By-product formation during ultraviolet disinfection of a pretreated surface water'

A low-pressure (LP-UV) and medium-pressure UV lamp (MP-UV) were compared for the formation of nitrite, assimilable organic carbon (AOC), and genotoxicity using pretreated surface water in a bench UV unit. The results have been compared with the by-products formed in pretreated surface water using a pilot unit equipped with four medium-pressure lamps identical to the one used in the bench unit. It was found that although significant nitrite formation occurred in the MP-UV bench tests, it remained well below the European standard (0.1 mg/L NO2-) in the pilot unit. The LP-UV gave no or very low amounts of nitrite (bench unit). The AOC and genotoxicity increase with LP-UV was negligible. The AOC content and genotoxicity after MP-UV irradiation in the bench unit was significant as well, whereas AOC was formed limitedly in the pilot unit. Genotoxicity was elevated but not significant.