Selenium recovery from wastewater based on exclusively extracellular selenium nanoparticles production

硒（Se）是美国经济和国家安全的关键元素。它也是废水中的一种污染物，必须去除以满足严格的环境排放限制。以前已经使用细菌通过将溶解的Se转化为可以从水中分离的Se纳米颗粒来从废水中去除Se。然而，该方法对于Se回收不是有效的，因为Se纳米颗粒通常在微生物细胞内，因此难以回收。该项目的目标是使硒去除和回收废水中使用新型生物阴极反应器。在这些系统中，特定的细菌在电极上生长，并在微生物细胞外产生Se纳米颗粒，用于有效的Se回收。这项研究的成功完成将提高我们对生物阴极反应器中硒纳米颗粒生产机制的理解。提高废水中硒的回收率对环境和社会有额外的好处。这一过程的潜在经济效益是显着的，因为硒回收只是从燃煤电厂的废物流可以满足所有美国对这个元素的需求。对社会的更广泛影响将来自于一个专注于细菌在这一过程中所起作用的教育和推广计划。这将通过纠正所有细菌都是人类病原体的错误观念来提高国民的科学素养。该项目的目标是开发一种新型的生物阴极反应器系统，以从燃煤发电厂的废水和其他富含硒的废水中回收硒（Se）。这项研究是由新的环境保护局法规大大降低了燃煤电厂废水中硒的排放限制。此外，许多不同产品和行业对硒的需求增加，使回收和再利用成为满足这种需求增加的更可持续的手段。微生物硒反应器利用溶解的硒酸盐到元素硒纳米颗粒的微生物转化。以前的研究硒生物反应器还没有能够证明有效的回收硒，因为元素硒纳米粒子产生细胞内，从而难以分离。在我们的实验室中使用新型生物阴极反应器的初步实验已经证明了特别富集的混合培养物在生物阴极上产生细胞外硒纳米颗粒的能力，而不管接种物。本项目的第一个目标是确定细胞外硒纳米颗粒的生物阴极生产的机制。潜在的干扰，如硝酸盐和硫酸盐，通常存在于含硒废水的影响也将进行研究。将通过综合数学建模与微生物群落结构、功能和动力学实验，开发防止硝酸盐和硫酸盐对硒酸盐还原的负面影响的技术。这项研究的成功完成有可能扩大到回收美国国家利益的其他矿物，如铬，钯，锑和铀。对社会产生更广泛的教育影响的教育和宣传计划，重点是制作有益细菌与有害细菌的教育视频，宣传工作，以吸引学生从代表性不足的群体在干的研究和教育，一场比赛-该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的学术价值和更广泛的影响审查标准。

Selenium (Se) is critical element to the US economy and national security. It is also a contaminant in wastewater that must be removed to meet strict discharge limits to the environment. Bacteria have been used previously to remove Se from wastewater by converting dissolved Se to Se nanoparticles that can be separated from the water. However, this process is not efficient for Se recovery because the Se nanoparticles are typically inside the microbial cells and thus difficult to recover. The goal of this project is to enable both Se removal and recovery from wastewater using novel biocathode reactors. In these systems, specific bacteria grow on electrodes and produce Se nanoparticles outside microbial cells for efficient Se recovery. Successful completion of this research will improve our understanding of the mechanisms of Se nanoparticle production in biocathode reactors. Additional benefits to the environment and society result from improving Se recovery from wastewater. The potential economic benefits of this process are significant, as Se recovery just from coal-fired power plant waste streams alone could meet all the US demand for this element. Broader impacts to society will result from an education and outreach plan focused on the role that bacteria play in the process. This will improve the scientific literacy of the Nation by correcting misperceptions that all bacteria are human pathogens.The goal of this project is to develop a novel biocathode reactor system to recover selenium (Se) from wastewater at coal-fired power plants and other Se-rich waste streams. This research is driven by new Environmental Protection Agency regulations greatly reducing the Se effluent limit from coal-fired power plant wastewater. Additionally, increased demand for Se in many different products and industries makes recovery and re-use a more sustainable means of meeting this increased demand. Microbial Se reactors exploit the microbial conversion of dissolved selenate to elemental Se nanoparticles. Previous research on Se bioreactors has not been able to demonstrate efficient recovery of Se because the elemental Se nanoparticles are produced intracellularly and thereby difficult to separate. Preliminary experiments in our laboratory using novel biocathode reactors have demonstrated the ability of specially enriched mixed cultures to produce extracellular Se nanoparticles on the biocathode regardless of inoculum. The first objective of this project is to determine the mechanisms of extracellular Se nanoparticle production on the biocathode. The effect of potential interferences like nitrate and sulfate that are commonly present in Se-laden wastewater will also be investigated. Techniques to prevent the negative effects of nitrate and sulfate on selenate reduction will be developed through integrated mathematical modeling with experiments on microbial community structure, function, and kinetics. Successful completion of this research has potential to be expanded for the recovery of other minerals of US national interests such as Cr, Pd, Sb, and U. Broader educational impacts to society result from an education and outreach plan focused on the production of an educational video of beneficial versus harmful bacteria, outreach efforts to attract students from underrepresented groups in STEM research and education, and a competition-based design project to accelerate knowledge transfer to engineers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.