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，必须去除才能满足严格的环境排放限制。以前已经使用细菌将溶解的硒转化为可从水中分离的硒纳米粒子，从而从废水中去除硒。然而，这种方法对硒的回收效率不高，因为硒纳米颗粒通常在微生物细胞内，因此难以回收。该项目的目标是利用新型生物阴极反应器从废水中去除和回收硒。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硒纳米粒子，以有效地回收硒。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产生机制的理解。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巨大的，因为仅从燃煤电厂的废物流中回收硒就可以满足美国对这种元素的所有需求。针对细菌在这一过程中所起作用的教育和推广计划将对社会产生更广泛的影响。这将纠正所有细菌都是人类病原体的误解，从而提高国民的科学素养。该项目的目标是开发一种新型生物阴极反应器系统，用于从燃煤电厂的废水和其他富硒废物流中回收硒。这项研究是由环境保护署的新规定推动的，该规定大大降低了燃煤电厂废水的硒排放限制。此外，许多不同的产品和行业对硒的需求不断增加，使得回收和再利用成为满足这种需求的更可持续的手段。微生物硒反应器利用微生物将溶解的硒酸盐转化为元素硒纳米粒子。由于硒元素纳米粒子是在细胞内产生的，因此难以分离，因此以前对硒生物反应器的研究未能证明硒的有效回收。我们实验室使用新型生物阴极反应器进行的初步实验表明，无论接种量如何，特别富集的混合培养物都能在生物阴极上产生细胞外硒纳米颗粒。该项目的第一个目标是确定细胞外硒纳米颗粒在生物阴极上产生的机制。还将研究含硒废水中常见的硝酸盐和硫酸盐等潜在干扰因素的影响。通过对微生物群落结构、功能和动力学的综合数学建模，将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对美国国家利益的其他矿物的回收，如Cr， Pd， Sb和U.对社会产生更广泛的教育影响，教育和推广计划侧重于制作有益细菌与有害细菌的教育视频，推广努力吸引STEM研究和教育中代表性不足的群体的学生，以及一个以竞赛为基础的设计项目，以加速知识向工程师的转移。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.