Utah State University DigitalCommons@USU Reports Utah Water Research Laboratory January 1982 Reverse Osmosis in the Treatment of Drinking Water R. Ryan Dupont Talbert N. Eisenberg E. Joe Middlebrooks Follow this and additional works at: https://digitalcommons.usu.edu/water_rep Part of the Civil and Environmental Engineering Commons, and the Water Resource Management Commons Recommended Citation Dupont, R. Ryan; Eisenberg, Talbert N.; and Middlebrooks, E. Joe, "Reverse Osmosis in the Treatment of Drinking Water" (1982). Reports. Paper 505. https://digitalcommons.usu.edu/water_rep/505 This Report is brought to you for free and open access by the Utah Water Research Laboratory at DigitalCommons@USU. It has been accepted for inclusion in Reports by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Reverse Osmosis In The Treatment Of Drinking Water R. Ryan Dupont Talbert N. Eisenberg E. Joe Middlebrooks Utah Water Research Laboratory Utah State University Logan, Utah 84322 WATER QUALrry SERIES December 1982 UWRL/Q-82/05 REVERSE OSMOSIS IN THE TREATMENT OF DRINKING WATER by R. Ryan Dupont, Talbert N. Eisenberg, and E. Joe Middlebrooks WATER QUALITY SERIES UWRL/Q-82/05 Utah Water Research Laboratory Utah State University Logan, Utah 84322 December 1982 ABSTRACT An extensive review of the literature was conducted and results were evaluated for the use of the, reverse osmosis process in the treatment of drinking water supplies. All aspects of reverse osmosis technology, including pretreatment requirements; membrane type and configuration; membrane cleaning and mainten­ ance; and reverse osmosis removal of organics, inorganics, and microbial contaminants were incorporated into the literature evaluation. A survey (Appendix E) of existing full scale reverse osmosis installations was also carried out and results of the survey are discussed. In light of data presented in the literature and results of the survey conducted, the following recommendations were made to prevent catastrophic membrane fouling occurrences and costly plant shutdowns in the future. 1) Conduct a comprehensive raw water quality evaluation. 2) M,aintain cont inuous feed and product water qual ity monitoring. 3) Incororate process automation and system upset warning provisions in future installations. 4) Provide greatly improved training for reverse osmosis installation operators. The reverse osmosis system is particularly well suited for the treatment of water supplies which contain a number of con­ taminants that would otherwise require a combination of treatment processes for their removal, due to the ability of the reverse osmosis process to remove salts, organics, and a number of microbial contaminants. Effective pretreatment and routine backwashing, membrane cleaning, and disinfecLion must be carried out; however, if adequate system operation is to be assured. iii TABLE OF CONTENTS Chapter Page I INTRODUCTION . 1 Fundamental Considerations 1 General Principles • 1 Operating Principles 2 Historical Development 4 II PRETREATMENT • 7 Particulate Removal • 7 Filtration • 7 Coagulation-Flocculation­ Sedimentation 7 Scale Prevention 8 pH Control • 8 Scale Inhibitors 8 Iron and Manganese Removal 8 Disinfection 9 Oxidants 9 III MEMBRANES 11 Cellulosic Membranes 11 Polyamide Membranes • 12 Composite Membranes • 13 Summary . 15 IV MODULE CONFIGURATION • 17 Plate and Frame Modules • 17 Tubular Modules • 17 Spiral Wound Modules 19 Hollow Fiber Modules 21 Summary • 23 V MEMBRANE CLEANING AND MAINTENANCE 25 Operational Considerations 25 v TABLE OF CONTENTS (Continued) Page Organic Foulants 26 Bacterial Growth 26 Hardness Scale 27 Inorganic Colloids and Metal Oxides • 28 Membrane Rejuvenation 28 VI REMOVAL OF INORGANICS USING REVERSE OSMOSIS 31 Single Component Systems 31 Multicomponent Systems 35 Ionic Charge Relationships 37 Water and Wastewaters 38 Summary • 42 VII REVERSE OSMOSIS REMOVAL OF THE INORGANIC CONTAMINANTS CONTROLLED BY THE NATIONAL INTERIM PRIMARY DRINKING WATER REGULATIONS 43 Arsenic • 43 Barium . , 45 Cadmium • 45 Chromium 46 Fluoride 47 Lead 48 Mercury • 48 Nitrates 49 Selenium 50 Silver 51 Radiation 51 Summary • 52 VIII REMOVAL OF ORGANICS USING REVERSE OSMOSIS 53 Single Components Systems 53 Multicomponent Systems 56 Chlorinated Organics/Pesticides • 57 Drinking Water Treatment 59 Wastewater Treatment 60 Summary • 61 IX REMOVAL OF MICROORGANISMS 63 Bacteria 63 Viruses • 64 Summary • 64 vi TABLE OF CONTENTS (Continued) Page x PERFORMANCE EVALUATION OF REVERSE OSMOSIS INSTALLATIONS 65 Water Sources and Treatment Objectives 65 Pretreatment 65 System Operation 66 Operators 66 Operating Problems and Recommendations 67 Recommendations For Future Reverse Osmosis Installations • 67 XI SUMMARY, CONCLUSIONS, AND RECOMMENDA­ TIONS 69 Summary and Conclusions • 69 Recommendations • 70 REFERENCES 73 APPENDICES 83 Appendix A: Chemical Cleaning Reagents for Reverse Osmosis Membranes • 85 Appendix B: Reverse Osmosis Membrane Cleaning Procedures 89 Appendix C: Reverse Osmosis Membrance Rejuvenation Procedures 91 Appendix D: Reverse Osmosis Installations Included in Operational Survey 93 Appendix E: Operational Survey 98 vii LIST OF FIGURES Figure Page 1. Simple osmosis. 1 2. Simple reverse osmosis • 3 3. Asymmetric structure of typical reverse osmosis membranes (Johnston and Lim 1973) 3 4. Plate and frame configuration of (a) first generation and (b) second generation design (Nielsen et ale 1980) 18 5. Second generation plate and frame configuration (OWRT 1979) 18 6. The tubular module element (OWRT 1979) • 19 7. The spiral bound module element (OWRT 1979). 20 8. The hollow fiber module (DuPont 1977a) • 22 9. Flow characteristics of selected solution systems (Sourirajan 1964b) • 33 ix LIST OF TABLES Table Page 1. Effects of membrane foulants (DuPont 1977b) • 27 2. Separation of some related solutes aqueous solution under identical experimental conditions using S & S cellulose acetate membranes (Sourirajan 1964b) 32 3. Metal removal efficiencies by reverse osmosis (Johnston and Lim 1973) • 34 4. Reduction ratios of sodium and magnesium salts (Burns and Roe 1979 35 5. Reduction ratios of metal chlorides (Burns and Roe 1979) 36 6. Rejection of various compounds by reverse osmosis at 400 psi (2800 kN/m2) , pH 6, and membrane type ROGA #4101 (Nusbaum and Riedinger 1980) • 39 7. Separation of selected water pollutants by reverse osmOS1S (Hauck and Sourirajan 1969) 40 8. Average percent reductions of constituents by various reverse osmosis configurations treating secondary wastewater effluents (Boenand Johannsen 1974) 41 9. National Interim Primary Drinking Water Standards for selected inorganic con- taminants 44 10. National Interim Primary Drinking Water Standards for fluoride 44 11. A summary of operator training and experience 67 12. A summary of operator maintenance training and experience . 67 x CHAPTER I INTRODUCTION Fundamental Considerations 7T, and is related to the solution's vapor pressure and temperature as shown General Principles 1.n Equation 1. 0 Osmosis is defined as the spontane­ RT PA ous movement of a solvent through a 7T = - In- (1) semipermeable membrane from a less VA PA concent rated to a more concent rated solution. The ideal semipermeable where membrane impedes solute movement but allows solvent flow. Solvent will pass 7T = osmotic pressure, atmosphere through the membrane in both directions; however, it will pass more rapidly in R = 0.0882 l-atm/mole oK the direction of the more concentrated solution until a hydrostatic pressure T = oK develops that produces equilibrium conditions of equal flow of solvent in VA = l/mole of solvent both directions across the membrane, 0 Figure 1. This hydrostatic pressure, PA = vapor pressure of sol vent in ~h, is defined as the osmotic pressure, dilute solution SOLUTION WI LL RI SE TO THIS POINT WHERE Ah= 7r T SEMI- PERMEABLE MEMBRANE MORE CONCENTRATED LESS CONCENTRATED SOLUTION SOLUTION WATER FLOW Figure 1. Simple osmosis. 1 PA = vapor pressure of solvent in structure of this layer. Two distinct concentrated solution descript ions of surface morphology are supported by distinct transport theories Raoult's law relates the vapor labeled the solution diffusion theory pressure of a dilute solution to the and the pore theory_ The solution concentration of particles in the diffusion theory characterizes the solution. From this relationship, passage of molecules and ions across Equation 1 can be used to express the nonporous membrane boundary layers as osmotic pressure in terms of the solute occurring through a solution diffusion molar concentration as: mechanism with surface pores being regarded as membrane imperfections that allow largely nonselective transport 'IT = CRT (2) through them. The pore theory on the other hand proposes that materials are preferentially adsorbed onto the where membrane surface and that their trans­ port through the membrane occurs through C = solute concentration, gm/mole the surface pores while no transport is assumed to occur by diffus ion through Equation 2 is valid only for dilute the polymer matrix. solutions where Raoult's law remains true. Both the solution diffusion theory and the pore theory have strengths The osmotic pressure of a solution and weaknesses. The appl ication of increases with solution concentration as either theory depends upon the specific shown in Equation 2 and a rule of thumb problem at hand and the conceptual based on sodium chloride is a 0.01 psi simplicity either theory has in quanti­ osmotic pressure