Fouling-free ultrafiltration for humic acid removal.

Membrane fouling is a serious concern that significantly affects the membrane filtration process. In this study, an ultrafiltration (UF) membrane was developed with surface auto-regeneration potential by immobilizing a photocatalyst [titanium dioxide nanoparticles (TiO2 NPs)] on a hybrid polyvinylidene fluoride (PVDF) membrane to reduce fouling. The combination of photocatalysis and UF, namely, photocatalytic UF, induced the surface auto-regeneration potential to the membrane. The photocatalytic process was initiated after UV light reached the TiO2 NPs through a quartz window in the membrane containing cell. The membrane, with an optimized distribution of TiO2 NPs (3.04 g m-2), could completely regenerate itself during photocatalytic UF [with 2 mg L-1 humic acid (HA)] without experiencing membrane fouling during 90 min of filtration. The impact of temperature, an important factor for increasing the kinetic rate of the photocatalyst, was also studied. The results showed that an increase in temperature did not affect the photocatalytic process, but increased the permeate flux, which was attributed to the decrease in kinematic viscosity of the water. Finally, four consecutive photocatalytic UF cycles demonstrated the stability of the membrane for a fouling-free UF process.

Size effect of anaerobic granular sludge on biogas production: A micro scale study.

This study investigated the influence of anaerobic granular sludge size on its bioactivity at COD concentration of 1000, 3000 and 6000 mg/L. Based on size, granules were categorized as large (3-3.5 mm), medium (1.5-2 mm) and small (0.5-1 mm). A positive relationship was obtained between granule size and biogas production rate. For instance, at COD 6000 mg/L, large granules had highest biogas production rate of 0.031 m(3)/kgVSS/d while medium and small granules had 0.016 and 0.006 m(3)/kgVSS/d respectively. The results were reaffirmed by applying modified Fick's law of diffusion. Diffusion rates of substrate for large, medium and small granules were 1.67×10(-3), 6.1×10(-4)and 1.8×10(-4) mg/s respectively at that COD. Large granules were highly bio-active due to their internal structure, i.e. big pore size, high porosity and short diffusion distance as compared to medium and small granules, thus large granules could improve the performance of reactor.