Thermophilic aerobic granular biomass for enhanced settleability

Area of Science:

• Environmental Microbiology
• Biotechnology
• Wastewater Treatment

Background:

• Aerobic biological wastewater treatment at thermophilic temperatures (around 55°C) typically results in poorly flocculating biomass.
• Poor biomass settling characteristics hinder efficient solid-liquid separation in wastewater treatment processes.

Purpose of the Study:

• To investigate methods for cultivating well-settling aerobic thermophilic biomass.
• To characterize the biomass structure and identify key microbial players under specific aeration conditions.

Main Methods:

• Culturing thermophilic aerobic biomass in sequencing batch reactors under controlled headspace gas recirculation (containing air).
• Comparison with a control reactor using conventional air sparging.
• Isolation and identification of dominant bacterial species using 16S rDNA sequencing.
• Measurement of sludge volume index (SVI) and granule characteristics.

Main Results:

• Biomass with a low sludge volume index (SVI) as low as 60mL/g was achieved.
• Recirculated headspace gas promoted a mixture of granular and flocculant biomass, while air-only sparging resulted in dispersed, non-flocculating growth.
• Maximum granule diameter ranged from 1.2 to 1.9mm, with disintegration resistance comparable to mesophilic granules.
• Anoxybacillus flavothermus and Pseudoxanthomonas taiwanensis were identified as key species.

Conclusions:

• Controlled aeration using recirculated headspace gas can induce granulation and improve settling of thermophilic aerobic wastewater treatment biomass.
• High alkalinity and CO2, potentially influenced by Anoxybacilli species, may play a role in selecting for flocculating and granulated aerobic thermophilic microbial communities.
• This approach offers a potential solution for enhancing the efficiency of thermophilic aerobic wastewater treatment.