inorganic nitrates and sulfates in aerosols, the molar ratio of sulfates to nitrates in the aerosols resulting from these emissions should be the same as the molar ratio of sulfur dioxide to nitric oxides in the emissions. On all the days on which the highest sulfate concentrations (more than 20 pg/m3) were measured-which are also days on which trajectories indicate transport from the Ohio River Valley area-the molar ratios of sulfate to nitrate age greater than 13 to 1and on most of these days, the molar ratio exceeds 50 to 1. Thus, it is likely that nitric oxides and/or nitrates are reacting to form compounds other than nitrates in the air masses that contain these relatively high sulfate concentrations. It is possible that nitric acid, which has a higher vapor pressure than sulfuric acid, is present in the air in gaseous form and, therefore, is not observed in the particulates. The molar ratio of sulfate to nitrate in precipitation collected by Battelle Northwest Laboratories (IO) at Whiteface Mountain and vicinity is about 2 to 1 in the summertime. Since more nitrate is observed in precipitation than is observed in the aerosol, it is likely that the nitrate is present in gaseous form, either as nitric acid or some other gaseous compound which forms nitrate in water, and is scrubbed from the atmosphere by the precipitation. The pH of this precipitation is often less than 4.5, indicating the presence of acid. Quickert et al. ( I I ) , in a study of transport to the Ottawa area, observed that the heating filter extracts released nitric oxide in excess of that which would be expected from the amount of nitrate measured on the filters. They postulate that nitrogen containing organic compounds were present in the aerosols. Such compounds are another possible sink for the nitric oxides. Conclusions
Regions of high sulfur dioxide emissions to the west and south of New York State are very likely the source of high sulfate concentrations recorded in rural areas across the state. Air that has not passed over industrialized regions in the last 1000 km before reaching New York State contains sulfate concentrations less than 5 llg/m3. Conversely, air that has stagnated over an industrial region such as the Ohio River Valley area can contain, upon reaching the state, a 24-h av-
erage sulfate concentration in excess of 20 hg/m3. Nitric oxide emissions from these industrialized regions are not found in these air masses as inorganic nitrates. Investigation of the fate of the nitrogen compounds is needed to resolve this question. Acknowledgments
The authors thank the Atmospheric Sciences Research Center of the State University of New York a t Albany for use of their site at Whiteface Mountain, and also Stanley House, John Cline, Doug Wolfe, and Jerry Wolfe for their excellent work in sampling and analysis. Literature Cited (1) Likens, G. E., Bormann, F. H., Science, 184,1176-9 (1974). (2) Schofield, C. L., “Dynamics and Management of Adirondack Fish
Populations”, Project No. F-28-R-3, New York State Dept. of Environmental Conservation, Albany, N.Y., 1975. (3) Stasiuk, W. N., Coffey, P. E., McDermott, R. F., “Relationships Between Suspended Sulfates and Ozone at a Non Urban Site”, presented a t 68th APAC Conf., #75-627, Boston, Mass., June 15, 1975. (4) Lioy, P. J., Wolff, G. E., Czachor, J. S.,Coffey, P. E., Stasiuk, W. N., Romano, D., J. Enuiron. Sci. Health, A12 (1821, 1-14 (1977). (5) Mulik, J. R., Williams, D., Sawiki, E., Anal. Lett., 9, 653-63 (1976). (6) Heffter, J. L., Taylor, A. D., Ferber, G. J., “A Regional-Continental Scale Transport, Diffusion, and Deposition Model”, 28 pp, NOAA Tech. Me. ERL ARL-50, Air Resources Lab, Silver Springs, Md., 1975. (7) Hidy, G. M., Tong, E. Y., Mueller, P. K., Rao, S.,Thomson, I., Berlandi, F., Muldoon, D., McNaughton, D., Majahad, A., “Design of the Sulfate Regional Experiment”, 1pp (4) 17-(4) 21 (1976). (8) Nisbet, I., “Sulfates and Acidity in Precipitation: Their Relationship to Emissions and Regional Transport of Sulfur Oxides”, in National Academy of Sciences, Air Quality and Stationary Source Emission Control, Rep. by Commission on Natural Resources, Senate Public Works Committee, No. 94-4,1975. (9) U.S. Environmental Protection Agency, Office of Air and Waste Management, Office of Air Quality Planning and Standards, Research Triangle Park, N.C., AP-42, “Supplement No. 6 for Compilation of Air Pollutant Emission Factors”, 1976. (10) Battelle Northwest Laboratories (1977), Multi State Atmospheric Power Production Study, Monthly Precipitation Chemistry Reports, 1977. (11) Quickert N., Wallworth, B., Dubois, L., Sci. Total Enuiron., 5, 79-93 (1976).
Received for reuiew August 4, 1977. Accepted November 11, 1977.
Breaking Emulsions in Navy Bilge Collection and Treatment Systems Ralph C. Little* and Robert L. Patterson Naval Research Laboratory, Washington, D.C. 20375
Environmental Protection Agency requirements necessitate removal of oil from oily wastes before discharge from Naval ships or installations into environmental waters. Specifically, the Federal Pollution Control Acts of 1969, as amended in 1972 with DOD Directives 5100.50 and 6050.1 together with OPNAVINST 6240.2, call for implementation of a new level of environmental pollution control practices. As a result it has been necessary to drastically change the previous methods used in the treatment and disposal of wastewaters to meet the new regulations. Refinements in the processing of oily wastes are expected to improve within the framework of increasing restrictions on the allowable levels of pollutants up to the FY-85 Standards which call for “Zero Discharge of Pollutants”. At this point final specific limits on individual pollutants will be established by law. Within the framework of increasing controls on the discharge of oily waste pollutants into the environment, the new bilge waste collection and treatment system represents an 584
Environmental Science & Technology
intermediate solution to this difficult problem ( I ) . The system consists of a waste oil raft (WOR or donut), which serves as the collector, transporter, and gravity separator for ship’s bilge waste; and a mobile modular oil/water separation and removal (OWS&R) subsystem. Ideally, the OWS&R subsystem maintains the donut by removing and storing gravity-separated oil and sludge, mechanically separating oil/water emulsion via a filter/coalescer, and circulating fresh seawater through the donut to prevent stagnation. The capacity of the donut is 26000 gal. The OWS&R subsystem contains a 100-gpm pump which can be attached to the intake in the reskimming boxes and a 350-gpm pump to remove the oxygen-depleted bilge water remaining in the donut. While the new waste oil raft with its OWS&R subsystem represents a significant advance in the handling and treatment of oily bilge waste waters, operational problems in the separation of oil and water can be expected in the presence of surface-active material (1,2).Although a vast literature exists
This article not subject to U S . Copyright. Published 1978 American Chemical Society
The new bilge waste collection and treatment system, which serves as the collector, transporter, and gravity separator for ship’s bilge waste, was a suitable medium for the application of chemical demulsification techniques. Chemical demulsification methods were especially suitable for emulsified oily wastes that are reluctant to separate into the constituent phases. Laboratory tests indicated that certain quaternary ammonium compounds were effective in breaking 5% oil-in-seawater emulsions over a 20-h period at temperatures ranging from 4 to 45 “C. The demulsifier concentration re-
quired to break the emulsions generally ranged from 1to 2% at 4 “C to 0.1 to 0.2% a t 45 “C. At the low temperature the oil concentration in the separated water ranged from 100 to 500 ppm; a t the higher temperature no more than 55 ppm was observed with most oil level readings of the order of 25 ppm or less. The demulsifiers were useful in breaking emulsions of Navy Distillate, used motor oil, turbine oil, and bilge wastes containing unknown oil mixtures. A field demonstration supported the laboratory tests.
on methods and apparatus that are presumably useful in breaking both water-in-oil and oil-in-water emulsions ( 3 , 4 ) , chemical methods enjoy the advantage of not requiring the purchase and installation of specialized and often expensive equipment or facilities. However, since the bilge waste collection and treatment system lacks the sophistication and controls of a well-designed shore oily waste treatment facility, some rather severe real world constraints must be imposed on a chemically based demulsification system. The successful chemical demulsifier must have the following characteristics ( 5 ) :be unaffected by pH of oily waste, be insensitive to the nature of the waste, be incapable of reemulsifying the oil if excess amounts are used, have high demulsifying power in the presence of particulate matter, have reasonably low cost per treatment, and have low toxicity. Another question that must be answered is whether or not the waste oil raft is a suitable medium for the chemical demulsification technique (6). The combined capacity of the two pumps that service the donut would require approximately 1 h to completely recirculate a maximum load of 26 000 gal of emulsified material. It is difficult to say a priori whether or not this is a suitable level of agitation to efficiently mix a
candidate demulsifier with the oily waste. It is even conceivable that some sort of metering pump might be necessary to properly mix the emulsion and the demulsifier under these conditions. These considerations, then, form the basis for the search for suitable chemical demulsifier, the subject matter of this report. Experimental M a t e r i a l s . All inorganic reagents used were ACS grade. Table I lists the chemical agents used in the tests. The emulsifiers used were Myrj 45 and Tween 85 (IC1 America) and Navy Bilge Cleaner (Mil Spec C-22230A). The oil phases were Navy Distillate (ND), Navy Turbine oil (TO),and used motor oil (MO) drained from an automobile engine sump. Distilled water was used to make up any necessary solutions. Artificial seawater was made up from “Sea Salt” (Lake Products Co.) using the recommended proportions of product and distilled water. L a b o r a t o r y E q u i p m e n t a n d M e t h o d s . Emulsions were prepared by combining the desired quantity of emulsifier, oil, and water to make a total volume of 250 mL and mixed a t 13 000 rpm in a Virtis “45” homogenizer for 5 min. With a good
Table 1. Demulsifier Agents Investigated
Agent a
A B C D E F
G H I J K L M N 0 P
Q R
S T U V W X Y
z
AA
Chemical descrlption
Cocotrimethylammoniumchloride Dicocodimethylammoniumchloride KTallow pentamethyl propane diammonium dichloride Dicocodimethylammoniumchloride Proprietary surfactant Proprietary surfactant Polyelectrolyte blend Mixed mono and dialkyl quaternary ammonium chlorides, av mol wt = 394 Organic compound of polymeric type Proprietary surfactant Cationic surfactant Modified quaternary ammonium compound Polymeric amine liquid Polymeric amine liquid Polymeric amine liquid Polymeric amine liquid Cationic amine liquid Cationic quaternary amine liquid Cationic quaternary amine liquid Sodium dioctylsulfosuccinate Alkylamine-quanidine polyoxyethanol (cationic) Antifoam additive; fatty alcohol? Quaternary ammonium compound Quaternary ammonium compound Polyoxyethylene-polyoxypropylenecopolymer, MW = 2000 Polyoxyethylene-polyoxypropylene copolymer, MW = 2500 Polyoxyethylene-polyoxypropylene copolymer, MW = 3800
20-h Demulslflcatlon actlvlty (room temp)
None Acceptable None Acceptable None None None None None None None Acceptable None None None None None None None None None None None None None None None
All agents are proprietary with the exception of A, 6. D, and T.
Volume 12, Number 5, May 1978
585
emulsifier this typically produced a stable emulsion having Glass test tubes were an oil droplet size ranging from 1to 5 I.L. filled to 15 ml with emulsion, and the demulsifier was added in varying concentration. The tubes were shaken and placed in a rack. The degree of separation was determined after 19-20 h. Low-temperature samples were stored in a refrigerator at 4 “C. Room-temperature samples were stored on the bench at 22 “C, and high-temperature samples were stored in a water bath at 45 “C. The critical demulsifier concentration (CDC) was determined to be the smallest amount of demulsifier that achieved reasonable separation after 20 h. In general, demulsifier concentrations greater than 5 times the CDC neither promoted emulsification nor inhibited phase separation. This concentration, in general, corresponded to a break in the plot of water layer turbidity vs. demulsifier concentration (see Figure 1).The turbidity was determined as follows. Five-
PERCENT DEMULSIFIER
Figure 1. Effect of demulsifier (Agent L) on 5 % oil-in-seawater emul-
sion Emulsion stabilized with 1 % Bilge Cleaner. Critical demulsifier concentration (CDC) indicated by arrow
i
I
I
I
l0,000-
I
milliliter samples of water were withdrawn from below the oily layer with a syringe and placed in a clean sample tube. The amount of turbidity was measured in a Klett-Summerson photoelectric calorimeter. This gave a numerical comparison between samples. An estimate of oil content in the separated water layer was accomplished by determining the turbidity produced by a known concentration of emulsified oil. Figure 2 reports this “calibration curve” and also gives ranges of turbidity that correspond to the appearance of the separated water layer in the tube. Vapor-pressure osmometry data were obtained by means of a commercial thermoelectric device-the Mechrolab Model 301A osmometer. Field Equipment and Methods. In the San Diego tests, a number of preliminary experiments were run in 55-gal drums. The amount of oil ranged from 5 to 10%.In general, 40 gal of emulsion were prepared. Emulsifiers included Bilge Cleaner, Superlode, Protein Foam, and light water chemicals. The oil, seawater, and emulsifier were added to the drum and circulated with a small 30-50-gpm pump until an emulsion was formed in each of the two drums (approximately 3-5 min). Demulsifier L (see Table I) was then added to one drum, and the results were observed. After 20-30 min samples of water were siphoned from 6 or 8 in. below the surface and collected in containers to check for clarity of the separated aqueous phase. No laboratory was available; therefore, oil concentrations could not be determined on a real time basis. Some samples of separated water were added to harbor water in another container to demonstrate that a visible sheen of oil did not result. Two major experiments were conducted in the new waste oil raft (refer to Figure 3). The raft was essentially clean at the start and contained roughly 1 2 000 gal of seawater in each side. Approximately 800 gal of oil were added, and enough Bilge cleaner, in the first experiment, or Superlode in the second, was added to give a concentration of approximately 0.5% emulsifier. This was circulated with a 300-gpm pump, moving the hose around and the return hose above the surface of the liquid, until an emulsion was formed after about 30 min that filled nearly all of the raft. Demulsifier L (at 0.4% level) was then added to the emulsion while the 300-gpm Onan pump circulated the emulsion with the outlet hose above the surface and the inlet hose near the bottom. To get good mixing the pump must run 45-60 min with the outlet hose moving over the surface. A separation time of 8-20 h is required. Samples were removed from the water layer with a weighted bottle that could be lowered below the oil before the stopper was pulled.
-
TURBID
I
O I L CONCENTRATION (ppm)
Figure 2. Plot of Klett-Summerson instrument readings vs. oil con-
centration 586
Environmental Science & Technology
Figure 3. Schematic of Waste Oil Raft (WOR) featuring pipe arrange-
ment for mixing demulsifier
Table II. Demulsifier Interactions with Various Oil-Water Systems a Demulslfler
011 type
Agent “L”
ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND
011 concn.
50 50 50 50 50 50 50 50 50 5 5 50 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
MO TO
Agent “D”
Agent “B”
ND ND ND ND ND ND ND
N D Navy Distillate, MO: used
Aqueous medium
YO
DW 1 % NaCl 1% NaCl 1 % NaCl DW DW DW DW DW DW DW DW 1 % NaCl 1% NaCl
sw 1 % NaCl sw 1% NaCl 1 % NaCl
+ 0.1 solids
SW-DW
sw sw sw DW DW
sw sw
Bilge Cleaner concn, YO
Demui concn required, YO
0.5 0.5 0.5 1 .o 0.1 1 .o 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1 .o 1 .o 0.5 0.5 0.5 0.5 0.5 0.5 0.5
0.5 1 .o 0.2
Inorganic salt concn, O h
0.2 0.1 0.8 0.5 0.4 1 .o 1,pH=2
0.2 0.2 0.4 0.5 0.5 0.5 0.3 0.1 0.2 0.2 1 .o 0.2 0.5 0.2 0.2 0.6 0.5 1 .o 0.15 0.2 0.3 0.2 0.5 1 .o
1,pH=7 1, pH = 10 0.2 10 min 0.6 0.1 0.2
... 0.6
... , . .
1 .o
... ... ... ... 0.2 0.5
... ...
Time required for separation
Appearance of water layer
5 min 15 min 5 min 5 min
Clear Clear Clear Clear Overnight Clear 6 min Clear Overnight Clear Overnight 75% Sep Overnight Clear Overnight Clear Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight Overnight
Cloudy Cloudy Clear Clear Clear Clear Clear Clear Clear Clear Clear Cloudy Clear Clear Clear Clear
motor oil, TO: Shell Turbine oil, DW: distilled water, SW: artificial seawater.
Results and Discussion Preliminary Screening of Candidate Demulsifiers. Table I also lists the demulsifiers and surfactants, most of which are proprietary materials, screened for demulsification activity. The agents listed in Table I were screened by carrying out preliminary demulsification tests with a 5% Navy Distillate-in-seawater standard emulsion containing l% bilge cleaner as emulsifier and using a 0.5%trial level of candidate demulsifier to test for activity. To qualify for an “acceptable” rating, it was necessary that the separated water layer contain no more than 200 ppm of dispersed oil after a 20-h period. A persistent turbidity in the water layer disqualified the agent, resulting in a “none” rating for overall demulsification effectiveness even though gross separation of phases had occurred. Three agents B, D, and L successfully passed the
preliminary screening. All three acceptable agents are quaternary amine salts and are cation active; that is, the hydrocarbon moiety bears a positive charge. This is the opposite case for the vast majority of natural and synthetic surfactants (Le., soaps and detergents),the bulk of which are anion active-the hydrocarbon-based group bears a negative charge. Agents B and D are, chemically, dicocodimethyl ammonium chloride. Their average chemical structures are
While agent L is a proprietary product, vapor-pressure osmometry indicates it has a molecular weight approximately twice that of the dicocodimethyl salt, suggesting a tetracocoammonium chloride structure. Figures 4 and 5 report the vapor-pressure osmometry results. A calibration constant of
0.6:
V
2
0.6C
d
0.54
IO
15
20
CONCENTRATION ( p / l )
Flgure 4. Calibration curve of vapor-pressure osmometer response in acetone solution
AR
Figure 5.
Vapor-pressure osmometry of Agent L in acetone Volume 12, Number 5,May 1978
587
however, slightly high demulsifier concentrations may be required in some instances. All the demulsifiers show a working range of 0.1-1.0% with 0.2% considered to be a good working concentration for the majority of laboratory-prepared emulsions a t the 22 "C test condition used. The demulsifiers are useful over a pH range of 2-10 in the presence of ionic material (soluble salts). E f f e c t o f T e m p e r a t u r e , C o n c e n t r a t i o n , and S o l i d s on t h e E m u l s i o n - B r e a k i n g Process/Laboratory Tests. Table I11 reports the influence of temperature, concentration, and solids content on demulsifier efficiency. Three types of emulsifier at several concentrations were used to make 5% oil-in-seawater emulsions of Navy Distillate. The critical demulsifier concentration (see Figure 1) was studied as a function of temperature. Also reported in Table IiI are water layer turbidity readings using the Klett-Summerson photometer together with estimates of the oil content of the water layer using the calibration curve (Figure 2). Table I11 supports the generalization put forth in Table I1 and, in addition, provides the following additional observations: For a given concentration of emulsifier or detergent, much less demulsifier is required a t higher temperatures (45 "C) than lower ones (4 "C) (see Table I11 for specific comparisons as function of emulsifier type and concentration). When emulsifier concentration is increased, corresponding increases in demulsifier concentration are required for emulsion breaking. All other factors being equal, the oil content of the separated water layer was much less at higher temperatures (45 "C) than low ones (4 "C); values of 0-55 ppm of oil were observed at 45 "C compared to 74-520 ppm a t 4 "C. Emulsions containing solid particulate matter (pumice and jeweler's rouge) were easily broken. Hydrophobic particles (jeweler's rouge) stayed with the oil layer; hydrophilic particles (pumice) flocculated somewhat and settled to the bottom of the water layer. The demonstration held at the Naval Station in San Diego represented the culmination of nearly one year of laboratory
582 ohm-L-mol-l was obtained for the acetone solutions. An intercept value of 0.715 ohm-L-g-l was obtained for Agent L consistent with a molecular weight of 814. Since agent L is also a quaternary ammonium chloride, it might be conjectured that its structure may possibly be: CH~(CH~)I~.~)~N+C~or essentially a tetracocoammonium chioride. An alternative structure (though less likely) might be
CH~(CH~)~~.I)~(CH~)~N'C~I n t e r a c t i o n o f A c c e p t a b l e A g e n t s with V a r i o u s E m u l s i o n Systems. Table I1 lists the interaction of the three
acceptable agents from Table I with various emulsion systems which include distilled water (DW), salt solution (1%NaCl), seawater (SW), and salt solution plus solids (1%NaCl 0.1% solids). In the latter case the solids were a mixture of pumice and finely divided rust (jeweler's rouge). Most of the experiments in Table I1 illustrate the effectiveness of agent L. However, a sufficient number of experiments for agent B and D are included to show that they are fully equivalent to agent L in their demulsification activities. Moreover, while many experiments are listed which utilize Navy Distillate (ND) as the oil phase, several other oils are included, Le., dirty automobile motor oil and an additive-containing Shell Turbine oil. The following generalized conclusions were obtained from the collected data of Table 11: Oil-in-fresh water emulsions require, in addition to the demulsifier, a small amount of an inorganic salt to hasten separation and clarify both the oil and water phases. The amount of added inorganic salt required is generally no more than twice the working concentration of the demulsifier. Agents B, D, and L are equally effective in breaking oilin-seawater emulsions. Emulsions containing solids were also broken by the demulsifiers. The solid, being more dense than water, fell to the bdttom of the test cylinder. Oil-in-seawater emulsions containing large amounts of oil-soluble additives were also broken by the demulsifier;
+
Table 111. Effect of Temperature, Concentration, and Solids in Emulsion-Breaking Process Emuisifler
Solids content
,
Myrj 45 0 0 Myrj 45 0 Tween 85 0 Tween 85 0 Bilge Cleaner Bilge 0 Cleaner 0 Tween 85 0 Bilge Cleaner Tween 85 0.05% clay
0.05% F e A Tween 85 0.05% clay 0.05 % Fen03 Bilge 0.05% clay 0.05% Cleaner F e A Bilge 0.05% clay 0.05% Cleaner
4
Critical demulsifier concn, turbidity, and estlmated oli (after 20 h) 24 OC 45
oc
Emu16 concn, %
Demuisifler
0.2 1.o 0.1 1.0 1.o
DCDMAC DCDMAC DCDMAC DCDMAC DCDMAC
...
...
0.8 -1.5 0.6
230 270 61
5.0 0.1 1.o
DCDMAC MQAC MQAC
2.0 0.5 0.7
0.1
DCDMAC
0.1
Oil,
* ppm
oc
CDC, %
Turb
Oil, ppm
CDC, %
Turb
31 135 125 58 38
32 190 170
900
Arbitrary Klett Summerson instrument readings. Estimatedfrom calibration curve of instrument response to emulsions of known oil Content.
588
011, pprn
Table IV. Summary of San Diego Field Tests Run
#
Te.1 geometry
Emulsifier
1 55-gal drum M.S. Bilge Cleaner
Manuf
Phipps
2 3 55-gal drum Superlode degreaser West
Ernuis concn, YO
0.6
Oil phase a
Waste fuel mix
Dernuls concn, %
Control 0.6
Chemical Products
Used Navy motor oil
0.6
Control
4 5 55-gal drum AFFF fire flighting fluid
3M
0.6
Waste fuel
0.6
6
Control
7 WOR 8 9 55-gal drum 10
M.S. Bilge Cleaner
Phipps
0.3
Waste fuel
0.3
Control M.S. protein fire fighting fluid
Mearl Corp.
0.5
Waste fuel
0.3
Control
11 Oil recovery Unknown but contains boat tank paint plus motor oil
...
...
Mixed oils, engine oils, fuel oils, etc.
0.8
0.3
Waste fuel
0.2
0.3
Waste fuel
0.2
additives 12 55-gal drum Superlode degreaser West
Chemical Products 13 WOR
a
Superlode degreaser West Chemical Products
Remarks
Bulk of oil separated after 15 min; water
0.6
layer cloudy but cleared overnight No separation observed; emulsion stable Good separation after 10 min; water hazy but cleared overnight Slight separation of oil overnight; bulk of oil remained emulsified Emulsion broken easily within 3 or 4 min; water layer hazy Emulsion broken spontaneously over course of several hours; water layer very cloudy Results confirm drum experiment (Run #1) Water layer cloudy, same as Run #2 Emulsion broken after about 10 min; water layer cloudy Emulsion slowly separates over period of several hours, water layer very cloudy Emulsion was inverse type, i.e., water-in-oil. Demulsification generally useful only for oilin-water types but raising demulsifier concentration to 0.8% broke emulsion overnight Same as Run #3, but emulsion was concentrated, i.e., was -50% oil-in-water rather than 5 YO oil-in-water as in other experiments Results similar to Run #7, but emulsion was concentrated, Le., 50 % oil-in-water. Water layer hazy but cleared overnight
Except for Run 11, oil concentrationswere approximately 5 % .
tests and experiments and the opportunity to get data on the utility of selected demulsifiers under realistic field conditions. Table IV reports the results of the five-day tests in concise summary form. In general, the field tests bore out the laboratory experiments. The geometry of the test container whether drum, WOR, or OR vessel was not important provided mixing o f demulsifier with oily waste was adequate and of sufficient duration. In the case of the WOR, for example, orientation of the mixing hoses used with the 300-gpm Onan pump is crucial to good mixing as previously mentioned in the Experimental section (see Figure 3). One hour should be allowed for thorough mixing when a 300-gpm pump is used. The toxicity of agents B and D is extremely low and corresponds to an oral LD50 per kilogram of 1.1g (7). Agent L, for which no data were obtainable from the manufacturer, is probably also virtually nontoxic since its molecular weight is much higher than related agents B and D, and toxicity usually decreases with increases in molecular weight due to decreased solubility. This preliminary information on agents B and D suggests that there should be a minimum of concern over their use in controlled demulsification procedures. A demulsifier that meets all of the qualifications listed in the introduction-especially for use in the waste oil raft-has not been found. The practical demulsifier must be a compromise demulsifier in which the requirements are hopefully at least partially met. Within the experimental designs of the empirical laboratory testing done so far, the required characteristics have been met by agents B, D, and L (see Tables I1 and 111). Since the cost of organic materials has increased considerably in recent years, it is particularly important that preliminary tests be made of emulsion type and salinity. Frequently, ship emulsions that are only mildly brakish can be easily broken by merely increasing the salinity, i.e., by
adding seawater to the emulsion. Figure 6 outlines the procedures to be used to make most effective use of chemical demulsifiers in the waste oil raft. In general, concentrations of demulsifier in excess of 0.5%will greatly increase the cost of operations. Such stubborn emulsions are best sent to the oily waste treatment plant where treatment temperatures in
0 WASTE
WATER LAYER
ADD'I CHEMICAL TREATMENT
'OPTIONA? (TREATMENT)
=TO
ENVIRONMENT
Logic diagram for handling and treatment of oily waste contained in WOR upon arrival at dockside Figure 6.
Volume 12, Number 5, May 1978 589
excess of 150 O F will probably break the emulsion with no further addition of agent required. Emulsions of the waterin-oil type are best treated at the oily waste treatment plant using recommended procedures or other even more effective methods (8).
Literature Cited (1) Naval Facilities Engineering Command, “Scenario for the Operation of a System for the Collection and Treatment of Ship’s Bilge
Waste”, circa 1975. (2) Jefferson, T. H., Boulware, S. B., “Surfactants and Their Effects on Filter Separators”, Rep. 2066, MERDC, Fort Belvoir, Va., June 1973. (3) Becher, P., “Emulsions: Theory and Practice”, 2nd ed., Reinhold, New York, N.Y., 1965.
(4) Sumner, G. G., “Clayton’s Theory of Emulsions and Their Technical Treatment”, 5th ed., Blakiston, New York, N.Y., 1954. (5) Little, R. C., Patterson, R. L., “Breaking Emulsions in Navy Donut Oilmater Separators”, Quarterly Status Rep. No. 3 to NAVFAC, 17 Feb. 1976. (6) Little, R. C., “Breaking Emulsions in Navy Donut Oilmater Separators”, Rep. No. 1to NAVFAC, 3 June 1975. (7) Cutler, R. A., Drobeck, H. P., “Toxicology of Cationic Surfactants”, in “Cationic Surfactants”, E. Jungermann, Ed., p 527, Surfactant Science Series, Dekker, New York, N.Y., 1970. (8) Little, R. C., Fuel, 53,246 (1974).
Received for review April 7,1977. Accepted November 21,1977.
Environmental Tritium Oxidation in Surface Soil James C. McFarlane”, Robert D. Rogers, and Donald V. Bradley, Jr. Monitoring Systems Research and Development Division, Environmental Monitoring and Support Laboratory, P.O. Box 15027, Las Vegas, Nev. 891 14
The site, rate, and method of oxidation of elemental tritium (T2 or H T ) to tritiated water (HTO) were determined. Exposures of leaves (attached or detached), sterilized clay loam, and various extractable nonliving soil components to H T resulted in less than 4% conversion to HTO after 48 h. However, exposure of natural (unsterilized) clay loam or of sterilized soil inoculated with a water extract from the former yielded over 97% conversion. This reaction occurred primarily near the soil surface. Microbial isolations from the soil yielded bacteria that were able to reproduce this reaction in solution. This reaction is considered important due to the expectation of increasingly large atmosphereic tritium discharges from nuclear fuel reprocessing plants, which may result in significant contamination of food and water with HTO. In the production of electricity by nuclear reactors, approximately 50 mCi of tritium are produced for each megawatt-day of energy generated ( 1 ) . Most of the tritium produced is retained within the fuel element and released to the environment during reprocessing. Estimates vary between 25 and 90% as to the amount of tritium that will be released in the elemental form during reprocessing (1-3). Because of its low solubility and the relative stability of hydrogen gas, the importance of gaseous tritium ( H T or T2) as a biological hazard is not great compared to that of tritiated water (HTO). Consequently, the maximum permissible concentrations for occupational exposure to elemental tritium ( 4 ) are higher than for exposures to tritiated water vapor. Maximum permissible concentrations of tritium gas and tritiated water vapor are 400 and 5 picocuries per cubic centimeter (pCi cm-3), respectively. Eakins and Hutchinson ( 5 )determined the conversion times of H T to HTO in the presence of various catalyzing surfaces and reported that the reaction half-times varied from 4 years in the presence of platinum to 1151 years for glass. On the basis of these findings, they suggested that elemental tritium was of little consequence as a local contaminant and proposed that exposure guidelines for H T be further relaxed. However, when lettuce plants in a growth chamber were exposed to Tz, rapid tritium accumulation occurred in both the water and organic components of plants ( 3 ) .This rapid rate of contamination was contrary to what had been expected from the data in the available literature and suggested that elemental tritium in the environment should be considered not as an innocuous pollutant but as one with a significant 590
Environmental Science & Technology
potential for contaminating food and water. Based on those data, it was postulated that the reaction converting H T to HTO existed in either the plant leaves or in the soil. Whether it was a catalytic reaction or one which involved metabolism by plants or soil microorganisms was not known at that time. In expectation of large releases of gaseous tritium into the atmosphere, knowledge of the nature, site, and kinetics of this oxidation or exchange reaction becomes important. To answer these questions, a series of experiments was conducted to determine whether the conversion of H T to HTO was due to oxidation or exchange and to identify the site or sites of the reaction.
Methods Leaf exposures were conducted in a Plexiglas chamber (14 X 25 X 7 cm). The leaf was supported in the center of the chamber on a nylon monofilament grid. The petiole entered through the side of the chamber and was sealed with an oil base clay. The leaf chamber was supported on a ring stand and positioned to allow leaf enclosure without disturbing the plant. Exposures were conducted within an environmentally controlled chamber in which the temperature was maintained at 25 f 1 “C and the photosynthetic photon flux density (PPFD) of 32.5 nanoEinsteins per square centimeter per second (nE cm-2 s-l) was produced by a combination of fluorescent and incandescent lamps. Air was circulated in Teflon tubing from the leaf chamber through a temperature-controlled water bath, dew point sensor, infrared COz analyzer, and back to the chamber. The concentration of COz was maintained at 350 ppm by adjusting the rate of COZ injection. This was done by altering the speed on a syringe pump (syringe filled with 100% COP) until the COz concentration continued unchanged. At this point the COz injection rate equaled the COz assimilation rate, and this value was used as an indication of net photosynthesis. The COz assimilation rate for bean plants was 0.008 cc cm-2 h-1. The corresponding transpiration rate was 15 mg ern+ h-1. These rates are typical of actively growing, healthy leaves and assured us that the stomates were open and normal physiological processes were occurring. Other leaf exposures were conducted without trying to control COz concentration. During some of these trials, the COz concentration was monitored and found to decrease rapidly to the compensation point in 0.5-1 h, depending on plant species and leaf size. It remained within this range during the light periods but in-
This article not subject to U.S. Copyright. Published 1978 American Chemical Society
