In recent years, carbon-based nanomaterials have advanced significantly in terms of synthesis and chemical modifications for diverse applications in nanotechnology. Among the carbon-based nanomaterials, single-walled carbon nanotubes (SWNT) and graphene oxides (GO) have been attracting researchers' interest due to their unique electronic and physicochemical properties. On the other hand, studies focusing on the understanding of their toxicological properties and potential antimicrobial applications are still in their infancy. The major barriers for such applications are their poor dispersion in most mediums, high cost and high cytotoxicity towards mammalian cells. In this study, we overcome these limitations by incorporating only 3% (weight %) of these nanomaterials into aromatic polymer matrices of poly-vinyl carbazole (PVK) to improve their dispersion and antibacterial effects. The higher antimicrobial effects of PVK-SWNT and PVK-GO nanocomposites were attributed to a better contact of the nanomaterial with the bacterial cells by enhanced dispersion of the nanomaterial in the polymer matrix. The antimicrobial property of theses nanocomposites was observed on free swimming cells and on biofilms in solutions and coated surfaces, respectively. Cytotoxic effects of PVK-SWNT nanocomposite to mammalian cells was also found to be minimal due to low amount of the nanomaterial (only 3%) in the nanocomposite, which is promising in terms of applications where humans can be exposed to these nanomaterials, such as biomedical devices and water treatment systems. Furthermore, nanomaterials, such as SWNT and GO, were also demonstrated to be effective in removing biofouling agents, like protein, from aqueous solutions. GO exhibited the highest protein sorption capacity (~500 mg protein/g nanomaterial). The adsorption phenomena were found to be dependent on the surface charge of the nanomaterial and solution chemistry. Besides investigating the potential applications for these nanomaterials, their fate and impact in the environment were investigated. Acute exposure of GO to wastewater microbial communities involved in the carbon, nitrogen and phosphorous biogeochemical cycles was investigated. A dose dependent inhibitory effect of GO was observed on the wastewater microbial metabolic activity. Furthermore, GO was found to adversely affect the bioremoval of carbon, nitrogen and phosphorus in the wastewater treatment process at concentrations as low as 10 mg/L.