health risk assessment of heavy metals on some vegetable

American Journal of Engineering, Science and Technology (AJEST) Volume 5, 2020

1

Health Risk Assessment of Heavy Metals on Some Vegetable Crops

Irrigated by Treated and Untreated Sewage Water

A. M. Khattab 1

, Zakia A. M. Ahmed2, M. A. Mahmoud

3, A. H. Osman

3, Hala M. F. El-

Miniawy3, and M. A. Zaki Ewiss

4

1Botany Department, Faculty of Agriculture, Cairo University, 12613, Giza, Egypt.

2Department of Veterinary Hygiene and Management; Faculty of Veterinary Medicine, Cairo

University, Egypt. 3Department of Pathology, Faculty of Veterinary Medicine, Cairo University, 12613, Giza, Egypt

4Department of Physics, Faculty of Science, Cairo University, 12613, Giza, Egypt

Corresponding author: M. A. Zaki Ewiss, Email: [email protected])

Abstract

This paper is a part of a multi-disciplinary research project “Application of Decentralized On-Site

Water Treatment System in Egypt for Use in Agriculture and Producing Safe Fish and Animal

Proteins". The project aimed to investigate the environmental impact of implementing sewage

water, before and after treatment, using the effluent of the on-site decentralized Japanese'

Johkasou system in agriculture. The further aim is to establish such system in Egypt to strengthen

the sanitary conditions of water resources. A pot experiment was carried out in the green house of

Botany Department, Faculty of Agriculture, Cairo University; 2015 and 2016, aiming to

determine the effect of using raw and treated sewage water for irrigation of some edible vegetable

crops and then evaluate the hazard effect of heavy metals on human health. The results indicated

that, the plants irrigated with wastewater exhibited the greatest values of all the vegetative growth

and yield characters compared with plants irrigated with treated water and control plants.

Vegetable tissues were analyzed for heavy metals and the Hazard Quotient (HQ) and the Health

Risk Index (HRI) were calculated. All the heavy metals in vegetable tissues irrigated by waste or

treated water, except Zn, remarkably exceeded the international permissible limits.

Key words: Sewage water, Vegetable crops, Morphological characters, Yield features, Heavy

metals.

Introduction

Food safety is a major public concern around the world. The great demands for food safety

encouraged researchers and different agricultural institutes to search for scientific solutions

concerning the consumption of food crops contaminated either by heavy metals or other toxic

compounds. In the recent time, the critical problem in some areas around the world is the use of

wastewater in agriculture due to the shortage in clean water. Sewage is a type of wastewater

produced from sinks, toilets and washing machines in city buildings which travels through

pumps and tubes to different areas (Corcoran et al., 2010). In addition, the industrialization

mailto:[email protected]


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releases huge amounts of wastewater contaminated by various types of dangerous complex

mixture of chemicals and toxic metals in drainages then to rivers. Using wastewater,

contaminated by toxic metals, in irrigation may transfer and accumulate in vegetables tissues

(Singh and Kumar, 2004; Balkhair and Ashraf, 2016). This wastewater may contain high

concentrations of heavy metals, i.e. Ni, Pb, Cu, Mn, Co, Cr, Cd and Zn. Moreover, wastewater is

a carrier of different pathogenic organisms which can transmit very dangerous diseases to

humans and animals, in addition to the occurring eco-toxicity (Harrison Ellen et al., 1999) These

toxic materials may reach to human by consumption of contaminated vegetables, drinking

contaminated water or inhalation of dust (Cambra et al., 1999; Prosser and Sibley, 2015),

causing, in a long-term, very inconvenient side effects and dangerous diseases, i.e. vomiting,

cardiovascular, hemoglobinuria, kidney failure and cirrhosis of the liver (Jarup, 2003). So, the

critical point before using wastewater to irrigate edible crops is to determine if the levels of

heavy metals are within the permissible limits of EU (2002) or FAO (1985). Measuring

Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) in wastewater is also

very important to determine water quality (Harrison et al., 2009; Poddar and Sahu, 2017; Younas

et al., 2017). In fact, farmers in many developing African countries are still using wastewater to

irrigate their crops regardless the potential dangerous health risk; the reason is often the non-

availability of other alternatives.

In Egypt and many other developing countries, it is well known that vegetable crops are always

grown at the edges of cities. Lands in these areas are mostly contaminated with heavy metals

resulting from pesticides, chemical fertilizers and factories wastes. Consequently, vegetables

growing in these lands will be contaminated with high concentrations of heavy metals. The main

reasons for using treated water to irrigate the edible crops are; 1) to enhance the public health by

the reuse of treated water properly, 2) to solve a great environmental pollution problem by the

reuse of official treated water, 3) to save the hard currency by using the fresh water properly, 4)

to protect river or seas from bacteriological and chemical pollution which led to disrupt the

ecological system and 5) to protect the desert ground water.

So, the main objectives of this study are to determine the effect of using wastewater and treated

water, obtained from Japanese's Johkasou system as an adequate technology in irrigation, on the

vegetative growth characters and the chemical constituents of some edible vegetable crops and to

evaluate the hazard effects on human public health in case of consuming the contaminated

vegetable plants.

Material and Methods

Experimental site

A pot experiment was performed in the greenhouse and laboratory of Botany Department,

Faculty of Agriculture, Cairo University, Giza, Egypt. The experiment was carried out in two

seasons; 2015 and 2016 during the period from June to October of each season.

Source of waste and treated water


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Wastewater (100%) and treated water samples used to irrigate the plants of the chosen vegetable

crops were obtained from the Japanese's Johkasou System, Faculty of Science, Cairo University,

Giza, Egypt and kept in pre cleaned polyethylene tanks. Tanks were transferred immediately to

the experimental site and used directly to irrigate the vegetable plants. The following table

represents the parameters of water analyses of these types of water.

Cultivation media and experimental design

Black plastic pots, 30 cm in diameter, were used and filled with peat moss and clean sand at a

ratio of 2:1 (v/v). Peat moss was fermented by spreading the volume of each plastic bag on

sunlight and irrigated by tap water then left for 24 hr before using as planting media. The

experiment was designed as randomized complete block with three replicates, each replicate

contained 30 pots. Each two pots represented one vegetable crop (Fig.1).

Table 1: Parameters of Water analyses of waste, treated and tab waters

Parameters Waste

Water

Treated

Water

Tap

Water

Analysis methods

pH 7.2 7.3 7.3 pH meter

Total Suspended Solids mg/l 88 N.D N.D APHA (2005).

Ammonia mg/l 0.84 N.D N.D micro-Kjeldahl (Helrich, 1990)

Nitrate (NO3-N) mg/l 0.40 0.35 0.30 (Bagshaw et al. 2000).

Total Phosphate (PO4-P) mg/l 1.7 N.D N.D (Bagshaw et al. 2000).

Chemical Oxygen Demand (COD)

mgO2/l

254 10 7 Standard Methods for the

Examination of Water and

Wastewater, (1975)

Biological Oxygen Demand (BOD)

mgO2/l

140 5.5 2.1 Young et al. (1981)

N.D: Not detectable


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Fig. 1. Digital photo representing the experimental replicates

Materials

Growing media

Table (2) represent the physical and chemical characteristics of the media used (peat

moss and clean sand at a ratio of 2:1 (v/v)) for growing the vegetable crops.

Table 2: Physical and Chemical characteristics of the media used for growing the vegetable crops

Parameter Average

Physical and chemical characteristics

Texture Sand and peat moss

pH 7.2

EC (mmhos/cm) 0.92

Soluble Cations (meq/l)

Ca++

2.31

Mg++

0.31

Na+

1.76

K+

Soluble Anions (meq/l)

HCO3-

0.35

Cl-

1.06

SO4--

3.2

Available N (ppm) 58

Available k (ppm) 430


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Types of vegetable crops.

Seeds of five edible vegetable crops (Table 3) were obtained from the Experimental Farm,

Faculty of Agriculture, Cairo University, Giza, Egypt. Seeds were sown on the 1st of June of

each season; 2015 and 2016.

Table 3: Families, Accepted and English names, and edible parts of the vegetable crops

Species Family English name Edible part

Cucumber sativus L. Cucumberaceae Cucumber Fruits

Pisum sativam L. Fabaceae Pea Pods

Apium petroselinum L. Apiaceae Parsley Leaves

Eruca sativa Mill. Brassicaceae Roquette Fruits

Chorcorous olitorious L. Malvaceae Molokia Leaves

Agricultural procedures

Seeds were sown in plastic pots, 30 cm in diameter, filled with peat moss and clean sand at a

ratio of 2:1 (v/v). Seeds were irrigated firstly with tap water for fifteen days till the emergence of

the uniform seedling. Then starting from 16th of June, the plants in each replicate were irrigated

with equal volume (300 ml) of tap water, wastewater (100%) and treated water once a week.

Mineral fertilizer NPK was applied according to the recommended doses. Each pot received

about 2g ammonium sulphate (20.6% N), 1g calcium superphosphate (15.5% P2O5) and 0.5 g

potassium sulphate (48% K2O).

Heavy metals analysis

Heavy metals; Ni, Cu, Pb, Zn, Cr, Co and Cd were determined by using an atomic absorption

spectrophotometer apparatus (Model 6220, Germany) at the Central Laboratory, Faculty of

Agriculture, Cairo University, Giza, Egypt. The following equations were used to calculate the

health risk assessment of heavy metals in plant tissues were obtained from Alloway (1990),

Jarup (2003), Hodson (2004), Wang et al. (2005), Rattan (2005), Yang et al. (2009), Augustsson

et al. (2015), Balkhair and Ashraf (2016) and Zhou et al. (2016).

HQ (Hazard Quotient) = [Wplant] x [Mplant] /RFd x B

Where, Wplant is the dry weight of contaminate plant material consumed; Mplant, is the

concentration of metals in vegetable tissues; Rfd, is the food reference doses for the metals (0.02,

0.04, 0.004, 0.02, 1.50 and 0.30 mg/kg dw/day for Ni, Cu, Pb, Cr, Cd and Zn, respectively) and

B is the average body mass of consumer (70 kg av.).

DDI (Daily Dietary Index )= X * Y * (Z / B)

Where, X is the concentration of metals in vegetable tissues; Y is the dry weight of

vegetable tissues and Z is the proximate daily intake consumed (40 g/daily av.) (Chien et al.,

2002).


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DIM ( Daily Intake of Metals) = Cmetal * Cfactor *( Dfood intake / Beverage weight)

Where, Cmetal is the heavy metal concentrations in plant tissues; Cfactor is the conversion

factor (0.085); Dfood intake, is the value of the daily intake of vegetable consumed and Beverage

weight, is the average body mass of consumer (70 kg av.).

HRI (Health Risk Index) = DIM / Rfd

Digested plant samples for chemical analysis

Plants sample were digested for chemical analysis according to Aallen et al. (1986).

Data Record

At the end of the experiment at each season, twelve plants from each treatment, four from each

replicate, were chosen in order to record the vegetative growth characters and yield components

of the vegetable plants. The chemical constituents of the dry weight of each plant tissues were

also recorded. The recorded characters were as follows:

The morphological characters

The morphological characters recorded on the vegetable plants were; plant height (cm), number

of branches/plant, number of leaves/plant, leaf area (cm2), total fresh weight (g/plant), total dry

weight (g/plant) and number of fruit or pods/plant.

The chemical constituents in plant stem and leaf

The chemical constituents of the vegetable plants were; Nitrogen (N) g/kg, the total nitrogen

content of the dried leaves was determined using the modified- micro-Kjeldahl method as

described by (Helrich, 1990). Phosphorus (P) g/kg, was determined calorimetrically by using the

chlorostannous molybdophosphoric blue color method in sulphuric acid according to Jackson

(1973). Potassium (K) g/kg, was determined by using the flame photometer apparatus (Corning

M 410, Germany). Magnesium (Mg) g/kg, was calculated according to (Hanson et al., 1993).

Sulphur (S) g/kg, was determined according to Ion chromatographic determination of sulfate

(Dick and Tabatabai 1979).

Statistical Analysis

Data on the morphological characters of the vegetative growth and chemical analysis were

subjected to conventional methods of analysis of variance according to (Snedecor and Cochran

1982). The least significant difference (L.S.D. at 0.05%) level was calculated.

Results and Discussion

Morphological characters

Concerning the data in Table (4), the values of all the vegetative growth characters of the

Cucumber, Pea, Parsley, Roquette and Molokia plants increased significantly when irrigated with

either wastewater (100%) or treated water compared to those plants irrigated with tap water. For

example, in the Cucumber plant, the averages of vegetative growth treated with wastewater


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significantly increased by 9.3, 46.2, 54.6, 53.7, 15.1, 10.2 and 47.6% more than the control

plants for plant height, number of branches/plant, number of leaves/plant, leaf area, total fresh

weight, total dry weight and number of fruit/plant, respectively. While these averages, when

irrigated with treated water were 3.0, 15.4, 15.2, 31.3, 8.5, 8.5 and 13.3% more than the control

plants, in the same order of aforementioned growth parameters. The same trend, to some extent,

has been noticed with the other vegetable crops irrigated with the waste or treated water (Table

4).

These results could be attributed to the fact that wastewater and treated water contain most of the

elements and salts required by the plant. In this concern, it should be stated that the healthy

performance of plants irrigated with these types of water, is not a sign indicating the edibility of

these plants where, plant tissues should be analyzed first to determine the quantities of heavy

metals or any other chemical components present. In this connection, (Wang et al., 2010) on the

growth of wheat and cucumber and (Dantas et al., 2014) and (Khan et al., 2009) on radish

obtained quite similar results.

Yield characters

The highest yield values were obtained for Cucumber plant in number of fruits (46.8) and for Pea

plant in number of pods (45.1) which significantly exceeded in the plants irrigated with

wastewater and treated water compared to those plants irrigated with tap water. These values

were higher by (47.6 and 29.6%) and (13.3 and 9.8%), for wastewater and treated water,

respectively (Table 4). The reason for increasing the number of fruits and pods in the plants

irrigated by these types of water reflects the increase occurred in the vegetative growth. The

present results were in agreement with Vega et al., (2004) and Rattan et al., (2005) on some

crops.

Chemical analysis

Regarding NPK contents in the economic plant organs of the studied vegetable crops, data

presented in Fig. (2) proved that, N P K contents (g/kg) varied according to type of irrigation

water and plant species. So, concerning N content in plant tissues, the highest N content was

found in Pea (26.8 g/kg) and in Molokia plants (22.5 g/kg) irrigated with treated water compared

with the other two water treatments. On the other hand, the lowest N content was recorded in

Cucumber (2.3 g/kg) plants irrigated with wastewater followed by Parsley plants (10.0 g/kg).

Regarding P content in tissues, it is obvious that, Cucumber and Molokia plants irrigated with

wastewater showed the lowest P content; 0.02 and 1.8 g/kg, respectively. The highest P contents;

4.1 and 3.9 g/kg were recorded in Roquette plants irrigated with treated and wastewater,

respectively. In case of K content, the highest amounts of K; 43.8 and 42.5 g/kg were observed

in Roquette and in Pea plants irrigated with wastewater, respectively. The previous results

indicates that irrigating plants with waste or treated water will increase the NPK contents in

plants which, in turn, will reflect on the whole vegetative growth.

The highest amount of Mg; 4.8 g/kg was noted in Pea plants irrigated with treated water. The

highest S content in tissues; 42.4 g/kg was noticed in Molokia plants irrigated with wastewater

while the lowest content of S ; 6.0 g/kg was tabulated in Cucumber plant irrigated by treated


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water. Molokia and Parsley plants irrigated by wastewater recorded the highest amount of Mn;

2.56 and 2.18 mg/kg, respectively.

Table 4: Morphological and yield characters of some vegetable plants irrigated by waste, treated and tap

water (av. means of 12 plants of each treatment)

Cucumber plant (Cucumber sativus L.)

Treatments Plant

height

cm

No. of

branches/plant

No. of

leaves/plant

Leaf area

mm2

Total

F.W.

g/plant

Total D.W.

g/plant

No. of fruits

or pods / plant

Tap water 109.5 13.0 33.0 296.0 122.0 30.5 31.7

Treated water 112.8 15.0 38.0 326.0 132.4 33.1 35.9

Wastewater 119.7 19.0 51.0 455.0 140.4 33.6 46.8

Mean 114.0 15.6 40.7 359.0 131.6 32.4 38.1

LSD 5% 2.9 0.8 3.7 24.9 17.9 1.2 2.3

Pea plant (Pisum sativam L.)

Tap water 15.2 4.4 14.5 54.0 36.6 9.2 34.8

Treated water 16.4 4.7 14.9 59.0 41.0 10.2 38.2

Wastewater 20.6 6.9 19.8 69.0 51.8 12.9 45.1

Mean 17.4 5.3 16.4 60.7 43.1 10. 8 39.4

LSD 5% 0.8 0.3 0.4 4.2 1.3 0.2 2.8

Parsley plant (Apium petroselinum L.)

Tap water 13.9 5.8 36.8 17.6 26.9 6.7 NA

Treated water 15.6 6.2 40.7 17.9 28.0 7.0 NA

Wastewater 17.9 9.2 55.2 21.9 37.8 9.4 NA

Mean 15.8 7.1 44.2 19.1 30.9 7.7 NA

LSD 5% 1.0 0.8 3.2 0.2 1.4 0.1

Roquette plant (Eruca sativa Mill.)

Tap water 22.6 5.2 7.8 44.6 41.2 10.3 NA

Treated water 23.9 5.8 9.3 49.1 45.2 11.3 NA

Wastewater 29.6 7.2 10.3 59.7 51.1 12.8 NA

Mean 25.4 6.1 9.1 51.1 45.8 11.5 NA

LSD 5% 0.8 0.1 0.7 2.7 1.7 0.1

Molokia (Chorcorous olitorious L.)

Tap water 28.7 7.4 34.8 32.7 90.4 22.6 NA

Treated water 31.5 7.8 37.2 35.4 101.5 25.1 NA


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Fig.2: Chemical analysis of the whole vegetable plant irrigated with waste, treated and tap water.

Key: left column: Tap Water, Mid column: Treated water, Right Column: Sewage water

Evaluation of health risk assessment of heavy metals

Heavy metals have been considered as one of the most disastrous pollutants. Heavy

metals concentrations in vegetable tissues (Table 5) remarkably varied based on the type of

irrigation water and the used species. Using the contaminated wastewater to irrigate the

vegetable crops may increase the amount of accumulated heavy metals in plant tissues over the

international limits (European Union standard, 2002). So before concerning a crop is for

edibility, it is necessary to calculate the Health Risk Assessment values to determine its effects

on human or animal health. The health risk assessment was calculated for the studied vegetables

irrigated with waste, treated and tap water by using some equation mentioned earlier.

Wastewater 39.1 9.3 45.7 40.7 121.0 30.4 NA

Mean 33.1 8.2 39.2 36.3 104.3 26.0 NA

LSD 5% 2.7 0.4 2.1 1.1 11.0 1.2


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Data in Table (5) showed that, the concentrations of heavy metals in the leafy vegetable plants;

Parsley and Molokia, irrigated by waste and treated water were higher than the other

vegetables which have fruit or pods; Cucumber, Pea and Roquette. In this concern, Sinha et al.,

(2006) reported that the cereal crops have low heavy metal concentrations in tissues compared

with the leafy vegetables. This variation in the heavy metal concentrations may be due to the

ability of the leafy plants to absorb, accumulate and translocate these metals within tissues

(Vousta et al., 1996; Balkhair and Ashraf, 2016). While, Ashok et al., (2009) stated that this

variation may be due to the morphological and physiological differences of the leafy vegetables

than cereals in its ability to uptake, translocate and accumulate the heavy metals. Many other

researchers have dealt with the hazardous effect of heavy metals, i.e. Chien, et al., 2002; Kim et

al., 2007; Khan et al., 2008 and Sharma et al., 2009.

Table 5: Heavy metal contents on some vegetable plant irrigated with waste, treated and tap water

Crop name /

Treatments

Ni

mg/l

Cu

mg/l

Pb

mg/l

Zn

mg/l

Cr

mg/l

Co

mg/l

Cd

mg/l

Cucumber

Tap water

Treated water

Wastewater

0.89

1.43

2.82

5.35

11.00

18.41

0.35

0.48

0.64

1.15

0.62

0.92

0.13

0.15

0.28

0.08

0.13

0.32

0.10

0.12

0.31

Pea

Tap water

Treated water

Wastewater

0.91

1.37

2.57

6.01

13.00

20.60

0.38

0.69

0.82

0.28

0.80

1.21

0.20

0.26

0.50

0.13

0.24

0.35

0.16

0.19

0.42

Parsley

Tap water

Treated water

Wastewater

1.09

1.95

3.51

6.48

15.51

23.56

0.51

1.46

1.74

0.38

1.46

1.68

0.49

0.54

1.04

0.22

0.59

0.97

0.26

0.32

0.69

Roquette

Tap water

Treated water

Wastewater

0.85

1.29

2.41

5.70

11.57

18.90

0.29

0.57

0.72

0.21

0.66

1.01

0.16

0.22

0.36

0.10

0.18

0.31

0.13

0.17

0.35

Molokia

Tap water

Treated water

Wastewater

1.19

2.19

4.44

7.06

18.01

27.00

0.56

1.66

2.56

0.64

1.66

2.51

0.58

0.63

1.22

0.36

0.77

1.43

0.37

0.53

0.92

European Union standard (2002): Ni 1.04, Cu 0.05, Pb 0.10, Zn 5.00, Mn 0.10, Cr 0.05, Co 0.05 and Cd 0.010


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Among the studied vegetables, the concentration of Cu was the maximum (27.0 mg/l) in

Molokia plants irrigated with wastewater followed by Parsley (23.36 mg/l). While the lowest

concentration was noticed in Cd (0.12 mg/l) in Cucumber plants irrigated with treated water.

By applying the health risk assessment equations mentioned earlier, data in Table (6) showed

that the Hazard Quotient (HQ) of the vegetable plants irrigated with wastewater or treated water

exceeded the international limits (1 mg/l) for all heavy metals, except for Zn in Cucumber, Pea,

Parsley and Roquette. While in Molokia plants, the HQ was very high for all concentrations of

heavy metals when irrigated with waste or treated water compared with other vegetables. The

HQ of Roquette plants irrigated with treated water was above 1.0 mg/l, except for Zn and Co.

Calculating the Health Risk Index (HRI), only Zn, Cr and Co were beneath the international

limits, while the other metals exceeded the limits in all vegetables. The population will not

suffered from any dangerous effect of heavy metals if the HQ and HRI values are less than 1.0

mg/l, but if this ratio is equal or greater than 1.0 mg/l the population will pose high health risk by

time (Sinha et al., 2006; Jaishankar, 2014).

Table 6: Calculation the HQ and HRI of heavy metals in all vegetable species

Treat.

Heavy

metals

Cucumber

fruits

Pea pods

Parsley leaves

Roquette fruits

Molokia leaves

HQ HRI HQ HRI HQ HRI HQ HRI HQ HRI

Tap

water

Ni

Cu

Pb

Zn

Cr

Co

Cd

19.389

58.276

38.125

1.670

2.832

1.162

43.571

2.150

6.500

4.250

0.187

0.300

0.133

5.000

5.980

19.747

12.486

0.123

1.314

0.570

21.029

2.200

7.300

4.500

0.047

0.500

0.200

8.000

5.216

15.506

12.204

0.121

2.345

0.702

24.886

2.650

7.875

6.250

0.063

1.200

0.367

13.000

6.234

20.968

10.668

0.103

1.177

0.491

19.129

2.050

6.925

3.500

0.033

0.400

0.167

6.000

30.671

56.984

45.200

0.689

9.363

3.874

119.457

2.900

8.575

6.750

0.103

1.400

0.600

18.000

Treated

water

Ni

Cu

Pb

Zn

Cr

Co

Cd

3.381

130.036

56.743

0.977

3.546

2.049

56.743

3.500

13.350

5.750

0.100

0.350

0.200

6.000

9.981

47.357

25.136

4.335

1.894

1.166

27.686

3.350

15.775

8.500

0.130

0.650

0.400

9.000

9.750

38.775

36.500

0.487

2.700

1.967

32.000

4.750

18.825

17.750

0.237

1.500

0.967

16.000

10.412

46.693

23.004

0.355

1.776

0.969

27.443

3.150

14.050

7.000

0.107

6.300

0.300

8.000

39.264

161.447

148.807

1.984

11.295

9.203

190.043

5.300

21.875

20.250

0.270

1.550

1.233

26.000


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Waste

water

Ni

Cu

Pb

Zn

Cr

Co

Cd

67.680

220.920

7.680

1.472

0.672

5.120

148.800

6.850

22.35

7.750

0.150

0.700

0.533

15.000

23.681

94.907

37.779

0.743

4.607

2.150

77.400

6.250

24.975

10.000

0.197

0.048

0.049

20.000

23.567

79.094

58.414

0.752

6.983

4.342

92.657

8.500

28.600

21.000

0.273

2.550

1.567

34.000

22.034

86.400

32.914

0.616

3.291

1.890

64.000

5.850

22.925

8.750

0.167

0.900

0.500

17.000

82.457

250.714

237.714

3.108

22.657

17.705

341.714

10.800

32.750

31.000

0.407

2.950

2.300

45.000

Conclusion

From the previous results, it could be concluded that, using wastewater in irrigation, the

performance of the morphological and yield characteristics of the vegetable plants will

significantly be enhanced and improved. But this improvement is not a true sign for these plants

to be edible. Vegetable crops contaminated with heavy metals are very dangerous to be

consumed, because these metals are accumulated in human, plants and animal tissues and cause,

in a long-term, very inconvenient side effect, i.e. cardiovascular, kidney and different liver

diseases. The study suggested the necessity of measuring the health risk assessment of heavy

metals in the contaminated vegetable crops irrigated by wastewater before using. In addition,

using the waste or treated water in irrigation of the edible crops should be prohibited by law.

Other intensive studies on the effect of wastewater before and after treatment using the Johkasou

decentralized system on producing fish and animals proteins are in progress in our group.

Acknowledgement

The authors dedicate this research to the spirit of Professor T. Hasegawa (Former

Director, CISRA Centre, Eco-Topia Institute, Nagoya University, Japan), he died in August

2020. The active and sincere support of Mrs. M. Takeuchi (Former Project Manager at the same

Institute) is highly appreciated. The financial support of Cairo University is acknowledged.

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