Ammonium nitrogen (NH4+-N) removal and recovery from wastewater have been critical issues worldwide and key to achieving a sustainable nitrogen cycle and circular economy. In this study, we designed and constructed a pilot-scale air stripping system integrated with a nutrient-capture unit and evaluated the effective pH, temperature, and airflow conditions for maximising NH4+-N removal and recovery from dairy processing wastewater (DPW). Our results demonstrated that increasing pH and temperature substantially enhances NH4+-N removal via air stripping, with higher airflow rates further improving performance. Under these conditions (pH 11, 32 °C, and 300 L min−1), NH4+-N removal from synthetic wastewater reached ≈40% after 6 h air stripping. In comparison, real DPW exhibited slightly lower removal efficiency under the same conditions, achieving ≈34%, likely due to its more complex matrix. Additionally, incorporating a chemical precipitation step followed by filtration prior to air stripping removed NH4+-N from DPW, achieving ≈43%. However, extending the stripping duration under identical conditions significantly improved removal performance, increasing NH4+-N removal in DPW to ≈70%. The downstream capturing system, consisting of acid bath and granulated activated carbon (GAC), consistently recovered 70–95% of the released ammonia (NH3) when even upstream NH4+-N removal via air stripping was moderate. The GAC effectively adsorbed the volatilised NH3, achieving adsorption capacities of up to ≈18 mg/kg. Overall, this integrated system demonstrates strong potential for simultaneous NH4+-N removal and recovery from industrial wastewater streams, offering notable environmental benefits.

Synergistic ammonia recovery from high-ammonia anaerobic digestate via coupled bipolar electrodialysis and membrane contactor system.

From waste to high-value nitrogen: Optimizing and validating direct nitrogen stripping from anaerobic digestate for sustainable microbial protein production.

Ammonia (NH₃), a vital nutrient for biological metabolism, is also increasingly recognized as a promising carbon-free energy carrier. However, its production is dominated by the energy-intensive Haber–Bosch process, which consumes approximately 35–50 MJ per kilogram of nitrogen and accounts for nearly 2% of global energy use, contributing roughly 1.6% of global CO₂ emissions. The primary commercial application of NH₃ is as a nitrogen-based fertilizer, with an estimated 30% of the applied fertilizer eventually entering the wastewater stream. This substantial ammonia runoff negatively impacts the activity of anaerobic microorganisms and contributes to eutrophication and other environmental concerns. Conventional ammonia treatment technologies typically aim to convert NH₃ into inert N₂ gas. However, recovery-oriented approaches are more desirable and increasingly necessary. Although physical, chemical, and biological methods for NH₃ recovery exist, their economic viability remains limited. In this study, we propose a novel electrochemical strategy employing a gas diffusion electrode (GDE) to recover ammonia from ammonia-rich wastewater, particularly in its gaseous form. The system is distinguished by a carbon-based GDE that facilitates efficient oxygen delivery as an electron acceptor via airflow, enabling direct redox reactions at the electrode surface. A key design feature is the narrow, physically and chemically isolated cathodic compartment between the cation exchange membrane (CEM) and the GDE. This configuration maintains a highly alkaline environment, promoting the immediate conversion of transported NH₄⁺ to NH₃, which is then stripped by the supplied airflow—eliminating the need for a separate stripping unit. Electrochemical operation with an airflow of 20 mL/min effectively suppressed NH₃ back-diffusion. Continuous operation using both synthetic and real livestock wastewater (LW) achieved nitrogen fluxes of 890 g N/m²·d and 770 g N/m²·d, respectively, at a current density of 10 mA/cm². The specific energy input was 7.42 kWh/kg N for synthetic LW and 9.44 kWh/kg N for real LW. Compared to traditional air stripping, economic analysis demonstrated that the GDE-based electrochemical system significantly reduces energy consumption—13.44 kWh/kg N versus 27.6 kWh/kg N—primarily due to decreased demand for chemicals, air supply, and pumping, resulting in a 51.3% reduction in total energy usage. Overall, the findings highlight the potential of GDE-based electrochemical systems as an energy-efficient and cost-effective method for ammonia recovery in gaseous form from livestock wastewater.

Landfill leachate that is directly discharged without treatment may jeopardize aquatic environments and human health because it has high organic matter concentrations and high toxicity. This review summarizes the latest research progress on landfill leachate treatment technologies and identifies the mechanisms underlying various treatment technologies, including chemical treatment technologies (e.g., advanced oxidation process, chemical precipitation, and coagulation/flocculation), physicochemical treatment technologies (e.g., adsorption, ion exchange, air stripping, and membrane filtration), biological treatment technologies (e.g., aerobic and anaerobic), and integrated treatment technologies. Additionally, it evaluates the performance of each treatment technology using the pollutant removal rate as an indicator, compares the advantages and disadvantages of each treatment technology, and explores the mechanisms underlying the factors that influence the efficiency of each treatment technology (e.g., pH, temperature, dissolved oxygen). Finally, future research directions on landfill leachate treatment technology are proposed, including membrane contamination problems, adsorbent or ion exchange resin adsorption capacity and regeneration, and new pollutant removal rates and toxicity changes. Additionally, economic and efficient integrated treatment technologies should be developed to promote the application and development of landfill leachate treatment technology.

Enhancement of high-solid chicken manure anaerobic digestion: Insights into ammonia air stripping pretreatment for microbial resilience and hydraulic retention stabilization

Deuterated ammonia (ND3) exhibits growing market demand in the fields of chemical analysis, pharmaceutical industry and semiconductor manufacturing. Currently, industrial production of ND3 relies on harsh conditions and complex processes, leading to high production cost and security risk. Herein, we propose a sustainable relay strategy to produce ND3 by using air and deuterium oxide (D2O) as raw materials, including plasma-driven air-to-NOx conversion and electrocatalytic NOx --to-ND3 conversion. The insufficient supply of reactive deuterium (*D) leads to sluggish kinetics of electrocatalytic deuterium reaction. The well-designed F modified cobalt (F-Co) catalyst exhibits a remarkable yield of 0.75mmol h-1cm-2 and a Faradaic efficiency of 80.43% for ND3 at 200mA cm-2. The combined results of characterizations reveal that fluorine (F) atom can boost D2O dissociation and suppress competing deuterium evolution reaction, thereby providing abundant *D for deuteration reaction. Notably, a pilot-scale demonstration system, consisting of non-thermal plasma, flow electrolyzer, air stripping and ammonia absorber, is constructed to produce practicable ND3 solution (2.8 wt%) with ∼21.45mmol h-1 ND3 production capability by using air and D2O as sources.

Chemical-free electrochemical system with membrane cathode assembly Enables efficient ammonia recovery from urine

This study explores the kinetics of oxygen removal from water using sodium metabisulfite (Na₂S₂O₅) in the presence of iron(II) ions as a catalyst. The research addresses the urgent need for effective and environmentally safe deoxygenation methods, particularly in thermal energy systems where dissolved oxygen causes severe corrosion of metallic surfaces, especially in steam generation processes. Conventional corrosion inhibitors are often ineffective or unsafe for use in such systems. Therefore, deoxygenation remains the most viable approach for preventing oxygen-induced corrosion in industrial water systems. The paper provides a comprehensive analysis of existing water deoxygenation techniques, including physical methods (thermal, vacuum, barbotage), gas-based methods (air stripping, nitrogen or hydrogen saturation), and chemical methods. Among chemical reagents, hydrazine is recognized as highly effective; however, its high toxicity and handling complexity limit its industrial application. Sodium sulfite and its derivatives offer safer alternatives, though their effectiveness can be limited by slow reaction kinetics and the need for subsequent removal of oxidation by-products such as sodium sulfate. To enhance the efficiency of sulfite-based deoxygenation, the authors investigate the catalytic role of iron(II) ions in accelerating the oxidation of sodium metabisulfite by dissolved oxygen. The experimental work involves adding controlled concentrations of sodium metabisulfite and iron(II) sulfate to aerated distilled water and measuring the concentration of oxygen over time using a dissolved oxygen meter. Experiments were conducted under static conditions at room temperature, with variations in Na₂S₂O₅ concentration (50–300 mg/dm³) and Fe²⁺ concentration (0.1–0.5 mg/dm³). The results demonstrate a strong dependence of the oxygen removal rate on both the concentration of the reducing agent (sulfite) and the catalyst (iron ions). At low concentrations of both reagents, the oxygen binding process follows third-order reaction kinetics, with the rate depending simultaneously on the concentrations of oxygen, sulfite, and iron. As the concentrations increase, the reaction order decreases, transitioning to second-order and, eventually, first-order kinetics. At higher levels of sulfite (200–300 mg/dm³) and iron (≥0.5 mg/dm³), the rate-limiting step becomes the oxygen concentration alone, indicating that excess reductant and catalyst are present throughout the reaction duration. The authors calculated reaction rate constants for various concentration combinations and confirmed the reaction order using integrated rate equations. The findings highlight the significant catalytic effect of iron(II) on the rate of oxygen removal, even at low concentrations. The study also proposes a reaction mechanism involving the formation of iron hydroxide complexes and their subsequent oxidation–reduction cycles with sulfite and oxygen. The research contributes to the optimization of chemical deoxygenation processes in water treatment systems, especially for thermal power and heating applications. By understanding the kinetic dependencies and optimizing reagent dosages, industrial operators can achieve faster and more efficient deoxygenation while minimizing reagent consumption and environmental impact. The study emphasizes the potential of sodium metabisulfite as a practical and safer alternative to hydrazine in oxygen removal applications. Future work will focus on evaluating the influence of pH and temperature on the kinetics of oxygen removal by sodium sulfite and metabisulfite, with the goal of further refining deoxygenation technologies under varying operational conditions.

In the processing of agates, the gemstone pieces are submitted to dyeing processes. One of the dyeing processes applied is with Rhodamine B, which provides a reddish-pink colouration. The practice generates a wastewater containing residual amounts of the dye and ethylic alcohol with high polluting potential. Thus, the objective of this paper is to investigate the chemical parameters of the Fenton´s oxidation process to treat this effluent. The main parameters evaluated were [H2O2]:[Fe2+] molar ratio and the concentration of the reagents H2O2 and FeSO4·7H2O. The wastewater contained a concentration of 772 mg L−1 of Rhodamine B and 3% of ethanol in its composition, giving the effluent a high colour, organic load, and toxicity. In the Fenton reaction treatment, 11.1 g L−1 of ferrous sulphate and 20 mL L−1 of oxygen peroxide (in a molar ratio [H2O2]:[Fe2+] of 7.5:1) were defined as the best dosage, which allowed complete alcohol removal, an average absorbance reduction of 99.9% at 554 nm, a TOC reduction of 93.3%, an increase in surface tension from 58.9 to 64.4 mN m−1 and a toxicity factor (TF) decrease from 526 to 16 with respect to the organism Daphnia similis. The Fenton process combines oxidation, coagulation and air stripping mechanisms that substantially reduces pollutants present in this effluent, at a rougher stage. The results obtained are useful, both for the gemstone sector and others that make use of Rhodamine B dye.

This work aims to purify real tannery wastewater (TWW) after a physicochemical characterization. A pretreatment using air stripping (aerobic pretreatment; AP) was first applied and compared to anaerobic pretreatment (ANP). The COD and BOD5 were highly removed by AP, reaching 86% and 88% compared to ANP, which only achieved 48% and 55%, respectively. Following the AP, the sono-photo-Fenton (SPF) process was applied as post-treatment. The optimal conditions pH = 3, [H2O2] = 1834 mg/L, and [Fe2+] = 1281 mg/L improved the COD, color and BOD5 removal of 96%, 98%, and 98%, respectively. Turbidity, N-NO3 -, and N-NO2 - were completely removed (100%) by the combined processes (AP+SPF), while Cr, Cl-, and N-NH4 + were reduced to 99%, 97%, and 99%, respectively. Finally, phytotoxicity tests were performed to confirm the efficiency of the sequential processes. The highest germination percentage, germination rate index, and seedling vigor index for the grains wheat and Medicago sativa were observed using the TWW treated by the AP+SPF, followed by those treated by AP alone. In contrast, no germination indicators were noticed in raw TWW. These findings highlight the significant purification effectiveness of the sequential processes of AP and SPF post-treatment, which suggests the potential use of this combination for the efficient treatment of real liquid effluents.

Optimizing Ammonia Recovery from Biogas Digestate Using Air Stripping: Experimental and Simulation Insights for Sustainable Waste Management

Traditionally, the removal of nitrogenous pollutants from wastewater relied on conventional anaerobic denitrification as well as aerobic nitrification and anoxic denitrification. However, anaerobic denitrification is complicated since it requires stringent environmental conditions as well as a large land, therefore, denitrification and nitrification were performed in two separate reactors. Although high pollutant removal efficiency has been achieved via aerobic nitrification and anoxic denitrification, the demerits of this approach include high operational costs. Other traditional nitrogen removal methods include air stripping, reverse osmosis, adsorption, ion exchange, chemical precipitation, advanced oxidation process, and breakpoint chlorination. Traditional nitrogen removal methods are not only complicated but they are also uneconomical due to the high operational costs. Researchers have discovered that denitrification can be carried out by heterotrophic nitrification-aerobic denitrification (HNAD) microorganisms which remove nitrogen in a single aerobic reactor that does not require stringent operating conditions. Despite the significant effort that researchers have put in, there is still little information known about the mechanisms of antibiotic removal during HNAD. This review begins with an update on the current state of knowledge on the removal of nitrogenous pollutants and antibiotics from wastewater by HNAD. The mechanisms of antibiotic removal via HNAD were examined in detail. Followed by, the enhancement of antibiotics removal via co-metabolism and oxidation of sulfamethoxazole (SMX) as well as the response of microbial communities to antibiotic toxicity. Lastly, the conditions favorable for antibiotic biodegradation and mechanisms for nitrogen removal via HNAD were examined. The findings in this review show that co-metabolism and oxidation of SMX were the main antibiotic biodegradation mechanisms, pathways for antibiotic removal by co-metabolism and oxidation of SMX were also proposed in the discussion. This research indicated the potential of aerobic denitrification in the removal of antibiotics from wastewater. Understanding the mechanisms and pathways of antibiotic removal by HNAD helps wastewater engineers and researchers apply the technology more efficiently. PRACTITIONER POINTS: The mechanisms of antibiotic removal via HNAD were examined in detail. Co-metabolism and oxidation of SMX were the main antibiotic biodegradation mechanisms. Pathways for antibiotic removal by co-metabolism and oxidation of SMX were also proposed. Conditions favorable for antibiotic biodegradation were examined. This research indicated the potential of aerobic denitrification in the removal of antibiotics from wastewater.

This study compared the quality of northern pike eggs collected using traditional methods (hand stripping) and pneumatic methods (air stripping). The effects of different activation solutions (0.4% NaCl, 0.8% NaCl, and hatchery water) on egg fertilization under controlled conditions were also investigated. After egg collection, the Pseudo-Gonado-Somatic Index (PGSI) was measured; the PGSI values in the samples obtained using the pneumatic method (13.8 ± 3.9%) were lower, but did not differ statistically from those obtained by hand stripping (16.5 ± 5.4%). The 0.4% NaCl solution proved to be the most effective for sperm activation, as assessed by the Computer-Assisted Sperm Analysis (CASA) system, compared to the 0.8% NaCl solution. The pneumatic method achieved a higher egg collection efficiency (93.7% occlusion) than the traditional method, with significant differences observed in groups activated with water. The average hatching percentage of larvae was 89.5% in groups using the pneumatic method, compared to 71.2% in the traditional groups, highlighting the advantages of this modern approach. The application of the pneumatic method and 0.4% NaCl for the artificial fertilization of northern pike resulted in higher fertilization and hatching rates compared to other techniques, making this method a promising option for the artificial reproduction of other fish species.

ABSTRACT A 4 L/min pilot study of a pretreatment process for brackish water desalination, known as the Mineral Recovery Enhanced Desalination process, was designed and tested. The objectives of the process are to (1) reduce the volume and mass of concentrate requiring disposal, (2) remove scale-forming constituents, (3) recover commodity minerals, and (4) increase feed water recovery by a subsequent desalination system. The process consists of (1) air stripping to remove dissolved inorganic carbon (DIC), (2) high pH precipitation and membrane filtration to remove high-purity magnesium hydroxide, (3) ion exchange (IX) to remove calcium, and (4) nanofiltration (NF) to remove sulfate. The pretreated water consists of a monovalent salt solution with low scaling potential that allows increased feed water recovery and reduced waste production. The IX regenerant containing calcium can be combined with the high sulfate concentrate from the NF process to precipitate gypsum. The system achieved more than 98% removal of calcium, magnesium, and sulfate and more than 90% removal of DIC. No fouling of NF and reverse osmosis membranes was observed. A steady-state model was developed and calibrated to calculate the chemical quality and material balances for water and major ions.

Wastewater treatment plants play a vital role in resource recovery, particularly through biogas production, a key renewable energy source. Beyond biogas, the digestate from anaerobic digestion is rich in nutrients like ammonia. This study explored the feasibility of recovering ammonia from sewage sludge digestate using air stripping. The process was modeled using Aspen Plus® software, utilizing real data from As-Samra WWTP in Jordan. Various operational parameters, such as digestate feed flow, air flow rate, temperature, and pressure, were analyzed to optimize ammonia recovery. The results showed that with a feed flow rate between 10,000 and 30,000 kg/hr, ammonia recovery reached 85%, with production exceeding 100 kg/hr, where the effect of the flow rate appears mostly at elevated feeding temperatures. Increased air flow rates significantly boosted recovery, achieving 90% efficiency at 60 °C with 50,000 kg/h as air flow. Flashing pressure peaked at 1.5 bar, with 85% efficiency at 95 °C, while higher pressures yielded diminishing returns, stabilizing production around 106 kg/hr. The NaOH feed rate also influenced output, rising from 100 kg/hr at a 50 kg/hr feed rate to 107 kg/hr at 750 kg/hr, with recovery efficiency exceeding 85%. The economic analysis showed that the project had a payback period of 6.07 years, reflecting a reasonable recovery of the initial investment. The net present value was 122,924 USD over 15 years, with 8% amortization rate, indicating that the project created value beyond the initial cost. The internal rate of return was 14.23%, surpassing the discount rate and highlighting the project's financial attractiveness.

Steam stripping of ammonia from ammonia-rich wastewater (5000–20,000 mg/L) was conducted in a continuous-flow rotating packed bed (RPB) at a pH of 11. This study aimed to elucidate the influence of key operational parameters, including the steam-to-liquid ratio, rotational speed (ω), initial ammonia concentration, steam inlet temperature (TSi), and liquid inlet temperature (TLi), on critical performance metrics such as the ammonia removal efficiency (ARE), the volumetric liquid mass transfer coefficient (KLa), and the concentration of the recovered ammonia solution (CR). The findings revealed that a CR of 22.88 wt.% was achieved under the optimal conditions of a steam-to-liquid ratio of 0.175 kg/kg, an initial concentration of 20,000 mg/L, a TSi of 120 °C, and a TLi of 70 °C. Key experimental factors, including the initial ammonia concentration, TSi, and TLi, significantly impacted the achievement of higher ARE and CR values. The KLa values exhibited a decrease with the increase in the steam-to-liquid ratio, while they increased with ω. However, the KLa remained relatively consistent with ω values within the range of 600 to 1200 rpm. In comparison with prior studies, steam stripping of ammonia exhibits a higher ARE than air stripping with RPB and a higher CR than conventional stripping methods. Moreover, RPB requires a smaller size to achieve equivalent ARE compared to conventional stripping apparatuses. Thus, the steam stripping process with RPB equipment emerges as a suitable method for ammonia recovery from ammonia-rich wastewater.

Ultrahigh-purity ammonia recovery from synthetic coke wastewater via membrane contactor: Overcoming phenolic interference and assessing cost efficiency

Development of an efficient pretreatment process and multi-functional acetate co-metabolism strategy for the treatment of high strength biogas slurry using a newly isolated Chlorella sorokiniana

Leveraging organic acids in bipolar membrane electrodialysis (BPMED) can enhance ammonia recovery from scrubber effluents