Removal of nitrate and COD from wastewater using denitrification process: kinetic, optimization, and statistical studies

Denitrification process studies were carried out for removal of N–NO₃ ⁻ and organic carbon from waste water. Recent researches have shown the efficacy of N–NO₃ ⁻ removal process from synthetic waste water; however, they are lacking the data related to kinetics and optimization that may aid in developing guidance for field-scale implementation. Various incubation parameters were varied such as nitrate and carbon source keeping biomass concentration invariable. For nitrate variation two different nitrates were used such as potassium nitrate (KNO₃) and calcium nitrate [Ca(NO₃)₂] and for organic source glucose (C₆H₁₂O₆) and sodium acetate (CH₃COONa). The denitrifying bacteria were isolated from agricultural soil. The dentrification rates increased with the increase of nitrate as well as organic source. The denitrification rates were faster in case of CH₃COONa compared to C₆H₁₂O₆. The regeneration time was also calculated which varied 1–3 days. Analysis of variance studies indicated that both nitrate and organic concentrations played significant role in terms of dentrification as well as emission of nitrous oxide (N₂O) rates. Principal components analysis studies were also carried out. Optimization studies were carried out using response surface model to evaluate the incubation parameters to minimize the N₂O emission and at the same time maximize the removal efficiency of N–NO₃ ⁻ and COD.