Deciphering the Interplay of Sludge Age and Aeration on Reactor Performance and Microbial Dynamics in High-Rate Contact Stabilization

Redirecting wastewater organics from conventional energy-consuming aerobic biological removal to an energy-producing process can transform wastewater treatment plants into energy-neutral or energy-positive resource recovery facilities. This study explores the influence of solids retention times (SRTs) and the absence or presence of aeration in the contact phase on the reactor performance and the microbial community in high-rate contact stabilization (HiCS) reactors. Through high-throughput sequencing, we unveil the diversity and complexity of these microbial communities, pinpointing Aquabacterium and Acinetobacter as dominant species particularly susceptible to these parameters. The shifts in microbial communities had clear correlations with reactor performance, impacting carbon capture efficiency, total chemical oxygen demand removal, extracellular polymeric substances, and polyhydroxyalkanoate production. SRT of 1.3 days with aeration in the contact phase resulted in significantly higher carbon capture efficiency. This work elucidates the intricate interplay between HiCS reactor settings, microbial dynamics, and process performance, paving the road for future work optimizing operational conditions in scaled HiCS reactors.