Denitrification Of Wastewater Research Articles

A New Method for Nitrogen Removal in Wastewater Treatment: Synergistic Nitrogen Removal Using Feammox and Nitrate-Dependent Fe(II) Oxidation Within Organic Carbon Environments

Feammox, one of the potential pathways for nitrogen loss in the environment, plays an essential role in nitrogen cycling and provides new ideas for the biological denitrification of wastewater. However, the Feammox reaction has low nitrogen removal efficiency and stagnates due to insufficient Fe(III) sources. It strongly depends on an Fe(III) source supply, significantly limiting its development. In this study, a synergistic nitrogen removal system using Feammox and Nitrate-Dependent Fe(II) Oxidation (NDFO) driven by NO3−-N was constructed within an organic carbon environment. It uses the synergy between Feammox and NDFO to improve nitrogen removal. The removal efficiency of NH4+-N reaches over 70% in stages III-V, with a maximum removal efficiency of 89.4%. NH4+-N oxidation and Fe(III) reduction are positively coupled in the Feammox reaction. The Fe(II)/Fe(III) cycle process driven by Feammox and NDFO improves the utilization of the iron source, thus guaranteeing the sustainability of the NH4+-N oxidation reaction. In addition, the organic carbon environment also enriched NDFO bacteria (Thermomonas and Acinetobacter) and increased the reaction rate of NDFO, which enhanced the transformation of Fe(II). We improved the nitrogen removal efficiency of Feammox and provided a new approach for nitrogen removal in wastewater treatment.

Research progress on solid-phase electron donors for the denitrification of wastewater: A review

Electron donor-mediated biological denitrification, the most extensively employed method for the treatment of nitrate nitrogen (NO3−-N), involves NO3−-N directly or indirectly by acquiring electrons provided by electron donors and converting them into N2. Currently, the most widely researched electron donors are gaseous, liquid, and solid forms. Owing to the difficulties in storing and transporting gaseous and liquid electron donors, and their potential for causing secondary pollution, solid-phase electron donors (SPEDs), which can be slowly utilized by microorganisms, have gradually gained attention. SPEDs not only serve as a carrier for microbial attachment, but most SPEDs are also low-cost and readily available, making them advantageous for practical applications. In this review, the different types of SPEDs are classified and their microbial utilization mechanisms in the biological denitrification process discussed based on their classification. Their denitrification performance, influencing factors, practical applications, and existing issues are summarized. This review provides a reference for future research on SPED and its applications. It also provides an outlook on SPED-mediated mixotrophic denitrification and SPED-coupled electrochemical technology for enhanced nitrogen removal processes, in view of this hot direction in SPED research.

Autotrophic nitrification and denitrification of poultry wastewater in an anoxic-aerobic fixed bed reactor composed of elemental sulfur and dolomitic limestone

This study promoted the autotrophic denitrification of poultry slaughterhouse wastewater in anoxic reactor with fix bed of elementary sulfur a dolomitic limestone and, posteriorly, nitrification was coupled to this system in an anoxic-aerobic reactor. The anoxic reactor was operated under constant nitrogen concentration of 71,1±4,2 mg NOx L-1 and HTR of 14, 10 and 6 hours. In this reactor, the efficiencies and denitrification tax obtained were 94,4±2,0, 94,9±2,3 and 71,1±7,8%, for the HRT of 14, 10 and 6 hours, respectively. The reactor anoxic-aerobic was operated with HRT of 16 hours and fed with effluent in rate ammonified: nitrified of 3:1 (E1), 1:1 (E2) and 1:3 (E3). In this reactor, the efficiencies of ammoniacal nitrogen removal and total nitrogen removal were 67,3±6,4, 63,4±6,7 and 14,2±4,4% and 64,2±6,3, 53,1±7,1 and 33,8±1,7%, to the conditions E1, E2 and E3, respectively. The application of autotrophic denitrification from the elementary sulfur can be considerate a viable technology in wastewater nitrified treatment.

Carbon-based conductive carriers promote coupled Fe(II)-driven autotrophic and heterotrophic denitrification of wastewater with low C/N ratios

Denitrification of wastewater with a low organic carbon to NO3--N ratio (C/N ratio) faces challenges due to slow rates and low efficiency. This study reported that carbon-based conductive carriers are able to enhance the removal of nitrogen from wastewater with low C/N ratio by coupling Fe(II)-driven autotrophic and heterotrophic bioelectrochemical denitrification. When Fe(II) was the sole electron donor, the bioreactor using conductive carrier achieved a denitrification rate constant (kDN) of 0.016 h−1, 1.7 times of that with non-conductive materials. This enhancement was due to the conductive carrier boosting direct electron transfer and supporting the growth of electroactive microorganisms. For wastewater with a low C/N ratio of 0.76, the bioreactor featuring both Fe(II) and the conductive carrier reached a kDN of 0.095 h−1, five times higher than without Fe(II). The presence of Fe(II) promoted denitrification by enhancing electron transfer and serving as a mediator. Microbial analysis showed that adding Fe(II) enriched electroactive bacteria like Comamonas and denitrifiers such as Chryseobacterium. Our findings suggest a promising strategy to enhance denitrification in wastewater treatment systems with low C/N ratios.

Core-shell bioactive capsule for aquaculture wastewater denitrification

The lack of denitrifying bacteria and organic carbon sources, and the inhibition of dissolved oxygen (DO) result in nitrate accumulation in aquaculture wastewater. In order to solve this problem, an encapsulation method was introduced to prepare a novel bioactive capsule, which can provide organic carbon source, denitrifying bacteria, and anoxic microenvironment for aquaculture wastewater denitrification. And can reduce the recovery time of the enclosed denitrifying bacteria. The morphology of the capsule, its nitrate removal rate, and nitrogen conversion pathway in synthetic aquaculture wastewater were investigated. The capsule had a porous surface and the pore diameter ranged from 150.0 nm to 300.0 nm. The enclosed denitrifying bacteria had a reduced recovery time and excellent denitrification performance. The nitrate removal rate reached 86.2 % on the first day and was maintained at 99.7 %. Nitrogen conversion pathways in the capsule include denitrification, assimilatory/dissimilatory nitrate reduction, and nitrogen fixation. The denitrifying capsule has short recovery time and good denitrification performance, which would help to achieve denitrification in aquaculture wastewater or other low C/N wastewater.

Towards stable and efficient nitrogen removal in wastewater treatment processes via an adaptive neural network based sliding mode controller

Advanced controllers often offer an innovative solution to proper quality control in wastewater treatment processes (WWTPs). However, nonlinearity and uncertain disturbances usually make the conventional control strategies inadequate or impossible for the stable operations of WWTPs. To guarantee the stability of ammonia nitrogen concentration (SNH) control in WWTPs, a direct adaptive neural networks-based sliding mode control (ANNSMC) strategy has been proposed in this article. A sliding mode controller is designed and implemented with the help of an adaptive Neural Network (ANN), named Radial Basis Function Neural Network (RBFNN), which can approach the desired control law accurately. Also, the stability of a system installed with the ANNSMC is analyzed by using the Lyapunov theorem, which ensures system robustness and adaptability. Additionally, to deal with high energy consumption and low treatment efficiency problems in the wastewater denitrification processes, this paper proposes a dual-loop denitrification control strategy and validates it in the Benchmark Simulation Model No.2 (BSM2) platform. The strategy can strengthen the denitrification efficiency by collaborating the SNH with nitrate nitrogen (SNO) concentration in the WWTPs properly. The experimental results demonstrate that the proposed strategy can obtain remarkable stability and robustness, reducing energy consumption effectively compared with other standard and advanced control strategies.

Highly selective urea electrooxidation coupled with efficient hydrogen evolution

Electrochemical urea oxidation offers a sustainable avenue for H2 production and wastewater denitrification within the water-energy nexus; however, its wide application is limited by detrimental cyanate or nitrite production instead of innocuous N2. Herein we demonstrate that atomically isolated asymmetric Ni–O–Ti sites on Ti foam anode achieve a N2 selectivity of 99%, surpassing the connected symmetric Ni–O–Ni counterparts in documented Ni-based electrocatalysts with N2 selectivity below 55%, and also deliver a H2 evolution rate of 22.0 mL h–1 when coupled to a Pt counter cathode under 213 mA cm–2 at 1.40 VRHE. These asymmetric sites, featuring oxygenophilic Ti adjacent to Ni, favor interaction with the carbonyl over amino groups in urea, thus preventing premature resonant C⎓N bond breakage before intramolecular N–N coupling towards N2 evolution. A prototype device powered by a commercial Si photovoltaic cell is further developed for solar-powered on-site urine processing and decentralized H2 production.

A novel simultaneous short-course nitrification, denitrification and fermentation process: bio-enhanced phenol degradation and denitrification in a single reactor.

The feasibility of a simultaneous nitrification, denitrification and fermentation process (SNDF) under electric stirrer agitation conditions was verified in a single reactor. Enhanced activated sludge for phenol degradation and denitrification in pharmaceutical phenol-containing wastewater under low dissolved oxygen conditions, additional inoculation with Comamonas sp. BGH and optimisation of co-metabolites were investigated. At a hydraulic residence time (HRT) of 28h, 15mg/L of substrate as strain BGH co-metabolised substrate degraded 650 ± 50mg/L phenol almost completely and was accompanied by an incremental increase in the quantity of strain BGH. Strain BGH showed enhanced phenol degradation. Under trisodium citrate co-metabolism, strain BGH combined with activated sludge treated phenol wastewater and degraded NO2--N from 50 ± 5 to 0mg/L in only 7h. The removal efficiency of this group for phenol, chemical oxygen demand (COD) and TN was 99.67%, 90.25% and 98.71%, respectively, at an HRT of 32h. The bioaugmentation effect not only promotes the degradation of pollutants, but also increases the abundance of dominant bacteria in activated sludge. Illumina MiSeq sequencing research showed that strain BGH promoted the growth of dominant genera (Acidaminobacter, Raineyella, Pseudarcobacter) and increased their relative abundance in the activated sludge system. These genera are resistant to toxicity and organic matter degradation. This paper provides some reference for the activated sludge to degrade high phenol pharmaceutical wastewater under the action of biological enhancement.

Disintegrated Waste-Activated Sludge (NO2/FNA Method) as a Source of Carbon for Denitrification in the Mainstream of a WWTP

The deficiency of readily biodegradable organic carbon can be a significant limitation to effective nitrogen removal during wastewater denitrification. Waste-activated sludge (WAS) is a source of carbon produced directly at wastewater treatment plants (WWTPs). Raw WAS has a large molecular weight and complex chemical structure molecules that are not easily available for microorganisms. In this study, easily biodegradable organic fractions were released using pH control and/or nitrites and nitric acid (NO2/FNA). The obtained results indicated that WAS can be a sufficient carbon source for denitrification in WWTPs that are at risk of minor effluent violations. The implementation of WAS disintegration with the use of pH control and NO2/FNA allowed for the denitrification of an additional 0.5 and 0.8 mgN-NO3/L. WAS disintegration, besides being a source of carbon generation, reduces the volume of sludge and leads to the implementation of a closed-loop system.

Wastewater denitrification driven by mechanical energy through cellular piezo-sensitization

Wastewater denitrification driven by mechanical energy through cellular piezo-sensitization

Unraveling the Mechanism of Ammonia Electrooxidation by Coupled Differential Electrochemical Mass Spectrometry and Surface-Enhanced Infrared Absorption Spectroscopic Studies.

Ammonia electrooxidation has received considerable attention in recent times due to its potential application in direct ammonia fuel cells, ammonia sensors, and denitrification of wastewater. In this work, we used differential electrochemical mass spectrometry (DEMS) coupled with attenuated total reflection-surface-enhanced infrared absorption (ATR-SEIRA) spectroscopy to study adsorbed species and solution products during the electrochemical ammonia oxidation reaction (AOR) on Pt in alkaline media, and to correlate the product distribution with the surface ad-species. Hydrazine electrooxidation, hydroxylamine electrooxidation/reduction, and nitrite electroreduction on Pt have also been studied to enhance the understanding of the AOR mechanism. NH3, NH2, NH, NO, and NO2 ad-species were identified on the Pt surface with ATR-SEIRA spectroscopy, while N2, N2O, and NO were detected with DEMS as products of the AOR. N2 is formed through the coupling of two NH ad-species and then subsequent further dehydrogenation, while the dimerization of HNOad leads to the formation of N2O. The NH-NH coupling is the rate-determining step (rds) at high potentials, while the first dehydrogenation step is the rds at low potentials. These new spectroscopic results about the AOR and insights could advance the search and design of more effective AOR catalysts.

Efficient nitrogen removal from mainstream sewage in tidal flow constructed wetlands: Targeted migration and conducive spatial distribution for pollutants removal

The tidal flow constructed wetland (TFCW) effectively removes nitrogen from mainstream wastewater but encounters limitations in denitrification, resulting in the accumulation of nitrate and nitrite nitrogen (NOx--N). In this study, we investigated the spatial distribution characteristics of pollutants and migration-transformation processes within the TFCW using the stratified analysis theories proposed. The results indicated that during the influent stage, 82.60 % of ammonia nitrogen (NH4+-N) and 87.77 % of COD were adsorbed by the top and middle layers. In the drain stage's oxygen-rich environment, microorganisms and atmospheric oxygen oxidized NH4+-N to NOx--N, achieving in-situ regeneration of NH4+-N adsorption sites. Furthermore, 61.87 % of the NOx--N was washed into the bottom in the next influent stage, subsequently adsorbed by the biofilm, and finally reduced to gaseous nitrogen using carbon source as the electron donor at the drain stage. Consequently, inconsistent locations of carbon source and NOx--N were identified as limiting factors for denitrification in TFCW. Based on this, the study designed a two-way influent tide flow constructed wetland (TTFCW) by altering the influent pattern. It facilitated targeted carbon source addition for denitrification, resulting in a 3.30-fold improvement in actual carbon source utilization efficiency of TFCW. Ultimately, this approach resulted in a notable increase in NOx--N removal rate by 64.51 %, accompanied by a 28.32 % reduction in accumulation levels. This study fills the research gap in the internal distribution and migration-transformation of pollutants within TFCW, providing methods support for enhancing nitrogen removal in TFCW and ideas for denitrification in mainstream wastewater.

Effects of initial alkalinity and elemental sulfur: dolomitic limestone ratio on autotrophic denitrification of poultry wastewater

Autotrophic denitrification from elemental sulfur is an alternative to heterotrophic denitrification for substrates with a low C/N ratio. In this process, nitrogen compounds are reduced from elemental sulfur instead of carbon, as in the conventional process. However, it may be limited by the low concentration of alkalinity in these effluents. Thus, this study evaluated the performance of autotrophic denitrification of nitrified poultry effluent in four fixed bed reactors with a ratio of elemental sulfur/dolomitic limestone (1:0, 3:1, 1:1, 1:3 v/v) under conditions of the decline of initial alkalinity (1000, 800, 600, 400 and 200 mg CaCO3 L-1). Denitrification efficiencies greater than 84.8% were observed in conditions of initial alkalinity greater than 600 mg CaCO3 L-1 in the four reactors, associated with maximum yields of 445.1 mg SO4-2 L-1. The slow dissolution of dolomitic limestone may have impaired denitrification efficiency in conditions of initial alkalinity lower than 600 mg CaCO3 L-1. The autotrophic denitrification process proved viable for the treatment of nitrified effluent, and its efficiency was linked to the food substrate and the dissolution of dolomitic limestone.

Application of immobilized biological fillers for the hydrolytic acidification and denitrification of sulfide-containing tannery wastewater

This study investigated the application of immobilized biological fillers in the hydrolytic acidification (HA) and denitrification (DN) of actual sulfide-containing tannery wastewater (TWW) through pilot-scale systematic experiments, which provided technical insights for the engineering application of immobilized bio-filler in practical TWW treatment. HA fillers and DN fillers could effectively realize the enrichment and maintenance of functional flora even under long-term inhibition of high sulfide concentration. The HA fillers demonstrated efficient conversion of organic nitrogen. At a hydraulic retention time (HRT) in the range of 3–6 h, the HA reactor achieved an average organic nitrogen conversion concentration of about 100 mg/L, accounting for 56.2 %-68.5 % of the total organic nitrogen in the TWW. Under this condition, the highest average organic nitrogen conversion and mean chemical oxygen demand (COD) degradation efficiencies were achieved, at 32.95 mgNH4+-N/(L·h) and 179.42 mgCOD/(L·h), respectively. Free ammonia (FA) may contribute to pH stabilization in the HA reactor. Denitrification fillers could utilize the endogenous organic matter in the actual TWW hydrolyzed acidified solution, and realize stable biological nitrogen removal effect with no additional carbon source. The denitrification rate reached 76.3 mg NO3--N/(L·h) and the ΔC/ΔN of the denitrification ranged from 3 to 4.

High nitrogen removal and electricity generation of anaerobic fluidized bed coupled microbial fuel cell for Anammox

The current challenge in wastewater denitrification lies in the treatment of low carbon to nitrogen ratio(C/N) wastewater. Integrating Anaerobic Ammonia Oxidation(Anammox) with a microbial fuel cell(MFC) enables simultaneous pollutant removal and electricity generation, leading to enhanced treatment efficiency and reduced energy consumption. However, achieving stable and effective treatment effects under high nitrogen concentration conditions remains a general research difficulty. The Anaerobic fluidized bed MFC(AFB-MFC) experiment successfully integrated Anammox ammonia oxidizing bacteria (AnAOB) into the anode and cathode chambers, resulting in a continuous operation for 258 days. The reactor successfully initiated operation within 48 days and maintained stable performance within an NLR range of 0.5–1.0 kgN/m3/d. The system performance was found to be influenced by DO and substrate concentration, demonstrating consistent high nitrogen removal ability across different HRT. Ultimately, the Anammox AFB-MFC achieved a nitrogen removal efficiency (NRE) of 96.89%, while its power generation performance gradually improved, yielding a final output voltage ranging from 370 to 420 mV. The microbial community within the reactor comprised diverse electricity-producing bacteria and AnAOB. This study highlights the excellent denitrification and power generation potential of Anammox AFB-MFC under low energy consumption conditions and provides theoretical groundwork for the practical implementation of Anammox.

Efficient denitrification of pharmaceutical wastewater using a coral-like CuO-ZIF-Co/NF cathode through reasonable matching of nitrate and nitrite reduction

Electrochemical NO3− reduction reaction (NO3RR) is an effective method for removing nitrate from industrial wastewater. The commonly used Cu based cathode can effectively reduce NO3− to NO2−. However, how to achieve a reasonable match between NO3− reduction and subsequent NO2− reduction is a key scientific issue in improving the efficiency of electrochemical NO3RR. A coral-like CuO-ZIF-Co/NF cathode is synthesized through the electrodeposition of Cu particles on the surface of ZIF-Co/NF skeleton combined with annealing. Excessive 2-methylimidazole in ZIF-Co is prone to self-deprotonation which enables effective binding of Co3O4 and CuO on the surface. Electrochemical characterizations reveal that compared to NO3−-N reduction, CuO-ZIF-Co/NF has lower over potential and faster reduction rate for NO2−-N reduction. Further kinetic studies also exhibit that the removal rate of NO2−-N by CuO-ZIF-Co/NF is 1.4 times higher than that of NO3−-N. This difference in reduction rate results in CuO-ZIF-Co/NF exhibiting higher rates of NO3−-N removal (0.97 mg-N (L∙min)-1) and NH4+-N generation (0.37 mg-N (L∙min)-1) than other reported materials at the current density as low as 10 mA cm−2, without any accumulation of NO2−-N during the NO3RR. Moreover, the electrode has shown excellent advantages in the actual pharmaceutical wastewater treatment process. It can not only remove the total nitrogen below the WHO emission limit standard, but also remove hardness and COD from the wastewater simultaneously.

Effects and mechanisms of oxytetracycline and norfloxacin on microbial extracellular polymeric substances (EPS) in biological denitrification of aquaculture wastewater

The direct equalizing ray method was employed to design three groups of mixtures of oxytetracycline(OTC) and norfloxacin(NOR) with varying proportions(Group R1 had a higher proportion of OTC, while R2 had similar concentrations of both antibiotics, and R3 had a higher proportion of NOR).The effects of these mixtures on the content and properties of extracellular polymeric substances (EPS) in the biological denitrification process were investigated using an sequencing batch reactor activated sludge reactor (SBR). The results revealed that the removal rates of ammonia nitrogen(NH3-N) decreased in all three groups with the addition of antibiotics. As the antibiotic concentration increased, the EPS content decreased by 68.46%, 55.53%, and 65.03% in R1, R2, and R3, respectively. To understand the interaction mechanism of mixed antibiotics on EPS in activated sludge, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques were employed. The findings demonstrated significant effects of mixed antibiotics on functional groups such as C-O, CO, and C-O-C. Specifically, hydrogen bonding was found to be the primary influencing factor in the R1 ratio, while Π-Π conjugation played a major role in the R3 ratio.

Low-voltage stimulated denitrification performance of high-salinity wastewater using halotolerant microorganisms

Nitrate is a common contaminant in high-salinity wastewater, which has adverse effects on both the environment and human health. However, conventional biological treatment exhibits poor denitrification performance due to the high-salinity shock. In this study, an innovative approach using an electrostimulating microbial reactor (EMR) was explored to address this challenge. With a low-voltage input of 1.2 V, the EMR reached nitrate removal kinetic parameter (kNO3-N) of 0.0166–0.0808 h−1 under high-salinities (1.5 %-6.5 %), which was higher than that of the microbial reactor (MR) (0.0125–0.0478 h−1). The mechanisms analysis revealed that low-voltage significantly enhanced microbial salt-in strategy and promoted the secretion of extracellular polymeric substances. Halotolerant denitrification microorganisms (Pseudomonas and Nitratireductor) were also enriched in EMR. Moreover, the EMR achieved a NO3-N removal efficiency of 73.64 % in treating high-salinity wastewater (salinity 4.69 %) over 18-cycles, whereas the MR only reached 54.67 %. In summary, this study offers an innovative solution for denitrification of high-salinity wastewater.

Research Progress,Problems and Future Prospects of A New Combined Anaerobic Ammonia Oxidation and Nitrogen Removal Process

Anaerobic ammonium oxidation (Anammox) is a cost-effective and efficient process for nitrogen removal, which has attracted widespread attention in the field of wastewater treatment due to its significant advantages. However, the slow rate of growth of anaerobic ammonium oxidizing bacteria (AnAOB) and its sensitivity to operational and environmental conditions hinder its wide application. Although various control strategies have been explored and developed, the application of Anammox process still faces many challenges, including unstable nitrogen removal performance and the necessity for additional treatment of effluent nitrate nitrogen. Due to the importance and necessity of Anammox in wastewater denitrification, this paper first introduces the present biological denitrification system based on Anammo. In view of the insufficient source of nitrite nitrogen in nitrogen-containing wastewater, nitrite nitrogen can be provided by partial nitrification (PN) or partial denitrification (PD) , however, the stability of system operation and efficiency of denitrification are still the difficulties in Anammox engineering applications. It is especially crucial to study the combined new processes based on Anammox to achieve stable deep biological nitrogen removal from wastewater. Therefore, this paper focuses on latest research progress in Anammox coupled simultaneous partial nitrification, denitrification and anammox (SPNDA) , constructed wetland (CW) , phosphorus removal/ recovery process, sulfur denitrification removal (SDA) and denitrifying anaerobic methane oxidation (ADAMO) . The nitrogen removal performance, influencing factors, operation advantages, research progress, application prospects and challenges are reviewed. Compared with the single Anammox process, the combined process offers several advantages, including overcoming the issue of nitrate in the effluent (SPNDA, A-DAMO, SDA) , alleviate the inhibition of organic matter on AnAOB (SPNDA, SDA) , recover non-renewable resources (HAP) , and achieve a clean environment with significant economic benefits (A-CW) , providing flexibility for the promotion and application of Anammox process. The study outlines future directionsfor researching, developing, and applying the Anammox combined nitrogen removal process, and at the same time provides as a reference for lowering energy consumption, achieving efficient and stable nitrogen removal processes, and broadensing the scope of engineering application.

Abstract 1211 Determination of efficient alternative carbon sources for wastewater denitrification

Abstract 1211 Determination of efficient alternative carbon sources for wastewater denitrification