4th ARSCP UV Presentation

UV BASICS: 

UV BASICS

INTRODUCTION ULTRAVIOLET (UV) LIGHT: 

Categories of UV Light UV light is comprised of electromagnetic radiation of wavelengths ranging from 10 nm to 400 nanometers (nm) UV-A (Long Wave UV): 315-400 nm UV-B (Middle Wave UV): 280-315 nm UV-C (Short Wave UV): 200-280 nm Vacuum UV: 10-200 nm Note: 1 nm = 10-9 m = 10 Angstroms (one billionth of a meter) INTRODUCTION ULTRAVIOLET (UV) LIGHT

INTRODUCTION ULTRAVIOLET (UV) LIGHT: 

INTRODUCTION ULTRAVIOLET (UV) LIGHT Beyond violet Ultraviolet means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelength of visible light Ultraviolet (UV) light is electromagnetic radiation UV light has a wavelength shorter than that of visible light, but longer than that of soft X-rays. It is invisible to the human eye Categorized by wavelength UV can be subdivided based on its wavelength, as measured in nanometers. It is typically divided into near UV (200-380nm) and extreme or vacuum UV (10-200nm) The sun is the greatest source of UV light The sun emits ultraviolet light in both near UV and vacuum UV wavelengths, but because of absorption in the atmosphere's ozone layer, 99% of the ultraviolet light that reaches the Earth's surface is 315-380nm (referred to as UV-A)

UV LIGHT ADVANTAGES: 

UV LIGHT ADVANTAGES Fast acting Application of UV light triggers a reaction almost instantly No disinfection byproducts UV light does not result in the creation of harmful disinfection byproducts Safe and chemical-free UV does not introduce any of the hazards associated with chemicals, such as handling and disposal. It is an environmentally responsible and increasingly championed technology No chemical addition to water UV does not alter water chemistry and its constituents, such as pH, taste, odor, color, etc. Proven and trusted UV is widely used to disinfect drinking water and wastewater worldwide, and has been for many years. UV is also extensively used for industrial applications including food & beverage, pharmaceutical, and semiconductor manufacturing

UV LIGHT LIMITATIONS: 

UV LIGHT LIMITATIONS No known residual UV does not provide any post-treatment residual effect Influenced by water quality Turbidity, suspended solids and color affect performance Application specific UV is well suited to disinfection, and to the destruction of organics and chemicals – it has no effect on water quality parameters such as suspended solids

UV LIGHT APPLICATIONS FOR WATER TREATMENT: 

Municipal Wastewater Municipal Drinking Water Private Potable Water Industrial Process Water Industrial Wastewater Consumer Drinking Water Municipal Wastewater Municipal Drinking Water Groundwater Remediation Industrial Process Water Industrial Wastewater Groundwater Remediation Industrial Process Water Industrial Wastewater UV LIGHT APPLICATIONS FOR WATER TREATMENT

UV DOSE CALCULATION: 

UV DOSE CALCULATION UV Dose is a product of: Intensity (quantity of UV light per unit area falling on a surface) and Residence Time (contact time in the reaction chamber) UV Dose is expressed in: µWsec/cm2 (Microwatt seconds/cm2) mWsec/cm2 (Milliwatt seconds/cm2) mJ/cm2 (Millijoules/cm2 )

UV DOSE INFLUENCING FACTORS: 

UV DOSE INFLUENCING FACTORS Fast Flow = Low Dose Slow Flow = High Dose

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS UV Transmittance (UVT) The ratio of light entering the water to that exiting the water – usually reported for a path length of 1 cm. UVT is often represented as a percentage and is related to the UV absorbance by the following equation: %UVT = 100 x 10-A As the UV absorbance increases, the UV transmittance decreases. Examples: DI/RO Water = 99% UVT Fresh Water (Post AGC) = 95% UVT Municipal Tap Water = 85-95% UVT

UV DOSE WATER QUALITY FACTORS: 

Performance is highly dependent on how “clear” (transmissive) the water is to UV light UVT has a cumulative effect, reducing the UV intensity based on the thickness of the water layer that UV light must pass through Sizing and lamp spacing is very sensitive to UVT of the water Proper system design and sizing is dependent on accurate water sample analysis UV DOSE WATER QUALITY FACTORS Effects of UV Transmittance

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS Turbidity (NTU) Turbidity is a measurement of suspended matter in water. Turbidity is normally reported in Nephelometric Turbidity Units (NTU) which represent the light scattering and absorbing properties of the suspended matter present in a given sample of water. Turbidity is an important consideration because suspended matter can shield pathogens from disinfection treatment

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS Dose can be significantly influenced by turbidity Turbidity may harbor pathogens and impede the effectiveness of disinfection Higher levels of turbidity means more uncertainty in disinfection process Turbidity is can be influential on system design and sizing

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS Sleeve Fouling Sleeve fouling can affect UV transmittance (%UVT) and disinfection performance. Many variables (water quality, lamp technology, flow, etc.) can contribute to sleeve fouling Iron content in source water is often a factor in sleeve fouling Sleeve cleaning systems offer a means to treat fouling but also have variability (system type, wiper design, wiper frequency, maintenance schedule, water quality, etc). An effective system with an appropriate cleaning schedule is critical

UV DOSE WATER QUALITY FACTORS: 

UV DOSE WATER QUALITY FACTORS 25,000 GPD to 1.5 MGD 1.5 MGD to 20 MGD

UV APPLICATIONS DISINFECTION: 

UV APPLICATIONS DISINFECTION What is Disinfection? Disinfection, in terms of microorganisms, is a reduction of at least 3 log (or 99.9%) Disinfection is not sterilization

UV APPLICATIONS DISINFECTION: 

How does UV disinfect? UV light at the 254 nm wavelength penetrates the cell wall of the microorganism The amount of UV delivered to the organism is called the intensity The UV energy permanently alters the DNA structure of the microorganism in a process called thymine dimerization The microorganism is “inactivated” and rendered unable to reproduce or infect UV APPLICATIONS DISINFECTION UV Energy

UV APPLICATIONS DISINFECTION: 

UV APPLICATIONS DISINFECTION Efficacy of UV light for microbial disinfection peaks at the wavelength of 254 nm Above and below this wavelength, the drop-off in effectiveness is quite rapid

HOW UV TREATMENT WORKS: 

HOW UV TREATMENT WORKS Disinfection UV Oxidation Destruction of bacteria, viruses and other pathogens through DNA disruption by UV photons Destruction of chemical contaminants via UV photolysis and UV light- induced activation of hydrogen peroxide

UV APPLICATIONS DISINFECTION: 

UV APPLICATIONS DISINFECTION

UV APPLICATIONS DISINFECTION: 

UV APPLICATIONS DISINFECTION Typical Disinfection Applications Point of entry Post activated carbon Pre-reverse osmosis (RO) system Post RO storage tank Post demineralization Prior to process and distribution loops Point of use Anywhere there is biofilm potential or a bio-contamination problem Simple syrup up to 67 brix.

MUNICIPAL DRINKING WATER TREATMENT Installed in over 100 communities: 

MUNICIPAL DRINKING WATER TREATMENT Installed in over 100 communities from New York City, Los Angeles, and Rotterdam to small communities

Slide24: 

MUNICIPAL WASTEWATER TREATMENT Santa Rosa, CA - 60 million gals/day (227,000 m3/d)