Magnetic ion exchange (MIEX®) resin in submerged membrane hybrid system (SMHS) for wastewater treatment and reuse

Publication Type:
Thesis
Issue Date:
2008
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NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- Wastewater reuse has gradually become an alternative water resource to cope with the water shortage in recent years. Membrane filtration has been widely applied in tertiary (advanced) treatment process to obtain high quality treated water, which is suitable for different reuse purpose and eliminate health hazards. High-pressure membrane filtration processes (including nanofiltration and reverse osmosis) can yield high quality effluent. However, the operating cost (such as energy cost, membrane cleaning etc.) and capital cost are relatively high. Low-pressure membrane filtration processes (microfiltration and ultrafiltration) are commonly used in wastewater reuse as an alternative to physico-chemical processes and biological processes. One of the major hurdles in the application of membranes is the membrane fouling. Different pre-treatment processes are used to reduce membrane fouling by reducing the organic matter present in the biologically treated sewage effluent (BTSE). Magnetic Ion Exchange Resin (MIEX®) can effectively remove natural organic matter (NOM) from water. MIEX® process is an effective pre-treatment process for organic removal, especially when followed by flocculation. When MIEX® process is used as a pre-treatment to microfiltration in tertiary/advanced wastewater treatment, organic loading to membrane process is reduced significantly. Consequently, membrane filtration process can be operated longer with less membrane-cleaning requirement. In this study, MIEX® resin could effectively remove a majority of organic matter from biologically treated sewage effluent, especially small molecular weight organic matter (500-1000 Da). MIEX® process is specifically useful in removing the hydrophilic portion of dissolved organic carbon (DOC) in the secondary effluent, which is the major component in water. At an optimal concentration of 10 mL/L, MIEX® process was able to remove as high as 60% of DOC in the wastewater. It is noted that other pretreatment methods such as flocculation and adsorption remove predominantly the hydrophobic fraction of organic matter. Thus, MIEX® can successfully be used in combination with flocculation/adsorption. MIEX® resin reduced a significant dose of flocculant when it was used before flocculation. When the MIEX® process was combined with FeCl₃ flocculation, more than 80% - 90% DOC removal was achieved with minimal trans-membrane pressure (TMP) increase in the submerged membrane reactor (which was used as a post-treatment). Two other kinds of ion exchange resin (A860 and A500P) were also used as pretreatment to submerged membrane reactor (SMBR). The results show that these two resins gave low organic removal efficiency, thus higher organic load to the SMR, severe membrane fouling was observed and the operating time was shortened. Conventional batch ion exchange process needs large area for mixing and settling. Fluidised bed MIEX® contactor developed in this study effectively removed the organic matter from the wastewater effluent in a consistent manner. The fluidised bed MIEX® reactor could be operated up to a bed volume of 100 before any regeneration of MIEX® becomes necessary (for the wastewater studied). The regeneration of MIEX® resin (number of regeneration, regeneration time etc.) did not have any adverse effect on the organic removal by MIEX®. When used as pre-treatment to submerged membrane, fluidised bed MIEX® contactor could be able to remove a significant amount of organic matter in the wastewater. A dissolved organic carbon (DOC) removal of 90% was achieved. This pre-treatment helped to reduce the membrane fouling and keep the transmembrane pressure low during the membrane operation. MIEX® regeneration can be carried out during the continuous operation and maintain well the organic removal ability of MIEX® resin. A combined system of fluidised bed MIEX® reactor and post-flocculation as pre-treatment for submerged membrane reactor led to high organic removal and low transmembrane pressure development. This study was carried out both with synthetic and real BTSE and similar results were obtained.
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