Disinfection by in-duct ultraviolet lamps under different environmental conditions in turbulent airflows.

In this study, we investigated the effects of environmental factors such as airflow velocity, relative humidity (RH), temperature, and duct reflectance on the performance of in-duct UVC lamps. Staphylococcus epidermidis, Pseudomonas alcaligenes, and Escherichia coli were used as the test bacteria. The UV irradiance, disinfection efficacy, and UV susceptibility constant (Z value) of the test bacteria were experimentally determined. The results showed that the UV disinfection efficacy decreased as the airflow velocity and RH increased. The maximum UV disinfection efficacy was obtained at temperature of 20-21°C compared with the performance at lower temperature (15-16°C) and higher temperature (25-26°C). When the RH increased from 50% to 90%, the Z values of airborne bacteria reduced by 40%, 60%, and 38% for S epidermidis, P alcaligenes, and E coli, respectively. Besides, susceptibility constants had lower values under both cooling temperature (15-16°C) and heating temperature (25-26°C) compared with that under the temperature of 20-21°C. It was observed that S epidermidis generally had the highest resistance to the UV irradiance. The results also showed that the UV disinfection efficacy was lower in the duct with a black surface than in the clean duct.

Dataset on the patterns of electricity consumption in public universities in southwestern Nigeria.

In this data article, a thorough dataset on patterns of electricity use in Nigerian public universities was presented. Three relatively old public universities with staff and students' halls of residences were purposively selected. The selected universities were Obafemi Awolowo University, Ile-Ife (OAU), Federal University of Technology, Akure (FUTA), and University of Ibadan (UI). Data were obtained through the administration of a structured questionnaire on electricity end users in the universities sampled. For the data collection, the electricity end users in public universities were stratified into users in university staff offices, staff residences, student residences, and commercial units. Electricity users were selected using systematic random sampling and accidental sampling techniques. In OAU, FUTA and UI, 217, 137 and 164 students, respectively were sampled; 30, 3, and 61 households in OAU, FUTA, and UI, respectively were sampled while 28, 6, and 18 commercial units in OAU, FUTA and UI, respectively were also sampled. The sample size determined for staff in OAU, FUTA and UI were 139, 81 and 182, respectively. The data obtained were analyzed using radar charts. The information provided in this data article will encourage investigation into electricity management strategies, critical success factors for electricity management, planning, and policy formulation towards the realization of sustainable campuses.

Disinfection efficacy of ultraviolet germicidal irradiation on airborne bacteria in ventilation ducts.

A full-scale ventilation duct ultraviolet germicidal irradiation (in-duct UVGI) system was designed to investigate its disinfection efficacy on five airborne pathogens: Serratia marcescens, Pseudomonas alcaligenes, Escherichia coli, Salmonella enterica, and Staphylococcus epidermidis, with airflow Reynolds numbers from 4 × 104 to 8 × 104 . By varying the UV intensity, the susceptibility constants (Z-values) of the bacteria were experimentally determined to be 1.2, 1.0, 0.60, 0.39, and 0.37 m2 /J for S. marcescens, P. alcaligenes, E. coli, S. enterica, and S. epidermidis, respectively. The disinfection efficacy was numerically investigated on the basis of the predicted irradiance, which included emissive irradiance and diffuse refection irradiance. The results suggest that it is vital to properly evaluate the UV dose (irradiance intensity) received by airborne bacteria to determine their Z-values. In-duct UVGI inactivated nearly all of the test bacteria with Reynolds numbers of 4 × 104 (inlet velocity = 3 m/s), and the disinfection efficacy decreased as Reynolds numbers increased. The in-duct UVGI system would potentially provide a supplementary solution for improving indoor air quality (IAQ) within mechanical ventilated/air-conditioned environment.