Giardia is a protozoa that is protected by an outer shell that makes it highly resistant to chlorine disinfection. The symptoms from a Giardia infection can last from 2 to 6 weeks. Although Giardia is often referred to as a camping or backpacking-related disease (Beaver Fever), anyone can easily be exposed through contaminated drinking water.

Traditional methods of chlorine based disinfection require high concentrations and contact times to eliminate Giardia, a situation that is further exacerbated by cold water conditions and leads to increase disinfection by-product formation. UV disinfection easily inactivates Giardia at low doses, without the production of disinfection by-products associated with high chlorine contact time (see the USEPA UV Disinfection Guidance Manual for more information).

Where the design of chlorine based disinfection systems is governed by chlorine resistant organisms like Giardia (as is typically the case in North America), UV disinfection offers a very cost effective treatment solution to reduce the chlorine contact time. As an added benefit to reducing chlorine contact time, UV can form part of a disinfection by-product reduction strategy by reducing the amount of chlorine used. Its small footprint can also provide significant cost and space savings compared to the design and construction of a chlorine contact chamber expansion.