REVIEWS REVIEWS REVIEWS
Constructed wetlands in China: recent
developments and future challenges
Dong Liu1, Ying Ge1, Jie Chang1*, Changhui Peng2, Binhe Gu3, Gilber t YS Chan4, and Xiaofu Wu5
Constructed wetlands (CWs) are an emerging, environmentally friendly engineering system employed in
China. They require lower investment and operation costs while providing higher treatment efficiency and
more ecosystem services than conventional wastewater treatment methods. Introduced to China in 1987, CW
systems used for wastewater treatment have rapidly increased in number, particularly since the late 1990s.
This review summarizes the state-of-the-art application of CW systems for water pollution treatment by
reviewing the basics of the technology and its historical development and performance efficiency. Current
progress, limitations, future concerns, and the challenges of CW technologies are also discussed. Also highlighted is the need for sufficient and appropriate data to assist in the further development of CW systems and
the implementation of integrated “bottom-up” and “top-down” approaches by both the public in general and
government bodies in particular.
Front Ecol Environ 2008; 6, doi:10.1890/070148
C
onstructed wetlands (CW) are artificially constructed
wetlands, built in areas where wetland ecosystems do
not naturally occur (Sundaravadivel and Vidneswaran
2001). According to the Ramsar Convention (RCW
2006), CW systems include constructed treatment wetlands (CTW), water storage areas and drainage ditches,
salt exploitation sites, seasonally flooded agricultural land,
aquaculture ponds (fish and shrimp), and irrigated agricultural lands (rice paddy fields). CTW systems are the most
beneficial of these, due to their superior wastewater treatment capabilities (Cooper and Green 1995; Sundaravadivel and Vidneswaran 2001).
CTW systems are engineered systems designed and
In a nutshell:
• Constructed wetland (CW) systems will probably be the primary technology for minimizing water shortages and pollution, while meeting sustainable development goals in China,
in the future
• The application of CW systems to treat lightly polluted water,
residential and industrial wastewater, and effluent from wastewater treatment plants is highly beneficial
• Great effort is still required, focusing on further research, policy decisions, public education, and management training to
promote the development of CW systems in China
1
College of Life Sciences, Zhejiang University, Hangzhou 310058,
China *(jchang@zju.edu.cn); 2Institut des sciences de l’environnement,
Département des sciences biologiques, Université du Quebec à
Montréal, Montreal, QC, Canada H3C 3P8; 3Everglades Division,
South Florida Water Management District, West Palm Beach, FL
33406; 4Department of Applied Biology and Chemical Technology, and
State Key Laboratory of Chinese Medicine and Molecular
Pharmacology, The Hong Kong Polytechnic University, Hong Kong,
China; 5Centre–South Forest University of Technology, Hunan, China
© The Ecological Society of America
constructed to use physical, chemical, and biological
processes to treat wastewater (Kadlec and Knight 1996;
Vymazal 2005). Water purification by CTW systems is
increasingly recognized as a feasible and efficient global
technology (Seidel 1976; Kickuth 1977; Cooper and
Green 1995; Kivaisi 2001). However, it must be noted
that, at present, the term “constructed wetland” is used
synonymously with “constructed treatment wetland”.
Our literature survey from the Scirus database
(www.scirus.com; viewed 4 Dec 2007) indicated that
most published literature (1162 out of 1171 papers) used
the title “constructed wetlands” and the keyword “constructed wetland” when referring to a constructed treatment wetland. To eliminate confusion and because the
term “constructed wetland” is preferred by most scientists
today, we will use the initials CW instead of CTW in this
paper, unless otherwise specified.
Efforts to develop CW systems have been undertaken
by both governments and private research interests
around the world. In Europe, there are at least 6000 CW
systems in operation, while more than 1000 CW systems
have been developed in North America (Shi et al. 2004),
with an increasing number being established in Central
and South America, Australia, and New Zealand, as well
as in both Africa and Asia (Senzia et al. 2003).
The benefits of CW systems have also attracted
increasing attention in the field of water pollution control in China, where water pollution has become a major
environmental issue due to the country’s rapid economic
growth over the past two decades (Liu and Diamond
2005). China’s insufficient water resources have exacerbated the problem, and freshwater shortages have become
severe. Although municipal sewage treatment facilities
have been erected in some large cities within China, in
most smaller cities, sewage is still discharged untreated
www.frontiersinecology.or g
Constructed wetlands in China
D Liu et al.
Amount of wastewater (billions of tons)
2005 (NBS 1995–2005). The estimated economic losses from water polDomestic wastewater
lution and ecological damage ranged
Industrial wastewater
50
from 7% to 20% of the gross domestic
product (GDP) per year for the past
two decades (Guo 2004). In addition
40
to heavy economic losses, wastewater
pollution imposes further costs through
30
its impact on human health (Greenway 2005). Moreover, pollution and
20
water resource competition have triggered social upheaval in China.
10
The Chinese government has recognized the necessity for wastewater
0
treatment since the 1970s (Liu and
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Diamond 2005). The treatment rate of
Year
urban wastewater has improved from
Figure 1. Annual amount of wastewater discharged in China from 1995 to 2005 5% in the late 1980s to 20% in the
(NBS 1995–2005).
1990s, and increased to 46% in 2004
(White Paper on China Environment
directly into water bodies. Due to the immense cost asso- Protection [1996–2005] 2006). However, treatment
ciated with the deployment of traditional treatment approaches are still limited to traditional techniques; that
methods, the CW approach – with its low construction is, wastewater treatment plants (WTPs) are still in the
and operation costs and high treatment efficiency – has preliminary stages (Jiang 2004). More than 60% of cities
become an accepted technology (Haberl et al. 1995; in China do not have wastewater treatment facilities
Kivaisi 2001).
(Weng et al. 2005), and secondary and tertiary treatment
The objective of this paper is to provide an overview of stages are still under development (Jiang 2004).
the development of the CW approach to date, with a focus
Treatment facilities not only are limited, but are not
on the present and future use of CW systems for wastewater running at full capacity. Among the existing 532 WTP
treatment in China. We also evaluate the treatment perfor- facilities, 275 (51.7%) are not operating at an optimum
mance and the overall function of CW systems based upon level, according to statistics from the State Environment
a comprehensive dataset collected from publications and Protection Agency (SEPA 2005), as evidenced by an
websites within China. Treatment efficiency and land average wastewater treatment rate of approximately 55%
requirements for various flow types were compared and var- in 36 metropolitan centers, a rate lower than that of
ious scenarios analyzed, with government and local com- many developed countries (Kivaisi 2001).
munity interests in mind. Lastly, we offer recommendations
Taking into account China’s economic expansion and
for future CW development and public education.
the expected demand for wastewater purification, lowcost approaches will play a critical role in future wastewater treatment and management.
Water
management
and
wastewater
treatment
in
China
Constructed wetlands: an ecological technology
China has a shortage of freshwater resources. The amount of
for wastewater treatment in China
freshwater available per capita is approximately one-quarter
of the global average of 8513 m3 per year (Shao et al. 2006). In the past decades, conventional wastewater treatment
Over 400 of the 668 largest cities in China, for example, are systems had large capital investments and operating costs
suffering from water shortages (Yang and Pang 2006).
in China; CW systems are therefore gaining importance
The water quality of most Chinese rivers and ground- as effective and low-cost alternatives (Vymazal 2005).
water sources is poor and continues to decline. Increasing The cost of building a CW system is only one-third to
water shortages and wastewater discharge have exacer- one-half that of a WTP system in China (1000 to 2800
bated the problem, as has water pollution caused by rapid yuan RMB [renminbi, the Chinese currency] for a CW
urbanization, leading to further shortages of accessible system and 1500 to 4000 yuan RMB for a WTP system
drinking water (Shao et al. 2006). Wastewater discharge per ton for building costs, respectively; 7.5 yuan RMB =
has also increased steadily (Figure 1). The total amount US$1 as of December, 2007). Additionally, CW systems
of industrial wastewater produced in China has risen from have extremely low operating and maintenance costs
19.4 billion tons in 2000 to 24.3 billion tons in 2005. (approximately 0.05 to 0.20 yuan RMB per ton of wasteDomestic sewage discharge rose from 15.1 to 22.1 billion water, which includes power for pumps, harvesting of vegtons between 1995 and 2000, and to 28.1 billion tons in etation, and insect pest control, compared to 0.7 to 1.5
60
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© The Ecological Society of America
D Liu et al.
Constructed wetlands in China
yuan RMB per ton for WTP systems;
Free-floating
plants
Weng et al. 2005; Yang et al. 2008).
Aside from performing wastewater
Floating
Surface
treatment functions like a traditional
leaved plants
flow
WTP system, CW systems can provide
Horizontal flow
Submerged
additional ecosystem service benefits,
plants
such as biomass production, carbon
Emergent
sequestration, seasonal agriculture,
plants
Sub-surface
Constructed
Horizontal flow
flow
wetlands
reusable water supply, regional climate
regulation, habitat conservation, and
educational and recreational usage
Downflow
Combined
Vertical flow
(Knight 1997). Traditional WTP syssystems
Surface
tems deliver better treatment funcflow
tions, but provide no other services,
Upflow
except for a reusable water supply and
Integrated vertical flow
educational opportunities. Natural
Mesophyte
Downflow
wetlands, on the other hand, provide
much greater ecosystem services, in
terms of carbon sequestration, educa- Figure 2. Classification of constructed wetlands and physical layouts for wastewater
tion, and amenity and recreational treatment in China. Bold arrows within the boxes indicate the direction of flow;
uses, but provide a low capacity for hatched lines represent substrates in the CW.
wastewater treatment. Like a natural
wetland, CW systems can be integrated into sustainable CW systems were developed and widely applied throughout
landscape systems (Campbell and Ogden 1999), which much of Europe and the US beginning in the late 1970s.
could represent a possible sustainable alternative or sup- During the period from 1989 to 1999, there were fewer than
10 annual scientific publications concerning CW systems
plementary system for wastewater treatment in China.
Based upon hydrological flow patterns, CW systems can (Gao 2006) in China; by 2005, there were 143 published
be divided into surface flow (SF) and sub-surface flow research papers. Such an increase suggests that research
(SSF) systems (Kadlec and Knight 1996; Tanner et al. effort on CW systems in China is increasing dramatically.
An investigation of the literature found that, by 2006,
2002; Stottmeister et al. 2003). Sub-surface flow can, in
turn, be divided into horizontal flow (HF) and vertical flow more than 200 CW systems, ranging in area from 100 m2 to
(VF) types (Figure 2). For SF wetland systems, the sub- 8 000 m2 (with the largest – 100 000 m2 – located in
strate bed is densely vegetated, with the water column is Shenzhen, Guangdong Province), were in operation
located above the surface of the bed. In contrast, the water throughout China (Figure 3). Of these, 16.4% are SF syslevel is maintained below the surface of the substrate bed tems, 29.3% are SSF systems, and 54.3% are VF or comfor SSF wetland systems (Sundaravadivel and Vidneswaran bined IVF systems. Survey results excluded pilot-scale CW
2001). Various types of CW systems may be combined systems (average area of a pilot scale system is 1 m2 to 10 m2,
(also referred to as “hybrid systems”) to achieve greater minimum 0.4 m2) that were designed mainly for research,
treatment efficiency (Vymazal 2005). A new type of CW is and recently built CW systems that have not yet been
the integrated vertical flow (IVF) system, first introduced reported. The actual number of CW systems constructed in
to China by the European Union in 1996; IVF–CW sys- China could therefore be greater than recognized here.
CW systems in China have been established mostly to
tems consist of two VF chambers. Wastewater goes via
downflow into the first chamber and then via upflow verti- treat domestic, industrial, and agricultural wastewater, and
cally into the following one (see Figure 2; Yue et al. 2003). are usually constructed in parks, either on the periphery of or
Costs associated with development and operation are low- within urban living area properties, rural villages, areas
est for SF CWs; however, this type of system requires more where effluent is discharged from WTP systems, tourism
land to operate, and SF systems feature the lowest per-unit landscapes, and riparian areas containing polluted rivers and
treatment efficiency of all CW systems (Scholz and Lee lakes (WebTable 1). In recent years, much progress has been
2005). In contrast, the VF CW requires the least amount made on high concentration sewage treatment and the
of land area while offering the highest treatment efficiency. removal of algal blooms from eutrophic waters in small residential areas of cities and towns (Bian 2006). Non-point
source pollution, such as storm water and agricultural runoff,
The
state
of
constructed
wetlands
in
China
is more difficult to control. In this respect, China’s pollution
Research on CW-based wastewater treatment in China water control measures are far behind those of developed
began as early as the period of the “Seventh 5-year plan”, countries (MacDonald et al. 1998; Chimney and Goforth
from 1986 to 1990 (Li and Zheng 1993), with the first CW 2001), as CW systems are being increasingly recognized as
system built in 1987 (Ding and Shen 2006). In contrast, effective tools for controlling non-point source pollution.
© The Ecological Society of America
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Constructed wetlands in China
D Liu et al.
Constructed wetland treatment
performance
˚E
The treatment efficiency for various
contaminants in CW systems in
China is generally high (Table 1). The
average removal rates of NH4+–N
(ammonium nitrogen), TN (total
nitrogen), TP (total phosphorus),
COD (chemical oxygen demand), and
BOD5 (five day biochemical oxygen
demand) are 59.8%, 44.3%, 62.1%,
73.4%, and 81.8%, respectively. The
average (± SD) effluent concentration
is 5.9 (± 5.4) mg L–1 for NH4+–N, 13.4
(± 15.8) mg L–1 for TN, 1.1 (± 1.0) mg
L–1 for TP, 20.6 (± 26.1) mg L–1 for
BOD5, and 62.5 (± 67.8) mg L–1 for
COD. Despite the wide range of pollutant concentrations in the influent
(untreated wastewater that flows into
a treatment facility), as is evident from
˚N the high standard deviation (see Table
1), most CW systems perform well.
Figure 3. Distribution of constructed wetlands in China. Vertical bars represent quantities Effluent from CW systems meet the
of CW systems built in each province. Brackets indicate the number of CW systems in each Class I B (GB18918-2002; Table 1)
province. Sampling locations: (1) Jilin [5]; (2) Liaoning [10] (3) Tianjin [4]; (4) Beijing discharge standards for pollutants
[13]; (5) Neimenggu [1]; (6) Xinjiang [2]; (7) Hebei [5]; (8) Shandong [11]; (9) Shaanxi from municipal wastewater treatment
[2]; (10) Henan [3]; (11) Jiangsu [20]; (12) Shanghai [10]; (13) Anhui [1]; (14) Hubei plants in China, while the Class III
[14]; (15) Zhejiang [51]; (16) Chongqing [5]; (17) Sichuan [5]; (18) Hunan [2]; (19) (GB3838-2002; Table 1) limits for surFujian [3]; (20) Guangdong [49]; (21) Guangxi [2]; (22) Yunnan [7].
face water standards were not met.
Removal rates of NO3––N were relaChina possesses the largest aquaculture industry in the tively low, which could be attributed to the preferential
world, and treating aquaculture wastewater poses another biological uptake of the reduced form of dissolved inorchallenge (Liu and Diamond 2005). While CW systems ganic nitrogen (ammonium) within the influent. At the
hold potential for this type of treatment (Lin et al. 2005), same time, the low removal rate may imply that the total
there are concerns about their feasibility and cost effec- dissolved nitrogen concentration of the influent may have
tiveness. Moreover, the application of CW systems for exceeded the capacity of wetland treatment. Despite high
treatment of recirculating aquaculture water is largely removal efficiency, effluent concentrations for phosphorus
absent in China.
and nitrogen in Chinese CW systems are still very high,
Table 1. Performance of constructed wetlands in China
Effluent standards (mg L–1)
of China (SEPA 2007)
GB3838-2002 GB18918-2002
Class III
Class 1B
Parameter
Influent in
mg L–1 (± SD)
Effluent in
mg L–1 (± SD)
Average removal
rate (%)
NH4+–N
14.6 (12.5)
5.9 (5.4)
59.8
1
8
31
3
2.1 (0.8)
1.8 (0.8)
14.1
nd
nd
99
TN
24.1 (21.4)
13.4 (15.8)
44.3
1
20
149
TP
2.9 (1.6)
1.1 (1.0)
62.1
0.2
1
140
NO –N
Number in
dataset
BOD5
113 (109.7)
20.6 (26.1)
81.8
4
20
168
COD
234.7 (236.8)
62.5 (67.8)
73.4
20
60
187
Notes: nd = no data, since NO3––N is not set as a pollutant parameter in Chinese effluent standards. GB3838-2002 are the environmental quality standards for surface water,
while Class III applies mainly to concentrated surface water for drinking. GB18918-2002 Class I B are the discharge standards for pollutants in municipal wastewater treatment plants as reusable water in China.
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© The Ecological Society of America
D Liu et al.
Effluent (mg L–1)
200
SF
SSF
VF
160
120
Traditionally, water resource development and management in China has been financed by the central government or by regional or local governments. This “top-down”
policy demands enormous capital investment and is normally used in constructing traditional wastewater treatment plants. However, this approach causes fewer CW systems to be constructed. Furthermore, some CW systems
constructed by government bodies are poorly operated, due
to inappropriate wastewater transportation and management. The underlying reason may be that the public and
communities in general have not been adequately
informed and, consequently, no liability or requirements
exist for wastewater treatment – an example of the tragedy
of the commons, as described by Hardin (1968).
© The Ecological Society of America
3
40
1
0
40
240
80
120 160 200
TN
0
1
2
3
4
5
28
TP
24
200
20
160
16
120
12
80
8
40
4
0
0
0
Effluent (mg L–1)
NO3––N
4
2
500
Driving forces behind CW development in China
5
80
0
The role of vegetation in constructed wetlands
Macrophytes in CW systems not only absorb nutrients,
but also support microorganisms in the soil (Brix 1994).
Macrophytes frequently used in CW systems include
emergent plants (eg Phragmites australis, Typha latifolia,
and Canna indica), submerged plants (eg Ceratophyllum
demersum), floating leaved plants (eg Nymphaea tetragona
and Nymphoides peltata), and free-floating plants (eg
Eichhornia crassipes and Lemna minor). Although more
than 80 plant species have been utilized in CW systems
globally, according to the literature (Yang et al. 2005),
only half of the CW systems in China employ one or two
of these species (WebFigure 1). Species richness should be
increased to boost biodiversity and to increase nutrient
removal efficiency and ecosystem sustainability (Phillip
and Horne 2000). The new CW type, IVF–CW, reserves
more than half its area for mesic habitat, favoring the
growth of mesophytic species (eg Lolium perenne, Coix
lacryma-jobi, and Arundo donax). The number of plant
species growing in IVF–CW is higher than in other types
(Jiang et al. 2004; Yang et al. 2005), since mesophyte
species are far more numerous than hydrophyte species.
NH4+–N
0
Effluent (mg L–1)
due to high influent concentrations. Further treatment of
CW system effluent is necessary to protect water bodies
receiving this output.
Among different CW flow systems used in China, there
are few obvious differences in treatment efficiency for a
variety of parameters, with the exception that VF systems
may be more effective for NH4+–N removal and SSF systems more effective for BOD5 reduction (Figure 4).
However, SSF systems are generally thought to be more
efficient than SF systems, particularly at high hydraulic
loading rates (Shutes 2001). The newly developed IVF
systems, based mainly on VF, combine the advantages of
VF aerobic processes that stimulate nitrification with the
SSF anaerobic processes that promote denitrification. For
this reason, IVF systems are considered the most effective
CW type (Yue et al. 2003).
Constructed wetlands in China
40
80 120 160 200 240
BOD5
0
500
400
400
300
300
200
200
100
100
0
4
8 12 16 20 24 28
COD
0
0
100 200 300 400 500
–1
Influent (mg L )
0
100 200 300 400 500
Influent (mg L–1)
Figure 4. Influent and effluent concentrations of nutrients, COD,
and BOD5 in constructed wetlands in China within the dataset.
Instead of government-driven development, a new
grassroots mechanism has recently emerged in China,
reflecting the development of the economic strength of the
private sector. These private companies are capable of, and
have expressed interest in, financing and managing public
facilities, including CW systems, due to their positive
impact and benefits. Meanwhile, public curiosity in CW
technology is increasing, especially in its operational function for wastewater treatment and its contribution to
ecosystem services. Community-driven management is
thought to be more sensitive to local conditions and
knowledge (Reynolds et al. 2007) and would maximize
CW efficiency. Therefore, it is urgent to enhance the role
of local communities in policy development and to
strengthen local autonomy in governance.
Some successful CW case studies in China have emerged
that apply environmental measures to responsible human
activity. One example is the Jade Spring Ornamental Pond
in Hangzhou (Figure 5). After its water became eutrophic
in the 1980s, and in response to public complaints, the
pond’s managers chose to introduce a CW system in 2001,
to improve water quality (Panel 1). The CW system acts to
recycle the fishpond water, and has now been in operation
for over 6 years. It is estimated that the economic value of
the CW would equal 23.04 million yuan (over US$1.2
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Constructed wetlands in China
(a)
D Liu et al.
(b)
fewer CW systems than other regions
with lower GDPs. For example, in
2005, Shanghai, the most highly
developed region in China, generated
2.2 billion tons of wastewater, with a
treatment rate of 70.2% (Shanghai
Statistical Bulletin 2005). It has been
suggested that the surge in economic
development in this region has
(c)
(d)
resulted in the use of a large amount of
fossil-fuel energy and other resources
in wastewater treatment, due to an
emphasis on short-term solutions. The
potential for CW system usage in the
Shanghai region is enormous. On the
other hand, the number of CW systems has increased along with the
rapid economic development experiFigur e 5. Constructed wetland for treating fishpond water in Jade Spring Pond in enced in Guangdong and Zhejiang
Hangzhou, China. Photos of (a) Jade Spring Pond with clean water; (b) species of provinces.
plants in the CW; (c) polluted water with an unpleasant appearance in the pond; and
Although only a few CW systems
(d) black carp (Mylopharyngodon piceus) in pond after applying the CW.
have been built in provinces with low
GDPs, those regions would also benefit
million) within a 20-year period (Yang et al. 2008).
from the implementation of CW systems, and plans for their
Both the top-down and grassroots mechanisms relate to construction should be included in the development plans
the economic and social development of a region; gener- for these areas. One current example is Tibet, where there is
ally speaking, the application of this new ecological tech- great potential for increased wastewater discharge due to the
nology tends to be developed simultaneously with eco- completion of the Qinghai–Tibet Railway (Peng et al. 2007).
nomic growth (Figure 6). While the relationship between
GDP and the number of CW systems in China is, for the Future concerns and challenges
most part, positive – that is, as GDP increases, so too does
the number of CW systems constructed , this relationship There is growing recognition in China that CW systems
does not always hold. Some regions with high GDPs have offer a viable alternative, or at least a supplementary technology, for wastewater treatment.
Panel 1. Case study of CW: harmony between policy makers and the public
Although challenges still exist, there
are encouraging signs. Most provinces
Jade Spring Pond has been a famous tourist attraction in the historical city of Hangzhou,
in China have been implementing
in southeastern China, for over a thousand years. The pond, with a total water volume of
CW systems in conjunction with
600 tons, has been stocked with black carp (Mylopharyngodon piceus) with a total biomass
of over 5000 kg (Figure 5a). As tourism has increased greatly since the 1980s, the pond
increases in economic development
has become polluted (Figure 5b).To improve water quality, the eutrophic water was withover the past two decades; research on
drawn and replaced with groundwater.This practice was costly, as high as 160 000 yuan
the technology is also growing. The
(~ US$23 000) per year, including the charge for groundwater consumption. Despite this
quantity and scale of CW systems are,
effort, local people and tourists complained about the pollution, and the pond was closed
2
however, still few and small in contrast
to the public in 1999. A CW system with a total area of 600 m was built in 2001, after
to the huge quantity of wastewater
comparing alternative technologies, considering both the construction and operation
produced in China. Can CW technolcosts, as well as the benefit of recycled water and ecological services. Since then, concentrations of TN,TP, COD, and BOD5 in the effluent of the CW have been lower than in
ogy be used in concert with other
the groundwater (Yue et al. 2003), and the effluent was recycled back into the pond.
treatment methods in the near future,
After operating for a 1-year period, the springs that had disappeared for more than 20
to accommodate accelerating wasteyears were stocked with fish and the water was purified (Figure 5c). Over 86 plant
water production? Several suggestions
species were planted in the CW (Yang et al. 2005; Figure 5d) including one endangered
are offered below.
species; animals such as snakes and birds were also added. Net primary productivity
–2
–1
Policy makers in China should
(NPP) within the CW reached 1.8 kg m yr , indicating its high carbon sequestration
emphasize the fact that any new
ability.An estimate of the economic value of the ecosystem services provided by the CW
development plan must take into consuggested a total value of 23 million yuan within a 20-year period (Yang et al. 2008).The
operation of the CW system is profitable due to the accord between both the top-down
sideration the capacity of local water
and grassroots mechanisms. It integrates local management and policy experience with
resources. China is presently in a transcience-based knowledge, achieving a win–win outcome that benefits all, as described by
sitional period, moving from a high
Reynolds et al. (2007).
resource consumption and low-effiwww.fr ontiersinecology.or g
© The Ecological Society of America
D Liu et al.
© The Ecological Society of America
60
Provincial quantity of CWs in China
ciency economic development pattern to a low resource
cost and high-efficiency economic pattern (Fleisher and
Chen 1997). It is particularly important to improve wateruse efficiency in various regions of China to sustain its
economic growth. Long-term cost–benefit analyses should
be performed when considering not only construction
costs, but also the operation of any new technologies for
wastewater treatment that would make CW technology a
priority choice.
Wastewater and stormwater share the same discharge systems in most cities in China. Although pollutant concentrations (TN, TP, and organic matter) are lower in
stormwater than in wastewater, stormwater requires a much
larger treatment area due to the high volume of runoff,
especially during rainy seasons. However, since wastewater
treatment plants are inefficient in treating water that contains low concentrations of contaminants, CW systems
could be used to supplement traditional stormwater treatment systems. To further reduce pollutant levels in treated
wastewater, more CW systems should be constructed downstream of treatment plants to meet Chinese standards for
reuse and surface-water quality.
Despite their many advantages, the limitations of CW
technology must also be evaluated. When treating high concentrations of wastewater, large areas of land are required.
Unfortunately, the available land allotted to CW systems is
typically restricted to flat areas, which are in extremely limited supply in China. Trade-offs among various CW types,
land resources, funding limitations, and treatment efficiency
should be considered before decisions are made.
There is still an enormous gap in the transfer of knowledge about the value of CW systems for wastewater treatment in China, especially as the principles of CW technology are already well known in most developed countries. A
much greater exchange of information from wastewater
experts in developed countries to their counterparts in
developing countries is needed. A successful example of
such an exchange is the IVF–CW, which was introduced to
China from Europe beginning in 1996, and which has
since become the most effective type of CW in China;
IVF–CWs require smaller land areas and attain the highest
rates of efficiency of all types of CWs in use in China.
Training requirements for the sustainable development
of CW technology have been highlighted by Denny (1997).
Long-term efficiency and sustainability of CW systems are
dependent on an integrated understanding of their biological, chemical, and hydrological processes. In China, trained
managers and technicians are rare, which is one of the many
reasons why improper operation of CW systems commonly
occurs shortly after construction. Thus, there is a critical
need for research and training to reinforce the sustainable
operation of CW’s.
The Chinese government has provided the public with
environmental knowledge through the country’s network of
environmental education organizations. In addition, more
than 40 environmental non-governmental organizations are
now active in a variety of environmental protection activi-
Constructed wetlands in China
50
X
r2 = 0.2054
P < 0.001, n = 22
40
30
20
+
10
0
0
10
20
30
40
50
60
Per capita GDP (thousands of ynan RMB)
Figure 6. The relationship between GDP and the number of CW
systems per region. Data on provincial GDP in China is provided
by the NBS (2005), at which time 1 USD ($) = 8.2 yuan RMB.
Each symbol represents the quantities of CW systems in respective
provinces. Symbols within circles indicate the uncommon data
points, Zhejiang (), Guangdong (x) and Shanghai (+), which
are not included in the regression.
ties in China (Morse et al. 2007). There are, however, still
no national or regional professional associations championing CW knowledge and education. Training for managers
and technicians of these units should be a major priority.
Conclusions
The Chinese government, the research community, and the
public in general have realized that, for water management to
become sustainable, CW technology – an effective, low-cost
wastewater treatment strategy – must be deployed. Although
the number of CW systems in operation is still relatively
small, their development has accelerated in recent years. In
addition, CW systems are not only used for wastewater treatment, but also for other ecosystem services, especially in the
preservation of biodiversity. However, land availability, institutional limitations, and public education will be ongoing
challenges for the development of CW technology in China.
Although economic and social concerns related to the effective use of CW technology still exist, the high performance
and environmental benefits make it increasingly attractive
and practical for use in the near future.
Acknowledgements
This study was supported by the National Natural
Science Foundation of China (No 30370146), the YC
Tang Disciplinary Development Fund, and the Canada
Research Chair Program for C Peng. The authors thank B
Doonan for editorial improvements.
www.frontiersinecology.or g
Constructed wetlands in China
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