OZONE GENERATION BY VACUUM ULTRAVIOLET RADIATION (Λ = 172 NM) IN A CONTEXT OF DECENTRALIZED DRINKING WATER PRODUCTION

Abstract

The main problem with centralized drinking water production in isolated communities is the recontamination of water during distribution and storage. Therefore, a disinfection step at the point of consumption is important. A disinfection module, on a household scale, with a vacuum ultraviolet ozone generator operating with ambient air and powered by a 24 V source was built. The aim was to evaluate the production capacity of the photochemical ozone generator fed with ambient air without a gas dryer. The effect of relative humidity (RH) in air on photochemical ozone generation at different gas flow rates was investigated. The maximum ozone outputs with extra-dry air were 2.8 g-O₃/h and 3.7 g-O₃/h at lamp power levels of 20 W and 35 W, respectively (specific energy consumption: 7.1 kWh/kg-O₃ and 9.4 kWh/kg-O₃). The generator fed with water-saturated air produces nitric acid-free gas with ozone productions of 0.15 g-O₃/h to 0.79 g-O₃/h (25.3 kWh/kg-O₃). As the gas flow rate increases, ozone production rises until a plateau is reached. Increasing of the RH of the gas from 0 % to 20 % reduces ozone production by 35 % to 57 % for the lamp set at 20 W. A similar reduction occurred for 35 W.  As the RH rises from 20 % to 100 %, the ozone output of the 20 and 35 W lamp plateaus at a non-zero value for each gas flow rate. The absence of nitric acid in the gas produced from humid air validates the use of the photochemical ozone generat