Rich Stummer Daman Superior LLC UltraTech UV Systems UV Topics - - PowerPoint PPT Presentation

Rich Stummer Daman Superior LLC UltraTech UV Systems

UV Topics

 History of UV  Types of UV Systems  How does UV Disinfect Wastewater  UV vs Other Disinfectant Systems  Components of UV Systems  Advantages & Disadvantages  Design Considerations  Maintenance of Systems

History of UV

 in 1878 discovered that sunlight kills microbes in

broth.

 In 1904, the first quartz lamp was developed  In 1910, the first UV system used to disinfect drinking

water

 1938 Westinghouse Electric introduced the fluorescent

gas discharge tube

 1940’s lamps and ballasts improved  Late 1970’s, US EPA discouraged use of chlorine

History of UV (continued)

• Late 1970’s, US EPA started funding research and

grants for UV systems

• 1978, full scale UV system for wastewater successfully

demonstrated at NW Bergen WWTP (Waldwick, NJ)

• 1982, modular UV system for open channel to disinfect

wastewater introduced (gravity fed system with lamps parallel to flow (horizontal)

• Use of UV for wastewater growing since 1982

A survey in 2003 by the Water Environment Federation showed that of all the respondents , 24% used UV disinfection in their wastewater treatment plants and 66 % were planning to switch to UV (Water Environment Federation 2004)

UV Systems – Early Designs

 Problems with early systems

 Replacement of bulbs, sleeves & ballasts required shut

down of system

 Poor cleaning systems  Poor/inadequate hydraulics – short circuiting  Improper cooling of ballasts – failures  Ballasts & lamps not matched – lamp failures  Difficulties in maintenance  Lack of scientific knowledge to properly size UV systems

for wastewater

UV Patents

 1972, A. Landry issued patent for water flow through

teflon tube, UV lamps surrounded tube

 1978, S. Ellner issued patent using rectangular, gravity

flow chamber with lamps perpendicular to flow with in-place chemical cleaning and UV sensors (installed in Suffern WWTP, Suffern, NY – still in use toady)

 Numerous patents since on design and features for UV

systems

Types of UV Systems

 Closed Channel UV System

Types of UV Systems

 Open Channel Vertical System

Sample Design – Vertical Modular System

60 “ Water Depth 28 Lamp 16” or 20” Wide Modules 40 Lamp 24” Wide Modules High Output UV Lamps or Long Life Standard Intensity Lamps Air Scrub Cleaning Mechanical Wiper Cleaning Chemical Cleaning (optional)

How Does UV Disinfect?

 UV light part of electromagnetic spectrum  Radiation with wavelengths between 30 and 400

nanometers (nm)

 Shorter wavelengths than visible light  Sometimes referred to as “black light” – can not be

seen by human eye

 UV spectrum divided into 3 parts

 UV-A (315 – 400 nm)  UV-B (280 – 315 nm)  UV-C

(200 – 280 nm) (UV output 254nm)

How Does UV Disinfect

 Transfer of electromagnetic energy from mercury arc

lamp to organisms genetic material (DNA and RNA)

 UV penetrates cell wall and destroys cell ability to

reproduce

 Organisms can’t reproduce and eventually die off

How Does UV Disinfect

 Wavelengths of UV

 UV-A 315 – 400 nm  UV- B 280 – 315 nm  UV - C

200 – 280 nm

 Optimum wavelength to effectively inactivate

microorganisms is range of 250 – 270 nm (UV – C)

Methods of Disinfection

 Chlorination – different forms

 Chlorine gas  Chlorine dioxide  Sodium Hypochlorite  Calcium Hypochlorite

 Ozone – Gas  Ultraviolet Light – UV Radiation

Chlorination

 Special handling and storage requirements  De-chlorination required  Low equipment costs  Corrosive  Toxic  Formation of carcinogenic by-products

(trihalomethanes)

 Requires chemical feed system  Effectiveness depends on water quality

Ozone

 Strong oxidizer, non-selective  Highest equipment costs  Short life span but still requires neutralization  Corrosive  Toxic  Requires feed gas and injection system  Effectiveness depends on water quality  High output systems require ozone off gas destruction

Ultraviolet

 No special handling  No post treatment  Moderate equipment costs  Frequent preventative maintenance cycles  Fouling can reduce effectiveness  Performance dependant on water quality

Low-Pressure vs Medium Pressure Lamps

 Low-Pressure Lamps

 Wavelength of 253.7 nm  Lengths of 0.75 and 1.5 meters with diameter of 1.5 – 2.0 cm.

 Medium-Pressure Lamps

 15-20 times germicidal UV intensity of low-pressure lamps  Disinfect faster  Greater penetration capacity  Operate at higher temperatures; higher energy consumption

Components of UV System

 Mercury Arc Lamps – pressure refers to pressure inside

lamps; intensity refers to energy output

 Low-pressure Low-intensity (lp-li)  Low-pressure High-intensity (lp-hi)  Medium-pressure High-intensity (mp-hi)

 Reactor  Ballasts

Low-Pressure Low-Intensity Lamps

 Most energy efficient for UV disinfection  Operating temperature is 40 – 60 degrees Celsius  Lamps contain mercury vapor and argon gas  Emits nearly monochromatic radiation  About 85% of emissions are at 253.7nm – peak

germicidal effectiveness

 Emit approximately 0.2 germicidal watts per

centimeter arc length (W/cm)

Low-pressure High intensity

 Operating temperature of 180 – 200 degrees celsius  Emits broader, polychromatic radiation therefore less

efficient than lp-li

 High-intensity = higher capacity : requires fewer lamps  Germicidal output 13 W/cm  Lamp costs 3+ times cost of lp-li

High-pressure High intensity

 Operating temperature of 600 – 800 degrees celcius  Emits broader, polychromatic radiation therefore less

efficient than lp-li

 High-intensity = higher capacity : requires fewer lamps  Germicidal output 16 W/cm  Lamp costs 5 times cost of lp-li  Power costs about 4 times higher than lp-hi

High-intensity or Low-intensity

 Low-intensity best suited for smaller systems  High-intensity best suited for larger systems  Example : Southtowns WWTP 16 MGD  The lp-li system is not considered cost effective at the

large flow rates experienced at the Southtowns WWTP because of the number of lamps required. The lp-li alternatives would require approximately 2,160 lamps, while the lp-hi system would need 360 lamps (6 times less) and the mp-hi alternative would need 176 lamps (12 times less).

Horizontal UV System

 Utilized when channel depth too shallow for vertical

system

 Electrical connections under water  Disinfecting area limited to arc length of UV lamp  Rack must be removed from channel and underwater

seal disassembled to change UV lamp

 Lamp change takes 10 minutes

Vertical UV System

 Requires channel depth of at least 60”  All electrical connections above water  Flow perpendicular – area of UV energy expanded  Lamps changed without removing module from

channel

 Lamp change takes 15 seconds

Example

 UV System with 300 lamps  Horizontal system would take 50 hours of labor to

change lamps

 Vertical system would take 1 hour and 25 minutes to

change lamps

UV Dosage Comparison

 UV Dosage is a function of the UV Intensity times

the Contact Time

 Engineer should require suppliers to provide

 UV output of specific lamp  Number of UV lamps  Contact time at maximum flow rate

 (# of UV lamps) x (UV output) = Total UV watts in

system

 (Total UV watts) x (contact time) = UV Watt

Seconds

EXAMPLE

 Mfg X proposes 98 UV lamps  Output of 65 watts (at 254nm)  Contact time of 12 seconds  98 x 65 =6,370  6,370 x 12 = 76,440  This system rates at 76,440 watt seconds  Contact Time is cheaper than Intensity  Since no harm in over dosing, design of 2-3 times

minimum dose is common

Understanding UV Disinfection

 Terms

 Ultraviolet Dose  Collimated Beam Test  UV Lamp Life  UV Lamp Description  UV Lamp Comparisons

Ultraviolet Dose

 UV Dose = Intensity x Time expressed in

uWattseconds/cm2, Mwattseconds/cm2 or Jewels

 Problem – UV Transmittance of effluent impact on

true UV dose; “average” UV intensity; “average” contact time; hydraulics

 Solution – Bioassay – performance based validation

(Delivered Dose is actual dose received by targeted

• rganism)

Collimated Beam Test

 Test conducted with MS2 phage in solutions of

effluent will indicate the additional contact time to achieve specific levels of disinfection

 Does not provide information relating to actual UV

dose

UV Lamp Life

 UV lamps will continue to provide the same amount of

visible light after the germicidal output has diminished below safe disinfecting levels (solarization of the lamp glass)

 Effective Lamp Life – where UV output has diminished

to 70% of the new lamp output after 100 hours of

• peration

 Lamp Life is not the number of hours of operation

until the lamp goes out

UV Lamp Life (cont.)

 Lamp Manufacturer Certification for operating hours

possible before UV output drops to 70% of new lamp after 100 hours of operation

 Specify intensity @254nm since polychromatic

medium pressure UV lamps have different operating hours for specific wave lengths

 Drop off in UV intensity @254nm is quicker than other

wavelengths produced by polychromatic medium pressure lamps

UV Lamp Descriptions

 “Low Pressure Lamp”

 Monochromatic UV  Output primarily 254nm  30-40% of input energy converted to UV @254nm  Available in lengths 8”-64”, 8 watts to 300 watts

 “Medium Pressure Lamp”

 Polychromatic UV 200nm to 700nm, higher pressure &

temps than Low Pressure Lamps

 5-7% of input energy converted to UV@254nm

UV Lamp Descriptions (cont.)

 Parameters for describing UV Lamps

 Lamp Grouping – Medium or Low Pressure  Lamp Length  Lamp Diameter  Electrical input  UV output @ 254mm  Manufacturer’s lamp life certification  Source of Lamps (proprietary?)  Size of quartz jacket  Wall thickness of quartz jacket

UV Lamp Descriptions (cont.)

 Eliminate Misleading Data

 “It is possible to inactivate cryptosporidium with

medium pressure UV but not with low pressure UV.” UV dose is UV dose regardless of lamp used.

 “One medium pressure lamp will replace 6 low pressure

lamps.” What is electrical input and UV output @254nm, what is lamp length, diameter, etc.

 You could claim 1 fluorescent lamp could replace 300

incandescent lamps if we compare an 8’ fluorescent lamp with a .5 watt flashlight incandescent lamp

UV Lamp Comparisons

 Industry Standard in G64T5 low pressure lamp

 58” arc length  5/8” diameter  65 watt electrical input  26.5 UV output @ 254nm  Effective lamp life – 10,000 hours

 Manufacturer “X” claims his lamp will replace 10

standard UV lamps

 Require Manufacturer “X” to set up pilot demonstrating

claim – compare actual results

Conclusions

 UV dose should only refer to actual dose determined

by Biassay

 UV dose should only be expressed in uWatt

seconds/cm2

 Bioassay protocol employ universal standards

 MS2 phage  Buffered sterile distilled water titer  1 cm depth in petri dish  Phage concentrations of 1,000,000/ml  Minimum 3 flow rates & 3 separate runs for each

Conclusions (cont.)

 Effective Lamp Life - # of hours of operation until lamp

• utput @ 254nm drops to 70% of output of new lamp after

100 hours operation

 UV Lamp Description to include

 Lamp grouping  Lamp dimensions  Electrical input  UV output at 254nm only  Manufacturers who produce lamp  Dimensions of quartz jacket – diameter & wall thickness  Claims to UV Lamp reductions based on side by side test

Source of Information

 Let’s Take the Mystery Out of UV Design

 Abstract published by WEF  Author – Sidney Ellner, Technical Director for UltraTech

Systems, Inc.

Reactors

 Contact Reactor –Lamps with quartz sleeve, placed in

wastewater stream

 Parallel or Perpendicular to flow  Flap gates or Weirs control wastewater flow  Ballast provides starting voltage and maintains continuous

current

 Non-Contact Reactor – Lamps suspended outside

transparent conduit

 Conduit carries wastewater to be disinfected  Ballast provides starting voltage and maintains continuous

current

Contact Reactors

Ballasts

 Ballasts must be compatible with lamps  Should be ventilated

 Over heating shortens life of ballast  Over heating can cause fire

Life Cycle of Components

 Lamps – average life of 8,760 to 14,000 hours

 Cycling on/off reduces efficacy of lamp  Usually replaced after 12,000 hours

 Ballast – average life 10 to 15 years

 Usually replaced after 10 years

 Quartz Sleeves – average life 5 to 8 years

 Usually replaced every 5 years

Advantages of UV

 Effective at inactivating most viruses, spores and cysts  Physical process rather than chemical – not handling

• r storing hazardous/corrosive chemicals

 No residual effect  User friendly for operators  Shorter contact time (20 – 30 seconds for lp-li)  Smaller footprint for equipment

Disadvantages

 Low dosage may not inactivate some viruses, spores

and cycts

 Organisms can sometimes repair and reactivate -

Photoreactivation

 Preventative maintenance program necessary to

control fouling of tubes

 Turbidy and Total Suspended Solids (TSS) can render

UV disinfection ineffective

 UV disinfection not as cost effective as chlorination

until dechlorination and costs of meeting fire codes included

Transmittance

 UV transmittance represents the percentage of UV

energy in the water that reaches the microorganisms. The lower the transmittance, the lower the amount of UV light that reaches the microorganism. UV transmission is dependent on the spacing of lamps and the water quality of the liquid. The water quality characteristics that affect transmittance include iron, hardness, suspended solids, humic materials and

• rganic dyes.

Photoreactivation, Nucleotide Excision Repair (NER) and Recombination Repair

 Cell’s ability to repair damage from UV once light is

removed

 All mechanisms performed by enzymes – affected by

temperature, pH and ionic strength

Design Characteristics

 Flow Rate  Reactor Design  Suspended and Colloidal Solids (microscopic solids

suspended in liquid – milk)

 Initial Bacteria Density  Footprint of Equipment

Reactor Design

 Channel design

 Short circuiting, dead zones

 UV dose required

 Suspended and colloidal solids  Bacterial density

 Flow – prevent “short circuiting”

 Prevent particle “shading”  Eliminate “dead zones”

 Ensure proper contact time

 Lamp fouling, scaling

Design Considerations

 Plug Flow – flow is in one direction with little or no

mixing or turblence.

 Reynolds Number – high number = turbulent flow;

low number = smooth flow

 Turbulent flow is desired (Reynold’s Number above

5,000) – reduces occurrance of “particle shading”

Operation and Maintenance

 UV Light Process Training Highlights  Recommended Typical Maintenance Activity for UV

Processes

 Process Checks  Electrical Checks  Michanical Checks

UV Light Process Training Highlights

 Design Flows and Characteristics  Alarm Systems  Mechanical Checks  Electrical Checks  Control Logic for Programmable Logic Controller  Replacement of Basic Components

Recommended Typical Maintenance Activities for UV Processes

 Check on-line UV transmittance analyzer calibration

(weekly)

 Cheek sleeves and wipers for leaks (monthly)  UV intensity calibration check (monthly)  Check cleaning efficiency (monthly)  Check cleaning fluid reservoir (semiannually)  Test-trip ground fault interrupt breakers (annually)

Recommended Typical Maintenance Activities for UV Processes

 Replace lamps (mfg recommendation)  Check flowmeter calibration (mfg recommendation)  Properly dispose of lamps (when changed)  Properly dispose of quartz sleeves (when changed)  Clean and calibrate transmittance monitor (mfg

recommendations)

Process Checks

 Effluent Transmittance  Effluent total suspended solids concentration  Ultraviolet spectra  Effluent color  Industrial dischargers  Algae  Iron/manganese/hardness  Microbial testing procedures

Electrical Checks

 Lamps are energized  Lamps are connected  Useful lamp life  Ballast output

Mechanical Checks

 Cleaning system to ensure acceptable performance  Proper delivery of chemical  On-line transmittance measurements  On-line intensity measurements  Flowmeter calibration  Ballasts closed loop-cooing system

Altoona Water Authority Wastewater Division

 Chlorine System – 1991

 Stored chlorine onsite – 2,000# canisters  80-150# added daily to chlorine tank  Effluent with residual chlorine threatened aquatic life  Exposure risk for employees – several times workers

forced to wear protective breathing equipment due to toxic leaks

Altoona Water Authority Wastewater Division

 UV System Installed in December 1991 – Ultraviolet

Purification Systems

 2 horizontal stainless steel reactors installed  Each reactor contains 348 UV lamps, 2 banks  1 reactor handles flows of 10 MGD  Alarm activated if lamp burns out or intensity drops

below effective range

 UV unit can be remotely operated

Altoona Water Authority Wastewater Division

 Results

 Environmentally responsible, convenient and cost

effective solution for disinfecting wastewater discharge

 Performance equal to chlorine  Effluent meets NPDES permit requirements  Local aquatic life protected  Reduced worker exposure to chlorine gas

Altoona Water Authority Wastewater Division

 Advantages

 Safety – no hazardous chemicals  Simplified compliance - easier compliance with NPDES

permit requirements and Fire Code regulations

 Reduced Effluent Toxicity – no residue discharged  Maintenance & Cleaning – lamp jackets cleaned twice a

month; jackets cleaned 3 times a year; lamps replaced after 7,500 hours use

 Reliability – in-place cleaning, system detects decreased

UV intensity

Acknowledgments

 The History of UV and Wastewater by G. Elliott

Whitby1,2 and O. Karl Scheible3

 Evaluation of Ultraviolet (UV) Radiation

Disinfection Technologies for Wastewater Treatment Plant Effluent by New York State Energy Research and Development

 Evaluation of Disinfection Units for Onsite

Wastewater Treatment Systems by Center for Environmental and Water Resources Engineering

Acknowledgments (cont.)

 Wastewater Technology Fact Sheet Ultraviolet

Disinfection by US EPA 832-F-99-064

 Ultraviolet Disinfection by US EPA WWFS0M20  Abstract – Let’s Take the Mystery Out of UV Design by

Sidney Ellner, Technical Director UltraTech Systems, Inc.