摘要：Dissolved organic nitrogen (DON) is the main precursor for the formation of disinfection by-products (DBPs), especially nitrogenous disinfection by-products (N-DBPs), in water treatment. Reducing the DON concentration in water before the disinfection process can help to minimize the formation of N-DBPs. However, new DON may be produced during the bio-filtering process. In this study, the rule of mutual transformation of nitrogen in biofilters was analyzed, and the relationship between nitrogen transformation and biomass in biofilters was preliminarily investigated. The results show that non-dissolved organic nitrogen (NDON) could be removed by biofilters. The quartz sand filter showed the best NDON removal efficiency, followed by ceramisite, activated carbon and anthracite coal filters. After filtration, total nitrogen (TN) and dissolved inorganic nitrogen (DIN) in water showed decreasing trends, whereas DON showed an increasing trend. Generally, TN was reduced, and the reduction in DIN showed a weak correlation with the increase in DON. Nitrification is not the only pathway of nitrogen removal. Assimilation and anoxic denitrification also play a role in nitrogen transformation during the bio-treatment process. The biomass at different depths in the filter showed a linear positive correlation with the decrease in TN at the corresponding depth, and the correlation coefficient was highest for the top layer of the filter. The study results provide a basis for controlling DON concentration and DBP formation in drinking water treatment plants.
