Electrocoagulation as a treatment component for polluted stormwater (2020)

Electrocoagulation as a treatment component for polluted stormwater, is a project that aims to investigate the treatment efficiency of an electrocoagulation process. The process is financed through the J. Gust. Richert Foundation.

Ponds and settling basins are standard treatment systems for road runoff in Sweden. The treatment occurs primarily by sedimentation and pollutants are entrained in the sludge. Such systems perform satisfactorily for larger particles that will settle during the targeted residence times, but not for smaller particle fractions (<20 µm). These fractions tend to stay in suspension as the drag forces acting upon them are stronger than the gravitational force. From a water quality perspective, these smaller fractions are important to remove, as they present a much larger surface area for pollutants to adsorb onto. An unsatisfactory removal of this particle fraction would result in overall low treatment performance.

Coagulation/flocculation is a treatment method that increases the particle’s settling potential by counteracting the natural forces stopping particle aggregation. This increases the removal efficiency and gives rise to precipitation reactions that may reduce the amount of dissolved organic material and metals.

Electrocoagulation is primarily used today as a treatment for industrial waters. It is a development of coagulation where instead of adding chemicals, an equivalent reaction is attained using electrodes in an electrolysis cell. There exist a number of benefits with the use of electrocoagulation, such as lower energy demand, a more stable sludge, a higher removal efficiency due to redox reactions, and emulsion breaking properties.

In the project, a laboratory-scale reactor will be constructed to treat polluted stormwater under different conditions and parameters. One of the advantages of this approach is that multiple parameters can be measured in-situ continuously, resulting in a detailed process description. Treatment effect, process characteristics, and energy consumption will be analyzed and evaluated in the experiments. The purpose is to generate information that can be used for future implementation schemes.

This project is financed through the J. Gust. Richert foundation. The project is ongoing and experiments will be run in spring 2020.

Fredrik Nyström, Inga Herrmann och Annelie Hedström