Fouling of submerged hollow fiber membrane filtration in turbulence: Statistical dependence and cost-benefit analysis

Abstract

In the present study, we expanded the scope to a full range of turbulence conditions with a total of 79 experiments, to establish the statistical dependence between the energy consumption due to turbulence dissipation and improved productivity with reduced membrane fouling so that the cost-benefit tradeoff can be evaluated. The turbulence was generated by vibrating perforated plates. Increasing vibration frequency/stroke or solidity of the perforated plate resulted in more intense turbulence inside the reactor, and that the eddy length scale increased with solidity in general. Hollow fiber membrane filtration experiments were then performed within the turbulence ambient in both inorganic Bentonite and organic yeast suspensions. The variance analysis of the results further confirmed the link between the membrane fouling rate and both turbulence kinetic energy and eddy length scale and their cross interactions, as well as that an optimum eddy length scale existed beyond which its influence diminished. Higher TKE induced more fouling reduction, but it also required larger power consumption. A cost-benefit analysis of membrane fouling in turbulence is then presented for evaluation of the tradeoff between membrane filtration performance and power consumption. Finally, the effect of turbulence on membrane filtration performance was also examined in conjunction with the fiber bundle characteristics of the membrane module. An optimized fiber spacing and fiber looseness were identified that consistently performed the best in all experiments, allowing the fluctuating turbulence eddies to penetrate and mobilize the fibers in the most efficient manner against fouling.