California Department of Public Health Webcast

1. California Department of Public Health Webcast Evaluation and Design of Small Water Systems Design of Disinfection Systems Dale Newkirk, P.E.

2. Lecture Objectives • Learn about pros and cons of different disinfectants • Learn how the different disinfection systems work • Learn how to design various disinfection systems

3. Dosage Calculation

4. Ozone System Design For Small Water Systems

5. When Would You Use Ozone? • TOC>2mg/L waters where TTHM potential is high • Taste and Odors • Iron and manganese, H2S, nitrite, cyanide, algae problems • Inactivation of Giardia • Presence of color • Bromide is low in source water

6. Advantages • Possesses strong oxidizing power and requires short reaction time, which enables the germs, including viruses, to be killed within a few seconds • Produces no taste or odor • Provides oxygen to the water after disinfecting • Requires no chemicals • Oxidizes iron and manganese • Destroys and removes algae • Reacts with and removes all organic matter • Decays rapidly in water, avoiding any undesirable residual effects • Removes color, taste, and odor • Aids coagulation

7. Disadvantages • Cost of ozonation is high compared with chlorination • Installation can be complicated • Ozone-destroying device is needed at the exhaust of the ozone-reactor to prevent toxicity and fire hazards • May produce undesirable aldehydes and ketones by reacting with certain organics • No residual effect is present in the distribution system, thus post-chlorination is required • Much less soluble in water than chlorine; thus special mixing devices are necessary • It will not oxidize some refractory organics or will oxidize too slowly to be of practical significance.

8. CT Tables for Ozone

9. Growth of Ozone Use in U.S.

10. Who Uses Ozone?

11. pH Effects on Ozone

12. Basic Components of Ozone System

13. Ozone Generator

14. Characteristics of Low, Medium, and HighFrequency Ozone Generators

15. Ozone Contact Basin Designs • Diffused Bubbles • U-Tube Positive Pressure Injection • Negative Pressure Venturi Tubes • Turbine Mixers

16. Design Considerations • All pipe and fittings should be a minimum of 304 stainless steel • Connections should be welded or flanged inside the tank • A check valve installed in the gas feed line prior to the contactor to prevent backflow of water into the gas line. • The water depth in the tank should be 18-20 (10 psi) feet to provide maximum transfer efficiency. • Countercurrent bubble contactors are considered to be the most efficient and cost effective in bubble diffuser designs. • Ozone is such a quick actor, only 3-10 minutes of contact time is required.

17. Large Scale Ozone Generator

18. Small Water System Example

19. Injector Systems

21. Injector System

22. Advantages/Disadvantages

23. Diffused Bubble Contactor Design

24. Advantages/Disadvantages

25. Turbine Design

26. Advantages/Disadvantages

27. Ozone Gas Removal

28. Minimum Ozone Dosages for Common Contaminants Contaminant Iron (Fe) Manganese (Mn) Hydrogen Sulfide (H2S) Disinfection Contaminant (Ozone per mg of Contaminant) • 0.43 mg • 0.87 mg • 3.00 mg • 0.50 mg

29. Estimating Ozone Demand • Fe demand = C x 0.43 = mg/LMn demand = C x 0.87 = mg/LH2S demand = C x 3.0 = mg/LDisinfection, add 0.5 mg/LSum Total = mg/L = O3D • Multiply O3D by L/hr to calculate mg/hr. • Divide by 1,000 to convert to grams per hour needed to treat the water.

30. Many Equipment Suppliers • Fuji Electric Corp. • IN USA Inc. • Mazzei injector/GDT Corp. • Mitsubishi Electric • Ozone Water Systems • Ozonia North America, Inc. • Pacific Ozone • Wedeco, Inc. wedeco spartan ozonia

31. Chlorine Dioxide Systems For Small Water Systems

32. Chlorine Dioxide Reactions 2NaClO2 + Cl2(g) = 2ClO2(g) + 2NaCl 2NaClO2 + HOCl = 2ClO2(g) + NaCl + NaOH 5NaClO2 + 4HCl = 4ClO2(g) + 5NaCl + 2H20 ClO2

33. Advantages • Chlorine dioxide is more effective than chlorine and chloramines for inactivation of viruses, Cryptosporidium, and Giardia. • Chlorine dioxide oxidizes iron, manganese, and sulfides. • Chlorine dioxide may enhance the clarification process. • Taste and odors resulting from algae and decaying vegetation, as well as phenolic compounds, are controlled by chlorine dioxide. • Under proper generation conditions (i.e., no excess chlorine), halogen-substituted DBPs are not formed. • Chlorine dioxide is easy to generate. • Biocidal properties are not influenced by pH. • Chlorine dioxide provides residuals.

34. Disadvantages • The chlorine dioxide process forms the specific byproducts chlorite and chlorate. • Generator efficiency and optimization difficulty can cause excess chlorine to be fed at the application point, which can potentially form halogen-substitute DBPs. • Costs associated with training, sampling, and laboratory testing for chlorite and chlorate are high. • Equipment is typically rented, and the cost of the sodium chlorite is high. • Measuring chlorine dioxide gas is explosive, so it must be generated on-site. • Chlorine dioxide decomposes in sunlight. • Chlorine dioxide must be made on-site. • Can lead to production noxious odors in some systems.

35. CT Inactivation Table (Giardia/Viruses Giardia Virus

36. CT for Giardia

37. CT for Viruses

38. Types of Generators

39. Types of Generators

40. Chlorine-Chlorite Method

41. Chlorine Dioxide Generator

42. Properties of Sodium Chlorite as Commercially Available

43. Chemical Feed Systems • Fiberglass Reinforced vinyl ester Plastic (FRP) or High Density Linear Polyethylene (HDLPE) tanks with no internal insulation or heat probes are recommended for bulk storage of 25 to 38 percent solution sodium chlorite. • Transfer pumps should be centrifugal with 316 stainless steel, fiberglass, Hypalonä, wetted Teflonä parts, or epoxy resins. • The pump should be sealless or equipped with double mechanical seals. • The recommended piping material is CPVC, although vinyl ester or Teflon ä piping systems are acceptable. Carbon steel and stainless steel piping systems are not recommended. • Depending upon system size, sodium chlorite can be purchased in 55-gallon drums. • Sodium chlorite solution feed pumps are commonly diaphragm-metering pumps for liquid feed rate control.

44. Dosages for Iron and Mn • 1.2 mg/L of chlorine dioxide is required to remove 1.0 mg/L of iron • 2.5 mg/L of chlorine dioxide are required to remove 1.0 mg/L of manganese • High concentrations of iron and manganese, the use of chlorine dioxide is limited to the 1.0 mg/L chlorite/chlorate ion byproduct

45. Design of UV Disinfection For Small Water Systems

46. What is UV Disinfection? • Inactivation of pathogenic organisms by UV radiation to prevent replication (physical disinfection) • UV penetrates cell wall and damages DNA/RNA • Effective for protozoa (Giarida & Crypto), bacteria (E.coli) and viruses

47. Advantages • No hazardous chemicals storage • No known byproducts • No residuals to remove • Not affected by pH or temperature • Requires short contact time (seconds vs. minutes) = smaller contact chamber • No danger of overdosing • Low maintenance

48. Disadvantages • Higher Equipment Cost • No disinfectant residual (Drinking Water) • Not as effective for certain viruses (i.e. Adenovirus) - (Drinking water)

49. UV Dose Requirements

50. What is UV?