Treatment Of Landfill Leachate By Using Fenton And Electro-Fenton Processes

The expansion of societies and the evolvement of the world state have led to increase in waste generation.On the waste composting or disposal facilities,the physical and chemical deterioration produce a contaminated liquid called leachate.In this topic,experiments have been made to remove pollutants such as total suspended solid?TSS?,heavy metals?Cd,Hg,As Co,Pb,Cu,Ni,Zn,Hg and As?,total organic carbon?TOC?,color,ammonia nitrogen?NH₄⁺-N?,phosphate,turbidity and chemical oxygen demand?COD?,of leachate using Fenton and electro-Fenton processes.Hence,leachate raw water was collected from landfill of a city in Heilongjiang province,China.Diverse operating parameters like reaction time,initial pH,initial concentration of hydrogen peroxide?H₂O₂?and ferrous salt?FeSO₄,7H₂O?,stirring speed,distance between electrode,current intensity,ration(H₂O₂/Fe²⁺)and determination of optimal range by Fenton and electro-Fenton processes to remove recalcitrant organic pollutant from leachate have been studied.The Fenton process was assessed in a jar-test apparatus equipped with six beakers of 1 liter of countenances,where sample has been introduced and treated with 3000mg/L of hydrogen peroxide and 1600mg/L of ferrous salt at different mixing speed?10-700rpm?and time?15-210 minutes?.The highest removal efficiencies were 56.63%and 49.1%for COD,58%and39%for NH₄⁺-N,58.4%and 55%for phosphate,48%and 55.6%for TOC,50.04%and55.09%for turbidity,46.82%and 61.25%for color,79.82%and 51.32%for Cd,52.78%and 47.91%for Co,66.41%and 47.8%for Zn,70.27%and 59.10%for Pb,43.72%and36.5%for Ni,51.92%and 49.82%for Cu under the operating conditions at rapid and slow stirring respectively.These efficiencies have been achieved between 90-500rpm after 90minutes'treatment with an initial pH value of 3.Then,Fenton's reagent assisted by electrolysis was performed in a beaker of 1L capacity,undivided and fitted with two electrodes:one being carbon felt and other platinum plate.The working electrode consisted of carbon felt?4.5×16×1.2 cm?was used as the cathode.The counter electrode?platinum plate:4.5×3.1 cm?used as the anode was located in the center of electrochemical reactor in order to have a better distribution of the electrical potential.The inter-electrodes distance was 3 cm.An amount of 50 mg sodium sulfate?Na₂SO₄?was added to the solution as support electrolyte.50mg/L of iron sulfate FeSO4.7H2O as a catalyst for the Fenton reaction was added to reaction before to start electrolysis and 20mg/L of hydrogen peroxide solution?30%?was used to activate electro-Fenton reaction in manually and in a single step before the electric current was turned on.During the treatment,current intensity fluctuated between 50mA to 300mA at different reaction time?15-180 minutes?.The highest removal was achieved after 30 minutes of treatment,at 200mA of current intensity for all pollutants except heavy metal which achieved best removal at 300mA after 90 minutes,at 3cm of distance between electrode and at initial pH 3.The removal rate was for 75.02%COD,80.61%for NH₄⁺-N,62.37%for phosphate,56.15%for TOC,70.3%for turbidity,91.05%for color,99.78%for Cd,for52.92%Co,91.75%for Zn,72.85%for Pb,48.12%for Ni,81.55%for Cu,93.66 for Hg60.83%under the operating conditions.The results revealed that the electro-Fenton process is a flexible technology for treating these leachates than Fenton process and resolve some disadvantages observed during Fenton treatment such as the high amount of chemical products used and sludge generated.The mineralization of pollutant is also most efficiency by electro-Fenton.