Nitrate Removal Research Articles

Electrocatalytically active and charged natural chalcopyrite for nitrate-contaminated wastewater purification extended to energy storage Zn-NO3− battery

Charged natural chalcopyrite (CuFeS2, Ncpy) was developed for a three-dimensional electrochemical nitrate reduction (3D ENO3−RR) system with carbon fiber cloth cathode and Ti/IrO2 anode and Zn-NO3− battery. The 3D ENO3−RR system with Ncpy particle electrodes (PEs) possessed superior nitrate removal of 95.6 % and N2 selectivity of 76 % with excellent reusability under a broad pH range of 2–13 involving heterogeneous and homogeneous radical mechanisms. The Zn-NO3− battery with Ncpy cathode delivered an open-circuit voltage of 1.03 V and a cycling stability over 210 h. It was found that Ncpy PEs functioned through self-oxidation, surface dynamic reconstruction (Cu1.02Fe1.0S1.72O1.66 to Cu0.61Fe1.0S0.27O2.98), intrinsic micro-electric field (CuI, S2− anodic and FeIII cathodic poles), and reactive species (•OH, SO4•−, 1O2, •O2− and •H) generation. Computational analyses reveal that CuFeS2(112) surface with the lowest surface energy preferentially exposes Fe and Cu atoms. Cu site is beneficial for reducing NO3− to NO2−, Fe and Fe−Cu dual sites are conducive to N2 selectivity, lowering the overall reaction barriers. It paves the way for selective NO3− reduction in wastewater treatment and can be further extended to energy storage devices by utilizing low-cost Ncpy.

Self-supported copper/copper oxide microspheres for efficient electrocatalytic removal of low-concentration nitrate from aqueous solutions

The electrochemical removal of nitrate (NO3−) from aqueous solutions is a promising strategy for wastewater treatment; however, highly active catalysts are required. In this study, self-supported Cu/copper oxide (CuO) microspheres (ms) on Ni foam (NF) (Cu/CuOms/NF) were fabricated for NO3− removal from water using an electrochemical method, achieving a transformation efficiency of up to 99.72 % and N2 selectivity of 97.97 %. Cu/CuOms/NF also exhibited excellent NO3− removal performance over a wide pH range, while maintaining extremely low levels of toxic ammonia residues. The Cu/CuOms/NF-driven NO3− removal rate remains as high as 95.45 % even after recycling for five times, demonstrating the remarkable electrochemical stability of the catalyst. The Cu/CuOms supported on NF provided active sites and accelerated the oxidation cycle involving Cl−, leading to the complete transformation of NO3− into harmless N2 gas. Therefore, this study not only achieved the environmentally friendly treatment of NO3− pollutants in wastewater but also provided a promising strategy for developing catalysts for electrochemical NO3− removal.

Catalytic enhancement of microbial denitrification by FeVO4@biochar: Insight into the extra cellular polymeric matrix mechanism

The biological denitrification is being considered as one of the best methods for nitrate removal from wastewaters, however it suffers with lower efficiency which needs to be improved effectively. The present study was aimed to prepare FeVO4@biochar and investigated its role as electron shuttle in enhancing the biological denitrification through various batch experiments. Significantly higher rates of denitrification were observed after addition of FeVO4@biochar in different concentrations and the highest efficiency was observed in 15 wt% FeVO4@biochar (BF-15) where 87.6 % denitrification was achieved after 7 days (from 100 mg/L to 12.7 mg/L of nitrate) compared to pure biochar (65.7 mg/L; 34.3 %) and sludge (72.7 mg/L; 27.3 %). FeVO4@biochar increased the transfer of external electron to bacteria and enhanced the denitrification activity. The variations in NAR (nitrate reductase), NIR (nitrite reductase) and ETSA (electron transport system activity) were investigated to understand the changes in microbial-community during denitrification. The FeVO4@biochar and extracellular polymeric substance (EPS) both acted as the media for electron transport along with the decreased repulsions between nitrate and the catalyst surface that further provides higher nitrate reduction efficiency. The electroactive bacteria could easily utilize the photogenerated electrons from FeVO4@biochar and facilitate excellent denitrification. The microbial-diversity analysis revealed Bacteroidota, Firmicutes, Proteobacteria, Chloroflexi, Desulfobacterota, Acidobacteriota, Actinobacteriota, and Gemmatimonadota were observed as the most predominant phyla actively participated in enhanced denitrification. This study suggested that the addition of photoactive catalyst strongly enhanced the electron transfer during denitrification and provides new ideas to the biological denitrification

Effect of humic acid on aerobic denitrification by Achromobacter sp. strain GAD-3

Humic acid (HA), a common natural organic matter, could affect conventional anoxic denitrification. Aim of this study was to investigate effect of HA on the process of aerobic denitrification in Achromobacter sp. GAD-3, an aerobic denitrifying strain. The findings demonstrated that an increase in HA concentrations (≥5mgL-1) promoted the aerobic denitrification process (excluding N2O reduction), manifesting as higher rates of nitrate removal (6.67-11.1mgL-1h-1) and lower levels of nitrite accumulation (30.2-20.7mgL-1). This was attributed to the increased electron transfer activities and denitrifying reductase activities (including NAR, NIR and NOR) facilitated by HA. Accordingly, the expression of denitrification genes such as napA, cnorB, and nirS was enhanced by HA. Nonetheless, the nosZ gene and N2OR activity underwent suppression by HA, which was accountable for N2O emission. It is crucial to understand the HA mechanism towards aerobic denitrifiers for wastewater treatment plants to enhance nitrogen removal.

Synergistic nitrate removal: Coupling electrocatalysis and chemical reduction for exceptional nitrogen selectivity

Nitrate pollution in natural water bodies poses a severe threat to human health and the environment. Developing efficient and environmentally friendly nitrate removal methods has become a global need. Electrochemical techniques offer a cost-effective strategy for nitrate remediation; however, the complexity of the reaction and the formation of multiple by-products make the selective production of harmless nitrogen a challenging task. This study proposes a novel two-step strategy to achieve high efficiency and selectivity in converting nitrate into nitrogen. First, a membrane electrode consisting of silver nanowires (Ag NWs) is used to electrochemically reduce nitrate to nitrite through a direct electron transfer pathway. Whether in a static electrolytic cell or a flow cell, the process has very high nitrite selectivity and Faraday efficiencies, with Faraday efficiency up to 98.40 % and selectivity up to 99.90 % at −1.0 V vs Ag/AgCl. Subsequently, the nitrite is converted into nitrogen through a specific reaction with sulfamic acid with near 100 % conversion and selectivity. By coupling these two reactions, the selectivity for converting nitrate to nitrogen can reach more than 99 %. In addition, the membrane electrode can be readily used in a flow-through electrolytic cell to treat nitrates at a maximum rate of 150 L h−1 m−2. When operated at 50 L h−1 m−2, the membrane electrode demonstrates relatively stable performance for 100 h, reducing nitrates at 1.61 mM to below 0.81 mM (50 ppm), as recommended by the World Health Organization for drinking water. This novel synergistic approach not only enhances nitrogen selectivity but also simplifies the process of electrocatalytic nitrate reduction, making it a promising method for nitrate removal.

Nitrate and ammonium removal in constructed wetlands: Experimental insights and zero-dimensional numerical modeling

Constructed wetlands (CWs) have emerged as effective wastewater treatment systems, mimicked natural wetland processes but engineered for enhanced pollutant removal efficiency. Ammonium (NH4+) and nitrate (NO3−) are among common pollutants in wastewater, posing significant environmental and health risks. The primary objective of this study is to compares the performance of CWs using gravel and three sizes of natural pumice, along with phragmites australis, in horizontal and horizontal-vertical CWs for nitrate and ammonium removal in the complementary treatment of domestic wastewater. Additionally, the study aims to develop and validate a numerical model using MATLAB software to predict the removal efficiency of these pollutants, thereby contributing to the optimization of CW design and operation. The model operates as a zero-dimensional model based on the law of mass conservation, treating the wetland as a completely mixed reactor, thus avoiding complexities associated with solute movement in porous media. It accurately could predict removal efficiency of chemical, biochemical, and biological indicators while considering active and passive absorption mechanisms by plant uptake. Notably, the determination of coefficients in the model equation does not rely on potentially error-prone laboratory measurements due to sampling issues. Instead, optimization techniques alongside field data robustly estimate these coefficients, ensuring reliability and practicality. Results indicate that higher pollutant concentrations increase reaction rates, particularly enhancing CW efficiency in ammonium removal. Pumice, especially in larger sizes, exhibits superior absorption due to increased porosity and surface area. Overall, the model accurately predicts nitrates concentrations, demonstrating its potential for CW performance optimization and confirming the significance of effective pollutant removal strategies in wastewater treatment.

Simultaneous removal of nitrate, manganese, zinc, and bisphenol a by manganese redox cycling system: Performance and mechanism

The manganese(Mn) redox cycling system in this work was created by combining Mn(IV)-reducing bacteria MFG10 with Mn(II)-oxidizing bacteria HY129. The biomanganese oxides (BMO) generated by strain HY129 were transformed by strain MFG10 to Mn(II), finishing the Mn redox cycling, in which nitrate (NO3–-N) was converted to nitrite, which was further reduced to nitrogen gas. The system could achieve 85.7 % and 98.8 % elimination efficiencies of Mn(ⅠⅠ) and NO3–-N, respectively, at Mn(ⅠⅠ) = 20.0 mg/L, C/N = 2.0, pH = 6.5, and NO3–-N = 16.0 mg/L. The removal of bisphenol A (BPA) and zinc (Zn(II)) at 36 h reached 91.7 % and 89.7 % under the optimal condition, respectively. Furthermore, the Mn redox cycling system can reinforce the metabolic activity and electron transfer activity of microorganisms. The findings showed that the adsorption by bioprecipitation throughout the Mn cycling was responsible for the elimination of Zn(II) and BPA.

Mechanisms underlying episodic nitrate and phosphorus leaching from poorly drained agricultural soils.

Poorly drained depressions within tile-drained croplands can have disproportionate environmental and agronomic impacts, but mechanisms controlling nutrient leaching remain poorly understood. We monitored nitrate and soluble reactive phosphorus (SRP) leaching using zero-tension soil lysimeters across a depression to upland gradient over 2 years in a corn-soybean (Zea mays L.-Glycine max [L.] Merr.) field in Iowa. We also measured stable isotopes (δ15N and δ18O) of nitrate to examine its sources and transformations. SRP concentrations peaked during winter and early spring after phosphorus (P) fertilization (mean=3mg P L-1), with highest values in the depression, and SRP was relatively stable thereafter (mean=0.3mg P L-1) irrespective of periods of high soil moisture that led to widespread iron (Fe) reduction across the field. During a near-average precipitation year, nitrate stable isotopes indicated direct leaching of fertilizer nitrate within days of application, followed by nitrification of fertilizer ammonium and several weeks of denitrification in depressional soils. Nevertheless, nitrate concentrations remained high (mean=28mg N L-1) in the depression despite strong isotopic evidence for denitrification (>48% N removal). During a wet year, nitrate concentrations were lower in the depression than upland and nitrate isotopes were highly variable, consistent with nearly complete nitrate removal by denitrification in the depression and significant denitrification in upland soils. We conclude that poorly drained depressional soils can potentially decrease nitrate leaching via denitrification under sustained wet conditions, but they inconsistently denitrify and are vulnerable to high nitrate and SRP losses when soils are not saturated, especially following fertilization.

Anaerobic manganese oxidation coupled to denitrification by novel autotrophic microbial consortium

Human activities have more than doubled the pre-industrial supply of reactive nitrogen to the biosphere, while manganese is the fifth most abundant metal in the crust of Earth with main redox states of Mn(II) and Mn(IV), which could provide electrons for denitrification driving nitrogen cycling. Although few microorganisms performing nitrate-dependent anaerobic manganese oxidation (NDMO) were identified, their active metabolic pathways have not been confirmed. Here, a microbial consortium was enriched from the mixture of freshwater sediment and activated sludge with nitrate and dissolved divalent manganese. After 528 days of enrichment, the nitrate and Mn(II) removal rate was stable at 7.54 mg N L−1 d−1 and 19.60 mg Mn L−1 d−1, respectively. The mass balance showed that nitrate was reduced into N2, and Mn(II) was converted into manganese oxides. Three novel bacteria were uniquely identified in this microbial consortium: Candidatus Nitratireduceret manganoxidans (17 %) and Candidatus Nitratoreduceret manganoxydans (3.27 %) within the order of Anaerolineales, Candidatus Nitrooxidireductor manganoxidant (6.33 %) affiliated to the order of Phycisphaerales. Ca. N. manganoxidans and Ca. N. manganoxydans encode cotA and moxA for Mn(II) oxidation and denitrification gene for NO3- reduction to N2O, while genes in Ca. N. manganoxidant, moxA, and nosZ only encoded manganese oxidase and nitrous-oxide reductase, which convert N2O further to N2. The two orders of bacteria cooperated in completing a NDMO process, which could be a profound link between nitrogen and manganese cycling in environments that should be investigated in future research. SynopsisThree novel bacteria cooperate to perform autotrophic denitrification coupled with manganese oxidation, and metagenomic analysis revealed their metabolic pathway.

Comprehensive study on pilot nitrification-sludge fermentation coupled denitrification system with extended sludge retention time

The sludge fermentation-coupled denitrification process, utilized for sludge reduction and nitrogen removal from wastewater, is frequently hindered by its hydrolysis step’s efficacy. This study addresses this limitation by extending the sludge retention time (SRT) to 120 days. As a result, the nitrate removal efficiency (NRE) of the nitrification-sludge fermentation coupled denitrification (NSFD) pilot system increased from 67.1 ± 0.2 % to 96.7 ± 0.1 %, and the sludge reduction efficiency (SRE) rose from 40.2 ± 0.5 % to 62.2 ± 0.9 %. Longer SRT enhanced predation and energy dissipation, reducing intact cells from 99.2 % to 78.0 % and decreasing particle size from 135.2 ± 4.6 μm and 19.4 ± 2.1 μm to 64.5 ± 3.5 μm and 15.5 ± 1.6 μm, respectively. It also created different niches by altering the biofilm’s adsorption capacity, with interactions between these niches driving improved performance. In conclusion, extending SRT optimized the microbial structure and enhanced the performance of the NSFD system.

Biopolymeric Composite Columns for Improving Water Quality in a Freshwater Stream Receiving Wastewater Treatment Plant Effluents

AbstractInefficiently treated wastewater, which contains a high concentration of pollutants, is hazardous when it is mixed with the clean water of rivers and lakes. Nitrate in particular is a major global problem that leads to eutrophication and poses a threat to both aquatic ecosystems and human health. To address this issue, this work assessed the efficiency of polymeric cryogel (PC) and biopolymer (EPS)-blended composites (EPS@PC) in removing nitrates. Tests were also conducted to quantify the decrease in phosphate, chloride ions, and chemical oxygen demand (COD) in real water samples taken from the Ankara stream, which receives effluents from both urban (UWTP) and industrial (IWTP) wastewater treatment plants. Five different columns with varying adsorptive properties were prepared, some of which were combined with iron. The EPS-@PC-C5 column demonstrated the highest adsorption ratio for nitrate removal compared to the other tested columns. The EPS@PC-C5 achieved a high removal efficiency of 126.38 mg nitrate/g and showed COD reduction ranging from 60.2 to 94.1%. The removal ratio of chloride concentration varied between 56.0 and 75.7%, while the removal of phosphates ranged from 87 to 99%. Columns composed of EPS (EPS@PC) with both negatively and positively charged ligands are dependable and suitable options for water remediation. Graphical Abstract

Insight into a single-chamber air-cathode microbial fuel cell for nitrate removal and ecological roles.

Bioelectrochemical systems are sustainable and potential technology systems in wastewater treatment for nitrogen removal. The present study fabricated an air-cathode denitrifying microbial fuel cell (DNMFC) with a revisable modular design and investigated metabolic processes using nutrients together with the spatiotemporal distribution characteristics of dominated microorganisms. Based on the detection of organics and solvable nitrogen concentrations as well as electron generations in DNMFCs under different conditions, the distribution pattern of nutrients could be quantified. By calculation, it was found that heterotrophic denitrification performed in DNMFCs using 56.6% COD decreased the Coulombic efficiency from 38.0% to 16.5% at a COD/NO3 --N ratio of 7. Furthermore, biological denitrification removed 92.3% of the nitrate, while the residual was reduced via electrochemical denitrification in the cathode. Correspondingly, nitrate as the electron acceptor consumed 16.7% of all the generated electrons, and the residual electrons were accepted by oxygen. Microbial community analysis revealed that bifunctional bacteria of electroactive denitrifying bacteria distributed all over the reactor determined the DNMFC performance; meanwhile, electroactive bacteria were mainly distributed in the anode biofilm, anaerobic denitrifying bacteria adhered to the wall, and facultative anaerobic denitrifying bacteria were distributed in the wall and cathode. Characterizing the contribution of specific microorganisms in DNMFCs comprehensively revealed the significant role of electroactive denitrifying bacteria and their cooperative relationship with other functional bacteria.

Unacclimated activated sludge improved nitrate reduction and N2 selectivity in iron filling/biochar systems

Iron (Fe)-based denitrification is a proven technology for removing nitrate from water, yet challenges such as limited pH preference range and low N2 selectivity (reduction of nitrate to N2) persist. Adding biochar (BC) can improve the pH preference range but not N2 selectivity. This study aimed to improve nitrate reduction and N2 selectivity in iron filling/biochar (Fe/BC) systems with a simplified approach by coupling unacclimated microbes (M) in the system. Factors such as initial pH, Fe/BC ratio, and Fe/BC dosage on nitrate removal efficiency and N2 selectivity were evaluated. Results show that the introduction of microbes significantly enhanced nitrate removal and N2 selectivity, achieving 100 % nitrate removal and 79 % N2 selectivity. The Fe/BC/M system exhibited efficient nitrate reduction at pH of 2–10. Moreover, the Fe/BC/M system demonstrated an improved electrochemical active surface area (ECSA), lower electron transfer resistance and lower corrosion potential, leading to enhanced nitrate reduction. The high i0 value in Fe/BC/M system means more Hads could be generated, thus improving the N2 selectivity. This study provides valuable insights into a novel approach for effective nitrate removal, offering a potential solution to the environmental challenges posed by excessive nitrate in wastewater, surface water and ground water.

Application of Floating Beds Constructed with Woodchips for Nitrate Removal and Plant Growth in Wetlands

Constructed wetlands and constructed floating wetlands are widely used for nitrogen (N) removal from surface water to combat eutrophication in freshwaters. Two main N removal pathways in freshwaters are plant biomass N uptake and denitrification, i.e. transformation of nitrate (NO3-) to nitrous oxide (N2O) or nitrogen gas (N2) by different microbes possessing nirK, nirS, nosZI, and nosZII genes. In this study, we tested woodchips-based floating beds (WFBs) as a nature-based and environment-friendly method to remove nitrate-nitrogen (NO3-N) from water. Moreover, we tested whether WFBs could support the growth of three selected plant species and the abundance of microbes on plant roots and woodchips as a proxy for WFBs’ denitrification potential. We conducted a greenhouse experiment for 90 days and measured NO3-N removal rates from water in WFBs mesocosms during five sampling occasions. Plant biomass production, biomass N uptake, and plant morphology related to N uptake and abundance of denitrifying organisms were measured at the end of the experiment. NO3-N removal rates were 29.17 ± 11.07, 28.18 ± 12.62, 25.28 ± 9.90, and 22.16 ± 7.79 mg L–1 d–1 m–2 (mean ± standard deviation) in Glyceria maxima, Juncus effusus, Filipendula ulmaria, and unplanted WFBs treatments, respectively for whole experimental period. N content in above- and belowground biomass of studied species ranged between 0.98 – 1.15 and 1.09 – 1.28 (% dry weight), respectively. Plant relative biomass production was 215 ± 61, 67 ± 18, and 7 ± 17 (% dry weight) for G. maxima, J. effusus and F. ulmaria, respectively. Denitrifiers were detected both on plant roots and woodchips, indicating WFBs’ denitrification potential. Our study highlights that WFBs could be applied to enhance NO3-N removal from surface water through plant biomass uptake and denitrification processes. Future studies should consider the long-term in situ application of WFBs for NO3-N removal from water.

Superior nitrate and chromium reduction synergistically driven by multiple electron donors: Performance and the related biochemical mechanism

Nitrate and Cr(VI) are the typical and prevalent co-contaminants in the groundwater, how to synchronously and effectively diminish them has received growing attention. The most problem that currently limits the nitrate and Cr(VI) reduction technology for groundwater remediation is with emphasis on exploring the optimal electron donors. This study investigated the feasibility of utilizing the synergistical effect of inorganic electron donors (pyrite, sulfur) and inherently limited organics to promote synchronous nitrate and Cr(VI) removal, which meets the requirement of naturally low-carbon and eco-friendly technologies. The NO3−-N and Cr(VI) removal efficiencies in the pyrite and sulfur involved mixotrophic biofilter (PS–BF: approximately 90.8 ± 0.6% and 99.1 ± 2.1%) were substantially higher than that in a volcanic rock supported biofilter (V–BF: about 49.6% ± 2.8% and 50.0% ± 9.3%), which was consistent with the spatial variations of their concentrations. Abiotic and biotic batch tests directly confirmed the decisive role of pyrite and sulfur for NO3−-N and Cr(VI) removal via chemical and microbial pathways. A server decline in sulfate production correlated with decreasing COD consumption revealed that there was sulfur disproportionation induced by limited organics. Metagenomic analysis suggested that chemoautotrophic microbes like Sulfuritalea and Thiobacillus were key players responsible for sulfur oxidation, nitrate and Cr(VI) reduction. The metabolic pathway analysis suggested that genes encoding functional enzymes related to complete denitrification, S oxidation, and dissimilatory sulfate reduction were upregulated, however, genes encoding Cr(VI) reduction enzymes (e.g. chrA, chrR, nemA, and azoR) were downregulated in PS-BF, which further explained the synergistical effect of multiple electron donors. These findings provide insights into their potential cooperative interaction of multiple electron donors on greatly promoting nitrate and Cr(VI) removal and have implications for the remediation technology of nitrate and Cr(VI) co-contaminated groundwater.

Algal-biochar and Chlorella vulgaris microalgae: a sustainable approach for textile wastewater treatment and biodiesel production

Microalgae technology is a viable solution for environmental conservation (carbon capture and wastewater treatment) and energy production. However, the nutrient cost, slow-kinetics, and low biosorption capacity of microalgae hindered its application. To overcome them, algal-biochar (BC) can be integrated with microalgae to treat textile wastewater (TWW) due to its low cost, its ability to rapidly adsorb pollutants, and its ability to serve as a nutrient source for microalgal-growth to capture CO2 and biodiesel production. Chlorella vulgaris (CV) and algal-BC were combined in this work to assess microalgal growth, carbon capture, TWW bioremediation, and biodiesel production. Results showed the highest optical density (3.70 ± 0.07 OD680), biomass productivity (42.31 ± 0.50 mg L−1 d−1), and dry weight biomass production (255.11 ± 6.01 mg L−1) in an integrated system of CV-BC-TWW by capturing atmospheric CO2 (77.57 ± 2.52 mg L−1 d−1). More than 99% bioremediation (removal of MB-pollutant, COD, nitrates, and phosphates) of TWW was achieved in CV-BC-TWW system due to biosorption and biodegradation processes. The addition of algal-BC and CV microalgae to TWW not only enhanced the algal growth but also increased the bioremediation of TWW and biodiesel content. The highest fatty acid methylesters (biodiesel) were also produced, up to 76.79 ± 2.01 mg g−1 from CV-BC-TWW cultivated-biomass. Biodiesel’s oxidative stability and low-temperature characteristics are enhanced by the presence of palmitoleic (C16:1) and linolenic (C18:3) acids. Hence, this study revealed that the integration of algal-biochar, as a biosorbent and source of nutrients, with living-microalgae offers an efficient, economical, and sustainable approach for microalgae growth, CO2 fixation, TWW treatment, and biodiesel production.Graphical

Linking Pattern Shifts of Dissolved Organic Nitrogen Fractional Removal with Microbial Species Richness in a Cascade Upflow Biofiltration Process

Nutrient pollution has become an important issue to solve in stormwater runoff due to the fast population growth and urbanization that impacts water quality and triggers harmful algal blooms. There is an acute need to link the dissolved organic nitrogen (DON) decomposition with the coupled nitrification and denitrification pathways to realize the pattern shifts in the nitrogen cycle. This paper presented a lab-scale cascade upflow biofiltration system for comparison of nitrate and phosphate removal from stormwater matrices through two specialty adsorbents at three influent conditions. The two specialty adsorbents are denoted as biochar iron and perlite integrated green environmental media (BIPGEM) and zero-valent iron and perlite-based green environmental media (ZIPGEM). An initial condition with stormwater runoff, a second condition with spiked nitrate, and a third condition with spiked nitrate and phosphate were used in this study. To differentiate nitrifier and denitrifier population dynamics associated with the decomposition of DON, integrative analysis of quantitative polymerase chain reaction (qPCR) and 21 tesla Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were performed in association with nitrate removal efficiencies for both media with or without the presence of phosphate. While the qPCR may detect one gene for a single microbe or pathogen and realize the microbial population dynamics in the bioreactors, the 21 T FT-ICR MS can separate and assign elemental compositions to identify organic compounds of DON. Results indicated that ZIPGEM obtained a higher potential for nutrient removal than BIPGEM when the influent was spiked with nitrate and phosphate simultaneously. The sustainable, scalable, and adaptable upflow bioreactors operated in sequence (in a cascade mode) can be expanded flexibly on an as-needed basis to meet the local water quality standards showing process reliability, resilience, and sustainability simultaneously.

Prediction of nitrate, phosphate and ammonia removal in wastewater by phytoremediation-vortex system using artificial neural network

Abstract Clean water is an essential component for human survival. However, the growing global population and the relentless pace of industrial development have resulted in an alarming increase in water contamination. This renders many bodies of water as unfit for consumption or usage. In order to safeguard our natural resources, it is imperative that wastewater should be treated to follow a standard set by environmental specialists. In the Philippines, the enactment of the DAO 2021-19 has updated the requirements for release to more stringent standards. Because of this, a tertiary treatment, such as a phytoremediation bed, can be employed as an additional step in a wastewater treatment process. This study involves a comprehensive approach that consists of a phytoremediation setup, which includes the use of three plant species and specialized soil matrices, and a vortex system. The three plant species, Phragmites australis, Vetiveria zizanioides, and Canna indica are known for their capability for removal of the three pollutants, nitrates, phosphates and ammonia. The phytoremediation-vortex system was able to remove the pollutants and effectively reduce the pollutant concentration that the treated wastewater passes the standards for release. The predictive model, artificial neural network (ANN), was employed to assess the results. By using this technique, the study aimed to not only understand the intricate workings of the vortex system but also to optimise its performance for the effective reduction of pollutants, such as, nitrates, phosphates and ammonia, in wastewater. This research represents a critical step towards developing sustainable and efficient solutions for addressing the pressing challenges posed by water pollution, thereby fostering the availability of clean and potable water for human consumption and various industrial purposes.

Mixotrophic aerobic denitrification enhanced by inorganic electron donor: Novel insights into iron valence and nirS-type denitrifying bacterial community model

Nitrogen pollution was the main factor leading to reservoir eutrophication. The removal of low-concentration nitrate pollutants in water source reservoirs is an international problem to be solved. Insufficient organic electron donors in natural reservoir are a crucial limiting factor for in situ denitrification. Microbial mixotrophic aerobic denitrification using iron as the assisted electron donor is a potential pathway to treat micropolluted water bodies. The iron/activated carbon (IAC) was used to be an assisted electron provider to advance the mixotrophic aerobic denitrification performance of denitrifying bacterial community in micro-polluted reservoir water. Upon adding IAC into the reactors, the total nitrogen (TN) reduction capacity improved >41.10 %. A slight increase in organic matter removal efficiency observed in the IAC reactors compared to the control reactors. High-throughput sequencing revealed that IAC altered the richness, and co-occurrence of denitrifying bacterial community, further advancing nitrate transformation and removal. The relative abundant of Thauera, Dechloromonas, Cupriavidus, Alicycliphilus, and Azoarcus increased and presented predominant in the IAC reactors. Meanwhile, network analysis, niche width model, neutral community model, and species abundance distribution supported this finding. The Jinpen reservoir (JP; 34°32'38" N, 107°53'53" E, located in Xi’an, North China) and Xikeng reservoir (XK; 34°32'38" N, 107°53'53" E, located in Shenzhen, South China) raw water treatment experiments demonstrated excellent TN (> 60 %) and organic matter removal efficiencies (> 44 %).

Experimental soil matrix, vortex and oil skimming technology as a tertiary treatment of wastewater effluent

Abstract Water is a necessary resource that must be carefully managed. Hazardous chemicals are produced with increased industrial activities and contamination has been detrimental to both people and the environment. An experimental investigation was performed to evaluate the efficiency of vortex technology, soil matrices, and oil skimmer separately for combination as a tertiary wastewater treatment in the design of a phytoremediation system. The objective of the study is to evaluate the performance of each component in removing oil and grease, reducing the concentration of ammonia, nitrate, and phosphate; quality control measures for dissolved oxygen, total dissolved solids, and chemical oxygen demand. One-way ANOVA, kinetics analysis, and adoption isotherm analysis were applied to determine the significance of the parameters. Analysis of results for the oil skimmer exhibited an efficiency of 96% in removing oil and grease after 5 hours of treatment. The vortex technology results were fluctuating with percentage removal of nitrates at 11% while ammonia with an initial concentration of 5.24 mg/L was reduced to 4.12 mg/L. Phosphate decreased after treatment from an initial of 0.87 mg/L to 0.809 mg/L. The analysis of pollutant concentration in the soil matrix after a 5-day period indicated a greater efficiency compared to the vortex technology in the removal of ammonia and phosphate. The ammonia concentration decreased from 18.7 mg/L and 21.4 mg/L to <0.1 mg/L. Similarly, phosphate concentration decreased from 15.5 mg/L to 1.13 mg/L and from 32.5 mg/L to 0.948 mg/L. The research finding underscores the efficiency of the soil matrix in removing ammonia and phosphate but recommends the need for additional intervention to lower nitrate. Overall, the three technologies showed potential and greater efficiencies in mitigating wastewater streams resulting in a notable reduction in oil and pollutant concentrations.