Chlorine Disinfection. Sidney Innerebner, PhD, PE, CWP Indigo Water Group Littleton, Colorado

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1 Chlorine Disinfection Sidney Innerebner, PhD, PE, CWP Indigo Water Group Littleton, Colorado

Wastewater Exam Cram Disinfection is Awesome! Source: http://www.

2 Wastewater Exam Cram Disinfection is Awesome! Source:

destruction of all microorganisms Source: https://commons.wikimedia.

3 3 Purpose of Disinfection Disinfection accomplishes the destruction or inactivation of pathogens to very low levels Sterilization is the destruction of all microorganisms Source: Source:

coli) Total Coliforms One subset of the enteric bacteria.

4 Wastewater Exam Cram Testing Disinfection Efficacy Total Coliforms Fecal Coliforms (Picks for Packers) Escherichia coli (E. coli) Total Coliforms One subset of the enteric bacteria. Divided into smaller categories. Fecal Coliforms (Draft Pool) Includes E. coli and Klebsiella. (End of PreSeason Team)

5 Indicator Organisms Fecal Coliforms and E. coli live in symbiosis with us Not normally pathogenic Since they live in our intestines, their presence in water and wastewater is indicative of fecal matter contamination Source: National Institutes of Health

6 6 Forms of Chlorine Why chlorine? Strong oxidant Relatively inexpensive Generally effective Used for disinfection in water and wastewater treatment Mixes with water to form Hypochlorous Acid (HOCl) and Chlorite ion (OCl ) Photo by Indigo Water Group

7 7 Forms of Chlorine Disinfection Chemicals Gaseous chlorine Liquid hypochlorite Onsite generation of hypochlorite Chlorine dioxide Chloramines

8 Chlorine Strengths Gaseous Chlorine 100% Calcium Hypochlorite 65% 70% Sodium Hypochlorite 5% 15%

9 9 Chlorine Gas Free Chlorine Reactions Cl 2 + H 2 O HOCl + H + + Cl Hypochlorous Acid Hydrochloric Acid HOCl H + + OCl Hypochlorite ion

10 10 Free Chlorine Reactions Cl 2 + H 2 O HOCl + H + + Cl HOCl H + + OCl Hypochlorous acid and hypochlorite ions provide disinfection Acid formation may DROP ph Reduces alkalinity by up to 1.4 mg/l for every 1 mg/l of chlorine Alkalinity Drops Slightly

11 11 Wastewater Exam Cram

12 Best Disinfection Below ph 7.2 ACRP 2010

13 13 Contact Time, ph, and Temperature ph Temp Required Contact Time (CT), minutes 5 o C o C o C o C Contact Times (CT) for 99.9 Percent Giardia Removal With 0.6 mg/l Chlorine Residual

14 14 Hypochlorite Reactions NaOCl + H 2 O HOCl + Na + + OH HOCl H + + OCl Alkalinity Increases Slightly

15 Dose, Demand, and Residual

16 16 Dose, Demand, Residual Dose = Demand + Residual Dose is the total quantity of chlorine applied Demand is the quantity of chlorine required as soon as the chlorine is added to the wastewater Residual is the quantity of chlorine remaining after meeting the additional demand

17 17 Reactions Create Demand Nitrite (1.5 mg//l) Ferrous iron (0.6 mg/l) Manganese (1.3 mg/l) Sulfide to Sulfur (2.1 mg/l) Sulfide to Sulfate (6.2 mg/l)

18 18 Chloramines Combine ammonia with chlorine to form a new disinfectant Monochloramine = 1 chlorine Dichloramine = 2 chlorines Trichloramine = 3 chlorines As effective disinfectant as Chlorine for most things, but reaction times are slower Not as effective at inactivating viruses or protozoal cysts Cl

19 Breakpoint Chlorination 7 Free Chlorine Total Chlorine Chlorine Residual, mg/l Combined residual Chlorine Added (Dose), mg/l

20 Chloramine Species at ph 6.5 to 8.5 Cl 2 :N Ratio <5:1 by weight Monocloramine

21 Chloramine Species at ph 6.5 to 8.5 Cl 2 :N Ratio increases from 5:1 to 7.6:1

22 Chloramine Species at ph 6.5 to 8.5 Breakpoint

23 Chloramine Species at ph 6.5 to 8.5 Cl 2 :N Ratio greater than 7.6:1

24 Here s Where It Gets Tricky Influent NH 3 N, mg/l and ppd Effluent NH 3 N concentration Effluent NH 3 N, mg/l and Flow, MGD

25 Breakpoint Chlorination 7 Free Chlorine Total Chlorine Chlorine Residual, mg/l Combined residual Chlorine Added (Dose), mg/l

26 26 Measuring Residual Starch iodide test DPD tests Amperometric titration Oxidation reduction potential

27 27 Wastewater Exam Cram

28 A word about detection limits... Can the instrument see all the way down to zero? Think about an eye chart and your own detection limit The top line is easy to see, the bottom line is a little fuzzy..

29 Testing Residual Chlorine Residual, mg/l Combined residual 1 Total Chlorine Chlorine Added (Dose), mg/l

30 Testing Residual Chlorine Residual, mg/l Total Chlorine Combined residual Chlorine Added (Dose), mg/l

31 UV Disinfection

32 32 Ultraviolet Light Bacteria controlled when exposed to 260 nm Mercury vapor light produces 254 nm Effective with bacteria and viruses ACRP 2010

33 33 Why UV Disinfection Works Light generated at 254 nm damages DNA Bacteria may still be alive, but can t reproduce Some may be able to repair themselves under the right conditions

34 34 UV Equipment ACRP 2010

36 36 UV Disinfection Depends on TIME and Transmissivity Efficacy impacted by High TSS Dissolved Iron Dissolved Manganese High Turbidity Dose expressed as mw*s/cm 2

37 37

38 38 How many burned out bulbs do you see? How well is this UV system working?

39 39 Resources The Chlorination / Dechlorination Handbook (2002) Water Environment Federation O&M of Chlorine Systems (1997) ACR Publications

40 Try our online training classes. Approved for TU s in Ohio. Download a copy of this presentation. Password is 2017OhioWEAInd

41 Chlorine Gas

42 42 Chlorine Gas Detectable at concentrations of 0.02 to 0.2 PPM Smells like laundry bleach Greenish yellow in color Gas is 2.5 times heavier than air. It sinks to low spots Liquid is 1.5 times heavier than water Reacts with many organic compounds, oils, solvents sometimes explosively!

43 43 Liquid Chlorine Liquid chlorine reverts to gas when the pressure is reduced 1 volume of liquid chlorine yields 456 volumes of gas 1 lbs liquid = 5 cu ft gas 1 lb is about 300 ml Liquid chlorine is more hazardous than gaseous chlorine

44 44 Wastewater Exam Cram Container Types for Chlorine Gas 150# cylinder 1 Ton Container Rail car (55 90 tons)

45 Wastewater Exam Cram Chlorine Feed Systems

46 Typical Chlorine Gas Room ACRP 2010

47 47 Anatomy of a Cylinder 100 lb or 150 lb 88% liquid at 70 F 85 psi at 70 F Liquid boils at minus 29 F

48 48 New Weight Scales for 100 and 150 pound Cylinders Tare weight for each cylinder should be stamped directly on cylinder Automatic switch over to new cylinder ACRP 2010

ejector with check valve Indicating flow meter

49 49 Chlorine Gas Ejector Vacuum regulator with outside vent Feed rate control Venturioperated ejector with check valve Indicating flow meter Source water creates a vacuum which draws in gaseous chlorine

50 Valve ¼ Turn to Open or Close

51 51 Liquid to Gas Withdrawal from a 150# cylinder is 40 lbs/day Withdrawal from a 1 Ton Container is 400 lbs/day Excessive withdrawal from a chlorine vessel can cause freeze ups

52 52 Chlorinator Keep dry to prevent hydrochloric acid formation Cleaning steps Water to remove water soluble deposits Wood alcohol Drying Alternatively, heat to remove traces of moisture

53 53 Fusible Plugs One fusible plug on a 150 lb cylinder There 6 fusible plugs in a ton container Three fusible plugs on each end Plugs spaced 40 degrees apart Fusible plugs are a safety devices that will melt at temperatures of degrees F to release pressure from the vessel.

54 Source: net/stepchange/stepincidents_ showsingleincidentitem.aspx?id= Wastewater Exam Cram

55 55 150# Cylinder Valve

56 56 Ton container fusible plug

57 57 Fusible Plugs Gaseous chlorine (long runs) Liquid Chlorine (short runs)

58 Inside a Chlorine Container

59 59 Chlorine Gas Advantages/Disadvantages Well known Least cost Safety Shipping Plant monitoring Public notification requirements

60 Sodium Hypochlorite (Bleach)

61 61 Sodium Hypochlorite Bleach Liquid solution Strength 5 15 % available chlorine Delivery size 15 gallons, 55 gallons, bulk

62 62 Sodium Hypochlorite

63 63 Sodium Hypochlorite Formed by mixing chlorine gas and sodium hydroxide (caustic soda) Degrades over time (solution strength decreases) Impurities Sunlight Don t store longer than 60 days

64 64 Hypochlorite System Design Issues Gas bubbles form in pumps, pipes, tanks Air release valves on piping and tanks Pump design to allow to release air maintenance issue Scaling potential Discharge pipes, diffusers plug and backpressure develops potential to burst pipes Flush lines with water

Liquid solution: Chances of ingestion are higher Splash proof

65 65 Keeping Safe Has different safety issues than gaseous chlorine ph of Sodium hypochlorite is Liquid solution: Chances of ingestion are higher Splash proof goggles necessary to protect eyes Full face shields should be used to protect skin on face Access to eye wash

66 Calcium Hypochlorite (or HTH High Test Hypochlorite)

67 67 Calcium Hypochlorite Characteristics Solid Tablets, Granular crystals Strength 6570 % active chlorine Dissolves slowly in water 1 lb HTH = 0.65 lb Cl2

68 68 Some facts Calcium hypochlorite is often called HTH High Test Hypochlorite Chlorine reacts with water to form Hydrochloric and Hypochlorous ACID Cl 2 + H2O = HCl + HOCl Reaction drives ph of water up ph of HTH 1011

Appealing for small systems because system has virtually no moving

69 69 Calcium hypochlorite Added to water with a tablet feeder Imprecise method of adding chemical Difficult to flow pace Appealing for small systems because system has virtually no moving parts Easy to maintain Source:

70 Try our online training classes. Approved for TU s in Ohio. Download a copy of this presentation. Password is 2017OhioWEAInd

71 71 Wastewater Exam Cram Resources The Chlorination / Dechlorination Handbook (2002) Water Environment Federation O&M of Chlorine Systems (1997) ACR Publications

Disinfection. Disinfection is used to treat both domestic water and wastewater.

Disinfection. Disinfection is used to treat both domestic water and wastewater. Disinfection Disinfection is the selective destruction of disease causing organisms (viruses, bacteria, protozoans). It destroys most recognized pathogenic microorganisms, but not necessarily all microbial