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Resources, Conservation and Recycling 105 (2015) 1–10

Contents lists available at ScienceDirect

Resources, Conservation and Recycling

jo ur nal home p age: www.elsev ier .com/ locate / resconrec

eview

verview of membrane technology applications for industrialastewater treatment in China to increase water supply

iang Zhenga,∗, Zhenxing Zhangb,∗, Dawei Yua, Xiaofen Chena, Rong Chenga,hang Mina, Jiangquan Wanga, Qingcong Xiaoa, Jihua Wangc

School of Environment & Natural Resources, Renmin University of China, Beijing 100872, ChinaIllinois State Water Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Champaign, IL 61820, USAFedEx Corporate, Memphis, TN 38125, USA

r t i c l e i n f o

rticle history:eceived 16 July 2015eceived in revised form9 September 2015ccepted 21 September 2015

eywords:embrane technologyastewater treatment

ndustrial wastewaterater reuse

hina

a b s t r a c t

Treating and reusing industrial wastewater is one of many means to improve water supply capacity,especially within developing countries. In the past 15 years, remarkable progress has been achievedon the commercial applications of membrane technology in China. The membranes demand in Chinaexceeded 30 billion yuan (US$ 4.8 billion) in 2010, amounting for about 15% of the world total. However,the sate-of-the-art of membrane applications in industrial wastewater treatment is not well understoodand documented. This study performs a national survey of membrane plants and membrane manufac-turers to investigate the characteristics of membrane technology applications for industrial wastewatertreatment to increase water supply in China. The data obtained from the survey of membrane plants wereconfirmed with the survey of membrane manufacturers. It is aimed to provide comprehensive informa-tion of membrane technology applications for industrial wastewater treatment in China to guild the futuredevelopment of the same kind of applications. The results indicate that 6.7 million m3 of wastewater perday (2.4 billion m3 per year) treatment capacity applies membrane technology. 580 membrane plantshave been successfully applied in practice for different industrial wastewater treatment. Petrochemical,power generation, and steel industries account for the majority of membrane technology applications,from both of number of membrane plants and treatment capacity. Northern Chinese provinces which arerich in coal, crude petroleum, and ferrous ore but scarce in water resources have seen the most of mem-brane practices. Water withdrawal for the power generation industry decreased substantially recently,as water use and reuse efficiency has been improved due to wide applications of advanced wastewatertreatment methods such as membrane technology. With increasingly stringent emission standards faced

by industry and water resources shortages confronted with China, it is expected membrane technologywill play key role to address water quality and quantity issues in China. Membrane market in China isexpected to grow at a relative high annual rate of approximate 15% for the next decade. It is worthy tonote that environmental impacts due to membrane technology applications for industrial wastewatertreatment, including membrane pollution and high salinity water, shall be addressed.

© 2015 Elsevier B.V. All rights reserved.

ontents

. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

. Industrial wastewater treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

. Industry sector distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

. Geographic distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

. Engineering process features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Outlook of membrane applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Discussions and conclusions and recommendations . . . . . . . . . . . . . . . . . . . . . . . .

∗ Corresponding authors.E-mail addresses: zhengxiang7825@hotmail.com (X. Zheng), zzx509@yahoo.com (Z. Z

ttp://dx.doi.org/10.1016/j.resconrec.2015.09.012921-3449/© 2015 Elsevier B.V. All rights reserved.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

hang).

2 X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 . . . . . .

1

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Introduction

Water supply nowadays increasingly relies on alternative waterources (i.e. treated wastewater, seawater, and rainwater) in addi-ion to surface and groundwater (Zhang and Balay, 2014). Waterupply and industry are vital and intertwined components ofn urban system (Minne et al., 2011). The need for industrialastewater treatment in China is of importance due to the three

actors: water shortage, vast wastewater discharge, and increas-ngly stringent wastewater discharge standards. China is facing

ater shortages and will be facing this issue in the foreseeableuture (Gu et al., 2015; Guo et al., 2004; Zhang et al., 2001a; Zhengt al., 2014). China has to support 22% of world’s population withnly 8% of world’s water resources. The annual per capita renew-ble water resources in China is only 25% of the world averageCheng et al., 2009). Chinese industrialization in last two decadess unprecedented. No developing country has ever grown by morehan 10% per year without interruption for two decades. Coupledith the industrialization is increasing industrial water use andastewater discharge. Environment pollution in China especiallyater pollution is spreading from cities to county side. Public envi-

onmental awareness has been gradually increasing as the livingtandard is improving. Therefore, national and local wastewa-er discharge standards have become increasingly stringent (Xiaot al., 2014; Zheng and Wei, 2013). The industrial wastewater dis-harge in China has increased steadily in the last decades andeached 22.2 billion m3 in 2012, accounting for 32.4% of the totalastewater discharge. It pollutes environment and waste water

esources. Effective and efficient industrial wastewater treatmentould increase water supply by providing reclaimed water andecrease water pollution by removing contaminants in the waste-ater. Much of the treated industrial wastewater is reclaimed

nd reused, especially in power generation and steel industries.hus, wastewater treatment and reuse has attracted much atten-ion because it will provide water for industry, decrease wastewaterischarge, and minimize the effluent pollutant concentration toeet wastewater discharge standards.Membrane technology is a general term for a range of differ-

nt separation processes. These processes are of the same kind inhat all employs membrane. Membrane technology has become aeading separation technology over the past decade (Ordónez et al.,011; Purkait et al., 2009; Swamy et al., 2013; Zheng et al., 2010).he main advantage of membrane technology is that it generatestable water without the addition of chemicals, with a relativelyow energy use, easy and well-arranged process (Yu et al., 2012).he capital and operational cost of membrane technology appli-ations decreased over the years so that extensive applicationsf the technology are economically feasible (Zheng et al., 2010,012). For example, the membrane technology using both UF andO to treat wastewater originated from power generation industryould approximately require 1800 yuan (US$290) for wastewater

f per m3/day for a wastewater treatment plant (WWTP) with theapacity of 10,000 m3/day. This is much higher than the other con-entional treatment methods. The operational cost for the sameize WWTP is about 0.9 yuan (US$0.15) per m3/day. When the

WTP capacity reaches 100,000 m3/day, the capital cost for theembrane application drops to 1050 yuan (US$169) per m3/dayhich is almost the same as other conventional treatment methods.

Applications of membrane technology in industrial wastewaterreatment has increased remarkably, especially in treating waste-ater from petrochemical industry, steel industry, and power

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

generation (Chen, 2008; Chen et al., 2007, 2009; Wang et al., 2002,2006; Zhang et al., 2007). Presently, membrane technology is usedfor treating 6.7 million m3 of wastewater per day in China. Thereare 580 membrane plants in practice to treat industrial wastewa-ter. A range of famous membrane manufacturers and suppliers havebeen promoting membrane technology applications for industrialwastewater treatment in China for years. These membrane man-ufacturers include Dow Chemical Company (U.S.), Hydranautics– a Nitto Group Company (Japan), Toray Industries, Inc. (Japan),Woongjin Chemical (South Korea), and Vontron Membrane Tech-nology Co., Ltd. (China). Taking boiler makeup water as an example,there were over 30 engineering applications of membrane technol-ogy (Chen et al., 2007). In the last 15 years, Chinese membranetechnology market has grown dramatically with annual growthrate of approximate 25%. The total market volume of membrane hasreached 30 billion yuan ($4.8 billion), accounting for about 15% ofthe world membrane market share. The Chinese membrane marketshare will increase over the next decade as it is expected to keepgrow with annual rate of about 15% while the global membranemarket only grows with 9% annually (Zheng and Wei, 2013; Zhenget al., 2014, 2010).

Traditionally, water resources professionals are focused on sur-face and groundwater sources to provide sustainable and affordablewater to citizens and industries and water resources planningand management is often applied to facilitate water supply anddevelopment (Nair et al., 2014; Zhang et al., 2009b, 2001b, 2008).Reclaimed water is one of the alternative water resources whichcould assist to increase water supply (Garcia and Pargament, 2015;Piadeh et al., 2014). However, there are limited literature on com-prehensive survey and review of the state-of-the-art of membranetechnology applications in industrial wastewater treatment asattentions usually are focused on the engineering process of mem-brane technology (Nicolaidis and Vyrides, 2014; Santasmasas et al.,2013; Zheng and Wei, 2013). Membrane technology practices insteel industry wastewater treatment has been summarized in (Liuand Yang, 2009; Tian and Zhang, 2009; Wang, 2009; Yu et al.,2012; Zhang et al., 2009a, 2007; Zheng and Wei, 2013; Zheng et al.,2014). Yu et al. (2012) performed a survey of membrane technol-ogy applications in power generation (Yu et al., 2012). The statusof membrane technology applications in petrochemical industryhas been reported and updated recently (Chen, 2008; Wang et al.,2002, 2006; Zheng and Wei, 2013; Zheng et al., 2014). Nonetheless,a national survey and review of membrane technology applica-tions for industrial wastewater treatment is absent. However, acomprehensive and complete investigation of the state-of-the-artof membrane technology applications of industrial wastewatertreatment is of critical importance for the following factors. (1)It provides contemporary status of the membrane technologyapplications in industrial wastewater treatment for researchersto identify the need for further research and development. (2) Itgenerates timely information for membrane manufacturers andmembrane plants to understand the social need for membranetechnology. (3) It assists national and local environmental protec-tion and resources conservation agencies to discern regulations andtechnical standards to promote – or demote thereof – membranetechnology development and applications in China.

This study presents a complete and comprehensive review of thestate-of-the-art of membrane technology applications for indus-

trial wastewater treatment in China. This study is based on anational survey of membrane applications for industrial wastewa-ter treatment. The results of the survey are complemented with

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ublished reports and onsite investigations. The study investi-ates various perspectives of membrane technology applicationsor industrial wastewater treatment, including the magnitude, geo-raphic distributions, water sources, and engineering processes.s many membrane technology plants are applied for treatingetrochemical, steel, and power generation industrial wastewa-er, these three industries are paid more attention in the study.he goal is to provide comprehensive information of membraneechnology applications for industrial wastewater treatment inhina to guild the future development of the same kind ofpplications.

The following section of the paper discusses industrial waste-ater treatment and membrane technology practices. Then theistribution of the membrane technology practices in different

ndustry sectors is discussed. This is followed by the analysesf geographic distribution of membrane plants. The character-stics of engineering processes are presented. The outlook of

embrane applications based on the aforementioned analysesnd broad national social economic planning is discussed. Con-lusions and recommendations are provided to conclude theaper.

. Industrial wastewater treatment

The industry classification used in this study is based onhe Industrial Classification Standards of China (GB/T4754-2011)ssued by National Bureau of Statistics in 2011 (National Bureau oftatistics of the PRC, 2011). The standards were originally issuedn 1984, and were revised sequentially in 1994, 2002, and 2011National Bureau of Statistics of the PRC, 2011). According to theB/T4754-2011, there are three divisions of industries: mining,anufacturing, and utilities (including electricity, fuel, and water

upply). There are 41 classes of industries which are denoted by-digit industry codes. Based on the features of membrane technol-gy applications and industrial wastewater discharge, the 2-digitndustry codes are clustered to 8 groups in this study, i.e. petro-hemical, power generation, steel, textiles, paper, food, mining, andhe other industry which includes the remaining 2-digit industriesTable 1).

As of 2012, China discharged 22.2 billion m3 of industrial waste-ater. The top 5 provinces of industrial wastewater discharged are

iangsu, Shandong, Zhejiang, Guangdong, and Fujian. The wastewa-er discharges for each of the 8 industries are shown in Fig. 1. The top

wastewater discharge industries are petrochemical, paper, min-ng and textiles. While power generation and steel industries do notischarge as much as wastewater as paper and mining industries,here are many more membrane applications in power generationnd steel industries.

The national survey shows that totally 580 membrane plantsave been successfully applied in practice for different industrialastewater treatment, primarily petrochemical, power generation,

nd steel industries. The total treatment capacity is 6.7 million m3

f wastewater per day. The individual plant treatment capacitiesange from 500 to 100,000 m3/day with the average capacity ofpproximate 12,000 m3/day. Fig. 2 shows the histogram of var-ous treatment capacities. The number of plants with capacityf less than 1000 m3/day is 54, which is only 9% of the totalumber of plants. 55% of the 580 plants have treatment capacityetween 1000 and 10,000 m3/day. 19% of the plants have capaci-ies between 10,000 and 20,000 m3/day. 30 plants have capacitiesf 50,000 m3/day or above which is only 5% of the total num-

er of membrane plants. In general, the majority of membranelants have medium treatment capacities, while the number of

arge scale membrane plants has been growing steadily recentlyut still accounting for a very small portion.

and Recycling 105 (2015) 1–10 3

3. Industry sector distribution

Approximately 80% of membrane plant capacity is in petro-chemical, power generation, and steel industries. Fig. 3 shows thedistribution of membrane plant capacities in different industries.The membrane technology treatment capacities in petrochemi-cal, power generation, and steel industries are 2.77, 1.49, and1.03 million m3/day, which account for 41%, 22%, and 15% of thetotal capacity, respectively. Each of textiles, paper, food, and min-ing accounts about 3% of the total capacity. The other industrieshave 7% of the total treatment capacity.

From the perspective of the number of membrane plants, petro-chemical, power generation, and steel industries account for themajority as well. Fig. 4 demonstrates the number of membraneplants in various industries. Approximately 70% of the plants areemployed in these three industries. 38%, 22%, and 9% of the mem-brane plants are used in petrochemical, power generation, and steelindustries, respectively. Textiles, paper, food, and mining grasp 5%,1%, 8%, and 3% of all membrane plants, respectively. 13% of all mem-brane plants are used in other industry.

Fig. 5 shows the individual membrane plant treatment capacity.Most industries have similar average individual treatment capacity.Paper industry has the smallest amount of membrane plants butthe average individual plant treatment capacity is the highest with438,000 m3/day. The average individual plant treatment capacityin steel industry is 20,000 m3/day. Food industry has the lowestaverage treatment capacity of 5,000 m3/day.

Based on the performance of the surveyed membrane plants inChina, the current membrane technology applications for industrialwastewater treatment is relatively advantageous when it reachescertain scale. For power generation and steel industries, a capacityof 10,000 m3/day is considered advantageous. The minimum capac-ities at which the membrane technology is advantageous are 5000,5000 and 500 m3 for petrochemical, paper, and food industries,respectively.

Table 2 demonstrates the capacities of industrial wastewa-ter treatment facilities and membrane plants and the percentageof treatment capacity of all facilities that applies membranetechnology. The total capacity of all treatment facilities is314.1 million m3/day and the capacity of all membrane plants is6.7 million m3/day. On average, 2.1% of the total industrial waste-water treatment capacity has involved membrane plants. Steel,power generation, and mining industries have the highest capac-ities of all treatment facilities. 8.1% of treatment capacity inpetrochemical industry employs membrane technology, which isthe highest among the 8 industry groups. Petrochemical factoriesare often located in water scarce regions such as northwestern andnorthern China. The implication of this is that water resources areof extreme importance for this industry. National and local regula-tions also incentivize recycle and reuse of water for petrochemicalindustry. Due to several highly publicized petrochemical factoryaccidents in the last decade, petrochemical industry wastewaterdischarge standards are much more strictly complied. Furthermore,reverse osmosis (RO) and membrane bioreactor (MBR) are verycapable to treat many pollutants in petrochemical industry waste-water. On contrary, only 0.4% of the treatment capacity in miningindustry appears to use membrane technology. The remaining 6industries has a range of 0.9–2.9% of treatment capacity using mem-brane technology.

4. Geographic distribution

As discussed in previous sections, membrane technology isprimarily applied in power generation, petrochemical, and steelindustries. The development of these three industries is closely

4 X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10

Table 1Industries classification used in the study.

Industry class 2-Digit industry code Description

Mining 06–13 Mining of coal; crude petroleum and natural gas; ferrous metals; nonferrousmetals; nonmetal minerals; and others

Food 14 Manufacture of food products15 Manufacture of wine, beverage, and tea16 Manufacture of tobacco products

Textiles 17 Manufacture of textiles18 Manufacture of apparel

Paper 22 Manufacture of paper and paper products

Petrochemical 25 Petroleum products26 Manufacture of chemicals and chemical products27 Manufacture of medical and pharmaceutical products28 Manufacture of chemical fibers29 Manufacture of rubber and plastic products

Steel 31 Smelting of ferrous metals

Power generation 44 Electricity and heat generation and supply

Other 19–21, 23, 24, 30, 32–43, 45, 46 Other industries

Fig. 1. Industrial wastewater discharge for different industries.Data from (Wen and Liu, 2013).

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Fig. 2. The histogram of me

elated to the geographic distribution of coal, crude petroleum,nd ferrous ore. The need for industrial wastewater treatment and

euse is more pressing for water scarce regions than for waterich regions. The spatial distribution of water resources also hasubstantial impact on membrane technology applications. Gen-rally speaking, the water scarce provinces with rich coal, crude

e plant treatment capacity.

petroleum, and/or ferrous ore appear to have much more mem-brane applications for treating industry wastewater.

The number of membrane plants for each provinces is shown inFig. 6. It can be seen that most of membrane plants are locatedin northern China including the provinces of Shangdong, Hebei,Shangxi, Liaoning, Inner Mongolia, Ningxiao, Henan, Shanxi, and

X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10 5

Fig. 3. Membrane plant treatment capacities for different industries.

Fig. 4. The number of membrane plants applied in different industries.

12 11

20

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25

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40

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Fig. 5. The average membrane plant treatment capacities for different industries.

Table 2Treatment capacities of industrial wastewater treatment facilities and membrane plants.

Capacity of all treatmentfacilities (million m3/d)

Capacity of membrane plants(million m3/d)

Percentage of capacity usingmembrane plants (%)

Petrochemical 34.5 2.77 8.1Power generation 67.7 1.49 2.2Steel 95.9 1.03 1.1Textiles 11.9 0.29 2.4Paper 27.1 0.23 0.9Food 6.9 0.20 2.9Mining 46.5 0.17 0.4Other 23.6 0.49 2.1

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Total 314.1

ata from (Wen and Liu, 2013).

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6 X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10

Fig. 6. The number of membrane plant by provinces.

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Fig. 7. The membrane plant treatm

ianjing. 53% of the membrane plants are located within these 9rovinces. In southern China, Guangdong has applied 47 membranelants which is about 8% of the national total. Jiangshu and Zhen-

ian are the other two southern provinces that constructed manyembrane plants, accounting for 7% and 6% of the national total,

espectively. These 12 provinces constructed 73% of national totalembrane plants. The capacity of membrane applications for each

pacity by provinces (1000 m3/day).

provinces are shown in Fig. 7. Primary treatment capacities arelocated in northern China such as Shangdong, Hebei, Shanxi, Liao-ning, Inner Mongolia, Ningxiao, Henan, Shanxi, and Tianjing. 58% of

the national treatment capacity is within these 9 provinces. Guang-dong, Jiangshu, and Zhejiang account for 21% of the national totaltreatment capacity. The 9 northern provinces plus the 3 southernprovinces account for 79% of the national treatment capacity.

X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10 7

Fig. 8. Membrane plant treatment capacity distribution in petrochemical industry.

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Fig. 10. Membrane plant treatment capacity distribution in power generationindustry.

through the membrane. UF is cable to filter suspended solids and

ig. 9. The number of membrane plant distribution in petrochemical industry.

The spatial distribution of treatment capacities and membranelants in petrochemical industry are shown in Figs. 8 and 9,espectively. For petrochemical industry, Shangdong, Ningxiao, anduandong have the most treatment capacities, accounting 14%,0%, and 9%, respectively. The top 10 provinces account for 72%f the national total treatment capacity in petrochemical industry.or the number of membrane plants, the 10 provinces have 68% ofotal membrane plants in petrochemical industry with Shangdongrovince at the top. Most of the top 10 provinces are located inorthern China with rich coal and crude petroleum resources butithout rich water resources (Fig. 10).

For power generation industry, Shangdong has also the mostreatment capacity in the nation, accounting 26% of the totalreatment capacity. Shangdong province has 38 membrane plants,ccounting 29% of the national total. Zhejiang has only 6 membranelants treating power generation wastewater but has 13% of theational total treatment capacity. Inner Mongolia has 13 membranelants with 7% of the national treatment capacity (Fig. 11).

For steel industry, Hebei is the top user of membrane tech-ology, accounting 36% of national treatment capacity with 15

embrane plants. Shanxi is the second biggest user of mem-

rane technology with 4 membrane plants to treat 11% of nationalteel industry wastewater. Liaoning is third biggest user and has 3

Fig. 11. The number of membrane plants in power generation industry.

membrane plants to treat 8% of the national steel industry waste-water (Figs. 12 and 13).

5. Engineering process features

The membrane units, pretreatment and post-treatment areexamined to explore the engineering process of membrane appli-cations herein. The widely used membrane separation technologiesin industrial wastewater treatment include RO, ultrafiltration (UF),and Membrane bioreactor (MBR). RO membrane manufacturing isstandardized and the operation is very stable. RO is the finest sepa-ration membrane process with pore sizes ranging from 0.0001 �mto 0.001 �m. The disadvantage of RO is that it requires substan-tial pretreatment. If the permeate only pass one RO membrane, themethod is refereed as single RO. It the permeate passes two ROmembranes, the method is defined as double RO. UF is a varietyof membrane filtration to perform separation via a semipermeablemembrane by forces like pressure or concentration. Pore size of UFis between 0.01 �m and 0.1 �m. Solutes of high molecular weightare retained while water and low molecular weight solutes pass

microbe so that RO membrane is protected from these pollutants.The facility with UF pretreatment will use much less area and thequality of generated water is very stable. MBR is the combination

8 X. Zheng et al. / Resources, Conservation and Recycling 105 (2015) 1–10

Fig. 12. Membrane plant treatment capacity distribution in steel industry.

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Fig. 14. Engineering process of membrane technology for petrochemical industry.

Fig. 15. Engineering process of membrane technology for power generation indus-try.

coupled with UF, MMF, or both. 46% of membrane plants use RO

Fig. 13. The number of membrane plants in steel industry.

f a membrane process with a suspended growth bioreactor. Thisrocess has high biochemical treatment efficiency with good sepa-ation of solids and liquids. MBR facility also takes small amount ofrea to build and could be controlled automatically. MBR is widelysed for municipal and industrial wastewater treatment.

Among many pretreatment and post-treatment methods, rapidltration (RF), multi-medium filtration (MMF), and precision fil-ration (PF) are commonly employed with membrane separationrocess. Rapid filtration usually only uses single or double layersf quartz sand and has a high flow rate. MMF employs multi-layeredium for filtration. It is a common used pretreatment technol-

gy to remove dissolved organics. PF uses tens to hundreds layersf high strength filters such as stainless steel filters to achieve highltration efficiency. Precision filtration is usually employed withembrane separation process.Due to varying wastewater features of different industries,

ngineering processes are diversified. Therefore, the engineeringrocess features for petrochemical, power generation, and steel

ndustries are analyzed separately. Fig. 14 shows the engineering

rocesses composition in petrochemical industry. It is easy to seehat MBR accounts for the majority membrane process used in thendustry. 75% of membrane plants use MBR alone and 13% uses

Fig. 16. Engineering process of membrane technology for steel industry.

MBR coupled with RO. Overall, 88% of membrane plants use MBRtechnology. RO is employed in 25% of the membrane plants and itis often used with MBR.

Engineering process of membrane technology in power gener-ation industry is demonstrated in Fig. 15. RO technology is used inall the membrane plants in this industry and sometimes double ROtechnology is used. Single or double RO are often employed withUF, PF or RF. 74% of the membrane plants use single RO and 26% ofthem use double RO. 42% of the membrane plants uses single ROcoupled with rapid filtration. This may be due to the fact that sin-gle RO coupled rapid filtration is the most cost efficient treatmentmethod and still generate water of acceptable quality.

Applications in steel industry also focuses on RO. RO is either

coupled with UF. 45% of membrane plants use RO coupled withMMF. Only 9% of the membrane plants use RO coupled with bothUF and MMF. It is easy to see from Figs. 14–16 that the engineering

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rocess in different industries are varying. This is due to the fol-owing facts. The wastewater originating from different industriesave a broad range of different contaminants and thus have differ-nt features. The purpose of the wastewater treatment is varyingor different industries. For example, water treated by RO is oftenimed to be recycled and reused as makeup water or cooling water.

. Outlook of membrane applications

After 30 years of fast economic growth, the gross domestic prod-ct (GDP) in China is anticipated to reach 80 trillion yuan (US$ 12.9rillion) in 2020 which doubles the GDP in 2010 (Hu, 2013). Mean-hile, water professionals are faced with daunting task of securingater supply and fighting water pollution. Industrial wastewater

reatment capacity and efficiency will improve over the foreseeableuture. With the advancement of membrane technology and dwin-ling cost of membrane technology applications, it is expected thatembrane technology will play a bigger role in industrial waste-ater treatment.

Take steel industry as an example, crude steel production willncrease by about 25% from 2010 to 2020 according to the nationallan (Yuan et al., 2012). Considering the water use efficiency

mprovement, the total water use and wastewater discharge willot increase much and could decrease a bit in the next decade.resently, the wastewater discharge per ton of steel is about 2 m3

n China. The total wastewater discharge is about 1.2 billion m3 perear. Developed countries discharge about 1 m3 wastewater to pro-uce 1 ton of crude steel. To achieve the same water use efficiency aseveloped countries, the water use efficiency needs to be doubled.

f membrane applications will increase proportionally, the treat-ent capacity of membrane plants in steel industry will rise to

pproximately 2 million m3/day.Membrane technology market has grown noticeably with

nnual growth rate of approximate 25% in the recent 15 years.he total market volume of membrane technology has reached0 billion yuan, accounting for about 15% of the world membranearket share. The Chinese membrane market share will increase

ver the next decade as it is expected to keep grow with annualate of about 15% while the global membrane market only growsith approximately 9% annually (Zheng et al., 2014, 2010).

It is noted that the membrane technology has its own disadvan-ages, mainly a range of chemical agents used during the process.hese chemicals could be very detrimental to environment whent is discharged. Thus, the future development of membrane tech-ology and its applications in industrial wastewater treatment inhina could be limited by the secondary pollution originated fromembrane manufacturing and applications. It is critically valuable

o develop environmental friendly membrane in the future to pro-ote membrane applications in China.

. Discussions and conclusions and recommendations

This study conducted a national survey on the state-of-the-artf membrane technology practice treating industrial wastewatern China. The industry sector distribution of membrane applica-ions, geophysical distributions of membrane plants, and featuresf engineering process of chemicals, power generation, and steelndustries are analyzed based on the results of the national survey.ased on the results of the national survey and industrial water useata, it appears that membrane technology application for indus-rial wastewater treatment in China has improved the efficiency

f industrial water use and thus lessened industrial water demandrom surface or groundwater sources. For example, as membraneechnology application in power generation industry has increasedver the last decade, the water withdrawal by power generation

and Recycling 105 (2015) 1–10 9

industry decreased from 67.5 billion m3 to 53.7 billion m3 in 5 years.This is partially due to the fact that the power generation indus-try reuse and recycle its water more efficiently while the newlyavailable technology such as membrane technology could treat thewastewater to the level allowing reuse and recycle treated waste-water. Membrane technology has increased the water reuse insteel industry as well. To produce 1 ton of crude steel, the aver-age water withdrawal was 4.1 m3 and it is decreased to 3.4 m3 asmembrane technology among other advanced treatment methodsincreased the water use efficiency and effectiveness. Treatmentcapacity using membrane technology has reached 2.4 billion m3

per year and is expected to increase steadily, which increased sub-stantially water reuse in Chinese industry and decreased industrialwastewater discharge. Thus, it reduces industrial water demandon surface and groundwater sources and lessens environmentalpressure by releasing less wastewater to environment.

The following conclusions have been reached based on theresults of the national survey.

1. Generally, membrane plants treating industrial wastewater havemedium treatment capacity. 55% of the membrane plants havetreatment capacity between 1000 and 20,000 m3/day. Largescale membrane plants have been built recently but still accountfor a small portion of the national total.

2. Membrane technology is primarily applied to treat petrochemi-cal, power generation, and steel industries’ wastewater in China.These 3 industries provide 80% of the national membrane appli-cation capacities for industrial wastewater treatment. The otherindustries have seen sporadic membrane applications. About 8%petrochemical industry wastewater treatment capacity employsmembrane technology and only approximately 2% overall indus-trial wastewater treatment capacity uses membrane technology.

3. Membrane technology applications are most located in north-ern Chinese provinces such as Shangdong, Shanxi, Henan, Hebei,Inner Mongolia, and Liaonin. This is because these provinceshave rich coal, crude petroleum, and/or ferrous ore reserve butlimited surface water and groundwater resources to supportindustrialization. Guangdong and Zhejiang are the two southernprovinces that have substantial membrane applications.

4. The engineering processes of membrane applications are diver-sified with membrane units and pre- and post-treatment. Withthe development of membrane technology, the engineering pro-cesses to treat industrial wastewater will be further advancedand diversified based on water source and quality.

5. With the robust economic development and industrialization inChina in the foreseeable future and the advancement of mem-brane technology and engineering practices, it is expected thatmembrane technology will play bigger role in the future to treatindustrial wastewater. Larger scale of membrane plants is antic-ipated to be built to provide much treatment capacity and drivedown the operation and maintenance cost of membrane plants.

Membrane technology is of critical importance to providereliable and sustainable water supply for industry development,especially in developing countries. Based on the analysis of thestate-of-the-art of membrane technology applications for indus-trial wastewater treatment, regulations and incentives shall beadopted to improve membrane technology applications in petro-chemicals, power generation, and steel industries. Membranetechnology applications to treat wastewater in food, printing, andpharmaceutical industries shall be encouraged since wastewa-

ter generated in these industries are very suited to be treatedwith membrane technology. For example, a national regulationwhich restrict wastewater effluent and promote wastewater reuseby factories of printing industry took effect in 2012. Due to this

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egulations, wastewater originating from printing industries nowas to be treated further and membrane technology provides aeasonable and convenient option for the industry. To facilitateembrane applications, it is important to develop membrane

ndustry standard and guidance on designing and testing mem-rane manufacturing and applications.

In the future, this study could be improved from the follow-ng perspectives. One of the shortcomings of the national surveyonducted in this study is that data and information of small scaleembrane plants with the capacity of 500 m3 or less may be

nderrepresented. As these plants generate ignorable capacity, theurvey still provides the best available snapshot of membrane tech-ology applications. It is noteworthy that membrane technologypplications for municipal wastewater treatment are not includedn the survey. It is valuable and informative to assess the applica-ions of membrane technology in industrial wastewater treatmentn China if a complete comparison of the applications in China withhose in other countries is performed. Due to the absence of datan the literature, the comparison is not conducted in this study.

cknowledgements

The authors in Renming University of China were partiallyupported by the Fundamental Research Funds for the Central Uni-ersities, and the Research Funds of Renmin University of ChinaGrant No. 11XNK016, Grant No. 10XNJ062), the Program for Newentury Excellent Talents in University (Grant No. NCET-12-0531)nd the National Key Technology Research and Development Pro-ram of the Ministry of Science and Technology of China (Granto. 2012BAJ19B02). The trademarks, companies, or products men-

ioned in this paper do not necessarily imply the authors endorse orecommend the goods or service. Any opinions, findings, and con-lusions are those of the authors and no official endorsement shoulde inferred. We are grateful to Dr. Ming Xu and two anonymouseviewers for their insightful comments and suggestions whichmproved the quality of the original manuscript.

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