Membrane Fouling Propensity Research Articles

Colloidal adhesion to hydrophilic membrane surfaces

Colloidal adhesion to membrane surfaces is an important parameter in determining membrane fouling propensity and in optimizing membrane cleaning strategies. It has previously been demonstrated that acid–base interactions can significantly affect colloid–membrane interaction as a colloid approaches a membrane surface, however, the effect of acid–base interactions on adhesion has received less attention. In this investigation, the approach and adhesion of a silica and polystyrene colloid was measured on three commercially available hydrophilic water treatment membranes using an atomic force microscope and the colloid probe technique. It was found that the hydrophobic polystyrene colloid adhered more weakly to each membrane compared to the hydrophilic silica colloid. These results could not be resolved through classic DLVO analysis alone and were in direct contrast to the expected interaction based on the strong hydrophobic character of the polystyrene colloid. However, the results could be explained by considering the magnitude of the surface’s electron-acceptor ( γ +) and electron-donor ( γ −) components. It is hypothesized that through hydrogen bonding with surface γ + and γ − groups, structured water layers exist to varying extents at the surfaces of the silica colloid and the hydrophilic membranes, and that their removal results in the formation of strong adhesive bonds between reciprocal γ + and γ − groups. Furthermore, even when surface roughness is substantial, γ + and γ − groups appear to play some role in determining the magnitude of the measured adhesion. The lack of such groups on the polystyrene colloid, and thus the lack of hydrogen bonding capacity, was responsible for its weaker adhesion with the membranes.

The influence of bovine oocyte type on in vitro-fertilization and subsequent development in vitro

Microalgae technology is attractive for simultaneously treating wastewater and producing valuable biomass. However, biofuel application demands a very low net-energy input that can hardly be fulfilled. Therefore, exploration of a more direct-use of microalgae biomass and selection of appropriate microalgae species are necessary to fine-tune viable applications. This study assesses performance of sequencing batch membrane photobioreactors (SB-MPBRs) for simultaneously polishing secondary effluent by cultivating Staurastrum sp., a species suitable as aquaculture feed. The effect of feed composition (high and low phosphorous, P) on microalgae growth, membrane fouling propensity, nutrient removal, as well as oxygen enrichment capacity were evaluated. Overall results demonstrate the effectiveness of SB-MPBR to cultivate Staurastrum sp. in secondary effluent by achieving biomass concentration of 0.45 and 0.6 g/L and very low nutrients concentrations in the effluents (≈ 0, 10 and 2 mg/L, for chemical oxygen demand (COD), TN and TP respectively). The actual biomass productivity of the SM-MPBRS are 40.0 and 30.0 g/(day m3) for the low-P and high-P feeds, corresponding to production costs of 11.3 and 15.1 $/kg biomass, respectively. Low-P feed results in a slightly higher biomass productivity of 33% compare to high-P feed, but slightly higher fouling propensity. The growth in both SB-MPBRS seems to be limited by the inorganic carbon supply. Too-short HRT leads to nutrients accumulation of the nutrients and eventually reduced their removal efficiencies. Overall results show a new cultivation method for aquaculture feed while at the same time polish secondary effluent and enrich its oxygen concentration.