Effectiveness of ozonation with zirconium and tin tetrachloride for stabilized anaerobic landfill leachate treatment

Landfill leachate can threaten the environment and human life. Therefore, this study aims to investigate the efficiency of ozone (O3 ), O3 with zirconium tetrachloride (O3 /ZrCl4 ), and O3 with tin tetrachloride (O3 /SnCl4 ) in remediating the stabilized anaerobic landfill leachate (SAL) from Alor Pongsu, Perak. Hydroxyl radical (OH•) is an important oxidizing agent in the ozonation process. Its presence was tested using tert-butyl alcohol. Results showed that using ZrCl4 and SnCl4 in ozonation boosted the generation of hydroxyl radical, thereby enhancing the oxidation process and pollutant removal inside the sample. The O3 /ZrCl4 mix at chemical oxygen demand (COD) to ZrCl4 ratio of 1:1.5, pH 8-9, and 90-min reaction time resulted in the highest reduction rates of COD and color at 91.9% and 99.6%, respectively. All results demonstrated that the optimum performance occurred at alkaline conditions (pH > 8), proving that OH radicals primarily oxidized the pollutants through an indirect reaction pathway. The biodegradability (biochemical oxygen demand/COD) ratio was also considerably improved from 0.02 (raw) to 0.37 using O3 /ZrCl4 , compared with using O3 alone and using O3 /SnCl4 , which only recorded 0.23 and 0.28, respectively, after the treatment. The study demonstrated that O3 /ZrCl4 was the most efficient combination. PRACTITIONER POINTS: The O3 /ZrCl4 recorded the highest COD and color removals. The O3 /ZrCl4 combination also recorded higher OH• concentrations. The biodegradability of leachate (BOD5 /COD ratio) improved from 0.02 to 0.37.