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.