The concept of water management has existed since prehistoric times. When states were formed, water management became one of the most important pillars of government power.



While water is a resource that people cannot live without, it can also bring irreparable damage. It thus has to be kept in check as well as managed for human use. Reservoirs or embankments would normally be used to maintain water flow but were ineffective as a means to control water during floods (Joongang Daily, 2001).



Until modern times, water management was linear in a sense, and its sole purpose was to manage supply and make the most effective use of it. In other words, people would intervene through social and economic means to utilize and manage the water from the rain that flows into the rivers and lakes, after which the water would once again be released into the ocean.



Today, water management has to be cyclic in nature in order to meet increasing demands, not simply due to climate change or economic considerations. Water needs to be managed in a sustainable way through the generations because this is what is required by the times. To that end, it is necessary to develop the relevant policies.

 

While Seoul realized compressed economic growth in a relatively short period of time, its water management system (including waterworks and sewer lines) has also improved dramatically. We will examine Seoul’s policy changes and experiences and what lessons can be learned.

Introduction

Seoul sources all its water from the Han River. After treatment, it is piped to taps all over the city.

Geographic Conditions & Overview

Located in the central west section of the Korean peninsula, Seoul is divided through its center by the Han River. On the northern end of the city is the administrative district called Dobong-dong (Dobong-gu); on the eastern end is Sangil-dong (Gangdong-gu); the southern end is Wonji-dong (Seocho-gu); and the western end is Ogok-dong (Gangseo-gu). The city is comprised of 25 administrative gu-districts, with 423 dong-districts. As of December 2014, the population was 10,103,000, or 19.7% of the nation’s population 51,328,000. Seoul is 605.41 km² in area, or about 0.28% of the Korean Peninsula (0.61 % of South Korea), and is 30.3 km-long from north to south, and 36.78 km-long from east to west.

When the Joseon Dynasty was founded in 1394, Seoul became the kingdom’s capital, which it has remained ever since. It is now the center of politics, economics, industry, society, culture and transportation.

The administrative zone increased to 593.75 km² in January 1963, and by March 1973, encompassed 605.30 km². In the 1970s, rapid urbanization sent developers to the south of the Han River, and through the Asian Games in 1986 and the Olympics in 1988, Seoul entered the world stage.

In 1991, local governments were granted more power to govern themselves through a policy of local autonomy. The year 1994 was the 600th anniversary of Seoul as the capital city.

Seoul is located at 37.34 N latitude and 126.59 E longitude, is divided by the river system of the Han River and 4 streams (Cheonggye, Jungnang, Tan, and Anyang), and surrounded by mountains on all 4 sides. To the north is Bugak Mountain, to the east is Nak Mountain, to the south is Nam Mountain, and to the west is Inwang Mountain. On the outer edge are Bukhan Mountain (north), Deogyang Mountain (west), Gwanak Mountain (south), and Yongma Mountain (east), together forming a double basin.

The city center is at 25–40m altitude, with some 40% of the total area at or below 30m; 27% is above 70m, precluding development as a city area; 27% is at the middle range; and 6% is occupied by the river systems.
To the east, the average altitude is within the 35m range, both north and south of the Han River. In Jongno, Jung-gu, Seongbuk, Seodaemun (all north of the Han) in the center, the average altitude is higher, at around 50m, with a similar situation in the Gwanak and Dongjak areas south of the river. Mapo, west of the Han, and Yongsan to the north are relatively low, at 25m.

River & Water Systems

Changes in Urban Development & the Water Reclamation System

The population of Seoul began growing in earnest in the 1960s when urban development began to take off, and continued to grow until the early 1990s. This growth decreased somewhat in the 1990s but stabilized within the 10 million range in the 2000s (Figure 1).

<Figure 1> Population & Household Changes in Seoul / <Figure 2> Changes in People/Household in Seoul
 

The impervious surface area as a percentage of Seoul was 7.8% in 1962 and 47.1% by 2002, an approximately six-fold increase. During the rainy season, surface runoff that had equaled 502,000 m3/day (1962–1971) had also increased six fold to 2,990,000 m3/day (1995–2004). The total runoff in the dry season was 375,000 m3/day between 1962 and 1971, but had fallen to 183,000 m3/day between 1995 and 2004, a decrease of about 49% (Kim Yeong-ran 2012).

The increase in impervious surface area due to urbanization also brought the peak flow up during heavy rainfall while reducing natural flow, causing streams to run dry on clear days.

Seoul’s population density grew 3.5 times, from 5,001 persons/km2 in 1962 to 17,472 persons/km2 as of 2010 (Kim Yeong-ran 2012). The amount of daily floating population from the surrounding satellite cities also jumped. The rising population and density caused many issues in water management such as reduction of the natural flow and increased stream intake, use of groundwater, expelled stormwater and wastewater, incidence of dry stream beds, ecological risks, and urban pollution.

Water Volume & Quality Management

The total volume of water resources in Seoul is 940 million m³/year, with 690 million m³/year available for use (Seoul Development Institute, 2011). Water use equaled 13.4 billion m³/year as of 2009, and is steadily increasing. The water resources reserve accounts for 70.3% of total water use, 12.6 billion m³/year (94.1%) of which is supplied from outside, while only 78 million m³/year (5.9%) is sourced internally. The city depends heavily on the outside for its water. This is detrimental not only to overall supply but also to the sustainability of water reclamation in the long term.

With the launch of the Comprehensive Han River Development Plan, more sewage treatment centers were built in the 1980s. The quality of water began to improve thanks to continued construction of septic tanks and sanitation facilities and strengthening of regulations on wastewater discharge facilities. From 1994 however, droughts began to occur in the winter while more domestic wastewater was drained upstream of the Han River from large apartment complexes. The situation was made worse by the increasing number of restaurants and accommodation facilities near the protected reservoir area, degrading water quality again. This degradation continued until 1997 (Seoul Metropolitan Government, 2014).

The improvement of water quality after 1997 was largely due to action at the government level, including: i) institutional support such as development of the Special Water Quality Management Plan for Paldang Reservoir and the Han River System (1998), enactment and promulgation of the Act on the Improvement of Water Quality & Support for Residents of the Riverhead of the Han River System (1999), and designation of the Jamsil Water Reservoir Protection Area (1995) and Waterfront Areas (1999); and ii) continued efforts to improve water quality by strengthening guidelines and regulations on wastewater discharge facilities (Seoul Metropolitan Government, 2014).

Upstream of the Han, water quality is maintained at a higher level (BOD 1.6 mg/L or lower) than midstream and downstream, where BOD levels are between 2.1 and 2.2 mg/L.

In Jamsil, BOD was 2.6 mg/L in 1997, but from the following year, this began steadily decreasing to 1.7 mg/L in 2004 and 1.4 mg/L in 2005, thanks to measures taken to improve water quality at the upstream reservoir. Since 2006, BOD levels have remained between 1.1 and 1.9 mg/L – ‘Good (I b)’ – for reasons that include introduction of non-point source pollutants in the dry season and changes in the precipitation and discharge rate from Paldang Dam. At Gayang Point, the level was 5.5 mg/L in 1997, falling to 2.9 mg/L in 2005 and remaining between 2.5 and 4.5 mg/L (‘Fair (III)’) between 2006 and 2010. After 2010, quality improved again and is normally 2.2 mg/L.

As for the tributaries, the BOD level depends on the quality of the upstream water. Those with higher levels were the Tan (6.9), Jungnang (14.1), and Anyang streams (5.0) (Table 2).

<Table 2> Water Quality Improvement Goals & Performance for the Han River & Major Tributaries in Seoul (Seoul Metropolitan Government, 2014)

	2010	Performance	2011	Performance	2012	Performance	2013	Performance
Jamsil	1.6	1.5	1.5	1.1	1.5	1.2	1.5	1.3
Gayang	3.0	3.1	3.0	2.6	3.0	2.5	3.0	2.2
Jungnang Stream	11.0	8.8	8.0	4.5	7.5	5.8	7.5	14.1
Tan Stream	20.0	10.7	15.0	6.6	13.0	6.4	11.0	6.9
Anyang Stream	8.0	6.9	7.0	4.5	6.5	4.1	6.0	5.0

 <Table 3> Han River Water Quality by Point & Parameter in 2013 (Seoul  Metropolitan  Government, 2014) 
 

Item	Amsa	Gueui	Jamsil	Ttukdo	Bogwang	Noryangjin	Yeongdeungpo	Gayang
Environmental (Standards Target)	II	II	II	II	II	II	II	III
Temperature	13.2	13.6	13.2	13.3	13.4	14.0	14.1	14.8
pH	7.9	8.0	7.9	7.6	7.5	7.6	7.4	7.6
DO	11.7	12.0	12.1	11.8	11.5	10.3	10.8	11.0
BOD	1.2	1.4	1.3	1.6	2.1	2.1	2.1	2.2
COD	3.4	3.9	3.6	3.9	4.3	4.7	4.7	4.6
SS	5.9	6.7	6.4	6.9	6.7	8.5	7.4	10.7
Total Coliform Count	10,675	1,346	12,845	24,473	92,482	68,290	53,364	34,461
Fecal Coliform Count	33	163	159	668	3,330	8,862	1,262	1,578
Total Nitrogen	2.156	2.262	2.277	2.649	3.029	3.412	3.481	3.409
Total Phoshorus	0.053	0.035	0.027	0.037	0.069	0.138	0.124	0.118
Cadmium	ND	ND	ND	ND	ND	ND	ND	ND
Cyanide	ND	ND	ND	ND	ND	ND	ND	ND
Lead	ND	ND	ND	ND	ND	ND	ND	ND
6 Chrmium VI	ND	ND	ND	ND	ND	ND	ND	ND
Arsenic	ND	ND	ND	ND	ND	ND	ND	ND
Mercury	ND	ND	ND	ND	ND	ND	ND	ND
ABS	ND	ND	ND	ND	ND	ND	ND	ND
Phenol	ND	ND	ND	ND	ND	ND	ND	ND

 

<Figure 4> Water Quality at Major Points of the Han River (BOD mg/L) & Water Renewal Facilities (㎥/day)

 

Upstream Reservoir & Stream Management Policies

So far, policies implemented to preserve water quality of the Han River have focused on installation of sewage treatment facilities in urban areas and management of the sources of pollution. However, quality management of Han River water is only of limited scope without management of non-point source pollution inside the city. Many development projects (industrial complexes, site development, farmland and forest management, roads, parking lots, etc.) have been pursued without much consideration for non-point source pollution. As pollution from such city sources continues to affect the Han, a new approach is imperative that takes non-point source pollution into account.

Foundation for Basic Environmental Protection Facilities

The 4 water treatment centers of Jungnang, Nanji, Tancheon, and Seonam were processing a total 3.16 million m³/day as of the end of 2013, an amount which covers all wastewater produced in Seoul. Facilities capable of processing 1.75 million m³/day will be installed at the 4 centers to comply with stronger discharge water quality standards and the assigned total maximum daily load.

Stronger Management of Wastewater Discharge Facilities

Wastewater discharge facilities subject to guidance and inspections are provided with continued guidance and inspected by the SMG. They are encouraged to replace any deteriorating facilities and improve their efforts to prevent industrial wastewater from contaminating the water supply (Seoul Metropolitan Government, 2014).
 

Citizens Environment Watch

To monitor for and stop pollution, a Citizens Environment Watch was organized in 2004 and is a collaborative organization involving regulatory authorities, local residents, and private entities. Designed to jointly address pollution, it will lead to the establishment of a private-public environmental watch network which will enhance transparency and effectiveness of the guidance and inspection of pollutant discharging facilities while ensuring that the environmental watch and preservation activities are led by the private sector.
 

Water Pollution Alert

The Water Pollution Alert system was initiated in 1998 in response to dead fish found in the Han River and its tributaries and has been in practice ever since to respond to other such incidents.

Automatic Monitoring System

A full-time monitoring system was introduced to prevent water pollution from the introduction of harmful chemicals into the streams, sewer pipes, and receiving waters at the water renewal facilities, while minimizing damage should such contamination occur. The system is designed to monitor for and track unauthorized discharges.

The automatic system looks at 14 parameters, including cyanide, at 9 points on the main river (6 at the upstream reservoir and 3 at the streams themselves) and at 3 points along the tributaries. The water is monitored at 8 points for the presence of any of sixteen harmful chemicals, including the receiving water at the treatment center. Furthermore, oil fences and oil absorbents are available to handle oil spills, and emergency simulation training is held at the Han River every year. 

Total Maximum Daily Load

The Water Use Fee System

Changes in Waterworks Policies

Modern waterworks service began in Seoul when two Americans, Henry Collbran and Harold Bostwick, obtained permission from Korea’s Emperor Gojong to operate waterworks facilities and built a purification center in Ttukdo, which was completed on September 1, 1908, to supply water. At the time, the production capacity was 12,500 m³/day, with water supplied to 125,000 people.

In 1946, 3 purification centers were built, a number which grew to 5 by 1977. By 2004, some parts of the aging Gueui Purification Center and the purification centers in Noryangjin, Shinwol, Seonyu and Bogwang were closed. Today, there are 6 purification centers (Gwangam, Amsa, Gueui, Ttukdo, Yeongdeungpo, and Gangbuk) (Figure 5). As of the end of 2013, production capacity was 4.35 million m³/day, and the waterworks service rate is 100%, meaning all citizens have access to the waterworks.
 

<Figure 5> Intake Points in Seoul (Seoul Metropolitan Government, 2014)

As mentioned, in 1908 the purification capacity was 12,500 m³ of water per day, supplied to 125,000 people. As of the end of 2013, the capacity was 4.35 million m³/day, giving access to some 10.38 million people, representing and 348-fold increase in facility capacity and an 83-fold increase in the number of people with access.

<Figure 6> Waterworks Service Rate in Seoul

Until 1992, facility capacity was insufficient for water demand, and there were difficulties with operation and supply. After 1998 however, the facilities reached sufficient capacity, ensuring stability of supply (Figure 6). In 2013, 11.6 billion m³ of tap water was used in Seoul, with the daily average being about 3.19 million m³.

Introduction of Advanced Purification Facilities

From the 1960s to the 1980s, the major focus of waterworks policy was on quantitative expansion, but thereafter, policies began targeting the assurance of water quality and stability of supply. Into the 2000s, the city’s waterworks system improved in both quantitative and qualitative terms, and the policies focused on providing taste-free, safe tap water to residents.

Alongside these changes, there was a growing need for countermeasures to potential degradation of water quality at source and pollution due to climate change and urbanization. Accordingly, more advanced purification facilities were introduced. With the Ttukdo Arisu Purification Center as the last target in 2015, all purification centers will have installed these advanced purification systems. The currently-installed system is primarily focused on controlling odor- and taste-generating particles from algae, but also seeks to respond to the potential for issues to be caused by new trace particles. When these new facilities are completed in 2015, the citizens of Seoul will have access to cleaner, safer tap water.

Flow Rate Improvement

When the Seoul Metropolitan Government’s Office of Waterworks was launched in 1989, the flow rate in Seoul was 55.2%. By 2000, it had jumped to 72.0%, and by 2014 to 95.1% - a level of success unprecedented in the world. Flow rate refers to the amount collected in fees as a percentage of the tap water produced and supplied by a purification center. For instance, the flow rate is 90% if 100 m³ of tap water is supplied to users and fees collected amount to the cost of producing 90 m³ of tap water. The higher the flow rate, the lower the outside funding necessary for production and supply (e.g., raw water acquisition, purification chemicals, power, etc.), thereby improving the financial health of waterworks management.

From 1989 to 2013, the flow rate improved by 39.2% (55.2% → 94.4% ); in financial terms, this is equivalent to savings of KRW 4.665 trillion (by unit price) since the launch of the Office of Waterworks. Seoul has been able to improve flow rate in several ways: continuing to repair old, leak-prone pipes; securing distribution stations; and switching to a run-of-river type to stabilize the water pressure and prevent related leaks. In addition, a flow monitoring system was adopted to monitor the flow and water pressure in real time. An effective leak detection method was employed as well. Seoul was divided into 2,037 small blocks and systematic leak detection carried out to quickly identify leaks and take appropriate action. Medium blocks (100 as of 2013) were also set up to analyze and manage flow rate at the medium block level. By 2017, Seoul aims to increase flow rate to 96.5% and will work to find the latest technologies that will improve and lead to its better management.

Distribution System Management

There were 13,721 km of distribution pipes installed in Seoul as of 2014. To improve water quality and flow rate in the process of distribution, Seoul replaced deteriorating piping (13,192 km of all 13,728 km) between 1984 and 2013. By 2018, all deteriorating pipes will be replaced (Figure 7).

<Figure 7> Improved Flow Rate After Pipe Replacement

The distribution stations are capable of processing 2.42 million m3 of water, equal to about 13.9 hours of supply in case of an emergency. The capacity will be increased to 2.48 million m3 by 2030, to provide about 15 hours of emergency supply. This will enable constant and direct supply that does not require water tanks at the customers’ end. The stability of water supply will be considerably enhanced, not to mention higher water quality during the process of distribution.

Water Quality Management

In 1990, South Korea had 28 water quality inspection parameters. The number of parameters has gradually increased, and as of 2013, there were a total of 85 – 59 statutory and 26 general monitoring parameters. As of 2012, Seoul conducted regular inspections according to 164 parameters (59 statutory and 105 parameters set by the city ) (Figure 8).

<Figure 8> Changes in Water Quality Management (Parameters) & Purified Water Quality (Turbidity)

Seoul Water-Now System

The Seoul Water-Now System monitors water quality in real time 24 hours a day, from source to faucet. Monitors are installed at 200 locations: intake points, purification centers, distribution stations, pumping stations, parks, and faucets (during the supply process) (Figure 9). The water quality thus monitored is disclosed to the public in real time to enhance transparency and reliability of waterworks administration. The Seoul Water-Now System has been recognized by the international community for its excellence in providing administrative services to satisfy residents’ right to know and to protect their health. Along with Arisu Quality Certification, it won the grand prize at the UN Public Service Awards (UNPSA) on June 23, 2009.

<Figure 9> Seoul Water-Now System

Changes in Sewer-Related Policies

During the Joseon Dynasty, sewage flowed on street surfaces or in low-lying areas, passing through low ditches and flowing into the streams or underground. There were virtually no facilities or efforts at management. However, Cheonggye Stream, one of Seoul’s major streams, had undergone dredging and other related works. In the 12th year of King Taejong (1412), full construction works were carried out at Cheonggye Stream and other streams so as to prevent them from flooding.

During the years of the Korean Empire (1897-1910), a 6,832 m-long culvert was built as part of the city sewer project, making it the nation’s first modern sewer pipe. Since then however, there is no record of maintenance or management.
The modern concept of a sewer system was applied when the 225 km-long main and branch sewer lines were installed over 4 occasions, from 1921 to 1945, after Korea was forcibly annexed by Japan. This system was constructed to prevent pollution from urban flooding and wastewater and to process fecal material that was being discharged without control.

Until the 1960s, the main purpose of the sewers was to expel stormwater from the city, and lines were built in efforts to improve the street environment. After that decade, South Korea began experiencing dramatic economic growth accompanied by rapid industrialization and urbanization, improved quality of life, and change of method in treatment of fecal material, amplifying the pollution load from wastewater. Accordingly, people began to take interest in the construction of sewage treatment facilities and a separate sewer system. The sewer system as we know it began, thanks to international aid South Korea received since 1954 for post-war restoration.

In 1959, the first construction to cover Cheonggye Stream began. In 1966, the Sewerage Act was passed, and the Cheonggye Stream Wastewater Treatment Center (150,000 m³/day) began construction with a USAID loan, and was completed in 1976. The early 1960s were politically challenging for South Korea, but this did not stop the government from pursuing the sewage system project. Consequently, the pre-1961 sewer pipe network more than doubled in length from 631 km to 1,462 km (Figure 10).

The 1970s was a decade of sewer expansion: the existing sewer system was actively repaired while new facilities were built and renovated with fervor. From 1987, the number of wastewater treatment facilities jumped, mainly to prepare for the Olympics in 1988. Between 1986 and 1999, sewerage capacity grew 39 times, from 150,000 m³/day to 5.81 million m³/day.

In 2005, the purpose and concept of wastewater treatment were clearly defined. To ensure that the system remains sustainable and ready for future climate changes, the facilities, usually referred to as wastewater treatment facilities, were called water treatment centers.

In line with higher standards on water discharged from water treatment centers, an advanced treatment system was introduced. In 2007, the new system, which had a capacity of 460,000 m3/day, was applied to Jungnang Water Treatment Center; by 2012, the system was also installed at 4 other centers, representing a total capacity of 3.91 million m3/day. At Jungnang and Seonam water treatment centers, the system was installed while some of their facilities were incorporated into the underground system. The aboveground space was modernized and transformed into a park for local residents (Table 5).

<Table 5> Introduction of Advanced Treatment System in Seoul

As mentioned earlier, focus was placed on quantitative expansion of sewerage capacity in the late 1980s. Sewer pipes were added and improved as well. The total length of the sewer network, which was 6,559 km in 1980, had increased 1.4 times to 9,122 km by 1990. In each year since, 200 km of piping has been improved.

<Figure 11> Sewer Service Rate in Seoul (Ministry of Environment, 2015; Seoul Metropolitan Government, 2010)

In the 1990s, projects were implemented to restore the functions of sewer pipes as they are fundamental urban facilities that protect the environment. From 1992 to 2001, the network was examined by zone to replace deteriorating and damaged pipes in a systematic manner (Table 5).
 
By 2007, all citizens had access to the sewer system. From then on, Seoul placed more focus on quality management of the system, user satisfaction, and policy tasks designed to ensure safety (Figure 11).
Such change and policy direction for the future are well represented in the 2020 Seoul Sewerage Vision. The policy directions as seen in the Vision are as follows:
 

• Enhanced capabilities to prevent potential disasters caused by climate change;
• Efficient and systematic repair and maintenance of deteriorating pipes;
• Improved living environment and services to the public;
• More realistic water billing to secure sufficient financing;
• Advanced sewage treatment and modernization;
• People-friendly water treatment centers;
• Reduced energy consumption at water treatment centers;
• Operational efficiency at water treatment centers;
• Launch of renewable energy programs.

Restoration of the Environment & Ecosystem

Restoration of the environment and ecosystem, one of Seoul’s water management policies, and policy indicators and objectives are well described in the Seoul Water Quality and Ecosystem Preservation Plan 2014-2018 (Seoul Metropolitan Government, 2014). The vision of this plan is to create a “City with a Healthy Water Environment for Peaceful Cohabitation of People and Nature” so as to restore the balance of the city’s aquatic ecosystem. The Plan includes 5 strategies and 12 programs (Figure 12)

<Figure 12> The Seoul Water Quality & Ecosystem Preservation Plan: Strategies & Programs (Seoul Metropolitan Government, 2014)

Besides steps to preserve water quality and the ecosystem, the Plan also includes action and strategies that encompass the entirety of the sustainable water reclamation system.This is significant in that it changes the policy paradigm from water quality management to preservation and maintenance of a healthy aquatic ecosystem through various means, such as restoring stream and river ecosystems to their natural, healthy state, and conducting assessments and inspections of those ecosystems (Table 6)

<Table 7> Water Quality Targets from the Seoul Water Quality & Ecosystem Preservation Plan (Seoul Metropolitan Government, 2014)

Reducing Flood Risk

In the past decade, Seoul’s annual average rainfall has been 1,550 mm, 70% or more of which comes in the torrential rains occurring during the summer months (June–August). The city suffered major damage in 1987, 1990, 1998, 2001, 2010, and 2011. Every decade or so, Seoul sees 2 or 3 major floods. Most of the damage has been to buildings and facilities, crippling urban functions (blocking traffic, causing blackouts, suspending communications etc.) (Figure 13).
 

<Figure 13> Losses in Seoul from Flooding (Unit: KRW 1 million)

1. Joongang Daily, 2001, Managing & Taking Advantage of Water, http://article.joins.com/news/article/article.asp?total_id=4083435&ctg=10
2. Seoul Development Institute, 2011, Urbanization & Water Reclamation (presentation for the 2011 Water Reclamation Symposium).
3. The Office of Waterworks, 2015, 2014 Major Programs Status (internal data).
4. Kim Yeong-ran, 2012, The Effect of Urbanization on Water Reclamation & Status in Seoul (presentation for the 2012 Water Reclamation City Forum).
5. Seoul Metropolitan Government, 2009, Seoul Comprehensive Plan for the Water Environment.
6. Seoul Development Institute, 2011, Urbanization & Water Reclamation (presentation for the 2011 Water Reclamation Symposium).
7. Seoul Metropolitan Government, 2013 The City of Seoul Environment White Paper: the Environment of Seoul, 2014.
8. Seoul Metropolitan Government, 2009 Guide to the Sewage System in Seoul, 2010.
9. Ministry of Environment, 2015, Environment Statistics, http://stat.me.go.kr/nesis/mesp2/webStatistics/stat_main.jsp?tblID=DT_106N_ZZZ_001217&inq_gubun=1#
10. WHO, Protecting drinking-water sources through regulation, http://www.who.int/water_sanitation_health/dwq/sheet4.pdf
11. EPA, 2011, Treating Contaminants of Emerging Concern, US EPA Office of Water, EPA-820-R-10-002.
12. Seoul Metropolitan Government, 2014, Seoul Water Quality & Ecosystem Preservation Plan 2014 – 2018, Water Management Policy, Seoul Metropolitan Government.