Manoj K. Tiwari

Influence of extrinsic factors on granulation in UASB reactor

The aim of this mini-review is to synthesize and analyze information on how the process of granulation is affected by environmental and operational conditions in the reactor. The factors reviewed are temperature, pH, alkalinity, organic loading rate, upflow velocity, nature and strength of substrate, nutrients, multivalent cations and heavy metals, microbial ecology of seed sludge, exo-cellular polymer, and addition of natural and synthetic polymers. Careful temperature control and adequate alkalinity is required for generation and maintenance of granules. Nature and strength of substrate in conjunction with intra-granular diffusion to a large extent determines the microstructure of the granules. The divalent cations such as calcium and iron may enhance granulation by ionic bridging and linking exo-cellular polymers. However, their presence in excess may lead to cementation due to precipitation leading to increased ash content and mass transfer limitation. The addition of external additives such as ionic polymers may enhance granulation in the upflow anaerobic sludge blanket reactors.

Kinetics of the biodegradation pathway of endosulfan in the aerobic and anaerobic environments.

The enriched mixed culture aerobic and anaerobic bacteria from agricultural soils were used to study the degradation of endosulfan (ES) in aqueous and soil slurry environments. The extent of biodegradation was ∼95% in aqueous and ∼65% in soil slurry during 15 d in aerobic studies and, ∼80% in aqueous and ∼60% in soil slurry during 60 d in anaerobic studies. The pathways of aerobic and anaerobic degradation of ES were modeled using combination of Monod no growth model and first order kinetics. The rate of biodegradation of β-isomer was faster compared to α-isomer. Conversion of ES to endosulfan sulfate (ESS) and endosulfan diol (ESD) were the rate limiting steps in aerobic medium and, the hydrolysis of ES to ESD was the rate limiting step in anaerobic medium. The mass balance indicated further degradation of endosulfan ether (ESE) and endosulfan lactone (ESL), but no end-products were identified. In the soil slurries, the rates of degradation of sorbed contaminants were slower. As a result, net rate of degradation reduced, increasing the persistence of the compounds. The soil phase degradation rate of β-isomer was slowed down more compared with α-isomer, which was attributed to its higher partition coefficient on the soil.

Simultaneous analysis of endosulfan, chlorpyrifos, and their metabolites in natural soil and water samples using gas chromatography-tandem mass spectrometry.

Analysis of endosulfan, chlorpyrifos, and their nonpolar metabolites in extracts from environmental aqueous and soil samples was performed using a gas chromatography-tandem mass spectrometry (GC–MS/MS) technique. Full-scan GC–MS analysis showed poor sensitivity for some of the metabolites (endodiol and endosulfan ether). A multisegment MS/MS method was developed and MS/MS parameter isolation time, excitation time, excitation voltage, and maximum excitation energy were optimized for chosen precursor ions to enhance selectivity and sensitivity of the analysis. The use of MS/MS with optimized parameters quantified analytes with significantly higher accuracy, and detection limits were lowered to ~1/6th compared with the full-scan method. Co-eluting compounds, chlorpyrifos and chlorpyrifos oxon, were also analyzed successfully in the MS/MS mode by choosing exclusive precursor ions. Analysis of soil and water phase samples from contaminated soil slurry bioreactors showed that the MS/MS method could provide more reliable estimates of these pesticide and metabolites (especially those present in low concentrations) by annulling interferences from soil organic matter.

Multivariate optimization for electrochemical oxidation of methyl orange: Pathway identification and toxicity analysis

Electrochemical oxidation of methyl orange (Sodium 4-[(4-dimethylamino) phenyldiazenyl] benzenesulfonate) with lead dioxide coated on mild steel was modelled using response surface methodology (RSM) to analyze the influence of pH, NaCl dose and current on color and chemical oxygen demand (COD) removal. Higher current, acidic pH and 0.8–1.2 g L−1 NaCl dose had an enhancing effect on the removal efficiencies. Interaction effect of the variables highlights the action of •OH and HOCl in the oxidation of methyl orange, where HOCl has effect at lower current range. More than 90% COD removal efficiency and ∼100% color removal efficiency was obtained in 5 h at optimum conditions for an initial concentration of 50 mg L−1. High performance liquid chromatography–mass spectroscopy (HPLC-MS) analysis carried out to identify degradation intermediates revealed the absence of chlorinated intermediates, which was further verified with Fourier transform infrared spectroscopy (FTIR) analysis. The postulated pathway of degradation indicated breakdown through dealkylation, deamination, desulfonation and cleavage of an azo bond and benzene ring. The degradation of methyl orange to smaller compounds was also confirmed by Ion Chromatography (IC). Cytotoxicity analysis on HaCaT cells revealed the intermediates to be more cytotoxic than the dye, possibly due to the aromatic amines and diazines formed during the degradation process.

Asset liability management model with decision support system for life insurance companies: Computational results

Abstract Big Data Analytics is an important and flexible tool available for data analysis and informed decision making. In this paper, we look at the use of Big Data Analytics in asset liability management and asset allocation in uncertain economic situations using stochastic linear programming (SLP). In particular, this paper is an extension of our earlier work and we contribute to the existing literature by conducting experiments on the stochastic model through DSS. In particular, for this SLP based DSS, we address issues like the optimal number of scenarios required for good results, and the impact of the change in the number of scenarios on the stability of the model. The paper also addresses the impact of the change in the number of scenarios on the policy holders’ as well as shareholders’ reserves. In particular, we show the relevance of employing a larger number of scenarios and also present the experimental design developed to test the relevance of this model. We also show that a stochastic model employing fewer scenarios produced marked improvements in both return side measures as well as risk side measures compared to a mean value model or a partial mean value model.

Endonasal Endoscopic Approach for Skull Base Neurofibroma: Is It Viable?

Anterior skull base and sinonasal schwannomas are rare entities. Earlier, safest way to remove these tumors, with best success rates, was open craniofacial surgery but recently with introduction of endoscopic endonasal approach; complete resection of these rare entities is possible. We present one such case of skull base neurofibroma which was resected in entirety via a purely endoscopic endonasal approach.