Specific Removal Rate Research Articles

Enhanced anammox-mediated nitrogen removal in bioelectrochemical systems at prolonged negative electrode potentials.

Bioelectrochemical anaerobic ammonium oxidation (anammox) systems allow eco-friendly removal of nitrogen from reject wastewater coming from biogas processing as the anammox bacteria have previously shown to have c-type cytochromes acting in the extracellular electron transport (EET) mechanism between the bacteria and electrode. The anammoxosome compartment present in anammox bacteria features a highly curved membrane and contains tubular structures along with electron-dense particles that contain iron, which could enhance the process of EET and enhance nitrogen removal by properly applied potentials. In this study, nitrogen removal was investigated in the electrostimulated anammox nitrogen removal (EANR) cells operated comparatively at open circuit and at applied potentials of - 300mV, - 500mV, and - 700mV vs. Ag/AgCl. At peak performance (at - 700mV vs. Ag/AgCl), the EANR showed up to 140% higher specific nitrogen removal rate (11.2 ± 0.3g N/m2/day) compared to the control reactors without applied potential (8.3 ± 0.2g N/m2/day). The microbial community on the cathode with the applied potential had a higher relative proportion of unclassified Candidatus Brocadia (7.5%) compared to inoculum (> 0.01%), in contrast to cathode without potential (0.74%) and control (0.2%). The EANR system demonstrated to achieve ammonium and nitrite removal efficiencies of 91% and 53%, respectively, during a 24-h test cycle from an initial TN concentration of ~ 100mg N/L. After 150h, it achieved complete removal of all nitrogen compounds, reaching a 100% removal efficiency. The EANR would be very useful in the establishment of field-scale bilateral anammox-bioelectrochemical technology combining microbial fuel cell bioanodes and EANR biocathodes for wastewater treatment.

Cyclic biomachining of copper: Maximum metal removal rate with minimum depleted solution

Bacterially assisted leaching has been proposed for many innovative applications, such as urban mining or micromachining, but many technical challenges including substrate toxicity and downstream processing of the leach liquor must be solved before its industrial implementation. This study was conducted with the final goal of improving the average specific metal removal rate (SMRR) and reducing the amount of depleted solution generated in the leaching process of copper workpieces, with special attention paid to the detection of microbial activity inhibition.The copper leaching rate is almost entirely dependent upon the Fe3+ concentration with Fe3+/Fe2+ ratios higher than 0.3, after which A. ferrooxidans oxidation action becomes relevant. In both biotic and abiotic experiments, the SMRR peaked after the first hour of treatment, and it decreased sharply after three hours. A consecutive process alternating bioleaching and oxidant regeneration stages was proposed to improve performance, which considerably reduced both the time needed to dissolve a certain amount of metal and waste generation. The decrease in copper removal (25 %) and the increase in the time required for oxidant regeneration after five leaching cycles (longer than 90 h) were attributed to bacterial inhibition in the presence of 10.7 g Cu2+ L−1, which was established as the limiting metal concentration for reusing the biologically active solution.

Mathematical Model of Vibration-Centrifugal Processing of Parts Using Loose Abrasive

The article presents some new theoretical and experimental solution of a scientific and applied problem of technological support for vibratory centrifugal processing of complex-profiled parts in a bulk abrasive environment. This solution aims to increase productivity while ensuring the desired quality of the processed surfaces. The authors have developed a mathematical model that describes the action of abrasive particles on the surface of the parts, taking into account the parameters of the granular abrasive medium based on Voigt’s law. This allows the description of dynamic processes in the processing environment for a wide range of material types. The natural frequencies of oscillations of the processed medium layer have been determined, which depend on the amplitude of its vibrations for different densities of soft and hard materials of the processed medium and the medium with linear-elastic properties. The methodology includes the use of test equipment to conduct experimental research on the process, which involves determining changes in specific metal removal rates and surface roughness using the frequency converter Altivar 71 with the PowerSuite v.2.5.0 software.

Response of aerobic granular sludge under acute inhibition by polystyrene microplastics: Activity, aggregation performance, and microbial analysis

In this study, the activity, aggregation performance, microbial community and functional proteins of aerobic granular sludge (AGS) in response to acute inhibition by different concentrations of polystyrene microplastics (PS-MPs) were investigated. As the PS-MPs concentration increased from 0 mg/L to 200 mg/L, the specific nitrogen removal rate and the activity of enzymes were inhibited. The inhibition of specific nitrite reduction rate (SNIRR) and specific nitrate reduction rate (SNRR) was most obvious at the PS-MPs concentration of 100 mg/L, and that of nitrite reductase (NIR) and nitrate reductase (NR) was most obvious at the concentration of 50 mg/L. But the inhibitory effects were mitigated at the concentration of 200 mg/L. The increase of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) indicated that the cells were damaged with the increase of PS-MPs concentration. The content of proteins and polysaccharides in extracellular polymeric substances (EPS) decreased, especially the polysaccharides were more affected. Analysis of zeta potential, hydrophobicity and surface thermodynamics of AGS revealed that addition of PS-MPs was unfavorable for AGS aggregation. It was also found that bacteria genera associated with EPS secretion and nitrogen removal functions were inhibited, while functions associated with cell metabolism, protein synthesis and cell repair were enhanced. This also confirmed that acute inhibition of PS-MPs had a detrimental effect on the nitrogen removal and aggregation performance of AGS. This study can provide theoretical support for the operation of AGS reactors under microplastics impact load.

Grinding optimization using nondestructive testing (NDT) and empirical models

Proper choice of grinding parameters is important because productivity is limited by the possibility of grinding burns. Nondestructive testing (NDT), as Barkhausen noise (BN), can provide a tool for determining parameter limits. However, BN requires a threshold value for approval and requires multiple experiments to provide grinding parameters corresponding to high productivity. Other limiting process outputs, such as surface roughness, need to be fulfilled. In this study, process modeling, experiments and NDT are combined to produce optimized grinding parameters that fulfill the process output requirements and reduces the number of experiments for a new component. Design of experiments (DOE) grinding tests were performed with cutting power measurements. The outcome was verified with BN and surface roughness outputs. Then, using polynomial fitting, regression models were fitted into the BN, surface roughness and cutting power data. Malkin’s temperature model was utilized to analyze the temperature rise in the grinding zone. Combining all models, a grinding productivity optimization problem was defined from a specific material removal rate perspective. The polynomial fits of BN results and cutting power showed good prediction capability, as expressed by their R2 values. The study provides a novel method to choose grinding parameters to produce quality parts with minimal loss of productivity.

Characterization of the performance of microbial-based metalworking fluids in grinding using cell analogues

In grinding, the applied metal working fluid plays a decisive role in terms of minimizing (i) process energy consumption and (ii) thermal impact on surface and subsurface of the workpiece owing to lubrication and cooling effect of the fluid. For microbial-based metalworking fluids (MWFs), the presence of bacterial cells has been shown to be beneficial for MWF performance in grinding. The interaction of the cell bodies with other components of MWFs and their influence on the performance in grinding operations has not been investigated so far due to the difficulty of ensuring defined boundary conditions. As a novel approach, the present work investigates the individual influence of the presence of cell analogues and other MWF properties on the performance of water-based MWF in surface grinding of ball bearing steel. The evaluation is based on the specific material removal rate, which, when exceeded in the process, results in the onset of white layer formation. It has been shown that the physical presence of bacterial cells and extracellular polymeric substances have positive effects, while droplet size has only a minor influence on MWF performance.

Quantification of micro-damage evolution process in ceramics through extensive analysis of multi-source heterogeneous data

Due to the randomness of hard and brittle material damage evolution, assessing damage and interpreting mechanisms is challenging. This study focuses on analyzing material damage mechanisms by employing extensive multi-source heterogeneous data to extract quantitative information. A machine vision-based method for detecting and assessing defects in ceramics was proposed, achieving 98 % accuracy. Leveraging this method in scratching experiments, the progression of damage and micro-failure mechanisms in Si3N4 was investigated through the analysis of defect area distribution, force and acoustical signals. Results revealed that the distribution of defect areas conforms to a three-parameter Weibull distribution. At scratch depths of 0.01, 0.02 mm, approximately 90 % of damage accumulated within 1e2–1e4 μm2; conversely, 0.03–0.06 mm led to a decrease to 30 – 40 %. Extensive crack propagation occurs within 0.02–0.03 mm, resulting in the intersecting formation of spalling blocks. Damage evolution occurs in three stages: shallow and small cracks with scattered spalling blocks in the first stage, deep and long cracks with continuous and irregularly shaped spalling blocks in the second stage, and nearly no cracks with continuous and regularly shaped blocks in the third stage. This study not only proposes an efficient method to detect and evaluate ceramic defects, but also deeply understands the evolution process of material damage mechanism. Considering defect distribution and statistical trends, this research not only provide guidance for the optimization of machining parameters, especially in the scene of specific precision and high removal rate. At the same time, the damage evolution and failure mechanism of Si3N4 provide useful experimental basis and data support for deepening the understanding of material behavior during ultra-precision grinding.

Use of Heat-killed Aspergillus ochraceus NRRL 3174 Discs as Biosorbent for petroleum Removal

The purpose of this work was to evaluate the petroleum sorption capacity of heat-killed fungal discs obtained from Aspergillus ochraceus strain. Effect of various parameters such as biosorbent dose (0.5g-2.5g/100mL), petroleum concentration (0.5-5%), pH (4.0-8.0), contact time (1-12h) and re-usability of biosorbent (1-6) were investigated. Accordingly, the highest biosorption capacity was obtained with 1% petroleum concentration, 1.5 g/100mL heat-killed fungal discs, 10h contact time at pH: 5.0 and room temperature. Additionally, each disc was able to actively use for at least 6 more cycles in biosorption experiments. The specific removal rate was calculated as 0.114 day−1, the rate constant and half-life period were also 1.609 day-1, t1/2 = 0.431, respectively. The kinetic study was described by the pseudo-second order model and the equilibrium modeling was found to be well fitted with Langmuir isotherm. The biosorbent(s) were characterized by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM). Over 80% removal of long-chain n-alkanes by the heat-killed fungal discs was confirmed by GC-MS analysis. Since there has been no similar study investigating the sorption of petroleum with heat-killed Aspergillus ochraceous discs, this novel bio-based sorbent with its low cost, environmentally friendly and easy-to-apply properties can be used in advanced biosorption studies.

Grey Relational Analysis-based Interactions of Machining Parameters for Optimal Process Response: An Experimental Initiative

This study, investigated the optimal combining of tool nose radius and cutting variables for the overall performance for both AISI 4140 steel and IS-2062 steel. The both materials were machined on a centre lathe and measurements were taken. The data collected was analysed through grey relational analysis. Results showed that grey relational optimal interactions of machining parameters for the overall performance were: N R (0.35mm), U o (0.5mm), V w (65m/min), R f (0.2mm/rev) for both materials. Also, grey relational grade improved by 1.2767 (24.69%) for the expected optimal design for AISI-4140 steel, and improved by 1.7417 (33.68%) for the expected optimal design for IS-2062 steel. The expected responses were: cutting power 11.157 kW, specific metal removal rate 9.710 mm3/min.kW, cutting force 173.110 N, thrust force 77.207 N, shear force 124.838 N, surface roughness 5.00 , and Shear work 7945.9kNm/min for AISI-4140 steel; and cutting power 5.544 kW, specific metal removal rate 19.541 mm3/min.kW, cutting force 86.074 N, thrust force 39.440 N, shear force 65.688 N, surface roughness 6.165 , and shear work 4158.67 KNm/min for IS-2062 steel. Grey relational analysis reduced the factors affecting on the dependent variables to feed rate and depth of cut.

Bioaugmentation Potential Investigation Using a Phenol Affinity Analysis of Three Acinetobacter Strains in a Multi-Carbon-Source Condition

Bioaugmentation potential and phenol substrate affinity in a multi-carbon-source condition for three Acinetobacter strains (Acinetobacter towneri CFII-87, Acinetobacter johnsonii CFII-99A and Acinetobacter sp. CFII-98) were demonstrated. First, the phenol biodegradation ability of the strains was analyzed in batch experiments with phenol as the sole carbon source. All strains degraded phenol at 100 and 500 mg·L−1 initial concentrations; the maximum specific growth rates were 0.59 and 0.30 d−1 for A. towneri CFII-87, 0.50 and 0.20 d−1 for A. johnsonii CFII-99A, and 0.64 and 0.29 d−1 for A. sp. CFII-98, respectively. For the two tested phenol concentrations, no lag phase was observed for the A. towneri CFII-87 strain, A. sp. CFII-98 presented 4 h and 8 h lag phase, while A. johnsonii CFII-99A presented 3 h and 12 h lag phases. Phenol carbon source dependency of the strains was tested in a multi-carbon-source condition (on phenol-rich synthetic wastewater), both for individual strains and for a consortium prepared as an equal mixture of the three strains. The strains A. towneri CFII-87 and A. sp. CFII-98 and the consortia degraded phenol in 16 h while there was no other significant carbon source consumption during the 48 h trial, as shown by the constant non-phenolic residual chemical oxygen demand (COD) and volatile suspended solids (VSS) concentration after the depletion of phenol. The strain A. johnsonii CFII-99A, however, consumed phenol within 24 h and a further decrease in non-phenolic COD and increase in biomass was also observed upon the depletion of phenol. The highest specific phenol removal rate of 282.11 mg phenol·g VSS∙h−1 was observed in the case of the strain A. towneri CFII-87, followed by A. sp. CFII-98, the consortium and A. johnsonii CFII-99A with 178.84, 146.76 and 141.01 mg phenol·g VSS∙h−1, respectively. Two bacterial strains (A. towneri CFII-87, A. sp. CFII-98) presented a strong affinity to phenol, utilizing it as a primary carbon source, and thus, their use in the bioaugmentation of wastewater bioreactors indicated the viable potential to increase the phenol removal rate of these systems.

Investigation on high-shear and low-pressure grinding with CBN liquid-body-armor-like wheel for Inconel718

In this study, a CBN liquid-body-armor-like grinding wheel was developed for high-shear and low-pressure (HSLP) grinding of Inconel718 alloy. The material removal mechanism of the novel CBN liquid-body-armor-like wheel was introduced in detail. Particle clustering effect of the new wheel was studied via the finite element method. A series of grinding tests were carried out to investigate the grinding performance under the various conditions. It was shown that the surface roughness Ra of the ground workpiece decreased from initial 0.3 to 0.094 μm. Simultaneously, the specific material removal rate of 1.069 × 105 μm3/mm·s was attained. The power spectral density function (PSDF) was employed to reveal the percentage of waviness and roughness of the surface profile, which was mainly concentrated in 0–40k Hz as compared with 60–120k Hz before grinding. It indicated that particle clustering effect was generated in the grinding zone. Besides, the maximum peak amplitude of the cross-correlation function coefficient of the ground workpiece surfaces before and after grinding was less than 0.3. The original scratches were completely removed. New and smooth textures generated after grinding. The experimental results demonstrated that the newly developed CBN liquid-body-armor-like grinding wheel was effective for surface finishing of the Inconel718 workpiece.

Mitigation of N2O emissions via enhanced denitrification in a biological landfill leachate treatment using external carbon from fermented sludge

The effects of an external carbon source (C-source) on the mitigation of N2O gas (N2O(g)) emissions from landfill leachate were investigated via enhanced denitrification using anaerobically fermented sewage sludge. Anaerobic fermentation of sewage sludge was conducted under thermophilic conditions with progressively increasing organic loading rates (OLR). Optimal conditions for fermentation were determined based on the efficiency of hydrolysis and the concentrations of sCOD and volatile fatty acids (VFAs) as follows: at an OLR of 40.48 ± 0.77 g COD/L·d with 1.5 days of solid retention time (SRT), 14.68 ± 0.59% of efficiency of hydrolysis, 14.42 ± 0.30 g sCOD/L and 7.85 ± 0.18 g COD/L of VFAs. Analysis of the microbial community in the anaerobic fermentation reactor revealed that degradation of sewage sludge might be potentially affected by proteolytic microorganisms producing VFAs from proteinaceous materials. Sludge-fermentate (SF) retrieved from the anaerobic fermentation reactor was used as the external C-source for denitrification testing. The specific nitrate removal rate (KNR) of the SF-added condition was 7.54 mg NO3−N/g VSS·hr, which was 5.42 and 2.43 times higher than that of raw landfill leachate (LL) and a methanol-added condition, respectively. In the N2O(g) emission test, the liquid phase N2O (N2O–N(l)) of 20.15 mg N/L was emitted as N2O(g) of 19.64 ppmv under only LL-added condition. On the other hand, SF led to the specific N2O(l) reduction rate (KN2O) of 6.70 mg N/g VSS hr, resulting in mitigation of 1.72 times the N2O(g) emission compared to under the only-LL-added condition. The present study revealed that N2O(g) emissions from biological landfill leachate treatment plants can be attenuated by simultaneous reduction of NO3−N and N2O(l) during enhanced denitrification via a stable supply of an external C-source retrieved from anaerobically fermented organic waste.

Laser Ablation Study of Cutting Ceramics with Consideration of the Beam Inclination Angle

Silicon alumina nitride (SiAlON) and alumina toughened zirconia (ATZ) ceramics are applied for ceramic cutting tools to machine, e.g., cast iron, nickel base alloys and other difficult-to-machine materials. The state of the art technology for manufacturing of the cutting tool geometry is grinding. Laser processing of ceramics is already studied in terms of ablation rate and roughness evaluation with the application of dental implant manufacturing. In the present study, laser machining of the mentioned ceramics is explored with a laser beam source of 1064 nm wavelength and 10 ps pulse duration (FWHM). The angle dependent energy specific removal rate is described in a model and the optimal pulse fluence for the different materials and the irradiation angles can be derived. For processing at irradiation angle of up to 75° no decrease of the relative absorption could be observed. For ATZ, lowest surface roughness is determined for both, orthogonal and quasi-tangential processing angle. For SiAlON, the roughness decreases constantly for higher tilt angles. A significant difference in the material answer with change of the sample composition can be detected and the results show the potential of further developing SiAlON ceramics towards machineability for laser ablation.

Application of Chlorella vulgaris for nutrient removal from synthetic wastewater and MBR-treated bio-park secondary effluent: growth kinetics, effects of carbon and phosphate concentrations

Application of Chlorella vulgaris for polishing secondary effluent of a wastewater treatment (containing C, N and P) was investigated. As a first step, batch experiments were conducted in Bold's Basal Media (BBM) to quantify the effects of orthophosphates (0.1-107mg/L), organic carbon (0-500mg/L as acetate) and N/P ratio on the growth of Chlorella vulgaris. The results revealed that the orthophosphate concentration was found to control the removal rates of nitrates and phosphates; however, both were effectively removed (> 90%) when the initial orthophosphate concentration was 4-12mg/L. The maximum nitrate and orthophosphate removals were observed at an N:P ratio of ~ 11. However, the specific growth rate (µ) was significantly increased (from 0.226 to 0.336g/g/day) when the initial orthophosphate concentration was 0.1-4.3mg/L. On the other hand, the presence of acetate had significantly improved the specific growth and specific nitrate removal rates of Chlorella vulgaris. The specific growth rate increased from 0.34g/g/day in a purely autotrophic culture to 0.70g/g/day in the presence of acetate. Subsequently, the Chlorella vulgaris (grown in BBM) was acclimated and grown in the membrane bioreactor (MBR)-treated real-time secondary effluent. Under the optimised conditions, 92% nitrate and 98% phosphate removals (with a growth rate of 0.192g/g/day) were observed in the bio-park MBR effluent. Overall, the results indicate that coupling Chlorella vulgaris as a polishing treatment in existing wastewater treatment units could be beneficial for highest level of water reuse and energy recovery goals.

Visible Light Activated Fe-N-SiO2/TiO2 Photocatalyst: Providing an Opportunity for Enhanced Photocatalytic Degradation of Antibiotic Oxytetracycline in Aqueous Solution

To probe advantages in Fe-N-SiO2/TiO2 nanocomposite system, the visible photocatalytic degradation of the nonbiodegradable antibiotic oxytetracycline (OTC) by unsupported TiO2 and its modified composites by incorporating each of the Fe, N, and SiO2 dopants under a series of conditions were investigated. The structural and optical properties as well as the morphology of the prepared nanocomposites were also characterized applying Fourier transform infrared (FT-IR), X-ray diffraction, photoluminescence spectroscopy, UV-visible diffuse reflectance spectra and field emission scanning electron microscopy/Energy-dispersive X-ray spectroscopy (FESEM/EDX). In order to develop two models portraying appropriate functional relationships between two main responses (OTC removal efficiency and its specific removal rate (SRR)) and four numerical variables (OTC concentration, catalysis loading, initial pH and reaction time), two separate multivariate analysis pathways under response surface methodology (RSM) were taken. The results obtained all came down to the maximum SRR (220 OTC mg OTC removed/g cat. h) found at the maximum catalyst dosage of 1.5 g/l, and acidic pH of 3 after 0.5 h. Furthermore, the Fe-N-SiO2/TiO2 proved a stable photocatalytic activity during three subsequent reusability experiments, shedding light on its reliable potential for future application.

Response of partial nitritation/anammox granules to biodegradable organic input in bacterial community and functions

Biodegradable organic input is considered as a critical factor influencing the stability of the partial nitritation/anammox (PN/A) process for autotrophic nitrogen removal. In this study, the response of PN/A granules to stepwise increasing the organic loading rate (OLR) was investigated in a continuous-flow reactor, according to the nitrogen removal activity, sludge morphology, bacterial community composition and nitrogen cycle pathways. Results show that the increased OLR from 0.47 to 3.36 kg·m−3·d−1 with different influent organic and nitrogen (COD/N) ratios from 0.25 to 1.0 caused the specific nitrogen removal rate of the granules to decrease by 60.9 %, which was accompanied by a looser granular structure and poor settling property. Inorganic feeding was then used to recover the performance of the granules, and the removal of total inorganic nitrogen rose to 78.4 % at a nitrogen loading rate of 3.36 kg·m−3·d−1. Based on high-throughput sequencing, biodegradable organics shaped the bacterial community structure in the granules by enriching symbiotic heterotrophs (such as Chloroflexi, Proteobacteria and Bacteroidetes) and washing out the anammox biomass. Candidatus Kuenenia dominated the anammox biomass, while Candidatus Brocadia was also found, which coordinated with aerobic ammonium-oxidizing bacteria (Nitrosomonas) in the PN/A process. Metagenomic analysis indicates that biodegradable organic stress and performance recovery significantly changed the composition of nitrogen cycle-related genes in the granules, in terms of a lower capacity of anammox and higher risk of nitrous oxide emission. These findings provide insight into the self-adaption strategy of PN/A granules in response to biodegradable organic input into wastewater treatment engineering applications.

Evaluation of electroactive denitrifiers at different potentials, temperatures and buffers based on microcalorimetry

Electroactive denitrifiers contribute to the nitrate removal in a bioelectrochemical system, but their metabolism and growth parameters remain vague. In this study, microcalorimetry as a suitable method was used to evaluate the metabolism and growth parameters of electroactive denitrifiers at different cathode potentials, temperatures and buffer solutions. The suitable cathode potential and temperature for electroactive denitrifiers were deemed as −100 mV and 30 °C, respectively. The suitable buffer was found to be phosphate buffer solution but can be replaced by bicarbonate buffer solution. When cultivated with bicarbonate buffer solution at −100 mV and 30 °C, electroactive denitrifiers achieved a specific nitrate removal rate of 2.20 ± 0.08 × 10−10 mg NO3−-N·(min·cell)−1 and two growth rate constants (k1 = 0.0051 ± 0.0004 min−1, k2 = 0.0030 ± 0.0004 min−1), with gaseous nitrogen as the end product. The bioelectrochemical denitrification behaved as a two-step process, in which the nitrite reduction to gaseous nitrogen was the rate-limiting step.

Characterization of Pseudochloris wilhelmii potential for oil refinery wastewater remediation and valuable biomass cogeneration

The microalgae of the genus Pseudochloris/Picochlorum are characterized by fast growth, and wide nutrient (type and concentration) and salinity tolerance, all contributing towards exploration of their use in high-density biomass production and wastewater bioremediation. In this study, removal of nitrogen and phosphorus nutrients from oil refinery wastewater was monitored during growth of the marine eukaryotic microalgae Pseudochloris wilhelmii, with emphasis on biochemical analyses of its biomass quality to evaluate suitability for biodiesel production. A series of growth experiments under various nutrient and light regimes were performed in a temperature range of 20-30°C to evaluate nutrient removal and biomass growth dependence on temperature. The highest removal rate of dissolved inorganic nitrogen reached under the given experimental conditions was 0.823 mmol/(gday) accompanied by the corresponding biomass productivity of 115.2 mg/(Lday). Depending on light and temperature, the final lipid concentration ranged 181.5 – 319.8 mg/L. Furthermore, increase in nutrient load decreased the maximum specific growth rate by 25%, and the maximum specific removal rate of the dissolved inorganic nitrogen by 19%, whereas the duration of bioremediation process was nearly doubled. In contrast, constant light exposure expedited the nitrogen removal, i.e. bioremediation process, by almost 40%, while supporting over three times higher biomass productivity and the highest maximum specific growth rate of 0.528 g/(gday). The conditions favoring the highest nitrogen removal and highest toxicity reduction in oil refinery wastewater are met at 24°C and 130 µmol phot/(m2s). The highest proportion of carbon-binding to the P. wilhelmii biomass was noticed under the same conditions, thus indicating them as the most favorable conditions for hydrocarbon removal as well as for CO2 sequestration. Pseudochloris wilhelmii therefore represents a promising candidate for oil refinery wastewater remediation and valuable biomass cogeneration on a large-scale.

PHA stimulated denitrification through regulation of preferential cofactor provision and intracellular carbon metabolism at different dissolved oxygen levels by Pseudomonas stutzeri

Denitrification, a typical biological process mediated by complex environmental factors, i.e., carbon sources and dissolved oxygen (DO), has attracted great attention due to its contribution to the control of eutrophication and the biochemical cycling of nitrogen. However, the effects of carbon source on electron distribution and enzyme expression for enhanced denitrification under competition of electron acceptors (DO and nitrate) remain unclear. Here, we profile the carbon metabolic pathway of polyhydroxybutyrate (PHB) and glucose (Glu) at high and low DO levels (50% and 10% saturated DO, respectively). It was found that PHB enhanced the growth of Pseudomonas stutzeri (model denitrifying bacterium) and improved the specific nitrogen removal rate (SNRR) at all DO levels. The functional proteins had a better affinity for the cofactor nicotinamide-adenine dinucleotide (NADH) than for nicotinamide adenine dinucleotide phosphate (NADPH); thus, more electrons were involved in nitrogen reduction and intracellular PHB production in the PHB groups than in the Glu groups. Furthermore, the expression difference of enzymes in glucose and PHB metabolism was demonstrated by metaproteomic and target protein analysis, implying that PHB-driven intracellular carbon accumulation could optimize the intracellular electron allocation and correspondingly promote nitrogen metabolism. Our work integrated the mechanisms of intracellular carbon metabolism with preferences for electron transfer pathways in denitrification, providing a new perspective on how the selective parameters regulated microbial functions involved in denitrification.

Kinetic Study for Startup of Aerobic Moving Bed Biofilm Reactor in Treatment of Textile Dye Wastewater.

Due to high augmentation in population and low availability of land, the quantum of wastewater production has surged resulting in advancements in wastewater treatment systems. To cope under such stressful circumstances, moving bed biofilm reactor (MBBR) proves to be an upgraded treatment technology for industrial and municipal wastewater treatment. The present startup study has been carried out using a laboratory-scale aerobic MBBR with working volume of 25L for textile dye wastewater treatment having AnoxKaldnes K3 media at filling percentage of 50%. In order to acclimatize the microorganisms on textile dye wastewater, the startup of the reactor was carried out using lactose as readily degradable co-substrate with textile dye wastewater in different ratios at hydraulic retention time (HRT) of 24h. The biofilm on the media was developed in 63days duration and the reactor attained pseudo-steady state (PSS) in 185days period. During PSS condition of the MBBR, the maximum chemical oxygen demand (COD) removal efficiency of 92% with mixed liquor suspended solids (MLSS) concentration of 4224 ± 22mg/L has been achieved. The kinetic study for biodegradation of textile dye wastewater has also been carried out using the Monodgrowth kinetics. The values of bio-kinetic coefficients of yieldof heterotrophic biomass (Y) and endogenousdecay coefficient for heterotrophic biomass (Kd) recorded are 0.394 mgVSS/mgCOD.d and 0.087day-1, respectively. The values of specific substrate removal rate (k), Monodhalf saturation constant (Ks), and maximumspecific growth rate for heterotrophic biomass (µmax) are 0.024 mgCOD/mgVSS.d, 53.203mg/L, and 0.0095day-1, respectively, demonstrating the suitability and healthy performance of MBBR for textile dye wastewater treatment.