Treatment of hazardous wastewater generated from metal finishing and electro-coating industry via self-coagulation: Case study.

The aim of this study is to find out a sustainable and cost-effective solution to manage hazardous shock loads from metal finishing and electro-coating industry. Results indicated that the main sources of hazardous wastewater are coming from batch chemical cleaning of degreasing basin (CCDB) (pH 13) and contains very hazardous chemicals, batch chemical cleaning of phosphating basin (CCPB) (pH 1.03) and contains high concentrations of iron (2300 mg/L) and zinc (2400 mg/L) and degreasing basin contents (DBC). Different treatment approaches were investigated. Results indicated that mixing CCDB with CCPB at their actual discharge allowed to form a self-coagulant of metal hydroxide which was utilized to treat the (DBC) followed by sedimentation. Removal efficiency of COD (87%), TSS (94%), and oil and grease (92%) were achieved. To compare the efficiency of this treatment approach, conventional chemical coagulation of DBC was carried out using FeCl but the amount was very high. In conclusion, results proved the advantage of using self-coagulation to treat DBC since it eliminates the use of external chemicals and provides an integrated solution for the three main sources of hazardous pollutants. PRACTITIONER POINTS: The manuscript provide an innovative and sustainable solution to the shock loads of hazardous wastewater generated from metal finishing and E-coating industry by utilizing iron-rich wastewater from chemical cleaning of phosphating basin and alkaline wastewater from chemical cleaning of degreasing basin to produce metal hydroxide. The metal hydroxide was cost-effective and technically effectively than external coagulant in treating highly polluted degreasing basin content at due discharge time. Iron-rich wastewater could be used to produce self-coagulant of iron hydroxide. Mixing iron rich wastewater and alkaline wastewater produce iron hydroxide. Iron hydroxide is cost-effective in treating hazardous wastewater of degreasing basin.