Modeling of chromium (VI) biosorption by immobilized Spirulina platensis in packed column.

This study describes biosorption of chromium (VI) by immobilized Spirulina platensis, in calcium alginate beads. Three aspects viz. optimization of bead parameters, equilibrium conditions and packed column operation were studied and subsequently modeled. Under optimized bead diameter (2.6mm), calcium alginate concentration (2%, w/v) and biomass loading (2.6%, w/v) maximum biosorption was achieved. 140 g l(-1) loading of optimized beads resulted in 99% adsorption of chromium (VI) ions from an aqueous solution containing 100 mg l(-1) of chromium (VI). The quantitative chromium (VI) uptake was effectively described by Freundlich adsorption isotherm. The immobilized S. platensis beads were further used in a packed bed column wherein the effects of bed height, feed flow rate, inlet chromium (VI) ion concentration were studied by assessing breakthrough time. The performance data were tested for various models fitting in order to predict scale up-design parameters such as breakthrough time and column height. Results were encouraging.

Kinetic and equilibrium modeling of chromium (VI) biosorption on fresh and spent Spirulina platensis/Chlorella vulgaris biomass.

Biosorption of chromium (VI) was studied using both fresh and spent algal biomass of Spirulina platensis and Chlorella vulgaris. Both showed comparable behavior suggesting that biosorption is primarily a surface phenomenon. Biosorption rate was very fast during the first five minutes, in which almost 50% of the chromium (VI) was adsorbed. Two step kinetic model was proposed for biosorption. Equilibrium data obeyed Freundlich and Langmuir adsorption isotherms. Fresh algal biomass of S. platensis gave maximum of 73.6% biosorption of chromium (VI) in 100 ppm solution at 1 g l(-1) cell loading. For improved economics, beta-carotene was extracted from S. platensis and the spent biomass was used for chromium (VI) biosorption. The maximum biosorption by spent biomass was increased to 86.2%. Thus, this two step process not only showed improved efficiency in biosorption ( approximately 17% increase) but also gave valuable byproduct, namely beta-carotene.

Effect of cavitation on chemical disinfection efficiency.

This study brings out the potential efficacy of hybrid techniques for water disinfection. The techniques studied include hydrodynamic cavitation, acoustic cavitation and treatment with chemicals like hydrogen peroxide and ozone. The hybrid techniques which combine hydrodynamic cavitation, acoustic cavitation and hydrogen peroxide appear to be an attractive alternative to any one technique on its own for the reduction in the heterotropic plate count bacteria as well as indicator microorganisms like the total coliforms, fecal coliforms and fecal streptococci.

Hybrid cavitation methods for water disinfection: simultaneous use of chemicals with cavitation.

This study brings out the potential efficacy of hybrid techniques for water disinfection. The techniques studied include, hydrodynamic cavitation, acoustic cavitation and treatment with chemicals such as ozone and hydrogen peroxide. The phenomena of cavitation which involves formation, growth and violent collapse of vapor bubbles in a liquid media is known to generate a high intensity pressure which affects the cell and microorganism viability. The hybrid technique which combines hydrodynamic cavitation, acoustic cavitation, hydrogen peroxide and/or ozone appears to be an attractive alternative to a single technique for the reduction in the heterotropic plate count bacteria as well as indicator microorganisms like the Total coliforms, Fecal coliforms and Fecal streptococci.