Influence of backwashing, flux and temperature on microfiltration for wastewater reuse

• Published in: Separation and purification technology Vol. 96; pp. 147 - 153
• Main Authors: Raffin, M., Germain, E., Judd, S.J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 21.08.2012; Elsevier
• Subjects: Applied sciences; Backwash; Chemical engineering; economics; Exact sciences and technology; Flux; fouling; Fouling rate; General purification processes; Membrane separation (reverse osmosis, dialysis...); Microfiltration; Municipal wastewater; Pollution; pretreatment; process control; reverse osmosis; temperature; turbidity; ultrafiltration; wastewater; Wastewaters; Water quality; water reuse; Water treatment and pollution; Flux; Microfiltration; Backwash; Fouling rate; Water quality; Municipal wastewater; Fouling; Process control; Reuse; Optimization; Operating conditions; Waste water; Membrane separation; Ultrafiltration; Turbidity; Urban waste water; Reverse osmosis
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2012.05.030

► Microfiltration fouling relationships in wastewater reuse pilot plant quantified. ► Fouling rate increases exponentially both with feedwater turbidity and operating flux. ► Newtonian viscosity correction insufficient to account for temperature influence. ► Non-turbid water quality component contributes significantly to reversible fouling. ► Irreversible fouling sensitive to backwash frequency, flux and threshold pressure. Microfiltration (MF) and ultrafiltration (UF) membranes, widely used for pre-treatment of reverse osmosis (RO) processes in wastewater recovery, are nonetheless subject to fouling which considerably reduces the process throughput. In this study, reversible and irreversible fouling of a pilot MF process treating secondary wastewater effluent were measured over an 18month period and data pertaining to common feedwater quality determinants collated. Fouling rates were quantified as a function of the key operating parameters (flux and backwash interval) and water quality determinants (turbidity and temperature). Fouling was found to increase exponentially with turbidity. Irreversible fouling was promoted only by increased flux and backwash interval, while reversible fouling rate depended on flux, turbidity and temperature. Some residual fouling, following the same exponential or power relationship with the flux as that manifested at different turbidities, was observed at zero turbidity. Operation above the so-called critical flux was sustained through appropriate backflushing. It was concluded that the sustainable flux concept was a more appropriate basis for process control and optimisation than critical flux, since the latter does not take into account process economics.