Combining submerged membrane technology with anaerobic and ...

Objectives and summaryThis thesis is framed in the field of industrial and municipal wastewater treatment.Increasingly strict legislations lead to the need of developing compact and efficientsystems for the removal of both organic matter and nutrients. The application of membranefiltration processes to wastewater treatment was originated in the late sixties, through theuse of tubular membrane modules in external (side-stream) configuration with biologicalreactors for the treatment of industrial wastewaters. However during the next 20 years theuse of membranes was limited to the treatment of industrial wastewaters, since the highenergy and operational costs made unfeasible its application for the treatment of municipalwastewaters. This situation changed in the early nineties, when submerged membranemodules were developed. These modules can be directly placed in the mixed liquor of thebiological reactor and the membranes (flat sheet and hollow fiber), which are cheaper, areapplied in replacement of secondary settlers, resulting in the so-called membranebioreactor (MBR). The combination of low-pressure membrane filtration technology withbiological processes for the treatment wastewaters has evolved, resulting in differentconfigurations and applications such as, anaerobic membrane bioreactors (AnMBR) orhybrid biofilm membrane bioreactors. These systems, with different configurations areemployed for the removal of organic matter and nutrients in both industrial and municipalwastewaters. Moreover, submerged membrane technology is also being applied for tertiaryfiltration of secondary effluents.Tertiary 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 and guarantees theproduction of higher quality reclaimed water. However, in recent years, the use of tertiarymembrane filtration systems is becoming more common. Low-pressure tertiarymembranes have been proved to meet increasingly stringent standards for discharge orreuse. The use of TMF could be the right choice for removing suspended solids ormicroorganism of the treated water, but this technology is unable to manage dissolvedpollutant (salts and micropollutants) that should be treated using other technologies(adsorption using activated carbon, reverse osmosis). Moreover, TMF is being more and21