Water Science and Technology (Jul 2023)
Investigation of factors affecting sodium alginate fouling mechanisms in a microfiltration process under non-constant-flux and non-constant-pressure conditions
Abstract
Variations in transmembrane pressure and permeate flux are closely related to membrane fouling. In this study, a laboratory-scale submerged microfiltration system was used to investigate the influence of sodium alginate (SA) concentration and peristaltic pump rotation speed on the fouling under the conditions of (1) the same driving force and non-aerated-PAC, (2) different driving forces and non-aerated-PAC, and (3) different driving forces and aerated-PAC. The results showed that the normalized transmembrane pressure (TMP') increased linearly with decreasing normalized permeate flux (J') during the early microfiltration stage regardless of the operating conditions, indicating that the SA microfiltration process controlled by the peristaltic pump was non-constant-flux and non-constant-pressure. The latter filtration stage was considered constant-pressure filtration when 200–1,200 mg/L of SA was filtrated at the same rotation speed. During filtration of 800 mg/L of SA under the non-aerated-PAC condition, the later filtration stage was considered constant-pressure filtration when the peristaltic pump rotated at slower speeds of 15 and 30 rpm. This approached constant-flux filtration when the peristaltic pump rotated at faster speeds of 60 and 90 rpm, and PAC-aeration scouring was an effective measure for mitigating membrane fouling by SA. HIGHLIGHTS SA microfiltration controlled by the peristaltic pump was non-constant-flux and non-constant-pressure filtration.; TMP' increased linearly with a decrease in J' during SA microfiltration.; SA concentration and the peristaltic pump rotation speed were the major factors that affected the filtration process and membrane fouling.; Aerated-PAC offered an effective measure to control membrane fouling.;
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