Measurement of Dispersed and Dissolved Oil / Reference Method Precision Ming Yang NEL Presentation for 2015 PW Club Meeting 11 June 2015 Slide 1
Overview Measurement of Dispersed and Dissolved Oil Why Does It Matter? What Is Dispersed and Dissolved Oil? Common Oil in Water Methods and What Do They Measure? How to Measure Dispersed and Dissolved Oil? Reference Method Precision Slide 2
Why Does It Matter? OSPAR Performance Standard: 30 mg/l refers to dispersed oil OSPAR discharge data: collected in terms of dispersed and dissolved (BTEX) Measurement impacts on Compliance Assessment of performance of treatment technologies PWRI (if PW is being re-injected) Understanding the subject helps select better treatment technologies Slide 3
Why Does It Matter? Discharge of PW in the OSPAR Nations in 2012 Source: OSPAR Slide 4
What Is Dissolved / Dispersed / Free Oil? Dissolved oil in the dissolved form in produced water. HCs may include BETX, NPDs and PAHs. Non-HCs may include organic acids and phenols. Dispersed oil in the form of small droplets, say in the range from submicron to hundreds of microns. Free oil- floating on the surface of water or in the forms of large droplets that will settle quickly Slide 5
What Is Dissolved / Dispersed / Free Oil? Our interest Source: John Walsh, SPE Webinar, presentation, 2015 Slide 6
What Is Dispersed and Dissolved Oil? Total Oil Dissolved Dispersed Aromatics Acids Phenols Aromatics Acids Aliphatics BTEX Fatty acids BTEX Fatty acids PAHs Naphthenic NPDs Naphthenic PAHs Slide 7
Hydrocarbon Chemistry Common Organics in PW Aliphatic Aromatic Phenol Organic acid Aromatic Aromatic Source of the table: John Walsh, SPE Webinar presentation, 2015 Slide 8
Organic Acids Found in PW in the North Sea Organic acids found in PW from fields operated by Norsk Hydro (now Statoil) 2002 Source: Utvik, NEL PW Workshop, 2003 Slide 9
Aromatics Found in PW in the North Sea Aromatic hydrocarbons found in PM from North Oil and Gas fields (1999-2001) Source: OGP Report 324, 2002 Slide 10
Phenols Found in PW in Indonesian and North Sea Phenols in Produced Water (mg/l) from 3 facilities in Indonesian and 5 facilities in the North Sea Source: OGP Report 364, 2005 Slide 11
Measurement of Dispersed Oil Old OSPAR IR Method(s) DTI/OSPAR Method 1 2 SAMPLING PRETREATMENT OF THE SAMPLE 3 4 EXTRACTION ANALYSE AT 2925 cm -1 Modified IP Method 10 YES the oil-water separation is adequate 5 oil content lower than 40 mg/1 NO 6 determine extinction at 3040 3015 cm -1 2975 2950 cm -1 2940 2915 cm -1 YES 8 the alkane content is lower than 40 ppm 7 calculate the alkane content by subtracting the aromatics content from the total oil content NO 9 oil-water separation is not adequate Slide 12
Old OSPAR IR Method(s) What Does It Measure? General: all hydrocarbons and other organics present in the samples that are extracted into the solvent Question: Is what is measured dispersed? Answer: almost certainly Not What is included in the extract? Dispersed (aliphatics, aromatics, and other organics extracted into the solvent) Dissolved (aromatics, other organics extracted by the solvent) What is measured? Single wavelength: dispersed and dissolved, but missing most of the aromatics; Three wavelengths: dispersed and dissolved, including aromatics and aliphatics Slide 13
Measurement of Dispersed Oil OSPAR GC-FID Method Dispersed oil in water is defined as anything extractable by n-pentane and detectable by GC-FID within a specific retention-time or carbon range in C7 to C40 excluding TEX (Toluene, Ethyl-Benzene and Xylene) Solvent diesel lube Slide 14
OSPAR GC-FID Method What Does it Measure? General: anything extracted by n-pentane and detectable by GC-FID within a specific retention-time or carbon range in C7 to C40 excluding TEX (Toluene, Ethyl-Benzene and Xylene) Question: Is what is measured dispersed? Answer: almost certainly Not What is measured? Dispersed (aliphatics, aromatics, within C7 to C40. Those below C7,and those above C40, not included, also, TEX in the dispersed phase will be excluded!!) Dissolved (dissolved aromatics, e.g. NPDs, within C7 to C40 except TEX) Slide 15
Measurement of Oil & Grease Gravimetric Method Principle Measure anything extractable by a solvent, not removed by solvent evaporation and capable of being weighed 03/07/15 Slide 16
Gravimetric Method Method 1664 A HEM SGT- SGT-HEM 03/07/15 Slide 17
Gravimetric Method (EPA 1664 A) - What Does It Measure? General: HEM those extracted into hexane but not evaporated at 85 o C, which is termed as oil and grease SGT-HEM those extracted into hexane not absorbed by silica gel and not evaporate at 85 o C Question: Is what is measured dispersed? Answer: almost certainly Not What is measured as HEM (Oil and Grease)? Dispersed (aliphatics, aromatics, and other organics extracted into hexane, not evaporated at 85 o C) Dissolved (aromatics, other organics extracted by hexane, not evaporated at 85 o C) WSOs = HEM (SGT-HEM) All the polar components: acids, phenols, other non-hydrocarbon organics both in the dispersed and dissolved Slide 18
Relationship between Dissolved, Dispersed, Total Oil and Grease and WSOs (USA / GOM) (SGT-HEM) Source: John Walsh, SPE Webinar, presentation, 2015 Slide 19
Measurement of Dissolved and Dispersed Possible Method Filtration method: Take sample, filter it with say 0.45 µm filter Dispersed oil: defined as those left on the filter, which is washed off using a solvent and then measured with an appropriate method. Dissolved oil: those passing through the filter, which is solvent extracted and analyzed using an appropriate method. Definition here is that those oil droplets passing through the filter (0.45 µm) are now counted as dissolved! Slide 20
Measurement of Dissolved and Dispersed Summary OSPAR region Dissolved = BETX at the present time Dispersed = C7-C40 minus TEX as measured by the OSPAR GC- FID method GOM / USA Oil and Grease = HEM (by the EPA method 1664) WSOs = HEM (SGT- HEM) (essentially those retained by the SGT process procedure) WSOs Dissolved Possible method to measure disperse and dissolved: by filtration Slide 21
Useful Reference: John Walsh, SPE Webinar, 2015, Water Treating Taking the Mystery out of Water Soluble Organics http://eo2.commpartners.com/users/spe/downloads/140610_present ation_slides.pdf Available for download as of 11 June 2015 Slide 22
Reference Method Precision Reference Method OSPAR FID GC- Principle Solvent extraction and GC-FID C7 to C40 hydrocarbon Meas. range 0.1 mg/l 150 mg/l Precision Information Respective precision of 11.4%, 20.1%, 21.7%, 21.4% and 36.0% were respectively found at oil concentration of 6 mg/l, 18 mg/l, 25 mg/l, 43 mg/l and 100 mg/l. Reference Method IP 426/98 (Energy Institute) Principle Tetrachloroethylene and IR using Florisil Meas. range 0.5 150 mg/kg Precision Information Repeatability = 1 mg/kg over 0.5 mg/kg 5 mg/kg range Repeatability = 0.2127 (x+5) mg/kg where x is the mean of the oiw concentration over 5 mg/kg 150 mg/kg range Examples repeatability: at oiw 5 mg/kg; 20%; 10 mg/kg; 32%; 50 mg/kg; 24% Slide 23
Reference Method Precision Reference Method USA EPA 413.2 [4] ASTM 3921-85 [5] ASTM D 7066-04[6] Principle Freon extraction & IR Freon extraction & IR S-316 extraction & IR Measurem ent range 0.2-1000 mg/l 0.5 100 mg/l 5 100 mg/l, could be extended with a larger or smaller sample Precision Information 14 mg/l oil and grease, recovery was 99% with a standard deviation of ±1.4 mg/l Overall precision in the concentration range of 0.6 to 66 mg/l may be expressed: S t =0.167 x + 0.333 where S t is the overall precision and x is the oil and grease concentration, mg/l Precision of 47.1%, 49.9%, 66.3%, 50.3%, 37.2% and 24.7% were found for mean values respectively at 30.5 mg/l, 21.2 mg/l, 6.6 mg/l., 6.4 mg/l, 429.9 mg/l, 551.2 mg/l Status Superseded Superseded In use, but not commonly used Slide 24
Reference Method Precision Reference Method EPA 1664 B[3] Principle N-Hexane extraction & gravimetric Measurement range 5-1000 mg/l (oil and grease) with a minimum detection limit of 0.91mg/l Precision Info Initial precision of 11% is acceptable. Status In use, official oil and grease measurement method in the USA Precision (defined here as the relative standard deviation) of EPA Method 1664 for HEM or Oil and Grease is quoted as 8.7 percent. However, an initial precision of 11 percent (from analysis of 4 samples of Precision and Recovery, or PAR, standards) is acceptable for a laboratory practicing the method Precision and recovery (PAR) standard - Using a pipet, spike 10.0 ± 0.1 ml of the hexadecane/ stearic acid spiking solution (Section 7.10) into 950-1050 ml of reagent water to produce concentrations of approximately 20 mg/l each of hexadecane and stearic acid. The PAR standard is used for the determination of initial (Section 9.2.2) and ongoing (Section 9.6) precision and recovery. Slide 25
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