Construction of a novel ternary synergistic CuFe2O4-SnO2-rGO heterojunction for efficient removal of cyanide from contaminated water.

Many industrial effluents release cyanide, a well-known hazardous and bio-recalcitrant pollutant, and thus, the treatment of cyanide wastewater is a major challenge. In the current study, a CuFe2O4-SnO2-rGO nanocomposite was synthesized to remove cyanide from an aqueous system. The structural and morphological characterizations of the nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectra (EDX) analysis. The results revealed that almost 97.7% cyanide removal occurred using the nanocomposite at an initial concentration of 100 mg L-1 within 1 h. The experimental data were fitted to various adsorption models, among which the Langmuir model fitted the data very well, confirming the monolayer adsorption process. The kinetic investigation revealed that the cyanide adsorption process followed a pseudo-second-order kinetic model, indicating a chemisorption process with a high cyanide adsorption capacity of 114 mg g-1. The result of the intraparticulate diffusion model fitting revealed a decreasing slope value (K) from stage 1 to stage 2, indicating that external mass transfer is the predominating step. Moreover, the CuFe2O4-SnO2-rGO nanocomposite shows excellent reusability.

Multifunctional Dy2NiMnO6/Reduced Graphene Oxide Nanocomposites and Their Catalytic, Electromagnetic Shielding, and Electrochemical Properties.

Multifunctional nanocomposites have shown great interest in clean energy systems and environmental applications in recent years. Herein, we first reported the synthesis of Dy2NiMnO6 (DNMO)/reduced graphene oxide (rGO) nanocomposites utilizing a hybrid approach involving sol-gel and solvothermal processes. Subsequently, we investigated these nanocomposites for their applications in catalysis, electromagnetic interference shielding, and supercapacitors. A morphological study suggests spherical-shaped DNMO nanoparticles of an average size of 382 nm that are uniformly distributed throughout the surface without any agglomeration. The as-prepared nanocomposites were used as catalysts to investigate the catalytic reduction of 4-nitrophenol in the presence of NaBH4. DNMO/rGO nanocomposites demonstrate superior catalytic activity when compared with bare DNMO, with the rate of reduction being influenced by the composition of the DNMO/rGO nanocomposites. In addition, novel multifunctional DNMO/rGO was incorporated into polyvinylidene difluoride (PVDF) to develop a flexible nanocomposite for electromagnetic shielding applications and exhibited a shielding effectiveness of 6 dB with 75% attenuation at a frequency of 8.5 GHz compared to bare PVDF and PVDF-DNMO nanocomposite. Furthermore, the electrochemical performance of DNMO/rGO nanocomposites was investigated as an electrode material for supercapacitors, exhibiting the highest specific capacitance of 260 F/g at 1 A/g. These findings provide valuable insights into the design of DNMO/rGO nanocomposites with remarkable performance in sustainable energy and environmental applications.

Multi-model exploration of groundwater quality and potential health risk assessment in Jajpur district, Eastern India.

The presence of fluoride and nitrate is a serious groundwater quality issue in India impacting human health. In the present study, 14 different hydrochemical parameters for 76 groundwater samples collected from the Jajpur district of Odisha, India, were evaluated. Entropy-weighted water quality index (EWQI), fixed-weight groundwater quality index (GWQI), principal component analysis (PCA), and rotated factor loading-based water quality index (PCWQI) were employed to assess groundwater quality. About 65.79 ± 4.68%, 33.55 ± 3.95%, and 0.66 ± 0.76% of the samples were rated as "excellent," "good," or "medium" quality, respectively, across the four different water quality indices, with a nominal rating discrepancy of 13.15%. Though 86% of samples consistently received excellent or good ratings across all WQI frameworks, concentrations of F- and NO3- in 36.8% and 11.84% of the samples exceeded the WHO permissible limit. In health risk assessment, about 38.15% of samples surpassed the F- hazard quotient (HQ > 1) posing non-carcinogenic health risks for children. The non-carcinogenic health risks due to NO3- were evident in 55.26% and 11.84% of samples for children and adults, respectively. The higher concentration of NO3- in some of the water samples, together with its positive correlation with HCO3-, may worsen groundwater pollution. The moderate correlation between Ca2+ and HCO3- (r = 0.410) and the insignificant correlation between Mg2+ and HCO3- (r = 0.234) suggests calcite dissolution is far more common than dolomite.

Biodegradation of Phenol Using the Indigenous Rhodococcus pyridinivorans Strain PDB9T NS-1 Immobilized in Calcium Alginate Beads.

Phenolic compounds are the major contaminants identified from various industrial effluents, which pose an extreme threat to the environment. Therefore, investigating an effective technique to remove these toxic phenolic compounds from the contaminated environment is very essential. In the present investigation, batch tests were performed to assess the biodegradation of phenol using an indigenous Rhodococcus pyridinivorans strain PDB9T NS-1 encapsulated in a calcium alginate bead system. In order to improve the mechanical stability, silica was added to the cell-embedded Ca-alginate beads. The impact of experimental conditions such as contact time, pH, and initial phenol doses was investigated. The biodegradation of phenol was examined over a wide range of phenol, and the results showed that more than 99.6% degradation was achieved at an initial phenol dose of 1000 mg/L in 70 h at 30 °C. Among the various sorption isotherm tested, the Freundlich isotherm was the best fitted to the experimental data. This behavior indicated a multilayer biosorption process and was controlled by heterogeneous surface energy. Based on an intra-particle diffusion model, internal mass transfer or pore diffusion predominated over exterior mass transfer in controlling the entire phenol biosorption process. The biosorption of phenol onto the cell encapsulated in the Ca-alginate bead follows pseudo-first-order kinetics with a superior phenol biosorption capacity of 155 mg/g of Ca-alginate. Further stability study revealed that the bead could be recycled successfully without any substantial decline in phenol degradation efficiency, indicating that the immobilized microbe possesses exceptional operating stability.

Alleviation of dental caries by use of isolated potential probiotic and its characterization.

Streptococcus mutans plays a major role in biofilm formation and pathogenic bacterial adhesion. Here we investigated the abilities of our isolates from diverse conventional sources to characterize the beneficial bacteria for inhibition of S. mutans. Enterobacter cloacae PS-74, a beneficial bacteria isolated from yoghurt, is gram negative, rod shaped, and resistant to acid, bile salt, and amylase. PS-74 cell-free supernatants (CFS) demonstrated highest zone of inhibition of 29 ± 1.7 mm. Further, the minimum inhibitory concentration (MIC) value of CFS PS-74 was recorded to be 10 µL and its minimum bactericidal concentration (MBC) value was found to be 15µL which led to 99.9% log reduction of S. mutans. Moreover, the biofilm formation was reduced by 84.91% at MIC15 of CFS PS-74 which alleviate the dental caries formation by S. mutans. This is the first report on E. cloacae PS-74, which was studied for its probiotic properties to inhibit S. mutans MTCC-890 due to the production of organic acids and employed in oral treatment.

Inconsistency of PCA-based water quality index - Does it reflect the quality?

The formalization of a stable water quality index (WQI) from measured hydrogeochemical parameters is essential for the identification and classification of water resources. In the principal component analysis (PCA) based WQI approach, the parameter weight is derived using either PC loading or rotated factor loading from a large number of samples pooled for WQI measurement. The PCA-based approach is paradoxical, as the calculated WQI rating of a sample would rather be dependent on the size, and composition of the population. Though this issue is well anticipated, no attempt has been made to regularize or measure the extent of WQI disagreement. In the present study, the WQI of 106 groundwater samples analyzed for 12 different hydrochemical parameters were modelled using PC loading or rotated factor loading (referred to as PCQ-1, PCQ-2, respectively) approach. Analysis reveals PCQ-1 to be positively biased in 78 % of samples and rating disagreements were evident in 9.43 % of samples. WQI of the data set was estimated using repeated (1000) random non-overlapping 2 to 5-fold data partitioning (containing 21 to 83 samples in each fold) adopting either an in-sample (test set) or out-sample (train set) modelling approach. The mean of WQI deviations in repeated resampling from the reference (i.e., using the entire dataset) has been positive in most of the samples using the PCQ-1 model, irrespective of the fold partition size. The median root mean square deviation values of the data set increased with the number of fold partitioning for in-sample calibration for both PCQ-1 and PCQ-2 approaches. The exclusion of a single water quality parameter from the PCA model can cause up to a 60 % deviation of the WQI score in some water samples. The cross-validation and Monte Carlo resampling approach can serve as a framework to test the stability of PCA-based WQI.

Assessment of groundwater geochemistry using multivariate water quality index and potential health risk in industrial belt of central Odisha, India.

Groundwater in India has been shown to have a variety of water quality issues, including fluoride, nitrate, and uranium pollution, all of which pose a health risk to humans. In the present study, a total of 106 groundwater samples from the Angul district of Odisha, an industrialized region in India, were analyzed for 14 different hydrochemical parameters. In almost 30%, 34.9%, and 4.7% of the groundwater samples, the concentrations of F-, NO3- and uranium, respectively, exceeded the permissible limit set by WHO. In addition to the fixed-weight groundwater quality index (GWQI), the entropy-weighted water quality index (EWQI), the principal component analysis (PCA) factor (or rotated factor) loading based water quality index (PCWQI) and human health risk assessment were used. Depending on the models, about 19.1 ± 0.9%, 70.5 ± 1.9% and 10.38 ± 1.9% of water samples were classified as "Excellent", "Good" and "Medium" quality, respectively, across four water quality indexes with a nominal rating disagreement of 11.3%. More than 90% of samples are unanimously classified as excellent or good across the WQI rating. For children and adults, approximately 54.7% and 24.5% of samples exceeded the permitted limit for F-, (hazard quotient HQ > 1), posing non-carcinogenic health hazards, respectively. In contrast, 71.7% and 34.9% of NO3- samples respectively, surpassed the allowed limit and caused non-carcinogenic health concerns for children and adults. In terms of carcinogenic HQ values, about 13.2% and 7.5% of samples exhibit an uranium related carcinogenic health risk in children and adults, respectively. The existence of significant amounts of Cl -, NO3-, and especially HCO3- ions in groundwater in some samples, as well as their positive interdependence, may increase uranium pollution in the future through uranium dissolution.

Co-metabolic biodegradation of 4-bromophenol in a mixture of pollutants system by Arthrobacter chlorophenolicus A6.

Brominated phenols are listed as priority pollutants together with nitrophenol and chlorophenol are the key components of paper pulp wastewater. However, the biodegradation of bromophenol in a mixed substrate system is very scanty. In the present investigation, simultaneous biodegradation kinetics of three substituted phenols 4-bromophenol (4-BP), 4-nitrophenol (4-NP), and 4-chlorophenol (4-CP) were investigated using Arthrobacter chlorophenolicus A6. A 23 full factorial design was applied with varying 4-BP and 4-CP from 75-125 mg/L and 4-NP from 50-100 mg/L. Almost complete degradation of this mixture of substituted phenols was achieved at initial concentration combinations of 125, 125, and 100 mg/L of 4-CP, 4-BP, and 4-NP, respectively, in 68 h. Statistical analysis of the results revealed that, among the three variables, 4-NP had the most prominent influence on the degradation of both 4-CP and 4-BP, while the concentration of 4-CP had a strong negative interaction effect on the biodegradation of 4-NP. Irrespective of the concentration levels of these three substrates, 4-NP was preferentially biodegraded over 4-CP and 4-BP. Furthermore, 4-BP biodegradation rates were found to be higher than those of 4-CP, followed by 4-NP. Besides, the variation of the biomass yield coefficient of the culture was investigated at different initial concentration combinations of these substituted phenols. Although the actinomycetes consumed 4-NP at a faster rate, the biomass yield was very poor. This revealed that the microbial cells were more stressed when grown on 4-NP compared to 4-BP and 4-CP. Overall, this study revealed the potential of A. chlorophenolicus A6 for the degradation of 4-BP in mixed substrate systems.

Hydro-geochemical analysis based on entropy and geostatistics model for delineation of anthropogenic ground water pollution for health risks assessment of Dhenkanal district, India.

Consumption of poor quality water causes serious human health hazards. Therefore, it is very crucial to investigate factors influencing the quality of groundwater and its suitability for drinking purpose. In the present study, groundwater quality of the Dhenkanal district of Odisha, India was characterized and the spatial distribution of different water quality parameters were analyzed using the multivariate statistics, entropy theory, and geostatistics techniques. In the present study 112 number of groundwater tube well samples were collected from the study area. The entropy theory revealed that SO42-, Mg+2 and Cl- were the most influencing parameters. A similar observation was also observed based on the correlation coefficient analysis. Groundwater quality index (GWQI) and entropy-weighted water quality index (EWQI) classifications indicated that 78.57 and 43.75% of the collected groundwater samples were categorized under excellent water quality, whereas, the rest of the samples were varying from good to medium drinking water quality. In addition, the result of EWQI classification offers more realistic assessment than that of GWQIs owing to its high precision, simplicity and without application of artificial weight. The correlation coefficient between Ca+2 and HCO3-, Mg+2 and PO4- were significantly high which might be due the presence of CaHCO3 and MgPO4 in the groundwater samples. The GWQI revealed a weak spatial dependence of groundwater quality.

Evaluation of N doped rGO-ZnO-CoPc(COOH)8 nanocomposite in cyanide degradation and its bactericidal activities.

In the present study, an attempt has been made to design a solar light driven N-rGO-ZnO- CoPc(COOH)8 nanocomposite for the degradation of cyanide. The morphological and structural characterization of the synthesized nanocomposite was performed by XRD, FT-IR, XPS, UV-vis DRS, FESEM, TEM, EDS, PL spectra and BET surface area. The results revealed that almost 91% degradation and 86% toxicity removal occurred at 25 mgL-1 of initial cyanide concentration by the N-rGO-ZnO-CoPc(COOH)8 nanocomposite under illumination of solar light within 120 min. Analysis of free radicals reveals that the generation of OH. radicals was the predominant species in the photocatalytic degradation process. The cyanide degradation follows pseudo-first order kinetics. The estimated apparent rate constant (Kapp) of the above nanocomposite was 3 times higher than that of the ZnO photocatalyst alone together with a very good recycle activities. This might be due to the application of metallpthalocyanine photosensitizer CoPc(COOH)8 which enhances the rate of visible light absorption efficiency and activates the higher band gap ZnO photocatalyst under visible light. In addition, the presence of residual oxygen in N-rGO also promotes nucleation and anchor sites for interfacial contact between ZnO and N-rGO for effective charge transfer. Further, the N-rGO-ZnO-CoPc(COOH)8 photocatalytic system showed significant antibacterial activities against mixed culture systems. Therefore, the N-rGO-ZnO-CoPc(COOH)8 nanocomposite may be an alternative solar light driven photocatalyst system for the removal of cyanide from the wastewater along with its strong disinfectant activities.

Mycoremediation and toxicity assessment of textile effluent pertaining to its possible correlation with COD.

Globally, textile industries are one of the major sectors releasing dye pollutants. This is the first report on the positive correlation between toxicity and chemical oxygen demand (COD) of textile effluent along with the proposed pathway for enzymatic degradation of acid orange 10 using Geotrichum candidum within a very short stretch of time (18 h). Removal efficiency of this mycoremedial approach after 18 h in terms of chemical oxygen demand, biological oxygen demand, total suspended solids, salinity, color and dye concentration in the treated effluent reached to 98.5%, 56.3%,73.2%, 64%, 89% and 87% respectively. Also there was a decrease in pH of the treated effluent. FTIR analysis of the treated effluent confirmed biodegradation. The LCMS analysis showed the degradation of acid orange 10, which was confirmed by the formation of two biodegradation products, 7-oxo-8-iminonapthalene-1,3-disulfonate and nitrosobenzene, which subsequently undergoes stepwise hydrogenation and dehydration to form aniline via phenyl hydroxyl amine as intermediate. The X-ray diffraction studies showed that heavy metal content in the treated effluent has reduced along with decrease in % crystallinity, indicating biodegradation. The connection between toxicity and COD was also inveterated using Pearson's correlation coefficient. Further the toxicological studies indicated the toxicity of raw textile effluent and relatively lower toxic nature of metabolites generated after biodegradation by G. candidum.

Photocatalytic degradation of cyanide using polyurethane foam immobilized Fe-TCPP-S-TiO2-rGO nano-composite.

An attempt has been made for the treatment of cyanide contaminated wastewater using a S-TiO2@rGO heterogeneous photocatalyst system immobilized on polyurethane foam (PUF) supporting materials. Further, to make the photocatalytic system more efficient and active under visible light, a highly efficient iron porphyrin derivative sensitizer viz. Fe-TCPP was synthesized and employed for cyanide degradation. To investigate the synthesized heterogeneous nano-composite S-TiO2@rGO-FeTCPP photocatalytic system, advanced techniques such as XRD, XPS, FT-IR, PL spectra, UV-vis DRS, FESEM, and EDS were utilized. The photocatalytic performance of the nanocomposite was evaluated in a suspended system and results revealed that about 75% of cyanide degradation was obtained at 100 mg/L of initial cyanide within 2 h. Whereas, at the same condition, more than 91% of cyanide degradation as well as 88% toxicity removal occurred by the PUF immobilized S-TiO2@rGO-FeTCPP solid-state photocatalytic system. First-order kinetics was applied to investigate the degradation of cyanide by the photocatalytic nanocomposite. From the kinetic study, the estimated first-order rate constant (Kf) in a solid-state photocatalytic system of the nanocomposite was 1.7 times superior to that of the suspended system. Further, the rate of photocatalytic activity was nearly 10.8 times greater than that of pure TiO2. This study demonstrated that the immobilized S-TiO2@rGO-FeTCPP photocatalytic system could be an efficient technique for degrading cyanide from industrial effluent.

Evaluation of 4-bromophenol biodegradation in mixed pollutants system by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor.

Bromophenol is listed as priority pollutant by U.S. EPA, however, there is no report so far on its removal in mixed pollutants system by any biological reactor operated in continuous mode. Furthermore, bromophenol along with chlorophenol and nitrophenol are usually the major constituents of paper pulp and pesticide industrial effluent. The present study investigated simultaneous biodegradation of these three pollutants with specially emphasis on substrate competition and crossed inhibition by Arthrobacter chlorophenolicus A6 in an upflow packed bed reactor (UPBR). A 2(3) full factorial design was employed with these pollutants at two different levels by varying their influent concentration in the range of 250-450 mg l(-1). Almost complete removal of all these pollutants and 97 % effluent toxicity removal were achieved in the UPBR at a pollutant loading rate of 1707 mg l(-1) day(-1) or lesser. However, at higher loading rates, the reactor performance deteriorated due to transient accumulation of toxic intermediates. Statistical analysis of the results revealed a strong negative interaction of 4-CP on 4-NP biodegradation. On the other hand, interaction effect between 4-CP and 4-BP was found to be insignificant. Among these three pollutants 4-NP preferentially degraded, however, 4-CP exerted more inhibitory effect on 4-NP biodegradation. This study demonstrated the potential of A. chlorophenolicus A6 for biodegradation of 4-BP in mixed pollutants system by a flow through UPBR system.

Biodegradation of 4-bromophenol by Arthrobacter chlorophenolicus A6 in batch shake flasks and in a continuously operated packed bed reactor.

The present study investigated growth and biodegradation of 4-bromophenol (4-BP) by Arthrobacter chlorophenolicus A6 in batch shake flasks as well as in a continuously operated packed bed reactor (PBR). Batch growth kinetics of A. chlorophenolicus A6 in presence of 4-BP followed substrate inhibition kinetics with the estimated biokinetic parameters value of µ max = 0.246 h(-1), K i = 111 mg L(-1), K s  = 30.77 mg L(-1) and K = 100 mg L(-1). In addition, variations in the observed and theoretical biomass yield coefficient and maintenance energy of the culture were investigated at different initial 4-BP concentration. Results indicates that the toxicity tolerance and the biomass yield of A. chlorophenolicus A6 towards 4-BP was found to be poor as the organism utilized the substrate mainly for its metabolic maintenance energy. Further, 4-BP biodegradation performance by the microorganism was evaluated in a continuously operated PBR by varying the influent concentration and hydraulic retention time in the ranges 400-1,200 mg L(-1) and 24-7.5 h, respectively. Complete removal of 4-BP was achieved in the PBR up to a loading rate of 2,276 mg L(-1) day(-1).

Biodegradation of 4-bromophenol by Arthrobacter chlorophenolicus A6T in a newly designed packed bed reactor.

Bromophenol is listed as a priority pollutant by the U.S. EPA. However, there has been no report on the removal of bromophenol in any biological system that is operated in a continuous mode. The efficiency of Arthrobacter chlorophenolicus A6(T) on the biodegradation of 4-bromophenol (4-BP) in a newly designed packed bed reactor (PBR) was evaluated with different influent 4-BP concentrations between 400 mg l(-1) and 1200 mg l(-1) and hydraulic retention times (HRTs) between 24 h and 7.5 h. The response of the PBR to 4-BP shock loadings was also tested, and the bioreactor was found to adequately handle these shock loadings. The percentage of effluent toxicity in the PBR was tested using mixed microbial consortia as the test species; this experiment was performed using a 4-BP influent concentration of 1200 mg l(-1) and HRTs between 24 h and 7.5 h. A maximal 98% effluent toxicity removal was achieved when the PBR was operated at an HRT of 24 h. In the present study, 4-BP was used as the sole source of carbon and energy, and the complete removal of 4-BP was achieved with 4-BP loading rates of up to 2277 mg l(-1) day(-1).

Enhanced Cellulase Production from Bacillus subtilis by Optimizing Physical Parameters for Bioethanol Production.

Effect of physical parameters such as initial pH, agitation (rpm), and temperature (°C) for cellulase production from Bacillus subtilis AS3 was investigated. Central composite design of experiments followed by multiple desirability function was applied for the optimization of cellulase activity and cell growth. The effect of the temperature and agitation was found to be significant among the three independent variables. The optimum levels of initial pH, temperature, and agitation for alkaline carboxymethylcellulase (CMCase) production predicted by the model were 7.2, 39°C, and 121 rpm, respectively. The CMCase activity with unoptimized physical parameters and previously optimized medium composition was 0.43 U/mL. The maximum activity (0.56 U/mL) and cell growth (2.01 mg/mL) predicted by the model were in consensus with values (0.57 U/mL, 2.1 mg/mL) obtained using optimized medium and optimal values of physical parameters. After optimization, 33% enhancement in CMCase activity (0.57 U/mL) was recorded. On scale-up of cellulase production process in bioreactor with all the optimized conditions, an activity of 0.75 U/mL was achieved. Consequently, the bacterial cellulase employed for bioethanol production expending (5%, w/v) NaOH-pretreated wild grass with Zymomonas mobilis yielded an utmost ethanol titre of 7.56 g/L and 11.65 g/L at shake flask and bioreactor level, respectively.

A novel mechanism for ERK-dependent regulation of IL4 transcription during human Th2-cell differentiation.

We demonstrate that the mitogen-activated protein kinases extracellular signal-regulated kinase (ERK)-1 and ERK-2 have a central role in mediating T-cell receptor-dependent induction of IL4 expression in human CD4(+) T cells. Significantly, this involved a novel mechanism wherein receptor cross-linking induced activated ERK to physically associate with a promoter element on the IL4 gene. The proximally localized ERK then facilitated recruitment of the key transcription factors necessary for initiating IL4 gene transcription. Although both ERK-1 and ERK-2 bound to the promoter, recruitment of either one alone was found to be sufficient. We thus identify a novel mode of function for ERK wherein its physical association with the promoter serves as a prerequisite for enhanceosome assembly. This unusual pathway is also indispensable for human Th2-cell differentiation.

Batch biodegradation of para-nitrophenol using Arthrobacter chlorophenolicus A6.

The present study reports the kinetics of p-nitrophenol (PNP) biodegradation by Arthrobacter chlorophenolicus A6 in batch shake flasks for initial PNP concentrations in the range of 25-225 mg l(-1). Results of batch growth kinetics of A. chlorophenolicus A6 at various initial PNP concentrations revealed that the culture followed substrate inhibition kinetics with estimated decay coefficient value of 0.0132 h(-1). Biokinetic constants involved in the process were estimated by fitting the experimental data to several substrate inhibition kinetics models available from the literature. Among the models tested, Webb model fitted the experimental data best with the least root mean square error value, and the estimated model constants values were µ = 0.161 h(-1), K (i) = 128 mg l(-1), K (s) = 60.15 mg l(-1), and K = 100 mg l(-1). In addition, observed and theoretical yield coefficients, maintenance energy, and specific growth rate of the culture at various initial PNP concentrations were also investigated in the study.

Biodegradation of p-nitrophenol using Arthrobacter chlorophenolicus A6 in a novel upflow packed bed reactor.

A novel packed bed reactor (PBR) was designed with cross flow aeration at multiple ports along the depth to improve the hydrodynamic conditions of the reactor, and the biodegradation efficiency of Arthrobacter chlorophenolicus A6 on p-nitrophenol (PNP) removal in PBR at different PNP loading rates were evaluated. The novel PBR was designed to improve the hydrodynamic features such as mixing time profile (t(m95)), oxygen mass transfer coefficient (k(L)a), and overall gas hold up capacity (ɛ(G)) of the reactor. PNP concentration in the influent was varied between 600 and 1400 mg l(-1) whereas the hydraulic retention time (HRT) in the reactor was varied between 18 and 7.5h. Complete removal of PNP was achieved in the reactor up to a PNP loading rate of 2787 mg l(-1)d(-1). More than 99.9% removal of PNP was achieved in the reactor for an influent concentration of 1400 mg l(-1) and at 18 h HRT. In the present study, PNP was utilized as sole source of carbon and energy by A. chlorophenolicus A6. Furthermore, the bioreactor showed good compatibility in handling shock loading of PNP.

Decolourization of synthetic wastewater containing azo dyes by immobilized Phanerochaete chrysosporium in a continuously operated RBC reactor.

A laboratory-scale rotating biological contactor (RBC) reactor with immobilized fungal biomass of Phanerochaete chrysosporium was investigated for its performance in decolourizing synthetic wastewater containing single or mixture of azo dyes, Direct Red-80 (DR-80) and Mordant Blue-9 (MB-9). Decolourization efficiency in the continuously operated bioreactor was studied by varying dye inlet concentration and disc rotation speed at two different wastewater hydraulic retention times (HRTs), i.e. 24 and 48 h. Results from the single dye-containing experiments showed that the system could completely decolourize the wastewater for a maximum inlet dye concentration within the range 25-200 mg L(-1) and 48 h HRT in the reactor; for an inlet dye concentration above 200 mg L(-1), the decolourization efficiency slightly reduced up to 85% for the same HRT. However, wastewater containing DR-80 was found to be decolourized more efficiently compared to that containing MB-9. Further, the effect of increase in the disc rotation speed from 2 to 6 rpm in the study revealed no large differences in the decolourization efficiencies of the wastewaters. Similar results were obtained with wastewater containing the dyes together at various concentration combinations as per the two-level factorial design of experiments. Enzyme activities of lignin peroxidase and manganese peroxidase by the fungus were also analysed in the study, and the results indicated that while DR-80 showed a large negative effect on both the enzymes, MB-9 affected mainly the MnP activity by the fungus.