Western Michigan University ScholarWorks at WMU
Master's Theses Graduate College
12-1995
Reverse Osmosis Treatment of Deinking Effluents
Lei Zhao
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Recommended Citation Zhao, Lei, "Reverse Osmosis Treatment of Deinking Effluents" (1995). Master's Theses. 4919. https://scholarworks.wmich.edu/masters_theses/4919
This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. REVERSE OSMOSIS TREATMENT OF DEINKING EFFLUENTS
by
Lei Zhao
A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Paper and Printing Science and Engineering .
Western Michigan University Kalamazoo, Michigan December 1995 ACKNOWLEDGEMENTS
I would like to express my sincere thanks to my advisor, Dr. Raymond L.
Janes, for his valuable assistance, advice and guidance throughout my project; and also to Dr. Ellsworth H. Shriver and Dr. Raja G. Aravamuthan, and my committee members for their continuous support and advice.
I also would like to thank Mr. William K. Forester and Mr. Richard Reames for their support during the study.
Special thanks to Mr. Tim Pond from The Dow Chemical Company and to
Mr. Jerry Campbell from Stream International, Inc. for their support and help in offering the equipment and materials.
Appreciation is also expressed to Mr. Jay Unwin, the regional manager of
NCASI, for his permission to use their lab.
Appreciation is also due to Ms. Dannette Shaw, from Water Quality Lab,
WMU for her help in analysis of samples.
Many thanks are also expressed for the support and help from others who contributed in different ways.
Finally, I wish to thank my family for their love and support.
Lei Zhao
ii REVERSE OSMOSIS TREATMENT OF DEINKING EFFLUENTS
Lei Zhao, M.S.
Western Michigan University, 1995
The application of the reverse osmosis process for treatment of preclarified deinking effluent was studied for its efficiency and capacity to remove the total suspended and dissolved solids. Seven coagulants and flocculents were studied in the pretreatment to determine the best coagulant. Two variables, temperature and coagulant dose, were studied to determine the optimum conditions. For the reverse osmosis treatment, two types of thin film composite membranes, sea water and brackish water were used in the research. A set of orthogonal experiments and regression analyses were conducted to study the effects of pressure, temperature, feed concentration, and feed pH on permeate flux and solute percent rejection. The optimum operation conditions were determined according to the factor effect study.
The relationships between feed recovery ratio and permeate flux, permeate concentration and feedconcentration were studied to determine the optimum recovery ratio. Comprehensive water analyses of components were conducted to determine the component removal efficiency at each stage. The treatment process had greater than
95% removal ratio for IDS, TSS, turbidity, BOD, COD, TOC and metal elements.
The treated water could be reused as high quality water in the process. TABLE OF CONTENTS
ACKNOWLEDGEMENTS ...... ii
LIST OF TABLES ...... xi
LIST OF FIGURES ...... xvi
CHAPTER
I. INTRODUCTION ...... 1
II. REVIEW OF RELATED LITERATURE ...... 5
Basic Principles of Reverse Osmosis ...... 9
Mechanism of Reverse Osmosis and Ultrafiltration Separation ...... 10
Hydrogen-Bonding Theory ...... 11
The Preferential Sorption-Capillary Flow Membrane Theory ...... 11
Dissolving-Diffusion Mechanism ...... 12
Ultrafiltration Separation Mechanism ...... 13
Crossflow Membrane Technology ...... 13
Membranes ...... 14
Microfiltration (MF) Membrane ...... 14
Ultrafiltration (UF) Membrane ...... 14
Reverse Osmosis (RO) Membrane ...... 16
Membrane Module Configurations ...... 17
iii Table of Contents--Continued
CHAPTER
Tubular ...... 17
Spiral-Wound ...... 17
Hollow Fiber ...... 19
Characteristics of Reverse Osmosis and Ultrafiltration ...... 19
Applications of Reverse Osmosis and Ultrafiltration ...... 22
Applications of Reverse Osmosis and Ultrafiltration in Pulp and Paper Industry ...... 23
Treatment of Spent Sulfite Liquors ...... 23
Treatment of Bleaching Caustic Extraction E-stage Effluent...... 25
Treatment of RO for Waste Water From Washing Pulp Stage ...... 26
Characteristics and Composition of Deinking Effluent ...... 27
BOD5, IDS and TSS ...... 27
Other Specific Chemical Constituents ...... 30
Chlorinated Aromatic Compounds ...... 31
Heavy Metals ...... 32
Potential Problems From Water Reuse ...... 33
Paper Properties ...... 34
IV Table of Contents--Continued
CHAPTER
Microbial Contamination of Process Water ...... 34
Water System Corrosion ...... 34
Limitations of Biological Treatment and Chemical Sedimentation ...... 35
III.PROBLEM STATEMENT ...... 37
Pretreatment ...... 38
Reverse Osmosis ...... 38
IV. EXPERIMENTAL PART ...... 39
Experimental Design ...... 39
Preparation of Effluent ...... 40
WMU Pilot Plant and Laboratory Equipment ...... 40
Waste Paper Source ...... 42
Effluent Preparation Procedure ...... 42
Pulping, Flotation, Washing and Clarification ...... 42
Effluent Pretreatment ...... 45
Natural Sedimentation ...... 45
Chemical Clarification by Coagulant ...... 45
Phase I: Preliminary Screening Experiments ...... 46
Phase TI: Optimization Experiments ...... 47
V Table of Contents--Continued
CHAPTER
Prefiltration ...... 49
Reverse Osmosis Treatment ...... 49
Equipment and Membrane ...... 49
Reverse Osmosis Equipment Unit ...... 49
Reverse Osmosis Membrane ...... 49
Phase I: Preliminary Operating Factor Screening Experiments ...... 51
Data Collection Methods ...... 52
Method I: Orthogonal Array Experiment ...... 53
Method II: Regression Analysis ...... 54
Phase II: Effects of Factors Pressure, Temperature, and Feed Concentration on Flux ...... 54
Phase III: Determination of Optimum Operating Condition ...... 57
Water Analysis ...... 57
Turbidity ...... 58
Total Solids ...... 58
Total Dissolved Solids ...... 58
Total Suspended Solids ...... 59
Biochemical Oxygen Demand (BOD) ...... 59
Chemical Oxygen Demand (COD) ...... 59
vi Table of Contents--Continued
CHAPTER
Total Organic Carbon (TOC) ...... 59
Metal Elements: (Ca, Mg, Na, Cr, Cu, Ni, Pb, Zn, Al, Fe) ...... 60
Conductivity ...... 60
V. RESULTS AND DISCUSSION ...... 61
Effluent and Its Pretreatment ...... 61
Effluent Components and Natural Sedimentation ...... 61
Phase I: Screening Experiments for Polymer Effectiveness in Clarification ...... 62
Phase II: Optimization of Addition Conditions of Coagulant 7157 ...... 70
Orthogonal Experiment ...... 70
Effects of Temperature and Coagulant 7157 Dose on Turbidity ...... 70
Reverse Osmosis Treatment ...... 73
Method I: Two-Level, L16 Orthogonal Experiments ...... 76
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for SW Membrane ...... 76
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for BW Membrane ...... 76
vii Table of Contents--Continued
CHAPTER
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R % for SW Membrane ...... 81
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R % for BW Membrane ...... 81
Method II: Regression Analysis for Flux and R%...... 85
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for SW Membrane ...... 85
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for BW Membrane ...... 86
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R % for SW Membrane ...... 90
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R% for BW Membrane ...... 91
Pressure Effect on Flux ...... 93
Temperature Effect on Flux ...... 93
Effect of Feed IDS Concentration on Flux ...... 99
Results of Other Factor Effects ...... 102
Determination of Optimum Operation Condition ...... 105
Comparison Between Membranes SW and BW 105
viii Table of Contents--Continued
CHAPTER
Determination of Operating Pressure and Temperature ...... 106
Relationship Between Feed Recovery Percent and Flux, Permeate IDS Concentration, Feed IDS Concentration 108
Determination of Optimal Feed Recovery Percent ...... 112
Summary of Optimal Operating Condition ...... 112
Discussion of Component Removal Efficiency ...... 115
TS, IDS, Conductivity, TSS, Turbidity ...... 115
BOD, COD, TOC ...... 118
Metal Elements ...... 120
VI. SUMMARY OF RESULTS ...... 124
VII. CONCLUSIONS ...... 128
VIII. SUGGESTIONS FOR FURTHER STUDY ...... 130
REFERENCES ...... 132
APPENDICES ...... 136
A. Flow Diagram of Treatment System of Deinking Effluent ...... 137
B. Principles of Osmosis and Reverse Osmosis ...... 139
C. Membrane Separation and Filtration Spectrum ...... 141
D. Concentration Polarization 143
IX Table of Contents--Continued
CHAPTER
E. Definitions of Solute Rejection Percentage, Permeate Flux, and Feed Recovery Percentage 145
F. Supporting Data ...... 147
BIBLIOGRAPHY ...... 176
X LIST OF TABLES
1. Data of Closed Water Loop 300T/D Newsprint De inking Mill ...... 6
2. Some Commercial Membranes ...... 15
3. Comparison of Crossflow Membrane Configurations ...... 18
4. Characteristics of Reverse Osmosis and Ultrafiltration ...... 20
5. Indicated Cost Savings-Membrane Process Over Conventional Evaporation ...... 25
6. Deinking Raw Effluent Characteristics ...... 28
7. Summary Regulations,40 CFR Part 430 Subpart Q (Deinking) ...... 28
8. Effluent Characteristics of Different Deink Categories ...... 29
9. Average Deinking Effluent Composition ...... 30
10. Chemicals Identified in Effluent ...... 31
11. Metal Contents in Recycled Fiber Mill Effluent ...... 32
12. Potential Problems Encountered in Water Reuse ...... 33
13. Components of Mixed Office Waste ...... 42
14. Variables and Their Levels ...... 47
15. 2-Level, L8, Experiment Array ...... 48
16. Variable Levels for Factor Effect Study ...... 48
17. Membrane Specifications ...... 51
xi List of Tables--Continued
18. Variables Levels for Screening Experiments-SW Membrane ...... 52
19. Variables Levels for Screening Experiments-BW Membrane ...... 53
20. Factor and Factor Level of Orthogonal Experiment for Membranes SW and BW ...... 54
21. 2 Level, 4 Factor, 16 L Experiment Design Array ...... 55
22. Experimental Matrix of Phase II for SW Membrane ...... 56
23. Experimental Matrix of Phase II for BW Membrane ...... 56
24. Effectof Sedimentation and Clarification on Suspended Solids and Turbidity ...... 62
25. Turbidity Results of Feed Water Treated With Polymers and Alum ...... 63
26. Turbidity Results of Feed Water Treated With Polymers and Alum ...... 64
27. Turbidity Results of Feed Water Treated With Polymers and Alum ...... 64
28. Turbidity Results of Feed Water Treated With Polymers and Alum ...... 65
29. Turbidity Results of Feed Water Treated With Polymers and Alum ...... 65
30. Variables and Their Levels ...... 71
31. Effect of Coagulant at Different Temperature and Alum Dosage Levels ...... 71
32. The ANOVA Table for Turbidity ...... 72
33. 2 Level, 4 Factor, 16 L Experiment Array With R % and Flux Results for SW and BW Membranes ...... 77
Xll List of Tables--Continued
34. ANOV A Results and Means for Flux With Membrane SW ...... 78
35. ANOV A Results and Means for Flux With Membrane BW ...... 80
36. ANOV A Results and Means for R % With SW Membrane ...... 82
37. ANOVA Results and Means for R% With BW Membrane ...... 83
38. Results of Best Subsets Regression for Flux With SW Membrane ...... 86
39. Results of Regression Analysis for Flux With SW Membrane ...... 87
40. Results of Best Subsets Regression for Flux With BW Membrane ...... 88
41. Results of Regression Analysis for Flux With BW Membrane ...... 89
42. Results of Best Subsets Regression for R% With SW Membrane ...... 90
43. Results of Best Subsets Regression for R% With BW Membrane ...... 91
44. Results of RO Performance for SW Membrane at Condition of 500 psi, 25 °C ...... : ...... 113
45. Results of RO Performance for BW Membrane at Condition of 350 psi, 25°C ...... 114
46. Water Analyses Before and After Various Treatments 116
47. Component Removal Percentage Before and After Various Treatments ...... 117
48. Results of Analysis of BOD, COD, TOC ...... 119
49. The Results of Analysis of Major Metal Elements ( Ca, Mg, Na, Al and Zn) ...... 120
Xlll List of Tables--Continued
50. The Results of Analysis of Minor Metal Elements ( Pb, Fe, Cr, Cu and Ni ) ...... 122
51. Data Points for Regression Analysis for SW Membrane 148
52. Data Points for Regression Analysis for BW_ Membrane 151
53. Effects of Temperature and Coagulant 7157 Dose on the Turbidity ...... 154
54. Turbidity Results of Feed Water Treated With Seven Coagulants and Flocculents With Alum (150mg/I Alum) ...... 154
55. Conductivity Data of Permeate and Feed for SW Membrane ...... 155
56. Conductivity Data of Permeate and Feed for BW Membrane ...... 157
57. Results of IDS and R % of IDS for SW Membrane at Feed pH 7.5, Temperature 25°C 159
58. Results of IDS and R% of IDS for BW Membrane at Feed pH 7.5, Temperature 25 °C ...... 160
59. Relationship Between Feed Recovery % and Permeate TDS ...... 161
60. Results of Effect of Temperature on R % for SW Membrane ...... 162
61. Results of Effect of Temperature on R% for B W Membrane ...... 164
62. Results of Effect of Feed pH on Feed R % ...... 166
63. Flux Data for SW Membrane ...... 167
64. Flux Data for BW Membrane ...... 170
xiv List of Tables--Continued
65. Relationship Between Feed Recovery % and Flux for SW Membrane ...... 172
66. Relationship Between Feed Recovery % and Flux for BW Membrane ...... 173
67. Results of Effect of Temperature on Flux for SW Membrane ...... 174
68. Results of Effect of Temperature on Flux for B W Membrane ...... 175
xv LIST OF FIGURES
1. Experimental Schematic ...... 41
2. Flow Diagram for Preparation of Deinking Effluent ...... 43
3. Flow Diagram of SRO - 400 RO Unit ...... 50
4. Effect of Polymers and Alum (15 mg/L) on Turbidity Removal ...... 66
5. Effect of Polymers and Alum (30 mg/L) on Turbidity Removal ...... 67
6. Effect of Polymers and Alum (45 mg/L) on Turbidity Removal ...... 67
7. Effect of Polymers and Alum (60 mg/L) on Turbidity Removal ...... 68
8. Effect of Polymers and Alum (100 mg/L) on Turbidity Removal ...... 68
9. Effect of Polymers and Alum (150 mg/L) on Turbidity Removal ...... 69
10. Turbidity of Feed Water Treated With Alum ...... 69
11. Effect of Coagulant 7157 on Turbidity at Constant Temperature ...... 7 4
12. Effect of Coagulant 7157 on Turbidity at Constant Temperature ...... 7 4
13. Effect of Temperature on Turbidity at Constant Polymer Level ...... 75
14. Effect of Temperature on Turbidity at Constant Polymer Level ...... 75
XVI List of Figures--Continued
15. Effect of Pressure on Flux for SW Membrane ...... 94
16. Effect of Pressure on Flux for SW Membrane ...... 94
17. Effect of Pressure on Flux for BW Membrane ...... 95
18. Effect of Pressure on Flux for BW Membrane ...... 95
19. Effect of Pressure on Flux for BW Membrane ...... 96
20. Effect of Temperature on Flux for SW Membrane ...... 96
21. Effectof Temperature on Flux for SW Membrane ...... 97
22. Effectof Temperature on Flux for SW Membrane ...... 97
23. Effect of Temperature on Flux for BW Membrane ...... 98
24. Effect of Temperature on Flux for BW Membrane ...... 98
25. Effect of Temperature on Flux for BW Membrane ...... 99
26. Effect of Feed TDS on Flux for SW Membrane ...... 100
27. Effect of Feed TDS on Flux for SW Membrane ...... 100
28. Effect of Feed TDS on Flux for BW Membrane 101
29. Effect of Feed TDS on Flux for BW Membrane 101
30. Effect of Temperature on Feed TDS R% for BW Membrane ...... 103
31. Effect of Pressure on R% for SW Membrane 103
32. Effect of Pressure on R% for BW Membrane 104
33. Effect of Feed TDS on R% for BW Membrane ...... 104
xvn List of Figures--Continued
34. Effect of Feed pH on R % for Different Membranes and Pressures ...... 105
35. Relationship Between Feed Recovery and Flux for SW Membrane ...... 108
36. Relationship Between Feed Recovery and Flux for BW Membrane ...... 109
37. Relationship Between Feed Recovery and Permeate TDS for SW Membrane ...... 110
38. Relationship Between Feed Recovery and Permeate IDS for SW Membrane ...... 110
39. Relationship Between Feed Recovery and Feed TDS for SW Membrane ...... 111
40. Relationship Between Feed Recovery and Feed TDS for BW Membrane ...... 111
41. Summary of Typical Results of Recovered Feed ( at 500 psi, 25 °C, pH 7 .5 and SW Membrane ) ...... 115
xviii CHAPTER I
INTRODUCTION
Environmental effects of industrial waste water are of great concern to the paper industry. The waste waters from pulp and paper manufacture have high color, toxicity, BOD (biochemical oxygen demand) and corrosivity, rendering total recycle back to the process difficult [1]. Conventional physical sedimentation and biological treatment are not completely effective,especially in removing dissolved ions. An ideal solution is to have a zero effluent process.
By 1995, the U.S paper industry has set the goal of 40 percent paper recovery for recycling. This means that by that time about 40 million tons of paper will be recovered. Therefore, it will become more and more important to purify and recover the waste waters from recycling paper or board mills [2].
With more stringent laws controlling water pollution being placed in effect nationwide, pulp and paper mills require higher levels of pollution abatement, particularly for reduction of BOD. In addition to removal of BOD, there is a strong trend that dissolved organic and inorganic solids be removed from waste to a greater degree. State-issued discharge permits often are more restrictive than the technology based federal standards, especially when discharges enter water-quality limited sa:eams. A number of mills are also limited in mass loadings for additional parameters
1 2 such as heavy metals, PCBs, pentachlorophenol and trichlorophenol [2].
As with other pulp and paper mills seeking the most economical pathway to environmental compliance, recycled paper and paperboard mills look first toward in plant measures of water and fiber capture and reuse. Since recycled paper and board mills reuse water extensively, waste water from ·these mills (even after extensive treatment)can be relatively concentratedin dissolved salts and other dissolved organic compounds.
At present, most paper mills mainly employ sedimentation and biological treatment [3,4,5]. However, conventional sedimentation and biological treatment are relatively ineffective in treatment of the color, toxicity and dissolved solids in the effluent so that these compositions become limiting factors in the reuse of waste water.
The reverse osmosis (RO) and ultrafiltration (UF) membrane processes [6,7] are relatively new technologies used to treat waste waters, in comparison to many of the other conventional processes such as biological, chemical, physical, mechanical methods.
Since the first practical L-S (Loeb - Sourirajan) type membrane for desalting water was developed by S. Sourirajan and Sidney Loeb in 1959 [8, 9], the reverse osmosis process began to enter the stage of industrial application and received widespread attention. The potential of the process as a new unit operation for separation was recognized. Up to now, RO and UF have been employed in fluid processing, water purification, and waste water treatment/recovery of beverage, dairy, 3 food, textile, pharmaceutical, chemical, petroleum, metal and paper industries.
Reverse osmosis and ultrafiltration use a semipermeable membrane as the separating agent and pressure as the driving force to achieve separation. Reverse osmosis mainly involves the separation between water and small molecules or ions.
Ultrafiltration mainly involves the separation between water, small molecules, ions and high molecularweight compounds, even colloidal and suspended materials. There are important differences, however, which lead to different applications.
With the development of RO and UF modules, crossflow membrane technology [10,11] was used in RO and UF membrane separation. Normal macrofiltrationor particle filtrationhistorically has not been run in a crossflow design.
The term "perpendicular" flow may be most appropriate, with the solution to be filtered approaching the filtermedia in a perpendicular direction. Crossflow membrane filtration is fundamentally different in design, in that the influent stream is separated into two effluents, known as permeate and concentrate. The concept of crossflow membrane filtration not only includes reverse osmosis and ultrafiltration but also nanofiltration (NF) and microfiltration (MF).
Previous research [12,13,14,15,16] has indicated that UF and RO have efficiencies of as great as 90% removal of a variety of dissolved materials which produce color, toxicity and corrosion. Also they have the advantages of low energy demand [15,16] and no phase change. The water recovered by reverse-osmosis processing of pulp-mill effluentsis characterizedby low levels of color and dissolved materials and by zero levels of suspended solids. 4
It could be economically and technologically advantageous to choose these membrane processes as effective alternatives to conventional biological oxidation methods of waste treatment [17, 18]. CHAPTER II
REVIEW OF RELATED LITERATURE
Hamilton [19] and Vanderhoff [20] have suggested that modem considerations of environmental protection, which require closed- cycled water systems and control of hazardous substances such as polychlorinated biphenyls, will lead to new approaches to the design of secondary fiber deinking mills.
Generally the waste water treatment plant serves as the end of pipe treatment facility for the effluent from the deink mill. However, under the totally closed operating concept, the effluentwill be treatedand reused. The treated effluent will be recycled as the make-up water for the deinking process. Therefore, recycled paper mills look first toward in-plant measures of water and fibercapture and reuse. Reuse of effluent from deinking processes has become an important consideration for deinking mills. However, at present, there are still no closed water cycle deinking mills.
In a research report [21], Rust Engineering discusses closed water cycle treatment system of hypothetical deinking operations. In a waste water treatment schematic given in the report, primary clarification, biological treatment and reverse
osmosis consist of the most important operation units. Appendix A gives a process flow diagram of a hypothetical deinking operation [21]. Data from the diagram are
5 6 given in Table 1.
Table 1
Data of Closed Water Loop 300T/D Newsprint Deinking Mill [21]
Unit Q,gpm TSS,mg/L BOD,mg/L TDS,mg/L Operation
Deink Mill 1495 1500 400 3500 Effluent
Primary Clarifier
(feed) 1624 1535 393 3500
(effluent) 1506 83 254 3500
SBR
(feed) 1552 107 273 3500
(effluent) 1535 30 30 3500
Multimedia Filter
(feed) 1535 30 30 3500
(effluent) 1489 3 3 3500
Micro filter
(feed) 669.9 3 3 3500
(effluent) 669.9 1 1 3500
Reverse osmosis 7 Table 1--Continued
Unit Q,gpm TSS,mg/L BOD,mg/L TDS,mg/L Operation
(feed) 669.9 1 1 3500
(effluent) 535.9 0 0 437
(reject) 134 5 5 15750
Evaporator & Crystallizer
(feed) 134 5 5 15750
(condense) 131 0 0 0
The following is the description of the treatment system of deinking waste water [21].
Bar Screen: the deinking effluent collected in a save-all basin is directed through a bar screen to remove large debris. TSS, BOD, TDS remain unchanged in passing through this unit. The wastewater is mixed with polymer for enhanced settling before flowing into the primary clarifier.
Primary Clarifier: the screened effluent is directed to a reactor type primary clarifier. Overflow from the primary clarifier is discharged by gravity to a biological reactor. The settled primary sludge is pumped to a sludge storage tank to be dewatered by a sludge press. Through this unit, TSS is reduced from 1535 to 83 8
(94.5% ), BOD is reduced from 393 to 254 (35.4% ).
Biological Secondary Treatment: the primary effluent is treated biologically by sequencing batch reactors (SBRs). The treated effluent quality is generally lower than 30 mg/1 of TSS and 30 mg/1 of BOD. After SBR, TSS is reduced by 98% and
BOD by 92.5%.
Pressure Filters: pressure type multimedia filters are used to further reduce the
TSS so that much of the water can be reused in the deinking process.
Microfilters: a portion of filtrate from the pressure filters requires advanced treatment to reduce the concentration of IDS. Microfilters are used as the pretreatment equipment to reduce suspended solids ahead of RO. TSS in original effluent is removed by 99%. The filtrate is collected in a filtrate storage tank to be fed to RO.
Reverse Osmosis: the purpose of using RO is to remove and separate the IDS from the water. The operation of RO involves pumping the filtrate from the microfilters under high pressure through a membrane. The IDS is concentrated in the rejects stream which represents 20% of the original volume. The 80% of permeate is recycled to reuse. The TDS of 87% is removed during RO. The filtrate from RO is collected in a water storage tank to be recycled. The rejects are discharged to an evaporator to further concentrate the TDS.
In analyzing the above flow diagram, it is evident that the main function of primary clarification is to remove most of the suspended solids. Biological treatment
(such as an activated sludge system) mainly removes BOD. At present, most paper 9 mills are using the above two treatment methods and have accumulated much experience. However, biological treatment and chemical clarification have their limitations. They can not effectively remove the dissolved organic and inorganic components which result in the color, toxicity and corrosion. Therefore, the removal of IDS in the effluent has become an important factorin whether the treatedeffluent can be reused successfully.
Basic Principles of Reverse Osmosis
Osmosis has been known for more than 200 years as a natural process involving flow across a semipermeable membrane that is selective in that certain components of a solution, usually the solvent, can pass through it while others, usually dissolved solids, cannot.
The earliest work was done with naturally occurring biological membranes.
The concept of osmotic pressure was first described by Abbe Nollet in 1748, when he observed that an animal bladder permitted diffusion of water but not of alcohol
[22]. The name "reverse osmosis" was originally derived because the water transport in reverse osmosis is the opposite of the water transport in normal osmosis, where water flows from a less concentrated solution through a semi-permeable membrane to a more concentrated solution [23].
If pure water is in contact with both sides of a semipermeable membrane at equal pressure and temperature, no net flow occurs across the membrane because the chemical potential is equal on both sides. If a soluble salt is added on one side of the 10 membrane, the chemical potential of the water on that side is reduced. Osmosis flow, from the pure - water side to the salt solution side, will occur across the membrane until equilibrium of solvent chemical potential is restored (See Appendix B).
There is a potential energy difference between any two solutions of differing concentration separated by a semi-permeable membrane. This potential energy is termed II osmotic pressure 11• The osmotic pressure must be overcome in order to produce a less concentrated solution from a more concentrated solution. Thus a limiting factor in reverse osmosis is the solution's potential energy.
At equilibrium, the osmotic pressure of the solution is given [23] by
n = -(RTN) 1n rx
Where n = osmotic pressure of solution, R = gas constant, T = absolute temperature,
V = partial molar volume of the solvent, r = activity coefficient of the solvent, and x = mole fraction of the solvent.
If a pressure greater than the osmotic pressure is applied to the solution, the system will seek a new equilibrium by forcing the solvent out of solution. So the external pressure applied to the salt solution must exceed the osmotic pressure of the solution for reverse osmosis to occur.
Mechanism of Reverse Osmosis and Ultrafiltration Separation
Basically there are two schools of thought. 11
Hydrogen-Bonding Theory [24]
Reid and Breton think that the membrane has a thin, dense, non-porous layer through which water migrates via hydrogen bonding. Salt can not migrate through this layer and is therefore excluded from passage through the membrane. Organic rejection is explained in a similar fashion, although there are problems in explaining the transfer of low molecular weight organics through the membrane, because the fact is that some low molecular weight organics do pass through the membrane at the same rate as water.
The Preferential Sorption - CapillaryFlow Membrane Theory [8]
The second school of thought states that there is a thin porous layer on the surface of the membrane. It contains a multitude of micropores. Because of the physico-chemical interaction between the membrane and solution, salt rejection occurs, allowing only water to pass through the pores. Organic rejection is satisfactorily explained in this case, since the organics are sieved or screened, depending on the size. The size of an organic molecule is directly related to its molecular weight, although there are certain exceptions. This mechanism of reverse osmosis was presented by S. Sourirajan [8].
The theory states that if only the surf ace of a porous membrane in contact with the solution is of such a chemical nature that it has a preferential sorption for water or preferential repulsion for the solute, then a multimolecular layer of preferentially 12 sorbed pure water could exist at the membrane - solution interface. A continuous removal of this interfacial water can then be effected by letting it flow under pressure through the membrane capillaries.
This model also gives rise to the concept of a critical pore diameter for maximum separation and permeability. This is obviously twice the thickness, t, of the interfacial pure water layer. If the pore diameter is bigger, permeability will be higher but solute separation will be lower since the effective feed solution will also flow through the pore; if the diameter is smaller, the separation could be maximum, but permeability will be reduced. For maximum separation and permeability, it is necessary to maintain the pore size equal to 2t only on the area of the film at the interface.
The mechanism for salt rejection is different from the mechanism for organic rejection. Salt rejection occurs because of the repulsion of the salt ions from surface of the membrane and the adsorption of water to the membrane surface. Organic rejection is based on a sieve mechanism related entirely to the size and shape of the organic molecule. Organic molecules are not repelled from the surface of the membrane. In fact, because organics tend to lower the interfacial tension between the solution and membrane, Low-molecular-weight organics (less than 100 molecular weight) are enriched at the membrane surface.
Dissolving - Diffusion Mechanism [25]
This theory states that the membrane is a nonporous diffusion barrier. All 13 molecular species dissolve in the membrane accordance with phase equilibrium considerations and diffuse through the membrane. In the solution - diffusion model, each component of the high-pressure solution dissolves in the membrane in accordance with an equilibrium distribution law and diffuses through the membrane in response to the concentration and pressure differences.
Ultrafiltration Separation Mechanism [7 ,23]
For ultrafiltration, the actual mechanism by which solvent passes through the membrane is somewhat obscure, as are the differences between reverse osmosis and ultrafiltration. Although the polymeric membranes used in ultrafiltration do not have discernible holes in them, they are characterized by an intramolecular pore size that is dependent on the selection of monomer base, the degree of crosslinking, and other details of the membrane preparation. Solute molecules of sufficient size are excluded basically by a sieving action at the surface of the membrane.
Crossflow Membrane Technology [ 10, 11, 26]
As has been described in Chapter I, crossflow membrane technology is employed in RO and UF processes. Crossflow membrane filtration is fundamentally different in design, in that the influent stream is separated into two effluent streams, known as permeate and concentrate. The permeate is that fraction which has passed through the "semipermeable" membrane. The concentrate is that stream which has been enriched with the solutes or suspended solids which have not passed through the 14 membrane. The advantage of this design approach is that the membrane media is operated in a continuously self-cleaning mode, with solutes and solids swept away by the concentrate stream which is running parallel to the membrane.
Membranes
Basically, the membranes are classified into three groups [27 ,28]: cellulosic membranes, non-cellulosic membranes and composite membranes. Today there are three major membranes: cellulose acetate, aramid, and thin-filmcomposite [29]. Some commercial membranes are listed in Table 2.
Microfiltration (MF) Membrane
MF has generally come to be regarded as effecting separation in the 0.2-2.0 um range. MF membranes almost always have an isotropic and homogeneous morphology, i.e. their pore structure and material are the same throughout the membrane. They have historically been run in the perpendicularflow mode. Now, MF crossflow technology has been used and use of this membrane class in various crossflow configurations is also increasing.
Ultrafiltration (UF) Membrane
UF is generally defined as effecting separation in the 0.002- 0.2 um range.
This is perhaps more usefully described as the 500 - 300,000 molecular-weight cut-off range. Nearly all UF membranes are anisotropicin morphology [7 ,30], i.e., they have 15 a dense "skin" layer on top, which defines the degree of separation effected, and a spongy support layer underneath. Because the transport of matter across a UF
Table 2
Some Commercial Membranes
Commercial Manufacturer Membrane Temp. pH Names Material oc Range
Reverse Osmosis Membrane
AS Membrane Abcor(USA) Cellulose Acetate ~40 3-7 DDS DDS Cellulose ~50 3-8 Membrane (Denmark) Acetate
W.T Membrane PCl(USA) Cellulose ~30 3-7 Acetate
D.P Membrane DuPont Aromatic (USA) Nylon ~35 4-11 Ultrafiltration Membrane
Diaflo Amico(USA) Polymeric ~55 2-12 UM Membrane Electrolyte Composite
Diaflo- Amico Aromatic ~120 1-13 PM Membrane Polysulfone
Diaflo- ~60 1-13 XM Membrane Amico I
HFA Abcor Cellulose ~50 3-8 Membrane Acetate 16
Table 2--Continued
Commercial Manufacturer Membrane Temp. pH Names Material oc Range
RFD Abcor I ~70 4-12 Membrane
G Membrane Japan Polymeric ~55 2-12 Electrolyte Composite
TRTS Rhnoe-Poutene I ~40 1-10 Membrane (France)
SM Membrane Sartorius I (Germany)
membrane involves viscous flow through a porous structure, the physical structure of the membrane will control the flow rate and rejection.
Reverse Osmosis (RO) Membrane
RO is defined as effecting separation both at the small-molecular and ionic size ranges. Pore sizes ranging from 5 to 15 A effect separation of the solutes down to a molecular weight of 150 and often lower. Like UF, RO membranes are also anisotropic.
A relative newcomer to the types of membrane morphology is the "thin-filmed composite" (TFP) membrane [31], generally considered to be in the polyamide family. 17
This membrane consists of a very thin "barrier layer" reacted "in-situ" on top of a more porous UF membrane support which is in turn supported on a fabric support material. Appendix C gives a membrane separation spectrum.
Membrane Module Configurations
Reverse osmosis and ultrafiltration membranes can be made into three basic modules: tubular, spiral and hollow fiber [10,26]. These modules are used as building blocks in manufacturing a system. Table 3 gives the comparison of crossflow membrane configurations.
The three established membrane configurations are described below.
Tubular
The first RO device, commercialized in the mid-1960s, was a tubular device using a cellulose acetate membrane. The membrane is either inserted into, or coated onto the surface of a porous tube designed to withstand the operating pressure. The tubular configuration has a membrane on the inside or the outside of a porous tube.
Generally the tubular configuration is used for food processing where particles are suspended in the solution.
Spiral-Wound
The spiral configuration contains a high percentage of membrane wrapped around a center permeate water tube in the same fashion as parchment around the 18 center rod on a scroll.
Table 3
Comparison of Crossflow Membrane Configurations [32]
Characteristics Spiral-Wound Fibers Tubular
Cost Low-Medium Low High
Packing Moderate UF-High Low Capability RO-Very High
Pressure High UF-Low UF-Low Capability RO-High RO-Medium
Membrane Polymer Many Few Few Choices
Fouling Good UF-Good Very Good Resistance RO-Poor
Cleanability Good UF-Good Good RO-Poor
This configuration uses economical sheet membrane wound around a central permeate collection tube to yield a very high membrane packing density. The specific packing density depends upon the size of spacer material used, which may vary widely depending upon the application. The feed passes over the membrane through the spacer material which also acts as a turbulence promoter to keep the membrane clean at relatively low velocities. A recent innovation for spiral-wound elements is the 19 use of corrugated spacer material. The corrugations form triangular channels with much the same fluid dynamics as small tubes. Thus the many advantages of the spiral wound configuration are coupled with the fouling resistance of the tubular design.
The spiral is superior in all application where the feed solution can be filtered to 100 mesh or 140 microns.
Hollow Fiber
In 1970, Du Pont developed the aramid membrane(B-9) and extruded it into the form of hollow fiber [33].
The hollow fiber configuration uses thousands of small fibers about the size of human hair. The fibers are hollow and pure water permeates from outside of the fiber to the inside. The fibers are bundled together and potted with epoxy. The permeate rate per square foot of area for fibers is extremely low. The major drawbacks with the fiber configuration are its tendency to plug with even slight impurities in the water and the fragility of the fibers under varying flow rates.
Characteristics of Reverse Osmosis and Ultrafiltration
As has been described, reverse osmosis mainly involves the separationbetween water and small molecules or ions. Ultrafiltration mainly involves the separation between water, small molecules, ions and high molecular weight compounds, even colloidal , suspended materials. There areimportant differences, however, which lead 20 to different applications. The characteristics of both processes are shown in Table 4.
The advantages of membrane separation processes include [6]:
1. Gentle and require no heat or chemical additions which can harm the properties of materials such as pharmaceuticals, foods and colloids.
Table 4
Characteristics of Reverse Osmosis and Ultrafiltration [6]
Reverse Osmosis Ultrafiltration
Size of Solut Molecular weight Molecular weights Retained less than 500-1000 over 1000
Osmotic Pressures Important Generally negligible of Feed Solution
Operating Greater than 100 10 to 100 psi Pressure psi, up to 2000 psi
Nature of Membrane Diffusive transport Molecular screening Retention barrier; possibly molecular screening
Chemical Nature Important in Unimportant in affect- of Membrane affecting trans- ing transport properties port properties so long as proper pore size and pore size distribution are obtained
Flux of Membrane One order larger than RO
2. Economical at both small and large sizes, because of their modular 21
nature.
3. Very simple to operate, since they involve primarily the pumping of
liquids.
4. Quite versatile in carrying out more than one function as in the case
of simultaneous fractionation and purification.
5. Energy requirements of the processes are quite low since operation
proceeds through the transfer of liquids with no phase changes.
Low energy consumption of RO and UF is a significant advantage and has
been proved by the previous researche and production [29]. For example, a reverse
osmosis system operating at 68 atm (1000 psi), with a 60% efficient pump and 50%
recovery of permeate,requires only 23 KJ electric input/kgpermeate , which is about
1/100 of the energy required by the simple evaporator, and 1/10 that needed by more
complex "energy-efficient"evaporation schemes [23]. Typical energy consumption for
brackish-water plants is 1.6-2.1 kWh/m3 of product water. Seawater plants consume
about 9.2-10.6 kWh/m3 of product water. The energy consumption of UF is lower than
RO because of its characteristics of low pressure operation and high permeate flux
rate [7].
Although there are many benefits of RO, the process has limitations. Based on
the fundamental transport equations for RO, the applied pressure must exceed the
osmotic pressure to obtain product flow and separate the solute from the solvent.
Therefore, RO is usually not applicable for concentrated solutions. The detrimental
effect of osmotic pressure is compounded by a phenomenon known as concentration 22 polarization [30,23]. It refers to the accumulation of solute at the surface of the membrane because water permeates through membrane but solutes do not. A figure of concentration polarization is given in Appendix D.
Applications of Reverse Osmosis and Ultrafiltration·
In the last few years, RO has been used to treat waste and industrial streams in a variety of operations such as electropainting, electroplating processing, textile fiber, finishing, and waste water treatment. Three main areas of applications are for potable water, industrialuses and waste treatment. The largest RO plants are generally built for municipal water distribution systems.
3 An example of a municipal RO plant is the 11,355 M /d (3 millions gal/d) seawater facility at Key West [34]. Since its start-up in 1980, the plant has been treating seawater containing 38,000 mg/LIDSand producing water containing about
375 mg/L TDS and less than 200 mg/L chloride ion. The experience with this plant has shown the ease of operation possible with a well-designed and maintained facility.
Reverse osmosis is used to treat water for many industrial applications including ultrapure water to rinse silicon chips in the semiconductor industry, ultrapure water for boiler feed in power generation, water for brewing and bottling, and many other process uses. An example of a RO system for ultrapure water is the
4,360 m3/d (1.15 millions gal/d) plant in Windsor, Colorado [35]. This uses spiral wound cellulose acetate membranes operating at 2,760 kPa (400 psig) to remove 80- 23 85% dissolved solids from brackish feedwater containing about 300mg/L TDS. The permeate is treated further by ion exchange to produce ultrapure water for the manufacturing facility.
For waste treatment, one of the largest uses for RO is in industrial and municipal waste treatment. The largest RO plant· treating municipal waste is the
18,925 m3/d (5 millions gal/d) unit using spiral-wound cellulose acetate membrane at
Fountain Valley, California [40,36]. The RO plant reduces the dissolved salts of secondary treated sewage from about 1,200mg/L to less than 120 mg/L, while operating at 85% conversion and at a feed pressure of 2,415-3,175 kPa (350-460 psig).
Applications of Reverse Osmosis and Ultrafiltration in Pulp and Paper Industry
RO and UF mainly are employed for treatment of waste waters and liquors from pulp and paper industry.
Treatment of Spent Sulfite Liquors
The Institute of Paper Chemistry employed UF and RO for the treatment the spent sulfite liquors (SSL) [15,37]. The research results indicated that SSL was concentrated from 10% of solids to 30% by UF. The concentrated SSL was evaporated to 60% of solids. The permeate of UF was further treated by RO. After
RO, the concentration of permeate was reduced to less than 0.3%. IDS, BOD5 were 24 reduced by 96-98%. The treated water can be reused for production.
Gaddis, Fong, and Tay [38] conducted research on recycling spent sulfite liquor from the digester of a sulfonated chemi-mechanical pulping process. In this research, a new ultrafiltration membrane system was used. UF of SCMP spent liquor was shown to retain color and turbid material, but pass sulfite to produce a permeate estimated to be satisfactory for continuous recycling. Compared with pulp produced using untreated recycled liquor, pulp strength was improved with ultrafiltration.
Bansal and Wiley [15] made a positive conclusion to the economical advantage of membrane processes. Their studies were made comparing the capital and operating costs of the proposed system of concentration and fractionation that employed membrane processes with obtaining the same level of concentration by using a conventional evaporation plant. These costs were calculated for a plant that would concentrate 100,000 gal of spent sulfite liquor from 100 g/liter total solids to 600 g/liter ( 10-60% solids). In the proposed system, membrane processes were employed to fractionate spent sulfite liquor to produce purified lignosulfonate and sugar fractions. These could then be further concentrated in a small evaporation unit. The research data indicate a saving of 15% in costs of the proposed UF and RO combining with smaller 3-effect evaporation system over the conventional evaporation alone.
From the standpoint of higher sales value of the purified lignosulfonate and reducing sugar fraction, the cost savings can be further improved and become more significant over that for the crude spent liquor solids.
Table 5 presents data which indicate cost savings of membrane processes 25 combining with 3-effect evaporation over conventional evaporation.
Table 5
Indicated Cost Savings- Membrane Process Over Conventional Evaporation [15]
Basis
100,000 gal/day of spent sulfite liquor to be concentrated from 100 to 600 g/liter of solids.
Capital Costs
3-Effect evaporation = $5.00 per daily gal water removed UF system=$ 1.50 per daily gal water removed RO systems = $ 2.00 per daily gal water removed
Operating Costs
3-Effect evaporation = $5.00 per 1000 gal water removed UF system= $1.50 per 1000 gal water removed RO systems= $2.00 per 1000 gal water removed
Saleable Value
Crude spent sulfite liquor solids= $0.01 /lb Purified lignosulfonate solids= $0.02 /lb Purified reducing sugars= $0.02 /lb
Treatment of Bleaching Caustic Extraction E-stage Effluent
The effluentfrom bleaching E-stage has the characteristics of high toxicity and high color so that it results in serious pollution. The biological and sedimental 26
treatments to the effluent showed a relatively low efficiency in removing color and
toxicity.
Iggesunds Bruk Kraft pulp mill employed UF equipment to treat bleaching caustic extraction effluent. The results indicate that color was removed by 90%, COD by 80%, BOD by 25-50%, and toxicity by 50%. The treated water could be reused for washing of bleached pulp.
Japan Sanyo lwakuni employed UF to treat the bleaching E-stage effluent.
COD and color in effluent were reduced by 80% and 90% respectively.
RO is also employed forthe treatment of bleaching effluent. A research report
[39] describes the treatment of RO for bleaching caustic extraction effluent. The results indicate that IDS removal reached 98.7% and BOD5 to 94.8-99.2%. The recovery of effluent was 92%.
Dorica [ 40] studied ultrafiltration and reverse osmosis for the treatment of bleaching plant effluent. The RO filtrates were found to be suitable for recycling to the bleach plant. The concentrates produced were treated for separation of chlorides using diafiltration techniques. The chloride-rich filtratesresulting fromthe diafiltration treatment of concentrates might be suitable for generation of sodium chlorate and chlorine dioxide, while the organic concentrate could be incinerated.
Treatment of RO for Waste Water From Washing Pulp Stage
RO membrane process was employed early (Wiley, 1967) for treatment of effluent from washing stage of kraft and sulfite pulping processes. 27
The Institute of Paper Chemistry developed a membrane treatment apparatus
which had a capacity of 190-380 tons/day. In the experiment, waste water could be
concentrated from 1 % to 6-12%.
Pepper [16] employed P.C.I. RO tubular module system to concentrate diluted
black liquor from 1% to 11%.
All the RO research results indicate that TDS, BOD, and COD in effluent can
be reduced by 80-90% or higher.
Characteristics and Composition of Deinking Effluent
Effluent wastewater characteristicsof direct repulping and deinking mills differ
from conventional pulp mill effluent. The differences are mainly reflected in these following aspects.
Effluent BOD5 loadings and flows are usually lower for direct repulping operations. Deinking effluent contain fewer color materials but higher concentrations
of heavy metals and total suspended solids.
BOD5, TDS and TSS
The waste loads from deinking mills and effluentlimitations guidelines of EPA
are shown in Tables 6 and 7. Data are fromoperations in 1988- 1989 period, therefore
will be reduced in most modem plants as shown in Table 8.
Because Tables 6 and 8 show considerable variation, composite average
compositions of deinking effluents are summarized in Table 9. 28
Table 6
Deinking Raw Effluent Characteristics [2]
Raw Effluent Raw Effluent Loads Concentration
Flow, Gal/f 10,900-30,000 I Avg. 17,000 I
BOD5 50- 256 lb/T 549 - 1,023 mg/L Avg. 128 lb/T 903 mg/L
TSS 60-990 lb/T 659 - 3,960 mg/L Avg. 468 lb/T 3,290 mg/L
Table 7
Summary Regulations,40 CFR Part 430 Subpart Q (Deinking) [2]
a Pollutant or BPT AND BCT NSPS Characteristic Daily 30-Day Daily 30-Day Maximum Average Maximum Average
kg/1000 kg product
Fine PaRer BOD5 18.1 9.4 5.7 3.1 TSS 24.05 12.95 8.7 4.6
Tissue PaRer BOD5 18.1 9.4 9.6 5.2 TSS 24.05 12.95 13.1 6.8 29
Table 7--Continued
Pollutant or BPT AND BCT NSPSa Characteristic Daily 30-Day Daily 30-Day Maximum Average Maximum Average
Newsprint B0D5 18.1 9.4 6.0 3.2 TSS 24.05 12.95 12.0 6.3
Note: a: BPT=best practical technology. BCT=best conventional technology. NSPS=new source performance standard. Effluent pH: 5.0-9.0.
Table 8
Effluent Characteristics of Different Deink Categories[21]
Category TSS BOD TDS pH Temp. mg/L mg/L mg/L op
Fine Paper 2000 800 5500 8.0-8.5 100-110
Tissue 2000 750 5500 8.0-8.5 90-105 (W. T)8
Tissue 2000 800 5500 8.0-8.5 90-110 (F.W.)8
Newsprint 1500 400 3500 7.5-8.0 90-110 (W.T)
Newsprint 1500 550 5000 7.5-8.0 95-105 (F.W)
Note: a: W.T.= Washing Technology. F.W.= Flotation and Washing. 30
Table 9
Average Deinking Effluent Composition
Average Range
TSS mg/L 2,500 700-4,000
BOD mg/L 800 400-1,000
TDS mg/L 5,000 3500-5500
Gallons/ton 10,900-30,000
Gallons/min 1,500-6,300* (for 300T/day pulp production)
Note: * Normally, one would treat about 50% of total effluent through the RO unit (750 to 3200 gpm fora 300 T/day mill). The other 50% would be returnedfor process dilution without RO treatment.
From the above tables, it is apparent that if the removal ratio of BOD reaches 80% and the removal ratio of TSS reaches 95%, the discharge standards can be satisfied.
Theoretically, reverse osmosis and ultrafiltrationcan remove 100% of TSS and reverse osmosis can remove 90% of BOD.
Other Specific Chemical Constituents
A number of mills are also limited in mass loadings for additionalparameters such as some of the heavy metals, PCBs, pentachlorophenol and trichlorophenol (the phenols if the mill is using a chlorophenol-based slimicide ).
Table 10 lists the main specific chemical constituents in deinking effluents. 31
Table 10
Chemicals Identified in Effluent [2]
Category Chemical Average Concentra- tion in Effluent ug/L
Fine Paper Chloroform 4190 Naphthalene 142 Pentachlorophenol 15 Tetrachloroethylene 95 Toluene 58 Trichloroethy lene 493 PCB 1242 3 Lead 149
Newsprint Butyl Benzyl Phthalate 5 Cyanide 1560
Tissue Trichlorophenol 48 Chloroform 1367 Naphthalene 48 Pentachlorophenol 38 Phenol 119 PCB 1254 1 PCB 1260 1
Chlorinated Aromatic Compounds
Polychlorinated biphenyls (PCBs) have been detected in effluent of a variety of paper products. The incorporation of PCB- containing carbonless copy paper into the recycled fiber stream has been identified as the source of PCB contamination. 32
Chlorinated organic compounds such as dioxins, furans, and chloroform have their
origin in bleaching with chlorine or chlorine containing compounds. These compounds are a source of toxicity in effluents.
Heavy Metals
The heavy metals are another source of toxicity in effluent. In Table 11, the metal contents in effluents from three recycled paper mills are listed.
Table 11
Metal Contents in Recycled Fiber Mill Effluent [2]
Cr Cu Ni Pb Zn Hg ug/L
Mill WM 42 34 4 ca.100 1200 0.3
Mill WN 120 44 9 170 910
Mill WO 430 330 27 390 580
In addition, deinking chemicals generally added in flotationor washing stages include collectors [41,42] such as fatty acid soaps, dispersants [41,42] such as non ionic and anionic surfactants or detergents. These chemicals can be present in effluent as pollutants. 33 Potential Problems From Water Reuse [1,21]
Table 12 lists paper industry problems which may result from extensive water reuse. The problems are broken down into three general classes: those arising from the presence of higher levels of suspended solids, those arising from the accumulation of dissolved solids, and those arising from the increased retention of heat.
Table 12
Potential Problems Encountered in Water Reuse
Dissolved Solids Suspended Solids Thermal Energy Build-up Build-up Build-up
Slime Dirt Temperature Foam Erosion Sizing problems Pitch Fines Corrosion Felt plugging Sizing Wire plugging Product mottling Wire life Color Felt life pH control Reduced drainage rate Precipitation Scale Odor Retention
For deinking mills, recycling water may cause the following consequences.
Closing water systems in deinking and paper mill operations lead to a considerable increase of dissolved solids, suspended solids, volatile organic compounds, and 34 process water temperature. Some of the inorganic chemicals which may build up in the closed process water loops include sulfate, chloride, calcium, magnesium, iron, aluminum, and zinc. Generally, dissolved and colloidal materials probably present a more serious problems than suspended solids. After long periods of running under conditions of low fresh water use, the problems emerge.
Paper Properties
Dissolved solids buildup in process water can unfavorably affect the spectral reflectance factor. Another noticeable effect of water reuse on paper quality is the slime spots and crushing of the sheet.
Microbial Contamination of Process Water
Microbial activity in the rinse of process water is quite common due to the buildup of dissolved organic solids. The increase of concentration of dissolved solids will increase carbohydrate and nutrient levels which constitute a favorable environment for bacterial growth, which can results in the problems of slime and odor.
Water System Corrosion
In large or completely closed water systems, corrosion problems are frequent handicaps, even if stainless steel is used. Corrosion is the deterioration of metal by electrochemical processes. The corrosion rate is affected by the complex interactions 35 of numerous factors [ 1].
The metal ions present in a system are important factors.In addition, microbial attacks on iron or steel usually appear in many forms, from more or less uniform corrosion to pitting. In most cases, corrosion becomes visible in the formof physically unstable crusts, made up either of black ferrous sulfide or white ferrous hydroxide.
Corrosion attacks on steel are, as a rule, in the form of pitting.
Another cause of corrosion due to closing of water loops is the buildup of hydrogen sulfides in water circuits due to the action of sulfate-reducing bacteria in anaerobic environments. Regular cleanout and sometimes the use of hydrogen peroxide at higher pH helps eliminate such conditions.
In addition, the accumulation of carbonates, silicates, and sulfates can cause deposition problems in the process. Acids, such as acetic acid and propionic acid produced by anaerobic degradations, may, in connection with slim deposits, lower the pH.
Limitations of Biological Treatment and Chemical Sedimentation
Biological treatment and chemical clarification cannot effectively remove dissolved substances. Chemical clarification can only remove suspended solids.
Actually, sometimes, this method increases the dissolved solids due to the use of chemical additives. Biological treatment can only degrade the part of the dissolved substance which can be used by microorganisms. The principle of biological treatment 36 is to transform the compounds from their reducing state to an oxidizing state rather than remove them (though H2O and CO2 are final products). Therefore, although biological treatment can considerably reduce BOD, TDS in the effluent still remains at high levels [21]. Usually, secondary biological treatmentplants can provide, at best, a 30% reduction in color load [1]. Some biological treatment systems actually create color. In addition, biological treatment is not very suitable for the treatment of toxicants. Toxicity can be caused by the compounds such as phenols, chloro-organics, cyanide and heavy metals. Bacterial growth will be inhibited by a toxic material above a certain concentration.
Compared with biological treatment, the principle of the RO membrane separation process is to remove the substances which result in BOD, COD, color, toxicity and corrosion. Technologically, reverse osmosis can remove most of the dissolved materials to produce high quality water forreuse. The solute separation ratio can reach 95% or higher. If the removal of suspended or colloidal materials in effluent is just considered, nanofiltration, ultrafiltration or microfiltration can reach the removal ratio of 90-100%. CHAPTER III
PROBLEM STATEMENT
In deinking mills, closing water systems in deinking and paper mill operations leads to a considerable increase in dissolved solids, suspended solids and temperature.
The dissolved substances in water present a more serious problem. The high dissolved solids concentration can cause problems of paper properties and quality, microbial contamination and corrosion. Traditional biological and chemical clarification treatments show significant limitations in removing the dissolved solids.
The application of RO in the treatment of deinking pulping waste waters is a new exploration. Although some research has been performed before on the application of membrane processes in the treatment of other effluent such as pulp washing and bleaching effluent [12,13,15,37,38,40,43,44], the research on the application of recycling and deinking effluent is limited.
The purpose of this research project is to investigate the utility,efficiency and capacity of the reverse osmosis process for the treatment of deinking waste water to the point that treated water may be reused in the process rather than released to the environment. If possible, the research results will provide not only theoretical results, but also give insight into larger scale industrial applications.
The concrete objectives include:
37 38 Pretreatment
Determine the pretreatment methods to remove most of the suspended solids in the effluent. The considered pretreatment include natural sedimentation, chemical
clarificationand prefiltration. The research will study an effectivepretreatment method
which can reduce TSS and turbidity to an acceptable content level to enter the reverse
osmosis process.
Reverse Osmosis
Reverse osmosis will be the most important element in this research. The research will determine the capacity of reverse osmosis to remove 90% or higher level of dissolved solids.
The experiment data will be evaluated to:
1. Study how the permeate flux and solute rejection percent (Appendix E) are affected by the factors: operation pressure, feed TDS concentration, pH, temperature and recovery of feed water for two types of RO membranes and determine which factors are important to flux and solute rejection.
2. Determine optimum operation conditions, which include operating
pressure, temperature, and feed recovery.
3. Determine the percent removal efficiencyof components in feed water.
The components include: total solids (TS), total suspended solid (TSS), total dissolved
solids (TDS), turbidity, conductivity, biochemical oxygen demand (BOD), chemical
oxygen demand (COD), total organic carbon (TOC), and metal elements. CHAPTER IV
EXPERIMENTAL PART
Experimental Design
Although there are a variety of compositions in deinking effluent, they can be
classified into two basic components, suspended solids and dissolved solids. The
traditional treatment methods have shown high removal of TSS and BOD, but low
success in removal of IDS. Therefore, the removal of IDS is the most important
function of membrane treatment and a successful pretreatment is also a necessary
condition so that reverse osmosis can be successfully employed.
Based on the above consideration, experiments included three stages: (1) the
preparation of feed water (effluent); (2) pretreatment of effluent to remove most of
the TSS and turbidity so that feed water can meet the feed requirements of the RO process; and (3) reverse osmosis treatment of feed water to remove more than 90% of the IDS.
The WMU pilot plant recycling unit was used to prepare the effluent.
Pretreatment of the effluent included: (a) natural sedimentation to remove most of
TSS, (b) chemical clarification by coagulant to remove up to 99% TSS and to reduce turbidity to about 1 NT, (c) prefiltration before RO to filter solid particles so that membrane and pump can be protected. Reverse osmosis experiments were carried out
39 40 to determine the optimum operating conditions.
Water analyses were used to evaluate the removal efficiency of treatment and quality of effluent, feed water and permeate water. TS, TSS, turbidity, TDS, conductivity, BOD, COD, TOC, metal elements were tested.
An experimental flow chart is given in Figure 1 (which will be described in the following section).
Preparation of Effluent
Since deinking equipment is available in the WMU pilot plant, simulation of a commercial deinking process was used to prepare deinking waste water for this study.
WMU Pilot Plant and Laboratory Equipment
WMU has a complete pilot plant scale deinking process which includes pulping, screening, cleaning, flotation and washing equipment.
The main equipment includes: (a) Hydrapulper, (b) Pressure screen, (c)
Flotation cell, and (d) Side Hill Washer.
The laboratory scale equipment was used formaking small amount of effluent forevaluation beforebigger pilot scale experiments were run. The equipment included a morden slush maker, a laboratory scale flotation cell and a sidehill screen. 41
Mixed Ofce Wate l Pilot Plat Deinking Pulping
Effuent Water Component Anayses: TS, TDS, TSS, 1------BOD, COD, Tubidity, Conductivity, TOC, Metl Element.
Sedimenttion Witout Coagulat
Turidity, TSS Analyss
Clafcation Wit Coagult: 1. Peliminary Coagulat Screening Expriment 2. Optmizton Exprment
Turbidity, TSS Analyses
Revers Osmosis Eprment:
1. Pelimina Factor Screening Epriment: Study of Efet of Pssue, Temprture, Concenta• lon ad pH on Perete Flux ad R% to Dterine te Impornt Factrs. Final Perete Anyses: TS, TS, TSS, Conductvity, 2. - Stdy How te imprt Fators Turbidity, BOD, COD, TO, Affect te Flux ad R% Met Elements 3. Optmizton Expriment to Dterine Optium Lvels of Pessure, Temprtu, ad Fe Reove %
Figure 1. Experimental Schematic. 42
Waste Paper Source
Standardized 250 lb batches of mixed office waste paper have been sorted fromcommercial sources. Table 13 gives the components of the mixed office waste.
Table 13
Components of Mixed Office Waste
Components of Mixed Office Waste Percent (By Weight)
Post Consumer White Ledger 60
Post Consumer Colored Ledger 20
Coated Sulfate Book 10
Computer Print Outs 5
Groundwood Computer Print Outs 5
Effluent Preparation Procedure
A flow diagram for making deinking effluent using the facilities at the WMU pilot plant is given in Figure 2.
Pulping, Flotation, Washing and Clarification
250 lb of mixed office waste was placed in hydrapulper to pulp. Pulp 43
mixed office waste (2501b)
pulper 8% consistency 0.5% surfactant, l00'F, fresh or recycled water 30 min, 9.0 pH 376 gal.
1500 gal. clarified water
pressure screen (0.008 in slots) rejects 2% consistency
water 1500 gal.
flotation cycles ( 6) 1.0 % consistency 400 gpm l00"F 60 min. 3000 gal. I ink, fines, filler
side hill washers 5% consistency, pulp 500 gal.
filtrate 2500 gal.
natural experimental clarification samples or clarified back to water process for dilution
Figure 2. Flow Diagram for Preparation of Deinking Effluent. 44 consistency was adjusted to 8%. Pulp pH was adjusted to 9.0 with caustic. Non-ionic surfactant, 0.5% on pulp was also added prior to repulping at 100 °F for 30 min.
The surfactant Lionsurf FA-709 is a liquid fatty acid polymeric surfactant collector for use in both floatation and floatation-washing deinking systems. It contains no emulsifiers and has excellent biodegradability and low aquatic toxicity.
Its typical properties are listed bellow:
Appearance: clear amber liquid
Density: 7.9 lbs/gal.
pH: 6-8 ( 10% solution )
Flash point: > 200°F.
After pulping, pulp was discharged fromhydrapulper to a chest where the pulp was diluted to a consistency of 2%. Then, the pulp was sent through a pressure screen
(0.008 in. slots) to remove large-size rejects. After screening, the pulp was diluted to a consistency of 1.0% and pumped to the flotation cell where, ink (and some fines and filler) was removed by flotation. The operating conditions of flotation used: pulp consistency 1.0%, temperature 100°F, flotation flow rate 400 g.p.m., and six cycles in 60 minutes.
After flotation, pulp was sent to the side hill screen to wash. The sidehill screen is a simple and effective washing unit. Pulp was introduced to the screen through a headbox. As pulp tumbled and slid down to a discharge box, free water drained through the screen and was collected in a water compartment. About 2500 gallons of filtrate were collected and sent to a chest for clarification by the 45 sedimentation process (24 hrs).
Six batches of pulp were run to build up the required IDS concentration. From the second to sixth batches, the dilution water used in the pulper, pressure screen and flotation cell was the filtrate from the clarification tank instead of fresh water.
The final clarified effluent samples were collected in 55 gallon drums and used for the pretreatment and RO experiments. Effluent samples were stored in a cold room
(about O - 4°C).
Effluent Pretreatment
Natural Sedimentation
Gravity settling for 24 hours was the process used in natural sedimentation.
During this time, more than 90% turbidity and TSS were removed.
After sedimentation, there was less than 10 % turbidity and TSS remaining in the effluent. This part of the components could not be effectively removed by natural sedimentation or prefiltration.
Chemical Clarification by Coagulant
Since the maximum turbidity limit of feed water for a reverse osmosis membrane element is about 1 NTU, chemical clarification with the use of a polymer coagulant was found necessary. 46
Phase I: Preliminary Screening Experiments
Seven different kinds of coagulants and flocculents were used in experiments.
They are:
1. ULTRION liquid cationic coagulant 7157, which are low-molecular weight cationic coagulant.
2. ULTRION liquid cationic coagulant 7155.
3. Liquid cationic coagulant 7655.
4. Liquid cationic coagulant 7653.
5. Anionic flocculent 625.
6. Anionic flocculent 634.
7. Cationic flocculent 89PD078.
The coagulant is usually a high-charge, low-molecular-weightcationic polymer and can form small floes. The flocculent is often a low-to-high charge, high molecular-weight anionic polymer and can make the small floes form a larger loose structure [45]. The above coagulants and flocculents are the products of Nalco
Chemical Company.
Alum was used either in combination with other polymers or alone. Polymer dosage was varied between O - 5 mL/L while alum dosage was varied between 15 to
150 mg/L.
According to the turbidity results obtained fromthe above experiments (Tables
25-27), the polymer which has the largest effect on reducing turbidity (coagulant 47
7157) was selected for optimization experiments in phase II.
Phase II: Optimization Experiments
A two-level, L8 orthogonal array experiment [46] was designed to study the
factor effects so that the factors which had significant effects on dependent variable
(turbidity) could be selected for further experiments. The experimental details are
presented in Tables 14 and 15.
Table 14
Variables and Their Levels
Variables Levels -1 +1
Temperature °C (T) 20 32
Polymer 7157 Dose mL/L (P) 0.4 1.0
Alum mg/L (A) 15 60
From the results of these experiments, the factors temperature and coagulant dose were found to be significant. To determine their effects on the turbidity, additional experiments were carried out by varying their levels (Table 16).
The final optimum conditions to achieve the turbidity of 1 NTU were determined from this factor effect study. 48
Table 15
2-Level, L8, Experiment Array
Trial Factor and Factor Level No. T p A TP TA PA TPA
1 -1 -1 -1 +1 +1 +1 -1 2 +1 -1 -1 -1 -1 +1 +1 3 -1 +1 -1 -1 +1 -1 +1 4 +1 +1 -1 +1 -1 -1 -1 5 -1 -1 +1 +1 -1 -1 +1 6 +1 -1 +1 -1 +1 -1 -1 7 -1 +1 +1 -1 -1 +1 -1 8 +1 +1 +1 +1 +1 +1 +1
Note: T=temperature oc, P=polymer dosage mL/L, A= alum dosage mg/L. TP=interaction of T and P. TA=interaction of T and A. PA=interaction of P and A. TPA=interaction of T, P and A.
Table 16
Variable Levels for Factor Effect Study
Variable Levels
Temperature, °C 18 20 25 28 32 37 40
Coagulant 7157 Q2 Q3 Q4 Q6 Q8 1.0 1.2 Dose, mL/L 1.4 1.5 49 Prefiltration
Cartridge filters were installed with the reverse osmosis unit. The cartridge filters were fitted with five micron filter media. The filters removed solid particles-5 microns and above-from the feed water.
Reverse Osmosis Treatment
Equipment and Membrane
Reverse Osmosis Equipment Unit
The SRO-400 RO unit was loaned by Stream International Inc., Houston,
Texas. Figure 3 gives the flow diagram of the reverse osmosis system. The system includes feed tank, low pressure feed pump, cartridge filters, high pressure pump and
RO membrane module elements.
The feed centrifugal pump pumps the feed water through the cartridge filters into the RO unit at pressure 30-35 psi. The high pressure pump is a positive displacement vane type pump. It raised the lower pressure feed water to a high enough pressure to feed the RO elements. The maximum operating pressure is 1000 psi.
Reverse Osmosis Membrane
The RO membrane module was a spiral wound element of the following Feed Water
Feed Tank CartridgeFilter
High Pressure Pump Low Pressure Pump
Membrane Module
Permeate
Concentrate
Figure 3. Flow Diagramof SRO - 400RO Unit.
VI 0 51 specifications (Table 17) and is made of an aromatic polyamide, Filmtec thin film composite type reverse osmosis membrane. The Dow Chemical Company supplied the membranes.
Table 17
Membrane Specifications
Membrane SW30-2521 BW30-2521
Regular usage Seawater Brackish
Maximum operating 1000 600 pressure psi
Maximum operating 45 45 temperature °C
Maximum feed 1 1 turbidity NTU
pH range tolerance 2-11 2-11
Maximum flux rate 22.3 27.0 gallon/feet2 day
Phase I: PreliminaryOperating Factor Screening Experiments
The purpose of phase I was to select and determine the important factors which could have significant effects on solute rejection ( R % of TDS and conductivity) and permeate flux (F). The solute percent rejection (R%) and permeate 52
flux (F) are two basic dependent variables used in all RO experiments to analyze
membrane separation efficiency and membrane permeability for feed water. The
definitions of R% and Flux (GFD, gallon/feet2 day) are given in appendix E.
Four independent variables were studied in the screening experiments: pH,
temperature, feed water IDS concentration (cone.), and operating pressure.
Data Collection Methods
The experimental matrix consisted of four variables at the three levels stated in Tables 18 and 19 for membranes SW and BW respectively. Thus, there are 34 =
81 experiments in Table 18.
Table 18
Variable Levels for Screening Experiments-SW Membrane
Variable Levels pH 5.0· 7.5 9.0
Feed IDS, mg/L 2159 4255 8240
Temperature,°C 15 25 35
Pressure, psi 400 600 800
Note: 8 additional experiments were included in Table 18. Thus, two additional feed TDS were studied from four pressures.
Table 19 contains 72 experiments since only two temperature levels (with 53 additional experiments at the third temperature level) were studied.
Table 19
Variable Levels for Screening Experiments-BW Membrane
Variable Levels pH 5.0 7.5 9.0
Feed TDS, mg/L 2159 4122 6280
° Temperature, °C 15 (25) 35
Pressure, psi 250 350 450
Note:additional experiment conditions at 25°C were: pH 7.5, 25°C, pressures at 300, 400, 500 psi.
The experiments were done by varying one variable while the others were kept constant.
Method I: Orthogonal Array Experiment
The statistical method, orthogonal array experiment was used to analyze the results from the above RO experiments to study the effectsof pH, feed concentration, temperature and pressure on flux and R%. A 2-level, 4 factor, 16 L arrayexperiment was designed. Table 20 gives the factors and factor levels for this experiment. Table
21 gives the experimental design array. 54
Table 20
Factor and Factor Level of Orthogonal Experiment for Membranes SW and BW
Factor Level SW BW
Factor -1 +1 -1 +1
pH 5.0 9.0 5.0 9.0
IDS cone., mg/L 2159 8240 2159 6280
Temperature,°C 15 35 15 35
Pressure, psi 400 800 250 450
Method II: Regression Analysis
All data obtained from the phase I RO experiments (Table 18, 19) were used in this analysis to get the analysis of variance (ANOVA) and regression model. All the input data used in the Minitab program run are given in Table 51 and Table 52 in Appendix F.
Phase II: Effects of Factors Pressure, Temperature, and and Feed Concentration on Flux
Based on the study results of phase I, the factors which had significant effects on R % or flux were selected to study further in the phase II experiments. The study 55 emphasized how these factors affect the R % or flux. The factor effects selected for phase II were: effects of pressure, temperature, and feed TDS concentration on flux.
Table 21
2 Level, 4 Factor, 16 L Experiment Design Array
Trial No. Factor and Factor Level pH C T p
1 -1 -1 -1 -1 2 -1 -1 -1 +1 3 -1 -1 +1 -1 4 -1 -1 +1 +1 5 -1 +1 -1 -1 6 -1 +1 -1 +1 7 -1 +1 +1 -1 8 -1 +1 +1 +1 9 +1 -1 -1 -1 10 +1 -1 -1 +1 11 +1 -1 +1 -1 12 +1 -1 +1 +1 13 +1 +1 -1 -1 14 +1 +1 -1 +1 15 +1 +1 +1 -1 16 +1 +1 +1 +1
Not: C=TDS concentration mg/L. T=temperature,°C. P=pressure, psi.
Because data collected fromphase I could be combined with data from phase
II, repetitions between phase I and phase II were avoided. Table 22 and Table 23 give the experiment matrix respectively for membrane SW and BW in phase II experiments. Temperature and pH during all the experiments were maintained at 25°C 56
and pH 7.5, respectively.
Table 22
Experimental Matrix of Phase II for SW Membrane
Variables Levels
Feed IDS, mg/L 2159 4255 6290 8240 10405
Pressure, psi 400 500 600 700 800
Note: constant variable levels: pH 7 .5, temperature 25°C.
Table 23
Experimental Matrix of Phase II for BW Membrane
Variables Levels
Feed TDS, mg/L 2159 4285 6530 8095 10090
Pressure, psi 250 300 350 400 450 500
Note: constant variable levels: pH 7 .5, temperature 25°C.
All the data from the phase I and phase II were used to study factor effects.
Although effects of pressure, temperature, feed concentration and pH on R % as well as the effectof pH on flux were not studied in phase II, some supporting data were collected to confirm the results of phase I. 57
Phase III: Determination of Optimum Operating Condition
From the results of the factor effect study in phase II, optimized operating pressure and temperature conditions were determined first. Then, under the optimized operating pressure and temperature conditions, further experiments were conducted to study: (a) the relationship between feed recovery percentage and flux; (b) the relationship between feed recovery percentage and feed TDS concentration; and (c) the relationship between feed recovery percentage and permeate TDS concentration.
From the above three relationships, optimized feedrecovery percentage (Appendix E) could be determined.
Water Analysis
Water analysis methods were used to determine: (a) the concentration of each component in the original effluent, in the feed water of each middle treatment stage, and in the final permeate (product water) and (b) percent removal efficiency of each component in feed water at each treatment stage and the final overall removal efficiency.
These water analysis items included: pH, total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), turbidity and conductivity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), metal elements, and total organic carbon (TOC).
Turbidity was used as a basic analysis item in experiments of chemical 58 clarification with coagulants. TDS and conductivity were used as the basic analysis items in determining membrane solute rejection percentage (R%) in all RO experiments. BOD, COD, TOC, and metal element tests were used in the final RO performance under the optimal operation conditions.
These water analysis methods are described" below:
Turbidity
Standard methods for examination of water and wastewater - 2130B (47] was used to measure the turbidity by using a Hach Model 2100A Turbidimeter, with the range of 0-1000 NTU. Turbidity in water is caused by suspended matter. Turbidity is an expression of the optical property that causes light to be scattered and absorbed rather than transmitted in straight line through the sample.
Total Solids
Standard method for examination of water and wastewater - 2540B [47] was used to measure the total solids dried at 103-105°C
Total Dissolved Solids
Standard method for examination of water and wastewater - 2540C (47] was used to measure the total dissolved solids. 59
Total Suspended Solids
Standard method for examination of water and wastewater - 2540D [47] was used to measure the total suspended solids dried at 103-105°C .
Biochemical Oxygen Demand (BOD)
Standard method for examination of water and wastewater - 5210B [47] was used to measure the BOD5• The test measures the oxygen utilized during the 5 day incubation period for the biochemical degradation of organic material and the oxygen
_used to oxidize inorganic material such as sulfides and ferrous iron.
Chemical Oxygen Demand (COD)
Standard method for examination of water and wastewater - 5220 [47] was used to measure the COD by closed reflux method. The chemical oxygen demand is used as a measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant such as potassium dichromate.
Total Organic Carbon (TOC)
Combustion - coulometric titration method was used to measure the TOC.
TOC is a more convenient and direct expression of total organic content than either
BOD and COD. The organic carbon is determined using a coulometric total carbon 60 apparatus (UIC Inc.)
Organic carbon is converted to CO2 by catalytic combustion. The CO2 is then measured by coulometric titration. TOC assay was done in the Western Michigan
University, Water Quality Lab, Institute for Water Sciences.
Metal Elements: (Ca, Mg, Na, Cr, Cu, Ni, Pb, Zn, Al, Fe)
Standard method for examination of water and wastewater - 3120B [ 47] was used to measure metal elements by inductively coupled plasma (ICP) method.
Instrument: PS 1000 - ICP/Eechelle Spectrometers. Manufacturer: Leeman Labs.
Metal element analyses were done in the WMU Water Quality Lab, Institute for
Water Sciences.
Conductivity
Standard method for examination of water and wastewater -2501B [47] was used to measure the conductivity. Conductivity is a measure of the ability of an aqueous solution to carry an electric current. This ability depends on the presence of ions, their total concentration, mobility and valence. The measurement of electrical conductivity can provide an accurate assessment of ionic concentration. Conductivity was measured by using a YSI Model 32 Conductance Meter, with the conductance range of 2 uv - 200 mv. Manufacturer: Yellow Springs Instrument Co. Inc .. CHAPTER V
RESULTS AND DISCUSSION
The results and discussion are divided into three parts: Part I, effluent and its pretreatment. This part includes : (a) effluent components; (b) natural sedimentation;
(c) polymer coagulant screening and optimization. Part II, reverse osmosis treatment.
This part includes: (a) preliminary operating factor screening; (b) effects of three operating factors, pressure, temperature, concentration on flux; and (c) optimization of operating conditions. Part III: the comprehensive discussion of components and their removal efficiency.
Effluent and Its Pretreatment
Effluent Components and Natural Sedimentation
The results of the turbidity and suspended solids analyses presented in Tables
24 and 25 indicate that natural sedimentation removed 95.5% of TSS and 98.7% of turbidity. It means that most TSS and turbidity did not exist in water in stable dispersed form. As a result of natural sedimentation, TSS of the effluent was reduced from 1973 mg/L to 88.5 mg/L and turbidity from3400 to 45 NTU. However, turbidity was still too high to satisfy the feed water specification for the RO unit. The module type of RO membrane is spiral wound and has limited spacers to tolerate the high
61 62
TSS and turbidity content in feed water. Maximum tolerance forfeed water turbidity to RO membrane is about 1 NTIJ.
Table 24
Effect of Sedimentation and Clarification on Suspended Solids and Turbidity
Particulars TS TSS Turbidity
mg/L Removal, mg/L Removal, NTIJ Removal, % % %
Original 4093 1973 4300 Effluent
Sedimen- 2209 46.0 88.5 95.5 45 98.7 tation
Clarifi- cation With 2168 47.0 8.5 99.6 1.0 99.96 Coagulant 7157
Therefore, the decrease of turbidity from 45 to 1 NTIJ was a crucial step for this treatment process. Chemical clarification with coagulants or flocculents was used to achieve this low a turbidity.
Phase I: Screening Experiments for Polymer Effectiveness in Clarification
Seven commercial polymers-coagulants and flocculents-were used in these 63 screening experiments. Tables 25-29 give the turbidity values obtained after treatment with the seven polymers at different dosage rates in combination with varying amounts of alum. The turbidity of the feed water was 45 NTU. It is easily seen that polymers 7655, 625 and 89PD078 were of no use in decreasing the turbidity of the feed water.
Table 25
Turbidity Results of Feed Water Treated With Polymers and Alum
Turbidity, NTU
Polymer Alum Coagulant Flocculent mL/L mg/L 7157 7155 7653 7655 634 625 89PD078
1 15 0.9 24 26 >45 38 >45 >45
2 15 1.0 23 25 >45 32 >45 >45
3 15 1.0 21 27 >45 30 >45 >45
4 15 1.2 19.5 23 >45 33 >45 >45
5 15 1.0 17 23 >45 32 >45 >45
Figures 4-9 compare the turbidity results of polymers 7155, 7157, 7653 and
634 at varying dosage rates of alum. Results indicate that coagulant 7157 significantly reduced turbidity of feed water to about 1 NTU. The other three polymers 7155, 7653 and 634 had comparatively smaller effects. These three polymers can not satisfy the 64
Table 26
Turbidity Results of Feed Water Treated With Polymers and Alum
Turbidity, NTU
Polymer Alum Coagulant Flocculent mL/L mg/L 7157 7155 7653 7655 634 625 89PD078
1 30 1.0 26 23 >45 36 >45 >45
2 30 1.2 23 27 >45 35 >45 >45
3 30 1.2 20 24 >45 29 >45 >45
4 30 1.1 22.5 24 >45 29 >45 >45
5 30 0.8 15 22 >45 29 >45 >45
Table 27
Turbidity Results of Feed Water Treated With Polymers and Alum
Turbidity, NTU
Polymer Alum Coagulant Flocculent mL/L mg/L 7157 7155 7653 7655 634 625 89PD078
1 45 1.0 23 24 >45 35 >45 >45
2 45 1.3 24 23 >45 34 >45 >45
3 45 0.9 23 25 >45 33 >45 >45
4 45 0.8 20.5 24 >45 31 >45 >45
5 45 1.0 20 24 >45 28 >45 >45 65
Table 28
Turbidity Results of Feed Water Treated With Polymers and Alum
Turbidity, NTU
Polymer Alum Coagulant Flocculent mL/L mg/L 7157 7155 7653 7655 634 625 89PD078
1 60 0.9 25 26 >45 39 >45 >45
2 60 1.2 22 25 >45 31 >45 >45
3 60 1.2 22 24 >45 30 >45 >45
4 60 1.0 18 26 >45 30 >45 >45
5 60 0.8 15 25 >45 30 >45 >45
Table 29
Turbidity Results of Feed Water Treated With Polymers and Alum
Turbidity, NTU
Polymer Alum Coagulant Flocculent mL/L mg/L 7157 7155 7653 7655 634 625 89PD078
1 100 1.5 20 28 >45 36 >45 >45
2 100 1.3 21 26 >45 32 >45 >45
3 100 1.5 19 23 >45 31 >45 >45
4 100 1.0 20 22 >45 27 >45 >45
5 100 1.0 16 20 >45 28 >45 >45 66 requirements of the RO unit, as the turbidity values (about 20 NTU) were well above the 1 NTU (maximum).
Aill1I 15 IIJ&/'L •o�------,
+-
ID
D
,_j__J!!•!=::=::::;;:::::=:::!!•�==::;::::==�-===::==�·�==:==•�___Jo., u PY,n/L 1--- 7157- 71! -1. -7H3 I
Figure 4. Effect of Polymers and Alum (15mg/L) on Turbidity Removal.
Figure 10 gives the turbidity results of the addition of alum alone. Alum by itself, is able to reduce the turbidity from 45 to only 35 NTU, even at a very high dosage of 200 mg/L. Hence, polymer coagulant 7157 was selected as the coagulant to be used in phase II optimizationexperiments. Figures 4-9 also show that increasing the coagulant 7157 dose from 1 to 5 mL/L resulted in no significant difference in turbidity. Hence, in phase II experiments, the addition dose of coagulant 7157 was maintained around 1 mL/L. 67
A30 J 40
GI-- H
50 � 8 EJ
in �20
! 15
10
5
0 • • • • • 1.1 2-0 u u u I • 1Y,/L 1--- 7157 -+- 71!15 -B-1.M -715 1
Figure 5. Effect of Polymers and Alum (30mg/L) on Turbidity Removal.
A 45 J J5
50
%5 ?::: ;Jc izo �:.::::: : I 1, 10
I
0 • • • • 01 1.1 2-0 u u u I • 1Y,m/L 1--- 7157 -+- 71!15 -B-1.M -715 1
Figure 6. Effect of Polymers and Alum (45mg/L) on Turbidity Removal. 68
A 60 m •o�--=------,
JD
10
5 • • • • u u u z J 4 lYm/L
- 15 -1. -M-7153 1 1-7157 7
Figure 7. Effect of Polymers and Alum (60mg/L) on Turbidity Removal.
A100 m 40-.------,
JD �--
10
5
o---�-�--• •- ----•-- • u u u z J 4 lY,m/L
1 - 15 -134 -M-7153 1 1-7 57 7
Figure 8. Effect of Polymers and Alum (100mg/L) on Turbidity Removal. 69
A150 q 4D
ss
JO
:::, 25
gzo I 15 1D
5 • • • • u 1 u u J 1Y,/L
1---7157 -+-71U -B-IJA -M-715.l I
Figure 9. Effect of Polymers and Alum (150mg/L) on Turbidity Removal.
,,�------�
4D
J5
15
1D
5 0+--�-�--�-�-�-�--�-�-�----1 IO 1JO 11D 200 2D ID 100 1AD 110 AUlil,mg/L
Figure 10. Turbidity of Feed Water Treated With Alum. 70
Phase II: Optimization of Addition Conditions of Coagulant 7157
Orthogonal Experiment
A 2-level, L8, orthogonal array experiment was designed to do the analysis of effects of temperature (T), polymer dose (P), and alum dose (A) and their interaction on dependent variable turbidity (Turb.) of treated feed water ( Table 15, page 46 ).
The levels of the various variables are presented in Table 30 below.
Tables 31 and 32 present the turbidity results and the corresponding ANOV A results. Results indicate that the percent contributionof temperature, polymer dose and alum to total sum of squares are respectively 38.9%, 58.6%, and 0.32%. Their factor effect values are -1.1, -1.35, -0.1. This indicates that temperature and coagulant dose had a significant effect on turbidity. Also, the polymer dose was more significant than temperature. Alum had a very small contribution percentage and factor effect values, which confirms the results presented in Figure 10. Therefore, alum had no significant effect on turbidity either in combination with coagulant 7157 or by itself. In addition, the small contribution percentage values of interaction of T*P, P*A, and T*P*A indicate that the interaction of these factors had no significant effects on turbidity.
Effects of Temperature and Coagulant 7157 Dose on Turbidity
For this phase of experiments, temperature was maintained at 7 different levels
(18 - 40°C) and the coagulant addition was maintained at 9 different levels (0.2 - 1.5 mL/L) (Table 16 on page 48). Thus a set of 63 (7x9) experiments were carried out. 71
Table 30
Variables and Their Levels
Variables Levels -1 +1
Temperature°C (T) 20 32
Polymer 7157 Dose mL/L (P) 0.4 1.0
Alum mg/L (A) 15 60
Table 31
Effect of Coagulant at Different Temperature and Alum Dosage Levels
Trial Factor and Factor Level Turbidity No. T P A TP TA PA TPA NTU
1 -1 -1 -1 +1 +1 +1 -1 3.6 2 +1 -1 -1 -1 -1 +1 +1 2.2 3 -1 +1 -1 -1 +1 -1 +1 1.9 +1 +1 -1 +1 -1 -1 -1 1.1 -1 -1 +1 +1 -1 -1 +1 3.4 +1 -1 +1 -1 +1 -1 -1 2.1 -1 +1 +1 -1 -1 +1 -1 1.9 +1 +1 +1 +1 +1 +1 +1 1.0
Note: TP: interaction of T and P. TA: interaction of T and A. PA: interaction of P and A. TPA: interaction of T, P and A. 72
Table 32
The ANOVA Table for Turbidity
Analysis of Variance for Turb.
Source DF Seq SS Adj SS Adj MS Contribution% T 1 2.420 2.420 2.420 38.91 1 3.645 3.645 3.645 58.60 A 1 0.020 0.020 0.020 0.32 T*P 1 0.125 0.125 0.125 2.01 T*A 1 0 0 0 0 P*A 1 0.005 0.005 0.005 0.08 T*P*A 1 0.005 0.005 0.005 0.08 Error 0 0 0 0 Total 7 6.22000 100
Source Factor Effect
T(Temp.) -1.1 P(Polymer) -1.35 A(Alum) -0.1
Figures 11 and 12 give the effect of coagulant 7157 dose on turbidity at constant temperatures. Results indicate that in the range of 0-1.0 mL/L, turbidity reduced rapidly with increase of coagulant dose, but increasing the coagulant dose further from 1.0 to 1.5 mL/L no longer reduced turbidity significantly. So 1.0 mL/L of dose was used as an optimum dosage level. Figures 13 and 14 give the effect of temperature on turbidity at constant coagulant dosage levels. Results indicate that turbidity was reduced with the increase of temperature.
In order to avoid the problems caused by adding too much coagulant in RO 73
operation, a relatively high temperature was selected. Hence, coagulant dose of 1.0 mL/L, and a temperature of 32°C were determined as the optimal addition conditions that could reduce turbidity to 1 NTU.
From Figures 11 to 14, it can be concluded that coagulant dose reduced turbidity more significantly than temperature. This conclusion is consistent with the results obtained from orthogonal experiments.
The above coagulant is an aqueous solution of aluminum hydroxy chloride and amine polymer (polyquatemary amine chloride). This is a low-molecular-weight, cationic coagulant. The product usually is used in the following applications: (a) lime softening, (b) oily waste water clarification, (c) industrial raw water clarification, and
(d) primary and secondary waste water clarification. This coagulant offers the following benefits: (a) eliminates the need for alum or other inorganic coagulants; (b) is effective at cold temperature; (c) has little effect on water pH and reduces or eliminates the need for pH adjustment; (d) is effective over a broad pH range; (e) forms a large, rapid setting floe; (f) reduces sludge volume; and (g) is effective on both low and high turbidity.
Reverse Osmosis Treatment
In the preliminary operating factor screening study of phase I, four operating factors, temperature, operating pressure, feed IDS concentration, and feed pH were studied as independent variables. The purpose of the preliminary factor screeningwas to determine which factors had significant effects on the two dependent variables 74
Ttu R 18-32 ·c 11
1D • g • � . z
0-' 1.2 0. O.I o.a POL lri./LYIIR
-M-21"C,a·c ....-+-urc J2'C -e-z,·c 1--- I
Figure 11. Effect of Coagulant 7157 on Turbidity at Constant Temperature.
Tt Ranee28- ° C 11
10 • a •
z
0 0 0. o.a 1.2 OJ! 1.4 o.a FY r/L 1---a·c - u·c - Jrc - ,o·c I
Figure 12. Effect of Coagulant 7157 on Turbidity at Constant Temperature. 75
Polymer 0.2--0.BmL/L 11�------�
1D
2
04----�----�---��---�---� 115 a0 mffRAl\llE• C
--- 0.2 rn/1* -- 0.5 llf/l -S- 0.4 �I -M- D.I rn/1 D.I �I
Figure 13. Effect of Temperature on Turbidity at Constant Polymer Level.
,-.------,P' 0.8-1.5m
5
aft. ffll./L -- 1.0 nL/1.. -e-1.z * I -M- 1.4 ffll./L 1..5 nL/1.. 1---0..■
Figure 14. Effect of Temperature on Turbidity at Constant Polymer Level. 76 solute rejection% (R%) and flux. Statistical methods of orthogonal array experiments and regression analysis were used to treat the data from RO study.
Method I: Two-Level, L16 Orthogonal Experiments
Table 33 gives the results of R% and flux for experimental design given in tables 20-21 (pages 54,55). The four sets of 16 data points each in table 33 were used as input data to generate ANOVA tables 34-37.
Effects of Factors pH. Temperature. Pressure, and Feed Concentration on Flux for SW Membrane
Table 34 gives the results of analysis of variance (ANOVA) and means for flux with membrane SW. Results indicate that factors T, P have high contribution values of 32.8% and 58.1 %. The next largest contributing factor was C with 3.8%.
The three factors also had large factor effect absolute values. They were -5.17, 15.2,
20.22 respectively for factors C, T, P. The values indicate that the flux increased with decreasing concentration and increasing temperature and pressure. pH had a very a small contribution percentage (0.0071 %), so this factor has no significant effect on flux. In addition, the factor interaction T*P had a contribution value of 4.53%. It indicates that this interaction also affected the flux to some extent.
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for BW Membrane
Table 35 gives the results of analysis of variance (ANOV A) and means for 77
Table 33
2 Level, 4 Factor, 16 L Experiment Array With R% and Flux Results for SW and BW Membranes
Factor and Factor Level Test Results No. pH C T P R% F,GFD
SW BW SW BW
1 -1 -1 -1 -1 98.4 97.9 14.5 13.7 2 -1 -1 -1 +1 99.0 98.0 30.0 26.0 3 -1 -1 +1 -1 98.5 97.5 25.7 24.0 4 -1 -1 +1 +1 99.2 97.9 52.8 46.3 5 -1 +1 -1 -1 98.7 97.2 11.5 10.3 6 -1 +1 -1 +1 98.8 97.5 25.0 202 7 -1 +1 +1 -1 98.5 97.0 19.3 17.8 8 -1 +1 +1 +1 98.7 97.2 44.6 35.1 9 +1 -1 -1 -1 98.8 97.8 13.8 13.4 10 +1 -1 -1 +1 99.0 98.0 29.1 25.6 11 +1 -1 +1 -1 98.7 97.6 25.1 245 12 +1 -1 +1 +1 98.7 97.9 52.2 45.8 13 +1 +1 -1 -1 98.8 97.6 11.9 10.9 14 +1 +1 -1 +1 99.0 97.7 25.9 20.7 15 +1 +1 +1 -1 98.6 97.3 19.8 175 16 +1 +1 +1 +1 98.8 97.1 43.8 35.7
Not: C=Feed TDS concentration, mg/L; T=temperature,°C; P=pressure, psi; R %=percent rejection of conductivity in rejects stream; F=permeate flux,GFD. flux with membrane BW. Results indicate that factors C, T, P had large contribution
% values. They were 8.49 %, 36.46 % and 49.42% respectively. The three factors also had large factor effect absolute values. They were -6.39, 13.24, 15.41 respectively for factors C, T, P. The values indicate that the flux increased with decreasing 78 concentration and increasing temperature and pressure. pH had a negligible contribution percent value (0.00156%). In addition, the factor interaction T*P had a contribution percent value of 3.96%. It indicates that this interaction also affected the flux to some extent.
Table 34
ANOV A Results and Means for Flux With Membrane SW
Factor Levels Values pH 2 -1 +1 C 2 -1 +1 T 2 -1 +1 p 2 -1 +1
Analysis of Variance for Flux
Source DF Seq SS Adj SS Adj MS Contrib % pH 1 0.20 0.20 0.20 0.0071% C 1 107.12 107.12 107.12 3.8% T 1 924.16 924.16 924.16 32.8% p 1 1636.20 1636.20 1636.2 58.1% pH*C 1 0.90 0.90 0.9 * pH*T 1 0.09 0.09 0.09 * pH*P 1 0.06 0.06 0.06 * C*T 1 14.44 14.44 14.44 * C*P 1 4.20 4.2 4.2 * T*P 1 127.69 127.69 127.69 4.53% pH*C*T 1 0.25 0.25 0.25 * pH*C*P 1 0.02 0.02 0.02 * pH*T*P 1 0.16 0.16 0.16 * C*T*P 1 0.16 0.16 0.16 * pH*C*T*P 1 0.25 0.25 0.25 * Error 0 0.00 0.00 0.00 * Total 15 2815.92 79
Table 34--Continued
Means for Flux
Factor Level Mean Factor Effect pH -1 27.92 -0.22 +1 27.70 C -1 30.40 -5.17 +1 25.23 T -1 20.21 15.2 +1 35.41 -1 17.70 20.22 +1 37.92 T*P -1 24.99 5.65 +1 30.64
Comparing the results of membranes SW and BW, it can be seen that SW membrane had a bigger pressure contribution value (58.1% ) than BW membrane
(49.42%). This means that pressure affected the flux relatively more significantly for
SW membrane than BW membrane. The BW membrane has a slightly larger temperature contribution value (36.46%) than SW membrane (32.80% ). The larger contribution value of factor C for BW membrane (8.49%) than for SW membrane
(3.80%) means that feed concentration had a more significant effect on flux for BW membrane than for SW membrane. For SW membrane, the order of factor effects was pressure > temperature > interaction of temperature and pressure > feedconcentration.
For B W membrane, the order of factor effects was pressure > temperature > feed concentration > interaction of temperature and pressure. For both SW and BW 80 membranes, pressure and temperature had much more significant effect on flux than feed concentration and interaction of temperature and pressure.
Table 35
ANOV A Results and Means for Flux With Membrane BW
Factor Levels Values pH 2 -1 +1 C 2 -1 +1 T 2 -1 +1 p 2 -1 +1
Analysis of Variance for Flux
Source DF Seq SS Adj SS Adj MS Contrib % pH 1 0.03 0.03 0.03 0.00156% C 1 163.2 163.2 163.2 8.49% T 1 700.93 700.93 700.93 36.46% p 1 950.18 950.18 950.18 49.42% pH*C 1 0.28 0.28 0.28 * pH*T 1 0 0 0 * pH*P 1 0.01 0.01 0.01 * C*T 1 20.03 20.03 20.03 * C*P 1 10.40 10.40 10.40 * T*P 1 76.13 76.13 76.13 3.96% pH*C*T 1 0.14 0.14 0.14 * pH*C*P 1 0.23 0.23 0.23 * pH*T*P 1 0 0 0 * C*T*P 1 0.68 0.68 0.68 * pH*C*T*P 1 0.23 0.23 0.23 * Error 0 0.00 0.00 0.00 * Total 15 1922.44 81
Table 35--Continued
Means for Flux
Factor Level Mean Factor Effect pH -1 24.17 0.09 +1 24.26 C -1 27.41 -6.39 +1 21.02 T -1 17.60 13.24 +1 30.84 -1 16.51 15.41 +1 31.92 T*P -1 22.04 4.36 +1 26.40
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R% for SW Membrane
Table 36 gives the results of analysis of variance (ANOV A) and means for R % with membrane SW. Results indicate that Total SS had a small value 0.68 and factors pH, C, T, P had very small effect (absolute) values. They were, respectively, 0.08,
0.05, -0.1, 0.28. So, the four factors had no significant effect on R%.
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R% for BW Membrane
Table 37 gives the results of analysis of variance (ANOVA) and means for R % with membrane BW. Results indicate that Total SS had a small value 1.67. The factors pH, C, T, P had very small effect (absolute) values. They were, respectively, 82 0.09, -0.51, -0.27, 0.17. So, the four factors had no significant effects on R%.
Table 36
ANOVA Results and Means for R % With SW Membrane
Factor Levels Values pH 2 -1 +1 C 2 -1 +1 T 2 -1 +1 p 2 -1 +1
Analysis of Variance for R %
Source OF Seq SS Adj SS Adj MS pH 1 0.0225 0.0225 0.0225 C 1 0.01 0.01 0.01 T 1 0.04 0.04 0.04 p 1 0.302499 0.302499 0.302499 pH*C 1 0.01 0.01 0.01 pH*T 1 0.04 0.04 0.04 pH*P 1 0.0625 0.0625 0.0625 C*T 1 0.022499 0.022499 0.022499 C*P 1 0.039999 0.039999 0.039999 T*P 1 0 0 0 pH*C*T 1 0.0225 0.0225 0.0225 pH*C*P 1 0.09 0.09 0.09 pH*T*P 1 0.009999 0.009999 0.009999 C*T*P 1 0.0025 0.0025 0.0025 pH*C*T*P 1 0.0025 0.0025 0.0025 Error 0 0 0 0 Total 15 0.677499 83
Table 36--Continued
Means for R%
Factor Level Mean Factor Effect
pH -1 98.72 0.08 +1 98.80
C -1 98.79 -0.05 +1 98.74
T -1 98.81 -0.1 +1 98.71
p -1 98.62 0.28 +1 98.90
Table 37
ANOVA Results and Means for R% With BW Membrane
Factor Levels Values pH 2 -1 +1 C 2 -1 +1 2 -1 +1 p 2 -1 +1
Analysis of Variance for R%
Source DF Seq SS Adj SS Adj MS pH 1 0.04 0.04 0.04 C 1 1.00 1.00 1.00 T 1 0.3025 0.3025 0.3025 p 1 0.1225 0.1225 0.1225 84
Table 37--Continued
Analysis of Variance for R%
Source DF Seq SS Adj SS Adj MS pH*C 1 0.04 0.04 0.04 pH*T 1 0.0025 0.0025 0.0025 pH*P 1 0.0225 0.0225 0.0225 C*T 1 0.0225 0.0225 0.0225 C*P 1 0.0225 0.0225 0.0225 T*P 1 0 0 0 pH*C*T 1 0.0225 0.0225 0.0225 pH*C*P 1 0.0225 0.0225 0.0225 pH*T*P 1 0.01 0.01 0.01 C*T*P 1 0.04 0.04 0.04 pH*C*T*P 1 0 0 0 Error 0 0 0 0 Total 15 1.67001
Means for R%
Factor Level Mean Factor Effect pH -1 97.53 0.09 +1 97.62
C -1 97.83 -0.51 +1 97.32
T -1 97.71 -0.27 +1 97.44 p -1 97.49 0.17 +1 97.66 85
Method II: Regression Analysis for Flux and R%
The results from all of the 89 sets of data collected with SW membranes were used in this analysis. 81 data points came from a set of 4 factors (pH, C, P, T) at 3 levels each. The additional 8 data points arose from the fact that at the operating conditions of pH 7.5, temperature 25°C, and IDSconcentration 4255 and 8240 mg/L, pressure was maintained at 4 additional levels of 500, 650, 700 and 750 psi.
Similarly for BW membranes, a set of 72 data points were used in this analysis. They arose mainly from 3 different levels of pH, feed IDS concentration and pressure, and 2 levels of temperature. Additional data points were contributed by additional pressure levels (Table 19 on page 53). The complete set of data points used in this analysis is presented in the Appendix F (Tables 51 and 52).
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for SW Membrane
Table 38 gives the results of the best subset regression for flux with SW membrane. R2 values of factors P, T and C were respectively 59.1, 32.8 and 3.8. This means that P, Tor C by themselves were not able to explain the observed variance.
The R2 value for the regression equation including three independent variables,
P, T and C was 96.2%. The value is the same as the R2 value for the regression equation including the four independent variables, P, T, C, and pH. This means that the factors pressure, temperature, and feed concentration were important factorswhich had a significant functional relationship with flux and that pH has no effect on flux. 86
From these results and the earlier results of ANOVA and factor effects (Table
34), factors T, P and C and the interaction P*T had significanteffects on flux. Hence, they were included in the regression equation.
Table 38
Results of Best Subset Regression for Flux With SW Membrane
Best Subset Regression for Flux
Variables R-sq Adj. R-sq pH C T p
1 59.1 58.6 X 1 32.8 32.0 X 1 3.8 2.7 X 2 91.9 91.7 X X 2 63.3 62.5 X X 2 59.1 58.2 X X 3 96.2 96.0 X X X 3 91.9 91.6 X X X 3 63.4 62.1 X X X 96.2 96.0 X X X X
Table 39 gives the results of regression analysis for flux with SW membrane.
The R2 value for the regression equation is 99.2%, which means a good correlation between independent variables and dependent variable.
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on Flux for BW Membrane
Table 40 gives the results of the best subset regression for flux with BW 87
membrane. R2 values of factors P, T and C are respectively 49.8, 38.2 and 8.0. It
means that P, T, C are significant effect factors and P and T had more significant
effects than C.
Table 39
Results of Regression Analysis for Flux With SW Membrane
The Regression Equation Is
Flux = 3.45 - 0.000856 C - 0.0843 T + 0.0152 P + 0.00142 T*P
Predictor Coeff. Stdev t-ratio p
Constant 3.448 1.360 2.53 0.013 C -0.000856 0.00004175 -20.51 0.000 T -0.08426 0.05122 -1.65 0.104 p 0.015184 0.002162 7.02 0.000 T*P 0.001419 0.00008237 17.23 0.000 s = 0.9884 R-sq = 99.2% R-sq(adj) = 99.1%
Analysis of Variance
Source DF ss MS F p
Regression 4 9610.5 2402.6 2459.27 0.000 Error 84 82.1 1.0 Total 88 9692.6
Source DF SEQ SS
C 1 369.2 T 1 3180.1 p 1 5771.0 T*P 1 290.1 88
Table 40
Results of Best Subset Regression forFlux With BW Membrane
Best Subset Regression for Flux
Variables R-sq Adj. R-sq pH C T p
1 49.8 49.1 X 1 38.2 37.3 X 1 8.0 6.7 X 2 88.0 87.7 X X 57.8 56.5 X X 2 49.8 48.3 X X 3 96.0 95.8 X X X 3 88.0 87.5 X X X 3 57.8 55.9 X X X 4 96.0 95.7 X X X X
The R2 value for the regression equation which included three independent variables, P, T and C was 96.0%. The value is the same as the R2 value for the regression equation including fourindependent variables, P, T, C, and pH. This means that pressure, temperature, feed concentration are important factors which have a significant functional relationship with flux and that pH had no significant effect on flux.
These results and the results of ANOVA and factoreffects in Table 35 indicate that the factorsT, P and C and the interaction of P*T have significanteffects on flux.
Hence, they are included in the regression equation.
Table 41 gives the results of regression analysis forflux with BW membrane. 89
The R2 value for the regression equation was 98.8%, which indicates good correlation between independent variables and dependent variable.
Table 41
Results of Regression Analysis for Flux With BW Membrane
The Regression Equation Is
Flux = 5.77 - 0.00153 C - 0.099 T + 0.0236 P + 0.00214 T*P
Predictor Coeff. Stdev t-ratio p
Constant 5.771 1.701 3.39 0.001 C -0.001529 0.00007393 -20.69 0.000 T -0.09903 0.06325 -1.57 0.122 p 0.023638 0.004646 5.09 0.000 T*P 0.0021417 0.000176 12.17 0.000 s = 1.056 R-sq = 98.8% R-sq(adj) = 98.7%
Analysis of Variance
Source OF ss MS F p
Regression 4 5904.0 1476.0 1323.97 0.000 Error 67 74.7 1.1 Total 71 5978.7
Source OF SEQ SS
C 1 477.0 T 1 2285.4 p 1 2976.5 T*P 1 165.1 90
Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R % for SW Membrane
Table 42 gives the results of the best subset regression for R % with SW membrane. R2 values of factors P, T and C were respectively 16.3, 5.9 and 5.1. The
R2 value for the regression equation including the three independent variables P, T and
C was 28.2% and the R2 value for the regression equation including the four independent variables P, T, C and pH was 28.4%. The low value means that the four factors, pressure, temperature, feedconcentration and pH were not sufficientto predict the change in R%. There was no significant functional relationships between the four factors and R%.
Table 42
Results of Best Subsets Regression for R% With SW Membrane
Best Subsets Regression for R%
Variables R-sq Adj. R-sq pH C T p
1 16.3 15.3 X 1 5.9 4.8 X 1 5.1 4.0 X 2 22.3 20.5 X X 2 22.2 20.3 X X 2 16.5 14.6 X X 28.2 25.7 X X 3 22.5 19.8 X X X 3 22.4 19.7 X X X 4 28.4 25.0 X X X X 91 Effects of Factors pH, Temperature, Pressure, and Feed Concentration on R % for BW Membrane
Table 43 gives the results of the best subset regression for R% with BW membrane. R2 values of factors C, T and P were respectively 37.2%, 9.1 % and 6.8%.
The R2 value for the regression equation including the three independent variables P,
T and C was 53.1% and the R2 value for regression equation including the four independent variables P, T, C and pH was 53.4%. The low value indicates that the four factors pressure, temperature, feed concentration and pH were not sufficient to predict the change in R %. There were no significant functional relationships between the four factors and R % .
Table 43
Results of Best Subset Regression forR % With BW Membrane
Best Subset Regression for R%
Variables R-sq Adj. R-sq pH C T p
1 37.2 36.3 X 1 9.1 7.8 X 1 6.8 5.5 X 2 46.4 44.8 X 2 44.0 42.4 X X 2 37.5 35.7 X X 3 53.1 51.1 X X X 3 46.6 44.2 X X X 3 44.2 41.8 X X X 4 53.4 50.6 X X X X 92 Summarizing the above results, we can conclude that:
1. The SW and BW membranes had very similar factor effect properties.
This is because the two types of membranes belong to the same type membrane series. They have the same membrane structure of thin film composite and the same membrane material of aromatic polyamide.
2. The main difference between the SW and BW membrane was that the
SW membrane had slightly higher solute rejection than the BW membrane. SW membrane permits a higher pressure operating range than BW membrane (Table 17).
3. The two statistical methods, orthogonal experiment and regression analysis led to similar results.
4. The operating factorstemperature, pH, feedconcentration and pressure had no significant effects on R% for the SW and BW membranes.
5. Pressure, temperature and feedconcentration had significant effects on flux. The pressure and temperature had much more significant effects than feed concentration and pH had no significant effecton flux. The interaction of pressure and temperature affected the flux to some extent. Similar results were obtained with SW and BW membranes.
According to the above results, the following area were suggested for furthur study: (a) how the factors temperature, pressure and feedconcentration affectthe flux; and (b) present the results obtained by the statistical methods through the regular graph expression methods. 93
Pressure Effect on Flux
Figures 15 and 16 present the effect of pressure on flux for membrane SW.
Figure 15-16 indicate that in the range of pressure 400-800 psi, flux increased with
the increase of pressure while T and C were kept constant. The relationships basically
were linear. The line of 35°C, TDS concentration 2159 mg/L had the fastest increase
with pressure and the line of 15°C, IDS concentration 10405 mg/L had the least
increase with pressure. This means that the higher temperature and lower concentration gave a faster increase of flux with pressure.
Figures 17, 18 and 19 present the effectof pressure on flux for membrane BW.
The figures indicate that in the range of pressure 250-500 psi, flux increased with the increase of pressure while T and C were kept constant. The functional relationship between pressure and flux was basically linear. The higher temperature and lower concentration gave a greater increase of flux with pressure. The change patterns of flux with pressure for both membranes were very similar.
Temperature Effect on Flux
Figures 20-25 give the relationships between flux and temperature for both membranes SW and BW. These figures show a slightly non-linear relationship
between temperature and flux. At higher pressure and higher temperature, flux increased more quickly with the increase of temperature. Comparing Figures 20-22 with Figures 23-25, the change patterns of flux with temperature for the both 94
SJ llmllnne, FffllpH 7.5 55� ------50 �
AO
25
20
15
10+--�--...--�--...-----...-----�-�-----1 350 550 750 150 4DO &00 7D0 100
--•11111 ,.JI.. 10·c -+-IDS 1111 ,.,JL.zo·c -B-TD1S11111 .,.../\.55 ·c -M-1111'255 25 ...A ·c • IDII UAO25 ,.II, ·c
Figure 15. Effect of Pressure on Flux for SW Membrane.
SJ llmllnne, FffllpH 7.5 DD�------�
A5
<40
15
10
I o+--�--...--�--...------�--�-�-----1 550 "50 550 750 150 <4DO &00 100 700 100 PIIESSIIIE,pal
---TIii 1110 11'111. 15 • C -+-TIii 1110 '"1/L.25 • C -9-TIIS IZIG55 '"1/L. • C -M-11ll10AD5 1111/l. 15 'C ....11ll10A05 1111/l.25 • C ...... TDSI55 DAGO1111/l. • C
Figure 16. Effect of Pressure on Flux for SW Membrane. 95
nm PD7.5, BJ Membrane 55
50
45
40
� 55
�!O C: 25
ZD
15
1D 260 '50 40 JGCI H f pl- - UI •C 1151 ...al\.-+- 25 •c 11l ...al\. -Jl •c T1! ...al\. - 15 •c 1 ...al\. . Z • C 1 ...al\.- J5 'C T21 ...al\.
Figure 17. Effect of Pressure on Flux for BW Membrane.
nm PD .5,7 BJ Membrane 4D
Jl
JO
25 �
�ZD
1!I
1D
260 iliO 40 JGCI H f pl- - Il 'C T 1015nL - Z! 'C T 1015,L - J 'C T 1015,L -15 •c 110010nL . 25 'C TI00IO"L -!5 °C TI00t0"L
Figure 18. Effect of Pressure on Flux for BW Membrane. 96
25 • C, PU 7.5, BJ Melnlnne 50
45
40
H
� so
.25
It 20
15
10
6
lliO '50 460 P PI -TDS Z 1541 IG/L -+- 1DS 42141111,/L -e- T1IS IHO t11,/l -T I5 ML * 1 1 DO ML
Figure 19. Effect of Pressure on Flux for BW Membrane.
SJ lrcmbrule, FeedTIE2159 mr/1. pH7.5
50
40
ZO
10
O+------t 10 ..--- ..--- ,-- JO.-- .-- 16 Z& TEMPERA'IIJIE °C
-40D pol -+-5D0 po1-e-100 pol -M- 70D pol * IDD pol
Figure 20. Effect of Temperature on Flux for SW Membrane. 97
S'f Membrane. feedmu o.womi/I. 7.5 pH ID
50
AD
H !f � JD
10 -
10 20 JO 15
.COD 1111 -+-50D .... -e-100 • 1--M-7DDp,I ...IOD 1111 I Figure 21. Effect of Temperature on Flux for SW Membrane.
1111�------,SJ MiembraDe,7.5 Feedpll
$0
AD
Z!I
20
15
10-1----�--�--�--�--�--�--�------1 Ill 211 10 10 ,0 40 'lnl'ERA'TIE 'C
---500 - 2151 .....,.L -+-100 PIL 11111 ,,./1..-8-7DD - Zl!II ...a/1. -M- 500 - A205 .....,.L ... IOO PIL 7DD'2115 ,,./1...... - A� ...a/1.
Figure 22. Effect of Temperature on Flux for SW Membrane. 98
FmI 2159 m.c,/L m 7.5, BJMm1brane ,,�------�
4D
n
2D
10+----�---�---�---�---�-----l 10 20 30 11i Iii
--- Z50 l'9 -+- SOO PII -B- 350I'll -M- 4110 ..* "50 1191---500 I'll
Figure 23. Effect of Temperature on Flux for BW Membrane.
Feed 8095 mr/1. PH7.5, BJ Memlnne 40�------,
H
so
15
1D
S+----�---�---�---�--��-----l 10 20 30 11i
--- 150 l'9 -+- SOD PII -B- 350I'll -M- 4110 ...... "50 1191 ---500 I'll
Figure 24. Effect of Temperature on Flux for BW Membrane. 99
PH 7.5, B1f Membrane 50
-45
-40
J5
� JO
f'... 20
15
ID •
11 H 10 10 JO TDl'ERATl.llE•c
1---- 215""8/L.!00Pll-+-Tlll 2.15I,.,L.A001111-B-1DSA1�IOOpol-H-1111-415�-Ml0PII I
Figure 25. Effect of Temperature on Flux for BW Membrane. membrane were very similar.
Effect of Feed TDS Concentration on Flux
Figures 26 and 27 give the effects of feed IDS concentration on flux for membrane SW and Figures 28 and 29 give the effects of feed TDS concentration for membrane BW. They indicate that flux decreased with the increase of feed TDS concentration. This result is consistent with the result obtained by the statistical methods.
The above three factor effect properties can be explained by the following basic reverse osmosis equation:
F=K(P-N) 100
Sf Kembrair,7.5, FeedpH 25 • C ID
50
AD • Cl )( .. e ii< ... .. - 50 13 61 61 .. I £1 I -B I 2D • • • • ID
A I I 10 6 7 11 I Fe«len--.>'TllS, mg,/1.
0 • -+-,oo 1111 -s-100 po1 40 I ----M-70D ...... IDOIIII 1
Figure 26. Effect of Feed IDS on Flux for SW Membrane.
Sf Kembrair,7.5, FeedpH 25 ° C
ss
JD
25
ID
5
o+----..-----..-----..-----..-----.------110 14 ' IZ Feeden--.> Tl)S, mg/L
Figure 27. Effect of Feed TDS on Flux for SW Membrane. 101
Condition; 25 ° C, pH 7.5, Bf Membrane 50�------�
A5
10
I ---- o--�--�-�--�-�--�-��-�----, I 10 ' I 11
--- HO 11111 -+- HD pol -B- l50"" -M- AIID pol '5D... pol -a- 500 p,I
Figure 28. Effect of Feed TDS on Flux for BW Membrane.
Condition;7.5, :pll 25 ·c. Bflll:mlnm: 50
'$
-40
55
H �
� ZS
. 20
15
1D
I
10 ' 1Z ,,
1--- 30D pol 5-+- 3 D pol -8-AOO "" I
Figure 29. Effect of Feed TDS on Flux for BW Membrane. 102
F = permeate flux, (gal/fr/day).
K = water permeability constant of membrane, (gal/ft2)/(day.psi).
P = feed pressure, (psi).
N = osmotic pressure of solute, (psi).
The equation indicates that flux F increases with feed pressure P. Because the
osmotic pressure of solute N increases with increase of feed concentration and the
increase of N results in the decrease of F, so fluxdecreases with the increase of feed
concentration. Temperature affects the permeability constant K. The increase of
temperature results in the increase of K value, which means that the water permeability of membranes increases. A larger K value at higher temperature gives
a higher flux.
Results of Other Factor Effects
Figure 30 gives the relationship between R% and temperature. Figure 30
indicates that in the range of 10-400C, R% basically remained constant, although a
slight decrease of R % occurred as temperature was increased.
Figures 31 and 32 give the relationship between R% and pressure. The figures
show that in the range of pressure 400-800 psi for SW membrane and in the range of
pressure 250-500 psi for BW membrane, R % was essentially constant, although a
slight upward trend was observed.
Figure 33 gives the relationship between R % and feed IDS concentration. 103
pl7.5, BJ Membrme 1DO " ta . - - 17 M
� w "15
� ... tJ
t2
11
10 10 20 ,0 15 Z5 TElof'ERA TUE•C
1---TDI21lillftWL. -+-TDI !OOp,11 2,51,.(L.AG0pol -9-lDI ..,� JOCIIIII -M-1111 Al5""8/\.A00p,II I
Figure 30. Effect of Temperature on Feed TDS R% for BW Membrane.
SW lrembnlne, 25 •c, pH 7.5 100 , " - - - _.--i]
17 �
1:14 F1 H
12
II
10 400 500 100 700 100 4li0 55D 150 750 PRESSUI[ pll
,--- 1DS 2151 "255 "'411'\.-+-IDS rro/1.-9-TDI 1240 1111/1. I
Figure 31. Effect of Pressure on R % for SW Membrane. 104
BJ llembmJe, 25 • C. pH7.5 100 " ti - -� - t7 - " !: � " tl
t:'L ,, to 4IO HO 400 5DO PRESSUIE pal
1--- T1JS 11,1 ...al\.4122 -+-TIii ...al\.-a- T1JS ....o...al\. I
Figure 32. Effect of Pressure on R% for BW Membrane.
350 JBi. 25 ·c p 7.5, Bl"llemlnm! 100 -·· - • - • • • - - 15
10
�H ! 10
1,
70 10 14 • I 12 rw>�/L
Figure 33. Effect of Feed TDS on R % for BW Membrane. 105
�1m216V m,/1.. 25 ·c ID - - •• - � 17
I ti" � " tl
t:L
ti
to u u 7A • 1 I t F'llDpH
1----- IGO .. -+-IW - 700 I'll -B-IW - !00 ...... ,_ AGO.. I
Figure 34. Effect of Feed pH on R% for Different Membranes and Pressures.
Figure 33 indicates R% stayed constant with changing concentration.
Figure 34 gives the relationship between R % and pH. The figure indicates that
R% remained constant in the range of pH 5-9.
Determination of Optimum Operation Condition
Comparison Between Membranes SW and BW
Summarizing the results discussed above, the following points can be made:
Membranes SW and BW have essentially similar factor effect properties. This is because they are the same type of membrane, aromatic polyamide, thin film composite membrane. This kind of membrane has many advantageous properties over the cellulose acetate membrane. The very stable response of solute R % to change in 106
pH, temperature, pressure and feed concentration is one of the important properties
for this type of membrane.
The main difference between SW and BW membrane was that SW membranes
had slightly higher solute rejection than BW membranes. Their IDS R % were,
respectively, about 98% and 97%. SW membranes permit a higher pressure operating
range than BW membranes. (SW membrane: 400-800 psi and BW membrane: 250-
500 psi). SW membranes are recommended for high feed concentrations.
Determination of Operating Pressure and Temperature
The basic strategy to determine the optimal operation condition is to achieve
as high a productivity (flux rate) as possible. In order to acquire a higher productivity,
the higher the flux, the better it is, as long as a rejection percent can be satisfactory
enough to provide for adequate product water quality.
The discussed results have indicated that R% reached a high and stable values
and the levels of the operational factors did not affect R%. So, R% does not need to
be considered in determining the optimal condition.
Two concerns form the basis for determining the optimal conditions. One is the effect of temperature and pressure on flux. The other is the operating
specifications of the membranes.
Because flux increased with increase of temperature and pressure, the higher the temperature and pressure chosen, the higher the flux that can be achieved. The highest flux for the SW membrane was 52.6 GFD at a temperature of 35°C, pressure 107
of 800 psi and feed concentration of 2159 mg/L. The highest flux for the BW
membrane was 50.7 GFD at a temperature of 35°C, pressure of 500 psi and feed concentration of 2159 mg/L.
However, the membrane manufacturer gave the followingmaximum permeate flux limits:
SW membrane: 22.3 GFD.
BW membrane: 27.0 GFD.
The maximum flux limits are an essential prerequisite and should not be exceeded if running for extended periods. The optimal conditions should be determined according to this maximum flux limit. Either pressure or temperature can be controlled to keep the flux at this maximum limit.
Because it is easier to control pressure than temperature, the temperature was controlled at 25°C initially. The proper pressure for the SW membrane can be determined according to Figure 26 or Figure 27 as follows: At 25°C, for a feed concentration < 8000 mg/L, a pressure of 500psi can be used to keep the flux around the flux upper limit of 22.3 GFD. For feed concentrations > 8000 mg/L, a pressure
of 600 psi can be used to keep the flux around the maximum upper limit. Thus, a pressure of 500 psi is correct for feed concentrations < 8000 mg/L and a pressure of
600 psi is correct for feed concentrations > 8000 mg/L.
The proper pressure for the BW membrane can be determined according to
Figure 28 or Figure 29 as follows: At 25°C, a pressure of 350 psi can be used to keep the flux aroundthe maximum upper limit of 27.0 GFD when feedIDS concentrations 108 are < 6000 mg/L and 400 psi is the correct pressure for feed IDS concentrations >
6000 mg/L.
Relationship Between Feed Recovery Percent and Flux, Permeate TDS Concentration, Feed IDS Concentration
Figures 35 and 36 give the relationships between the feed recovery percent and flux respectively for SW and BW membranes. The results indicate that the flux reduced slowly with increasing recovery percent, remaining basically linear until a recovery ratio of 60%, where the flux gradually decreased as recovery increased.
When recovery reached 80%, the flux was reduced sharply. The BW membrane had a more rapid decrease in flux than the SW membrane.
SI' llembnDe, 1mlpB7..5, 25 ° C
10
5
o+------1 2.0 «l 10 ID 1D ! I 70 ID F'EID RECOVERY,i:
Figure 35. Relationship Between Feed Recovery and Flux for SW Membrane. 109
25 • � p 7.5, 2159 mI m b 50
45
40 n
� H
5 f ... 2D
15
10 • 0 0 10 JO 5D 70 10 FEED IID0VERY lll: 1--- 3DD pol -+-35D ""' -e- -"" I
Figure 36. Relationship Between Feed Recovery and Flux for BW Membrane.
Figure 37 and Figure 38 give the relationships between feed recovery percent and permeate TDS concentrationrespectively for SW and BW membranes. The results indicate that permeate concentration increased non-linearly with the increase of recovery percent. The higher the recovery percent, the more rapidly the concentration increased. When recovery percent reached 80%, the permeate TDS concentration increased exponentially.
Figures 39 and 40 give the relationship between recovery percent and feed
TDS concentration respectively for SW and BW membranes. The results indicate that feed concentration increased non-linearly with the increase of recovery percent. The higher the recovery percent, the more rapidly the feed concentration increased. When recovery percent reached 80%., the feed TDS concentrationincreased exponentially. 110
P 7.5, 25 •c 500 P S M SD
250
2D )
�150 � i 1D
�
20 10 ,o
Figure 37. Relationship Between Feed Recovery and Permeate TDS for SW Membrane.
25 • r., 350 p p 7.5. B 1 400
.150
JOO .., }2/io
B2.00 j,,o
100
50
,o I 100 10 30 ,0 7D ID Fm> RECOYEIIY X
Figure 38. Relationship Between Feed Recovery and Permeate TDS for SW Membrane. 111
pH 7.5, 25°C, 500 lEi, SI Membrane 11000
uooo
12000
1DOOO )
� IGOO � - 1000
ZIICIO
10 30 50 70 10 rEID IEXMRY X
Figure 39. Relationship Between Feed Recovery and Feed TDS for SW Membrane.
B l 350 i 25 ° C p 7.5 14000
12000
10000
r 100D
1000 '
400D
2000
20 10 .JD
Figure 40. Relationship Between Feed Recovery and Feed TDS for B W Membrane. 112
Comparing the above three relationships, they have very similar change patterns of recovery percent with independent variables. This is because feed concentration built up non-linearly with recovery percent. The non-linear increase of feed concentration resulted in the non-linear increase of permeate concentration at the same time, since solute rejection percent (R % ) -remained constant. When feed concentration non-linearly increased rapidly, it resulted in the solute osmotic pressure increasing rapidly; hence, the flux decreased correspondingly. Therefore, the three factor effect relationships showed similar patterns.
Determination of Optimal Feed Recovery Percent
As discussed above, at a recovery ratio of 80%, flux decreased sharply and permeate concentration increased exponentially. This means that at 80% of recovery, productivity of reverse osmosis begins to decrease and product water quality becomes poor. So 80% of feed recovery is a point which can be used as a proper recovery ratio in determining the optimal recovery ratio.
Summary of Optimal Operating Condition
Summarizing the above discussion, the optimal conditions are: at 25°C, when feed IDS concentration is < 6000 mg/L, a BW membrane should be used at a pressure of 350 psi. When feed TDS concentration is > 6000 mg/L, the choice should be the SW membrane at a pressure of 500 - 600 psi. Feed water recovery percent is optimum around 80%. 113
Table 44 gives the operating results for the SW membrane under the conditions of pressure at 500 psi, temperature 25°C. Results indicate when 80% feed water was recovered, feed TDS was concentrated from 2159 mg/L to 10487 mg/L.
The final overall recovered permeate (at 80% of recovery ratio) had TDS concentration 80 mg/L. Flux varied over the range 24.3 - 17.8 GFD. The average flux was 21.05 GFD.
Table 44
Results of RO Performance forSW Membrane at Condition of 500 psi, 25°C
Overall Feed Feed TDS Recovered Permeate Recovery Concentration Permeate TDS Flux % mg/L mg/L GFD
0 2159 24.5 24.3 10 2394 42 24.1 20 2580 46 23.5 30 3064 47 23.5 40 3464 49 23.2 50 4263 55 22.1 60 5208 62 21.9 65 6052 63 21.3 70 7041 65 20.0 75 8323 71 19.6 80 10487 80 17.8 85 13810 85 14.9
Table 45 gives the operating results for the BW membrane under a pressure of 350 psi, a temperature of 25°C. Results indicate that when feed water was 114
recovered to 80%, feed IDS was concentrated from 2159 mg/L to 10237 mg/L. The
final overall recovered permeate (at 80% recovery ratio) had TDS 140 mg/L. Flux
varied over the range 26.5 - 15.4 GFD. The average flux was 20.95 GFD. Figure 41
summarizes the typical results obtained.
Table 45
Results of RO Performance for BW Membrane at Condition of 350 psi, 25°C
Overall Feed Feed TDS Recovered Permeate Recovery Concentration Permeate TDS Flux % mg/L mg/L GFD
0 2159 55 26.5 10 2290 79 25.9 20 2678 82 25.8 30 2947 89 25.4 40 3536 93 24.0 50 4118 102 23.5 60 5233 109 21.8 65 5855 117 20.5 70 6913 122 19.5 75 8148 132 17.8 80 10237 140 15.4 85 13420 152 11.6 115
Volume: 100 gallons Volume: 80 gallons Feed TDS: 2159 mg/L Permeate TDS: 80 mg/L Original Feed RO UNIT 1----- Permeate (Recovered Water)
Concentrated Feed Volume: 20 gallons Concentrated Feed TDS: 10487 _mg/L
Figure 41. Summary of Typical Results of Recovered Feed ( at 500 psi, 25°C, pH 7 .5 and SW Membrane ).
Discussion of Component Removal Efficiency
This section discusses each component percent removalratio by each treatment
stage. Tables 46 - 50 give the water analysis results for major components and their
removal percentage. The following conditions were used: Natural sedimentation for
24 hrs; clarification with coagulant 7157 at 32°C and 1 mL/L; RO SW membrane at
25°C and 500 psi; and RO BW membrane at 25°C, 350 psi.
TS, IDS, Conductivity, TSS, Turbidity
Tables 46 and 47 give the results of feed water analysis and removal
percentages of components TS, TDS, conductivity, TSS and turbidity. 116
Table 46
Water Analyses Before and After Various Treatments
Treatments TS, TDS, Conduc- TSS, Turbidity, tivity, mg/L mg/L uv/cm mg/L NTU
Original 4093 2120 1185 1973 3400 Effluent
Sedimenta- 2209 2120 1225 88.5 45 tion without Addition
Clarification 2168 2159 1330 8.5 1.0 with Coagulant
RO Treatment 24.5 24.5 11.97 0 0.08 Membrane SW
RO treatment 55.0 55.0 26.6 0 0.11 Membrane BW
Note: RO permeates were the initial samples without feed recovery.
The original effluent had total solids (TS) of 4093 mg/L which comprised IDS
2120 mg/L and TSS 1973 mg/L. TSS gave an extremely high turbidity of 3400 NTU.
Conductivity was 1185 uv/cm. After sedimentation without coagulant addition, 95.5% of TSS and 98.7% of turbidity were removed. Turbidity and TSS were reduced to 45
NTU and 88.5 mg/L, respectively. However, turbidity of the treated water was still much higher than the 1 NTU of maximum limit for RO input. 117
Table 47
Component Removal Percentage Before and After Various Treatments
Component Removal, %
Treatments TS, TDS, Conduc- TSS, Turbidity, tivity,
Sedimenta- 46.0 95.5 98.7 tion without Addition
Clarification 47.0 99.6 99.96 with Coagulant
RO Treatment 99.4 98.7 99.1 100 >99.99 Membrane SW
RO treatment 98.6 97.5 98.0 100 >99.99 Membrane BW
Note: RO permeates were the initial samples without feed recovery.
After clarificationwith coagulant 7157, turbidity of the feed water was reduced to about 1.0 NTU. At this point, turbidity, TSS and TS were removed respectively by 99.96% , 99.6% and 47.0%. TSS and TS were reduced respectively to 8.5 mg/L and 2168 mg/L. The natural sedimentation did not change the TDS, but the addition of coagulant increased TDS slightly from2120 mg/L to 2159 mg/L.Pretreatment also increased conductivity slightly from 1185 uv/cm to 1330 uv/cm. The cause of these results is that the addition of coagulant increased the dissolved materials and ions in 118 the feed water.
RO treatments showed a high TDS rejection percentage (removal percentage).
R% for the SW and BW membranes were respectively 98.9% and 97.5% and TDS of permeate were respectively reduced to 24.5 mg/L and 55.0 mg/L. At this point, turbidity and TSS of permeate were respectively 0.08-0.11 NTU and O mg/L. Their overall removal percentage were both about 100%.
The RO treatment also showed high reduction of conductivity of 99.1 % and
98.0 % respectively for the SW and BW membranes. The final conductivity of permeate was reduced to 11.97 uv/cm and 26.60 uv/cm respectively for the SW and
BW membranes. IDS and conductivity showed a very close solute rejection percentage (R % ). Conductivity is an assessment of total ionic concentration in an aqueous solution. Hence, conductivity can substitute the IDS in evaluating R %.
The very low levels contents of TS and IDS, and zero level of TSS indicate that the permeate was high quality water.
BOD,COD,TOC
Table 48 gives the results of analysis of BOD, COD and TOC and their removal percentage. Sedimentation without coagulant addition removed 5.8 % of
BOD, 29.4 % of COD and 25.0 % of TOC. The clarification with coagulant removed
26.2% of BOD, 39.2% of COD and 25.4 % of TOC. Thus, about one-fourth to one third of BOD, COD and TOC were removed by pretreatment. Also, most of BOD,
COD and TOC existed in the TDS. 119
Table 48
Results of Analysis of BOD, COD, TOC
Treatment BOD, COD, TOC,
mgOJL mgOifL · mg C/L Removal,% Removal,% Removal,%
Original 1431 4080 548 Effluent
Sedimen- 1349 5.76 2880 29.4 411 25.0 tation Without Addition
Clarifi- 1056 26.2 2480 39.2 409 25.4 cation with Coagulant
RO Treatment 35.7 97.5 88.0 97.8 0.0 100 Membrane SW
RO treatment 42.3 97.0 108 97.4 <1.0 >99.8 Membrane BW
RO treatment reduced BOD from 1056 mg/L to 35.7 mg/L and 42.3 mg/L respectively for the SW and BW membranes. The overall removal of BOD was 97.5
% and 97 .0 % respectively for the SW and BW membranes. RO treatment also showed a high rejection percentage for COD and TOC. COD was reduced from 4080 mg/L of effluent to 88 - 108 mg/L of permeate. The overall percent removal of COD was 97.8% and 97.4% respectively for the SW and BW membranes. TOC was 120 reduced from 548 mg/L to less than 1.0 mg/L (removal, > 99.8%).
Metal Elements
Tables 49 and 50 give the results of analysis of metal elements and their removal percentage. About 99% of the weight of total elements tested consisted of fourmajor metal elements, Ca, Na, Al and Mg (Table 49). Other metal elements, Fe,
Zn and Cu had very low levels of concentration. Cr and Pb were at extremely low concentration and Ni was not detected.
Table 49
The Results of Analysis of Major Metal Elements ( Ca, Mg, Na, Al and Zn )
Treatment Ca Mg Na Al Zn
Solute Concentration, mg/L
Original 298 14.4 125 18.3 0.573 Effluent
Sedimenta- 211 9.52 0.194 tion without Addition
Clarification 132 9.22 0.081 with Coagulant
RO Treatment 1.14 0.04 0.019 Membrane SW 121
Table 49--Continued
Treatment Ca Mg Na Al Zn
Solute Concentration, mg/L
RO treatment 1.46 0.06 2.39 ND* 0.043 Membrane BW
Solute Removal, %
Sedimenta- 29.2 33.9 66.4 tion without Addition
Clarification 55.7 36.0 86.0 with Coagulant
RO Treatment 99.6 99.7 96.7 Membrane SW
RO treatment 99.5 99.6 98.1 100 92.6 Membrane BW
Note: ND = not detectable.
The pretreatment showed a very high removal ratio of 86.0% for Zn. This indicates that most of Zn existed in the TSS. Ca also showed a high removal percentage of 55.7 % by pretreatment.
RO treatment gave high percent removal values for all the metal elements. The overall removal percentages forCa, Mg, Na, Al, and Fe were respectively 99.5-99.6%, 122
99.6-99.7%, 98.1 %, 100% and >99.0%. The contents of the metal elements in the permeates were very low (Ca: 1.14-1.46 mg/L, Mg: 0.04-0.06 mg/L, Na: 2.39 mg/L,
Al: 0 mg/L, Fe: <0.014 mg/L). Zn had an overall removal percent value of 92.6-
96.7%, which was slightly lower than other element but still high. Because Cr, Cu,
Pb already had very low concentrations in the feed, they were not detected in the RO permeate.
Table 50
The Results of Analysis of Minor Metal Elements ( Pb, Fe, Cr, Cu and Ni )
Treatment Pb Fe Cr Cu Ni
Solute Concentration, mg/L
Original <0.06 1.37 <0.05 0.052 ND Effluent
Sedimenta- ND ND <0.03 ND tion without Addition
Clarification ND ND <0.03 ND with Coagulant
RO Treatment ND ND <0.03 ND Membrane SW
RO treatment ND <0.014 ND <0.03 ND Membrane BW (removal >99.0%)
Note: ND = not detectable. 123
In summary, the overall treatment processes showed a very high removal efficiency for all the components and generated high quality water which had very low IDS and zero TSS. The product water should be reusable as high quality water in production. The RO process should serve to remove dissolved solids from waters which are in a closed-water loop. Dissolved solids -build-up in the water would be eliminated. CHAPTER VI
SUMMARY OF RESULTS
The reverse osmosis membrane process and chemical clarification were employed to treat deinking pulping effluent. The results of pretreatment experiments indicated that natural sedimentation and chemical clarification with ULTRION liquid cationic coagulant 7157 effectively removed TSS by 99.6% and turbidity by 99.9%.
The TSS of effluent was reduced from 1973 mg/L to 8.5 mg/L and turbidity of the effluent was reduced from 3400 NTU to 1 NTU. At temperature 32°C, an additional dose of 1.0 mL/L of coagulant 7157 reduced turbidity of feedwater to 1 NTU which was required for the subsequent RO process.
The factors of temperature and coagulant 7157 dose had significanteffects on turbidity. Increasing the coagulant dose in the range of O - 1.0 mL/L reduced turbidity significantly. Increasing temperature in the range of 18 to 40°C also reduced the turbidity.
Results of reverse osmosis operating experiments indicated that the pressure, temperature, and feed concentration had significant effects on permeate flux. In the range of 400 - 800 psi for the SW membrane and in the range of 250 - 500 psi for the BW membrane, the permeate flux increased with pressure linearly. At high temperature-and low concentration of feed-flux showed a faster increase of the flux
124 125 with pressure than at low temperature and high concentration of feed. Increasing the temperature increased the flux. At the high pressure and temperature, the effect of temperature was more significant. The flux decreased with the increase of the feed concentration.
The results of two-level L16 orthogonal experiments and regression analysis indicate that pressure and temperature had more significant effects on flux than feed concentration. The order of their effect extent was pressure > temperature > feed concentration. The factor interaction of pressure and temperature also showed a significant effect on flux. The feed pH factor had basically no effect on flux in the range of pH 5 - 9.
In the same range of pH, pressure, temperature and feed concentration as above, the factors of pressure, temperature, feed concentration and feed pH, showed no significant or no effects on solute rejection. This indicates that the thin film composite RO membrane had very stable property of solute rejection.
Membranes SW and BW had basically similar factor effects of properties on flux and R%. This is probably due to similar membrane structures of the thin film composites and the same membrane materials. The SW had slightly higher quantity solute R% than the BW membrane. The BW membrane had slightly higher quantity flux with the lower operating pressure range.
The regression models between the dependent variable flux and independent variables pressure, temperature, feed concentration, feed pH and the interaction of pressure and temperature gave high correlation coefficient values for the both 126 membranes. This indicates a good correlation between these independent variables and dependent variable. The regression models between dependent variable R % and independent variables pressure, temperature, feed concentration and feed pH for both the membranes gave very low correlation coefficient values, which indicates a poor functional relationship between these independent variables and the dependent variable.
The results of relationships between feed recovery percentage and permeate flux, permeate TDS concentration, feed TDS concentration indicate that flux reduced slowly with feed recovery increasing until a recovery of 60%; the decrease of flux gradually become faster thereafter. At a recovery beyond 80% the flux reduced sharply. The permeate concentration and feed concentration increased non-linearly with the increase of recovery. The higher the recovery percentage, the more rapidly the concentration increased. At recovery of great than 80 %, the feed and permeate concentration increased exponentially.
The results of RO operating of SW membrane under the conditions of pressure
500 psi and temperature 25°C indicate that when the feed recovery achieved 80%, the feed water TDS could be concentratedfrom 2160 mg/Lto 10500 mg/L. Flux was 24.3 and 17.8 GFD. The average flux was 21.05 GFD. The results of RO operating with the BW membrane under the conditions of pressure 350 psi and temperature 25°C indicate that when feed water was recovered to 80 %, feedTDS could be concentrated from 2160 mg/Lto 10200 mg/L.Flux was 26.5 and 15.4 GFD. The average flux was
20.95 GFD. 127
For the original feed of TDS concentration 2159 mg/L, the proper operating conditions were: (a) for the BW membrane, temperature: 25°C, pressure: 350-400 psi; and (b) for the SW membrane, temperature: 25°C, pressure: 500-600 psi. The proper feed recovery for both membranes was 80%.
The results of water analysis for the components in the effluent, feed water and permeate indicate that the whole treatment process had very high solute removal efficiency for all the components tested. TS was reduced by 99.4 % and 98.6 % respectively for the SW and BW membranes. TDS was reduced by 98.7 % and 97.5
% respectively for the SW and BW membranes. TSS and turbidity were reduced respectively by 100 % and >99.99 %. BOD was reduced by 97.0 % - 97.5 % and
COD reduced by 97.4 % - 97.8 %. TOC was reduced by over 99.8 %. Metal elements, Ca, Mg, Al, were reduced in excess of 99.0 %. Na and Fe were reduced in excess of 98.0 %. Zn was reduced by 92.6 to 96.7 %. The final RO permeate (product water) showed very low contents for all the components. The product water would be feasible to reuse as high quality production process water. CHAPTER VII
CONCLUSIONS
1. The application of reverse osmosis ih combination with pretreatment of chemical clarification with coagulant to treatthe deinking pulping effluent showed good utility and efficiency. The whole process showed a very high overall removal efficiency for TS, IDS, TSS, turbidity, BOD, COD, TOC and metal elements in effluent. The final RO permeate (product water) gave very low contents for all the components tested. The product water could be reused as high quality water in the production process.
2. The ULTRION liquid cationic coagulant under optimum addition conditions showed a very high removal efficiencyin decreasingthe turbidity and TSS.
The pretreated feed water achieved the requirement of turbidity tolerance limit of the
RO process.
3. Coagulant addition amount and temperature were significant factors.
Increasing the amount of coagulant and temperature reduced turbidity of the feed.
4. Pressure, temperature, and feedconcentration had significant effects on permeate flux in the reverse osmosis process. Pressure and temperature had more significant effects than feed concentration. Increasing pressure and temperature increased the permeate flux and increasing concentration decreased the flux.
128 129
5. The SW and BW membranes resulted in very consistent solute rejection
%, which was not affected significantly by pressure, temperature, feed concentration, and pH.
6. Eighty percent of the effluent could be recovered. At this recovery percentage, the IDS of the concentrated feed was five times higher than that of the original effluent and the volume of the concentrated feed was one fifth that of the original effluent. CHAPTER VIII
SUGGESTIONS FOR FURTHERSTUDY
1. This research indicates that the flux higher than maximum flux specification limit could be obtained at the higher pressure and higher temperature.
If the membrane elements can be run under the condition of the flux higher than the specification for long term, higher productivity can be obtained. Whether membrane elements can stand the higher flux for long-term running at the higher pressure and temperature condition should be ascertained in further studies.
2. The effect of the types of membrane element feed spacer on RO performance is suggested for further study. Elements with wider spacers may allow a higher TSS and turbidity of feed water.
3. A study should be made on the effect of velocity of feed water on the membrane surfaces of RO performance. The higher velocity of the feed water on the membrane surface may allow a higher TSS and turbidity.
4. Membranes SW and BW used in this research showed a very high solute rejection. The product water can be reused as high quality water. In the practical production, it may be not always necessary to produce such high quality water. So, RO membranes with lower solute rejection of 85 - 90 % should be investigated. Usually, RO membranes with lower rejection have a higher flux and
130 131 lower pressure operating range which may give a higher productivity with lower energy consumption.
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36. Applegate, L. E. "Membrane Separation Process", Chemical Engineering. 91(6):74(1984).
37. Bansale, I. K., " How to Purify Effluents, Recover By-products with Reverse Osmosis" Pulp & Paper 49(5):118 (1975).
38. Gaddis, J. L., Fong, D. S., Tay, C. H., Urbantas, R. G., Lindgren,D., "New Ultrafiltration Membrane System for Spent Sulfite Liquor Recovery" Tappi Journal, 7 4(9): 121 (1991).
39. Simpson, M. J., "Treatment of Pulp and Paper Bleach Effluent By Reverse Osmosis" Desalination, 47(5): 327 (1983).
40. Dorica, J., Wong, A., Gomer, B. C., "Complete Effluent Recycling in the 135
Bleach Plant With Ultrafiltration and Reverse Osmosis", Tappi Journal, 69(5):122 (1986).
41. Ferguson, L. D., "Deinking Chemistry Part 1" Tappi Journal, 75(7):75 (1992).
42. Ferguson, L. D., "Deinking Chemistry Part 2" Tappi Journal, 75(8):49 (1992).
43. Buisson, H., Zaidi, A., Koski, K., "Bench-Scale Evaluation of Ultrafiltration and N anofiltration Membranes for the Treatment of A Kraft - Caustic Extraction Stage Effluent From A Softwood Line" 1992 Environmental Conference,Tappi Press, p.585(1992).
44. Muratore, E. etc, "Bleach Plant EffluentTreatment by Ultrafiltration - Mill Site Experimentation", Pulp and Paper Canada, 84(6):79(1983).
45. Ferguson, L. D., "Deinking Chemistry Part 2" Tappi Journal. 75(8):49(1992).
46. Ross, P. J., Taguchi Techniques For Quality Engineering. McGraw-Hill Book Company, New York (1988).
47. Greenberg, A. E., Trussell, R. R., Clesceri, L.S., Standard Methods for the Examination of Water and Wastewater, American Public Health Association, Washington, D.C. 18th Edition, (1992). APPENDICES
136 Appendix A
Flow Diagram of Treatment System of Deinking Effluent
137 138
a ._ I
!--! ·u•
t..... ! • ------r-711
:i--l!£1 UI - ! I
1111 I Iii 11 I 11 ii .- II r--- 11 D .1.. I •5u '"IU I I I ·111
11 t
!!t! ·111
a, II ! ii ll .. •i' a I •I C I . . . I Appendix B
Principles of Osmosis and Reverse Osmosis
139 140
P>n
Solvent' Solvent solutt Solutt
P� solvent Purt so lve�t II, Reven� osmosis•
Appendix B
Principles of Osmosis and Reverse Osmosis [23] Appendix C
Membrane Separation and Filtration Spectrum
141 Ionic Range Molecular Macro Molecula Micro Particle Range Range Range
0.01 0.01 0.1 1.0 10 10 (micrometer) I I I I I REVERSE UL TRAFIL TRATION PARTICLE FILTRATION OSMOSIS I I NANOFI- MICROFILTRATION TRATION I I
APPENDIXC
Membrane Separation and FiltrationSpectrum[lO] Appendix D Concentration Polarization
143 144
Cf
J
Cp X
Membrane
er: solute concentrations in the bulk reed solution · Cw: concentration ot the membrane surface Cp: concentration in the permeate solution
Appendix D
Concentration Polarization [6] Appendix E
Definitions of Solute Rejection Percentage, Permeate Flux, and Feed Recovery Percentage
145 146 Definitions of solute rejection percentage, permeate flux, and feed recovery percentage.
1. Solute Rejection Percentage = R %:
R%= Cf -CPx100% cf
Cr: solute concentration in feed water. CP: solute concentration in permeate water.
2. Membrane Permeate Flux:
F(GFD) =-p m 2 xt
F: membrane permeate flux. P: permeate volume ( gallon ).
2 m : membrane area ( square feet ). t: time ( day ).
GFD = gallon/feet2 day
3. Feed Recovery Percentage ( Recovery % ):
Recovery%= P x100% V
P: total permeate water volume. V: total feed water volume.
Appendix E Appendix F
Supporting Data
147 148 Table 51
Data Points for Regression Analysis for SW Membrane
R% Row pH C T p F
1 7.5 2159 15 400 98.9 14.2 2 7.5 2159 15 600 99.0 21.9 3 7.5 2159 15 800 99.1 29.5 4 7.5 2159 15 400 98.6 18.5 5 7.5 2159 25 600 99.1 28.8 6 7.5 2159 25 800 99.0 39.7 7 7.5 2159 35 400 98.6 25.4 8 7.5 2159 35 600 99.1 39.0 9 7.5 2159 35 800 99.0 52.6 10 7.5 4255 15 400 98.6 13.1 11 7.5 4255 15 600 99.1 20.6 12 7.5 4255 15 800 99.2 28.0 13 7.5 4255 25 400 98.9 17.6 14 7.5 4255 25 500 99.0 22.6 15 7.5 4255 25 600 98.5 27.6 16 7.5 4255 25 650 99.0 29.5 17 7.5 4255 25 700 98.8 33.0 18 7.5 4255 25 750 99.1 34.7 19 7.5 4255 25 800 98.9 38.1 20 7.5 4255 35 400 98.4 23.2 21 7.5 4255 35 600 99.0 36.4 22 7.5 4255 35 800 98.7 49.5 23 5.0 4255 35 400 98.6 23.5 24 5.0 4255 35 600 99.0 36.0 25 5.0 4255 35 800 99.2 49.0 26 5.0 4255 15 400 99.0 13.5 27 5.0 4255 15 600 98.9 20.9 28 5.0 4255 15 800 99.3 28.1 29 5.0 4255 25 400 98.5 17.8 30 5.0 4255 25 600 99.0 27.2 31 5.0 4255 25 800 99.2 38.4 32 9.0 4255 15 400 98.8 13.8 33 9.0 4255 15 600 99.0 20.2 34 9.0 4255 15 800 98.5 28.5 149 Table 51--Continued
Row pH C T p R% F
35 9.0 4255 25 400 99.0 17.3 36 9.0 4255 25 600 99.1 28.0 37 9.0 4255 25 800 99.0 38.8 38 9.0 4255 35 400 98.6 22.7 39 9.0 4255 35 600 98.7 36.7 40 9.0 4255 35 800 99.0 49.6 41 5.0 2159 15 400 98.4 14.5 42 5.0 2159 15 600 99.1 21.5 43 5.0 2159 15 800 99.0 30.0 44 5.0 2159 25 400 98.9 18.7 45 5.0 2159 25 600 99.2 28.5 46 5.0 2159 25 800 99.0 39.6 47 5.0 2159 35 400 98.5 25.7 48 5.0 2159 35 600 99.1 39.1 49 5.0 2159 35 800 99.2 52.8 50 9.0 2159 35 400 98.7 25.1 51 9.0 2159 35 600 98.8 38.5 52 9.0 2159 35 800 98.7 52.2 53 9.0 2159 15 400 98.8 13.8 54 9.0 2159 15 600 98.9 21.1 55 9.0 2159 15 800 99.0 29.1 56 9.0 2159 25 400 99.0 18.1 57 9.0 2159 25 600 99.1 28.2 58 9.0 2159 25 800 98.9 39.3 59 7.5 8240 25 400 98.5 14.4 60 7.5 8240 25 500 98.6 19.7 61 7.5 8240 25 600 98.6 24.0 62 7.5 8240 25 650 98.7 26.8 63 7.5 8240 25 700 98.8 28.5 64 7.5 8240 25 750 98.6 31.5 65 7.5 8240 25 800 99.0 33.8 66 7.5 8240 15 400 98.8 11.2 67 7.5 8240 15 600 99.1 18.4 68 7.5 8240 15 800 98.9 25.4 69 7.5 8240 35 400 98.5 19.5 70 7.5 8240 35 600 98.6 31.9 150 Table 51--Continued
Row pH C T p R% F
71 7.5 8240 35 800 98.7 44.2 72 5.0 8240 35 400 98.5 19.3 73 5.0 8240 35 600 98.6 31.5 74 5.0 8240 35 800 98.7 44.6 75 5.0 8240 15 400 98.7 11.5 76 5.0 8240 15 600 98.7 18.1 77 5.0 8240 15 800 98.8 25.0 78 5.0 8240 25 400 98.6 14.0 79 5.0 8240 25 600 98.7 24.5 80 5.0 8240 25 800 98.7 33.5 81 9.0 8240 25 400 98.6 14.7 82 9.0 8240 25 600 98.6 23.8 83 9.0 8240 25 800 98.8 33.2 84 9.0 8240 35 400 98.6 19.8 85 9.0 8240 35 600 98.7 31.2 86 9.0 8240 35 800 98.8 43.9 87 9.0 8240 15 400 98.8 11.9 88 9.0 8240 15 600 98.9 18.8 89 9.0 8240 15 800 99.0 25.9
Note: C, Feed IDS mg/L; T, temperature °C; P, pressure psi; R%, solute rejection percentage; F, permeate flux GFD. 151 Table 52
Data Points fr Regression Analysis fr BW Membrane
Row pH C T p R% F
1 7.5 2159 15 250 98.1 13.1 2 7.5 2159 15 350 97.3 19.7 3 7.5 2159 15 450 98.0 25.8 4 7.5 2159 25 250 97.8 18.2 5 7.5 2159 25 300 98.0 21.9 6 7.5 2159 25 350 98.0 26.5 7 7.5 2159 25 400 98.1 30.6 8 7.5 2159 25 450 98.2 34.3 9 7.5 2159 25 500 98.1 38.9 10 11 7.5 2159 35 250 97.7 24.2 7.5 2159 35 350 97.7 34.6 12 7.5 2159 35 450 97.9 46.0 13 5.0 2159 35 250 97.5 24.0 14 5.0 2159 35 350 98.2 34.3 15 5.0 2159 35 450 97.9 46.3 16 9.0 2159 15 250 97.8 13.4 17 9.0 2159 15 350 97.9 20.0 18 9.0 2159 15 450 98.0 25.6 19 9.0 2159 35 250 97.6 24.5 20 9.0 2159 35 350 97.6 34.1 21 9.0 2159 35 450 97.9 45.8 22 7.5 4122 25 250 97.8 15.3 23 7.5 4122 25 300 97.8 19.6 24 7.5 4122 25 350 97.9 23.5 25 7.5 4122 25 400 97.6 27.3 26 7.5 4122 25 450 98.0 31.7 27 7.5 4122 25 500 98.2 34.9 28 7.5 4122 35 250 97.8 20.6 29 7.5 4122 35 350 97.8 30.7 30 7.5 4122 35 450 98.0 40.0 31 5.0 2159 15 250 97.9 13.7 32 5.0 2159 15 350 98.1 19.8 33 5.0 2159 15 450 98.0 26.0 34 7.5 4122 15 250 98.0 11.9 152 Table 52--Continued
Row pH C T p R% F
35 7.5 4122 15 350 98.1 17.3 36 7.5 4122 15 450- 98.1 23.4 37 5.0 4122 15 250 98.1 11.7 38 5.0 4122 15 350 98.0 17.2 39 5.0 4122 15 450 98.2 23.6 40 5.0 4122 35 250 97.6 20.4 41 5.0 4122 35 350 97.8 30.2 42 5.0 4122 35 450 98.0 40.2 43 9.0 4122 35 250 98.0 20.9 44 9.0 4122 35 350 97.8 30.5 45 9.0 4122 35 450 98.1 41.0 46 9.0 4122 15 250 98.1 12.2 47 9.0 4122 15 350 98.0 17.6 48 9.0 4122 15 450 98.2 23.0 49 7.5 6280 25 250 97.6 13.2 50 7.5 6280 25 300 97.3 16.4 51 7.5 6280 25 350 97.5 20.7 52 7.5 6280 25 400 97.8 23.5 53 7.5 6280 25 450 97.8 27.4 54 7.5 6280 25 500 98.0 30.9 55 7.5 6280 35 250 96.9 17.0 56 7.5 6280 35 350 96.9 26.3 57 7.5 6280 35 450 97.1 35.3 58 7.5 6280 15 250 97.2 10.5 59 7.5 6280 15 350 97.3 15.4 60 7.5 6280 15 450 97.5 20.8 61 5.0 6280 15 250 97.2 10.3 62 5.0 6280 15 350 97.5 15.3 63 5.0 6280 15 450 97.5 20.2 64 5.0 6280 35 250 97.0 17.8 65 5.0 6280 35 350 96.9 26.8 66 5.0 6280 35 450 97.2 35.1 67 9.0 6280 35 250 97.3 17.5 68 9.0 6280 35 350 97.0 26.4 69 9.0 6280 35 450 97.1 35.7 70 9.0 6280 15 250 97.6 10.9 153
Table 52--Continued
Row pH C T p R% F
71 \ 9.0 6280 15 350 97.7 15.8 72 9.0 6280 15 450· 97.7 20.7 154
Table 53
Effects of Temperature and Coagulant 7157 Dose on the Turbidity
Temperature °C Coagulant 18 20 25 28 32 37 40 Dose(mL/L)
Turbidity (NTIJ)
0.2 10.4 9.8 8.8 8.2 8.2 7.6 7.2 0.3 6.0 4.7 4.0 3.2 3.0 2.7 2.6 0.4 4.5 3.8 3.0 2.3 2.3 1.8 1.6 0.6 3.6 3.2 2.1 1.9 1.5 1.4 1.3 0.8 3.0 2.4 1.9 1.4 1.2 1.2 1.0 1.0 2.4 2.0 1.5 1.2 1.0 0.9 0.9 1.2 2.3 1.8 1.4 1.2 1.0 1.1 0.7 1.4 2.0 1.7 1.3 1.3 1.0 0.8 1.0 1.5 2.0 1.6 1.3 1.1 1.0 0.9 0.8
Table 54
Turbidity Results of Feed Water Treated with Seven Coagulants and Flocculents with Alum (150mg/L Alum)
Polymer Coagulants and Flocculents Dose mL/L 7157 7155 634 7653 7655 625 89PD078
Turbidity (NTIJ)
1 1.7 23 40 25 >45 >45 >45 2 1.5 21 30 23 >45 >45 >45 3 1.2 19 29 24 >45 >45 >45 4 1.1 17 32 24 >45 >45 >45 5 1.2 19 31 22 >45 >45 >45 155
Table 55
Conductivity Data of Permeate and Feed for SW Membrane
Temperature°C Feed Feed Feed Pressure 15 25 35 IDS pH Conducti- psi mg/L vity Permeate Conductivity uv/cm uv/cm
400 14.63 14.6 18.62
2159 7.5 1330 600 13.3 17.32 11.97
800 11.95 13.3 13.3
400 32.27 25.36 36.88 500 23.05 600 20.75 34.58 23.01 4255 7.5 2305 650 23.07 700 27.66 750 20.74 800 18.44 25.32 29.97
400 50.76 63.45 63.45 500 59.22 600 38.07 59.61 59.22 8240 7.5 4230 650 54.99 700 50.76 750 59.45 800 46.53 42.3 54.79
400 22.18 15.25 20.79 2159 5.0 1386 600 12.48 11.09 12.56 800 13.86 13.95 11.21 156
Table 55--Continued
Temperature°C Feed Feed Feed Pressure 15 25 35 TDS pH Conducti- psi mg/L vity Permeate Conductivity uv/cm uv/cm
400 16.5 14.18 18.27 2159 9.0 1406 600 15.46 12.65 16.87 800 14.06 15.26 18.4
400 23.62 35.16 32.77 4255 5.0 2341 600 25.75 23.75 23.41 800 16.39 18.91 18.73
400 28.56 23.64 33.32 4255 9.0 2380 600 23.8 21.42 30.94 800 35.7 24.01 23.41
400 55.32 59.64 63.6 8240 5.0 4240 600 56.01 56.05 59.36 800 50.88 55.87 55.12
400 52.62 61.75 61.42 8240 9.0 4411 600 48.52 61.5 57.34 800 44.17 52.93 52.76 157
Table 56
Conductivity Data of Permeate and Feed for BW Membrane
Temperature°C Feed Feed Feed Pressure 15 25 35 TDS pH Conducti psi mg/L vity Permeate Conductivity uv/cm uv/cm
250 25.27 29.26 31.59 300 26.6 2159 7.5 1330 350 35.91 26.4 31.06 400 25.3 450 26.6 24.94 27.93 500 25.35
250 44.1 49.28 49.3 300 49.67 4122 7.5 2240 350 42.58 47.04 49.32 400 53.76 450 42.44 44.8 44.7 500 40.32
250 92.51 79.1 102.61 300 88.95 6280 7.5 3295 350 89.71 82.35 103.01 400 72.49 450 82.34 72.01 96.12 500 65.9
250 28.28 34.15 2159 5.0 1347 350 25.29 24.29 450 26.94 28.50 158
Table 56--Continued
Temperature°C Feed Feed Feed Pressure 15 25 35 TDS pH Conducti psi mg/L vity Permeate Conductivity uv/cm uv/cm
250 31.17 34.0 2159 9.0 1417 350 29.76 34.17 450 28.34 29.59
250 43.96 55.56 4122 5.0 2315 350 46.31 50.93 450 41.6 46.3
250 46.8 49.32 4122 9.0 2466 350 49.22 54.25 450 44.4 46.85
250 94.24 100.44 6280 5.0 3348 350 84.41 103.79 450 83.93 93.74
250 83.5 93.93 6280 9.0 3479 350 80.02 104.37 450 80.1 100.8 159
Table 57
Results of TDS and R% of TDS for SW Membrane at Feed pH 7.5, Temperature 25 °C,
Feed Pressure Permeate TDS R% TDS psi TDS mg/L mg/L
400 30 98.6 500 30 98.6 600 32 98.5 2159 650 28 98.7 700 24 98.9 750 21.5 99.0 800 24 98.9
400 59 98.6 500 59 98.6 600 63 98.5 4255 650 55 98.7 700 46 98.9 750 42 99.0 800 46 98.9
400 157 98.1 500 148 98.2 600 156.5 98.1 8240 650 140 98.3 700 140 98.3 750 157 98.1 800 132 98.4 160
Table 58
Results of IDS and R% of IDS for BW Membrane at Feed pH 7.5, Temperature 25 °C
Feed Pressure Permeate TDS R% TDS psi TDS mg/L mg/L
250 58 97.3 300 58 97.3 2159 350 54 97.5 400 48 97.8 450 45 97.9 500 46 97.9
250 111 97.3 300 107 97.4 4122 350 104 97.4 400 99 97.6 450 95 97.7 500 93 97.8
250 182 97.1 300 194 96.9 6280 350 183 97.1 400 169 97.3 450 170 97.3 500 163 97.4 161
Table 59
Relationship between Feed Recovery % and Permeate IDS
Feed Pem1eate TDS Permeate TDS Recovery% for SW Membrane forBW Membrane mg/L mg/L
10 43 81 20 50 88 30 54 101 40 60 114 50 74 137 60 91 163 65 101 185 70 113 208 75 134 244 80 172 289 85 248 360
Note: operating conditions for SW membrane, 500 psi, 25°C, pH 7.5 and for BW membrane, 350 psi, 25°C, pH 7.5. 162
Table 60
Results of Effect of Temperature on R% for SW Membrane
Feed Feed Pressure Temp. Permeate Conductivity TDS Conductivity psi oc Conductivity R% mg/L uv/cm uv/cm
10 10.64 99.2 15 11.99 99.1 20 11.95 99.1 2159 1330 600 25 13.3 99.0 30 14.63 98.9 35 13.4 99.0 40 15.96 98.8
10 10.68 99.2 15 10.75 99.2 2159 1330 700 20 13.46 99.0 25 13.39 99.0 30 15.72 98.8 35 15.84 98.8 40 17.29 98.7
10 20.66 99.1 15 32.14 98.6 20 22.96 99.0 4205 2296 600 25 27.55 98.8 30 29.85 98.7 35 34.44 98.5 40 32.42 98.6 163
Table 60--Continued
Feed Feed Pressure Temp. Permeate Conductivity TDS Conductivity psi oc Conductivity R% mg/L uv/cm uv/cm
10 22.79 99.0 15 22.72 99.0 20 20.72 99.1 4205 2296 700 25 25.26 98.9 30 29.85 98.7 35 27.63 98.8 40 32.35 98.6
Note: Feed pH 7.5. 164
Table 61
Results of Effect of Temperature on R% for BW Membrane
Feed Pressure Temp. Permeate TDS IDS psi oc IDS R% mg/L mg/L
10 41 98.1 15 43 98.0 20 48 97.8 2159 300 25 51 97.6 30 52 97.6 35 54 97.5 40 56 97.4
10 41 98.1 15 41 98.1 20 43.5 98.0 2159 400 25 47 97.8 30 52 97.6 35 50 97.7 40 53 97.5
10 87 97.9 15 91 97.8 20 96 97.7 4155 300 25 95 97.7 30 104 97.5 35 108 97.4 40 108 97.4 165
Table 61--Continued
Feed Pressure Temp. Permeate TDS TDS psi oc TDS R% mg/L mg/L
10 91 97.8 15 92 97.8 20 103 97.5 4155 400 25 108 97.4 30 108 97.4 35 104 97.5 40 112 97.3 166
Table 62
Results of Effect of Feed pH on TDS R%
Membrane Feed Pressure Feed pH Permeate TDS Type IDS psi TDS mg/L R% mg/L
2159 7.3 28 98.7 2092 6.2 23 98.7 SW 2112 600 4.9 30 98.6 2123 8.1 30 98.6 2163 9.0 26 98.8
2159 7.3 30 98.6 2092 6.2 31 98.5 SW 2112 700 4.9 25 98.8 2123 8.1 25 98.8 2163 9.0 28 98.7
5.0 54 97.5 6.1 43 98.0 BW 2159 300 7.2 47 97.8 8.0 52 97.6 9.1 49 97.7
5.0 56 97.4 6.1 52 97.6 BW 2159 400 7.2 45 97.9 8.0 51 97.6 9.1 48 97.8
Note: Temperature, 25°C. 167
Table 63
Flux Data for SW Membrane
Temperature °C Feed Feed Pressure 15 25 35 TDS pH psi mg/L Flux, GFD
400 14.2 18.5 25.4 500 17.5 24.3 31.8 600 21.9 28.8 39.0 2159 7.5 650 23.2 32.0 42.4 700 25.2 34.0 45.2 750 27.6 37.1 49.2 800 29.5 39.7 52.6
400 13.1 17.6 23.2 500 22.5 600 20.6 27.6 36.4 4255 7.5 650 29.5 700 33.0 750 34.7 800 28.0 38.1 49.5
400 12.1 15.8 21.3 500 15.4 21.1 27.2 600 19.4 25.9 34.1 6290 7.5 650 700 23.1 30.3 40.4 750 800 26.2 35.6 46.3 168 Table 63--Continued
Temperature °C Feed Feed Pressure 15 25 35 TDS pH psi mg/L Flux, GFD
400 11.2 14.4 19.5 500 14.3 19.7 25.2 600 18.4 24.0 31.9 8240 7.5 650 26.8 700 21.4 28.5 37.6 750 31.5 800 25.4 33.8 44.2
400 10.2 14.0 17.6 500 14.2 18.2 24.3 10405 7.5 600 17.2 22.8 29.7 700 20.7 27.9 35.6 800 24.6 31.9 42.0
400 14.5 18.7 25.7 2159 5.0 600 21.5 28.5 39.1 800 30.0 39.6 52.8
400 13.8 18.1 25.1 2159 9.0 600 21.1 28.2 38.5 800 29.1 39.3 52.2
400 13.5 17.8 23.5 4255 5.0 600 20.9 27 .2 36.0 800 28.1 38.4 49.0
400 13.8 17.3 22.7 4255 9.0 600 20.2 28.0 36.7 800 28.5 38.8 49.6 169
Table 63--Continued
Temperature °C Feed Feed Pressure 15 25 35 IDS pH psi mg/L Flux, GFD
400 11.5 14.0 19.3 8240 5.0 600 18.1 24.5 31.5 800 25.0 33.5 44.6
400 11.9 14.7 19.8 8240 9.0 600 18.8 23.8 31.2 800 25.9 33.2 43.9 170
Table 64
Flux Data for BW Membrane
Temperature °C Feed Feed Pressure 15 25 35 TDS pH psi mg/L Flux, GFD
250 13.1 18.2 24.2 300 16.6 21.9 29.7 2159 7.5 350 19.7 26.5 34.6 400 22.3 30.6 40.6 450 25.8 34.3 46.0 500 28.9 38.9 50.7
250 11.9 15.3 20.6 300 19.6 4122 7.5 350 17.3 23.5 30.7 400 27.3 450 23.4 31.7 40.0 500 34.9
250 11.7 15.6 19.8 300 14.6 18.9 25.4 4285 7.5 350 17.0 23.3 30.4 400 20.4 27.1 34.7 450 23.2 30.3 40.2 500 25.6 34.6 45.1
250 10.5 13.2 17.0 300 16.4 6280 7.5 350 15.4 20.7 26.3 400 23.5 450 20.8 27.4 35.3 500 30.9 171
Table 64--Continued
Temperature °C Feed Feed Pressure 15 25 35 TDS pH psi mg/L Flux, GFD
250 9.8 12.2 16.7 300 12.0 16.4 21.3 6530 7.5 350 15.2 20.0 25.4 400 17.8 23.0 30.4 450 20.0 27.0 34.9 500 23.1 30.4 38.7
250 8.5 11.6 14.3 300 11.5 14.5 18.7 8095 7.5 350 13.6 18.5 23.7 400 16.6 21.2 27.2 450 18.7 24.5 31.0 500 21.2 27.2 35.6
250 7.5 9.1 11.6 300 9.5 12.8 15.7 10090 7.5 350 11.8 15.4 19.2 400 14.6 18.5 23.6 450 16.6 22.0 27.5 500 18.9 24.6 30.7 172
Table 65
Relationship Between Feed Recovery% and Flux for SW Membrane
Pressure, psi Recovery% Feed TDS 500 600 rng/L Flux, GFD
0 2159 24.3 29.4 10 2395 24.1 29.2 20 2580 23.5 28.7 30 3064 23.5 28.6 40 3464 23.2 28.3 50 4263 22.1 27.2 60 5208 21.9 26.8 65 6052 21.3 26.1 70 7041 20.0 24.9 75 8323 19.6 24.3 80 10487 17.8 22.5 85 13810 14.9 19.4
Note: operating condition, 25 °C, pH 7.5. 173
Table 66
Relationship Between Feed Recovery% and Flux for BW Membrane
Pressure, psi Recovery% Feed TDS 300 350 400 mg/L Flux, GFD
0 2159 22.4 26.5 30.6 10 2290 21.9 25.9 30.5 20 2678 21.8 25.8 29.5 30 2947 21.4 25.4 29.4 40 3536 20.0 24.0 28.3 50 4118 19.7 23.5 26.8 60 5233 18.1 21.8 26.0 65 5855 17.5 20.5 24.5 70 6913 16.0 19.5 22.5 75 8148 14.5 17.8 21.1 80 10237 11.8 15.4 18.3 85 13420 9.0 11.6 14.1
Note: Feed Temperature 25 °C; pH 7.5. 174
Table 67
Results of Effect of Temperature on Flux for SW Membrane
Pressure, psi Feed TDS Temperature 500 600 700 mg/L oc · Flux, GFD
10 14.9 18.0 21.2 15 17.5 21.9 25.7 20 21.2 25.1 29.5 2159 25 24.3 29.4 34.5 30 27.5 34.0 40.3 35 32.2 38.5 45.5 40 36.8 44.6 52.3
10 14.5 17.1 20.2 15 16.9 20.1 24.4 20 19.8 24.2 28.0 4205 25 23.1 27.7 32.6 30 26.1 31.4 37.6 35 29.9 36.5 42.7 40 34.5 41.6 49.1
Note: Feed pH 7 .5. 175
Table 68
Results of Effect of Temperature on Flux for BW Membrane
Pressure, psi Feed TDS Temperature 300 400 mg/L oc Flux, GFD
10 13.7 18.8 15 16.1 22.8 20 19.5 26.2 2159 25 22.4 30.6 30 25.3 35.6 35 29.7 40.1 40 33.9 46.3
10 12.2 17.1 15 14.4 20.5 20 17.6 23.4 4155 25 19.6 27.3 30 22.5 31.3 35 25.1 35.7 40 29.1 40.3
Note: Feed pH 7.5. BIBLIOGRAPHY
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