Abstract
Bacterial contamination of drinking water sources is a serious problem. Here, we investigated the inactivation of bacterial indicators, namely total heterotrophic bacteria, total and fecal coliform in real drinking water using UVC-LED devices. Real drinking water samples collected every fortnight for a year from five different sampling sites showed significant prevalence of bacterial indicators. Each device was made up of 9 UVC-LED chips arranged in a line on a heat sink, covered with quartz tube, and submersible in water. A UVC-LED chip had an emission maximum, wall plug efficiency, and radiant power of around 276 nm, 0.018, and 10–12 mW, respectively. Inactivation was performed with 4 UVC-LED devices placed in series in a rectangular stainless-steel chamber with 1.2 L effective volume. With 30 LPH flow rate, and corresponding energy dosage of about 10.8 mJ/cm2, all bacterial indicators (initial load about 103 CFU/100 mL) were inactivated, as required by regulatory bodies. Notably, dark repair of bacterial indicators was not significant (<1 %) up to 24 h of storage in clean opaque (dark) vessel, whereas slight photo repair of bacterial indicators was observed (<10 %). Electrical energy (EE3) for complete inactivation and cost for water disinfection were determined to be about 1.397 kWh/m3 and ₹ 9.03 (€ 0.09 or $ 0.10), respectively. The estimated cost is affordable in developing countries. The study may be a referral to develop applications of UVC-LED irradiation for point-of-use drinking water disinfection and useful for resource-poor communities challenged with bacterial contaminated drinking water.
Published Version
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