Abstract: OBJECTIVE:The purpose of this study was to determine the purification effect of modified biological slow filter, with activated alumina and activated carbon as defluorizers, on fluoride and related pollutants in high-fluorine water. METHODS: The chemical oxygen demand (COD_Mn), ammonia nitrogen (NH₄⁺-N),chromaticity and pH value were measured by fluoride ion-selective electrode method,acid potassium permanganate method, Nessler's reagent colorimetric method, platinum cobalt standard colorimetric method, and glass electrode method, respectively. The purification effects of the modified biological slow filter on fluoride and related pollutants in high-fluorine water were analyzed and evaluated. RESULTS: The average instantaneous fluoride removal rates,24 h-post-treatment fluoride removal rates,CODMn removal rates, NH₄⁺-N removal rates,standard-reaching rates of pH value and colority removal rates of the modified biological slow filters,using activated aluminium oxide/activated carbon as fluoride removal agents,were 73.17%/6.14%,87.57%/18.33%,41.77%/18.28%,37.66%/21.17%,100%/85.71%,and 65.71%/22.14%,respectively. CONCLUSION:The modified biological slow filter,with activated aluminium oxide as fluoride removal agent,has relatively good purification effects on fluoride and related pollutants and can be considered for application.

Key words: modified biological slow filter, high-fluorine water, F^- specific adsorption capacity, activated aluminium oxide, activated carbon