Arsenic Removal from Water Using Manga,nese Greensand: Laboratory Scale Batch and Column Studies by: New Mexico State University Box 30001 Las Cruces, NM 88003-8001 Contract No. 142596-FC-81-05016 Water Treatment Technology Program Report No. 41 June 1999 U.S. Department of the Interior Bureau of Reclamation Technical Service Center Water Treatment Engineering and Research Group REPORT DOCUMENTATION PAGE 6. FUNDING NUMSERS Arsenic Removal From Water Using Manganese Greensanrl: I&xatoly Scale Batch and Cohmm Studies Assistance Agreement No s. AulnOR,S, 142596-FC-81-05016 Adrian Hanson, Jared Bates - NMSUICAGE Dean Heil - CSU Soil Chemistry Andrew Bristol - NMSUiSWA? Lab -._--...~. 7. PERFORMlNO ORGANIZATION NAMEIS) AND ADDRESSIES, 8. PERFORMlNG ORGANlZATtON REPORT NUMBER New Mexico State University Box 3cwJl Las Cmces NM 88003-8001 9.SPONS0RINO~~NITORINOA Bureau of Reclamation AGENCY REPORT NUMBER Denver Federal Center WTTP Report No. 4 1 PO Box 25007 Denver CO 802250007 11. SUPPLEMENTARY N&- 12a. MSTNIS”TION,A”AILASlLlTY STATEMEM Available from the National Technical Information Service, Operations Division, 5285 Port Royal Road, Springfield, Virginia 22161 - - Future drink&g water regulatiora for arsenic are expected to be lowered from the present 50 @gK to somewhere between 2 - 20 pg/L Two rxer& studies inlkakd that manganese greensand could be very effective in removing ares&c. Manganese greensand is a minera alIed glauccmite that is coated with a manganese oxide coating and used to remove iron and manganese hardness from drinking water This study evtid several important parameters for arsenic removal using manganese greensand. The parameters chosen to In w&.ated were contact time;. pH, iron concentration, anal potential of sulfate interference. In addition, b&b the common oxidation form Bf aresenic, arsenite and arsenate, were studied. The greensand c&mm successfully removed arsenic, but only after the media hsr Rwpf&mtedwithdihdencd. Jllsihlations~areseni c IS present with both iron and manganese, this technology has great pmmise __I-- 14. SVSJECT TERMS-- 15. NVHSER OF PAGES Arsenic Removal from Water Using Manganese Greensand: Laboratory Scale Batch and Column Studies by: New Mexico State University Box 30001 Las Cruces, NM 88003-8001 Contract No. 1425-96-FC-81-05016 Water Treatment Technology Program Report No. 41 June 1999 U.S. Department of the Interior Bureau of Reclamation Technical Service Center Water Treatment Engineering and Research Group Mission Statement 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 tribes. The mission of the Bureau of Reclamation is m manage, develop, and protect water and related resources in an environmentally sound manner in the interest of the American Public. Disclaimer The information contained in this report regarding commercial products or tinns may not be used for advertising or promotional purposes and is not m 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. ACKNOWLEDGMENTS This research was funded in part through the Water Treatment technology Program Department of the Interior grant (solicitation no. 142%96-FC-81-05016). The authors would also like to thank the Waste Education Management and Research Consortium (WERC) for support through their seed grant program, the Engineering Research Center NMSU, and the Engineering College at NMSU. This work has been presented in a number of formats at a number of forums. The citations are listed below. Bates, J., A. Hanson, D. Heil, M. Johnson, G. Rayson, A. Bristol, Manganese Greensand for the Removal of Arsenic From Drinking Water, AWWA Water Quality Technology Conference, San Diego, California, November 1 - 5, 1998. Bates, J., A. Hanson , D. Heil, M. Johnson, G. Rayson, A. Bristol, Batch studies of Arsenic Removal From Drinking Water Using Manganese Greensand, AWWA Annual National Conference, Dallas TX, June 21-25, 1998 (Third Place Poster). A. Hanson , D. Heil, J. Bates, M. Johnson, G. Rayson, A. Bristol, Removal of Arsenic From Drinking Water Using Manganese Dioxide Coated Filter Media, AWWA Inorganics Workshop, San Antonio TX, February 23, 1998. Bates, J., A. Hanson, F. Cadena, B. Thomson, A. Bristol, Technologies for the Removal of Arsenic From Drinking Water in New Mexico, New Mexico Science Journal, 1998. Bates, J., Batch Studies of Arsenic Removal From Drinking Water Using Manganese Greensand, Masters Thesis, New Mexico State University, May, 1998. EXECUTIVE SUMMARY Future drinking water regulations for arsenic arc expected to be lowered from the present 50 ug/L to somewhere between 2 and 20 ug/L. Two recent studies have indicated that manganese greensand could be very effective in removing arsenic. Manganese greensand is a mineral called glauconite that is coated with a manganese oxide coating and used to remove iron and manganese hardness from drinking water. The purpose of this study is to evaluate several important parameters for arsenic removal using manganese greensand. The parameters chosen to be evaluated were contact time, pH, iron concentration, and potential of sulfate interference. In addition both of the common oxidation forms of arsenic, arsenite and arsenate, were studied. The experimental procedure was carried out under laboratory conditions. Adjustment of pH was accomplished by the addition of acid or base. Iron-arsenic solutions were mixed for ten minutes. One gram of manganese greensand was added to solution and mixed for the contact time desired. The solution was filtered to separate the liquid phase from the sand. The solution was analyzed by a commercial 1,ab using inductively coupled plasma mass spectrophotometery with a detection limit for arsenic of ti.4 ug/L. A range of pH’s from 3 to 9 was evaluated. A pH of 5 was found to be optimal for arsenic removal in the arsenate and arsenite form. For an initial arsenic concentration of 50 ug/L, the final arsenic concentration ranged from 1.8 pg/L to 4.2 pg/L for a pH of 5. Two more batch sets were performed at this optimal pH with similar results. Varying ferrous chloride concentrations were added to the solution from zero to 20 times the arsenic concentration in terms of molar ratio of ferrous chloride to arsenic. At all the pHs no significant correlation between iron dose and arsenic removal can be seen. Contact times from 15 minutes to 24 hours were evaluated at a pH of 5. The results indicate that arsenic adsorption to manganese greensand has reached its maximum by 15 minutes of contact time. Sulfate interference was evaluated at a pH to 5. Based on the results from the batch testing, sulfate did not interfere with arsenic removal. The greensand columns successfully removed arsenic, but only after the media had been pre- treated with dilute acid. A solution of dilute HCI was passed through the media until the influent and effluent pH came to steady state. This allowed the operator to control the operational pH. With the bed properly prepped, 400+ bed-volumes of water were treated with no evidence of impending breakthrough. The bed was regenerated and another 200+ bed-volumes were treated. It appears that the appropriate preparation of the media will allow manganese greensand to act as an effective arsenic removal media. It appears that neither BlRM nor Anthrasand is an adequate replacement for manganese greensand. i There are a number of simple technologies, such as ion exchange, coagulation/microtiltration, iron oxide based filtration, and activated alumina, which are on the market for treatment of arsenic in water. In a situation where only arsenic is to be removed, or where arsenic and fluoride are to be removed, the technology discussed here is probably not cost effective. However, in a situation where Fe & Mn are present with As this technology has great promise. This technology is especially interesting to utilities where Fe and Mn are already being removed using a manganese greensand filter. It is possible that a small pH adjustment from 8+ to 6.5 may be all that is required to bring the facility into compliance. ii TABLE OF CONTENTS PageNo. LISTOFTABLES ............................................................ vi LISTOFFIGURES .......................................................... vii 1. INTRODUCTION ........................................................ . . 1 1.1 Arsenic Background ............................................... 1 1.1 .l Arsenic Chemistry ......................................... 1 1.1~ .2 Drinking Water Regulations ................................. 1 1 .I~.3 Health Implications of Arsenic ............................... 2 1.1..4 Occurrences of Arsenic ..................................... 4 1.15 Arsenic Removal Techniques ................................ 5 1.1.5.1 Iron Coagulation ................................... 5 1.1.5.2 Alum Coagulation .................................. 6 1.1.5.3 Softening ......................................... 6 1.1.5.4 Activated Alumina Filtration ......................... 6 1.2 Manganese Greensand Filtration Background ........................... 7 1.2.1 Glauconite Background ..................................... 7 1.2.2 Manganese Dioxide Background .............................. 1 0 1.2.3 Potassium Permanganate Background .......................... . l l 1.2.4 Manganese Greensand Filtration .............................. .I2 1.2.4.1 Chemistry ........................................ .12 1.2.4.2 Typical Physical Characteristics and Operating Parameters . .13 1.2.4.3 Full Scale Arsenic Removal Study .13 1.2.4.4 Pilot Scale Arsenic Removal Study .................... .14 1.3 Objectives ....................................................... 1 5 2. MATERIALS AND METHODS ............................................ 1 7 2.1 Chemicals and Media Used ......................................... 1 7 2.1.1 Arsenate Solution .......................................... 1 7 2.1.2 Arsenite Solution ..................... . . 1 7 2.1.3 Ferrous Iron Solution .................. . . . .I7 2.1.4 Potassium Permanganate Solution ........ . . . . . . .18 2.1.5 Manganese Greensand ................. . .18 2.2 Experimental Procedure ....................... . . .18 2.2.1 Pre-Treatment of Glassware and Test Tubes . .18 2.2.2 Optimum pH and Fe Dose .............. . .18 2.2.3 Optimum Contact Time ................ . . .19 2.2.4 Sulfate Interference ................... . .19 2.2.5 Arsenite Study ....................... . . . . . . . .19 3. RESULTS AND DISCUSSION ........................ . . . . .21 3.1 OptimumpHandFeDose ..................... . . .21 3.2 Optimum Contact Time ....................... .30 3.3 Sulfate Interference ........................... .32 Table of Contents Page No. 3.4 ArseniteStudy......................................................34 3.5 Chemical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...36 3.5.1 Freundlich Isotherm . . . . . .36 3.5.2 Langmuir Isotherm . . . . . . .37 3.5.3 Ion Exchange Model . . . . . . 41 4. COLUMN STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...47 5. ALTERNATE MANGANESE DIOXIDE COATED MEDIA . . 1. .5 1 5.1BlRMMedia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...51 5.2 Anthrasand Media . . . . . . . .53 6. CONCLUSIONS...........................................................55 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...57 APPENDICES BATCH TESTS: EFFECT OF FE AND PH BATCH TESTS: EFFECT OF CONTACT TIME BATCH TESTS: EFFECT OF SULFATE BATCH TESTS: EFFECT OF USING ARSENITE INSTEAD OF ARSENATE FREUNDLICH ISOTHERMS FOR VARIED PH LANGMUIR ISOTHERMS FOR VARIED PH COLUMN TESTS ARSENIC REMOVAL TECHNOLOGIES PAPER BATES, J., A. HANSON, F. CADENA, B. THOMSON, A. BRISTOL, TECHNOLOGIES FOR THE REMOVAL OF ARSENIC FROM DRINKING WATER IN NEW MEXICO, NEW MEXICO SCIENCE JOURNAL, 1998 LIST OF TABLES Table 1: Summary of Arsenic Regulation in the U.S. (summarized from Pontius) . . . 2 Table 2: Typical Arsenic Concentrations in Various Materials . . . . . 4 Table 3: Typical Greensand Physical Properties (Inversand) . . . . . 13 Table 4: Typical Operating Parameters for Manganese Greensand Filters (Inversand) . 13 Table 5: Arsenic Removal using Manganese Greensand in Kelliher, Saskatchewan (Magyar,1992) . . . . . . . . . . . . . . . 14 Table 6: Summary of Freundlich Constants From Figure 31 . . . . 36 Table 7: Summary of Freundlich Constants From Figure 32 . 36 Table 8: Summary of Langmuir Constants From Figure 33 . . . ::41 Table 9: Summary of Langmuir Constants From Figure 34 . . . . . . . .41 iv LIST OF FIGURES Page No. Figure 1: Idealized Structure of Glauconite (from Nesse, 1991) ....................... 8 Figure 2: Scanning Electron Microscope Photograph of Greensand Particles ............ .9 Figure 3: Scanning Electron Microscope Elemental Analysis of Greensand Surface ....... 9 Figure 4: Idealized Schematic of Manganese Dioxide Ion Exchange (Posselt, Anderson, and Weber,1968) .................................................... ..10 Figure 5: Final Arsenic Concentrations @g/L) at a pH of 3 . . . .21 Figure 6: Final Arsenic Concentrations @g/L) at a pH of 5 ......................... .22 Figure 7: Final Arsenic Concentrations @g/L) at a pH of 6 ......................... .22 Figure 8: Final Arsenic Concentrations (ug/L) at a pH of 7 ......................... .23 Figure 9: Final Arsenic Concentrations @g/L) at a pH of 9 . 23 Figure 10: Final Arsenic Concentrations (pg/L) at an Initial As Cont. of 500 ug/L ......... 24 Figure 11: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 200 ug/L ........ .24 Figure 12: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 100 ug/L ......... 25 Figure 13: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 50 pg/L ......... .25 Figure 14: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 25 ug!L ........ .26 Figure 15: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 10 pg/L 26 Figure 16: Final Arsenic Concentrations @g/L) at an Initial As Cont. of 5 pg/L .......... .27 Figure 17: Arsenic Removal Percentages at a pH of 5 (FeCl,:As molar ratio of 20) ....... .28 Figure 18: Arsenic Removal Percentages at a pH of 5 (FeCl,:As molar ratio of 5) ........ .28 Figure 19: Arsenic Removal Percentages at a pH of 5 (FeCl,:As molar ratio of 0) ........ .28 Figure 20: Difference in As Removal Percentages at a pH of 5 between set l:(FeCl,:As molar ratio of 20) & set 2:(FeCl,:As molar ratio of 0) ............................ 29 Figure 21: Arsenic Removal Percentages at a pH of 5 (considering iron has no effect, 95% confidencelevel) ................................................. ..2 9 Figure 22: Final Arsenic Concentrations @g/L) for Varied Contact Times (for pH of 5 and initialAsconcof5pg/L) ........................................... .30 Figure 23: Final Arsenic Concentrations @g/L) for Varied Contact Times (for pH of 5 and initialAsconc.of50pg/L) ......................................... ..3 I Figure 24: Final Arsenic Concentrations @g/L) for Varied Contact Times (for pH of 5 and initialAsconc.of5OOpgk) ......................................... .31 Figure 25: Final Arsenic Concentrations @g/L) at a pH of 5 (sulfate ion present) .......... 32 Figure 26: Final Arsenic Concentrations @g/L) at a pH of 5 (chloride ion present) ......... 33 Figure 27: Difference in Arsenic Removal % at a pH of 5 between set l:(chloride ion present) & set 2:(sulfate ion present) ............................................ .33 Figure 28: Arsenite Study (Initial Arsenic Cont. of 5 pg/L) .......................... .34 Figure 29: Arsenite Study (Initial Arsenic Cont. of 50 ug/L) ......................... .35 Figure 30: Arsenite Study (Initial Arsenic Cont. of 500 pg/L) ......................... 35 Figure 3 1: Freundlich Isotherms for Varied pHs . 37 Figure 32: Freundlich Isotherms, pH=5 for three sets ................................ 37 Figure 33: Langmuir Isotherms for Varied pHs .................................... .40 Figure 34: Langmuir Isotherms, pH=5 for three sets ................................. 40 Figure 35: Zero Point of Charge of Ferric Hydroxide (Peng and Di,1994) ............... .42 V