Hybrid treatment of textile wastewater through catalytic thermolysis and catalytic heterogeneous Fenton processes

Textile wastewater pollution is one of the primary global environmental concerns. The textile wastewater contains complex inorganic dyes, which are difficult to treat with conventional treatment processes. A single treatment method is usually insufficient to treat the wastewater up to the level that it meets the stringent textile effluent standards. Hence, a hybrid approach by combining the thermolysis catalyzed by CuSO₄ 5H₂O with heterogeneous Fenton process catalyzed by modified coal fly ash was evaluated in this study for the treatment of textile wastewater. A combination of catalytic thermolysis and coagulation with poly aluminum chloride (PAC) was also studied for comparative purposes. Optimization of treatment processes was done by Response Surface Methodology (RSM) using Minitab software. Catalytic thermolysis was optimized at a pH of 7.05, CuSO₄ 5H₂O dose of 1629 mg/L, and a temperature of 65.3 ℃. Coagulation was optimized at pH of 8.1 and PAC dose of 286.3 mg/L, and the heterogeneous Fenton process was optimized at pH 7.75, a ratio of H₂O₂/Fe⁺² of 3.02, Fe⁺² dose of 15 mg/L, and reaction time of 53.5 min. At optimized conditions, two hybrid treatments were run. It was found that the novel combination of catalytic thermolysis with the heterogeneous Fenton process was more effective for removal of COD (89.5%), Color (98.5%), TSS (95.9%) than the second combination (catalytic thermolysis followed by coagulation using PAC). The BOD₅/COD ratio was increased from 0.28 to 0.53 in the novel combination, indicating an effective increase in the biodegradability of wastewater.