Energy Optimization and Life Cycle Assessment of an Industrial-Scale Ammonia Stripping Process for Aging Landfill Leachate Pretreatment

To address the issues of high carbon source consumption and high operating costs in traditional biological denitrification processes caused by the low carbon-to-nitrogen (COD/NH3-N) ratio in municipal solid waste leachate from aging landfills. This study focused on the Shanghai Laogang Leachate Treatment Plant, it systematically investigated the thermodynamic equilibrium of free ammonia, mass transfer separation mechanisms, process optimization pathways, and environmental and economic benefits of the steam stripping ammonia removal pretreatment technology. Statistical analysis of continuous operational data over seven months revealed a significant positive correlation (P < 0.05) between daily steam consumption and deamination efficiency. Multiple linear regression analysis further indicated that daily influent flow rate is the primary factor influencing steam consumption (standardized coefficient Beta = 0.863). Based on the established energy consumption model, a specific process optimization scheme was proposed: reducing the bottom pressure of the deamination tower by an average of 0.013 MPa while increasing the bottom pressure of the stripping tower by an average of 0.016 MPa, which corresponds to raising the vacuum pump frequency by 3.804 Hz. This is expected to reduce steam consumption by approximately 10%. Operating cost analysis indicated that the steam ammonia stripping pretreatment saved approximately 11.82 yuan per cubic meter of leachate in carbon source costs. Life cycle assessment (LCA) results show that the new process reduces system-wide carbon emissions by 15.7% and electricity consumption by approximately 60%. This study provides a data-driven theoretical basis and optimization pathway for energy conservation, consumption reduction, and stable operation of large-scale thermal steam ammonia stripping processes for leachate.