Water Treatment Processes

1. Water Treatment Processes Water Treatment Plant Operation

2. Water Treatment Processes • Section 1: Water Treatment Concerns • Section 2: Well Considerations • Section 3: Conventional Water System Processes • Section 4: Disinfection By-Product Control • Section 5: Corrosion Control • Section 6: Demineralization Processes • Section 7: Coagulation Process Control • Section 8: Water Softening Florida Rural Water Association Water Treatment Plant Operation

3. Section 1:Water Treatment Concerns • Microbial Contamination Concerns • Barriers to Contaminants Reaching the Public • Where Contamination Comes From • Bacterial Indicators and Pathogens • Primary Standards • Secondary Standards Florida Rural Water Association Water Treatment Plant Operation

4. Microbial Contamination is Primary Concern of Water Operators Coliform bacteria Common in the environment and are generally not harmful but their presence in drinking water indicates that the water may be contaminated and can cause disease. Fecal Coliform and E coli Bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Microbes in these wastes can cause short-term effects, such as diarrhea, cramps, nausea, headaches, or other symptoms. Turbidity Has no health effects. However, turbidity can interfere with disinfection and provide a medium for organisms that include bacteria, viruses, and parasites that can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. Florida Rural Water Association Water Treatment Plant Operation

5. Multiple Barrier Approach Source: Selection and Protection Treatment: Methods and Efficiencies Distribution: Maintenance and Monitoring Florida Rural Water Association Water Treatment Plant Operation

6. Where Contamination Comes From * Multiple Sources, ie. runoff, septic tanks, CAFOs Florida Rural Water Association Water Treatment Plant Operation

7. Microbial Contaminants found in Surface Water or UDI Sources Cryptosporidium and Giardia Parasites that enters lakes and rivers through sewage and animal waste. These typically cause mild gastrointestinal diseases. However, the disease can be severe or fatal for people with severely weakened immune systems. EPA and CDC have prepared advice for those with severely compromised immune systems who are concerned about these organisms. Florida Rural Water Association Water Treatment Plant Operation

8. Some Facts About Bacteria • Bacteria are widely distributed on earth • They have been found 4 miles above earth and 3 miles below sea sediments. • One gram of fertile soil contains up to 100,000,000 bacteria. • Bacteria are inconceivably small and measured in microns. One micron is equal to 1/1,000,000 of a meter. • During the rapid growth phase bacteria undergo fission (cell division) about every 20 to 30 minutes. • One bacterial cell after 36 hrs of uncontrolled growth, could fill approximately 200 dump trucks. Florida Rural Water Association Water Treatment Plant Operation

9. Bacteria and PathogenicIndicators in Water Treatment Photo: CDC. E. coli 0157:H7 11 of 140 cause gastrointestinal disease

10. Identifying Source of Contaminants Florida Rural Water Association Water Treatment Plant Operation

11. Primary or Inorganic Contaminants Mineral-Based Compounds These include metals, nitrates, and asbestos. These contaminants are naturally-occurring in some water, but can also get into water through farming, chemical manufacturing, and other human activities. Potential health effects include learning disorders, kidney and liver damage. EPA has set legal limits on 15 inorganic contaminants. Florida Rural Water Association Water Treatment Plant Operation

12. Primary Standards and their Maximum Contaminant Levels (MCLs) Contaminant MCL (mg/l) Arsenic 0.010 Asbestos 7 (MFL) Fluoride 4.0 Mercury 0.002 Nickel 0.1 Nitrate 10 Nitrite 1 Total Nitrate+Nitrite 10 Sodium 160 Florida Rural Water Association Water Treatment Plant Operation

13. Disinfectants and Disinfection By-Products • Disinfectants are water additives that are used to control microbes • Disinfection By-products are created when chlorine is added in the presence of naturally occurring low levels of organic materials found in drinking water • Both are regulated because of health concerns Florida Rural Water Association Water Treatment Plant Operation

14. Secondary Standards and Concerns • These compounds cause aesthetic concerns such as taste, odor and color. • EPA recommends MCL limits • Some states such as Florida have set regulatory limits on these contaminants Florida Rural Water Association Water Treatment Plant Operation

15. Secondary StandardMaximum Contaminant Levels Contaminant MCL (mg/l) Chloride 250 Sulfate 250 TDS 500 Copper 1.0 Fluoride 2.0 Iron 0.30 Manganese 0.05 Silver 0.1 pH (MRCL) 6.5 to 8.5 Color (MCRL) 15 cfu Florida Rural Water Association Water Treatment Plant Operation

16. Prevent movement of water between aquifer formations Preserve quality of producing zones Preserve Yield Prevent water intrusion from surface Protect Casing against Corrosion! Protecting Well by Grouting Pressure Testing of Grout Seal @ ~10 psi for 1 hr. Should be Performed. Florida Rural Water Association Water Treatment Plant Operation

17. Section 2Well Considerations • Floridan Aquifer • Well Contaminants • Preventing Contamination at the Well Head Florida Rural Water Association Water Treatment Plant Operation

18. Floridian Aquifer Across Florida Florida Rural Water Association Water Treatment Plant Operation

19. TDS Total Hardness Total Fe and Mn Chlorides & Sulfates Total Alkalinity Nitrate pH Corrosivity CO2 H2S Fluoride Well Source Water ParametersQuality and Quantity Dictates Depth of Well Florida Rural Water Association Water Treatment Plant Operation

20. Preventing Contamination at the Well Head

21. Preventing Contamination at the Well Head (continued) Florida Rural Water Association Water Treatment Plant Operation

22. Preventing Contamination at the Well Head (continued) Florida Rural Water Association Water Treatment Plant Operation

23. Preventing Contamination at the Well Head (continued) Florida Rural Water Association Water Treatment Plant Operation

24. Preventing Contamination at the Well Head (continued) Florida Rural Water Association Water Treatment Plant Operation

25. Preventing Contamination at the Well Head (continued) Florida Rural Water Association Water Treatment Plant Operation

26. Section 3:Conventional Water System Processes • TOC in Source Water • Disinfection and Uses of Chlorine • Aeration and Aerator Types • Iron and Hydrogen Sulfide Control • Filtration • Sedimentation Florida Rural Water Association Water Treatment Plant Operation

27. Organic Carbon (TOC) in Natural Waters mg/l Mean Surface Water 3.5 Sea Water Ground Water Surface Water Swamp Wastewater Wastewater Effluent .1 .2 .5 1.0 2 5 10 20 50 100 200 500 1000 Florida Rural Water Association Water Treatment Plant Operation

28. Disinfection with Chlorine • The primary methods of disinfection is the use of chlorine gas, chloramines, ozone, ultraviolet light, chlorine dioxide, and hypochlorite. • Generally Chlorine will be used by small systems and may be applied as a gas, solid or liquid. • The most common chlorine application is sodium hypochlorite or bleach. • Primary Disinfectants are used to inactivate microbes and Secondary Disinfectants are used to provide for a residual chlorine concentration that prevents microbial regrowth. Florida Rural Water Association Water Treatment Plant Operation

29. Reactions of Chlorine with Water Constituents • Reducing Compound (inorganics) • Production of Chloramines • Production Chlororganics • Combined Chlorine • Breakpoint Chlorination • Free Chlorine Residual Florida Rural Water Association Water Treatment Plant Operation

30. Fe Mn H2S DISINFECTION BYPRODUCTS REMAIN Add NH3 Dichloromine 0.6 0.2 0 Chloromine 0 Breakpoint Chlorination Curve Florida Rural Water Association Water Treatment Plant Operation

31. Other Chlorine Uses • Chlorine is often used as an oxidant to remove inorganic impurities such as iron and hydrogen sulfide • When used in this manner particulate matter is formed that often must be removed. • Chlorine is also used to prevent the growth of algae on tank walls and other surfaces exposed to sunlight and to prevent bacteria from growing inside filters and tanks • Chlorine has been used to remove color, taste and odors but will produce disinfection by-products which are regulated Florida Rural Water Association Water Treatment Plant Operation

32. Aeration • Aeration is generally used in small systems to remove naturally occurring dissolved gasses from the water such as CO2 and H2S. • Aeration may also be used to oxidize iron which then drops out as precipitate and must be filtered. • Special aerators called Packed Towers are sometimes used to remove VOCs Florida Rural Water Association Water Treatment Plant Operation

33. Cascade Tray Aerator • Even distribution of water over top tray • Loading Rates of 1 to 5 GPM for each sft. of Tray area. • Trays ½” openings perforated bottoms • Protection from insects with 24 mesh screen Florida Rural Water Association Water Treatment Plant Operation

34. Forced Draft Aeration System • Includes weatherproof blower in housing • Counter air through aerator column • Includes 24 mesh screened downturned inlet/outlet • Discharges over 5 or more trays Florida Rural Water Association Water Treatment Plant Operation

35. Packed Tower Odor Removal System • Uses Henry’s Law constants for mass transfer • Usually requires pilot testing • Used to Remove VOCs below MCL • Col to Packing >7:1 ratio • Air to water at pk >25:1 with max 80:1 • Susceptible to Fouling from CaCO3 > 40 PPM Florida Rural Water Association Water Treatment Plant Operation

36. Iron Problems - Most Prevalent in Unconfined, Surficial, and Biscayne Aquifers • Iron dissolved by reaction with CO2 • Iron from well sources will be in a dissolved state • When exposed to O2 precipitants form • Visible as red and brown color • Will stain fixtures and clothes • Imparts taste and odor Florida Rural Water Association Water Treatment Plant Operation

37. Iron, Turbidity/TOC Relationships Florida Rural Water Association Water Treatment Plant Operation

38. Dissolved Iron Problems • Soluble iron passing into the water distribution systemwill encourage the growth of iron bacteria • Precipitates will form in the distribution system • Iron particles will stain clothes and fixtures (Red Water Complaints) Florida Rural Water Association Water Treatment Plant Operation

39. Treatment of Dissolved Iron Florida Rural Water Association Water Treatment Plant Operation

40. Fe++ AerationPlot of pH vs. Time for Iron Removal at 90%Efficiency(min 30 minutesdetention) Florida Rural Water Association Water Treatment Plant Operation

41. Filtration Requirements forIron and Manganese • Requires bé DEP at > 1.0 mg/l Fe • Turbidity must be no more than 2 NTUs above Source Water • Oxidized particles must generally be removed • Anthracite filters are frequently employed with higher iron content Florida Rural Water Association Water Treatment Plant Operation

42. Sulfide (mg/l) Recommended Treatment Process Achievable Range of Removal 100% < 0.3 Direct Chlorination > 0.3 Direct Chlorination (requires filtration) 100% 0.3 to 0.6 Conventional Aeration 50% 0.6 to 3.0 Forced Draft Aeration 90% > 3.0 Packed Tower Aeration > 90% Hydrogen Sulfide Removal Techniques (DEP) Florida Rural Water Association Water Treatment Plant Operation

43. Hydrogen Sulfide Removal Dynamics Gas Soluble Florida Rural Water Association Water Treatment Plant Operation

44. Clarification • Clarifiers are often used in water treatment to allow particles to settle prior to filtration. • Special clarifiers called “Upflow Clarifiers” are used in surface water treatment plants that used coagulants and in softening plants that use lime. These types of clarifiers perform several treatment processes in one tank Florida Rural Water Association Water Treatment Plant Operation

45. Causes of Poor Clarifier Performance • If Surface water plant flocculators are not adjusted for rate of flow • Sludge removal is not routine • There is no test to control sludge quantities • Settled water turbidities are not measured or are not measured routinely (e.g., minimum of once per shift) Florida Rural Water Association Water Treatment Plant Operation

46. Filtration • Filters are primarily used to remove particulate matter and turbidity from the water. • The primary types of filters used in water treatment are Rapid Sand or gravity and Pressure Filters • Special Membrane Filters are used for Particulate and Microbial removal. • Special Filters employ Resins and Media such as greensand and are used to remove select contaminants such as iron and manganese. Activated carbon filters are used to remove organic compounds. Florida Rural Water Association Water Treatment Plant Operation

47. Filter Applications Nanofiltration Florida Rural Water Association Water Treatment Plant Operation

48. Media Configurations forGravity Filters • Single media (sand) • Dual Media (sand and anthracite) • Mixed or multi-media (sand, anthracite and garnet) Florida Rural Water Association Water Treatment Plant Operation

49. Characteristics of Various Filters

50. Calculating Filter Flow Rate • Determine Surface Area of Filter • Measure Filter Rise with stopwatch and tape measure (often meters are out of calibration) Example: 150 sft surface area, 10.7” rise in 20 seconds (10.7 in / 12 in/ft) x 150 sft x 7.48 gal/cft = 1000 gal. (20 seconds / 60 min ) = 0.333 min Flow Rate = 1000 gal / 0.333 min = 20 gpm / sft 150 sf Florida Rural Water Association Water Treatment Plant Operation