The use of membrane technology in drinking water treatment has increaseddramatically in recent years. Membrane separation processes, such as reverseosmosis (RO) and nanofiltration (NF), are becoming more popular for severalreasons, some of which include their ability to produce a superior quality ofwater, to reduce the size of the treatment facilities, and to simplify watertreatment processes. The declining quality of source waters and increasinglystringent drinking water standards are further expanding the utilization of thesetreatment alternatives in full-scale water utilities. However, operationalproblems, such as membrane fouling have hampered the acceptance of RO and NFtechnologies as a treatment of choice for low quality source waters. Sourcewaters with high fouling potentials require extensive feed water pretreatment tomaintain membrane productivity. In addition, frequent chemical cleaning is oftenrequired to remove foulants adsorbed onto the surface of the membrane. Despiterigorous pretreatment and cleaning, membranes often suffer irreversible losses inproductivity. Irreversible fouling results in the gradual deterioration ofmembrane performance and will inevitably lead to the replacement of the membraneelements in the system. In order to minimize the costs associated with foulingcontrol and membrane replacement, it is of paramount importance to select RO andNF membranes that possess properties that inherently resist fouling. Membranesurface characteristics, regardless of fouling types, are major factors affectingthe rate and extent of membrane fouling. Among such factors are surfaceroughness, charge, and hydrophobicity for RO and NF membranes. Presently, theselection of new or replacement membranes for full-scale membrane water treatmentfacilities is typically based on either bench-scale or pilot scale evaluation ofseveral membranes commercially available at the time of testing. A morefundamental approach, based on membrane surface properties, has not been fullyexplored for the selection of membranes. In order to achieve this goal, acorrelation between membrane properties and membrane fouling potential must beestablished. In this study, the surfaces of various RO/NF membranes werethoroughly characterized in terms of roughness, charge, and hydrophobicity usingvarious surface analytical techniques. The techniques used included Atomic ForceMicroscopy (AFM) and Scanning Electron Microscopy (SEM) for surface roughness,Streaming Potential Analysis (SPA) for surface charge, and Contact Anglemeasurements for hydrophobicity. These characteristics were then correlated tomembrane fouling potential as evaluated by bench-scale filtration experimentsusing a high organic surficial groundwater from Plantation City, Florida. Basedon the results of these studies, the impact of surface properties on membranefouling was assessed and a correlation between these properties and foulingbehavior was delineated. Lastly, a total of nine years of daily operating datawere obtained from the Plantation Central Water Treatment Facility and weresystematically analyzed to document the effect of membrane replacement on theperformance of each individual stage, as well as the overall system. Includes 6 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 800 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 24 |
| Published : | 05/01/2001 |
