State of the art of osmotic membrane bioreactors for water reclamation.

In the last few years, extensive research has been dedicated to development of a novel osmotic membrane bioreactor (OMBR), which combines high-retention osmotic separation and biological reactions in a single vessel. Although promising results have been reported in the literature, some challenges associated with applications of OMBR remain unresolved at the present stage of development, including lack of a high performance forward osmosis (FO) membrane, identification of an ideal draw solute and effect of salt accumulation on biological activity. Therefore, this paper attempts to provide a comprehensive review of state of the art of OMBR for water and wastewater reclamation.

Fouling propensity of forward osmosis: investigation of the slower flux decline phenomenon.

Forward Osmosis (FO) is a membrane process that uses the natural osmotic pressure of a concentrated draw solution to extract pure water from a feed stream. The attraction of the FO process is that it uses dense membranes, while operating at ambient pressure. This means that the FO process could potentially produce high quality water with lower energy consumption, as compared to the other desalination or reclamation processes. As FO does not entail the use of hydraulic pressure, FO has been hypothesized to have lower fouling propensity than pressure driven membrane processes. Membrane fouling has significant impact on the operational sustainability and economics of the process. This study examines the possible contributing factors to the slower flux decline observed in FO experiments based on a combined experimental and modelling approach. It was found that these factors could include low water fluxes, use of hydrophilic and smooth membranes, and the effect of internal concentration polarisation that is inherent of FO. It was also found that the transmission of draw solutes from the draw solution into the feed can have significant effect on FO performance.

Impacts of salinity on the performance of high retention membrane bioreactors for water reclamation: A review.

Recent efforts in the field of used water treatment and water reclamation have led to the development of a number of innovative high retention membrane bioreactor (HRMBR) systems. These systems invariably combine a high rejection membrane separation with a biological treatment. A common positive outcome of these systems is that smaller size organic contaminants are effectively retained, which facilitates their biodegradation and thus produces high quality product water. This provides the desired high level of separation, but also leads to salt accumulation with potentially adverse effects on the operations. The effects of elevated salt condition are complex, and impact on aspects covering physicochemical parameters, microbiology and membrane performance. The salt concentration factor is an important operating parameter to be optimised in the HRMBR systems. This paper aims to elucidate the important issues associated with the use of HRMBR systems under elevated salt conditions up to 50gL(-1).