Nitrate pollution in aquatic systems is a significant issue on global and national scales. Contamination from anthropogenic sources, including the heavy application of synthetic fertilizer, has led to a heavy nitrogen load in soil, resulting in significant accumulation of nitrate in groundwater. The mobility of the nitrate ion and its toxic effects on humans pose a threat to the natural environment and to public health. Traditional treatment techniques either physically separate the ion without chemically altering the species, or introduce toxic heavy metals, resulting in costly post-treatment methods. Furthermore, nitrate can be converted to ammonia, which is a valuable chemical precursor. A viable approach to reducing nitrate is to use ultraviolet (UV) technology to convert the nitrate to other nitrogen species, including nitrogen gas and ammonia. The goal of this dissertation is to investigate novel photochemical reduction techniques to effectively reduce nitrate to other nitrogen species and optimize the reaction conditions to control the speciation of products. First, synthetic TiO2 nanocrystals with surface-grafted diethylene-glycol (DEG) ligands were investigated for their reduction performance. Under Medium-Pressure UV (MP-UV) irradiation, the nanocrystals exhibited tremendous performance for nitrate removal kinetics compared to standard or traditional TiO2. Furthermore, the nitrogenous product speciation was analyzed, and ammonium formation was observed. The synthesis temperature was investigated and revealed that higher synthesis temperature improved the yield of ammonium. Second, the effect of chloride and bicarbonate, two common ionic intermediates in groundwater, were evaluated for their effects on MP-UV reduction of nitrate in the presence of formate. Chloride and bicarbonate both had nominal effects on system performance, highlighting the robustness of MP-UV photoreduction. Furthermore, kinetic modeling provided insight into the photochemical reduction pathways of nitrate forming nitrogenous gas species. Finally, Vacuum-UV (VUV) photolysis of water was investigated for nitrate reduction to ammonium. VUV emits light at 185 nm which photolyzes the water molecules to produce hydrogen atom, hydroxyl radical and aqueous electron. The effects of organic electron donors, including methanol, ethanol, formate, and phenol were investigated and revealed that methanol exhibited the greatest nitrate reduction kinetics. Furthermore, nitrite formation was minimal and eventually reduced to ammonium for all electron donors. The optimal methanol dosage with respect to nitrate and the effects of pH were evaluated. In summary, this research highlights the efficacy of photochemical and photocatalytic technologies for nitrate reduction. This work has the potential to replace outdated nitrate removal methods and can be integrated into water treatment facilities.