The Research Of Landfill Leachate Concentrate Treatment

Concentration of landfill leachate using membrane technology was popular in recent years.However,landfill leachate concentrates produced during this treatment were difficult to remove.The problem concerned on many technical staffs,This paper used electrocoagulation(EC),catalytic ozonation,adsorption on activated carbon(AC)and its combined processes to treat landfill leachate concentrates(LLC).The concentration change of parameters such as chemical oxygen demand(COD),total oxygen carbon(TOC)and ammonium nitrogen(NH4+-N)were observed in these processes to find out the feasible treatment in LLC.Samples were collected from Landfill Leachate Treatment Station of Domestic Waste in Xiamen.The main consequences of this experiment were as follows:Firstly,the EC process stirred by air under initial acidic environment(pH=3～4)with Fe electrode was found to be more efficient to remove 48%of COD of NF concentrate at the condition of 6.7 mA/cm2 of current density and 90 min of reaction time.Under the same condition(pH=5～6)above,TOC removal rate of RO concentrate was 21%.While the stirrer was changed to ozone produced by air source,COD removal efficiency was determined to be 54%under 180 min of reaction time.Also,under the same condition(pH=5～6)above,TOC removal rate of RO concentrate was 10%.When the reaction time was extended to 300 min,COD removal rate of NF concentrate was increased by 6 percentage.With the perspective of economic benefits,it is better to adopt no aeration or air aeration in EC.Neither NF concentrate nor RO concentrate,its concentration of NH4+-N was found to be decrease during the EC process.Secondly,the effluent of different EC processes was utilized as the influent of diverse catalytic ozonation processes.The results revealed as follows:(1)Single ozonation in treating partial effluent of EC had greater degrading efficiency.After applying EC patterns by initial acid condition with air aeration and initial acid condition with air aeration,COD removal rates of NF concentrate on single ozonation then reached to 17%,8%,respectively.While effluent COD concentrations were down to 1681 mg/L,3689 mg/L,respectively.However,TOC removal rates of RO concentrate had no obvious performance on singe ozonation.(2)Catalytic ozonation with nano-ZnO in treating all kinds of effluent of EC had greater degrading efficiency.COD removal efficiencies of NF concentrate behind EC method by initial acid condition with air aeration could reach 24%,while effluent COD concentrations was 1684 mg/L,respectively.TOC removal rates of RO concentrate under EC method by initial acid condition with ozone aeration was 4%,while effluent TOC concentrations was 109 mg/L.(3)Combine ozonation with ultraviolet(UV)was more suitable in treating effluent of landfill leachate concentrate without too much humic acid.COD removal rates of NF concentrate under EC method by initial acid condition with air aeration and initial neutral condition with air aeration were both of 9%,while effluent COD concentrations were 2018 mg/L and 2587 mg/L,respectively.TOC removal efficiencies of RO concentrate effluent from initial acid condition with ozone aeration of EC process was achieved to be 4%.And effluent TOC concentrations was 121 mg/L.(4)Comparing with catalysis by UV and nano-ZnO alone,put these two catalytic ways together had greater result in treating RO concentrate,but did not improve COD removal rate of NF concentrate.COD removal rates of NF concentrate with EC method stirred by air under acid conditions was up to 9%.While effluent COD concentrations was 1999 mg/L.TOC removal rates of RO concentrate with EC method by initial acid condition with air aeration was achieved to 9%.While effluent TOC concentrations was 104 mg/L.(5)After catalytic ozonation,the most of NH4+-N concentration on NF concentrate continued to increase,but NH4+-N concentration on RO concentrate basically behaved a downward trend.Thirdly,as for NF concentrate,after acidification,it went through 180 min of reaction time on EC process with auxiliary aeration of air,90 min of reaction time on catalytic ozonation with 0.2 g/L of nano-ZnO dosage and 5 g/100 mL of AC dosage on adsorption process.The total COD removal rate of NF concentrate above was achieved to be 81%.As for RO concentrate,after acidification,it went through 90 min of reaction time on EC process with auxiliary aeration of air,120 min of reaction time on photocatalytic ozonation with ultraviolet and 0.2 g/L of nano-ZnO dosage and 5 g/100 mL of AC dosage on adsorption process.The total TOC removal rate of RO concentrate above reached 36%.