1 / 43

WTP Operator Training: Water Chemistry

WTP Operator Training: Water Chemistry. Missouri Water and Wastewater Conference Dr. John T. O ’ Connor, PE Tom O ’ Connor, PE. Elements of Water Chemistry. Molecular Properties of Water Acids and Bases - pH, pOH, Alkalinity Solubility Equilibria - Precipitation

vondra
Download Presentation

WTP Operator Training: Water Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

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

  3. The Atom

  4. Water Molecule - - + +

  5. Hydrogen Bonding - H18O9

  6. Hydrophobia

  7. Ionization of H2O

  8. What are Acids & Bases? An Acid is a Proton (H+) Donor A Base is a Proton (H+) Acceptor H2O + H2O = H3O+ +OH- [H+] = [OH-], moles/litre = 10-7 M pH + pOH = pKw constant 7 + 7 = 14 8 + 6 = 14

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

  10. HCl + H2O  H3O+ + Cl-

  11. Acids and Bases Acid pK Base HCl -3 strongCl- H2SO4 -3 SO42- HNO3 -1 NO3 - H2CO3 6.3 HCO3 - H2S 7.1 HS - NH4 + 9.3 NH3 HCO3- 10.3 weak CO32-

  12. Carbonate Equilibria H2CO3HCO3-  CO32-

  13. Alkalinity Acid Neutralizing Capacity of Water (Ability to accept protons) = HCO3- + 2CO3- + OH- - H+ Titration End-Point: H2CO3 (pH≈4.5)

  14. Hydrogen Sulfide H2S  HS- S2-

  15. Ammonium Ion Ammonia NH4+ NH3

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

  17. Coagulation withFerric Hydroxide

  18. Inorganic Coagulants • Aluminum Sulfate ( Filter Alum) Al2(SO4)3 · 14H2OAl(OH)3 • Ferric Sulfate Fe2(SO4)3 · 9H2O Fe(OH)3

  19. Metal Solubility • OH- : Zn(OH) 2Cu(OH) 2Cd(OH) 2 • CO32- :ZnCO3 CuCO3 CdCO3 • S2- : ZnS CuS CdS

  20. Metal Hydroxide Solubility vs pH

  21. Metals Removal in WWTP At.Wt. Influent Effluent g/mole µg/l µg/l Zinc 65.4 5730 690 Copper 63.5 2760 297 Cadmium 112.4 94 15 Lead 207.2 100 0 Nickel 58.7 37 13 Iron 55.8 1700 100

  22. Oxidation-Reduction Oxidation is the loss of an electron Fe2+(ferrous ion)- e- Fe3+ (ferric ion) Reduction is the gain of an electron Clo (chlorine) + e- Cl- (chloride ion) Rapid to glacially slow reaction rates

  23. Oxidation-Reduction

  24. Oxidizing Agents Oxygen O°2 - 4e- O2- (H2O) Chlorine Cl°2 - 2e- 2Cl- Potassium Permanganate KMnO4 - 3e-MnO2 Hydrogen Peroxide H2O2 - 2e- O2 + H2O

  25. Reducing Agents Hydrogen Sulfide H2S + 2e- S0 Nitrite Ion NO2- + 2e- NO3- Ferrous Ion Fe2+ + e- Fe3+ Carbon C° + 4e- CO2

  26. Chlorination Cl2 + H2S  Cl-+S0 Cl2 + NO2-Cl-+NO3- Cl2 + 2Fe2+ 2Cl-+2Fe3+ Rapid Reaction - Immediate Chlorine Demand

  27. Ozonation O3 + H2S O2+S° O3 + NO2-O2 +NO3- O3 + 2Fe2+ O2+2Fe3+ Rapid Reduction: O°  O2- - 2e-

  28. The Human Elements

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

  30. Inorganic Constituents Major Ions: Ca2+, Mg2+, Na+; HCO3-, SO42-, Cl- Nonionic: SiO2 Minor Ions: NH4+, K+; F-, PO4 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

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

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

  33. TOC in Missouri Waters • Source WaterTOC (avg) • Lakes 4.8 • Rivers 3.6 • Wells < 100 ft. 1.2 • Wells > 100 ft. 0.2

  34. Dissolved Gas Composition Abundance in Ground Waters Methane CH4 Nitrogen N2 Carbon dioxide CO2 Hydrogen sulfide H2S Radon Rn

  35. Methane • up to 77 mg CH4/l in Illinois Groundwaters • early methane wells used for home heating, cooking • wellhouse explosions • flaming the tap

  36. Groundwater Characteristics Midwestern United States 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

  37. Microbially-Mediated Reducing Conditions in Midwestern U.S. Ground Waters GASES DO absent (converted to carbon dioxide) H2S: 0 to 1 mg/l (sulfate converted to sulfides) Methane: 0 to ~ 70 mg CH4/lMETALS Iron, manganese, lead, copper, cadmium, zinc concentrations limited by carbonate, sulfide Arsenic (AsO2-) - commonly 0 to 50 µg /l NITROGEN Ammonium Ion: 0 to > 5 mg N/l Nitrate Ion: low (converted to nitrogen gas, N2) Nitrite Ion: low

  38. Historical TOC DataMissouri Finished Drinking Water Supplies

  39. Missouri Finished Drinking Water Supplies

  40. Metals in Municipal WatersMissouri Finished Drinking Water Supplies

  41. Hardness + Sodium Missouri Finished Drinking Water Supplies

  42. Missouri Finished Drinking Water Supplies

  43. Hardness - MO Surface Waters

More Related