Strategical approach to prevent ammonia formation during electrocoagulation of landfill leachate obtained from a biofiltration process

Biofiltration followed by electrocoagulation represents an alternative approach to efficiently treat landfill leachates. However, the drawback related to this combination is the formation of ammonium during electrocoagulation used as tertiary treatment. Nitrate can be transformed into ammonium by electro-reduction at the cathode. To overcome this issue, different cathode materials (Fe, Al, SS, Cu, and (Ti/Pt)) were investigated using voltammetry study. Subsequently, electrocoagulation experiments were conducted using landfill leachate pre-treated by biofiltration. The initial concentration of NH4 in bio-filtrated landfill leachate (BFLL) was very low (<0.2 mg N/L), whereas 300 mg N-NO3/L was recorded. During electrocoagulation of BFLL, Ti/Pt was more effective to avoid NH4 formation (1.2 mg N/L), followed by Cu, Al, SS and Fe (10.5, 13.7, 21.0 and 23.5 mg N/L, respectively). In order to further minimize the residual NH4 concentration using SS cathode, additional experiments were conducted using different electrode areas (27.5, 55, 82.5 and 110 cm2). For a constant current density of 9.1 mA/cm2, the residual NH4 concentration could be optimally diminished by reaching the limiting value recommended (10 mg N/L) and around 61% of refractory chemical oxygen demand (COD) could be removed when 55 cm2 of SS surface was imposed.