BEHAVIOUR OF HEAVY METALS IN SEWAGE-SLUDGE AMENDED SOIL WAS DISCUSSED

1. BEHAVIOUR OF HEAVY METALS IN
SEWAGE-SLUDGE AMENDED SOIL
Sourav Bhattacharyya
and
Prof. P. K. Mani
DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCE
FACULTY OF AGRICULTURE
BIDHAN CHANDRA KRISHI VISWAVIDYALAYA
Mohanpur, Nadia, 741252, India
pabitramani@gmail.com

2. Essential heavy metal Non essential heavy
metal
Fe, Zn, Cu, Mn, Mo, Ni Pb, Hg, Cd, Cr, Se
Heavy metals :
 Atomic no. > 20
 Specific gravity > 5
Brady N.C. (2002)

3. Sewage : Sewage is water-carried waste, in
solution or suspension, that is intended to
be removed from a community.*
Sludge: A mixture of solid and water,
produced during the treatment of waste
water or sewage.*
*Central Pollution Control Board(1993)

4. Table 1. Agricultural use of sewage sludge in different
countries:
Country Year Sludge
production
(t/yr)
Agriculture
(t/yr) % of total
Germany* 2007 2056486 1439540 70
Spain* 2006 1064972 692231 65
Sweden* 2006 210000 30000 14
UK* 2006 1544919 1050544 68
Austria* 2006 252800 38400 16
Italy* 2006 1070080 189554 18
USAa 1998 6900000 2800000 41
*United Nations Human Settlement Program (2008)
 In India production of sewage sludge is estimated to be
around 1000-1300 tonnes/day.
Deshbhratar et al. (2001)

5. Table 2: The content of heavy metals in agricultural soils (mg/kg)
Country Cr Cu Pb Zn Ni Cd Hg Reference
Spain 63.48 107.65 213.93 427.80 34.75 1.42 -
Zimakowska-
Gnoinska et al.,
2000
America - 95.00 23.00 - 57.00 0.78 - Han et al., 2002
Korea - 2.98 5.25 4.78 - 0.12 0.05
Kim and Kim,
1999
Slovakia - 65.00 139.00 140.00 29.00 - - Wilcke, 2005
USA 48.5 48 55 88.5 29 13.5 -
Jean-Philippe
et al., 2012
India 1.23 2.62 2.82 4.65 0.14 0.05
Prajapati and
Meravi, 2014
Iran 10.36 9.62 5.17 11.56 11.28 0.34 -
Sayyed and
Sayadi, 2011
Zojaji et al.,
2014

6. Samples Standards Fe Zn Cu Pb Cd Mn Cr
Water
(mg L-1)
Indian Standard (Awashthi,
2000)
NA 5.0 0.05 0.10 0.01 0.1 0.05
WHO/FAO (2007) NA 2.0 0.20 5.0 0.01 0.2 0.10
European Union
Standards (EU2002)
- - - - - - -
USEPA (2010) NA 2.00 1.00 .015 .005 .05 0.10
Kabata-Pendias(2010) 0.80 NA NA NA NA NA NA
Soil
(mg kg-1)
Indian Standard (Awashthi
2000)
NA 300-600 135-270 250-500 3-6 NA NA
WHO/FAO (2007) - - - - - -
European Union
Standards(EU2002)
NA 300 140 300 3.0 NA 150
USEPA (2010) NA 200 50 300 3.0 80 NA
Kabata-Pendias (2010) 1000 NA NA NA NA NA NA
Plant
(mg kg-1)
Indian Standard (Awashthi,
2000)
NA 50.0 30.0 2.5 1.5 NA NA
WHO/FAO (2007) 450 60.0 40.0 5.0 0.2 500 5.0
European Union Standards
(EU2002)
NA 60 40 0.30 0.20 NA NA
USEPA (2010) - - - - - - -
Table 3. Guidelines for safe limits of some heavy metals in water,
soil & plants

7. Behaviour of heavy metals in sewage sludge-
amended soils and their impact on food composition
 The concentrations of heavy metals in sludge-amended
soils.
 The bioavailability of these heavy metals to crops.
 Effects of soil properties on the bioavailability of heavy
metals.
 Changes in bioavailability during the residual period.
 Differences between crop species and cultivars in the
uptake and accumulation of heavy metals in edible
organs.
 Movement of heavy metals in the soil profile and the
potential risk of groundwater pollution.

8. Heavy metal availability
in sewage sludge
amended soils

9. ‘Available’ heavy metals - fraction of the total concentration
of heavy metals in the soil, which is present in the soil
solution or easily exchangeable from the soil exchange
surfaces.
Total heavy
metal (M)
M in soil solution
Exchangeable
M bound to carbonates
M bound to Fe & Al oxides
M bound to organic matter
Residual fraction
Readily available
Naoum et al. (2001)
=
+
+
+
+
+

10. Factors affecting heavy metal availability to plant
A)Soil properties
B)Plant factors
C)Soil-plant transfer coefficient

11. Soil properties
a) pH
 Availability of cationic
heavy metals decreases with
increase in pH
pH
(Alloway and Jackson, 1991)
 Whereas, availability of Mo
and elements with anionic
species increases with
increasing soil pH
pH
(Smith, 1996)

12. b) Organic matter
 Application of organic matter reduces the mobility of metals in soil
and thus lowers their availability to plants.
Environmental Protection Capacity (EPC) factor = DxH2K
Dx - thickness of the soil layer (cm)
H - soil humus content
K - constant depending on the humus quality.
Sludge + O.M Soil humus
EPC Heavy metal
availability
Hargitai (1989)
 Humic acids bind metals and reduce their availability to plants and
thus, metal retention by the soil increases when sewage sludge is
applied. Piccolo (1989)

13. C) Clays and hydrous oxides
Clays and hydrous oxides determine metal availability by -
2) Non-specific adsorption (exchange)
1) Specific adsorption to surface hydroxyl groups
(Miller et al., 1987)
3) Co-precipitation (Martinez and McBride, 1998)
4) Precipitation as the discrete metal oxide or
hydroxide
(Martinez and McBride, 1998).
(Basta and Tabatabai, 1992)

14. d) Redox potential-
Flooded condition-
SO4
2- → SO3 - → S2-
S2- + M2+ → MS
 H2S precipitates with Cd in the form of CdS, which is an
insoluble compound. Evans (1989)
 Metals expected to precipitate as sulphides include
Ag+, Ni2+, Zn2+, Hg2+ and Fe3+.

15.  With high P contents, at neutral to alkaline pH, a
precipitation of Cd3(PO4)2 takes place.
 Increase in the Ca2+ concentration in the solution
from 10-3 to 10-2 M, Cd concentration decreases by
67%.
 Sulfur, inhibits the transport of Pb in the plants from
roots to shoots and it was found that S-deficiency
increased Pb movement to the tops.
e) Effects of other elements-
Jing and Logan (1992)
Alloway (1995)
Kabata-Pendias and Pendias(1992)
Antagonistic effect-

16. f) CaCO3 content-
 At high pH and high pCO2 (partial pressure
of CO2) values, calcite (CaCO3) sorbs Cd as
CdCO3 and diminishes its availability.
Evans (1989)
Other metals likely to precipitate as
carbonates at high pCO2 and pH values
include: Fe2+, Zn2+ and Pb2+
Evans(1989)

17. Movement of metals within the profiles of sludged soil
 Cd, Cr, Cu, Mo, Ni, Pb and Zn all moved from the surface to within
the top 10 cm of the profile, but an average of 87% of metals (range
60-100%)remained in the upper 5 cm after application of sewage-
sludge in grassland.
Applications of composted sewage sludge 150 and300 dry t ha-1 on
a silt loam soil Zn and Cu concentrations increased down upto 75cm
depth with most of the movement occurring in the first year.
 In California, found that even after applications of sludges
amounting to a maximum of 1800 dry t ha- 1 on a loam soil, Cd, Zn, Ni,
and Co tended to remain in the zone of incorporation over a 9 year
period.
Williams et al. (1987)
Evans, L.J (1989)
Darmody et al. (1993)

18. Table 5. Average heavy metal concentration at different
depths in a sewage irrigated soil(mg kg-1)
Depth
(cm)
Cd Cr Ni Cu Zn Pb As Hg
0-20 0.85 91.21 64.19 41.17 276.41 41.56 17.72 1.72
20-40 0.32 28.18 26.39 8.96 17.25 15.33 15.24 0.83
40-60 0.20 25.29 24.91 7.74 10.26 14.29 6.84 0.21
60-80 0.49 26.08 24.43 7.22 39.60 13.31 2.88 0.09
Wang et al, (2012)

19. g) Other factors-
Soil moisture
Soil temperature
Soil aeration

20. Table 5. Total heavy metals content (mg kg−1) in waste
water irrigated soils of peri-urban Kolkata(0-20cm)
Parameters Zn Cu Pb Cd Ni
Mean 66.56 27.81 102.9 15.95 36.81
Median 67.42 26.39 106.02 16.72 37.33
Minimum 52.60 13.20 80.08 8.80 19.50
Maximum 84.35 47.40 121.78 18.08 55.40
SD 10.36 10.33 10.22 2.27 9.60
(Saha et al, 2015)

21. Parameters Unamended soil 6 kg m-2 SSA 9 kg m-2 SSA 12 kg m-2 SSA
pH (1:5) 8.18 8.06 8.09 7.85
EC (mScm-1) 0.24 0.29 0.32 0.39
Organic C (%) 0.77 1.41 1.52 1.74
Total N (%) 0.18 0.20 0.20 0.21
P (mg kg-1) 54.43 111.81 124.2 132.8
Cu (mg kg-1) 3.51 8.50 10.81 11.13
Mn (mg kg-1) 13.27 34.36 41.17 42.05
Zn (mg kg-1) 2.11 11.95 22.95 30.91
Cr (mg kg-1) 0.34 0.77 1.50 1.66
Cd (mg kg-1) 1.51 6.39 6.44 7.36
Ni (mg kg-1) 4.95 9.69 10.29 10.75
Pb (mg kg-1) 2.83 8.49 10.04 11.06
Singh & Agrawal (2010)
Table 6. Effect of sewage sludge on nutrient and heavy metal
content in soil

22. Heavy metal accumulation
in soils and plants

23. Plant factors
a) Plant species
Metal High accumulations Low accumulations
Cd Spinach, Lettuce, Celery,
Cabbage
Potato, Maize, French bean,
Peas
Pb Rye grass, Celery, Kale Some barley cultivars,
Potato, Maize
Cu Sugar beet, Certain barley
cultivars,
Cabbage, Onion,Leek
Ni Sugar beet, Rye grass, Turnip Maize, Leek, Barley, onion
Zn Spinach, Sugar beet, Beetroot Potato, Leek, Tomato, Onion
McCutcheon & Schnoor (2003)

24. Table 8. Accumulation of heavy metals (mg kg−1) in crops
grown in sewage-irrigated soils
Crops Zn Cu Pb Cd Ni
Sesame (n=10) 24.4 7.9 66.3 13.5 23.8
Chilli (n=6) 32.4 11.2 65.5 11.8 15.4
Okra (n=9) 34.2 9.0 73.3 13.0 19.3
Jute (n=10) 30.7 4.8 68.4 12.7 16.9
Brinjal (n=6) 35.5 6.9 76.4 12.6 23.5
Poi (n=10) 37.5 6.8 79.9 13.1 19.1
Amaranthus (n=4) 33.9 4.8 84.8 13.3 26.6
Colocasia (n=4) 39.3 21.3 91.9 16.8 21.1
Cowpea (n=6) 37.1 4.9 84.1 12.9 21.4
Cauliflower (n=6) 37.3 3.8 70.7 11.6 13.4
All values are mean values Saha et al. (2015)

25. Other plant factors:
b) Cultivars
15 cultivars of potato varied widely in Cd
concentrations on the same soil with ranges
of 9-39 μgkg-1 on one site and 29-56 μgkg-1 at
others.
McLaughlin et al. (1994)
c) Genotype
The differences between plant genotypes in
term of Cd uptake have also been reported.
Hocking & McLaughlin (2000)

26. Soil-Plant Transfer Coefficient
Transfer Coefficient (TC)= ----------------
[M]plant
[M]soil
[M]plant- concentration of an metal in the test plant tissues
[M]soil- total concentration of the same metal in the soil
where this plant is grown

27. Table 9. Transfer coefficient (TC) of metals from soil to
plants in waste water-irrigated soils of peri-urban
Kolkata
Metal Sesame Chilli Okra Brinjal Cauliflower
Zn 0.26–0.70 0.38–0.56 0.28–0.77 0.48–0.65 0.46–0.83
Cu 0.19–0.93 0.15–0.66 0.16–0.69 0.16–0.30 0.07–0.24
Pb 0.44–0.87 0.50–0.77 0.57–1.05 0.59–0.97 0.56–0.71
Cd 0.72–0.94 0.46–0.97 0.52–1.03 0.68–0.83 0.51–0.82
Ni 0.50–1.25 0.22–0.63 0.19–0.93 0.40–0.73 0.22–0.67
Saha et al. (2015)

28. Effect of sewage sludge amendment on
microorganisms activity
 A 50% reduction in nitrogen fixation is obesrved in a soil
following sewage sludge application. McGrath et al. (1988)
 Application of sludge containing low concentration of
heavy metals improved soil microbial activities.
 Elevated metal concentration have been shown to reduce soil
microbial biomass levels, inhibit nitrogen fixation and reduce
enzyme activities.
High levels of sludge application (200 t ha–1) significantly
reduced the functional diversity of soil community.
Powlson (2002)
Akmal (2005)
Banerjee et al. (1997)

29. Changes in the availability of heavy metals to
crops during the residual period
Any changes which are observed in the bioavailability of metals
through time could be due to combinations of several factors-
 soil physical properties
 changes in soil pH
 Presence of amount of organic matter
 the reactivity of soil minerals (hydrous
oxides of Fe and Mn)
Two types of reversion occurred-
 Reduction in the formation of soluble ligands due to
microbial action.
 Slow reaction of metals with minerals in solid-solution
reactions. Chang et al. (1987)

30. Changes in the availability of heavy metals to crops during the residual period
(contd.)
 The metals remained available for uptake, giving
anomalously high concentrations of metals in plant
organs for many years after application. Chaney et al. (1988)
 Availability remained roughly the same.
Chang et al. (1982)
 Heavy metal concentration decreases after
the last sludge application. Hinesly et al. (1979)
 McGrath (1987) points out that 9 out of 11 papers
showed availability to remain more or less constant
over several years.
Changes in the availability of heavy metals to
crops during the residual period(contd.)

31. Table 10. Concentration of heavy metals (mg kg-1) in leaves
of Chinese cabbage grown in soil amended with
various content of sewage sludge
Heavy
metal
Control 5% a 10% a 15% a 20% a 25% a Limits b
As 2.1 5.8 5.9 7.4 10 7.9 0.05
Cd 0.14 0.15 0.25 0.25 0.41 0.24 0.2
Cr 0.7 2.4 3.1 3.2 5.5 5.8 0.5
Pb 0.08 0.17 0.24 0.27 0.19 0.22 9
Ni 1.2 0.6± 1.6 1.6 2.1 3.1 10
Cu 2.6 4.7 5.6±1.1 4.2±0.8 3.6 4.2 20
Zn 43.4 63.3 65.9 78.9 72.5 69.5 100
a Percentages of sewage sludge in soil
b Maximum permissible limits of metal contaminants
(CEPA)
wang et al. (2008)

32. Table 11. Concentrations of heavy metals in
vegetable edible parts (mg kg-1)
Vegetable
Type
Vegetable
Species
Pb (mg kg-
1)
Cd (mg kg-
1)
Cu (mg kg-
1)
Zn (mg kg-
1)
Root (n=3) Carrot 0.23 0.02 0.22 1.59
Sweet potato 0.61 0.13 0.01 4.67
Solanaceou
s (n=3)
Brinjal 0.42 0.28 0.93 2.78
Tomato 0.07 0.02 0.46 1.41
Leafy (n=8) Cabbage 0.67 0.03 0.31 9.92
Spinach 0.97 0.51 0.96 20.81
Lettuce 1.16 0.46 0.77 11.79
Legume
(n=2)
Asparagrass
bean
0.70 0.01 1.99 6.68
Kidney bean 0.03 0.01 1.31 5.66
Zhou et al., 2016

33. Cumulative accumulation of heavy metals (Cd, Cr, Ni) in edible parts of
vegetables (mg kg−1 dry weight) grown in treated sewage water irrigated
soils
Ghosh et al., (2011)

34. Table 12. Yield parameters of mung bean plants grown at
different Sewage Sludge amended rates(SSA)
Treatment No. of pods/plant Yield (g m-2) Harvest index (g
g-1)
Unamended soil 24.0 102.88 0.34
6kg m-2 SSA 28.67 143.34 0.40
9kg m-2 SSA 36.67 180.78 0.41
12kg m-2 SSA 33.3 164.50 0.42
Table13 . Heavy metal concentrations in seed of mung bean at
different sewage-sludge amendment rates(SSA)
Treatment Cu Mn Zn Cr Cd Ni Pb
Unamended
soil
0.48 1.43 11.58 0.32 0.23 0.43 0.42
6kg m-2 SSA 0.77 1.92 20.58 0.83 0.80 1.47 1.88
9kg m-2 SSA 1.65 2.18 20.62 1.18 1.35 2.85 2.62
12kg m-2 SSA 2.22 2.82 22.07 1.47 1.62 5.67 3.47
Singh and Agrawal (2008)
Singh and Agrawal (2008)

35. Way outs
A) Prevention of heavy
metal contamination
B) Management of
contaminated soil

36. Prevention of heavy metal contamination
i) Reducing heavy metal content of sewage
sludge-
Acid thermal hydrolysis
Alkaline thermal hydrolysis

37. Table14. Concentration (mg kg-1 dry solid) of heavy
metals in the sludge cake after subjected to hydrolysis
Heavy metals Untreated Acid thermal
hydrolysis
Alkaline thermal
hydrolysis
Cd 2.05 0.83 2.17
Cr 25.5 15.4 14.7
Cu 183 189 45
Pb 158 148 57
Ni 12.7 2.1 13.2
Zn 2144 370 1712
Dewil et al. (2006)
Order of metal removal from sewage sludge -
 Acid thermal hydrolysis : Zn = Ni > Cd > Cr >Pb> Cu > Hg
 Alkali thermal hydrolysis : Cu >Pb> Cr > Zn > Cd = Hg =Ni

38. Management of contaminated soil
Increasing the soil pH to 6.5 or higher
Draining wet soils
Applying phosphate
Careful selection of plants
Application of organic matter

39. Conclusions
Heavy metal content of both sewage sludge and soil
should be considered during making decisions regarding
sewage sludge use in agriculture.
Risks of heavy metal contamination of crops grown in
sewage sludge amended soils can be minimized to some
extent by altering various physico-chemical properties of
the soil.
Use of sewage sludge should be avoided in crops that
accumulate heavy metals in levels toxic to humans
without themselves showing any toxicity symptoms.
For safe agricultural use of sewage sludge, regular
monitoring of soil and crop edible parts for heavy metal
accumulation is necessary.