The word ‘Arisu’ is the current name of Seoul’s tap water bran, but it used to be the name for Han River that flows through the heart of Seoul. In fact, the word is a combination of an old Korean word ‘Ari’ that means big, and ‘Su’ which means water. Having had more than 100 years of managing tap water policies and evolving throughout the time, Seoul’s water supply policy today is recognized as one of the best in the world.

1908~1944, The First Urban Water Supply System
Though Seoul was the first city in Korea to adopt a modern urban water supply system, the Korean War halted its continuous development. Therefore, it was not until after 1960s that the tap water technology truly took off in full swing. The foremost priority in water policies for Seoul was hygiene at the time. Water-borne diseases such as cholera, typhoid was rampant among those who used untreated, unhygienic water from wells and spring water, costing the lives of many citizens. The dire situation called for a water supply that is stable and hygiene. The first modern water purification plant was built in 1908, and water began to flow through the pipes of the system to
Seoulites every day. The modern system, however, would inevitably displace many water peddlers whose livelihood relied on selling buckets of drinking water to each household. The then operating agency Korea Works Company hired the peddlers to minimize the damage of confusion in the transition to a modern water supply system.
 
1945~1960, Recovery of Purification Centers after Korean War
The 3-year Korean War that broke out in 1950 destroyed most of Seoul’s water supply facilities, including 30~90% of purification stations. Despite the odds, officials did their best to continue operating water supply even during the wartime. A special law was passed that allowed funding for waterworks recovery projects, and timely foreign assistance also played an important role. From 1954 for the following 5 years, thanks to the assistance of the central government and the UN, repair and maintenance projects could take place. Water facility expansion took off in earnest with Guui purification station plant 2 in 1956 which was constructed without relying on any foreign technical assistance. Since then, expansion and repair works continued, resulting in a 3-fold increase in water service per capita from 59ℓ in 1945 to 163ℓ in 1960.
 
1961~1979, Water Facility Expansion
A rapid economic growth of the nation in the 1960s drove industrialization, urbanization, and a surge in Seoul’s population, which in turn inevitably caused an explosive demand for water in the city. To address water shortage, Seoul responded by expanding and upgrading already existing purification facilities as well as constructing additional ones from 1961 to 1979. Seoul also laid out a 10-year plan (1972~1981) to build and expand production facilities. All resources and efforts were geared toward meeting the explosive growth in water demand.
 
1980~1988, Stability in Water Supply
By 1980s more than 90% of residents were supplied with Seoul’s tap water, and the daily water supply per person reached 400ℓ. As was supply itself became quite stable, Seoul focused on building pressuring stations or booster pump stations to reach the population residing in higher altitude as well as upgrading old pipes to reduce leakages.
The water quality control was facilitated by a computer system which made an automatic, remote control possible. Seoul then began channeling its resources and efforts to quality. Accordingly, Seoul established the Water Technology Institute and strengthened water quality standards to deliver high quality tap water to as many people as possible.
 
1989~Present, Seoul’s Tap Water Reborn as ‘Arisu’
Seoul’s tap water is now known as Arisu. Quality of Arisu is maintained through testings for 163 substances as recommended by WHO. All information, from water intake to supply, is disclosed to the public, ensuring public confidence in safety and cleanliness of the water that they are drinking. Having achieved stability in production, Seoul has pushed itself a step further to ensure good taste of the water. To this end, Seoul is working on adopting an advanced water purification system in all of its purification centers by 2015.
 
Clean Water for Everyone in Seoul
Seoul’s purification capacity and service population jumped to an astonishing level: from 1908 to 2013, purification capacity jumped 348 times from 12,500 tons to 4.35 million tons, and its service population jumped by 83 times, from 125,000 to 10.39 million people per day. In fact, the total amount of water used in 2013 was 1,164,636,000 tons in cumulative terms or 3,191,000 tons on a daily average. The astonishing progress was made possible by continuous efforts in upgrading and building new water facilities, which helped resolve water shortage and ensure supply stability from 1998.
Having achieved production stability, the Office of Waterworks at Seoul Metropolitan Government has shifted its focus on quality of water. To this end, Seoul has begun to adopt an environmental-friendly, advanced purification system using the ozone and GCA (Granular activated carbon). The system was first introduced to Yeongdeungpo Arisu Center in 2010 and is expected to be adopted in all purification centers in Seoul by 2015.

Around-the-clock Water Quality Monitoring
Since Seoul utilizes surface water of Han River as its source water, it is paramount that Seoul works closely with the municipalities near the river to most effectively protect its source water from contamination. To this end, Seoul is operating a Han River Watch Group who guards against illegal waste dumping and indiscriminate development in the area. Seoul’s effort is complemented the central government, manifested by the fund created by the Ministry of Environment. Created in 1999, the Han River source water management fund (KRW 3.9804 trillion as of 2011) is used to monitor and improve water quality as well as to support community activities.
Seoul is constantly monitoring and guarding its source water from contamination. For instance, Seoul conducts testings on 41 substances in 31 source water points and 142 substances in 6 intake points on a regular basis. In particular, the automatic water quality meter that can check the algae and phenol levels around the clock is in place. In addition, intake stations are equipped with a biological alert system that utilizes microorganism, algae, water flea and fish. Seoul is also investing in devices that help block oil leaks from penetrating into intake stations. Also, an algae alert system is in place which issues an alert when water temperature exceeds 20°C or when odor-causing materials (geosmin or 2-BIM) is detected in the purification facilities.
 
Guideline for Healthy and Tasty Water
To meet the growing demand for healthy and tasty tap water, Seoul has come forward with a new guideline that includes 3 categories regarding health and 6 categories regarding taste of tap water.
 
Quality Testing on 163 Substances
Today, Arisu undergoes tap water quality tests for 163 substances as recommended by WHO. Water in purification centers are under daily testing while water at faucets of 860 points also undergo stringent monthly testings. Besides, water at 120 water supply sites is tested on a quarterly basis. At purification centers, an automatic water quality monitoring system is in place to check the level of 6 substances. Such multilayered monitoring system keeps Arisu clean and safe.
 
Advanced Purification System
To deliver upgraded, premium quality tap water that satisfies cleanliness, safety, health and even taste, Seoul has adopted the Advanced Water Purification System which strengthens the current purification method by incorporating ozone and granular activated carbon (GAC, or charcoal). The two materials completely remove unpleasant taste and odor caused by algae, disinfection by-products and other micro-organic matters. With the introduction of the advanced system, Seoul can now deliver cleaner, safer water in which minerals are kept intact.
 
Membrane Filtering Purification System
The Ministry of Environment, Seoul Metropolitan Government and private companies joined forces to install an advanced version of filtering system, membrane filtering purification system or membrane integrity test.
Replacing the traditional sand filters, the new system removes contaminant particles in water more thoroughly, contributing to better quality and taste of water for end consumers. The cutting edge, eco-friendly method also eliminates the need for chemicals by 50% and simplifies management which, in turn, saves budget. Seoul’s membrane filters, which are made by 100% Korean technology, are the first of its kind to be introduced in Korea.

Chlorine Re-dispersion Facility
Although chlorine plays an essential role at reservoirs as disinfectant, it comes with unpleasant odor, driving many citizens away from drinking it. To tackle the odor, a small amount of chlorine is dispersed at multiple points, first at purification plants, then at the water supply reservoirs, instead of concentrating all chlorine at purification plants.

Large Reservoirs Ensuring Emergency Water Supply and Constant Water Supply Free of Outage
Reservoir is an important facility in urban water supply because it serves to ensure stability of water supply without outages as well as providing water in times of emergencies, such as power outage. Previously, a direct water supply system was used by which pressurizing stations or purification centers directly supply water to households. However, because the direct system comes with many disadvantages such as waste and instability in supply, Seoul saw the need to shift to an indirect system whereby water is supplied through water reservoirs. Understanding the importance of reservoir, Seoul built a large-scale reservoir through which water can flow naturally to service area. Since 1999, Seoul also turned some of the upper parts of the reservoir into recreational amenities for residents to use anytime they wish.
 
94.4% Revenue Water Rate (RWR)
Revenue water rate (RWR) refers to the percentage of supplied water that is not lost due to leakages or other factors. In other words, high RWR means higher revenue that is earned from the total water produced in the city. To raise RWR, Seoul introduced various measures, one of which deals with replacing old pipes that have traditionally caused water contamination; in fact, by 2013, 13,668km (95.4%) out of 13,034 km of old pipes past their life cycle were replaced with new ones. The remaining 634km of pipes are set to be replaced by 2015. Besides replacement, Seoul also built an additional 1,663km of pipe sized 400~2,800mm.
Seoul also successfully divided its complex water pipeline network into small 2,037 blocks and 100 middle-sized ones, making overall operation very easy and maintenance/repair more effective. With the subdivided system, only a very limited area would be affected during the time of leakage. In addition, emergency water supply and recovery became far easier. Diving the complicated network into smaller units even made it easy to detect which block was experiencing leak and the precise amount of leaks, pushing RWR even further. Seoul also applies a scientific and systematic detection mechanism. Examples include checking minimum flow level night when the use is minimal and a multi-point leak detection.
Seoul is also equipped with a science-based, real time water flow monitoring system. The system enables early detection of leak by checking water volume, pipe pressure on a real-time basis at 443 spots including pipes, pressuring stations, reservoirs.
Such measures helped Seoul to achieve a level of RWR on par with advanced nations in the field of tap water. Seoul recorded 94.4% of RWR in 2013, a 39.2% jump from 55.2% of 1989, which translates into a cost reduction of KRW 4.6 trillion.
 
Water Supply Geographic Information System
In the past, location and property information of water facilities were hand-marked on paper maps. This system caused some staff to unintentionally omit or enter wrong data, compromising accuracy which directly affects analysis, statistics while costing much time and energy overall. To address the issue, Seoul created the Water Supply Geographic Information System that utilizes GIS technology to create a digital database of design and properties information of water pipes, supporting components, and other urban facilities in general. It is an information system comprised of hardware, a software, and an application allowing input, output, and analysis of digital data. Today, GIS is applied to 13,841 km of water pipes, 260,000 valves, 1,991,00 water meters, and 301 reservoirs and pressuring stations. A survey method with satellite-based GPS and the latest tools using absolute coordinates based on the World Geodetic System.

Cheapest Water Bills
Seoul strives to rationalize its business practices to push the water bill down, which can alleviate financial burden on the citizens. To this end, Seoul began outsourcing water metering operations, such as meter reading, to a private enterprise. Furthermore, the city government rearranged agencies working under SMG to streamline the administrative staff and work process while digitizing as much work process as possible, including billing and accounting. The efforts contributed to putting Seoul’s water bills one of the lowest in all cities around the world.
 
Arisu Integrated Information System
The Arisu Integrated Information Center monitors and analyzes all necessary information from water intake, purification, storage, distribution, and faucet quality management, contributing to producing and delivering stable and clean water to Seoulites. This system is capable of collecting and analyzing the operational information of the entire water supply system in real-time basis (6 purification stations and 8 branch offices), all of which used to be managed separately previously. With the center, Seoul is able to respond more effectively in cases of outage, shortage.
 
Seoul Water Now System
Seoul Water Now System is a real-time, automatic water quality assessment and online data disclosure service. The system analyzes water related data (pH, turbidity, residual chlorine, etc.) on 9 categories, and the data comes from automatic readers installed throughout 186 water facilities (6 water intake points, 6 purification stations, 84 reservoirs, 13 pressuring stations, and 77 faucets). The system issues alert or warning depending on how far the current situation exceeds or falls short of the permissible level. Most importantly, the system allows citizens to access up-to-date information on the quality of water via Seoul’s website at http://arisu.seoul.go.kr or phone call (Seoul Mobile Portal Service), etc.
 
Arisu Quality Verification Service
Many citizens trusted the safety of water produced in the purification centers, yet they were hesitant to drink tap water mainly because questionable conditions of pipes or water tanks. To eliminate this mistrust, Seoul adopted the Arisu Quality Verification System that provides free checkup services to citizen who request inspecting agents to visit their houses to verify water quality in their faucets. Households can get free water quality assessment on 5 indicators (turbidity, pH, iron, copper, residual chlorine) on the spot. The faucets that have passed the standard are given a certificate. In case the test results are not satisfactory, 7 additional items such as bacteria and colon bacterium are tested to identify the underlying cause. The information is then relayed to the operators to recommend water tank cleaning, old pipe replacement, etc.
 
Eco-friendly Energy and Renewable Energy
Committed to creating purification centers that pursue low carbon and green growth, Seoul set up a geothermal heating and cooling system in 3 purification centers (Yeongdeungpo, Gwangam, Amsa) and additionally set up PV facilities in Yeongdeungpo and Amsa purification centers. Seoul is currently working to develop a technology that can turn sludge to green energy in order to cut waste treatment cost while enhancing efficiency.
 
Waterworks Research Institute
Seeking to find the best ways to make tap water safe and tasty, Waterworks Research Institut conducts in-depth testing on WHO-recommended 163 substances and discloses the result online to the public on a regular basis. It is working in line with the government’s low carbon, green growth initiative by focusing on technology development. Another main responsibility of the institute is fostering experts, facilitated by its 16 different training programs.
The institute has achieved outstanding outcome, some of which include the membrane separation technology, eco-friendly ozone process, anti-rust pipe among many others. So far 8 patents have been awarded to the Waterworks Research Institute. This leading institute is at the forefront of sharing its accumulated knowhow and insights to help other businesses in water sector.
 
Bottled Tap Water
Seoul began producing bottled tap water in May 2001. The decision was made to promote Arisu to the wider general public by making it more accessible to people, and use as relief items in case of emergency. Currently, the production center for bottled Arisu is located in Yeongdeungpo facility that boast production capacity of 86,000 bottled Arisu daily. Since 2001, both demand and supply grew gradually for the bottled water; In fact, it was particularly useful for those affected by droughts in Korea and other natural disasters that hit many parts of the world. For instance, Seoul offered bottled Arisu to victims of the 2008 earthquake in Sichuan, China in 2008, the typhoon in Kaohsiung, Taiwan in 2009, and the earthquake in Japan in 2011. In addition, Seoul also sent bottled Arisu during Beijing Olympics. Seoul actively promoted its Arisu to the global community at the 2010 Shanghai Expo in its own pavilion. Clearly, Arisu is becoming a well-known tap water around the world.

Winner of the United Nations Public Service Awards, 2009
The United Nations Public Administration Network (UNPAN) awarded Seoul Water Now System and the Arisu Quality Verification System the highest recognition for its transparency and reliability of water supply service. In particular, Seoul was recognized for Seoul Water Now System, an electronic water quality service that allows citizens of Seoul to access up-to-date information on the quality of water supplied to their homes as well as the Water Quality Verification System, a free inspection service delivered to households upon their request.
 
Global Water Industry Innovation Award, 2010
International Water Association (IWA), the world’s largest water-related association composed of 85 countries, awarded Seoul the Project Innovation Award in June 2010, and again in October 2010 for Seoul’s premium Seoul tap water. It recognized Seoul’s highest RWR in the world, management improvement, and its focus on paradigm shift from safety to taste of water.
 
2010, International Business Awards
Seoul was chosen as the New product & Product Management and Product Development Department of the Year by Stevie Awards. Inc in recognition of creativity and management that led to the world’s highest RWR and business innovation.
 
2012 National Sanitation Foundation (NSF) Certification
Seoul’s Arisu acquired the NSF certification for satisfying water quality testing of all 167 substances. The passage demonstrates that Arisu is qualified as drinking water in the United States, proving the quality of Arisu worldwide.