Municipalities in arid regions are acutely aware of the need to conserve their community’s drinking water supplies. One very effective way they are accomplishing this is by treating and reusing wastewater. Recycled wastewater provides a cost-effective, local and sustainable water supply for multiple non-potable uses. Communities can save their drinking water supplies for just that – drinking.
Wastewater treatment for non-potable reuse involves a series of well-established biological and physical process steps including filtration and disinfection to ensure the water is clean and safe for distribution. The recycled water can be used or sold for a variety of purposes including recreational and agricultural irrigation, industrial processes, construction, street sweeping and more.
Disinfection is the critical last step in the reuse treatment process to destroy any harmful microorganisms in the water.
UV Protects Against Bacteria, Viruses and Protozoa
UV is an effective, safe, and environmentally-friendly way to disinfect wastewater to the stringent limits required for reuse. It provides broad-spectrum protection against a wide range of pathogens, including bacteria, viruses and chlorine-resistant protozoa such as Cryptosporidium and Giardia. UV disinfection is a physical process that rapidly disinfects microorganisms as they pass by ultraviolet lamps submerged in the water. Within only a few seconds of exposure, the DNA of the microorganisms is permanently altered and the bacteria can no longer reproduce or infect those coming in contact with the water.
UV is ideal for Water Reuse
Chlorine, while an effective disinfectant, is a toxic, hazardous chemical that can be harmful in the event of a leak or spill. It also has the potential to create carcinogenic by-products which can be harmful to receiving waters and aquatic life. Balancing the high chlorine doses required for reuse water disinfection and the stringent low limit on chlorine residuals is a complex task. UV is a simpler and safer alternative. There is no transportation of chemicals and UV doesn’t create disinfection by-products.
The UV process adds nothing to the water but light, and therefore, has no impact on the chemical composition of the water. Finally, Cryptosporidium and Giardia are protozoa typically found in surface water sources that can reach drinking water supplies through run-off or inadequate treatment. They are resistant to chlorine, but can be easily inactivated with a low UV dose.