Mainstream partial nitritation/anammox with integrated fixed-film activated sludge: Combined aeration and floc retention time control strategies limit nitrate production.

Implementation of mainstream partial nitritation/anammox (PN/A) can lead to more sustainable and cost-effective sewage treatment. For mainstream PN/A reactor, an integrated fixed-film activated sludge (IFAS) was operated (26 °C). The effects of floccular aerobic sludge retention time (AerSRT), a novel aeration strategy, and N-loading rate were tested to optimize the operational strategy.

High-resolution mapping and modeling of anammox recovery from recurrent oxygen exposure.

Oxygen inhibits anammox, a bioconversion executed by anoxic ammonium oxidizing bacteria (AnAOB). Nonetheless, oxygen is mostly found in the proximity of AnAOB in nitrogen removal applications, being a substrate for nitritation. The experiments performed to date were mostly limited to batch activity tests where AnAOB activity is estimated during oxygen exposure.

Synergistic Exposure of Return-Sludge to Anaerobic Starvation, Sulfide, and Free Ammonia to Suppress Nitrite Oxidizing Bacteria.

A key step toward energy-positive sewage treatment is the development of mainstream partial nitritation/anammox, a nitrogen removal technology where aerobic ammonium-oxidizing bacteria (AerAOB) are desired, while nitrite-oxidizing bacteria (NOB) are not. To suppress NOB, a novel return-sludge treatment was investigated. Single and combined effects of sulfide (0-600 mg S L), anaerobic starvation (0-8 days), and a free ammonia (FA) shock (30 mg FA-N L for 1 h) were tested for immediate effects and long-term recovery.

Pinpointing wastewater and process parameters controlling the AOB to NOB activity ratio in sewage treatment plants.

Even though nitrification/denitrification is a robust technology to remove nitrogen from sewage, economic incentives drive its future replacement by shortcut nitrogen removal processes. The latter necessitates high potential activity ratios of ammonia oxidizing to nitrite oxidizing bacteria (rAOB/rNOB). The goal of this study was to identify which wastewater and process parameters can govern this in reality.

Success of mainstream partial nitritation/anammox demands integration of engineering, microbiome and modeling insights.

Twenty years ago, mainstream partial nitritation/anammox (PN/A) was conceptually proposed as pivotal for a more sustainable treatment of municipal wastewater. Its economic potential spurred research, yet practice awaits a comprehensive recipe for microbial resource management. Implementing mainstream PN/A requires transferable and operable ways to steer microbial competition as to meet discharge requirements on a year-round basis at satisfactory conversion rates.