| Abstrakt: |
A novel method to control effluent organic matters (EfOM) fouling of microfiltration (MF) membrane during the wastewater reclamation process has been investigated by applying salt cleaning. To determine the efficiency of salt cleaning, experiments were carried out using feed waters containing (i) single foulant and (ii) mixed foulants of humic acids, polysaccharides, and protein which are representative organic matters of EfOM. In addition, real wastewater obtained from the wastewater treatment plant was used to investigate the applicability of salt cleaning. Among three EfOM substances, polysaccharides in the presence of Ca2+ caused severe flux decline, however, the declined flux due to fouling was recovered greatly after salt cleaning. In the case of mixed foulants, flux decline accelerated when the polysaccharides portion of the mixed foulants increased. Similar to the case of single foulant, salt cleaning was quite effective to recover the declined flux due to the fouling with mixed foulants. In addition, the salt cleaning efficiency tends to be more effective for fouling caused by feed water containing more polysaccharide than the other foulants. The mechanisms of salt cleaning can be attributed to the combination of osmotic disruption and cross-transport of ions in the boundary of the fouling layer, which weakens the structure of the cross-lined gel-type fouling layer on the membrane surface and, thus, the easy detachment from the membrane by crossflow shear effect. Fluorescence excitation--emission matrix and Fourier transform infrared spectroscopy analyses of cleaning solutions obtaining after salt cleaning also confirmed that EfOM accumulated on the membrane surface during fouling detached during salt cleaning. It was also confirmed that salt cleaning was efficient for cleaning of the membrane fouled by the real wastewater. In addition, when salt cleaning was applied periodically during MF of the real wastewater, flux decline due to fouling was delayed sufficiently by periodic flux recovery. This result suggests that the clean-in-place (CIP) cycle can be extended by salt cleaning and thus, the saving of chemical cost as well as the prevention of membrane damage. [ABSTRACT FROM AUTHOR] |
