Removal Rates Of NH4 Research Articles

The efficacy of bioretention systems amended with iron-modified biochar for the source-separated and component-specific treatment of rainwater runoff: A microbiome perspective.

Bioretention systems offer advantages in controlling non-point source pollution from runoff rainwater. However, the systems frequently encounter challenges, including insufficient stability of nitrogen and phosphorus removal. Limited research has been performed on bioretention systems which integrate actual data from non-point source pollution cases for the quantitative and qualitative refinement of initial and non-initial rainwater. Moreover, the potential linkages between amended media and microbial communities in bioretention systems with the addition of novel functional filler have not been explored. In this study, a system for treating both initial and non-initial rainwater was established through measurements including iron-modified biochar (FeBC) packing and the optimization of the layer structures. In system treating initial rainwater, the systems loaded with FeBC maintained stable NH4+-N and NO3--N removal rates of over 95% and 80%, respectively under 12 rainfall simulation events. After a 10-day antecedent drying duration (ADD), the removal rates for NH4+-N and PO43--P remained above 78% and 85%. In systems designed to process non-initial rainwater, increasing the height of the transition layer effectively enhanced the NH4+-N removal stability. Meanwhile, increasing the height of the drainage layer could promote PO43--P removal rates to over 75%. The addition of FeBC facilitated the growth of certain denitrifiers improved overall NO3--N removal during successive rainfall events. The microbial communities may adapt to variations in the external environment by enhancing the synthesis of ribosome and the metabolism of pyrimidine and purine, further improving the stability of NH4+-N removal. This study provides a theoretical basis for the precise enhancement of nitrogen and phosphorus removal and the design of bioretention systems for differentiated treatment of rainwater, guiding their design and applications in different regions.

Harnessing natural light: Novel nanoheterojunction photocatalyst NaGdF4:Yb,Tm@TiO2/Cu2(OH)2CO3 for actual wastewater remediation

This study introduces NaGdF4:Yb,Tm@TiO2/Cu2(OH)2CO3 (UTCu), an innovative nanophotocatalyst designed to address global energy crises and water contamination issues. Our developed photocatalyst, NaGdF4:Yb,Tm@TiO2/0.5mol%Cu2(OH)2CO3 (UTCu0.5), demonstrated exceptional efficiency, degrading 96.3% of malachite green (MG) within 2 h under Xenon lamp irradiation. The photocatalytic degradation rate of UTCu0.5 surpassed those of UT, Cu2(OH)2CO3, and P25 (Commercial TiO2) by 3.3, 9, and 2.8 times, respectively. The process effectively mineralized MG into less harmful compounds, marking its potential for eco-friendly wastewater treatment. Furthermore, UTCu0.5 exhibited robust degradation capabilities across various organic dyes and maintained its efficacy in mixed dye systems. Detailed mechanistic analysis revealed that the ·OH and ·O2− radicals play pivotal roles in the degradation process, facilitated by the formation of heterojunctions that enhance carrier separation and photocatalytic performance. Theoretical studies supported the significance of S-scheme heterojunctions in boosting the photocatalytic activity of UTCu0.5. Additionally, the catalyst was effective in degrading organic pollutants in different water matrices under both Xenon lamp irradiation and direct sunlight. Remarkably, it achieved a 77.4% removal rate of NH4⁺-N in real municipal wastewater under natural sunlight, with a selective conversion rate of 95.3% to N2, underscoring its practical applicability in environmental remediation. This research not only progresses photocatalysis technology but also provides vital insights for enhancing natural condition wastewater treatment strategies.

Effect of the residual levofloxacin on hydroponic vegetables with sewage treatment plant tailwater: Microbial community, discharge risk and control strategy

Tailwater-based hydroponic vegetable is a promising strategy for domestic wastewater recycling. However, the effect of residual antibiotics on the hydroponic vegetable system and the relation between hydroponic culture parameters and the residual water quality are still unclear. Here, the typical antibiotic Levofloxacin (LVFX) was employed, and the effect of LVFX (5 mg/L) on the residual water quality, plant growth and microbial community of water spinach hydroponic culture system were investigated under different hydraulic residence times (HRT). Obvious toxic effects on water spinach were observed, and the highest removal rate of LVFX (about 6 %) and TN (25.67±1.43 %) was observed when HRT was 7 days. Hydroponic culture increased the microbial abundance, diversity, and microbial community stability. To optimize the hydroponic culture, actual sewage plant tailwater spiked with 20 μg/L LVFX, along with three common planting substrates (sponge, ceramsite, and activated carbon) were used for the hydroponic culture of lettuce (seasonal reasons). The inhibition effect of LVFX on the removal of NO3--N and TN was observed even as the LVFX concentration decreased significantly (from 14.62 ± 0.44 μg/L to 0.65 ± 0.07 μg/L). The best growth situation of lettuce and removal rates of NH4+-N, NO3--N, TN, especially LVFX (up to 95.65 ± 0.54 %) were observed in the activated carbon treated group. The overall results indicate the negative effect of residual antibiotics on the hydroponic vegetable systems, and adding activated carbon as substrate is an effective strategy for supporting plant growth and controlling discharged risk.

Evaluation of baffle-plate bioreactor coupling with adsorption column for the remediation of aquaculture wastewater

In this study, a baffle-plate bioreactor was designed and coupled with an adsorption column for the remediation of aquaculture wastewater. Specifically, baffle-plate was installed in the bioreactor to improve the removal of carbon (C) and nitrogen (N), while the ceramsite prepared from steel slag and river sediment was filled into the column for the adsorptive removal of phosphorus (P). To evaluate the performance of the bioreactor, the operation conditions (e.g., hydraulic retention time (HRT) and C/N ratio) were tentatively optimized. Under the optimal operation conditions, the effects of sulfamethoxazole (SMX) on the performance of the bioreactor and the microbial community were comprehensively investigated. Satisfactorily, the removal rates of NH4+-N, NO3−-N and permanganate index (IMn) were all above 88 % before adding SMX. Moreover, neither IMn nor NH4+-N was influenced by the SMX shock, whereas the NO3−-N removal was significantly deteriorated owing to the inhibitory effect of SMX on denitrifying bacteria. As revealed by the analysis of microbial communities, the microbial abundance obviously increased in the aerobic (e.g., Azohydromonas and Chitinophagaceae) and anaerobic (e.g., Alkaliflexus) zone as compared to the initially inoculated sludge. Nevertheless, the abundance of most denitrifying genera decreased after adding SMX, leading to the inefficient denitrification. In addition, the ceramsite prepared under the optimum conditions had great void fraction (55.2 %) and water absorbency (29.5 %). The average removal rate of phosphorus by the adsorption column was 71.6 %. Overall, these findings may shed new lights into the coupling of bioreactor and adsorption column for the remediation of aquaculture wastewater.

Effectiveness of cyclic treatment of municipal wastewater by Tetradesmus obliquus – Loofah biofilm, its internal community changes and potential for resource utilization

Microalgae biofilm has garnered significant attention from researchers in the field of sewage treatment due to its advantages such as ease of collection and stable sewage treatment capabilities. Using agricultural waste as biofilm carriers has become a hotspot in reducing costs for this method. This study first combined Tetradesmus obliquus with loofah to form a microalgae biofilm for the study of periodic nitrogen and phosphorus removal from municipal wastewater. The biofilm could stably treat 7 batches of wastewater within one month. The removal rate of TP almost reached 100 %, while the removal rates of NH4+ and TN both reached or exceeded 80 %. The average biomass yield over 25 days was 102.04 mg/L/day. The polysaccharide content increased from 8.61 % to 16.98 % during the cyclic cultivation. The lipid content gradually decreased from 40.91 to 26.1 %. The protein content increased from 32.93 % in the initial stage to 41.18 % and then decreased to 36.31 % in the later stage. During the mid-stage of culturing, the richness of anaerobic bacteria decreased, while the richness of aerobic and facultative bacteria increased, which was conducive to the construction of the microalgae-bacteria symbiotic system and steadily improved the effect of nitrogen and phosphorus removal. As the culturing progressed, the Rotifers that emerged during the mid-stage gradually damaged the biofilm over time, leading to a decline in the effectiveness of sewage treatment in the later stages. This study offers technical support for carrier selection in microalgae biofilm methods and for the periodic removal of nitrogen and phosphorus from wastewater.

Enhanced ammonia nitration by Bio-Electrochemical systems with constructed wetlands

The insufficient abundance of electron acceptors for ammonia during electron transfer in constructed wetlands (CWs) results in low nitrification rates. This study developed a green, low-carbon CWs enhanced by a bio-electrochemical systems (BESs-CWs) to achieve efficient ammonia (NH4+-N) removal. Electrode enhancement significantly promoted NH4+-N removal. Compared with traditional CWs, the average removal efficiency of NH4+-N in the BESs-CWs increased from 62.9 % to 90.6 %. The intermittent voltage driven by the photovoltaic power system caused minimal plant stress. However, electrode enhancement significantly affected microbial communities involved in short-path nitrification and denitrification within the biofilm. Specifically, the removal rate of NH4+-N by BESs-CWs under electrode enhancement was increased by 27.7 % compared to traditional CWs, enhancing the electron output of NH4+-N in the BESs-CWs. This system provides a method of ammonia nitration for CWs under poor electron acceptor conditions.

Synergistic optimization of baffles and aeration to improve the Light/Dark cycle of microalgae photobioreactor for enhanced nitrogen removal performance: Computational fluid dynamics and experimental verification

Microalgae photobioreactor (PBR) is a kind of efficient wastewater treatment system for nitrogen removal. However, there is still an urgent need for process optimization of PBR. Especially, the synergistic effect and optimization of light and flow state poses a challenge. In this study, the computational fluid dynamics is employed for simulating the optimization of the number and length of the internal baffles, as well as the aeration rate of PBR, which in turn leads to the optimal growth of microalgae and efficient nitrogen removal. After optimization, the Light/Dark cycle of the reactor B is shortened by 51.6 %, and the biomass increases from 0.06 g/L to 3.94 g/L. In addition, the removal rate of NH4+-N increased by 106.0 % to 1.56 mg L−1 h−1. This work provides a feasible method for optimizing the design and operational parameters of PBR aiming the engineering application.

Effects of carrier surface hydrophilic modification on sludge granulation: From sludge characteristics, extracellular polymeric substances, and microbial community

Aerobic granular sludge (AGS) is a powerful biotechnological tool capable of treating multiple pollutants simultaneously. However, the granulation process and pollutant removal efficiency still need to be further improved. In this study, Fe2O3- and MnO2-surface-modified straw foam-based AGS (Fe2O3@SF-AGS and MnO2@SF-AGS), with an average particle size of 3 mm, were developed and evaluated. The results showed that surface modification reduced the hydrophobic groups of carriers, facilitating the attachment and proliferation of microorganisms. Notably, MnO2@SF-AGS showed excellent granulation performance, reaching a stable state about one week earlier than the unmodified SF-AGS. The polymeric substance content of MnO2@SF-AGS was found to be 1.28 times higher than that of the control group. Furthermore, the removal rates for NH4+-N, TN, and TP were enhanced by 27.28%, 12.8%, and 32.14%, respectively. The bacterial communities exhibited significant variations in response to different surface modifications of AGS, with genera such as Saprospiraceae, Terrimonas, and Ferruginibacter playing a crucial role in the formation of AGS and the removal of pollutants specifically in MnO2@SF-AGS. The charge transfer of metal ions of MnO2@SF promotes the granulation process and pollutant removal. These results highlight that MnO2@SF-AGS is an effective strategy for improving nitrogen and phosphorus removal efficiency from wastewater.

Surface Modification of PVDF and PTFE Hollow Fiber Membranes for Enhanced Nitrogen Removal in a Membrane-Aerated Biofilm Reactor

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

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.

Conversion behavior of heterotrophic nitrification - aerobic denitrification bacterium Paracoccus denitrificans HY-1 in nitrogen and phosphorus removal

The heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria harbored remarkable removal capacity in eliminating single nitrogen pollutant, but their comprehensive performance in dealing with mixed nitrogen sources remained unknown. In this study, the denitrification capacity of HN-AD bacteria Paracoccus denitrificans HY-1 was explored through whole-genome sequencing and nitrogen metabolic pathway analysis, and the complex nitrogen sources with gradient concentration were used to validate its nitrogen removal efficiency under both aerobic and anaerobic conditions. The results demonstrated that strain HY-1 harbored an efficient degradation capacity on three nitrogen sources, and the removal rates of NH4+-N, NO2−-N and NO3−-N were 10.67 mg·L−1·h−1, 27.81 mg·L−1·h−1, and 22.05 mg·L−1·h−1, respectively. The denitrification rate of 15.33 mg·L−1·h−1 was obtained under anaerobic condition with mixed nitrogen sources. Also, the simultaneous nitrification denitrification phosphorus removal (SNDPR) trial revealed that strain HY-1 could eliminate PO43−-P with a rate of 0.38 mg·L−1·h−1 under coexistence condition of the three nitrogen sources. Combined with the nitrogen balance analysis, the results indicated that strain HY-1 possesses a great potential for application in complex nitrogen and phosphorus contaminated environments.

Comprehensive impacts of the presence of proton exchange membrane on the efficiency of Mg-air fuel cell to remove nutrients and recover struvite

Mg-air fuel cell (MAFC) can achieve simultaneous recovery of phosphorus and nitrogen from wastewater in the form of struvite while generating electricity. This article investigated the comprehensive impacts of the presence of proton exchange membrane (PEM) on the efficiency of MAFC in treating synthetic wastewater, including phosphate and ammonium removal, power generation, and struvite generation. The results showed that the PO43−-P was completely removed within 20 min in the dural-chamber (DC) cell and the removal rate was 6.30 mg-P·cm−2·h−1, which was 1.55 times that of the single-chamber (SC) cell. The removal rate of NH4+-N in the DC cell was 3.37 mg-P·cm−2·h−1, which was 2.70 times that of the SC cell. However, the SC cell produced 63.10 mW·h of electricity, which was 4.61 times that of the DC cell. The precipitates were confirmed to be struvite, with a purity of 99.31 %(DC) and 93.95 % (SC). The low corrosion potential of Mg leads to hydrogen evolution corrosion during the reaction, resulting in low current efficiency, but the current efficiency increased with reaction time. PEM accelerated the hydrogen evolution corrosion, aggravated the magnesium corrosion, increased the internal resistance, and impaired electrical generation capacity, but provided more Mg2+ and alkalinity for the precipitation of struvite. In conclusion, the DC cell had a great capacity for removing nutrients (PO43− and NH4+) and producing high-purity struvite, while the SC cell had a strong ability to generate electricity.

Study on the impact of hydraulic loading rate (HLR) on removal of nitrogen under low C/N condition by modular moving bed constructed wetland (MMB-CW) system

Traditional constructed wetlands often exhibit low nitrogen removal efficiency when treating low C/N wastewater, prompting the need for targeted technological innovation. Modular moving bed constructed wetlands (MMB-CWs) have demonstrated superior performance, achieving over 15% higher TN removal compared to traditional subsurface flow wetlands, even without the addition of carbon, further research is required to fully understand the operational effects of different hydraulic loads and the underlying nitrogen removal mechanisms. To address this gap, the contrast performance of MMB-CWs with three different substrate addition ratios 90% (unit A), 60% (unit B), 30% (unit C) was studied under low C/N conditions and different hydraulic loading rates (HLRs). Results show that there are no significant differences in TN removal among the three systems at 250 mm/d and 500 mm/d. NH4+-N and NO3--N removal rates don't significantly decrease (p>0.05). High HLR leads to significantly lower effluent NO2--N concentrations. HLR minimally affects CODCr removal, with unit C exhibiting better resistance. Functional gene analysis reveals a minor role of nitrification, emphasizing the crucial role of anaerobic ammonium oxidation. The copy number of the Anammox gene is 1.2–4.0 times that of the NIR gene, with a larger ratio in the secondary unit, indicating that denitrification is mainly driven by Anammox. The dominant genera in the first unit are Azospira, Thauera, and Denitratisoma, while Defluviicoccus, Mycobacterium, and Nocardioides dominate the ceramsite and biochar of the second unit. The addition of biochar enhances the composition and abundance of microbial communities in the system, and as biochar addition increases, the removal rates of NH4+-N and TN gradually increase, ensuring effective denitrification under varying loads.

Phytohormone Supplementation for Nutrient Removal from Mariculture Wastewater by Oocystis borgei in Sequential Batch Operation

To enhance the nutrient removal efficiency of Oocystis borgei for mariculture wastewater (MW), the effects and processes of three phytohormones on nitrogen and phosphorus removal from synthetic mariculture wastewater (SMW) by O. borgei under sequential batch operation were compared. The findings revealed that the supplementation with 10−6 M 3-indoleacetic acid (IAA), gibberellic acid (GA3), and zeatin (ZT) resulted in the most effective elimination, while there was no appreciable difference among them. The nitrogen and phosphorus indices of the effluent dramatically reduced (p < 0.01) upon the supplementation of phytohormones, and the removal effects were ranked as NO3−-N > PO43−-P > NH4+-N > NO2−-N. The removal rates for NH4+-N and PO43−-P were 0.72–0.74 mg·L−1·d−1 and 1.26–1.30 mg·L−1·d−1, respectively. According to physiological studies, phytohormones enhanced the levels of photosynthetic pigments and chlorophyll fluorescence parameters (Fv/Fm and φPSII), thereby improving photosynthetic activity. Additionally, they stimulated Nitrate Reductase (NR) and Glutamine Synthetase (GS) activities to promote nitrogen metabolism and increased Superoxide Dismutase (SOD), Catalase (CAT), and carotenoid contents to mitigate oxidative stress damage caused by abiotic stress. These activities contribute to the proliferation of O. borgei, which in turn resulted in an increase in the assimilation of nitrogen and phosphorus from SMW. In conclusion, phytohormone supplementation significantly increased nutrient removal from SMW by O. borgei in a sequential batch reactor, which has potential application in MW treatment.

Factors affecting the enrichment of heterotrophic nitrifying aerobic denitrifying bacteria in municipal wastewater treatment systems and analysis of differences in nitrogen metabolism

In this study, a four-stage MPSR process was employed for the treatment of urban wastewater. Three different conditions were established by controlling dissolved oxygen (DO) concentration, organic load rate (OLR), and influent pH value to examine pollutant removal effects and the changes of the heterotrophic nitrification-aerobic denitrification (HN-AD) functional bacteria communities. The factors driving changes in the HN-AD bacterial community and differences in nitrogen metabolism were revealed in the urban wastewater treatment system. The results showed that by forming anoxic/aerobic alternate oxygen environments and increasing influent OLR and pH, various HN-AD bacteria (Pseudomonas, Aeromonas, Flavobacterium) were enriched in the system, leading to improved removal capacity for NH4+-N and TN. Under optimal condition, the removal rates of NH4+-N and TN were 94.0 % and 78.7 % respectively. The dominant species of HN-AD bacteria were influenced by OLR and pH. The HN-AD bacteria exhibited the capacity for heterotrophic nitrification and aerobic denitrification within the system. This study provides a technological basis for the application of HN-AD bacteria for wastewater treatment.

Impact analysis of hydraulic residence time and dissolved oxygen on performance efficiency and microbial community in N, N-dimethylformamide wastewater treated by an AnSBR-ASBR

Suitable operating parameters are one of the key factors to efficient and stable biological wastewater treatment of N, N-dimethylformamide (DMF) wastewater. In this study, an improved AnSBR-ASBR reactor (anaerobic sequencing batch reactor, AnSBR, and aerobic SBR, ASBR, run in series) was used to investigated the effects of operating conditions such as hydraulic residence time (HRT), AnSBR stirring speed and ASBR dissolved oxygen (DO) for DMF wastewater treatment. When HRT decreased from 24 h to 12 h, the average removal rates of COD by the AnSBR were 34.59% and 39.54%, respectively. Meanwhile, the removal rate of NH4+-N by ASBR decreased from 88.38% to 62.81%. The DMF removal rate reached the best at 18 h and the expression of dehydrogenase was the highest in the AnSBR. The abundance of Megasphaera, the dominant sugar-degrading bacteria in the AnSBR, continued to decline due to the decrease of HRT. The relative abundance of Methanobacterium gradually increased to 80.2% with the decrease of HRT and that hydrotrophic methanogenesis dominated the methanogenic process. The HRT decrease promoted butyrate and pyruvate metabolism in anaerobic sludge, but the proportion of glycolysis and methane metabolism decreased. The AnSBR-ASBR reactor had the best operation performance when HRT was 18 h, AnSBR speed was 220 r/min, and ASBR DO content was 3–4 mg/L. This study provided an effective reference for the reasonable selection of operating parameters in the treatment of DMF-containing wastewater by the AnSBR-ASBR.

Metabolomic insight into regulatory mechanism of heterotrophic bacteria nitrification-aerobic denitrification bacteria to high-strength ammonium wastewater treatment

This work aimed to elucidate the metabolic mechanism of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria influenced by varying concentrations of ammonium nitrogen (NH4+-N) in high-strength synthetic wastewater treatment. The results showed that the removal rates of NH4+-N and total nitrogen, along with enzymatic activities related to nitrification and denitrification, increased with rising NH4+-N concentrations (N500:500 mg/L, N1000:1000 mg/L and N2000:2000 mg/L). The relative abundances of HN-AD bacteria were 50 %, 62 % and 82 % in the three groups. In the N2000 group, the cAMP signaling pathway, glycerophospholipid metabolites, purines and pyrimidines related to DNA/RNA synthesis, electron donor NAD+-related energy, the tricarboxylic acid (TCA) cycle and glutamate metabolism were upregulated. Therefore, influent NH4+-N at 2000 mg/L promoted glutamate metabolism to accelerate the TCA cycle, and enhanced cellular energy and advanced denitrification activity of bacteria for HN-AD. This mechanism, in turn, enhanced microbial growth and the carbon and nitrogen metabolism of bacteria for HN-AD.

Isolation and identification of Chlorella sorokiniana HDMA-16 and its cultivation potential in flax retting wastewater

The utilization of microalgae for wastewater treatment presents a promising and cost-effective solution due to their ability to remove pollutants while simultaneously synthesizing biomass from wastewater nutrients. This research identified a novel strain of Chlorella sorokiniana and investigated its growth ability in flax retting wastewater (FRW), as well as its potential for FRW treatment. Chlorella sorokiniana HDMA-16 was inoculated into FRW, both with and without additional nutrient supplementation. The biomass, lipid content, and fatty acid profile of Chlorella sorokiniana HDMA-16 were determined, along with the changes in total nitrogen (TN), ammonia nitrogen (NH4+-N), total phosphorus (TP), and chemical oxygen demand (COD) in FRW. The results revealed that Chlorella sorokiniana HDMA-16 exhibited moderate growth in FRW without the need for additional nutrients. The strain achieved maximum biomass and lipid productivity levels of 785.7 mg L−1 and 151.5 RFU L−1 d−1. The lipid produced by Chlorella sorokiniana HDMA-16 displayed a favorable fatty acid profile, making the strain a potential candidate for the synthesis of by-products such as biodiesel. The removal rates of NH4+-N, TP, and COD in FRW reached a maximum of 26.86 %, 99.59 %, and 29.39 %. This study is significant in that it shows that the newly discovered Chlorella sorokiniana HDMA-16 can thrive in FRW and effectively remove pollutants. These findings provide a novel approach for FRW treatment and the large-scale cultivation of microalgae, offering promising prospects for sustainable wastewater treatment and microalgae-based industries.

Simultaneous change of microworld and biofilm formation in constructed wetlands filled with biochar

As the regulator of constructed wetlands (CWs), biochar is often used to enhance pollutant removal and reduce greenhouse gas emission. Biochar is proved to have certain effects on microbial populations, but its effect on the aggregation of microbial flocs and the formation of biofilms in the CWs has not been thoroughly investigated. Therefore, the above topics were studied in this paper by adding a certain proportion of biochar in aerated subsurface flow constructed wetlands. The results indicated that after adding biochar in the CWs, pollutant removal was enhanced and the removal rate of NH4+-N was increased from 80.76% to 99.43%. The proportion of hydrophobic components in extracellular polymeric substances (EPS) was reduced by adding biochar from 0.0044 to 0.0038, and the affinity of EPS on CH3-SAM was reduced from 5.736 L/g to 2.496 L/g. The weakened hydrophobic and the reduced affinity of EPS caused the initial attachment of microorganisms to be inhibited. The relative abundance of Chloroflexi was decreased after adding biochar, reducing the dense structural skeleton of biofilm aggregates. Correspondingly, the abundance of Bacteroidetes was increased, promoting EPS degradation. Biochar addition helped to increase the proportion of catalytic active proteins in extracellular proteins and decrease the proportion of binding active proteins, hindering the combination of extracellular proteins and macromolecules to form microbial aggregates. Additionally, the proportions of three extracellular protein structures promoting microbial aggregation, including aggregated chain, β-sheet, and 3-turn helix, were decreased to 23.83%, 38.37% and 7.76%, respectively, while the proportions of random coil and antiparallel β-sheet that inhibited microbial aggregation were increased to 14.11% and 8.11%, respectively. An interesting conclusion from the experimental results is that biochar not only can enhance pollutants removal, but also has the potential of alleviating biological clogging in CWs, which is of great significance to realize the sustainable operation and improve the life cycle of CWs.

Enhancing the sewage treatment effect, reducing membrane fouling, and increasing microbial community diversity by a novel biofiller-carrying functional bacteria Rhodococcus sp. CPZ24 in a moving bed biofilm reactor

The feasibility of using a novel moving bed biofilm reactor (fbMBBR) with biofiller-carrying functional bacteria, Rhodococcus sp. CPZ24, to alleviate membrane pollution and improve wastewater treatment was studied. Three membrane reactors, namely, a biofilm reactor (MBR), a convention moving bed biofilm reactor (MBBR), and fbMBBR, were compared. The results showed that the efficiency of sewage treatment by the fbMBBR was significantly better than that of the MBR and MBBR. When the HRT and DO were 6 h and 3 mg·L−1, the removal rates of NH4+-N, COD, TN, and TP in the fbMBBR reached 92.76 %, 89.89 %, 82.24 %, and 68.23 %, respectively, and membrane fouling was effectively alleviated. Furthermore, the novel biofiller improved the abundance of dominant microbial community species on the membrane module and strengthened microbial community functions. In summary, this study presented a novel fbMBBR with excellent performance in sewage treatment, reducing membrane pollution.