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  9-04. Sewage Treatment   Network   Screen Room

    1. Welcome to the Seonam sewage treatment plant.     It is a pleasure to have you with us here today.

Water of which the history began with the birth of the earth is both the origin of all lives including humans, and a necessary and important source of human life in the past, present and future.
  2. Water grows flowers and trees, with its dewdrops, ripens crops and fruits, and makes us enjoy the joy and richness of harvest in the autumn.
And it quenches the thirst of man, and is used not only in cooking but also in transportation of goods and productive activities in industry.
    3. But water we use always becomes polluted. As the amount of water used increased by population increase, industrialization and urbanization after 1960's, the amount of pollutants grew and water pollution. become more serious.
Therefore when we return used water to nature, we must purify it.   It is the sewage treatment plant that is in charge of purifying contaminated water.
  4. Leaves in the forests die, fall on the earth and rot when autumn comes. The rotten leaves contaminate brooks in the forest with organisms.
But, while the brook flows down ward, it becomes clean naturally. This is called self-purification.
This phenomenon occurs because microorganisms in water decompose the organisms to obtain nutrients and energy needed for growth.
    5. Using this principle, sewage treatment treats a lot of sewage in a short time, by cultivating many microorganisms.
This sewage treatment method is called conventional activated sludge process. Because it does n`t use chemicals, it is used widely as a safe method without secondary pollution.
  6. Seoul city treats sewage by the conventional activated sludge process, and has constructed sewage treatment plants to prevent water pollution of Han river, which is the lifeline of the people and driving force of economic development.
In 1976 when economic development was at its height, Chong-Gye Chun sewage treatment plant with a capacity of about 150,000tons of sewage a day was first completed in our we country and began modern sewage treatment.
    7. After that, Seoul city continued to construct sewage treatment plants, and now there are four sewage treatment plants in Jung-Rang, Tan-cheon, Ga-Yang, and Nan-Ji.
With Han-river Complex Development, Seoul city installed sewer facilities on the river banks and made water used by Seoul citizens flow into the four sewage treatment plants.

8. The capacity of sewage treatment facility was 150,000ton a day in 1976, and a total of 3,710,000ton in 1995.
And as the four sewage treatment plants are enlarged in preparation for increased sewage amount, they will have 5,080,000ton capacity in 1996, 5,560,000ton in 1997, and 7,040,000ton by 2001, not only to treat sewage completely but also to heighten our quality of life and hand over clean and pleasant Han-river to our descendants

    9. The place where you have come to see is the Seonam sewage treatment plant.   Seonam sewage treatment plant is located is Ma-gok dong of Gang-So Gu, Seoul, Korea
And has a total area of 1,065,000 square meters with 2,000,000 ton sewage treatment facility and 2,000 ton septic tank sludge treatment facility and is operated day and night for 24 hours in 3 cycles.
  10. It's treatment covers 9 districts and a city, namely Tongjak, Kwanak, Young Deung Po, Kuro, KumChun, Kangsu GU, and parts of Kangnam, Seocho GU and Kwang Myung city.
Its main facility are water treatment facility which purify sewage and discharge it to the Han-river, and sludge treatment facility handling wastes produced in water treatment facilities. Now let us look into the treatment.
    11. process in our sewage treatment plant.   The sewage produced in each house flows into grit chamber through sewer line .
The role of grit chamber is to sink sands mixed in the sewage to eliminate them, and to prevent blocking and trouble in all devices in the next process, eliminating such matters as vinyl, splinters, plastics and luminum by screens installed before and behind the grit chamber.

12. Because the sewage produced in each house flows naturally through a long sewer line, its surface is much lower when it comes to our treatment plant.
We use inflow pumps to draw it up to the height.
The water drawn up by pump is sent to primary settling tank.

    13. The primary settling tanks makes sewage stay for about 2 hours and settles suspended solid sinkable.
At this time pollutants like biochemical oxygen demand and suspended solids are eliminated to about 30 - 35%.
The water from the primary settling tank is sent to aeration tank.

14. Aeration tank is the most important in the process of sewage treatment and are the place to decompose most pollutants.
Because aeration tank cultivates aerobic bacteria in high density, it has a tinge of brown.
And it inspires air 24 hours a day using blowers.

    15. While staying in aeration tank for about 6 hours, the water inflow from primary settling tank contacts micro organisms in aeration tanks and the microorganisms decompose pollutants.
At this time micro organisms, are too small to be seen, but they exist in small particles, making flocs flow into final settling tank mixed with pured water.

16. After final settling tank makes the mixture from aeration tank, stay for about 3 and a half hours and sinks micro organism flocs, they return flocs to aeration tanks to provide microorganisms for aeration tanks, and remaining micro organism flocs are sent to thickener as excess sludge.
And purified water flows to Han-river, and part of it is re-used as industrial water and water for sundry use in our sewage treatment plant after filtration.
At this point , the outflow water quality is under 20ppm in BOD with more than 90% of inflow water pollutants eliminated.

    17. The waste produced in water treatment facilities is treated in sludge treatment process.
In the first place the waste of raw sludge sunk in primary settling tanks and sent to thickener by pumps.
Thickener makes sludge stay for about 12 hours and helps raise digestion and dehydration efficiency in the next process, making it thickened sludge in 96% water content by gravitation.

18. Thickened sludge is sent to digestion tanks.
The goal of digestion is to prevent secondary decomposition possible in landfill, reducing and stablizing sludge by decomposition of organism in sludge using anaerobic bacteria.
sludge in digestion tank stays in 35℃ for about 35 days, and in digestion process, methane gas is produced as a by product.

    19. The methane gas is used for fuel of generator and boiler, after eliminating sulfur by means of desulfuration device.
Digested sludge is sent to dehydrators after being thickened in about 95% water content in secondary digestion tanks.

20. The dehydrators are in a belt press type, they dehydrate sludge and make it a cake in about 75% water content, the sludge cake is sent to Kimpo landfill by truck.
Our Ga Yang sewage treatment plant has septic tank sludge treatment facilities in addition to sewage treatment.

    21. Every house has a septic tank to treat feces and urine, and it shows efficiency when cleaned once a year.
At this time waste collected by truck is called septic tank sludge.
It is sent to digestion facilities in the sewage treatment plant after filtering adulterations and being thickened in septic tank sludge treatment facilities.

22. And the upper part of the thickener is sent to the grit chamber in sewage treatment plant and is mixed and treated with sewage.
The above treatment facilities, can have an unpleasant odor because they treat contaminated sewage.
The odor is eliminated in soil-deodorization filters after transport by ducts and blower.

    23. The central control system in the head quaters of Seonam sewage treatment plant watches the operation state of each spot 24 hours a day, automates the treatment facilities, and records, stores and controls all data about treatment state and applies them to efficient sewage treatment.
At the laboratory, we analyze water quality in each process precisely, and this makes assurance double sure in sewage treatment.

24. Besides, the facilities in sewage treatment plant is used as a nature studying place for students and citizens And as conference room, tennis court, and park in the sewage treatment plant are open to neighboring residents, they are used as convenient facilities.

    25. Water is the most valuable and most important source of life in the world. But contaminated water does harm to man and destroys natural environment.
Therefore to prevent water pollution when we pour out sewage we must mind the followings.

26. First, adulterations like splinters and vinyls should not be then away in a ditch. These adulterations not only block ditches, but also cause trouble in devices.
Second, oils such as gasoline and thinner should not be poured in a ditch, Oil causes explosion and hinders sewage treatment because it blocks growth of microorganism.

    27. Third, food refuse should not be thrown away into dustbins before squeezing water from it and detergent powder should be used in optimum quantity.
Food refuse and detergent are causes of worsening water quality because they are not decomposed easily.
Fourth, sewage amount should be reduced by saving water.
If a person saves 20ℓ of water a day, we can save 730 billion won in national budget including 150 billion won for sewage treatment spending and, 580 billion won for tap water producing spent in a year.

28. Our country is famous for beautiful mountains and rivers from ancient times. It is our duty to keep the valuable water clean and hand it down to our descendants.
·"Water is our valuable source"
·"But pour it out, it becomes sewage"
·"Preserve clean environment by saving water"
Thank you.

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