Assessing generic UV LED lamp on disinfection process for reducing coliform in rainwater harvesting system

With the typical annual precipitation of 1,917 mm, people living in Malang possess the potential to employ rainwater harvested from roofs more publicly. Nonetheless, post-harvesting rainwater collected in the tank may contain pathogens, e.g., coliform, resulting from sewage contamination and animal faecal litter. In contrast, people may find the available disinfection system quite costly and sophisticated since many systems are designed on a laboratory or industrial scale. To make the disinfection system more accessible for domestic use, a widely available generic UV-LED lamp (5 and 20 W) preceded by multimedia filtration was arranged and evaluated against the total coliform originating from collected rainwater. The optimum disinfection time was assessed using variable UV module's HRTs (i.e., 5, 15, 30, 45, 60, and 90 minutes) in a continuous flow system, as well as percentage reduction of coliform in CFU/100mL respective to each HRT, showing a positively correlated exposure. The study generated the optimum irradiation dose of UV exposure ranging between 85.79 to 155.18 mJ/cm2. Following the first-order kinetics of inactivation rate, the specific coefficient k was calculated as 0.05611 and 0.05775 for 5 and 20 W lamps, respectively. It can be concluded that the generic UV-LED lamps also have the potential to be used widely in the rainwater harvesting system.