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The authors have proposed a novel biofilm-membrane reactor (BMR) in which nitrifying biofilm is fixed on the surface of the rotating membrane disk. With this reactor, both strict solid-liquid separation and oxidation of ammonia nitrogen can be simultaneously performed. Based on the knowledge obtained in the previous experiments with the bench-scale equipment, a pilot scale study was conducted using river water at a water purification plant. The results obtained in the pilot study can be summarized as follows: (1) A pilot scale BMR worked successfully even with the water from an actual drinking water source. By implementation of pre-treatment (coagulation and sedimentation), the filter run could be continued for more than 8 months without any chemical washing. (2) The sponge cleaning developed in this study was found to be very effective. This indicates that the accumulated cake resistance is dominant in the practical situation. (3) Sufficient nitrification was observed when water temperature was high. (4) In addition to the nitrification, biological oxidation of AOC and manganese can be expected with the BMR. In this study, both AOC and manganese concentration in the permeate decreased to a level less than 10 μg/L.

The tubular type and plate-and-frame type are two conventional kinds of membrane modules used for collected human excreta treatment. However. such modules are hindered by high power consumption. blocking of the membrane by fiber components. the need for frequent cleaning and other such problems. Here, the authors investigated the performance and stability of a collected human excreta treatment plant utilizing rotary disk modules developed for the separation of highly concentrated liquid. As a result, it was found that, whether treating activated sludge or coagulated sludge, continuous operation over more than six months can be achieved at a low power consumption and without chemical cleaning. By this the authors have shown that rotary disk modules can be applied to the treatment of highly concentrated residential wastewater.