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Quality of Artesian Water | Analysis

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Evaluation of the microbiological and physicochemical quality of Artesian well water used for irrigation in ArRiyadh

Sulaiman Ali Alharbi1*, M.E.Zayed1, Arunachalam Chinnathambi1, Naiyf S. Alharbi1 and Milton Wainwright1,2

Abstract

The quality of water from artesian wells used for irrigation was analyzed. Water samples were collected from 12 wells from different farms along a 8.5 km transect of the Hayer which is an area located approximately 35 km south of ArRiyadh. The major parameters for assessment of the groundwater quality used here were analysis of the major cations (K+, Na+and NH4 +) and the major anions (Cl-, SO42-, NO3- and PO43-). A total dissolved solid (TDS) is a summation of the all major constituents. pH, temperature and electrical conductivity (EC) were also measured as important indicators of groundwater quality. The samples were also tested for the presence of total and fecal coliforms bacteria. All the samples were free from contamination by coliforms bacteria; the physicochemical parameters of the all of the samples were not however, within the acceptable limits prescribed by WHO and FAO.

Key words: Physicochemical quality, Artesian well water quality, Irrigation, coliforms, Cations     

Introduction

Water from rivers, lakes, reservoirs, and groundwater aquifers is an essential human resource and is needed for direct consumption as well as for recreational purposes1. Groundwater is a vital source for fresh water in Saudi Arabia and the surrounding Gulf states2; groundwater being the major source of both potable and irrigation waters in Saudi Arabia. As the population of Saudi continues to increase, especially in the big cities such as ArRiyadh, the demand for adequate and high-quality groundwater resources continues to increase. The Kingdom of Saudi Arabia (about 2.25 million km2) is one of hottest and most arid countries in the world, with an average summer temperatures of 46oC and an average rainfall of 120 mm per year over most of the country2. The available surface water and groundwater resources is limited, precipitation rates are low, while evaporation is high. With increasing population and agricultural use there is an increasing need for high quality water in Saudi Arabia 3.

The total population of Saudi Arabia has increased from about 7.7 million in 1970 to 11.8 million in 1990 and is expected to reach 19 million in 2010, if the present growth rate of 3 per cent per annum continues. Consequently, domestic water demand has increased from about 446 MCM in 1980 to about 1,563 MCM in 1997, and is expected to reach 2,800 MCM in 20104,5. Agriculture accounts for some 88% of water use, while industry consumes only around 3%6. Saudi Arabia faces severe water problems and as a result, is in need of new water policies to achieve sustainable development in its harsh environment. Problems include balancing supply and demand while facing aridity and water scarcity, nonrenewable supplies, poor quality of ground water, poor distribution of supplies, salt water intrusion, and the overuse and contamination of aquifers7.

Available water resources in Saudi Arabia are a) conventional, i.e. groundwater and surface water, and b) non-conventional such as desalinated seawater and treated waste water. About 88 percent of the water consumption in Saudi Arabia is met from groundwater supplies2.Groundwater is generally presumed to be ideal for human consumption and is used as a potential source of drinking water, agricultural development, urbanization and industrialization8. Around 47% of the water supplied in ArRiyadh is groundwater pumped from local aquifers9.

It is estimated that 18% of worldwide cropland is irrigated, producing 40% of all food. Irrigation water and any foliar applied water, in intimate contact to the developing or mature edible portions of fresh produce, is likely to lead to contamination with human waste, although irrigation using surface water is likely to pose a greater risk to human health than irrigation water obtained from deep aquifers drawn from properly constructed and protected wells10.

Water-borne pathogens infect around 250 million people and result in 10 to 20 million deaths world-wide each year. An estimated 80% of all illness in developing countries is related to water and sanitation, with some 5% of all child deaths under the age of five years occurring in developing countries resulting from diarrheal diseases 11,12. Pathogens pose a risk to human health as a result of the various uses of water (Figure 2). For example, it was suggested that contaminated irrigation water was a possible source of a recent outbreak of E. coli across USA13. Fruit and vegetables are frequently contaminated impacted by fecally-polluted irrigation water14. As a general rule, surface water resources are more susceptible to microbial contamination than are groundwater supplies. Microbial contamination introduced through sprinkler irrigation systems may also affect the surface of a crop for varying periods of time, and the risk is increased when the irrigated crop is consumed raw and sometimes unwashed15.

Pathogen-contamination of fresh, ready-to-eat fruits and vegetables is a significant issue in agriculture. In many cases, fecal-oral pathogens such as toxin-producing E. coli, Salmonella spp., and norovirus are the causative agents16. Fecally contaminated irrigation water is frequently a possible or likely source of contamination of fresh, ready-to-eat fruits and vegetables17. According to the Center for Disease Control and Prevention (CDC)18, at least 12 percent of foods borne outbreaks during the 1990s were attributable to fresh produce, and the economic cost of food borne illness is estimated at around $10 to $83 billion per year19.

Water is subject to varying degrees of fecal pollution, and consequently fresh waters are a vector transmission of many pathogenic bacteria, viruses, and protozoa. Fecal pollution can reach water resources as the result of human activities, such as sewage treatment plants and communities where sewage treatment is not available. Many diseases are related to fecal polluted water, but the majority is caused by enteropathogenic microorganisms, and not surprisingly therefore, the presence of enteric pathogens in waters is of considerable concern. For this reason, maintaining the microbiological safety of water is very important issue relating to the protection of public health1. Washing and disinfection practices are less effective against pathogens which in penetrate the plant interior20., and for this reason the prevention of water-borne contamination is considered to be an important primary means of controlling health risk associated with food borne pathogens19.

The quality and safety of farm irrigation water determines the quality and safety of the resultant crop, and the safety of water depends on its source. Human pathogens can be introduced into irrigation water via run-off of manure from animal production facilities, from domestic/urban sewage systems or directly from wildlife. Extreme rainfall (which lead to storm overflows), spills of manure, or human waste can all increase the probability of the occurrence of contamination21. The quality of water needed for various uses is determined by its physical characteristics, chemical composition, biological parameters and the conditions of use and all surface or sub-surface waters contain varying amounts of salts which increase in irrigated soil due to evaporation.

The aim of the work reported here was to determine the microbiological and physicochemical quality of waters obtained from artesian wells used for irrigation near the city of Riyadh.

Materials and methods

Description of the artesian wells:

The samples were taken from wells of depth ranging from (60-100 m); some wells were open while others were closed.

Sampling collection:

Sampling: All ground water sampling (chemical or microbial) was conducted with the existing well pumps which were run for a sufficient time (10-15 minutes) in order to replace the old water in the pipes with fresh water and thereby obtain reliably stable readings of pH, specific conductance and temperature. Well water depths were measured with a graduated (l/l00th foot) steel tape.

A total of three water samples were collected from 12 different wells located in different farms along a 8.5 km transect of the Hayer, which is an area located some 35 km south of Riyadh, during November 2010. The water samples were collected in plastic bottles, pH, EC and TDS were measured on site; samples were subsequently transported to the laboratory in an ice box. Each sample was divided into three portions; one for cation analysis, one for anion determinations and the third for coliform analysis. The concentration of total dissolved ions, Na, K, P, Cl, S04, NH4 and N03 were determined. The analytical procedures used for these determinations were those described in standard methods or the examination of water and wastewater.

The evaluation of the suitability of groundwater for irrigation purpose is based here on the irrigation water specification provided by the Saudi Arabian Standards organization (SASO), irrigation water standards 1993, and water quality for use in agriculture by the FAO (1994). (Table 1) shows the concentration (mg/l) of individual constituents, groundwater, hardness, electrical conductance and pH of the groundwater.

Coliform determination:

Sample Preparation:

The samples were diluted in the range- 10-1 to 10-6 and the original water sample were aseptically diluted into 9 ml buffered peptone prepared in three series. The number of total and fecal coliforms was determined using the MPN method and statistical tables were used to interpret the results. From each dilution, 1ml was removed and added aseptically to triplicate tubes containing 5ml of lauryl tryptose broth (LSB). The tubes were then incubated at 37 °C for 48 hours. Tubes showing color change or gas production were recorded as positive, and the number of positive tubes at each dilution was referred to MPN tables to obtain the number of bacteria present in the original sample.

Results and Discussion

Microbiological analysis:

None of the water samples obtained from any of the wells contained coliforms, a fact which shows that the general sanitary conditions around the wells are excellent.

Analysis of physicochemical parameters:

Physical Characteristics:

Table 1 shows the laboratory determinations used, together with the acceptable range to evaluate common irrigation water quality, as prepared by FAO 1994.

Table 1. Laboratory determinations used to evaluate common irrigation water quality problems.

Water parameter

Symbol

Unit1

Usual range in irrigation water

SALINITY

Salt content

Electrical Conductivity

ECw

dS/m

0 - 3

dS/m

(or)

Total Dissolved Solids

TDS

mg/l

0 - 2000

mg/l

Cations and anions

Calcium

Ca++

me/l

0 - 20

me/l

Magnesium

Mg++

me/l

0 - 5

me/l

Sodium

Na+

me/l

0 - 40

me/l

Carbonate

CO--3

me/l

0 - .1

me/l

Bicarbonate

HCO3-

me/l

0 - 10

me/l

Chloride

Cl-

me/l

0 - 30

me/l

Sulphate

SO4--

me/l

0 - 20

me/l

NUTRIENTS2

Nitrate-Nitrogen

NO3-N

mg/l

0 - 10

mg/l

Ammonium-Nitrogen

NH4-N

mg/l

0 - 5

mg/l

Phosphate-Phosphorus

PO4-P

mg/l

0 - 2

mg/l

Potassium

K+

mg/l

0 - 2

mg/l

MISCELLANEOUS

Boron

B

mg/l

0 - 2

mg/l

Acid/basicity

pH

1-14

6.0 - 8.5

Sodium Adsorption Ratio3

SAR

(me/l)1, 2

0 - 15

1 dS/m = deciSiemen/metre in S.I. units (equivalent to 1 mmho/cm = 1 millimmho/centi-metre)

mg/l = milligram per litre ≃ parts per million (ppm).

me/l = milliequivalent per litre (mg/l ÷ equivalent weight = me/l); in SI units, 1 me/l= 1 millimol/litre adjusted for electron charge.

Table 2. Physical parameters of analyzed groundwater samples

Sample ID

Parameters

Temperature

(Degree Celsius)

pH

E.C*

(ms/cm)

T.D.S**

(mg/L)

Turbidity

(NTU)

Total Hardness

(mg/L as CaCO3)

A

25.0

8.15

3.87

2476

11.30

1800

B

25.5

8.13

8.89

5689

28.70

3000

C

24.5

8.17

4.48

2867

20.50

1200

D

25.5

7.98

3.74

2393

18.00

1400

E

23.5

8.19

5.49

3513

6.24

1000

F

24.5

8.05

9.41

6022

2.98

2600

G

28.0

8.02

9.19

5881

0.73

2800

H

25.0

7.84

10.78

6899

21.90

3600

I

26.5

8.29

9.41

6022

0.94

3200

J

26.0

8.07

10.29

6585

5.78

3200

K

27.0

8.06

11.13

7123

12.30

3800

L

27.0

8.11

10.16

6502

5.63

3600

* E.C = Electrical Conductivity ** T.D.S = Total Dissolved Solids

Table 2 shows the physical parameters of the groundwater samples; the data reveals the following:

pH:

The pH values of all gr the groundwater samples tested was alkaline (around 8); a pH which is generally not conducive to optimal crop plant growth

Total dissolved solids (TDS) :

Suspended solids and total dissolved solids (TDS) are indicators of polluted water. The value for TDS of the samples ranged from 2393-7123 mg/l. Most of these values are outside the standard values generally considered to be suitable for irrigation purposes. TDS values exceeding 3000 mg/l are high values for irrigation of some crop types. The high TDS values found in groundwater sampled from the study area are likely to be due to high concentrations of sodium, chloride, sulfate and nitrate.

Conductivity:

Electrical conductivity gives a measure of all of the dissolved ions in solution. Electrical conductivity values measured in this study varied from 3.74 to 11.13 ms/cm with sample-K exhibiting the highest conductivity (11.13) and sample D the lowest, (3.74). The acceptable limit of conductivity is 1.5 ms /cm22. Generally, the conductivity of clean water is lower but as water moves down the soil profile it leaches and dissolves ions and also picks up organic from the biota and detritus23. Generally the conductivity values recorded for wells sampled here were not within the acceptable limit prescribed by WHO and FAO limits.

Total Water Hardness:

Water hardness is primarily a measure of the amount of calcium and magnesium, and to a lesser extent, iron in a water sample. Water hardness is measured by summing the concentrations of calcium, magnesium and converting this value to an equivalent concentration of calcium carbonate (CaCO3); a value which is expressed in milligrams per liter (mg/L) of water. Water with hardness greater than 200 mg/L is considered to be of poor quality and water with hardness greater than 500 mg/L is normally considered to be unacceptable for domestic purposes. The analyzed samples for hardness, had hardness concentrations ranges between 1200 to 3800 mg/L been found then the samples would be assessed as belonging to the fourth category with very hard water and unacceptable for domestic purpose without treatment.

Cations and anion loads of the groundwater samples:

Table 3 shows the cations and anions loads of groundwater samples, the data shows the following:

Sodium:

An infiltration problem related to water quality occurs when the normal infiltration rate for the applied water or rainfall is appreciably reduced and water remains on the soil surface for long periods, or infiltrates too slowly to supply the crop with sufficient water to maintain acceptable yields. The infiltration rate of water into soil varies widely and can be greatly influenced by the quality of the irrigation water. The two most common water quality factors which influence the normal infiltration rate are water salinity (total quantity of salts in the water) and sodium content relative to the content of calcium and magnesium. Water which is highly saline will increase infiltration, while a low salinity water, or a sample with high sodium to calcium ratio will decrease infiltration; both of these factors may operate simultaneously. One serious side effect of an infiltration problem is the potential to develop plant disease and vector (mosquito) problems.

An infiltration problem related to water quality in most cases occurs in the surface few centimetres of soil and is linked to the structural stability of this surface soil and its low calcium content relative to that of sodium. When a soil is irrigated with sodium-rich water, a high sodium surface soil develops which weakens soil structure. The surface soil aggregates then disperse into much smaller particles which clog soil pores. The problem may also be caused by an extremely low calcium content of the surface soil. In some cases, water low in salt can cause a similar problem but this is related to the corrosive nature of the low salt water and not to the sodium content of the water or soil. In the case of the low salt water, the water dissolves and leaches most of the soluble minerals, including calcium, from the surface soil. Analyses of the ground water samples tested here shows that that all have sodium ranges over 500 (mg/L);sodium contents greater than 500 mg/L are normally considered unacceptable for irrigation according to water quality standards used by the FAO for agricultural use.

Table 3. Cations and anion loads of the groundwater samples

Sample ID

Parameters

Sodium

Na

(mg/L)

Potassium

K

(mg/L)

Phosphorus

P

(mg/L)

Sulphate

SO4

(mg/L)

Ammonia

NH3

(mg/L)

Nitrate

NO3

(mg/L)

Chloride

Cl

(mg/L)

A

500

17.0

0.53

1437

0

2.0

1250

B

1375

28.0

0.37

3275

0

10.0

2500

C

750

15.0

0.15

1302

0

5.5

1500

D

500

15.0

0.11

1380

0

2.0

1250

E

750

23.0

0.10

1607

0

4.0

1500

F

1500

27.0

0.00

3675

0

3.5

2850

G

1375

26.0

0.33

3275

0

13.5

2500

H

1375

27.0

0.25

2587

0

49.5

3000

I

1125

30.0

0.81

1737

0

138.0

2750

J

1375

27.0

0.00

2987

0

35.0

2750

K

1375

31.0

0.00

3075

0

142.0

3250

L

1125

30.0

0.25

1595

0

158.0

3000

Nitrates:

The nitrate content of the analyzed groundwater samples ranges between 2 mg/l in well A and D and reaches a maximum of 158mg/l in well L .Many of the sampled groundwater wells contain nitrate exceeding the guideline values for irrigation water prescribed by FAO (0-10 mg/l), with most of the nitrogen present being probably derived from the biosphere. The nitrogen originally fixed from the atmosphere, is mineralized by soil bacteria into ammonium, which is converted into nitrate by nitrifying bacteria under aerobic conditions24.

The main sources of nitrate result from either natural or anthropogenic activities - rainfall and dry fall out, soil nitrogen, nitrate deposit, sewage, septic tank and animal waste, manure or compost, green manure and plant residues, atmospheric nitrogen fixation, fertilizer nitrogen from irrigated overflow water outlets and industrial effluent25. Nitrate is the end product of the oxidation of nitrogen in the environment. Particularly high nitrate concentrations indicate pollution from either sewage or agricultural fertilizer waste. Nitrate is without doubt an essential plant nutrient, but is equally a potential threat to human health when present in excess concentrations in the drinking water 26. The data obtained from the samples tested here shows that the ground waters examined contain high level of nitrate, concentrations which exceed the permissible limits for drinking purposes (Table 3).

Ammonia:

The term ammonia includes the non-ionized (NH3) and ionized (NH4+) species. Ammonia originates in the environment from metabolic, agricultural and industrial processes and from disinfection with chloramines. Natural levels in groundwater and surface water are usually below 0.2 mg/liter27. Anaerobic ground waters may contain up to 3mg/liter. Intensive rearing of farm animals can give rise to much higher levels in surface water. Ammonia contamination can also arise from cement mortar pipe linings. Ammonia in water samples is an indicator of possible bacterial, sewage and animal waste pollution27. The samples analyzed here showed that all of the well waters were ammonia-free (Table 3).

Phosphates:

Slight increases may cause numerous undesirable effects, such as: accelerated plant growth, algal blooms and low dissolved oxygen levels. Phosphate levels below 0.03 mg/L are generally considered to be unpolluted. The concentration of phosphate encountered in the natural water environment is normally not sufficient to causes any detrimental health effect on humans or animals. Phosphate like any other nutrient is harmless in low concentrations but become harmful only in higher doses. Higher doses of Phosphate are known to interfere with digestion in both humans and animals28. Levels between 0.03 and 0.1 mg/l are sufficient to stimulate plant growth. However, the Po4 concentration of analyzed groundwater samples was found within permissible limit according to water quality for agriculture guidelines by FAO 1994(0-2 mg/l).

Chloride:

The chloride content of the water sampled here ranged from 1250 to 3250 mg/l. The FAO standard for chloride in irrigation water is 0 - 30 mg/l so all of the samples exceeded the acceptable limits prescribed by FAO (Table3). Chlorine is an active chemical which has disinfecting capabilities. Chlorine in natural water may originate from mine drainage waste and from dissolving rocks. The closeness of the water source to the sea can also influence the chloride content since the sea is characteristically saline. Chloride in water may react with sodium to form sodium chloride. A salinity problem exists if salt accumulates in the crop root zone to a concentration that causes a loss in yield. In irrigated areas, these salts often originate from a saline, high water table or from salts in the applied water. Yield reductions occur when the salts accumulate in the root zone to such an extent that the crop is no longer able to extract sufficient water from the salty soil solution, resulting in a water stress for a significant period of time. If water uptake is appreciably reduced, the plant slows its rate of growth.

Sulphate:

Sulfate salts affect sensitive crops by limiting the uptake of calcium and increasing the adsorption of sodium and potassium, resulting in a disturbance in the cationic balance within the plant. The sulphate content of the water samples tested here, ranged from 1302 to 3675 mg/l. (Table 3), The FAO standard for the concentration of sulphate in irrigation water is 0-20 mg/l, so the samples tested here all exceeded the acceptable limits prescribed by FAO.

Potassium:

High concentration of potassium may introduce magnesium deficiency and iron chlorosis into a soil. An imbalance of magnesium and potassium may be toxic to plants, but the effects of both can be reduced by high calcium levels. The potassium content of the water sampled here ranged from 15 to 31mg/l (Table 3).The FAO standard for potassium in irrigation water is 0-2mg/l, so the samples tested here were all within the acceptable limits prescribed by FAO.

Recommendations

Based on the outcome of the study the following is recommended;

  1. The high physicochemical values of all samples make them, under class 5 (unsuitable for irrigation waters).
  2. It is vital to create the necessary awareness of irrigation water quality among the involved agencies, such as the Ministries of Agriculture and Water, Health, and Environment, as well as other stakeholders. It has proven efficient and successful to initiate national interdisciplinary working groups with specialists of the involved authorities for the elaboration of guidelines and monitoring programs. Furthermore it is not sufficient to intervene in only one field of activities, such as guidelines for irrigation water quality. Other relevant issues including agricultural use of groundwater, crop quality monitoring and awareness campaigns have to be included and to complement each other.
  3. A carefully review should be made of the geology and geothermal nature of the study area because the geology may reveal unique or explanatory features.
  4. It is recommended that water quality analysis be carried out on all the wells in the district at least once every two years. This will ensure that incidences of contamination are noticed earlier for remedial action to be taken.
  5. Communities should be educated on the need to keep their surroundings clean, especially in the region of groundwater sources.

Acknowledgements

Authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project No. RGP-VPP-332.

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