Analysis of Sediment and Pore Water samples of a Contaminated Lake - A Case Study of Hussain Sagar

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 3, Issue 3, March 2013)

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Analysis of Sediment and Pore Water samples of a

Contaminated Lake - A Case Study of Hussain Sagar

S.Umamaheswara Reddy

1

, Dr.P.Venugopal Rao

2

1_{General Manager, Department of Construction Technology, Soma Enterprise Limited, Hyderabad} 2_{Professor in Civil Engineering (Retired), Jawaharlal Nehru Technological Institute, Hyderabad.}

Abstract— Lakes sediments consists of biological and non

biological matter accumulated since from formation of the lake. Sediment sequence in lake represents information about the activities within the lake and in its catchment area over a period of time since its inception. Hussain Sagar Lake located in the heart of Twin Cities of Hyderabad and Secunderabad receives toxic substances from the industrial effluent discharges in to it through incoming nallas. Pollutants entering the lake undergo either absorption or adsorption by fine particles present in the lake water, which may in turn settle down in the form of sludge. The sludge is further classified into pore water and sediments. This paper aims to explain the Physico chemical characteristics of sediments and pore water of Hussain Sagar Lake.

The experimental results show that the mean value of organic content in sediment is 5.6% with almost 100% settlement of suspended particles in the detention time of about 317 days. Higher pollutant concentrations observed in sediments and pore water is attributed to accumulation of pollutants generated in the catchment area and transported through inlet nallas in to the lake. The concentrations of heavy metals like Chromium and Lead have shown relatively elevated over a period of one decade.

Keywords— Lake Sediments, Pore Water, Physico Chemical Parameters, GPS, Modified Ekman sampler, Toxic Substances

I. INTRODUCTION

Hussainsagar, the picturesque lake situated between the twin cities of Hyderabad and Secunderabad is an ecological and cultural landmark in Hyderabad. Lake was excavated in 1562 AD, mainly to harvest drinking water from Musi River by Balkapur Canal. However with passage of time the lake lost its importance as a source of drinking water supply with the increase in pollution levels. The deterioration of lake water quality is due to unplanned industrialization and urbanization around the lake after 1960’s.

The pollution of aquatic ecosystem by heavy metals has assumed serious proportions due to their toxicity and accumulative behaviour. Heavy metals entering into an aquatic system by natural and anthropogenic sources distributed between different compartments of aquatic ecosystems such as water, sediments.

The added heavy metals then undergo different chemical changes whereby high degree of variations in metal concentration occurs. Sediments play an important role in buffering higher metal concentrations in water particularly by adsorption and/or precipitation.

Important limnological studies on Hussain Sagar lake have been conducted during 1998 [1], 2004 [2], 2008 [3] & [4] and these studies have shown progressive deterioration in the sediment quality. In 1992, EPTRI has estimated an inflow of settleable solids with the concentration of 280 mg/l in dry weather inflow of 25.73 M.Cum / year, the maximum siltation would be 3602 tons per year assuming only 50% of the solids are settled and the study further added that there is an inflow of 18 tons and 70 tons of phosphorus and nitrogen along with settleable solids.

The studies conducted on the lake reveled that there has been considerable increase of contamination level since past four decades and accumulation of pollutants in the lake bed in the form of sediments posing a potential threat of contributing pollution to the surrounding ground water.

II. MATERIALS AND METHODS

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International Journal of Emerging Technology and Advanced Engineering

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Figure 1: Sediment and Pore Water Sampling Locations in Hussainsagar Lake.

In the present paper an effort is made to represent Physico chemical characteristics of Sediments and pore water and increase in concentrations of Lead (Pb), Chromium (Cr) and Cadmium (Cd) in the Sediment samples over a period of one decade from 1998 to 2008.

III. RESULTS AND DISCUSSION

Sediments and Pore water samples extracted from core and grab sediment samples were analysed for several parameters which are essential to assess the Sediment Quality of water body. Sediment samples after extraction of pore water have been analysed for Physico chemical parameters. The analysis was carried out as per Guidelines for Analysis of Contaminated Soils, USEPA – 1995.

A. Physical Analysis of Sediments:

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1) Loss of Ignition:Loss of Ignition is frequently used as a measure of the organic content of lake sediments. The Loss on Ignition values of sediment samples are represented in Table I. The mean value of Loss on Ignition was 5.6 % with maximum value of 7.2% in B5 and minimum value of 2.48% in D1. These results indicate presence of high organic content in the sediments located in the middle of the lake and low in the periphery of the lake where there is presence of inert material/sand.

Table I

Percentage Loss on Ignition values of sediment samples of Hussain Sagar lake

S.No Sample % Loss on Ignition

1 A1 6.33

2 A2 4.54

3 A3 5.94

4 A4 6.65

5 B1 5.64

6 B2 5.91

7 B3 6.42

8 B4 6.70

9 B5 7.20

10 C1 6.90

11 C2 7.05

12 C3 3.20

13 D1 2.48

14 D2 5.20

15 D3 6.38

16 D4 3.04

Graphical representation of variation in Ignition Losses among sediment samples are shown in Figure 2.

Figure 2: Loss on Ignition of Sediment samples in %

2) Grain Size Distribution: Grain size distribution forms one of the key parameters of understanding nature of sediments. This test is carried out on both grab samples and core samples. The analysis is done for bottom 1ft of the core samples, which is extremely hard in nature and has a lot of clay material. The grain size distribution test was carried out on dry sediment samples using sieve analysis. The results indicates that the particles are well graded and size varies between <0.075 mm to 4.75 mm. Results of grain size distribution of different samples are provided in Table II and graphical representation is shown in Fig. 3.

0 1 2 3 4 5 6 7 8

A1 A2 A3 A4 B1 B2 B3 B4 B5 C1 C2 C3 D1 D2 D3 D4

%

L

o

ss

o

n

Ig

ni

ti

o

n

Sample Location

Average 5.6%

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Table II

Dry Sieve analysis of Sediment Samples.

Particle size Distribution

(mm)

Cumulative % Finer Samples

C1 C3 A1 D4

4.75 97.55 98.77 98.6 80.56

2 93.87 96.3 90.2 69.45

1 75.47 83.91 62.04 50.57 0.6 61.98 72.76 50.84 42.24 0.5 59.53 69.05 49.44 41.69 0.425 49.72 55.42 34.04 31.14

0.3 42.36 46.75 27 25.59

0.15 16.66 17 12.92 10.04

0.075 1.94 0.89 1.72 0.6

<0.075 0.72 0.28 0.32 0.05

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Graphical representation of variation in Physical parameters by Grain size distribution is given in Fig 3.

Figure 3: Graph showing % Finer particles of dried sediments passing through respective sieve sizes.

3) Sedimentation Analysis: As per APPCB report (1990), the volume of the Hussain Sagar Lake is 28.6 M.Cum with an Inflow of 90.3 MLD providing settling time of about 317 days for the water entering through various Nallahs. This settling time is too long and facilitates sediments with micron size also find its place in the sediment bed. The sedimentation analysis of the samples was carried out using a hydrometer to find out the settlability of sediment particles. The mean, minimum and maximum values of percentage of settlement of different sizes of sediment particles over a period of time are represented in Table III. Graphical representation of Hydrometer Analysis of various sediment samples as shown in Fig 4.

Table III

Hydrometric analysis of Sediment Samples.

S.No

Elapsed Time in min (t)

D in mm

Mean Max Min

% Finer particles

1 0.5 0.0554 97.98 99.99 91.60 2 1 0.0411 94.08 99.99 91.60 3 2 0.0295 92.13 99.99 88.25 4 4 0.0213 89.89 99.99 86.50 5 8 0.0126 86.87 96.57 84.92 6 20 0.0099 82.69 93.24 79.92 7 60 0.0061 73.54 88.25 71.60 8 120 0.0044 67.98 81.58 66.60 9 240 0.0032 61.33 74.30 59.94 10 1440 0.0014 45.23 61.61 39.96

Figure 4: Hydrometer Analysis of Sediment samples with maximum, minimum and Mean values.

B. Chemical Analysis of Sediments and Pore water: Chemical analysis of Sediment and Pore water samples was conducted in the year 1998 and compared these values with the present status to observe the change occurred over a period of one decade.

0 20 40 60 80 100 120

%

F

in

er

Particle size in mm

C1

C3

A1

D4

0 20 40 60 80 100 120

Max

Min

Mean

%

Fi

n

er

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International Journal of Emerging Technology and Advanced Engineering

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Mean values of chemical parameters of Sediments and Pore water are represented in Table IV and Fig 5, and variation in concentrations of Cadmium and Lead in the sediment samples collected in 1998 and 2008 are represented in Fig 6. The levels of Cadmium and Lead shows 150 to 200% increase in pollution level of the lake.

Table IV

Characteristics of sediments and Pore Water, increased levels of Cadmium and Lead from 1998 to 2008.

S.N

o Parameters

Year of Studies

Sediments Pore water

1 pH 8.4 (8.0)* 8.0

2 Cadmium (mg/Kg) 6.8 (17.4)* -

3 Chlorides (ppm) 21.0 113

4 Sulphates (ppm) 41.0 7.85

5 Chromium (ppm) 40.0 46

6 Lead (ppm) 39.2 (121.0)* 0.13

7 Potassium (ppm) 7.0 34

8 Sodium (ppm) 15.5 175

9 Total Hardness (ppm) 98.0 2117.3 10 Mg Hardness(ppm) 45.0 1627 12 Ca Hardness (ppm) 52.6 498 13 Calcium Ions (ppm) 25.5 199.4

14 Magnesium Ions 10.8 393

15 Zinc(mg/kg) 68.0 1.08

16 Phosphates 0.0179

* Values indicated in brackets are in the year 2008 Analytical results of Sediment and Pore water quality of lake are shown separately to highlight the difference in concentrations of various parameters. Concentrations of Chloride, Sodium, Chromium, Total Hardness, Potassium, Magnesium Hardness, Calcium Hardness and Calcium & Magnesium ions are higher in the Pore Water and considerably low in dried sediments. The concentrations of pH, Zinc, Lead and Sulphates are marginally lower in the Pore Water than in Sediments.

i) Difference in concentrations of pH, Dissolved Solids and Heavy Metals in lake sediments and Pore Water.

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ii) Difference in Hardness levels and Ca and Mg ions in lake sediments and Pore Water.

Figure 5: Variation in concentration of Pollutants in Sediment and Pore water samples of the Lake

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190

C

o

n

ce

n

tr

a

ti

o

n

i

n

p

m

(

ex

ce

p

t

p

H)

Pollutants

Lake Sediment

Pore water

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400

Hardness Mg

Hardness Ca Hardness

Ca+ Mg+

C

o

n

ce

n

tr

a

ti

o

n

(

p

m

)

Pollutants

Lake Sediment

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International Journal of Emerging Technology and Advanced Engineering

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Figure 6: Variation in pH, Cd and Pb concentrations in lake sediments from 1998 to 2008.

Analytical results of Sediment and Pore water quality of lake are shown separately to highlight the difference in concentrations of various parameters. Concentrations of Chloride, Sodium, Chromium, Total Hardness, Potassium, Magnesium Hardness, Calcium Hardness and Calcium & Magnesium ions are higher in the Pore Water and considerably low in dried sediments. The concentrations of pH, Zinc, Lead and Sulphates are marginally lower in the Pore Water than in Sediments.

IV. CONCLUSION

Physical characteristics of Sediments indicate well graded distribution of the particles and presence of organic content in it. Hydrometric test conducted on microns indicate very good settling rate of the particles in still water. Chemical analysis conducted on Sediments and Pore water indicates relatively higher concentrations presence in the pore water than in the dry sediments.

A higher concentration of chemical parameters present in the Pore water indicates potential threat of ground water pollution where lake is the source of water recharge. Increased concentrations of Lead and Cadmium from 1998 to 2008 in the sediments indicate increase of manmade activities in the catchment and the measures undertook to abate pollution of the lake are inadequate. Acknowledgements

The author wishes to thank the authorities of Chaitanya Bharathi Institute of Technology (CBIT) for allowing to make use of Environmental Engineering Laboratory for Physico chemical analysis of lake sediments and All India Council for Technical Education (AICTE) for sponsoring the project.

REFERENCES

[1 ] S.Umamaheswara Reddy, Dr.P.Venugopal Rao and

Dr.A.V.S.Prabhakar Rao (2001). ―Analysis of surface and surrounding ground water of a contaminated lake – a case study of Hussainsagar‖, International Conference on Industrial pollution control technologies, 7-10 December, 2001, organized by Jawaharlal Nehru Technological University, Hyderabad, India

[2 ] V.V.S.Gurunadha Rao, Mitstio Yoshida (2004). Environmental

Impact of Human Activities to Urban Lake Sediments: Potentially Toxic Elements (PTEs) Contamination in Hussainsagar Lake,

Hyderabad. The 11th_{National Symposium on Hydrology,}

National Institute of Hydrology, Roorkee (India), November 22-23, 2004

[3 ] M.Suneela, G.Radha Krishna, K.Vamsi Krishna, V.Manga Sai,

V.Bhargav, K.Syama Sundara Reddy, D.S.S.Srinivas and J.S.Srinivas (2008). ―Water and Sediment Analysis of Hussain

Sagar Lake, Hyderabad‖, Proceedings of Taal 2007: The 12th

World Lake Conference:304-306.

[4 ] V.V.S.Gurunadha Rao, C.K.Jain, B.A.Prakash, and K.Mahesh

Kumar, Mitstio Yoshida (2008). Metal Fractionation Study on bed sediments in Hussainsagar Lake, Hyderabad, India, Environ

Monit Assess.2010 Jul;166(1-4):57-67. Doi:

10.1007/s10661-009-0984-8. Epub 2009 May 27. 0