Abstract
Coagulation, magnetic ion exchange resin (MIEX) and biological activated carbon (BAC) were examined at lab scale as standalone, and sequential pre-treatments for controlling the organic fouling of a microfiltration membrane by biologically treated secondary effluent (BTSE) using a multi-cycle approach. MIEX gave slightly greater enhancement in flux than coagulation due to greater removal of high molecular weight (MW) humic substances, although it was unable to remove high MW biopolymers. BAC treatment was considerably more effective for improving the flux than coagulation or MIEX. This was due to the biodegradation of biopolymers and/or their adsorption by the biofilm, and adsorption of humic substances by the activated carbon, as indicated by size exclusion chromatography. Coagulation or MIEX followed by BAC treatment further reduced the problematic foulants and significantly improved the flux performance. The unified membrane fouling index showed that the reduction of membrane fouling by standalone BAC treatment was 42%. This improved to 65%, 70%, and 93% for alum, ferric chloride and MIEX pre-treatment, respectively, when followed by BAC treatment. This study showed the potential of sequential MIEX and BAC pre-treatment for controlling organic fouling and thus enhancing the performance of microfiltration in the reclamation of BTSE.
Highlights
Low pressure membrane (LPM) processes such as microfiltration (MF) and ultrafiltration (UF)systems are attractive and reliable for the treatment of potable water and secondary effluent since they have many advantages such as small footprint, high pollutant removal efficiency, low energy consumption and good mechanical and chemical stability
magnetic ion exchange resin (MIEX) led to greater removal of dissolved organic carbon (DOC), UVA254 and colour than biological activated carbon (BAC) treatment, which in turn was greater than for coagulation by alum or ferric chloride
Coagulation with ferric chloride gave marginally greater removal of DOC, UVA254 and colour content compared with alum, which was attributed to the larger floc sizes [25] and higher charge density [26] than for alum
Summary
Systems are attractive and reliable for the treatment of potable water and secondary effluent since they have many advantages such as small footprint, high pollutant removal efficiency, low energy consumption and good mechanical and chemical stability. These membranes are subject to fouling by effluent organic matter (EfOM) during the filtration of biologically treated secondary effluent (BTSE) [1,2], since it contains nucleic acids, polysaccharides, proteins, amino-sugars, humic materials, cell components and organic acids [3]. Coagulation has been used to mitigate membrane fouling during drinking water and secondary effluent treatment
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