Computational fluid dynamics modeling of effect of baffles in star shaped microfiltration membranes for water treatment

Abstract

Star shaped microfilter with inserted rod baffle for waste water treatment was studied by the Computational Fluid Dynamics in three dimensions. The composition of substances in waste water consisted of seven substances including peptone 160 mg/L, meat extraction 110 mg/L, urea 30 mg/L, anhydrous di-potassium hydrogen phosphate (K2HPO4) 28 mg/L, sodium chloride (NaCl) 7 mg/L, calcium chloride dehydrate (CaCl2.2H2O) 4 mg/L, and magnesium sulphate heptahydrate (Mg2SO4.7H20) 2 mg/L. The geometry of the star-shaped microfilter in this study was built based on the system applied by Chiu et al. (2006). It consisted of seven star-shaped channels, that were 4.6x10-3 m in diameter and 0.3m long, and rod baffles with 9x10-4 m in diameter and 0.3 m long. The critical flux and trans-membrane pressure from the published experimental-study were compared with the simulation results by using the RNG k-ε turbulence model and discrete phase model to describe flow behavior inside the star shaped microfilter. Which yielded 8-14% deviation from the experimental data. After that, the parametric study was conducted by varying the parameters which could be easily changed in practice and could affect column performance. First, the inlet velocity of waste water was varied from 2.5-4.0 m/s. The result showed that the optimal inlet velocity, which gave the highest critical flux, was 4.0 m/s. Then, the effect of particles size of meat extraction was varied from 3.75x10-7m to 5x10-6m. The result showed that the large particle range size gave the highest critical flux. Then, coefficient of restitution was varied from 0.1-1. The result showed that the coefficient of restitution did not affect the critical flux. Moreover, it was found that by inserting the special rod baffle the critical flux was improved.