Removal of recalcitrant contaminants from stabilized landfill leachate by a combination of advanced oxidation process (AOP) and granular activated carbon (GAC) adsorption.

摘要

Hong Kong has experienced water pollution problems partly due to the generation of landfill leachate. The common features of raw leachate in local landfills are a high concentration of NH3-N (2,500-5,000 mg/L), a moderately high strength of organic compounds (5,000-20,000 mg/L), and a low BOD5/COD ratio of less than 0.1. Unless treated, the leachate poses serious threats to the environment and public health.;The laboratory studies reported in this thesis investigate the treatment performance of various individual and/or combined techniques of advanced oxidation processes (AOP) including ozone or H2O2, and granular activated carbon (GAC) adsorption or ammonium stripping for the removal of recalcitrant compounds from stabilized leachate. To improve its performance, surface modification of GAC with NaOH and/or ozone was conducted. The removal performances of refractory compounds and NH3-N by all types of treatments employed in this study were evaluated.;Of the treatments investigated, at the same initial concentrations (COD: 8,000 mg/L; NH3-N: 2,620 mg/L), an integrated process of ozonation and ozone-treated GAC adsorption had a substantially higher removal performance for recalcitrant compounds and NH3-N from the NENT landfill (Hong Kong) (COD: 86%; NH3-N: 92%) than did H2O2-catalyzed GAC adsorption (COD: 80%; NH3-N: 57%). A combined treatment of ammonium stripping and ozone-treated GAC adsorption showed its effectiveness in treating stabilized leachate from the Likang landfill (China). An almost complete removal (99%) of NH3-N and 90% of COD could be accomplished with an NH3-N concentration of 2,546 mg/L and a COD concentration of 30,010 mg/L.;Although most integrated treatments have shown promising results for leachate samples from the NENT or the Likang landfills, they were still unable to generate treated effluents that complied with the COD limit of lower than 200 mg/L and the NH3-N discharge standard of less than 5 mg/L. This suggests that further treatments need to be undertaken not only to complement the degradation of refractory compounds, but also to meet the strict effluent limits imposed by local environmental legislation.