Population dynamics in an aerobic submerged fixed bed reactor (ASFBR) process

Area of Science:

• Environmental microbiology
• Wastewater treatment engineering
• Biofilm dynamics

Background:

• Aerobic submerged fixed bed reactors (ASFBRs) are crucial for wastewater treatment.
• Understanding microbial population dynamics within ASFBRs is key to optimizing performance.
• Previous studies have not fully elucidated the impact of varying organic loads and oxygen concentrations on ASFBR microfauna.

Purpose of the Study:

• To investigate the population dynamics of microfauna in an ASFBR.
• To determine the behavior of microbial communities under different organic load (OL) and oxygen concentration conditions.
• To correlate microbial community structure with operational parameters in synthetic wastewater treatment.

Main Methods:

• Utilized an aerobic submerged fixed bed reactor (ASFBR) fed with synthetic wastewater.
• Varied organic load (16-65 g COD/m2/d), influent COD concentration (40-400 g COD/m3), and specific air flow (15-127 m3air/kgCOD).
• Collected biofilm samples from the reactor's top for microfauna analysis.

Main Results:

• Microfauna composition and abundance varied significantly with experimental conditions.
• Organic load was a major driver, influencing all studied groups differently; sessile ciliates, metazoa, and flagellates dominated low loads, while crawling forms prevailed at high loads.
• Influent concentration had no significant effect, but aeration intensity impacted most groups, excluding Peranema and Vorticella spp.

Conclusions:

• ASFBR microbial community structure is highly sensitive to organic loading and aeration intensity.
• Despite good treatment yields, the protozoa community differed from conventional systems, with a notable absence of certain sessile and crawling ciliate classes.
• Significant nitrifying activity was observed up to 20 cm depth, beyond which heterotrophic and nitrifying populations became inactive.