Removal of soluble organics and manganese by a hybrid MF hollow fiber membrane system

For the removal of turbidity, natural organic matter, manganese and ammonia nitrogen from river water, the performance of a hybrid MF membrane system with circulating powdered activated carbon (PAC) and sludge has been studied using a pilot plant. The PAC was intermittently added to the system for adsorbing the natural organic matter, mainly humic substances. Manganese ions and ammonia nitrogen were biologically oxidized by the iron-oxidizing bacteria and ammonia oxidizing bacteria inhibiting the sludge. While raw water temperatures were higher than 5 degrees C, removal efficiency of soluble manganese and ammonia were almost 100%. However, removal efficiency decreased with decreasing water temperature. The removal efficiency of E260 was about 70% compared to 35% by the MF membrane filtration alone. In the hybrid MF membrane system, the decreasing rate of membrane permeability was much less than that of a conventional MF membrane process. This may result from the reduced organic loading to the membrane due to the adsorption of humic substances on the PAC.