Immobilization and in-situ biodegradation of microcystins using engineered biofiltration for drinking water production

地表水中有害的藻类水华(HAB)是由藻类的大量生长引起的，通常伴随着由蓝藻产生的被称为“氰毒素”的相关毒素。哈巴病威胁着国家的供水，每年因此而造成数百万美元的损失和收入损失。微囊藻毒素是淡水湖蓝藻水华产生的最常见的蓝藻毒素。微囊藻毒素对人和动物都有很高的毒性，高浓度的藻毒素已导致整个市政饮用水系统暂时关闭。尽管在缓解赤潮方面投入了大量资金，但氰基毒素仍然是安全饮用水生产的一个巨大挑战。该项目的目标是通过开发新型工程纳米材料来消除饮用水中的微囊藻毒素并将其分解为无毒产品来应对这一挑战。这种工程纳米材料将使用生物炭(从植物中产生的木炭)制造，并具有特定的修饰表面，以捕获微囊藻毒素并将其从水中去除。然后，特殊细菌在微型生物反应器中降解捕获在表面的毒素。这种“诱捕和摧毁”技术的成功开发，有可能改变我们从饮用水中去除氰基毒素的能力。通过培养多学科的研究生来提高国家的STEM工作能力，也带来了额外的社会效益。本研究项目的目标是开发新型三维网状功能水凝胶-生物炭复合材料，选择性地捕获和降解饮用水中的微囊藻毒素。这一目标将通过四个具体目标实现：i)开发通过互补孔径、离子交换和π-π电子供体-受体相互作用来选择性吸附微囊藻毒素的材料；ii)通过强大的静电相互作用或与带正电的季铵盐基的离子交换来优化微囊藻毒素的吸收动力学；iii)将降解微囊藻毒素的菌群包裹到功能生物材料中，以便能够就地生物降解微囊藻毒素；以及iv)通过化学强化反冲洗来消除生物过滤系统中的堵塞，并重新生成吸附剂结合部位。本研究的新进展包括合成了一种新型的阳离子poly(diallyldimethylammonium-co-styrene)-grafted纤维素纳米纤维/生物炭复合材料，用Thomas、Adams-Bohart和CXTFIT模型阐明了微囊藻毒素的吸附/生物降解机理，并用密度泛函理论表征了微囊藻毒素的吸附位置。通过扫描电子显微镜和培养相结合的方法，对包裹在生物材料复合材料中的微囊藻毒素降解菌的活性和功能进行评估。我们将利用逆转录酶定量聚合酶链式反应、16S rRNA基因测序和元基因组学分析来深入了解微囊藻毒素的降解机制。这项研究的成功完成将有助于通过将新的靶向生物降解与新的功能纳米材料作为有效的水处理技术相结合来促进水处理技术的进步。用于去除微囊藻毒素的有效和低成本处理技术将带来社会效益，以保护国家饮用水供应不受HAB的影响。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。

Harmful algal blooms (HABs) in surface waters are caused by massive growth of algae often with associated toxins called ‘cyanotoxins’ produced by cyanobacteria. HABs threaten the Nation’s water supplies and cost millions of dollars per year in responses and lost revenue. Microcystin is the most common cyanotoxin produced by cyanobacteria blooms in freshwater lakes. Microcystin is highly toxic to humans and animals, and large concentrations have resulted in the temporary shutdown of an entire municipal drinking water system. Despite large investments in HAB mitigation, cyanotoxins continue to be a great challenge for safe drinking water production. The goal of this project is to address this challenge through the development of novel engineered nanomaterials to remove microcystin from drinking water and break it down to non-toxic products. The engineered nanomaterials will be fabricated using biochar (charcoal produced from plants) with specific modified surfaces to trap microcystin and remove it from water. Special bacteria then degrade the toxins trapped on the surface in a microscale bioreactor. Successful development of this ‘trap and destroy’ technology has potential to transform our ability to remove cyanotoxins from drinking water. Additional societal benefits result from the training of graduate students in multidisciplinary science to enhance the Nation’s STEM workforce.The goal of this research project is to develop new three-dimensional net-like functional hydrogel-biochar composite materials to selectively capture and degrade microcystin in drinking water. This goal will be achieved through four specific objectives to: i) develop materials for selective microcystin adsorption through complementary pore size, ion exchange, and π-π electron donor-acceptor interactions; ii) optimize microcystin uptake kinetics through strong electrostatic interactions or ion exchange with positively charged quaternary ammonium groups; iii) encapsulate microcystin-degrading bacterial consortia into functional biomaterials to enable in situ biodegradation of microcystin; and iv) remove clogging and regenerate adsorbent binding sites in the biofiltration system through a chemically enhanced backwash. Novel advances in this research include the synthesis of a new cationic poly(diallyldimethylammonium-co-styrene)-grafted cellulose nanofibril and biochar composite, elucidation of microcystin adsorption/biodegradation mechanisms using Thomas, Adams-Bohart, and CXTFIT models, and sorption site characterization using density functional theory. The viability and function of microcystin-degrading bacteria encapsulated in biomaterial composites will be evaluated by coupling scanning electron microscope and culturing methods. Reverse transcriptase quantitative PCR, 16S rRNA gene sequencing, and metagenomics analysis will be used to develop genotypic insight into microcystin degradation mechanisms. Successful completion of this research will help advance water treatment technologies by integrating novel targeted biodegradation with new functional nanomaterials as an effective water treatment technology. Societal benefits will result from effective and low-cost treatment technology for microcystin removal to protect the Nation’s drinking water supplies from HABs.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.