Treatment of real printing and packaging wastewater by combination of coagulation with Fenton and photo-Fenton processes

Printing and packaging process wastewater (PPPW) with high flow rates causes severe damage to the environment due to high organic pollution (3830.0 mg O₂/L of COD and 813.6 mg/L of TOC) and turbidity (9110 NTU). This study examined the efficiencies of coagulation, Fenton, and photo-Fenton procedures, and their combinations in the treatment of PPPW. The three inorganic salts (FeCl₃, Al₂(SO₄)₃, and Fe₂(SO₄)₃) were used in a wide range of pH (2.5–10) as a coagulant, and FeCl₃ was chosen as the optimum coagulant. The 71.3% of TOC removal and the decreasing of turbidity up to 5.8 NTU were obtained at 0.5 g/L FeCl₃ and pH of 6.0. Then, Fenton and photo-Fenton processes were applied to the effluent of the coagulation process. The Fenton process engaged the TOC removal efficiencies up to 85.2% in the presence of 7.350 g/L iron catalysts and 36.0 mL/L H₂O₂. The combined coagulation and Fenton process is a promising way to decrease the COD up to 119 mg O₂/L, meeting the wastewater discharge standards of COD (200 mg O₂/L) in Turkey. However, adding UV sources to the Fenton process showed a little bit of engagement (only %1.4 extra removal). When evaluated for PPPW, it is seen that the usage of combined coagulation and the Fenton process is an important treatment alternative. Furthermore, Zeta potential measurements and size exclusion chromatography were used to understand the removal mechanism.