A new seawater reverse osmosis (SWRO) pretreatment unit has been evaluated for treating high-turbidity seawater. The pretreatment unit consists of a double-stage fibre filter and ultrafiltration. An RO unit operated with the pretreatment unit showed stable performance.
The Korean company Hyosung Goodsprings has developed new seawater reverse osmosis (SWRO) desalination technologies, through the construction and operation of an SWRO research facility with 2000 m3/day production capacity.
The pilot plant includes a new compact pretreatment system to treat high-turbidity seawater. The pretreatment system includes a double-stage stretching-releasing type fibre filter (FF) followed by an ultrafiltration unit.
This configuration is successful in producing consistent quality of feed water to the RO membrane of less than 3 SDI15 (15 minute silt density index), even during periods of high-turbidity seawater reaching levels of 52 NTU.
The FF pretreatment has a very small footprint, and competitive operating costs in terms of chemical and energy consumption.
However, the main concern with the stretching-releasing type fibre filter is the physical integrity of the fibres over the equipment lifetime. Field results for two years of operation show that fibre bundles made of polypropylene break frequently, and need to be replaced annually with new bundles.
Thus the durability of the fibre material and the filter equipment need to be improved for application of the fibre filter in commercial desalination plants.
Stable operation of the RO unit supports the above conclusion, that the compact pretreatment process evaluated in this study may be adequate for membrane desalination systems treating high-turbidity seawater.
