Engineering Test Study On A Short Process RO Seawater Desalination Pretreatment System

As the world's freshwater increasingly scarce,the RO desalination technology has developed rapidly as a reliable source of freshwater resources.The RO membrane has stringent requirements for the inflow water quality,so the seawater must be pretreated before enter the RO system.The traditional RO pretreatment technology is complex and lack of reliability,and the large area has also brought high investment cost.These have led to the rise of membrane RO pretreatment technology.The traditional RO pretreatment technology and membrane RO pretreatment technology have been compared in this paper.It has been found that the coagulation-ultrafiltration integrated RO desalination pretreatment technology has great advantages when compared with other technologies,and a set of pilot device has been designed according to the coagulation-ultrafiltration integrated technology.During the six-month experiment in Huaneng Yuhuan Power Plant,the operation difficulty of the system was increased by setting different operating conditions,so the reliability and stability of this system can be examined.The following conclusions can be drawn from the pilot experiment(1)The system can run normally under the poor water quality with high suspended matter concentration and turbidity.The system's product water flux is greater than 33L/m2h and the transmembrane pressure is less than 0.03MPa.The product Water turbidity can reach less than 0.1NTU,and SDI15 less than 1,which can fully meet the RO system's water quality requirements.(2)The greater the product water flux,the faster the product water flux decay rate.It can be used to reduce the fouling rate of the membrane by take smaller product water flux under the premise that the RO system inflow water can be adequate provided.At the same time,the periodic backwash of the system can make the product water flux Stable at an acceptable level.(3)The Extension of the production cycle will result in the fouling of the membrane surface increase,but it also can increased the total water production.For the coagulation-ultrafiltration integrated RO desalination pretreatment process,the use of 30min water cycle is basically able to take into account the water production,membrane fouling and water recovery rate.(4)The amount of coagulant added should not be too large,it should be appropriate with the water quality.At the beginning of the experiment,15 mg/L FeCl3 was added,which result in the high water turbidity.After adjusted the dosage to 10 mg/L,the turbidity of the product water was rapidly reduced to 0.1 NTU.Therefore,this paper suggests that 7.5?10mg/L coagulant dosage should be used under the circumstance of inflow water turbidity of 100 to one 1000 NTU.