Characteristic and mechanism of biological nitrogen and phosphorus removal facilitated by biogenic manganese oxides (BioMnOx) at various concentrations of Mn(II).

Biogenic manganese oxides (BioMnOx) have attracted considerable attention as active oxidants, adsorbents, and catalysts. However, characteristics and mechanisms of nitrification-denitrification in biological redox reactions mediated by different concentrations of BioMnOx are still unclear. Fate of nutrients (e.g., NH4+-N, TP, NO3--N) and COD were investigated through different concentrations of BioMnOx produced by Mn(II) in the moving bed biofilm reactor (MBBR). 34% and 89.2%, 37.8% and 89.8%, 57.3% and 88.9%, and 62.1% and 90.4% of TN and COD by MBBR were synchronously removed in four phases, respectively. The result suggested that Mn(II) significantly improved the performance of simultaneous nitrification and denitrification (SND) and TP removal based on manganese (Mn) redox cycling. Characteristics of glutathione peroxidase (GSH-Px), reactive oxygen species (ROS), and electron transfer system activity (ETSA) were discussed, demonstrating that ROS accumulation reduced the ETSA and GSH-Px activities when Mn(II) concentration increased. Extracellular polymeric substance (EPS) function and metabolic pathway of Mn(II) were explored. Furthermore, effect of cellular components on denitrification was evaluated including BioMnOx performances, indicating that Mn(II) promoted the non-enzymatic action of cell fragments. Finally, mechanism of nitrification and denitrification, denitrifying phosphorus and Mn removal was further elucidated through X-ray photoelectron spectroscopy (XPS), high throughput sequencing, and fourier transform infrared reflection (FTIR). This results can bringing new vision for controlling nutrient pollution in redox process of Mn(II).

Effect of antibiotics on the performance of moving bed biofilm reactor for simultaneous removal of nitrogen, phosphorus and copper(II) from aquaculture wastewater.

Co-existence of NO3--N, antibiotics, phosphorus (P), and Cu2+ in aquaculture wastewater has been frequently detected, but simultaneous removal and relationship between enzyme and pollutants removal are far from satisfactory. In this study, simultaneous removal of NO3--N, P, antibiotics, and Cu2+ by moving bed biofilm reactor (MBBR) was established. About 95.51 ± 3.40% of NO3--N, 61.24 ± 3.51% of COD, 18.74 ± 1.05% of TP, 88% of Cu2+ were removed synchronously in stage I, and antibiotics removal in stages I-IV was 73.00 ± 1.32%, 79.53 ± 0.88%, 51.07 ± 3.99%, and 33.59 ± 2.73% for tetracycline (TEC), oxytetracycline (OTC), chlortetracycline hydrochloride (CTC), sulfamethoxazole (SMX), respectively. The removal kinetics and toxicity of MBBR effluent were examined, indicating that the first order kinetic model could better reflect the removal of NO3--N, TN, and antibiotics. Co-existence of multiple antibiotics and Cu2+ was the most toxicity to E. coli growth. Key enzyme activity, reactive oxygen species (ROS) level, and its relationship with TN removal were investigated. The results showed that enzymes activities were significantly different under the co-existence of antibiotics and Cu2+. Meanwhile, different components of biofilm were extracted and separated, and enzymatic and non-enzymatic effects of biofilm were evaluated. The results showed that 70.00%- 94.73% of Cu2+ was removed by extracellular enzyme in stages I-V, and Cu2+ removal was mainly due to the action of extracellular enzyme. Additionally, microbial community of biofilm was assessed, showing that Proteobacteria, Bacteroidetes, and Gemmatimonadetes played an important role in the removal of NO3--N, Cu2+, and antibiotics at the phylum level. Finally, chemical bonds of attached and detached biofilm were characterized by X-ray photoelectron spectroscopy (XPS), and effect of nitrogen (N) and P was proposed under the co-existence of antibiotics and Cu2+. This study provides a theoretical basis for further exploring the bioremediation of NO3--N, Cu2+, and antibiotics in aquaculture wastewater.

Microbial degradation of tetracycline in the aquatic environment: a review.

Tetracycline residues have frequently been detected in multi-environmental media, and it could induce antibiotic resistance genes (ARGs) in microorganisms, which has attracted great attention. Where biodegradation processes may be a promising strategy to remove tetracycline. Thus, this study mainly considers: (i) the degradation of tetracycline by microorganisms including single microorganisms and microbial flora; (ii) the elimination of tetracycline during biochemical treatment processes and advanced treatment systems in wastewater treatment plants (WWTPs) and constructed wetlands (CWs); (iii) the degradation of tetracycline by biological coupling processes; (iv) the confusion and problem of tetracycline biodegradation. Furthermore, the characteristics and comparison of tetracycline biodegradation have been discussed in detail. Additionally, future research directions are suggested to reduce tetracycline in the aquatic environment, especially tetracycline biodegradation and the nitrogen conversion process. Highlights Degradation of tetracycline by pure culture strains and microflora was significant. Degradation of tetracycline by biochemical treatment process was summarized. Advanced treatment process in CWs could eliminate tetracycline. Future research directions on biodegradation of tetracycline are proposed.

Action of oxytetracycline (OTC) degrading bacterium and its application in Moving Bed Biofilm Reactor (MBBR) for aquaculture wastewater pre-treatment.

In this study, the characteristics of biodegradation of oxytetracycline (OTC) by strain Ochrobactrum sp. KSS10 were studied under various environmental conditions, including initial OTC concentrations, variable temperature, initial pH, and diverse carbon sources. The capability of this bacterial strain for performing simultaneous OTC degradation and nitrate reduction was also explored under aerobic conditions. An OTC degradation ratio of 63.33% and a nitrate removal ratio of 98.64% were obtained within 96 h. In addition, removal of OTC and ammonia from synthetic aquaculture wastewater by a Moving Bed Biofilm Reactor (MBBR) and changes in the resistant genes of microbial communities were also investigated. The results demonstrated that the strain KSS10 was the dominant contributor in OTC and ammonia removal in the MBBR chamber. It removed almost all ammonia and approximately 76.42% of OTC. The abundances of genes tetL, tetX and intI1 were reduced by the MBBR, but the abundance of tetG and tetM were increased due to horizontal and vertical gene transfers. Such a result can potentially be used by the strain KSS10 for removing antibiotics and nitrogen from aquaculture wastewater during pre-treatment.

Biodegradation mechanism of tetracycline (TEC) by strain Klebsiella sp. SQY5 as revealed through products analysis and genomics.

Although it has been proved that abiotic processes can transform tetracycline (TEC), little is known about how microbial processes may degrade TEC in aquatic environment. The objective of this study is to investigate the biodegradation pathway of TEC by strain Klebsiella sp. SQY5 and molecular mechanism of TEC resistance under the aerobic conditions. Effects of mycelium, intracellular, and extracellular enzyme on TEC degradation process were explored, suggesting that mycelium contributed the most of TEC degradation with a maximum efficiency of 58.64%. Biodegradation characteristic of TEC and its degradation products were studied. The results showed that nine possible biodegradation products were identified, and a potential biodegradation pathway was proposed including the removal of methyl, carbonyl, and amine groups. The functional genes of this bacterium were also determined by genomics, and analysis indicated that functional genes that could be relevant to hydrolysis, ring opening and oxidation played an important role in the process of TEC biodegradation. Results from this study can provide a theoretical basis for better estimating the fate, transportation, and degradation of antibiotics in aquatic environment.

Research progress on distribution, migration, transformation of antibiotics and antibiotic resistance genes (ARGs) in aquatic environment.

Antimicrobial and antibiotics resistance caused by misuse or overuse of antibiotics exposure is a growing and significant threat to global public health. The spread and horizontal transfer of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) by the selective pressure of antibiotics in an aquatic environment is a major public health issue. To develop a better understanding of potential ecological risks die to antibiotics and ARGs, this study mainly summarizes research progress about: (i) the occurrence, concentration, fate, and potential ecological effects of antibiotics and ARGs in various aquatic environments, (ii) the threat, spread, and horizontal gene transfer (HGT) of ARGs, and (iii) the relationship between antibiotics, ARGs, and ARB. Finally, this review also proposes future research direction on antibiotics and ARGs.

Isolation, identification, and algicidal activity of aerobic denitrifying bacterium R11 and its effect on Microcystis aeruginosa.

Recently, algicidal bacteria have attracted attention as possible agents for the inhibition of algal water blooms. In this study, an aerobic denitrifying bacterium, R11, with high algicidal activity against the toxic Microcystis aeruginosa was isolated from lake sediments. Based on its physiological characteristics and 16S rRNA gene sequence, it was identified as Raoultella, indicating that the bacterium R11 has a good denitrifying ability at 30 °C and can reduce the concentration of nitrate-N completely within 36 h. Additionally, different algicidal characteristics against Microcystis aeruginosa were tested. The results showed that the initial bacterial cell density and algal cell densities strongly influence the removal rates of chlorophyll a. Algicidal activity increased with an increase in the bacterial cell density. With densities of bacterial culture at over 2.4 × 10(5) cell/mL, algicidal activity of up to 80% was obtained in 4 days. We have demonstrated that, with the low initial algal cell density (OD680 less than 0.220), the algicidal activity reached was higher than 90% after 6 days.

New insights into nitrogen removal by divalent iron-enhanced moving bed biofilm reactor: Performance, interfacial interaction and co-occurrence network.

A divalent iron-mediated moving bed biofilm reactor with intermittent aeration was developed to enhance the nitrogen removal at low carbon-to-nitrogen ratios. The study demonstrated thatammonia removal increased from 51 ± 4 % to 79 ± 4 % and nitrate removal increased from 72 ± 5 % to 98 ± 4 % in phases I-IV, and 2-5 mg·L-1 of divalent iron significantly increased the anoxic denitrification process. Divalent iron stimulated the secretion of extracellular polymeric substances, which facilitated the formation of cross-linked network between microbial cells. Furthermore, the cycle between divalent and trivalent iron decreased the energy barrier between the biofilm and the pollutant. The microbial community further revealed that Proteobacteria (relative abundance: 40-48 %) andBacteroidota(relative abundance: 31-37 %) were the dominant phyla, supporting the synchronous nitrification and denitrification processes as well as the lower accumulation of nitrite. In conclusion, iron redox cycling significantly enhanced the nitrogen removal. This study proposes a viable strategy for the efficient treatment of nutrient wastewater.

New perspective on effect of ß-cyclodextrin on nitrification-denitrification and denitrification phosphorus removal in biogenic manganese oxides driven moving bed biofilm reactor: Performance evaluation, microbial community and process.

Effect of ß-cyclodextrin (ß-CD) on simultaneous removal of NH4+-N, NO3--N, COD, and phosphorus (P) in biogenic manganese oxides (BioMnOx) driven moving bed biofilm reactor (MBBR) was investigated. 58.64% and 86.32%, 79.65% and 98.39%, 62.45% and 97.30%, and 24.80% and 95.90% of TN and COD were removed in phases I-IV, indicating that simultaneous nitrification and denitrification (SND) efficiencies were 75.44%, 83.91%, 72.71%, and 35.83%, respectively. Composition and fluorescence spectral characteristics of extracellular polymeric substance (EPS) were evaluated including the removal kinetics of TN and COD. Metabolic activity of Mn2+, decolorization performance of BioMnOx, and reactive oxygen species (ROS) characteristics were determined in biofilm. Furthermore, intermediate Mn3+ and BioMnOx concentration were analyzed. Finally, the removal process of nitrogen (N) and P was proposed based on characterizations of elemental characterization, electrochemistry, and microbial community. This study provides new insights into the N and P removal mediated by BioMnOx and ß-CD.

Performance of nitrification-denitrification and denitrifying phosphorus removal driven by in-situ generated biogenic manganese oxides in a moving bed biofilm reactor.

Simultaneous removal of NH4+-N, NO3--N, COD, and P by manganese redox cycling in nutrient wastewater was established with two moving bed biofilm reactors (MBBRs) with in-situ generated biogenic manganese oxides (BioMnOx) and non-BioMnOx. In-situ generated BioMnOx preferentially promoted the denitrification, and the average removal of NO3--N, NH4+-N, and TN in the experimental MBBR with BioMnOx increased to 89.00%, 70.64%, and 76.06% compared with the control MBBR with non-BioMnOx. The relevant enzymes activity, extracellular polymeric substance (EPS), electron transport system activity (ETSA), and reactive oxygen species (ROS) were investigated. The element valence and morphology of purified BioMnOx were characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), as well as the effect of BioMnOx on nitrogen and phosphorus removal. The results suggested that BioMnOx could improve nitrogen conversion. Electrochemical characteristic and microbial community were detected. This study provided a new strategy for nutrients removal in BioMnOx-mediated wastewater treatment.

Performance and mechanism of simultaneous nitrification-denitrification and denitrifying phosphorus removal in long-term moving bed biofilm reactor (MBBR).

The long-term moving bed biofilm reactor (MBBR) with carrier-attached biofilm was successfully operated for simultaneous removal of nitrogen, phosphorus, and COD at various C/N ratios. Results indicated that 99.60%, 63.58%, 78.94%, and 59.64% of NH4+-N, NO3--N, TN, and TP were removed at C/N ratio, hydraulic retention time (HRT), and carrier film amount of 5, 40 h, and 1.2 mg·g-1. Nitrogen balance analysis showed that more than 89% of nitrogen (C/N = 20, 15, 10, 5) was converted to gas products. Extracellular polymeric substances (EPS), electron transport system activity (ETSA), and enzyme activity of biofilm were evaluated. Protein (PN)/polysaccharose (PS) values and ETSA decreased with the decrease of C/N ratios. Metagenomics sequencing further revealed that the prominent phyla for nitrogen and phosphorus removal were identified including Proteobacteria, Acidobacteria, Nitrospirae, and Chloroflexi. Proteobacteriaand Gammaproteobacteria were identified as the dominant denitrifying phosphate accumulating organisms (PAO) at the phylum and class level, respectively.

Performance of simultaneous nitrification-denitrification and denitrifying phosphorus and manganese removal by driving a single-stage moving bed biofilm reactor based on manganese redox cycling.

Simultaneous removal of NH4+-N, NO3--N, COD, and P by manganese redox cycling in nutrient wastewater was established with a single-stage moving bed biofilm reactor (MBBR) under low C/N ratio. When sodium succinate replaced the conventional denitrifying carbon source, removal efficiencies of TN, NO3--N, NH4+-N, TP, and Mn2+ were 65.13 %, 79.63 %, 92.79 %, 51.57 %, and 68.10 %, respectively. Based on modified Stover-Kincannon model, 11.03 and 10.05 mg TN·L-1·h-1 of Umax values were obtained with sodium acetate and sodium succinate as substrates. Extracellular polymeric substances were used to evaluate the characteristics of biofilm, and microbial community of biofilm was identified. Transformation processes of NO3--N, NH4+-N, Mn2+, and P were investigated, suggesting that the main functional groups (e.g., CO, Mn-O, and CN bonds) participated in N, P, and Mn2+ removal, and MnO2 was the main component of biogenic manganese oxides. This study provides a new strategy for nutrients removal by Mn2+ driven MBBR.

Effects of carbon source, nitrogen source, and natural algal powder-derived carbon source on biodegradation of tetracycline (TEC).

The present study aimed to investigate Klebsiella sp. SQY5-mediated tetracycline (TEC) degradation, nitrogen (N) conversion, and mechanisms underlying this process as influenced by various carbon and N sources under aerobic conditions. Effects of additional organic carbon sources on TEC degradation and N conversion processes were explored, and we found that 34.71% of TEC was degraded at removal rates of 0.97 mg·L-1·h-1 for NH4+-N and 1.97 mg·L-1·h-1 for NO3--N. A study examining powder natural algal powder in aquaculture wastewater as a carbon source for TEC degradation and denitrification process was also discussed. It suggested that 49.95% of TEC and 60.45% of NO3--N were removed with a reduction and denitrification rate of 0.11 mg·L-1·h-1 and 1.34 mg·L-1·h-1, respectively, within 72-108 h. Mechanisms underlying TEC degradation and N conversion processes were also proposed, and analysis indicated that specific functional genes played an important role in this process.

Simultaneous Cr(VI) reduction and electricity generation in Plant-Sediment Microbial Fuel Cells (P-SMFCs): Synthesis of non-bonding Co3O4 nanowires onto cathodes.

Development of low-cost cathode materials for Plant-Sediment Microbial Fuel Cells (P-SMFCs) has gained increasing interest, due to improved performance levels in terms of power and pollutant removal. A novel low cost three-dimensional cathode prepared by simple three-step strategy with growth of Co3O4 in-situ biofilm was successfully prepared. Different cathodes were applied to the six parallel P-SMFCs systems (reactor: R1-R6), such as graphite felt (GF), Pt/C, GF@Co3O4 (non-bonding Co3O4 nanowires on GF), GF@SG-Co3O4 (using argon as shielding gas (SG)). Its performances (R1, R2: control groups) were evaluated by electricity generation and Cr(VI) reduction at initial cadmium concentrations (4.97, 10.29 and 21.16 mg L-1). A significant Cr(VI) removal efficiency of 99.76%, maximum power density of 75.12 ±â€¯2.90 mW m-2 and Cr(VI) adsorption capacity of 1.67 mg g-1 were obtained at initial Cr(VI) concentration of 21.16 mg L-1 with non-bonding GF@Co3O4 and bio-GF@SG-Co3O4 as cathodes. This indicated that these two materials were better than others (GF, Pt/C and GF@Co3O4) as cathodes. Characterization analysis including scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Polarization curve, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed that high current generation Cr(VI) removal mainly attributed to transportation of plants, adsorption of bio-cathode, formation of a relatively high concentration region and abundant oxygen vacancies of GF@SG-Co3O4. The results show that P-SMFCs with GF@SG-Co3O4 cathode may be a potentially novel approach for remediating Cr(VI) contaminated waster or soil.

Simultaneous degradation of tetracycline and denitrification by a novel bacterium, Klebsiella sp. SQY5.

Polluted waters with a high residue of tetracycline also have a high concentration of nitrate. Thus, screening for both, highly efficient tetracycline biodegradation and nitrate transformation, is a key technical strategy. In this study, a novel tetracycline degrading strain, SQY5, which was identified as Klebsiella sp., was isolated from municipal sludge. Biodegradation characteristics of tetracycline were studied under various environmental conditions; including inoculation dose (v/v), initial tetracycline concentration, temperature, and pH. Response surface methodology (RSM) analysis demonstrated that the maximum degradation ratio of tetracycline can be obtained under the condition with an initial tetracycline concentration of 61.27 mg L-1, temperature of 34.96 °C, pH of 7.17, and inoculation dose of 29.89%. Furthermore, this was the first report on the relationship between the degradation of tetracycline and the denitrification effect, showing that a maximum tetracycline reduction rate of 0.113 mg L-1·h-1 and denitrification rate of 4.64 mg L-1·h-1 were observed within 32 h and 92 h of SQY5 inoculation, respectively. The data of this study has the potential for use in engineering processes designed for the simultaneous biological removal of nitrates while degrading antibiotics.