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Strategies for ammonia recovery from wastewater: a review
Mohamed Farghali, Zhonghao Chen, Ahmed I. Osman, Israa Ali +4
KI-Zusammenfassung
55 % KonfidenzThis review examines ammonia recovery and nitrogen removal from wastewater across biological, physicochemical, and emerging technologies. For bioelectrochemical systems (MES), the paper identifies them as an emerging technology alongside electrochemical oxidation and photocatalytic methods, but provides limited mechanistic detail on operating windows, electrode potentials, current densities, or nitrogen species accumulation. The review emphasizes that partial nitrification–anammox and membrane bioreactors achieve 25–40% energy savings and 33–75% sludge reduction, but does not isolate MES performance metrics or trade-offs specific to cathode/anode potential, HRT, or N2O/NO2− dynamics in electrochemical systems.
Zentrale Erkenntnisse
Zielkonflikt Partial nitrification–denitrification saves 25% aeration energy and 40% carbon source compared to full nitrification–denitrification, while reducing reactor volume.
Was heißt das. Operators should target incomplete nitrification to nitrite (not full nitrate) to reduce operating costs and footprint, especially for high-ammonia streams.
Zielkonflikt Anammox combined with partial nitrification saves 100% of exogenous carbon and 62.5% of aeration compared to full nitrification–denitrification.
Was heißt das. Designers should prioritize partial nitrification–anammox for energy-constrained or carbon-limited applications, but must ensure stable nitrite supply and manage low-temperature inhibition.
Schwellenwert Nitrite accumulation during partial nitrification is destabilized by temperature and water quality fluctuations, and requires continuous suppression of nitrite-oxidizing bacteria activity.
Was heißt das. Operators must implement aggressive sludge retention time control and intermittent aeration to maintain nitrite-oxidizing bacteria at shallow levels; process is sensitive to feed variability.
Mechanismus In partial nitrification–anammox, 80% of N2O is produced during aeration phase and 20% during non-aeration phase; nitrite limitation is predicted to decrease N2O under anoxic coupling.
Was heißt das. Operators should minimize aeration intensity and duration, and maintain low nitrite concentrations during anoxic phases to suppress N2O emissions in coupled partial nitrification–anammox systems.
Schwellenwert Anammox leaves approximately 11% of total nitrogen behind as residual nitrate, limiting its applicability for complete nitrogen removal from industrial wastewaters.
Was heißt das. Designers should not rely on anammox alone for complete nitrogen removal; combine with partial denitrification or post-treatment to achieve >90% removal targets.
Ansatzpunkte6
Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.
Hoch Bioelectrochemical systems (MES) are mentioned as an emerging technology but no specific cathode potential, anode potential, current density, or applied voltage ranges are provided for nitrogen cycling.
Paper states 'bioelectrochemical systems...show significant promise for efficient ammonia removal' and lists them as one of three 'prominent bench-scale membrane hybrid systems' but provides zero operating window data, electrode material specifications, or electrochemical kinetics.
Versuch. Vary cathode potential (−0.4 to −0.8 V vs. Ag/AgCl), anode potential (+0.4 to +1.0 V), and current density (0.5–5 A/m²) in a two-chamber MES; measure NH4+, NO3−, NO2−, N2O, and N2 production rates as functions of these parameters.
Hoch No comparison of N2O or NO2− accumulation in bioelectrochemical systems vs. biological partial nitrification–anammox under matched HRT and C/N ratio.
Paper emphasizes N2O production in partial nitrification–anammox (80% during aeration, 20% during non-aeration) but does not report whether MES systems produce more or less N2O, or under what electrochemical conditions N2O is suppressed.
Versuch. Run parallel MES and partial nitrification–anammox reactors at HRT 4–8 h, C/N 2–4, and measure N2O, NO2−, and NO3− profiles over 30 days; correlate with cathode potential and dissolved oxygen.
Mittel Catholyte pH effect on nitrification, denitrification, and anammox in MES is not addressed; only biological systems discuss pH sensitivity.
Paper notes that nitrifying bacteria are inhibited by high free nitrite acid and that pH affects nitrification rates, but does not specify how MES cathode pH (typically 7–9 in alkaline catholyte) influences nitrogen species distribution or recovery.
Versuch. Vary catholyte pH (6.5–9.5) in MES with fixed cathode potential and current density; measure NH4+, NO2−, NO3−, and N2O at each pH; determine optimal pH for ammonia recovery vs. complete denitrification.
Mittel Hydraulic residence time (HRT) trade-offs in MES are not quantified; biological systems show HRT sensitivity for anammox and partial nitrification stability.
Paper states that 'low-temperature conditions...may lead to the accumulation of ammonia and nitrite, requiring adjustment of hydraulic residence time' but does not provide MES-specific HRT ranges or kinetic data.
Versuch. Test MES at HRT 2, 4, 6, 8, and 12 h with fixed cathode potential and current density; measure ammonia removal rate, nitrite accumulation, and N2O production; identify minimum HRT for stable operation.
Mittel Membrane hybrid systems incorporating MES are described as 'promising' but no performance data (removal %, recovery %, energy input, N2O/NO2− levels) are provided.
Paper lists 'bioelectrochemical system-based' membrane hybrid systems as one of three prominent bench-scale approaches but provides no table, figure, or quantitative results for this category.
Versuch. Characterize a bioelectrochemical membrane hybrid system (e.g., MES + forward osmosis or MES + hollow-fiber membrane contactor) for ammonia recovery; measure NH4+ removal, recovery efficiency, N2O/NO2− production, and energy consumption per kg N recovered.
Mittel Dissolved oxygen control in MES cathode compartment and its effect on partial nitrification vs. complete nitrification is not discussed.
Paper emphasizes that low dissolved oxygen triggers N2O in partial nitrification–denitrification and that anammox is inhibited by high dissolved oxygen, but does not specify how MES cathode aeration (or lack thereof) should be managed.
Versuch. Operate MES cathode under anaerobic, microaerobic (DO 0.5–2 mg/L), and aerobic (DO >4 mg/L) conditions; measure nitrification pathway (NH4+ → NO2− vs. NO3−), N2O production, and current density; determine optimal DO for target nitrogen product.
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Zusammenfassung
Abstract The circular economy requires advanced methods to recycle waste matter such as ammonia, which can be further used as a fuel and a precursor of numerous value-added chemicals. Here, we review methods for the recovery of ammonia from wastewater with emphasis on biological and physicochemical techniques, and their applications. Biological techniques involve nitrification, denitrification, and anammox processes and the use of membrane bioreactors. Physicochemical techniques comprise adsorption, membrane filtration, ion exchange, chemical precipitation, ammonia stripping, electrochemical oxidation, photocatalytic oxidation, bioelectrochemical systems, and membrane hybrid systems. We found that nitrification and anammox processes in membrane bioreactors stand out for their cost-effectiveness, reduced sludge production, and energy efficiency. The use of struvite precipitation is an efficient, environmentally friendly, and recyclable method for ammonia removal. Membrane hybrid systems are promising for ammonia recovery, nutrient concentration, and wastewater treatment, with applications in fertilizer production and water purification. Overall, nitrogen removal ranges from 28 to 100%, and nitrogen recovery ranges from 9 to 100%.
Schlagwörter
Kennungen
- Zeitschrift
- Environmental Chemistry Letters
- Jahr
- 2024
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