Biofilm Growths with Sucrose as Substrate

This study was conducted to: (1) Evaluate the effect of DO on cell yield in a fixed film reactor using 1,000 mg/L sucrose as a substrate; (2) evaluate the correlations of the biofilm thickness and density with DO and their resultant substrate stabilization rates; and (3) examine the response of biofilm communities as a result of DO and biofilm thickness changes. Data obtained from this study indicate that DO has only a minor effect on the cell yield. However, the thickness of aerobic biofilm is definitely related to DO, or thickness $\left(\mathrm{mm}\right)=(2.08\times \mathrm{DO})/(9.2+\mathrm{DO})\text{.}$ The biofilm density is also related to its thickness. At a DO of 5 mg/L or lower, the biofilm texture is firm and has a wet density of $27-48\mathrm{mg}/{\mathrm{cm}}^3\text{.}$ At a higher DO (5–16 mg/L), the biofilm becomes porous and filled with air pockets, with its density being reduced to $25\mathrm{mg}/{\mathrm{cm}}^3\text{.}$ The biological community in biofilm at a high DO environment (16 mg/L) is predominantly short rods grouped in a chain structure. At a low DO environment (0.5 mg/L), however, the prevalent forms are large rods, none of which are in chain grouping.