Feasibility of anaerobic ammonium oxidation process for treatment of pretreated printed circuit board wastewater.

The treatment of pretreated printed circuit board (PCB) wastewater by anaerobic ammonium oxidation (anammox) process has been rarely reported. This study sought to investigate the performance of the anammox process during various phases of pretreated PCB wastewater treatment. The nitrogen removal efficiency (NRE) reached 90 ± 10% at a Cu2+ concentration of 2.5 mg·L-1, but declined to 22 ± 11% as the Cu2+ level increased to 10.3  mg·L-1. During phase III, there was a 38% increase in the relative abundance of Candidatus Kuenenia compared to phase I. By adjusting the substrate concentration and introducing synthetic wastewater into the reactor, the anammox performance was nearly restored to that of phase I. These findings underscore the potential of the anammox process for treating pretreated PCB wastewater and expanding its practical applications to industrial wastewater treatment.

Effects of Ion Combinations and Their Concentrations on Denitrification Performance and Gene Expressions of an Aerobic Strain Marinobacter Hydrocarbonoclasticus RAD-2.

Salinity is one of the most important factors affecting the nitrogen-removal efficiency of denitrifying bacteria. A series of different ion combinations and salinity gradients were carried out to clarify the effects of ion types and concentrations on nitrogen removal by halophilic aerobic denitrifying bacteria RAD-2. Nitrate concentrations, nitrite concentrations, TAN concentrations, and OD600 were monitored to investigate their effects on denitrification in each group. The results showed that Na+, K+, and Cl- accelerated the denitrification process and improved nitrogen-removal efficiency at moderate additions, while Ca2+ and Mg2+ showed no significant effect. Na+ was effective alone, while K+ or Cl- needed to be combined with at least one of Na+, K+, or Cl- to achieve similar efficiency. The batch tests of salinity confirmed that the addition of a moderate concentration of NaCl/Na2SO4 could effectively improve nitrogen-removal efficiency, while excessive salinity might hinder denitrification metabolism. In the salinity range of 5~40‱, a 5‱ dosage might be the most economical method for strain RAD-2. Real-time PCR experiments on 17 key nitrogen metabolism-related genes revealed that chloride was widely involved in the nitrogen and carbon metabolism of microorganisms by altering cell osmotic pressure and opening ion channel proteins, thereby affecting the efficiency of denitrification. The results of this study may contribute to a better understanding of the different roles of various ions in aerobic denitrification and highlight the importance of salinity control in highly salted wastewater treatment.

Performance of Aerobic Denitrification by the Strain Pseudomonas balearica RAD-17 in the Presence of Antibiotics.

Aerobic denitrification, one of the important nitrate metabolic pathways in biological denitrification, has been attracting increasing interest recently due to its functional advantages. In order to evaluate the effect of antibiotics on aerobic denitrification and guide practical engineering application of aerobic denitrification techniques, we evaluated the performance of aerobic denitrification by the strain Pseudomonas balearica RAD-17 in the presence of ciprofloxacin (CFX) and oxytetracycline (OTC). No significant negative impact on the performance of aerobic denitrification in the presence of CFX or OTC within the range of 50 to 300 µg L-1 was found. Significant degradation of OTC was found within the range of 50 µg L-1 to 300 µg L-1 under aerobic denitrification conditions, while no degradation was found for CFX. Stimulation of cell growth occurred within the investigated range of antibiotics. Under anoxic or aerobic conditions, the addition of CFX or OTC changed the N2O production trend. The results in the present study may play an important role in informing the use of aerobic denitrification techniques in the presence of antibiotics within environmentally relevant concentrations (<1 mg/L).

Carbon availability shifts the nitrogen removal pathway and microbial community in biofilm airlift reactor.

This study investigated the response of nitrogen removal performance and microbial community to different carbon composites in biofilm airlift reactors for wastewater treatment. Three reactors were filled with poly (butylene succinate) and bamboo powder composite at the blending ratio of 9:1, 1:1 and 1:9. Increasing the component of bamboo powder in the carrier reduced the carbon availability and had an adverse effect on nitrate removal efficiency. However, bamboo powder improved the ammonia removal rate which mainly through autotrophic nitrification. Three reactors exhibited distinct microbial compositions in both bacterial and fungal diversity. High inclusion of bamboo power decreased the relative abundance of denitrifiers Denitromonas and increased the relative abundance of nitrifiers, including Nitromonas, Nitrospina and Nitrospira. Moreover, correlation network revealed a competitive interaction between the taxa responsible for ammonia removal and nitrate removal processes. Those results indicated the feasibility of steering nitrogen removal pathway through carrier formulation in wastewater treatment.

Simultaneous aerobic denitrification and antibiotics degradation by strain Marinobacter hydrocarbonoclasticus RAD-2.

Simultaneous denitrification and antibiotics (oxytetracycline, OTC and ciprofloxacin, CFX) degradation was evaluated using a typical aerobic denitrifying strain Marinobacter hydrocarbonoclasticus RAD-2. There was no significant influence on the aerobic nitrate removal efficiency of strain RAD-2 in the presence of these two antibiotics. Along with denitrification, the average degradation rate of 2.92 µg OTC L-1h-1 was achieved, while no degradation was observed for CFX. The growth behavior indicated that an insignificant inhibition effect could have occurred at an antibiotics dosage lower than 300 µg/L. The transcriptional results revealed that antibiotics exposure caused (<2h) down-regulation of the denitrifying related genes, but triggered a significant subsequent up-regulation (4 h). Less nitrous oxide productions were observed in both aerobic and anoxic denitrification processes with antibiotics. Overall, the hormesis effect caused by antibiotics exposure indicated a potential approach to enhance the co-metabolism degradation performance for nitrate and antibiotics in aerobic denitrification.

Kinetic affinity index informs the divisions of nitrate flux in aerobic denitrification.

Aerobic denitrification is attracting increasing attention since its advantage of complete nitrogen removal in a single aerobic reactor with simplified configurations. This study investigated the nitrate kinetic affinity (half-saturation index, Km) by an isolated aerobic denitrifier named P. balearica strain RAD-17. It turned out that strain RAD-17 had a high Km of 162.5 mg-N/L and maximum nitrate reduction rate of 21.7 mg-N/(L•h), enabling it to treat high-strength nitrogen wastewater with high efficiency. Further analysis illustrated that Km was the critical value for the change of growth yield rate along initial nitrate concentrations. Nitrogen balance results elucidated an opposite nitrogen flux to cell synthesis and nitrogen loss during aerobic denitrification. Moreover, the expression of functional genes provided proofs for these phenotypic results at transcriptional level. Consequently, Km could be an indicator for nitrate flux division directing to respiration and assimilation in aerobic denitrifiers, shedding light on its regulation for wastewater treatment.

Denitrification performance and microbial communities of solid-phase denitrifying reactors using poly (butylene succinate)/bamboo powder composite.

This study explored the denitrification performance of solid-phase denitrification (SPD) systems packed with poly (butylene succinate)/bamboo powder composite to treat synthetic aquaculture wastewater under different salinity conditions (0‰ Vs. 25‰). The results showed composite could achieve the maximum denitrification rates of 0.22 kg (salinity, 0‰) and 0.34 kg NO3--N m-3 d-1 (salinity, 25‰) over 200-day operation. No significant nitrite accumulation and less dissolved organic carbon (DOC) release (<15 mg/L) were found. The morphological and spectroscopic analyses demonstrated the mixture composites degradation. Microbial community analysis showed that Acidovorax, Simplicispira, Denitromonas, SM1A02, Marinicella and Formosa were the dominant genera for denitrifying bacteria, while Aspergillus was the major genus for denitrifying fungus. The co-network analysis also indicated the interactions between bacterial and fungal community played an important role in composite degradation and denitrification. The outcomes provided a potential strategy of DOC control and cost reduction for aquaculture nitrate removal by SPD.

Nitrogen Removal Performance and Metabolic Pathways Analysis of a Novel Aerobic Denitrifying Halotolerant Pseudomonas balearica strain RAD-17.

An aerobic denitrification strain, Pseudomonas balearica RAD-17, was identified and showed efficient inorganic nitrogen removal ability. The average NO3--N, NO2--N, and total ammonium nitrogen (TAN) removal rate (>95% removal efficiency) in a batch test was 6.22 mg/(L∙h), 6.30 mg/(L∙h), and 1.56 mg/(L∙h), respectively. Meanwhile, optimal incubate conditions were obtained through single factor experiments. For nitrogen removal pathways, the transcriptional results proved that respiratory nitrate reductases encoded by napA, which was primarily performed in aerobic denitrification and cell assimilation, were conducted by gluS and gluD genes for ammonium metabolism. In addition, adding the strain RAD-17 into actual wastewater showed obvious higher denitrification performance than in the no inoculum group (84.22% vs. 22.54%), and the maximum cell abundance achieved 28.5 ± 4.5% in a ratio of total cell numbers. Overall, the efficient nitrogen removal performance plus strong environmental fitness makes the strain RAD-17 a potential alternative for RAS (recirculating aquaculture system) effluent treatment.

Multi-omics analysis reveals niche and fitness differences in typical denitrification microbial aggregations.

Suspended floc and fixed biofilm are two commonly applied strategies for heterotrophic denitrification in wastewater treatment. These two strategies use different carbon sources and reside within different ecological niches for microbial aggregation, which were hypothesized to show distinct microbial structures and metabolic fitness. We surveyed three floc reactors and three biofilm reactors for denitrification and determined if there were distinct microbial aggregations. Multiple molecular omics approaches were used to determine the microbial community composition, co-occurrence network and metabolic pathways. Proteobacteria was the dominating and most active phylum among all samples. Carbon source played an important role in shaping the microbial community composition while the distribution of functional protein was largely influenced by salinity. We found that the topological network features had different ecological patterns and that the microorganisms in the biofilm reactors had more nodes but less interactions than those in floc reactors. The large niche differences in the biofilm reactors explained the observed high microbial diversity, functional redundancy and resulting high system stability. We also observed a lower proportion of denitrifiers and higher resistance to oxygen and salinity perturbation in the biofilm reactors than the floc reactors. Our findings support our hypothesis that niche differences caused a distinct microbial structure and increased microbial ecology distribution, which has the potential to improve system efficiency and stability.

Effect of stock density on the microbial community in biofloc water and Pacific white shrimp (Litopenaeus vannamei) gut microbiota.

Biofloc technology is an efficient approach for intensive shrimp culture. However, the extent to which this process can influence the composition of intestinal microbial community is still unknown. Here, we surveyed the shrimp intestinal bacteria as well as the floc water from three biofloc systems with different stock densities. Our study revealed a similar variation trend in phylum taxonomy level between floc bacteria and gut microbiota. Microbial community varied notably in floc water from different stock densities, while a core genus with dominating relative abundance was detected in gut samples. Extensive variation was discovered in gut microbiota, but still clustered into groups according to stock density. Our results indicated that shrimp intestinal microbiota as well as bacteria aggregated in flocs assembled into distinct communities from different stock densities, and the intestinal communities were more similar with the surrounding environment as the increase of stock density and resulting high floc biomass. The high stock density changed the core gut microbiota by reducing the relative abundance of Paracoccus and increasing that of Nocardioides, which may negatively influence shrimp performance. Therefore, this study helps us to understand further bacteria and host interactions in biofloc system.

Characterization of oligotrophic AnAOB culture: morphological, physiological, and ecological features.

Anaerobic ammonium oxidation (anammox) process is regarded as a promising nitrogen removal technology to treat ammonium wastewaters in a wide concentration range. Oligotrophic anaerobic ammonia oxidation bacteria (O-AnAOB) culture has been successfully achieved from a new anammox system to treat superlow ammonium concentration wastewaters. In this work, the O-AnAOB culture was compared with the eutrophic AnAOB (E-AnAOB) culture to reveal its physiological, morphological, and ecological features. Results showed that the specific anammox activity (SAA) of O-AnAOB culture was 0.07 kgN/(kgVSS·d) with the nitrogen removal rate (NRR) of 0.20 kgN/ (m3 d) in the reactor, while the SAA of E-AnAOB culture was 2.11 kgN/(kgVSS·d) with the NRR of 11.10 kgN/(m3 d). The hzs gene transcription levels (hzs-mRNA) of O-AnAOB and E-AnAOB cultures were 1.32 × 109 copies/gVSS and 1.51 × 1010 copies/gVSS, respectively. Morphologically, the O-AnAOB culture took on the unique brown color rather than the typical red color of E-AnAOB. The O-AnAOB cells lived in a disperse pattern in the culture. The cells were seriously deformed with deep craters on the cell wall. The size of anammoxsome and paryphoplasm compartments inside the O-AnAOB cells was smaller than that inside the E-AnAOB cells. Ecologically, the O-AnAOB culture had special microbial community with a higher bacterial diversity than the E-AnAOB. The most dominant genera in O-AnAOB were Anaerolineaceae (33.7%, fermentative bacteria), Candidatus Kuenenia (17.4%, anammox bacteria), and Nitrospira (7.3%, nitrite oxidizing bacteria). This study provided an insight into the new anammox process for deep nitrogen removal from wastewaters.

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4.

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Simultaneous ammonia and nitrate removal in an airlift reactor using poly(butylene succinate) as carbon source and biofilm carrier.

In this study, an airlift inner-loop sequencing batch reactor using poly(butylene succinate) as the biofilm carrier and carbon source was operated under an alternant aerobic/anoxic strategy for nitrogen removal in recirculating aquaculture system. The average TAN and nitrate removal rates of 47.35±15.62gNH4-Nm(-3)d(-1) and 0.64±0.14kgNO3-Nm(-3)d(-1) were achieved with no obvious nitrite accumulation (0.70±0.76mg/L) and the dissolved organic carbon in effluents was maintained at 148.38±39.06mg/L. Besides, the activities of dissimilatory nitrate reduction to ammonium and sulfate reduction activities were successfully inhibited. The proteome KEGG analysis illustrated that ammonia might be removed through heterotrophic nitrification, while the activities of nitrate and nitrite reductases were enhanced through aeration treatment. The microbial community analysis revealed that denitrifiers of Azoarcus and Simplicispira occupied the dominate abundance which accounted for the high nitrate removal performance. Overall, this study broadened our understanding of simultaneous nitrification and denitrification using biodegradable material as biofilm carrier.

Acute toxicity assessment of ANAMMOX substrates and antibiotics by luminescent bacteria test.

Acute toxicities of anaerobic ammonia oxidation (ANAMMOX) substrates and four antibiotics from pharmaceutical wastewaters on ANAMMOX process were reported. Individual and joint acute toxicity assays were performed using 50% inhibitory concentration (IC50). Results showed that IC50 values and their 95% confidence interval of ammonium chloride (A), sodium nitrite (B), penicillin G-Na (C), polymyxin B sulfate (D), chloramphenicol (E) and kanamycin sulfate (F) were 2708.9 (2247.9-3169.9), 1475.4 (1269.9-1680.9), 5114.4 (4946.4-5282.4), 10.2 (1.8-18.6), 409.9 (333.7-486.1) and 5254.1 (3934.4-6573.8) mgL(-1) respectively, suggesting toxicities were in the order of D>E>B>A>C>F. Joint acute toxicities of bicomponent mixtures A and B, C and D, C and F, D and F were independent; D and E, E and F were additive while C and E were synergistic. Joint acute toxicities of multicomponent mixtures were synergistic or additive. Luminescent bacteria test is an easy and robust method for forecasting the feasibility of ANAMMOX process for pharmaceutical wastewater treatment.

Nitrate-dependent anaerobic ferrous oxidation (NAFO) by denitrifying bacteria: a perspective autotrophic nitrogen pollution control technology.

The nitrate-dependent anaerobic ferrous oxidation (NAFO) is an important discovery in the fields of microbiology and geology, which is a valuable biological reaction since it can convert nitrate into nitrogen gas, removing nitrogen from wastewater. The research on NAFO can promote the development of novel autotrophic biotechnologies for nitrogen pollution control and get a deep insight into the biogeochemical cycles. In this work, batch experiments were conducted with denitrifying bacteria as biocatalyst to investigate the performance of nitrogen removal by NAFO. The results showed that the denitrifying bacteria were capable of chemolithotrophic denitrification with ferrous salt as electron donor, namely NAFO. And the maximum nitrate conversion rates (qmax) reached 57.89 mg (g VSS d)−1, which was the rate-limiting step in NAFO. Fe/N ratio, temperature and initial pH had significant influences on nitrogen removal by NAFO process, and their optimal values were 2.0 °C, 30.15 °C and 8.0 °C, respectively.

Effect of particle size on the performance of autotrophic nitrogen removal in the granular sludge bed reactor and microbiological mechanisms.

The effect of particle size on the performance of autotrophic nitrogen removal in the granular sludge bed reactor (GSB-ANR) and microbiological mechanisms were investigated. The results indicated that performance of GSB-ANR process decreased gradually with the increase of the granular sludge size. Indeed small granules ranging between 0.5 and 0.9mm had a higher nitrogen removal capacity than large ones. The reasons of this effect were that (i) the aerobic ammonium oxidizing capacity of microorganisms was the bottle neck of nitrogen removal in GSB-ANR process, and the increase of aerobic ammonium oxidizing activity enhances nitrite production in nitrification and promotes subsequent nitrite consumption during anaerobic ammonia oxidation; (ii) the aerobic/anaerobic zone separation in granular sludge was the key factor affecting the aerobic ammonium oxidizing capacity of microorganisms. The small granules had a larger aerobic functional zone (75.1%) which was profitable for up-regulating the expression level of functional gene in aerobic ammonium oxidizing microorganisms.

[Start-up of a full-scale system for short-cut nitrification and Anammox in treatment of pharmaceutical wastewater].

In order to broaden the application area of the new nitrogen removal technology, a full-scale system for short-cut nitrification and anaerobic ammonium oxidation (Anammox) was investigated in the nitrogen removal from a strong-ammonium pharmaceutical wastewater. When the influent ammonium concentration was (430.40 ± 55.43) mg/L, ammonia removal efficiency was (81.75 ± 9.10)%. The short-cut nitrification and Anammox system could successfully remove nitrogen from the pharmaceutical wastewater. The start-up of short-cut nitrification system took about 74 d and the nitrite accumulation efficiency was (52.11 ± 9.13)%, the two-step mode using synthetic wastewater and actual wastewater was suitable for the start-up of short-cut nitrification system. The start-up of Anammox system took about 145 d and the maximum volumetric nitrogen removal rate was 6.35 kg N/(m3·d), dozens of times higher than those for the conventional nitrification-denitrification process. The strategy achieving Anammox sludge by self-growth and biocatalyst addition was suitable for the start-up of Anammox system.

The morphological and settling properties of ANAMMOX granular sludge in high-rate reactors.

Digital macro photography and settling tests were carried out to investigate the morphological and settling characteristics of ANAMMOX granules in a high-rate reactor. The ANAMMOX granules could be divided into settling and floating granules. The settling granules with an average diameter of 2.96±0.99 mm were smaller than the floating granules with an average diameter of 4.58±1.22 mm. A settling model was established and validated to correlate the settling velocity with the density (ρG), mass shape factor (ψmass), shape-correction factor (characterized by sphericity (Φ(')) or roundness (ξ)) and projected area equivalent sphere diameter (dP) of ANAMMOX granules. The sphericity was more suitable than the roundness for describing the settling behavior. The sensitivity of four parameters was in the order of ρG,ψmass, dP and Φ('). Based on the settling model, ANAMMOX granules with diameter of 1.75-4.00 mm were supposed to be optimal for the ANAMMOX process.

Physical characteristics and formation mechanism of denitrifying granular sludge in high-load reactor.

The physical characteristics of denitrifying granular sludge and their granulation mechanism were investigated in two denitrifying reactors (R1 and R2). The results showed that the denitrifying granular sludge was streamlined in shape with the aspect ratio (AR) of 0.62 ± 0.05, large in size with the diameter of 2.39 ± 0.05 mm, and fast in settlement with the average settling velocity (VS) of 126.36 ± 13.32 m/h at the nitrate loading rate (NLR) of 35.14 ± 0.38 kg/(m(3)d). The dominance of denitrifying granular sludge with good settleability was attributed to the enhanced growth of granular sludge by extracellular polymers (EPS) and the shaping of granular sludge by shear force.

Toxicity assessment of anaerobic digestion intermediates and antibiotics in pharmaceutical wastewater by luminescent bacterium.

In order to evaluate the effect of anaerobic digestion intermediates and antibiotics in pharmaceutical wastewaters on anaerobic digestion process, their acute toxicities were tested using the 15 min median inhibitory concentration (IC(50)) at pH 7.00 ± 0.05. The results showed that the IC(50) of ethanol, acetate, propionate and butyrate were 19.40, 20.71, 10.47 and 12.17 g L(-1) respectively, which suggested the toxicity descended in the order of propionate, butyrate, ethanol and acetate. The IC(50) of aureomycin, polymyxin and chloromycetin were 12.06, 6.24 and 429.90 mg L(-1) respectively, which indicated the toxicity descended in the order of polymyxin, aureomycin and chloromycetin. Using equitoxic ratio mixing method, the joint toxicities of five groups referred by A (four anaerobic digestion intermediates), B (four anaerobic digestion intermediates and aureomycin), C (four anaerobic digestion intermediates and polymyxin), D (four anaerobic digestion intermediates and chloromycetin) and E (four anaerobic digestion intermediates, aureomycin, polymyxin and chloromycetin) were investigated respectively. Their interactions were additive (A), synergistic (B), additive (C), synergistic (D) and synergistic (E). The investigation would lay a basis for the optimization of anaerobic biotechnology for pharmaceutical wastewater treatment.