Analysing the Reciprocity Law for UV-LEDs in Water Disinfection of Escherichia coli, Enterococcus faecalis, and Clostridium perfringens

Abstract

The aim of this study is to verify the reciprocity law in the wastewater disinfection process using UV light. The optical power UV-LEDs used were 1.6 mW and 50 mW, and the wavelengths were 265 nm and 275 nm. E. coli, Enterococcus faecalis, and Clostridium perfringens were the three microorganisms analysed in the study. The results showed lower inactivation rates around 0.063–0.065 cm2/mJ for 265 nm and 0.047–0.049 cm2/mJ for 275 nm for the Clostridium perfringens compared with the other two bacteria. For E. coli and Enterococcus faecalis, the inactivation rate was almost identical; 0.28 and 0.21 cm2/mJ, respectively, using 265 nm wavelength. There was a slightly better inactivation performance using the medium-power 275 nm UV-LEDs of 0.39 cm2/mJ and 0.29 cm2/mJ for E. coli and Enterococcus faecalis, respectively, and 0.33 cm2/mJ and 0.26 cm2/mJ using the low-power 275 nm UV-LEDs. The analysed data justify the reciprocity law for UV-LEDs disinfection using 265 nm and 275 nm UV-LEDs with two optical powers of 1.6 mW and 50 mW.

Study of the Bunsen–Roscoe Reciprocity Law in Solar Water Disinfection (Optical Effect) for E. coli, E. faecalis and C. perfringens

“…In addition, in the three studies, E. coli was shown to be the test organism most sensitive to UV, followed by E. faecalis; and C. perfringens was the most resistant. These facts were also corroborated by Kamel et al [15] for all three bacteria in real wastewater samples, during a similar experimentation for the reciprocity law with UV LEDs. On the other hand, the slow inactivation of C. perfringens (vegetative + including spores) indicated the low susceptibility of this strain to solar disinfection, mainly due to its high resistance as a bacterial spore-forming species.…”

“…They observed that at the shortest wavelength (265 nm), the inactivation rate of E. coli depended solely on the UV dose, whereas at longer wavelengths (275, 285 and 295 nm), the inactivation rate did not follow the law of reciprocity, as it depended on both irradiance and exposure time. On the other hand, Kamel et al [15] argued that this law was valid when they tested the disinfection of E. coli, E. faecalis, and C. perfringens in natural wastewater samples, using 265 nm LEDs with optical powers of 2.5 mW and 50 mW, and 275 nm LEDs with powers of 1.6 mW and 50 mW.…”

“…In this test, the highest UV doses were reached with 47. 15 Experiment #1a was carried out between 10:30 h and 13:05 h, under a total sun exposure of 2 h and 35 min (2.58 h). In contrast, experiment #1b was conducted between 13:30 h and 15:31 h, under a total sun exposure of 2 h and 1 min (2.02 h).…”

“…From another perspective, in terms of the research carried out in this paper, the scientific literature has studied the reciprocity law for water disinfection under UV LEDs for different wavelengths and power levels [14,15], under exposure to sunlight (SODIS) [16,18,19] or simulated sunlight [17]. Bacterial inactivation can be equivalent under the same UV dose (reciprocity law), regardless of whether (a) low radiation is applied over a prolonged time or (b) high radiation is employed over a shorter time.…”

A Real-time Comparative Study of Sliding Mode and State Feedback Control for the Centrifugal Motor Pump in an Ultraviolet Water Treatment System Using the Bond Graph Approach

“…This process is generally straightforward and does not require the addition of chemicals. However, managing UV lamps, monitoring UV intensity, and integrating with other methods can introduce some complexity [1][2][3][4]21].…”