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Location, Water Quality Monitoring Points of Dong Nai River Basin



Regular monitoring will help water resources and environmental managers make appropriate adjustments for more sustainable development.

The results of monitoring the water quality of Dong Nai River are shown in Table 3.3 with actual measured values ​​in 5 years from 2011 - 2015. Based on those actual measured values, we compare them with the allowable limits (GHCP) of Table 3.1 to determine whether the river water is polluted or not.

Table 3.2. Locations and water quality monitoring points in Dong Nai river basin


TT

Symbol

Monitoring location

Monitoring point

1

DN1

Upstream of Dong Nai River

Nam Cat Tien Ferry Terminal

2

DN2

Midpoint of Dong Nai River

Thien Tan Pumping Station

3

DN3

End of Dong Nai River

Red Light

4

SG1

Upstream Saigon River

Tha La Bridge

5

SG2

Midpoint of Saigon River

Ben Suc Bridge

6

SG3

End of Saigon River

Tan Thuan Port

7

SB1

Upstream of Be River

Thac Mo Lake

8

SB2

Midpoint of Be River

Phuoc Hoa Lake

9

SB3

The end of the Be River

Be River Estuary

10

VCD1

Upstream of the Dong Nai River

Go Chai Bridge

11

VCD2

Midpoint of the Dong Nai River

An Ha - VCĐ canal confluence

12

VCD3

End of the river

Dong Nai River

Long Dinh Industrial Park

- Long Cang

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Table 3.3. Results of monitoring water quality of Dong Nai River


Station

Year

Parameter

pH

BOD5

COD

DO

TSS

DN1

2011

6.9

1

4

5.5

50.5


2012

7.2

6

11

7.54

72


2013

7.43

7

13

6.86

58.9


2014

8

6

9

7.9

35


2015

6.9

4

7

7.66

35

DN2

2011

7.2

3

12

5.5

22.5


2012

7.4

5

8

6.56

52


2013

7.37

7

13

5.74

41


2014

7.5

7

13

5.4

149


2015

6.86

9

15

5.74

54

DN3

2011

6.9

12

29

4.6

23


2012

6.9

27

54

4.18

137.5


2013

7.05

7

16

4.34

71


2014

7.5

6

10

4.3

59


2015

7.04

6

10

4.12

49

SG1

2011

6.7

16

29

5

44


2012

6.8

16

24

4.91

141


2013

6.93

6

10

6.62

36


2014

7.4

4

7

4.7

68


2015

6.87

5

8

6.65

52

SG2

2011

5.9

2

4

4.3

83


2012

6.7

10

19

6.2

60


2013

6.87

5

13

4.04

54


2014

6.7

6

10

4.1

95


2015

6.51

4

6

4.11

32


SG3

2011

7

3

12

2.8

104.5


2012

6.9

30

56

3.69

127


2013

7.15

8

16

1.25

19


2014

7.2

9

17

2.7

21


2015

6.79

6

9

4.17

60

SB1

2011

6.9

3

11

5.5

85


2012

7.5

8

14

6.5

79


2013

7.49

6

13

6.82

58


2014

7.3

5

8

6.7

127


2015

6.68

10

17

7.13

250

SB2

2011

6.9

3

9

5.7

31.5


2012

7.4

4

7

6.03

78.5


2013

7.24

4

7

6.09

22


2014

7.4

5

9

7.9

104


2015

7.15

3

6

7.45

48

SB3

2011

7.1

2

8

5.8

41


2012

7.4

5

7

6.71

52.5


2013

7.28

5

15

6.57

41


2014

7.7

5

9

6.8

53


2015

6.78

5

8

7.38

126

VCD1

2011

6.6

8

17

2

33.5


2012

6.9

25

42

2.39

174.5


2013

6.75

4

10

1.54

117


2014

6.9

5

8

2.8

65


2015

6.57

7

10

1.95

175

VCD2

2011

4.2

12

25

3.7

5


2012

4.9

7

15

4.62

7.5


2013

5.3

8

13

3.56

4



2014

6.9

7

10

3

71


2015

5.62

4

6

4.65

15

VCD3

2011

4.8

19

67

3.2

3.5


2012

6.3

9

20

3.78

29


2013

6.45

7

17

2.4

13


2014

6.3

5

9

4

22


2015

6.32

3

6

2.62

12

GHCP


6 - 8.5

6

15

≥ 5

30


3.1.2.1. pH

There are many parameters to evaluate the quality of river water, in which pH is considered one of the important parameters to evaluate the hardness of water, the ability to corrode in assessing the level of water pollution. pH represents the content of hydrogen ions H + which determines the alkalinity or acidity in river water. Because the nature of pH represents the acidity and alkalinity in water, the actual measured value in water lower or higher than the allowable limit is not good for aquatic organisms. In fact, when using river water for domestic purposes or as a habitat for aquatic species, pH assessment is very important because it is directly related to survival and development.

According to the analysis results of pH concentration at 12 monitoring points in 5 years, it shows that the pH of river water in the basin is basically within the allowable limit, from 6 - 8.5. Particularly at monitoring points VCĐ3 in 2011, SG2 in 2011 and VCĐ2, 4/5 years the pH was less than 6 (2011, 2012, 2013, 2015). The results of pH concentration analysis are shown in Map 3.1.




3.1.2.2. Biochemical oxygen demand (BOD 5 )

Biochemical oxygen demand is the amount of oxygen required by microorganisms to biologically oxidize organic matter that undergoes decomposition in the dark under standard conditions of temperature and time. BOD assessment helps determine the level of organic pollution in water, so to accurately assess the value of organic pollution, samples must be analyzed under stable thermal conditions for 5 days.

BOD 5 is the amount of oxygen needed for the first 5 days at a temperature of 20 0 C. The monitoring results shown in Map 3.2 show that at points DN1 and SG2, only 1 year did the BOD 5 value exceed the allowable value, while the remaining points DN2, DN3, SG1, SG3, SB1, VCĐ1, VCĐ2, VCĐ3 all exceeded the allowable value from 2 to 4 years. In particular, in 2012 at SG3, Tan Thuan port area, BOD 5 increased 5 times compared to the allowable standard. BOD 5 appears in river water mainly due to the discharge of wastewater from industrial zones flowing into rivers in the Dong Nai River Basin. The monitoring results show that in the downstream of the Dong Nai River Basin, where industry and seaports are strongly developed , the BOD 5 pollution level is most evident. Therefore, in environmental planning and development planning of the region, it is necessary to pay attention to solutions to minimize pollution sources from industrial zones, thereby ensuring good quality water sources for Dong Nai River Basin.

In the solutions to protect the water environment of Dong Nai River Delta, especially in the downstream area of ​​the River Delta, in addition to legal solutions, it is also necessary to upgrade the water pollution treatment system in industrial parks, factories, and residential areas before discharging into the environment. The process of industrial and seaport development is increasingly strong, so in the long term, it is still necessary to control the source of discharge from the source to ensure that the water quality of the River Delta is within the GHCP according to the regulations of QCVN.




3.1.2.3. Chemical oxygen demand (COD)

Chemical oxygen demand is the amount of oxygen required for the complete oxidation of organic substances in water. COD is an important parameter to assess the pollution level of surface water, it reflects the content of organic substances in water, the higher the measured index, the more organic substances pollute the water.

Based on the results of monitoring at 12 measuring points in the Dong Nai river basin, it shows that 4 measuring points are within the allowable limits according to QCVN, which are points DN1, DN2, SB1, SB2, SB3. In 2012, the COD value increased dramatically by 3 to 4 times at points DN3 (54 mg/l), SG3 (56 mg/l) and VCĐ1 (42 mg/l). During this period, the amount of organic pollutants increased sharply. However, thanks to measures to improve the quality of the water environment, in the following years, the COD content in the water decreased significantly, and the water was slightly polluted. The research results are shown in Map 3.3.

3.1.2.4. Dissolved oxygen (DO)

Dissolved oxygen DO is the amount of oxygen dissolved in water necessary for the respiration of aquatic organisms such as shrimp, fish, etc. DO in water is often created by the dissolution of air and a small part is due to the photosynthesis of algae. When water is polluted by organic substances that are easily decomposed by microorganisms, DO in water will be consumed less, so the DO value is often low, this is considered an indicator to assess the level of surface water pollution of organic origin.

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