Background and Objectives: leachate from municipal solid waste landfill is a strong sewage having hazardous toxic substances. It should be treated by choosing a simple, economical, and eco-friendly method. The aim of this study is reduction of COD from the Qom City landfill leachate using electrocoagulation process.  
Materials and Methods: The experimental study was carried out at bench scale using a batch reactor during 2010.  We used a Plexiglas reactor having 0.7 liter capacity, containing nine plate aluminum electrodes connected to a DC power supply (10-60V, 1-5A). Samples were collected in the middle of cell at regular (every 10 minutes) time intervals. The concentration of COD was determined using a COD analyzer. The effects of different parameters including current density (52.08, 69.44 mA/cm²), electrolyte time (10, 20,30,40,50 and 60 min), and voltage range (10, 20, 30, 40, 50 and 60 volt) were investigated.
Results: For a voltage of 60 V and electrolysis time 60 min, the COD removal efficiency was increased from 48.7% for 52.08 mA/cm² to 77.4% for 69.44 mA/cm². The highest TSS removal efficiency was obtained at the largest current input when the voltage and electrolysis time were kept at 60V and 60 min respectively.
Conclusion: The results showed that the highest COD removal efficiency (77.4%) was obtained when the current density was 69.44 Ma/cm² and the voltage and electrolysis time were kept at 60V and 60 min respectively. Power consumption for this removal level was measured to be 431.26 kWh per kg COD removal. The results obtained revealed that the electrocoagulation technology is an effective treatment process for landfill leachate.