Enhanced removal of refractory humic- and fulvic-like organics from biotreated landfill leachate by ozonation in packed bubble columns.

Biotreated landfill leachate contains much refractory organics such as humic and fulvic acids, which can be degraded by O. However, the low O mass transfer and high energy cost limit its wide application in landfill leachate treatment. Previous studies proved that packed bubble columns could enhance the O mass transfer and increase the synthetic humic acids wastewater degradation, but the performance of packed bubble columns in real wastewater treatment has not been investigated. Therefore, this study aims to evaluate the feasibility of application of packed bubble column in the real biotreated landfill leachates treatment and provide insights into the transformation of organic matters in leachates during ozonation. Packed bubble columns with lava rocks or metal pall rings (LBC or MBC) were applied and compared with a non-packed bubble column (BC). At an applied O dose of 8.35 mg/(L min), the initial COD (400 mg/L) was only removed for 26% in BC and 32% in MBC while this was 46% in LBC, indicating LBC has the best performance. GC-MS analysis shows that raw biotreated leachate contains potential endocrine disruptors such as di(2-ethylhexyl) phthalate (DEHP). 61% of DEHP was removed in LBC and the least intermediate oxidation products from humic- and fulvic-like organics was detected in LBC. The highest O utilization efficiency (89%) and hydroxyl radical (OH) exposure rate (3.0 × 10 M s) were observed in LBC with lowest energy consumption (E) for COD removal of 18 kWh/m. The enhanced ozonation efficiency in LBC and MBC was attributed to the improved O mass transfer. Besides, LBC had additional adsorptive and catalytic activity that promoted the decomposition of O to generate OH. This study demonstrates that a packed bubble column increases removal and decreases energy use when treating landfill leachate, thus promoting the application of ozonation.