T. Murugesan

Box-Behnken design in the development of optimized complex medium for phenol degradation using Pseudomonas putida (NICM 2174)

Abstract The biodegradation of phenol by Pseudomonas putida (NICM 2174), a potential biodegradent of phenol has been investigated for its degrading potential under different operating conditions. Box-Behnken design has been employed to study the effect of different experimental variables. Four variables of maltose (0.25, 0.5, 0.75u2009g/l), phosphate (3, 12.5, 22u2009g/l), pH (7, 8, 9) and temperature (30u200a°C, 32u200a°C, 34u200a°C) were used to identify the significant effects and interactions in the batch studies. A second order polynomial regression model, has been developed using the experimental data. It was found that the degrading potential of Pseudomonas putida (NICM 2174) was strongly affected by the variations in maltose, phosphate, pH and temperature. The experimental values were in good agreement with the predicted values, the correlation coefficient was found to be 0.9980. Optimum conditions of the variables for the growth of Pseudomonas putida (NICM2174) and for maximum biodegradation of phenol are maltose (0.052u2009g/l), phosphate (8.97u2009g/l), pH (7.9) and temperature (31.5u200a°C).

Design of experiments in the biodegradation of phenol using immobilized Pseudomonas pictorum (NICM-2077) on activated carbon

Pseudomonas pictorum (NICM-2077) immobilized on various matrices are used to protect the microbes from confronting shock loads of concentrated phenol. The cells were immobilized in activated carbon and were used in biodegradation of phenol. Biodegradation of phenol using immobilized Activated Carbon matrix played an important role in reducing the toxicity of phenol. The degradation was carried and using the Box-Behnken model and analysis of variance have been applied to the experimental degradation studies. Response surface method with three levels of phenol concentration (0.200, 0.400, 0.600u2009g/l), activated carbon (0.5, 1.0, 1.5u2009g/l) and pH (7, 8, 9) were used in the identification of significant effects and interactions in the biodegradation studies. Phenol removal rate increases especially when the degradation medium was supplemented with utilizable carbon sources. A first-order polynomial regression model, which was used at first for analysis of the experiment had a significant lack of fit. Therefore, linear and quadratic terms were incorporated into the regression model through variable selection procedures. Effect of incubation phenol concentration, activated carbon and pH were significant. The predicted values using Box-Behnken model was found to be in close agreement with the experimental values, as indicated by the correlation coefficient values of 0.9463.

Critical impeller speed for solid suspension in turbine agitated contactors

The present study in solid-liquid contactors, an attempt has been made to calculate the minimum/critical impeller speed required for complete suspension of solids. A new correlation, involving Reynolds number, modified Froude number, along with the agitation characteristics is proposed. The effect of impeller geometry as well as impeller clearance are clearly established for 6-blade (flat) turbine agitated contactors.

Gas phase hold up in gas-liquid cocurrent upflow packed bed reactors at low Reynold's number

Abstract Experimental measurements of gas phase hold up in two phase gas–liquid cocurrent upflow packed bed reactors have been made at very low gas ((NRe)gu2009<u200955) as well as liquid ((NRe)lu2009<u20098) velocities using air–water systems with two different types of packing materials. The gas hold up values thus obtained are correlated in terms of Reg, Rel and ɛ, the voidage.

Suspension of solid particles in turbine agitated contactors

In this present study in liquid-solid contactors using 6-blade (flat) turbine agitators, an attempt has been made to correlate the system parameters useful for scale-up under turbulent agitation conditions, where the power number is constant. A new correlation involving modified Froude number along with the agitation characteristics, is proposed for the estimation of minimum speed required to maintain complete suspension.