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Conventional biological nitrogen removal (BNR) processes for mainstream municipal wastewater (MMW) treatment have high energy and chemical costs. Partial nitritation/anammox (PN/A) has the potential to reduce the carbon footprint of BNR; however, its implementation for MMW treatment has been limited by the low ammonium and high organic matter concentrations in MMW, which prevent suppression nitrite oxidizing bacteria (NOB) and heterotrophic denitrifiers. In this study, after organic carbon diversion, ammonium was separated from MMW in a novel bench-scale sequencing batch biofilm reactor (SBBR) containing chabazite, a natural zeolite mineral with a high ammonium ion exchange (IX) capacity. After breakthrough, chabazite was bioregenerated by PN/A biofilms. Recirculation was applied from the bottom to the top of the column to create an aerobic zone (top) for ammonia-oxidizing microorganisms (AOM) and an anoxic zone (bottom) for anammox bacteria. Rapid IX-PN/A SBBR startup was observed after inoculation with PN/A enrichments. The time required for bioregeneration decreased with increasing recirculation rate, with high total inorganic nitrogen (TIN) removal efficiency (81 %) and ammonium removal rate (0.11 g N/L/day) achieved at recirculation velocity of 1.43 m/h. The core microbiome of the IX-PN/A SBBR contained a high abundance of bacteria of the phylum Pseudomonadota (15.27–20.62 %), Patescibacteria (12.38–20.05 %), Chloroflexota (9.36–14.23 %), and Planctomycetota (7.55–12.82 %), while quantitative PCR showed the highest ammonia monooxygenase (amoA, 2.0 × 102) and anammox copy numbers (amx, 1.0 × 104) in the top layers. The single-stage IX-PN/A SBBR achieved stable BNR for >two years without chemical inputs, media replacement or brine waste production.
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This content will become publicly available on May 1, 2026
Evaluating Ion Exchange Resins as Ecological Niches for Biofilm Formation and Legionella pneumophila Persistence
Ion exchange (IX) systems are widely used in drinking water treatment to remove charged constituents such as metals, nitrates, and other dissolved ions. While effective for chemical contaminant removal, IX resins may also provide a niche for microbial colonization, including opportunistic pathogens such as Legionella pneumophila. Despite the growing prevalence of residential and commercial IX systems, limited research has examined their potential to support biofilm formation or pathogen persistence. This study developed a bench-scale experimental method to assess the behavior of L. pneumophila in cationic (sulfonic acid functional group) and anionic (quaternary ammonium functional group) exchange resins over a 14-day period. Resins were conditioned for two weeks in the vessels to foster biofilm growth, after which they were inoculated with L. pneumophila and monitored under static batch conditions. Quantification of L. pneumophila was performed using IDEXX Legiolert and mip gene-targeted qPCR, while total bacterial biomass was assessed using 16S rRNA gene qPCR. The results showed consistent detection of L. pneumophila on resin surfaces over time, with higher persistence observed in the resin phase compared to the liquid phase. qPCR results demonstrated relatively stable gene copy concentrations throughout the study, contrasting with declining cultivability observed in Legiolert assays. This discrepancy suggests potential transitions to viable but non-culturable (VBNC) states or persistence of non-viable DNA associated with resin biofilms. Total bacterial concentrations remained high in all experiments, including in both cation and anion resins. While antimicrobial effects of QA resins could not be ruled out, further analyses are needed to evaluate resistance selection or inhibition.
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- Award ID(s):
- 2147106
- PAR ID:
- 10635504
- Publisher / Repository:
- ASU Library
- Date Published:
- Format(s):
- Medium: X
- Institution:
- Arizona State University
- Sponsoring Org:
- National Science Foundation
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