2. WTP Operator Training: Water Chemistry Missouri Water and Wastewater Conference Dr. John T. O’Connor, PE Tom O’Connor, PE

3. Elements of Water Chemistry Molecular Properties of Water Acids and Bases - pH, pOH, Alkalinity Solubility Equilibria - Precipitation Oxidation-Reduction Reactions

4. The Atom

5. Water Molecule ++ -

6. Hydrogen Bonding - H 18 O 9

7. Hydrophobia

8. Ionization of H 2 O

9. What are Acids & Bases? An Acid is a Proton (H + ) Donor A Base is a Proton (H + ) Acceptor H 2 O + H 2 O = H 3 O + + OH - [H + ] = [OH - ], moles/litre = 10 -7 M pH + pOH = pKw constant 7+7=14 8+6=14

10. Chemical Shorthand pH = - log [H + ] pOH = - log [OH - ] pK = - log [K] e.g., [10 -7 M] = 7

11. HCl + H 2 O  H 3 O + + Cl -

12. Acids and Bases AcidpK Base HCl-3 strong Cl - H 2 SO 4 -3SO 4 2- HNO 3 -1NO 3 - H 2 CO 3 6.3HCO 3 - H 2 S 7.1HS - NH 4 + 9.3NH 3 HCO 3 - 10.3 weak CO 3 2-

13. Carbonate Equilibria H 2 CO 3  HCO 3 -  CO 3 2-

14. Alkalinity Acid Neutralizing Capacity of Water (Ability to accept protons) = HCO 3 - + 2CO 3 - + OH - - H + Titration End-Point: H 2 CO 3 (pH≈ 4.5)

15. Hydrogen Sulfide H 2 S  HS -  S 2-

16. Ammonium Ion  Ammonia NH 4 +  NH 3 NH 4 +  NH 3

17. Precipitation & Solution Precipitation of Iron, Manganese Formation of Coagulant Floc Corrosion of Copper, Lead Calcium Carbonate Stability

18. Coagulation with Ferric Hydroxide

19. Inorganic Coagulants Aluminum Sulfate ( Filter Alum)Aluminum Sulfate ( Filter Alum) Al 2 (SO 4 ) 3 · 14H 2 OAl(OH) 3 Ferric SulfateFerric Sulfate Fe 2 (SO 4 ) 3 · 9H 2 OFe(OH) 3

20. Metal Solubility OH - : Zn(OH) 2  Cu(OH) 2 Cd(OH) 2 CO 3 2- : ZnCO 3 CuCO 3 CdCO 3 S 2- : ZnS CuS CdSS 2- : ZnS CuS CdS

21. Solubility Products, K sp [Cu 2+ ] [OH - ] 2 =10 -18.8 [Zn 2+ ] [OH - ] 2 =10 -16.3 [Ni 2+ ] [OH - ] 2 =10 -15.8 [Cd 2+ ] [OH - ] 2 =10 -14.3

22. Metal Hydroxide Solubility vs pH

23. Solubility Products, K sp [Cd 2+ ] [CO 3 2- ]=10 -11.3 [Zn 2+ ] [CO 3 2- ]=10 -10.8 [Cu 2+ ] [S 2- ]=10 -36.1 [Cd 2+ ] [S 2- ]=10 -27.0 [Zn 2+ ] [S 2- ]=10 -24.7

24. At.Wt. Influent Effluent g/mole µg/l µg/l Zinc65.4 5730 690 Copper63.5 2760 297 Cadmium112.4 94 15 Lead207.2 100 0 Nickel58.7 37 13 Iron55.8 1700 100 Metals Removal in WWTP

25. Oxidation-Reduction Oxidation is the loss of an electron Fe 2 + (ferrous ion) - e -  Fe 3 + (ferric ion) Reduction is the gain of an electron Cl o (chlorine) + e -  Cl - (chloride ion) Rapid to glacially slow reaction rates

26. Oxidation-Reduction

27. Oxidizing Agents Oxygen O° 2 - 4e -  O 2- (H 2 O) Chlorine Cl° 2 - 2e -  2Cl - Potassium Permanganate KMnO 4 - 3e -  MnO 2 Hydrogen Peroxide H 2 O 2 - 2e -  O 2 + H 2 O

28. Reducing Agents Hydrogen Sulfide H 2 S + 2e -  S 0 Nitrite Ion NO 2 - + 2e -  NO 3 - Ferrous IonFe 2+ + e -  Fe 3+ CarbonC°+ 4e -  CO 2

29. Chlorination  Cl 2 + H 2 S  Cl - + S 0  Cl 2 +NO 2 -  Cl - + NO 3 - Cl 2 +2Fe 2+  2Cl - + 2Fe 3+ Rapid Reaction - Immediate Chlorine Demand

30. Ozonation  O 3 + H 2 S  O 2 + S °  O 3 +NO 2 -  O 2 + NO 3 - O 3 +2Fe 2+  O 2 + 2Fe 3+ Rapid Reduction: O°  O 2- - 2e -

31. Organic (Carbon) Molecules

32. The Human Elements

33. Hydrogen Isotopes

34. Hydrogen, Carbon Isotopes

35. Groundwater Constituents All water is the same. It is only the stuff in it that is different. INORGANIC ORGANIC GAS

36. Inorganic Constituents Major Ions: Ca 2+, Mg 2+, Na + ; HCO 3 -, SO 4 2-, Cl - Nonionic: SiO 2 Minor Ions: NH 4 +, K + ; F -, PO 4 3- Trace Constituents: Al, As, Ba, B, Br, Cd, Cs, Cr, Co, Cu, I, Fe, Pb, Mn, Hg, Mo, Ni, Ra, Ru, Se, Ag, Sr, Sn, Ti, U, Zn

37. Electroneutrality Conditions Missouri River Dec. 2000 Kansas City Well Water

38. Organic Constituents Total Organic Carbon (TOC) = Purgeable organic carbon (e.g., methane) + Non-Purgeable organic carbon (NPOC) Dissolved (natural color) (DOC) + Particulate (bacteria, algae)

39. TOC in Missouri Waters Source Water TOC (avg) Lakes4.8 Rivers3.6 Wells < 100 ft.1.2 Wells > 100 ft.0.2

40. Dissolved Gas Composition Abundance in Ground Waters MethaneCH 4 Nitrogen N 2 Carbon dioxideCO 2 Hydrogen sulfideH 2 S Radon Rn

41. Methane up to 77 mg CH 4 /l in Illinois Groundwaters early methane wells used for home heating, cooking wellhouse explosions flaming the tap

42. Physical & Inorganic Water Qualities - Constant Cations:Hardness (calcium, magnesium), sodium, potassium, ammonium ions Anions:Alkalinity (bicarbonate), chloride, sulfate fluoride, arsenite ions; little or no nitrate Temperature:12 ± 2 °Celsius; density, viscosity constant Groundwater Characteristics Midwestern United States

43. GASESDO absent (converted to carbon dioxide) H 2 S: 0 to 1 mg/l (sulfate converted to sulfides) Methane: 0 to ~ 70 mg CH 4 /l METALSIron, manganese, lead, copper, cadmium, zinc concentrations limited by carbonate, sulfide Arsenic (AsO 2 - ) - commonly 0 to 50 µg /l NITROGENAmmonium Ion: 0 to > 5 mg N/l Nitrate Ion: low (converted to nitrogen gas, N 2 ) Nitrite Ion: low Microbially-Mediated Reducing Conditions in Midwestern U.S. Ground Waters

44. Missouri Surface Water Supplies Surface (stream and lake waters) vary seasonally in temperature, algal blooms; runoff from farmland and feedlots.

45. Historical TOC Data Missouri Finished Drinking Water Supplies

46. Missouri Finished Drinking Water Supplies

47. Metals in Municipal Waters Missouri Finished Drinking Water Supplies

48. Hardness + Sodium Missouri Finished Drinking Water Supplies Hardness + Sodium Missouri Finished Drinking Water Supplies

49. Missouri Finished Drinking Water Supplies

50. Hardness - MO Surface Waters