Tianjin is an important coastal industrial city. The municipal wastewater plants accept a certain amount of industrial wastewater, and as a consequence, the quality and quantity of the raw wastewater are unstable. Further optimisation of the operation and management of the wastewater plants are needed to improve the quality of the produced secondary effluents.
The main problems in water quality of secondary effluents, used as the source water for water reclamation plants, are the high salinity, pathogenic microorganisms, colour, odour and toxic micropollutants that may cause ecological and health risks.
For this reason, the membrane technology was selected to improve recycled water quality, as well as the ozonation, which helps to remove colour and odour in addition to disinfection.
Lifetime and stability of membrane operation
The combination of micro- or ultrafiltration membranes with reverse osmosis is selected as the best available technology enabling to ensure the stability of the reclaimed water quality. Several pre-treatment processes (chlorination, coagulation/sedimentation and pre-filtration) are used to reduce membrane fouling. To improve the reliability of operation, equipment operation management systems and technical operation manuals were established. Since 2002, the membrane systems have steadily been used for nearly a decade, which is far beyond the design lifetime of 5 years.
Application of ozone in wastewater reclamation processes
The purpose of ozonation is mainly to decolorize, eliminate odour and disinfect the recycled water. After several pilot studies to compare various technologies, the Ji Zhuangzi wastewater reclamation project was the first in China to implement ozone technology as a core process for wastewater reclamation. Currently, ozone technology has been widely applied to other water reclamation plants in Tianjin, as well as to some water reclamation projects in Beijing.
6.3 WATER REUSE APPLICATIONS
The repartition of the volumes of recycled water used for the major water reuse applications in the central city of Tianjin is shown in Table 6.4.
In 2007, 20% of the recycled water was used for industrial uses, 15% for landscaping (scenic environment) and 65% for urban miscellaneous uses. In 2010 the industrial water reuse reached nearly 69%, while landscape water went down to 10%. According to the city planning, the recycled water demand of the city will reach 797 Mm3in 2020, from which 52%
Table 6.4 Structure of reclaimed water reuse in Tianjin (2010 and 2020).
Year
2010 68.5 18.9 (toilet flushing 8.9%) 10.2 2.4
2020 28.0 14.0 52.0 6.0
RoleofWaterReuseforTianjin
will be used for scenic environment (Figure 6.3a), 28% for industrial use (Figure 6.3c), 10% for municipal miscellaneous purposes, 4% for residential miscellaneous purposes (Figure 6.3b) and 6% for other purposes.
The first end-users of the first wastewater reclamation demonstration project of Ji Zhuangzi, launched in 2002, were the Tianjin Meijiang ecological living community and the surrounding residential housing. The main uses of the recycled water were toilet flushing, landscape irrigation and water ponds. These non-potable applications were well accepted and approved by the local residents because of the good and stable water quality and secure water supply. Since the recycled water pipeline network of the Ji Zhuangzi water reclamation plant was built and extended, more communities and parks have started to use reclaimed water for landscaping, green space irrigation and street cleaning. Because the community landscapes and irrigation systems require large amounts of water, the utilization of reclaimed water enabled a significant reduction in the cost of landscape irrigation, as well as a reduction in water pollution; increase in water use efficiency, and finally accomplishment of the goal of potable water saving.
In 2008, the four artificial lakes surrounding one of the major landscape projects of the Tianjin Olympic Stadium, the European Icicle and the Water Drop, a large fountain project, and the nearby green spaces of these projects, have all been using recycled water as the main source of water. Using“water”as the design theme has reflected the purpose of the 2008 Olympic Games– “green Olympics, technical Olympics, and humanitarian Olympics,”with the Water Drop representing
“the source of life”.
The Tianjin Road is an“ecological landscape road”that represents the ecological and environmental protection ideologies.
It is the major road that connects the central city of Tianjin and the new coastal city. The green spaces on the side and at the center buffer zone along the road are all using recycled water as water source.
In 2009, recycled water was applied to the Chen Tang Zhuang thermal power plant and the Dong Bei Jiao thermal power plant as circulating cooling water, which marked the end of the first stage of recycled water development: the extension of water reuse to industrial end-users.
In September 2010, the Annual Meeting of Tianjin Summer Davos Forum for New Leaders was hosted in the Meijiang Convention Center. Fifteen-hundred representatives from over 90 countries and regions gave the world an impressive meeting of ideas and economics. In order to express our nation’s environmental protection ideology and to achieve sustainable social development, recycled water was used as the water source for miscellaneous purposes, such as green space irrigation and toilet flushing at the convention center, providing thus a secure water source and ecological friendly environment for the convention.
Evolution of the volume of supplied recycled water
Tianjin’s water reclamation has experienced 10 years of developments, with a steady increase in recycled water volumes (Table 6.5). Since the end of 2009, the major proportion of recycled water usage was not for urban miscellaneous purposes, but for industrial cooling which has accounted for over 50% of the total recycled water volume. The most important increase in water reuse was observed in 2010 (+333% compared to 2009).
Figure 6.3 Illustrations of water reuse applications in Tianjin: a) reuse for scenic environment, b) toilet flushing, c) industrial use for heating and d) cooling water.
Table 6.5 The amount of reclaimed water in Tianjin urban area (2006–2010).
Year 2006 2007 2008 2009 2010 2011
Recycled water volume, m3 1,809,000 3,280,000 3,526,000 3,720,000 12,373,000 14,270,000
As percentage of treated wastewater (%) 1.40 2.54 2.73 2.88 9.85 11.06
MilestonesinWaterReuse:TheBestSuccessStories88
Relations and contracts with end-users
To satisfy consumer demands, the Water Co. formed a management system including water supply planning, pipeline network construction, market research, client development, water supply contract signing and specific client services. The water supply contracts play the most important part in the water supply relationships. Currently, the recycled water supply contracts can be divided into residential contracts, industrial (thermal power plants and heating) contracts, and other contracts including city administration contracts. The residential contract is the only one signed with individual residents through a third party (property companies), while other contracts are signed directly by the client and the water company. The signing process is completed during the recycled water connection process.
6.4 ECONOMICS OF WATER REUSE
Project funding and costs
The Water Co. is responsible for the construction of the Tianjin central city water reclamation projects. The funding mainly comes from the Water Co. funding and loans, with some government investment supports.
For example, the total investment for building a membrane+ozone+RO water reclamation plant with 50,000 m3/d water production capacity is approximately 110–125 million Yuan (€14.0–15.9 million): 26% for construction expenses, 51% for infrastructure investments and approximately 23% for other expenses. The cost of construction is approximately 2200– 2500 Yuan/m3(279–317€/m3).
The specific cost of recycled water is 2.5–2.6 Yuan/m3(0.32–0.33€/m3), including energy consumption cost of 0.55–0.65 Yuan/m3(0.07–0.08€/m3) and the chemical consumption costs of 0.4–0.8 Yuan/m3(0.05–0.10€/m3).
Pricing strategy of recycled water
The city government established the cost of recycled water from a promotional point of view. In 2003, the price department of Tianjin approved the sales price of recycled water as shown in Table 6.6.
The sales price was adjusted in April 2009 and the recycled water rates were categorized depending on the purpose of use, which can be divided into four categories including residential water, power plant water, special industry and industrial water, administrational water and water for business services (Table 6.7). Currently, the Tianjin government is attempting to lower the cost of recycled water by tax promotions and subsidy policies, along with increasing the price of potable water from traditional water sources in order to make reclaimed water more competitive.
Table 6.6 Recycled water rates in 2003.
Water for schools, government, hospitals and nursery schools 0.15 (1.2) 0.56 (4.4)
Process water, cooling water in industry 0.17 (1.3) 0.59 (4.6)
Reclaimed water for municipal reuse, public building, gardens, scenic environment, road spraying, etc.
0.19 (1.5) 0.59 (4.6)
Reclaimed water for vehicle cleaning and construction 0.23 (1.8) 2.29 (18.0)
Table 6.7 Recycled water rates in 2009.
Reclaimed water used in heat-engine plant 0.19 (1.5) 0.85 (6.7)
Reclaimed water used in industry, administration services, service industry 0.38 (3.0) 0.85 (6.7) Reclaimed water used in special trade (vehicle cleaning, temporary use) 0.51 (4.0) 2.69 (21.1)
RoleofWaterReuseforTianjin
Benefits of water recycling
The economic analysis shows that water recycling does not have high economic benefits for reclaimed water suppliers.
However, there are certain benefits to industrial clients such as owners of power plants, heating stations, etc. since they are using cheaper recycled water. In addition, for the city of Tianjin as a whole, water recycling reduces the cost and avoids new expenses for water conveyance and seawater desalination, providing thus financial benefits to the city.
In addition, water reclamation has very high non-economic benefits. Water reuse not only relieves water scarcity, but also reduces pollution and improves the water environment. In particular, the reduction of the amount of water conveyance has high ecological impacts upstream. The implementation of wastewater reclamation also promotes more stringent requirements for plant’s operation and enhances resident consciousness toward environmental protection and water conservation.
6.5 HUMAN DIMENSION OF WATER REUSE
Public education and communication strategies
To educate the public, the Water Co. launched a series of activities to improve communication with clients, including periodic client meetings. The Water Co. is now becoming the public education foundation for environmental protection.
To improve the communication in water recycling, the company has built a work service hotline and the“12319”Tianjin city development hotline to provide customers with continuous services 24 hours a day, 365 days a year. The service provides information on insurance, emergencies, reports, complaints, suggestions, complements, consulting, etc., which also represents an efficient tool for complaint monitoring.