Ammonia Nitrogen Removal Research Articles

Application of physicochemical techniques to the removal of ammonia nitrogen from water: a systematic review.

Ammonia nitrogen is a common pollutant in water and soil, known for its biological toxicity and complex removal process. Traditional biological methods for removing ammonia nitrogen are often inefficient, especially under varying temperature conditions. This study reviews physicochemical techniques for the treatment and recovery of ammonia nitrogen from water. Key methods analyzed include ion exchange, adsorption, membrane separation, struvite precipitation, and advanced oxidation processes (AOPs). Findings indicate that these methods not only remove ammonia nitrogen but also allow for nitrogen recovery. Ion exchange, adsorption, and membrane separation are effective in separating ammonia nitrogen, while AOPs generate reactive species for efficient degradation. Struvite precipitation offers dual benefits of removal and resource recovery. Despite their advantages, these methods face challenges such as secondary pollution and high energy consumption. This paper highlights the development principles, current challenges, and future prospects of physicochemical techniques, emphasizing the need for integrated approaches to enhance ammonia nitrogen removal efficiency.

Firmicutes and Bacteroidetes as the dominant microorganisms for ammonium nitrogen wastewater treatment with a low C/N ratio in BCOR

Improving nitrogen removal is a significant concern in the biological treatment of ammonium nitrogen (NH4+-N) wastewater with low chemical oxygen demand (COD)/NH4+-N (C/N) ratio, and microorganisms are the critical factor affecting nitrogen removal. In this study, a laboratory-scale biological contact oxidation reactor (BCOR) system was successfully started up (day 1 to day 47) and stabilized (day 48 to day 320). A 16S rRNA gene sequencing analysis showed that the phyla Firmicutes and Bacteroidetes were first observed as the dominant microorganisms in the BCOR for the ammonium nitrogen wastewater treatment with a low C/N ratio. The genera Bacteroides (phylum Bacteroidetes), Porphyromonas (phylum Bacteroidetes), Dialister (phylum Firmicutes), and Anaerococcus (phylum Firmicutes) also became the main microorganisms in this system for the first time. These microbial communities enabled the system to achieve an average ammonium nitrogen removal efficiency and total nitrogen removal efficiency of 95.8 % and 88.1 %, respectively, during the operational period. It indicated that these dominant microorganisms in the BCOR system played an essential role in improving the performance of biological nitrogen removal. This conclusion will play a critical role in promoting the microbial mechanism research and technology engineering application of the BCOR system for treating ammonium nitrogen wastewater with a low C/N ratio.

Effects of Co3O4 modified with MoS2 on microbial fuel cells performance

In this study, Co3O4@MoS2 is prepared as anodic catalytic material for microbial fuel cells (MFCs). As the mass fraction of MoS2 is 20%, the best performance of Co3O4@MoS2 composite catalytic material is achieved, and the addition of MoS2 enhances both the electrical conductivity and catalytic performance of the composite catalyst. Through the structural characterization of Co3O4@MoS2 composite catalytic material, nanorod-like Co3O4 and lamellar MoS2 interweaved and stacked each other, and the agglomeration of Co3O4 is weakened. Among the four groups of single-chamber MFCs constructed, the Co3O4@MoS2-MFC shows the best power production performance with a maximum stable output voltage of to 539 mV and a maximum power density of up to 2221 mW/m2. Additionally, the ammonia nitrogen removal rate of the MFCs loaded with catalysts is enhanced by about 10% compared with the blank carbon cloth MFC. Overall, the findings suggest that Co3O4@MoS2 composite catalysts can significantly improve the performance of MFCs, making them more effective for both energy production and wastewater treatment.

Source separation and anaerobic co-digestion of blackwater and food waste for biogas production and nutrient recovery.

Anaerobic co-digestion of source-separated blackwater (BW) and food and kitchen waste (FW) offers decentralized circular economy solutions by enabling local production of biogas and nutrient-rich byproducts. In this study, a 2 m3 pilot-scale continuously stirred tank reactor (CSTR) operated under mesophilic conditions was utilized for co-digestion of BW and FW. The process obtained a CH4 yield of 0.7 ± 0.2 m3/kg influent-volatile solid (VS), reaching a maximum yield of 1.1 ± 0.1 m3/kg influent-VS, with an average organic loading rate of 0.6 ± 0.1 kg-VS/m3/d and HRT of 25 days. The CH4 production rate averaged 0.4 ± 0.1 m3/m3/d, peaking at 0.6 ± 0.1 m3/m3/d. Treatment of digestate through flocculation followed by sedimentation recovered over 90% of ammonium nitrogen and potassium, and 80-85% of total phosphorus in the liquid fraction. This nutrient-rich liquid was used to cultivate Chlorella vulgaris, achieving a biomass concentration of 1.2 ± 0.1 g/L and 85 ± 3% and 78 ± 5% ammonium nitrogen and phosphorus removal efficiency, respectively. These findings not only highlight the feasibility of anaerobic co-digestion of source-separated BW and FW in local biogas production but also demonstrate the potential of microalgae cultivation as a sustainable approach to converting digestate into nutrient-rich algae biomass.

Effects of rice husk biochar attachment biofilm with microorganisms on nitrogen removal of digested swine wastewater

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.

Research and Application of Gangue for the Preparation of Polymerized Aluminum Magnesium Chloride Flocculant

Polymerized aluminum magnesium chloride (PAMC) flocculant was prepared from gangue as a raw material, and the effects of pH, the polymerization time, and the polymerization temperature on the performance of the PAMC were investigated by a one-factor test, based on which, orthogonal experiments (three-factor and two-level) were conducted to optimize the relevant parameters. Meanwhile, FTIR and SEM were used to characterize the polymerized aluminum magnesium chloride, and the sample was applied in printing and dyeing wastewater treatment. The results showed that a pH value of 2.2 and a reaction at 60 °C for 4.5 h were the optimal preparation conditions; the characterization analysis showed that the synthesized product was polymerized aluminum magnesium chloride; the turbidity removal rate of the PAMC for printing and dyeing wastewater was increased by 2.1%, the COD removal rate was increased by 3.1%, the ammonia nitrogen removal rate was increased by 2.1%, and the chromaticity removal rate was increased by 9.2% compared with that of PAC.

Simultaneous removal of nitrate nitrogen and ammonium nitrogen by partial denitrification coupled with anammox synergy by zero-valent iron

The implications of zero-valent iron (ZVI) on performance of partial denitrification (PD) coupled with anammox process (PD-anammox) and microbial community structures were assessed in present investigation. The results indicated that removal efficiencies of nitrate nitrogen, ammonium nitrogen and total nitrogen (TN) reached 86.28 ± 0.04%, 81.05 ± 0.06% and 82.90 ± 0.80%, respectively, with 30-day addition of ZVI under ratio of ZVI to nitrate (ZVI/N), carbon to nitrate (C/N) respectively for 3 and 2.3. Moreover, the content of extracellular polymer substance elevated by ZVI, and which could substitute carbon sources, mediated electron transfer and promoted nitrogen removal efficiency. Additionally, microbiological analysis revealed that ZVI enhanced nitrogen removal process by promoting the growth of genus Ignavibacterium and Denitratisoma, which coexist with anaerobic ammonia oxidation bacterium (AnAOB) and also induced other nitrogen removal process such as heterotrophic nitrate reduction to ammonium (DNRA), nitrate-dependent anaerobic ferrous oxide (NAFO), and iron-based anammox (Feammox) process. This study offers new insights into the enhancement of the nitrogen removal process by ZVI in PD-anammox process.

Mechanism Study on the Effect of Surface Electrical Property on Microbial Membrane Formation Efficiency of TiO2-SiC Composite Filler in Recirculating Aquaculture System.

Recirculating aquaculture systems (RASs) offer significant advantages in aquaculture by markedly decreasing water usage and increasing culture density. A vital component within a RAS is the filler material, which serves as a surface for microbial colonization. Effective microbial treatment is crucial for the efficient operation of a RAS as it assists in purifying the wastewater generated within the system. Nevertheless, traditional fillers often show low efficiency in biofilm formation. The commercial silicon carbide used in this study is a foam ceramic filter with a density of about 0.4-0.55 g/cm3, a number of holes of about 10, and a through porosity of 80.9%, with a diameter of about 5 cm. This research investigates the utilization of a titanium dioxide-silicon carbide (TiO2-SiC) composite filler to improve the purification efficiency of ammonia nitrogen and chemical oxygen demand (COD) in aquaculture wastewater. The study involved the application of titanium dioxide films onto the surface of silicon carbide to produce the composite filler. This method takes advantage of the dipole interaction between titanium dioxide and microorganisms, which enhances biofilm culturing efficiency on the silicon carbide surface. The performance of three different fillers was assessed for their ability to purify aquaculture wastewater. Results showed that the TiO2-SiC composite filler was 1.67 times more effective in removing COD and 1.07 times more effective in removing ammonia nitrogen compared to using silicon carbide alone. These results demonstrate that the incorporation of a titanium dioxide coating substantially boosts the microbial colonization efficiency of silicon carbide, thereby enhancing the overall wastewater purification efficiency in RAS.

Characterization and Comparison of Anammox Immobilization in Polyvinyl Alcohol, Polyethylene Glycol and Water-Borne Polyurethane

Anammox bacteria were embedded with different mass fractions of polyvinyl alcohol (PVA), polyethylene glycol (PEG) and water-based polyurethane (WPU) materials. The embedded immobilized pellets with different particle sizes of about 2.8–3.2 mm were prepared. The effects of the mass fraction of the embedding material (PVA 6–12%, PEG 6–9%, WPU 10%) and the concentration of activated carbon added in the embedding process (0–4%) on the pellet was investigated. The performance of pellet formation, sedimentation rate, mechanical strength, expansion coefficient, and elasticity were compared and analyzed under different immobilization conditions, and the parameters of each embedding step were optimized. Anammox immobilized pellets prepared with 10% polyvinyl alcohol (PVA), 2% sodium alginate (SA), and 2% powdered activated carbon were proposed. The effects of salinity on anammox were investigated through a batch test, and the optimal reaction conditions were selected to carry out the operation test. The functional groups of embedded and unembedded anammox sludge were detected using the infrared spectrum. A continuous flow sequencing batch reactor (SBR) demonstrated stable operation with immobilized anammox. Scanning electron microscopy revealed that the immobilized anammox pellets appeared as irregular particles, with each micro-unit predominantly being spherical. Additionally, a minor presence of rod-shaped bacteria was also noted. After 30 days of stable operation of the reactor, the ammonia nitrogen removal rate reached 84.7%.

Significant enhancement on ammonia removal by thermal/peroxymonosulfate system with bromide ion: Performance, influencing factors and mechanism

Although thermal-activated peroxymonosulfate (PMS) system possesses good performance on the removal of organic pollutants, thermal/PMS system exhibited poor capacity to remove ammonia nitrogen (NH4+-N). This study demonstrated the huge enhancement on the removal of NH4+-N by thermal/PMS system with the commonly coexistent bromide ion (Br-). The elimination of NH4+-N by thermal/PMS/Br- system fitted the pseudo-zero-order kinetics model well, while the corresponding kobs in the presence of 200 μM Br- was 5.76 times greater than that by thermal/PMS system. Bromine (HBrO) was confirmed as the dominant oxidant responsible for removing NH4+-N and TN, while the radicals of HO⋅, SO4⋅- and Br⋅ were also generated but made minor contribution to removing NH4+-N. HBrO was mostly produced by PMS reacting directly with Br-, while these radicals were produced from the cleavage of the O-O bond in PMS and the reaction between PMS and HBrO under high temperature. Thermal/PMS/Br- system exhibited superior performance on TN removal (up to 90 %) than that by thermal/PMS system (less than 5 %) and Cl--enhanced system (about 80 %). The main removal product of NH4+-N was identified as the environmentally friendly gas of N2, although nitrate was also detected. Neutral pH condition was the optical pH for NH4+-N removal. Increasing reaction temperature, PMS dosage and Br- concentration were beneficial to accelerating the removal of NH4+-N. Cations of Cu2+ and Fe3+, anions of SO42-, CO32- and NO3-, humic acid and the actual water matrix of landfill leachate negligibly influenced the removal of NH4+-N, while Cl- exhibited strong enhancement on NH4+-N removal. In summary, this study provided an effective method to improve the oxidizing capacity of thermal/PMS system, especially for NH4+-N removal in wastewater containing Br-.

Ammonium nitrogen and phosphorus removal by bacterial-algal symbiotic dynamic sponge bioremediation system in micropolluted water: Operational mechanism and transformation pathways

Construct a bacteria-algae symbiotic dynamic sponge bioremediation system to simultaneously remove multiple pollutants under micro-pollution conditions. The average removal efficiencies of NH4+-N, PO43−-P, total nitrogen (TN), and Ca2+ were 98.35, 78.74, 95.64, and 84.92 %, respectively. Comparative studies with Auxenochlorella sp. sponge and bacterial sponge bioremediation system confirmed that NH4+-N and TN were mainly removed by bacterial heterotrophic nitrification - aerobic denitrification (HN-AD). PO43−-P was removed by algal assimilation and the generation of Ca3(PO4)2 and Ca5(PO4)3OH, and Ca2+ was removed by algal electron transfer formation of precipitates and microbially induced calcium precipitation (MICP) by bacteria. Algae provided an aerobic environment for the bacterial HN-AD process through photosynthesis, while respiration produced CO2 and adsorbed Ca2+ to promote the formation of calcium precipitates. Immobilization of Ca2+ with microalgae via bacterial MICP helped to lift microalgal photoinhibition. The bioremediation system provides theoretical support for research on micropolluted water treatment while increasing phosphorus recovery pathways.

Research on Ammonium Removal from Wastewater by Adsorption and Ozonation Processes

With the ongoing amendment of the European Union legislation on the treatment of municipal wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Our research was focused on the removal of ammonium nitrogen from municipal wastewater by nontraditional processes based on the use of adsorption processes on zeolite (ZEO) and ozone. Adsorption, adsorption-regeneration, and adsorptive ozonation processes were applied. All processes were carried out in a completely stirred reactor (CSR) and a jet-loop reactor (JLR) with external recirculation of the reaction mixture. Experimental measurements were carried out with real municipal wastewater after mechanical treatment. The best results were achieved in the adsorption-regeneration process, which was implemented in a current loop reactor. An average ammonium nitrogen removal efficiency of 53.1% was obtained by adjusting the pH value to 10.0. Average values of 46.2% and 49.2% for chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies are an added value of the process. The values of ammonium nitrogen, COD, and TOC removal efficiencies in individual cycles confirm the high stability of the process.

Combined treatment of domestic wastewater with landfill leachate using aerobic moving bed bioreactor (AeMBBR)

In this study, the treatment of landfill leachate (LFL) and domestic wastewater using an aerobic moving bed biofilm reactor (AeMBBR) was investigated. AeMBBR was filled with 30 % (v:v) biocarrier material (Kaldnes K1). The effect of different hydraulic retention times (HRTs) (6- 24 h) at a constant dissolved oxygen (DO) of 3.2 mg/L was investigated for system optimization. AeMBBR was successfully operated for LFL and domestic wastewater treatment corresponding to 94 %, and 78 % ammonium nitrogen (NH4-N) and total organic carbon (TOC) removals, respectively. Additionally, Proteobacteria (66%) have been identified as the predominant culture in the biofilm layer, which plays an important role in the co-treatment of domestic wastewater and LFL. Considering the results obtained; it was found that a significant amount of NH4-N was successfully removed.

Synthesis of 4A Zeolite Molecular Sieves by Modifying Fly Ash with Water Treatment Residue to Remove Ammonia Nitrogen from Water

The widespread presence of ammonia nitrogen (NH4+–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH4+–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH4+–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”.

Potential effects of Cu2+ stress on nitrogen removal performance, microbial characteristics, and metabolism pathways of biofilm reactor

Sequencing batch biofilm reactors (SBBR) were utilized to investigate the impact of Cu2+ on nitrogen (N) removal and microbial characteristics. The result indicated that the low concentration of Cu2+ (0.5 mg L−1) facilitated the removal of ammonia nitrogen (NH4+-N), total nitrogen (TN), nitrate nitrogen (NO3−-N), and chemical oxygen demand (COD). In comparison to the average effluent concentration of the control group, the average effluent concentrations of NH4+-N, NO3−-N, COD, and TN were found to decrease by 40.53%, 17.02%, 10.73%, and 15.86%, respectively. Conversely, the high concentration of Cu2+ (5 mg L−1) resulted in an increase of 94.27%, 55.47%, 22.22%, and 14.23% in the aforementioned parameters, compared to the control group. Low concentrations of Cu2+ increased the abundance of nitrifying bacteria (Rhodanobacter, unclassified-o-Sacharimonadales), denitrifying bacteria (Thermomonas, Comamonas), denitrification-associated genes (hao, nosZ, norC, nffA, nirB, nick, and nifD), and heavy-metal-resistant genes related to Cu2+ (pcoB, cutM, cutC, pcoA, copZ) to promote nitrification and denitrification. Conversely, high concentration Cu2+ hindered the interspecies relationship among denitrifying bacteria genera, nitrifying bacteria genera, and other genera, reducing denitrification and nitrification efficiency. Cu2+ involved in the N and tricarboxylic acid (TCA) cycles, as evidenced by changes in the abundance of key enzymes, such as (EC:1.7.99.1), (EC:1.7.2.4), and (EC:1.1.1.42), which initially increased and then decreased with varying concentrations of Cu2+. Conversely, the abundance of EC1.7.2.1, associated with the accumulation of nitrite nitrogen (NO2−-N), gradually declined. These findings provided insights into the impact of Cu2+ on biological N removal.

Improving treatment performance in mature wetlands: The impact of emergent plant species

Improving the treatment performance of mature surface flow constructed wetlands (SFCWs) is critical for long-term sustainability. Nevertheless, the mechanisms of plant species affecting the treatment performance of mature SFCWs remain largely unexplored. In this study, three 6-year-old field-scale SFCWs were subjected to orthogonal tests, with Nelumbo nucifera, Typha angustifolia, and Zizania latifolia as plant species. The aim was to understand how the emergent plant species selected for the newly constructed wetlands influenced the nitrogen and phosphorus treatment performance at maturity. The results showed that plant species significantly affected total nitrogen (TN) treatment performance through dissolved oxygen and water temperature. Typha and Zizania had larger above-ground biomass and denser canopies than Nelumbo, significantly increasing anaerobic zones and water temperature. Therefore, SFCWs with Typha or Zizania had the best organic nitrogen and nitrate nitrogen treatment performance compared to those with Nelumbo. However, the integrated ability of microbes and plants to remove ammonia nitrogen was not affected by internal factors in mature wetlands. Plant species significantly affected total phosphorus (TP) treatment performance through local flow patterns. Although plant species did not significantly affect general hydraulic performance, Zizania had denser tillers and thicker stalks than Nelumbo and Typha, increasing flow velocity near the wetland bottom. Therefore, SFCWs with Nelumbo or Typha were more capable of TP removal than those with Zizania. Overall, Typha was the optimal plant species compared to Nelumbo and Zizania for efficient removal of TN and TP. Therefore, appropriate plant species for newly constructed wetlands are crucial for enhancing nitrogen and phosphorus treatment performance at maturity. From a long-term perspective, SFCWs should be planted with emergent plants with large above-ground parts and sparse tillers. This study provides a mechanistic understanding of the plant species affecting nitrogen and phosphorus in mature SFCWs.

Efficient removal of ammonia nitrogen using biochar derived from the co-fermentation residue of waste activated and orange peel waste: Linking structure properties and reaction kinetics

Elevating ammonia nitrogen (NH4+-N) levels pose substantial threats to both human health and ecological systems. Employing adsorption as a strategic approach for NH4+-N removal is appealing due to its operational simplicity and high efficiency. Prior studies have successfully harnessed valuable volatile fatty acids through the anaerobic co-fermentation of waste activated sludge (WAS) and orange peel waste (OPW). Nevertheless, the proper disposal of the resulting fermentation residue remains a critical concern. This study highlights the effectiveness of biochar derived from WAS/OPW co-fermentation residue in adsorbing NH4+-N in aquatic environments. The highest NH4+-N removal rates were attained at 9.76, 44.1, 76.0, and 97.8 % for biochar dosages of 3, 5, 8, and 10 g/L, respectively. The adsorption of NH4+-N by biochar closely aligns with the Langmuir model and exhibits compatibility with both pseudo-first and pseudo-second kinetic models. This implies a single-layer adsorption process with the simultaneous occurrence of physical and chemical adsorption. Subsequent analysis revealed that, relative to fermentation residue, biochar exhibited a more porous structure post-pyrolysis, with a specific surface area 3.43 times larger, increased pore volume, and additional mesopores. Furthermore, the biochar displayed a higher abundance of functional groups and metal oxides after pyrolysis, collectively contributing to its robust adsorption capability for NH4+-N. This research introduces a promising approach for mitigating NH4+-N pollution in aquatic environments while concurrently enhancing the resource utilization of organic solid waste.

Influence and mechanism of typical transition metal ions on the denitrification performance of heterotrophic nitrification-aerobic denitrification bacteria

To investigate the inhibitory effects of various transition metal ions on nitrogen removal and their underlying mechanisms, the single and combined effects of Cu2+ Ni2+ and Zn2+ on Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria Acinetobacter sp. TAC-1 were studied in a batch experiment system. The results revealed that increasing concentrations of Cu2+ and Ni2+ had a detrimental effect on the removal of ammonium nitrogen (NH4+-N) and total nitrogen (TN). Specifically, Cu2+ concentration of 10 mg/L, the TN degradation rate was 55.09%, compared to 77.60% in the control group. Cu2+ exhibited a pronounced inhibitory effect. In contrast, Zn2+ showed no apparent inhibitory effect on NH4+-N removal and even enhanced TN removal at lower concentrations. However, when the mixed ion concentration of Zn2++Ni2+ exceeded 5 mg/L, the removal rates of NH4+-N and TN were significantly reduced. Moreover, transition metal ions did not significantly impact the removal rates of chemical oxygen demand (COD). The inhibition model fitting results indicated that the inhibition sequence was Cu2+ > Zn2+ > Ni2+. Transcriptome analysis demonstrated that metal ions influence TAC-1 activity by modulating the expression of pivotal genes, including zinc ABC transporter substrate binding protein (znuA), ribosomal protein (rpsM), and chromosome replication initiation protein (dnaA) and DNA replication of TAC-1 under metal ion stress, leading to disruptions in transcription, translation, and cell membrane structure. Finally, a conceptual model was proposed by us to summarize the inhibition mechanism and possible response strategies of TAC-1 bacteria under metal ion stress, and to address the lack of understanding regarding the influence mechanism of TAC-1 on nitrogen removal in wastewater co-polluted by metal and ammonia nitrogen. The results provided practical guidance for the management of transition metal and ammonia nitrogen co-polluted water bodies, as well as the removal of high nitrogen.

Enhancing immobilized Chlorella vulgaris growth with novel buoyant barium alginate bubble beads

Microalgae immobilization in alginate beads shows promise for biomass production and water pollution control. However, carrier instability and mass transfer limitations are challenges. This study introduces buoyant barium alginate bubble beads (BABB), which offer exceptional stability and enhance Chlorella vulgaris growth. In just 12 days, compared to traditional calcium alginate beads, BABB achieved a 20 % biomass increase while minimizing cell leakage and simplifying harvesting. BABB optimization involved co-immobilization with BG-11 medium, enrichment of CO2 in internal bubbles, and the integration of Fe nanoparticles (FeNPs). In the open raceway pond reactor, these optimizations resulted in a 39 % increase in biomass over 7 days compared to the unoptimized setup in closed flasks. Furthermore, enhancements in pigment and organic matter production were observed, along with improved removal of ammonia nitrogen and phosphate. These results highlight the overall advantages of BABB for microalgae immobilization, offering a scientific foundation for their effective utilization.

Mechanisms of anammox granular sludge reactor effluent as biostimulant: Shaping microenvironment for anammox metabolism

Effluent from anammox granular sludge (AnGS) bioreactor contains microbes and microbial products. This study explored mechanisms of utilizing AnGS-effluent as biostimulant for anammox process enhancement. Compared with no AnGS-effluent supplemented control reactor, 5.0 and 1.3 times higher ammonium nitrogen and total inorganic nitrogen removal rates, respectively were obtained with continuous AnGS-effluent supplementation after 98 days’ operation. Anammox bacteria from Candidatus Brocadia accounted for 0.1 % (DNA level) and 1.3 %–1.5 % (RNA level) in control reactor, and 2.9 % (DNA level) and 54.5 %–55.4 % (RNA level) in the AnGS-effluent-fed reactor. Influent microbial immigration evaluation showed that bacterial immigration via AnGS-effluent supplementation was not the main contributor to active anammox community development. Amino acids biosynthesis, B-vitamins and coenzymes metabolism related pathways were facilitated by AnGS-effluent supplementation. AnGS-effluent supplementation aided anammox metabolic activity by shaping microenvironment and microbial interactions. This study provides insights into enhancing anammox bacterial metabolism with AnGS-effluent microbial products as biostimulant.