Combining submerged membrane technology with anaerobic and ...

IntroductionSubmerged MBR system in municipal applications, represent the 99% of the installedmembrane surface in Europe in the period 2002–05. On the other hand, side-streamconfiguration is commonly used in industrial applications. In general, submerged MBRrequire higher initial investment costs, and aeration with respect to side-stream membraneconfigurations. In contrast, pumping costs are lower and operating, requiring loweroperating flows and cleaning frequencies (Stephenson et al., 2000). The selection betweensubmerged and side-stream configurations for aerobic MBRs seems somehow settled, infavour of submerged MBRs. In fact, nowadays, most of the commercial applications arebased on the submerged configuration, due to lower associated energy requirements(Judd, 2011).Today there are approaching 60 MBR membrane module products available and thenumber of technology suppliers continues to expand. On table 1.2 can be observed themanufacturers of submerged membrane technology, both flat sheet and hollow fiber.1.4. Tertiary membrane filtrationTertiary filtration, especially depth filtration, has been traditionally used to removesuspended solids from secondary treated waters. They can also be used to removeparticulate and colloidal matter from settled secondary effluents, which increases theeffectiveness of disinfection with either ultraviolet radiation or ozone for reuse applications(Tchobanoglous et al., 1998; Lubello et al., 2003). However, in recent years, the use oftertiary membrane filtration systems is becoming more common.For tertiary filtration applications, MF and UF membrane systems can be divided intwo different types: submerged, when the membranes are submerged in a feed water tankwhere permeate is sucked (via vacuum) into the inside of the membrane (dead-endfiltration); and pressurized (or contained), when the membranes are housed in moduleswhere pressurized feed water is forced through the fiber and permeate is collect on theoutside (cross-filtration). In turn, FS or HF membranes can be used in submerged systemswhereas contained systems are composed by HF or MT ones (Li et al. 2008). Submergedmembrane modules have gained popularity, especially for low solids feeds, because of thelower costs associated and the acceptance of modest fluxes and low transmembranepressures (TMP).Low-pressure tertiary membranes have been proved to meet increasingly stringentstandards for discharge or reuse. In fact, more than 78% of wastewater reclamation plantsused low-pressure membranes as a pretreatment for the reverse osmosis process39