Interpreting collimated beam ultraviolet photolysis rate data in terms of electrical efficiency of treatment

Abstract

A novel approach is presented for using fluence-based rate constants from collimated beam ultraviolet (UV) degradation kinetics to estimate electrical efficiencies for large-scale treatment of chemical contaminants. Atrazine (ATZ) and N-nitrosodimethylamine (NDMA) are given as examples. The relative electrical efficiencies of medium-pressure (MP) and low-pressure (LP) mercury lamps for treating these contaminants estimated from collimated beam data compare favorably with data collected using a bench-scale annular reactor and two different waters. For the water with higher UV transmittance, ATZ degradation was more efficient with the MP lamp by 8%, while for the water with lower transmittance the LP lamp was more efficient by 4%. For NDMA, the LP lamp was more efficient than the MP lamp in both waters tested: it was 29% more efficient in the water with higher transmittance and 58% more efficient in the water with lower transmittance. Key words: chemical treatment, water treatment, ultraviolet radiation, pesticides, photochemical reactions, potable water, electric power demand.