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PHYSICO-CHEMICAL ANALYSIS OF DRINKING WATER SOURCES AT SAMPLING POINT OF BILLITANG, KDA, NASRAT
KHEL AND CHONGEE OF DISTRICT KOHAT, K.P.K., PAKISTAN
Ijaz Ahmad*1, Khan Bahadar1, Hussain Ullah1, Ali Rehman1, Hamid Iqbal2, Abdul Wahab3, Azhar Ul Haq1, Murad Ali
Khan1 and Fozia Ijaz4
1Department of Chemistry, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, Pakistan;
3Department of Microbiology, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, Pakistan;
3Department of Pharmacy, Kohat University of Science and Technology, Kohat, Khyber Pakhtunkhwa, Pakistan;
4KMU Institute of Medical Sciences (KIMS), Khyber Medical University, Kohat-26000, Khyber Pakhtunkhwa, Pakistan
INTRODUCTION
ISSN:2249-5347
IJSID
International Journal of Science Innovations and Discoveries An International peerReview Journal for Science
Research Article Available online through www.ijsidonline.info
Received: 10-11-2012
Accepted: 11-12-2012
*Corresponding Author
Address:
Name:
Dr.Ijaz Ahmad
Place:
Pakhtunkhwa, PakistanE-mail:
ABSTRACT
The aim of this research work is to assess the quality of drinking water. For the
assessment, of water quality, total 18 drinking water samples were collected from
different sources including Hand pumps, Well, Streams, storage and Tube Wells of District
Kohat at sampling points of Billitang, KDA, Nasrat Khel and Chongee. All these samples
were subjected for physicochemical analysis. All these samples were analyzed for
parameters like pH, Electrical conductivity, TS, TDS, TSS, Alkalinity, Chlorides, Total
hardness, Ca+2 , Mg+2 , Na+1 , K+1 , using the standard methods of APHA. The value of few
heavy metals like As, Pb and Se were determined using Atomic Absorption
Spectrophotometer. The results showed variation from the WHO/Pakistan standard for
drinking water. The results indicated that most of the samples were contaminated due to
geological strata. Among the sources, storage and Wells were found highly polluted while
tube wells were found to be the most suitable source for drinking water.
KEY WORDS: Heavy Metals, Drinking water, Physico-chemical Parameters
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INTRODUCTION
Water is the most common, wide distributed and useful liquid on the earth [1]. The average human adult
contain two third of water by weight, the brain is 85 % water, muscles contain 77% and bones 33% [1]. Good
quality drinking water is of Fundamental importance to human physiology [2]. Water covers approximately 75% o
the Earth surface existing in all the three states as ice, liquid and steam. It is used in many ways from drinking to
industrial and agricultural purposes [3].
As water contains minerals, important for human as well as for other living beings, so it is an essentia
component for survival of life on earth [4]. Water quality changes due to physical, biological and chemica
conditions that occur as results of physical and anthropogenic activities [5]. Water quality has direct impact on
public health. When water gets contaminated with various pathogenic microorganisms and toxic chemica
compounds, then it serves as the main source of infectious diseases. According to WHO, 80% diseases in the world
are caused by inadequate sanitation, pollution and unavailability of clean water. Polluted drinking water causes
several diseases like typhoid, cholera, dysentery, which are responsible for mortalities and morbidities in a large
scale[6].
Arsenic is one of the poisonous materials which enter into the human body through drinking water causing
many diseases [7]. In some areas of Pakistan, shallow and deep water reservoirs are highly contaminated with
arsenic [8]. Water occurs on earth as salt water and fresh water. About 94% of the water on earth is salt water. The
remaining 6% of water constitutes the fresh water resource of the total earth water, 68.7% is held in ice caps and
glaciers, 30.1% is ground water, 03% is surface water and 0.04% is atmospheric water [9-12]. Water pollution is
defined as the introduction into a water body of substances of such character and in such quality to alter the water
body. This alteration impairs its usefulness, affects the health of living organisms or renders it offensive to the
senses of sight, taste or smell [13].
Substance that contaminates groundwater can be divided into two basic categories, substances that occur
naturally and substances produced by mans activities. Naturally occurring substance includes minerals such as
iron, calcium, selenium etc, substances produced as a results of mans activities include synthetic organic chemicals
and hydrocarbons (e.g. pesticides, petroleum products etc) and landfill and ponds [14]. Majority of today
groundwater contamination problems arise from mans activities and can be introduced to the groundwater from
variety of sources. One of the major sources of groundwater contamination is the improper surface disposition of
the variety of liquid wasted and wastewater [15]. In Pakistan, there is scarcity of water particularly in rural areas[16].The available water is of very poor quality [17]. At the present situation, in case of urban areas only 80% and
in case of rural areas only 11% of the population has access to the piped water supply whereas [18]. In most of the
areas the population is dependent on irrigation water for their domestic needs rather than drinking water [19]. In
K.P.K the situation is still worse, where only about 50 % of the total population has access to proper water supply
schemes[20].
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EXPERIMENTAL METHODS
EQUIPMENTS: Perkin-Elmer 3110 model flame atomic absorption spectrometer, Perkin-Elmer 400 model atomic
absorption spectrometer, pH meter [HI 8428,Hana], conductivity meter [PC m3-Jenwary]
CHEMICALS: double ionized distilled water, 0.02N (H2SO4, silver nitrate (0.043N, complex-metric EDTA, potassium
chromate
Collection of water Samples
All the samples were collected in the month of June 2010. The locations selected for the investigation are
from Tehsil and District Kohat at sampling points of Billitang, KDA, Nasrat Khel and Chongee as shown in Fig 1-
15. Before the collection of samples each bottle was first rinsed with sample for pre-concentration. The
collected samples were analyzed on various physico-chemical parameters.
Analysis of Samples
The instruments were calibrated before analysis for each parameter. All the stocks solutions were
prepared with double ionized distilled water. All the chemicals used for analysis were of analytical grade
(Merck and BDH) and were use d wi tho ut a ny f urt her pur ific ati on. PH of water was determined by
using pH meter [HI 8428,Hana]. Conductance of water was determined by using conductivity meter [PC m3
Jenwary]. Total solids (TS), Total dissolved solids (TDS) and total suspended solids were determined by using
standards methods of American Public Health Association [21].
The alkalinities were determined by titrating 0.02N (H2SO4) solution with the samples. Chlorides were estimated
by titration method using silver nitrate (0.043N) as standard solution and potassium chromate as indicator. Tota
hardness including calcium and magnesium were investigated by complex-metric EDTA titration method. Alkal
metals (Na and K) were determined by using Perkin-Elmer 3110 model flame atomic absorption spectrometer
Determination of Ca. Mg, As, Pb and Se were carried out by using Perkin-Elmer 400 model atomic absorption
spectrometer. Physical measurement and chemical analysis were carried out triplicate for each sample and
the average values were recorded.
RESULTS AND DISCUSSION
The different parameters of the drinking water exhibited considerable variations from sample to sample.
All the measurements were carried out at room temperature. Experiments were carried out to ascertain the
contamination levels of drinking water. Results of present study are presented in Table 1-2 respectively. The
results are also analyzed graphically (Figure 1-15). Blink spaces in figures shows non availability of anycontaminant. The values of parameters are in between the minimum and maximum and they were graphically
plotted individually. This effort has enabled us to determine the pH, Electrical conductivity, Total Solids(TS), Tota
dissolved solids(TDS), Total suspended solids (TSS), Alkalinity, Chlorides, total hardness, Ca+2 , Mg+2 , Na+1 K+1 and
Heavy Metal (As, Pb & Se) of the samples.
The pH range recommended by WHO and Pakistan Council of Research in water Resources (PCRWR) is 6.5
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8.5, while the highest desirable level according to PCRWR is in the range of 7-8.5. As shown in the Tabel-1, all the
water samples are slightly alkaline and had pH in the range of 7.25-8.2. Concentration less than 1000ppm is
accepted as the limit for TDS both by the WHO and Pakistan Standard. Nasrat Khel well sample has the highest TDS
values and KDA tube well with lowest.
The tested water samples for conductivity lie in the range between 607-3030 S/cm which is below the
permissible limit (400 S/cm). The total solids (TS) of drinking water samples taken from various locations varied
from 685-4325ppm) while the recommended limit for Ts is 1000ppm. Out of the total 18 samples studied,only 6
samples possessed total solids in the permissible limits. Concentration less than 1000ppm is accepted as the limit
for TDS both by the WHO and Pakistan standards. Nasrati Khel sample has the highest TDS value, i.e. 4152ppm.The
values of TSS in the water were also higher than the WHO and Pakistan limits. However values up to 50ppm, is
generally accepted in drinking water sources, after considering the accuracy of experiment. Alkalinity is the term
traditionally used for the quantity measured by titration to pH 8.3. When it is zero then carbonates and hydroxide
are absent and the bicarbonates alkalinity represents the total alkalinity. WHO/Pakistan standard value for tota
alkalinity in drinking water is 500ppm. It was found that the drinking water samples were having Total alkalinity
values within the permissible WHO/Pakistan limits. It varied in the range 104-317ppm as shown in table 1-2
respectively. As the entire water sample analysed had pH less than 8.3; therefore, only bicarbonate alkalinity was
present.
Total hardness is defined as the sum of calcium and magnesium concentration both expressed as CaCO3
Ground water is usually harder than surface water. There are two types of hardness, temporary and permanent
hardness respectively. Temporary hardness is caused due to the presence of bicarbonate of calcium magnesium
and other bivalent metals. This is known as carbonates hardness. Permanent hardness is caused due to the
presence of sulphates and chlorides hardness constituting cat-ions. This is also known non-carbonate hardness
These salts are very corrosive, deposits scales in steam boilers. Hard water may cause inflammation of intestines
The total limit of hardness is recommended by WHO and PCRWR are 500ppm and 200ppm, respectively. Tota
hardness of the water samples was in the range of 173-2393ppm.So out of the total 18 samples 16 samples were
having hardness higher than the prescribe limits of WHO and PCRWR. Calcium is present in all natural water and
its level depends upon the types of rocks through which the water passes. It is usually present in the form of
carbonates, bicarbonates, sulphates, chlorides and nitrates. Calcium contributes to the hardness of water. WHO
Standard for chlorides in drinking water is 250ppm. Only 6 samples have chloride concentration in the permissiblelimits of WHO Standard. A high level of Chlorides may cause gastrointestinal problems, irritation and dehydration.
Only 12 out of 18 samples were containing sodium concentration in the WHO permissible limits i.e
200ppm. 16 out of 18 samples contained potassium in the acceptable WHO limits i.e. 12ppm. WHO standard for
Arsenic is 0.01ppm in drinking water so the values are higher than standard in the samples ranges from 0.001
0.042ppm. High level of Arsenic in drinking water causes skin damage, circulatory system problems, increase risk
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of cancer. Arsenic is the 20th most common element in the earths crust, sedimentary rocks and soil.
WHO/Pakistan standard values for lead is 0.015ppm in drinking water, therefore, all the Samples wer
contaminated with lead, ranges from 0.001-0.078ppm.The first reason of high value of Pb may be due to the releas
of dust by Kohat Cement Company limited throughout the year, resulting in serious ground water contamination
The second reason may be the use of chemicals in irrigation area in the fields. The third reason may be wate
collected from road sides. Smokes and wastes of vehicles are deposited on the soil surface and in rainy season i
result in considerable rise in the contamination of wells water. This high level of Pb would cause anemia, dizzines
irresistibility, weakness of muscles, hallucination and renal damage. The WHO standard for Selenium is 0.01ppm i
drinking water. Most of the samples contain Selenium higher than the standard value, ranges from 0.003-0.042ppm
High level of Selenium causes hair or fingernail loss, numbness in fingers or toes, circulatory problems. The ma
source of selenium intake for humans is through plant foods in which the plants concentrate the selenium found i
soil or taken from ground water used for irrigation. The presence of selenium in well water depends on the rock an
soil type in the area. Weathering and erosion in these areas can lead to the presence of selenium in ground wate
As rocks are mostly prevalent in district Kohat so this might be one of the possible reasons of selenium existence i
drinking water.
Table-1: Selected quality indices of drinking waters of Billitang, KDA, Nasrat Khel and Chongee of District Kohat,
KP, Pakistan.
Parameters Hand pumps Streams Storages Tube wells Wells
pH 7.42-7.75 7.95-8.2 7.63-7.7 7.35-7.76 7.25-7.76
Electrical conductivity (S/cm) 937-2818 789-2855 785-1515 607-1639 953-3030
TS (ppm) 973-4078 812-4198 852-1765 685-1898 970-4325
TDS (ppm) 932-3897 786-3793 803-1537 653-1892 832-4152
TSS (ppm) 41-247 26-405 47-228 32-147 106-174
Alkalinity (ppm) 181-264 104-213 168-317 129-186 153-211
Total hardness (ppm) 173-1246 549-624 461-714 456-1280 563-2393
Ca+2 hardness (ppm) 144-832 285-334 281-397 290-829 337-1727
Mg+2 hardness (ppm) 34-573 265-295 99-352 171-456 127-671
Chlorides (ppm) 208-788 93-177 192-697 170-702 292-1992
Na+1 (ppm) 101-955 29-129 61-397 99-115 85-509
K+1 (ppm) 4.4 13 4.8 13 2.9 - 6 2 - 5 3.5 - 8.2
Table-2: Heavy metal levels (mg/l) in drinking waters of Billitang, KDA, Nasrat Khel and Chongee of District Kohat
KP, Pakistan.
Parameters Hand pumps Streams storages Tube wells WellsARSENIC (ppm) 0.003-0.01 0.007-0.008 0.018-0.039 0.001-0.006 0.021-0.042
LEAD (ppm) 0.005-0.009 0.001-0.005 0.069-0.078 0.003-0.007 0.043-0.066
SELLENIUM (ppm) 0.004-0.008 0.005-0.009 0.018-0.042 0.003-0.009 0.014-0.032
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6.66.8
7
7.27.47.67.8
88.28.4
pH
Sampling Area
pH
Hand pump
Stream
Storage
Tube well
Well
Fig 1: Level of pH in drinking water samples of the selected areas
0
500
1000
1500
2000
2500
3000
3500
EC(S/cm)
Sampling Area
EC
Hand pump
Stream
Storage
Tube well
Well
Fig 2: Level of Electrical Conductivity in drinking water samples of the selected areas
0
50010001500200025003000350040004500
Con
c.ppm
Sampling Area
TDS
Hand pump
Stream
Storage
Tube well
Well
Fig 3: Level of Total Dissolved Solids in drinking water samples of the selected areas
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0500
10001500
2000250030003500400045005000
Co
nc.ppm
Sampling Area
TS
Hand pump
Stream
Storage
Tube well
Well
Fig 4: Level of Total Solids in drinking water samples of the selected areas
050
100150200250300350400450
500
Conc.ppm
Sampling Area
TSS
Hand pump
Stream
Storage
Tube well
Well
Fig 5: Level of Total Suspended Solids in drinking water samples of the selected areas
0
50
100
150
200
250
300
350
Conc.ppm
Sampling Area
Alkalinity as Bicarbonates
Hand pump
Stream
Storage
Tube well
Well
Fig 6: Level of Alkalinity in drinking water samples of the selected areas
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Ca + Mg Hardness
0
500
1000
1500
2000
2500
3000
Billit
ang
KD
A
NasratK
hel
Cho
ngee
Sampling Areas
Conc.ppm
Hand pump
Stream
Storage
Tube well
Well
Fig 7: Level of Total Hardness in drinking water samples of the selected areas
Fig 8: Level of Calcium Hardness in drinking water samples of the selected areas
0100
200300400500600700800
Conc.ppm
Sampling Area
Mg hardness
Hand pump
Stream
Storage
Tube well
Well
Fig 9: Level of Mg Hardness in drinking water samples of the selected area
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Fig 10: Level of Chlorides in drinking water samples of the selected areas
0
200
400
600
800
1000
1200
Conc.ppm
Sampling Areas
Na
Hand pump
Stream
Storage
Tube well
Well
Fig 11: Level of Sodium in drinking water samples of the selected areas
Fig 12: Level of Potassium in drinking water samples of the selected areas
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00.0050.01
0.015
0.020.0250.03
0.0350.04
0.045
Co
nc.ppm
Sampling Area
As
Hand pump
Stream
Storage
Tube well
Well
Fig 13: Level of Arsenic in drinking water samples of the selected areas
0
0.010.020.03
0.040.05
0.060.070.08
0.09
Bil li tang K D A Nasrat Khel Chongee
Conc.ppm
Sampling Area
Pb
Hand pump
Stream
storage
Tube well
Well
Fig 14: Level of Lead in drinking water samples of the selected areas
0
0.0050.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
Billitang K D A Nasrat Khel Chongee
Conc.ppm
Sampling Area
Se
Hand pump
Stream
Storage
Tube well
Well
Fig 15: Level of Selenium in drinking water samples of the selected areas
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CONCLUSION
The complete study of this research results reveals that drinking water has polluted in Kohan, Pakistan. In
this research 18 samples were collected from different drinking water sources of Tehsil & district Kohat (Pakistan)
for important physicochemical parameters using the Standard methods of APHA. The results were compared with
WHO Standard for drinking water. This study indicated that most of the samples were contaminated either due to
one or more reason. Only the pH, total alkalinity and Potassium value of the samples were in permissible range
while Electrical Conductivity, TS, TDS, Chlorides, TSS, calcium, Total hardness, Magnesium, Sodium, Arsenic, Lead
and selenium of samples were found higher than the WHO standards. These results compelled us to conclude that
the quality of drinking water of District & Tehsil Kohat (Pakistan) is highly contaminated and it is suggested that
only treated water should be used for drinking purposes.
REFERENCES
1. R. Qadeer,Journal of the Chemical Society of Pakistan, 26, 293 (2005).
2. Arunabh Mishra and Vasishta Bhatt, Nirav Sevak, Pinal Shah, Kirit Patel, Chatanya Patel, Journal of Chemica
and Pharmaceutical Research, 2, 174 (2010).
3. M. Shakir Ullah, S. khatoon, I. Ahmad, H.U. R. Rehman, A. A. Shah, A. Mulk,Journal of Chemical Society of
Pakistan, 26, 171 (2004).
4. Kumar, A,Environmental chemistry, 5th Ed, New Age International (P) Limited. PP 4, 56 (2003).
5. D. Kar, P. Sur, S. K.Mandal, T. Saha, R.k. Kole, International Journal of Environmental Science and Technology, 5
119 (2008).
6. Andrea Versari, Giuseppina Paola Parpinello, Sergio Galassi,Journal of food composition and analysis, 15, 251
(2002).
7. Zhaohui Li, Jiin-Shuh Jean, Wei-The Jiang, Po-Hasiang Chang, Chun-Jung Chen, Libing Liao,journal of Hazardous
Materials, 187, 318 (2011).
8. Shiklomanov, 1.A; Water international, 25, 11 (2000).
9. Amir Haider Malik, Zahid Mehmood Khan, Qaiser Mehmood, Sadia Nasreen, Zulfiqar Ahmad Bhati, Journal of
Hazardous Materials, 168, 1 (2009).
10. Maqbool. A, M.S. thesis, Center of Excellence in Water resources Engineering, Lahore, Pakistan, (2007).
11. World Health Organization and United Nations Childrens Fund; Water Supply and Sanitation Collaborative
Council, in; Global Water supply and sanitation Assessment (Report), pp; 77f, New 11. York/Geneva, (2000).12. Guisse, El Hadji; Relationship between the enjoyments of economic. Social and cultura
rights and the promotion of the realization of the right to drinking water supply and sanitaton. Final report o
the Special Reporter, U.N. Doc E/CN.4/Sub.2/2004/20,Article 4, 5 and 8, Geneva, (2004).
13. WHO; Guideline for drinking water quality, supporting Documentation to the Guidelines, 3rd Edn, Vol 1
Geneva, Switzerland, (2004).
-
7/29/2019 Physico-chemical Analysis of Drinking Water Sources at Sampling Point of Billitang, Kda, Nasrat Khel and Chongee
12/12
Ijaz Ahmad et al., IJSID, 2012, 2 (6), 598-609
International Journal of Science Innovations and Discoveries, Volume 2, Issue 6, November-December 2012
609
14. Pakistan Council of Research and Water resources (PCRWR); National Water Quality Monitoring Programme
Report, Islamabad, (2005).
15. Hutton; Field water sampling techniques for developing countries, (1996).
16. Avcievala, S; the nature of water pollution in developing countries, Natural resource Series, Vol 26, UNDTCD
United Nations, New York, (1991).
17. M. Ismail Khan, Pakistan Water Borne complications The News International, Tuesday, June 13, (2006).
18. M.A. Khalown, Water Quality Status in Pakistan Report, PCRWR Islamabad, (2004).
19. A.N. Cheema, Management of Water Resources in PakistanProceeding of Firs International Conference, 40th
Annual Convention, the Institution of Engineers of Pakistan.
20. Muhammad Saleem, Poisoned Water Daily Dawn, May14, (2005).
21. American Public Health Association (APHA), American Water Works Association (AWWA). Standards Methods
for the examination of water and waste water.21stED, (2005).