Study on technologic condition of sand in immobilized biological activated carbon purification technology

In order to insure biological safety of immobilized biological activated carbon (IBAC), underling sand under IBAC is adopted. By means of immobilizing activated carbon and advanced water by ozone as influent, it's studied the influence between the thickness of the sand underlain IBAC and IBAC purification effect. The results show that the effluent quality of the double deck filter composed by IBAC and sand is better than simplex IBAC filter. The depressed ratio of 11.5% and the mean advanced removal ratios of 34.7% and 26.3% have been obtained for turbidity, bacteria amount and particle amount, but there is no obvious distinction in removal UV₂₅₄ and COD_Mn. Therefore, sand can effectively insure the biological safety of IBAC. The correlation coefficients between sand thickness and turbidity, biomass, particles count removal rate of IBAC effluent are 0.9649, 0.8739 and 0.9888. By the analytical result of curvilinear equation, the best sand thickness range of IBAC filter from 200 mm to 300 mm is ascertained.