Effectiveness of Ultraviolet Irradiation in Dechlorinationas Influenced by Ultraviolet Transmittance

摘要

Under various circumstances, treatment is required to remove free residual- and total- chlorine after chlorination. Among several dechlorination technoloiges, ultraviolet (UV) treatment, the latest available approach, has advantages over the others as it does not use chemicals. This study was conducted to evaluate the effect of UV treatment on dechlorination, and to investigate the influence of operation conditions, including UV dose and water UV transmittance (UVT) on chlorine removal efficiency. Results from both the field and the laboratory tests showed that under UV treatment degradation of both free residual- and total-chlorine followed the first-order kinetics and that the rate of chlorine removal is enhanced with increases in UV dose and/or in UVT. The maximum UV dose of 513 mJ cm -2 resulted in 25% reduction of total-chlorine concentration, suggesting that in practical applications, a much higher UV dose is required for 100% chlorine removal. The lower the UVT, the lower the UV dose, and the less the chlorine removal.