Study On Treatment Of Landfill Leachate By Combined Technology Of US/UV-Aged Refuse Bioreactor

The landfill leachate has high concentration of the pollutants and great changes in quality and quantity, which can pollute the surrounding environment. But the leachate usually appears the characteristic of the mature leachate. This kind of leachate contains lots of refractory organic and has a bad biodegradability (BOD/COD is about 0.1). Therefore, the traditional treatment processes have been disabled. In this study, the landfill leachate from Chongqing Changshengqiao Waste Sanitary Landfill Site is the main object and treated by'Ultrasonic/Ultraviolet-Aged Refuse Bioreactor'combined process. The main results are as follows:The property of landfill leachate in this study was 4000⁷000mg/L of COD, 500～900mg/L of BOD, 1300～1800mg/L of NH₃-N and 8～9 of pH value. It showed that the leachate had a mature characteristic.â‘ US, UV and US/UV processes were used to treat the landfill leachate in this study. The effects of different working conditions to the treatment efficiency were investigated and the optimum parameters of every technique unit were obtained:●US process was used to treat 500mL landfill leachate in this experiment. With the US frequency of 40kHz and the US power of 100W, after reacting 3 hours, the removal rates of COD and color were 20% and 60%, respectively.●UV process was used to treat 500mL landfill leachate in this experiment. With the UV power of 100W and the UV wavelength of 254nm, after reacting 3 hours, the removal rates of COD and UV254 were over 30% and near 5%, respectively.●US/UV synergistic process was used to treat 500mL landfill leachate in this experiment. The best result could be achieved by using 6mL 30% H2O2 as oxidant. With the US frequency of 40kHz, the US power of 100W, the UV power of 100W and the UV wavelength of 254nm, after reacting 3 hours, the removal rates of COD and UV190 were 30.72% and over 9%, respectively. Meanwhile, the synergistic effect could also increase the value of BOD/COD from 0.1 to 0.35 and thus the biodegradability of the leachate was improved, which might meet the subsequent biological treatment demand.â‘¡Two-stage Aged Refuse Bioreactor process was also used to treat the effluent of the physical-chemical treatment in this experiment. At the hydraulic loading of 1000mL/d, the COD removal rates of the two stages aged refuse bioreactor were both kept over 50% all the time and had a strong capacity of resistance to impact load besides. The effluents of the first stage and the second stage bioreactor were about 1500mg/L and under 800mg/L, respectively.â‘¢Finally, the'US/UV-Aged Refuse Bioreactor'process was used to treat the landfill leachate in this study. The COD of the combined process effluent was less than 800mg/L and the COD removal rate was over 80%.The results above indicate that the physical-chemical treatment unit can effectively remove the refractory organic and improve the biodegradability of the leachate. The effluent quality of the'US/UV - Aged Refuse Bioreactor'process is able to meet the requirements of class 3 of the national wastewater discharge standard. The selected combined process in the study has a positive reference meaning for the practical treatment project of the mature landfill leachate.