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Developing an organic template-free zeolite coated on a low-cost ceramic support is essential to reduce the overall cost of the membrane for heavy metal separation. In this study, a low-cost and highly durable kaolin-supported zeolite-coated composite membrane was fabricated and tested for removal of cerium metal ions from its aqueous solution. Different strategies were followed to fabricate the composite membrane through the organic template-free hydrothermal synthesis method, such as coating the ceramic tubes solely on the interior surface, exterior surface, and both sides. The results obtained from X-ray diffraction, field emission scanning electron microscopy, and field emission transmission electron microscopy indicated that the hydrothermal synthesis route produced pure, ultrafine, and uniform particles of chabazite zeolite with a cation exchange capacity of 3.96 meq/g. The effect of coating on the membrane surface(s) was investigated by measuring the weight increment, porosity, pore size, and pure water permeability; the results revealed that the ceramic tube coated on both sides has the highest amount of zeolite loading, that is, 1.82 ± 0.18 g, along with a porosity of 30.50 ± 0.50%, a water permeability of 1.74 L/m2h bar, and an average pore diameter of 36 nm. The average pore diameter of the composite membrane (both-side-coated tubes) obtained from BET analysis (34 nm) was in good agreement with the pore size (36 nm) estimated through the pure water permeability test. Furthermore, the performance of the composite membrane coated on both sides was evaluated toward removing cerium ions from aqueous solutions. The effect of applied pressure, pH, and concentration of the feed solution was investigated. During the cross-flow filtration tests, the permeate flux decline was not observed for all the applied pressures. More than 99.9% removal of cerium was achieved under the different conditions of feed concentration and pH. This study establishes the application of the prepared composite membrane for cerium removal from aqueous solutions.

The performance of a packed bed reactor (PBR) containing immobilized sulphate reducing bacteria for sulphate removal from wastewater, utilizing carbon monoxide (CO) as the sole electron donor, is demonstrated. The performance of the PBR system in terms of CO and sulphate removal efficiencies (%RECOand %REsulphate, respectively) was predicted using three parameters, i.e.the hydraulic retention time (HRT, h), inlet concentrations of CO (ICCO, mg/L) and sulphate (ICsulphate, mg/L). An artificial neural network (ANN) model with 3-14-2 topology was developed by training the experimental data through the Levenberg Marquardt (LM) algorithm. Using genetic algorithm (GA) with appropriate objective functions, optimal sets of inputs were obtained to ensure maximum RE at a minimum HRT. The ANN had an overall accuracy above 98%, with a correlation coefficient of 0.99 and a root mean square error of 1.66%, suggesting its good performance. The automation of sulphate-rich wastewater industry through GA identified solutions might be leveraged for efficient operation in terms of saving time and resources.

Mercury, emitted from various industries, is toxic and has devastating environmental consequences. Therefore, it becomes imperative to monitor the levels of mercury closely. This work mainly focuses on preparing inexpensive zeolite-coated kaolin membranes for separating Hg2+from water. The membrane support was prepared using kaolin (50 wt.%), quartz (25 wt.%), and calcium carbonate (25 wt.%). This mixture was blended with a 3% hydroxypropyl methylcellulose (HPMC) solution and then passed through an extruder to obtain tubular support, which was further sintered at 950 oC. The zeolite-coated membrane (ZP membrane) was fabricated by subjecting the sintered support to a 48-hour hydrothermal synthesis in 7 Na2O: 1 Al2O3: 10 SiO2: 205 H2O gel at 90 oC. The isoelectric point of the ZP membrane was estimated to be 4.5. The zeolite-coated membrane displayed a pure-water permeability of 22.7×10-9m3/m2s kPa, a porosity of 31.72 ± 0.86%, and a pore size of 90 nm. The performance of the ZP membrane in separating the Hg2+ion from an aqueous solution was investigated by pressure variations (69-345 kPa) and feed concentration (0.5-10 ppm). The results clearly showed that in all cases, the zeolite-P membrane exhibited more than 99% rejection of Hg2+ions from aqueous solutions during the filtration experiments. Thus, the prepared ZP membrane can effectively be used for the separation of Hg2+ions from wastewater.

This study investigated simultaneous heavy metals removal and anthracene biodegradation by Rhodococcus opacusat different initial anthracene concentrations in the range 50–200 mg L−1. The heavy metals tested were Fe(III), Cu(II), Zn(II), Cd(II), Ni(II), and Pb(II) at 10 mg L−1initial concentration: The organism was found to be well capable of removing the heavy metals along with high anthracene biodegradation efficiency. However, anthracene biodegradation rate by the organism was reduced due to these heavy metals. In addition, the heavy metals effect on R. opacusbiomass growth followed the order: Cd > Ni > Pb > Cu > Zn > Fe. The total time to anthracene biodegradation increased from 144 to 216 h in the presence of Fe, Zn, Cu, or Pb, and it was up to 240 h in the presence of Cd or Ni. Compared with 70.2% (w/w) lipid accumulation by the bacterium in the absence of these heavy metals, a significant decline in the same was observed in the presence of the different heavy metals. These values were 41.2, 44.1, 52.1, 54.1, 58.6, and 63.1% (w/w) for Cd, Ni, Pb, Cu, Zn, and Fe, respectively. Field emission scanning electron microscopy integrated with energy dispersive X-ray spectroscopy and transmission electron microscopy of the biomass grown in the presence and absence of these heavy metals further confirmed a change in morphology of the bacterium due to the heavy metals. Fourier transmission infrared spectroscopy spectra of the biomass obtained during its growth in the presence and absence of the heavy metals confirmed the involvement of N–H, C–H bend, –CH2–(C=O), C–N stretch, C–H and O–H bending, and –C–Cl groups on the biomass for heavy metal uptake by the bacterium.

Dimethyl phthalate (DMP) and diethyl phthalate (DEP) are environmental toxicants that can interfere with the endocrine system and cause adverse health impacts by mimicking the natural hormone activity. The present study focused on the biodegradation of DMP and DEP mixture by Cellulosimicrobiumbacteria in a bioreactor under batch, fed-batch, continuous and continuous with biomass recycle modes. Biomass recycling was done followed by microfiltration using an indigenous low-cost tubular ceramic membrane. Under the batch mode of operation, maximum degradation values of 85 % and 58 % were observed at 1000 and 2000 mg/L initial concentrations of DMP and DEP, respectively, in mixture, whereas, complete degradation was achieved in the fed-batch system at the same initial concentrations. In continuous operation mode at 24 h hydraulic retention time, complete degradation was achieved for all inlet DMP and DEP concentrations. The biomass recycle operation mode was found to be the best strategy owing to complete degradation of the phthalates, even at very high inlet concentrations and at a short hydraulic retention time (HRT) of 16 h. A high germination index (GI) value of 91.86 % and 0 % brine shrimp mortality further demonstrated the potential of the biomass recycle system for the treatment of phthalate containing wastewater.

In this study, effect of different parameters, viz. concentration of photosensitizer (PS), pH of the bacterial cell suspension and initial cell count, on photo-inactivation of Escherichia coliand Enterococcus hiraebacteria using methylene blue (MB) and sodium anthraquinone-2-sulphonate (SAQS) was investigated employing the statistically valid full factorial design of experiments. The inactivation efficiency of E. hiraeusing MB ranges between 10.81 and 48.55 %, whereas in the case of E. coliit ranges between 10.41 and 46.44 %. Using SAQS, the inactivation efficiency of E. hiraewas within 5.26–39.03 %, and in the case of E. coliit varied in the range 4.65–37.66 %. Statistical analysis of the photo-inactivation results in the form of analysis of variance (ANOVA) and student ‘t’ test revealed significant individual effect of these process parameters. In addition, an increase in dark incubation period with MB or SAQS resulted in enhanced photo-inactivation efficiency against both the microorganisms. Reactive oxygen species measurement and analysis of lipid peroxidation and protein carbonyl index helped in a better understanding of the photo-inactivation mechanism.

AbstractThis study evaluated the potential of the biosurfactant-producing yeast Candida bombicolain treating wastewater containing fats and oils from a dairy industry in a laboratory scale bioreactor. The dairy wastewater contains high chemical oxygen demand (COD) (2,480 mg/L) and fats and oils (407 mg/L) and was supplemented with sugarcane molasses (1% w/v) and yeast extract (0.1% w/v) to support the growing yeast in batch, fed-batch, and continuous operations. The yeast was able to remove fats and oils completely (more than 95% COD removal) under batch and continuous operation. The study suggested that wastewater containing high fats and oils can be efficiently treated using C. bombicola.

This study evaluated the potential of the biosurfactant-producing yeast Candida bombicolain treating wastewater containing fats and oils from a dairy industry in a laboratory scale bioreactor. The dairy wastewater contains high chemical oxygen demand (COD) (2,480 mg/L) and fats and oils (407 mg/L) and was supplemented with sugarcane molasses (1% w/v) and yeast extract (0.1% w/v) to support the growing yeast in batch, fed-batch, and continuous operations. The yeast was able to remove fats and oils completely (more than 95% COD removal) under batch and continuous operation. The study suggested that wastewater containing high fats and oils can be efficiently treated using C. bombicola.

This study examined the valorization of dairy wastewater in the production of lipids by Rhodococcus opacusfor biodiesel application. Using synthetic media based on dextrose and ammonium nitrate as the carbon and nitrogen source, respectively, the bacterium accumulated 71% (w/w) of lipids. Using only the raw dairy wastewater, the bacterium accumulated 14.28% w/w lipid and reduced the initial wastewater chemical oxygen demand (COD) by 30%. These values were, however, enhanced to 30–33% w/w and 62%, respectively, by supplementing the dairy wastewater with mineral salt media in the ratio 1:3. Bioreactor experiments were further performed using raw dairy wastewater and mineral salt medium in 1:3 ratio under both uncontrolled and controlled temperature and pH conditions. Interestingly biomass growth, lipid accumulation in the bioreactor experiments were found to be lower as compared to those in the shake flask experiments, whereas the wastewater COD removal was much higher in the bioreactor study. 1H nuclear magnetic resonance (NMR) spectroscopy of the fatty acids accumulated by the bacteria using dairy wastewater based media revealed that it contained more saturated fatty acids than unsaturated fatty acids. Gas chromatography (GC) analysis of the biodiesel produced by either ex-situor in-situtransesterification of the bacterial lipids further revealed the presence of methyl palmitate (34.90%), methyl stearate (35.48%) methyl myristate (29.79%), methyl linoleate (27.87%), and methyl palmitate (25.85) as the main esters. The estimated properties of the transesterified product indicated its potential for biodiesel applications.

Biodegradation of phenol by predominantly Pseudomonasspecies isolated from a sewage wastewater treatment plant was investigated in batch shake flasks. Phenol with a lower concentration of 100 mg/L was degraded in 10 h and a highest of 800 mg/L in 69 h. The phenol degradation rate was observed to vary largely with the concentrations of phenol used and was found to be less than 10 mg/L/h at both the extremes of the initial concentrations. The degradation kinetics was found follow the three half-order kinetic model with the regression greater than 0.97. The specific substrate utilization rates of the culture at various initial phenol concentrations were fitted to modified substrate inhibition kinetic models of Edward, Haldane, Luong, Han–Levenspiel and Yano–Koga. Among these models the Edward was found to fit the data well with a minimum Root Mean Square error value of 0.0039.

Biodegradation of phenol by predominantly Pseudomonasspecies isolated from a sewage wastewater treatment plant was investigated in batch shake flasks. Phenol with a lower concentration of 100 mg/L was degraded in 10 h and a highest of 800 mg/L in 69 h. The phenol degradation rate was observed to vary largely with the concentrations of phenol used and was found to be less than 10 mg/L/h at both the extremes of the initial concentrations. The degradation kinetics was found follow the three half-order kinetic model with the regression greater than 0.97. The specific substrate utilization rates of the culture at various initial phenol concentrations were fitted to modified substrate inhibition kinetic models of Edward, Haldane, Luong, Han–Levenspiel and Yano–Koga. Among these models the Edward was found to fit the data well with a minimum Root Mean Square error value of 0.0039.

In this study, novel poly(3-hydroxybutyrate) (PHB) based Calcium–Iron Layered Double Hydroxide (Ca–Fe LDH) nanocomposites were investigated for sustained drug delivery application using the antibiotic norflaxacin (NFX) as a model drug. Compared with other LDH and montmorillonite nanoclays, Ca–Fe LDH showed a high drug loading capacity. In vitrodrug release experiments with PHB/NFX, PHB/NFX LDH, and PHB/PEG/NFX LDH were performed using two different phosphate buffer solutions of pH 5.3 and pH 7.4. Among these nanocomposites, the PHB/PEG/3 NFX LDH nanocomposite showed a very high drug release efficiency of 95.91% in pH 5.3 and 73.40 ± 3.41% in pH 7.4, which was followed by PHB/3 NFX LDH with a drug release efficiency of 82.60% in pH 5.3 and 66.81 ± 2.25% in pH 7.4. Furthermore, the drug release kinetics due to PHB/PEG/3 NFX LDH in pH 5.3 and pH 7.4 followed zero-order and Higuchi model kinetics, respectively. Characterization results of the polymer nanocomposite films using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission transmission electron microscopy (FETEM) and field emission scanning electron microscopy (FESEM) analysis as well as antibacterial activity of the PHB formulations against Staphylococcus aureusand Escherichia colirevealed excellent potential of the PHB based LDH nanocomposites for sustained drug release applications.

This study was aimed at investigating the performance of anaerobic rotating biological contactor reactor treating synthetic wastewater containing a mixture of heavy metals under sulfate reducing condition. Statistically valid factorial design of experiments was carried out to understand the dynamics of metal removal using this bioreactor system. Copper removal was maximum (>98%), followed by other heavy metals at their respective low inlet concentrations. Metal loading rates less than 3.7 mg/L∙h in case of Cu(II); less than 1.69 mg/L∙h for Ni(II), Pb(II), Zn(II), Fe(III) and Cd(II) are favorable to the performance of the An-RBC reactor. Removal efficiency of the heavy metals from mixture depended on the metal species and their inlet loading concentrations. Analysis of metal precipitates formed in the sulfidogenic bioreactor by field emission scanning electron microscopy along with energy dispersive X-ray spectroscopy (FESEM-EDX) confirmed metal sulfide precipitation by SRB. All these results clearly revealed that the attached growth biofilm bioreactor is well suited for heavy metal removal from complex mixture.