A mechanistic approach and response surface optimization of the removal of oil and grease from restaurant wastewater by electrocoagulation and electroflotation

Electrocoagulation and electroflotation are effective technologies for restaurant wastewater treatment, especially for the removal of oil and grease. The response surface methodology was used to establish a model of restaurant wastewater treatment using electrocoagulation and electroflotation. The model provides the optimum operation conditions. In addition, the contributions of electrocoagulation and electroflotation to the removal of oil and grease were determined under different conditions. The optimum operation conditions are an inter-electrode distance of 3.6 cm, a reaction time of 34 min, and a current density of 43 A/m(2). The removal efficiency of oil and grease was above 95% under such conditions. When wastewater conductivity was less than 3,000 mu s/cm, electrocoagulation played the dominant role, and the contribution rates ranged from 68.1 to 72.5%. When the wastewater conductivity was above 3,500 mu s/cm, electroflotation played the dominant role, and the contribution rates ranged from 51.6 to 65.8%. Hence, electrocoagulation dominated, whose contribution rates ranged from 68.1 to 90.7%, 68.1 to 75.8%, and 66.0 to 89.1% with the changes of the inter-electrode distance, reaction time, and current density, respectively.