Safe Treatment Of Landfill Leachate By The Electrochemical Oxidation Process

The sanitary landfill is still the main disposal of municipal waste in China which has theadvantage of low processing cost. However, landfill leachate has high concentration andhigh toxicity. It can cause serious pollution problems if disposed inadequately. Thegeneral methods mainly include: biochemical method, chemical method and advancedoxidation process. The electrochemical oxidation which has the advantages of simpleoperation, fast response speed and friendly environment has a good prospect in theapplication of refractory organic wastewater treatment.The electrochemical oxidation system with porous carbon cathode andTi/SnO2-Sb2O5-IrO2anode has been constructed and used for the advanced treatment ofthe bio-treated landfill leachate. The effect of cathode potential and Fe2+concentration onTOC removal as well as the performance of COD, NH3-N, total nitrogen (TN) and colourremoval were investigated. The toxicity of leachate were analyzed by applying thebiological method. Moreover, the evolution of organic compounds in the landfill leachateduring the treatment was studied by gas chromatograph-mass spectrometer-computer(GC-MS). The following conclusions were obtained:(1) The results showed that the presented electrochemical process is able to degrade theorganic compounds contained in leachate by anodic oxidation and electro-Fentonoxidation simultaneously.(2) When the electrochemical treatment was carried out at-1.0V of cathodic potentialusing0.5mmol·L-1Fe2+,58%TOC removal was achieved by the treatment of120min. Inthis case,55%COD removal,99%NH3-N removal,60%TN removal and almost complete colour removal were obtained by the treatment of480min.（3）Under the same conditions with biological method and treatment of waste leachate,the electrochemical treatment of garbage leachate can obviously improve the biochemical.untreated leachate after biological treatment of COD removal rate is almost zero, theelectrochemical process360min after biological treatment of leachate COD removal ratereached22.5%.(4) Garbage leachate toxicity decreased significantly. The untreated waste leachate withactivated sludge mixed culture after480min, dehydrogenase activity was only11.3ugTF·mL-1·h-1. By the electrochemical process120min of garbage leachate with activatedsludge mixed culture after480min, dehydrogenase activity was63.83ugTF·mL-1·h-1, andby the electrochemical process240min of garbage leachate with activated sludge mixedculture after480min, dehydrogenase activity was90.5ugTF·mL-1·h-1.（5）GC-MS analysis shows that the main organic compounds of humics contained inthe leachate can be degraded to small molecular compounds during the treatment andfinally be mineralized. Therefore, the electrochemical process united anodic oxidationand electro-Fenton oxidation may present an alternative method for the advancedtreatment of landfill leachate.