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R-03-01
EVALUATION OF REVERSE OSMOSIS SCALING PREVENTION DEVICES AT HIGH RECOVERY
Advanced Water Treatment Program Report No. 91
March 2003
U.S. DEPARTMENT OF THE INTERIOR Bureau of Reclamation Technical Service Center
Environmental Resources Services Division Water Treatment Engineering and Research Group

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March 2003

Evaluation of Reverse Osmosis Scaling Prevention Devices at High Recovery

5. FUNDING NUMBERS
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6. AUTHOR(S)
Brent E. Corbett, Charles D. Moody, Michael D. Morris

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

U.S. Department of the Interior Bureau of Reclamation Water Quality Improvement Center Yuma Area Office 7301 Calle Agua Salada Yuma AZ 85364

Burns and Roe Services Corporation 2809 South Lynnhaven Road, Suite 100 Virginia Beach VA 23452

8. PERFORMING ORGANIZATION
R-03-01 AWTR No. 91

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

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Bureau of Reclamation, Colorado River Basin Salinity Control Act Title 1, Yuma AZ Bureau of Reclamation, Science & Technology Program, Denver CO

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Available from the National Technical Information Service, Operations Division, 5285 Port Royal Road, Springfield, Virginia 22161

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13. ABSTRACT (Maximum 200 words)

This study evaluated the effectiveness of a magnetic device (MD) and a high voltage capacitance device (HVC) as possible alternatives to the dosing of chemical antiscalants for preventing scaling during reverse osmosis (RO) operation at high product water recovery. The tests were conducted on feedwater to the Bureau of Reclamation’s 72-MGD Yuma Desalting Plant located in Yuma AZ. High overall recoveries of greater than 90 percent were achieved by operating a two-stage 4-gal/min RO pilot unit (membrane unit 1 [MU1]) on the concentrate from a 200-gal/min RO unit operating at a water recovery of 70-percent. In these tests, neither the MD nor the HVC were effective in preventing calcium sulfate scaling at 91-percent water recovery. In contrast, the addition of 2 mg/L of sodium hexametaphosphate (SHMP) to MU1 feedwater was successful in avoiding scale at recoveries of 93 percent. Dosing of SHMP (or other chemical antiscalant) remains the recommended method for achieving high recovery operation without scaling at the Yuma Desalting Plant.

14. SUBJECT TERMS--
Reverse osmosis, membrane scaling, scaling prevention, calcium sulfate scale, antiscalant, sodium hexametaphosphate, magnetic water conditioner, Descal-A-Matic, Zeta Rod, Yuma Desalting Plant, Water Quality Improvement Center

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36
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NSN 7540-01-280-5500

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Standard Form 298 (Rev. 2-89)
Prescribed by ANSI Std. 239-18 298-102

EVALUATION OF REVERSE OSMOSIS SCALING PREVENTION DEVICES AT HIGH RECOVERY
Brent E. Corbett, Engineering Supervisor Burns and Roe Services Corporation
Operations and Maintenance Contractor Yuma Desalting Plant, Yuma, AZ
Charles D. Moody, Chemical Engineer United States Bureau of Reclamation Phoenix Area Office, Phoenix, AZ Michael D. Norris, Research Coordinator United States Bureau of Reclamation
Yuma Area Office, Yuma, AZ
R-03-01
ADVANCED WATER TREATMENT PROGRAM REPORT NO. 91
MARCH 2003
U.S. Department of the Interior Bureau of Reclamation Technical Service Center
Environmental Resources Services Division Water Treatment Engineering and Research Group

MISSION STATEMENTS
U.S. Department of the Interior The mission of the Department of the Interior is to protect and provide access to our Nation's natural and cultural heritage and honor our trust responsibilities to Indian tribes and our commitments to island communities.
Bureau of Reclamation The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public.
Disclaimer
Information contained in this report regarding commercial products or firms was supplied by those firms. It may not be used for advertising or promotional purposes and is not to be construed as an endorsement of any product or firm by the Bureau of Reclamation. The information contained in this report was developed for the Bureau of Reclamation; no warranty as to the accuracy, usefulness, or completeness is expressed or implied.

TABLE OF CONTENTS
Page
Executive Summary .............................................................................................................. v
Chapter 1 — Introduction.................................................................................................... 1
Chapter 2 — Background .................................................................................................... 3 2.1 Yuma Desalting Plant ............................................................................................ 3 2.2 Water Quality Improvement Center....................................................................... 4
Chapter 3 — Equipment ...................................................................................................... 7 3.1 Magnetic Device .................................................................................................... 7 3.2 High Voltage Capacitance Device ......................................................................... 8 3.3 Pilot System 1 ........................................................................................................ 9 3.4 Pilot System 2 and 3............................................................................................... 10 3.5 Membrane Units..................................................................................................... 10
Chapter 4 — Test Results..................................................................................................... 13 4.1 High Recovery with Antiscalant Addition............................................................. 13 4.2 Control ................................................................................................................... 18 4.3 High Voltage Capacitance Device Installed on MU 1 Feed .................................. 23 4.4 High Voltage Capacitance Device Installed on MU 1 Interstage .......................... 25 4.5 Magnetic Device Installed on MU 1 Feed Tank .................................................... 28
Chapter 5 — Conclusions and Recommendations............................................................. 31
Chapter 6 — Acknowledgments .......................................................................................... 33
Chapter 7 — References....................................................................................................... 35
LIST OF PHOTOS
Photo 1: Water Quality Improvement Center .................................................................. 4 Photo 2: Circulation Skid for Magnetic Device .............................................................. 7 Photo 3: Magnetic Device ............................................................................................... 8 Photo 4: High Voltage Capacitance Device .................................................................... 8 Photo 5: Fluid Systems Reverse Osmosis Unit ............................................................... 10 Photo 6: Membrane Unit ................................................................................................. 11 Photo 7: Calcium Sulfate Scaling - High Recovery ........................................................ 17 Photo 8: Calcium Sulfate Scaling – Control.................................................................... 21 Photo 9: Calcium Sulfate Scaling - HVC Installed on MU 1 Feed ................................. 25 Photo 10: Calcium Sulfate Scaling - HVC Installed on MU 1 Interstage ......................... 27 Photo 11: Calcium Sulfate Scaling - MD Installed on MU 1 Feed Tank .......................... 30
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TABLE OF CONTENTS – CONTINUED

LIST OF FIGURES

Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: Figure 7: Figure 8: Figure 9: Figure 10: Figure 11: Figure 12: Figure 13: Figure 14: Figure 15: Figure 16: Figure 17:

Page
Total Capacitance - High Voltage Capacitance Device .................................... 9 Flow Schematic - High Recovery ..................................................................... 14 Recovery - High Recover .................................................................................. 15 Calcium Sulfate Scaling – High Recovery........................................................ 16 Water Transport Coefficient – MD Installed on MU 1 Feed Tank ................... 16 Recovery – MD Installed on MU 1 Feed Tank ................................................. 18 Recovery – Control ........................................................................................... 20 Water Transport Coefficient – Control ............................................................. 21 Flow Schematic - HVC Installed on MU 1 Feed .............................................. 23 Recovery - HVC Installed on MU 1 Feed......................................................... 24 Water Transport Coefficient - HVC Installed on MU 1 Feed........................... 24 Flow Schematic - HVC Installed on MU 1 Interstage ...................................... 25 Recovery - HVC Installed on MU 1 Interstage................................................. 26 Water Transport Coefficient - HVC Installed on MU 1 Interstage................... 27 Flow Schematic - MD Installed on MU 1 Feed Tank ....................................... 28 Recovery - MD Installed on MU 1 Feed Tank.................................................. 29 Water Transport Coefficient - MD Installed on MU 1 Feed Tank.................... 29

Table 1: Table 2:

LIST OF TABLES
Laboratory Data - MU 1 Feed ........................................................................... 19 Laboratory Data - MU 1 Concentrate................................................................ 22

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∆P AWTR BRSC CRADA E4 E7 FS gfd gpm HR HWS HVC MD mg/L Minute MODE MU P.L. PS 1 PS 2 PS 3 Reclamation River RO SCADA SHMP STC WQIC WTC YAO YDP

LIST OF ACRONYMS
pressure differential Advanced Water Treatment Research Program Burns and Roe Services Corporation cooperative research and development agreement lead element of MU 1 vessel 3B tail-end element of MU 1 vessel 3B Fluid Systems gallons per square foot per day gallons per minute High Recovery with Antiscalant Addition Hydranautics high voltage capacitance device magnetic device milligrams per liter Minute No. 242 of the International Boundary and Water Commission main outlet drainage extension membrane unit public law Pilot System 1 Pilot System 2 Pilot System 3 United States Bureau of Reclamation Colorado River reverse osmosis supervisory control and data acquisition sodium hexametaphosphate salt transport coefficient Water Quality Improvement Center water transport coefficient Yuma Area Office Yuma Desalting Plant

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EXECUTIVE SUMMARY
The objective of this study was to evaluate the effectiveness of a magnetic device (MD) and a high voltage capacitance device (HVC) as possible alternatives to chemical addition for reducing scaling and improving the performance of reverse osmosis (RO) systems [1]. The control of scaling would enable RO operation at higher recoveries in the treatment of almost all water supplies. The HVC and MD were determined to be ineffective alternatives for reducing RO scaling at high recovery. Significant calcium sulfate scaling was observed with the MD installed on membrane unit 1 (MU 1) feed tank and with the HVC installed on both the suction line to the MU 1 high pressure feed pump and on MU 1 interstage. The overall recovery, where calcium sulfate scaling occurred, was approximately 91 percent. The addition of approximately 2.0 milligrams per liter (mg/L) of sodium hexametaphosphate (SHMP) was successful in avoiding scale at recoveries of approximately 93 percent and is recommended for high recovery operation on main outlet drainage extension (MODE) water.
The MD and HVC were tested at the Water Quality Improvement Center (WQIC). The MD tested was a 316 stainless steel Descal-A-Matic® device, and the HVC tested was the Zeta RodTM ZR18S. The spiral-wound RO elements used were Desal CD 2540T1078 (2½-inch diameter by 40-inch-long) cellulose acetate elements. The concentrate from Pilot System 1 Fluid Systems RO was the feed source, and the membrane units were operated at an average element flux of 10 gallons per square foot per day (gfd). Response variables include the change in the water transport coefficient (WTC), salt transport coefficient (STC), and second stage pressure differential (∆P).
During this study, measuring the individual performance of the tail-end element was determined to provide a sensitive and prompt detection of RO scaling. This prompt detection enables the plant engineer to immediately correct the condition(s) that created the scaling environment and prevent further scaling of the RO equipment. Based on these experiences, we recommend that the design of RO membrane equipment for research and production plants should consider including the instrumentation to monitor the performance of some of the lead elements, where degradation and biological fouling may occur, and some of the tail-end elements, where scaling and inorganic fouling may be most severe.
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Evaluation Of Reverse Osmosis Scaling Prevention Devices At