Hybrid Process Combining Electrocoagulation and Electro-Oxidation Processes for the Treatment of Restaurant Wastewaters

The present study investigates the electrocoagulation-electro-oxidation (EC-EO) process for the treatment of restaurant wastewater (RWW) loaded with organic and inorganic matter, oil, grease, and suspensions solids. The EC-EO process was evaluated in terms of its capability to simultaneously produce an oxidant and coagulant agents by using either iron or aluminum electrodes arranged in a bipolar configuration or graphite electrodes arranged in a monopolar configuration in the same electrolytic cell. Relatively high concentrations of active chlorine (9.6 mg/min) and aluminum (20–40 mg Al/L) or iron (40–60 mg Fe/L) were produced in situ. The best performance for RWW treatment was obtained by using aluminum and graphite plates alternated in the electrode pack and operated at current of 0.4 A during 90 min of treatment with pH adjusted to approximately 7.0. Under these conditions, more than 98% of oil and greases (O&G) were removed, whereas chemical oxygen demand (COD) and biological oxygen demand (BOD) removal reached 90% and 86%, respectively. Likewise, more than 88% of soluble phosphate was removed, and the process was effective in removing turbidity (98%) and suspended solids (98%). The EC-EO process operated under the best conditions involved a total cost of US$1.56±0.01/m3 of treated restaurant effluent. This cost includes energy and electrode consumption, chemicals, and sludge disposal.