With the increase in industrial and agricultural activities, a large amount of nitrogenous compounds are released into the environment, leading to nitrate pollution. The perilous effects of nitrate present in the environment pose a major threat to human and animal health. Bioremediation provides a costeffective and environmental friendly method to deal with this problem. The process of aerobic denitrification can reduce nitrate compounds to harmless dinitrogen gas. This review provides a brief view of the exhaustive role played by aerobic denitrifiers for tackling nitrate pollution under different ecological niches and their dependency on various environmental parameters. It also provides an understanding of the enzymes involved in aerobic denitrification. The role of aerobic denitrification to solve the issues faced by the conventional method (aerobic nitrification-anaerobic denitrification) in treating nitrogenpolluted wastewaters is elaborated. verts the iron centre of haemoglobin from Fe 2+ to Fe 3+ Role of heterotrophic aerobic denitrifying bacteriaA. Rajta et al.

It has long been established that a suspension of nanosized solid particles in liquids provide useful advantages in industrial heat transfer fluid systems. Numerous investigations on nanofluids show a significant enhancement in thermal conductivity over the base fluid in which these nanoparticles are dispersed. However, the stability of the suspension is critical in the development and application of these new kind of heat transfer fluids. Rather, high discrepancy in the published data for the same nanoparticles on the physical and thermal characteristics of nanofluids is primarily due to different methods adopted by different researchers to obtain stable nanofluids. Sedimentation and agglomeration of nanoparticles in nanofluids and their dispersion stability has not been well addressed in the literature. Hence, there is a need to establish a standard method of preparation of these nanofluids so as to obtain a unified data which can eventually be utilized for the application of nanofluids. This chapter focuses on the stability of nanofluids prepared via two step process. Different parameters that affect the stability of nanofluids have been discussed. Different techniques that have been used for the evaluation of the stability characteristics of nanofluids have been elucidated.

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