Selenium recovery from wastewater based on exclusively extracellular selenium nanoparticles production

硒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，必须去除才能满足对环境的严格排放限制。以前，细菌通过将溶解的Se转化为可从水中分离的Se纳米颗粒来去除废水中的Se。然而，这一过程对回收Se并不有效，因为Se纳米颗粒通常位于微生物细胞内，因此很难回收。该项目的目标是使用新型生物催化反应器从废水中去除和回收Se。在这些系统中，特定的细菌生长在电极上，并在微生物细胞外产生纳米Se颗粒，以有效地回收Se。这项研究的成功完成将提高我们对生物催化反应器中Se纳米颗粒产生机理的理解。提高从废水中回收Se还可以给环境和社会带来额外的好处。这一过程的潜在经济效益是显著的，因为仅从燃煤电厂的废气中回收Se就可以满足美国对这种元素的所有需求。一项教育和宣传计划将对社会产生更广泛的影响，该计划的重点是细菌在这一过程中发挥的作用。这将通过纠正所有细菌都是人类病原体的误解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催化反应器系统，从燃煤发电厂和其他富硒废水中回收硒(Se)。这项研究是由美国环保局的新法规推动的，大大降低了燃煤电厂废水的排放限制。此外，许多不同产品和行业对Se的需求增加，使得回收和再利用成为满足这种增加的需求的一种更可持续的手段。微生物硒反应器利用微生物将溶解的亚硒酸盐转化为元素硒纳米颗粒。以前对硒生物反应器的研究还不能证明有效地回收硒，因为元素硒纳米颗粒是在细胞内产生的，因此很难分离。我们实验室使用新型生物催化反应器的初步实验已经证明，无论接种量如何，特别浓缩的混合培养物都能够在生物催化材料上产生胞外纳米Se。该项目的第一个目标是确定细胞外纳米Se颗粒在生物催化体上的产生机制。还将调查含硒废水中常见的硝酸盐和硫酸盐等潜在干扰的影响。防止硝酸盐和硫酸盐对硒还原的负面影响的技术将通过结合微生物群落结构、功能和动力学的实验进行综合数学建模来开发。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。这项研究对社会的广泛教育影响来自一项教育和推广计划，该计划侧重于制作有益细菌与有害细菌的教育视频，扩大努力以吸引STEM研究和教育中未被充分代表的群体的学生，以及一个基于竞争的设计项目，以加速知识向工程师的转移。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.