Paper and Cardboard Industries Wastewater Treatment by Coagulation and Flocculation Process and Optimization with Response Surface Methodology: A Laboratory Study

Abstract

Background and Objectives: Wastewater treatment of paper recycling and cardboard industries with the aim of water recycling and reducing environmental impact is one of the daily needs of industries. Therefore, the aim of the present study was to optimize the conditions of coagulation and flocculation process in wastewater treatment of paper recycling industries using the response surface method. Materials and Methods:In this laboratory study, response surface method and central composite design were used to design the experiments and to determine the effects of the studied variables (pH, concentrations of alum, Poly aluminum chloride (PAC), and cationic polymer) on the total suspended solid (TSS) and chemical oxygen demand (COD) removal efficiency. Data analysis was done using ANOVA statistical test with a significant level of 0.05. Results:The results showed that in the combination of PAC with cationic polymer (optimal conditions; pH=7.5, PAC concentration=450 mg/L, cationic polymer concentration=1.5 mg/L), the TSS and COD removal efficiency were 97.34% and 75.76%, respectively. In combination of alum with cationic polymer (optimal conditions; pH=8.5, alum concentration=550 mg/L, cationic polymer concentration=2 mg/L), removal efficiencies were 98.96% and 77.83%, respectively. The simultaneous effects of two independent variables, pH and concentration, had a significant effect (p<0.05) in removing TSS and COD variables. Conclusion:The results showed that the combination of PAC with cationic polymer had a better efficiency. Also, the COD and TSS in the final effluent were higher and lower than the standard values, respectively. Therefore, chemical coagulation process is proposed as pretreatment.

A comparative study on polyaluminum chloride (PACl) and Moringa oleifera (MO) chemically enhanced primary treatment (CEPT) in enhanced biogas production: anaerobic digestion performance and the Gompertz model

“…Zarei et al (2022) reported that the highest TSS (97.34%) and COD (75.76%) removal efficiency in the CEPT process with PACl was observed at pH 7.5, which is consistent with the results obtained in this study. 41 The most possible reason for choosing the optimal pH of 7 in this study was the effect of neutral pH on the coagulant performance, proper sedimentation of materials and elements in wastewater and significant removal of TSS. In the case of the CEPT process with Moringa oleifera , the highest removal efficiency of TSS (72%), COD (63%) and VS (35%) in supernatant were observed at pH 7.…”