FilmTec Technical Manual - Chester Paul Company

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With a recovery of, for example, 75% (Y = 0.75), the ionic strength of the concentrate becomes⎛ 1 ⎞I c = 0.0444⎜⎟⎝ 1−0.75 ⎠= 0.178Ic2.4.2 Calcium Carbonate Scale Prevention2.4.2.1 Brackish WaterFor brackish waters with TDS < 10,000 mg/L in the concentrate stream, the Langelier Saturation Index (LSI) is used toexpress the scaling potential for calcium carbonate /6/.The following data are needed to calculate the LSI of the concentrate stream (LSI c ):Ca f = Calcium concentration in feed as CaCO 3 , mg/LTDS f = Concentration of total dissolved solids in the feed, mg/LAlk f = Alkalinity in feed as CaCO 3 , mg/LpH f = pH of the feed solutionT = Temperature of the feed solutionY = Recovery of the reverse osmosis system, expressed as a decimalCalculations1. Calculate the calcium concentration in the concentrate stream, Ca c , as CaCO 3 in mg/L:⎛ 1 ⎞Ca c = Caf⎜ ⎟Eq. 6⎝ 1−Y⎠2. Calculate the total dissolved solids in the concentrate stream, TDS c in mg/L:⎛ 1 ⎞TDSc= TDSf ⎜ ⎟Eq. 7⎝1−Y ⎠3. Calculate the alkalinity in the concentrate stream, Alk c , as CaCO 3 in mg/L:⎛ 1 ⎞Alk c = Alkf⎜ ⎟Eq. 8⎝ 1−Y⎠4. Calculate the free carbon dioxide content (C) in the concentrate stream by assuming that the CO 2 concentration in theconcentrate is equal to the CO 2 concentration in the feed: C c = C f . The concentration of free carbon dioxide in the feedsolution is obtained from Figure 2.2 as a function of the alkalinity and the pH of the feed solution.5. Calculate the pH of the concentrate stream (pH c ) using the ratio of alkalinity Alk c to free CO 2 in the concentrate,Figure 2.2.6. From Figure 2.3 obtain: pCa as a function of Ca c , pAlk as a function of Alk c , “C” as a function of TDS c and temperature(temperature of the concentrate is assumed equal to temperature of the feed solution).7. Calculate pH at which the concentrate stream is saturated with CaCO 3 (pH s ) as follows:pHs= pCa + pAlk+"C"Eq. 98. Calculate the Langelier Saturation Index of the concentrate (LSI c ) as follows:LSI = pH − pHEq. 10ccsAdjustments of LSI cIn most natural waters, LSI c would be positive without pretreatment. To control CaCO 3 scaling, LSI c has to be adjusted to anegative value, except if adding a scale inhibitor (Section 2.3.3) or preventive cleaning (Section 2.3.7) is applied.Page 30 of 180 ® Trademark of The Dow Chemical <strong>Company</strong> ("Dow") or an affiliated company of Dow Form No. 609-00071
The conditions for CaCO 3 scale control are:LSI c < 0 when no antiscalant is addedLSI c ≤1 when 20 mg/L sodium hexametaphosphate is in the concentrate streamLSI c > 1 possible with polymeric organic scale inhibitors. For the maximum LSI c and required dosages, please referto the scale inhibitor manufacturer’s literature.If LSI c is not within the above conditions, adjustments can be made by one of the following means. A new LSI c can then becalculated:• The recovery, Y, can be lowered and LSI c can be calculated as above by substituting a new value for the recovery.• Decreasing the calcium concentration in the feed solution by means of sodium cycle ion exchange. This will increase thepCa and will therefore decrease the LSI c . Softening will not change the alkalinity or pH of the feed solution and the slightchange in TDS f may be considered negligible. After softening, the LSI c can be calculated as above using the lower valuefor calcium concentration.• Adding acid (HCl, CO 2 , H 2 SO 4 , etc.) to the feed solution changes the Alk f , C f , and pH. The slight change in TDS f canusually be neglected. Acid addition will decrease the LSI c ; however, since many variables change with acidification, trialand error computations are required to determine the amount of acid needed to obtain the desired LSI c . The number oftrial and error computations required to determine the amount of acid needed can be reduced greatly by using the pH scalculated in Eq. 9. Since pH c will usually be 0.5 units higher than the pH f , the first computation can be made with anacidified feed solution that is 0.5 units lower than the pH s .For an assumed pH (pH acid ), obtained from addition of acid to the feed solution, obtain the ratio of Alk acid /C acid fromFigure 2.3. From this ratio, Alk f , and C f , calculate the mg/L of acid used (x). For example, for H 2 SO 4 addition (100%):Alk Alkf−1.02xacid= Eq. 11C C + 0.90xacidfCalculate the total alkalinity of the acidified feed water (Alk acid ) and the CO 2 content in the acidified feed water (C acid ) asfollows:Alk acid= Alkf−1.02xEq. 12C acid= Cf+ 0. 90xEq. 13Using Alk acid and C acid for the new pH, calculate the LSI c .If HCl (100%) is used for acidification, Eq. 11 is:Alk Alkf−1.37yacid= Eq. 14C C + 1.21yacidwhere:y = HCl (100%), mg/LfReverse Osmosis and Nanofiltration in OperationOnce a reverse osmosis or nanofiltration system is operating, the Langelier Saturation Index can be directly calculated fromthe analysis of Alk c , Ca c , TDS c , and pH c of the concentrate stream and compared with the projected LSI c .Use of ComputersThe LSI c and the acid dosage required to adjust a certain LSI c can be determined using a personal computer and theFILMTEC Reverse Osmosis System Analysis (ROSA) computer program. The ROSA computer program can bedownloaded here, www.dow.com/liquidseps/design/rosa.htm.Page 31 of 180 ® Trademark of The Dow Chemical <strong>Company</strong> ("Dow") or an affiliated company of Dow Form No. 609-00071
Page 1 and 2: DowWater SolutionsFILMTEC Reverse O
Page 3: 2.6 Biological Fouling Prevention .
Page 7 and 8: 1. Basics of Reverse Osmosis and Na
Page 9 and 10: Nanofiltration (NF)Nanofiltration r
Page 11 and 12: How to Use Reverse Osmosis and Nano
Page 13 and 14: 1.4 Membrane DescriptionThe FILMTEC
Page 15 and 16: Membrane systems are typically desi
Page 17 and 18: 1.8 Element CharacteristicsFILMTEC
Page 19 and 20: 2. Water Chemistry and Pretreatment
Page 21 and 22: SeawaterSeawater with TDS of 35,000
Page 23 and 24: Table 2.5 Water analysis for RO/NFS
Page 25 and 26: Table 2.7 Solubility products of sp
Page 27 and 28: In this process, only Ca 2+ , Ba 2+
Page 29: For the concentration ranges presen
Page 33 and 34: Figure 2.3 Langelier saturation ind
Page 35 and 36: These computations have been descri
Page 37 and 38: Figure 2.5 “K” versus ionic str
Page 39 and 40: Figure 2.6 Ksp for CaSO 4 versus io
Page 41 and 42: 2.4.6 Calcium Fluoride Scale Preven
Page 43 and 44: Figure 2.8 K sp for SrSO 4 versus i
Page 45 and 46: 2.4.7 Silica Scale PreventionDissol
Page 47 and 48: Table 2.10 Solubility of SiO 2 vers
Page 49 and 50: 2.4.8 Calcium Phosphate Scale Preve
Page 51 and 52: Table 2.9 Various fouling indicesIn
Page 53 and 54: Frequent shutdowns and start-ups sh
Page 55 and 56: If the differential pressure across
Page 57 and 58: 1. Intake (surface) or well, before
Page 59 and 60: or combined residual chlorine (CRC)
Page 61 and 62: 2.6.5 DBNPADBNPA (2,2, dibromo-3-ni
Page 63 and 64: 2.6.11 Use of Fouling Resistant Mem
Page 65 and 66: 2.11 Treatment of Feedwater Contain
Page 67 and 68: 2.13 Summary of Pretreatment Option
Page 69 and 70: 26. Handbook of Industrial Membrane
Page 71 and 72: Table 3.1 System design information
Page 73 and 74: 3.2 Batch vs. Continuous ProcessAn
Page 75 and 76: 3.4 Single-Stage SystemIn a single-
Page 77 and 78: The apparent salt passage of the sy
Page 79 and 80: Instead of having a separate high-p
Page 81 and 82:
3.9.1 Membrane System Design Guidel
Page 83 and 84:
In Table 3.6, the small commercial
Page 85 and 86:
Table 3.8 Number of stages of a sea
Page 87 and 88:
3.11 System Performance Projection3
Page 89 and 90:
3.11.2 Design Equations and Paramet
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Table 3.10 Design equations for pro
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3.11.3 Comparing Actual Performance
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The high-pressure concentrate is fe
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If the product water from an RO sys
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Besides the above recommendations,
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4. Loading of Pressure VesselsThis
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The process of shimming is performe
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4.5.2 Summary of Large Element Inte
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5. System Operation5.1 Introduction
Page 109 and 110:
5.2.3 Start-Up SequenceProper start
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5.2.4 Membrane Start-Up Performance
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5.5.3 SeawaterIn principle, the ope
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Table 5.1 Reverse osmosis operating
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A. Normalized Permeate FlowQS=ΔPsP
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For the operating conditions we hav
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4. During recirculation of cleaning
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2. The cleaning pump should be size
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6.7 Effect of pH on Foulant Removal
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Cleaning ProcedureThere are seven s
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If the organic fouling is the resul
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There are two factors that greatly
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7. Handling, Preservation and Stora
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7.4 Preservation of RO and NF Syste
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If the normalized actual performanc
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8.3.3 Localization of High Solute P
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Figure 8.2 Permeate probing apparat
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8.4.5 Performance TestThe standard
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8.5.1.1 Low Flow and Normal Solute
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. Metal Oxide FoulingMetal oxide fo
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. Organic FoulingThe adsorption of
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8.5.3 High Pressure DropHigh differ
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In case of fullfit or heat sanitiza
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Breakpoint chlorinationBreak tankBr
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FeedThe input solution to a treatme
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Milligram per litre (mg/L)Mixed-bed
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SBS Sodium bisulfite, NaHSO 3.Scale
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9.2 Specific Conductance of Sodium
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Figure 9.1 Conductivity of ionic so
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9.6 Temperature Correction FactorTa
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9.9 Osmotic Pressure of Sodium Chlo
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Details - TestEquipment andSpecific
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satisfactory for such a determinati
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case for almost all tested biocides
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9.12 Key Word IndexAbrasion - 150 B
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Positive displacement pump - 95 Shu
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FilmTec Technical Manual - Chester Paul Company

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