| Microfiltration and ultrafiltration (membrane filtration) are becoming accepted technologies for production of municipal drinking water. These technologies are superior to granular filtration for the removal of particulate matter from natural waters. To address non-particulate water treatment objectives, however, membrane filtration must be coupled with other treatment technologies. Coagulation can remove organic matter from water, which may be beneficial for reducing disinfection by-product formation or meeting other water treatment objectives. Coagulation may also be beneficial for reducing the rate of membrane fouling by organic matter, which is one of the significant technical obstacles to widespread application of membrane filtration. Understanding of the impact of coagulation on membrane performance and the mechanisms of fouling by organic matter has been limited.; One objective of this research was to develop a better understanding of the interaction between dissolved organic matter, coagulants, and membranes. This research used natural surface waters from five utilities across the United States, batch coagulation experiments, and batch dead-end membrane filtration tests. The main experimental variables were source water, coagulant type, coagulant dose, membrane material, and membrane feed pressure. A second objective of this research was to develop a better understanding of the components in natural waters that cause fouling and affect treatment performance. Sequential filtration experiments, scanning electron microscopy, attenuated total reflectance Fourier-transform infrared spectrometry, and X-ray photoelectron spectrometry were used to develop an understanding of the mechanisms of fouling by organic matter.; This research accomplished two significant goals with important implications for the water treatment industry. First, an understanding of the conditions under which coagulation can improve membrane performance has been developed. Improved understanding of this relationship allows microfiltration and ultrafiltration to be applied to a wider variety of water treatment situations. In situations where coagulation can reduce membrane fouling, overall treatment costs may be reduced. Second, the experimental results have been used to develop a theoretical explanation for membrane fouling by natural waters. This theory can guide future research, which may identify methods to relate raw water quality to membrane performance or techniques to reduce fouling and improve overall membrane treatment effectiveness. |
