE OF PHOTOGRAPHY - July 25, 1978
Figure 2
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