This paper was presented at AMTA and the IDA. It shows that allowing calcium phosphate scale to form will result in silica scaling. It also compares the performance of different antiscalants in control of calcium phosphate.

1. Mo Malki American Water Chemicals, Inc. (AWC) A RELATIONSHIP BETWEEN CALCIUM PHOSPHATE AND SILICA FOULING IN WASTEWATER RO SYSTEMS

5. Background – Membrane Autopsy - SEM

6. Background – Membrane Autopsy – SEM

7. Background – Membrane Autopsy - EDS

10. HIGH SILICA, NO PHOSPHATE, NO ANTISCALANT Water chemistry of high silica case, recovery=68%, Temp=25°C Measured turbidity same that of deionized water as upon mixing anion and cation solutions - this indicates no crystal nucleation Feed Reject Calcium 10.91 28.12 Magnesium 1.50 3.87 Bicarbonate 9.60 30.00 Orthophosphate 0.00 0.00 Silica 93.37 291.78 Iron 0.05 0.16 Aluminum 0.10 0.31 pH 7.1 7.4

11. HIGH SILICA, NO PHOSPHATE, NO ANTISCALANT 30 minute hold time prior to filtering in order to ensure sufficient time for silica polymerization Element Wt % At % Si K 4.48 8.54 Fe K 95.52 91.46

12. HIGH SILICA, NO PHOSPHATE, NO ANTISCALANT Reactive Silica was Measured Before and After Filtration using UV/VIS Spectrometer It was therefore established that even when silica was ~300 ppm, no silica polymerization occurred in the absence of scale formation. 0 min 30 min Filtrate Silica 291 291 291 pH 7.38 7.41 7.41

13. WASTEWATER PLANT FEEDWATER ANALYSIS (PPM) Raw Feed Reject@85% recovery Ca 80.70 80.70 538.00 Mg 25.20 25.20 168.00 Na 256.45 256.45 1709.67 K 18.80 18.80 125.33 Fe 0.12 0.12 0.80 Mn 0.05 0.05 0.33 Al 0.006 0.006 0.04 Cl 252.00 252.00 1680.00 SO4 233.00 316.81 2112.07 HCO3 408.70 302.15 2014.33 PO4 4.35 4.35 29.00 SiO2 22.20 22.20 148.00 pH 7.80 7.00 7.50

14. WASTEWATER RO FEED, NO IRON Feed PO 4 =4.35 ppm, Fe=0, Feed pH=7.0, Temp=31°C, Antiscalant Dosage=5 ppm, Recovery=85%

15. No Iron, No Antiscalant - SEM Filtered deposit of solution without antiscalant

16. No Iron, No Antiscalant - EDS Amorphous Calcium Phosphate Ca 9 (HPO 4 ) x (PO 4 ) 6-x (OH) x Elemental Analysis of Filter Deposit – No Antiscalant Element Weight% Atomic% Na K 6.78 9.18 Mg K 2.03 2.60 Al K 1.93 2.23 Si K 36.79 40.77 P K 15.33 15.40 S K 2.54 2.47 Cl K 4.92 4.32 Ca K 29.66 23.03

17. No Iron, No Antiscalant – Elemental Mapping

18. No Iron, Product H - SEM Filtered deposit from solution using Product H

19. No Iron, Product H - EDS Localized elemental analysis of colloidal particle Element Weight% Atomic% Mg K 0.48 0.76 Al K 1.93 2.73 Si K 7.88 10.72 P K 1.14 1.40 Ca K 88.57 84.39

20. No Iron, Product H - SEM Filtered deposit from solution using Product H – another particle

21. No Iron, Product H - EDS Localized elemental analysis of colloidal particle Element Weight% Atomic% Al K 1.87 1.96 Si K 94.81 95.24 P K 2.22 2.03 Ca K 1.10 0.77

22. No Iron, Product H – Elemental Mapping Elemental Mapping of colloidal particle

23. WASTEWATER RO FEED, NO CALCIUM Feed PO 4 =4.35 ppm, Feed Fe=0.12 ppm, Ca=0, Feed pH=7.0, Temp=31°C, Antiscalant Dosage=5 ppm, Recovery=85%

24. No Calcium, No Antiscalant - SEM Filtered deposit of solution without antiscalant

25. No Calcium, No Antiscalant - EDS Elemental Analysis of Filter Deposit Elemental ratios indicate co-deposition of ferric phosphate, magnesium phosphate and aluminum phosphate with silica Ferric phosphate typically precipitates as Amorphous Ferric Hydroxyphosphate General Formula: Fe r PO 4 (OH) 3r-3 Most Common: Fe 2 PO 4 (OH) 3 Reference: D.W.De Haas et al, The use of simultaneous chemical precipitation in modified activated sludge systems exhibiting biological excess phosphate removal Part 4: Experimental periods using ferric chloride, Water SA, 26, 4 (2000) Element Weight% Atomic% Na K 1.93 3.08 Mg K 6.58 9.92 Al K 2.25 3.06 Si K 19.00 24.80 P K 24.71 29.25 Fe K 45.53 29.89

26. No Calcium, No Antiscalant – Elemental Mapping Elemental Mapping of Filter Deposit

27. No Calcium, Product B (Non-Linear Polymer) - SEM Filtered deposit of solution using Product B

28. No Calcium, Product B (Non-Linear Polymer) - EDS Elemental Analysis of Filter Deposit Element Weight% Atomic% Mg K 10.93 16.41 Al K 2.16 2.92 Si K 18.82 24.45 P K 22.33 26.31 Fe K 45.75 29.90

29. No Calcium, Product B (Non-Linear Polymer) Elemental Mapping of Filter Deposit

30. WASTEWATER RO FEED, COMPLETE Feed PO 4 =4.35 ppm, Feed Fe=0.12 ppm, Ca=80.7 ppm, Feed pH=7.0, Temp=27°C, Antiscalant Dosage=5 ppm, Recovery=85%

31. Complete Feedwater, No Antiscalant - SEM Filtered deposit of solution without antiscalant

32. Complete Feedwater, No Antiscalant - EDS Elemental Analysis of Filter Deposit Elemental ratios indicate co-precipitation of calcium and iron phosphates with silica Amorphous Ferric Calcium Hydroxyphosphate? Fe 1.66 CaPO 4 (OH) 4 Element Weight% Atomic% Na K 7.55 11.39 Mg K 1.53 2.18 Al K 2.57 3.31 Si K 22.17 27.40 P K 17.30 19.39 S K 1.33 1.44 Cl K 6.47 6.33 Ca K 12.40 10.74 Fe K 28.67 17.81

33. Complete Feedwater, No Antiscalant – Elemental Mapping Elemental Mapping of Filter Deposit

34. Complete Feedwater, Product D - SEM Filtered deposit of solution using Product D

35. Complete Feedwater, Product D - EDS Elemental Analysis of Filter Deposit Element Weight% Atomic% Mg K 1.66 2.38 Al K 1.54 1.99 Si K 29.58 36.71 P K 25.48 28.68 Cl K 2.11 2.07 Ca K 13.97 12.15 Fe K 25.67 16.02

36. Complete Feedwater, Product D – Elemental Mapping Elemental Mapping of Filter Deposit

37. Complete Feedwater, Product G (Silica Antiscalant) SEM of Filtered deposit of solution using Product G

38. Complete Feedwater, Product G (Silica Antiscalant) Elemental Analysis of Filter Deposit Elemental ratios indicate co-precipitation of calcium and iron phosphates with silica Silica polymerization was not inhibited by the Silica Antiscalant when phosphate salts formed. Element Weight% Atomic% Na K 1.18 1.84 Mg K 1.83 2.69 Al K 1.83 2.43 Si K 22.65 28.84 P K 23.10 26.66 S K 1.51 1.68 Ca K 20.68 18.44 Fe K 27.22 17.43

39. Complete Feedwater, Product G (Silica Antiscalant) Elemental Mapping of Filter Deposit

40. Complete Feedwater, Product I - SEM Filtered deposit of solution using Product I

41. Complete Feedwater, Product I - EDS LOCALIZED ANALYSIS Localized elemental analysis of colloidal particle Element Weight% Atomic% Na K 3.46 4.19 Al K 3.12 3.22 Si K 93.42 92.59

42. Complete Feedwater, Product I – Elemental Mapping Elemental Mapping of Filter Deposit

43. Complete Feedwater, Product I - SEM Filtered deposit of solution using Product I – another particle

44. Complete Feedwater, Product I - EDS Localized Analysis Localized elemental analysis of colloidal particle Element Weight% Atomic% Na K 8.43 15.81 Al K 3.15 5.03 Si K 14.26 21.89 P K 10.75 14.97 S K 12.51 16.82 K K 1.54 1.70 Ca K 8.49 9.13 Fe K 3.95 3.05 Ba L 36.92 11.59

45. Complete Feedwater, Product I – Elemental Mapping Elemental Mapping of Filter Deposit

46. Feed Water Analysis – Municipal RO - Florida Feed Concentrate Ca 120 490 Mg 3.8 16 Ba 0.0069 0.029 Sr 0.62 2.6 Fe 2+ 0.42 0.69 Total Fe 0.43 1.8 Al <0.05 <0.05 Mn 0.025 0.1 Na 18 69 Cl 35.75 141 HCO 3 384.117 1684.7712 SO 4 <10 <10 PO 4 1.51 6 SiO 2 29.13 122.53 pH 7.29 7.79 Recovery ~75%

47. Membrane Autopsy – RO – Florida - SEM

48. Membrane Autopsy – RO – Florida – EDS Weight% Atomic% Al 0.6 0.89 Si 1.59 2.25 P 12.8 16.4 S 26.6 33 Ca 20.9 20.7 Fe 37.5 26.7

49. Membrane Autopsy – RO – Florida – Elemental Mapping Si Ka1

50. Membrane Autopsy – Texas - SEM

51. Membrane Autopsy – Texas - EDS Element Wt % At % NaK 1.08 2.02 MgK 0.91 1.61 AlK 0.23 0.36 SiK 13 19.98 P K 3.32 4.63 S K 0.76 1.03 CaK 26.18 28.21 FeK 54.53 42.16 Total 100 100

52. Membrane Autopsy – Texas – Elemental Mapping

53. [(OH) 4 SiOH] - + HOSi(OH) 3  (OH) 3 Si-O-Si(OH) 3 + H 2 O + OH - Reference: R.K.Iler, The Chemistry of Silica, Wiley (1979) OH OH OH OH Si OH - OH OH OH OH Si OH O  H H OH OH OH OH Si OH - OH O  H H OH OH OH OH Si OH - OH O  H H O  H H OH - OH

55. OH OH OH OH Si OH - OH OH OH Fe 2 PO 4 OH O  H H OH OH OH OH Si OH - O OH OH OH OH Si OH - OH O  H H O OH - OH OH  H H OH OH OH OH Si O  H H  H H OH OH OH OH Si O  H H O  H H

56. Membrane Surface Calcium phosphate formation will result in a disproportionate amount of Silica deposition on the membrane surface Amorphous Calcium Phosphate Ca 9 (HPO 4 ) x (PO 4 ) 6-x (OH) x PO 4 3 ¯ Ca 2+ Ca 2+ -Si-O-Si- I I I I PO 4 3 ¯ -Si-O-Si- I I I I -Si-O-Si- I I I I PO 4 3 ¯ Ca 2+ PO 4 3 ¯ Ca 2+ PO 4 3 ¯ Ca 2+ PO 4 3 ¯ Ca 2+ -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I -Si-O-Si- I I I I OH-Si-OH I I OH OH OH-Si-OH I I OH OH -Si-O- S- I I I I O O -Si-O- Si- I I I I O OH - Si-O-Si- I I I I O -Si-O-Si- I I I I O O O -Si-O-Si- I I I I O -Si-O-Si- I I I I O O -Si-O-Si- I I I I OH OH OH OH - Si- I I I O O O -Si-O-Si- I I I I O O O -Si-O-Si- I I I I O O -Si-O-Si- I I I I O O -Si-O-Si- I I I I O O O -Si-O-Si- I I I I O -Si-O-Si- I I I I O O O -Si-O-Si- I I I I O -Si-O-Si- I I I I O O O -Si-O-Si- I I I I O O O I I O -Si-OH I I O OH -Si-O-Si- I I I I O O OH-Si- I I O O -Si-O-Si- I I I I OH O - Si-O-Si- I I I I O O O OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH OH -Si-OH OH OH OH

57. Membrane Autopsy – Pilot RO - Florida RO Pilot Feedwater Analysis Feed Concentrate Ca 470.00 783.33 Mg 61.00 101.67 Ba 0.11 0.18 Sr 1.20 2.00 Fe ND ND Mn ND ND Al ND ND Na 310.00 516.67 Cl 865.00 1441.67 HCO3 1097.90 1829.84 SO4 135.24 225.40 PO4 0.37 0.61 SiO2 135.24 225.40 pH 7.58 7.80 Temperature (°c) 25.40 26.20

58. Membrane Autopsy – Pilot RO – Florida – SEM

59. Membrane Autopsy – Pilot RO – Florida - EDS Element Weight% Atomic% Na K 0.75 1.11 Mg K 2.50 3.48 Al K 0.30 0.37 Si K 10.07 12.13 P K 26.78 29.26 S K 20.18 21.30 Cl K 1.57 1.50 Ca K 35.59 30.05 Fe K 0.56 0.34 I L 1.69 0.45 Totals 100.00

60. Membrane Autopsy – Pilot RO – Florida – Elemental Map

61. Membrane Autopsy – Pilot RO – Florida - SEM

62. Membrane Autopsy – Pilot RO – Florida - EDS Element Weight% Atomic% Na K 1.27 1.82 Mg K 1.69 2.30 Al K 0.32 0.39 Si K 18.92 22.27 P K 21.15 22.58 S K 22.76 23.46 Cl K 2.25 2.10 Ca K 29.48 24.31 Fe K 0.61 0.36 I L 1.55 0.41 Totals 100.00

63. Membrane Autopsy – Pilot RO – Florida – Elemental Map

64. Membrane Autopsy – Pilot RO – Florida – Elemental Map

67. Thank you Mo Malki, American Water Chemicals E-mail: momalki@amh2ochem.com www.membranechemicals.com

68. Product A King Lee PTP100 Product B PWT Spectraguard Product C Avista Vitec 3000 Product D Genesys LF Product E Nalco PC-191 Product F Flocon 260 Product G Avista Vitec 4000 Product H AWC A-109 Product I AWC A-110