Enhanced performance and kinetics of marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater with Mn(II) and Ni(II) addition

Exogenous magnetite (Fe3O4) nanoparticles for rapid start-up of anammox bioreactor under high nitrogen-loading conditions: Instant boost to anammox activity

This study examines the impact of integrating exogenous magnetite particles (Fe3O4) on the performance of anaerobic ammonium oxidation (anammox).Two sequencing batch bioreactors were operated as magnetite-anammox (M-AMX) and control-anammox (C-AMX) systems at nitrogen loading rates (NLR) of 0.4 and 0.7 kgN.m-3.d-1. The research revealed that magnetite significantly influences granulation and the efficacy of nitrogen removal. The M-AMX system removed 80 % of nitrogen in 30 days, whereas the C-AMX system removed 50 %. The M-AMX system exhibited superior performance at elevated NLR (0.7 kgN.m-3.d-1), achieving 90 % nitrogen removal after 100 days. The M-AMX system produced increased levels of ATP, heme c, and hydrazine synthase, signifying a direct correlation with nitrogen removal. The phylum Planctomycetes and the genus Ca. Brocadia predominantly inhabit both C-AMX and M-AMX systems, with minimal shifts in abundance. Therefore, the incorporation of Fe3O4 can be advantageous in achieving swift and improved nitrogen removal within a short time frame.

Efficient degradation of tetracycline by Mn(III)-microbial complexes mediated by mnOx@ACF in sequencing batch reactors: performance, mechanism, and effect on microbial community structure

Engineered nanomaterials are widely used in water and wastewater treatment processes, and minimizing their adverse effects on biological treatment processes in wastewater treatment plants has become the primary focus. In this study, activated carbon fiber (ACF)-loaded manganese oxide nanomaterials (MnOx@ACF) were synthesized. A small-scale sequencing batch reactor (SBR) was constructed to simulate the synergistic degradation of pollutants by nanomaterials and microorganisms and the effects of nanomaterials on the structure of the microbial community in a wastewater treatment plant. The MnOx@ACF exhibited efficient removal of pollutants (98.7% in 30 cycles) and chemical oxygen demand (COD 96.4% in 30 cycles) through the formation of Mn-microbial complexes and enhanced cycling between Mn(III) and Mn(II) over 30 operating cycles. Metagenome analysis results showed that the microbial population composition and functional abundance increased when the SBR was exposed to different dosages of MnOx@ACF for a long time, among which 0.2 g/L MnOx@ACF exhibited the highest stimulation and influence on the functional abundance of microorganisms, which showed optimum ecological effects.

Insights into the individual and combined effects of Cu(Ⅱ) and Ni(Ⅱ) on anammox: Nitrogen removal performance, enzyme activity and microbial community

Anaerobic ammonium oxidation (anammox) is an efficient and economical nitrogen removal process for treating ammonium-rich industrial wastewaters. However, Cu(Ⅱ) and Ni(Ⅱ) present in industrial wastewaters are toxic to anaerobic ammonium-oxidizing bacteria (AnAOB). Unfortunately, the effects of Cu(Ⅱ) and Ni(Ⅱ) on anammox have not been thoroughly investigated, especially when Cu(Ⅱ) and Ni(Ⅱ) coexist. This work comprehensively investigated the individual and combined effects of Cu(Ⅱ) and Ni(Ⅱ) on anammox and revealed the inhibitory mechanisms. With the influent NH4+-N and NO2--N concentration of 230 and 250 mg L-1, the inhibition thresholds on anammox are 2.00 mg L-1 Cu(Ⅱ), 1.00 mg L-1 Ni(Ⅱ) and 1.00 mg L-1 Cu(Ⅱ) + 1.00 mg L-1 Ni(Ⅱ), and higher Cu(Ⅱ) or Ni(Ⅱ) concentrations resulted in sharp deteriorations of nitrogen removal performance. The inhibition of Ni(Ⅱ) on anammox was mainly attributed to the adverse effect on NiR activity, while the inhibition mechanism of Cu(Ⅱ) seemed to be unrelated to the four functional enzymes, but associated with disruption of cellular and organellar membranes. The behavior of extracellular polymeric substances (EPS) contributed to the antagonistic effect between Cu(Ⅱ) and Ni(Ⅱ) on anammox. In addition, the niche of Candidatus Brocadia and Candidatus Jettenia shifted under the Cu(II) and Ni(II) stress, and Candidatus Jettenia displayed greater tolerance to Cu(II) and Ni(II) stress. In conclusion, this research clarified the combined effect and the inhibitory mechanism of multiple heavy metals on anammox, and provide the guidances for anammox process application in treating high-ammonium industrial wastewaters containing heavy metals.

Enhanced nitrogen removal performance of nitrogen-rich saline wastewater by marine anammox bacteria: Based on different influent loading strengths

In an anaerobic sequential batch reactor (SBR), marine anammox bacteria (MAB) were able to enhance microbial activity in nitrogen-rich saline wastewater and it was significantly affected by influent substrate composition and loading strength. This study therefore enhanced nitrogen removal efficiency by adjusting the influent nitrogen loading strength of MAB-inoculated anaerobic SBRs and assessed the correlation with the bacterial community. The results displayed that the system obtained optimal nitrogen removal efficiency (TN = 83.52%, NH4-N = 90.14%, and NO2-N = 83.57%) as the strength of influent nitrogen loading was increased to 201.35 mg L-1 for NH4-N and 266.42 mg L-1 for NO2-N. Moreover, the increase in the strength of influent nitrogen loading also enhanced the anammox 16S rRNA abundance (4.09 × 108 copies g-1) and ladderanes content (22.49 ng g-1dw). Analysis of 15N isotope further illustrated that all systems were dominated by anammox (average ra = 95.22%). In conclusion, these findings provide scientific guidance for the management of eutrophic seawater and contribute to the realization of industrial applications for the treatment of nitrogen-rich saline wastewater.

Anammox process for aquaculture wastewater treatment: operational condition, mechanism, and future prospective

Treatment of ammonia- and nitrate-rich wastewater, such as that generated in the aquaculture industry, is important to prevent environmental pollution. The anaerobic ammonium oxidation (anammox) process has been reported as a great alternative in reducing ammoniacal nitrogen concentration in aquaculture wastewater treatment compared to conventional treatment systems. This paper will highlight the impact of the anammox process on aquaculture wastewater, particularly in the regulation of ammonia and nitrogen compounds. The state of the art for anammox treatment systems is discussed in comparison to other available treatment methods. While the anammox process is viable for the treatment of aquaculture wastewater, the efficiency of nitrogen removal could be further improved through the proper use of anammox bacteria, operating conditions, and microbial diversity. In conclusion, a new model of the anammox process is proposed in this review.

Short-term responses of the anammox process to Ni(II): nitrogen removal, mechanisms and inhibition recovery

Anaerobic ammonia oxidizing (anammox) has already been recognized as an innovative and economical nitrogen removal technology. However, the effect of heavy metals on anammox bacteria in aquatic ecosystem remains largely unknown. Ni(II) is a common kind of heavy metals detected in industrial wastewater and municipal sewage treatment plants. Hence, the responses of the anammox process to Ni(II) were studied here. The results showed that anammox was the dominant reaction with Ni(II) concentrations no more than 25 mg/L. 1 mg/L of Ni(II) addition promoted nitrogen removal by anammox. The higher the Ni(II) concentrations and longer exposure time, the more inhibition for anammox bacteria was gotten. The IC₅₀ of Ni(II) to anammox was determined as 83.86 mg/L by an exponential regression equation. The inhibition of Ni(II) on anammox activity was mainly attributed to intracellular accumulation Ni(II) inhibition to HDH activity. Two times increase of IC₅₀ after 4 times circles of domestication suggests multiple intermittent domestication can increase the tolerance of anammox bacteria to Ni(II). EDTA washing can eliminate the inhibition of anammox activity by Ni(II) with Ni(II) addition no more than 25 mg/L.

A critical review of exogenous additives for improving the anammox process

Anammox achieves chemoautotrophic nitrogen removal under anaerobic and anoxic conditions and is a low-carbon wastewater biological nitrogen removal process with broad application potential. However, the physiological limitations of AnAOB often cause problems in engineering applications, such as a long start-up time, unstable operation, easily inhibited reactions, and difficulty in long-term strain preservation. Exogenous additives have been considered an alternative strategy to address these issues by retaining microbes, shortening the doubling time of AnAOB and improving functional enzyme activity. This paper reviews the role of carriers, biochar, intermediates, metal ions, reaction substrates, redox buffers, cryoprotectants and organics in optimizing anammox. The pathways and mechanisms of exogenous additives, which are explored to solve problems, are systematically summarized and analyzed in this article according to operational performance, functional enzyme activity, and microbial abundance to provide helpful information for the engineering application of anammox.

Effects of Mn2+ and humic acid on microbial community structures, functional genes for nitrogen and phosphorus removal, and heavy metal resistance genes in wastewater treatment

Considering the wide occurrence of Mn²⁺ and humic acid (HA) in environmental media, the effects of Mn²⁺ (5-16 mg/L) and HA (10 mg/L) on microbial community structures, functional genes for nitrogen and phosphorus removal, and heavy metal resistance genes (HMRGs) were investigated in wastewater treatment using sequencing batch bioreactors (SBRs). The treatment efficiencies of influent chemical oxygen demands (COD), NH₄⁺-N, and PO₄^3--P were unaffected during the entire operational processes irrespective of whether Mn²⁺ and HA were supplied. Although the functional prediction of genetic information via sequencing analysis showed that the microbial activity was not influenced by Mn²⁺ and HA from different SBRs, the abundance of dominant phyla (Proteobacteria, Actinobacteriota, Firmicutes, and Bacteroidota), classes (Saccharimonadia, Gammaproteobacteria, and Bacilli), and genera (unidentified_Chloroplast, TM7a, Micropruina, Candidatus_Competibacter, Lactobacillus, OLB12, and Pediococcus) was different. Compared to the SBR without Mn²⁺ and HA supplementation, the abundance of functional genes for nitrogen and phosphorus removal (narG, nirS, nosZ, ppk, and phoD) and HMRGs (corA and mntA) significantly increased under Mn²⁺ stress, but significantly decreased with the addition of HA except for genes nirS and ppk. The abundance of genes corA and mntA was related to the partially dominant microbes and functional genes, and might be reduced by supplying HA. This study provides insight into the effects of Mn²⁺ and HA on functional genes for nitrogen and phosphorus removal and HMRGs in wastewater treatment.

Exerting applied voltage promotes microbial activity of marine anammox bacteria for nitrogen removal in saline wastewater treatment

To date, the application of marine anammox bacteria (MAB) is still a challenge in saline wastewater treatment due to the low growth rate and high sensitivity. Herein, bioelectrochemical system with applied voltage was exerted for the first time to promote the activity of MAB for removing nitrogen from saline wastewater. At the optimal voltage of 1.5 V, the mean total nitrogen removal rate (TNRR) reached the maximum of 0.65 kg/m³•d, which was 27.45% higher than that without applied voltage. Besides, applied voltage reduced the microbial diversity of MAB-based consortia, but the relative abundance of Candidatus Scalindua increased by 4.63% at 1.5 V compared with that without applied voltage. Also, proper applied voltage promoted the secretion of EPS and heme c, which resulted in the enhancement of MAB activity. Based on the remodified Logistic model analysis, the lag time of the nitrogen removal process was shortened by 0.72 h at the voltage of 1.5 V. Furthermore, it was found that higher voltage (> 2.0 V) had a negative effect on the MAB activity for low TNRR of 0.33 kg/m³•d (2.5 V). However, TNRR increased back to 0.61 kg/m³•d after removing the high applied voltage, which implied that the bioactivity was recoverable after being inhibited. These findings demonstrated that external electrical stimulation is an effective strategy to promote nitrogen removal and MAB activity for treating saline wastewater.

Long-Term Limitation Effects of Se(VI), Zn(II), and Ni(II) on Start-Up of the Anammox Process Using Gel Carrier

Anaerobic ammonia oxidation (anammox) bacteria are inhibited by heavy metals at high concentrations but require trace amounts of some heavy-metal elements for growth and activity maintenance. The present study evaluates the long-term limitation effects of Se(VI), Zn(II), and Ni(II) on the start-up period of an anammox reactor. To strictly limit the levels of heavy metals in the reactor, all tests used ultrapure water as the influent synthetic wastewater and all reactors were installed in a clean booth. The anammox biomass was maintained through the gel entrapment technique. In the absence of Se(VI) and Ni(II), the anammox reactor start-up was 18.9 kg-N (m³-carrier d)⁻¹ (nitrogen conversion rate (NCR) per gel carriers), indicating that Se(VI) and Ni(II) are not required or need not be continuously added to maintain the anammox process. Under Zn(II) limitation, the anammox process failed to start-up and the NCR tended to decrease rapidly. After readdition of 0.005 mg L⁻¹ of Zn(II), the NCR did not decline further and instead partially recovered at a very slow rate. The NCR was completely recovered after adding 0.020 mg L⁻¹ of Zn(II). These results reveal that Zn(II) limitation seriously affects the start-up of the anammox process while Se(VI) and Ni(II) are not required or need not be continuously added to the anammox process.

Insights into nitrogen removal from seawater-based wastewater through marine anammox bacteria under ampicillin stress: Microbial community evolution and genetic response

Global spread of ampicillin (AMP) in the aquatic environment have attracted much attention recently. Marine anammox bacteria (MAB) have potentials in saline wastewater treatment due to their good salt tolerance. However, to date, the effect resulting from AMP on MAB is still unknown. Herein, the effect of AMP on MAB, involving microbial community evolution and genetic response, was investigated for the first time. A lab-scale reactor inoculated by MAB sludge was operated under saline condition (35 g/L) and AMP stress of different gradients. Within 200 cycles, nitrogen removal performance was monitored and sludge samples were withdrawn for high-throughput sequencing analyses and qPCR. The results confirmed that the nitrogen removal capacity of MAB declined with increasing AMP dosage, and almost collapsed at 300 mg/L AMP. The total nitrogen removal rate and specific anammox activity finally dropped to 0.17 kg N m^-3 d^-1 and 101.86 mg N g^-1VSS d^-1, respectively. Pseudoalteromonas (38.13%) dominated the reactor on Cycle 190, which formed a new symbiosis with MAB. And the emergence of oleophilic bacteria such as Colwellia (2.53%) was also observed. Moreover, antibiotic resistance genes were detected with increased abundance and diversity, indicating the AMP dosing significantly promoted microbial community evolution and genetic response.

Evaluation of the joint effects of Cu2+, Zn2+ and Mn2+ on completely autotrophic nitrogen-removal over nitrite (CANON) process

The completely autotrophic nitrogen-removal over nitrite (CANON) process has merits in energy saving and consumption reducing, thus being considered as an attractive alternative over the common denitrification technology. In this study, the effects of three common heavy metals (Cu²⁺, Zn²⁺ and Mn²⁺) in wastewater to the CANON process were evaluated comprehensively. A central composite design with response surface methodology was utilized to investigate the joint effect of these three metal ions on the nitrogen removal performance of CANON process. In accordance with the determined optimal dosage in batch tests, four bioreactors were established with different amounts of heavy metal dosage in long-term operation, which determined the optimal concentrations for Cu²⁺, Zn²⁺ and Mn²⁺ to be 0.25, 0.81 and 1.00 mg/L, respectively. However, the optimal dosing level determined in batch tests showed no promotion during long-term experiment. This indicated that the actual concentration of heavy metals in bioreactors during long-term operation could be higher than expectation, leading to the difference between short-term tests and long-term experiment. The distribution of metal ions revealed that Mn²⁺ was mainly absorbed in anammox bacteria cells while Cu²⁺ and Zn²⁺ were mostly identified inside AOB cells. Moreover, the addition of heavy metals consistently showed positive effects for the relative abundance of AOB, while only a low level of dosage could promote the abundance of anammox bacteria. Furthermore, a mathematical model was established to simulate the CANON system considering the impacts of heavy metals, which was calibrated and validated using independent dataset in this study.

The effects of magnetite on anammox performance: Phenomena to mechanisms

Low temperature is adverse to anaerobic ammonium oxidation (anammox) reaction while proper Fe addition can enhance anammox performance. Therefore, batch assays were conducted to investigate the potential effects of magnetite (100 μm, 20 μm and 200 nm) on anammox performance which were achieved from the reactor operated at 10-25 °C. After 3 runs, the results indicated that nano-scale magnetite improved the nitrogen elimination significantly. The specific anammox activity (SAA) of the group with nano-magnetite amendments was greater than the other groups after 3 runs (13.5, 12.9, 14.3, 15.4 and 15.7 mgTN/(gVSS·h)), reaching 18.0 mgTN/(gVSS·h). The distribution of magnetite in the granules were then analyzed using X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The results indicated that nano-magnetite was more feasible to attached to the surface of the granules which might accelerate the release of Fe(II) or Fe(III) to enhance anammox performance.

Unraveling the nitrogen removal properties and microbial characterization of "Candidatus Scalindua"-dominated consortia treating seawater-based wastewater

"Candidatus Scalindua", as known as marine anammox bacteria (MAB), was engineered to remove nitrogen from seawater-based wastewater (SWW). In this study, "Candidatus Scalindua" was successfully enriched within 106 days with marine sediments as inoculated sludge. The operating temperature was 20 ± 2 °C, and influent pH was 7.5 ± 0.1. Ammonia (NH₄⁺-N) removal rate (ARR) was 0.53 kg/(m³·d) with the NH₄⁺-N loading rate of 0.68 kg/(m³·d), and nitrite (NO₂^--N) removal rate (NRR) was 0.57 kg/(m³·d) at 0.89 kg/(m³·d) NO₂^--N loading rate. Nitrogen removal was negatively affected at an influent NO₂^- above 224 mg/L, which decreased the ARR and NRR to 0.36 and 0.31 kg/(m³·d), respectively. The genus "Ca. Scalindua" dominated the reactor, and it synergistically coexisted with Marinicella to achieve efficient nitrogen removal. This work would help to better understand the nitrogen removal properties and microbial characterization of MAB in SWW wastewater treatment under low temperature.

Effects of Recirculating Aquaculture System Wastewater on Anammox Performance and Community Structure

Recirculating aquaculture systems (RAS) are good candidates for the sustainable development of the aquaculture sector. A current limitation of RAS is the production and accumulation of nitrogenous waste, which could affect fish health. We investigated the potential of the anaerobic ammonia oxidation (anammox) process to treat marine wastewater from a cold-water RAS. We show that the marine anammox bacteria Candidatus Scalindua is a promising candidate. However, its activity was affected by unknown compounds in the RAS wastewater and/or the sub-optimum content of essential trace elements (TEs). Anammox activity dropped to 2% and 13% in NH4+ and NO2− removal, respectively, when NO3-rich RAS wastewater was used as a medium in the absence of TE supplementation. A TE supplementation was added to the RAS wastewater in a subsequent phase, and a recovery in anammox activity was shown (25% and 24% in NH4+ and NO2− removal, respectively). Future studies need to identify the unknown factor and determine the specific needs regarding TE for optimal RAS wastewater treatment by Candidatus Scalindua.

Biological stimulation with Fe(III) promotes the growth and aerobic denitrification of Pseudomonas stutzeri T13

Certain metal ions can contribute to the functional microorganisms becoming dominant by stimulating their metabolism and activity. Therefore, Pseudomonas stutzeri T13 was used to investigate the impacts of biological stimulation with certain metal ions on aerobic denitrifying bacteria. Results showed that with the addition of 0.036 mmol/L Fe³⁺ ions, the nitrogen-assimilation capacity of P. stutzeri T13 significantly increased by 43.99% when utilizing ammonium as the sole nitrogen source. Kinetic models were applied to analyze the role of Fe³⁺ ions in the growth, and results indicated that increasing Fe³⁺ ion concentrations decreased the decay rate. The maximum nitrate reduction rate increased from 9.55 mg-N L^-1 h^-1 to 19.65 mg-N L^-1 h^-1 with Fe³⁺ ion concentrations increasing from 0.004 to 0.036 mmol/L, which was due to the increased level of napA gene transcription and activity of nitrate reductase. This study provides a theoretical foundation for further understanding of the mechanism of Fe³⁺ ion stimulation of aerobic denitrification, benefiting the practicable application of aerobic denitrifiers.

Alleviating the nitrite stress on anaerobic ammonium oxidation by pyrolytic biochar

The nitrite (NO₂^-) inhibition in anaerobic ammonium oxidation (anammox) process is widely reported. Here, the effects of three pyrolytic biochars (CS300, CS550 and CS800) were investigated to alleviate NO₂^- stress on anammox process under exposure of varied NO₂^--N concentrations (70, 200, 400 and 600 mg L^-1). No nitrite inhibition was observed at 70 mg N L^-1. However, the total nitrogen removal efficiency (TNREs) decreased with NO₂^--N concentration increased, while the biochar-amended groups achieved higher TNREs than the control (CK). At 200 mg N L^-1, the TNREs were 60.2%, 99.0%, 98.5% and 86.6% for CK, CS300, CS550 and CS800, respectively. At 400 mg N L^-1, the TNREs were 23.3%, 56.0%, 37.1% and 29.7% for CK, CS300, CS550 and CS800, respectively. At 600 mg N L^-1 in which severe inhibition was observed, the TNREs were increased by 231% (p = 0.002), 149% (p = 0.014), and 51.0% (p = 0.166) for CS300, CS550 and CS800, respectively, as compared to CK, with the corresponding specific anammox activity increased by 3.1-, 2,0- and 1.1-folds, respectively. CS300 enriched the relative abundance of Candidatus Kuenenia and increased the gene copies of functional genes (hzsA, hdh, nirS and nirK). Besides, CS300 effectively alleviated the suppression of three membrane-associated enzyme complexes for anammox electron transport chain, indicating the possible contribution of redox-active moieties of CS300 to energy conversion metabolism for mitigating the NO₂^--N inhibition. This study provided an effective strategy for alleviating NO₂^--N stress by applying an environmentally compatible material (biochar) on anammox process.

Insights into microbial community variability and functional genes of various Candidatus Scalindua-based anammox processes treating nitrogen-rich saline wastewater

Marine anammox bacteria (MAB) has been enriched in four sequencing batch reactors to treat nitrogen-rich saline wastewater. The community variability and cell activity of MAB were studied under different operating conditions. Besides, a novel hydrazine oxidoreductase (Hzo) primer set was designed and used for fast detection of MAB. The results indicated that, independent of operating conditions, Candidatus Scalindua wagneri was the dominant species in nitrogen-rich saline wastewater treatment. Low inoculation pretreatment temperature was a useful operational method to enhance the MAB abundance. Both the enzyme synthesis and cell penetrativity were promoted by Fe(III) addition, which benefited to improve the nitrogen removal performance. High influent NH₄⁺-N and NO₂^--N could decrease the synthesis of enzyme and protein which related with nitrogen removal from saline wastewater through MAB. The Hzo gene was an effective functional gene for specific and fast detection of MAB in engineered systems.

Sulfate dependent ammonium oxidation: A microbial process linked nitrogen with sulfur cycle and potential application

Sulfate dependent ammonium oxidation (Sulfammox) is a potential microbial process coupling ammonium oxidation with sulfate reduction under anaerobic conditions, which provides a novel link between nitrogen and sulfur cycle. Recently, Sulfammox was detected in wastewater treatments and was confirmed to occur in natural environments, especially in marine sediments. However, knowledge gaps in the mechanism of Sulfammox, functional bacteria, and their metabolic pathway, make it challenging to estimate its environmental significance and potential applications. This review provides an overview of recent advances in Sulfammox, including possible mechanisms, functional bacteria, and main influential factors, and discusses future challenges and opportunities. Future perspectives are outlined and discussed, such as exploration of microbial community structure and metabolic pathways, possible interactions with other microbes, environmental significance, and potential applications for nitrogen and sulfate removal, to inspire more researches on the Sulfammox process.

Biostimulation of a marine anammox bacteria-dominated bioprocess by Co(II) to treat nitrogen-rich, saline wastewater

The biostimulation of a marine anammox bacteria (MAB)-dominated bioprocess with Co(II) was studied in a sequencing batch reactor (SBR) treating nitrogen-rich saline wastewater at 15 °C. The low Co(II) load of 0.0015 kgCo²⁺_added/(m^3.d) had little effect on the removal of nitrogen. The nitrite removal rate (NRR), ammonia removal rate (ARR), and specific anammox activity (SAA) reached 0.73 kg/(m³·d), 0.59 kg/(m³·d), and 0.23 kg/(kg·d), respectively, under the Co(II) load of 0.009 kgCo²⁺_added/(m^3.d). However, the loadings of Co(II) at 0.024-0.03 kgCo²⁺_added/(m^3.d) negatively affected the activity of MAB. Besides, the values of ΔNO₂^--N/ΔNH₄⁺-N (1.15-1.29) were lower than the theoretical ratio values (around 1.32) likely because of the marine commamox process. The removal of nitrogen from nitrogen-rich saline wastewater was achieved by the synergy between Candidatus Scalindua (27.11%) and Candidatus Kuenenia (9.55%). The nitrogen removal with Co(II) addition could be well described by a modified Logistic model.

Deciphering pollutants removal mechanisms and genetic responses to ampicillin stress in simultaneous heterotrophic nitrification and aerobic denitrification (SHNAD) process treating seawater-based wastewater

Pollutants removal and genetic responses of simultaneous heterotrophic nitrification and aerobic denitrification (SHNAD) treating seawater-based wastewater were studied under ampicillin stress. Marine SHAND bacteria exhibited good tolerance to 10 mg/L ampicillin with nitrogen removal efficiency and organics removal efficiency of 94.5% and 82.6%, respectively. Besides, the half-inhibitory concentration of ampicillin on marine SHAND bacteria was 50 mg/L. The relative abundances of antibiotic resistance genes (ARGs) first decreased and then increased with ampicillin addition. The blaVIM played an important role to resist 25 mg/L ampicillin, which contributed to the recovery of pollutants removal. BlaSHV and blaTEM dominated ARG subtypes, which accounted for 96.6% of ARGs abundance. At 50 mg/L ampicillin, reactive oxygen species (ROS) production and cell numbers of apoptosis increased by 47.9% and 367.5%, respectively. The overproduction of ROS was stimulated by ampicillin, which caused bacterial cell apoptosis. Marine SHNAD bacteria produced more extracellular polymeric substances to resist ampicillin.

Modeling, instrumentation, automation, and optimization of water resource recovery facilities (Review of 2018 Literature) DIRECT

A review of the literature published in 2018 on topics relating to water resource recovery facilities (WRRF) in the areas of modeling, automation, measurement and sensors and optimization of wastewater treatment (or water resource reclamation) is presented. PRACTITIONER POINTS: Summary of advances in the field of modeling, instrumentation, automation, and optimization in 2018. This review outlines the major contributions of researchers and practitioners that have been published in peer-reviewed journals and conference proceedings. The article is organized into sections for ease of reference, but several reviewed articles are related to more than one section.

The performance of freshwater one-stage partial nitritation/anammox process with the increase of salinity up to 3.0

The freshwater anammox-based process would usually experience performance fluctuation and need adoption period when subjected to saline wastewater according to previous studies. In this study, the performance of nitrite-limited freshwater one-stage partial nitritation/anammox (PNA) process subjected to saline wastewater was investigated. The results showed that the nitrite-limited freshwater system could smoothly adapt to the salinity of 0.25%. The stable nitrogen removal could be achieved until the salinity of 2.5%, at which the desirable average NRR of 0.74 ± 0.1 kg/m³/d was achieved. The microbial community analysis showed that during the whole experiment, the main functional microbes were from genus Nitrosomonas and genus Kuenenia, which were through to be the crucial factors for achieving the excellent performance. This study indicates the nitrite-limited strategy is admissible for stabilizing the performance of freshwater one-stage PNA process subjected to saline wastewater in actual application.

Bioaugmentation of marine anammox bacteria (MAB)-based anaerobic ammonia oxidation by adding Fe(III) in saline wastewater treatment under low temperature

This work investigated a new method of using Fe(III) to enhance the reactor performance enriched with marine anammox bacteria (MAB). The experiments were conducted in a sequencing batch reactor at low temperature (15 °C), high salinity (35 g/L) and varying Fe(III) concentrations (0-250 mg/l). The results of this study showed that at low Fe(III) (6 mg Fe/L), the rate of ammonium removal, nitrite removal and specific anammox activity remarkably increased to 0.42 kg/(m³·d), 0.53 kg/(m³·d), 0.56 kg/(kg·d), respectively. However, Fe(III) at above 120 mg Fe/L, the reaction time was significantly shortened from 5 to 2 h. MAB-based nitrite removal could be predicated based on the change of pH (ΔpH) and oxidation-reduction potential (ΔORP). Kinetics analysis demonstrated, the "Remodified Logistic Model" could simulate the Fe(III) enhanced anammox process. Overall, this research shed the light of designing a new high-rate anaerobic nitrogen removal technology for carbon insufficient, nitrogen-laden saline wastewater.

Nitrogen removal performance of marine anammox bacteria treating nitrogen-rich saline wastewater under different inorganic carbon doses: High inorganic carbon tolerance and carbonate crystal formation

With different inorganic carbon (IC) doses, nitrogen removal performance of marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater was investigated in a sequencing batch reactor. Ammonium removal efficiency (ARE) was above 99% at 108-3600 mg/L IC, which indicated MAB had a good tolerance to high IC dose. When IC was 108-1200 mg/L, ARE reached 90% within 2.5 h. MAB activity was greatly promoted by providing adequate IC. Besides, the maximal substrate conversion rate (3.4 kg/(m³ d)) was achieved at 180 mg/L IC. Both the modified Logistic and Boltzmann models were appropriate to describe nitrogen removal at low IC doses, while the modified Gompertz model was more accurate at high IC doses. Calcium carbonate crystal was formed on the surface of MAB granule at high IC doses, which resulted in a significant deterioration of nitrogen removal performance.

Enhanced nitrogen removal through marine anammox bacteria (MAB) treating nitrogen-rich saline wastewater with Fe(III) addition: Nitrogen shock loading and community structure

Marine anammox bacteria (MAB) were used to treat nitrogen-rich saline wastewater with Fe(III) addition under nitrogen shock loading. Ammonia loading rate (ALR) and nitrite loading rate (NLR) gradually increased from 0.033 and 0.039 to 0.68 and 0.89 kg/(m³·d), respectively. With 5 mg/L Fe(III) addition, ammonia removal rate (ARR) and nitrite removal rate (NRR) reached maximal values of 0.56 and 0.60 kg/(m³·d), respectively. The value of ΔNO₂^--N/ΔNH₄⁺-N was lower than theoretical ratio due to existing marine Feammox process. The growth rate of MAB was accelerated by Fe(III) and it dominated the reactor (27.70%). Besides, MAB were synergized with Marinicella and Caldithrix to achieve higher total nitrogen removal. Haldane model was proper to analyze and predict the effect resulting from nitrite on the activity of MAB under nitrogen shock loading. Overall, this study provides novel insights into the effect of Fe(III) on MAB treating nitrogen-rich wastewater.

Nitrogen removal through "Candidatus Brocadia sinica" treating high-salinity and low-temperature wastewater with glycine addition: Enhanced performance and kinetics

Freshwater-derived anaerobic ammonia oxidation (anammox) bacteria ("Candidatus Brocadia sinica") were investigated to remove nitrogen from high-salinity and low-temperature wastewater with glycine addition. The reactor was operated at 15 ± 0.5 °C with influent pH of 7.5 ± 0.1. When glycine were 0.2, 0.4, and 0.6 mM, respectively, nitrite removal rate (NRR) increased by 27.7%, 47.3%, and 70.4% accordingly. Optimal ammonia removal rate (0.32 kg/(m³·d)) and NRR (0.45 kg/(m³·d)) were achieved at 0.8 mM glycine. Effect resulting from glycine on nitrite reductase was higher than hydrazine synthase. Moreover, ΔNO₂^--N/ΔNH₄⁺-N increased with glycine addition while ΔNO₃^--N/ΔNH₄⁺-N first increased and then decreased. The remodified Logistic model and modified Boltzmann model were appropriate to describe nitrogen removal with glycine addition. Kinetic parameter λ achieved through the remodified Logistic model revealed that "Candidatus Brocadia sinica" had a shorter lag phase than that of marine anammox bacteria.