Treatment of pulp and paper wastewater by lab-scale coagulation/SR-AOPs/ultrafiltration process: optimization by Taguchi

In this study, the treatment of pulp and paper wastewater using combined approach of coagulation/sulfate radical-advanced oxidation process (SR-AOPs)/ultrafiltration (UF) was studied in the lab scale. In the beginning of this system, the performance of three coagulants such as polyaluminum chloride (PACl), ferric chloride (FeCl3) and alum was evaluated to achieve high recycled fiber. According to the results yielded, the FeCl3, with high fiber recycling (98%) and removal efficiency, was more efficacious. In the next step, the potassium persulfate (PPS)-Fe(II) and PPS-Fe(III) efficiency in the removal of the chemical oxygen demand (COD), aromatic compounds (UV254) and the value of sludge volume index were evaluated using Taguchi design of the experiment. The results showed that the removal efficiency of COD and UV254 in the process of PPS-Fe(II) was 92.6% and 95.8% which had the better performance than the process of PPS-Fe(III). The results showed that electrical conductivity (EC) in coagulation/SR-AOPs had increased to 30.64%. Moreover, there was a significant amount of sulfate in the effluent; whereas, UF was applied. Accordingly, using UF after pretreatment by coagulation/PPS-Fe(II), the removal efficiency of sulfate, EC, COD and UV254 increased to 99.44%, 62.05%, 97.35% and 98.75%, respectively.