Successful bacterial incorporation into activated sludge flocs using alginate

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Bioremediation

Background:

• Urban wastewater treatment faces challenges with microbial community stability.
• Bioaugmentation aims to introduce beneficial microorganisms to enhance treatment processes.
• The survival and integration of introduced bacteria are critical for successful bioaugmentation.

Purpose of the Study:

• To evaluate the effectiveness of bioaugmentation using Microvirgula aerodenitrificans in an aerobic continuous stirred tank reactor (CSTR) for urban wastewater treatment.
• To investigate the fate and survival strategies of the introduced bacterial strain.
• To assess the impact of immobilization on bacterial persistence and integration.

Main Methods:

• Experiments were conducted in an aerobic continuous stirred tank reactor (CSTR) treating urban wastewater.
• The introduced bacterium, Microvirgula aerodenitrificans, was monitored using a specific fluorescent oligonucleotide probe targeting 16S rRNA.
• Bacteria were initially added directly and later embedded within an alginate matrix before inoculation.

Main Results:

• Direct inoculation of Microvirgula aerodenitrificans resulted in rapid disappearance, attributed to grazing by indigenous microorganisms.
• Immobilization within an alginate matrix led to improved survival.
• Alginate fragments adhered to existing flocs and were colonized by indigenous flora, facilitating the incorporation of microcolonies of the exogenous bacterium into the flocs.

Conclusions:

• Direct bioaugmentation with M. aerodenitrificans is limited by predation in CSTRs.
• Alginate immobilization provides a protective strategy, enhancing the survival and integration of introduced bacteria into the wastewater microbial community.
• This approach shows potential for improving the efficacy of bioaugmentation in wastewater treatment systems.