Title : Impact of ferric chloride coagulant residuals on the performance and structural integrity of hollow fiber ultrafiltration membranes in a Zero-Liquid-Discharge (ZLD) system
Abstract:
This study investigates the impact of ferric chloride residuals on the performance and integrity of hollow fiber ultrafiltration (UF) membranes within a zero-liquid- discharge (ZLD) treatment system. The ZLD unit at Abu Qir Fertilizers use ferric chloride (20ppm FeCl₃) as a primary coagulant for suspended solids removal prior to biological and membrane filtration stages. Despite of proper clarification, trans membrane pressure (TMP) rises and reduced UF permeability were observed. Despite repeated alkaline and acidic CIP treatments, there was no measurable improvement in flux or trans membrane pressure. A complete membrane autopsy was conducted on a DuPont Integra Pac IP-51 module, revealing iron-dominated fouling, biological colonization, and fiber breakage. Energy-dispersive spectroscopy (EDS) confirmed that iron constituted up to 41% of the foulant on the fiber exterior and 11–14% internally. Water analyses showed residual iron concentrations of 0.018–0.07 mg/L in UF and RO feed. These findings demonstrate that ferric chloride residuals promote Fe (OH)₃ precipitation and bio- iron complexation, leading to irreversible fouling and structural degradation of hollow fiber membranes. Cleaning optimization using Ro Clean P903 achieved significant permeability recovery, highlighting the importance of appropriate pretreatment and cleaning strategies.
Keywords: Ferric chloride, iron fouling, ultrafiltration, ZLD, hollow fiber membrane, membrane integrity, fouling mechanisms
