ADVANCED REDUCTION PROCESS: NITRATE REDUCTION BY SULPHITE/ULTRAVIOLET LIGHT

Abstract

Advanced Reduction Processes (ARPs) present a new mechanism for water treatment using the combination of activation methods and reducing agents, resulting in the formation of highly reactive radicals that cause destruction of oxidized contaminants by reduction. The combination of sulphite with low-pressure ultraviolet light (UV-L) has been tested as the most effective ARP to date. ARPs employ a source of activation energy to cause reductants to produce highly reactive reducing free radicals. The sulphite/UV-L ARP involves adding sulphite to solutions that contain the target contaminant and irradiating them with low-pressure ultraviolet light. Irradiation of sulphite leads to formation of the hydrated electron (eaq-) and the sulphite radical anion (SO3 •-) which act as reducing agents. In this study, batch kinetic experiments were to be conducted to characterize the kinetics of nitrate destruction by sulphite/UV-L ARP. The results of the preliminary experiments showed that the sulphite/UV-L ARP could degrade nitrate. A comparison was also made to assess the relative degradation carried out by Sulphite individually, UV individually and a combination of Sulphite and UV together. The dissertation also attempts to simulate radical reactions occurring in ARPs though a kinetic model. The limitations and future prospects of the kinetic model have also been discussed.