Treatment of restaurant wastewater by pilot-scale electrocoagulation- electroflotation: Optimization of operating conditions

In the present study, restaurant wastewater containing high concentrations of chemical oxygen demand (COD), total suspended solids (TSS), and oil and grease (OG) was treated by the combined electrocoagulation-electroflotation (EC-EF) process on a pilot scale. A central composite design was applied to the experiment design and the response surface methodology was adopted to build the response surface models of effluent COD, TSS, and OG. The sequential quadratic programming method was utilized to optimize the operating conditions of the treatment process. The analysis of variance of the experimental data shows that the coefficients of determination of the response surface models of effluent COD, TSS, and OG were 0.98, 0.982, and 0.989, respectively. The validity of these models was tested by confirmation experiments with satisfactory results. Zero trade effluent surcharges were achieved under optimized operating conditions. In spite of the operating cost calculated with respects to energy, electrode, and chemical consumptions, up to Hong Kong Dollar 1.3/m3 water or 52% of the concession in trade effluent surcharge can be saved, revealing the cost-effectiveness of the combined EC-EF technique and its potential for full-scale implementation.