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Effectiveness of centralized bilge water treatment — a field study
Environment International Vol. 2, pp. 177-182 Pergamon Press Ltd. 1979. Printed in Great Britain
Effectiveness of Centralized Bilge Water Treatment -A Field Study ihor Lysyj Rockwell International, Environmental Monitoring 8 Services Center, 2421 West Hillcrest Drive, Newbury Park, CA 91320, U. S. A. 3nd
Edward C. Russell U.S. Army MERADCOM, Fort Belvoir, VA 22060, U.S.A.
Instrumentation and procedures were developed for gross and detailed characterization of oily wastewaters. The methodology was applied to the assessment of effectiveness of a centralized oily waste treatment facility. Generated data included total, dissolved, and suspended organic content and detailed chemical characteristics of oily water samples. The usefulness of the methodology was demonstrated in a real-life field study involving operation of a centralized oily waste treatment facility operated by the U.S. Army at Fort Eustis, Virginia, in 1976. It was found that the concentration of suspended organics ranged between 5 and 335 ppm and dissolved organics between 14 and 156 ppm in untreated bilge water. Treated bilge waste effluents contained essentially no suspended oil, but rather high (769-1262 ppm) amounts of dissolved organic matter. It was determined that physical methods of waste treatment based on gravity separation and coalescence are effective in removal of suspended petroleum, and that prolonged contact between an oil film and water results in water solubilization of petroleum, leading to very high concentrations of dissolved organic material in the treated effluent.
Introduction Analyses of oily wastewaters, as promulgated by the American Society for Testing and Materials (ASTM 77) and in other official publications, address themselves principally to the determination of the water-insoluble petroleum fraction, which is usually present as a film or suspension in the oily wastewaters. To obtain deeper insight into the chemical nature of organic matter associated with oily wastewaters, those methods were augmented by an analytical protocol described here. Special attention was accorded in this study to the dissolved petroleum fraction which is neither removed by physical methods of treatment, nor detected by conventional methods of analysis for oil in water. The chemical composition of this fraction was characterized by the computerized gas chromatography mass spectroscopy system (GC-MS) and its aromatic and polynuclear aromatic content was analyzed by highpressure liquid chromatography (HPLC).
Analytical protocol A two-part protocol provides for gross and detailed characterization of oily wastewater. The gross characterization includes: total, suspended, and 177
dissolved organic content determination and the amount of chloroform extractables in the dissolved fraction. The Total Organic Carbon (TOC) is determined before and after micro-filtration, providing data on total and dissolved organic content of the sample. The amount of suspended oil is calculated as a difference between those two values. The amount of chloroform extractables is determined gravimetrically. Detailed chemical characterization of chloroformextractable fraction includes computerized GC-MS profiling of principal types of petroleum material present and HPLC characterization of traces of aromatic and polynuclear aromatic compounds. The overall scheme of analysis is shown in Fig. 1.
Sampling Reprdsentative sampling of bilge wastewaters on board watercraft could be rather difficult. Access to bilge compartments in many instances is cumbersome. The depth of bilge wastewater typically ranges between a fraction of an inch and a few feet. A hand-held, battery-operated pump, designed for bilge removal from small boats, was used as a sampling device in this work (Fig. 2). This pump is manufactured by McMaster-Carr Company and delivers approximately 4 1/min of water. The pump inlet was usually submerged a
178
lhor Lysyj and Edward C. Russell
I
Bilgewaste [
I
I mac
= analysis
J iic~-fi,tration I
~ ' analysis
I t GC- MS analysis
I
Chloroform extract
I
I
I t
Total,suspended+ dissolved organics
Y t
Accumulator (~olumn
1
Reverve phase
HPLC
ID by GCMS
f
IR,UV
Fig. 1.
Fig. 2. Sampling of bilge waste onboard army watercraft.
few inches below the surface of bilge water during the collection operation. The collected samples contained dissolved and dispersed oil, but not the surface film oil. Wide-mouthed, screw-capped polypropylene bottles were used for sample collection. To arrest biodegradation during transport, the pH of the samples was reduced to approximately 2 by the addition of sulfuric acid.
Analysis A neat sample of oily wastewater (500 ml) is homogenized in a Waring blender and subjected to ultrasonic vibration in an ultrasonic bath for 30 min. Fifty #1 of homogenized sample are injected into Beckman or Dohrmann TOC analyzers and the total organic content of the sample is determined. Next, the suspended organic matter (which is primarily of a
Centralized bilge water treatment
petroleum, water-insoluble character) is separated from water-soluble organics by micro-filtration using Type HA, 0.45 /al filters obtained from Millipore Corp., Bedford, Massachusetts. The TOC analysis is then performed on the filtrate, providing data on concentration of dissolved organic compounds in the oily waste sample. The difference between total and dissolved organic fraction corresponds to suspended or free oil. A 250-ml aliquot of optically clear, micro-filtrated solution is transferred into a 400-ml separatory funnel and extracted into three 50-ml volumes of chloroform. Chloroform extracts are combined and solvent is evaporated on a water bath. The amount of organic residue is determined gravimetrically; it corresponds to dissolved, petroleum-related matter. The organic residue is dissolved in 1 ml of chloroform and subjected to computerized GC-MS analysis. Conditions for GC separation are as follows: Column: 183 cm x 0.64 cm glass tube filled with 3% silicone oil (50070 phenyl) OV-17 on Chromosorb Temperature program: From 75 to 300°C at 8°C/min Carrier: Nitrogen, flow, 25 m l / m i n . Mass-spectral identification is performed by a Probability-Based Matching technique using the computer facility of Cornell University (McLafferty, 74). The analysis for trace and ultra-trace amounts of persistent, potentially toxic aromatic and polynuclear' aromatic hydrocarbons (PAH) is carried out by HighPressure Liquid Chromatography (HPLC) using the Reverse Phase mode of operation. Standard operating conditions are as follows: Instrument: Spectra Physics H P L C Model 3500B Column: Partisil PXS/10/25, ODS-2, 25 cm long, Whatman Corp. Detector: u.v. at 254 nm Mobile phase: 15070 water, 85070 methanol, isocratic Flo wrate: 1.2 ml/min. Pressure: 2224 kg/cm 2 Sample size: lO la1 Recorder speed: 0.64 cm/min. The lower detection limit for polynuclear aromatic hydrocarbons (a signal twice the baseline noise) using the described procedure is in the range of 0.01 and 0.02 parts per billion (ppb). The aqueous phase which remains after chloroform extraction could contain substantial amounts of watersoluble organic compounds. These are for the most part derived from petroleum matter which is significantly oxidized or metabolized by living organisms. High levels of such water-soluble organics were found in effluents from gravity separation oil treatment operations, especially in cases when treatment residence time is long. Detailed chemical characterization of this fraction can best be performed after column chromatographic separation using spectroscopic methods of analysis. Field study
As a result of Coast Guard regulations regarding discharge of bilge and ballast wastewaters, centralized collection and treatment of such wastes became an
179
acceptable and widely used practice. The size of treatment facilities ranges from relatively small facilities such as were evaluated in this study, to facilities handling millions of gallons of waste per day, such as is the case in Port Valdez, Alaska. The simplest form of oily waste treatment involves gravity separation of oil from water in holding tanks, ponds, or other suitable vessels. The separation step is usually followed by skimming of the surface oil film and discharge o f the separated water to the environment. More complex operations assist gravity separation by the air or gas flotation. The flotation step is often augmented by the addition of flocculating agent and may be followed by additional gravity separation as a safety precaution. Such practices of oily wastewater treatment effectively reduce suspended oil levels below 10 ppm concentration level and usually produce effluents that are free of oil film, sheen, or discoloration. This method, however, does little to remove dissolved organic content which is ass,ociated with oily wastewaters. Such petroleum-related dissolved organic matter can be present in oily wastewaters in rather high concentrations and have a significant effect on the receiving environment (Winters, 77). It has been shown in our previous laboratory studies (Lysyj, 74) that substantial amounts of dissolved organic matter can be introduced into water as a result of contact between the oil film and water. Such transfer of organic matter from an oil film into the aqueous phase derives partially from dissolution of water-soluble components of petroleum and partially as a result of chemical changes in the oil film most likely induced by oxidation and biological action leading to formation of water-soluble and metabolic products from the original petroleum stock. The rate of transfer accelerates with time. A study by Exxon (Frankenfield, 76) addressed toxicological aspects of suspended and dissolved petroleum fractions, and disclosed that the dissolved petroleum fraction could be more toxic to aquatic life than suspended oil.
Treatment facility The facility whose operation was studied here is located at the U.S. Army Transportation Center at Fort Eustis, Virginia. The port facility of this center is located in the estuary of the James River in Virginia. It serves a fleet of Army transport ships, landing craft of various types, tug boats, and other specialized watercraft. The physical plant of this oily waste treatment facility consists of a converted barge with three separate holding tanks. The treatment facility shown in Fig. 3 is assembled from four pontoon sections used to assemble a sectionalized barge. The pontoon sections are welded to the deck of a common deck cargo barge. Each pontoon section is 7.7 m long at the top, and 5.2 m long at the bottom, 3 m wide and 2. l m deep. The volume of each pontoon section is approximately 39000 I. Three of the sections are interconnected by a 15 cm length of pipe about 30 cm above the bottom so they all have a common liquid level. The fourth section is independent of the other three and is used to store separated water-
180
lhor Lysyi and Edward C. Russell
Fig. 3. Centralized bilge water treatment.
free oil. The overall dimensions o f the facility are 33 m by 10m. In the past, when the sludge barge was full it was taken by an A r m y tug to a U.S. Navy facility on Craney Island, Virginia, for disposal o f its contents. In September 1975 an experimental 378 l/min oil-water separator was installed on the sludge barge to assess its potential for augmenting removal of the oil from the oily wastewater and returning the water to the harbor with a level of quality that would meet or exceed existing regulations. The experimental oil-water separator is a three-stage (one pre-filter, two coalescers) filter-coalescer type system with a 5 cm double-diaphragm, air-operated supply pump. The supply p u m p takes suction about 30 cm above the bottom of one of the three interconnected pontoon sections. A large duplex strainer was installed on the suction side of the p u m p to remove debris. Separated oil that accumulates in the top o f the three stages of the system during the processing is pumped by the system supply p u m p to the oil storage section. The system is plumbed so that the supply p u m p can also be used to p u m p out watercraft tied up along either side of the barge, and to p u m p the oil in the oil storage section ashore to a railroad tank car. In a normal mode of operation, bilge water can be stored for two weeks or more in gravity separation tanks
prior to secondary treatment by a coalescence device and discharge into the harbor. There are no records or e s t i m a t ~ of how much oily wastewater has been processed in the system since startup. However, records show that during the first year of operation approximately 190000 l o f recovered oil were sent to the post steam plant and burned in the boilers. This type of oily wastewater treatment is a highly effective and economical means for removal of suspended petroleum from the water, and results in an effluent that is free from visible sheen, discoloration, oil film, or emulsion. It is, in one word, in full conformity with current regulations regarding discharge of oily waste. The effluent does not contain petroleum waste as it is currently defined by the law, and chemical analysis for free oil usually indicates concentrations well below l0 ppm. The treated effluent from the barge, however, contains significant amounts of truly dissolved, and on some occasions, colloidal organic matter. Such dissolved organic matter is partially derived directly from petroleum stock and partially originates as a result of biodegradation of an oil film during storage periods (usually more than 2 weeks) in gravity separators. It can be easily assumed that physical separation methods, such as gravity separation and coalescence, do not remove dissolved organics and the dissolved fraction of
Centralized bilge water treatment
181
petroleum waste finds its way into the environment. Our observations also indicated a similar fate for colloidally suspended organics which were found to be present in large quantities during the winter months of port operation. Results In order to assess seasonal impact on oily waste treatment, field studies were carried out during the warm and cold periods of the year. The first set of samples were collected in the port facility of Fort Eustis, Virginia, in April, 1976. The air temperature at the time of sampling was 18-20°C, while the water temperature in the treatment tanks was 16°C. The second sampling was carried out in December, 1976. The air temperature at that time ranged between 0 and 4°C, while the water in the tanks was at 4°C. In both instances, representative samples of untreated bilge waste were collected from three main types of watercraft operating from this port: tug boat, landing craft utility (LCU), and transport ship. Treated wastewater was collected at the point of discharge into the harbor. The physical appearance of treated waste collected in April was essentially clear, and the effluent was odorless. The effluent collected in December, on the other hand, was cloudy in appearance and appeared to contain organic matter in the colloidal state. It also had the distinct odor associated with anaerobic decomposition processes. Gross chemical characteristics of treated and untreated oily wastewater are shown in Table 1. As can be seen from Table 1, samples collected in the winter contained considerably higher amounts of total, suspended, and dissolved organic matter in all the cases studied. This applies equally to compositions of untreated and treated bilge wastewaters. In addition to generally higher levels of organics in winter samples, there were substantial amounts (50°7o of total load) of suspended organic matter in the treated effluent. This was in sharp contrast to the spring sampling when the treated effluent was essentially free of suspended organic matter. There could be two possible explanations for this observation: (a) the coalescence treatment device was operating poorly with cold (4°C) waste effluent, and (b) the effluent contained large amounts of biologically-derived organic matter in colloidal solution, and such solutions are not effectively separated by the coalescence device. The organic load in bilges of different types of watercraft was generally
higher in smaller boats such as the tug boat, and lower in larger ships such as transports. Smaller boats have, as a rule, more congested engine rooms and maintenance of the bilge compartments is more difficult. The difference between dissolved organic content in untreated bilge waste and treated waste effluent was quite striking. During the spring sampling, the average dissolved organic content in untreated bilge waste collected from three boats was 28 mg C/l, while treated waste effluent contained dissolved organics at 769 mg C/1 level. This amounts to a more than 20-fold increase in dissolved organic fraction as a result of waste treatment. The winter samples of untreated bilge wastewater (dissolved fraction) averaged to 79 mg C/l, while dissolved organic content in treated effluent was 1262 mg C/l. The explanation for this observation can be found in our previous laboratory studies (Lysyj, 74), where it was shown that lubricants and fuel oils which are left in prolonged contact with water can produce a very high dissolved organic content in the aqueous phase. This phenomenon is believed to be caused by degradation of an oil film on a water surface due to chemical and biological action. The resulting watersoluble organics are composed of partially oxidized petroleum stock and metabolic products of saprophytic bacteria. In order to gain additional insight into the nature of dissolved organics in treated and untreated oily wastewaters, chloroform-extractable organics were determined and characterized by computerized GC-MS and H P L C . Two samples were selected for this determination during the Spring of 1976 study: untreated waste from a tug boat, and treated waste effluent. The winter samples of untreated waste were combined (one part each from the tug boat, LCU, and transport ship) and this mixture was used as an average model for incoming untreated bilge waste. The treated waste effluent was collected in the same manner as Spring samples. The results are shown in Table 2. Examination of Table 2 reveals that approximately two-thirds of the dissolved organics found in untreated bilge wastewater are chloroform-extractable and can be defined as petroleum fraction or oil, since the procedure used for this determination is similar to the ones specified for oil analysis. The dissolved fraction of treated bilge effluent, on the other hand, contains less than 10°70 of petroleum-type materials, with the great bulk of organics being of a highly water-soluble polar
Table 1. Gross chemical characterization of oily wastewaters Source Untreated bilge wastewater* Tug Boat Landing craft utility (LCU) Transport ship Treated bilge wastewater effluent from treatment facility
Total
Organic concentration, mgC/1 Spring sampling Winter sampling Suspended Dissolved Total Suspended Dissolved
151
104
47
496
335
156
30 79
5 65
25 14
162 86
110 59
53 27
769
0
769
2573
1311
1262
*Analyses reflect dissolved and suspended organics, but not the oil present in the surface film.
182
lhor Lysyjand Edward C. Russell Table 2. Chloroformextract of dissolved organics from bilge wastewater Dissolved organics, mg/l Spring Winter Chloroform NonChloroformNonSource Total extractable petroleum Total extractable petroleum Untreated 54 37 17 92 62 30 bilge (100%) (69o70) (31%) (100%) (67%) (33%) Treated. 897 61 836 1472 116 1367 bilge (100%) (7%) (93%) (100%) (8%) (92%) effluent
nature. The nature of this water-soluble (and not extractable by chloroform) fraction was characterized by IR spectrometry. The sample of treated waste effluent was evaporated to dryness under a stream of nitrogen at room temperature. The residue was extracted into chloroform and then into ethanol. From the IR data, it appears that the bulk of dissolved organic compounds found in treated bilge effluent are glycolic in nature and are most likely biologically derived. In addition to this largely harmless composition, the dissolved fraction in treated oily effluents contains significant amounts of chloroform-extractable, petroleum-related matter. This petroleum-type fraction was determined in treated effluent as 60 mg/1 concentration during the spring field study, and as 116 mg/1 concentration during winter investigations. A closer examination of chloroform-extractable dissolved organics in treated and untreated bilge wastewaters was undertaken using computerized GCMS. Examination of gas chromatograms of treated and untreated waste extracts revealed significant differences. The general pattern o f gas chromatographic peaks observed in untreated bilge waste was similar to ones obtained from extracts from military-grade fuels and lubricants. The pattern of treated waste extract was quite different from those. Mass spectral identification of a number of peaks in gas chromatographs of chloroform extract from untreated bilge waste revealed the presence of hydrocarbons (such as 5, 6 methylenedecane; 3, 7 dimethyl-l-octane) and a number of alcohols including l-nonanol, 2, 7 dimethyl octanol. The treated waste effluent extracts contained, in addition to unsaturated hydrocarbons, a number of nitrogen-containing compounds (3-methylpyrosole; pmethyl-N-phenyl-pyrrole) and phenolic and cryosolic compounds. Analyses were carried out for polynuclear aromatic hydrocarbons by H P L C . The sample of untreated bilge waste produced 20 peaks in the polynuclear aromatic region of the
chromatogram. The detected compounds ranged between two and six benzene ring configurations. Six of the detected compounds were identified on the basis of retention times and quantified using standard solutions for comparison. The sample of treated bilge waste contained only seven peaks in the polynuclear aromatic range, and three peaks were identified by retention times and quantified using standard solutions also. The results are shown in Table 3. Table 3. Polynucleararomatic hydrocarbonsin treated and untreated bilge wastewater Concentration (ppb) Untreated waste Treated waste Naphthalene 5.6 0 Fluorene 0.2 0 Phenanthrene 3.7 2.8 Fluoranthene 5.0 2.6 Pyrene 6.4 0 Chrysene 0.1 0 Pyrelene 0 0.9
Presented, in parts, at the 173rd ACS Meeting, New Orleans, Louisiana, March 1977, and the Symposium on the Effects of Treatment on Organics in Water, CIC/ACS Joint Conference, Montreal, Canada, May-June 1977. This work was supported by the U.S. Army, Contract No. DAAK-02-74-C-031!.
Acknowledgement - -
References American Societyfor Testing Materials, ASTM Book, Part 31 (1977), American Societyfor Testing and Materials, Philadelphia, PA. J.W. Frankenfeld (1976) Toxic effects of oil discharged from ships, U.S. Coast Guard Report USCG-D-16-76,Washington, DC. I. Lysyj and E.C. Russell (1974) Dissolution of petroleum-derived products in water. Water Res. 8,863-868. F.W. McLafferty, R.H. Hartel and R.D. Willwock(1974) Org. Mass Spectrometry 9, 690.
R. Winters and L.P. Parker (1977) Water-soluble compounds of crude oils, fuel oils, and crankcase oils, Proceedings of Oil Spill Conference, U.S. Environmental Protection Agency, Washington, DC.
Effectiveness of Centralized Bilge Water Treatment -A Field Study ihor Lysyj Rockwell International, Environmental Monitoring 8 Services Center, 2421 West Hillcrest Drive, Newbury Park, CA 91320, U. S. A. 3nd
Edward C. Russell U.S. Army MERADCOM, Fort Belvoir, VA 22060, U.S.A.
Instrumentation and procedures were developed for gross and detailed characterization of oily wastewaters. The methodology was applied to the assessment of effectiveness of a centralized oily waste treatment facility. Generated data included total, dissolved, and suspended organic content and detailed chemical characteristics of oily water samples. The usefulness of the methodology was demonstrated in a real-life field study involving operation of a centralized oily waste treatment facility operated by the U.S. Army at Fort Eustis, Virginia, in 1976. It was found that the concentration of suspended organics ranged between 5 and 335 ppm and dissolved organics between 14 and 156 ppm in untreated bilge water. Treated bilge waste effluents contained essentially no suspended oil, but rather high (769-1262 ppm) amounts of dissolved organic matter. It was determined that physical methods of waste treatment based on gravity separation and coalescence are effective in removal of suspended petroleum, and that prolonged contact between an oil film and water results in water solubilization of petroleum, leading to very high concentrations of dissolved organic material in the treated effluent.
Introduction Analyses of oily wastewaters, as promulgated by the American Society for Testing and Materials (ASTM 77) and in other official publications, address themselves principally to the determination of the water-insoluble petroleum fraction, which is usually present as a film or suspension in the oily wastewaters. To obtain deeper insight into the chemical nature of organic matter associated with oily wastewaters, those methods were augmented by an analytical protocol described here. Special attention was accorded in this study to the dissolved petroleum fraction which is neither removed by physical methods of treatment, nor detected by conventional methods of analysis for oil in water. The chemical composition of this fraction was characterized by the computerized gas chromatography mass spectroscopy system (GC-MS) and its aromatic and polynuclear aromatic content was analyzed by highpressure liquid chromatography (HPLC).
Analytical protocol A two-part protocol provides for gross and detailed characterization of oily wastewater. The gross characterization includes: total, suspended, and 177
dissolved organic content determination and the amount of chloroform extractables in the dissolved fraction. The Total Organic Carbon (TOC) is determined before and after micro-filtration, providing data on total and dissolved organic content of the sample. The amount of suspended oil is calculated as a difference between those two values. The amount of chloroform extractables is determined gravimetrically. Detailed chemical characterization of chloroformextractable fraction includes computerized GC-MS profiling of principal types of petroleum material present and HPLC characterization of traces of aromatic and polynuclear aromatic compounds. The overall scheme of analysis is shown in Fig. 1.
Sampling Reprdsentative sampling of bilge wastewaters on board watercraft could be rather difficult. Access to bilge compartments in many instances is cumbersome. The depth of bilge wastewater typically ranges between a fraction of an inch and a few feet. A hand-held, battery-operated pump, designed for bilge removal from small boats, was used as a sampling device in this work (Fig. 2). This pump is manufactured by McMaster-Carr Company and delivers approximately 4 1/min of water. The pump inlet was usually submerged a
178
lhor Lysyj and Edward C. Russell
I
Bilgewaste [
I
I mac
= analysis
J iic~-fi,tration I
~ ' analysis
I t GC- MS analysis
I
Chloroform extract
I
I
I t
Total,suspended+ dissolved organics
Y t
Accumulator (~olumn
1
Reverve phase
HPLC
ID by GCMS
f
IR,UV
Fig. 1.
Fig. 2. Sampling of bilge waste onboard army watercraft.
few inches below the surface of bilge water during the collection operation. The collected samples contained dissolved and dispersed oil, but not the surface film oil. Wide-mouthed, screw-capped polypropylene bottles were used for sample collection. To arrest biodegradation during transport, the pH of the samples was reduced to approximately 2 by the addition of sulfuric acid.
Analysis A neat sample of oily wastewater (500 ml) is homogenized in a Waring blender and subjected to ultrasonic vibration in an ultrasonic bath for 30 min. Fifty #1 of homogenized sample are injected into Beckman or Dohrmann TOC analyzers and the total organic content of the sample is determined. Next, the suspended organic matter (which is primarily of a
Centralized bilge water treatment
petroleum, water-insoluble character) is separated from water-soluble organics by micro-filtration using Type HA, 0.45 /al filters obtained from Millipore Corp., Bedford, Massachusetts. The TOC analysis is then performed on the filtrate, providing data on concentration of dissolved organic compounds in the oily waste sample. The difference between total and dissolved organic fraction corresponds to suspended or free oil. A 250-ml aliquot of optically clear, micro-filtrated solution is transferred into a 400-ml separatory funnel and extracted into three 50-ml volumes of chloroform. Chloroform extracts are combined and solvent is evaporated on a water bath. The amount of organic residue is determined gravimetrically; it corresponds to dissolved, petroleum-related matter. The organic residue is dissolved in 1 ml of chloroform and subjected to computerized GC-MS analysis. Conditions for GC separation are as follows: Column: 183 cm x 0.64 cm glass tube filled with 3% silicone oil (50070 phenyl) OV-17 on Chromosorb Temperature program: From 75 to 300°C at 8°C/min Carrier: Nitrogen, flow, 25 m l / m i n . Mass-spectral identification is performed by a Probability-Based Matching technique using the computer facility of Cornell University (McLafferty, 74). The analysis for trace and ultra-trace amounts of persistent, potentially toxic aromatic and polynuclear' aromatic hydrocarbons (PAH) is carried out by HighPressure Liquid Chromatography (HPLC) using the Reverse Phase mode of operation. Standard operating conditions are as follows: Instrument: Spectra Physics H P L C Model 3500B Column: Partisil PXS/10/25, ODS-2, 25 cm long, Whatman Corp. Detector: u.v. at 254 nm Mobile phase: 15070 water, 85070 methanol, isocratic Flo wrate: 1.2 ml/min. Pressure: 2224 kg/cm 2 Sample size: lO la1 Recorder speed: 0.64 cm/min. The lower detection limit for polynuclear aromatic hydrocarbons (a signal twice the baseline noise) using the described procedure is in the range of 0.01 and 0.02 parts per billion (ppb). The aqueous phase which remains after chloroform extraction could contain substantial amounts of watersoluble organic compounds. These are for the most part derived from petroleum matter which is significantly oxidized or metabolized by living organisms. High levels of such water-soluble organics were found in effluents from gravity separation oil treatment operations, especially in cases when treatment residence time is long. Detailed chemical characterization of this fraction can best be performed after column chromatographic separation using spectroscopic methods of analysis. Field study
As a result of Coast Guard regulations regarding discharge of bilge and ballast wastewaters, centralized collection and treatment of such wastes became an
179
acceptable and widely used practice. The size of treatment facilities ranges from relatively small facilities such as were evaluated in this study, to facilities handling millions of gallons of waste per day, such as is the case in Port Valdez, Alaska. The simplest form of oily waste treatment involves gravity separation of oil from water in holding tanks, ponds, or other suitable vessels. The separation step is usually followed by skimming of the surface oil film and discharge o f the separated water to the environment. More complex operations assist gravity separation by the air or gas flotation. The flotation step is often augmented by the addition of flocculating agent and may be followed by additional gravity separation as a safety precaution. Such practices of oily wastewater treatment effectively reduce suspended oil levels below 10 ppm concentration level and usually produce effluents that are free of oil film, sheen, or discoloration. This method, however, does little to remove dissolved organic content which is ass,ociated with oily wastewaters. Such petroleum-related dissolved organic matter can be present in oily wastewaters in rather high concentrations and have a significant effect on the receiving environment (Winters, 77). It has been shown in our previous laboratory studies (Lysyj, 74) that substantial amounts of dissolved organic matter can be introduced into water as a result of contact between the oil film and water. Such transfer of organic matter from an oil film into the aqueous phase derives partially from dissolution of water-soluble components of petroleum and partially as a result of chemical changes in the oil film most likely induced by oxidation and biological action leading to formation of water-soluble and metabolic products from the original petroleum stock. The rate of transfer accelerates with time. A study by Exxon (Frankenfield, 76) addressed toxicological aspects of suspended and dissolved petroleum fractions, and disclosed that the dissolved petroleum fraction could be more toxic to aquatic life than suspended oil.
Treatment facility The facility whose operation was studied here is located at the U.S. Army Transportation Center at Fort Eustis, Virginia. The port facility of this center is located in the estuary of the James River in Virginia. It serves a fleet of Army transport ships, landing craft of various types, tug boats, and other specialized watercraft. The physical plant of this oily waste treatment facility consists of a converted barge with three separate holding tanks. The treatment facility shown in Fig. 3 is assembled from four pontoon sections used to assemble a sectionalized barge. The pontoon sections are welded to the deck of a common deck cargo barge. Each pontoon section is 7.7 m long at the top, and 5.2 m long at the bottom, 3 m wide and 2. l m deep. The volume of each pontoon section is approximately 39000 I. Three of the sections are interconnected by a 15 cm length of pipe about 30 cm above the bottom so they all have a common liquid level. The fourth section is independent of the other three and is used to store separated water-
180
lhor Lysyi and Edward C. Russell
Fig. 3. Centralized bilge water treatment.
free oil. The overall dimensions o f the facility are 33 m by 10m. In the past, when the sludge barge was full it was taken by an A r m y tug to a U.S. Navy facility on Craney Island, Virginia, for disposal o f its contents. In September 1975 an experimental 378 l/min oil-water separator was installed on the sludge barge to assess its potential for augmenting removal of the oil from the oily wastewater and returning the water to the harbor with a level of quality that would meet or exceed existing regulations. The experimental oil-water separator is a three-stage (one pre-filter, two coalescers) filter-coalescer type system with a 5 cm double-diaphragm, air-operated supply pump. The supply p u m p takes suction about 30 cm above the bottom of one of the three interconnected pontoon sections. A large duplex strainer was installed on the suction side of the p u m p to remove debris. Separated oil that accumulates in the top o f the three stages of the system during the processing is pumped by the system supply p u m p to the oil storage section. The system is plumbed so that the supply p u m p can also be used to p u m p out watercraft tied up along either side of the barge, and to p u m p the oil in the oil storage section ashore to a railroad tank car. In a normal mode of operation, bilge water can be stored for two weeks or more in gravity separation tanks
prior to secondary treatment by a coalescence device and discharge into the harbor. There are no records or e s t i m a t ~ of how much oily wastewater has been processed in the system since startup. However, records show that during the first year of operation approximately 190000 l o f recovered oil were sent to the post steam plant and burned in the boilers. This type of oily wastewater treatment is a highly effective and economical means for removal of suspended petroleum from the water, and results in an effluent that is free from visible sheen, discoloration, oil film, or emulsion. It is, in one word, in full conformity with current regulations regarding discharge of oily waste. The effluent does not contain petroleum waste as it is currently defined by the law, and chemical analysis for free oil usually indicates concentrations well below l0 ppm. The treated effluent from the barge, however, contains significant amounts of truly dissolved, and on some occasions, colloidal organic matter. Such dissolved organic matter is partially derived directly from petroleum stock and partially originates as a result of biodegradation of an oil film during storage periods (usually more than 2 weeks) in gravity separators. It can be easily assumed that physical separation methods, such as gravity separation and coalescence, do not remove dissolved organics and the dissolved fraction of
Centralized bilge water treatment
181
petroleum waste finds its way into the environment. Our observations also indicated a similar fate for colloidally suspended organics which were found to be present in large quantities during the winter months of port operation. Results In order to assess seasonal impact on oily waste treatment, field studies were carried out during the warm and cold periods of the year. The first set of samples were collected in the port facility of Fort Eustis, Virginia, in April, 1976. The air temperature at the time of sampling was 18-20°C, while the water temperature in the treatment tanks was 16°C. The second sampling was carried out in December, 1976. The air temperature at that time ranged between 0 and 4°C, while the water in the tanks was at 4°C. In both instances, representative samples of untreated bilge waste were collected from three main types of watercraft operating from this port: tug boat, landing craft utility (LCU), and transport ship. Treated wastewater was collected at the point of discharge into the harbor. The physical appearance of treated waste collected in April was essentially clear, and the effluent was odorless. The effluent collected in December, on the other hand, was cloudy in appearance and appeared to contain organic matter in the colloidal state. It also had the distinct odor associated with anaerobic decomposition processes. Gross chemical characteristics of treated and untreated oily wastewater are shown in Table 1. As can be seen from Table 1, samples collected in the winter contained considerably higher amounts of total, suspended, and dissolved organic matter in all the cases studied. This applies equally to compositions of untreated and treated bilge wastewaters. In addition to generally higher levels of organics in winter samples, there were substantial amounts (50°7o of total load) of suspended organic matter in the treated effluent. This was in sharp contrast to the spring sampling when the treated effluent was essentially free of suspended organic matter. There could be two possible explanations for this observation: (a) the coalescence treatment device was operating poorly with cold (4°C) waste effluent, and (b) the effluent contained large amounts of biologically-derived organic matter in colloidal solution, and such solutions are not effectively separated by the coalescence device. The organic load in bilges of different types of watercraft was generally
higher in smaller boats such as the tug boat, and lower in larger ships such as transports. Smaller boats have, as a rule, more congested engine rooms and maintenance of the bilge compartments is more difficult. The difference between dissolved organic content in untreated bilge waste and treated waste effluent was quite striking. During the spring sampling, the average dissolved organic content in untreated bilge waste collected from three boats was 28 mg C/l, while treated waste effluent contained dissolved organics at 769 mg C/1 level. This amounts to a more than 20-fold increase in dissolved organic fraction as a result of waste treatment. The winter samples of untreated bilge wastewater (dissolved fraction) averaged to 79 mg C/l, while dissolved organic content in treated effluent was 1262 mg C/l. The explanation for this observation can be found in our previous laboratory studies (Lysyj, 74), where it was shown that lubricants and fuel oils which are left in prolonged contact with water can produce a very high dissolved organic content in the aqueous phase. This phenomenon is believed to be caused by degradation of an oil film on a water surface due to chemical and biological action. The resulting watersoluble organics are composed of partially oxidized petroleum stock and metabolic products of saprophytic bacteria. In order to gain additional insight into the nature of dissolved organics in treated and untreated oily wastewaters, chloroform-extractable organics were determined and characterized by computerized GC-MS and H P L C . Two samples were selected for this determination during the Spring of 1976 study: untreated waste from a tug boat, and treated waste effluent. The winter samples of untreated waste were combined (one part each from the tug boat, LCU, and transport ship) and this mixture was used as an average model for incoming untreated bilge waste. The treated waste effluent was collected in the same manner as Spring samples. The results are shown in Table 2. Examination of Table 2 reveals that approximately two-thirds of the dissolved organics found in untreated bilge wastewater are chloroform-extractable and can be defined as petroleum fraction or oil, since the procedure used for this determination is similar to the ones specified for oil analysis. The dissolved fraction of treated bilge effluent, on the other hand, contains less than 10°70 of petroleum-type materials, with the great bulk of organics being of a highly water-soluble polar
Table 1. Gross chemical characterization of oily wastewaters Source Untreated bilge wastewater* Tug Boat Landing craft utility (LCU) Transport ship Treated bilge wastewater effluent from treatment facility
Total
Organic concentration, mgC/1 Spring sampling Winter sampling Suspended Dissolved Total Suspended Dissolved
151
104
47
496
335
156
30 79
5 65
25 14
162 86
110 59
53 27
769
0
769
2573
1311
1262
*Analyses reflect dissolved and suspended organics, but not the oil present in the surface film.
182
lhor Lysyjand Edward C. Russell Table 2. Chloroformextract of dissolved organics from bilge wastewater Dissolved organics, mg/l Spring Winter Chloroform NonChloroformNonSource Total extractable petroleum Total extractable petroleum Untreated 54 37 17 92 62 30 bilge (100%) (69o70) (31%) (100%) (67%) (33%) Treated. 897 61 836 1472 116 1367 bilge (100%) (7%) (93%) (100%) (8%) (92%) effluent
nature. The nature of this water-soluble (and not extractable by chloroform) fraction was characterized by IR spectrometry. The sample of treated waste effluent was evaporated to dryness under a stream of nitrogen at room temperature. The residue was extracted into chloroform and then into ethanol. From the IR data, it appears that the bulk of dissolved organic compounds found in treated bilge effluent are glycolic in nature and are most likely biologically derived. In addition to this largely harmless composition, the dissolved fraction in treated oily effluents contains significant amounts of chloroform-extractable, petroleum-related matter. This petroleum-type fraction was determined in treated effluent as 60 mg/1 concentration during the spring field study, and as 116 mg/1 concentration during winter investigations. A closer examination of chloroform-extractable dissolved organics in treated and untreated bilge wastewaters was undertaken using computerized GCMS. Examination of gas chromatograms of treated and untreated waste extracts revealed significant differences. The general pattern o f gas chromatographic peaks observed in untreated bilge waste was similar to ones obtained from extracts from military-grade fuels and lubricants. The pattern of treated waste extract was quite different from those. Mass spectral identification of a number of peaks in gas chromatographs of chloroform extract from untreated bilge waste revealed the presence of hydrocarbons (such as 5, 6 methylenedecane; 3, 7 dimethyl-l-octane) and a number of alcohols including l-nonanol, 2, 7 dimethyl octanol. The treated waste effluent extracts contained, in addition to unsaturated hydrocarbons, a number of nitrogen-containing compounds (3-methylpyrosole; pmethyl-N-phenyl-pyrrole) and phenolic and cryosolic compounds. Analyses were carried out for polynuclear aromatic hydrocarbons by H P L C . The sample of untreated bilge waste produced 20 peaks in the polynuclear aromatic region of the
chromatogram. The detected compounds ranged between two and six benzene ring configurations. Six of the detected compounds were identified on the basis of retention times and quantified using standard solutions for comparison. The sample of treated bilge waste contained only seven peaks in the polynuclear aromatic range, and three peaks were identified by retention times and quantified using standard solutions also. The results are shown in Table 3. Table 3. Polynucleararomatic hydrocarbonsin treated and untreated bilge wastewater Concentration (ppb) Untreated waste Treated waste Naphthalene 5.6 0 Fluorene 0.2 0 Phenanthrene 3.7 2.8 Fluoranthene 5.0 2.6 Pyrene 6.4 0 Chrysene 0.1 0 Pyrelene 0 0.9
Presented, in parts, at the 173rd ACS Meeting, New Orleans, Louisiana, March 1977, and the Symposium on the Effects of Treatment on Organics in Water, CIC/ACS Joint Conference, Montreal, Canada, May-June 1977. This work was supported by the U.S. Army, Contract No. DAAK-02-74-C-031!.
Acknowledgement - -
References American Societyfor Testing Materials, ASTM Book, Part 31 (1977), American Societyfor Testing and Materials, Philadelphia, PA. J.W. Frankenfeld (1976) Toxic effects of oil discharged from ships, U.S. Coast Guard Report USCG-D-16-76,Washington, DC. I. Lysyj and E.C. Russell (1974) Dissolution of petroleum-derived products in water. Water Res. 8,863-868. F.W. McLafferty, R.H. Hartel and R.D. Willwock(1974) Org. Mass Spectrometry 9, 690.
R. Winters and L.P. Parker (1977) Water-soluble compounds of crude oils, fuel oils, and crankcase oils, Proceedings of Oil Spill Conference, U.S. Environmental Protection Agency, Washington, DC.