CHOOSING THE RIGHT UV SYSTEM FOR DISINFECTION OF MUNICIPAL DRINKING WATER

Transcription

1 CHOOSING THE RIGHT UV SYSTEM FOR DISINFECTION OF MUNICIPAL DRINKING WATER

2 QUESTIONS TO ASK WHEN SELECTING A UV SYSTEM 1. What validation is required? (i.e. what would the regulatory jurisdiction require?) 2. What is your water source? Surface or groundwater? 3. What is your flow rate? 4. What is your target contaminant? 5. What is your priority: low energy or low maintenance? Both? 6. Do you expect to have fouling? 7. What is your UV transmittance?

3 OVERVIEW OF UV SYSTEMS

4 WHAT IS UV LIGHT? Ultraviolet (UV) light is invisible to the human eye UV is comprised of electromagnetic radiation of wavelengths ranging from 10 nm to 400 nm Certain wavelengths of UV light are germicidal

5 HOW DOES UV DISINFECT? UV light penetrates the cell wall UV Energy The UV energy permanently alters the DNA structure of the microorganism Cell Wall The microorganism is inactivated and unable to reproduce or infect DNA Nucleic Acid

6 UV LAMPS: HOW DO THEY WORK? 1. Power is applied to the lamp electrodes 2. Ionized gas conducts electricity 3. Mercury in lamp converts to a gaseous state 4. Mercury gas conducts electricity and completes circuit 5. Mercury excitation results in the release of UV photons

7 TYPES OF UV LAMPS Three (3) distinct types of UV lamps used for municipal drinking water applications Low-Pressure (LPLO) Low-Pressure, High-Output (LPHO) Medium-Pressure, High-Output (MP) Characterized by the mercury vapor pressure inside the lamp and the nature of UV energy they produce

8 LOW PRESSURE AND LOW PRESSURE HIGH-OUTPUT LAMPS Low Pressure Lamps (LPLO) Low Pressure High Output Lamps (LPHO) Differentiated from TrojanUV Solo Lamp - Very High Output Lamps (VHO) Monochromatic spectral emission (single wavelength output at 254 nm) Variable output: 60 to 100 % Specifications (Standard LPHO lamp): Guaranteed Lamp Life: 12,000 hours EOLL: (lamp-dependent) Lamp Length: 58 Power Consumption: 250 W

9 LOW PRESSURE HIGH-OUTPUT LAMPS Absorbance Spectrum of Microbial DNA Emission Spectrum of LPLO and LPHO UV Lamps Wavelength of Light (nm)

10 MEDIUM PRESSURE LAMPS Polychromatic spectral emission Variable output capability 30 to 100 % Electrical efficiency: 12% to 17% Specifications: Lamp Life: 5,000 to 9,000 hours EOLL: Lamps Length: 12, 24, 30 Power Consumption: 2.9 kw, 9.1 kw, 12.5 kw

11 MEDIUM PRESSURE LAMPS Absorbance Spectrum of Microbial DNA Emission Spectrum of MP UV Lamps Wavelength of Light (nm)

12 UV LAMP SUMMARY LOW PRESSURE LAMPS Low Energy Higher Efficiency More Lamps Required MEDIUM PRESSURE LAMPS High Energy Lower Efficiency Less Lamps Required UV users seek both high efficiency and low lamp count

13 TROJAN UV SOLO LAMP TECHNOLOGY TrojanUV Solo Lamp (1,000W) High efficiency lamp, 254 nm output Over 6 years lab & field testing Guaranteed 15,000 hour lamp life Lamp dimming from 100 to 30% Solo Lamp delivers both high efficiency and low lamp count

14 TROJANUV SOLUTIONS FOR DRINKING WATER LP and LPHO Lamps Automatic mechanical wiping (optional) DVGW and USEPA validation Medium Pressure Lamps Compact (up to 30 flange) USEPA validation TrojanUV Solo Lamp High electrical efficiency Large-capacity reactor (48 flange) USEPA validation

15 ALL UV REACTORS HAVE SIMILAR BASIC COMPONENTS Control / Power Panel Interconnecting Cable UV Reactor

16 UV REACTOR COMPONENTS - CONTINUED 1. Stainless steel reactor chamber with flanges 2. UV lamps 3. Quartz sleeves 4. Cleaning system 5. UV sensors

17 UV LAMPS AND SLEEVES UV lamps produce germicidal UV energy Quartz sleeves house the UV lamps and protect them from water Quartz is used because it has a high UV transmittance

18 UV SENSORS Sensors are installed to monitor several parameters: UV Intensity Temperature Water level Types of UV intensity sensors: Duty sensors Reference sensors (used in calibration) Two possible sensor locations: Wall-mounted (shown) Internal

19 WALL-MOUNTED UV INTENSITY SENSOR

20 INTERNALLY-MOUNTED UV INTENSITY SENSOR Installed in a similar way as a UV lamp Multiple viewing windows on sensors allows monitoring of multiple lamps

21 UV SYSTEM COMPONENTS CONTROL PANEL Function: 1. Power distribution 2. Houses drivers (ballasts) 3. Operator interface 4. Modem connection 5. SCADA connection

22 UV CONTROL PANEL COMPONENTS Drivers (Ballasts) Control the amount of power transferred to UV lamps HMI (Display) Local operator interface at the reactor Facilitates local control Provides operational information (lamp status, dose, etc.) PLC (Controller) Automatically adjusts system performance based on information provided from sensors and other instruments (e.g. flow meter)

23 UV CONTROL PANEL - FRONT Disconnect Operator Interface

24 UV CONTROL POWER PANEL - OPEN Power Panel Control Panel PLC Communications & Discrete Contacts Electronic Ballasts

25 WHAT AFFECTS SYSTEM CHOICE?

26 WHAT AFFECTS SYSTEM CHOICE? UV VALIDATION Regulatory requirements may influence the choice of UV system Regulatory requirements vary by geography Different countries Different states/provinces/regions UV systems are validated for specific regulatory requirements Need validation according to EPA? Select TrojanUVSwift Select TrojanUVSwift SC Select TrojanUVTorrent Need DVGW? Select TrojanUVSwift SC

27 WHAT AFFECTS SYSTEM CHOICE? SOURCE WATER Groundwater and Surface water tend to have different water quality Groundwater Tends to be relatively higher UVT Lower potential for fouling due to lower organics content Regulatory requirements are often different (e.g. Groundwater Rule) Plants tend to be smaller, un-manned Surface Water Tend to be larger, manned facilities Tends to be relatively lower UVT Can have higher concentrations of organic matter that lead to higher fouling potential

28 WHAT AFFECTS SYSTEM CHOICE? TARGET CONTAMINANT Validated Treatment of: Virus Bacteria Cryptosporidium Giardia Validated Treatment of: Bacteria Cryptosporidium Giardia Validated Treatment of: Bacteria Cryptosporidium Giardia

29 WHAT AFFECTS SYSTEM CHOICE? FOULING POTENTIAL Each lamp is contained within a protective quartz sleeve: protects lamp from direct water contact Quartz: high UV Transmittance Surface of the quartz tubes can foul Sleeves should be cleaned regularly to ensure optimum disinfection Fouled Quartz Sleeve

30 MAINTAINING QUARTZ SLEEVES - FOULING Fouling can occur from deposition of material on the outside of the sleeve due to elements in the water Water quality parameters influencing fouling: Iron (site specific but concentrations as low as 150 ppb can lead to increased fouling) Calcium, magnesium, aluminum Other inorganics Organics Fouling is difficult to predict based on water quality data

31 MAINTAINING QUARTZ SLEEVES - FOULING Quartz sleeves need to be cleaned periodically in order to prevent fouling and maintain proper UV transmittance and system performance Methods of cleaning quartz sleeves include: 1. Manual (by hand) 2. Mechanical 3. Dual Action (Chemical-Mechanical) Manual sleeve cleaning involves taking the system offline, removing the lamps and sleeves and using chemicals and detergents to clean sleeves

32 MECHANICAL CLEANING Rubber wipers move along sleeves providing physical removal of organic material, algae and other constituents Over time, may need to augment with chemical cleaning Cleaning occurs while system is online Sleeve Nut Motor

33 DUAL ACTION CLEANING SYSTEMS - ACTICLEAN Highly-effective combination of food grade cleaning gel and mechanical action Operates while disinfecting, minimizing the downtime Reduces power consumption Available with TrojanUVSwift and TrojanUVTorrent systems

34 DESIGN CONSIDERATIONS WATER QUALITY UV Transmittance (UVT) High UVT Low UVT The ratio of light entering the water to that exiting the water Typically expressed as a % through 1 cm of water

35 TYPICAL UV TRANSMITTANCE Filtered Surface Water: 85 95% Unfiltered Surface Water: 80 95% Groundwater: 90 98% Secondary Wastewater: 50 70% Can be monitored using a bench-top or online UV transmittance monitor (e.g Trojan OptiView UVT monitor option) Reactor adjusts power level automatically according to UVT value

36 LAMP AGING End-of-lamp-life (EOLL) value: the fraction of UV light emitted from aged lamps compared to the fraction emitted from new lamps Measured by a radiometer with lamp operated on a test stand Considered in design to ensure UV system performs throughout the lamp s life Typical values Medium pressure: Low pressure, high output:

37 INSTALLATION & OPERATION OF UV

38 INSTALLING AND OPERATING A UV REACTOR Once an appropriate system is selected it must be installed appropriately and monitored to ensure optimum performance This involves proper: Installation and start-up of the UV system Operation and dose monitoring of the UV system in response to changing water conditions Maintenance and replacement of UV system components Reporting on system status to regulators in accordance with local regulations

39 VALIDATION AND INSTALLATION HYDRAULICS USEPA (Recommended): flow profile through the reactor in the water plant should be better than the flow profile during validation UVDGM outlines 3 options: 1. WTP installation straight pipe equals that at validation, plus 5 upstream straight pipe diameters 2. Exact match for 10 upstream and 5 downstream pipe diameters 3. Velocity profiling within 20 percent Validation Configuration: WTP Configuration: DVGW allows an elbow immediately upstream

40 SYSTEM OPERATION The operational interface provides up-to-date information on system performance A well-automated installation requires minimal operator attention

41 SYSTEM OPERATION A UV system monitors performance and can be set up to automatically adjust operation in response to changes in: UVT, resulting from: Source water changes Upstream treatment process changes Flow rate Diurnal Seasonal Fouling of Quartz Sleeves Lamp aging

42 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec % UVT Flow Rate (MGD) SYSTEM OPERATION FLUCTUATIONS IN WATER PARAMETERS Dose pacing ensures that as water quality and demand fluctuates, the optimal UV dose is delivered to the water 90 Average Flow Rate Water Quality

43 REPORTING Periodic operation reports are generally required by regulatory bodies Included information varies by state Percentage of water treated at offspecification is a common requirement UV system provides information to enable calculation of off-spec water

44 OFF-SPECIFICATION The UVDGM describes off spec operation (Section 3.5.2) as: UV intensity below setpoint A flow rate higher than validated range A UVT lower than validated range In the U.S., a common requirement is that no more than 5% of water treated per month be during off-spec events Off-spec events are detected by the UV system and are signaled by built in alarm systems

45 UV OXIDATION FOR CONTAMINANT TREATMENT

46 WATER QUALITY GLOBAL TRENDS Contaminants are being detected regularly in the water supply Many regulators are now requiring routine testing of chemicals that were virtually unknown just a few years ago (e.g. nitrosamines by California DPH & UCMR 2) Supplies are tightening as population increases and water sources are more heavily tapped

47 GROWING APPLICATIONS OF UV-OXIDATION FOR ECT Drinking Water Contaminated groundwater or surface water sources Indirect/Direct Potable Reuse (IPR) Wastewater treated to drinking water quality Groundwater Remediation Plume containment, site cleanup Total Flow Rate for Trojan Municipal UV-Oxidation Projects in: 2000: <10 MGD (38 MLD) vs. 2012: >600 MGD (2.3 BLD)

48 UV-PHOTOLYSIS Chemical Bonds are Broken by UV Light

49 UV-OXIDATION Hydroxyl radical Hydrogen peroxide Chemical bonds are broken by hydroxyl radicals

50 UV-Photolysis/UV-Oxidation Contribution to Total Contaminant Reduction (relative to NDMA) PHOTOLYSIS + OXIDATION - CONTAMINANT DESTRUCTION BALANCE UV Oxidation UV Photolysis NDMA Atrazine Geosmin Microcystin-LR

51 TASTE & ODOR TREATMENT USING UV-OXIDATION Seasonal occurrence in surface waters (earthy/musty T&O: MIB & geosmin) MIB and geosmin are very difficult with conventional technologies More UV is required for T&O Control than for Disinfection For T&O event turn on more UV light and inject hydrogen peroxide Alliance, OH local example using UV-Ox approach

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53 ENVIRONMENTAL CONTAMINANT TREATMENT PRODUCTS

54 UV FOR VIRUS TREATMENT

55 UV FOR VIRUS TREATMENT Many jurisdictions require treatment for viruses UV hasn t been considered a viable treatment technology (reasons later) Chlorine used for virus treatment in many cases, but there are limitations Water providers want alternatives/options to chemical use

56 REGULATORY REVIEW Groundwater Rule requires 4-log reduction of virus if indicators detected Adenovirus was the basis of virus definition in LT2ESWTR, UVDGM New pic needed Adenovirus is relatively resistant to UV Led to UV dose requirement for 4-log inactivation of 186 mj/cm 2 Other viruses are less resistant

57 ADENOVIRUS IS RELATIVELY RESISTANT COMPARED TO OTHERS 186 mj/cm 2 includes add l safety factor 36 mj/cm 2 treats other viruses

58 COMPARISON OF SURROGATES

59 Why UV for Virus?

60 WHEN CUSTOMERS DON T WANT HIGHER CHLORINE Increasing CT for virus either means increasing: Storage/contact time Chlorine concentration With existing distribution systems, increasing chlorine is an obvious step Increasing chlorine leads to: Chemical, chlorinous taste Higher cost associated with additional chemicals Potential disinfection by-product formation UV enables 4-log virus compliance without increasing chlorine concentrations

61 WHEN THE FIRST CUSTOMER IS CLOSE TO THE PLANT In many existing systems, the first customer is close to the plant This compliance point for CT, may be too close to achieve required CT Solutions include: Looping piping underground Larger storage tank Can lead to: High construction costs Destruction of property UV enables 4-log virus compliance without digging/tank construction

62 WHEN TANK EXPANSION IS NOT AN OPTION Expanding the tank is not always an option due to: Footprint/site constraints Cost Aesthetic issues due to larger, more visually prominent tank UV enables 4-log virus compliance without tank expansion

63 WHEN AMMONIA IS PRESENT Ammonia in water in leads to formation of chloramines when free chlorine is added Ammonia in source water can come from: Fertilizer application Runoff from animal feed lots Manufacturing of fibers, plastics, explosives, paper, and rubber Some geographies have consistently high background ammonia If ammonia is present in source water, chloramines formed are ineffective for virus treatment UV enables 4-log virus compliance in the presence of source-water ammonia

64 SUMMARY UV disinfection is now an established & approved technology for a wide-range of applications: Disinfection credits for surface water treatment Contaminant removal including taste and odor compounds 4-log virus removal for groundwater treatment Multiple installations exist in OH and across North America

65 Represented in Southern Ohio by: The Henry P. Thompson Company Tel. (513) Represented in Northern Ohio by: Pelton Environmental Products Tel. (440) John Faber Regional Manager Trojan Technologies