| Research Abstract |
Three items were investigated in this reseach. They are: (1) unsteady-state mass transfer into the attached microbial film on a rotating disk and the mass transfer scale-up, (2) growth characteristics of the attached biofilm and the suspended biological mass in the contactor, and (3) effect of intermediate settling tank on the performance of rotatring biological disks.
On the first item, the modeling of the unsteady-state oxygen uptake and the substrate utilization for the nitrification processe in a RBC was presented and verified experimentally. The following conclusions were obtained. Under oxygen limitation, an increase in rotational speed had no effect on the amonium removal efficiency and smaller disk achieved higher maximum value of the removal rate. Under substrate limitation, the rotational speed had a large effect on the removal rate. Smaller disk needs higher rotational speed to obtained the same results in larger disk operation.
On the second item, the treatment of artificial wastewater was conducted by using single-stage and two-stages laboratory scale RBC to determine the growth yield and so on. The observed growth yields in single-stage and two-stage operation were 0.27-0.47 and 0.21-0.27, respectively. The net yield was 0.55 and decay constant was 0.05 1/d under oxygen rich condition and was 0.12 1/d under oxygen insufficient condition. The decay constant of MLSS was greater than that of the attached microbial film.
On the last item, it was very effective to the stability of the process, esspecially against shockloading, to use intermediate settling tank between 1st and 2nd stages of RBC.
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