Taking Hong Kong as an Example to Introduce Sustainable Drainage

Systems and Wastewater Treatment Technologies

Chuyu Chen

The Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong

Keywords: Sustainability, Drainage Systems, Wastewater Treatment Technologies.

Abstract: Due to the rapid development of recent society, the amount of pollutants has become larger and larger,

especially the amount of wastewater, which has become a crucial challenge around the world. It is significant

to understand the paramount importance of efficient sewage drainage and wastewater treatment systems in

safeguarding human health and ecological balance. This study mainly focuses on the progress in sewage

drainage and wastewater treatment infrastructure and then shifts to emphasize the strategic implementation of

sustainable solutions. This paper explores the design and operational aspects of advanced systems, including

Sustainable Drainage Systems (SuDS) and innovative technologies like green roofs and membrane bioreactors

(MBRs), used in Hong Kong as a model. Apart from acknowledging the challenges behind such systems, such

as knowledge gaps, financial barriers, and technical complexities, this study proposes solutions like

educational initiatives and financial support. With the integration of innovative technologies, including

Artificial Intelligence (AI) and the Internet of Things (IoT), these systems can effectively enhance their

efficiency and sustainability. This futuristic approach aims to build urban resilience and guarantee effective

sewage management, thereby mitigating environmental pollution and fostering a healthier, sustainable urban

landscape.

1 INTRODUCTION

In recent decades, with the high development of

industrialization and urbanization, there has an

increasing environmental pollution, particularly in

the form of sewage. Such wastewater without proper

management may contribute to terrible effects on

both human health and the entire ecosystem. It is

important to realize that sewage drainage and

wastewater treatment are significant nowadays.

Firstly, as long as the wastewater without treatment is

left in rivers, lakes, and oceans, those drinking water

sources may be contaminated. Polluted water sources

may also harm aquatic life and even disrupt the

ecosystem. For human activities, polluted water

sources will have an effect on the human body,

agriculture, and so on. What is also worth noticing is

that there are several chemicals and pathogens that

may cause diseases in humans and animals. The

pollutants in sewage, such as chemicals, heavy

metals, pathogens and so on, need fastidious

https://orcid.org/0009-0008-8125-9482

treatment to avoid contaminating water bodies, soil,

and air quality.

In China, wastewater treatment has received

attention: the number of wastewater treatment plants

is continuously increasing from 481 in 2000-3717 in

2014, and the treatment capacity achieves 1.57

million m³ d

ିଵ

(Ben et al., 2018). The focus of

sustainable development is to balance economic

growth with environmental protection and social

well-being. Recently, sustainable development has

been the main cornerstone to reduce pollution and

protect the environment. For wastewater, including

drainage systems and sewage treatment, sustainable

development is also the main concentration.

Researchers and the government are increasingly

focusing on innovative and sustainable methods for

sewage identification, purification, and drainage,

which is crucial for achieving long-term

environmental sustainability. Through improving

wastewater treatment methods and processes, it is

possible to reduce carbon footprint and pollution.

202

Chen, C.

Taking Hong Kong as an Example to Introduce Sustainable Drainage Systems and Wastewater Treatment Technologies.

DOI: 10.5220/0013268200004558

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 202-207

ISBN: 978-989-758-738-2

Proper sewage drainage and purification can

prevent illness from spreading. Also, it is extremely

effective to reuse the energy and nutrients in

wastewater during the process of management and

purification. For instance, treated wastewater can be

reused for irrigation, industrial processes, and even as

potable water in some cases, thus reducing the

demand for fresh water and promoting resource

efficiency. With the continuous advancement of the

entire world, it is imperative to deal with the

environmental challenges they bring, particularly in

the aspect of wastewater drainage and treatment.

The article will briefly introduce the design of

drainage systems, the technology of wastewater

treatment and the sustainability of them. At the same

time, taking Hong Kong, a harbor city, is an example

to explain the methods and process of wastewater

treatment. What is more, is that some innovative

technologies which can be used in drainage systems

and wastewater treatment will be mentioned to further

achieve sustainable development.

2 INTRODUCTION OF

DRAINAGE SYSTEM AND

WASTEWATER TREATMENT

TECHNOLOGY

2.1 the Design and Operation of

Drainage Systems and Wastewater

Treatment Technologies

The design and operation of the drainage system and

wastewater treatment technologies are extremely

important for water resources management, public

health improvement, and environmental protection.

The relationship between drainage systems and

wastewater treatment technologies is integral and

symbiotic. While the drainage system is responsible

for collection and conveyance, the wastewater

treatment plants will remove contaminants before the

wastewater is discharged or reused. It is significant to

understand and further improve the strategies of

design and operation of drainage systems and

wastewater treatment technologies.

2.1.1 Drainage Systems

The main purpose of a drainage system is to convey

sewage to wastewater treatment plants. The drainage

can be divided into three types: stormwater drainage,

sanitary drainage, and combined systems. The

stormwater drainage manages the runoff from rainfall

to prevent flooding and erosion, while the sanitary

drainage transports wastewater from bathrooms,

sinks, kitchens, and other plumbing components to

treatment facilities (Greater Lansing Regional

Committee, 2024). The combined systems are the

systems to handle both sewage at the same time. It is

available in normal situations; however, during

extreme weather such as heavy rainfall, water

quantity in the systems will exceed the maximum

amount, which results in overflow. As a result, such

systems are less commonly used.

The design of the drainage system should

concentrate on several aspects. Firstly, the hydraulic

design, such as pipe diameter, roughness, and flow

rate, can ensure pipes and channels can handle peak

flow rates without causing backups or overflows.

Also, the gravity flow can effectively minimize the

utilization of pumping stations. At the same time,

proper slope and elevation can enhance flow

efficiency and stagnation prevention. Apart from

these, choosing different materials based on the type

of waste and environmental conditions is also

significant. The last point is to establish manholes and

cleanouts for maintenance and inspection.

2.1.2 Wastewater Treatment Technologies

In order to remove contaminants from wastewater so

that wastewater can be discharged or reused,

wastewater treatment technologies have been

introduced. The process of wastewater treatment can

be divided into several steps: preliminary treatment,

primary treatment, secondary treatment, tertiary

treatment, and sludge treatment. The initial treatment

mainly focuses on the removal of large objects or

debris from raw sewage, which can effectively

neutralize the smell and protect the purification

machines from breakdown. Also, the purpose of

primary treatment is to separate solid macrobiotic

matter from wastewater with a grit chamber and

sedimentation tank. Then, the secondary treatment,

also known as the activated sludge process, will

remove the organic compounds by introducing

oxygen into the wastewater. At the tertiary treatment

stage, due to chlorination, ozone treatment,

disinfection with ultraviolet light, and nitrogen

reduction, wastewater will be further purified and

achieve the level of drinking water. Finally, the

sludge from primary and secondary treatments will be

divided into water and sludge. The remaining water

will discharge to the large aeration tank, while the

sludge will be used for agriculture (Wastewater

Treatment Process, 2023).

Taking Hong Kong as an Example to Introduce Sustainable Drainage Systems and Wastewater Treatment Technologies

203

During the process of sewage treatment, it is

significant to monitor and control the flow rates,

pollutant levels, and system performance. Data

monitoring can effectively identify potential

problems in a timely manner and guide subsequent

maintenance. At the same time, regular maintenance

of mechanical and electrical components of drainage

systems is effective to prevent erosion and failure of

machines. Apart from ensuring effective monitoring

and maintenance of sewage treatment systems, the

standard of effluent quality and techniques should

also comply with local and national regulations.

2.2 Sustainability of Drainage Systems

and Wastewater Treatment

Technologies

In order to improve water quality and achieve the goal

of sustainable development, sustainable drainage

systems (SuDS) and sustainable wastewater

treatment technologies are invited, thus protecting the

environment, conserving resources, and ensuring

public health.

2.2.1 SuDS

During the late 2000s, the tendency for researchers

and governments was to take action to protect,

manage and restore ecosystems. The natural-based

solution (NBS) emerged to devise management

strategies that synergize with ecosystems, aiming to

tackle escalating urban sustainability issues while

simultaneously fostering economic prosperity and

employment opportunities within the framework of a

green economy. In such a situation, improvement of

the water environment can effectively affect the

social economy and public health, which results in the

development of SuDS. The SuDS are structured as a

series of interconnected stormwater management

practices and technologies. The comprehensive

management training they consist can efficiently

store, attenuate, and treat surface runoff, thereby

mitigating the risk of flooding and reducing the

overall volume of runoff. The main principle for

sustainable drainage systems is to mimic natural

horological processes which utilize vegetated land

surfaces for drainage (Cotterill & Bracken, 2020).

The SuDS includes green infrastructure, natural

waterways, retention and detention basins, swales and

bioswales, and rainwater harvesting systems. There

are three working concepts for SuDS. Initially, the

systems should encourage rainwater to infiltrate into

ground. Also, preventing runoff from contamination

is also important. Finally, the flow rate of runoff for

SuDS should not exceed the undeveloped area

(Hamilton, 2014).

2.2.2 Sustainable Wastewater Treatment

Technologies

Currently, the sustainable development goals (SDGs)

becomes the main concentration around the world.

Wastewater management plays an important role in

achieving 11 out of 17 SDGs. For example,

mitigating the impact of wastewater, providing

income sources, increasing water availability,

improving public health, reusing waste to generate

energy, and so on (Obaideen et al., 2022).

Thus, utilizing sustainable technologies and

strategies for wastewater treatment is significant.

Firstly, reducing the energy consumption of

wastewater treatment plants by using energy efficient

pumps, blowers, and other equipment. Also, reusing

the resources during the treatment process, such as

nitrogen and phosphorus. Decentralizing treatment is

also effective to mitigate the burden on centralized

facilities and minimize the need for extensive sewer

networks. Apart from these, it is efficient for wetlands,

lagoons, and other natural systems to treat wastewater

with minimal energy input. At the same time,

enhancing the wastewater treatment level can reuse

water in agriculture, industry, or even potable water

supplies. The last one, which is also the most effective

and needs further development, is to utilize

innovative technologies such as ultrasound technique,

hydrodynamic cavitation technology, advanced

oxidation processes (AOP), advanced green

technologies, and membrane bioreactors (MBRs)

(Obaideen et al., 2022). Firstly, the ultrasound

technique can be utilized in pre-treatment, sludge

disintegration, and enhanced chemical reactions to

breakdown the pollutants through the high

temperature and pressures created by collaption of

bubbles. With the same working principles,

hydrodynamic cavitation technology is widely used

in pollutant degradation, disinfection, and pre-

treatment process. At the same time, it is effective to

utilize AOP to degrade recalcitrant compounds,

remove color, and disinfection with the generation

and oxidation of highly reactive species. Furthermore,

advanced green technologies apply natural processes

and materials to treat wastewater in phytoremediation,

constructed wetlands, and biofiltration. The MBRs

can combine biological treatment with membrane

filtration to allow wastewater to pass through

membranes to filter out suspended solids, bacteria,

and other contaminants in municipal wastewater

treatment, industrial wastewater treatment, and water

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reuse aspects (Kumar et al., 2022). Apart from high

efficiency, hydrodynamic cavitation technology is

cost-effective and scalability, while advanced green

technologies are sustainable with the reduction of

carbon footprint and recovery of resources.

3 TAKING HONG KONG AS AN

EXAMPLE TO INTRODUCE

SUDS

3.1 Introduction of the Current

Wastewater Situation in Hong

Kong

Due to the large amount of sewage, Hong Kong

generates by population and factories every day,

sewage treatment becomes a serious challenge for the

Hong Kong government. As a harbour city with a

large population, Hong Kong has devoted efforts to

sewage treatment for several years to provide

residents a safe and healthy environment. Managing

sewage in Hong Kong is a significant challenge,

requiring both efficiency and cost-effectiveness. Over

93% of the population is connected to the public

sewerage system, which includes a network of

approximately 1900 kilometers of sewers and around

300 sewage pumping stations and treatment plants.

This system handles and processes 2.8 million cubic

meters of sewage daily. At the same time, harbour

area treatment scheme (HATS) was applied in 2001

to upgraded the harbour area sewage treatment at a

strategic level (GovHK, 2023). Besides these, Hong

Kong government also implement several practical

solutions. For example, for constructional sewage,

applying water pollution control ordinance (WPCO)

license from the EPD before it is discharged;

constructing wastewater treatment facilities to ensure

that the quality of discharge water meets WPCO

standards; separating domestic sewage from

construction wastewater and surface runoff to

separate treatment for different wastewater;

conducting regular inspection and maintenance to

make sure the effluent discharged meets the required

standards.

3.2 Sustainable Technologies

3.2.1 SuDS in Hong Kong

Hong Kong has applied SuDS to manage storm water

runoff and mitigate the impacts of urbanization and

industrialization on the environment. Such systems

aim to mimic natural hydrological processes, improve

water quality, and reduce flood risks. SuDS typically

include several components and techniques, such as

green roofs, permeable pavements, swales,

infiltration basins and trenches, rain gardens and

bioretention ponds, detention basins, wetlands, and so

on. As one of the techniques of SuDS, green roofs can

manage rainfall in a sustainable way.

Firstly, the green roofs, which are vegetated

spaces that are constructed on the top of buildings, are

installed on several buildings in Hong Kong. There

are two main types of green roofs: extensive green

roofs and intensive green roofs. The extensive green

roofs are designed with lightweight, thin soil, and

lower maintenance cost. Also, they are suitable for

large areas without irrigation. However, such green

roofs cannot be accessed for recreation or other uses.

At the same time, the plant species that can be used in

extensive green roofs are limited. On the other hand,

intensive green roofs contain deep soils, and a wide

plant range, and can be used as recreational spaces by

human beings. However, such green roof contains

relatively higher cost and are not suitable for green

roof retrofit projects. Also, energy, water, and

materials are needed more than extensive green roofs.

Both types of roofs have been applied, while the

intensive green roofs are more widely used in Hong

Kong. Despite the buildings in most old areas in Hong

Kong being tall and finger-like, there are still some

areas with green roofs. At the same time, other

infrastructure buildings such as walkways, noise

enclosures, ferry piers, pumping stations and vent

buildings can also provide green areas. The

application of green roofs effectively manages the

peak flow of runoff during extreme weather and

reduces the heat island effect in Hong Kong.

3.2.2 Sustainable Wastewater Treatment

Technologies in Hong Kong

In order to keep sewage treatment more sustainable,

it is significant to make the treatment process more

efficient and cost-effective, which becomes a huge

challenge for Hong Kong. In 2015, Hong Kong

government set up a pilot compact sewage treatment

plant with mechanical filter mesh and membrane

bioreactors (MBRs) at Shatin Sewage Treatment

Works (STSTW). With such technologies, the

footprint required for a mechanical filter mesh is

much less than the conventional primary

sedimentation tank, which is 1/8th of the original. At

the same time, the amount of removal suspended solid

of mechanical filter mesh is comparable to the

primary sedimentation tank and is capable of

Taking Hong Kong as an Example to Introduce Sustainable Drainage Systems and Wastewater Treatment Technologies

205

managing the diurnal peak and shock loads at the

STSTW (Poon, 2016). Additionally, the installation

of a deodorization unit effectively eliminates odour

questions. The mechanical filter mesh also filters out

hair and fibre, thereby protecting the downstream

MBRs from fouling. In Hong Kong, such compacted

sewage treatment plants with innovative technologies

can provide high-quality effluent and clean water

suitable for reuse, which complies with achieving

sustainable development goals.

3.3 Challenges

3.3.1 Challenges for Green Roofs in Hong

Kong

As one of the infrastructures of sustainable drainage

systems, green roofs contain several constraints and

barriers. There are five categories of green roof

constraints. The first is the lack of knowledge and

awareness. The design, installation, and maintenance

of green roofs require specialized knowledge and

skills, which may not be available for all regions.

Additionally, the limited number of contractors and

professionals with experience in green roof

technology contributes to difficulty in finding

qualified engineers and workers. The second

constraint is the lack of an incentive mandate. For

example, the building codes and zoning regulations in

Hong Kong do not accommodate or encourage the

installation of green roofs. Economic constraints are

also worth noticing. The installation costs for green

roofs can be significantly higher than those for

traditional roofing systems due to the need for

specialized materials, structural reinforcement, and

professional expertise. At the same time, the

maintenance cost for green roofs is also higher

compared to the conventional ones. Besides these

barriers, the lack of available roof areas is also a

serious problem. The buildings in Hong Kong are

always tall and finger-like, and the small total area of

Hong Kong contributes to the less available area for

green roofs. Finally, the technical issues and risks

associated with uncertainty are also crucial. Potential

leaks and water damage to the building structure can

deter property owners from installing green roofs.

Also, some stakeholders may be sceptical about the

long-term benefits and cost-effectiveness of green

roofs due to high setup costs.

3.3.2 Challenges of Using Mechanical Filter

Mesh and Membrane Bioreactor in

Hong Kong

There are also several challenges to the utilization of

mechanical filter mesh and membrane bioreactors in

Hong Kong. The first challenge is complexity and

expertise due to the special and complex knowledge

to apply mechanical filter mesh and membrane

bioreactor. Secondly, the capital and operational costs

for initial investment and operational expenses, which

include energy and chemicals for cleaning and

membrane replacement due to the limited lifespan of

the membrane, may be substantial. At the same time,

the fouling problem is also crucial, which will reduce

permeability, working efficiency, and operational

costs.

4 FUTURE PROSPECTS AND

RECOMMENDATIONS

With the highly developed society, several innovative

technologies have emerged to improve the

sustainability of the entire water cycle. For example,

smart monitoring and control with the Internet of

Things (loT) and artificial intelligence (AI).

Integrating artificial intelligence and the Internet of

Things in sustainable drainage systems and

wastewater treatment can improve efficiency and

sustainability.

Firstly, AI and loT can be used for sustainable

drainage systems and for real-time monitoring and

data collection. The application of loT sensors can

effectively monitor parameters such as water levels,

flow rates, rainfall quantity, soil moisture, and water

quality in real-time and transmit the data to a central

system for analysis. At the same time, AI models can

be used to analyze historical and real-time data to

predict potential flooding events and optimize

drainage operations. The implementation of AI-

driven decision support systems to take proactive

measures, such as adjusting the operation of pumps

and valves or diverting water flows to prevent

flooding. Apart from these, AI are also beneficial for

predictive maintenance. As long as the sensor data

predicts that the systems should be maintenance, the

sensor will inform system managers about the data,

which can reduce the risk of system failures and

optimize maintenance schedules.

Additionally, for wastewater treatment, AI and

loT can also play significant role in optimizing the

entire treatment process (Gupta et al., 2024).

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Integrating loT sensors and AI control systems to

monitor key parameters such as pH, turbidity,

dissolved oxygen, and contaminant levels throughout

the treatment process. Also, implementing AI

algorithms to detect anomalies in water quality data,

triggering automated responses to address potential

issues. With the sensor of loT to monitor energy

consumption and the analyzer of AI, it is easy to

discover energy usage patterns and optimize energy-

intensive processes, such as aeration and pumping, to

reduce operational costs and carbon footprints.

Besides such benefits. AI is able to control and

optimize nutrient recovery systems and enhance the

efficiency of extracting valuable resources like

phosphorus and nitrogen.

By utilizing the combined AI and loT systems, the

performance and sustainability of drainage systems

and wastewater treatment infrastructure can be

enhanced. Apart from AI and loT, there will be more

and more technologies that can be used to create a

more resilient and sustainable urban environment.

With the effort of all residents around the world,

sewage drainage and treatment can be more effective

and sustainable.

5 CONCLUSIONS

In conclusion, in order to solve the questions of

pollutants, especially sewage, generated from rapid

industrialization and urbanization, proper

management of wastewater is crucial to mitigate its

detrimental effects on human health and ecosystems.

Sustainable development, which balances economic

growth with environmental protection and social

well-being, is essential for addressing pollution and

protecting the environment. Apart from properly

handling the management processes, the SuDS and

sustainable wastewater treatment technologies are

also crucial to reducing the detrimental effects on

human activities, agriculture, and public health.

This study takes Hong Kong as an example to

introduce the significance of utilization of green roofs,

which are the component of SuDS, and the

application of mechanical filter mesh and membrane

bioreactor, which are included in sustainable

wastewater treatment technologies. However,

challenges such as lack of knowledge, economic

constraints, and technical issues must be addressed.

The educational campaigns and financial support

should be applied to deal with these challenges.

Future prospects, which are to construct a healthy,

safe, and sustainable living environment for humans

and creatures, include the integration of smart

technologies like AI and IoT to enhance the

efficiency and sustainability of drainage systems and

wastewater treatment processes. By leveraging these

advancements, we can create a more resilient and

sustainable urban environment, ensuring effective

and sustainable sewage drainage and treatment for the

future.

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