Evaluation of Using Sequential Electrocoagulation and Chemical Coagulation for Urea Removal from Synthetic and Domestic Wastewater

Abstract

The presence of urea in wastewater can give rise to many issues, including the proliferation of algae as a consequence of eutrophication as well as the discharge of ammonia, which exerts a detrimental impact on aquatic organisms. To assess the efficacy of several treatment strategies for lowering urea concentrations, this study compared the removing performances of electrocoagulation (EC) with those of conducting electrocoagulation and chemical coagulation in sequence (EC-CC) or vice versa (CC-EC). Many effective parameters of electrocoagulation have been studied, such as current density, spacing between electrodes, electrolyte type, and electrolysis time. A scanning electron microscope was used to investigate the electrode morphology, and a Fourier transform infrared was conducted to analyze the formed sludge. The electrocoagulation was carried out at its optimum conditions at 30 A/m2, and the chemical coagulation was conducted using three types of iron coagulants: FeSO4, Fe2(SO4)3, and FeCl3. The results showed insufficient improvement in urea removal for synthetic and domestic wastewater via EC-CC, regardless of the coagulant type. The urea removal efficiency via EC-CC improved by less than 0.5% and 5.5% for synthetic and domestic wastewater, respectively. In contrast, CC-EC proved a better improvement for urea removal for both synthetic and domestic wastewater, but only for FeCl3. Treatment by CC-EC at 30 A/m2 for 60 min using iron electrodes and 0.5 g/L of FeCl3 resulted in an improvement in the removal efficiency of urea by about 3.4% and 10.40% for synthetic and domestic wastewater, respectively. CC-EC achieved better removal of COD from domestic wastewater than that achieved by EC-CC by 6%. The results obtained from the study indicate that the CC-EC process is a cost-effective method for removing urea from both synthetic and domestic wastewater.