DEVELOPMENT OF NEW ROTATING BIOLOGICAL CONTACTOR WITH SURFACE PROTRUSIONS AND SOLID-LIQUID SEPARATION

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A new disk media,i.e.,reticulated media with the surface protrusions,has been proposed to promote the external diffusion of soluble substrates to the biofilm attached to the Rotating Biological contactor(RBC).The height of protrusions was 5 mm. The diffusion layer thickness with 8 protrusions at 2 rpm was about 100 m,while it was about 200 m without protrusion. In order to reduce the disk weight,a reticulated media was used and it was found that the biofilm was well developed on this type of media, and ammonia fluxes were the almost the same in the solid and reticulated media.In a conventional RBC system,the final clarifier has been used to separate the treated waste-water and detached biomass. The detached biomass is exposed to the turbulent shear in the trough during the transport process to the final clarifier. Such an exposure breaks down the detached biomass into smaller particles which can not settle in the clarifier. As a result,it has been reported that the effluent from the RBC system containes a lot of small organic particles which offer the additional BOD. in this research,a two-story RBC was constructed to achieve the simul-taneous removal of the detached biomass in the trough. Its upper part and lower part function as the RBC and storage space of the settled biomass,respectively. The two-story RBC was operated in a four-staged unit. Experimental investigation showed that the removal efficiency of detavhed biomass in the two-story RBC was very hig to result in the effluent suspended solid concentra-tion of about 10 ppm. It means that the final clarifier may not be necessary in the two-story RBC