Introduction to UV For Wastewater & Drinking Water

Ultraviolet (UV) light is a form of light that is invisible to the human eye. The wavelength of UV light is shorter (i.e., stronger) than visible light, yet weaker than X-ray light. Specific UV wavelengths, between 200 and 300 nanometers, are categorized as germicidal. These wavelengths are able to destroy microorganisms in water, specifically bacteria, viruses and protozoa.

UV treatment causes damage to the organism’s DNA and RNA, which destroys its capacity for reproduction.

How UV Light Disinfects

Microorganisms in the water are exposed to UV light when they pass by the special germicidal lamps in UV disinfection systems. The UV energy instantly destroys the genetic material (DNA) within bacteria, viruses and protozoa, eliminating their ability to reproduce. 

Applications For UV Disinfection

  • Disinfection of primary, secondary or tertiary wastewater effluent
  • Disinfection of high quality wastewater for reuse purposes
  • Treatment of stormwater, combined or storm sewer overflows
  • Disinfection of groundwater or surface water for drinking
  • Advanced oxidation (UV + hydrogen peroxide) for indirect potable reuse (aquifer recharge) and destruction of chemical contaminants such as pesticides and algal toxins in drinking water
Protozoa (e.g., Cryptosporidium and Giardia)

Why Disinfect With TrojanUV?

  • UV has been used to disinfect water since the early 1900’s
  • Bacteria, viruses and protozoa are inactivated – eliminating their ability to cause infection
  • Inactivates Cryptosporidium and Giardia – two dangerous protozoa that are resistant to chlorine
  • Cost-effective for both new treatment plants and existing plants that are upgrading or adding disinfection
  • Safe for operators and the community – UV is a physical, chemical-free process that adds nothing to the water but light
  • Safe for the environment – UV does not create disinfection by-products
  • Requires a small physical footprint – reducing construction time and costs
  • Highly reliable – provides consistent, confident disinfection through proper design, validation and product features
  • TrojanUV systems have been installed globally – disinfecting billions of gallons of water every day

Wastewater Treatment

Disinfection is the final step in the wastewater treatment process. Bacteria, virus and protozoa populations are inactivated before wastewater is discharged into oceans, lakes and rivers. Wastewater disinfection is critical for the protection of public health and the environment. Discharged wastewater becomes the drinking and recreational water for downstream communities and has a major effect on aquatic and plant life in receiving water bodies.
An image showing the typical wastewater treatment process

Why Disinfect Wastewater With UV

  • UV is very cost-competitive with chemical disinfection – new treatment plant construction can be significantly cheaper than chlorine
  • UV offers much lower operation & maintenance costs than chlorine
  • Unlike chlorine, UV cannot be overdosed and has easy, automatic dosing
  • UV is extremely safe – no transportation, storage or handling of toxic, corrosive chemicals is required
  • UV treats wastewater and returns it to water sources with no carcinogenic or harmful by-products
The cost of disinfection options were evaluated for a new wastewater plant in Brazil with a flow rate of 2,365 m3/h (15 MGD). Factors accounted for include capital cost, equipment installation & construction, chemicals, lamp and power and maintenance costs. Their choice to implement UV over chemical alternatives would save the municipality between $1.3 – $2 million dollars over a 20-year period.

Drinking Water Treatment

Disinfection is the critical final step in the treatment of drinking water. If untreated and ingested, bacteria, viruses and protozoa can cause severe, even fatal health conditions. Cryptosporidium and Giardia are chlorine-resistant protozoa that are ubiquitous in nature. Disinfection with UV inactivates these microorganisms – protecting public health and providing water confidence. Different microorganisms have different sensitivity to UV and chlorine, so it’s critical to know what’s in your water and your regulatory requirements. Alternatively, UV and chlorine can be used simultaneously to provide protection against the full spectrum of microbes, providing reliable multi-barrier protection.

Municipalities around the world – from rural wells to cities serving millions of people – have installed UV disinfection to protect their residents.

Why Disinfect Drinking Water With UV

  • UV costs 1/ 5th that of ozone disinfection and 1/10th the cost of membrane filtration
  • UV protects against all microorganisms treated by chlorine – including viruses – as well as chlorine-resistant protozoa (Cryptosporidium and Giardia)
  • UV provides public safety and peace of mind when added as an additional disinfection step to chlorine, called a multi-barrier approach
  • UV enables municipalities to be proactive in meeting and exceeding new regulations

UV is a simple and cost-effective disinfection solution that can be easily retrofitted into existing treatment plants. The contact time required for the UV process is only seconds so the footprint required for treatment is relatively small, eliminating the need for large contact tanks and lowering construction costs.
An image showing the typical drinking water treatment process

Features incorporated into UV systems minimize the time and expense needed to operate and maintain them. Cleaning the quartz sleeves that enclose lamps can be completed without operator involvement, using an automatic cleaning system. A touch-screen operator interface allows for easy monitoring of each UV system and can have a lamp dimming feature that allows operators to match UV dose to actual disinfection requirements.

Demonstrated Performance

All TrojanUV drinking water systems are bioassay validated according to United States Environmental Protection Agency (USEPA) recommendations and/ or German DVGW protocol. DVGW validations offer the assurance of 40 mJ/ cm2 dose delivery while USEPA validations offer treatment flexibility, lower costs and energy while delivering a specified log reduction of target contaminant. Bioassay validation demonstrates that the regulated or required UV dose is delivered for the specified operating conditions. This validation ensures dose delivery and water confidence.