Membrane technology and water treatment inenvironmental protectionREN J ianxin1 , ZHANGBaocheng2(1. China National Blue Star Chemical Cleaning Co. , No. 9 West Road , Beitucheng Chaoyang District ,Beijing 100029 , China ;2. Department of Chemical Engineering , Polytechnic of Turin , Corso Duca degli Abruzzi 24 ,Torino 10129 , Italy)Abstract : The paper present s a general summary on the state of the water resource and membrane industry of China. Now the water pollution is becoming more grave , and the water resource is shorter and shorter in the earth. China has 660 cities ,360 cities of them are short of water. The situation in 110 cities is serious , and the situation in 40 cities is dangerous. It was predicted that the water could be a main cause of local conflict s and international wars. The water pollution in China is also very astonished. 77 % untreated wastewater is discharged ,and 46. 6 % river is polluted. Membrane is a clean production technology ,which could be used to improve the quality of drink water ,treat the waste to reduce the pollution and save the water resource. China has a lot of researchers and research institute on membrane. The paper present s some data of Chinese membrane research and manufacture.Key words : membrane ; water treatment ; environment protectionCLC number : TQ028. 8 Document code : A1 IntroductionWater is a main resource for our human being ,but the problem of water is more serious than before.China is a developing country while it s economy goes forward rapidly. However , along with the development of economy , the eco - environmental problem is becoming worse and worse , such as shortage of resources , ecological damage , environmental pollution and etc. all these are bound to have fatal impact s on the improvement of ourliving standard and on the substantial development of economy. Now the central government is focusing on the development over the western part of China , in which the economic development and the environmental protection bear key importance.Membrane separation technology is an advanced technology that has been developing very quickly during the past several decades. In 1952 , Reid introduced the idea to desalinate the seawater with RO for the first time. In 1960 , Loeb and Sourirajin produced the first RO membrane with the potential practical application , which was a symbol of the birth of membrane science and technology. China has a 40 – year history of research and development of membrane. In this period , RO , NF , UF , MF , electric dialysis , pervaporation membrane , liquid membrane , membrane reactor were developed , and have been put into application in the fields of energy , electronics ,petroleum , petrochemical , pharmacy , heavy industry , light industry , food and brewery ind ustry , people’s daily life and the environmental protection. Especially in the water treatment , the application of membrane technology turns wider and wider , and plays an increasingly important role.2 The state of water resource and water pollution in ChinaIn range of environmental problems , water problem is extremely severe. There are one third of people on the earth facing with how to solve the shortage of water and how to treat the wastewater. This number will be doubled in the next 30 years. It is forecast by some experts that water , rather than oil , is going to be the main cause of conflicts regionally even globally.There are 660 cities in China. Among them , more than 360 are short of water and 110 are in urgent situation. Further more , 40 cities are in the list of the cities that are ext remely short of water. It is estimated that the water shortage will be 40 billion tons annually , and that China will lack 60 billion tons water in 2030. Due to the water shortage , the product output decreases by 240 billion RMB yuan annually.The water quality in China was deteriorated over the past few years. The polluted river length increased every year. According to the statistical data in 1999 , 46. 5 % ofrivers were polluted in 100 000 km monitored rivers , but the wastewater treated ratio was only 23 %. [1 ]Water pollution has become the obstacle of economic development and social progress. In Sanxia reservoir of Yangzi River , there are 21 counties discharging wastes into Yangzi River. The height of the float above water reaches 2～4 m , sometimes 6. 5 m. It has directly affected the work of Ge Zhou Ba water power station. It causes frequent breakdown of Erjiang power station. The worst case happened was that once a time the float caused severe power plants breakdown with an electricity loss of 14 000 kW , equal to the capacity of a small power station.Water pollution not only becomes an impediment of the economic development , but also endangers the existence of the people. The water quality in Yangteng Lake drops to grade 3 from grade 2 , which causes the water undrinkable.3 State of membrane industryChina has a lot of research unit s and researchers on membrane. The research on electric dialysis and ion exchange membrane began in 1958[2 ] . RO membrane began in 1965 and UF membrane in 1970s.The earliest prepared UF membrane , cellulose acetate UF membrane , was used in electric coat system in 1980s , after polysulfone hollow fiber UF membrane was manufactured. The researches and the development also went ahead rapidly on NF membrane , gas membrane , inorganic membrane , pervaporation membrane and liquid membrane.Although the membrane industry of China is not big , it grows up very quickly. According to the statistical data in 1997 , there were 13 big companies of membrane with the output over ＄1. 2 million in China ( Tab. 1) . The output of solo membrane was ＄45 million , within which the imported value was ＄27 million. The industrial output relevant to membrane was estimated ＄0. 17 billion and it will be ＄0. 3 billion this year. The imported membrane is about 70 % sales in China. The output of locally manufactured membrane increased by 30 % annually.In 1997 , the global output value of membrane and it s relevant equipment was about＄10 billion. It is estimated that the output value will be increased to ＄14 billion in 2000. The output of membrane industry of USA was ＄1. 1 billion in 1997 and will reach ＄1. 6 billion in 2001 with the annual growth rate of 8. 0 %. In 1997 , the sales of membrane product s for water treatment was ＄0. 97 billion in Europe. It is reckoned to be ＄1. 65 billion in 2004 with the annual growth rate of 7. 9 %. According to these growth rates , China will catch up with USA and Europe in the coming years as shown in Fig. 1.Fig. 1 The output increases of membrane products in USA , Europe and ChinaThere are tens of research institutes in China , of which more than 20 are on UF and MF membrane. Meanwhile , there are two research bases on membrane. One is the aqueous membrane research institute —The Development Center of Water Treatment Technology , SOA Hangzhou China , and the other is the gas membrane research base —National Engineering Research Center of Membrane Technology ,Dalian , China.4 Application of membrane in water treatmentThe application of membrane in water treatment depends on it s effectiveness of separation and cost of process. As an advanced separation technology , it is endowed with many advantages : high selectivity , applicability under ambient temperature without phase change , low cost of energy , high level of automation ,low pollution and etc.4. 1 Desalination of seawater and black waterRO is the most economical way for the desalination of seawater and black water.The energy consumption is less than 5 kW·h/ t for seawater or 0. 5～3 kW·h/ t for black water. The biggest plant of RO for seawater desalination can produce water 2. 1 ×105m3/ d , for black water is 1. 3 ×105 m3/ d. It seems that RO is the best method to solve the problem of drinking water and industrial water in the draught areas. It can be verified by the fact that most of the largest desalination plant s are located in Middle East as shown in tab. 2[3 ].4. 2 Purification of drinking waterMembrane is the best tool for the purification of drinking water because it can remove the suspended substance , bacteria , toxic metallic components and organic components to improve the water quality. 90 % of the city water is productive water, only 9 % supplied water is the domestic water and only 1 % is drinking water. To supply water separately for the resident zones is an effective way to improve the quality of drinking water. Supplying water separately is to treat the 1 % supplied water with membrane for special purpose. Separate supply system has been built in some resident zones of Beijing and Shenyang , which mainly use RO membrane.The world total capacity of desalination in 1998 is 22 735 000 m3/ d.4. 3 Reuse of municipal domestic sewageCity sewage is an important potential water resource. Recycled water for different purposes can be produced from the domestic sewage with membrane. It is an effectiveway to solve the shortage of water resource.There are 3 domestic sewage treatment factories in Beijing , and another 4 are under const ruction. In addition , 15 more are to be built . The sewage treat ratio will mount to 80 % in 2006. Two million tons of the treated water will flow out from these wastewater treatment factories. After treated with membrane , the water can be reused for industrial purpose , green area and other fields. In this way , the municipal supplied water can be reduced , and the water resource can be fully utilized. If the membrane technology is applied in the deep treatment of the city sewage ,more than one million tons of discharged wastewater will be reduced every day only in Beijing. At the same time , more than one million tons of the water resource can be saved. So it would retrench 0. 36 billion tons of water per year. This method can reduce the water pollution , as well preserve the water resource.4. 4 Treatment of industrial wastewaterIndustrial wastewater has many types in large quantity and it is very harmful. If the wastewater can be treated , it would not only preserve the resource ,but also protect the environment because the wastewater contains some deleterious substances such as oil ,metallic ions , phenol and etc. The membrane technology bears splendid significance in the industrial wastewater treatment . In early 1970s , RO membrane began to make the electric plating wastewater recycled ; Charged UF membrane turned the electro coating system in automatic company into clean producing line. The wastewater treatment with membrane recycled the wastewater in dyeing process ; UF membrane is a key technology for the reuse of oil wastewater.5 Future of membrane application in water treatmentThe essence of membrane technology is a highly effective material. The material should provide high flux , high selectivity and so on. In the wastewater treatment , we often encounter hazardous condition. Under such kind of circumstances , organic membrane sometimes cannot meet the requirement . Consequently , more attention ispaid to the inorganic membrane now that has fulfilled a considerable progress in these years with a rate of 30 %. Currently China can produce tube ceramic membrane on industrial scale. With the decrease of water resource and the increase of water pollution , it is definitely that the membrane technology , the separation technology of the lowest energy cost , will realize a brilliant future. RO , NF ,UF , MF , ion - exchange , dialysis etc which are mainly used in water treatment will be the center of membrane technology. China is a country with a large population of nearly 1. 3 billion people , which covers one fifth of the world population , but the water resource is only 1/ 20 of world. Therefore the water resource per capita is only 1/ 4 of that of the world. Membrane is an effective means to solve water problem. The advantage of membrane in water treatment is more and more obvious while it s application is wider and wider. The membrane industry of China marches rapidly at a rate of 30 % annually. However , the difference from the developed count ry is still big. The membrane output per capita is merely 1/ 32 of that of USA and 1/ 12 of that of the world. The membrane market in China is huge with a bright outlook. To enhance the application of membrane in water treatment , we should : Ó Promote the application of membrane technology.Ó Develop new - fashion membrane.膜技术和环境保护中的水处理任建新1 张保成2(1 中国蓝星化学清洗总公司, 中国北京朝阳区北土城西路9号,1000292. 意大利都灵理工大学化工系, Corso Duca degli Abruzzi 24 ,Torino 10129 , 意大利)摘要：这篇文章简单介绍了目前中国水资源和膜工业的现状。