Aeration effects on Beggiatoa in a laboratory fixed-film growth system

The enrichment of Beggiatoa was derived in a lab-scale continuous flow fixed-film growth system. Under a low aeration and high BOD organic loading condition, the enrichment of Beggiatoa was easily achieved on the glucose-fed slime while it took fairly long time on the acetate-fed one. An increased aeration resulted in a decrease in the Beggiatoa population for the acetate-fed slime, but not for the glucose-fed slime, except slightly at very high aeration level. Sulfate removal rate in both Beggiatoa dominated slimes was generally low, between 10-30%. The glucose-fed slime showed a much higher sulfate removal at high organic loading. The aeration effects on Beggiatoa and sulfate removal were understandable in the context of the Beggiatoa-Desulfovibrio interaction, diffusion and uptake rate of substrate. Glucose diffusion and uptake rate may more rapid, thus air could not penetrate as efficiently into the sulfide-emitting anaerobic layer inhabited by sulfate reducing bacteria such as Desulfovibrio. This may have resulted in less inhibitory effects on the sulfate reducing bacteria.