Nutrient pollution caused by nitrogen imbalances in the environment is a concerning environmental issue worldwide, leading to eutrophication, harmful algal blooms, and hypoxic zones. Microbial interactions that naturally transform nitrogen-based compounds are used extensively for biological nutrient removal (BNR) from wastewater. Deammonification, or partial nitritation/anammox (PN/A), is a novel BNR technology with lower energy requirements and chemical and sludge disposal costs than conventional BNR. However, the low-ammonia concentrations in mainstream wastewater treatment present a challenge to PN/A implementation due to the specialized requirements of the microbial communities carrying out this process. In this study, we implemented a strategy of concentrating ammonium on chabazite, a natural mineral with a high ion exchange (IX) capacity for ammonium ions. Once the chabazite was saturated with ammonium, the mineral was bioregenerated via PN/A. A 2-L sequencing batch biofilm reactor (SBBR) with chabazite medium and inoculated with PN/A biofilms was constructed and used to perform IX-PN/A as a single process. We showed that chabazite successfully removed large ammonium loads from low ammonia-strength wastewater (40 mg/L NH4+-N). Once the IX process reached the breakpoint (Ceffluent/Cinfluent = 30%), bioregeneration was initiated by applying recirculation to provide aeration. During the bioregeneration stage of the cycle, the ammonium concentration progressively decreased due to the activity of ammonia oxidizing microorganisms (AOM) and anammox, with suppression of nitrite oxidizing bacteria (NOB). Once the ammonium and nitrite concentrations were &lt;1 mg/L (as N), the zeolite was ready to start the next IX treatment cycle. Bioregeneration with PN/A eliminated the need for chemical inputs or brine regenerant waste production. As the natural chabazite minerals can be reused for many treatment cycles, this process offers a sustainable strategy for a circular economy. Hence, coupling IX with PN/A is a promising technology for BNR of mainstream wastewater, with low costs, environmental impacts and carbon footprint.

Deammonification as a novel and sustainable strategy to remove ammonium from mainstream wastewater

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