In this study, an experiment was conducted on influent water with low concentrations of organic matter, such as river water or secondary treatment water of a sewage treatment plant, according to HRT changes by using aerobic biofilm. In the biofilm process, as the biofilm increases in thickness, the inner membrane can be low in oxygen transfer rate and become anaerobic conditions, while the detachment of biomass from biofilm occurs. To overcome these limitations in the detachment of microorganisms in biofilm, the yarn, which was made from poly propylene(PP), was weaved and manufactured into a tube. Then, a test was carried out by injecting air so that the interior of the biofilm could create aerobic conditions. The results of the experiment showed that the removal efficiency of TCODcr reached 66.1∼81.2% by HRT 2hr, and 50.9 ∼61.8% after HRT 1 hr. The removal efficiency of SCODcr was 45.9 to 55.1% by HRT 1hr, and 26.1% in HRT 0.5hr, showing the highest removal efficiency in HRT 1hr. The SS removal efficiency was at 81.8 to 94.6%, and the effluent SS concentration was very low, indicating less than 2.2 mg/L in all HRT's. As a result, the SCODcr and NH4 +-N that were removed per specific surface area and attached to microbial biofilm showed the highest efficiency in HRT 1hr with 8.37 gSCODcr/m2·d, 2.93 gNH4 +-N/m2·d. From the result of reviewing the characteristics of biofilm growth, microorganisms were found to be attached, and increased by 36 days. Later, they decreased in number through detachment, but showed a tendency to increase again 41 days later due to microbial reproduction.

The research was performed to compare to the biofilm characteristics and phenol removal efficiency in RBCs(Rotating Biological Contactor) using Rhodococcus sp. EL-GT(single population) and activated sludge(mixed population) as inoculum. Both reactors showed similar tendency on variations of dry weight, thickness and dry density of biofilm. However, the growth of biofilm thickness in 3 and 4 stage of single population reactor has sustained longer than that of the mixed population reactor. Unlike the mixed population reactor, the dry density of biofilm in the single population reactor had a difference between 1, 2 stage and 3, 4 stage. The single population reactor was stably operated without the decrease of phenol removal efficiency in the range of pH 6～9 and 15mM phenol was completely degraded in these pH ranges. But in case of the mixed population reactor, the phenol degradability was dramatically decreased at over 5mM phenol concentration because of the overgrowth and detachment of its biofilm.

This research was performed to investigate the dynamics of microbial community by RBC (Rotating Biological Contactor) using Rhodococcus sp. EL-GT and activated sludge. Cell counts revealed by DAPI were compared with culturable bacterial counts from nutrient agar. Colony counts on nutrient agar gave values 20∼25% and 1∼15% of cell counts (DAPI). The cell counts for the dynamics of bacterial community were determined by combination of in situ hybridization with fluorescently-labelled oligonucleotide probes and epifluorescence microscopy. Around 90∼80% of total cells visualized by DAPI were also detected by the bacteria probe EUB 338. For both reactors proteobacteria belonging to the gamma subclass were dominant in the first stage (1 and 2 stage) and proteobacteria belonging to the gamma subclass were dominant in the last stage (3 and 4 stage).

A mathematical model for organic removal efficiency was investigated in a fluidized bed biofilm reactor by changing the feed flow rate, the residence time and the recycle flow rate. In batch experiment, organic removal could be assumed as first order and an intrinsic first order rate constant(kl) was found 6.4 x 10 exp (-6) ㎤/㎎ sec at influent COD range of 3040 - 6620 ㎎/L. In continuous experiment, at the condition of the influent COD, 3040 ㎎/L, the superficial upflow velocity, 0.47 ㎝/sec, the biofilm thickness 336 ㎛ and the biofilm dry density 0.091 g/mL, the calculated COD removal efficiency from the mathematical model gave 60 % which was very close to the observed value of 66 %. As the feed flow rate was increased, the COD removal efficiency was sharply decreased and at constant feed flow rate, the COD removal efficiency was decreased also as the residence time being decreased.

A number of experiments were conducted in order to investigate the organic removal efficiency and biomass characteristics according to the organic shock loading rate in a fluidized bed biofilm reactor. At the operation conditions of HRT, 8.44 hour, superficial upflow velocity, 0.9 ㎝/sec and temperature, 22±1 ℃, the removal efficiency of SCOD was founded to be 96.5, 92 and 90 % with the organic shock loading rate of 3.5, 10.8 and 33 kgCOD/㎥·day, respectively. Within the F/M ratio ranged 0.4 to 2.0 ㎏COD/㎏VSS·day, the SCOD removal efficiency was shown as 90% at F/M ratio of 2.0 ㎏COD/㎏VSS·day, but the TCOD removal efficiency was 72 % at F/M ratio of 1.8 kgCOD/kgVSS·day. The average biomass concentrations were 7800, 14950 and 27532 ㎎/l on the organic shock loading rate of 3.5, 10.8 and 33 ㎏COD/㎥·day, respectively. This result was agreed with the fact that more biomass could be produced at high concentration of substrate, but some biomass was detached at the onset of shock and easily acclimated at the shock condition.