the above section is a summary of what is thought of as ex situ solutions. many of the features described in this section are being used in situ, that is, within the subsurface. examples include the extraction and assimilation of co2, the production of methane, and the development of engineered microbial communities to remove pollutants from soil. some of these topics will be developed in the last section of the chapter, the in situ section.
the study of electrokinetics is relatively new. electrokinetics was developed in the 1980s and has gained considerable interest as a new tool for the management of pollutants. studies on the separation of electrolytes by electrokinetic methods have been conducted for many years. however, the major advantage of electrokinetics is the ability to handle large volumes of fluids, generate high-intensity shear forces, and apply forces to charged and uncharged species in aqueous solutions. this paper examines the applications of electrokinetics, which include the separation of electrolytes, demulsification, the filtration of colloidal particles, the separation of biological components, the removal of pollutants from soil and groundwater, the enhanced recovery of oil and gas, and the treatment of groundwater. some of the challenges in developing applications of electrokinetics are examined, including the need to overcome local electrical resistance, the need to better understand electrochemical and electrochemical engineering principles, and the need to develop instrumentation and electrochemical cell configurations. the review concludes with a discussion of the current status of electrokinetic applications and directions for future research.