Occurrence of PAOI in a low temperature EBPR system

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Microbial ecology

Background:

• Accumulibacter Type I (PAO I) are key organisms in enhanced biological phosphorus removal (EBPR).
• Understanding PAO I physiology is crucial for optimizing EBPR systems, especially concerning competitors like glycogen-accumulating organisms (GAO).
• Low temperatures and specific operational conditions can influence microbial community dynamics in wastewater treatment.

Purpose of the Study:

• To investigate the dominance and metabolic behavior of Accumulibacter Type I (PAO I) in an EBPR system under low-temperature conditions.
• To determine if PAO I can switch to a GAO-like metabolism under poly-P limiting conditions at low temperatures.
• To elucidate the microbial ecology and physiology of PAO I in a controlled EBPR environment.

Main Methods:

• Cultivation of a PAO-enriched system from a GAO-enriched culture in an anaerobic-aerobic EBPR setup.
• Operation at a low temperature (10°C) with acetate as the carbon source and a net aerobic solids retention time (SRT) of 6 days.
• Monitoring microbial community shifts and assessing the metabolic response of PAO I under poly-P limiting conditions.

Main Results:

• Accumulibacter Type I (PAO I) became the dominant organism after shifting from a GAO-enriched culture.
• Low temperature (10°C) and a 6-day SRT suppressed the growth of Accumulibacter Type II (PAO II).
• PAO I maintained their phosphorus-accumulating metabolism and did not switch to a GAO-like metabolism under poly-P limiting conditions at low temperatures.

Conclusions:

• The study successfully enriched for Accumulibacter Type I (PAO I) under specific low-temperature EBPR conditions.
• Low temperatures and applied SRT appear to be critical factors in selecting for PAO I over PAO II and potentially GAO.
• Accumulibacter Type I (PAO I) exhibit robust phosphorus-accumulating metabolism at low temperatures, even under nutrient-limiting conditions, contributing valuable insights into EBPR microbial ecology.