NANOFILTRATION AS A MEANS OF ACHIEVING HIGHER TBT OF GREATER-THAN-OR-EQUAL-TO-120-DEGREES-C IN MSF

The Saline Water Conversion Corporation, Research an Development Cente r (SWCC-RDC) carried out exploratory research study to evaluate the ad aptability of the brackish water softening nanofiltration technique as a permeation pretreatment of feed to seawater reverse osmosis (SWRO) and as make-up to MSF. This exploratory work was designated as part I of an applied research project that was carried out from March 1997 to May 1998. Based on initial remarkable results, SWCC applied for a pat ent on the process during 1997. This paper reports on the pretreatment approach and its application to thermal desalination using MSF. The w ork carried out in part I of this project is reported where make-up to a 20 kiloliter/d MSF pilot plant distiller was either fresh nanofiltr ation permeate (NFP) or SWRO reject (while SWRO was fed with NFP). Thi s paper also addresses the plan of elevating MSF top brine temperature (TBT) to as high as 160 degrees C since operation at TBT of 120 degre es C with very little or no scale control treatment gave excellent res ults.