Comparison of Self-Recirculation and Sequencing Recirculation in Bioreactor Landfill

With 2 bioreactors that filled with the fresh refuse landfilled for 3 months from Shanghai LaoGang landfill, two leachate recirculation patterns, which named self-recirculation and sequencing recirculation in the paper, were investigated to determine the leachate treatment efficiency. The experiment includes four stages. In the first and second stage, varying patterns and characteristics of COD, pH and/or VFAs (volatile fatty acids) were analyzed to study the stabilization level of the fresh refuse. In the third and fourth stage, leachates from the equalization basin and sump well of 6-year-old cell in Shanghai LaoGang Landfill were treated. The results of experiments indicated that the sequencing recirculation technology can accelerate the degradation of the refuse and improve the quality of leachate from fresh refuse reactor in comparison with self-recirculation technology. Under the rational hydraulic and organic loads, the effluent COD and NH3-N concentration of the sequencing recirculation can be steadily below 1,000 mg/L and 15 mg/L, respectively. In the treatment of leachate from equalization basin, COD and NH3-N removal ratio of sequencing recirculation were 80%~96% and 99%, which are higher than that of self-recirculation, which were 10%~47% and 0.5%, respectively. In the treatment of leachate from sump well of 6- year-old cell, COD and NH3-N removal ratio of sequencing recirculation were 61%~73% and 99%, which are higher than that of self-recirculation, which were < 4% and 2.5%, respectively.