| Leachate generated in the landfill process was seriously harmful to human health and survival environment. After long-term research and development, gradually formed a "pretreatment+membrane bioreactor (MBR)+nanofiltration (NF)/reverse osmosis (RO) combined process. The effluent of membrane bioreactor still contained considerable amount of refractory organics. Nanofiltration and reverse osmosis process can realize good effluent quality, but it also produced a lot of concentrate. Concentrate has a higher concentration of refractory organics and the secondary pollution need to be solved urgently. Therefore, the removal of refractory organics worthy of further research. In this paper, the two stage Fenton process and ultraviolet photo-Fenton process were used for the degradation test of MBR effluent and NF concentration. Fenton and ultraviolet photo-Fenton process could fundamentally solved the secondary pollution of concentrate. This paper also analyzed the removal performance of phthalic acid ester (PAE). monoaromatic hydrocarbons (MACH) and polycyclic aromatic hydrocarbons (PAH) during the two stage Fenton process and Fenton-UV assisted Fenton process. The main conclusions are as follows:(1) The degradation effect of MBR effluent A, B and NF concentrate C were significant in the two stage Fenton process. The removal rates of COD were 81%,84%, 89%, respectively. The concentration of refractory organics was significantly reduced. The removal rates of UV254 were 92%,93%,96%, respectively. The refractory organics of leachate have been well degraded. The color removal rates were 92%,93%,97%, respectively. The color of effluent were less than 16 dilution, which was satisfied with the national emission standards. The two stage Fenton process can effectively reduce the dosage of Fenton reagent and the cost of degradation process.(2) The degradation effect of MBR effluent A, B and NF concentrate C were enhanced by ultraviolet. The removal rates of COD were 81%,91%,93%, respectively. The concentration of refractory organics was lower than that of the two stage Fenton process. The removal rates of UV254 were 96%,97%,96%, respectively. Ultraviolet could not only enhanced the degradation effect of Fenton process, but also led the degradation of some organic matters. The color removal rates were 98%,99%,98%, respectively. The color of effluent were less than 8 dilution, which was satisfied with the national emission standards.(3) The biodegradable degree of leachate was significantly improved during the two stage Fenton process and ultraviolet photo-Fenton process. The effluent of Fenton process was easily biodegradable. A good reaction condition was provided for the subsequent biological treatment process.(4) Detected a total of 7 kinds of PAE, three of them were released by the U.S. EPA priority pollutants, were diethyl phthalate, di(2-ethylhexyl) phthalate and dioctyl phthalate. Detected a total of 13 kinds of MACH, one of them belong to the China’s announcement of priority control pollutants, was 3-Methylphenol, one of them was released by the U.S. EPA priority pollutants, was 2-Nitrotoluene. Detected a total of 12 kinds of PAH, one of them belong to the China’s announcement of priority control pollutants, five were released by the U.S. EPA priority pollutants, were naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, respectively. The concentrations of PAE, MACH and PAH were all decreased in different degree before and after degradation.(5) Continuous test of MBR effluent A was carried out by using the two stage Fenton and biological aerated filter process. Under the conditions of pH=4.0,4 mmol/L Fe2+,12 mmol/L H2O2,200 r/min stirring rate,4:1 gas water ratio and 4 h residence time, COD was nearly 100 mg/L. |
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