Fouling mechanism of PVDF ultrafiltration membrane for secondary effluent treatment from paper mills

Papermaking industry discharges a huge amount of effluent and recycling of processed water with membrane technology has become predominate treatment protocol. In this study, poly(vinylidene fluoride) (PVDF) ultrafiltration membrane was employed to treat the effluent of secondary sedimentation tank from a paper mill. The results of 600-hs continuous running showed that the PVDF membrane was seriously fouled with increased surface roughness during the filtrating process. Characterization of the fouled PVDF membrane revealed that pore blockage and cake deposition were the main fouling mechanism. The foulants in the pores were mainly oxygen-contained organics, and the foulants on the surface were mainly metal complexes and large particle. Wastewater analysis indicated the co-existence of PVA (1.0 mg/L) and Ca2+ (16.7 mg/L) in the secondary effluent. Pores blocking mechanism was caused by strong adheresion of PVA-217 and cake deposition mechanism was induced with macromolecular complexes of calcium ions bonding to PVA-217. The results obtained in this study demonstrated the fouling mechanism in the secondary effluent treatment. The understanding could help to find a feasible chemical method to clean the fouled polymeric membrane with washing agents as NaClO, NaOH and HCl in steps. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The papermaking industry generates a large amount of wastewater, and membrane technology has become the predominant treatment method. A PVDF ultrafiltration membrane was utilized to treat secondary sedimentation tank effluent from a paper mill. The study identified pore blockage and cake deposition as the main fouling mechanisms, with oxygen-contained organics and metal complexes as the primary foulants. Understanding the fouling mechanism could help in finding a feasible chemical method for cleaning the fouled polymeric membrane.