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

表面沃茨中的有害藻华（HAB）是由藻类的大量生长引起的，通常与蓝藻产生的称为“蓝藻毒素”的毒素相关。有害生物威胁着国家的水供应，每年花费数百万美元用于应对和损失收入。微囊藻毒素是淡水湖泊蓝藻水华产生的最常见的蓝藻毒素。微囊藻毒素对人类和动物具有高度毒性，高浓度已导致整个城市饮用水系统暂时关闭。尽管在减少有害藻华方面进行了大量投资，但蓝藻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应对这一挑战，以从饮用水中去除微囊藻毒素并将其分解为无毒产品。工程纳米材料将使用具有特定改性表面的生物炭（从植物中产生的木炭）制造，以捕获微囊藻毒素并将其从水中去除。然后，特殊的细菌在微型生物反应器中降解表面上捕获的毒素。这种“捕获和破坏”技术的成功开发有可能改变我们从饮用水中去除蓝藻毒素的能力。本研究项目的目标是开发新的三维网状功能水凝胶-生物炭复合材料，以选择性地捕获和降解饮用水中的微囊藻毒素。这一目标将通过以下四个具体目标来实现：i）通过互补的孔径、离子交换和π-π电子供体-受体相互作用来开发用于选择性微囊藻毒素吸附的材料; ii）通过强静电相互作用或与带正电荷的季铵基团的离子交换来优化微囊藻毒素吸收动力学; iii）将微囊藻毒素降解细菌聚生体包封到功能性生物材料中，以使微囊藻毒素能够原位生物降解;和iv）通过化学增强的生物过滤去除堵塞并再生生物过滤系统中的吸附剂结合位点。在这项研究中的新进展包括一种新的阳离子聚（二烯丙基二甲基铵-co-苯乙烯）接枝纤维素纳米纤维和生物炭复合材料的合成，阐明微囊藻毒素的吸附/生物降解机制，使用托马斯，亚当斯-Bohart，和CXTFIT模型，和吸附位点表征密度泛函理论。利用扫描电镜结合培养方法对微囊藻毒素降解菌在生物复合材料中的活性和功能进行了评价。逆转录酶定量PCR，16 S rRNA基因测序和宏基因组学分析将用于开发微囊藻毒素降解机制的基因型洞察。这项研究的成功完成将有助于推进水处理技术，将新的有针对性的生物降解与新的功能性纳米材料相结合，作为一种有效的水处理技术。社会效益将产生有效和低成本的处理技术，去除微囊藻毒素，以保护国家的饮用水供应从有害生物。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.