Bench scale electrocoagulation studies of bio oil-in-water and synthetic oil-in-water emulsions

Electrocoagulation (EC) test runs of oil-in-water (O/W) emulsions (0.6% and 2%) prepared from bio oils and synthetic oils with stainless steel (SS) or aluminum (Al) anode were performed in a batch mode with a novel bench scale EC apparatus. The efficiency of EC for breaking O/W emulsions was evaluated versatilely by measuring COD, TOC, total surface charge (TSC) and turbidity. Particle sizes with laser diffraction and BOD were also measured for a number of test runs. The turbidity of the studied emulsions decreased the most, between 75% and 100% whereas COD, TSC and TOC reductions were in the range of 25–95%, 40–98% and 20–75%, respectively. The most successful reductions were measured for tall oil and synthetic oil emulsions. BOD values were also found to decrease during test runs. Laser diffraction measurements proved that the emulsification of the oils, as well as the breaking of the emulsions, were both successful. There was no significant difference between treatment results when using a SS or Al anode. However the sludge produced using a SS anode was substantially thicker in structure and thus easier to separate. To summarize, the EC of O/W emulsions studied in this work was found to be cost-effective and feasible even without specific optimization of the process parameters.

► Electrocoagulation of oil-in-water emulsions of bio oils and synthetic oils.
► Versatile analytical techniques proved the breaking of O/W emulsions.
► The best reductions were measured for tall oil and synthetic oil emulsions.
► Electrocoagulation is a feasible treatment method for stable oily waters.