V-/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-192 Oct. 1981
Project Summary
Treatment Effectiveness
Oil Tanker Ballast
Water Facility
Ihor Lysyj
The large, modern ballast water
treatment plant at the Valdez, Alaska,
marine terminal was studied using
specially developed chemical analyt-
ical methods to determine the effec-
tiveness of each unit process and to
characterize compositional changes in
the process stream. The studies
disclosed that the state-of-the-art
processes are generally effective in
reducing the free oil content of the oily
wastewater discharged from arriving
tankers. A reduction of more than
99.8% in the organic load of the
process stream is realized with ballast
water treatment by gravity separation,
dissolved air flotation, and retention in
polishing ponds.
Less effectively removed, however,
are the water soluble fractions of the
oily wastewaters, which often include
five priority pollutants: benzene,
toluene, ethylbenzene, phenol, and
naphthalene. Such priority pollutants
make up more than 50% of the total
organic load in the effluent from the
ballast treatment plant, and they are
discharged in significant quantities
into the receiving waters of Port
Valdez. The plant discharges approx-
imately half a metric ton of organic
carbon each day. Included in this daily
discharge are 102 L of benzene, 91 L
of toluene, 45 L of ethylbenzene/
xylenes, 27 kg of phenol, and 2.8 kg of
naphthalene.
Because benzene, toluene, and
ethylbenzene/xylenes constitute a
significant fraction of the total organic
discharge, their distribution in the
receiving waters was studied. During
the summer months, when the waters
of the fjord are stratified, the effluent
does not mix uniformly with the
receiving waters, but forms a sub-
merged field of diluted effluent. The
aromatic hydrocarbons are contained
at a depth of 50 to 70 m in a thin trap
zone that spreads horizontally as far as
2 to 3 km from the plant outfall. The
top of the trap zone moves progres-
sively farther below the surface as the
summer heating season progresses—
from 50 m in June to 65 m in
September. No aromatic hydrocarbons
were found in the fjord outside the
confines of the trap zone.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory. Cincin-
nati, OH, to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Current technology for the physical
treatment of oily wastewater is based
on gravity separation followed by air or
gas flotation and impoundment. State-
of-the-art ballast water treatment
plants are designed primarily for
removal of suspended organic matter or
water-insoluble petroleum (commonly
called "free oil"). This assessment of
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the technology's effectiveness indicates
that, when properly operated, the
treatment can produce effluents with
very low levels of free oil. The water
soluble fraction of oily wastes, however,
remains essentially unaffected by the
treatment and enters receiving waters
uncontrolled in significant amounts.
Our studies have shown that the
dissolved fraction of oily wastewaters
quite often contain five priority pollu-
tants: benzene, toluene, ethylbenzene,
phenol, and naphthalene. Because
aromatic compounds are lexicologically
important and the five principal types
found in oily wastewaters are designated
as priority pollutants by the U.S.
Environmental Protection Agency (EPA),
their role in the treatment process and
ultimate fate in the receiving environ-
ment is of prime environmental concern.
The object of this study was to
determine the capabilities and limita-
tions of a modern, state-of-the-art oily
waste treatment technology for removing
conventional and unconventional pollu-
tants, including priority toxic pollutants.
The plant selected for this study is one
of the largest on-shore oily wastewater
treatment installations. The plant is
located in Port Valdez, Alaska, in the
northernmost part of Prince William
Sound. This plant first came on stream
in August 1977, when the TransAlaska
Pipeline began operations bringing
large tankers with large volumes of
ballast to Port Valdez. The oil tankers
arrive from southern ports partially
loaded with ballast water (up to 40% of
the tanker's capacity). The latter is
discharged to the plant for treatment
and ultimate disposal into Port Valdez,
and the tankers are reloaded with
Prudhoe Bay crude from the pipeline for
shipment south. Average daily water
discharge rate of this plant is 40,000 to
45,000 m3.
The Port Valdez ballast water treat-
ment facility uses gravity separation
under quiescent aging conditions in
above-ground, 68,000-m3, steel-cone-
roof storage tanks, followed by chemi-
cally aided flocculation and a dissolved
air flotation process (with capability for
a final pH adjustment), and an effluent
impoundment basin. Final disposal of
the treated water is through a sub-
merged diffuser line laid into Port
Valdez.
The effluent from the gravity separa-
tors enters a secondary aeration flotation
process unit. This system is the effluent
recirculation type, in which a side
stream of treated water is pressurized,
aerated, and mixed with wastewater
undergoing treatment.
The separation of oil from water by
aeration was initially aided by the
addition of flocculating chemical agents
(alum and polyelectrolytes). In late
1978, the use of alum and polyelectro-
lyte was stopped, and the plant switched
to using demulsifiers. The effluent from
the secondary treatment unit enters the
holding ponds before discharge to the
receiving waters of Port Valdez. The
processing elements are sized for
treating the entire contents of the
primary separation and storage tanks
within a 36-hr period, and effluent
impounding facilities are sized to hold
the initial average flow for a mean time
of approximately 10 hr before its
discharge into Port Valdez waters.
Objectives
Objectives of this study included
determining the effectiveness of or-
ganics removal in a modern oily waste-
water treatment operation and charac-
terization of compositional changes in
the process stream. To accomplish
those objectives, it was necessary to
monitor the organic content of the
process stream in terms of the total
material balance. When the results
indicated a substantial discharge of
priority pollutants (dissolved aromatics),
brief surveys to indicate the distribution
of these substances in Port Valdez were
also carried out.
Procedures
Preliminary tests carried out on
samples of process water from the
Alyeska ballast treatment plant disclosed
that organic matter present in the
stream included volatile organic matter
(lower molecular weight [mw] hydro-
carbons), dissolved nonvolatile organic
matter (including phenolic and naphtha-
lenic compounds), and suspended oil. To
develop information on the effectiveness
of oil removal and to characterize the
compositional changes taking place in
the process, it was necessary to mea-
sure the concentrations of each organic
fraction and to characterize the chemical
nature of principal compounds present.
An analytical protocol (Figure 1) was
devised that included:
1. Determination and chemical
characterization of the volatile
fraction,
2. Determination and chemical
characterization of the dissoved
nonvolatile fraction, and
3. Determination of the suspended
organic matter.
The total organic load (TOL) (the
overall organic concentration in the
process stream expressed in mg C/L) is
defined as the sum of the volatile
organics, dissolved nonvolatile organic
matter, and suspended organic materi-
als. Daily samples were collected from
the plant for analysis during three 10-
day periods (in August 1978, February
1979, and June 1979).
A more sensitive protocol was also
devised for analyzing samples collected
from the fjord in June 1979, September
1979, and June 1980.
Results
Treatment
The effectiveness of oily wastewater
treatment can be defined as its ability to
remove petroleum and related organic
matter from the water. Determination of
organic load reduction in the process
stream can be considered a measure of
process effectiveness.
The process stream in a ballast water
treatment plant originates with un-
treated ballast entering from tankers,
and it ends with treated effluent leaving
through a diffuser laid on the bottom of
Port Valdez. During its passage through
the plant, ballast water undergoes two
principal physical separations: quiescent
gravity separation in primary holding
tanks, and dissolved air flotation in
flowthrough chambers. Consequently,
the chemical composition of the process
water is expected to be qualitatively and
quantitatively different at three major
points in the process: incoming ballast,
effluent from the gravity separator, and
final treated effluent. Those three points
were selected as the principal sampling
points during this study.
Analyses of primary and final effluents
conducted during the study periods of
summer 1978, winter 1979, and sum-
mer 1979 indicated very little difference
(qualitative or quantitative) in the 10-
day average chemical compositions of
the process streams from season to
season. This result was in spite of a
large day-to-day fluctuation in the
chemical composition of the stream
observed during each study sequence.
The reason for this may lie in the
averaging effect of the large volumes of
water processed, consistency of plant
operational procedures, and relative
similarity in the chemical composition
of incoming ballast water. For this
reason, all the experimental data
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-I
Sparging
Sp
\
.
1
IisUiiemun ui
Microfiltration Vo/atiles
\
TOO Analysis
of Dissolved
Nonvolatiles
1
Gas Chromatography
of Volatiles
(Verification by GC/MS)
Figure 1. Protocol for ballast water hydrocarbons analysis
obtained during this study for primary
and final effluent chemical compositions
were averaged and used in subsequent
discussions. Using these data, it was
possible to develop complete organic
material balances for the primary and
final effluents.
Difficulties were experienced in
representative sampling of incoming
untreated ballast water. The ballast in
taker compartments is heterogeneous,
and oil and water are fairly well
separated. This fact makes represent-
ative sampling of incoming water
extremely difficult. The problem was
overcome by combined use of plant
operating records and the experimental
data to produce an organic material
balance for incoming untreated ballast
waters. The plant records contained
information on the amount of water
processed and the amount of free oil
removed. Based on the 2 years of plant
operation records, it was estimated that
incoming ballast water contained an
average of 7,200 mg C/L of suspended
(recoverable) oil. The concentration of
dissolved organic matter (volatile and
nonvolatile) in the incoming untreated
ballast was determined during the 10
days of the winter 1979 study. A
combination of those two sources of
data provided an organic material
balance in the incoming ballast.
The 2-year average for suspended oil
was estimated to be 7,200 mg C/L, and
the level of all dissolved organics was
experimentally determined at approx-
imately 20 mg C/L. Consequently, the
total organic load of incoming, untreated
ballast is estimated at 7,200 mg C/L.
The dissolved organics were composed
of approximately 13 mg C/L of volatile
hydrocarbons and 5 mg C/L nonvolatile
organic compounds. The organic load of
incoming ballast was reduced to approx-
imately 17 mg C/L by the gravity
separator treatment and then was
finally reduced to approximately 11 mg
C/L by the secondary treatment of
aeration-flotation and in-pond retention.
The overall organic load reduction by
the treatment plant was on the order of
99.8% to 99.9% (Table 1).
The elimination of suspended organic
matter (the oil) was almost complete:
99.97% of it was removed by the
process. But the dissolved organic
matter was reduced by only 50%. The
overall reduction of volatile hydrocar-
bons was approximately 62%, with
reduction of volatile aliphatic hydro-
carbons being almost complete (95%).
The concentration of the dissolved
nonvolatile fraction was reduced by only
20%, however.
The gravity separator reduced the
total organic load by 99.8%. The
dissolved air flotation unit improved on
this reduction by less than 0.1%, as it
removed about half of the remaining
load.
The effectiveness of plant operation
can be summarized in the following
manner: the gravity separator removes
almost all of the suspended oil, and
some of the dissolved (both volatile and
nonvolatile) organic compounds. The
dissolved aeration-flotation operation
contributes to further reduction of
volatile organic matter, but it has very
little effect on the concentration of
dissolved nonvolatile organics.
The studies also disclosed that
treated effluent contained a substantial
amount of petroleum-derived, dissolved
organic matter, including five priority
pollutants: benzene, toluene, ethylben-
zene, phenol, and naphthalene. The
average chemical composition of treated
effluent is shown in Table 2.
Volatile aromatic hydrocarbons con-
stitute almost half of all organic
compounds present in the treated
effluent. The principal compounds
present are benzene, toluene, xylenes,
and ethylbenzene. The nonvolatile
dissolved fraction (35% to 40% of the
total organic load) contains significant
amounts of phenols and of naphthalene
and its derivatives.
Because of the large volume of ballast
water processed, significant amounts of
aromatic hydrocarbons and nonvolatile
organic compounds are discharged
daily. The daily average discharge of
aromatic hydrocarbons during 2 years
of treatment plant operation was
estimated at 230 to 260 L.
Disposal
The treated effluent from the terminal
facility is discharged into the Port Valdez
fjord, which is about 5 km wide by 18 km
long, with a mean depth of about 180 m.
The port is shaped somewhat like a
bathtub, with steep sides on the north
and south; it has a nearly horizontal
bottom at a depth of about 240 m over
three-quarters of its length. The bottom
of the easternmost quarter of the fjord
rises rather uniformly to the eastern
shore at the former townsite of Valdez.
The waters of Port Valdez and Valdez
Arm exhibit a pronounced annual
density cycle, varying between strongly
stratified summer and early autumn
conditions and a nearly homogeneous
state that persists from late fall to early
spring.
Treated effluent is discharged from
the diffuser about 380 m from the plant
depths of 65 to 75 m through dispersion
ports as turbulent jets, providing for
highly efficient mixing of the effluent
and receiving water over a distance of
approximately 60 m. The buoyant
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Table 1. Reduction of Organic Content of Process Water by Treatment Process,
Port Valdez, Alaska, August 1978 to June 1979
Type of
Organic Material
Untreated
Ballast %
(mg C/L) Reduction
Gravity
Separator
Effluent %
(mg C/L) Reduction
Final
Effluent
(mg C/L)
Total %
Reduction
by the
Process
Volatile hydrocarbons
Benzene 4 25 3
Toluene 303
Xylenes/ethylbenzene 202
Other 4 50 2
Total 13 30 9
33
33
50
90
44
2
2
1
02
5
50
33
50
95
62
2 Dissolved nonvolatile
organic matter
3. Suspended organic
matter (free oil)
Total organic load
5
-7200
-7220
20
99.9
4
4
17
0
50
35
4
2
11
20
9997
99.8
Table 2. Average Hydrocarbon Content of Port Valdez, Alaska, Treated Ballast
Water. August 1978 to June 1979
Item
Benzene
Toluene
Xylenes/ethylbenzene
Aliphatic hydrocarbons
Total volatile hydrocarbons
Total dissolved organics
Total suspended organics
A verage total organic
load of the effluent
mgC/L
2.0
1.8
0.9
0.2
4.9
4.3
1.5
10.7
Confidence
Interval (E)
at 95% limit
0.5
0.3
0.1
0.05
0.8
0.5
0.9
1.6
% of TOL
19
17
8
2
46
40
14
100
effluent plume will entrain fjord water
and will rise toward the surface until it
reaches a level with the same density as
that of the plume mixture. At this
neutral buoyancy level, known as the
trap level, the plume spreads horizon-
tally, creating a submerged field of
diluted effluent.
Aromatic hydrocarbons in the receiv-
ing waters were sampled and analyzed
in June to July 1979, September 1979,
and June 1980 (Figure 2). In the June-
July 1979 study, sampling was carried
out at 40- and 60-m depths at Stations
42 and 51 and at a 60-m depth at a
station 2 km to the north. Detectable.
amounts of aromatic hydrocarbons
were found at all three stations.
In the September 1979 study, at the
end of the summer warm period, an
attempt was made to determine the
vertical profile of aromatic hydrocarbons
on the boundary of the diffuser mixing
zone. The arm surface layer at the time
extended to the depth of the diffuser
(approximately 75 m). Sampling was
carried out at Stations 32, 34, 42, 44,
and 51. At Station 42, the maximum
concentration of 21 (ig/L was found at a
depth of 77 m (within 2 m of the bottom).
The concentration decayed rather
rapidly in the vertical plane, and at a
depth of 70 m (9 m above the bottom), it
was only 2.4/yg/L. The centerline of the
contaminated zone was at an average
depth of approximately 65 m, or within
10 m of the depth of the diffuser.
In the June 1980 study, a further brief
attempt was made to define the position
and geometry of the effluent plume.
During this period, the low-density
surface layer extended to depths of 40 to
50 m. Station 42 on the northwestern
border and Station 34 on the north-
eastern border of the diffuser mixing
zone were sampled, plus Stations 45
and 56 (located 175 m from each other).
Four to five water samples were
collected at each station at 10-m
vertical intervals from depths of 40 to 70
m. The centerline (maximum concen-
tration of aromatic hydrocarbons) of the
submerged field on the boundaries of
the mixing zone was at a depth of 50 m,
or approximately 20 m above the mean
depth of the diffuser (Figure 3). The
submerged hydrocarbon field was
contained in a very narrow vertical zone
(approximately 10 m) on the boundaries
of the mixing zone. A minimum dilution
of approximately 1:2600 was achieved
approximately 0.5 km from the point of
discharge.
Conclusions
This 2-year study of the operation and
effectiveness of a large-scale ballast
treatment facility at the Port Valdez,
Alaska, marine terminal has disclosed
that the plant removed more than 99%
of all the suspended organic matter (oil)
and that volatile aromatic hydrocarbons
(primarily benzene, toluene, xylenes,
and ethylbenzene) constitute the princi-
pal and lexicologically important com-
ponent of the treated effluent discharged
to the environment. Because of the
large volume of ballast water processed
(40,000 to 45,000 mVday), significant
quantities of volatile aromatic compounds
are discharged daily into the Port Valdez
fjord. The average daily discharge of
aromatic hydrocarbons was 230 to 260
L, which totaled approximately 175,000
L of aromatic hydrocarbons between
August 1977 and August 1979.
Three short-term studies of the
aromatic hydrocarbon distribution in
the fjord during the summers of 1979
and 1980 indicated that the effluent
plume from the diffuser rose to the level
of a density discontinuity and then
spread horizontally in a thin, pancake-
like layer. The depth to the discontinuity
was about 50 m in June and 75 m in
September. The aromatic layer was
some 20 m thick at the diffuser and was
found to extend up to 3 km from it.
The full report was submitted in ful-
fillment of Contract No. 68-03-2648 by
Rockwell International Corporation,
Newbury Park, CA 91320, under the
sponsorship of the U.S. Environmental
Protection Agency
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Valdez Marine Terminal
Figure 2. Hydrocarbon sampling stations nearest the terminal. June 1979, September 1979, and June 1980.
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Surface
10
20
£30
9)
0)
§ 40
50
60
70
Q June 1980
• June 1979
/ 10 20 30 40 50 60 70 80 90 100 120 140
Bottom
Concentration in ng/L (ppb)
Figure 3. Vertical distribution of aromatic hydrocarbons at Station 42, Port
Valdez. Alaska.
IhorLysyj is with Rockwell International Corporation, NewburyPark, CA 91320.
John S. Farlow is the EPA Project Officer (see below).
The complete report, entitled "Treatment Effectiveness: Oil Tanker Ballast
Water Facility," (Order No. PB 82-101 361; Cost: $15.50, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
U. S. GOVERNMENT PRINTING OFFICE: I98I/559-092/33I4
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United States Center for Environmental Research Fees Paid
Environmental Protection Information Environmental
Agency Cincinnati OH 45268 Protection
Agency
EPA 335
Official Business
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