Electrokinetics is being applied in combination with common in-situ remediation technologies, e.g. permeable reactive barriers, bioremediation and in-situ chemical oxidation, to overcome experienced limitations in remediation of chlorinated ethenes in low-permeable subsurface soils. The purpose of this review is to evaluate state-of-the-art for identification of major knowledge gaps to obtain robust and successful field-implementations. Some of the major knowledge gaps include the behavior and influence of induced transient changes in soil systems, transport velocities of chlorinated ethenes, and significance of site-specific parameters on transport velocities, e.g. heterogeneous soils and hydrogeochemistry. Furthermore, the various ways of reporting voltage distribution and transport rates complicate the comparison of transport velocities across studies. It was found, that for the combined EK-techniques, it is important to control the pH and redox changes caused by electrolysis 2 for steady transport, uniform distribution of the electric field etc. Specifically for electrokinetically enhanced bioremediation, delivery of lactate and biodegrading bacteria is of the same order of magnitude. This review shows that enhancement of remediation technologies can be achieved by electrokinetics, but major knowledge gaps must be examined to mature EK as robust methods for successful remediation of chlorinated ethene contaminated sites.

Harmful chlorinated ethenes threaten the drinking water resource and its consumers  Transformation of PCE in electrochemical flow-through reactors was studied  Influence of various reactor design parameters was investigated, reaching 86% removal  Normalization of data improved understanding of mechanisms across tests and studies  Electrochemical reduction and oxidation can reduce mass flux of simulated PCE plumes *Highlights (for review : 3 to 5 bullet points (maximum 85 characters including spaces per bullet point)

Highlights: Identification of knowledge gaps in applied in situ electrochemical remediation  High complexity using natural geology and field-extracted contaminated groundwater  Corrosion of the cast iron anode prompted significant precipitation of iron oxides  A simple geochemical model captured the overall observed system response  Rankings of parameter influence on the execution of electrochemical remediation