Generally, the production of crude oil and natural gas brings to the surface fossil water, termed “produced water.” By far the largest by-product or waste stream by volume associated with oil and gas extraction, this water is always cleaned to some extent and the level of cleaning is determined by the intended use and/or current discharge regulations. Existing technologies are not usually capable of reaching the new levels of cleanliness demanded. This investigation focuses on the characterization of permeate flux using newly developed ceramic microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF) membranes for efficient treatment of oilfield produced water. Results for average flux rates and flux degradation are shown

Czermak, Peter

Ebrahimi, Mehrdad

Engel, Larisa

Mund, Peter

Shams-Ashaghi, Kikavous

K-State Research Exchange

FEASIBILITY OF USING CERAMIC MICRO-, ULTRA- AND NANOFILTRATION MEMBRANES FOR EFFICIENT TREATMENT OF PRODUCED WATER  Peter Czermak1,2, Mehrdad Ebrahimi1, Kikavous Shams Ashaghi1, Larisa Engel1,  Peter Mund3 1University of Applied Sciences Giessen-Friedberg,  Wiesenstrasse 14, 35390 Giessen, Germany 2Kansas State University, Dept. of Chemical Engineering, Manhattan KS, USA 3Atech Innovations GmbH, Gladbeck, Germany  ABSTRACT  Generally, the production of crude oil and natural gas brings to the surface fossil water, termed “produced water.”  By far the largest by-product or waste stream by volume associated with oil and gas extraction, this water is always cleaned to some extent and the level of cleaning is determined by the intended use and/or current discharge regulations.  Existing technologies are not usually capable of reaching the new levels of cleanliness demanded. This investigation focuses on the characterization of permeate flux using newly developed ceramic microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF) membranes for efficient treatment of oilfield produced water. Results for average flux rates and flux degradation are shown.  KEYWORDS  Ceramic Membrane, Water Treatment, Crude Oil, Microfiltration, Ultrafiltration, Nanofiltration, Membrane Fouling, Permeate Flux  1. Introduction  Every oilfield is characterized by a concomitant presence of fossil water and gas that come to the surface together during oil extraction.  The separated water, called“produced water” in the scientific literature, accounts for the majority of the waste derived from the production of crude oil [1].  The quantity of water produced per unit volume of hydrocarbons varies greatly, but typically increases with the age of the producing field.  As well as free and emulsified hydrocarbons, this water may contain a wide variety of salts, fine silts of both silicon and clay compositions and in some cases, active biological materials.  Produced water is always cleaned to some extent with the level of cleaning dependent upon the intended use and/or current discharge regulations.  Current technologies used to treat produced water consist of clarifiers, dissolved air flotation, hydrocyclones, and disposable filters/absorbers [2].  Typically, these technologies are not capable of achieving the new standards of cleanliness demanded by regulations without using additional expensive chemicals for coagulation, settling and the like. As a result, operating expenses increase and greater volumes of hazardous wastes are produced.  After a primary process of separation from the oil, the water still contains drops of oil in emulsion in concentrations as high as 2000 mg/l, necessitating further treatment before it can be discharged.  The international standards require more efficient separation systems.  Volume_II_M_Sessions.pdf   140 17.03.2008   22:01:5410th World Filtration Congress Page II - 140To meet the challenges posed by more stringent regulations, operators have turned to membrane filtration schemes for their potential to minimize additional costs and disposal issues associated with current technologies.  Both polymeric and ceramic membranes have been tried under many field conditions.  While these membranes are effective in separating the oils, emulsions, and silts, they are prone to fouling by waxes and asphaltenes.  The issues that need to be addressed are modification of the waxes and asphaltenes to prevent their fouling of the membranes during operation and the provision of an expedient, cost effective, and non-hazardous means of cleaning the membranes when they become fouled.  The key technical obstacles for the integration of MF/UF/NF membrane filtration into the oilfield water treatment process are reviewed [4, 5].  However, membrane fouling constitutes a major obstacle to the application of membrane-based processes for the treatment of produced water for beneficial uses.  This investigation focuses on the characterization of permeate flux using newly developed ceramic micro-, ultra-, and nanofiltration membranes.  Results for average flux rates, flux degradation, total organic carbon (TOC) removal and oil removal efficiency are shown.  2. Materials and Methods ChemicalsAll chemicals were obtained from VWR international GmbH (Darmstadt/Germany).   MembranesDifferent types of commercial tubular ceramic membranes for micro-, ultra- and nanofiltration were investigated. Table 1 lists the properties of the ceramic membranes used in this investigation.Table 1: Material and properties of the ceramic membranes Membrane MF- Al2O3 MF- Al2O3 UF- TiO2 NF- TiO2Membrane material Al2O3 Al2O3 TiO2 / Al2O3 TiO2 / TiO2 cut-off 0.1 μm1 0.2 μm1 20 kD1 1 kD1 pH range 0 - 14 0 - 14 0 - 14 0 - 14 temp. Max. [°C] 121 121 121 150 1 as indicated by the manufacturer Figure 2: Module and ceramic membranes (SEM-micrograph). Membrane-assisted continuous reactor Cross-flow filtration processes (MF, UF, NF) were studied in a continuous stirred tank reactor (max. volume 3 l) with a membrane module as shown in Figure 1.  The Volume_II_M_Sessions.pdf   141 17.03.2008   22:01:5410th World Filtration Congress Page II - 141influence of different pore sizes of the ceramic membranes used on the separation behaviors were investigated by the measurement of permeate flux, total organic carbon (TOC) and oil removal efficiency, respectively.  The pressure readings of P1 and P2 remained approximately equal; this pressure is reported as the trans-membrane pressure (TMP).  All filtration experiments were carried out at 60°C.Treatment Pre - treatment permeate outputTmembrane module source feed  concentrate recovery/disposal pump ceramic membranepump P2 TT Tmembrane module TP1 TTT Figure 1: Schematic diagram of the laboratory scale cross-flow filtration system with liquid circulation. Preparation of model solution The oily wastewater (model solution) was prepared in a heated stirred tank by mixing waste oil (5%) with distilled water for 30 min at 70°C.  As a simulated primary process of separation from the oil, the mixture was left for 30 min for clarification.  The free oil is recovered and pumped back to the waste oil tank. The mixture showed a uniform yellowish color. Oil in water determination n-Hexane ( 95 % grade purity) was used as an extraction solvent for measuring average oil concentration in feed solution and in permeate.  The samples were analyzed by the TD-500D handheld fluorometer (Nordatec GmbH, Bremerhaven/Germany). The standard solution was prepared by dissolving a known amount of oil in 100 ml of n-Hexane.  100 ml of feed or permeate sample was collected in a suitable glass container.  6N HCL was added until the pH of the water sample was <2.  Extraction solvent (10 ml) was added and the container was securely capped.  The container was shaken vigorously for 2 minutes to extract the oil from the water.  After 1 minute, 1 ml of the solvent extract was removed from the top of the water and analyzed by the fluorometer on channel A.   Total organic hydrocarbon (TOC) determination The total organic hydrocarbon concentrations were determined with the TOC cell test (measuring range: 5.0 – 80.0 mg/L TOC) in the photometer Photolab S6 (WTW, Weilheim/Germany).  3. Results The MF, UF and NF processes ran for 2 h continuously.  Figure 3 shows the change in membrane fluxes and flux degradation for different ceramic membranes with filtration time.  At the beginning, permeation fluxes declined gradually until an Volume_II_M_Sessions.pdf   142 17.03.2008   22:01:5410th World Filtration Congress Page II - 142invariable flux value was obtained.  The results here indicate that membrane fouling of different membranes used and different operation modes produce completely different fouling situations, as reported previously [3].  01002003004005006007005 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120time [min]Flux [l/h.m².bar]0,2 μm 0,1 μm 20 kD 1 kD Figure 3. Average flux rates and flux degradation for different ceramic membranes.  Model solution used (produced water from waste oil) in a membrane-assisted continuous reactor, experiments conditions were TMP: 1 bar, Temp.: 60°C, running time: 2 hours.  In order to investigate the water quality for each filtration process, feed and permeation water were analyzed, respectively. The percentages of removal for oil and TOC measured in steady state after 2 hours are shown in Table 2.  Table 2: Summary of the results derived from different ceramic membranes measured after  2 h filtration across the membranes. NA: not available. Membranes Coil, Feed Oil Removal CTOC, Feed TOC Removal cut-off [ppm] [%] [ppm] [%] 0,2 μm 113 67 94 13 0,1 μm 113 NA 94 38 20 kD 113 84 94 27 1 kD 113 80 94 13  The microfiltration process ran for 32 h continually. Figure 4 shows the profile of flux degradation within the operation time.0501001502002503003502 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32time [h]Flux [l/h.m².bar]0,2 μmFigure 4. Average flux rates and flux degradation for the ceramic membrane with a 0.2 μm pore size, model solution (produced water from waste oil) was used in a membrane-assisted continuous reactor, experiments conditions were TMP:1 bar, Temp.: 60°C, running time 32 hours continuously. Volume_II_M_Sessions.pdf   143 17.03.2008   22:01:5510th World Filtration Congress Page II - 143The average percentages of feed concentrations and removal for microfiltrated oil and TOC measured in steady state after 32 hours are shown in Table 3.   Table 3: Results derived from ceramic membrane with a 0.2 μm pore size after 32 h filtration across the membranes.. Membranes Coil, Feed Oil Removal CTOC, Feed TOC Removal cut-off [ppm] [%] [ppm] [%]         0.2 μm 113 82 94 27 4. Conclusions  The investigated ceramic membrane systems under micro-, ultra-, and nanofiltration conditions have proven to be economically attractive for the removal of oil from produced water (model solution). The results indicate that the investigated membranes are not suitable to reach an acceptable level of removed TOC under present experiment conditions (Table 2, 3).  Significantly, in the case of investigated nanofiltration ceramic membranes the average percentage of removed oil and TOC are lower in comparison to micro-, and ultrafiltration membranes.  These results demonstrate that the effective molecular weight cut-off of the nanofiltration membrane is perhaps larger than their nominal 1.000 Da value, as indicated by the manufacturer.  For this reason, further modified ceramic membranes under varying conditions (TMP, feed concentration, cross-flow velocity) and different cleaning methods need to be investigated.  The key obstacles for the integration of membrane filtration into produced water treatment are: high filtrate flux, low fouling properties, easy cleaning, chemical and thermal stability.     Acknowledgements The authors gratefully thank the Federal Ministry of Education and Research, Germany for the financial support (FKZ: 1731X07).  References  [1] Ciarapica, F. E., G. Giacchetta, 2003. The treatment of produced water in offshore rig: comparison between traditional installations and innovative systems. In Proceedings of the Fifth International Membrane Science & Technology Conference, Nov. 2003, Sydney, Australia.  [2] Shams Ashaghi K., M. Ebrahimi, P. Czermak: Ceramic Ultra- and Nanofiltration Membranes for Oilfield Produced Water Treatment - A Mini Review. Open Env J 2007, 1:1-8 [3] Czermak P, Ebrahimi M, Mund P, Bolduan P, Wickramasinghe RS: Efficient oil field water treatment - investigations on the use of ceramic ultra- and nanofiltration membranes, 5th IWA Specialized Conference on Assessment and Control of Micropollutants/Hazardous Substances in Water; 2007; Frankfurt, Germany [4] Farnand BA, Krug TA. Oil removal from oilfield produced water by cross flow ultrafiltration. J Can Pet Technol 1989; 28: 18-24. [5] Jeffrey M, Yanwei C, Robert HD. Crossflow microfiltration of oily water. JMembr Sci 1997; 129: 221-235. Volume_II_M_Sessions.pdf   144 17.03.2008   22:01:5510th World Filtration Congress Page II - 144WFC1010th World Filtration Congress April 14–18, 2008 Leipzig, GermanyCONGRESS PROCEEDINGSVOLUME II – M-SessionsCONTENT VOLUME II M-SessionsScientific Committee II -2 – 3Session Survey II -4 – 5Congress Programme II -6 – 18Invited Lecture 2 II-19 – 29Invited Lecture 5 II-30 – 39Papers M-Sessions II-40 – 563Keyword List (Page Indicator) II -564hosted bysupported byVenue:Congress Center Leipzig · Messeallee 1 · 04356 Leipzig · GermanyCongress Secretariat:Filtech Exhibitions Germany PO Box 1225 · 40637 Meerbusch – Germanyphone: +49 (0) 2132 93 57 60fax: +49 (0) 2132 93 57 62e-mail: Info@wfc10.comweb: www.wfc10.comDiscover the Future ofFiltration & Separation10th World Filtration Congress Page II - 1

Feasibility Of Using Ceramic Micro-, Ultra- And
Nanofiltration Membranes For Efficient Treatment Of
Produced Water

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Feasibility Of Using Ceramic Micro-, Ultra- And Nanofiltration Membranes For Efficient Treatment Of Produced Water

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