Treatment of landfill leachate with high proportion of refractory materials by electrocoagulation: System performances and sludge settling characteristics

•The COD removal with aluminum electrodes fits the French landfill Company.•Electrocoagulation has an influence on nitrate removal.•Electrocoagulation has an effect on both color and COD removal efficiency.•With optimal conditions, residual turbidity was 7.5 NTU.•Sludge settling was a sedimentation type piston.

The purpose of this study is to examine the feasibility of electrocoagulation (EC) in treating landfill leachate which has low biodegradability and a high level of inorganic compounds. Landfill leachate was taken from a French landfill which wants to cut down the organic matter present in the leachate especially the concentration of chemical oxygen demand (COD) which must be less than 120 mg O2/L. For this purpose, the effects of the operating parameters of EC, such as the current density j (23–95 A/m2), electrode gap (2–4 cm), and cathode natures were evaluated to find optimum operating conditions. These parameters were evaluated via COD, turbidity, absorbance at 254 nm, color, NH4+NH4+, NO3−NO3−, and electrical energy consumption. The COD objective of the French landfill has been obtained after 135 min of electrocoagulation with the following optimum conditions: j = 95 A/m2, 2 cm gap between aluminum electrodes. In this experimental condition, residual turbidity was around 5 NTU and 80% discoloration ratio was acquired. The decrease absorbance at 254 nm showed a removal of humic substances. Nitrate removal was 40% but EC treatment was not appropriate for removing NH4+NH4+. The sludge aptitude to settling was studied in terms of sludge volume index.