Cost-effective instant air disinfection for building ventilation system by a combination of UV and micro-static electricity

The increased threats of pathogenic bioaerosol make air disinfection in heating, ventilation, and air conditioning (HVAC) systems crucial to occupants' health. To satisfy the high efficiency, superspeed, and wide temperature range of HVAC air disinfection, UV irradiation (UV254/ UV185+254) and its combination with micro-static electricity were studied in two full-scale ducted ventilation systems. UV254 could efficiently disinfect S.albus (>99 %) at high temperatures (31 +/- 2 degrees C) and low airflow rates (1.2 m s(-1)) but was weakened at lower temperatures and higher airflow rates. Its combination with micro-static electricity could remarkably overcome these adverse factors and realize efficient disinfection within the retention time of 0.21 s. Especially for the relatively stubborn B.subtilis var. niger, the combination process improved the disinfection efficiency to 82 % at 16 +/- 2 degrees C and the airflow rate of 2.4 m s(-1), while UV254 was only 52.9 %. Since the UV185+254 disinfection was more effective than that of UV254, the UV185+254 based combination could further enhance the B.subtilis var. niger to 93.1 %. Besides the disinfection stability, the combination process has advantages in pressure drop (around 50 Pa), energy consumption (e.g., 0.115 kW.h km(-3)), and equipment costs (1,500-3,000 CNY), making it potentially cost-effective for air disinfection in HVAC systems.