Earth Link and Advanced Resources Development s a. r L. (Elard) Submitted to: Council for Development and Reconstruction


Water Quality and Treatment Process



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3.4Water Quality and Treatment Process

      1. Raw Water Quality


The raw water will be delivered to the plant by the use of tunnels that belong to the existing hydroelectric system. There are two main sources of water:

  1. Karaoun lake;

  2. Awali River.

The quality for each source over the period of at least a full year must be analyzed in detail before start of construction phase. For this purpose a new sampling campaign was adapted and had started in April and is still ongoing.

The source of water supply is very important to the project as the Karaoun lake and Awali River differ from each other in terms of water quality. According to past water quality monitoring data which formed the basis for previous studies and designs, the Karaoun lake has a better water quality when compared to the Awali source. This may have been affected however by reported increase in industrial and agricultural activity in the lower Beqa’a valley, the feeder catchment of the Litani River.

Raw water quality has been analyzed several times in the past with the first one being in 1968/1972, the second one in August 1984 and the third one in 1994/1995. The most recent water quality analysis was conducted in 2001. The first two can be considered outdated as it is suspected that the condition and status of the tunnels, hydroelectric power plant and dams may have changed during the proceeding period. The analysis conducted in 1994/1995 contained some information on the most important parameters; however the feasibility report and the preliminary design report of Montgomery Watson did not cover comprehensive water quality information on a seasonal basis for both the Karaoun and Awali sources.

The 2001 analyses provided further and detailed information on specific chemical substances and also herbicides/pesticides which seemed to be either below the detection limits or lower than the effluent requirements. Specific and detailed assessment will be provided in a later stage. The results did not indicate issues that could have had a potential impact on the treatment scheme. In fact, the water quality did not differ much from the one given in the earlier feasibility report, however it is noteworthy that the 2001 sampling and analyses campaign seemed to be limited in the number of samples taken and lacking in seasonal water quality results which is the most crucial information that must be obtained for finalizing the treatment scheme.

The 2001 analyses report contains information on separate water sources such as the Awali and Litani Rivers, based on samples taken in winter and spring of 1994/1995. This information could not be located in the 1994 feasibility report.

From a treatment plant design perspective, this information was found to be more valuable as it showed how both sources deteriorated in quality in winter when it is suspected that wet weather events might have occurred although these have not been clearly stated. It is therefore prudent to take into consideration the results obtained from the sampling and analysis program conducted in 1994 and 1995.

The new sampling and analysis campaign to determine the current water quality of the Litani and Awali sources must be a combination of the 1994/1995 and 2001 analyses. The combination can be defined by the need:


  1. To derive the seasonal water quality and associated changes;

  2. To include all the chemical, microbiological and indicator parameters as outlined and classified in the latest 98/83/EC drinking water directive and the Lebanese Environmental Quality Standards & Criteria for water listed in Ministerial Decision No. 52/1, MoE.

The results of the sampling and analysis campaign are given in Appendix O.

Apart from the numerical results, both the Awali and Litani sources were characterized as being noncorrosive, moderately hard and low in organics. It was also observed that there were no point discharges of wastewater of either domestic or industrial type. However, due to agricultural activities, pesticides could be a threat to the water source and testing of this regard must be made a key consideration during the engineering design.

It is not possible to immediately verify the conclusions and assumptions which were the basis of the 1994 feasibility study or the subsequent preliminary design. This is due to lack of recent detailed water quality monitoring data at the points of concern to this project, and the fact that new data would need to be collected over long periods to capture seasonal variations. Accurate up-to-date analysis results will not only help in a better and an efficient design of the potable water treatment plant but also aid in defining the chemical dosage and consumption. It is noteworthy that the correct selection and dosing requirement of the coagulation chemicals will have to be determined via jar tests which have not been done up to now. The raw water quality as estimated in the 1994 feasibility report is shown in Table 3 -30., based on the combined range of quality parameters from both the Liatni and the Awali sources

Table 3 30 Raw Water Quality


Parameter

Unit

Mean

Maximum

Minimum

Temperature

oC

14

18

10

PH




8 (typ)

8.4

6.9

Color

PE/Co

2.0

7.5

1.0

Turbidity

FTU

20

155

1

Suspended Solids

mg/L

14

28

6

Conductivity

µS/cm

265

409


200

TDS

mg/L (CACO3)

253

288

232

Alkalinity

mg/L (CaCO3)

158

240

140

Hardness

mg/L

175

240

150

Calcium

mg/L

58

80

42

Magnesium

mg/L

9

12

5

Sodium

mg/L

10

13

7

Ammonia

mg/L

0.1

0.4

0


Nitrate

mg/L

0.9

1.0

0.7

Chloride

mg/L

18

25

12

Fluoride

mg/L

0.12

0.15

0.07

Iron

mg/L

0.16

0.33

0.1

BOD

mg/L

2.6

5.5

0.9

Dissolved Oxygen

mg/L

5.1

11.8

1.0

Coliforms

No./100mL

115

370


5

THM Potential

mg/L




<34

<21

Total Organic Carbon

mg/L

0.7

0.93

0.58

The influent parameters suggest that the raw water has a mild to moderate quality. However due to variable raw water quality linked to seasonal changes especially for the Awali source; specific new analysis should be conducted to determine the raw water quality during wet weather events. There is no information as to when the sampling and analysis were conducted to derive the above given water quality, and most important of all, it is not known whether the maximum values correspond to wet weather events or they are the maximum influent parameters corresponding to the dry season. Seasonal raw water analysis plays an important role in defining the water quality and hence the most efficient and economical process. Furthermore, manganese concentration is missing in the estimated raw water quality which has a prime importance in the design.

The result of raw water analysis conducted on specific sources in 1994 and 1995 are summarized in Table 3 -31. Only the parameters which have significant importance to the process have been shown. It can be seen that influent parameters vary greatly between summer and winter months and can reach to very high levels especially for suspended solids and turbidity. Again, it is clearly illustrated that the Litani River source has a better quality than the Awali River source.

Table 3 31 Water Quality Analysis (1994 and 1995)


Parameter

14.02.1994

04.07.1994

13.01.1995




Awali

Litani

Awali

Litani

Awali

Litani

TSS (mg/L)

n/a

n/a

n/a

n/a

22

14

Turbidity (NTU)

150

80

n/a

n/a

5.5




T, Coliform (No./100mL)

n/a

n/a

n/a

n/a

67




pH

8.2

7.8


n/a

n/a

7.1




Parameter

07.02.1995

18.03.1995

18.05.1995

TSS (mg/L)

n/a

n/a

110

n/a

16

14

Turbidity (NTU)

350

22

59

n/a

0.7

1.8

T, Coliform (No./100mL)

n/a

n/a

58

n/a

0

3

pH

8.1

7.7

7.55

n/a

7.5


7.3

It is suspected that the samples taken on 14.02.1994, 07.02.1995 and 18.03.1995 may have coincided with wet weather events however nothing has been noted to justify this. If this is the case then it can be concluded that Awali river water quality during wet weather events deteriorates more than the Litani source with TSS and turbidity levels reaching up to 110 mg/L and 350 NTU respectively.. It is also important to note that inlet pH can be below 7.

It has been nearly 16 years since the last sampling and analysis campaign was conducted and it is imperative that up to date raw water quality must be derived to validate the latest situation of the raw water quality to be used as the basis for design. The possibility of a lower water quality in both the Awali and Litani sources should not be ruled out as over the years, residential and commercial developments.

Increase in agricultural activity and industrialization may have affected the water sources and to ascertain this, a new sampling and analysis campaign was recommended by Montgomery Watson.




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