Steel slag, maifanite and bamboo charcoal have a small particle size and irregular shape, while maifanite and bamboo charcoal materials are softer and easier to adsorb pollutants; therefore, their turbidity removal efficiencies are better. When HRT reaches 5 days, the average effluent turbidity concentrations for all four substrates reach 16.4 NTU, 26.3 NTU, 11.5 NTU and 13.3 NTU respectively.