A bench-scale assessment of ozone pre-treatments for landfill leachates

Abstract

Leachate from stabilized landfill can pose unique challenges to conventional biological wastewater treatment. Ozone-based advanced oxidation processes have garnered recent consideration as an option to reduce the organic strength and recalcitrance of aged landfill leachate. With a bench-scale investigation, the reported work examines the potential for leachate conditioning for further biological treatment by treatment with low-mg/L doses of ozone (0–7.5 mg/L O₃). While not sufficient for significant organics mineralization, the tested ozone doses could potentially produce both selective and non-selective oxidation of recalcitrant leachate organic compounds leaving bio-available products in the pre-treated leachate. Leachate conditioning by O₃ or O₃/H₂O₂ was assessed via monitoring of three anthropogenic organic leachate contaminants(tris-(2-chloroethyl) phosphate, tris-(butoxyethyl)-phosphate and 17β-estradiol (E2)) with ozonation, and ozonation followed by anaerobic incubation. In addition, chemical oxygen demand (COD) and BOD₅ analysis of the ozonated leachate, and methane and total gas formation during the anaerobic incubation were used to assess the degree of leachate conditioning. When treated with O₃ alone, 58% removal of E2 was observed with an ozone dose of 4.5–5.4 mg/L. Direct oxidation of the three leachate contaminants was limited with O₃/H₂O₂ pre-treatment. However, this pre-treatment was observed to have significantly improved degradation of E2 during anaerobic incubation of ozonated leachates (removal rate of E2 was 53.7% with 15 days of incubation), indicating the potential for ozone synthesized co-metabolism. However, overall anaerobic microbial activity was not significantly impacted by the applied ozone pre-treatments, as measured by methane formation, total gas formation, and COD removal during incubation.

Keywords:

• advanced oxidation processes
• ozone
• landfill
• leachate
• anaerobic

Acknowledgements

The authors would like to acknowledge the financial support for this research provided by the Hinkley Center for Solid and Hazardous Waste Research (University of Florida, Gainesville, FL, USA).