Assessment and understanding of the impact of zwitterionization of polyethersulfone on the fouling of the polymeric membranes used for ultrafiltration of abattoir wastewater

Abstract

Ultrafiltration is a promising technique applied in wastewater treatment. The potential application of UF in abattoir wastewater treatment has not been given much attention due to its drawback of being prone to organic fouling. To be efficient, it is necessary to assess fouling mechanisms involved to establish suitable mitigation actions, which is not widely reported. Membrane zwitterionization has proven efficient in mitigating membrane organic fouling through hydration layer formation that acts as a barrier. An understanding of the fouling mechanism of membranes assists with the overall optimum application of polymeric membranes. Herein, a thorough design of experiments was carried out to investigate the effects of the zwitterionization of PES on permeate flux and its fouling mechanisms of the membranes. Hermia models were used to elucidate fouling mechanisms in the study. The results of the Hermia model showed that the hydration layer formed delayed the pollutant-membrane surface interaction, leading to smaller molecules behaving like larger molecules. As a result, it was observed that both Z2 and Z4 membranes followed intermediate mechanism prior to the formation of the cake layer. Whereas, pristine favoured mostly the standard mechanism of fouling due to the absence of any barrier between the surface of the membrane and the pollutants, resulting in the narrowing of the pores and a faster flux decline. Furthermore, after backwashing with deionised water, the zwitterionic membranes exhibited reversible fouling. These observations imply that zwitterionic membranes have the potential to be more cost-effective and have a longer lifespan than the pristine PES membranes.