Marine Anammox Bacteria Research Articles

Deciphering performance and microbial characterization of marine anammox bacteria-based consortia treating nitrogen-laden hypersaline wastewater: Inhibiting threshold of salinity

Hypersaline wastewater posed a challenge to microbial nitrogen removal processes. Herein, halophilic marine anammox bacteria (MAB) were applied to treat nitrogen-rich wastewater with 35–90 g/L salts for the first time. It was found that MAB, with low relative abundance (2.3–6.9 %), still exhibited good nitrogen removal efficiency (>90 %) under 35–70 g/L salts. The specific anammox activity peaked at 180.16 mg N/(g·VSS·d) at 65 g/L salts. MAB secreted more extracellular polymeric substances to resist the adverse effects of hypersaline stress. Nevertheless, the nitrogen removal deteriorated at 75 g/L salts, and further collapsed as the salinity increased. At 90 g/L salts, total nitrogen removal rate decreased by 74 % compared with that of 35 g/L salts. Besides, SBR1031 increased from 12.0 % (35 g/L salts) to 17.4 % (90 g/L salts) and became the dominant bacterial genus in the reactor. This work shed light on the treatment of hypersaline wastewater through MAB.

Response of marine anammox bacteria to long-term hydroxylamine stress: Nitrogen removal performance and microbial community dynamics

The response of anammox bacteria to hydroxylamine has not been well explained. Herein, hydroxylamine was long-term added as the sole substrate to marine anammox bacteria (MAB) in saline wastewater treatment for the first time. MAB could tolerate 5 mg/L hydroxylamine. However, MAB activity was inhibited by the high dose of hydroxylamine (40 mg/L), and hydroxylamine removal efficiency was only 3 %. Remarkably, when hydroxylamine reached 20 mg/L, ammonium was produced the most at 2.88 mg/L, mainly by the hydroxylamine and hydrazine disproportionations. Besides, the relative abundance of Candidatus Scalindua decreased from 4.6 % to 0.6 % as the hydroxylamine increased from 0 to 40 mg/L. MAB secreted more extracellular polymeric substances to resist hydroxylamine stress. However, long-term hydroxylamine loading led to the disintegration of MAB granules. This work shed light on the response of MAB to hydroxylamine in saline wastewater treatment.

Microbial electrolysis drives ammonium removal from saline wastewater through marine anammox bacteria

Currently, ammonium removal from saline wastewater still poses a challenge to conventional biological nitrogen removal process. Herein, the conversion of NH4+-N to N2 was successfully driven by marine anammox bacteria (MAB) in a single chamber microbial electrolytic cell (MEC) using NH4+-N as the sole substrate. Compared with no ammonium removal in the abiotic reactor with applied voltage (0–1.5 V), the maximum ammonium and total nitrogen removal rate (ARR and TNRR) of 55 and 50 g/m3•d were obtained at the voltage of 1.1 V, which were 78 % and 76 % higher than that of 0.5 V, respectively. At the voltage ≥ 1.1 V, the accumulation of NO2–-N and NO3–-N was observed in the MEC, and the nitrifying bacteria Nitrosmonas and Nitrospira were detected on the anode surface with the relative abundances of 0.84 % and 0.21 %, respectively. It was proved that the production of NO2–-N and NO3–-N was an electrochemical biological process by electroactive nitrifying bacteria. Candidatus Scalindua was the main functional genus for ammonium removal at anode biofilm with the relative abundance of 19.27 %. Therefore, ammonium was successfully removed by integrating anodic anammox and anodic nitrification. Applied voltage increased the microbial diversities at anode surface and promoted the formation of electrode biofilm. These findings indicated a promising saline wastewater treatment by employing salt-tolerant MAB for ammonium removal.

Ladderane and lipid biomarker estimate of the sources and distributions of anammox activities in Laizhou Bay of the Bohai Sea, China

Anaerobic ammonium oxidation (anammox) plays an important role in nitrogen removal in coastal seas, and ladderanes, as specific biomarkers of anammox bacteria, can be used to indicate the anammox activity. However, the origins of ladderanes and their controlling factors in the coastal seas influenced by anthropogenic activities are still not well constrained. To address this, we reported ladderanes, long-chain n-alkanols (terrestrial biomarker) and sterols (marine biomarker) in suspended particulates from the estuaries and inner area of Laizhou Bay in North China, to study ladderane sources and its distribution patterns. This study proposed a novel index, Rlad, using ladderane ratio of ladderane III to ladderane IV, and by correlating this index with other biomarker distributions to evaluate the source of ladderanes. High Rlad values (> 0.9) indicated biosynthesis by terrestrial anammox bacteria Ca. Brocadia and Ca. Kuenenia, while low Rlad values (< 0.9) indicated biosynthesis by marine anammox bacteria Ca. Scalindua. High Rlad values and high ladderane concentrations in particulates from the estuaries and nearshore area of Laizhou Bay revealed sources from the terrestrial input via riverine inflow as well as in situ production in oxygen-depleted estuaries, supported by high concentrations of terrestrial biomarkers; Low Rlad values and low ladderane concentrations in particulates from offshore area indicated sources from marine environment via the cold hypoxia water input by the Bohai circulation. Comparison of ladderane concentrations of our study with previously published results from a wide range of environments with human influences from Chinese coastal area revealed that high ladderane concentrations synthesized by terrestrial anammox bacteria could contribute significantly to coastal seas, and the anammox process in river-estuary-bay system might be underestimated. This study provides new understandings about the evaluation of the source and distribution of ladderanes under anthropogenic influences in coastal seas.

Insights into nitrogen removal and microbial response of marine anammox bacteria-based consortia treating saline wastewater: From high to moderate and low salinities

Marine anammox bacteria (MAB) have promising nitrogen removal performance in high saline wastewater treatment. Nevertheless, the impact resulting from moderate and low salinities on MAB is still unclear. Herein, MAB were applied to treat saline wastewater from high to moderate and low salinities for the first time. Independent of salinities (35–3.5 g/L), MAB consistently exhibited good nitrogen removal performance, and maximum total nitrogen removal rate (0.97 kg/(m3·d)) occurred at 10.5 g/L salts. More extracellular polymeric substances (EPSs) were secreted by MAB-based consortia to resist hypotonic surroundings. However, a sharp EPS decrease was accompanied by the collapse of MAB-driven anammox process, and MAB granules disintegrated due to long-term exposure to salt-free environment. The relative abundance of MAB varied from 10.7% to 15.9% and 3.8% as salinity decreased from 35 to 10.5 and 0 g/L salts. These findings will provide practical implementation of MAB-driven anammox process treating wastewater with different salinities.

Bacterial physiology highlighted by the δ13C fractionation of bacteriohopanetetrol isomers

Lipid biomarkers, such as the various bacteriohopanetetrol (BHT) isomers studied here, are useful tools in tracing bacterially mediated nitrogen and carbon cycle processes affecting greenhouse gas emissions, including the anaerobic oxidation of ammonia. Three BHT isomers occur commonly in the environment. By gas chromatography, BHT-34S elutes first; it is produced by numerous bacteria. The two later eluting isomers are more constrained in their origin. The marine anammox bacteria ‘Ca. Scalindua’ is the only known producer of a BHT isomer of unknown stereochemistry (BHT-x), making BHT-x a diagnostic biomarker in anoxic marine settings. The BHT-34R isomer is produced by three freshwater aerobic heterotrophic producers (Frankia spp., Acetobacter pasteurianus, and Komagataeibacter xylinus), a freshwater serine-cycle (Type II) methanotroph (Methylocella palustris), and the freshwater anammox ‘Ca. Brocadia’, which makes the detection of freshwater anammox using BHT-34R more complicated. We investigated whether the source of BHT-34R in freshwater environments could be ascertained via its δ13C value. We used conventional on-column gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) (as opposed to high temperature GC-C-IRMS) to determine the δ13C composition of acetylated BHT isomers in cultured bacteria and bacterial enrichments. We combined these with bulk biomass and substrate δ13C compositions to establish carbon isotopic fractionation factors. The two anammox genera had large fractionation factors from dissolved inorganic carbon (DIC) to biomass (Δ13Cbiomass – DIC = –43.8 to –26.4 ‰) and to BHTs (Δ13CBHT – DIC = –53.8 to –38.2 ‰), which clearly distinguished them from the freshwater aerobic heterotrophic producers (Δ13Cbiomass – substrate = –2.3 to –0.1 ‰; Δ13CBHT – substrate = –12.8 to 5.2 ‰). Methylocella assimilated mainly carbon from DIC, rather than from methane, into its biomass and BHT, and previous work suggested this assimilation comes with relatively small fractionation. Thus, in peatlands, the BHT δ13C values of Methylocella would not reflect the low δ13C values of biogenic methane. Consequently, the presence of BHT-34R with low δ13C values relates to ‘Ca. Brocadia’ and presents a novel tool to trace anammox in freshwater environments.

Candidatus Scalindua, a Biological Solution to Treat Saline Recirculating Aquaculture System Wastewater

Recirculating aquaculture systems (RAS) are promising candidates for the sustainable development of the aquaculture industry. A current limitation of RAS is the production and potential accumulation of nitrogenous wastes, ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−), which could affect fish health and welfare. In a previous experiment, we have demonstrated that the marine anammox bacteria Candidatus Scalindua was a promising candidate to treat the wastewater (WW) of marine, cold-water RAS. However, the activity of the bacteria was negatively impacted after a direct exposure to RAS WW. In the current study, we have further investigated the potential of Ca. Scalindua to treat marine RAS WW in a three-phase experiment. In the first phase (control, 83 days), Ca. Scalindua was fed a synthetic feed, enriched in NH4+, NO2− and trace element (TE) mix. Removal rates of 98.9% and 99.6% for NH4+ and NO2−, respectively, were achieved. In the second phase (116 days), we gradually increased the exposure of Ca. Scalindua to nitrogen-enriched RAS WW over a period of about 80 days. In the last phase (79 days), we investigated the needs of TE supplementation for the Ca. Scalindua after they were fully acclimated to 100% RAS WW. Our results show that the gradual exposure of Ca. Scalindua resulted in a successful acclimation to 100% RAS WW, with maintained high removal rates of both NH4+ and NO2− throughout the experiment. Despite a slight decrease in relative abundance (from 21.4% to 16.7%), Ca. Scalindua remained the dominant species in the granules throughout the whole experiment. We conclude that Ca. Scalindua can be successfully used to treat marine RAS WW, without the addition of TE, once given enough time to acclimate to its new substrate. Future studies need to determine the specific needs for optimal RAS WW treatment by Ca. Scalindua at pilot scale.

North-south differences in hypoxia and nitrogen cycle of the East China Sea over the last century indicated by sedimentary bacteriohopanepolyols

Coastal hypoxic zones are expanding due to anthropogenic activities and climate changes. Increased hypoxia has greatly affected the marine nitrogen cycle. There are two typical seasonal hypoxic core areas in the north and south of the East China Sea (ECS). However, the interannual variations, north-south differences in hypoxia and their effects on the nitrogen cycle are still poorly understood. This study investigated bacteriohopanepolyols (BHPs), especially newly developed marine anammox bacteria and hypoxic biomarker bacteriohopanetetrol stereoisomer (BHT-x) and cyanobacterial nitrogen fixation biomarker 2-methyl BHT in two sediment cores, aiming to reconstruct hypoxia and nitrogen cycle records in the northern and southern hypoxic zones of the ECS over the last century. The results showed that BHT-x ratio in northern core 3100–2 presented higher values since 1960s (>0.2) and increased after 2000 (0.25–0.57), while it decreased in southern core DH6–1 after 2000 (0.03–0.11), indicating the continuously intensified hypoxia in the northern area and significantly weakened hypoxia in the southern area. Hypoxia is mainly associated with organic matter degradation and seawater stratification. The similar temporal increases of BHT-x ratios and marine-derived organic matter (MOM) contents in core 3100–2 suggest that eutrophication-driven MOM degradation is the main reason for hypoxia formation, which is exacerbated by strong water stratification there. Differently, although MOM contents still increased in core DH6–1 after 2000, the hypoxia weakened and even disappeared due to lessened stratification. In addition, the temporal variations of BHT-x and 2-methyl BHT in both cores indicated that anammox and nitrogen fixation simultaneously increased during periods of hypoxia. The co-variation suggests that hypoxia promotes anammox, and nitrogen loss may induce an increase in nitrogen fixation to compensate for nitrogen availability.

The responses of marine anammox bacteria-based microbiome to multi-antibiotic stress in mariculture wastewater treatment

Saline mariculture wastewater containing multi-antibiotics poses a challenge to anaerobic ammonia oxidation (anammox) process. Herein, the halophilic marine anammox bacteria (MAB)-based microbiome was used for treating mariculture wastewater (35‰ salinity) under multi-antibiotics (enrofloxacin + oxytetracycline + sulfamethoxazole, EOS) stress. And the main focus of this study lies in the response of MAB-based microbiome against multi-antibiotics stress. It is found that MAB-based microbiome shows stable community structure and contributes high nitrogen removal efficiency (>90%) even under high stress of EOS (up to 4 mg·L−1). The relative abundance of main functional genus Candidatus Scalindua, responsible for anammox, had little change while controlling the influent EOS concentration within 4 mg·L−1, whereas, significantly decreased to 2.23% at EOS concentration of as high as 24 mg·L−1. As an alternative, antibiotic resistance bacteria (ARB) species Rheinheimera dominated the microbial community of MAB-based biological reactor under extremely high EOS stress (e.g. 24 mg·L−1 in influent). The response mechanism of MAB-based microbiome consists of extracellular and intracellular defenses with dependence of EOS concentration. For example, while EOS within 4 mg·L−1 in this study, most of the antibiotics were retained by extracellular polymeric substances (EPS) via adsorption; If increasing the EOS concentration to 8 and even 24 mg·L−1, part of antibiotics could intrude into the cells and cause the intracellular accumulation of antibiotic resistance genes (ARGs) (total abundance up to 2.44 × 10−1 copies/16S rRNA) for EOS response. These new understandings will facilitate the practical implementation of MAB-based bioprocess for saline nitrogen- and antibiotics-laden wastewater treatment.

Oxytetracycline stress stimulates antibiotic resistance gene proliferation and quorum sensing response of marine anammox bacteria in seawater-based wastewater treatment

Seawater-based wastewater is characterized by high concentrations of oxytetracycline (OTC) and salt, which is a huge challenge for conventional biological nitrogen removal processes. Marine anammox bacteria (MAB) are recently employed for nitrogen removal from saline wastewater due to their good salt tolerance. This study focuses on the impacts of OTC on MAB for nitrogen removal from seawater-based wastewater for the first time, particularly highlighting the antibiotic resistance gene (ARG) proliferation and quorum sensing (QS) response. At low OTC doses (≤7 mg L−1), MAB had a good tolerance and the total nitrogen removal efficiency was maintained at 77%. When OTC dose reached 22 mg L−1, the activity of MAB was inhibited obviously. The relative abundance of MAB drastically decreased to 4.1% from 14.41% when OTC dose increased to 22 from 0 mg L−1. On contrary, antibiotic resistance bacteria gradually became the dominant population in reactor with increasing OTC content, accompanying along with the increase of relative abundance of ARGs. The tolerance of MAB-based consortia to OTC toxicity was enhanced by the high expression of ARGs. Besides, more extracellular polymeric substance was secreted to enhance anammox granule tolerance against OTC toxicity, which was promoted by the high release of signal molecule (3OC6-HSL). Furthermore, the expression of hdh and tetM was regulated by QS to enhance MAB-based consortia tolerance under OTC stress. Therefore, the tolerance of anammox consortia to OTC was mainly attributed to proliferated ARGs and active QS. This work exploited the significant potential of MAB in seawater-based wastewater treatment.

High-throughput sequencing reveals the main drivers of niche-differentiation of bacterial community in the surface sediments of the northern South China sea

Studies on marine bacterial communities have revealed endemism in local communities, yet the underlying mechanisms remained elusive. Environmental gradient settings can benefit the straightaway study of community composition changes and the mechanisms explaining them. Here, MiSeq-based 16S rRNA gene sequencing was performed on 12 surface sediment samples from the northern South China Sea (nSCS) revealing that shallow-sea samples had a higher alpha diversity than deep-sea samples, and were differentiated from them significantly based on beta diversity. Temperature, seawater depth, and salinity were the top three influential factors. Bacterial 16S rRNA gene abundance was positively correlated with temperature, and negatively correlated with salinity. Sulfate-reducing bacteria including Desulfobacteraceae, Desulfobulbaceae, and Syntrophobacteraceae were enriched in shallow-sea sediments, co-abundant with nitrite-oxidizing Nitrospira and potential sulfur-oxidizing shallow-sea specific Woeseiaceae/JTB255 clade. Meanwhile, the co-existing and co-abundant of marine anammox and n-damo bacteria were enriched in deep-sea sediments, which was firstly evidenced in this study. The global deep-sea cosmopolitans, OM1 clade, and deep-sea specific Woeseiaceae/JTB255 clade were also found enriched in deep-sea sediments of nSCS. The discovery of novel taxa which were differentially enriched in shallow-/deep-sea sediments not only shed light on enigmatic physiological properties and the natural selection mechanism, but also provided the potential ecological-functional links which invoked further genomics-based metabolic characteristics.

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.

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.

Startup of pilot-scale single-stage nitrogen removal using anammox and partial nitritation (SNAP) reactor for waste brine treatment using marine anammox bacteria

This study is the first to demonstrate the startup of a pilot-scale single-stage nitrogen removal using anammox and partial nitritation (SNAP) reactor utilizing marine anammox bacteria. A complete mixing type reactor, continuously fed with waste brine obtained from a natural gas plant (salinity 3%, NH4+-N 130-180mg/L) and having an effective volume of 2m3, achieved stable operation at temperatures of 20-30°C with a maximum nitrogen removal rate of 1.43kg-N/m3/day. During the startup process, along with a small amount of seed sludge, granular sludge was additionally inoculated as a biomass carrier for the enrichment of ammonia oxidizing bacteria (AOB), followed by the enrichment of anammox bacteria. A mesh screen equipped at the outlet of the reactor facilitated the successful sludge retention in the reactor. Analysis of bacterial community composition indicated that Candidatus Scalindua was successfully enriched in the pilot SNAP reactor. These methods for stable sludge retention in the reactor greatly contributed to the startup of the first pilot-scale SNAP reactor using marine anammox bacteria.

Insight into quorum sensing and microbial community of an anammox consortium in response to salt stress: From “Candaditus Brocadia” to “Candaditus Scalindua”

The shift of microbial community and signaling molecules release were studied to explore the potential mechanism of anammox consortium under salt stress. Due to increased salinity, the abundance of “Candidatus Brocadia” decreased from 29.5% to 1.9%. “Candidatus Brocadia” was reduced by the salinity shock. Besides, “Candidatus Scalindua”, marine anammox bacteria, was detected at 18 g L−1 NaCl and dominated the reactor. Principle coordinates analysis further proved that salinity was the driving force on the distribution and diversity of anammox consortium. Also, quorum sensing feedback mechanism of anammox bacteria under salt stress was investigated for the first time. The concentration of N-(3-oxohexanoyl)-DL-homoserine lactone (3OC6-HSL) increased from 0.27 ± 0.02 to 1.24 ± 0.09 μM at 7 to 9 g L−1 NaCl. The concentration of 3OC6-HSL maintained at a high level at 9 to 12 g L−1 NaCl. Nacylated-l-homoserine lactones (AHLs)-mediated QS became more active and then improved the coordinated interaction in anammox consortium. High concentration of AHLs promoted the bacteria to produce more extracellular polymeric substances, which increased the bacterial tolerance to salt stress.

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.

From freshwater anammox bacteria (FAB) to marine anammox bacteria (MAB): A stepwise salinity acclimation process

An investigation into the effect of stepwise saline introduction (3–20 g·L−1 NaCl) on the anaerobic ammonium oxidation (anammox) process in a lab-scale sequencing batch reactor was carried out for 252 days by evaluating the changes in influent and effluent nitrogen concentrations, conductivity, microbial extracellular polymeric substances' (EPS) ionic content, as well as stresses due to salinity, via microbial ATP analysis. It was observed that, effluent nitrogen concentrations remained stable at low saline levels of 3 g·L−1 to 10 g·L−1. Nonetheless, midway through 10 g·L−1 and the preliminary phase of 15 g·L−1 salinity presented a very unstable, highly fluctuating as well as deteriorating effluent nitrogen concentrations. A more satisfactory nitrogen removal efficiency of 83.7 ± 5.9% was obtained at higher saline concentrations implying that, the adaptation mechanism to tolerate increasing salinity was taking place. Saline induced stress, which measures the variation in viable anammox bacteria, was correlative to the formation of EPS and changes in its cationic contents along the increasing salinity. Although the specific anammox activity (SAA) dropped by approximately 15% from the beginning of the process to the midpoint, the drop in SAA after the midpoint was not as drastic as the initial phase. A change in microbial aggregation and dominance proved the existence of new saline-dependent species that can withstand high saline stresses. Recovery from abrupt high saline shocks in batch experiment was seen to be almost impossible.

Synergistic biological removal of nitrogen and sulfide from saline mariculture wastewater by halophilic consortia

Halophilic marine anammox bacteria (MAB)-based sulfide-based autotrophic denitratation and anammox (MSADA) process was investigated to treat seawater-based wastewater under different influent sulfide to nitrate (S/N) ratios. This study firstly presented a novel method with merely inoculating halophilic MAB-based sludge to start up the MSADA process in a sequencing batch reactor. Nitrogen and sulfide could be efficiently removed from seawater-based wastewater at the total nitrogen removal efficiency of 93.7% and sulfide removal efficiency of 100% under the optimum S/N ratio of 0.75 in the MSADA process. Meanwhile, anammox and sulfide-based autotrophic denitrification respectively accounted for about 94.2% and 5.8% of the total nitrogen removal with the high nitrite accumulation efficiency of 92.7%. At the optimum S/N ratio of 0.75, “Candidatus Scalindua” (3.28%), Sulfurimonas (18.68%) and Sulfurovum (11.04%) were the main functional microorganisms, which had the excellent salt tolerance. The dominating functional microorganisms dynamically changed with the different S/N ratios. The microbial community composition was similar and steady when the S/N ratios were 0.33–0.75. Nitrate reductase activity was much higher than nitrite reductase activity in the MSADA system, which made it possible to keep the NO3−-N reduction products at NO2−-N level and provide sufficient NO2−-N for MAB. The coupled process provides a new perspective in the treatment of seawater-based wastewater.

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.

Unraveling nitrogen removal and microbial response of marine anammox bacteria-dominated consortia to Mo(VI) addition in nitrogen-laden saline wastewater treatment

Enhanced performance of anammox process has attracted public attention in treating saline wastewater with marine anammox bacteria. The addition of some key metal elements would enhance metabolic activity in wastewater treatment. Herein, responses of marine anammox bacteria (MAB) to Mo(VI) addition were explored in nitrogen-laden saline wastewater treatment. The experiment was conducted at a low temperature (15 ± 1 °C). With the optimal Mo(VI) concentration of 2.1 mg/(g VSS), the substrate removal rate reached the maximum of 1.41 kg N/(m3·d). Specific anammox activity and substrate conversion rate increased by 16.0% and 36.9%, respectively. The lower ΔNO2--N/ΔNH4+-N indicated the presence of the potential electron acceptor. Moreover, the relative abundance of Cadidatus Scalindua increased by 4.18% during this experiment. Dynamic analysis showed that the remodified Logistic model was proper to analyze nitrogen removal with Mo(VI) addition. An appropriate Mo(VI) dosage (0.5–4 mg/L) would shorten the lag time of anammox process greatly.