Enhancing Nitrate Removal With Industrial Wine Residue: Insights From Laboratory Batch and Column Experiments Using Chemical, Isotopic and Numerical Modeling Tools

Agricultural run-off exposes recipient water bodies to nitrate (NO₃⁻) pollution. Biological denitrification is a suitable method for removing NO₃⁻ in water resources that can be induced by the use of industrial organic liquid waste as an electron donor source. In light of this, batch and column laboratory experiments were performed to assess the potential of two industrial wine residues (lías and vínico) to induce biological denitrification of NO₃⁻ contaminated water from a constructed wetland and to evaluate the efficiency of these treatments using chemical and isotopic tools. In batch experiments (performed at a C/N ratio of 1.25), vínico was not efficient enough in removing N species, attenuating only 35% NO₃⁻ and was not used in column experiments. In similar experimental conditions, lías completely removed N species from water in both batch and column experiments. The calculated isotope fractionation (ε¹⁵N_NO3 and ε¹⁸O_NO3) was the same in both batch and column experiments biostimulated with lías and differed from those for vínico. The isotopic data confirmed that denitrification was the principal NO₃⁻ attenuation pathway in all the experiments. The isotopic fractionation can be later applied to field studies to quantify the efficiency of biologically enhanced denitrification. A numerical geochemical model that accounts for the changes in nitrate, nitrite concentration and isotopic composition due to the degradation of lías and vínico, including transport in the case of the column experiment, was performed to simulate the experimental results and can be up-scaled in field treatments.