Bioremediation of a Sewage-Contaminated Tropical Swamp Through Bioaugmentation with a Microalgae-Predominant Microbial Consortium.

Bioaugmentation has many applications as a bioremediation technique. It is usually performed by bacteria but microalgal consortia also have great potential for bioremediation. This study evaluated the ability of a microbial consortium with predominance of microalgae (MCPM) to decontaminate the water of the Mallorquín tropical swamp. The Mallorquín Swamp is a natural water reservoir, essential for the ecological and hydric balance of the region, as well as for the fishermen, but has received sewage for more than 20 years. Microalgae for bioremediation purposes were isolated from the swamp, selected, cultured in bioreactors, and poured back into the Mallorquín waters. After bioaugmentation, there was a significant reduction in the BOD5 (98%), nitrates (58%), enterococci (92%), and total coliforms (100%). Notably, despite the MCPM bioaugmentation, the original richness and abundance of phytoplankton in the Mallorquín swamp was not disrupted. These results confirm the benefits of phycoremediation as an effective tool for on-site bioremediation of natural water bodies and show an effective phycoremediation at a large scale without altering the autochthonous microalgae community. This constitutes the first report of a successful MCPM intervention performed at this scale in a natural swamp in Colombia. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-021-00990-y.

Electrocoagulation using commercial grade aluminium electrode for the removal of crystal violet from aqueous solution.

The current research work studies the removal of crystal violet (also known as gentian violet), a kind of dye, from simulated wastewater by electrocoagulation using scrap aluminium roofing sheet as electrode in a batch electrochemical cell. Optimization of different operational parameters - pH, current density, time, initial concentration - was carried out experimentally. The equilibrium was attained at 1 hour and at pH 11. After suitable optimization, a removal of above 90% was achieved at an optimum current density of 20 mA/m2. Also, the adsorption behaviour of crystal violet in electrocoagulation was also studied and the isothermal and kinetic models were proposed to be the Dubinin-Radushkevich model and pseudo-first order model. The mechanism involved during the process was suggested as chemisorption. The adsorption thermodynamic studies were a clear indication that the process is spontaneous and endothermic as well as thermodynamically favourable too. Both chemical and physical characterization of the flocs generated during the electrolysis was explained by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) respectively.

Fano resonance between coherent acoustic phonon oscillations and electronic states near the bandgap of photoexcited GaAs.

Impulsive photo-excitation of solids results in a travelling strain pulse which manifests itself as coherent acoustic phonon oscillations. These oscillations have been extensively studied using time-resolved pump-probe spectroscopy. In the present work, we report the generation of extremely long-lived, coherent longitudinal acoustic phonon oscillations in intrinsic GaAs (100), with clear and unambiguous evidence of Fano interference between these oscillations and the continuum of electronic states close to the bandgap. Fano resonance is a widespread phenomenon observed in atomic systems and condensed media that arises from quantum interference between a continuum of quantum states and a discrete quantum state. Among other techniques, Fano resonance has been investigated with respect to optical phonons studied with Raman Spectroscopy. In the present work, we investigate Fano resonance in coherent phonon oscillations generated without the aid of any capping layer, dopants or substrate/interface effects. Since Fano resonance is sensitive to changes in electronic structure, doping and defects, these observations are important to the field of picosecond ultrasonics which is used for non-destructive depth profiling of solids and for carrier diffusion studies.

Novel application of high-density polyethylene mesh as self-forming dynamic membrane integrated into a bioreactor for wastewater treatment.

In the present study, self-forming dynamic membrane (SFDM) on rigid high-density polyethylene (HDPE) mesh with a large pore size of 2 mm is reported for the first time. The system was investigated for utilisation in simulated wastewater treatment by integrating the mesh with an aerobic bioreactor. The SFDM was analysed using Fourier transform infra-red (FT-IR) spectroscopy and visualised by scanning electron microscopy (SEM). The effect of the operating parameter on the change in composition of SFDM was also investigated. The system was used as a single unit for treatment of wastewater and showed stability over long-term treatment. The system could achieve a chemical oxygen demand (COD) reduction of 82.16 ± 6.47% at an influent COD concentration of 613.93 ± 72.13 mg/l and ammonia removal efficiency of 97.21 ± 0.62% at an influent ammonia concentration of 55.54 ± 2.23 mg/l. The reactor generated high-quality effluent and the turbidity recorded was less than 2NTU. In addition, the operational parameters, namely hydraulic retention time and organic loading rate, were optimised.

Optimization of dextran production by Weissella cibaria NITCSK4 using Response Surface Methodology-Genetic Algorithm based technology.

The most influencing factor on dextran production by Weissella cibaria NITCSK4 were screened using Plackett Burman design at 95% confidence limit with higher value of co-efficient of determination (R2) 99.58%. The combined effects of significant factors, namely, sucrose, temperature, dipotassium hydrogen phosphate (K2HPO4) and yeast extract were studied and optimized using Response Surface Methodology (RSM). The input parameters of non-linear models predicted by RSM were subsequently optimized using the genetic algorithm (GA) for obtaining a maximum dextran yield. The maximum yield was obtained with sucrose concentration of 15.78%, yeast extract 1.27%, K2HPO4 1.25%, and at 26°C. The predicted conditions were experimentally validated and 43.79mg/ml of dextran was produced. The dextran yield was 51% higher as compared to unoptimized medium. The molecular weight of resulting dextran produced at 26°C is >2000kDa. The NMR spectroscopic analysis demonstrated that the NITCSK4 produced linear dextran with predominant α (1-6) linkage.

Vibrational spectroscopic and computational studies on diisopropylammonium bromide.

Diisopropylammonium bromide (DIPAB) can be crystallized either in an orthorhombic (P212121) or in a monoclinic (P21) structure at room temperature depending on synthesis conditions. The non-polar orthorhombic structure exhibits a subtle, irreversible transformation into the ferroelectric monoclinic-II (m-II) phase above ~421K. At a slightly higher temperature of 426K this m-II (P21) phase reversibly transforms into a disordered, paraelectric monoclinic-I (P21/m) structure. We synthesized DIPAB in the orthorhombic structure, heated it to obtain the m-II phase and carried out a systematic study of their Raman and IR spectra. We obtained the phonon irreducible representations from factor group analysis of the orthorhombic and m-II structures based on the reported structural information. DIPAB is an organic molecular crystal, and the vibrational spectra in the intramolecular region (200-3500cm-1) of the two different phases are identical to each other, indicating weak inter-molecular interactions in both crystalline structures. In the low wavenumber region (10-150cm-1) the Raman spectra of the two phases are different due to their sensitivity to molecular environment. We also carried out first principles calculations using Gaussian 09 and CASTEP codes to analyze the vibrational frequencies. Mode assignments were facilitated by isolated molecule calculations that are also in good agreement with intramolecular vibrations, whereas CASTEP (solid state) results could explain the external modes.

Biosorptive removal of malachite green from aqueous solution using chemically modified brown marine alga Sargassum swartzii.

Sargassum swartzii, marine macro brown alga, showed a high malachite green (MG) biosorption capacity in batch mode of operation. The analytical evidence from Fourier transform infrared spectra confirmed the involvement of amine group in the biosorption of MG and electrostatic interaction type of mechanism was proposed to occur between the amine group of dye and the cationic MG dye solution. Scanning electron micrograph shows the morphological features and the attachment of dye onto the biosorbent. pH edge experiment shows that biosorption capacity was maximum at pH 10. The effect of biosorbent concentration, pH, temperature, adsorption time was studied for the biosorption of MG using S. swartzii. Langmuir, Freundlich and Temkin models were used to describe the isotherm data, of which Langmuir model described the isotherm data with high coefficient of determination R2 = 0.999. The maximum dye uptake of 111.1 mg/g was reported at pH 10 based on Langmuir model. Kinetics and temperature profiles were evaluated and reported. Desorption study was carried out with 0.1 M HCl. Efforts were also made to continuously treat MG bearing wastewater using up-flow packed column. Investigations proved that S. swartzii is an excellent biosorbent for the sequestration of MG in aqueous media.

Fabrication of hybrid biosorbent nanoscale zero-valent iron-Sargassum swartzii biocomposite for the removal of crystal violet from aqueous solution.

A novel nanoscale zero-valent iron-Sargassum swartzii (nZVI-SS) biocomposite was synthesized and evaluated for its ability to adsorb crystal violet (CV) from aqueous solutions. Involvement of various functional groups of the biosorbent in preferential adsorption of cationic dye was observed using Fourier transform infrared (FTIR) spectroscopy. Morphological changes occurring on the biocomposite materials were characterized using scanning electron microscopy (SEM). Significant increase (∼90%) in the biosorption of cationic dye was observed with gradual increase in pH of the medium from 3 to 12. The effect of biosorbent concentration, initial pH, temperature, agitation rate, adsorption time, and initial dye concentration was studied for the biosorption of CV using nZVI biocomposite. During the optimization study, maximum biosorption capacity was observed at pH of 8. At various initial CV concentrations (20-100 mg/L), attainment of batch sorption equilibrium was observed within 120 min of reaction time. The Langmuir isotherm model expressed high coefficient of determination (R2 = 0.999). The maximum dye uptake of 200 mg/g was reported at pH 8. Kinetics and temperature profiles were evaluated and reported. Desorption study was carried out with 0.1 M HCl. Investigations proved that nZVI-SS is an excellent biosorbent for the sequestration of CV in aqueous media.

Synthesis of magnetic biocomposite for efficient adsorption of azo dye from aqueous solution.

A novel magnetic biocomposite was synthesized using metal chlorides and aquatic macrophytes by co-precipitation method. The resulting product, magnetic biocomposite was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and Scanning electron microscope (SEM). The adsorption performance of the magnetic biocomposite was tested with removal of Metanil Yellow dye from aqueous solution. The effect of influencing parameters such as initial dye concentration, solution pH and agitation were investigated. The equilibrium isotherm was well described by the Langmuir model with the with maximum adsorption capacity of 90.91mg/g. Adsorption kinetics experiments were carried out and the data were well fitted by a pseudo-second-order equation. The results revealed that the magnetic biocomposite could efficiently adsorb the azo dyes from aqueous solution, and the spent adsorbents could be recovered completely by magnetic separation process. Therefore, the prepared magnetic biocomposite could thus be used as promising adsorbent for the removal of azo dyes from polluted water.

Kinetic study on the effect of temperature on biogas production using a lab scale batch reactor.

In the present study, biogas production from food waste through anaerobic digestion was carried out in a 2l laboratory-scale batch reactor operating at different temperatures with a hydraulic retention time of 30 days. The reactors were operated with a solid concentration of 7.5% of total solids and pH 7. The food wastes used in this experiment were subjected to characterization studies before and after digestion. Modified Gompertz model and Logistic model were used for kinetic study of biogas production. The kinetic parameters, biogas yield potential of the substrate (B), the maximum biogas production rate (Rb) and the duration of lag phase (λ), coefficient of determination (R(2)) and root mean square error (RMSE) were estimated in each case. The effect of temperature on biogas production was evaluated experimentally and compared with the results of kinetic study. The results demonstrated that the reactor with operating temperature of 50°C achieved maximum cumulative biogas production of 7556ml with better biodegradation efficiency.

Enzymatic and non-enzymatic antioxidant potentials of Chlorella vulgaris grown in effluent of a confectionery industry.

Enzymatic and non-enzymatic antioxidant potentials of Chlorella vulgaris have gained considerable importance in recent decades. C. vulgaris strain highly tolerant to extreme pH variations was isolated and mass-cultivated in the wastewater from a confectionery industry. C.vulgaris showed better growth in wastewater than in improvised CFTRI medium. The microalgal biomass was then screened for the following antioxidants: peroxidase, superoxide dismutase, polyphenol oxidase, glutathione peroxidase, chlorophyll a, ascorbic acid, α-tocopherol and reduced glutathione. The total polyphenol content of the strain was also studied. The strain showed a high degree of enzymatic antioxidant activity (0.195 × 10(-5) ± 0.0072 units/cell peroxidase, 0.04125 × 10(-5) ± 0.001 units/cell superoxide dismutase, 0.2625 × 10(-5) ± 0.003 units/cell polyphenol oxidase and 0.025 × 10(-5) ± 0.003 glutathione peroxidase). The microalgal biomass also showed, per milligram weight, 0.2182 ± 0.005 µg of ascorbic acid, 0.00264 ± 0.001 µg of α-tocopherol and 0.07916 ± 0.004 µg of reduced glutathione. These results represent the possibility of using C. vulgaris grown in confectionery industry wastewater as a source of nutritious supplement, which is highly promising in terms of both economic and nutritional point of view.

Composition and temperature-induced structural changes in lead-tellurite glasses on different length scales.

Processes occurring at macroscopic and microscopic length scales across the glass transition (T(g)) in lead-tellurite glass (PbO)(x)(TeO(2))(1-x) (x = 0.1-0.3) are investigated using Brillouin and Raman spectroscopy, respectively. For all the samples, the temperature dependence of the longitudinal acoustic (LA) mode is found to exhibit a universal scaling below T(g) and a rapid softening above T(g). The lower value of elastic modulus at a higher concentration of network modifier PbO, estimated from Brillouin data, arises due to loss of network rigidity. From quantitative analysis of the reduced Raman spectra, several modes are found to exhibit anomalous changes across T(g). Instead of the expected anharmonic behaviour, several modes exhibit hardening, suggesting stiffening of the stretching force constants with temperature, the effect being more pronounced in glasses with higher x. In addition, incorporation of PbO in the glass is also found to narrow down the bond-length distribution, as evident from the sharpening of the Raman bands. The stiffening of the force constants of molecular units at a microscopic length scale and the decrease of elastic constant attributed to loss of network rigidity on a macroscopic length scale appear to be opposite. These different behaviours at two length scales are understood on the basis of a microscopic model involving TeO(n) and PbO units in the structure.

Is phycovolatilization of heavy metals a probable (or possible) physiological phenomenon? An in situ pilot-scale study at a leather-processing chemical industry.

Using algae to treat industrial effluents containing heavy metals presents an alternative to the current practice of using other biosorbents and physical and chemical methods. In this study, effluent from a leather-processing chemical industry in Ranipet, Tamil Nadu, India, was treated for the removal of heavy metals using the microalga, Chlorella vulgaris, which was isolated from the effluent itself. The objectives of this study were to (1) assess the mass balance of a model parameter, lead, in laboratory conditions and estimate the lead adsorption capabilities of the microalga and (2) conduct pilot-scale studies for the removal of heavy metals, using the microalga, from the effluent and the solid waste accumulated over the years generated by conventional treatment methods. The results of the study show that after 8 hours, Chlorella vulgaris exhibited a better adsorption capacity under sunlight compared to laboratory conditions (i.e., 30.6 mg/g dry weight vs 10.5 mg/g dry weight, respectively). Similarly, reduction of heavy metals and mass balance in pilot-scale field studies conducted in a high-rate algal pond showed that the microalga, apart from adsorption, complexation, and entrapment mechanisms, is likely to possess phycovolatilization capability probably via biotransformation processes.

Cytology of the F 1 hybrid of Solanum zuccagnianum Dun. × S. melongena L.

A study on the breeding behaviour of a hitherto unstudied Solanum species, i.e. S. zuccagnianum with S. melongena, is reported. Meiosis in the F1 hybrid, S. zuccagnianum X S. melongena, although normal, was characterized by quadrivalent formation. It is suggested that this is due to segmental interchange and that this is one of the causes of the sterility observed in the hybrid. Cryptic structural differences were also observed by pachytene study.