World-class water purification system
To deliver upgraded, premium-quality tap water to all citizens of Seoul, the Office of Waterworks has adopted the “Advanced Water Purification System” after years of thorough preparation. As we continue to expand the service, all households in Seoul will be provided with tap water treated by the advanced water purification system by 2015.
The system strengthens the current purification method by incorporating ozone and granular activated carbon (GAC, or charcoal), which perfectly remove unpleasant taste and odor caused by algae, disinfection byproducts, and other micro-organic matters. With the introduction of the advanced system, Seoul can now deliver cleaner, safe water in which minerals are kept intact.
Overview of the Policy
<< Adopting an advanced water purification process that utilizes ozone and activated carbon
- Ozone can effectively eliminate substances that cause unpleasant odor, taste, disinfection byproducts, and microorganisms.
- The GAC (granular activated carbon) process can reduce materials that cause unpleasant taste and odor.
Recently, the unpleasant odor caused by algal bloom – one of the side effects of climate change -- and unexpected presence of unknown organic matter in tap water gave rise to concerns among the people. To deliver the finest-tasting water that is free of unknown matter, we needed to adopt a new, more advanced water purification system that can eliminate unknown organic matter and enhance taste at the same time.
Process of Policy Implementation
• 2007 : A plan to adopt the “Advanced Water Purification Facility” was formulated.
• 2010 : The construction of the advanced water purification facility was completed in the Yeongdeungpo purification center (450,000㎥/day).
• 2012 : Construction was completed in the Gwang-am purification center (700,000㎥/day).
• 2014 : Construction is set to be completed in Gangbuk, Amsa by October and Guui by December (3.2 million ㎥/day).
• 2015 : Construction is set to be completed in Ttukdo (3.8 million ㎥/day).
Details of the Policy
Seoul’s water purification plants for Arisu adopt the Advanced Water Purification Facility.
To provide premium Arisu to all Seoulites, we have been making aggressive investments; In fact, from 2007 to 2015, 528.5 billion won was spent on constructing advanced water purification facilities in 6 centers (capacity of 3.8 million m/day) and upgrading the existing purification plants in Seoul. The facility utilizes granular activated carbon and ozone on top of the standard purification process. The first construction was carried out in March 2007 in Yeongdeungpo, and the second one, in Gwang-am in 2014. The same facilities will be built for Amsa, Gangbuk, and Guui by the end of 2014 and Ttukdo by 2015.
We also adopted the “Ubiquitous Process Management System,” which incorporates IT to control the entire process automatically by computer.
Process of the Advanced Water Purification System
Tap water is provided to households after 6 different processes: mixing (blending), flocculation/coagulation, sedimentation, filtration, ozone treatment, and granular carbon treatment. Water taken from the intake stations go through the following steps before reaching the reservoirs:
• Intake station: Water acquired from Han River’s intake stations is released by pumps.
• Pre-chlorination: This process disinfects source water in advance to kill bacteria and improve water quality.
• Mixing basin: Source water and purifying chemicals, or coagulants, are mixed together in the basins.
• Coagulation station: Small impurities in the water, which are mixed with coagulants, are condensed into larger particles or lumps.
• Sedimentation station: Big, condensed lumps are deposited and allowed to settle.
• Filtering station: Fine particles that did not settle in the previous step are now filtered.
• Advanced water purification: The strong oxidation power of ozone and adsorptive power of GAC used in this process produce cleaner, safer water.
• Post-chlorination: Chlorine is added to the water at this stage to eliminate any source of contaminants and make the effect of disinfectants reach the faucets.
• Reservoir: The purified water is stored here.
• Pump: Purified water flows to reservoir or households by pump.
• Discharging reservoir: Water is stored at a high location temporarily so that it can be delivered to each household in a stable manner.
Know-how & Insights
The Office of Waterworks adopted the “Ubiquitous Process Management System,” which incorporates IT to control the entire process automatically by computer. The “Advanced Water Purification System” -- which utilizes ozone and GAC (granular activated carbon) -- ensures the safety and taste of tap water.
The system allows us to protect tap water against any possible unknown organic matter that may contaminate water and against any change in source water.
Policy Outcome & Evaluation
GAC absorbs and removes taste and odor from the water as well as unknown organic matter. Therefore, adding GAC can reduce the use of chlorine by up to 30~50%.
Because of its excellent disinfection and oxidation qualities, ozone is widely used for drinking water treatment -- especially to remove disinfection byproducts and remaining dissolved organic matter -- far more effectively than the traditional method.
This “Advanced Water Purification System” completely eliminates sandy or moldy taste caused by algal bloom. In fact, its effectiveness and safety were proven during algal blooms in Han River during the cold days of Nov. 2011 and warmer ones in August 2012; equipped with the system, the Yeongdeungpo purification station was found to have removed all algae and other organic/inorganic matter.
Applicability of the Policy
Areas subject to high level of industrialization, contamination of source water, algal blooms due to climate change, and/or concentrated use of agricultural pesticides can adopt the “Advanced Purification System” to eliminate concerns over the compromised quality of source water.
What are the greatest strengths of Seoul’s “Advanced Water Purification System”?
With the standard purification system, materials that give rise to odor and taste issues cannot be easily eliminated. The advanced purification system remedies this shortcoming by incorporating ozone and GAC and advanced oxidation process. The additional processes ensure that all odor/taste-causing materials are completely removed from the water including the remaining antibiotics and micro-organic matter. In other words, this system is an effective prevention mechanism to ensure thorough water treatment.