Improved Drinking Water Disinfection with UVC-LEDs for Escherichia Coli and Bacillus Subtilis Utilizing Quartz Tubes as Light Guide

Abstract

Abstract:A new approach is investigated utilizing light guidance capabilities of optical pure quartz glass in order to maximize drinking water disinfection efficiency with UVC-light-emitting diodes (LEDs). Two experimental setups consisting of soda-lime AR ® glass (VWR, Darmstadt, Germany) or HSQ ® 100 quartz glass (Heraeus, Wasserburg, Germany) reactors were designed to compare disinfection rates with and without total reflection of UVC radiation along the reactor walls. Each reactor was filled with 9 mL bacteria samples containing either E. coli DSM (Deutsche Sammlung von Mikroorganismen) 498 or B. subtilis DSM 402 strains (concentration 1-3 × 10 6 colony forming units (CFU)/mL) with and without additional mixing and irradiation periods of 10, 40, and 90 s. Disinfection rates were increased up to 0.95 log10 (E. coli) and 0.75 log10 (B. subtilis) by the light guide approach in stagnant samples. The same experiments with mixing of the samples resulted in an increased disinfection efficiency of 3.07 log10 (E. coli) and 1.59 log10 (B. subtilis). Optical calculations determine that total reflection is achieved with the applied UVC-LED's viewing angle of 15°. Furthermore measurements show that HSQ ® 100 quartz has a transmittance of 92% at 280 nm UVC irradiation compared to the transmittance of soda-lime glass of 2% (1 mm wall thickness).

Efficient Disinfection of Tap and Surface Water with Single High Power 285 nm LED and Square Quartz Tube

“…This leads to a penetration depth of As mentioned before, this water filled quartz tube acts as an efficient light guide for the LED radiation. Almost no UV light can leave the system due to total reflection at the walls of the tube, which generates high efficiency disinfection rates [15]. Furthermore, this system should be equipped with an ultrasonic transducer at a free end of the tube for biofilm removal inside the tube [22].…”

“…For this reason several systems with multiple LEDs were proposed in the past. However, in combination with a straight quartz tube that acts as a light guide, this low power radiation of a single LED can be used very efficiently [15]. Such systems could not only be used in the Third World [16].…”

Detection of contaminants in water supply: A review on state-of-the-art monitoring technologies and their applications

“…In relation to water quality monitoring, the detection of E. coli and B. subtilis in drinking water by employing quartz tubes as optical light guidance tools with UVC-light emitting diodes (LEDs) has been developed by Gross et al [329]. The experimental setup consisted of two containers, a soda-lime AR glass and a 100 cm quartz glass, filled with 9 mL of E. coli and B. subtilis.…”

Using indicators to assess microbial treatment and disinfection efficacy

“…Though this technology has been available for most of the 20th century, its acceptance for wastewater treatment was only widespread until the mid-1980. UV radiation has been reported to efficiently inactivate pathogens (bacteria, protozoa, and some viruses) by directly damaging microbial nucleic acids (Gross et al, 2015). This disinfection method is an attractive and ecofriendly technology, as it does not cause the generation of by-products during the wastewater treatment process (Winward et al, 2008).…”