On the dynamics and function of ciliates in sequencing batch biofilm reactors

Area of Science:

• Environmental Microbiology
• Wastewater Engineering
• Protistology

Background:

• Ciliates are key in wastewater treatment, primarily consuming suspended particles.
• Biofilm communities in wastewater treatment plants (WWTPs) are complex and influence treatment efficiency.
• Understanding protist roles in biofilm formation is vital for optimizing WWTP performance.

Purpose of the Study:

• To investigate the succession and impact of ciliate communities in lab-scale sequencing batch biofilm reactors (SBBRs).
• To quantify the influence of specific ciliate species on biofilm structure and function.
• To elucidate the role of ciliates in nutrient transport and water flux within biofilms.

Main Methods:

• Monitoring two lab-scale SBBRs with different carrier materials (expanded shale vs. Kaldnes particles) over one year.
• Identification and quantification of ciliate species, alongside rotifer and nematode abundances.
• Video processing to visualize and measure water flux generated by ciliate motility.

Main Results:

• Peritrichia, particularly Epistylis cf. coronata and Opercularia asymmetrica, dominated the protozoan community.
• Ciliate colonies significantly increased surface area for bacterial colonization.
• Measured water flux generated by ciliates extended over 500 micrometers, with currents up to 180 micrometers/second.

Conclusions:

• Ciliates play a multifaceted role in wastewater biofilms, extending beyond particle ingestion.
• Their motility influences water and nutrient transport within the biofilm matrix.
• Protist monitoring is essential for a comprehensive understanding of biofilm development and WWTP efficiency.