Mixed zooplankton cultures, collected in tows such as this, indicated lethal concentrations to animals
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DONALD W. HOOD, BERNADETTE STEqENSON, and LELA M. JEFFREY Texas Agricultural and Mechanical College, College Station, Tex.
Deep Sea Disposal of Industrial Wastes
IN
1953, the Shell Chemical Corp. investigated ocean disposal to solve certain air pollution problems encountered a t its Deer Park chemical plant ( 2 ) . The wastes are largely chlorinated hydrocarbons with specific gravities ranging from lighter than sea water to considerably heavier. When burned, they produce hydrochloric acid, a serious air contaminant, and are highly toxic to living organisms. Studies were made on two barge loads of such wastes. The material is stored in tanks until removed by the specially constructed barge which holds 1100 tons of liquid and makes its 48-hour round trip via the 50mile Houston ship channel. At sea it is towed a t the end of a 1ZOO-foot hawser by a tugboat. The wastes are pumped from the moving barge through a 4-inch discharge line which, when the barge is full, reaches down 8 feet into the sea. About 5 hours are required to empty the barge over its 30-mile disposal route in an area about 110 miles south of Galveston, which is 200 to 800 fathoms deep. One-gallon samples of sea water, collected from depths to 500 feet, were extracted with toluene and the organic chloride was determined by reaction with metallic sodium in liquid ammonia fol-
lowed by potentiometric titration of the organic chloride (7). Muds were analyzed in the same manner, using 200 grams of surface sediments. Marine bacteria were relatively insensitive to the waste, but phytoplankton and zooplankton were. Mostly phytoplankton cultures were used and the effect of waste on photosynthesis was determined by light and dark bottle techniques. Oxygen evolution or carbon-I4 dioxide (6) uptake indicated photosynthetic production. For hydrocarbons heavier than water, samples were obtained a t several depths a t all stations, but only those having significant concentrations are indicated in Figure 1. Maximum concentration in surface waters was 1.5% saturated, and in deeper water the maximum was 0.8% (saturation is 5.3 meq. organic chloride per gallon). All mud samples contained small amounts of waste; this indicated general fallout of small amounts of the material over the ocean bottom. For wastes lighter than water, (Figure 2) a maximum concentration of 35% saturation (saturation, 5.2 meq. organic chloride per gallon) was in the wake of the barge and the material (chlorinated hydrocarbons plus secondary butyl alco-
hol polymer) tended to form an emulsion with sea water and dispersed much slower; however, concentrations were beyond detectable levels in approximately 9 hours. The effect of wastes on organisms endemic to the area was determined by the flora and fauna of Sargassum sp. weed, oxygen uptake of the zooplankton, and the photosynthetic production of phytoplankton. Sargassum sp. weed provides a bountiful supply of small shrimp (noncommercial), crabs, fish, snails, tube worms, and many other forms. Those organisms which came into immediate contact with the waste were killed or seriously impaired. However, in 3 to 8 hours, the area had again assumed normal features with little or no evidence of the waste disposal. The patchy distribution of microorganisms of the sea makes adequate sampling for statistically significant results impractical. Consequently, the toxicity levels of the wastes to both phytoplankton and zooplankton were established under controlled laboratory conditions. According to these laboratory studies, photosynthetic inhibition should occur in water having the maximum concentrations of waste found in the area during these disposal operations. However, field VOL. 50, NO. 6
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two concentrations of waste for varying time periods was studied (Figure 3). The organisms were collected on millipore filters a t a designated time and inoculated into waste free water. Threshold toxicity level for the four organisms studied occurred a t about O . O O l ~ o saturation, whereas the acute toxicity is at about 1% (Figure 4). Thus, it was estimated that harmful effects to plants will not occur when dilution had exceeded 0.001% of saturation. Acute toxicity levels are estimated a t 1 and 10% for phytoplankton and zooplankton, respectively.
B6Mi. NE OFBUOY 2
1/50-04%S $-1,5% S
Figure 1.
Sampling pattern for wastes heavier than water
Water samples, March 1954: 0 27th; R 28th; and A 29th. X, microequiv. per 100 grams of mud
experiments indicating organic production in the disposal waters showed no significant differences from data obtained in the control areas. This may result from difficulties in adequate sampling because of the patchy distribution of both wastes and plants.
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Plankton tow, solid line to triangles.
The laboratory data applies when plants are exposed to waste concentrations on a continuous basis. However, in the environment, rapid dilution of waste occurs because of high mixing rates. To determine the effect of exposure time on growth of Chlamydomonas sp. exposure to
FROM GALVESTC
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Figure 2.
Sampling pattern for wastes lighter than water
0 Fixes; X, stations; concentration in per cent of saturation
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Diffusion Studies Diffusion processes in the sea are not well understood, and pumping from a moving vessel to some depth complicates such rates. A limited amount of data have been obtained. Ketchum and Ford (5) however, reported on such a study and some of their prediction equations can be applied here. The discharge rate of this waste in the wake of the barge was approximately 1200 grams per centimeter. If an average diffusion coefficient of 2.5 X loa sq. cm. per second is used, the predicted concentration in the middle of the wake after 5 minutes is approximately 0.3 gram per sq. cm. of sea surface. Assuming that uniform mixing occurs to a depth of 100 meters, this is equivalent to about 30 mg. of waste per liter. Except for one high value, 35 mg. per liter, the actual amount found was 3 mg. per liter. I n this study, 200 pounds of fluorescein dye was evenly distributed into 245,000 gallons (density, 10.3 pounds per gallon) of black liquor wastes which was pumped from a moving barge at a depth of about 10 feet in water 400 fathoms deep. By a continuous sampling and recording system, concentration of fluorescein in the wake was determined (Figure 5). Because the dye was clearly visible, a course approximately in the center of the wake could be maintained. At 300 feet the maximum concentration of dye was 88.4 p.p.b. and the minimum was 3.4. Because of a sampling lag time of about 5 seconds and hold time in the sample cell of about 2 seconds, the extremes have probably been modified to some undetermined degree. These data demonstrate the stirring and mixing processes in compressible fluids described by Eckart ( 3 ) . Rapid fluctuations as samples were taken along the axis of the wake at constant time after the tracer was introduced indicate sharp gradients between the interfaces of the waste and water. Energy dissipated by the tug, barge, and pumping of the waste is probably a major factor in causing the distorted masses of the two fluids. The 1000-foot data (Figure 5) show a decrease in the extremes of
D E E P SEA WASTE DISPOSAL concentration gradients in the liquids.
A difference in mixing time for the two traces is about 100 seconds. Continuous traces were also taken a t other distances behind the barge and average values for concentration in the center of the wake were computed by graphical integration of several minutes of continuous record at each distance. These data have been represented by a straight line to fit a distribution equation derived by Moon, Bretschneider, and Hood ( 6 ) , and Sverdrup, Johnson, and Fleming ( 7 7). However, a decreasing slope of the diffusion line might also be obtained from these data. Such a wave may result from increased mixing induced by the dispersal process. More data is needed to determine the exact diffusion pattern. Fluorescein pumped at a rate of 0.123 gram per centimeter was diluted to 32 p.p.b. in 6 minutes. If wastes behave similarly, their concentration in 6 minutes should be 4 p.p.m. About 5 minutes after pumpigg, the maximum for chlorinated hydrocarbons varied between 2.2 and 5.1 p.p.m. This agreement is remarkable and may indicate that, although generally immiscible with water, the hydrocarbons may in this case be considered water soluble. Thus, a prediction equation can be,
TIME IN MINUTES
Figure 3. decreases
As exposure time increases, waste toxicity for Chlamydomonas sp. 0.1%;
Per cent saturation:
X , 0.01%; growing period, 22 hours
where Cis concentration in p.p.m., pumping rate is grams per centimeter; and t is time in minutes. Diffusion levels observed here are thought to be higher than those reported by Ketchum and Ford because in com-
rate c = pumping 0.63t
5.2r
puting diffusion constants, average concentrations for tracers were used rather than only high values. I n another diffusion experiment, fluorescein was carefully dispersed in a path behind the R/V A.A. Jakkula in a manner
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Figure 4.
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-3 -2 LOG % SATURATION
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Toxicity of wastes heavier than water for phytoplankton
Exposure time, 90 minutes. X, Chhmydomonas sp.) 0 , Phorphyridium eruenfum; Nifzechia sp.; U, unidentified diatom
TIME (SSECONOS0PER D I V I S I O N )
l
Figure 5. By a continuous sampling and recording system, concentration of fluorescein in center of the wake was determined A, 300 feet; 8, 1000 feet; pumping rate: of waste, 1.56 X 1O* grams per cm.; of tluorescein, surface temperature, 78' C. wind speed, 10 knots
1.23 X
lo-'
grams per cm. Sea Strong thermocline a t 150 feet;
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TIME
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TIME (MINUTES1
Figure 6. Concentration envelope of fluorescein observed in crossing wake Sea temperature, 82’ F.; thermocline at 175 feet; wind speed, 2 knots
to minimize ship effects. The pseudo wake was then transected perpendicular to the path while continuous sampling was being done (Figures 6 and 7). Under these conditions, the equation for the line may be used to determine when the desired concentration will occur. These data, showing a diffusion rate approximately one third that for the moving barge, are thought to represent better diffusion which occurs from an established wake. The difference could result from added mixing caused by the disposal operation and different environmental situations. These data may be applied to hydrocarbon wastes. A concentration of 0.5y0 of saturation (0.7 p.p.m.) should diffuse to 0.001% (1 p.p.b.) in about 220 minutes. Analytical data on the hydrocarbons are not adequate to check this prediction further. Conclusions
Disposal of toxic wastes beyond the littoral zone of the sea can be accomplished with only a slight effect on organisms in the biomass within a limited area. Concentration of wastes per unit area can be kept low by a slow pumping rate and by keeping the barge underway a t the full speed of the tug. Concentrations a t the threshold of toxicity to phytoplankton is only about 1 X 10-5 grams per liter, but the method of dumping coupled with diffusion processes of surface waters rapidly disperses the waste. Slow dispersal is expected in deep w7a-
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Figure 7. Log of fluorescein concentration vs. time after discharge
ter. I n this work, slow diffusion occurred in water 50 to 100 meters deep during the first operation; therefore, wastes might work their way to bottoms of fishing grounds or regions of up-welling if the currents and topography make this possible. To avoid this, disposal in this area of the Gulf of Mexico should begin beyond the 400-fathom line. In the second operation, maximum concentration of waste behind the barge was about 40% of saturation, which is well beyond toxic levels to both plants and animals and a high incidence of dead organisms was found in the wake. Such high concentrations, however, were spotty because of the eddy type of mixing which occurs. After the waste had diffused from the more concentrated patches, the organisms from the low level areas would provide seed for replenishment. The higher concentration of waste in the wake of the barge during the second operation may have resulted from secondary butyl alcohol polymer forming a moderately stable emulsion with water which retarded dispersal and increased toxicity. However, the disposal area had sufficiently cleared of waste in 6 to 8 hours to near the threshold toxicity level to plants and below the lethal level to animals. Each new waste needs careful study before deep-sea disposal operations are undertaken; however, after careful study of all factors involved, many wastes can be dumped in this manner.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Acknowledgment
The authors acknowledge with thanks the helpful interest of J. W. Eberman and D. K. Peterson, Shell Chemical Corp. They are indebted to Jerome E. Stein and LVilliam Bradley for assistance in collecting the field data, and to the Champion Paper and Fibre Co. for cooperation in the diffusion experiments. References (1) Chablay, F., Ann. chim. 15, 10 (1914). (2) Eberman, J. W., Sewage .and Ind. Wastes 28, 1365 (1956). (3) Eckart, Carl, J . Marine Research V I I , 269 (1948). (4) IND.EKG.CHEM.49, 29A (1957). (5) Ketchum, Bostwick, H., Ford, William L., Trans. A m . Geophvs. Union 33, 680 (1952). (6) Moon, F., Bretschneider, C. E., Hood, D. W., Inst. .Marine Sciences Publ., University of Texas, 1957. (7) Nielsen, E. Steeman, Nu‘ature 169,
956 (1952).
(8) Pringsheim, E. G., “Pure Cultures of Algae,” Cambridge University
Press, 1949.
(9) Redfield, A. C., Walford, L. A . ,
Nat. Research Council Publ. 201, p. 1, 1951. (10) Richards, Francis, J . Marine Research XI, 147 (1952). (11) Sverdrup, H. V., Johnson, M. W., Fleming, R. H. “The Oceans”, Prentice-Hall, New York, 1946. RECEIVED for review December 6, 1955 ACCEPTED June 6, 1957 Based on work done for the Texas Agricultural and Mechanical Research Foundation through sponsorship of the Shell Chemical Corp., and the Champion Paper and Fiber Co.
