Status of construction and operation of large wastewater treatment plants in South Korea

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Wal. ScL Teclt. Vol. 33. No. 12. pp. 11-18. 1996. Copyright C 1996 IAWQ. Published by Elsevier Science lid Printed In Great Britain. All rightl reserved. 0273-1223196 SI"00 + 0-00

Pergamon

PH: S0273-1223(96)00452-O

STATUS OF CONSTRUCTION AND OPERATION OF LARGE WASTEWATER TREATMENT PLANTS IN SOUTH KOREA I. S. Kim*, 1. Y. Ryu** and J. 1. Lee*** • Department of Environmental Science and Engineering. Kwangju Institute of Science and Technology. Kwangju, Korea •• Sewage Treatment Division, Water Quality Management Bureau. Ministry of Environment. Seoul, Korea ... Depanment of Environmental Engineering, Chonnam National University, Kwangju. Korea

ABSTRACT The history of wastewater treatment in Korea began in 1976 with construction of Chongke sewage treatment

plant in the cuy of Seoul. At present. there are 48 large municipal sewage treatment planlS for 42 cities with a total treatment capacity of 7.841.000 m3/d. This indicates that the population receiving sewage treatment is 42% of the total nallonal population. The government IS planning to extend the populallon receiving wastewater treatment to 73% by the year 1997. It turned out that activated sludge processes are the most popular type (39 out of 48 plants) for the treatment of mUnicipal wastewater. The present lawful effluent criteria for BOD. COD. and SS from large municipal wastewaler treatment plant are changing from 30 mgll. SO mgll. and 70 mgll. to 20 mgll. 40 mgll. and 20 mgll. respectively, by the year 1996. Regulation of the total concentrations of nitrogen and phosphorus are also added as 60 mgll and 8 mgll. respectively. The enactmenlto control the nutrienl concentrations in the lake and pond is Inevitable for the protection of drinking water in South Korea. Copyright ~ 1996 IAWQ. Published by ElseVier Science Ltd.

KEYWORDS Large wastewater treatment plant; Korea; effluent criteria; construction; environmental law; operation; sewerage network.

INTRODUCTION Attention to environmental protection has been greatly increased with rapid economic development in Korea. At the same time, rapid industrialization has caused severe water pollution since 1960 and this has required an enonnous amount of funding for the construction of municipal wastewater treatment plant within a short period of time. Several regulations, acts and laws for environmental protection and reclamation were put into effect in the 1970s. Treatment of night soil and wastewater generated from each industry was the major target during this period. In the 1980s, main stress has been put on the construction of publicly owned large municipal sewage treatment plants and treatment plants for large industrial complexes. The paper presents the status of II

I. S. KIM et al.

12

construction and operation of large municipal sewage treatment plants in Korea, and legal aspects on environmental conservation and reclamation. Problems and difficulties with regard to the management of plant area are also discussed. CONSTRUCfION OF SEWAGE TREATMENT PLANT Wastewater discharge. Wastewaters can be classified as municipal sewage generated from cooking, washing, shower, flushing toilet and cleaning, wastewaters generated by business activities from office, shopping complex, and hospital and industrial wastewaters from manufacturing factories. Wastewaters discharged from small point sources like mining areas, and some other non-point sources like rural agricultural areas were not considered as serious problems in the past so that statistical calculation was not included in this study. However, attention to non-point source pollution control is increasing in these days. Population increase and movement into cities have doubled for the past thirty years. Rapid increase of the water use per capita per day and the distribution of flush toilets contributed not only to the total wastewater generation but to the pollution loading. Table I indicates that total wastewater generation increased to almost double from 9.4 million m 3/d in 1986 to 17.1 million m 3/d in 1991 over ten years. Table I. The variation of wastewater generation (The Ministry of Construction, Korea, 1988) (unit: 1,000 mIld) Year

1986

1991

1996

2001

2006

Municipal wastewater

7,276

10,100

13,226

16,130

19,000

Industrial wastewater

2,080

2,909

3,831

4,852

6,000

Total

9,356

13,009

17,057

20,982

25,000

ConstructIonal status. The Chongke municipal sewage treatment plant at Seoul was the first one built in 1976, and treats septic tank effluent by primary treatment. Sewage treatment plants are categorized into three groups. The first group is the large municipal sewage treatment plants (300,000-1,500,000 m 3/d) which have a pump station collecting the wastewater from two or three wide discharge areas. The second group is medium sized plants treating the wastewater collected from two or three small cities or counties. The last group is the one which is relatively small compared to the previous two groups having just one plant in one area. Table 2. Process type and size for large sewage treatment plants by the year 1993 (The Ministry of Environment, Korea, 1994)

Process S or smaller

5-10 Io-SO 50-100 100-SOO

Sedlmen· tat ion

Oxidation Ditch

Anaerobic Lagoon

Activated Sludge

Extended Aeration

I

SOO or larger

2 2

Total

4

5 10 5

Total 2 6

13

5

16

2 39

RBC

2

18 4 48

By 1993, there were 48 large municipal sewage treatment plants for 42 cities having the total capacity of 7,841,000 m3/d (Table 2). Of those, four plants are operating at present time (1993) with only primary

Large wastewater trealment plants in South Korea

13

treatment and are going to extend to secondary treatment in 1995. Table 2 also shows the process type and size for 48 large municipal sewage treatment plants. 39 plants out of 48 are activated sludge processes that are the most popular type. Table 3 shows details of each sewage treatment plant in Korea with information on construction period. population, and discharge river. The map of Figure 1 illustrates the number of sewage treatment plants and treatment capacity based on the four large receiving rivers. Table 3. Sewage treatment plants in Korea (1993) City

Plant name

Const.

Capacity

Population

(I0'm'/d)

(thousand)

Process

Dischage

3,500

A.S.

river

Period Seoul

Pusan Daegu

Jungyang

'70-'76

150

'75·'79

210

'83·'87

700

Tanchon

'83·'87

SOO

1,729

A.S.

Gayang

'87·'87

1,000

4,622

A.S.

Nanji

'83·'88

SOO

2,000

A.S.

Suyoung

'86-'90

230

1,220

A.S.

Janglim

'86·'90

300

638.S

A.S.

S

Talseu

'83·'87

2S0

S97

A.S.

2

S

Shinchon

'87·'92

3S0

1,081.8

A.S.

2

Inchon

Gagya

'87·'91

190

691.S

A.S.

S

Kwangju

Kwangju

'8S·'90

300

122.S

A.S.

4

Daejon

Daejon

'83·'90

ISO

1,086.2

A.S.

3

Anyang

Anyang

'87·'92

ISO

8S7.S

A.S.

Euijeungbu

Euijeungbu

'83·'87

60

227

A.S.

Seungnam

Seungnam

'87·'93

340

S40

A.S.

Goyang

llsan

'90-'92

13S

80

A.S.

Kwachon

Kwachon

'83·'86

30

72

A.S.

I

Ansan

Ansan

'81·86

121

267

A.S.

S

Kuri

Kuri

'8S·'89

SO

101.7

A.S.

I

Yongin

Yongin

'89·'92

18

SO

A.S.

I

Kwangju

Kwangju

'90·'92

II

46.2

A.S.

I

Namyangju

Hwado

'90·'92

10

29

A.S.

I

Yangpyong

Yangpyong

'90·'92

7.8

14.1

A.S.

I

Chunchon

Chllllchon

'8S·'89

7S

149.8

A.S.

I

Cheungju

Cheungju

'87·'91

ISO

39S

A.S.

3

Cheungwon

Muneui

'8S·'91

I

2.1

E.A.

3

Poun

Poun

'90·'92

6

19

A.S.

3

Youngdong

Youngdong

'90·'92

8

18.3

A.S.

3

Danyang

Danyang

'90·'92

S

12.S

E.A.

I

14

I. S. KIM el al.

(continue) Const.

Dischage

Capacity (lO'm1/day)

Population (thousand)

Process

river

18

40

A.S.

3

City

Plant name

Okchon

Okchon

'90-'92

Chechon

Chechon

'89-'93

3S

144

A.S.

Chonju

Chonju

'83·'90

100

SIS

A.S.

S

Naju

Naju

'90-'92

22.S

4S

A.S.

4

Donggwangya

Gwangyang

'90-'92

S.S

17

A.S.

S

Kumi

Kumi

'81-'87

124

210.2

A.S.

2

Kyongju

Kyongju

'7S·'78

2S

1412

A.L.

S

Ulsan

Hoiya

'87·'89

32

3S.S

A.S.

S

Youngchon

Youngchon

'90-'92

2S

49.6

A.S.

2

Uljin

Onjung

'92·'93

6.S

7.8

A.S.

S

Chilgok

Oegwan

'92-'93

20

2.3

A.S.

2

Chinju

Chinju

'88·'93

110

260

A.S.

S

Cheju

Cheju

'87·'93

60

192

A.S.

S

Seugwipo

Seugwi

'8D-'82

S

S.6

A.S.

S

Hwasun

Hwasun

'86-'90

2

12

A.S.

S

Period

ng

A.S. : Activated sludge E.A. : Extended aeration A.L. : Anaerobic lagoon Dischage river : I. Han River 2. Nakdong River 3. Kum River 4. Yongsan River 5. The others Table 4, Yearly planning for expansionlupgrading and new construction (The Ministry of Environment, Korea, 1994) Expansion or Upgrading

Year of

Complet 1994 1995 1996 1997 Total

Plant 7 3 5 I

16

Capacity 904 489 2,154 250 3,797

Total

New construction Plant 15 22 14

Capacity 1,151 1,994 1,190.5

Plant 22 25 19

51

4335.5

67

I

Capacity 2,055 2,447 3,344.5 250 8\32.5

Table 4 presents the future planning of plant expansion and new construction with the year of completion during the period 1994 to 1991, 16 plants are going to be expanded or upgraded, and S I plants are going to be newly built. Extra expansion of the treatment capacity is increasing from 2.1 million tons per day in 1994 and 8.1 million tons per day by 1991. When we add the extra capacity to the existing plant, the total capacity for wastewater treatment will be 9,940,800 m3/d by 1994, 12,381,800 m3/d by 1995, and 15,132,300 m 3/d by 1996.

Large wastewater treatment plants in South Korea

Figure J. Sewage treatment plants based on 4 large receiving riven in Korea

Table S. Population receiving sewage treatment (The Ministry of Environment. Korea, 1994) Year

'89

'90

'91

'92

'93

'94

'96

'97

Total Pop.

42T44

42867

43268

43668

44056

44453

45248

45642

Applied Pop.

11800

13289

14144

16117

17258

19397

29411

33350

29

31

33

37

39

44

65

73

Population (Thousand) (Thousand)

'Treatment (%) i. (Population

receiving treatmentffotal population) x 100

I. S. KIM et al.

16

Total population in Korea was 42.1 million in 1989, and increased to 44 million by 1993. It is expected to be 45.6 million by 1997 (Table 5). The percentage ratio of population linked to wastewater treatment out of the total population has changed from 29% in 1989 to 39% in 1993. The ratio is expected to rapidly increase to 73% by 1997 which is the same value as the USA in 1986. OPERATION The wastewaters have been collected in the past by a combined system and conveyed to the treatment plant. These wastewaters have generally low organic strength than the design flow because the wastewaters are primarily treated in a septic tank. In this case. suspended solids contained in the wastewaters are settled down in the network pipe due to the slow flow velocity during dry period, and then washed off by the high rainfall intensity. These are discharged into the receiving water body directly without being treated in the treatment plant. However, sewage treatment plants connected to the separate system perform well to produce the designed effluent criteria. Table 6 shows the operational results of treatment plants. The concentration of BOD and SS for the influent and effluent are specified based on the combined. separate. and mixed system. Table 6. Operational results of municipal wastewater treatment plants of 1992 (The Ministry of Environment. Korea. 1988) Concentration (Influent, mgll) BOD SS Combined 44.3-190 55.6-220 (118) (137) System(A) 14 72-251.5 41-253.7 Separated (156.2) (139) System(B) 6 76-142.9 82-180.1 (106) (128) 6 A+B 44.3-251.5 41-253.7 Total 26 (123) (135) The numbers in parenthesis represent the average value Plants

Concentration (effluent, mgtl) BOD SS 9.4-38 4.3-41 (17) (17) 3.2-75 6.4-78.3 (30) (32) 11.5-64 15.4-65 (30) (30) 3.2-75 4.3-78.3 (23) (23)

Average concentrations of BOD and SS. (numbers in parenthesis) flowing into the plants are 123 mg/l and 135 mg/l. respectively. The treated concentrations are 23 mg/l for both BOD and SS showing 81.3% and 83% of removal efficiency. These concentrations meet the legal effluent criteria well but, are not low enough to meet the criteria for 1996 (Table 7). Table 7. Effluent criteria from municipal treatment plant (The Ministry of Environment. Korea. 1994) Parameter

BOD

COD

SS

1995

30

50

70

1996

20

40

20

Year

T-N

T-P

60

8

The permissible effluent concentration from municipal sewage treatment plants becomes more strict in 1996. In addition to the more strict effluent criteria. obligatatory nutrient removal of nitrogen and phosphorus is also legislated. The enforcement of the environmental conservation law on the regulation of the total nitrogen and total phosphorus will also be effective on January I, 1996.

Large wastewater trealment plants in South Korea

17

Average maintenance cost per cubic meter of wastewater for the operation of sewage treatment plants is 46 cents (Table 8). Table 8. Management cost of sewage treatment plant of 1992 (The Ministry of Environment, Korea, 1988) Number of plant

Quantity of Treatment (1,000 ml/d)

26

2,654,951

Total Cost DollarNear)

(1,000

122,519

Cost perm' (Cent) 46

ENVIRONMENTAL LAW AND REGULATION There are about ten regulations and laws administered by five governmental departments regarding the control of wastewaters and night soil. Sewer Network Control Act, Water Quality Protection Act, and Act for Municipal Sewage, Night Soil, and Livestock Farming Wastewater Treatment are the major three regulations. The Sewer Network Control Act was made in 1966 based on the Urban Planning Law, and controls the planning, construction, and maintenance of sewer network. Determination of the effluent criteria from municipal sewage treatment plants, effluent control facilities from industry, and construction of the final treatment plant for industrial complexes are controlled by the Water Quality Protection Act made in 1990. This Act is based on the Environmental Protection Law (1990) which is made for overall environmental conservation of water, air, noise, and vibration. The Act for Municipal Sewage, Night Soil, and Livestock Farming Wastewater Treatment legislated in 1991 is based on the Waste Management Law (1982) and is controlling regulations relevant only to the water matrix. It is necessary to reorganize these complex laws and acts in a systematic fashion to operate efficiently. FUTURE NEEDS The analysis of the statistical results on the construction and operation of large municipal wastewater treatment plants reveals some problems and difficulties as follows. I. As mentioned above, reorganization or updating the laws and acts is badly needed in order to operate the regulations systematically for the application and control of pollution problems.

2. The amount of wastewater will increase due to the improvement of life style and industrialization. Construction of more treatment plants and upgrading of the performance of existing facilities is required. 3. The existing length of sewerage network is about 50% of that required, and most of them were designed for rainfall flow in the past not for the separate transportation of wastewater. Construction and renovation of pipes is needed. This should be revised on a regular basis at a certain period of time simultaneously with urban planning. 4. The operation of wastewater treatment plant needs various experts from civil, mechanical, electrical, and environmental areas. Regular training and education are necessary for the improvement of engineers' skill. 5. The charge for expense of treating wastewater is only 30 to 50% of clean water usage. Costs for maintenance and repair should be maintained reasonably by increasing the waste taxes.

I. S. KIM ~t al.

18

SUMMARY There are 48 large municipal sewage treatment plants for 42 cities having the total capacity of 7,841,000 m3/d in Korea at the present time. This indicates that the population receiving sewage treatment is 42% of the total national population. Population receiving wastewater treatment will be 73% by 1997.39 plants out of 48 are activated sludge processes; the most popular type. The lawful effluent criteria for BOD, COD, and SS for large municipal wastewater treatment plants are changing from 30 mgll, and 70 mgll to 20 mgll. 40 mgll. and 20 mgll, respectively, by 1996. Total concentrations of nitrogen and phosphorus are also going to be regulated as 60 mgll and 8 mgll, respectively. An enactment for controlling the nutrient concentrations in the lake and pond is inevitable for the protection of drinking water resources.

REFERENCES The Ministry of ConslIUction, Korea (1988). Study on th~ D~t~rmination 01 Strat~gic Dir~ction 01 S~w~rag~ N~twork. The Ministry of Environment. Korea (1994). Study on th~ Combin~d Tr~atm~nt of Night Soil. Uv~stock Farming Wast~water. and S~ptic Tank EfJlu~nt in Municipal Wast~WQtu Tr~atm~nt Plant. pp. 28-41. The Ministry of Environment, Korea (1994). Manual 01 Environm~nt, pp. 120-127.