Abstract:
In this research, a fixed-film bioscrubber was developed for hydrogen sulfide
removal. The new strains of microorganisms from the fixed-film bioscrubber systems
found were Acinetobacter sp. MU1_03 and Alcaligenes faecalis MU2_03. Under
certain conditions, they exhibited more than 91 % hydrogen sulfide removal
efficiency. In addition, the mixture of the two strains was capable of 98 % hydrogen
sulfide removal. The removal efficiencies increased with decreasing inlet gas flow
rates, increasing the height of packing and the empty bed retention time. During the
operation, the pH values decreased but not lower than 6.4 which may be due to the
appropriate liquid media used in the recirculation tank. However, the sulfate
production increased when the efficiencies increased which is usually due to the
oxidation of hydrogen sulfide to sulfate. In addition, the intensely decreased
dissolved oxygen could be due to the same reaction. Temperature did not affect the
experiments.
Furthermore, A. faecalis MU2_03 biofilm developments were observed by the
confocal laser scanning microscope (CLSM) and the scanning electron microscope
(SEM). The biofilm thickness was in the trend of increasing from 21.39 μm on day 2
to 37.50 μm on day 3 when the H2S removal efficiency increased from 90 % to 95
%. The thickest of MU2_03 biofilm was illustrated on day 11 of the operation and
the H2S removal was 95 %. The initial adhesion and the exopolysaccharide
production were shown after day 2 of the operation. The excellent structure of A.
faecalis MU2_03 biofilm was illustrated on days 3, 9, and 11 and the H2S removal
efficiency achieved was 95 %. The removal efficiency was decreased to 90 % on day
13. This could be due to the thinning of biofilm because the dead cells were scoured
off by recirculating liquid as a result of the nutrient and oxygen limitation in the
bioscrubber system.