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Constructed wetlands (CWs) are considered an environmentally friendly and low-cost wastewater treatment method. For nitrogen removal, CWs have gained extensive attention due to the superior performance. It is noteworthy that plants can affect the microbial community and nitrogen removal. Thus, in this study, the performances of nitrogen removal by CWs with different plant species and seasons were investigated. Panhe constructed wetland, an actual and stable operating artificial wetland, was used as the research object to investigate the nitrogen removal in the real environment. As a whole, the performance of nitrogen removal using CWs in autumn was higher than that in winter. The highest removal of total nitrogen was achieved by the CWs of Acorus calamus L., which reached 49% (autumn) and 37% (winter), respectively. The relationship between microbial community structure and nitrogen removal by CWs was also studied. Microbial community analysis showed that Proteobacteria, Chloroflexi, Acidobacteria and Bacteroidetes accounted for 73.9% of all phyla. This study could provide theoretical support for clarifying the effect of the plant species and seasons on the performance of CWs. [ABSTRACT FROM AUTHOR]

Ecological floating bed (EFB) has been widely used to remove nitrogen and phosphorus from eutrophic water. However, its effects on nitrogen and phosphorus removal are different in various studies. Presently it has not been systematically clear what factors produce effects on EFB removing nitrogen and phosphorus from eutrophic water. In this study, we performed a meta-analysis of 169 articles to discuss the effects of EFB characteristics and experimental conditions on EFB removing nitrogen and phosphorus. Results showed that EFB generally decreased nitrogen and phosphorus concentrations in eutrophic water regardless of EFB characteristics and experimental conditions. EFB showed better effects on simultaneously removing TN, NH4+-N, and TP when it had one of the characteristics: constructed by monocots, 2–3 plant species, an area of 1.1–3.0 m2, and the coverage of 21%-40%. However, NO3−-N removal by EFB was complicated due to the effects of nitrification and denitrification. Moreover, EFB plant density also showed different effects on nitrogen and phosphorus removal. Experimental conditions produced evident effects on EFB removing nitrogen and phosphorus, and it showed better effects under one of the conditions: water temperature of 16–25℃, experimental duration of 31–60 days, long hydraulic retention time, and aeration. This study indicates that EFB can significantly remove nitrogen and phosphorus from eutrophic water, and it is an effective technology to control water eutrophication, but the effects of EFB characteristics and environmental conditions on EFB function should be considered in application. [ABSTRACT FROM AUTHOR]

Microalgal solutions to clean waste streams and produce biomass were evaluated in Nordic conditions during winter, spring, and autumn in Southeast Sweden. The study investigated nitrogen (N) removal, biomass quality, and safety by treating industrial leachate water with a polyculture of local microalgae and bacteria in open raceway ponds, supplied with industrial CO2 effluent. Total N (TN) removal was higher in spring (1.5 g−2d−1), due to beneficial light conditions compared to winter and autumn (0.1 and 0.09 g−2d−1). Light, TN, and N species influenced the microalgal community (dominated by Chlorophyta), while the bacterial community remained stable throughout seasons with a large proportion of cyanobacteria. Winter conditions promoted biomass protein (19.6–26.7%) whereas lipids and carbohydrates were highest during spring (11.4–18.4 and 15.4–19.8%). Biomass toxin and metal content were below safety levels for fodder, but due to the potential presence of toxic strains, biofuels or fertilizer could be suitable applications for the algal biomass. Practitioner points: Microalgal removal of nitrogen from leachate water was evaluated in Nordic conditions during winter, spring, and autumn.Total nitrogen removal was highest in spring (1.5 g−2d−1), due to beneficial light conditions for autotrophic growth.Use of local polyculture made the cultivation more stable on a seasonal (light) and short‐term (N‐species changes) scale.Toxic elements in produced algal biomass were below legal thresholds for upcycling. [ABSTRACT FROM AUTHOR]

The rising aquaculture industry has induced an increase in aquaculture waste, calling for advanced methods to recycle waste in the context of the circular economy. Here, we review methods to treat aquaculture wastewater such as the biofloc technique, aquaponic-aquaculture, rice-fish co-culture, microalgae culture, algal–bacterial culture, membrane and moving bed bioreactors, and electrochemical techniques. We discuss nitrogen cycling, resources recovery, and nitrous oxide emission and mitigations. We observed that aquaculture wastewater irrigation allows for enhanced plant biomass, and biofloc technology improves fish biomass. Nitrogen removal processes, including anammox and partial nitrification, show improved performance. Nitrous oxide emission is mainly dependent on the total ammonia and nitrite concentration. [ABSTRACT FROM AUTHOR]

In the process of flue gas desulfurization and denitrification, the generation of high-sulfate wastewater containing nitrogen is a significant challenge for biological wastewater treatment. In this study, halophilic activated sludge was inoculated in a Sequencing Batch Reactor to remove nitrogen from wastewater with a high sulfate concentration (60 g/L). With the influent concentration of 180 mg/L, the removal rate of total nitrogen was more than 96.7%. The effluent ammonium nitrogen concentration was lower than 1.94 mg/L, and the effluent nitrate nitrogen and nitrite nitrogen concentrations were even lower than 0.77 mg/L. The salt tolerance of activated sludge is mainly related to the increase in the content of ectoine in microbial cells. The Specific Nitrite Oxidation Rate is quite low, while the Specific Nitrite Reduction Rate and Specific Nitrate Reduction Rate are relatively strong. In the system, there are various nitrogen metabolic processes, including aerobic nitrification, anaerobic denitrification, and simultaneous nitrification–denitrification processes. By analyzing the nitrogen metabolic mechanisms and microbial community structure of the reaction system, dominate bacteria can be identified, such as Azoarcus, Thauera, and Halomonas, which have significant nitrogen removal capabilities. [ABSTRACT FROM AUTHOR]

The nitrogen removal performance of bioretention urgently needs to be improved, and sponge iron has great potential to address this challenge. This study reported the results of a long-term investigation on bioretention columns improved by sponge iron, examining the durability of sponge iron from nitrogen removal performance, sponge iron properties, and the evolution of biological elements. The results showed that after 9 months of continuous operation, the removal rates of ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), and total nitrogen (TN) in the bioretention columns with an appropriate proportion of sponge iron could reach 80% (some even over 90%). However, the long-term stress of sponge iron exposure, combined with the cumulative effect of pollutants, might lead to the excessive accumulation of reactive oxygen species (ROS) in plants, thereby posing risks of diminished chlorophyll content and enzyme activity. Simultaneously, the extended exposure could also have detrimental effects on microbial diversity and the abundance of dominant bacteria such as Proteobacteria and Sphingorhabdus. Therefore, it is necessary to select plant species and functional genes that demonstrate high adaptability to iron-induced stress. [ABSTRACT FROM AUTHOR]

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen ( NH 4 + - N ) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m3·m−2·h−1) or a shortened empty bed residence time (EBRT) of 30 min. Residual NH 4 + - N in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior NH 4 + - N removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent NH 4 + - N concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m3). [ABSTRACT FROM AUTHOR]

This study elucidates the impact of fluctuating influent conditions and in situ ultrasonic wave exposure on the stability of aerobic granular sludge (AGS) in the treatment of simulated wastewater emanating from rare earth mining operations. During a stable influent period spanning from Day 1 to Day 95, the seed granules underwent an initial disintegration followed by a re-granulation phase. The secondary granulation was achieved on Day 80 and Day 40 for the ultrasonic reactor (R1) and the control reactor (R2), respectively. Notably, granules formed in R1 exhibited a more porous structure compared to those generated in R2. Subsequently, when the ammonia nitrogen in the influent oscillated between 100 and 500 mg/L during Days 96-140, both reactors yielded compact and densely structured granules. Nitrogen removal profiles were comparable between the two reactors: the removal efficiencies for ammonia nitrogen and total inorganic nitrogen escalated from 95% and 80%, respectively, during Days 1-95, to 95% and 90%, respectively, post-Day 140. A suite of performance metrics indicated that steady-state granules from R1 outperformed those from R2 across several parameters. Specifically, the nitrification/denitrification rates, and relative abundance of denitrifying bacteria were all higher in granules from R1. Conversely, the relative abundance of nitrifying bacteria was comparable between granules from both reactors. However, R1 granules demonstrated lower sludge concentration and smaller average particle size than their R2 counterparts. In conclusion, the AGS system demonstrated robust resilience to fluctuating ammonia nitrogen, and the application of ultrasonic waves significantly enhanced granular activity while achieving in situ sludge reduction. [ABSTRACT FROM AUTHOR]

Interactions between anammox bacteria and ammonium-oxidizing archaea, complete ammonia-oxidizing bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing microorganisms offer a novel approach for the supply of nitrite to anammox bacteria for nitrogen removal from low-ammonium wastewater. Advances in material science reveal that interactions between anammox bacteria and carbonaceous materials, such as graphene oxide, granular activated carbon, biochar, and various forms of iron, can enhance anammox activity and nitrogen removal. The discovery of the extracellular electron transfer capability of anammox bacteria suggests a promising energy-efficient method for nitrogen removal with simultaneous energy recovery. The intrinsic adaptation of marine anammox bacteria to saline conditions positions them as a key tool for treating saline wastewater streams. Anaerobic ammonium oxidation (anammox) is an energy-efficient method for nitrogen removal that opens the possibility for energy-neutral wastewater treatment. Research on anammox over the past decade has primarily focused on its implementation in domestic wastewater treatment. However, emerging studies are now expanding its use to novel biotechnological applications and wastewater treatment processes. This review highlights recent advances in the anammox field that aim to overcome conventional bottlenecks, and explores novel and niche-specific applications of the anammox process. Despite the promising results and potential of these advances, challenges persist for their real-world implementation. This underscores the need for a transition from laboratory achievements to practical, scalable solutions for wastewater treatment which mark the next crucial phase in the evolution of anammox research. [ABSTRACT FROM AUTHOR]

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Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Anaerobic digestion (AD) produces useful biogas and waste streams with high levels of dissolved methane (CH4) and ammonium (NH4+), among other nutrients. Membrane biofilm reactors (MBfRs), which support dissolved methane oxidation in the same reactor as simultaneous nitrification and denitrification (ME-SND), are a potential bubble-less treatment method. Here, we demonstrate ME-SND taking place in single-stage, AD digestate liquid-fed MBfRs, where oxygen (O2) and supplemental CH4 were delivered via pressurized membranes. The effects of two O2 pressures, leading to different O2 fluxes, on CH4 and N removal were examined. MBfRs achieved up to 98% and 67% CH4 and N removal efficiencies, respectively. The maximum N removal rates ranged from 57 to 94 mg N L−1 d−1, with higher overall rates observed in reactors with lower O2 pressures. The higher-O2-flux condition showed NO2− as a partial nitrification endpoint, with a lower total N removal rate due to low N2 gas production compared to lower-O2-pressure reactors, which favored complete nitrification and denitrification. Membrane biofilm 16S rRNA amplicon sequencing showed an abundance of aerobic methanotrophs (especially Methylobacter, Methylomonas, and Methylotenera) and enrichment of nitrifiers (especially Nitrosomonas and Nitrospira) and anammox bacteria (especially Ca. Annamoxoglobus and Ca. Brocadia) in high-O2 and low-O2 reactors, respectively. Supplementation of the influent with nitrite supported evidence that anammox bacteria in the low-O2 condition were nitrite-limited. This work highlights coupling of aerobic methanotrophy and nitrogen removal in AD digestate-fed reactors, demonstrating the potential application of ME-SND in MBfRs for the treatment of AD's residual liquids and wastewater. Sensor-based tuning of membrane O2 pressure holds promise for the optimization of bubble-less treatment of excess CH4 and NH4+ in wastewater. [ABSTRACT FROM AUTHOR]

In this paper, a lab-scale reactor designed to simulate the operations of the North Water Saline Wastewater Treatment Plant (SWWTP) located in Delfzijl, The Netherlands, was constructed and assessed. Unlike conventional municipal wastewater treatment facilities, this industrial plant deals with wastewater containing stubborn chemicals that are difficult to break down, along with a high ratio of chemical oxygen demand (COD) to nitrogen and elevated sodium chloride levels. Furthermore, its treatment process diverges from standard industrial setups by employing an aerobic process preceding the anaerobic phase. The proposed lab-scale reactors were proven stable and effective in mimicking the conditions of the studied industrial SWWTP, particularly in the presence of abundant glycerol, a factor not explored in similar lab-scale models. Throughout the experiment, the removal of COD (specifically glycerol) and nitrogen were monitored, alongside changes in the microbial community within both reactors. The data enabled us to examine the proliferation of microbial populations within the sludge. The results indicated the complete removal of glycerol and ammonia from the system, with some residual nitrate detected in the effluent. The soluble COD decreased in the first reactor (R1) to approximately 50% of the influent and reduced further to less than 100 mg/L in the second reactor (R2), while nitrogen was majorly removed in the R1. By the experiment's conclusion, Actinomycetales was identified as the dominant order in the anaerobic reactor (sometimes even exceeding 70% of the population), which is known for its utilization of glycerol as a carbon source and its tolerance to high salt concentrations in the influent. Conversely, the aerobic reactor was predominantly inhabited by the order Flavobacteriales, which correlates with ammonia concentration. [ABSTRACT FROM AUTHOR]

Simultaneous partial nitrification, anammox, denitrification, and fermentation (SNADF) is a novel process achieving simultaneous advanced sludge reduction and nitrogen removal. The influence of low temperatures on the SNADF reactor was explored to facilitate the application of mainstream anammox. When temperature decreased from 32 to 16 °C, efficient nitrogen removal was achieved, with a nitrogen removal efficiency of 81.9–94.9%. Microbial community structure analysis indicated that the abundance of Candidatus Brocadia (dominant anaerobic ammonia oxidizing bacteria (AnAOB) in the system) increased from 0.03% to 0.18%. The abundances of Nitrospira and Nitrosomonas increased from 1.6% and 0.16% to 2.5% and 1.63%, respectively, resulting in an increase in the ammonia-oxidizing bacteria (AOB) to nitrite-oxidizing bacteria (NOB) abundance ratio from 0.1 to 0.64. This ensured sufficient nitrite for AnAOB, promoting nitrogen removal. In addition, Candidatus Competibacter, which plays a role in partial denitrification, was the dominant denitrification bacteria (DNB) and provided more nitrite for AnAOB, facilitating AnAOB enrichment. Based on the findings from microbial correlation network analysis, Nitrosomonas (AOB), Thauera, and Haliangium (DNB), and A4b and Saprospiraceae (fermentation bacteria), were center nodes in the networks and therefore essential for the stability of the SNADF system. Moreover, fermentation bacteria, DNB, and AOB had close connections in substrate cooperation and resistance to adverse environments; therefore, they also played important roles in maintaining stable nitrogen removal at low temperatures. This study provided new suggestions for mainstream anammox application. [ABSTRACT FROM AUTHOR]

Abstract The biofloc environment needs specific heterotrophic nitrifying bacteria for optimal system performance, hence screening perfect bacterial strains is crucial. Enterobacter cloacae sp. was identified as a novel heterotrophic bacterium isolated from freshwater pond sediment during July, 2022. Through high-throughput sequencing, the isolated bacterium was identified as E. cloacae CAUCoF_BF_01, which demonstrated potential nitrogen removal via heterotrophic nitrification and aerobic denitrification, as well as a preference for different C/N ratios (C/N10, 15, 20, and 25) for consuming nitrogen sources. The bacteria performed superior (p

Artificial zeolite was used as an adsorbent to treat sewage with low C/N from an expressway service area. The effect of zeolite dosage on nitrogen removal from sewage was investigated. The factors affecting the adsorption effect of NH3-N by artificial zeolite were discussed by orthogonal experiments. The mechanism of NH3-N removal by artificial zeolite was discussed by means of adsorption kinetics and thermodynamics, specific surface area analysis (BET) and scanning electron microscopy (SEM). The results showed that artificial zeolite could significantly remove NH3-N and TN in sewage in a short time, and could effectively increase the C/N of sewage. After 24 h reaction, 40 g/L artificial zeolite could reduce NH3-N and TN in sewage to (13.45±0.39) mg/L and (19.23±0.21) mg/L, with the removal rates of (91.14±0.32)% and (87.12±0.10)%, respectively. Meanwhile, the C/N increased from 1.30±0.01 to 5.47±0.07. The orthogonal experiments showed that the effect of various factors on nitrogen removal of artificial zeolite was as follows: zeolite dosage>aeration volume>initial concentration of NH3-N. The adsorption process of NH3-N by artificial zeolite conformed to the quasi-secondary reaction kinetic model (R2=0.990), and the adsorption was a heat-absorbing process. The efficient removal of NH3-N by artificial zeolite was mainly due to its large specific surface area (493.23 m2/g) and its mesoporous pores with a wide distribution range. After adsorption, the particles on zeolite surface became smooth, compact and reduced in number.

Integration of biological activities of the algal and bacterial communities enhances the bioremediation potency of aquaculture systems. The effects of nitrogen removal mediated by Ulva lactuca on the bacterial community structure and the abundance of nitrogen cycle functional genes were investigated using an integrated multi-trophic aquaculture (IMTA) system mainly composed of sea cucumber (Stichopus japonicus), shrimp (Penaeus japonicus), and crab (Portunus trituberculatus). The experimental treatments were separated into two groups: control group (C: without U. lactuca) and algae treatment (A: with U. lactuca). Microbial diversity and abundance indexes, including the Sobs, Shannon, Ace, and Chao1 indexes, were higher in the U. lactuca treatment group in both water and sediment. Flavobacteriaceae and Rhodobacteraceae were the dominant families in both the U. lactuca and control treatment groups in October and November, respectively. In sediment, Bacillaceae was the dominant family in the U. lactuca treatment group throughout the experimental period, whereas Desulfocapsaceae was the dominant family in the control group in October and November. Moreover, the nitrogen cycle functional genes nifH, amoA, nxrB, norB, and nrfA were more abundant in the U. lactuca treatment group than in the control group. Results of water quality and its correlation with bacterial community were comprehensively investigated, revealing that U. lactuca influenced the bacterial community structure and nitrogen cycle by increasing DO in the IMTA system. In conclusion, U. lactuca co-cultured in an IMTA system could represent a novel approach for enhancing nitrogen removal, based on the interaction between the algal and bacterial communities. [ABSTRACT FROM AUTHOR]

The completely autotrophic nitrogen removal over nitrite (CANON) process is significantly hindered by prolonged start-up periods and unstable nitrogen removal efficiency. In this study, a novel umbrella basalt fiber (BF) carrier with good biological affinity and adsorption performance was used to initiate the CANON process. The CANON process was initiated on day 64 in a sequencing batch reactor equipped with umbrella BF carriers. During this period, the influent NH4+-N concentration gradually increased from 100 to 200 mg·L−1, and the dissolved oxygen was controlled below 0.8 mg L−1. Consequently, an average ammonia nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TNRE) of ∼90 and 80% were achieved, respectively. After 130 days, ARE and TNRE remained stable at 92 and 81.1%, respectively. This indicates a reliable method for achieving rapid start-up and stable operation of the CANON process. Moreover, Candidatus Kuenenia and Candidatus Brocadia were identified as dominant anammox genera on the carrier. Nitrosomonas was the predominant genus among ammonia-oxidizing bacteria. Spatial differences were observed in the microbial population of umbrella BF carriers. This arrangement facilitated autotrophic nitrogen removal in a single reactor. This study indicates that the novel umbrella BF carrier is a highly suitable biocarrier for the CANON process. HIGHLIGHTS The umbrella basalt fiber (BF) carrier CANON reactor achieved rapid start-up and stable operation.; There were spatial distribution differences between AOB and anammox bacteria in the umbrella BF carrier.; Umbrella BF carriers enhance the abundance and diversity of microbial communities.;

Nitrogen in digested swine wastewater is currently difficult to directly degrade by an activated sludge process in a sequencing batch reactor (SBR), with resulting failure of the effluent to meet emission standards. In this study, rice husk biochar was optionally added into SBR to enhance biochemical properties for digested swine wastewater, especially for nitrogen degradation. The relative nitrogen removal mechanism for microbial community was probed by means of high-throughput sequencing. The results indicated that chemical oxygen demand (COD), ammonia (NH4+-N), and total nitrogen (TN) removal efficiency of digested swine wastewater was separately at 85.3%, 81.3%, and 65.2% using rice husk biochar with biofilm, which was 3.5%, 24.4%, and 14.7% higher than that of activated sludge, under influent of 2609 mg·L-1 COD, 337.0 mg·L-1 NH4+-N, 344 mg/L TN, and 7.77 C/N. High-throughput sequencing revealed that rice husk biochar with biofilm contained Proteobacteria, Thauera, Comamonas, Acinetobacter, Pseudomonas, Flavobacterium, and Corynebacterium to enhance nitrogen removal of digested swine wastewater. The results not only provide theoretical support for biochar with biofilm to improve digested piggery wastewater treatment, but also have great significance in resource utilization of agricultural waste and eco-environmental protection.

Abstract Decentralized wastewater reclamation and reuse systems have drawn much attention due to their capability for reducing the energy demand for water conveyance and reclaiming wastewater for local re-use. While membrane bioreactor (MBR) stands as a mature technology offering comprehensive solid and liquid separation, membrane capacitive deionization (MCDI) presents a promising avenue for ion separation. Unfortunately, MCDI has seldom been incorporated into decentralized wastewater reclamation and reuse systems. This study aims to exemplify the design and the operation of the synergistic integration of MBR and MCDI system with a practical capacity of 1 m3 d− 1, showcasing its efficacy in reclaiming and reusing water at regional level. The integrated system demonstrated significant high removal of total organic carbon (from 97 to 2 mg L− 1) and chemical oxygen demand (COD, from 218 to 92% TN removal). A significant milestone of MCDI unit was reached with the remarkable removal efficiency of total ions (93%) and water recovery (80%) using a stop-flow regeneration approach coupled with an optimized voltage of 2.0 V. The MCDI unit not only proved its high stability but also featured low energy consumption (0.44 kWh m− 3). Overall, synergizing MBR and MCDI systems emerges as a sustainable and effective solution for decentralized wastewater reclamation and reuse, contributing to a more environmentally friendly and resource-efficient water management paradigm.

Johkasou systems have emerged as quintessential examples of decentralized wastewater treatment technologies due to their compact design, easy operation, and robust resistance to mechanical impact attributes that are particularly effective in mitigating and treating rural domestic wastewater. Although the efficiency of the Johkasou process in removing nitrogen and phosphorus has been well-documented, a comprehensive synthesis of the underlying mechanisms and influencing factors is still elusive. This review seeks to elucidate these aspects by detailing the biogeochemical pathways involved in nitrogen and phosphorus removal, characterizing the key microbial consortia, and addressing the potential accumulation of nitrous oxide (N2O). Furthermore, the review critically examines the impact of various media used in Johkasou systems on nutrient removal efficacy, with a particular emphasis on nitrogen. It also proposes a range of practical adjustments to design parameters, including dissolved oxygen (DO), pH, temperature, and hydraulic retention time (HRT), to enhance process performance. Finally, the practical implementation of Johkasou systems and their integration with ancillary processes in actual domestic sewage treatment scenarios are synthesized, providing a theoretical foundation for advancing Johkasou methodologies in rural areas. [ABSTRACT FROM AUTHOR]

Lumen pressure is of crucial importance to achieve simultaneous nitrification and denitrification (SND) in the membrane aerated biofilm reactor (MABR); so, in this study, a laboratory-scale MABR was operated under different lumen pressures (7 kPa, 10 kPa, 13 kPa, and 16 kPa) successively to verify its impact on nitrogen removal. The results showed that NH4+-N oxidation was deficient under 7 kPa due to inadequate oxygen supply, while denitrification was depressed under 16 kPa. Total nitrogen removal efficiency was similar under 10 kPa and 13 kPa (around 78.9%), much higher than that under 7 kPa and 16 kPa (approximately 50%). The biomass density (22.35 g/m2) and biofilm thickness (500.3 µm) were the highest under 13 kPa, and EPS was increasingly secreted along with the increase in lumen pressure. The relative abundance of Nitrospirae was highest under 16 kPa (3.53%), indicating a higher lumen pressure could promote nitrifiers. The denitrifying-related microbes, such as β-proteobacteria, α-proteobacteria and ε-proteobacteria, showed an increasing and then decreasing pattern along with lumen pressure increase, and were enriched at 10 kPa. The results could draw the conclusion that SND could be achieved at moderate lumen pressure, i.e., 10 kPa and 13 kPa in this study. [ABSTRACT FROM AUTHOR]

Nitrogen and phosphorous compounds are significant pollutants in urban stormwater runoff. In this study, three lab-scale bioretention cells, namely a control reactor CM, and reactors M1 and M2 containing Scrap Iron Filings (SIF) with granulated brick (M1) and pumice pellets (M2), respectively, were used to evaluate the simultaneous removal of nitrate, nitrite, ammonia, total nitrogen, phosphorous, and COD using simulated runoff. Under unsaturated conditions, M1 with the ZVI-brick combination removed 91.37% TP, while M2 with the ZVI-pumice combination removed 89.76% TP. Under saturated conditions, M2 removed 72.02% TN, and M1 removed 66.1% TN. It was found that the presence of saturation zones benefitted TN removal which can be attributed to the creation of anoxic conditions within saturation zones, which favoured denitrification, as well as the prolongation of influent retention and reaction time, while it hindered TP removal. TP removal percentages for CM, M1, and M2 declined from 86.77%, 91.37%, and 89.76% in unsaturated conditions to 63.99%, 83.67%, and 71.74% in saturated conditions due to the propensity of soil-bound P to leach in anoxic environments. The media amendments were further characterized using Scanning Electron Microscopy (SEM) and X Ray Diffraction analysis (XRD), as well as adsorption and leaching tests. Significantly, the highest pollutant leaching was observed in the assessed conditions for CM, underscoring the usefulness of including media like ZVI, brick powder, and pumice pellets. This incorporation not only heightened the effectiveness of pollutant removal but also fortified their retention in potential future stormwater events. In consideration of this, M1 emerged as the preferred design option, as its non-leaching characteristics were verified through flushing with distilled water after post-stormwater influent loading cycles when compared to traditional designs. [ABSTRACT FROM AUTHOR]

Environments with aquatic vegetation can mitigate excess nitrogen (N) loads to downstream waters. However, complex interactions between multiple hydro‐biogeochemical processes control N removal within these environments and thus complicate implementation of aquatic vegetation as a management solution. Here, we conducted controlled experiments using a canopy of artificial rigid emergent vegetation in a recirculating flume mesocosm to quantify differences in rates of mass transport and nitrate (NO3−N) removal between the open channel‐canopy interface across a range in nominal water velocities. We found NO3−N removal rates were 86% greater with the canopy present compared to no canopy control experiments and were always greatest at intermediate velocity (6 cms−1). With the canopy present, a hydrodynamically distinct mixing layer formed at the open channel‐canopy interface, and resources, such as carbon (C), CN ratios, and dissolved oxygen, differed between open channel and vegetated canopy. The dimensionless Damköhler (Da) number indicated NO3−N removal rates were reaction limited (Da << 1) for all canopy experiments, yet across all velocities NO3−N removal was more reaction limited in the open channel than the canopy due to higher rates of mixing and less contact time with reactive surfaces. We found significant relationships between NO3−N removal rates and Da with hydrodynamic metrics (mixing zone width and Reynolds number, respectively), suggesting that NO3−N removal in the presence of rigid vegetation can be enhanced by manipulating flow conditions. These findings demonstrate that rigid emergent vegetation‐open channel interfaces create conditions conducive for NO3−N removal and with effective management can improve overall water quality. Plain Language Summary: Persistent excess nitrate (NO3−N) in surface waters is a major threat to water quality. Environments with aquatic plants, like wetlands, vegetated ditches or streams, can improve water quality by removing NO3−N from water ways, yet reasons for increased removal capacity, especially under different flow conditions, are unclear. Using a controlled, yet realistic experimental set up, we investigated how flow conditions impact rates of mass transport and NO3−N removal near model canopies of rigid emergent aquatic vegetation. We found that the rate NO3−N is removed from the water is greater when the model vegetation is present, but regardless NO3−N removal rates were greatest at intermediate velocity. When the canopy was present, the transport of water and resources occurred much faster than the removal of NO3−N. We observed predictive relationships between flow conditions with removal rates and the ratio of mass transport to NO3−N removal rate which can be useful for predicting or increasing NO3−N removal in real environments. Our findings show the transformative role rigid aquatic vegetation can have in improving water quality within flowing waters, offering a promising pathway for sustainable water management. Key Points: Nitrate removal rates were 86% higher with the artificial canopy present than the no canopy control experimentsMaximum nitrate removal occurred at intermediate velocity (6 cms−1) for both the canopy and no canopy control experimentsMixing, induced by the canopy‐open water interface, enhanced open channel nitrate removal rates [ABSTRACT FROM AUTHOR]

This study aims to examine the nitrogen removal characteristics and microbial community variation at low hydraulic retention time (HRT) in a shallow constructed wetland (SCW) using iron–carbon (Fe–C) porous filter material (PFM) as substrate. Effects of influent nitrogen forms and chemical oxygen demand (COD)/N ratio on nitrogen removal performance at HRT of 1 day were investigated. Results showed that total nitrogen (TN) removal declined with the decrease of influent NH4+‐N‐to‐NO3−‐N ratio. When the influent NH4+‐N/NO3−‐N ratio was 0.1, TN removal decreased by 15.4% compared with that at ratio of 2.0. The increase of influent COD/N ratio enhanced NO3−‐N reduction, and TN removal reached 74.5% at influent COD/N ratio 7.0. The microbial community was analyzed for the biofilm samples on Fe–C PFM at front (WF), middle (WM), and back (WB) of SCW. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes were dominant bacteria phyla. The relative abundance of genera involved in the nitrification and denitrification decreased with the influent flow. The iron autotrophic denitrifying and macromolecular organics degrading bacteria were abundant in the middle and back of SCW. Microbial nitrification and denitrification, plant uptake, and plant synergism contributed to 86.3%, 7.41%, and 19.9% of N removal, respectively. These results demonstrated that the SCW with Fe–C PFM as substrate was efficient in nitrogen removal at low HRT. [ABSTRACT FROM AUTHOR]

This study investigated the effect of low DO operation on the performance of membrane bioreactors (MBRs) in treating wastewater with low carbon to nitrogen ratios(C/N = 3.5), the microbiological communities in them, and on membrane fouling. Two bench-scale MBRs were operated in tandem under different DO regimes: one maintained at an average DO of 0.5 mg/L and the other at 2 mg/L. Both systems exhibited high organic carbon removal efficiencies above 97%, with the low-DO reactor demonstrating a slight advantage. While the low DO conditions limited nitrification due to oxygen depletion affecting nitrifying bacteria, these conditions favored improved total nitrogen removal by achieving simultaneous nitrification and denitrification (SND) process. This improvement is attributed to the facilitation of denitrification and other nitrogen transformations, including the anammox and comammox pathways. Furthermore, the low DO environment was associated with reduced membrane fouling rates, suggesting that reduced aeration does not compromise membrane fouling mitigation. Microbial community analysis revealed that lower DO concentrations significantly increased diversity, as evidenced by alpha and beta diversity metrics. Redanduncy Analysis (RDA) confirmed the proliferation of nitrogen-transforming bacteria under low DO conditions, and the detection of anammox and comammox bacteria in the sludge samples confirmed the operation of these alternative nitrogen removal pathways. [ABSTRACT FROM AUTHOR]

Reports regarding the composition and functions of microorganisms in activated sludge from wastewater treatment plants for treating tuna processing wastewater remains scarce, with prevailing studies focusing on municipal and industrial wastewater. This study delves into the efficiency and biological dynamics of activated sludge from tuna processing wastewater, particularly under conditions of high lipid content, for pollutant removal. Through metagenomic analysis, we dissected the structure of microbial community, and its relevant biological functions as well as pathways of nitrogen and lipid metabolism in activated sludge. The findings revealed the presence of 19 phyla, 1,880 genera, and 7,974 species, with Proteobacteria emerging as the predominant phylum. The study assessed the relative abundance of the core microorganisms involved in nitrogen removal, including Thauera sp. MZ1T and Alicycliphilus denitrificans K601, among others. Moreover, the results also suggested that a diverse array of fatty acid-degrading microbes, such as Thauera aminoaromatica and Cupriavidus necator H16, could thrive under lipid-rich conditions. This research can provide some referable information for insights into optimizing the operations of wastewater treatment and identify some potential microbial agents for nitrogen and fatty acid degradation. [ABSTRACT FROM AUTHOR]

In order to explore the operation performance, kinetic characteristics and bacterial community of the short-cut nitrification and denitrification (SND) system, the SND system with pre-cultured short cut nitrification and denitrification sludge was established and operated under different ferrous ion (Fe (II)) conditions. Experimental results showed that the average NH4+–N removal efficiency (ARE) of SND system was 97.3% on Day 5 and maintained a high level of 94.9% ± 1.3% for a long operation period. When the influent Fe(II) concentration increased from 2.3 to 7.3 mg L−1, the sedimentation performance, sludge concentration and organic matter removal performance were improved. However, higher Fe(II) of 12.3 mg L−1 decreased the removal of nitrogen and CODCr with the relative abundance (RA) of Proteobacteria and Bacteroidetes decreased to 30.28% and 19.41%, respectively. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in SND system. Higher Fe(II) level of 12.3 mg L−1 increase the RA of denitrifying genus Trichococcus (33.93%), and the denitrifying genus Thauera and Tolumonas dominant at Fe(II) level of no more than 7.3 mg L−1. [ABSTRACT FROM AUTHOR]

Moving bed bioreactors are efficient for the removal of nitrogen effluents by simultaneous nitrification and denitrification (SND), which is particularly challenging for effluents with low C/N ratio due to insufficient carbon available for denitrification. The addition of external organic carbon in such cases increases treatment costs. Endogenous degradation of biomass offers a cost-effective and persistent source of carbon. Internal carbon leads to low denitrification rates and optimizing the biomass content leads to a sustainable solution for treating such effluents. The present study aims to optimize the process of SND using endogenous carbon by investigating the effect of operational parameters like dissolved oxygen, influent ammonium (NH4–N) loading, hydraulic retention time (HRT) and carrier filling ratio (CFR). The synthetic wastewater used in the study does not inherently contain any organic carbon, thus indicating the responsible carbon for denitrification to be of internal origin. Using a novel carrier for multispecies biofilm development, initial NH4–N concentration variation showed an insignificant effect on SND efficiency. At higher loading, nitrite accumulation due to incomplete denitrification was observed. The effect of CFR was investigated in a range of 20–35%, beyond which non-homogeneous mixing was caused in the reactor. Under controlled DO and temperature of about 5 mg/L and 28 ± 2°C, respectively, an optimum filling ratio of 35% was finalised, resulting in an SND efficiency of 97.9% at 22 h HRT for high influent NH4–N concentration of 500 mg/L. Bacteriological species identification revealed the coexistence of nitrogen-fixing, aerobic nitrifying and anaerobic denitrifying bacteria in the biofilm growing on the biocarrier. Mechanism of SND occurring in aerobic moving bed bioreactors: Laboratory-scale aerobic Moving Bed Bioreactor setup for a continuous study evaluating the influence of operational parameters on SND Occurrence of aerobic and anoxic zones in biofilm grown on the surface of novel carriers due to diffusional gradient of dissolved oxygen [ABSTRACT FROM AUTHOR]

The effects of salinity gradients (500–4000 mg·L−1 NaCl) on electricity generation, nitrogen removal, and microbial community were investigated in a constructed wetland-microbial fuel cell (CW-MFC) system. The result showed that power density significantly increased from 7.77 mW m−2 to a peak of 34.27 mW m−2 as salinity rose, indicating enhanced electron transfer capabilities under saline conditions. At a moderate salinity level of 2000 mg·L−1 NaCl, the removal efficiencies of NH4+–N and TN reached their maximum at 77.34 ± 7.61% and 48.45 ± 8.14%, respectively. This could be attributed to increased microbial activity and the presence of critical nitrogen-removal organisms, such as Nitrospira and unclassified Betaproteobacteria at the anode, as well as Bacillus, unclassified Rhizobiales, Sphingobium, and Simplicispira at the cathode. Additionally, this salinity corresponded with the highest abundance of Exiguobacterium (3.92%), a potential electrogenic bacterium, particularly at the cathode. Other microorganisms, including Geobacter, unclassified Planctomycetaceae, and Thauera, adapted well to elevated salinity, thereby enhancing both electricity generation and nitrogen removal. [ABSTRACT FROM AUTHOR]

This research explored the denitrification potential of a submerged zone incorporated into the present permeable interlocking concrete pavement (PICP) design. The following three main factors controlling denitrification were investigated through a laboratory study: (i) detention time, (ii) inclusion of a carbon source (newspaper), and (iii) submerged zone depth. The study used 10 columns, each fully packed with 50– 63 mm washed aggregate and including a 1.5 m deep submerged zone. Columns were paired according to detention time (1, 2, 5, 10 and ‘varied’ days) with one set including newspaper, the other set not. All columns were loaded with synthetic stormwater over a 4-month period. Samples were taken from different submerged depths (0, 300, 600, 900, 1200 and 1 500 mm) and analysed for concentrations of ammonia (NH3), nitrate (NO3 −) and phosphate (PO4 3−) every 10 days. This study found that 10 – or more – days detention and the provision of a carbon source had the most significant impact on denitrification – providing an overall mean NO3 − and nitrogen removal above 41% and 59%, respectively. Moreover, a submerged depth of 300 mm was sufficient to achieve a minimum NO3 − removal of 41% in columns which included a carbon source and had 10 days detention. Generally, an increase in detention time resulted in an increase in NH3 and PO4 3− removal with overall mean values of 86% and 30%, respectively, achieved with 10-day detention periods. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Constructed wetlands (CWs) are widely applied for decentralized wastewater treatment. However, achieving efficient removal of ammonia ( NH 4 + − N ) has proven challenging due to insufficient oxygen. In this study, natural hematite (Fe2O3) was employed as a CW substrate (H-CWs) for the first time to drive anaerobic ammonia oxidation coupled with iron(III) reduction (Feammox). Compared to gravel constructed wetlands (G-CWs), ammonia removal was enhanced by 38.14% to 54.03% and nitrous oxide (N2O) emissions were reduced by 34.60% in H-CWs. The synergistic removal of ammonia and nitrate by H-CWs also resulted in the absence of ammoxidation by-products. Inhibitor and 15N isotope tracer incubations showed that Feammox accounting for approximately 40% of all ammonia removal in the H-CWs. The enrichment of iron phosphate (Fe3Fe4(PO4)6) promoted the accumulation of the Feammox intermediate compound FeOOH. Microbial nanowires were observed on the surface of H-CW substrates as well, suggesting that the observed biological ammoxidation was most likely related to extracellular electron transfer (EET). Microbial and metagenomics analysis revealed that H-CWs elevated the integrity and enhanced the abundance of functional microorganisms and genes associated with nitrogen metabolism. Overall, the efficient ammonia removal in the absence of O2 together with a reduction in N2O emissions as described in this study may provide useful guidance for hematite-mediated anaerobic ammonia removal in CWs. [ABSTRACT FROM AUTHOR]

This study investigated the improvement effect of the addition of exogenous calcium ions on the nitrogen removal efficiency of activated sludge in laboratory scale bioreactors fed various Ca concentrations. The long-term nitrogen removal performance was significantly greater in bioreactors supplemented with 150 mg/L extra Ca than in the no-addition control. The characteristics of the bacterial communities and the abundances of ammonium-oxidizing bacteria and genes related to nitrogen cycling were different between bioreactors with 150 mg/L Ca and those with other Ca concentrations (0, 30, 50 and 200 mg/L). Ca addition caused variations in the microbial abundance and distribution of nitrifiers and denitrifiers and in the synergistic effects of nitrogen functional genes in the activated sludge system, which ultimately affected the removal of nitrogen in the bioreactors. Obviously, adding an appropriate amount of Ca to activated sludge systems modifies the microbial community, which creates a beneficial environment for enhancing the removal of nitrogen from wastewater. [ABSTRACT FROM AUTHOR]

Copyright of Technology of Water Treatment is the property of Technology of Water Treatment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Decentralized wastewater reclamation and reuse systems have drawn much attention due to their capability for reducing the energy demand for water conveyance and reclaiming wastewater for local re-use. While membrane bioreactor (MBR) stands as a mature technology offering comprehensive solid and liquid separation, membrane capacitive deionization (MCDI) presents a promising avenue for ion separation. Unfortunately, MCDI has seldom been incorporated into decentralized wastewater reclamation and reuse systems. This study aims to exemplify the design and the operation of the synergistic integration of MBR and MCDI system with a practical capacity of 1 m3 d− 1, showcasing its efficacy in reclaiming and reusing water at regional level. The integrated system demonstrated significant high removal of total organic carbon (from 97 to 2 mg L− 1) and chemical oxygen demand (COD, from 218 to < 3 mg L− 1). Meantime, nearly complete transformation (approximately 91%) of NH3 to NO3− within the MBR effluent was observed with a hydraulic retention time of 4.3–4.8 h and a food-to-microorganism of 0.15–0.20 kg COD kg− 1 MLSS d− 1 which can be further removed through the MCDI system (> 92% TN removal). A significant milestone of MCDI unit was reached with the remarkable removal efficiency of total ions (93%) and water recovery (80%) using a stop-flow regeneration approach coupled with an optimized voltage of 2.0 V. The MCDI unit not only proved its high stability but also featured low energy consumption (0.44 kWh m− 3). Overall, synergizing MBR and MCDI systems emerges as a sustainable and effective solution for decentralized wastewater reclamation and reuse, contributing to a more environmentally friendly and resource-efficient water management paradigm. [ABSTRACT FROM AUTHOR]

Highlights: Plasma-grafting acrylic acid composite membrane for MABR was prepared. Higher O2 transfer rate and better hydrophilicity for modified membranes than pristine. Modified PVDF membrane demonstrated superior nitrogen removal during startup. Activity of denitrifying bacteria was enhanced in the modified PVDF MABR. Microporous membranes such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) often exhibit suboptimal hydrophilicity and microbial adhesion, which impede effective nitrogen removal in membrane-aerated biofilm reactors (MABRs), particularly during initial operational phases. To address this issue, the present study introduced acrylic acid (AA) following plasma treatment (P) to enhance membrane performance, thereby engineering a novel composite material optimized for MABR applications. Four MABRs—Reactor with pristine PVDF membrane (R-PVDF), Reactor with composite PVDF membrane (R-PVDF-P-AA), Reactor with pristine PTFE membrane (R-PTFE), and Reactor with composite PTFE membrane (R-PTFE-P-AA)—were evaluated. The modified membranes displayed enhanced roughness and hydrophilicity, which improved biocompatibility and variably increased the oxygen transfer efficiency. Notably, the R-PVDF-P-AA configuration showed a significant enhancement in the removal rates of NH4+-N and total nitrogen (TN), achieving 78.5% and 61.3%, respectively, which was markedly higher than those observed with the original membranes. In contrast, the modified R-PTFE-P-AA exhibited lower removal efficiencies, with NH4+-N and TN reductions of approximately 60.0% and 49.5%. Detailed microbial community analysis revealed that the R-PVDF-P-AA membrane supported robust commensalism between ammonia-oxidizing and denitrifying bacteria, underpinning the improved performance. These findings highlight the critical role of surface chemistry and microbial ecology in optimizing the function of MABRs. [ABSTRACT FROM AUTHOR]

Aquaponics is a promising solution for addressing food security concerns. Nonetheless, an effective water-purification system is necessary to achieve high and stable yields of fish and vegetables. This study aimed to evaluate the nitrification and oxygen transfer performance of a laboratory-scale down-flow hanging sponge (DHS) reactor with a Brassica oleracea aquaponics system to treat water in an Oreochromis niloticus closed-aquaculture system. The DHS reactor showed a higher oxygen transfer coefficient (KLa) than the conventional aerator and provided an adequate dissolved oxygen (DO) concentration of approximately 5.5 mg/L essential for O. niloticus growth throughout the experimental period. The evaluated DHS-based aquaponic system maintained high water quality in an aquaculture tank, with a survival rate of 97%. The O. niloticusgrew at a low feed conversion ratio of 1.5–2.1 and a low feeding rate of 0.5% at high stocking densities of 17.5–22.2 kg-fish-weight/m3. 16S rRNA gene sequencing indicated that the DHS sponge carrier effectively retained nitrifying bacteria such as Nitrosomonas and Nitrospira. This study demonstrated that the DHS reactor provided a high DO concentration and that a simultaneous DHS reactor with a hydroponic tank provided a low-cost aquaponic system that could be applied for food production in the aquaculture industry. [ABSTRACT FROM AUTHOR]

Strategies, such as the biological denitrification process, must be adopted to treat rich-nitrate water from biofloc systems, making it suitable for culture or proper disposal. This study evaluated the effect of water reuse from a BFT system after being subjected to a biological anaerobic denitrification process on shrimp performance and water quality in the rearing of Litopenaeus vannamei. A 63-day experiment was carried out at the Marine Station of Aquaculture of the Federal University of Rio Grande. L. vannamei juveniles (1.30 ± 0.48 g) were stocked in 150-L tanks at a density of 500 shrimp/m3. Four treatments (with three replicas each) were tested: natural seawater and denitrified seawater, both with and without biofloc inoculum. Temperature, salinity, dissolved oxygen, pH, ammonia, nitrite, nitrate, alkalinity, and total suspended solids (TSS) in the water were monitored. Ammonia and nitrite levels were higher without biofloc inoculum, while nitrate levels increased with inoculum use. Alkalinity and TSS were significantly higher in denitrified water with inoculum, driven mainly by the initial higher concentrations. A 100% mortality was found in the treatment using denitrified water without inoculum, probably due to the presence of byproducts after the denitrification process, but no differences in survival (>89%) were found in the other treatments. The biofloc inoculum helped with higher productivity (3.03 ± 0.08 kg/m3) and lower FCR (1.48 ± 0.05) in the treatment using seawater compared to the treatment in which no inoculum was used (2.62 ± 0.18 kg/m3 and 1.79 ± 0.16), in addition to serving as a biological treatment in denitrified seawater, readjusting the water for shrimp farming. As the growth performance of shrimp raised in denitrified water showed no differences compared to natural seawater, utilizing denitrified seawater from a biofloc system seems feasible for shrimp cultivation. However, alternatives for water treatment after the denitrification process need to be investigated. [ABSTRACT FROM AUTHOR]

The adsorption and utilization of Fe(Ⅲ) can be impeded by precipitation in anaerobic reactors. In this study, we investigated whether the bioavailability of Fe(Ⅲ) can be enhanced by EDTA-Fe(Ⅲ), thereby improving the stability of anammox system. Fe(Ⅲ) and EDTA-Fe(Ⅲ) were added to two parallel up-flow anaerobic sludge blanket (UASB) reactors, respectively. After 186 days of operation, when the nitrogen loading rate (NLR) was 0.8 g-N/L/d, the nitrogen removal rate (NRR) of R2 was stable at 0.675 g-N/L/d, which was higher than that of R1 at 0.557 g-N/L/d. The anammox activity of R2 reached its peak in phase Ⅲ (158.55 ± 4.53 mg-N/g-VSS/d), while the anammox activity of R1 was only 28.37 ± 5.96 mg-N/g-VSS/d. Moreover, in phase Ⅱ-Ⅴ, the bioavailability of Fe(Ⅲ) in R2 was increased by 15.63%, 38.37%, 65.90%, and 39.63%, respectively, compared with R1. The results showed that EDTA-Fe(Ⅲ) can prevent precipitation encasing anammox granular sludge, which can enhance substrate transport and Fe(Ⅲ) adsorption utilization. High throughput sequencing suggested that EDTA-Fe(Ⅲ) could better increase the abundance of anammox bacteria (AnAOB). In conclusion, this research proved that EDTA could increase the bioavailability of Fe(Ⅲ) and thereby ensuring the stability of the reactors. [Display omitted] • EDTA-Fe(Ⅲ) could enhance the bioavailability of Fe(Ⅲ) by 15.63%-65.90%. • EDTA-Fe(Ⅲ) could stabilize the Anammox granule sludge system. • EDTA-Fe(Ⅲ) could facilitate the granulation of Anammox sludge. • EDTA-Fe(Ⅲ) better increase the abundance of Anammox Bacteria. [ABSTRACT FROM AUTHOR]

In response to the problems of insufficient denitrification and poor denitrification effect of traditional constructed wetlands for the treatment of livestock biogas slurry, in this study Chlorella sorokiniana was used as an additional carbon source for the construction of C. sorokiniana - constructed wetland systems to treat piggery biogas slurry. The effect of the system on the removal of water quality of piggery biogas slurry and the change rule of the dissolved organic matters (DOMs) through the addition of C. sorokiniana under different concentrations (0, 0.25, 0.5 and 1.0 g/L) were investigated, and the mechanism of en- hanced nitrogen removal was explored from the perspective of microorganisms. The results showed that compared with the constructed wetland without the addition of C. sorokiniana, the removal of total nitrogen was obviously increased up to 70.24%, and the removal of nitrate nitrogen reached up to 93.45%. Based on the three-dimensional fluorescence parallel factor analysis, the three components in DOMs were fulvic acid/humic acid-like substances, polymer aromatic substances and humic acid-like substances, while the addition of C. sorokiniana enhanced the removal of DOMs from piggery biogas slurry and reduced the content of humic acid-like substances. The addition of C. sorokiniana evidently increased the Alpha diversity of microorganisms in the constructed wetland. Particularly, at the phylum level the relative abundance of dominant bacteria related to denitrification (Proteobacteria) increased obviously, while at the genus level the genera Nitrosomonas and Limnobacter played important roles in the ammonia oxidation and denitrification processes of the system. This study provides theoretical support for the use of C. sorokiniana as an additional carbon source to enhance nitrogen and phosphorus removal in constructed wetlands. [ABSTRACT FROM AUTHOR]

Simultaneous nitrification and denitrification (SND) is cost-effective, and therefore it is a promising process for biological nitrogen removal. In this study, SND microbes were obtained through domestication of the sludge from Wuhan municipal wastewater treatment plant to enrich effective nitrogen removal SND microbes, to reveal the microbial structure of SND and the denitrogenation mechanism through the high-throughput sequencing technology and quantitative PCR. When NH4+-N (~ 90.7 mg/) as a sole nitrogen source, the removal efficiency (RE) of NH4+-N in 24 h was 99.35%, and there was no accumulation of NO3−-N or NO2−-N. When NO3−-N (~ 101.79 mg/L) or NO2−-N (~ 106.00 mg/L) was the sole nitrogen source, respectively, it was almost completely removed. Furthermore, when NH4+-N (~ 105.68 mg/L) and NO3−-N (~ 100.40 mg/L) were the composite nitrogen sources, the RE of NH4+-N and NO3−-N were 99.17% and 94.07% in 24 h, respectively. The RE of NH4+-N was up to 99.31% when NH4+-N (~ 102.33 mg/L) and NO2−-N (~ 114.56 mg/L) used as composite nitrogen sources, and NO2−-N was completely removed. Community composition analysis revealed that the dominant phyla were Proteobacteria and Bacteroidetes; and the dominant genera were Paracoccus, Pannonibacter, Taibaiella, Pelagibacterium and Stappia. Gene functional analysis for the nitrogen cycle showed the presence of amoB, hao, narG, nirS, nirK, and nosZ genes; however, nxrA, hzo, hzs, napA, and nasA were not detected. These findings revealed that a possible novel mechanism of nitrogen removal using hao gene to oxidize NH2OH to NO instead of NO2−-N by SND microbes. [ABSTRACT FROM AUTHOR]

A novel heterotrophic, cold-tolerant bacterium, designated Pseudomonas zhanjiangensis 25A3ET, was isolated from mangrove sediment and demonstrated excellent efficiency in cold wastewater treatment. Phylogenetic analysis based on 16S rRNA gene sequences positioned strain 25A3ET within the genus Pseudomonas, showing the highest similarity (98.7%) with Pseudomonas kurunegalensis LMG 32023T. Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values were below the species delineation thresholds (70% for dDDH, 95% for ANI), indicating that strain 25A3ET represents a novel species. This strain demonstrated high efficiency in removing nitrogen (N) and organic pollutants under low-temperature conditions. Specifically, it achieved 72.9% removal of chemical oxygen demand (COD), 70.6% removal of ammoniacal nitrogen (NH4+-N), and 69.1% removal of total nitrogen (TN) after 96 h at 10°C. Genomic analysis identified key genes associated with cold adaptation, nitrogen removal and organic matter degradation. These findings indicate that Pseudomonas zhanjiangensis 25A3ET holds significant potential for application in cold temperature wastewater treatment, offering a promising solution for environmental remediation in regions with low ambient temperatures.

Study Region, Shanghai, China, Study FocusUrban riparian zones can mitigate or even control nitrogen pollution in rivers through nitrification and denitrification processes. However, these processes also produce N2O, a potent greenhouse gas. During urbanization, various types of revetments have been constructed in riparian zones. These revetments alter the exchange of materials and energy between the riparian zone and the river, which in turn affects the nitrification and denitrification processes in the riparian zone. However, the mechanisms by which revetments impact nitrogen removal and N2O emissions in riparian zones are not yet clear, and the ways in which revetments balance nitrogen removal and N2O emissions remain unknown. Therefore, in a single river section, natural (NR), permeable (PR), and impervious revetment (IR) types were replicated. Measurements are taken of nitrogen removal, N2O emissions, and related environmental indicators in both the river-riparian interface (RRI) and the riparian zone area outside the RRI (RZ). The study analyzes the differences in environmental factors, nitrification and denitrification potentials, and N2O emission rates among the different revetments to identify the main factors affecting nitrogen removal and N2O emissions in the riparian zone. It also explores the potential mechanisms by which revetments influence the spatial distribution of nitrogen removal and N2O emissions in the summer riparian zone.New Hydrological Insights for the Region: PR exhibit greater denitrification potential and lower N2O emission rates. The denitrification potential is higher in the RRI compared to RZ, while the N2O emission rate is lower than in RZ. nirK is the primary factor influencing denitrification potential, whereas nosZII predominantly affects N2O emissions. The lower soil carbon-to-nitrogen ratio in PR increases the abundance of nirK, thereby enhancing the riparian zone's denitrification potential. Moreover, greater aboveground vegetation biomass increases the abundance of nosZII, reducing the N2O emission rate. The study results could provide guidance for urban ecological restoration and greenhouse gas emission reduction.

Macrophytes influence nitrogen (N) removal from wetlands. However, the specific plant traits responsible for this effect and the related microbial mechanisms remain largely unknown, especially root traits. In a mesocosm experiment, we determined the rhizosphere effect (RE) on microbial N removal processes by incubating rhizosphere and bulk soils collected from 11 macrophyte species. In addition, we examined root traits (involved in chemistry and morphology), along with examining the diversity, compositions, and abundance of bacterial communities involved in denitrification (nirS and nirK) and anammox (hzsB). Across the 11 macrophyte species, the positive RE on denitrification ranged from 66% to 412%, with an average of 194.72%. RE on denitrification was significantly and positively correlated with the recruitment of nir-type denitrifiers in the rhizosphere. We found that higher specific root length (SRL) root promoted the stronger RE, by increasing the abundance of nir-type denitrifiers and further enhancing N removal. Net N removal from water in the wetlands increased with a higher positive RE on nir-type denitrifiers. In addition, SRL significantly influenced the compositions of denitrifiers in the rhizosphere soil. We further found that the enrichment of Azospira, Bradyrhizobium, Sinorhizobium, Rhodopseudomonas, Alcaligenaceae, Bradyrhizobiaceae, and Pleomorphomonas improved the denitrification rate. These findings highlight the potential of root morphology in regulating plant–microbe interactions, thereby improving water purification.

Nitrite-oxidizing bacteria (NOB) are undesirable in the anaerobic ammonium oxidation (anammox)-driven nitrogen removal technologies in the modern wastewater treatment plants (WWTPs). Diverse strategies have been developed to suppress NOB based on their physiological properties that we have understood. But our knowledge of the diversity and mechanisms employed by NOB for survival in the modern WWTPs remains limited. Here, Three NOB species (NOB01–03) were recovered from the metagenomic datasets of a full-scale WWTP treating duck breeding wastewater. Among them, NOB01 and NOB02 were classified as newly identified lineage VII, tentatively named Candidatus (Ca.) Nitrospira NOB01 and Ca. Nitrospira NOB02. Analyses of genomes and in situ transcriptomes revealed that these two novel NOB were active and showed a high metabolic versatility. The transcriptional activity of Ca. Nitrospira could be detected in all tanks with quite different dissolved oxygen (DO) (0.01–5.01 mg/L), illustrating Ca. Nitrospira can survive in fluctuating DO conditions. The much lower Ca. Nitrospira abundance on the anammox bacteria-enriched sponge carrier likely originated from the intensification substrate (NO2−) competition from anammox and denitrifying bacteria. In particular, a highlight is that Ca. Nitrospira encoded and treanscribed cyanate hydratase (CynS), amine oxidase, urease (UreC), and copper-containing nitrite reductase (NirK) related to ammonium and NO production, driving NOB to interact with the co-existed AOB and anammox bacteria. Ca. Nitrospira strains NOB01 and NOB02 showed quite different niche preference in the same aerobic tank, which dominanted the NOB communities in activated sludge and biofilm, respectively. In addition to the common rTCA cycle for CO2 fixation, a reductive glycine pathway (RGP) was encoded and transcribed by NOB02 likely for CO2 fixation purpose. Additionally, a 3b group hydrogenase and respiratory nitrate reductase were uniquely encoded and transcribed by NOB02, which likely confer a survival advantage to this strain in the fluctuant activated sludge niche. The discovery of this new genus significantly broadens our understanding of the ecophysiology of NOB. Furthermore, the impressive metabolic versatility of the novel NOB revealed in this study advances our understanding of the survival strategy of NOB and provides valuable insight for suppressing NOB in the anammox-based WWTP.

Urban surface water pollution poses significant threats to aquatic ecosystems and human health. Conventional nitrogen removal technologies used in urban surface water exhibit drawbacks such as high consumption of carbon sources, high sludge production, and focus on dissolved oxygen (DO) concentration while neglecting the impact of DO gradients. Here, we show an ecological filter walls (EFW) that removes pollutants from urban surface water. We utilized a polymer-based three-dimensional matrix to enhance water permeability, and emergent plants were integrated into the EFW to facilitate biofilm formation. We observed that varying aeration intensities within the EFW's aerobic zone resulted in distinct DO gradients, with an optimal DO control at 3.19 ± 0.2 mg L−1 achieving superior nitrogen removal efficiencies. Specifically, the removal efficiencies of total organic carbon, total nitrogen, ammonia, and nitrate were 79.4%, 81.3%, 99.6%, and 79.1%, respectively. Microbial community analysis under a 3 mg L−1 DO condition revealed a shift in microbial composition and abundance, with genera such as Dechloromonas, Acinetobacter, unclassified_f__Comamonadaceae, SM1A02 and Pseudomonas playing pivotal roles in carbon and nitrogen elimination. Notably, the EFW facilitated shortcut nitrification-denitrification processes, predominantly contributing to nitrogen removal. Considering low manufacturing cost, flexible application, small artificial trace, and good pollutant removal ability, EFW has promising potential as an innovative approach to urban surface water treatment.