Applying the Nernst Equation to Control ORP in Denitrification Process for Uranium-Containing Nuclear Effluent with High Loads of Nitrogen and COD

Abstract

Several reviews of denitrification have shown it to be an efficient process for treating high nitrate-loaded effluents from nuclear industries. However, stressful conditions adversely affect biological kinetic parameters and performance. Additionally, actual nuclear effluents contain multiple pollutants and radioactive emissions that could render implementation difficult. The objective of this study was to treat and recycle water from nuclear industries by using a mixture of blended real nuclear wastewater (BRNW). The process was carried out under physicochemical parameters control in a biological model to established a technical setup and to model the denitrification process in a real nuclear wastewater effluent. Denitrification processes were carried out in the wastewater sample under controlled ORP conditions by the Hill model to establish the kinetic model. The results show a complete elimination of nitrate by the bacteria. Indicators of biochemical reactions were used to obtain a model based on Monod and controlled ORP. The good fit of the proposed model was verified under empirical and simulated conditions. To establish optimal performance, it was necessary to add 3% v/v of methanol, as a carbon source, to remove the nitrate in BRNW. Isolation techniques confirmed that Pseudomonas spp. was the dominant bacteria. Gene expression demonstrated the lack of inhibition of the NosZ gene responsible for the reduction in nitric oxide, a “greenhouse gas”. Finally, COD and uranium were removed from the liquid by precipitation. At the end of the process, the treated effluent could potentially be reused in industrial processes, recycling most of the wastewater effluents.