Efficiency evaluation of the membrane/AOPs for paper mill wastewater treatment

ABSTRACT

The treatment of pulp and paper mill wastewater by combining an ultrafiltration (UF) membrane and advanced oxidation processes (AOPs) was investigated at a bench scale. In the present study, the effects of impressive parameters on membrane fouling such as CaCl₂ (mg/L), pH, and temperature (°C) were studied using response surface methodology (RSM). According to the results yielded, at the temperature of 45°C, pH of 10 and CaCl₂ concentration of 400 mg/L, the fouling reached its minimum (32%). Therefore, scanning electron microscopy (SEM) analyses showed that the average thickness of cake layer on the UF surface decreased from approximately 75.37 µm to 11.38 µm by optimizing the operating conditions. The results showed the UF permeate quality is not sufficient. Thus, AOPs applied for permeate. In this way, the performance of sulfate and hydroxyl radicals, generated by the activation of oxidants, such as persulfate () and H₂O₂, by Fe(II) for removal efficiencies was examined. Accordingly, under the optimum conditions of Filtration/Fenton ([H₂O₂] = 15 mM, [Fe(II)] = 6 mM, pH = 3), the removal efficiency of chemical oxygen demand (COD), UV₂₅₄, and UV₂₈₀ was 95.02%, 86.74%, and 87.08%, respectively. This is while, in the optimum conditions of Filtration//Fe(II) ([] = 7 mM, [Fe(II)] = 2 mM and pH = 6), the removal efficiency of COD, UV₂₅₄, and UV₂₈₀ reached 94.96%, 92.04%, and 90.16%, respectively. This is indicative of the fact that the process of Filtration//Fe(II), with a lower oxidant and catalyst concentration and pH close to the neutral range is more efficient than that of Filtration/Fenton.

KEYWORDS:

• Filtration
• membrane fouling
• advanced oxidation
• sulfate radicals
• hydroxyl radicals

Acknowledgement

We thank the Environmental Research Institute and the Iran Pulp and Paper Industry (Chuka) for their support.

Disclosure statement

No potential conflict of interest was reported by the authors.