The use of an electric field to modify the surface charge of the algal cells and stimulate flocculation holds the potential for improved harvesting since, in theory, the method would not require addition of chemicals and could be easily run as a continuous system. The hurdles for general applicability of these technologies are development of electrodes that do not add metals to the system and reducing the cost of the power required.

Electrocoagulation using metal electrodes employs similar chemical phenomena as tradition coagulation, but rather than introducing a dry chemical, such as alu­minum chloride, metal ions are typically released from the reactive metal electrode into the water through electrolysis. The metal ions then act similarly to the dry chemicals. The use of electricity also helps influence the particle charges. Envi­ronmental parameters such as pH and salinity must be optimized for electrocoag­ulation to work efficiently. Therefore, the trade-offs between electrocoagulation and chemical methods are (1) higher energy cost but lower raw material cost assuming the same environmental adjustment, (2) fewer introduced counterions (e. g., chlo­rides), and (3) replacement costs for sacrificial plates.

One study used aluminum anodes for electrocoagulation of algae from a wastewater treatment plant. This study found that removal after 15 min reached as high as 99.5 % (based on chlorophyll content) with a power input of 550 W (Azarian et al. 2007). At a reduced energy usage (100 Wdm-3), the same separation efficiency could be achieved in 30 min. They did not analyze the Al ion released but recommended this as a further issue in need of optimization before the wide use of this method.

Electroflocculation using inert electrodes does not add metal ions to the culture since the electrodes are inert. The electric force is used to drive cells to the anode where the cells lose charge and flocculate. One study showed that 80-95 % of the algal cells from a wastewater treatment plant could be removed from a 100-L vessel in 35 min (Poelman et al. 1997). These techniques are typically higher in both operating and capital costs due to higher energy requirement and more valuable metals.