Indra Mani Mishra

Pretreatment of petrochemical wastewater by coagulation and flocculation and the sludge characteristics

In the present study, coagulation-flocculation was investigated as a pretreatment process for the treatment of purified terephthalic acid (PTA) wastewater. The effect of various inorganic and organic coagulants on the treatment of wastewater collected from flow equalization tank of an effluent treatment plant was studied. The settling and filtration characteristics of the sludge were also studied. The jar tests revealed that the wastewater was best treated when 3000 mg l(-1) of ferric chloride was dosed at pH 5.6. At optimum conditions, COD of the wastewater was reduced by 75.5%. The results of the gravity filtration of the treated wastewater showed that the addition of cationic polyacrylamide (175 mg l(-1)) to ferric chloride coagulation improved the filtration characteristics and reduced the specific cake resistance. Scanning electron microscopy and energy dispersive spectroscopy studies were also conducted to know the sludge structure and composition, respectively. Thermal analysis of the sludge showed that the oxidation of the sludges in the present study is a three step process. However, with the addition of C-PAA to ferric chloride coagulation system, the oxidation was found to be a two step process.

Modelling Individual and Competitive Adsorption of Cadmium(II) and Zinc(II) Metal Ions from Aqueous Solution onto Bagasse Fly Ash

Abstract The present study deals with the competitive adsorption of cadmium (Cd(II)) and zinc (Zn(II)) ions onto bagasse fly ash (BFA) from binary systems. BFA is a waste obtained from the bagasse‐fired boilers of sugar mills. The initial pH≈6.0 is found to be the optimum for the individual removal of Cd(II) and Zn(II) ions by BFA. The equilibrium adsorption data were obtained at different initial concentrations (C 0 = 10–100 mg/l), 5 h contact time, 30°C temperature, BFA dosage of 10 mg/l at pH 0 = 6. The Redlich–Peterson (R–P) and the Freundlich models represent the single ion equilibrium adsorption data better than the Langmuir model. The adsorption capacities in the binary‐metal mixtures are in the order Zn(II)>Cd(II) and is in agreement with the single‐component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined action of Cd(II) and Zn(II) ions on BFA is found to be antagonistic. Equilibrium isotherms for the binary adsorption of Cd(II) and Zn(II) ions on BFA have been analyzed by non‐modified Langmuir, modified Langmuir, extended‐Langmuir, Sheindorf–Rebuhn–Sheintuch (SRS), non‐modified R–P and modified R–P adsorption models. The isotherm model fitting has been done by minimizing the Marquardts percent standard deviation (MPSD) error function using MS Excel. The SRS model satisfactory fits for most of the adsorption equilibrium data of Cd(II) and Zn(II) ions onto BFA.

Optimization of structural and operational variables for the energy efficiency of a divided wall distillation column

Abstract In the present work, the optimization of different structural and process parameters of a divided wall column (DWC) for the energy efficiency has been presented. The optimal design and operation of divided wall distillation columns involve a number of variables and is a non-linear problem. Rigorous simulation of a DWC was carried out using Multifrac model of ASPEN Plus software. Box–Behnken design (BBD) under response surface methodology (RSM) was used for the optimization of the parameters and to evaluate the effects of these parameters and their interactions on the energy efficiency of a DWC. The process variables were found to have significant effect on the energy efficiency of a DWC as compared to the effect of structural variables, and the predictions from the BBD optimization agree well with the results of the rigorous simulation.

Treatment of catechol bearing wastewater in an upflow anaerobic sludge blanket (UASB) reactor: sludge characteristics.

This paper deals with the characteristics of anaerobic microbial granules grown in an UASB reactor treating catechol bearing synthetic wastewater (SWW). The specific methanogenic activity of the sludge showed an increase in trend with an increase in the organic loading rate and the catechol concentration in the SWW. The settling velocity of individual granules in the size range of 0.5-2.5mm was found to be in the range of 30-75mh(-1). The ash content in the sludge was 11.7% with a sludge volume index of 18-20mlg(-1). The inorganic elemental distribution within the granules showed a decrease except that for phosphorous and cobalt, which increased by approximately 12% and 18%, respectively, after the treatment of SWW. Scanning electron microscopy (SEM) coupled with electron disperse X-ray analysis showed an increase in the sulphur content by approximately 300% after the treatment of SWW. Surface mineral composition of the granules determined by XRD analysis indicated the existence of vuagnatite (CaAlSiO(4)(OH)). SEM observation of the granules showed the predominance of Methanosaeta and Methanobacterium type of species on the surface along with a variety of other species.

Isotherm and kinetics study for acrylic acid removal using powdered activated carbon.

The potential of powdered activated carbon (PAC) for the adsorption of acrylic acid (AA) from aqueous solution was studied at the initial concentration (C(0)) in the range of 50-500 mg/l over the temperature range of 303-348 K. The equilibrium adsorption studies were carried out to evaluate the effect of adsorbent dosage and contact time, change in pH by adding adsorbents and the initial concentration. Langmuir, Freundlich and Redlich-Peterson (R-P) equilibrium isotherm models were tested to represent the data. Error functions were used to test their validity to fit of the adsorption data with the isotherm and kinetic models. The Freundlich isotherm equation is found to best represent the equilibrium separation data in the temperature range of 303-348 K. The maximum adsorption capacity of AA onto PAC was obtained as q(m)=36.23 mg/g with an optimum PAC dosage w=20 g/l at 303 K for C(0)=100 mg/l. The pseudo-second-order kinetics is found to represent the experimental AA-PAC data. The negative value of DeltaG(ad)(o) (-16.60 to -18.18 kJ/mol K) indicate the feasibility and spontaneity of the adsorption process.

Critical analysis of engineering aspects of shaken flask bioreactors

Shaking bioreactors are the most frequently used reaction vessels in biotechnology. Since their inception, shaking bioreactors have been playing a significant role in medicine, agriculture, food, environmental, and industrial research. In spite of their huge practical importance, very little is known about the characteristic properties of shaken cultures from an engineering point of view. In this paper, a critical analysis is presented of the mixing characteristics, aeration, mass and heat transfer, power consumption, and suitability for on-line monitoring and control of various environmental and other operating parameters in aerated and anaerobic/anoxic conditions. Aspects of cell damage due to shear stress generated in shaken flask and loss of sterility due to contamination are also discussed.

ADSORPTION OF CATECHOL, RESORCINOL, HYDROQUINONE, AND THEIR DERIVATIVES: A REVIEW

In recent years, there has been an increasing interest in finding innovative solutions for the efficient removal of contaminants from water, soil, and air. The present study reviews the adsorptive removal of catechol (C), resorcinol (R), hydroquinone (HQ), and their derivatives from various adsorbents. As an effective, efficient, and economic approach for water purification, adsorbents and adsorption processes have been widely studied and applied in different aspects for a long time. The role of various adsorbent materials like activated carbon, activated carbon cloth, carbon nanotubes, polymeric resins, organic clays, Fe(OH)2, and TiO2 was discussed together with that of other experimental parameters. In all the synthetic resins, particularly, aminated hypercrosslinked polymers have good adsorption capability for phenols. These polymeric adsorbents are suitable for industrial effluents containing C, R, HQ, and their derivatives. The adsorption capacities of the adsorbents reviewed here vary significantly depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentrations of solutes.

Study of Catechol and Resorcinol Adsorption Mechanism through Granular Activated Carbon Characterization, pH and Kinetic Study

The present article reports results of the studies on adsorptive removal of catechol and resorcinol from aqueous solution by granular activated carbon (GAC). Physico-chemical characterization including surface area, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) of the GAC before and after catechol and resorcinol adsorption have been done to understand the adsorption mechanism. Bulk density and heating value of GAC were found to be 725 kg/m3 and 8.26 MJ/kg, respectively. The BET surface area was 977.6 m2/g whereas the BET average pore diameter was 18.79 Å. Different experimental parameters like initial pH, initial dosage, contact time, and initial concentration were evaluated for their effect on the adsorption of catechol and resorcinol onto GAC. The kinetics of adsorption was found to be described by the pseudo-second order equation. Results of the intra-particle diffusion model show that the pore diffusion is not the only rate limiting step. The effective diffusion coefficient of catechol and resorcinol were of the order of 2.9 × 10−10 and 2.2 × 10−10 m2/s.

Effectiveness of coagulation and acid precipitation processes for the pre-treatment of diluted black liquor

The effectiveness of coagulation (using aluminium-based chemicals and ferrous sulfate) and acid precipitation (using H(2)SO(4)) processes for the pre-treatment of diluted black liquor obtained from a pulp and paper mill is reported. Commercial alum was found to be the most economical among all the aluminium and ferrous salts used as a coagulant. A maximum removal of chemical oxygen demand (COD) (ca. 63%) and colour reduction (ca. 90%) from the wastewater (COD = 7000 mg l(-1)) at pH 5.0 was obtained with alum. During the acid precipitation process, at pH < 5.0, significant COD reductions (up to 64%) were observed. Solid residue obtained from the alum treatment at a temperature of 95 degrees C showed much better (3 times) settling rate than that for the residue obtained after treatment with the same coagulant at a temperature of 25 degrees C. The settling curves had three parts, namely, hindered, transition and compression zones. Tory plots were used to determine the critical height of suspension-supernatant interface that is used in the design of a clarifier-thickener unit. High heating values and large biomass fraction of the solid residues can encourage the fuel users to use this waste derived sludge as a potential renewable energy source.

On the kinetics and effectiveness of immobilized whole-cell batch cultures

Abstract A model for growth-associated fermentations is presented for batch cultures of immobilized whole cells. The model encompasses exponential and steady-state growth phases and the effectiveness of the biocatalyst. Based on the model equations, experimental methods have been developed for the determination of the kinetic parameters: maximum specific growth rate (μ max ), Monod constant ( K m ) and effectiveness factor (η). These methods are illustrated by ethanol fermentations using Saccharomyces cerevisiae cells entrapped in alginate beads. The kinetic parameters obtained show consistency with those determined for free-cell systems.