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The removal of natural organic matter (NOM) from boreal lake water by a novel capillary nanofiltration (NF) membrane was predicted using a computational fluid dynamics (CFD) modelling approach. The 2-dimensional axis-symmetric model was based on a 48 m 3 /day NF pilot plant operating in cross-flow mode on water containing 8 mg/L total organic carbon (TOC) at fluxes ranging from 10 to 25 L/m 2 /h and velocities ranging from 0.25 to 1.0 m/s. A “mass jump” source code developed using the solution diffusion model was used to simulate water flux and variations in NOM content as a function of axial and radial position in the capillary fibres. The model was validated within 3% inaccuracy using pilot data for filtrate TOC and UV254 absorbance and longitudinal pressure drop. The model was subsequently used to compare the effect of module length and number of stages on the design performance of a 110,000 m 3 /day NF plant. Simulations indicated that 1.5 m long modules operated in a double pass configuration removed 33% more NOM compared with 3.0 m long modules in a single pass. Moreover, the use of 1.5 m modules in the full-scale plant configured in a 10:5:3:2 four stage array achieved greater NOM removal than a 10:5:3 three stage at the same plant water recovery (90.5%) using lower recycle rates and lower net energy consumption. The paper demonstrates that the combination of experimental and numerical methods can be an effective tool for the design of nanofiltration plants for enhanced NOM removal. [ABSTRACT FROM AUTHOR]

A preliminary study was carried out on the morphological design of tubular single-channel alumina membranes prepared by stereolithography, an additive manufacturing process. The geometry of the ring-patterned inner surface of membranes was optimized using computational fluid dynamics calculations and validated in microfiltration tests with aqueous suspensions of P. aeruginosa. Patterning of the inner surface of tubular membranes helped reduce cake formation at a higher value of the average crossflow velocity. The results highlight benefits of stereolithography-based approach to the morphological design of ceramic membranes. [Display omitted] • 3D-printed patterned tubular ceramic membranes are prepared by stereolithography. • CFD modeling guides membrane surface morphology design at the mesoscale. • Ring-patterning of the feed-facing surface helps alleviate membrane fouling. • Crossflow microfiltration tests with P. aeruginosa corroborate CFD predictions. • Additive manufacturing shows promise for morphological design of ceramic membranes. [ABSTRACT FROM AUTHOR]

The influence of back-shock frequency on the net flux at different transmembrane pressures and cross-flow velocities has been studied. The mathematical model used in the investigation solves the continuity equation in a two-dimensional domain near the membrane surface. An osmotic pressure model is used to calculate the concentration at the membrane surface. The highest value of the normalized net flux was found at high transmembrane pressure and high cross-flow velocity. The normalized net flux at optimal conditions was 1.36 times higher than the flux without back-shocking. The optimal forward filtration time at the highest transmembrane pressure and the highest cross-flow velocity is approximately 5 s, corresponding to a frequency of 0.18 Hz. The optimal forward filtration time decreases as a function of both increasing transmembrane pressure and increasing cross-flow velocity. [ABSTRACT FROM AUTHOR]

Small devices of cross-flow nanofiltration (NF) may become a tool to concentrate small samples of valuable substances, if the concentration polarization can be minimized by designing new feed channels with bas-reliefs similar to the ones that have been developed for efficient passive micromixers. These bas-reliefs may have a complex 3D shape and the recourse to intensive CFD simulations is necessary to optimize the geometry. To speed up the simulations, a hybrid, semi empirical approach is used where the average and local mass transfer coefficients are first computed by CFD, using a dissolving wall instead of a semi-permeable membrane boundary condition. The computed mass transfer coefficients are then used to predict the local and average concentration polarization, using a mass transfer correction factor correlation. This computational approach was validated using detailed CFD simulations and experimental concentration distributions obtained by holographic interferometry. A NF ribbed-wall rectangular channel with 2 mm height was used, with potassium sulfate solutions, transmembrane pressures lower than 8 bar and Reynolds numbers between 1 and 125. Using this computational approach, local and average concentration polarization and permeate flux were predicted with an error less than 15%. With these findings, it is possible to speed up the simulation and design of small nanofiltration cross-flow devices. [ABSTRACT FROM AUTHOR]