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UV For Developing Countries. A new tool for the disinfection toolbox?. UV Disinfection. Prof. Bill Larsen’s system. First UC Berkeley UV Tube. Next Model. Sri Lankan Neighborhood Scale Installation. B9 Plastics Better Water Maker. Ultra-Violet Light. UVA (315 – 400 nm): sun tans

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Uv for developing countries

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


Uv for developing countries

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.


Uv for developing countries

Poly-alum added

Sedimentation

Lake Ontario

Gravel, sand, and GAC filters

Chlorine residual added

Storage

UV

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.


Uv system components
UV System Components

  • UV Bulbs and Ballast (AC or DC)

    • Mercury-argon lamps (an electrical arc ignites the mercury vapor which emits UV light)

    • Hopefor LEDs in the future…

  • Chamber

  • Quartz Sleeve

    • passes UV

    • maintains bulb temperatures

  • Sensor

    • to monitor bulb output

  • Cleaning Mechanism


Mercury vapor bulbs
Mercury Vapor Bulbs

  • Like florescent bulbs except:

    • Quartz not glass

    • No phosphor coating

  • 88% of the output at 253.7 nm

  • Lamp is susceptible to cooling by the effluent

  • Limited Lamp Life—1 year continuous operation


Uv for developing countries

Determining Dose (Fluence)

Dose (Fluence) = Intensity * Exposure Time

(J/m2) (W/m2) (s)

Function of bulb and water characteristics

Function of hydrodynamics

&

Geometry of reactor


Uv for developing countries

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

99.999% inactivated, 0.001% surviving


Uv for developing countries

?

and imbedded bacteria

A More Complicated Response

  • Explanation of Shoulder

  • Threshold of DNA “hits” to inactivate?

  • Reactivation?

  • Explanation of Tailing

  • “Shielding” depends on particle absorbance

  • Imbedded bacteria

  • UV resistant bacteria


Water composition
Water Composition

Turbidity

  • Can lead to scattering, reflection, blocking of microorganisms by particles

  • Considered negligible up to 5 NTU

  • Theoretically, overall intensity is not reduced, but, energy is lost through interactions with particulates

  • Embedded microorganisms present the real limitation

  • Precede by filtration or flocculation/sedimentation

    Absorption Coefficient

  • Certain particles absorb at germicidal wavelengths

  • Fe, sulfites, aromatic organics, humic acid, dechlorination with Sodium Thiosulfate

  • Presence can greatly increase attenuation


Uv regulatory standards
UV Regulatory Standards

US

  • 1966: Dept. Health, Education & Welfare – 160 J/m2

  • 1999: NY State still required 160 J/m2 when I started working with UV

  • ~2000: WHO Recommends 380 J/m2

  • 2002: ANSI/NSF Standard 55 set at 400 J/m2


Estimation of dose fluence

Bulb Holders

UV Bulb

Aluminum Plate

Collimating Box

Concentric Apertures

Quasi Collimated UV rays

Manual UV Shutter

Petri Dish with sample and stir bar

Magnetic Stir Plate

Estimation of Dose (Fluence)

  • Biological Assays with Virus

    • Develop dose (fluence) inactivation relationship with Quasi Collimated Beam Apparatus

    • Measure Log inactivation in UV device



Estimation of dose
Estimation of Dose

  • Chemical Actinometry

    • Photochemical reaction rate

      • Molecules react with UV photos

      • Products of the reaction used to determine quantity of photons absorbed (dose)


Dose estimation point source summation

p

R

H

O

i

,

j

I

N

T

E

N

S

I

T

Y

:

=

·

e

x

p

(

s

·

R

·

w

i

,

j

2

R

p

4

·

n

·

·

R

H

O

i

,

j

x

R

RHO

σw= abs of water

Intensity

y

Dose Estimation: Point Source Summation

)

  • 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


Benefits of uv
Benefits of UV

  • No known byproducts

  • Short contact time (sec, instead of min)

  • No danger of overdosing

  • Ability to inactivate cyst forming organisms (e.g. Giardia, Cryptosporidium) at doses used for water treatment

  • No transportation of hazardous chemicals


Limitations
Limitations

Add chlorine residual

  • No residual disinfectant

  • Photoreactivation and dark repair possible

  • Bulb fouling

    • Organic constituents, hardness, algae and biofilm on quartz sleeve

  • Requires electricity

  • Shield from visible light for 1-2 hrs

     Overdose

  • Clean sleeve

  • Suspend bulb


Design ss pvc

Side View

(transparent)

65 cm

water outlet

G-8 germicidal UV bulb

water level

Design: ss-PVC


Ferro cement uv tube

Figure 1: Cross Section and Side View of the Ferro Cement UV-Tube

Cable

Ballast

Ferro cement cover

Nut and Bolt

Metal Cover

Bulb

Ferro cement trough

Inlet

Water

Outlet

Ferro Cement UV-Tube


Laboratory testing

Constant Head Tank UV-Tube

Flowmeter

UV-Tube

Mixing Tank with Pump

Laboratory Testing

All UV-Tube Designs

  • Microbial Testing

  • Hydrodynamic Tracer Tests

  • Materials Degradation Testing

    Bulb Studies

  • Cycling

  • Warm-Up Time


Ms2 challenge test
MS2 UV-TubeChallenge Test


Ms2 microbial testing
MS2 Microbial Testing UV-Tube

MS2 Fluence Response Curve

Avg: 4.38

95% CI: 2.98 – 5.77

643

967

1292


Rhodamine tracer testing
Rhodamine Tracer Testing UV-Tube

  • Pulse input with syringe

  • Samples every 3 seconds

  • Measure on spectrophotometer 555 nm


Materials degradation
Materials Degradation UV-Tube

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.


Materials degradation results
Materials Degradation Results UV-Tube

  • PVC alone  carcinogenic volatile organics

  • ABS alone  Benzene!

  • Galvanized steel  High zinc levels (taste)

  • Lined PVC  low levels of vocs, acceptable

  • Stainless with PVC endcaps  low levels, acceptable

  • Copper and aluminum have not been tested.


Bulb studies

Bulb Covers UV-Tube

Cycling Timers

Bulb Studies

Cycling Study

  • One cycle daily: 12 hours on, 12 hours off

  • Four cycles daily: 3 hours on, 3 hours off

  • Twelve cycles daily: 1 hour on, 1 hour off

    Warm up Study


Uv issues challenges
UV Issues/Challenges UV-Tube

  • Electricity requirements

  • Safety: UV exposure and electric shock

  • Material interactions with UV

  • Water depth and hydraulics (UV dose)

  • Water Characteristics

    • Embedded Bacteria

    • Fe, sulfites, aromatic organics, humic acid, & dechlorination with sodium thiosulfate absorb UV

  • Safe storage (no residual disinfectant)

  • Bulb life

  • *****Dissemination *****


Important facts
Important Facts: UV-Tube

  • UV is bad for your eyes, skin

  • Turbidity, chemicals affect UV transmittance

  • Bulb life is limited

  • Water depth and hydraulics are important

  • No residual disinfectant


Materials and uv c
Materials and UV-C UV-Tube

  • Reflects UV:

    • Aluminum

  • Reacts with UV:

    • PVC

    • ABS

    • Other plastics?

  • Blocks UV:

    • Glass

    • Plexiglass

  • Transmits UV:

    • Quartz

    • Teflon


Design features
Design Features: UV-Tube

  • Effective

    • Eliminate microorganisms

  • Portable or built in place

    • Size, weight

    • Construction

  • Simple

    • Local materials

    • Simple tools


Design features1
Design Features: UV-Tube

  • Reliable

    • Easy operation

    • Little maintenance required

    • Long term use

  • Cheap!

  • Fast (2 lpm or more)

  • Safe

    • NO UV Exposure

    • Visual cue telling if light is on or not


Challenges
Challenges UV-Tube

  • Compatible with 15 W (G15T8) or 30 W (G30T8) UV bulb

  • 12 V DC or 110 V AC ballast

  • Flow regulation

  • Filtration

  • Uniform and optimal UV exposure


The biggest challenge
The Biggest Challenge: UV-Tube

Final production price:

< $100 US


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