Mainstream partial denitrification-anammox in sand and expanded clay deep-bed polishing filters under practical loading rates and backwashing conditions

An Advanced Synergy of Partial Denitrification-Anammox for Optimizing Nitrogen Removal from Wastewater: A Review

Anammox is a widely adopted process for energy-efficient removal of nitrogen from wastewater, but challenges with NOB suppression and NO₃^- accumulation have led to a deeper investigation of this process. To address these issues, the synergy of partial denitrification and anammox (PD-anammox) has emerged as a promising solution for sustainable nitrogen removal in wastewater. This paper presents a comprehensive review of recent developments in the PD-anammox system, including stable performance outcomes, operational parameters, and mathematical models. The review categorizes start-up and recovery strategies for PD-anammox and examines its contributions to sustainable development goals, such as reducing N₂O emissions and saving energy. Furthermore, it suggests future trends and perspectives for improving the efficiency and integration of PD-anammox into full-scale wastewater treatment system. Overall, this review provides valuable insights into optimizing PD-anammox in wastewater treatment, highlighting the potential of simultaneous processes and the importance of improving efficiency and integration into full-scale systems.

Insights into integrated glycerol-driven partial denitrification-anaerobic ammonium oxidation system using bioinformatic analysis: The dominance of Bacillus spp. and the potential of nitrite producing via assimilatory nitrate reduction

Partial denitrification-anaerobic ammonium oxidation (PD/A) was considered a novel technology for biological nitrogen removal. In this study, a glycerol-driven PD/A granular sludge reactor was constructed, and its nitrogen removal efficiency and microbial mechanisms were investigated systematically. After optimization, the PD/A reactor achieved 92.3 % of the nitrogen removal (~90 % by anammox) with the influent COD/NO₃^--N ratio of 2.6, and approximate 1.36 mol NO₃^--N was required for removing 1 mol NH₄⁺-N. Granular sludge with layered structure (anaerobic ammonium oxidizing bacteria (AnAOB) was wrapped by the heterotrophic bacteria) was successfully developed, which resulted in the sludge floating. Bacillus was firstly found to be the dominant genus in PD/A system with an abundance of 46.1 %, whereas the AnAOB only accounted for 0.2-2.8 %. Metatranscriptomic analysis showed that the metabolic characteristics obviously changed during the operation, and the differential expressing genes mainly belonged to ABC transport and quorum sensing pathway. Further analysis about the expressing patterns of nitrogen metabolism related genes indicated that the anammox related genes (mainly from Candidatus Brocadia and Candidatus Jettenia) exhibited a much higher expressing level than other genes. Interestingly, the assimilatory nitrate reduction process in Bacillus showed great NO₂^--N producing potential, so it was considered to be an essential pathway participating in PD/A process. This study provided a comprehensive insight into the glycerol-driven PD/A system.

Full-scale transition from denitrification to partial denitrification-anammox (PdNA) in deep-bed filters: Operational strategies for and benefits of PdNA implementation

This study shows for the first time more than 2 years of operation of a mainstream anammox application at full-scale under temperate climate. This implementation of partial denitrification-anammox (PdNA) in deep bed filters at the HRSD York River treatment plant was demonstrated to achieve the benefits of shortcut nitrogen removal without nitrite oxidizing bacteria (NOB) out-selection. The transition from denitrification to PdNA filters required bleeding ammonium to the filters using an optimized ammonium versus NOx (AvN) control in the upstream aeration tanks and maintaining a nitrate residual in the filter effluent through feedforward/feedback control. The latter actions led to savings of 85% in methanol, 100% in alkalinity, and 35% in capacity enhancement. Up to 6 mg NH₄ ⁺ -N/L with an average of 2.2 ± 0.98 mg NH₄ ⁺ -N/L was removed through the anammox pathway, which accounted for about 15% of the overall plant nitrogen removal. Anammox enrichment was confirmed by activity testing and molecular analysis. The large excess of AnAOB capacity present in the filters (5-10 times more than normal operation) resulted in stable and reliable operation through winter conditions and showed potential for further intensification. PRACTITIONER POINTS: For the first time, long-term mainstream anammox was established full-scale through PdNA implementation in deep-bed filters. PdNA implementation required upstream aeration control optimization to provide a blend of ammonium and nitrate to the filters. Efficient anammox enrichment and retention resulted in reliable PdNA performance under different seasonal and influent conditions. PdNA implementation resulted in significant methanol and alkalinity savings and upstream capacity enhancement as ammonia removal depended less on aerobic nitrification. In the event of NOB out-selection and presence of nitrite, carbon savings in PdNA polishing filters can be enhanced via partial nitritation-anammox.