Nitrate removal efficiency of bacterial consortium (Pseudomonas sp. KW1 and Bacillus sp. YW4) in synthetic nitrate-rich water

Ammonia transformation by potential consortium in the aquatic system

In the present research, the removal of high concentration of ammonia, nitrite and nitrate was determined by using the efficient ammonia-oxidizing bacterial isolates (AOB AMS 1, AOB AMS 2, AOB AMS 5 and AOB AMSS 1) along with the consortium of all four bacterial isolates from the aquaculture both in lab-scale as well as in-situ at bioreactor level. It was found that the highest percentage of ammonia was degrade by AOB AMS 2 (99.64%± 5) followed by AOB AMS 5 (99.51%± 4.6), AOB AMSS 1 (99.38%± 5) and AOB AMS 1 (89.66%± 3.5) from an initial concentration of 30 mg/L whereas from an initial concentration of 60 mg/L, the removal rate of each strain was AOB AMS 5 (99.36%± 5), AOB AMSS 1 (99.15%± 5.60), AOB AMS 2 (98.78%± 5.3) and AOB AMS 1 (88.36%± 3.2) and their consortium removes (99.97%± 5.20)at 60 mg/L. Further, in-situ transformation was carried out in the river water with 5% of inoculum. Their growth was monitored (initial and final) by observing the colony forming unit (CFU) and transformation of ammonia and nitrite was also observed and it was found that (100 ± 2%)of ammonia was removed. The growth of consortium was 3 × 102CFU/ml on 1st day, 2.5 × 104 CFU/ml on 5th day and 4.2 × 105 CFU/ml on 10th day. This study proved that the bacterial consortium of AOB AMS 1, AOB AMS 2, AOB AMS 5 and AOB AMSS 1 was highly efficient for the removal of ammonia, nitrite and nitrate from the aquatic system to reduce the toxic level from aquaculture environment.Currently we observed the transformation efficiency at lab-scaleand in-situ level.

Nitrate removal from industrial wastewater using six newly isolated strains of aerobic heterotrophic denitrifiers in an attached growth

BACKGROUND

The objective of this study was to isolate specific heterotrophic aerobic denitrifying bacteria from a wastewater treatment plant and employ them in an attached growth system for wastewater denitrification.

METHODS

To isolate and screen aerobic denitrifiers, Denitrifying Medium (DM) and Screen Medium (GN) were utilized. The Polymerase Chain Reaction (PCR) technique and 16S rDNA sequencing were used to identify the isolates. The formation of biofilms by selected isolates on ceramic media was examined using a Scanning Electron Microscope (SEM). This study also investigated various variables for nitrate removal, including temperature, Carbon/Nitrogen ratio (C/N), and the carbon source. A series of experiments were conducted to gauge nitrate removal under optimal variable values.

RESULTS

Six purified strains exhibited the highest denitrification efficiency in less than 30 h. Pseudomonas species were chosen for additional experiments. Denitrification efficiencies ranged from a low of 71.4% (at a temperature of 30 °C, C/N ratio of 17, and citrate as the carbon source) to a high of 98.9% (at a temperature of 33 °C, C/N ratio of 8, and citrate as the carbon source). The average denitrification efficiency was 84.02%. Optimal nitrate removal occurred at temperatures around 30-31 °C and C/N ratios of approximately 5.8-6.5.

CONCLUSION

This study demonstrates that aerobic denitrifying bacteria can effectively remove nitrate from aqueous solutions.

Nitrogen removal capability and mechanism of a novel heterotrophic nitrifying-aerobic denitrifying strain H1 as a potential candidate in mariculture wastewater treatment

The nitrogen removal performance and mechanisms of Bacillus subtilis H1 isolated from a mariculture environment were investigated. Strain H1 efficiently removed NH4+-N, NO2--N, and NO3--N in simulated wastewater with removal efficiencies of 85.61%, 90.58%, and 57.82%, respectively. Strain H1 also efficiently degraded mixed nitrogen (NH4+-N mixed with NO2--N and/or NO3--N) and had removal efficiencies ranging from 82.39 to 89.54%. Nitrogen balance analysis revealed that inorganic nitrogen was degraded by heterotrophic nitrification-aerobic denitrification (HN-AD) and assimilation. 15N isotope tracing indicated that N2O was the product of the HN-AD process, while N2 as the final product was only detected during the reduction of 15NO2--N. The nitrogen assimilation and dissimilation pathways by strain H1 were further clarified using complete genome sequencing, nitrification inhibitor addition, and enzymatic activity measurement, and the ammonium oxidation process was speculated as NH4+ → NH2OH → NO → N2O. These results showed the application prospect of B. subtilis H1 in treating mariculture wastewater.

Experimental study and modeling of denitrification in an MBBR reactor

A denitrification mathematical model was used to describe the nitrates and organic carbons use by the denitrify biomass in the Moving Bed Biofilm Reactor (MBBR). The model integrates the diffusive mass transfer mechanism as well as double substrates Monod kinetics. Preliminary experiments were realized in order to assess the operating conditions for growth of attached biomass, the determination of the optimal (COD/NO3-N) ratio, moreover the results of the previous study of the residence time distribution in this MBBR established the optimal hydrodynamic operating conditions with a dead volume of 22%. In this reactor, seeded with a mixed liquor from a purification station, kaldnesk1 were used as carriers. A total of 6 kinetic and stoichiometric constants under anoxic conditions were determined by batch-test pulsed respirometry; some parametric have been determined experimentally, such as YHD, YNO, μ ˆ HD ${\widehat{\mu }}_{\text{HD}}$ and KS, and with their values 0.4 mgCOD (mgCOD)−1, 0.6 mg COD (mgCOD)−1,0.864 d−1 and 12.48 mg COD L −1, respectively. The other constants were determined using the model fitting (using MATLAB), such as KNO3 and bHD with its values, 0.25 mg NO3-N. L−1 and 0.061 d−1, respectively. The model was used to simulated different operating condition and the results included the concentration profiles of NO3-N, COD and XBH, which showed good agreement with the experimental ones, mainly by using the effective volume determined experimentally in the hydrodynamic study (RTD test) and which can reach 62% of the total volume under some operating. Additionally, these findings demonstrate that moving bed reactor characterization may be accomplished using in situ pulsed respirometry (MBBR).

Key enzymes involved in anammox-based processes for wastewater treatment: An applied overview

The anaerobic ammonium oxidation (anammox) process has attracted significant attention as an economic, robustness, and sustainable method for the treatment of nitrogen (N)-rich wastewater. Anammox bacteria (AnAOB) coexist with other microorganisms, and particularly with ammonia-oxidizing bacteria (AOB) and/or heterotrophic bacteria (HB), in symbiosis in favor of the substrate requirement (ammonium and nitrite) of the AnAOB being supplied by these other organisms. The dynamics of these microbial communities have a significant effect on the N-removal performance, but the corresponding metabolic pathways are still not fully understood. These processes involve many common metabolites that may act as key factors to control the symbiotic interactions between these organisms, to maximize N-removal efficiency from wastewater. Therefore, this work overviews the current state of knowledge about the metabolism of these microorganisms including key enzymes and intermediate metabolites and summarizes already reported experiences based on the employment of certain metabolites for the improvement of N-removal using anammox-based processes. PRACTITIONER POINTS: Approaches knowledge about the biochemistry and metabolic pathways involved in anammox-based processes. Some molecular tools can be used to determine enzymatic activity, serving as an optimization in nitrogen removal processes. Enzymatic evaluation allied to the physical-chemical and biomolecular analysis of the nitrogen removal processes expands the application in different effluents.

Response of nitrogen removal performance and microbial community to a wide range of pH in thermophilic denitrification system

Thermophilic biological nitrogen removal would be a promising alternative to conventional approaches for the treatment of high-temperature wastewater. In this study, the response of thermophilic denitrification system (50 °C) to a wide range of pH (3-11) was investigated. The results showed that thermophilic denitrification could adapt to pH 5-11, but suffered from obvious nitrite and ammonia accumulation at pH 3. Microbial insights indicated that the enrichment of specific functional thermophiles has contributed to the tolerance towards unfavorable pH. Besides, the potential selecting advantage of nitrate reducing bacteria over nitrite reducing bacteria and the enrichment of dissimilatory nitrate reduction to ammonium (DNRA) bacteria could be responsible for the nitrite and ammonia accumulation at pH 3. Moreover, the functional gene prediction denoted higher narG/(nirK + nirS) and nrfA at pH 3, which could facilitate partial denitrification and DNRA. These findings could provide new insight into the application of thermophilic biological nitrogen removal.

Nitrates in the environment: A critical review of their distribution, sensing techniques, ecological effects and remediation

Nitrate pollution is eminent in almost all the developing nations as a result of increased natural activities apart from anthropogenic pollution. The release of nitrates in more than critical quantities into the water bodies causes accretion impacts on living creatures, environmental receptors, and human vigour by accumulation through the food chain. Nitrates have recently acquired researchers' huge attention and extend their roots in environmental contamination of surface and groundwater systems. The presence of nitrate in high concentrations in surface and groundwater triggers several health problems, for instance, methemoglobinemia, diabetes, eruption of infectious disorders, harmfully influence aquatic organisms. Sensing nitrate is an alternate option for monitoring the distribution of nitrate in different water bodies. Here we review electrochemical, spectroscopic, and electrical modes of nitrate sensing. It is concluded that, among the various sensors discussed in this review, FET sensors are the most desirable choice. Their sensitivity, ease of use and scope for miniaturisation are exceptional. Advanced functional materials need to be designed to satiate the growing need for environmental monitoring. Different sources of nitrate contamination in ground and surface water can be estimated using different techniques such as nitrate isotopic composition, co contaminants, water tracers, and other specialized techniques. This review intends to explore the research work on remediation of nitrate from wastewater and soil using different processes such as reverse osmosis, chemical denitrification, biological denitrification, ion exchange, electrodialysis, and adsorption. Denitrification proves as a promising alternative over previously reported techniques in terms of their nitrate removal because of its high cost-effectiveness.

Variability of the structure of winter microbial communities in Chelyabinsk lakes

Microorganisms form complex and dynamic communities that play a key role in the biogeochemical cycles of lakes. A high level of urbanization is currently a serious threat to bacterial communities and the ecosystem of freshwater bodies. To assess the contribution of anthropogenic load to variations in the structure of winter microbial communities in lakes, microorganisms of four water bodies of Chelyabinsk region were studied for the first time. We used cultural, chromatography-mass spectrometric, and modern methods of statistical data processing (particularly, multivariate exploratory analysis and canonical analysis of correspondences). The research showed that the composition of winter microbial communities in lakes Chebarkul’, Smolino, Pervoye, and Shershenevskoye Reservoir did not differ significantly between the main phyla of microorganisms. The dominant microorganisms were found to be of the Firmicutes phylum and Actinobacteria phylum. The structure of bacterial communities had special features depending on the characteristics of the water body and the sampling depths. Thus, in the lakes Smolino, Pervoye, and Shershenevskoye Reservoir, an important role was played by associations between microorganisms – indicators of fecal contamination: coliform bacteria and Enterococcus. On the contrary, in Chebarkul’ Lake, members of the genus Bacillus, which are natural bioremediators, formed stable winter associations. However, the differences between water bodies and sampling depths reflected 28.1% and 9.8% of the variability of the winter microbial communities, respectively. The largest contribution (about 60%) to the variability of the structure was made by intra-water processes, which determined the high heterogeneity of samples from different water areas. We assume that an important role in this variability was played by the high anthropogenic impact in a large industrial metropolis. In our opinion, this line of research is very promising for addressing key environmental issues.

Variability of the structure of winter microbial communities in Chelyabinsk lakes

Microorganisms form complex and dynamic communities that play a key role in the biogeochemical cycles of lakes. A high level of urbanization is currently a serious threat to bacterial communities and the ecosystem of freshwater bodies. To assess the contribution of anthropogenic load to variations in the structure of winter microbial communities in lakes, microorganisms of four water bodies of Chelyabinsk region were studied for the first time. We used cultural, chromatography-mass spectrometric, and modern methods of statistical data processing (particularly, multivariate exploratory analysis and canonical analysis of correspondences). The research showed that the composition of winter microbial communities in lakes Chebarkul’, Smolino, Pervoye, and Shershenevskoye Reservoir did not differ significantly between the main phyla of microorganisms. The dominant microorganisms were found to be of the Firmicutes phylum and Actinobacteria phylum. The structure of bacterial communities had special features depending on the characteristics of the water body and the sampling depths. Thus, in the lakes Smolino, Pervoye, and Shershenevskoye Reservoir, an important role was played by associations between microorganisms – indicators of fecal contamination: coliform bacteria and Enterococcus. On the contrary, in Chebarkul’ Lake, members of the genus Bacillus, which are natural bioremediators, formed stable winter associations. However, the differences between water bodies and sampling depths reflected 28.1% and 9.8% of the variability of the winter microbial communities, respectively. The largest contribution (about 60%) to the variability of the structure was made by intra-water processes, which determined the high heterogeneity of samples from different water areas. We assume that an important role in this variability was played by the high anthropogenic impact in a large industrial metropolis. In our opinion, this line of research is very promising for addressing key environmental issues.

Moving bed biofilm reactor developed with special microbial seed for denitrification of high nitrate containing wastewater

Biological denitrification is the most promising alternative approach for the removal of nitrate from wastewater. MBBR inoculated with activated sludge is a widely studied approach, but very few studies have focused on the bioaugmentation of biofilm forming bacteria in MBBR. Our study revealed that the use of special microbial seed of biofilm forming denitrifying bacteria Diaphorobacter sp. R4, Pannonibacter sp. V5, Thauera sp. V9, Pseudomonas sp.V11, and Thauera sp.V14 to form biofilm on carriers enhanced nitrate removal performance of developed MBBR. Various process parameters C/N ratio 0.3, HRT 3 h at Nitrate loading 2400 mg L^-1, Filling ratio 20%, operated with Pall ring carrier were optimized to achieve highest nitrate removal. After 300 days of continuous operation results of whole genome metagenomic studies showed that Thauera spp. were the most dominant and key contributor to the denitrification of nitrate containing wastewater and the reactor was totally conditioned for denitrification. Overall, findings suggest that bench-scale MBBR developed with biofilm forming denitrifying microbial seed accelerated the denitrification process; therefore in conclusion it is suggested as one of the best suitable and effective approach for removal of nitrate from wastewater.

Efficacy of inorganic nitrogen removal by a salt-tolerant aerobic denitrifying bacterium, Pseudomonas sihuiensis LK-618

An aerobic denitrifying bacterium, stain LK-618, was isolated from lake sediment surface and the efficacy of inorganic nitrogen removal was tested. Stain LK-618 identified as Pseudomonas sihuiensis by 16S rRNA sequencing analysis. Trisodium citrate was found to be the ideal carbon source for this strain. When an initial nitrogen sources of approximately 50 mg/L nitrate, ammonium, or nitrite was solely selected as the nitrogen source, the nitrogen removal efficiencies were 91.4% (3.86 mg/L/h), 95.07% (2.47 mg/L/h) and 97.7% (2.41 mg/L/h), respectively. Nitrogen balance analysis revealed that 55.12% NO₃^--N was removed as N₂. Response surface methodology (RSM) analysis demonstrated that the optimal Total Nitrogen (TN) removal ratio for strain LK-618 was under C/N ratio of 12.63, shaking speed of 52.06 rpm, temperature of 28.5 °C and pH of 6.86. In addition, strain LK-618 could tolerate NaCl concentrations up to 20 g/L, and its most efficient denitrification capacity was presented at NaCl concentrations of 0-10 g/L. Therefore, strain LK-618 has potential application on the removal of inorganic nitrogen from saline wastewater under aerobic conditions.

The role of Ulva fasciata in the evolution of the microbial community and antibiotic resistance genes in maricultural sediments

This study explored changes in the microbial community and antibiotic resistance genes (ARGs) in maricultural clam sediment after 3-month co-culture with different densities (0, 5 and 12 g L^-1) of seaweed Ulva fasciata (U. fasciata). The maximum removal rates of NO₃^--N, PO₄^3--P, and inhibition of Vibrio culturability occurred at presence of 12 g L^-1U. fasciata. A significant decrease by 14.0% of the total ARGs was found in control sediment without U. fasciata after separation from the original niches, while the total ARGs further increased by 5.58%and 4.65% at presence of 5 and 12 g L^-1 of U. fasciata in compared with control sediment, respectively, strongly related with Chloroflexi, Spirochaetes, Proteobacteria and Bacteroidetes hosts. In addition, U. fasciata favored the decline of absolute gene numbers of some tetracycline resistance genes (tetPB, tetW, otrA, tetT, tetO) and class 1 integron-integrase gene.

Efficacy of zero nitrous oxide emitting aerobic denitrifying bacterium, Methylobacterium gregans DC-1 in nitrate removal with strong auto-aggregation property

A novel aerobic denitrifying strain Methylobacterium gregans DC-1 was isolated and identified. Strain DC-1 removed 98.4% of nitrate-nitrogen (NO₃^--N) and 80.7% of total organic carbon with initial concentrations of 50 and 2400 mg/l, respectively. The N balance showed that most NO₃^--N was converted to N₂ (62.18%) without nitrous oxide (N₂O) emission. Response surface analysis showed that the optimal conditions for total N removal were carbon (C):N ratio of 18.7, temperature of 26.8 °C, pH of 6.5 and shaking speed of 180 rpm. In combination with the N balance and successful amplification of napA, nirK and nosZ genes, the metabolic pathway was as follows: NO₃^-NO₂^- → NO → N₂O → N₂. Strain DC-1 had strong auto-aggregation rate (maximum 38.7%), produced large amounts of extracellular polymeric substances (EPS; maximum of 781.4 mg/g cell dry weight) and had corresponding strong hydrophobicity (maximum 83.2%). Pearson correlation analysis showed that EPS content and hydrophobicity were significantly positively correlated with auto-aggregation.

Role of heterotrophic aerobic denitrifying bacteria in nitrate removal from wastewater

With the increase in industrial and agricultural activities, a large amount of nitrogenous compounds are released into the environment, leading to nitrate pollution. The perilous effects of nitrate present in the environment pose a major threat to human and animal health. Bioremediation provides a cost-effective and environmental friendly method to deal with this problem. The process of aerobic denitrification can reduce nitrate compounds to harmless dinitrogen gas. This review provides a brief view of the exhaustive role played by aerobic denitrifiers for tackling nitrate pollution under different ecological niches and their dependency on various environmental parameters. It also provides an understanding of the enzymes involved in aerobic denitrification. The role of aerobic denitrification to solve the issues faced by the conventional method (aerobic nitrification-anaerobic denitrification) in treating nitrogen-polluted wastewaters is elaborated.

Characterization of an aerobic denitrifier Pseudomonas stutzeri strain XL-2 to achieve efficient nitrate removal

An aerobic denitrifier was newly isolated and identified as Pseudomonas stutzeri strain XL-2. Strain XL-2 removed 97.9% of nitrate with an initial concentration about 100 mg/L. Nitrogen balance indicates that 12.4% of the initial nitrogen was converted to N₂O, and 62.4% was converted to N₂. Single factor experiments indicate that the optimal conditions for nitrate removal were C/N ratio of 10, temperature of 30 °C and shaking speed of 120 rpm. Sequence amplification indicates that the denitrification genes of napA, nirS, norB and nosZ were present in strain XL-2. Combined with nitrogen balance, strain XL-2 presents the metabolic pathway of NO₃^- → NO₂^- → NO  →  N₂O → N₂ under aerobic conditions. The expression of napA and nirS might be responsible for the tolerance of dissolved oxygen by strain XL-2 during denitrification process.

Pyrosequencing reveals microbial community dynamics in integrated simultaneous desulfurization and denitrification process at different influent nitrate concentrations

Integrated simultaneous desulfurization and denitrification (ISDD) process has proven to be feasible for the coremoval of sulfate, nitrate, and chemical oxygen demand (COD). In this study, we aimed to reveal the microbial community dynamics in the ISDD process with different influent nitrate (NO₃^-) concentrations. For all tested scenarios, full denitrification was accomplished while sulfate removal efficiency decreased along with increased influent NO₃^- concentrations. The proportion of S⁰ to influent SO₄^2- maintained a low level (5.6-17.0%) regardless of the increased influent NO₃^- concentrations. Microbial community analysis results showed that higher influent NO₃^- concentrations affected the microbial community structure greatly. Phyla Proteobacteria, Spirochaetae, Firmicutes, Synergistetes, and Chloroflexi dominated in all the community compositions, of which Proteobacteria exhibited a clear difference among eight microbial samples. Members of δ-Proteobacteria, with 16S rRNA gene sequences related to Desulfobulbus, were clearly decreased at influent NO₃^- = 3000 and 3500 mg/L, suggesting an inhibitory effect of NO₃^- on sulfate reduction. In contrast, as influent NO₃^- concentration increased, microbial community was notably enriched in γ-Proteobacteria and ε-Proteobacteria, which revealed the enrichment of 16S rRNA gene sequences related to Pseudomonas (γ-Proteobacteria), and Arcobacteria and Sulfurospirillum (ε-Proteobacteria).

Screening of assimilatory and dissimilatory denitrifying microbes isolated from nitrate-contaminated water and soil

Nitrate NO(3)(-) contamination of groundwater resources is a serious problem. Such contamination in drinking water is regulated by environmental agencies around the world since at higher concentrations it can cause several health problems in infants. The aim of the present study was to identify the efficiency of the bacterial species isolated from nitrate-contaminated water and soil samples collected from Erode, Salem, Dharmapuri, and Krishnagiri districts of Tamilnadu, India. There are 74 morphologically different bacterial species were isolated and evaluated by a dissimilatory and assimilatory nitrate reduction test. Among the isolates, DW-27, DS-29, DS-31, DS-45, DS-46, and DS-47 were found to be potential dissimilatory and EW-6, ES-15, DS-39, DS-41, DS-48, DS-55, and SW-59 were potential assimilatory nitrate reducers. The results of bacterial analysis revealed that the isolated nitrate-reducing bacteria belonged to the genera Bacillus (64%) and Corynebacterium (22%), family Enterobacteriaceae (11%), and genus Alcaligenes (3%). This observation has led to the conclusion that these bacterial species showed efficiency of nitrate removal.

In situ bioremediation of surface waters by periphytons

Environmentally benign and sustainable biomeasures have become attractive options for the in situ remediation of polluted surface waters. In this paper, we review the current state of reported experiments utilizing naturally occurring periphyton. These are microbial communities consisting of heterotrophic and photoautotrophic microorganisms that are reportedly capable of remediating surface waters which suffer from pollution due to a variety of contaminants. In our review, we focus on four aspects of bioremediation: multiple contaminant removal, the processes involved in contaminant removal, successful cell immobilization technologies and finally, the consideration of safety in aquaculture. It has been noted that recent developments in immobilization technologies offer a fresh approach facilitating the application of periphyton. The use of periphyton biofilm overcomes several disadvantages of single species microbial aggregates. The inclusion of periphyton, as a stable micro-ecosystem, is a promising in situ strategy to restore decimated surface water ecosystems.

Viscera-associated bacterial diversity among intertidal gastropods from Northern-Atlantic coast of Portugal

Culture-dependent evaluation of the bacteria was carried out on gastropods, such as Monodonta lineata, Gibbula umbilicalis, Nucella lapillus and Patella intermedia, and the environmental samples (biofilm and surrounding sea water) collected from six different locations of Northern Portugal coastal area to investigate the interactions between the microbes in the viscera of gastropods and in the environment. A total of 141 isolates and 39 operational taxonomic units were identified. Phylogenetic analysis based on the 16S rRNA gene showed that bacterial isolates are highly diverse and most of them were found in other marine environment. The observed bacterial diversity was distributed over five different classes (Gammaproteobacteria, Alphaproteobacteria, Flavobacteria, Bacilli and Actinobacteria) with the greatest number of 16S rRNA gene sequence derived from the Gammaproteobacteria (77 %). Vibrio is found to be the dominant one among the different bacterial species isolated. The results suggest that the microorganisms in the environment are maintained in the viscera of the gastropods which may have a key role in the metabolic functions.

16S rDNA-based metagenomic analysis of bacterial diversity associated with two populations of the kleptoplastic sea slug Elysia chlorotica and its algal prey Vaucheria litorea

The molluscan sea slug Elysia chlorotica is best known for its obligate endosymbiosis with chloroplasts (= kleptoplasty) from its algal prey Vaucheria litorea and its ability to sustain itself photoautotrophically for several months. This unusual photosynthetic sea slug also harbors an array of undescribed bacteria, which may contribute to the long-term success of the symbiosis. Here, we utilized 16S rDNA-based metagenomic analyses to characterize the microbial diversity associated with two populations of E. chlorotica from Halifax, Nova Scotia, Canada, and from Martha's Vineyard, Massachusetts, USA. Animals were examined immediately after collection from their native environments, after being starved of their algal prey for several months, and after being bred in the laboratory (second-generation sea slugs) to characterize the effect of varying environmental and culturing conditions on the associated bacteria. Additionally, the microbiome of the algal prey, laboratory-cultured V. litorea, was analyzed to determine whether the laboratory-bred sea slugs obtained bacteria from their algal food source during development. Bacterial profiles varied between populations and among all conditions except for the F2 laboratory-bred samples, which were similar in diversity and abundance, but not to the algal microbiome. Alpha-, beta-, and gamma-proteobacteria dominated all of the samples along with Actinobacteria, Bacilli, Flavobacteria, and Sphingobacteria. Bacteria capable of polysaccharide digestion and photosynthesis, as well as putative nitrogen fixation, vitamin B(12) production, and natural product biosynthesis were associated with the sea slug and algal samples.

The removal of nutrients from non-point source wastewater by a hybrid bioreactor

The aim of this project was to establish an economical and environmentally benign biotechnology for removing nutrients from non-point source wastewater. The proposal involves a hybrid bioreactor comprised of sequential anaerobic, anoxic and aerobic (A(2)/O) processes and an eco-ditch being constructed and applied in a suburban area, Kunming, south-western China, where wastewater was discharged from an industrial park and suburban communities. The results show that the hybrid bioreactor fosters heterotrophic and autotrophic microorganisms. When the hydraulic load is 200 m(3) per day with the running mode in 12h cycles, the removal efficiencies of the nutrients were 81% for TP, 74% for TDP, 82% for TN, 79% for NO(3)-N and 86% for NH(4)-N. The improved bacterial community structure and bacterial habitats further implied enhanced water quality and indicates that the easily-deployed, affordable and environmentally-friendly hybrid bioreactor is a promising bio-measure for removing high loadings of nutrients from non-point source wastewater.

Effect of pine bark and compost on the biological denitrification process of non-hazardous landfill leachate: focus on the microbiology

In an attempt to optimize the cost-efficiency of landfill leachate treatment by biological denitrification process, our study focused on finding low-cost alternatives to traditional expensive chemicals such as composted garden refuse and pine bark, which are both available in large amount in South African landfill sites. The overall objective was to assess the behaviour of the bacterial community in relation to each substrate while treating high strength landfill leachates. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests with immature compost and pine bark. High strength leachate was simulated using a solution of water and nitrate at a concentration of 500 mg l(-1). Results suggest that pine bark released large amounts of phenolic compounds and hydroxylated benzene rings, which both can delay the acclimatization time and inhibit the biological denitrification (only 30% efficiency). Furthermore, presence of potential pathogens like Enterobacter and Pantoea agglomerans prevents the applicability of the pine bark in full-scale operations. On the other hand, lightly composted garden refuse (CGR) offered an adequate substrate for the formation of a biofilm necessary to complete the denitrification process (total nitrate removal observed within 7 days). CGR further contributed to a rapid establishment of an active consortium of denitrifiers including Acinetobacter, Rhizobium, Thermomonas, Rheinheimera, Phaeospirillum and Flavobacterium. Clearly the original composition, nature, carbon to nitrogen ratio (C/N) and degree of maturity and stability of the substrates play a key role in the denitrification process, impacting directly on the development of the bacterial population and, therefore, on the long-term removal efficiency.

Nitrogen removal capability through simultaneous heterotrophic nitrification and aerobic denitrification by Bacillus sp. LY

The heterotrophic nitrification and aerobic denitrification capabilities of Bacillus sp. LY were investigated under the aerobic condition. The results indicate that Bacillus sp. LY is not only a heterotrophic nitrifier, but also an aerobic denitrifier. Experiments were carried out in an attempt to determine and quantify the contribution of heterotrophic nitrification and aerobic denitrification to total N removal. By taking the nitrogen balance under the culture condition of 41.1 mg/L of initial NH(4+)-N at a C/N ratio of 15 in 96 h, 8.0% of the initial NH(4)+-N still remained in the medium in the forms of hydroxylamine, nitrite, nitrate and organic N; 40.5% of NH(4+)-N was converted to biomass and 45.9% of NH(4+)-N was estimated to be finally removed in the formation of N2. This conversion of ammonium to N2 with the intermediate formation of N2O under the aerobic condition was confirmed by gas chromatography. Single step nitrogen removal by simultaneous heterotrophic nitrification and aerobic denitrification has great potential in wastewater treatment.

Nitrate removal by electro-bioremediation technology in Korean soil

The nitrate concentration of surface has become a serious concern in agricultural industry through out the world. In the present study, nitrate was removed in the soil by employing electro-bioremediation, a hybrid technology of bioremediation and electrokinetics. The abundance of Bacillus spp. as nitrate reducing bacteria were isolated and identified from the soil sample collected from a greenhouse at Jinju City of Gyengsangnamdo, South Korea. The nitrate reducing bacterial species were identified by 16s RNA sequencing technique. The efficiency of bacterial isolates on nitrate removal in broth was tested. The experiment was conducted in an electrokinetic (EK) cell by applying 20V across the electrodes. The nitrate reducing bacteria (Bacillus spp.) were inoculated in the soil for nitrate removal process by the addition of necessary nutrient. The influence of nitrate reducers on electrokinetic process was also studied. The concentration of nitrate at anodic area of soil was higher when compared to cathode in electrokinetic system, while adding bacteria in EK (EK+bio) system, the nitrate concentration was almost nil in all the area of soil. The bacteria supplies electron from organic degradation (humic substances) and enhances NO(3)(-) reduction (denitrification). Experimental results showed that the electro-bio kinetic process viz. electroosmosis and physiological activity of bacteria reduced nitrate in soil environment effectively. Involvement of Bacillus spp. on nitrification was controlled by electrokinetics at cathode area by reduction of ammonium ions to nitrogen gas. The excellence of the combined electro-bio kinetics technology on nitrate removal is discussed.