Bacteria are single-cell micro-organisms that can be found virtually everywhere. Population growth and rapid urbanization strains environmental and infrastructure systems. Drinking water contaminated with microbes such as E. coli cause gastrointestinal disease, which in turn leads to further food or water contamination. This creates a vicious circle where the disease can spread quickly through a population.

In large cities there is an escalating concern in airborne transmission. Tuberculosis (TB), while relatively uncommon in developed regions, is latent in 25 percent of the world’s population with some 10 million people developing active TB each year and 1.7 million deaths from the infection.

Scope of problem

Non-spore forming bacteria, while less challenging in terms of disinfection than their spore forming cousins, are of increasing concern because of the growing resistance to antibiotics. Health experts have warned that if antibiotics lose their effectiveness that many of today’s key procedures (e.g. organ transplant, chemotherapy, joint replacement) could become dangerous to perform.

Escherichia coli

Escherichia Coli (E. coli) is a bacterium present in very high numbers in human and animal feces. The presence of E. coli in water indicates recent fecal contamination of water supplies and may indicate the possible presence of other disease-causing pathogens.

For this reason, E. coli is an indicator organism or reference pathogen for the presence of pathogenic bacteria in water. Many systems are designed around achieving 3 log reductions or greater of E. coli with the expectation that if E. coli is controlled, other pathogenic bacteria is as well.

The EPA Standard for Microbiological Water Purifiers & the associated NSF standards for Class A UV microbiological treatment systems require a minimum 6 log reduction/inactivation of E. coli.

This chart shows water disinfection performance by a single Klaran WD Series UVC LED against E. coli in a consumer point-of-use flowing water application. The water flow rate through the UVC LED reactor was held constant at two liters per minute and LED output modified by adjusting forward drive current.