Electrochemical treatment of wastewater from a bakery industry: Experimental and modeling study

The typical treatment of wastewater from the bakery industry in skimming tanks and bioreactors has some limitations, such as low removal of grease, and partial degradation of organic matter. The primary aim of this investigation was to evaluate the use of electrocoagulation as an alternative/complementary method to treat efficiently such an effluent, with focus on the determination of the best operating conditions, and on the kinetics of electrocoagulation at the optimal defined set of process variables. To search for the optimal, a 23 factorial design of electrocoagulation experiments with iron and aluminum electrodes was applied in the pH range from 4.6 to 7.0, at 6 and 12 V for 1200 s and 2400 s. A reliable statistical model revealed that the results of removal of chemical oxygen demand (6-8%) and turbidity (32-98%) by using aluminum electrodes, which were in average about twice as high as those with iron electrodes, were influenced by almost all the considered factors (p ≤ 0.05). At the best determined values of pH (7.0) and voltage (12 V), kinetic experiments of electrocoagulation with aluminum electrodes were performed by monitoring periodically the pH, turbidity, apparent color, concentration of oil/grease, chemical oxygen demand, concentration of chloride anion and electric conductivity of the wastewater for 2400 s. Almost all the examined pollutant parameters, and in particular the content of oil/grease (traditionally poorly removed in fat traps) were reduced to negligible values in a short treatment time. A reliable semi-empirical kinetic model described properly the high rates of disappearance of turbidity and apparent color.