Experimental Studies On Treatment Of Nanofiltration Concentrates From Landfill Leachate By UV-catalytic Wet Oxidation Process

The treatment of nanofiltration concentrates from landfill leachate is a new issue due to the large-scale use of membrane separation technology on landfill leachate. However, the membrane separation processes do not degrade the contaminants and only concentrate them into the left nanofiltration concentrates, which is the by-products of the membrane treatment and can lead to even more damage to the environment than common landfill leachate. The nanofiltration concentrates with a low biodegradation were collected from a municipal landfill located in Shenzhen, China. At present, the leachate was treated through coagulation sedimentation, high-efficiency ammonia stripping treatment, expanded granular sludge bed(EGSB), anoxic–aerobic-oxic(A/A/O), membrane bioreactor treatment(MBR), and nanofiltration separation. The nanofiltration concentrates were unbiodegradable.In this dissertation, the UV-Catalytic Wet Oxidation Process(UV-CWOP), which is a novel method and operated at room temperature and pressure, was used for completely degrading the nanofiltration concentrates from landfill leachate. The feasibility of large-scale application was also investigated. Previous experiments show the degradation efficiency’s difference of UV-CWOP, UV/H2O2 and Fenton. The results indicate that UV-CWOP is superior to the others. The optimization of different operating conditions including initial FeSO4?7H2O concentration, H2O2 dosage, initial pH, feeding mode of H2O2, launch temperature and the treatment time was investigated and founded. Under optimal conditions, the COD removal efficiency of 3 h was 92.8% with launch temperature of 25 ℃, initial pH of 3.0, the continuous H2O2 dosage of 0.4 M and initial FeSO4?7H2O concentration of 2 g/L, and the terminal COD results below 100 mg/L can fulfill Chinese effluent discharge standard. The GC-MS spectrogram demonstrates that the long-chain hydrocarbons were abundant in the concentrates. The arboxylic acids, esters, phenols and amine were also found in the concentrates. The content of organic contaminants significantly decreased after the treatment with an excellent degradation efficiency. The acetic acid was found during the treatment and the percentage of acetic acid was 54.9% in the composition of COD after 2 h.With the fundamental support of lab-scale experiments, a pre-industrial scale treatment was performed to assess the feasibility of industrial application in the landfill. The results indicate that The UV-CWOP could effectively remove the organic matters with different level of nanofiltration concentrates, and make the effluent under 200 mg/L. This process is a promising alternative to degrade the concentrates with a great removal rate of refractory contaminants and the good performance of decolorizing effect as well as disinfection. The UV-CWOP gives a novel and possible access to the degradation of nanofiltration concentrates from landfill leachate.