Abstract: he initial rainwater pollution mainly contributes to rainwater runoff pollution. In this paper, the adsorption effects of fly ash and modified fly ash (MFA) on the removal of total phosphorus and chemical oxygen demand (COD) in the initial rainwater were investigated under various conditions such as different dosage, adsorption time, and pH.  Moreover, optimal adsorption conditions were determined, and the adsorption results were fitted with the data to establish the adsorption isotherm and kinetic models. The result showed that the adsorption effect of MFA was considerably improved. The adsorption efficiency of total phosphorus reached 93.83% when the dosage of MFA in rainwater, pH, and adsorption time were 1.5 g, 8, and 40 min; the adsorption efficiency of COD reached 77.66% when the dosage, pH, and adsorption time were 1.0 g, 6, and 40 min. Furthermore, the adsorption process of total phosphorus using MFA fits the Freundlich adsorption isotherm model and second-order kinetic model, and the adsorption process of COD fits the Langmuir adsorption isotherm model and second-order kinetic model.

Key words: initial rainwater, fly ash, total phosphorus, COD, adsorption