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A Systematic View Is Key: The Successful Case of Suzhou Creek Rehabilitation Zuxin Xu and Zhenliang Liao* Institute of Water Environment Rehabilitation, College of Environmental Sciences and Engineering, Tongji University, Shanghai, China, 200092 overflow of the combined sewage pumping stations at its banks was discharged into the river during rainstorms; the sewage plume was stagnated in the downtown reaches because of the tide effect of Huangpu River; and waters in tributaries became “dead waters” because the gates of tributaries were always locked except during the flooding period.2 Several efforts were made to eliminate Suzhou Creek’s pollution before 1998, but little effect was achieved, and it seemed the pollution became more serious. In 1998, the Suzhou Creek Rehabilitation Project (SCRP) was launched, which was the No. 1 project in the Shanghai municipal government’s water environmental improvement plan. The rehabilitation objectives included (1) by 2000, eliminating the color distinction in the river mouth, and (2) by 2010, recovering the river ecosystem basically. The total investment surpassed 14 billion yuan RMB, of which 8.96 billion yuan RMB (1.41 billion US dollar) was used in improving water quality. The principle engineering measures included wastewater interception and treatment, low flow augmentation, reaeration, sediment dredging, pump stations and gate construction/reconstruction, and flood walls reconstruction, among others. Systems analysis methodology was employed to n the last three decades, the urbanization of mainland China optimize the project based on mathematical models.2 has increased, with the percentage of population in cities After over 10 years of such efforts, the objectives of SCRP increasing from less than 20% (in 1982) to more than 50% (in were achieved. Water quality of Suzhou Creek met the water 2012), that is, 700 million people.1 Simultaneously, the standard of recreation use on an annual average basis. The environmental issues in urban areas cause increasing concern, ecosystem of Suzhou Creek restored gradually. Biological and water environmental issue is central among them. assessment showed species number and diversity of aquatic Campaigns to unfold water environmental rehabilitation in organisms (benthos) had increased remarkably.2,3 cities are ongoing across the country. Unfortunately, it seems In an urban water environmental rehabilitation project, that most of these cites do not achieve the expected outcomes upstream and downstream, mainstream and tributaries, water after huge investments. Scientific theories and methodologies and land, and all the measures can interact with each other, thus are urgently demanded to guide urban water environmental forming an integrated whole. It has typical characteristics of a rehabilitation practices in China. Suzhou Creek Rehabilitation “system”.4 As a complex systems engineering issue, a systemic in Shanghai is regarded as a successful case and is paid extensive view is required. For SCRP, the system was SCRP itself, and attention both at home and abroad. the problem to be solved was the pollution issue of Suzhou Originating from Taihu Lake and pouring into Huangpu Creek. The system included two stages’ objectives: by 2000 and by 2010, respectively. Measures were proposed correspondRiver, Suzhou Creek is about 125 km long, of which about 53.1 ingly, and they were variables of the system. Investment was km passes through the metropolis (23.8 km in city region) regarded as a constraint. If such a huge and important project (Figure 1). With an average flux of 6.0 m3/s and width of 70− was not handled properly and could not meet its objectives, the 80 m at high tide, the flow is tidal. Suzhou Creek is an waste would be tremendous. important historical surface water body in Shanghai. Chinese SCRP can be regarded as a successful case for using systems modern industrial civilization originated at its banks. Suzhou engineering theory and methodology. At the beginning, a Creek was once a clean river but with industrialization and urbanization, Suzhou Creek was severely polluted. Before 1999, the river water was always anaerobic, and the “blackness and Received: September 23, 2013 stink” phenomena occurred all year round. The main causes Revised: October 5, 2013 were as follows: A large amount of sewage was discharged into Accepted: October 11, 2013 Published: October 24, 2013 Suzhou Creek and its tributaries without any treatment; the
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© 2013 American Chemical Society
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Environmental Science & Technology
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Figure 1. Suzhou Creek2,3,5 (The photos were taken in the same place, that is, the confluence point with Huangpu River).
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thorough investigation was made to find out the reasons of pollution and thus to characterize the problem. On this basis, the system objectives were demonstrated and set by stages considering investment’s constraint. Measures were proposed aiming at pollution reasons and objectives. Models were developed to simulate and evaluate effects of the measures. Scenario analyses were performed. The project was optimized in terms of both environmental effectiveness and economic efficiency. Decisions were made after cyclic demonstration rounds, and feedbacks were collected and corrections were made during the project’s implementation continuously.5 Concretely, aiming at the fundamental causes of the pollution, that is, Suzhou Creek’s rehabilitation targeted interception and treatment of pollution, and improved the interception ratio significantly. Considering the disadvantageous bidirectional hydrodynamic condition, we proposed low flow augmentation as an important auxiliary measure. This measure changed the hydrodynamic condition substantially and promptly improved the water quality. With respect to the “black and stink” phenomena which happened in localized and short-term instances, an aeration ship was built and it could quickly improve dissolved oxygen concentration in local sections. We suggested postponing sediment dredging to the last stage because water and sediment actually interacted with each other, and if water quality did not improve, it was useless to get rid of sediment. Based on these, we optimized the initial scheme, strengthened and postponed some measures. By implementing the modified scheme, we improved effects and saved investment simultaneously. We hope the story of Suzhou Creek Rehabilitation can be shared by more cities. We think the main reason for the failure of many urban water environmental rehabilitation projects is the lack of sound systems analysis and integrated engineering plan, deferring instead to subjective/experiential decisions of the leader. The last point: we realize that urban water environmental rehabilitation is a kind of project to repay historical debt, that is, pollution first, treatment later. The investment is huge. If we want to avoid doing it, then prevention first and protection preferential policy has to be implemented.
AUTHOR INFORMATION
Corresponding Author
*Phone: +86(0)21-65981650; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Ru, X.; Lu, X. Y.; Li, P. L. Blue Book of China’s Society 2012: Society of China Analysis and Forecast (2012); Beijing: Social Sciences Academic Press (China), 2011 (in Chinese) (2) Xu, Z. X.; Liao, Z. L. Optimization of Suzhou Creek Rehabilitation Project Stage I: Based on water quality model. Environ. Eng. Sci. 2006, 23 (2), 253−262. (3) Liao, Z. L.; Xu, Z. X. Impacts of upstream input and local pollution loads on the water quality of Suzhou Creek based on mathematical models. Environ. Eng. Sci. 2008, 25 (2), 507−518. (4) Wikipedia. System. http://en.wikipedia.org/wiki/System (accessed September 20, 2013). (5) Liao, Z. L.; Xu, Z. X.; Wang, D. B.; Lu, S. Q.; Hannam, P. M. River environmental decision support system development for Suzhou Creek in Shanghai. J. Environ. Manage. 2011, 92 (9), 2211−2221.
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