Airless Ammonia Stripping from Leachate via Hydrodynamic Cavitation

This study introduces an ammonia stripping method without the need of aeration from landfill leachate using cavitation bubbles generated by hydrodynamic cavitation. Leachate is known to cause excessive foaming during air-stripping processes, which effects operational stability and increases costs. Cavitation offers a promising alternative by enabling ammonia removal without aeration. Therefore, this study investigates a cavitation based alternative process for ammonia removal from leachate in the presence and absence of aeration. The effects of cavitation geometry, cavitation number (Cv), airflow rate, and no-air conditions were evaluated at fixed 30 °C and pH 11.0. Additionally, comparisons were made using both synthetic ammonia wastewater and actual landfill leachate. At 0.28 Cv, different cavitation geometries achieved 63–68% removal from both wastewaters. Venturi with 7 mm throat diameter had lower inlet pressure at the same Cv, providing advantage in cavitation inception and intesity. Decrease in Cv improved ammonia removal until 0.17 Cv, and further decreased efficiency. HC without aeration achieved 75% ammonia removal from leachate, and 79% from synthetic wastewater under selected conditions (30 °C, pH 11.0, Cv 0.17). These results suggest that airless hydrodynamic cavitation offer a viable solution for ammonia removal from wastewaters that cause severe foaming challenges under aerated conditions. It is believed that the hydrodynamic cavitation has potential for further improvements on this matter.