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UV For Developing Countries. A new tool for the disinfection toolbox? UV Disinfection.

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Presentation on theme: "UV For Developing Countries. A new tool for the disinfection toolbox? UV Disinfection."— Presentation transcript:

1 UV For Developing Countries

2 A new tool for the disinfection toolbox? UV Disinfection

3 Prof. Bill Larsen’s system

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5 First UC Berkeley UV Tube

6 Next Model

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8 Sri Lankan Neighborhood Scale Installation

9 B9 Plastics Better Water Maker

10 Ultra-Violet Light UVA (315 – 400 nm): sun tans UVB (280 – 315 nm): sun burns UVC* (200 – 280 nm): disinfection ( * Nearly 100% filtered by the atmosphere.) Interferes with DNA Replication/ Reproduction

11 History of UV Drinking Water Disinfection 1910 Marseilles, France: UV is first used to treat drinking water. Abandoned for free chlorine (by-product of soda production) 1970’s: Disinfection by-products discovered. UV disinfection of drinking water common in Europe. 1990’s: Outbreaks in the US lead to concern that chlorine is not effective against some organisms. March 1993: a cryptosporidium outbreak in Milwaukee leads to 400,000 illnesses and 100+ deaths.

12 History of UV Water Disinfection 1999: Town of Ontario, NY becomes the first community in North America to disinfect surface source drinking water with UV light. Currently: there are over 1500 wastewater treatment plants using UV in the US. Lake Ontario Poly-alum added Sedimentation Gravel, sand, and GAC filters Chlorine residual added Storage UV

13 UV System Components UV Bulbs and Ballast (AC or DC) UV Bulbs and Ballast (AC or DC) –Mercury-argon lamps (an electrical arc ignites the mercury vapor which emits UV light) –Hope for LEDs in the future… Chamber Chamber Quartz Sleeve Quartz Sleeve –passes UV –maintains bulb temperatures Sensor Sensor –to monitor bulb output Cleaning Mechanism Cleaning Mechanism

14 Mercury Vapor Bulbs Like florescent bulbs except: Like florescent bulbs except: –Quartz not glass –No phosphor coating 88% of the output at nm 88% of the output at nm Lamp is susceptible to cooling by the effluent Lamp is susceptible to cooling by the effluent Limited Lamp Life—1 year continuous operation Limited Lamp Life—1 year continuous operation

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16 Determining Dose (Fluence) Dose (Fluence) = Intensity * Exposure Time  J/m 2 ) (W/m 2 ) (s) Function of bulb and water characteristics Function of hydrodynamics & Geometry of reactor

17 Simple Microbial Response 0% inactivated 90% inactivated, 10% surviving 99% inactivated, 1% surviving 99.9% inactivated, 0.1% surviving 99.99% inactivated, 0.01% surviving % inactivated, 0.001% surviving

18 A More Complicated Response and imbedded bacteria ? Explanation of Shoulder Threshold of DNA “hits” to inactivate? Reactivation? Explanation of Tailing “Shielding” depends on particle absorbance Imbedded bacteria UV resistant bacteria

19 Turbidity Can lead to scattering, reflection, blocking of microorganisms by particles Can lead to scattering, reflection, blocking of microorganisms by particles Considered negligible up to 5 NTU Considered negligible up to 5 NTU Theoretically, overall intensity is not reduced, but, energy is lost through interactions with particulates Theoretically, overall intensity is not reduced, but, energy is lost through interactions with particulates Embedded microorganisms present the real limitation Embedded microorganisms present the real limitation Precede by filtration or flocculation/sedimentation Precede by filtration or flocculation/sedimentation Absorption Coefficient Certain particles absorb at germicidal wavelengths Certain particles absorb at germicidal wavelengths Fe, sulfites, aromatic organics, humic acid, dechlorination with Sodium Thiosulfate Fe, sulfites, aromatic organics, humic acid, dechlorination with Sodium Thiosulfate Presence can greatly increase attenuation Presence can greatly increase attenuation Water Composition

20 US 1966: Dept. Health, Education & Welfare – 160 J/m : Dept. Health, Education & Welfare – 160 J/m : NY State still required 160 J/m 2 when I started working with UV 1999: NY State still required 160 J/m 2 when I started working with UV ~2000: WHO Recommends 380 J/m 2 ~2000: WHO Recommends 380 J/m : ANSI/NSF Standard 55 set at 400 J/m : ANSI/NSF Standard 55 set at 400 J/m 2 UV Regulatory Standards

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22 Estimation of Dose (Fluence) Biological Assays with Virus Biological Assays with Virus –Develop dose (fluence) inactivation relationship with Quasi Collimated Beam Apparatus –Measure Log inactivation in UV device Magnetic Stir Plate Collimating Box Concentric Apertures Petri Dish with sample and stir bar UV Bulb Manual UV Shutter Quasi Collimated UV rays Aluminum Plate Bulb Holders

23 MS2 Colifage response to UV

24 Chemical Actinometry Chemical Actinometry –Photochemical reaction rate Molecules react with UV photos Molecules react with UV photos Products of the reaction used to determine quantity of photons absorbed (dose) Products of the reaction used to determine quantity of photons absorbed (dose) Estimation of Dose

25 Dose Estimation: Point Source Summation ) INTENSITY i,j := p 4 · n ·  · RHO i,j 2 · exp–(  w ·R · RHO i,j R R Intensity x RHO y σ w = abs of water Bulb is considered a line of point sources distributing light equally in all directions Intensity at each point is calculated as the sum of all point sources

26 No known byproducts No known byproducts Short contact time (sec, instead of min) Short contact time (sec, instead of min) No danger of overdosing No danger of overdosing Ability to inactivate cyst forming organisms (e.g. Giardia, Cryptosporidium) at doses used for water treatment Ability to inactivate cyst forming organisms (e.g. Giardia, Cryptosporidium) at doses used for water treatment No transportation of hazardous chemicals No transportation of hazardous chemicals Benefits of UV

27 No residual disinfectant No residual disinfectant Photoreactivation and dark repair possible Photoreactivation and dark repair possible Bulb fouling Bulb fouling –Organic constituents, hardness, algae and biofilm on quartz sleeve Requires electricity Requires electricity Limitations  Add chlorine residual  Shield from visible light for 1-2 hrs  Overdose  Clean sleeve  Suspend bulb

28 65 cm water outlet water level Side View (transparent) G-8 germicidal UV bulb Design: ss-PVC

29 Ferro Cement UV-Tube Outlet Water Ferro cement trough Bulb Nut and Bolt Ballast Metal Cover Ferro cement cover Cable Figure 1: Cross Section and Side View of the Ferro Cement UV-Tube Inlet

30 Laboratory Testing All UV-Tube Designs Microbial Testing Microbial Testing Hydrodynamic Tracer Tests Hydrodynamic Tracer Tests Materials Degradation Testing Materials Degradation Testing Bulb Studies Cycling Cycling Warm-Up Time Warm-Up Time Constant Head Tank Flowmeter Mixing Tank with Pump UV-Tube

31 MS2 Challenge Test

32 MS2 Microbial Testing Avg: % CI: 2.98 – MS2 Fluence Response Curve

33 Rhodamine Tracer Testing Pulse input with syringe Pulse input with syringe Samples every 3 seconds Samples every 3 seconds Measure on spectrophotometer 555 nm Measure on spectrophotometer 555 nm Date 4/25/ /29/ /05/ 20055/7/2005 New Design  tbar q/tbar

34 Materials Degradation Interactions of UV-Tube Materials with UV in the presence of water… –Flow through, minimal flow. –Overnight test, 16 hours. –Vacation test, 8 days. –Total Evaporation, 35 days. Test for volatile organic compounds and metals.

35 Materials Degradation Results PVC alone  carcinogenic volatile organics PVC alone  carcinogenic volatile organics ABS alone  Benzene! ABS alone  Benzene! Galvanized steel  High zinc levels (taste) Galvanized steel  High zinc levels (taste) Lined PVC  low levels of vocs, acceptable Lined PVC  low levels of vocs, acceptable Stainless with PVC endcaps  low levels, acceptable Stainless with PVC endcaps  low levels, acceptable Copper and aluminum have not been tested. Copper and aluminum have not been tested.

36 Bulb Studies Cycling Study One cycle daily: 12 hours on, 12 hours off One cycle daily: 12 hours on, 12 hours off Four cycles daily: 3 hours on, 3 hours off Four cycles daily: 3 hours on, 3 hours off Twelve cycles daily: 1 hour on, 1 hour off Twelve cycles daily: 1 hour on, 1 hour off Warm up Study Cycling Timers Bulb Covers

37 UV Issues/Challenges Electricity requirements Electricity requirements Safety: UV exposure and electric shock Safety: UV exposure and electric shock Material interactions with UV Material interactions with UV Water depth and hydraulics (UV dose) Water depth and hydraulics (UV dose) Water Characteristics Water Characteristics –Embedded Bacteria –Fe, sulfites, aromatic organics, humic acid, & dechlorination with sodium thiosulfate absorb UV Safe storage (no residual disinfectant) Safe storage (no residual disinfectant) Bulb life Bulb life *****Dissemination ***** *****Dissemination *****

38 Important Facts: UV is bad for your eyes, skin UV is bad for your eyes, skin Turbidity, chemicals affect UV transmittance Turbidity, chemicals affect UV transmittance Bulb life is limited Bulb life is limited Water depth and hydraulics are important Water depth and hydraulics are important No residual disinfectant No residual disinfectant

39 Materials and UV-C Blocks UV: Blocks UV: –Glass –Plexiglass Transmits UV: Transmits UV: –Quartz –Teflon Reflects UV: Reflects UV: –Aluminum Reacts with UV: Reacts with UV: –PVC –ABS –Other plastics?

40 Design Features: Effective Effective –Eliminate microorganisms Portable or built in place Portable or built in place –Size, weight –Construction Simple Simple –Local materials –Simple tools

41 Design Features: Reliable Reliable –Easy operation –Little maintenance required –Long term use Cheap! Cheap! Fast (2 lpm or more) Fast (2 lpm or more) Safe Safe –NO UV Exposure –Visual cue telling if light is on or not

42 Challenges Compatible with 15 W (G15T8) or 30 W (G30T8) UV bulb Compatible with 15 W (G15T8) or 30 W (G30T8) UV bulb 12 V DC or 110 V AC ballast 12 V DC or 110 V AC ballast Flow regulation Flow regulation Filtration Filtration Uniform and optimal UV exposure Uniform and optimal UV exposure

43 The Biggest Challenge: Final production price: < $100 US


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