Study On The Treament Of Seawater From Bohai Gulf By A Hybrid Ultrafiltration-reverse Osmosis Process

Coastal provinces and cities in northern China water resources per capita is only263m3, water shortage has become a major problem limiting economic development in coastal areas. In some newly developed islands, freshwater resources are extremely lacking, fresh water often rely on input from the inland, but the water that input from the inland is in high cost and poor reliability. Membrane desalination technology is an effective solution to water shortages in coastal areas and islands. This paper mostly studies performance and operational stability of seawater treatment by ultrafiltration-reverse osmosis, in order to provide reference for the design of small and medium sized double membrane desalination equipment, Optimize the operating parameters of the double membrane technology.By changing the ultrafiltration operating conditions, fluxes, cleaning cycle and cleaning methods to study the effects on membrane fouling, the water production rate and water quality studies produced, we can find that transmembrane pressure is higher when seawater treated by ultrafiltration, membrane surface contaminants can be removed before forming the contamination layer, it contribute to the recovery of flux. While the forward and reverse flush simultaneously, the pressure of flushing increases, the effects of remove pollutants on the surface of the film has been strengthened to help reduce transmembrane pressure. In the same time, supplementary chemically enhanced backwash, we can effectively control the increase in transmembrane pressure, and the transmembrane pressure differential will be maintained at a low level. Under the experimental conditions, the water flux of ultrafiltration selected for83L/m2h, cleaning cycle35min, cleaning method is being carried out simultaneously recoil impulse and rinse45s, while every12h supplementary chemically enhanced backwash, chemically enhanced backwash by acid alkali alternately cleaning. Ultrafiltration produces high water quality, the water fully meet the requirements of reverse osmosis water, ultrafiltration water SDI relatively stable and little change in value, stabilized at around3.2, ultrafiltration flux, cleaning cycle and changes in the way the cleaning effect on the ultrafiltration membrane water SDI smaller, ultrafiltration water turbidity less than0.09NTU. Changes the pressure and the concentrated water back flow of reverse osmosis to study the impact of water production, recovery, desalination and output freshwater quality. It can be found that with the pressure increased, reverse osmosis water production increased and recovery rate rises, while basically unchanged through the salt, so the salt content of fresh produce to reduce, reverse osmosis desalination systems become larger. Concentrated water return system can effectively increase recovery rate, but reduce the reverse osmosis water production and recovery rate of membrane reactor, increasing the production of fresh water salinity, in the same time the reverse osmosis water salinity is relatively stable, so the reverse osmosis desalination of system to reduce. The larger the return flow, resulting in a rapid increase in the salt content of output freshwater, increased energy consumption. Under the experimental conditions, the reverse osmosis water pressure chosen to5.5MPa, concentrated water flow back to select50%of the total concentration of water. In this condition a longer time (30d) during operation, the occurrence of reverse osmosis water is decreased, remained at60L/h, the system was21.7%product water recovery; salinity of the water is about117mg/L, desalination was99.45%; UV254and EEM fluorescence spectroscopy indicates that the system of dissolved organic matter in seawater has good removal; this system product water quality test results meet the national drinking water quality indicators, to drinking standards and can be consumed.