Microbial response on the first full-scale DEMON® biomass transfer for mainstream deammonification

Area of Science:

• Environmental Microbiology
• Wastewater Engineering
• Biotechnology

Background:

• Sidestream partial nitritation and deammonification (pN/A) is effective for high-strength ammonia wastewater.
• Mainstream pN/A expansion is hindered by poor anaerobic ammonia oxidizing bacteria (AnAOB) retention and nitrite oxidizing bacteria (NOB) activity.

Purpose of the Study:

• To investigate methods for establishing AnAOB in mainstream wastewater treatment.
• To monitor microbial community evolution and process performance during mainstream pN/A implementation.

Main Methods:

• Full-scale monitoring of a municipal wastewater treatment plant over 1.5 years.
• Utilized sidestream DEMON® biomass transfer and hydrocyclone operation for granular AnAOB enrichment.
• Employed molecular tools, ex-situ activity tests, and AnAOB quantification (particle tracking, heme measurement).

Main Results:

• Successful establishment of a stable AnAOB biomass in the mainstream system.
• Observed simultaneous anaerobic depletion of ammonia and nitrite, with increased nitrite generation.
• Dissolved oxygen control influenced nitrite levels and NOB community, favoring Nitrobacter over Nitrospira.
• Microbial community shifts, including Chloroflexi and Chlorobi emergence, occurred during unfavorable conditions (winter, high organic load).
• Bioaugmentation with aerobic ammonia oxidizing bacteria (AerAOB) further repressed NOB.
• Mainstream nitrogen removal rate doubled without impairing sidestream pN/A performance.

Conclusions:

• Combining regular sidestream biomass transfer and hydrocyclone operation is crucial for AnAOB establishment in mainstream wastewater treatment.
• Controlled dissolved oxygen and strategic bioaugmentation can manage NOB and enhance nitrite production.
• Wastewater treatment under challenging conditions can unexpectedly promote microbial community shifts beneficial for deammonification.