CBET 1150255-Rodrigues Among all the carbon-based nanomaterials (e.g., fullerenes, carbon nanotubes and graphene), graphene-based nanomaterials have been shown to be the least cytotoxic to humans and animals; however, like other nanomaterials, they have antimicrobial properties and may therefore have serious impacts on wastewater treatment. In wastewater treatment plants, microorganisms are responsible for cleaning the water by digesting organic materials and other contaminants. Antimicrobial pollutants can seriously hinder the functionality of the native microbial population, leading to ineffective removal of biological and chemical wastes in the water. Since the market for graphene-based products is projected to be as large as $67 million in 2015 and reach nearly $675 million by 2020, it is expected graphene-based wastes to be generated. Wastewater treatment plants will be one of the ultimate repositories for these wastes. Therefore, it is essential to understand the effect of these graphene-based nanomaterials on microbial populations responsible for the wastewater treatment. At this time, most toxicological studies with graphene-based nanomaterials have focused on the effects of single compositions of graphene-based nanomaterials on one or two bacteria in laboratory settings. It is likely that these studies do not reflect the real effects of graphene-based nanomaterials on the environment. The overarching goal of this research is to understand the mechanisms of microbial toxicity of graphene-based nanomaterials and determine the toxic concentrations that affect the functionality of microbial communities involved in various biogeochemical cycles important in wastewater treatment, such as nitrogen, sulfur, and carbon cycles. Intellectual Merit: This project will enable transformative research in nanotoxicological science by using a new approach that integrates the fields of microbial ecology and environmental biotechnology with traditional environmental engineering to better address challenges in environmental quality, sustainability and security of these nanomaterials. This will be the first study to employ molecular biology techniques to assess the mechanisms of toxicity of graphene-based nanomaterials to answer mechanistic questions that cannot be answered with traditional toxicological assays. Furthermore, this study will also use a molecular biotechnology approach to determine the effects of different concentrations of graphene-based nanomaterials on different nutrient cycles in wastewater. Using this approach, thousands of genes and biogeochemical pathways will be analyzed simultaneously with a DNA microarray platform. At the same time, traditional environmental engineering techniques will be used to set acceptable release concentration limits for graphene-based nanomaterials in the environment. In this study, we will investigate the environmental effects of pure and nanocomposite forms of graphene-based nanomaterials on microorganisms and their biogeochemical cycles in wastewater treatment plants. Results of preliminary studies conducted by the PI show that graphene-based nanomaterials for "clean," well-controlled systems with several microorganisms are toxic to bacteria. However, real aquatic systems are more complex than the simplified system used in the preliminary study. In the proposed project, a systematic investigation will be conducted to understand the impact of graphene-based nanomaterials on microbial communities and their biogeobiochemical cycles under real aquatic system conditions. Broader Impact: The project can potentially impact the use and applications of graphene-based nanomaterials in various technologies. The results will contribute to the body of knowledge required to assess the risk of nanomaterials by policy makers, regulatory officials, and environmental scientists. However, one of the most important impacts of this project is the education and training of young scientists and researchers who will be skilled to determine how safe these new materials are in the environment. This project includes three education and outreach components: (1) Mentoring of teachers in environmental research as part of a new research experience for teachers (RET) program recently funded by NSF in order to allow them to learn about the field of engineering and be able to mentor their students in this path; (2) Development of a pilot program to provide summer research experiences to girls in Grades 8-12 to expand diversity in science and engineering; (3) Integration of environmental engineering, environmental biotechnology, and microbial ecology into the environmental engineering undergraduate and graduate curriculum at UH. The PI brings her experiences as a minority to the mentoring of under-represented students. Diversity is not only a goal, but a cornerstone of her research group. The PI has successfully engaged three female graduate students in research, one of which is Hispanic-American Ph.D. student.
