PREVENTING/MITIGATION IRREVERSIBLE RO MEMBRANES FOULING TENDENCIES CAUSED BY COLLOIDAL MATERIALS DURING FILTRATION OF SURFACE WATERS

The use of reverse osmosis (RO) technology for water treatment is rapidly growing due to its improved membrane technology and lower operational costs. During filtration, and depending on the composition of the source water, there is a growing concern of irreversible fouling tendencies observed in RO membranes that are mostly caused by colloidal materials such as silica/silicates (inorganic minerals) and dissolved natural organic matter (DNOM) (humic substances), however, these fouling has led to higher costs of operations, energy, permeate flux decline, and maintenance. In order to prevent these fouling issues, pretreatments (e.g. coagulation, flocculation, sedimentation, and membrane filter(s)) will be necessary upstream of an RO system. Therefore, this pilot study/dissertation work will examine and recommend optimized membrane pretreatment methods (optimization of coagulant dose and/or flocculation speed and sedimentation mechanisms and time), effective antiscalant dosage in the RO influent, and an optimized pH control that will reduce silt density index (SDI), DNOM, silica/silicate and any corresponding total organic carbon (TOC) upstream and downstream of the UF and RO stages. These techniques, will likely help in mitigating and preventing irreversible RO fouling caused by DNOM/silica/silicate that was experienced during the first pilot study. This study, however, will also recommend effective operational techniques (such as cleaning in place (CIP) (with limited chemical use) methods, running modes and cleaning modes) that will help improve RO system performance, reduce operational costs and cleaning frequencies, while increasing the lifespan of the RO membranes. In addition, the proposed work will research an effective, intermediate treatment method(s) that will help reduce the volume of RO process concentrate (brine) in between RO stages by minimizing liquid discharges while removing scale-forming constituents.