MEMORANDUM

TO: Public Record for the Effluent Limitations Guidelin es and Standards for Drinking

Water Treatment Facilities EPA Docket Number: EPA-HQ-OW-2008-0517 ( www.regulations.gov ), DCN 10003

FROM: Paul Hanson, P.E.

PG Environmental LLC (PG)

DATE: 30 August 2010

SUBJECT: Ion Exchange for Produced Water Treatment

EPA requested PG assemble literature data on ion ex change. Ion exchange has several applications in water treatment processes such as hardness removal, desalination, alkalinity removal, radioactive wast e removal, ammonia removal, and heavy metal removal ( ALL 2006a). Ion exchange is considered to be an efficient process, with low energy demand, possible continuous regeneration of resin, and systems can be mobile (ALL 2006a). Ion exchange is the primary produced water treatmen t method in the Powder River Basin (PRB) (ALL 2006b). This memorandum discusses the process, performance, and residuals.

Description of the Treatment Process

Ion exchange (IX) is a physical-chemical process by which ionic contaminants are removed from the water (US EPA 2000). The ion exchange process effec tively removes arsenic, heavy metals, nitrates, radium, barium, strontium, salts, uranium, and othe r elements from produced water (ALL 2006a). Ion exchange is a reversible chemical reaction wherein positively or negatively charged ions present in th e water are replaced by similarly charged ions presen t within the resin (ALL 2006a). The resins immersed in the water are either naturally occurring inorgan ic zeolites or synthetically produced organic resin s (ALL 2006a). To accomplish this exchange of ions, f eed water is continuously passed through a bed of ion exchange resin beads in a down-flow or up-flow mode until the resin is exhausted (i.e., when all s ites on the resin beads have been filled by contaminant ions) (US EPA 2000). When the replacement ions on the resin are exhausted, the resin is recharged/reg enerated with more replacement ions (ALL 2006a). Th e number of bed volumes that can be treated before ex haustion varies with resin type and influent water quality. Typically 300 to 60,000 (up to 300,000) be d volumes can be treated before regeneration is required, depending on the adsorptive capacity of t he resin and the feed water quality. (US EPA 2000). Residuals include backwash/rinses and regeneration waste. Product water and regeneration wastes may require pH stabilization.

Ion exchange resins are classified as cation exchan gers, which exchange positively charged ions, and anion exchangers, which exchange negative ly charged ions. The resins are further

classified as:

Strong Acid Cation (SAC) Resins (ALL 2006a): The hydrogen or sodium forms of the cation resins a re highly dissociated and H + or Na + ions are readily exchangeable over the entire pH range. Equation 1 shows an example of salt

removal with SAC.

(1) 2(R – SO 3 H) + NiCl 2 → (R – SO 4 )Ni + 2HClEquation 2 shows an example of Ca+ softening with S AC.

(2) 2(R – SO 3 H) + Ca + → (R – SO 3 ) 2 Ca + 2H +

These resins would be used in the hydrogen form for complete deionization (Na, Ca, Mg, Ba, etc. removal); they are used in the sodium form for water softening (Ca and Mg removal). After exhaustion, the resin is regenerated to the hydroge n form by contact with a strong acid solution, or to the sodium form with a sodium chlor ide solution.

Weak Acid Cation (WAC) Resins (ALL 2006a): Weak acid resin has carboxylic acid (COOH) group as opposed to the sulfonic acid group (SO 3 H) used in strong acid resins. These resins behave sim ilarly to organic acids that are weakly dissociated. WAC has high affinity for divalent sal ts. Equation 3 shows an example of Ca + softening with WAC. Alkalinity present in bicarbona te form also can be removed by WAC.

(3) 2(R – COOH) + Ca + → (R – COO) 2 Ca + 2H +

Free H + ions can react with bicarbonate (present as hardne ss, Ca(HCO 3 ) 2 ) to form carbonic acid. The carbonic acid decomposes in carbon dioxid e as shown in equation 4. Removal of carbon dioxide or decarbonation (Moftah 2002) is ne cessary during the water treatment

process.

(4) HCO 3 - + H + → H 2 CO 3 → CO 2 + H 2 O

Weak acid resins exhibit a much higher affinity for hydrogen ions compared to strong acid resins. This characteristic allows regeneration to the hydrogen form with significantly less acid than is required for strong acid resins. Almost com plete regeneration can be accomplished with stoichiometric amounts of acid. The degree of disso ciation of a WAC is strongly influenced by the solution pH. Consequently, resin capacity depen ds in part on solution pH.

Strong Base Anion Resins (ALL 2006a): Strong base resins are highly ionized and can be us ed over the entire pH range. These resins are used in the hydroxide (OH

- ) form for water deionization. They will react with anions in solution and can convert an acid solution to nearly pure water. Equation 5 shows the reaction involved in an anion exchange step.

(5) (R – NH 3 OH) + HCl → (R – NH 3 Cl) + HOH

Regeneration with concentrated sodium hydroxide con verts the exhausted resin to the hydroxide form.

Weak Base Anion Resins (ALL 2006a): Weak base resins exhibit minimum exchange capacity above a pH of 7. The weak base anion

resins sorbs anions associated with weak acid.

EPA observed numerous ion exchange installations in the Powder River Basin as part of its site visit program (see Attachment A). EMIT Water Discharge T echnology, LLC (EMIT) Higgins Loop TM
continuous counter-current IX systems are the most commonly used IX systems in the PRB (Johnston 2010b). The EMIT process utilizes a strong acid ca tion exchange resin, which has a sulfonic acid grou p that exchanges sodium, barium, calcium, and magnesi um ions with hydrogen ions (ALL 2006a). Because divalent ions (Ca, Mg, etc.) are favored over monov alent (Na, etc.) ions by the resin for replacement,calcium and magnesium often need to be added back t o the treated water to reduce the Sodium

Absorption Ratio (SAR). EPA observed a pilot scale Drake Water Technologies, Inc. (Drake) process that selectively targets the removal of the sodium ion from CBM produced water (U.S. EPA, 2010).

Operational Limitations

TDS Limitations The average TDS application range is between 500 mg /L and 7,000 mg/L (CSM 2009). EMIT estimated a cation load of 1,600 to1,700 mg/L is the approximat e breakpoint when it becomes uneconomical to treat CBM produced waters. EMIT has successfully treated CBM produced waters at cation loads up to 1,500 mg/L (Johnston 2010b).

Fouling and Scaling Ion exchange requires pretreatment against fouling agents, including suspended solids, oxidized metals

, and scaling minerals (e.g., CaSO4) (CSM 2009). Oil and grease and iron bacteria are two constituents t hat must be removed prior to ion exchange (ALL 2006b). Occasional chemical disinfection of the resins may be required to mitigate biofouling and will typical ly consist of H 2 O 2 or NaOCl cleaning solutions (CSM 2009). Additionally, many IX resins are sensitive to free chlorine oxidation. IX processes must also be carefully managed to reduce osmotic shock and mecha nical abrasion of IX resin, which will lead to physical loss of the resin (Dow Chemical 2005).

Temperature Acid cation resins should not be exposed to feed te mperatures in excess of 120°C, while base anion res ins are limited to 100°C or lower (CSM 2009).

Variable Feed Water Volumes In order to handle variable quantities of water, so me operators are exploring using two or more smalle r capacity units and bringing on line the number of u nits to handle the capacity as needed instead havin g one large capacity unit (ALL 2006b) EMIT reported units treating as little as 6,000 bbls/day, and tha t they recently completed a 125,000 bbl/day treatment system. (Johnston 2010b)

Performance Data and Costs (What discharge levels c an these treatment systems meet? Do costs vary with levels of discharge? Are final effluent c oncentrations independent from influent concentrations?)

Ion exchange resins are chosen to preferentially ad sorb the particular contaminant of concern (US EPA 2000). Ion exchange can achieve a wide range of res ults depending on the concentrations in the influen t stream and how the system is operated and maintaine d. For example, different types of ion exchange resins are available that will yield different perf ormance. The frequency of backwashing, replacement of resins, and the nature of pretreatment steps all co ntribute to how well the system will perform and ho w costly the treatment process will be. (Argonne Nati onal Laboratory 2006) Treatment process permeate quality is dependent on feed water salinity and ope rating conditions with greater than 93 percent reje ction of target ions achievable (CSM 2009).

Potential Data Sources

CBM Detailed Questionnaire EPA received questionnaire responses from 11 ion ex change treatment processes in the PRB basin (WY and MT) and the Green River basin.Office of Ground Water and Drinking Water (OGWDW)

Note for Brian: OGWDW may have some useful data, bu t drinking water IX is typically focused on Ca and Mg softening or anion removal.

Vendors

See Attachment A for a list of vendor information i n or to be posted to the CBM record.

Drake provided confidential sampling data from a 7- day continuous demonstration of the Drake ion exchange process. Drake design goals are presen ted in Table 1:

Table 1. Drake Process Effluent Water Quality Desig n Goals

Parameter Value

SAR 3 Sodium <100 mg/L Electrical conductivity (EC) 1000 μS/cm pH 6.5

Source: US EPA 2007a

EMIT stated that for the PRB standards that they ha ve been requested to evaluate, they have been

able to treat water to those standards. EMIT has a wealth of performance data to use in predictive modeling because they regularly sample incoming and outgoing water from their systems (as well as some intermediate water sampling). EMIT noted t hat their cost data and monitoring data is sensitive customer data. (Johnston 2010b) A sample of EMIT performance data is provided in

Table 2:

Table 2: EMIT Performance of Higgins Loop Treatmen t for a Field Trial at a Powder

River Basin Site

Constituents Influent

Produced

Water Treated

Water Removal %

Na, ppm 486 12 97.53

Ca, ppm 22.2 113 -409

Mg, ppm 13.2 <1 >93

K, ppm 13.5 <1 >93

Ba, ppm 0.72 ND 100

Carbonate, ppm <1 <1

-
Bicarbonate, ppm 1430 311 78.52

Chloride, ppm 18 42 -133.33

Sulfate, ppm 1 1.1 -10

SAR 20.2 0.3 98.51 pH 8.1 6.5 19.75

Source: ALL 2006a

Colorado Department of Health and Environment (CDPH E) Gary Beers noted that the State of Colorado Water Q uality Control Division (WQCD) has issued 3 to 6 permits where advanced treatment is applied to prod uced waters before discharge to surface waters. Discussions were held with developers and manufactu rers of these technologies with a focus onperformance and general costs. The information on t he various technologies and provided cost

information is to be sent to EPA. (Johnston 2010a) It is unclear at this time if any of this data is f or ion exchange.

Montana Department of Environmental Quality’s (MDEQ ) MDEQ’s Board of Environmental Review (BER) proposed technology based limits (MDEQ’s Proposed Rule VIII) in 2005 to restrict discharges or CBNG p roduced water.

NEW RULE VIII TRATMENT-BASED EFFLUENT LIMITATIONS (1) If the department grants a waiver from the zer o discharge requirement for all or a portion of the wastewater pursuant to [New Rules II and III], the amount of wastewater that obtains the waiver shall achieve the following minimum technolo gy based effluent limitations at the end of the pipe prior to discharge: (a) calcium average concentration between 0.1 mg/L and 0.2 mg/L; (b) magnesium average concentration between 0.1 mg/ L and 0.6 mg/L; (c) sodium average concentration of 10 mg/L; (d) bicarbonate average concentration of 30 mg/L an d instantaneous maximum concentration of 115 mg/L; (e) sodium adsorption ratio instantaneous maximum o f 0.5; (f) electrical conductivity average concentration o f 233 μmhos/cm; (g) total dissolved solids average concentration of 170 mg/L; (h) ammonia average concentration of 0.1 mg/L and i nstantaneous maximum concentration of 0.3 mg/L; and (i) arsenic concentration of <0.0001 mg/L.”

Comments on Proposed Rule VIII questioned the achie vability and affordability of the Montana limits,

and noted inconsistent treatment levels for several parameters. Comments also noted that the proposed limits were below drinking water standards, creatin g water that may be detrimental for beneficial use (e.g., leaching minerals and metals from soil), as well as noting additional environmental impacts fro m increased waste volumes (e.g., waste hauling traffi c). (ALL 2006b, Sattler 2006, Argonne National Laboratory 2006). One report provided costs, but n oted that the costs for the proposed Montana standa rd may be as much as an order of magnitude greater tha n current costs for treatment and discharge (ALL 2006b).

Bureau of Reclamation Desalting Costs The Water Treatment Estimation Routine (WaTER) User Manual (Wilbert 1999) provides ion exchange

costs.

U.S. Department of Energy Desalting Costs The U.S. Department of Energy provided cost estimat es for ion exchange in the PRB based on TDS limits of 500 and 1000 mg/L (Bank 2006).

University of Wyoming The University of Wyoming dev eloped a decision model for treating CBM water (Sajtar 2008).

Colorado School of Mines The Colorado School of Mines is developing a Produc ed Water Treatment and Beneficial Use Screening Tool. This tool will provide water quality (based o n geographic location), suggest suitable treatment trains, and provide a cost-benefit analysis of diff erent beneficial reuse options for the water.Typical Disposal Practices of Waste Streams and Vol umes of Waste as Compared to Volumes of

Treated Influent

Brines are produced from rinsing, regenerating, and backwashing the ion exchange unit. The spent media residuals are mainly solid waste media and the cont aminants absorbed to it.

The waste characteristics are highly dependent on t he nature of the process water and the treatment processes incorporated. The predominant ion in the spent regenerate streams is often the co-ion in th e regenerant (e.g., chloride, sulfate, carbonate, or sodium) (AWWA, ASCE 1996). The other ions present are those removed by the resin and reclaimed by the regenerant. With chlorides present, brine is corro sive to materials it contacts. The pH of the spent regen erant could be low or high depending on the type of resin used. For example, a cationic exchange resin may be regenerated using concentrated sulfuric or hydrochloric acid, while an anionic exchange resin may be regenerated using a strong base(U.S. EPA 2007b). In addition to the spent regenerant waste, IX generates backwash water used before and after regeneration.

Table 3 summarizes the typical residuals generated from drinking water ion exchange and potential pollutants in each waste stream. (AWWA, ASCE 1996; AWWA & AWWARF 1987).

Table 3. Drinking Water Treatment Processes and Was te Streams
Typical Residual Waste

Streams Typical Waste Stream

Constituents

Brine stream (regenerate waste) TDS

Metals

Hardness

Calcium Magnesium

Sodium

Sulfate

Chloride

Nitrates

Radionuclides Rinse water and/or backwash Dilutes regenerate wast e

Of these streams, the regeneration stream contains the highest levels of TDS, ranging from 10 to 300 times the levels found in drinking water feed water (US EPA 1993). This high TDS content is due to the ions removed from the exchange resin during regener ation and excess regeneration ions (US EPA 1993). Note that drinking water ion exchange is typically used for calcium and magnesium softening and often regenerated using sodium chloride while produced wa ter ion exchange is typically used for sodium removal (typically also removing calcium and magnes ium) and regenerated using acids. The regeneration

stream is often mixed with the rinse and backwash s treams, diluting the regenerant by as much as an or der of magnitude (US EPA 1993).

Regeneration volumes are dependent on regeneration needs, but is typically requires less than 2 percen t of the product water (2 to 20 bed volumes of rinse wat er) to restore the adsorptive capacity of the IX re sin (CSM 2009). EMIT reports concentrated brine volumes average approximately 1.0 percent or less of the total loop feed volume in the PRB, depending on the cation loading that is removed from the treated wa ter (All 2006b, Johnston 2010b). Drake reported the vo lume of brine is approximately 1 to 3 percent of th e influent flow to the treatment units (US EPA 2007a) . Drinking water ion exchange concentrated brine i s reported to vary between 1.5 and 10 percent and to average 15,000 to 35,000 mg/L (US EPA 1993). Notethat the PRB contains relatively low TDS concentrat ions and the concentrated brine volumes increase

with influent TDS concentrations.

Disposal Depending on the ionic species removed, disposal of this material can cause problems, especially if discharged to a waterway. High-TDS residuals are of ten disposed via underground injection, or used as a deep fracking fluid; however, the availability of d isposal options is highly dependent on geographic location and regulatory requirements. Technologies to further concentrate IX residuals include evaporation, crystallization, and thermal distillat ion. POTW’s are not designed to remove TDS and Region 3 recently limited POTW’s to accept no more than 1 percent of their daily flow from fracking

water.

References

AWWA, ASCE 1996. American Society of Civil Engineer s, American Water Work Association, U.S. Environmental Protection Agency. Management of Water Treatment Plant Residuals: Tech nical Transfer

Handbook . April 1996. EPA-HQ-OW-2008-0465-0728.

ALL 2006a. ALL Consulting. A Guide to Practical Management of Produced Water f rom Onshore Oil and Gas Operations in the United States . October 2006. Prepared for US DOE, National Pet roleum Technology Office. EPA-HQ-OW-2008-0517 (DCN 10000).

ALL 2006b. ALL Consulting. Feasibility Study of Expanded Coal Bed Natural Gas Produced Water Management Alternatives in the Wyoming Portion of t he Powder River Basin, Phase One . Prepared For U.S. Department of Energy National Energy Technolog y Laboratory Wyoming State Planning Office, January 2006. EPA-HQ-OW-2004-0032-2524.

Argonne National Laboratory 2006. Observations on a Montana Water Quality Proposal. Prepared by Environmental Science Division, Argonne National Laboratory, January 2006. ANL/EVS/R-06/2. EPAHQ-OW-2008-0517 (DCN 10004).

AWWA & AWWARF 1987. American Water Works Associatio n Research Foundation. 1987. Water Treatment Plant Waste Management . EPA-HQ-OW-2008-0517 (DCN 10018).

Bank 2006. The Economics of Powder River Basin Coalbed Methane Development. Prepared for: U.S. Department of Energy. Prepared by: Gregory C. Bank, Vello A. Kuuskraa. Advanced Resources International, Inc. January 2006. EPA-HQ-OW-2004-00 32-2451.

CSM 2009. An Integrated Framework for Treatment and Managemen t of Produced Water: TECHNICAL

ASSESSMENT OF PRODUCED WATER TREATMENT TECHNOLOGIES 1st Edition. RPSEA Project

07122-12. November 2009. EPA-HQ-OW-2008-0517 (DCN 10007).

Dow Chemical 2005. Dow Chemical Company, DOWEXTM Ion Exchange Resins Pr actical Guidelines

. Form 177-01537-1006, 2005, http://www.dow.com/PublishedLiterature/dh_0064/0901 b80380064a0d.pdf?filepath=liquidseps/pdfs/nore g/177-01537.pdf&fromPage=GetDoc . EPA-HQ-OW-2008-0517 (DCN 10019).

Johnston 2010a. Notes from 29 January 2010 Teleconference with Gar y Beers, Colorado Department of
Public Health and Environment, on the Colorado Gene ral NPDES Permit for Produced Water Treatment Facilities (COG840000). July 27, 2010. EPA-HQ-OW-2008-0517 (DCN 10014).Johnston 2010b. Summary of EMIT Water Discharge Technology (an Ext erran Company) held on 18

February 2010. July 27, 2010. EPA-HQ-OW-2008-0517 (DCN 10020).

Moftah, K. 2002. High pH RO for Wastewater Treatment , Pollution Engineering. October 2002. EPAHQ-OW-2008-0517 (DCN 10021).

Sajtar 2008, Sajtar, Eric T., M.S.; David M. Bagley Ph.D. P.E. Toolbox to Evaluate Treatment Technologies for PRB CBM Water. Department of Civil and Architectural Engineering, University of Wyoming. February 2008. EPA-HQ-OW-2008-0517 (DCN 10 017).

Sattler 2006. Allan R. Sattler, Malynda A. Aragon, M. Michael Hightower. Technical Review of Proposed Changes in Montana Water Quality Standards for Coal Bed Natural Gas Produced Water . Printed January 2006, Prepared by Sandia National Laborator ies Albuquerque, New Mexico 87185 and Livermore, California 94550. SAND2006-0312. EPA-HQ- OW-2008-0517 (DCN 10011).

U.S. EPA 1993. Large Water System Byproducts Treatment and Disposa l Cost Document . EPA 811-D93-002. EPA-HQ-OW-2008-0517 (DCN 10013).

U.S. EPA 2000. Technologies and Cost for Removal of Arsenic from D rinking Water . EPA 815-R-00-

028. EPA-HQ-OW-2008-0465-0728.

U.S. EPA 2007a. Final Site Visit Report: Drake Water Technologies, Inc. Gillette, WY (Powder River Basin), November 30, 2007. EPA-HQ-OW-2006-0771-0975.

U.S. EPA 2007b. Identification and Characterization of Typical Drin king Water Treatment Residuals

. September 2007. EPA-HQ-OW-2008-0465-0555.

U.S. EPA, 2010. Final Site Visit Report: Drake Water Technologies, Inc. J une 16, 2009, Powder River
Basin, WY. EPA-HQ-OW-2008-0517 (DCN 10032).

Wilbert 1999. Water Treatment Estimation Routine (WaTER) User Manual. Bureau of Reclamation. Water Desalination Research and Development Report No. 43. August 1999. EPA-HQ-OW-2008-0517 (DCN 10016).Attachment A. Ion Exchange VendorsTechnology NameVendorTechnology in Use orPilot?Operators, if in useSite visitcompleted?Reference Materials / OtherInformationHiggins LoopContinuous IonExchangeEMIT, SevernTrent ServicesIn use Pinnacle GasResources, BlackDiamond Energy,Lance Oil and Gas,Fidelity Exploration &Production Co.Yes EPA-HQ-OW-2006-0771-0974;EPA-HQ-OW-2004-0032-2524Remco Metal RecoveryIon Exchange ProcessRemco In use Not available No EPA-HQ-OW-2006-0771-0927Drake Process Drake The Drake Process hasoperated under severalWyoming DEQ “Permitsto Construct” and hasreceived approval for pittreatment by the WyomingOil & Gas ConservationCommission.Bill Barrett Corporationat their Willow CreekPlan of DevelopmentYes EPA-HQ-OW-2006-0771-0980;EPA-HQ-OW-2006-0771-0953;EPA-HQ-OW-2006-0771-0962;EPA-HQ-OW-2008-0517 (DCN10032)Ion Exchange Triwatech,LLCTreatmentSystemTriwatech, LLC Pilot Plant Yes EPA-HQ-OW-2006-0771-1048RecoPur water treatmentsystem /RecoFlo ShortBed Ion ExchangeTechnologyPureTechLLC, Eco-TecequipmentNear Completion Marathon Oil Company Yes EPA-HQ-OW-2006-0771-1774EPA-HQ-OW-2006-0771-1341;EPA-HQ-OW-2006-0771-1342;EPA-HQ-OW-2008-0517 (DCN10034)Fixed-bed dynamic flowion exchange, withfiltrationSET Corp(formerly RGGlobalLifestyles,Inc.)In use Yates Petroleum Corp(Gilette, WY)Yes EPA-HQ-OW-2006-0771-1338;EPA-HQ-OW-2008-0517 (DCN10036)Attachment A. Ion Exchange VendorsTechnology NameVendorTechnology in Use orPilot?Operators, if in useSite visitcompleted?Reference Materials / OtherInformationAdvanced “Amberpack”Ion Exchange TreatmentSystemsWatergyProducedWaterSolutions, Inc.(in associationwith Rohmand Haas)Not available Not available No http://www.energyexposition.com/exhibitor_list.htmhttp://www.watergypws.com/watergy_technology.htmlGroundwater ionexchange system forarsenic, nitrate,perchlorate, uranium,and chromium VIBasin Water Not available Not available No http://www.energyexposition.com/exhibitor_list.htmhttp://www.basinwater.com/Ion exchange treatmentsystemRohm andHaasNot operational at time ofsite visitAnardarko Yes EPA-HQ-OW-2006-0771-1002Ion exchange (or reverseosmosis), as acomponent of completepre-, polishing, and posttreatmentTriwatech,LLCField pilot Field pilot for BPAmerica, Inc.’s CBMoperations in WallaceGulch, Colorado; plustests for several otheroperatorsYes EPA-HQ-OW-2006-0771-1048;Testing has been completed on 20different CBM produced waterstreams from several operators tocategorize water quality and to targetmarkets for treatment; however, thetest results and operator names areconfidential and were not supplied toEPA.