Nitrate and Ammonium Removals from Groundwater by Permeable Reactive Barrier Method (PRB): Column Experiments

With the growth of industry and agriculture, nitrogenous compounds like nitrate and ammonium have contributed significantly to the contamination of groundwater. These pollutants cause intoxication and even may lead to stomach cancer. Permeable reactive barrier (PRB) is considered an in situ and low-cost method for groundwater treatment. This research aims to evaluate six different inexpensive reactive substances such as perlite and sand (1:1), cocopeat and sand (1:1), activated carbon, sawdust and sand (1:1), zeolite, and pumice for removing nitrate with an initial concentration of 100 mgL(-1) and three reactive materials such as Leca, vermiculite and pumice (1:1), and cocopeat and pumice (1:1) for removing ammonium with two initial concentrations of 20 mgL(-1) and 40 mgL(-1) utilizing column experiments. Some of these absorbents have been rarely used in PRB to remove nitrogenous compounds. The plexiglass column utilized in column experiments and water flow through the layer in the column is due to the constant head difference. Results showed that all the reactive materials that have been used in removing nitrate had good performance with a minimum removal percentage above 73%. The best performance among these reactive substances belonged to a mixture of perlite and sand (1:1) with a maximum removal efficiency of 100%. The mixture of cocopeat and pumice (1:1) had the best performance among the materials were chosen for the ammonium treatment, with maximum removal percentages of 80% and 70% for initial concentrations of 20 mgL(-1) and 40 mgL(-1), respectively. Variations in the permeability coefficient of the reactive materials were investigated in this study, as an essential factor in the lifespan of the reactant during the column experiments. Results of constant head permeability tests revealed that a rapid drop was observed in the reactive layer's permeability coefficient during the period leading up to the maximum removal percentage and then a subsequent minor decline occurred.