# Design of a Device Based on an LED Matrix for Water Sterilization
## 4 Discussion
perfringens_ is a facultative anaerobe capable of producing endospores, allowing it to survive in adverse conditions such as extreme temperatures and lack of nutrients, which hinders its elimination [17; 18]. In this regard, LED 2 also showed its effectiveness against endospores, successfully eliminating them in less than 5 min under agitation. Although the presence of pathogenic yeasts in aquatic environments has recently raised concerns about their impact on human health [19], the risk of waterborne fungal infections is a less studied aspect. The results of this study showed that LED 2 was able to eliminate _C. albicans_ and _S. cerevisiae_ with great efficiency, particularly under stirring. _C. albicans_ was more resistant under static conditions, whereas _S. cerevisiae_ showed less sensitivity under agitation. These results were consistent with previous studies indicating that inactivation kinetics depend on the yeast strain, among other factors. Cellular adhesion to particles or suspended surfaces and the formation of aggregates that protect cells can diminish the bactericidal efficacy of radiation. Additionally, the structural characteristics of each strain may influence the LED effect [20]. Parameters required for drinking water typically refer to a bacterial concentration of 0 CFU/100 mL. For this reason, it is necessary to develop a method that can sterilize high concentrations of bacteria and large volumes of water. To analyze the effect of concentration on bacterial viability after UV radiation exposure, bacterial cultures were irradiated at different concentrations for 5 min, under both stirring and static conditions. The results showed a decrease in efficiency with increasing concentrations of microorganisms under static conditions, but high efficiency under stirring, even at the highest concentrations. The effect of parameters such as bacterial concentration and water volume on sterilizing capacity was also analyzed. The use of microbial concentrations ranging from \(5\times 10^{3}\) to \(5\times 10^{8}\) CFU/mL showed species-dependent effects under static conditions, but nearly total mortality at all concentrations under stirring. Regarding volume, total sterilization was achieved at bacterial concentrations from \(5\times 10^{3}\) up to at least 320 mL, and up to 80 mL at concentrations as high as \(5\times 10^{8}\) CFU/mL. These results are consistent with previous studies showing that surface area and volume influence the bactericidal properties of LEDs because they are related to the radiation distance [4; 21]. With the information obtained, a prototype was constructed using an array of LED 2. The design was flexible to allow adaptability to containers and integrated a total of 18 LEDs,with dimensions of 300 \(\times\) 200 mm. The goal was to sterilize volumes of up to 5 L of water. The device proved capable of sterilizing bacterial mixtures in laboratory conditions in less than 5 min under stirring. As a final test, it was tested against an environmental sample of contaminated water, yielding results dependent on exposure time and stirring, but achieving total sterilization of the samples. These results align with the described fact that the antibacterial effect is dependent on volume and exposure time [22]. An operational suggestion on how to apply the agitation device in a practical application is shown in Supplementary Figure S1. According to their manufacturers, a useful lifespan of approximately 25 years is guaranteed for the polymers utilized in encapsulating the prototype. EVA was specifically selected for its favorable plastic properties, high adhesion, and exceptional transparency, which may diminish due to degradation from prolonged exposure to solar radiation. ETFE, on the other hand, is lightweight, flexible, and resistant to degradation or yellowing under extreme environmental conditions or UV radiation. Over time, there may be a risk of adhesion loss and delamination between the different layers.