Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign, 4151 Newmark Civil Engineering Laboratory, 205 North Mathews Avenue, Urbana, Illinois 61801, United States.
Environ Sci Technol. 2012 Mar 20;46(6):3188-95. doi: 10.1021/es203614y. Epub 2012 Mar 1.
Low permeability regions such as clay lenses are difficult to remediate using conventional treatment methods. Bacterial chemotaxis (directed migration toward a contaminant source) may be helpful in enhancing bioremediation of such contaminated sites. This study experimentally simulates a two-dimensional dual-permeability groundwater contamination scenario using a microfluidic device (MFD) and evaluates transverse chemotactic migration of bacteria from high to low permeability regions under various flow velocities. Chemotaxis of Escherichia coli (E. coli) HCB33 to the chemoattractant dl-aspartic acid was quantified in terms of change in total bacterial counts in pore throats in low permeability regions containing attractant. An increase in total bacterial counts, ranging from 1.09 to 1.74 times, was observed in low permeability regions in experiments under chemotactic conditions. Experiments with no attractant showed no increase in total bacterial counts in low permeability regions. A large increase in bacterial counts in the pore throats just outside the low permeability region was also observed in chemotaxis experiments. The bacterial chemotactic response was observed to decrease linearly with increase in flow velocity, with no observed response at the highest flow velocity (Darcy velocity = 0.22 mm/s), where chemotaxis was offset by advective flow.
低渗透性区域，如粘土层，难以用传统的处理方法进行修复。细菌趋化性（朝着污染物源的定向迁移）可能有助于增强此类污染场地的生物修复。本研究使用微流控装置（MFD）实验模拟二维双渗透地下水污染情景，并在各种流速下评估细菌从高渗透性区域向低渗透性区域的横向趋化迁移。用微孔道中含有的趋化物 dl-天冬氨酸酸的总细菌计数的变化来定量评估大肠杆菌（E. coli）HCB33 的趋化性。在趋化条件下的实验中，低渗透性区域的总细菌计数增加了 1.09 到 1.74 倍。在没有趋化物的实验中，低渗透性区域的总细菌计数没有增加。在趋化实验中，也观察到在低渗透性区域外的微孔道中细菌计数大量增加。细菌的趋化反应随流速的增加呈线性下降，在最高流速（达西速度= 0.22mm/s）下没有观察到反应，因为趋化作用被对流流抵消。
