Simultaneous Nitrogen Removal Research Articles

Enhanced Simultaneous Nitrogen and Phosphorus Removal in a Continuous-Flow Granular Sludge System under Gradient-Controlled Hydraulic Loading

The feasibility of the aerobic granulation of activated sludge was investigated in a continuous-flow anaerobic–anoxic–oxic system under gradient-controlled hydraulic loading on the surface of a cyclone separator. Concentrated domestic sewage was used. After 80 days of operation, 80% of activated sludge in the system was in the form of granular sludge with an average particle size of 373 μm. High removal efficiency was achieved for chemical oxygen demand (94.40%), NH4+-N (99.93%), total nitrogen (89.44%), and total phosphorus (96.92%). A batch study revealed that Pseudomonas (1.34%) and Dechloromonas (1.05%) as the main denitrifying phosphorus-accumulating organisms could efficiently remove phosphorus using nitrate as an electron acceptor, which improved the utilization efficiency of carbon sources and achieved simultaneous denitrification and phosphorus removal. Overall, the study demonstrates the feasibility of enhanced denitrification and phosphorus removal in a continuous-flow granular sludge system. The sludge system enables simultaneous nitrogen and phosphorus removal under low carbon-to-nitrogen ratios.

Simultaneous methane mitigation and nitrogen removal by denitrifying anaerobic methane oxidation in lake sediments

Methane (CH4) is a potent greenhouse gas, with lake ecosystems significantly contributing to its global emissions. Denitrifying anaerobic methane oxidation (DAMO) process, mediated by NC10 bacteria and ANME-2d archaea, links global carbon and nitrogen cycles. However, their potential roles in mitigating methane emissions and removing nitrogen from lake ecosystems remain unclear. This study explored the spatial variations in activities of nitrite- and nitrate-DAMO and their functional microbes in Changdanghu Lake sediments (Jiangsu Province, China). The results showed that although the average abundance of ANME-2d archaea (5.0 × 106 copies g−1) was significantly higher than that of NC10 bacteria (2.1 × 106 copies g−1), the average potential rates of nitrite-DAMO (4.59 nmol 13CO2 g−1 d−1) and nitrate-DAMO (5.01 nmol 13CO2 g−1 d−1) showed no significant difference across all sampling sites. It is estimated that nitrite- and nitrate-DAMO consumed approximately 6.46 and 7.05 mg CH4 m−2 d−1, respectively, which accordingly achieved 15.07–24.95 mg m−2 d−1 nitrogen removal from the studied lake sediments. Statistical analyses found that nitrite- and nitrate-DAMO activities were both significantly related to sediment nitrate contents and ANME-2d archaeal abundance. In addition, NC10 bacterial and ANME-2d archaeal community compositions showed significant correlations with sediment organic carbon content and water depth. Overall, this study underscores the dual roles of nitrite- and nitrate-DAMO processes in CH4 mitigation and nitrogen elimination and their key environmental impact factors (sediment organic carbon and inorganic nitrogen contents, and water depth) in shallow lake, enhancing the understanding of carbon and nitrogen cycles in freshwater aquatic ecosystems.

Dissecting the negative influence mechanisms of microplastics on plant and microbial mediated nitrogen removal in constructed wetlands

The escalating prevalence of microplastics (MPs) in constructed wetlands (CWs) raises concerns about their potential effects on nitrogen (N) removal within these ecosystems. Despite this, systematic investigations into the influence of MPs on N-transformation in CWs, encompassing both phytological and microbial dimensions, are notably lacking. Thus, polyethylene (PE) and polyamide (PA), commonly found in wastewater plants, were studied as typical MPs in CWs over 240 days. Extended accumulation time increased nitrogen inhibition in CWs with PE and PA MPs, notably in PA, reducing TN removal by 7.0 % and 10.5 %. For nitrification process, MPs inhibited the relative abundances (RAs) of genes involved in nitrification and carbon fixation metabolisms in nitrifiers through metagenomic analysis, with PA more significantly inhibiting nitrifying enzyme activities. Regarding denitrification, MPs, especially PA, inhibited the RAs of genes involved in electron production, transport, consumption, ATP production and central carbon metabolism in denitrifiers, and activities of denitrifying enzymes. MPs, particularly PA, were found to elevated ROS level and lactate dehydrogenase release, thus hindering nitrogen transformation. Moreover, MPs caused a reduction in c-di-GMP levels and inhibited genes relevant to biofilm regulation (c-di-GMP signaling and quorum sensing), thereby disturbing extracellular polymeric substance metabolism. Regarding plant systems, MPs, particularly PA, were observed to decrease nitrogen uptake, crucial for N-removal. Additionally, inhibited root activity, reduced photosynthesis, and a compromised antioxidant system also contributed to the diminished N-removal in CWs. Overall, our study systematically reveals how MPs, especially PA, impede nitrogen removal in CWs, contributing to further realize the simultaneous removal of MPs and nitrogen in CWs.

Simultaneous Nitrogen Removal and Phosphorus Recovery by Anammox-Induced Magnesium Phosphate Mineralization: Interaction Mechanism between Microorganisms and Mineral Formation

Simultaneous Nitrogen Removal and Phosphorus Recovery by Anammox-Induced Magnesium Phosphate Mineralization: Interaction Mechanism between Microorganisms and Mineral Formation

Simultaneous removal of nitrogen, phosphorus, and organic matter from oligotrophic water in a system containing biochar and construction waste iron: Performances and biotic community analysis

The issue of combined pollution in oligotrophic water has garnered increasing attention in recent years. To enhance the pollutant removal efficiency in oligotrophic water, the system containing Zoogloea sp. FY6 was constructed using polyester fiber wrapped sugarcane biochar and construction waste iron (PWSI), and the denitrification test of simulated water and actual oligotrophic water was carried out for 35 days. The experimental findings from the systems indicated that the removal efficiencies of nitrate (NO3−−N), total nitrogen (TN), chemical oxygen demand (COD), and total phosphorus (TP) in simulated water were 88.61%, 85.23%, 94.28%, and 98.90%, respectively. The removal efficiencies of actual oligotrophic water were 83.06%, 81.39%, 81.66%, and 97.82%, respectively. Furthermore, the high−throughput sequencing data demonstrated that strain FY6 was successfully loaded onto the biological carrier. According to functional gene predictions derived from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, the introduction of PWSI enhanced intracellular iron cycling and nitrogen metabolism.

Simultaneous removal of ammonia nitrogen and manganese by anoxic/oxic (A/O) process from electrolytic manganese residue leachate

Ammonia nitrogen and manganese contained in the leachate of electrolytic manganese residue are causing serious damage to the ecological environment. In this study, anaerobic/oxic (A/O) process as a biological method to achieve simultaneous removal of nitrogen and manganese produced during the actual production of manganese. Results indicated that after 137 d of operation, the system achieved 96.73 ±1.25%, 98.42 ± 0.60%, 96.97 ± 0.19%, and 100% removal of Mn(II), NH4+-N, TN, and chemical oxygen demand (COD), respectively. Extracellular Polymeric Substances (EPS) secreted by microorganisms was converted to carbon source to promote denitrification. Scanning electron microscopy (SEM) showed that Mn(II) formed manganese crystals in the process of complete reflection with sludge, acting as electron donor to achieve simultaneous removal of nitrogen and manganese, and removal of Mn(II) was found by X-ray photoelectron spectroscopy (XPS) through redox and valence changes. 16S rRNA indicated that Proteobacteria, Deinococcus-Thermus, Bacteroidete, and Firmicutes were involved in the process of removal nitrogen and manganese. The presence of Limnobacter allowed a more stable accumulation of NO2--N in reactor, thus achieving shortcut nitrification-denitrification, and Flavihumibacter promoted the secretion of EPS. Collectively, the study reveals that the interaction of autotrophic denitrifying bacteria (Chryseolinea), heterotrophic denitrifying bacteria (Fusibacter, Thauera), and manganese-oxidizing bacteria (Pseudaminobacter, Bacillus, Pedomicrobium, Aeromonasr) achieved simultaneously removal of nitrogen and manganese from the reactor shortcut nitrification-denitrification. This study provides a new insight for the treatment of electrolytic manganese residue leachate produced in the process of manganese production.

Co-occurrence of simultaneous carbon and nitrogen removal and in-situ sludge separation in a novel single unit combined airlift bioreactor (CALBR) for milk processing wastewater treatment

Combined anaerobic-aerobic bioreactors offer considerable potential for treating different industrial wastewaters. However, difficulty in maintaining a stable coexistence of anaerobic, anoxic, and aerobic microbial communities and the necessity of space-consuming external settlers remain as crucial drawbacks associated with these systems. In this study, an innovative single stage combined airlift bioreactor (CALBR) comprising multiple bioreactors (anaerobic/anoxic/aerobic) and an internal settler (a rotating spiral separator for in-situ separation of biomass) was exploited to achieve simultaneous carbon and nitrogen removal from milk processing wastewater (MPW). Results demonstrated that the anaerobic pre-treatment zone made a substantial contribution towards COD and TN removal. Successful biomass separation and high effluent quality revealed that the rotating spiral separator can be used as a coupled clarifier to sustain higher biomass concentration through boosting the sludge compressibility and settleability which further upgrades the overall treatment bioprocess. sCOD removal, TN removal, SVI, and effluent turbidity of ˃96%, ˃75%, ˂90mL/g, and ˂10 NTU were reached, respectively under optimum condition. The outcomes suggested that the novel CALBR is a promising technology which has a great potential to be transferred into practical implementation for high-rate combined biological wastewater treatment and sludge separation.

Aerobic granulation and resource production under continuous and intermittent saline stress

Three sequential batch reactors (SBR) were operated to evaluate salt addition’s impact on granulation, performance, and biopolymer production in aerobic granular sludge (AGS) systems. System R1 was fed without adding salt (control); system R2 operated with saline pulses, i.e., one cycle with salt (2.5 g NaCl/L) addition followed by another without salt; and R3 received continuous supplementation of 2.5 g NaCl/L. The results indicated that the reactors supplemented with salt presented higher concentrations of mixed liquor volatile suspended solids (MLVSS) and better settleability than R1, showing that osmotic pressure contributed to biomass growth, accelerated granulation, and improved physical characteristics. The faster granulation occurred in R2, thus proving the beneficial effects of intermittent salt addition through alternating pulses. Salt addition did not impair the simultaneous removal of carbon, nitrogen, and phosphorus. In fact, R2 showed better carbon removals. In conclusion, continuous or intermittent (pulsed) supplementation of 2.5 g NaCl/L did not lead to increased production of extracellular polymeric substances (EPS) and alginate-like exopolymers (ALE). This outcome could be attributed to the low saline concentration employed, a higher food-to-microorganism (F/M) ratio observed in R1, and possibly greater endogenous consumption of biopolymers in the famine period in R2 and R3 due to the greater solids retention time (SRT). Therefore, this study brings important results that contribute to a better understanding of the effect of salt in continuous dosing or in pulses as a selection pressure strategy to accelerate granulation, as well as the behavior of the AGS systems for saline effluents.

New insights into microbial community for simultaneous removal of carbon and nitrogen via heterotrophic nitrification aerobic denitrification process

Heterotrophic nitrification aerobic denitrification (HNAD) process is considered to be a promising strategy for efficient removal of nitrogen and refractory organic pollutants from aquatic environments. However, isolated single strains or microbial communities of HNAD in most studies suffer from severe inadaptability in the face of complex aquatic environments. Therefore, the existence of fundamental microbial communities that is able to adapt to contaminants through shaping its structure and then remove the pollutants is a promising solution to this deficiency. Herein, we introduced three aromatic compounds (ACs) (2,4,6-Trinitrotoluene, Aniline, and Phenanthrene), and established HNAD microcosms containing the different ACs and nitrogen through aeration. Impressively, the removal efficiencies of aerobic microcosms were nearly 94.5%, 99.4% and 100% for 2,4,6-Trinitrotoluene, Aniline and Phenanthrene, respectively, and above 90% for total nitrogen (TN), demonstrating superior ACs and nitrogen elimination capabilities. Meanwhile, analysis of microbial community structure and symbiont networks exhibited that there are eight commonly dominant genera in different microcosms, namely Arthrobacter, Bacillus, Sphingobium, Massilia, Novosphingobium, Noviherbaspinrillum, Lysobacter and Azohydromonas. Notably, these core bacteria changed only in relative abundance with the microcosms, and had been proven that they all have laudable carbon and nitrogen conversion capabilities. This finding confirmed the existence of basic microbial communities whose dominant species coordinate with each other to adapt to different water environments for the purpose of water purification. Finally, the mechanism of nitrogen transformation at both gene and enzyme levels was revealed by KEGG enrichment analysis. Summarily, this study will provide valuable references for future development of water treatment technologies.

Simultaneous removal of ammonia nitrogen, calcium and cadmium in a biofilm reactor based on microbial-induced calcium precipitation: Optimization of conditions, mechanism and community biological response

With the enhancement of environmental governance regulations, the discharge requirements for reverse osmosis wastewater have become increasingly stringent. This study proposes an innovative approach utilizing heterotrophic nitrification and aerobic denitrification (HNAD)-based biomineralization technology, combined with coconut palm silk loaded biochar, to offer a novel solution for resource-efficient and eco-friendly treatment of reverse osmosis wastewater. Zobellella denitrificans sp. LX16 were loaded onto modified coir silk and showed removal efficiencies of up to 97.38, 94.58, 86.24, and 100% for NH4+-N (65 mg L−1), COD (900 mg L−1), Ca2+ (180 mg L−1), and Cd2+ (25 mg L−1). Analysis of the metabolites of microorganisms reveals that coconut palm silk loaded with deciduous biochar (BCPS) not only exerts a protective effect on microorganisms, but also enhances their growth, metabolism, and electron transfer capabilities. Characterization of precipitation phenomena elucidated the mechanism of Cd2+ removal via ion exchange, precipitation, and adsorption. Employing high-throughput and KEGG functional analyses has confirmed the biota environmental response strategies and the identification of key genes like HNAD.

Fe(II)-driven spatiotemporal assembly of heterotrophic and anammox bacteria enhances simultaneous nitrogen and phosphorus removal for low-strength municipal wastewater

The mainstream anaerobic ammonium oxidation (anammox) faces considerable challenges with low-strength municipal wastewater. A Fe(Ⅱ)-amended partial denitrification coupled anammox (PD/A) process was conducted and achieved a long-term and efficient nitrogen and phosphorus removal, yielding effluent total nitrogen and phosphorus concentrations of 1.97 ± 1.03 mg/L and 0.23 ± 0.13 mg/L, respectively, which could well meet more stringent effluent discharge standard of some wastewater treatment plants in specific geographical locations, e.g., estuaries. Fe(Ⅱ)-driven vivianite formation provided key nucleuses for the optimization of the spatial distribution of heterotrophic and anammox bacteria with enhanced extracellular polymeric substances as key driving forces. Metagenomics analysis further revealed the increase of key genes, enhancing anammox bacteria homeostasis, which also bolstered the resistance to environmental perturbations. This study provided a comprehensive sight into the function of Fe(Ⅱ) in mainstream PD/A process, and explored a promising alternative for synergetic nitrogen and phosphorus removal for low-strength municipal wastewater treatment.

Nitrogen and phosphorus removal from synthetic aquaculture water through electrocoagulation

In this research, we utilized multivariate analysis to evaluate the efficient removal of nitrogen and phosphorus from synthetic aquaculture water using the electrocoagulation process. The elimination of nitrogen and phosphorus is a critical issue in various wastewater treatment plants and aquaculture systems, especially in instances of intensive or super-intensive cultivation. To avert the buildup of pollutants in the water, be it within internal recirculation systems or bodies of water receiving effluents from rearing tanks, it is imperative to employ treatment methodologies designed to effectively eliminate nitrogen and phosphorus nutrients. These nutrients have the potential to induce eutrophication in aquatic ecosystems. However, conventional biological treatment technologies can be ineffective, as they often only remove one pollutant or the other. Furthermore, the individual operations for these systems are complex and require substantial space. Electrocoagulation is a compact and promising technology for treating aquaculture water and effluents for raw nutrient removal. In this context, our findings showcase the simultaneous removal of both nitrogen and phosphorus through the electrocoagulation method. The best treatment was verified for the highest electrical current density (74 A. m-2), the shortest distance between electrodes (4 cm), and the lowest electrolysis time (50 min). In these conditions, the efficiency removal in ammonia nitrogen and total phosphorus were 30.5% and 100% respectively.
 Keywords: electrochemical treatment, eutrophication, water pollution control.

Simultaneous removal of ammonia nitrogen, phosphate, zinc, and phenol by degradation of cellulose in composite mycelial pellet bioreactor: Enhanced performance and community co-assembly mechanism

In this experiment, the prepared tea biochar-cellulose@LDH material (TB-CL@LDH) was combined with mycelium pellets to form the composite mycelial pellets (CMP), then assembled and immobilized with strains Pseudomonas sp. Y1 and Cupriavidus sp. ZY7 to construct a bioreactor. At the best operating parameters, the initial concentrations of phosphate (PO43--P), ammonia nitrogen (NH4+-N), chemical oxygen demand (COD), zinc (Zn2+), and phenol were 22.3, 25.0, 763.8, 1.0, and 1.0 mg L−1, the corresponding removal efficiencies were 80.4, 87.0, 83.4, 91.8, and 96.6%, respectively. Various characterization analyses demonstrated that the strain Y1 used the additional carbon source produced by the strain ZY7 degradation of cellulose to enhance the removal of composite pollutants and clarified the principle of Zn2+ and PO43--P removal by adsorption, co-precipitation and biomineralization. Pseudomonas and Cupriavidus were the dominant genera according to the high-throughput sequencing. As shown by KEGG results, nitrification and denitrification genes were affected by phenol. The study offers prospects for the simultaneous removal of complex pollutants consisting of NH4+-N, PO43--P, Zn2+, and phenol.

Aerobic granulation in a continuous-flow simultaneous nitrification, endogenous denitrification, and phosphorus removal system fed with low-strength wastewater: Granulation mechanism and microbial succession

The culture of aerobic granular sludge (AGS) in continuous-flow system for treating low-strength municipal wastewater is still a challenge for its widespread application. This study developed a continuous-flow reactor based on metabolic and hydraulic selection pressure to explore the feasibility of culturing AGS in conventional continuous-flow mode. The results showed that aerobic granulation was successfully achieved with a mean particle size of 373 μm and almost all granules (95.6 %) were larger than 200 μm. An obvious three-stages granulation process comprised of initial adhesion, the formation of early aggregates that acted as nuclei of granules, and the final AGS maturation, was observed in this work. The selective enrichment of slow-growing bacteria in alternating feast/famine condition played a critical role in the aerobic granulation. The analysis results of extracellular polymeric substances revealed that β-polysaccharides and proteins distributed uniformly within the mature granules, while α-polysaccharides were found mainly concentrated around the granules, which was believed to enhance the mechanical strength of granules. The continuous-flow AGS system exhibited an excellent simultaneous carbon, nitrogen, and phosphorus removal performance with high removal efficiencies of NH4+-N (97.6 %), TIN (91.0 %), COD (93.7 %), and TP (94.8 %). Moreover, a low sludge yield of 0.1 gMLSS/gCOD was obtained for dramatic in situ sludge reduction. Illumina MiSeq sequencing results confirmed the outstanding accumulation of GAOs (Candidatus_Competibacter) and PAOs (Rhodocyclaceae) in the system, which were responsible for simultaneous C, N, P removal and sludge reduction. Overall, this study demonstrated the feasibility of aerobic granulation in conventional continuous-flow mode and offered insights into the granulation mechanism, providing implications and references for the application of AGS technology in existing wastewater treatment plants.

Interactions and coupling mechanisms between Anammox, partial denitrification (PD) and hydroxyapatite (HAP) biomineralization in a PD/A-HAP system

In this study, hydroxyapatite (HAP) crystallization was introduced into a partial denitrification/Anammox (PD/A) process to develop PD/A-HAP granules and achieve simultaneous removal of nitrogen and phosphorus from wastewater. During the formation of PD/A-HAP granules, an unbalanced relationship between the biomass growth and phosphorus crystallization was observed, which resulted in a mass transfer inhibition inside the system. PD and Anammox activities were both impacted by the impeded nutrient contact, and PD process was revealed to be more susceptible to inhibition. Through the regulation of COD and NO3–-N, a dynamic balance between microbial proliferation and phosphorus crystallization was achieved. As a result, high nitrogen removal efficiency (NRE) was attained at 97.8±1.2 % in the final stage of operation, accompanied by a phosphorus removal efficiency (PRE) of 59.4±2.9 %. Furthermore, the recovered phosphorus was transformed into HAP crystals and encapsulated by the PD/A biomass to form granules, which greatly promoted the settling performance of the sludge. This study underlines the importance of reconciling biomass and HAP growth for a strengthened PD/A granular sludge and an enhanced nitrogen removal system. The constructed PD/A-HAP process will expand the application of PD/A with its ability to remove phosphorus while efficiently removing nitrogen.

Simultaneous removal of manganese and ammonium nitrogen from mine water using sodium hexametaphosphate modified natural zeolite loaded by 3D MnOx

Manganese and ammonia nitrogen pollution are widespread in the water of northern Chinese mines, exacerbating regional water scarcity and potential ecological issues. This study aimed to remova dissolved manganese(II) and ammonia nitrogen from mine water using a natural zeolite (NZ) modified with sodium hexametaphosphate impregnation (SHMP-NZ) and loaded with 3D manganese(III)/(IV) oxide nanosheets (SHMP-NZ/MnOx). The influence of factors such as pH value, dissolved oxygen, and coexisting ions on adsorption was investigated. The capacity of NZ to removing ammonium was determined by SHMP impregnation, while the capability to remove manganese was determined by 3D manganese(III)/(IV) oxide nanosheets. Compared to NZ, SHMP-NZ/MnOx exhibited an increased efficiency of 39.93% and 41.54% in the simultaneously removing low-concentration manganese(II) and ammonia nitrogen, respectively. Adsorption processes of manganese and ammonia nitrogen onto NZ and SHMP-NZ/MnOx followed the Elovich and pseudo second order kinetic models, respectively. Both materials exhibited stages of external diffusion, internal diffusion, and reaction equilibrium during adsorption. The maximum adsorption capacities of SHMP-NZ/MnOx for manganese(II) and ammonia nitrogen were 10.12 mg/g and 26.24 mg/g, representing improvements of 72.7% and 113.2%, respectively, compared to NZ. The primary mechanism for ammonia nitrogen removal by SHMP-NZ/MnOx was based on ion exchange, while manganese(II) removal was mediated by Mn3+/Mn4+ species. A regeneration study over five cycles indicated that SHMP-NZ/MnOx possessed promising reusability potential.

Intensifying the simultaneous removal of nitrogen and phosphorus of an integrated aerobic granular sludge-membrane bioreactor by Acinetobacter junii

This work aims at intensifying the simultaneous removal of nitrogen and phosphorus of an integrated aerobic granular sludge (AGS) - membrane bioreactor (MBR) by Acinetobacter junii. After acclimation and enrichment in a sequencing batch reactor (SBR), Acinetobacter junii, a kind of denitrifying phosphate accumulating organism (DPAO), was successfully screened in the used SBR. Then it was verified to be capable of effectively enhancing the performance in the simultaneous removal of nitrogen and phosphorus of AGS-MBR. In the system, DPAO (Acinetobacter junii) mainly occurred in AGS, and the highest ratio even reached 22.8%, but its competitive advantages highly depend on the size of AGS. The presented results can cultivate AGS and enrich DPAO simultaneously to improve the removal of nitrogen and phosphorus of an AGS-MBR, which provide an environmentally friendly approach to upgrade traditional wastewater treatment processes.

Modeling Free Nitrous Acid Inhibition on the Removal of Nitrogen and Atenolol during Sidestream Partial Nitritation Processes.

Sidestream serves as an important reservoir collecting pharmaceuticals from sludge. However, the knowledge on sidestream pharmaceutical removal is still insufficient. In this work, atenolol biodegradation during sidestream partial nitritation (PN) processes characterized by high free nitrous acid (FNA) accumulation was modeled. To describe the FNA inhibition on ammonia oxidation and atenolol removal, Vadivelu-type and Hellinga-type inhibition kinetics were introduced into the model framework. Four inhibitory parameters along with four biodegradation kinetic parameters were calibrated and validated separately with eight sets of batch experimental data and 60 days' PN reactor operational data. The developed model could accurately reproduce the dynamics of nitrogen and atenolol. The model prediction further revealed that atenolol biodegradation efficiencies by ammonia-oxidizing bacteria (AOB)-induced cometabolism, AOB-induced metabolism, and heterotrophic bacteria-induced biodegradation were 0, ∼ 60, and ∼35% in the absence of ammonium and FNA; ∼ 14, ∼ 29, and ∼28% at 0.03 mg-N L-1 FNA; and 7, 15, and 5% at 0.19 mg-N L-1 FNA. Model simulation showed that the nitritation efficiency of ∼99% and atenolol removal efficiency of 57.5% in the PN process could be achieved simultaneously by controlling pH at 8.5, while 89.2% total nitrogen and 57.1% atenolol were removed to the maximum at pH of 7.0 in PN coupling with the anammox process. The pH-based operational strategy to regulate FNA levels was mathematically demonstrated to be effective for achieving the simultaneous removal of nitrogen and atenolol in PN-based sidestream processes.

Development and modeling of an integrated fixed-film activated sludge (IFAS) system for simultaneous nitrogen and carbon removal from an industrial estate wastewater

The potential of an integrated fixed film activated sludge (IFAS) bioreactor for developing simultaneous aerobic and anoxic micro-zones under continuous aeration regime to promote carbon and nitrogen removal from Faraman industrial estate wastewater was evaluated in the present research. The effects of three independent variables on carbon and nitrogen removal were assessed. Overall, the optimum condition with 94 %, 77 %, and 2 NTU of COD (chemical oxygen demand) removal, Total nitrogen (TN) removal, and effluent turbidity has been specified with hydraulic retention time (HRT) of 11 h, air flow rate (AFR) of 3.5 L/min, and filling ratio (FR) of 50 %. To assess the stability of treating processes in the system, the IFAS system was operated in this optimal condition. Moreover, the simulation of the bioreactor was accomplished via calibration and verification of GPS-X model. GPSX simulation results and experimental data were compared using an independent sample T-test, which the T-test result confirmed that there was no significant difference between them.

Advanced electrolysis sulfur-based biofiltration for simultaneous total nitrogen removal and estrogen toxicity reduction from low carbon-to-nitrogen ratio wastewater

A sulfur-based biofilter enhanced by phosphate modified activated carbon as particle electrodes was constructed to simultaneously remove total nitrogen (TN) and estrogen from low carbon-to-nitrogen ratio (C/N) wastewater containing 1 mg/L 17-alpha-ethinylestradiol (EE2). Results showed that the enhanced biofilter achieved outstanding performance in EE2 removal (93.2 %) and TN reduction (effluent < 5 mg/L), demonstrating robustness against C/N fluctuations. It was noteworthy that it successfully reduced both acute toxicity (59.5 %) and estrogenic activity (88.6 %). Comprehensive characterization investigations and microbial community structure analysis revealed that enhanced electron transfer and increased microbial abundance likely contributed to improved biofilter performance. Core microorganisms, such as Pseudomonas and Chryseobacterium were identified as key contributors to synergistic estrogen degradation and denitrification. This study presented a feasible and promising strategy of combined process with three-dimensional electrodes and sulfur-based biofilter, highlighting substantial potential for advanced purification and safe reuse of wastewater.