Research on Recycle and Utilization of Reused Water in Shenzhen

Biyu Lei

Institute of Environment, Zhejiang University of Technology, Hangzhou, Zhejiang, China

Keywords: Reused Water, Urban Water, Conservancy.

Abstract: China has put great effort into alleviating the severe water shortage. Among all the methods, reused water is

the most effective and likely to be promoted. This paper gathers data on urban water use, existing domestic

sewage treatment, the policy being implemented, and the domestic sewage recycling project in Shenzhen.

Through relevant data and surveys, this paper analyses the feasibility of the reused water industry and the

barriers it faces. The research has found that reused water can effectively relieve water use pressure, what’s

more, it also pointed out people’s low acceptance, immature market systems, and technology are the problems

that need to be solved. Finally, this paper points out that the project of reused water should cooperate with the

industrial structure and people’s willingness of the city. Besides, in order to make sure the reused water project

is steady in the long term, more relevant laws and regulatory measures should also be taken. As an

experimental unit, Shenzhen has taken the lead in this country-scale project, so the experiences will contribute

a lot to other cities’ projects. This research can provide a reference for the reused water projects construction.

1 INTRODUCTION

China is a country with a severe shortage of water

resources, per capita water resources is only a quarter

of the world standard. Typically, in big cities, like

Shenzhen, water management faces a more serious

situation. Shenzhen, a first-tier city in China, has an

area of 1997 square kilometers and a population of

8806 per square kilometer. As a result of insufficient

water storage capacity, over 80% of water use relies

on remote flow. The construction land contains a large

amount of population, and the industries are mostly

high-end manufacturing, which requires huge water

consumption. Therefore, seeking an effective way to

use water has become one of the most urgent.

Reused water, as a resultful method to manage

water resources, has been proven to improve the

efficiency of urban water use. Reuse water has rich

experience in many countries, such as Singapore,

Israel, and America. Singapore has a high-density of

population and a shortage of fresh water. Since the

‘90s, they have put great effort into deep treatment of

domestic sewage, and blending the reuse water in tap

water. Used water is collected and purified by

membrane and ultraviolet rays to become reused

water (Teng, 2023). According to data, reused water

https://orcid.org/0009-0009-3394-4810

accounts for 30% of the total water supply. Five water

treatment plants produce 227.3 thousand m³ reused

water per day. Israel is located in western Asia, where

the average annual rainfall is below 200mm. Since

2000, Israel has invested 750 million dollars in

sewage treatment. The proportion of water cycling

has ranked high in the world. Thanks to the advanced

water purification equipment, 90% of sewage in

Israel can become reused water, which will be used in

desert agriculture. In America, water distribution is

unequal. Some states, such as California, Texas,

Florida, and Arizona, still lack water resources and

overly exploit underground water. In this respect, not

only does America have a detailed plan, but also has

a complete law and regulatory system. Take Florida

as an example, it has concentrated water use. Based

on that, the state uses a double pipes water supply

system on a large scale, selling the reuse water to golf

courses, rain gardens, and so on with a 40% price of

tap water. The method wins considerable benefits for

both economy and society. In conclusion, through

corresponding government support, process

management, and terminal supervision, the reused

water industry can be copied into different regions

with different climates, environments, and cultures.

Shortage of water resources is a barrier to sustainable

Lei, B.

Research on Recycle and Utilization of Reused Water in Shenzhen.

DOI: 10.5220/0013268100004558

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 1st International Conference on Modern Logistics and Supply Chain Management (MLSCM 2024), pages 197-201

ISBN: 978-989-758-738-2

197

development in China, the reuse of water can be an

effective method to ease the contradiction between

supply and demand. Those international experiences

are positive references to developing the reused water

industry.

Based on existing research and data, the paper is

aimed at exploring the feasibility of domestic sewage

collection, purification, and reuse, and inferring the

premises and problems.

2 EXPERIENCE IN REUSED

WATER DEVELOPMENT

Reused water is a kind of water that meets certain

water quality standards through proper treatment, and

reaches the requirement of recycling (Zhang et al.,

2024). In general, reused water has three practical

features. Firstly, reused water comes from urban

sewage, so in theory, the source of reused water is

stable (Yang et al., 2024). Reused water is convenient,

as a result of receiving little seasonal and

geographical influence. From a societal point of view,

reused water can promote sustainable development,

which brings huge economic and ecological benefits.

The basis of the reused water industry is sewage

treatment, so it is important to know exactly how the

water is processed. The existing sewage treatment

includes three steps. The primary treatment, also

named preconditioning, is mostly physical treatment.

The grills, grit basins, and settling basins will remove

the solid contaminants. The secondary treatment is

mostly biochemical treatment, aiming at eliminating

organic pollutants in water. So far, the most advanced

treatments are the activated sludge process and the

biofilm process. The tertiary treatment is also named

advanced treatment. It mainly removes nitrogen,

phosphorus, and organic pollutants that are hard to

remove in the last treatment. Once the water has been

advanced treated, it is mostly used for reusing.

So far, the recycling of urban sewage is still in

exploration in China. Guiding Opinions on

Promoting the Utilization of Sewage Resources,

released in January 2021, provides guides for

unconventional water resources including reuse water.

During the exploration, the pilot project that set up

experimental units in 13 cities provided valuable

experience. Among them, Shenzhen has used 335

million m³ of reuse water in the first half of 2023, with

a utilization rate of 34% (Fan & Li, 2024). The

experience of Shenzhen has shown the update of

sewage treatment is beneficial to effectively alleviate

the contradiction between the supply and demand of

regional water resources and promote the application

of water economical application.

3 EXISTING SEWAGE WATER

PROJECT

Urban sewage can be classified into domestic sewage,

industrial sewage, and incipient rainwater. This paper

mainly discusses the reuse of domestic sewage.

3.1 Features of Domestic Sewage and

Frequently Used Sewage Water

Treatment

Domestic sewage is mainly from residential buildings

and public buildings. Domestic sewage has three

features. First of all, its quantity and quality changes

with the seasons. Secondly, in terms of composition,

it hardly contains toxic and harmful substances. And

the last, it can be easily processed by biochemical

methods. However, bacteria and odor of the sewage

can spread the disease easily, and untreated emissions

may cause serious environmental issues. That is why

sewage treatment is an important research project.

Advanced treatment is an indispensable part of

reused water production. The methods that are

commonly used can be classified as physical,

chemical, and biological methods. One of the

industrialized water treatment methods is adsorption,

using adsorption resin to remove organic pollutants.

It can control the SS under 5mg/L and reduce the

chroma to 1/20 of the sewage (Huang et al., 2024).

However, due to the material capacity, the speed of

treatment is slower than other methods, limiting its

development. Ozone catalytic oxidation is the most

advanced chemical method, which is useful when

there are complex organic pollutants. However, it is

not universally used due to the uncomprehending

produce condition and the limited technology.

Biological methods include the activated sludge

method, ecological revetment, solar restoration, and

constructed wetlands. Among them, the constructed

wetland is one of the most promising methods

because of its high penetration and low emission. The

constructed wetland has low cost and less secondary

pollution. 60 acres of wetland of reeds and wild rice

stems in Linfen County can degrade 404.8kg BOD

per day (Gao, 2024). Constructed wetland is the most

promising method if seasonal and regional constraints

can be solved. To sum up, these treatments have some

barriers that limit their development. Technology

needs to be improved to become the foundation of the

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reused water industry.

3.2 Present Situation of Reused Water

Treatment in Shenzhen

According to the data released in 2022, Domestic

sewage in Shenzhen is 844 million m³, accounting for

38.9% of total sewage. Shenzhen does not have any

technical reused water plant, but it has 43 water

purification plants that produce 5.84 million m³

reused water per day, which meets the demand of

water quality standards (Cai et al., 2024).

Not only Shenzhen but also most big cities in

China have similar problems in developing the reused

water industry. Firstly, the proportion of reused water

use is low. And, the supply target users is simplex.

The reasons for this situation are obvious. The higher

cost, immature technology, insufficient investment,

and the low accept rate of users. To deal with these

barriers, the government and the market took different

measures. Governments made relevant laws and set

experimental units in different provinces, which

reaped great experience in Shenzhen.

4 REUSE THE PROCESSED

WAT ER

4.1 Analysis of Concentrated Use of

Reused Water in Shenzhen

Relative agencies conducted a detailed survey of 83

potential users, including municipal and industry use.

The survey made the regions and industries that need

reused water more clear. The result revealed that the

potential reused water will likely replace

conventional water resources for 100 million m³ in

2025, and the consumption of reused water will reach

85-106 billion m³in 2030 (Liu et al., 2024). In

Shenzhen, reused water was mostly industry cooling

water, urban miscellaneous water, and river recharge.

In the new reused water project, three phases

target different users. In the first phase (to 2025), the

reused water will be used for industry cooling water

and municipal miscellaneous water, such as road

flushing and greenbelt watering. In the second phase

(2025-2030), the reused water will be also used for

central cooling. In the last phase (2030-2035), it will

be gradually used in electronic equipment

manufacturing, communication, the computer

industry, and other high-quality users. These are the

most economical uses for reused water in existing

technology, and they are more acceptable to people

than delivering the reused water directly to the urban

water supply pipes.

4.2 Reused Water Programme

As one of the first experimental cities, Shenzhen

made great achievements in the reused water industry.

Moreover, Shenzhen set 4 experiment units in the city

to detail the goal, providing valuable experiences for

reused water development in the big city. There are

Guangming District, Pingshan High-tech zone,

Longhua District Jiulong mount region, and

Longgang District Henggang region. As built-up

areas, these regions have complete water supply

projects and balanced population and industry density,

which provides a good condition for building a water

recycling system. These regions have 4 reasons why

they were chosen to be the experiment units: big

demand for reused water, concentrated object, strong

using willingness, and high feasibility of facility

construction. Reused water systems were first built in

these regions to explore constructed experiences.

These experiences will be used for building water

recycling systems in other regions and other cities.

Shenzhen is a template for efficient and sustainable

development of domestic sewage reuse.

In addition, the government set five directions to

explore the decentralized utilization of reused water.

Combined utilization of reused water and rainwater,

distributed reused water circulation, regional water

recycling without sewage discharge, reused water

utilization in high-density development zones, and

diverse reused water source construction and

utilization. Aiming to build high-efficiency and low-

discharge water recycling systems, incentive

measures are also taken to fuel policy implementation.

5 POSITIVE CONDITIONS AND

PROBLEMS OF REUSED

WATER DEVELOPMENT IN

SHENZHEN

Setting Shenzhen as one of the first cities that built a

comprehensive reused water system has five aspects

of the reasons. First of all, Shenzhen, an economic

special area, is where most policies are preferred.

Governments are likely to set Shenzhen as an

experimental zone because of its flexibility and

containment. Secondly, the economy is booming. The

market plays an important role in reused water.

Beijing, also a first-tier city, attracted private

company investment to promote the government

Research on Recycle and Utilization of Reused Water in Shenzhen

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project. The mainstream of reused water facilities in

Shenzhen is business format franchising, the

government invests to build most infrastructure and

private companies account for a small part (Zhang,

2023). Thirdly, infrastructure construction is easier

than in other cities with a longer history. Shenzhen is

a young and dynamic city, the space for creation is

abundant and the technology it applies is mostly first-

tier, and it is more adjustable and flexible. Moreover,

Shenzhen released policies and welfare for scientific

and technological talents. The last is high social

inclusion. According to the data in August 2023, the

average age of Shenzhen citizens is 32.02, which is

the lowest in first-tier cities. Creation has been a

fashion in the city since the Reform and Opening Up.

So, people have a higher acceptability of new water

resources, which makes policy implementation easier.

However, there are problems in promoting reused

water recycling. Four existing problems limit the

development of reused water. Firstly, the relative laws

and the supervision systems are inadequate. Secondly,

the price and the ROI do not have an acknowledged

standard. Thirdly, the immature technology restricts

the speed and quality of reused water production. And

last, many people do not accept reused water because

of the worry of water quality. Subsequent projects

should emphasize these barriers.

To deal with these problems, governments have

taken corresponding measures. In policy, the

Shenzhen reused water layout project (2008-2020)

has expired, as the requirements have changed. So,

the new Shenzhen reused water layout project (2021-

2035) is in progress. In the market, exploration of a

combination of government-led and market-based

models is necessary for the operation of reused water.

Referring to the pricing principle of tap water, the

price of reused water should be set by the government

(Hu & Yang, 2021). However, the key to breaking the

barriers is letting people accept reused water.

6 OUTLOOK

Over decades, Shenzhen has long been constrained by

severe water shortage, which has made it necessary to

explore effective ways to promote reused water. For

the call from the central government, Shenzhen will

be the model for the future establishment of reused

water systems in different cities, which means it

shoulders great responsibility and lack of experience.

A lot of work has been invested in policies, standards,

technology, infrastructure, and markets. Undoubtedly,

a lot of problems need to be summarized. In the future,

Shenzhen will keep developing high-tech industries

including chips and precision instruments, which

require a lot of water. However, the domestic sewage

system still has multiple barriers before

industrialization. One of the most important factors is

the will of people. It is not only in consideration of

the safety but also the water rate. So the publicity of

the process of water treatment and the formulation of

supervise laws are necessary. Meanwhile, it is

essential to reduce the water rate by researching

reused water technology. The reused water industry is

the foundation of Shenzhen’s economy in the future,

so the project is of great significance. What’s more,

the project of reused water in Shenzhen is very useful

for other cities, especially coastal cities with

developed economies.

7 CONCLUSION

Through research, this paper summarizes the situation

of reused water in Shenzhen and finds the prospect of

reused water in Shenzhen is promising. In detail, this

paper finds that the most practical method is

constructing wetlands at present, and the processed

water can be mostly used for industrial cooling water,

urban miscellaneous water, and river recharge. To

ensure the normal operation of the reused water

system, the government has put forward many related

policies, such as reducing water costs and attracting

investment. However, this paper also finds several

problems to solve. For example, supervision systems

and pricing standards are not mature yet. What’s more,

the safety of reused water causes a low willingness of

people to use it. As a result, reused water lacks market

vitality and is difficult to expand. Although the

government has put great effort deal with these

problems, it will still take a long time to solve the

problem of water shortage. So far, the study still has

shortcomings. Firstly, the judgment of reused water

quality can be more detailed. Municipal departments

can classify water use according to its quality to save

the cost of treatment. Secondly, more surveys can be

conducted. The government should know which

regions and industries need more reused water. Based

on that, sewage treatment plants, pipes, and other

facilities can be set up in proper places. Finally,

industrial structure and funding are very important for

a city that is going to construct reused water systems.

Before construction, research and surveys are

necessary. This paper’s investigation can contribute

to future water infrastructure, and provide

experiences for water system construction in other

cities.

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REFERENCES

Cai, Z., Luo, Y., Liu, C., et al. 2024. Exploration of

renewable water resource allocation in Shenzhen high-

density built-up areas. China Water Resources, (7), 67-

72.

Fan, L., Li, J. 2024. Summary of experiences and

suggestions on the construction of pilot projects for the

utilization and disposition of reclaimed water in typical

areas. Water Resources Development Research, 24(07),

12-17.

Gao, J. 2024. Combined eco-engineering process for

advanced treatment of urban sewage plant tailwater.

Create Living, (6), 10-12.

Huang, J., Luo, J., Hu, X., et al. 2024. Research progress on

advanced treatment technology of tailwater. Resources

Economization & Environmental Protection, (3), 114-

119, 125.

Hu, A., Yang, S. 2021. Situation, problems, and strategies

of unconventional water resources utilization in

Shenzhen. In 2021 China Urban Planning Annual

Conference; 2021: 8.

Liu, X., Shen, J., Yin, X., et al. 2024. Research progress on

the environmental and ecological impact of reuse water

discharge and recycling in wastewater treatment plants.

Journal of Environmental Engineering, 1-17. [2024-08-

13].

Teng, Y. 2023. International experience in reuse water

utilization. Environmental Economy, (06), 56-59.

Yang, M., Fang, K., Wang, G., et al. 2024. Research on the

value realization mechanism of reclaimed water

ecological products. China Water Resources, (2), 33-

36.

Zhang, X. 2023. Research on reclaimed water utilization

strategies in Shenzhen. Pearl River, 44(09), 1-6+32.

Zhang, Z., Li, Y., Yan, W., et al. 2024. Corrosion, scaling

and microbiological risks associated with water

reclamation and reuse. Environmental Protection

Science, 50(3), 10-19.

Research on Recycle and Utilization of Reused Water in Shenzhen

201