Drexel Un niversity RPSEA: Project #1112 22-31, RFP #2011UN001 # Developm ment of Plasm ma Technology y For Water Management M of Frac/Produuced Water Principal Investigator: Young I. Ch ho, PhD Revision Date: D May 15, 2013

OLOGY STA ATUS ASSES SSMENT TECHNO The objecct of this task k was to perfo orm a Techno ology Status Assessment aand submit a summary repport describing g the state-off-the-art of th he produced water treatm ment technoloogy with plassma. The repport includes both b positive and negative aspects of each technologyy.  The objecctive of the project p at Dreexel Universitty named aboove is to deveelop a plasma technologyy for the manag gement of pro oduced waterr from hydrau ulic fracturingg for shale gas. Drexel University’s foocus for the RP PSEA projectt is to use non n-thermal plassma technologgy for softeniing, filtration, and distillattion. Plasma-arrc dischargess pre-treat prroduced wateer so that caalcium ions ddo not causee fouling durring distillation n. Because of o plasma pree-treatment, pure p water caan be evaporrated and re-ccondensed in the distillation n unit at the energy e cost siignificantly leess than that oof thermal disstillation for ssafe discharge or reuse. T s Existing Technologies Frac/prod duced water is i convention nally treated through t a vaariety of diffeerent physicaal, chemical, and biologicall methods. Since there arre multiple neeeds that shoould be addreessed in fracc/produced w water treatment,, a number off different co onventional methodologies m s are used [1]], including thhe following [2]: activated carbon, vario ous forms of filtration f (such h as sand filteers, cartridge filters, multi--media filtrattion, membranee filtration), organic-clay o adsorbers, ch hemical oxidaation, UV dissinfection, chhemical biociddes, air strippeers, chemicall precipitation n, water-softeening by appllying lime sooda, clarifierss, settling ponnds, ion exchaange, reverse osmosis, ev vaporation, stteam strippinng, and acidiffication. In nnearly all of the above casses, each mod dality of techn nology can hit a single tarrget, i.e., eachh process hass application to a limited nu umber of basic functions.

Table 1. Various treaatment metho ods: each meethod has sinngle target, requiring muultiple treatm ment methods. 1

The challenge in the treatment of produced water is the large amounts of calcium, magnesium, sodium, and chloride ions, in addition to smaller amounts of various hydrocarbons, fracking chemicals, bacteria, and suspended particles. In order to treat produced water so that treated water can be safely discharged or reused, various different constituents must be removed, including the following: sodium and chloride ions (desalination or “de-brining”); calcium, magnesium and bicarbonate ions (softening); bacteria (disinfection), hydrocarbon (de-oiling), and suspended particles (filtration). Currently, a number of physical and chemical methods are used for the frac water treatment to remove one species at a time as shown in Table 1 [2]. Because of the risk of mineral fouling caused by calcium, magnesium, bicarbonate, and sulfate ions, the control of these inorganic dissolved ions is a key step enabling other concomitant technologies to be applied efficiently. Chemical Treatment The concentrations of calcium and magnesium ions in the produced water are reported to be very high, with the maximum concentration of 51,000 ppm and 4,000 ppm, respectively [1, 3]. Chemical treatment is often used to reduce these mineral ions so that the mineral fouling can be prevented or significantly reduced. Hardness can be removed by lime, Ca(OH)2, and soda ash, Na2CO3, and the addition of magnesium oxide, MgO. The drawbacks of chemical treatment include the consumption of large amounts of these chemicals, requiring additional logistical facilities for delivery and storage. Furthermore, the addition of these chemicals increases the sludge volume, thus increasing the final cost of disposal. The plasma water treatment technology to be developed at Drexel University plans not to use any chemicals and minimizes the sludge volume. Physical Treatment – Membrane Filtration When compared to chemical treatment methods, membrane filtration methods have several advantages, including the following: relatively low cost of treatment, no toxic chemicals, relatively small footprint for installation at facilities, and no secondary pollution. Thus, the membrane technology is widely accepted as a means of producing various qualities of water from surface water, well water, brackish water and seawater. There are four commonly used membrane technologies: microfiltration (MF) removes particles of 50 nm or larger; "ultrafiltration" (UF) removes particles of roughly 3 nm or larger; "nanofiltration" (NF) removes particles of 1 nm or larger; and reverse osmosis (RO), which is the final category of membrane filtration and removes particles larger than 0.1 nm [4]. MF is for the separation of suspended particles, UF is for the separation of macromolecules, and RO is for the separation of dissolved and ionic components [5]. NF membranes are generally designed to be selective for multivalent ions rather than for univalent ions. RO membranes are designed to reject all species other than water. Membrane technology is being applied intensively in the areas of oil field produced water treatment [6, 7]. The advantages of employing membrane technology for treatment of produced water are numerous, including the following: reduced sludge volumes and high quality of permease [4], relatively small physical and logistical footprint, moderate capital costs and ease of operation. These features of membrane technology make it a very competitive alternative to conventional technologies such as gravity separators and coalesce plates [8]. Although membrane microfiltration can successfully treat produced waters, permeates decline in throughput or flux as a result of fouling. In general, membrane fouling is the most important factor that has limited the use of membrane technology [5]. In addition to the decline in the permeate flux, fouling reduces plant efficiency, shortens membrane life, and increases operating pressure and cleaning frequency. In particular, the permeate flux decline is due to the adsorption and accumulation of rejected oil, suspended solids, and other components of produced water 2

f or in the membranne pores (inteernal fouling) [8]. on the meembrane surfaace (external fouling) Physical Treatment T – Reverse R Osmo osis Reverse osmosis o (RO)) is a purificaation technology that usess a semiperm meable membrrane. The RO O is widely ussed in the desalination of sea s water, wh here the total ddissolved solid (TDS) leveel is in the raange of 30,000-40,000 mg/L L [9]. Note th hat the TDS is generally ddefined as maaterial that caan pass througgh a 2-m filtter. When RO R is used for f desalinatiion of seawaater, the brinne reject is uusually returrned convenien ntly to the so ource water body, b i.e., seaawater. Currrent technological limitatiions on the T TDS levels in the t feed wateer to an RO membrane m are estimated tto be 60,000--80,000 mg/L L [10]. If the RO membranee is operated at a TDS leveel higher than n these threshhold levels, precipitation coould occur onn the surface off the RO mem mbrane, leadin ng to the mem mbrane’s perm rmanent foulinng [10]. Sincce the TDS leevel of producced water can n be as high as a 360,000 mg g/L [1], the eefficacy of RO O treatment iis greatly lim mited by the hig gh TDS conccentration of produced p watter. In additiion, the lack of a receivinng water bodyy to accept thee RO reject brrines is also a major challeenge in the usse of RO for tthe produced water treatm ment. Furthermo ore, even for feed waters having h TDS concentrations c s of 60,000-880,000 mg/L, the RO rejecttion rate can often o be greatter than 50% [10]. Accord dingly, for thhe produced w water, the RO O rejection ratte is expected to t be much hiigher than 50%. The high TDS levels in i produced water w are mainly due to thhe high salinitty (i.e., dissolved sodium and chloride). RO is utillized mainly for the remo oval of the ssalinity, not the removal of calcium and magnesium ions. Since a large amo ount of calcium (i.e., maxim mum of 51,0000 mg/L, [1])) and magnesiium (i.e., max ximum of 4,300 mg/L, [1]]) ions are prresent in the feed water tto RO in the produced w water treatment,, the RO mem mbrane could d foul, signifficantly reduccing its efficiiency. Hencee, ion exchannge, which rem moves these mineral m ion fo oulants, is ofteen utilized prrior to the RO O membrane ffor the protecttion as depicteed in Fig. 1. In fact, the lack of success of RO inn the produceed water treaatment is larggely responsible to these fouling f probleems [2, 11]. The advanttage of RO is its ability to separate any dissolved ionic compon nents [1]. Th herefore, if thee calcium andd magnesium m ions could be removed inn the pretreatment stage, thee RO can rem move the sod dium and chlloride, thus eeffectively redducing the brrine volume [2 2]. In summaary, consideriing these chaallenges, the hhigh TDS levvel in producced water is w well above the technologicaal limit for thee RO membraane [10].

uced water treeatment Figure 1. Block diagraam of RO system for produ Physical Treatment T – Evaporation E and a Distillatio on The evap poration of produced wateer and subseequent re-conndensation reepresent a vaalid fundamental approach for the treatm ment of produ uced water. The T strength oof the evaporaation approacch is the prosppect of the red ducing chemical treatmentt steps so thaat the overall costs associaated with watter treatment are

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d or significaantly reduced d, including th he cost of chhemicals, dispposal of chem mical sludge, and eliminated handling and a storage faacility of chem micals. The use of o falling film m in either vertical or horizzontal tubes aand vapor coompression diistillation (VC CD) are known n methods fo or produced water w treatmeent [12, 13]. The operatinng temperaturre of large V VCD systems for fo the desalin nation of sea water w is often n at 60-70oC ffor the prevenntion or mitiggation of minneral fouling [14, 15]. Thermal evaporation-d e distillation requires the co onsumption oof thermal ennergy of apprroximately 2,600 kJ/kg, wh hich is the sum s of the latent l heat an nd sensible hheat [16]. W With the vappor compresssion distillation n method, on ne can signifiicantly reducee the energy requirement as the evapooration is carrried out not by b heat but by b vacuum. Using the vacuum v approoach, evaporration and distillation cann be performed d at a fraction n of the energy y compared to the thermall evaporation--distillation. However,, it is critical to t note that th he concentratiion of the minneral ions succh as calcium m and magnesiium gradually increases in nside the evaaporation unit as pure waater continuees to evaporaate, unless thhese mineral io ons are remo oved by a prre-treatment system s such as ion exchaange or withh water-softenning chemicalss (i.e., lime, soda ash, etc.)). In fact, mo ost commerciaally availablee VCD units rrequire near zzero calcium leevels in the feed f water to the VCD uniit to avoid callcium foulingg problem as shown in Figg. 2. The operaation of an ion i exchangee system with h feed waterr containing calcium ionss at a maxim mum concentraation 51,000 mg/L m [1] is a technological t l and economiic challenge.

hnologies New Tech

Figure 2. Block diagraam of VCD sy ystem for produced water ttreatment New tech hnologies are under develo opment at private and pubblic research organizationns to address the importantt problem off produced water w treatmen nt. These eemerging techhnologies incclude innovaative polymers,, biopolymerrs, and other absorbent materials, m whhich are desiigned to absoorb organic and inorganic impurities in i produced water. Another emergiing technoloogy is membbrane distillattion (Memsys Clearwater Pte. P Ltd.), wh hich uses inno ovative materrials and geoometry to com mbine distillattion with mem mbrane filtratiion. There are a also numeerous innovat ations, which are applied tto older existting methods such as new w automated monitoring m teechnologies ((Beitzel Corpp.) for evapooration pondss to prevent an nd detect leak kage or overfllow at evaporration ponds. ons Conclusio Because produced p water characterisstics vary from m one well too another and also with thee age of the w well, the existin ng water treaatment methods, or even an a integrated system of vaarious existinng methods, m may not be applicable a to all wells for f achieving g all environnmental stanndards, recyccling, and reeuse 4

requirements [1]. Since the plasma water treatment method being developed in the current project is less sensitive to the produced water characteristics, we hope to be able to develop a universal solution for all produced water. In our assessment, the energy-efficient VCD concept is promising for produced water treatment as long as one can prevent mineral fouling in the evaporation-distillation unit. Furthermore, if one can operate this evaporation-distillation unit without water-softening chemicals or ion exchange, but still without mineral fouling problems, CVD could represent a definitive solution for produced water treatment. The current project attempts to accomplish this using plasma technology.

References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

F. l.-R. Ahmadun, A. Pendashteh, L. C. Abdullah, D. R. A. Biak, S. S. Madaeni, and Z. Z. Abidin, "Review of technologies for oil and gas produced water treatment," Journal of Hazardous Materials, vol. 170, pp. 530-551, 2009. T. Hayes and D. Arthur, "Overview of emerging produced water treatment technologies," in 11th Annual International Petroleum Conference, Albuquerque, NM, 2004. B. M. Johnson, L. E. Kanagy, J. H. Rodgers, and J. W. Castle, "Chemical, physical, and risk characterization of natural gas storage produced waters," Water, Air, & Soil Pollution, vol. 191, pp. 33-54, 2008. K. S. Ashaghi, M. Ebrahimi, and P. Czermak, "Ceramic Ultra- and Nanofiltration Membranes for Oilfield Produced Water Treatment: A Mini Review," The Open Environmental Journal, vol. 1, pp. 1-8, 2007. S. Madaeni, "The application of membrane technology for water disinfection," Water Research, vol. 33, pp. 301-308, 1999. B. Nicolaisen, "Developments in membrane technology for water treatment," Desalination, vol. 153, pp. 355-360, 2003. M. Ebrahimi, K. S. Ashaghi, L. Engel, D. Willershausen, P. Mund, P. Bolduan, et al., "Characterization and application of different ceramic membranes for the oil-field produced water treatment," Desalination, vol. 245, pp. 533-540, 2009. J. Mueller, Y. Cen, and R. H. Davis, "Crossflow microfiltration of oily water," Journal of Membrane Science, vol. 129, pp. 221-235, 1997. V. L. Snoeyink and D. Jenkins, Water chemistry. New York: John Wiley, 1980. E. Wunz, "A Summary of Marcellus Wastewater Treatment and Disposal," Ben Franklin Shale Gas Innovation and Commercialization Center, State College, PAAugust, 2012 2012. G. Doran and L. Leong, "Developing a cost effective solution for produced water and creating a’new’water resource," DOE/MT/95008–4. United Sates Department of Energy2000. W. Heins and D. Peterson, "Use of evaporation for heavy oil produced water treatment," Journal of Canadian Petroleum Technology, vol. 44, pp. DOI 10.2118/05-01-01, 2005. R. Becker, "Produced and process water recycling using two highly efficient systems to make distilled water," in SPE Annual Technical Conference and Exhibition, 2000. M. Lucas and B. Tabourier, "The mechanical vapour compression process applied to seawater desalination: a 1,500 ton/day unit installed in the nuclear power plant of Flamanville, France," Desalination, vol. 52, pp. 123-133, 1985. Z. Zimerman, "Development of large capacity high efficiency mechanical vapor compression (MVC) units," Desalination, vol. 96, pp. 51-58, 1994. Y. A. Cengel, M. A. Boles, and M. Kanoğlu, Thermodynamics: an engineering approach vol. 3: McGraw-Hill New York, 2011.

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