A comparative investigation of chemical coagulation and electrocoagulation for the post-treatment of confectionery wastewater

The confectionery wastewater contains high amount of biodegradable organic matter with an acidic characterization that should be treated before the discharge to receiving water bodies. The post-treatment method should be combined with biological treatment in order to enhance the treatment performance. In this study, chemical coagulation (CC) and electrocoagulation (EC) processes were studied as post-treatment methods for anaerobically treated confectionery wastewater. The influences of operational conditions such as pH, coagulant dosage for CC process and pH, current density, treatment time, electrode connection type for EC process were investigated. The conditions were optimized based on treatment performance and operating cost. Scanning electron microscopy–energy-dispersive index (ESEM–EDX) analysis was performed for the sludge samples. The removals of 65% COD, 84% SS and 93% DFZ436 were obtained using ferric chloride in CC process. EC process with Fe electrode achieved better removals compared with CC providing 77% COD, 93% SS, 93% DFZ436, 84% sulphate and 60% chloride removals under the optimized conditions (pH 8, 90 A/m2, 75 min, MP–P). Although EC process provided a higher operating cost (5.9 $/m3) compared with CC process (5.4 $/m3), it was able to meet the discharge standards for confectionery industry effluent.